Prepreg and fiber-reinforced plastic

Abstract

Provided are: a prepreg from which it is possible to obtain a fiber-reinforced plastic having improved strength in the fiber-orthogonal direction when carbon fibers are used as reinforcing fibers; and a fiber-reinforced plastic having improved strength in the fiber-orthogonal direction. A prepreg according to the present invention comprises a matrix resin composition and carbon fibers. The matrix resin composition contains: [A] an isocyanuric acid derivative that has a glycidyl group and that is represented by formula (1) (in formula (1), X1-X3 each represent a glycidyl group, an allyl group, an alkyl group, or a hydrogen atom, and at least one thereof is a glycidyl group); [B] a curing agent; [C] a compound having a (meth)acryloyl group but not having a glycidyl group; and [D] an epoxy resin excluding component [A].

Description

Prepreg and Fiber Reinforced Plastics

[0001] The present invention relates to prepregs and fiber-reinforced plastics, which are suitable for use in sports and leisure, general industrial applications, aircraft materials, etc. This application claims priority based on Japanese Patent Application No. 2023-125417, filed on August 1, 2023, the contents of which are incorporated herein by reference.

[0002] Fiber-reinforced plastics are lightweight, strong, and rigid, and are therefore widely used in a variety of applications, from sports and leisure to industrial applications such as automobiles and aircraft. One method for producing fiber-reinforced plastics is to use an intermediate material, i.e., a prepreg, in which a reinforcing material made of long fibers (continuous fibers) such as reinforcing fibers is impregnated with a matrix resin. This method makes it easy to control the reinforcing fiber content of the fiber-reinforced plastic, and can increase the fiber content. A molded product can be obtained by stacking multiple prepregs and heat-curing them.

[0003] Physical properties required for fiber-reinforced plastics include elastic modulus and toughness. For example, Patent Document 1 discloses a prepreg using an epoxy resin and a matrix resin containing a (meth)acrylic monomer having a specific structure.

[0004] International Publication No. 2022 / 196624

[0005] An object of the present invention is to provide a prepreg from which a fiber-reinforced plastic having improved strength in the direction perpendicular to the fibers can be obtained when carbon fibers are used as reinforcing fibers, and to provide a fiber-reinforced plastic having improved strength in the direction perpendicular to the fibers.

[0006] The present invention includes the following embodiments: [1]: A prepreg made of a matrix resin composition and carbon fibers, wherein the matrix resin composition contains the following components [A] to [D]: [A] An isocyanuric acid derivative having a glycidyl group, represented by the following formula (1):

[0007]

[0008] (In formula (1), X１ ~X ３ represents a glycidyl group, an allyl group, an alkyl group, or a hydrogen atom; X １ ~X ３ At least one of the components is a glycidyl group.) [B] a curing agent; [C] a compound having a (meth)acryloyl group but no glycidyl group; [D] an epoxy resin excluding the component [A]; [2]: The prepreg according to [1], which contains an isocyanuric acid derivative as the component [C]; [3]: The prepreg according to [1] or [2], which contains 50 to 200 parts by mass of the component [A] relative to 100 parts by mass of the component [C]; [4]: ​​The prepreg according to any one of [1] to [3], which contains 10 to 30% by mass of the component [A] relative to the total mass of the components [A] and [D]; [5]: In the formula (1), X １ ~X ３are all glycidyl groups. [6]: The prepreg according to any one of [1] to [5], which contains a novolac epoxy resin as component [D], and the novolac epoxy resin accounts for 20 to 60 mass% of the total mass of components [A] and [D]. [7]: The prepreg according to [6], in which the novolac epoxy resin contains at least one member selected from the group consisting of cresol, bisphenol A, biphenyl, naphthalene, and dicyclopentadiene derivatives as a partial skeleton. [8]: The prepreg according to any one of [1] to [5], which contains 10 to 30 mass% of a bisphenol epoxy resin, based on the total mass of components [A] and [D]. [9]: The prepreg according to [8], in which the bisphenol epoxy resin includes a bisphenol F epoxy resin.

[10] : The prepreg according to any one of [1] to [9], wherein the component [B] contains at least one selected from the group consisting of dicyandiamide, aromatic amines, ureas, and imidazoles.

[11] : The prepreg according to

[10] , wherein the component [B] contains dicyandiamide.

[12] : The prepreg according to any one of [1] to

[11] , wherein the component [B] contains 50 mass% or more of a component [B1] having a melting point of 70°C or higher, relative to the total mass of the component [B].

[13] : The prepreg according to any one of [1] to

[12] , wherein the component [C] contains 10 to 40 mass parts, relative to a total of 100 mass parts of the components [A] and [D].

[14] : The prepreg according to any one of [1] to

[13] , wherein the component [C] contains an isocyanuric acid derivative having a (meth)acryloyl group, represented by the following formula (2):

[0009]

[0010] (In formula (2), Y １ ~Y ３ represents a (meth)acryloyl group or a hydrogen atom, Y １ ~Y ３ At least one of the groups represented by Y is a (meth)acryloyl group. １ ~Y ３are all (meth)acryloyl groups.

[16] : The prepreg according to any one of [1] to

[15] , wherein the matrix resin composition further contains the following component [E]: [E] a radical polymerization initiator.

[17] : The prepreg according to

[16] , wherein the component [E] contains an organic peroxide.

[18] : The prepreg according to

[16] or

[17] , wherein the 10-hour half-life temperature of the component [E] is 70°C or higher.

[19] : The prepreg according to any one of [1] to

[18] , wherein the viscosity of the matrix resin composition at 70°C is 10 Pa s or higher.

[20] : The prepreg according to any one of [1] to

[19] , wherein the prepreg is a unidirectional prepreg in which unidirectionally aligned carbon fibers are impregnated with a matrix resin composition.

[21] : A fiber-reinforced plastic obtained by curing the prepreg according to any one of [1] to

[20] .

[22] : The fiber reinforced plastic according to

[21] , which is tubular.

[0011] According to the present invention, when carbon fibers are used as reinforcing fibers, a prepreg can be obtained that can produce a fiber-reinforced plastic having improved strength in the direction perpendicular to the fibers, and a fiber-reinforced plastic having improved strength in the direction perpendicular to the fibers can be obtained.Fiber-reinforced plastic having improved strength in the direction perpendicular to the fibers can also be obtained when carbon fibers with a high elastic modulus are used as reinforcing fibers.

[0012] [Prepreg] One embodiment of the present invention relates to a prepreg. The prepreg according to the embodiment comprises a matrix resin composition and carbon fibers, and the matrix resin composition contains the following components [A] to [D]. [A] An isocyanuric acid derivative having a glycidyl group, represented by the following formula (1):

[0013]

[0014] (In formula (1), X １ ~X ３ represents a glycidyl group, an allyl group, an alkyl group, or a hydrogen atom; X １ ~X ３At least one of the components is a glycidyl group.) [B] A curing agent; [C] A compound having no glycidyl group but having a (meth)acryloyl group; [D] An epoxy resin other than component [A]. The matrix resin composition may further contain the following component [E], a thermoplastic resin, and other additives. [E] A radical polymerization initiator.

[0015] When the prepreg is heated, a curing reaction occurs between components [A] and [D] and component [B]. That is, the matrix resin composition of the fiber-reinforced plastic contains a polymer of component [A] and a cured product of component [D].

[0016] <Component [A]> Component [A] is an isocyanuric acid derivative represented by the following formula (1) and having one or more glycidyl groups in the molecule.

[0017]

[0018] In formula (1), X １ ~X ３ represents a glycidyl group, an allyl group, an alkyl group, or a hydrogen atom; X １ ~X ３ At least one of X is a glycidyl group. １ ~X ３ Preferably, two or more of X are glycidyl groups. １ ~X ３ It is more preferable that all of the groups are glycidyl groups.

[0019] The prepreg according to the embodiment can produce a fiber-reinforced plastic with improved strength in the direction perpendicular to the fibers. This is presumably due to improved adhesion between the matrix resin composition and the carbon fiber. Component [A] improves adhesion between the carbon fiber and the matrix resin composition, thereby improving the mechanical properties of the fiber-reinforced plastic. This is thought to be because the isocyanuric acid skeleton of component [A] has a high proportion of heteroatoms that can serve as interaction points with the carbon fiber, thereby strengthening the intermolecular forces between the matrix resin composition and the carbon fiber and improving adhesion. Component [A] is also an epoxy resin, and hereinafter, component [A] and component [D], described below, are collectively referred to as "epoxy resin." Using component [A] as an epoxy resin is preferable because it increases the crosslink density of the cured product and increases the rigidity of the molecular structure, thereby improving the elastic modulus and strength of the cured product.

[0020] The increased crosslink density and rigidity of the molecular structure of the cured product increase the modulus and strength of the cured product, and also improve adhesion to carbon fibers. Therefore, the content of component [A] in the matrix resin composition is preferably 10% by mass or more, more preferably 15% by mass or more, relative to the total mass of components [A] and [D]. From the viewpoint of improving the heat resistance of the cured product, the content of component [A] is preferably 30% by mass or less, more preferably 25% by mass or less, relative to the total mass of components [A] and [D]. The lower and upper limits of the content of component [A] can be arbitrarily combined; for example, 10 to 30% by mass is preferred, and 15 to 25% by mass is more preferred. Furthermore, the matrix resin composition preferably contains 50 to 200 parts by mass of component [A] per 100 parts by mass of component [C], which will be described later.

[0021] Examples of component [A] include triglycidyl isocyanurate, monoallyl diglycidyl isocyanurate, and diallyl monoglycidyl isocyanurate. As component [A], one of these may be used alone, or two or more may be used in combination. In particular, triglycidyl isocyanurate or monoallyl diglycidyl isocyanurate is preferably used, and triglycidyl isocyanurate is more preferably used, because the strength of the cured product is improved.

[0022] Of the components [A], commercially available triglycidyl isocyanurate products include TEPIC-G and TEPIC-S (manufactured by Nissan Chemical Industries, Ltd.). Commercially available monoallyl diglycidyl isocyanurate products include MA-DGIC (manufactured by Shikoku Chemical Industries, Ltd.). Commercially available diallyl monoglycidyl isocyanurate products include DA-MGIC (manufactured by Shikoku Chemical Industries, Ltd.).

[0023] <Component [B]> Component [B] is a curing agent, and is not particularly limited as long as it is a compound that contributes to curing of the epoxy groups of the epoxy resin. Examples of component [B] that can be used include amine-based curing agents such as dicyandiamide, aliphatic amines, alicyclic amines, and aromatic amines, as well as ureas, imidazoles, acid anhydrides, phenols, and boron chloride amine complexes. Among these, it is preferable to use at least one curing agent selected from the group consisting of dicyandiamide, aromatic amines, ureas, and imidazoles, because these tend to provide excellent storage stability for the matrix resin composition and good mechanical properties for the cured product.

[0024] From the viewpoint of sufficiently promoting the curing of the epoxy resin, the content of component [B] in the matrix resin composition is preferably 1 part by mass or more, and more preferably 2 parts by mass or more, per 100 parts by mass of the total of components [A] and [D]. From the viewpoint of the storage stability of the matrix resin composition, the content of component [B] is preferably 60 parts by mass or less, and more preferably 50 parts by mass or less, per 100 parts by mass of the total of components [A] and [D]. The lower and upper limits of the content of component [B] can be arbitrarily combined; for example, 1 to 60 parts by mass is preferred, and 2 to 50 parts by mass is more preferred.

[0025] Dicyandiamide has a melting point of approximately 210°C, making it difficult to dissolve in epoxy resins at low temperatures. Therefore, when dicyandiamide is used as a curing agent, the storage stability of the matrix resin composition is excellent. Commercially available dicyandiamide products include DICY7 and DICY15 (both manufactured by Mitsubishi Chemical Corporation) and DICYANEX1400F (manufactured by Evonik Japan Co., Ltd.).

[0026] When dicyandiamide is used as component [B], the content of dicyandiamide in the matrix resin composition is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 15 parts by mass or less, more preferably 10 parts by mass or less, per 100 parts by mass of the total of components [A] and [D]. The lower and upper limits of the dicyandiamide content can be arbitrarily combined, for example, preferably 1 to 15 parts by mass, more preferably 2 to 10 parts by mass. Since the cured product tends to have better heat resistance and mechanical properties, the ratio of the number of moles of active hydrogen in dicyandiamide to the total number of moles of epoxy groups in the epoxy resin contained in the matrix resin composition is preferably 0.3 times or more, more preferably 0.4 times or more, and preferably 0.9 times or less, more preferably 0.8 times or less. The lower and upper limits of the ratio of the number of moles of active hydrogen in dicyandiamide can be arbitrarily combined, for example, preferably 0.3 to 0.9 times, more preferably 0.4 to 0.8 times.

[0027] Examples of aromatic amines include 3,3'-diisopropyl-4,4'-diaminodiphenylmethane, 3,3'-di-t-butyl-4,4'-diaminodiphenylmethane, 3,3'-diethyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-diisopropyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-di-t-butyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetraethyl-4,4'-diaminodiphenylmethane, 3,3'-diisopropyl-5,5'-diethyl-4,4'-diaminodiphenylmethane, 3,3'-di-t-butyl-5,5 Examples of suitable curable compounds include, but are not limited to, 4,4'-diethyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetraisopropyl-4,4'-diaminodiphenylmethane, 3,3'-di-t-butyl-5,5'-diisopropyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetra-t-butyl-4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 4,4'-methylene-bis[2-isopropyl-6-methylaniline], m-phenylenediamine, m-xylylenediamine, and diethyltoluenediamine. Among these, it is preferable to use 4,4'-diaminodiphenylsulfone or 3,3'-diaminodiphenylsulfone, which can provide a cured product that has excellent heat resistance and mechanical properties and exhibits little decrease in linear expansion coefficient and heat resistance due to moisture absorption. 4,4'-Diaminodiphenyl sulfone is preferred because it can maintain the tack life of the prepreg for a long period of time. 3,3'-Diaminodiphenyl sulfone is preferred because it can increase the elastic modulus and strength of the cured product. 4,4'-Diaminodiphenyl sulfone and 3,3'-Diaminodiphenyl sulfone may also be blended together. These aromatic amines may be used alone or in combination with other curing agents.

[0028] When an aromatic amine is used as component [B], the content of the aromatic amine in the matrix resin composition is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 60 parts by mass or less, more preferably 50 parts by mass or less, per 100 parts by mass of the total of components [A] and [D]. The lower and upper limits of the aromatic amine content can be arbitrarily combined, for example, 1 to 60 parts by mass is preferred, and 2 to 50 parts by mass is more preferred. When the aromatic amine content is equal to or greater than the lower limit, the heat resistance and elastic modulus tend to be excellent. On the other hand, when the aromatic amine content is equal to or less than the upper limit, the toughness tends to be excellent. The active hydrogen equivalent number of the amino group of the aromatic amine is preferably 0.5 times or more, more preferably 0.6 times or more, and preferably 1.5 times or less, more preferably 1.4 times or less, of the epoxy equivalent number of all epoxy resins contained in the matrix resin composition. The upper and lower limits of the active hydrogen equivalent number of the amino group of the aromatic amines can be arbitrarily combined, and are, for example, preferably 0.5 to 1.5 times, more preferably 0.6 to 1.4 times. By blending these aromatic amines so that the active hydrogen equivalent number of the amino group is within the above-mentioned range of the epoxy equivalent number of the total epoxy resin, the elastic modulus, toughness, and heat resistance of the cured product tend to be within good ranges.

[0029] Among aromatic amines, commercially available products of 4,4'-diaminodiphenyl sulfone include, for example, Seikacure S (active hydrogen equivalent 62 g / eq, manufactured by Wakayama Seika Kogyo Co., Ltd.) and Sumicure S (active hydrogen equivalent 62 g / eq, manufactured by Sumitomo Chemical Co., Ltd.). Commercially available products of 3,3'-diaminodiphenyl sulfone include, for example, 3,3'-DAS (active hydrogen equivalent 62 g / eq, manufactured by Mitsui Fine Chemicals, Inc.). Other commercially available aromatic amines include, for example, MDA-220 (active hydrogen equivalent: 50 g / eq, manufactured by Mitsui Chemicals, Inc.), jER Cure W (active hydrogen equivalent: 45 g / eq, manufactured by Mitsubishi Chemical Corporation), Lonzacure M-DEA (active hydrogen equivalent: 78 g / eq), Lonzacure M-DIPA (active hydrogen equivalent: 92 g / eq), Lonzacure M-MIPA (active hydrogen equivalent: 78 g / eq), and Lonzacure DETDA 80 (active hydrogen equivalent: 45 g / eq) (all manufactured by Lonza Corporation).

[0030] Ureas have a dimethylureido group in the molecule, and when heated at high temperatures, they generate an isocyanate group and dimethylamine, activating the epoxy group. Examples of ureas include aromatic dimethylurea, in which the dimethylureido group is bonded to an aromatic ring, and aliphatic dimethylurea, in which the dimethylureido group is bonded to an aliphatic compound. Among these, aromatic dimethylurea is preferred because it tends to increase the heat resistance and bending strength of the cured product.

[0031] When ureas are used as component [B], the content of the ureas in the matrix resin composition is preferably 1 part by mass or more, and preferably 15 parts by mass or less, and more preferably 10 parts by mass or less, per 100 parts by mass of the total of components [A] and [D]. The lower and upper limits of the urea content can be arbitrarily combined, and are preferably 1 to 15 parts by mass, and more preferably 1 to 10 parts by mass. When the ureas content is equal to or greater than the lower limit, curing of the epoxy resin contained in the matrix resin composition tends to be accelerated, and the mechanical properties and heat resistance of the cured product tend to be improved. On the other hand, when the ureas content is 15 parts by mass or less, the pot life and toughness of the cured product tend to be maintained at high levels.

[0032] Suitable examples of aromatic dimethylureas include phenyldimethylurea, tolylenebis(dimethylurea), and methylenebis(phenyldimethylurea). Specific examples include 3-phenyl-1,1-dimethylurea (PDMU), 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea, 2,4-bis(3,3-dimethylureido)toluene (TBDMU), 4,4'-methylenebis(phenyldimethylurea) (MBPDMU), and dimethylurea obtained from m-xylylene diisocyanate and dimethylamine. Among these, PDMU, DCMU, TBDMU, and MBPDMU are more preferred in terms of curing acceleration ability and imparting heat resistance to the cured product. Examples of aliphatic dimethylureas include dimethylurea obtained from isophorone diisocyanate and dimethylamine, and dimethylurea obtained from hexamethylene diisocyanate and dimethylamine. These ureas may be used alone or in combination of two or more.

[0033] Commercially available ureas include PDMU, such as Omicure 94 (manufactured by PTI Japan Co., Ltd.). DCMU, such as DCMU-99 (manufactured by Hodogaya Chemical Co., Ltd.). TBDMU, such as Omicure 24 (manufactured by PTI Japan Co., Ltd.) and U-CAT 3512T (manufactured by San-Apro Co., Ltd.). MBPDMU, such as Technicure MDU-11 (manufactured by A&C Catalysts) and Omicure 52 (manufactured by PTI Japan Co., Ltd.). Aliphatic dimethylurea, such as U-CAT 3513N (manufactured by San-Apro Co., Ltd.).

[0034] Imidazoles have a nitrogen atom with an unshared electron pair in their structure, which can activate the epoxy group and promote curing. Examples of imidazoles that can be used include imidazole, imidazole adduct, clathrate imidazole, microencapsulated imidazole, and imidazole compounds coordinated with a stabilizer.

[0035] When an imidazole is used as component [B], the content of the imidazole in the matrix resin composition is preferably 1 part by mass or more, and preferably 15 parts by mass or less, and more preferably 10 parts by mass or less, per 100 parts by mass of the total of components [A] and [D]. The lower and upper limits of the imidazole content can be arbitrarily combined, and are preferably 1 to 15 parts by mass, and more preferably 1 to 10 parts by mass. When the imidazole content is equal to or greater than the lower limit, the curing and curing acceleration of the epoxy resin contained in the matrix resin composition and the heat resistance of the cured product tend to be sufficient. On the other hand, when the imidazole content is equal to or less than the upper limit, the cured product tends to have better mechanical properties.

[0036] Specific examples of imidazoles include 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazolium trimellitate, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazolium trimellitate, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2-methylimidazole ... ,4-diamino-6-(2'-methylimidazolyl-(1'))-ethyl-s-triazine, 2,4-diamino-6-(2'-undecylimidazolyl-(1'))-ethyl-s-triazine, 2,4-diamino-6-(2'-ethyl-4-methylimidazolyl-(1'))-ethyl-s-triazine, 2,4-diamino-6-(2'-methylimidazolyl-(1'))-ethyl-s-triazine Examples of imidazoles that can be used include, but are not limited to, imidate-isocyanuric acid adduct, 2-phenylimidazole-isocyanuric acid adduct, 2-methylimidazole-isocyanuric acid adduct, 1-cyanoethyl-2-phenyl-4,5-di(2-cyanoethoxy)methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, and 2-phenyl-4-methyl-5-hydroxymethylimidazole. Imidazoles that have been subjected to adduct treatment, inclusion treatment with a foreign molecule, microencapsulation treatment, or coordination with a stabilizer are imidazoles modified by the process. The modification reduces activity, allowing for excellent pot life at low temperatures while accelerating the curing of epoxy resins at high temperatures. These imidazoles may be used alone or in combination of two or more.

[0037] Commercially available imidazoles include, but are not limited to, 2E4MZ, 2P4MZ, 2PZ-CN, C11Z-CNS, C11Z-A, 2MZA-PW, 2MAOK-PW, 2P4MHZ-PW, and 2PHZ-PW (all manufactured by Shikoku Chemicals Corporation). Commercially available imidazole adducts include, but are not limited to, PN-50, PN-50J, PN-40, PN-40J, PN-31, PN-23, and PN-H (all manufactured by Ajinomoto Fine-Techno Co., Inc.), which have a structure in which an imidazole compound is ring-opened and added to the epoxy group of an epoxy resin. Commercially available products of clathrate imidazole include, but are not limited to, TIC-188, KM-188, HIPA-2P4MHZ, NIPA-2P4MHZ, TEP-2E4MZ, HIPA-2E4MZ, and NIPA-2E4MZ (all manufactured by Nippon Soda Co., Ltd.). Commercially available products of microencapsulated imidazole include, but are not limited to, Novacure HX3721, Novacure HX3722, Novacure HX3742, and Novacure HX3748 (all manufactured by Asahi Kasei E-Materials Corporation), and LC-80 (manufactured by A&C Catalysts). The imidazole compound coordinated with a stabilizer can be prepared by combining Cureduct P-0505 (bisphenol A diglycidyl ether / 2-ethyl-4-methylimidazole adduct), an imidazole adduct manufactured by Shikoku Chemical Industry Co., Ltd., with L-07N (epoxy-phenol-boric acid ester blend), a stabilizer manufactured by Shikoku Chemical Industry Co., Ltd. Similar effects can be obtained by using imidazole compounds such as the various imidazoles and imidazole adducts listed above instead of Cureduct P-0505.

[0038] Examples of acid anhydrides include hydrogenated methylnadic anhydride and methylhexahydrophthalic anhydride.

[0039] Component [B] preferably contains component [B1] having a melting point of 70°C or higher, and preferably contains component [B1] in an amount of 50% by mass or higher relative to the total mass of component [B]. Having the melting point and content of component [B1] within this range makes it possible to suppress compatibility between the epoxy resin and the curing agent in the low temperature range, and to easily suppress immediate reaction between the epoxy resin and the curing agent. In other words, a matrix resin composition with a long pot life can be obtained, making it easy to obtain a prepreg with a long usable time.

[0040] Specific examples of component [B1] include dicyandiamide (melting point 208°C), 4,4'-diaminodiphenyl sulfone (melting point 175°C), 3,3'-diaminodiphenyl sulfone (melting point 170°C), 4,4'-methylene-bis[2-isopropyl-6-methylaniline] (melting point 72°C), 4,4'-methylenebis(phenyldimethylurea) (melting point 216°C), 3-phenyl-1,1-dimethylurea (melting point 126°C), 3-(3,4-dichlorophenyl)-1,1-dimethylurea (melting point 159°C), and 2,4-bis(3,3-dimethylureido)toluene. Examples of the hydroxymethylimidazole include, but are not limited to, 2-phenylimidazole (melting point 180°C), 2-phenylimidazole (melting point 137°C), 2,4-diamino-6-(2'-ethyl-4-methylimidazolyl-(1'))-ethyl-s-triazine (melting point 248°C), 2,4-diamino-6-(2'-methylimidazolyl-(1'))-ethyl-s-triazine isocyanuric acid adduct (melting point 260°C or higher), 2-phenyl-4,5-dihydroxymethylimidazole (melting point 230°C or higher), and 2-phenyl-4-methyl-5-hydroxymethylimidazole (melting point 191°C).

[0041] <Component [C]> Component [C] is a compound that does not contain a glycidyl group in its molecule but has one or more acryloyl groups in its molecule. Component [C] contributes to improving the modulus and toughness of the cured product. Epoxy resins are known for their excellent adhesive properties, and adhesion to carbon fibers is typically optimized by adjusting the type of epoxy resin and curing agent. However, adhesion to high-modulus carbon fibers with highly developed crystalline portions is difficult. As a result, adhesion between matrix resin compositions and high-modulus carbon fibers is insufficient, and fiber-reinforced plastics using high-modulus carbon fibers as reinforcing fibers tend to have low strength in the direction perpendicular to the fibers. Blending component [C] with a matrix resin composition containing component [A] improves adhesion even to difficult-to-bond high-modulus carbon fibers. Furthermore, the combination of component [A] and component [C] achieves similar effects with medium-modulus and standard-modulus carbon fibers. Although the detailed mechanism is unclear, it is believed that the interaction between the isocyanuric acid skeleton of component [A] and the carbon fiber is further strengthened by the presence of component [C], thereby improving the adhesion between the carbon fiber and the matrix resin composition. Furthermore, component [A] tends to have low reactivity due to its high crystallinity, but the coexistence of component [C], which has low crystallinity, is thought to facilitate the dissolution of the crystals of component [A], thereby increasing the reactivity. Furthermore, it is thought that the ease of dissolution of the crystals of component [A] improves the wettability of component [A] to the carbon fiber surface. In other words, in the presence of component [C], it is thought that the curing reaction proceeds after component [A] has sufficiently approached the carbon fiber surface, thereby improving the adhesion between the carbon fiber and the matrix resin composition. Additionally, component [C] tends to form a rigid network structure in its polymer, thereby improving the strength of the cured product.

[0042] The content of component [C] in the matrix resin composition is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, per 100 parts by mass of the total of components [A] and [D]. The content of component [C] is preferably 40 parts by mass or less, more preferably 35 parts by mass or less, per 100 parts by mass of the total of components [A] and [D]. The lower and upper limits of the content of component [C] can be arbitrarily combined; for example, 10 to 40 parts by mass is preferred, and 15 to 35 parts by mass is more preferred. When the amount of component [C] in the matrix resin composition is equal to or greater than the lower limit, the concentration of structures in the matrix resin composition that can serve as interaction points with the carbon fiber surface increases, and the dissolution of component [A] is promoted, resulting in good adhesion to the carbon fiber. On the other hand, when the content of component [C] is equal to or less than the upper limit, the crosslink density becomes appropriate, and the cured product is more likely to maintain toughness.

[0043] Component [C] preferably contains an isocyanuric acid derivative that does not have a glycidyl group in the molecule. Examples of substituents that the isocyanuric acid derivative may have include an allyl group, an alkyl group, and a hydroxyethyl group. It is believed that the inclusion of an isocyanuric acid derivative in component [C] further enhances the interaction with the carbon fiber and improves the adhesion between the carbon fiber and the matrix resin composition. As described above, component [A] tends to have low reactivity due to its high crystallinity. However, the coexistence of component [C], which has a similar structure to component [A], is thought to facilitate the dissolution of the crystals of component [A] and increase the reactivity. As a result, it is thought that the adhesion between the carbon fiber and the matrix resin composition is further improved. From the viewpoint of the adhesion between the carbon fiber and the matrix resin composition, it is more preferable that component [C] contains an isocyanuric acid derivative represented by the following formula (2):

[0044]

[0045] In formula (2), Y １ ~Y ３ represents a (meth)acryloyl group or a hydrogen atom, Y １ ~Y ３ At least one of the groups is a (meth)acryloyl group. The term "(meth)acryloyl group" refers to an acryloyl group or a methacryloyl group.

[0046] In formula (2), the strength of the cured product is improved, so Y １ ~Y ３ Preferably, two or more of Y are (meth)acryloyl groups. １ ~Y ３ It is more preferable that all of the groups are (meth)acryloyl groups.

[0047] When component [C] contains an isocyanuric acid derivative, examples of the isocyanuric acid derivative include tris-(2-(meth)acryloxyethyl)isocyanurate, bis-(2-acryloxyethyl)isocyanurate, and mono-(2-acryloxyethyl)isocyanurate, which are ester compounds produced by reacting 1 to 3 molecules of (meth)acrylic acid with tris(2-hydroxyethyl)isocyanurate. One of these may be used alone, or two or more may be used in combination. In particular, tris-(2-(meth)acryloxyethyl)isocyanurate and bis-(2-acryloxyethyl)isocyanurate are preferred because they provide excellent strength to the cured product, and tris-(2-(meth)acryloxyethyl)isocyanurate is more preferred.

[0048] A commercially available product of tris-(2-(meth)acryloxyethyl)isocyanurate is, for example, A-9300S (manufactured by Shin-Nakamura Chemical Co., Ltd.). A commercially available product of bis-(2-acryloxyethyl)isocyanurate is, for example, Aronix M-215 (manufactured by Toagosei Co., Ltd.). A commercially available product of a mixture of tris-(2-(meth)acryloxyethyl)isocyanurate and bis-(2-acryloxyethyl)isocyanurate is, for example, Aronix M-313 and Aronix M-315 (both manufactured by Toagosei Co., Ltd.).

[0049] Examples of the component [C] other than the isocyanuric acid derivative include monofunctional (meth)acrylic monomers and difunctional or higher functional (meth)acrylic monomers (sometimes referred to as polyfunctional (meth)acrylic monomers). As the component [C], these monomers may be used in combination with the isocyanuric acid derivative.

[0050] Examples of monofunctional (meth)acrylic monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 4-hydroxybenzyl (meth)acrylate, 4-hydroxyphenyl (meth)acrylate, cyclohexanedimethanol mono(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, phenoxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, norbornyl (meth)acrylate, 2-(meth)acryloyloxymethyl-2-methylbicycloheptane, adamantyl (meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, tetracyclododecanyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, p) acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, icosyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, butoxyethyl (meth)acrylate, methoxydipropylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, polyethylene glycol monomethyl ether (meth)acrylate, polypropylene glycol monomethyl (meth)acrylate, 4-acryloyloxymethyl-2-methyl-2-ethyl-1,3-dioxolane, 4-acryloyloxymethyl-2-methyl-2-isobutyl-1,Examples of the (meth)acrylic acid esters include 3-dioxolane, o-phenylphenol (meth)acrylate, ethoxylated o-phenylphenol (meth)acrylate, N-(meth)acryloyloxyethyl hexahydrophthalimide, para-cumylphenol (meth)acrylate, ethoxylated para-cumylphenol (meth)acrylate, and trimethylolpropane formal (meth)acrylate; and (meth)acrylamides such as acrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N-methylolacrylamide, N-methoxymethylacrylamide, N-butoxymethylacrylamide, N-t-butylacrylamide, N-benzyl(meth)acrylamide, N-phenyl(meth)acrylamide, N-(4-hydroxybenzyl)(meth)acrylamide, N-(4-hydroxyphenyl)(meth)acrylamide, acryloylmorpholine, hydroxyethylacrylamide, and methylenebisacrylamide. Monofunctional (meth)acrylic monomers having one or more oxyethylene groups in the molecule or monofunctional (meth)acrylic monomers having one or more cyclic skeletons in the molecule are preferred, as they can reduce the volatility of the monomer and improve the toughness of the cured product, and monofunctional (meth)acrylic monomers having one or more oxyethylene groups and one or more cyclic skeletons in the molecule are more preferred.

[0051] Examples of bifunctional (meth)acrylic monomers include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, 1,3-butylene glycol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 2-methyl- Examples of suitable diols include 1,8-octanediol, 1,10-decanediol, neopentyl glycol hydroxypivalate, tricyclodecane dimethanol, cyclohexane dimethanol, bisphenol A, hydrogenated bisphenol A, bisphenol F, dioxane glycol, and bisphenoxyfluorene ethanol, as well as di(meth)acrylates obtained by esterifying diols obtained by adding ethylene oxide, propylene oxide, or caprolactone to these diols with (meth)acrylic acid. Bifunctional (meth)acrylic monomers having one or more oxyethylene groups in the molecule or bifunctional (meth)acrylic monomers having one or more cyclic skeletons in the molecule are preferred, as they can achieve a high balance of elastic modulus, strength, and toughness in the cured product. Bifunctional (meth)acrylic monomers having one or more oxyethylene groups and one or more cyclic skeletons in the molecule are more preferred.

[0052] Examples of trifunctional (meth)acrylic monomers include triols and tetraols such as trimethylolpropane, tris(2-hydroxyethyl)isocyanurate, glycerol, and pentaerythritol, and tri(meth)acrylates obtained by esterifying triols or tetraols obtained by adding ethylene oxide, propylene oxide, caprolactone, or the like to these triols or tetraols with (meth)acrylic acid. Trifunctional (meth)acrylic monomers having one or more oxyethylene groups in the molecule or trifunctional (meth)acrylic monomers having one or more cyclic skeletons in the molecule are preferred, as they can achieve a high balance of elastic modulus, strength, and toughness of the cured product, and trifunctional (meth)acrylic monomers having one or more oxyethylene groups and one or more cyclic skeletons in the molecule are more preferred.

[0053] Examples of tetrafunctional or higher (meth)acrylic monomers include polyols such as ditrimethylolpropane, pentaerythritol, dipentaerythritol, and tripentaerythritol, as well as poly(meth)acrylates obtained by esterifying polyols obtained by adding ethylene oxide, propylene oxide, or caprolactone to these polyols with (meth)acrylic acid. Because they can achieve a high balance between the modulus of elasticity, strength, and toughness of the cured product, tetrafunctional or higher (meth)acrylic monomers having one or more oxyethylene groups in the molecule or tetrafunctional or higher (meth)acrylic monomers having one or more cyclic skeletons in the molecule are preferred, and tetrafunctional or higher (meth)acrylic monomers having one or more oxyethylene groups and one or more cyclic skeletons in the molecule are more preferred.

[0054] The composition may contain an oligomer or prepolymer having a radically polymerizable double bond. Specific examples include macromonomers, acrylic acrylates, epoxy acrylates, urethane acrylates, and polyester acrylates. These may be used alone or in combination of two or more.

[0055] <Component [D]> Component [D] is an epoxy resin, and is not particularly limited as long as it is a compound having an epoxy group. However, component [D] is an epoxy resin other than component [A]. Examples of component [D] include glycidylamine-type epoxy resins, novolac-type epoxy resins, and bisphenol-type epoxy resins.

[0056] (Glycidylamine-Type Epoxy Resin) The use of a glycidylamine-type epoxy resin as component [D] is preferred because it increases the crosslink density of the cured product, thereby improving the modulus of elasticity, strength, and heat resistance. Trifunctional or higher glycidylamine-type epoxy resins are particularly preferred from the viewpoint of providing a cured product with high modulus of elasticity, strength, and heat resistance. Since an increased crosslink density increases the modulus of elasticity and strength of the cured product, the content of the glycidylamine-type epoxy resin in the matrix resin composition is preferably 10% by mass or more, and more preferably 15% by mass or more, relative to the total mass of components [A] and [D]. Since this improves the toughness of the cured product, the content of the glycidylamine-type epoxy resin is preferably 40% by mass or less, and more preferably 35% by mass or less, relative to the total mass of components [A] and [D]. The lower and upper limits of the content of the glycidylamine-type epoxy resin can be arbitrarily combined; for example, 10 to 40% by mass is preferred, and 15 to 35% by mass is more preferred.

[0057] Examples of glycidylamine-type epoxy resins include diglycidylaniline, diglycidyltoluidine, triglycidylaminophenol, triglycidylaminocresol, tetraglycidyldiaminodiphenylmethane, and tetraglycidyl-m-xylenediamine. One of these may be used alone, or two or more may be used in combination. In particular, triglycidylaminophenol or triglycidylaminocresol is preferred, and triglycidyl-m-aminophenol is more preferred, as they provide an excellent balance between the elastic modulus and toughness of the cured product.

[0058] Among glycidylamine-type epoxy resins, a commercially available product of diglycidyl aniline is, for example, GAN (manufactured by Nippon Kayaku Co., Ltd.). A commercially available product of diglycidyl toluidine is, for example, GOT (manufactured by Nippon Kayaku Co., Ltd.). Commercially available products of triglycidyl-m-aminophenol include, for example, YH-513 (manufactured by Nippon Steel Chemical & Material Co., Ltd.), Araldite MY0600, and MY0610 (all manufactured by Huntsman Advanced Materials). Commercially available products of triglycidyl-p-aminophenol include, for example, jER630 (manufactured by Mitsubishi Chemical Corporation), YH-523 (manufactured by Nippon Steel Chemical & Material Co., Ltd.), Araldite MY0500, and MY0510 (all manufactured by Huntsman Advanced Materials). A commercially available product of triglycidyl aminocresol is, for example, Sumiepoxy ELM-100 (manufactured by Sumitomo Chemical Co., Ltd.). Commercially available tetraglycidyldiaminodiphenylmethane products include jER604 (manufactured by Mitsubishi Chemical Corporation), YH-404 (manufactured by Nippon Steel Chemical & Material Co., Ltd.), Sumiepoxy ELM-434 (manufactured by Sumitomo Chemical Co., Ltd.), and Araldite MY720 and MY721 (all manufactured by Huntsman Advanced Materials). Commercially available tetraglycidyl-m-xylylenediamine products include TETRAD-X (manufactured by Mitsubishi Gas Chemical Company, Inc.).

[0059] (Novolac Epoxy Resin) Using a novolac epoxy resin as the epoxy resin is preferable because it increases the crosslink density of the cured product, thereby improving the modulus of elasticity, strength, and heat resistance. Since an increased crosslink density improves the modulus of elasticity, strength, and heat resistance of the cured product, the content of the novolac epoxy resin in the matrix resin composition is preferably 20% by mass or more, and more preferably 25% by mass or more, relative to the total mass of components [A] and [D]. Since the toughness of the cured product is improved, the content of the novolac epoxy resin is preferably 60% by mass or less, and more preferably 55% by mass or less, relative to the total mass of components [A] and [D]. The lower and upper limits of the content of the novolac epoxy resin can be arbitrarily combined; for example, 20 to 60% by mass is preferred, and 25 to 55% by mass is more preferred.

[0060] Examples of novolac epoxy resins include phenol novolac epoxy resins, cresol novolac epoxy resins, bisphenol A novolac epoxy resins, biphenyl aralkyl epoxy resins, naphthol cresol novolac epoxy resins, trisphenolmethane epoxy resins, and dicyclopentadiene epoxy resins. One of these may be used alone, or two or more may be used in combination. Because of the excellent balance between the elastic modulus and toughness of the cured product, it is preferable to use a novolac epoxy resin containing at least one selected from the group consisting of cresol, bisphenol A, biphenyl, naphthalene, and dicyclopentadiene derivatives as a partial skeleton. It is more preferable to use a novolac epoxy resin containing at least one selected from the group consisting of cresol, bisphenol A, and biphenyl as a partial skeleton.

[0061] Among novolac epoxy resins, commercially available phenol novolac epoxy resins include jER152 and jER154 (manufactured by Mitsubishi Chemical Corporation), EPICLON N-740, EPICLON N-770, and EPICLON N-775 (manufactured by DIC Corporation), and YDPN-638 (manufactured by Nippon Steel Chemical & Material Co., Ltd.). Commercially available cresol novolac epoxy resins include EPICLON N-660, EPICLON N-670, EPICLON N-680, and EPICLON N-690 (manufactured by DIC Corporation). Commercially available bisphenol A novolac epoxy resins include jER 157S70 (manufactured by Mitsubishi Chemical Corporation), EPICLON N-865, and EPICLON N-885 (all manufactured by DIC Corporation). Commercially available biphenyl aralkyl epoxy resins include NC-3100, NC-3000-L, NC-3000, NC-3000-H, and NC-3500 (all manufactured by Nippon Kayaku Co., Ltd.). Commercially available naphthol cresol novolac epoxy resins include NC-7000L, NC-7000H, and NC-7300L (all manufactured by Nippon Kayaku Co., Ltd.). Commercially available trisphenolmethane epoxy resins include jER 1032H60 (manufactured by Mitsubishi Chemical Corporation), EPPN-501H, EPPN-501HY, EPPN-502H, and EPPN-503 (all manufactured by Nippon Kayaku Co., Ltd.). Commercially available dicyclopentadiene epoxy resins include EPICLON HP-7200L, EPICLON HP-7200, EPICLON HP-7200H, and EPICLON HP-7200HHH (all manufactured by DIC Corporation), and XD-1000-2L, XD-1000, and XD-1000-H (all manufactured by Nippon Kayaku Co., Ltd.).

[0062] (Bisphenol-type Epoxy Resin) Using a bisphenol-type epoxy resin as the epoxy resin is preferable because the crosslink density of the cured product is not too high, resulting in a cured product with an excellent balance between elastic modulus and toughness. From the viewpoint of toughness of the cured product, the content of the bisphenol-type epoxy resin in the matrix resin composition is preferably 10% by mass or more, and more preferably 15% by mass or more, relative to the total mass of components [A] and [D]. From the viewpoint of strength and elastic modulus of the cured product, the content of the bisphenol-type epoxy resin is preferably 40% by mass or less, and more preferably 35% by mass or less, relative to the total mass of components [A] and [D]. The lower and upper limits of the content of the bisphenol-type epoxy resin can be arbitrarily combined; for example, 10 to 40% by mass is preferable, and 15 to 35% by mass is more preferable.

[0063] Examples of bisphenol-type epoxy resins include bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol S-type epoxy resins, and epoxy resins obtained by modifying these with isocyanates. One of these may be used alone, or two or more may be used in combination. In particular, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, and epoxy resins obtained by modifying these with isocyanates are preferred, as they provide an excellent balance between the elastic modulus and toughness of the cured product, and bisphenol F-type epoxy resins are more preferred.

[0064] Among bisphenol type epoxy resins, commercially available examples of bisphenol A type epoxy resins having a molecular weight of 500 or less and being liquid at 25°C include jER827 and jER828 (both manufactured by Mitsubishi Chemical Corporation), YD-127 and YD-128 (both manufactured by Nippon Steel Chemical & Material Co., Ltd.), EPICLON840 and EPICLON850 (both manufactured by DIC Corporation), and D.E.R331 and D.E.R332 (both manufactured by The Dow Chemical Company). Commercially available bisphenol F epoxy resins having a molecular weight of 500 or less and being liquid at 25°C include, for example, jER806 and jER807 (manufactured by Mitsubishi Chemical Corporation), YDF-170 (manufactured by Nippon Steel Chemical & Material Co., Ltd.), EPICLON830 and EPICLON835 (manufactured by DIC Corporation), and D.E.R354 (manufactured by The Dow Chemical Company). Commercially available bisphenol A epoxy resins having a molecular weight of 500 or more and being semi-solid or solid at 25°C include jER1001, jER1002, jER1004, jER1007, and jER1009 (all manufactured by Mitsubishi Chemical Corporation), EPICLON 2050, EPICLON 3050, EPICLON 4050, and EPICLON 7050 (all manufactured by DIC Corporation), and YD-011, YD-012, YD-013, YD-014, YD-902, YD-903N, YD-904, YD-907, YD-7910, and YD-6020 (all manufactured by Nippon Steel Chemical & Material Co., Ltd.). Examples of bisphenol F epoxy resins that have a molecular weight of 500 or more and are semi-solid or solid at 25°C include jER4004P, jER4005P, jER4007P, and jER4010P (all manufactured by Mitsubishi Chemical Corporation), and YDF-2001, YDF-2004, and YDF-2005RD (all manufactured by Nippon Steel Chemical & Material Co., Ltd.).Examples of isocyanate-modified epoxy resins that have a molecular weight of 500 or more and are semi-solid or solid at 25°C include ACR1348 (manufactured by ADEKA CORPORATION), DER852, DER858 (all manufactured by THE DOW CHEMICAL COMPANY), TSR-400 (manufactured by DIC Corporation), and YD-952 (manufactured by Nippon Steel Chemical & Material Co., Ltd.).

[0065] (Other Epoxy Resins) The matrix resin composition may contain one or more epoxy resins other than the above-mentioned epoxy resins. Examples of other epoxy resins include epoxy resins containing a biphenol skeleton, epoxy resins containing a naphthalene skeleton, epoxy resins containing a fluorene skeleton, resorcinol-type epoxy resins, and pyrogallol-type epoxy resins.

[0066] Commercially available epoxy resins containing a biphenol skeleton include, for example, jER YX4000 and jER YL6121HA (manufactured by Mitsubishi Chemical Corporation). Commercially available epoxy resins containing a naphthalene skeleton include, for example, EPICLON HP-4032SS, EPICLON HP-4700, EPICLON HP-4710, and EPICLON HP-4770 (manufactured by DIC Corporation). Commercially available epoxy resins containing a fluorene skeleton include, for example, OGSOL PG-100, OGSOL CG-500, OGSOL EG-200, and OGSOL EG-280 (manufactured by Osaka Gas Chemicals Co., Ltd.). Commercially available resorcinol-type epoxy resins include, for example, Denacol EX-201 (manufactured by Nagase ChemteX Corporation). An example of a commercially available pyrogallol type epoxy resin is EPICLON EXA-7190 (manufactured by DIC Corporation).

[0067] (Average Epoxy Equivalent) The average epoxy equivalent of the entire epoxy resin, i.e., the entire components [A] and [D], can be, for example, 100 to 400 g / eq. From the viewpoint of toughness of the cured product, the average epoxy equivalent of the entire epoxy resin is preferably 150 g / eq or more, more preferably 160 g / eq or more, and even more preferably 170 g / eq or more. From the viewpoint of heat resistance of the cured product, the average epoxy equivalent of the entire epoxy resin is preferably 300 g / eq or less, more preferably 290 g / eq or less, and even more preferably 280 g / eq or less.

[0068] The epoxy equivalent of the glycidylamine epoxy resin can be, for example, 90 to 140 g / eq, with 95 to 110 g / eq being preferred from the viewpoint of the elastic modulus of the cured product. The epoxy equivalent of the novolac epoxy resin can be, for example, 160 to 300 g / eq, with 180 to 220 g / eq being preferred from the viewpoint of the elastic modulus and heat resistance of the cured product. The epoxy equivalent of the bisphenol epoxy resin can be, for example, 150 to 5000 g / eq, with 500 to 3000 g / eq being preferred from the viewpoint of the toughness of the cured product.

[0069] When multiple epoxy resins are used in combination, the average epoxy equivalent can be calculated as follows. For example, the calculation method will be explained using an example in which three types of epoxy resins are used in combination. When W1 parts by mass of epoxy resin 1 having an epoxy equivalent of E1 (g / eq), W2 parts by mass of epoxy resin 2 having an epoxy equivalent of E2 (g / eq), and W3 parts by mass of epoxy resin 3 having an epoxy equivalent of E3 (g / eq) are blended, the average epoxy equivalent can be calculated using the following formula: Average epoxy equivalent = (W1 + W2 + W3) / (W1 / E1 + W2 / E2 + W3 / E3)

[0070] <Component [E]> Component [E] is a radical polymerization initiator and can be used as the radical polymerization initiator for component [C]. Radical polymerization initiators include thermal radical polymerization initiators that are activated by heat and photoradical polymerization initiators that are activated by light irradiation. However, it is preferable to use a thermal radical polymerization initiator because it can generate radicals simultaneously with the thermal curing of the epoxy resin. In other words, by incorporating component [E] into the matrix resin composition, the polymerization of component [C] can proceed simultaneously with the thermal curing of component [D].

[0071] Examples of thermal radical polymerization initiators include azo compounds and organic peroxides, but it is preferable to use organic peroxides, which do not generate gas during thermal decomposition and can therefore produce high-quality fiber-reinforced plastics without voids. Component [E] is preferably at least one peroxide compound selected from the group consisting of diacyl peroxides, alkyl peroxy esters, peroxydicarbonates, peroxyketals, dialkyl peroxides, and hydroperoxides.

[0072] The content of component [E] in the matrix resin composition is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, per 100 parts by mass of component [C] in order to sufficiently promote the polymerization of component [C]. Furthermore, from the viewpoint of the storage stability of the prepreg, the content of component [E] is preferably 10 parts by mass or less, more preferably 9 parts by mass or less, per 100 parts by mass of component [C]. The lower and upper limits of the content of component [E] can be arbitrarily combined; for example, 0.1 to 10 parts by mass is preferred, and 0.2 to 9 parts by mass is more preferred.

[0073] From the viewpoint of the storage stability of the prepreg, the 10-hour half-life temperature of component [E] is preferably 70° C. or higher, and more preferably 100° C. or higher. Furthermore, in order to allow the polymerization of component [C] to proceed sufficiently during the curing process of the epoxy resin composition, the 10-hour half-life temperature of component [E] is preferably 150° C. or lower.

[0074] Specific examples of component [E] include ketone peroxides such as methyl ethyl ketone peroxide (110°C) and acetylacetone peroxide (130°C), 1,1-di(t-butylperoxy)3,3,5-trimethylcyclohexane (95°C), 1,1-di(t-hexylperoxy)cyclohexane (87.1°C), 1,1-di(t-butylperoxy)cyclohexane (90.7°C), 2,2-di(t-butylperoxy)cyclohexane (91.7°C), and 2,2-di(t-butylperoxy)cyclohexane (92.7°C). peroxyketals such as n-butyl 4,4-di(t-butylperoxy)butane (103.1°C), n-butyl 4,4-di(t-butylperoxy)valerate (104.5°C), 2,2-di(4,4-di-t-butylperoxycyclohexyl)propane (94.7°C), 1,1-di(t-hexylperoxy)3,3,5-trimethylcyclohexane (86.7°C), and 1,1-di(t-butylperoxy)cyclododecane (95°C); p-menthane hydroperoxy Hydroperoxides such as di(2-t-butylperoxyisopropyl)benzene (119.2°C), dicumyl peroxide (116.4°C), diisopropylbenzene hydroperoxide (145.1°C), 1,1,3,3-tetramethylbutyl hydroperoxide (152.9°C), cumene hydroperoxide (157.9°C), and t-butyl hydroperoxide (166.5°C), di(2-t-butylperoxyisopropyl)benzene (119.2°C), and dicumyl peroxide (116.4°C). , 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (117.9°C), t-butylcumyl peroxide (119.5°C), di-t-hexyl peroxide (116.4°C), di-t-butyl peroxide (123.7°C), 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3 (128.4°C), and other dialkyl peroxides, diisobutyryl peroxide (32.7°C), di(3,5,diacyl peroxides such as di(5-trimethylhexanoyl) peroxide (59.4°C), lauroyl peroxide (61.6°C), disuccinic acid peroxide (65.9°C), m-toluoyl peroxide (73.1°C), dibenzoyl peroxide (73.6°C), dioctanoyl peroxide (63°C), di-n-propyl peroxydicarbonate (40.3°C), diisopropyl peroxydicarbonate (40.5°C), di(4-t-butylcyclohexane) peroxydicarbonates such as di(2-ethylhexyl)peroxydicarbonate (40.8°C), di(2-ethylhexyl)peroxydicarbonate (43.6°C), di-sec-butylperoxydicarbonate (40.5°C), and di(3-methoxybutyl)peroxydicarbonate (43°C); cumyl peroxyneodecanoate (36.5°C), 1,1,3,3-tetramethylbutylperoxyneodecanoate (40.7°C), t-hexylperoxyneodecanoate (44.5°C), t-butyl peroxyneodecanoate (46.4°C), t-hexyl peroxypivalate (53.2°C), t-butyl peroxypivalate (54.6°C), 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (65.3°C), 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane (66.2°C), t-hexylperoxy-2-ethylhexanoate (69.9°C), t-butylperoxy 2-ethylhexanoate (72.1°C), t-hexylperoxyisopropyl monocarbonate (95°C), t-butylperoxy-3,5,5-trimethylhexanoate (97.1°C), t-butylperoxylaurate (98.3°C), t-butylperoxyisopropyl monocarbonate (98.7°C), t-butylperoxy-2-ethylhexyl monocarbonate (99°C), t-hexylperoxybenzoate (99.4°C), 2,5-dimethyl-2,Examples of peroxyesters include 5-di(benzoylperoxy)hexane (99.7°C), t-butyl peroxyacetate (101.9°C), t-butyl peroxybenzoate (104.3°C), t-butyl peroxymaleic acid (96.1°C), and t-butyl peroxyisobutyrate (75°C). The values ​​in parentheses indicate the 10-hour half-life temperature. The exemplified compounds can be used alone or in combination of two or more as component [E].

[0075] <Thermoplastic Resin> The matrix resin composition can contain a thermoplastic resin. Examples of the thermoplastic resin include polyamide, polyester, polycarbonate, polyethersulfone, polyphenylene ether, polyphenylene sulfide, polyetheretherketone, polyetherketone, polyimide, polytetrafluoroethylene, polyether, polyolefin, liquid crystal polymer, polyarylate, polysulfone, polyacrylonitrilestyrene, polystyrene, polyacrylonitrile, polymethyl methacrylate, ABS (acrylonitrile-butadiene-styrene copolymer), AES (acrylonitrile-ethylene-propylene rubber-styrene copolymer), ASA (acrylonitrile-acrylic rubber-styrene copolymer), polyvinyl chloride, polyvinyl formal, polyvinyl butyral, phenoxy resin, and block copolymer, but are not limited thereto. Among these, polyvinyl formal, polyvinyl butyral, polyethersulfone, and phenoxy resin are more preferred due to their excellent solubility in epoxy resins and resin flow controllability. Polyvinyl formal is more preferred because it has excellent resin flow controllability even when blended in a small amount.The thermoplastic resins may be used alone or in combination of two or more.

[0076] The content of the thermoplastic resin in the matrix resin composition is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of the total of components [A] and [D] contained in the matrix resin composition. It is also preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. The lower and upper limits of the content of the thermoplastic resin can be arbitrarily combined. For example, 1 to 30 parts by mass is preferred, more preferably 2 to 20 parts by mass, and even more preferably 3 to 10 parts by mass. A content of the thermoplastic resin of 1 part by mass or more is preferred because resin flow controllability tends to be well exhibited. On the other hand, a content of the thermoplastic resin of 30 parts by mass or less is preferred because the increase in viscosity of the matrix resin composition is small.

[0077] <Other Additives> The matrix resin composition may contain various known additives as needed, provided that they do not impair the effects of the present invention. Examples of such additives include epoxy resin curing accelerators, phosphorus-based flame retardants, hydrated metal compound inorganic flame retardants, other flame retardant aids, silicone oil, wetting and dispersing agents, antifoaming agents, defoamers, natural waxes, synthetic waxes, metal salts of straight-chain fatty acids, acid amides, esters, paraffins, and other mold release agents; inorganic fillers such as powders of crystalline silica, fused silica, calcium silicate, alumina, calcium carbonate, talc, and barium sulfate, glass fibers, and carbon fibers; colorants such as carbon black and red iron oxide; and silane coupling agents. Examples of phosphorus-based flame retardants include phosphorus-containing epoxy resins, red phosphorus, phosphazene compounds, phosphates, and phosphoric acid esters. Examples of hydrated metal compound flame retardants include aluminum hydroxide and magnesium hydroxide. Other flame retardant aids include, for example, antimony compounds, zinc borate, zinc stannate, Mo compounds, ZrO, zinc sulfide, zeolite, and titanium oxide nanofillers. These may be used alone or in combination of two or more.

[0078] <Method for Producing Matrix Resin Composition> The matrix resin composition can be obtained by heating and mixing the above-described components. Examples of methods for mixing the components include using a mixer such as a three-roll mill, planetary mixer, kneader, homogenizer, or homodisper. <Viscosity of Matrix Resin Composition> The viscosity of the matrix resin composition at 70°C is preferably 10 Pa·s or higher. This prevents resin repellency on the substrate surface during film production in the <Method for Producing Prepreg> described below, allowing for the production of a uniform film. In addition, the shape of the produced prepreg can be maintained, thereby suppressing cracking, excessive resin flow during molding, and variations in fiber content. From the perspective of processability, such as prepreg tack and drape, the viscosity of the matrix resin composition at 70°C is more preferably 20 Pa·s or higher, and even more preferably 30 Pa·s or higher. The viscosity of the matrix resin composition at 70°C is preferably 200 Pa·s or less, more preferably 150 Pa·s or less, because this can suppress blurring during film production and reduce unimpregnated areas during resin impregnation into the reinforcing fiber substrate. For example, using a high-molecular-weight epoxy resin as the aforementioned component [D] can increase the viscosity of the matrix resin composition at 70°C, while using a low-molecular-weight epoxy resin can decrease the viscosity of the matrix resin composition at 70°C. In particular, novolac epoxy resins with the same repeating unit structure have little effect on the mechanical properties of the resulting fiber-reinforced plastic, so the viscosity can be easily adjusted by using novolac epoxy resins with different molecular weights. Furthermore, increasing the content of the aforementioned <thermoplastic resin> can increase the viscosity of the matrix resin composition at 70°C, while decreasing the content of the <thermoplastic resin> can decrease the viscosity of the matrix resin composition at 70°C. The viscosity here refers to the complex viscosity η* obtained by placing an uncured matrix resin composition on a plate and measuring the temperature dependence under the following measurement conditions.Apparatus: Rheometer ("HAAKE MARS 40" manufactured by Thermo Fisher Scientific) Plates used: 25φ parallel plates Plate gap: 0.5 mm Measurement frequency: 10 rad / sec Measurement temperature: 30 to 130°C Stress: 300 Pa

[0079] <Reinforcing Fiber> The reinforcing fiber can be present in the prepreg as a reinforcing fiber substrate, i.e., an aggregate of reinforcing fibers, and is preferably in the form of a sheet. The orientation of the fibers in the reinforcing fiber substrate may be such that the reinforcing fibers are aligned in a single direction or in a random direction. Examples of the form of the reinforcing fiber substrate include a woven fabric of reinforcing fibers, a nonwoven fabric of reinforcing fibers, and a sheet in which long reinforcing fibers are aligned in one direction. From the viewpoint of being able to mold a fiber-reinforced plastic with high specific strength and specific modulus, it is preferable to use a sheet made of a bundle of reinforcing fibers in which continuous fibers are aligned in a single direction for the prepreg. From the viewpoint of ease of handling, it is preferable to use a woven fabric of reinforcing fibers for the prepreg. The weight per unit area of ​​the reinforcing fiber substrate is 10 g / m ２ More than 4000g / m ２ It can be as follows:

[0080] The prepreg according to the embodiment of the present invention uses carbon fiber as the reinforcing fiber. This allows the resulting fiber-reinforced plastic to have good mechanical properties and be lightweight. Other reinforcing fibers, such as glass fiber, aramid fiber, and boron fiber, may also be used.

[0081] The fiber diameter of the carbon fibers is preferably 3 to 12 μm. The number of carbon fibers in the carbon fiber bundle is preferably 1,000 to 70,000. A sheet-like reinforcing fiber substrate may be formed by using a plurality of carbon fiber bundles and aligning the fibers in one direction, or a sheet-like reinforcing fiber substrate may be formed by scattering chopped carbon fiber bundles obtained by chopping carbon fiber bundles.

[0082] From the viewpoint of the rigidity of the resulting fiber-reinforced plastic, the strand tensile strength of the carbon fiber is preferably 1.5 to 9 GPa, and the matrix resin composition described above can improve adhesion even to carbon fibers with a tensile strength of 5 GPa or more. The strand tensile modulus of the carbon fiber is preferably 150 to 400 GPa. Here, the strand tensile strength and strand tensile modulus of the carbon fiber are values ​​measured in accordance with JIS R7601:1986.

[0083] <Method for Producing Prepreg> Prepreg can be obtained by impregnating a reinforcing fiber substrate with a matrix resin composition. Examples of methods for impregnating a reinforcing fiber substrate with the matrix resin composition include, but are not limited to, a wet method in which the matrix resin composition is dissolved in a solvent such as methyl ethyl ketone or methanol to reduce the viscosity and then impregnated into the reinforcing fiber substrate, and a hot-melt method (dry method) in which the matrix resin composition is heated to reduce the viscosity and then impregnated into the reinforcing fiber substrate. The impregnation temperature is set according to the viscosity of the matrix resin composition. However, from the viewpoint of preventing the initiation of a curing reaction of the matrix resin composition and ensuring that the matrix resin composition is sufficiently impregnated into the reinforcing fibers, a temperature of 40 to 120°C is preferred, and a temperature of 50 to 110°C is more preferred.

[0084] The wet method involves immersing a reinforcing fiber substrate in a solution of a matrix resin composition, then removing it, and evaporating the solvent using an oven or the like. The hot melt method includes a method in which a matrix resin composition whose viscosity has been reduced by heating is directly impregnated into a reinforcing fiber substrate, and a method in which the matrix resin composition is first applied to the surface of a substrate such as release paper to form a film, and then the film is placed on both sides or one side of the reinforcing fiber substrate and heated and pressurized to impregnate the reinforcing fiber substrate with the resin. The coating layer obtained by applying the composition to the surface of a substrate such as release paper may be used in the hot melt method in an uncured state, or the coating layer may be cured and then used in the hot melt method. According to the hot melt method, substantially no solvent remains in the prepreg.

[0085] The content of the matrix resin composition in the prepreg (hereinafter referred to as "resin content") is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 15% by mass or more, and preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less, relative to the total mass of the prepreg. The lower and upper limits of the resin content can be arbitrarily combined; for example, 10 to 60% by mass is preferred, 15 to 55% by mass is more preferred, and 15 to 50% by mass is even more preferred. If the resin content is equal to or greater than the lower limit, sufficient adhesion between the reinforcing fibers and the matrix resin composition can be ensured, and if it is equal to or less than the upper limit, the mechanical properties of the fiber-reinforced plastic are further improved.

[0086] The content of reinforcing fibers in the prepreg (hereinafter referred to as "fiber content") is preferably 30% by volume or more, more preferably 35% by volume or more, even more preferably 40% by volume or more, and preferably 85% by volume or less, more preferably 80% by volume or less, and even more preferably 80% by volume or less, relative to the total volume of the prepreg. The lower and upper limits of the fiber content can be arbitrarily combined; for example, 30 to 85% by volume is preferred, 35 to 80% by volume is more preferred, and 40 to 80% by volume is even more preferred. If the fiber content is equal to or greater than the lower limit, the mechanical properties of the fiber-reinforced plastic are further improved, and if it is equal to or less than the upper limit, sufficient adhesion between the reinforcing fibers and the matrix resin composition can be ensured.

[0087] [Fiber-reinforced plastic] One embodiment of the present invention relates to a fiber-reinforced plastic. Fiber-reinforced plastic is obtained by curing a prepreg. That is, fiber-reinforced plastic includes a cured product of a matrix resin composition contained in the prepreg and reinforcing fibers. A cured product can be obtained from a laminate in which one or more prepregs are laminated. For example, a molded product made of fiber-reinforced plastic can be obtained by laminating one or more of the above-mentioned prepregs and then molding the resulting laminate by a method such as heat curing while applying pressure. In addition to the prepregs described above, prepregs made of a thermoplastic resin composition and reinforcing fibers or prepregs made of an epoxy resin composition and reinforcing fibers may also be laminated together. The form of the fiber-reinforced plastic can be appropriately selected depending on the application, and can be, for example, tubular.

[0088] Examples of molding methods include, but are not limited to, press molding, autoclave molding, bagging molding, wrapping tape molding, internal pressure molding, sheet wrap molding, RTM (Resin Transfer Molding), VaRTM (Vacuum Assisted Resin Transfer Molding), filament winding, and RFI (Resin Film Infusion), which impregnate a reinforcing fiber filament or preform with a matrix resin composition and harden it to obtain a molded product. Among these, autoclave molding is preferred from the viewpoint of easily obtaining a high-quality fiber-reinforced plastic, and press molding is preferred from the viewpoint of obtaining high productivity.

[0089] When producing fiber-reinforced plastics by press molding, it is preferable to clamp a prepreg or a preform made by laminating prepregs in a mold adjusted to a curing temperature in advance and heat and pressurize the prepreg or preform to cure it. The temperature inside the mold during press molding is preferably 100 to 180°C. It is also preferable to cure the prepreg or preform for 1 to 20 minutes under conditions of 1 to 15 MPa.

[0090] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these. The raw materials used in the examples and comparative examples are shown below.

[0091] <Raw materials used> (Component [A]) TEPIC-S: Triglycidyl isocyanurate (manufactured by Nissan Chemical Industries, Ltd., product name "TEPIC-S") MA-DGIC: Monoallyl diglycidyl isocyanurate (manufactured by Shikoku Chemical Industries, Ltd., product name "MA-DGIC") DA-MGIC: Diallyl monoglycidyl isocyanurate (manufactured by Shikoku Chemical Industries, Ltd., product name "DA-MGIC").

[0092] (Component [B]) DICYANEX 1400F: dicyandiamide (active hydrogen equivalent 21 g / eq, manufactured by Evonik Japan Co., Ltd., product name "DICYANEX 1400F") Omicure 94: 1,1-dimethyl-3-phenylurea (manufactured by PTI Japan Co., Ltd., product name "Omicure 94").

[0093] (Component [C]) A-9300S: Tris-(2-acryloxyethyl) isocyanurate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK Ester A-9300S"). A-LEN-10: Ethoxylated o-phenylphenol acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK Ester A-LEN-10"). DPE-6A: Dipentaerythritol hexaacrylate (Kyoeisha Chemical Co., Ltd., product name "Light Acrylate DPE-6A").

[0094] (Component [D]) D-1: Triglycidyl-m-aminophenol (Huntsman Japan, product name "ARALDITE MY 0600"). D-2: Bisphenol F epoxy resin (Mitsubishi Chemical, product name "jER 807"). D-3: Solid bisphenol F epoxy resin (Mitsubishi Chemical, product name "jER 4007P"). D-4: Cresol novolac epoxy resin (DIC, product name "EPICLON N-660" or "EPICLON N-680" or "EPICLON N-690"). D-5: Tetraglycidyldiaminodiphenylmethane (Mitsubishi Chemical, product name "jER 604").

[0095] (Component [E]) PERCUMYL D: dicumyl peroxide (10-hour half-life temperature 116.4°C, product name "Percumyl D", manufactured by NOF Corporation).

[0096] (Thermoplastic Resin) VINYLEC K: Polyvinyl formal resin (manufactured by JNC Corporation, product name "VINYLEC K").

[0097] (Carbon fiber) HR40: manufactured by Mitsubishi Chemical Corporation, product name "PYROFIL HR 40 12M", tensile modulus: 375 GPa, tensile strength: 4.41 GPa.

[0098] Examples 1 to 7, Comparative Examples 1 to 6 Preparation of Matrix Resin Compositions Resin compositions were prepared as follows using TEPIC-S, MA-DGIC, and DA-MGIC as component [A], DICYANEX 1400F and Omicure 94 as component [B], A-9300S, A-LEN-10, and DPE-6A as component [C], D-1 to D-5 as component [D], PECUMYL D as component [E], and VINYLEC K as the thermoplastic resin. First, according to the composition shown in Table 1, the curing agent (component [B], solid) and D-1 (liquid) were weighed into a container so that the mass ratio of the solid component to the liquid component was 1:1, and then stirred and mixed. This was further mixed finely using a three-roll mill to obtain a masterbatch containing the curing agent (component [B]). Next, among the compositions listed in Table 1, D-1 and VINYLEC K, excluding those used in the masterbatch containing the curing agent (component [B]), were weighed into a flask (3 parts by mass per 100 parts by mass of epoxy resin) and heated and stirred at 140°C using an oil bath to dissolve and mix the VINYLEC K. Subsequently, component [A] and component [D] were added according to the composition listed in Table 1, and the mixture was stirred and mixed at 130°C to obtain a uniform viscous liquid. The viscosity of the matrix resin composition was adjusted by appropriately using component D-4 to a level that would maintain coatability with a hot melt coater in the preparation of the prepreg described below. After cooling to 80°C, component [C] was further added and stirred and mixed to obtain a uniform viscous liquid. After cooling to approximately 65°C, the masterbatch containing the curing agent (component [B]) and component [E] were added and stirred and mixed to obtain an uncured matrix resin composition.

[0099] <Preparation of Cured Matrix Resin Composition> The uncured matrix resin composition was degassed in a vacuum at about 65°C and then poured between two glass plates to form a plate. The temperature was raised at a rate of 2°C / min and the plate was heated and cured by maintaining the plate at an oven ambient temperature of 150°C for 120 minutes, producing cured products with thicknesses of 2 mm and 3.2 mm.

[0100] <Preparation of Prepreg> Using a hot melt coater (manufactured by Hirano Tecseed Co., Ltd., "R-HC"), an uncured matrix resin composition was applied to a release paper in a resin basis weight of 27 g / m.２ A resin film was prepared by coating the carbon fiber on the resin film to a fiber basis weight of 125 g / m. ２ The carbon fiber sheet was then wound on a drum winding device to form a sheet of 179 g / m2. Another resin film was then attached to the carbon fiber sheet on the drum winding device. The carbon fiber sheet sandwiched between the two resin films was passed through a fusing press (manufactured by Asahi Textile Machinery Co., Ltd., "JR-600LTSW") under conditions of a temperature of 100°C, a pressure of 0.4 MPa, and a feed rate of 3 m / min, and the carbon fiber sheet was impregnated with the uncured matrix resin composition, resulting in a prepreg having a basis weight of 179 g / m2. ２ A unidirectional prepreg having a resin content of 30% by mass was obtained.

[0101] The prepreg was cut into a 300 mm × 300 mm piece, and 18 pieces were stacked with the carbon fibers aligned in the same direction to obtain a laminate. The laminate was heated to 150°C at a rate of 2°C / min in an autoclave under a pressure of 0.7 MPa, and then heat-cured at 150°C for 120 minutes to obtain a 2 mm-thick fiber-reinforced plastic panel.

[0102] The matrix resin compositions, their cured products, and fiber-reinforced plastics prepared were subjected to various measurements and evaluations according to the evaluation methods described below. The results are shown in Table 1.

[0103] <Measurement of Resin Viscosity at 70°C> The uncured matrix resin composition obtained in <Preparation of Matrix Resin Composition> above was placed on a plate, and the temperature dependence of the complex viscosity η* was measured under the following measurement conditions to obtain the resin viscosity at 70°C. Apparatus: Rheometer ("HAAKE MARS 40" manufactured by Thermo Fisher Scientific) Plates used: 25φ parallel plates Plate gap: 0.5 mm Measurement frequency: 10 rad / sec Measurement temperature: 30 to 130°C Stress: 300 Pa

[0104] <Measurement of Flexural Modulus and Flexural Strength of Cured Matrix Resin Composition> Test pieces measuring 60 mm in length and 8 mm in width were cut from the 2 mm-thick cured product obtained in the <Preparation of Cured Matrix Resin Composition> section above. The flexural modulus and flexural strength of the cured matrix resin composition were measured using a universal testing machine (INSTRON 5965, manufactured by INSTRON Corporation) equipped with a three-point bending jig (indenter R = 3.2 mm, support R = 3.2 mm, support distance L = 32 mm) at a crosshead speed of 2 mm / min under conditions of 23°C and 50% RH. Specifically, the stress-strain curve obtained under the above measurement conditions was used to calculate the flexural modulus (unit: GPa) in the flexural strain range of 0.05 to 0.25% by the secant method. The maximum flexural stress of the stress-strain curve obtained under the above measurement conditions was used to obtain the flexural strength (unit: MPa).

[0105] <Measurement of Plane Strain Fracture Toughness KIc of Cured Matrix Resin> A test piece measuring 44 mm in length and 10 mm in width was cut from the 3.2 mm thick cured product obtained in the <Preparation of Cured Matrix Resin Composition> section above. This test piece was subjected to a crosshead speed of 10 mm / min and deformation mode I (open-end type) using a universal testing machine (INSTRON Corporation, "INSTRON 5965") equipped with a three-point bending jig (indenter R = 5 mm, support R = 5 mm, support distance L = 40 mm) at a temperature of 23°C and a humidity of 50% RH. The load at fracture was obtained, and the plane strain fracture toughness KIc was determined according to ASTM D5045 (2014). An initial pre-crack was introduced into the test piece by sliding a razor blade across the test piece.

[0106] <Measurement of 90° flexural strength of fiber-reinforced plastic> A test piece measuring 50.8 mm in length and 12.7 mm in width was cut from the 2 mm thick panel obtained in the <Preparation of fiber-reinforced plastic>. The test piece was cut so that the longitudinal axis of the test piece was perpendicular to the carbon fiber orientation direction. The test piece was measured for the 90° flexural strength of the fiber-reinforced plastic at a crosshead speed of 0.85 mm / min using a universal testing machine (INSTRON Corporation, "INSTRON 5965") equipped with a three-point bending jig (indenter R = 5.0 mm, support R = 3.2 mm, support distance L = 32 mm) in accordance with ASTM D790 under an environment of 23°C and 50% RH. Specifically, the maximum bending stress of the stress-strain curve obtained under the above measurement conditions was taken as the 90° flexural strength (unit: MPa).

[0107]

[0108] (Examples 1-4, Comparative Examples 1-2) As shown in Table 1, Examples 1-2, which used TEPIC-S as component [A] and A-9300S as component [C], exhibited greater flexural strength while maintaining the same KIc of the cured product compared to Comparative Example 1, which did not contain component [C], despite the same component [D]. Furthermore, Examples 1-2 exhibited greater KIc of the cured product compared to Comparative Example 2, in which component [A] was replaced with D-5. Example 3, which used A-LEN-10 as component [C], and Example 4, which used DPE-6A, also exhibited better flexural strength and KIc of the cured product compared to Comparative Examples 1-2. Furthermore, for fiber-reinforced plastics, Example 1 exhibited higher 90° flexural strength compared to Comparative Examples 1-2. The 90° flexural strength of fiber-reinforced plastics depends not only on the performance of the matrix resin cured product but also on the adhesion at the interface between the carbon fiber and the matrix resin composition. In other words, it can be said that the matrix resin composition containing both component [A] and component [C] improved the adhesion between the carbon fiber and the matrix resin composition, and exhibited high 90° bending strength in addition to the bending strength and KIc of the cured product.

[0109] (Examples 5-6, Comparative Examples 2-4) As shown in Table 1, Example 5, which used MA-DGIC as component [A] and contained A-9300S as component [C], exhibited greater flexural strength while maintaining the same KIc of the cured product compared to Comparative Example 3, which did not contain component [C], despite the same component [D]. A similar trend was observed in Example 6 and Comparative Example 4, which used DA-MGIC as component [A]. Furthermore, compared to Comparative Example 2, in which component [A] was replaced with D-5, Examples 5-6 exhibited greater KIc of the cured product. Furthermore, with regard to fiber-reinforced plastics, Examples 5-6 exhibited higher 90° flexural strength compared to Comparative Examples 2-4.

[0110] (Example 7, Comparative Examples 5 and 6) As shown in Table 1, Example 7, which used TEPIC-S as component [A] and A-9300S as component [C], exhibited greater flexural strength while maintaining the same KIc of the cured product compared to Comparative Example 5, which did not contain component [C], despite the fact that the component [D] was the same. Furthermore, Example 7 exhibited a greater KIc of the cured product compared to Comparative Example 6, which did not contain component [A].

[0111] (Effects of the Examples) While the flexural strength and KIc of a cured product are usually in a trade-off relationship, the combined use of component [A] and component [C] made it possible to achieve a high level of compatibility between the two, as described above. Furthermore, the combined use of component [A] and component [C] resulted in a fiber-reinforced plastic exhibiting high 90° flexural strength, as described above. The 90° flexural strength of a fiber-reinforced plastic depends not only on the performance of the cured matrix resin, but also on the adhesion at the interface between the carbon fiber and the matrix resin composition. In other words, it can be said that the matrix resin composition containing both component [A] and component [C] improved the adhesion between the carbon fiber and the matrix resin composition, and thus exhibited high 90° flexural strength in addition to the flexural strength and KIc of the cured product.

[0112] By using the prepreg of the above-described form, it is possible to obtain a fiber-reinforced plastic having excellent mechanical properties, particularly strength in the direction perpendicular to the fibers. Therefore, according to the present invention, a fiber-reinforced plastic molded article having excellent mechanical properties can be produced, and the molded article can be widely used in a wide range of applications, from molded articles for sports and leisure applications such as fishing rods, golf shafts, and rackets to molded articles for industrial applications such as aircraft and automobiles.

Claims

1. A prepreg comprising a matrix resin composition and carbon fibers, the matrix resin composition comprising the following components [A] to [D]: [A] an isocyanuric acid derivative having a glycidyl group, represented by the following formula (1): (In formula (1), X １ ~X ３ represents a glycidyl group, an allyl group, an alkyl group, or a hydrogen atom; X １ ~X ３ At least one of the above is a glycidyl group.) [B] A curing agent; [C] A compound having no glycidyl group but having a (meth)acryloyl group; [D] An epoxy resin other than the component [A].

2. The prepreg according to claim 1, comprising an isocyanuric acid derivative as the component [C].

3. The prepreg according to claim 1 or 2, comprising 50 to 200 parts by mass of said component [A] per 100 parts by mass of said component [C].

4. The prepreg according to claim 1 or 2, comprising 10 to 30 mass% of component [A] relative to the total mass of components [A] and [D].

5. In the formula (1), X １ ~X ３ The prepreg according to claim 1 or 2, wherein all of are glycidyl groups.

6. The prepreg according to claim 1 or 2, which contains a novolac type epoxy resin as component [D], and contains 20 to 60 mass% of the novolac type epoxy resin based on the total mass of components [A] and [D].

7. The prepreg according to claim 6, wherein the novolac type epoxy resin contains at least one member selected from the group consisting of derivatives of cresol, bisphenol A, biphenyl, naphthalene, and dicyclopentadiene as a partial skeleton.

8. The prepreg according to claim 1 or 2, comprising 10 to 40 mass% of a bisphenol type epoxy resin relative to the total mass of the components [A] and [D].

9. The prepreg according to claim 8, wherein the bisphenol type epoxy resin comprises a bisphenol F type epoxy resin.

10. The prepreg according to claim 1 or 2, wherein the component [B] contains at least one member selected from the group consisting of dicyandiamide, aromatic amines, ureas, and imidazoles.

11. The prepreg according to claim 10, wherein the component [B] contains dicyandiamide.

12. A prepreg according to claim 1 or 2, comprising 50 mass% or more of component [B1] having a melting point of 70°C or higher relative to the total mass of component [B].

13. The prepreg according to claim 1 or 2, comprising 10 to 40 parts by mass of said component [C] per 100 parts by mass of the total of said components [A] and [D].

14. The prepreg according to claim 2, wherein the component [C] contains an isocyanuric acid derivative having a (meth)acryloyl group represented by the following formula (2): (In formula (2), Y １ ~Y ３ represents a (meth)acryloyl group or a hydrogen atom; Y １ ~Y ３ At least one of these is a (meth)acryloyl group.

15. In the formula (2), Y １ ~Y ３ The prepreg according to claim 14, wherein all of are (meth)acryloyl groups.

16. The prepreg according to claim 1 or 2, wherein the matrix resin composition further contains the following component [E]: [E] a radical polymerization initiator 17. The prepreg according to claim 16, wherein component [E] comprises an organic peroxide.

18. The prepreg according to claim 16, wherein the 10-hour half-life temperature of component [E] is 70°C or higher.

19. The prepreg according to claim 1 or 2, wherein the viscosity of the matrix resin composition at 70°C is 10 Pa·s or more.

20. The prepreg according to claim 1 or 2, wherein the prepreg is a unidirectional prepreg in which carbon fibers aligned in one direction are impregnated with a matrix resin composition.

21. A fiber-reinforced plastic obtained by curing the prepreg according to claim 1 or 2.

22. The fiber-reinforced plastic of claim 21, which is tubular.

Images