Epoxy resin curing agent, epoxy resin composition and cured product thereof, fiber-reinforced composite material, and high-pressure gas container

Abstract

Provided are: an epoxy resin curing agent comprising a component (A-1) that is a reaction composition containing a polycondensation reaction product of an aniline derivative and formaldehyde and a component (A-2) that is a reaction composition containing a reaction product of styrene and a compound represented by general formula (1) H2N-CH2-A-CH2-NH2 (wherein A represents a 1,2-phenylene group, a 1,3-phenylene group or a 1,4-phenylene group), in which the contents of the component (A-1) and the component (A-2) in the epoxy resin curing agent are 50 to 95% by mass and 5 to 50% by mass, respectively; an epoxy resin composition; a cured product of the epoxy resin composition; a fiber-reinforced composite material; and a high-pressure gas container comprising the fiber-reinforced composite material.

Description

Epoxy resin curing agents, epoxy resin compositions and their cured products, fiber-reinforced composite materials, high-pressure gas cylinders

[0001] The present invention relates to an epoxy resin curing agent, an epoxy resin composition and a cured product thereof, a fiber-reinforced composite material, and a high-pressure gas cylinder containing the fiber-reinforced composite material.

[0002] In recent years, environmentally friendly natural gas vehicles (CNG vehicles) and fuel cell vehicles (FCVs) have become increasingly popular. Fuel cell vehicles are powered by fuel cells, making it essential to develop hydrogen stations where hydrogen, the fuel used for fueling these vehicles, is compressed to high pressure and filled into the vehicles. Until now, steel tanks have been used as high-pressure gas storage tanks at hydrogen stations for fuel cell vehicles, or as on-board fuel tanks for CNG vehicles and fuel cell vehicles. However, progress has been made in the development of lighter high-pressure gas storage tanks that use resin materials for the tank liner or outer layer. Reducing the weight of on-board fuel tanks has the advantage of improving the fuel efficiency of vehicles equipped with them.

[0003] Pressure vessels such as high-pressure gas storage tanks typically have a metal liner and an outer layer that covers the outer surface of the liner. However, in recent years, in order to produce lighter pressure vessels, the production of linerless pressure vessels has also been considered.

[0004] A known method for producing pressure vessels involves filament winding a tow prepreg (also referred to as a towpreg) in which reinforcing fibers have been pre-impregnated with an epoxy resin composition. For example, Patent Document 1 discloses that a towpreg, in which a reinforcing fiber bundle is impregnated with an epoxy resin composition that contains an epoxy resin that does not have a hydroxy group in its main chemical structure, an aromatic amine that is liquid at 25°C, and a toughening agent and that satisfies certain conditions, exhibits good tow spreadability during filament winding, and the impregnated epoxy resin composition exhibits good pot life, fracture toughness, and elongation. Furthermore, in the examples of Patent Document 1, diethyltoluenediamine and 3,3'-diethyl-4,4'-diaminodiphenylmethane are used as the liquid aromatic amine.

[0005] Japanese Patent Application Laid-Open No. 2021-116403

[0006] High-pressure gas containers for storing hydrogen gas, such as hydrogen stations for fuel cell vehicles or on-board fuel tanks for CNG vehicles, fuel cell vehicles, etc., require high barrier properties against hydrogen gas. In particular, when the high-pressure gas container is linerless, the material used for the high-pressure gas container must have even higher hydrogen gas barrier properties. Furthermore, as described in Patent Document 1, epoxy resin compositions for towpregs used in filament winding molding are required to have a long pot life.

[0007] In addition to the above, resin materials generally tend to have a reduced gas barrier property when they absorb moisture, so when resin materials are used in the manufacture of high-pressure gas containers, there is a risk that oxygen, water vapor, etc. may penetrate from the outside in a high-humidity environment. The technology disclosed in Patent Document 1 leaves room for improvement in this regard.

[0008] An object of the present invention is to provide an epoxy resin curing agent, an epoxy resin composition, a cured product thereof, a fiber-reinforced composite material, and a high-pressure gas container containing the fiber-reinforced composite material, which have high hydrogen gas barrier properties, are not significantly reduced in gas barrier properties even under high-humidity conditions, and can achieve a long pot life.

[0009] The present inventors have found that the above-mentioned problems can be solved by an epoxy resin curing agent containing two types of polyamines with specific structures containing an aromatic ring in a predetermined ratio. That is, the present invention relates to the following: [1] Component (A-1) and Component (A-2) below: (A-1) A reaction composition containing a polycondensation reaction product of an aniline derivative and formaldehyde (A-2) A reaction composition H containing a reaction product of styrene and a compound represented by the following general formula (1): ２ N-CH ２ -A-CH ２ -NH ２(1) An epoxy resin curing agent containing the formula (1), wherein A is a 1,2-phenylene group, a 1,3-phenylene group, or a 1,4-phenylene group, wherein the content of component (A-1) in the epoxy resin curing agent is 50 to 95 mass % and the content of component (A-2) in the epoxy resin curing agent is 5 to 50 mass %. [2] An epoxy resin composition containing an epoxy resin and the epoxy resin curing agent described in [1] above. [3] A cured product of the epoxy resin composition described in [2] above. [4] A fiber-reinforced composite material containing a cured product of the epoxy resin composition described in [2] above and reinforcing fibers. [5] A high-pressure gas container containing the fiber-reinforced composite material described in [4] above.

[0010] According to the present invention, there are provided an epoxy resin curing agent, an epoxy resin composition, a cured product thereof, a fiber-reinforced composite material, and a high-pressure gas container containing the fiber-reinforced composite material, which have high hydrogen gas barrier properties, are less susceptible to deterioration in gas barrier properties even under high-humidity conditions, and further achieve a long pot life. The high-pressure gas container can be manufactured by filament winding molding, and can also be a linerless high-pressure gas container. Furthermore, because the high-pressure gas container has high hydrogen gas barrier properties, it is suitable as a container for storing high-pressure hydrogen gas.

[0011] [Definition] In this specification, the term "reaction composition containing a reaction product of X and Y" refers to a composition obtained by reacting X and Y, which contains not only the reaction product (adduct) of X and Y, but also by-products other than the reaction product, and unreacted raw materials such as X and Y. In this specification, the effect of suppressing the deterioration of gas barrier properties under high humidity conditions is evaluated using the increase rate of oxygen permeability, which is calculated from the oxygen permeability of a cured product of an epoxy resin composition under dry conditions at 23°C (0% R.H.) and the oxygen permeability at 23°C and 80% R.H. using the following formula. The oxygen permeability can be measured by the method described in the Examples. Increase rate of oxygen permeability (%) = [(oxygen permeability at 23°C and 80% R.H.) - (oxygen permeability at 23°C and 0% R.H.)] / (oxygen permeability at 23°C and 0% R.H.) × 100

[0012] [Epoxy Resin Curing Agent] The epoxy resin curing agent of the present invention (hereinafter also referred to as "the curing agent of the present invention") comprises the following component (A-1) and component (A-2): (A-1) a reaction composition containing a polycondensation reaction product of an aniline derivative and formaldehyde; (A-2) a reaction composition containing a reaction product of styrene and a compound represented by the following general formula (1): H ２ N-CH ２ -A-CH ２ -NH ２ (1) (In formula (1), A is a 1,2-phenylene group, a 1,3-phenylene group, or a 1,4-phenylene group), wherein the content of component (A-1) in the epoxy resin curing agent is 50 to 95 mass %, and the content of component (A-2) in the epoxy resin curing agent is 5 to 50 mass %. By having the above-mentioned structure, the curing agent of the present invention can provide an epoxy resin composition that has high hydrogen gas barrier properties, is less susceptible to deterioration in gas barrier properties even under high humidity conditions, and can achieve a long pot life.

[0013] The reason why the above-mentioned effects are achieved in the present invention is unclear, but is thought to be as follows. Component (A-1), a reaction composition containing a polycondensation reaction product of an aniline derivative and formaldehyde, acts as an amine-based epoxy resin curing agent. Component (A-1) is a low-viscosity composition that is likely to achieve a long pot life, making it suitable for use as an epoxy resin composition for towpregs used in filament winding molding. Furthermore, because component (A-1) is an amine-based curing agent, it exhibits relatively high gas barrier properties (particularly high hydrogen gas barrier properties). On the other hand, it has been found that cured products of epoxy resin compositions using component (A-1) as an epoxy resin curing agent experience a decrease in gas barrier properties under high-humidity conditions. Therefore, the present inventors conducted research and found that by blending components (A-1) and (A-2) in a specific ratio to create an epoxy resin curing agent, it is possible to suppress the decrease in gas barrier properties under high-humidity conditions while maintaining low viscosity, high hydrogen gas barrier properties, and a long pot life. Component (A-2), an amine-based curing agent, has low viscosity and high gas barrier properties, similar to component (A-1). Component (A-2) is fast-curing, which is disadvantageous in terms of ensuring pot life, but by setting the content of component (A-2) in the curing agent within a specific range, a long pot life can be maintained. Furthermore, component (A-2) has low water absorption, which is thought to prevent a decrease in gas barrier properties under high-humidity conditions.

[0014] <Component (A-1): Reaction Composition Comprising a Polycondensation Reaction Product of an Aniline Derivative and Formaldehyde> Component (A-1) is a reaction composition comprising a polycondensation reaction product of an aniline derivative and formaldehyde. Component (A-1) is an amine-based curing agent that exhibits low viscosity, high hydrogen gas barrier properties, and a long pot life. From the viewpoints of reactivity with formaldehyde and function as an amine-based curing agent, the aniline derivative used in component (A-1) is preferably a compound in which the nitrogen atom of the aniline is not substituted and at least one hydrogen atom on the aromatic ring of the aniline is substituted with a substituent. Examples of the substituent include at least one selected from the group consisting of alkyl groups, alkenyl groups, aryl groups, aralkyl groups, alkoxy groups, and hydroxy groups. From the viewpoints of reactivity with formaldehyde and function as an amine-based curing agent, the substituent is preferably at least one selected from the group consisting of alkyl groups and aryl groups. It should be noted that the aniline derivatives defined in the present invention do not include aniline. Diaminodiphenylmethane, a polycondensation reaction product of aniline and formaldehyde, is a solid compound at room temperature (25°C), so epoxy resin curing agents and epoxy resin compositions containing diaminodiphenylmethane become solids or highly viscous liquids and are unsuitable for filament winding molding.

[0015] From the viewpoint of obtaining a curing agent that can achieve low viscosity, high hydrogen gas barrier properties, and a long pot life, the aniline derivative is more preferably a compound represented by the following general formula (2): (In formula (2), R １ is an alkyl group having 1 to 6 carbon atoms or an aryl group. p is a number from 1 to 3.

[0016] In formula (2), R １The alkyl group in formula (2) is preferably an alkyl group having 1 to 4 carbon atoms, more preferably 1 to 3 carbon atoms, and even more preferably 1 to 2 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a neopentyl group, and an n-hexyl group. Preferably, it is a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, or a tert-butyl group, more preferably a methyl group, an ethyl group, an n-propyl group, or an isopropyl group, and even more preferably a methyl group or an ethyl group. In formula (2), R １ Examples of the aryl group in formula (2) include a phenyl group, a toluyl group, a mesityl group, a biphenyl group, and a naphthyl group, and a phenyl group is preferred. In formula (2), p is preferably 1 to 2, and more preferably 1. When p is 2 or 3, a plurality of R １ may be the same or different, but are preferably the same.

[0017] Specific examples of the aniline derivative used in component (A-1) include 2-methylaniline, 3-methylaniline, 4-methylaniline, 2-ethylaniline, 3-ethylaniline, 4-ethylaniline, 2,3-dimethylaniline, 2,4-dimethylaniline, 2,5-dimethylaniline, 2,6-dimethylaniline, 3,4-dimethylaniline, 3,5-dimethylaniline, 2-propylaniline, 3-propylaniline, 4-propylaniline, 2-isopropylaniline, and 3-isopropylaniline. Examples of the aniline include propylaniline, 4-isopropylaniline, 2-ethyl-6-methylaniline, 2-sec-butylaniline, 2-tert-butylaniline, 4-n-butylaniline, 4-sec-butylaniline, 4-tert-butylaniline, 2,3-diethylaniline, 2,4-diethylaniline, 2,5-diethylaniline, 2,6-diethylaniline, 2-isopropyl-6-methylaniline, and 4-aminobiphenyl, and one or more of these can be used.

[0018] Among the above, from the viewpoint of obtaining an epoxy resin composition that can achieve low viscosity, high hydrogen gas barrier properties, and a long pot life, the aniline derivative is preferably at least one selected from the group consisting of 2-methylaniline, 3-methylaniline, 4-methylaniline, 2-ethylaniline, 3-ethylaniline, 4-ethylaniline, 3-propylaniline, 4-propylaniline, 2-isopropylaniline, 3-isopropylaniline, 4-isopropylaniline, 2-sec-butylaniline, 2-tert-butylaniline, 4-n-butylaniline, 4-sec-butylaniline, and 4-tert-butylaniline, and 2-methylaniline, 3-methylaniline, 4-ethylaniline, 3-propylaniline, 4-propylaniline, 2-isopropylaniline, 3-isopropylaniline, 4-isopropylaniline, 2-sec-butylaniline, 2-tert-butylaniline, 4-n-butylaniline, 4-sec-butylaniline, and 4-tert-butylaniline. At least one selected from the group consisting of 2-methylaniline, 3-methylaniline, 4-methylaniline, 2-ethylaniline, 3-ethylaniline, 4-ethylaniline, 3-propylaniline, 4-propylaniline, 2-isopropylaniline, 3-isopropylaniline, and 4-isopropylaniline is more preferred, at least one selected from the group consisting of 2-methylaniline, 3-methylaniline, 4-methylaniline, 2-ethylaniline, 3-ethylaniline, and 4-ethylaniline is even more preferred, at least one selected from the group consisting of 2-ethylaniline, 3-ethylaniline, and 4-ethylaniline is even more preferred, and 2-ethylaniline is even more preferred.

[0019] Component (A-1) is obtained by polycondensation reaction of an aniline derivative with formaldehyde by a known method. From the viewpoint of effectively obtaining the effects of the present invention, the content of the polycondensation reaction product of the aniline derivative and formaldehyde in the reaction composition of component (A-1) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more, and 100% by mass or less. For example, when the aniline derivative is 2-ethylaniline, the polycondensation reaction product of 2-ethylaniline and formaldehyde means 3,3'-diethyl-4,4'-diaminodiphenylmethane.

[0020] Commercially available products of component (A-1) can also be used, such as "KAYAHARD AA" (a reaction composition containing a polycondensation reaction product of 2-ethylaniline and formaldehyde (3,3'-diethyl-4,4'-diaminodiphenylmethane)) manufactured by Nippon Kayaku Co., Ltd.

[0021] <Component (A-2): Reaction composition containing a reaction product of styrene and a compound represented by general formula (1)> Component (A-2) is a reaction composition containing a reaction product of styrene and a compound represented by the following general formula (1). Component (A-2) is an amine-based curing agent that has low viscosity and high hydrogen gas barrier properties, and can suppress a decrease in gas barrier properties under high humidity conditions. ２ N-CH ２ -A-CH ２ -NH ２ (1) (In formula (1), A is a 1,2-phenylene group, a 1,3-phenylene group, or a 1,4-phenylene group.)

[0022] In general formula (1), A is preferably a 1,3-phenylene group or a 1,4-phenylene group, and more preferably a 1,3-phenylene group. That is, the compound represented by general formula (1) is one or more xylylenediamines selected from the group consisting of o-xylylenediamine, m-xylylenediamine (meta-xylylenediamine; MXDA), and p-xylylenediamine (para-xylylenediamine; PXDA), preferably one or more selected from the group consisting of meta-xylylenediamine and para-xylylenediamine, and more preferably meta-xylylenediamine.

[0023] Component (A-2) preferably contains 10% by mass or more of a compound represented by the following general formula (1-1). (In formula (1-1), A is the same as defined above.) The compound represented by the general formula (1-1) above is a reaction product (hereinafter also referred to as a "1:1 adduct") of 1 mole of styrene and 1 mole of the starting polyamine, among the reaction products of styrene and the compound represented by the general formula (1) above (hereinafter also referred to as the "raw material polyamine"). Component (A-2) may contain, in addition to the 1:1 adduct of styrene and the starting material polyamine, which is the compound represented by the general formula (1-1) above, multiple adducts such as a 2:1 adduct, a 3:1 adduct, or a 4:1 adduct of styrene and the starting material polyamine, but among the above adducts, the 1:1 adduct of styrene and the starting material polyamine has the lowest active hydrogen equivalent. The active hydrogen equivalent (hereinafter also referred to as "AHEW") is the molecular weight per equivalent of active hydrogen that can react with the epoxy resin, which is the main component of the epoxy resin composition. Therefore, an epoxy resin curing agent using component (A-2) containing the compound represented by general formula (1-1) as a main component can exhibit good curing performance even when incorporated in a small amount into an epoxy resin composition.

[0024] From the viewpoint of obtaining the above-mentioned effects, the content of the compound represented by the general formula (1-1) in component (A-2) is more preferably 20% by mass or more, even more preferably 30% by mass or more, and even more preferably 45% by mass or more, and is 100% by mass or less. The content of the compound represented by the general formula (1-1) in component (A-2) can be determined by gas chromatography (GC) analysis.

[0025] The active hydrogen equivalent weight (AHEW) of component (A-2) is preferably 130 or less, more preferably 120 or less, and even more preferably 110 or less, from the viewpoint of exhibiting good curing performance even when incorporated in a small amount into the epoxy resin composition. Furthermore, from the viewpoint of ease of production, it is preferably 80 or more, more preferably 90 or more. The AHEW of component (A-2) can be determined, for example, by titration.

[0026] Component (A-2) can be obtained by reacting styrene with a compound represented by the general formula (1) by a known method. More specifically, it can be obtained by subjecting styrene and a starting polyamine to an addition reaction in the presence of a basic catalyst such as an alkali metal, alkali metal amide (represented by the general formula MNRR', where M is an alkali metal, N is nitrogen, and R and R' are each independently hydrogen or an alkyl group), or an alkylated alkali metal, preferably at 50 to 120°C, more preferably 70 to 100°C. In the addition reaction of styrene with the starting polyamine, the amount of the basic catalyst used is preferably 0.1 to 20 mol%, more preferably 0.5 to 15 mol%, even more preferably 1.0 to 12 mol%, and even more preferably 1.5 to 10 mol%, based on 100 mol% of the total amount of the starting polyamine and styrene used. Furthermore, from the viewpoint of obtaining the compound represented by the general formula (1-1) with high selectivity, the amounts of styrene and raw material polyamine used in the addition reaction are such that the molar ratio of styrene to 1 mole of raw material polyamine is preferably in the range of 0.1 to 5.0 mol, more preferably 0.4 to 3.0 mol, even more preferably 0.5 to 1.5 mol, and still more preferably 0.8 to 1.2 mol.

[0027] As the component (A-2), commercially available products such as "Gaskamine 240" manufactured by Mitsubishi Gas Chemical Co., Ltd. can also be used.

[0028] From the viewpoint of obtaining an epoxy resin composition having high hydrogen gas barrier properties, with little deterioration in gas barrier properties even under high humidity conditions, and capable of achieving a long pot life, the content of component (A-1) in the epoxy resin curing agent of the present invention is 50 to 95 mass %, and the content of component (A-2) is 5 to 50 mass %. When the content of component (A-1) in the epoxy resin curing agent is 50 mass % or more and the content of component (A-2) is 50 mass % or less, a long pot life is easily achieved. Furthermore, when the content of component (A-1) in the epoxy resin curing agent is 95 mass % or less and the content of component (A-2) is 5 mass % or more, deterioration in gas barrier properties under high humidity conditions can be suppressed. From the viewpoint of obtaining an epoxy resin composition having high hydrogen gas barrier properties, with little deterioration in gas barrier properties even under high humidity conditions, and capable of achieving a long pot life, the content of component (A-1) in the epoxy resin curing agent is preferably 60 to 95 mass %, more preferably 70 to 95 mass %, and even more preferably 75 to 92 mass %. The content of component (A-2) in the epoxy resin curing agent is preferably 5 to 40% by mass, more preferably 5 to 30% by mass, and even more preferably 8 to 25% by mass.

[0029] The epoxy resin curing agent of the present invention may be a curing agent consisting only of component (A-1) and component (A-2), or may contain other epoxy resin curing agents. Examples of other epoxy resin curing agents include amine-based curing agents, phenol-based curing agents, acid anhydride-based curing agents, and hydrazide-based curing agents. From the viewpoint of gas barrier properties, amine-based curing agents are preferred.

[0030] For example, the curing agent of the present invention may further contain a compound represented by the following general formula (3) as component (A-3). When the curing agent of the present invention contains component (A-3), the gas barrier properties can be further improved. (In formula (3), R ２ is an alkyl group, alkoxy group, or alkylthio group having 1 to 6 carbon atoms; and q is a number from 0 to 3.

[0031] In formula (3), R ２Examples of the alkyl group having 1 to 6 carbon atoms in formula (3) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a neopentyl group, and an n-hexyl group. Among these, an alkyl group having 1 to 4 carbon atoms is preferred, and an alkyl group having 1 to 2 carbon atoms is more preferred. ２ The alkoxy group in formula (3) is preferably an alkoxy group having 1 to 4 carbon atoms, and examples thereof include a methoxy group, an ethoxy group, an n-propoxy group, and an n-butoxy group. ２ The alkylthio group in the formula (I) is preferably an alkylthio group having 1 to 4 carbon atoms, and examples thereof include a methylthio group, an ethylthio group, a propylthio group, and a butylthio group.

[0032] In formula (3), q is preferably 0 to 2, more preferably 0. When q is 2, a plurality of R ２ may be the same or different, but are preferably the same.

[0033] Specific examples of component (A-3) include 1,2-phenylenediamine, 1,3-phenylenediamine, 1,4-phenylenediamine, 4-methyl-1,2-phenylenediamine, 4-ethyl-1,2-phenylenediamine, 2-methyl-1,4-phenylenediamine, 2-ethyl-1,4-phenylenediamine, 5-methyl-1,3-phenylenediamine, 5-ethyl-1,3-phenylenediamine, dimethyltoluenediamine, diethyltoluenediamine, dimethylthiotoluenediamine, etc., and one or more of these can be used. Among these, from the viewpoints of improving the hardness of the cured product of the obtained epoxy resin composition and of availability, at least one selected from the group consisting of 1,2-phenylenediamine, 1,3-phenylenediamine, and 1,4-phenylenediamine is preferred as component (A-3), and 1,3-phenylenediamine is more preferred.

[0034] When the epoxy resin curing agent of the present invention contains component (A-3), the content of component (A-3) in the curing agent is preferably 1 to 30 mass%, more preferably 2 to 25 mass%, even more preferably 3 to 20 mass%, and still more preferably 5 to 15 mass%. When the content of component (A-3) in the curing agent is 1 mass% or more, it tends to contribute to improving the gas barrier properties of the resulting epoxy resin composition, and when it is 30 mass% or less, it is possible to maintain the effect of suppressing the deterioration of gas barrier properties under high humidity conditions and a long pot life.

[0035] The epoxy resin curing agent of the present invention may contain an amine-based curing agent other than components (A-1) to (A-3). Examples of such amine-based curing agents include polyamine compounds having two or more amino groups in the molecule, and modified products thereof. Examples of such polyamine compounds include linear aliphatic polyamine compounds such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexamethylenediamine, 2-methylpentamethylenediamine, and trimethylhexamethylenediamine; aromatic ring-containing aliphatic polyamine compounds such as orthoxyxylylenediamine, metaxylylenediamine (MXDA), and paraxylylenediamine (PXDA); isophoronediamine (IPDA), menthenediamine, norbornanediamine, tricyclodecanediamine, adamantanediamine, diaminocyclohexane, 1,2-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)cyclohexane, and 1,4-bis(aminomethyl)cyclohexane. 4,4'-diaminodicyclohexylmethane; aromatic polyamine compounds such as diaminodiphenyl sulfone; polyamine compounds having a heterocyclic structure such as N-aminoethylpiperazine and N,N'-bis(aminoethyl)piperazine; polyether polyamine compounds, etc. Modified products of the polyamine compounds include Mannich-modified products, epoxy-modified products, Michael adducts, Michael addition / polycondensation products, styrene-modified products (excluding component (A-2)), and polyamide-modified products of the above compounds. These may be used alone or in combination of two or more.

[0036] However, from the viewpoint of obtaining an epoxy resin composition that has high hydrogen gas barrier property, exhibits little deterioration in gas barrier property even under high humidity conditions, and can achieve a long pot life, the total content of components (A-1) and (A-2) in the epoxy resin curing agent of the present invention is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, still more preferably 75% by mass or more, still more preferably 80% by mass or more, still more preferably 85% by mass or more, still more preferably 90% by mass or more, and 100% by mass or less. Furthermore, the total content of components (A-1) to (A-3) in the epoxy resin curing agent of the present invention is preferably 70% by mass or more, more preferably 75% by mass or more, still more preferably 80% by mass or more, still more preferably 85% by mass or more, still more preferably 90% by mass or more, and 100% by mass or less.

[0037] [Epoxy Resin Composition] The epoxy resin composition of the present invention contains an epoxy resin and the epoxy resin curing agent of the present invention. By containing the epoxy resin curing agent of the present invention, the epoxy resin composition of the present invention has high hydrogen gas barrier properties, is less susceptible to deterioration in gas barrier properties even under high humidity conditions, and can achieve a long pot life.

[0038] <Epoxy Resin> The epoxy resin used in the epoxy resin composition of the present invention is not particularly limited as long as it is a polyfunctional epoxy resin having two or more epoxy groups, but from the viewpoint of high hydrogen gas barrier property and suppressing deterioration of gas barrier property under high humidity conditions, a polyfunctional epoxy resin containing an aromatic ring or an alicyclic structure in the molecule is preferred. Furthermore, from the viewpoint of having low viscosity and being easily applicable to filament winding molding, the epoxy resin used in the present invention preferably includes a liquid epoxy resin. The term "liquid epoxy resin" refers to one that has fluidity at 25°C.

[0039] Specific examples of the polyfunctional epoxy resin include at least one selected from the group consisting of epoxy resins having a glycidylamino group derived from meta-xylylenediamine, epoxy resins having a glycidylamino group derived from para-xylylenediamine, epoxy resins having a glycidylamino group derived from 1,3-bis(aminomethyl)cyclohexane, epoxy resins having a glycidylamino group derived from 1,4-bis(aminomethyl)cyclohexane, epoxy resins having a glycidylamino group derived from diaminodiphenylmethane, epoxy resins having a glycidylamino group and / or a glycidyloxy group derived from para-aminophenol, epoxy resins having a glycidyloxy group derived from resorcinol, epoxy resins having a glycidyloxy group derived from bisphenol A, epoxy resins having a glycidyloxy group derived from bisphenol F, and epoxy resins having a glycidyloxy group derived from phenol novolac. One or more of the above epoxy resins can be used.

[0040] Among the above, from the viewpoints of low viscosity and high hydrogen gas barrier property, suppression of reduction in pot life, and suppression of the occurrence of burning during molding, the epoxy resin preferably contains 10 to 80 mass% of an epoxy resin (B1) having a glycidyl group derived from resorcinol and 20 to 90 mass% of an epoxy resin (B2) other than (B1) that contains an aromatic ring, and more preferably the epoxy resin (B2) contains at least one selected from the group consisting of an epoxy resin (b2-1) having a glycidyl group derived from bisphenol F and an epoxy resin (b2-2) having a glycidyl group derived from phenol novolac. The epoxy resin (B1) having a glycidyloxy group derived from resorcinol (hereinafter simply referred to as "epoxy resin (B1)" or "component (B1)") has a low viscosity among epoxy resins and exhibits high hydrogen gas barrier property. On the other hand, the epoxy resin (B1) has a low epoxy equivalent and tends to react rapidly with an epoxy resin curing agent during heat curing, thereby generating heat. Therefore, if the content of epoxy resin (B1) in the epoxy resin is too high, there is a risk of reduced pot life and the occurrence of discoloration or scorching of the cured product. Here, epoxy resin (B2) other than (B1) containing an aromatic ring (hereinafter simply referred to as "epoxy resin (B2)" or "component (B2)") is relatively more likely to exhibit hydrogen gas barrier properties than other epoxy resins, and can also suppress heat generation during heat curing due to the epoxy resin (B1). Furthermore, among epoxy resins (B2), epoxy resin (b2-1) having a glycidyl group derived from bisphenol F and epoxy resin (b2-2) having a glycidyl group derived from phenol novolac do not impair the low viscosity and high hydrogen gas barrier properties inherent to the epoxy resin (B1). Therefore, by using epoxy resin (B1) and epoxy resin (B2) in a predetermined ratio, it is thought that it is possible to maintain low viscosity and high hydrogen gas barrier properties and suppress reduced pot life and the occurrence of scorching during molding.

[0041] (Epoxy Resin (B1)) The epoxy resin (B1) is an epoxy resin having a glycidyloxy group derived from resorcinol. When the epoxy resin contains the epoxy resin (B1), an epoxy resin composition can be obtained that has low viscosity and can achieve high hydrogen gas barrier properties. The epoxy resin (B1) is typically resorcinol diglycidyl ether, and may contain an oligomer in addition to resorcinol diglycidyl ether. As the epoxy resin (B1), a commercially available product such as "Denacol EX-201" manufactured by Nagase ChemteX Corporation can be used.

[0042] The content of the epoxy resin (B1) in the epoxy resin is preferably 10 to 80 mass%, more preferably 20 to 80 mass%, even more preferably 30 to 80 mass%, still more preferably 35 to 80 mass%, still more preferably 40 to 80 mass%, still more preferably 50 to 80 mass%, still more preferably 60 to 80 mass%, and still more preferably 70 to 80 mass%. When the content of the epoxy resin (B1) in the epoxy resin is 10 mass% or more, high hydrogen gas barrier properties are likely to be exhibited, and when it is 80 mass% or less, a decrease in pot life and the occurrence of scorching during molding can be suppressed.

[0043] (Epoxy Resin (B2)) The epoxy resin (B2) is an aromatic ring-containing epoxy resin other than (B1). The epoxy resin (B2) preferably contains at least one selected from the group consisting of an epoxy resin (b2-1) having a glycidyl group derived from bisphenol F and an epoxy resin (b2-2) having a glycidyl group derived from phenol novolac. This is thought to achieve low viscosity, high hydrogen gas barrier properties, and a long pot life, and also to suppress the occurrence of burning during molding.

[0044] [Epoxy Resin (b2-1)] The epoxy resin (b2-1) is an epoxy resin having a glycidyloxy group derived from bisphenol F. The epoxy resin (b2-1) is typically bisphenol F diglycidyl ether, and may contain an oligomer in addition to bisphenol F diglycidyl ether. As the epoxy resin (b2-1), a commercially available product such as "jER807" manufactured by Mitsubishi Chemical Corporation can be used.

[0045] [Epoxy Resin (b2-2)] The epoxy resin (b2-2) is an epoxy resin having a glycidyl group derived from phenol novolac. The epoxy resin (b2-2) is typically a multifunctional epoxy resin obtained by reacting a phenol novolac resin with epichlorohydrin. As the epoxy resin (b2-2), commercially available products such as phenol novolac epoxy resins (N-730A, N-740, N-770, N-775, N-740-80M, N-770-70M, N-865-80M) from the "EPICLON" series manufactured by DIC Corporation can be used.

[0046] The epoxy resin (B2) may contain only one of the epoxy resin (b2-1) and the epoxy resin (b2-2), or may contain both of them. From the viewpoints of achieving low viscosity, high hydrogen gas barrier property, and a long pot life, and suppressing the occurrence of burnt parts during molding, the total content of the epoxy resin (b2-1) and the epoxy resin (b2-2) in the epoxy resin (B2) is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, still more preferably 80% by mass or more, and still more preferably 90% by mass or more, but 100% by mass or less.

[0047] Specific examples of the epoxy resin (B2) other than the epoxy resin (b2-1) and the epoxy resin (b2-2) include at least one selected from the group consisting of the above-mentioned epoxy resins having a glycidylamino group derived from meta-xylylenediamine, epoxy resins having a glycidylamino group derived from para-xylylenediamine, epoxy resins having a glycidylamino group derived from diaminodiphenylmethane, epoxy resins having a glycidylamino group and / or a glycidyloxy group derived from para-aminophenol, and epoxy resins having a glycidyloxy group derived from bisphenol A.

[0048] The content of epoxy resin (B2) in the epoxy resin is preferably 20 to 90 mass%, more preferably 20 to 80 mass%, even more preferably 20 to 70 mass%, still more preferably 20 to 65 mass%, still more preferably 20 to 60 mass%, still more preferably 20 to 50 mass%, still more preferably 20 to 40 mass%, and still more preferably 20 to 30 mass%. When the content of epoxy resin (B2) in the epoxy resin is 20 mass% or more, a long pot life is achieved and the occurrence of burnt components during molding is easily suppressed. When the content is 90 mass% or less, an epoxy resin composition can be obtained that does not impair the low viscosity and high hydrogen gas barrier property derived from epoxy resin (B1).

[0049] The epoxy resin may contain an epoxy resin other than the epoxy resin (B1) and the epoxy resin (B2). Examples of such epoxy resins include aliphatic epoxy resins having no aromatic ring. Examples of aliphatic epoxy resins having no aromatic ring include linear aliphatic epoxy resins and aliphatic epoxy resins having an alicyclic structure. However, from the viewpoint of exhibiting high hydrogen gas barrier properties, the total content of the epoxy resin (B1) and the epoxy resin (B2) in the epoxy resin is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more, but 100% by mass or less.

[0050] From the viewpoint of low viscosity of the epoxy resin composition, the epoxy equivalent (functional group equivalent) of the epoxy resin is preferably 500 g / equivalent or less, more preferably 300 g / equivalent or less, even more preferably 250 g / equivalent or less, still more preferably 220 g / equivalent or less, still more preferably 200 g / equivalent or less, still more preferably 180 g / equivalent or less, still more preferably 160 g / equivalent or less, and still more preferably 150 g / equivalent or less. From the viewpoint of suppressing the occurrence of burnt deposits during molding, the epoxy equivalent is preferably 120 g / equivalent or more, more preferably 125 g / equivalent or more.

[0051] <Other Components> The epoxy resin composition of the present invention may further contain other components depending on the intended use, such as a filler, a modifying component such as a plasticizer, a flow-adjusting component such as a thixotropic agent, a curing accelerator, a reactive or non-reactive diluent, a pigment, a leveling agent, a tackifier, or a stress relaxation component.

[0052] Among the above, examples of the curing accelerator include phenolic compounds such as bisphenol A and styrenated phenol and their salts; sulfonic acid compounds such as p-toluenesulfonic acid and methanesulfonic acid and their salts or esters; carboxylic acid compounds such as salicylic acid and benzoic acid and their salts; mercaptan-terminated polysulfide compounds; guanidine compounds; and alkanolamine compounds. These may be used alone or in combination of two or more. When the epoxy resin composition contains a curing accelerator, its content is preferably 0.01 to 15 mass%, more preferably 0.1 to 10 mass%, of the solid content of the epoxy resin composition. The "solid content of the epoxy resin composition" refers to the amount of the total epoxy resin composition excluding water and organic solvents.

[0053] Among the above, examples of the stress relaxation component include elastomer particles such as silicone-based elastomer particles, butyl acrylate-based elastomer particles, polyetheramine-based elastomer particles, and other rubber particles. Liquid rubber components such as epoxidized polybutadiene can also be used. Commercially available stress relaxation components include Kane Ace B series, FM series, M series, and MX series manufactured by Kaneka Corporation, and liquid epoxidized polybutadienes such as Ebolide PB3600 and Ebolide PB4700 manufactured by Daicel Corporation. When the epoxy resin composition contains a stress relaxation component, the content thereof is preferably 0.1 to 15 mass %, more preferably 0.5 to 10 mass %, of the solid content of the epoxy resin composition.

[0054] <Solvent> The epoxy resin composition of the present invention may further contain a solvent from the viewpoint of improving the impregnation ability into reinforcing fibers. Examples of the solvent include alcohol-based solvents such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol, 2-butoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and 1-propoxy-2-propanol; ester-based solvents such as ethyl acetate and butyl acetate; ketone-based solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ether-based solvents such as diethyl ether and diisopropyl ether; and hydrocarbon-based solvents such as toluene. One or more of these may be used. From the viewpoint of the solubility of the blended components and the ease of removing the solvent, the solvent is preferably at least one selected from the group consisting of alcohol-based solvents, ester-based solvents, ketone-based solvents, and hydrocarbon-based solvents having 8 or less carbon atoms, and more preferably at least one selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and toluene.

[0055] <Contents> The content ratio of the epoxy resin to the epoxy resin curing agent in the epoxy resin composition of the present invention is such that the ratio of the number of active hydrogens in the epoxy resin curing agent to the number of epoxy groups in the epoxy resin (number of active hydrogens in the epoxy resin curing agent / number of epoxy groups in the epoxy resin) is preferably 1 / 0.5 to 1 / 2, more preferably 1 / 0.75 to 1 / 1.5, and even more preferably 1 / 0.8 to 1 / 1.2. This ratio should ultimately be within the above range, and may be constant during molding of the epoxy resin composition or may be varied during molding.

[0056] The content of the epoxy resin in the epoxy resin composition of the present invention is not limited as long as the content ratio of the epoxy resin to the epoxy resin curing agent is preferably within the above-mentioned range, but from the viewpoint of exhibiting low viscosity and high hydrogen gas barrier properties, it is preferably 40 to 90 mass%, more preferably 50 to 85 mass%, and even more preferably 60 to 80 mass%, of the solid content of the epoxy resin composition. When the epoxy resin composition does not contain a solvent, the content of the epoxy resin in the epoxy resin composition is preferably 40 to 90 mass%, more preferably 50 to 85 mass%, and even more preferably 60 to 80 mass%.

[0057] The content of the epoxy resin curing agent in the epoxy resin composition of the present invention is not limited as long as the content ratio of the epoxy resin to the epoxy resin curing agent is preferably within the above-mentioned range, but from the viewpoint of exhibiting low viscosity and high hydrogen gas barrier property, it is preferably 10 to 60 mass%, more preferably 15 to 50 mass%, and even more preferably 20 to 40 mass%. When the epoxy resin composition does not contain a solvent, the content of the epoxy resin curing agent in the epoxy resin composition is preferably 10 to 60 mass%, more preferably 15 to 50 mass%, and even more preferably 20 to 40 mass%.

[0058] From the viewpoint of effectively exhibiting the effects of the present invention, the total content of the epoxy resin and the epoxy resin curing agent in the epoxy resin composition of the present invention is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and still more preferably 95% by mass or more, but 100% by mass or less, of the solid content of the epoxy resin composition.

[0059] When the epoxy resin composition contains a solvent, the content is not particularly limited, but from the viewpoint of improving impregnation into reinforcing fibers, the content of the solvent in the epoxy resin composition is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, and from the viewpoint of ease of solvent removal, the content is preferably 80% by mass or less, more preferably 70% by mass or less. The epoxy resin composition of the present invention may be a solvent-free composition that does not substantially contain a solvent. A solvent-free epoxy resin composition is one in which the solvent content in the epoxy resin composition is preferably less than 5% by mass, more preferably 2% by mass or less, even more preferably 1% by mass or less, even more preferably 0.5% by mass or less, and even more preferably 0% by mass.

[0060] <Hydrogen Gas Permeability Coefficient> The cured product of the epoxy resin composition of the present invention exhibits high hydrogen gas barrier properties. The hydrogen gas permeability coefficient of the cured product of the epoxy resin composition having a thickness of 1 mm is preferably 1.0 × 10 －１０ [cc・cm / (cm ２ · sec · cmHg)] or less, more preferably 8.0 × 10 －１１ [cc・cm / (cm ２ · sec · cmHg)] or less, more preferably 7.0 × 10 －１１ [cc・cm / (cm ２ ·sec·cmHg)] or less, and even more preferably 5.0 × 10 －１１ [cc・cm / (cm ２ The hydrogen gas permeability coefficient of the cured epoxy resin composition can be measured under dry conditions at 23°C by the method described in the examples.

[0061] <Oxygen Permeability Coefficient> The cured product of the epoxy resin composition of the present invention exhibits high oxygen barrier properties. Specifically, the oxygen permeability coefficient of a 1 mm thick cured product of the epoxy resin composition at 23°C in a dry state is preferably 1.5 [cc cm / (cm ２ · sec · cmHg)] or less, more preferably 1.0 [cc · cm / (cm ２ ·sec·cmHg)] or less, more preferably 0.8 [cc·cm / (cm ２·sec·cmHg)] or less, and even more preferably 0.6 [cc·cm / (cm ２ The oxygen permeability coefficient of the cured product of the epoxy resin composition can be measured under dry conditions at 23°C by the method described in the examples.

[0062] <Pot life> The epoxy resin composition of the present invention has a long pot life (usable time). For example, the pot life of the epoxy resin composition at 45°C is preferably 50 minutes or more, more preferably 60 minutes or more, even more preferably 120 minutes or more, and still more preferably 150 minutes or more. Specifically, the pot life of the epoxy resin composition can be measured by the method described in the examples.

[0063] <Viscosity> From the viewpoint of use in filament winding molding, the epoxy resin composition of the present invention preferably has a low viscosity. Specifically, the viscosity of the epoxy resin composition at 60°C is preferably 1 Pa s or less, more preferably 0.8 Pa s or less, and even more preferably 0.5 Pa s or less. There is no particular lower limit to the viscosity, but it is usually 50 mPa s or more. The viscosity of the epoxy resin composition can be measured using an E-type viscometer.

[0064] The epoxy resin composition of the present invention can be prepared by mixing the epoxy resin, epoxy resin curing agent, and other components, if necessary, using known methods and equipment. The order of mixing the components of the epoxy resin composition is also not particularly limited. To prevent gelation from progressing before use, it is preferable to contact and mix the components of the epoxy resin composition immediately before use. The temperature at which the components of the epoxy resin composition are mixed can be adjusted appropriately depending on the viscosity of the epoxy resin. To prevent viscosity increase, the temperature is preferably 120°C or less, more preferably 100°C or less. To ensure compatibility with the epoxy resin, the temperature is preferably 20°C or higher, more preferably 25°C or higher. The mixing time is preferably 0.1 to 15 minutes, more preferably 0.2 to 10 minutes, and even more preferably 0.3 to 5 minutes.

[0065] [Cured Product] The cured product of the epoxy resin composition of the present invention (hereinafter also simply referred to as "the cured product of the present invention") is obtained by curing the above-mentioned epoxy resin composition of the present invention by a known method. The curing conditions for the epoxy resin composition are appropriately selected depending on the application and form, and are not particularly limited. The form of the cured product of the present invention is also not particularly limited and can be selected depending on the application. For example, when the epoxy resin composition is used as a paint, the cured product of the composition is usually in the form of a film. From the viewpoint of effectively exerting the effects of the present invention, it is preferable that the cured product of the present invention is a matrix resin for a fiber-reinforced composite material, which will be described later.

[0066] [Fiber-reinforced composite material] The fiber-reinforced composite material of the present invention (hereinafter also simply referred to as "composite material") comprises a cured product of the epoxy resin composition and reinforcing fibers, and can be obtained by impregnating the reinforcing fibers with the epoxy resin composition and then curing the composition. By comprising the cured product of the epoxy resin composition, the fiber-reinforced composite material of the present invention has high hydrogen barrier properties and suffers little deterioration in gas barrier properties even under high humidity conditions.

[0067] Examples of the form of the reinforcing fiber include short fiber, long fiber, and continuous fiber. Among these, from the viewpoint of using the obtained prepreg as a material for constituting a high-pressure gas container described later, long fiber or continuous fiber is preferred, and continuous fiber is more preferred. In this specification, short fiber refers to a fiber length of 0.1 mm or more and less than 10 mm, and long fiber refers to a fiber length of 10 mm or more and 100 mm or less. Furthermore, continuous fiber refers to a fiber bundle having a fiber length of more than 100 mm.

[0068] Examples of the shape of the continuous fiber include unidirectional (UD) materials in which monofilaments or multifilaments are arranged in one direction or alternately crossing each other, fabrics such as knitted or woven fabrics, nonwoven fabrics, and mats. From the viewpoint of use in filament winding molding, the shape of the continuous fiber is preferably a tow or tape, and more preferably a tow. The number of continuous fiber bundles (number of filaments) constituting the tow is preferably 3K to 50K, more preferably 6K to 40K, from the viewpoint of easily obtaining high strength and high elastic modulus.

[0069] In the case of continuous fibers, the average fiber length of the continuous fiber bundle is not particularly limited, but from the viewpoint of molding processability, it is preferably 1 to 10,000 m, more preferably 100 to 10,000 m. From the viewpoint of molding processability and the viewpoint that high strength and high elastic modulus can be easily obtained, the average fineness of the continuous fiber bundle is preferably 50 to 2,000 tex (g / 1,000 m), more preferably 200 to 1,500 tex, and even more preferably 500 to 1,500 tex. The average tensile elastic modulus of the continuous fiber bundle is preferably 50 to 1,000 GPa.

[0070] Examples of reinforcing fiber materials include inorganic fibers such as carbon fiber, glass fiber, basalt fiber, metal fiber, boron fiber, and ceramic fiber; and organic fibers such as aramid fiber, polyoxymethylene fiber, aromatic polyamide fiber, polyparaphenylene benzobisoxazole fiber, and ultra-high molecular weight polyethylene fiber. Among these, inorganic fibers are preferred from the viewpoint of achieving high strength. At least one fiber selected from the group consisting of carbon fiber, glass fiber, and basalt fiber is preferred because of its light weight, high strength, and high elastic modulus. Carbon fiber is more preferred from the viewpoint of strength and light weight. That is, the fiber-reinforced composite material of the present invention is more preferably a carbon fiber-reinforced composite material (CFRP) containing a cured product of the epoxy resin composition and carbon fiber. Examples of carbon fibers include polyacrylonitrile-based carbon fiber and pitch-based carbon fiber. Carbon fibers derived from plant-derived materials such as lignin and cellulose can also be used.

[0071] The reinforcing fibers may be treated with a treatment agent. Examples of the treatment agent include a surface treatment agent and a sizing agent. The surface treatment agent is preferably a silane coupling agent. Examples include a silane coupling agent having a vinyl group, a silane coupling agent having an amino group, a silane coupling agent having an epoxy group, a silane coupling agent having a (meth)acrylic group, and a silane coupling agent having a mercapto group.

[0072] Examples of the sizing agent include urethane-based sizing agents, epoxy-based sizing agents, acrylic-based sizing agents, polyester-based sizing agents, vinyl ester-based sizing agents, polyolefin-based sizing agents, polyether-based sizing agents, and carboxylic acid-based sizing agents, and these can be used alone or in combination of two or more. Examples of sizing agents that combine two or more types include urethane / epoxy-based sizing agents, urethane / acrylic-based sizing agents, and urethane / carboxylic acid-based sizing agents.

[0073] The amount of the treatment agent is preferably 0.001 to 5% by mass, more preferably 0.1 to 3% by mass, and even more preferably 0.5 to 2% by mass relative to the reinforcing fiber, from the viewpoint of improving the interfacial adhesion between the epoxy resin composition and the cured product and further improving the strength and impact resistance of the resulting prepreg and composite material.

[0074] Commercially available products can also be used as reinforcing fibers. Commercially available continuous carbon fibers (tows) include, for example, the Torayca yarns "T300", "T300B", "T400HB", "T700SC", "T800SC", "T800HB", "T830HB", "T1000GB", "T100GC", "M35JB", "M40JB", "M46JB", "M50JB", "M55J", "M55JB", "M60JB", "M30SC", and "Z600" series manufactured by Toray Industries, Inc.; and Tenax "HTA40" series, "HTS40" series, "HTS45" series, and "HTS45P12" manufactured by Teijin Limited. series, "STS40" series, "UTS50" series, "ITS50" series, "ITS55" series, "IMS40" series, "IMS60" series, "IMS65" series, "IMS65P12" series, "HMA35" series, "UMS40" series, "UMS45" series, "UMS55" series, and "HTS40MC" series; carbon fiber tows of PYROFIL "HT", "IM", and "HM" series, GRAFIL "HT" series, and "DIALEAD" series manufactured by Mitsubishi Chemical Corporation; and the like.Commercially available continuous carbon fibers other than tow include Toray Industries, Inc.'s Torayca cloths "CO6142," "CO6151B," "CO6343," "CO6343B," "CO6347B," "CO6644B," "CK6244C," "CK6273C," "CK6261C," "UT70" series, "UM46" series, "BT70" series, "T300" series, "T300B" series, "T400HB" series, "T700SC" series, "T800SC" series, "T800HB" series, "T1000GB" series, "M35JB" series, and "M40 JB series, M46JB series, M50JB series, M55J series, M55JB series, M60JB series, M30SC series, and Z600GT series; carbon fiber fabrics such as PYROFIL "TR3110M", "TR3523M", "TR3524M", "TR6110HM", "TR6120HM", "TRK101M", "TRK510M", "TR3160TMS", "TRK979PQRW", "TRK976PQRW", "TR6185HM", and "TRK180M" manufactured by Mitsubishi Chemical Corporation; and the like.

[0075] <Content> From the viewpoint of obtaining high strength and high elastic modulus, the content of reinforcing fibers in the fiber-reinforced composite is preferably in a range such that the volume fraction of the reinforcing fibers in the fiber-reinforced composite is 0.10 or more, more preferably 0.20 or more, even more preferably 0.30 or more, and even more preferably 0.40 or more. From the viewpoint of hydrogen gas barrier properties, impact resistance, and moldability, the content is preferably 0.85 or less, more preferably 0.80 or less, and even more preferably 0.70 or less. The volume fraction Vf of the reinforcing fibers in the fiber-reinforced composite can be calculated using the following formula: Vf = {mass (g) of reinforcing fibers / specific gravity of reinforcing fibers} ÷ [{mass (g) of reinforcing fibers / specific gravity of reinforcing fibers} + {mass (g) of cured product of epoxy resin composition / specific gravity of cured product of epoxy resin composition}]

[0076] <Method for Producing Fiber-Reinforced Composite Material> The method for producing a fiber-reinforced composite material is not particularly limited as long as it includes the steps of impregnating reinforcing fibers with the epoxy resin composition, curing the epoxy resin composition, and molding the composition. Because the epoxy resin composition of the present invention has a long pot life, it is suitable as an epoxy resin composition for towpregs used in filament winding molding. From this perspective, it is preferable that the fiber-reinforced composite material is obtained by filament winding molding. That is, the method for producing a fiber-reinforced composite material of the present invention preferably includes a filament winding molding method. In the filament winding molding method, first, an epoxy resin composition containing an epoxy resin, an epoxy resin curing agent, and an optional solvent is impregnated into a reinforcing fiber tow, and then the tow is subjected to a drying step to remove the solvent. Next, the tow impregnated with the epoxy resin composition is wound around the outer surface of a balloon, mandrel, or liner, and then heat-cured to produce a composite material of the desired shape.

[0077] As a manufacturing method of a fiber reinforced composite material other than the filament winding molding method, a known braiding method, a 3D printer method, etc. can also be used.

[0078] The heat curing conditions for the epoxy resin composition are not particularly limited, and the heat curing is carried out by a known method at a temperature and for a time sufficient to cure the epoxy resin composition. For example, the curing temperature can be selected in the range of 10 to 180°C, and the curing time can be selected in the range of 5 minutes to 200 hours. From the viewpoint of productivity, the curing temperature is preferably 80 to 180°C, and the curing time is preferably in the range of 10 minutes to 5 hours.

[0079] From the viewpoint of production by a filament winding molding method, the composite material of the present invention is suitably used for hollow molded articles such as pipes, shafts, cylinders, tanks, etc. The composite material has excellent hydrogen gas barrier properties and shows little deterioration in gas barrier properties even under high humidity conditions, making it particularly suitable as a material for forming high-pressure gas containers.

[0080] [High-Pressure Gas Container] The high-pressure gas container of the present invention contains the fiber-reinforced composite material. It is sufficient that at least a portion of the high-pressure gas container of the present invention is made of the fiber-reinforced composite material. For example, in the case of a high-pressure gas container having a liner and an outer layer provided so as to cover the outer surface of the liner, at least one of the liner and the outer layer may be made of the fiber-reinforced composite material. Furthermore, in the case of a linerless high-pressure gas container, the entire container may be made of the fiber-reinforced composite material.

[0081] Specific embodiments of high-pressure gas containers containing a fiber-reinforced composite material include (1) a configuration having a metal liner and an outer layer made of the fiber-reinforced composite material of the present invention, (2) a configuration having a resin liner and an outer layer made of the fiber-reinforced composite material of the present invention, (3) a configuration having a liner made of the fiber-reinforced composite material of the present invention and an outer layer made of a material other than the fiber-reinforced composite material, and (4) a configuration consisting only of a container made of the fiber-reinforced composite material of the present invention (linerless).

[0082] Examples of the metal used for the "metallic liner" in (1) above include light alloys such as aluminum alloys and magnesium alloys.

[0083] The resin used for the "resin liner" in (2) above is not particularly limited as long as it has excellent hydrogen gas barrier properties and pressure resistance, and examples thereof include thermoplastic resins, cured products of thermosetting resins, and cured products of photocurable resins. Among these, thermoplastic resins are preferred from the viewpoint of ease of molding the liner. Examples of such thermoplastic resins include polyamide resins, polyester resins, polyolefin resins, polyimide resins, polycarbonate resins, polyetherimide resins, polyamideimide resins, polyphenylene etherimide resins, polyphenylene sulfide resins, polysulfone resins, polyethersulfone resins, polyarylate resins, liquid crystal polymers, polyetheretherketone resins, polyetherketone resins, polyetherketoneketone resins, polyetheretherketoneketone resins, and polybenzimidazole resins. One or more of these resins may be used in combination. From the viewpoint of hydrogen gas barrier properties and pressure resistance, the thermoplastic resin is preferably at least one resin selected from the group consisting of polyamide resins and polyolefin resins, and more preferably polyamide resin. In addition, from the viewpoint of improving impact resistance, the resin liner may contain the above-mentioned stress relaxation component.

[0084] The "outer layer made of a material other than the fiber-reinforced composite material" in (3) above is preferably an outer layer made of a fiber-reinforced composite material other than the fiber-reinforced composite material of the present invention, from the viewpoint of improving reinforcement.

[0085] In the above embodiments (1) to (3), the outer layer can be formed so as to cover the outer surface of the main body of the liner without any gaps. The outer layer may be provided directly on the outer surface of the liner. Alternatively, one or more other layers may be provided on the outer surface of the liner, and the outer layer may be provided on the surface of the other layers. For example, an adhesive layer may be provided between the liner and the outer layer to improve adhesion between the liner and the outer layer.

[0086] When the high-pressure gas container is of the above embodiment (1) or (2), the thickness of the outer layer made of the fiber-reinforced composite material of the present invention can be appropriately selected depending on the capacity, shape, etc. of the high-pressure gas container. From the viewpoint of imparting high hydrogen gas barrier properties and impact resistance, the thickness is preferably 100 μm or more, more preferably 200 μm or more, and even more preferably 400 μm or more, and from the viewpoint of reducing the size and weight of the high-pressure gas container, the thickness is preferably 80 mm or less, more preferably 60 mm or less.

[0087] When the high-pressure gas container is of the above-mentioned embodiment (3), the thickness of the liner made of the fiber-reinforced composite material of the present invention can be appropriately selected depending on the capacity, shape, etc. of the high-pressure gas container. From the viewpoint of hydrogen gas barrier properties and pressure resistance, the thickness is preferably 100 μm or more, more preferably 200 μm or more, and even more preferably 400 μm or more, and from the viewpoint of miniaturization and weight reduction of the high-pressure gas container, the thickness is preferably 60 mm or less, more preferably 40 mm or less.

[0088] When the high-pressure gas container is of the above embodiment (4), the thickness of the container made of the fiber-reinforced composite material of the present invention can be appropriately selected depending on the capacity, shape, etc. of the high-pressure gas container. From the viewpoint of hydrogen gas barrier properties and pressure resistance, the thickness is preferably 1 mm or more, more preferably 2 mm or more, and even more preferably 5 mm or more, and from the viewpoint of miniaturization and weight reduction of the high-pressure gas container, the thickness is preferably 80 mm or less, more preferably 60 mm or less.

[0089] The content of reinforcing fibers in a liner, outer layer, or high-pressure gas container made of the fiber-reinforced composite material of the present invention is preferably in a range such that the volume fraction of reinforcing fibers is 0.10 or more, more preferably 0.20 or more, even more preferably 0.30 or more, and even more preferably 0.40 or more, from the viewpoint of obtaining high strength and high elastic modulus. Furthermore, from the viewpoint of hydrogen gas barrier properties, impact resistance, and moldability, the volume fraction is preferably 0.85 or less, more preferably 0.80 or less, even more preferably 0.75 or less, and even more preferably 0.70 or less. The volume fraction of reinforcing fibers can be calculated in the same manner as above.

[0090] Among the above, from the viewpoint of light weight and the requirement for high hydrogen barrier properties for the fiber-reinforced composite material, the high-pressure gas container is preferably any one of the above-mentioned embodiments (2), (3) and (4), and embodiment (3) or (4) is more preferable.

[0091] The high-pressure gas container may further include components made of materials other than the fiber-reinforced composite material, such as a mouthpiece, a valve, etc. The surface of the high-pressure gas container may be formed with any layer, such as a protective layer, a paint layer, or a rust-preventing layer.

[0092] The gas to be stored in the high-pressure gas container may be any gas that is in a gaseous state at 25°C and 1 atm, and examples thereof include hydrogen, oxygen, carbon dioxide, nitrogen, argon, LPG, alternatives to chlorofluorocarbons, methane, etc. Among these, hydrogen is preferred from the viewpoint of the effectiveness of the present invention.

[0093] The method for producing the high-pressure gas container of the present invention can be the same as the method for producing the fiber-reinforced composite material described above. When the high-pressure gas container is in the above-mentioned embodiment (1) or (2), a filament winding method is used to wind reinforcing fiber tows impregnated with an epoxy resin composition so as to cover the outer surface of a metal or resin liner, followed by heat curing to form an outer layer made of a fiber-reinforced composite material, thereby producing the high-pressure gas container. When the high-pressure gas container is in the above-mentioned embodiment (3) or (4), a high-pressure gas container can be produced by molding reinforcing fiber tows impregnated with an epoxy resin composition into a container shape by a filament winding method, a braiding method, a 3D printer method, or the like, followed by heat curing.

[0094] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Measurements and evaluations in the examples were carried out by the following methods.

[0095] <Hydrogen gas permeability coefficient [cc cm / (cm ２The epoxy resin composition prepared in each example was poured into a mold (120 mm x 120 mm x 1 mm) coated with a mold release agent ("FREKOTE 770-NC" manufactured by Henkel), and cured by heating at 120°C for 1 hour to obtain a plate-shaped test piece (thickness 1 mm). The hydrogen gas permeability coefficient [cc cm / (cm Hg)] of this test piece in a dry state at 23°C was measured by a differential pressure method using a gas permeability measuring device ("GTR-30X" manufactured by GTR Tech). ２ ·sec·cmHg)] was measured. In the table, it is shown in exponential notation. Specifically, "9.8E-11" is "9.8 × 10 －１１ " means.

[0096] <Oxygen permeability coefficient [cc cm / (cm ２ The epoxy resin composition prepared in each example was poured into a mold (120 mm x 120 mm x 1 mm) coated with a mold release agent (Henkel's "FREKOTE 770-NC"), and cured by heating at 120°C for 1 hour to obtain a plate-shaped test piece (1 mm thick). The oxygen permeability coefficient [cc cm / (cm )] of this test piece was measured at 23°C under dry conditions (0% R.H.) and high humidity conditions (80% R.H.) using a gas permeability measuring device (GTR-30X manufactured by GTR Tech) by the differential pressure method. ２ ·sec·cmHg)] was measured.

[0097] <Increase in oxygen permeability coefficient> The increase in oxygen permeability coefficient under high humidity conditions was calculated using the following formula. A smaller value indicates less deterioration in oxygen barrier properties under high humidity conditions. Increase in oxygen permeability coefficient (%) = [(oxygen permeability coefficient at 23°C, 80% RH) - (oxygen permeability coefficient at 23°C, 0% RH)] / (oxygen permeability coefficient at 23°C, 0% RH) x 100

[0098] <Pot life> After measuring the initial viscosity at 45°C of the epoxy resin composition prepared in each example, 10 g of the epoxy resin composition was placed in a plastic cup (diameter 46 mm) and stored at 45°C. The time [min] until the viscosity of the epoxy resin composition became at least twice the initial viscosity was measured and is shown in the table. The viscosity of the epoxy resin composition was measured using an E-type viscometer "TVE-22H Cone-Plate Type Viscometer" (manufactured by Toki Sangyo Co., Ltd.).

[0099] <Appearance of Molded Article> The epoxy resin composition prepared in each example was diluted with methyl ethyl ketone to prepare a solution with a concentration of 50% by mass. In addition, unidirectional non-crimp fiber "UT70-30G" (300 g / m) manufactured by Toray Industries, Inc. was used as a continuous reinforcing fiber. ２ ) was used to prepare a molded body (fiber-reinforced composite material) by the following method, and the presence or absence of scorching was evaluated. The above fiber was impregnated with a 50% by mass epoxy resin composition solution, and heated at 80°C for 20 minutes to remove the solvent, producing a prepreg. A total of six layers of the obtained prepreg were laminated so that the filament directions alternated (0° / 90° / 0° / 90° / 0° / 90°). This was subjected to heat and pressure molding in a vacuum press at a temperature of 160°C and a pressure of 0.3 MPa for two hours, producing a molded body with a reinforcing fiber volume fraction Vf of 0.50 and a thickness of 4 mm. The appearance of the obtained molded body was visually observed and evaluated according to the following criteria. (Evaluation criteria) A: No scorching or discoloration of the molded body, and the appearance was good. B: Discoloration of the molded body was observed, but scorching was almost suppressed. C: Scorching was observed on the molded body, and it turned brown, impairing the appearance.

[0100] Example 1 (Preparation and Evaluation of Epoxy Resin Compositions) A reaction composition containing a polycondensation reaction product of 2-ethylaniline and formaldehyde (3,3'-diethyl-4,4'-diaminodiphenylmethane) as component (A-1) ("KAYAHARD AA" manufactured by Nippon Kayaku Co., Ltd.), and a reaction composition containing a reaction product of styrene and metaxylylenediamine ("Gaskamine 240" manufactured by Mitsubishi Gas Chemical Company, Inc.) were used as component (A-2). Furthermore, as the epoxy resins, resorcinol diglycidyl ether (Denacol EX-201 manufactured by Nagase ChemteX Corporation), which is component (B1), and bisphenol F diglycidyl ether (jER807 manufactured by Mitsubishi Chemical Corporation), which is component (b2-1), were used. The above components were blended and mixed in the parts by mass shown in Table 1 to obtain an epoxy resin composition. The ratio of the number of active hydrogens in the epoxy resin curing agent to the number of epoxy groups in the epoxy resin (number of active hydrogens in epoxy resin curing agent / number of epoxy groups in epoxy resin) was 1 / 1. The obtained epoxy resin composition was evaluated by the methods described above. The results are shown in Table 1.

[0101] Examples 2 to 10, Comparative Examples 1 and 2 Epoxy resin compositions were prepared and evaluated in the same manner as in Example 1, except that the types and amounts of the components were changed as shown in Table 1. The results are shown in Table 1. The amounts (parts by mass) in Table 1 are all amounts of active ingredients.

[0102]

[0103] The components listed in Table 1 are as follows. <Epoxy resin> *1: (B1) Denacol EX-201, resorcinol diglycidyl ether, "Denacol EX-201" manufactured by Nagase ChemteX Corporation, epoxy equivalent: 117 g / equivalent *2: (b2-1) jER807, bisphenol F diglycidyl ether, "jER807" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 168 g / equivalent *3: (b2-2) EPICLON N730-A, phenol novolac epoxy resin, "EPICLON N730-A" manufactured by DIC Corporation, epoxy equivalent: 176 g / equivalent <Epoxy resin curing agent> *4: (A-1) KAYAHARD AA, a reaction composition containing a polycondensation reaction product of 2-ethylaniline and formaldehyde (3,3'-diethyl-4,4'-diaminodiphenylmethane), manufactured by Nippon Kayaku Co., Ltd., "KAYAHARD AA", purity > 95% by mass, AHEW: 64 * 5: (A-2) G-240, a reaction composition containing a reaction product of styrene and metaxylylenediamine, manufactured by Mitsubishi Gas Chemical Co., Ltd., "Gaskamine 240", AHEW: 103 * 6: (A-3) 1,3-phenylenediamine, manufactured by Tokyo Chemical Industry Co., Ltd., AHEW: 27 <Stress relaxation component> * 7: Kane Ace MX136, a liquid masterbatch in which core-shell rubber particles (polybutadiene) are dispersed as single particles in a bisphenol F type epoxy resin at a concentration of 25%, manufactured by Kaneka Corporation, "Kane Ace MX136"

[0104] Table 1 shows that the cured product of the epoxy resin composition containing the epoxy resin curing agent of the present invention has high hydrogen gas barrier properties and shows little deterioration in oxygen barrier properties even under high humidity conditions. The resulting epoxy resin composition also has a long pot life. In contrast, the epoxy resin composition of Comparative Example 1, which used an epoxy resin curing agent containing only component (A-1) as the epoxy resin curing agent, showed a decrease in gas barrier properties under high humidity conditions. Furthermore, the epoxy resin composition of Comparative Example 2, which used an epoxy resin curing agent in which the contents of components (A-1) and (A-2) were outside the ranges specified in the present invention, did not achieve a sufficient pot life.

[0105] According to the present invention, there are provided an epoxy resin curing agent, an epoxy resin composition, a cured product thereof, a fiber-reinforced composite material, and a high-pressure gas container containing the fiber-reinforced composite material, which have high hydrogen gas barrier properties, are less susceptible to deterioration in gas barrier properties even under high-humidity conditions, and further achieve a long pot life. The high-pressure gas container can be manufactured by filament winding molding, and can also be a linerless high-pressure gas container. Furthermore, because the high-pressure gas container has high hydrogen gas barrier properties, it is suitable as a container for storing high-pressure hydrogen gas.

Claims

1. The following components (A-1) and (A-2): (A-1) Reaction composition containing a polycondensation reaction product of an aniline derivative and formaldehyde (A-2) A reaction composition containing a reaction product of styrene and a compound represented by the following general formula (1): H ２ P ２ -A-CH ２ -NH ２ (1) (In formula (1), A is a 1,2-phenylene group, a 1,3-phenylene group, or a 1,4-phenylene group.) An epoxy resin curing agent comprising: The epoxy resin curing agent has a content of the component (A-1) of 50 to 95 mass % and a content of the component (A-2) of 5 to 50 mass %.

2. 2. The epoxy resin curing agent according to claim 1, wherein the aniline derivative is a compound represented by the following general formula (2): 【Chemistry 1】 (In formula (2), R １ is an alkyl group having 1 to 6 carbon atoms, or an aryl group. p is a number from 1 to 3.

3. 2. The epoxy resin curing agent according to claim 1, wherein, in the general formula (1), A is a 1,3-phenylene group or a 1,4-phenylene group.

4. The epoxy resin curing agent according to claim 1, further comprising a compound represented by the following general formula (3) as component (A-3): 【Chemistry 2】 (In formula (3), R ２ is an alkyl group, an alkoxy group, or an alkylthio group having 1 to 6 carbon atoms; and q is a number from 0 to 3.

5. An epoxy resin composition comprising an epoxy resin and the epoxy resin curing agent according to any one of claims 1 to 4.

6. 6. The epoxy resin composition according to claim 5, wherein the epoxy resin comprises 10 to 80 mass% of an epoxy resin (B1) having a glycidyl group derived from resorcinol and 20 to 90 mass% of an epoxy resin (B2) other than (B1) that contains an aromatic ring, the epoxy resin (B2) comprising at least one selected from the group consisting of an epoxy resin (b2-1) having a glycidyl group derived from bisphenol F and an epoxy resin (b2-2) having a glycidyl group derived from phenol novolac.

7. The epoxy resin composition according to claim 6, wherein the total content of the epoxy resin (b2-1) and the epoxy resin (b2-2) in the epoxy resin (B2) is 50 mass% or more.

8. The hydrogen gas permeability coefficient of the cured product of the epoxy resin composition is 1.0×10 －１０ [cc・cm / (cm ２ 6. The epoxy resin composition according to claim 5, wherein the viscosity is less than or equal to [sec·cmHg].

9. A cured product of the epoxy resin composition according to claim 5.

10. A fiber-reinforced composite material comprising a cured product of the epoxy resin composition according to claim 5 and reinforcing fibers.

11. The fiber-reinforced composite material according to claim 10, wherein the reinforcing fiber is at least one selected from the group consisting of carbon fiber, glass fiber, and basalt fiber.

12. The fiber-reinforced composite material according to claim 10, which is obtained by filament winding molding.

13. A high pressure gas bottle comprising the fiber reinforced composite material of claim 10.

Images