Epoxy resin hardener

Abstract

One problem addressed by the present invention is to provide a curing agent for an epoxy resin that yields a resin composition having low viscosity and rapid curing and a cured product having high impact strength. The present invention provides a curing agent for an epoxy resin, etc., in which there are combined (A) a liquid aromatic polyamine and (B) a solid aromatic polyamine including a secondary amino group, and in which (C) an aliphatic cyclic polyamine is furthermore used in combination when the (B) solid aromatic amine including a secondary amino group does not include (B1) a solid aromatic amine in which the number of secondary amino groups is greater than the total number of primary amino groups and tertiary amino groups.

Description

[Technical Field]

[0001] The present invention relates to a curing agent for epoxy resins, etc. The present invention also relates to a resin composition containing the curing agent for epoxy resins and an epoxy resin, a composite material containing a cured product of the resin composition and carbon fiber, a method for producing the curing agent for epoxy resins, a method for producing the cured product, and a method for curing an epoxy resin. [Background technology]

[0002] Fiber-reinforced composite materials, which are made of reinforcing fibers such as carbon fibers and thermosetting materials such as epoxy resins, are used in many fields, including aircraft and automobiles, because they have excellent physical properties such as light weight and high strength.

[0003] Diaminodiphenyl sulfone has traditionally been widely used as a curing agent for epoxy resins used in composite materials. Cured products of epoxy resin compositions using diaminodiphenyl sulfone as a curing agent exhibit excellent properties, such as high heat resistance and high strength. However, diaminodiphenyl sulfone has a high melting point of 180°C, making it difficult to dissolve in epoxy resins. Furthermore, the resin composition tends to become highly viscous, making it difficult to quickly impregnate reinforcing fibers such as carbon fibers. On the other hand, when commonly known liquid polyamines are used as curing agents for epoxy resins, it is possible to reduce the viscosity of the resin composition, but curing takes a long time and the impact strength of the cured product is insufficient.

[0004] Patent Documents 1 and 2 describe epoxy resin compositions that use a curing agent in which diaminodiphenyl sulfone is dissolved in a liquid aromatic polyamine. However, epoxy resin compositions that use this curing agent require a long time to cure, and the impact strength of the resulting cured product is unsatisfactory. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4396274 [Patent Document 2] Patent No. 5228853 Summary of the Invention

[0006] One of the problems to be solved by the present invention is to provide a curing agent for epoxy resins that provides a resin composition with low viscosity and fast curing properties and a cured product with high impact strength.

[0007] As a result of intensive research conducted by the present inventors to solve the above-mentioned problems, they have found that by combining (A) a liquid aromatic polyamine with (B) a solid aromatic polyamine containing a secondary amino group, and when (B) the solid aromatic amine containing a secondary amino group does not contain (B1) a solid aromatic amine in which the number of secondary amino groups is greater than the total number of primary amino groups and tertiary amino groups, and further combining it with (C) an aliphatic cyclic polyamine, it is possible to obtain a curing agent for epoxy resins that provides a low-viscosity, fast-curing resin composition and a cured product with high impact strength, and have completed the present invention. That is, the present invention includes the following aspects.

[0008] [1] A curing agent for epoxy resins, comprising (A) a liquid aromatic polyamine and (B) a solid aromatic amine containing a secondary amino group, An epoxy resin curing agent, wherein (B) the solid aromatic amine containing a secondary amino group may or may not contain (B1) a solid aromatic amine in which the number of secondary amino groups is greater than the total number of primary amino groups and tertiary amino groups, and when the solid aromatic amine does not contain (B1), the epoxy resin curing agent further contains (C) an aliphatic cyclic polyamine. [2] The epoxy resin curing agent according to [1] above, wherein (B) the solid aromatic amine containing a secondary amino group comprises (B1) a solid aromatic amine in which the number of secondary amino groups is greater than the total number of primary amino groups and tertiary amino groups. [3] The epoxy resin curing agent according to [2] above, wherein (B1) the solid aromatic amine in which the number of secondary amino groups is greater than the total number of primary amino groups and tertiary amino groups comprises (B1') a solid aromatic amine containing only secondary amino groups as amino groups. [4] (B1') The solid aromatic amine containing only secondary amino groups as amino groups is N-phenyl-1-naphthylamine, octylated diphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, N-(p-tolyl)-1-naphthylamine, N-phenyl-3-biphenylamine, bis(3-biphenylyl)amine, 2-(3-biphenylyl)amino-9,9-dimethylfluorene, bis(4-tert-butylphenyl)amine, 4 -tert-Butylphenylphenylamine, Bis-α-methylbenzylphenothiazine, Reaction products of diphenylamine with 2,4,4-trimethylpentene, Diphenylamine, N-Phenylbenzylamine, 3-Methyldiphenylamine, 3,4-Dimethyldiphenylamine, 4,4'-Dimethyldiphenylamine, 3-Methoxydiphenylamine, 10-Methoxy-2,2'-iminostilbene, N-Benzyl-2-naphthylamine, 1,2'-Dinaphthylamine diphenylamine, 1,1'-dinaphthylamine, 4-isopropylaminodiphenylamine, 2,6-bis[(2-hydroxyethyl)amino]toluene, 4-(2-octylamino)diphenylamine, N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 1,3-diphenylguanidine, p-(p-toluenesulfonylamido)diphenylamine, N-phenyl- The epoxy resin curing agent according to [3] above, which is selected from the group consisting of N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine, bis(2-benzamidophenyl)disulfide, N,N'-diphenyl-1,4-phenylenediamine, 1,3-di-o-tolylguanidine, 1,5-diphenylcarbonohydrazide, N,N'-diphenylethylenediamine, and 5-(acetoacetamido)-2-benzimidazolinone. [5] The epoxy resin curing agent according to any one of the above [2] to [4], wherein (B) the solid aromatic amine containing a secondary amino group further contains (B2) a solid aromatic polyamine in which the number of secondary amino groups is equal to or less than the total number of primary amino groups and tertiary amino groups. [6] The epoxy resin curing agent according to [5] above, wherein (B2) the solid aromatic polyamine in which the number of secondary amino groups is equal to or less than the total number of primary amino groups and tertiary amino groups is selected from the group consisting of 4-aminodiphenylamine, 2,4-diaminodiphenylamine, 2-aminodiphenylamine, 4-amino-4'-methoxydiphenylamine, 1-phenylbiguanide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, 2,6-naphthoic acid dihydrazide, 4,4'-bisbenzenedihydrazide, 1,4-naphthoic acid dihydrazide, naphthalene-2,6-dicarbohydrazide, and 3-hydroxy-2-naphthoic acid hydrazide. [7] The epoxy resin curing agent according to any one of the above [2] to [6], further comprising (C) an aliphatic cyclic polyamine. [8] The epoxy resin curing agent according to [1] above, wherein (B) the solid aromatic amine containing a secondary amino group does not contain (B1) a solid aromatic amine in which the number of secondary amino groups is more than the total number of primary amino groups and tertiary amino groups, and contains (B2) a solid aromatic polyamine in which the number of secondary amino groups is equal to or less than the total number of primary amino groups and tertiary amino groups. [9] (B2) The epoxy resin curing agent according to [8] above, wherein the solid aromatic polyamine in which the number of secondary amino groups is equal to or less than the total number of primary amino groups and tertiary amino groups is selected from the group consisting of 4-aminodiphenylamine, 2,4-diaminodiphenylamine, 2-aminodiphenylamine, 4-amino-4'-methoxydiphenylamine, 1-phenylbiguanide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, 2,6-naphthoic acid dihydrazide, 4,4'-bisbenzenedihydrazide, 1,4-naphthoic acid dihydrazide, naphthalene-2,6-dicarbohydrazide, and 3-hydroxy-2-naphthoic acid hydrazide.

[10] The epoxy resin curing agent according to any one of the above [7] to [9], wherein the boiling point of the aliphatic cyclic polyamine (C) is 140°C or higher.

[11] The epoxy resin curing agent according to any one of the above [7] to

[10] , wherein the aliphatic cyclic polyamine (C) contains a primary amino group or a secondary amino group.

[12] The epoxy resin curing agent according to any one of the above [7] to

[11] , wherein the aliphatic cyclic polyamine (C) contains only secondary amino groups as amino groups in the ring structure.

[13] The epoxy resin curing agent according to any one of the above [7] to

[12] , wherein the aliphatic cyclic polyamine (C) does not form a complex or a salt structure.

[14] The epoxy resin curing agent according to any one of the above [7] to

[13] , wherein in the aliphatic cyclic polyamine (C), all of the substituents of the element adjacent to the amino group in the ring structure and / or the element adjacent to the element to which the amino group on the ring structure is bonded are hydrogen atoms.

[15] The epoxy resin curing agent according to any one of the above [7] to

[14] , wherein the aliphatic cyclic polyamine (C) has a piperazine skeleton.

[16] The epoxy resin curing agent according to any one of the above [7] to

[15] , wherein the aliphatic cyclic polyamine (C) is piperazine.

[17] The epoxy resin curing agent according to any one of the above [1] to

[16] , wherein the melting point of the solid aromatic amine containing a secondary amino group (B) is 160°C or lower.

[18] The epoxy resin curing agent according to any one of the above [1] to

[17] , wherein the liquid aromatic polyamine (A) contains two or more primary amino groups, two or more secondary amino groups, or one or more primary amino groups and one or more secondary amino groups.

[19] The epoxy resin curing agent according to

[18] , wherein the liquid aromatic polyamine (A) is selected from the group consisting of dimethylthiotoluenediamine, diethyltoluenediamine, and 4,4'-methylenebis[N-(1-methylpropyl)aniline].

[20] The epoxy resin curing agent according to any one of the above [1] to

[19] , which is liquid.

[21] A resin composition comprising the epoxy resin curing agent according to any one of [1] to

[20] above and an epoxy resin.

[22] A cured product of the resin composition described in

[21] above.

[23] A composite material comprising the cured product according to

[22] above and carbon fibers.

[0009] The present invention can provide a curing agent for epoxy resins that produces a low-viscosity, fast-curing resin composition and a cured product having high impact strength. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail. Note that the present invention is not limited to the following embodiments. Furthermore, in this specification, unless otherwise specified, "A (numerical value) to B (numerical value)" means "A or more and B or less," and a ratio means a mass ratio. Note that the preferred and more preferred embodiments exemplified below can be used in appropriate combinations with each other regardless of expressions such as "preferred" or "more preferred." Furthermore, the descriptions of numerical ranges are merely examples, and ranges obtained by appropriately combining the upper and lower limits of each range and the numerical values ​​of the examples can also be preferably used regardless of expressions such as "preferred" or "more preferred." Furthermore, terms such as "contain" or "comprise" may be interpreted as "essentially consisting of" or "consisting only of," as appropriate. The present invention relates to an epoxy resin curing agent comprising (A) a liquid aromatic polyamine and (B) a solid aromatic amine containing a secondary amino group, wherein (B) the solid aromatic amine containing a secondary amino group may or may not contain (B1) a solid aromatic amine in which the number of secondary amino groups is greater than the total number of primary amino groups and tertiary amino groups, and when (B) the solid aromatic amine containing a secondary amino group does not contain (B1), the epoxy resin curing agent further comprises (C) an aliphatic cyclic polyamine.

[0011] (A) Liquid aromatic polyamine In the present invention, the term "liquid" aromatic polyamine refers to an aromatic polyamine having a melting point lower than room temperature (25°C), that is, an aromatic polyamine that is in a liquid state at room temperature (25°C).

[0012] Liquid aromatic polyamines are aromatic compounds having two or more amino groups. In this specification, unless otherwise specified, the term "amino group" includes "primary amino group," "secondary amino group," and "tertiary amino group." Tertiary amino groups tend to promote self-polymerization of epoxy resins and reduce the heat resistance of the resulting cured product. Therefore, from the viewpoint of obtaining a highly heat-resistant cured product, it is preferable that the liquid aromatic polyamine contains two or more primary amino groups, two or more secondary amino groups, or one or more primary amino groups and one or more secondary amino groups.

[0013] From the viewpoint of reducing the viscosity of the resin composition, the liquid aromatic polyamine preferably has a viscosity of 100 cP or less under heating conditions of 80° C. or higher, more preferably 0.001 to 60 cP, and even more preferably 0.01 to 20 cP. The viscosity of the liquid aromatic polyamine can be measured using a commercially available viscosity measuring device, for example, RheoStress 6000 manufactured by HAAKE.

[0014] The liquid aromatic polyamine preferably has a boiling point of 140° C. or higher, more preferably 150° C. to 500° C., even more preferably 160° C. to 400° C., and even more preferably 180° C. to 350° C. If the boiling point is 140° C. or higher, it is sufficiently higher than the temperature when the resin composition is impregnated into the reinforcing fibers in the process of producing a fiber-reinforced composite material using an epoxy resin as the matrix resin, and therefore volatilization of the liquid aromatic polyamine component can be suppressed, and as a result, structural defects and a decrease in strength of the fiber-reinforced composite material can be suppressed.

[0015] Preferred examples of the liquid aromatic polyamine include dimethylthiotoluenediamine, diethyltoluenediamine, and 4,4'-methylenebis[N-(1-methylpropyl)aniline].

[0016] Examples of commercially available liquid aromatic polyamines include dimethylthiotoluenediamine ("Ethacure 300" manufactured by Albemarle Corporation, and "Heartcure 30" manufactured by Kumiai Chemical Industry Co., Ltd.), diethyltoluenediamine ("Ethacure 100 Plus" manufactured by Albemarle Corporation, and "Heartcure 10" manufactured by Kumiai Chemical Industry Co., Ltd.), and the like.

[0017] The liquid aromatic polyamine may be used alone or in combination of two or more. When two or more liquid aromatic polyamines are used in combination, the liquid aromatic polyamine containing two or more primary amino groups is preferably contained in a proportion of 50 to 90 mass%, more preferably 60 to 80 mass%, based on the total mass of the liquid aromatic amines, from the viewpoint of improving the strength and heat resistance of the cured product.

[0018] When the curing agent is taken as 100% by mass, the liquid aromatic polyamine is contained in the curing agent in an amount of preferably 40 to 97% by mass, more preferably 50 to 95% by mass, and even more preferably 55 to 93% by mass, from the viewpoint of obtaining a low-viscosity resin composition.

[0019] (B) Solid aromatic amine containing a secondary amino group In the present invention, the term "solid" aromatic amine refers to an aromatic amine having a melting point higher than room temperature (25°C), that is, an aromatic amine that is in a solid state at room temperature (25°C).

[0020] The solid aromatic amine of the present invention contains a secondary amino group, which can increase the impact strength of the cured product.

[0021] The solid aromatic amine containing a secondary amino group preferably has a melting point of 160° C. or lower, for example, 155° C. or lower, or 150° C. or lower. The solid aromatic amine containing a secondary amino group preferably has a melting point of, for example, 30° C. or higher, 40° C. or higher, 50° C. or higher, 60° C. or higher, or 70° C. or higher. If the melting point is 160° C. or lower, the solid aromatic amine can be easily dissolved in a liquid aromatic polyamine in a short time.

[0022] Examples of solid aromatic amines containing a secondary amino group and having a melting point of 160°C or less include N-phenyl-1-naphthylamine, octylated diphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, N-(p-tolyl)-1-naphthylamine, N-phenyl-3-biphenylamine, bis(3-biphenylyl)amine, 2-(3-biphenylyl)amino-9,9-dimethylfluorene, bis(4-tert-butylphenyl)amine, 4-tert-butyl Phenylphenylamine, bis-α-methylbenzylphenothiazine, reaction products of diphenylamine with 2,4,4-trimethylpentene, diphenylamine, N-phenylbenzylamine, 3-methyldiphenylamine, 3,4-dimethyldiphenylamine, 4,4'-dimethyldiphenylamine, 3-methoxydiphenylamine, 10-methoxy-2,2'-iminostilbene, N-benzyl-2-naphthylamine, 1,2'-dinaphthylamine, 1,1'-dinaphthylamine toluene, 4-isopropylaminodiphenylamine, 2,6-bis[(2-hydroxyethyl)amino]toluene, 4-(2-octylamino)diphenylamine, N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 1,3-diphenylguanidine, p-(p-toluenesulfonylamido)diphenylamine, N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)diphenylamine Examples of such compounds include N,N'-p-phenylenediamine, bis(2-benzamidophenyl)disulfide, N,N'-diphenyl-1,4-phenylenediamine, N,N'-diphenylethylenediamine, 5-(acetoacetamido)-2-benzimidazolinone, 1-(o-tolyl)biguanide, phenylbiguanide, polymeric biguanide compounds containing terminal amino groups, 4-phenylsemicarbazide, 4-phenyl-3-thiosemicarbazide, and 1,2,3-triphenylguanidine.

[0023] The solid aromatic amine containing a secondary amino group preferably has a boiling point of 140° C. or higher, more preferably 145° C. to 550° C., even more preferably 150° C. to 500° C., even more preferably 160° C. to 450° C., and particularly preferably 170° C. to 400° C. If the boiling point is 140° C. or higher, it is sufficiently higher than the temperature when the resin composition is impregnated into the reinforcing fibers in the process of producing a fiber-reinforced composite material using an epoxy resin as the matrix resin, and therefore volatilization of the solid aromatic amine component containing a secondary amino group can be suppressed, and as a result, structural defects and a decrease in strength of the fiber-reinforced composite material can be suppressed.

[0024] Examples of solid aromatic amines containing a secondary amino group and having a boiling point of 140°C or higher include N-phenyl-1-naphthylamine, octylated diphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, N-(p-tolyl)-1-naphthylamine, N-phenyl-3-biphenylamine, bis(3-biphenylyl)amine, 2-(3-biphenylyl)amino-9,9-dimethylfluorene, bis(4-tert-butylphenyl)amine, 4-tert-butylphenylphenylamine, Bis-α-methylbenzylphenothiazine, reaction products of diphenylamine with 2,4,4-trimethylpentene, diphenylamine, N-phenylbenzylamine, 3-methyldiphenylamine, 3,4-dimethyldiphenylamine, 4,4'-dimethyldiphenylamine, 3-methoxydiphenylamine, 10-methoxy-2,2'-iminostilbene, N-benzyl-2-naphthylamine, 1,2'-dinaphthylamine, 1,1'-dinaphthylamine, 4-isopropylaminodiphenylamine, 2, 6-bis[(2-hydroxyethyl)amino]toluene, 4-(2-octylamino)diphenylamine, N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 1,3-diphenylguanidine, p-(p-toluenesulfonylamido)diphenylamine, N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine, bis(2-benzamidophenyl)disulfonate Examples of such compounds include 1-(o-tolyl)biguanide, N,N'-diphenyl-1,4-phenylenediamine, 1,3-di-o-tolylguanidine, 1,5-diphenylcarbonohydrazide, N,N'-diphenylethylenediamine, 5-(acetoacetamido)-2-benzimidazolinone, 1-(o-tolyl)biguanide, 1-phenylguanidine, phenylbiguanide, polymeric biguanide compounds containing a terminal amino group, 4-phenylsemicarbazide, 4-phenyl-3-thiosemicarbazide, and 1,2,3-triphenylguanidine.

[0025] The solid aromatic amine containing a secondary amino group may include a monoamine having one secondary amino group, or a polyamine having two or more amino groups, at least one of which is a secondary amino group. From the viewpoint of improving the curing rate of the resin composition and the mechanical properties of the cured product, the solid aromatic amine containing a secondary amino group preferably includes (B1) a solid aromatic amine in which the number of secondary amino groups is greater than the total number of primary and tertiary amino groups. The solid aromatic amine (B1) in which the number of secondary amino groups is greater than the total number of primary and tertiary amino groups preferably includes (B1') a solid aromatic amine containing only secondary amino groups as amino groups (the number of secondary amino groups is one, two, or three or more, and the total number of primary and tertiary amino groups is zero).

[0026] Examples of (B1) solid aromatic amines having more secondary amino groups than the total number of primary and tertiary amino groups include solid aromatic monoamines having only one secondary amino group as the amino group (corresponding to B1'), solid aromatic polyamines having only two or more secondary amino groups as the amino groups (corresponding to B1'), solid aromatic polyamines having one primary amino group and two secondary amino groups, solid aromatic polyamines having two secondary amino groups and one tertiary amino group, solid aromatic polyamines having one primary amino group and three or more secondary amino groups, and solid aromatic polyamines having three or more secondary amino groups and one tertiary amino group.

[0027] Preferred examples of solid aromatic monoamines (corresponding to B1') having only one secondary amino group as the amino group include N-phenyl-1-naphthylamine, octylated diphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, N-(p-tolyl)-1-naphthylamine, N-phenyl-3-biphenylamine, bis(3-biphenylyl)amine, 2-(3-biphenylyl)amino-9,9-dimethylfluorene, bis(4-tert-butylphenyl)amine, 4-tert- butylphenylphenylamine, bis-α-methylbenzylphenothiazine, reaction product of diphenylamine and 2,4,4-trimethylpentene, diphenylamine, N-phenylbenzylamine, 3-methyldiphenylamine, 3,4-dimethyldiphenylamine, 4,4'-dimethyldiphenylamine, 3-methoxydiphenylamine, 10-methoxy-2,2'-iminostilbene, N-benzyl-2-naphthylamine, 1,2'-dinaphthylamine, 1,1'-dinaphthylamine, and the like.

[0028] Preferred examples of the solid aromatic polyamine (corresponding to B1') having only two or more secondary amino groups as amino groups include 4-isopropylaminodiphenylamine, 2,6-bis[(2-hydroxyethyl)amino]toluene, 4-(2-octylamino)diphenylamine, N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymers, 1,3-diphenylguanidine, p-(p -toluenesulfonylamido)diphenylamine, N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine, bis(2-benzamidophenyl)disulfide, N,N'-diphenyl-1,4-phenylenediamine, 1,3-di-o-tolylguanidine, 1,5-diphenylcarbonohydrazide, N,N'-diphenylethylenediamine, 5-(acetoacetamido)-2-benzimidazolinone, and the like.

[0029] (B1) Other examples of solid aromatic amines in which the number of secondary amino groups is greater than the total number of primary and tertiary amino groups include 1-(o-tolyl)biguanide, 1-phenylguanidine, phenylbiguanide, polymeric biguanide compounds containing terminal amino groups, 4-phenylsemicarbazide, 4-phenyl-3-thiosemicarbazide, 1,2,3-triphenylguanidine, etc.

[0030] The solid aromatic amine containing secondary amino groups may include (B2) a solid aromatic polyamine in which the number of secondary amino groups is equal to or less than the total number of primary and tertiary amino groups. For example, the solid aromatic amine containing secondary amino groups (B) may not include (B1) a solid aromatic amine in which the number of secondary amino groups is greater than the total number of primary and tertiary amino groups, but may include (B2) a solid aromatic polyamine in which the number of secondary amino groups is equal to or less than the total number of primary and tertiary amino groups. In this case, the epoxy resin curing agent may further include (C) an aliphatic cyclic polyamine, as described below. Alternatively, the solid aromatic amine containing secondary amino groups (B1) may be a solid aromatic amine in which the number of secondary amino groups is greater than the total number of primary and tertiary amino groups, and (B2) a solid aromatic polyamine in which the number of secondary amino groups is equal to or less than the total number of primary and tertiary amino groups. In this case, the epoxy resin curing agent may or may not further include (C) an aliphatic cyclic polyamine, as described below.

[0031] (B2) Examples of solid aromatic polyamines having the number of secondary amino groups equal to or less than the total number of primary amino groups and tertiary amino groups include solid aromatic polyamines containing primary and secondary amino groups (e.g., solid aromatic polyamines having one primary and one secondary amino group, solid aromatic polyamines having two primary and one secondary amino group, etc.), solid aromatic polyamines containing secondary and tertiary amino groups (e.g., solid aromatic polyamines containing one secondary and one tertiary amino group, etc.), and solid aromatic polyamines containing primary, secondary and tertiary amino groups.

[0032] Preferred examples of (B2) solid aromatic polyamines in which the number of secondary amino groups is equal to or less than the total number of primary amino groups and tertiary amino groups include 4-aminodiphenylamine, 2,4-diaminodiphenylamine, 2-aminodiphenylamine, 4-amino-4'-methoxydiphenylamine, 1-phenylbiguanide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, 2,6-naphthoic acid dihydrazide, 4,4'-bisbenzenedihydrazide, 1,4-naphthoic acid dihydrazide, naphthalene-2,6-dicarbohydrazide, and 3-hydroxy-2-naphthoic acid hydrazide.

[0033] (B) The solid aromatic amine containing secondary amino groups may be used alone or in combination of two or more. For example, (B1) a solid aromatic amine having more secondary amino groups than the total number of primary and tertiary amino groups may be used in combination with (B2) a solid aromatic polyamine having less than or equal to the total number of primary and tertiary amino groups. Alternatively, (B) the solid aromatic amine containing secondary amino groups may be used in combination of two or more (B1) solid aromatic amines having more secondary amino groups than the total number of primary and tertiary amino groups, or two or more (B2) solid aromatic polyamines having less than or equal to the total number of primary and tertiary amino groups.

[0034] The (B) solid aromatic amine containing a secondary amino group may have a substituent such as a halogen on the aromatic ring. By using the (B) solid aromatic amine containing a secondary amino group having a halogen substituent on the aromatic ring, it is possible to improve the viscosity stability of the resin composition.

[0035] Commercially available examples of solid aromatic polyamines containing secondary amino groups include 1-(o-tolyl)biguanide (Ouchi Shinko Chemical Industry Co., Ltd.'s "Noccela BG," HUNTSMAN's "Aradur 2844," and Thomas Swan's "Casamine OTB"), 4-isopropylaminodiphenylamine (Ouchi Shinko Chemical Industry Co., Ltd.'s "Nocrac 810-NA," and Kawaguchi Chemical Industry Co., Ltd.'s "Antage 3C"), 4-aminodiphenylamine (Seiko Chemical Industry Co., Ltd.'s "4-aminodiphenylamine," and LANXESS's "4-ADPA"), 2,2,4-trimethyl-1,2-dihydroquinoline polymers (Ouchi Shinko Chemical Industry Co., Ltd.'s "Nocrac 224 (224-S)," and Seiko Chemical Industry Co., Ltd.'s "Non-Furfen"). Examples include N-phenyl-1-naphthylamine (Ouchi Shinko Chemical Industry Co., Ltd.'s Nocrac PA), 1,3-diphenylguanidine (Ouchi Shinko Chemical Industry Co., Ltd.'s Noccela D, Sansela D, DG), 4,4'-bis(α,α-dimethylbenzyl)diphenylamine (Ouchi Shinko Chemical Industry Co., Ltd.'s Nocrac CD, Seiko Chemical Industry Co., Ltd.'s Nonflex DCD).

[0036] When the curing agent is taken as 100% by mass, the solid aromatic polyamine containing a secondary amino group is contained in the curing agent in an amount of preferably 1 to 45% by mass, more preferably 2 to 40% by mass, and even more preferably 3 to 35% by mass, from the viewpoint of increasing the impact strength of the cured product.

[0037] From the viewpoint of improving the mechanical properties such as elongation and bending strength of the cured product, the curing agent of the present invention may optionally contain a solid aromatic amine having a melting point of 160° C. or less and containing a primary amino group but not a secondary amino group. Preferred examples of the solid aromatic amine having a melting point of 160° C. or less and containing a primary amino group but not a secondary amino group include 4,4′-methylenebis(2-ethyl-6-methylaniline), 2,2′-diisopropyl-6,6′-dimethyl-4,4′-methylenedianiline, 2,2′,6,6′-tetraisopropyl-4,4′-methylenedianiline, 4,4′-methylenebis(2,6-diethylaniline), 4,4′-methylenebis(3-chloro-2,6-diethylaniline), 1,3-phenyl- Examples thereof include diamine, 2,4-diaminotoluene, 2,6-diaminotoluene, 2,4,6-trimethyl-1,3-phenylenediamine, 3-aminobiphenyl, 3-amino-4-methoxybiphenyl, 2-aminofluorene, 2-amino-9-fluorenone, 2,7-diaminofluorene, 3-aminobenzophenone, 3,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 3,4-diaminobenzophenone, and 3,3'-diaminobenzophenone.

[0038] (C) Aliphatic cyclic polyamine The epoxy resin curing agent of the present invention further comprises (C) an aliphatic cyclic polyamine when the (B) solid aromatic amine containing secondary amino groups does not include (B1) a solid aromatic amine in which the number of secondary amino groups is greater than the total number of primary and tertiary amino groups (i.e., when the (B) solid aromatic amine containing secondary amino groups includes only (B2) a solid aromatic polyamine in which the number of secondary amino groups is equal to or less than the total number of primary and tertiary amino groups).Furthermore, when the (B) solid aromatic amine containing secondary amino groups includes (B1) a solid aromatic amine in which the number of secondary amino groups is greater than the total number of primary and tertiary amino groups, the epoxy resin curing agent of the present invention may or may not further comprise (C) an aliphatic cyclic polyamine.

[0039] The aliphatic cyclic polyamine (C) in the curing agent has the effect of promoting the curing of the epoxy resin formed by the liquid aromatic polyamine (A) and the solid aromatic amine (B) containing a secondary amino group. That is, by including the aliphatic cyclic polyamine, the curing agent of the present invention can promote the curing of the resin composition and increase the curing rate. The aliphatic cyclic polyamine may be an aliphatic hydrocarbon having two or more amino groups as substituents on the ring structure (i.e., bonded to the ring), or may be a heterocyclic amine having two or more amino groups in the ring structure (i.e., constituting the ring). Alternatively, the aliphatic cyclic polyamine may be a heterocyclic amine having one or more amino groups as substituents on the ring structure and one or more amino groups in the ring structure. The amino group as a substituent on the ring structure may be a primary amino group or a secondary amino group, with a primary amino group being preferred. The amino group in the ring structure of the heterocyclic amine is preferably a secondary amino group.

[0040] The alicyclic polyamine in the present invention is preferably one in which the nitrogen atoms or amino groups do not form a complex or salt structure. In the case of an alicyclic polyamine having free amino groups that do not form a complex or salt structure, the curing rate of the resin composition can be increased more than in the case of an alicyclic polyamine in which the nitrogen atoms or amino groups are stabilized by forming a complex or salt structure.

[0041] In the ring structure of the aliphatic cyclic polyamine of the present invention, it is preferable that all of the substituents of the element (carbon atom, etc.) adjacent to the amino group (preferably a secondary amino group) in the ring structure and / or the element (carbon atom, etc.) adjacent to the element (carbon atom, etc.) to which the amino group on the ring structure is bonded are hydrogen atoms. When all of the substituents are hydrogen atoms, there is no steric hindrance to the reaction of the amino group with the epoxy resin, compared to when a substituent other than a hydrogen atom (e.g., an alkyl group, etc.) is bonded, and the curing rate of the resin composition can be further increased. When there are two or more amino groups in the ring structure, it is sufficient that the substituents of at least two elements adjacent to one amino group in the ring structure are all hydrogen atoms, but it is preferable that the substituents of all elements adjacent to all amino groups in the ring structure are all hydrogen atoms. When two or more amino groups are bonded as substituents to the ring structure, it is sufficient that the substituents of at least two elements adjacent to one element to which an amino group is bonded are all hydrogen atoms, but it is preferable that the substituents of all elements adjacent to all elements to which an amino group is bonded are all hydrogen atoms. More preferably, a ring structure in which all substituents of elements (carbon atoms, etc.) other than the amino group (preferably a secondary amino group) in the ring structure and / or elements (carbon atoms, etc.) other than the element (carbon atom, etc.) to which the amino group on the ring structure is bonded are hydrogen atoms is selected.

[0042] The aliphatic cyclic polyamine preferably has a boiling point of 140° C. or higher, more preferably 145° C. to 250° C. If the boiling point is 140° C. or higher, it is sufficiently higher than the temperature when reinforcing fibers are impregnated with a resin composition in the process of producing a fiber-reinforced composite material using an epoxy resin as the matrix resin, and therefore volatilization of the aliphatic cyclic polyamine component can be suppressed, thereby suppressing structural defects and strength reduction in the fiber-reinforced composite material.

[0043] The aliphatic cyclic polyamine preferably has a melting point of 160° C. or lower, for example, 150° C. or lower, 140° C. or lower, 130° C. or lower, or 120° C. or lower. If the melting point is 160° C. or lower, the aliphatic cyclic polyamine can be easily dissolved in the liquid aromatic polyamine in a short time.

[0044] The aliphatic cyclic polyamine is preferably a compound having one, two or three ring structures, from the viewpoint of reducing the viscosity of the resin composition.

[0045] The aliphatic cyclic polyamine preferably contains a primary amino group or a secondary amino group from the viewpoint of improving the heat resistance of the cured product. From the viewpoint of reactivity, it is more preferable that the amino group in the ring structure contains a secondary amino group, even more preferable that it contains only a secondary amino group, and it is more preferable that the amino group as a substituent contains a primary amino group. If a primary amino group or a secondary amino group is contained, it may also contain a tertiary amino group to the extent that it does not adversely affect the physical properties such as the heat resistance of the cured product.

[0046] The aliphatic cyclic polyamine containing a secondary amino group is preferably one having a piperazine skeleton, such as piperazine, 2-methylpiperazine, homopiperazine, trans-2,5-dimethylpiperazine, cis-2,6-dimethylpiperazine, (S)-(+)-2-methylpiperazine, N-(2-aminoethyl)piperazine, 1-butylpiperazine, 1-methylpiperazine, 2-piperazinone, etc. Among these, piperazine is more preferred as the aliphatic cyclic polyamine because of its high reactivity and ability to shorten the curing time.

[0047] Other preferred examples of the aliphatic cyclic polyamine containing a secondary amino group include 1,3-bis(aminomethyl)cyclohexane, dexrazoxane, 3-aminopyrrolidine, 3-(methylamino)pyrrolidine, 3-(ethylamino)pyrrolidine, (1S,6S)-2,8-diazabicyclo[4.3.0]nonane, 3-acetamidopyrrolidine, 4-aminopiperidine, 3-amino-2-piperidone, and 3-(aminomethyl)piperidine. Lysine, 2-piperidinecarboxamide, 3-acetamidopiperidine, 4-amino-2,2,6,6-tetramethylpiperidine, 4,4'-bipiperidine, DL-α-amino-ε-caprolactam, 1,2,3,4-cyclobutanetetracarboxylic acid diimide, trans-N,N'-dimethylcyclohexane-1,2-diamine, (1S,2S)-(+)-N,N'-dimethylcyclohexane-1,2-diamine, (1R,2R)-(-)-N,N'-dimethylcyclohexane-1,2-diamine, N-(3-aminopropyl)cyclohexylamine, N-(1-adamantyl)ethylenediamine, trans-N,N'-diacetylcyclohexane-1,2-diamine, 1-adamantylthiourea, (1S,2R)-N1-(tert-butoxycarbonyl)-1,2-cyclohexanediamine, (1R,2S)-N1-(te (1S,2S)-N1-(tert-butoxycarbonyl)-1,2-cyclohexanediamine, (1R,2R)-N1-(tert-butoxycarbonyl)-1,2-cyclohexanediamine, 1,3-dicyclohexylurea, 1,3-dicyclohexylthiourea, 1-cyclohexylguanidine, 1-cyclohexylbiguanide, and the like.

[0048] When the curing agent is taken as 100 mass%, the alicyclic polyamine, if present, is contained in the curing agent in an amount of preferably 1 to 15 mass%, more preferably 2 to 12 mass%, and even more preferably 3 to 10 mass%. If the alicyclic polyamine is 1 mass% or more, the curing rate of the resin composition can be increased, and if it is 15 mass%, the heat resistance of the cured product will not be impaired.

[0049] The epoxy resin curing agent of the present invention may optionally contain additional components such as borate compounds, titanate compounds, zirconate compounds, silane compounds, carboxylic acid compounds, phenol compounds, halogen compounds, etc., within the range that does not impair the effects of the present invention. These additional components may be contained in the form of a salt with (B) a solid aromatic amine containing a secondary amino group.

[0050] The curing agent of the present invention may be in a liquid form obtained by dissolving a solid aromatic amine containing a secondary amino group and, if present, an aliphatic cyclic polyamine in a liquid aromatic polyamine, or in the form of a suspension in which the solid aromatic amine containing a secondary amino group and, if present, an aliphatic cyclic polyamine are present as solids in the liquid aromatic polyamine. The curing agent of the present invention is preferably in a liquid form. By dissolving other components in the liquid aromatic polyamine to make the curing agent in a liquid state, the resin composition can be quickly impregnated into fibers during the production process of a fiber-reinforced composite material having an epoxy resin as the matrix resin.

[0051] The method for producing an epoxy resin curing agent of the present invention, for example, in the case of a liquid curing agent, includes a step of dissolving a solid aromatic amine containing secondary amino groups in a liquid aromatic polyamine to obtain the epoxy resin curing agent. When the (B) solid aromatic amine containing secondary amino groups does not include (B1) a solid aromatic amine in which the number of secondary amino groups is greater than the total number of primary and tertiary amino groups, the method further includes a step of dissolving (C) an aliphatic cyclic polyamine. When the (B) solid aromatic amine containing secondary amino groups includes (B1) a solid aromatic amine in which the number of secondary amino groups is greater than the total number of primary and tertiary amino groups, the method for producing a liquid epoxy resin curing agent may further include a step of dissolving (C) an aliphatic cyclic polyamine in addition to the step of dissolving (B) a solid aromatic amine containing secondary amino groups in (A) a liquid aromatic polyamine. The dissolving means is not particularly limited; for example, the raw materials may be mixed and then heated and dissolved using a heating device such as an oven or a heated tank. When using an oven, heating may be performed, for example, at a temperature of 80 to 120°C, 90 to 110°C, or 95 to 105°C for a time of 20 to 90 minutes, 30 to 60 minutes, or 40 to 50 minutes. The heating temperature and heating time can be adjusted appropriately depending on the heating device used and the scale of the raw materials.

[0052] As one aspect of the present invention, a resin composition can be provided that includes an epoxy resin curing agent and an epoxy resin.

[0053] The epoxy resin contained in the resin composition can be any conventionally known epoxy resin without any particular limitation. The epoxy resin can be appropriately selected depending on the application and the desired properties of the cured product. For example, from the viewpoint of the impact strength of the cured product, a bifunctional or higher epoxy resin is preferred, and a trifunctional or higher epoxy resin is more preferred.

[0054] The tri- or higher functional epoxy resin is preferably a glycidyl amine type epoxy resin, such as diaminodiphenylmethane type epoxy resin, diaminodiphenyl sulfone type epoxy resin, aminophenol type epoxy resin, metaxylenediamine type epoxy resin, 1,3-bisaminomethylcyclohexane type epoxy resin, isocyanurate type epoxy resin, etc. The tri- or higher functional epoxy resin may be preferably a glycidyl ether type epoxy resin, such as phenol novolac type epoxy resin, orthocresol novolac type epoxy resin, trishydroxyphenylmethane type epoxy resin, tetraphenylolethane type epoxy resin, dicyclopentadiene type epoxy resin, etc.

[0055] Commercially available examples of trifunctional or higher glycidylamine epoxy resins include diaminodiphenylmethane epoxy resins (Sumitomo Chemical Co., Ltd.'s "ELM434," Mitsubishi Chemical Co., Ltd.'s "jER604," Huntsman Advanced Materials' "Araldite MY720," "Araldite MY721," "Araldite MY9512," and "Araldite MY9663," and Tohto Kasei Co., Ltd.'s "Epotohto YH-434"), aminophenol epoxy resins (diaminodiphenylmethane epoxy resins), and glycidylamine epoxy resins (diaminodiphenylmethane epoxy resins). Examples of epoxy resins include "jER630" manufactured by Japan Epoxy Resins, "Araldite MY0510", "Araldite MY0600", and "Araldite MY0610" manufactured by Huntsman, metaxylenediamine type epoxy resins ("TETRAD-X" manufactured by Mitsubishi Gas Chemical Company, Inc.), 1,3-bisaminomethylcyclohexane type epoxy resins ("TETRAD-C" manufactured by Mitsubishi Gas Chemical Company, Inc.), and isocyanurate type epoxy resins ("TEPIC-P" manufactured by Nissan Chemical Industries, Ltd.).

[0056] Commercially available examples of tri- or higher functional glycidyl ether epoxy resins include phenol novolac epoxy resins (Dow Chemical Company's "DEN431" and "DEN438" and Japan Epoxy Resins' "jER152"), orthocresol novolac epoxy resins (Nippon Kayaku Co., Ltd.'s "EOCN-1020" and DIC Corporation's "Epiclon N-660"), trishydroxyphenylmethane epoxy resins (Huntsman Advanced Materials' "TactiX742"), tetraphenylolethane epoxy resins (Japan Epoxy Resins' "jER1031S"), and dicyclopentadiene epoxy resins (DIC Corporation's "Epiclon HP7200").

[0057] The epoxy resin may be bifunctional. Preferred bifunctional epoxy resins are glycidyl ether epoxy resins, such as bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, naphthalene epoxy resins, biphenyl epoxy resins, urethane-modified epoxy resins, and hydantoin epoxy resins.

[0058] Commercially available examples of bifunctional glycidyl ether epoxy resins include bisphenol A epoxy resins ("jER828" and "jER825" manufactured by Mitsubishi Chemical Corporation, "Epicron 850" manufactured by DIC Corporation, "Epotohto YD-128" manufactured by Tohto Kasei Co., Ltd., and "DER-331" and "DER-332" manufactured by The Dow Chemical Company), bisphenol F epoxy resins ("jER806", "jER807", and "jER1750" manufactured by Mitsubishi Chemical Corporation, "Epicron 830" manufactured by DIC Corporation, and "Epotohto YD-170" manufactured by Tohto Kasei Co., Ltd.), biphenyl epoxy resins ("NC-3000" manufactured by Nippon Kayaku Co., Ltd.), urethane-modified epoxy resins ("AER4152" manufactured by Asahi Kasei Epoxy Corporation), and hydantoin epoxy resins ("AY238" manufactured by Huntsman Advanced Materials).

[0059] The epoxy equivalent of the epoxy resin contained in the resin composition is preferably 50 to 500, more preferably 75 to 300, and even more preferably 100 to 200. An epoxy resin with an epoxy equivalent of 50 or more is preferred because it has low volatility, does not have a low viscosity, and has a viscosity that is easy to handle. Furthermore, an epoxy resin with an epoxy equivalent of 500 or less does not have a high viscosity, and is therefore preferred in terms of handling. Here, the epoxy equivalent is the mass of an epoxy resin containing one equivalent of epoxy groups, and can be measured, for example, in accordance with JIS K 7236 (2009).

[0060] The epoxy resin may be used alone or in combination of two or more. The epoxy resin may be liquid or solid. A mixture of a liquid resin and a solid resin may also be used. Here, "liquid" and "solid" refer to the state of the epoxy resin at room temperature (25°C). From the viewpoint of processability, it is preferable that at least 10% by mass of the total epoxy resin used be liquid epoxy resin.

[0061] The content of the epoxy resin in the resin composition is not particularly limited, but is preferably 1 to 99 mass %, more preferably 20 to 95 mass %, and even more preferably 50 to 90 mass %.

[0062] When the epoxy resin is taken as 100% by mass, the epoxy resin curing agent of the present invention is contained in the resin composition in an amount of preferably 10 to 75% by mass, more preferably 15 to 65% by mass, and even more preferably 20 to 55% by mass, from the viewpoint of reducing the viscosity of the resin composition.

[0063] The resin composition of the present invention may further contain one or more selected from the group consisting of a curing agent, a curing accelerator, a thermosetting resin, a thermoplastic resin, an inorganic filler, an organic filler, a thickener, an antifoaming agent, a leveling agent, an adhesion promoter, a colorant, and an organic solvent.

[0064] The curing agent means an epoxy resin curing agent other than the epoxy resin curing agent of the present invention, and examples thereof include acid anhydride compounds, thiol compounds, guanidine compounds, hydrazide compounds, phenol compounds, naphthol compounds, active ester compounds, benzoxazine compounds, cyanate ester compounds, and carbodiimide compounds.

[0065] Examples of the thiol compound include thiol compounds obtained by the esterification reaction of a polyol, such as trimethylolpropane tris(thioglycolate), pentaerythritol tetrakis(thioglycolate), ethylene glycol dithioglycolate, trimethylolpropane tris(3-mercaptopropionate), trimethylolpropane tris(β-thiopropionate), pentaerythritol tetrakis(β-thiopropionate), and dipentaerythritol poly(β-thiopropionate), with a mercapto organic acid; alkyl polythiol compounds, such as 1,4-butanedithiol, 1,6-hexanedithiol, and 1,10-decanedithiol; terminal thiol group-containing polyethers; terminal thiol group-containing polythioethers; thiol compounds obtained by the reaction of an epoxy compound with hydrogen sulfide; and thiol compounds having terminal thiol groups obtained by the reaction of a polythiol compound with an epoxy compound. Examples of acid anhydride compounds include tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, methylbicyclo[2.2.1]heptane-2,3-dicarboxylic anhydride, tetrapropenyl succinic anhydride (3-dodecenyl succinic anhydride), octenylsuccinic anhydride, ethylene glycol bisanhydrotrimellitate, methylendomethylenetetrahydrophthalic anhydride, 3,4-dimethyl-6-(2-methyl-1-propenyl)-4-cyclohexene-1,2-dicarboxylic anhydride, and mixtures of the above compounds with 1-isopropyl-4-methylbicyclo[2.2.2]oct-5-ene-2,3-dicarboxylic anhydride. Examples of commercially available acid anhydrides include HN-2200 (methyltetrahydrophthalic anhydride) and HN-5500 (methyltetrahydrophthalic anhydride) manufactured by Hitachi Chemical Co., Ltd. Examples of guanidine compounds include dicyandiamide, 1-methylguanidine, 1-ethylguanidine, dimethylguanidine, trimethylguanidine, tetramethylguanidine, pentamethylguanidine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1-methylbiguanide, 1-ethylbiguanide, 1-n-butylbiguanide, 1-n-octadecylbiguanide, 1,1-dimethylbiguanide, 1,1-diethylbiguanide, and 1-allylbiguanide. Dicyandiamide is particularly preferred as a guanidine compound. Commercially available guanidine compounds include "jER Cure DICY-7" (dicyandiamide) manufactured by Japan Epoxy Resins Co., Ltd. Examples of hydrazide compounds include carbohydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, iminodiacetic acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecanediohydrazide, hexadecanedihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, diglycolic acid dihydrazide, tartaric acid dihydrazide, malic acid dihydrazide, citric acid trihydrazide, etc. Furthermore, commercially available hydrazide compounds include, for example, Amicure VDH and Amicure UDH manufactured by Ajinomoto Fine-Techno Co., Ltd. Specific examples of phenol compounds and naphthol compounds include "MEH-7700," "MEH-7810," and "MEH-7851" manufactured by Meiwa Chemical Industry Co., Ltd.; "NHN," "CBN," and "GPH" manufactured by Nippon Kayaku Co., Ltd.; "SN170," "SN180," "SN190," "SN475," "SN485," "SN495," "SN375," and "SN395" manufactured by Nippon Steel & Sumitomo Metal Corporation; and "LA7052," "LA7054," "LA3018," "EXB-9500," and "TD2090" manufactured by DIC Corporation. The active ester compound is not particularly limited, but compounds having two or more highly reactive ester groups per molecule, such as phenol esters, thiophenol esters, N-hydroxyamine esters, and esters of heterocyclic hydroxy compounds, are generally preferred. The active ester compound is preferably one obtained by the condensation reaction of a carboxylic acid compound and / or a thiocarboxylic acid compound with a hydroxy compound and / or a thiol compound. Specifically, active ester compounds containing a dicyclopentadiene-type diphenol structure, active ester compounds containing a naphthalene structure, active ester compounds containing an acetylated product of phenol novolac, and active ester compounds containing a benzoylated product of phenol novolac are preferred. The term "dicyclopentadiene-type diphenol structure" refers to a divalent structural unit consisting of phenylene-dicyclopentylene-phenylene. Commercially available active ester compounds include "EXB9451," "EXB9460," "EXB9460S," and "HPC-8000-65T" (manufactured by DIC Corporation) as active ester compounds containing a dicyclopentadiene-type diphenol structure, "EXB9416-70BK" (manufactured by DIC Corporation) as an active ester compound containing a naphthalene structure, "DC808" (manufactured by Mitsubishi Chemical Corporation) as an active ester compound containing an acetylated phenol novolac, and "YLH1026" (manufactured by Mitsubishi Chemical Corporation) as an active ester compound containing a benzoylated phenol novolac. Specific examples of benzoxazine compounds include "HFB2006M" manufactured by Showa Polymer Co., Ltd., and "Pd" and "Fa" manufactured by Shikoku Chemicals Corporation. Examples of cyanate ester compounds include bifunctional cyanate resins such as bisphenol A dicyanate, polyphenol cyanate, oligo(3-methylene-1,5-phenylene cyanate), 4,4'-methylenebis(2,6-dimethylphenyl cyanate), 4,4'-ethylidene diphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanate)phenylpropane, 1,1-bis(4-cyanatephenylmethane), bis(4-cyanate-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanatephenyl-1-(methylethylidene))benzene, bis(4-cyanatephenyl)thioether, and bis(4-cyanatephenyl)ether; multifunctional cyanate resins derived from phenol novolac and cresol novolac; and prepolymers in which these cyanate resins are partially converted to triazine. Specific examples of cyanate ester curing agents include "PT30" and "PT60" (both phenol novolac type multifunctional cyanate ester resins) manufactured by Lonza Japan Co., Ltd., and "BA230" (a prepolymer in which part or all of bisphenol A dicyanate has been triazine converted to a trimer). Specific examples of the carbodiimide compound include "V-03" and "V-07" manufactured by Nisshinbo Chemical Inc.

[0066] The curing accelerator does not include the aliphatic cyclic polyamine of the present invention, and examples thereof include phosphorus-based curing accelerators, amine-based curing accelerators, imidazole-based curing accelerators, guanidine-based curing accelerators, etc. The curing accelerators may be used alone or in combination of two or more. Examples of phosphorus-based curing accelerators include triphenylphosphine, phosphonium borate compounds, tetraphenylphosphonium tetraphenylborate, n-butylphosphonium tetraphenylborate, tetrabutylphosphonium decanoate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, and butyltriphenylphosphonium thiocyanate, with triphenylphosphine and tetrabutylphosphonium decanoate being preferred. Examples of the amine curing accelerator include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and 1,8-diazabicyclo(5,4,0)-undecene, with 4-dimethylaminopyridine and 1,8-diazabicyclo(5,4,0)-undecene being preferred. Examples of the imidazole curing accelerator include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2, 4-Diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, Examples of the imidazole compound include imidazole compounds such as phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, and 2-phenylimidazoline, as well as adducts of imidazole compounds with epoxy resins, with 2-ethyl-4-methylimidazole and 1-benzyl-2-phenylimidazole being preferred. As the imidazole-based curing accelerator, commercially available products may be used, for example, "P200-H50" manufactured by Mitsubishi Chemical Corporation. As the guanidine-based curing accelerator, the same compounds as the guanidine compounds as the curing agent can be used, for example, dicyandiamide, 1-methylguanidine, 1-ethylguanidine, 1-cyclohexylguanidine, 1-phenylguanidine, 1-(o-tolyl)guanidine, dimethylguanidine, diphenylguanidine, trimethylguanidine, tetramethylguanidine, pentamethylguanidine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 7 ... 1-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1-methylbiguanide, 1-ethylbiguanide, 1-n-butylbiguanide, 1-n-octadecylbiguanide, 1,1-dimethylbiguanide, 1,1-diethylbiguanide, 1-cyclohexylbiguanide, 1-allylbiguanide, 1-phenylbiguanide, 1-(o-tolyl)biguanide, and the like are included, and dicyandiamide and 1,5,7-triazabicyclo[4.4.0]dec-5-ene are preferred. The content of the curing accelerator in the resin composition is not particularly limited, but it is preferably used in the range of 0.05% by mass to 3% by mass.

[0067] The thermosetting resin means a thermosetting resin other than the above-mentioned epoxy resin, and examples thereof include vinylbenzyl compounds, acrylic compounds, maleimide compounds, and blocked isocyanate compounds.

[0068] Examples of thermoplastic resins include phenoxy resins, polyvinyl acetal resins, polyolefin resins, polybutadiene resins, polyimide resins, polyamideimide resins, polyetherimide resins, polysulfone resins, polyethersulfone resins, polyphenylene ether resins, polycarbonate resins, polyetheretherketone resins, and polyester resins, with phenoxy resins being preferred. The thermoplastic resins may be used singly or in combination of two or more. The polystyrene-equivalent weight-average molecular weight of the thermoplastic resin is preferably in the range of 8,000 to 70,000, more preferably in the range of 10,000 to 60,000, and even more preferably in the range of 20,000 to 60,000. The polystyrene-equivalent weight-average molecular weight of the thermoplastic resin is measured by gel permeation chromatography (GPC). Specifically, the polystyrene-equivalent weight-average molecular weight of the thermoplastic resin is measured using an LC-9A / RID-6A measuring device manufactured by Shimadzu Corporation, a Shodex K-800P / K-804L / K-804L column manufactured by Showa Denko K.K., and chloroform or the like as the mobile phase at a column temperature of 40°C, and can be calculated using a calibration curve of standard polystyrene. Examples of the phenoxy resin include phenoxy resins having one or more skeletons selected from the group consisting of a bisphenol A skeleton, a bisphenol F skeleton, a bisphenol S skeleton, a bisphenolacetophenone skeleton, a novolac skeleton, a biphenyl skeleton, a fluorene skeleton, a dicyclopentadienyl skeleton, a norbornene skeleton, a naphthalene skeleton, an anthracene skeleton, an adamantane skeleton, a terpene skeleton, and a trimethylcyclohexane skeleton. The terminal of the phenoxy resin may be any functional group such as a phenolic hydroxyl group or an epoxy group. One type of phenoxy resin may be used alone, or two or more types may be used in combination. Specific examples of phenoxy resins include "1256" and "4250" (both phenoxy resins containing a bisphenol A skeleton), "YX8100" (phenoxy resin containing a bisphenol S skeleton), and "YX6954" (phenoxy resin containing a bisphenol acetophenone skeleton), all manufactured by Mitsubishi Chemical Corporation. Other examples include "FX280" and "FX293" manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., and "YL6954BH30," "YX7553," "YL7769BH30," "YL6794," "YL7213," "YL7290," and "YL7482" manufactured by Mitsubishi Chemical Corporation. Examples of polyvinyl acetal resins include polyvinyl formal resins and polyvinyl butyral resins, with polyvinyl butyral resins being preferred. Specific examples of polyvinyl acetal resins include Denka Butyral 4000-2, Denka Butyral 5000-A, Denka Butyral 6000-C, and Denka Butyral 6000-EP manufactured by Denki Kagaku Kogyo Co., Ltd., and S-LEC BH series, BX series, KS series, BL series, and BM series manufactured by Sekisui Chemical Co., Ltd. Specific examples of polyimide resins include "Rikacoat SN20" and "Rikacoat PN20" manufactured by New Japan Chemical Co., Ltd. Specific examples of polyamide-imide resins include "Vylomax HR11NN" and "Vylomax HR16NN" manufactured by Toyobo Co., Ltd. Specific examples of polyamide-imide resins also include modified polyamide-imides such as "KS9100" and "KS9300" (polysiloxane skeleton-containing polyamide-imides) manufactured by Hitachi Chemical Co., Ltd. A specific example of the polyethersulfone resin is "PES5003P" manufactured by Sumitomo Chemical Co., Ltd. Specific examples of polysulfone resins include polysulfones "P1700" and "P3500" manufactured by Solvay Advanced Polymers K.K. The content of the thermoplastic resin in the resin composition is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and even more preferably 1 to 5% by mass.

[0069] The inorganic filler is not particularly limited, but examples thereof include silica, alumina, glass, cordierite, silicon oxide, barium sulfate, barium carbonate, talc, clay, mica powder, zinc oxide, hydrotalcite, boehmite, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, magnesium oxide, boron nitride, aluminum nitride, manganese nitride, aluminum borate, strontium carbonate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, titanium oxide, zirconium oxide, barium titanate, barium titanate zirconate, barium zirconate, calcium zirconate, zirconium phosphate, zirconium tungstate phosphate, iron, iron oxide, ferrite, alloys, other conductive fillers, magnetic fillers, thermally conductive fillers, etc. One embodiment of the present invention is an epoxy resin composition containing at least one selected from the group consisting of silica, conductive fillers, magnetic fillers, and thermally conductive fillers.

[0070] Specific examples of silica include amorphous silica, fused silica, crystalline silica, synthetic silica, and hollow silica. Spherical silica is preferred. The average particle size is not particularly limited, but is preferably 600 nm or less, more preferably 300 nm or less, and even more preferably 200 nm or less. The lower limit of the average particle size is not particularly limited, but is preferably 5 nm or more. Examples of commercially available products include "SO-C2," "SO-C1," and "SO-C4" manufactured by Admatechs Co., Ltd. The average particle size of the inorganic filler can be measured by a laser diffraction / scattering method based on the Mie scattering theory.

[0071] Specific examples of conductive fillers include metal particles such as solder particles, nickel particles, nano-sized metal crystals, particles in which the surface of a metal is coated with another metal, and gradient particles of copper and silver, as well as resin particles such as styrene resin, urethane resin, melamine resin, epoxy resin, acrylic resin, phenolic resin, and styrene-butadiene resin coated with a conductive thin film of gold, nickel, silver, copper, solder, etc. Conductive fillers are usually spherical fine particles of about 1 to 20 μm.

[0072] Specific examples of the magnetic filler include pure iron powder, Fe-Si alloy powder, Fe-Si-Al alloy powder, Fe-Ni alloy powder, Fe-Ni-Mo alloy powder, Fe-Ni-Mo-Cu alloy powder, Fe-Co alloy powder, Fe-Ni-Co alloy powder, Fe-Cr alloy powder, Fe-Cr-Si alloy powder, Fe-Ni-Cr alloy powder, and Fe-Cr-Al alloy powder, as well as Fe alloys such as Fe-based amorphous and Co-based amorphous. Examples of such ferrites include amorphous alloys, spinel ferrites such as Mg-Zn ferrite, Mn-Zn ferrite, Mn-Mg ferrite, Cu-Zn ferrite, Mg-Mn-Sr ferrite, and Ni-Zn ferrite, hexagonal ferrites such as Ba-Zn ferrite, Ba-Mg ferrite, Ba-Ni ferrite, Ba-Co ferrite, and Ba-Ni-Co ferrite, and garnet ferrites such as Y ferrite.

[0073] Specific examples of thermally conductive fillers include aluminum nitride, alumina, boron nitride, silicon nitride, graphite powder, and silicon carbide. Commercially available aluminum nitride products include "Shapal H" manufactured by Tokuyama Corporation, and commercially available silicon nitride products include "SN-9S" manufactured by Denki Kagaku Kogyo Kabushiki Kaisha. Commercially available alumina products include "AHP300" manufactured by Nippon Light Metal Co., Ltd., "Alnabeads (registered trademark) CB" (e.g., "CB-P05" and "CB-A30S") manufactured by Showa Denko K.K., and "DAW-45," "DAW-05," and "ASFP-20" manufactured by Denka Company Limited.

[0074] Examples of organic fillers include silicon powder, nylon powder, fluorine powder, acrylic rubber particles, polyamide microparticles, silicone particles, etc. Specific examples of acrylic rubber particles include any resin microparticles that are insoluble and infusible in organic solvents and are obtained by chemically crosslinking a resin exhibiting rubber elasticity, such as acrylonitrile butadiene rubber, butadiene rubber, or acrylic rubber, and specific examples include XER-91 (manufactured by Japan Synthetic Rubber Co., Ltd.), Staphyloid AC3355, AC3816, AC3832, AC4030, AC3364, and IM101 (all manufactured by Aica Kogyo Co., Ltd.), and Paraloid EXL2655 and EXL2602 (all manufactured by Kureha Chemical Industry Co., Ltd.). Specific examples of polyamide microparticles include any microparticles of 50 microns or less made of a resin having an amide bond, such as an aliphatic polyamide such as nylon, an aromatic polyamide such as Kevlar, or even polyamideimide.Specific examples include VESTOSINT 2070 (manufactured by Daicel-Huls Co., Ltd.) and SP500 (manufactured by Toray Industries, Inc.).

[0075] Examples of thickeners include Orben and Bentone.

[0076] Examples of the antifoaming agent include silicone-based antifoaming agents, fluorine-based antifoaming agents, and polymer-based antifoaming agents.

[0077] As the leveling agent, commercially available surfactants can be used, and examples thereof include silicone-based, fluorine-based, ester-based, cationic, anionic, nonionic, and amphoteric surfactants, and these may be used alone or in combination of two or more. Examples of the surfactant include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyethylene glycol diesters, sorbitan fatty acid esters, fatty acid-modified polyesters, tertiary amine-modified polyurethanes, and polyethyleneimines, as well as trade names such as KP (manufactured by Shin-Etsu Chemical Co., Ltd.), Polyflow (manufactured by Kyoeisha Chemical Co., Ltd.), F-Top (Mitsubishi Materials Electronic Chemicals Co., Ltd.), Megafac (manufactured by DIC Corporation), Fluorad (manufactured by Sumitomo 3M Limited), Asahi Guard (manufactured by Asahi Glass Co., Ltd.), Surflon (manufactured by AGC Seimi Chemical Co., Ltd.), Solsperse (manufactured by Zeneca Corporation), EFKA (manufactured by CIBA), and Ajisper (manufactured by Ajinomoto Fine-Techno Co., Ltd.).

[0078] Examples of adhesion promoters include imidazoles, thiazoles, triazoles, silane coupling agents, etc. Specific examples include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane.

[0079] Examples of colorants include phthalocyanine blue, phthalocyanine green, iodine green, disazo yellow, and carbon black.

[0080] Examples of organic solvents include ketones such as acetone, methyl ethyl ketone (MEK), and cyclohexanone, acetate esters such as ethyl acetate, butyl acetate, cellosolve acetate, propylene glycol monomethyl ether acetate, and carbitol acetate, carbitols such as cellosolve and butyl carbitol, aromatic hydrocarbons such as toluene and xylene, and amide solvents such as dimethylformamide, dimethylacetamide (DMAc), and N-methylpyrrolidone. The organic solvents may be used alone or in combination of two or more.

[0081] From the viewpoint of workability during impregnation of reinforcing fibers in the production of fiber-reinforced composite materials, the resin composition preferably has an initial viscosity of 100 cP or less, more preferably 99 cP or less, and even more preferably 98 cP or less, under heating conditions of 80°C or higher (e.g., 90°C). The resin composition may have a viscosity of 10 cP or more, 20 cP or more, 30 cP or more, or 40 cP or more, under heating conditions of 80°C or higher (e.g., 90°C). "Initial viscosity" refers to the viscosity measured immediately after mixing the epoxy resin and the epoxy resin curing agent. The viscosity can be measured using a commercially available viscosity measuring device, such as the RheoStress 6000 manufactured by HAAKE. A "low viscosity" resin composition refers to a resin composition having an initial viscosity of 100 cP or less under heating conditions of 80°C or higher (e.g., 90°C).

[0082] By using the curing agent of the present invention, a fast-curing resin composition can be obtained. The curing speed of the resin composition can be evaluated, for example, by measuring the exothermic peak of a cured product of the resin composition obtained under specific curing conditions using a commercially available differential scanning calorimeter, such as a Hitachi High-Tech Science DSC7000X differential scanning calorimeter. If uncured resin composition remains, an exothermic peak will appear. In the case of a "fast-curing" resin composition, no exothermic peak will be observed, or even if observed, the amount of heat generated will be small, as determined from the area of ​​the exothermic peak.

[0083] As another embodiment of the resin composition of the present invention, a two-component kit containing a base agent containing an epoxy resin and a curing agent for epoxy resin can be provided.

[0084] The resin composition (kit) of the present invention can be used as an epoxy resin material in various fields such as architecture, civil engineering, automobiles, ships, aerospace, industrial machinery, robots, communications, electrical and electronics, semiconductors, and displays, and is particularly suitable as a matrix resin for composite materials used in aircraft, etc.

[0085] The present invention further relates to a cured product of the epoxy resin composition, a method for producing a cured product, and a method for curing an epoxy resin, the method comprising the steps of mixing an epoxy resin with an epoxy resin curing agent and curing the epoxy resin to obtain a cured product.

[0086] The epoxy resin and the epoxy resin curing agent can be mixed by any conventional mixing method without any particular limitations. For example, a commercially available planetary centrifugal stirring and defoaming machine may be used for stirring and defoaming. Heating is preferred as a curing method, and the epoxy resin may be cured by holding the mixture at a temperature of 120 to 250°C, 150 to 220°C, or 170 to 190°C for, for example, 30 minutes to 4 hours, 1 to 3 hours, or 1.5 to 2.5 hours.

[0087] The cured product of the resin composition of the present invention has excellent mechanical properties such as high impact strength. The mechanical properties of the cured product can be evaluated, for example, by measuring the modulus of elasticity, flexural strength, elongation, etc. using a three-point bending compression test using a Tensilon universal testing machine, or by measuring the impact strength using a commercially available impact tester. The cured product of the resin composition of the present invention also has high heat resistance. Heat resistance can be evaluated by the glass transition temperature of the cured product.

[0088] In another aspect of the present invention, a composite material can be provided that includes a cured product of the resin composition of the present invention and reinforcing fibers. Examples of composite materials include composite materials used in resin transfer molding, composite materials used in filament winding, and prepregs. The reinforcing fibers are not particularly limited, and commonly used reinforcing fibers such as carbon fibers, glass fibers, and aramid fibers can be used. From the viewpoint of achieving both lightweight and strong composite materials, carbon fibers are particularly preferred. For example, in the case of resin transfer molding, a fiber-reinforced composite material can be obtained by injecting a resin composition into reinforcing fibers placed in a mold and then heat-curing the resin composition.

[0089] The resin composition of the present invention has a low initial viscosity and is fast-curing, making it suitable for use in resin transfer molding. Furthermore, since the cured product of the resin composition of the present invention has excellent mechanical properties, composite materials containing the cured product can be particularly applied in fields requiring high performance, such as aircraft components.

[0090] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples. [Example]

[0091] <Preparation example of hardener> To a liquid mixture of 19.8 g of dimethylthiotoluenediamine (viscosity 3 cP (90°C, 70 rpm)), 16.4 g of diethyltoluenediamine (viscosity 1 cP (90°C, 70 rpm)), and 10 g of 4,4-methylenebis[N-(1-methylpropyl)aniline] (viscosity 7 cP (90°C, 70 rpm)), 2.0 g of 1-(o-tolyl)biguanide (solid) and 2.0 g of anhydrous piperazine were added, and the mixture was heated and dissolved in an oven at 100°C for 45 minutes to prepare the curing agent of Example 1. Curing agents of Examples 2 to 24 and Comparative Examples 1 to 22 were prepared in the same manner as Example 1, except that the types and amounts of the liquid aromatic polyamine, solid aromatic polyamine, and aliphatic polyamine were changed as shown in Tables 1 to 7, respectively. Regarding solubility, the state after heating for 45 minutes was visually observed, and samples in which solid matter was observed were rated as "insoluble," and samples in which no solid matter was observed were rated as "soluble."

[0092] <Resin Composition Preparation Example 1> To 70 parts by mass of tetraglycidyldiaminodiphenylmethane epoxy resin (jER604, manufactured by Mitsubishi Chemical Corporation, epoxy equivalent weight 110 to 130), 30 parts by mass of triglycidyl-p-aminophenol (Araldite MY0510, epoxy equivalent weight 101) was added, and the curing agents of Examples 1 to 14 and Comparative Examples 1 to 14 were added in the ratios shown in Tables 1 to 4. The mixture was stirred at 2000 rpm for 2 minutes in a planetary centrifugal stirring and defoaming machine (ARE-300 "Awatori Rentaro" manufactured by Thinky Corporation), and then vacuum degassed at 1000 rpm for 6 minutes in a planetary centrifugal stirring and defoaming machine (Hymerger HM-200WV manufactured by Kyoritsu Seiki Co., Ltd.), to obtain a resin composition.

[0093] <Resin Composition Preparation Example 2> Resin compositions were obtained in the same manner as in Preparation Example 1, except that the resin was changed to 100 parts by mass of a bisphenol A liquid epoxy resin (jER828, manufactured by Mitsubishi Chemical Corporation, epoxy equivalent weight 184 to 194) and the curing agents of Examples 15 to 24 and Comparative Examples 15 to 22 were added in proportions shown in Tables 5 to 7.

[0094] <Preparation of cured product> A mold was created by clamping 2mm x 10mm or 3.5mm x 7mm outer frame spacers around the three edges of a 75cm x 120cm aluminum plate with clips. The resin composition was then heated in an oven at 100°C for 5 minutes, then injected using a syringe into the mold, filling the edges and placing it upright in the oven. The temperature was increased from 25°C at a rate of 2°C / min until the aluminum plate surface temperature reached 180°C. After holding for 2 hours, the temperature was decreased to room temperature at a rate of 3°C / min. The cured product was removed from the mold to produce 2mm or 3.5mm thick resin plates. The 3.5mm thick resin plates were visually inspected for the presence of 10 or more bubbles, and plates with 10 or fewer bubbles were rated as "foamed" and "no bubbles." For the curing agents of Comparative Examples 1 to 5, 8, and 17 to 20, for which the solubility evaluation result after preparation was "insoluble," the undissolved solid components were concentrated at the bottom of the resin composition, and a uniform cured product was not obtained. Therefore, the state of the cured product was evaluated only for Comparative Example 1. For the cured product for which the evaluation result of the state of the cured product was "no bubbles," the following physical properties were evaluated.

[0095] <Initial viscosity measurement> Immediately after preparation, each resin composition was measured for initial viscosity using a rotational rheometer (RheoStress6000 manufactured by HAAKE) under conditions of parallel plates with a diameter of 20 mm, a gap of 0.5 mm, a sample amount of 0.2 ml, 90°C, and 20 rpm.

[0096] <Measurement of elastic modulus, bending strength, and elongation> A 3.5 mm thick resin plate was cut into a size of 10 mm x 96 mm, and a three-point bending compression test was performed at 25°C and 5 mm / min using a Toyo Baldwin Tensilon universal testing machine to determine the elastic modulus, bending strength, and elongation.

[0097] <Measurement of glass transition temperature Tg> A 2 mm thick resin plate was cut into a size of 7 mm x 60 mm, and measurements were performed using a dynamic viscoelasticity measuring device, EXSTAR6000, manufactured by Hitachi High-Tech Science Corporation, at a heating rate of 5°C / min, a frequency of 1 Hz, and bending mode. The intersection of two tangent lines drawn to the inflection point of the storage modulus E' was determined as the glass transition temperature Tg.

[0098] <Impact strength measurement> Resin plates having a thickness of 2 mm were cut into pieces of 20 mm x 40 mm for Examples 1 to 14 and Comparative Examples 1 to 14, and 10 mm x 40 mm for Examples 15 to 24 and Comparative Examples 15 to 22, and the impact strength was measured under no load using an Izod impact tester CIT-40I manufactured by Orientec Co., Ltd.

[0099] <Measurement of degree of cure> A 2mm thick resin plate was cut with pliers, and 5mg was weighed into a sample pan. Measurements were performed using a Hitachi High-Tech Science DSC7000X differential scanning calorimeter, heating from 30 to 300°C at a rate of 5°C / min. For samples showing an exothermic peak, the heat generation amount was calculated from its area. Samples showing no exothermic peak and no residual curing were rated "◎" (best), samples with a heat generation amount of less than 10mJ / mg were rated "〇" (good), samples with a heat generation amount of 10mJ / mg to 20mJ / mg were rated "△" (passable), and samples with a heat generation amount of more than 20mJ / mg were rated "×" (unacceptable).

[0100] [Table 1] [Table 2] [Table 3] [Table 4] [Table 5] [Table 6]

Table 7

Claims

1. A curing agent for epoxy resins, comprising (A) a liquid aromatic polyamine and (B) a solid aromatic amine containing a secondary amino group, An epoxy resin curing agent, wherein (B) the solid aromatic amine containing a secondary amino group either contains or does not contain (B1) a solid aromatic amine in which the number of secondary amino groups is greater than the total number of primary amino groups and tertiary amino groups, and when (B1) the solid aromatic amine does not contain, the epoxy resin curing agent further contains (C) an aliphatic cyclic polyamine.

2. 2. The epoxy resin curing agent according to claim 1, wherein (B) the solid aromatic amine containing a secondary amino group comprises (B1) a solid aromatic amine in which the number of secondary amino groups is greater than the total number of primary amino groups and tertiary amino groups.

3. 3. The epoxy resin curing agent according to claim 2, wherein (B1) the solid aromatic amine in which the number of secondary amino groups is greater than the total number of primary amino groups and tertiary amino groups comprises (B1') a solid aromatic amine containing only secondary amino groups as amino groups.

4. (B1') Solid aromatic amines containing only secondary amino groups as amino groups include N-phenyl-1-naphthylamine, octylated diphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, N-(p-tolyl)-1-naphthylamine, N-phenyl-3-biphenylamine, bis(3-biphenylyl)amine, 2-(3-biphenylyl)amino-9,9-dimethylfluorene, bis(4-tert-butylphenyl)amine, 4-t tert-Butylphenylphenylamine, bis-α-methylbenzylphenothiazine, reaction products of diphenylamine with 2,4,4-trimethylpentene, diphenylamine, N-phenylbenzylamine, 3-methyldiphenylamine, 3,4-dimethyldiphenylamine, 4,4'-dimethyldiphenylamine, 3-methoxydiphenylamine, 10-methoxy-2,2'-iminostilbene, N-benzyl-2-naphthylamine, 1,2'-dinaphthylamine diphenylamine, 1,1'-dinaphthylamine, 4-isopropylaminodiphenylamine, 2,6-bis[(2-hydroxyethyl)amino]toluene, 4-(2-octylamino)diphenylamine, N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 1,3-diphenylguanidine, p-(p-toluenesulfonylamido)diphenylamine, N-phenyl- 4. The epoxy resin curing agent according to claim 3, which is selected from the group consisting of N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine, bis(2-benzamidophenyl)disulfide, N,N'-diphenyl-1,4-phenylenediamine, 1,3-di-o-tolylguanidine, 1,5-diphenylcarbonohydrazide, N,N'-diphenylethylenediamine, and 5-(acetoacetamido)-2-benzimidazolinone.

5. 5. The epoxy resin curing agent according to claim 2, wherein (B) the solid aromatic amine containing a secondary amino group further contains (B2) a solid aromatic polyamine in which the number of secondary amino groups is equal to or less than the total number of primary amino groups and tertiary amino groups.

6. 6. The epoxy resin curing agent according to claim 5, wherein (B2) the solid aromatic polyamine in which the number of secondary amino groups is equal to or less than the total number of primary amino groups and tertiary amino groups is selected from the group consisting of 4-aminodiphenylamine, 2,4-diaminodiphenylamine, 2-aminodiphenylamine, 4-amino-4'-methoxydiphenylamine, 1-phenylbiguanide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, 2,6-naphthoic acid dihydrazide, 4,4'-bisbenzenedihydrazide, 1,4-naphthoic acid dihydrazide, naphthalene-2,6-dicarbohydrazide, and 3-hydroxy-2-naphthoic acid hydrazide.

7. The epoxy resin curing agent according to any one of claims 2 to 6, further comprising (C) an aliphatic cyclic polyamine.

8. 2. The epoxy resin curing agent according to claim 1, wherein (B) the solid aromatic amine containing secondary amino groups does not contain (B1) a solid aromatic amine in which the number of secondary amino groups is more than the total number of primary amino groups and tertiary amino groups, and contains (B2) a solid aromatic polyamine in which the number of secondary amino groups is equal to or less than the total number of primary amino groups and tertiary amino groups.

9. The epoxy resin curing agent according to claim 8, wherein (B2) the solid aromatic polyamine in which the number of secondary amino groups is equal to or less than the total number of primary amino groups and tertiary amino groups is selected from the group consisting of 4-aminodiphenylamine, 2,4-diaminodiphenylamine, 2-aminodiphenylamine, 4-amino-4'-methoxydiphenylamine, 1-phenylbiguanide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, 2,6-naphthoic acid dihydrazide, 4,4'-bisbenzenedihydrazide, 1,4-naphthoic acid dihydrazide, naphthalene-2,6-dicarbohydrazide, and 3-hydroxy-2-naphthoic acid hydrazide.

10. The epoxy resin curing agent according to any one of claims 7 to 9, wherein the boiling point of the aliphatic cyclic polyamine (C) is 140°C or higher.

11. The epoxy resin curing agent according to any one of claims 7 to 10, wherein the aliphatic cyclic polyamine (C) contains a primary amino group or a secondary amino group.

12. 12. The epoxy resin curing agent according to claim 7, wherein the aliphatic cyclic polyamine (C) contains only secondary amino groups as amino groups in the ring structure.

13. The epoxy resin curing agent according to any one of claims 7 to 12, wherein the aliphatic cyclic polyamine (C) does not form a complex or a salt structure.

14. The epoxy resin curing agent according to any one of claims 7 to 13, wherein in the aliphatic cyclic polyamine (C), all of the substituents of the element adjacent to the amino group in the ring structure and / or the element adjacent to the element to which the amino group on the ring structure is bonded are hydrogen atoms.

15. The epoxy resin curing agent according to any one of claims 7 to 14, wherein the aliphatic cyclic polyamine (C) has a piperazine skeleton.

16. The epoxy resin curing agent according to any one of claims 7 to 15, wherein the aliphatic cyclic polyamine (C) is piperazine.

17. The epoxy resin curing agent according to any one of claims 1 to 16, wherein the melting point of the solid aromatic amine containing a secondary amino group (B) is 160°C or lower.

18. The epoxy resin curing agent according to any one of claims 1 to 17, wherein the liquid aromatic polyamine (A) contains two or more primary amino groups, two or more secondary amino groups, or one or more primary amino groups and one or more secondary amino groups.

19. 19. The epoxy resin curing agent according to claim 18, wherein the liquid aromatic polyamine (A) is selected from the group consisting of dimethylthiotoluenediamine, diethyltoluenediamine, and 4,4'-methylenebis[N-(1-methylpropyl)aniline].

20. The epoxy resin curing agent according to any one of claims 1 to 19, which is liquid.

21. A resin composition comprising the epoxy resin curing agent according to any one of claims 1 to 20 and an epoxy resin.

22. A cured product of the resin composition according to claim 21.

23. A composite material comprising the cured product of claim 22 and carbon fibers.

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