Epoxy resin composition for fiber-reinforced composite material, fiber-reinforced composite material, and method for producing fiber-reinforced composite material

Abstract

An object of the present invention is to provide an epoxy resin composition that can ensure sufficient resin impregnation time into reinforcing fibers and achieve rapid curing, thereby imparting high levels of physical properties (heat resistance, high compressive strength) to fiber-reinforced composite materials, and to provide a fiber-reinforced composite material using the same. [Solution] A two-component epoxy resin composition for fiber-reinforced composite materials is comprised of an epoxy base component containing [A] a glycidyl amine-type epoxy resin and [B] a sulfonic acid ester, and a curing agent component containing [C] an aromatic amine that has a melting point and is solid at room temperature.

Description

[Technical Field]

[0001] The present invention relates to an epoxy resin composition for a fiber-reinforced composite material, a fiber-reinforced composite material using the same, and a method for producing the fiber-reinforced composite material. [Background technology]

[0002] Fiber-reinforced composite materials, which consist of reinforcing fibers and a matrix resin, can be designed to take advantage of the advantages of both the reinforcing fibers and the matrix resin, and as a result, their applications are expanding to a variety of fields, including aerospace, sports, and general industry.

[0003] Examples of reinforcing fibers include glass fiber, aramid fiber, carbon fiber, and boron fiber. While both thermosetting and thermoplastic resins are used as the matrix resin, thermosetting resins are often used because they are easy to impregnate into the reinforcing fibers. Examples of thermosetting resins that can be used include epoxy resin, unsaturated polyester resin, vinyl ester resin, phenolic resin, bismaleimide resin, and cyanate resin.

[0004] Fiber-reinforced composite materials are molded using methods such as the prepreg method, hand layup method, filament winding method, pultrusion method, and RTM (Resin Transfer Molding) method. The prepreg method involves laminating prepregs, in which reinforcing fibers are impregnated with an epoxy resin composition, into a desired shape and then heating them to obtain a molded product. While the prepreg method is suitable for producing fiber-reinforced composite materials with the high material strength required for structural applications such as aircraft and automobiles, it requires numerous processes, such as prepreg fabrication and lamination, making it unsuitable for mass production and resulting in productivity problems. On the other hand, the RTM method involves injecting a liquid epoxy resin composition into a reinforcing fiber substrate placed in a heated mold, allowing it to impregnate, and then heat-curing the composition within the mold to obtain a molded product. This method not only allows fiber-reinforced composite materials to be molded in a short time without the need for a prepreg fabrication process, but also has the advantage of easily molding fiber-reinforced composite materials with complex shapes.

[0005] Liquid epoxy resin compositions can be one-component or two-component. A one-component epoxy resin composition is one in which all components, including the epoxy resin and curing agent, are premixed together. In contrast, a two-component epoxy resin composition is one that consists of an epoxy base component containing an epoxy resin as the main component and a curing agent component containing a curing agent as the main component, and is prepared by mixing the two components, the epoxy base component and the curing agent component, immediately before use.

[0006] In the case of one-component epoxy resin compositions, the curing reaction continues even during storage, requiring refrigeration. Furthermore, in one-component epoxy resin compositions, a solid curing agent with low reactivity is often selected, and impregnation of the one-component epoxy resin composition into the reinforcing fibers requires high pressure, such as using a press roll. In two-component epoxy resin compositions, both the epoxy base component and the curing agent component are liquid, allowing the mixture of the base component and the curing agent component to be a low-viscosity liquid, facilitating impregnation of the epoxy resin composition into the reinforcing fibers. Furthermore, in two-component epoxy resin compositions, the epoxy base component and the curing agent component are stored separately, allowing for long-term storage without particular restrictions on storage conditions.

[0007] In RTM and other methods, ensuring sufficient resin impregnation time for the reinforcing fibers and rapid curing are essential for producing high-quality, highly efficient fiber-reinforced composite materials. In this regard, two-component epoxy resin compositions are preferred because curing only begins after the epoxy base component and curing agent component are mixed. Rapid-curing epoxy resin compositions containing highly reactive curing agents and accelerators are therefore easily applicable. Furthermore, for aircraft structural applications, which require extremely high quality, it is also necessary to impart high levels of physical properties (heat resistance, high compressive strength) to fiber-reinforced composite materials.

[0008] In response to this situation, an epoxy resin composition containing an acid ester as an accelerator has been disclosed, and a method has been proposed for rapid curing while ensuring sufficient time for resin impregnation into reinforcing fibers (Patent Document 1). Also, an epoxy resin composition containing 4,4'-methylenebis(2-isopropyl-6-methylaniline) (M-MIPA) has been disclosed, and a method has been proposed for sufficiently rapid curing at 180°C, with the resin being sufficiently cured by the time of the demolding process after molding, thereby imparting a high level of fiber-reinforced composite material physical properties (Patent Documents 2 and 3). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Special Publication No. 9-507262 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-150310 [Patent Document 3] International Publication No. 2020 / 008847 Summary of the Invention [Problem to be solved by the invention]

[0010] The method described in the aforementioned Patent Document 1 ensures sufficient time for resin impregnation into reinforcing fibers and enables rapid curing, but has the problem of not achieving sufficiently high heat resistance or compressive strength because it uses only bisphenol A epoxy resin, which has poor heat resistance and elastic modulus.

[0011] The methods described in the above-mentioned Patent Documents 2 and 3 can impart high heat resistance and mechanical properties to fiber-reinforced composite materials, but have the problem of not being able to achieve sufficiently high-speed curing properties.

[0012] Thus, in the prior art, there was no epoxy resin composition that simultaneously satisfied the four requirements of ensuring the resin impregnation time for the reinforcing fibers, rapid curing, high heat resistance, and high compressive strength. Therefore, an object of the present invention is to provide an epoxy resin composition that can be rapidly cured while ensuring the resin impregnation time for the reinforcing fibers, and that can impart to fiber-reinforced composite materials the high level of physical properties (heat resistance, high compressive strength) required for aircraft structural applications. Furthermore, by using such an epoxy resin composition, a fiber-reinforced composite material can be provided that exhibits excellent glass transition temperatures and 0°C compressive strength under wet heat conditions after curing. [Means for solving the problem]

[0013] In order to solve the above problems, the two-component epoxy resin composition for fiber-reinforced composite materials of the present invention has the following configuration: It is a two-component epoxy resin composition for fiber-reinforced composite materials comprising an epoxy base component containing [A] a glycidyl amine-type epoxy resin and [B] a sulfonic acid ester, and [C] a curing agent component containing an aromatic amine that has a melting point and is solid at room temperature.

[0014] The fiber-reinforced composite material of the present invention comprises a cured product of the two-component epoxy resin composition for a fiber-reinforced composite material of the present invention and a reinforcing fiber substrate. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a two-component epoxy resin composition for fiber-reinforced composite materials, which can ensure the resin impregnation time into reinforcing fibers and also achieve high-speed curing, thereby imparting high levels of physical properties (heat resistance, high compressive strength) to the fiber-reinforced composite materials. DETAILED DESCRIPTION OF THE INVENTION

[0016] Preferred embodiments of the present invention will be described below.

[0017] First, the two-component epoxy resin composition for fiber-reinforced composite materials of the present invention will be described.

[0018] The two-component epoxy resin composition for fiber-reinforced composite materials of the present invention comprises an epoxy base component containing [A] a glycidyl amine-type epoxy resin and [B] a sulfonic acid ester, and [C] a curing agent component containing an aromatic amine that has a melting point and is solid at room temperature. Hereinafter, these components may be simply referred to as component [A], component [B], and component [C], respectively. The two-component epoxy resin composition for fiber-reinforced composite materials may also be simply referred to as the epoxy resin composition.

[0019] The epoxy resin composition containing components [A], [B], and [C] allows for both sufficient resin impregnation time into the reinforcing fibers and rapid curing, which was difficult with conventional technology, and can impart high levels of physical properties (heat resistance, high compressive strength) to fiber-reinforced composite materials.

[0020] Component [A] in the present invention is a glycidylamine-type epoxy resin. Component [A] is a necessary component for imparting high heat resistance and mechanical properties to epoxy resin cured products and fiber-reinforced composite materials. Here, the glycidylamine-type epoxy resin of component [A] includes polyfunctional glycidylamine-type epoxy resins such as N,N,N',N'-tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, N,N-diglycidylaniline, N,N,N',N'-tetraglycidylxylylenediamine, and their alkyl-, aryl-, alkoxy-, aryloxy-, and halogen-substituted derivatives, isomers, and hydrogenated products. Such epoxy resins contribute to increasing the crosslink density of cured resin products, and their use can improve the heat resistance of fiber-reinforced composite materials. Among the above-mentioned polyfunctional glycidylamine-type epoxy resins, trifunctional or higher glycidylamine-type epoxy resins, particularly trifunctional or higher glycidylamine-type aromatic epoxy resins, are preferred. In the present invention, "polyfunctional" means having two or more glycidyl groups, and "trifunctional" means having three glycidyl groups.

[0021] As the tri- or higher functional glycidylamine type epoxy resin, N,N,N',N'-tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, or derivatives or isomers thereof are preferably used.For example, N,N,N',N'-tetraglycidyldiaminodiphenylmethane or its derivatives or isomers include N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-3,3'-dimethyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-3,3'-diethyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-3,3'-diisopropyl-4,4'-diamino Diphenylmethane, N,N,N',N'-tetraglycidyl-3,3'-di-t-butyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-3,3'-diisopropyl-5,5'-diethyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-3,3'-diisopropyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane Phenylmethane, N,N,N',N'-tetraglycidyl-3,3'-di-t-butyl-5,5'-diethyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-3,3'-di-t-butyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-3,3',5,5'-tetraethyl-4,4'-diaminodiphenylmethane phenylmethane, N,N,N',N'-tetraglycidyl-3,3',5,5'-tetraisopropyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-3,3',5,5'-tetra-t-butyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-3,3'-dichloro-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-3,3'-dibromo-4,4'-diaminodiphenylmethane, and the like can be mentioned.Furthermore, examples of triglycidylaminophenol or its derivatives or isomers include N,N,O-triglycidyl-p-aminophenol, N,N,O-triglycidyl-m-aminophenol, etc. Furthermore, component [A] may contain two or more of these glycidylamine-type epoxy resins.

[0022] Commercially available N,N,N',N'-tetraglycidyldiaminodiphenylmethane products include "Sumiepoxy (registered trademark)" ELM434 (manufactured by Sumitomo Chemical Co., Ltd.), YH434L (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.), "jER (registered trademark)" 604 (manufactured by Mitsubishi Chemical Corporation), "Araldite (registered trademark)" MY720, and "Araldite (registered trademark)" MY721 (all manufactured by Huntsman Japan Co., Ltd.). Commercially available triglycidylaminophenol products include "Araldite (registered trademark)" MY0600 and "Araldite (registered trademark)" MY0510 (all manufactured by Huntsman Japan Co., Ltd.).

[0023] In the present invention, component [A] preferably contains 70% by mass or more but less than 100% by mass of a glycidylamine-type epoxy resin selected from tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, or a derivative or isomer thereof, relative to 100% by mass of the total epoxy resin. When component [A] contains 70% by mass or more of a glycidylamine-type epoxy resin selected from tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, or a derivative or isomer thereof, relative to 100% by mass of the total epoxy base component, the cured epoxy resin exhibits high heat resistance and improves the 0° compressive strength of fiber-reinforced composite materials under wet heat conditions. In the present invention, the term "cured epoxy resin" refers to a cured product obtained by curing an epoxy resin composition.

[0024] The two-component epoxy resin composition for fiber-reinforced composite materials of the present invention may contain an epoxy resin other than component [A], as long as the amount is 50% by mass or less based on 100% by mass of the total epoxy base components. Examples of such epoxy resins other than component [A] include bisphenol-type epoxy resins, phenol novolac-type epoxy resins, cresol novolac-type epoxy resins, resorcinol-type epoxy resins, phenol aralkyl-type epoxy resins, naphthol aralkyl-type epoxy resins, dicyclopentadiene-type epoxy resins, epoxy resins having a biphenyl skeleton, isocyanate-modified epoxy resins, tetraphenylethane-type epoxy resins, triphenylmethane-type epoxy resins, and triglycidylamine-type epoxy resins. One or more types of epoxy resins other than component [A] may be contained.

[0025] More specifically, epoxy resins other than component [A] include bisphenol F diglycidyl ether, bisphenol A diglycidyl ether, tetrabromobisphenol A diglycidyl ether, bisphenol AD ​​diglycidyl ether, 2,2',6,6'-tetramethyl-4,4'-biphenol diglycidyl ether, diglycidyl ether of 9,9-bis(4-hydroxyphenyl)fluorene, triglycidyl ether of tris(p-hydroxyphenyl)methane, and tetraglycidyl ether of tetrakis(p-hydroxyphenyl)ethane. Examples of epoxy resins include glycidyl ether, phenol novolac glycidyl ether, cresol novolac glycidyl ether, glycidyl ether of a condensation product of phenol and dicyclopentadiene, glycidyl ether of biphenyl aralkyl resin, triglycidyl isocyanurate, 5-ethyl-1,3-diglycidyl-5-methylhydantoin, oxazolidone-type epoxy resins obtained by the addition of bisphenol A diglycidyl ether and tolylene isocyanate, phenol aralkyl-type epoxy resins, and triglycidyl aminophenol. Among these, bisphenol-type epoxy resins are preferred because they contribute to an excellent balance between toughness and heat resistance of the cured epoxy resin. Liquid bisphenol-type epoxy resins, in particular, are preferred as epoxy resins other than component [A] because they contribute to excellent impregnation of reinforcing fibers. In this specification, "liquid" refers to a viscosity of 1000 Pa·s or less at 25°C. Furthermore, "solid" means that the material has no fluidity or extremely low fluidity at 25°C, specifically, a viscosity of greater than 1000 Pa·s at 25°C. Here, viscosity is measured in accordance with JIS Z8803 (1991) "Viscosity measurement method using a cone-plate rotational viscometer" using an E-type viscometer (for example, TVE-30H manufactured by Tokimec Inc.) equipped with a standard cone rotor (1°34' x R24).

[0026] Here, bisphenol-type epoxy resins are those in which two phenolic hydroxyl groups of a bisphenol compound have been glycidylated. Examples of bisphenol-type epoxy resins include bisphenol F-type epoxy resins, bisphenol A-type epoxy resins, bisphenol AD-type epoxy resins, and bisphenol S-type epoxy resins, and also include those in which the bisphenol compound moiety of these bisphenol-type epoxy resins has been halogen-substituted, alkyl-substituted, or hydrogenated. Furthermore, the bisphenol-type epoxy resin is not limited to a monomer, and high-molecular-weight compounds having multiple repeating units can also be suitably used. From the viewpoint of the balance between toughness and heat resistance of the epoxy resin cured product, the content of bisphenol-type epoxy resins, when included, is preferably 50% by mass or less based on 100% by mass of the total epoxy base component.

[0027] Commercially available bisphenol F epoxy resins include jER (registered trademark) 806, jER (registered trademark) 807, jER (registered trademark) 1750, jER (registered trademark) 4004P, jER (registered trademark) 4007P, and jER (registered trademark) 4009P (all manufactured by Mitsubishi Chemical Corporation), EPICLON (registered trademark) 830 (manufactured by DIC Corporation), Epotohto (registered trademark) YDF-170, Epotohto (registered trademark) YDF2001, and Epotohto (registered trademark) YDF2004 (all manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd.). Commercially available alkyl-substituted tetramethylbisphenol F epoxy resins include Epotohto (registered trademark) YSLV-80XY (Nippon Steel & Sumitomo Metal Chemical Co., Ltd.).

[0028] Commercially available bisphenol A type epoxy resins include "jER (registered trademark)" 825, "jER (registered trademark)" 826, "jER (registered trademark)" 827, "jER (registered trademark)" 828, "jER (registered trademark)" 834, "jER (registered trademark)" 1001, "jER (registered trademark)" 1002, "jER (registered trademark)" 1003, "jER (registered trademark)" 1004, and "jER (registered trademark)" 1005. Examples of suitable ethylene glycol acrylates include Epiclon (registered trademark) 1004AF, jER (registered trademark) 1007, and jER (registered trademark) 1009 (all manufactured by Mitsubishi Chemical Corporation), Epiclon (registered trademark) 850 (manufactured by DIC Corporation), Epotohto (registered trademark) YD-128 (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.), DER (registered trademark) -331, and DER (registered trademark) -332 (manufactured by The Dow Chemical Company).

[0029] Commercially available bisphenol S type epoxy resins include "EPICLON (registered trademark)" EXA-1515 (manufactured by DIC Corporation).

[0030] Component [B] in the present invention is a sulfonate ester. Component [B] is an accelerator necessary for ensuring both sufficient resin impregnation time into reinforcing fibers and rapid curing. Component [B] may be a sulfonate ester synthesized according to known techniques, and the synthesis method is not limited. For example, it can be obtained by reacting a sulfonic acid chloride with an alcohol compound. Among these, sulfonate esters of aromatic compounds are preferred because they tend to contribute in a well-balanced manner to the heat resistance of cured epoxy resin materials and the compressive strength of fiber-reinforced composite materials. They are preferably contained in an amount of 1% by mass or more and 10% by mass or less of the total epoxy base component. When 1% by mass or more of the sulfonate ester of an aromatic compound is contained as component [B] in 100% by mass of the total epoxy base component, sufficient curing acceleration effect is obtained, while when 10% by mass or less is contained, sufficient heat resistance of the cured resin is exhibited. Commercially available sulfonate esters include methyl p-toluenesulfonate, ethyl p-toluenesulfonate, Tokyo Chemical Industry Co., Ltd.'s propyl p-toluenesulfonate, hexyl p-toluenesulfonate, cyclohexyl p-toluenesulfonate, methyl methanesulfonate, and ethyl methanesulfonate (all manufactured by Tokyo Chemical Industry Co., Ltd.).

[0031] Accelerators other than component [B] may include compounds having an active group capable of accelerating the reaction between the epoxy resin and the curing agent. Examples of active groups capable of accelerating the reaction between the epoxy resin and the curing agent include a hydroxyl group, an amino group, and an acid anhydride group. Commercially available accelerators other than [B] include 4,4'-isopropylidenediphenol, 4,4'-sulfonyldiphenol, and 4-tert-butylcatechol (all manufactured by Tokyo Chemical Industry Co., Ltd.).

[0032] Component [C] in the present invention is an aromatic amine that has a melting point and is solid at room temperature. Note that "room temperature" refers to 20 to 25°C, and component [C] is solid at this temperature. [C] is a component necessary for achieving rapid curing of the resin composition while maintaining a gel time, which is an indicator of the resin impregnation time into the reinforcing fibers, and for imparting high mechanical properties to cured epoxy resins and fiber-reinforced composite materials. Examples of aromatic amines that have such a melting point and are solid at room temperature include diaminodiphenylmethane, diaminodiphenylsulfone, and their derivatives, isomers, hydrogenated products, etc., substituted with alkyl, aryl, alkoxy, aryloxy, or halogen. Commercially available diaminodiphenylmethane products include Primacure (registered trademark) M-MIPA (4,4'-methylenebis(2-isopropyl-6-methylaniline)), Primacure (registered trademark) M-CDEA (4,4'-methylenebis(3-chloro-2,6-diethylaniline)), Primacure (registered trademark) M-DIPA (4,4'-methylenebis(2,6-diisopropylaniline)), and Primacure (registered trademark) M-DEA (4,4'-methylenebis(2,6-diethylaniline), all manufactured by Arcsada Japan Co., Ltd.). Commercially available diaminodiphenyl sulfone products include Seikacure S (manufactured by Wakayama Seika Kogyo Co., Ltd.) and 3,3'-DAS (manufactured by Mitsui Chemicals, Inc.). Among these, 4,4'-methylenebis(2-isopropyl-6-methylaniline) and 4,4'-methylenebis(3-chloro-2,6-diethylaniline) are preferably used because they tend to provide a well-balanced contribution to the toughness and heat resistance of cured epoxy resins and the compressive strength of fiber-reinforced composite materials.

[0033] The melting point of component [C] in the present invention is preferably 60°C or higher and 90°C or lower. When the melting point of component [C] is 60°C or higher, the molecular skeleton of the compound contained in component [C] is sufficiently rigid, making it easy to exhibit high heat resistance and mechanical properties. Furthermore, when the melting point of component [C] is 90°C or lower, the curing reaction caused by preheating above the melting point to make component [C] liquid when mixed with the epoxy resin is suppressed, and non-impregnation due to increased viscosity can be suppressed.

[0034] In the present invention, the component [C] is preferably contained in an amount of 80% by mass or more and 100% by mass or less, based on 100% by mass of all curing agent components. When the component [C] is contained in an amount of 80% by mass or more, based on 100% by mass of all curing agent components, rapid curing at high temperatures such as 180°C is achieved, and the 0° compressive strength of the fiber-reinforced composite material under wet heat conditions is also improved.

[0035] The curing agent other than component [C] may contain a compound having an active group capable of reacting with the epoxy resin, such as an amino group or an acid anhydride group.

[0036] The curing agent other than component [C] is preferably an aromatic amine. Furthermore, from the viewpoints of heat resistance and mechanical properties, the curing agent other than component [C] more preferably has 1 to 4 phenyl groups in the molecule. Furthermore, since imparting flexibility to the molecular skeleton improves the resin elastic modulus and contributes to improved mechanical properties, it is even more preferable that the epoxy resin curing agent be an aromatic polyamine compound in which at least one phenyl group contained in the skeleton is a phenyl group having an amino group at the ortho- or meta-position.

[0037] Specific examples of aromatic polyamine compounds include metaphenylenediamine, metaxylylenediamine, diphenyl-p-dianiline, and various derivatives of these alkyl-substituted compounds, as well as isomers with different amino group positions. These curing agents can be used alone or in combination of two or more types.

[0038] Commercially available aromatic polyamine compound curing agents include "jER Cure (registered trademark)" W (manufactured by Mitsubishi Chemical Corporation) and "Kayahard (registered trademark)" AA (PT) (manufactured by Nippon Kayaku Co., Ltd.).

[0039] Furthermore, the epoxy resin composition for fiber-reinforced composite materials of the present invention may contain other components such as a curing accelerator, a plasticizer, a dye, a pigment, an inorganic filler, an antioxidant, an ultraviolet absorber, a coupling agent, a surfactant, etc., as needed.

[0040] The epoxy resin composition for fiber-reinforced composite materials of the present invention may contain core-shell rubber particles. Of these, component [D] is preferred, which is core-shell rubber particles having a volume average particle diameter of 50 nm or more and 300 nm or less and containing epoxy groups in the shell portion. Core-shell rubber particles are advantageous in that they tend to impart high toughness to fiber-reinforced composite materials. Here, core-shell rubber particles refer to particles in which the core portion is primarily composed of a polymer such as crosslinked rubber, and the core surface is partially or entirely coated by a method such as graft polymerization of a polymer different from the core portion.

[0041] The component constituting the core portion of the core-shell rubber particle may be a polymer polymerized from one or more selected from conjugated diene monomers, acrylic acid ester monomers, and methacrylic acid ester monomers, or a silicone resin. Specific examples of conjugated diene monomers include butadiene, isoprene, and chloroprene. The polymer used as the component constituting the core portion is preferably a crosslinked polymer composed of one or more of these conjugated diene monomers. Because the resulting polymer has particularly good properties and is easily polymerizable, it is preferable to use butadiene as the conjugated diene monomer, i.e., the polymer used as the component constituting the core portion is preferably a polymer polymerized from a monomer containing butadiene.

[0042] The shell portion of the core-shell rubber particles is preferably graft-polymerized to the core portion and chemically bonded to the polymer particles constituting the core portion. Examples of components constituting the shell portion include polymers polymerized from one or more species selected from (meth)acrylic acid esters, aromatic vinyl compounds, and the like. Furthermore, to stabilize the dispersion state, the component constituting the shell portion preferably contains a functional group reactive with the component contained in the epoxy resin composition for fiber-reinforced composite materials of the present invention, i.e., the epoxy resin or its curing agent. The introduction of such a functional group improves affinity with the epoxy resin and ultimately allows the functional group to react with the epoxy resin composition and be incorporated into the cured epoxy resin, thereby achieving good dispersibility. As a result, even a small amount of the functional group can achieve a sufficient toughness improvement effect, enabling the toughness to be improved while maintaining the glass transition temperature Tg and modulus of elasticity. Examples of such functional groups include hydroxyl groups, carboxyl groups, and epoxy groups. Among these, epoxy groups are preferred because they enhance the affinity between the shell component and the epoxy resin composition of the present invention and enable good dispersibility. That is, the core-shell rubber particles preferably contain epoxy groups in the shell portion.

[0043] Examples of methods for introducing such functional groups into the shell portion include graft polymerization of one or more components, such as acrylic acid esters or methacrylic acid esters, containing such functional groups onto the core surface as part of the monomer.

[0044] The core-shell rubber particles preferably have a volume average particle diameter of 50 nm or more and 300 nm or less, and more preferably 50 nm or more and 150 nm or less. The volume average particle diameter can be measured using a Nanotrac particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., dynamic light scattering method). Alternatively, thin sections of a cured epoxy resin prepared with a microtome can be observed by TEM, and the volume average particle diameter can be measured from the resulting TEM image using image processing software. In this case, it is necessary to use the average value of at least 100 particles. When the volume average particle diameter is 50 nm or more, the specific surface area of ​​the core-shell rubber particles is appropriately small, which is energetically advantageous, making aggregation less likely to occur and improving toughness. On the other hand, when the volume average particle diameter is 300 nm or less, the distance between the core-shell rubber particles becomes appropriately small, resulting in a high toughness improvement effect.

[0045] The epoxy resin composition for a fiber-reinforced composite material of the present invention more preferably contains core-shell rubber particles containing epoxy groups in the shell portion, and the volume average particle diameter of the core-shell rubber particles is in the range of 50 nm to 300 nm. That is, the epoxy resin composition for a fiber-reinforced composite material of the present invention more preferably contains core-shell rubber particles containing epoxy groups in the shell portion, having a volume average particle diameter [D] in the range of 50 nm to 300 nm. When the epoxy resin composition for a fiber-reinforced composite material contains core-shell rubber particles satisfying these conditions, the core-shell rubber particles are easily dispersed particularly uniformly and well in the epoxy resin composition, and an excellent toughness-improving effect is more easily exhibited.

[0046] There are no particular limitations on the method for producing the core-shell rubber particles, and those produced by known methods can be used. Commercially available core-shell rubber particles include "Paraloid (registered trademark)" EXL-2655 (manufactured by Rohm & Haas) made from a butadiene-alkyl methacrylate-styrene copolymer, "Staphyloid (registered trademark)" AC-3355 and TR-2122 (manufactured by Ganz Chemical Co., Ltd.) made from an acrylic acid ester-methacrylic acid ester copolymer, and "PARALOID (registered trademark)" EXL-2611 and EXL-3387 (manufactured by Rohm & Haas) made from a butyl acrylate-methyl methacrylate copolymer. Core-shell rubber particles with a three-layer structure, such as Staphyloid IM-601 and IM-602 (both manufactured by Ganz Chemical Co., Ltd.), can also be used. These core-shell rubber particles have a core layer made of a glassy polymer with a glass transition temperature above room temperature, covered with an intermediate layer made of a rubbery polymer with a low Tg, and further covered with a shell layer. Typically, these core-shell rubber particles are extracted in bulk form and then crushed into powder, which is then dispersed again in a thermosetting resin composition. However, this method presents a problem in that it is difficult to stably disperse the particles in a state without aggregation, i.e., in the form of primary particles. To address this problem, a preferable dispersion state can be achieved by using core-shell rubber particles that are never extracted in bulk form during the production process, but are ultimately dispersed as primary particles in a component of the thermosetting resin, such as an epoxy resin, in the form of a masterbatch. Core-shell rubber particles that can be handled in this masterbatch state can be produced, for example, by the method described in JP 2004-315572 A. In this production method, the core-shell rubber is first polymerized in an aqueous medium, typically by emulsion polymerization, dispersion polymerization, or suspension polymerization, to obtain a suspension in which the core-shell rubber particles are dispersed.Next, this suspension is mixed with an organic solvent that is partially soluble in water, such as a ketone solvent such as acetone or methyl ethyl ketone, or an ether solvent such as tetrahydrofuran or dioxane, and then contacted with a water-soluble electrolyte such as sodium chloride or potassium chloride to cause phase separation into an organic solvent layer and an aqueous layer. The aqueous layer is then separated and removed to obtain an organic solvent in which the core-shell rubber particles are dispersed. An epoxy resin is then mixed in, and the organic solvent is evaporated and removed to obtain a masterbatch in which the core-shell rubber particles are dispersed in the epoxy resin as primary particles. The core-shell rubber particle-dispersed epoxy masterbatch produced by this method can be "Kane Ace (registered trademark)" commercially available from Kaneka Corporation.

[0047] When core-shell rubber particles are included, the content is preferably 1% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 8% by mass or less, relative to 100% by mass of the total epoxy base component. When the content is 1% by mass or more, a highly tough epoxy resin cured product is likely to be obtained. When the content is 10% by mass or less, a highly elastic epoxy resin cured product is likely to be obtained, and the dispersibility of the core-shell rubber particles in the resin is also likely to be good. Note that even if the core-shell rubber particles have epoxy groups, the core-shell rubber particles do not fall under the category of an epoxy resin component.

[0048] Commonly used dispersion methods can be used to mix core-shell rubber particles into epoxy resin compositions for fiber-reinforced composite materials. Examples include methods using a three-roll mill, ball mill, bead mill, jet mill, homogenizer, or planetary / revolving mixer. Alternatively, the method of mixing the aforementioned core-shell rubber particle-dispersed epoxy masterbatch is also preferred. However, even if the particles are dispersed in the primary particle state, excessive heating or a decrease in viscosity can cause re-agglomeration. Therefore, when dispersing and compounding the core-shell rubber particles, and when mixing and kneading them with other components after dispersion, it is preferable to do so within a temperature and viscosity range that does not cause re-agglomeration of the core-shell rubber particles. Specifically, although this varies depending on the composition, kneading at temperatures above 150°C can reduce the viscosity of the composition and cause agglomeration, so kneading at a lower temperature is preferred. However, if the temperature reaches 150°C or higher during the curing process, gelation occurs during the heating process, preventing re-agglomeration.

[0049] In the present invention, H / E, which is the ratio of the total number of epoxy groups (E) contained in the epoxy resin to the total number of active hydrogens (H) of the amine compound contained in the curing agent, is preferably 1.0 or more and 1.4 or less. H / E is more preferably 1.1 or more and 1.3 or less. When H / E is 1.0 or more, the effect of improving the plastic deformation ability of the epoxy resin cured product is more likely to be obtained. Furthermore, when H / E is 1.4 or less, high heat resistance is more likely to be exhibited.

[0050] The epoxy resin composition for fiber-reinforced composite materials of the present invention preferably has a glass transition temperature (Tg) of 150°C or higher and 190°C or lower after curing at 180°C for 120 minutes. The heat resistance of a fiber-reinforced composite material depends on the glass transition temperature of the cured epoxy resin obtained by curing the epoxy resin composition. By setting the Tg at 150°C or higher, the heat resistance of the cured epoxy resin is more likely to be ensured. Furthermore, by setting the Tg at 190°C or lower, cure shrinkage of the epoxy resin composition is suppressed and deterioration of the surface quality of the fiber-reinforced composite material caused by the difference in thermal expansion between the epoxy resin composition and the reinforcing fiber is more likely to be prevented. Furthermore, in view of the relationship between heat resistance and surface quality, the glass transition temperature (Tg) is more preferably 160°C or higher and 190°C or lower. Here, the glass transition temperature (Tg) of the cured epoxy resin obtained by curing the epoxy resin composition is determined by measurement using a dynamic viscoelasticity measurement (DMA) device. Specifically, DMA measurement is performed at elevated temperatures using rectangular test specimens cut from the cured resin plate, and the temperature at the inflection point of the storage modulus (G') obtained is taken as Tg. The measurement conditions are as described in the Examples.

[0051] The fiber-reinforced composite material of the present invention comprises a cured product of the epoxy resin composition for a fiber-reinforced composite material of the present invention and a reinforcing fiber substrate.

[0052] The fiber-reinforced composite material of the present invention can be obtained, for example, by injecting an epoxy resin composition comprising an epoxy resin and a curing agent into a reinforcing fiber substrate placed in a heated mold, allowing the composition to impregnate the substrate, and then curing the composition in the mold. As described above, the RTM method is a preferred molding method, given its productivity and flexibility in the shape of the resulting molded product. Furthermore, in producing such fiber-reinforced composite materials, it is preferable to use a mold with multiple injection ports and inject the epoxy resin composition through the multiple injection ports simultaneously or sequentially with a time lag, selecting appropriate conditions depending on the fiber-reinforced composite material to be obtained, thereby providing flexibility in accommodating molded products of various shapes and sizes. While there are no limitations on the number or shape of the injection ports, the more injection ports there are, the better, allowing for faster injection. Their placement is also preferred, as it shortens the resin flow length depending on the shape of the molded product.

[0053] The reinforcing fiber substrate used in fiber-reinforced composite materials is often a preform, which is made by laminating and shaping a sheet-like substrate such as a reinforcing fiber woven fabric using a hot-melt binder (tackifier) ​​and processing it into a shape similar to the desired product. Both thermoplastic and thermosetting resins can be used as hot-melt binders. The form of the binder is not particularly limited, but may be in the form of a film, tape, long fiber, short fiber, spun yarn, woven fabric, knit, nonwoven fabric, net, or particle. Among these, particle or nonwoven fabric forms are particularly suitable. Note that binders in particle form are called binder particles, and binders in nonwoven fabric form are called binder nonwoven fabric.

[0054] When a particulate binder is used, the average particle size is preferably 10 μm or more and 500 μm or less. Here, the average particle size refers to the median diameter, and the average particle size of the binder particles can be measured, for example, using a laser diffraction particle size distribution analyzer. If the average particle size is smaller than 10 μm, the adhesive strength and workability may decrease when the binder is made into a preform. From this perspective, the average particle size is more preferably 30 μm or more. If the average particle size is larger than 500 μm, the reinforcing fibers may become wavy when the binder is made into a preform, which may result in a decrease in the mechanical properties of the resulting fiber-reinforced composite material. From this perspective, the average particle size is more preferably 300 μm or less.

[0055] When a nonwoven fabric is used as the binder, the average diameter of the fibers constituting the nonwoven fabric is preferably 10 μm or more and 300 μm or less. Here, the average diameter is determined by observing the cross section of the binder nonwoven fabric with a scanning electron microscope, measuring the diameters of 100 randomly selected fibers, and calculating the arithmetic mean value. If the cross section of the fiber is not a perfect circle, the minor axis is used as the diameter. If the average diameter is less than 10 μm, the adhesive strength of the preform may decrease. If the average diameter is more than 300 μm, the reinforcing fibers of the preform may become wavy, resulting in a decrease in the mechanical properties of the resulting fiber-reinforced composite material. From this perspective, the average diameter is more preferably 100 μm or less.

[0056] The binder is attached to at least the surface of the reinforcing fiber substrate to form a binder-coated reinforcing fiber substrate. The binder-coated reinforcing fiber substrate has the binder on at least the surface thereof and is used for a preform.

[0057] In the fiber-reinforced composite material of the present invention, the reinforcing fiber substrate is preferably a preform bound by a binder in the form of a nonwoven fabric. By using a preform bound by a binder in the form of a nonwoven fabric, the binder can be uniformly distributed on the substrate, ensuring impregnation paths for the epoxy resin composition. This results in particularly excellent impregnation and extremely low void generation. Furthermore, even if the amount of binder attached is less than that of a particulate binder, the effect of fixing the shape when made into a preform can be maintained to an equivalent extent, and the high heat resistance and mechanical properties inherent to the matrix resin can be easily exhibited when made into a fiber-reinforced composite material.

[0058] In the fiber-reinforced composite material of the present invention, the nonwoven fabric binder preferably comprises a polyamide having a melting point of 165°C or higher and 180°C or lower. Polyamides with a melting point of 165°C or higher are preferred because they can maintain their shape during curing, making it easier to ensure a uniform interlayer thickness that allows for sufficient plastic deformation, and because the nonwoven fabric is a continuous phase, they can more efficiently block cracks and provide impact resistance. Polyamides with a melting point of 180°C or lower are preferred because they begin to melt at a temperature lower than the gelation temperature of the epoxy resin composition, allowing the epoxy resin composition to penetrate into the gaps between the loosened polyamide molecular chains. The epoxy resin then gels and hardens in this state, entangling the resin and polyamide molecular chains, improving interfacial adhesive strength and potentially further improving compressive strength, impact resistance, and microcrack resistance.

[0059] In the fiber-reinforced composite material of the present invention, the binder in the form of a nonwoven fabric is preferably attached to one or both surfaces of the fiber-reinforced substrate.

[0060] In the fiber-reinforced composite material of the present invention, the amount of the binder in the form of nonwoven fabric attached to the surface of the fiber-reinforced substrate is 0.5 g / m per side. 2 More than 10g / m 2 The amount of adhesion is preferably 1 g / m or less. 2 More than 7g / m 2 It is more preferable that the coating amount is 0.5 g / m or less. 2 If the density is 10 g / m or more, it is easy to fix the shape when made into a preform. 2 When the binder is in the form of a nonwoven fabric, the binder can have a smaller adhesion amount than when it is in the form of particles, while still maintaining the same effect. Specifically, when a normal binder such as a particle binder is applied to the surface, the adhesion amount is 0.5 g / m per side. 2 More than 50g / m 2 Less than 1 g / m 2 More than 30g / m 2The preferred amount of adhesion is 0.5 g / m2 or less, while for nonwoven binders, the effect of fixing the shape when made into a preform is maintained at the same level. 2 More than 10g / m 2 The following deposition amounts are also possible:

[0061] As a method for obtaining a preform, for example, a method of laminating binder-attached reinforcing fiber substrates having the above-mentioned binder on at least the surface and fixing the shape can be mentioned. More specifically, for example, a binder is attached to at least the surface of at least one side of a reinforcing fiber substrate by heating to form a binder-attached reinforcing fiber substrate, and then a plurality of these are laminated to obtain a laminate having a binder at least between the laminated layers. This is heated and cooled, and the binder bonds between the substrate layers to fix the shape, thereby obtaining a preform having a binder at least between the laminated layers.

[0062] Typically, a preform can be produced by cutting a binder-attached reinforcing fiber substrate to a predetermined shape, laminating them on a mold, and applying appropriate heat and pressure. The pressurization method can be a press, or a method in which the substrate is surrounded by a vacuum bag film and the inside is suctioned with a vacuum pump to apply pressure at atmospheric pressure.

[0063] In the fiber-reinforced composite material of the present invention, the fiber volume content of the reinforcing fibers is preferably in the range of 45% to 70%, and more preferably in the range of 50% to 65%. When the fiber volume content is 45% or more, a fiber-reinforced composite material with a higher elastic modulus and excellent weight reduction effect can be obtained. Furthermore, when the fiber volume content is 70% or less, a fiber-reinforced composite material is obtained that is free from a decrease in strength due to friction between the reinforcing fibers and that has excellent mechanical properties such as tensile strength.

[0064] The reinforcing fibers constituting the reinforcing fiber substrate in the present invention 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 be mixed and used. Among these, carbon fibers and graphite fibers are preferably used to obtain a lighter, more durable fiber-reinforced composite material. In particular, for applications requiring a lighter and stronger material, carbon fibers are preferred as the reinforcing fibers constituting the reinforcing fiber substrate in the fiber-reinforced composite material of the present invention, since they have excellent specific modulus and specific strength.

[0065] Although any type of carbon fiber can be used depending on the application, carbon fibers having a tensile modulus of 230 GPa or more and 400 GPa or less are preferred from the viewpoint of impact resistance. Furthermore, from the viewpoint of strength, carbon fibers having a tensile strength of 4.4 GPa or more and 6.5 GPa or less are preferred, since this results in a composite material with high rigidity and mechanical strength. Furthermore, tensile elongation is also an important factor, and high-strength, high-elongation carbon fibers of 1.7% or more and 2.3% or less are preferred. Therefore, carbon fibers having the combined properties of 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.

[0066] Commercially available carbon fibers include "TORAYCA (registered trademark)" T800G-24K, "TORAYCA (registered trademark)" T800S-24K, "TORAYCA (registered trademark)" T700G-24K, "TORAYCA (registered trademark)" T300-3K, and "TORAYCA (registered trademark)" T700S-12K (all manufactured by Toray Industries, Inc.).

[0067] As described above, the fiber-reinforced composite material of the present invention comprises a cured epoxy resin product of the epoxy resin composition for a fiber-reinforced composite material of the present invention and a reinforcing fiber substrate. When used in the aircraft field, particularly, fiber-reinforced composite materials are required to have high heat resistance and mechanical properties. The fiber-reinforced composite material of the present invention preferably has a glass transition temperature of 150°C or higher and 190°C or lower, which is the matrix resin of the cured epoxy resin. Having a glass transition temperature within this range ensures excellent heat resistance and reflects the high mechanical properties of the cured epoxy resin. Therefore, the fiber-reinforced composite material of the present invention can exhibit a high H / W 0° compressive strength (0° compressive strength under wet heat conditions), preferably 1100 MPa or higher, and more preferably 1200 MPa or higher.

[0068] The method for producing a fiber-reinforced composite material of the present invention involves injecting a two-component epoxy resin composition for a fiber-reinforced composite material, obtained by mixing an epoxy base component and a curing agent component at 60°C to 130°C, into a reinforcing fiber substrate placed in a mold heated to 90°C to 180°C, allowing the composition to impregnate the substrate, and then curing the composition in the mold. The epoxy resin composition for a fiber-reinforced composite material is heated to a temperature selected from the range of 60°C to 130°C before injection, based on the relationship between the initial viscosity and viscosity increase of the epoxy resin composition, in order to facilitate impregnation into the reinforcing fiber substrate. If the epoxy resin composition is highly reactive at the injection temperature, its viscosity may increase during the injection process, making molding difficult. Furthermore, the mold temperature is preferably 90°C to 180°C. Setting the mold temperature to 90°C to 180°C shortens the curing time and simultaneously alleviates thermal shrinkage after demolding, resulting in a fiber-reinforced composite material with excellent surface quality.

[0069] The injection pressure of the epoxy resin composition for fiber-reinforced composite materials is usually 0.1 MPa or more and 1.0 MPa or less. Vacuum-assisted resin transfer molding (VaRTM) can also be used, in which the epoxy resin composition is injected into a mold while evacuating the mold. From the standpoints of injection time and equipment economy, the injection pressure of the epoxy resin composition for fiber-reinforced composite materials is preferably 0.1 MPa or more and 0.6 MPa or less. Even when pressurized injection is used, it is preferable to evacuate the mold before injecting the epoxy resin composition for fiber-reinforced composite materials, as this prevents voids from forming.

[0070] The fiber-reinforced composite material of the present invention has excellent mechanical properties, compressive strength under wet heat, impact resistance, and microcrack resistance, and therefore can be preferably used for many structural materials, including aircraft parts such as fuselages, main wings, tail parts, moving surfaces, fairings, cowls, doors, seats, and interior materials, spacecraft parts such as motor cases and main wings, artificial satellite parts such as bodies and antennas, automobile parts such as outer panels, chassis, aerodynamic parts, and seats, railway vehicle parts such as bodies and seats, and ship parts such as hulls and seats. [Example]

[0071] The epoxy resin composition for fiber-reinforced composite materials of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0072] <Resin raw materials> The following resin raw materials were used to obtain the epoxy resin compositions of each Example and Comparative Example. The numerical values ​​for each component in the "Epoxy Resin Composition" column in the tables indicate the content, in parts by mass unless otherwise specified, and the numbers in parentheses are mass%. The numerical values ​​expressed in mass% for [A] and [B] refer to the percentage of the mass of [A] and [B] when the mass of all epoxy base components is 100% by mass. The numerical value expressed in mass% for [C] refers to the percentage of the mass of [C] when the mass of all curing agent components is 100% by mass.

[0073] 1. [A] Glycidylamine epoxy "Araldite (registered trademark)" MY721 (N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, epoxy equivalent: 113 g / mol, manufactured by Huntsman Japan Co., Ltd.) "Araldite (registered trademark)" MY0600 (N,N,O-triglycidyl-m-aminophenol, epoxy equivalent: 106 g / mol, manufactured by Huntsman Japan Co., Ltd.) "Araldite (registered trademark)" MY0510 (N,N,O-triglycidyl-p-aminophenol, epoxy equivalent: 101 g / mol, manufactured by Huntsman Japan Co., Ltd.) GAN (N,N-diglycidylaniline, epoxy equivalent: 125 g / mol, manufactured by Nippon Kayaku Co., Ltd.)

[0074] 2. Epoxy resins other than [A] "EPICLON (registered trademark)" 830 (diglycidyl ether of bisphenol F, epoxy equivalent: 172 g / mol, manufactured by DIC Corporation) "EPICLON (registered trademark)" 850 (diglycidyl ether of bisphenol A, epoxy equivalent: 188 g / mol, manufactured by DIC Corporation)

[0075] 3. [B] Sulfonic acid ester Methyl p-toluenesulfonate, manufactured by Tokyo Chemical Industry Co., Ltd. Ethyl p-toluenesulfonate, manufactured by Tokyo Chemical Industry Co., Ltd. Propyl p-toluenesulfonate, manufactured by Tokyo Chemical Industry Co., Ltd. Hexyl p-toluenesulfonate, manufactured by Tokyo Chemical Industry Co., Ltd. Cyclohexyl p-toluenesulfonate, manufactured by Tokyo Chemical Industry Co., Ltd. Methyl methanesulfonate, manufactured by Tokyo Chemical Industry Co., Ltd. Ethyl methanesulfonate, manufactured by Tokyo Chemical Industry Co., Ltd.

[0076] 4. Accelerators other than [B] 4,4'-Isopropylidenediphenol, manufactured by Tokyo Chemical Industry Co., Ltd. 4,4'-Sulfonyldiphenol, manufactured by Tokyo Chemical Industry Co., Ltd. 4-tert-butylcatechol, manufactured by Tokyo Chemical Industry Co., Ltd.

[0077] 5. [C] Aromatic amines that are solid at room temperature and have a melting point "PrimaCure (registered trademark)" M-MIPA (4,4'-methylenebis(2-isopropyl-6-methylaniline), active hydrogen equivalent: 78 g / mol, melting point: 72°C, manufactured by ArcSada Japan Co., Ltd.) "PrimaCure (registered trademark)" M-CDEA (4,4'-methylenebis(3-chloro-2,6-diethylaniline), active hydrogen equivalent: 95 g / mol, melting point: 88°C, manufactured by ArcSada Japan Co., Ltd.) "PrimaCure (registered trademark)" M-DIPA (4,4'-methylenebis(2,6-diisopropylaniline), active hydrogen equivalent: 93 g / mol, melting point: 61°C, manufactured by ArcSada Japan Co., Ltd.) "PrimaCure (registered trademark)" M-DEA (4,4'-methylenebis(2,6-diethylaniline), active hydrogen equivalent: 78 g / mol, melting point: 88°C, manufactured by ArcSada Japan Co., Ltd.)

[0078] 6. Hardeners other than [C] "jER Cure (registered trademark)" W (diethyltoluenediamine, active hydrogen equivalent: 45 g / mol, manufactured by Mitsubishi Chemical Corporation) "Ethacure (registered trademark)" 300 (dimethylthiotoluenediamine, active hydrogen equivalent: 54 g / mol, manufactured by Mitsui Fine Chemicals, Inc.)

[0079] 7. [D] Core-shell rubber particles containing epoxy groups in the shell portion, with a volume average particle diameter of 50 nm or more and 300 nm or less. Kane Ace (registered trademark) MX-416 (masterbatch of Araldite (registered trademark) MY721: 75% by mass / core-shell rubber particles (volume average particle diameter: 100 nm, core part: cross-linked polybutadiene, shell part: methyl methacrylate / glycidyl methacrylate / styrene copolymer): 25% by mass, manufactured by Kaneka Corporation)

[0080] 8. Core-shell rubber particles other than [D] "Staphyloid (registered trademark)" AC-3355 (core-shell rubber particles (volume average particle diameter: 500 nm, core: cross-linked polybutyl acrylate, shell: cross-linked polystyrene, manufactured by Aica Kogyo Co., Ltd.)

[0081] <Preparation of Epoxy Resin Composition> Each component was mixed in the proportions shown in the table to prepare an epoxy resin composition.

[0082] <Preparation of cured resin board> The epoxy resin composition prepared above was degassed under reduced pressure and then poured into a mold set to a thickness of 2 mm using a 2 mm Teflon (registered trademark) spacer. It was cured at 180°C for 120 minutes to obtain a 2 mm thick cured resin plate.

[0083] <Evaluation> The evaluations in each example were carried out as follows: The number of measurements was 1 unless otherwise specified.

[0084] (1) Measurement of gel time and vitrification time of epoxy resin composition The specimen to be measured was placed on a stage heated to 180°C using a thermosetting measuring device ATD-1000 (manufactured by Alpha Technologies Co., Ltd.), and dynamic viscoelasticity was measured at a frequency of 1.0 Hz and a strain of 1%, to determine the complex viscosity. 3 The time required for the gelation to reach Pa·s is 1.0×10 6 The time required for the viscosity to reach Pa·s was defined as the vitrification time. The specimen was an epoxy resin composition prepared by mixing the components and stirring for 1 minute.

[0085] (2) Measurement of the glass transition temperature (Tg) of cured epoxy resin A test piece measuring 12.7 mm in width and 40 mm in length was cut out from the resin-cured plate, and Tg measurement was performed using a DMA device ARES (manufactured by TA Instruments). The measurement conditions were a temperature rise rate of 5°C / min. The temperature at the inflection point of the storage modulus G' obtained in the measurement was taken as Tg.

[0086] (3) Measurement of 0° compressive strength of fiber-reinforced composite materials under wet heat A 395mm x 395mm sheet of unidirectional carbon fiber fabric (plain weave, warp: carbon fiber T800S-24K-10C manufactured by Toray Industries, Inc., carbon fiber basis weight 295g / m², warp density 7.2 threads / 25mm; weft: glass fiber ECE225 1 / 0 1Z manufactured by Nittobo Co., Ltd., weft density 7.5 threads / 25mm) was placed in a mold having a 400mm x 400mm x 1.2mm plate-shaped cavity. Four sheets were stacked with the fiber direction at 0°, aligned in the 0° direction, and placed in the mold. The mold was then clamped. The mold was then heated to 120°C, and an epoxy resin composition preheated to 80°C was injected into the mold using a resin injection device at an injection pressure of 0.2MPa. After injection, the mold was heated from 120°C to 180°C at a rate of 1.5°C / min, cured at 180°C for 2 hours, and then cooled to 30°C to obtain a fiber-reinforced composite material.

[0087] From the fiber-reinforced composite material obtained by the above method, a 12.7 mm wide, 79.4 mm long test piece was cut so that the 0° direction and the length direction were the same to prepare a 0° compression strength test piece. This test piece was immersed in 72°C warm water for 14 days, and then the 0° compression strength of the fiber-reinforced composite material was measured. The 0° compression strength was measured in accordance with ASTM D695 using a universal testing machine (Instron Model 4208, manufactured by Instron Japan Co., Ltd.) at a crosshead speed of 1.27 mm / min and a temperature of 82°C.

[0088] Example 1 As shown in Table 1-1, 50 parts by mass (47.6% by mass) of Araldite® MY721 was used as component [A], 50 parts by mass (47.6% by mass) of EPICLON® 830 was used as an epoxy resin other than component [A], and 5 parts by mass (4.8% by mass) of methyl p-toluenesulfonate was used as component [B]. The mixture was stirred at 80°C for 10 minutes to prepare an epoxy base component. To this mixture, 57 parts by mass (100% by mass) of Primacure® M-MIPA, the curing agent component of component [C], was added and stirred at 80°C for 1 minute to prepare an epoxy resin composition. The gelation time and vitrification time of the epoxy resin composition were measured as described above. The gelation time was 80 seconds, indicating good impregnation into the reinforcing fibers, and the vitrification time was 30 minutes, indicating good curability. Furthermore, a cured resin was prepared using the above-described method, and its Tg was measured to be 150°C, indicating good heat resistance. Furthermore, a fiber-reinforced composite material was produced using this epoxy resin composition, and the 0° compressive strength under wet heat was measured, resulting in a favorable value of 1100 MPa.

[0089] (Example 2-28) Epoxy resin compositions were prepared in the same manner as in Example 1, except that the blending amounts of each component were changed as shown in Tables 1-1, 1-2, 1-3, and 1-4. The gelation time and vitrification time of the epoxy resin compositions were measured as described above. The gelation times were all 30 seconds or longer, indicating good impregnation into the reinforcing fibers, and the vitrification times were 30 minutes or shorter, indicating good curability. Furthermore, cured resins were prepared using the method described above, and the Tg values ​​of the cured products were measured. The Tg values ​​were all 150°C or higher, indicating good heat resistance. Furthermore, fiber-reinforced composite materials were prepared using these epoxy resin compositions, and the 0°C compressive strengths under wet heat conditions were measured. The results were good, at 1100 MPa or higher.

[0090] (Comparative Examples 1-5) Epoxy resin compositions were prepared in the same manner as in Example 1, except that the blending amounts of each component were changed as shown in Table 1-5. As described above, the gelation time and vitrification time of the epoxy resin composition, the Tg of the cured resin, and the 0° compressive strength under wet heat of the fiber-reinforced composite material were measured. As a result, in all cases, one or more of the properties of impregnation into the reinforcing fiber, curability, heat resistance, and mechanical properties were poor.

[0091] [Table 1-1]

[0092] [Table 1-2]

[0093] [Table 1-3]

[0094] [Table 1-4]

[0095] [Table 1-5] [Industrial Applicability]

[0096] The two-component epoxy resin composition for fiber-reinforced composite materials of the present invention has excellent impregnation properties for reinforcing fibers, curing properties, and heat resistance, making it possible to provide high-quality fiber-reinforced composite materials with high productivity by RTM method, etc. This is expected to promote the application of fiber-reinforced composite materials, particularly in aircraft and automobile applications, and contribute to improved fuel efficiency through further weight reduction and reduced greenhouse gas emissions.

Claims

1. A two-component epoxy resin composition for fiber-reinforced composite materials, comprising an epoxy base component containing [A] a glycidyl amine-type epoxy resin and [B] a sulfonic acid ester, and a curing agent component containing [C] an aromatic amine having a melting point and being solid at room temperature.

2. 2. The two-component epoxy resin composition for fiber-reinforced composite materials according to claim 1, wherein [A] contains a glycidylamine-type epoxy resin selected from tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, or a derivative or isomer thereof in an amount of 70% by mass or more but less than 100% by mass, based on 100% by mass of the total epoxy main component.

3. 2. The two-component epoxy resin composition for fiber-reinforced composite materials according to claim 1, wherein [B] is a sulfonic acid ester of an aromatic compound and is contained in an amount of 1% by mass to 10% by mass based on 100% by mass of the total epoxy main component.

4. 2. The two-component epoxy resin composition for fiber-reinforced composite materials according to claim 1, wherein the melting point of [C] is 60°C or higher and 90°C or lower.

5. The two-component epoxy resin composition for fiber-reinforced composite materials according to claim 4, wherein [C] contains an aromatic amine selected from 4,4'-methylenebis(2-isopropyl-6-methylaniline) and 4,4'-methylenebis(3-chloro-2,6-diethylaniline).

6. The two-component epoxy resin composition for fiber-reinforced composite materials according to claim 1, further comprising: [D] core-shell rubber particles having a volume average particle diameter in the range of 50 nm to 300 nm and containing epoxy groups in the shell portion.

7. 2. The two-component epoxy resin composition for fiber-reinforced composite materials according to claim 1, wherein H / E, which is the ratio of the total number of epoxy groups (E) contained in the epoxy main component to the total number of active hydrogens (H) of the amine contained in the curing agent component, is 1.0 or more and 1.4 or less.

8. A fiber-reinforced composite material comprising a cured product of the two-component epoxy resin composition for fiber-reinforced composite materials according to claim 1 and a reinforcing fiber substrate.

9. The fiber-reinforced composite material according to claim 8, wherein the reinforcing fibers constituting the fiber-reinforced substrate are carbon fibers.

10. A method for producing a fiber-reinforced composite material, comprising: injecting a two-component epoxy resin composition for a fiber-reinforced composite material, which is prepared by mixing the epoxy main component and the curing agent component according to claim 1 at a temperature of 60°C or higher and 130°C or lower, into a reinforcing fiber substrate placed in a molding die heated to 90°C or higher and 180°C or lower, allowing the composition to impregnate the substrate, and curing the composition in the molding die.

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