Method for synthesizing poly(butylene succinate-co-butylene adipate)

A method for synthesizing poly(butylene succinate-co-butylene adipate) (PBSA), comprising:

• a) adding raw materials comprising succinic acid, adipic acid, and 1,4-butanediol to a reaction still, a molar ratio of the succinic acid to the adipic acid being between 0.2:0.8 and 0.8:0.2, and a ratio of a mole number of the 1,4-butanediol to a total mole number of two carboxylic acids being between 1.05:1.0 and 1.5:1.0;
• increasing a temperature in the reaction still to 130° C. under inert gas atmosphere, and stiffing the raw materials for complete dissolution, then keeping the temperature in the reaction still at a temperature of 170-200° C., and dehydrating for 1-3 hours at atmospheric pressure, to yield an oligomer of PBSA with a weight average weight average molecular weight of 4000-6000 Da;
• and
• b) decreasing the temperature of the reaction still to 100° C., and adding a composite catalyst system comprising a main catalyst and a cocatalyst with a molar ratio thereof being 1:1, the main catalyst being a biocompatible organic guanidine, the cocatalyst being an ortho-titanate compound, and a total addition of the composite catalyst system accounting for one ten-thousandth to one ten-millionth of a total weight percentage of the raw materials;
• uniformly stiffing and mixing the composite catalyst system and reactants under the inert gas atmosphere, slowly vacuum pumping the reaction still for 0.5-2 hrs until an absolute pressure therein is below 200 Pa, heating the reaction still to a temperature of 200-240° C. and allowing the composite catalyst system and the reactants to react for 10-20 hrs, to yield a copolymer of PBSA having a weight average molecular weight over 100,000 Da.