Patent ID: 6245879
Filing Date: 2001-06-12
Classification: C07C,C08G

Abstract:
A process for preparing a 1,3-propanediol-based polyester comprising:(a) contacting, in a polymerization reaction mixture at a temperature within the range of about 200 to about 280.degree. C. under less than atmospheric pressure, terephthalic acid and a molar excess of 1,3-propanediol, to produce a reaction product mixture comprising polytrimethylene terephthalate and a distillate comprising excess 1,3-propanediol, by-product carbonyl compounds and less than 20 wt % water;(b) adding a sufficient amount of a base to impart to the distillate a pH higher than 7, said addition of base achieved without raising the water content of the base-containing distillate above 20 wt %;(c) heating the base-containing distillate to a temperature sufficient to distill a major portion of the 1,3-propanediol therefrom; and(d) passing at least a portion of said distilled 1,3-propanediol to the polymerization reaction mixture as a recycle stream.