the invention provides biodegradable vinyl ester copolymers of one or more monomers selected from the group of vinyl esters of unbranched or branched alkylcarboxylic acids having from 1 to 18 carbon atoms , which contain from 0 . 1 to 40 % by weight , based on the total weight of the copolymer , of one or more cyclic ketene acetals selected from the group consisting of 2 - methylene - 1 , 3 - dioxepane , 2 - methylene - 1 , 3 - dioxolane , 2 - methylene - 1 , 3 - dioxane and have a molecular weight & gt ; 50 , 000 .