BATCH PROCESS FOR MAKING POLYBUTYLENE TEREPHTHALATE

A batch process for preparing polybutylene terephthalate (PBT) includes heating a solid PBT oligomer having an intrinsic viscosity (IV) of 0.1 to 0.2 dL/g and a carboxylic acid end group concentration [CEG] of 90 to 180 mmol/kg at a temperature and pressure defined herein to form melted homogeneous PBT oligomer containing 0 to 300 ppm tetra(C1-C8 alkyl) titanate catalyst, and polycondensing the melted homogeneous PBT oligomer in the presence of a tetra(C1-C8 alkyl) titanate catalyst, reducing the pressure, and maintaining the temperature at approximately 245-260° C. for a sufficient time to provide PBT having an IV of 0.55 and 1.20 dL/g. The PBT oligomer can be prepared by heating a mixture of 1,4-butane diol and purified terephthalic acid in the presence of a tetra(C1-C8 alkyl) titanate catalyst.