JP5061813B2 - Prepreg and golf club shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a golf club shaft having a sufficient static bending strength and a high safety to cause no fragmentation by a shock damage. <P>SOLUTION: A prepreg is composed of a carbon fiber satisfying the conditions [A] to [D] wherein [A] a tensile modulus is within 295&plusmn;10, [B] a tensile strength is in a range from 5,400 to 6,500 MPa, [C] the cross section is substantially of a perfect circle, and [D] an average diameter of the fiber is in the range from 5.0 to 7.0 &mu;m; and an epoxy resin composition containing [a] an epoxy resin containing 20 to 50 pts.wt. of an amine type epoxy resin with three or more functionalities, [b] 50 to 80 pts.wt. of a bisphenol F type epoxy resin, and [c] 2 to 10 pts.wt. based on 100 pts.wt. of the epoxy resin of dicyandiamide or its derivative, the cured resin composition showing a bending modulus of 3.8 to 5.0 GPa. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a fiber reinforced composite material using carbon fibers and a matrix resin, and relates to a highly safe golf shaft molding material that is lightweight and has a sufficient static bending strength but does not easily break upon impact. It is.

  Carbon fiber reinforced composite materials using carbon fibers as reinforced fibers are used for structural materials such as aircraft and automobiles, tennis rackets, golf shafts, fishing rods, etc. by utilizing their light weight and high specific strength and specific modulus. Widely used in sports applications. Among these applications, the golf club shaft is one of the requirements for an extremely light weight.

  In the method of manufacturing the finely reinforced composite material, a prepreg that is a sheet-like intermediate material in which reinforcing fibers are impregnated with an uncured matrix resin is used. A resin transfer molding method, in which a liquid resin is poured into the arranged reinforcing fibers and heat-cured, is used. Among these production methods, the method using a prepreg is capable of strictly controlling the orientation of reinforcing fibers, and has a high degree of freedom in designing a laminated structure, so that there is an advantage of easily obtaining a high-performance fiber-reinforced composite material. It is widely used in carbon fiber reinforced composite materials that pursue extreme performance such as golf club shafts.

  In golf club shafts, weight reduction has been promoted by applying carbon fiber reinforced composite materials. However, as a premise, it is necessary to maintain a certain mechanical strength, that is, withstand the load of stacking during transportation, A high static bending strength that can withstand bending deformation at the time of take-out is required.

  Also, in actual use, in addition to normal use (striking the ball), it is unpredictable that the ground, stones, or trees will be struck with a miss shot, or the ball hit by another player will hit the side of the golf club shaft. There is a possibility that a strong impact due to the above situation may be applied to the golf club shaft, and even in such a case, it is preferable that the golf club shaft is not easily divided.

  As described above, the golf club shaft is required to have high static bending strength and not to be divided even when a strong impact is applied, but sacrifices characteristics such as lightness originally required for the golf club shaft. No technology has been obtained that satisfies both of the above characteristics.

  For example, Patent Document 1 discloses a technique for suppressing the division of the golf club shaft at the time of impact damage by blending high elongation organic fibers in addition to carbon fibers as reinforcing fibers. However, when such a high elongation organic fiber is used, the static bending strength of the shaft becomes insufficient, and the frequency of breakage tends to increase. Further, in the cited document 2, a technique for improving the static bending strength of the tubular body by increasing the matrix resin of the layer having carbon fibers oriented in the longitudinal direction of the golf club shaft is disclosed. In this technique, the effect of suppressing the breakage against the impact is insufficient.

As described above, there has been a demand for a prepreg capable of obtaining a golf club shaft having static mechanical characteristics and resistance to breaking during impact without sacrificing characteristics such as lightness.
International Publication No. 98/47693 Pamphlet Japanese Patent Laid-Open No. 2002-067176

  An object of the present invention is to provide a golf club shaft that has high static bending strength and does not break when impact is damaged.

In order to solve the above problems, a prepreg formed by combining the carbon fiber and the epoxy resin composition of the present invention has the following constitution. That is, carbon fiber satisfying the conditions [A] to [E] , [a] 20 to 50 parts by weight of tri- or higher functional amine type epoxy resin, and [b] 50 to 80 parts by weight of bisphenol F type epoxy resin. And epoxy resin containing [c] dicyandiamide or a derivative thereof in an amount of 2 to 10 parts by weight with respect to 100 parts by weight of the epoxy resin, and the flexural modulus of the cured product is 3.8 to 5.0 GPa A prepreg formed by combining resin compositions.
[A] Tensile elastic modulus is in the range of 280 to 350 GPa [B] Tensile strength is in the range of 5600 to 6500 MPa [C] It has a substantially circular cross section [D] Average diameter Is in the range of 5.0 to 7.0 μm
[E] The surface area ratio measured using an atomic force microscope is 1.00 to 1.05, the surface roughness Ra is 1 to 10 nm, and the golf club shaft of the present invention cures the prepreg. Can be obtained.

  According to the present invention, it is possible to obtain a golf club shaft having sufficient static bending strength and high safety that does not break when an impact breaks.

The prepreg in the present invention comprises carbon fibers satisfying the following conditions [A] to [E] , [a] 20 to 50 parts by weight of a trifunctional or higher amine type epoxy resin, and [b] bisphenol F type epoxy resin. The epoxy resin containing 50 to 80 parts by weight, [c] dicyandiamide or a derivative thereof is contained in an amount of 2 to 10 parts by weight with respect to 100 parts by weight of the epoxy resin, and the flexural modulus of the cured product is 3.8 to 5. A golf club shaft having a desired static bending strength and not being broken at the time of impact breakage is obtained by laminating and curing a prepreg satisfying the above conditions by combining epoxy resin compositions of 0 Gpa. .
[A] Tensile elastic modulus is in the range of 280 to 350 GPa [B] Tensile strength is in the range of 5600 to 6500 MPa [C] It has a substantially circular cross section [D] Average diameter Is in the range of 5.0 to 7.0 μm
[E] The surface area ratio measured using an atomic force microscope is 1.00 to 1.05, and the surface roughness Ra is 1 to 10 nm. In the present invention, the term “splitting” means that the golf club shaft is bent When impact stress or the like is applied, it is cut into two independent pieces. In a conventional golf club shaft that does not have a fragmentation suppressing effect, impact energy propagates directly to the entire circumferential direction of the cylinder, and is easily divided. On the other hand, since the golf club shaft of the present invention has sufficient carbon fiber tensile strength and energy absorption capability, it avoids breaking of the entire carbon fiber in the circumferential direction, and even at the time of impact breakage, the bending impact imparting side, or At least a part of the carbon fibers on at least one side opposite to the side and the circumferential direction does not break, thereby showing a connected form.

In the present invention, by using a prepreg using carbon fiber satisfying the above conditions [A] to [E] as a reinforcing fiber, an epoxy resin composition of a specific composition having a specific range of elastic modulus as a matrix resin, It found that it is possible to obtain the Ku has a golf club shaft to significantly cut into surprisingly high static bending at impact damage while maintaining the strength. Although the detailed mechanism is unknown, the energy absorption at the interface between the carbon fiber and the matrix resin becomes remarkable due to the effect of suppressing the fragmentation due to the high tensile strength of the carbon fiber and the cross-sectional shape being substantially circular and relatively large in diameter. It is thought that. Moreover, it seems that energy absorption became remarkable also in matrix resin because this epoxy resin composition has sufficient plastic deformation capability.

  The carbon fiber used in the present invention has a tensile elastic modulus of 295 ± 10 GPa (condition [A]). Since carbon fibers with such elastic modulus can obtain sufficient rigidity and static bending strength, they are often used in the shaft axis direction of golf club shafts, and prepregs using carbon fibers with such elastic modulus are prevented from being divided. This is because if it is possible to provide an effect, it is very advantageous in designing the golf club shaft.

    Here, the tensile elastic modulus of 295 ± 10 GPa means that the variation in characteristics of about 3% is within an allowable range.

  The carbon fibers used in the present invention are required to have a tensile strength in the range of 5400 to 6500 MPa (condition [B]), and preferably 5600 to 6500 MPa. When the tensile strength is less than 5400 MPa, the golf club shaft is likely to be divided at the time of impact breakage. On the other hand, the higher the tensile strength, the higher the tensile strength from the viewpoint that the golf shaft is less likely to be broken at the time of impact. However, at the present stage, carbon fibers having a tensile strength exceeding 6500 Mpa are difficult to obtain, so the upper limit is set. Is. In the future, when a carbon fiber having a higher tensile strength becomes available, it can be preferably applied.

  The tensile elastic modulus and tensile strength of carbon fiber here mean the strand tensile elastic modulus and strand tensile strength measured according to JIS R7601 (1986).

  The carbon fibers used in the present invention are classified into acrylic, pitch, rayon and the like. Among these, acrylic carbon fibers having high tensile strength are preferable. The acrylic carbon fiber that can be suitably used in the present invention can be produced, for example, through the steps described below. A spinning solution containing polyacrylonitrile obtained from a monomer containing acrylonitrile as a main component is spun by a wet spinning method, a dry wet spinning method, a dry spinning method, or a melt spinning method. The spun coagulated yarn can be made into an acrylic precursor through a spinning process, and then an acrylic carbon fiber can be obtained through processes such as flame resistance and carbonization. Here, the spinning method is preferably a wet spinning method or a dry and wet spinning method. Furthermore, since it does not have fine irregularities on the fiber surface and has extremely high smoothness, the spreadability of the yarn during prepreg production, the quality of the prepreg, and the handleability of the prepreg are good. Carbon fiber manufactured using a precursor obtained by dry and wet spinning of a spinning stock solution containing polyacrylonitrile from the viewpoint that the fiber surface is smooth and stress concentration does not easily occur, so that it is easy to obtain a golf club shaft split control effect. It is more preferable to use

  As the form of the carbon fiber, a flammable yarn, a flame retardant yarn, a nonflammable yarn and the like can be used, but a non-twisted yarn having good yarn spreading property, prepreg quality and handleability is preferable. The term “untwisted yarn” as used herein generally means a yarn having a twist number of 0.5 turns / m or less.

  The carbon fiber used in the present invention needs to have a substantially circular cross section (condition [C]). Here, the fact that the cross-sectional shape is substantially circular means that the ratio (r / R) of the major axis R to the minor axis r of the section of the single yarn measured using an optical microscope is 0.9 or more. That means. Here, the long diameter R indicates the diameter of the circumscribed circle of the single yarn, and the short diameter r indicates the diameter of the inscribed circle of the single yarn. If it is not a perfect circle, the golf club shaft will be easily broken when it is damaged.

Further, the carbon fiber used in the present invention has a surface area ratio of 1.00 to 1.05 and a surface roughness Ra of 1 to 10 nm (condition [E]) measured using an atomic force microscope. It is preferable that the ratio is 1.00 to 1.03 and the surface roughness Ra is 1 to 7 nm. When Ra is less than 1 nm, the surface of the prepreg is smooth, which is preferable, but at present there is no such carbon fiber. The surface area ratio is the ratio of the actual surface area of the reinforcing fiber surface to the projected area, and represents the degree of surface roughness, and is 1.00 when the reinforcing fiber surface has no irregularities. If the surface area ratio exceeds 1.05 or the surface roughness Ra exceeds 10 nm, the golf club shaft may be easily broken when broken.

  Further, the carbon fiber in the present invention has a specific range of the atomic ratio of oxygen O to carbon C measured by X-ray photoelectron spectroscopy, that is, the surface specific oxygen concentration (hereinafter abbreviated as O / C). The effects of the invention can be fully exhibited. Specifically, the carbon fiber in the present invention preferably has an O / C in the range of 0.05 to 0.15, more preferably in the range of 0.07 to 0.12. . If O / C exceeds 0.15, the golf club shaft may be easily broken at the time of impact breakage. If the O / C is less than 0.05, the static bending strength of the golf club shaft may decrease.

  The carbon fiber used in the present invention is required to have an average fiber diameter measured using an optical microscope in the range of 5.0 to 7.0 μm (condition [D]), and 5.3 to 6 It is preferably 5 μm. When the average diameter is less than 5.0 μm, the golf club shaft is likely to be divided at the time of impact breakage. On the other hand, when exceeding 7.0 micrometers, static bending strength will fall.

Examples of the carbon fiber product satisfying such conditions [A] to [E] include “Torayca (registered trademark)” T800S (manufactured by Toray Industries, Inc.).

  The flexural modulus of the cured product obtained by curing the epoxy resin composition used in the present invention needs to be 3.8 to 5.0 GPa, and more preferably 4.2 to 4.5 GPa. Such a cured product is obtained by curing the epoxy resin composition from room temperature at a heating rate of 1.5 ° C./min and then curing at 130 ° C. for 2 hours. When the flexural modulus is less than 3.8 GPa, the static bending strength of the golf club shaft becomes insufficient. When it exceeds 5.0 GPa, the plastic deformation ability becomes insufficient, and the golf club shaft is likely to be divided at the time of impact breakage. The flexural modulus here is measured according to JIS K7171 (1999).

  The epoxy resin composition used in the present invention comprises: [a] an epoxy resin containing 20 to 50 parts by weight of a trifunctional or higher functional amine type epoxy resin and [b] 50 to 80 parts by weight of a bisphenol F type epoxy resin; , [C] By containing 2 to 10 parts by weight of dicyandiamide or a derivative thereof with respect to 100 parts by weight of the epoxy resin, the cured product exhibits a desired heat resistance and has a balance between elastic modulus and plastic deformation ability. It will be better than ever. By combining a predetermined carbon fiber with such an epoxy resin composition, the effect of suppressing the breakage at the time of impact breakage of the golf club shaft becomes remarkable, and the effect of the present invention is exhibited for the first time.

  In this invention, it is necessary to contain 20-50 weight part among 100 weight part of all the epoxy resins as an [a] component, and it is preferable that it is 25-45 weight part, More preferably, it is trifunctional or more. It is desirable to contain 30-40 parts by weight. Thereby, an elastic modulus can be improved, maintaining the heat resistance and toughness of hardened | cured material. When it is less than 20 parts by weight, the elastic modulus of the cured product becomes insufficient, and the static bending strength of the golf club shaft becomes insufficient. When it exceeds 50 parts by weight, the plastic deformation ability becomes insufficient, and the golf club shaft is likely to be divided at the time of impact breakage.

  Examples of the tri- or higher functional amine type epoxy resin include, for example, tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, triglycidylaminocresol, tetraglycidylxylylenediamine, halogens thereof, alkyl-substituted products, and hydrogenated products thereof. Can be used. In particular, since a high resin elastic modulus can be imparted, a trifunctional aminophenol type epoxy resin such as triglycidylaminophenol or triglycidylaminocresol can be preferably used.

  Examples of the tetraglycidyldiaminodiphenylmethane include “Sumiepoxy (registered trademark)” ELM434 (manufactured by Sumitomo Chemical Co., Ltd.), YH434L (manufactured by Tohto Kasei Co., Ltd.), and “jER (registered trademark)” 604 (Japan Epoxy Resin Co., Ltd.). ), “Araldide (registered trademark)” MY720, “Araldide (registered trademark)” MY721 (manufactured by Huntsman Advanced Materials) and the like can be used. As triglycidylaminophenol or triglycidylaminocresol, “Sumiepoxy (registered trademark)” ELM100, “Sumiepoxy (registered trademark)” ELM120 (manufactured by Sumitomo Chemical Co., Ltd.), “Araldide (registered trademark)” MY0500, Uses “Araldide (registered trademark)” MY0510, “Araldide (registered trademark)” MY0600 (above, manufactured by Huntsman Advanced Materials), “jER (registered trademark)” 630 (manufactured by Japan Epoxy Resin Co., Ltd.), etc. can do. As the tetraglycidylxylylenediamine and hydrogenated product thereof, “TETRAD (registered trademark)”-X, “TETRAD (registered trademark)”-C (manufactured by Mitsubishi Gas Chemical Co., Inc.) and the like can be used.

  In the present invention, as the component [b], the bisphenol F-type epoxy resin needs to contain 50 to 80 parts by weight, preferably 55 to 75 parts by weight, more preferably 60 to 60 parts by weight based on 100 parts by weight of the total epoxy resin. It is desirable to include 70 parts by weight. When the amount is less than 50 parts by weight, the plastic deformation ability becomes insufficient, and the golf club shaft is likely to be divided at the time of impact breakage. When it exceeds 80 parts by weight, the heat resistance of the cured product becomes insufficient, and the golf club shaft is warped and distorted.

  Commercially available bisphenol F type epoxy resins include “jER (registered trademark)” 806, “jER (registered trademark)” 807, “jER (registered trademark)” 4002P, “jER (registered trademark)” 4004P, “jER (registered trademark)” Trademark) "4007P", "jER (registered trademark)" 4009P (manufactured by Japan Epoxy Resin Co., Ltd.), "Epototo (registered trademark)" YDF2001, "Epototo (registered trademark)" YDF2004 (manufactured by Toto Kasei Co., Ltd.) Etc. Examples of the tetramethylbisphenol F type epoxy resin include YSLV-80XY (manufactured by Nippon Steel Chemical Co., Ltd.).

  The component [b] in the present invention preferably has an average epoxy equivalent in the range of 300 to 800, more preferably in the range of 350 to 750, and still more preferably in the range of 400 to 700. When the average epoxy equivalent is less than 300, the crosslink density of the resin becomes high, and the golf club shaft may be easily broken at the time of impact breakage. If it exceeds 800, the heat resistance of the cured product becomes insufficient due to a decrease in the crosslinking density, and the golf club shaft may be warped or distorted. Such an average epoxy equivalent can be obtained by a titration test described in JIS K7236 (2001), but can be estimated as follows when a plurality of epoxy resins having known epoxy equivalents are used in combination. Consider the case of using three types together. For example, an epoxy resin X having an epoxy equivalent of Ex (g / eq) is Wx parts by weight, an epoxy resin Y having an epoxy equivalent of Ey (g / eq) is Wy parts by weight, and an epoxy resin having an epoxy equivalent of Ez (g / eq) When blending Z with Wz parts by weight, the average epoxy equivalent is determined by the following formula.

Average epoxy equivalent = (Wx + Wy + Wz) / (Wx / Ex + Wy / Ey + Wz / Ez)
In 100 wt% of the epoxy resin in the present invention, the sum of the [a] component and the [b] component is preferably 80 to 100 wt%, more preferably 90 to 100 wt%. Thereby, the elastic modulus can be greatly improved while ensuring the plastic deformation ability of the resin. When it is less than 70% by weight, the elastic modulus of the cured product is not sufficiently improved, and the strength characteristics of the fiber-reinforced composite material may be insufficient.

  [C] component in this invention is a component required in order to harden an epoxy resin composition, and is dicyandiimide or its derivative (s).

  The blending amount of the component [c] needs to be 1 to 10 parts by weight, preferably 2 to 8 parts by weight with respect to 100 parts by weight of the epoxy resin in the epoxy resin composition from the viewpoint of heat resistance and mechanical properties. It is desirable that If it is less than 1 part by weight, the heat resistance of the cured product becomes insufficient, and the golf club shaft is warped and distorted. When the amount exceeds 10 parts by weight, the plastic deformation ability of the cured product is insufficient, and the golf club shaft is likely to be divided at the time of impact breakage. The component [c] is preferably used as a powder from the viewpoint of storage stability at room temperature and viscosity stability during prepreg formation. In the present invention, the average particle size of the component [c] is preferably 10 μm or less, and more preferably 7 μm or less. When the thickness exceeds 10 μm, for example, when used in prepreg applications, when the resin composition is impregnated into the reinforcing fiber bundle by heating and pressing, the component [c] may not enter the reinforcing fiber bundle and may remain in the fiber bundle surface layer. is there.

  Examples of commercially available dicyandiamide include DICY-7 and DICY-15 (manufactured by Japan Epoxy Resin Co., Ltd.).

  The diandiamide may be used alone or in combination with a curing catalyst for dicyandiamide or a curing agent for other epoxy resins. Examples of curing catalysts for dicyandiamide to be combined include ureas, imidazoles, Lewis acid catalysts, and other epoxy resin curing agents include aromatic amine curing agents, alicyclic amine curing agents, and acid anhydride curing agents. Agents and the like. Commercially available ureas include 3- (3,4-dichlorophenyl) -1,1-dimethylurea (DCMU 99, manufactured by Hodogaya Chemical Co., Ltd.), 1,1′-4 (methyl-m-phenylene) bis ( 3,3′dimethylurea (“Omicure®” 24), 4,4′-methylenebis (phenyldimethylurea) (“Omicure®” 52), 3-phenyl-1,1′-dimethyl Urea ("Omicure (registered trademark)" 94) (above, PTI Japan Co., Ltd.). Commercially available imidazoles include 2-methylimidazole (“Curazole®” 2MZ), 2-phenylimidazole (“Curazole®” 2PZ), 2-ethyl-4methylimidazole (“Curazole® Trademark) “2E4MZ” (manufactured by Shikoku Kasei Co., Ltd.). Lewis acid catalysts include boron trifluoride / piperidine complex, boron trifluoride / monoethylamine complex, boron trifluoride / triethanolamine complex, boron trichloride / octylamine complex, etc. Is mentioned.

  In addition, the epoxy resin composition used in the present invention improves the workability by adjusting the viscoelasticity when uncured, and for the purpose of improving the elastic modulus and heat resistance of the cured resin, [a] component and Epoxy resins other than the component [b] can be added. These may be added in combination of not only one type but also a plurality of types. Specifically, bisphenol A type epoxy resins obtained from bisphenol A, bisphenol S type epoxy resins obtained from bisphenol S, tetrabromobisphenol A type epoxy resins obtained from tetrabromobisphenol A, and the like, phenol novolacs Type epoxy resin, cresol novolac epoxy resin, resorcinol type epoxy resin, phenol aralkyl type epoxy resin, dicyclopentadiene type epoxy resin, epoxy resin having biphenyl skeleton, urethane modified epoxy resin and the like. These halogens, alkyl-substituted products, hydrogenated products, and the like can also be used.

  Commercially available bisphenol A type epoxy resins include “jER (registered trademark)” 825, “jER (registered trademark)” 828, “jER (registered trademark)” 834, “jER (registered trademark)” 1001, “jER ( Registered trademark) 1002, “jER (registered trademark)” 1003, “jER (registered trademark)” 1004, “jER (registered trademark)” 1007, “jER (registered trademark)” 1009, “jER (registered trademark)” 1010 (Epototo (registered trademark) YD-128, Epototo (registered trademark) YD-011, Epototo (registered trademark) YD-014, Epototo (registered trademark) ) “YD-017”, “Epototo (registered trademark)” YD-019, “Epototo (registered trademark)” YD-022, (Toto Kasei Co., Ltd.) ), "Epicron (registered trademark)" 840, "Epicron (registered trademark)" 850, "Epicron (registered trademark)" 1050, "Epicron (registered trademark)" 3050, "Epicron (registered trademark)", HM-101 ( As mentioned above, Dainippon Ink and Chemicals Co., Ltd.), "Sumiepoxy (registered trademark)" ELA-128 (Sumitomo Chemical Co., Ltd.), DER331 (Dow Chemical Co., Ltd.) and the like can be mentioned.

  Commercially available products of bisphenol S type epoxy resin include “Denacol (registered trademark)” EX-251 (manufactured by Nagase Kasei Kogyo Co., Ltd.), “Epicron (registered trademark)” EXA-1514 (Dainippon Ink Chemical Co., Ltd.) Manufactured).

  Commercial products of tetrabromobisphenol A type epoxy resin include “Epicoat (registered trademark)” 5050 (manufactured by Japan Epoxy Resin Co., Ltd.) and “Epicron (registered trademark)” 152 (manufactured by Dainippon Ink & Chemicals, Inc.). "Sumiepoxy (registered trademark)" ESB-400T (manufactured by Sumitomo Chemical Co., Ltd.), "Epototo (registered trademark)" YBD-360 (manufactured by Toto Kasei Co., Ltd.).

  Commercially available products of phenol novolac type epoxy resins include “Epicoat (registered trademark)” 152, “Epicoat (registered trademark)” 154 (manufactured by Japan Epoxy Resin Co., Ltd.), and “Epicron (registered trademark)” N-740. "Epiclon (registered trademark)" N-770, "Epiclon (registered trademark)" N-775 (manufactured by Dainippon Ink & Chemicals, Inc.), and the like.

  Examples of commercially available cresol novolac epoxy resins include “Epicron (registered trademark)” N-660, “Epicron (registered trademark)” N-665, “Epicron (registered trademark)” N-670, and “Epicron (registered trademark)”. “N-673”, “Epicron (registered trademark)” N-695 (above, manufactured by Dainippon Ink & Chemicals, Inc.), EOCN-1020, EOCN-102S, EOCN-104S (above, manufactured by Nippon Kayaku Co., Ltd.) ) And the like.

  Specific examples of the resorcinol type epoxy resin include “Denacol (registered trademark)” EX-201 (manufactured by Nagase ChemteX Corporation).

  Commercially available dicyclopentadiene type epoxy resins include “Epicron (registered trademark)” HP7200, “Epicron (registered trademark)” HP7200L, “Epicron (registered trademark)” HP7200H (above, Dainippon Ink & Chemicals, Inc.) , Tactix 558 (manufactured by Huntsman Advanced Materials), XD-1000-1L, XD-1000-2L (manufactured by Nippon Kayaku Co., Ltd.), and the like.

  As commercially available products of epoxy resins having a biphenyl skeleton, “Epicoat (registered trademark)” YX4000H, “Epicoat (registered trademark)” YX4000, “Epicoat (registered trademark)” YL6616 (above, manufactured by Japan Epoxy Resins Co., Ltd.), NC-3000 (made by Nippon Kayaku Co., Ltd.) etc. are mentioned.

  Examples of commercially available urethane and isocyanate-modified epoxy resins include AER4152 (produced by Asahi Kasei Epoxy Co., Ltd.) and ACR1348 (produced by Asahi Denka Co., Ltd.) having an oxazolidone ring.

  The epoxy resin composition used in the present invention controls the viscoelasticity to improve the tack and drape characteristics of the prepreg, and to improve the mechanical characteristics of the golf club shaft. It is preferable to contain 2 to 10 parts by weight, and more desirably 3 to 8 parts by weight.

  As such a thermoplastic resin, a thermoplastic resin having a hydrogen bonding functional group that can be expected to improve the adhesion between the resin and the reinforcing fiber is preferably used.

  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 include polyamide, polyimide, polyvinyl pyrrolidone, and heat having a sulfonyl group. An example of the plastic resin is 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 and “Denka Formal (registered trademark)” (manufactured by Denki Kagaku Kogyo Co., Ltd.), “Vinylec (registered trademark)” (manufactured by Chisso Corporation), “UCAR (registered trademark)” PKHP (manufactured by Union Carbide) as phenoxy resin, “Macromelt (registered trademark)” as polyamide resin (Henkel Hakusui) Co., Ltd.), “Amilan (registered trademark)” CM4000 (manufactured by Toray Industries, Inc.), “Ultem (registered trademark)”, (manufactured by General Electric Co., Ltd.), “Matrimid (registered trademark)” 5218 (manufactured by Ciba) ), “Victrex (registered trademark)” as a polysulfone (manufactured by Mitsui Chemicals, Inc.), UDEL (registered trademark) "(manufactured by Union Carbide Corporation), as polyvinylpyrrolidone," Luviskol (registered trademark) ", and (manufactured by BASF Japan Ltd.).

  In addition, the acrylic resin has high compatibility with the epoxy resin, and is preferably used for controlling the viscoelasticity. Examples of commercially available acrylic resins include “Dianar (registered trademark)” BR series (manufactured by Mitsubishi Rayon Co., Ltd.), “Matsumoto Microsphere (registered trademark)” M, and “Matsumoto Microsphere (registered trademark)”. “M100,” “Matsumoto Microsphere (registered trademark)” M500 (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.), and the like.

  The epoxy resin composition used in the present invention preferably contains organic particles such as rubber particles and thermoplastic resin particles, inorganic particles, and the like in order to improve the impact resistance of the golf club shaft.

  As the rubber particles, cross-linked rubber particles and core-shell rubber particles obtained by graft polymerization of a different polymer on the surface of the cross-linked rubber particles are preferably used from the viewpoint of handleability and the like.

  Commercially available cross-linked rubber particles include FX501P (made by Nippon Synthetic Rubber Industries) made of a crosslinked product of carboxyl-modified butadiene-acrylonitrile copolymer, and CX-MN series made by fine particles of acrylic rubber (made by Nippon Shokubai Co., Ltd.). YR-500 series (manufactured by Toto Kasei Co., Ltd.) can be used.

  Commercially available core-shell rubber particles include, for example, “Paraloid (registered trademark)” EXL-2655 (manufactured by Kureha Chemical Co., Ltd.), acrylic ester / methacrylic ester, composed of a butadiene / alkyl methacrylate / styrene copolymer. "STAPHYLOID (registered trademark)" AC-3355 made of a copolymer, TR-2122 (manufactured by Takeda Pharmaceutical Co., Ltd.), "PARALOID (registered trademark)" EXL made of a butyl acrylate / methyl methacrylate copolymer -2611, EXL-3387 (manufactured by Rohm & Haas), “Kane Ace (registered trademark)” MX series (manufactured by Kaneka Corporation), and the like can be used.

  As the thermoplastic resin particles, polyamide particles and polyimide particles are preferably used, and as commercially available polyamide particles, SP-500 (manufactured by Toray Industries, Inc.), “Orgasol (registered trademark)”, (manufactured by Arkema Inc.), etc. Can be used.

  In the present invention, the organic particles such as rubber particles and thermoplastic resin particles are used in an amount of 0.1 to 30 parts by weight with respect to 100 parts by weight of the total epoxy resin from the viewpoint of achieving both the elastic modulus and toughness of the obtained cured product. More preferably, it is 1 to 15 parts by weight, and further preferably 2 to 10 parts by weight.

  For the preparation of the epoxy resin composition used in the present invention, a kneader, a planetary mixer, a three-roll extruder, a twin-screw extruder, and the like are preferably used. When the thermoplastic resin is added after kneading the epoxy resin, the temperature of the composition is raised to an arbitrary temperature (for example, 90 to 120 ° C.) while stirring, and then the thermoplastic resin is stirred while stirring at that temperature. Dissolve. Thereafter, while stirring, the temperature is preferably lowered to 100 ° C. or lower, more preferably 80 ° C. or lower, and the component [c] and the curing catalyst are added and kneaded.

When the epoxy resin composition used in the present invention is used for prepreg applications, the viscosity at 50 ° C. is preferably 100 to 10,000 Pa · s, more preferably 200 to 5000 Pa · s from the viewpoint of processability such as tack and drape. s, more preferably in the range of 500 to 3000 Pa · s. If it is less than 100 Pa · s, the shape retention of the prepreg may be insufficient and cracking may occur, and a large resin flow may occur during molding, resulting in variations in fiber content. If it exceeds 10,000 Pa · s, the resin composition may be blurred during the film-forming process, or an unimpregnated portion may be generated in the impregnation step into the reinforcing fiber. The viscosity here is determined by using a dynamic viscoelasticity measuring device (for example, ARES: manufactured by TA Instruments), using a parallel plate with a diameter of 40 mm, and simply raising the temperature at a rate of temperature rise of 2 ° C./min. It refers to the complex viscoelastic modulus η ^* measured at 5 Hz and a gap of 1 mm.

  The bending deflection amount of the cured product obtained by curing the epoxy resin composition used in the present invention is preferably 8 to 20 mm, more preferably 12 to 20 mm, and still more preferably 14 to 20 mm. It is desirable to be in When the amount of bending of the cured product is less than 8 mm, the plastic deformation ability is insufficient, and the golf club shaft may be easily broken at the time of impact breakage. On the other hand, from the aspect that the golf club shaft is less likely to be broken at the time of impact, the higher the amount of bending deflection, the better. However, since the amount of bending deflection and the bending elastic modulus are in a trade-off relationship, The flexural modulus is not preferable because it may be less than 3.8 GPa. The amount of bending deflection here is measured according to JIS K7171 (1999).

  The epoxy resin composition used in the present invention preferably has a glass transition temperature of 100 to 180 ° C., more preferably 110 to 150 ° C., as measured by a differential scanning calorimeter (DSC) of the cured product when cured. More preferably, it is desirable that it is 120-140 degreeC. When the glass transition temperature is less than 100 ° C., the heat resistance of the molded product after curing becomes insufficient, the golf club shaft may be warped or distorted, and deformation occurs when used in a high temperature environment. There is a case. This is because if the glass transition temperature exceeds 180 ° C., the cured resin may become brittle.

  The prepreg of the present invention is produced by impregnating a fiber base material with the epoxy resin composition. Examples of the impregnation method include a wet method in which the epoxy resin composition is dissolved in a solvent such as methyl ethyl ketone and methanol to lower the viscosity and impregnation, and a hot melt method (dry method) in which the viscosity is reduced by heating and impregnation. it can.

  The wet method is a method in which the reinforcing fiber is immersed in a solution of the epoxy resin composition and then lifted and the solvent is evaporated using an oven or the like. The hot melt method directly applies the epoxy resin composition whose viscosity has been reduced by heating. A method of impregnating reinforcing fibers, or a film in which an epoxy resin composition is once coated on a release paper or the like is prepared, and then the films are laminated from both sides or one side of the reinforcing fibers and heated and pressed to form reinforcing fibers. This is a method of impregnating a resin. The hot melt method is preferable because substantially no solvent remains in the prepreg.

The prepreg of the present invention preferably has a reinforcing fiber amount per unit area of 50 to 150 g / m ² . More preferably, it is 70-140 g / m < ² >, More preferably, it is desirable to contain 90-130 g / m < ² >. When the amount of the reinforcing fiber is less than 50 g / m ^2, it is necessary to increase the number of laminated layers in order to obtain a predetermined thickness at the time of forming the fiber reinforced composite material, and the work may be complicated. On the other hand, when the amount of reinforcing fibers exceeds 150 g / m ² , the prepreg drape property may tend to deteriorate.

  The fiber weight content of the prepreg of the present invention is preferably 70 to 87% by weight, more preferably 72 to 80% by weight, and further preferably 74 to 78% by weight. When the fiber weight content is less than 70% by weight, the amount of the resin is too large, and the advantages of the fiber reinforced composite material having excellent specific strength and specific modulus cannot be obtained. The amount of heat generated may be too high. On the other hand, if the fiber weight content exceeds 87% by weight, resin impregnation failure occurs, and the resulting composite material may have many voids.

  After laminating the prepreg of the present invention, the fiber-reinforced composite material tubular body of the present invention, particularly a golf club shaft, is produced by a method of heat curing the resin while applying pressure to the laminate.

  As a method for applying heat and pressure, a press molding method, an autoclave molding method, a bagging molding method, a wrapping tape method, an internal pressure molding method, or the like is employed. Among them, the wrapping tape method is a method of forming a tubular body made of a fiber reinforced composite material by winding a prepreg on a mandrel or other core metal, and is a suitable method for producing a golf club shaft. More specifically, a prepreg is wound around a mandrel, a wrapping tape made of a thermoplastic film is wound around the outside of the prepreg for fixing and applying pressure, and the resin is heated and cured in an oven, and then a cored bar. This is a method for extracting a tube to obtain a tubular body.

  Also, the internal pressure molding method is to set a preform in which a prepreg is wound on an internal pressure applying body such as a tube made of a thermoplastic resin in a mold, and then introduce a high pressure gas into the internal pressure applying body to apply pressure. At the same time, the mold is heated and molded. This method is preferably used when molding a complicated shape such as a golf club shaft, a bad, a racket such as tennis or badminton.

The in-plane shear strength of the laminate obtained by curing the prepreg of the present invention is preferably in the range of 130 to 150 MPa, more preferably 135 to 145 MPa. Such a laminated plate has a laminated structure of [+ 45 / −45] _ns (n is a positive integer) so that the fiber direction is ± 45 degrees by a method described later, and the plate thickness is about 2 mm. A predetermined number of layers are laminated so as to be obtained and cured and molded at a predetermined temperature and pressure in an autoclave. The in-plane shear strength of the obtained material is measured according to JIS K7079 (1991). If the in-plane shear strength is less than 130 MPa, sufficient static bending strength may not be obtained when a golf club shaft is obtained. On the other hand, if it exceeds 150 MPa, the golf club shaft may be easily broken at the time of impact damage.

  The tubular body made of a fiber reinforced composite material obtained by curing the prepreg of the present invention into a tube includes at least a part of a straight layer in which the prepregs are laminated so that the orientation of the carbon fibers is substantially parallel to the axial direction of the tubular body. . Such a straight layer bears the bending rigidity and bending strength of such a tubular body. In order to obtain a sufficient effect in the fiber-reinforced composite material tubular body of the present invention, it is necessary to use the prepreg of the present invention at least in the straight layer. If necessary, a bias layer in which prepregs are laminated with the orientation of the carbon fibers tilted by about 45 degrees with respect to the tubular body axis direction, and the orientation of the carbon fibers substantially orthogonal to the tubular body axis direction. The hoop layer in which the prepreg is laminated and various reinforcing layers may be appropriately introduced.

  The tubular body made of fiber-reinforced composite material of the present invention can be suitably used particularly for a golf club shaft.

  In a golf club shaft, a bias layer in which prepregs are laminated so that the orientation of carbon fibers is inclined by about 45 degrees with respect to the shaft axis direction is generally arranged inside, and the orientation of carbon fibers is substantially parallel to the shaft axis direction. The straight layer which laminated | stacked the prepreg in the form which was made is arrange | positioned outside, and is comprised. In this case, the bias layer bears the torsional rigidity and torsional strength of the golf club shaft, and the straight layer bears the bending rigidity and the bending strength of the golf club shaft.

  In order to obtain a sufficient effect in the golf club shaft of the present invention, it is necessary to use the prepreg of the present invention at least in the straight layer. By using the prepreg of the present invention at least in the straight layer, when a bending impact stress or the like is applied, the carbon fiber on the bending impact imparting side or at least one of the side and the side opposite to the circumferential direction is provided. This is because the golf club shaft can be prevented from being cut into two independent pieces by preventing at least a part of the golf club shaft from breaking. Moreover, it is preferable to apply the prepreg of the present invention to the bias layer as well as the straight layer because a more excellent effect can be obtained. If necessary, a hoop layer or various reinforcing layers in which prepregs are laminated in such a manner that the orientation of carbon fibers is substantially orthogonal to the shaft axial direction may be introduced.

Hereinafter, the present invention will be described in more detail with reference to examples. Various physical properties were measured by the following methods. These physical properties were measured in an environment at a temperature of 23 ° C. and a relative humidity of 50% unless otherwise specified. The results are also shown in the last table.

(1) Measurement of tensile strength and tensile modulus of carbon fiber 1000 g (100 parts by weight) of “Bakelite (registered trademark)” ERL-4221 manufactured by Union Carbide Co., Ltd. A resin composition in which 30 g (3 parts by weight) of ethylamine (BF ₃ · MEA) and 40 g (4 parts by weight) of acetone are mixed is impregnated, and then heated at 130 ° C. for 30 minutes to be cured, and a resin-impregnated strand is obtained. Obtained. Tensile strength and tensile modulus were determined by the resin impregnated strand test method JIS R7601 (1986). The number of test samples was n = 10, and the average value was adopted.

(2) Measurement of Fiber Surface Area Ratio and Surface Roughness Ra A reinforcing fiber to be used for measurement was fixed to a sample table, and an image of a three-dimensional surface shape was obtained under the following conditions using DigitalScopes NanoScope III.
Probe: Si cantilever integrated probe (OMCL-AC120TS manufactured by Olympus Optical Co., Ltd.)
・ Measurement environment: Room temperature (20 ° C. to 30 ° C.) in the atmosphere ・ Observation mode: Tapping mode ・ Scanning speed: 0.3 to 0.4 Hz
・ Scanning range: 2.5μm × 2.5μm
-Number of pixels: 512 × 512
The entire image obtained was processed by the software attached to the previous term equipment (using NanoScope III version 4.22r2, 1st flatten filter, lowpass filter, 3rd plane fit filter), and in addition to surface roughness Ra, actual surface area and projection The area was calculated. In addition, about the projected area, the surface area ratio was calculated | required with the following formula using what calculated the projected area to the quadratic curved surface which considered the curvature of the fiber cross-sectional area.
Surface area ratio = actual surface area / similar measurement was performed twice, and the average value was defined as the surface area ratio of the fiber.

  (3) Measurement of surface specific oxygen concentration O / C of carbon fiber The surface specific oxygen concentration O / C was determined by X-ray photoelectron spectroscopy according to the following procedure.

  First, the sizing agent and the like were removed from the carbon fiber bundle to be measured with a solvent, cut to about 5 mm, spread on a stainless steel sample support, and then measured under the following conditions.

-Photoelectron escape angle: 90 degrees-X-ray source: MgKα1,2
・ Vacuum degree in sample chamber: 1 × 10 ⁻⁸ Torr
Then, for correction of the peak due to the measurement time of the charging, the binding energy value of the main peak of C _1S B. E. Was adjusted to 284.6 eV.

Next, the C _1s peak area [O _1s ] is obtained by drawing a straight base line in the range of 282 to 296 eV, and the O _1s peak area [C _1s ] is obtained by drawing a straight base line in the range of 528 to 540 eV. Asked.

The surface specific oxygen concentration O / C was obtained from the ratio of the O _1s peak area [O _1s ], the C _1s peak area [C _1s ], and the sensitivity correction value specific to the apparatus according to the following equation.
O / C = ([O _1s ] / [C _1s ]) / (sensitivity correction value)
Here, ESCA-750 manufactured by Shimadzu Corporation was used as the measuring device, and the sensitivity correction value unique to the device was set to 2.85. The number of test samples was n = 3, and the average value was adopted.

(4) Measurement of average fiber diameter of carbon fiber After embedding a carbon fiber bundle with an embedding epoxy resin and polishing it in a direction orthogonal to the fiber using sandpaper, the cross section was magnified 1000 times with an optical microscope. Observed. Select 20 single yarns randomly from the field of view, measure their long diameter R and short diameter r, calculate the average value of each, {(average value of R) + (average value of r)} / 2 was the average fiber diameter. Further, when (average value of r) / (average value of R) exceeded 0.9, it was judged to be substantially circular.

(5) Production of carbon fiber Carbon fibers [I] to [X] were produced by the following production method. These various characteristic values are shown in Table 2.

<Carbon fiber [I]>
An acrylic precursor fiber having a single fiber fineness of 0.08 tex and a filament count of 12,000 was obtained by a dry and wet spinning method using a copolymer consisting of 99.4% acrylonitrile and 0.6 mol% methacrylic acid.

This precursor fiber is heated in the air at 240 to 280 ° C. at a draw ratio of 1.05, converted to flame-resistant fiber, and further the rate of temperature increase in the temperature range of 300 to 900 ° C. in a nitrogen atmosphere is 200 ° C./min. Then, after heating at a draw ratio of 1.10, it was fired to 1400 ° C. and carbonized. The obtained carbon fiber had a basis weight of 0.50 g / m and a density of 1.80 g / cm ³ .

  Next, an electrolytic oxidation treatment was performed using an aqueous solution of ammonium hydrogen carbonate having a concentration of 1.0 mol / l as an electrolytic solution in an electric quantity of 30 coulomb / g. Next, the carbon fiber after the electrolytic oxidation treatment was washed with water and dried in air at 150 ° C. to obtain carbon fiber [I].

  Carbon fiber [I] has a tensile modulus of 294 GPa, a tensile strength of 6100 MPa, a surface specific oxygen concentration O / C of 0.18, an average fiber diameter of 5.5 μm, and a cross-sectional shape of r / R of 0.95. There was a substantially circular shape.

<Carbon fiber [II]>
The carbon fiber [II] was obtained under the same conditions as the carbon fiber [I] except that the amount of electricity during the electrolytic oxidation treatment was 3 coulomb / g · tank.

  Carbon fiber [II] has a tensile modulus of 294 GPa, a tensile strength of 5800 MPa, a surface specific oxygen concentration O / C of 0.08, an average fiber diameter of 5.5 μm, and a cross-sectional shape of r / R of 0.95. There was a substantially circular shape.

<Carbon fiber [III]>
The acrylic precursor fiber was made under the same conditions as the carbon fiber [II] except that the spinning method of the acrylic precursor fiber was changed to a wet spinning method and the single fiber fineness of the obtained acrylic precursor fiber was 0.09 tex. Carbon fiber [III] was obtained. The obtained carbon fiber had a basis weight of 0.50 g / m and a density of 1.80 g / cm ³ .

  Carbon fiber [III] has a tensile modulus of 294 GPa, a tensile strength of 5600 MPa, a surface specific oxygen concentration O / C of 0.05, an average fiber diameter of 5.4 μm, and a cross-sectional shape of r / R of 0.8. It was flat.

<Carbon fiber [IV]>
Except that the single fiber fineness of the obtained acrylic precursor fiber was 0.07 tex, it was produced under the same conditions as carbon fiber [II] to obtain carbon fiber [IV]. The obtained carbon fiber had a basis weight of 0.45 g / m and a density of 1.80 g / cm ³ .

  Carbon fiber [IV] has a tensile modulus of 294 GPa, a tensile strength of 6000 MPa, a surface specific oxygen concentration O / C of 0.11, an average fiber diameter of 4.8 μm, and a cross-sectional shape of r / R of 0.96. There was a substantially circular shape.

<Carbon fiber [V]>
After the carbonization step, the carbon fiber [V] was obtained under the same conditions as the carbon fiber [II] except that the graphitization was performed by firing to 2300 ° C. The obtained carbon fiber [V] had a basis weight of 0.50 g / m and a density of 1.80 g / cm ³ .

  Carbon fiber [V] has a tensile modulus of 380 GPa, a tensile strength of 4500 MPa, a surface specific oxygen concentration O / C of 0.10, an average fiber diameter of 5.5 μm, and a cross-sectional shape of r / R of 0.93. There was a substantially circular shape.

<Carbon fiber [VI]>
Carbon fiber, except that the resulting acrylic precursor fiber has a single fiber fineness of 0.075 tex, the stretch ratio during carbonization was changed to 1.05, and the maximum temperature during carbonization was changed to 1450 ° C. Fabricated under the same conditions as [II], carbon fiber [VI] was obtained. The obtained carbon fiber had a basis weight of 0.50 g / m and a density of 1.80 g / cm ³ .

  Carbon fiber [III] has a tensile modulus of 294 GPa, a tensile strength of 5400 MPa, a surface specific oxygen concentration O / C of 0.09, an average fiber diameter of 5.6 μm, and a cross-sectional shape of r / R of 0.94. There was a substantially circular shape.

<Carbon fiber [VII]>
Carbon fiber, except that the single fiber fineness of the resulting acrylic precursor fiber is 0.085 tex, the draw ratio during carbonization is changed to 1.15, and the maximum temperature during carbonization is changed to 1350 ° C. Fabricated under the same conditions as [II], carbon fiber [VII] was obtained. The obtained carbon fiber had a basis weight of 0.50 g / m and a density of 1.80 g / cm ³ .

  Carbon fiber [VII] has a tensile modulus of 294 GPa, a tensile strength of 6400 MPa, a surface specific oxygen concentration O / C of 0.10, an average fiber diameter of 5.5 μm, and a cross-sectional shape of r / R of 0.97. There was a substantially circular shape.

<Carbon fiber [VIII]>
Carbon fiber, except that the single fiber fineness of the obtained acrylic precursor fiber was 0.07 tex, the stretch ratio during carbonization was changed to 1.00, and the maximum temperature during carbonization was changed to 1200 ° C. Fabricated under the same conditions as [II], carbon fiber [VIII] was obtained. The obtained carbon fiber had a basis weight of 0.51 g / m and a density of 1.82 g / cm ³ .

  Carbon fiber [VIII] has a tensile modulus of 230 GPa, a tensile strength of 5200 MPa, a surface specific oxygen concentration O / C of 0.12, an average fiber diameter of 5.5 μm, and a cross-sectional shape of r / R of 0.94. There was a substantially circular shape.

<Carbon fiber [IX]>
Carbon fiber, except that the single fiber fineness of the obtained acrylic precursor fiber is 0.085 tex, the draw ratio during carbonization is changed to 1.15, and the maximum temperature during carbonization is changed to 1500 ° C. Fabricated under the same conditions as [II], carbon fiber [IX] was obtained. The obtained carbon fiber had a basis weight of 0.49 g / m and a density of 1.78 g / cm ³ .

  Carbon fiber [IX] has a tensile modulus of 330 GPa, a tensile strength of 5400 MPa, a surface specific oxygen concentration O / C of 0.10, an average fiber diameter of 5.5 μm, and a cross-sectional shape of r / R of 0.96. There was a substantially circular shape.

<Carbon fiber [X]>
Carbon fiber, except that the single fiber fineness of the obtained acrylic precursor fiber is 0.075 tex, the stretch ratio during carbonization is changed to 1.05, and the maximum temperature during carbonization is changed to 1300 ° C. Fabricated under the same conditions as [II], carbon fiber [X] was obtained. The obtained carbon fiber had a basis weight of 0.50 g / m and a density of 1.81 g / cm ³ .

  Carbon fiber [X] has a tensile modulus of 270 GPa, a tensile strength of 5400 MPa, a surface specific oxygen concentration O / C of 0.08, an average fiber diameter of 5.5 μm, and a cross-sectional shape of r / R of 0.95. There was a substantially circular shape.

(6) Preparation of Resin Composition In the kneader, a predetermined amount of components other than the curing agent / curing accelerator is added, and while kneading, the temperature is raised to 160 ° C., and kneading is performed at 160 ° C. for 1 hour. A preparation was obtained. The temperature was lowered while kneading to 80 ° C., and a predetermined amount of a curing agent and a curing accelerator were added and kneaded to obtain epoxy resin compositions I to VI. The compounding ratios of the epoxy resin compositions I to VI are as shown in Table 1. The raw materials used here are as shown below.

<Trifunctional or higher amine type epoxy resin (component [a])>
"Sumiepoxy (registered trademark)" ELM434 (tetraglycidyldiaminodiphenylmethane, epoxy equivalent: 120, manufactured by Sumitomo Chemical Co., Ltd.)
"Sumiepoxy (registered trademark)" ELM120 (triglycidyl-m-aminophenol, epoxy equivalent: 118, manufactured by Sumitomo Chemical Co., Ltd.)
“JER (registered trademark)” 630 (triglycidyl-m-aminophenol, epoxy equivalent: 90 to 105, manufactured by Japan Epoxy Resins Co., Ltd.)
<Bisphenol F type epoxy resin (component [b])>
"Epiclon (registered trademark)" 830 (bisphenol F-type epoxy resin, epoxy equivalent: 172, manufactured by Dainippon Ink & Chemicals, Inc.)
"JER (registered trademark)" 4004P (bisphenol F type epoxy resin, epoxy equivalent: 800, manufactured by Japan Epoxy Resins Co., Ltd.)
<Dicyandiamide (component [c])>
・ DICY7 (made by Japan Epoxy Resin Co., Ltd.)
<Other ingredients>
"JER (registered trademark)" 828 (bisphenol A type epoxy resin, epoxy equivalent: 189, manufactured by Japan Epoxy Resins Co., Ltd.)
"JER (registered trademark)" 1001 (bisphenol A type epoxy resin, epoxy equivalent: 475, manufactured by Japan Epoxy Resins Co., Ltd.)
・ "Vinylec (registered trademark)" K (polyvinyl formal, manufactured by Chisso Corporation)
DCMU99 (3- (3,4-dichlorophenyl) -1,1-dimethylurea, curing accelerator, manufactured by Hodogaya Chemical Co., Ltd.)
(7) Viscosity measurement of epoxy resin composition The viscosity of the epoxy resin composition was measured using a dynamic viscoelasticity measuring device (ARES: manufactured by TA Instruments), using a parallel plate with a diameter of 40 mm, and a temperature increase rate of 2 ° C. The temperature was simply raised at / min, and measurement was performed at a frequency of 0.5 Hz and a gap of 1 mm.

(8) Measurement of glass transition temperature of cured product After defoaming an uncured resin composition in a vacuum, 130 was placed in a mold set to a thickness of 2 mm by a 2 mm thick “Teflon (registered trademark)” spacer. Curing was performed at a temperature of 0 ° C. for 2 hours to obtain a cured resin having a thickness of 2 mm. A small amount of this was cut out, and the glass transition temperature was measured using a differential scanning calorimeter (MDSC2910: manufactured by TA Instruments). The midpoint temperature obtained based on JIS K7121 (1987) was defined as the glass transition temperature. The measurement conditions were a nitrogen atmosphere, a temperature increase rate of 10 ° C./min, and a measurement temperature range of 0 ° C. to 350 ° C. The number of test samples was n = 3, and the average value was adopted.

(9) Measurement of flexural modulus and amount of flexure of resin cured product After defoaming the uncured resin composition in a vacuum, the thickness is set to 2 mm with a 2 mm thick “Teflon (registered trademark)” spacer. The cured mold was cured at a temperature of 130 ° C. for 2 hours to obtain a cured resin having a thickness of 2 mm. This was cut into a 2 mm thick resin cured product, a test piece with a width of 10 mm and a length of 60 mm was cut out, and an Instron universal testing machine (Instron 3369 type) was used, using a load cell with a maximum capacity of 5 kN, A three-point bending was performed in accordance with JIS K7171 (1999) with an interval length of 32 mm and a crosshead speed of 2.5 mm / min to obtain a bending elastic modulus and a bending deflection amount. The number of samples was set to n = 5, and the average value was compared.

(10) Preparation of prepreg The resin composition was applied to a release paper using a reverse roll coater to prepare a resin film. Next, two resin films are stacked on both sides of the carbon fiber on the carbon fiber aligned in one direction in a sheet shape, and heated and pressed to impregnate the resin composition, and the weight of the carbon fiber per unit area is 125 g / m ^2. A unidirectional prepreg with a fiber weight content of 76% was produced.

  The carbon fibers used in each example and comparative example are as shown in Table 2. The carbon fiber characteristics used here are shown together in Table 2.

(11) the plane shear strength unidirectional prepreg sheets laminated structure of as [+ 45 / _{-45] 5S} which direction of the fibers is ± 45 °, and 20ply laminated, temperature 135 ° C. in an autoclave, pressure 3 kg / mm ² Was cured by heating and pressing for 2 hours to prepare a unidirectional composite material. Next, the in-plane shear strength of the obtained material was measured according to JIS K7079 (1991). The number of test samples was n = 5, and the average value was adopted.

  Table 1 and Table 2 collectively show the results of producing epoxy resin compositions, prepregs, and fiber-reinforced composite material tubular bodies for each of the Examples and Comparative Examples by the above-described method and aiming at the characteristics.

(12) Production of tubular body made of composite material for cylindrical bending test A test tubular body was produced by the following method. By the following operations (a) to (e), the carbon fiber unidirectional prepreg produced in (10) is alternately arranged so that the fiber direction is 45 ° and −45 ° with respect to the cylindrical axis direction. A total of 3 ply was laminated, 3 ply was laminated so that the same unidirectional prepreg was parallel to the cylindrical axis direction, and a composite material tubular body having an inner diameter of 10 mm was produced. As the mandrel, a stainless steel round bar having a diameter of 10 mm and a length of 1000 mm was used. In addition, this test tubular body is a very general laminated structure of golf club shafts except that it does not have a taper and does not use a reinforcing material, and reflects the characteristics of the golf club shaft.
(A) Two sheets were cut out from the unidirectional prepreg produced in the above (10) into a rectangular shape of 105 mm long by 800 mm wide (so that the fiber axis direction was 45 degrees with respect to the direction of the long side). The two prepreg fibers were laminated so that the directions of the fibers intersected each other and shifted by 16 mm (a half of the mandrel) in the short side direction.
(B) The mandrel was wound so that the long side of the rectangular shape of the prepreg bonded to the mandrel subjected to the mold release treatment and the mandrel axial direction were the same direction.
(C) On top of that, the unidirectional prepreg produced in (10) above was cut into a rectangular shape of 115 mm in length and 800 mm in width (the long side direction was the fiber axis direction), and the direction of the fiber was a mandrel. The mandrel was wound so as to be in the same direction as the axis.
(D) Further, a wrapping tape (heat-resistant film tape, width 10 mm) was wrapped around the wound with a tension of 3 kg from above, and the wound product was covered, and was heated and molded at 130 ° C. for 90 minutes in a curing furnace. (E) Thereafter, the mandrel was extracted and the wrapping tape was removed to obtain a composite material tubular body.

(13) Cylindrical bending test Using the composite material tubular body (inner diameter: 10 mm) obtained in the procedure of (12) above, "Golf Club Shaft Certification Criteria and Standard Confirmation Method" (Product Safety Association, edited by Commerce Industry) The bending strength was measured in accordance with the three-point bending test method described in Minister's Approval No. 5 (2087, 1993). Here, the distance between fulcrums was 300 mm, and the test speed was 10 mm / min.

(14) Production of Composite Material Tubular Body for Charpy Impact Test A test tubular body was produced by the following method. By the following operations (a) to (e), the carbon fiber unidirectional prepreg produced in (10) above is alternately arranged so that the fiber direction is 45 ° and −45 ° with respect to the cylindrical axis direction. A total of 3 ply was laminated, 3 ply was laminated with the same unidirectional prepreg so that the fiber direction was parallel to the cylindrical axis direction, and a composite material tubular body having an inner diameter of 6.3 mm was produced. The mandrel was a stainless steel round bar with a diameter of 6.3 mm and a length of 1000 mm. In addition, this test tubular body is a laminated structure of a general golf club shaft except that it does not have a taper and does not use a reinforcing material, and reflects the characteristics of the golf club shaft well.
(A) Two sheets were cut out from the unidirectional prepreg produced according to the above (7) into a rectangular shape of 68 mm in length and 800 mm in width (so that the fiber axis direction was 45 degrees with respect to the direction of the long side). The two prepreg fibers were laminated so that the directions of the fibers crossed each other and shifted by 10 mm (half the mandrel half circumference) in the short side direction.
(B) The mandrel was wound so that the long side of the rectangular shape of the prepreg bonded to the mandrel subjected to the mold release treatment and the mandrel axial direction were the same direction.
(C) A unidirectional prepreg produced according to the above (10) is cut into a rectangular shape of 80 mm in length and 800 mm in width (the long side direction is the fiber axis direction), and the fiber direction is the mandrel axis. Wrapped around a mandrel so that it is the same as the direction of
(D) Further, a wrapping tape (heat-resistant film tape, width 10 mm) was wrapped around the wound with a tension of 3 kg from above, and the wound product was covered, and was heated and molded at 130 ° C. for 90 minutes in a curing furnace.
(E) Thereafter, the mandrel was extracted and the wrapping tape was removed to obtain a composite material tubular body.

(15) Charpy impact test of composite material tubular body The composite material tubular body obtained in (14) above was cut to a length of 60 mm to prepare a test piece having an inner diameter of 6.3 mm and a length of 60 mm. A Charpy impact test was performed by applying an impact from the side of the tubular body at a weight of 300 kg · cm. From the swing angle, the following formula:
E = WR [(cosβ-cosα) − (cosα′−cosα) (α + β) / (α + α ′)]
E: Absorbed energy (J)
WR: Moment around the rotation axis of the hammer (N · m)
α: Hammer lift angle (°)
α ': Swing angle when the hammer is swung from the lift angle α (°)
β: Hammer swing angle after breakage of specimen (°)
The absorbed energy of impact was calculated according to

  Note that notches (notches) are not introduced into the test piece. The number of samples was n = 10 and compared from the average value.

Moreover, after the test, when the sample was divided into two pieces at the impact location, it was determined that the sample was divided. In addition, when all parts are divided, the division occurrence rate is 100%, and when five of the ten pieces are divided, the division occurrence rate is 50%.
Example 1
As shown in Table 2, as a result of using [I] as the carbon fiber and [i] having an elastic modulus of 3.8 GPa as the epoxy resin composition, it has a good static bending strength and at the time of impact breakage. Only three of the ten tubular bodies were cut.
(Example 2)
A prepreg and a tubular body were obtained in the same manner as in Example 1 except that [II] was used as the carbon fiber. As a result of a slight decrease in the in-plane shear strength, energy absorption during peeling at the interface became significant, and the Charpy impact strength was improved while maintaining static bending strength. Further, in the Charpy impact test, the tubular body was not divided at the time of impact.
(Examples 3, 4, and 5)
Implementation was performed except that a trifunctional aminophenol type epoxy resin having a high resin elastic modulus was used as the [a] component and the epoxy resin compositions [ii] to [iv] were used in which the blending ratio of the [b] component was changed. A prepreg and a tubular body were obtained in the same manner as in Example 2. As a result of further improvement in the resin flexural modulus, the static bending strength was further improved. In the Charpy impact test, the tubular bodies of Examples 3 and 4 were not divided at all at the time of impact. For Example 5, only 2 of 10 samples were divided.
(Example 6)
A prepreg and a tubular body were obtained using the epoxy resin composition [v] in which the blending ratio of the component [b] in Example 1 was changed and using [II] as the carbon fiber. As a result of a slight decrease in the in-plane shear strength, energy absorption during peeling at the interface became significant, and in the Charpy impact test, the tubular body was not broken at the time of impact.
(Examples 7 and 8)
A prepreg and a tubular body were obtained in the same manner as in Example 4 except that [VI] having a slightly low tensile strength and [VII] having a high tensile strength were used as carbon fibers. As the tensile strength of carbon fiber increased, static bending strength and Charpy impact strength improved. In the Charpy impact test, with respect to Example 7, the number of divided tubular bodies was 1 out of 10, and Example 8 was not divided at all.
(Comparative Example 1)
Except for using the epoxy resin composition [vi] in which the blending amount of the epoxy resin composition [a] component was reduced to 20 parts by weight and the composition ratio of the [b] component was slightly changed, the same as in Example 4. A prepreg and a tubular body were obtained. In the Charpy impact test, these tubular bodies did not easily break, but as a result of the decrease in the flexural modulus of the resin composition, the static bending strength was insufficient.
(Comparative Example 2)
A prepreg and a tubular body were obtained in the same manner as in Example 4 except that [III] whose cross-sectional shape was not a perfect circle was used as the carbon fiber. As a result of the in-plane shear strength being too high, in the Charpy impact test, the tubular body was all broken during impact.
(Comparative Example 3)
A prepreg and a tubular body were obtained in the same manner as in Example 4 except that [IV] having an average fiber diameter as small as 4.8 μm was used as the carbon fiber. As a result of the in-plane shear strength being too high, in the Charpy impact test, the tubular body was all broken during impact.
(Comparative Example 4)
A prepreg and a tubular body were obtained in the same manner as in Example 4 except that [V] was used as the carbon fiber. As a result of the low tensile strength of carbon fiber and the significant decrease in in-plane shear strength, static bending strength and Charpy impact strength were very low. Moreover, in the Charpy impact test, all the tubular bodies were divided at the time of impact.
(Comparative Example 5)
Except for using the epoxy resin composition [vii] in which the amount of the epoxy resin composition [a] component was increased to 60 parts by weight and the composition ratio of the [b] component was slightly changed, the same as in Example 4. A prepreg and a tubular body were obtained. As a result of the bending elastic modulus of the resin composition being too high, in the Charpy impact test, 8 out of 10 tubular bodies were cut during impact.
(Comparative Example 6)
A prepreg and a tubular body were obtained in the same manner as in Example 4 except that [VIII] was used as the carbon fiber. As a result of both the tensile modulus of elasticity and the tensile strength of the carbon fiber being too low, the static bending strength and the Charpy impact strength were very low. In the Charpy impact test, the tubular body was all broken during the impact.
(Comparative Example 7)
A prepreg and a tubular body were obtained in the same manner as in Example 4 except that [IX] was used as the carbon fiber. As a result of the tensile modulus of the carbon fiber being too high, in the Charpy impact test, 6 of the 10 tubular bodies were cut during impact.
(Comparative Example 8)
A prepreg and a tubular body were obtained in the same manner as in Example 4 except that [X] was used as the carbon fiber. As a result of the tensile modulus of the carbon fiber being too low, the static bending strength and Charpy impact strength were low. In the Charpy impact test, the tubular body was cut into 5 pieces out of 10 pieces.

  The prepreg of the present invention provides a tubular body made of a fiber reinforced composite material that has sufficient static bending strength and does not break when impact is damaged, and is particularly unprecedented when used as a golf club shaft. Safety can be added. Further, the tubular body made of fiber-reinforced composite material of the present invention can be suitably used for other sports applications, general industrial applications, and aerospace applications by taking advantage of its high static strength characteristics and impact characteristics. is there.

Claims (10)

Carbon fiber satisfying the following conditions [A] to [E], [a] 20 to 50 parts by weight of trifunctional or higher amine type epoxy resin, and [b] 50 to 80 parts by weight of bisphenol F type epoxy resin And epoxy resin containing [c] dicyandiamide or a derivative thereof in an amount of 2 to 10 parts by weight with respect to 100 parts by weight of the epoxy resin, and the resin cured product has a flexural modulus of 3.8 to 5.0 GPa A prepreg formed by combining a resin composition.
[A] Tensile modulus is in a range of 295 ± 10 GPa [B] Tensile strength is in a range of 5400 to 6500 MPa [C] Has a substantially round cross section [D] Average fiber The diameter is in the range of 5.0 to 7.0 μm [E] The surface area ratio measured using an atomic force microscope is 1.00 to 1.05, and the surface roughness Ra is 1 to 10 nm. The prepreg according to claim 1, wherein an in-plane shear strength of a laminate obtained by curing the prepreg is in a range of 130 to 150 MPa. The prepreg according to claim 1 or 2, wherein the component [a] is a trifunctional aminophenol type epoxy resin. The prepreg according to any one of claims 1 to 3, wherein the epoxy equivalent of the component [b] is in the range of 300 to 800. The prepreg in any one of Claims 1-4 whose viscosity in 50 degreeC of the said epoxy resin composition exists in the range of 100-10000 Pa * s. The prepreg according to any one of claims 1 to 5, wherein the epoxy resin composition contains 2 to 10 parts by weight of a thermoplastic resin with respect to 100 parts by weight of the epoxy resin. Carbon fibers per unit area is within 50 to 150 g / ^{m 2} range, the prepreg according to any one of claims 1 to 6. The prepreg according to claim 7, wherein the fiber weight content is in the range of 70 to 87% by weight. A tubular body made of a fiber reinforced composite material, wherein the prepreg according to any one of claims 1 to 8 is laminated in a tubular shape so as to include at least a straight layer and cured. A golf club shaft comprising the fiber-reinforced composite material tubular body according to claim 9.