Preparation And Characterization Of The Ring Lactone

The ring lactone polymer has good biodegradability and biocompatibility, it has been concerned by more and more people. The ring lactone polymer manufacturing cost is high,which has greatly restricted its application in real life. Polyglycolide and polylactide are the most used ring lactone polymers. Glycolide and lactide are the monomers of polyglycollide and polylactide, respectively. The cost and product performance of glycolide and lactide have an extremely important role in the popularization of the ring lactone polymer.In this paper, glycolic acid was used as raw material with the melt method and azeotropic solvent method to synthesize glycolide. By controlling variables, the effects of reaction conditions on the yield of glycolide were studied, such as the catalyst system, the content of catalyst, the heating rate of depolymerization, the molecular weight of depolymerization agent, the temperature of depolymerization and the high boiling point organic solvent. Glycolide was purified with different solvent systems. The alpha and beta crystal were prepared under different recrystallization temperature. The structure of glycolide was characterized by melting point, IR, 1H-NMR, X-ray diffraction, thermal analysis and microscopic analysis. The results of research showed that the optimum conditions for the synthesis of glycolide as follows: when the heating rate of depolymerization reaction stage was 150C /min and the temperature of depolymerization was 225?, the crude yield of glycolide could reached to 91.61% under the conditions of the high boiling point organic solvent NHD and TGDE. The mixed solvent of ethyl acetate and acetone was the best recrystallization solvent for glycolide and the volume ratio of ethyl acetate and acetone was (3-9): 1, the total yield of glycolide was 79.4%. Through the polarizing microscopic observation, we found that the alpha crystal was flaky and the beta crystal was granular, the beta crystal was easier to form dimer that was favorable for polymerization.With L-lactic acid as raw material, L-lactide was synthesized with the melting method and azeotropic solvent method. By controlling variables, the effects of reaction conditions on the yield of L-lactide were studied, such as the catalyst system, the content of catalyst,the time of polymerization, the temperature of depolymerization, and the recrystallization times effect on the purity of L-lactide were studied. Water content and L-lactic acid content in the L-lactide were determined by acid base titration. The structure of L-lactide was characterized by melting point, IR,1H-NMR, X-ray diffraction, thermal analysis. The results of research showed that the optimum conditions for the synthesis of L-lactide as follows: the molar ratio of the catalyst of ZnO and Sn(Oct)2 was 7:3, the content of catalyst was 1% of L-lactic acid quality, the time of polymerization was 4h, the temperature of depolymerization was 240?, the crude yield of L-lactide could reached to 89.57% under the use of azeotropic method. Ethyl acetate was used as solvent, the recrystallization times was 3, which was best to the yield and purity of L-lactide.Finally, material balance calculations were made for the process of synthesizing glycolide and L-lactide, which provides a certain basis for the large-scale production of glycolide and L-lactide.