Patent ID: 7235673

Claim:
A glycolide production process including a step of depolymerization by heating of a glycolic acid oligomer, wherein: a depolymerization reaction is carried out through the following steps (i) to (iv): step (i) of heating a depolymerization reaction system comprising a glycolic acid oligomer plus a polar organic solvent to depolymerize the glycolic acid oligomer into glycolide in a reaction vessel, step (ii) of distilling the glycolide formed by de-polymerization and the polar organic solvent out of the depolymerization reaction system, step (iii) of recovering the glycolide from distillates obtained by distillation, and step (iv) of charging the glycolic acid oligomer and the polar organic solvent in fresh amounts that make up for the amount of distillates, continuously or intermittently into the depolymerization reaction system comprising the glycolic acid oligomer and the polar organic solvent remaining in the reaction vessel, in which: (v) during the depolymerization reaction, in order to reduce a decrease in the formation rate of glycolide, a compound (A) having an alcoholic hydroxyl group is permitted to exist in the de-polymerization reaction system, provided that the amount of the compound (A) in the depolymenzation reaction system is controlled such that the alcoholic hydroxyl group amount of said compound (A) is kept at 0.5 equivalent or greater with respect to the total carboxyl group amount of an organic acid (B) comprising diglycolic acid, methoxy acetic acid and oxalic acid formed upon hydrolysis of the depolymerization reaction system under alkaline conditions, wherein the amount of compound (A) in the depolymerization reaction system is controlled at said amount of 0.5 equivalent or greater by a) adding the compound (A) into the reaction vessel in the step (i), and then adding the compound (A) continuously or intermittently into the depolymerization reaction system in the step iv) before the total carboxyl group amount of the organic acid (B) in the depolymerization reaction system reaches the said equivalent or greater with respect to the alcoholic hydroxyl group amount of the originally added compound (A); or b) using as the glycolic acid oligomer a alycolic acid oligomer obtained by condensation of glycolic acid in the presence of the compound (A); and wherein the depolymerization reaction is carried out continuously or repeatedly in said depolymerization reaction system.