Method for producing aliphatic polyester, aliphatic polyester resin, and aliphatic polyester resin composition
An object of the present disclosure is to provide a method for producing an aliphatic polyester resin which substantially does not contain impurities, such as metals, and which has high molecular weight, particularly a polylactic acid having high molecular weight and high optical purity. The method for producing an aliphatic polyester resin of the present disclosure has a step of contacting a solution containing a cyclic ester with a cyclic amine catalyst and a polymerization initiator to initiate a reaction, a step of conducting the reaction by flow-type polymerization, and a step of subjecting the product obtained in the flow-type polymerization to further reaction by postpolymerization by stirring.
1 . A method for producing an aliphatic polyester, comprising a step of contacting a solution containing a cyclic ester with a cyclic amine catalyst and a polymerization initiator and lowering the temperature from room temperature to initiate a reaction, a step of conducting the reaction by flow-type polymerization, and a step of subjecting the product obtained in the flow-type polymerization to further reaction by postpolymerization by stirring,
wherein the product obtained in the flow-type polymerization has a polymer conversion of 45 to 90%.
2 . The method according to claim 1 , wherein the reaction temperature for the flow-type polymerization is 5° C. or lower, and the reaction temperature for the postpolymerization is 5° C. or lower.
3 . The method according to claim 1 , wherein the postpolymerization by stirring is batch polymerization.
4 . The method according to claim 1 , wherein the cyclic ester is L-lactide or D-lactide.
5 . The method according to claim 2 , wherein the postpolymerization by stirring is batch polymerization.