Solid state polymerization process for poly(trimethylene terephthalate) utilizing a combined crystallization/preheating step

摘要

In a process for producing poly(trimethylene terephthalate) (PTT) wherein 1,3-propanediol (PDO), and optionally other diols, and an aromatic diacid or diester thereof, and optionally other diacids or diesters, are esterified or transesterified and the esterification or transesterification product is polycondensed to produce a prepolymer which is solid state polymerized to produce a polymer with a desired intrinsic viscosity (IV). The crystallizing and preheating the PTT polymer is carried out in one step, without a drying/annealing step in between. Thus, the prepolymer from feed hopper 1 still has a substantial moisture content when it is first exposed to the SSP reaction temperature inside the crystallizer/preheater, 2, before it is passed to reactor 3. The product is cooled in cooler 4, e.g. a fluid bed or agitated heat exchanger.