Abstract: This invention is a process for increasing the toughness of solid state polymerized (SSP) poly(trimethylene terephthalate) (PTT) pellets which have an intrinsic viscosity of about 0.7 dl/g or greater prior to extrusion. The process comprises extruding the PTT SSP pellets at a temperature of about 245 to about 280° C for from about 1 minute to about 20 minutes, cutting the PTT into pellets, and crystallizing the PTT pellets to about 10 to about 45 percent crystallinity.

Abstract: An improved process for the polymerization of polytrimethylene terephthalate by esterification of terephthalic acid or dimethylterephthalate with 1,3-propanediol (PDO), precondensation of the esterification product to produce a precondensation product, and polycondensation of the precondensation product to produce polytrimethylene terephthalate wherein excess PDO is removed from the esterification and/or polycondensation stages and PDO vapor is separated from the high boiling fraction (solid byproduct). The improvement 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 100° C. to about 240° C.