Patent ID: 8053584

Claim:
A process for the purification of lactide from a crude lactide vapour product stream comprising at least said lactide, lactic acid, water and linear lactic acid oligomers, said crude lactide vapour product stream being produced by depolymerisation of low molecular weight polylactic acid in a reactor, which process comprises the steps of: (a) feeding said vapour product stream to a rectification column having a feed inlet at the lower end of the column and an overhead vapour outlet at the upper end of the column, through the said feed inlet, said column being mounted onto the reactor such that components from the vapour product stream liquefying within the column are allowed to flow back into the reactor; (b) establishing at the upper end of the column a first overhead vapour fraction consisting essentially of water, lactic acid and lactide, and at the lower end of the column a high-boiling fraction consisting essentially of lactide and higher-boiling linear lactic acid oligomers; (c) condensing from said first overhead vapour fraction by means of a condenser at least the lactide to obtain a first liquid lactide containing condensate fraction; (d) removing the first liquid lactide containing condensate fraction.