Patent ID: 8614287

Claim:
A method for preparing polytrimethylene terephthalate polymer with sustained-release crystallinity, comprising following steps of: (1). combining the raw materials and an esterification catalyst to carry out an esterification reaction at 220° C.-260° C. and under pressure of 0.05-0.30 MPa, and completing the reaction when there is no water produced from esterification, wherein said raw materials consists essentially of 1,3-propylene glycol, terephtalic acid and a third monomer, wherein said third monomer can produce steric hindrance in said polymer, wherein said third monomer is a combination of a non-para aromatic dicarboxylic acid and a C3-C10 aliphatic dihydric alcohol having branched chains or naphthenic group, wherein the amount of said 1,3-propylene glycol, terephtalic acid and third monomer is in a molar ratio of carboxyl to hydroxyl being 1:1.16-1.85, and the amount of said third monomer used is 0.5%-6.5% of the total weight of said raw materials; and (2). adding a polymerization catalyst after step (1) and carrying out a polymerization reaction at 240° C.-280° C. to yield said polytrimethylene terephthalate polymer with sustained-release crystallinity.