Curable 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

Curable compositions, fiber composites, sheet molding compounds, and molded articles

[0001] The present invention relates to a curable composition that produces a high-strength cured product and is suitable for use in fiber composite materials, a fiber composite material using the curable composition, a sheet molding compound that is less sticky and has good film peelability, and a molded article that has excellent surface smoothness.

[0002] CFRP, a thermosetting resin reinforced with carbon fiber, has attracted attention for its lightweight yet excellent heat resistance and mechanical strength, and its use is expanding in a variety of applications, including automobiles, aircraft, and industrial parts. In particular, sheet molding compounds (hereinafter sometimes abbreviated as "SMC") using discontinuous carbon fibers as the carbon fiber can be molded into more complex shapes than those using continuous carbon fiber. They also have advantages in terms of high productivity and a wide range of design applications, such as the ability to reuse scrap and insert components made of different materials. Traditionally, unsaturated polyester resins and vinyl ester resins have been widely used as matrix resins for sheet molding compounds. However, the presence of volatile components such as styrene has raised concerns about the safety of the working environment and environmental impact, and the use of epoxy resins as an alternative to these resin materials has recently been considered.

[0003] Known sheet molding compounds using epoxy resins include those that use a resin composition as the matrix resin, which contains an epoxy resin and its curing agent, a polyisocyanate compound, and a polyol with a hydroxyl group equivalent of 20 or more and 120 or less (see, for example, Patent Document 1). The sheet molding compound described in Patent Document 1 is characterized by relatively excellent strength of the cured product, but is very sticky, posing a problem in film releasability, and also has poor surface smoothness of the molded product.

[0004] Patent No. 6447791

[0005] Therefore, the problem to be solved by the present invention is to provide a curable composition which produces a high-strength cured product and can be suitably used for fiber composite materials, a fiber composite material using the curable composition, a sheet molding compound which is less sticky and has good film peelability, and a molded product which has excellent surface smoothness.

[0006] As a result of extensive research, 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 group equivalent in the range of 125 to 600 g / equivalent, as essential components, gives a cured product with high strength and can be suitably used for fiber composite materials, and that a sheet molding compound using the same has little stickiness and good film peelability, resulting in excellent workability, and further that the molded product has excellent surface smoothness, thereby completing the present invention.

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

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

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

[0010] The present invention further relates to (IV) the curable composition according to any one of (I) to (III), wherein 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 (V) the curable composition according to any one of (I) to (IV), wherein the epoxy group-containing compound (A) comprises a bisphenol epoxy resin (A1) having an epoxy equivalent in the range of 160 to 260 g / equivalent and a polyglycidyl ether of an aliphatic polyol having 2 to 6 carbon atoms (A2), and the mass ratio between the two, (A1) / (A2), is in the range of 60 / 40 to 95 / 5.

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

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

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

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

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

[0017] The present invention further relates to a method for producing a molded article, comprising the steps of (XI) peeling a carrier film from a sheet molding compound having a carrier film on its back side, and 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 which produces a high-strength cured product and is suitable for use in fiber composite materials, a fiber composite material using the curable composition, a sheet molding compound which is less sticky and has good film peelability, and a molded article which has excellent surface smoothness. The sheet molding compound and molded article of the present invention can be suitably used in a variety of applications, such as exteriors and structures of automobile parts, railway vehicle parts, aerospace aircraft parts, ship parts, housing equipment parts, sports parts, light vehicle parts, building and civil engineering parts, and office automation equipment.

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

[0020] The epoxy group-containing compound (A) may have a wide variety of structures without any particular limitations, as long as it has an epoxy group in its molecular structure. The epoxy group-containing compound (A) may be used alone or in combination of two or more. The epoxy group-containing compound (A) may also have a functional group other than an epoxy group. Among these, compounds having two or more epoxy groups in their molecular structure are preferred, as they result in curable compositions with excellent curing reaction. The proportion of compounds having two or more epoxy groups in their molecular structure in the entire epoxy group-containing compound (A) is preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0021] Examples of the epoxy group-containing compound (A) include diglycidyloxybenzene, diglycidyloxynaphthalene, biphenol-type epoxy resins, bisphenol-type epoxy resins, polyglycidyl ethers of aliphatic polyols, novolac-type epoxy resins, alicyclic epoxy resins, glycidylamine-type epoxy resins, heterocyclic epoxy resins, glycidyl ester-type epoxy resins, triphenolmethane-type epoxy resins, phenol or naphthol aralkyl-type epoxy resins, phenylene or naphthylene ether-type epoxy resins, oxolidone-modified epoxy resins, brominated epoxy resins thereof, and epoxy resins obtained by elongating these epoxy group-containing compounds with an elongator.

[0022] Examples of the biphenol-type epoxy resin include biphenol compounds such as biphenol and tetramethylbiphenol, and polyglycidyl ethers of one or more alkylene oxide adducts of these biphenol compounds with epihalohydrin.

[0023] Examples of the bisphenol type epoxy resin include bisphenol compounds such as bisphenol A, bisphenol F, bisphenol S, bisphenol fluorene, and biscresol fluorene, and polyglycidyl ethers of one or more alkylene oxide adducts of these bisphenol compounds with epihalohydrin.

[0024] Examples of the polyglycidyl ether of an aliphatic polyol include polyglycidyl ethers of one or more of various aliphatic polyol compounds and their alkylene oxide adducts with epihalohydrin. Examples of the aliphatic polyol compound include 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, Examples include aliphatic diol compounds such as 6-hexanediol, 1,4-bis(hydroxymethyl)cyclohexane, and 2,2,4-trimethyl-1,3-pentanediol; alicyclic diol compounds such as 2,2-bis(4-hydroxyphenyl)propane; and tri- or higher functional aliphatic polyol compounds such as trimethylolethane, trimethylolpropane, glycerin, hexanetriol, pentaerythritol, ditrimethylolpropane, and dipentaerythritol.

[0025] Examples of the novolac epoxy resin include polyglycidyl etherified novolac resins made of one or more phenolic compounds such as phenol, dihydroxybenzene, cresol, xylenol, naphthol, dihydroxynaphthalene, bisphenol, and biphenol with epihalohydrin.

[0026] Examples of the alicyclic epoxy resin include those obtained by hydrogenating the biphenol compounds or bisphenol compounds, and those obtained by polyglycidyl etherifying one or more of their alkylene oxide adducts with epihalohydrin, as well as 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate and 1-epoxyethyl-3,4-epoxycyclohexane.

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

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

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

[0030] Examples of extenders for epoxy resins include the above-mentioned various biphenol compounds and hydrogenated products thereof, the above-mentioned various bisphenol compounds and hydrogenated products thereof, dibasic acid compounds, and acid group-containing polyester resins.

[0031] Among these, the bisphenol-type epoxy resins are preferred because they provide excellent strength of the cured product and excellent fiber impregnation when used in a fiber-reinforced composite material, and bisphenol-type epoxy resins having an epoxy equivalent ranging from 160 to 260 g / equivalent are more preferred. The proportion of the bisphenol-type epoxy resin in the entire 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. Furthermore, it is preferably 95% by mass or less, and more preferably 90% by mass or less.

[0032] Furthermore, in terms of achieving even better fiber impregnation when used in a fiber-reinforced composite material, polyglycidyl ethers of the above-mentioned aliphatic polyols are preferred, and polyglycidyl ethers of aliphatic polyols having 2 to 6 carbon atoms are more preferred. The proportion of the bisphenol-type epoxy resin in the entire epoxy group-containing compound (A) is preferably 5% by mass or more, more preferably 10% by mass or more. Furthermore, it is preferably 50% by mass or less, more preferably 35% by mass or less.

[0033] When the bisphenol epoxy resin and the polyglycidyl ether of an aliphatic polyol are used in combination, the mass ratio of the two (bisphenol epoxy resin) / (polyglycidyl ether of an 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] The curing agent or curing accelerator (B) for epoxy group-containing compounds can be any of various compounds commonly used as curing agents or curing accelerators for epoxy group-containing compounds, without any particular limitation. 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 compounds, organic acid metal salts, Lewis acids, and amine complex salts.

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

[0037] Examples of the amide compound include dicyandiamide and polyamidoamine, etc. Examples of the polyamidoamine include those obtained by reacting an aliphatic dicarboxylic acid such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, or azelaic acid, or a carboxylic acid compound such as a fatty acid or dimer acid, with an aliphatic polyamine or a polyamine having a polyoxyalkylene chain.

[0038] Examples of the acid anhydride include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and methylhexahydrophthalic anhydride.

[0039] Examples of the phenolic hydroxyl group-containing resin include 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, and aminotriazine-modified phenol resins.

[0040] Examples of the phosphorus compound include alkyl phosphines such as ethylphosphine and butylphosphine, primary phosphines such as phenylphosphine, dialkyl phosphines such as dimethylphosphine and dipropylphosphine, secondary phosphines such as diphenylphosphine and methylethylphosphine, and tertiary phosphines such as trimethylphosphine, triethylphosphine and triphenylphosphine.

[0041] Examples of the imidazole compound include 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, 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 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 socyanuric acid adduct, 2-methylimidazole isocyanuric acid 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, and the like.

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

[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, and 4,4'-methylenebisphenyldimethylurea.

[0044] Among these, amine compounds, amide compounds, imidazole compounds, and urea compounds are preferred because they cure quickly and have excellent strength in the cured product.

[0045] When a compound having a functional group reactive with an epoxy group, such as an amine compound, an amide compound, an acid anhydride, or a phenolic hydroxyl group-containing compound, is used, the amount of the curing agent or curing accelerator in the epoxy resin composition is preferably in a range of 0.5 to 1.2 moles of functional group or active hydrogen per mole of epoxy group in the epoxy group-containing compound (A). When a phosphorus compound, an imidazole compound, an imidazoline compound, or a urea-based compound is used, the amount of the curing agent or curing accelerator is preferably in a range 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)) essentially comprises a polyhydroxy compound (C1) having a hydroxyl equivalent in the range of 125 to 600 g / equivalent, and 70 mass% or more of the polyhydroxy compound (C) is the polyhydroxy compound (C1). By satisfying these conditions, a curable composition is obtained that not only has excellent strength in the cured product, but also has excellent fiber impregnation properties when used in a fiber-reinforced composite material, excellent film peelability when used as a sheet molding compound, and excellent surface smoothness of molded products. Furthermore, the proportion of the polyhydroxy compound (C1) in the polyhydroxy compound (C) is preferably 80 mass% or more, and more preferably 90 mass% or more.

[0047] The polyhydroxy compound (C1) may have a molecular structure containing multiple hydroxyl groups and a hydroxyl group equivalent weight in the range of 125 to 600 g / equivalent, and a wide variety of compounds may be used without any particular limitations on their specific structure. The polyhydroxy compound (C) may be the polyhydroxy compound (C1) alone or in combination with two or more other compounds. In the present invention, polyhydroxy compounds containing epoxy groups are considered to be 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 resins, phenylene or naphthylene ether resins, and alkylene oxide adducts thereof.

[0049] Examples of the aliphatic polyol compound include 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 aliphatic diol compounds such as 2,2-bis(4-hydroxyphenyl)propane; and trifunctional or higher aliphatic polyol compounds such as trimethylolethane, trimethylolpropane, glycerin, hexanetriol, pentaerythritol, ditrimethylolpropane, and dipentaerythritol.

[0050] Examples of the biphenol compound include biphenol and tetramethylbiphenol.

[0051] Examples of the bisphenol compound include bisphenol A, bisphenol F, bisphenol S, bisphenol fluorene, and biscresol fluorene.

[0052] Examples of the alicyclic polyol compound include cyclohexanediol and hydrogenated compounds of the biphenol compounds and bisphenol compounds.

[0053] Examples of the novolac resin include novolac resins made of one or more of various phenolic compounds such as phenol, dihydroxybenzene, cresol, xylenol, naphthol, dihydroxynaphthalene, bisphenol, and biphenol.

[0054] Among these, the polyhydroxy compound (C1) having a hydroxyl group equivalent in the range of 125 to 600 g / equivalent is preferably an alkylene oxide adduct of various polyhydroxy compounds, since this results in a curable composition that is 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. That is, one having a (poly)alkylene oxide structure in its molecular structure is preferred. Furthermore, alkylene oxide adducts of the aliphatic polyol compounds or the bisphenol compounds are more preferred, and the aliphatic polyol compounds are more preferably those having 2 to 6 carbon atoms. Furthermore, the hydroxyl group 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, and a wide variety of compounds can be used as long as it has a plurality of isocyanate groups in its molecular structure. One type of polyisocyanate compound (D) may be used alone, or two or more types may be used in combination. Specific examples include aliphatic diisocyanate compounds such as butane diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and dimer acid diisocyanate; alicyclic diisocyanate compounds such as norbornane diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, and hydrogenated diphenylmethane diisocyanate; toluene diisocyanate, and xylylene diisocyanate. aromatic diisocyanate compounds such as tetramethylxylylene diisocyanate, tolidine diisocyanate, diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, and polymethylene polyphenyl polyisocyanate; modified products of these isocyanate compounds, such as isocyanurate modified products, biuret modified products, allophanate modified products, carbodiimide modified products, and urethane imine modified products, and polyol modified products modified with a polyol having a number average molecular weight of 1,000 or less, such as diethylene glycol or dipropylene glycol.

[0056] Among these, aromatic polyisocyanate compounds or their various modifications are preferred because they provide a sheet molding compound with less stickiness and good film peelability. Furthermore, the isocyanate group content is preferably 15% by mass or more, more preferably 20% by mass or more, and is preferably 40% by mass or less.

[0057] In the present invention, the blending ratio of the polyhydroxy compound (C) (excluding those corresponding to the component (A)) and the polyisocyanate compound (D) is optional and is appropriately adjusted depending on the desired performance and intended use of the curable composition, etc.

[0058] A preferred formulation design for the curable composition of the present invention is such that the molar ratio of isocyanate groups in the polyisocyanate compound (D) to 1 mole of hydroxyl groups in the polyhydroxy compound (C) is preferably 0.5 or more, more preferably 0.8 or more, and is preferably 3.0 or less, more preferably 1.5 or less, and particularly preferably 1.2 or less, in order to obtain a sheet molding compound with less stickiness and good film releasability, and further to obtain a molded product with excellent surface smoothness.

[0059] The amount of the polyhydroxy compound (C) to be blended is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and more preferably 50 parts by mass or less, more preferably 30 parts by mass or less, relative to 100 parts by mass of the epoxy group-containing compound (A), in order to obtain a curable composition that is excellent in strength of the cured product, film releasability when used in a sheet molding compound, and surface smoothness of the molded product.

[0060] The curable composition of the present invention may contain a urethanization catalyst as needed. One urethanization catalyst may be used alone, or two or more may be used in combination. Examples of urethanization catalysts include amine compounds such as triethylamine, dibutylamine, triethylenediamine, and pyridine; phosphorus compounds such as triphenylphosphine and triethylphosphine; organic tin compounds such as dibutyltin dilaurate, octyltin trilaurate, octyltin diacetate, dibutyltin diacetate, and tin octylate; organic zinc 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; organic aluminum compounds such as aluminum triethoxide; and organic titanium compounds such as titanium tetrabutylate and titanium ethylacetoacetate. Among these, organic zinc compounds and organic bismuth compounds are preferred because of their superior safety to living organisms and storage stability.

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

[0062] A water-absorbing agent may also be added to control the urethanization reaction in the curable composition. A single water-absorbing agent may be used alone, or two or more may be used in combination. Examples of water-absorbing agents include silica gel, activated alumina, and molecular sieves. Among these, molecular sieves are preferred due to their excellent water absorption efficiency. Their pore diameters are preferably in the range of 0.1 to 0.5 nm, more preferably 0.2 to 0.4 nm. Their particle diameters are preferably 50 μm or less, more preferably 10 μm or less. When using the water-absorbing agent, its amount is preferably in the range of 0.1 to 5 mass% based on the total mass of the epoxy group-containing compound (A), the curing agent or curing accelerator for the epoxy group-containing compound (B), 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 for the epoxy group-containing compound (B), the polyhydroxy compound (C), the polyisocyanate compound (D), the urethane-forming catalyst, and the water-absorbing agent. Examples of other components include thermosetting resins other than the components (A) to (D), thermoplastic resins, inorganic fillers, low-shrinkage agents, mold release agents, thickeners, viscosity reducers, pigments, antioxidants, plasticizers, flame retardants, antibacterial agents, UV stabilizers, and reinforcing materials. These other components are added appropriately depending on the desired performance and application of the curable composition, and the amount added is also optional. In particular, the effects of the present invention are more significantly exhibited when the total mass of the epoxy group-containing compound (A), the curing agent or curing accelerator for the epoxy group-containing compound (B), the polyhydroxy compound (C), and the polyisocyanate compound (D) in the curable composition is preferably 80% by mass or more, and particularly preferably 90% by mass or more.

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

[0065] The curable composition of the present invention is useful as a curable resin material, and the cured product thereof is characterized by excellent heat resistance and strength. It can also be combined with reinforcing fibers to form a fiber-reinforced composite material, and is particularly useful as a matrix resin for sheet molding compounds.

[0066] The reinforcing fibers used in the present invention may be, for example, those commonly used in sheet molding compound applications, and a wide variety of fibers can be used without particular limitation. Specific examples include glass fibers, carbon fibers, silicon carbide fibers, pulp, hemp, cotton, nylon, polyester, acrylic, polyurethane, polyimide, and polyamide fibers made of aramids such as Kevlar (registered trademark) and Nomex. Among these, carbon fibers are preferred because they provide excellent strength and lightweight molded products. Various types of carbon fibers, such as polyacrylonitrile-based, pitch-based, and rayon-based fibers, can be used, with polyacrylonitrile-based fibers being more preferred due to their particularly high strength.

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

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

[0069] The reinforcing fiber content in the fiber-reinforced composite material can be set arbitrarily depending on the desired physical properties of the molded article, the application, etc., but is preferably in the range of 20 to 80 mass%, more preferably in the range of 40 to 70 mass%, in order to obtain a molded article with superior strength.

[0070] The method for producing the sheet molding compound of the present invention is not particularly limited and can be produced by a conventional method. Specifically, the compound can be produced by a method including some or all of the following steps: uniformly mixing the curable composition using a mixer such as a mixer, roll mill, kneader, or extruder; applying the curable composition to a carrier film at a uniform thickness; spraying the reinforcing fibers on the resin surface of the resulting resin-coated carrier film; sandwiching the reinforcing fibers between the resin surfaces of another resin-coated carrier film; applying pressure using an impregnation roll or impregnation belt to impregnate the reinforcing fibers with the curable composition; winding or zigzag the sheet obtained by the impregnation step; and aging the sheet at room temperature or at a temperature of 20 to 60°C. The carrier film can be a conventional film such as a polyethylene film, a polypropylene film, a polyethylene terephthalate film, a nylon film, or a laminate of multiple films.

[0071] The thickness of the sheet molding compound of the present invention can be appropriately set depending on the desired performance and application, but is preferably 1 mm or more, more preferably 1.2 mm or more, and particularly preferably 1.5 mm or more, because this provides excellent moldability and strength of the cured product, etc. 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 molding can be performed using methods similar to those used for general sheet molding compounds. One example is heat compression molding, which can be produced by a method that includes some or all of the following steps: peeling the carrier film from a sheet molding compound having carrier films on both sides; stacking one or more sheets of the sheet molding compound from which the carrier films have been peeled; placing the sheet molding compound in a mold; and molding using a compression molding machine. As described above, the sheet molding compound of the present invention has low stickiness and excellent film peelability, allowing for efficient production of molded articles. The temperature of the mold can be set as desired, but is preferably in the range of 110 to 180°C, and it is preferable to preheat the mold to this temperature. The molding pressure of the compression molding machine can be set as desired, but is preferably in the range of 0.1 to 30 MPa. The molding time can be set as desired, but it is preferable to clamp the mold to shape the curable composition over a period of several tens of seconds to several minutes, while simultaneously curing the curable composition.

[0073] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0074] Examples 1 to 5 and Comparative Examples 1 and 2 Curable compositions, sheet molding compounds, and molded articles were produced as follows, and various evaluation tests were carried out. The blending compositions of the curable compositions and the results of various evaluations are shown in Tables 1 and 2.

[0075] Preparation of Curable Compositions Curable compositions were obtained by mixing the components in the proportions shown in Tables 1 and 2 below. Details of each component in the tables are as follows. Epoxy group-containing compound (A1): bisphenol A type epoxy resin, "Epicron 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 Co., Ltd., 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 Corporation, epoxy equivalent 141 g / equivalent, viscosity 150 mPa·s (25°C) Curing agent or curing accelerator for epoxy group-containing compounds (B1): dicyandiamide, "DICY7" manufactured by Mitsubishi Chemical Corporation Curing agent or curing accelerator for epoxy group-containing compounds (B2): alkylurea-based curing 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, Ltd., hydroxyl value 276 mg KOH / g, hydroxyl equivalent calculated from the hydroxyl value 203 g / equivalent, viscosity 278 mPa·s (60°C). Polyhydroxy compound (C1-2): propylene oxide adduct of glycerol, "Sannyx GP-600" manufactured by Sanyo Chemical Industries, Ltd., hydroxyl value 280 mg KOH / g, hydroxyl equivalent calculated from the hydroxyl value 200 g / equivalent, viscosity 275 mPa·s (25°C). Polyisocyanate compound (D): a mixture of partially modified diphenylmethane diisocyanate (including, in addition to diphenylmethane diisocyanate, a carbodiimide modified product represented by the following structural formula), "Cosmonate LL" manufactured by Mitsui Chemicals SKC Polyurethanes, Inc., isocyanate group content 29% by mass, viscosity 20 to 60 mPa s (25°C, catalog value)

[0076]

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

[0078] Measurement of Viscosity of Curable Composition The viscosity of each curable composition at 25° C. was measured using a digital viscometer (VISCO (registered trademark) manufactured by Atago Co., Ltd.) The viscosity measurement was carried out within 10 minutes after the preparation of the curable composition.

[0079] Preparation of sheet molding compound The curable composition obtained above was applied to a polypropylene film at an average coating amount of 0.5 kg / m ２ The film was coated so that the thickness would be 12.5 mm. Carbon fiber roving ("T700SC-12000-50C" manufactured by Toray Industries, Inc., filament count 12,000) cut to 12.5 mm was sprayed from the air onto the surface coated with the curable composition, so that the fibers had no directionality and the thickness of the resulting sheet molding compound was uniform. The amount of carbon fiber sprayed was adjusted so that the carbon fiber content of the resulting sheet molding compound would be 50 mass%. Another polypropylene film with the same curable composition as above was prepared, and the carbon fiber was sandwiched between the surfaces coated with the curable composition. This was pressed with a roller to impregnate the carbon fiber with the curable composition, and then left to stand 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 It was.

[0080] Evaluation of film peelability The polypropylene film was peeled from the obtained sheet molding compound at a temperature of 25°C. The state of peeling was visually confirmed and evaluated according to the following criteria. The mass of the deposit per unit area (mg / m ２ A: Peeling was easy and no residue remained on the polypropylene film. B: Some residue remained on the polypropylene film, but peeling was possible. C: Peeling was difficult and a large amount of residue remained on the film.

[0081] Manufacturing of molded products Two sheets of the sheet molding compound obtained above, cut into 260 mm x 260 mm pieces, were stacked to make a 30 x 30 cm ２ The mixture was placed in the center of a flat mold of 150°C, pressed for 3 minutes, and pressed under a pressure of 12 MPa to obtain a flat molded product of 2 mm in thickness.

[0082] Evaluation of flexural strength and flexural modulus of molded product Eight evaluation samples measuring 150 mm x 25 mm were cut out from the molded product obtained above. Four of the eight samples had the long side in the X-axis direction of the molded product, and the remaining four had the long side in the Y-axis direction of the molded product. A three-point bending test was conducted in accordance with JIS K7074 to measure the flexural strength and flexural modulus. The values ​​were the average of a total of eight samples. (Evaluation criteria for flexural strength) A: 300 MPa or more B: Less than 300 MPa (Evaluation criteria for flexural modulus) A: 20 GPa or more B: Less than 20 GPa

[0083] Evaluation of surface smoothness of molded article The amount of bubbles on the surface of the molded article obtained above was visually counted.

[0084]

[0085]

Claims

1. A curable composition comprising an epoxy group-containing compound (A), a curing agent or curing accelerator for an epoxy group-containing compound (B), a polyhydroxy compound (C) (excluding those corresponding to component (A)), and a polyisocyanate compound (D), 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; A curable composition, characterized in that 70 mass % or more of the polyhydroxy compound (C) is a polyhydroxy compound (C1) having a hydroxyl group equivalent in the range of 125 to 600 g / equivalent.

2. 2. The curable composition according to claim 1, wherein the number of moles of isocyanate groups in said polyisocyanate compound (D) per mole of hydroxyl groups in said polyhydroxy compound (C) is in the range of 0.5 to 3.

0.

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

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

5. 4. The fiber reinforced composite material of claim 3 which is a sheet molding compound.

6. 6. The sheet molding compound of claim 5 having a carrier film on both sides.

7. A molded article made from the fiber-reinforced composite material according to claim 3.

8. A method for manufacturing a molded product, comprising the steps of peeling the carrier film from the sheet molding compound described in claim 6, and molding the sheet molding compound from which the carrier film has been peeled off.

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