CONTINUOUS PROCESS FOR PRODUCING POLY(TRIMETHYLENE TEREPHTHALATE)

摘要

A continuous process for the production of poly(trimethylene terephthalate) is disclosed. According to the process, a liquid feed mixture comprising bis-3- hydroxypropyl terephthalate and/or low molecular weight polyesters of 1,3- propanediol and terephthalic acid, the liquid feed mixture having a mole rat io of propylene groups to terephthalate groups of 1.1 to 2.2 is fed to a prepolymerizer. Bis-3-hydroxypropyl terephthalate and the low molecular weig ht polyesters are continuously polymerized to form a poly(trimethylene terephthalate) prepolymer and a first stream of gaseous by-products. Poly(trimethylene terephthalate) prepolymer having a relative viscosity of a t least about 5 is continuously withdrawn from the prepolymerizer and continuously fed to a final polymerizer, where it is continuously polymerize d to form a higher molecular weight poly(trimethylene terephthalate) and a second stream of gaseous by-products. Higher molecular weight poly(trimethylene terephthalate) having a relative viscosity of at least abo ut 17 is continuously withdrawn from the final polymerizer.