these are the copolymers of vinylchloride, with vinylidene chloride, vinyl-esters of carboxylic acids (e.g., vinyl acetate, vinyl propionate, vinyl butyrate, and the like); esters of unsaturated acids (e.g., alkyl acrylates such as methyl acrylate and the like) and the correspondingesters of methacrylic acid and the like.