JPH0725985A - Curing agent for epoxy resin - Google Patents

Abstract

PURPOSE:To obtain a curing agent, containing carboxylic acid esters and an acid anhydride in a specific proportion and capable of providing a cured product of the epoxy resin having a high heat distortion temperature and excellent in impact and crack resistance. CONSTITUTION:The objective curing agent contains (A) carboxylic acid esters expressed by formula I [R<1> is aromatic residue or (saturated)alicyclic residue; R<2> is aromatic residue], (B) carboxylic acid esters expressed by formula II and an acid anhydride so as to provide (60/40) to (90/10) ratio of the components (A)/(B) and (95/5) to (20/80) ratio of the acid anhydride/[components (A) and (B)] expressed in terms of equiv. ratio of the acids.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an epoxy resin curing agent.

[0002]

2. Description of the Related Art Epoxy resin has excellent properties such as mechanical strength, electrical insulation, adhesiveness and chemical resistance.
Widely used in electrical and electronic materials, paints, civil engineering and construction materials, adhesives, etc.

The epoxy resin cured product may have cracks depending on the use conditions, and the following methods have been conventionally proposed in order to improve the crack resistance. That is, use of an epoxy resin having a large epoxy equivalent, use of a long-chain curing agent such as dodecenylsuccinic anhydride, addition of a modifier such as reactive polybutadiene, use of an acrylic acid type half ester curing agent, and the like. However, all of these conventional methods have a drawback that the heat resistance of the cured product is significantly reduced.

Further, Japanese Patent Publication No. 55-43007 discloses dicarboxylic acids and polycarboxylic acid anhydrides having a specific structure in order to produce a molded product having a high impact strength and a high heating strain temperature. A thermosetting composition based on an epoxy resin is disclosed, which comprises a predetermined proportion. But,
Even with the composition, it was still not sufficient to prevent the decrease in heat resistance.

[0005]

The present invention provides an epoxy resin curing agent which has a high heat distortion temperature and can give an epoxy resin cured product which is excellent in impact resistance and crack resistance. is there.

[0006]

The present inventors have made use of an epoxy resin curing agent containing a carboxylic acid ester having the following structure and an acid anhydride in a predetermined ratio to obtain a heat-resistant epoxy resin cured product. It has been found that the deterioration of the properties can be significantly improved and the excellent impact resistance and crack resistance can be imparted, and the present invention has been completed.

That is, the present invention provides a carboxylic acid ester represented by the following formula (I), a carboxylic acid ester represented by the following formula (II) and an acid anhydride in an acid equivalent ratio of (I) /
An epoxy resin curing agent containing (II) 60/40 to 90/10 and acid anhydride / {(I) + (II)} 95/5 to 20/80.

[0008]

[Chemical 2] (Here, each R ¹ independently represents an aromatic residue or a saturated or unsaturated cycloaliphatic residue, and each R ² independently represents an aromatic residue).

The carboxylic acid ester represented by the formula (I) and the carboxylic acid ester represented by the formula (II) of the present invention are obtained by reacting a dicarboxylic acid anhydride with an aromatic compound having two hydroxyl groups. Can be manufactured by. In the production, the carboxylic acid ester represented by the formula (I) and the carboxylic acid ester represented by the formula (II) may be produced separately or may be produced simultaneously. It is preferable to manufacture them at the same time because of the simplicity of the manufacturing process. In this case, each R ¹ and each R ² in formulas (I) and (II) are the same.

Suitable dicarboxylic acid anhydrides for producing the carboxylic acid esters include, for example, phthalic anhydride and 3
-Methyl phthalic anhydride, 4-methyl phthalic anhydride, 3-
Ethyl phthalic anhydride, 4-ethyl phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, 3-
Methyltetrahydrophthalic anhydride, 4-Methyltetrahydrophthalic anhydride, 3-Methylhexahydrophthalic anhydride, 4-Methylhexahydrophthalic anhydride, 3-Ethyltetrahydrophthalic anhydride, 4-Ethyltetrahydrophthalic anhydride, 3- Ethyl hexahydrophthalic anhydride, 4
-Ethylhexahydrophthalic anhydride, 3,6-Endomethylenetetrahydrophthalic anhydride, 3,6-Endomethylenehexahydrophthalic anhydride, 3-Methyl-3,6-
Endomethylenetetrahydrophthalic anhydride, 4-methyl-3,6-endomethylenetetrahydrophthalic anhydride,
Examples thereof include 3-methyl-3,6-endomethylenehexahydrophthalic anhydride and 4-methyl-3,6-endomethylenehexahydrophthalic anhydride.

As the aromatic compound having two hydroxyl groups, for example, hydroquinone, 2-methylhydroquinone, 3-methylhydroquinone, resorcin, 4-methylresorcin, 5-methylresorcin, catechol, 3
-Methylcatechol, 4-methylcatechol, tert-butylcatechol and the like can be mentioned.

The preferred reaction conditions are described below. First, the charging molar ratio of the dicarboxylic acid anhydride and the aromatic compound having two hydroxyl groups is preferably 2 or more, and particularly preferably 3 or more. When the molar ratio is less than 2, the amount of carboxylic acid ester represented by the formula (II) is increased, which is not preferable.

Further, it is preferable to use a catalyst in the reaction. As the catalyst, for example, tertiary amines such as dimethylbenzylamine, imidazoles such as 2-ethyl-4-methylimidazole, basic compounds such as alkali metal compounds and alkaline earth metal compounds are preferable. By using the catalyst, the content of the compound represented by the formula (I) in the product can be made higher than that of the compound represented by the formula (II), and the acid equivalent ratio of the present invention can be easily obtained. it can. The amount of catalyst used is dicarboxylic acid anhydride and 2
It is preferably 0.1 to 10 mol%, particularly preferably 0.1%, based on the total amount of aromatic compounds having one hydroxyl group.
It is 2 to 5 mol%. When the amount of catalyst used is less than 0.1 mol%, the catalytic action is small, and when it exceeds 10 mol%, there is no particular effect.

The reaction temperature is preferably 70 to 250 ° C., particularly preferably 100 to 200 ° C., and the reaction time is preferably 0.1 to 24 hours, particularly preferably 0.5 to 10 hours. Is. A solvent may be used in the reaction, and high-boiling aromatic hydrocarbons such as xylene, mesitylene, tetralin and α-methylnaphthalene are preferable. By using the above conditions,
The acid equivalent ratio of (I) / (II) can easily fall within the range of the present invention.

The acid anhydride in the epoxy resin curing agent of the present invention can be selected from those listed as suitable for the production of the above-mentioned carboxylic acid esters.

In the epoxy resin curing agent of the present invention, the acid equivalent ratio (I) / (II) of the carboxylic acid esters is 60/40.
90/10, preferably 70/30 to 90/10
Is. The acid equivalent ratio of acid anhydride / {(I) + (II)} is 95/5 to 20/80, preferably 90/1.
It is 0-40 / 60. The acid equivalent ratio of (I) / (II) is 6
If it is less than 0/40, the cured product has insufficient mesh formation,
If it exceeds 90/10, the impact resistance and crack resistance of the cured product deteriorate, which is not preferable. Similarly, acid anhydride /
When the acid equivalent ratio of {(I) + (II)} is less than 20/80,
When the cured product has insufficient network formation and exceeds 95/5, impact resistance and crack resistance of the cured product deteriorate, which is not preferable. Here, the acid equivalent ratio is calculated by using 2 equivalents of the carboxylic acid ester represented by the formula (I), 1 equivalent of the carboxylic acid ester represented by the formula (II), and 2 equivalents of the acid anhydride. is there.

The epoxy resin in which the curing agent of the present invention is used is not particularly limited, and examples thereof include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, polyglycidyl ether of polyhydric alcohol, and polybasic acid. Polyglycidyl ester of 3,
4-epoxycyclohexylmethyl (3,4-epoxycyclohexane) carboxylate, vinylcyclohexene diepoxide, cresol novolac type epoxy resin, epoxy resin having a hydantoin ring and the like can be mentioned. The compounding ratio of the epoxy resin curing agent of the present invention and the epoxy resin is 3/2 to 2 in terms of an equivalent ratio of curing agent / epoxy resin.
It is preferably within the range of / 3.

Further, in addition to the epoxy resin and the epoxy resin curing agent, a stabilizer, a plasticizer, a lubricant, a flame retardant, a flame retardant auxiliary agent, an antistatic agent, a colorant, a charge imparting agent, and a slidability improving agent. A conventional additive such as an impact resistance improver may also be added.

There is no particular limitation on the method for producing a resin composition by mixing an epoxy resin, an epoxy resin curing agent and other additives and the curing method thereof, and conventionally known means can be adopted.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0021]

EXAMPLES The carboxylic acid esters used in the examples and comparative examples are those produced as follows. <Carboxylic Acid Esters A> In a 1 liter four-necked flask equipped with a stirrer and a thermometer, 498 g of methyltetrahydrophthalic anhydride (MeTHPA, pentahard 5000, trademark, manufactured by Tonen Kagaku KK) and hydroquinone (Tokyo Kasei Co., Ltd.) I made 110 grams (made by company). 2 mol% of dimethylbenzylamine (BDMA, manufactured by Tokyo Kasei Co., Ltd.) was added as a catalyst to the total of these,
The temperature was raised to 160 ° C. with stirring under a nitrogen atmosphere, and the reaction was completed by holding for 2 hours. Then, the unreacted material was distilled off under a reduced pressure of 5 mmHg.

The residue in the flask weighed 392 grams, and a portion of this was dissolved in tetrahydrofuran and analyzed using high performance liquid chromatography (HLC, Shimadzu Corp.). According to the factor calculated in advance, the dicarboxylic acid diester represented by the formula (I) was 309 g and the formula (I
The dicarboxylic acid monoester represented by I) was calculated to be 83 grams, and (I) / (II) had an acid equivalent ratio of 82/18. <Carboxylic Acid Ester B> It was produced in the same manner as A except that the reaction temperature was 150 ° C. and the reaction time was 1 hour.

The residue was 359 grams. As a result of HLC analysis, the dicarboxylic acid diester represented by the formula (I) was 221 g, the dicarboxylic acid monoester represented by the formula (II) was 138 g, and (I) / (II) was 67 / in acid equivalent ratio. It was 33. <Carboxylic Acid Ester C> Hydroquinone was replaced with catechol (manufactured by Tokyo Kasei Co., Ltd.) and produced in the same manner as in A, except that the reaction time was 3 hours.

The residue was 367 grams. As a result of HLC analysis, the dicarboxylic acid diester represented by the formula (I) was 243 g, the dicarboxylic acid monoester represented by the formula (II) was 124 g, and the acid equivalent ratio of (I) / (II) was 71 / It was 29. <Carboxylic acid ester D> Hydroquinone was replaced with resorcin (manufactured by Tokyo Kasei Co., Ltd.) and produced in the same manner as in A, except that the reaction time was 3 hours.

The residue was 376 grams. As a result of HLC analysis, the dicarboxylic acid diester represented by the formula (I) was 265 g, the dicarboxylic acid monoester represented by the formula (II) was 111 g, and the acid equivalent ratio of (I) / (II) was 75 / It was 25. <Carboxylic acid ester E> Hydroquinone was replaced with 166 g of tertiary butyl catechol (manufactured by Tokyo Kasei Co., Ltd.), and the reaction time was changed to 3 hours.

The residue was 412 grams. As a result of HLC analysis, the dicarboxylic acid diester represented by the formula (I) was 239 g, the dicarboxylic acid monoester represented by the formula (II) was 173 g, and the acid equivalent ratio of (I) / (II) was 65 / It was 35. <Carboxylic Acid Ester F> MeTHPA is added with 504 g of methylhexahydrophthalic anhydride (MeHHPA,
It was manufactured in the same manner as A except that it was replaced with RIKACID MH-700, trademark, manufactured by Shin Nippon Rika Co., Ltd.

The residue was 399 grams. As a result of HLC analysis, the dicarboxylic acid diester represented by the formula (I) was 321 g, the dicarboxylic acid monoester represented by the formula (II) was 78 g, and the acid equivalent ratio of (I) / (II) was 84 / It was 16. <Carboxylic Acid Ester G> MeTHPA was replaced with 540 g of methyl-3,6-endomethylenehexahydrophthalic anhydride (HMeNA, manufactured by Tonen Kagaku Co., Ltd.),
It was produced in the same manner as in A, except that the reaction time was 3 hours.

The residue was 407 grams. As a result of HLC analysis, the dicarboxylic acid diester represented by the formula (I) was 306 g, the dicarboxylic acid monoester represented by the formula (II) was 101 g, and the acid equivalent ratio of (I) / (II) was 79 /. It was 21. <Carboxylic Acid Esters H: Comparative Example> Reaction Temperature 130
It was produced in the same manner as in A, except that the catalyst was not used and the reaction time was 1 hour.

The residue was 318 grams. As a result of HLC analysis, the dicarboxylic acid diester represented by the formula (I) was 111 g, the dicarboxylic acid monoester represented by the formula (II) was 207 g, and the acid equivalent ratio of (I) / (II) was 40 /. It was 60. <Carboxylic Acid Esters I: Comparative Example> Produced in the same manner as in A, except that the reaction time was 5 hours.

The residue was 420 grams. As a result of HLC analysis, the dicarboxylic acid diester represented by the formula (I) was 385 g, the dicarboxylic acid monoester represented by the formula (II) was 35 g, and the acid equivalent ratio of (I) / (II) was 93 / It was 7. <Carboxylic Esters J: Comparative Example> 1 Hydroquinone
It was produced in the same manner as in A except that 04 g of neopentyl glycol (manufactured by Tokyo Kasei Co., Ltd.) was used, the reaction temperature was 130 ° C., the reaction time was 3 hours, and no catalyst was used.

The residue was 440 grams. As a result of HLC analysis, it was a single component of the dicarboxylic acid diester (R ^{2 of the} formula (I) is neopentyl, and the compound of the formula (II) does not exist). <Carboxylic Acid Esters K: Comparative Example> Hydroquinone 9
It was produced in the same manner as A except that 0 g of 1,4-butanediol (manufactured by Tokyo Kasei Co., Ltd.) was used, the reaction temperature was 130 ° C., the reaction time was 3 hours, and no catalyst was used.

The residue was 425 grams. As a result of HLC analysis, it was a single component of dicarboxylic acid diester (R ^{2 of the} formula (I) is butylene, and the compound of the formula (II) does not exist).

[0033]

Examples 1 to 10 and Comparative Examples 1 to 9 The following compounds were used in the following Examples and Comparative Examples.

Acid anhydride: -Methyltetrahydrophthalic anhydride (MeTHPA, pentahard 5000, trademark, manufactured by Tonen Kagaku KK, acid anhydride equivalent 166) -Methylhexahydrophthalic anhydride (MeHHPA, RIKACID MH-700, trademark , Manufactured by Shin Nippon Rika Co., Ltd., acid anhydride equivalent 168) ・ Dodecenyl succinic anhydride (manufactured by Sanyo Chemical Co., Ltd., acid anhydride equivalent 270) Epoxy resin: ・ Epicoat 828 (trademark, manufactured by Yuka Shell Co., Ltd., epoxy equivalent) 190) ・ Araldite CT-200 (trademark, manufactured by Ciba Geigy, epoxy equivalent 390) Curing accelerator: benzyldimethylamine (manufactured by Tokyo Kasei Co., Ltd.) To obtain a uniform mixture. This composition was cured at 100 ° C. for 2 hours and subsequently at 130 ° C. for 5 hours, and further slowly cooled to 30 ° C. over 5 hours to prepare test pieces to be tested for the following various properties. <Heat distortion temperature (HDT)> The heat distortion temperature was measured according to JIS K6911. <Charpy impact strength> In accordance with JIS K6911,
The impact strength at 23 ° C was determined. <Cracking temperature> A C-type washer having an outer diameter of 21 mm was set in an aluminum cup having a diameter of 50 mm and a depth of 20 mm, 35 g of the compound was injected, and the mixture was cured as described above, and then the aluminum cup was removed and tested. It was a piece. Using a thermal cycle tester, the test piece was kept constant at 100 ° C. for 1 hour on the high temperature side, lowered from 30 ° C. to 5 ° C. on the low temperature side, held at each temperature for 1 hour, and the crack generation temperature was measured. .

The results of these evaluations are shown in Tables 1 and 2.

[0036]

[Table 1]

[0037]

[Table 2] Examples 1 to 10 are epoxy resin 3 cured products cured using the epoxy resin curing agent of the present invention, and all had excellent heat distortion temperature, Charpy impact strength, and crack generation temperature. In Comparative Examples 1 to 4, as compared with Example 1, (I)
/ (II) acid equivalent ratio or acid anhydride / {(I) + (II)}
The acid equivalent ratio of is different. Comparative Example 1 is a case where the (I) / (II) acid equivalent ratio of the carboxylic acid ester is less than 60/40, and the Charpy impact strength is lower than that of Example 1. Comparative Example 2 is (I) / (I of carboxylic acid esters.
In the case where the acid equivalent ratio of I) exceeds 90/10, the Charpy impact strength is low and the crack initiation temperature is high as compared with Example 1. Comparative Example 3 is acid anhydride / {(I) + (I
The acid equivalent ratio of (I)} exceeds 95/5, the Charpy impact strength is low and the crack generation temperature is high as compared with Example 1. Comparative Example 4 is acid anhydride / {(I) + (I
The acid equivalent ratio of (I)} is less than 20/80, and both the heat distortion temperature and the Charpy impact strength are low as compared with Example 1. Comparative Examples 5 and 6 contain carboxylic acid diesters in which R ² of the chemical formula (I) is an aliphatic residue, and have the chemical formula (I
This is the case where the carboxylic acid ester of I) is not included. The heat distortion temperature is low compared to any of the examples. Comparative Example 7-
No. 9 is a case where only acid anhydride is contained without containing carboxylic acid esters, which is inferior to Example 1 in any one or more of heat distortion temperature, Charpy impact strength and crack generation temperature.

[0038]

According to the present invention, it is possible to provide an epoxy resin curing agent which has a high heat distortion temperature and can give an epoxy resin cured product excellent in impact resistance and crack resistance.

Claims (1)

[Claims] 1. A carboxylic acid ester represented by the following formula (I), a carboxylic acid ester represented by the following formula (II) and an acid anhydride having an acid equivalent ratio of (I) / (II) of 60. /
40 to 90/10 and acid anhydride / {(I) +
(II)} in an amount of 95/5 to 20/80 (Here, each R ¹ independently represents an aromatic residue or a saturated or unsaturated cycloaliphatic residue, and each R ² independently represents an aromatic residue).