Patent ID: 7317069

Claim:
An aliphatic polyester which comprises an aliphatic diol unit, an aliphatic dicarboxylic acid unit and a unit of an organic acid having a pKa value of 3.7 or below at 25° C., wherein a content of a carbonate bond contained in the polyester is less than 1 mol %, a content of a urethane bond is less than 0.06 mol %, a content of an aliphatic monooxymonocarboxylic acid unit is less than 0.02 mol %, a content of the phosphorus atom derived from a phosphorus compound selected from among an organic phosphinic acid, an organic phosphonic acid, and a hydrogen phosphate salt is less than 10 −9 mol %, based on the whole monomer units constituting the polyester, and a reduced viscosity (ηsp/C) is 1.6 or more, wherein the content of the unit of the organic acid having a pKa value of 3.7 or below at 25° C. is from 0.0001 to 0.4 mol %, based on the aliphatic dicarboxylic acid unit.