Solvent scrubbing recovery of lactide and other dimeric cyclic esters

Claim 1

In the gas-assisted process for depolymerizing an oligomeric poly(hydroxycarboxylic acid) to a dimeric cyclic ester of the formula (I): ##STR2## wherein each R group is independently H or a C 1 -C 6 hydrocarbyl, which process comprises: (a) heating the corresponding oligomer in a reaction zone at a suitable temperature and pressure and for a time effective to generate the cyclic ester; (b) passing a stream comprising an inert gas through the oligomeric material at a rate and in an amount sufficient to sweep the cyclic ester and any water present from the reaction zone and to form a gas stream containing the cyclic ester and any water entrained therewith; and (c) scrubbing the gas stream with a solvent to remove the cyclic esters therefrom, the improvement comprising: (i) the solvent is nonpolar and water-immiscible, (ii) scrubbing step (c) is conducted at a first temperature which is below said suitable temperature of step (a) and at which the solvent is liquid, the cyclic ester is removed from the gas stream to form a phase comprising the cyclic ester and solvent, and is such that any water removed from the gas stream forms an aqueous phase separate from the solvent and cyclic ester phase, and (iii) the phase containing the solvent and cyclic ester is recovered.