Zimmer Aktiengesellschaft

Manfred Kyber

Wolfgang Schmidt

Ulrich Thiele

Uwe Schollar

Process for producing polybutylene terephthalate with less than 1.0 wt % units derived from ethylene glycol from polyethylene terephthalate scrap by diolysis and ester exchange with 1,4-butanediol and subsequent polycondensation.

Process for preparing polybutylene terephthalate from pet scrap

Process for continuous production of polyesters by esterification of terephthalic acid with 1,4-bis(hydroxymethyl)cyclohexane with a split feed in the presence of a titanium catalyst at 265.degree. to 305.degree. C. and 0.8 to 1.5 bar up to a conversion of 98.0% to 99.0%, then performing precondensation at 290.degree. to 305.degree. C. and 0.01 to 1.5 bar up to a conversion of 99.4% to 99.7% and finally performing polycondensation at 295.degree. to 310.degree. C. and less than 1.5 mbar up to a conversion corresponding to 50% to 95% of the maximum possible viscosity after adding more titanium catalyst.

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Maintal, Germany

Manfred Kyber