Patent ID: 6916939

Claim:
A process for production of a cyclic ester by depolymerization of an aliphatic polyester, which comprises the steps of: (I) heating a mixture containing the aliphatic polyester (A) and a polyalkylene glycol ether (B), which is represented by the following formula (1) where R 1 is a methylene group, or a straight-chain or branched-chain alkylene group with 2-8 carbons, X 1 is a hydrocarbon group, Y is an alkyl or aryl group with 2-20 carbons, p is an integer not smaller than 1 and when p is 2 or greater, a plurality of R 1 groups may be identical or different, and has a boiling point of 230-450° C. and a molecular weight of 150-450, under normal or reduced pressure to a temperature at which depolymerization of said aliphatic polyester (A) takes place, (II) forming a substantially homogeneous solution phase consisting of the melt phase of said aliphatic polyester (A) and the liquid phase of said polyalkylene glycol ether (B), (III) continuing to heat said solution phase to form the cyclic ester by depolymerization and distil out the cyclic ester together with said polyalkylene glycol ether (B), and (IV) recovering the cyclic ester from the distillate, wherein said polyalkylene glycol ether (B) is a polyalkylene glycol ether in which the cyclic ester is soluble in the range of 0.1-10% at 25° C.