Lactide Production from Polymer Waste

The method of thermal depolymerization of polylactide wastes and products from it has been studied. At a temperature of 200-250 °C and a pressure of 5-10 mbar the maximum yield of crude lactide and pure lactide is 40 and 5.5 % by weight accordingly. The addition of catalysts (Zn, ZnO, SnO, C 16 H 30 O 4 Sn, Sb 2 O 3 ) in an amount from 0.5 to 2.0 % by weight make it possible to intensify the process and increase the monomer yield by 3-10 times. The maximum amount of lactide (~60 wt %) is achieved by using of tin octoate (1.5 % wt) as the catalyst. The findings product is a mixture that consist of D-, L-lactide (~80 wt %) and m-lactide (~4 wt %) isomers, lactic acid (~2 wt %), oligomer of lactic acid (~14 wt %), water (<1 wt %), and has a melting point 92-96 °C.