Conventional Catalyst-Based L-Lactide Synthesis

As an indispensable material to prepare poly-L-lactide,the purity and cost of L-lactide affect the quality and price of poly-L-lactide greatly.With L-lactic acid as raw material and SnCl2 or Zn as catalyst, L-lactide was synthesized by oligomerization and depolymerization and its optical purity reaches 99%.Effects of a series of technical conditions on the yield and purity of lactide are discussed.This paper researches molecular weight of oligomers, dosage of catalyst,oligomerization time on the yield and purity of L-lactide and the relationship between oligomerization temperature,depolymerization temperature and the yield of lactide.The optimum conditions are that SnCl2 is catalyst,which dosage is 0.5%,dehydration remains 8 h,oligomerization temperature and depolymerization temperature is under 170 ℃ and 220 ℃ sepatately and the maximal yield of lactide could reach 93.2%