Patent ID: 6353062
Filing Date: 2002-03-05
Classification: C08G

Abstract:
A continuous process for the production of poly(trimethylene terephthalate) comprising the steps of:(a) continuously feeding a liquid feed mixture to a prepolymerizer, the liquid feed mixture comprising a catalyst, at least one of bis-3-hydroxypropyl terephthalate and low molecular weight polyesters containing propylene groups and terephthalate groups, the liquid feed mixture having a mole ratio of propylene groups to terephthalate groups of 1.1 to 2.2; (b) continuously polymerizing in the prepolymerizer the at least one of bis-3-hydroxypropyl terephthalate and low molecular weight polyesters to form a poly(trimethylene terephthalate) prepolymer and a first stream of gaseous by-products, wherein the pressure in a top portion of the prepolymerizer is maintained at about 4 to about 18 mm of Hg; (c) continuously withdrawing the poly(trimethylene terephthalate) prepolymer from the prepolymerizer, the prepolymer having a relative viscosity of at least about 5; (d) continuously feeding the poly(trimethylene terephthalate) prepolymer to a final polymerizer and continuously polymerizing in the final polymerizer the poly(trimethylene terephthalate) prepolymer to form a higher molecular weight poly(trimethylene terephthalate) and a second stream of gaseous by-products, wherein the pressure in the final polymerizer is maintained at about 0.5 to about 3.0 mm of Hg; and (e) 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.