METHOD FOR MANUFACTURING LACTIC ACID-GLYCOLIC ACID COPOLYMER AND METHOD FOR MANUFACTURING SALT THEREOF

摘要

An object of the invention is to produce a purified lactic acid-glycolic acid copolymer, preferably in the form of powder, having a reduced content of dimers such as residual lactide and glycolide by a simple industrial process without the use of any high-shear special device. Another object of the invention is to realize industrial simple production of a high-purity lactic acid-glycolic acid copolymer which has small amounts of dimers such as residual lactide and glycolide and small amounts of a low-molecular weight lactic acid-glycolic acid copolymer or a salt thereof and which has a small ratio of weight average molecular weight to number average molecular weight (Mw/Mn). In the invention, a purified lactic acid-glycolic acid copolymer (A2) or a salt thereof is produced by a process including the steps of (1-1) dissolving a lactic acid-glycolic acid copolymer (A1) containing lactic acid units and glycolic acid units or a salt thereof into at least one organic solvent (B1) having a solubility at 25°C of not less than 1 wt% to prepare a solution of the lactic acid-glycolic acid copolymer (A1) or the salt thereof; (1-2) adding at least one solvent (S1) selected from water and aliphatic alcohols (B2) to the solution of the lactic acid-glycolic acid copolymer (A1) or the salt thereof to prepare a mixture liquid including the lactic acid-glycolic acid copolymer (A1) or the salt thereof; (2) adding the mixture liquid prepared in the step (1-2) to a solvent (S2') including at least one selected from water and aliphatic alcohols (B2) to precipitate a purified lactic acid-glycolic acid (A2) or a salt thereof; and (3) recovering the precipitate of the purified lactic acid-glycolic acid copolymer (A2) or the salt thereof.