Resin composition, composite material, and cured product thereof

Abstract

[Problem] To provide: a resin composition that can cure rapidly and at low temperatures; and a composite material containing this resin composition and a fibrous base material. [Solution] The resin composition contains a vinyl ester resin (A), an ethylenically unsaturated group-containing monomer (B), a metal-containing compound (C), an organic peroxide (D), and an imidazole compound (E). The vinyl ester resin (A) is an epoxy group-bearing vinyl ester resin; the metal-containing compound (C) is a compound that contains a metal element from groups 7 to 11; and the content as metal of the metal-containing compound (C) is 0.1 × 10-6 to 2,000 × 10-6 mass parts per 100 mass parts of the total of the vinyl ester resin (A) and the ethylenically unsaturated group-containing monomer (B).

Description

Resin composition, composite material, and cured product thereof

[0001] The present invention relates to a vinyl ester resin composition, a composite material containing the composition, and a cured product thereof.

[0002] Fiber-reinforced plastics, a type of fiber-reinforced composite material, are lightweight, strong, and rigid, and are therefore used in a wide range of fields, including aviation, space, automobiles, railway vehicles, ships, civil engineering and construction, sports, and leisure.

[0003] 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 has the advantage that the reinforcing fiber content of the resulting fiber-reinforced plastic can be easily controlled and can be designed to be higher. A fiber-reinforced plastic molded product can be obtained by stacking multiple sheets of this prepreg and heat-curing them.

[0004] Specific methods for obtaining fiber-reinforced plastics using prepregs include, for example, molding using an autoclave, press molding, internal pressure molding, oven molding, etc. In any of these methods, two or more prepregs are typically laminated, shaped into the desired shape, and then heated and cured. This requires approximately 2 to 6 hours at temperatures of approximately 160°C or higher to cure. In other words, the production of fiber-reinforced plastics requires high-temperature and long-term processing. Therefore, in order to improve the molding cycle, it is necessary to be able to mold the plastic at a relatively low temperature in a short time, such as several minutes to several tens of minutes.

[0005] Epoxy resin compositions that are excellent in mechanical properties, heat resistance, and handleability are widely used as matrix resins for prepregs, but generally require high temperatures and a long time to cure the epoxy resin compositions. Patent Document 1 discloses an epoxy resin composition and prepreg that can be cured completely in a short time even at low temperatures to give fiber-reinforced plastics that are excellent in mechanical properties such as flexural strength, flexural modulus, and breaking strain, and in heat resistance, and that have a flexural strength of 155 MPa or more and a flexural modulus of 3.3 GPa or more when heat-cured at 140°C for 30 minutes.

[0006] Japanese Patent Application Laid-Open No. 2021-116349

[0007] High-temperature, long-term treatment consumes a large amount of heat and requires time for curing the resin composition and for cooling and allowing it to cool, resulting in problems that production efficiency is not necessarily good. In recent years, there has been a demand for energy conservation and an improvement in the production cycle. However, epoxy resin compositions commonly used to obtain fiber-reinforced plastics currently require heating at high temperatures for long periods of time to obtain a cured product, and no compositions have been proposed that can be cured at relatively low temperatures in a period of several minutes to several tens of minutes.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a resin composition that can be cured at a low temperature in a short time, and a composite material containing the resin composition and a fiber substrate. That is, the present invention relates to the following [1] to

[15] . [1] A resin composition containing a vinyl ester resin (A), an ethylenically unsaturated group-containing monomer (B), a metal-containing compound (C), an organic peroxide (D), and an imidazole compound (E), wherein the vinyl ester resin (A) is a vinyl ester resin having an epoxy group, the metal-containing compound (C) is a compound containing a metal element of Groups 7 to 11, and the metal-equivalent content of the metal-containing compound (C) is 0.1 × 10 per 100 parts by mass of the total of the vinyl ester resin (A) and the ethylenically unsaturated group-containing monomer (B). -6 ~2000 x 10 -6parts by mass. [2] The resin composition according to [1], wherein the metal element contained in the metal-containing compound (C) is at least one selected from iron, nickel, cobalt, manganese, and copper. [3] The resin composition according to [2], wherein the metal-containing compound (C) is at least one carboxylate selected from iron, nickel, cobalt, manganese, and copper, or at least one β-diketone complex selected from iron, nickel, cobalt, manganese, and copper. [4] The resin composition according to [3], wherein the metal-containing compound (C) comprises at least one selected from copper naphthenate, copper bis(2,4-pentanedionato), nickel(II) bis(2,4-pentanedionato)hydrate, cobalt octoate, manganese octoate, and iron naphthenate. [5] The resin composition according to any one of [1] to [4], further comprising: 45 to 95 parts by mass of the vinyl ester resin (A); 5 to 55 parts by mass of the ethylenically unsaturated group-containing monomer (B); 0.5 to 4 parts by mass of an organic peroxide (D); and 0.1 to 10 parts by mass of an imidazole compound (E), relative to a total of 100 parts by mass of the vinyl ester resin (A) and the ethylenically unsaturated group-containing monomer (B). [6] The resin composition according to any one of [1] to [5], further comprising: a mercapto group-containing compound (F). [7] The resin composition according to any one of [1] to [6], wherein the vinyl ester resin (A) is a reaction product of an epoxy compound (a-1) having two or more epoxy groups per molecule and an unsaturated monobasic acid (a-2), and wherein the total number of acid groups in the unsaturated monobasic acid (a-2) is 20 to 80 moles relative to 100 moles of the total number of epoxy groups in the epoxy compound (a-1). [8] The resin composition according to [7], wherein the epoxy compound (a-1) is a bisphenol-type epoxy resin. [9] The resin composition according to [7], wherein the unsaturated monobasic acid (a-2) is at least one selected from (meth)acrylic acid and crotonic acid.

[10] The resin composition according to [1] to [8], wherein the organic peroxide (D) is at least one selected from peroxyester-based organic peroxides, hydroperoxide-based organic peroxides, dialkyl peroxide-based organic peroxides, and peroxyketal-based organic peroxides.

[11] The resin composition according to any one of [1] to

[10] , wherein the imidazole compound (E) is at least one selected from 2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 2-methylimidazole, imidazole, and 1,2-dimethylimidazole.

[12] The resin composition according to [6], wherein the mercapto group-containing compound (F) is a polyfunctional thiol.

[13] A composite material comprising the resin composition according to any one of [1] to

[12] and a fiber substrate (G).

[14] The composite material according to

[13] , wherein the fiber substrate (G) is at least one selected from carbon fiber and glass fiber.

[15] A cured product of the composite material according to

[14] .

[0009] The resin composition of the present invention and a composite material containing the resin composition and a fiber substrate can be cured efficiently at low temperature in a short time, and therefore can be molded using a molding method that requires a high production cycle.

[0010] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the embodiments described below.

[0011] In this specification, when "to" is used to describe a numerical range, the numerical values ​​at both ends are the upper and lower limits, respectively, and are included in the numerical range. When multiple upper or lower limits are listed, numerical ranges can be created using all combinations of the upper and lower limits. Similarly, when multiple numerical ranges are listed, separate numerical ranges can be created by individually selecting and combining the upper and lower limits from those numerical ranges.

[0012] In this specification, "(meth)acrylic acid" means methacrylic acid or acrylic acid, "(meth)acrylate" means acrylate or methacrylate, and "(meth)acryloyloxy" means acryloyloxy or methacryloyloxy.

[0013] [Resin Composition] The resin composition of the present embodiment contains a vinyl ester resin (A), an ethylenically unsaturated group-containing monomer (B), a metal-containing compound (C), an organic peroxide (D), and an imidazole compound (E). In addition to these, the resin composition may contain other components described below. From the viewpoint of favorably obtaining the effects of the present invention, the total content of the vinyl ester resin (A), the ethylenically unsaturated group-containing monomer (B), the metal-containing compound (C), the organic peroxide (D), and the imidazole compound (E) in the resin composition is preferably 80 to 100 mass%, more preferably 90 to 100 mass%, and even more preferably 95 to 100 mass%.

[0014] [Vinyl Ester Resin (A)] The vinyl ester resin (A) of this embodiment is a vinyl ester resin having at least one epoxy group. The vinyl ester resin is a reaction product of an epoxy compound (a-1) having two or more epoxy groups per molecule and an unsaturated monobasic acid (a-2). Generally, a vinyl ester resin is a compound having a polymerizable unsaturated bond obtained by a ring-opening reaction between the epoxy group in the epoxy compound (a-1) and the carboxy group in the unsaturated monobasic acid (a-1). The vinyl ester resin (A) of this embodiment can be obtained by adjusting the amount of the carboxy group in the unsaturated monobasic acid (a-1) to be reacted with the epoxy group in the epoxy compound (a-1) to an equivalent weight or less, and allowing the epoxy group to remain. When the reaction is carried out at such a quantitative ratio, an equivalent amount of the unsaturated monobasic acid (a-1) reacts stoichiometrically, and a component not having an epoxy group and, conversely, a component with which the unsaturated monobasic acid (a-1) has not reacted are also contained. In the present disclosure, these are also collectively referred to as the vinyl ester resin (A).

[0015] From the viewpoints of adhesion and rapid curing, the epoxy equivalent of the vinyl ester resin (A) is preferably 140 to 9,500, more preferably 160 to 7,000, and even more preferably 190 to 5,000. When the epoxy equivalent of the vinyl ester resin (A) is 140 or more, the resin has excellent adhesion to carbon fibers for epoxy resins, which are widely used as reinforcing fibers. When the epoxy equivalent of the vinyl ester resin (A) is 9,500 or less, the resin has excellent adhesion to carbon fibers for vinyl ester resins and can be cured at low temperatures in a short time.

[0016] (Epoxy Compound (a-1)) The epoxy compound (a-1) is a compound having two or more epoxy groups in one molecule, and a monomer, oligomer, or polymer in general can be used, with no particular limitation on the molecular weight and molecular structure. The epoxy compound (a-1) may be used alone or in combination of two or more. Examples of the epoxy compound (a-1) include biphenyl-type epoxy resins; bisphenol-type epoxy resins such as bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol S-type epoxy resins, bisphenol AF-type epoxy resins, tetrabromobisphenol A-type epoxy resins, and tetramethylbisphenol F-type epoxy resins; stilbene-type epoxy resins; novolac-type epoxy resins such as phenol novolac-type epoxy resins and cresol novolac-type epoxy resins; polyfunctional epoxy resins such as triphenolmethane-type epoxy resins and alkyl-modified triphenolmethane-type epoxy resins; phenol aralkyl-type epoxy resins such as phenol aralkyl-type epoxy resins having a phenylene skeleton and phenol aralkyl-type epoxy resins having a biphenylene skeleton; dihydroxy naphthol-type epoxy resins such as sinaphthalene-type epoxy resins and epoxy resins obtained by glycidyl etherifying a dimer of dihydroxynaphthalene; triazine nucleus-containing epoxy resins such as triglycidyl isocyanurate and monoallyl diglycidyl isocyanurate; alicyclic polyepoxy compounds such as alicyclic diepoxy acetal, alicyclic diepoxy adipate, alicyclic diepoxy carboxylate and vinylcyclohexene dioxide; bridged cyclic hydrocarbon compound-modified phenol-type epoxy resins such as dicyclopentadiene-modified phenol-type epoxy resins; glycidyl ester-type epoxy resins obtained by reacting a polybasic acid such as dimer acid with epichlorohydrin; and oxazolidone ring-containing epoxy resins obtained by reacting the above-mentioned epoxy resins with diisocyanates.Among these, from the viewpoints of toughness imparting, versatility, and cost, bisphenol type epoxy resins are preferred, and one or more selected from bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, and bisphenol AF type epoxy resins are more preferred, and from the viewpoint of a good balance between toughness and strength as a fiber-reinforced plastic, bisphenol A type epoxy resins are even more preferred. The bisphenol structure makes it possible to extend the molecular weight of the epoxy compound.

[0017] The epoxy equivalent of the epoxy compound (a-1) is preferably 170 to 1,000, more preferably 170 to 500, even more preferably 170 to 400, and still more preferably 170 to 300, so that the epoxy compound can be obtained without gelling the vinyl ester resin (A) and from the viewpoint of workability. From the viewpoint of workability, the epoxy compound (a-1) is preferably liquid at 25°C, and more preferably has an epoxy equivalent of 300 or less.

[0018] (Unsaturated Monobasic Acid (a-2)) The unsaturated monobasic acid (a-2) is preferably a monocarboxylic acid having an ethylenically unsaturated group, and may be used alone or in combination of two or more. Examples of the unsaturated monobasic acid (a-2) include (meth)acrylic acid, crotonic acid, cinnamic acid, etc. Among these, from the viewpoints of versatility, reactivity during synthesis of the vinyl ester resin (A), and obtaining a resin composition having good curability, at least one selected from (meth)acrylic acid and crotonic acid is preferred, and from the viewpoint of workability, liquid (meth)acrylic acid is more preferred, and methacrylic acid is even more preferred.

[0019] Furthermore, as the unsaturated monobasic acid (a-2), a half ester of a compound having one hydroxy group and one or more (meth)acryloyl groups with a dibasic acid or a dibasic acid anhydride may be used.

[0020] Examples of acrylic monomers having one hydroxy group and one or more (meth)acryloyl groups include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, hydroxyhexyl (meth)acrylate, polyethylene glycol monomethyl ether (meth)acrylate, polypropylene glycol monomethyl ether (meth)acrylate, polytetramethylene glycol monomethyl ether (meth)acrylate, phenoxy diethylene glycol (meth)acrylate, phenoxy polyethylene glycol (meth)acrylate, nonylphenoxy polyethylene glycol (meth)acrylate, and phenoxy polypropylene glycol (meth)acrylate. Among these, compounds having a hydroxy group and an acryloyl group are preferred from the viewpoint of mechanical properties (elongation at break).

[0021] Known dibasic acids and dibasic acid anhydrides can be used. Examples include succinic acid, glutaric acid, adipic acid, sebacic acid, phthalic acid, fumaric acid, maleic acid, itaconic acid, tetrahydrophthalic acid, hexahydrophthalic acid, dimer acid, ethylene glycol-2 mole maleic anhydride adduct, polyethylene glycol-2 mole maleic anhydride adduct, propylene glycol-2 mole maleic anhydride adduct, polypropylene glycol-2 mole maleic anhydride adduct, dodecanedioic acid, tridecanedioic acid, octadecanedioic acid, 1,16-(6-ethylhexadecane)dicarboxylic acid, 1,12-(6-ethyldodecane)dicarboxylic acid, and butadiene-acrylonitrile copolymer having carboxy groups at both ends (trade name: Hycar CTBN). In this embodiment, a half ester of 2-hydroxyethyl (meth)acrylate and succinic acid is preferred.

[0022] The amount of unsaturated monobasic acid (a-2) is preferably such that the total amount of acid groups of the unsaturated monobasic acid (a-2) is 20 to 80 moles, more preferably 30 to 75 moles, and even more preferably 40 to 65 moles, per 100 moles of the total amount of epoxy groups of the epoxy compound (a-1). If the total amount of acid groups of the unsaturated monobasic acid (a-2) is 20 moles or more per 100 moles of the total amount of epoxy groups of the epoxy compound (a-1), a sufficient amount of ethylenically unsaturated groups is introduced into the vinyl ester resin (A), and the resin composition is likely to exhibit good curability. Furthermore, if the total amount of acid groups of the unsaturated monobasic acid (a-2) is 80 moles or less, a sufficient amount of unreacted epoxy groups remains in the vinyl ester resin (A), resulting in good adhesion to the fiber substrate (G).

[0023] From the viewpoints of ease of reaction and workability, the weight average molecular weight Mw of the vinyl ester resin (A) is preferably 400 or more, more preferably 500 or more, and even more preferably 600 or more. From the viewpoint of impregnation into the fibrous base material (G), the weight average molecular weight Mw is preferably 6,000 or less, more preferably 3,000 or less, and even more preferably 1,500 or less.

[0024] From the viewpoints of ease of reaction and workability, the number average molecular weight Mn of the vinyl ester resin (A) is preferably 200 or more, more preferably 300 or more, and even more preferably 400 or more. From the viewpoint of impregnation into the fibrous base material (G), the number average molecular weight Mn is preferably 3,000 or less, more preferably 2,000 or less, and even more preferably 1,000 or less.

[0025] Mw / Mn is an index of molecular weight distribution; a ratio of 1 indicates a monodisperse polymer, and a larger ratio indicates a wider molecular weight distribution. From the viewpoint of ease of control of synthesis conditions, Mw / Mn of the vinyl ester resin (A) is preferably 1.0 or more, more preferably 1.1 or more, and even more preferably 1.2 or more. Furthermore, from the viewpoint of suppressing variation in the physical properties of the resin composition, it is preferably 3.0 or less, more preferably 2.7 or less, and even more preferably 2.5 or less.

[0026] From the viewpoints of workability, moldability, and curability, it is preferable that the viscosity of the vinyl ester resin (A) be adjusted using a solvent, a reactive diluent, or the like. The adjusted viscosity is preferably 0.01 to 1.2 Pa s, more preferably 0.05 to 1.0 Pa s, and even more preferably 0.1 to 0.8 Pa s, in a 25°C environment. The vinyl ester resin (A) of this embodiment may be used alone or in combination of two or more types.

[0027] The vinyl ester resin (A) may be a commercially available product, or may be produced by the following production method.

[0028] (Method for Producing Vinyl Ester Resin (A)) For example, the vinyl ester resin (A) can be produced by mixing the epoxy compound (a-1) and the unsaturated monobasic acid (a-2) with at least one of a solvent and a reactive diluent, as necessary, in a reaction vessel capable of being heated and stirred, and heating the mixture in the presence of a catalyst at preferably 70 to 150°C, more preferably 80 to 140°C, and even more preferably 90 to 130°C for 1 to 8 hours while mixing.

[0029] Examples of the catalyst include tertiary amines such as triethylamine, triethylenediamine, N,N-dimethylbenzylamine, N,N-dimethylaniline, 2,4,6-tris(dimethylaminomethyl)phenol, and diazabicyclooctane; phosphorus compounds such as triphenylphosphine and benzyltriphenylphosphonium chloride; diethylamine hydrochloride; and quaternary ammonium salts such as trimethylbenzylammonium chloride and tetradecyldimethylbenzylammonium chloride. These may be used alone or in combination of two or more. Among these, from the viewpoints of gently accelerating the synthesis reaction rate of the vinyl ester resin, suppressing gelation of the resin, and making it easy to control the molecular weight distribution, at least one selected from phosphorus compounds and quaternary ammonium salts is preferred, and at least one selected from quaternary ammonium salts is more preferred.

[0030] The amount of the catalyst used is preferably 0.01 to 3 parts by mass, more preferably 0.03 to 2 parts by mass, and even more preferably 0.05 to 1 part by mass, relative to 100 parts by mass of the epoxy compound (a-1) and the unsaturated monobasic acid (a-2) in total, from the viewpoints of promoting the reaction, suppressing thickening of the vinyl ester resin (A), and ensuring the storage stability of the obtained reaction product.

[0031] The solvent and reactive diluent are used as needed to facilitate uniform mixing of the epoxy compound (a-1) and the unsaturated monobasic acid (a-2). The mixing method is not particularly limited and can be performed by a known method. The solvent is not particularly limited as long as it is inactive to the epoxy compound (a-1) and the unsaturated monobasic acid (a-2). For example, known solvents having a boiling point of 70 to 150°C at 1 atmosphere, such as methyl isobutyl ketone (MIBK), can be used. The solvent may be used alone or in combination of two or more. As the reactive diluent, one inactive to the epoxy compound (a-1) and the unsaturated monobasic acid (a-2) is used, but in this embodiment, it is also possible to use the ethylenically unsaturated group-containing monomer (B) described later as the reactive diluent.

[0032] A polymerization inhibitor may be added from the viewpoint of suppressing the progress of the polymerization reaction of the vinyl ester resin (A). The polymerization inhibitors described below in the section "Other Components" are preferably used. When a polymerization inhibitor is added, the amount added may be, for example, 0.0001 to 10 parts by mass, preferably 0.001 to 1.0 part by mass, and more preferably 0.01 to 0.3 part by mass, per 100 parts by mass of the epoxy compound (a-1) and the unsaturated monobasic acid (a-2) combined.

[0033] [Ethylenically unsaturated group-containing monomer (B)] The ethylenically unsaturated group-containing monomer (B) is not particularly limited as long as it has an ethylenically unsaturated group, but one having a vinyl group or a (meth)acryloyl group is preferred. In the present invention, the vinyl ester resin (A) and the ethylenically unsaturated group-containing monomer (B) are contained in a predetermined ratio. The ethylenically unsaturated group-containing monomer (B) contributes to reducing the viscosity of the resin composition and further contributes to the fiber impregnation ability of the composite material.

[0034] Among the ethylenically unsaturated group-containing monomers (B), those having a vinyl group include, for example, styrene, p-chlorostyrene, vinyltoluene, α-methylstyrene, dichlorostyrene, divinylbenzene, t-butylstyrene, vinyl acetate, diallyl phthalate, triallyl isocyanurate, etc. Further examples include vinylbenzyl compounds such as vinylbenzyl butyl ether, vinylbenzyl hexyl ether, vinylbenzyl octyl ether, and divinylbenzyl ether.

[0035] Among the ethylenically unsaturated group-containing monomers (B), those having a (meth)acryloyl group include, for example, (meth)acrylic acid, (meth)acrylate, etc. The (meth)acrylate may be monofunctional or polyfunctional.

[0036] Examples of monofunctional (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, stearyl (meth)acrylate, tridecyl (meth)acrylate, phenoxyethyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, ethylene glycol monomethyl ether (meth)acrylate, ethylene glycol monoethyl ether (meth)acrylate, ethylene glycol monobutyl ether (meth)acrylate, and ethylene glycol monohexyl ether (meth)acrylate. , ethylene glycol mono 2-ethylhexyl ether (meth)acrylate, diethylene glycol monomethyl ether (meth)acrylate, diethylene glycol monoethyl ether (meth)acrylate, diethylene glycol monobutyl ether (meth)acrylate, diethylene glycol monohexyl ether (meth)acrylate, diethylene glycol mono 2-ethylhexyl ether (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, caprolactone-modified hydroxyalkyl (meth)acrylate, and allyl (meth)acrylate.

[0037] Examples of polyfunctional (meth)acrylates include alkanediol di(meth)acrylates such as ethylene glycol di(meth)acrylate, 1,2-propylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, and 1,6-hexanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate. and polyoxyalkylene glycol di(meth)acrylates such as these, as well as trimethylolpropane di(meth)acrylate, glycerin di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, pentaerythritol diacrylate monostearate, 1,3-bis((meth)acryloyloxy)-2-hydroxypropane, ethoxylated bisphenol A di(meth)acrylate, and tris-(2-(meth)acryloxyethyl)isocyanurate.

[0038] Among the ethylenically unsaturated group-containing monomers (B), examples of those having a (meth)acryloyl group other than (meth)acrylate include acryloylmorpholine, 2-hydroxyethyl(meth)acrylamide, 2-hydroxyethyl-N-methyl(meth)acrylamide, and 3-hydroxypropyl(meth)acrylamide.

[0039] These ethylenically unsaturated group-containing monomers (B) may be used alone or in combination of two or more.

[0040] Among these, from the viewpoints of workability, curability, fiber impregnation property, and the like of a composite material containing the resin composition, at least one selected from styrene, methyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, and neopentyl glycol (meth)acrylate is more preferred, at least one selected from styrene, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, diethylene glycol di(meth)acrylate, and neopentyl glycol (meth)acrylate is more preferred, and styrene is even more preferred.

[0041] [Metal-containing compound (C)] The metal-containing compound (C) is used to promote the curing of the resin composition. As the metal compound (C), a compound containing a metal element of Groups 7 to 11 of the periodic table is used. The metal-containing compound (C) may be used alone or in combination of two or more types.

[0042] Examples of the metal element include manganese, technetium, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, and gold. As the metal element, from the viewpoint of high curing-accelerating effect and curing at low temperature in a short time, manganese, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, copper, palladium, platinum, silver, and gold are preferred, manganese, iron, cobalt, nickel, copper, ruthenium, rhodium, palladium, and silver are more preferred, and from the viewpoints of cost, versatility, and availability, manganese, iron, cobalt, nickel, and copper are even more preferred. From the viewpoint of fast curing, cobalt, nickel, and copper are even more preferred.

[0043] In this embodiment, the metal-containing compound (C) is preferably a carboxylate of the metal or a β-diketone complex of the metal. Examples of the carboxylic acid include heptanoic acid, octylic acid, nonanoic acid, decanoic acid, neodecanoic acid, undecanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, eicosanoic acid, docosanoic acid, tetracosanoic acid, hexacosanoic acid, octacosanoic acid, triacontanoic acid, behenic acid, naphthenic acid, oleic acid, linoleic acid, linolenic acid, rosin acid, linseed oil fatty acid, soybean oil fatty acid, tall oil acid, formic acid, acetic acid, citric acid, oxalic acid, and benzoic acid.

[0044] Examples of the β-diketones include 2,4-pentanedione (acetylacetone), 2,2,6,6-tetramethylheptane-3,5-dione, 2,6-dimethyl-3,5-heptanedione, ethyl acetoacetate, α-acetyl-γ-butyrolactone, N-pyrrolidininoacetoacetamide, N,N-dimethylacetoacetamide, 2-isobutyryl-1-cyclohexanone, 6-methyl-2,4-heptanedione, hexafluoroacetylacetone, and 3-methylnonane-2,4-dione.

[0045] From the viewpoint of the effect of accelerating the curing of the resin composition, naphthenic acid, octylic acid, and octenoic acid are preferred as the carboxylic acid, and 2,4-pentanedione is preferred as the β-diketone.

[0046] From the viewpoint of the curing-accelerating effect of the resin composition, the metal-containing compound (C) is preferably copper naphthenate, copper bis(2,4-pentanedionato), bis(2,4-pentanedionato)nickel(II) hydrate, bis(2,4-pentanedionato)nickel(II) dihydrate, bis(2,4-pentanedionato)cobalt(II), bis(2,4-pentanedionato)platinum(II), cobalt octylate, manganese octylate, iron octylate, nickel octylate, iron naphthenate, manganese naphthenate, or cobalt naphthenate, and more preferably copper naphthenate, bis(2,4-pentanedionato) ) copper, bis(2,4-pentanedionato)nickel(II) hydrate, cobalt octylate, manganese octylate, iron octylate, iron naphthenate, manganese naphthenate, and cobalt naphthenate are more preferred, and from the viewpoint of curability, copper naphthenate, bis(2,4-pentanedionato)copper, bis(2,4-pentanedionato)nickel(II) hydrate, cobalt octylate, manganese octylate, and iron naphthenate are even more preferred.

[0047] [Organic Peroxide (D)] The organic peroxide (D) is not particularly limited as long as it is used as a radical curing agent for the vinyl ester resin (A) and the ethylenically unsaturated group-containing monomer (B). From the viewpoint of stability after mixing with the resin, it is preferable to use an organic peroxide having a 10-hour half-life temperature of 60 to 180°C, more preferably 90 to 175°C, and even more preferably 100 to 160°C.

[0048] Examples of the organic peroxide (D) include diacyl peroxides such as benzoyl peroxide, peroxyesters such as t-butyl peroxybenzoate, hydroperoxides such as cumene hydroperoxide, dialkyl peroxides such as dicumyl peroxide, ketone peroxides such as methyl ethyl ketone peroxide and acetylacetone peroxide, peroxyketals such as 1,1-di(t-butylperoxy)cyclohexane, alkyl peresters, and percarbonate organic peroxides. Among these, peroxyester organic peroxides, hydroperoxide organic peroxides, dialkyl peroxide organic peroxides, and peroxyketal organic peroxides are preferred from the viewpoint of curability, and peroxyester organic peroxides and hydroperoxide organic peroxides, which have a good synergistic effect with metal-containing compounds, are more preferred.

[0049] Among the above, one or more selected from cumene hydroperoxide, t-butyl peroxybenzoate, 1,1-di(t-butylperoxy)cyclohexane, and benzoyl peroxide are preferred, and among these, cumene hydroperoxide, which has excellent low-temperature curing properties, and t-butyl peroxybenzoate, which has excellent stability after mixing, are more preferred, and cumene hydroperoxide is even more preferred.

[0050] [Imidazole Compound (E)] The resin composition of this embodiment contains an imidazole compound (E). By combining the imidazole compound (E) with the vinyl ester resin (A), a composition that can be cured in a short time can be obtained. In addition, curing of the epoxy groups contained in the vinyl ester resin (A) proceeds in parallel, further improving physical properties.

[0051] As the imidazole compound (E), from the viewpoint of compatibility with the vinyl ester resin (A) and the ethylenically unsaturated group-containing monomer (B), one in which the 2-position of the 5-membered ring of the imidazole is substituted with an alkyl group, an aryl group, or an aralkyl group may be used. Furthermore, one in which in addition to the 2-position, any one of the 1-, 4-, or 5-position of the 5-membered ring of the imidazole is substituted with an alkyl group, an aryl group, an aralkyl group, or a cyanoethyl group is also desirable, and from the viewpoints of compatibility, curability, and versatility, one in which any one of the 1-, 4-, or 5-position of the 5-membered ring of the imidazole is substituted with an alkyl group, an aryl group, or an aralkyl group may also be used. From the viewpoint of compatibility with the vinyl ester resin (A) and the ethylenically unsaturated group-containing monomer (B), the alkyl group may have 1 to 6 carbon atoms, and preferably 1 to 3 carbon atoms, the aryl group may have 6 to 20 carbon atoms, and preferably 6 to 12 carbon atoms, and the aralkyl group may have 7 to 20 carbon atoms, and preferably 7 to 12 carbon atoms.

[0052] Examples of the imidazole compound (E) include imidazole, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-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 isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo-[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-phenylimidazoline, and the like.

[0053] From the viewpoint of curability, the imidazole compound (E) is preferably 2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 2-methylimidazole, imidazole, or 1,2-dimethylimidazole. Among these, from the viewpoint of workability, 2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, or 1,2-dimethylimidazole is more preferred.

[0054] [Mercapto Group-Containing Compound (F)] The resin composition of the present embodiment may contain a mercapto group-containing compound (F) as needed. By combining the mercapto group-containing compound (F), a resin composition that can be cured at low temperature in a short time can be obtained.

[0055] The mercapto group-containing compound (F) is preferably a polyfunctional thiol compound, and from the viewpoint of odor, a secondary thiol compound in which a mercapto group is bonded to a secondary carbon atom or a tertiary thiol compound in which a mercapto group is bonded to a tertiary carbon atom is preferred, and a secondary thiol compound is preferred in terms of a good balance between reactivity and storage stability, heat resistance, moisture resistance, water resistance, etc.

[0056] In addition, a polyfunctional thiol compound containing two or more mercapto groups in the molecule also functions well as a curing accelerator. The term "polyfunctional thiol" used herein refers to a mercapto group-containing compound having two or more mercapto groups, which are functional groups. For this reason, a polyfunctional secondary thiol compound is preferred in the present invention.

[0057] Examples of the mercapto group-containing compound (F) include monofunctional primary thiol compounds such as 3-mercaptobutyric acid and 1-dodecanethiol; polyfunctional primary thiol compounds having two or more mercapto groups bonded to a primary carbon atom in the molecule include pentaerythritol tetrakis(3-mercaptopropionate), dipentaerythritol hexakis(3-mercaptopropionate), tetraethylene glycol bis(3-mercaptopropionate), ethylene glycol bis(3-mercaptopropionate), 1,4-butanediol bis(thioglycolate), and dipentaerythritol hexakis(3-mercaptopropionate). Examples of secondary thiol compounds having a mercapto group bonded to a secondary carbon atom in the molecule include monofunctional secondary thiol compounds such as 2-mercaptobutyric acid and 3-mercaptobutanoic acid (manufactured by Resonac Corporation, product name: 3MBA); Examples of polyfunctional secondary thiol compounds having two or more mercapto groups bonded to a secondary carbon atom in the molecule include 1,4-bis(3-mercaptobutyryloxy)butane (manufactured by Resonac Corporation, Karenz MT (registered trademark) BD1), pentaerythritol tetrakis(3-mercaptobutyrate) (manufactured by Resonac Corporation, Karenz MT (registered trademark) PE1), 1,3,5-tris(3-mercaptobutyryloxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (manufactured by Resonac Corporation, Karenz MT (registered trademark) NR1), trimethylolethane tris(3-mercaptobutyrate) (manufactured by Resonac Corporation, TEMB), and trimethylolethane tris(3-mercaptobutyrate). Trimethylolpropane tris(3-mercaptobutyrate) (manufactured by Resonac Corporation, TPMB), trimethylolpropane tris(3-mercaptobutyrate), dipentaerythritol hexakis(2-mercaptopropionate), ethylene glycol bis(4-mercaptovalerate), diethylene glycol bis(4-mercaptovalerate), butanediol bis(4-mercaptovalerate), octanediol bis(4-mercaptovalerate), trimethylolpropane tris(4-mercaptovalerate), pentaerythritol tetrakis(4-mercaptovalerate), dipentaerythritol hexakis(4-mercaptovalerate),Ethylene glycol bis(3-mercaptovalerate), propylene glycol bis(3-mercaptovalerate), diethylene glycol bis(3-mercaptovalerate), butanediol bis(3-mercaptovalerate), octanediol bis(3-mercaptovalerate), trimethylolpropane tris(3-mercaptovalerate), pentaerythritol tetrakis(3-mercaptovalerate), dipentaerythritol hexakis(3-mercaptovalerate), hydrogenated bisphenol A bis(3-mercaptobutyrate), bisphenol A dihydroxyethyl ether-3-mercaptobutyrate, 4,4'-(9-fluorenylidene)bis(2-phenoxyethyl(3-mercaptobutyrate)), ethylene glycol Examples of such esters include coalbis(3-mercapto-3-phenylpropionate), propylene glycol bis(3-mercapto-3-phenylpropionate), diethylene glycol bis(3-mercapto-3-phenylpropionate), butanediol bis(3-mercapto-3-phenylpropionate), octanediol bis(3-mercapto-3-phenylpropionate), trimethylolpropane tris(3-mercapto-3-phenylpropionate), tris-2-(3-mercapto-3-phenylpropionate)ethyl isocyanurate, pentaerythritol tetrakis(3-mercapto-3-phenylpropionate), and dipentaerythritol hexakis(3-mercapto-3-phenylpropionate). Examples of tertiary thiol compounds having a mercapto group bonded to a secondary carbon atom in the molecule include di(2-mercaptoisobutyl) phthalate, ethylene glycol bis(2-mercaptoisobutyrate), propylene glycol bis(2-mercaptoisobutyrate), diethylene glycol bis(2-mercaptoisobutyrate), butanediol bis(2-mercaptoisobutyrate), octanediol bis(2-mercaptoisobutyrate), trimethylolethane tris(2-mercaptoisobutyrate), trimethylolpropane tris(2-mercaptoisobutyrate), pentaerythritol tetrakis(2-mercaptoisobutyrate), and dipentaerythritol hexakis(2-mercaptoisobutyrate).Examples thereof include di(3-mercapto-3-methylbutyl phthalate), ethylene glycol bis(3-mercapto-3-methylbutyrate), propylene glycol bis(3-mercapto-3-methylbutyrate), diethylene glycol bis(3-mercapto-3-methylbutyrate), butanediol bis(3-mercapto-3-methylbutyrate), octanediol bis(3-mercapto-3-methylbutyrate), trimethylolethane tris(3-mercapto-3-methylbutyrate), trimethylolpropane tris(3-mercapto-3-methylbutyrate), pentaerythritol tetrakis(3-mercapto-3-methylbutyrate), and dipentaerythritol hexakis(3-mercapto-3-methylbutyrate).

[0058] Of these mercapto group-containing compounds (F), pentaerythritol tetrakis(3-mercaptopropionate), trimethylolpropane tris-3-mercaptobutyrate, and pentaerythritol tetrakis(3-mercaptobutyrate) are preferred, and pentaerythritol tetrakis(3-mercaptobutyrate) is more preferred.

[0059] [Other Components] The resin composition of the present embodiment may contain, as other components, additives such as, for example, catalysts, thickening aids, polymerization inhibitors, thixotropic agents, cure retarders, cure accelerators, photopolymerization initiators, surfactants, interface modifiers, wetting and dispersing agents, antifoaming agents, leveling agents, coupling agents, light stabilizers, waxes, flame retardants, fillers, plasticizers, internal mold release agents, low-shrinkage agents, toners, viscosity reducers, separation inhibitors, and compatibilizers. The content of the additives is not particularly limited as long as it is within a range that does not impair the effects of the present invention.

[0060] [Polymerization inhibitor] A polymerization inhibitor can be used to inhibit the progress of the polymerization reaction of the resin composition. Known polymerization inhibitors can be used, and examples include hydroquinone, methylhydroquinone, phenothiazine, catechol, 4-t-butylcatechol, and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl. These can be used alone or in combination of two or more. From the viewpoint of inhibiting the progress of the reaction and facilitating control of curability, hydroquinone, methylhydroquinone, catechol, and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl are preferred.

[0061] [Curing Accelerator] A curing accelerator can be used to adjust the curing rate of the resin composition. The curing accelerator is not particularly limited, and examples thereof include phosphorus compounds, amines such as amine salts, and β-diketones. Specific examples of phosphorus compounds include trimethylphosphine and triphenylphosphine. Specific examples of amines include aniline, N,N-dimethylaniline, N,N-diethylaniline, p-toluidine, N,N-dimethyl-p-toluidine, N,N-bis(2-hydroxyethyl)-p-toluidine, 4-(N,N-dimethylamino)benzaldehyde, 4-[N,N-bis(2-hydroxyethyl)amino]benzaldehyde, 4-(N-methyl-N-hydroxyethylamino)benzaldehyde, and N,N-bis(2-hydroxypropyl)-p-toluidine. Examples thereof include toluidine, N-ethyl-m-toluidine, triethanolamine, m-toluidine, diethylenetriamine, pyridine, phenylmorpholine, piperidine, N,N-bis(hydroxyethyl)aniline, diethanolaniline and other N,N-substituted anilines, N,N-substituted-p-toluidine, 4-(N,N-substituted amino)benzaldehyde, etc. Specific examples of β-diketones include acetylacetone, ethyl acetoacetate, α-acetyl-γ-butyrolactone, N-pyrrolidininoacetoacetamide, N,N-dimethylacetoacetamide, etc. These may be used alone or in combination of two or more.

[0062] [Composition of Resin Composition] The content of the vinyl ester resin (A) in the resin composition is preferably 45 to 95 parts by mass, more preferably 50 to 90 parts by mass, and even more preferably 55 to 85 parts by mass, per 100 parts by mass of the total of the vinyl ester resin (A) and the ethylenically unsaturated group-containing monomer (B).

[0063] When the content of the vinyl ester resin (A) is 45 parts by mass or more, a cured product with good strength can be obtained. When the content of the vinyl ester resin (A) is 95 parts by mass or less, the viscosity of the resin composition is reduced by the ethylenically unsaturated group-containing monomer (B), and the resin composition can be easily impregnated into a fiber substrate.

[0064] The content of the ethylenically unsaturated group-containing monomer (B) is preferably 5 to 55 parts by mass, more preferably 15 to 40 parts by mass, and even more preferably 20 to 35 parts by mass, relative to 100 parts by mass of the total of the vinyl ester resin (A) and the ethylenically unsaturated group-containing monomer (B). If the content of the ethylenically unsaturated group-containing monomer (B) is more than 5 parts by mass, the viscosity of the resin composition is reduced, making it easier to impregnate the fibrous substrate. If the content of the ethylenically unsaturated group-containing monomer (B) is less than 55 parts by mass, a cured product with good strength can be obtained.

[0065] The content of the metal-containing compound (C) in the composition in terms of the metal component (hereinafter referred to as the "metal component content") is 0.1 × 10 relative to 100 parts by mass of the vinyl ester resin (A) and the ethylenically unsaturated group-containing monomer (B) in total, from the viewpoint of rapid curing of the resin composition. -6 ~2000 x 10 -6 parts by mass, preferably 0.5×10 -6 ~1000 x 10 -6 parts by mass, more preferably 0.5×10 -6 ~500 x 10 -6 The content of the metal-containing compound (C) converted into a metal component is 0.1 × 10 -6 By using an amount of at least 2000 parts by mass, it is possible to obtain a resin composition having sufficient hardness and a cured product of a composite material containing the resin composition. -6When the content of the metal-containing compound (C) is 1 / 2 parts by mass or less, the composite material containing the resin composition and the fiber substrate can be cured more efficiently at a low temperature in a short time. Note that the "content of the metal-containing compound (C) converted into a metal component" means the content by mass of the metal element contained in the metal-containing compound (C).

[0066] The content of the organic peroxide (D) is preferably 0.5 to 4 parts by mass, more preferably 0.7 to 3 parts by mass, and even more preferably 0.8 to 2.5 parts by mass, relative to 100 parts by mass of the total of the vinyl ester resin (A) and the ethylenically unsaturated group-containing monomer (B). When the content of the organic peroxide (D) is within the above range, a composition that can be cured in a short time can be obtained, and the strength of the cured product can also be good.

[0067] The imidazole compound (E) is preferably contained in an amount of 0.1 to 10 parts by mass per 100 parts by mass of the vinyl ester resin (A) and the ethylenically unsaturated group-containing monomer (B) combined. It is more preferably 0.2 to 8 parts by mass, and even more preferably 0.3 to 6 parts by mass. When the content of the imidazole compound (E) is within the above range, a composition that can be sufficiently cured in a short time can be obtained, and the strength of the cured product can also be good. Some imidazole compounds are N-methylpyrrolidone solutions or ethanol solutions, and the solid content should be within the above range.

[0068] When the mercapto group-containing compound (F) is contained, its content is preferably 0.5 to 5 parts by mass, more preferably 1 to 4 parts by mass, and even more preferably 1.5 to 3 parts by mass, per 100 parts by mass of the vinyl ester resin (A) and the ethylenically unsaturated group-containing monomer (B) combined. When the mercapto group-containing compound (F) is contained within this range, curing can be carried out efficiently. When the resin composition of this embodiment contains a polymerization inhibitor, the content of the polymerization inhibitor in the resin composition is preferably 0.0001 to 5 parts by mass, more preferably 0.0005 to 4 parts by mass, and even more preferably 0.01 to 1 part by mass, per 100 parts by mass of the vinyl ester resin (A) and the ethylenically unsaturated group-containing monomer (B) combined. When the content is within this range, the progress of the polymerization reaction of the resin composition can be effectively suppressed.

[0069] When the resin composition of the present embodiment contains a curing accelerator, the content of the curing accelerator in the resin composition is preferably 0.01 to 5 parts by mass, more preferably 0.05 to 4 parts by mass, and even more preferably 0.1 to 3 parts by mass, relative to 100 parts by mass of the total of the vinyl ester resin (A) and the ethylenically unsaturated group-containing monomer (B). When the content is within this range, curability can be easily adjusted.

[0070] [Method for Producing Resin Composition] The method for producing the resin composition of this embodiment is not particularly limited, and the resin composition can be produced by mixing a vinyl ester resin (A), an ethylenically unsaturated group-containing monomer (B), a metal-containing compound (C), an organic peroxide (D), and an imidazole compound (E). In addition to the vinyl ester resin (A), the ethylenically unsaturated group-containing monomer (B), the metal-containing compound (C), the organic peroxide (D), and the imidazole compound (E), optional components such as the other components described above, such as a mercapto group-containing compound (F), may also be mixed.

[0071] The mixing method is not particularly limited, and can be carried out using, for example, a disper, a planetary mixer, a kneader, etc. The mixing temperature is preferably 10 to 50°C, more preferably 15 to 40°C, and from the viewpoint of ease of mixing, etc., still more preferably 20 to 30°C.

[0072] Furthermore, from the viewpoint of facilitating uniform mixing of the vinyl ester resin (A), the ethylenically unsaturated group-containing monomer (B), the metal-containing compound (C), the organic peroxide (D), the imidazole compound (E), and the mercapto group-containing compound (F) used as needed, and adjusting the viscosity, the vinyl ester resin (A) may be diluted in advance with at least one of a solvent and a reactive diluent.

[0073] [Method of curing resin composition] The method for curing the resin composition of this embodiment may be any method that can heat the resin composition to the temperature required for curing, and for example, a method of heating using a heating furnace or heater can be used. The resin composition of this embodiment can usually be molded at a relatively low temperature in a short time of several minutes to several tens of minutes. The curing temperature can be, for example, 20 to 120°C. The heating time is, for example, 1 to 40 minutes, preferably 1 to 30 minutes, and is selected appropriately depending on the curing temperature. As long as the resin composition can be cured and does not denature or decompose, the curing conditions are not particularly limited, and there is no particular problem even if the temperature is lower than the above range or the heating time is long.

[0074] [Composite Material] The composite material in this embodiment includes the above-mentioned resin composition and a fiber base material (G). Specific examples of the composite material include prepreg, sheet molding compound (SMC), preform, etc., and can be suitably used for the manufacture of various molded products and the construction of structures. Prepreg or SMC is particularly preferred as the composite material in this embodiment. SMC is a sheet-like material in which fiber base materials cut into several centimeters are dispersed in a resin composition.

[0075] The content of the fiber base material (G) in the composite material is preferably 20 to 90 mass%, more preferably 30 to 85 mass%, and even more preferably 45 to 75 mass%, relative to 100 mass% of the composite material, from the viewpoints of moldability, ease of handling, mechanical strength, and the like.

[0076] When a resin composition is impregnated into a fiber substrate, the resin composition may be used as a mixture containing additives such as fillers such as calcium carbonate and aluminum hydroxide, shrinkage reducing agents such as polystyrene, viscosity reducing agents, and colorants. In this case, these additives may also be included in the composite material.

[0077] [Fiber substrate (G)] From the viewpoint of mechanical strength, the fiber substrate (G) may include, for example, so-called reinforcing fibers such as synthetic fibers such as polyamide (nylon), aramid fiber, vinylon, polyester, and phenolic resin, carbon fiber, glass fiber, metal fiber, and ceramic fiber, as well as composite fibers thereof. These may be used alone or in combination of two or more. Among these, aramid fiber, carbon fiber, and glass fiber are preferred, and carbon fiber and glass fiber are more preferred from the viewpoint of strength, hardness, availability, price, etc.

[0078] Any carbon fiber manufactured by various manufacturing methods can be used. For example, pitch-based, PAN (polyacrylonitrile)-based, and vapor-phase growth-based carbon fibers can be used. Any glass fiber manufactured by various manufacturing methods can be used. For example, glass fibers such as E-glass, T-glass, and NE-glass can be used. The glass fiber may be either long or short fiber, and the type is selected appropriately depending on the fiber substrate.

[0079] Examples of the form of the fiber substrate (G) include sheets, chopped strands, chopped fibers, milled fibers, etc. Examples of sheets include those formed by aligning multiple reinforcing fibers in one direction, bidirectional woven fabrics such as plain weave and twill weave, multiaxial woven fabrics, non-crimp woven fabrics, nonwoven fabrics, mats, knits, braids, and paper made from reinforcing fibers, etc. The fiber substrate (G) may be used alone or in combination of two or more types.

[0080] In addition, in the case of a sheet, the sheet may be a single layer or may be a laminate of multiple layers. From the viewpoint of impregnation with the resin composition, the thickness of the sheet is, for example, preferably 0.01 to 5 mm in the case of a single layer, and in the case of a laminate of multiple layers, the total thickness is preferably 1 to 20 mm, more preferably 1 to 15 mm.

[0081] [Method for producing composite material] The method for producing the composite material of this embodiment is not particularly limited, and the composite material can be obtained by mixing the above-mentioned resin composition and the fibrous base material (G) by a known method. As a method for producing the composite material of this embodiment, a method of impregnating the fibrous base material (G) with the resin composition is particularly preferred.

[0082] [Method for Molding Composite Material] Examples of methods for molding the composite material of this embodiment include hand lay-up, spray-up, autoclave molding, resin transfer molding (RTM), vacuum-assisted resin transfer molding (VaRTM), injection molding, infusion molding, press molding, press molding using sheet molding compound (SMC), filament winding, sheet winding, and pultrusion.

[0083] The resin composition of the present embodiment cures at low temperatures in a short time. Therefore, from the viewpoint of obtaining a molded product with high hardness, the hand lay-up method, the RTM method, the pultrusion molding method, and the press molding method (including the case where SMC is used) are preferred, and from the viewpoint of rapid curing, the pultrusion molding method and the press molding method (including the case where SMC is used) are more preferred, and the press molding method is even more preferred because of the ease of introducing the molding method.

[0084] In the SMC press molding process, a resin composition is applied to a carrier film moving at a constant speed, and short fibers, which are made by chopping continuous fibers with a rotary cutter, are randomly deposited on the coated lower carrier film. The upper carrier film, coated with the resin composition, is then placed resin-side down on top of the chopped fibers, and the sheet is sent through a series of pressure rollers, which forces out the air trapped in the sheet and impregnates the fibers with the resin paste, forming a sheet mold compound.

[0085] [Curing of Composite Material] The composite material of this embodiment is molded into a desired shape, and then subjected to radical polymerization by heating under appropriate pressure or normal pressure to form a cured product.

[0086] The mechanical strength required for a cured composite material varies depending on the intended use. For example, in the case of fiber-reinforced plastics (CFRP) using a carbon fiber substrate, the flexural strength of CFRP is generally about 200 to 3000 MPa. The flexural modulus of CFRP is also about 5 to 150 GPa. The flexural strength and flexural modulus values ​​are measured in accordance with JIS K7171:2016.

[0087] The present invention will be described below based on examples. The present invention is not limited to the examples shown below. The vinyl ester resins used in the examples and comparative examples shown below are as follows.

[0088] [Synthesis of Vinyl Ester Resin] First, a vinyl ester resin for preparing a resin composition was synthesized according to the following Synthesis Example. Details of the epoxy compounds used in the synthesis of the vinyl ester resin in the Synthesis Example are shown below. Epoxy compound (a-1): bisphenol A-type epoxy resin; "Epomic (registered trademark) R140P", manufactured by Mitsui Chemicals, Inc., epoxy equivalent: 188. The epoxy equivalent is a value measured in accordance with JIS K7236:2001.

[0089] Synthesis Example 1 3271 g of epoxy compound (1) was placed in a 5 L four-neck separable flask equipped with a stirrer, a reflux condenser, a gas inlet tube, and a thermometer, and heated to 110° C. Next, 1.2 g of methylhydroquinone ("MH", manufactured by Seiko Chemical Co., Ltd.) (0.03 parts by mass relative to 100 parts by mass of the epoxy compound and methacrylic acid described below) as a polymerization inhibitor, 0.2 g of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl ("Polystrip 7300P", manufactured by Hakuto Co., Ltd.) (0.005 parts by mass relative to 100 parts by mass of the epoxy compound and methacrylic acid), and benzyltriphenylphosphonium chloride ("TPP-ZC") as an esterification catalyst were added. 3.2 g (0.08 parts by mass per 100 parts by mass of the total of the epoxy compound and methacrylic acid) of methacrylic acid (manufactured by Hokko Chemical Industry Co., Ltd.) and 896 g (0.6 moles of methacrylic acid acid groups per 100 moles of the total of the epoxy groups of the epoxy compound) of methacrylic acid (manufactured by Mitsubishi Chemical Corporation) as the unsaturated monobasic acid (a-2) were added dropwise over approximately 30 minutes, and the mixture was heated to 125°C and reacted for approximately 2 hours. The reaction was terminated when the acid value reached 1 KOHmg / g or less, yielding vinyl ester resin (A1). The epoxy equivalent of this vinyl ester resin (A1) was 459, the acid value was 0 KOHmg / g, the weight average molecular weight Mw was 651, and the number average molecular weight Mn was 515.

[0090] To 4172 g of this vinyl ester resin (A1), 0.02 g (0.0005 part by mass relative to a total of 100 parts by mass of the vinyl ester resin (A1) and the styrene monomer to be added later) of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl was added, and the mixture was cooled to 100°C. 1390 g of styrene ("styrene monomer", manufactured by Idemitsu Kosan Co., Ltd.) was added as a reactive diluent to obtain a mixture of 75% by mass (based on the total mass of the blended components) of vinyl ester resin and 25% by mass of styrene.

[0091] <Epoxy Equivalent Weight> The epoxy equivalent weight was measured in accordance with JIS K7236:2001.

[0092] <Acid Value> The acid value of the vinyl ester resin (A1) was determined in accordance with JIS K6901:2008 "Partial acid value (indicator titration method)" by measuring the mass of potassium hydroxide required to neutralize the acid component contained in the vinyl ester resin (A1).

[0093] Specifically, a mixture was prepared by diluting the vinyl ester resin (A1) obtained in the above Synthesis Example with styrene, which is the ethylenically unsaturated group-containing monomer (B), so that the content was 75% by mass, and the mass of potassium hydroxide required to neutralize the acid component contained in the mixture was measured. The acid value of the vinyl ester resin was then calculated based on the measured value. An "Autoburette UCB-2000" (manufactured by Hiranuma Sangyo Co., Ltd.) titration apparatus was used, and a mixed indicator of bromothymol blue and phenol red was used as the indicator.

[0094] <Weight-average molecular weight Mw, number-average molecular weight Mn, and molecular weight distribution Mw / Mn> Mw and Mn were measured by GPC under the following measurement conditions, and Mw / Mn was calculated from these measured values. (Measurement conditions) Apparatus: "Shodex (registered trademark) GPC-101" (manufactured by Resonac Corporation) Column: "Shodex (registered trademark) LF-804" (manufactured by Resonac Corporation) Detector: Differential refractometer "Shodex (registered trademark) RI-71S" (manufactured by Resonac Corporation) Column temperature: 40°C Sample: 0.2% by mass solution of vinyl ester resin in tetrahydrofuran Developing solvent: tetrahydrofuran Flow rate: 1.0 mL / min Sample injection amount: 20 μL Standard sample: polystyrene

[0095] [Example 1] A mixture of 75 parts by mass of vinyl ester resin (A1) as vinyl ester resin (A) and 25 parts by mass of styrene as ethylenically unsaturated group-containing monomer (B) was used, and 0.001 parts by mass of copper naphthenate (manufactured by Toei Kako Co., Ltd., copper content 5% by mass) as metal-containing compound (C) (metal conversion content 50 × 10 -6parts by mass), 100 parts by mass total of the vinyl ester resin (A) and the ethylenically unsaturated group-containing monomer (B), 1 part by mass of cumene hydroperoxide ("Percumyl H-80" manufactured by NOF Corporation) as the organic peroxide (D), 0.5 parts by mass of 2-ethyl-4-methylimidazole (manufactured by Shikoku Chemical Industry Co., Ltd.) as the imidazole compound (E), and 2 parts by mass of pentaerythritol tetrakis(3-mercaptobutyrate) ("Karenz MT (registered trademark) PE1" manufactured by Resonac Corporation) as the mercapto group-containing compound (F) were added, and the mixture was mixed at 2000 to 3000 rpm for 20 minutes using a Disper (high-speed dispersion base "Homodisper 2.5 type" manufactured by Primix Corporation) to obtain a resin composition (X-1).

[0096] [Examples 2 to 10, Comparative Examples 1 to 15] Resin compositions (X-2) to (X-10) and (X'-1) to (X'-15) were obtained in the same manner as in Example 1, except that the raw materials and compounding ratios were as shown in Tables 1-1 and 1-2. Examples 2 to 6 and Comparative Examples 1 to 13 were obtained by changing the type of metal-containing compound (C) in Example 1, and Examples 7 to 10 and Comparative Examples 14 to 15 were obtained by changing the amount of metal-containing compound (C) or the amount of mercapto group-containing compound (F) in Example 1.

[0097] The resin compositions obtained were subjected to the following measurement and evaluation tests, and the results are summarized in Tables 1-1 and 1-2 below.

[0098] <80°C curability> The obtained resin composition was placed in a test tube (outer diameter 18 mm, length 165 mm) at room temperature to a depth of 100 mm, placed in an oil bath heated to 80°C, and the test tube and contents were heated. The temperature of the resin composition in the contents was measured using a thermocouple. The time required for the temperature of the resin composition to reach the maximum temperature from 65°C was defined as the "minimum curing time," and the maximum temperature was defined as the "maximum exothermic temperature," and these were measured in accordance with JIS K-6901:2021. The measurement was performed twice and the average value was taken.

[0099] <Barcol Hardness> The surface hardness of a cured resin composition was measured using a Barcol hardness tester ("GYZJ 934-1" (HBI-A), manufactured by Barber-Coleman) in accordance with JIS K6911:1995, and was taken as the Barcol hardness. The value is expressed as 0 to 100, with a larger value indicating a harder object. Measurement samples were prepared by the following method.

[0100] A tin cup (40 mm diameter x approximately 8 mm depth) was placed on a stainless steel plate (5 mm thick) preheated to 80°C, and approximately 10 g of the resin composition was placed in the cup. The cup was sealed with a release-treated film (125 μm thick), and another stainless steel plate was placed on top of that. The tin cup sandwiched between the two stainless steel plates was heated in a heating device at 80°C for 15 minutes. Next, the tin cup was removed from the heating device and cured in a constant temperature room (23°C x 24 hours), after which the release film was peeled off, and the surface hardness of the cured resin composition was measured.

[0101] <Flexural Strength and Flexural Modulus> Flexural strength and flexural modulus were evaluated by preparing test specimens as follows. A U-shaped spacer having an outer size of 150 mm x 150 mm, a thickness of 3 mm, and a width of 1.5 mm was sandwiched between two glass plates (150 mm x 150 mm x 3 mm) with a release film attached to the surface and fixed to form a glass mold. Approximately 50 g of the resin composition was poured from the top of the glass mold, which was placed with the opening of the spacer facing up. The glass mold was heated at 110 ° C for 30 minutes to cure the resin composition.

[0102] The cured product was cut into a length of 80 mm, a width of 25 mm, and a thickness of 3 mm to prepare three test pieces. In accordance with JIS K 6911-1995, the flexural strength and flexural modulus were measured in an environment of 23°C and 50% humidity using a universal testing machine ("Tensilon UCT-1T", manufactured by Orientec Co., Ltd., test speed 1.5 mm / min). Measurements were taken for three test pieces each, and the average was calculated. The results are summarized in Tables 1-1 and 1-2.

[0103]

[0104]

[0105] The compositions of the Examples all showed shorter minimum curing times in terms of 80°C curing than the Comparative Examples. This indicates that they are capable of curing at low temperatures in a short time. Furthermore, all of the Examples showed high hardness, and both flexural strength and flexural modulus were sufficient. On the other hand, many of the Comparative Examples were insufficiently cured and could not be evaluated, and even those that could be evaluated had low flexural strength.

[0106] Examples 11 to 15 Resin compositions (X-11) to (X-15) were produced in the same manner as in Example 1, except that the raw materials and compounding ratios were as shown in Table 1-3. In Examples 11 to 14, the imidazole compound (E) in Example 1 was changed to the following, and in Example 15, the mercapto group-containing compound (F) was changed to pentaerythritol tetrakis(3-mercaptopropionate): 2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, imidazole (50% solution in N-methylpyrrolidone), 2-methylimidazole (50% solution in ethanol), 1,2-dimethylimidazole, all of which are manufactured by Shikoku Chemical Industry Co., Ltd. Pentaerythritol tetrakis(3-mercaptopropionate) manufactured by Sakai Chemical Industry Co., Ltd.

[0107] The resulting resin composition was measured and evaluated for the same items as in Example 1. The results of these measurements and evaluations are shown in Tables 1-3 below.

[0108] The amounts in parentheses for imidazole and 2-methylimidazole are 50% solution amounts.

[0109] Examples 16 to 19 Evaluation of Carbon Fiber Reinforced Composite Materials In Example 16, composition (Y-1) was used. In Examples 17 to 19, compositions (Y-2) to (Y-4) were prepared in the same manner as in Example 1 above so as to have the compositions shown in Table 2, and were used. In Example 16, cumene hydroperoxide (Percumyl H-80) was used as the organic peroxide, and in Examples 17 to 19, t-butyl peroxybenzoate (manufactured by NOF Corporation, "Perbutyl Z") was used as the organic peroxide. In each case, carbon fiber reinforced composite materials were prepared as follows, using "TRK101 M" (manufactured by Mitsubishi Chemical Corporation, TR50S 12L cloth plain weave = thickness 0.46 mm) as the carbon fiber.

[0110] In Example 16 for preparing the cured product, the carbon fiber cross sheet TRK101 M was cut to a size of 200 mm x 200 mm, and six sheets were laminated in the same direction while thoroughly impregnating each layer with resin composition (Y-1). 2 mm thick spacers were placed parallel to the left and right sides of the carbon fiber cross sheet, and the carbon fiber cross sheet impregnated with the resin composition was sandwiched between two glass plates by covering it with a glass plate. A 5 kg weight was placed on the upper glass plate, and the mixture was left at 25°C for 24 hours to perform primary curing. The mixture was then heated at 120°C for 2 hours to perform secondary curing. This method is referred to as the hand layup method.

[0111] In Examples 17 to 19, cured carbon fiber reinforced composite material samples were prepared by pressing. Seven layers of carbon fiber cross sheets cut to 298 mm x 218 mm were stacked in the same direction, and 80 g of resin compositions (Y-2) to (Y-4) were impregnated into each layer of the carbon fiber cross sheets. The resulting mixture was placed in a mold with an inner size of 300 mm x 220 mm. 3 mm thick spacer rings were placed at the four corners of the mold, and the mold was pressed at a pressure of 7.4 MPa using a hydraulic molding machine (manufactured by Toho Press Manufacturing Co., Ltd.). Primary curing was performed at 120°C for 2 minutes or 120°C for 3 minutes. No secondary curing was performed.

[0112] The following items were measured and evaluated for each of the obtained cured products. Fiber volume content (Vf) and fiber content (mass%) in the cured product The cured product was cut into a 15 mm x 15 mm x 2 mm rectangular parallelepiped to prepare a test specimen. The mass of the test specimen was measured, and the test specimen was heated in a crucible in an air atmosphere at 350°C for 3 hours using a muffle furnace (Yamato Scientific, "Muffle Fumace FO510"), and then heated at 625°C for 10 minutes. Note that carbon fiber does not burn under these conditions. After natural cooling, the mass of the residual carbon fiber was measured to evaluate the carbon fiber content (mass%) and fiber volume content per unit volume in the cured product. The density of the cured resin was 1.15 g / cm 3 , the density of carbon fiber is 1.81 g / cm 3 Two test pieces were prepared and the average value was taken.

[0113] Flexural properties: In accordance with JIS K 7074-1988, the cured product was cut into a length of 140 mm and a width of 15 mm to prepare test specimens in Example 16, and into a length of 140 mm and a width of 35 mm to prepare test specimens in Examples 17 to 19. The thickness of the obtained test specimens was 2 mm. Flexural strength and flexural modulus were measured in an environment of 23°C and 50% RH using a universal testing machine ("Tensilon UCT-1T", manufactured by Orientec Co., Ltd., support distance 100 mm, test speed 7 mm / min). The results are shown in Table 2.

[0114]

Claims

1. A resin composition comprising a vinyl ester resin (A), an ethylenically unsaturated group-containing monomer (B), a metal-containing compound (C), an organic peroxide (D), and an imidazole compound (E), wherein the vinyl ester resin (A) is a vinyl ester resin having an epoxy group, the metal-containing compound (C) is a compound containing a metal element of Groups 7 to 11, and the metal-equivalent content of the metal-containing compound (C) is 0.1 x 10 relative to 100 parts by mass of the total of the vinyl ester resin (A) and the ethylenically unsaturated group-containing monomer (B). -6 ~2000 x 10 -6 Parts by mass of the resin composition.

2. The resin composition according to claim 1, wherein the metal element contained in the metal-containing compound (C) is at least one selected from the group consisting of iron, nickel, cobalt, manganese and copper.

3. The resin composition according to claim 2, wherein the metal-containing compound (C) is at least one carboxylate selected from iron, nickel, cobalt, manganese, and copper, or at least one β-diketone complex selected from iron, nickel, cobalt, manganese, and copper.

4. The resin composition according to claim 3, wherein the metal-containing compound (C) comprises at least one selected from the group consisting of copper naphthenate, copper bis(2,4-pentanedionato), nickel(II) bis(2,4-pentanedionato), cobalt octoate, manganese octoate, and iron naphthenate.

5. The resin composition according to claim 1 or 2, comprising 45 to 95 parts by mass of the vinyl ester resin (A), 5 to 55 parts by mass of the ethylenically unsaturated group-containing monomer (B), 0.5 to 4 parts by mass of the organic peroxide (D), and 0.1 to 10 parts by mass of the imidazole compound (E), relative to a total of 100 parts by mass of the vinyl ester resin (A) and the ethylenically unsaturated group-containing monomer (B).

6. The resin composition according to claim 1 or 2, further comprising a mercapto group-containing compound (F).

7. The resin composition according to claim 1 or 2, wherein the vinyl ester resin (A) is a reaction product of an epoxy compound (a-1) having two or more epoxy groups per molecule and an unsaturated monobasic acid (a-2), and the total number of acid groups in the unsaturated monobasic acid (a-2) is 20 to 80 moles per 100 moles of the total number of epoxy groups in the epoxy compound (a-1).

8. The resin composition according to claim 7, wherein the epoxy compound (a-1) is a bisphenol-type epoxy resin.

9. The resin composition according to claim 7, wherein the unsaturated monobasic acid (a-2) is at least one selected from the group consisting of (meth)acrylic acid and crotonic acid.

10. A resin composition according to claim 1 or 2, wherein the organic peroxide (D) is at least one selected from the group consisting of peroxyester-based organic peroxides, hydroperoxide-based organic peroxides, dialkyl peroxide-based organic peroxides, and peroxyketal-based organic peroxides.

11. The resin composition according to claim 1 or 2, wherein the imidazole compound (E) is at least one selected from the group consisting of 2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 2-methylimidazole, imidazole, and 1,2-dimethylimidazole.

12. The resin composition according to claim 6, wherein the mercapto group-containing compound (F) is a polyfunctional thiol.

13. A composite material comprising the resin composition according to claim 1 and a fiber substrate (G).

14. The composite material according to claim 13, wherein the fiber substrate (G) is at least one selected from carbon fiber and glass fiber.

15. A cured product of the composite material according to claim 14.

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