Rhone-poulenc Viscosuisse Sa

Josiane Enggasser

Roland Stahlin

Paul Gesche

Process for making a polyester having polyethylene terephthalate units including transesterifying a terephthalic acid ester with a glycol using a manganese salt as catalyst and then subjecting the product to a polycondensation reaction using a germanium-containing catalyst to form a polyester; adding phosphorous compounds to block 80 to 99% by weight of the active manganese salt thus leaving an unblocked portion of the manganese salt prior to the polycondensation; and adding 10 to 100 ppm of Ge at the end of a ethylene glycol stage of the polymerization so that the Ge and the unblocked portion of the manganese salts provide the germanium-containing catalyst for the polycondensation reaction. The P/Mn molar ratio being less than 1. The reaction mixture contains 10 to 100 ppm of manganese during the reaction.

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Emmenbrucke, Switzerland

Josiane Enggasser