GB673214A - Improvements in or relating to insulated electrical coils - Google Patents

Abstract

Electrical coils are impregnated with fluid polymerizable compositions which are then polymerized to solids by heating. Suitable compositions comprise (a) styrene, the reaction product made by heating at 240 DEG C. one mol. of maleic anhydride, one mol. of adipic acid and 2 mols. of propylene glycol and adding 2 mols. of n-butanol until the product has an acid number of 5, and t.-butyl hydroperoxide as catalyst; (b) styrene, the reaction product made by heating at 150 DEG C. tall oil and glycerol, adding maleic anhydride, heating to an acid number of 5, and benzoyl peroxide as catalyst. Alternatively a single polymerizable compound such as diallyl phthalate, diallyl succinate, diallyl maleate, diallyl adipate, allyl alcohol, methallyl acrylate, diallyl ether, allyl acrylate, allyl crotonate or a partially condensed organisiloxane may be used. There may also be employed unsaturated alkyd resins produced from maleic acid, fumaric acid, maleic anhydride, monochloromaleic acid, itaconic acid, itaconic anhydride, citraconic acid or citraconic anhydride, and glycol, glycerol, pentaerythritol or epoxides. Part of the unsaturated acid may be replaced by saturated acids such as succinic, adipic, sebacic and phthalic acids. Castor oil maleate ester may be used. The alkyd resins may be dissolved in styrene, alpha methyl styrene, 2,4-dichlorostyrene, paramethyl styrene, vinyl acetate, methyl methacrylate, ethyl acrylate, diallyl phthalate, diallyl succinate, diallyl maleate, allyl alcohol, methallyl alcohol, acrylonitrile, methyl vinyl ketone, diallyl ether, vinylidene chloride, butyl methacrylate, allyl acylate, allyl crotomate, 1,3-chloroprene and divinyl benzene. Other specified catalysts are tert.-butyl perbenzoate, tert.-butyl hydro-peroxide, di-t.-butyl diperphthalate, 1-hydroxy-cyclohexyl hydroperoxide-1 and ascaridol. Polymerization may be effected in compressible moulds of rubber, polychloroprene or silicone rubber.