Epoxy resin composition, molding material for fiber-reinforced composite material, fiber-reinforced composite material, and structural member

Abstract

[Problem] To provide: an epoxy resin composition which has excellent impregnation into reinforcing fibers, enables high-order control of the crosslinked structure of a cured object, and achieves both high elastic modulus and high toughness; and a fiber-reinforced composite material in which a decrease in TgH / W with respect to TgDRY is inhibited, and which has excellent water resistance even in a severe environment, can be used over a long period, and exhibits high mechanical characteristics. [Solution] The epoxy resin composition comprises the following components (A) to (D), wherein the component (C) includes a chloride as an anion species. (A) an epoxy resin; (B) an acid anhydride; (C) a quaternary amine salt and / or a quaternary phosphonium salt; (D) core / shell rubber particles.

Description

Epoxy resin composition, molding material for fiber-reinforced composite material, fiber-reinforced composite material and structural member

[0001] The present invention relates to an epoxy resin composition used in a fiber-reinforced composite material, a molding material for the fiber-reinforced composite material, a fiber-reinforced composite material, and a structural member using the same.

[0002] Thermosetting resins are liquid and easy to handle before curing, and when cured by heat, they form a crosslinked structure, becoming insoluble and infusible resins that exhibit excellent heat resistance and chemical resistance, and are therefore used in a variety of fields. Epoxy resins, in particular, are widely used in paints, electrical and electronic materials, civil engineering and construction materials, adhesives, fiber-reinforced composite materials, and other applications because they do not outgas during curing, have little cure shrinkage, and exhibit excellent adhesion, rigidity, toughness, and other properties after curing.

[0003] Amine-curing, phenol-curing, and acid anhydride-curing curing agents are commonly used to cure epoxy resins. In recent years, as the market for fiber-reinforced composite materials has expanded, the daily production volume and part size have tended to increase. Therefore, there is a demand for resins that have fast curing properties that allow for mass production and excellent viscosity stability for long-term use. Furthermore, from the perspective of safety, fiber-reinforced composite materials used in mobility fields such as aircraft and automobiles must have extremely high levels of mechanical properties and water resistance in harsh environments.

[0004] In order to develop an epoxy resin composition that satisfies the above-mentioned requirements, the following studies have been conducted. Patent Document 1 discloses a resin composition in which the amounts of an acid anhydride curing agent and a curing accelerator are adjusted. Patent Document 2 discloses an epoxy resin composition using an acid anhydride curing agent, characterized by a rubber-state elastic modulus of 10 MPa or less and a Tg of 95°C or more. Patent Document 3 discloses a resin composition using a glycidyl ether-type epoxy resin in combination with an acid anhydride and core-shell rubber particles. Patent Document 4 discloses a resin composition using an epoxy resin in combination with an acid anhydride, diazabicycloundecene or diazabicyclononene, a salt with an organic compound, and core-shell rubber particles.

[0005] Furthermore, the following studies have been conducted so far on molding materials for fiber-reinforced composite materials, particularly those combined with carbon fiber. In the aforementioned Patent Document 1, a phosphonium salt or the like is used as a curing accelerator for acid anhydride-cured epoxy, and Torayca T300-3K is used for the carbon fiber. In the aforementioned Patent Document 2, a tertiary amine or the like is used as a curing accelerator for acid anhydride-cured epoxy, and Torayca T700SC-12K is used for the carbon fiber. In the aforementioned Patent Document 4, a DBU complex or the like is used as a curing accelerator for acid anhydride-cured epoxy, and Torayca T700SC-12K is used for the carbon fiber.

[0006] International Publication No. 2016 / 158757 Japanese Patent Application Laid-Open No. 2017-119812 Japanese Patent Application Laid-Open No. 2018-35210 International Publication No. 2013 / 115152

[0007] The epoxy resin composition described in Patent Document 1 is excellent in fast curing property and viscosity stability, but the cured product obtained from the epoxy resin composition still has insufficient water resistance and flexural modulus.

[0008] Although the cured product of the epoxy resin composition described in Patent Document 2 has excellent mechanical properties, the water resistance of this cured product is still insufficient.

[0009] The epoxy resin composition described in Patent Document 3 has a low viscosity, and the cured product of the epoxy resin composition exhibits a high toughness-improving effect, but the water resistance and flexural modulus are still insufficient.

[0010] Although the cured product of the epoxy resin composition described in Patent Document 4 has an excellent balance of mechanical properties, the cured product still has insufficient water resistance.

[0011] The first object of the present invention is to provide an epoxy resin composition and a fiber-reinforced composite material having the following properties. The provided epoxy resin composition overcomes the drawbacks of the prior art and has excellent impregnation ability into reinforcing fibers. Furthermore, the cured product obtained by curing the provided epoxy resin composition has high toughness and suppresses a decrease in Tg in a hydrated state relative to Tg in a dry state. Furthermore, a fiber-reinforced composite material using the epoxy resin composition exhibits excellent water resistance even in harsh environments and can be used for a long period of time while maintaining high mechanical properties.

[0012] Furthermore, the molding material for fiber-reinforced composite materials described in the above-mentioned Patent Document 1 can produce molded articles that are less susceptible to cracking after demolding, but the compressive strength is insufficient, and this does not lead to weight reduction of the molded articles.

[0013] The molding material for fiber-reinforced composite materials described in Patent Document 2 mentioned above has excellent impregnation properties and can produce molded articles that are less likely to crack after demolding, but its compressive strength under wet heat conditions is insufficient, and it has not yet led to weight reduction of molded articles.

[0014] The molding material for fiber-reinforced composite materials described in Patent Document 4 mentioned above has excellent impregnation properties and can produce molded articles that are less likely to crack after demolding, but its compressive strength under wet heat conditions is insufficient, and it has not yet led to weight reduction of molded articles.

[0015] A second object of the present invention is to provide a molding material for fiber-reinforced composites that overcomes the drawbacks of the prior art. This molding material has excellent resin impregnation properties for reinforcing fibers, and its use enables the production of molded articles that are less susceptible to cracking after demolding, and also enables the realization of fiber-reinforced composites that have high compressive strength under both dry and hot and humid conditions.

[0016] The present invention, which has been made to solve the above problems, has the following configuration. [1] An epoxy resin composition comprising the following components (A) to (D), wherein component (C) contains chloride as the anion species: (A): epoxy resin (B): acid anhydride (C): quaternary amine salt and / or quaternary phosphonium salt (D): core-shell rubber particles. [2] The epoxy resin composition according to [1], wherein component (A) contains a glycidylamine-type epoxy resin. [3] The epoxy resin composition according to [1] or [2], wherein the cured product obtained by curing the epoxy resin composition under the following curing conditions satisfies the following formula 1: Curing conditions: The epoxy resin composition is heat-treated at 120°C for 2 hours, then at 150°C for 1 hour, and then dried at 80°C under vacuum for 8 hours. 0<Abs1 / Abs2≦0.100 (Formula 1), where Abs1 is the peak at 1780 cm in a spectrum obtained by infrared absorption spectroscopy (IR). －１ Absorbance at 1730 cm in the spectrum obtained by infrared absorption spectroscopy (IR) －１[4] The epoxy resin composition according to [2], containing 15% by mass or more and 100% by mass or less of a glycidylamine-type epoxy resin relative to 100% by mass of the component (A). [5] The epoxy resin composition according to any one of [1] to [4], containing 0.1 parts by mass or more and 25 parts by mass or less of the component (C) relative to 100 parts by mass of the component (A). [6] The epoxy resin composition according to any one of [1] to [5], containing at least one selected from the group consisting of ammonium chloride, imidazolium chloride, pyridinium chloride, and phosphonium chloride as the component (C). [7] A molding material for a fiber-reinforced composite material, comprising the epoxy resin composition according to any one of [1] to [6] and reinforcing fibers. [8] The molding material for a fiber-reinforced composite material according to [7], wherein the reinforcing fibers are carbon fibers. [9] A molding material comprising an epoxy resin composition containing the following components (A) to (C) and carbon fibers satisfying the following conditions [a] to [c]: (A): Epoxy resin (B): Acid anhydride (C): Quaternary amine salt and / or quaternary phosphonium salt [a]: Strand tensile strength is 4 GPa or more and 8 GPa or less [b]: Strand tensile modulus is 230 GPa or more and 350 GPa or less [c]: Surface specific oxygen concentration O / C is 0.05 or more and 0.20 or less

[10] The molding material according to [9], wherein the epoxy resin composition further contains the following component: (D): Core-shell rubber particles

[11] The molding material according to [9] or

[10] , wherein the component (A) contains a glycidyl amine-type epoxy resin.

[12] The molding material according to any one of [9] to

[11] , wherein the carbon fiber further satisfies the following condition: [d]: The cross-sectional shape is substantially circular

[13] A fiber-reinforced composite material obtained by curing the molding material according to any one of [7] to

[12] .

[14] A structural member made of the fiber-reinforced composite material according to

[13] .

[0017] The epoxy resin composition of the present invention is an epoxy resin composition that has excellent impregnation ability into reinforcing fibers, and the toughness of a cured product obtained by curing this epoxy resin composition is high, and the decrease in Tg in a hydrated state relative to Tg in a dry state is suppressed. Use of the epoxy resin composition of the present invention provides a fiber-reinforced composite material that has excellent water resistance even under harsh environments, can be used for a long period of time, and exhibits high mechanical properties.

[0018] Furthermore, the molding material of the present invention has excellent resin impregnation properties into reinforcing fibers, and the fiber-reinforced composite material obtained by curing the molding material is less likely to crack when demolded. Furthermore, the fiber-reinforced composite material obtained by curing the molding material of the present invention not only exhibits high compressive strength in the fiber direction when dried at room temperature, but also maintains high compressive strength in the fiber direction even in a humid and hot environment.

[0019] First, we will explain the epoxy resin composition, which is a first aspect of the present invention. The epoxy resin composition of the present invention is an epoxy resin composition containing the following components (A) to (D), with component (C) containing chloride as the anion species: Component (A): epoxy resin, Component (B): acid anhydride, Component (C): quaternary amine salt and / or quaternary phosphonium salt, and Component (D): core-shell rubber particles.

[0020] Component (A) is an epoxy resin. The epoxy resin used as component (A) is not particularly limited as long as it is a compound having an epoxy group in the molecule. Specific examples include bisphenol A type epoxy resins, bisphenol F type epoxy resins, amine type epoxy resins, aliphatic epoxy resins, etc. These epoxy resins can be used alone or in combination of two or more types.

[0021] Commercially available bisphenol A epoxy resins include, for example, jER (registered trademark) 825 and jER (registered trademark) 828 (both manufactured by Mitsubishi Chemical Corporation), Epotohto (registered trademark) YD-128 and Epotohto (registered trademark) YD-8125 (both manufactured by Nippon Steel Chemical & Material Co., Ltd.), DER (registered trademark) 331 and DER (registered trademark) 332 (both manufactured by The Dow Chemical Company, Ltd.), and the like.

[0022] Commercially available bisphenol F epoxy resins that can be used include, for example, jER (registered trademark) 806, jER (registered trademark) 807, and jER (registered trademark) 4004P (all manufactured by Mitsubishi Chemical Corporation), EPICLON (registered trademark) 830 (manufactured by DIC Corporation), Epototo (registered trademark) YD-170, and Epototo (registered trademark) YDF-8170C (all manufactured by Nippon Steel Chemical & Material Co., Ltd.).

[0023] Examples of amine-type epoxy resins include tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, and diglycidylaniline.

[0024] Examples of aliphatic epoxy resins include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, polyethylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether.

[0025] Commercially available examples of the aliphatic epoxy resins listed above include "Denacol (registered trademark)" EX-810, "Denacol (registered trademark)" EX-841, "Denacol (registered trademark)" EX-211, "Denacol (registered trademark)" EX-212, "Denacol (registered trademark)" EX-214, "Denacol (registered trademark)" EX-252, and "Denacol (registered trademark)" EX-931 (all manufactured by Nagase ChemteX Corporation), "ADEKA GLYCIROL (registered trademark)" ED-503, "ADEKA GLYCIROL (registered trademark)" ED-523, and "ADEKA GLYCIROL (registered trademark)" ED-506 (all manufactured by ADEKA Corporation), and the like.

[0026] Among the epoxy resins listed above, glycidylamine-type epoxy resins, particularly diglycidylaniline, are preferably used as component (A) in the epoxy resin composition of the present invention because they provide an excellent balance between the viscosity of the epoxy resin composition and the mechanical properties such as flexural modulus and strength of the resulting cured product. Considering the magnitude of the effect of improving the mechanical properties of the cured product obtained by including a glycidylamine-type epoxy resin in an epoxy resin composition, the glycidylamine-type epoxy resin is preferably contained in an amount of 15 to 100 mass%, more preferably 25 to 100 mass%, and even more preferably 35 to 100 mass%, per 100 mass% of component (A).

[0027] Component (B) is an acid anhydride, specifically a compound having one or more acid anhydride groups per molecule that can react with the epoxy groups of component (A), and acts as a curing agent for epoxy resins. Specific examples include carboxylic acid anhydrides. Component (B) preferably contains four or fewer acid anhydride groups per molecule.

[0028] Component (B) may be an acid anhydride that does not have an alicyclic structure, such as phthalic anhydride or succinic anhydride. However, acid anhydrides that have an alicyclic structure are preferably used because they are low-viscosity liquids and easy to handle, and the mechanical properties of the cured products obtained using them are good. Of the acid anhydrides that have an alicyclic structure, compounds that have a cycloalkane ring or a cycloalkene ring are more preferably used.

[0029] Specific examples of acid anhydrides having such an alicyclic structure include hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyldihydronadic anhydride, 1,2,4,5-cyclopentanetetracarboxylic dianhydride, 1,2,3,6-tetrahydrophthalic anhydride, methyl-1,2,3,6-tetrahydrophthalic anhydride, nadic anhydride, methylnadic anhydride, bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, and 4-(2,5-dioxotetrahydrofuran-3-yl)-3-methyl-1,2,5,6-tetrahydrophthalic anhydride. Among these, acid anhydrides selected from hexahydrophthalic anhydride, tetrahydrophthalic anhydride, nadic anhydride, and alkyl-substituted versions thereof are preferably used as component (B) because they provide an excellent balance between the viscosity of the epoxy resin composition using these and the mechanical properties such as flexural modulus and strength of the cured product obtained from the composition.

[0030] Regarding the blending ratio of component (A) and component (B), the ratio of the number of acid anhydride groups (H) in component (B) to the total number of epoxy groups (E) in component (A), i.e., the H / E ratio, is preferably in the range of 0.8 to 1.2, more preferably in the range of 0.85 to 1.15, and even more preferably in the range of 0.9 to 1.1. If the H / E ratio is below 0.8, the epoxy resin of component (A) will be present in excess, which may lead to polymerization between these epoxy resins and result in a deterioration in the physical properties of the cured product. Similarly, if the H / E ratio exceeds 1.2, the curing agent component of component (B) will be present in excess, which may result in a deterioration in the mechanical properties of the resulting cured product.

[0031] Here, the number of acid anhydride groups (H) and the number of epoxy groups (E) can be measured by any method, for example, titration.

[0032] Component (C) is a quaternary amine salt and / or a quaternary phosphonium salt, particularly one containing chloride as an anion species, which acts as a curing accelerator to induce rapid curing in the epoxy resin composition.

[0033] It has been newly discovered that the use of a quaternary amine salt and / or a quaternary phosphonium salt having chloride as the anion species reduces the number of acid anhydride structures present in the crosslinked structure of the cured product of an epoxy resin composition, thereby enabling the production of a cured product with high water resistance.

[0034] In the spectrum obtained by measuring the cured product of the epoxy resin composition by infrared absorption spectroscopy (IR), the characteristic absorption band of acid anhydride, 1780 cm －１ The absorbance of the stretching vibration absorption spectrum of the ester group is Abs1, and the characteristic absorption band of the ester group is 1730 cm －１ When the absorbance of the stretching vibration absorption spectrum of the epoxy resin composition is Abs2, the ratio of these values, Abs1 / Abs2, can be used to quantify the proportion of acid anhydride structures after curing. The value of Abs1 / Abs2 is preferably greater than 0 and less than or equal to 0.100. The cured product to be subjected to IR measurement is obtained by heat-treating the epoxy resin composition at 120°C for 2 hours, then at 150°C for 1 hour, and then drying at 80°C under vacuum for 8 hours. IR measurement is performed using a Fourier transform infrared spectrophotometer under the conditions described in the examples.

[0035] The epoxy resin composition of the present invention preferably contains, as component (C), at least one selected from the group consisting of ammonium chloride, imidazolium chloride, pyridinium chloride, and phosphonium chloride. From the viewpoint of cost, it is more preferable that component (C) contains at least one selected from the group consisting of ammonium chloride, pyridinium chloride, and phosphonium chloride. Furthermore, from the viewpoint of low melting point and excellent handleability, it is even more preferable that component (C) contains ammonium chloride and / or pyridinium chloride. Furthermore, from the viewpoint of storage stability, it is particularly preferable that component (C) contains ammonium chloride. The above-mentioned compound of component (C) may be used alone or in combination of two or more types.

[0036] Examples of ammonium chloride include tetraethylammonium chloride, tributylmethylammonium chloride, tetrabutylammonium chloride, phenyltriethylammonium chloride, and benzyltriethylammonium chloride.

[0037] Examples of imidazolium chloride include 1-butyl-3-methylimidazolium chloride, 1-butyl-2,3-dimethylimidazolium chloride, and 1,3-dimethylimidazolium chloride.

[0038] Examples of pyridinium chlorides include 1-dodecylpyridinium chloride, 1-butyl-4-methylpyridinium chloride, 1-(cyanomethyl)pyridinium chloride, and 1-acetonylpyridinium chloride.

[0039] Examples of phosphonium chlorides include tributyl(cyanomethyl)phosphonium chloride, tetraphenylphosphonium chloride, benzyltriphenylphosphonium chloride, and methoxymethyltriphenylphosphonium chloride.

[0040] The content of component (C) is preferably 0.1 parts by mass or more and 25 parts by mass or less, relative to 100 parts by mass of component (A). By ensuring that the content of component (C) is 0.1 parts by mass or more, more preferably 3.0 parts by mass or more, and even more preferably 6.0 parts by mass or more, the desired fiber-reinforced composite material can be obtained in a shorter curing time than when component (C) is not included. Furthermore, by ensuring that the content is 25 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, an epoxy resin composition with excellent viscosity stability after blending the components can be obtained. Any of the above upper and lower limits may be combined.

[0041] On the other hand, when a phosphine or an amine is used as a catalyst instead of component (C), the total number of unreacted acid anhydride structures in the cured product of the epoxy resin composition increases, resulting in a cured product with poor water resistance.

[0042] Component (D) is a core-shell rubber particle. Due to the toughness-improving effect of component (D), the resulting cured product has excellent toughness and impact resistance.

[0043] In order to strike a balance between the ease of handling of the epoxy resin composition containing component (D) and the effect of component (D) in improving the toughness of the cured product, the epoxy resin composition of the present invention preferably contains 0.5 to 30 parts by mass, more preferably 1 to 25 parts by mass, even more preferably 2 to 20 parts by mass, and particularly preferably 3 to 15 parts by mass of component (D) per 100 parts by mass of component (A).

[0044] A molding material for a fiber-reinforced composite material containing the epoxy resin composition of the present invention and reinforcing fibers, and a fiber-reinforced composite material obtained from this molding material for a fiber-reinforced composite material, are also aspects of the present invention. The molding material for a fiber-reinforced composite material of the present invention is not particularly limited as long as it contains reinforcing fibers and the above-mentioned epoxy resin composition. It may be in a state where the entire reinforcing fibers are completely impregnated with the epoxy resin composition, or in a state where only a portion of the reinforcing fibers are impregnated with the epoxy resin composition. Furthermore, it may be in an unreacted state, or in a state where a portion of the epoxy resin composition has reacted and become B-staged.

[0045] In the molding material for a fiber-reinforced composite material, the reinforcing fiber content is preferably in the range of 40% by mass or more and 90% by mass or less. If the reinforcing fiber content is 40% by mass or more, the mass of the resulting fiber-reinforced composite material is not excessively large, and the resulting fiber-reinforced composite material is more likely to fully exhibit the advantages of fiber-reinforced composite materials, such as excellent specific strength and specific modulus. Furthermore, if the reinforcing fiber content is 90% by mass or less, the impregnation of the reinforcing fibers with the epoxy resin composition is excellent.

[0046] The fiber-reinforced composite material refers to a fiber-reinforced composite material obtained by curing the molding material for the fiber-reinforced composite material.

[0047] Suitable reinforcing fibers include glass fibers, aramid fibers, carbon fibers, boron fibers, etc. Among these, carbon fibers are preferred because they are lightweight and yet can be used to obtain fiber-reinforced composite materials that are excellent in mechanical properties such as strength and elastic modulus.

[0048] The reinforcing fibers may be either short fibers or continuous fibers, or a combination of both. Continuous fibers are preferred to obtain a fiber-reinforced composite material having excellent mechanical properties and a high reinforcing fiber mass content.

[0049] When continuous fibers are used as reinforcing fibers, examples thereof include long fibers aligned in one direction, single tows, woven fabrics, knitted fabrics, nonwoven fabrics, mats, braided cords, and other fiber structures, and those having an average fiber diameter of 3 μm or more and 12 μm or less are preferably used.

[0050] In fiber-reinforced composite materials, reinforcing fibers are sometimes used in the form of strands, but substrates made of reinforcing fibers processed into forms such as mats, woven fabrics, knits, braids, unidirectional sheets, etc. are preferably used. Among these, woven fabrics are preferably used because they allow fiber-reinforced composite materials with a high fiber volume content (hereinafter, in this specification, fiber volume content may be abbreviated as "Vf") to be easily obtained and are easy to handle.

[0051] The molding method for the fiber reinforced composite material is not particularly limited, but methods such as RTM (Resin Transfer Molding), film bag molding, pultrusion, and press molding, which are excellent in productivity, are preferably used.

[0052] Next, a molding material for fiber-reinforced composite materials, which is a second aspect of the present invention, will be described. The molding material for fiber-reinforced composite materials of the present invention comprises an epoxy resin composition containing the following components (A) to (C), and carbon fibers that satisfy the following conditions [a] to [c]: (A): epoxy resin (B): acid anhydride (C): quaternary amine salt and / or quaternary phosphonium salt [a]: strand tensile strength is 4 GPa or more and 8 GPa or less [b]: strand tensile modulus is 230 GPa or more and 350 GPa or less [c]: surface specific oxygen concentration O / C is 0.05 or more and 0.20 or less.

[0053] In the molding material for a fiber-reinforced composite material, the details of components (A) and (B) are as explained in the first aspect of the present invention.

[0054] In the molding material for a fiber-reinforced composite material, component (C) is preferably a compound containing at least one cationic species selected from the group consisting of quaternary ammonium, quaternary imidazolium, quaternary pyridinium, and quaternary phosphonium, and from the viewpoint of the balance between moldability and cured product properties, it is more preferably a compound containing at least one cationic species selected from the group consisting of quaternary ammonium and quaternary phosphonium.

[0055] In the molding material for a fiber-reinforced composite material, the anion species constituting the salt of component (C) is not particularly limited, and preferred anion species include halides such as chloride, bromide, and fluoride, borates such as tetrafluoroborate, phosphates such as hexafluorophosphate, carboxylates such as octylate, and sulfates.

[0056] Among these, chloride and bromide are preferably used as the anion species. In particular, when chloride is used as the anion species, as explained in the first aspect of the present invention, the number of acid anhydride structures present in the crosslinked structure in the cured product of the epoxy resin composition is reduced, resulting in a cured product with high water resistance, and as a result, the cured product retains a high elastic modulus even in a humid and hot environment. On the other hand, when bromide is used as the anion species, the cured product exhibits a high elastic modulus when dried at room temperature due to the crosslinked structure formed when bromide is used.

[0057] In the molding material for a fiber-reinforced composite material, the epoxy resin composition preferably contains (D): core-shell rubber particles. Details of (D): core-shell rubber particles are as described in the first aspect of the present invention.

[0058] In the molding material for a fiber-reinforced composite material, the epoxy resin composition preferably contains, as component (A), a glycidylamine-type epoxy resin. Details of the glycidylamine-type epoxy resin are as described in the first aspect of the present invention.

[0059] In the molding material for a fiber-reinforced composite material, the carbon fiber has a strand tensile strength of 4 GPa or more and 8 GPa or less, preferably 5 GPa or more and 8 GPa or less. If the strand tensile strength of the carbon fiber is less than 4 GPa, the strength characteristics of the resulting fiber-reinforced composite material will be insufficient, which will not lead to weight reduction of the member. On the other hand, the higher the strand tensile strength of the carbon fiber, the better, but usually 8 GPa is sufficient.

[0060] In the molding material for a fiber-reinforced composite material, the carbon fiber has a strand tensile modulus of 230 GPa or more and 350 GPa or less. If the strand tensile modulus of the carbon fiber is less than 230 GPa, the rigidity of the resulting fiber-reinforced composite material will be insufficient, which will not lead to weight reduction of the component. On the other hand, if the strand tensile modulus of the carbon fiber exceeds 350 GPa, the strength characteristics of the fiber-reinforced composite material will be insufficient, which will also not lead to weight reduction of the component.

[0061] In the molding material for fiber-reinforced composite materials, the carbon fiber has a surface specific oxygen concentration O / C of 0.05 to 0.20, preferably 0.08 to 0.20, and more preferably 0.10 to 0.20. Here, the surface specific oxygen concentration is determined by calculating the surface specific oxygen concentration O / C = ([O1s] / [C1s]) / (sensitivity correction value) from the O1s peak area [O1s] and the C1s peak area [C1s] in X-ray photoelectron spectroscopy. A method for adjusting the surface specific oxygen concentration O / C within the above range includes, for example, changing the amount of electricity during electrolytic oxidation treatment. If the surface specific oxygen concentration O / C of the carbon fiber is less than 0.05, the adhesion between the carbon fiber and the resin may be insufficient, resulting in cracks occurring after demolding or insufficient strength properties of the fiber-reinforced composite material.

[0062] In the molding material for fiber-reinforced composite materials, the carbon fibers preferably have a substantially circular cross-sectional shape. Having a substantially circular cross-sectional shape of the carbon fibers improves resin impregnation and allows for a higher fiber volume fraction (Vf) of the fiber-reinforced composite material, leading to a lighter component. Here, the cross-sectional shape of the carbon fibers can be measured using an optical microscope and used as an indicator of the ratio (r / R) of the major axis R to the minor axis r of the cross section of a single yarn. The major axis R refers to the diameter of the circumscribing circle of the cross-sectional shape of the single yarn, and the minor axis r refers to the diameter of the inscribing circle of the cross-sectional shape of the single yarn. A substantially circular cross-sectional shape of the carbon fiber refers to an r / R of 0.9 or more, and a flat cross-sectional shape of the carbon fiber refers to an r / R of less than 0.9.

[0063] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the descriptions of these examples.

[0064] <Resin Raw Materials> In the present examples, the raw materials used as each component are as follows. 1. Component (A): Epoxy resin "GAN (registered trademark)" (N,N'-diglycidylaniline, manufactured by Nippon Kayaku Co., Ltd.) "EPICLON (registered trademark)" 830 (bisphenol F type epoxy resin, manufactured by DIC Corporation) 2. Component (B): Acid anhydride "MHAC-P (registered trademark)" (methyl-3,6-endomethylene-1,2,3,6-tetrahydrophthalic anhydride, manufactured by Resonac Co., Ltd.) 3. Component (C): Quaternary amine salt or quaternary phosphonium salt Benzyltriethylammonium chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) Tetraphenylphosphonium chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) 1-ethyl-3-methylimidazolium chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) 1-dodecylpyridinium chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) Benzyltriethylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.) "TPP-PB (registered trademark)" (tetraphenylphosphonium bromide, manufactured by Hokko Sangyo Co., Ltd.) 1-ethyl-3-methylimidazolium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.) 4. Component (D): Core-shell rubber particles Kane Ace (registered trademark) MX-267 (masterbatch consisting of 63 parts by mass of liquid bisphenol F epoxy resin (EPON (registered trademark) 863, manufactured by Momentive Specialty Chemicals) and 37 parts by mass of core-shell polymer particles, manufactured by Kaneka Corporation) 5. Other components used in comparative examples Curesol (registered trademark) 1,2-DMZ (1,2-dimethylimidazole, manufactured by Shikoku Kasei Corporation) Hokuko TPP (registered trademark) (triphenylphosphine, manufactured by Hokko Sangyo Co., Ltd.) U-CAT (registered trademark) SA102 (DBU 2-ethylhexanoate, manufactured by San-Apro Co., Ltd.) <Method of preparing epoxy resin composition> Component (A): epoxy resin and component (D): core-shell rubber particles were added to a plastic container and appropriately kneaded until the added components were compatible with each other, thereby obtaining an epoxy base liquid.

[0065] In a separate plastic container, component (B): acid anhydride and component (C): quaternary amine salt or quaternary phosphonium salt were added to obtain a curing agent liquid. At this time, the curing agent liquid was heated as necessary to make the components in the curing agent liquid compatible. Predetermined amounts of the epoxy base liquid and curing agent liquid were mixed and kneaded for 2 minutes with a universal mixer to obtain an epoxy resin composition. The compositions of the epoxy resin compositions of each example and comparative example are as shown in Tables 1 to 4.

[0066] <Method for producing cured product of epoxy resin composition> The epoxy resin composition obtained according to the above <Method for preparing epoxy resin composition> was heat-treated at 120°C for 2 hours in a mold set to a thickness of 2 mm or 6 mm using 2 mm or 6 mm Teflon (registered trademark) spacers, and then heat-treated at a temperature of 150°C for 1 hour to obtain a cured resin product of a thickness of 2 mm or 6 mm. The obtained cured resin product was then processed to a size suitable for measurement and dried overnight under vacuum at 80°C to obtain a cured product.

[0067] <Measurement of Dynamic Viscoelasticity of Epoxy Resin Composition> Using a dynamic viscoelasticity measuring device (ARES-G2: manufactured by TA Instruments), the viscosity of the epoxy resin composition prepared according to the above <Method for Preparing Epoxy Resin Composition> immediately after preparation (hereinafter referred to as "initial viscosity") and the viscosity two hours after preparation (hereinafter referred to as "viscosity after two hours") were measured under the measurement conditions of a plate gap of 1.0 mm, a torsional vibration frequency of 6.28 rad / s, a strain of 5.0%, and a temperature of 25° C. Here, "immediately after preparation" refers to a measurement within 5 minutes after preparation.

[0068] <Measurement of Dynamic Viscoelasticity of Cured Epoxy Resin Composition> Using a dynamic viscoelasticity measuring device (ARES-G2: manufactured by TA Instruments), the dynamic viscoelasticity (DMA) of a 12.7 mm x 2 mm x 45 mm cured product prepared according to the above <Method for Preparing Cured Epoxy Resin Composition> was measured in torsional mode under the measurement conditions of a torsional vibration frequency of 6.28 rad / s, a strain of 0.08%, and a heating rate of 5°C / min. The temperature at the inflection point of the storage modulus G' obtained in this dynamic viscoelasticity measurement was taken as the Tg in a dry state (hereinafter referred to as Tg in this specification).ＤＲＹ In addition, another test piece of the cured product of the same size as above was immersed in water at 98°C for 48 hours, and then the dynamic viscoelasticity was measured under the same measurement conditions as above. The temperature at the inflection point of the storage modulus G' was taken as the Tg in a hydrated state (hereinafter, in this specification, Tg Ｈ／Ｗ (hereinafter referred to as "(

[0069] The dynamic viscoelasticity (DMA) in torsion mode of a 12.7 mm x 2 mm x 45 mm fiber reinforced composite material prepared according to the above <Method for preparing a fiber reinforced composite material for dynamic viscoelasticity measurement> was measured under the same conditions as in <Measurement of dynamic viscoelasticity of a cured epoxy resin composition>. The Tg ＤＲＹ and Tg Ｈ／Ｗ was calculated.

[0070] <Measurement of flexural modulus of cured epoxy resin composition> The flexural modulus of a 10.0 mm × 2 mm × 60 mm cured product prepared according to the above <Method for preparing cured epoxy resin composition> was measured using a 5 kN universal testing machine (manufactured by TA Instruments) under measurement conditions in accordance with JIS K 7171:2016.

[0071] <IR Measurement of Cured Epoxy Resin Composition> Using a Fourier transform infrared spectrophotometer (FT-IR8400S, manufactured by Shimadzu Corporation), the ATR method was performed using an apodization function Happ-Genzel, 10 integrations, and a resolution of 4 cm. －１ The infrared absorption spectrum of a 2 mm-thick cured product prepared according to the above <Method for preparing a cured product of an epoxy resin composition> was measured under the measurement conditions of －１ The absorbance value of Abs1, 1730 cm －１ The absorbance value was taken as Abs2, and Abs1 / Abs2 was calculated.

[0072] <Fracture toughness value (K ＩＣ ) Measurement of the fracture toughness (K) of the cured product was performed using a 5 kN universal material testing machine (manufactured by TA Instruments) in accordance with ASTM D5045-99, using a 12.7 mm x 6 mm x 180 mm cured product test piece prepared according to the above <Method for preparing a cured product of an epoxy resin composition>. ＩＣ ) was measured.

[0073] <Measurement of Strand Tensile Strength and Strand Tensile Modulus of Carbon Fiber> A carbon fiber bundle to be measured was prepared by adding 1,000 g (100 parts by mass) of Bakelite (registered trademark) ERL-4221 manufactured by Union Carbide Corporation, boron trifluoride monoethylamine (BF ３ The carbon fiber bundle was impregnated with a resin composition prepared by mixing 30 g (3 parts by mass) of ethylenediamine diamine (MEA) and 40 g (4 parts by mass) of acetone, and the resin-impregnated carbon fiber bundle was then heated at 130°C for 30 minutes to cure the resin, yielding a resin-impregnated strand. The strand tensile strength and strand tensile modulus were determined according to the resin-impregnated strand test method JIS R 7601:1986. The number of test samples (n = 10) was used, and the average values ​​were employed.

[0074] <Measurement of specific surface oxygen concentration O / C of carbon fiber> The specific surface oxygen concentration O / C was determined by X-ray photoelectron spectroscopy according to the following procedure.

[0075] First, a solvent was used to remove sizing agents and the like from the carbon fiber bundle to be measured, and then the bundle was cut into pieces of about 5 mm and spread out and arranged on a stainless steel sample support table, after which measurement was performed under the following conditions.

[0076] Photoelectron escape angle: 90 degrees X-ray source: MgKα1,2 Vacuum degree in sample chamber: 1×10 －８ Torr Next, to correct the peak due to charging during measurement, C １Ｓ The binding energy value B.E. of the main peak of was set to 284.6 eV.

[0077] Next, C １ｓ Peak area [C １ｓ ] is determined by drawing a straight baseline in the range of 282 to 296 eV, and １ｓ Peak area [O １ｓ ] was determined by drawing a straight baseline in the range of 528 to 540 eV.

[0078] The surface specific oxygen concentration O / C is the above O １ｓ Peak area [O １ｓ ], C １ｓ Peak area [C １ｓ ] and the sensitivity correction value specific to the device, the following formula was used to calculate the O / C ratio: １ｓ] / [C １ｓ ]) / (sensitivity correction value) Here, the measurement device used was an ESCA-750 manufactured by Shimadzu Corporation, and the sensitivity correction value inherent to this device (ESCA-750) was set to 2.85. The number of test samples was set to n=3, and the average value of the obtained surface specific oxygen concentration O / C values ​​was adopted.

[0079] <Measurement of the average fiber diameter of carbon fibers> Carbon fiber bundles were embedded in an embedding epoxy resin, and the embedded samples were polished using sandpaper in a direction perpendicular to the fibers. The cross sections of the carbon fibers were then observed under an optical microscope at a magnification of 1,000x. Twenty single fibers were randomly selected from the field of view, and the major axis R and minor axis r of the cross sections of the single fibers were measured. The average values ​​were calculated, and {(average value of R) + (average value of r)} / 2 was defined as the average fiber diameter. Furthermore, when the ratio (average value of r) / (average value of R) of the cross sections of the single fibers exceeded 0.9, the cross section of the carbon fiber was determined to be substantially circular.

[0080] <Preparation of Carbon Fibers> Carbon fibers [I] to [V] were prepared by the following method.

[0081] <Carbon Fiber [I]> Using a copolymer consisting of 99.4 mol % of acrylonitrile and 0.6 mol % of methacrylic acid, an acrylic precursor fiber having a single fiber fineness of 0.08 tex and a filament count of 12,000 was obtained by a dry / wet spinning method.

[0082] This acrylic precursor fiber was converted into a flame-resistant fiber by heating in air at 240 to 280°C with a draw ratio of 1.05. The flame-resistant fiber was then further heated in a nitrogen atmosphere at a temperature range of 300 to 900°C at a temperature increase rate of 200°C / min with a draw ratio of 1.10, and then heated to 1,400°C for calcination and carbonization.

[0083] Next, the carbon fiber was subjected to electrolytic oxidation treatment in a tank with an electric charge of 30 C / g using an aqueous ammonium bicarbonate solution with a concentration of 1.0 mol / L as an electrolyte. The carbon fiber after this electrolytic oxidation treatment was then washed with water and dried in air at 150°C to obtain carbon fiber [I].

[0084] The carbon fiber [I] had a strand tensile strength of 6.1 GPa, a strand tensile modulus of 294 GPa, a surface specific oxygen concentration O / C of 0.18, and a cross-sectional shape of r / R of 0.95, which was substantially circular.

[0085] <Carbon Fiber [II]> Carbon fiber [II] was obtained by producing it under the same conditions as carbon fiber [I], except that the amount of electricity during the electrolytic oxidation treatment was set to 3 C / g·tank.

[0086] The carbon fiber [II] had a strand tensile strength of 5.8 GPa, a strand tensile modulus of 294 GPa, a surface specific oxygen concentration O / C of 0.08, and a cross-sectional shape of r / R of 0.95, which was substantially circular.

[0087] <Carbon fiber [III]> Carbon fiber [III] was obtained by producing it under the same conditions as carbon fiber [I], except that the amount of electricity during the electrolytic oxidation treatment was 1 C / g·tank.

[0088] The carbon fiber [III] had a strand tensile strength of 6.0 GPa, a strand tensile modulus of 294 GPa, a surface specific oxygen concentration O / C of 0.03, and a cross-sectional shape of r / R of 0.95, which was substantially circular.

[0089] <Carbon fiber [IV]> Carbon fiber [IV] was obtained by production under the same conditions as carbon fiber [II], except that the single fiber fineness of the obtained acrylic precursor fiber was 0.07 tex, the draw ratio during carbonization was changed to 1.00, and the maximum temperature during carbonization was changed to 1,200°C.

[0090] The carbon fiber [IV] had a strand tensile strength of 5.2 GPa, a strand tensile modulus of 230 GPa, a surface specific oxygen concentration O / C of 0.12, and a cross-sectional shape of r / R of 0.94, which was substantially circular.

[0091] <Carbon fiber [V]> Carbon fiber [V] was obtained by production under the same conditions as carbon fiber [IV], except that the spinning method for the acrylic precursor fiber was changed to a wet spinning method and the single fiber fineness of the obtained acrylic precursor fiber was 0.08 tex.

[0092] The carbon fiber [V] had a strand tensile strength of 3.5 GPa, a strand tensile modulus of 230 GPa, a surface specific oxygen concentration O / C of 0.10, and a flat cross-sectional shape with r / R of 0.80.

[0093] <Preparation of reinforcing fiber substrate> The carbon fibers obtained in the above <Preparation of carbon fibers> were aligned in one direction, and the aligned carbon fibers were stitched together with a stitch thread to obtain a reinforcing fiber substrate with a basis weight of 190 g / m ２ A reinforcing fiber substrate of the above was obtained. The stitch yarn was a 56 dtex polyester yarn consisting of 24 filaments with a melting point Tma of 260 ° C. The knitting structure was a 1 × 1 irregular tricot knit with a stitch length of 2.3 mm and a gauge length of 5 mm.

[0094] <Preparation of Fiber-Reinforced Composite Material for 0° Compression Test> Eleven sheets of the reinforcing fiber substrate obtained in the above <Preparation of Reinforcing Fiber Substrate>, cut into 395 mm x 395 mm pieces, were stacked with the carbon fiber orientation aligned and placed in a mold with a 400 mm x 400 mm x 2 mm plate-shaped cavity. The mold was then clamped using a press. The mold was then maintained at 50°C, and the pressure was reduced to atmospheric pressure -0.1 MPa using a vacuum pump. The epoxy resin composition obtained in the above <Preparation of Epoxy Resin Composition>, which had been preheated to 50°C, was then injected at a pressure of 0.2 MPa. The temperature was raised to 120°C and heat-treated for 2 hours. The mold was then placed in a hot air oven at 150°C for 1 hour. The mold was then opened and demolded, yielding a fiber-reinforced composite material with a fiber volume content (Vf) of 58%.

[0095] <Evaluation of Impregnation> In the above <Preparation of Fiber-Reinforced Composite Material for 0° Compression Test>, the void fraction was evaluated by observing the cross section of the molded article. The void fraction in this measurement is the percentage of the area occupied by voids relative to the area of ​​any region when the polished cross section of the molded article is observed under an optical microscope. Such void fraction refers to not only internal voids in the molded article, but also general voids such as surface pits, resin withering, and impregnation defects. Impregnation was evaluated on a three-level scale: good, medium, and poor. A void fraction of less than 0.3% was considered good, a void fraction of 0.3% to less than 1.0% was considered medium, and a void fraction of 1.0% or more was considered poor.

[0096] <Evaluation of cracks after demolding> In the above <Preparation of fiber-reinforced composite material for 0° compression test>, after demolding, the molded product was cooled to room temperature and then visually observed to evaluate cracks in the molded product. Using a stereomicroscope with a magnification of 10x, the number of cracks present throughout the product, including the edges, was counted. The cracks after demolding were evaluated on a three-level scale of good, medium, and poor, with less than one crack per molded product being good, one to less than five being medium, and five or more being poor.

[0097] <Evaluation of 0° Compression Strength> A sample having a width of 12.5 mm and a length of 78 mm was cut from the 2 mm thick fiber reinforced composite material prepared in the above <Preparation of Fiber Reinforced Composite Material for 0° Compression Test> using a diamond cutter. A 0° compression test of the fiber reinforced composite material was performed on this sample using an Instron universal testing machine (manufactured by Instron) in accordance with JIS K 7076:1991 to measure the compressive strength. The 0° compression strength at room temperature after drying was obtained by subjecting a sample vacuum dried at 80°C for 1 day to a compression test at a temperature of 23°C. The 0° compression strength at high temperatures after water absorption was obtained by subjecting a sample immersed in 71°C hot water for 14 days to a compression test at a temperature of 82°C.

[0098] The sample preparation method and measurement results for each example are described below.

[0099] Example 1 An epoxy resin composition was obtained in the same manner as in the above <Method for preparing an epoxy resin composition> using 91.5 parts by mass of EPICLON (registered trademark) 830 as component (A), 13.5 parts by mass of Kane Ace (registered trademark) MX-267 as component (D), 100 parts by mass of MHAC-P (registered trademark) as component (B), and 6 parts by mass of benzyltriethylammonium chloride as component (C). Note that when compatibilizing the components in the curing agent liquid, the curing agent liquid was heated at 80°C.

[0100] Using the obtained epoxy resin composition, a cured product was produced according to the above-mentioned <Method for producing a cured product of an epoxy resin composition>. This cured product was subjected to the above-mentioned <Measurement of dynamic viscoelasticity of a cured product of an epoxy resin composition>, <Measurement of flexural modulus of a cured product of an epoxy resin composition>, <IR measurement of a cured product of an epoxy resin composition>, and <Measurement of K values ​​of a cured product of an epoxy resin composition>. ＩＣ Measurement was carried out according to the method described above, and the results are shown in Table 1.

[0101] The cured product obtained by curing the obtained epoxy resin composition has a good balance between flexural modulus and toughness, and Tg ＤＲＹ Tg at 141°C Ｈ／Ｗ It was confirmed that the decrease in Tg at 130°C when containing water was small, and that the film had sufficient water resistance.

[0102] Examples 2 to 5 Epoxy resin compositions were prepared and various evaluations were carried out in the same manner as in Example 1, except that the resin compositions were as shown in Table 1.

[0103] The epoxy resin compositions of Examples 2 to 5 all had a good balance between flexural modulus and toughness, and Tg ＤＲＹ Tg Ｈ／Ｗ It was confirmed that the flexural modulus was not easily reduced. In addition, the addition of "GAN (registered trademark)" improved the flexural modulus, and the greater the amount of GAN added, the greater the improvement.

[0104] The results are shown in Table 1.

[0105] Examples 6 to 8 Epoxy resin compositions were prepared and various evaluations were carried out in the same manner as in Example 1, except that the resin compositions were as shown in Table 1.

[0106] The epoxy resin compositions of Examples 6 to 8 all had a good balance between flexural modulus and toughness, and Tg ＤＲＹ Tg Ｈ／Ｗ It was confirmed that the value is unlikely to decrease.

[0107] The results are shown in Table 1.

[0108] Examples 9 and 10 Epoxy resin compositions were prepared and various evaluations were carried out in the same manner as in Example 1, except that the resin compositions were as shown in Table 1.

[0109] The epoxy resin compositions of Examples 9 and 10 both had a good balance between flexural modulus and toughness. ＤＲＹ Tg Ｈ／Ｗ was less likely to decrease.

[0110] The results are shown in Table 1.

[0111] Examples 11 and 12 Epoxy resin compositions were prepared and various evaluations were carried out in the same manner as in Example 1, except that the resin compositions were as shown in Table 1.

[0112] The epoxy resin compositions of Examples 11 and 12 both had a good balance between flexural modulus and toughness, and Tg ＤＲＹ Tg Ｈ／Ｗ It was confirmed that the value is unlikely to decrease.

[0113] The results are shown in Table 1.

[0114] Comparative Examples 1 to 5 Epoxy resin compositions were prepared and various evaluations were carried out in the same manner as in Example 1, except that the resin compositions were as shown in Table 2.

[0115] The epoxy resin compositions of Comparative Examples 1 to 5 all had a good balance between flexural modulus and toughness, but ＤＲＹ Tg Ｈ／Ｗ The resistance was significantly reduced, and the water resistance was insufficient.

[0116] The results are shown in Table 2.

[0117] Comparative Example 6 An epoxy resin composition was prepared and various evaluations were carried out in the same manner as in Example 1, except that the resin composition was as shown in Table 2. The cured product of this epoxy resin composition had a good flexural modulus and a Tg ＤＲＹ Tg Ｈ／Ｗ The strength was not easily reduced, but the toughness was insufficient.

[0118] The results are shown in Table 2.

[0119] Examples 13 to 17 Epoxy resin compositions were prepared in the same manner as in Example 1, except that the resin compositions were as shown in Table 3. In addition to the various evaluations similar to those in Example 1, measurements were also carried out in accordance with the above-mentioned <Measurement of dynamic viscoelasticity of epoxy resin compositions>.

[0120] The epoxy resin compositions of Examples 13 to 17 all had a good balance between flexural modulus and toughness, and Tg ＤＲＹ Tg Ｈ／Ｗ It was confirmed that the value is unlikely to decrease.

[0121] Furthermore, Examples 13 to 16 had excellent viscosity stability.

[0122] Among Examples 13 to 17, Examples 13 to 15 were particularly excellent in terms of fast curing properties.

[0123] On the other hand, Example 17 suggests the possibility of a problem with viscosity stability.

[0124] The results are shown in Table 3.

[0125] Example 18 An epoxy resin composition was prepared according to the above <Method for preparing an epoxy resin composition> using 100 parts by mass of EPICLON (registered trademark) 830 as component (A), 104 parts by mass of MHAC-P (registered trademark) as component (B), and 6 parts by mass of benzyltriethylammonium chloride as component (C). The curing agent liquid was heated at 80°C for compatibilization. A fiber-reinforced composite material was prepared from the obtained epoxy resin composition according to the above <Method for preparing a fiber-reinforced composite material for 0° compression test> using carbon fiber [II] prepared according to the above <Preparation of carbon fiber>.

[0126] This fiber-reinforced composite material was evaluated according to the above-mentioned <Evaluation of impregnation property>, <Evaluation of cracks after demolding>, and <Evaluation of 0° compression strength>, and the results are shown in Table 4. Both the impregnation property and the cracks after demolding were good, and the 0° compression strength was good both at room temperature after drying and at high temperature after water absorption.

[0127] Example 19 An epoxy resin composition was prepared and various evaluations were carried out in the same manner as in Example 18, except that 50 parts by mass of EPICLON (registered trademark) 830 as component (A) was replaced with GAN. The impregnation ability was good, cracking after demolding was moderate, and the 0° compressive strength was excellent both at room temperature after drying and at high temperatures after water absorption.

[0128] (Examples 20 to 22) Except for replacing component (C), epoxy resin compositions were prepared and various evaluations were carried out in the same manner as in Example 18. The impregnation property and cracking after demolding were both good or medium, and the 0° compressive strength was excellent at room temperature after drying and was at an acceptable level even at high temperatures after water absorption.

[0129] Example 23 An epoxy resin composition was prepared and various evaluations were carried out in the same manner as in Example 19, except that 13.5 parts by mass of Kane Ace (registered trademark) MX-267 was blended as component (D) and carbon fiber [IV] was used. After demolding, cracking was improved to a good level, and the 0° compressive strength was excellent both at room temperature after drying and at high temperatures after water absorption.

[0130] (Example 24) Except for using carbon fiber [I], an epoxy resin composition was prepared and various evaluations were carried out in the same manner as in Example 19. After demolding, cracking was improved to a good level, and the 0° compressive strength was excellent at room temperature after drying and good even at high temperatures after water absorption.

[0131] Comparative Example 7 An epoxy resin composition was prepared and various evaluations were carried out in the same manner as in Example 18, except that Curesol (registered trademark) 1,2-DMZ was used instead of component (C). Both the impregnation property and cracking after demolding were not good, and the 0° compressive strength was also at an insufficient level at room temperature after drying.

[0132] (Comparative Example 8) Except for using carbon fiber [III], an epoxy resin composition was prepared and various evaluations were carried out in the same manner as in Example 21. Because the adhesion to the carbon fiber was reduced, cracking worsened after demolding, and the 0° compressive strength at high temperatures after water absorption was also at an insufficient level.

[0133] (Comparative Example 9) Except for using carbon fiber [V], an epoxy resin composition was prepared and various evaluations were carried out in the same manner as in Example 21. The cross-sectional shape of the carbon fiber [V] used was flattened, which resulted in poor impregnation and a decrease in strand tensile strength. As a result, the 0° compressive strength decreased at room temperature after drying and reached an insufficient level at high temperatures after water absorption.

[0134] Comparative Example 10 An epoxy resin composition was prepared and various evaluations were carried out in the same manner as in Example 18, except that U-CAT (registered trademark) SA102 was used instead of component (C). Impregnation property and cracking after demolding deteriorated, and the 0° compressive strength at high temperatures after water absorption became insufficient.

[0135]

[0136]

[0137]

[0138]

[0139] The units of each component in the table are parts by mass.

[0140] The epoxy resin composition of the present disclosure can provide a molding material for a fiber-reinforced composite material in which the epoxy resin composition is sufficiently impregnated into a substrate. Use of this molding material for a fiber-reinforced composite material enables high-speed production by RTM molding, and compared with conventional materials, the resulting fiber-reinforced composite material has a good balance between flexural modulus and toughness, and excellent water resistance. The excellent properties of the present invention will lead to the widespread application of fiber-reinforced composite materials in aerospace and automotive applications, where environmental resistance is required, as well as sports and industrial applications in general. This lightweighting of transportation equipment will improve fuel efficiency, leading to reduced energy consumption, primarily from fossil fuels, and is expected to contribute to the mitigation of global warming.

Claims

1. An epoxy resin composition comprising the following components (A) to (D), wherein component (C) contains chloride as an anionic species: (A): epoxy resin, (B): acid anhydride, (C): quaternary amine salt and / or quaternary phosphonium salt, and (D): core-shell rubber particles.

2. The epoxy resin composition according to claim 1, wherein component (A) comprises a glycidylamine type epoxy resin.

3. The epoxy resin composition according to claim 1, wherein the cured product obtained by curing the epoxy resin composition under the following curing conditions satisfies the following formula 1. Curing conditions: The epoxy resin composition is heat-treated at 120°C for 2 hours, then at 150°C for 1 hour, and then dried at 80°C under vacuum for 8 hours. 0<Abs1 / Abs2≦0.100 (Formula 1), where Abs1 is the peak at 1780 cm in the spectrum obtained by infrared absorption spectroscopy (IR). －１ Absorbance at 1730 cm in the spectrum obtained by infrared absorption spectroscopy (IR) －１ absorbance of 4. The epoxy resin composition according to claim 2, wherein the component (A) contains 15% by mass or more and 100% by mass or less of a glycidylamine type epoxy resin.

5. The epoxy resin composition according to claim 1, which contains 0.1 parts by mass or more and 25 parts by mass or less of component (C) when the mass of component (A) is 100 parts by mass.

6. The epoxy resin composition according to claim 1, wherein component (C) comprises at least one selected from the group consisting of ammonium chloride, imidazolium chloride, pyridinium chloride, and phosphonium chloride.

7. A molding material for a fiber-reinforced composite material, comprising the epoxy resin composition of claim 1 and reinforcing fibers.

8. The molding material for a fiber-reinforced composite material according to claim 7, wherein the reinforcing fibers are carbon fibers.

9. A molding material for fiber-reinforced composite materials, comprising an epoxy resin composition containing the following components (A) to (C) and carbon fibers that satisfy the following conditions [a] to [c]: (A): epoxy resin (B): acid anhydride (C): quaternary amine salt and / or quaternary phosphonium salt [a]: strand tensile strength is 4 GPa or more and 8 GPa or less [b]: strand tensile modulus is 230 GPa or more and 350 GPa or less [c]: surface specific oxygen concentration O / C is 0.05 or more and 0.20 or less 10. The molding material for fiber-reinforced composite materials according to claim 9, wherein the epoxy resin composition further contains the following component: (D): core-shell rubber particles.

11. The molding material for a fiber-reinforced composite material according to claim 9, wherein component (A) contains a glycidylamine-type epoxy resin.

12. The molding material for a fiber-reinforced composite material according to claim 9, wherein the carbon fibers further satisfy the following conditions: [d]: The cross-sectional shape is substantially circular 13. A fiber-reinforced composite material obtained by curing the molding material for fiber-reinforced composite materials according to any one of claims 7 to 12.

14. A structural member made of the fiber-reinforced composite material according to claim 13.

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