Abstract: A resin composition comprising (a) an unsaturated polyester, (b) a vinyl monomer, (c) a thermoplastic resin, (d) a curing agent and (e) a hollow filler with a number average particle diameter of not more than 20 .mu., wherein (e) occurs in a proportion of 10 to 150 parts by weight to 100 parts by weight of (a), (b) and (c) combined, and the molding compounds obtainable by impregnating glass fiber with the said resin composition are very useful in that, because of their lower specific gravity, they provide lightweight products with excellent surface quality which are great use as automotive exterior body panels and other parts.

Abstract: Curable unsaturated polyester resin compositions from which molded products with superior surface smoothness can be obtained include a block copolymer of a specified form, an unsaturated polyester, a vinyl monomer, a filler, a curing catalyst and a reinforcing fiber. The block copolymer is of the form A--(B).sub.n where A is non-hydrogenated polyisoprene block having viscosity average molecular weight of 10000 or more, B is saturated polyester block obtainable by condensation of organic dicarboxylic anhydride and 1,2-epoxide, more than 50 mol % of terminal groups of the polyester block being carboxylic acid group, A and B are connected by ester linkage and n is not less than 2. Block copolymers of this type can be formed by starting with carboxylic acid or hydroxyl group in polyisoprene and by alternate condensation of organic dicarboxylic anhydride and 1,2-epoxide.

Abstract: A quickly curable unsaturated polyester composition with high surface quality contains an unsaturated polyester, a vinyl monomer, either an alkane polyol polyacrylate or an alkane polyol polymethylacrylate, a thermoplastic resin, and one or more curing catalysts selected from t-butylperoxy benzoate, t-butylperoxy octoate and 2,5-dimethyl-2,5-di(benzoilperoxy) hexane. Molding compounds are obtained by impregnating glass fibers with such composition and molded products obtained by curing such molding material have improved surface smoothness.

Abstract: Unsaturated polyester compositions which are quickly curable and from which molded products with superior surface quality can be obtained are characterized as being composed of an unsaturated polyester, an olefinic unsaturated monomer, an aromatic vinyl-conjugated diene block copolymer or a hydrogenated aromatic vinyl-conjugated diene block copolymer, a mixture of t-butylperoxy benzoate, t-butylperoxy octoate and 1,1-bis(t-butylperoxy) 3,3,5-trimethyl cyclohexane, and at least one selected from organic compounds of cobalt, copper and manganese.