Patent ID: 8614338

Claim:
Method for chemical stereospecific recycling of a mixture of polymers containing polylactic acid (PLA), the method comprises the steps of: a. combining the mixture of polymers and a lactic acid alkyl ester into a solution, wherein the lactic acid alkyl ester is capable of dissolving in the PLA fraction; b. depolymerizing the dissolved PLA fraction of step (a) by catalytic transesterification of said fraction at a temperature comprised between 80 and 180° C. and at a pressure comprised between a negative pressure or a pressure lying between atmospheric pressure and 10 bar; c. controlling the catalytic transesterification reaction by GPC to measure the molecular weight of the oligoesters formed during step (b); d. stopping the catalytic transesterification reaction when the molecular weight measured in step (c) of the oligoesters reaches a value comprised between about 400 and about 5000 amu; e. separating the residual lactic acid alkyl ester from the oligoester mixture; f. subjecting the oligoester mixture obtained in step (b) to a catalytic and thermal cyclisation step to form a vapor phase rich in lactide and a liquid phase rich in oligoester; and g. subjecting the raw lactide of step (f) to a stereospecific purification to recover a purified lactide fraction, the meso-lactide fraction of which is comprised between about 0.1% wt and 40% wt.