JP5516768B2 - Prepreg and carbon fiber reinforced composites - Google Patents

Description

  The present invention relates to a prepreg and carbon fiber reinforced composite material suitably used for aircraft members, spacecraft members, automobile members, ship members, sports applications such as golf shafts and fishing rods, and other general industrial applications. More specifically, the present invention has excellent mechanical properties under severe environments such as low temperatures, and when an epoxy resin suitable as a structural material is used as a matrix resin, it has excellent adhesion between the matrix resin and carbon fibers. The present invention relates to a prepreg and a carbon fiber reinforced composite material capable of suppressing deterioration of mechanical properties during long-term storage.

  In recent years, fiber reinforced composite materials using carbon fibers, aramid fibers, etc. as reinforcing fibers have been used for structural materials such as aircraft and automobiles, tennis rackets, golf shafts, fishing rods, etc. by utilizing their high specific strength and specific modulus. It has been used in sports and general industries.

  Such a fiber reinforced composite material is formed by forming a prepreg, which is a sheet-like intermediate material obtained by impregnating carbon fibers with an uncured matrix resin, and curing the prepreg, or by using a liquid matrix resin on the carbon fibers disposed in the mold. The resin is produced by a resin transfer molding method in which an intermediate is obtained by pouring the resin into the intermediate. Among these production methods, in a method using a prepreg, a carbon fiber reinforced composite material molded article is usually obtained by laminating a plurality of prepregs and then applying heat and pressure. As the matrix resin used for the prepreg, a thermosetting resin, particularly an epoxy resin is often used from the viewpoint of productivity such as processability.

  In particular, structural materials such as aircraft and automobiles are strongly demanded to further reduce weight and improve material strength as demand increases in recent years. Therefore, high heat resistance is required for the epoxy resin used as the matrix resin.

  In general, an epoxy resin composition having a high glass transition temperature Tg has a high curing temperature, and such a resin composition tends to have a large amount of volatile components during curing and molding that are exposed to a high temperature. If there is a large amount of volatile components at the time of curing, for example, in the honeycomb material, the gasified volatile components are sealed in the honeycomb when the surface is formed, and it expands in the honeycomb without an outlet, and adheres between the surface material and the honeycomb core material. It becomes a factor to inhibit. Further, in autoclave molding of a prepreg laminate, volatile matter may cause voids during molding, which may impair the strength of the carbon fiber reinforced composite material.

  For a highly heat-resistant epoxy resin composition having a low volatile content, a method of combining a polyfunctional epoxy resin and polyisocyanate has been proposed (see Patent Document 1). However, this proposal does not mention the strength of the carbon fiber reinforced composite material obtained by laminating and curing the prepreg.

  In addition, increasing the strength of carbon fiber reinforced composite materials requires increasing the strength of carbon fibers and increasing the content of high volume carbon fibers (higher Vf), and a method for obtaining high strength carbon fibers has been proposed. (See Patent Document 2). However, in this proposal, there is no mention of the strength developed when the carbon fiber reinforced composite material is used. In general, the higher the strength of carbon fiber, the more difficult it is to utilize the original strength of carbon fiber. For example, even if the strand strength of the carbon fiber is improved, the tensile strength cannot be sufficiently utilized, and the tensile strength utilization factor (tensile strength of carbon fiber reinforced composite material / (strand strength of carbon fiber × volume carbon fiber contained) (Rate) × 100) tends to decrease. Therefore, even if such a high-strength carbon fiber can be obtained, it is necessary to further solve technical problems in order to develop the strength as a carbon fiber-reinforced composite material.

  Furthermore, it is known that even when carbon fibers have the same strength, the tensile strength utilization rate varies greatly depending on the matrix resin to be combined and the molding conditions. In particular, when the curing temperature condition is 180 ° C. or higher, there is a problem that high strength is difficult to be expressed from the thermal stress remaining in the carbon fiber reinforced composite material during the curing. For this reason, studies have been made on the modification of matrix resins so as to obtain sufficient tensile strength even when cured at a temperature of 180 ° C.

  It is known that when the tensile elongation at break of the matrix resin is increased, the tensile strength utilization rate of the carbon fiber reinforced composite material is improved. In order to improve the tensile elongation at break of the matrix resin, it is effective to lower the crosslink density of the matrix resin. However, the heat resistance of the carbon fiber reinforced composite material may decrease due to the decrease of the crosslink density, There is a problem that it is limited. In order to solve this, it has been proposed that a high tensile strength utilization rate can be obtained if the tensile fracture elongation and the fracture toughness KIc satisfy a specific relationship (see Patent Document 3). However, when a large amount of a thermoplastic resin or a rubber component is added to the matrix resin in order to improve the fracture toughness KIc, the viscosity generally increases, and the processability and handling of prepreg production may be impaired.

  On the other hand, various sizing agents for carbon fibers have been proposed for the purpose of improving the adhesion and sizing properties of carbon fibers. As a sizing agent, a compound having a plurality of aliphatic type epoxy groups, an epoxy adduct of polyalkylene glycol, a diglycidyl ether of bisphenol A, a polyalkylene oxide adduct of bisphenol A, a polyalkylene oxide adduct of bisphenol A An epoxy group-added one has been proposed, but a sizing agent composed of one kind of epoxy compound cannot be said to have sufficient adhesiveness and convergence, and two or more kinds of epoxy compounds are used in combination depending on the desired function. Techniques have been proposed recently.

  For example, a sizing agent that combines two or more epoxy compounds that define surface energy has been proposed (see Patent Documents 4 to 7). Patent Document 4 discloses a combination of an aliphatic epoxy compound and an aromatic epoxy compound. According to Patent Document 4, the sizing agent that is abundant in the outer layer has a blocking effect on the sizing agent component that is abundant in the inner layer, and prevents the epoxy groups from opening due to moisture in the atmosphere. . Further, in this document, the ratio of the aliphatic epoxy compound and the aromatic epoxy compound is defined as 10/90 to 40/60 with respect to a preferable range of the sizing agent, and it is preferable that the amount of the aromatic epoxy compound is large. Yes.

  Patent Documents 6 and 7 disclose sizing agents that use two or more epoxy compounds having different surface energies. Since Patent Documents 6 and 7 are intended to improve the adhesiveness with a matrix resin, the combination of an aromatic epoxy compound and an aliphatic epoxy compound is not limited as a combination of two or more epoxy compounds, and adhesiveness is not limited. There is no general example of the aliphatic epoxy compound selected from the viewpoint of the above.

  Furthermore, the sizing agent which mix | blends a bisphenol A type epoxy compound and aliphatic polyepoxy resin by mass ratio 50 / 50-90 / 10 is disclosed (refer patent document 8). However, Patent Document 8 also has a large amount of bisphenol A type epoxy compound, which is an aromatic epoxy compound.

  In addition, as a sizing agent that defines a combination of an aromatic epoxy compound and an aliphatic epoxy compound, a polyfunctional aliphatic compound on the surface of the carbon fiber bundle, an epoxy resin on the upper surface, an alkylene oxide adduct and an unsaturated dibasic acid A combination of a condensate and an alkylene oxide adduct of phenols is disclosed (see Patent Document 9).

  Furthermore, as a combination of two or more epoxy compounds, a combination of an aliphatic epoxy compound and a bisphenol A type epoxy compound that is an aromatic epoxy compound is disclosed. The aliphatic epoxy compound is a cycloaliphatic epoxy compound and / or a long-chain aliphatic epoxy compound (see Patent Document 10).

  Further, combinations of epoxy compounds having different properties are disclosed. A combination of two types of epoxy compounds that are liquid and solid at 25 ° C. is disclosed (see Patent Document 11). Furthermore, combinations of epoxy resins having different molecular weights and combinations of monofunctional aliphatic epoxy compounds and epoxy resins have been proposed (see Patent Documents 12 and 13).

However, the adhesion between the carbon fiber and the matrix resin and the stability during long-term storage in the prepreg are simultaneously satisfied even in a sizing agent (for example, Patent Documents 10 to 13) in which two or more of the above are mixed. I couldn't say that. The reason for this is that it is necessary to satisfy the following three requirements in order to satisfy both high adhesion and suppression of deterioration of mechanical properties during long-term storage with prepreg. This is because they did not meet these requirements. The first of the three requirements is that an epoxy component with high adhesiveness is present inside the sizing layer (carbon fiber side), and the carbon fiber and the epoxy compound in the sizing interact strongly. The sizing layer surface layer (matrix resin side) has a function of inhibiting the reaction between the epoxy compound having high adhesion to the carbon fiber in the inner layer and the matrix resin, and the third is the matrix resin In order to improve the adhesiveness, the sizing agent surface layer (matrix resin side) must have a chemical composition capable of strong interaction with the matrix resin.
For example, Patent Document 4 discloses that the sizing agent has an inclined structure in order to enhance the adhesion between the carbon fiber and the sizing agent, but Patent Document 4 and any other documents (Patent Documents 5 to 5). 8), the sizing layer surface suppresses the reaction between the carbon fiber, the highly adhesive epoxy compound, and the components in the matrix, and at the same time, it can be said that there is no philosophy that satisfies high realization with the matrix resin. .
Further, Patent Document 9 discloses that a polyfunctional aliphatic compound is present in the inner layer of the sizing agent and an aromatic epoxy resin and an aromatic reactant that are less reactive are present in the outer layer, which is retained for a long time. In such a case, it can be expected that the change of the prepreg with time is suppressed, but since there is no polyfunctional aliphatic compound having high adhesion on the surface layer of the sizing agent, it is difficult to achieve high adhesion with the matrix resin.

JP 2001-31838 A Japanese Patent Laid-Open No. 11-241230 Japanese Patent Laid-Open No. 9-235397 JP 2005-179826 A JP 2005-256226 A International Publication No. 03/010383 JP 2008-280624 A JP 2005-213687 A JP 2002-309487 A Japanese Patent Laid-Open No. 02-307979 JP 2002-173873 A JP 59-71479 A JP 58-41973 A

  The present invention has been made in view of the above, and is excellent in adhesion between the matrix resin and the carbon fiber and long-term storage stability, has low volatile content during curing, has excellent heat resistance and low temperature, etc. An object of the present invention is to provide a prepreg capable of obtaining a carbon fiber reinforced composite material having excellent mechanical properties in a severe use environment.

In order to solve the above-described problems and achieve the object, the present invention is a prepreg obtained by impregnating a sizing agent-coated carbon fiber coated with a sizing agent with a thermosetting resin composition, and the sizing agent includes: The aliphatic epoxy compound (A) and the aromatic compound (B) include at least the aromatic epoxy compound (B1), and the sizing agent-coated carbon fiber has a sizing agent surface coated on the carbon fiber as an X-ray source with AlKα _{1 Of the} C _1s core spectrum measured by X-ray photoelectron spectroscopy using X-ray photoelectron spectroscopy using ₂ and ₂ (a) of the binding energy (284.6 eV) attributed to CHx, CC, C = C. The ratio (a) / (b) between the height (cps) of the component and the height (cps) of the component energy (286.1 eV) attributed to (b) C—O is 0.5. The thermosetting resin composition has at least the following component (D): an amine-type glycidyl group having two or more 4-membered ring structures and directly linked to the ring structure Or an epoxy resin having one or two ether type glycidyl groups, (E): an epoxy resin having three or more functional groups, and (F): an epoxy resin composition comprising a latent curing agent, The epoxy resin composition contains 5 to 60% by mass of the epoxy resin (D) and 40 to 80% by mass of the epoxy resin (E) with respect to 100% by mass of the total amount of the epoxy resin blended.

  Further, in the prepreg of the present invention, in the above invention, the epoxy resin composition is an epoxy having one amine-type glycidyl group or ether-type glycidyl group directly linked to a ring structure with respect to 100% by mass of the total amount of the epoxy resin blended. It contains 10 to 40% by mass of the resin (D).

（式（１）中、Ｒ^１とＲ^２は、それぞれ炭素数１〜４の脂肪族炭化水素基、炭素数３〜６の脂環式炭化水素基、炭素数６〜１０の芳香族炭化水素基、ハロゲン原子、アシル基、トリフルオロメチル基およびニトロ基からなる群から選ばれた少なくとも一つを表す。ｎは０〜４の整数、ｍは０〜５の整数である。Ｒ^１とＲ^２が複数存在する場合、それぞれ同じであっても異なっていてもよい。Ｘは、−Ｏ−、−Ｓ−、−ＣＯ−、−Ｃ（＝Ｏ）Ｏ−、−ＳＯ_２−、−Ｃ（＝Ｏ）ＮＨ−から選ばれる１つを表す。）で示される構造を有し、前記エポキシ樹脂組成物は、配合したエポキシ樹脂総量１００質量％に対して、該エポキシ樹脂（Ｄ）を２５〜５０質量％含むことを特徴とする。 The prepreg of the present invention is the above-described invention, wherein the epoxy resin (D) is represented by the following general formula (1):

(In formula (1), R ¹ and R ² are each an aliphatic hydrocarbon group having 1 to 4 carbon atoms, an alicyclic hydrocarbon group having 3 to 6 carbon atoms, and an aromatic hydrocarbon having 6 to 10 carbon atoms. Represents at least one selected from the group consisting of a group, a halogen atom, an acyl group, a trifluoromethyl group, and a nitro group, n is an integer of 0 to 4, and m is an integer of 0 to 5. R ¹ and R ^{When two} or more are present, they may be the same or different, and X is —O—, —S—, —CO—, —C (═O) O—, —SO ₂ —, —C. (= O) represents one selected from NH-), and the epoxy resin composition contains 25 epoxy resin (D) with respect to 100% by mass of the total amount of the epoxy resin blended. It is characterized by containing -50 mass%.

  Moreover, the prepreg of the present invention is characterized in that, in the above-mentioned invention, in the general formula (1), X is —O—.

（式（２）中、Ｒ^３〜Ｒ^６は、水素原子、炭素数１〜４の脂肪族炭化水素基、炭素数４以下の脂環式炭化水素基、ハロゲン原子からなる群から選ばれた少なくとも一つを表す。Ｙは、−ＣＨ_２−、−Ｏ−、−Ｓ−、−ＣＯ−、−Ｃ（＝Ｏ）Ｏ−、−ＳＯ_２−、−Ｃ（＝Ｏ）ＮＨ−から選ばれる１つを表す。）で示される構造を有することを特徴とする。 Moreover, the prepreg of the present invention is the above invention, wherein the epoxy resin (E) is represented by the following general formula (2):

(In the formula (2), R ^{3 to} R ⁶ were selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group having 1 to 4 carbon atoms, an alicyclic hydrocarbon group having 4 or less carbon atoms, and a halogen atom. Y represents at least one, Y is selected from —CH ₂ —, —O—, —S—, —CO—, —C (═O) O—, —SO ₂ —, —C (═O) NH—. It is characterized by having a structure represented by

The prepreg of the present invention is characterized in that, in the above-described invention, Y in the general formula (2) is —CH ₂ —.

In the prepreg of the present invention, in the above invention, the epoxy resin (E) has a structure represented by the general formula (2) in which Y is —CH ₂ —, and an epoxy equivalent is 100 to 115 g / eq. It is characterized by being.

  The prepreg of the present invention is characterized in that, in the above invention, the latent curing agent (F) is an aromatic amine curing agent (F1).

  The prepreg of the present invention is characterized in that, in the above invention, the aromatic amine curing agent (F1) contains a diphenyl sulfone skeleton.

  The prepreg of the present invention is characterized in that, in the above invention, the thermosetting resin includes thermoplastic resin particles (G).

  Further, in the prepreg of the present invention, in the above invention, the thermoplastic resin particles (G) are 90 to 100% by mass in a range of 20% from both sides in the thickness direction of the prepreg. It is characterized by existing.

  Moreover, the prepreg of the present invention is characterized in that, in the above-mentioned invention, the thermosetting resin composition contains a thermoplastic resin (H) that is dissolved in the epoxy resin (D) or the epoxy resin (E). .

  The prepreg of the present invention is characterized in that, in the above invention, the thermoplastic resin (H) is polyethersulfone.

  The prepreg of the present invention is characterized in that, in the above invention, the polyether sulfone has an average molecular weight of 15,000 to 30,000 g / mol.

  In the prepreg of the present invention, the epoxy equivalent of the sizing agent is 350 to 550 g / eq. The prepreg according to claim 1, wherein the prepreg is a prepreg.

  In the prepreg of the present invention, in the above invention, the sizing agent is at least 35 to 65% by mass of the aliphatic epoxy compound (A) and the aromatic compound (B) with respect to the total amount of the sizing agent excluding the solvent. It is characterized by containing 35-60 mass%.

  The prepreg of the present invention is characterized in that, in the above invention, the mass ratio of the aliphatic epoxy compound (A) to the aromatic epoxy compound (B1) is 52/48 to 80/20.

  In the prepreg of the present invention, the aliphatic epoxy compound (A) is a polyether type polyepoxy compound and / or a polyol type polyepoxy compound having two or more epoxy groups in the molecule. Features.

  In the prepreg of the present invention, the aliphatic epoxy compound (A) is ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetra Propylene glycol, polypropylene glycol, trimethylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, polybutylene glycol, 1,5-pentanediol, neo Pentyl glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, glycerol, diglycerol, polyglycerol, trimethylolpropane, pentaerythritol Le, characterized in that sorbitol, and a compound selected from arabitol, glycidyl ether type epoxy compound obtained by reaction with epichlorohydrin.

  The prepreg of the present invention is characterized in that, in the above invention, the aromatic epoxy compound (B1) is a bisphenol A type epoxy compound or a bisphenol F type epoxy compound.

  In the prepreg of the present invention, in the above invention, the sizing agent contains 2 to 35% by mass of an ester compound (C) having no epoxy group in the molecule with respect to the total amount of the sizing agent excluding the solvent. It is characterized by.

In the prepreg of the present invention, the sizing agent-coated carbon fiber is measured at a photoelectron escape angle of 55 ° by X-ray photoelectron spectroscopy using 400 eV X-rays. The height (cps) of the component of the binding energy (284.6 eV) attributed to (a) CHx, C—C, C = C in the C _1s inner-shell spectrum, and (b) the bond attributed to C—O. The values of (I) and (II) obtained from the ratio (a) / (b) with the height (cps) of the component of energy (286.1 eV) satisfy the relationship of (III) Features.
(I) Value of (a) / (b) on the surface of the sizing agent-coated carbon fiber before sonication (II) Sizing agent adhesion by sonicating the sizing agent-coated carbon fiber in an acetone solvent (A) / (b) value (III) 0.50 ≦ (I) ≦ 0.90 and 0.60 <on the surface of the sizing agent-coated carbon fiber washed to 0.09 to 0.20% by mass (II) / (I) <1.0

  The prepreg of the present invention is the prepreg according to the above invention, wherein the sizing agent is a mixture of an aqueous emulsion liquid containing at least the aromatic epoxy compound (B1) and a composition containing at least the aliphatic epoxy compound (A). It is characterized by that.

  In the prepreg of the present invention, the sizing agent and the aromatic amine curing agent (E1) are the same as the sizing agent and the aromatic amine curing agent (F1), and the amine equivalent / epoxy equivalent is 0. After mixing at a ratio of .9, the glass transition point rises when stored in an atmosphere of 25 ° C. and 60% RH for 20 days.

  Moreover, the carbon fiber reinforced composite material of the present invention is formed by molding the prepreg according to any one of the above.

  According to the present invention, it is possible to obtain a carbon fiber reinforced composite material having excellent heat resistance and strength properties while having excellent adhesion between the matrix resin and the carbon fiber, little change with time during long-term storage and little volatilization during curing. Can do.

  Hereinafter, the prepreg and the carbon fiber reinforced composite material according to the embodiment of the present invention will be described in more detail.

The present invention is a prepreg formed by impregnating a sizing agent-coated carbon fiber coated with a sizing agent with a thermosetting resin composition, and the sizing agent includes an aliphatic epoxy compound (A) and an aromatic compound (B). The sizing agent-coated carbon fiber includes at least an aromatic epoxy compound (B1), and the sizing agent-coated carbon fiber has a C _1s core spectrum measured on the surface of the sizing agent coated on the carbon fiber at a photoelectron escape angle of 15 ° by X-ray photoelectron spectroscopy. (A) the height (cps) of the component of the bond energy (284.6 eV) attributed to CHx, C—C, C═C, and (b) the bond energy (286.1 eV) attributed to C—O. ) Ratio (a) / (b) to the height (cps) of the component is 0.50 to 0.90, and the thermosetting resin composition has at least the following component (D): 4 An epoxy resin having two or more ring structures of at least a ring and one or two amine-type glycidyl groups or ether-type glycidyl groups directly linked to the ring structure, (E): having three or more functional groups Epoxy resin, (F): an epoxy resin composition comprising a latent curing agent, and the epoxy resin composition contains 5 to 5% of the epoxy resin (D) with respect to 100% by mass of the total epoxy resin content. 60 mass% and 40-80 mass% of said epoxy resins (E) are included.

  First, the sizing agent used in the prepreg of the present invention will be described. The sizing agent according to the present invention includes at least the aromatic epoxy compound (B1) as the aliphatic epoxy compound (A) and the aromatic compound (B).

  According to the knowledge of the present inventors, such a range has excellent interfacial adhesion between the carbon fiber and the matrix, and also when the prepreg is stored for a long time even when the sizing agent-coated carbon fiber is used for the prepreg. The change is small and suitable for carbon fibers for carbon fiber reinforced composite materials.

  When the sizing agent according to the present invention is applied to carbon fibers, a large amount of the aliphatic epoxy compound (A) is present inside the sizing layer (carbon fiber side), so that the carbon fiber and the aliphatic epoxy compound (A) are present. In addition to enhancing the adhesion and enhancing the adhesion, the presence of a large amount of the aromatic compound (B) containing the aromatic epoxy compound (B1) in the sizing layer surface layer (matrix resin side) allows the aliphatic in the inner layer An aromatic epoxy compound containing a predetermined proportion of epoxy groups as a chemical composition capable of strong interaction with the matrix resin on the sizing layer surface (matrix resin side) while inhibiting the reaction between the epoxy compound (A) and the matrix resin Since (B1) and the aliphatic epoxy compound (A) are present at a predetermined ratio, the adhesion with the matrix resin is also improved. That.

  When the sizing agent consists only of the aromatic epoxy compound (B1) and does not contain the aliphatic epoxy compound (A), the reactivity between the sizing agent and the matrix resin is low, and the mechanical properties change when the prepreg is stored for a long time Has the advantage of being small. There is also an advantage that a rigid interface layer can be formed. However, it has been confirmed that the aromatic epoxy compound (B1) is slightly inferior in adhesion between the carbon fiber and the matrix resin as compared with the aliphatic epoxy compound (A) because of the rigidity of the compound. .

  Further, when the sizing agent is composed only of the aliphatic epoxy compound (A), it has been confirmed that the carbon fiber coated with the sizing agent has high adhesiveness with the matrix resin. Although the mechanism is not certain, the aliphatic epoxy compound (A) is derived from a flexible skeleton and a structure having a high degree of freedom, and the functional group of the carbon fiber surface with a carboxyl group and a hydroxyl group and the aliphatic epoxy compound (A) Are thought to be capable of forming strong interactions. However, the aliphatic epoxy compound (A) exhibits high adhesiveness due to the interaction with the carbon fiber surface, while having high reactivity with the compound having a functional group represented by the curing agent in the matrix resin, When stored for a long time in this state, it has been confirmed that the structure of the interface layer changes due to the interaction between the matrix resin and the sizing agent, and the mechanical properties of the carbon fiber reinforced composite material obtained from the prepreg deteriorate. .

  In the present invention, when the aliphatic epoxy compound (A) and the aromatic compound (B) are mixed, the aliphatic epoxy compound (A) having higher polarity is unevenly distributed on the carbon fiber side, and the sizing on the opposite side to the carbon fiber is performed. There is a phenomenon that the aromatic compound (B) having a low polarity tends to be unevenly distributed in the outermost layer of the layer. As a result of the gradient structure of the sizing layer, the aliphatic epoxy compound (A) has a strong interaction with the carbon fiber in the vicinity of the carbon fiber, thereby enhancing the adhesion between the carbon fiber and the matrix resin. In addition, when the sizing agent-coated carbon fiber is used as a prepreg, the aromatic compound (B) present in a large amount in the outer layer plays a role of blocking the aliphatic epoxy compound (A) from the matrix resin. As a result, the reaction between the aliphatic epoxy compound (A) and the highly reactive component in the matrix resin is suppressed, so that stability during long-term storage is exhibited. When the aliphatic epoxy compound (A) is almost completely covered with the aromatic compound (B), the interaction between the sizing agent and the matrix resin is reduced and the adhesiveness is lowered. The abundance ratio of the aliphatic epoxy compound (A) and the aromatic compound (B) is important.

  The sizing agent according to the present invention preferably contains at least 35 to 65% by mass of the aliphatic epoxy compound (A) and at least 35 to 60% by mass of the aromatic compound (B) based on the total amount of the sizing agent excluding the solvent. . By blending the aliphatic epoxy compound (A) in an amount of 35% by mass or more based on the total amount of the sizing agent excluding the solvent, the adhesion between the carbon fiber and the matrix resin is improved. Moreover, when it is set to 65% by mass or less, even when the prepreg is stored for a long period of time, the mechanical properties when molded into a carbon fiber reinforced composite material are improved. As for the compounding quantity of an aliphatic epoxy compound (A), 38 mass% or more is more preferable, and 40 mass% or more is further more preferable. Moreover, 60 mass% or less is more preferable, and, as for the compounding quantity of an aliphatic epoxy compound (A), 55 mass% or less is further more preferable.

  In the sizing agent of the present invention, the composition of the aromatic compound (B) in the outer layer of the sizing agent is blended by adding 35% by mass or more of the aromatic compound (B) to the total amount of the sizing agent excluding the solvent. Since it can maintain high, the mechanical characteristic fall by reaction with the highly reactive aliphatic epoxy compound (A) at the time of long-term storage of a prepreg and the reactive compound in a matrix resin is suppressed. Moreover, the gradient structure in a sizing agent can be expressed by setting it as 60 mass% or less, and the adhesiveness of carbon fiber and matrix resin can be maintained. 37 mass% or more is more preferable, and, as for the compounding quantity of an aromatic compound (B), 39 mass% or more is further more preferable. Moreover, 55 mass% or less is more preferable, and, as for the compounding quantity of an aromatic compound (B), 45 mass% or less is further more preferable.

  The sizing agent in the present invention includes, as an epoxy component, an aromatic epoxy compound (B1) that is an aromatic compound (B) in addition to the aliphatic epoxy compound (A). The mass ratio (A) / (B1) of the aliphatic epoxy compound (A) and the aromatic epoxy compound (B1) is preferably 52/48 to 80/20. By setting (A) / (B1) to 52/48 or more, the ratio of the aliphatic epoxy compound (A) present on the carbon fiber surface is increased, and the adhesion between the carbon fiber and the matrix resin is improved. As a result, the obtained carbon fiber reinforced composite material has high mechanical properties such as tensile strength. Further, by setting (A) / (B1) to 80/20 or less, the amount of the highly reactive aliphatic epoxy compound (B) present on the carbon fiber surface is reduced, and the reactivity with the matrix resin is suppressed. This is preferable because it is possible. The mass ratio of (A) / (B1) is more preferably 55/45 or more, and still more preferably 60/40 or more. Further, the mass ratio of (A) / (B1) is more preferably 75/35 or less, and further preferably 73/37 or less.

  The aliphatic epoxy compound (A) in the present invention is an epoxy compound that does not contain an aromatic ring. Since it has a flexible skeleton with a high degree of freedom, it can have a strong interaction with carbon fibers. As a result, the adhesion between the carbon fiber coated with the sizing agent and the matrix resin is improved.

  In the present invention, the aliphatic epoxy compound (A) has one or more epoxy groups in the molecule. As a result, a strong bond between the carbon fiber and the epoxy group in the sizing agent can be formed. The number of epoxy groups in the molecule is preferably 2 or more, and more preferably 3 or more. If the aliphatic epoxy compound (A) is an epoxy compound having two or more epoxy groups in the molecule, even if one epoxy group forms a covalent bond with an oxygen-containing functional group on the surface of the carbon fiber, the remaining The epoxy group can form a covalent bond or a hydrogen bond with the matrix resin, and the adhesion between the carbon fiber and the matrix resin can be further improved. There is no particular upper limit on the number of epoxy groups, but 10 is sufficient from the viewpoint of adhesion.

  In the present invention, the aliphatic epoxy compound (A) is preferably an epoxy compound having 3 or more functional groups of 2 or more, more preferably an epoxy compound having 4 or more of 2 or more functional groups. preferable. The functional group possessed by the epoxy compound is preferably selected from a hydroxyl group, an amide group, an imide group, a urethane group, a urea group, a sulfonyl group, or a sulfo group in addition to the epoxy group. When the aliphatic epoxy compound (A) is an epoxy compound having three or more epoxy groups or other functional groups in the molecule, one epoxy group forms a covalent bond with an oxygen-containing functional group on the surface of the carbon fiber. Even in this case, the remaining two or more epoxy groups or other functional groups can form a covalent bond or a hydrogen bond with the matrix resin, and the adhesion between the carbon fiber and the matrix resin is further improved. There is no particular upper limit on the number of functional groups containing an epoxy group, but 10 is sufficient from the viewpoint of adhesiveness.

  In the present invention, the epoxy equivalent of the aliphatic epoxy compound (A) is 360 g / eq. Is preferably less than 270 g / eq. Less, more preferably 180 g / eq. Is less than. The epoxy equivalent of the aliphatic epoxy compound (A) is 360 g / eq. If it is less than this, the interaction with the carbon fiber is formed at a high density, and the adhesion between the carbon fiber and the matrix resin is further improved. There is no particular lower limit of epoxy equivalent, but 90 g / eq. The above is sufficient from the viewpoint of adhesiveness.

  In the present invention, specific examples of the aliphatic epoxy compound (A) include, for example, a glycidyl ether type epoxy compound derived from a polyol, a glycidyl amine type epoxy compound derived from an amine having a plurality of active hydrogens, and a polycarboxylic acid. Examples thereof include an induced glycidyl ester type epoxy compound and an epoxy compound obtained by oxidizing a compound having a plurality of double bonds in the molecule.

  Examples of the glycidyl ether type epoxy compound include a glycidyl ether type epoxy compound obtained by a reaction between a polyol and epichlorohydrin. For example, as a glycidyl ether type epoxy compound, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, polypropylene glycol, trimethylene glycol, 1, 2 -Butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, polybutylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,4 -Cyclohexanedimethanol, hydrogenated bisphenol A, hydrogenated bisphenol F, glycerol, diglycerol, polyglycerol, trimethylolpropane, Pentaerythritol, sorbitol, and one and selected from arabitol, glycidyl ether type epoxy compound obtained by reaction with epichlorohydrin. Examples of the glycidyl ether type epoxy compound include a glycidyl ether type epoxy compound having a dicyclopentadiene skeleton.

  Examples of the glycidylamine type epoxy compound include 1,3-bis (aminomethyl) cyclohexane.

  Examples of the glycidyl ester type epoxy compound include a glycidyl ester type epoxy compound obtained by reacting dimer acid with epichlorohydrin.

  Examples of the epoxy compound obtained by oxidizing a compound having a plurality of double bonds in the molecule include an epoxy compound having an epoxycyclohexane ring in the molecule. Furthermore, the epoxy compound includes epoxidized soybean oil.

  Examples of the aliphatic epoxy compound (A) used in the present invention include epoxy compounds such as triglycidyl isocyanurate in addition to these epoxy compounds.

  The aliphatic epoxy compound (A) according to the present invention is selected from one or more epoxy groups and a hydroxyl group, an amide group, an imide group, a urethane group, a urea group, a sulfonyl group, a carboxyl group, an ester group, and a sulfo group. It preferably has at least one functional group. Specific examples of the functional group possessed by the aliphatic epoxy compound (A) include, for example, a compound having an epoxy group and a hydroxyl group, a compound having an epoxy group and an amide group, a compound having an epoxy group and an imide group, and an epoxy group and a urethane group. A compound having an epoxy group and a urea group, a compound having an epoxy group and a sulfonyl group, and a compound having an epoxy group and a sulfo group.

  Examples of the aliphatic epoxy compound (A) having a hydroxyl group in addition to the epoxy group include sorbitol-type polyglycidyl ether and glycerol-type polyglycidyl ether. Specifically, Denacol (registered trademark) EX-611, EX -612, EX-614, EX-614B, EX-622, EX-512, EX-521, EX-421, EX-313, EX-314 and EX-321 (manufactured by Nagase ChemteX Corporation) It is done.

  Examples of the aliphatic epoxy compound (A) having an amide group in addition to the epoxy group include an amide-modified epoxy compound. The amide-modified epoxy can be obtained by reacting an epoxy group of an epoxy compound having two or more epoxy groups with a carboxyl group of an aliphatic dicarboxylic acid amide.

  Examples of the aliphatic epoxy compound (A) having a urethane group in addition to the epoxy group include a urethane-modified epoxy compound, specifically, Adeka Resin (registered trademark) EPU-78-13S, EPU-6, EPU- 11, EPU-15, EPU-16A, EPU-16N, EPU-17T-6, EPU-1348, EPU-1395 (manufactured by ADEKA Corporation) and the like. Alternatively, by reacting the terminal hydroxyl group of polyethylene oxide monoalkyl ether with a polyvalent isocyanate equivalent to the amount of the hydroxyl group, and then reacting the isocyanate residue of the obtained reaction product with the hydroxyl group in the polyvalent epoxy compound. Can be obtained. Here, examples of the polyvalent isocyanate used include hexamethylene diisocyanate, isophorone diisocyanate, and norbornane diisocyanate.

  Examples of the aliphatic epoxy compound (A) having a urea group in addition to the epoxy group include a urea-modified epoxy compound. The urea-modified epoxy compound can be obtained by reacting the epoxy group of an epoxy compound having two or more epoxy groups with the carboxyl group of the aliphatic dicarboxylic acid urea.

  The aliphatic epoxy compound (A) used in the present invention is ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, from the viewpoint of high adhesiveness as described above. Tetrapropylene glycol, polypropylene glycol, trimethylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, polybutylene glycol, 1,5-pentanediol, Neopentyl glycol, 1,6-hexanediol, glycerol, diglycerol, polyglycerol, trimethylolpropane, pentaerythritol, sorbitol, and arabito One and selected from a glycidyl ether type epoxy compound obtained by reaction of epichlorohydrin is more preferable.

  Among the above, the aliphatic epoxy compound (A) in the present invention is preferably a polyether type polyepoxy compound and / or a polyol type polyepoxy compound having two or more epoxy groups in the molecule from the viewpoint of high adhesiveness.

  In the present invention, the aliphatic epoxy compound (A) is more preferably polyglycerol polyglycidyl ether.

  In the present invention, the aromatic compound (B) has one or more aromatic rings in the molecule. The aromatic ring may be an aromatic ring hydrocarbon consisting only of carbon, or a heteroaromatic ring such as furan, thiophene, pyrrole or imidazole containing a heteroatom such as nitrogen or oxygen. The aromatic ring may be a polycyclic aromatic ring such as naphthalene or anthracene. In a carbon fiber reinforced composite material composed of a carbon fiber coated with a sizing agent and a matrix resin, a so-called interface layer in the vicinity of the carbon fiber is affected by the carbon fiber or the sizing agent and may have different characteristics from the matrix resin. . When the sizing agent contains the aromatic compound (B) having one or more aromatic rings, a rigid interface layer is formed, the stress transmission ability between the carbon fiber and the matrix resin is improved, and the carbon fiber reinforced composite material Mechanical properties such as 0 ° tensile strength are improved. Moreover, since the interaction with the carbon fiber is weaker than the aliphatic epoxy compound (A) due to the hydrophobicity of the aromatic ring, the aliphatic epoxy compound (A) is more on the carbon fiber side due to the interaction with the carbon fiber. As a result, a large amount of the aromatic compound (B) is present in the outer layer of the sizing layer. Thereby, since the aromatic compound (B) suppresses the reaction between the aliphatic epoxy compound (A) and the matrix resin, the carbon fiber coated with the sizing agent according to the present invention is stored for a long period of time. This is preferable because the change with time can be suppressed. By selecting a compound having two or more aromatic rings as the aromatic compound (B), long-term storage stability when used as a prepreg can be further improved. There is no particular upper limit on the number of aromatic rings, but 10 is sufficient from the viewpoint of suppressing the reaction with the mechanical properties and the matrix resin.

  In the present invention, the aromatic compound (B) can have one or more functional groups in the molecule. Moreover, the aromatic compound (B) may be one kind or a combination of a plurality of compounds. The aromatic compound (B) contains at least an aromatic epoxy compound (B1) having one or more epoxy groups and one or more aromatic rings in the molecule. The functional group other than the epoxy group is preferably selected from a hydroxyl group, an amide group, an imide group, a urethane group, a urea group, a sulfonyl group, a carboxyl group, an ester group or a sulfo group, and two or more functional groups in one molecule. May be included. As the aromatic compound (B), in addition to the aromatic epoxy compound (B1), an aromatic ester compound and an aromatic urethane compound are preferably used in order to improve the stability and high-order processability of the compound.

  In the present invention, the number of epoxy groups of the aromatic epoxy compound (B1) is preferably 2 or more, and more preferably 3 or more. Moreover, it is preferable that it is 10 or less.

  In the present invention, the aromatic epoxy compound (B1) is preferably an epoxy compound having three or more functional groups, and more preferably an epoxy compound having four or more functional groups. preferable. The functional group possessed by the aromatic epoxy compound (B1) is preferably selected from a hydroxyl group, an amide group, an imide group, a urethane group, a urea group, a sulfonyl group, or a sulfo group in addition to the epoxy group. When the aromatic epoxy compound (B1) is an epoxy compound having three or more epoxy groups or one epoxy group and two or more other functional groups in the molecule, one epoxy group is bonded to the carbon fiber surface. Even when a covalent bond is formed with an oxygen-containing functional group, the remaining two or more epoxy groups or other functional groups can form a covalent bond or a hydrogen bond with the matrix resin, and adhesion between the carbon fiber and the matrix resin. The nature is further improved. There is no particular upper limit on the number of functional groups containing an epoxy group, but 10 is sufficient from the viewpoint of adhesiveness.

  In the present invention, the epoxy equivalent of the aromatic epoxy compound (B1) is 360 g / eq. Is preferably less than 270 g / eq. Less, more preferably 180 g / eq. Is less than. The epoxy equivalent of the aromatic epoxy compound (B1) is 360 g / eq. If it is less than that, covalent bonds are formed at a high density, and the adhesion between the carbon fibers and the matrix resin is further improved. There is no particular lower limit of epoxy equivalent, but 90 g / eq. The above is sufficient from the viewpoint of adhesiveness.

  In the present invention, specific examples of the aromatic epoxy compound (B1) include, for example, a glycidyl ether type epoxy compound derived from an aromatic polyol, a glycidyl amine type epoxy compound derived from an aromatic amine having a plurality of active hydrogens, Examples thereof include glycidyl ester type epoxy compounds derived from aromatic polycarboxylic acids, and epoxy compounds obtained by oxidizing aromatic compounds having a plurality of double bonds in the molecule.

  Examples of the glycidyl ether type epoxy compound include bisphenol A, bisphenol F, bisphenol AD, bisphenol S, tetrabromobisphenol A, phenol novolac, cresol novolac, hydroquinone, resorcinol, 4,4′-dihydroxy-3,3 ′, 5. , 5′-tetramethylbiphenyl, 1,6-dihydroxynaphthalene, 9,9-bis (4-hydroxyphenyl) fluorene, tris (p-hydroxyphenyl) methane, and tetrakis (p-hydroxyphenyl) ethane The glycidyl ether type epoxy compound obtained by reaction with 1 type and epichlorohydrin is mentioned. Examples of the glycidyl ether type epoxy compound include a glycidyl ether type epoxy compound having a biphenylaralkyl skeleton.

  Examples of the glycidylamine type epoxy compound include N, N-diglycidylaniline, N, N-diglycidyl-o-toluidine, m-xylylenediamine, m-phenylenediamine, 4,4′-diaminodiphenylmethane and 9 , 9-bis (4-aminophenyl) fluorene, and a glycidyl ether type epoxy compound obtained by reaction with epichlorohydrin.

  Further, for example, as a glycidylamine type epoxy compound, both the hydroxyl group and amino group of aminophenols of m-aminophenol, p-aminophenol, and 4-amino-3-methylphenol are reacted with epichlorohydrin. And an epoxy compound obtained.

  Examples of the glycidyl ester type epoxy compound include glycidyl ester type epoxy compounds obtained by reacting phthalic acid, terephthalic acid, and hexahydrophthalic acid with epichlorohydrin.

  In addition to these epoxy compounds, the aromatic epoxy compound (B1) used in the present invention is an epoxy compound synthesized from the above-mentioned epoxy compound, for example, oxazolidone from bisphenol A diglycidyl ether and tolylene diisocyanate. An epoxy compound synthesized by a ring formation reaction is exemplified.

  In the present invention, the aromatic epoxy compound (B1) is selected from a hydroxyl group, an amide group, an imide group, a urethane group, a urea group, a sulfonyl group, a carboxyl group, an ester group, and a sulfo group in addition to one or more epoxy groups. At least one functional group is preferably used. For example, compounds having epoxy group and hydroxyl group, compounds having epoxy group and amide group, compounds having epoxy group and imide group, compounds having epoxy group and urethane group, compounds having epoxy group and urea group, epoxy group and sulfonyl Examples thereof include compounds having a group and compounds having an epoxy group and a sulfo group.

  Examples of the aromatic epoxy compound (B1) having an amide group in addition to the epoxy group include glycidyl benzamide and an amide-modified epoxy compound. The amide-modified epoxy can be obtained by reacting an epoxy group of an epoxy compound having two or more epoxy groups with a carboxyl group of a dicarboxylic acid amide containing an aromatic ring.

  Examples of the aromatic epoxy compound (B1) having an imide group in addition to the epoxy group include glycidyl phthalimide. Specific examples include Denacol (registered trademark) EX-731 (manufactured by Nagase ChemteX Corporation).

  As the aromatic epoxy compound (B1) having a urethane group in addition to the epoxy group, the terminal hydroxyl group of the polyethylene oxide monoalkyl ether is reacted with a polyvalent isocyanate containing an aromatic ring equivalent to the amount of the hydroxyl group, and then obtained. It can obtain by making the isocyanate residue of the obtained reaction product react with the hydroxyl group in a polyhydric epoxy compound. Here, examples of the polyvalent isocyanate used include 2,4-tolylene diisocyanate, metaphenylene diisocyanate, paraphenylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, and biphenyl-2,4,4′-triisocyanate. It is done.

  Examples of the aromatic epoxy compound (B1) having a urea group in addition to the epoxy group include a urea-modified epoxy compound. The urea-modified epoxy can be obtained by reacting the epoxy group of an epoxy compound containing an aromatic ring having two or more epoxy groups with the carboxyl group of the dicarboxylic acid urea.

  Examples of the aromatic epoxy compound (B1) having a sulfonyl group in addition to the epoxy group include bisphenol S-type epoxy.

  Examples of the aromatic epoxy compound (B1) having a sulfo group in addition to the epoxy group include glycidyl p-toluenesulfonate and glycidyl 3-nitrobenzenesulfonate.

  In the present invention, the aromatic epoxy compound (B1) is preferably either a phenol novolac epoxy compound, a cresol novolac epoxy compound, or tetraglycidyldiaminodiphenylmethane. These epoxy compounds have a large number of epoxy groups, a small epoxy equivalent, and have two or more aromatic rings. In addition to improving adhesion between carbon fibers and matrix resins, carbon fiber reinforced composites Improve mechanical properties such as 0 ° tensile strength of the material. The aromatic epoxy compound (B1) is more preferably a phenol novolac epoxy compound and a cresol novolac epoxy compound.

  In the present invention, when the prepreg is stored for a long time, the aromatic epoxy compound (B1) is a phenol novolac type epoxy compound, a cresol novolac type epoxy compound, tetraglycidyl diaminodiphenylmethane, a bisphenol A type epoxy compound or a bisphenol F type epoxy compound. From the viewpoint of the stability of the resin and the adhesion between the carbon fiber and the matrix resin, a bisphenol A type epoxy compound or a bisphenol F type epoxy compound is more preferable.

  Further, the sizing agent used in the present invention may contain one or more components other than the aliphatic epoxy compound (A) and the aromatic epoxy compound (B1) which is the aromatic compound (B). Adhesion promoting component that enhances adhesion between carbon fiber and sizing agent, and sizing agent-coated carbon fiber is blended with a material that imparts convergence or flexibility to improve handling, scratch resistance and fluff resistance, and matrix The impregnation property of the resin can be improved. In the present invention, compounds other than (A) and (B1) can be contained for the purpose of improving long-term storage stability in a prepreg. For the purpose of long-term storage stability of the sizing agent, auxiliary components such as a dispersant and a surfactant may be added.

  In addition to the aliphatic epoxy compound (A) and the aromatic epoxy compound (B1), an ester compound (C) having no epoxy group in the molecule can be added to the sizing agent used in the present invention. The sizing agent concerning this invention can mix | blend 2-35 mass% of ester compounds (C) with respect to the sizing agent whole quantity except a solvent. More preferably, it is 15-30 mass%. By blending the ester compound (C), the convergence is improved, the handleability is improved, and at the same time, the deterioration of the mechanical properties when the prepreg due to the reaction between the matrix resin and the sizing agent is stored for a long time can be suppressed. .

  The ester compound (C) may be an aliphatic ester compound having no aromatic ring, or may be an aromatic ester compound having one or more aromatic rings in the molecule. When the aromatic ester compound (C1) is used as the ester compound (C), the aromatic ester compound (C1) is included in the ester compound (C) having no epoxy compound in the molecule. In the present invention, it is included in the aromatic compound (B). In this case, not all of the aromatic compound (B) becomes the aromatic ester compound (C1), and the aromatic compound (B) is composed of the aromatic epoxy compound (B1) and the aromatic ester compound (C1). Consists of. When the aromatic ester compound (C1) is used as the ester compound (C), the handleability of the sizing agent-coated carbon fiber is improved, and at the same time, the aromatic ester compound (C1) has a weak interaction with the carbon fiber. It exists in the outer layer of the resin, and the effect of suppressing the deterioration of mechanical properties during long-term storage of the prepreg is enhanced. In addition to the ester group, the aromatic ester compound (C1) has a functional group other than an epoxy group, such as a hydroxyl group, an amide group, an imide group, a urethane group, a urea group, a sulfonyl group, a carboxyl group, and a sulfo group. You may have. As the aromatic ester compound (C1), specifically, an ester compound composed of a condensate of an alkylene oxide adduct of bisphenols and an unsaturated dibasic acid is preferably used. The unsaturated dibasic acid includes an acid anhydride lower alkyl ester, and fumaric acid, maleic acid, citraconic acid, itaconic acid and the like are preferably used. As the alkylene oxide adducts of bisphenols, ethylene oxide adducts, propylene oxide adducts, butylene oxide adducts of bisphenol are preferably used. Among the condensates, a condensate of fumaric acid or maleic acid and bisphenol A ethylene oxide or / and propylene oxide adduct is preferably used.

  The method for adding alkylene oxide to bisphenols is not limited, and known methods can be used. If necessary, a saturated dibasic acid or a small amount of a monobasic acid can be added to the unsaturated dibasic acid as long as the properties such as adhesiveness are not impaired. Further, ordinary glycols, polyether glycols and small amounts of polyhydric alcohols and monohydric alcohols can be added to the alkylene oxide adducts of bisphenols as long as the properties such as adhesiveness are not impaired. A known method can be used as the condensation method of the alkylene oxide adduct of bisphenol and the unsaturated dibasic acid.

  Further, the sizing agent according to the present invention is a tertiary amine compound and / or tertiary amine salt, cation that is a component that promotes adhesion for the purpose of enhancing the adhesion between the carbon fiber and the epoxy compound in the sizing agent component. At least one compound selected from a quaternary ammonium salt having a moiety, a quaternary phosphonium salt, and / or a phosphine compound can be blended. In the sizing agent according to the invention, the compound is preferably blended in an amount of 0.1 to 25% by mass based on the total amount of the sizing agent excluding the solvent. 2-8 mass% is more preferable.

  A tertiary amine compound and / or a tertiary amine salt, a quaternary ammonium salt having a cation site, a quaternary phosphonium salt and / or an aliphatic epoxy compound (A) and an aromatic epoxy compound (B1) as an adhesion promoting component A sizing agent using at least one compound selected from phosphine compounds is further improved in adhesion to the carbon fiber when the sizing agent is applied to the carbon fiber and heat-treated under specific conditions. Although the mechanism is not certain, first, after the compound acts on oxygen-containing functional groups such as carboxyl groups and hydroxyl groups of the carbon fiber used in the present invention, the hydrogen ions contained in these functional groups are extracted and anionized. The anionized functional group and the epoxy group contained in the aliphatic epoxy compound (A) or aromatic epoxy compound (B1) component are considered to undergo a nucleophilic reaction. Thereby, it is presumed that a strong bond between the carbon fiber used in the present invention and the epoxy group in the sizing agent is formed, and the adhesiveness is improved.

  Specific examples of the adhesion promoting component include N-benzylimidazole, 1,8-diazabicyclo [5,4,0] -7-undecene (DBU) and salts thereof, or 1,5-diazabicyclo [4, 3,0] -5-Nonene (DBN) and a salt thereof are preferable, and 1,8-diazabicyclo [5,4,0] -7-undecene (DBU) and a salt thereof, or 1,5- Diazabicyclo [4,3,0] -5-nonene (DBN) and its salts are preferred.

  Specific examples of the DBU salt include DBU phenol salt (U-CAT SA1, manufactured by San Apro), DBU octylate (U-CAT SA102, manufactured by San Apro), DBU p. -Toluenesulfonate (U-CAT SA506, manufactured by San Apro), DBU formate (U-CAT SA603, manufactured by San Apro), DBU orthophthalate (U-CAT SA810), and DBU Phenol novolac resin salts (U-CAT SA810, SA831, SA841, SA851, 881, manufactured by San Apro Co., Ltd.) and the like can be mentioned.

  In the present invention, as an adhesion promoting component to be blended with the sizing agent, tributylamine or N, N-dimethylbenzylamine, diisopropylethylamine, triisopropylamine, dibutylethanolamine, diethylethanolamine, triisopropanolamine, triethanolamine, N, N-diisopropylethylamine is preferable, and triisopropylamine, dibutylethanolamine, diethylethanolamine, triisopropanolamine, and diisopropylethylamine are particularly preferable.

  In addition to the above, examples of additives such as surfactants include polyalkylene oxides such as polyethylene oxide and polypropylene oxide, higher alcohols, polyhydric alcohols, alkylphenols, and polyalkylenes such as polyethylene oxide and polypropylene oxide in styrenated phenols. Nonionic surfactants such as compounds added with oxides and block copolymers of ethylene oxide and propylene oxide are preferably used. Moreover, you may add a polyester resin, an unsaturated polyester compound, etc. suitably in the range which does not affect the effect of this invention.

  Next, the carbon fiber used in the present invention will be described. Examples of the carbon fiber used in the present invention include polyacrylonitrile (PAN) -based, rayon-based, and pitch-based carbon fibers. Of these, PAN-based carbon fibers having an excellent balance between strength and elastic modulus are preferably used.

  In the carbon fiber according to the present invention, the strand strength of the obtained carbon fiber bundle is preferably 3.5 GPa or more, more preferably 4 GPa or more, and further preferably 5 GPa or more. Moreover, it is preferable that the strand elastic modulus of the obtained carbon fiber bundle is 220 GPa or more, More preferably, it is 240 GPa or more, More preferably, it is 280 GPa or more.

  In the present invention, the strand tensile strength and elastic modulus of the carbon fiber bundle can be determined according to the following procedure in accordance with the resin impregnated strand test method of JIS-R-7608 (2004). As a resin formulation, “Celoxide (registered trademark)” 2021P (manufactured by Daicel Chemical Industries, Ltd.) / 3 boron fluoride monoethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) / Acetone = 100/3/4 (parts by mass) As a curing condition, normal pressure, 130 ° C., and 30 minutes are used. Ten strands of the carbon fiber bundle were measured, and the average value was defined as the strand tensile strength and the strand elastic modulus.

  The carbon fiber used in the present invention preferably has a surface roughness (Ra) of 6.0 to 100 nm. More preferably, it is 15-80 nm, and 30-60 nm is suitable. Carbon fiber with a surface roughness (Ra) of 6.0 to 60 nm has a highly active edge portion on the surface, so the reactivity with the epoxy group of the sizing agent described above is improved and the interfacial adhesion is improved. This is preferable. Moreover, since the carbon fiber whose surface roughness (Ra) is 6.0-100 nm has an unevenness | corrugation on the surface, it can improve interface adhesiveness by the anchor effect of a sizing agent, and is preferable.

  In order to control the surface roughness (Ra) of the carbon fiber within the above-mentioned range, a wet spinning method is preferably used as a spinning method described later. The surface roughness (Ra) of the carbon fiber is determined depending on the type of coagulation liquid in the spinning process (for example, an aqueous solution of an organic solvent such as dimethyl sulfoxide, dimethylformamide, dimethylacetamide, an inorganic compound such as zinc chloride or sodium thiocyanate). It can also be controlled by combining the aqueous solution) and the concentration and coagulating liquid temperature, the take-up speed and drawing ratio of the coagulated yarn, and further the drawing ratios in the respective flameproofing, pre-carbonization and carbonization processes. Further, by combining the electrolytic treatment, the surface roughness (Ra) of the predetermined carbon fiber can be controlled.

The surface roughness (Ra) of the carbon fiber can be measured by using an atomic force microscope (AFM). For example, a carbon fiber cut to several millimeters in length is prepared, fixed on a substrate (silicon wafer) using a silver paste, and 3 atomic fibers at the center of each single fiber by an atomic force microscope (AFM). What is necessary is just to observe the image of a three-dimensional surface shape. As an atomic force microscope, a Dimension 3000 stage system or the like can be used in NanoScope IIIa manufactured by Digital Instruments and can be observed under the following observation conditions.
・ Scanning mode: Tapping mode ・ Probe: Silicon cantilever ・ Scanning range: 0.6μm × 0.6μm
・ Scanning speed: 0.3Hz
-Number of pixels: 512 × 512
・ Measurement environment: Room temperature, in air

  In addition, for each sample, an image obtained by observing one single fiber from one point at a time approximates the roundness of the fiber cross section with a cubic surface, and the average roughness (Ra) for the entire image obtained. It is preferable to calculate the average roughness (Ra) and evaluate the average value for five single fibers.

  In the present invention, the total fineness of the carbon fibers is preferably 400 to 3000 tex. Moreover, the number of filaments of carbon fiber is preferably 1000 to 100,000, and more preferably 3000 to 50000.

  In the present invention, the single fiber diameter of the carbon fiber is preferably 4.5 to 7.5 μm. Since it is 7.5 micrometers or less, since a carbon fiber with high intensity | strength and elastic modulus can be obtained, it is used preferably. More preferably, it is 6 μm or less, and further preferably 5.5 μm or less. When the thickness is 4.5 μm or more, it is difficult to cause single fiber cutting in the process, and productivity is hardly lowered.

  In the present invention, the carbon fiber has a surface oxygen concentration (O / C), which is a ratio of the number of atoms of oxygen (O) and carbon (C) on the fiber surface measured by X-ray photoelectron spectroscopy. The thing within the range of 05-0.50 is preferable, More preferably, it is a thing within the range of 0.06-0.30, More preferably, it is a thing within the range of 0.07-0.25. When the surface oxygen concentration (O / C) is 0.05 or more, an oxygen-containing functional group on the surface of the carbon fiber can be secured and strong adhesion with the matrix resin can be obtained. Moreover, when the surface oxygen concentration (O / C) is 0.50 or less, a decrease in strength of the carbon fiber itself due to oxidation can be suppressed.

The surface oxygen concentration of the carbon fiber is determined by X-ray photoelectron spectroscopy according to the following procedure. First, carbon fibers from which dirt and the like adhering to the carbon fiber surface were removed with a solvent were cut into 20 mm, spread and arranged on a copper sample support base, and then AlKα ₁ and ₂ were used as X-ray sources. The inside of the chamber was kept at 1 × 10 ⁻⁸ Torr, and measurement was performed at a photoelectron escape angle of 90 °. As a correction value for the peak accompanying charging during measurement, the binding energy value of the C _1s main peak (peak top) is adjusted to 284.6 eV. The C _1s peak area is obtained by drawing a straight base line in the range of 282 to 296 eV, and the O _1s peak area is obtained by drawing a straight base line in the range of 528 to 540 eV. The surface oxygen concentration (O / C) is represented by an atomic ratio calculated by dividing the ratio of the O _1s peak area by the sensitivity correction value unique to the apparatus. When ESCA-1600 manufactured by ULVAC-PHI Co., Ltd. is used as the X-ray photoelectron spectroscopy apparatus, the sensitivity correction value unique to the apparatus is 2.33.

  The carbon fiber used in the present invention has a surface carboxyl group concentration (COOH / C) represented by the ratio of the number of carbon group (COOH) and carbon (C) atoms measured by chemical modification X-ray photoelectron spectroscopy. ) Is preferably in the range of 0.003 to 0.015. A more preferable range of the carboxyl group concentration (COOH / C) on the carbon fiber surface is 0.004 to 0.010. The carbon fiber used in the present invention has a surface hydroxyl group concentration (COH / C) expressed by the ratio of the number of hydroxyl groups (OH) and carbon (C) on the surface of the carbon fiber measured by chemical modification X-ray photoelectron spectroscopy. ) Is preferably in the range of 0.001 to 0.050. The surface hydroxyl group concentration (COH / C) on the carbon fiber surface is more preferably in the range of 0.010 to 0.040.

  The surface carboxyl group concentration (COOH / C) and hydroxyl group concentration (COH / C) of the carbon fiber are determined by X-ray photoelectron spectroscopy according to the following procedure.

The surface hydroxyl group concentration (COH / C) is determined by chemical modification X-ray photoelectron spectroscopy according to the following procedure. First, carbon fiber bundles from which a sizing agent or the like has been removed with a solvent are cut, spread and arranged on a platinum sample support, and placed in a dry nitrogen gas containing 0.04 mol / L of anhydrous trifluoride acetic acid gas at room temperature. After 10 minutes of exposure and chemical modification treatment, it was mounted on an X-ray photoelectron spectrometer with a photoelectron escape angle of 35 °, AlKα ₁ and ₂ were used as the X-ray source, and the inside of the sample chamber was vacuumed at 1 × 10 ⁻⁸ Torr. Keep it up. As correction of the peak accompanying charging during measurement, first, the binding energy value of the main peak of C _1s is adjusted to 284.6 eV. The C _1s peak area [C _1s ] is obtained by drawing a straight base line in the range of 282 to 296 eV, and the F _1s peak area [F _1s ] is obtained by drawing a straight base line in the range of 682 to 695 eV. Desired. Moreover, reaction rate r is calculated | required from _C1s peak division _| segmentation of the polyvinyl alcohol chemically modified simultaneously.
The surface hydroxyl group concentration (COH / C) is represented by a value calculated by the following equation.
COH / C = {[F _1s ] / (3k [C _1s ] −2 [F _1s ]) r} × 100 (%)
Note that k is the sensitivity correction value of the F _1s peak area with respect to the C _1s peak area unique to the apparatus, and when using the model SSX-100-206 manufactured by SSI of the United States, the sensitivity correction value specific to the apparatus is 3.919. .

The surface carboxyl group concentration (COOH / C) is determined by chemical modification X-ray photoelectron spectroscopy according to the following procedure. First, carbon fiber bundles from which the sizing agent and the like have been removed with a solvent are cut and spread and arranged on a platinum sample support, and 0.02 mol / L trifluorinated ethanol gas and 0.001 mol / L dicyclohexylcarbodiimide gas. And a chemical modification treatment in an air containing 0.04 mol / L pyridine gas at 60 ° C. for 8 hours, and then mounted on an X-ray photoelectron spectrometer with a photoelectron escape angle of 35 °, and AlKα _{1, 2} is used and the inside of the sample chamber is kept at a vacuum of 1 × 10 ⁻⁸ Torr. As correction of the peak accompanying charging during measurement, first, the binding energy value of the main peak of C _1s is adjusted to 284.6 eV. The C _1s peak area [C _1s ] is obtained by drawing a straight base line in the range of 282 to 296 eV, and the F _1s peak area [F _1s ] is obtained by drawing a straight base line in the range of 682 to 695 eV. Desired. Simultaneously, the reaction rate r is determined from the C _1s peak splitting of the polyacrylic acid chemically modified, and the residual rate m of the dicyclohexylcarbodiimide derivative is determined from the O _1s peak splitting.
The surface carboxyl group concentration COOH / C was represented by the value calculated by the following formula.
COOH / C = {[F _1s ] / (3k [C _1s ] − (2 + 13 m) [F _1s ]) r} × 100 (%)
Note that k is the sensitivity correction value of the F _1s peak area with respect to the C _1s peak area unique to the apparatus, and the sensitivity correction value specific to the apparatus when using the model SSX-100-206 manufactured by SSI of the United States is 3.919. is there.

The carbon fibers used in the present invention, it is preferred polar component of the surface free energy is of 8 mJ / ^{m 2} or more 50 mJ / ^{m 2} or less. Since the polar component of the surface free energy is 8 mJ / m ² or more, the aliphatic epoxy compound (A) is closer to the carbon fiber surface, so that the adhesion is improved and the sizing layer is unevenly distributed. . When the polar component of the surface free energy is 50 mJ / m ² or less, the convergence property between the carbon fibers is increased, so that the impregnation property with the matrix resin is improved. When used as a carbon fiber reinforced composite material Applications are widespread and preferable.

Polar component of the surface free energy of the carbon fiber surface is more preferably 15 mJ / ^{m 2} or more 45 mJ / ^{m 2} or less, and most preferably 25 mJ / ^{m 2} or more 40 mJ / ^{m 2} or less. The polar component of the surface free energy of the carbon fiber was calculated using an Owens approximation formula based on the contact angles measured by the Wilhelmi method in each liquid of water, ethylene glycol, and tricresole phosphate. Polar component of surface free energy.

The aliphatic epoxy compound (A) used in the present invention only needs to have a surface free energy polar component of 9 mJ / m ² or more and 50 mJ / m ² or less. Further, the aromatic epoxy compound (B1) is a polar component of surface free energy 0 mJ / ^{m 2} or more, as long as it is less than 9 mJ / ^{m 2.}

  The polar component of the surface free energy of the aliphatic epoxy compound (A) and the aromatic epoxy compound (B1) is obtained by immersing the carbon fiber bundle in a solution composed only of the aliphatic epoxy compound (A) or the aromatic epoxy compound (B1). After being pulled up and then dried at 120 to 150 ° C. for 10 minutes, as described above, in each liquid of water, ethylene glycol, and tricresol phosphate, an approximation of the Owens based on each contact angle measured by the Wilhelmi method It is the polar component of the surface free energy calculated using the equation.

In the present invention, the polar component E _CF of the surface free energy of the carbon fiber and the polar components E _A and E _B1 of the surface free energy of the aliphatic epoxy compound (A) and the aromatic epoxy compound (B1) are E _CF ≧ E _A > It is preferable to satisfy E _B1 .

Next, a method for producing a PAN-based carbon fiber will be described.
As a spinning method for obtaining a carbon fiber precursor fiber, spinning methods such as wet, dry, and dry-wet can be used. From the viewpoint of easily obtaining high-strength carbon fibers, it is preferable to use a wet or dry wet spinning method.

  In order to further improve the adhesion between the carbon fiber and the matrix resin, a carbon fiber having a surface roughness (Ra) of 6.0 to 100 nm is preferable. In order to obtain a carbon fiber having the surface roughness, a wet spinning method is used. Preferably, the precursor fiber is spun by.

  As the spinning dope, a solution obtained by dissolving a homopolymer or copolymer of polyacrylonitrile in a solvent can be used. As the solvent, an organic solvent such as dimethyl sulfoxide, dimethylformamide, or dimethylacetamide, or an aqueous solution of an inorganic compound such as nitric acid, sodium rhodanate, zinc chloride, or sodium thiocyanate is used. Dimethyl sulfoxide and dimethylacetamide are suitable as the solvent.

  The above spinning solution is spun through a die, discharged in a spinning bath or in the air, and then coagulated in the spinning bath. As the spinning bath, an aqueous solution of a solvent used as a solvent for the spinning dope can be used. It is preferable to use a spinning solution containing the same solvent as the spinning solution, and a dimethyl sulfoxide aqueous solution and a dimethylacetamide aqueous solution are preferable. The fiber solidified in the spinning bath is washed with water and drawn to obtain a precursor fiber. The obtained precursor fiber is subjected to flameproofing treatment and carbonization treatment, and if necessary, further subjected to graphitization treatment to obtain carbon fiber. As conditions for carbonization treatment and graphitization treatment, the maximum heat treatment temperature is preferably 1100 ° C. or higher, more preferably 1400 to 3000 ° C.

The obtained carbon fiber is usually subjected to an oxidation treatment in order to improve the adhesiveness with the matrix resin, whereby oxygen-containing functional groups are introduced. As the oxidation treatment method, vapor phase oxidation, liquid phase oxidation, and liquid phase electrolytic oxidation are used. From the viewpoint of high productivity and uniform treatment, liquid phase electrolytic oxidation is preferably used.
In the present invention, the electrolytic solution used in the liquid phase electrolytic oxidation includes an acidic electrolytic solution and an alkaline electrolytic solution. From the viewpoint of adhesion between the carbon fiber and the matrix resin, the electrolytic solution was subjected to liquid phase electrolytic oxidation in the alkaline electrolytic solution. It is more preferable to apply a sizing agent later.

  Examples of the acidic electrolyte include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, boric acid, and carbonic acid, organic acids such as acetic acid, butyric acid, oxalic acid, acrylic acid, and maleic acid, or ammonium sulfate and ammonium hydrogen sulfate. And the like. Of these, sulfuric acid and nitric acid exhibiting strong acidity are preferably used.

  Specific examples of the alkaline electrolyte include aqueous solutions of hydroxides such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide and barium hydroxide, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, Aqueous solutions of carbonates such as barium carbonate and ammonium carbonate, aqueous solutions of bicarbonates such as sodium bicarbonate, potassium bicarbonate, magnesium bicarbonate, calcium bicarbonate, barium bicarbonate and ammonium bicarbonate, ammonia, tetraalkylammonium hydroxide And an aqueous solution of hydrazine. Among these, from the viewpoint of not containing an alkali metal that causes curing inhibition of the matrix resin, an aqueous solution of ammonium carbonate and ammonium hydrogen carbonate or an aqueous solution of tetraalkylammonium hydroxide exhibiting strong alkalinity is preferably used.

  The concentration of the electrolytic solution used in the present invention is preferably in the range of 0.01 to 5 mol / L, more preferably in the range of 0.1 to 1 mol / L. When the concentration of the electrolytic solution is 0.01 mol / L or more, the electrolytic treatment voltage is lowered, which is advantageous in terms of operating cost. On the other hand, when the concentration of the electrolytic solution is 5 mol / L or less, it is advantageous from the viewpoint of safety.

The temperature of the electrolytic solution used in the present invention is preferably in the range of 10 to 100 ° C, more preferably in the range of 10 to 40 ° C. When the temperature of the electrolytic solution is 10 ° C. or higher, the efficiency of the electrolytic treatment is improved, which is advantageous in terms of operating cost. On the other hand, when the temperature of the electrolytic solution is less than 100 ° C., it is advantageous from the viewpoint of safety.
In the present invention, the amount of electricity in the liquid phase electrolytic oxidation is preferably optimized in accordance with the carbonization degree of the carbon fiber, and a larger amount of electricity is required when processing the carbon fiber having a high elastic modulus.

In the present invention, the current density in the liquid phase electrolytic oxidation is preferably in the range of 1.5 to 1000 amperes / m ² per 1 m ² of the surface area of the carbon fiber in the electrolytic treatment solution, more preferably 3 to 500 amperes. / M ² within the range. When the current density is 1.5 amperes / m ² or more, the efficiency of the electrolytic treatment is improved, which is advantageous in terms of operating cost. On the other hand, when the current density is 1000 amperes / m ² or less, it is advantageous from the viewpoint of safety.

  In the present invention, it is preferable to wash and dry the carbon fiber after the electrolytic treatment. As a cleaning method, for example, a dip method or a spray method can be used. Especially, it is preferable to use a dip method from a viewpoint that washing | cleaning is easy, Furthermore, it is a preferable aspect to use a dip method, vibrating a carbon fiber with an ultrasonic wave. In addition, if the drying temperature is too high, functional groups present on the outermost surface of the carbon fiber are likely to disappear due to thermal decomposition, so it is desirable to dry at the lowest possible temperature. Specifically, the drying temperature is preferably 260 ° C. or lower. More preferably, drying is performed at 250 ° C. or lower, more preferably 240 ° C. or lower.

  Next, the sizing agent-coated carbon fiber obtained by applying the sizing agent to the above-described carbon fiber will be described. The sizing agent according to the present invention includes at least an aromatic epoxy compound (B1) that is an aliphatic epoxy compound (A) and an aromatic compound (B), and may include other components.

  In the present invention, as a method of applying the sizing agent to the carbon fiber, the aromatic compound (B) containing at least the aliphatic epoxy compound (A) and the aromatic epoxy compound (B1) in the solvent, and other components are simultaneously used. Using a sizing solution that has been dissolved or dispersed, a sizing solution in which the compound (A), (B1), (B) and other components are arbitrarily selected and dissolved or dispersed individually in a solvent. A method of applying to carbon fiber in a plurality of times is preferably used. In the present invention, it is more preferable to adopt a one-step application in which a sizing liquid containing all components of the sizing agent is applied to carbon fibers at a time from the viewpoint of the effect and ease of processing.

  The sizing agent according to the present invention can be used as a sizing solution obtained by diluting a sizing agent component with a solvent. Examples of such a solvent include water, methanol, ethanol, isopropanol, acetone, methyl ethyl ketone, dimethylformamide, and dimethylacetamide. Among them, handling is easy and advantageous from the viewpoint of safety. Therefore, an aqueous dispersion or aqueous solution emulsified with a surfactant is preferably used.

  The sizing liquid is preferably prepared by mixing a solution containing at least the aliphatic epoxy compound (A) by preparing a water emulsion liquid by emulsifying a component containing at least the aromatic compound (B) with a surfactant. . At this time, when the aliphatic epoxy compound (A) is water-soluble, a method of dissolving in water in advance to form an aqueous solution and mixing with an aqueous emulsion liquid containing at least the aromatic compound (B) is an emulsion stability. From this point, it is preferably used. In addition, it is preferable to use a water dispersant obtained by emulsifying the aliphatic epoxy compound (A), the aromatic compound (B) and other components with a surfactant from the viewpoint of long-term storage stability of the sizing agent. .

  The concentration of the sizing agent in the sizing liquid is usually preferably in the range of 0.2% by mass to 20% by mass.

  Examples of the means for applying (coating) the sizing agent to the carbon fiber include a method of immersing the carbon fiber in a sizing liquid through a roller, a method of contacting the carbon fiber with a roller to which the sizing liquid is attached, and a sizing liquid being atomized. There is a method of spraying on carbon fiber. Further, the sizing agent applying means may be either a batch type or a continuous type, but a continuous type capable of improving productivity and reducing variation is preferably used. At this time, it is preferable to control the sizing solution concentration, temperature, yarn tension, and the like so that the amount of the sizing agent active ingredient attached to the carbon fiber is uniformly attached within an appropriate range. Moreover, it is also a preferable aspect that the carbon fiber is vibrated with ultrasonic waves when the sizing agent is applied.

  The liquid temperature of the sizing liquid when applying the sizing liquid to the carbon fibers is preferably in the range of 10 to 50 ° C. in order to suppress the concentration fluctuation of the sizing agent due to solvent evaporation. Further, by adjusting the amount of squeezing out the excess sizing liquid after the sizing liquid is applied, the amount of sizing agent attached can be adjusted and uniformly applied to the carbon fibers.

  After applying the sizing agent to the carbon fiber, it is preferable to heat-treat in the temperature range of 160 to 260 ° C. for 30 to 600 seconds. The heat treatment conditions are preferably in a temperature range of 170 to 250 ° C. for 30 to 500 seconds, and more preferably in a temperature range of 180 to 240 ° C. for 30 to 300 seconds. When the heat treatment condition is less than 160 ° C. and / or less than 30 seconds, the interaction between the aliphatic epoxy compound (A) of the sizing agent and the oxygen-containing functional group on the carbon fiber surface is not promoted, and the carbon fiber In some cases, the adhesiveness with the matrix resin becomes insufficient, or the solvent cannot be sufficiently removed by drying. On the other hand, when the heat treatment condition exceeds 260 ° C. and / or exceeds 600 seconds, decomposition and volatilization of the sizing agent occurs, the interaction with the carbon fiber is not promoted, and the adhesion between the carbon fiber and the matrix resin is increased. It may be insufficient.

  The heat treatment can also be performed by microwave irradiation and / or infrared irradiation. When the sizing agent-coated carbon fiber is heat-treated by microwave irradiation and / or infrared irradiation, the microwave penetrates into the carbon fiber and is absorbed, so that the carbon fiber which is the object to be heated can be heated to a desired temperature in a short time. Can be heated. In addition, since the inside of the carbon fiber can be quickly heated by microwave irradiation and / or infrared irradiation, the temperature difference between the inside and outside of the carbon fiber bundle can be reduced, and the adhesion unevenness of the sizing agent can be reduced. It becomes possible to do.

The carbon fiber coated with the sizing agent according to the present invention produced as described above is obtained by using AlKα ₁ and ₂ with the sizing agent surface of the carbon fiber coated with the sizing agent as an X-ray source, and an X-ray with an electron escape angle of 15 °. The height (cps) of the component of the binding energy (284.6 eV) attributed to (a) CHx, C-C, C = C in the C _1s core spectrum measured by photoelectron spectroscopy, and (b) C- The ratio (a) / (b) of the height (cps) of the component of the binding energy (286.1 eV) attributed to O is 0.50 to 0.90. The sizing agent-coated carbon fiber according to the present invention has excellent adhesion to the matrix resin when (a) / (b) is in a specific range, that is, 0.50 to 0.90, and is a prepreg. It was made by finding that there was little decrease in mechanical properties even when stored for a long time in this state.

The sizing agent-coated carbon fiber according to the present invention belongs to (a) CHx, C-C, C = C of the C _1s inner shell spectrum measured on the sizing agent surface by X-ray photoelectron spectroscopy at a photoelectron escape angle of 15 °. The ratio (a) / () of the height (cps) of the component of the binding energy (284.6 eV) to be produced and (b) the height (cps) of the component of the binding energy (286.1 eV) attributed to C—O b) is preferably 0.55 or more, more preferably 0.57 or more. Moreover, ratio (a) / (b) becomes like this. Preferably it is 0.80 or less, More preferably, it is 0.74 or less. A large (a) / (b) indicates that there are many aromatic compounds on the surface and few aliphatic compounds.

  X-ray photoelectron spectroscopy measurement method is an analysis method that irradiates a sample carbon fiber with X-rays in an ultra-high vacuum and measures the kinetic energy of photoelectrons emitted from the surface of the carbon fiber with an apparatus called an energy analyzer. That's it. By examining the kinetic energy of the photoelectrons emitted from the carbon fiber surface of the sample, the binding energy converted from the energy value of the X-rays incident on the carbon fiber of the sample is uniquely determined. From the binding energy and the photoelectron intensity The type and concentration of elements present on the outermost surface (˜nm) of the sample and the chemical state thereof can be analyzed.

In the present invention, the peak ratio of (a) and (b) on the surface of the sizing agent-coated carbon fiber is determined by X-ray photoelectron spectroscopy according to the following procedure. Cut the sizing agent-coated carbon fiber to 20 mm, spread and arrange it on a copper sample support, and then use AlKα _1,2 as the X-ray source and keep the sample chamber at 1 × 10 ⁻⁸ Torr for measurement. Is called. As correction of the peak accompanying charging during measurement, first, the binding energy value of the main peak of C _1s is adjusted to 286.1 eV. At this time, the peak area of C _1s is obtained by drawing a straight baseline in the range of 282 to 296 eV. Further, a linear base line of 282 to 296 eV obtained by calculating the area at the C _1s peak is defined as the origin (zero point) of the photoelectron intensity, and (b) the peak of the binding energy 286.1 eV attributed to the CO component is obtained. The height (cps: photoelectron intensity per unit time) and (a) the peak height (cps) of the binding energy 284.6 eV attributed to CHx, C—C, C = C are obtained, and (a) / ( b) is calculated.

The sizing agent-coated carbon fiber used in the present invention has a C _1s inner-shell spectrum (measured at a photoelectron escape angle of 55 ° by X-ray photoelectron spectroscopy using 400 eV X-rays on the surface of the sizing agent coated on the carbon fiber. a) the height (cps) of the component of the bond energy (284.6 eV) attributed to CHx, C—C, C═C, and (b) the bond energy (286.1 eV) attributed to C—O. It is preferable that the values of (I) and (II) obtained from the ratio (a) / (b) to the component height (cps) satisfy the relationship (III).
(I) The value of (a) / (b) on the surface of the sizing agent-coated carbon fiber before sonication (II) The sizing agent-coated carbon fiber is sonicated in an acetone solvent to reduce the sizing agent adhesion amount. The value of (a) / (b) (III) 0.50 ≦ (I) ≦ 0.90 and 0.60 <(II) on the surface of the sizing agent-coated carbon fiber washed to 0.09 to 0.20% by mass. ) / (I) <1.0

  The fact that (I), which is the (a) / (b) value on the surface of the sizing agent-coated carbon fiber before ultrasonic treatment, falls within the above range means that there are many aromatic-derived compounds on the surface of the sizing agent. It shows that there are few compounds. The (a) / (b) value (I) before sonication is preferably 0.55 or more, more preferably 0.57 or more. Moreover, (I) which is (a) / (b) value before ultrasonic treatment is preferably 0.80 or less, more preferably 0.74 or less.

The fact that (II) / (I), which is the ratio of (a) / (b) values on the sizing agent-coated carbon fiber surface before and after the ultrasonic treatment, falls within the above range, indicates that the inner layer of the sizing agent compared to the sizing agent surface. Indicates that the ratio of the aliphatic compound is large. (II) / (I) is preferably 0.65 or more. Further, (II) / (I) is preferably 0.85 or less.
It is preferable that the values of (I) and (II) satisfy the relationship of (III) because the adhesive property with the matrix resin is excellent and the mechanical properties are not deteriorated even when stored for a long time in a prepreg state.

  In the present invention, the epoxy equivalent of the sizing agent applied to the carbon fiber is 350 to 550 g / eq. It is preferable that Epoxy equivalent is 550 g / eq. By being below, the adhesiveness of the carbon fiber and matrix resin which apply | coated the sizing agent improves. In addition, the epoxy equivalent applied to the carbon fiber is 350 g / eq. As described above, when the sizing agent-coated carbon fiber is used for the prepreg, the reaction between the matrix resin component used in the prepreg and the sizing agent can be suppressed, so even when the prepreg is stored for a long time. The obtained carbon fiber reinforced composite material is preferable because the mechanical properties are improved. The epoxy equivalent of the applied sizing agent was 360 g / eq. The above is preferable, and 380 g / eq. The above is more preferable. Moreover, the epoxy equivalent of the applied sizing agent was 530 g / eq. The following is preferable, and 500 g / eq. The following is more preferable. In order to set the epoxy equivalent of the applied sizing agent in the above range, an epoxy equivalent of 180 to 470 g / eq. It is preferable to apply the sizing agent. 313 g / eq. By being below, the adhesiveness of the carbon fiber and matrix resin which apply | coated the sizing agent improves. In addition, 222 g / eq. As described above, when the sizing agent-coated carbon fiber is used for the prepreg, the reaction between the resin component used in the prepreg and the sizing agent can be suppressed. The resulting carbon fiber reinforced composite material has good mechanical properties.

  The epoxy equivalent of the sizing agent in the present invention can be determined by acid-base titration by dissolving the sizing agent from which the solvent has been removed in a solvent typified by N, N-dimethylformamide, opening the epoxy group with hydrochloric acid. . Epoxy equivalent is 220 g / eq. Or more, preferably 240 g / eq. The above is more preferable. In addition, 310 g / eq. The following is preferable, and 280 g / eq. The following is more preferable. The epoxy equivalent of the sizing agent applied to the carbon fiber in the present invention is eluted from the fiber by immersing the sizing agent-coated carbon fiber in a solvent typified by N, N-dimethylformamide and performing ultrasonic cleaning. Then, the epoxy group can be opened with hydrochloric acid, and acid-base titration can be used. In addition, the epoxy equivalent of the sizing agent applied to the carbon fiber can be controlled by the epoxy equivalent of the sizing agent used for application and the heat history in drying after application.

  In this invention, it is preferable that the adhesion amount to the carbon fiber of a sizing agent is the range of 0.1-10.0 mass part with respect to 100 mass parts of carbon fibers, More preferably, 0.2-3. The range is 0 part by mass. When the sizing agent adhesion amount is 0.1 parts by mass or more, when prepreg and weaving the sizing agent-coated carbon fiber, it can withstand friction caused by a metal guide that passes therethrough, and generation of fluff is suppressed. Excellent quality such as smoothness of fiber sheet. On the other hand, when the adhesion amount of the sizing agent is 10.0 parts by mass or less, the carbon fiber reinforcement is obtained by impregnating the matrix resin inside the carbon fiber without being inhibited by the sizing agent film around the sizing agent-coated carbon fiber. In the composite material, void formation is suppressed, the quality of the carbon fiber reinforced composite material is excellent, and at the same time, the mechanical properties are excellent.

  The amount of sizing agent attached was measured by measuring the change in mass before and after the heat treatment when about 2 ± 0.5 g of sizing agent-coated carbon fiber was sampled and heat-treated at 450 ° C. for 15 minutes in a nitrogen atmosphere. The mass change is divided by the mass before heat treatment (mass%).

  In the present invention, the thickness of the sizing agent layer applied to the carbon fiber and dried is preferably within a range of 2.0 to 20 nm, and the maximum value of the thickness does not exceed twice the minimum value. With such a uniform sizing agent layer, a large effect of improving adhesiveness can be obtained stably, and further, stable high-order workability can be obtained.

  In this invention, it is preferable that the adhesion amount of an aliphatic epoxy compound (A) is the range of 0.05-5.0 mass parts with respect to 100 mass parts of carbon fibers, More preferably, it is 0.2-2. The range is 0.0 parts by mass. More preferably, it is 0.3-1.0 mass part. It is preferable that the adhesion amount of the aliphatic epoxy compound (A) is 0.05 parts by mass or more because the adhesion between the sizing agent-coated carbon fiber and the matrix resin is improved by the aliphatic epoxy compound (A) on the carbon fiber surface.

In the manufacturing method of sizing agent coated carbon fiber of the present invention, it is preferred that the polar component of the surface free energy is applied sizing agent to 8 mJ / m ² or more 50 mJ / m ² or less of carbon fiber. Since the polar component of the surface free energy is 8 mJ / m ² or more, the aliphatic epoxy compound (A) is closer to the carbon fiber surface, so that the adhesion is improved and the sizing layer is unevenly distributed. At 50 mJ / m ² or less, the convergence between the carbon fibers is increased, and the impregnation with the matrix resin is improved. Polar component of the surface free energy of the carbon fiber surface is more preferably 15 mJ / ^{m 2} or more 45 mJ / ^{m 2} or less, and most preferably 25 mJ / ^{m 2} or more 40 mJ / ^{m 2} or less.

  The sizing agent-coated carbon fiber of the present invention is used in the form of, for example, tow, woven fabric, knitted fabric, braided string, web, mat, and chopped. In particular, for applications that require high specific strength and high specific modulus, a tow in which carbon fibers are aligned in one direction is most suitable, and a prepreg impregnated with a matrix resin is preferably used.

Next, details of the prepreg and the carbon fiber reinforced composite material in the present invention will be described.
In the present invention, the prepreg includes the above-described sizing agent-coated carbon fibers and a thermosetting resin as a matrix resin.

  The thermosetting resin used in the present invention is an epoxy resin composition containing at least the following components, (D), (E) and (F). The epoxy resin (D) has two or more ring structures having four or more members, and one or two amine-type glycidyl groups or ether-type glycidyl groups directly connected to the ring structure. The epoxy resin (E) is an epoxy resin having three or more functional groups, and (F) is a latent curing agent. The epoxy resin composition according to the present invention is characterized by containing 5 to 60% by mass of the epoxy resin (D) and 40 to 80% by mass of the epoxy resin (E) with respect to 100% by mass of the total amount of the epoxy resin blended. To do.

  In the present invention, the epoxy resin (D) contained in the epoxy resin composition has two or more ring structures having 4 or more member rings, such as cyclohexane, benzene, pyridine, etc. Or at least one condensed ring structure composed of four or more ring members such as phthalimide, naphthalene, and carbazole.

  The amine-type glycidyl group or ether-type glycidyl group directly linked to the ring structure of the epoxy resin (D) has a structure in which an N atom is bonded to a ring structure such as benzene or phthalimide, and an O atom is bonded to an ether type. In the case of amine type, it has one or two epoxy groups, and in the case of ether type, it has one epoxy group (hereinafter, epoxy resin (D) having one epoxy group is referred to as (D1), The epoxy resin (D) having two epoxy groups is sometimes referred to as (D2) .In the present invention, (D2) is used as the epoxy resin (D) as described later). If the amount of the epoxy resin (D) is small in the matrix resin, there is almost no effect of improving the mechanical properties of the carbon fiber reinforced composite material. If the amount is too large, the heat resistance is significantly impaired. Therefore, the compounding quantity of an epoxy resin (D) needs to be 5-60 mass% with respect to the compounded epoxy resin total amount. Moreover, in the epoxy resin (D), the epoxy resin (D1) having one epoxy group is more excellent in the effect of expressing the mechanical properties, and the epoxy resin (D2) having one epoxy group is more excellent in heat resistance. Therefore, when the epoxy resin (D1) is used, the amount of the epoxy resin (D) is preferably 10 to 40% by mass, more preferably 15 to 30 parts by mass with respect to the total amount of the epoxy resin compounded. . And when an epoxy resin (D2) is used, 25-60 mass% is preferable with respect to the compounded epoxy resin total amount, More preferably, it is 30-50 mass parts.

  Examples of the epoxy resin (D1) include glycidylphthalimide, glycidyl-1,8-naphthalimide, glycidylcarbazole, glycidyl-3,6-dibromocarbazole, glycidylindole, glycidyl-4-acetoxyindole, and glycidyl-3-methyl. Indole, glycidyl-3-acetylindole, glycidyl-5-methoxy-2-methylindole, o-phenylphenylglycidyl ether, p-phenylphenylglycidyl ether, p- (3-methylphenyl) phenylglycidyl ether, 2,6- Dibenzylphenyl glycidyl ether, 2-benzylphenyl glycidyl ether, 2,6-diphenylphenyl glycidyl ether, 4-α-cumylphenyl glycidyl ether, o-phenoxy Phenyl glycidyl ether, p- phenoxyphenyl glycidyl ether.

（式（１）中、Ｒ^１とＲ^２は、それぞれ炭素数１〜４の脂肪族炭化水素基、炭素数３〜６の脂環式炭化水素基、炭素数６〜１０の芳香族炭化水素基、ハロゲン原子、アシル基、トリフルオロメチル基およびニトロ基からなる群から選ばれた少なくとも一つを表す。ｎは０〜４の整数、ｍは０〜５の整数である。Ｒ^１とＲ^２が複数存在する場合、それぞれ同じであっても異なっていてもよい。Ｘは、−Ｏ−、−Ｓ−、−ＣＯ−、−Ｃ（＝Ｏ）Ｏ−、−ＳＯ_２−、−Ｃ（＝Ｏ）ＮＨ−から選ばれる１つを表す。）で示される構造を有し、エポキシ樹脂組成物は、配合したエポキシ樹脂総量１００質量％に対して、エポキシ樹脂（Ｄ２）を２５〜５０質量％含むことが好ましい。 The epoxy resin (D2) having two epoxy groups is represented by the following general formula (1)

(In formula (1), R ¹ and R ² are each an aliphatic hydrocarbon group having 1 to 4 carbon atoms, an alicyclic hydrocarbon group having 3 to 6 carbon atoms, and an aromatic hydrocarbon having 6 to 10 carbon atoms. Represents at least one selected from the group consisting of a group, a halogen atom, an acyl group, a trifluoromethyl group, and a nitro group, n is an integer of 0 to 4, and m is an integer of 0 to 5. R ¹ and R ^{When two} or more are present, they may be the same or different, and X is —O—, —S—, —CO—, —C (═O) O—, —SO ₂ —, —C. (= O) represents one selected from NH-), and the epoxy resin composition has an epoxy resin (D2) of 25 to 50 with respect to 100% by mass of the total amount of the epoxy resin blended. It is preferable to contain the mass%.

Examples of the epoxy resin (D2) used in the present invention include N, N-diglycidyl-4-phenoxyaniline, N, N-diglycidyl-4- (4-methylphenoxy) aniline, N, N-diglycidyl-4- (4 -Tert-butylphenoxy) aniline and N, N-diglycidyl-4- (4-phenoxyphenoxy) aniline. In many cases, these resins are obtained by adding epichlorohydrin to a phenoxyaniline derivative and cyclizing with an alkali compound. Since the viscosity increases as the molecular weight increases, N, N-diglycidyl-4-phenoxyaniline, in which both R ¹ and R ² of the epoxy resin (D2) are hydrogen, is particularly preferably used from the viewpoint of handleability. .

  Specific examples of the phenoxyaniline derivative include 4-phenoxyaniline, 4- (4-methylphenoxy) aniline, 4- (3-methylphenoxy) aniline, 4- (2-methylphenoxy) aniline, 4- (4 -Ethylphenoxy) aniline, 4- (3-ethylphenoxy) aniline, 4- (2-ethylphenoxy) aniline, 4- (4-propylphenoxy) aniline, 4- (4-tert-butylphenoxy) aniline, 4- (4-cyclohexylphenoxy) aniline, 4- (3-cyclohexylphenoxy) aniline, 4- (2-cyclohexylphenoxy) aniline, 4- (4-methoxyphenoxy) aniline, 4- (3-methoxyphenoxy) aniline, 4- (2-methoxyphenoxy) aniline, 4- (3-phenoxyf) Noxy) aniline, 4- (4-phenoxyphenoxy) aniline, 4- [4- (trifluoromethyl) phenoxy] aniline, 4- [3- (trifluoromethyl) phenoxy] aniline, 4- [2- (trifluoro) Methyl) phenoxy] aniline, 4- (2-naphthyloxyphenoxy) aniline, 4- (1-naphthyloxyphenoxy) aniline, 4-[(1,1′-biphenyl-4-yl) oxy] aniline, 4- ( 4-nitrophenoxy) aniline, 4- (3-nitrophenoxy) aniline, 4- (2-nitrophenoxy) aniline, 3-nitro-4-aminophenyl phenyl ether, 2-nitro-4- (4-nitrophenoxy) Aniline, 4- (2,4-dinitrophenoxy) aniline, 3-nitro-4-phenoxyaniline, -(2-chlorophenoxy) aniline, 4- (3-chlorophenoxy) aniline, 4- (4-chlorophenoxy) aniline, 4- (2,4-dichlorophenoxy) aniline, 3-chloro-4- (4- Chlorophenoxy) aniline, 4- (4-chloro-3-tolyloxy) aniline, and the like.

  Next, the production method of the epoxy resin (D2) used in the present invention will be illustrated and described.

The epoxy resin (D2) used in the present invention has the following general formula (3)

(In formula (3), R ¹ and R ² are each an aliphatic hydrocarbon group having 1 to 4 carbon atoms, an alicyclic hydrocarbon group having 3 to 6 carbon atoms, and an aromatic hydrocarbon having 6 to 10 carbon atoms. Represents at least one selected from the group consisting of a group, a halogen atom, an acyl group, a trifluoromethyl group, and a nitro group, n is an integer of 0 to 4, and m is an integer of 0 to 5. R ¹ and R ^{When two} or more are present, they may be the same or different, and X is —O—, —S—, —CO—, —C (═O) O—, —SO ₂ —, —C. It can be produced by reacting a phenoxyaniline derivative represented by (═O) representing one selected from NH— and epichlorohydrin.

  That is, as with a general method for producing an epoxy resin, the method for producing an epoxy resin (D2) is obtained by adding two molecules of epichlorohydrin to one molecule of a phenoxyaniline derivative, and the following general formula (4)

(In formula (4), R ¹ and R ² are each an aliphatic hydrocarbon group having 1 to 4 carbon atoms, an alicyclic hydrocarbon group having 3 to 6 carbon atoms, and an aromatic hydrocarbon having 6 to 10 carbon atoms. Represents at least one selected from the group consisting of a group, a halogen atom, an acyl group, a trifluoromethyl group, and a nitro group, n is an integer of 0 to 4, and m is an integer of 0 to 5. R ¹ and R ^{When two} or more are present, they may be the same or different, and X is —O—, —S—, —CO—, —C (═O) O—, —SO ₂ —, —C. (= O) represents one selected from NH-), followed by an addition step in which a dichlorohydrin product is generated, followed by dehydrochlorination of the dichlorohydrin compound with an alkali compound, and the following general formula having two epoxy groups Formula (1)

(In formula (1), R ¹ and R ² are each an aliphatic hydrocarbon group having 1 to 4 carbon atoms, an alicyclic hydrocarbon group having 3 to 6 carbon atoms, and an aromatic hydrocarbon having 6 to 10 carbon atoms. Represents at least one selected from the group consisting of a group, a halogen atom, an acyl group, a trifluoromethyl group, and a nitro group, n is an integer of 0 to 4, and m is an integer of 0 to 5. R ¹ and R ^{When two} or more are present, they may be the same or different, and X is —O—, —S—, —CO—, —C (═O) O—, —SO ₂ —, —C. (= O) represents a cyclization step for producing an epoxy compound represented by NH-).

  As commercially available products of the epoxy resin (D1), “Denacol (registered trademark)” Ex-731 (glycidylphthalimide, manufactured by Nagase ChemteX Corporation), OPP-G (o-phenylphenylglycidyl ether, manufactured by Sanko Co., Ltd.) ) And PxGAN (diglycidyl-p-phenoxyaniline, manufactured by Toray Fine Chemical Co., Ltd.) and the like are listed as commercial products of the epoxy resin (D2).

  The epoxy resin (E) having three or more functional groups used in the present invention is a compound having three or more epoxy groups in one molecule, or at least one functional group other than an epoxy group and an epoxy group. Is a compound having 3 or more in total. The epoxy resin (E) having 3 or more functional groups is preferably a compound having 3 or more epoxy groups in one molecule. Examples of the epoxy resin (E) having three or more functional groups include glycidylamine type epoxy resins and glycidyl ether type epoxy resins.

  In the epoxy resin (E) having three or more functional groups, the number of functional groups is preferably 3 to 7, and more preferably 3 to 4. If the number of functional groups is too large, the cured matrix resin may become brittle and impair impact resistance.

（式（２）中、Ｒ^３〜Ｒ^６は、水素原子、炭素数１〜４の脂肪族炭化水素基、炭素数４以下の脂環式炭化水素基、ハロゲン原子からなる群から選ばれた少なくとも一つを表す。Ｙは、−ＣＨ_２−、−Ｏ−、−Ｓ−、−ＣＯ−、−Ｃ（＝Ｏ）Ｏ−、−ＳＯ_２−、−Ｃ（＝Ｏ）ＮＨ−から選ばれる１つを表す。）で示される構造を有するものであることが好ましい。 Epoxy resin (E) used in the present invention, the following general formula (2)

(In the formula (2), R ^{3 to} R ⁶ were selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group having 1 to 4 carbon atoms, an alicyclic hydrocarbon group having 4 or less carbon atoms, and a halogen atom. Y represents at least one, Y is selected from —CH ₂ —, —O—, —S—, —CO—, —C (═O) O—, —SO ₂ —, —C (═O) NH—. It is preferable that it has the structure shown by this.

In the formula (2), if the structure of R ³ , R ⁴ , R ⁵ , R ⁶ is too large, the viscosity of the epoxy resin composition becomes too high and the handleability is impaired, or other components in the epoxy resin composition R ³ , R ⁴ , R ⁵ , and R ⁶ are each a hydrogen atom, an aliphatic hydrocarbon group having 1 to 4 carbon atoms, or a carbon number. It is preferably at least one selected from the group consisting of 4 or less alicyclic hydrocarbon groups and halogen atoms.

  Examples of the epoxy resin (E) include tetraglycidyl-3,4′-diaminodiphenyl ether, tetraglycidyl-3,3′-diaminodiphenyl ether, tetraglycidyl-3,4′-diamino-2,2′-dimethyldiphenyl ether, Tetraglycidyl-3,4'-diamino-2,2'-dibromodiphenyl ether, tetraglycidyl-3,4'-diamino-5-methyldiphenyl ether, tetraglycidyl-3,4'-diamino-2'-methyldiphenyl ether, tetra Glycidyl-3,4′-diamino-3′-methyldiphenyl ether, tetraglycidyl-3,4′-diamino-5,2′-dimethyldiphenyl ether, tetraglycidyl-3,4′-diamino-5,3′-dimethyldiphenyl ether Tetra Lysidyl-3,3′-diamino-5-methyldiphenyl ether, tetraglycidyl-3,3′-diamino-5,5′-dimethyldiphenyl ether, tetraglycidyl-3,3′-diamino-5,5′-dibromodiphenyl ether, Tetraglycidyl-4,4′-diaminodiphenyl ether, tetraglycidyl-4,4′-diamino-2,2′-dimethyldiphenyl ether, tetraglycidyl-4,4′-diamino-2,2′-dibromodiphenyl ether, tetraglycidyl- 4,4′-diamino-5-methyldiphenyl ether, tetraglycidyl-4,4′-diamino-2′-methyldiphenyl ether, tetraglycidyl-4,4′-diamino-3′-methyldiphenyl ether, tetraglycidyl-4,4 '-Diamino 5,2′-dimethyldiphenyl ether, tetraglycidyl-4,4′-diamino-5,3′-dimethyldiphenyl ether, tetraglycidyl-4,4′-diamino-5,5′-dimethyldiphenyl ether, tetraglycidyl-4,4 '-Diamino-5,5'-dibromodiphenyl ether, tetraglycidyl-3,4'-diaminodiphenylmethane, tetraglycidyl-3,3'-diaminodiphenylmethane, tetraglycidyl-3,4'-diamino-2,2'-dimethyl Diphenylmethane, tetraglycidyl-3,4'-diamino-2,2'-dibromodiphenylmethane, tetraglycidyl-3,4'-diamino-5-methyldiphenylmethane, tetraglycidyl-3,4'-diamino-2'-methyldiphenylmethane Tetragri Sidyl-3,4′-diamino-3′-methyldiphenylmethane, tetraglycidyl-3,4′-diamino-5,2′-dimethyldiphenylmethane, tetraglycidyl-3,4′-diamino-5,3′-dimethyldiphenylmethane Tetraglycidyl-3,3′-diamino-5-methyldiphenylmethane, tetraglycidyl-3,3′-diamino-5,5′-dimethyldiphenylmethane, tetraglycidyl-3,3′-diamino-5,5′-dibromo Diphenylmethane, tetraglycidyl-4,4′-diaminodiphenylmethane, tetraglycidyl-4,4′-diamino-2,2′-dimethyldiphenylmethane, tetraglycidyl-4,4′-diamino-2,2′-dibromodiphenylmethane, tetra Glycidyl-4,4′-diamino-5-me Rudiphenylmethane, tetraglycidyl-4,4′-diamino-2′-methyldiphenylmethane, tetraglycidyl-4,4′-diamino-3′-methyldiphenylmethane, tetraglycidyl-4,4′-diamino-5,2′- Dimethyldiphenylmethane, tetraglycidyl-4,4′-diamino-5,3′-dimethyldiphenylmethane, tetraglycidyl-4,4′-diamino-5,5′-dimethyldiphenylmethane, tetraglycidyl-4,4′-diamino-5 , 5′-dibromodiphenylmethane, tetraglycidyl-3,4′-diaminodiphenylsulfone, tetraglycidyl-3,3′-diaminodiphenylsulfone, tetraglycidyl-3,4′-diamino-2,2′-dimethyldiphenylsulfone, Tetraglycidyl-3,4 -Diamino-2,2'-dibromodiphenylsulfone, tetraglycidyl-3,4'-diamino-5-methyldiphenylsulfone, tetraglycidyl-3,4'-diamino-2'-methyldiphenylsulfone, tetraglycidyl-3, 4′-diamino-3′-methyldiphenylsulfone, tetraglycidyl-3,4′-diamino-5,2′-dimethyldiphenylsulfone, tetraglycidyl-3,4′-diamino-5,3′-dimethyldiphenylsulfone, Tetraglycidyl-3,3′-diamino-5-methyldiphenylsulfone, tetraglycidyl-3,3′-diamino-5,5′-dimethyldiphenylsulfone, tetraglycidyl-3,3′-diamino-5,5′- Dibromodiphenyl sulfone, tetraglycidyl-4,4'-diamino Diphenylsulfone, tetraglycidyl-4,4′-diamino-2,2′-dimethyldiphenylsulfone, tetraglycidyl-4,4′-diamino-2,2′-dibromodiphenylsulfone, tetraglycidyl-4,4′-diamino -5-methyldiphenylsulfone, tetraglycidyl-4,4'-diamino-2'-methyldiphenylsulfone, tetraglycidyl-4,4'-diamino-3'-methyldiphenylsulfone, tetraglycidyl-4,4'-diamino -5,2'-dimethyldiphenylsulfone, tetraglycidyl-4,4'-diamino-5,3'-dimethyldiphenylsulfone, tetraglycidyl-4,4'-diamino-5,5'-dimethyldiphenylsulfone, tetraglycidyl -4,4'-diamino-5,5'-dibromodi Enylsulfone, tetraglycidyl-4,4'-diaminodiphenylthioether, tetraglycidyl-4,4'-diaminobenzanilide, tetraglycidyl-3,3'-diaminobenzanilide, tetraglycidyl-3,4'-diaminobenzanilide Etc.

Among these, R ³ , R ⁴ , R ⁵ and R ⁶ are preferably hydrogen atoms from the viewpoint of compatibility with other epoxy resins, and from the viewpoint of heat resistance, tetraglycidyl-3,4'-diaminodiphenyl ether, Tetraglycidyl-3,3′-diaminodiphenyl ether, tetraglycidyl-4,4′-diaminodiphenylmethane, tetraglycidyl-4,4′-diaminodiphenylsulfone, and tetraglycidyl-3,3′-diaminodiphenylsulfone are more preferable. From the viewpoint of flame retardancy, it is also a preferred form that is substituted with a halogen atom such as Cl or Br.

  Next, the production method of the epoxy resin (E) used in the present invention will be illustrated and described.

The epoxy resin (E) used in the present invention has the following general formula (5)

(In formula (5), R ^{3 to} R ⁶ were selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group having 1 to 4 carbon atoms, an alicyclic hydrocarbon group having 4 or less carbon atoms, and a halogen atom. Y represents at least one, Y is selected from —CH ₂ —, —O—, —S—, —CO—, —C (═O) O—, —SO ₂ —, —C (═O) NH—. Can be produced by reacting a diaminodiphenyl derivative represented by (2) with epichlorohydrin.

That is, like the general method for producing an epoxy resin, the method for producing an epoxy resin (E) is obtained by adding 4 molecules of epichlorohydrin to 1 molecule of a diaminodiphenyl derivative, and the following general formula (6)

(In formula (6), R ^{3 to} R ⁶ were selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group having 1 to 4 carbon atoms, an alicyclic hydrocarbon group having 4 or less carbon atoms, and a halogen atom. Y represents at least one, Y is selected from —CH ₂ —, —O—, —S—, —CO—, —C (═O) O—, —SO ₂ —, —C (═O) NH—. And the following dichlorohydrin compound is dehydrochlorinated with an alkali compound to produce a dichlorohydrin compound represented by the following general formula (2):

(In the formula (2), R ^{3 to} R ⁶ were selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group having 1 to 4 carbon atoms, an alicyclic hydrocarbon group having 4 or less carbon atoms, and a halogen atom. Y represents at least one, Y is selected from —CH ₂ —, —O—, —S—, —CO—, —C (═O) O—, —SO ₂ —, —C (═O) NH—. A cyclization step in which an epoxy compound represented by

  In the matrix resin of the present invention, if the amount of the epoxy resin (E) is too small, the heat resistance is impaired, and if it is too large, the crosslink density becomes high and may become a brittle material. Impact and tensile strength may be impaired. The compounding amount of the epoxy resin (E) is preferably 40 to 80% by mass with respect to 100% by mass of the epoxy resin (total amount of epoxy resin) in which the epoxy resin (D) and the epoxy resin (E) are combined. Yes, more preferably 50 to 70% by mass.

  In the present invention, an epoxy resin other than the epoxy resin (D) and the epoxy resin (E), a copolymer of an epoxy resin and a thermosetting resin, or the like may be included. Examples of the thermosetting resin used by being copolymerized with an epoxy resin include unsaturated polyester resin, vinyl ester resin, epoxy resin, benzoxazine resin, phenol resin, urea resin, melamine resin, and polyimide resin. It is done. These resin compositions and compounds may be used alone or in combination as appropriate. Incorporation of at least an epoxy resin other than the epoxy resin (D) and the epoxy resin (E) has both the fluidity of the matrix resin and the heat resistance after curing. In order to improve the fluidity of the resin, an epoxy resin that is liquid at room temperature (25 ° C.) is preferably used. The term “liquid” as used herein refers to a thermosetting property when a piece of metal having a specific gravity of 7 or more at the same temperature as the thermosetting resin to be measured is placed on the thermosetting resin and immediately buried by gravity. The resin is defined as liquid. Examples of the metal piece having a specific gravity of 7 or more include iron (steel), cast iron, and copper. Also, blending at least one liquid epoxy resin and at least one solid epoxy resin makes the prepreg tack and drape suitable. From the viewpoints of tackiness and draping properties, the epoxy resin composition according to the present invention contains liquid epoxy resin including epoxy resin (D) and epoxy resin (E) with respect to 100% by mass of the total amount of the epoxy resin blended. The total content is preferably 20% by mass or more.

  Commercially available epoxy resin (E) diaminodiphenylmethane type epoxy resins include “Sumiepoxy (registered trademark)” ELM434, ELM100, ELM120 (manufactured by Sumitomo Chemical Co., Ltd.), YH434L (manufactured by Nippon Steel Chemical Co., Ltd.). ), “JER (registered trademark)” 604, 630 (manufactured by Mitsubishi Chemical Corporation), “Araldide (registered trademark)” MY720, MY721, MY725, MY9512, MY9663 (above, manufactured by Huntsman Advanced Materials, Inc.) ) And the like. Examples of commercially available diaminodiphenylsulfone type epoxy resins include TG4DAS and TG3DAS (manufactured by Mitsui Chemicals Fine Co., Ltd.).

  When a diaminodiphenylmethane type epoxy resin is used as the epoxy resin (E), the epoxy equivalent is particularly 100 to 134 g / eq. Tetraglycidyldiaminodiphenylmethane is preferably used, and more preferably the epoxy equivalent is 100 to 120 g / eq. More preferably, the epoxy equivalent is 100 to 115 g / eq. It is. Such an epoxy equivalent is 100 g / eq. If it does not satisfy the formula, production of tetraglycidyldiaminodiphenylmethane becomes difficult, the production yield may be low, and the epoxy equivalent is 134 g / eq. If it exceeds 1, the viscosity of the resulting tetraglycidyldiaminodiphenylmethane will be too high, so only a small amount can be dissolved when the thermoplastic resin is dissolved to impart toughness to the thermosetting resin, and the thermosetting has high toughness. May not be obtained. Especially, epoxy equivalent is 100-120 g / eq. When a thermoplastic resin is dissolved in tetraglycidyldiaminodiphenylmethane, a large amount of thermoplastic resin can be dissolved within a range where there is no problem in the prepreg process, and high toughness is imparted to the cured product without impairing heat resistance. As a result, the tensile strength can be expressed in the carbon fiber reinforced composite material.

  Examples of commercially available metaxylenediamine type epoxy resins (E) include TETRAD-X and TETRAD-C (manufactured by Mitsubishi Gas Chemical Co., Inc.).

  Examples of commercially available 1,3-bisaminomethylcyclohexane type epoxy resins (E) include TETRAD-C (manufactured by Mitsubishi Gas Chemical Co., Inc.).

  As a commercially available product of the isocyanurate type epoxy resin (E), TEPIC-P (manufactured by Nissan Chemical Co., Ltd.) can be mentioned.

  As a commercially available product of the trishydroxyphenylmethane type epoxy resin (E), Tactix 742 (manufactured by Huntsman Advanced Materials Co., Ltd.) can be mentioned.

  As a commercially available product of the tetraphenylolethane type epoxy resin (E), “jER (registered trademark)” 1031S (manufactured by Japan Epoxy Resins Co., Ltd.) may be mentioned.

  Commercially available products of aminophenol type epoxy resin (E) include ELM120 and ELM100 (above, manufactured by Sumitomo Chemical Co., Ltd.), “jER (registered trademark)” 630 (manufactured by Japan Epoxy Resin Co., Ltd.), and “Araldite” (Registered trademark) “MY0500, MY0510, MY0600, MY0610 (manufactured by Huntsman Advanced Materials Co., Ltd.), and the like.

  Examples of commercially available phenol novolac epoxy resins (E) include DEN431 and DEN438 (above, manufactured by Dow Chemical Japan Co., Ltd.) and “jER (registered trademark)” 152, 154 (manufactured by Japan Epoxy Resin Co., Ltd.), “ Epicron (registered trademark) “N-740, N-770, N-775 (above, manufactured by DIC Corporation) and the like.

  Commercial products of ortho-cresol novolac type epoxy resin (E) include “Epiclon (registered trademark)” N-660, N-665, N-670, N-673, N-695 (above, manufactured by DIC Corporation) ), EOCN-1020, EOCN-102S, EOCN-104S (manufactured by Nippon Kayaku Co., Ltd.), and the like (E).

  As a commercial item of dicyclopentadiene type epoxy resin (E), "Epiclon (trademark)" HP7200, HP7200L, HP7200H, HP7200HH (made by DIC Corporation) etc. are mentioned.

  Among the epoxy resins used in the present invention other than the epoxy resin (D) and the epoxy resin (E), the epoxy resin having two or more functional groups is preferably a glycidyl ether type epoxy resin having a phenol as a precursor. Used. Examples of such epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, naphthalene type epoxy resins, biphenyl type epoxy resins, urethane-modified epoxy resins, hydantoin type and resorcinol type epoxy resins. It is done.

  Since the liquid bisphenol A type epoxy resin, bisphenol F type epoxy resin and resorcinol type epoxy resin have low viscosity, it is preferable to use them in combination with other epoxy resins.

  In addition, the solid bisphenol A type epoxy resin gives a structure having a lower crosslink density compared to the liquid bisphenol A type epoxy resin, so that the heat resistance is low, but a tougher structure is obtained, so that a glycidylamine type epoxy resin is obtained. Or liquid bisphenol A type epoxy resin or bisphenol F type epoxy resin.

  An epoxy resin having a naphthalene skeleton provides a cured resin having a low water absorption and high heat resistance. Biphenyl type epoxy resins, dicyclopentadiene type epoxy resins, phenol aralkyl type epoxy resins and diphenylfluorene type epoxy resins are also preferably used because they give a cured resin having a low water absorption rate. Urethane-modified epoxy resins and isocyanate-modified epoxy resins give cured resins having high fracture toughness and high elongation.

  Commercial products of bisphenol A type epoxy resin, which is an example of an epoxy resin having two or more functional groups, include “EPON (registered trademark)” 825 (manufactured by Japan Epoxy Resin Co., Ltd.), “Epicron (registered trademark)”. 850 (manufactured by DIC Corporation), “Epototo (registered trademark)” YD-128 (manufactured by Toto Kasei Co., Ltd.), and DER-331 and DER-332 (manufactured by Dow Chemical Japan Co., Ltd.) It is done.

  Examples of commercially available products of bisphenol F type epoxy resin, which is an example of an epoxy resin having two or more functional groups, include “jER (registered trademark)” 806, “jER (registered trademark)” 807, and “jER (registered trademark)”. 1750 (manufactured by Japan Epoxy Resin Co., Ltd.), “Epiclon (registered trademark)” 830 (manufactured by DIC Corporation), “Epototo (registered trademark)” YD-170 (manufactured by Toto Kasei Co., Ltd.), etc. It is done.

  As a commercial product of a resorcinol type epoxy resin which is an example of an epoxy resin having two or more functional groups, “Deconal (registered trademark)” EX-201 (manufactured by Nagase ChemteX Corporation) and the like can be mentioned.

  Examples of commercially available glycidyl aniline type epoxy resins that are examples of epoxy resins having two or more functional groups include GAN and GOT (manufactured by Nippon Kayaku Co., Ltd.).

  Examples of commercially available biphenyl type epoxy resins that are examples of epoxy resins having two or more functional groups include “jER (registered trademark)” YX4000H, YX4000, YL6616 (above, manufactured by Mitsubishi Chemical Corporation), NC-3000. (Nippon Kayaku Co., Ltd.).

  AER4152 (Asahi Kasei Epoxy Co., Ltd.) etc. are mentioned as a commercial item of the urethane-modified epoxy resin which is an example of the epoxy resin which has two or more functional groups.

  AY238 (manufactured by Huntsman Advanced Materials Co., Ltd.) is an example of a commercially available product of a hydantoin type epoxy resin that is an example of an epoxy resin having two or more functional groups.

  From the balance between adhesion with carbon fibers and mechanical properties, it is preferable that 30 to 70 parts by mass of glycidylamine type epoxy resin is blended in the total epoxy resin composition, and a more preferable blending amount is 40 to 60 parts by mass. .

  The epoxy resin composition according to the present invention may be used by blending the latent curing agent (F). The latent curing agent described here is a curing agent for an epoxy resin contained in the epoxy resin composition of the present invention, and is a curing agent that is activated by applying a temperature and reacts with an epoxy group. The reaction is preferably activated as described above. Here, activation at 70 ° C. means that the reaction start temperature is in the range of 70 ° C. Such reaction start temperature (hereinafter referred to as activation temperature) can be determined by, for example, differential scanning calorimetry (DSC). Specifically, an epoxy equivalent of 184 to 194 g / eq. Of the tangent of the inflection point of the exothermic curve obtained by differential scanning calorimetry and the tangent of the baseline for an epoxy resin composition obtained by adding 10 parts by mass of the curing agent to be evaluated to 100 parts by mass of the bisphenol A type epoxy compound It is requested from.

  The latent curing agent (F) is preferably an aromatic amine curing agent (F1), dicyandiamide or a derivative thereof. The aromatic amine curing agent is not particularly limited as long as it is an aromatic amine used as an epoxy resin curing agent. Specifically, 3,3′-diaminodiphenylsulfone (3,3′- DDS), 4,4′-diaminodiphenylsulfone (4,4′-DDS), diaminodiphenylmethane (DDM), 3,3′-diisopropyl-4,4′-diaminodiphenylmethane, 3,3′-di-t- Butyl-4,4′-diaminodiphenylmethane, 3,3′-diethyl-5,5′-dimethyl-4,4′-diaminodiphenylmethane, 3,3′-diisopropyl-5,5′-dimethyl-4,4 ′ -Diaminodiphenylmethane, 3,3'-di-t-butyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3 ', 5,5'-tetra Ethyl-4,4′-diaminodiphenylmethane, 3,3′-diisopropyl-5,5′-diethyl-4,4′-diaminodiphenylmethane, 3,3′-di-t-butyl-5,5′-diethyl- 4,4′-diaminodiphenylmethane, 3,3 ′, 5,5′-tetraisopropyl-4,4′-diaminodiphenylmethane, 3,3′-di-t-butyl-5,5′-diisopropyl-4,4 '-Diaminodiphenylmethane, 3,3', 5,5'-tetra-t-butyl-4,4'-diaminodiphenylmethane, diaminodiphenyl ether (DADPE), bisaniline, benzyldimethylaniline, 2- (dimethylaminomethyl) phenol ( DMP-10), 2,4,6-tris (dimethylaminomethyl) phenol (DMP-30), 2,4,6 2-ethylhexanoic acid ester of tris (dimethylaminomethyl) phenol, 4,4'-diamino benzanilide, can be used 3,4'-diaminodiphenyl benzanilide, 3,3'-diamino benzanilide like. These may be used alone or in admixture of two or more.

  Commercially available aromatic amine curing agents include Seika Cure S (manufactured by Wakayama Seika Kogyo Co., Ltd.), MDA-220 (manufactured by Mitsui Chemicals), “jER Cure (registered trademark)” W (Japan Epoxy Resin ( ), And 3,3′-DAS (Mitsui Chemicals), “Lonacure (registered trademark)” M-DEA, M-DIPA, M-MIPA (Lonza), DETDA 80 As mentioned above, Lonza Co., Ltd.) etc. are mentioned.

  A dicyandiamide derivative or a derivative thereof is a compound reacted with at least one of an amino group, an imino group and a cyano group. For example, o-tolylbiguanide, diphenylbiguanide, dicyandiamide amino group, imino group or cyano group. In this group, the epoxy group of the epoxy compound used in the epoxy resin composition is pre-reacted. Examples of commercially available dicyandiamide include DICY-7 and DICY-15 (manufactured by Japan Epoxy Resin Co., Ltd.).

  As curing agents other than the aromatic amine curing agent (F1), amines such as alicyclic amines, phenol compounds, acid anhydrides, polyaminoamides, organic acid hydrazides, and isocyanates are used in combination with aromatic amine curing agents. Also good.

  As a combination of the sizing agent according to the present invention and the latent curing agent (F), the following combinations are preferable. The sizing agent and the latent curing agent (F) are mixed at an amine equivalent / epoxy equivalent ratio of 0.9, which is the ratio of the amine equivalent to the epoxy equivalent of the sizing agent to be applied and the latent curing agent (F). The glass transition point is measured immediately after storage for 20 days in an environment of a temperature of 25 ° C. and 60% RH. A combination of a sizing agent having a glass transition point increase of 25 ° C. or less after 20 days and a latent curing agent (F) is preferable. When the glass transition point rises to 25 ° C. or lower, the reaction in the sizing agent outer layer and the matrix resin is suppressed when the prepreg is formed, and the tensile strength of the carbon fiber reinforced composite material after the prepreg is stored for a long period of time. This is preferable because a decrease in the mechanical properties of is suppressed. Moreover, it is more preferable that the increase in the glass transition point is 15 ° C. or less. More preferably, it is 10 ° C. or lower. The glass transition point can be determined by differential scanning calorimetry (DSC).

  Moreover, it is preferable that the total amount of a hardening | curing agent contains the quantity from which an active hydrogen group becomes the range of 0.6-1.2 equivalent with respect to 1 equivalent of epoxy groups of all the epoxy resin components, More preferably, 0.7- Including an amount in the range of 0.9 equivalents. Here, the active hydrogen group means a functional group that can react with the epoxy group of the curing agent component, and when the active hydrogen group is less than 0.6 equivalent, the reaction rate, heat resistance, and elastic modulus of the cured product. In some cases, the glass transition temperature and tensile strength of the carbon fiber reinforced composite material may be insufficient. If the active hydrogen group exceeds 1.2 equivalents, the reaction rate, glass transition temperature, and elastic modulus of the cured product are sufficient, but the plastic deformation ability is insufficient, so the impact resistance of the carbon fiber reinforced composite material May be insufficient.

  Moreover, a hardening accelerator can also be mix | blended for the purpose of accelerating hardening.

  Examples of the curing accelerator include urea compounds, tertiary amines and salts thereof, imidazoles and salts thereof, triphenylphosphine or derivatives thereof, carboxylic acid metal salts, Lewis acids, Bronsted acids and salts thereof, and the like. Of these, urea compounds are preferably used from the balance between long-term storage stability and catalytic ability. In particular, a combination of a urea compound and the latent curing agent (F) dicyandiamide is preferably used.

  Examples of the urea compound include N, N-dimethyl-N ′-(3,4-dichlorophenyl) urea, toluenebis (dimethylurea), 4,4′-methylenebis (phenyldimethylurea), 3-phenyl-1, 1-dimethylurea or the like can be used. Examples of commercially available urea compounds include DCMU99 (manufactured by Hodogaya Chemical Co., Ltd.), “Omicure (registered trademark)” 24, 52, 94 (manufactured by Emerald Performance Materials, LLC).

  It is preferable that the compounding quantity of a urea compound shall be 1-4 mass parts with respect to 100 mass parts of all the epoxy resin components. When the compounding quantity of this urea compound is less than 1 mass part, reaction may not fully advance and the elasticity modulus and heat resistance of hardened | cured material may be insufficient. Moreover, when the compounding quantity of this urea compound exceeds 4 mass parts, since the self-polymerization reaction of an epoxy compound inhibits reaction with an epoxy compound and a hardening | curing agent, the toughness of hardened | cured material is insufficient, and an elasticity modulus May decrease.

  Moreover, the thing which made these epoxy resin and hardening | curing agent, or some of them pre-react can be mix | blended in a composition. This method may be effective for viscosity adjustment and long-term storage stability improvement.

  In the present invention, it is also a preferred embodiment that the thermoplastic resin (H) is dissolved in the above epoxy resin composition. As such a thermoplastic resin (H), generally, a main chain includes a carbon-carbon bond, an amide bond, an imide bond, an ester bond, an ether bond, a carbonate bond, a urethane bond, a thioether bond, a sulfone bond, and a carbonyl bond. A thermoplastic resin having a bond selected from the group consisting of In addition, the thermoplastic resin (H) may have a partially crosslinked structure, and may have crystallinity or may be amorphous. In particular, polyamide, polycarbonate, polyacetal, polyphenylene oxide, polyphenylene sulfide, polyarylate, polyester, polyamideimide, polyimide, polyetherimide, polyimide having phenyltrimethylindane structure, polysulfone, polyethersulfone, polyetherketone, polyetherether It is preferable that at least one resin selected from the group consisting of ketone, polyaramid, polyethernitrile, and polybenzimidazole is dissolved in the epoxy resin (D) or the epoxy resin (E).

  Among these, in order to obtain good heat resistance, the glass transition temperature (Tg) of the thermoplastic resin (H) is at least 150 ° C. or higher and preferably 170 ° C. or higher. When the glass transition temperature of the thermoplastic resin (H) to be blended is less than 150 ° C., it may be easily deformed by heat when used as a molded body. Furthermore, as a terminal functional group of this thermoplastic resin (H), things, such as a hydroxyl group, a carboxyl group, a thiol group, and an acid anhydride, can react with a cationically polymerizable compound, and are used preferably. Examples of the thermoplastic resin having a hydroxyl group include polyvinyl acetal resins such as polyvinyl formal and polyvinyl butyral, polyvinyl alcohol, and phenoxy resin, and examples of the thermoplastic resin having a sulfonyl group include polyethersulfone. it can.

  Among them, polyethersulfone having an average molecular weight of 10,000 to 60000 g / mol is preferably used, more preferably the average molecular weight is 12000 to 50000 g / mol, and still more preferably the average molecular weight is 15000 to 30000 g / mol. If the average molecular weight is too low, the prepreg tack may be excessive and handling may be reduced, or the toughness of the cured product may be reduced. If the average molecular weight is too high, the tackiness of the prepreg may be reduced and handling may be reduced, or the resin may have a high viscosity when dissolved in a thermosetting resin, and may not be converted into a prepreg. In particular, when a polyethersulfone having a high heat resistance with an average molecular weight of 15000 to 30000 g / mol is dissolved in a thermosetting resin, a large amount of the thermoplastic resin is converted into a thermosetting resin as long as there is no problem in the prepreg process. It is possible to dissolve the carbon fiber reinforced composite material, to impart high toughness to the cured product, and to impart high tensile strength to the carbon fiber reinforced composite material while maintaining heat resistance and impact resistance.

  Specifically, "Sumika Excel (registered trademark)" PES3600P, PES5003P, PES5200P, PES7600P, "PES7200P (above, manufactured by Sumitomo Chemical Co., Ltd.)", "Ultrason (registered trademark)", which are commercially available polyethersulfone products. E2020P SR, E2021SR (above, manufactured by BASF Corporation), “GAFONE (registered trademark)” 3600RP, 3000RP (above, manufactured by Solvay Advance Polymers Co., Ltd.), “Virantage (registered trademark)” PESU VW-10200, PESU VW -10700 (registered trademark, manufactured by Solvay Advance Polymers Co., Ltd.) can be used, and a polyether sulfone and a polyether ether sulfone as described in JP-T-2004-506789 can be used. Examples include coalesced oligomers and “Ultem (registered trademark)” 1000, 1010, 1040 (above, manufactured by SABIC Innovative Plastics Japan LLC), which is a commercially available polyetherimide. A polymer having a relatively low molecular weight in which a finite number of monomers are bound.

  When the thermoplastic resin (H) is dissolved in an epoxy resin, better results are often given than when they are used alone. The brittleness of the epoxy resin is covered with the toughness of the thermoplastic resin (H), and the molding difficulty of the thermoplastic resin (H) is covered with the epoxy resin, thereby providing a well-balanced base resin. From the viewpoint of balance, the epoxy resin, the thermoplastic resin (H), and the usage ratio (% by mass) are preferably 100% by mass of the thermosetting resin composition, and preferably the mixing ratio of the thermoplastic resin (H) is 1. It is -40 mass%, More preferably, it is 5-30 mass%, More preferably, it is the range of 8-20 mass%. If the amount of the thermoplastic resin is too large, the viscosity of the thermosetting resin composition increases, which may impair the processability and handling of the thermosetting resin composition and the prepreg. If the amount of the thermoplastic resin is too small, the toughness of the cured product of the thermosetting resin composition may be insufficient, and the resulting carbon fiber reinforced composite material may have insufficient impact resistance and tensile strength.

  As a combination of the epoxy resin (E) and the thermoplastic resin (H) of the present invention, tetraglycidyldiaminodiphenylmethane, which is excellent in heat resistance and adhesion to carbon fibers, and polyethersulfone, which is excellent in heat resistance and toughness, This combination is preferably used because the resulting cured product has high heat resistance and toughness. In particular, an average epoxy equivalent of 100 to 115 g / eq. The combination of tetraglycidyldiaminodiphenylmethane and polyethersulfone having an average molecular weight of 15,000 to 30000 g / mol can dissolve a large amount of polyethersulfone having high heat resistance in tetraglycidyldiaminodiphenylmethane, thus reducing heat resistance. High toughness can be imparted to the cured product obtained without any problem, and high tensile strength can be imparted to the carbon fiber reinforced composite material while maintaining heat resistance and impact resistance.

  In the epoxy resin composition used in the present invention, components (components) other than the latent curing agent (F) such as epoxy resin (D) and epoxy resin (E) are first heated to a temperature of about 150 to 170 ° C. It is preferable to heat and knead the mixture uniformly and then cool to a temperature of about 60 ° C., then add the latent curing agent (F) and knead. However, the blending method of each component is not particularly limited to this method. Absent.

  Moreover, it is also suitable to mix the thermoplastic resin particles (G) with the epoxy resin composition used in the present invention. By blending the thermoplastic resin particles (G), the toughness of the matrix resin is improved and the impact resistance is improved when a carbon fiber reinforced composite material is obtained.

  The thermoplastic resin particles (G) used in the present invention are the same as the various thermoplastic resins (H) exemplified above, and can be used by being mixed with the epoxy resin composition. Can be used. Among them, polyamide is most preferable. Among polyamides, nylon 12, nylon 6, nylon 11, nylon 6/12 copolymer, and epoxy compound described in Example 1 of JP-A No. 01-104624 are semi-IPN (polymer). Nylon (semi-IPN nylon) having an interpenetrating network structure gives particularly good adhesive strength with epoxy resin (D) and epoxy resin (E). The shape of the thermoplastic resin particles (G) may be spherical particles, non-spherical particles, or porous particles, but the spherical shape is superior in viscoelasticity because it does not deteriorate the flow characteristics of the resin, and stress concentration is high. This is a preferred embodiment in that it has no starting point and gives high impact resistance. Commercially available products of polyamide particles include SP-500, SP-10, TR-1, TR-2, 842P-48, 842P-80 (manufactured by Toray Industries, Inc.), “Trepearl (registered trademark)” TN (Toray). “Orgasol (registered trademark)” 1002D, 2001UD, 2001EXD, 2002D, 3202D, 3501D, 3502D, (manufactured by Arkema Co., Ltd.) and the like can be used.

  The epoxy resin composition used in the present invention has a coupling agent, conductive particles such as carbon particles and metal plating organic particles, thermosetting resin particles, silica gel, clay, etc., as long as the effects of the present invention are not hindered. Inorganic fillers or conductive fillers can be blended. The use of conductive particles and conductive fillers is preferably used because the conductivity of the resulting resin cured product and carbon fiber reinforced composite material can be improved.

  Examples of the conductive filler include carbon black, carbon nanotube, vapor grown carbon fiber (VGCF), fullerene, metal nanoparticles, and the like, which may be used alone or in combination. Among these, inexpensive and highly effective carbon black is preferably used, and as such carbon black, for example, furnace black, acetylene black, thermal black, channel black, ketjen black, and the like can be used. Blended carbon black is also preferably used.

  The epoxy resin composition used in the present invention contains the above-mentioned materials in a predetermined ratio so that it has a low volatile content during curing, excellent heat resistance, and dynamics under severe environments such as low temperatures. It becomes possible to provide a prepreg having excellent characteristics. When the epoxy resin composition used in the present invention is a prepreg, the volatilization amount when the prepreg is left in a hot air dryer for 20 minutes is preferably 0.2 to 5% by mass or less. Is 0.02 to 3 mass% or less. By controlling the volatilization amount, it is possible to suppress the generation of voids when molding the carbon fiber reinforced composite material with high heat resistance.

  The volatilization amount of the epoxy resin composition tends to increase in proportion to the increase in the exposure temperature, but the epoxy resin composition gels in a short time and does not generate volatile matter as the temperature rises, so it is below the curing temperature. In many cases, the volatilization amount reaches a peak at this temperature. For example, in the case of aromatic amines that require high temperature conditions for curing, the volatilization amount reaches a peak at a temperature of 150 to 180 ° C., depending on the rate of temperature increase. For example, in the case of curing at 180 ° C., it is preferable to measure the volatilization amount at a temperature of 160 ° C. where the influence of the temperature rising rate is small.

Next, the manufacturing method of the prepreg of this invention is demonstrated.
The prepreg of the present invention is obtained by impregnating a carbon fiber bundle coated with a sizing agent with an epoxy resin composition that is a matrix resin. The prepreg can be produced by, for example, a wet method in which a matrix resin is dissolved in a solvent such as methyl ethyl ketone or methanol to lower the viscosity and impregnated, or a hot melt method in which the viscosity is lowered by heating and impregnated.

  In the wet method, after sizing agent-coated carbon fiber bundles are immersed in a liquid containing a matrix resin, the prepreg can be obtained by pulling up and evaporating the solvent using an oven or the like.

  In addition, in the hot melt method, a method of directly impregnating a carbon resin bundle coated with a sizing agent with a matrix resin whose viscosity has been reduced by heating, or a film in which a matrix resin composition is once coated on release paper or the like is first prepared. A prepreg can be produced by a method in which the film is laminated from both sides or one side of the sizing agent-coated carbon fiber bundle and heated and pressed to impregnate the sizing agent-coated carbon fiber bundle into the sizing agent-coated carbon fiber bundle. The hot melt method is a preferable means because there is no solvent remaining in the prepreg.

  In order to form a carbon fiber reinforced composite material using the prepreg of the present invention, a method of heat-curing a matrix resin while applying pressure to the laminate after laminating the prepreg can be used.

  Examples of methods for applying heat and pressure include a press molding method, an autoclave molding method, a bagging molding method, a wrapping tape method, and an internal pressure molding method. Especially for sporting goods, the wrapping tape method and the internal pressure molding method are preferably employed. The For aircraft applications where higher quality and higher performance laminated composite materials are required, the autoclave molding method is preferably employed. A press molding method is preferably used for various vehicle exteriors.

  The carbon fiber mass fraction of the prepreg of the present invention is preferably 40 to 90 mass%, more preferably 50 to 80 mass%. If the carbon fiber mass fraction is too low, the mass of the resulting carbon fiber reinforced composite material becomes excessive, and the advantages of the carbon fiber reinforced composite material having excellent specific strength and specific elastic modulus may be impaired. If the fraction is too high, poor impregnation of the matrix resin composition occurs, and the resulting carbon fiber reinforced composite material tends to have a lot of voids, and its mechanical properties may be greatly deteriorated.

  The prepreg of the present invention can clearly confirm the state in which the thermoplastic resin particles (G) are localized when the layer rich in the thermoplastic resin particles (G), that is, the cross section thereof is observed. The layer (hereinafter sometimes abbreviated as a particle layer) preferably has a structure formed in the vicinity of the surface of the prepreg.

  By taking such a structure, when the prepreg is laminated and the epoxy resin is cured to form a carbon fiber reinforced composite material, a resin layer is easily formed between the prepreg layers, that is, the carbon fiber reinforced composite material layer, As a result, the adhesion and adhesion between the carbon fiber reinforced composite material layers are enhanced, and the resulting carbon fiber reinforced composite material exhibits a high level of impact resistance.

  From such a viewpoint, the particle layer is preferably 20% deep, more preferably 10% deep from the surface of the prepreg in the thickness direction starting from the surface with respect to 100% of the thickness of the prepreg. It is preferable that it exists in the range. Further, the particle layer may be present only on one side, but care must be taken because the prepreg can be front and back. If the layers of the prepreg are mistaken and there are layers with and without particles, a carbon fiber reinforced composite material that is weak against impacts is obtained. In order to eliminate the distinction between front and back and facilitate lamination, the particle layer should be present on both the front and back sides of the prepreg.

  Furthermore, the abundance ratio of the thermoplastic resin particles (G) present in the particle layer is preferably 90 to 100% by mass, more preferably 100% by mass with respect to the total amount of the thermoplastic resin particles (G) in the prepreg. Is 95 to 100% by mass.

  The abundance of the thermoplastic resin particles (G) can be evaluated by, for example, the following method. That is, the prepreg is sandwiched between two smooth polytetrafluoroethylene resin plates with a smooth surface, and the temperature is gradually raised to the curing temperature over 7 days to gel and cure to cure the plate-like prepreg. Make a thing. Two lines parallel to the surface of the prepreg are drawn on both surfaces of the prepreg cured product from the surface of the prepreg cured product at a depth of 20% of the thickness. Next, the total area of the thermoplastic resin particles (G) existing between the surface of the prepreg and the line and the total area of the thermoplastic resin particles (G) existing over the thickness of the prepreg are obtained, The abundance ratio of the thermoplastic resin particles (G) existing in a range of 20% depth from the surface of the prepreg is calculated with respect to the thickness of 100%. Here, the total area of the thermoplastic resin particles (G) is obtained by cutting out the thermoplastic resin particle (G) portion from the cross-sectional photograph and converting from the mass. In the case where it is difficult to discriminate the thermoplastic resin particles (G) dispersed in the resin after photography, a means for dyeing the thermoplastic resin particles (G) can also be employed.

  In addition, as a method for obtaining a carbon fiber reinforced composite material in the present invention, in addition to a method using a prepreg, hand layup, RTM, “SCRIMP (registered trademark)”, filament winding, pultrusion and resin film infusion. The molding method such as can be selected and applied according to the purpose. By applying any of these molding methods, a carbon fiber reinforced composite material containing the above-described sizing agent-coated carbon fiber and a cured product of the thermosetting resin composition can be obtained.

  The carbon fiber reinforced composite material of the present invention is used for computer structures such as aircraft structural members, windmill blades, automobile outer plates, IC trays and notebook PC housings, and golf shafts, bats, badminton, tennis rackets, etc. It is preferably used for sports applications.

  EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not restrict | limited by these Examples. The production environment and evaluation of the prepregs of the following examples are performed in an atmosphere at a temperature of 25 ° C. ± 2 ° C. and 50% RH (relative humidity) unless otherwise specified.

(1) X-ray photoelectron spectroscopy of sizing agent-coated carbon fiber sizing agent surface In the present invention, the peak ratio of (a) and (b) on the sizing agent-coated carbon fiber sizing agent surface is determined by X-ray photoelectron spectroscopy. Determined according to the following procedure. Sizing agent-coated carbon fibers were cut to 20 mm, spread and arranged on a copper sample support, and AlKα ₁ and ₂ were used as an X-ray source, and the inside of the sample chamber was kept at 1 × 10 ⁻⁸ Torr, photoemission Measurements were made at an angle of 15 °. As correction of the peak accompanying charging during measurement, first, the binding energy value of the main peak of C _1s was adjusted to 286.1 eV. At this time, the peak area of C _1s was obtained by drawing a straight baseline in the range of 282 to 296 eV. Further, a linear base line of 282 to 296 eV obtained by calculating the area at the C _1s peak is defined as the origin (zero point) of the photoelectron intensity, and (b) the peak of the binding energy 286.1 eV attributed to the CO component is obtained. The height (cps: photoelectron intensity per unit time) and the height (cps) of the component having a binding energy of 284.6 eV attributed to (a) CHx, C—C, C = C are obtained, and (a) / ( b) was calculated.
Incidentally, when the peak of from (a) is large _(b), when combined binding energy of the main peak of _{C 1s} to _286.1, the peak of _{C 1s} does not fall within the scope of 282～296EV. In that case, after adjusting the binding energy value of the C _1s main peak to 284.6 eV, (a) / (b) was calculated by the above method.

(2) Cleaning of sizing agent of sizing agent-coated carbon fiber 2 g of sizing agent-coated carbon fiber was immersed in 50 ml of acetone and subjected to ultrasonic cleaning for 30 minutes three times. Subsequently, the substrate was immersed in 50 ml of methanol, subjected to ultrasonic cleaning for 30 minutes once and dried.

(3) X-ray photoelectron spectroscopy at 400 eV of sizing agent-coated carbon fiber In the present invention, the peak ratio of (a) and (b) on the sizing agent-coated carbon fiber surface is determined by X-ray photoelectron spectroscopy. It was determined according to the following procedure. The sizing agent-coated carbon fiber and the sizing agent-coated carbon fiber washed with the sizing agent are cut to 20 mm, spread and arranged on a copper sample support, and then Saga synchroton radiation is used as an X-ray source, and the excitation energy is 400 eV. It carried out in. The measurement was performed while keeping the inside of the sample chamber at 1 × 10 ⁻⁸ Torr. The photoelectron escape angle was 55 °. As correction of the peak accompanying charging during measurement, first, the binding energy value of the main peak of C _1s was adjusted to 286.1 eV. At this time, the peak area of C _1s was obtained by drawing a straight baseline in the range of 282 to 296 eV. Further, a linear base line of 282 to 296 eV obtained by calculating the area at the C _1s peak is defined as the origin (zero point) of the photoelectron intensity, and (b) the peak of the binding energy 286.1 eV attributed to the CO component is obtained. Obtain the height (cps: photoelectron intensity per unit time) and (a) the height (cps) of the component having a binding energy of 284.6 eV attributed to CHx, C—C, C = C. (B) was calculated.
Incidentally, when the peak of from (a) is large _(b), when combined binding energy of the main peak of _{C 1s} to _286.1, the peak of _{C 1s} does not fall within the scope of 282～296EV. In that case, after adjusting the binding energy value of the C _1s main peak to 284.6 eV, (a) / (b) was calculated by the above method.

(4) Strand tensile strength and elastic modulus of carbon fiber bundles Strand tensile strength and strand elastic modulus of carbon fiber bundles were determined according to the following procedure in accordance with the resin-impregnated strand test method of JIS-R-7608 (2004). . As a resin formulation, “Celoxide (registered trademark)” 2021P (manufactured by Daicel Chemical Industries, Ltd.) / 3 boron fluoride monoethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) / Acetone = 100/3/4 (parts by mass) As the curing conditions, normal pressure, temperature of 125 ° C., and time of 30 minutes were used. Ten strands of the carbon fiber bundle were measured, and the average value was defined as the strand tensile strength and the strand elastic modulus.

(5) Surface oxygen concentration of carbon fiber (O / C)
The surface oxygen concentration (O / C) of the carbon fiber was determined by X-ray photoelectron spectroscopy according to the following procedure. First, the carbon fiber from which the dirt adhering to the surface with a solvent is removed is cut to about 20 mm and spread on a copper sample support. Next, the sample support was set in the sample chamber, and the inside of the sample chamber was kept at 1 × 10 ⁻⁸ Torr. Subsequently, AlKα ₁ and ₂ were used as the X-ray source, and the photoelectron escape angle was 90 °. In addition, the binding energy value of the C _1s main peak (peak top) was adjusted to 284.6 eV as a peak correction value associated with charging during measurement. The C _1s main area was determined by drawing a straight base line in the range of 282 to 296 eV. The O _1s peak area was determined by drawing a straight base line in the range of 528 to 540 eV. Here, the surface oxygen concentration is calculated as an atomic ratio by using a sensitivity correction value unique to the apparatus from the ratio of the O _1s peak area to the C _1s peak area. As the X-ray photoelectron spectroscopy apparatus, ESCA-1600 manufactured by ULVAC-PHI Co., Ltd. was used, and the sensitivity correction value unique to the apparatus was 2.33.

(6) Carbon fiber surface carboxyl group concentration (COOH / C), surface hydroxyl group concentration (COH / C)
The surface hydroxyl group concentration (COH / C) was determined by chemical modification X-ray photoelectron spectroscopy according to the following procedure.
The carbon fiber bundles from which the sizing agent and the like have been removed with a solvent are cut, spread and arranged on a platinum sample support, and 10% at room temperature in dry nitrogen gas containing 0.04 mol / L of anhydrous trifluoride acetic acid gas. After exposure to chemical modification for a minute, the sample was mounted on an X-ray photoelectron spectrometer with a photoelectron escape angle of 35 °, AlKα _1,2 was used as the X-ray source, and the inside of the sample chamber was adjusted to a vacuum of 1 × 10 ⁻⁸ Torr. keep. As correction of the peak accompanying charging during measurement, first, the binding energy value of the main peak of C _1s is adjusted to 284.6 eV. The C _1s peak area [C _1s ] is obtained by drawing a straight base line in the range of 282 to 296 eV, and the F _1s peak area [F _1s ] is obtained by drawing a straight base line in the range of 682 to 695 eV. Asked. Moreover, the reaction rate r was calculated | required from _C1s peak division _| segmentation of the polyvinyl alcohol chemically modified simultaneously.
The surface hydroxyl group concentration (COH / C) was represented by the value calculated by the following formula.
COH / C = {[F _1s ] / (3k [C _1s ] −2 [F _1s ]) r} × 100 (%)
Note that k is a sensitivity correction value of the F _1s peak area with respect to the C _1s peak area specific to the apparatus, and the sensitivity correction value specific to the apparatus in the model SSX-100-206 manufactured by SSI of the United States was 3.919. .

The surface carboxyl group concentration (COOH / C) was determined by chemical modification X-ray photoelectron spectroscopy according to the following procedure. First, carbon fiber bundles from which the sizing agent and the like have been removed with a solvent are cut and spread and arranged on a platinum sample support, and 0.02 mol / L trifluorinated ethanol gas and 0.001 mol / L dicyclohexylcarbodiimide gas. And a chemical modification treatment in an air containing 0.04 mol / L pyridine gas at 60 ° C. for 8 hours, and then mounted on an X-ray photoelectron spectrometer with a photoelectron escape angle of 35 °, and AlKα _{1, 2} is used and the inside of the sample chamber is kept at a vacuum of 1 × 10 ⁻⁸ Torr. As correction of the peak accompanying charging during measurement, first, the binding energy value of the main peak of C _1s is adjusted to 284.6 eV. The C _1s peak area [C _1s ] is obtained by drawing a straight base line in the range of 282 to 296 eV, and the F _1s peak area [F _1s ] is obtained by drawing a straight base line in the range of 682 to 695 eV. Asked. Simultaneously, the reaction rate r was determined from the C _1s peak splitting of the polyacrylic acid chemically modified, and the residual rate m of the dicyclohexylcarbodiimide derivative was determined from the O _1s peak splitting.
The surface carboxyl group concentration COOH / C was represented by the value calculated by the following formula.
COOH / C = {[F _1s ] / (3k [C _1s ] − (2 + 13 m) [F _1s ]) r} × 100 (%)
Note that k is a sensitivity correction value of the F _1s peak area with respect to the C _1s peak area unique to the apparatus, and the sensitivity correction value specific to the apparatus when the model SSX-100-206 manufactured by SSI of the United States is used is 3.919. Met.

(7) Epoxy equivalent of sizing agent, epoxy equivalent of sizing agent applied to carbon fiber Epoxy equivalent of sizing agent is obtained by dissolving a sizing agent from which a solvent has been removed in a solvent typified by N, N-dimethylformamide, The epoxy group was opened with hydrochloric acid, and acid-base titration was used. The epoxy equivalent of the sizing agent applied to the carbon fiber is determined by immersing the sizing agent-coated carbon fiber in N, N-dimethylformamide and elution from the fiber by ultrasonic cleaning, and then opening the epoxy group with hydrochloric acid. Ringed and determined by acid-base titration.

(8) Rise temperature of glass transition point The sizing agent and the latent curing agent (F) were mixed so that the amine equivalent / epoxy equivalent, which is the ratio of amine equivalent to epoxy equivalent, was 0.9, and JIS K7121 (1987). ), The glass transition temperature of the mixture prepared by a differential scanning calorimeter (DSC) was measured. A sealed sample container having a capacity of 50 μl was filled with 3 to 10 mg of a sample (test piece), heated to 30 to 350 ° C. at a heating rate of 10 ° C./min, and the glass transition temperature was measured. Here, a differential scanning calorimeter (DSC) manufactured by TA Instruments was used as a measuring device.
Specifically, in the portion showing the step change of the obtained DSC curve, the straight line equidistant from the extended straight line of each baseline in the vertical axis direction and the curve of the step change portion of the glass transition intersect. The temperature at the point was taken as the glass transition temperature.
Subsequently, after the prepared mixture was stored for 20 days in an environment of a temperature of 25 ° C. and 60% RH, the glass transition temperature was measured by the method described above, and the rising temperature from the initial stage was taken as the rising temperature of the glass transition point ( “ΔTg with curing agent” in the table corresponds to that).

(9) Measuring method of sizing adhesion amount Electric furnace set to a temperature of 450 ° C. in a nitrogen stream of 50 mL / min after weighing (W1) (reading to the fourth decimal place) about 2 g of sizing adhesion carbon fiber bundle Leave in (capacity 120 cm ³ ) for 15 minutes to completely pyrolyze the sizing agent. Then, the carbon fiber bundle is transferred to a container in a dry nitrogen stream of 20 L / min, cooled for 15 minutes, weighed (W2) (read to the fourth decimal place), and the sizing adhesion amount is determined by W1-W2. The value obtained by converting this sizing adhesion amount into an amount with respect to 100 parts by mass of the carbon fiber bundle (rounded off to the third decimal place) was taken as the mass part of the adhering sizing agent. The measurement was performed twice, and the average value was defined as the mass part of the sizing agent.

(10) Measurement of interfacial shear strength (IFSS) The interfacial shear strength (IFSS) was measured by the following procedures (a) to (d).
(A) Preparation of resin 100 parts by mass of a bisphenol A type epoxy compound “jER (registered trademark)” 828 (manufactured by Mitsubishi Chemical Corporation) and 14.5 parts by mass of metaphenylenediamine (manufactured by Sigma-Aldrich Japan Co., Ltd.) Each was placed in a container. Thereafter, the mixture was heated at a temperature of 75 ° C. for 15 minutes in order to reduce the viscosity of the jER828 and dissolve the metaphenylenediamine. Then, both were mixed well and vacuum defoaming was performed at a temperature of 80 ° C. for about 15 minutes.
(B) Fixing the carbon fiber single yarn to the dedicated mold The single fiber was extracted from the carbon fiber bundle, and both ends were fixed with an adhesive in a state where a constant tension was applied to the single fiber in the longitudinal direction of the dumbbell mold. Then, in order to remove the water | moisture content adhering to carbon fiber and a mold, it vacuum-dried for 30 minutes or more at the temperature of 80 degreeC. The dumbbell mold was made of silicone rubber, and the shape of the cast part was a central part width of 5 mm, a length of 25 mm, both end part widths of 10 mm, and an overall length of 150 mm.
(C) From resin casting to curing The resin adjusted in the above procedure (b) is poured into the mold after the vacuum drying in the above step (b), and the temperature rising rate is 1.5 ° C. / The temperature rises to 75 ° C in minutes and is held for 2 hours, then rises to a temperature of 125 ° C at a heating rate of 1.5 ° C / min, held for 2 hours, and then reaches a temperature of 30 ° C at a cooling rate of 2.5 ° C / min. The temperature dropped. Then, it demolded and the test piece was obtained.
(D) Measurement of interfacial shear strength (IFSS) A tensile force was applied to the test piece obtained in the above procedure (c) in the fiber axis direction (longitudinal direction) to cause a strain of 12%, and then the test piece was tested with a polarizing microscope. The fiber breakage number N (pieces) in the range of 22 mm at the center of each piece was measured. Next, the average broken fiber length la was calculated by the formula: la (μm) = 22 × 1000 (μm) / N (pieces). Next, the critical fiber length lc was calculated from the average breaking fiber length la by the formula of lc (μm) = (4/3) × la (μm). The strand tensile strength σ and the diameter d of the carbon fiber single yarn were measured, and the interfacial shear strength IFSS, which is an index of the bond strength between the carbon fiber and the resin interface, was calculated by the following equation. In the examples, the average of the number of measurements n = 5 was used as the test result.
Interfacial shear strength IFSS (MPa) = σ (MPa) × d (μm) / (2 × lc) (μm)

(11) Definition of 0 ° of carbon fiber reinforced composite material As described in JIS K7017 (1999), the fiber direction of the unidirectional carbon fiber reinforced composite material is defined as the axial direction, and the axial direction is defined as the 0 ° axis. The direction perpendicular to the axis was defined as 90 °.

(12) Measurement of 0 ° tensile strength of carbon fiber reinforced composite material Cut unidirectional prepreg within 24 hours after production into a predetermined size, laminate 6 sheets in one direction, perform vacuum bag, and autoclave It was cured at a temperature of 180 ° C. and a pressure of 6 kg / cm ² for 2 hours to obtain a unidirectional reinforcing material (carbon fiber reinforced composite material). The unidirectional reinforcing material was cut into a width of 12.7 mm and a length of 230 mm, and a glass fiber reinforced plastic tab having a length of 1.2 mm and a length of 50 mm was bonded to both ends to obtain a test piece. The test piece thus obtained was subjected to a tensile test at a crosshead speed of 1.27 mm / min using an Instron universal testing machine.
In the present invention, the value obtained by dividing the value of the 0 ° tensile strength by the value of the strand strength obtained in (B) was obtained as the strength utilization rate (%), and the following formula was obtained.
Strength utilization rate = tensile strength / ((CF basis weight / 190) × Vf / 100 × strand strength) × 100
CF (carbon fiber) basis weight = 190 g / m ²
Vf (volume carbon fiber content) = 56%

(13) 0 ° Tensile Strength Utilization after Storage of Prepreg After storing the prepreg at a temperature of 25 ° C. and 60% RH for 20 days, the 0 ° tensile strength measurement was performed in the same manner as in (12) to calculate the strength utilization.

(14) Measurement of glass transition temperature The glass transition temperature of the carbon fiber reinforced composite material was measured with a differential scanning calorimeter (DSC) in accordance with JIS K7121 (1987) using the test piece of item (12). A sealed sample container having a capacity of 50 μl was filled with 8 to 20 mg of sample (test piece), heated to 30 to 350 ° C. at a heating rate of 10 ° C./min, and the glass transition temperature was measured. Here, a differential scanning calorimeter (DSC) manufactured by TA Instruments was used as a measuring device. Specifically, in the portion showing the step change of the obtained DSC curve, the straight line equidistant from the extended straight line of each baseline in the vertical axis direction and the curve of the step change portion of the glass transition intersect. The temperature at the point was taken as the glass transition temperature.

(15) Measurement of prepreg volatile matter A prepreg is cut into 50 x 50 mm to obtain a test piece. After weighing the test piece (W1), the prepreg placed on an aluminum plate was kept still in a hot air dryer set at a temperature of 160 ° C. for 20 minutes and allowed to cool to 25 ° C. in a desiccator. Was weighed (W2). The prepreg volatile content (mass%) was calculated from the following formula.
・ PVC = (W1-W2) / W1 × 100
PVC: prepreg volatile matter (mass%)
Volatile content (mass%) = PVC x 100 / RC
RC: Resin content of prepreg (% by mass)

(16) Presence of particles existing in a 20% depth range of prepreg The prepreg is sandwiched between two smooth polytetrafluoroethylene resin plates on the surface and brought into close contact, and gradually over 7 days. Then, the temperature is raised to 150 ° C. to gel and cure to produce a plate-shaped resin cured product. After curing, the film was cut from the direction perpendicular to the contact surface, and the cross-section was polished, then magnified 200 times or more with an optical microscope, and photographed so that the upper and lower surfaces of the prepreg were within the visual field. By the same operation, the distance between the polytetrafluoroethylene resin plates was measured at five locations in the horizontal direction of the cross-sectional photograph, and the average value (n = 5) was taken as the thickness of the prepreg. With respect to both sides of the prepreg, two lines parallel to the surface of the prepreg are drawn from the surface of the prepreg at a depth of 20% of the thickness. Next, the total area of the particles existing between the surface of the prepreg and the line and the total area of the particles existing over the thickness of the prepreg are obtained, and from the surface of the prepreg with respect to 100% of the thickness of the prepreg. The abundance of particles present in the 20% depth range was calculated. Here, the total area of the fine particles was obtained by cutting out the particle portion from the cross-sectional photograph and converting it from the mass.

(17) Measurement of average particle diameter of thermoplastic resin particles (G) About the average particle diameter of the particles, the particles were magnified 1000 times or more with a microscope such as a scanning electron microscope, and the particles were randomly selected. The diameter of the circle circumscribing the particle was selected as the particle size, and the average value of the particle sizes (n = 50) was obtained.

(18) Measurement of compressive strength after impact of carbon fiber reinforced composite material [+ 45 ° / 0 ° / −45 ° / 90 °] A unidirectional prepreg is laminated in a pseudo-isotropic manner with 24 plies in a _{3 s} configuration and is autoclaveed. A pseudo isotropic material (carbon fiber reinforced composite material) was produced by molding at a temperature of 180 ° C. for 2 hours, a pressure of 6 kg / cm ² , and a heating rate of 1.5 ° C./min. A sample 150 mm long x 100 mm wide (thickness 4.5 mm) is cut out from this pseudo-isotropic material, and a falling weight impact of 6.7 J / mm is applied to the center of the sample in accordance with SACMA SRM 2R-94. The strength was determined.

  The materials and components used in each example and each comparative example are as follows.

-(A) component: A-1 to A-3
A-1: “Denacol (registered trademark)” EX-810 (manufactured by Nagase ChemteX Corporation)
Diglycidyl ether of ethylene glycol Epoxy equivalent: 113 g / eq. Epoxy group number: 2
A-2: “Denacol (registered trademark)” EX-611 (manufactured by Nagase ChemteX Corporation)
Sorbitol polyglycidyl ether Epoxy equivalent: 167 g / eq. Epoxy group number: 4
Number of hydroxyl groups: 2
A-3: “Denacol (registered trademark)” EX-521 (manufactured by Nagase ChemteX Corporation)
Polyglycerin polyglycidyl ether Epoxy equivalent: 183 g / eq. Epoxy group number: 3 or more

-(B1) component: B-1 to B-4
B-1: “jER (registered trademark)” 152 (manufactured by Mitsubishi Chemical Corporation)
Glycidyl ether of phenol novolac Epoxy equivalent: 175 g / eq. Epoxy group number: 3
B-2: “jER (registered trademark)” 828 (manufactured by Mitsubishi Chemical Corporation)
Diglycidyl ether of bisphenol A Epoxy equivalent: 189 g / eq. Epoxy group number: 2
B-3: “jER (registered trademark)” 1001 (manufactured by Mitsubishi Chemical Corporation)
Diglycidyl ether of bisphenol A Epoxy equivalent: 475 g / eq. Epoxy group number: 2
B-4: “jER (registered trademark)” 807 (manufactured by Mitsubishi Chemical Corporation)
Diglycidyl ether of bisphenol F Epoxy equivalent: 167 g / eq. Epoxy group number: 2

Epoxy resin (D) component: D-1 to D-4
D-1: N, N-diglycidyl-4-phenoxyaniline synthesized by the following method Into a four-necked flask equipped with a thermometer, a dropping funnel, a condenser, and a stirrer, 610.6 g of epichlorohydrin (6.6 eq. ), The temperature was raised to 70 ° C. while purging with nitrogen, and 203.7 g (1.1 eq.) Of p-phenoxyaniline dissolved in 1020 g of ethanol was added dropwise thereto over 4 hours. The mixture was further stirred for 6 hours to complete the addition reaction, whereby 4-phenoxy-N, N-bis (2-hydroxy-3-chloropropyl) aniline was obtained. Subsequently, after the temperature in the flask was lowered to 25 ° C., 229 g (2.75 eq.) Of a 48% NaOH aqueous solution was dropped into the flask over 2 hours, followed by further stirring for 1 hour. After completion of the cyclization reaction, ethanol was distilled off, followed by extraction with 408 g of toluene and washing with 5% saline twice. When toluene and epichlorohydrin were removed from the organic layer under reduced pressure, 308.5 g (yield 94.5%) of a brown viscous liquid was obtained. The purity of the main product, N, N-diglycidyl-4-phenoxyaniline, was 91% (GCarea%).

D-2: N, N-diglycidyl-4- (4-nitrophenoxy) aniline synthesized by the following method, except that the amine compound used as the precursor of the synthesized epoxy resin was changed to 4- (4-nitrophenoxy) aniline Was subjected to a glycidylation reaction under the same reaction conditions and procedures as those of N, N-diglycidyl-4-phenoxyaniline described above to obtain N, N-diglycidyl-4- (4-nitrophenoxy) aniline.

D-3: “Denacol (registered trademark)” Ex-731 (N-glycidylphthalimide, manufactured by Nagase ChemteX Corporation)
D-4: OPP-G (o-phenylphenyl glycidyl ether, manufactured by Sanko Co., Ltd.)

-Epoxy resin (E) component: E-1 to E-7
E-1: ELM434 (tetraglycidyldiaminodiphenylmethane, manufactured by Sumitomo Chemical Co., Ltd., epoxy equivalent: 125 g / eq.)
E-2: “jER (registered trademark)” 630 (triglycidyl-p-aminophenol, manufactured by Japan Epoxy Resins Co., Ltd.)

E-3: 34TGDDE (tetraglycidyl-3,4'-diaminodiphenyl ether) synthesized by the following method
A four-necked flask equipped with a thermometer, dropping funnel, condenser and stirrer was charged with 610.6 g (6.6 mol) of epichlorohydrin and the temperature was raised to 70 ° C. while purging with nitrogen. 22.4 g (1.1 mol) of 3,4'-diaminodiphenyl ether dissolved in 1020 g was added dropwise over 4 hours. The mixture was further stirred for 6 hours to complete the addition reaction, and N, N, N ′, N′-tetrakis (2-hydroxy-3-chloropropyl) 3,4′-diaminodiphenyl ether was obtained. Subsequently, the temperature in the flask was lowered to 25 ° C., and 229 g (2.75 mol) of a 48% NaOH aqueous solution was added dropwise to the flask over 2 hours, followed by further stirring for 1 hour. After completion of the cyclization reaction, ethanol was distilled off, followed by extraction with 408 g of toluene and washing with 5% saline twice. When toluene and epichlorohydrin were removed from the organic layer under reduced pressure, 416 g (yield 89%) of a brown viscous liquid was obtained. The purity of the main product, tetraglycidyl-3,4'-diaminodiphenyl ether, was 87% (GCarea%).

E-4: 33TGDDE (tetraglycidyl-3,3′-diaminodiphenyl ether) synthesized by the following method
The glycidylation reaction was carried out according to the same reaction conditions and procedure as the above-mentioned tetraglycidyl-3,4'-diaminodiphenyl ether, except that the amine compound used as the precursor of the synthesized epoxy resin was changed to 3,3'-diaminodiphenyl ether. This gave tetraglycidyl-3,3′-diaminodiphenyl ether.

E-5: 44TGDDE (tetraglycidyl-4,4′-diaminodiphenyl ether) synthesized by the following method
The glycidylation reaction was carried out under the same reaction conditions and procedure as the above-mentioned tetraglycidyl-3,4'-diaminodiphenyl ether except that the amine compound used as the precursor of the synthesized epoxy resin was changed to 4,4'-diaminodiphenyl ether. This gave tetraglycidyl-4,4′-diaminodiphenyl ether.

E-6: TG3DAS (Tetraglycidyl-3,3′-diaminodiphenylsulfone, Mitsui Chemicals Fine Co., Ltd.)
E-7: “Araldide (registered trademark)” MY721 (tetraglycidyldiaminodiphenylmethane, manufactured by Huntsman Advanced Materials, Inc., epoxy equivalent: 112 g / eq.)

Epoxy resins (D), bifunctional epoxy resins other than (E), “EPON (registered trademark)” 825 (bisphenol A type epoxy resin, Japan Epoxy Resins Co., Ltd.)
GAN (N-diglycidyl aniline, manufactured by Nippon Kayaku Co., Ltd.)

-Latent curing agent (F) component: F-1, F-2
F-1: “Seika Cure (registered trademark)” S (4,4′-diaminodiphenyl sulfone, manufactured by Wakayama Seika Co., Ltd.)
F-2: 3,3′-DAS (3,3′-diaminodiphenylsulfone, manufactured by Mitsui Chemicals Fine Co., Ltd.)

-Thermoplastic resin particles (G): G-1, G-2
G-1: “Trepearl (registered trademark)” TN (manufactured by Toray Industries, Inc., average particle size: 13.0 μm)
G-2: “Orgasol (registered trademark)” 1002D (ATOCHEM, average particle size: 21.0 μm)

-Thermoplastic resin (H): H-1, H-2
H-1: “Sumika Excel (registered trademark)” PES5003P (polyethersulfone, manufactured by Sumitomo Chemical Co., Ltd., average molecular weight: 47000 g / mol)
H-2: “Virantage (registered trademark)” VW-10700RP (polyethersulfone, manufactured by Solvay Advanced Polymers, average molecular weight: 21000 g / mol)

Example 1
This example comprises the following I step, II step and III step.
-Step I: Process for producing carbon fiber as raw material A copolymer composed of 99 mol% of acrylonitrile and 1 mol% of itaconic acid is spun and fired, the total number of filaments is 24,000, the total fineness is 1,000 tex, A carbon fiber having a specific gravity of 1.8, a strand tensile strength of 5.9 GPa, and a strand tensile elastic modulus of 295 GPa was obtained. Next, the carbon fiber was subjected to electrolytic surface treatment with an aqueous solution of ammonium hydrogen carbonate having a concentration of 0.1 mol / L as an electrolytic solution at an electric quantity of 80 coulomb per gram of carbon fiber. The carbon fiber subjected to the electrolytic surface treatment was subsequently washed with water and dried in heated air at a temperature of 150 ° C. to obtain a carbon fiber as a raw material. At this time, the surface oxygen concentration O / C was 0.15, the surface carboxylic acid concentration COOH / C was 0.005, and the surface hydroxyl group concentration COH / C was 0.018. This was designated as carbon fiber A.

Step II: A step of attaching a sizing agent to carbon fiber (B1) As a component, an aqueous dispersion emulsion comprising 20 parts by mass of (B-1), 20 parts by mass of component (C) and 10 parts by mass of an emulsifier was prepared. Thereafter, 50 parts by mass of (A-3) as the component (A) was mixed to prepare a sizing solution. As component (C), 2 mol of EO2 mol adduct of bisphenol A, 1.5 mol of maleic acid and 0.5 mol of sebacic acid, and polyoxyethylene (70 mol) styrenated (5 mol) cumylphenol were used as emulsifiers. . In addition, (C) component and an emulsifier are both aromatic compounds, and will also correspond to (B) component. The epoxy equivalent of the sizing agent excluding the solution in the sizing solution is as shown in Table 1. After this sizing agent was applied to the carbon fiber surface-treated by the dipping method, heat treatment was performed at a temperature of 210 ° C. for 75 seconds to obtain a sizing agent-coated carbon fiber bundle. The adhesion amount of the sizing agent was adjusted to be 1.0 part by mass with respect to 100 parts by mass of the surface-treated carbon fiber. Subsequently, epoxy equivalent of sizing agent, X-ray photoelectron spectroscopy measurement of sizing agent surface, interfacial shear strength (IFSS) of carbon fiber coated with sizing agent, glass transition point of mixture of sizing agent and latent curing agent (F) The rising temperature (ΔTg) of was measured. The results are summarized in Table 1. As a result, it was confirmed that the epoxy equivalent of the sizing agent, the chemical composition of the sizing agent surface, and ΔTg were as expected. Moreover, it turned out that the adhesiveness measured by IFSS is also high enough.

Step III: Production, molding and evaluation of unidirectional prepreg In a kneading apparatus, 40 parts by mass of (D-1) as the epoxy resin (D) component and (E-1) as the epoxy resin (E) component After 60 parts by mass of 10 parts by mass of (H-1) as a thermoplastic resin (H) component is dissolved, (F-1) 4,4′-diamino is added as a latent curing agent (F) component. 45 parts by mass of diphenylsulfone was kneaded to prepare a primary resin composition excluding the thermoplastic resin particles (G). The obtained primary resin composition was coated on a release paper with a resin basis weight of 32 g / m ² using a knife coater to prepare a primary resin film. A carbon fiber reinforced composite material is formed by superimposing the primary resin film on both sides of a sizing agent-coated carbon fiber (weight per unit area: 190 g / m ² ) aligned in one direction, using a heat roll at 100 ° C. and 1 atmosphere. An epoxy resin composition for use was impregnated to obtain a primary prepreg. Next, the secondary epoxy resin prepared by adding (G-1) as the thermoplastic resin particles (G) so that the epoxy resin composition of the final prepreg for carbon fiber reinforced composite material becomes the blending amount shown in Table 1. The composition was coated on a release paper with a resin basis weight of 20 g / m ² using a knife coater to prepare a secondary resin film. This secondary resin film was superimposed on both sides of the primary prepreg, and a heat roll was used to impregnate the epoxy resin composition for carbon fiber reinforced composite material while heating and pressing at 100 ° C. and 1 atm to obtain the desired prepreg. . About the obtained prepreg, the prepreg volatile matter was measured. Also, using the obtained prepreg, 0 ° tensile strength measurement of carbon fiber reinforced composite material, 0 ° tensile test after long-term storage, glass transition temperature measurement, and compression strength measurement after impact of carbon fiber reinforced composite material did. The results are shown in Table 1. It was confirmed that the initial 0 ° tensile strength utilization rate and the compressive strength after impact were sufficiently high, and the decrease in the tensile strength utilization rate after 20 days was small. It was also confirmed that the volatile content during curing was sufficiently small.

(Examples 2 to 8)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
Step II: Step of attaching sizing agent to carbon fiber Sizing agent-coated carbon in the same manner as in Example 1 except that the components (A) and (B1) shown in Table 1 were used as the sizing agent. Fiber was obtained. Subsequently, the epoxy equivalent of the sizing agent, the X-ray photoelectron spectroscopy measurement of the sizing agent surface, the interfacial shear strength (IFSS) of the sizing agent-coated carbon fiber, and ΔTg were measured. It was found that the epoxy equivalent of the sizing agent, the chemical composition of the sizing agent surface, and ΔTg were as expected, and the adhesiveness measured by IFSS was sufficiently high. The results are shown in Table 1.
Step III: Production, molding and evaluation of unidirectional prepreg A prepreg was produced, molded and evaluated in the same manner as in Example 1. It was confirmed that the initial 0 ° tensile strength utilization rate and the compressive strength after impact were sufficiently high, and the decrease in the tensile strength utilization rate after 20 days was small. It was also confirmed that the volatile content during curing was sufficiently small. The results are shown in Table 1.

(Examples 9 to 13)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
Step II: Step of attaching sizing agent to carbon fiber Sizing agent-coated carbon fiber was obtained in the same manner as in Example 2 except that the mass ratio shown in Table 2 was used as the sizing agent. Subsequently, the epoxy equivalent of the sizing agent, the X-ray photoelectron spectroscopy measurement of the sizing agent surface, the interfacial shear strength (IFSS) of the sizing agent-coated carbon fiber, and ΔTg were measured. It was found that the epoxy equivalent of the sizing agent, the chemical composition of the sizing agent surface, and ΔTg were as expected, and the adhesiveness measured by IFSS was sufficiently high. The results are shown in Table 2.
Step III: Production, molding and evaluation of unidirectional prepreg A prepreg was produced, molded and evaluated in the same manner as in Example 1. It was confirmed that the initial 0 ° tensile strength utilization rate and the compressive strength after impact were sufficiently high, and the decrease in the tensile strength utilization rate after 20 days was small. It was also confirmed that the volatile content during curing was sufficiently small. The results are shown in Table 2.

(Example 14)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
Step II: Step of attaching sizing agent to carbon fiber (A) As component (A-3) 55 parts by mass, (B1) As component (B-2) 22.5 parts by mass, (C) A sizing solution was prepared by dissolving 22.5 parts by mass of the components in DMF. As the component (C), a condensate of 2 mol of an EO2 mol adduct of bisphenol A, 1.5 mol of maleic acid and 0.5 mol of sebacic acid was used. Table 2 shows the epoxy equivalent of the sizing agent excluding the solution in the sizing solution. In the same manner as in Example 1, this sizing agent was applied to the carbon fiber surface-treated by the dipping method, and then heat treated at a temperature of 210 ° C. for 75 seconds to obtain a sizing agent-coated carbon fiber bundle. The adhesion amount of the sizing agent was adjusted to be 1.0 part by mass with respect to 100 parts by mass of the surface-treated carbon fiber. Subsequently, the epoxy equivalent of the sizing agent, the X-ray photoelectron spectroscopy measurement of the sizing agent surface, the interfacial shear strength (IFSS) of the sizing agent-coated carbon fiber, and ΔTg were measured. As a result, as shown in Table 2, it was confirmed that the epoxy equivalent of the sizing agent, the chemical composition of the sizing agent surface, and ΔTg were as expected. Moreover, it turned out that the adhesiveness measured by IFSS is also high enough.
Step III: Production, molding and evaluation of unidirectional prepreg A prepreg was produced, molded and evaluated in the same manner as in Example 1. It was confirmed that the initial 0 ° tensile strength utilization rate and the compressive strength after impact were sufficiently high, and the decrease in the tensile strength utilization rate after 20 days was small. It was also confirmed that the volatile content during curing was sufficiently small. The results are shown in Table 2.

(Example 15)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
Step II: Step of attaching sizing agent to carbon fiber (A) As component (A-3) 60 parts by mass, (B1) component (B-2) 40 parts by mass dissolved in DMF A sizing solution was prepared. Table 2 shows the epoxy equivalent of the sizing agent excluding the solution in the sizing solution. In the same manner as in Example 1, this sizing agent was applied to the carbon fiber surface-treated by the dipping method, and then heat treated at a temperature of 210 ° C. for 75 seconds to obtain a sizing agent-coated carbon fiber bundle. The adhesion amount of the sizing agent was adjusted to be 1.0 part by mass with respect to 100 parts by mass of the surface-treated carbon fiber. Subsequently, the epoxy equivalent of the sizing agent, the X-ray photoelectron spectroscopy measurement of the sizing agent surface, the interfacial shear strength (IFSS) of the sizing agent-coated carbon fiber, and ΔTg were measured. As a result, as shown in Table 2, it was confirmed that the epoxy equivalent of the sizing agent, the chemical composition of the sizing agent surface, and ΔTg were as expected. Moreover, it turned out that the adhesiveness measured by IFSS is also high enough.
Step III: Production, molding and evaluation of unidirectional prepreg A prepreg was produced, molded and evaluated in the same manner as in Example 1. It was confirmed that the initial 0 ° tensile strength utilization rate and the compressive strength after impact were sufficiently high, and the decrease in the tensile strength utilization rate after 20 days was small. It was also confirmed that the volatile content during curing was sufficiently small. The results are shown in Table 2.

(Examples 16 to 27)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
Step II: Step of attaching sizing agent to carbon fiber Sizing agent-coated carbon fiber was obtained in the same manner as in Example 2. Subsequently, the epoxy equivalent of the sizing agent, the X-ray photoelectron spectroscopy measurement of the sizing agent surface, the interfacial shear strength (IFSS) of the sizing agent-coated carbon fiber, and ΔTg were measured. The epoxy equivalent of the sizing agent, the chemical composition of the sizing agent surface, and ΔTg were as expected, and the adhesiveness measured by IFSS was at a level with no problem. The results are shown in Table 3.

Step III: Production, molding and evaluation of unidirectional prepreg As a thermosetting resin composition, epoxy resin (D), epoxy resin (E), thermoplastic resin (H), and thermoplastic resin shown in Table 3 After the particles (G) (and epoxy resins other than the epoxy resins (D) and (E) when blended) are blended in the proportions shown in Table 3 and dissolved, the latent curing agent (F And an epoxy resin composition for carbon fiber reinforced composite material.
The obtained epoxy resin composition was coated on a release paper with a resin basis weight of 52 g / m ² using a knife coater to prepare a resin film. This resin film is superposed on both sides of a sizing agent-coated carbon fiber (weight per unit area 190 g / m ² ) aligned in one direction, and a heat roll is used to heat and press at 100 ° C. and 1 atm. Was impregnated into carbon fiber coated with a sizing agent to obtain a prepreg. About the obtained prepreg, the prepreg volatile matter was measured. Also, using the obtained prepreg, 0 ° tensile strength measurement of carbon fiber reinforced composite material, 0 ° tensile test after long-term storage, glass transition temperature measurement, and compression strength measurement after impact of carbon fiber reinforced composite material did. The results are shown in Table 3. It was confirmed that the initial 0 ° tensile strength utilization rate and the compressive strength after impact were sufficiently high, and the decrease in the tensile strength utilization rate after 20 days was small. It was also confirmed that the volatile content during curing was sufficiently small.

(Examples 28 to 39)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
Step II: Step of attaching sizing agent to carbon fiber Sizing agent-coated carbon fiber was obtained in the same manner as in Example 2. Subsequently, the epoxy equivalent of the sizing agent, the X-ray photoelectron spectroscopy measurement of the sizing agent surface, the interfacial shear strength (IFSS) of the sizing agent-coated carbon fiber, and ΔTg were measured. The epoxy equivalent of the sizing agent, the chemical composition of the sizing agent surface, and ΔTg were as expected, and the adhesiveness measured by IFSS was at a level with no problem. The results are shown in Table 4.
Step III: Production, molding, and evaluation of unidirectional prepreg The epoxy resins (D) and (E), the thermoplastic resin particles (G), and the thermoplastic resin (H) shown in Table 4 are mixed in a mass ratio shown in Table 4. A prepreg was produced, molded, and evaluated in the same manner as in Example 1 except that the prepreg was used. The results are shown in Table 4. It was confirmed that the initial 0 ° tensile strength utilization rate and the compressive strength after impact were sufficiently high, and the decrease in the tensile strength utilization rate after 20 days was small. It was also confirmed that the volatile content during curing was sufficiently small.

(Comparative Examples 1-3)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
Step II: Step of attaching sizing agent to carbon fiber Sizing agent-coated carbon fibers were obtained in the same manner as in Example 2 except that the mass ratio shown in Table 5 was used as the sizing agent. Subsequently, the epoxy equivalent of the sizing agent, the X-ray photoelectron spectroscopy measurement of the sizing agent surface, the interfacial shear strength (IFSS) of the sizing agent-coated carbon fiber, and ΔTg were measured. Component of binding energy (284.6 eV) attributed to (a) CHx, C—C, C = C of C _1s inner shell spectrum measured by X-ray photoelectron spectroscopy on the sizing agent surface at a photoelectron escape angle of 15 ° The ratio (a) / (b) of the height (cps) of the component (b) and the height (cps) of the component of the binding energy (286.1 eV) attributed to C—O is greater than 0.90. Was out of range. Moreover, it turned out that the adhesiveness measured by IFSS is low.
Step III: Production, molding and evaluation of unidirectional prepreg A prepreg was produced, molded and evaluated in the same manner as in Example 1. Although the decrease rate of the tensile strength after 20 days was small, it was found that the initial 0 ° tensile strength utilization rate and the compressive strength after impact were low.

(Comparative Example 4)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
Step II: Step of attaching sizing agent to carbon fiber Sizing agent-coated carbon fibers were obtained in the same manner as in Example 2 except that the mass ratio shown in Table 5 was used as the sizing agent. Subsequently, the epoxy equivalent of the sizing agent, the X-ray photoelectron spectroscopy measurement of the sizing agent surface, the interfacial shear strength (IFSS) of the sizing agent-coated carbon fiber, and ΔTg were measured. Component of (a) CHx, C—C, C = C binding energy (284.6 eV) of C _1s core spectrum measured by X-ray photoelectron spectroscopy on the sizing agent surface at a photoelectron escape angle of 15 ° The ratio (a) / (b) of the height (cps) of the component (b) and the height (cps) of the component of the binding energy (286.1 eV) attributed to C—O is smaller than 0.50. Was out of range. It was found that the adhesion measured by IFSS was sufficiently high.
Step III: Production, molding and evaluation of unidirectional prepreg A prepreg was produced, molded and evaluated in the same manner as in Example 1. Although the initial utilization rate of 0 ° tensile strength and compressive strength after impact were good, it was found that the decrease rate of 0 ° tensile strength after 20 days was large.

(Comparative Examples 5 and 6)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
Step II: A step of attaching a sizing agent to carbon fiber As in the case of Example 2, using only the aliphatic epoxy compound (A) as the epoxy compound of the sizing agent, without using the aromatic epoxy compound (B1). The sizing agent-coated carbon fiber was obtained by the method described above. Subsequently, the epoxy equivalent of the sizing agent, the X-ray photoelectron spectroscopy measurement of the sizing agent surface, the interfacial shear strength (IFSS) of the sizing agent-coated carbon fiber, and ΔTg were measured. Component of (a) CHx, C—C, C = C binding energy (284.6 eV) of C _1s core spectrum measured by X-ray photoelectron spectroscopy on the sizing agent surface at a photoelectron escape angle of 15 ° The ratio (a) / (b) of the height (cps) of the component (b) and the height (cps) of the component of the binding energy (286.1 eV) attributed to C—O is smaller than 0.50. Was out of range. Moreover, it turned out that the adhesiveness measured by IFSS is high enough.
Step III: Production, molding and evaluation of unidirectional prepreg A prepreg was produced, molded and evaluated in the same manner as in Example 1. Although the initial 0 ° tensile strength utilization rate and compressive strength after impact were high, it was found that the rate of decrease in tensile strength after 20 days was large.

(Comparative Example 7)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
Step II: A step of attaching a sizing agent to carbon fiber As in the case of Example 2, using only the aromatic epoxy compound (B1) without using the aliphatic epoxy compound (A) as the epoxy compound of the sizing agent The sizing agent-coated carbon fiber was obtained by the method described above. Subsequently, the epoxy equivalent of the sizing agent, the X-ray photoelectron spectroscopy measurement of the sizing agent surface, the interfacial shear strength (IFSS) of the sizing agent-coated carbon fiber, and ΔTg were measured. Component of binding energy (284.6 eV) attributed to (a) CHx, C—C, C = C of C _1s inner shell spectrum measured by X-ray photoelectron spectroscopy on the sizing agent surface at a photoelectron escape angle of 15 ° The ratio (a) / (b) of the height (cps) of the component (b) and the height (cps) of the component of the binding energy (286.1 eV) attributed to C—O is greater than 0.90. Was out of range. Moreover, it turned out that the adhesiveness measured by IFSS is low.
Step III: Production, molding and evaluation of unidirectional prepreg A prepreg was produced, molded and evaluated in the same manner as in Example 1. Although the decrease rate of the tensile strength after 20 days was small, the initial tensile strength utilization rate and the compressive strength after impact were not sufficient values.

(Comparative Example 8)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
Step II: Step of attaching sizing agent to carbon fiber Sizing agent-coated carbon fiber was obtained in the same manner as in Example 2. Subsequently, the epoxy equivalent of the sizing agent, the X-ray photoelectron spectroscopy measurement of the sizing agent surface, the interfacial shear strength (IFSS) of the sizing agent-coated carbon fiber, and ΔTg were measured. The epoxy equivalent of the sizing agent, the chemical composition on the surface of the sizing agent, and ΔTg were as expected, and the adhesion measured by IFSS was at a level with no problem. The results are shown in Table 5.
-Step III: Production, molding and evaluation of unidirectional prepreg As a thermosetting resin composition, epoxy resin (D) or the like is used without using epoxy resin (E), and the same method as in Example 1. When the prepreg was produced, molded and evaluated, the surface of the carbon fiber reinforced composite material was cracked.

(Comparative Example 9)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
Step II: Step of attaching sizing agent to carbon fiber Sizing agent-coated carbon fiber was obtained in the same manner as in Example 2. Subsequently, the epoxy equivalent of the sizing agent, the X-ray photoelectron spectroscopy measurement of the sizing agent surface, the interfacial shear strength (IFSS) of the sizing agent-coated carbon fiber, and ΔTg were measured. The epoxy equivalent of the sizing agent, the chemical composition of the sizing agent surface, and ΔTg were also as expected, and the adhesiveness measured by IFSS was at a level with no problem. The results are shown in Table 5.
-Step III: Production, molding, and evaluation of unidirectional prepreg As a thermosetting resin composition, using epoxy resin (E) or the like without using epoxy resin (D), the same method as in Example 1 was used. A prepreg was produced, molded, and evaluated. Although the compressive strength after impact was good and the rate of decrease in tensile strength after 20 days was small, the initial tensile strength utilization rate was not a sufficient value.

(Comparative Examples 10-12)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
Step II: Step of attaching sizing agent to carbon fiber Sizing agent-coated carbon fiber was obtained in the same manner as in Example 2. Subsequently, the epoxy equivalent of the sizing agent, the X-ray photoelectron spectroscopy measurement of the sizing agent surface, the interfacial shear strength (IFSS) of the sizing agent-coated carbon fiber, and ΔTg were measured. The epoxy equivalent of the sizing agent, the chemical composition on the surface of the sizing agent, and ΔTg were as expected, and the adhesion measured by IFSS was at a level with no problem. The results are shown in Table 5.
-Step III: Preparation, molding and evaluation of unidirectional prepreg As a thermosetting resin composition, the epoxy resins (D) and (E) shown in Table 5 were blended at a mass ratio shown in Table 5, A prepreg was produced, molded, and evaluated in the same manner as in Example 1. In Comparative Examples 10 and 11, although the rate of decrease in tensile strength after 20 days was small, the initial tensile strength utilization rate and compressive strength after impact were not sufficient values. In Comparative Example 12, the initial 0 ° tensile strength utilization rate and the compressive strength after impact were high, and the decrease in the tensile strength utilization rate after 20 days was not large, but it was confirmed that the volatile matter was very large.

(Example 40)
2 g of the sizing agent-coated carbon fiber obtained in Example 1 was immersed in 50 ml of acetone, and subjected to ultrasonic cleaning for 30 minutes three times. Subsequently, the substrate was immersed in 50 ml of methanol, subjected to ultrasonic cleaning for 30 minutes once and dried. Table 6 shows the amount of sizing agent adhering remaining after washing.
Subsequently, the sizing agent surface of the sizing agent-coated carbon fiber before washing, and the sizing agent-coated carbon fiber sizing agent surface obtained by washing were assigned to (b) CO component by X-ray photoelectron spectroscopy at 400 eV. The peak height of the binding energy of 286.1 eV and the height (cps) of the component of the binding energy of 284.6 eV attributed to (a) CHx, C-C, C = C are obtained, and (I) before washing (A) / (b) on the sizing agent surface of the sizing agent-coated carbon fiber, (II) (a) / (b) on the sizing agent surface of the sizing agent-coated carbon fiber after washing. (I) and (II) / (I) were as shown in Table 6.

(Examples 41 to 44)
Similar to Example 40, C was obtained by X-ray photoelectron spectroscopy using 400 eV X-rays before and after cleaning using the sizing agent-coated carbon fibers obtained in Example 2, Example 6, Example 10, and Example 13. The height (cps) of the component of the bond energy (284.6 eV) attributed to (a) CHx, C—C, C = C in the _1s inner-shell spectrum, and (b) the bond energy attributed to C—O The ratio (a) / (b) to the height (cps) of the component (286.1 eV) was determined. The results are shown in Table 6.

(Comparative Example 13)
(A) CHx, C- of the C _1s inner shell spectrum by X-ray photoelectron spectroscopy using 400 eV X-rays before and after cleaning using the sizing agent-coated carbon fiber obtained in Comparative Example 5 as in Example 40. The height (cps) of the component of the bond energy (284.6 eV) attributed to C, C = C, and the height (cps) of the component of the bond energy (286.1 eV) attributed to (B) C—O. ) And the ratio (a) / (b). The results are shown in Table 6, and it was found that (II / I) was large and no grading structure was obtained in the sizing agent.

(Comparative Example 14)
(A) CHx, C- of the C _1s inner shell spectrum by X-ray photoelectron spectroscopy using 400 eV X-rays before and after washing using the sizing agent-coated carbon fiber obtained in Comparative Example 7 as in Example 40. The height (cps) of the component of the bond energy (284.6 eV) attributed to C, C = C, and the height (cps) of the component of the bond energy (286.1 eV) attributed to (B) C—O. ) And the ratio (a) / (b). The results are shown in Table 6, and it was found that (II / I) was large and no grading structure was obtained in the sizing agent.

  The prepreg of the present invention has excellent adhesion between carbon fibers and a matrix resin, and has long-term storage stability and high-order processability, and therefore is suitable for processing into woven fabrics and prepregs. Further, since the carbon fiber reinforced composite material obtained from the carbon fiber and the matrix resin according to the present invention is lightweight and excellent in strength and elastic modulus, it is an aircraft member, a spacecraft member, an automobile member, a ship member, a civil engineering building material, and It can be suitably used in many fields such as sports equipment.

Claims (25)

A prepreg formed by impregnating a sizing agent-coated carbon fiber coated with a sizing agent with a thermosetting resin composition,
The sizing agent contains at least an aromatic epoxy compound (B1) as the aliphatic epoxy compound (A) and the aromatic compound (B),
The sizing agent-coated carbon fiber has a C _1s core spectrum measured on the surface of the sizing agent coated on the carbon fiber by X-ray photoelectron spectroscopy using AlKα _1,2 as an X-ray source at a photoelectron escape angle of 15 °. (A) the height (cps) of the component of the binding energy (284.6 eV) attributed to CHx, C—C, C = C, and (b) the binding energy (286.1 eV) attributed to C—O. The ratio (a) / (b) to the height (cps) of the component is 0.50 to 0.90,
The thermosetting resin composition has at least the following component (D): two or more ring structures having four or more membered rings, and one amine-type glycidyl group or ether-type glycidyl group directly bonded to the ring structure. One or two epoxy resins,
(E): an epoxy resin having three or more functional groups,
(F): latent curing agent,
The epoxy resin composition comprises 5 to 60% by mass of the epoxy resin (D) and 100% by mass of the epoxy resin (E) with respect to 100% by mass of the total amount of the epoxy resin blended. A prepreg containing 40 to 80% by mass.   The said epoxy resin composition contains 10-40 mass% of epoxy resins (D) which have one amine type glycidyl group or ether type glycidyl group directly connected to the ring structure with respect to 100 mass% of total amount of the epoxy resin blended. The prepreg according to claim 1. The epoxy resin (D) is represented by the following general formula (1)

(In formula (1), R ¹ and R ² are each an aliphatic hydrocarbon group having 1 to 4 carbon atoms, an alicyclic hydrocarbon group having 3 to 6 carbon atoms, and an aromatic hydrocarbon having 6 to 10 carbon atoms. Represents at least one selected from the group consisting of a group, a halogen atom, an acyl group, a trifluoromethyl group, and a nitro group, n is an integer of 0 to 4, and m is an integer of 0 to 5. R ¹ and R ^{When two} or more are present, they may be the same or different, and X is —O—, —S—, —CO—, —C (═O) O—, —SO ₂ —, —C. (= O) represents one selected from NH-), and the epoxy resin composition contains 25 epoxy resin (D) with respect to 100% by mass of the total amount of the epoxy resin blended. The prepreg according to claim 1, comprising ˜50 mass%.   The prepreg according to claim 3, wherein X in the general formula (1) is —O—. The epoxy resin (E) has the following general formula (2)

(In the formula (2), R ^{3 to} R ⁶ were selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group having 1 to 4 carbon atoms, an alicyclic hydrocarbon group having 4 or less carbon atoms, and a halogen atom. Y represents at least one, Y is selected from —CH ₂ —, —O—, —S—, —CO—, —C (═O) O—, —SO ₂ —, —C (═O) NH—. The prepreg according to claim 1, wherein the prepreg has a structure represented by: The prepreg according to claim 5, wherein Y in the general formula (2) is —CH ₂ —. The epoxy resin (E) has a structure represented by the general formula (2) in which Y is —CH ₂ —, and an epoxy equivalent is 100 to 115 g / eq. The prepreg according to claim 6, wherein:   The prepreg according to any one of claims 1 to 7, wherein the latent curing agent (F) is an aromatic amine curing agent (F1).   The prepreg according to claim 8, wherein the aromatic amine curing agent (F1) contains a diphenyl sulfone skeleton.   The prepreg according to claim 1, wherein the thermosetting resin composition includes thermoplastic resin particles (G).   The thermoplastic resin particle (G) is characterized in that 90 to 100% by mass of the thermoplastic resin particle (G) is localized in a range of 20% from both sides in the thickness direction of the prepreg. The prepreg described in 1.   The said thermosetting resin composition contains the thermoplastic resin (H) which melt | dissolves in the said epoxy resin (D) or the said epoxy resin (E), It is any one of Claims 1-11 characterized by the above-mentioned. Prepreg.   The prepreg according to claim 12, wherein the thermoplastic resin (H) is polyethersulfone.   14. The prepreg according to claim 13, wherein the average molecular weight of the polyethersulfone is 15000 to 30000 g / mol.   The epoxy equivalent of the applied sizing agent is 350 to 550 g / eq. The prepreg according to claim 1, wherein the prepreg is a prepreg.   The sizing agent contains at least 35 to 65% by mass of the aliphatic epoxy compound (A) and 35 to 60% by mass of the aromatic compound (B) based on the total amount of the sizing agent excluding the solvent. The prepreg according to any one of claims 1 to 15.   The mass ratio of the aliphatic epoxy compound (A) and the aromatic epoxy compound (B1) is 52/48 to 80/20, according to any one of claims 1 to 16. Prepreg.   18. The aliphatic epoxy compound (A) is a polyether type polyepoxy compound and / or a polyol type polyepoxy compound having two or more epoxy groups in a molecule. The prepreg according to one.   The aliphatic epoxy compound (A) is ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, polypropylene glycol, trimethylene glycol, 1, 2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, polybutylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1, Select from 4-cyclohexanedimethanol, glycerol, diglycerol, polyglycerol, trimethylolpropane, pentaerythritol, sorbitol, and arabitol A compound, wherein the glycidyl ether type epoxy compound obtained by reaction between epichlorohydrin, prepreg according to claim 18.   The prepreg according to any one of claims 1 to 19, wherein the aromatic epoxy compound (B1) is a bisphenol A type epoxy compound or a bisphenol F type epoxy compound.   The sizing agent contains 2 to 35% by mass of an ester compound (C) having no epoxy group in the molecule, based on the total amount of the sizing agent excluding the solvent. The prepreg as described in one. The sizing agent-coated carbon fiber is obtained by measuring the sizing agent-coated carbon fiber by (a) CHx, C of C _1s inner shell spectrum measured at an electron escape angle of 55 ° by X-ray photoelectron spectroscopy using 400 eV X-rays. The height (cps) of the component of the bond energy (284.6 eV) attributed to -C, C = C and the height of the component of the bond energy (286.1 eV) attributed to (b) C-O ( The value of (I) and (II) calculated | required from ratio (a) / (b) with cps) satisfy | fills the relationship of (III), The one of Claims 1-21 The prepreg according to one.
(I) Value of (a) / (b) on the surface of the sizing agent-coated carbon fiber before sonication (II) Sizing agent adhesion by sonicating the sizing agent-coated carbon fiber in an acetone solvent (A) / (b) value (III) 0.50 ≦ (I) ≦ 0.90 and 0.60 <on the surface of the sizing agent-coated carbon fiber washed to 0.09 to 0.20% by mass (II) / (I) <1.0   The sizing agent is a mixture of a water emulsion liquid containing at least an aromatic epoxy compound (B1) and a composition containing at least an aliphatic epoxy compound (A). The prepreg as described in any one.   The sizing agent and the aromatic amine curing agent (F1) are prepared by mixing the sizing agent and the aromatic amine curing agent (F1) at a ratio of amine equivalent / epoxy equivalent of 0.9, 25 ° C., 60 ° C. 10. The prepreg according to claim 8, wherein the prepreg is used in a combination that raises the glass transition point when stored for 20 days in an atmosphere of% RH at 25 ° C. or less.   A carbon fiber reinforced composite material obtained by molding the prepreg according to any one of claims 1 to 24.