Patent ID: 8304490

Claim:
A process for manufacturing polylactic acid having a melting point of 195° C. or higher, consisting essentially of the steps of: (1) making a crystalline polymer (A) which is composed of 90 to 100 mol % of an L-lactic acid unit and 0 to 10 mol % of a D-lactic acid unit and/or a comonomer component unit other than lactic acid and has a melting point of 140 to 180° C. and a weight average molecular weight of 100,000 to 500,000 and a crystalline polymer (B-1) which is composed of 90 to 99 mol % of a D-lactic acid unit and 1 to 10 mol % of an L-lactic acid unit and/or a comonomer component unit other than lactic acid and has a melting point of 140 to 170° C. and a weight average molecular weight of 100,000 to 500,000 coexistent in an (A)/(B-1) weight ratio of 10/90 to 90/10, and heating once at 245 to 300° C., thereby obtaining the polylactic acid having a melting point of 195° C. or higher; or (2) making a crystalline polymer (B) which is composed of 90 to 100 mol % of a D-lactic acid unit and 0 to 10 mol % of an L-lactic acid unit and/or a comonomer component unit other than lactic acid and has a melting point of 140 to 180° C. and a weight average molecular weight of 100,000 to 500,000 and a crystalline polymer (A-1) which is composed of 90 to 99 mol % of an L-lactic acid unit and 1 to 10 mol % of a D-lactic acid unit and/or a comonomer component unit other than lactic acid and has a melting point of 140 to 170° C. and a weight average molecular weight of 100,000 to 500,000 coexistent in an (A-1)/(B) weight ratio of 10/90 to 90/10, and heating once at 245 to 300° C., thereby obtaining the polylactic acid having a melting point of 195° C. or higher.