METHOD FOR PRODUCING POLYLACTIC ACID

PROBLEM TO BE SOLVED: To provide a method for producing a polylactic acid having a high melting point and a low crystallization point. SOLUTION: The method for producing a polylactic acid comprises making (A) a polymer A which is mainly composed of an L-lactic acid unit and has a weight-average molecular weight of 50,000-500,000 and a melting point of 140-180°C and (B) a polymer B which is mainly composed of a D-lactic acid unit and has a weight-average molecular weight of 50,000-500,000 and a melting point of 140-180°C coexist in the weight ratio of (A/B) of 10/90-90/10 and heat-treating them at 240-300°C. At least one of the polymer A and the polymer B is obtained by subjecting a lactide to ring-opening polymerization in the presence of a branching initiator and a metal catalyst. COPYRIGHT: (C)2008,JPO&INPIT