Abstract: The present invention provides a method and apparatus for producing polylactic acid by depolymerizing lactic acid oligomers and subjecting the obtained lactide to ring-opening polymerization, through which lactide can be efficiently obtained. The present invention relates to a lactide production apparatus for continuously or intermittently producing lactide, comprising: a depolymerization device 11 for subjecting lactic acid oligomers to a depolymerization reaction; a catalyst regeneration device 27 for subjecting a residue in the depolymerization device to a depolymerization reaction in order to reduce the molecular weights of lactic acid oligomers contained in the residue; and a distillation column 29 for condensing lactide generated in a gas form as a result of the depolymerization reaction.

Abstract: The present invention is envisaged to provide an apparatus and a process for synthesizing lactide, according to which the water content in the produced lactide can be reduced. In operation of the system, lactic acid oligomer discharge valve 10 is closed, allowing transfer of lactic acid to its polycondensing apparatus 2, and concentration and polycondensation of lactic acid are advanced by heating and evacuation, with the produced water being evaporated. Lactic acid, lactic acid oligomer and lactide are removed from the produced gaseous body by condenser 11 and refluxed to the polycondensing apparatus, and then water content in the gaseous body is measured by pressure gauge 12. After confirming that the water content is below a specified value, lactic acid oligomer discharge valve 10 is opened to allow transfer of the lactic acid oligomer, said oligomer being depolymerized to produce gaseous lactide, which is condensed and recovered.