Resin composition for fiber-reinforced plastic, and fiber-reinforced plastic containing same

Abstract

Provided is a resin composition for a fiber-reinforced plastic, which is capable of obtaining a fiber-reinforced plastic having improved strength and has an excellent balance between stability and curability. The resin composition for fiber-reinforced plastics contains (A) an epoxy resin, (B) an acid anhydride, and (C) a catalyst that is liquid at 25 DEG C. The (C) catalyst that is liquid at 25 DEG C. is at least one selected from the group consisting of (c1) and (c2) described below. And (c1) a pair compound consisting of an acid and a base. And (c2) a compound consisting of a quaternary onium cation and an anion.

Description

[0001] This application is a divisional application of the application with application number "202080013448.0", application date March 4, 2020, and invention name "Resin composition for fiber-reinforced plastics, and fiber-reinforced plastics containing the composition". Technical Field

[0002] The present invention relates to a resin composition for fiber-reinforced plastics, a cured product thereof, and a fiber-reinforced plastic produced using the composition. Background Art

[0003] For fiber materials such as carbon fiber, glass fiber, it is known to use thermosetting epoxy resin, unsaturated polyester, polyamide resin or phenolic resin to make the method for molding as reinforcement.The fiber reinforced plastic manufactured using this method is widely used in the material of the structural body such as aircraft or ships, sporting goods such as tennis racket or golf club.The epoxy resin adhesiveness, heat resistance and chemical resistance as reinforcement are excellent, and cheap, thereby use more in the manufacture of fiber reinforced plastic as the material with good balance.

[0004] For example, Patent Documents 1 to 3 propose epoxy resin compositions for fiber-reinforced plastics containing an epoxy resin, an acid anhydride, and a curing catalyst. However, when the compounds described in these documents are used as curing catalysts, there is a problem in obtaining a resin composition for fiber-reinforced plastics that achieves a balance between stability and curability.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-3938

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 8-156115

[0009] Patent Document 3: Japanese Patent Application Laid-Open No. 2008-38082 Summary of the Invention

[0010] Problems to be solved by the invention

[0011] Therefore, an object of the present invention is to provide a resin composition for fiber-reinforced plastics that can provide a fiber-reinforced plastic having good strength, has low viscosity with little increase in viscosity, is excellent in permeability, and has an excellent balance between stability and curability.

[0012] Means for solving problems

[0013] The present inventors have diligently studied to solve the above problems and have found that a combination of an epoxy resin, an acid anhydride, and a specific catalyst that is liquid at 25° C. can provide a resin composition for fiber-reinforced plastics having excellent stability and curability, thereby completing the present invention.

[0014] That is, the present invention is a resin composition for fiber-reinforced plastics, comprising (A) an epoxy resin, (B) an acid anhydride, and (C) a catalyst that is liquid at 25°C.

[0015] (C) The catalyst that is liquid at 25°C is at least one selected from the following (c1) and (c2).

[0016] (c1) A pair of compounds consisting of an acid and a base.

[0017] (c2) A compound composed of a quaternary onium cation and an anion.

[0018] In the resin composition for fiber-reinforced plastics of the present invention, it is preferred that the epoxy resin (A) contains a polyglycidyl ether of an alkylene oxide adduct of a bisphenol.

[0019] The resin composition for fiber-reinforced plastics of the present invention preferably contains 10 to 80% by mass of a polyglycidyl ether of an alkylene oxide adduct of a bisphenol based on the (A) epoxy resin.

[0020] In the resin composition for fiber-reinforced plastics of the present invention, it is preferred that the epoxy resin (A) contains a dicyclopentadiene-type epoxy resin represented by the following formula (1).

[0021]

[0022] Where R 1 and R 2 Each independently represents a hydrogen atom or a methyl group.

[0023] The resin composition for fiber-reinforced plastics of the present invention preferably contains 0.1 to 30% by mass of the dicyclopentadiene epoxy resin represented by the above formula (1) relative to the (A) epoxy resin.

[0024] In the resin composition for fiber-reinforced plastics of the present invention, it is preferred that the acid anhydride (B) is liquid at 25°C.

[0025] In the resin composition for fiber-reinforced plastics of the present invention, it is preferred that the acid anhydride (B) is an anhydride of an unsaturated alicyclic polycarboxylic acid.

[0026] In the resin composition for fiber-reinforced plastics of the present invention, the catalyst (C) is preferably a pair of compounds (c1) consisting of an acid and a base, and (c1) is a pair of compounds derived from an aromatic compound and an organic basic compound.

[0027] In the resin composition for fiber-reinforced plastics of the present invention, (c1) is preferably a pair of compounds derived from a monocyclic aromatic compound and a nitrogen-containing heterocyclic compound.

[0028] In the resin composition for fiber-reinforced plastics of the present invention, it is preferred that the catalyst (C) is a compound (c2) consisting of a quaternary onium cation and an organic anion, and the quaternary onium cation is a phosphonium cation.

[0029] In the resin composition for fiber-reinforced plastics of the present invention, the organic anion in (c2) is preferably an alkylphosphorodithioate.

[0030] The resin composition for fiber-reinforced plastics of the present invention preferably contains 0.01 to 20 parts by mass of the (C) catalyst per 100 parts by mass of the (A) epoxy resin.

[0031] The resin composition for fiber-reinforced plastics of the present invention preferably further contains (D) a silane coupling agent.

[0032] The present invention also provides a cured product formed by curing the resin composition for fiber-reinforced plastics.

[0033] The present invention also provides a fiber-reinforced plastic formed by curing a composition containing the resin composition for fiber-reinforced plastics and reinforcing fibers.

[0034] Effects of the Invention

[0035] The resin composition for fiber-reinforced plastics of the present invention is a resin composition with low viscosity and minimal viscosity increase, excellent permeability, stability, and excellent curability. Therefore, by applying the resin composition of the present invention to fibers, fiber-reinforced plastics with excellent strength can be easily obtained. DETAILED DESCRIPTION

[0036] First, the resin composition for fiber-reinforced plastics of the present invention will be described. The resin composition for fiber-reinforced plastics of the present invention contains (A) an epoxy resin.

[0037] Examples of the epoxy resin as component (A) used in the present invention include polyglycidyl ether compounds of mononuclear polyphenol compounds such as hydroquinone, resorcinol, pyrocatechol, and phloroglucinol; dihydroxynaphthalene, biphenol, methylene bisphenol (bisphenol F), methylene bis(o-cresol), ethylene bisphenol, isopropylidene bisphenol (bisphenol A), isopropylidene bis(o-cresol), tetrabromobisphenol A, 1,3-bis(4-hydroxycumylbenzene), 1,4-bis(4-hydroxycumylbenzene), 1,1,3-tris(4-hydroxyphenyl)butane, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, thiobisphenol, sulfobisphenol, hydroxybisphenol, phenol novolac, o-cresol, Cresol novolac, ethylphenol novolac, butylphenol novolac, octylphenol novolac, resorcinol novolac, terpene phenol and other polynuclear polyphenol compounds polyglycidyl ether compounds; ethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, polyethylene glycol, polypropylene glycol, thioglycol, dicyclopentadiene dimethanol, 2,2-bis (4-hydroxycyclohexyl) propane (hydrogenated bisphenol A), glycerol, trimethylolpropane, pentaerythritol, sorbitol, bisphenols alkylene oxide adducts and other polyol compounds polyglycidyl ether compounds; maleic acid, fumaric acid, itaconic acid, succinic acid, glutaric acid, suberic acid, adipic acid, azelaic acid, sebacic acid, Glycidyl esters of aliphatic, aromatic or alicyclic polybasic acids such as dimer acid, trimer acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, trimesic acid, pyromellitic acid, tetrahydrophthalic acid, and terminal methylene tetrahydrophthalic acid, and homopolymers or copolymers of glycidyl methacrylate; N,N-diglycidyl aniline, bis(4-(N-methyl-N-glycidylamino)phenyl)methane, diglycidyl o-toluidine, N,N-bis(2,3-epoxypropyl)-4-(2,3-epoxypropyloxy)-2-methylaniline, N,N-bis(2,3-epoxypropyl)-4-(2,3-epoxypropyloxy)- Epoxy compounds having a glycidylamino group, such as aniline, N,N,N',N'-tetrakis(2,3-epoxypropyl)-4,4'-diaminodiphenylmethane; epoxides of cyclic olefin compounds, such as vinylcyclohexene diepoxide, cyclopentadiene diepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-6-methylcyclohexylmethyl-6-methylcyclohexanecarboxylate, and bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate; epoxidized conjugated diene polymers, such as epoxidized polybutadiene and epoxidized styrene-butadiene copolymers; and heterocyclic compounds, such as triglycidyl isocyanurate. These epoxy resins may also be internally crosslinked via a terminal isocyanate prepolymer or have their molecular weight increased by a polyvalent active hydrogen compound (such as a polyphenol, a polyamine, a carbonyl-containing compound, or a polyphosphate). Furthermore, the above-mentioned epoxy resins may be used alone or in combination of two or more.In the present invention, from the viewpoint of permeability into fiber materials, it is preferred to use an epoxy resin that is liquid at 25°C.

[0038] The epoxy resin as the component (A) preferably contains a polyglycidyl ether of an alkylene oxide adduct of a bisphenol, because this can increase the elongation at break of the cured product and follow the elongation of the fiber.

[0039] The polyglycidyl ether of an alkylene oxide adduct of a bisphenol can be obtained, for example, by the following steps.

[0040] For compounds having two phenolic hydroxyl groups (hydroxyl groups directly bonded to an aromatic ring) such as bisphenol A, bisphenol F and biphenol, at least two equivalents of alkylene oxide are added to one equivalent of the phenolic hydroxyl groups of the compound to obtain an alkylene oxide adduct. When adding the alkylene oxide, a catalyst may be used as needed. Then, by reacting epichlorohydrin with the obtained alkylene oxide adduct, a polyglycidyl ether of the alkylene oxide adduct of bisphenols may be obtained. When reacting epichlorohydrin, a catalyst and / or solvent may be used as needed. There is no particular limitation on the specific method for producing the polyglycidyl ether of the alkylene oxide adduct of bisphenols, and known methods may be used. In addition, there is no particular limitation on the reaction conditions, and known conditions may be used.

[0041] As said alkylene oxide, ethylene oxide, 1, 2- propylene oxide, 1, 2- butylene oxide, 1, 2- pentane oxide, etc. are mentioned, for example.

[0042] As catalysts used as needed when adding the above-mentioned alkylene oxide, acid catalysts and base catalysts can be mentioned. As acid catalysts, Bronsted acids such as sulfuric acid and phosphoric acid, and Lewis acids such as tin chloride and boron trifluoride can be mentioned. As base catalysts, tertiary amines, or hydroxides of alkali metals, alkaline earth metals, or quaternary ammoniums such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, calcium hydroxide, and barium hydroxide, and carbonates of alkali metals such as potassium carbonate and sodium carbonate can be mentioned. Among them, from the perspective of simplicity of the refining process after the reaction, it is preferred to use a base catalyst, more preferably an alkali metal or alkaline earth metal hydroxide, and most preferably an alkali metal hydroxide. These catalysts can be used alone or in combination of two or more.

[0043] As the catalyst used as needed to react the epichlorohydrin, in addition to that used when adding the above-mentioned alkylene oxide, phase transfer catalysts such as tetrabutylammonium salt, trioctylmethylammonium salt and benzyldimethyloctadecylammonium salt can also be listed. Among them, from the viewpoint of simplicity of the purification process after the reaction is completed, it is preferred to use a base catalyst, more preferably an alkali metal or alkaline earth metal hydroxide, and most preferably an alkali metal hydroxide. These catalysts can be used alone or in combination of two or more.

[0044] Examples of the solvent used as needed to react the epichlorohydrin include ketone solvents such as acetone and methyl ethyl ketone; alcohol solvents such as methanol, ethanol, 1-propanol, isopropanol, 1-butanol, sec-butanol, and tert-butanol; cellosolve solvents such as methyl cellosolve and ethyl cellosolve; ether solvents such as tetrahydrofuran, 1,4-dioxane, 1,3-dioxane, and diethoxyethane; and aprotic polar solvents such as acetonitrile, dimethyl sulfoxide, and dimethylformamide. These organic solvents may be used alone or in combination of two or more.

[0045] The amount of epichlorohydrin required for the reaction of the alkylene oxide adduct with epichlorohydrin is 1 to 10 equivalents per 1 equivalent of hydroxyl groups in the alkylene oxide adduct. After the reaction, excess epichlorohydrin is distilled off to obtain a more preferred polyglycidyl ether of the alkylene oxide adduct of a bisphenol.

[0046] The content of the polyglycidyl ether of an alkylene oxide adduct of bisphenol in the epoxy resin as component (A) is not particularly limited. The polyglycidyl ether of an alkylene oxide adduct of bisphenol preferably contains 10 to 80% by mass, more preferably 20 to 60% by mass, relative to the epoxy resin. The polyglycidyl ether of an alkylene oxide adduct of bisphenol preferably contains within the above range because it increases the elongation displacement, improves the toughness of the cured product, and enhances the heat resistance (Tg).

[0047] The epoxy resin as the component (A) preferably contains a dicyclopentadiene epoxy resin represented by the following formula (1) because this improves wettability to the fiber.

[0048]

[0049] Where R 1 and R 2 Each independently represents a hydrogen atom or a methyl group.

[0050] The content of the dicyclopentadiene epoxy resin represented by formula (1) in the epoxy resin as component (A) is not particularly limited, but the content of the dicyclopentadiene epoxy resin represented by formula (1) is preferably 0.1 to 30% by mass, more preferably 3 to 15% by mass, relative to the epoxy resin of component (A). The dicyclopentadiene epoxy resin content is preferably within the above range because the adhesion-improving effect is enhanced and the heat resistance (Tg) is further improved.

[0051] In the present invention, the epoxy resin as component (A) preferably contains both the polyglycidyl ether of the alkylene oxide adduct of the bisphenol and the dicyclopentadiene epoxy resin represented by the above formula (1) because the cured product can have excellent followability and wettability to fibers.

[0052] The resin composition for fiber-reinforced plastics of the present invention contains (B) an acid anhydride. Examples of the acid anhydride (B) used in the present invention include anhydrides of unsaturated aliphatic polycarboxylic acids, anhydrides of saturated aliphatic polycarboxylic acids, anhydrides of unsaturated alicyclic polycarboxylic acids, anhydrides of saturated alicyclic polycarboxylic acids, and anhydrides of aromatic polycarboxylic acids.

[0053] As the anhydride of the unsaturated aliphatic polycarboxylic acid, an anhydride having 4 to 20 carbon atoms is preferred, and examples thereof include maleic anhydride.

[0054] As the anhydride of a saturated aliphatic polycarboxylic acid, an anhydride having 4 to 20 carbon atoms is preferred, and examples thereof include succinic anhydride.

[0055] As the anhydride of the unsaturated alicyclic polycarboxylic acid, an anhydride having 3 to 7 carbon atoms constituting the ring is preferred, and examples thereof include bicycloheptenedicarboxylic anhydride, methylbicycloheptenedicarboxylic anhydride, tetrahydrophthalic anhydride, and methyltetrahydrophthalic anhydride.

[0056] The anhydride of the saturated alicyclic polycarboxylic acid is preferably an anhydride having 3 to 7 carbon atoms in the ring, and examples thereof include hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, hydrogenated methylnadic anhydride, and trialkyltetrahydrophthalic anhydride-maleic anhydride adduct.

[0057] Examples of the aromatic polycarboxylic acid include anhydrides of aromatic dicarboxylic acids such as phthalic anhydride, anhydrides of aromatic tricarboxylic acids such as trimellitic anhydride, and anhydrides of aromatic tetracarboxylic acids such as pyromellitic anhydride and benzophenonetetracarboxylic anhydride.

[0058] Among the above-mentioned acid anhydrides, it is preferred to use an acid anhydride that is liquid at 25°C because the miscibility with the above-mentioned (A) component and the impregnation into the fiber become good. As the acid anhydride that is liquid at 25°C, it is preferred to use anhydrides of unsaturated alicyclic polycarboxylic acids that are liquid at 25°C, such as methyltetrahydrophthalic anhydride, anhydrides of saturated alicyclic polycarboxylic acids that are liquid at 25°C, such as methylhexahydrophthalic anhydride, methylnadic anhydride and hydrogenated methylnadic anhydride. In the present invention, the viscosity of the acid anhydride (B) is preferably 100 Pa·s or less at 25°C. The viscosity of the acid anhydride can be measured, for example, by a cone-plate viscometer. The above-mentioned acid anhydrides may be used alone or in combination of two or more.

[0059] The content of the acid anhydride (B) in the resin composition for fiber-reinforced plastics of the present invention is not particularly limited, but the number of acid anhydride groups in the acid anhydride is preferably 0.7 to 1.6, and more preferably 0.9 to 1.2, per epoxy group in the epoxy resin. Setting the content of the acid anhydride (B) within the above range is preferred because the heat resistance of the resulting fiber-reinforced plastic is improved.

[0060] The resin composition for fiber-reinforced plastics of the present invention contains (C) a catalyst that is liquid at 25°C. The catalyst that is liquid at 25°C as the component (C) is used to promote the reaction between the epoxy resin and the acid anhydride used as a curing agent. The viscosity of the catalyst as the component (C) at 25°C is preferably 100 Pa·s or less. The viscosity can be measured, for example, by a cone-plate viscometer. The catalyst that is liquid at 25°C as the component (C) contains at least one selected from (c1) a pair of acid and base compounds and (c2) a compound composed of a quaternary onium cation and anion. The catalyst that is liquid at 25°C as the component (C) preferably contains only the component (c1) or the component (c2), and more preferably consists of only the component (c1) or only the component (c2).

[0061] Component (c1) includes para compounds derived from aromatic compounds and organic bases, and para compounds derived from fatty acids and organic bases. Examples of aromatic compounds include monocyclic compounds such as phenol and nonylphenol. Examples of fatty acids include fatty acids having 1 to 30 carbon atoms, such as octanoic acid, oleic acid, and acetic acid. Examples of organic bases include nitrogen-containing heterocyclic compounds such as cyclic amidines. Examples of cyclic amidines include 1,8-diazabicyclo[5.4.0]undecene-7 (DBU) and 1,5-diazabicyclo[4.3.0]nonene-5 (DBN). Examples of para compounds derived from cyclic amidines and aromatic compounds include 1,8-diazabicyclo[5.4.0]undecene-7 (DBU) phenolate. Examples of para-compounds derived from cyclic amidines and fatty acids include DBU octyl salt, DBU oleate, and 1,5-diazabicyclo[4.3.0]nonene-5(DBN)octanoate. Component (c1) is preferably a para-compound derived from an aromatic compound such as phenol and an organic basic compound such as a cyclic amidine, from the perspective of obtaining a resin composition with excellent stability and good curability. In the present invention, one of these components (c1) may be used alone, or two or more may be used in combination.

[0062] As component (c2), for example, phosphonium salts comprising quaternary phosphonium cations and organic anions, and imidazolium salts comprising anions such as imidazolium cations and organic anions can be listed. The quaternary phosphonium cation is preferably a tetraalkylphosphonium cation. The imidazolium cation is preferably a dialkylimidazolium cation. As organic anions, for example, alkyl dithiophosphates such as diethyl dithiophosphate, alkyl phosphates such as dimethyl phosphate, alkyl sulfates such as alkyl sulfates and ethyl sulfate, and acetates can be listed.

[0063] Examples of the phosphonium salt of the component (c2) include o,o-diethyldithiophosphate tetra-n-butylphosphonium and o,o'-dimethylphosphate tri-n-butylmethylphosphonium.

[0064] Examples of the imidazolium salt of the component (c2) include 1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium hydrogen sulfate, 1-butyl-3-methylimidazolium methyl sulfate, 1-ethyl-3-methylimidazolium ethyl sulfate, 1-butyl-3-methylimidazolium tetrachloride, 1-ethyl-3-methylimidazolium halide sulfate, 1-butyl-3-methylimidazolium tetrachloroaluminate, 1-ethyl-3-methylimidazolium hydrogen sulfate, 1-butyl-3 1-ethylimidazolium thiocyanate, 1-butyl-3-methylimidazolium thiocyanate, 1-ethyl-3-methylimidazolium methanesulfonate, 1-ethyl-3-methylimidazolium tetrachloroaluminate, 1-ethyl-3-methylimidazolium thiocyanate, 1-methylimidazolium hydrogensulfate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluoroantimonate and 1-butyl-3-methylimidazolium hexafluorophosphate, etc.

[0065] As component (c2), from the perspective of obtaining a resin composition with excellent stability and good curability, a compound containing a quaternary phosphonium cation and an organic anion is preferred, a phosphonium salt is more preferred, and o,o'-diethyldithiophosphate tetra-n-butylphosphonium is further preferred. In the present invention, one of the above components (c2) may be used alone, or two or more may be used in combination.

[0066] The content of the catalyst (C), a component that is liquid at 25°C, in the resin composition for fiber-reinforced plastics of the present invention is not particularly limited, but is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, relative to 100 parts by mass of the epoxy resin (A). Setting the content of the component (C) within the above range is preferred because a resin composition having sufficient curability and high storage stability can be obtained.

[0067] The resin composition for fiber-reinforced plastics of the present invention preferably further contains (D) a silane coupling agent in order to improve adhesion to fibers.

[0068] Examples of the silane coupling agent (component (D)) include amino group-containing silane coupling agents, glycidyloxy group-containing silane coupling agents, epoxy group-containing silane coupling agents, vinyl group-containing silane coupling agents, isocyanate group-containing silane coupling agents, (meth)acryloyl group-containing silane coupling agents, halogen-containing silane coupling agents, and mercapto group-containing silane coupling agents. Examples of the amino group-containing silane coupling agent include γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-N'-β-(aminoethyl)-γ-aminopropyltriethoxysilane, γ-anilinopropyltriethoxysilane, and N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltriethoxysilane. As a silane coupling agent containing a glycidyloxy group, for example, γ-glycidyloxypropyltriethoxysilane can be mentioned. As a silane coupling agent containing an epoxy group, for example, β-(3,4-epoxycyclohexyl)ethyltriethoxysilane can be mentioned. As a silane coupling agent containing a vinyl group, for example, vinyltriethoxysilane can be mentioned. As a silane coupling agent containing an isocyanate group, for example, γ-isocyanatopropyltriethoxysilane can be mentioned. As a silane coupling agent containing a (meth)acryloyl group, for example, γ-methacryloyloxypropyltrimethoxysilane can be mentioned. As a silane coupling agent containing a halogen, for example, γ-chloropropyltrimethoxysilane can be mentioned. As a silane coupling agent containing a mercapto group, for example, γ-mercaptopropyltrimethoxysilane can be mentioned. In the present invention, one of these silane coupling agents can be used alone, or two or more can be used in combination.

[0069] As the silane coupling agent, an amino group-containing silane coupling agent or a glycidyloxy group-containing silane coupling agent is preferably used because of its easy availability and low cost, and a glycidyloxy group-containing silane coupling agent is more preferably used. As the amino group-containing silane coupling agent, γ-aminopropyltriethoxysilane is preferably used. As the glycidyloxy group-containing silane coupling agent, γ-glycidyloxypropyltriethoxysilane is preferably used, and γ-glycidyloxypropyltriethoxysilane is more preferably used.

[0070] The content of the silane coupling agent, component (D), in the resin composition for fiber-reinforced plastics of the present invention is not particularly limited, but is preferably 0.1 to 50 parts by mass relative to 100 parts by weight of the total amount of the compound having an epoxy group. From the viewpoint of good miscibility with the resin and improved adhesion to the fiber, it is more preferably 1 to 20 parts by mass.

[0071] The fiber reinforced plastic resin composition of the present invention may contain a reactive diluent in order to adjust its viscosity to a desired value. Examples of the reactive diluent include n-butyl glycidyl ether, C 12 ~C 14Alkyl glycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, styrene oxide, phenyl glycidyl ether, cresyl glycidyl ether, 4-sec-butylphenyl glycidyl ether, tert-butylphenyl glycidyl ether, glycidyl methacrylate and tert-carboxylic acid glycidyl ether, etc.

[0072] The resin composition for fiber-reinforced plastics of the present invention may further contain other additives as needed. Examples of such other additives include non-reactive diluents (plasticizers) such as dioctyl phthalate, dibutyl phthalate, benzyl alcohol, and coal tar; pigments; lubricants such as candelilla wax, carnauba wax, wood wax, white wax, beeswax, lanolin, spermaceti, montan wax, petroleum wax, fatty acid wax, fatty acid esters, fatty acid ethers, aromatic esters, and aromatic ethers; thickeners; thixotropic agents; antioxidants; light stabilizers; ultraviolet absorbers; flame retardants; defoaming agents; and rust inhibitors.

[0073] The resin composition for fiber-reinforced plastics of the present invention preferably has a viscosity increase ratio of 200% or less as measured by the following method in order to further improve stability.

[0074] <Method for measuring viscosity increase>

[0075] 2000g of a resin composition for fiber-reinforced plastics was weighed and placed in a container. The temperature of the resin composition was adjusted to 25°C. The viscosity V1 of the resin composition at 25°C was then measured. An acceleration test was then performed on the resin composition, and the viscosity V2 of the resin composition after the test at 25°C was measured. The viscosity increase was calculated from the obtained V1 and V2 using the following formula. The acceleration test was performed by placing the container containing the resin composition in a water bath adjusted to 25°C for 4 hours. The viscosity was measured using a TVE-35H manufactured by Toki Sangyo Co., Ltd.

[0076] Thickening rate (%) = (V2 / V1) × 100

[0077] The resin composition for fiber-reinforced plastics of the present invention is preferably liquid at 25° C. from the viewpoint of use in producing fiber-reinforced plastics. The viscosity of the resin composition for fiber-reinforced plastics of the present invention at 25° C. is particularly preferably 100 to 3000 mPa·s.

[0078] The cured product is obtained by curing the resin composition for fiber-reinforced plastics of the present invention. The method and curing conditions for curing the fiber-reinforced plastics composition are not particularly limited, and known methods and conditions can be employed.

[0079] The resin composition for fiber-reinforced plastics of the present invention can be used to produce fiber-reinforced plastics. Fiber-reinforced plastics can be obtained, for example, by curing a composition containing the resin composition for fiber-reinforced plastics of the present invention and reinforcing fibers. The content of the resin composition for fiber-reinforced plastics and reinforcing fibers in the composition is not particularly limited, but preferably contains 5 to 150 parts by mass of the resin composition for fiber-reinforced plastics per 100 parts by mass of reinforcing fibers, and more preferably contains 15 to 70 parts by mass. There are no particular limitations on the method and conditions for curing the composition, and curing can be achieved using known methods and conditions.

[0080] The type of the reinforcing fibers is not particularly limited, and examples thereof include carbon fibers, glass fibers, aromatic polyamide fibers, boron fibers, alumina fibers, and silicon carbide fibers. One of these reinforcing fibers may be used alone, or two or more may be combined to form a mixed fiber.

[0081] Examples of the reinforcing fibers include a so-called tow sheet in which high-strength, high-elastic modulus fibers are arranged in one direction, a unidirectional fabric or bidirectional fabric in which the fibers are arranged in one or two directions, a triaxial fabric in which the fibers are arranged in three directions, and a multiaxial fabric in which the fibers are arranged in multiple directions. In a tow sheet, the fibers may be arranged so that appropriate gaps are maintained between the strands in order to improve the resin impregnation into the base material.

[0082] The method for molding the fiber-reinforced plastic obtained using the resin composition of the present invention is not particularly limited, and examples thereof include extrusion molding, blow molding, compression molding, vacuum molding, injection molding, RTM (Resin Transfer Molding) molding, VaRTM (Vacuum assist Resin Transfer Molding) molding, lamination molding, hand lay-up molding, filament winding molding, fiber-to-composite molding, and the like.

[0083] Fiber-reinforced plastics obtained using the resin composition for fiber-reinforced plastics of the present invention can be used in a variety of applications. Examples include structural materials for mobile vehicles such as automobiles, ships, and railway vehicles; general industrial applications such as drive shafts, leaf springs, windmill blades, pressure vessels, flywheels, papermaking rollers, roofing materials, cables, and repair reinforcement materials; aerospace applications such as fuselages, main wings, tail planes, rotor wings, fairings, engine cowls, doors, seats, interior materials, motor housings, and antennas; and sports applications such as golf clubs, fishing rods, tennis and badminton rackets, hockey sticks, and ski poles.

[0084] Example

[0085] Hereinafter, the present invention will be described in more detail based on Examples. Note that the numerical values of the components in the following Tables 1 and 2 are parts by mass.

[0086] [Example 1]

[0087] The components listed in Table 1 were added to a 500 mL disposable cup in the amounts (parts by mass) listed therein and stirred at 25° C. for 5 minutes with a spatula. The mixture was further stirred using a planetary mixer to obtain a resin composition. The components listed in Table 1 represent the following compounds.

[0088] epoxy resin

[0089] Adeka Resin EP-4901E: Bisphenol F epoxy resin, epoxy equivalent weight: 170 g / eq. (manufactured by Adeka Co., Ltd.)

[0090] Adeka Resin EP-4005: Polyglycidyl ether of propylene oxide adduct of bisphenol A, epoxy equivalent: 510 g / eq. (manufactured by ADEKA Co., Ltd.)

[0091] Adeka Resin EP-4088S: R in formula (1) 1 and R 2 Dicyclopentadiene-type epoxy resin containing hydrogen atoms, epoxy equivalent: 170 g / eq. (manufactured by ADEKA Co., Ltd.)

[0092] Acid anhydride

[0093] HN-2000: Methyltetrahydrophthalic anhydride, liquid at 25°C (viscosity at 25°C: 38 mPa·s) (manufactured by Hitachi Chemical Co., Ltd.)

[0094] catalyst

[0095] Hishicolin PX-4ET: o,o-diethyl tetrabutylphosphonium dithiophosphate (manufactured by Nippon Chemical Industry), liquid at 25°C (viscosity at 25°C: 1000 mPa·s)

[0096] U-CAT SA-1: DBU (1,8-diazabicyclo(5.4.0)-undecene-7) phenolate (manufactured by SAN-APRO), liquid at 25°C (viscosity at 25°C: 320 mPa·s)

[0097] ADEKA Hardner: 1,3,5-Tris-dimethylaminomethylphenol (manufactured by ADEKA Co., Ltd.)

[0098] Silane coupling agent

[0099] KBM-403: γ-Glycidyloxypropyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.)

[0100] [Example 2 and Comparative Examples 1 and 2]

[0101] A resin composition was obtained in the same manner as in Example 1 except that the blending amounts of the components were as shown in Table 1.

[0102] The content of the acid anhydride relative to the epoxy resin in the resin compositions obtained in Examples 1 and 2 and Comparative Examples 1 and 2 was such that the number of the acid anhydride group was 1 per epoxy group.

[0103] The following evaluations were performed using the resin compositions obtained in Examples 1 and 2 and Comparative Examples 1 and 2. The results are shown in Table 1.

[0104] <Thickness increase rate>

[0105] The viscosity increase (%) of the resin compositions obtained in Examples 1 and 2 and Comparative Examples 1 and 2 was determined by the above method. The viscosity at 25° C. of the resin compositions obtained in Examples 1 and 2 and Comparative Examples 1 and 2 was also measured by the above method.

[0106] <Cure degree>

[0107] The resin compositions obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were heated at 100° C. for 1 hour to be cured, thereby obtaining samples. The degree of cure of the obtained samples was measured by a method in accordance with JIS K 7148-1.

[0108] Table 1

[0109]

[0110] As is clear from Table 1, the resin compositions of Examples 1 and 2 have low viscosity increases, and therefore are clearly excellent in stability. Furthermore, the cured products obtained from the resin compositions of Examples 1 and 2 have high degrees of cure, and therefore are clearly suitable as resin raw materials for producing fiber-reinforced plastics.

[0111] [Examples 3 and 4]

[0112] Carbon fiber reinforced plastic (CFRP) was molded by filament winding for the following tests. CFRP was also molded into a 3-4 mm plate using a plate-shaped mandrel in a hoop-wound manner for evaluation purposes such as strength tests. The resin was impregnated into a roving in a resin bath placed just before winding it onto the mandrel while maintaining the temperature at 25°C. After the roving was wound to a specified thickness, it was cured by pressurizing and heating at 100°C for 1 hour to produce a fiber-reinforced composite material (resin composition: carbon fiber = 50:100 (mass ratio)).

[0113] The following evaluations were performed using the obtained test pieces. The results are shown in Table 2.

[0114] <Physical property test methods>

[0115] The flexural strength (MPa) of the cured product was measured by a method in accordance with JIS K 7074. The interlaminar shear strength (MPa) was also measured by a method in accordance with JIS K 7078.

[0116] Table 2

[0117]

[0118] As apparent from Table 2, the flexural strength and interlaminar shear strength of the CFRP obtained in Examples 3 and 4 are suitable for practical use.

Claims

1. A resin composition for fiber-reinforced plastics, comprising (A) an epoxy resin, (B) an acid anhydride, and (C) a catalyst that is liquid at 25°C. (C) The catalyst that is liquid at 25°C is at least one selected from the following (c1) and (c2): (c1) a pair of compounds consisting of an acid and a base, (c2) A compound composed of a quaternary onium cation and an anion.

2. The resin composition for fiber-reinforced plastics according to claim 1, wherein (A) The epoxy resin contains at least a polyglycidyl ether of an alkylene oxide adduct of a bisphenol.

3. The resin composition for fiber-reinforced plastics according to claim 2, wherein The polyglycidyl ether of an alkylene oxide adduct of a bisphenol is contained in an amount of 10 to 80% by mass relative to the (A) epoxy resin.

4. The resin composition for fiber-reinforced plastics according to any one of claims 1 to 3, wherein (A) The epoxy resin contains a dicyclopentadiene-type epoxy resin represented by the following formula (1), Where R 1 and R 2 Each independently represents a hydrogen atom or a methyl group.

5. The resin composition for fiber-reinforced plastics according to claim 4, wherein The dicyclopentadiene epoxy resin represented by the above formula (1) is contained in an amount of 0.1 to 30% by mass relative to the (A) epoxy resin.

6. The resin composition for fiber-reinforced plastics according to any one of claims 1 to 5, wherein (B) Acid anhydride is liquid at 25°C.

7. The resin composition for fiber-reinforced plastics according to any one of claims 1 to 6, wherein (B) The acid anhydride is an anhydride of an unsaturated alicyclic polycarboxylic acid.

8. The resin composition for fiber-reinforced plastics according to any one of claims 1 to 7, wherein (C) The catalyst is (c1) a compound consisting of an acid and a base, (c1) is a compound derived from an aromatic compound and an organic basic compound.

9. The resin composition for fiber-reinforced plastics according to any one of claims 1 to 8, wherein (c1) is a pair of compounds derived from a monocyclic aromatic compound and a nitrogen-containing heterocyclic compound.

10. The resin composition for fiber-reinforced plastics according to any one of claims 1 to 9, wherein (C) The catalyst is (c2) a compound consisting of a quaternary onium cation and an organic anion, The quaternary onium cation is a phosphonium cation.

11. The resin composition for fiber-reinforced plastics according to any one of claims 1 to 10, wherein The organic anion is an alkyl dithiophosphate.

12. The resin composition for fiber-reinforced plastics according to any one of claims 1 to 11, wherein The (C) catalyst is contained in an amount of 0.01 to 20 parts by mass based on 100 parts by mass of the (A) epoxy resin.

13. The resin composition for fiber-reinforced plastics according to any one of claims 1 to 12, wherein It further contains (D) a silane coupling agent. 14 . A cured product obtained by curing the resin composition for fiber-reinforced plastics according to claim 1 . 15 . A fiber-reinforced plastic obtained by curing a composition comprising the resin composition for fiber-reinforced plastics according to claim 1 and reinforcing fibers.

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