JP2007126637A - Resin composition, cured product of resin, prepreg and fiber-reinforced composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fiber-reinforced composite material having excellent various mechanical properties and to provide a resin composition and prepreg for obtaining the composite material without deteriorating the productivity. <P>SOLUTION: The resin composition comprises constituent elements of [A] a thermosetting resin, [B] a curing agent and [C] carbon nano-fibers. The aggregated size of the constituent element [C] in a cured product thereof is ≤10 μm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fiber-reinforced composite material excellent in various mechanical properties, a resin composition for obtaining the same, and a prepreg.

Fiber reinforced composite materials composed of reinforced fibers and matrix resins are widely used for sports and leisure applications, aerospace applications, general industrial applications and the like because of their excellent mechanical properties.
In such applications, carbon fibers, glass fibers, and aramid fibers are mainly used as reinforcing fibers. Among them, carbon fibers that are excellent in specific strength and specific elastic modulus and that can provide a high-performance composite material are often used.

  In the field of carbon fiber reinforced composite materials, materials that have been actively developed in recent years are materials containing carbon nanofibers. It has been found that the high tensile elastic modulus and nanosize effect of carbon nanofibers can improve the resin elastic modulus and the fiber direction compressive strength of the fiber-reinforced composite material (see Patent Documents 1 and 2). However, the present inventors examined a fiber reinforced composite material containing a specific carbon nanofiber, and due to the low affinity between the carbon nanofiber and the matrix resin, especially the in-plane shear strength. It has become apparent that the adhesive properties are adversely affected, and its use has been limited.

  On the other hand, attempts have been made to increase the affinity between the carbon nanofibers and the matrix resin. For example, in Patent Document 3, conductivity and elastic modulus are improved by blending carbon nanotubes having an acid content ratio of 2% or more with respect to carbon on the outer surface into a resin together with chopped carbon fibers. In this case, although the fiber direction compressive strength was improved, the in-plane shear strength was not improved.

On the other hand, the problem is the fluidity lowering effect that carbon nanofibers bring to the matrix resin, poor handling of the resin composition in prepreg production, poor impregnation of reinforcing fibers, poor curing in the molding process, There has been a problem that the fiber alignment is apt to be disturbed due to a decrease in the resin flow. These are greatly related to the productivity of the fiber reinforced composite material such as the production line speed of the material and the molding workability, and also affect the mechanical properties of the fiber reinforced composite material described above. On the other hand, in Patent Document 4, it is described that dispersibility and moldability in a synthetic resin are improved by adding carbon nanofibers having a diameter of 5 to 200 nm and a length of 50 nm to 10 μm to a golf shaft. In reality, however, carbon nanofibers are considerably cut in the dispersion process, and it is difficult to stably obtain sufficient mechanical properties.
JP 2003-201388 A JP 2004-3000221 A JP 2003-238816 A JP 2003-188191 A

  In the present invention, for the purpose of obtaining a prepreg that is lightweight and exhibits good mechanical properties of a fiber-reinforced composite material, a highly rigid and highly adhesive matrix resin is used, and the fiber direction compressive strength and in-plane shear strength are obtained. An object of the present invention is to provide a fiber-reinforced composite material having an excellent balance without reducing productivity.

In order to achieve the above object, the present invention has the following components. That is, a resin composition comprising the following components [A], [B] and [C], wherein the maximum aggregation size of the component [C] in the cured product is 10 μm or less It is a composition.
[A] Thermosetting resin [B] Curing agent [C] Carbon nanofiber Further, the prepreg in the present invention is characterized by comprising such a resin composition and a reinforcing fiber. The fiber-reinforced composite material in the invention is characterized by comprising a cured resin obtained by heat-curing such a resin composition and reinforcing fibers.

  ADVANTAGE OF THE INVENTION According to this invention, the fiber reinforced composite material excellent in the balance of fiber direction compressive strength and in-plane shear strength can be obtained, without reducing productivity.

  The present inventors have intensively studied the above-mentioned problems, and the main factor that hinders the improvement of the properties of the cured resin containing carbon nanofibers and the fiber-reinforced composite material is the stress distribution caused by carbon nanofiber reaggregation during molding. As a result of further investigation to identify the occurrence of unevenness and disturbance of the alignment of the reinforcing fibers and to avoid them, the present invention has been achieved.

  The thermosetting resin in the present invention is not particularly limited, and any thermosetting resin can be suitably used. Specifically, unsaturated polyester resins, vinyl ester resins, epoxy resins, phenol resins, urea resins, melamine resins, polyimides, copolymers thereof, modified products, and resins obtained by blending two or more types are used. be able to. Among these, an epoxy resin having an excellent balance of heat resistance, mechanical properties, and adhesiveness can be preferably used.

  The epoxy resin is not particularly limited, and any epoxy resin can be suitably used. Specifically, it is obtained by oxidizing a glycidyl ether obtained from polyol, a glycidyl amine obtained from an amine having a plurality of active hydrogens, a glycidyl ester obtained from a polycarboxylic acid, or a compound having a plurality of double bonds in the molecule. Polyepoxides that can be used are used.

  Specific examples of glycidyl ether include the following.

  First, bisphenol A type epoxy resin obtained from bisphenol A, bisphenol F type epoxy resin obtained from bisphenol F, bisphenol S type epoxy resin obtained from bisphenol S, tetrabromobisphenol A type epoxy resin obtained from tetrabromobisphenol A, etc. It is a bisphenol type epoxy resin. Commercially available bisphenol A type epoxy resins include “Epicoat (registered trademark)” 825, “Epicoat” 828, “Epicoat” 834, “Epicoat” 1001, “Epicoat” 1002, “Epicoat” 1003, “Epicoat” “1004”, “Epicoat” 1007, “Epicoat” 1009, “Epicoat” 1010 (above, manufactured by Japan Epoxy Resin Co., Ltd.), “Epototo (registered trademark, the same applies hereinafter)” YD-128 “Epototo” YD-011, “ "Epototo" YD-014, "Epototo" YD-017, "Epototo" YD-019, "Epototo" YD-022, (above, manufactured by Tohto Kasei Co., Ltd.), "Epicron (registered trademark, the same shall apply hereinafter)" 840, “Epicron” 850, “Epicron” 830, “Epicron” 1050, “ “Epicron” 3050, “Epicron” HM-101 (manufactured by Dainippon Ink & Chemicals, Inc.), “Sumiepoxy (registered trademark, the same applies hereinafter)” ELA-128 (manufactured by Sumitomo Chemical Co., Ltd.), DER331 (Dow Chemical) For example). Commercially available bisphenol F type epoxy resins include “Epicoat” 806, “Epicoat” 807, “Epicoat” E4002P, “Epicoat” E4003P, “Epicoat” E4004P, “Epicoat” E4007P, “Epicoat” E4009P, “Epicoat” E4010P (Above, manufactured by Japan Epoxy Resin Co., Ltd.), “Epiclon” 830 (produced by Dainippon Ink & Chemicals, Inc.), “Epototo” YDF-2001, “Epototo” YDF-2004 (above, manufactured by Toto Kasei Co., Ltd.) ) And the like. Commercially available products of bisphenol S type epoxy resin include “Denacol (registered trademark)” EX-251 (manufactured by Nagase Kasei Kogyo Co., Ltd.), “Epicron” EXA-1514 (manufactured by Dainippon Ink & Chemicals, Inc.) ). Commercially available tetrabromobisphenol A type epoxy resins include “Epicoat” 5050 (manufactured by Japan Epoxy Resin Co., Ltd.), “Epicron” 152 (manufactured by Dainippon Ink & Chemicals, Inc.), “Sumiepoxy” ESB-400T ( Sumitomo Chemical Co., Ltd.) and “Epototo” YBD-360 (manufactured by Toto Kasei Co., Ltd.).

  In addition, commercially available products of novolak type epoxy resins, which are glycidyl ethers of novolac obtained from phenol derivatives such as phenol, alkylphenol and halogenated phenol, are “Epicoat” 152, “Epicoat” 154, “Epicoat” 157 (above, Japan). Epoxy Resin Co., Ltd.), DER 438 (Dow Chemical Co., Ltd.), “Araldite (registered trademark, the same shall apply hereinafter)” EPN1138 (Ciba), “Araldite” EPN1139 (Ciba), “Epototo” YCPN-702 ( Toto Kasei Co., Ltd.) and BREN-105 (Nippon Kayaku Co., Ltd.).

  In addition, “Denacol” EX-201 (manufactured by Nagase Kasei Kogyo Co., Ltd.), which is resorcin diglycidyl ether, “Denacol” EX-203 (manufactured by Nagase Kasei Kogyo Co., Ltd.), hydroquinone diglycidyl ether, Tris ( TACTIX 742 which is triglycidyl ether of p-hydroxyphenyl) methane (manufactured by Dow Chemical Co.), “Epicoat” 1031S which is tetraglycidyl ether of tetrakis (p-hydroxyphenyl) ethane (Japan Epoxy Resin Co., Ltd.), Examples thereof include “denacol” EX-314 (manufactured by Nagase Kasei Kogyo Co., Ltd.) which is triglycidyl ether, “denacol” EX-411 (manufactured by Nagase Kasei Kogyo Co., Ltd.) which is a tetraglycidyl ether of pentaerythritol. .

  Specific examples of glycidylamine include diglycidylaniline, “Sumiepoxy” ELM434 (manufactured by Sumitomo Chemical Co., Ltd.) which is tetraglycidyldiaminodiphenylmethane, and TETRAD (registered trademark, hereinafter the same) which is tetraglycidyl-m-xylylenediamine. -X (Mitsubishi Gas Chemical Co., Ltd.) etc. can be mentioned, It can use in the range which does not impair resin elongation remarkably.

  Furthermore, as an epoxy resin having both structures of glycidyl ether and glycidyl amine, “Sumiepoxy” ELM120 (manufactured by Sumitomo Chemical Co., Ltd.) that is triglycidyl-m-aminophenol and “triglycidyl-p-aminophenol” Araldite “MY0510 (manufactured by Ciba Geigy Co., Ltd.) can be mentioned, and it can be used as long as the resin elongation is not significantly impaired.

  Specific examples of the glycidyl ester include phthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, and dimer acid diglycidyl ester.

  Furthermore, triglycidyl isocyanurate can be mentioned as an epoxy resin having a glycidyl group other than these.

  Examples of the epoxy resin obtained by oxidizing a compound having a plurality of double bonds in the molecule include an epoxy resin having an epoxycyclohexane ring. Specific examples thereof include ERL-4206, ERL-4221 of Union Carbide Corporation, And ERL-4234. Furthermore, epoxidized soybean oil can also be mentioned.

  Among these epoxy resins, it is preferable to include one or more epoxy resins having at least one skeleton selected from biphenyl, naphthalene, fluorene, dicyclopentadiene, and an oxazolidone ring. By including one or more of such epoxy resins, the mechanical properties are remarkably improved by the synergistic effect with the carbon nanofibers, and the heat resistance of the cured resin can also be improved.

  Examples of commercially available epoxy resins having a biphenyl skeleton include “Epicoat” YX4000, YX4000H, YL6121 (above, Japan Epoxy Resin Co., Ltd.), NC3000, NC3000H (above, Nippon Kayaku Co., Ltd.). be able to.

  Commercially available epoxy resins having a naphthalene skeleton include “Epiclon” HP4032, HP4032D, H4032H, EXA4750, EXA4700, EXA4701, (manufactured by Dainippon Ink Industries, Ltd.), NC7000L, NC7300L (Nippon Kayaku) Is mentioned.

  Commercially available epoxy resins having a fluorene skeleton include “Epon (registered trademark)”, HPT Resin 1079 (manufactured by Shell), “Ogsol (registered trademark, same hereinafter)” PG, EG (above, Nagase Chem) Tex Co., Ltd.).

  Commercially available epoxy resins having a dicyclopentadiene skeleton include “Epiclon” HP7200L, HP7200, HP7200H, HP7200HH (above, manufactured by Dainippon Ink & Chemicals, Inc.), XD-1000-L, XD-1000-2L ( As described above, Nippon Kayaku Co., Ltd.), “Tactix (registered trademark, the same shall apply hereinafter)” 556 (manufactured by Huntsman Inc.) and the like can be mentioned.

  Examples of commercially available epoxy resins having an oxazolidone ring skeleton include “Araldite” AER4152, XAC4151, and the like, manufactured by Asahi Kasei Epoxy Corporation.

  Among such epoxy resins, an epoxy resin having a skeleton selected from biphenyl, dicyclopentadiene type, and oxazolidone ring has a large effect of improving the in-plane shear strength when combined with the carbon nanofiber as the constituent element [C]. Is preferable. In particular, an epoxy resin having a biphenyl type or dicyclopentadiene type skeleton is preferable because the effect of improving the in-plane shear strength is great.

  In the component [A] in the present invention, an epoxy resin having at least one skeleton selected from biphenyl, naphthalene, fluorene, dicyclopentadiene, and an oxazolidone ring is 5 to 50% by weight, preferably 7 to 45% by weight. More preferably, it is 10 to 40% by weight. If the content of these epoxy resins is too small, the effect of improving the torsional strength and heat resistance is small. Conversely, if the content is too large, the impregnation property of the resin to the reinforcing fibers during prepreg production may be lowered.

  Among these epoxy resins, the solid epoxy resin is preferably 10 to 70% by weight of the constituent element [A] in order to improve the affinity between the constituent element [C] and the resin. The solid epoxy resin is an epoxy resin that is solid at room temperature, for example, 25 ° C., and among the above commercially available epoxy resins, the following are applicable. That is, “Epicoat” 1001, 1002, 1004, 1007, 1009, 1010, “Epotot” YD-011, 014, 017, 019, 022, “Epicoat” 4002P, 4003P, 4004P, 4007P, 4009P, 4010P, “Epotot” YDF-2001, 2004, “Denacol” EX-251, “Epicron” EXA-1514, “Epicoat” 5050 “Epicoat” 157, “Tactix” 742, “Epicoat” 1031S, “Epicoat” YX4000, YX4000H, YL6121, NC3000 , NC3000H, "Epiclon" HP4032, HP4032D, H4032H, EXA4750, EXA4700, EXA4701, NC7000L, NC7300L, "Epon" H T Resin 1079, "OGSOL" PG, EG, "Epichlone" HP7200L, HP7200, HP7200H, HP7200HH, XD-1000-L, XD-1000-2L, "Tactix" 556, "Araldite" AER4152, is XAC4151.

  The curing agent in the present invention brings about a curing reaction in the presence of a thermosetting resin, and is not only a general curing agent but also an initiator, a catalyst, a curing accelerator, a curing aid, and a combination thereof. Is included. Specifically, as the curing agent, activities such as 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone, m-phenylenediamine, and m-xylylenediamine are used. Aromatic amines with hydrogen, diethylenetriamine, triethylenetetramine, isophoronediamine, bis (aminomethyl) norbornane, bis (4-aminocyclohexyl) methane, aliphatic amines with active hydrogen such as dimer acid ester of polyethyleneimine, these Modified amines obtained by reacting an amine having active hydrogen with an epoxy compound, acrylonitrile, a compound such as phenol and formaldehyde, thiourea, dimethylaniline, dimethylbenzylamine, 2,4,6-tris (dimethylaminomethyl) E) Tertiary amines such as phenol and 1-substituted imidazole that do not have active hydrogen, dicyandiamide, tetramethylguanidine, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyl nadic acid Carboxylic anhydrides such as anhydrides, polycarboxylic acid hydrazides such as adipic acid hydrazide and naphthalenedicarboxylic acid hydrazide, polyphenol compounds such as novolak resins, polymercaptans such as esters of thioglycolic acid and polyols, boron trifluoride Examples include Lewis acid complexes such as ethylamine complexes and aromatic sulfonium salts, but are not particularly limited thereto. In particular, it is preferable to contain at least 2 to 8 parts by weight of dicyandiamide with respect to 100 parts by weight of the component [A] because the storage stability of prepreg tackiness and draping properties is excellent.

  These curing agents can be appropriately combined with a curing aid in order to increase the curing activity. Preferred examples include dicyandiamide, 3-phenyl-1,1-dimethylurea, 3- (3,4-dichlorophenyl) -1,1-dimethylurea (DCMU), 3- (3-chloro-4-methylphenyl). ) Examples of combining urea derivatives such as 1,1-dimethylurea and 2,4-bis (3,3-dimethylureido) toluene as curing aids, curing tertiary amines on carboxylic anhydrides and novolak resins An example of combination as an auxiliary agent is given. The compound used as a curing aid is preferably a compound having the ability to cure an epoxy resin alone.

  The resin composition of the present invention preferably contains at least one of a thermoplastic resin and an elastomer in order to improve the affinity between the component [C] and the resin. When the total amount of the thermoplastic resin and the elastomer is 1 to 30 parts by weight, preferably 5 to 15 parts by weight with respect to 100 parts by weight of the component [A], for example, oxygen atoms and carbon by elemental analysis as described later Even if the carbon nanofiber has a small atomic ratio (O / C) of atoms, the carbon nanofiber can be prevented from reaggregating, and the carbon nanofiber is aggregated in the cured product obtained by curing the resin composition. Various types of carbon nanofibers can be used, for example, the size can be reduced.

  When a thermoplastic resin is used in the present invention, the thermoplastic resin is preferably one that is soluble in the component [A]. Moreover, even if it is insoluble in the component [A], it is preferably pulverized and finely divided, and can be blended.

  Specifically, polyamide, polyamideimide, polyaramide, polyarylene oxide, polyarylate, polyimide, polyethylene terephthalate, polyetherimide, polyether terephthalate, polyetherimide, polyetheretherketone, polyethersulfone, polycarbonate, polycarbonate, poly Vinyl acetate, polystyrene, polysulfone, polyvinyl acetal, polyvinyl formal, polyphenylene oxide, polyphenylene sulfide, polypropylene, polybenzimidazole, polymethyl methacrylate and the like are used. In particular, when an epoxy resin is used as the constituent element [A], these thermoplastic resins are preferably used.

  Among them, a thermoplastic resin having a hydrogen bondable functional group in the molecule is preferably used for reasons such as compatibility with an epoxy resin and no adverse effects on physical properties of the fiber reinforced composite material. Examples of the hydrogen bonding functional group include an alcoholic hydroxyl group, an amide bond, and a sulfonyl group. Examples of the thermoplastic resin having an alcoholic hydroxyl group include polyvinyl acetal resins such as polyvinyl formal and polyvinyl butyral, polyvinyl alcohol, phenoxy resin, and thermoplastic resins having an amide bond as polyamide, polyimide, and thermoplastic resins having a sulfonyl group. May include polysulfone. Polyamide, polyimide and polysulfone may have a functional group such as an ether bond and a carbonyl group in the main chain. The polyamide may have a substituent on the nitrogen atom of the amide group.

  Examples of commercially available thermoplastic resins that are soluble in epoxy resins and have hydrogen-bonding functional groups include, as polyvinyl acetal resins, “denkabutyral (registered trademark, the same applies hereinafter)” and “denka formal (registered trademark, the same applies hereinafter). "(Electric Chemical Co., Ltd.)", "Vinylec (registered trademark, the same applies below)" (Chisso Co., Ltd.), and phenoxy resin as "UCAR (registered trademark, same applies hereinafter)" PKHP (made by Union Carbide) , “Macromelt (registered trademark, the same applies hereinafter)” (manufactured by Henkel Hakusui Co., Ltd.), “Amilan (registered trademark, same applies hereinafter)” CM4000 (manufactured by Toray Industries, Inc.), and “Ultem (registered trademark, The same shall apply hereinafter) ”(manufactured by General Electric),“ Matrimid (registered trademark, the same shall apply hereinafter) ”5218 (manufactured by Ciba), polysulfone and "Victrex (registered trademark, the same applies hereinafter)" (Mitsui Toatsu Chemical Co., Ltd.), "UDEL (registered trademark, same applies hereinafter)" (Union Carbide), polymethyl methacrylate as "Matsumoto Micros Fair (registered trademark, the same shall apply hereinafter) "M (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) and the like.

  When an elastomer is used in the present invention, the elastomer is not particularly limited, and any of liquid rubber, solid rubber, thermoplastic elastomer, core shell rubber particles, crosslinked rubber particles, and the like can be suitably used. Moreover, the component which uses an elastomer as raw materials, such as an elastomer modified epoxy, may be sufficient.

  In general, solid rubber has a large viscosity increase when the same amount is dissolved in epoxy resin compared to liquid rubber, and relatively maintains the heat resistance of the molded product while maintaining the resin composition in the molding process at an appropriate viscosity level. In addition, the temperature dependence of the viscoelastic function of the resin composition can be reduced, the handleability is not easily deteriorated even when there is a change in the working environment temperature for handling the prepreg, and the time-dependent change in tackiness due to leaving the prepreg can be reduced. Therefore, it is preferably used in the present invention.

  As the solid rubber, an acrylonitrile-butadiene copolymer which is a random copolymer of butadiene and acrylonitrile is preferable from the viewpoint of compatibility with the epoxy resin. The compatibility with the epoxy resin can be controlled by changing the copolymerization ratio of acrylonitrile. Furthermore, in order to raise adhesiveness with an epoxy resin, it is more preferable to use the solid rubber which has a functional group. Examples of such a functional group include a carboxyl group and an amino group. Hydrogenated nitrile rubber is also a preferred example of solid rubber because of its excellent weather resistance. As commercial products of liquid rubber and solid rubber, CTBN1300X13, ATBN1300X16 (manufactured by BF Goodrich) “NIPOL (registered trademark, the same shall apply hereinafter)” 1072, 1072J, 1472, 1472HV, 1042, 1043, DN631, DN601, 1001, “ ZETPOL (registered trademark, the same shall apply hereinafter) “2020, 2220, 3110 (manufactured by Nippon Zeon Co., Ltd.).

  Commercially available crosslinked rubber particles include FX-602P, FX-501P (manufactured by Nippon Synthetic Rubber Industry Co., Ltd.) and acrylic rubber fine particles made of a crosslinked product of a carboxyl-modified and epoxy-modified butadiene-acrylonitrile copolymer. CX-MN series (made by Nippon Shokubai Co., Ltd.), YR-500 series (made by Toto Kasei Co., Ltd.), etc. can be used. Commercially available core-shell rubber particles include “Paraloid (registered trademark, the same shall apply hereinafter)” EXL-2655 (manufactured by Kureha Chemical Industry Co., Ltd.), acrylate ester / methacrylic, which is a butadiene / alkyl methacrylate / styrene copolymer. "STAPHYLOID (Registered Trademark, hereinafter the same)" AC-3355, TR-2122 (manufactured by Takeda Pharmaceutical Co., Ltd.) made of an acid ester copolymer, "PARALOID" made of a butyl acrylate / methyl methacrylate copolymer Registered trademark, the same shall apply hereinafter) "EXL-2611, EXL-3387 (manufactured by Rohm & Haas), CSR masterbatch (manufactured by Kaneka Corporation), and the like.

Commercially available elastomer-modified epoxies include TSR-601, TSR-960 (above, manufactured by Dainippon Ink & Chemicals, Inc.), "ERISYS (registered trademark, the same applies hereinafter)" EMRA-95, RK-8-4, EMDA. -3-23 (made by PIT Japan Co., Ltd.).
The component [C] in the present invention is a carbon nanofiber, and examples thereof include general carbon nanotubes (CNT) and vapor grown carbon fibers (VGCF). These are preferable because the main structure is a chemical structure in which one surface of graphite (graphene or graphene sheet) is laminated in a cylindrical shape because high strength and elastic modulus can be obtained. The laminated structure of graphite can be examined with a high-resolution transmission electron microscope. The graphite layer is preferable so that it can be seen straight and clearly with a transmission microscope, but the graphite layer may be disordered. In general, carbon nanofibers can be manufactured by an arc discharge method, a laser evaporation method, a thermal CVD (abbreviation of Chemical Vapor Deposition) method, a plasma CVD method, or the like, but any method may be used. . The form of these carbon nanofibers can take any form such as a needle, coil, or tube. Moreover, what mixed these 2 or more types may be used.

  In the present invention, in the cured product obtained by curing the resin composition of the present invention, the constituent element [C] needs to have a maximum aggregate size of 10 μm or less, preferably 5 μm or less. Thereby, the occurrence of uneven stress distribution in the cured product and the disturbance of the alignment of the reinforcing fibers are suppressed, and a fiber-reinforced composite material having an excellent balance between the compressive strength in the fiber direction and the in-plane shear strength can be obtained. In the present invention, the maximum aggregate size of the constituent element [C] means the maximum aggregate size of the constituent element [C] specified by the method described later, and the aggregate of the constituent element [C] The size means the diameter of the minimum circumscribed circle of the aggregate formed by the component [C]. Such agglomerate is a collection of carbon nanofibers, and is a region where the abundance of carbon nanofibers is locally increased with respect to the original blending ratio. Such agglomerates include agglomerates generated in the resin preparation and molding processes in addition to the agglomerates present in the original carbon nanofibers. In FIG. 1, the image figure of the microscope image at the time of measuring the aggregate size in hardened | cured material in this invention is shown.

  Various methods are used to set the aggregate size to 10 μm or less, and the viscosity of the resin composition at 100 ° C. is set in a range as described later, or the component [C] is determined by elemental analysis. It is effective to use an oxygen atom / carbon atom ratio (O / C) within a range as described later.

  These constituent elements [C] desirably have an average fiber diameter D in the range of 3 nm to 300 nm, preferably 3 nm to 100 nm, more preferably 3 nm to 60 nm. If the average fiber diameter is too small, it may be difficult to uniformly disperse the resin in the resin. On the other hand, if the average fiber diameter is too large, a desired mechanical property imparting effect may not be obtained.

Moreover, it is desirable that these constituent elements [C] have an average fiber length L in the range of 0.01 μm to 100 μm, preferably 0.03 μm to 50 μm, more preferably 0.05 μm to 20 μm. If the average fiber length is too short, a desired effect of imparting mechanical properties may not be obtained. On the other hand, if the average fiber length is too long, it may be difficult to uniformly disperse in the resin.
In the resin composition or prepreg, these constituent elements [C] desirably have an average aspect ratio in the range of 10 to 200, preferably 30 to 200, more preferably 50 to 150. If the average aspect ratio is too small, it may not be possible to obtain the desired mechanical property imparting effect. On the other hand, if the average aspect ratio is too large, the fluidity of the matrix resin will decrease, resulting in poor curing and disordered reinforcement fiber alignment. Induces and may result in degradation of mechanical properties. Even if the same carbon nanofiber raw material is used, the fiber length and aspect ratio of the carbon nanofiber in the resulting resin composition vary greatly depending on the dispersion treatment conditions. It is meaningless to specify the ratio, and it is important to manage the aspect ratio of the carbon nanofibers in the resin composition and prepreg after the dispersion treatment.

This average aspect ratio is represented by the ratio (L / D) between the average fiber length L and the average fiber diameter D of the component [C]. The average fiber diameter D and the average fiber length L here can be obtained by a method such as observation with a high-resolution transmission electron microscope. In the case of the constituent element [C] contained in the resin composition or prepreg, the average fiber diameter and average fiber length are determined by heating the resin composition or prepreg, and then curing the resin or fiber reinforced composite. After processing the material into thin slices, observe with a transmission electron microscope (TEM), etc., and do not measure one carbon nanofiber redundantly. It can be obtained by measuring the fiber length and calculating the average value of each. If this method is used, the average fiber diameter D and the average fiber length L can be measured even for a cured resin or a fiber-reinforced composite material. As another method for measuring the average fiber diameter D and the average fiber length L, it is diluted with a solvent, cast on a substrate such as glass, observed with a scanning electron microscope (SEM), etc., and optionally 20 For the carbon nanofiber, a method of measuring the fiber diameter and the fiber length and calculating the average value of each is mentioned. From the viewpoint of measuring the average fiber diameter D and the average fiber length L with higher accuracy, the latter measurement by SEM is preferably used.

  These constituent elements [C] are contained in the resin composition of the present invention in an amount of 0.01 to 20% by weight, preferably 0.1 to 18% by weight, more preferably 0, per weight of the resin composition. It is preferable that it is contained at a content within the range of 5 wt% to 15 wt%. If the content is too small, the desired mechanical property imparting effect may not be obtained. On the other hand, if the content is too large, the fluidity during molding is extremely reduced, and voids are generated in the molded product. For this reason, the mechanical properties of the molded product may deteriorate.

  These constituent elements [C] have an oxygen atom to carbon atom ratio (O / C) of 0.01 to 0.20, preferably 0.01 to 0.15, more preferably 0.02 by elemental analysis. It is desirable to be within the range of ~ 0.12. The means for controlling the O / C ratio of the constituent element [C] within such a range is not particularly limited. For example, a polar polymer such as polyvinylpyrrolidone or a conjugated polymer such as poly (arylethynylene) on the surface of the carbon nanofiber. And non-covalently adhering method, a method of reacting with an oxidizing agent such as nitric acid and permanganic acid and oxidizing, a method of fluorinating the surface with fluorine gas and then substituting with a polar functional group such as amino group. If the O / C is too small, re-aggregation of the component [C] tends to occur at the time of curing, and the agglomeration size of the component [C] tends to increase, whereby the dynamics of the cured resin and the fiber-reinforced composite material On the other hand, when the properties tend to decrease, if the size is too large, the strength of the component [C] itself tends to decrease, and the mechanical properties of the cured resin and the fiber-reinforced composite material may decrease. In addition, O / C of component [C] can be calculated | required using an elemental analyzer.

  Regarding the fiber diameter, average aspect ratio, and O / C ratio of these constituent elements [C], a synergistic effect is recognized, and by setting each within a specified range, a dramatic improvement in mechanical properties is recognized.

  The method for dispersing these constituent elements [C] in the resin composition is not particularly limited, but a kneader, a planetary mixer, a twin screw extruder, a three roll, a homomixer, a dissolver, a ball mill, a bead mill, an ultrasonic wave, etc. Can be used.

  In the present invention, the viscosity at 50 ° C. of the resin mixture excluding the component [C] from the resin composition of the present invention is 5 Pa · s to 5000 Pa · s, preferably 10 to 1000 Pa · s, more preferably It is desirable to be within the range of 20 to 500 Pa · s. If the viscosity is too low, when the resin composition is used to form a prepreg, the prepreg tack becomes excessive, and workability during prepreg lamination may be extremely deteriorated. Is insufficient and the lamination accuracy is lowered, which may lead to a decrease in physical properties of the fiber-reinforced composite material.

  Furthermore, the resin composition of the present invention has a viscosity at 100 ° C. in the range of 0.1 Pa · s to 100 Pa · s, preferably 0.1 to 50 Pa · s, more preferably 0.5 to 30 Pa · s. It is desirable that If this viscosity is too low, re-aggregation of the component [C] tends to occur during curing, and the agglomeration size of the component [C] tends to increase, whereby the mechanical properties of the cured resin and the fiber-reinforced composite material are reduced. On the other hand, if it is too high, the fluidity at the time of molding is extremely lowered, voids or the like are easily generated in the molded body, and the mechanical properties of the molded product may be lowered.

  The thermosetting resin composition obtained in the present invention preferably has a Kasson viscosity at 80 ° C. of 0.1 to 100 Pa · s and a Kasson yield value of 0.1 to 20 Pa, more preferably at 80 ° C. Casson viscosity is 0.5 to 50 Pa · s, and the Kasson yield value is 0.2 to 10 Pa, more preferably, the Casson viscosity at 80 ° C. is 3 to 30 Pa · s and the Kasson yield value is 0.5 to 5 Pa. It is desirable that When the Kasson viscosity is less than 0.1 Pa · s, when the intermediate material (prepreg) in which the reinforcing fiber is impregnated with the thermosetting resin composition is used, it is difficult to maintain its form, such as tearing. On the other hand, when the Kasson viscosity exceeds 100 Pa · s, the tackiness or draping property of the prepreg may be insufficient and the lamination operation may be hindered. Further, when the Kasson yield value here is less than 0.1 Pa, the dispersion of the carbon nanofibers is insufficient, and a desired mechanical property imparting effect may not be obtained, while the Kasson yield value is 20 Pa. If exceeded, it may lead to poor impregnation of the reinforcing fiber, and the fluidity of the thermosetting resin composition in the molding process will be insufficient, leading to poor curing and disturbance of the alignment of the reinforcing fiber, and mechanical properties May be reduced.

  The Casson viscosity and the Kasson yield value mentioned here are the Casson (English notation: Casson) equation, which is a well-known formula that theoretically handles the rheological properties of a suspension in which solid particles are dispersed in a Newtonian fluid. Characteristic values used in equation 1).

τ ^0.5 = τy ^0.5 + η∞ ^0.5・ γ ^0.5・ ・ ・ ・ ・ ・ (Formula 1)
Here, τ: shear stress (Pa), γ: shear rate (s ⁻¹ ), η∞: Kasson viscosity (Pa · s), and τy: Kasson yield value (Pa).

  More specifically, the Kasson viscosity means a value obtained by extrapolating the viscosity when the shear rate becomes infinite, and the Kasson yield value is the minimum necessary to start the resin flow. It means the shear stress. The complex viscosity evaluation under a single strain amount condition using a parallel plate that is usually performed did not necessarily reflect the dispersion state of the carbon nanofibers and the handleability as a thermosetting resin composition, By controlling with the Kasson viscosity and the Kasson yield value, the dispersion state of the carbon nanofibers and the handleability as a thermosetting resin composition can be within an appropriate range.

  By impregnating the reinforcing fiber with the resin composition of the present invention, a prepreg as an intermediate substrate of the fiber-reinforced composite material is produced. Examples of the reinforcing fiber used for the prepreg include glass fiber, carbon fiber, aramid fiber, boron fiber, alumina fiber, silicon carbide fiber and the like. Two or more of these fibers may be used in combination, but carbon fibers are more preferably used in order to obtain a molded product that is lighter and more durable.

  In order to produce lightweight and high-strength sports equipment and aircraft parts, carbon fiber with a higher elastic modulus, specifically, a small amount of material so that sufficient product rigidity can be expressed. It is more preferable to use a material having a tensile modulus of 200 to 800 GPa, preferably 220 to 650 GPa. If the tensile modulus is too low, sufficient compression strength may not be obtained as a result of the molded body. On the other hand, if the tensile modulus is too high, the compression strength of the reinforcing fibers will be low. In such a case, sufficient bending characteristics and torsional characteristics of the tubular body may be impaired.

  The form and arrangement of the reinforcing fibers are not limited. For example, long fibers, tows, woven fabric (cross), mats, knits, braids and the like that are aligned in one direction are used.

  The prepreg is prepared by a wet method in which a resin composition as a matrix resin is dissolved in a solvent to lower the viscosity and impregnated into the reinforcing fibers, or a hot melt method (dry method) in which the viscosity is decreased by heating and impregnated into the reinforcing fibers. Manufactured. The hot melt method is a method for producing a prepreg by impregnating a resin composition by heating and pressurizing a film in which reinforcing fibers and a resin composition are coated on a release paper or the like from both sides or one side.

  In order to reduce the weight of the fiber reinforced composite material, the reinforced fiber content in the prepreg is preferably high, preferably 60% by weight or more, more preferably 70% by weight or more, and 75% by weight or more. Is most preferred. However, if the fiber content is too high, the absolute amount of the matrix resin is reduced, so that the tackiness of the prepreg and the impregnation property of the matrix resin into the reinforcing fiber are impaired, so that the workability is lowered or the fiber reinforcement It may be difficult to produce a high-quality fiber-reinforced composite material such as a composite material containing only a large amount of voids, and in that sense, the fiber content is 90% by weight or less. It is preferably 85% by weight or less.

  A fiber-reinforced composite material using a prepreg is produced by a method in which a pattern obtained by cutting a prepreg is laminated, and then a resin is heated and cured while applying pressure to the laminate. As methods for applying pressure, press molding and autoclave molding are representative methods, and other methods include sheet winding molding and internal pressure molding, and any of these methods can be used.

  The sheet winding method is a method of forming a cylindrical object by winding a prepreg around a mandrel or the like, and is suitable for producing a rod-shaped body such as a golf shaft or a hockey stick. Specifically, a film on the outside of the prepreg is used to wind the prepreg around the mandrel and fix the prepreg so that it does not peel from the mandrel, and to apply molding pressure to the prepreg using the heat shrinkability of the tape. -A tape (wrapping tape) is wound and the resin is heated and cured, and then the core metal is removed to obtain a cylindrical molded body.

  The internal pressure molding method is a method in which a preform prepared from a prepreg is set in a mold in advance, and then the mold is heated and molded at the same time as an internal pressure is applied to the preform. It is suitably used when molding a complicated shape such as a golf shaft, a golf club head, a bat, a racket such as tennis or badminton.

  Furthermore, a fiber-reinforced composite material can be produced by a molding method such as a filament winding method, a pultrusion method, a resin injection molding method, or the like, using the resin composition of the present invention and reinforcing fibers.

Hereinafter, the present invention will be described more specifically with reference to examples. In addition, the evaluation method of various characteristic values and the adjustment method of the raw material etc. which are used in a present Example are shown collectively below. Tables 1 and 2 collectively show the resin composition, prepreg characteristics, and fiber reinforced composite material characteristics of each example.
A. O / C by elemental analysis of component [C]
After the component [C] is vacuum-dried at 200 ° C. for 2 hours, the content of element C is measured from the gas generated by completely burning the sample at a high temperature of 950 ° C. using an elemental analyzer. On the other hand, the content of O element is measured from a gas generated by decomposing a sample at a decomposition furnace temperature of 1150 ° C. using an elemental analyzer. From the result, the atomic ratio O / C is calculated. In this example, when measuring the content of C element as an elemental analyzer, a varioEL elemental analyzer manufactured by Elemental Co. is used, and when measuring the content of O element, manufactured by HERAEUS A CHN-O RAPID elemental analyzer was used.
B. Production of carbon nanofiber [CNF-1]: carbon nanotube (CNT)
K. Hernadi, A.M. See the report by Fonseca et al. (Zeolites 17: 416-423, 1996), weigh iron acetate (2 g), cobalt acetate (2 g), Y-type zeolite (10 g), add methanol (100 ml) and shake. After stirring in a vessel for 1 hour, the methanol content was removed by drying to obtain a catalyst. Next, using a CVD reactor, 1 g of catalyst was set in advance on quartz wool in the reaction tube, heated to 600 ° C. in a nitrogen (30 cc / min) atmosphere, acetylene (6 cc / min), nitrogen (30 cc) / Min) Carbon nanofibers were synthesized by holding at 600 ° C. for 5 hours in an atmosphere. Then, it cooled to room temperature under nitrogen (30cc / min) atmosphere, and took out the reaction mixture.

The reaction mixture was stirred in a 10% aqueous solution of hydrofluoric acid for 3 hours, and then filtered using a filter paper (Toyo Roshi Kaisha, Filter Paper No. 125 mm). The solid on the filter paper was subjected to ion exchange water, acetone. After washing with a solution, it was dried to obtain carbon nanofiber (CNF-1). From the observation result of the transmission electron microscope of CNT-1, it was found that the average fiber diameter was 10 nm. Moreover, it was 0.002 as a result of calculating | requiring O / C by the elemental analysis.
[CNF-2]: Surface-treated CNT
5 g of CNF-1 was weighed into a flask, 150 g of concentrated sulfuric acid and 50 g of 60% nitric acid were added, and the mixture was heated at 100 ° C. for 30 minutes. The reaction solution was diluted with 500 ml of water, filtered through a membrane filter, and washed thoroughly with water to obtain surface-treated carbon nanofiber (CNF-2). As a result of obtaining O / C by elemental analysis, it was 0.04.
[CNF-3]: Surface-treated CNT
5 g of CNF-1 was measured in a flask, 150 g of concentrated sulfuric acid and 50 g of 60% nitric acid were added, and the mixture was heated at 100 ° C. for 1 hour. The reaction solution was diluted with 500 ml of water, filtered through a membrane filter, and washed well with water to obtain surface-treated carbon nanofiber (CNF-3). As a result of obtaining O / C by elemental analysis, it was 0.11.
[CNF-4]: Surface-treated CNT
5 g of CNF-1 was weighed into a flask, 150 g of concentrated sulfuric acid and 50 g of 60% nitric acid were added, and the mixture was heated at 100 ° C. for 2 hours. The reaction solution was diluted with 500 ml of water, filtered with a membrane filter, and washed well with water to obtain surface-treated carbon nanofibers (CNF-4). As a result of obtaining O / C by elemental analysis, it was 0.18.
[CNF-5]: vapor grown carbon fiber (VGCF1, manufactured by Showa Denko KK), average fiber diameter of 50 nm. Fiber length 20-50 μm. As a result of obtaining O / C by elemental analysis, it was 0.003.
[CNF-6]: Surface treatment VGCF1
5 g of CNF-5 was measured in a flask, 150 g of concentrated sulfuric acid and 50 g of 60% nitric acid were added, and the mixture was heated at 100 ° C. for 1 hour. The reaction solution was diluted with 500 ml of water, filtered with a membrane filter (PTFE, pore size: 1 μm), and then thoroughly washed with water to obtain surface-treated VGCF1 (CNF-6). As a result of obtaining O / C by elemental analysis, it was 0.07.
[CNF-7]: Vapor grown carbon fiber (VGCF2, manufactured by Showa Denko KK), average fiber diameter 150 nm, fiber length 20-50 μm. As a result of obtaining O / C by elemental analysis, it was 0.003.
[CNF-8]: Surface treatment VGCF2
5 g of CNF-7 was measured in a flask, 150 g of concentrated sulfuric acid and 50 g of 60% nitric acid were added, and the mixture was heated at 100 ° C. for 1 hour. The reaction solution was diluted with 500 ml of water, filtered through a membrane filter (PTFE, pore size: 1 μm), and then thoroughly washed with water to obtain surface-treated VGCF2 (CNF-8). As a result of obtaining O / C by elemental analysis, it was 0.05.
C. Resin preparation Using the following resin raw materials, the thermosetting resin shown in the column of the component [A] in Tables 1 and 2 and the component [C] carbon nanofibers are shown in Tables 1 and 2 with three rolls. The resin composition was prepared by kneading and kneading the [B] curing agent and other additives to the dispersion kneaded by treating the number of times.
Component [A]
・ "Epicoat" 828 (Japan Epoxy Resin Co., Ltd., bisphenol A type liquid epoxy resin)
・ "Epicoat" 807 (Japan Epoxy Resin Co., Ltd., bisphenol F type liquid epoxy resin)
"Sumiepoxy" ELM434 (manufactured by Sumitomo Chemical Co., Ltd., tetraglycidyldiaminodiphenylmethane, liquid)
・ "Epicoat" 1002 (Japan Epoxy Resin Co., Ltd., bisphenol A type solid epoxy resin)
・ "Epicoat" YX4000H (Japan Epoxy Resin Co., Ltd., tetramethylbiphenyl type solid epoxy resin)
・ "Epiclon" HP7200L (Dainippon Ink Chemical Co., Ltd., dicyclopentadiene type solid epoxy resin)
Component [B]
"SumiCure (registered trademark)" S (Sumitomo Chemical Co., Ltd., 4,4'-diaminodiphenylsulfone)
-DICY7 (Japan Epoxy Resin Co., Ltd., dicyandiamide)
DCMU99 (manufactured by Hodogaya Chemical Co., Ltd., 3- (3,4-dichlorophenyl) -1,1-dimethylurea)
Other additives ・ Vinyleck K (Chisso Corporation, polyvinyl formal)
・ "Nipol" 1072 (manufactured by Nippon Zeon Co., Ltd., carboxyl group-containing acrylonitrile butadiene rubber)
When the obtained resin composition was thinly stretched on a slide glass and observed with an optical microscope, no aggregate of carbon nanofibers exceeding 10 μm was found in any level.
D. Evaluation of Aggregated Size of Carbon Nanofiber When the evaluation object is a resin composition, the measurement is performed as follows. First, a small amount of the resin composition is taken on a slide glass and sandwiched between cover glasses to form a thin film having a thickness of about 10 μm. This was heated at a rate of temperature rise of 2 ° C./min until gelation was obtained to obtain an observation sample. This is measured with an optical microscope using a 10 × eyepiece and a 100 × objective lens to measure the aggregate size of the individual aggregates. That is, as shown in FIG. 1, a minimum circle circumscribing one aggregate is drawn and the diameter is measured to obtain the aggregate size. Three fields of view are arbitrarily selected, and the largest aggregate size in these fields of view is set as the maximum aggregate size. In addition, when there is no aggregate in which the aggregate size exceeds 10 micrometers in each visual field, it can be said that the aggregate size is 10 micrometers or less. In addition, when the compounding quantity of carbon nanofiber exceeds several weight%, as shown in the photograph shown in FIG. 4, the aggregate may be connected (as a continuous phase), but this is also an aggregate.

On the other hand, when the object to be evaluated is a fiber reinforced composite material, the measurement is performed as follows. First, using a microtome, a thin slice having a thickness of 10 microns is prepared from a fiber-reinforced composite material. This is measured with an optical microscope using a 10 × eyepiece and a 100 × objective lens to measure the aggregate size of the individual aggregates. That is, as shown in FIG. 1, a minimum circle circumscribing one aggregate is drawn and the diameter is measured to obtain the aggregate size. Three fields of view are arbitrarily selected from the matrix resin region, and the largest aggregate size in these fields of view is set as the maximum aggregate size. In addition, when there is no aggregate in which the aggregate size exceeds 10 micrometers in each visual field, it can be said that the aggregate size is 10 micrometers or less. In addition, when the compounding quantity of carbon nanofiber exceeds several weight%, although an aggregate may be connected and it may appear (as a continuous phase), this is also considered as an aggregate. In this example, an in-plane shear strength evaluation composite material was used as the fiber reinforced composite material to be observed, and SP1600 manufactured by Leica Microsystems Co., Ltd. was used as the microtome.
E. Viscosity measurement of resin mixture not containing component [C] at 50 ° C. Using a viscoelasticity measuring device, using parallel plates with a radius of 20 mm, a distance between parallel plates of 1.0 mm, a measurement temperature of 50 ° C., a measurement frequency of 0. Viscoelasticity is measured under conditions of 5 Hz and generated torque of 10 to 100 gf · cm, and the complex viscosity η ^* is read. In this example, a viscoelasticity measuring device ARES manufactured by TA Instruments was used as the viscoelasticity measuring device.
F. Viscosity measurement of resin composition at 100 ° C. Using a viscoelasticity measuring device, using a parallel plate with a radius of 20 mm, a distance between parallel plates of 1.0 mm, a measurement temperature of 100 ° C., a measurement frequency of 0.5 Hz, and a strain of 100% Measure the viscoelasticity below and read the complex viscosity η ^* . In this example, a viscoelasticity measuring device ARES manufactured by TA Instruments was used as the viscoelasticity measuring device.
G. Measurement of Kasson viscosity and Kasson yield value of resin composition at 80 ° C. For a masterbatch or thermosetting resin composition adjusted to 80 ° C. using a dynamic viscoelasticity measuring device and using a conical flat plate jig, The shear stress τ is measured by the procedures (1) to (3).
(1) A running time of 10 seconds is provided, and the shear rate applied to the masterbatch or the thermosetting resin composition is increased during this period until it reaches 100 s- ¹ .
(2) Continue to apply shear at the constant shear rate of 100 s ^-1 for the next 2 minutes.
(3) Decrease the shear rate to ^{0 s -1 in the} next 3 minutes.

Regarding the measurement data of the shear stress τ with respect to the shear rate γ obtained in the above item (3), based on the above (Equation 1), the linear line of the 0.5th power of the shear stress τ with respect to the 0.5th power of the shear rate γ Regression is performed, and the square of the slope of the obtained linear expression is defined as the Kasson viscosity, and the square of the intercept is determined as the Kasson yield value. In this example, a dynamic viscoelasticity measuring device ARES manufactured by TA Instruments Inc. is used as the dynamic viscoelasticity measuring device. In all of the present examples, the shear rate γ is raised to the 0.5th power. And the correlation coefficient between the shear stress τ and the 0.5th power was 0.997 or more, indicating a good correlation.
H. Preparation of prepreg A thermosetting resin composition was applied onto release paper using a reverse roll coater to prepare a resin film. Next, resin films are stacked on both sides of carbon fiber “Treca” T800H-12K (manufactured by Toray Industries, Inc.) having a tensile elastic modulus of 295 GPa arranged in one direction, and heated and pressurized (130 ° C., 0.4 MPa). As a result, the resin was impregnated to prepare a unidirectional prepreg having a fiber weight per prepreg unit area of 125 g / m ² and a fiber weight content of 76%.
I. Calculation of aspect ratio of component [C] in prepreg The prepreg is immersed in n-methylpyrrolidone, the resin component is completely eluted from the prepreg using an ultrasonic cleaner, and the carbon fibers are removed by filtration or the like. The concentration of the component [C] is about 0.1% by weight, and this is further diluted about 100 times with chloroform and sufficiently dispersed by an ultrasonic cleaner. This was dropped on a cover glass and then immersed in methyl ethyl ketone to wash away components other than the constituent element [C] to prepare a sample for SEM observation.

  Individual images of component [C] were obtained using a scanning electron microscope (SEM). From the obtained photograph, 20 pieces were selected at random, the average fiber diameter D and the average fiber length L were determined, and the aspect ratio (L / D) was calculated.

The observation conditions in this example were as follows.
Equipment: S-4000 manufactured by Hitachi, Ltd.
Acceleration voltage: 20 kV
Sample preparation: Pt + Pd Deposition magnification: 10,000 times Resin impregnation property in prepreg Resin impregnation property in prepreg was evaluated by visual and tactile sensation, and it was shown in the table as very good ○○, good ○, slightly unimpregnated Δ, impregnation poor ×. It was.
K. Evaluation of compressive strength in the fiber direction A unidirectional prepreg sheet was laminated so that the direction of the fibers was the same, and the thickness of the laminate was approximately 1 mm, and 2 in an autoclave at a temperature of 135 ° C. and a pressure of 290 MPa. The composition was cured by heating and pressing for a time to produce a unidirectional composite material. The obtained unidirectional composite material was measured according to JISK7076.

The fiber volume content (Vf) is calculated from the thickness, fiber basis weight, fiber density, and number of laminated plies of the unidirectional composite material, and the obtained 0 ° compressive strength is converted to the value when the volume content of the reinforcing fiber is 60%. did.
L. Evaluation of in-plane shear strength Sixteen unidirectional prepreg sheets were laminated in a [+ 45 / −45] 4 s configuration so that the fiber direction is ± 45 °, and 2 in an autoclave at a predetermined temperature of 135 ° C. and a pressure of 290 Pa. It was cured by heating and pressing for a time to produce a composite material. Next, the in-plane shear strength of the obtained material was measured according to JISK 7079.
Example 1
Resin compositions as shown in Table 1 were obtained in which only liquid components were used for component [A] and 1% by weight of surface-treated CNT was blended as component [C]. In the cured product of this resin composition, aggregates having a size of 3 μm were observed, but the fiber-reinforced composite material produced using this resin composition had a level of no problem.
(Comparative Example 1)
A resin composition as shown in Table 2 was obtained in the same manner as in Example 1 except that the constituent element [C] was not included. The fiber reinforced composite material produced using this resin composition has insufficient characteristics.
(Examples 2 to 10)
A solid component was blended with the component [A], and the carbon nanofibers surface-treated as the component [C] were blended in various blending amounts to obtain resin compositions as shown in Table 1. As a result, as shown in FIG. 2, the aggregates are less than 1 μm in the cured products of these resin compositions, and the fiber-reinforced composite materials produced using these resin compositions generally have a sufficient level of characteristics. Had. In addition, although the characteristic of a fiber reinforced composite material improved, so that the compounding quantity of component [C] was increased, when it increased too much, the tendency which fell conversely was seen. Moreover, regarding the surface treatment amount of the carbon nanofibers, it can be seen that if the O / C ratio is too large, the properties of the resulting fiber-reinforced composite material are deteriorated and there is an appropriate range.
(Comparative Example 2)
Resin compositions as shown in Table 2 were obtained in the same manner as in Examples 2 to 10 except that the constituent element [C] was not included. The fiber-reinforced composite material produced using this resin composition has insufficient characteristics.
(Comparative Examples 3 and 4)
Resin compositions as shown in Table 2 were obtained in the same manner as in Comparative Example 2 except that carbon nanofibers not subjected to surface treatment were blended as the component [C]. In the cured product of this resin composition, as shown in FIGS. 3 and 4, aggregates having a size exceeding 10 μm are observed, and the fiber-reinforced composite material produced using this resin composition has a fiber direction compressive strength. Although a slight improvement was observed, the in-plane shear strength was greatly reduced.
(Examples 11 and 12)
A resin composition as shown in Table 1 was obtained in the same manner as in Example 4 except that a part of the solid component of the component [A] was changed to a biphenyl type epoxy resin or a dicyclopentadiene type epoxy resin. The fiber reinforced composite material produced using this resin composition had extremely high characteristics.
(Example 13)
Further, a resin composition was obtained in the same manner as in Comparative Example 3 except that carboxyl group-terminated acrylonitrile butadiene rubber was blended. In the cured product of this resin composition, the aggregate size was 7 μm, but the fiber-reinforced composite material produced using this resin composition had a level with no problem. (Example 14)
A resin composition was obtained in the same manner as in Example 13 except that the number of times of three-roll treatment was set to 10. As a result, the agglomerated size reached less than 1 μm and the Kasson yield value reached 5 respectively, and the impregnation property was improved. The aspect ratio was within a preferable range of 100, and the fiber-reinforced composite material produced using this resin composition was further improved in characteristics as compared with Example 13. Thus, it can be seen that the carbon nanofibers are cut and the aspect ratio is reduced by the dispersion treatment.
(Example 15)
A resin composition was obtained in the same manner as in Example 9 except that the number of times of the three-roll treatment was 10 times. As a result, the aspect ratio deviated from the preferable range of 9, and as a result, the fiber reinforced composite material produced using this resin composition was found to have an acceptable level of deterioration in properties as compared with Example 9. .

In this invention, it is an image figure of the microscope image used for the aggregate size evaluation of carbon nanofiber. 4 is an optical microscopic image used in Example 3 to evaluate the aggregate size of carbon nanofibers in the cured resin composition. 5 is an optical microscope image used for evaluating the aggregate size of carbon nanofibers in a cured product of a resin composition in Comparative Example 3. FIG. 6 is an optical microscope image used for evaluating the aggregate size of carbon nanofibers in a cured product of a resin composition in Comparative Example 4. FIG.

Claims (14)

A resin composition comprising the following components [A], [B] and [C], wherein the maximum aggregate size of the component [C] in the cured product is 10 μm or less: .
[A] Thermosetting resin [B] Curing agent [C] Carbon nanofiber The resin composition according to claim 1, wherein the constituent element [A] is an epoxy resin. The resin composition according to claim 1 or 2, comprising 10 to 70% by weight of a solid epoxy resin in the constituent element [A]. The resin composition according to any one of claims 1 to 3, comprising at least one of the following components [D] and [E].
[D] Thermoplastic resin [E] Elastomer The resin composition according to any one of claims 1 to 4, wherein the component [C] has a blending amount of 0.01 to 20% by weight. The resin composition according to any one of claims 1 to 5, wherein the constituent element [C] has an average fiber diameter of 3 to 300 nm. The resin composition according to any one of claims 1 to 6, wherein the constituent element [C] has an average aspect ratio of 10 to 200. The resin composition according to any one of claims 1 to 7, wherein the resin mixture in a state in which the constituent element [C] is excluded has a viscosity at 50 ° C in the range of 5 to 5000 Pa · s. The resin composition according to any one of claims 1 to 8, which has a Casson viscosity of 0.1 to 100 Pa · s and a Casson yield value of 0.1 to 20 Pa at 80 ° C. The resin composition according to claim 1, wherein the constituent element [C] has an atomic number ratio (O / C) of oxygen atoms to carbon atoms by elemental analysis in the range of 0.01 to 0.20. object A cured resin product obtained by curing the resin composition according to claim 1. A prepreg comprising the resin composition according to any one of claims 1 to 10 and a reinforcing fiber. The prepreg according to claim 12, wherein the reinforcing fibers are carbon fibers. A fiber-reinforced composite material comprising the cured resin according to claim 11 and reinforcing fibers.