JPS6248684B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an epoxy resin composition, and more particularly to an epoxy resin composition for electrical insulation that has good adhesion to metals and crack resistance in a cured state. Epoxy resin has excellent insulation and mechanical properties, and is widely used as a material for various electrical insulations. It is widely used as a material for casting resins because it has particularly excellent adhesive properties, fluid hardening properties, and heat resistance. However, since epoxy resin is generally a brittle material, it contains various parts such as aluminum electrodes, hermetic seal terminals, ceramic capacitors, various plastics, etc.
When a coil or the like is embedded, cracks or peeling may occur due to curing shrinkage or stress caused by the difference in thermal expansion coefficient between the component and the epoxy resin, and internal components may be damaged. Furthermore, adhesion to metals is generally weak, and metals embedded as internal parts require complex processes such as sandblasting, acid treatment, or primer treatment. For example, methyl-tetrahydrophthalic anhydride (HN-2200,
When using a general acid anhydride-based epoxy cured product containing Hitachi Chemical Co., Ltd. (trade name) with an adhesive layer of 10 mm and butt jointing aluminum with mechanically polished surfaces, the tensile adhesive strength is 0.05 Kg/mm ² , and the oriphant The legal crack resistance index was 0. Conventional techniques for improving these drawbacks include adding a flexibility imparting agent and using a flexibility curing agent, but a satisfactory solution has not yet been reached. Namely, bisphenol A diglycidyl ether (Epicote #828), urethane modified epoxy resin (EPU-6, trade name of Asahi Denka Co., Ltd.), and methyl-tetrahydrophthalic anhydride (HN-
2200), the adhesive strength was 0.12 Kg/mm ² and the orifant method crack resistance index was 1.5. Also, bisphenol A diglycidyl ether (Epicote #828), dimer acid diglycidyl ester (Epicote #871,
methyl-hexahydrophthalic anhydride (MH-700, trade name of Shin Nippon Rika Co., Ltd.) and carboxyl-terminated butadiene-acrylonitrile copolymer (CTBN-1300, trade name of Ube Industries, Ltd.). The adhesive strength of the cured epoxy resin was 0.36 Kg/mm ² and the crack resistance index was 12. Although the crack resistance index is improved in this way, the adhesive strength is not significantly improved. Further, addition of such a flexibility imparting agent lowers the heat distortion temperature, and addition of a large amount poses a risk of impairing the inherent properties of the epoxy resin. An object of the present invention is to provide an epoxy resin composition which has excellent adhesive strength and crack resistance, which could not be obtained by conventional methods, and which does not impair the inherent properties of the epoxy resin. The epoxy resin composition of the present invention will be explained in detail below. The epoxy resin used in the present invention refers to all uncured resins widely known as epoxy resins,
Examples include epoxy resins obtained from bisphenol A diglycidyl ether and its dimers, trimers, and novolak type phenolic resins and epichlorohydrin, and epoxy resins obtained from polyhydric alcohols, polyalkylene oxides, and epichlorohydrin. , epoxy resins containing cyclohexene oxide groups, etc. The dimer acid to be reacted with the epoxy resin is produced by heating and polymerizing two molecules of unsaturated fatty acids, and one containing some trimer acid as a by-product can also be used. The reason why the conditions for the esterification reaction between the epoxy resin and the dimer acid were limited to 120 to 180°C and 2 to 6 hours is as follows. If the conditions are below this range, the esterification reaction will be insufficient, and if the conditions are above this range, the composition will become highly viscous due to the initiation of intermolecular reactions, making it unusable for practical use. As the polybutadiene with a carboxyl group at the end used in the present invention, C-1000 is a commercially available product.
(Nippon Soda Co., Ltd. product name) and CTBN-1300 (Ube Industries Co., Ltd. product name). This polybutadiene having a carboxyl group at its terminal is used in an amount of 5 to 20 parts by weight per 100 parts by weight of the above-mentioned modified epoxy resin. Examples of the acid anhydride curing agent of the present invention include phthalic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methyl-hexahydrophthalic anhydride, methyl-tetrahydrophthalic anhydride, methyl-nadic anhydride, dodecenyl succinic anhydride, Examples include pyromellitic anhydride. The amount of acid anhydride used is 0.75 to 0.95 per equivalent of modified epoxy resin.
Equivalent amounts are preferred. The curing accelerator used in the present invention includes 2-
Ethyl-4-methyl-imidazole, 1-benzyl-2-methyl-imidazole, 2,4,6-tris(dimethylaminomethyl)phenol, benzyldimethylamine, tetradecyldimethylbenzylammonium chloride, etc., and one of these Or a mixture of two or more types is used. The amount used is per 100 parts by weight of modified epoxy resin.
0.1 to 1.5 parts by weight is preferred. The epoxy resin composition of the present invention can be used as it is, but in order to further improve workability, it is also possible to add a compound containing one epoxy group in the molecule used as an epoxy resin diluent. Furthermore, inorganic fillers such as silica, alumina, talc, and calcium carbonate may be appropriately added and blended to adjust the coefficient of thermal expansion. Next, examples of the present invention will be described. The parts used herein are parts by weight. Example 1 and Comparative Example 1 100 parts of bisphenol A diglycidyl ether (Epicote #828) and dimer acid (Versadime)
216, Daiichi General Co., Ltd. product name) 100 copies at 140℃, 4
100 parts of time-esterified modified epoxy resin;
An epoxy resin composition containing 5 parts of carboxyl-terminated butadiene-acrylonitrile copolymer (CTBN-1300), 33 parts of methyl-tetrahydrophthalic anhydride (HN-2200) and 0.5 parts of 2-ethyl-4-methyl-imidazole was prepared. Example 1 was cured at 70°C for 8 hours and at 100°C for 5 hours.
And so. Comparative Example 1 had the same composition as Example 1, but used the epoxy resin and dimer acid as they were mixed instead of reacting with each other. Table 1 shows a comparison of their characteristics.

【table】

[Table] The adhesive strength is measured by mechanically polishing the adhesive surface (▽▽▽)
The tensile strength of a test piece made by butt-jointing a round aluminum bar with an adhesive layer of 10 mm was measured, and the crack resistance was determined by the orifant method. In Comparative Example 1, the dimer acid formed a separated layer and a uniform cured product could not be obtained, but in Example 1, a completely uniform cured product was obtained. In addition, the adhesive strength and crack resistance of Example 1 were twice as high as those of Comparative Example 1. Examples 2-5 3,4-epoxycyclohexylmethyl-3'.
A modified epoxy resin obtained by esterifying 100 parts of 4′-epoxycyclohexane carboxylate (CX-221, trade name of Chitsuso Corporation) and 60, 80, 100, and 120 parts of dimer acid (Versadime 216) at 120°C for 6 hours, and a terminal Cured by curing an epoxy resin composition containing carboxyl group butadiene-acrylonitrile copolymer (CTBN-1300), hexahydrophthalic anhydride (Rikashido HH, trade name of Shin Nippon Rika Co., Ltd.) and benzyldimethylamine at 100°C for 7 hours. Examples 2 to 5 are shown in Table 2.

[Table] The maximum adhesive strength was obtained in Example 4, and the maximum crack resistance was obtained in Example 3. Examples 6 to 10 Bisphenol F diglycidyl ether (Epomic R-114, Mitsui Oil Epoxy Co., Ltd. trade name) 100
80 parts of dimer acid (Empol 1022, trade name of Emery Co., Ltd.) was added to the mixture, and the mixture was heated at 130°C for 2 hours at 130°C.
4 hours, 130℃ x 6 hours, 150℃ x 4 hours, 170℃
100 parts of a modified epoxy resin that was subjected to an esterification reaction for 4 hours, 5 parts of carboxyl-terminated polybutadiene (C-1000), 40 parts of methyl-hexahydrophthalic anhydride (MH-700), and tetradecyldimethylbenzylammonium An epoxy resin composition containing 1.2 parts of chloride (M ₂ -100, trade name of Nissan Chemical Industries, Ltd.) was heated at 80℃ x 10 hours + 100℃ x 2
Examples 6 to 10 are the cured products cured over time, and the third
Shown in the table.

[Table] Comparative Examples 2 to 5 The properties of Comparative Examples 2 to 5 obtained using the compositions and curing conditions shown in Table 4 are shown.

[Table] As is clear from the above comparative examples, the epoxy resin composition according to the present invention provides a high degree of adhesive strength and crack resistance that could not be obtained with conventional flexibility imparting agents. Furthermore, it is clear that the composition of the present invention shows less decrease in heat resistance than a composition in which a conventional flexibility-imparting agent is simply added, and that the original properties of the epoxy resin are maintained.

Claims (1)

[Scope of Claims] 1 (a) 60 to 120 parts by weight of dimer acid is added to 100 parts by weight of epoxy resin, and 2 to 6 parts by weight are added at 120 to 180°C.
An epoxy resin composition comprising one or more of the following: a modified epoxy resin subjected to a time esterification reaction, (b) polybutadiene having a carboxyl group at the end, (c) an acid anhydride curing agent, and (d) a curing accelerator.