JPH0873567A - Epoxy resin curing composition - Google Patents

Abstract

PURPOSE: To obtain an epoxy resin curing composition having low-temperature rapid curability and excellent room temperature storage stability. CONSTITUTION: This composition comprises an epoxy resin and a solid solution comprising a compound having a nitrogen base and having no prim. amino group in the molecule and a phenol/formaldehyde resin comprising a phenol/ formaldehyde condensate having an average molecular weight (in terms of the molecular weight of the polystyrene) of 2000-10000 as determined by gel permeation chromatography.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a latent curing agent for epoxy resins.

[0002]

2. Description of the Related Art Epoxy resins are desired to be one-pack type epoxy resins because of their ability to prevent compounding mistakes, continuity, and line formation rather than the conventional two-pack type epoxy resins.
A one-pack type epoxy resin requires a curing agent that does not react with the epoxy resin at room temperature, but that reacts and cures when heated, a so-called latent curing agent.

Several latent curing agents have been proposed so far, and typical examples thereof include boron trifluoride-amine complex, dicyandiamide, dibasic acid dihydrazide, amine-epoxy adduct and the like. To be However, the boron trifluoride-amine complex is highly hygroscopic,
Although dicyandiamide and dibasic acid dihydrazide have excellent storage stability, they adversely affect various properties of the cured product.
It has the drawback of requiring a high temperature of 0 ° C or higher and long-term curing.
Further, as for the amine-epoxy adduct, a low-temperature fast-curing one has poor storage stability, and a good storage stability tends to lack a low-temperature fast-curing property. In particular, when using epoxy resin as a sealing material for electronic parts, etc., in order not to damage the electronic parts,
Lower temperature curing is strongly desired.

In order to solve this problem, a method is known in which diamines or polyamines are salted with a phenol novolac resin, which is a condensation product of phenols and aldehydes by an acid catalyst, and have low activity at room temperature. There is. (JP-A-60-49025, JP-A-63-117032) However, the low temperature curable salt has low activity with the epoxy resin at room temperature or below, but has poor storage stability at around 40 ° C.
Storage in the summer is difficult. Further, those having storage stability at around 40 ° C. do not have low temperature curability, and require high temperature and long time curing.

[0005]

The present invention has a low temperature fast curing property,
Another object is to develop a latent curing agent for epoxy resins, which has excellent storage stability at room temperature.

[0006]

Means for Solving the Problems As a result of intensive studies to develop a latent curing agent having low-temperature curability and excellent storage stability, the present inventor has found that (1) a primary amino group in a molecule. A phenol-formaldehyde system comprising a condensate of phenols and formaldehydes, which has a nitrogen-base-free compound and (2) a polystyrene-reduced average molecular weight of 2,000 or more and 10,000 or less by gel permeation chromatography (GPC) It was found that a solid solution with a resin is an excellent latent curing agent, and the composition of the latent curing agent (b) and the epoxy resin (a) is an excellent curable composition, and the present invention is completed. Came to let.

The solid solution in the present invention means a compound in which (1) a compound having a nitrogen base having no primary amino group in the molecule and (2) a phenol / formaldehyde resin form a single solid phase. To tell. Specifically, the above 2
Although the components form a single solid phase by hydrogen bonding, salt formation, etc., each component does not necessarily have to be present in a stoichiometric amount, and one component may exist in excess of the other. Absent.

The epoxy resin (a) used in the composition of the present invention may be any one as long as it has two or more epoxy groups in one molecule. Specifically, compounds generally well known in the art, such as bisphenol A, bisphenol F, catechol,
Polyglycidyl ether obtained by reacting polyhydric phenols such as resorcinol or polyhydric alcohols such as glycerin and polyethylene glycol with epichlorohydrin, hydroxycarboxylic acids such as p-oxybenzoic acid and β-oxynaphthoic acid Glycidyl ether ester obtained by reacting epichlorohydrin, polyglycidyl ester obtained from polycarboxylic acid such as phthalic acid and terephthalic acid, glycidyl amine obtained from 4,4′-diaminodiphenylmethane and m-aminophenol Examples of the compound include epoxidized novolak and epoxidized polyolefin.

The solid solution (b) of the present invention is a phenol / formaldehyde resin (constituted product of phenol and formaldehyde, which has a polystyrene-reduced average molecular weight of 2,000 or more and 10,000 or less by gel permeation chromatography (GPC)). Hereinafter, a compound having a phenol / formaldehyde resin and a nitrogen base having no primary amino group in the molecule (hereinafter,
It can be prepared by heating together a compound having a nitrogen base) for obtaining a clear liquid and then cooling until forming a solid product. If the heating temperature is too low, the resin consisting of the condensate of the phenol / formaldehyde resin of the present invention will not melt, and a solid solution cannot be obtained.If the heating temperature is too high, the nitrogen base may evaporate or sublime before the solid solution is formed. Therefore, the preferable temperature in manufacturing is 100 to 200 ° C.

Alternatively, the above-mentioned phenol-formaldehyde resin is dissolved in a lower alcohol such as methanol or ethanol at room temperature, and then a compound having a nitrogen base having no primary amino group in the molecule (a solution of the solvent) is used. Even if) is added to the obtained solution, heated and stirred in a reaction vessel equipped with a reflux device if necessary,
After completion of the reaction, the solvent may be removed by a conventional method. Regardless of the method of manufacture, the product is converted to a powder before it is used as a hardener in the composition of the present invention.

The weight ratio of the phenol-formaldehyde resin to the compound having a nitrogen base in solid solution (b) is selected to give a solid, stable product and is usually within the range of 1: 1 to 20: 1. Preferably 2: 1 to 10:
It is within the range of 1.

The solid solution (b) used as the curing agent in the composition of the present invention is manufactured and powdered before being mixed with the epoxy resin (a).

The compound having a nitrogen base having no primary amino group in the molecule used for producing the solid solution (b) means a secondary or tertiary amine, or a base such as imidazole. It is a heterocyclic compound containing a nitrogen atom. Specifically, secondary monoamines such as diisobutylamine, diisopropanolamine, piperidine and pipecoline, 2- (N, N-dimethylamino) ethanol, triethanolamine, benzyldimethylamine,
Tertiary monoamines such as 2- (dimethylaminomethyl) phenol, N, N'-diethylenediamine, secondary diamines such as piperazine, N, N, N ', N'.
-Tetramethylbutanediamine, 1,7-bis (dimethylamino) heptane, bis (4-dimethylaminophenyl) methane, N, N'-dimethylpiperazine, 1,4-
Tertiary diamines such as diazabicyclo (2,2,2) octane, tertiary triamines such as 2,4,6-tris (dimethylaminomethyl) phenol, 1-methylimidazole, 2-methylimidazole, Nitrogen-containing heterocyclic compounds such as 2-ethyl-4-methylimidazole, 2-phenylimidazole and quinoline can be mentioned. The nitrogen base can be used in a mixture of two or more.

The phenol-formaldehyde resin used for producing the solid solution (b) can be obtained by the following method. First, phenol and formalin are reacted in the presence of an acid catalyst (usually 0.2 to 2%) under conditions such that the molar ratio of phenols to formaldehyde is 1: 0.8 to 1.5 (novolak). Reaction), and then the reaction is allowed to proceed further in the presence of a basic catalyst (usually 0.2 to 2%) (resolization reaction). That is, first, a linear condensate is produced by a novolac reaction, and then a cross-linking point is provided by a resole reaction.

The novolak reaction can be carried out under known conditions and methods. Usually, the reaction is carried out at about 100 ° C. for a few hours in the presence of an acid catalyst. Then, water is poured into the system, and after cooling, the resin is precipitated and recovered. Also, the resolization reaction can be carried out under known conditions and methods. Usually 60-100
The reaction is carried out under a basic catalyst for about 1 hour at 0 ° C., then the mixture is allowed to cool and the resin is recovered.

Phenols which can be used in the present invention include phenol, cresol, xylenol, resorcinol, catechol, hydroquinone and the like, but may be a mixture of two or more thereof.

The formaldehyde may be formalin, paraformaldehyde, glyoxal, trioxane, etc. at various concentrations, and may be a mixture of two or more thereof.

As the acidic catalyst, hydrochloric acid, sulfuric acid, formic acid, oxalic acid, paratoluenesulfonic acid, phenolsulfonic acid and the like can be used.

As the basic catalyst, sodium hydroxide,
Inorganic alkali compounds such as hydroxides or oxides of alkali metals or alkaline earth metals such as potassium hydroxide, calcium hydroxide, sodium carbonate, carbonates of alkali metals, bicarbonates, various amines, ammonia water, hexa One or more organic alkali compounds such as methylenetetramine are used.

The phenol-formaldehyde resin produced in this manner is (1) substantially composed of carbon, hydrogen and oxygen atoms, and (2) a trifunctional group of methylene group, methylol group and phenols. (3) The trifunctional residue binds to a methylene group at one of the 2.4 and 6-positions of phenols, and has a methylol group at at least one of the other positions. Group and / or methylene group, and (4) the polystyrene-converted average molecular weight by gel permeation chromatography (GPC) is 2000 or more and 10000 or less. Particularly preferred is GP
The polystyrene-converted average molecular weight by C is 3000 or more 7
It is 000 or less.

This phenol-formaldehyde resin has an absorption intensity of 1600 cm ^-1 in the far infrared absorption spectrum by the KBr tablet method of D1600, 990-990.
The maximum absorption intensity in the range of 1015 cm ^-1 is D990
When the absorption intensity at -1015 and 890 cm ^-1 is represented by D890, D990 to 1015 / D1600 = 0.2 to
It is characterized by being 9.0 and D890 / D1600 = 0.09-1.0. Particularly preferred is D990-
1015 / D1600 = 0.4 to 5.0, D890 / D
It has a characteristic of 1600 = 0.12 to 0.3.

In the infrared absorption spectrum, D160
The peak of 0 indicates absorption attributed to the benzene nucleus, and D99
It is already widely known for phenol-formaldehyde resins that the peaks of 0 to 1015 show absorption attributable to a methylol group, and the peak of D890 belongs to isolated hydrogen of a benzene nucleus.
A characteristic value of 5 / D1600 = 0.2 to 9.0 indicates that this resin contains a certain amount of methylol groups, and further D890 / D1600 = 0.09 to 1.0.
The characteristic value indicates that the reaction sites (ortho and para) of the phenol molecule involved in increasing the molecular weight are appropriately blocked by a methylene bond or a methylol group.

Conventionally, novolak resins and resole resins have been known as typical phenol / formaldehyde resins. Usually, the novolak resin has a molar ratio of phenol to formaldehyde of, for example, 1: 0.7-0.9.
It is produced by reacting phenol with formalin in the presence of an acid catalyst such as oxalic acid (usually 0.2 to 2%) under an excess of phenol such that The novolak resin obtained by such a method is mainly composed of a trimer to pentamer in which phenol is bound mainly by a methylene group, and has a molecular weight of about 1,000 or less. It also contains almost no free methylol groups and therefore D990
The value of -1015 / D1600 is 0.2 or less, which is different from the phenol-formaldehyde resin used in the present invention.

Ordinary resole resins also have a molar ratio of phenol to formaldehyde of 1 to 1 to 2 in the presence of a basic catalyst (usually 0.2 to 2%) such as sodium hydroxide, ammonia or an organic amine. It is manufactured by reacting under the formaldehyde excess condition.
The resole resin obtained in this manner is mainly composed of a phenolic 1-3 mer and has a molecular weight of about 100 to 300. Further, since a relatively large amount of free methylol group blocks many of the reaction sites (ortho and para) of the phenol molecule involved in the increase in molecular weight, D8
The value of 90 / D1600 is 0.09 or less, which is different from the phenol / formaldehyde resin used in the invention of the present application, like ordinary novolacs.

The amount of the solid solution (b) in the curable composition in the present invention is usually preferably 0.5 to 50 parts by weight with respect to 100 parts by weight of the epoxy resin (a). When the solid solution (b) is less than 0.5 parts by weight, sufficient curability is not exhibited, and when it exceeds 50 parts by weight, the performance of the cured product may be deteriorated.

The curable composition of the present invention is manufactured by adding the solid solution (b) to a predetermined amount of the epoxy resin and thoroughly mixing and mixing in a mortar.

In addition to the epoxy resin (a) and the solid solution (b), known curatives such as acid anhydride, dicyandiamide, dibasic acid dihydrazide, guanamines and melamine are used in combination in the curable composition of the present invention. sell.

The curable composition of the present invention is cured by placing it in a gear oven at a constant temperature for a predetermined time.

[0029]

EXAMPLES The present invention will now be specifically described with reference to synthesis examples and examples, but the present invention is not limited to these examples.
The abbreviations of the raw materials used in the synthesis examples and examples are as follows. (A) Polyfunctional epoxy resin Epicoat # 828 (trade name, Shell Kagaku Co., Ltd.) Bisphenol A epoxy resin Epoxy equivalent 184-194 (b) Nitrogen base PI: Piperazine TEA: Triethanolamine DMP-10: 2-Dimethylamino Methylphenol MZ: 2-Methylimidazole EMZ: 2-Ethyl-4-methylimidazole

Curing Agent Production Example 1 A mixed aqueous solution containing 20% by weight hydrochloric acid and 8% by weight formaldehyde preheated to 30 ° C. was equipped with a thermometer, a reflux condenser, a stirring device, a heating and cooling jacket. Placed in reactor. Then, a mixed aqueous solution containing 70% by weight of phenol and 6% by weight of formaldehyde was added dropwise to the above mixed aqueous solution. After the dropping, the mixture was left standing for 24 hours to collect the reaction, water was added to the reaction system, and the cooled contents were taken out and washed with water. After washing with water, treatment in a 1.0% by weight aqueous ammonia solution at a temperature of 50 ° C. for 60 minutes, further washing with water,
It was dried at 70 ° C. for 3 hours. The obtained product was designated as Resin No.
Set to 1. The polystyrene reduced molecular weight of this resin by GPC was 4000. Also, 990 to 1015 cm with respect to 1600 cm -1 by infrared absorption spectrum method
−1 and 890 cm −1 have absorption wavelength intensity ratios of 1.
23 and 0.23. In a metal beaker equipped with a thermometer and a stirrer, resin No. 100g of 1 is weighed,
40 g of PI was added and well stirred with heating. 150
After the reaction was concentrated at ℃ for 1 hour, heating was stopped and the mixture was cooled to room temperature to obtain a yellow solid. This solid was crushed to obtain a curing agent No. It was set to 1.

Curing agent production example 2 A resin beaker was placed in a metal beaker equipped with a thermometer and a stirrer.
o. 100 g of 1 was weighed, 40 g of TEA was added, and well stirred while heating. After the reaction was concentrated at 150 ° C. for 1 hour, heating was stopped and the mixture was cooled to room temperature to obtain a yellow solid. This solid was crushed to obtain a curing agent No. And 2.

Curing Agent Production Example 3 A resin beaker was placed in a metal beaker equipped with a thermometer and a stirrer.
o. 100 g of 1 was weighed, 50 g of DMP-10 was added,
Stir well with heating. After the reaction was concentrated at 150 ° C. for 1 hour, heating was stopped and the mixture was cooled to room temperature to obtain a yellow solid. This solid was crushed to obtain a curing agent No. Three
And

Curing Agent Production Example 4 A resin N was placed in a metal beaker equipped with a thermometer and a stirrer.
o. 100 g of 1 was weighed, 30 g of MZ was added, and well stirred while heating. After the reaction was concentrated at 150 ° C. for 1 hour, heating was stopped and the mixture was cooled to room temperature to obtain a yellow solid. This solid was crushed to obtain a curing agent No. It was set to 4.

Curing agent production example 5 In a metal beaker equipped with a thermometer and a stirrer, resin N was added.
o. 100 g of 1 was weighed, 30 g of EMZ was added, and well stirred while heating. After the reaction was concentrated at 150 ° C. for 1 hour, heating was stopped and the mixture was cooled to room temperature to obtain a yellow solid. This solid was crushed to obtain a curing agent No. It was set to 5.

Curing Agent Production Example 6 A mixed aqueous solution containing 20% by weight hydrochloric acid and 8% by weight formaldehyde preheated to 60 ° C. was equipped with a thermometer, a reflux condenser, a stirring device, a heating and cooling jacket. Placed in reactor. Then, a mixed aqueous solution containing 70% by weight of phenol and 6% by weight of formaldehyde was added dropwise to the above mixed aqueous solution. After the dropping, the mixture was left standing for 24 hours to collect the reaction, water was added to the reaction system, and the cooled contents were taken out and washed with water. did. After washing with water, it was treated in a 1.0 wt% aqueous ammonia solution at a temperature of 50 ° C. for 60 minutes, further washed with water, and then dried at 70 ° C. for 3 hours. The obtained product is referred to as resin N
o. Set to 2. The polystyrene reduced molecular weight of this resin by GPC was 5,000. . In addition, 990 to 101 for 1600 cm −1 by the infrared absorption spectrum method
The absorption wavelength intensity ratios at 5 cm-1 and 890 cm-1 are 1.40 and 0.18, respectively. there were. In a metal beaker equipped with a thermometer and a stirrer, resin No. 100 g of 2
Weighed out, added 40 g of PI, and stirred well while heating. After the reaction was concentrated at 150 ° C. for 1 hour, heating was stopped and the mixture was cooled to room temperature to obtain a yellow solid. This solid was crushed to obtain a curing agent No. It was set to 6.

Curing Agent Production Example 7 A resin N was placed in a metal beaker equipped with a thermometer and a stirrer.
o. 100 g of 2 was weighed, 40 g of TEA was added, and well stirred while heating. After the reaction was concentrated at 150 ° C. for 1 hour, heating was stopped and the mixture was cooled to room temperature to obtain a yellow solid. This solid was crushed to obtain a curing agent No. It was set to 7.

Curing Agent Production Example 8 A resin N was placed in a metal beaker equipped with a thermometer and a stirrer.
o. 2. Weigh 100 g of 2 and add 50 g of DMP-10,
Stir well with heating. After the reaction was concentrated at 150 ° C. for 1 hour, heating was stopped and the mixture was cooled to room temperature to obtain a yellow solid. This solid was crushed to obtain a curing agent No. 8
And

Curing Agent Production Example 9 A resin N was placed in a metal beaker equipped with a thermometer and a stirrer.
o. 100 g of 2 was weighed, 30 g of MZ was added, and well stirred while heating. After the reaction was concentrated at 150 ° C. for 1 hour, heating was stopped and the mixture was cooled to room temperature to obtain a yellow solid. This solid was crushed to obtain a curing agent No. It was set to 9.

Curing Agent Production Example 10 In a metal beaker equipped with a thermometer and a stirrer, resin N was added.
o. 100 g of 2 was weighed, 30 g of EMZ was added, and well stirred while heating. After the reaction was concentrated at 150 ° C. for 1 hour, heating was stopped and the mixture was cooled to room temperature to obtain a yellow solid. This solid was crushed to obtain a curing agent No. It was set to 10.

Curing Agent Preparation Example 11 In a reactor equipped with a thermometer, a reflux condenser, a stirrer, a heating and cooling jacket, 390 g of phenol, 37% by weight
Formalin 370g, oxalic acid 1.5g and water 390
g, and while stirring, raise the temperature to 90 ° C. in 60 minutes,
The mixture was stirred and heated at a temperature of 90 to 92 ° C for 60 minutes. Then 3
1.0 g of 5 wt% hydrochloric acid was added, and the mixture was further stirred and heated at a temperature of 90 to 92 ° C. for 60 minutes. Next, 500 g of water was added and cooled, the water was removed by a siphon, the mixture was heated under a reduced pressure of 30 mmHg, heated at 100 ° C. for 3 hours, and further heated at 180 ° C. for 3 hours. The resulting novolak resin was obtained as a tan solid on cooling. The obtained product was designated as Resin No. It was set to 3. The polystyrene reduced molecular weight of this resin by GPC was 900. In addition, 1600 cm-by infrared absorption spectrum method
990 to 1015 cm-1 and 890 cm-1 for 1
The absorption wavelength intensity ratios were 0.12 and 1.02, respectively. In a metal beaker equipped with a thermometer and a stirrer,
Resin No. 100 g of 3 was weighed, 40 g of PI was added, and well stirred while heating. After the reaction was concentrated at 150 ° C. for 1 hour, heating was stopped and the mixture was cooled to room temperature to obtain a yellow solid. This solid was crushed to obtain a curing agent No. 11
And

Curing Agent Production Example 12 A resin beaker was placed in a metal beaker equipped with a thermometer and a stirrer.
o. 100 g of 3 was weighed, 30 g of MZ was added, and well stirred while heating. After the reaction was concentrated at 150 ° C. for 1 hour, heating was stopped and the mixture was cooled to room temperature to obtain a yellow solid. This solid was crushed to obtain a curing agent No. It was set to 12.

Hardener Preparation Example 13 282 g of distilled phenol and 3 in a reactor equipped with a thermometer, a reflux condenser, a stirrer, a heating and cooling jacket.
368 g of 7% by weight formalin and 150 g of 26% by weight ammonia water were added, the temperature was raised from room temperature to 70 ° C. in 60 minutes while stirring, and further 9 to 70 ° C. to 72 ° C.
Stir and heat for 0 minutes. Then, the mixture was allowed to cool and dehydrated by azeotropic distillation under reduced pressure of 40 mmHg while adding 300 g of methanol little by little, and methanol was added as a solvent to 70%.
0 g was added and a yellow transparent resol resin solution was taken out.
This resin is It was set to 4. The polystyrene reduced molecular weight of this resin by GPC was 500 or less. Also,
The absorption wavelength intensity ratios of 990 to 1015 cm −1 and 890 cm −1 with respect to 1600 cm −1 according to the infrared absorption spectrum method were 5.47 and 0.08, respectively. In a beaker equipped with a thermometer and a stirrer, resin No. Four to one
00 g was weighed and 20 g of PI was added. The resulting precipitate was filtered off, washed with ether and then dried under reduced pressure at 50 ° C. The solid obtained was crushed to obtain a hardener No. It was set to 13.

Curing Agent Production Example 14 Resin No. 1 was placed in a beaker equipped with a thermometer and a stirrer. Four
Was weighed, and 15 g of MZ was added. The resulting precipitate was filtered off, washed with ether and then dried under reduced pressure at 50 ° C. The solid obtained was crushed to obtain a hardener No. 1
It was set to 4.

Examples 1 to 10, Comparative Examples 1 to 4 100 parts by weight of epoxy resin (Epicoat # 828), curing agent Nos. 1 to 10 or curing agent No. 1 obtained in Production Examples 11 to 14 of curing agent. 1
1 to 14 parts by weight, and 1 part by weight of fine particle silica (Aerosil # 200, manufactured by Nippon Aerosil Co., Ltd.) were degassed and mixed under reduced pressure using a vacuum raider machine (manufactured by Ishikawa Factory Co., Ltd.) and dispersed. , Their curability, storage stability, glass transition point and tensile shear adhesive strength were evaluated. The results obtained are shown in Table 1.

The curability, storage stability, glass transition point and tensile shear adhesive strength were measured by the following methods. 1. Evaluation of Curability A sample of about 0.1 to 0.2 g was placed on a hot plate set to a predetermined temperature, and the time until gelation was measured. 2. Storage stability The sample was put in a constant temperature bath at 40 ° C, and the number of days until the viscosity measured by a BH type rotational viscometer was doubled was measured. 3. Glass transition point (Tg) A sample cured at 100 ° C for 1 hour was measured for Tg by a TMA penetration method using a thermomechanical analyzer (TMA, manufactured by Rigaku Denki Co., Ltd.). Measurement conditions Temperature rising rate 10 ° C / min Overweight 10g Needle diameter 1mm 4. Tensile shear bond strength The tensile shear bond strength is 25 after degreasing and polishing.
25 mm x 100 mm x 1.6 mm mild steel plate
Adhesion was performed in a wrap area of mm × 12.5 mm, the sample was pressed with a clip, cured at 100 ° C. for 1 hour, and then tensile shear adhesive strength was measured at 25 ° C. (Unit is kg / cm
2)

[0046]

[Table 1]

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 8, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0035

[Correction method] Change

[Correction content]

Curing Agent Production Example 6 A mixed aqueous solution containing 20% by weight hydrochloric acid and 8% by weight formaldehyde preheated to 60 ° C. was equipped with a thermometer, a reflux condenser, a stirring device, a heating and cooling jacket. Placed in reactor. Then, a mixed aqueous solution containing 70% by weight of phenol and 6% by weight of formaldehyde was added dropwise to the above mixed aqueous solution. After the dropping, the mixture was left standing for 24 hours to collect the reaction, water was added to the reaction system, and the cooled contents were taken out and washed with water. did. After washing with water, it was treated in a 1.0 wt% aqueous ammonia solution at a temperature of 50 ° C. for 60 minutes, further washed with water, and then dried at 70 ° C. for 3 hours. The obtained product is referred to as resin N
o. Set to 2. The polystyrene reduced molecular weight of this resin by GPC was 5,000. In addition, 990 to 1015 for 1600 cm −1 by the infrared absorption spectrum method
The absorption wavelength intensity ratios at cm-1 and 890 cm-1 were 1.40 and 0.18 , respectively . In a metal beaker equipped with a thermometer and a stirrer, resin No. 100 g of 2 was weighed, 40 g of PI was added, and well stirred while heating. 1
After keeping the mixture at 50 ° C. for 1 hour, after the reaction was collected, heating was stopped and the mixture was cooled to room temperature to obtain a yellow solid. This solid was crushed to obtain a curing agent No. It was set to 6.

Claims (1)

[Claims] 1. (a) Epoxy resin (b) (1) Compound having nitrogen base without primary amino group in molecule, and (2) polystyrene-reduced average molecular weight by gel permeation chromatography (GPC). Is 2000 or more and 10000 or less, and a curable composition comprising a solid solution of a phenol / formaldehyde resin which is a condensate of a phenol and a formaldehyde.