GB868432A - Improvements in and relating to polyepoxide compositions - Google Patents

Abstract

A heat curable composition comprises 4vinylcyclohexene dioxide and a polycarboxylic acid anhydride in amount such that 0,1 to 0,8 carboxyl equivalent of the anhydride is present per epoxide equivalent of the dioxide. Suitable polycarboxylic anhydrides can be represented by the formula: <FORM:0868432/IV (a)/1> wherein X represents two or more carbon atoms interconnected by single or double bonds to which there can be attached alkyl, hydrogen, hydroxyl, chloro, iodo, bromo or cyclic groups; carbon atoms interconnected by oxydicarbonyl groups; or cyclic or phenylene groups to which one or more oxidicarbonyl groups can be attached, a number are listed. Mixtures of anhydrides, polymeric anhydrides or mixed polymeric anhydrides of sebacic, adipic, pimelic, cyclohexane-1, 4-dicarboxylic, terephthalic and isophthalic acids can also be used. Catalysts which may be added to promote curing are mineral acids, sulphonic acids, metal halide Lewis acids, alkali metal hydroxides and amines. Mixture with the curable composition can be effected in an organic solvent. There may also be employed active hardeners, which are organic compounds containing two or more groups reactive with epoxy groups. Specified hardeners are polycarboxylic acids, polyesters containing free carboxyl groups, (preferably prepared from di-, tri- or tetra-hydric aliphatic or oxa-aliphatic alcohols), and polyols. A number of specific catalysts and hardeners are listed. The invention also includes solutions of the curable and partially cured compositions in, for example, xylene, methyl isobutyl ketone, butyl acetate, ethyl acetate, toluene and amyl acetate, which, alone or with the addition of wetting or thixotropic agents, can be used as coating compositions. In Examples (1) 0,05% by weight of dimethylbenzylamine is added to a mixture of 4-vinylcyclohexene dioxide, maleic anhydride and glycerol containing 0,67 carboxyl equivalent of anhydride and 0,33 hydroxyl equivalent of polyhydric alcohol per epoxy equivalent of diepoxide. After gelling, the product is postcured by heating; (28) 4-vinylcyclohexene dioxide (0,1 carboxy equivalent) and chlorendic anhydride (1,0 epoxy equivalent) are stirred together at 26 DEG C. and the mixture is then gelled and cured by heating; (51) 4-vinylcyclohexene dioxide and polyadipic anhydride, in amounts providing 0,5 carboxyl equivalent of anhydride per 1,0 epoxide group of diepoxide were heated at 160 degrees to give a viscous polymer. A solution of this in methyl isobutyl ketone is used as a coating composition. The polyadipic anhydride is obtained by refluxing a mixture of adipic acid and acetic anhydride with continuous removal of acetic acid at the still head, followed by recovery of the polyanhydride by distillation of excess acetic anhydride.