[CH2:1]1[O:8]C(=O)C[O:4][C:2]1=[O:3].[CH3:9][C@@H:10]1[O:17]C(=O)[C@H](C)[O:13][C:11]1=[O:12].CCCCC(C([O-])=O)CC.CCCCC(C([O-])=O)CC.[Sn+2].C(O)CCCCCCCCCCC>C1(C)C=CC=CC=1>[C:2]([OH:4])(=[O:3])[CH2:1][OH:8].[C:11]([OH:13])(=[O:12])[CH:10]([CH3:9])[OH:17]1161 g (10 mols) of glycolide and 1441 g (10 mols) of L-lactide were placed in a glass reactor, and 10 ml of a toluene solution containing 0.26 g of stannous octoate and 9.0 g of lauryl alcohol were added to the reactor. Afterward, deaeration was carried out for 2 hours under reduced pressure, and the atmosphere in the reactor was then replaced with a nitrogen gas. This mixture was heated at 220° C. for 2 hours with stirring under the nitrogen atmosphere. While the temperature was maintained as it was, the deaeration was slowly preformed by means of a vacuum pump through an exhaust pipe to reduce the pressure in the reactor to 3 mm Hg. One hour after the start of the deaeration, the monomers and low-molecular substances were not extracted any more, and the interior of the reactor was replaced with nitrogen and a resultant glycolic acid-lactic acid copolymer (hereinafter referred to as "PLGA") was then taken out.
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