Abstract: The invention concerns a novel melt-processible poly(ester urethane) and a process and a prepolymer for the preparation thereof. The poly(ester urethane) contains structural units derived from a polyester and structural units derived from a diisocyanate and, according to the invention, the bonds between the structural units are at least mainly comprised of urethane bonds, the number average molar mass, M.sub.n, of the prepolymer is at least 10,000 g/mol, its mass-average molar mass, M.sub.w, is over 20,000 g/mol and its molar mass distribution, expressed as the ratio of M.sub.w /M.sub.n, is over 2, and the prepolymer is essentially free from free isocyanate groups. The poly(ester urethane) is hydrolytically decomposable and it can be used as a biodegradable polymer, e.g., for manufacturing injection molded pieces and thermoformed and blow molded packages, bags, sacks and bottles, for coating of sacks, bags and films made of paper or cardboard, and for manufacturing fibers and non-woven fabrics.

Abstract: The invention relates to a process for thermoplasticizing starch, a melt-processible polymer composition, which contains a starch-based component and a thermoplastisized polymer component, and a method for preparating such a composition. According to the invention the starch component, which contains hydroxyl groups capable of reacting with isocyanate groups, is modified so that it can be dissolved or gelatinized/plastisized in the melt of a hydroxy acid polymer. The starch component is then reacted with a thermoplastic component formed by a hydroxy acid polymer, in particular a lactic acid polymer, in order to produce a melt-processible, biologically degradable starch-based polymer, which can be used as an adhesive and for coating of paper and cardboard products and for preparation of injection moulded and thermoformed articles.