Abstract: The invention covers a process to manufacture biodegradable starch esters which can be processed into extrudates, formed parts and sheeting. The starch is activated with a carboxylic acid/carboxylic anhydride mixture through partial swelling and the onsetting esterification reaction at simultaneous conversion of the water entrained in the starch and partially esterified with a carboxylic anhydride up to the desired degree of substitution with progressing swelling and disintegration.

Abstract: Biodegradable thermoplastic materials made of blends of starch esters and polyalkylene glycols with additions of polybasic aliphatic carboxylic acids and oxycarboxylic acids are improved with respect to water stability and mechanical characteristics and barrier properties by admixing to the blends aliphatic polycarbonates at levels of from 5:95 to 95:5 with the optional addition of ecologically compatible plasticizers and fillers.These materials can be used for all goods which are to be packaged in films, in particular tobacco products, but also soap, paper tissues, toilet articles, and the like. In addition to biodegradability, said materials are characterized in that they may be fed to a special recycling process, but also to conventional recycling processes without adversely affecting them.