Patent ID: 7057007

Claim:
A process for continuously producing polybutylene terephthalate by esterification of an aromatic dicarboxylic acid with a glycol and subsequent polycondensation of the esterification product obtained, comprising: (a) continuously feeding said aromatic dicarboxylic acid and said glycol into a first esterification reactor as a first process stage; (b) carrying out esterification during the first process stage at temperatures of 220° C. to 250° C. and at 33 kPa to 150 kPa; (c) precondensing the esterification product from the first process stage during a second stage at temperatures of 230° C. to 255° C. and at 100 kPa to 0.133 kPa, to produce a precondensate; (d) continuously polycondensing said precondensate at temperatures of 230° C. to 255° C. and at 0.665 kPa to 0.067 kPa; (e) removing water and tetrahydrofuran from an output volatile component from said first esterification reactor to produce said glycol; (f) condensing an output volatile component obtained in steps (c) and (d); and (g) recycling to the first esterification reactor said glycol obtained in step (e) and condensed component obtained in step (f).