| 摘要 |
A method of purifying a cyclic ester, comprising: mixing a co-distillated liquid comprising a cyclic ester produced by heating depolymerization of a hydroxycarboxylic acid oligomer in the presence of a depolymerization solvent and the depolymerization solvent with an organic solvent for washing which is mutually soluble with the depolymerization solvent and has a lower boiling point than the cyclic ester; subjecting the resultant mixture liquid to liquid-liquid separation into an organic solvent phase containing the depolymerization solvent and a cyclic ester phase containing the organic solvent; and then evaporating the organic solvent from the cyclic ester phase containing the organic solvent to recover the cyclic ester containing a reduced amount of the depolymerization solvent. As a result, purified cyclic ester is recovered at high heat efficiency, purification efficiency and operation efficiency, from the co-distillate liquid containing the depolymerization solvent and the cyclic ester from the depolymerization system for thermal decomposition of the hydroxycarboxylic acid oligomer in the presence of the depolymerization solvent.
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