Hardening composition, fiber composite material, sheet molding compound, and molded article

Abstract

The present invention provides: a curable composition, a cured product of which has high strength and which is suitable for use in a fiber composite material; a fiber composite material which uses this curable composition; a sheet molding compound which is suppressed in stickiness and has good film releasability; and a molded article which has excellent surface smoothness. A curable composition according to the present invention contains (A) an epoxy group-containing compound, (B) a curing agent or curing accelerator for epoxy group-containing compounds, (C) a polyhydroxy compound (excluding the component (A)), and (D) a polyisocyanate compound, and is characterized in that 70% by mass or more of the polyhydroxy compound (C) is a polyhydroxy compound (C1) that has a hydroxyl equivalent within the range of 125 to 600 g / equivalent.

Description

Technical Field

[0001] The present invention relates to a curable composition in which a cured product has high strength and can be suitably used for fiber composite materials, a fiber composite material using the curable composition, a sheet molding compound having little stickiness and good film releasability, and a molded product having excellent surface smoothness.

Background Art

[0002] CFRP obtained by reinforcing a thermosetting resin with carbon fiber has attracted attention for its characteristics of being lightweight and having excellent heat resistance and mechanical strength, and its use in various applications such as automobiles, aircraft, and industrial parts is expanding. Among them, a sheet molding compound (hereinafter, may be abbreviated as "SMC") using discontinuous fibers as the carbon fiber can be molded into a more complex shape compared with the case of using continuous carbon fibers, and also has advantages such as reusability of end materials and insertability of members made of different materials, in terms of high productivity and wide design application range. Conventionally, unsaturated polyester resins and vinyl ester resins have been widely used as the matrix resin of sheet molding compounds, but due to the inclusion of volatile components such as styrene, the safety of the working environment and the environmental load have become issues, and recently, the use of epoxy resins has been considered instead of these resin materials.

[0003] As a sheet molding compound using an epoxy resin, a resin composition containing an epoxy resin, its curing agent, a polyisocyanate compound, and a polyol having a hydroxyl equivalent of 20 or more and 120 or less as a matrix resin is known (for example, see Patent Document 1). The sheet molding compound described in Patent Document 1 has relatively excellent strength of the cured product, but has strong stickiness, a problem with film releasability, and also inferior surface smoothness of the molded product.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent No. 6447791 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] Therefore, the problems to be solved by the present invention are to provide a curable composition in which the cured product has high strength and can be suitably used for fiber composite materials, a fiber composite material using the curable composition, a sheet molding compound with little stickiness and good film releasability, and a molded product with excellent surface smoothness. [Means for Solving the Problems]

[0006] As a result of intensive studies, the present inventors have found that a curable composition containing an epoxy resin, a polyisocyanate compound, and a polyhydroxy compound, wherein the polyhydroxy compound has a hydroxyl equivalent weight in the range of 125 to 600 g / equivalent, has a cured product with high strength and can be suitably used for fiber composite materials. Also, a sheet molding compound using this composition has little stickiness and good film releasability, so it has excellent workability. Furthermore, it has been found that the molded product has excellent surface smoothness, and the present invention has been completed.

[0007] That is, the present invention relates to a curable composition containing (I) an epoxy group-containing compound (A), a curing agent (B) for the epoxy group-containing compound, a polyhydroxy compound (C) (excluding those corresponding to component (A)), and a polyisocyanate compound (D), wherein 70% by mass or more of the polyhydroxy compound (C) is a polyhydroxy compound (C1) having a hydroxyl equivalent weight in the range of 125 to 600 g / equivalent.

[0008] The present invention further relates to the curable composition according to (I) above, wherein (II) the molar ratio of the isocyanate groups of the polyisocyanate compound (D) to 1 mol of the hydroxyl groups in the polyhydroxy compound (C) is in the range of 0.6 to 3.0.

[0009] The present invention further relates to the curable composition according to (I) or (II) above, wherein (III) the epoxy group-containing compound (A) contains a bisphenol type epoxy resin (A1) having an epoxy equivalent of 160 to 260 g / equivalent.

[0010] The present invention further relates to the curable composition according to any one of (I) to (III) above, wherein (IV) the epoxy group-containing compound (A) contains a polyglycidyl ether (A2) of an aliphatic polyol having 2 to 6 carbon atoms.

[0011] The present invention further relates to the curable composition according to any one of (I) to (IV) above, wherein (V) the epoxy group-containing compound (A) contains a bisphenol type epoxy resin (A1) having an epoxy equivalent of 160 to 260 g / equivalent and a polyglycidyl ether (A2) of an aliphatic polyol having 2 to 6 carbon atoms, and the mass ratio (A1) / (A2) of both is in the range of 60 / 40 to 95 / 5.

[0012] The present invention further relates to a fiber-reinforced composite material containing the curable composition according to any one of (I) to (V) above and a reinforcing fiber.

[0013] The present invention further relates to the fiber-reinforced composite material according to (VI) above, wherein (VII) the reinforcing fiber is a carbon fiber.

[0014] The present invention further relates to the fiber-reinforced composite material according to (VI) or (VII) above, which is a sheet molding compound.

[0015] The present invention further relates to the sheet molding compound according to (VIII) above, which has a carrier film on both sides.

[0016] The present invention further relates to a molded article of the fiber composite material according to any one of (VI) to (VIII) above or the sheet molding compound according to (IX) above.

[0017] The present invention further relates to a method for manufacturing a molded article, which includes a step of peeling a carrier film from a sheet molding compound having a carrier film on the back side (XI), and a step of molding the sheet molding compound from which the carrier film has been peeled.

[0018] According to the present invention, it is possible to provide a curable composition in which a cured product has high strength and can be suitably used for fiber composite materials, a fiber composite material using the curable composition, a sheet molding compound with less stickiness and good film peelability, and a molded article with excellent surface smoothness. The sheet molding compound and the molded article of the present invention can be suitably used for various applications such as exterior and structures of automotive members, railway vehicle members, aerospace members, ship members, housing equipment members, sports members, light vehicle members, construction civil engineering members, OA equipment, etc.

Embodiments for Carrying Out the Invention

[0019] The curable composition of the present invention is a curable composition containing an epoxy group-containing compound (A), a curing agent (B) for the epoxy group-containing compound, a polyhydroxy compound (C) (excluding those corresponding to component (A)), and a polyisocyanate compound (D), characterized in that 70% by mass or more of the polyhydroxy compound (C) has a hydroxyl equivalent in the range of 125 to 600 g / equivalent.

[0020] The epoxy group-containing compound (A) is not particularly limited as long as it has an epoxy group in its molecular structure, and various types can be used. The epoxy group-containing compound (A) may be used alone or in combination of two or more. Further, the epoxy group-containing compound (A) may have a functional group other than the epoxy group. Among them, a compound having two or more epoxy groups in its molecular structure is preferable because it results in a curable composition excellent in curing reaction. The proportion of the compound having two or more epoxy groups in its molecular structure in the whole epoxy group-containing compound (A) is preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0021] The epoxy group-containing compound (A) is, for example, diglycidyl oxybenzene, diglycidyl oxynaphthalene, biphenol type epoxy resin, bisphenol type epoxy resin, polyglycidyl ether of aliphatic polyol, novolak type epoxy resin, alicyclic epoxy resin, glycidyl amine type epoxy resin, heterocyclic type epoxy resin, glycidyl ester type epoxy resin, triphenol methane type epoxy resin, phenol or naphthol aralkyl type epoxy resin, phenylene or naphthylene ether type epoxy resin, oxazolidone-modified epoxy resin, brominated epoxy resin thereof, and epoxy resin obtained by extending these epoxy group-containing compounds with an extender, etc.

[0022] The biphenol type epoxy resin is, for example, a biphenol compound such as biphenol or tetramethylbiphenol, or a polyglycidyl etherified product of one or more kinds of alkylene oxide adducts of these biphenol compounds with epihalohydrin.

[0023] The bisphenol type epoxy resin is, for example, a bisphenol compound such as bisphenol A, bisphenol F, bisphenol S, bisphenol fluorene, or biscresol fluorene, or a polyglycidyl etherified product of one or more kinds of alkylene oxide adducts of these bisphenol compounds with epihalohydrin.

[0024] The polyglycidyl ether of the aliphatic polyol includes, for example, those obtained by polyglycidyl etherifying one or more of various aliphatic polyol compounds and their alkylene oxide adducts with epihalohydrin. Examples of the aliphatic polyol compounds include aliphatic diol compounds such as ethylene glycol, propylene glycol, 1,3-propanediol, 2-methylpropanediol, 1,2,2-trimethyl-1,3-propanediol, 2,2-dimethyl-3-isopropyl-1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 3-methyl-1,3-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,4-bis(hydroxymethyl)cyclohexane, 2,2,4-trimethyl-1,3-pentanediol; alicyclic diol compounds such as 2,2-bis(4-hydroxyphenyl)propane; and polyfunctional aliphatic polyol compounds having three or more functional groups such as trimethylolethane, trimethylolpropane, glycerin, hexanetriol, pentaerythritol, ditrimethylolpropane, and dipentaerythritol.

[0025] The novolac type epoxy resin includes, for example, those obtained by polyglycidyl etherifying a novolac resin composed of one or more of various phenol compounds such as phenol, dihydroxybenzene, cresol, xylenol, naphthol, dihydroxynaphthalene, bisphenol, and biphenol with epihalohydrin.

[0026] The alicyclic epoxy resin includes, for example, those obtained by hydrogenating the biphenol compound or bisphenol compound, and polyglycidyl etherifying one or more of their alkylene oxide adducts with epihalohydrin. In addition, 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate, 1-epoxyethyl-3,4-epoxycyclohexane, etc. are also included.

[0027] Examples of the glycidylamine type epoxy resin include N,N-diglycidylaniline, triglycidylaminophenol, tetraglycidylxylylenediamine, 4,4'-methylenebis[N,N-diglycidylaniline], and the like.

[0028] Examples of the heterocyclic type epoxy resin include 1,3-diglycidyl-5,5-dimethylhydantoin, triglycidyl isocyanurate, and the like.

[0029] Examples of the glycidyl ester type epoxy resin include diglycidyl phthalate, diglycidyl tetrahydrophthalate, diglycidyl-p-oxybenzoic acid, glycidyl dimer acid ester, and the like.

[0030] Examples of the extender for the epoxy resin include the various biphenol compounds and their hydrogenated products, the various bisphenol compounds and their hydrogenated products, dibasic acid compounds, acid group-containing polyester resins, and the like.

[0031] Among these, the bisphenol type epoxy resin is preferable because of its excellent strength of the cured product and fiber impregnation property when used in a fiber-reinforced composite material. A bisphenol type epoxy resin having an epoxy equivalent in the range of 160 to 260 g / equivalent is more preferable. The proportion of the bisphenol type epoxy resin in the whole epoxy group-containing compound (A) is preferably 40% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more. Further, it is preferably 95% by mass or less, and more preferably 90% or less.

[0032] Further, in terms of further excellent fiber impregnation properties when used in fiber-reinforced composite materials, the polyglycidyl ether of the aliphatic polyol is preferable, and the polyglycidyl ether of an aliphatic polyol having 2 to 6 carbon atoms is more preferable. The proportion of the bisphenol type epoxy resin in the whole epoxy group-containing compound (A) is preferably 5% by mass or more, more preferably 10% by mass or more. Further, it is preferably 50% by mass or less, more preferably 35% by mass or less.

[0033] When the bisphenol type epoxy resin and the polyglycidyl ether of the aliphatic polyol are used in combination, the mass ratio of both (bisphenol type epoxy resin) / (polyglycidyl ether of aliphatic polyol) is preferably in the range of 60 / 40 to 95 / 5, and more preferably in the range of 70 / 30 to 85 / 15.

[0034] As the curing agent or curing accelerator (B) for the epoxy group-containing compound, various compounds generally used as a curing agent or curing accelerator for epoxy group-containing compounds can be used without particular limitation. Further, the curing agent or curing accelerator may be used alone or in combination of two or more.

[0035] Examples of the curing agent or curing accelerator (B) include amine compounds, amide compounds, acid anhydrides, phenolic hydroxyl group-containing compounds, phosphorus compounds, imidazole compounds, imidazoline compounds, urea-based compounds, organic acid metal salts, Lewis acids, amine complex salts, and the like.

[0036] The amine compound includes, for example, aliphatic amine compounds such as ethylenediamine, tetramethylethylenediamine, diethylenetriamine, hexamethylenediamine, triethylenetetramine, guanidine derivatives; alicyclic and heterocyclic amine compounds such as piperidine, piperazine, isophoronediamine, 1,8-diazabicyclo-[5.4.0]-undecene (DBU); aromatic amine compounds such as phenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, benzylmethylamine, dimethylbenzylamine, xylenediamine, pyridine; boron trifluoride amine complex, and the like.

[0037] The amide compound includes, for example, dicyandiamide, polyamideamine, and the like. The polyamideamine is obtained, for example, by reacting aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, carboxylic acid compounds such as fatty acids, dimer acids, with aliphatic polyamines, polyamines having a polyoxyalkylene chain, and the like.

[0038] The acid anhydride includes, for example, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, and the like.

[0039] The phenolic hydroxyl group-containing resin includes, for example, various novolak resins, dicyclopentadiene phenol addition type resins, phenol or naphthol aralkyl resins, triphenolmethane resins, phenol or naphthol aralkyl resins, phenylene or naphthylene ether resins, aminotriazine-modified phenol resins, and the like.

[0040] The phosphorus compound includes, for example, alkylphosphines such as ethylphosphine and butylphosphine, primary phosphines such as phenylphosphine; dialkylphosphines such as dimethylphosphine and dipropylphosphine; secondary phosphines such as diphenylphosphine and methylethylphosphine; tertiary phosphines such as trimethylphosphine, triethylphosphine, and triphenylphosphine.

[0041] The imidazole compound includes, for example, imidazole, 1-methylimidazole, 2-methylimidazole, 3-methylimidazole, 4-methylimidazole, 5-methylimidazole, 1-ethylimidazole, 2-ethylimidazole, 3-ethylimidazole, 4-ethylimidazole, 5-ethylimidazole, 1-n-propylimidazole, 2-n-propylimidazole, 1-isopropylimidazole, 2-isopropylimidazole, 1-n-butylimidazole, 2-n-butylimidazole, 1-isobutylimidazole, 2-isobutylimidazole, 2-undecyl-1H-imidazole, 2-heptadecyl-1H-imidazole, 1,2-dimethylimidazole, 1,3-dimethylimidazole, 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, 1-phenylimidazole, 2-phenyl-1H-imidazole, 4-methyl-2-phenyl-1H-imidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 2-phenylimidazole isocyanurate adduct, 2-methylimidazole isocyanurate adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 1-cyanoethyl-2-phenyl-4,5-di(2-cyanoethoxy)methylimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 1-benzyl-2-phenylimidazole hydrochloride, etc.

[0042] Examples of the imidazoline compound include 2-methylimidazoline, 2-phenylimidazoline, and the like.

[0043] Examples of the urea compound include p-chlorophenyl-N,N-dimethylurea, 3-phenyl-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-N,N-dimethylurea, N-(3-chloro-4-methylphenyl)-N',N'-dimethylurea, 4,4'-methylenebis(phenyldimethylurea), and the like.

[0044] Among these, amine compounds, amide compounds, imidazole compounds, and urea compounds are preferred because they have fast curing and excellent strength of the cured product.

[0045] When using a compound having a functional group capable of reacting with an epoxy group, such as an amine compound, an amide compound, an acid anhydride, a phenol group-containing compound, etc., as the curing agent or curing accelerator in the epoxy resin composition, it is preferably blended in a ratio such that the functional group or active hydrogen in the curing agent is in the range of 0.5 to 1.2 moles per mole of the epoxy group in the epoxy group-containing compound (A). Further, when using a phosphorus compound, an imidazole compound, an imidazoline compound, a urea-based compound, etc., it is preferably blended in a ratio of 0.5 to 20 parts by mass per 100 parts by mass of the epoxy group-containing compound (A).

[0046] The polyhydroxy compound (C) (excluding those corresponding to component (A)) contains, as an essential component, a polyhydroxy compound (C1) having a hydroxyl equivalent in the range of 125 to 600 g / eq, and 70% by mass or more of the polyhydroxy compound (C) is the polyhydroxy compound (C1). By satisfying such conditions, in addition to the strength of the cured product, the fiber impregnation property when used in a fiber-reinforced composite material, the film peelability when made into a sheet molding compound, and the surface smoothness of the molded product are excellent curable compositions. Further, the proportion of the polyhydroxy compound (C1) in the polyhydroxy compound (C) is preferably 80% by mass or more, and more preferably 90% by mass or more.

[0047] The polyhydroxy compound (C1) has a plurality of hydroxyl groups in its molecular structure, and as long as the hydroxyl equivalent is in the range of 125 to 600 g / eq, its specific structure is not particularly limited, and a wide variety of them can be used. The polyhydroxy compound (C) may use the polyhydroxy compound (C1) alone, or may use two or more kinds in combination with other ones. In the present invention, those having an epoxy group among the polyhydroxy compounds are to be treated as the epoxy group-containing compound (A).

[0048] Examples of the polyhydroxy compound (C) include aliphatic polyol compounds, dihydroxybenzenes, dihydroxynaphthalenes, trihydroxybenzenes, trihydroxynaphthalenes, triphenol alkanes, biphenol compounds, bisphenol compounds, alicyclic polyol compounds, novolak resins, phenol or naphthol aralkyl type resins, phenylene or naphthylene ether type resins, and alkylene oxide adducts thereof.

[0049] The aliphatic polyol compound includes, for example, aliphatic diol compounds such as ethylene glycol, propylene glycol, 1,3-propanediol, 2-methylpropanediol, 1,2,2-trimethyl-1,3-propanediol, 2,2-dimethyl-3-isopropyl-1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 3-methyl-1,3-butanediol, 1,5-pentanediol, 3-methyl 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,4-bis(hydroxymethyl)cyclohexane, 2,2,4-trimethyl-1,3-pentanediol; alicyclic diol compounds such as 2,2-bis(4-hydroxyphenyl)propane; and trifunctional or higher-functional aliphatic polyol compounds such as trimethylolethane, trimethylolpropane, glycerin, hexanetriol, pentaerythritol, ditrimethylolpropane, dipentaerythritol, etc.

[0050] The biphenol compound includes, for example, biphenol, tetramethylbiphenol, etc.

[0051] The bisphenol compound includes, for example, bisphenol compounds such as bisphenol A, bisphenol F, bisphenol S, bisphenol fluorene, biscresol fluorene, etc.

[0052] The alicyclic polyol compound includes, for example, cyclohexanediol, and those obtained by hydrogenating the biphenol compound and bisphenol compound, etc.

[0053] The novolak resin includes, for example, novolak resins composed of one or more of various phenol compounds such as phenol, dihydroxybenzene, cresol, xylenol, naphthol, dihydroxynaphthalene, bisphenol, biphenol, etc.

[0054] Among these, as the polyhydroxy compound (C1) in which the hydroxyl equivalent is in the range of 125 to 600 g / equivalent, since it becomes a curable composition excellent in the strength of the cured product, the film releasability when used in a sheet molding compound, and the surface smoothness of the molded product, it is preferably an alkylene oxide adduct of various polyhydroxy compounds, that is, those having a (poly)alkylene oxide structure in the molecular structure are preferred. Further, it is more preferably an alkylene oxide adduct of the aliphatic polyol compound or the bisphenol compound, and the aliphatic polyol compound preferably has 2 to 6 carbon atoms. Also, its hydroxyl equivalent is more preferably in the range of 150 to 400 g / equivalent.

[0055] The polyisocyanate compound (D) is not particularly limited in its specific structure as long as it has a plurality of isocyanate groups in the molecular structure, and a wide variety of them can be used. The polyisocyanate compound (D) may be used alone or in combination of two or more. Specific examples include, for example, aliphatic diisocyanate compounds such as butane diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, dimer acid diisocyanate; alicyclic diisocyanate compounds such as norbornane diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate; aromatic diisocyanate compounds such as toluene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, tolidine diisocyanate, diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, polymethylene polyphenyl polyisocyanate; modified products of these isocyanate compounds such as isocyanurate modified products, biuret modified products, allophanate modified products, carbodiimide modified products, urethane imine modified products, polyol modified products modified with polyols having a number average molecular weight of 1,000 or less such as diethylene glycol and dipropylene glycol, etc.

[0056] Among these, an aromatic polyisocyanate compound or its various modified products are preferred because a sheet molding compound with less stickiness and good film releasability can be obtained. Further, the isocyanate group content is preferably 15% by mass or more, more preferably 20% by mass or more. Also, it is preferably 40% by mass or less.

[0057] In the present invention, the blending ratios of the polyhydroxy compound (C) (excluding those corresponding to component (A)) and the polyisocyanate compound (D) are arbitrary and are appropriately adjusted according to the desired performance of the curable composition, the intended use, etc.

[0058] As a preferable blending design in the curable composition of the present invention, a sheet molding compound with less stickiness and good film releasability is obtained, and further, a molded article with excellent surface smoothness is obtained. Therefore, the molar number of the isocyanate group of the polyisocyanate compound (D) relative to 1 mol of the hydroxyl group in the polyhydroxy compound (C) is preferably 0.5 or more, more preferably 0.8 or more. Also, it is preferably 3.0 or less, more preferably 1.5 or less, and particularly preferably 1.2 or less.

[0059] Also, the blending amount of the polyhydroxy compound (C) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, with respect to 100 parts by mass of the epoxy group-containing compound (A), because a curable composition excellent in the strength of the cured product, the film releasability when used in a sheet molding compound, and the surface smoothness of the molded article is obtained. Also, it is preferably 50 parts by mass or less, more preferably 30 parts by mass or less.

[0060] The curable composition of the present invention may contain a urethanization catalyst as needed. One type of urethanization catalyst may be used alone, or two or more types may be used in combination. Examples of the urethanization catalyst include amine compounds such as triethylamine, dibutylamine, triethylenediamine, and pyridine; phosphorus compounds such as triphenylphosphine and triethylphosphine; organotin compounds such as dibutyltin dilaurate, octyltin trilaurate, octyltin diacetate, dibutyltin diacetate, and tin octylate; organozinc compounds such as zinc amine, zinc carboxylate, zinc stearate, and zinc octylate; organic bismuth compounds such as bismuth carboxylate; organic zirconium compounds such as zirconium acetylacetonate and zirconium tetraethanolate; organoaluminum compounds such as aluminum triethoxide; and organic titanium compounds such as titanium tetrabutyrate and titanium ethyl acetoacetate. Among them, organic zinc compounds and organic bismuth compounds are preferred because of their excellent safety to the living body and storage stability.

[0061] When using the urethanization catalyst, the addition amount is preferably in the range of 0.002 to 1% by mass, more preferably in the range of 0.01 to 0.8% by mass, based on the total mass of the epoxy group-containing compound (A), the curing agent or curing accelerator (B) for the epoxy group-containing compound, the polyhydroxy compound (C), and the polyisocyanate compound (D).

[0062] Also, for the purpose of controlling the urethanization reaction in the curable composition, a water absorbent may be added. One type of water absorbent may be used alone, or two or more types may be used in combination. Examples of the water absorbent include silica gel, activated alumina, molecular sieve, etc. Among these, molecular sieve is preferred from the viewpoint of excellent water absorption efficiency. The pore diameter thereof is preferably in the range of 0.1 to 0.5 nm, more preferably in the range of 0.2 to 0.4 nm. Also, the particle size is preferably 50 μm or less, more preferably 10 μm or less. When using the water absorbent, the addition amount is preferably in the range of 0.1 to 5% by mass based on the total mass of the epoxy group-containing compound (A), the curing agent or curing accelerator (B) for the epoxy group-containing compound, the polyhydroxy compound (C), and the polyisocyanate compound (D).

[0063] The curable composition of the present invention may contain other components in addition to the epoxy group-containing compound (A), the curing agent or curing accelerator (B) for the epoxy group-containing compound, the polyhydroxy compound (C), the polyisocyanate compound (D), the urethanization catalyst, and the water absorbent. Examples of the other components include thermosetting resins, thermoplastic resins, inorganic fillers, low shrinkage agents, mold release agents, thickeners, viscosity reducers, pigments, antioxidants, plasticizers, flame retardants, antibacterial agents, ultraviolet stabilizers, reinforcing materials, etc. other than the components (A) to (D). These other components are appropriately added according to the desired performance and use of the curable composition, and the addition amount thereof is also arbitrary. Among them, since the effects exhibited by the present invention are more significantly manifested, the total mass of the epoxy group-containing compound (A), the curing agent or curing accelerator (B) for the epoxy group-containing compound, the polyhydroxy compound (C), and the polyisocyanate compound (D) in the curable composition is preferably 80% by mass or more, particularly preferably 90% by mass or more.

[0064] Since the curable composition of the present invention is excellent in fiber impregnation when used in a fiber-reinforced composite material, the viscosity at 25°C is preferably 100 mPa·s or more, more preferably 300 mPa·s or more. Also, it is preferably 10,000 mPa·s or less, more preferably 6,000 mPa·s or less. In the present invention, the viscosity measurement of the curable composition is the value measured within 10 minutes after all the ingredients of the curable composition are mixed.

[0065] The curable composition of the present invention is useful as a curable resin material, and its cured product has excellent heat resistance and strength. It can also be made into a fiber-reinforced composite material in combination with reinforcing fibers. In particular, it is useful as a matrix resin for sheet molding compounds.

[0066] The reinforcing fibers used in the present invention may be those generally used for sheet molding compound applications, and various types can be used without particular limitation. Specifically, glass fibers, carbon fibers, silicon carbide fibers, pulp, hemp, cotton, nylon, polyester, acrylic, polyurethane, polyimide, or polyamide fibers such as aramid fibers such as Kevlar (registered trademark) and Nomex, etc. can be mentioned. Among them, carbon fibers are preferred because they are excellent in strength and lightweight molded products can be obtained. As the carbon fibers, various types such as polyacrylonitrile-based, pitch-based, and rayon-based can be used, and polyacrylonitrile-based ones are more preferred from the viewpoint of particularly high strength.

[0067] The carbon fibers are usually cut to a length of 2.5 to 50 mm, but carbon fibers cut to 5 to 40 mm are more preferred because the fluidity in the mold during molding, the strength, and the surface smoothness of the molded product are further improved.

[0068] The number of filaments in the fiber bundle of the carbon fibers is preferably in the range of 1,000 to 60,000, more preferably in the range of 5,000 to 30,000, because the impregnation property of the curable composition and the strength of the molded product are further improved.

[0069] In the fiber-reinforced composite material, the fiber content of the reinforcing fibers can be arbitrarily set according to desired molded product physical properties, applications, etc. However, since it results in a molded product with more excellent strength, it is preferably in the range of 20 to 80% by mass, and more preferably in the range of 40 to 70% by mass.

[0070] The method for manufacturing the sheet molding compound of the present invention is not particularly limited and can be manufactured by general methods. Specifically, a step of uniformly mixing the curable composition using various mixers, roll mills, kneaders, extruders, and other mixers, a step of applying the curable composition to a carrier film with a uniform thickness, a step of spraying the reinforcing fibers on the resin surface of the obtained carrier film with resin, a step of sandwiching the reinforcing fibers between the resin surfaces of another carrier film with resin, a step of applying pressure by an impregnation roll, an impregnation belt, etc. to impregnate the reinforcing fibers with the curable composition, a step of winding the sheet obtained by the impregnation step into a roll or folding it in a concertina shape, etc., and a step of aging under normal temperature or temperature conditions of 20 to 60°C. It can be manufactured by a method having some or all of these steps. As the carrier film, general ones such as a polyethylene film, a polypropylene film, polyethylene terephthalate, nylon, a laminate of a plurality of films, etc. can be used.

[0071] The thickness of the sheet molding compound of the present invention can be appropriately set according to desired performance and applications. However, since it is excellent in moldability, strength in the cured product, etc., it is preferably 1 mm or more, more preferably 1.2 mm or more, and particularly preferably 1.5 mm or more. Also, it is preferably 10 mm or less, more preferably 5 mm or less, and particularly preferably 4 mm or less.

[0072] The method for obtaining a molded article from the sheet molding compound of the present invention is not particularly limited, and it can be molded by a method similar to that of a general sheet molding compound. As an example, thermocompression molding can be mentioned. For example, a step of peeling the carrier film from a sheet molding compound having carrier films on both the front and back, a step of stacking one or more sheets of the sheet molding compound from which the carrier film has been peeled, a step of placing the sheet molding compound in a mold, and a step of molding with a compression molding machine. It can be manufactured by a method having some or all of these steps. As described above, since the sheet molding compound of the present invention has less stickiness and excellent film peelability, a molded article can be efficiently obtained. The temperature of the mold can be arbitrarily set, but it is preferably in the range of 110 to 180°C, and it is preferably preheated to the same temperature. The molding pressure of the compression molding machine can be arbitrarily set, but it is preferably in the range of 0.1 to 30 MPa. The molding time can be arbitrarily set, but it is preferable to close the mold over several tens of seconds to several minutes to shape it and cure the curable composition.

Examples

[0073] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

[0074] Examples 1 to 2, Reference Examples 1 to 3 And Comparative Examples 1 and 2 A curable composition, a sheet molding compound, and a molded article were produced in the following manner, and various evaluation tests were conducted. The blending compositions of the curable compositions and various evaluation results are shown in Tables 1 and 2.

[0075] Production of Curable Composition Each component was mixed at the ratios shown in Tables 1 and 2 below to obtain a curable composition. The details of each component in the table are as follows. Epoxy group-containing compound (A1): Bisphenol A type epoxy resin, "Epiclon 840" manufactured by DIC Corporation, epoxy equivalent 180 g / equivalent, viscosity 10,000 mPa·s (25°C) Epoxy group-containing compound (A2): 1,4-butanediol diglycidyl ether, "XY-622" manufactured by ANHUI XINYUAN Chemical, epoxy equivalent 115 g / equivalent, viscosity 14.9 mPa·s (25°C) Epoxy group-containing compound (A3): Glycerol polyglycidyl ether, "Denacol EX-313" manufactured by Nagase ChemteX, epoxy equivalent 141 g / equivalent, viscosity 150 mPa·s (25°C) Hardening agent or hardening accelerator (B1) for epoxy group-containing compound: Dicyandiamide, "DICY7" manufactured by Mitsubishi Chemical Corporation Hardening agent or hardening accelerator (B2) for epoxy group-containing compound: Alkyl urea-based hardening accelerator, "B-605-IM" manufactured by DIC Corporation Polyhydroxy compound (C1-1): Ethylene oxide adduct of bisphenol A, "Newpol BPE-40" manufactured by Sanyo Chemical Industries, hydroxyl value 276 mgKOH / g, hydroxyl equivalent calculated from hydroxyl value 203 g / equivalent, viscosity 278 mPa·s (60°C) Polyhydroxy compound (C1-2): Propylene oxide adduct of glycerol, "Sunnex GP-600" manufactured by Sanyo Chemical Industries, hydroxyl value 280 mgKOH / g, hydroxyl equivalent calculated from hydroxyl value 200 g / equivalent, viscosity 275 mPa·s (25°C) Polyisocyanate compound (D): A mixture in which a part of diphenylmethane diisocyanate is modified (including a part of a carbodiimide-modified product represented by the following structural formula in addition to diphenylmethane diisocyanate), "Cosmonate LL" manufactured by Mitsui Chemicals SKC Polyurethane, isocyanate group content 29% by mass, viscosity 20 - 60 mPa·s (25°C, catalog value)

[0076]

Chemical formula

[0077] Urethane-forming catalyst: Zinc amine catalyst, "K-KAT XK-614" manufactured by KING INDUSTRIES Water absorbent: Molecular sieve, "Molecular Sieve 4A Powder" manufactured by Union Showa Co., Ltd.

[0078] Viscosity Measurement of the Sclerosing Composition Using a digital viscometer ("VISCO" (registered trademark) manufactured by ATAGO CO., LTD.), the viscosity of each sclerosing composition at 25°C was measured. The viscosity measurement was performed within 10 minutes after the preparation of the sclerosing composition.

[0079] Manufacture of Sheet Molding Compound On the polypropylene film, the sclerosing composition obtained above was applied so that the average coating amount was 0.5 kg / m 2 . Carbon fiber rovings ("T700SC-12000-50C" manufactured by Toray Industries, Inc., number of filaments 12,000) cut to 12.5 mm were scattered from the air so that there was no fiber directionality and the thickness of the resulting sheet molding compound was uniform on the sclerosing composition application surface. The amount of carbon fiber scattered was adjusted so that the carbon fiber content of the resulting sheet molding compound was 50% by mass. Another polypropylene film with the same sclerosing composition as above was prepared, and the carbon fiber was sandwiched between the sclerosing composition application surfaces. This was pressed with a roller, and after impregnating the carbon fiber with the sclerosing composition, it was left standing at a temperature of 40°C for 72 hours to obtain a sheet molding compound with a thickness of 2 mm. The basis weight of the sheet molding compound was 2 kg / m 2 .

[0080] Evaluation of Film Peelability Under the temperature condition of 25°C, the polypropylene film was peeled from the obtained sheet molding compound. The state at the time of peeling was visually confirmed and evaluated according to the following criteria. In addition, the mass (mg / m 2 ) per unit area of the deposit was calculated. A: Can be easily peeled off, and no deposit remains on the polypropylene film B: Some deposits remain on the polypropylene film, but peeling is possible C: Difficult to peel off, and a large amount of deposit remains on the film

[0081] Manufacture of Molded Products Two sheets of the sheet molding compound obtained previously, cut into 260 mm × 260 mm, were stacked and set in the center of a flat mold of 30×30 cm 2 They were molded under the conditions of a mold temperature of 150 °C, a pressing time of 3 minutes, and a pressing pressure of 12 MPa to obtain a flat molded product with a thickness of 2 mm.

[0082] Evaluation of Bending Strength and Bending Modulus of Elasticity of Molded Products Eight evaluation samples of 150 mm × 25 mm were cut out from the molded products obtained previously. Four of the eight samples had the long side in the X-axis direction of the above-mentioned molded product, and the remaining four had the long side in the Y-axis direction of the above-mentioned molded product. A three-point bending test was conducted in accordance with JISK7074, and the bending strength and bending modulus of elasticity were measured. The values were the average values of a total of eight samples. (Evaluation Criteria for Bending Strength) A: 300 MPa or more B: Less than 300 MPa (Evaluation Criteria for Bending Modulus of Elasticity) A: 20 GPa or more B: Less than 20 GPa

[0083] Evaluation of Surface Smoothness of Molded Products The amount of air bubbles on the surface of the molded product obtained previously was counted visually.

[0084] [Table 1]

[0085] [Table 2]

Claims

1. A curable composition containing an epoxy group-containing compound (A), a curing agent or curing accelerator for the epoxy group-containing compound (B) (excluding those falling under component (C)), a polyhydroxy compound (C) (excluding those falling under component (A)), and a polyisocyanate compound (D), wherein the epoxy group-containing compound (A) contains a bisphenol type epoxy resin having an epoxy equivalent in the range of 160 to 260 g / equivalent and 1,4-butanediol diglycidyl ether, and the mass ratio of the two, (the bisphenol type epoxy resin) / (the 1,4-butanediol diglycidyl ether), is in the range of 60 / 40 to 95 / 5, at least 70% by mass of the polyhydroxy compound (C) is an ethylene oxide adduct of bisphenol A (C1-1) or a propylene oxide adduct of glycerol (C1-2), and is a polyhydroxy compound (C1) having a hydroxyl equivalent in the range of 125 to 600 g / equivalent. The curable composition is characterized by this.

2. The curable composition according to Claim 1, wherein the molar number of the isocyanate groups of the polyisocyanate compound (D) with respect to 1 mol of the hydroxyl groups in the polyhydroxy compound (C) is in the range of 0.5 to 3.

0.

3. A fiber-reinforced composite material containing the curable composition according to Claim 1 or 2 and reinforcing fibers.

4. The fiber-reinforced composite material according to Claim 3, wherein the reinforcing fibers are carbon fibers.

5. The fiber-reinforced composite material according to Claim 3, which is a sheet molding compound.

6. The sheet molding compound according to Claim 5, which has carrier films on both the front and back.

7. A molded article of the fiber-reinforced composite material according to Claim 3.

8. A method for manufacturing a molded article, which includes a step of peeling the carrier film from the sheet molding compound according to Claim 6 and a step of molding the sheet molding compound from which the carrier film has been peeled.

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