Synthesis of Lactide from Oligomeric PL A:Effects of Temperature,Pressure,and Catalyst

摘要

Lactide was produced from oligomeric PLA by back-biting reaction of the OH end groups.For optimization of the reaction conditions,the effects of temperature,pressure,PLA molecular weight,and catalyst type on the lactide synthesis were examined.The fraction of D,L-lactide decreased with increasing temperature.Among the various Sn-based catalysts,the D,L-lactide fraction was maximized when SnO was used.A higher yield with lower racemi-zation was observed at lower pressure.The conversion of PLA was maximized at an oligomeric PLA molecular weight of ca.1380.The yield of lactide increased but the fraction of D,L-lactide decreased with increasing molecular weight.The highest conversion with the lowest racemization degree was obtained at a catalyst concentration of 0.1 wt%.The lactide was more sensitive to racemization because of the entropic effect.