Epoxy resin composition for sheet molding compound, sheet molding compound, and molded article

Abstract

To provide an epoxy resin composition for a sheet molding compound that is excellent in handleability such as film releasability and tackiness, and from which a molded article excellent in flexural strength and flexural modulus can be obtained, a sheet molding compound, and a molded article of the same.SOLUTION: An epoxy resin composition for a sheet molding compound contains an epoxy resin (A), an epoxy resin (B), polyisocyanate (C), an urethanization catalyst (D) and a curing agent (E) for an epoxy resin, wherein an epoxy equivalent of the epoxy resin (A) is 300-800 g / eq and a hydroxyl value thereof is 85-160 mgKOH / g, and an epoxy equivalent of the epoxy resin (B) is 160-260 g / eq and a hydroxyl group thereof is 80 mgKOH / g or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an epoxy resin composition for a sheet molding compound, a sheet molding compound, and a molded article. [Background technology]

[0002] Fiber-reinforced plastics (FRP), which are thermosetting resins reinforced with fiber reinforcement, are widely used in industrial parts, housing components, automotive components, and other applications. Furthermore, fiber-reinforced resin composites, which use carbon fiber as a fiber reinforcement and reinforce thermosetting resins such as epoxy resins and unsaturated polyester resins, have attracted attention for their lightweight yet excellent heat resistance and mechanical strength, and are increasingly being used in a variety of structural applications. Furthermore, sheet molding compounds (hereinafter sometimes abbreviated as "SMC") are widely used because they use discontinuous fibers as the fiber reinforcement, which allows for a wider range of molding shapes than continuous fibers, allows for the reuse of scrap materials, and allows for the insertion of components made from different materials, thereby improving productivity and design applicability. Currently, SMCs made from unsaturated polyester resins and vinyl ester resins, which are commonly used as thermosetting resins for SMCs, have issues such as volatile organic compound emissions. For this reason, research is underway to develop SMCs using epoxy resins.

[0003] As an SMC containing an epoxy resin as the main component, an epoxy resin composition for sheet molding compounds is known, which is characterized by containing an epoxy resin having an α-glycol group in the range of 0.1 to 1 g / eq, a polyisocyanate, and an epoxy resin curing agent (see, for example, Patent Document 1). However, although this resin composition has excellent moldability, impregnation into fibers is poor, and the mechanical strength of the resulting molded product may be insufficient. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-33511 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide an epoxy resin composition for a sheet molding compound which has excellent handleability such as film peelability and tackiness and which can give molded articles which are excellent in flexural strength and flexural modulus; a sheet molding compound; and a molded article made from the same. [Means for solving the problem]

[0006] The present inventors have discovered that an epoxy resin composition for sheet molding compounds, which contains a specific epoxy resin, polyisocyanate, a urethane-forming catalyst, and an epoxy resin curing agent, can solve the above-mentioned problems, and have completed the present invention.

[0007] Specifically, the present invention relates to an epoxy resin composition for sheet molding compounds, which comprises an epoxy resin (A), an epoxy resin (B), a polyisocyanate (C), a urethane catalyst (D), and an epoxy resin curing agent (E), wherein the epoxy resin (A) has an epoxy equivalent of 300 to 800 g / eq and a hydroxyl value of 85 to 160 mgKOH / g, and the epoxy resin (B) has an epoxy equivalent of 160 to 260 g / eq and a hydroxyl value of 80 mgKOH / g or less, and to a sheet molding compound and a molded article using the same. [Effects of the Invention]

[0008] The sheet molding compound obtained from the epoxy resin composition for sheet molding compounds of the present invention has excellent handleability, and the molded articles obtained have excellent flexural strength and flexural modulus, and therefore can be suitably used for 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, office automation equipment, etc. DETAILED DESCRIPTION OF THE INVENTION

[0009] The epoxy resin composition for sheet molding compounds of the present invention comprises an epoxy resin (A), an epoxy resin (B), a polyisocyanate (C), a urethane catalyst (D), and an epoxy resin curing agent (E), wherein the epoxy resin (A) has an epoxy equivalent of 300 to 800 g / eq and a hydroxyl value of 85 to 160 mgKOH / g, and the epoxy resin (B) has an epoxy equivalent of 160 to 260 g / eq and a hydroxyl value of 80 mgKOH / g or less.

[0010] The epoxy resin composition for sheet molding compounds of the present invention contains epoxy resin (A) and epoxy resin (B) having different epoxy equivalents and hydroxyl values, and therefore an SMC having excellent handleability, excellent impregnation of fiber reinforced materials with the resin composition, and excellent strength of molded products can be obtained.

[0011] The epoxy equivalent of the epoxy resin (A) is 300 to 800 g / eq, and is preferably 350 to 600 g / eq, as this improves the handleability of the SMC and the impregnation of the resin composition into the fiber reinforcement.

[0012] The hydroxyl value of the epoxy resin (A) is 85 to 160 mgKOH / g, and is preferably 88 to 130 mgKOH / g, as this further improves the handleability of the SMC.

[0013] The number average molecular weight of the epoxy resin (A) is preferably 400 to 2,000 g / mol, more preferably 500 to 1,500 g / mol, in order to further improve handling properties and impregnation properties into fiber reinforcement materials.

[0014] The epoxy equivalent of the epoxy resin (B) is 160 to 260 g / eq, and is preferably 160 to 220 g / eq, as this further improves the strength of the molded product.

[0015] The hydroxyl value of the epoxy resin (B) is 80 mgKOH / g or less, and is preferably 75 mgKOH / g or less in order to further improve the impregnation into the fiber reinforcement material.

[0016] The number average molecular weight of the epoxy resin (B) is preferably 100 to 1,000, more preferably 100 to 500, since this improves the impregnation into fiber reinforcement materials and the strength of molded articles.

[0017] Examples of the epoxy resin (A) and the epoxy resin (B) include bisphenol type epoxy resins such as bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol fluorene type epoxy resins, and biscresol fluorene type epoxy resins, novolac type epoxy resins such as phenol novolac type epoxy resins and cresol novolac type epoxy resins, oxazolidone-modified epoxy resins, and brominated epoxy resins of these resins, such as glycidyl ethers of phenol, trimethylolpropane triglycidyl ether, and alkylene ethers of bisphenol A. Examples of suitable epoxy resins include diglycidyl ethers of oxide adducts, glycidyl ethers of polyhydric alcohols such as diglycidyl ether of hydrogenated bisphenol A, alicyclic epoxy resins, glycidyl esters such as phthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, diglycidyl-p-oxybenzoic acid, and dimer acid glycidyl ester, glycidyl amines such as tetraglycidyldiaminodiphenylmethane, triglycidyl-p-aminophenol, and N,N-diglycidylaniline, and heterocyclic epoxy resins such as triglycidyl isocyanurate. Among these, aromatic epoxy resins are preferred because of their superior molded article strength and fluidity during molding of the molding material, with bifunctional aromatic epoxy resins being more preferred, and bisphenol A epoxy resins and bisphenol F epoxy resins being particularly preferred. These epoxy resins can be used alone or in combination of two or more.

[0018] In the epoxy resin composition of the present invention, it is preferable to use an epoxy diluent in addition to the epoxy resin (A) and the epoxy resin (B) in order to facilitate viscosity adjustment.

[0019] As the epoxy diluent, glycidyl ethers obtained by reacting various phenols or alcohols with epihalohydrin, or various commercially available products can be used.

[0020] Examples of the epoxy diluent include phenyl glycidyl ether, alcohol glycidyl ether, alkyl glycidyl ether, alkyl glycidyl ester, α-olefin epoxide, alkylphenyl glycidyl ether, alkylphenol glycidyl ether, etc. Here, the alkyl group is preferably a linear or branched alkyl group having 1 to 20 carbon atoms.

[0021] Among these, it is preferable to use phenyl glycidyl ether, alcohol glycidyl ether, alkylphenyl glycidyl ether, and butanediol diglycidyl ether, since they have a lower viscosity and the viscosity of the composition can be easily adjusted.

[0022] The viscosity of the epoxy diluent is preferably 1 to 1,000 mPa·s, and more preferably 1 to 500 mPa·s, since this further improves the fiber impregnation ability of the epoxy resin composition.

[0023] The amount of the epoxy diluent used is preferably 5 to 200 parts by mass, more preferably 5 to 80 parts by mass, per 100 parts by mass of the epoxy resin (A) and the epoxy resin (B) in total, since this further improves the fiber impregnation ability of the epoxy resin composition.

[0024] The polyisocyanate (C) reacts with the hydroxyl groups of the epoxy resin and acts as a thickener. Examples of the polyisocyanate (C) include diphenylmethane diisocyanate (4,4'-, 2,4'-, or 2,2'-isomer, or a mixture thereof), carbodiimide-modified diphenylmethane diisocyanate, nurate-modified diphenylmethane diisocyanate, biuret-modified diphenylmethane diisocyanate, urethaneimine-modified diphenylmethane diisocyanate, and other diphenylmethane diisocyanate-modified polyols modified with polyols having a number average molecular weight of 1,000 or less, such as diethylene glycol and dipropylene glycol, tolylene diisocyanate, and tolidine diisocyanate. Examples of suitable polyisocyanates include aromatic polyisocyanates such as isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, and norbornene diisocyanate; and aliphatic polyisocyanates such as hexamethylene diisocyanate, nurate-modified hexamethylene diisocyanate, biuret-modified hexamethylene diisocyanate, and adducts thereof, as well as dimer acid diisocyanates. Among these, aromatic polyisocyanates are preferred because they provide molding materials with excellent handleability (film peelability and tackiness) and glass transition temperatures, and carbodiimide-modified diphenylmethane diisocyanate and polymethylene polyphenyl polyisocyanate are more preferred. The carbodiimide-modified diphenylmethane diisocyanate includes not only those having a carbodiimide group but also those having a urethane imine structure in which an isocyanate group is further added to the carbodiimide group. These polyisocyanates (C) can be used alone or in combination of two or more. Furthermore, they can be used in combination with a polyol to react with the hydroxyl groups of the polyol.

[0025] The viscosity of the polyisocyanate (C) is preferably 1 to 1,000 mPa·s, more preferably 1 to 500 mPa·s, since it has an effect as a diluent and improves impregnation properties.

[0026] The molar ratio (NCO / OH) of the isocyanate groups (NCO) of the polyisocyanate (C) to the hydroxyl groups (OH) of the epoxy resin (A) is preferably 0.4 to 2, more preferably 0.6 to 1.5, since this further improves the handleability of the sheet molding compound and the strength of the molded product.

[0027] The urethane catalyst (D) promotes the urethane reaction between the hydroxyl groups of the epoxy resin (A) and the isocyanate groups of the polyisocyanate (C).

[0028] Examples of the urethanization catalyst (D) 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. However, organic zinc compounds and organic bismuth compounds are preferred because of their superior safety to living organisms and storage stability.

[0029] The urethane catalyst (D) promotes the urethane reaction between the hydroxyl groups of the epoxy resin (A) and the isocyanate groups of the polyisocyanate (C). In order to further improve the balance between impregnation and handling properties, the urethane catalyst (D) is preferably added in an amount of 0.002 to 1 part by mass, more preferably 0.01 to 0.8 parts by mass, per 100 parts by mass of the epoxy resin (A) and the epoxy resin (B) in total.

[0030] In order to control the urethane reaction and achieve more appropriate viscosity increase, dehydrating agents such as silica gel, activated alumina, molecular sieves, etc. Among these, molecular sieves are preferred because they have a narrow pore size distribution that contributes to dehydration and can selectively adsorb moisture, and their pore size is preferably 0.1 to 0.5 nm, more preferably 0.2 to 0.4 nm.

[0031] The dehydrating agent preferably has particles of 50 μm or less, more preferably 10 μm or less, in order to provide a molded article with a better appearance and uniform dispersion.

[0032] The amount of the dehydrating agent is preferably 0.5 to 5 parts by mass relative to 100 parts by mass of the total of the epoxy resin (A) and the epoxy resin (B).

[0033] Examples of the epoxy resin curing agent (E) include amine compounds, amide compounds, acid anhydride compounds, and phenol compounds. Examples of amine compounds include diaminodiphenylmethane, diethylenetriamine, triethylenetetramine, diaminodiphenylsulfone, isophoronediamine, imidazole, BF3-amine complex, and guanidine derivatives. Examples of amide compounds include dicyandiamide and polyamide resins synthesized from a dimer of linolenic acid and ethylenediamine. Examples of acid anhydride compounds include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and methylhexahydrophthalic anhydride. Examples of phenol compounds include phenol novolac resin, cresol novolac resin, aromatic hydrocarbon formaldehyde resin-modified phenolic resin, dicyclopentadiene phenol addition type resin, and phenol aralkyl resin (Xyloc resin). ), polyhydric phenol novolac resins synthesized from polyhydric hydroxy compounds such as resorcinol novolac resins and formaldehyde, naphthol aralkyl resins, trimethylolmethane resins, tetraphenylolethane resins, naphthol novolac resins, naphthol-phenol co-condensed novolac resins, naphthol-cresol co-condensed novolac resins, biphenyl-modified phenolic resins (polyhydric phenol compounds in which phenol nuclei are linked by bismethylene groups), biphenyl-modified naphthol resins (polyhydric naphthol compounds in which phenol nuclei are linked by bismethylene groups), aminotriazine-modified phenolic resins (polyhydric phenol compounds in which phenol nuclei are linked by melamine, benzoguanamine, etc.), and alkoxy group-containing aromatic ring-modified novolac resins (polyhydric phenol compounds in which phenol nuclei and alkoxy group-containing aromatic rings are linked by formaldehyde). These epoxy resin curing agents (E) can be used alone or in combination of two or more.

[0034] Among these, amide compounds and amine compounds are preferred because they have high curability and excellent rapid curing properties, and dicyandiamide and imidazole are more preferred.

[0035] The amount of the epoxy resin curing agent (E) is preferably 1 to 40 parts by mass, more preferably 3 to 20 parts by mass, per 100 parts by mass of the epoxy resin.

[0036] The use of an epoxy resin curing accelerator can accelerate the reaction of the epoxy resin, and urea compounds are preferred in terms of improving the mechanical properties of the molded product, while imidazole compounds are preferred in terms of improving the thermal properties (heat resistance) of the fiber-reinforced composite material. These epoxy resin curing accelerators can be used alone or in combination of two or more.

[0037] Examples of the urea compound include 3-phenyl-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea, 2,4-bis(3,3-dimethylureido)toluene, 1,1'-(4-methyl-1,3-phenylene)bis(3,3-dimethylurea), etc. These urea compounds can be used alone or in combination of two or more.

[0038] Examples of the imidazole compound include imidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, etc. These imidazole compounds can be used alone or in combination of two or more.

[0039] The amount of the epoxy resin curing accelerator is preferably 1 to 40 parts by mass relative to 100 parts by mass of the epoxy resin.

[0040] The viscosity of the epoxy resin composition of the present invention is preferably 1000 to 40,000 mPa·s, and more preferably 1500 to 35,000 mPa·s at 25° C., as this further improves handling properties and impregnation into fiber reinforcement materials.

[0041] The SMC of the present invention contains the above-mentioned epoxy resin composition for an SMC and a fiber reinforcement (F) as essential components, and is excellent in productivity, has versatility in design and in joining different materials, and is excellent in moldability.

[0042] The fiber reinforcement (F) is used in the form of fibers cut to a length of 2.5 to 50 mm, but fibers cut to a length of 5 to 40 mm are more preferred because this improves the flowability in the mold during molding, the appearance of the molded product, and the mechanical properties.

[0043] Examples of the fiber reinforcing material (F) include glass fiber, carbon fiber, silicon carbide fiber, pulp, hemp, cotton, nylon, polyester, acrylic, polyurethane, polyimide, and polyamide fibers made of aramids such as Kevlar and Nomex, etc. Among these, carbon fiber is preferred because it can give a molded product with high strength.

[0044] As the carbon fiber, various types such as polyacrylonitrile, pitch, and rayon can be used, but among these, polyacrylonitrile-based fibers are preferred because high-strength carbon fibers can be easily obtained.

[0045] The number of filaments in the fiber bundle used as the carbon fiber is preferably 1,000 to 60,000, as this further improves resin impregnation and the mechanical properties of the molded product.

[0046] The content of the fiber reinforcing material (F) in the components of the SMC of the present invention is preferably 25 to 80 mass%, more preferably 40 to 70 mass%, and particularly preferably 45 to 65 mass%, because the mechanical properties of the resulting molded article are further improved. If the fiber content is too low, a high-strength molded article may not be obtained, whereas if the carbon fiber content is too high, resin impregnation into the fibers may be insufficient, causing blistering in the molded article and preventing a high-strength molded article from being obtained.

[0047] Furthermore, the carbon fibers in the SMC of the present invention are impregnated with the resin in a state where the fiber directions are random.

[0048] Components other than the epoxy resin composition for an SMC and the fiber reinforcement (F) described above may be used as components of the SMC of the present invention. For example, the SMC may contain thermosetting resins other than the above-mentioned epoxy resins, thermoplastic resins, polymerization inhibitors, curing accelerators, fillers, low-shrinkage agents, mold release agents, thickeners, viscosity reducers, pigments, antioxidants, plasticizers, flame retardants, antibacterial agents, UV stabilizers, storage stabilizers, reinforcing materials, photocuring agents, etc.

[0049] Examples of the thermosetting resin include vinyl ester resin, vinyl urethane resin, unsaturated polyester resin, acrylic resin, phenol resin, melamine resin, furan resin, etc. These thermosetting resins can be used alone or in combination of two or more.

[0050] Examples of the thermoplastic resin include polyamide resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polycarbonate resin, urethane resin, polypropylene resin, polyethylene resin, polystyrene resin, acrylic resin, polybutadiene resin, polyisoprene resin, and those modified by copolymerization, etc. These thermoplastic resins can be used alone or in combination of two or more.

[0051] The fillers include inorganic compounds and organic compounds, and can be used to adjust the physical properties of the molded product, such as strength, elastic modulus, impact strength, and fatigue durability.

[0052] Examples of the inorganic compound include calcium carbonate, magnesium carbonate, barium sulfate, mica, talc, kaolin, clay, celite, asbestos, barite, baryta, silica, silica sand, dolomite limestone, gypsum, aluminum fine powder, hollow balloons, alumina, glass powder, aluminum hydroxide, kansuiite, zirconium oxide, antimony trioxide, titanium oxide, molybdenum dioxide, and iron powder.

[0053] Examples of the organic compounds include powders of natural polysaccharides such as cellulose and chitin, and synthetic resin powders. Examples of synthetic resin powders include organic powders composed of hard resins, soft rubbers, elastomers, or polymers (copolymers), and particles with multilayer structures such as core-shell structures. Specific examples include particles composed of butadiene rubber and / or acrylic rubber, urethane rubber, silicone rubber, polyimide resin powder, fluororesin powder, and phenolic resin powder. These fillers can be used alone or in combination of two or more.

[0054] Examples of the release agent include zinc stearate, calcium stearate, paraffin wax, polyethylene wax, carnauba wax, and fluorine-based compounds. Fluorine compounds and paraffin wax are preferred. These release agents can be used alone or in combination of two or more.

[0055] Examples of the thickener include metal oxides and hydroxides such as magnesium oxide, magnesium hydroxide, calcium oxide, and calcium hydroxide, and acrylic resin-based fine particles, and can be appropriately selected depending on the handleability of the fiber-reinforced molding material of the present invention. These thickeners can be used alone or in combination of two or more.

[0056] The SMC of the present invention can be produced by mixing and dispersing the components (e.g., epoxy resin (A), epoxy resin (B), polyisocyanate (C), urethane catalyst (D), and epoxy resin curing agent (E)) using a mixer such as a conventional mixer, intermixer, planetary mixer, roll mill, kneader, or extruder. The resulting resin composition is then uniformly coated onto upper and lower carrier films. The fiber reinforcement (F) is sandwiched between the resin composition on the upper and lower carrier films. The entire assembly is then passed through impregnation rolls to apply pressure to impregnate the fiber reinforcement (F) with the resin composition, followed by winding into a roll or zigzag folding. Furthermore, the resulting mixture is preferably aged at room temperature or at a temperature of 20 to 60°C to thicken it. Examples of suitable carrier films include polyethylene film, polypropylene film, polyethylene-polypropylene laminate film, polyethylene terephthalate, and nylon.

[0057] The molded article of the present invention can be obtained from the SMC, and from the viewpoints of excellent productivity and design versatility, heat compression molding is the preferred molding method.

[0058] The heat compression molding method may involve, for example, weighing a predetermined amount of the SMC, placing it in a mold preheated to 110-180°C, clamping the mold with a compression molding machine, shaping the molding material, maintaining a molding pressure of 0.1-30 MPa to cure the molding material, and then removing the molded product to obtain a molded article. Specific molding conditions are preferably a mold temperature of 120-160°C and a molding pressure of 1-10 MPa maintained for 1-2 minutes per mm of molded article thickness; more preferably, a mold temperature of 140-160°C and a molding pressure of 1-10 MPa maintained for 30-90 seconds per mm of molded article thickness, as this further improves productivity.

[0059] The SMC of the present invention is excellent in productivity, moldability, etc., and the molded articles obtained can be suitably used for automobile parts, railway vehicle parts, aerospace aircraft parts, ship parts, housing equipment parts, sports parts, light vehicle parts, construction and civil engineering parts, housings for office automation equipment, etc. [Example]

[0060] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0061] Example 1 Epoxy resin (A-1) (DIC Corporation "Epicron 1055", bisphenol A type epoxy resin, epoxy equivalent 450 g / eq, hydroxyl value 125 mg KOH / g) 20 parts by mass, epoxy resin (B-1) (DIC Corporation "Epicron 840", bisphenol A type epoxy resin, epoxy equivalent 180 g / eq, hydroxyl value 15 mg KOH / g) 80 parts by mass, epoxy diluent (ANHUI XINYUAN 10 parts by mass of "XY-622" manufactured by Mitsui Chemicals SKC Polyurethanes Co., Ltd., 1,4-butanediol diglycidyl ether, epoxy equivalent: 131 g / eq), 8 parts by mass of polyisocyanate (C-1) ("Cosmonate LL" manufactured by Mitsui Chemicals SKC Polyurethanes, a carbodiimide-modified diphenylmethane diisocyanate), 10 parts by mass of epoxy resin curing agent (E-1) ("DICY7" manufactured by Mitsubishi Chemical Corporation, dicyandiamide), 2 parts by mass of epoxy resin curing accelerator ("B-605-IM" manufactured by DIC Corporation, alkyl urea type), 0.05 parts by mass of urethanization catalyst (D-1) ("K-KAT 348" manufactured by KING INDUSTRIES, bismuth carboxylate), and 2 parts by mass of dehydrating agent ("Molecular Sieve 4A Powder" manufactured by Union Showa Co., Ltd., molecular sieve) were mixed using a triple roll mill to obtain epoxy resin composition (1) for SMC.

[0062] [Preparation of SMC] The epoxy resin composition (1) for SMC obtained above was applied to a polyethylene and polypropylene laminate film in an average amount of 860 g / m 2On top of this, carbon fibers cut into 12.5 mm lengths from carbon fiber roving ("T700SC-12000-50C" manufactured by Toray Industries, Inc.) were uniformly dropped from the air so that the fibers had no fiber orientation, were uniform in thickness, and had a carbon fiber content of 57% by mass. The carbon fibers were then sandwiched between laminate films similarly coated with the epoxy resin composition (1) for SMC, allowing the resin to be impregnated into the carbon fibers. The resulting material was then packaged in an aluminum-deposited film and allowed to stand at 40°C for 48 hours to obtain SMC (1). The weight of this SMC was 2 kg / m 2 It was.

[0063] [Evaluation of handling (film peelability)] The SMC (1) obtained above was checked for releasability when peeled from a polypropylene film at 25°C, and evaluated according to the following criteria. ○: The molding material is not sticky and no deposits remain on the film. △: The molding material is sticky and some of the material remains on the film. ×: The molding material and the film are in close contact with each other, and a large amount of deposits remain on the film.

[0064] [Evaluation of handling (tackiness)] The SMC (1) obtained above was peeled off from the polypropylene film at 25°C, and the tackiness was evaluated according to the following criteria. ○: No molding material adhered to fingers. △: A small amount of molding material adhered to the fingers. ×: Molding material was stuck to the fingers.

[0065] [Production of molded products] The SMC (1) obtained above was peeled off from the film and cut into 260 mm x 260 mm pieces. Two pieces were stacked together to form a 30 x 30 cm 2 The mixture was placed in the center of a flat mold and molded at a mold temperature of 160°C for 5 minutes under a pressure of 12 MPa to obtain a flat molded product (1) having a thickness of 2 mm.

[0066] [Bending strength evaluation] Four samples were cut out from the molded product (1) obtained above in the horizontal direction and four samples were cut out from the molded product (1) in the vertical direction. The samples were subjected to a three-point bending test in accordance with JIS K7074 and the bending strength was evaluated according to the following criteria. ○:280MPa or more ×: Less than 280 MPa

[0067] [Evaluation of flexural modulus] Four samples were cut out from the molded article (1) obtained above in the horizontal direction and four samples were cut out from the molded article (1) in the vertical direction. The samples were subjected to a three-point bending test in accordance with JIS K7074 and evaluated for their bending modulus according to the following criteria. ○: 18GPa or more ×: Less than 18 GPa

[0068] Examples 2 to 5 Epoxy resin compositions for SMC (2) to (5), SMC (2) to (5), and molded articles (2) to (5) were obtained in the same manner as in Example 1, except that the compositions were as shown in Table 1, and then each evaluation was performed.

[0069] (Comparative Examples 1 to 3) Epoxy resin compositions for SMC (R1) to (R3), SMC (R1) to (R3), and molded articles (R1) to (R3) were obtained in the same manner as in Example 1, except that the compositions shown in Table 2 were used, and then each evaluation was carried out.

[0070] [Table 1]

[0071] [Table 2]

[0072] The abbreviations in the table are as follows: Epoxy resin (B-2): DIC Corporation's "Epicron 860", bisphenol A type epoxy resin, epoxy equivalent 235g / eq, hydroxyl value 55mgKOH / g Polyisocyanate (C-2): BASF INOAC Polyurethanes "Lupranate MI", liquid monomeric diphenylmethane diisocyanate Urethane catalyst (D-2): KING INDUSTRIES "K-KAT XK-614", zinc amine catalyst Epoxy resin (RA-1): DIC Corporation's "Epicron 4050", bisphenol A type epoxy resin, epoxy equivalent 950g / eq, hydroxyl value 160mgKOH / g

[0073] It was confirmed that the epoxy resin compositions for SMC of the present invention in Examples 1 to 5 were excellent in handling such as film peelability and tackiness, and could give molded articles excellent in flexural strength and flexural modulus.

[0074] On the other hand, Comparative Example 1 is an example in which an epoxy resin with a large epoxy equivalent was used instead of the epoxy resin (A) of the present invention, but the viscosity became high, the impregnation ability was poor, and the flexural strength and flexural modulus of the molded product were insufficient.

[0075] In Comparative Example 2, the epoxy resin (A), an essential component of the present invention, was not used, and only the epoxy resin (B) was used. However, the viscosity did not increase after impregnation with the fiber reinforcement, and the film peelability and tackiness were insufficient. Furthermore, the resin and the fiber separated during molding, and no molded product was obtained.

[0076] Comparative Example 3 is an example in which the urethane catalyst (D), an essential component of the present invention, was not used, and a sufficient thickening effect was not obtained after impregnation of the fiber reinforcement, and the film peelability and tackiness were insufficient.

Claims

1. 1. An epoxy resin composition for use in a sheet molding compound, comprising an epoxy resin (A), an epoxy resin (B), a polyisocyanate (C), a urethanization catalyst (D), and an epoxy resin curing agent (E), wherein the epoxy resin (A) has an epoxy equivalent of 300 to 800 g / eq and a hydroxyl value of 85 to 160 mgKOH / g, and the epoxy resin (B) has an epoxy equivalent of 160 to 260 g / eq and a hydroxyl value of 80 mgKOH / g or less.

2. 2. The epoxy resin composition for sheet molding compounds according to claim 1, wherein the content of the urethanization catalyst (D) is 0.002 to 1 part by mass per 100 parts by mass of the epoxy resin (A) and the epoxy resin (B) combined.

3. A sheet molding compound comprising the epoxy resin composition for sheet molding compounds according to claim 1 or 2 and a fiber reinforcing material (F).

4. A molded article made from the sheet molding compound of claim 3.

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