JPH09241353A - Epoxy hardner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impart high heat resistance and toughness to a thermosetting resin based on an epoxy resin by using a specified resin as a principal component. SOLUTION: A solution prepared by dissolving 0.5-60wt.% organic polyisocyanate in a solvent is subjected to decarboxylation condensation at 20-200 deg.C in the presence of 0.001-30 pts.wt., per 100 pts.wt. organic polyisocyanate, carbodiimidation catalyst to obtain a polycarbodiimide having repeating units represented by the formula: N=C=N-R<1> (wherein R<1> is a bivalent organic group derived from the polyisocyanate compound) and having a number-average molecular weight (in terms of PS, gel permeation chromatography) of 400-100,000. This polycarbodiimide is reacted with a compound having a graft-reactive group and a carboxylic anhydride group and used in such an amount that the graft-reactive groups are present in an amount of 0.01-1mol per mol of the repeating units represented by the formula at 100 deg.C or below to obtain an epoxy hardner comprising a resin having a number- average molecular weight of 500-200,000.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a curing agent for an epoxy resin, and more particularly to a curing agent for an epoxy resin containing a specific modified polycarbodiimide as a main component.

[0002]

2. Description of the Related Art Epoxy resins have hitherto been cured by various curing agents such as acid anhydride type curing agents and amine type curing agents to obtain mechanical properties, electrical properties, heat resistance, water resistance and chemical resistance. It becomes a cured product with excellent properties and is used in various industrial fields such as molding materials, electrical insulation materials, adhesives, paints, etc., but due to its good heat resistance and electrical insulation properties, it is especially for electrical and electronic parts. Widely used as a material. by the way,
With higher integration of integrated circuits and higher densification of mounting methods in recent years, higher heat resistance has been required for electrically insulating materials. From such a viewpoint,
Many attempts have been made to further improve the heat resistance of epoxy resins. For example, by using a highly heat-resistant component such as an aromatic acid anhydride or amine, or a high-melting point diazide as a curing agent, the softening point and thermal decomposition temperature of the final cured product can be increased to improve solder heat resistance. The material has been obtained. However, thermosetting resins generally have the drawback of being brittle, and have the problem that the impact resistance of the cured product is low and the elongation at break is small. This is also the case with epoxy resins, and improvement in toughness is due to the essence of epoxy resins. Has become a problem. Moreover, when an attempt is made to improve the heat resistance of the epoxy resin by using a curing agent having high heat resistance as described above, the toughness generally tends to decrease. It is a brittle material.
Therefore, when the epoxy resin is used not only as an electric insulating material but also as a structural material for aircrafts, automobiles and the like, overcoming brittleness is an important issue. On the other hand, polyimide and polycarbodiimide are known as thermosetting resins having excellent heat resistance, but since these resins have low solubility in ordinary solvents, there is a problem in terms of processability as compared with epoxy resins. Yes, it is an industrially large handicap. Further, for example, JP-A-62-1714 discloses a thermosetting resin obtained by reacting an epoxy compound with polycarbodiimide. The resin has relatively good heat resistance and strength, And in terms of toughness, it cannot be said that it is still at a satisfactory level. Therefore, the development of a resin that has both a high degree of heat resistance and toughness and is also excellent in processability is an essential issue for all thermosetting resins. Even for the thermosetting resin to be used, it is a major technical issue to make the resin have both heat resistance and toughness.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a curing agent for epoxy resin which can impart a high degree of heat resistance and toughness to a thermosetting resin based on epoxy resin. Especially.

[0004]

The present invention relates to a polycarbodiimide having a graft-reactive group and a carboxylic acid anhydride group (hereinafter referred to as "reactive compound") 1).
A curing agent for an epoxy resin, which comprises a resin (hereinafter, referred to as "modified polycarbodiimide") grafted with at least one species as a main component.

Hereinafter, the present invention will be described in detail. Modified polycarbodiimide <Polycarbodiimide> Polycarbodiimide used in the synthesis of modified polycarbodiimide is a resin obtained by decarboxylation condensation of a polyisocyanate compound, and specifically, is represented by the general formula (1) —N = C = NR ¹ -(1) (wherein R ¹ represents a divalent organic group derived from a polyisocyanate compound) is a resin having a repeating unit. The method for producing the polycarbodiimide is, for example,
Dy Makromol. Chem., 67, 1 (1963) by DJ Lyman et al.,
E. Deyer et al., J. Am. Chem. Soc., 80,5495 (1958),
LM Alberion et al. J. Appl. Polym. Sci., 21, 1999 (1
977), J. Org. Chem., 28, 2069 (196) by TW Campbell.
3), JP-A-51-61599, JP-A-4-26
It is disclosed in Japanese Patent No. 1428. The method for synthesizing the polycarbodiimide in the present invention is not particularly limited, but for example, an organic polyisocyanate is used as a catalyst for promoting a carbodiimidization reaction of an isocyanate group (hereinafter,
It is called "carbodiimidization catalyst". The polycarbodiimide can be synthesized by reacting in the presence of). The organic polyisocyanate is preferably an organic diisocyanate, and examples of such an organic diisocyanate include diphenylmethane-2,4′-
Diisocyanate, diphenylmethane-4,4'-diisocyanate, 2,4-tolylene diisocyanate,
2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, phenylene-1,3-diisocyanate, phenylene-1,4-diisocyanate, 1-methoxyphenylene-2,4-diisocyanate , 1-methylphenylene-2,4-diisocyanate, biphenylene-4,
4'-diisocyanate, 3,3'-dimethoxybiphenylene-4,4'-diisocyanate, 3,3'-dimethylbiphenylene-4,4'-diisocyanate, 3,
3'-dimethoxydiphenylmethane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-
4,4′-diisocyanate, naphthylene-1,5-diisocyanate, cyclobutylene-1,3-diisocyanate, cyclopentylene-1,3-diisocyanate, cyclohexylene-1,3-diisocyanate, cyclohexylene-1,4- Diisocyanate, 1-methylcyclohexylene-2,4-diisocyanate, 1-
Methylcyclohexylene-2,6-diisocyanate,
1-isocyanate-3,3,5-trimethyl-5-isocyanate methylcyclohexane, cyclohexane-
1,3-bis (methylisocyanate), cyclohexane-1,4-bis (methylisocyanate), isophorone diisocyanate, dicyclohexylmethane-2,
4'-diisocyanate, dicyclohexylmethane-
Chemistry of 4,4'-diisocyanate, ethylene diisocyanate, tetramethylene-1,4-diisocyanate, hexamethylene-1,6-diisocyanate, dodecamethylene-1,12-diisocyanate, lysine diisocyanate methyl ester, etc., and these organic diisocyanates Mention may be made of isocyanate-terminated prepolymers having both ends obtained by reacting a stoichiometric excess with a bifunctional active hydrogen-containing compound. Of these organic diisocyanates, diphenylmethane-4,4'-diisocyanate is particularly preferable. The organic diisocyanate is
They can be used alone or in combination of two or more.

It is also possible to use other organic polyisocyanates, optionally together with organic diisocyanates, in amounts not exceeding 20 mol% of the total organic polyisocyanate component. Examples of the other organic polyisocyanate include phenyl-1,3,5-triisocyanate, diphenylmethane-2,4,4'-triisocyanate, diphenylmethane-2,5,4'-triisocyanate and triphenylmethane-2. , 4 ', 4 "-triisocyanate, triphenylmethane-4,4', 4"-
Triisocyanate, diphenylmethane-2,4
2 ', 4'-tetraisocyanate, diphenylmethane-2,5,2', 5'-tetraisocyanate, cyclohexane-1,3,5-triisocyanate, cyclohexane-1,3,5-tris (methylisocyanate), 3 , 5-Dimethylcyclohexane-1,3,5-
Tris (methylisocyanate), 1,3,5-trimethylcyclohexane-1,3,5-tris (methylisocyanate), dicyclohexylmethane-2,4,2 ′
-Triisocyanate, dicyclohexylmethane-2,
Trifunctional or more trifunctional organic polyisocyanates such as 4,4′-triisocyanate, or a stoichiometric excess of these trifunctional or more polyfunctional polyisocyanates with a difunctional or more polyfunctional active hydrogen-containing compound The terminal isocyanate prepolymer obtained can be mentioned. The other organic polyisocyanates may be used alone or in admixture of two or more.

Further, in the synthesis of polycarbodiimide, the molecular weight of the polycarbodiimide obtained can be appropriately regulated by adding an organic monoisocyanate as necessary. Examples of such organic monoisocyanate include methyl isocyanate, ethyl isocyanate, n-propyl isocyanate, n-
Aliphatic monoisocyanates such as butyl isocyanate, lauryl isocyanate, stearyl isocyanate; alicyclic monoisocyanates such as cyclohexyl isocyanate, 4-methylcyclohexyl isocyanate, 2,5-dimethylcyclohexyl isocyanate;
Phenyl isocyanate, o-tolyl isocyanate,
m-tolyl isocyanate, p-tolyl isocyanate, 2-methoxyphenyl isocyanate, 4-methoxyphenyl isocyanate, 2-chlorophenyl isocyanate, 4-chlorophenyl isocyanate, 2-trifluoromethylphenyl isocyanate, 4-trifluoromethylphenyl isocyanate, naphthalene- 1
-Aromatic monoisocyanates such as isocyanates can be mentioned. The organic monoisocyanate may be used alone or in combination of two or more, and the amount thereof may vary depending on the desired molecular weight of the polycarbodiimide, the presence or absence of the other organic polyisocyanate, and the like.
It is usually 0 to 40 parts by weight, preferably 0 to 20 parts by weight, based on 100 parts by weight of the total organic polyisocyanate component.

The carbodiimidization catalyst is not particularly limited, and examples thereof include 1-phenyl-2-
Phosphorene-1-oxide, 1-phenyl-3-methyl-2-phosphorene-1-oxide, 1-phenyl-2-
Phosphorene-1-sulfide, 1-phenyl-3-methyl-2-phosphorene-1-sulfide, 1-ethyl-2
-Phospholen-1-oxide, 1-ethyl-3-methyl-2-phospholen-1-oxide, 1-ethyl-2-phospholen-1-sulfide, 1-ethyl-3-methyl-
2-phospholen-1-sulfide, 1-methyl-2-phosphorene-1-oxide, 1-methyl-3-methyl-2
-Phosphorene-1-oxide, 1-methyl-2-phosphorene-1-sulfide, 1-methyl-3-methyl-2-
Phosphorene-1-sulfide and phospholene compounds such as 3-phosphorene isomers thereof; iron pentacarbonyl,
Non-carbonyldiiron, tetracarbonylnickel, hexacarbonyltungsten, hexacarbonylchromium, and other metal carbonyl complexes; beryllium, aluminum, zirconium, chromium, iron, and other metals, acetylacetone complexes; trimethylphosphate, triethylphosphate, triisopropylphosphate, tri- Examples thereof include phosphoric acid esters such as t-butyl phosphate and triphenyl phosphate. The carbodiimidization catalysts may be used alone or in combination of two or more, and the amount thereof is usually 0.001 to 30 parts by weight, preferably 0.1 part by weight per 100 parts by weight of the total organic isocyanate component. It is from 01 to 10 parts by weight.

The synthesis reaction of polycarbodiimide is usually
It is carried out in a suitable solvent. As the solvent, any solvent may be used as long as it can dissolve polycarbodiimide by heating during the synthesis reaction, for example, 1,1-dichloroethane, 1,2.
-Dichloroethane, 1,1,1-trichloroethane,
1,1,2-trichloroethane, 1,1,1,2-tetrachloroethane, 1,1,2,2-tetrachloroethane, 1,1-dichloroethylene, 1,2-dichloroethylene, trichloroethylene, tetrachloroethylene, chlorobenzene, o- Halogenated hydrocarbon solvents such as dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, 1,2,4-trichlorobenzene and trichloromethylbenzene; dioxane, anisole, tetrahydrofuran, tetrahydropyran, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, Ether-based solvents such as diethylene glycol dipropyl ether and diethylene glycol dibutyl ether; methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, 2- Cetyl cyclohexanone, 2-
Ketone solvents such as methylcyclohexanone, 3-methylcyclohexanone, 4-methylcyclohexanone, cycloheptanone; aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, cumene; N-methyl-2-pyrrolidone, N- Acetyl-2-pyrrolidone, N-methyl-3-pyrrolidone, N-acetyl-3-
Amide solvents such as pyrrolidone, N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, N-methylpropionamide. Aprotic polar solvent such as dimethyl sulfoxide; 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-propoxyethyl acetate, 2-butoxyethyl acetate,
Acetate solvents such as 2-phenoxyethyl acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monopropyl ether acetate, and diethylene glycol monobutyl ether acetate can be mentioned. The solvent may be used alone or 2
A mixture of more than one species can be used. In the polycarbodiimide synthesis reaction, the solvent is used in such a proportion that the concentration of all organic isocyanate components is usually 0.5 to 60% by weight, preferably 5 to 50% by weight. In this case, if the concentration of all the organic isocyanate components is too high, the generated polycarbodiimide may gel during the synthesis reaction, and even if the concentration of all the organic isocyanate components is too low, the reaction rate becomes slow, Productivity decreases.

The temperature of the polycarbodiimide synthesis reaction is as follows:
The temperature is usually 20 to 200 ° C., though it is appropriately selected depending on the types of the organic isocyanate component and the carbodiimidization catalyst. In the polycarbodiimide synthesis reaction, the organic isocyanate component may be added in its entirety before the reaction, or a part or all of it may be added continuously or stepwise during the reaction. Further, in the present invention, a compound capable of reacting with an isocyanate group is added at an appropriate reaction stage from the initial stage to the latter stage of the polycarbodiimide synthesis reaction to seal the terminal isocyanate group of the polycarbodiimide to obtain a polycarbodiimide obtained. The molecular weight of the polycarbodiimide can be adjusted, or the molecular weight of the resulting polycarbodiimide can be regulated to a predetermined value by adding it at a later stage of the synthesis reaction of the polycarbodiimide. Examples of the compound capable of reacting with such an isocyanate group include alcohols such as methanol, ethanol, isopropanol and cyclohexanol; amines such as dimethylamine, diethylamine and benzylamine. The polycarbodiimide synthesized as described above is separated from the solution as needed. In this case, as a method for separating polycarbodiimide, for example, a polycarbodiimide solution is added to a non-solvent inert to the polycarbodiimide, and the resulting precipitate or oil is separated and collected by filtration or decantation. Method: Separation / collection by spray drying; Separation / collection using the change in solubility with temperature of the solvent used in the synthesis of the obtained polycarbodiimide, that is, a poly (vinyl chloride) dissolved in the solvent immediately after synthesis When carbodiimide is precipitated by lowering the temperature of the system, a method of separating / collecting the turbid liquid by filtration or the like can be mentioned, and further, these separating / collecting methods can be appropriately combined. The polystyrene reduced number average molecular weight (hereinafter referred to as “Mn”) of the polycarbodiimide obtained by gel permeation chromatography (GPC) of the present invention is usually 400 to 100,000, preferably 1,000 to 50,000. , Particularly preferably 1,000
〜１０10,000.

<Reactive Compound> Next, the reactive compound used for the synthesis of the modified polycarbodiimide is a compound having a graft reactive group and a carboxylic acid anhydride group, and the compound is an aromatic compound. It may be an aliphatic compound or an alicyclic compound, and in the case of a cyclic compound, it may be a carbocyclic compound or a heterocyclic compound. Here, the graft-reactive group means a group capable of reacting with polycarbodiimide to give a modified polycarbodiimide grafted with a residue having a carboxylic acid anhydride group. In such a reactive compound, the graft reactive group may have one or more identical or different groups, and the carboxylic acid anhydride group may have one or more. The graft reactive group may be a functional group having active hydrogen, and examples thereof include a carboxyl group or a primary or secondary amino group. Examples of the reactive compound include trimellitic anhydride, benzene-
1,2,3-tricarboxylic anhydride, naphthalene-1,
2,4-tricarboxylic anhydride, naphthalene-1,4
5-tricarboxylic anhydride, naphthalene-2,3,6-
Tricarboxylic acid anhydride, naphthalene-1,2,8-tricarboxylic acid anhydride, 4- (4-carboxybenzoyl)
Aromatic tricarboxylic acid anhydrides such as phthalic anhydride, 4- (4-carboxyphenyl) phthalic anhydride, 4- (4-carboxyphenoxy) phthalic anhydride: 3-carboxymethyl glutaric anhydride, butane -1, 2, 4-
Tricarboxylic acid-1,2-anhydride, propene-1,2,
Aliphatic tricarboxylic acid anhydrides such as 3-tricarboxylic acid-1,2-anhydride; 3-amino-4-cyano-5-methylphthalic anhydride, 3-amino-4-cyano-5,6-
Diphenylphthalic anhydride, 3-methylamino-4-cyano-5-methylphthalic anhydride, 3-methylamino-
Aminoaromatic dicarboxylic acid anhydrides such as 4-cyano-5,6-diphenylphthalic acid anhydride; aminosuccinic anhydride, 4-amino-1,2-butanedicarboxylic acid anhydride,
Aminoaliphatic dicarboxylic acids such as 4-aminohexahydrophthalic anhydride, N-methylaminosuccinic anhydride, 4-methylamino-1,2-butanedicarboxylic anhydride, and 4-methylaminohexahydrophthalic anhydride Acid anhydrides can be mentioned. Of these reactive compounds,
Particularly, trimellitic anhydride is preferable. The reactive compounds can be used alone or in combination of two or more.

<Synthesis of Modified Polycarbodiimide> Next,
A method for synthesizing the modified polycarbodiimide will be described. The modified polycarbodiimide is obtained by adding at least one reactive compound to at least one polycarbodiimide having a repeating unit represented by the general formula (1) at a suitable temperature in the presence or absence of a suitable catalyst. It can be synthesized by grafting (hereinafter, referred to as "modification reaction"). The amount of the reactive compound used in the modification reaction is appropriately adjusted depending on the type of the compound or the polycarbodiimide, the use of the epoxy resin, etc., but is 1 mol of the repeating unit represented by the general formula (1) of the polycarbodiimide. On the other hand, the graft reactive group in the reactive compound is usually 0.
It is used in an amount of from 01 to 1 mol, preferably from 0.02 to 0.8 mol. In this case, if the proportion of the graft-reactive group is less than 0.01 mol, it may be necessary to heat the epoxy resin for a long time or the storage stability as an epoxy resin composition solution may be deteriorated. , Again 1
When it exceeds the molar amount, the contribution of the original properties of polycarbodiimide in the cured product tends to be small. In the modification reaction, the reaction between the graft-reactive group in the reactive compound and the repeating unit of the polycarbodiimide represented by the general formula (1) proceeds quantitatively, and the graft corresponding to the amount of the reactive compound used. The reaction is achieved. The modification reaction can be carried out in the absence of a solvent, but it is preferably carried out in a suitable solvent. Such a solvent is not particularly limited as long as it is inactive with respect to polycarbodiimide and a reactive compound and can dissolve these, and examples thereof include the above-mentioned ones used in the synthesis of polycarbodiimide. Examples thereof include ether solvents, amide solvents, ketone solvents, aromatic hydrocarbon solvents, aprotic polar solvents and the like. These solvents can be used alone or in combination of two or more. When the solvent used in the synthesis of the polycarbodiimide can be used for the modification reaction, the polycarbodiimide solution obtained by the synthesis can be used as it is. The amount of the solvent used in the modification reaction is usually 10 to 10,000 parts by weight, preferably 50, per 100 parts by weight of the total amount of the reaction raw materials.
~ 5,000 parts by weight. The temperature of the modification reaction is appropriately selected according to the kind of polycarbodiimide or the reactive compound, but is usually 100 ° C. or lower, preferably −10 to +8.
0 ° C. Mn of the modified polycarbodiimide obtained as described above is usually 500 to 200,000, preferably 1,000 to 100,000, and more preferably 1,000 to 50,000. The modified polycarbodiimide obtained as described above can be used as a solution, but it is usually used after being separated from the solution. As a method of separating the modified polycarbodiimide obtained as a solution at the time of synthesis from the solvent, the same method as the above-mentioned separation method of polycarbodiimide can be mentioned. The modified polycarbodiimide in the present invention is a residue having a carboxylic acid anhydride group of the compound in which the grafting reactive group in the reactive compound reacts with the repeating unit of polycarbodiimide (-N = C = NR ^1- ). Has a grafted structure, and has a structure essentially different from that of the polycarbodiimide before the modification reaction. Therefore, the modified polycarbodiimide has different properties from the polycarbodiimide before the modification reaction, and by mixing with an epoxy resin and heating, the curing catalyst is used by the action of the carboxylic acid anhydride group in the modified polycarbodiimide. Even if not, it is usually 100 to 350 ° C., preferably 150 to 30
It has the property of easily curing an epoxy resin at a temperature of 0 ° C. The curing agent for an epoxy resin of the present invention contains the modified polycarbodiimide synthesized as described above as a main component, and may optionally contain a component other than the modified polycarbodiimide. Here, the main component is 90 by weight.
% Or more.

Epoxy Resin The epoxy resin which can be cured by the curing agent for an epoxy resin of the present invention is a compound having two or more epoxy groups in the molecule, and examples thereof include polyglycidyl of polyhydric phenol such as bisphenol-A. Ethers; polyglycidyl ethers of polyhydric alcohols such as 1,4-butanediol; polyglycidyl esters of polycarboxylic acids such as phthalic acid and hexahydrophthalic acid; compounds of nitrogen bases such as amines and amides Examples thereof include N-glycidyl derivatives; alicyclic epoxy resins; novolac epoxy resins such as phenol novolac epoxy resin and orthocresol novolac epoxy resin. These epoxy resins may be used alone or in combination of two or more. In the curing agent for epoxy resin of the present invention, all carbodiimide groups in the polycarbodiimide before modification are 0.
It is preferable to mix it in an amount of 05 to 1.5 equivalents, and it is particularly preferable to mix it in an amount of 0.1 to 1.0 equivalents. The epoxy resin composition containing the curing agent for epoxy resin of the present invention can be cured as it is, but may be used in combination with other curing agents for epoxy resin in some cases. Furthermore, tertiary amine, tertiary amine salt, 4
The curing time can be shortened by using a commonly used curing accelerator for epoxy resin such as a quaternary ammonium salt, imidazole or a metal salt. Further, the epoxy resin composition containing the curing agent for an epoxy resin of the present invention, if necessary, for example, a filler, a reinforcing material, an antioxidant, a heat stabilizer, an antistatic agent, a flame retardant, a colorant, Lubricant,
An antifogging agent, an adhesion improver, an antifungal agent and the like can also be added. The curing agent for an epoxy resin of the present invention can be very suitably used as a curing agent for an epoxy resin used as a protective material for electric / electronic parts, an electrical insulating material, and a sealing material for IC, LSI, etc. It is also useful as a curing agent for epoxy resins used in agents, paints, thermosetting films, cured films, prepregs, cured moldings, matrix resins for fiber reinforced resins and the like.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples as long as the gist thereof is not exceeded. In the examples,% and parts are by weight unless otherwise specified. Synthesis Example 1 <Synthesis of Polycarbodiimide> After the inside of a separable flask having an inner volume of 500 ml was replaced with nitrogen, 277 g of cyclohexanone was put therein. Then diphenylmethane-4,4'-diisocyanate (MDI) 60.
6 g and 3.13 g of phenyl isocyanate (PhI) were added, and the whole was stirred by a stirrer to form a uniform solution. 1-phenyl-3-methyl-2- as a catalyst was added to this solution.
Phosphorene-1-oxide (46.5 mg) was added, and the temperature was raised to 80 ° C. with stirring to start the reaction. After reacting for 6 hours, the reaction system was rapidly cooled to 25 ° C. with stirring. The obtained reaction liquid was poured into 1.5 liters of hexane,
After collecting the precipitated polymer powder by vacuum filtration,
After vacuum drying overnight at 40 ° C., 48.8 g of polycarbodiimide powder was obtained. The Mn of this polycarbodiimide was 7,800. <Synthesis of Modified Polycarbodiimide> Cyclohexanone (120 g) was added to the polycarbodiimide powder (30 g) under heating.
Then, 2.8 g of trimellitic anhydride dissolved in 12 g of acetone as a reactive compound was added dropwise over 30 minutes while maintaining the temperature of the reaction system at 80 ° C. After continuing the reaction for another 30 minutes, the mixture was cooled to room temperature, poured into 1 liter of hexane, and the precipitated polymer powder was collected by vacuum filtration and dried under reduced pressure at 40 ° C. overnight.
1 g of modified polycarbodiimide powder was obtained. The Mn of this modified polycarbodiimide was 4,100.

Synthesis Example 2 <Synthesis of Polycarbodiimide> S with an internal volume of 30 liters
After replacing the inside of the US autoclave with nitrogen, 16.6 kg of toluene was added. Then, diphenylmethane-4,4'-diisocyanate (MDI) 3.64 kg
And 188 g of phenyl isocyanate (PhI) are added,
The whole was made into a uniform solution by stirring with a stirrer. To this solution, 2.8 g of 1-phenyl-3-methyl-2-phospholen-1-oxide as a catalyst was added, and about 1 was added with stirring.
The temperature was raised to 10 ° C., and toluene was refluxed to start the reaction. After continuing the reaction for 5 hours, the reaction system was cooled to 50 ° C., 8.3 kg of acetone was gradually added, and the mixture was cooled to room temperature. Then, the precipitated polymer powder was collected by vacuum filtration and dried under reduced pressure at 40 ° C. overnight to obtain 2.93 kg of polycarbodiimide powder. The Mn of this polycarbodiimide was 9,200. <Synthesis of modified polycarbodiimide> After replacing the inside of an SUS autoclave with an internal volume of 30 liters with nitrogen,
After adding 11.3 kg of toluene, 2.0 kg of the polycarbodiimide powder was added and the temperature was raised to 110 ° C. with stirring to dissolve the polycarbodiimide. Then
As a reactive compound, 186 g of trimellitic anhydride dissolved in 744 g of acetone was injected for 30 minutes using a metering pump, and the mixture was further reacted for 30 minutes and then cooled to room temperature. Then, while stirring the contents, acetone 10.6
kg was added to precipitate a polymer, and the precipitated polymer powder was collected by vacuum filtration and dried under reduced pressure at 40 ° C. overnight to obtain 1.98 kg of a modified polycarbodiimide powder. The Mn of this modified polycarbodiimide was 3,900.

[0016]

【Example】

Example 1 100 parts of the modified polycarbodiimide obtained in Synthesis Example 1 and 100 parts of a liquid epoxy resin (trade name: Epicoat 828, manufactured by Yuka Shell Epoxy Co., Ltd.) were kneaded at 60 ° C. to prepare a molding epoxy resin composition. did. This composition was preheated in an oven at 120 ° C. for 30 minutes to prepare a composition in a B stage state, then press-molded under conditions of 100 kg / cm ² and 170 ° C. for 30 minutes, and further in an oven at 200 ° C.
After curing for 2 hours, a cured molded product was obtained. When the heat distortion temperature of this cured molded product was measured according to JIS K6911, it was 221 ° C. Further, the flexural strength, flexural modulus, Izod impact strength, water absorption and volume resistivity of this cured molded article were measured. The measurement results are shown in Table 1 together with the test standards.

Example 2 A cured molded article was obtained in the same manner as in Example 1 except that the modified polycarbodiimide used in Synthesis Example 2 was used. The measurement results of this cured molded product are shown in Table 1.

Example 3 The epoxy resin used was a solid epoxy resin (trade name: YX-4000, manufactured by Yuka Shell Epoxy Co., Ltd.),
A cured molded product was obtained in the same manner as in Example 1 except that the oven heating temperature after press molding was 220 ° C. The measurement results of this cured molded product are shown in Table 1.

Example 4 20 parts of the modified polycarbodiimide obtained in Synthesis Example 1 was added to 60 parts of cyclohexane and heated to 130 ° C. to dissolve it. After cooling this solution to room temperature, liquid epoxy resin (trade name Epicoat 828, Yuka Shell Epoxy Co., Ltd.)
After adding 20 parts, the mixture was stirred to obtain a uniform varnish. This varnish is a polyimide film laminated with copper foil (trade name: IFI-RM10, manufactured by Nikan Kogyo Co., Ltd.)
After coating with a doctor blade with a gap of 200 μm on the polyimide surface of, on a hot plate,
The solvent was evaporated and removed by heating at 80 ° C. for 20 minutes and subsequently at 120 ° C. for 60 minutes to form an epoxy resin composition film. Then, a copper-clad glass epoxy substrate (trade name: R-1705SX, manufactured by Matsushita Electric Works, Ltd.) was bonded onto this film so that the epoxy surface became an adhesive surface, and then 10
A load of 0 g / cm ² was applied, and heating was performed at 150 ° C. for 30 minutes, and then at 200 ° C. for 60 minutes. After that, the peel strength between the polyimide film and the glass epoxy substrate was measured according to JIS
According to H8630 and JIS C6481, the adhesion strength tester (manufactured by Yamamoto Plating Tester Co., Ltd.) measured 1.8 kgf / cm.

Example 5 The peel strength was measured in the same manner as in Example 4 except that the modified polycarbodiimide used in Synthesis Example 2 was used. The measurement results are shown in Table 2.

Example 6 A solid epoxy resin (trade name:
Peel strength was measured in the same manner as in Example 4 except that YX-4000, manufactured by Yuka Shell Epoxy Co., Ltd.) was used. The measurement results are shown in Table 2.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

EFFECT OF THE INVENTION The curing agent for epoxy resin of the present invention can cure the epoxy resin under mild conditions, can give an epoxy resin cured product having excellent heat resistance, and has problems of conventional epoxy resins. It is possible to obtain a cured product that is compatible with both heat resistance and toughness. Moreover,
The epoxy resin cured product cured using the epoxy resin curing agent of the present invention is also excellent in electrical insulation, moisture resistance, chemical stability to various solvents, adhesion to various substrates, and the like.

Claims (1)

[Claims] 1. A curing agent for an epoxy resin, which comprises, as a main component, a resin obtained by grafting polycarbodiimide with at least one compound having a graft reactive group and a carboxylic acid anhydride group.