Patent ID: 6657044
Filing Date: 2003-12-02
Classification: C08G

Abstract:
In a process for the polymerization of polytrimethylene terephthalate by esterification of terephthalic acid or dimethylterephthalate with 1,3-propanediol, precondensation of the esterification product to produce a precondensation product, and polycondensation of the precondensation product to produce polytrimethylene terephthalate wherein excess 1,3-propanediol is removed from the esterification and/or polycondensation stages and 1,3-propanediol vapor is separated from the high boiling fraction (solid byproduct) in a separation vessel, the improvement which comprises:(a) heating the solid byproduct in the presence of about 5 ppm to about 5000 ppm, based on metal, of a metal catalyst selected from the group consisting of one or more 3rd, 4th, or 5th row metal compounds from Groups 3-12 and Groups 14-15 of the Periodic Table (IUPAC 1989) at a temperature of from about 100Â° C. to about 240Â° C. for from about 5 minutes to about 24 hours, optionally in the presence of a diluent, and (b) optionally, recycling the reaction product into the polymerization process.