Study On The Synthesis Of Lactide Use Solid Superacid As Catalyst

The application of PLA and its copolymer is increasing in the fields of biomaterial,especially in the tissue engineering used as scaffold material. The synthesis of midbody lactide for the preparation of PLA is also catching more attention in this field.The present situation of lactide synthesis is high reaction temperature and low production ratio which lead to its high production cost and hamper its application in the material.The present research hot spot mainly focus on the improvement of reaction technique as well as the selection of catalyst.This article mainly focus on the selection and amelioration of catalyst. We think the mechanism of depolymerization reaction of the poly lactic acid(oligomer) is a intramolecular ester exchange reaction. By contrast the traditional zinc oxide catalyst and from the point of preparation cost,we decide use sulfuric acid activated solid superacid as synthesis catalyst.The main work and the conclusion of the article are:(1)Give a suggestion on the reaction mechanism and the principle of catalyst selection.(2)By comparison of the catalyst activity of solid superacid with the zinc oxide,stannous chlorde and tin(II) octate in the synthesis reaction.we find that although its activity is lower than tin(II) octate,obviously higher than that of traditional zinc oxide and stannous chlorde.from the point of preparation cost,we select solid superacid as catalyst.(3)Prepare a series of solid superacid sample and use as catalyst in the synthesis of lactide to select the most active sample.(4)Through the experiment we find that SO24/ZnO-SnO2(2:1)/ La3+ is most active among the samples,when use it as catalyst,.dehydration reaction last 1.5 hour,depolymerization temperature end at 230-240C and production ratio of crude lactide reach to 90%.(5)The article also investigate the recrystallization condition of crude lactide and point out that it also an important factor have influence on the purification production ratio.(6)Give the kinetics equation of depolymerization reaction. By determination the degree of polymerization(DP) of the reaction system,we can get the kinetics data of the reaction.