Epoxy resin composition, molding material, and fiber-reinforced composite material

Abstract

The purposes of the present invention are to provide an epoxy resin composition in which an additive contained therein can exhibit its effect efficiently even at high temperatures and to provide a molding material having reduced unevenness in physical property after curing, while enabling the additive to exhibit its effect, and a fiber-reinforced composite material having excellent mechanical properties, while enabling the additive to exhibit its effect.　This epoxy resin composition comprises the following components (A) to (E). The epoxy resin composition, when heated at a hardening temperature for two hours, gives a cured object containing component (B) having a dispersed-state diameter of 0.01-5 μm. Component (A): An epoxy resin having two or more epoxy groups in the molecule and having a viscosity at 25°C of 0.1-1,000 Pa·s Component (B): An additive having a viscosity at 25°C of 0.01-20 Pa·s Component (C): A compound undergoing a thickening reaction with the epoxy resin at a temperature not higher than the hardening temperature Component (D): An epoxy hardener Component (E): Particles for imparting thixotropic properties

Description

Technical Field

[0001] The present invention relates to an epoxy resin composition suitably used for fiber-reinforced composite materials such as aerospace members and automotive members, a molding material using the same, and a fiber-reinforced composite material.

Background Art

[0002] Fiber-reinforced composite materials composed of reinforcing fibers and an epoxy resin composition can be designed to take advantage of the properties of both the reinforcing fibers and the epoxy resin composition, and thus their applications are expanding in fields such as aerospace, automotive, sports, and general industries.

[0003] Fiber-reinforced composite materials are manufactured by methods such as the hand lay-up method, filament winding method, pultrusion method, resin transfer molding (RTM) method, autoclave molding method of prepregs, and press molding method of molding materials for fiber-reinforced composite materials.

[0004] Examples of molding materials for fiber-reinforced composite materials used in the press molding method include prepregs, towpregs, bulk molding compounds (BMC), sheet molding compounds (SMC), etc. These molding materials for fiber-reinforced composite materials are obtained by impregnating reinforcing fibers with an epoxy resin composition.

[0005] As the reinforcing fibers, glass fibers, aramid fibers, carbon fibers, boron fibers, etc. are used. As the matrix resin, either a thermosetting resin or a thermoplastic resin can be used. Among them, thermosetting resins that are easily impregnated into the reinforcing fibers are often used. Examples of thermosetting resins include epoxy resins, unsaturated polyester resins, vinyl ester resins, phenol resins, bismaleimide resins, cyanate resins, etc. Among these, epoxy resins are widely used from the viewpoints of adhesion to reinforcing fibers, dimensional stability, and mechanical properties such as the strength and rigidity of the resulting fiber-reinforced composite material.

[0006] Although epoxy resins may be used as they are, in many cases, various additives are used for the purpose of improving the properties of epoxy resin compositions. For example, consideration has been given to premixing an internal mold release agent in order to improve the mold release property of molded articles.

[0007] Generally, when different components are dispersed in an epoxy resin composition, the interfacial area between the epoxy resin composition and one of the components decreases, and it becomes difficult to exhibit the properties of one of the components, namely the additive here. Further, when the dispersion diameter of the additive increases, unevenness occurs in the dispersion structure, impairing the properties of the epoxy resin composition, such as heat resistance and mechanical properties. That is, the smaller the dispersion diameter, the larger the interfacial area, and the effect of the additive can be efficiently exhibited without impairing the properties of the epoxy resin composition. From such a situation, studies have been conducted on controlling the solubility parameter of the additive as a method for controlling the dispersion diameter of the additive (Patent Document 1).

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] According to the method described in Patent Document 1, it is possible to control the phase separation structure of the additive at room temperature, but there is a problem that the additive effect decreases at high temperatures when the epoxy resin composition reaches the curing reaction. Further, since the solubility parameter is limited, there is a problem that it cannot be widely applied to other additives.

[0010] Thus, in the prior art, there was no technology capable of controlling the phase separation structure of any additive in the high-temperature range. Therefore, an object of the present invention is to provide an epoxy resin composition capable of efficiently expressing the additive effect even at high temperatures. Furthermore, by using such an epoxy resin composition, a molding material with little unevenness in physical properties after curing is provided while expressing the effect of the additive. Furthermore, by using such a molding material, a fiber-reinforced composite material with excellent mechanical properties is provided while expressing the effect of the additive.

Means for Solving the Problems

[0011] To solve such problems, the inventors of the present invention have conducted intensive studies and found that, in the prior art, the reason for the decrease in the additive effect at high temperatures is that the viscosity of the epoxy resin composition significantly decreases at high temperatures and the phase separation structure changes. Then, through further intensive studies, it was found that by suppressing the decrease in the viscosity of the epoxy resin composition at high temperatures with particles that exhibit thixotropy, the epoxy resin composition has a low viscosity, excellent impregnation properties between reinforcing fibers, and suppresses the coarsening of the phase separation structure formed during curing, and thus the additive effect can be efficiently expressed without impairing the properties of the epoxy resin composition. The present invention having the following configuration was completed. That is, the epoxy resin composition of the present invention is an epoxy resin composition containing the following components (A) to (E), and the dispersion diameter of component (B) in the cured product obtained by heat-treating the epoxy resin composition at the curing temperature for 2 hours is 0.01 to 5 μm. Component (A): An epoxy resin having two or more epoxy groups in one molecule and having a viscosity at 25°C of 0.1 to 1000 Pa·s Component (B): An additive having a viscosity at 25°C of 0.01 to 20 Pa·s Component (C): A compound that undergoes a thickening reaction with the epoxy resin at a temperature equal to or lower than the curing temperature Component (D): An epoxy curing agent Component (E): Particles that exhibit thixotropy.

[0012] Further, the molding material of the present invention is composed of the epoxy resin composition of the present invention and reinforcing fibers.

[0013] In addition, the fiber-reinforced composite material of the present invention is formed by molding the molding material of the present invention.

Advantages of the Invention

[0014] The epoxy resin composition of the present invention can efficiently exhibit the additive effect even at high temperatures. The molding material of the present invention has little unevenness in mechanical properties after curing while exhibiting the effect of the additive. The fiber-reinforced composite material of the present invention is excellent in mechanical properties while exhibiting the effect of the additive.

Embodiments for Carrying Out the Invention

[0015] The following describes preferred embodiments of the present invention. First, the epoxy resin composition of the present invention will be described. In the present invention, component (A) is an epoxy resin having two or more epoxy groups and having a viscosity at 25°C of 0.1 to 1000 Pa·s. By including component (A), heat resistance and mechanical properties can be exhibited. Specific examples of component (A) include, as epoxy resins having two epoxy groups, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin, dicyclopentadiene type epoxy resin, and epoxy resins obtained by modifying these. Examples of epoxy resins having three or more epoxy groups include, for example, aliphatic epoxy resins, phenol novolak type epoxy resins, cresol type epoxy resins, cresol novolak type epoxy resins, glycidylamine type epoxy resins such as tetraglycidyl diaminodiphenylmethane, triglycidyl aminophenol, and tetraglycidylamine, xylylenediamine type epoxy resins, glycidyl ether type epoxy resins such as tetrakis(glycidyloxyphenyl)ethane and tris(glycidyloxymethane), and epoxy resins obtained by modifying these, and brominated epoxy resins obtained by brominating these epoxy resins, but are not limited thereto. Also, two or more of these epoxy resins may be used in combination. Among them, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolak type epoxy resin, and cresol novolak type epoxy resin can be particularly preferably used. When these epoxy resins are used, for example, compared with the case of using a highly rigid epoxy resin such as an epoxy resin having a naphthalene skeleton in one molecule, there is a further effect that the mechanical strength when made into a fiber-reinforced composite material is improved. This is presumably because a highly rigid epoxy resin is likely to generate strain due to an increase in crosslink density when cured in a short time, while when the above-mentioned epoxy resins are used, the possibility of such problems occurring is low.

[0016] Examples of commercially available aliphatic epoxy resins include "Denacol (registered trademark)" EX-313, EX-314, EX-321, EX-411, EX-421, EX-512, EX-521, EX-611, EX-612, EX-614, EX-614B, EX-622 (manufactured by Nagase ChemteX Corporation, etc.).

[0017] Examples of commercially available bisphenol A type epoxy resins include "jER (registered trademark)" 825, "jER (registered trademark)" 826, "jER (registered trademark)" 827, "jER (registered trademark)" 828, "jER (registered trademark)" 834, "jER (registered trademark)" 1001, "jER (registered trademark)" 1002, "jER (registered trademark)" 1003 (manufactured by Mitsubishi Chemical Corporation, etc.), "Epiclon (registered trademark)" 850 (manufactured by DIC Corporation), "Epotoate (registered trademark)" YD-128, YD-128G, YD-128S (manufactured by Nippon Steel Chemical & Material Co., Ltd., etc.), "DER (registered trademark)" -331 (manufactured by Dow Chemical Japan Co., Ltd.), etc.

[0018] Examples of commercially available bisphenol F type epoxy resins include "jER (registered trademark)" 806, "jER (registered trademark)" 807, "jER (registered trademark)" 1750 (manufactured by Mitsubishi Chemical Corporation, etc.), "Epiclon (registered trademark)" 830 (manufactured by DIC Corporation), "Epotoate (registered trademark)" YDF-170, "Epotoate (registered trademark)" YDF2001 (manufactured by Nippon Steel Chemical & Material Co., Ltd., etc.). Also, examples of commercially available tetramethyl bisphenol F type epoxy resins, which are alkyl-substituted products, include "Epotoate (registered trademark)" YSLV-80Y / X (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.).

[0019] Examples of commercially available bisphenol S type epoxy resins include "Epiclon (registered trademark)" EXA-1515 (manufactured by DIC Corporation).

[0020] Examples of commercially available phenol novolac type epoxy resins include "jER (registered trademark)" 152, "jER (registered trademark)" 154 (both manufactured by Mitsubishi Chemical Corporation), "Epiclon (registered trademark)" N-740, "Epiclon (registered trademark)" N-770, "Epiclon (registered trademark)" N-775 (all manufactured by DIC Corporation), etc.

[0021] Examples of commercially available cresol novolac type epoxy resins include "Epiclon (registered trademark)" N-660, "Epiclon (registered trademark)" N-665, "Epiclon (registered trademark)" N-670, "Epiclon (registered trademark)" N-673, "Epiclon (registered trademark)" N-695 (all manufactured by DIC Corporation), EOCN-1020, EOCN-102S, EOCN-104S (all manufactured by Nippon Kayaku Co., Ltd.), etc.

[0022] Examples of commercially available xylylenediamine type epoxy resins include TETRAD-X (manufactured by Mitsubishi Gas Chemical Company, Inc.). These may be used alone or in combination of two or more.

[0023] Component (A) is preferably a liquid at 1 atm and 25°C. When component (A) is a liquid, it becomes easier for component (A) and components other than component (A) to be uniformly mixed. In the present invention, the viscosity of component (A) at 25°C is 0.1 to 1000 Pa·s. Component (A) may be within the above viscosity range alone, or two or more epoxy resins having two or more epoxy groups in one molecule may be mixed to obtain the above viscosity range. With such a viscosity range, the mixing efficiency is improved. The upper limit of the viscosity is preferably 100 Pa·s or less, more preferably 50 Pa·s or less, and most preferably 15 Pa·s or less. Also, the lower limit of the viscosity is preferably 0.3 Pa·s or more, and more preferably 0.5 Pa·s or more. By setting the viscosity of component (A) at 25°C to 1000 Pa·s or less, the viscosity difference from liquid components other than component (A) can be reduced, making it easier to mix uniformly. Also, by setting the viscosity of component (A) at 25°C to 0.1 Pa·s or more, the shearing force is improved, making it easier to uniformly mix solid components other than component (A). Here, the viscosity of component (A) is measured by the method described below.

[0024] The epoxy resin composition of the present invention contains, as component (B), an additive having a viscosity at 25°C of 0.01 to 20 Pa·s. Examples of component (B) include flame retardants, internal mold release agents, ultraviolet absorbers, antioxidants, dispersants, conductivity-imparting agents, vibration damping agents, antibacterial agents, insect repellents, deodorants, anti-coloring agents, heat stabilizers, antistatic agents, plasticizers, lubricants, colorants, pigments, dyes, foaming agents, foam suppressants, coupling agents, and the like. Component (B) is preferably a liquid from the viewpoint of compatibility with component (A). The upper limit of the viscosity of component (B) at 25°C is preferably 10 Pa·s or less, more preferably 5 Pa·s or less, and even more preferably 3 Pa·s or less. Also, the lower limit of the viscosity is preferably 0.05 Pa·s or more, more preferably 0.1 Pa·s or more, and even more preferably 0.2 Pa·s or more. By setting the viscosity of component (B) at 25°C to 20 Pa·s or less, component (B) can be efficiently dispersed without impairing the compatibility with component (A). Here, the viscosity of component (B) is measured by the method described below.

[0025] Examples of the flame retardant include phosphate ester-based compounds and the like. Examples of commercially available flame retardants include TCP, TXP, PX-110, CR-733S, CR-741, TMCPP, CR-570, CR-504L (manufactured by Daihachi Chemical Industry Co., Ltd.), "ADEKA STAB (registered trademark)" FP-600, PFR, FP-900L (manufactured by ADEKA Corporation), and the like.

[0026] Examples of internal release agents include ester compounds of organic fatty acids and alcohols, ester compounds of polycarboxylic acids and alcohols, aliphatic alcohol compounds, fatty acid amides, silicone oils, plant waxes, animal waxes, fluorine-based compounds, etc. Examples of commercially available products include, for example, "MOLD WIZ (registered trademark)" INT-1846, INT-1836, INT-1850, INT-1854, INT-1888LE (all manufactured by AXEL PLASTICS RESEARCH LABORATORIES INC.), "Kemlease (registered trademark)" IC-35 (manufactured by Kemlease Japan Co., Ltd.), Licowax S, Licowax P, Licowax OP, Licowax PE190, Licowax PED (all manufactured by Clariant Japan), Stearyl stearate SL-900A (manufactured by Riken Vitamin Co., Ltd.), "Leodol (registered trademark)" 430V, 440V, SP-030V, "Exceparl (registered trademark)" PE-MO, BP-DL (all manufactured by Kao Corporation), KF-96, KF-965, KF-54 (all manufactured by Shin-Etsu Chemical Co., Ltd.), etc. Examples of ultraviolet absorbers include benzotriazole-based compounds, triazine-based compounds, hindered phenol-based compounds, etc. Examples of commercially available products include, for example, "Tinuvin (registered trademark)" 384-2, 400, 477, "Irganox (registered trademark)" 1135 (all manufactured by BASF Japan Ltd.), etc.

[0027] Examples of light stabilizers include hindered amine-based compounds, etc. Examples of commercially available products include, for example, "Tinuvin (registered trademark)" 123, 249, 292, 5100 (manufactured by BASF Japan Ltd.), "Adekastab (registered trademark)" LA-72, LA-81 (manufactured by ADEKA Corporation), etc.

[0028] Examples of antioxidants include phenylamine compounds, phenolic compounds, thioether compounds, etc. Commercially available products include, for example, "NA-LUBE (registered trademark)" AO-130, AO-142, AO-242 (manufactured by KING INDUSTRIES), "ADEKA STAB (registered trademark)" AO-503, AO-26 (manufactured by ADEKA CORPORATION), etc.

[0029] Examples of dispersants include surfactants, high molecular weight dispersants, surfactants and ionic liquids, etc.

[0030] Surfactants are mainly classified into anionic, cationic, nonionic, and amphoteric types. Surfactants can be appropriately selected and used in suitable types and blending amounts according to the required properties.

[0031] Examples of anionic surfactants include sulfate ester compounds or sulfonate compounds, fatty acid esters, etc.

[0032] Examples of cationic surfactants include alkylamine salts, quaternary ammonium salts, etc. More specifically, stearylamine acetate, trimethyl coconut ammonium chloride, trimethyl tallow ammonium chloride, dimethyldioleyl ammonium chloride, methyl oleyl diethanol chloride, tetramethyl ammonium chloride, lauryl pyridinium chloride, lauryl pyridinium bromide, lauryl pyridinium disulfate, cetyl pyridinium bromide, 4-alkyl mercapto pyridine, poly(vinyl pyridine)-dodecyl bromide, dodecyl benzyl triethyl ammonium chloride, tetradecyl dimethyl benzyl ammonium chloride, etc.

[0033] Examples of amphoteric surfactants include aminocarboxylates, etc.

[0034] Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyalkylene derivatives, polyoxyethylene phenyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, alkyl allyl ethers, etc. More specifically, polyoxyethylene lauryl ether, sorbitan fatty acid ester, polyoxyethylene octyl phenyl ether, etc. can be mentioned.

[0035] Examples of high molecular weight dispersants include polyurethane, polycarboxylic acid esters such as polyacrylate, unsaturated polyamides, polycarboxylic acids, polycarboxylic acid (partial) amine salts, polycarboxylic acid ammonium salts, polycarboxylic acid alkylamine salts, polysiloxanes, long-chain polyaminoamidine phosphates, hydroxyl group-containing polycarboxylic acid esters, and modified products thereof, oil-based dispersants such as amides and their salts formed by the reaction of poly(lower alkyleneimine) and a polyester having a free carboxyl group, (meth)acrylic acid-styrene copolymers, (meth)acrylic acid-(meth)acrylate copolymers, styrene-maleic acid copolymers, water-soluble resins and water-soluble polymer compounds such as polyvinyl alcohol and polyvinyl pyrrolidone, polyester-based resins, modified polyacrylate-based resins, ethylene oxide / propylene oxide adduct compounds, phosphate ester-based resins, etc. These can be used alone or in combination of two or more, but are not necessarily limited thereto.

[0036] Examples of commercially available dispersants include DISPERBYK-101, 103, 107, 108, 110, 111, 116, 130, 140, 154, 161, 162, 163, 164, 165, 166, 170, 171, 174, 180, 181, 182, 183, 184, 185, 190, 2000, 2001, 2020, 2025, 2050, 2070, 2095, 2150, 2155 or Anti-Terra-U, 203, 204, or BYK-P104, P104S, P9920, 220S, 6919, 9076, 9077 or Lactimon, Lactimon-WS or Bykumen (manufactured by BYK-Chemie GmbH), SOLSPERSE-3000, 9000, 13000, 13240, 13650, 13940, 16000, 17000, 18000, 20000, 21000, 24000, 26000, 27000, 28000, 31845, 32000, 32500, 32550, 33500, 32600, 34750, 35100, 36600, 38500, 41000, 41090, 53095, 55000, 76500 (manufactured by Lubrizol Japan Ltd.), EFKA-46, 47, 48, 452, 4008, 4009, 4010, 4015, 4020, 4047, 4050, 4055, 4060, 4080, 4400, 4401, 4402, 4403, 4406, 4408, 4300, 4310, 4320, 4330, 4340, 450, 451, 453, 4540, 4550, 4560, 4800, 5010, 5065, 5066, 5070, 7500, 7554, 1101, 120, 150, 1501, 1502, 1503 (manufactured by Ciba Japan K.K.), "Ajisper (registered trademark)" PA111, PB711, PB821, PB822, PB824 (manufactured by Ajinomoto Fine-Techno Co., Inc.), and the like.

[0037] Examples of ionic liquids include organic compound salts such as imidazolium salts, pyridinium salts, ammonium salts, and phosphonium salts that are liquid at room temperature.

[0038] It is also possible to use commercially available ionic liquids as they are. Examples of commercially available products include "3M (registered trademark)" ionic liquid type antistatic agent FC4400 (manufactured by 3M Japan Ltd.), CIL-313, CIL-312 (both manufactured by Nippon Carlit Co., Ltd.), IL-A2, IL-A5, IL-A12, IL-AP1, IL-AP3, IL-C1, IL-C3, IL-C5, IL-C6, IL-IM1, IL-IM4, IL-MA1, IL-MA2, IL-MA3, IL-P14, IL-P18, IL-OH9 (all manufactured by Koei Chemical Industry Co., Ltd.), and the like.

[0039] These additives can be used alone or in combination of two or more, but are not necessarily limited thereto.

[0040] In the present invention, with respect to 100 parts by mass of component (A), it is preferable that the dispersion diameter of component (B) in the mixture obtained by mixing 1 part by mass of component (B) at 25°C is 0.01 to 5 μm. By setting the dispersion diameter of component (B) to 0.01 μm or more, the characteristics of component (B) can be further enhanced. More preferably, the dispersion diameter of component (B) is 1 μm or less, still more preferably 0.5 μm or less, and most preferably 0.2 μm or less. By setting the dispersion diameter of component (B) to 5 μm or less, the characteristics of component (B) can be further enhanced without impairing the mechanical properties of the resin. In the present invention, the dispersion diameter of component (B) in the mixture obtained by mixing 1 part by mass of component (B) with 100 parts by mass of component (A) at 25°C is measured by the method described in <Evaluation of the Dispersion Diameter of Component (B) in Component (A)> below.

[0041] Component (C) in the present invention is a compound that undergoes a thickening reaction with an epoxy resin at a temperature below the curing temperature, and is not particularly limited as long as it is a component that thickens the epoxy resin by covalently bonding with the epoxy resin, but it is preferably an aliphatic amine, an acid anhydride, an isocyanate compound or a derivative thereof. In the present invention, the curing temperature refers to the temperature of the resin composition after thickening showing the lowest viscosity + 20°C. The definition of the lowest viscosity is as described below. The thickening reaction means that the epoxy resin becomes a semi-cured solid at 25°C.

[0042] An aliphatic amine is an amine having no aromatic ring, and is not particularly limited as long as it has one or more amino groups in the molecule. Examples thereof include polyalkylene polyamine, isophorone diamine, 3,3'-dimethylene bis(cyclohexylamine), 4,4'-diaminodicyclohexylmethane, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, 3,3'-diethyl-4,4'-diaminodicyclohexylmethane, n-aminoethyl piperazine, norbornanediamine, diethylene glycol diaminopropyl ether, adipic acid dihydrazide, hydrazine, cyanamide and derivatives thereof. The amino group is preferably bonded to a primary, secondary or tertiary carbon atom, and more preferably bonded to a primary or secondary carbon atom in order to easily thicken the resin.

[0043] An acid anhydride is a compound having one or more acid anhydride groups in the molecule. Examples of the acid anhydride include methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, methylnadic anhydride, maleic anhydride, succinic anhydride and the like.

[0044] The isocyanate compound is not particularly limited as long as it has an average of 1 or more isocyanate groups in one molecule, and known aliphatic isocyanates and aromatic isocyanates can be used. Examples of the aliphatic isocyanate include ethylene diisocyanate, trimethylene diisocyanate, dodecamethylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, propylene-1,2-diisocyanate, 2,3-dimethyltetramethylene diisocyanate, butylene-1,2-diisocyanate, butylene-1,3-diisocyanate, 1,4-diisocyanate hexane, cyclopentene-1,3-diisocyanate, isophorone diisocyanate, 1,2,3,4-tetraisocyanate butane, butane-1,2,3-triisocyanate and the like. Examples of the aromatic isocyanate that can be used as the polyisocyanate compound of component (C) include p-phenylene diisocyanate, 1-methylphenylene-2,4-diisocyanate, naphthalene-1,4-diisocyanate, tolylene diisocyanate, diphenyl-4,4-diisocyanate, benzene-1,2,4-triisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate (MDI), diphenylpropane diisocyanate, tetramethylene xylylene diisocyanate, aromatic isocyanates such as polymethylene polyphenyl polyisocyanate, and those having a structure in which these aromatic isocyanates are linked with a methylene group or the like.

[0045] In the present invention, in order to sufficiently exhibit the reduction of the viscosity of the epoxy resin composition, the viscosity of component (C) at 25 ° C is preferably 1 mPa·s or more and 10000 mPa·s or less, and more preferably 10 mPa·s or more and 10000 mPa·s or less.

[0046] Each compound of component (C) preferably satisfies the following conditions.

[0047] 1.5 ≤ α / β ≤ 10 α: Total number of epoxy groups in component (A) β: The number of functional groups that react with the epoxy resin of component (C).

[0048] More preferably, 3 ≦ α / β ≦ 10. By satisfying the above conditions, the epoxy group of component (A) reacts with the functional group of component (C), and the handleability of the epoxy resin composition before curing is improved.

[0049] Component (D) in the present invention is a component that cures an epoxy resin by covalently bonding with the epoxy resin and does not correspond to component (C). As long as it can cure the epoxy resin, it is not particularly limited, and examples include amine-based, phenol-based, acid anhydride-based, mercaptan-based, imidazoles, tertiary amines, organic phosphorus compounds, urea compounds, ammonium salts, sulfonium salts, and the like. Examples of amine-based curing agents include dicyandiamide, aromatic polyamines, amino benzoate esters, thiourea-added amines, and the like. Examples of phenol-based curing agents include bisphenol, phenol novolak resin, cresol novolak resin, polyphenol compounds, and the like. Examples of acid anhydride-based curing agents include phthalic anhydride, maleic anhydride, succinic anhydride, carboxylic acid anhydrides, and the like. Examples of mercaptan-based curing agents include polymercaptans, polysulfide resins, and the like. Among the exemplified ones, amine-based curing agents are preferred. Further, among these, dicyandiamide or its derivatives are particularly preferred. Dicyandiamide is excellent in that it imparts high mechanical properties and heat resistance to the cured epoxy resin and is widely used as a curing agent for epoxy resins. Also, since it has excellent storage stability of the resin composition, it can be preferably used. The derivative of dicyandiamide means a compound obtained by bonding dicyandiamide with various compounds. Similar to dicyandiamide, it is excellent in that it imparts high mechanical properties and heat resistance to the cured epoxy resin and also has excellent storage stability of the resin composition. Examples of the derivative of dicyandiamide include those obtained by bonding dicyandiamide with various compounds such as epoxy resins, vinyl compounds, acrylic compounds, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and the like. These may be used alone or in combination of two or more. They may also be used in combination with dicyandiamide. Examples of commercially available products of such dicyandiamide include dicyandiamide (manufactured by Nippon Carbide Industries Co., Ltd.).

[0050] The epoxy resin composition of the present invention may contain a catalyst as a curing accelerator. By containing the catalyst, the curing time can be shortened. Here, the catalyst is a component that promptly and smoothly accelerates the single-component curing reaction of the main agent and the curing reaction due to the bond-forming property between the main agent and the curing agent. Examples include imidazoles, tertiary amines, organic phosphorus compounds, urea compounds, ammonium salts, sulfonium salts, and the like. Two or more of these catalysts may be used in combination.

[0051] Component (E) in the present invention is a particle that exhibits thixotropic properties. From the viewpoints of the impregnation property of the resin into the reinforcing fiber and the control of the phase separation structure formed during curing, it is preferable that component (E) exhibits thixotropic properties when mixed with the resin component. Examples of particles that exhibit thixotropic properties when mixed with the resin component include insoluble polyimide particles, particles composed of poly(meth)acrylamide or its cross-linked product, particles composed of poly(meth)acrylic acid (salt) or its cross-linked product, particles composed of (meth)acrylamide alkyl sulfonic acid (salt) or its cross-linked product, hydroxymethyl cellulose particles, hydroxyethyl cellulose particles, xanthan gum particles, guar gum particles, carrageenan particles, gelatin particles, starch particles, silanol particles, organic bentonite particles, sepiolite particles, attapulgite particles, silica particles, calcium carbonate particles, titanium dioxide particles, carbon particles, and the like. Among them, from the viewpoints of handling properties and maintaining the mechanical properties of the resin, it is preferable that component (E) is silica particles or carbon particles.

[0052] Here, thixotropic properties refer to the property that the apparent viscosity temporarily decreases by applying deformation in an isothermal state. In the present invention, the specific surface area of component (E) is preferably 50 m 2 / g or more, and more preferably 100 m 2 / g or more. There is no particular limitation on the upper limit of the specific surface area, but from the viewpoint of the dispersibility of the particles, 1500 m 2It is preferably below / g. The specific surface area can be measured by the so-called BET method, in which molecules whose adsorbed occupation area on the surface of the powder particles is known are adsorbed at the temperature of liquid nitrogen, and the specific surface area of the sample is determined from the amount thereof.

[0053] Specific examples of the silica particles include dry silica and wet silica fine particles. Specific examples of the carbon particles include carbon black, graphite, graphite, activated carbon, carbon fiber, carbon nanotube, fullerene, etc. Further, for example, those obtained by heat treatment at a high temperature of 1000 ° C. or higher in an inert atmosphere using carbon black or activated carbon as a raw material and subjected to graphitization treatment may be used. Commercially available products of silica particles include "Aerosil (registered trademark)" 200, RY200S, R972, R976, R976S (manufactured by Nippon Aerosil Co., Ltd., etc.). Commercially available products of carbon particles include "Ketjenblack (registered trademark)" EC-300J, EC-600JD (manufactured by Lion Specialty Chemical Co., Ltd., etc.).

[0054] In the present invention, the content of the component (E) is preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the component (A). From the viewpoints of imparting thixotropy and suppressing coarsening of the phase separation structure due to thickening, the content of the component (E) is preferably 0.01 part by mass or more, more preferably 0.05 part by mass or more, and still more preferably 0.1 part by mass or more with respect to 100 parts by mass of the component (A). Further, when the epoxy resin composition is impregnated into the reinforcing fiber, if the viscosity increases too much, the handleability deteriorates. Therefore, the content of the component (E) is preferably 5 parts by mass or less, and more preferably 1 part by mass or less.

[0055] The epoxy resin composition of the present invention preferably has a viscosity at 25°C of 0.1 to 100 Pa·s. The viscosity at 25°C is more preferably 50 Pa·s or less, still more preferably 25 Pa·s or less, and particularly preferably 10 Pa·s or less. By setting the viscosity at 25°C to 0.1 Pa·s or more, the viscosity during resin impregnation does not become too low, the resin does not flow out externally, and it is easy to uniformly impregnate the reinforcing fibers. Also, by setting the viscosity at 25°C to 100 Pa·s or less, it is possible to suppress a decrease in impregnability and easily suppress the generation of voids when a carbon fiber reinforced composite material is formed. In the present invention, the viscosity of the epoxy resin composition at 25°C is measured by the method described in <Measurement of Viscosity of Epoxy Resin Composition at 25°C> which will be described later. As means for satisfying the above viscosity range, for example, reducing the content of solid components in the epoxy resin composition or using a component (A) with a lower viscosity can be mentioned.

[0056] In the epoxy resin composition of the present invention, the dispersion diameter of component (B) in the cured product obtained by heat-treating the epoxy resin composition at the curing temperature for 2 hours is 0.01 to 5 μm. By setting the dispersion diameter of component (B) in the cured product to 0.01 μm or more, the characteristics of component (B) can be exhibited. The dispersion diameter of component (B) is preferably 2 μm or less, more preferably 1 μm or less, and most preferably 0.5 μm or less. By setting the dispersion diameter of component (B) to 5 μm or less, the characteristics of component (B) can be exhibited without impairing the mechanical properties of the resin.

[0057] When the epoxy resin composition of the present invention is heated from 25°C to 200°C at a heating rate of 10°C / min with a rheometer, the viscosity at the lowest point is preferably 0.1 to 10,000 Pa·s. In the present invention, the "viscosity at the lowest point when the epoxy resin composition before curing is heated from 25°C to 200°C at a heating rate of 10°C / min with a rheometer" may be referred to as the minimum viscosity. The minimum viscosity is more preferably 5000 Pa·s or less. Further, the minimum viscosity is more preferably 0.5 Pa·s or more, still more preferably 1 Pa·s or more, and most preferably 10 Pa·s or more. By setting the minimum viscosity to 10,000 Pa·s or less, the viscosity during molding does not become too high, the lack of flesh of the molded product can be suppressed, and the quality of the molded product can be improved. Also, by setting the minimum viscosity to 0.1 Pa·s or more, the decrease in the viscosity of the epoxy resin composition can be suppressed, the coarsening of the structure of component (B) can be suppressed, and the characteristics of component (B) can be exhibited. As a means for setting the minimum viscosity within the above range, for example, a method of making the epoxy resin into a semi-cured solid at 25°C by a thickening reaction can be mentioned.

[0058] The dispersion diameter of component (B) in the cured product is obtained by observing a cross-section in the TD direction of the 500-μm inner layer from the outermost surface on the long side of the cross-section of a molded piece formed by heating and molding at the curing temperature for 2 hours with an optical microscope, a scanning electron microscope, a transmission microscope, etc., extracting the particles of component (B) from the obtained observation image using image processing software "Image Pro Premier 3D 64-bit Ver 9.2" manufactured by Media Cybernetics, and calculating the average particle diameter of the extracted particles.

[0059] In the epoxy resin composition of the present invention, it is preferable that the roundness Rs of component (B) in the surface layer portion of the resin cured product heated at the curing temperature for 2 hours is 1.00 to 1.50. More preferably, the roundness Rs of component (B) in the surface layer portion of the resin cured product is 1.30 or less, still more preferably 1.20 or less, and most preferably 1.10 or less. By setting the roundness Rc of component (B) in the cured product to 1.50 or less, the characteristics of component (B) can be exhibited without impairing the mechanical properties of the resin composition. As a means for setting Rs within the above range, for example, setting the minimum viscosity of the epoxy resin composition within the above range can be mentioned.

[0060] Further, when the roundness Rs of component (B) in the surface layer portion of the resin cured product is 1.00 to 1.50, the roundness Rc of component (B) in the central portion of the resin cured product heated at the curing temperature for 2 hours is 1.00 to 1.50, and the ratio Rr of Rc to Rs calculated by Rr = Rs / Rc from the roundness Rs and roundness Rc of component (B) in the surface layer portion of the resin cured product is preferably 0.50 to 1.40. As a means for setting Rc within the above range, for example, the dispersion diameter of component (B) in a mixture obtained by mixing 1 part by mass of component (B) with 100 parts by mass of component (A) at 25°C is set within the above range. As a means for setting Rr within the above range, for example, setting Rs and Rc within the above range can be mentioned.

[0061] More preferably, the roundness Rc of component (B) in the central portion of the resin cured product is 1.20 or less, still more preferably 1.10 or less, and most preferably 1.08 or less. By setting the roundness Rc of component (B) in the cured product to 1.50 or less, the characteristics of component (B) can be exhibited without impairing the mechanical properties of the resin composition.

[0062] Furthermore, the ratio Rr of Rc to Rs is more preferably 1.30 or less, still more preferably 1.20 or less, and most preferably 1.10 or less. Also, the ratio Rr of Rc to Rs is more preferably 0.60 or more, still more preferably 0.80 or more, and most preferably 0.90 or more. By setting Rr in the range of 0.50 to 1.40, component (B) can be uniformly dispersed, and the properties of component (B) can be exhibited without impairing the mechanical properties of the cured resin.

[0063] Here, the roundness is a value indicating that the closer it is to 1, the more circular it is. In the present invention, Rs, Rc, and Rr are measured by the methods described in <Evaluation of the roundness Rs of component (B) in the surface layer portion of the cured resin>, <Evaluation of the roundness Rc of component (B) in the central portion of the cured resin>, and <Evaluation of the ratio Rr of Rc to Rs of component (B) in the cured resin> described below. The surface layer portion of the cured resin refers to the cross-section in the TD direction of the inner layer within 20 μm from the outermost surface on the long side of the cross-section of the molded piece formed by heating and molding at the curing temperature for 2 hours, and the central portion refers to the cross-section in the TD direction of the inner layer within 500 μm from the long side of the cross-section of the molded piece. The method for producing the molded piece is as described in the examples.

[0064] When the dispersion diameter of component (B) in the cured resin, Rs, Rc, and Rr of the cured resin are within the above ranges respectively, when it is made into a fiber-reinforced composite material, the dispersion structure of component (B) in the fiber-reinforced composite material can be controlled, and the properties of component (B) can be further enhanced.

[0065] The heat resistance of the fiber-reinforced composite material using the epoxy resin composition of the present invention depends on the glass transition temperature (Tg) of the resin cured product obtained by curing the epoxy resin composition. In order to obtain a fiber-reinforced composite material having high heat resistance, for example, it is preferable that the glass transition temperature of the resin cured product cured by heating at the curing temperature for 2 hours is 110°C or higher. As a means for setting the glass transition temperature within the above range, for example, increasing the content of a rigid molecular structure such as an aromatic group in the epoxy resin composition can increase the glass transition temperature. Here, the degree of cure of the resin cured product is determined by calculating the degree of cure (%) = (QT - QR) / QT × 100 from the total heat of exotherm QT of the epoxy resin composition obtained at a heating rate of 10°C / min using a differential scanning calorimeter and the residual heat of exotherm QR of the cured product.

[0066] The upper limit of the glass transition temperature is not particularly limited, but the glass transition temperature is preferably 250°C or lower. More preferably, the glass transition temperature is 120°C or higher and 220°C or lower. If the glass transition temperature is 110°C or higher, it becomes easy to impart high heat resistance to the resin cured product obtained by curing the epoxy resin composition. If the glass transition temperature is 250°C or lower, the crosslink density of the three-dimensional crosslinked structure of the resin cured product obtained by curing the epoxy resin composition does not become too high, and high mechanical properties are likely to be exhibited. Here, the glass transition temperature of the epoxy resin cured product obtained by curing the epoxy resin composition is determined by measurement using a dynamic viscoelasticity measuring device (DMA). That is, using a rectangular test piece cut out from a resin cured plate, DMA measurement is performed under heating, and the temperature of the inflection point of the obtained storage elastic modulus G' is taken as Tg.

[0067] The mechanical properties of the fiber-reinforced composite material using the epoxy resin composition of the present invention depend on the mechanical properties of the resin cured product obtained by curing the epoxy resin composition. In order to obtain a fiber-reinforced composite material having high mechanical properties, for example, it is preferable that the flexural strength of the resin cured product cured by heating at the curing temperature for 2 hours is 110 MPa or more, more preferably 120 MPa or more. If the flexural strength of the resin cured product is 110 MPa or more, the fiber-reinforced composite material using the epoxy resin composition of the present invention can be used as an excellent member that does not break or deform even in an environment where it receives a strong external stress.

[0068] The molding material of the present invention is composed of the epoxy resin composition of the present invention and reinforcing fibers. By using the molding material of the present invention, a fiber-reinforced composite material with excellent fluidity regardless of the molding temperature can be obtained without the resin flowing ahead alone during press molding, and with very high homogeneity between the fibers and the resin. In the molding material of the present invention, the type, length of the reinforcing fibers, the content ratio of the reinforcing fibers and the resin, etc. are not particularly limited, but examples include glass fibers, carbon fibers, graphite fibers, aramid fibers, boron fibers, alumina fibers, and silicon carbide fibers. These reinforcing fibers may be used by mixing two or more kinds, but in order to obtain a lighter and more durable molded product, it is preferable to use carbon fibers or graphite fibers. In particular, in applications where there are high requirements for weight reduction and high strength of the material, due to its excellent specific elastic modulus and specific strength, it is preferable that the reinforcing fiber is a carbon fiber. As the carbon fiber, any type of carbon fiber can be used according to the application, but it is preferably a carbon fiber having a tensile elastic modulus of at most 400 GPa from the viewpoint of impact resistance. Also, from the viewpoint of strength, carbon fibers having a tensile strength preferably of 4.4 to 6.5 GPa are used because a composite material having high rigidity and mechanical strength can be obtained. Also, the tensile elongation is an important factor, and it is preferably a high-strength and high-elongation carbon fiber with a tensile elongation of 1.7 to 2.3%. Therefore, carbon fibers having the characteristics of having a tensile elastic modulus of at least 230 GPa, a tensile strength of at least 4.4 GPa, and a tensile elongation of at least 1.7% are most suitable.

[0069] Examples of commercially available carbon fibers include "Torayca (registered trademark)" T800G-24K, "Torayca (registered trademark)" T800S-24K, "Torayca (registered trademark)" T700G-24K, "Torayca (registered trademark)" T300-3K, and "Torayca (registered trademark)" T700S-12K (all manufactured by Toray Industries, Inc.).

[0070] As the form of the reinforcing fiber in the present invention, for example, long fibers aligned in one direction, tows, woven fabrics, mats, knits, braided cords, short fibers chopped to a length of less than 10 mm, etc. are used. The long fibers referred to here mean substantially continuous single fibers or fiber bundles of 10 mm or more. The short fibers are fiber bundles cut to a length of less than 10 mm.

[0071] The fiber-reinforced composite material of the present invention is formed by molding the molding material of the present invention. In the case of fiber-reinforced composite materials, especially in the case of fiber-reinforced composite materials used in the automotive field, mechanical properties such as high heat resistance and flexural strength are required. The fiber-reinforced composite material of the present invention is excellent in heat resistance and mechanical properties, and thus is also preferably used in the automotive field.

[0072] The method for manufacturing the fiber-reinforced composite material of the present invention is not particularly limited, but the hand lay-up method, filament winding method, pultrusion method, resin transfer molding (RTM) method, autoclave molding method of prepreg, and further, press molding methods of molding materials such as prepreg, towpreg, bulk molding compound (BMC), and sheet molding compound (SMC) are preferably used.

Examples

[0073] Hereinafter, the epoxy resin composition, molding material, and fiber-reinforced composite material of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0074] <Resin raw materials> To obtain the epoxy resin compositions of the respective examples and comparative examples, the following resin raw materials were used. In the column of the epoxy resin compositions in the table, the numerical values of the respective components indicate the contents, and the unit thereof ( "parts") is "parts by mass" unless otherwise specified.

[0075] 1. Component (A): An epoxy resin having two or more epoxy groups in one molecule and having a viscosity at 25°C of 0.1 to 1000 Pa·s · "Epotoate (registered trademark)" YD128 (manufactured by Nippon Steel Chemical & Material Co., Ltd.): Bisphenol A type epoxy resin (viscosity at 25°C: 14 Pa·s) · "jER (registered trademark)" 827 (manufactured by Mitsubishi Chemical Corporation): Bisphenol A type epoxy resin (viscosity at 25°C: 10 Pa·s) · "jER (registered trademark)" 807 (manufactured by Mitsubishi Chemical Corporation): Bisphenol A type epoxy resin (viscosity at 25°C: 4 Pa·s) · "jER (registered trademark)" 154 (manufactured by Mitsubishi Chemical Corporation): Phenol novolac type epoxy resin (viscosity at 25°C: 1950 Pa·s) · YED216M (manufactured by Mitsubishi Chemical Corporation): Alkyl diglycidyl ether (viscosity at 25°C: 0.02 Pa·s) · TETRAD-X (manufactured by Mitsubishi Gas Chemical Company, Inc.) (viscosity at 25°C: 2 Pa·s) · "Denacol (registered trademark)" EX-212 (manufactured by Nagase ChemteX Corporation): 1,6-Hexanediol diglycidyl ether (viscosity at 25°C: 0.02 Pa·s) · "Denacol (registered trademark)" EX-614 (manufactured by Nagase ChemteX Corporation): Sorbitol polyglycidyl ether (viscosity at 25°C: 21 Pa·s).

[0076] 2. Component (B): An additive (internal release agent) having a viscosity at 25°C of 0.01 to 20 Pa·s · "Chemlease (registered trademark)" IC-35 (manufactured by Chemlease Japan Co., Ltd.) (viscosity at 25°C: 0.4 Pa·s) · "Leodol (Registered Trademark)", 430V (manufactured by Kao Corporation) (viscosity at 25°C: 0.2 Pa·s) · "Exceparl (Registered Trademark)", BP-DL (manufactured by Kao Corporation) (viscosity at 25°C: 0.4 Pa·s).

[0077] 3. Component (C): A compound that undergoes a thickening reaction with the epoxy resin below the curing temperature · 1,4-Butanediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) · Isophoronediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) · HN-2200 (manufactured by Hitachi Chemical Co., Ltd.): 3 or 4-methyl-1,2,3,6-tetrahydrophthalic anhydride · "Lupranate (Registered Trademark)" M20S (manufactured by BASF INOAC Polyurethane Co., Ltd.): polymeric MDI (polymethylene polyphenyl polyisocyanate) · "Desmodur (Registered Trademark)" N3400 (manufactured by Sumika Covestro Urethane Co., Ltd.): HDI uretdione · "Desmodur (Registered Trademark)" I (manufactured by Sumika Covestro Urethane Co., Ltd.): isophorone diisocyanate.

[0078] 4. Component (D): Epoxy curing agent · Dicyandiamide (manufactured by Nippon Carbide Industries Co., Ltd.) · "Curezol (Registered Trademark)" 2MZA-PW (manufactured by Shikoku Chemicals Corporation) · "Amicure (Registered Trademark)" PN-23J (manufactured by Ajinomoto Fine-Techno Co., Inc.).

[0079] 5. Component (E): Particles that exhibit thixotropy · "Aerosil (Registered Trademark)" R976 (manufactured by Nippon Aerosil Co., Ltd.) · "Ketjenblack (Registered Trademark)" EC-300J (manufactured by Lion Specialty Chemicals Co., Ltd.).

[0080] <Preparation of Epoxy Resin Composition> Each component was mixed in the contents described in Tables 1 and 2 to prepare an epoxy resin composition.

[0081] <Measurement of Viscosity of Epoxy Resin Composition at 25°C> The epoxy resin composition prepared in the above <Preparation of Epoxy Resin Composition> was measured for complex viscosity at 25°C using a rheometer "Physica MCR501" manufactured by Anton Paar, with a 25φ parallel plate, a gap of 1 mm, vibration mode, swing angle φ = 0.0025 rad, frequency 1 Hz. As the specimen, the epoxy resin composition after mixing each component and stirring for 5 minutes was used.

[0082] <Measurement of Viscosity of Components (A) and (B) at 25°C> Using a rheometer "Physica MCR501" manufactured by Anton Paar, with a 25φ parallel plate, a gap of 1 mm, vibration mode, swing angle φ = 0.0025 rad, frequency 1 Hz, the complex viscosity at 25°C was measured.

[0083] <Evaluation of Dispersion Diameter of Component (B) in Component (A)> A mixture of component (A) and component (B) was prepared by mixing 1 part by mass of component (B) with respect to 100 parts by mass of component (A) at room temperature. 0.5 mg of the above-mentioned mixture of component (A) and component (B) was applied to a cover glass placed on a slide glass, and the cover glass was covered. The mixture of component (A) and component (B) was spread from above the cover glass and observed using an optical microscope "OPTIPHOT" manufactured by Nikon and a camera "AxioCam MRc" manufactured by Zeiss to obtain a dispersion image. The particles of component (B) were extracted from the obtained dispersion image using image processing software "Image Pro Premier 3D 64-bit Ver 9.2" manufactured by Media Cybernetics. The average diameter of each particle of component (B) extracted was calculated, and the average value of the average diameters of all the extracted particles was taken as the dispersion diameter of component (B).

[0084] <Evaluation of Minimum Viscosity of Thickened Resin Composition> The specimen to be measured was placed on a stage whose temperature was adjusted to 25°C using DMA (ARES manufactured by TA Instruments), and the temperature was raised to 200°C at a rate of 10°C / min to measure the viscosity. As the specimen, an epoxy resin composition in which each component was mixed and held at 40°C for 24 hours was used. For example, the viscosity at 70°C was the viscosity when the specimen reached 70°C. Similarly, the viscosities at each temperature were measured, and the lowest viscosity was taken as the minimum viscosity.

[0085] <Preparation of resin cured product> After degassing the epoxy resin composition prepared in the above <Preparation of epoxy resin composition> in vacuo, it was injected into a mold set to a thickness of 2 mm by a 2-mm-thick spacer made of "Teflon (registered trademark)". It was cured at the curing temperature for 2 hours to obtain a resin cured product with a thickness of 2 mm.

[0086] <Measurement of flexural strength of resin cured product> The flexural strength of the resin cured product obtained in the above <Preparation of resin cured product> was cut out to a width of 15 mm and a length of 100 mm in accordance with JIS K7074:1988. The cut-out molded piece was measured by a three-point bending test using an Instron universal testing machine (manufactured by Instron). The measurement was carried out at a crosshead speed of 5 mm / min, a span of 80 mm, a thickness diameter of 5 mm, and a fulcrum diameter of 2 mm, and the flexural strength was measured. The flexural strength was taken as the average of the values measured for 5 samples.

[0087] <Evaluation of dispersion diameter of component (B) in resin cured product> The TD cross-section of the inner layer 500 μm from the outermost surface on the long side of the cross-section of the molded piece prepared in the above <Measurement of flexural strength of resin cured product> was observed with a scanning electron microscope, and particles of component (B) were extracted from the obtained observation image using image processing software "Image Pro Premier 3D 64-bit Ver 9.2" manufactured by Media Cybernetics, and the average diameter of each extracted particle was calculated. The average value of the average diameters of all the extracted particles was taken as the dispersion diameter of component (B).

[0088] <Evaluation of roundness Rs of component (B) in the surface layer part of resin cured product> The TD cross-section of the inner layer 20 μm from the outermost surface on the long side of the cross-section of the molded piece prepared in the above <Measurement of Bending Strength of Resin Hardened Product> was observed with a scanning electron microscope. Particles of component (B) were extracted from the obtained observation image using the image processing software "Image Pro Premier 3D 64-bit Ver 9.2" manufactured by Media Cybernetics, and the roundness of each extracted particle was calculated. The average value of the roundness of all the extracted particles was defined as the roundness Rs of component (B) in the surface layer part of the resin hardened product.

[0089] <Evaluation of Roundness Rc of Component (B) in the Central Part of Resin Hardened Product> The TD cross-section of the inner layer 500 μm from the outermost surface on the long side of the cross-section of the molded piece prepared in the above <Measurement of Bending Strength of Resin Hardened Product> was observed with a scanning electron microscope. Particles of component (B) were extracted from the obtained observation image using the image processing software "Image Pro Premier 3D 64-bit Ver 9.2" manufactured by Media Cybernetics, and the roundness of each extracted particle was calculated. The average value of the roundness of all the extracted particles was defined as the roundness Rc of component (B) in the central part of the resin hardened product.

[0090] <Evaluation of Ratio Rr of Rc and Rs of Component (B) in Resin Hardened Product> From Rs and Rc obtained in the above <Evaluation of Roundness Rs of Component (B) in the Surface Layer Part of Resin Hardened Product> and <Evaluation of Roundness Rc of Component (B) in the Central Part of Resin Hardened Product>, the value calculated by the formula Rr = Rs / Rc was defined as Rr.

[0091] <Demolding Property Evaluation Method of Epoxy Resin Composition> The epoxy resin composition obtained according to the <Method for Preparing Epoxy Resin Composition> was filled into a fluororubber O-ring (manufactured by ESCO) with an inner diameter of 3 cm and a thickness of 4 mm, and sandwiched between small hot presses (manufactured by AS ONE Corporation) preheated to each curing temperature in advance, and pressurized at a pressure of 1.0 MPa for 3 hours. After 2 hours, it was demolded from the press mold to obtain a cured epoxy resin product. A straight line passing through the center of the cured epoxy resin product was defined as straight line (1), and a straight line passing through the center and perpendicular to straight line (1) was defined as straight line (2). The surface roughness between two points 5 mm inside from both ends of the cured epoxy resin product on each of the straight lines (1) and (2) was measured using a surface roughness measuring instrument Surfcom 480A (manufactured by Tokyo Seimitsu Co., Ltd.). As the measurement conditions, the arithmetic mean roughness Ra(1) and Ra(2) of each of the straight lines (1) and (2) were measured with a measurement stroke of 20 mm and a crosshead speed of 0.3 mm / s. The average value of Ra(1) and Ra(2) was defined as the average roughness Ra of the cured epoxy resin product, and the demoldability was judged according to the following criteria. A: The average roughness Ra of the surface of the cured epoxy resin product is less than 1 μm, smooth without deformation or warping. B: The average roughness Ra of the surface of the cured epoxy resin product is 1 μm or more and less than 5 μm, with slight deformation or warping. C: The average roughness Ra of the cured epoxy resin product is 5 μm or more, with significant deformation, warping and cracking.

[0092] (Example 1) Components (A), (B), (C), (D), and (E) were used in the contents described in Table 1, and a resin composition was prepared according to the preparation of the resin composition described above. The viscosity at 25°C and the minimum viscosity after thickening were measured. A cured plate of the resin composition was prepared by the above method, and the dispersion diameter of component (B) in the resin cured product, the roundness Rc of component (B) at the center, and the ratio Rr of Rc to Rs were measured. The minimum viscosity after thickening of the resin composition was in the range of 0.1 to 10,000 Pa·s. Also, the dispersion diameter of component (B) in the resin cured product was in the range of 0.01 to 5 μm. The roundness Rs of component (B) in the surface layer part was 1.00 to 1.50, the roundness Rc of component (B) at the center was 1.00 to 1.50, and the ratio Rr of Rc to Rs was in the range of 0.50 to 1.40. The demolding property was improved compared with Comparative Example 1 without adding components (B) and (E), and the addition effect was confirmed.

[0093] (Example 2) Components (A), (B), (C), (D), and (E) were used in the contents described in Table 1, and a resin composition was prepared according to the preparation of the resin composition described above. The viscosity at 25°C and the minimum viscosity after thickening were measured. A cured plate of the resin composition was prepared by the above method, and the dispersion diameter of component (B) in the resin cured product, the roundness Rc of component (B) at the center, and the ratio Rr of Rc to Rs were measured. The minimum viscosity after thickening of the resin composition was in the range of 0.1 to 10,000 Pa·s. Also, the dispersion diameter of component (B) in the resin cured product was in the range of 0.01 to 5 μm. The roundness Rs of component (B) in the surface layer part was 1.00 to 1.50, the roundness Rc of component (B) at the center was 1.00 to 1.50, and the ratio Rr of Rc to Rs was in the range of 0.50 to 1.40. The demolding property was improved compared with Comparative Example 2 without adding components (B) and (E), and the addition effect was confirmed.

[0094] (Examples 3, 4) Components (A), (B), (C), (D), and (E) were used in the contents described in Table 1, and a resin composition was prepared according to the preparation of the above-described resin composition. The viscosity at 25°C and the minimum viscosity after thickening were measured. A cured plate of the resin composition was prepared by the above method, and the dispersion diameter of component (B) in the resin cured product, the roundness Rc of component (B) at the center, and the ratio Rr of Rc to Rs were measured. The minimum viscosity after thickening of the resin composition was in the range of 0.1 to 10,000 Pa·s. Also, the dispersion diameter of component (B) in the resin cured product was in the range of 0.01 to 5 μm. The roundness Rs of component (B) in the surface layer was 1.00 to 1.50, the roundness Rc of component (B) at the center was 1.00 to 1.50, and the ratio Rr of Rc to Rs was in the range of 0.50 to 1.40. The demolding property was improved compared to Comparative Example 3 without adding components (B) and (E), and the addition effect was confirmed.

[0095] (Examples 5 to 7) Components (A), (B), (C), (D), and (E) were used in the contents described in Table 1, and a resin composition was prepared according to the preparation of the above-described resin composition. The viscosity at 25°C and the minimum viscosity after thickening were measured. A cured plate of the resin composition was prepared by the above method, and the dispersion diameter of component (B) in the resin cured product, the roundness Rc of component (B) at the center, and the ratio Rr of Rc to Rs were measured. The minimum viscosity after thickening of the resin composition was in the range of 0.1 to 10,000 Pa·s. Also, the dispersion diameter of component (B) in the resin cured product was in the range of 0.01 to 5 μm. The roundness Rs of component (B) in the surface layer was 1.00 to 1.50, the roundness Rc of component (B) at the center was 1.00 to 1.50, and the ratio Rr of Rc to Rs was in the range of 0.50 to 1.40. The demolding property was improved compared to Comparative Example 4 without adding components (B) and (E), and the addition effect was confirmed.

[0096] (Examples 8 and 9) Components (A), (B), (C), (D), and (E) were used in the contents described in Table 1, and a resin composition was prepared according to the preparation of the above-described resin composition. The viscosity at 25°C and the minimum viscosity after thickening were measured. A cured plate of the resin composition was prepared by the above method, and the dispersion diameter of component (B) in the resin cured product, the roundness Rc of component (B) in the central part, and the ratio Rr of Rc to Rs were measured. The minimum viscosity after thickening of the resin composition was in the range of 0.1 to 10,000 Pa·s. Also, the dispersion diameter of component (B) in the resin cured product was in the range of 0.01 to 5 μm. The roundness Rs of component (B) in the surface layer part was 1.00 to 1.50, the roundness Rc of component (B) in the central part was 1.00 to 1.50, and the ratio Rr of Rc to Rs was in the range of 0.50 to 1.40. The demolding property was improved compared with Comparative Example 5 in which components (B) and (E) were not added, and the addition effect was confirmed.

[0097] (Examples 10 to 13) Components (A), (B), (C), (D), and (E) were used in the contents described in Table 1, and a resin composition was prepared according to the preparation of the above-described resin composition. The viscosity at 25°C and the minimum viscosity after thickening were measured. A cured plate of the resin composition was prepared by the above method, and the dispersion diameter of component (B) in the resin cured product, the roundness Rc of component (B) in the central part, and the ratio Rr of Rc to Rs were measured. The minimum viscosity after thickening of the resin composition was in the range of 0.1 to 10,000 Pa·s. Also, the dispersion diameter of component (B) in the resin cured product was in the range of 0.01 to 5 μm. The roundness Rs of component (B) in the surface layer part was 1.00 to 1.50, the roundness Rc of component (B) in the central part was 1.00 to 1.50, and the ratio Rr of Rc to Rs was in the range of 0.50 to 1.40. The demolding property was improved compared with Comparative Example 6 in which components (B) and (E) were not added, and the addition effect was confirmed.

[0098] (Example 14) The resin composition was prepared according to the preparation method of the resin composition described above with components (A), (B), (C), (D), and (E) in the contents shown in Table 1, and the viscosity at 25°C and the minimum viscosity after thickening were measured. The cured plate of the resin composition was prepared by the above method, and the dispersion diameter of component (B) in the resin cured product, the roundness Rc of component (B) at the center, and the ratio Rr of Rc to Rs were measured. The minimum viscosity after thickening of the resin composition was in the range of 0.1 to 10,000 Pa·s. Also, the dispersion diameter of component (B) in the resin cured product was in the range of 0.01 to 5 μm. The roundness Rs of component (B) in the surface layer was 1.00 to 1.50, the roundness Rc of component (B) at the center was 1.00 to 1.50, and the ratio Rr of Rc to Rs was in the range of 0.50 to 1.40. The flexural strength of the resin cured product was 110 MPa or more. The demolding property was improved compared with Comparative Example 7 in which components (B) and (E) were not added, and the addition effect of the additive could be confirmed while maintaining the flexural strength.

[0099] (Example 15) The resin composition was prepared according to the preparation method of the resin composition described above with components (A), (B), (C), (D), and (E) in the contents shown in Table 1, and the viscosity at 25°C and the minimum viscosity after thickening were measured. The cured plate of the resin composition was prepared by the above method, and the dispersion diameter of component (B) in the resin cured product, the roundness Rc of component (B) at the center, and the ratio Rr of Rc to Rs were measured. The minimum viscosity after thickening of the resin composition was in the range of 0.1 to 10,000 Pa·s. Also, the dispersion diameter of component (B) in the resin cured product was in the range of 0.01 to 5 μm. The roundness Rs of component (B) in the surface layer was 1.00 to 1.50, the roundness Rc of component (B) at the center was 1.00 to 1.50, and the ratio Rr of Rc to Rs was in the range of 0.50 to 1.40. The flexural strength of the resin cured product was 110 MPa or more. The demolding property was improved compared with Comparative Example 8 in which components (B) and (E) were not added, and the addition effect of the additive could be confirmed while maintaining the flexural strength.

[0100] (Comparative Examples 1 to 6) The resin composition was prepared according to the preparation method of the resin composition described above with components (A), (C), and (D) at the contents shown in Table 2, and the viscosity at 25°C and the minimum viscosity after thickening were measured. The mold release property was C in all cases.

[0101] (Comparative Examples 7 and 8) The resin composition was prepared according to the preparation method of the resin composition described above with components (A), (C), and (D) at the contents shown in Table 2, and the viscosity at 25°C and the minimum viscosity after thickening were measured. The flexural strength of the cured resin was 110 MPa or more. The mold release property was C in all cases.

[0102] (Comparative Example 9) The resin composition was prepared according to the preparation method of the resin composition described above with components (A), (B), (C), and (D) at the contents shown in Table 2, and the viscosity at 25°C and the minimum viscosity after thickening were measured. A cured plate of the resin composition was prepared by the above method, and the dispersion diameter of component (B) in the cured resin, the roundness Rc of component (B) at the center, and the ratio Rr of Rc to Rs were measured. The minimum viscosity after thickening of the resin composition was in the range of 0.1 to 10,000 Pa·s. Also, the dispersion diameter of component (B) in the cured resin was in the range of 0.01 to 5 μm. The roundness Rc of component (B) at the center was in the range of 1.00 to 1.50, but the ratio Rr of Rc to Rs was a value greater than 1.50. The mold release property did not improve compared to Comparative Example 1 without adding component (B), and the addition effect could not be confirmed.

[0103] (Comparative Example 10) The resin composition was prepared according to the preparation of the above resin composition with components (A), (B), (C), and (D) in the contents described in Table 2, and the viscosity at 25°C and the minimum viscosity after thickening were measured. The cured plate of the resin composition was prepared by the above method, and the dispersion diameter of component (B) in the cured resin, the roundness Rc of component (B) at the center, and the ratio Rr of Rc to Rs were measured. The minimum viscosity after thickening of the resin composition was in the range of 0.1 to 10,000 Pa·s. Also, the dispersion diameter of component (B) in the cured resin was in the range of 0.01 to 5 μm. The roundness Rc of component (B) at the center was in the range of 1.00 to 1.50, but the ratio Rr of Rc to Rs was a value greater than 1.50. The demolding property did not improve compared to Comparative Example 2 without adding component (B), and the addition effect could not be confirmed.

[0104] (Comparative Example 11) The resin composition was prepared according to the preparation of the above resin composition with components (A), (B), (C), and (D) in the contents described in Table 2, and the viscosity at 25°C and the minimum viscosity after thickening were measured. The cured plate of the resin composition was prepared by the above method, and the dispersion diameter of component (B) in the cured resin, the roundness Rc of component (B) at the center, and the ratio Rr of Rc to Rs were measured. The minimum viscosity after thickening of the resin composition was in the range of 0.1 to 10,000 Pa·s. Also, the dispersion diameter of component (B) in the cured resin was in the range of 0.01 to 5 μm. The roundness Rc of component (B) at the center was in the range of 1.00 to 1.50, but the ratio Rr of Rc to Rs was a value greater than 1.50. The demolding property did not improve compared to Comparative Example 3 without adding component (B), and the addition effect could not be confirmed.

[0105] (Comparative Examples 12 to 14) The resin composition was prepared according to the preparation method of the above resin composition with components (A), (B), (C), and (D) in the contents described in Table 2, and the viscosity at 25°C and the minimum viscosity after thickening were measured. The cured plate of the resin composition was prepared by the above method, and the dispersion diameter of component (B) in the resin cured product, the roundness Rc of component (B) at the center, and the ratio Rr of Rc to Rs were measured. The minimum viscosity after thickening of the resin composition was in the range of 0.1 to 10,000 Pa·s. Also, the dispersion diameter of component (B) in the resin cured product was in the range of 0.01 to 5 μm. The roundness Rc of component (B) at the center was in the range of 1.00 to 1.50, but the ratio Rr of Rc to Rs was a value greater than 1.50. The demolding property did not improve compared to Comparative Example 4 without adding component (B), and the addition effect could not be confirmed.

[0106] (Comparative Example 15) The resin composition was prepared according to the preparation method of the above resin composition with components (A), (B), (C), and (D) in the contents described in Table 2, and the viscosity at 25°C and the minimum viscosity after thickening were measured. The cured plate of the resin composition was prepared by the above method, and the dispersion diameter of component (B) in the resin cured product, the roundness Rc of component (B) at the center, and the ratio Rr of Rc to Rs were measured. The minimum viscosity after thickening of the resin composition was in the range of 0.1 to 10,000 Pa·s. Also, the dispersion diameter of component (B) in the resin cured product was in the range of 0.01 to 5 μm. The roundness Rc of component (B) at the center was in the range of 1.00 to 1.50, but the ratio Rr of Rc to Rs was a value greater than 1.50. The demolding property did not improve compared to Comparative Example 5 without adding component (B), and the addition effect could not be confirmed.

[0107] (Comparative Examples 16 to 18) The resin composition was prepared according to the preparation of the above resin composition with components (A), (B), (C), and (D) at the contents described in Table 2, and the viscosity at 25°C and the minimum viscosity after thickening were measured. The cured plate of the resin composition was prepared by the above method, and the dispersion diameter of component (B) in the resin cured product, the roundness Rc of component (B) at the center, and the ratio Rr of Rc to Rs were measured. The minimum viscosity after thickening of the resin composition was in the range of 0.1 to 10,000 Pa·s. Also, the dispersion diameter of component (B) in the resin cured product was in the range of 0.01 to 5 μm. The roundness Rc of component (B) at the center was in the range of 1.00 to 1.50, but the ratio Rr of Rc to Rs was a value greater than 1.50. The demolding property was not improved compared with Comparative Example 6 without adding component (B), and the addition effect could not be confirmed.

[0108] (Comparative Example 19) The resin composition was prepared according to the preparation of the above resin composition with components (A), (B), (C), and (D) at the contents described in Table 2, and the viscosity at 25°C and the minimum viscosity after thickening were measured. The cured plate of the resin composition was prepared by the above method, and the dispersion diameter of component (B) in the resin cured product, the roundness Rc of component (B) at the center, and the ratio Rr of Rc to Rs were measured. The minimum viscosity after thickening of the resin composition was in the range of 0.1 to 10,000 Pa·s. Also, the dispersion diameter of component (B) in the resin cured product was in the range of 0.01 to 5 μm. The roundness Rc of component (B) at the center was in the range of 1.00 to 1.50, but the ratio Rr of Rc to Rs was a value greater than 1.50. The flexural strength of the resin cured product was inferior in mechanical properties compared with Comparative Example 7 at 106 MPa. The demolding property was not improved compared with Comparative Example 7 without adding component (B), and the addition effect could not be confirmed.

[0109] (Comparative Example 20) The resin composition was prepared according to the preparation of the above resin composition with components (A), (B), (C), and (D) in the contents described in Table 2, and the viscosity at 25°C and the minimum viscosity after thickening were measured. The cured plate of the resin composition was prepared by the above method, and the dispersion diameter of component (B) in the cured resin, the roundness Rc of component (B) at the center, and the ratio Rr of Rc to Rs were measured. The minimum viscosity after thickening of the resin composition was in the range of 0.1 to 10,000 Pa·s. Also, the dispersion diameter of component (B) in the cured resin was in the range of 0.01 to 5 μm. The roundness Rc of component (B) at the center was in the range of 1.00 to 1.50, but the ratio Rr of Rc to Rs was a value greater than 1.50. The flexural strength of the cured resin was inferior in mechanical properties compared to Comparative Example 8 at 105 MPa. The mold release property was not improved compared to Comparative Example 8 without adding component (B), and the addition effect could not be confirmed.

[0110]

Table 1

[0111]

Table 2

Industrial Applicability

[0112] Compared with the conventional epoxy resin composition, the epoxy resin composition of the present invention is excellent in the dispersibility of the solid curing agent and the impregnability to the reinforcing fiber, so that there is little unevenness in physical properties after curing, and it provides a molding material for a fiber-reinforced composite material with good appearance quality. Furthermore, by using such a molding material for a fiber-reinforced composite material, it is excellent in that it provides a fiber-reinforced composite material excellent in appearance quality and mechanical properties. Thereby, it is suitably used for fibers and the like in general for aerospace applications, automotive applications, and sports and industrial applications.

Claims

1. An epoxy resin composition comprising the following components (A) to (E), wherein the dispersion diameter of component (B) in the cured product obtained by heat-treating the epoxy resin composition at the curing temperature for 2 hours is 0.01 to 5 μm. Component (A): An epoxy resin having two or more epoxy groups in one molecule and a viscosity at 25°C of 0.1 to 1000 Pa·s Component (B): An additive having a viscosity at 25°C of 0.01 to 20 Pa·s, and the dispersion diameter of component (B) in the mixture obtained by mixing 1 part by mass of component (B) with 100 parts by mass of component (A) at 25°C is 0.01 to 5 μm Component (C): One or more compounds selected from the group consisting of acid anhydrides, isocyanate compounds or their derivatives, which react with the epoxy resin to increase the viscosity below the curing temperature Component (D): An amine-based epoxy curing agent Component (E): Particles that exhibit thixotropy, which are 0.01 to 5 parts by mass with respect to 100 parts by mass of component (A)

2. The epoxy resin composition according to Claim 1, wherein component (D) is dicyandiamide or a derivative thereof.

3. The epoxy resin composition according to Claim 1 or 2, wherein when the temperature is raised from 25°C to 200°C at a rate of 10°C / min using a rheometer, the lowest viscosity is 0.1 to 10000 Pa·s.

4. The epoxy resin composition according to any one of Claims 1 to 3, having a viscosity at 25°C of 0.1 to 100 Pa·s.

5. The epoxy resin composition according to any one of Claims 1 to 4, wherein the roundness Rc of component (B) at the center of the cured product obtained by heat-treating at the curing temperature for 2 hours is 1.00 to 1.

50.

6. The epoxy resin composition according to Claim 5, wherein the roundness Rc of component (B) at the center of the cured product obtained by heat-treating at the curing temperature for 2 hours is 1.00 to 1.50, and the ratio Rr of Rc to Rs, calculated as Rr = Rs / Rc from the roundness Rs and the roundness Rc, is 0.50 to 1.

40.

7. A molding material comprising the epoxy resin composition according to any one of Claims 1 to 6 and reinforcing fibers.

8. The molding material according to Claim 7, wherein the reinforcing fibers are carbon fibers.

9. A fiber-reinforced composite material formed by molding the molding material according to Claim 7 or 8.

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