Curable resin composition

Abstract: Herein are disclosed a latent curing agent for epoxy resin, comprising a reaction product obtainable by allowing (A) an epoxy compound having more than one (1) epoxy groups on the average in the molecule and (B) a compound having in the molecule both a tertiary amino group and at least one functional group selected from the group consisting of OH group, SH group, NH group, NH 2 group, COOH group and CONHNH 2 group, to react on each other in the presence of 0.05-5.0 equivalents of water per 1 equivalent of the epoxy group of Compound (A), and a curable epoxy resin composition comprising (y) such curing agent and (x) an epoxy compound having more than one epoxy groups on the average in the molecule. The epoxy resin composition is an epoxy resin composition excellent in storage stability and rapidly curable at low temperatures. Herein is also disclosed a latent curing agent for epoxy resin, comprising a reaction product obtainable by allowing(a) an alicyclic epoxy compound having 2 or more epoxy groups in the molecule; (b) a compound having in the molecule both a tertiary amino group and at least one functional group selected from the group consisting of OH group, SH group, NH group, NH 2 group, COOH group and CONHNH 2 group; and (c) a compound having in the molecule at least one functional group selected from the group consisting of NH 2 group and CONHNH 2 group or in the molecule at least 2 functional groups selected from the group consisting of OH group, SH group, NH group and COOH group (provided that a compound having an epoxy group or tertiary amino group in the molecule is excluded), to react on one another, which, when incorporated into an epoxy compound, gives a curable epoxy resin composition rapidly curable at low temperatures, excellent in heat resistance, electrical reliability, etc. and therefore, suitable in the electronics field such as encapsulants for semiconductor, anisotropic conductive films, conducting composites, etc.

Description: The present invention relates to a method of producing a latent curing agent for epoxy resin and for producing a curable epoxy resin composition having the latent curing agent incorporated therein, and in particular to a method for producing a curing agent for epoxy resin providing storage stability and low-temperature rapid curability to an epoxy resin composition, as well as for producing a curable epoxy resin composition having the curing agent incorporated therein which is excellent in storage stability and has low-temperature rapid curability. Based on the recent remarkable development in the field of electronics, the density of semiconductor element circuits has been rapidly increased and simultaneously, large-scale production thereof has become feasible, whereby the miniaturization and high-performance of electronic devices are now in rapid progress. Further, as these electronic devices have come into wide spread use, improved workability and reduced costs in large-scale production have been demanded. Further, with respect to epoxy resin used as adhesive for these electronic devices and latent curing agent for such epoxy resin, there is a need for improved high-performance in various physical properties. As a matter of course, the utilization of epoxy resin is not limited to this. Epoxy resin compositions include a two-pack type which is used by mixing an epoxy resin as the main agent with a curing agent just before use, and a one-pack type having an epoxy resin as the main agent previously mixed with a curing agent. Of the two, the one-pack type is preferably used because it can prevent erroneous formulation and enables machinery automation on line. For the one-pack type epoxy resin composition a so-called latent curing agent is needed which does not react with the epoxy resin compound at room temperature, but is caused to react and cure upon heating. As for the latent curing agent, some curing agents have been proposed so far, and typical examples thereof include dicyandiamide, dibasic acid dihydrazide, boron trifluoride amine complex salt, guanamines, melamine, imidazoles, etc. However, an epoxy resin composition resulting from mixing an epoxy compound with dicyandiamide, melamine or a guanamine is excellent in storage stability, but is disadvantageous in that it requires, for curing, a long time at high temperatures of 150 °C or more. Further, such epoxy resin composition is often used in combination with a curing accelerator to reduce curing time. The addition of a curing accelerator indeed leads to a reduction in the curing time of the curing epoxy resin composition but causes such problem that the storage stability thereof is significantly deteriorated. The epoxy resin compositions having a dibasic acid dihydrazide or an imidazole incorporated therein as the latent curing agent, are cured at relatively low temperatures but are poor in storage stability. The boron trifluoride amine complex is highly hygroscopic and exerts adverse effects on various characteristics of a cured product from an epoxy resin composition having said complex incorporated therein. In these circumstances, a latent curing agent for epoxy resin, which gives an epoxy resin composition excellent in storage stability with low-temperature rapid curability, is highly desired. To improve or solve these problems, JP 56-155222A and JP 57-100127A propose curing agents wherein dialkyl amines are addition-reacted with epoxy compounds, and JP 59-53526A proposes curing agents wherein an aminoalcohol or aminophenol is addition-reacted with an epoxy compound. Further, US Patent Nos. 406,625 and 4,268,656 propose curing agents wherein imidazole compounds or N-methyl piperazine is addition-reacted with epoxy compounds at their secondary amino groups. However, the curing agents described above do not sufficiently confer storage stability and low-temperature curability on epoxy resin compositions in which they have been incorporated. In particular, those epoxy resin compositions wherein bisphenol F type epoxy compounds or reaction diluents such as monoepoxy compounds or diepoxy compounds have been used, do not exhibit satisfactory storage stability. Further, phenol resin, dicyandiamide, hydrazide compounds or the like have been used heretofore as a latent curing agent, but they require, for curing, heating treatment in an oven at 150 to 200 °C for a long time. Recently, there is a need for rapidly curable resin compositions which can be cured in a short time, with the view of improving workability in the step of assembling semiconductor devices and reducing manufacturing costs. In addition, as circuits become highly densified on printed circuit boards, etc., a reduction in accuracy due to thermal stress upon high-temperature curing, has been worried about, and also from the viewpoint of energy costs, there has been a need for curing at relatively low temperatures to minimize the thermal history of printed circuit boards, etc. As typical examples of latent curing agents with low-temperature rapid curing properties, e.g. amine adduct type latent curing agents are known and JP 9-92029A, for example, describes an example where a commercial latent curing agent "Ajicure" (a product of Ajinomoto Co., Ltd.) is used as a conductive paste. On the other hand, as semiconductor production technology rapidly advances, it has become impossible to ignore the physical properties of a curing agent per se incorporated in curable epoxy resin compositions as well as its effect on electrical reliability, and there has been a need for latent curing agents more suitable in the field of electronics than those conventionally used. It is an object of the present invention to provide a latent curing agent which can give an epoxy resin composition excellent in storage stability and low-temperature rapid curable properties or curability, and furthermore, to a rapidly curable epoxy resin composition resulting from having the same mixed with an epoxy compound, which maintains excellent storage stability and is curable at relatively low temperatures, that is, 80 to 120 °C in a short time. As a result of their eager study in view of the various problems described above, the present inventors have found that an addition product obtainable by addition reaction in the presence of water, with an epoxy compound, of an compound having in the molecule both a tertiary amino group and a functional group such as OH group, SH group, NH group, NH 2 group, COOH group, CONHNH 2 group or the like capable of reacting with an epoxy compound, gives, when mixed with an epoxy compound, a curable epoxy resin composition superior in storage stability and low-temperature rapid curability. On the basis of these findings, the present inventors have completed a first invention. Accordingly, in a first aspect, the present invention provides a method for producing a latent curing agent for epoxy resin, comprising reacting together (A) an epoxy compound having more than one (1) epoxy groups on the average in the molecule and (B) a compound having in the molecule both a tertiary amino group and at least one functional group selected from the group consisting of OH group, SH group, NH group, NH 2 group, COOH group and CONHNH 2 group, to react on each other in the presence of 0.05-5.0 equivalents of water per 1 equivalent of the epoxy group of Compound (A). Incidentally, it is added that with respect to the relationship in equivalence between epoxy group and water, 1 epoxy group corresponds to 1 water molecule. In one embodiment, this aspect of the present invention also relates to a method for producing a latent curing agent for epoxy resin, comprising reacting together (A) an epoxy compound having more than one (1) epoxy groups on the average in the molecule, (B) a compound having in the molecule both a tertiary amino group and at least one functional group selected from the group consisting of OH group, SH group, NH group, NH 2 group, COOH group and CONHNH 2 group, and (C) a compound having in the molecule at least one functional group selected from the group consisting of NH 2 group and CONHNH 2 group or in the molecule at least 2 functional groups selected from the group consisting of OH group, SH group, NH group, NH 2 group, COOH group and CONHNH 2 group (provided that a compound having an epoxy group or tertiary amino group in the molecule is excluded), to react on one another in the presence of 0.05 to 5.0 equivalents of water per 1 equivalent of the epoxy group of Compound (A). Furthermore, in a second aspect, the present invention relates to a method for producing a curable epoxy resin composition comprising producing a latent curing agent by a method of the first aspect and combining it with (x) an epoxy compound having more than one (1) epoxy groups on the average in the molecule and optionally, (z) inorganic filler(s). Hereinafter, the present invention will be described in detail. Compound (A) as one of the starting materials for the synthetic reaction by which a latent curing agent for epoxy resin is produced, that is, an epoxy compound having more than one (1) epoxy group on the average in the molecule, is not particularly limited, and any epoxy compound having more than one epoxy group on the average in the molecule can be used. For example, mention can be made of epoxy compounds having more than one epoxy groups on the average in the molecule, which are represented by any of the general formulae (1) to (3) below. Further, mention is made of, e.g., epoxy compounds having more than one epoxy groups on the average in the molecule that are on the alicyclic hydrocarbon ring and/or that are bound directly to the carbon atom(s) forming the alicyclic hydrocarbon ring. Furthermore, any epoxy compounds having 2 kinds or more of these epoxy groups in the molecule where the number of such epoxy groups totals more than one on the average . which is a substituted or unsubstituted glycidyl ether group wherein Z is a hydrogen atom, a methyl group or an ethyl group. which is a substituted or unsubstituted glycidyl ester group wherein Z is a hydrogen atom, a methyl group or an ethyl group. which is a substituted or unsubstituted 1,2-epoxypropyl group wherein Z is a hydrogen atom, a methyl group or an ethyl group. The epoxy compounds containing more than one substituted or unsubstituted glycidyl ether groups on the average in the molecule, represented by the general formula (1) above, include substituted or unsubstituted glycidyl ether compounds obtainable by reacting an epihalohydrin with a polyhydric phenol compound such as bisphenol A, bisphenol F, bisphenol S, catechol, resorcinol, phenol novolak resin, resol resin or the like, or with a polyhydric alcohol compound such as a compound obtainable by subjecting glycerin, polyethylene glycol, or a polyhydric phenol compound to addition reaction with an alkylene oxide containing 2 to 4 carbon atoms. The epoxy compounds having more than one substituted or unsubstituted glycidyl ester groups on the average in the molecule, represented by the general formula (2) above, include substituted or unsubstituted glycidyl ester compounds obtainable by allowing an aliphatic polybasic carboxylic acid such as adipic acid, sebacic acid or the like, or an aromatic polybasic carboxylic acid such as phthalic acid, terephthalic acid or the like to react with an epihalohydrin. The epoxy compounds having more than one N-substituted or unsubstituted 1,2-epoxypropyl groups on the average in the molecule, represented by the general formula (3) above, include substituted or unsubstituted glycidylamine compounds obtainable by allowing, e.g., 4,4'-diaminodiphenyl methane, aniline, m-aminophenol or the like to react with an epihalohydrin. The epoxy compounds having more than one epoxy groups on the average in the molecule that are on the alicyclic hydrocarbon ring and/or that are bound directly to the carbon atom(s) forming the alicyclic hydrocarbon ring include, e.g., epoxy compounds represented by the following general formula (4) or (5). wherein Y represents an optionally substituted monocyclic, polycyclic or bridged cyclic hydrocarbon ring containing 2 to 8 carbon atoms. wherein Y has the same meanings as defined above in the general formula (4). Examples of the epoxy compounds represented by the general formula (5) above may be those shown by the formulae (5-1) to (5-8) below. Further, the epoxy compounds having 2 kinds or more of these epoxy groups in the molecule wherein the total number of the epoxy groups is more than one on the average include substituted or unsubstituted glycidyl ether ester compounds obtainable by allowing a hydroxycarboxylic acid such as p-oxybenzoic acid, β-oxynaphthoic acid or the like to react with an epihalohydrin, compounds having both a glycidyl ether group and an alicyclic epoxy group in the molecule as shown by the following formula (6), and the like. Further, these epoxy compounds may be accompanied by monoepoxy compounds within the range in which the effects of the invention are not inhibited. Such monoepoxy compounds include, e.g., monoepoxy compounds such as butyl glycidyl ether, phenyl glycidyl ether, p-tert-butyl phenyl glycidyl ether, sec-butyl phenyl glycidyl ether, and glycidyl methacrylate. Epihalohydrin referred to herein is represented by the general formula (7) below, and includes, e.g., epichlorohydrin, epibromohydrin, 1,2-epoxy-2-methyl-3-chloropropane, 1,2-epoxy-2-ethyl-3-chloropropane, etc. wherein Z represents a hydrogen atom, a methyl group or an ethyl group, and X represents a halogen atom. Compounds (A) described above may be used each singly or in combination of two or more thereof. Compound (B) as another starting material for the synthetic reaction to produce the latent curing agent for epoxy resin, that is, a compound having in the molecule both a tertiary amino group and at least one functional group selected from the group consisting of OH group, SH group, NH group, NH 2 group, COOH group and CONHNH 2 group is represented by, e.g., the following general formula (8). wherein W represents an OH group, SH group, NH group, NH 2 group, COOH group or CONHNH 2 group, R 1 and R 2 represent independently a C 1 to C 20 alkyl group, a C 2 to C 20 alkenyl group, an aralkyl group such as benzyl group, or one of the above groups wherein some carbon atom(s) in the carbon chain are replaced by other atom(s) (e.g., oxygen) or some hydrogen atom(s) on the carbon chain are replaced by a halogen, a functional group represented by W defined above or the like, and R 3 is a similar to R 1 and R 2 defined above but divalent residue. Furthermore, R 1 and R 2 or R 1 , R 2 and R 3 may be bound to one another to form a ring. As Compound (B), e.g., those compounds containing a tertiary amino group in the heterocyclic ring represented by the following general formula (9), (10) or (12) can also be mentioned as effective compounds. wherein R 4 , R 5 , R 6 and R 7 represent independently a hydrogen atom, one of the same groups as R 1 and R 2 defined in the general formula (8) above, an aryl group which may be substituted with an alkyl or aryl group, or a functional group represented by W in the general formula (8) above, and at least one of R 4 , R 5 , R 6 and R 7 represents a functional group represented by W or a group containing a functional group represented by W, except the case where R 7 is a hydrogen atom. Even in the case where R 7 is a hydrogen atom, R 4 , R 5 and R 6 can be a functional group represented by W or a group containing a functional group represented by W. wherein R 8 , R 9 and R 11 represent independently a hydrogen atom, one of the same groups as R 1 and R 2 defined in the general formula (8) above, or an aryl group which may be substituted with an alkyl or aryl group, R 10 is a similar to R 1 and R 2 in the general formula (8) above but divalent residue, or an arylene group which may be substituted with an alkyl or aryl group, and X' is a hydrogen or a group represented by the following general formula (11): wherein R 8 and R 9 have the same meanings as in the general formula (10) above, and R 12 is a hydrogen atom, one of the same groups as R 1 and R 2 defined in the general formula (8) above, or an aryl group which may be substituted with an alkyl or aryl group, and in the case where none of R 11 and R 12 are a hydrogen atom, at least one of R 8 , R 9 , R 10 , R 11 and R 12 represents a functional group represented by W or a group containing a functional group represented by W. Even in the case where R 11 and/or R 12 is a hydrogen atom, R 8 , R 9 , R 10 , R 11 and R 12 can be a functional group represented by W or a group containing a functional group represented by W. wherein R 13 is a functional group represented by W, or a similar group to R 1 or R 2 but containing a functional group represented by W. Such compound (B), that is, a compound containing, in the molecule, both a tertiary amino group and at least one functional group selected from the group consisting of OH group, SH group, NH group, NH 2 group, COOH group and CONHNH 2 group, includes, e.g., 2-dimethylaminoethanol, 1-methyl-2-dimethylaminoethanol, 1-phenoxymethyl-2-dimethylaminoethanol, 2-diethylaminoethanol, 1-butoxymethyl-2-dimethylaminoethanol, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 1-aminoethyl-2-methylimidazole, 1-(2-hydroxy-3-phenoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-phenoxypropyl)-2-ethyl-4-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-ethyl-4-methylimidazole, 1-(2-hydroxy-3-phenoxypropyl)-2-phenylimidazoline, 1-(2-hydroxy-3-butoxypropyl)-2-methylimidazoline, 2-methylimidazoline, 2,4-dimethylimidazoline, 2-ethylimidazoline, 2-ethyl-4-methylimidazoline, 2-benzylimidazoline, 2-phenylimidazoline, 2-(o-tolyl)-imidazoline, tetramethylene-bis-imidazoline, 1,1,3-trimethyl-1,4-tetramethylene-bis-imidazoline, 1,3,3-trimethyl-1,4-tetramethylene-bis-imidazoline, 1,1,3-trimethyl-1,4-tetramethylene-bis-4-methylimidazoline, 1,3,3-trimethyl-1,4-tetramethylene-bis-4-methylimidazoline, 1,2-phenylene-bis-imidazoline, 1,3-phenylene-bis-imidazoline, 1,4-phenylene-bis-imidazoline, 1,4-phenylene-bis-4-methylimidazoline, 2-(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminomethyl)phenol, N-β-hydroxyethylmorpholine, 2-dimethyl aminoethane thiol, 2-mercaptobenzoimidazole, 2-mercaptobenzothiazole, 2-mercaptopyridine, 4-mercaptopyridine, N,N-dimethylaminobenzoic acid, N,N-dimethylglycine, nicotinic acid, isonicotinic acid, picolinic acid, N,N-dimethyl glycine hydrazide, nicotinic acid hydrazide, isonicotinic acid hydrazide, dimethyl aminopropyl amine, diethyl aminopropyl amine, dipropyl aminopropyl amine, dibutyl aminopropyl amine, dimethyl aminoethyl amine, diethyl aminoethyl amine, dipropyl aminoethyl amine, dibutyl aminoethyl amine, N-aminoethyl piperazine, dimethyl aminoethyl piperazine, diethyl aminoethyl piperazine, etc. Compound (B) is preferably a compound having a tertiary amino group and at least one functional group selected from the group consisting of OH group, NH group and NH 2 group. Such compounds include tertiary amino group-containing alcohol compounds, such as 2-dimethylaminoethanol, 1-methyl-2-dimethylaminoethanol, 1-phenoxymethyl-2-dimethylaminoethanol, 2-diethylaminoethanol, 1-butoxymethyl-2-dimethylaminoethanol, N-β-hydroxyethyl morpholine, 1-(2-hydroxy-3-phenoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-phenoxypropyl)-2-ethyl-4-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-ethyl-4-methylimidazole, 1-(2-hydroxy-3-phenoxypropyl)-2-phenylimidazoline, 1-(2-hydroxy-3-butoxypropyl)-2-methylimidazoline, etc.; tertiary amino group-containing phenol compounds such as 2-(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminomethyl) phenol, etc.; and primary or secondary amino group-containing tertiary amine compounds such as 2-methylimidazoline, 2,4-dimethylimidazoline, 2-ethylimidazoline, 2-ethyl-4-methylimidazoline, 2-benzylimidazoline, 2-phenylimidazoline, 2-(o-tolyl)-imidazoline, tetramethylene-bis-imidazoline, 1,1,3-trimethyl-1,4-tetramethylene-bis-imidazoline, 1,3,3-trimethyl-1,4-tetramethylene-bis-imidazoline, 1,1,3-trimethyl-1,4-tetramethylene-bis-4-methylimidazoline, 1,3,3-trimethyl-1,4-tetramethylene-bis-4-methylimidazoline, 1,2-phenylene-bis-imidazoline, 1,3-phenylene-bis-imidazoline, 1,4-phenylene-bis-imidazoline, 1,4-phenylene-bis-4-methylimidazoline, dimethyl aminopropyl amine, diethyl aminopropyl amine, dipropyl aminopropyl amine, dibutyl aminopropyl amine, dimethyl aminoethyl amine, diethyl aminoethyl amine, dipropyl aminoethyl amine, dibutyl aminoethyl amine, N-aminoethyl piperazine, dimethyl aminoethyl piperazine, diethyl aminoethyl piperazine, etc. Particularly preferable among these are tertiary amino group-containing alcohol compounds and primary or secondary group-containing tertiary amine compounds. More preferable examples of the tertiary amino group-containing alcohol compounds described above are those having 5- or 6-membered nitrogenous heterocyclic ring structure, such as 1-(2-hydroxy-3-phenoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-phenoxypropyl)-2-ethyl-4-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-ethyl-4-methylimidazole, 1-(2-hydroxy-3-phenoxypropyl)-2-phenylimidazoline, 1-(2-hydroxy-3-butoxypropyl)-2-methylimidazoline, etc., and particularly preferable are those having an imidazole skeleton, such as 1-(2-hydroxy-3-phenoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-phenoxylpropyl)-2-ethyl-4-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-ethyl-4-methylimidazole, etc. More preferable examples of the primary or secondary group-containing tertiary amine compounds described above are those having a 5- or 6-membered nitrogenous heterocyclic ring structure, such as 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 1-aminoethyl-2-methylimidazole, 2-methylimidazoline, 2,4-dimethylimidazoline, 2-ethylimidazoline, 2-ethyl-4-methylimidazoline, 2-benzylimidazoline, 2-phenylimidazoline, 2-(o-tolyl)-imidazoline, tetramethylene-bis-imidazoline, 1,1,3-trimethyl-1,4-tetramethylene-bis-imidazoline, 1,3,3-trimethyl-1,4-tetramethylene-bis-imidazoline, 1,1,3-trimethyl-1,4-tetramethylene-bis-4-methylimidazoline, 1,3,3-trimethyl-1,4-tetramethylene-bis-4-methylimidazoline, 1,2-phenylene-bis-imidazoline, 1,3-phenylene-bis-imidazoline, 1,4-phenylene-bis-imidazoline, 1,4-phenylene-bis-4-methylimidazoline, N-aminoethyl piperazine, dimethyl aminoethyl piperazine, diethyl aminoethyl piperazine, etc., and particularly preferable are those having an imidazole skeleton, such as 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole and 1-aminoethyl-2-methylimidazole, etc. Compounds (B) described above may be used each singly or can be used in combination of two or more thereof, to react with Compound (A). Compound (C) as the remaining starting material for the synthetic reaction of the latent curing agent for epoxy resin, that is, a compound having in the molecule at least one functional group selected from the group consisting of NH 2 group and CONHNH 2 group, or in the molecule at least 2 functional groups selected from the group consisting of OH group, SH group, NH group, NH 2 group, COOH group and CONHNH 2 group (provided that those compounds having an epoxy group or a tertiary amino group in the molecule are excluded), includes, e.g., amine compounds such as piperazine, aniline and cyclohexyl amine; polybasic carboxylic acids such as adipic acid, phthalic acid, 3,9-bis(2-carboxyethyl)-2,4,8,10-tetraoxaspiro [5,5] undecane; polyvalent thiols such as 1,2-dimercaptoethane and 2-mercaptoethyl ether; hydrazide compounds such as phenyl acetic acid hydrazide; amino acids such as alanine and valine; compounds having 2 kinds or more of functional groups, such as 2-mercaptoethanol, 1-mercapto-3-phenoxy-2-propanol, mercaptoacetic acid, N-methyl ethanol amine, diethanol amine, hydroxyaniline, N-methyl-o-aminobenzoic acid, anthranilic acid, sarcosine, hydroxybenzoic acid and lactic acid; polyhydric alcohols such as pentaerythritol, sorbitol, trimethylolpropane, trimethylolethane and tris(hydroxyethyl) isocyanurate; and polyhydric phenols. Compound (C) is particularly preferably a polyhydric phenol compound, and examples thereof can be bisphenol A, bisphenol F, bisphenol S, hydroquinone, catechol, resorcinol, pyrogallol, phenol novolak resin and resol resin. Compounds (C) described above may be used each singly or can be used in combination of two or more thereof, to react with Compounds (A) and (B). In the case where the curing agent for epoxy resin is to be obtained by reacting the two compounds i.e., Compounds (A) and (B), when Compound (B) is a compound having in the molecule both a tertiary amino group and at least one functional group selected from the group consisting of OH group, SH group, COOH group and CONHNH 2 group, then the ratio of the respective compounds to be used for producing the curing agent for epoxy resin is a ratio of 0.8 to 2.5 equivalents, preferably 0.9 to 1.5 equivalents of the epoxy group of Compound (A) per 1 equivalent of the active hydrogen in the active hydrogen-containing functional group (i.e., the OH group, SH group, COOH group and CONHNH 2 group) of Compound (B), in other words, Compounds (A) and (B) are allowed to react on each other in such ratio that Compound (A) in an amount of 0.8 to 2.5 equivalents, preferably 0.9 to 1.5 equivalents in terms of the epoxy group thereof is allowed to react on Compound (B) in an amount of 1 equivalent in terms of the active hydrogen in the active hydrogen-containing functional group thereof. If the amount of the epoxy group is less than 0.8 equivalents per 1 equivalent of the active hydrogen, then the softening temperature of the resulting latent curing agent for epoxy resin is low, its grinding is difficult, and upon incorporation thereof as the latent curing agent into an epoxy compound, sufficient storage stability cannot be obtained, while given 2.5 equivalents or more, the softening temperature of the reaction product gets too high, and upon incorporation thereof as the latent curing agent into an epoxy compound, sufficient rapid curing properties are not exhibited while the resulting cured product becomes heterogeneous. Further, in the same case, when Compound (B) is a compound having in the molecule both a tertiary amine group and at least functional group selected from the group consisting of NH group and NH 2 group, the ratio for this reaction is a ratio of 0.4 to 1.1 equivalents of the epoxy group of Compound (A) to 1 equivalent of the active hydrogen of the active hydrogen-containing functional group (i.e., NH group and NH 2 group) of Compound (B). This is because if the epoxy group of Compound (A) is in an amount of less than 0.4 equivalents, sufficient storage stability cannot be obtained upon incorporation of the resulting reaction product as the latent curing agent into an epoxy compound, while given 1.1 equivalents or more, there occurs gelation during the addition reaction. Incidentally, with respect to the relationship in equivalence between active hydrogen and epoxy group, 1 epoxy group corresponds to 1 active hydrogen atom. In the case where the 3 compounds, that is, Compound (A), Compound (B) and Compound (C) are to be used to produce the curing agent for epoxy resin, when Compound (B) is a compound having, in the molecule, both a tertiary amino group and at least one functional group selected from the group consisting of OH group, SH group, COOH group and CONHNH 2 group, then the ratio of the respective compounds to be used for producing the curing agent for epoxy resin is a ratio of 0.5 to 2.5 equivalents, preferably 0.6 to 1.5 equivalents of the epoxy group of Compound (A) per 1 equivalent of the total active hydrogen in both Compounds (B) and (C), and simultaneously Compound (C) is used preferably in an amount of 2-fold moles or less relative to Compound (B). Less than 0.5 equivalents of the epoxy group from Compound (A) does not give sufficient storage stability upon incorporation of the resulting reaction product as the latent curing agent into an epoxy compound, while given 2.5 equivalents or more, the softening temperature of the reaction product gets too high, and upon incorporation thereof as the latent curing agent into an epoxy compound, sufficient rapid curing is not exhibited while the resulting cured product becomes heterogeneous. Further, if Compound (C) exceeds 2-fold moles relative to Compound (B), curing properties are worsened. In addition, in the same case where the 3 compounds, i.e., Compounds (A), (B) and (C) are to be used to produce the curing agent for epoxy resin, when Compound (B) is a compound having, in the molecule, both a tertiary amino group and at least one functional group selected from the group consisting of NH group and NH 2 group, then the ratio of the respective compounds to be used is a ratio of 0.2 to 1.1 equivalents of the epoxy group in Compound (A) per 1 equivalent of the total active hydrogen in both Compounds (B) and (C). If the epoxy group from Compound (A) is less than 0.2 equivalent, sufficient storage stability cannot be attained upon incorporation of the resulting reaction product as the latent curing agent into an epoxy compound, while in an amount of more than 1.1 equivalents, the softening temperature of the reaction product gets too high, and upon incorporation thereof as the latent curing agent, there does not occur sufficiently rapid curing while the resulting cured product is rendered heterogeneous. The 2 compounds, i.e., Compounds (A) and (B) or the 3 compounds, i.e., Compounds (A), (B) and (C) are allowed to react on each other or one another in the presence of 0.05 to 5.0 equivalents, preferably 0.1 to 2.0 equivalents of water, per 1 equivalent of the epoxy group of Compound (A), whereby the latent curing agent for epoxy resin can be obtained. Usually, trace amounts of water are also contained in Compounds (A), (B) and (C) as the starting materials but are insufficient to achieve the effects of the present invention. According to the present invention, water is further added for reaction in an amount of 0.05 to 5.0 equivalents per 1 equivalent of the epoxy group in Compound (A), whereby the inventive latent curing agent for epoxy resin can be obtained. If the amount of water is less than 0.05 equivalents, sufficient storage stability cannot be achieved upon incorporation of the resulting reaction product as the latent curing agent into an epoxy compound, while an amount of 5.0 or more equivalents is not practical because the more time and energy are required to remove the excessive water after reaction and before grinding. The curing agents for epoxy resin can be obtained as addition products having arbitrary softening temperatures by changing the kind and mixing ratio of Compounds (A), (B) and (C) and the ratio of water for reaction, and those having softening temperatures of 60 to 180 °C are preferable. If the latent curing agent with a softening temperature of less than 60 °C is incorporated into an epoxy compound, the resulting epoxy resin composition is inferior in storage stability at room temperature, while the latent curing agent with a softening temperature of more than 180 °C does not bring about sufficient curing property. The latent curing agent for epoxy resin can be obtained, e.g., by sufficiently mixing Compound (A), Compound (B) and water, or Compound (A), Compound (B), Compound (C) and water, gelatinizing the mixture at room temperature, completing the reaction at a temperature of 80 to 150 °C, then solidifying the resulting reaction mixture by cooling, and grinding the solidified mixture. This reaction may be conducted in a solvent such as toluene, tetrahydrofuran, methyl ethyl ketone or dimethylformamide, followed by removing the solvent, solidification and grinding. Further, water may be either completely dissolved in, or dispersed without being completely dissolved in, compounds (A) and (B), or Compounds (A), (B) and (C), or these compounds to which a solvent has been added. The latent curing agent for epoxy resin can also be used in combination with curing agents known in the art, such as acid anhydrides, dicyandiamide, hydrazide compounds, guanamines, melamines, etc. The latent curing agent for epoxy resin can be put in commercial distribution as such or after combination with a curing agent known in the art. Further, curable epoxy resin composition may be produced by combining (x) an epoxy compound having more than one (1) epoxy groups on the average in the molecule and (y) a latent curing agent for epoxy resin produced as described above, as the essential ingredients. The epoxy compound (x) having more than one epoxy group on the average in the molecule can be completely the same as Compound (A) as referred to above, that is, the epoxy compound having more than one epoxy groups on the average in the molecule, and various compounds known in the art, such as those illustrated above, can be mentioned. The amount of the curing agent for epoxy resin to be used (incorporated) in the inventive resin composition is preferably 0.3 to 50 parts by weight relative to 100 parts by weight of the epoxy compound (x). An amount of less than 0.3 part by weight cannot provide sufficient curable properties to the resulting resin composition, while an amount of more than 50 parts by weight may reduce the performance of the cured product. Further, other additives can be added, if necessary or desired, to the curable epoxy resin composition of the present invention. Such additives include, e.g., (z) fillers such as alumina, silica, aerozil, calcium carbonate, aluminum hydroxide, magnesium hydroxide, talk, bentonite, barium sulfate, and the like (inorganic fillers), and fluidity regulators such as acryl oligomers, silicone, etc., surface modifiers, diluents, and flame-retardants. EXAMPLES Hereinafter, embodiments of the present invention will be described in more detail by reference to Production Examples and Examples. The abbreviations for the starting materials used in Production Examples and Examples are as follows: (A) Epoxy compounds having more than one epoxy groups on the average in the molecule: EP#828: "Epicoat #828" (bisphenol A type epoxy resin (epoxy equivalent, 184 to 194) produced by Yuka Shell Epoxy K. K.), EP#834: "Epicoat #834" (bisphenol A type epoxy resin (epoxy equivalent, 230 to 270) produced by Yuka Shell Epoxy K. K.), EP#1001: "Epicoat #1001" (bisphenol A type epoxy resin (epoxy equivalent, 450 to 500) produced by Yuka Shell Epoxy K. K.), EP#807: "Epicoat #807" (bisphenol F type epoxy resin (epoxy equivalent, 160 to 175) produced by Yuka Shell Epoxy K. K.). (B) Compounds having, in the molecule, both a tertiary amino group and at least 1 functional group selected from the group consisting of OH group, SH group, NH group, NH 2 group, COOH group and CONHNH 2 group; DEAPA: diethylaminopropylamine (water content, 0.16 wt%), DEAE-OH: diethyl aminoethanol (water content, 0.18 wt%), 2PZL: 2-phenyl imidazoline (water content, 0.07 wt%), 2E4MZ: 2-ethyl-4-methyl imidazole (water content, 0.30 wt%), 2MZ: 2-methyl imidazole (water content, 0.06 wt%), PG-MZ: 1-(2-hydroxy-3-phenoxypropyl)-2-methyl imidazole (water content, 0.04 wt%), PG-EMZ: 1-(2-hydroxy-3-phenoxypropyl)-2-methyl-4-methyl imidazole (water content, 0.28 wt%), PG-PZL: 1-(2-hydroxy-3-phenoxypropyl)-2-phenyl imidazoline (water content, 0.04 wt%), DMP-10: 2-(dimethylaminomethyl) phenol (water content, 0.42 wt%), DMP-30: 2,4,6-tris(dimethylaminomethyl) phenol (water content, 0.09 wt%), SMZ: 2-mercapto-1-methyl imidazole (water content, 0.18 wt%), DMGH: N,N-dimethyl glycine hydrazide (water content, 0.34 wt%), NA: nicotinic acid (water content, 0.31 wt%). (C) Compounds having in the molecule at least one functional group selected from the group consisting of NH 2 group and CONHNH 2 group or in the molecule at least 2 functional groups selected from the group consisting of OH group, SH group, NH group, NH 2 group, COOH group and CONHNH 2 group (provided that those compounds having epoxy group(s) or tertiary amino group(s) are excluded); BA: bisphenol A (water content, 0.27 wt%), PNV: phenol novolak "Shonol BRG-555" (hydroxyl group equivalent, 103; water content, 0.57 wt%, a product of Showa Highpolymer Co., Ltd.), PIP: anhydrous piperazine (water content, 0.39 wt%), PAAH: phenyl acetic acid hydrazide (water content, 0.22 wt%), AL: aniline (water content, 0.14 wt%), HQ: hydroquinone (water content, 0.25 wt%), DEA: diethanolamine (water content, 0.09 wt%). Production Example 1 (Production of an addition product of DEAE-OH and "Epicoat #828") 110.3 g (0.584 equivalents) of "Epicoat #828", 39.1 g (0.334 equivalents) of DEAE-OH and 10.5 g (0.583 equivalents) of water were placed in a beaker and stirred vigorously at room temperature during which the temperature was gradually raised. The reaction proceeded rapidly exothermically at about 70 °C, and thereafter the reaction was allowed to proceed for 1 hour in such that the reaction mixture was maintained at about 110 °C by cooling or heating. After the reaction, the reaction mixture was cooled to room temperature to give a pale yellow solid. This addition product was roughly ground and then finely ground to give a powder of about 10 µm in the average diameter. This will be referred to as Latent curing agent for epoxy resin Sample No. 1. Production Example 2 (Production of an addition product of PG-MZ, DMP-30, BA and "Epicoat #828") A three-necked 3,000 ml flask equipped with a reflux condenser and a stirrer was charged with 116.1 g (0.5 equivalents) of PG-MZ, 26.6 g (0.1 equivalent) of DMP-30 and 57.1 g (0.5 equivalents) of BA, 1.8 g (0.1 equivalent) of water and 500 ml of methyl ethyl ketone as the solvent. Then, 189 g (1.0 equivalent) of "Epicoat #828" dissolved in 300 ml methyl ethyl ketone was added dropwise (about 3 hours) to the mixture under heating and stirring. After this addition, the mixture was further heated under reflux for 2 hours with stirring. Thereafter, the methyl ethyl ketone as the solvent was distilled off under reduced pressure, and the residue was cooled to room temperature to give a pale yellow solid. This addition product was roughly ground and then finely ground to give a powder of about 10 µm in the average diameter. This will be referred to as Latent curing agent for epoxy resin Sample No. 22. The sample number of the curing agents for epoxy resin synthesized according to Production Example No. 1 or 2, as well as the composition of the starting materials thereof, are shown in Table 1 below. Sample No. Ingredient (a) ( ) Ingredient (b) ( ) Ingredient (c) ( ) a/(b+c) (equivalent ratio) Amount of water added ( ) Water content ( ) 1 EP#828 (1.75) DEAE-OH (1.0) - 1.75 1.0 1.0130 2 EP#828 (1.8) DEAPA (2.0) - 0.90 1.0 1.0127 3 EP#828 (2.0) DMP-30 (1.0) - 2.00 1.0 1.0129 4 EP#828 (1.1) 2E4MZ (1.0) - 1.10 1.0 1.0230 5 EP#828 (1.1) 2PZL (1.0) - 1.10 1.0 1.0115 6 EP#828 (1.4) PG-MZ (1.0) - 1.40 1.0 1.0100 7 EP#828 (1.3) NA (1.0) - 130 1.0 1.0226 8 EP#828 (1.3) DMGH (1.0) - 1.30 1.0 1.0148 9 EP#828 (1.3) SMZ (1.0) - 130 1.0 1.0151 10 EP#834(1.5) PG-PZL (1.0) - 1.50 1.0 1.0127 11 EP#828 (1.5) DEAPA (1.0) BA (1.0) 0.75 1.0 1.0216 12 EP#828 (2.0) DMP-30 (1.0) BA (1.0) 1.00 1.0 1.0215 13 EP#828 (2.0) PG-EMZ (1.0) BA (1.0) 1.00 1.0 1.0352 14 EP#828 (1.8) 2E4MZ (1.0) PNV (1.0) 0.90 1.0 1.0346 15 EP#828 (1.8) PG-PZL (1.0) PNV (1.0) 0.90 1.0 1.0281 16 EP#828 (2.0) DMP-10 (1.0) PIP (1.0) 1.00 1.0 1.0286 17 EP#828 (2.0) DMP-30 (1.0) PAAH (1.0) 1.00 1.0 1.0129 18 EP#828 (2.0) DMP-30 (1.0) AL (1.0) 1.00 1.0 1.0129 19 EP#828 (2.0) DMP-30 (1.0) PIP (0.5) 1.00 1.0 1.0195 BA (0.5) 20 EP#828 (2.0) DMP-30 (1.0) DEA (1.0) 1.00 1.0 1.0129 21 EP#828 (2.0) SMZ (1.0) BA (1.0) 0.91 1.0 1.0241 DMP-10 (0.2) 22 EP#828 (2.0) PG-MZ (1.0) BA (1.0) 0.91 0.1 1.0188 DMP-30 (0.2) 23 EP#828 (2.0) PG-MZ (1.5) BA (1.5) 0.63 1.0 1.0243 DMP-30 (0.2) 24 EP#828 (2.5) PG-MZ (1.0) BA (1.5) 0.83 1.0 1.0213 DMP-30 (0.5) 25 EP#828 (2.0) DMP-10 (1.0) ADP (1.0) 1 1.0 1.0296 26 EP#828 (2.0) PG-MZ (1.0) DME (1.0) 1 1.0 1.0133 27 EP#828 (2.5) DEAPA (3.5) BA (1.5) 0.45 1.0 1.0273 DMP-30 (0.5) 28 EP#828 (1.5) 2MZ (1.0) BA (1.0) 0.68 1.0 1.0213 DMP-30 (0.2) 29 EP#834 (2.0) PG-MZ (1.0) BA (1.0) 0.91 1.0 1.0208 DMP-30 (0.2) 30 EP#828 (2.0) PG-EMZ (1.0) HQ (1.0) 0.91 1.0 1.0318 DMP-30 (0.2) 31 EP#1001(2.0) DEAE-OH (1.0) BA (1.0) 0.91 1.0 1.0369 DMP-30 (0.2) 32 EP#828 (2.0) PG-PZL (1.0) BA (1.0) 0.95 1.0 1.0188 DMP-30 (0.1) 33 EP#807(1.5) PG-MZ (1.0) PNV (1.0) 0.68 1.0 1.0316 DMP-30 (0.2) 34 EP#828 (3.0) DEAPA (5.0) PNV (3.0) 0.35 1.0 1.0498 DMP-30 (0.5) Comparative Production Example 1 A pale yellow solid was obtained in the same manner as in Production Example 1 except that no water was added. It was roughly ground and then finely ground to give a powder of about 10 µm in the average diameter. This will be referred to as Comparative Sample No. 1. Comparative Production Example 2 A three-necked 3,000 ml flask equipped with a reflux condenser and a stirrer was charged with 174.2 g (0.75 equivalents) of PG-MZ, 26.6 g (0.1 equivalent) of DMP-30 and 85.7 g (0.75 equivalents) of BA and 500 ml of methyl ethyl ketone as the solvent. Then, 189 g (1.0 equivalent) of "Epicoat #828" dissolved in 300 ml of methyl ethyl ketone was added dropwise(about 3 hours) to the mixture under heating and stirring. After this addition, the mixture was further heated under reflux for 2 hours with stirring. Thereafter, the methyl ethyl ketone as the solvent was distilled off under reduced pressure, and the residue was cooled to room temperature to give a pale yellow solid. This addition product was roughly ground and then finely ground to give a powder of about 10 µm in the average diameter. This will be referred to as Comparative Example No. 4. The number of the comparative samples produced according to Comparative Production Example 1 or 2, as well as the composition of the starting materials thereof, are shown in Table 2 below. Sample No. Ingredient (a) (*1) Ingredient (b) (*2) Ingredient (c) (*3) a/(b+c) (equivalent ratio) Water content (*5) Comparative 1 EP#828 (1.75) DEAE-OH (1.0) - 1.75 0.0130 Comparative 2 EP#828 (1.5) DEAPA (1.0) BA (1.0) 0.75 0.0216 Comparative 3 EP#828 (2.0) DMP-30 (1.0) DEA (1.0) 1.00 0.0129 Comparative 4 EP#828 (2.0) PG-MZ (1.5) BA (1.5) 0.63 0.0243 DMP-30 (0.2) Comparative 5 EP#828 (2.5) DEAPA (3.5) BA (1.5) 0.45 0.0273 DMP-30 (0.5) *1, *2, *3 and *5 mean the same meanings, respectively, as those indicated in the footnote to Table 1. Examples 1 to 34 and Comparative Examples 1 to 5: Each of the above latent curing agents for epoxy resin was added to an epoxy compound at the ratio shown in Table 3 below and the mass was mixed to give a curable epoxy resin composition. The curable properties (gel time) and storage stability of the thus prepared compositions were measured to evaluate thier performance. Epicoat #807 100 wt. parts Inventive latent curing agent or Curing agent of Comparative Production Example 20 wt. parts "Aerozil #200" ex Japan Aerozil Co.,Ltd. 1 wt part Method of preparing the curable epoxy resin compositions: The respective ingredients at the ratio shown in Table 3 above were mixed and defoamed for 30 minutes under reduced pressure in a vacuum mixing-grinding machine (Ishikawa Kojyo K. K.). Gel time: Determined using about 2.5 g of each curable epoxy resin composition at a predetermined temperature by means of a Yasuda-type gel timer (ex Yasuda Seiki Seisakusho K. K.). Storage stability: Each curable epoxy resin composition was placed in a sealed vessel, then stored in a thermostat at a predetermined temperature (40 °C) and the number of days until its fluidity was lost was determined. The obtained results are shown in Table 4 below for Examples and in Table 5 below for Comparative Examples. Sample No. Curability (Gel time) Storage stability (40 °C) Temperature Time 1 150 °C 20 min. more than 3 months 2 120 °C 10 min. 3 weeks 3 150 °C 10 min. more than 3 months 4 120 °C 5 min. 3 weeks 5 120 °C 5 min. 3 weeks 6 120 °C 7 min. 1 month 7 150 °C 10 min. more than 3 months 8 150 °C 23 min. more than 3 months 9 150 °C 5 min. 3 weeks 10 120 °C 7 min. 1 month 11 120 °C 15 min. 2 months 12 120 °C 10 min. more than 3 months 13 100 °C 9 min. 2 months 14 120 °C 8 min. 2 months 15 120 °C 10 min. 2 months 16 100 °C 5 min. more than 3 months 17 100 °C 6 min. more than 3 months 18 100 °C 7 min. more than 3 months 19 100 °C 5 min. more than 3 months 20 100 °C 5 min. 1 month 21 100 °C 6 min. 1 month 22 100 °C 4 min. 2 months 23 100 °C 4 min. more than 3 months 24 100 °C 5 min. more than 3 months 25 100 °C 8 min. 3 weeks 26 100 °C 8 min. 3 weeks 27 100 °C 8 min. more than 3 months 28 100 °C 5 min. more than 3 months 29 100 °C 8 min. more than 3 months 30 100 °C 6 min. more than 3 months 31 150 °C 3 min. more than 3 months 32 100 °C 12 min. more than 3 months 33 100 °C 6 min. more than 3 months 34 100 °C 5 min. 3 weeks Sample No. Curability (Gel time) Storage Sability (40 °C) Temperature Time Comparative 1 150 °C 20 min. 3 weeks Comparative 2 120 °C 15 min. 3 weeks Comparative 3 100 °C 5 min. 5 days Comoarative 4 100 °C 4 min. 2 weeks Comparative 5 100 °C 12 min. 2 weeks Examples 35 to 36 and Comparative Examples 6 to 7: To examine the performance of the latent curing agent for epoxy resin produced according to the invention when used in combination with other latent curing agents, curing epoxy resin compositions were formulated at the ratio shown in Table 6 below and then examined for gel time in the same manner as in Examples 1 to 34. Their storage stability was determined by storing in a thermostat at a predetermined temperature (50 °C) and measuring the number of days until their fluidity was lost. Epoxy Compound Epicoat #807 100 wt. parts Curing agent Dicyandiamide 8 wt. parts Curing accelerator Inventive latent curing agent or Curing agent of Comparative Production Example 5 wt. parts Additive "Aerozil #200" ex Japan Aerozil Co.,Ltd. 1 wt. part The obtained results are shown in Table 7 below. Curing accelerator Sample No. Curability (Gel time) Storage Stability (50 °C) temperature time Example 35 23 100 °C 13 min. more than 3 months Example 36 30 100 °C 16 min. more than 3 months Comparative Example 6 Comparative 4 100 °C 13 min. 2 weeks Comparative Eample 7 No curing accelerator 100 °C More than 60 min. more than 3 months Examples 37 to 38 and Comparative Examples 8 to 9: To examine the performance of the latent curing agent for epoxy resin produced according to the invention when used in combination with other latent curing agents, curable epoxy resin compositions were formulated at the ratio shown in Table 8 below and then examined for gel time and storage stability in the same manner as in Examples 1 to 34. Epoxy Compound Epicoat # 807 100 wt. parts Curing agent Adipic acid hydrazide 20 wt. parts Curing accelerator Inventive latent curing agent or Curing agent of Comparative Production Example 5 wt. parts Additive "Aerozil #200" ex Japan Aerozil Co.,Ltd. 1 wt. Part The obtained results are shown in Table 9 below. Curing accelerator Sample No. Curability (gel time) Storage Stability (40 °C) Temperature Time Example 37 23 100 °C 10 min. more than 3 months Example 38 30 100 °C 15 min. more than 3 months. Comparative Example 8 Comparative 4 100 °C 10 min. 3 weeks Comparative Example 9 No curing accelerator 100 °C More than 60 min. more than 3 months As can be seen from the foregoing, the method for producing a latent curing agent for epoxy resin of the present invention can confer very excellent storage stability and low-temperature rapid curable properties on an epoxy resin composition into which said curing agent was incorporated. According to the invention as has been described above, curable epoxy resin compositions which are very excellent in storage stability and rapidly curable at low temperatures, can be easily obtained. The curable epoxy resin composition produced according to the present invention is rapidly curable at low temperatures, is excellent in heat resistance, electrical reliability, etc., and is suitable for use in the electronics field such as encapsulants for semiconductor, anisotropic conductive films, conducting composites, etc.

Claims: A method for producing a latent curing agent for epoxy resin, comprising reacting together: (A) an epoxy compound having more than one (1) epoxy group on the average in the molecule; and (B) a compound having in the molecule both a tertiary amino group and at least one functional group selected from the group consisting of OH group, SH group, NH group, NH 2 group, COOH group and CONHNH 2 group; in the presence of 0.05-5.0 equivalents of water per 1 equivalent of the epoxy group of Compound (A). A method according to claim 1 comprising reacting said Compounds (A) and (B) together with (C) a compound having in the molecule at least one functional group selected from the group consisting of NH 2 group and CONHNH 2 group or in the molecule at least 2 functional groups selected from the group consisting of OH group, SH group, NH group, NH 2 group, COOH group and CONHNH 2 group (provided that a compound having an epoxy group or tertiary amino group in the molecule is excluded). The method according to claim 2 wherein said Compound (C) is a polyhydric phenol compound. The method according to any one of claims 1 to 3 wherein said Compound (B) is a phenol compound containing a tertiary amino or an alcohol compound containing a tertiary amino group. A method for producing a curable epoxy resin composition, comprising producing a latent curing agent by a method of any one of claims 1 to 4 and combining it with an epoxy compound having more than one epoxy group on average in the molecule. A method according to claim 5 wherein the latent curing agent is further combined with inorganic filler(s).

Inventors: HINOMA TETSUO, OHASHI JUNJI, HINOMA, TETSUO, OHASHI, JUNJI, Hinoma, Tetsuo, Ajinomoto Fine-techno Co., Inc., Ohashi, Junji, Ajinomoto Fine-techno Co., Inc.
Applicants: AJINOMOTO KK, AJINOMOTO CO., INC.
Application year: 1999
Main classification: C08G59
IPC codes: C08G59