Epoxy resin composition

Abstract

An epoxy resin composition containing an epoxy resin (A) and an epoxy resin curing agent (B), the epoxy resin (A) containing an epoxy resin (A1) having a glycidyl group derived from resorcinol and an epoxy resin (A2), which is an epoxy resin having a glycidyl group derived from bisphenol F, or the like, and the epoxy resin curing agent (B) containing resorcinol (B1) or the like, the content of the epoxy resin curing agent (B) is 7-60 mass%.

Description

Technical Field

[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 comprising the fiber-reinforced composite material. Background Art

[0002] In recent years, natural gas vehicles (CNG vehicles) and fuel cell vehicles (FCVs) have become more popular due to their environmental protection. Fuel cell vehicles use fuel cells as their power source, and hydrogen stations are essential for compressing hydrogen, which is their fuel, to high pressure and filling the vehicle.

[0003] High-pressure gas storage tanks used as fuel cell vehicle hydrogen stations, CNG vehicles, fuel cell vehicles, etc., have been made of steel until now, but the development of lighter high-pressure gas storage tanks using resin materials for the inner lining or outer layer of the tank is being promoted. By making the fuel tank for the vehicle lighter, it has the advantage of improving the fuel consumption of the vehicle on which it is mounted.

[0004] As resin materials constituting high-pressure gas storage tanks, it is known to use resins having gas barrier properties and fiber reinforced composite materials (FRP) in which the resin is impregnated in reinforcing fibers. For example, as a method for manufacturing a pressure vessel having an inner liner and an outer layer of the inner liner, wherein the outer layer is composed of a composite material containing reinforcing fibers and a matrix resin, Patent Document 1 discloses the following scheme: a composite material is wound around the outer periphery of the inner liner by a filament winding method or a tape winding method to form an outer layer.

[0005] When the matrix resin in the composite material is a cured product of a thermosetting resin rather than a thermoplastic resin, the winding method can also be used. In this case, a continuous reinforcing fiber bundle impregnated with a thermosetting resin (tow prepreg) is wound around the periphery of the liner, and then heated and cured to form.

[0006] Prepregs using epoxy resin compositions as matrix resins are also known. For example, Patent Document 2 discloses an epoxy resin composition comprising an epoxy resin, a compound having two functional groups in the molecule, and a curing agent, wherein the functional group has one active hydrogen that reacts with an epoxy group; and a prepreg and a fiber-reinforced composite material in which the epoxy resin composition is impregnated into reinforcing fibers.

[0007] In addition, as a thermosetting resin composition having gas barrier properties, for example, Patent Document 3 discloses a composition comprising a meta-substituted aromatic resin and an additional aromatic epoxy resin and having an oxygen permeability below a predetermined value as an oxygen barrier composition for electrical parts.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: International Publication No. 2016 / 084475

[0011] Patent Document 2: Japanese Patent Application Publication No. 2002-284852

[0012] Patent Document 3: Japanese Patent Application No. 2012-533643 Summary of the invention

[0013] Problem that the invention aims to solve

[0014] In the preparation of a tow prepreg in which a thermosetting resin composition is impregnated in reinforcing fiber filaments, for example, the following method is adopted: the reinforcing fiber filaments are impregnated with the thermosetting resin composition by immersing the reinforcing fiber filaments in a resin tank storing the thermosetting resin composition. The same process is also performed in the manufacture of a pressure vessel using a filament winding method or a tape winding method.

[0015] However, in the above method, when the thermosetting resin composition is of high viscosity, the thermosetting resin composition cannot be fully impregnated into the reinforcing fiber filaments, and degassing is difficult. In addition, the thermosetting resin composition with a short shelf life will solidify during storage or during the manufacturing process (for example, during storage in a resin tank), so there is a problem that it cannot be applied. In addition, if the thermosetting resin composition solidifies too quickly, heat is released during curing, sometimes causing undesirable conditions such as scorching in the obtained molded body.

[0016] In addition, high-pressure gas containers for hydrogen storage such as hydrogen stations for fuel cell vehicles or onboard fuel tanks for CNG vehicles, fuel cell vehicles, etc. require high barrier properties against hydrogen. However, even if the thermosetting resin compositions disclosed in Patent Documents 1 to 3 are used, they are still insufficient to solve the above problems.

[0017] Therefore, an object of the present invention is to provide an epoxy resin composition and a cured product thereof, which have a long pot life and low viscosity and are therefore suitable for filament winding molding, resin transfer molding, and the production of tow prepregs, and which also have a long storage life and less occurrence of scorching during molding, and can achieve high hydrogen gas barrier properties, and a prepreg, a fiber-reinforced composite material, and a high-pressure gas container using the epoxy resin composition.

[0018] Solutions for solving problems

[0019] The present inventors have found that an epoxy resin composition using two specific epoxy resins as main epoxy resins and further containing a predetermined amount of resorcinol or a pre-reaction product of resorcinol, epoxy resin and curing accelerator as an epoxy resin curing agent can solve the above problems.

[0020] That is, the present invention relates to the following.

[0021] [1] An epoxy resin composition comprising: an epoxy resin (A) and an epoxy resin curing agent (B),

[0022] The epoxy resin (A) comprises an epoxy resin (A1) and an epoxy resin (A2),

[0023] The epoxy resin (A1) is an epoxy resin having a glycidyl group derived from resorcinol.

[0024] The epoxy resin (A2) is at least one selected from the group consisting of an epoxy resin having a glycidyl group derived from bisphenol F (a21), an epoxy resin having a glycidyl group derived from bisphenol A (a22), an epoxy resin having a glycidyl group derived from novolac phenol (a23), an epoxy resin having a glycidyl group derived from triphenylmethane type phenol (a24), an epoxy resin having a glycidyl group derived from a polyol having a naphthalene skeleton (a25), and an epoxy resin having an aminoglycidyl group (a26),

[0025] The epoxy resin curing agent (B) comprises at least one selected from the group consisting of resorcinol (B1) and a pre-reaction product (B2) obtained from resorcinol (B1), the epoxy resin (A) and a curing accelerator (C), wherein the pre-reaction product (B2) is a reaction product obtained by reacting 100 parts by mass of the resorcinol (B1), 1 to 40 parts by mass of the epoxy resin (A) and 0.01 to 5 parts by mass of the curing accelerator (C),

[0026] The content of the epoxy resin curing agent (B) is 7 to 60% by mass when the total amount of the epoxy resin (A) and the epoxy resin curing agent (B) in the epoxy resin composition is 100% by mass.

[0027] [2] The epoxy resin composition according to [1] above, wherein

[0028] The aforementioned epoxy resin curing agent (B) further comprises an epoxy resin curing agent (B3),

[0029] The epoxy resin curing agent (B3) is at least one selected from the group consisting of phenolic curing agents (b31) other than resorcinol (B1) and dihydrazide curing agents (b32).

[0030] [3] The epoxy resin composition according to [2] above, wherein

[0031] The phenolic curing agent (b31) other than resorcinol (B1) is at least one selected from the group consisting of bisphenol F, bisphenol A, novolac phenol and triphenylmethane-type phenol.

[0032] [4] The epoxy resin composition according to any one of [1] to [3] above, wherein

[0033] The mass ratio [(A1) / (A2)] of the epoxy resin (A1) to the epoxy resin (A2) contained in the epoxy resin (A) is 1 / 99 to 90 / 10.

[0034] [5] The epoxy resin composition according to any one of [1] to [4] above, wherein

[0035] The mass ratio [(A1) / (A2)] of the epoxy resin (A1) to the epoxy resin (A2) contained in the epoxy resin (A) is 20 / 80 to 90 / 10.

[0036] [6] The epoxy resin composition according to any one of [2] to [5] above, wherein

[0037] The mass ratio [((B1)+(B2)) / (B3)] of the total amount of resorcinol (B1) and the preliminary reaction product (B2) contained in the epoxy resin curing agent (B) to the epoxy resin curing agent (B3) is 8 / 92 to 100 / 0.

[0038] [7] The epoxy resin composition according to any one of [1] to [6] above, wherein

[0039] It also contains a curing accelerator (C),

[0040] The curing accelerator (C) is at least one selected from the group consisting of imidazoles, tertiary amines and phosphorus compounds.

[0041] [8] The epoxy resin composition according to any one of [1] to [7] above, further comprising a stress relaxing component (D).

[0042] [9] The epoxy resin composition according to any one of [1] to [8], wherein the hydrogen permeability coefficient of the cured product of the epoxy resin composition is 8.4×10 -11 [cc·cm / (cm 2 ·s·cmHg)] or less.

[0043]

[10] A cured product of the epoxy resin composition according to any one of [1] to [9] above.

[0044]

[11] A prepreg comprising reinforcing fibers impregnated with the epoxy resin composition according to any one of [1] to [9] above.

[0045]

[12] The prepreg according to

[11] above, wherein the reinforcing fiber is at least one selected from the group consisting of carbon fiber, glass fiber and basalt fiber.

[0046]

[13] The prepreg according to

[11] or

[12] above, which is a tow prepreg.

[0047]

[14] The prepreg according to

[11] or

[12] above, wherein the prepreg is a UD tape.

[0048]

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

[10] to

[14] above.

[0049]

[16] A high-pressure gas container comprising the fiber-reinforced composite material described in

[15] above.

[0050] Effects of the Invention

[0051] According to the present invention, an epoxy resin composition and a cured product thereof, which have a long pot life and low viscosity and are therefore suitable for filament winding molding, resin transfer molding, and the production of tow prepregs, have a long storage life, are less prone to scorching during molding, and can achieve high hydrogen barrier properties, a prepreg using the epoxy resin composition, a fiber-reinforced composite material, and a high-pressure gas container can be provided. The high-pressure gas container has high hydrogen barrier properties and is suitable as a container for storing high-pressure hydrogen. DETAILED DESCRIPTION

[0052] [Epoxy resin composition]

[0053] The epoxy resin composition of the present invention is an epoxy resin composition, which contains: an epoxy resin (A) and an epoxy resin curing agent (B),

[0054] The epoxy resin (A) comprises an epoxy resin (A1) and an epoxy resin (A2),

[0055] The epoxy resin (A1) is an epoxy resin having a glycidyl group derived from resorcinol.

[0056] The epoxy resin (A2) is at least one selected from the group consisting of an epoxy resin having a glycidyl group derived from bisphenol F (a21), an epoxy resin having a glycidyl group derived from bisphenol A (a22), an epoxy resin having a glycidyl group derived from novolac phenol (a23), an epoxy resin having a glycidyl group derived from triphenylmethane type phenol (a24), an epoxy resin having a glycidyl group derived from a polyol having a naphthalene skeleton (a25), and an epoxy resin having an aminoglycidyl group (a26),

[0057] The epoxy resin curing agent (B) comprises at least one selected from the group consisting of resorcinol (B1) and a pre-reaction product (B2) obtained from resorcinol (B1), the epoxy resin (A) and a curing accelerator (C), wherein the pre-reaction product (B2) is a reaction product obtained by reacting 100 parts by mass of the resorcinol (B1), 1 to 40 parts by mass of the epoxy resin (A) and 0.01 to 5 parts by mass of the curing accelerator (C), and the content of the epoxy resin curing agent (B) in the epoxy resin composition is 7 to 60% by mass.

[0058] The epoxy resin composition of the present invention has the above-mentioned structure, and thus has a long pot life, a low viscosity, a long storage life, little scorching during molding, and can achieve high hydrogen barrier properties.

[0059] The reason why the above-mentioned effects are obtained in the present invention is not certain, but is considered as follows.

[0060] The present inventors have found that an epoxy resin (A1) having a glycidyloxy group derived from resorcinol (hereinafter also referred to simply as "epoxy resin (A1)" or "component (A1)") has fast curing properties among epoxy resins and exhibits high hydrogen barrier properties.

[0061] On the other hand, the epoxy resin (A1) has a low epoxy equivalent and is fast curing, so it tends to react rapidly with the epoxy resin curing agent during heat curing and easily release heat. Therefore, if the content of the epoxy resin (A1) in the epoxy resin is too much, it will cause undesirable problems such as discoloration and scorching during heat molding. In addition, there are problems such as the resulting epoxy resin composition having a shorter pot life and storage life, and being unsuitable for the production of tow prepregs and the production of high-pressure gas containers using a filament winding method.

[0062] Here, epoxy resin (A2) such as epoxy resin having a glycidyl group derived from bisphenol F (hereinafter also referred to as "epoxy resin (A2)" or "component (A2")) is more likely to exhibit hydrogen barrier properties among epoxy resins, and further, heat generation during heat curing can be suppressed compared to epoxy resin (A1).

[0063] It is further considered that in the present invention, by using resorcinol (B1) or a preliminary reaction product (B2) obtained from resorcinol (B1), the aforementioned epoxy resin (A) and a curing accelerator (C) as an epoxy resin curing agent, the viscosity can be reduced and the application life and storage life can be improved without impairing the hydrogen barrier properties.

[0064] <Epoxy resin (A)>

[0065] 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 resorcinol, and the epoxy resin (A2) is at least one selected from the group consisting of an epoxy resin having a glycidyl group derived from bisphenol F (a21), an epoxy resin having a glycidyl group derived from bisphenol A (a22), an epoxy resin having a glycidyl group derived from novolac phenol (a23), an epoxy resin having a glycidyl group derived from triphenylmethane type phenol (a24), an epoxy resin having a glycidyl group derived from a polyol having a naphthalene skeleton (a25), and an epoxy resin having an aminoglycidyl group (a26). It is considered that this can provide an epoxy resin composition that suppresses the occurrence of scorching during molding and can achieve high hydrogen gas barrier properties.

[0066] (Epoxy resin (A1))

[0067] The epoxy resin (A1) is an epoxy resin having a glycidyl group derived from resorcinol. When the epoxy resin (A) contains the epoxy resin (A1), an epoxy resin composition capable of achieving high hydrogen gas barrier properties can be obtained.

[0068] The epoxy resin (A1) is typically resorcinol diglycidyl ether, and may contain an oligomer other than resorcinol diglycidyl ether.

[0069] As the epoxy resin (A1), a commercially available item such as "Denacol (registered trademark) EX-201" manufactured by Nagase ChemteX Corporation can be used.

[0070] The content of the epoxy resin (A1) in the epoxy resin (A) is preferably 1 to 90% by mass, more preferably 10 to 90% by mass, further preferably 20 to 90% by mass, further preferably 20 to 85% by mass, further preferably 20 to 80% by mass, further preferably 25 to 80% by mass, further preferably 25 to 75% by mass, further preferably 30 to 75% by mass, further preferably 40 to 70% by mass, further preferably 40 to 65% by mass. When the content of the epoxy resin (A1) in the epoxy resin (A) is within the above range, high hydrogen barrier properties are easily exhibited, and the occurrence of scorching during molding can be suppressed.

[0071] The epoxy equivalent of the epoxy resin (A1) of the epoxy resin (A) is preferably 200 g / equivalent or less, more preferably 150 g / equivalent or less, and further preferably 120 g / equivalent or less. It is preferably 90 g / equivalent or more, more preferably 100 g / equivalent or more, and further preferably 110 g / equivalent or more.

[0072] (Epoxy resin (A2))

[0073] The epoxy resin (A2) is at least one selected from the group consisting of an epoxy resin having a glycidyl group derived from bisphenol F (a21), an epoxy resin having a glycidyl group derived from bisphenol A (a22), an epoxy resin having a glycidyl group derived from novolac phenol (a23), an epoxy resin having a glycidyl group derived from triphenylmethane type phenol (a24), an epoxy resin having a glycidyl group derived from a polyol having a naphthalene skeleton (a25), and an epoxy resin having an aminoglycidyl group (a26). One or more epoxy resins (A2) can be used. It is believed that by using the epoxy resin (A2), an epoxy resin composition that suppresses the occurrence of scorching during molding and can achieve high hydrogen barrier properties can be obtained.

[0074] 〔Epoxy resin (a21)〕

[0075] The epoxy resin (a21) is an epoxy resin having a glycidyl group derived from bisphenol F. The epoxy resin (a21) is typically bisphenol F diglycidyl ether, and may contain oligomers in addition to bisphenol F diglycidyl ether. One or more epoxy resins (a21) may be used.

[0076] As the epoxy resin (a21), commercially available products such as "jER (registered trademark) 807" and "jER (registered trademark) 4005P" manufactured by Mitsubishi Chemical Corporation can be used.

[0077] 〔Epoxy resin (a22)〕

[0078] The epoxy resin (a22) is an epoxy resin having a glycidyl group derived from bisphenol A. The epoxy resin (a22) is typically bisphenol A diglycidyl ether, and may contain oligomers in addition to bisphenol A diglycidyl ether. One or more epoxy resins (a22) may be used.

[0079] As the epoxy resin (a22), commercially available products such as "jER828", "jER (registered trademark) 834", and "jER (registered trademark) 1001" manufactured by Mitsubishi Chemical Corporation can be used.

[0080] 〔Epoxy resin (a23)〕

[0081] The epoxy resin (a23) is an epoxy resin having a glycidyl group derived from novolac phenol. The epoxy resin (a23) is typically a resin synthesized using a phenol novolac resin and epichlorohydrin.

[0082] The epoxy resin (a23) can be used alone or in combination of two or more.

[0083] Among epoxy resins (a23), from the viewpoint of obtaining a low-viscosity epoxy resin composition, low-molecular-weight epoxy resins (a23) are preferred. The molecular weight of epoxy resin (a23) is preferably 400 to 1500, more preferably 400 to 1000, and further preferably 400 to 900. In addition, from the viewpoint of operability, low-viscosity epoxy resins (a23) are preferred. The melt viscosity (150°C) of epoxy resin (a23) is preferably 9.0 Pa·s or less, more preferably 6.0 Pa·s or less, and further preferably 3.0 Pa·s or less.

[0084] As the epoxy resin (a23), commercially available products such as EPICLON (registered trademark) series "N730A", "N740", "N770", "N775", and "N865" manufactured by DIC Corporation can be used.

[0085] 〔Epoxy resin (a24)〕

[0086] The epoxy resin (a24) is an epoxy resin having a glycidyl group and derived from triphenylmethane-type phenol. One or more of the epoxy resins (a24) can be used.

[0087] As the epoxy resin (a24), commercially available products such as EPICLON (registered trademark) series "HP7250" and "HP7241" manufactured by DIC Corporation can be used.

[0088] 〔Epoxy resin (a25)〕

[0089] The epoxy resin (a25) is an epoxy resin having a glycidyloxy 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.

[0090] Furthermore, the number of glycidyloxy groups in the epoxy resin is preferably 2 to 4, more preferably 2 to 3, from the viewpoint of obtaining an epoxy resin composition having a long pot life and a long storage life and realizing high hydrogen barrier properties.

[0091] As the epoxy resin (a25), preferably, there can be mentioned an epoxy resin represented by any of the following general formulas (a251) and (a252).

[0092]

[0093] (In the formula, n is 1 to 3.)

[0094]

[0095] (In the formula, m1 is 0 to 2, m2 is 0 to 2, and the sum of m1 and m2 is 0 to 3.)

[0096] In the general formula (a251), n ​​is preferably 1 or 2, more preferably 1.

[0097] In the general formula (a252), m1 is preferably 0 or 1, m2 is preferably 0 or 1, and the total of m1 and m2 is preferably 0 to 2, more preferably 0.

[0098] More specifically, the epoxy resin (a25) may be an epoxy resin represented by any of the following formulae (a253) to (a256).

[0099]

[0100]

[0101] As the epoxy resin (a25), commercial products may also be used. For example, EPICLON (registered trademark) series "HP-4032SS" (epoxy resin represented by formula (a253)), "HP-4700", "HP-4710" (the above, epoxy resin represented by formula (a256)), "EXA-4750" (epoxy resin represented by formula (a255)), "HP-4770" (epoxy resin represented by formula (a254)), "HP-5000", "HP-9900-75M", "HP-9500" and the like manufactured by DIC Corporation can be cited.

[0102] One or more epoxy resins (a25) can be used. Among the above, from the viewpoint of obtaining an epoxy resin composition having a long pot life and a long storage life and being able to achieve high hydrogen barrier properties, the epoxy resin (a25) is preferably an epoxy resin represented by the above-mentioned general formula (a251), and more preferably an epoxy resin represented by the above-mentioned formula (a253).

[0103] 〔Epoxy resin (a26)〕

[0104] The epoxy resin (a26) is an epoxy resin having an aminoglycidyl group.

[0105] Examples of the epoxy resin (a26) include epoxy resins having a glycidylamino group derived from m-phenylenediamine, epoxy resins having a glycidylamino group derived from p-phenylenediamine, epoxy resins having a glycidylamino group derived from diaminodiphenylmethane, epoxy resins having a glycidylamino group derived from p-aminophenol, etc. The epoxy resin (a26) may be used alone or in combination of two or more.

[0106] As the epoxy resin (a26), commercially available products such as “TETRAD-X (registered trademark)” (N,N,N′,N′-tetraglycidyl-m-xylenediamine) and “TETRAD (registered trademark)-C” (1,3-bis(N,N-diglycidylaminomethyl)cyclohexane) manufactured by Mitsubishi Gas Chemical Co., Ltd. can be used.

[0107] From the viewpoint of obtaining an epoxy resin composition having a low viscosity and having high hydrogen barrier properties, the epoxy resin (A2) preferably contains at least one selected from the group consisting of an epoxy resin (a21) and an epoxy resin (a23), more preferably contains the epoxy resin (a23), and further preferably contains the epoxy resin (a21) and the epoxy resin (a23).

[0108] The content of the epoxy resin (A2) in the epoxy resin (A) is preferably 10 to 99% by mass, more preferably 10 to 90% by mass, further preferably 10 to 80% by mass, further preferably 15 to 80% by mass, further preferably 20 to 80% by mass, further preferably 25 to 80% by mass, further preferably 25 to 70% by mass, further preferably 30 to 60% by mass, further preferably 40 to 60% by mass. When the content of the epoxy resin (A2) in the epoxy resin (A) is 10% by mass or more, the occurrence of scorching during molding can be suppressed, and when it is 99% by mass or less, an epoxy resin composition can be obtained that does not impair the hydrogen barrier properties derived from the epoxy resin (A1).

[0109] The epoxy equivalent of the epoxy resin (A2) of the epoxy resin (A) is preferably 1200 g / equivalent or less, more preferably 500 g / equivalent or less, further preferably 250 g / equivalent or less, further preferably 220 g / equivalent or less, further preferably 200 g / equivalent or less. In addition, it is preferably 120 g / equivalent or more, more preferably 130 g / equivalent or more, further preferably 140 g / equivalent or more, further preferably 150 g / equivalent or more, further preferably 170 g / equivalent or more.

[0110] The mass ratio [(A1) / (A2)] of the epoxy resin (A1) to the epoxy resin (A2) contained in the epoxy resin (A) is preferably 1 / 99 to 90 / 10, more preferably 10 / 90 to 90 / 10, further preferably 15 / 85 to 90 / 10, further preferably 20 / 80 to 90 / 10, further preferably 20 / 80 to 85 / 15, further more preferably 25 / 75 to 80 / 20, further preferably 30 / 70 to 75 / 25, further preferably 40 / 60 to 70 / 30, further preferably 40 / 60 to 65 / 35, further preferably 40 / 60 to 60 / 40.

[0111] The epoxy resin (A) may also contain epoxy resins 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 aliphatic epoxy resins having no aromatic ring. Examples of aliphatic epoxy resins having no aromatic ring include chain aliphatic epoxy resins and aliphatic epoxy resins having an alicyclic structure.

[0112] Among them, from the viewpoint of exhibiting high hydrogen 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, further preferably 90% by mass or more, and still further preferably 95% by mass or more, and is 100% by mass or less.

[0113] From the viewpoint of curability, the epoxy equivalent of the epoxy resin (A) is preferably 400 g / equivalent or less, more preferably 300 g / equivalent or less, further preferably 250 g / equivalent or less, further preferably 220 g / equivalent or less, further preferably 200 g / equivalent or less. In addition, from the viewpoint of suppressing the occurrence of scorching during molding, it is preferably 100 g / equivalent or more, more preferably 110 g / equivalent or more, further preferably 120 g / equivalent or more.

[0114] <Epoxy resin curing agent (B)>

[0115] The epoxy resin curing agent (B) used in the epoxy resin composition of the present invention comprises at least one selected from the group consisting of resorcinol (B1) and a pre-reaction product (B2) obtained from resorcinol (B1), the epoxy resin (A) and a curing accelerator (C), wherein the pre-reaction product (B2) is a reaction product obtained by reacting 100 parts by mass of the resorcinol (B1), 1 to 40 parts by mass of the epoxy resin (A) and 0.01 to 5 parts by mass of the curing accelerator (C), and the content of the epoxy resin curing agent (B) in the epoxy resin composition is 7 to 60% by mass. It is believed that this can form a low viscosity, suppress heat generation during molding, and improve the pot life and storage life.

[0116] (Resorcinol (B1), and a preliminary reaction product (B2) obtained from resorcinol (B1), the aforementioned epoxy resin (A) and a curing accelerator (C))

[0117] In the present invention, the epoxy resin curing agent (B) comprises at least one selected from the group consisting of resorcinol (B1) and a preliminary reaction product (B2) obtained from resorcinol (B1), the aforementioned epoxy resin (A) and a curing accelerator (C). Among these, resorcinol (B1) is preferred.

[0118] Resorcinol (B1) is 1,3-dihydroxybenzene.

[0119] The preliminary reaction product (B2) obtained from resorcinol (B1), the aforementioned epoxy resin (A) and a curing accelerator (C) is a reaction product obtained by reacting 100 parts by mass of resorcinol (B1), 1 to 40 parts by mass of the aforementioned epoxy resin (A) and 0.01 to 5 parts by mass of a curing accelerator (C).

[0120] Here, the curing accelerator (C) is the same as the curing accelerator (C) that may be arbitrarily contained in the epoxy resin composition of the present invention described later. As the curing accelerator (C) used in the preliminary reaction product (B2), at least one selected from the group consisting of imidazoles, tertiary amines and phosphorus compounds is preferred.

[0121] Examples of the imidazoles include 1-cyanoethyl-2-ethyl-4-methylimidazole and 2-ethyl-4-methylimidazole.

[0122] Examples of the tertiary amines include tertiary amines or salts thereof that can accelerate curing with a phenolic curing agent, such as 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]-nonene-5 (DBN), and tris(dimethylaminomethylphenol).

[0123] Examples of the phosphorus compound include phosphine compounds such as triphenylphosphine and phosphonium salts such as tetraphenylphosphonium and tetraphenylborate.

[0124] The amount of the epoxy resin (A) to be reacted with resorcinol (B1) is preferably 1 to 40 parts by mass, more preferably 1 to 35 parts by mass, further preferably 1 to 30 parts by mass, and further preferably 1 to 25 parts by mass, based on 100 parts by mass of resorcinol (B1).

[0125] The amount of the curing accelerator (C) to be reacted with resorcinol (B1) is preferably 0.01 to 5 parts by mass, more preferably 0.01 to 4 parts by mass, further preferably 0.01 to 3 parts by mass, and further preferably 0.01 to 2 parts by mass, based on 100 parts by mass.

[0126] As a method for producing the preliminary reaction product (B2), that is, a method for reacting resorcinol (B1), the aforementioned epoxy resin (A) and a curing accelerator (C), the following method can be cited: resorcinol (B1), the aforementioned epoxy resin (A) and the curing accelerator (C) are mixed under conditions of preferably 0 to 160° C., more preferably 0 to 140° C., preferably for 1 to 24 hours, more preferably 1 to 15 hours, and the addition reaction is carried out while stirring the component (A), the component (B) and the curing accelerator (C).

[0127] The total content of resorcinol (B1) and the preliminary reaction product (B2) obtained from resorcinol (B1), the aforementioned epoxy resin (A) and the curing accelerator (C) in the epoxy resin curing agent (B) is preferably 50% by mass or more, more preferably 60% by mass or more, further preferably 70% by mass or more, further preferably 80% by mass or more, further preferably 85% by mass or more, further preferably 90% by mass or more, further preferably 95% by mass or more, and is 100% by mass or less, from the viewpoint of forming a low viscosity, suppressing heat generation during molding, and improving the pot life and storage life.

[0128] The epoxy resin curing agent (B) may also contain epoxy resin curing agents other than resorcinol (B1) or a pre-reaction product (B2) obtained from resorcinol (B1), the aforementioned epoxy resin (A) and a curing accelerator (C) within the range that does not impair the effect of the present invention. As epoxy resin curing agents other than resorcinol (B1) or a pre-reaction product (B2) obtained from resorcinol (B1), the aforementioned epoxy resin (A) and a curing accelerator (C), compounds having two or more groups with active hydrogen that can react with the epoxy group in the epoxy resin (A) can be cited. As the type of the epoxy resin curing agent, phenolic curing agents, hydrazide curing agents, anhydride curing agents, etc. other than resorcinol (B1) can be cited. Among these, phenolic curing agents other than resorcinol (B1) and hydrazide curing agents are preferred. Next, these are explained.

[0129] (Epoxy resin curing agent (B3))

[0130] The epoxy resin curing agent (B) further comprises an epoxy resin curing agent (B3) as an epoxy resin curing agent other than resorcinol (B1) or a pre-reaction product (B2) obtained by resorcinol (B1), the aforementioned epoxy resin (A) and a curing accelerator (C), wherein the aforementioned epoxy resin curing agent (B3) is at least one selected from the group consisting of a phenolic curing agent (b31) other than resorcinol (B1) and a dihydrazide curing agent (b32). It is believed that by including these curing agents, low viscosity can be maintained, heat generation during molding can be suppressed, and the application period and storage period can be improved. The epoxy resin curing agent (B3) is more preferably a phenolic curing agent (b31) other than resorcinol (B1).

[0131] (Phenolic curing agent (b31) other than resorcinol (B1))

[0132] The phenolic curing agent (b31) is preferably at least one selected from the group consisting of bisphenol F, bisphenol A, novolac phenol and triphenylmethane phenol. From the viewpoint of curability and high hydrogen barrier properties, novolac phenol is more preferred as the phenolic curing agent (b31).

[0133] The hydroxyl equivalent of the phenolic curing agent (b31) is generally 90 g / equivalent or more, preferably 100 g / equivalent or more, and from the viewpoint of curability and high hydrogen barrier properties, it is preferably 160 g / equivalent or less, more preferably 150 g / equivalent or less, further preferably 130 g / equivalent or less, and further preferably 120 g / equivalent or less.

[0134] From the viewpoint of curability and the viewpoint of exhibiting high hydrogen barrier properties, the softening point of the phenolic curing agent is preferably 70 to 250° C., more preferably 75 to 240° C., further preferably 75 to 200° C., further preferably 75 to 120° C., further preferably 75 to 100° C. The softening point can be measured, for example, using a thermomechanical analyzer (TMA).

[0135] As the phenolic curing agent, commercially available products may be used, for example, PHENOLITE (registered trademark) series "TD-2131", "TD-2106", "TD-2093", "TD-2091", "TD-2090", "VH-4150", "VH-4170", "KH-6021", "KA-1160", "KA-1163", "KA-1165" and the like manufactured by DIC Corporation may be cited.

[0136] (Dihydrazide curing agent (b32))

[0137] Examples of the dihydrazide curing agent (b32) include carboxylic acid hydrazides such as adipic acid dihydrazide, and bisaminozide obtained by reacting diisocyanate with hydrazine. Among them, carboxylic acid hydrazides are preferred, and adipic acid dihydrazide is more preferred.

[0138] The epoxy resin curing agent (B3) may be a phenolic curing agent (b31) other than resorcinol (B1) and a dihydrazide curing agent (b32) alone, or both of them may be used. The content of the phenolic curing agent (b31) other than resorcinol (B1) in the epoxy resin curing agent (B3) is preferably 70% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, and further preferably 95% by mass or more, and is less than 100% by mass.

[0139] The mass ratio of the total amount of resorcinol (B1) and the pre-reaction product (B2) contained in the aforementioned epoxy resin curing agent (B) to the epoxy resin curing agent (B3) [((B1)+(B2)) / (B3)] is preferably 8 / 92 to 100 / 0, more preferably 50 / 50 to 100 / 0, further preferably 60 / 40 to 100 / 0, further preferably 70 / 30 to 100 / 0, further preferably 80 / 20 to 100 / 0.

[0140] In particular, the mass ratio [(B1) / (B3)] of resorcinol (B1) to epoxy resin curing agent (B3) contained in the aforementioned epoxy resin curing agent (B) is preferably 8 / 92 to 100 / 0, more preferably 50 / 50 to 100 / 0, further preferably 60 / 40 to 100 / 0, further preferably 70 / 30 to 100 / 0, further preferably 80 / 20 to 100 / 0.

[0141] <Curing accelerator (C)>

[0142] The epoxy resin composition of the present invention may further contain a curing accelerator (C) as necessary. From the viewpoint of accelerating curing, it is preferred to further use a curing accelerator (C).

[0143] As the curing accelerator (C), at least one selected from the group consisting of imidazoles, tertiary amines and phosphorus compounds is preferred.

[0144] Examples of the imidazoles include 1-cyanoethyl-2-ethyl-4-methylimidazole and 2-ethyl-4-methylimidazole.

[0145] Examples of the tertiary amines include tertiary amines or salts thereof that can accelerate curing with a phenolic curing agent, such as 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]-nonene-5 (DBN), and tris(dimethylaminomethylphenol).

[0146] Examples of the phosphorus compound include phosphine compounds such as triphenylphosphine and phosphonium salts such as tetraphenylphosphonium and tetraphenylborate.

[0147] One or more curing accelerators (C) may be used. Among the above, from the viewpoint of improving curability, at least one selected from the group consisting of imidazoles and tertiary amines is preferred, imidazoles are more preferred, and at least one selected from the group consisting of 1-cyanoethyl-2-ethyl-4-methylimidazole and 2-ethyl-4-methylimidazole is further preferred.

[0148] <Solvents>

[0149] The epoxy resin composition of the present invention may further contain a solvent from the viewpoint of lowering the viscosity of the composition and improving the impregnation property into reinforcing fibers when used for the preparation of a prepreg.

[0150] Examples of the solvent include alcohol 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 solvents such as ethyl acetate and butyl acetate; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ether solvents such as diethyl ether and diisopropyl ether; hydrocarbon solvents such as toluene, and one or more of them can be used.

[0151] From the viewpoint of solubility of components (A) to (C) contained in the epoxy resin composition and the viewpoint of ease of removal of the solvent, the solvent is preferably at least one selected from the group consisting of alcohol solvents, ester solvents, ketone solvents and hydrocarbon solvents having a carbon number of 8 or less, 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.

[0152] <Content of each ingredient and other ingredients>

[0153] For the epoxy resin composition of the present invention, the content of the epoxy resin curing agent (B) is 7 to 60% by mass when the total amount of the epoxy resin (A) and the epoxy resin curing agent (B) in the epoxy resin composition is set to 100% by mass. That is, when the total amount of the epoxy resin (A) and the epoxy resin curing agent (B) is set to 100% by mass, the content of the epoxy resin curing agent (B) is 7 to 60% by mass. By making the content of the epoxy resin curing agent (B) within this range, an epoxy resin composition with excellent hydrogen barrier properties and low viscosity can be formed. At the same time, the storage period can be improved, and the occurrence of scorching during molding can also be reduced.

[0154] When the total amount of the epoxy resin (A) and the epoxy resin curing agent (B) is 100% by mass, the content of the epoxy resin curing agent (B) is preferably 10 to 60% by mass, more preferably 15 to 60% by mass, further preferably 20 to 50% by mass, further preferably 20 to 40% by mass, further preferably 25 to 40% by mass, further preferably 30 to 40% by mass.

[0155] When at least one selected from the group consisting of resorcinol (B1) and a pre-reaction product (B2) obtained from resorcinol (B1), the epoxy resin (A) and a curing accelerator (C) is used as the epoxy resin curing agent (B), the total content of resorcinol (B1) and the pre-reaction product (B2) obtained from resorcinol (B1), the epoxy resin (A) and the curing accelerator (C) is preferably 7 to 60% by mass when the total amount of the epoxy resin (A) and the epoxy resin curing agent (B) in the epoxy resin composition is 100% by mass. That is, when the total amount of the epoxy resin (A) and the epoxy resin curing agent (B) is 100% by mass, the content of resorcinol (B1) and the pre-reaction product (B2) obtained from resorcinol (B1), the epoxy resin (A) and the curing accelerator (C) is preferably 7 to 60% by mass. By setting the total content of resorcinol (B1) and the pre-reaction product (B2) within this range, an epoxy resin composition having excellent hydrogen barrier properties and low viscosity can be formed, while also improving the shelf life and reducing the occurrence of scorching during molding.

[0156] When the total amount of the epoxy resin (A) and the epoxy resin curing agent (B) is set to 100% by mass, the total content of resorcinol (B1) and the aforementioned preliminary reaction product (B2) is preferably 10 to 60% by mass, more preferably 15 to 60% by mass, further preferably 20 to 50% by mass, further preferably 20 to 40% by mass, further preferably 25 to 40% by mass, further preferably 30 to 40% by mass.

[0157] Furthermore, when only resorcinol (B1) is used as the epoxy resin curing agent (B), for the epoxy resin composition of the present invention, the content of resorcinol (B1) is preferably 7 to 60% by mass when the total amount of the epoxy resin (A) and the epoxy resin curing agent (B) in the epoxy resin composition is set to 100% by mass. That is, when the total amount of the epoxy resin (A) and the epoxy resin curing agent (B) is set to 100% by mass, the content of resorcinol (B1) is preferably 7 to 60% by mass. By making the content of resorcinol (B1) within this range, an epoxy resin composition with excellent hydrogen barrier properties and low viscosity can be formed. At the same time, the storage period can be improved, and the occurrence of scorching during molding can also be reduced.

[0158] When only resorcinol (B1) is used as the epoxy resin curing agent (B), the content of resorcinol (B1) is preferably 10 to 60 mass%, more preferably 15 to 60 mass%, further preferably 20 to 50 mass%, further preferably 20 to 40 mass%, further preferably 30 to 40 mass%, when the total amount of the epoxy resin (A) and the epoxy resin curing agent (B) is set to 100 mass%.

[0159] 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 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. As long as the ratio is ultimately within the above range, it may be constant or variable during the molding of the epoxy resin composition.

[0160] The content of the epoxy resin (A) in the epoxy resin composition of the present invention is not limited as long as the content ratio of the epoxy resin (A) to the epoxy resin curing agent (B) is preferably within the above range, and is preferably 40 to 90% by mass, more preferably 50 to 80% by mass, and further preferably 60 to 75% by mass in 100% by mass of the solid content in the epoxy resin composition. It should be noted that the "solid content in the epoxy resin composition" refers to the amount of water and organic solvents removed from the total amount of the epoxy resin composition.

[0161] When the epoxy resin composition does not contain a solvent, the content of the epoxy resin (A) in the epoxy resin composition is preferably 40 to 90% by mass, more preferably 50 to 80% by mass, and further preferably 60 to 75% by mass.

[0162] From the viewpoint of improving curability, the content of the curing accelerator (C) in the epoxy resin composition of the present invention is preferably 0.01 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, and even more preferably 0.05 to 1 part by mass based on 100 parts by mass of the epoxy resin (A).

[0163] It should be noted that the content of the curing accelerator (C) shown here does not include the amount of the curing accelerator (C) contained in the preliminary reaction product (B2).

[0164] When the epoxy resin composition contains a solvent, the content thereof is not particularly limited. However, from the viewpoint of lowering the viscosity of the composition and improving the impregnation property into the reinforcing fibers when used for the preparation of the prepreg, the content is preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 15% by mass or more in the epoxy resin composition. From the viewpoint of easy removal of the solvent, the content is preferably 95% by mass or less, more preferably 90% by mass or less, further preferably 80% by mass or less, and further preferably 70% by mass or less.

[0165] For 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, from the viewpoint of effectively reflecting the effect of the present invention, in 100% by mass of the solid content in the epoxy resin composition, preferably 70% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, further preferably 95% by mass or more, is 100% by mass or less. When the epoxy resin composition does not contain a solvent, the total content of the epoxy resin (A), epoxy resin curing agent (B) and curing accelerator (C) in the epoxy resin composition is preferably 70% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, further preferably 95% by mass or more, is 100% by mass or less.

[0166] In the epoxy resin composition of the present invention, other components such as fillers, modifying components such as plasticizers, flow regulating components such as thixotropic agents, reactive or non-reactive diluents, pigments, leveling agents, tackifiers, flame retardants, and stress relaxation components may be further contained according to the application. Among these, in the epoxy resin composition of the present invention, it is preferred to further include stress relaxation components (D). By including stress relaxation components (D), elastic modulus can be reduced, cracks can be suppressed, so it is preferred.

[0167] The stress relaxing component (D) is preferably at least one selected from the group consisting of silicone resins, butyl acrylate resins, polyetheramine resins, elastomer particles, thermoplastic resins, functional group-modified thermoplastic resins, rubber resins, and functional group-modified rubber resins, and more preferably elastomer particles and functional group-modified rubber resins.

[0168] The elastomer particles are preferably at least one selected from the group consisting of silicone particles, polydiene particles, butyl acrylate particles, polyetheramine particles, and other rubber particles, and silicone particles and polydiene particles are more preferred.

[0169] The functional group-modified rubber resin is preferably an epoxidized polydiene resin.

[0170] The content of the stress relaxing component (D) in the epoxy resin composition of the present invention is preferably 1% by mass or more, more preferably 3% by mass or more, further preferably 4% by mass or more, and further preferably 8% by mass or more, based on 100% by mass of the solid content in the epoxy resin composition, from the viewpoint of reducing the elastic modulus. In addition, from the viewpoint of reducing the elastic modulus, it is preferably 30% by mass or less, more preferably 20% by mass or less, further preferably 15% by mass or less, and further preferably 12% by mass or less.

[0171] It should be noted that, from the viewpoint of using the epoxy resin composition of the present invention for the preparation of the prepreg and fiber-reinforced composite material described later, and from the viewpoint of improving the impregnation property of the reinforcing fiber, it is preferred that the content of the filler in the epoxy resin composition is small. The content of the filler in the epoxy resin composition is preferably 30% by mass or less, more preferably 20% by mass or less, further preferably 15% by mass or less, further preferably 10% by mass or less, further preferably 5% by mass or less, and further preferably 0% by mass. As the filler, for example, inorganic powders such as silica powder and alumina powder can be cited.

[0172] <Hydrogen permeability coefficient>

[0173] 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 8.4×10 -11 [cc·cm / (cm 2 ·s·cmHg)] or less, more 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, more preferably 5.0×10 -11 [cc·cm / (cm 2 ·s·cmHg)] or less, more preferably 3.5×10 -11 [cc·cm / (cm 2 ·s·cmHg)] or less, more preferably 3.0×10 -11 [cc·cm / (cm 2 ·s·cmHg)] or less, more preferably 2.0×10 -11 [cc·cm / (cm 2 ·s·cmHg)] or less.

[0174] The hydrogen 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 according to the method described in Examples.

[0175] <Applicable period>

[0176] 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, further preferably 12 hours or more, and further preferably 24 hours or more. Specifically, the pot life of the epoxy resin composition can be measured by the method described in the Examples.

[0177] <Storage period>

[0178] 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 specifically measured by the method described in the Examples.

[0179] The preparation method of the epoxy resin composition of the present invention is not particularly limited, and the epoxy resin (A), the epoxy resin curing agent (B) and other components as required can be mixed using a known method and apparatus to prepare the epoxy resin composition. The mixing order of the components contained in the epoxy resin composition is also not particularly limited, and the components (A1) and (A2) constituting the epoxy resin (A) can be mixed and then mixed with other components, or the components (A1), (A2) and other components constituting the epoxy resin (A) can be mixed simultaneously to prepare the epoxy resin composition.

[0180] From the viewpoint of avoiding gelation before use, it is preferred that the components contained in the epoxy resin composition be brought into contact and mixed immediately before use. The temperature when mixing the components contained in the epoxy resin composition can be appropriately adjusted according to the viscosity of the epoxy resin. From the viewpoint of suppressing the increase in viscosity, it is preferably 120°C or less, more preferably 100°C or less, and from the viewpoint of the miscibility of the epoxy resin, it is preferably 20°C or more, more preferably 25°C or more. In addition, the mixing time is preferably in the range of 0.1 to 15 minutes, more preferably 0.2 to 10 minutes, and even more preferably 0.3 to 5 minutes.

[0181] [cured material]

[0182] The cured product of the epoxy resin composition of the present invention (hereinafter also referred to as "cured product of the present invention") is obtained by curing the epoxy resin composition of the present invention described above by a known method. The curing conditions of the epoxy resin composition are appropriately selected according to the application and form, and are not particularly limited.

[0183] The form of the cured product of the present invention is not particularly limited and can be selected according to the purpose. For example, when the epoxy resin composition is used as a coating, the cured product of the composition is usually film-like. It should be noted that from the viewpoint of effectively exerting the effect of the present invention, the cured product of the present invention is preferably the matrix resin of the fiber-reinforced composite material described later.

[0184] [Prepreg]

[0185] The prepreg of the present invention is obtained by impregnating reinforcing fibers with the epoxy resin composition.

[0186] <Reinforcement Fiber>

[0187] As the form of reinforcing fibers used in the prepreg, short fibers, long fibers, and continuous fibers can be cited. Among these, from the viewpoint of using the obtained prepreg to manufacture a high-pressure gas container by a filament winding method or a tape winding method, long fibers or continuous fibers are preferred, and continuous fibers are more preferred.

[0188] It should be noted that 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. In addition, continuous fibers refer to fiber bundles having a fiber length exceeding 100 mm.

[0189] Examples of the shape of the continuous fibers include tows, sheets, and tapes. Examples of the continuous fibers constituting the sheets or tapes include unidirectional (UD) materials, woven fabrics, and nonwoven fabrics.

[0190] From the viewpoint of manufacturing a high-pressure gas container using a prepreg by a filament winding method or a tape winding method, the shape of the continuous fiber is preferably a tow or a tape, and more preferably a tow. From the viewpoint of easily obtaining high strength and high elastic modulus, the number of continuous fiber bundles (number of filaments) constituting the tow is preferably 3K to 50K, and more preferably 6K to 40K.

[0191] In the continuous fibers, the average fiber length of the continuous fiber bundle is not particularly limited, but is preferably 1 to 10,000 m, more preferably 100 to 10,000 m, from the viewpoint of molding processability.

[0192] From the viewpoint of molding processability and the viewpoint of easily obtaining high strength and high elastic modulus, the average fineness of the continuous fiber bundle is preferably 50 to 2000 tex (g / 1000 m), more preferably 200 to 1500 tex, and even more preferably 500 to 1500 tex.

[0193] Furthermore, the average tensile elastic modulus of the continuous fiber bundle is preferably 50 to 1000 GPa.

[0194] As the material of reinforcing fiber, inorganic fibers such as carbon fiber, glass fiber, basalt fiber, metal fiber, boron fiber, ceramic fiber, etc. can be listed; organic fibers such as aramid fiber, polyoxymethylene fiber, aromatic polyamide fiber, polyparaphenylene benzobisoxazole fiber, ultra-high molecular weight polyethylene fiber. Among these, from the viewpoint of obtaining high strength, inorganic fiber is preferred. From the aspect of light weight and high strength, high elastic modulus, reinforcing fiber is preferably selected from at least one of the group consisting of carbon fiber, glass fiber and basalt fiber, from the viewpoint of strength and lightness, more preferably carbon fiber.

[0195] Examples of the carbon fiber include polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, etc. In addition, carbon fibers made from plant-derived raw materials such as lignin and cellulose may also be used.

[0196] The reinforcing fibers may be treated with a treatment agent. Examples of the treatment agent include a surface treatment agent and a sizing agent.

[0197] The surface treatment agent is preferably a silane coupling agent, and examples thereof 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)acryloyl group, and a silane coupling agent having a mercapto group.

[0198] Examples of the sizing agent include urethane sizing agents, epoxy sizing agents, acrylic sizing agents, polyester sizing agents, vinyl ester sizing agents, polyolefin sizing agents, polyether sizing agents, and carboxylic acid sizing agents, and one or more of these sizing agents may be used in combination. Examples of sizing agents used in combination of two or more of these sizing agents include urethane / epoxy sizing agents, urethane / acrylic sizing agents, and urethane / carboxylic acid sizing agents.

[0199] From the viewpoint of improving the interfacial adhesion with the cured product of the epoxy resin composition and further improving the strength and impact resistance of the obtained prepreg and composite material, 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 based on the reinforcing fiber.

[0200] As reinforcing fibers, commercial products may also be used. Commercial products of continuous carbon fibers (tows) include, for example, Torayca (registered trademark) yarns "T300", "T300B", "T400HB", "T700SC", "T800SC", "T800HB", "T830HB", "T1000GB", "T100GC", "M35JB", "M40JB", "M46JB", "M50JB", "M55J", "M55JB", "M60JB", "M30SC", "Z600" series, etc. manufactured by Toray Industries, Ltd.; Tenax (registered trademark) "HTA40" series, "HTS40" series, "HT40" series, "HT50" series, etc. manufactured by Teijin Limited. "S45" series, "HTS45P12" 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, "HTS40MC" series, etc.; carbon fiber tows of PYROFIL (registered trademark) "HT", "IM", and "HM" series, GRAFIL (registered trademark) "HT" series, and "DIALEAD (registered trademark)" series manufactured by Mitsubishi Chemical Corporation; etc.

[0201] In addition, as commercially available products of continuous carbon fibers other than tows, 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 manufactured by Toray Industries, Ltd. can be cited. "M40JB" series, "M46JB" series, "M50JB" series, "M55J" series, "M55JB" series, "M60JB" series, "M30SC" series, "Z600GT" series; PYROFIL (registered trademark) "TR3110M", "TR3523M", "TR3524M", "TR6110HM", "TR6120HM", "TRK101M", "TRK510M", "TR3160TMS", "TRK979PQRW", "TRK976PQRW", "TR6185HM", "TRK180M" and other carbon fiber fabrics manufactured by Mitsubishi Chemical Corporation; etc.

[0202] <Content>

[0203] 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 the range of 0.10 or more, more preferably 0.20 or more, further preferably 0.30 or more, and further preferably 0.40 or more in volume fraction. From the viewpoint of hydrogen barrier properties, impact resistance, and molding processability, it is preferably in the range of 0.85 or less, more preferably 0.80 or less, and further preferably 0.70 or less.

[0204] The volume fraction Vf1 of the reinforcing fibers in the prepreg can be calculated by the following formula.

[0205] Vf1 = {mass of reinforcing fiber (g) / specific gravity of reinforcing fiber} ÷ [{mass of reinforcing fiber (g) / specific gravity of reinforcing fiber} + {mass of solid content of epoxy resin composition impregnated (g) / specific gravity of solid content of epoxy resin composition}]

[0206] In order to obtain the effects of the present invention, the total content of the solid content and the reinforcing fibers of 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 further preferably 90% by mass or more, and the upper limit is 100% by mass.

[0207] <Prepreg shape and manufacturing method>

[0208] The shape of the prepreg varies depending on the form of the reinforcing fibers to be used, but from the viewpoint of manufacturing a high-pressure gas container by a filament winding method or a tape winding method, the prepreg is preferably a tow prepreg.

[0209] Furthermore, when continuous fibers in the form of unidirectional (UD) materials, woven fabrics, nonwoven fabrics, etc. are used, a sheet-shaped prepreg can be produced.

[0210] Among the sheet-shaped prepregs, the prepreg of the present invention is preferably a UD tape. The UD tape is in a tape shape and is therefore particularly suitable for use in the tape winding method. It should be noted that the UD tape may be cut into small pieces for use.

[0211] The method for producing the prepreg is not particularly limited and can be produced according to conventional methods. For example, after impregnating reinforcing fibers with an epoxy resin composition containing an epoxy resin (A), an epoxy resin curing agent (B), a curing accelerator (C) and a solvent used as required, the prepreg can be obtained by subjecting the reinforcing fibers to a drying step to remove the solvent.

[0212] The method for impregnating the reinforcing fiber with the epoxy resin composition is not particularly limited, and a known method can be appropriately used according to the form of the reinforcing fiber, etc. For example, the following method can be mentioned: when manufacturing a tow prepreg, a continuous fiber bundle rolled out from a roll is immersed in a resin bath filled with the above-mentioned epoxy resin composition, and after the composition is impregnated, it is pulled out from the resin bath. After that, a step of removing the excess epoxy resin composition using a deep drawing roll or the like can also be performed.

[0213] The impregnation with the epoxy resin composition may be performed under pressurized conditions or reduced pressure conditions as required.

[0214] Next, as needed, the reinforcing fiber impregnated with the epoxy resin composition is subjected to a drying process to remove the solvent. The drying conditions in the drying process are not particularly limited, but are preferably conditions that can remove the solvent and do not excessively cure the epoxy resin composition. From this viewpoint, for example, the drying temperature can be selected within the range of 30 to 120° C., and the drying time can be selected within the range of 10 seconds to 5 minutes.

[0215] The prepreg obtained through the drying process may be temporarily wound up to form a prepreg product, or may be continuously provided for the manufacture of a fiber-reinforced composite material after the drying process without winding up, etc. In particular, when forming a tape-shaped or sheet-shaped prepreg product, it is preferred to wind up to form a roll-shaped product.

[0216] [Fiber-reinforced composite materials]

[0217] The fiber-reinforced composite material (FRP, hereinafter also referred to as "composite material") of the present invention is a cured product of the aforementioned prepreg, which comprises a cured product of the aforementioned epoxy resin composition and reinforcing fibers. The fiber-reinforced composite material of the present invention has high hydrogen barrier properties by comprising a cured product of the aforementioned epoxy resin composition. The prepreg, epoxy resin composition, reinforcing fibers, and suitable forms thereof used in the manufacture of the composite material are the same as described above.

[0218] From the viewpoint of obtaining high strength and high elastic modulus, the content of the reinforcing fiber in the fiber-reinforced composite material is preferably in the range of 0.10 or more, more preferably 0.20 or more, further preferably 0.30 or more, and further preferably 0.40 or more. From the viewpoint of hydrogen barrier properties, impact resistance, and molding processability, it is preferably in the range of 0.85 or less, more preferably 0.80 or less, and further preferably 0.70 or less.

[0219] The volume fraction Vf of the reinforcing fibers in the fiber-reinforced composite material can be calculated by the following formula.

[0220] Vf = {mass of reinforcing fiber (g) / specific gravity of reinforcing fiber} ÷ [{mass of reinforcing fiber (g) / specific gravity of reinforcing fiber} + {mass of cured epoxy resin composition (g) / specific gravity of cured epoxy resin composition}]

[0221] <Method for producing fiber-reinforced composite material>

[0222] The composite material can be manufactured by preforming the prepreg into a desired shape and then curing the prepreg. For example, when the composite material of the present invention is used for a hollow molded body such as a pipe, a shaft, a gas cylinder, or a tank, the composite material can be manufactured by molding the prepreg using a tow method, a filament winding method, a yarn plating method, a 3D printing method, or the like.

[0223] In the filament winding method, specifically, a filament prepreg is wound around the outer surface of a ball, a core rod or a liner, and then heated and cured, thereby manufacturing a composite material of a desired shape.

[0224] In the inlay method, for example, the following steps are performed: a tow prepreg is braided into a unidirectional or cord structure using a braiding machine using a ball or a mandrel to form a prepreg, and then the prepreg is heated and cured. It should be noted that in the inlay method, the tow prepreg can also be braided and formed without using a ball or a mandrel.

[0225] When using a sheet-shaped prepreg such as a unidirectional (UD) material such as a UD tape, a woven fabric, or a nonwoven fabric, one or more prepregs can be stacked and placed in a mold, and heated and cured under vacuum or pressure to produce a composite material.

[0226] The curing method of the prepreg in the manufacture of the composite material is also not particularly limited, and is carried out according to a known method at a sufficient temperature and time required to cure the epoxy resin composition contained in the prepreg. The curing conditions of the prepreg also depend on the thickness of the prepreg and the composite material to be formed, and can be selected, for example, from a curing temperature range of 10 to 180° C. and a curing time 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 10 minutes to 5 hours.

[0227] From the viewpoint of manufacturing using tow prepreg, the composite material of the present invention is suitable for hollow-shaped molded bodies such as pipes, shafts, gas cylinders, tanks, and barrels (cylinders with two round plates closing both ends). The composite material has excellent hydrogen barrier properties and is therefore particularly suitable as a material for forming a high-pressure gas container.

[0228] [High-pressure gas container]

[0229] The high-pressure gas container of the present invention comprises the aforementioned fiber-reinforced composite material. The high-pressure gas container of the present invention only needs to be at least partially composed of the aforementioned fiber-reinforced composite material. For example, if it is a high-pressure gas container having an inner liner and an outer layer provided in a manner covering the outer surface of the inner liner, a container in which at least one of the inner liner and the outer layer is composed of the aforementioned fiber-reinforced composite material can be cited. In addition, if it is a high-pressure gas container without an inner liner, a container in which the entire container is composed of the aforementioned fiber-reinforced composite material can be cited.

[0230] Specific embodiments of high-pressure gas containers containing fiber-reinforced composite materials include: (1) a structure having a metal liner and an outer layer formed of the fiber-reinforced composite material of the present invention; (2) a structure having a resin liner and an outer layer formed of the fiber-reinforced composite material of the present invention; (3) a structure having an inner liner formed of the fiber-reinforced composite material of the present invention and an outer layer formed of a material other than the fiber-reinforced composite material; (4) a structure having only a container (without an inner liner) formed of the fiber-reinforced composite material of the present invention, etc.

[0231] Examples of the metal used for the "metal lining" in (1) above include light alloys such as aluminum alloys and magnesium alloys.

[0232] The resin used in the "resin lining" of (2) above is not particularly limited as long as it is a resin having excellent hydrogen barrier properties and pressure resistance, and examples thereof include thermoplastic resins, cured products of thermosetting resins, cured products of photocurable resins, etc. Among these, thermoplastic resins are preferred from the viewpoint of being able to easily form a lining.

[0233] Examples of the thermoplastic resin 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, polyetherketoneketone resins, polyetheretherketoneketone resins, polybenzimidazole resins, and the like. One of these resins may be used alone or two or more of these resins may be used in combination.

[0234] From the viewpoint of hydrogen barrier properties and pressure resistance, among thermoplastic resins, at least one selected from the group consisting of polyamide resins and polyolefin resins is preferred, and polyamide resins are more preferred.

[0235] Furthermore, from the viewpoint of improving impact resistance, the resin liner may contain the aforementioned stress relaxing component.

[0236] The "outer layer formed of a material other than the fiber-reinforced composite material" in (3) above means that, from the viewpoint of improving reinforcement properties, preferably, the outer layer is formed of a fiber-reinforced composite material other than the fiber-reinforced composite material of the present invention.

[0237] In the above-mentioned aspects (1) to (3), the outer layer may be formed so as to cover the outer surface of the main body portion of the liner without a gap.

[0238] The outer layer can be directly disposed on the outer surface of the inner liner. Alternatively, one or more other layers can be disposed on the outer surface of the inner liner and disposed on the surface of the other layers. For example, in order to improve the closeness between the inner liner and the outer layer, an adhesive layer can be disposed between the inner liner and the outer layer.

[0239] When the high-pressure gas container is of the above-mentioned form (1) or (2), the thickness of the outer layer formed by the fiber-reinforced composite material of the present invention can be appropriately selected according to the capacity, shape, etc. of the high-pressure gas container. From the viewpoint of imparting high hydrogen barrier properties and impact resistance, it is preferably 100 μm or more, more preferably 200 μm or more, and further preferably 400 μm or more. From the viewpoint of miniaturization and weight reduction of the high-pressure gas storage tank, it is preferably 80 mm or less, and more preferably 60 mm or less.

[0240] When the high-pressure gas container is of the aforementioned embodiment (3), the thickness of the lining formed by the fiber-reinforced composite material of the present invention can be appropriately selected according to the capacity, shape, etc. of the high-pressure gas container. From the viewpoint of hydrogen barrier properties and pressure resistance, it is preferably 100 μm or more, more preferably 200 μm or more, and further preferably 400 μm or more. From the viewpoint of miniaturization and lightweight of the high-pressure gas container, it is preferably 60 mm or less, and more preferably 40 mm or less.

[0241] When the high-pressure gas container is of the above-mentioned embodiment (4), the thickness of the container formed by the fiber-reinforced composite material of the present invention can be appropriately selected according to the capacity, shape, etc. of the high-pressure gas container. From the viewpoint of hydrogen barrier properties and pressure resistance, it is preferably 1 mm or more, more preferably 2 mm or more, and further preferably 5 mm or more. From the viewpoint of miniaturization and lightweight of the high-pressure gas container, it is preferably 80 mm or less, and more preferably 60 mm or less.

[0242] From the viewpoint of obtaining high strength and high elastic modulus, the content of reinforcing fibers in the liner, outer layer or high-pressure gas container formed of the fiber-reinforced composite material of the present invention is preferably in the range of 0.10 or more, more preferably 0.20 or more, further preferably 0.30 or more, and further preferably 0.40 or more in volume fraction of reinforcing fibers. In addition, from the viewpoint of hydrogen barrier properties, impact resistance and molding processability, it is preferably in the range of 0.85 or less, more preferably 0.80 or less, further preferably 0.75 or less, and further preferably 0.70 or less.

[0243] The volume fraction of the reinforcing fibers can be calculated using the same method as described above.

[0244] Among the above, from the viewpoint of lightness and the requirement for high hydrogen resistance of fiber-reinforced composite materials, the high-pressure gas container is preferably any of the above-mentioned forms (2), (3) or (4), and more preferably forms (3) or (4).

[0245] It should be noted that the high-pressure gas container may also have parts made of materials other than the fiber-reinforced composite material, such as a pipe head and a valve. In addition, any layer such as a protective layer, a coating layer, and a rust-proof layer may be formed on the surface of the high-pressure gas container.

[0246] The gas to be stored in the high-pressure gas container may be a gas at 25°C and 1 atm, and may include, in addition to hydrogen, oxygen, carbon dioxide, nitrogen, argon, LPG, freon substitutes, methane, etc. Among these, hydrogen is preferred from the viewpoint of effectiveness of the present invention.

[0247] <Method for manufacturing high-pressure gas container>

[0248] As a method for manufacturing a high-pressure gas container of the present invention, the manufacturing method described in the manufacturing method of the aforementioned fiber-reinforced composite material can be appropriately used according to the form of the reinforcing fiber or prepreg to be used. When a high-pressure gas container is manufactured using a tow prepreg, the high-pressure gas container can be manufactured by molding the tow prepreg according to a filament winding method, a yarn plating method, a 3D printing method, or the like.

[0249] In the case where the high-pressure gas container is of the above-mentioned method (1) or (2), the filament winding method is used to wind the filament prepreg in a manner to cover the outer surface of the metal or resin liner, and then heat and cure it, thereby forming an outer layer composed of a fiber-reinforced composite material and manufacturing a high-pressure gas container.

[0250] When the high-pressure gas container is of the aforementioned method (3) or (4), the filament prepreg is formed into a container shape according to a filament winding method, a yarn adding method, a 3D printing method, etc., and then heated and cured, thereby manufacturing a high-pressure gas container.

[0251] Example

[0252] Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. It should be noted that the measurements and evaluations in the present Examples were performed by the following methods.

[0253] <Hydrogen permeability coefficient [cc·cm / (cm 2 ·s·cmHg)]>

[0254] The epoxy resin composition prepared in each example was injected into a mold (120 mm × 120 mm × 1 mm) coated with a release agent ("FREKOTE (registered trademark) 770-NC" manufactured by Henkel Corporation), and heat-cured at 80 to 160°C for 2 hours to produce a plate-shaped molded body with a thickness of 1 mm. A circular test piece with a thickness of 1 mm and a diameter of 20 mm was prepared from the plate-shaped molded body. For the test piece, a gas permeability measuring device ("GTR-30X" manufactured by GTR TEC Co., Ltd.) was used to measure the hydrogen permeability coefficient [cc·cm / (cm 2 ·s·cmHg)].

[0255] <Moldability>

[0256] The epoxy resin composition prepared in each example was injected into a mold (50 mm × 50 mm × 2 mm) coated with a release agent ("FREKOTE (registered trademark) 770-NC" manufactured by Henkel) and heated and cured at 80 to 160° C. for 2 hours to produce a plate-shaped molded body with a thickness of 2 mm. The appearance of the obtained molded body was visually observed and evaluated according to the following criteria:

[0257] (Evaluation Criteria)

[0258] A: No scorching or discoloration of the molded body, good appearance

[0259] B: Discoloration of the molded body is visible, but scorching is basically suppressed

[0260] C: The molded body is charred and turns brown, which deteriorates the appearance.

[0261] <Applicable period>

[0262] After measuring the initial viscosity of the epoxy resin composition prepared in each example at 23°C, 10 g of the epoxy resin composition was placed in a plastic cup (diameter 46 mm) and stored at 23°C. The time [hours] for the viscosity of the epoxy resin composition to become more than twice the initial viscosity was measured and shown in the table. In the table, for those with a pot life of more than 24 hours, it is recorded as ">24". The longer the time, the better the pot life.

[0263] The viscosity of the epoxy resin composition was measured using an E-type viscometer "TV-100 Viscometer Cone-Plate Type" (manufactured by Toki Sangyo Co., Ltd.).

[0264] <Storage period>

[0265] 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. After a certain period of time, the epoxy resin composition was returned to room temperature (23°C) and the fluidity was visually observed. The table shows the number of days [days] until the fluidity disappears under 0°C storage. In the table, for those with a storage period of more than 30 days, it is recorded as ">30". The longer the time, the better the storage period.

[0266] <Glass transition temperature (Tg) of cured product>

[0267] For the glass transition temperature (Tg) of the cured product of the epoxy resin composition prepared in each example, each epoxy resin composition of each example was heated at 80 to 180°C for a predetermined time (10 minutes to 5 hours) and completely cured until the peak derived from the curing reaction in the differential scanning calorimetry (DSC) disappeared. For the cured epoxy resin composition, the dynamic viscoelasticity was measured at 30 to 200°C at a heating rate of 5°C / min using a dynamic viscoelasticity measuring device "DMA7100" (manufactured by Hitachi High-Tech Corporation), and the maximum value of tanδ obtained at this time was taken as the glass transition temperature (Tg). The higher the glass transition temperature (Tg) of the cured product, the better the heat resistance.

[0268] <Elastic modulus of cured product (GPa)>

[0269] The elastic modulus (GPa) of the cured product of the epoxy resin composition prepared in each example is measured as follows. For the epoxy resin composition prepared in each example, each epoxy resin composition of each example is heated at 80 to 180°C for a specified time (10 minutes to 5 hours) to be completely cured until the peak derived from the curing reaction in the differential scanning calorimetry (DSC) disappears. For the cured epoxy resin composition, the elastic modulus at 30°C is measured using a dynamic viscoelasticity measuring device "DMA7100" (manufactured by Hitachi High-Tech Corporation). The smaller the value of the elastic modulus, the lower the elastic modulus, the less likely it is to produce cracks, etc., and it is preferred.

[0270] <Viscosity>

[0271] The viscosity of the epoxy resin composition prepared in each example at 60°C was measured using an E-type viscometer "TV-100 Viscometer Cone and Plate Type" (manufactured by Toki Sangyo Co., Ltd.). The measurement was started after mixing the epoxy resin and the epoxy resin curing agent, and the value after 120 seconds at 60°C was read. In the table, those with a viscosity of 1 Pa·s or less are recorded as "A". Those with a viscosity exceeding 1 Pa·s are recorded as "B". The lower the viscosity, the lower the viscosity, the better. Those with a viscosity of 1 Pa·s or less are particularly good.

[0272] Example 1 (Preparation and Evaluation of Epoxy Resin Composition)

[0273] Component (A1): resorcinol diglycidyl ether ("Denacol (registered trademark) EX-201" manufactured by Nagase ChemteX Corporation, epoxy equivalent: 115 g / equivalent) and component (a21): bisphenol F diglycidyl ether ("jER (registered trademark) 807" manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 168 g / equivalent) are used as epoxy resin (A), and component (B1): resorcinol is used as epoxy resin curing agent (B). In addition, 2-ethyl-4-methylimidazole (manufactured by Tokyo Chemical Industry Co., Ltd.) is used as a curing accelerator (C). They are compounded and mixed in the mass parts 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 (the number of active hydrogens in the epoxy resin curing agent / the number of epoxy groups in the epoxy resin) is 1 / 1.

[0274] The obtained epoxy resin composition was evaluated by the above-mentioned method. The results are shown in Table 1.

[0275] Examples 2 to 8, 17 to 26 and Comparative Examples 1 to 8

[0276] The epoxy resin composition was prepared and evaluated in the same manner as in Example 1 except that the types and blending amounts of the epoxy resin (A), epoxy resin curing agent ((B) or tetraethylenepentamine) and curing accelerator (C) were changed as described in Tables 1, 3 and 4. The results are shown in Tables 1, 3 and 4. It should be noted that the pot life of Comparative Examples 7 and 8 was very short, and test pieces required for evaluation could not be obtained, so some of the evaluations were not performed.

[0277] Embodiments 9 to 16

[0278] The epoxy resin composition was prepared and evaluated in the same manner as in Example 1 except that the types and blending amounts of the epoxy resin (A), epoxy resin curing agent (B) and curing accelerator (C) were changed as described in Table 2, and when blending them, the components described in Table 2 were also blended and mixed as stress relaxation components (D). The results are shown in Table 2.

[0279] [Table 1]

[0280] Table 1

[0281]

[0282] [Table 2]

[0283] Table 2

[0284]

[0285] [Table 3]

[0286] Table 3

[0287]

[0288] [Table 4]

[0289] Table 4

[0290]

[0291] The components described in Tables 1 to 4 are as follows.

[0292] <Epoxy resin (A)>

[0293] (A1) Resorcinol diglycidyl ether ("Denacol (registered trademark) EX-201" manufactured by Nagase ChemteX Corporation, epoxy equivalent: 115 g / equivalent)

[0294] (a21) Bisphenol F diglycidyl ether (jER807) (“jER (registered trademark) 807” manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 168 g / equivalent)

[0295] (a21) Bisphenol F diglycidyl ether (jER4005P) (“jER (registered trademark) 4005P” manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 1026 g / equivalent, oligomer type)

[0296] (a22) Bisphenol A diglycidyl ether (jER828) (“jER (registered trademark) 828” manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 186 g / equivalent)

[0297] (a22) Bisphenol A diglycidyl ether (jER1001) (“jER (registered trademark) 1001” manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 483 g / equivalent, oligomer type)

[0298] (a23) Phenol novolac type epoxide ("N730A" manufactured by DIC Corporation, epoxy equivalent: 176 g / equivalent)

[0299] (a24) Triphenylmethane type epoxide ("HP7241" manufactured by DIC Corporation, epoxy equivalent: 171 g / equivalent)

[0300] (a25) Naphthalene epoxy resin ("HP-4032SS" manufactured by DIC Corporation, epoxy resin represented by formula (a253), epoxy equivalent: 143 g / equivalent)

[0301] <Epoxy resin curing agent>

[0302] (b1) Resorcinol

[0303] (b31) Novolac phenol (TD-2131) (“TD-2131” manufactured by DIC Corporation, hydroxyl value equivalent: 104 g / equivalent, softening point: 78 to 82° C.) (phenolic curing agent (b31))

[0304] (b32) Adipic acid dihydrazide (dihydrazide curing agent (b32))

[0305] Tetraethylenepentamine (amine curing agent)

[0306] <Curing accelerator (C)>

[0307] 2-Ethyl-4-methylimidazole (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0308] <Stress Relaxing Component (D)>

[0309] Kaneace MX-136: Core-shell rubber particle dispersed epoxy resin masterbatch (Kaneka Corporation's "Kaneace (registered trademark) MX-136", epoxy Bis-F type, particle polybutadiene / silicone, particle compounding amount 25%)

[0310] Epolead PB4700: epoxidized polybutadiene ("Epolead (registered trademark) PB4700" manufactured by Daicel Corporation, molecular weight 2000 to 3500)

[0311] ADEKA RESIN ERP-2000: Rubber-modified epoxy resin ("ADEKA RESIN (registered trademark) ERP-2000" manufactured by ADEKA Corporation, molecular weight 400 to 500)

[0312] Epolead PB3600: epoxidized polybutadiene ("Epolead (registered trademark) PB3600" manufactured by Daicel Corporation, molecular weight 5900)

[0313] <Manufacture of tubular molded article (fiber-reinforced composite material containing carbon fibers as reinforcing fibers) (filament winding molding)>

[0314] The epoxy resin compositions of Example 3, Example 8 and Example 12 and carbon fiber (T700SC12K) were used for filament winding molding.

[0315] The epoxy resin composition was applied continuously for 12 hours to impregnate the carbon fibers with the resin, and then heated at 80 to 180° C. to obtain a tubular molded body.

[0316] The obtained molded body was a tubular molded body in which the volume fraction of the reinforcing fibers (carbon fibers) in the molded body was 0.40 or more, there was no discoloration of the resin, the appearance was good, and there were no voids.

[0317] This shows that the epoxy resin composition of the present invention is also suitable for filament winding molding, and therefore is suitable for use in the production of containers for high-pressure gas storage.

[0318] On the other hand, when the epoxy resin compositions of Comparative Examples 7 and 8 were used, the compositions thickened 30 minutes after application, making it difficult to control the amount of the resin, and began to cure 2 hours after application, making it impossible to continue applying.

[0319] <Manufacturing of tubular molded body (fiber-reinforced composite material containing glass fiber as reinforcing fiber) (filament winding molding)>

[0320] The epoxy resin compositions of Examples 3, 8 and 12 and glass fibers (ECG 75 1 / 0 0.7Z, fineness 687 dtex, fiber count 400 f, manufactured by Nitto Bo Co., Ltd.) were used to perform filament winding molding.

[0321] The epoxy resin composition was applied continuously for 12 hours to impregnate the glass fiber as reinforcing fiber with the resin, and then heated at 80 to 180° C. to obtain a tubular molded body.

[0322] The obtained molded body was a tubular molded body in which the volume fraction of the reinforcing fiber (glass fiber) in the molded body was 0.40 or more, there was no discoloration of the resin, the appearance was good, and there was no void.

[0323] According to the results of the above examples, the viscosity of the epoxy resin composition of the examples, especially the viscosity at 60°C, is low, and even if heated to 160°C for molding, there is little scorching and discoloration, and the hydrogen barrier property of the obtained cured product is high. In addition, it can be seen that the epoxy resin composition has a sufficiently long shelf life and storage period. In this way, the epoxy resin composition of the present invention has a long shelf life and low viscosity, and is therefore suitable for filament winding molding, resin transfer molding, and the production of tow prepregs. In addition, the storage period is also long, and there is little scorching during molding, and high hydrogen barrier properties can be achieved. Therefore, it is particularly suitable for the manufacture of containers for high-pressure hydrogen storage.

Claims

1. An epoxy resin composition comprising: an epoxy resin (A) and an epoxy resin curing agent (B), 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 resorcinol, The epoxy resin (A2) is at least one selected from the group consisting of an epoxy resin having a glycidyl group derived from bisphenol F (a21), an epoxy resin having a glycidyl group derived from bisphenol A (a22), an epoxy resin having a glycidyl group derived from novolac phenol (a23), an epoxy resin having a glycidyl group derived from triphenylmethane type phenol (a24), an epoxy resin having a glycidyl group derived from a polyol having a naphthalene skeleton (a25), and an epoxy resin having an aminoglycidyl group (a26), The epoxy resin curing agent (B) comprises at least one selected from the group consisting of resorcinol (B1) and a pre-reaction product (B2) obtained from resorcinol (B1), the epoxy resin (A) and a curing accelerator (C), wherein the pre-reaction product (B2) is a reaction product obtained by reacting 100 parts by mass of the resorcinol (B1), 1 to 40 parts by mass of the epoxy resin (A) and 0.01 to 5 parts by mass of the curing accelerator (C), The content of the epoxy resin curing agent (B) is 7 to 60% by mass when the total amount of the epoxy resin (A) and the epoxy resin curing agent (B) in the epoxy resin composition is 100% by mass.

2. The epoxy resin composition according to claim 1, wherein The epoxy resin curing agent (B) further comprises an epoxy resin curing agent (B3), The epoxy resin curing agent (B3) is at least one selected from the group consisting of phenolic curing agents (b31) other than resorcinol (B1) and dihydrazide curing agents (b32).

3. The epoxy resin composition according to claim 2, wherein The phenolic curing agent (b31) other than resorcinol (B1) is at least one selected from the group consisting of bisphenol F, bisphenol A, novolac phenol and triphenylmethane-type phenol.

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) contained in the epoxy resin (A) is 1 / 99 to 90 / 10.

5. The epoxy resin composition according to any one of claims 1 to 4, wherein The mass ratio [(A1) / (A2)] of the epoxy resin (A1) to the epoxy resin (A2) contained in the epoxy resin (A) is 20 / 80 to 90 / 10.

6. The epoxy resin composition according to any one of claims 2 to 5, wherein The mass ratio of the total amount of resorcinol (B1) and the pre-reaction product (B2) contained in the epoxy resin curing agent (B) to the epoxy resin curing agent (B3) [((B1)+(B2)) / (B3)] is 8 / 92 to 100 / 0.

7. The epoxy resin composition according to any one of claims 1 to 6, wherein It also contains a curing accelerator (C), The curing accelerator (C) is at least one selected from the group consisting of imidazoles, tertiary amines and phosphorus compounds.

8. The epoxy resin composition according to any one of claims 1 to 7, wherein A stress relaxing component (D) is also contained.

9. The epoxy resin composition according to any one of claims 1 to 8, wherein The hydrogen permeability coefficient of the cured product of the epoxy resin composition at 23°C is 8.4×10 -11 [cc·cm / (cm 2 ·s·cmHg)] or less.

10. A cured product of the epoxy resin composition according to any one of claims 1 to 9. 11 . A prepreg comprising reinforcing fibers impregnated with the epoxy resin composition according to claim 1 .

12. The prepreg according to claim 11, wherein The reinforcing fiber is at least one selected from the group consisting of carbon fiber, glass fiber, and basalt fiber.

13. The prepreg according to claim 11 or 12, which is a tow prepreg.

14. The prepreg according to claim 11 or 12, wherein: The prepreg is a UD tape. 15 . A fiber-reinforced composite material, which is a cured product of the prepreg according to claim 11 .

16. A high-pressure gas container comprising the fiber-reinforced composite material according to claim 15.

Images