Patent ID: 6538076
Filing Date: 2003-03-25
Classification: C08G,Y10T

Abstract:
A continuous process for the production of poly(trimethylene terephthalate) comprising the steps of:(a) continuously feeding a liquid feed mixture to a flasher, the liquid feed mixture comprising a catalyst and at least one of bis-3-hydroxypropyl terephthalate and low molecular weight polyesters containing propylene groups and terephthalate groups, and the liquid feed mixture having a mole ratio of propylene groups to terephthalate groups of 1.1 to 2.2; (b) continuously vaporizing by-products in the flasher and removing the by-products from the flasher in a first stream of gaseous by-products, and continuously withdrawing a liquid flasher reaction product having a mole ratio of propylene groups to terephthalate groups of less than about 1.5 from the flasher; (c) continuously feeding the liquid flasher reaction product to a prepolymerizer, and continuously polymerizing the flasher reaction product in the prepolymerizer to form a poly(trimethylene terephthalate) prepolymer and a second stream of gaseous by-products; (d) continuously withdrawing the poly(trimethylene terephthalate) prepolymer from the prepolymerizer, the prepolymer having a relative viscosity of at least about 5; (e) continuously feeding the poly(trimethylene terephthalate) prepolymer to a final polymerizer, and continuously polymerizing the poly(trimethylene terephthalate) prepolymer in the final polymerizer to form a higher molecular weight poly(trimethylene terephthalate) and a third strewn of gaseous by-products; and (f) continuously withdrawing the higher molecular weight poly(trimethylene terephthalate) from the final polymerizer, the higher molecular weight poly(trimethylene terephthalate) having a relative viscosity of at least about 17.