Polylactic Acid Intermediate Lactide Preparation Process Of Exploration And Research

Preparation technology of lactide , a monomer of poly(lactid acid), was studied in this paper. The lactide was synthesized by using of industrial monomer D,L-lactic acid. After the research on the influence factors in the preparation of lactide , such as temperature catalyst pressure and etc , the best preparation technology of lactide was got as following:Using 4% ZnO or 5% Sn(Oct)2 as catalyst , first , the lactic acid was dehydrated in the normal pressure , secondly the pressure was decompressed slowly to 4KPa to eliminate the water produced by the reaction at 140℃ , after that the pressure was decompressed quickly to 0.3KPa at 260℃ , then the lactide was got . The yield of the raw lactide was 42% After purification by recrystallization with the solution of ethyl acetate , the refined yield of lactide was 35% . The final products were characterized by IR spectrum and NMR , the melting point of which was 124℃~125℃, and the purity was analyzed to be 100% nearly by HPLC .