Patent ID: 7214414

Claim:
A biodegradable thermoplastic composition formed by extruding a thermoplastic melt using an extruder, comprising: a synthetic thermoplastic biodegradable polymer portion comprising at least one polymer selected from the group consisting of polyethylene terephthalates modified by replacing a portion of terephthalate groups with aliphatic diacid ester groups, aliphatic-aromatic copolyesters formed from at least one aromatic diacid, at least one aliphatic diacid, and at least one aliphatic diol, polylactic acid, polyhydroxybutyrate, polyhydroxybutyrate-hydroxyvalerate copolymers, aliphatic polyesters including units formed from a lactide, aliphatic polyesters including units formed from a hydroxyacid having at least 5 carbon atoms, a polyester including units formed from succinic acid and an aliphatic diol, and terpolymers including units formed from each of glycolide, lactide and ε-caprolactone; and thermoplastic starch that is substantially free of high boiling liquid plasticizers selected from the group consisting of glycerin, propylene glycol and sorbitol and that is initially melted by heating and mixing the starch in the presence of water in an amount of at least the natural water content of native starch granules within an extruder so as to form a thermoplastic starch melt consisting of starch and at least the natural water content of native starch granules and then subsequently dried by venting after the starch is blended with the synthetic thermoplastic biodegradable polymer within the extruder, wherein the biodegradable composition is suitable for formation into at least one of sheets or films.