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

Abstract

The present invention aims to provide an epoxy resin composition capable of efficiently exhibiting the additive effect of an additive even at high temperatures, a molding material having less unevenness in properties after curing while exhibiting the effect of the additive, and a fiber-reinforced composite material excellent in mechanical properties while exhibiting the effect of the additive. To achieve the above object, the epoxy resin composition of the present invention is an epoxy resin composition comprising components (A) to (E) below, and the dispersion diameter of component (B) in a cured product obtained by heating the epoxy resin composition at a curing temperature for 2 hours is 0.01 to 5 μm. Component (A): an epoxy resin having a viscosity at 25°C of 0.1 to 1000 Pa·s and having two or more epoxy groups in one molecule, component (B): an additive having a viscosity at 25°C of 0.01 to 20 Pa·s, component (C): a compound that undergoes an adhesion reaction with the epoxy resin at or below the curing temperature, component (D): an epoxy curing agent, and component (E): a particle that exhibits thixotropy.

Description

Technical Field

[0001] This invention relates to epoxy resin compositions suitable for use in fiber-reinforced composite materials for aerospace components, automotive components, etc., and molding materials using the same, as well as fiber-reinforced composite materials. Background Technology

[0002] Fiber-reinforced composites, which are made of a combination of reinforcing fibers and epoxy resins, can be designed to take advantage of the strengths of both materials, thus expanding their applications in fields such as aerospace, automotive, and general industry.

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

[0004] Examples of molding materials for fiber-reinforced composites used in compression molding include prepreg preforms, towpregs, bulk molding compounds (BMCs), and sheet molding compounds (SMCs). These molding materials for fiber-reinforced composites are obtained by impregnating reinforcing fibers with an epoxy resin composition.

[0005] As reinforcing fibers, glass fibers, aramid fibers, carbon fibers, boron fibers, etc., can be used. As the matrix resin, any resin selected from thermosetting resins and thermoplastic resins can be used. Among these, thermosetting resins, which are easy to impregnate into the reinforcing fibers, are frequently used. As thermosetting resins, epoxy resins, unsaturated polyester resins, vinyl ester resins, phenolic resins, bismaleimide resins, cyanate ester resins, etc., can be used. Among these, epoxy resins are widely used from the viewpoint of adhesion to reinforcing fibers, dimensional stability, and the mechanical properties of the resulting fiber-reinforced composite material, such as strength and rigidity.

[0006] Epoxy resins are sometimes used directly, but in most cases, various additives are used to improve the properties of the epoxy resin composition. For example, studies have been conducted on the pre-mixing of internal release agents to improve the release properties 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 component decreases, making it difficult to exhibit the characteristics of that component, referred to here as the additive. Furthermore, if the dispersion diameter of the additive becomes large, inhomogeneity will form 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, allowing the additive's effect to be effectively expressed without compromising the properties of the epoxy resin composition. In view of this, as a method for controlling the dispersion diameter of the additive, research has been conducted on controlling the solubility parameter of the additive (Patent Document 1).

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: International Publication No. 2018 / 216524 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] According to the method described in Patent Document 1, the phase separation structure of the additive can be controlled at room temperature, but the following problems exist: the addition effect decreases at high temperatures where the epoxy resin composition can undergo a curing reaction. Furthermore, due to the limitation of the solubility parameter, it cannot be widely applied to other additives.

[0013] As stated above, in the prior art, there is no technology capable of controlling the phase separation structure of all additives in the high-temperature region. Therefore, the object of the present invention is to provide an epoxy resin composition that can efficiently exhibit the additive effect even at high temperatures; further, to provide a molding material that exhibits the additive effect and has minimal heterogeneity in physical properties after curing by using the epoxy resin composition; and further, to provide a fiber-reinforced composite material that exhibits the additive effect and has excellent mechanical properties by using the molding material.

[0014] Methods for solving problems

[0015] To address the aforementioned issues, the inventors of this invention conducted repeated and in-depth research, discovering that in the prior art, the reduced effect of additives at high temperatures is due to the significant decrease in viscosity of the epoxy resin composition at high temperatures, leading to changes in the phase separation structure. Furthermore, through repeated and in-depth research, they discovered that by utilizing particles exhibiting thixotropic properties to suppress the decrease in viscosity of the epoxy resin composition at high temperatures, a low viscosity composition with excellent impregnation between reinforcing fibers can be achieved. This also suppresses the coarsening of the phase separation structure formed during curing, thereby enabling the efficient expression of the additive effect without compromising the properties of the epoxy resin composition. Thus, the present invention, with the following structure, is completed. Specifically, the epoxy resin composition of the present invention is an epoxy resin composition containing the following components (A) to (E), and the cured product obtained by heating the epoxy resin composition at a curing temperature for 2 hours has a dispersion diameter of component (B) of 0.01 to 5 μm.

[0016] Component (A): An epoxy resin with a viscosity of 0.1–1000 Pa·s at 25°C and having more than two epoxy groups in one molecule.

[0017] Component (B): Additive with a viscosity of 0.01–20 Pa·s at 25°C.

[0018] Component (C): Compounds that undergo a tackifying reaction with epoxy resin below the curing temperature.

[0019] Component (D): Epoxy curing agent

[0020] Component (E): The particles that enable thixotropy.

[0021] Furthermore, the molding material of the present invention is formed from the epoxy resin composition of the present invention and reinforcing fibers.

[0022] Furthermore, the fiber-reinforced composite material of the present invention is formed by molding the molding material of the present invention.

[0023] Invention Effects

[0024] 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 exhibits the additive effect while showing minimal unevenness in mechanical properties after curing. The fiber-reinforced composite material of the present invention exhibits the additive effect while also possessing excellent mechanical properties. Detailed Implementation

[0025] Hereinafter, preferred embodiments of the present invention will be described. First, the epoxy resin composition of the present invention will be described. In the present invention, component (A) is an epoxy resin with a viscosity of 0.1 to 1000 Pa·s at 25°C and having two or more epoxy groups in one molecule. By including component (A), heat resistance and mechanical properties can be exhibited. Specific examples of component (A) include 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 them. Examples of epoxy resins having three or more epoxy groups include aliphatic epoxy resins, phenolic varnish-type epoxy resins, cresol-type epoxy resins, cresolic varnish-type epoxy resins, tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, tetraglycidylamine and other glycidylamine-type epoxy resins, phenylenediamine-type epoxy resins, tetra(glycidyloxyphenyl)ethane, tri(glycidyloxymethane) and other glycidyl ether-type epoxy resins, as well as epoxy resins obtained by modifying these resins, and brominated epoxy resins obtained by brominating these epoxy resins, but are not limited to these. Furthermore, two or more of these epoxy resins can be used in combination. Bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, phenolic varnish-type epoxy resins, and cresolic varnish-type epoxy resins are particularly preferred. Using these epoxy resins achieves a further improvement in the mechanical strength of fiber-reinforced composites compared to using, for example, epoxy resins with a naphthalene backbone in one molecule. This is presumably because rigid epoxy resins tend to have a higher crosslinking density during rapid curing, making them more prone to strain; conversely, the likelihood of such problems occurring is lower when using the aforementioned epoxy resins.

[0026] Commercially available aliphatic epoxy resins include, for example, "Denacor (registered trademark)" EX-313, EX-314, EX-321, EX-411, EX-421, EX-512, EX-521, EX-611, EX-612, EX-614, EX-614B, and EX-622 (all manufactured by Nagasekemtex Co., Ltd.).

[0027] Commercially available bisphenol A type epoxy resins include, for example, "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, and "jER (registered trademark)"... ” 1003 (the above are manufactured by Mitsubishi Microwave Co., Ltd.), “Etotron (registered trademark)” 850 (manufactured by DIC Co., Ltd.), “Etotron (registered trademark)” YD-128, Y D-128G, YD-128S (the above are manufactured by Nippon Steel Co., Ltd.), "DER (registered trademark)"-331 (manufactured by Nippon Steel Japan Co., Ltd.), etc.

[0028] Commercially available bisphenol F type epoxy resins include "jER" 806, "jER" 807, "jER" 1750 (all manufactured by Mitsubishi Kemica Co., Ltd.), "Epicon" 830 (manufactured by DIC Co., Ltd.), "Epotet" YDF-170, and "Epotet" YDF2001 (manufactured by Nippon Steel Kemica & Materia Co., Ltd.). Additionally, commercially available tetramethylbisphenol F type epoxy resins with alkyl substitution include "Epotet" YSLV-80Y / X (manufactured by Nippon Steel & Sumitomo Chemical Co., Ltd.).

[0029] Commercially available products made of bisphenol S-type epoxy resin include "Epicon" EXA-1515 (manufactured by DIC Corporation).

[0030] Commercially available phenolic varnish-type epoxy resins include "jER (registered trademark)" 152, "jER (registered trademark)" 154 (all manufactured by Mitsubishi Kemikal Co., Ltd.), "Epicon (registered trademark)" N-740, "Epicon (registered trademark)" N-770, and "Epicon (registered trademark)" N-775 (all manufactured by DIC Co., Ltd.).

[0031] Commercially available products of cresol phenolic resin varnish type epoxy resins include "Epicon" N-660, "Epicon" N-665, "Epicon" N-670, "Epicon" N-673, "Epicon" N-695 (all manufactured by DIC Co., Ltd.), EOCN-1020, EOCN-102S, and EOCN-104S (all manufactured by Nippon Kayaku Co., Ltd.).

[0032] Commercially available products of the phenylene dimethylamine type epoxy resin include TETRAD-X (manufactured by Mitsubishi Gas Chemical Co., Ltd.). These can be used alone or in combination of two or more types.

[0033] Component (A) is preferably a liquid at 1 atmosphere and 25°C. By making component (A) a liquid, component (A) can be easily and uniformly mixed with other components. In this invention, the viscosity of component (A) at 25°C is 0.1 to 1000 Pa·s. Component (A) can be used alone within the above-mentioned viscosity range, or it can be achieved by mixing two or more epoxy resins having two or more epoxy groups per molecule to achieve the above-mentioned viscosity range. By achieving the above-mentioned viscosity range, the mixing efficiency is improved. The upper limit of the above-mentioned viscosity is preferably 100 Pa·s or less, more preferably 50 Pa·s or less, and most preferably 15 Pa·s or less. In addition, the lower limit of the above-mentioned viscosity is preferably 0.3 Pa·s or more, more preferably 0.5 Pa·s or more. By making the viscosity of component (A) at 25°C 1000 Pa·s or less, the viscosity difference between component (A) and other liquid components can be reduced, making it easier to mix uniformly. Furthermore, by making the viscosity of component (A) at 25°C ≥ 0.1 Pa·s, the shear force is increased, making it easier to uniformly mix the solid components other than component (A). Here, the viscosity of component (A) can be determined using the method described later.

[0034] The epoxy resin composition of the present invention comprises an additive as component (B) having a viscosity of 0.01 to 20 Pa·s at 25°C. 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, deodorizing agents, anti-staining agents, heat stabilizers, antistatic agents, plasticizers, lubricants, colorants, pigments, dyes, foaming agents, foaming agents, coupling agents, etc. From the viewpoint of compatibility with component (A), component (B) is preferably a liquid. 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. In addition, the lower limit of the above 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 reducing the viscosity of component (B) at 25°C to below 20 Pa·s, component (B) can be efficiently dispersed without compromising its compatibility with component (A). The viscosity of component (B) can be determined using the method described later.

[0035] Examples of flame retardants include phosphate ester compounds. Commercially available flame retardants include, for example, TCP, TXP, PX-110, CR-733S, CR-741, TMCPP, CR-570, CR-504L (all manufactured by Daihachi Chemical Industry Co., Ltd.), "Adeka Studio" FP-600, PFR, FP-900L (manufactured by ADEKA Co., Ltd.), etc.

[0036] Examples of internal mold release agents include ester compounds formed from organic fatty acids and alcohols, ester compounds formed from polycarboxylic acids and alcohols, aliphatic alcohol compounds, fatty acid amides, silicone oils, vegetable waxes, animal waxes, and fluorinated compounds. Commercially available products include, for example, "MOLD WIZ (registered trademark)" INT-1846, INT-1836, INT-1850, INT-1854, INT-1888LE (manufactured by AXEL PLASTICS RESEARCH LABORATORIES INC.), "Kemuris (registered trademark)" IC-35 (manufactured by Kemuris Japan Co., Ltd.), Licowax S, Licowax P, Licowax OP, Licowax PE190, and Licowax... PED (the above products are manufactured by クラリアントジャパン Co., Ltd.), ステアリルステアレートSL-900 A (manufactured by Riken Micron Co., Ltd.), "Riken (registered trademark)" 430V, 440V, SP -030V, "Escor (registered trademark)" PE-MO, BP-DL (the above are manufactured by Kao Co., Ltd.), KF-96, KF-965, KF-54 (the above are manufactured by Shin-Etsu Chemical Industry Co., Ltd.), etc.

[0037] Examples of ultraviolet absorbers include benzotriazole compounds, triazine compounds, and hindered phenolic compounds. Commercially available examples include "Tinuvin" (registered trademark) 384-2, 400, 477, and "Irganox" (registered trademark) 1135 (all manufactured by BASF Japan Co., Ltd.).

[0038] Examples of light stabilizers include hindered amine compounds. Commercially available examples include "Tinuvin" 123, 249, 292, 5100 (manufactured by BASF Japan Co., Ltd.) and "Adekastab" LA-72, LA-81 (manufactured by ADEKA Co., Ltd.).

[0039] Examples of antioxidants include phenylamine compounds, phenolic compounds, and thioether compounds. Commercially available examples include "NA-LUBE" AO-130, AO-142, and AO-242 (manufactured by KING INDUSTRIES), and "Adekastab" AO-503 and AO-26 (manufactured by ADEKA Co., Ltd.).

[0040] Examples of dispersants include surfactants and high molecular weight dispersants, surfactants and ionic liquids, etc.

[0041] Surfactants are mainly classified into anionic, cationic, nonionic, and amphoteric types. The appropriate type and mixing ratio of surfactant can be selected based on the required properties.

[0042] Examples of anionic surfactants include sulfate esters, sulfonates, and fatty acid esters.

[0043] Examples of cationic surfactants include alkylamine salts and quaternary ammonium salts. More specifically, examples include stearylamine acetate, cocoyl trimethylammonium chloride, tallow trimethylammonium chloride, dimethyl dioleylammonium chloride, methyl oleyl diethanol chloride, tetramethylammonium chloride, lauryl pyridinium chloride, lauryl pyridinium bromide, lauryl disulfide pyridinium salt, cetyl pyridinium bromide, 4-alkyl mercaptopyridine, poly(vinylpyridine)-dodecyl bromide, dodecyl benzyl triethylammonium chloride, and tetradecyl dimethyl benzyl ammonium chloride.

[0044] Examples of amphoteric surfactants include aminocarboxylates.

[0045] Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene derivatives, polyoxyethylene phenyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and alkyl allyl ethers. More specifically, examples include polyoxyethylene lauryl ether, sorbitan fatty acid esters, and polyoxyethylene octylphenyl ether.

[0046] Examples of high molecular weight dispersants include polyurethanes, polycarboxylate esters such as polyacrylates, unsaturated polyamides, polycarboxylic acids, polycarboxylic acid (partial)amine salts, polycarboxylic acid ammonium salts, polycarboxylic acid alkylamine salts, polysiloxanes, long-chain polyaminoamide phosphates, hydroxyl-containing polycarboxylate esters, their modifiers, amides formed by the reaction of poly(lower alkylimides) with polyesters having free carboxyl groups, their salts, and other oily dispersants, (meth)acrylic acid-styrene copolymers, (meth)acrylic acid-(meth)acrylate copolymers, styrene-maleic acid copolymers, polyvinyl alcohol, polyvinylpyrrolidone, and other water-soluble resins, water-soluble polymers, polyester resins, modified polyacrylate resins, ethylene oxide / propylene oxide addition compounds, phosphate ester resins, etc. They can be used alone or in combination of two or more, but are not necessarily limited to these.

[0047] 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, 20 4. Or BYK-P104, P104S, P9920, 220S, 6919, 9076, 9077 or Lactimon, Lactimon-WS or Bykumen (all manufactured by Bickkeme), SOLSPERSE-3000, 9000, 13000, 13240, 13650, 13940, 16000, 17000, 18000, 20000, 21000, 24000, 26000, 27000, 28000, 31845, 3200 0. 32500, 32550, 33500, 32600, 34750, 35100, 36600, 38500, 41000, 41090, 53095, 55000, 76500 (the above are made by Japan R&D Co., Ltd.) , EFKA-46, 47, 48, 452, 4008, 4009, 4010, 4015, 4020, 4047, 4050, 4055, 4060, 4080, 4400, 4401, 4402, 4403, 4406, 440 8. 4300, 4310, 4320, 4330, 4340, 450, 451, 453, 4540, 4550, 4560, 4800, 5010, 5065, 5066, 5070, 7500, 7554, 1101, 120 , 150, 1501, 1502, 1503 (the above are manufactured by チバ・ジャパン Co., Ltd.), "アジスパー (registered trademark)" P A111, PB711, PB821, PB822, PB824 (the above are manufactured by Ajinomoto Chemical Co., Ltd.), etc.

[0048] Examples of ionic liquids include organic compound salts such as imidazolium salts, pyridinium salts, ammonium salts, and phosphonium salts, which are liquids at room temperature.

[0049] Ionic liquids can also be used directly from commercially available products. Examples of commercially available products include 3M (registered trademark) ionic liquid antistatic agent FC4400 (manufactured by 3M Japan Co., Ltd.), CIL-313, CIL-312 (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, and IL-OH9 (manufactured by Hiroei Chemical Industry Co., Ltd.).

[0050] These additives can be used alone or in combination of two or more, but are not necessarily limited to this.

[0051] In this 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 preferably 0.01 to 5 μm. By making the dispersion diameter of component (B) 0.01 μm or more, the properties of component (B) can be further elicited. The dispersion diameter of component (B) is more preferably 1 μm or less, more preferably 0.5 μm or less, and most preferably 0.2 μm or less. By making the dispersion diameter of component (B) 5 μm or less, the properties of component (B) can be further elicited without impairing the mechanical properties of the resin. It should be noted that, in this 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 can be measured using the method described in the section on <Evaluation of the Dispersion Diameter of Component (B) in Component (A)> described later.

[0052] In this invention, component (C) is a compound that undergoes a tackifying reaction with epoxy resin below the curing temperature. It is not particularly limited to any component that tackifies the epoxy resin through covalent bonding, but is preferably an aliphatic amine, acid anhydride, isocyanate compound, or its derivative. It should be noted that in this invention, the curing temperature refers to the temperature at which the tackified resin composition exhibits its lowest viscosity + 20°C. The definition of lowest viscosity is as described later. The tackifying reaction refers to the epoxy resin becoming a semi-cured solid at 25°C.

[0053] Aliphatic amines are amines without aromatic rings. There are no particular limitations as long as they have one or more amino groups in the molecule. Examples include polyalkylene polyamines, isophorone diamine, 3,3'-dimethylenedi(cyclohexylamine), 4,4'-diaminodicyclohexylmethane, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, 3,3'-diethyl-4,4'-diaminodicyclohexylmethane, n-aminoethylpiperazine, norbornene diamine, diethylene glycol diaminopropyl ether, adipic acid dihydrazide, hydrazine, cyanamide, and their derivatives. The amino group is preferably bonded to a primary, secondary, or tertiary carbon atom; for easier resin thickening, it is more preferably bonded to a primary or secondary carbon atom.

[0054] An anhydride is a compound having one or more anhydride groups in its molecule. Examples of anhydrides include methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, methylnadic anhydride, maleic anhydride, and succinic anhydride.

[0055] As an isocyanate compound, any compound having an average of one or more isocyanate groups per molecule is acceptable; there are no particular limitations, and known aliphatic and aromatic isocyanates can be used. Examples of aliphatic isocyanates include ethylene diisocyanate, trimethylene diisocyanate, dodecyl diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, 1,2-propane diisocyanate, 2,3-dimethyltetramethylene diisocyanate, 1,2-butane diisocyanate, 1,3-butane diisocyanate, 1,4-diisocyanatohexane, cyclopentene-1,3-diisocyanate, isophorone diisocyanate, 1,2,3,4-tetraisocyanatobutane, butane-1,2,3-triisocyanate, etc. Aromatic isocyanates that can be used as polyisocyanate compounds (C) include, for example, terephthalic diisocyanate, 1-methylphenyl-2,4-diisocyanate, naphthalene-1,4-diisocyanate, toluene diisocyanate, diphenyl-4,4-diisocyanate, benzene-1,2,4-triisocyanate, phenyl dimethylene diisocyanate, diphenylmethane diisocyanate (MDI), diphenylpropane diisocyanate, tetramethylene xylene diisocyanate, polymethylene polyphenyl polyisocyanate, and other aromatic isocyanates, as well as compounds having a structure in which these aromatic isocyanates are linked by methylene groups, etc.

[0056] In this invention, in order to fully express the low viscosity of the epoxy resin composition, the viscosity of component (C) at 25°C is preferably 1 mPa·s to 10000 mPa·s, more preferably 10 mPa·s to 10000 mPa·s.

[0057] The compounds of component (C) preferably satisfy the following conditions.

[0058] 1.5≤α / β≤10

[0059] α: Total number of epoxy groups in component (A)

[0060] β: The number of functional groups in component (C) that react with epoxy resin.

[0061] More preferably, 3 ≤ α / β ≤ 10. By satisfying the above conditions, the epoxy groups of component (A) react with the functional groups of component (C), thereby improving the workability of the epoxy resin composition before curing.

[0062] In this invention, component (D) is the component that cures the epoxy resin through covalent bonding with the epoxy resin, and is not a component (C). There are no particular limitations as long as it can cure the epoxy resin; examples include amine-based, phenolic-based, acid anhydride-based, thiol-based, imidazole-based, tertiary amines, organophosphorus compounds, urea compounds, ammonium salts, sulfonium salts, etc. Examples of amine-based curing agents include dicyandiamide, aromatic polyamines, aminobenzoates, thiourea addition amines, etc. Examples of phenolic-based curing agents include bisphenol, phenolic varnish resin, cresol phenolic varnish resin, polyphenol compounds, etc. Examples of acid anhydride-based curing agents include phthalic anhydride, maleic anhydride, succinic anhydride, carboxylic anhydride, etc. Examples of thiol-based curing agents include polythiols, polysulfide resins, etc. Among the listed curing agents, amine-based curing agents are preferred. Furthermore, among these, dicyandiamide or its derivatives are particularly preferred. Dicyandiamide excels in imparting high mechanical properties and heat resistance to cured epoxy resins and is widely used as a curing agent for epoxy resins. Furthermore, it is suitable for use due to its excellent storage stability in resin compositions. Dicyandiamide derivatives refer to compounds obtained by bonding dicyandiamide with various compounds. These derivatives, like dicyandiamide, excel in imparting high mechanical properties and heat resistance to cured epoxy resins, and also exhibit excellent storage stability in resin compositions. Examples of dicyandiamide derivatives include compounds obtained by bonding dicyandiamide with epoxy resins, vinyl compounds, acrylic compounds, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxides, and other compounds. These derivatives can be used alone or in combination of two or more. They can also be used in combination with dicyandiamide. Commercially available dicyandiamide products include dicyandiamide (manufactured by Nippon Carbid Industrial Co., Ltd.).

[0063] The epoxy resin composition of the present invention may contain a catalyst as a curing accelerator. By containing a catalyst, the curing time can be shortened. Here, a catalyst is a component that enables the individual curing reaction of the main agent and the curing reaction utilizing the bond formation between the main agent and the curing agent to proceed rapidly and smoothly. Examples include imidazoles, tertiary amines, organophosphorus compounds, urea compounds, ammonium salts, sulfonium salts, etc. Two or more of these catalysts may be used in combination.

[0064] In this invention, component (E) is a particle that exhibits thixotropy. From the viewpoint of controlling the impregnation of the resin into the reinforcing fibers and the phase separation structure formed during curing, component (E) preferably exhibits thixotropy when mixed with the resin component. Examples of particles that exhibit thixotropy when mixed with the resin component include, for example, insoluble polyimide particles, particles formed from poly(meth)acrylamide or its crosslinks, particles formed from poly(meth)acrylate (salt) or its crosslinks, particles formed from (meth)acrylamide alkyl sulfonic acid (salt) or its crosslinks, hydroxymethyl cellulose particles, hydroxyethyl cellulose particles, xanthan gum particles, guar gum particles, carrageenan particles, gelatin particles, starch particles, silanol particles, organobentonite particles, sepiolite particles, palygorskite particles, silica particles, calcium carbonate particles, titanium dioxide particles, and carbon particles. Among these, from the viewpoint of workability and maintaining the mechanical properties of the resin, component (E) is preferably silica particles or carbon particles.

[0065] Here, thixotropy refers to the property of temporarily reducing apparent viscosity by applying deformation under isothermal conditions. In this invention, from the perspective of imparting thixotropy, the specific surface area of ​​component (E) is preferably 50 m². 2 / g or more, preferably 100m 2 / g or higher. There is no particular limit to the upper limit of the specific surface area, but considering particle dispersibility, 1500m² is preferred. 2 / g or less. Specific surface area can be determined using the so-called BET method, which is as follows: at the temperature of liquid nitrogen, molecules with a known adsorption area are adsorbed onto the surface of powder particles, and the specific surface area of ​​the sample is calculated from the amount adsorbed.

[0066] Specifically, examples of silica particles include dry silica and wet silica microparticles. Examples of carbon particles include carbon black, graphite, graphite (lead black), activated carbon, carbon fibers, carbon nanotubes, and fullerenes. Alternatively, products obtained by heat-treating and graphitizing raw materials such as carbon black or activated carbon at temperatures above 1000°C in an inactive atmosphere can also be used. Commercially available silica particles include "Aerogel" 200, RY200S, R972, R976, and R976S (all manufactured by Aerogel Co., Ltd., Nippon). Examples of commercially available carbon particles include "Current Carbon (Registered Trademark)" EC-300J and EC-600JD (the above products are manufactured by Luxtec Carbon Co., Ltd.).

[0067] In this invention, the content of component (E) is preferably 0.01 to 5 parts by mass relative to 100 parts by mass of component (A). From the viewpoint of imparting thixotropy and suppressing the coarsening of the phase separation structure caused by tackification, the content of component (E) is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, relative to 100 parts by mass of component (A). Furthermore, when impregnating the epoxy resin composition with reinforcing fibers, excessive tackification reduces workability; therefore, the content of component (E) is preferably 5 parts by mass or less, more preferably 1 part by mass or less.

[0068] The viscosity of the epoxy resin composition of the present invention at 25°C is preferably 0.1 to 100 Pa·s. More preferably, the viscosity at 25°C is 50 Pa·s or less, even 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 will not decrease excessively, the resin will not flow outwards, and it is easy to uniformly impregnate the reinforcing fibers. Furthermore, by setting the viscosity at 25°C to 100 Pa·s or less, it is easy to suppress the decrease in impregnation, thereby suppressing the formation of voids when producing carbon fiber reinforced composite materials. It should be noted that, in the present invention, the viscosity of the epoxy resin composition at 25°C can be measured using the method described later in <Determination of the Viscosity of the Epoxy Resin Composition at 25°C>. As a means to satisfy the above viscosity range, examples include reducing the content of solid components in the epoxy resin composition and using a component with lower viscosity (A).

[0069] In the epoxy resin composition of the present invention, the dispersion diameter of component (B) in the cured product obtained by heating the epoxy resin composition at a curing temperature for 2 hours is 0.01 to 5 μm. By making the dispersion diameter of component (B) in the cured product 0.01 μm or more, the properties 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 making the dispersion diameter of component (B) 5 μm or less, the mechanical properties of the resin are not impaired, and the properties of component (B) can be exhibited.

[0070] The epoxy resin composition of the present invention preferably has a minimum viscosity of 0.1 to 10000 Pa·s when heated from 25°C to 200°C at a heating rate of 10°C / min using a rheometer. It should be noted that in the present invention, the "minimum viscosity when the epoxy resin composition before curing is heated from 25°C to 200°C at a heating rate of 10°C / min using a rheometer" is sometimes referred to as the minimum viscosity. The minimum viscosity is more preferably 5000 Pa·s or less. Furthermore, the minimum viscosity is more preferably 0.5 Pa·s or more, further preferably 1 Pa·s or more, and most preferably 10 Pa·s or more. By setting the minimum viscosity to 10000 Pa·s or less, the viscosity during molding will not become excessively high, thus suppressing defects in the molded article and improving the quality of the molded article. In addition, by setting the minimum viscosity to 0.1 Pa·s or more, the viscosity reduction 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 expressed. As a means of bringing the minimum viscosity within the aforementioned range, one example is a method of making the epoxy resin into a semi-cured solid at 25°C through a thickening reaction.

[0071] The dispersion diameter of component (B) in the cured material can be obtained as follows: using an optical microscope, scanning electron microscope, transmission microscope, etc., observe the cross-section of the inner layer in the TD direction of 500 μm from the outermost surface of the long side of the molded sheet obtained by heating at the curing temperature for 2 hours. From the obtained observation image, use the image processing software "Image Pro Premier 3D 64-bit Ver 9.2" to extract the particles of component (B) and calculate the average particle size of the extracted particles.

[0072] In the epoxy resin composition of the present invention, the roundness Rs of component (B) in the surface layer of the cured resin obtained by heating at the curing temperature for 2 hours is preferably 1.00 to 1.50. The roundness Rs of component (B) in the surface layer of the cured resin is more preferably 1.30 or less, further preferably 1.20 or less, and most preferably 1.10 or less. By making the roundness Rc of component (B) in the cured resin 1.50 or less, the properties of component (B) can be exhibited without impairing the mechanical properties of the resin composition. As a means to make Rs within the above range, for example, making the minimum viscosity of the epoxy resin composition within the above range.

[0073] Furthermore, when the sphericity Rs of component (B) in the surface layer of the cured resin is 1.00 to 1.50, it is preferable that the sphericity Rc of component (B) in the central layer of the cured resin obtained by heating at the curing temperature for 2 hours is 1.00 to 1.50, and the ratio Rr of Rc to Rs, calculated from the sphericity Rs and Rc of component (B) in the surface layer of the cured resin using Rr = Rs / Rc, is 0.50 to 1.40. As a means to ensure Rc is within the above range, for example, ensuring that 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 within the above range. As a means to ensure Rr is within the above range, for example, ensuring that Rs and Rc are within the above range.

[0074] The roundness Rc of component (B) in the center of the cured resin is more preferably 1.20 or less, further preferably 1.10 or less, and most preferably 1.08 or less. By making the roundness Rc of component (B) in the cured product 1.50 or less, the properties of component (B) can be exhibited without impairing the mechanical properties of the resin composition.

[0075] Furthermore, the ratio of Rc to Rs, Rr, is more preferably 1.30 or less, even more preferably 1.20 or less, and most preferably 1.10 or less. Additionally, the ratio of Rc to Rs, Rr, is more preferably 0.60 or more, even more preferably 0.80 or more, and most preferably 0.90 or more. By ensuring that Rr is within the range of 0.50 to 1.40, component (B) is uniformly dispersed, and the characteristics of component (B) can be exhibited without impairing the mechanical properties of the cured resin.

[0076] Here, roundness is defined as a value closer to 1, indicating greater roundness. In this invention, Rs, Rc, and Rr can be measured using the methods described later in <Evaluation of the roundness Rs of component (B) in the surface layer of the cured resin>, <Evaluation of the roundness Rc of component (B) in the center of the cured resin>, and <Evaluation of the ratio Rc to Rs of component (B) in the cured resin>. The surface layer of the cured resin refers to the TD direction cross-section of the inner 20 μm layer, measured from the outermost surface of the molded sheet obtained by heating at the curing temperature for 2 hours. The center layer refers to the TD direction cross-section of the inner 500 μm layer, measured from the long side of the molded sheet cross-section. The method for manufacturing the molded sheet is as described in the examples.

[0077] By making the dispersion diameter of component (B) in the resin cured product, and the Rs, Rc, and Rr of the resin cured product each fall within the above-mentioned ranges, the dispersion structure of component (B) in the fiber-reinforced composite material can be controlled when it is made, and the properties of component (B) can be further brought out.

[0078] 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 cured resin formed by curing the epoxy resin composition. To obtain a fiber-reinforced composite material with high heat resistance, the glass transition temperature of the cured resin obtained by curing at the curing temperature for 2 hours is preferably 110°C or higher. As a means to bring the glass transition temperature within the above range, for example, increasing the glass transition temperature by including more rigid molecular structures such as aromatics in the epoxy resin composition. Here, the degree of curing of the cured resin can be calculated as follows: the degree of curing (%) is calculated as (QT-QR) / QT×100, using the total calorific value QT of the epoxy resin composition obtained by heating at a rate of 10°C / min using a differential scanning calorimeter, and the residual calorific value QR of the cured product.

[0079] There is no particular upper limit to the glass transition temperature, but it is preferably below 250°C. A glass transition temperature of 120°C to 220°C is further preferred. When the glass transition temperature is above 110°C, it is easy to impart high heat resistance to the cured resin formed by curing the epoxy resin composition. When the glass transition temperature is below 250°C, the crosslinking density of the three-dimensional crosslinking structure of the cured resin formed by curing the epoxy resin composition does not become excessively high, and it is easy to exhibit high mechanical properties. Here, the glass transition temperature of the cured epoxy resin formed by curing the epoxy resin composition can be determined by measurement using a dynamic viscoelasticity (DMA) measuring device. That is, using a rectangular test piece cut from a resin curing plate, DMA measurement is performed under heating conditions, and the temperature of the inflection point of the obtained storage modulus G' is taken as Tg.

[0080] 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 cured resin formed by curing the epoxy resin composition. To obtain a fiber-reinforced composite material with high mechanical properties, the flexural strength of the cured resin obtained by curing at a curing temperature for 2 hours is preferably 110 MPa or more, more preferably 120 MPa or more. When the flexural strength of the cured resin 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 component that will not break or deform even under strong external stress.

[0081] The molding material of the present invention is formed from the epoxy resin composition of the present invention and reinforcing fibers. By using the molding material of the present invention, excellent flowability is exhibited during pressure molding, without the resin flowing first, regardless of molding temperature, resulting in a fiber-reinforced composite material with very high homogeneity of fiber and resin. In the molding material of the present invention, the type, length, and content ratio of reinforcing fibers to resin are not particularly limited, and examples include glass fibers, carbon fibers, graphite fibers, aramid fibers, boron fibers, alumina fibers, and silicon carbide fibers. Two or more of these reinforcing fibers may also be used in combination, but carbon fibers and graphite fibers are preferred for obtaining lighter and more durable molded articles. Especially in applications requiring high material weight and high strength, carbon fibers are preferred due to their excellent specific modulus of elasticity and specific strength. All types of carbon fibers can be used depending on the application, but carbon fibers with a tensile modulus of elasticity of up to 400 GPa are preferred from the perspective of impact resistance. Furthermore, from a strength perspective, to obtain a composite material with high rigidity and mechanical strength, carbon fibers with a tensile strength preferably of 4.4 to 6.5 GPa can be used. Tensile elongation is also an important factor, and high-strength, high-elongation carbon fibers with a tensile modulus of at least 1.7 to 2.3% are preferred. Therefore, carbon fibers possessing a tensile 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.

[0082] Commercially available carbon fiber products include "Treka" T800G-24K, "Treka" T800S-24K, "Treka" T700G-24K, "Treka" T300-3K, and "Treka" T700S-12K (all manufactured by Toreka Co., Ltd.).

[0083] As the reinforcing fiber in this invention, examples of suitable forms include unidirectionally plied long fibers, tows, fabrics, felts, knitted fabrics, braided tapes, and short fibers obtained by cutting to a length of less than 10 mm. Here, "long fiber" refers to a single fiber or fiber bundle that is substantially continuous with a length of 10 mm or more. "Short fiber" refers to a fiber bundle obtained by cutting to a length of less than 10 mm.

[0084] 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 those used in the automotive field, high heat resistance, flexural strength, and other mechanical properties are required. The fiber-reinforced composite material of the present invention exhibits excellent heat resistance and mechanical properties, and is therefore also suitable for use in the automotive field.

[0085] There are no particular limitations on the method for manufacturing the fiber-reinforced composite material of the present invention. Hand lay-up molding, fiber winding, pultrusion molding, resin transfer molding (RTM), autoclave molding of prepreg, and pressure molding of molding materials such as prepreg, towpreg, bulk molding compound (BMC), and sheet molding compound (SMC) are all suitable.

[0086] Example

[0087] The epoxy resin composition, molding material, and fiber-reinforced composite material of the present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0088] <Resin Raw Materials>

[0089] To obtain the epoxy resin compositions of each embodiment and comparative example, the following resin raw materials were used. It should be noted that the values ​​of each component in the epoxy resin composition column of the table represent the content, and unless otherwise specified, the unit ("parts") is "parts by mass".

[0090] 1. Composition (A): Epoxy resin with a viscosity of 0.1–1000 Pa·s at 25°C and having more than two epoxy groups in one molecule.

[0091] • "Epoxy" YD128 (manufactured by Nippon Steel Kemica & Materia Co., Ltd.): Bisphenol A type epoxy resin (viscosity at 25°C: 14 Pa·s)

[0092] • "jER (registered trademark)" 827 (manufactured by Mitsubishi Kemikal Co., Ltd.): Bisphenol A type epoxy resin (viscosity at 25°C: 10 Pa·s)

[0093] • "jER (registered trademark)" 807 (manufactured by Mitsubishi Kemikal Co., Ltd.): Bisphenol A type epoxy resin (viscosity at 25°C: 4 Pa·s)

[0094] • "jER (registered trademark)" 154 (manufactured by Mitsubishi Kemikal Co., Ltd.): Phenolic varnish type epoxy resin (viscosity at 25°C: 1950 Pa·s)

[0095] YED216M (manufactured by Mitsubishi Kemikal Co., Ltd.): Alkyl diglycidyl ether (viscosity at 25°C: 0.02 Pa·s)

[0096] ·TETRAD-X (manufactured by Mitsubishi SEX Chemicals Co., Ltd.) (viscosity at 25°C: 2 Pa·s)

[0097] • Denacol (registered trademark) EX-212 (manufactured by Nagasekemex Co., Ltd.): 1,6-hexanediol diglycidyl ether (viscosity at 25°C: 0.02 Pa·s)

[0098] • "Denacor (registered trademark)" EX-614 (made by Nagasekemex Co., Ltd.): Sorbitol polyglycidyl ether (viscosity at 25°C: 21 Pa·s).

[0099] 2. Component (B): An additive (internal release agent) with a viscosity of 0.01–20 Pa·s at 25°C.

[0100] · "Current (Registered Trademark)" IC-35 (manufactured by Cordron Co., Ltd.) (viscosity at 25°C: 0.4 Pa·s)

[0101] • "Leodore (registered trademark)" 430V (manufactured by Kao Corporation) (viscosity at 25°C: 0.2 Pa·s)

[0102] • "Ekissper (registered trademark)", BP-DL (manufactured by Kao Corporation) (viscosity at 25°C: 0.4 Pa·s).

[0103] 3. Component (C): Compounds that undergo a tackifying reaction with epoxy resin below the curing temperature.

[0104] ·1,4-Butanediamine (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0105] • Isophorone diamine (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0106] HN-2200 (manufactured by Hitachi Chemical Co., Ltd.): 3- or 4-methyl-1,2,3,6-tetrahydrophthalic anhydride

[0107] • "Luplanet (registered trademark)" M20S (manufactured by BASF INOAC Polyurethane Co., Ltd.): Polymer MDI (polymethylene polyphenyl polyisocyanate).

[0108] ·"Desulla (Registered Trademark)" N3400 (manufactured by Sumika Chemicals Co., Ltd.): HDI Ureadione

[0109] · "Tossure (registered trademark)" I (manufactured by Sumika Chemicals Co., Ltd.): isophorone diisocyanate.

[0110] 4. Component (D): Epoxy curing agent

[0111] • Dicyandiamide (manufactured by Carbid Industrial Co., Ltd., Japan)

[0112] • "Curezo (registered trademark)" 2MZA-PW (manufactured by Shikoku Chemical Industry Co., Ltd.)

[0113] · "Amitech (registered trademark)" PN-23J (manufactured by Ajinomoto Chemical Co., Ltd.).

[0114] 5. Component (E): The particles that enable thixotropy.

[0115] ·"AeRoker (registered trademark)" R976 (manufactured by Nippon Akoro Co., Ltd.)

[0116] ・"Current (registered trademark)" EC-300J (manufactured by Lacroix Co., Ltd.).

[0117] <Preparation of Epoxy Resin Compositions>

[0118] The components were mixed according to the contents recorded in Tables 1 and 2 to prepare an epoxy resin composition.

[0119] <Determination of viscosity of epoxy resin composition at 25°C>

[0120] For the epoxy resin composition prepared in the above-mentioned <Preparation of Epoxy Resin Composition>, the complex viscosity was measured using an Anton Paar Physica MCR501 rheometer with 25φ parallel plates at a gap of 1 mm, vibration mode, swing angle φ = 0.0025 rad, frequency of 1 Hz, and at 25°C. It should be noted that the epoxy resin composition after mixing and stirring the components for 5 minutes was used as the test sample.

[0121] <Determination of viscosity of components (A) and (B) at 25°C>

[0122] Using an Anton Paar Physica MCR501 rheometer with 25φ parallel plates, the complex viscosity was measured at a gap of 1 mm, vibration mode, swing angle φ = 0.0025 rad, frequency of 1 Hz, and temperature of 25°C.

[0123] Evaluation of the dispersion diameter of component (B) in component (A)

[0124] At room temperature, 1 part by mass of component (B) was mixed with 100 parts by mass of component (A) to prepare a mixture of components (A) and (B). 0.5 mg of the mixture of components (A) and (B) was spread onto a coverslip placed on a glass slide, and the coverslip was then placed on top. The mixture of components (A) and (B) was calendered from above the coverslip, and a dispersion image was obtained by observation using a Nikon optical microscope “OPTIPHOT” and a Zeiss camera “AxioCam MRc”. The obtained dispersion image was used to extract particles of component (B) using Media Cybertex image processing software “Image Pro Premier 3D64-bit Ver 9.2”. The average diameter of each extracted particle of component (B) was calculated, and the average of the average diameters of all extracted particles was taken as the dispersion diameter of component (B).

[0125] Evaluation of the lowest viscosity of the tackified resin composition

[0126] For the sample to be tested, a DMA (TA Instrument Menthols Corporation ARES) was used. The sample was placed in a worktable with the temperature adjusted to 25°C, and the temperature was increased to 200°C at a rate of 10°C / min. The viscosity was then measured. It should be noted that the sample used was a composition obtained by mixing the various components in an epoxy resin composition and then holding it at 40°C for 24 hours. For example, the viscosity at 70°C is the viscosity of the sample when it reaches 70°C. The same procedure was performed to measure the viscosity at various temperatures, and the viscosity that became the lowest was taken as the minimum viscosity.

[0127] <Preparation of cured resin products>

[0128] After degassing the epoxy resin composition prepared in the above-mentioned <Preparation of Epoxy Resin Composition> under vacuum, it is injected into a mold with a thickness of 2mm, using a 2mm thick "Teflon (registered trademark)" gasket. Curing is then performed at the curing temperature for 2 hours to obtain a 2mm thick cured resin product.

[0129] <Determination of Flexural Strength of Cured Resin>

[0130] The flexural strength of the resin cured product obtained in the above-mentioned <Preparation of Resin Cured Product> was measured according to JIS K7074:1988, with a width of 15 mm and a length of 100 mm. The cut molded pieces were tested using an Instron universal testing machine (manufactured by Instron Corporation) via a three-point bending test. The flexural strength was measured under the conditions of 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. The flexural strength was the average of the values ​​obtained from measuring five samples.

[0131] Evaluation of the dispersion diameter of component (B) in the cured resin

[0132] The TD cross-section of the inner layer, measuring 500 μm from the outermost surface of the long side of the molded sheet prepared in the above-mentioned <Determination of Flexural Strength of Cured Resin>, was observed using a scanning electron microscope. From the obtained observation images, particles of component (B) were extracted using the Media Cybernetics image processing software "Image Pro Premier 3D 64-bit Ver 9.2", and the average diameter of each extracted particle was calculated. The average of the average diameters of all extracted particles was taken as the dispersion diameter of component (B).

[0133] Evaluation of the roundness Rs of component (B) in the surface layer of the cured resin

[0134] The TD cross-section of the inner 20 μm layer, measured from the outermost surface of the long side of the molded sheet prepared in the above-mentioned <Determination of Flexural Strength of Resin-Curedled Products>, was observed using a scanning electron microscope. From the obtained observation images, particles of component (B) were extracted using the Media Cybernetics image processing software "Image Pro Premier 3D 64-bit Ver 9.2", and the roundness of each extracted particle was calculated. The average roundness of all extracted particles was taken as the roundness Rs of component (B) in the surface layer of the resin-cured product.

[0135] Evaluation of the roundness Rc of component (B) in the center of the cured resin

[0136] The TD cross-section of the inner layer (500 μm) measured from the outermost surface of the long side of the molded sheet prepared in the above-mentioned <Determination of Flexural Strength of Resin Cured Products> was observed using a scanning electron microscope. From the obtained observation images, particles of component (B) were extracted using the Media Cybernetics image processing software "Image Pro Premier 3D 64-bit Ver 9.2", and the roundness of each extracted particle was calculated. The average roundness of all extracted particles was taken as the roundness Rc of component (B) in the center of the resin cured product.

[0137] Evaluation of the Rc to Rs ratio (Rr) of component (B) in cured resin products.

[0138] The value of Rr obtained from the above-mentioned <Evaluation of the roundness Rs of component (B) in the surface layer of the resin cured product> and <Evaluation of the roundness Rc of component (B) in the center layer of the resin cured product> is calculated by the formula Rr = Rs / Rc.

[0139] <Evaluation Method for Mold Release Properties of Epoxy Resin Compositions>

[0140] The epoxy resin composition obtained according to the above <Preparation Method of 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. The resulting product was clamped in a small hot press (manufactured by Azuwan Co., Ltd.) that had been preheated to the curing temperature and pressurized at 1.0 MPa for 3 hours. After 2 hours, the product was demolded from the pressurized mold to obtain the epoxy resin cured product. A straight line passing through the center of the epoxy resin cured product was designated as line (1), and a straight line passing through the center and intersecting line (1) perpendicularly was designated as line (2). The surface roughness between two points on the inner side of each line (1) and line (2) 5 mm away from the two ends of the epoxy resin cured product was measured using a surface roughness measuring instrument Servocom 480A (manufactured by Tokyo Seimitsu Co., Ltd.). As the testing conditions, the arithmetic mean roughness Ra(1) and Ra(2) of straight lines (1) and (2) were measured under the conditions of 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 taken as the average roughness Ra of the epoxy resin cured product, and the release property was judged according to the following criteria.

[0141] A: The average surface roughness Ra of the cured epoxy resin is less than 1μm, and it is smooth without deformation or warping.

[0142] B: The average surface roughness Ra of the epoxy resin cured product is greater than 1μm and less than 5μm, with slight deformation and warping.

[0143] C: The average roughness Ra of the epoxy resin cured product is greater than 5μm, and there are significant deformations, warping and cracks.

[0144] (Example 1)

[0145] A resin composition was prepared by adjusting the contents of components (A), (B), (C), (D), and (E) as listed in Table 1, and the viscosity at 25°C and the lowest viscosity after thickening were measured. A cured plate of the resin composition was prepared using the above method, and the dispersion diameter of component (B), the roundness Rc of component (B) in the central portion, and the Rc / Rs ratio Rr in the cured resin were measured. The lowest viscosity of the resin composition after thickening was in the range of 0.1 to 10000 Pa·s. Furthermore, the dispersion diameter of component (B) in the cured resin was in the range of 0.01 to 5 μm. The roundness Rs of component (B) in the surface layer was in the range of 1.00 to 1.50, the roundness Rc of component (B) in the central portion was in the range of 1.00 to 1.50, and the Rc / Rs ratio Rr was in the range of 0.50 to 1.40. The release properties were improved compared to Comparative Example 1 without added components (B) and (E), confirming the effect of the addition.

[0146] (Example 2)

[0147] A resin composition was prepared by adjusting the contents of components (A), (B), (C), (D), and (E) as listed in Table 1, and the viscosity at 25°C and the lowest viscosity after thickening were measured. A cured plate of the resin composition was prepared using the above method, and the dispersion diameter of component (B), the roundness Rc of component (B) in the central portion, and the Rc / Rs ratio Rr in the cured resin were measured. The lowest viscosity of the resin composition after thickening was in the range of 0.1 to 10000 Pa·s. Furthermore, the dispersion diameter of component (B) in the cured resin was in the range of 0.01 to 5 μm. The roundness Rs of component (B) in the surface layer was in the range of 1.00 to 1.50, the roundness Rc of component (B) in the central portion was in the range of 1.00 to 1.50, and the Rc / Rs ratio Rr was in the range of 0.50 to 1.40. The release properties were improved compared to Comparative Example 2 without added components (B) and (E), confirming the effect of the addition.

[0148] (Examples 3 and 4)

[0149] A resin composition was prepared by adjusting the contents of components (A), (B), (C), (D), and (E) as listed in Table 1, and the viscosity at 25°C and the lowest viscosity after thickening were measured. A cured plate of the resin composition was prepared using the above method, and the dispersion diameter of component (B), the roundness Rc of component (B) in the central portion, and the Rc / Rs ratio Rr in the cured resin were measured. The lowest viscosity of the resin composition after thickening was in the range of 0.1 to 10000 Pa·s. Furthermore, the dispersion diameter of component (B) in the cured resin was in the range of 0.01 to 5 μm. The roundness Rs of component (B) in the surface layer was in the range of 1.00 to 1.50, the roundness Rc of component (B) in the central portion was in the range of 1.00 to 1.50, and the Rc / Rs ratio Rr was in the range of 0.50 to 1.40. The release properties were improved compared to Comparative Example 3 without added components (B) and (E), confirming the effect of the addition.

[0150] (Examples 5-7)

[0151] A resin composition was prepared by adjusting the contents of components (A), (B), (C), (D), and (E) as listed in Table 1, and the viscosity at 25°C and the lowest viscosity after thickening were measured. A cured plate of the resin composition was prepared using the above method, and the dispersion diameter of component (B), the roundness Rc of component (B) in the central portion, and the Rc / Rs ratio Rr in the cured resin were measured. The lowest viscosity of the resin composition after thickening was in the range of 0.1 to 10000 Pa·s. Furthermore, the dispersion diameter of component (B) in the cured resin was in the range of 0.01 to 5 μm. The roundness Rs of component (B) in the surface layer was in the range of 1.00 to 1.50, the roundness Rc of component (B) in the central portion was in the range of 1.00 to 1.50, and the Rc / Rs ratio Rr was in the range of 0.50 to 1.40. The release properties were improved compared to Comparative Example 4 without added components (B) and (E), confirming the effect of the addition.

[0152] (Examples 8 and 9)

[0153] A resin composition was prepared by adjusting the contents of components (A), (B), (C), (D), and (E) as listed in Table 1, and the viscosity at 25°C and the lowest viscosity after thickening were measured. A cured plate of the resin composition was prepared using the above method, and the dispersion diameter of component (B), the roundness Rc of component (B) in the central portion, and the Rc / Rs ratio Rr in the cured resin were measured. The lowest viscosity of the resin composition after thickening was in the range of 0.1 to 10000 Pa·s. Furthermore, the dispersion diameter of component (B) in the cured resin was in the range of 0.01 to 5 μm. The roundness Rs of component (B) in the surface layer was in the range of 1.00 to 1.50, the roundness Rc of component (B) in the central portion was in the range of 1.00 to 1.50, and the Rc / Rs ratio Rr was in the range of 0.50 to 1.40. The release properties were improved compared to Comparative Example 5 without added components (B) and (E), confirming the effect of the addition.

[0154] (Examples 10-13)

[0155] A resin composition was prepared by adjusting the contents of components (A), (B), (C), (D), and (E) as listed in Table 1, and the viscosity at 25°C and the lowest viscosity after thickening were measured. A cured plate of the resin composition was prepared using the above method, and the dispersion diameter of component (B), the roundness Rc of component (B) in the central portion, and the Rc / Rs ratio Rr in the cured resin were measured. The lowest viscosity of the resin composition after thickening was in the range of 0.1 to 10000 Pa·s. Furthermore, the dispersion diameter of component (B) in the cured resin was in the range of 0.01 to 5 μm. The roundness Rs of component (B) in the surface layer was in the range of 1.00 to 1.50, the roundness Rc of component (B) in the central portion was in the range of 1.00 to 1.50, and the Rc / Rs ratio Rr was in the range of 0.50 to 1.40. The release properties were improved compared to Comparative Example 6 without added components (B) and (E), confirming the effect of the addition.

[0156] (Example 14)

[0157] A resin composition was prepared by adjusting the contents of components (A), (B), (C), (D), and (E) as listed in Table 1, and the viscosity at 25°C and the minimum viscosity after thickening were measured. A cured plate of the resin composition was prepared using the above method, and the dispersion diameter of component (B), the roundness Rc of component (B) in the central portion, and the Rc / Rs ratio Rr in the cured resin were measured. The minimum viscosity of the resin composition after thickening was in the range of 0.1 to 10000 Pa·s. Furthermore, the dispersion diameter of component (B) in the cured resin was in the range of 0.01 to 5 μm. The roundness Rs of component (B) in the surface layer was in the range of 1.00 to 1.50, the roundness Rc of component (B) in the central portion was in the range of 1.00 to 1.50, and the Rc / Rs ratio Rr was in the range of 0.50 to 1.40. The flexural strength of the cured resin was 110 MPa or higher. The release properties were improved compared to Comparative Example 7 without added components (B) and (E), and the effect of the additive was confirmed while maintaining the bending strength.

[0158] (Example 15)

[0159] A resin composition was prepared by adjusting the contents of components (A), (B), (C), (D), and (E) as listed in Table 1, and the viscosity at 25°C and the minimum viscosity after thickening were measured. A cured plate of the resin composition was prepared using the above method, and the dispersion diameter of component (B), the roundness Rc of component (B) in the central portion, and the Rc / Rs ratio Rr in the cured resin were measured. The minimum viscosity of the resin composition after thickening was in the range of 0.1 to 10000 Pa·s. Furthermore, the dispersion diameter of component (B) in the cured resin was in the range of 0.01 to 5 μm. The roundness Rs of component (B) in the surface layer was in the range of 1.00 to 1.50, the roundness Rc of component (B) in the central portion was in the range of 1.00 to 1.50, and the Rc / Rs ratio Rr was in the range of 0.50 to 1.40. The flexural strength of the cured resin was 110 MPa or higher. The release properties were improved compared to Comparative Example 8 without added components (B) and (E), and the effect of the additive was confirmed while maintaining the flexural strength.

[0160] (Comparative Examples 1-6)

[0161] A resin composition was prepared by adjusting the contents of components (A), (C), and (D) as listed in Table 2, and the viscosity at 25°C and the minimum viscosity after thickening were measured. The release properties were all rated as C.

[0162] (Compare Examples 7 and 8)

[0163] A resin composition was prepared according to the above-described resin composition formulation, with components (A), (C), and (D) in the amounts listed in Table 2. The viscosity at 25°C and the minimum viscosity after thickening were measured. The flexural strength of the cured resin was ≥110 MPa. The release properties were all C.

[0164] (Comparative Example 9)

[0165] A resin composition was prepared according to the above-described resin composition formulation, with components (A), (B), (C), and (D) in the amounts listed in Table 2. The viscosity at 25°C and the lowest viscosity after thickening were measured. A cured resin composition was prepared using the above method, and the dispersion diameter of component (B), the roundness Rc of component (B) in the central portion, and the Rc / Rs ratio Rr in the cured resin were measured. The lowest viscosity of the thickened resin composition was in the range of 0.1 to 10000 Pa·s. Furthermore, 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) in the central portion was in the range of 1.00 to 1.50, but the Rc / Rs ratio Rr was greater than 1.50. The release properties were not improved compared to Comparative Example 1 without component (B), and the effect of addition could not be confirmed.

[0166] (Comparative Example 10)

[0167] A resin composition was prepared according to the above-described resin composition formulation, with components (A), (B), (C), and (D) in the amounts listed in Table 2. The viscosity at 25°C and the lowest viscosity after thickening were measured. A cured resin composition was prepared using the above method, and the dispersion diameter of component (B), the roundness Rc of component (B) in the central portion, and the Rc / Rs ratio Rr in the cured resin were measured. The lowest viscosity of the thickened resin composition was in the range of 0.1 to 10000 Pa·s. Furthermore, 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) in the central portion was in the range of 1.00 to 1.50, but the Rc / Rs ratio Rr was greater than 1.50. The release properties were not improved compared to Comparative Example 2 without component (B), and the effect of addition could not be confirmed.

[0168] (Comparative Example 11)

[0169] A resin composition was prepared according to the above-described resin composition formulation, with components (A), (B), (C), and (D) in the amounts listed in Table 2. The viscosity at 25°C and the lowest viscosity after thickening were measured. A cured resin composition was prepared using the above method, and the dispersion diameter of component (B), the roundness Rc of component (B) in the central portion, and the Rc / Rs ratio Rr in the cured resin were measured. The lowest viscosity of the thickened resin composition was in the range of 0.1 to 10000 Pa·s. Furthermore, 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) in the central portion was in the range of 1.00 to 1.50, but the Rc / Rs ratio Rr was greater than 1.50. The release properties were not improved compared to Comparative Example 3 without component (B), and the effect of addition could not be confirmed.

[0170] (Comparative Examples 12-14)

[0171] A resin composition was prepared according to the above-described resin composition formulation, with components (A), (B), (C), and (D) in the amounts listed in Table 2. The viscosity at 25°C and the lowest viscosity after thickening were measured. A cured resin composition was prepared using the above method, and the dispersion diameter of component (B), the roundness Rc of component (B) in the central portion, and the Rc / Rs ratio Rr in the cured resin were measured. The lowest viscosity of the thickened resin composition was in the range of 0.1 to 10000 Pa·s. Furthermore, 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) in the central portion was in the range of 1.00 to 1.50, but the Rc / Rs ratio Rr was greater than 1.50. The release properties were not improved compared to Comparative Example 4 without component (B), and the effect of addition could not be confirmed.

[0172] (Comparative Example 15)

[0173] A resin composition was prepared according to the above-described resin composition formula, with components (A), (B), (C), and (D) in the amounts listed in Table 2. The viscosity at 25°C and the lowest viscosity after thickening were measured. A cured resin composition was prepared using the above method, and the dispersion diameter of component (B), the roundness Rc of component (B) in the central portion, and the Rc / Rs ratio Rr in the cured resin were measured. The lowest viscosity of the thickened resin composition was in the range of 0.1 to 10000 Pa·s. Furthermore, 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) in the central portion was in the range of 1.00 to 1.50, but the Rc / Rs ratio Rr was greater than 1.50. The release properties were not improved compared to Comparative Example 5 without component (B), and the effect of addition could not be confirmed.

[0174] (Comparative Examples 16-18)

[0175] A resin composition was prepared according to the above-described resin composition formulation, with components (A), (B), (C), and (D) in the amounts listed in Table 2. The viscosity at 25°C and the lowest viscosity after thickening were measured. A cured resin composition was prepared using the above method, and the dispersion diameter of component (B), the roundness Rc of component (B) in the central portion, and the Rc / Rs ratio Rr in the cured resin were measured. The lowest viscosity of the thickened resin composition was in the range of 0.1 to 10000 Pa·s. Furthermore, 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) in the central portion was in the range of 1.00 to 1.50, but the Rc / Rs ratio Rr was greater than 1.50. The release properties were not improved compared to Comparative Example 6 without component (B), and the effect of addition could not be confirmed.

[0176] (Comparative Example 19)

[0177] A resin composition was prepared according to the above-described resin composition formulation, with components (A), (B), (C), and (D) in the amounts listed in Table 2. The viscosity at 25°C and the lowest viscosity after thickening were measured. A cured resin composition was prepared using the above method, and the dispersion diameter of component (B), the roundness Rc of component (B) in the central portion, and the Rc / Rs ratio Rr were measured. The lowest viscosity of the thickened resin composition was in the range of 0.1 to 10000 Pa·s. Furthermore, 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) in the central portion was in the range of 1.00 to 1.50, but the Rc / Rs ratio Rr was greater than 1.50. The flexural strength of the cured resin was 106 MPa, which was worse than that of Comparative Example 7. The release properties were not improved compared to Comparative Example 7 without component (B), so the effect of adding component (B) could not be confirmed.

[0178] (Comparative Example 20)

[0179] A resin composition was prepared according to the above-described resin composition formulation, with components (A), (B), (C), and (D) in the amounts listed in Table 2. The viscosity at 25°C and the lowest viscosity after thickening were measured. A cured resin composition was prepared using the above method, and the dispersion diameter of component (B), the roundness Rc of component (B) in the central portion, and the Rc / Rs ratio Rr were measured. The lowest viscosity of the thickened resin composition was in the range of 0.1 to 10000 Pa·s. Furthermore, 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) in the central portion was in the range of 1.00 to 1.50, but the Rc / Rs ratio Rr was greater than 1.50. The flexural strength of the cured resin was 105 MPa, which was worse than that of Comparative Example 8. The release properties were not improved compared to Comparative Example 8 without component (B), so the effect of addition could not be confirmed.

[0180]

[0181]

[0182] Industrial availability

[0183] Compared to conventional epoxy resin compositions, the epoxy resin composition of the present invention is superior in the following aspects: excellent dispersibility of the solid curing agent and excellent impregnation into the reinforcing fibers. Therefore, it can provide a molding material for fiber-reinforced composite materials with less unevenness in cured physical properties and good appearance quality. Furthermore, by using this molding material for fiber-reinforced composite materials, fiber-reinforced composite materials with excellent appearance quality and mechanical properties can be provided. Thus, it is suitable for fibers and the like in all applications, including sports and industrial applications, in addition to aerospace and automotive applications.

Claims

1. An epoxy resin composition comprising components (A) to (E) thereof, wherein the dispersion diameter of component (B) in the cured product obtained by heat-treating the epoxy resin composition at a curing temperature for 2 hours is 0.01 to 5 μm. Component (A): An epoxy resin with a viscosity of 0.1~1000 Pa·s at 25°C and having more than two epoxy groups in one molecule. Component (B): An additive with a viscosity of 0.01~20 Pa·s at 25℃. Component (C): A compound that undergoes a tackifying reaction with epoxy resin below the curing temperature. Ingredient (D): Amine-based epoxy curing agent. Component (E): The particles that enable thixotropy. The component (C) is an acid anhydride, an isocyanate compound, or a derivative thereof. The content of component (E) is 0.01 to 5 parts by weight relative to 100 parts by weight of component (A). When the epoxy resin composition is heated from 25°C to 200°C at a heating rate of 10°C / min using a rheometer, the lowest viscosity is 0.5~10000 Pa·s.

2. The epoxy resin composition according to claim 1 has a viscosity of 0.1~100 Pa·s at 25°C.

3. In the epoxy resin composition according to claim 1 or 2, 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 0.01~5 μm.

4. The epoxy resin composition according to claim 1 or 2, wherein the roundness Rs of component (B) in the surface layer of the cured product obtained by heat treatment at the curing temperature for 2 hours is 1.00 to 1.

50.

5. The epoxy resin composition according to claim 4, wherein the roundness Rc of component (B) in the center of the cured product obtained by heat treatment at the curing temperature for 2 hours is 1.00~1.50, and the ratio Rr of Rc to Rs, calculated from the roundness Rs and the roundness Rc by Rr=Rs / Rc, is 0.50~1.

40.

6. A molding material formed from the epoxy resin composition and reinforcing fibers according to any one of claims 1 to 5.

7. The molding material according to claim 6, wherein the reinforcing fiber is carbon fiber.

8. A fiber-reinforced composite material formed by molding the molding material according to claim 6 or 7.

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