Epoxy resin composition and cured product thereof, prepreg, fiber-reinforced composite material, and fiber-reinforced composite material

Abstract

The present invention pertains to: an epoxy resin composition which contains epoxy resins (A) and an epoxy resin curing agent (B), and in which the epoxy resins (A) include a prescribed epoxy resin (A1) and an epoxy resin (A2) at a prescribed ratio, and the epoxy resin curing agent (B) contains resorcinol (B1); a cured product thereof; a prepreg using said epoxy resin composition; a fiber-reinforced composite material; and a high-pressure gas container.

Description

Epoxy resin composition and cured product thereof, prepreg, fiber-reinforced composite material, and fiber-reinforced composite material

[0001] The present invention relates to an epoxy resin composition and a cured product thereof, a prepreg, a fiber-reinforced composite material, and a high-pressure gas container 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] It is known that resins having gas barrier properties and fiber-reinforced composites (FRPs) in which reinforcing fibers are impregnated with the resins are used as resin materials for high-pressure gas storage tanks. For example, Patent Document 1 discloses a method for manufacturing a pressure vessel having a liner and an outer layer of the liner, the outer layer being made of a composite material containing reinforcing fibers and a matrix resin, in which the outer layer is formed by winding the composite material around the outer periphery of the liner using a filament winding method or a tape winding method.

[0004] The winding method can also be used when the matrix resin in the composite material is a cured thermosetting resin rather than a thermoplastic resin. In this case, a continuous reinforcing fiber bundle impregnated with a thermosetting resin (tow prepreg) is wound around the outer periphery of a liner and then heated and cured to form a mold. Prepregs using an epoxy resin composition as the matrix resin are also known. For example, Patent Document 2 discloses an epoxy resin composition containing an epoxy resin, a compound having two functional groups, each of which has one active hydrogen atom reactive with an epoxy group, and a curing agent, as well as a prepreg and a fiber-reinforced composite material in which reinforcing fibers are impregnated with the epoxy resin composition.

[0005] Furthermore, as a thermosetting resin composition having gas barrier properties, for example, Patent Document 3 discloses a composition as an oxygen barrier composition for electrical parts, which comprises a meta-substituted aromatic resin and an additional aromatic epoxy resin and has oxygen permeability of a predetermined value or less.

[0006] International Publication No. 2016 / 084475 JP 2002-284852 A JP 2012-533643 A

[0007] Cured products of thermosetting resin compositions used in high-pressure gas containers for storing hydrogen gas are required to have high barrier properties against hydrogen gas and high heat resistance. Furthermore, from the viewpoint of improving the impact resistance of high-pressure gas containers, it is also desirable for the cured products to have high elongation. However, the techniques disclosed in Patent Documents 1 to 3 have difficulty in satisfying all of the above required properties.

[0008] An object of the present invention is to provide an epoxy resin composition that can be used to produce a cured product having high hydrogen gas barrier properties, heat resistance, and elongation; a cured product thereof; a prepreg, a fiber-reinforced composite material, and a high-pressure gas container that use the epoxy resin composition.

[0009] The present inventors have found that an epoxy resin composition using two specific epoxy resins as the main epoxy resin and further using an epoxy resin curing agent containing resorcinol can solve the above-mentioned problems. That is, the present invention relates to the following: [1] An epoxy resin composition containing an epoxy resin (A) and an epoxy resin curing agent (B), wherein the epoxy resin (A) comprises an epoxy resin (A1) and an epoxy resin (A2), the epoxy resin (A1) is an epoxy resin having a glycidyl group derived from a triphenylmethane-type phenol, and the epoxy resin (A2) is an epoxy resin (A2-1) having a glycidyl group derived from bisphenol F, an epoxy resin (A2-2) having a glycidyl group derived from bisphenol A, and an epoxy resin (A2-3) having a glycidyl group derived from bisphenol B. [2] The epoxy resin composition according to [1], wherein the epoxy resin (A) is at least one selected from the group consisting of an epoxy resin (A2-2) having a glycidyl group derived from a novolac phenol, an epoxy resin (A2-3) having a glycidyl group derived from a polyol having a naphthalene skeleton, and an epoxy resin (A2-4) having a glycidyl group derived from a polyol having a naphthalene skeleton, wherein the mass ratio [(A1) / (A2)] of the epoxy resin (A1) to the epoxy resin (A2) in the epoxy resin (A) is 1 / 99 to 90 / 10, and the epoxy resin curing agent (B) contains resorcinol (B1). [3] The epoxy resin composition according to [2], wherein the phenolic curing agent (B2-1) comprises at least one selected from the group consisting of bisphenol F, bisphenol A, novolac-type phenol, and triphenylmethane-type phenol. [4] The epoxy resin composition according to any one of [1] to [3], wherein the mass ratio [(A1) / (A2)] of the epoxy resin (A1) to the epoxy resin (A2) in the epoxy resin (A) is 5 / 95 to 70 / 30. [5] The epoxy resin composition according to any one of [1] to [4], further comprising a curing accelerator (C), wherein the curing accelerator (C) comprises at least one selected from the group consisting of imidazoles, tertiary amines, and phosphorus compounds.[6] The epoxy resin composition according to any one of [1] to [5], further comprising a stress relaxation component (D). [7] The epoxy resin composition according to any one of [1] to [6], further comprising a non-reactive diluent (E). [8] A cured product of the epoxy resin composition has a hydrogen gas permeability coefficient of 7.0 x 10 at 23°C. -11 [cc・cm / (cm 2

[10] A prepreg comprising the epoxy resin composition according to any one of [1] to [7], wherein the compressive strength (MPa) of the epoxy resin composition is 1 / 2 s / cmHg or less. [9] A cured product of the epoxy resin composition according to any one of [1] to [8].

[10] A prepreg comprising the epoxy resin composition according to any one of [1] to [8] and reinforcing fibers.

[11] The prepreg according to

[10] , wherein the reinforcing fibers are at least one type selected from the group consisting of carbon fibers, glass fibers, and basalt fibers.

[12] The prepreg according to

[10] or

[11] , wherein the prepreg is a tow prepreg or a tape prepreg.

[13] A fiber-reinforced composite material which is a cured product of the prepreg according to any one of

[10] to

[12] .

[14] A high-pressure gas container comprising the fiber-reinforced composite material according to

[13] .

[0010] The present invention provides an epoxy resin composition capable of producing a cured product having high hydrogen gas barrier properties, heat resistance, and elongation, the cured product, a prepreg using the epoxy resin composition, a fiber-reinforced composite material, and a high-pressure gas container. The high-pressure gas container has high hydrogen gas barrier properties and is suitable as a container for storing high-pressure hydrogen gas.

[0011] [Epoxy resin composition] The epoxy resin composition of the present invention is an epoxy resin composition containing an epoxy resin (A) and an epoxy resin curing agent (B), wherein the epoxy resin (A) comprises an epoxy resin (A1) and an epoxy resin (A2), the epoxy resin (A1) is an epoxy resin having a glycidyl group derived from a triphenylmethane-type phenol, the epoxy resin (A2) is at least one selected from the group consisting of an epoxy resin (A2-1) having a glycidyl group derived from bisphenol F, an epoxy resin (A2-2) having a glycidyl group derived from bisphenol A, an epoxy resin (A2-3) having a glycidyl group derived from a novolac-type phenol, and an epoxy resin (A2-4) having a glycidyl group derived from a polyol having a naphthalene skeleton, the mass ratio [(A1) / (A2)] of the epoxy resin (A1) to the epoxy resin (A2) in the epoxy resin (A) is 1 / 99 to 90 / 10, and the epoxy resin curing agent (B) contains resorcinol (B1). The epoxy resin composition of the present invention has the above-mentioned structure, and thus can produce a cured product having high hydrogen gas barrier properties, heat resistance, and elongation.

[0012] In this specification, the hydrogen gas barrier property of a cured product of an epoxy resin composition is determined based on a low hydrogen gas permeability coefficient, the heat resistance is determined based on a high glass transition temperature (Tg), and the elongation is determined based on a high tensile elongation value. The hydrogen gas barrier property, heat resistance, and elongation of a cured product of an epoxy resin composition can be specifically evaluated by the methods described in the examples.

[0013] The reason why the above-mentioned effects are achieved in the present invention is unclear, but is thought to be as follows. An epoxy resin (A1) having glycidyl groups derived from a triphenylmethane-type phenol (hereinafter simply referred to as "epoxy resin (A1)" or "component (A1)") has multiple aromatic rings and a polymer structure in which the aromatic rings extend two-dimensionally or three-dimensionally. This is thought to result in high hydrogen gas barrier properties and high heat resistance. Other epoxy resins, such as epoxy resins having glycidyl groups derived from resorcinol, can also exhibit high hydrogen gas barrier properties. However, the cured product of an epoxy resin having glycidyl groups derived from resorcinol has a problem in that it has a low glass transition temperature and is unable to achieve high heat resistance. Furthermore, because an epoxy resin having glycidyl groups derived from resorcinol has a low epoxy equivalent and is fast-curing, the pot life and shelf life of the resulting epoxy resin composition also tend to be short. In contrast, when the epoxy resin (A1) is used as the epoxy resin (A) in the epoxy resin composition of the present invention, the cured product has high hydrogen barrier properties and high heat resistance. Furthermore, since the epoxy resin (A1) has a relatively high epoxy equivalent, it is believed that the pot life and shelf life of the epoxy resin composition can also be improved.

[0014] On the other hand, when the epoxy resin (A) consists solely of the epoxy resin (A1), the elongation of the cured product of the obtained epoxy resin composition tends to be low. When the elongation of the cured product is low, the impact resistance of the cured product tends to be low, resulting in a problem that the cured product is not suitable for applications such as high-pressure gas containers.

[0015] Here, the epoxy resin (A2) (hereinafter simply referred to as "epoxy resin (A2)" or "component (A2)") has a higher elongation of the cured product compared to the epoxy resin (A1), and is relatively more likely to exhibit hydrogen gas barrier properties than other epoxy resins. Furthermore, the epoxy resins (A2-1) to (A2-4) have high heat resistance due to the presence of two or more ring structures in the molecule. Therefore, in the present invention, by using epoxy resins (A1) and (A2) in combination in a predetermined mass ratio as the epoxy resin (A), it is believed that a cured product with high elongation can be obtained without significantly impairing the hydrogen gas barrier properties and heat resistance inherent to the epoxy resin (A1). Furthermore, in the present invention, by using resorcinol (B1) as the epoxy resin curing agent (B), high hydrogen gas barrier properties inherent to the resorcinol skeleton can be obtained, and the pot life and shelf life can also be improved.

[0016] <Epoxy Resin (A)> The epoxy resin (A) used in the epoxy resin composition of the present invention comprises an epoxy resin (A1) and an epoxy resin (A2), wherein the epoxy resin (A1) is an epoxy resin having a glycidyl group derived from a triphenylmethane-type phenol, and the epoxy resin (A2) is at least one selected from the group consisting of an epoxy resin (A2-1) having a glycidyl group derived from bisphenol F, an epoxy resin (A2-2) having a glycidyl group derived from bisphenol A, an epoxy resin (A2-3) having a glycidyl group derived from a novolac-type phenol, and an epoxy resin (A2-4) having a glycidyl group derived from a polyol having a naphthalene skeleton, and the mass ratio of the epoxy resin (A1) to the epoxy resin (A2) in the epoxy resin (A), [(A1) / (A2)], is 1 / 99 to 90 / 10.

[0017] (Epoxy Resin (A1)) Epoxy resin (A1) is an epoxy resin having a glycidyl group derived from triphenylmethane-type phenol. When epoxy resin (A) contains epoxy resin (A1), an epoxy resin composition capable of producing a cured product having high hydrogen gas barrier properties and heat resistance is obtained. Epoxy resin (A1) is an epoxy resin having a glycidyl group derived from triphenylmethane-type phenol. Triphenylmethane-type phenol refers to a phenolic compound containing a triphenylmethane skeleton, and epoxy resin (A1) has a structure in which at least some of the hydrogen atoms of the phenolic hydroxyl groups in triphenylmethane-type phenol are substituted with glycidyl groups. Hereinafter, epoxy resins having a glycidyl group derived from triphenylmethane-type phenol are also simply referred to as "triphenylmethane-type epoxy resins." One or more types of epoxy resin (A1) can be used. As the epoxy resin (A1), commercially available products such as EPICLON series "HP-7250" and "HP-7241" manufactured by DIC Corporation can be used.

[0018] The epoxy equivalent of the epoxy resin (A1) is preferably 120 g / equivalent or more, more preferably 150 g / equivalent or more, from the viewpoint of improving hydrogen gas barrier properties and heat resistance. Furthermore, from the viewpoint of improving curability, it is preferably 800 g / equivalent or less, more preferably 500 g / equivalent or less, even more preferably 300 g / equivalent or less, and even more preferably 200 g / equivalent or less. When a mixture of two or more epoxy resins is used as the epoxy resin (A1), the epoxy equivalent of the epoxy resin (A1) refers to the epoxy equivalent of the mixture.

[0019] The content of the epoxy resin (A1) in the epoxy resin (A) is preferably 1.0 to 90 mass%, more preferably 2.0 to 80 mass%, even more preferably 3.0 to 70 mass%, still more preferably 3.0 to 60 mass%, still more preferably 3.0 to 50 mass%, still more preferably 4.0 to 45 mass%, still more preferably 5.0 to 35 mass%, still more preferably 6.0 to 30 mass%, still more preferably 10 to 30 mass%, and still more preferably 15 to 30 mass%. When the content of the epoxy resin (A1) in the epoxy resin (A) is within the above ranges, the cured product of the obtained epoxy resin composition is likely to exhibit high hydrogen gas barrier properties and heat resistance, and a decrease in elongation can be suppressed.

[0020] (Epoxy Resin (A2)) The epoxy resin (A2) is at least one selected from the group consisting of epoxy resins (A2-1) having a glycidyl group derived from bisphenol F, epoxy resins (A2-2) having a glycidyl group derived from bisphenol A, epoxy resins (A2-3) having a glycidyl group derived from novolac phenols, and epoxy resins (A2-4) having a glycidyl group derived from polyols having a naphthalene skeleton. It is believed that by including the epoxy resin (A2) in the epoxy resin (A), a cured product with a high elongation can be obtained without significantly impairing the hydrogen gas barrier properties and heat resistance inherent in the epoxy resin (A1).

[0021] [Epoxy Resin (A2-1)] The epoxy resin (A2-1) is an epoxy resin having a glycidyl group derived from bisphenol F. The epoxy resin (A2-1) is preferably bisphenol F diglycidyl ether or an oligomer thereof. The epoxy resin (A2-1) may be solid or liquid at room temperature (25°C). One or more types of epoxy resin (A2-1) can be used.

[0022] From the viewpoint of obtaining an epoxy resin composition that has a long pot life and shelf life and that can achieve high heat resistance, elongation, and hydrogen gas barrier properties, the epoxy equivalent of the epoxy resin (A2-1) is preferably 100 g / equivalent or more, more preferably 120 g / equivalent or more, and even more preferably 150 g / equivalent or more. Furthermore, from the viewpoint of improving curability, the epoxy equivalent is preferably 1200 g / equivalent or less, more preferably 1100 g / equivalent or less, and even more preferably 1050 g / equivalent or less. When a mixture of two or more epoxy resins is used as the epoxy resin (A2-1), the epoxy equivalent of the epoxy resin (A2-1) refers to the epoxy equivalent of the mixture. The same applies to the epoxy resins described below.

[0023] As the epoxy resin (A2-1), commercially available products such as "jER806", "jER806H", "jER807", "jER4005P", "jER4007P" and "jER4010P" manufactured by Mitsubishi Chemical Corporation can be used.

[0024] [Epoxy Resin (A2-2)] The epoxy resin (A2-2) is an epoxy resin having a glycidyl group derived from bisphenol A. The epoxy resin (A2-2) is typically bisphenol A diglycidyl ether or an oligomer thereof. The epoxy resin (A2-2) may be solid or liquid at room temperature (25°C). One or more types of epoxy resin (A2-2) can be used.

[0025] From the viewpoint of obtaining an epoxy resin composition that has a long pot life and shelf life and that can achieve high heat resistance, elongation, and hydrogen gas barrier properties, the epoxy equivalent of the epoxy resin (A2-2) is preferably 100 g / equivalent or more, more preferably 120 g / equivalent or more, and even more preferably 150 g / equivalent or more. From the viewpoint of improving curability, the epoxy equivalent is preferably 1200 g / equivalent or less, more preferably 1000 g / equivalent or less, even more preferably 800 g / equivalent or less, still more preferably 600 g / equivalent or less, still more preferably 500 g / equivalent or less, still more preferably 400 g / equivalent or less, still more preferably 300 g / equivalent or less, and still more preferably 250 g / equivalent or less.

[0026] As the epoxy resin (A2-2), commercially available products such as "jER825", "jER827", "jER828", "jER834", and "jER1001" manufactured by Mitsubishi Chemical Corporation can be used.

[0027] [Epoxy Resin (A2-3)] The epoxy resin (A2-3) is an epoxy resin having a glycidyl group derived from a novolac phenol. The epoxy resin (A2-3) is typically synthesized using a novolac phenol and epichlorohydrin. Examples of the novolac phenol include phenol novolac, bisphenol A novolac, and cresol novolac, with phenol novolac being preferred. From the viewpoint of improving handleability, the molecular weight of the epoxy resin (A2-3) is preferably 400 to 1,500, more preferably 400 to 1,000, and even more preferably 400 to 900. The melt viscosity (150°C) of the epoxy resin (A2-3) is preferably 9.0 Pa s or less, more preferably 6.0 Pa s or less, and even more preferably 3.0 Pa s or less. From the viewpoint of improving heat resistance, the melt viscosity is preferably 0.1 Pa s or more, more preferably 0.3 Pa s or more. The epoxy resin (A2-3) can be used alone or in combination of two or more.

[0028] From the viewpoint of obtaining an epoxy resin composition that has a long pot life and shelf life and that can achieve high heat resistance, elongation, and hydrogen gas barrier properties, the epoxy equivalent of the epoxy resin (A2-3) is preferably 100 g / equivalent or more, more preferably 120 g / equivalent or more, and even more preferably 150 g / equivalent or more. From the viewpoint of improving curability, the epoxy equivalent is preferably 500 g / equivalent or less, more preferably 400 g / equivalent or less, even more preferably 300 g / equivalent or less, still more preferably 250 g / equivalent or less, and even more preferably 200 g / equivalent or less.

[0029] As the epoxy resin (A2-3), commercially available products such as EPICLON series "N730A", "N740", "N770", "N775" and "N865" manufactured by DIC Corporation can be used.

[0030] [Epoxy Resin (A2-4)] Epoxy resin (A2-4) is an epoxy resin having a glycidyl group derived from a polyol having a naphthalene skeleton. The polyol having a naphthalene skeleton may have one or more naphthalene skeletons, and is preferably a polyol having one or two naphthalene skeletons. Furthermore, from the viewpoint of obtaining an epoxy resin composition that has a long pot life and shelf life and can achieve high hydrogen gas barrier properties, the number of glycidyl groups in epoxy resin (A2-4) is preferably 2 to 4, and more preferably 2 to 3.

[0031] From the viewpoint of obtaining an epoxy resin composition that has a long pot life and shelf life and that can achieve high heat resistance, elongation, and hydrogen gas barrier properties, the epoxy equivalent of the epoxy resin (A2-4) is preferably 100 g / equivalent or more, more preferably 120 g / equivalent or more, and even more preferably 130 g / equivalent or more. From the viewpoint of improving curability, the epoxy equivalent is preferably 500 g / equivalent or less, more preferably 400 g / equivalent or less, even more preferably 300 g / equivalent or less, still more preferably 250 g / equivalent or less, and even more preferably 200 g / equivalent or less.

[0032] The epoxy resin (A2-4) is preferably an epoxy resin represented by either of the following general formulas (A2-4-1) or (A2-4-2). (wherein n is 1 to 3.) (In the formula, m1 is 0 to 2, m2 is 0 to 2, and the sum of m1 and m2 is 0 to 3.) In general formula (A2-4-1), n ​​is preferably 1 or 2, and more preferably 1. In general formula (A2-4-2), m1 is preferably 0 or 1, m2 is preferably 0 or 1, and the sum of m1 and m2 is preferably 0 to 2, and more preferably 0.

[0033] More specifically, the epoxy resin (A2-4) may be any of the epoxy resins represented by the following formulas (A2-4-3) to (A2-4-6).

[0034] The epoxy resin (A2-4) may be one or more types. Among the above, from the viewpoint of obtaining an epoxy resin composition that has a long pot life and shelf life and can achieve high heat resistance, elongation, and hydrogen gas barrier properties, the epoxy resin (A2-4) preferably contains an epoxy resin represented by the general formula (A2-4-1) above, and more preferably contains an epoxy resin represented by the formula (A2-4-3) above. The content of the epoxy resin represented by the general formula (A2-4-1) in the epoxy resin (A2-4) 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 even more preferably 90% by mass or more, but not more than 100% by mass.

[0035] As the epoxy resin (A2-4), commercially available products such as EPICLON series "HP-4032SS" (epoxy resin represented by formula (A2-4-3)), "HP-4700", and "HP-4710" (epoxy resin represented by formula (A2-4-6)), "EXA-4750" (epoxy resin represented by formula (A2-4-5)), "HP-4770" (epoxy resin represented by formula (A2-4-4)), "HP-5000", "HP-9900-75M", and "HP-9500", manufactured by DIC Corporation, can be used.

[0036] From the viewpoint of obtaining an epoxy resin composition that has a long pot life and shelf life and can achieve high heat resistance, elongation, and hydrogen gas barrier properties, the epoxy resin (A2) preferably comprises at least one selected from the group consisting of epoxy resins (A2-1), (A2-2), and (A2-3), more preferably comprises epoxy resin (A2-3), even more preferably comprises epoxy resin (A2-1) or (A2-2) and epoxy resin (A2-3), and still more preferably comprises epoxy resin (A2-1) and epoxy resin (A2-3).

[0037] When the epoxy resin (A2) contains the epoxy resin (A2-3), the content of the epoxy resin (A2-3) in the epoxy resin (A2) is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, and still more preferably 60% by mass or more, but 100% by mass or less, from the viewpoint of obtaining an epoxy resin composition that has a long pot life and shelf life and can achieve high heat resistance, elongation, and hydrogen gas barrier properties.

[0038]

[0044] When the epoxy resin (A2) comprises an epoxy resin (A2-1) or (A2-2) and an epoxy resin (A2-3), the total content of the epoxy resins (A2-1) and (A2-2) in the epoxy resin (A2) is preferably 2.0% by mass or more, more preferably 3.0% by mass or more, and even more preferably 5.0% by mass or more, from the viewpoint of obtaining an epoxy resin composition that has a long pot life and shelf life and is capable of achieving high heat resistance, elongation, and hydrogen gas barrier property; and is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and still more preferably 10% by mass or less, from the viewpoint of obtaining an epoxy resin composition that is capable of achieving even higher hydrogen gas barrier property.

[0039] The epoxy equivalent of the epoxy resin (A2) is preferably 120 g / equivalent or more, more preferably 150 g / equivalent or more, from the viewpoint of obtaining an epoxy resin composition that has a long pot life and shelf life and that can achieve high heat resistance, elongation, and hydrogen gas barrier properties, and from the viewpoint of improving curability, it is preferably 800 g / equivalent or less, more preferably 500 g / equivalent or less, even more preferably 300 g / equivalent or less, and still more preferably 250 g / equivalent or less.

[0040] The content of the epoxy resin (A2) in the epoxy resin (A) is preferably 10 to 99 mass%, more preferably 20 to 98 mass%, even more preferably 30 to 97 mass%, still more preferably 40 to 97 mass%, still more preferably 50 to 97 mass%, still more preferably 55 to 96 mass%, still more preferably 65 to 95 mass%, still more preferably 70 to 94 mass%, still more preferably 70 to 90 mass%, and still more preferably 70 to 85 mass%. When the content of the epoxy resin (A2) in the epoxy resin (A) is within the above ranges, an epoxy resin composition can be obtained that has a longer pot life and shelf life and is capable of achieving high heat resistance, elongation, and hydrogen gas barrier properties.

[0041] From the viewpoint of obtaining an epoxy resin composition having a long pot life and shelf life and capable of achieving high heat resistance, elongation, and hydrogen gas barrier properties, the mass ratio of the epoxy resin (A1) to the epoxy resin (A2) [(A1) / (A2)] in the epoxy resin (A) is from 1 / 99 to 90 / 10, preferably from 2 / 98 to 80 / 20, more preferably from 3 / 97 to 70 / 30, even more preferably from 5 / 95 to 70 / 30, still more preferably from 5 / 95 to 60 / 40, still more preferably from 5 / 95 to 50 / 50, still more preferably from 5 / 95 to 40 / 60, still more preferably from 5 / 95 to 30 / 70, still more preferably from 10 / 90 to 30 / 70, still more preferably from 15 / 85 to 30 / 70, and still more preferably from 20 / 80 to 30 / 70.

[0042] The epoxy resin (A) may contain an epoxy resin other than the epoxy resin (A1) and the epoxy resin (A2). Examples of epoxy resins other than the epoxy resin (A1) and the epoxy resin (A2) include epoxy resins having an aminoglycosyl group and epoxy resins having a glycidyloxy group derived from a polyol having no aromatic ring. Examples of polyols having no aromatic ring include linear aliphatic polyols that may contain an ether bond and aliphatic polyols having an alicyclic structure. However, from the viewpoint of exhibiting high hydrogen gas barrier properties, the total content of the epoxy resin (A1) and the epoxy resin (A2) in the epoxy resin (A) 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 and 100% by mass or less.

[0043]

[0033] From the viewpoint of obtaining a cured product of an epoxy resin composition having a longer pot life and shelf life and high heat resistance, the epoxy resin (A) used in the present invention preferably contains an epoxy resin having a glycidyl group derived from resorcinol in an amount of 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, still more preferably 2% by mass or less, and still more preferably less than 1% by mass.

[0044] From the viewpoint of obtaining an epoxy resin composition that has a long pot life and shelf life and that can achieve high heat resistance, elongation, and hydrogen gas barrier properties, the epoxy equivalent of the epoxy resin (A) is preferably 100 g / equivalent or more, more preferably 120 g / equivalent or more, and even more preferably 150 g / equivalent or more. From the viewpoint of improving curability, the epoxy equivalent is preferably 1200 g / equivalent or less, more preferably 1000 g / equivalent or less, even more preferably 800 g / equivalent or less, still more preferably 600 g / equivalent or less, still more preferably 500 g / equivalent or less, still more preferably 400 g / equivalent or less, still more preferably 300 g / equivalent or less, and still more preferably 250 g / equivalent or less.

[0045] <Epoxy Resin Curing Agent (B)> The epoxy resin curing agent (B) used in the epoxy resin composition of the present invention contains resorcinol (B1), which is believed to achieve high hydrogen gas barrier properties and improve pot life and shelf life.

[0046] (Resorcinol (B1)) Resorcinol (B1) is 1,3-dihydroxybenzene. From the viewpoint of improving hydrogen gas barrier property, pot life, and shelf life, the content of resorcinol (B1) in the epoxy resin curing agent (B) is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, still more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 85% by mass or more, and still more preferably 90% by mass or more, and 100% by mass or less.

[0047] (Epoxy Resin Curing Agent (B2)) The epoxy resin curing agent (B) may further contain an epoxy resin curing agent (B2) other than resorcinol (B1) as long as the effects of the present invention are not impaired. Examples of the epoxy resin curing agent (B2) include compounds having two or more groups containing active hydrogen capable of reacting with the epoxy group in the epoxy resin (A). From the viewpoints of suppressing deterioration in pot life, shelf life, heat resistance, elongation, and hydrogen gas barrier property, the epoxy resin curing agent (B2) preferably contains a phenolic curing agent (B2-1) other than resorcinol (B1).

[0048] [Phenol-Based Curing Agent (B2-1) Other Than Resorcinol (B1)] The phenol-based curing agent (B2-1) may be any phenolic compound having two or more phenolic hydroxyl groups. From the viewpoint of suppressing deterioration in pot life, shelf life, heat resistance, elongation, and hydrogen gas barrier property, the phenol-based curing agent (B2-1) preferably contains at least one selected from the group consisting of bisphenol F, bisphenol A, novolac phenols, and triphenylmethane phenols, and more preferably contains at least one selected from the group consisting of novolac phenols and triphenylmethane phenols.

[0049] Examples of novolak-type phenols used as the phenolic curing agent (B2-1) include phenol novolak, bisphenol A novolak, and cresol novolak, and these can be used alone or in combination of two or more. Among these, phenol novolak is preferred from the viewpoint of suppressing deterioration in pot life, shelf life, heat resistance, elongation, and hydrogen gas barrier properties. Triphenylmethane-type phenol refers to a phenol compound having a triphenylmethane skeleton (excluding those corresponding to the epoxy resin (A1)).

[0050] From the viewpoint of improving heat resistance, the softening point of the novolac phenol is preferably 70 to 250° C., more preferably 75 to 240° C., even more preferably 75 to 200° C., still more preferably 75 to 120° C., and even more preferably 75 to 100° C. The softening point can be measured, for example, by a thermomechanical analyzer (TMA).

[0051] The hydroxyl group equivalent of the phenolic curing agent (B2-1) is usually 90 g / equivalent or more, preferably 95 g / equivalent or more, and from the viewpoint of improving curability, it is preferably 160 g / equivalent or less, more preferably 150 g / equivalent or less, even more preferably 130 g / equivalent or less, and still more preferably 120 g / equivalent or less.

[0052] Commercially available products can also be used as the phenol-based curing agent (B2-1). For example, examples of novolac-type phenols include the PHENOLITE series "TD-2131", "TD-2106", "TD-2093Y", and "TD-2090" (phenol novolacs), "VH-4150", "VH-4170", and "KH-6021" (bisphenol A novolacs), and "KA-1160", "KA-1163", and "KA-1165" (cresol novolacs) manufactured by DIC Corporation. Examples of triphenylmethane-type phenols include "S-TPM-105" manufactured by JFE Chemical Corporation.

[0053] The epoxy resin curing agent (B2) may contain, in addition to the phenolic curing agent (B2-1), other epoxy resin curing agents such as, for example, dihydrazide curing agents. However, from the viewpoint of suppressing deterioration in pot life, shelf life, heat resistance, elongation, and hydrogen gas barrier property, the content of the phenolic curing agent (B2-1) in the epoxy resin curing agent (B2) 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 and 100% by mass or less.

[0054] <Curing Accelerator (C)> From the viewpoint of improving curability, the epoxy resin composition of the present invention preferably further contains a curing accelerator (C). From the viewpoint of improving curability, the curing accelerator (C) preferably contains at least one selected from the group consisting of imidazoles, tertiary amines, and phosphorus compounds. Examples of imidazoles include 1-cyanoethyl-2-ethyl-4-methylimidazole and 2-ethyl-4-methylimidazole. Examples of tertiary amines include tertiary amines or salts thereof that can accelerate the curing of resorcinol (B1) and the phenolic curing agent (B2-1), such as 1,8-diazabicyclo[5.4.0]-undecene-7 (DBU), 1,5-diazabicyclo[4.3.0]-nonene-5 (DBN), and tris(dimethylaminomethylphenol). Examples of phosphorus compounds include phosphine compounds such as triphenylphosphine, and phosphonium salts such as tetraphenylphosphonium and tetraphenylborate.

[0055] The curing accelerator (C) may be used alone or in combination of two or more thereof. From the viewpoint of improving curability, the curing accelerator (C) preferably contains at least one selected from the group consisting of imidazoles and tertiary amines, more preferably contains an imidazole, and even more preferably contains 2-ethyl-4-methylimidazole.

[0056] <Stress Relaxation Component (D)> The epoxy resin composition of the present invention may further contain a stress relaxation component (D) for the purposes of suppressing an excessive increase in the elastic modulus of the cured product and reducing the occurrence of cracks. Examples of the stress relaxation component (D) 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 the "Kane Ace" B series, FM series, M series, and MX series manufactured by Kaneka Corporation, and liquid epoxidized polybutadienes such as "Epolead PB3600" and "Epolead PB4700" manufactured by Daicel Corporation.

[0057] <Non-reactive diluent (E)> The epoxy resin composition of the present invention may further contain a non-reactive diluent (E) for the purposes of improving the ease of incorporation of the curing accelerator (C), improving the tensile stress of the cured product, etc. "Improving the ease of incorporation of the curing accelerator (C)" means that by dissolving the curing accelerator (C) in the non-reactive diluent (E) in advance to prepare a solution, and then incorporating this solution into the epoxy resin composition, it becomes possible to uniformly dissolve or disperse even a small amount of the curing accelerator (C) in the composition.

[0058] The non-reactive diluent (E) may be at least one selected from the group consisting of benzyl alcohol, furfuryl alcohol, tetrahydrofurfuryl alcohol, and aromatic hydrocarbon formaldehyde resins. Among them, aromatic hydrocarbon formaldehyde resins are resins obtained by reacting aromatic hydrocarbons with formaldehyde, such as toluene formaldehyde resins obtained by reacting toluene with formaldehyde, xylene formaldehyde resins obtained by reacting xylene with formaldehyde, mesitylene formaldehyde resins obtained by reacting mesitylene with formaldehyde, and pseudocumene formaldehyde resins obtained by reacting pseudocumene with formaldehyde. Among these, from the viewpoints of improving the ease of incorporation of the curing accelerator (C), improving the tensile stress of the cured product, and maintaining various physical properties other than tensile stress of the cured product, the aromatic hydrocarbon formaldehyde resin preferably includes a xylene formaldehyde resin. Commercially available aromatic hydrocarbon formaldehyde resins include, for example, xylene formaldehyde resins (hereinafter also simply referred to as "xylene resins") manufactured by Fudow Co., Ltd., such as "NIKANOL Y-50," "NIKANOL Y-100," "NIKANOL Y-300," "NIKANOL Y-1000," "NIKANOL L," "NIKANOL LL," "NIKANOL LLL," "NIKANOL G," "NIKANOL H," and "NIKANOL H-80."

[0059] Among the above, from the viewpoints of improving the ease of compounding the curing accelerator (C), improving the tensile stress of the cured product, and maintaining various physical properties of the cured product other than tensile stress, the non-reactive diluent (E) preferably contains at least one selected from the group consisting of benzyl alcohol and aromatic hydrocarbon formaldehyde resins, and more preferably contains at least one selected from the group consisting of benzyl alcohol and xylene formaldehyde resins.

[0060] <Solvent> The epoxy resin composition of the present invention may further contain a solvent in order to reduce the viscosity of the composition and improve its impregnation into reinforcing fibers. Examples of such solvents include organic solvents other than the non-reactive diluent (E). Examples of such solvents 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. These solvents may be used singly or in combination. From the viewpoint of the solubility of the components contained in the epoxy resin composition 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.

[0061] <Contents> The content ratio of the epoxy resin (A) to the epoxy resin curing agent (B) in the epoxy resin composition of the present invention is an amount such that the functional group equivalent ratio [(B) / (A)] between the epoxy resin (A) and the epoxy resin curing agent (B) is preferably 0.5 to 2.0, more preferably 0.75 to 1.5, and even more preferably 0.8 to 1.2. In this specification, the functional group equivalent ratio [(B) / (A)] means (the number of active hydrogen atoms in the epoxy resin curing agent (B) / the number of epoxy groups in the epoxy resin (A)), unless otherwise specified.

[0062] The content of the epoxy resin (A) in the epoxy resin composition is preferably 40 to 95% by mass, more preferably 50 to 90% by mass, even more preferably 60 to 85% by mass, and even more preferably 65 to 80% by mass. When the epoxy resin composition contains water or the solvent, the content of the epoxy resin (A) in 100% by mass of the solid content of the epoxy resin composition is preferably 40 to 95% by mass, more preferably 50 to 90% by mass, even more preferably 60 to 85% by mass, and even more preferably 65 to 80% by mass. The "solid content of the epoxy resin composition" refers to the amount of the epoxy resin composition excluding water and the solvent. The content of the epoxy resin curing agent (B) in the epoxy resin composition is preferably 5.0 to 60% by mass, more preferably 10 to 50% by mass, even more preferably 15 to 40% by mass, and even more preferably 20 to 35% by mass. When the epoxy resin composition contains water or the solvent, the content of the epoxy resin curing agent (B) in 100% by mass of the solid content of the epoxy resin composition is preferably 5.0 to 60% by mass, more preferably 10 to 50% by mass, even more preferably 15 to 40% by mass, and still more preferably 20 to 35% by mass.

[0063] When the epoxy resin composition contains the curing accelerator (C), the content of the curing accelerator (C) in the epoxy resin composition is, from the viewpoint of improving curability, preferably 0.01 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, even more preferably 0.05 to 1 part by mass, and still more preferably 0.05 to 0.5 parts by mass, relative to 100 parts by mass of the total amount of the epoxy resin (A) and the epoxy resin curing agent (B).

[0064] From the viewpoint of effectively exhibiting the effects of the present invention, the total content of the epoxy resin (A), epoxy resin curing agent (B), and curing accelerator (C) 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 and 100% by mass or less. When the epoxy resin composition contains water or the solvent, the total content of the epoxy resin (A), epoxy resin curing agent (B), and curing accelerator (C) in 100% by mass of the solids content of the epoxy resin composition 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 and 100% by mass or less.

[0065] When the epoxy resin composition contains the stress relaxation component (D), the content of the stress relaxation component (D) in the epoxy resin composition is preferably 1.0 to 30 parts by mass, more preferably 3.0 to 20 parts by mass, even more preferably 5.0 to 15 parts by mass, and still more preferably 8.0 to 12 parts by mass, per 100 parts by mass of the total amount of the epoxy resin (A) and the epoxy resin curing agent (B).

[0066] When the epoxy resin composition contains the non-reactive diluent (E), the content of the non-reactive diluent (E) in the epoxy resin composition is preferably 0.1 to 20 parts by mass, more preferably 0.2 to 15 parts by mass, even more preferably 0.3 to 10 parts by mass, still more preferably 0.3 to 7 parts by mass, still more preferably 0.3 to 5 parts by mass, still more preferably 0.4 to 3 parts by mass, and still more preferably 0.5 to 2 parts by mass, relative to 100 parts by mass of the total amount of the epoxy resin (A) and the epoxy resin curing agent (B), from the viewpoints of improving the ease of blending the curing accelerator (C), improving the tensile stress of the cured product, and maintaining various physical properties other than the tensile stress of the cured product.

[0067] When the epoxy resin composition contains a solvent, the content thereof is not particularly limited, but from the viewpoint of reducing the viscosity of the epoxy resin composition, it is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, of the epoxy resin composition. Also, from the viewpoint of ease of solvent removal, it is preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 80% by mass or less, and still more preferably 70% by mass or less.

[0068] The epoxy resin composition of the present invention may be a solvent-free epoxy resin composition. Specifically, the content of the solvent in the epoxy resin composition may be less than 5% by mass, preferably less than 2% by mass, more preferably less than 1% by mass, and even more preferably less than 0.1% by mass.

[0069] Furthermore, the epoxy resin composition of the present invention is preferably a non-aqueous epoxy resin composition. Specifically, the water content in the epoxy resin composition is preferably less than 5% by mass, more preferably less than 2% by mass, even more preferably less than 1% by mass, and even more preferably less than 0.1% by mass. However, the non-aqueous epoxy resin composition referred to here means an epoxy resin composition in which the amount of water intentionally blended is small, and does not exclude the inclusion of unintentionally mixed water.

[0070] The epoxy resin composition of the present invention may further contain other components such as modifying components such as fillers and plasticizers, flow-adjusting components such as thixotropic agents, reactive diluents, pigments, leveling agents, tackifiers, and flame retardants depending on the intended use.

[0071] <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 of the present invention at 23°C is preferably 7.0 × 10 -11 [cc・cm / (cm 2 s cmHg)] or less, more preferably 6.0 × 10 -11 [cc・cm / (cm 2 s cmHg)] or less, and more preferably 5.0 × 10 -11 [cc・cm / (cm 2s cmHg)] or less, and even more preferably 3.5 × 10 -11 [cc・cm / (cm 2 The hydrogen gas permeability coefficient of the cured product of the epoxy resin composition is measured in accordance with JIS K 7126-1 under dry conditions at 23°C (23°C, humidity 0%). Specifically, it can be measured by the method described in the examples.

[0072] <Glass Transition Temperature> From the viewpoint of high heat resistance, the glass transition temperature (Tg) of the cured product of the epoxy resin composition of the present invention is preferably 100°C or higher, more preferably 105°C or higher, even more preferably 110°C or higher, and still more preferably 115°C or higher. There are no particular limitations on the upper limit of the glass transition temperature, but it may be, for example, 200°C or lower. The glass transition temperature of the cured product of the epoxy resin composition can be measured using a dynamic viscoelasticity measuring device, specifically by the method described in the examples.

[0073] <Tensile elongation> From the viewpoint of improving impact resistance and the like, the tensile elongation of the cured product of the epoxy resin composition of the present invention is preferably 3.0% or more, more preferably 3.5% or more, even more preferably 3.8% or more, and even more preferably 4.0% or more. The upper limit of the tensile elongation is not particularly limited, but from the viewpoint of improving mechanical strength, it may be, for example, 10% or less. The tensile elongation of the cured product of the epoxy resin composition can be measured in accordance with JIS K7161-1:2014 and JIS K7161-2:2014, specifically by the method described in the examples.

[0074] <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 23°C is preferably 3 hours or more, more preferably 6 hours or more, even more preferably 12 hours or more, and still more preferably 24 hours or more. Specifically, the pot life of the epoxy resin composition can be measured by the method described in the examples.

[0075] <Shelf Life> The epoxy resin composition of the present invention has a long shelf life. For example, the shelf life of the epoxy resin composition at 0°C is preferably 7 days or more, more preferably 14 days or more, and even more preferably 30 days or more. The shelf life of the epoxy resin composition can be measured specifically by the method described in the Examples.

[0076] The epoxy resin composition of the present invention can be prepared by mixing the epoxy resin (A), the epoxy resin curing agent (B), and, if necessary, other components using known methods and equipment. The order of mixing the components contained in the epoxy resin composition is also not particularly limited. Components (A1) and (A2) constituting the epoxy resin (A) may be mixed first and then mixed with other components. Alternatively, components (A1), (A2), and other components constituting the epoxy resin (A) may be mixed simultaneously to prepare the composition. To prevent gelation from progressing before use, it is preferable to mix the components contained in the epoxy resin composition immediately before use. The temperature at which the components contained in 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.

[0077] [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, the cured product of the present invention is preferably a matrix resin for a fiber-reinforced composite material, which will be described later.

[0078] [Prepreg] The prepreg of the present invention contains the epoxy resin composition and reinforcing fibers. More specifically, the prepreg of the present invention is obtained by impregnating reinforcing fibers with the epoxy resin composition.

[0079] <Reinforcing Fibers> Examples of the reinforcing fibers used in prepregs include short fibers, long fibers, and continuous fibers. Among these, from the viewpoint of producing high-pressure gas containers using the resulting prepregs by filament winding or tape winding, long fibers or continuous fibers are preferred, and continuous fibers are more preferred. In this specification, short fibers refer to fibers having a fiber length of 0.1 mm or more and less than 10 mm, and long fibers refer to fibers having a fiber length of 10 mm or more and 100 mm or less. Furthermore, continuous fibers refer to fiber bundles having a fiber length of more than 100 mm.

[0080] Examples of the shape of the continuous fiber include tow, sheet, tape, etc., and examples of the continuous fiber constituting the sheet or tape include unidirectional (UD) materials, woven fabrics, nonwoven fabrics, etc. From the viewpoint of producing high-pressure gas containers using prepregs by filament winding or tape winding, the shape of the continuous fiber is preferably tow or tape, and more preferably tow. The number of continuous fiber bundles constituting the tow (number of filaments) is preferably 3K to 50K, more preferably 6K to 40K, from the viewpoint of easily obtaining high strength and high elastic modulus.

[0081] 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.

[0082] Examples of materials for the reinforcing fibers 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 obtaining high strength. Because of their light weight, high strength, and high elastic modulus, the reinforcing fiber is preferably at least one selected from the group consisting of carbon fiber, glass fiber, and basalt fiber, and carbon fiber is more preferred from the viewpoint of strength and light weight. 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] Commercially available products of continuous carbon fibers (tows) include, for example, the Torayca (registered trademark) 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 the Tenax (registered trademark) "HTA40" series, "HTS40" series, "HTS45" series, and "HTS45P12" series manufactured by Teijin Limited. carbon fiber tows of the PYROFIL (registered trademark) "HT", "IM", "HM" series, GRAFIL (registered trademark) "HT" series, and "DIALEAD (registered trademark)" series manufactured by Mitsubishi Chemical Corporation; and the like.Commercially available continuous carbon fibers other than tow include Toray Industries, Inc.'s Torayca (registered trademark) 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 (registered trademark) TR3110M, TR3523M, TR3524M, TR6110HM, TR6120HM, TRK101M, TRK510M, TR3160TMS, TRK979PQRW, TRK976PQRW, TR6185HM, and TRK180M manufactured by Mitsubishi Chemical Corporation; and the like.

[0087] <Content> From the viewpoint of obtaining high strength and high elastic modulus, the content of reinforcing fibers in the prepreg of the present invention is preferably in a range such that the volume fraction of the reinforcing fibers in the prepreg 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. Furthermore, from the viewpoint of hydrogen gas barrier properties, impact resistance, and molding processability, the content is preferably in a range such that the volume fraction is 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 prepreg １ can be calculated from the following formula: １ = {mass (g) of reinforcing fiber / specific gravity of reinforcing fiber} ÷ [{mass (g) of reinforcing fiber / specific gravity of reinforcing fiber} + {mass (g) of solid content of impregnated epoxy resin composition / specific gravity of solid content of epoxy resin composition}]

[0088] Furthermore, from the viewpoint of obtaining the effects of the present invention, the total content of the solids content and reinforcing fibers in the epoxy resin composition constituting the prepreg of the present invention is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, but 100% by mass or less.

[0089] <Prepreg Shape and Manufacturing Method> The shape of the prepreg varies depending on the shape of the reinforcing fibers used. However, from the viewpoint of manufacturing high-pressure gas containers by a filament winding method or a tape winding method, the prepreg of the present invention is preferably a tow prepreg or a tape prepreg. Among tape prepregs, the prepreg of the present invention is preferably a unidirectional (UD) tape. Unidirectional tape (hereinafter also referred to as "UD tape") is particularly suitable for use in the tape winding method. Note that UD tape may be cut into small pieces and used. Alternatively, when continuous fibers in the form of a unidirectional (UD) material, woven fabric, nonwoven fabric, or the like are used, a sheet-shaped prepreg can also be produced.

[0090] The method for producing the prepreg is not particularly limited, and the prepreg can be produced according to a conventional method. For example, the prepreg can be obtained by impregnating a reinforcing fiber with an epoxy resin composition containing an epoxy resin (A), an epoxy resin curing agent (B), and other components used as needed, and then subjecting the impregnated fiber to a drying step to remove the solvent.

[0091] The method for impregnating the reinforcing fibers with the epoxy resin composition is not particularly limited, and any known method can be used as appropriate depending on the shape of the reinforcing fibers, etc. For example, when producing a tow prepreg, a method can be used in which a continuous fiber bundle unwound from a roll is immersed in a resin bath filled with the above-mentioned epoxy resin composition, and after impregnation with the composition, the bundle is pulled out of the resin bath. A step of removing excess epoxy resin composition using a squeeze roll or the like can then be carried out. The impregnation with the epoxy resin composition can also be carried out under pressurized or reduced pressure, as necessary.

[0092] Next, if necessary, the reinforcing fibers impregnated with the epoxy resin composition are subjected to a drying step to remove the solvent. The drying conditions in the drying step are not particularly limited, but are preferably conditions that allow the solvent to be removed and do not cause excessive curing of the epoxy resin composition. From this perspective, for example, the drying temperature can be selected in the range of 30 to 120°C, and the drying time can be selected in the range of 10 seconds to 5 minutes.

[0093] The prepreg obtained through the drying step may be temporarily wound up or otherwise processed to form a prepreg product, or it may be subjected to the drying step without being wound up or otherwise processed and then continuously supplied to the production of a fiber-reinforced composite material. In particular, when a tape-shaped or sheet-shaped prepreg product is to be produced, it is preferable to wind up the prepreg to form a roll-shaped product.

[0094] [Fiber-reinforced composite material] The fiber-reinforced composite material (FRP, hereinafter also simply referred to as "composite material") of the present invention is a cured product of the prepreg, and comprises a cured product of the epoxy resin composition and reinforcing fibers. The fiber-reinforced composite material of the present invention has high hydrogen barrier properties due to the inclusion of a cured product of the epoxy resin composition. The prepreg, epoxy resin composition, reinforcing fibers, and preferred embodiments thereof used in producing the composite material are the same as those described above.

[0095] From the viewpoint of obtaining high strength and high modulus of elasticity, 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}]

[0096] <Method for Producing Fiber-Reinforced Composite Material> A composite material can be produced by premolding the prepreg into a desired shape and then curing the prepreg. For example, when the composite material of the present invention is applied to a hollow molded article such as a pipe, shaft, cylinder, or tank, the composite material can be produced by molding the tow prepreg using a filament winding method, braiding method, 3D printer method, or the like. In the filament winding method, specifically, a tow prepreg is wound around the outer surface of a balloon, mandrel, or liner, and then heat-cured to produce a composite material of a desired shape. In the braiding method, for example, a balloon or mandrel is used to braid the tow prepreg into a unidirectional or braided structure, and the prepreg is then heat-cured. Note that the braiding method can also be used to braid and mold the tow prepreg without using a balloon or mandrel.

[0097] When using sheet-shaped prepregs such as unidirectional (UD) materials, woven fabrics, and nonwoven fabrics, a composite material can be produced by placing one or more prepregs in a mold and heating and curing them under vacuum or pressurized conditions.

[0098] The method for curing the prepreg in the production of the composite material is not particularly limited, and is carried out by a known method at a temperature and for a time sufficient to cure the epoxy resin composition contained in the prepreg. The prepreg curing conditions depend on the thickness of the prepreg and the composite material to be formed, but for example, the curing temperature can be selected in the range of 10 to 180°C and the curing time in the range of 5 minutes to 200 hours, and from the viewpoint of productivity, the curing temperature is preferably 80 to 180°C and the curing time in the range of 10 minutes to 5 hours.

[0099] From the viewpoint of manufacturing using tow prepreg, the composite material of the present invention is suitable for use in hollow molded articles such as pipes, shafts, bombs, tanks, cylinders (cylinders closed at both ends by two disks), etc. Because the composite material has excellent hydrogen gas barrier properties, it is particularly suitable as a material for forming high-pressure gas containers.

[0100] [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.

[0101] 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).

[0102] Examples of the metal used for the "metallic liner" in (1) above include light alloys such as aluminum alloys and magnesium alloys.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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 storage tank, the thickness is preferably 80 mm or less, more preferably 60 mm or less.

[0107] 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.

[0108] 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.

[0109] 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 still 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 still more preferably 0.70 or less. The volume fraction of reinforcing fibers can be calculated in the same manner as above.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] <Method for Manufacturing a High-Pressure Gas Container> As a method for manufacturing a high-pressure gas container of the present invention, the manufacturing methods described above for manufacturing fiber-reinforced composite materials can be used as appropriate, depending on the type of reinforcing fiber or prepreg used. When manufacturing a high-pressure gas container using a tow prepreg, the tow prepreg can be formed by a filament winding method, a braiding method, a 3D printer method, or the like to produce the high-pressure gas container. When the high-pressure gas container is in the above-mentioned embodiment (1) or (2), the tow prepreg can be wound around the outer surface of a metal or resin liner using a filament winding method, 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), the tow prepreg can be formed into a container shape by a filament winding method, a braiding method, a 3D printer method, or the like, followed by heat curing to produce the high-pressure gas container.

[0114] 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.

[0115] <Hydrogen gas permeability coefficient [cc cm / (cm2 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 ("Kemlease AF-7 EZ" manufactured by Chemtrend Japan Inc.), and heat-cured at 80 to 160°C for 2 hours to produce a 1 mm thick plate-shaped molded body. Circular test pieces with a thickness of 1 mm and a diameter of 20 mm were prepared from this plate-shaped molded body. The hydrogen gas permeability coefficient [cc cm / (cm Hg)] at 23°C was measured for each test piece using a gas permeability measuring device ("GTR-30X" manufactured by GTR Tech Co., Ltd.) by the differential pressure method in accordance with JIS K 7126-1:2006 (23°C, humidity 0%). 2 s cmHg)] was measured.

[0116] <Glass Transition Temperature (Tg)> The epoxy resin composition prepared in each example was molded into a 200 mm x 200 mm x 2 mm thick plate, and cured by heating at 120°C for 30 minutes and then at 160°C for 2 hours to produce a cured product. A 50 mm x 10 mm x 2 mm thick strip was cut from the cured product to serve as a dynamic viscoelasticity (DMA) measurement sample. Using the sample, DMA bending measurement was performed using a rotational rheometer "ARES G2" (manufactured by TA Instruments) under the following conditions. The vertical axis represents tan δ and the horizontal axis represents the measurement temperature. The peak top value of tan δ was taken as the Tg of the cured product. The higher the glass transition temperature (Tg) of the cured product, the more excellent its heat resistance. (Measurement Conditions) Measurement Mode: Bending DMA Measurement Measurement Temperature: 30 to 180°C Heating Rate: 5°C / min

[0117] <Tensile Stress, Tensile Elongation, and Tensile Modulus of Elasticity> The epoxy resin composition prepared in each example was molded into a 200 mm x 200 mm x 2 mm thick plate and cured by heating at 120°C for 30 minutes and then at 160°C for 2 hours to produce a cured product. A rectangular piece measuring 180 mm x 15 mm x 2 mm thick was cut from the cured product to serve as a tensile test specimen. Using the test specimen, a tensile test was performed under the following conditions (N=3) in accordance with JIS K7161-1:2014 and JIS K7161-2:2014 using a precision universal testing machine ("Autograph AGX-plus" manufactured by Shimadzu Corporation). The tensile stress, tensile elongation, and tensile modulus of elasticity were calculated using the following formula. The length of the test specimen at break was calculated from the displacement of the load cell at break. (Measurement conditions) Distance between grips: 115 mm Distance between gauge lines: 75 mm Load cell (tensile force): 1 kN Tensile speed: 1 mm / min (tensile direction: longitudinal direction of test piece) (Calculation formula) Tensile stress (MPa) = Load at break of test piece (N) / Initial cross-sectional area of ​​test piece (mm ２ ) Tensile elongation (%) = (length of test piece at break - initial length of test piece) / (initial length of test piece) × 100 Tensile modulus (GPa) = elastic modulus gradient (N / mm) × initial length of test piece (mm) / initial cross-sectional area of ​​test piece (mm ２ ) x 10 －３ The elastic modulus gradient here means the slope of the stress-strain curve corresponding to the two points where the tensile strain (the value obtained by dividing the increase in the gauge length by the gauge length) is 0.05% and 0.25%.

[0118] <Pot Life> After measuring the initial viscosity at 23°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 23°C. The time [h] until the viscosity of the epoxy resin composition became at least twice the initial viscosity was measured and shown in the table. In the table, pot lives exceeding 24 hours are indicated by ">24". The longer the time, the better the pot life. The viscosity of the epoxy resin composition was measured using a rotational rheometer "ARES G2" (manufactured by TA Instruments) in measurement mode: rotational mode, using a 25 mm circular plate.

[0119] <Shelf Life> 10 g of the epoxy resin composition prepared in each example was placed in a plastic cup (diameter 46 mm) and stored at 0°C. At regular intervals, the epoxy resin composition was returned to room temperature (23°C) and visually observed for fluidity. The number of days (days) until the composition began to lose fluidity after storage at 0°C is shown in the table. In the table, compositions with a shelf life of more than 30 days are indicated as ">30." The longer the time, the better the shelf life.

[0120] Example 1 (Preparation and Evaluation of Epoxy Resin Composition) As the epoxy resin (A), a triphenylmethane-type epoxy resin (HP-7241 manufactured by DIC Corporation, epoxy equivalent: 172 g / equivalent) as component (A1), and bisphenol A diglycidyl ether (jER828 manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 186 g / equivalent), a phenol novolac-type epoxy resin (N730A manufactured by DIC Corporation, epoxy equivalent: 176 g / equivalent), and a phenol novolac-type epoxy resin (N740 manufactured by DIC Corporation, epoxy equivalent: 183 g / equivalent) as component (A2) were used. Resorcinol (B1) was used as the epoxy resin curing agent (B). 2-Ethyl-4-methylimidazole (Tokyo Chemical Industry Co., Ltd.) was used as the curing accelerator (C). These components were blended and mixed in the parts by mass shown in Table 1 to obtain an epoxy resin composition. The functional group equivalent ratio [(B) / (A)] of the epoxy resin (A) to the epoxy resin curing agent (B) was 1 / 1. The obtained epoxy resin composition was evaluated by the above-mentioned methods. The results are shown in Table 1.

[0121] Examples 2 to 13 and Comparative Examples 1 to 5 Epoxy resin compositions were prepared and evaluated in the same manner as in Example 1, except that the types and amounts of the epoxy resin (A), epoxy resin curing agent (B), and curing accelerator (C) were changed as shown in Tables 1 to 3. The results are shown in Tables 1 to 3.

[0122] Examples 14 and 15 Epoxy resin compositions were prepared and evaluated in the same manner as in Example 1, except that the types and amounts of the epoxy resin (A), epoxy resin curing agent (B), and curing accelerator (C) were changed as shown in Table 2, and that when these were blended, the component shown in Table 2 was also blended as the stress relaxation component (D). The results are shown in Table 2.

[0123] Examples 16 to 17 The types and amounts of the epoxy resin (A), epoxy resin curing agent (B), and curing accelerator (C) were changed as shown in Table 2. In addition, epoxy resin compositions were prepared and evaluated in the same manner as in Example 1, except that a solution was prepared by dissolving the curing accelerator (C) in the non-reactive diluent (E) shown in Table 2, and the epoxy resin (A) and epoxy resin curing agent (B) were mixed with this solution. The results are shown in Table 2.

[0124]

[0125]

[0126]

[0127] The components listed in the table are as follows. <Epoxy resin (A)> (A1-1) Triphenylmethane type epoxy resin (HP-7241): "HP-7241" manufactured by DIC Corporation, epoxy equivalent: 172 g / equivalent (A2-1-1) Bisphenol F diglycidyl ether (jER807): "jER807" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 168 g / equivalent (A2-1-2) Bisphenol F diglycidyl ether oligomer (jER4005P): "jER4005P" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 1026 g / equivalent, oligomer type (A2-2-1) Bisphenol A diglycidyl ether (jER828): "jER828" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 186 g / equivalent (A2-2-2) Bisphenol A diglycidyl ether oligomer (jER1001): "jER1001" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 483 g / equivalent, oligomer type (A2-3-1) Phenol novolac type epoxy resin (N730A): "N730A" manufactured by DIC Corporation, epoxy equivalent: 176 g / equivalent (A2-3-2) Phenol novolac type epoxy resin (N740): "N740" manufactured by DIC Corporation, epoxy equivalent: 183 g / equivalent (A2-3-3) Phenol novolac type epoxy resin (N770): "N770" manufactured by DIC Corporation, epoxy equivalent: 188 g / equivalent, melt viscosity at 150°C: 0.48 Pa s (A2-4-1) Naphthalene epoxy resin (HP-4032SS): "HP-4032SS" manufactured by DIC Corporation, epoxy resin represented by formula (A2-4-3), epoxy equivalent: 142 g / equivalent

[0128] <Epoxy Resin Curing Agents (B)> (B1) Resorcinol: "Resorcin" manufactured by Sumitomo Chemical Co., Ltd. (B2-1-1) Triphenylmethane-type phenol: "S-TPM-105" manufactured by JFE Chemical Corporation, hydroxyl value equivalent: 99 g / equivalent (B2-1-2) Novolac-type phenol: "TD-2131" manufactured by DIC Corporation, hydroxyl value equivalent: 104 g / equivalent, softening point: 78 to 82°C

[0129] <Curing accelerator (C)> 2-ethyl-4-methylimidazole: manufactured by Tokyo Chemical Industry Co., Ltd.

[0130] <Stress relaxation component (D)> Kane Ace MX-136: Core-shell rubber particle dispersed epoxy resin masterbatch, "Kane Ace MX-136" manufactured by Kaneka Corporation, epoxy type Bis-F type, particle polybutadiene / silicone, particle content 25% Epolead PB4700: epoxidized polybutadiene, "Epolead PB4700" manufactured by Daicel Corporation, molecular weight 2000 to 3500

[0131] <Non-reactive diluent (E)> Xylene resin: xylene formaldehyde resin, "NIKANOL Y-300" manufactured by Fudow Co., Ltd., viscosity at 25°C: 285 mPa·s, hydroxyl equivalent: 2,805 g / equivalent (hydroxyl value: 20 mgKOH / g) Benzyl alcohol: manufactured by Tokyo Chemical Industry Co., Ltd.

[0132] As can be seen from Tables 1 and 2, the cured products of the epoxy resin compositions of this example all had a viscosity of 7.0 (×10 －１１ cc cm / cm ２ It can be seen that the epoxy resin compositions can achieve a hydrogen gas permeability coefficient of 0.1 sq. sec.cmHg or less, a glass transition temperature of 100°C or higher, and a tensile elongation of 3.0% or more. Furthermore, the pot life and shelf life of the epoxy resin compositions are also good. In contrast, the cured products of the epoxy resin compositions of Comparative Examples 1 to 5 listed in Table 3 were inferior in either hydrogen gas barrier property, glass transition temperature, or tensile elongation. The cured products of the epoxy resin compositions of Examples 14 and 15, by adding the stress relaxation component (D), exhibited lower tensile stress and tensile modulus values ​​while maintaining comparable hydrogen gas barrier property, glass transition temperature, and tensile elongation values ​​compared to the other examples, demonstrating a stress relaxation effect. Furthermore, the cured products of the epoxy resin compositions of Examples 16 and 17, which contained the non-reactive diluent (E), exhibited improved tensile stress compared to Example 6.

[0133] The present invention provides an epoxy resin composition capable of producing a cured product having high hydrogen gas barrier properties, heat resistance, and elongation, the cured product, a prepreg using the epoxy resin composition, a fiber-reinforced composite material, and a high-pressure gas container. The high-pressure gas container has high hydrogen gas barrier properties and is suitable as a container for storing high-pressure hydrogen gas.

Claims

1. An epoxy resin composition containing an epoxy resin (A) and an epoxy resin curing agent (B), wherein the epoxy resin (A) comprises an epoxy resin (A1) and an epoxy resin (A2), the epoxy resin (A1) is an epoxy resin having a glycidyl group derived from a triphenylmethane type phenol, the epoxy resin (A2) is at least one selected from the group consisting of an epoxy resin (A2-1) having a glycidyl group derived from bisphenol F, an epoxy resin (A2-2) having a glycidyl group derived from bisphenol A, an epoxy resin (A2-3) having a glycidyl group derived from a novolac type phenol, and an epoxy resin (A2-4) having a glycidyl group derived from a polyol having a naphthalene skeleton, and the mass ratio [(A1) / (A2)] of the epoxy resin (A1) to the epoxy resin (A2) in the epoxy resin (A) is 1 / 99 to 90 / 10, The epoxy resin composition, wherein the epoxy resin curing agent (B) comprises resorcinol (B1).

2. The epoxy resin composition according to claim 1, wherein the epoxy resin curing agent (B) further comprises an epoxy resin curing agent (B2) other than resorcinol (B1), and the epoxy resin curing agent (B2) comprises a phenol-based curing agent (B2-1) other than resorcinol (B1).

3. The epoxy resin composition according to claim 2, wherein the phenol-based curing agent (B2-1) comprises at least one member selected from the group consisting of bisphenol F, bisphenol A, novolac-type phenols, and triphenylmethane-type phenols.

4. The epoxy resin composition according to any one of claims 1 to 3, wherein the mass ratio [(A1) / (A2)] of the epoxy resin (A1) to the epoxy resin (A2) in the epoxy resin (A) is 5 / 95 to 70 / 30.

5. The epoxy resin composition according to any one of claims 1 to 4, further comprising a curing accelerator (C), said curing accelerator (C) comprising at least one member selected from the group consisting of imidazoles, tertiary amines, and phosphorus compounds.

6. The epoxy resin composition according to any one of claims 1 to 5, further comprising a stress relaxation component (D).

7. The epoxy resin composition according to any one of claims 1 to 6, further comprising a non-reactive diluent (E).

8. The hydrogen gas permeability coefficient of the cured product of the epoxy resin composition at 23°C is 7.0 x 10 -11 [cc・cm / (cm 2 The epoxy resin composition according to any one of claims 1 to 7, wherein the viscosity of the epoxy resin composition is less than or equal to [. s. cmHg).

9. A cured product of the epoxy resin composition according to any one of claims 1 to 8.

10. A prepreg comprising the epoxy resin composition according to any one of claims 1 to 8 and reinforcing fibers.

11. The prepreg according to claim 10, wherein the reinforcing fibers are at least one type selected from the group consisting of carbon fibers, glass fibers, and basalt fibers.

12. The prepreg according to claim 10 or 11, wherein the prepreg is a tow prepreg or a tape prepreg.

13. A fiber-reinforced composite material which is a cured product of the prepreg according to any one of claims 10 to 12.

14. A high pressure gas container comprising the fiber reinforced composite material of claim 13.

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