In a method for producing a cyclic ester according to an embodiment of the present invention, a mixture (I) containing an aliphatic polyester, a specific polyalkylene glycol diether, and a sulfonic acid compound as a thermal stabilizer is prepared and heated in predetermined conditions to obtain a mixture (II) in a state of solution. Furthermore, heating of the mixture (II) is continued to distill, together with the polyalkylene glycol diether, a cyclic ester formed by the depolymerization reaction, and thus a distillate (III) is obtained. The cyclic ester is recovered from the distillate (III). At this time, a specific solubilizing agent is added to at least one of the mixture (I) or (II). In this production method, the sulfonic acid compound as the thermal stabilizer is contained in the mixtures (I) and (II) and the distillate (III).
根据本发明的一个实施例,在生产环酯的方法中,制备含有脂肪族聚酯、特定的聚 烃二醇
二醚和作为热稳定剂的
磺酸化合物的混合物(I),并在预定条件下加热,得到溶液状 态的混合物(II)。此外,继续加热混合物 (II),与聚烷基二醇
二醚一起蒸馏由解聚反应形成的环酯,从而得到蒸馏物 (III)。从馏分(III)中回收环酯。此时,在混合物(I)或(II)中的至少一种中加入特定的
增溶剂。在这种生产方法中,作为热稳定剂的
磺酸化合物包含在混合物(I)和(II)以及蒸馏物(III)中。