Zimmer Aktiengesellschaft

Werner Gey

Helmut Heinze

Peter Freund

Hans-Jochen Rothe

Hans-Joachim Rothe

Wolfgang R Langhauser

Wolfgang Langhauser

Polyethylene terephthalate having an acetaldehyde content of less than 2.5 ppm and suitable for packing of food and beverages intended for human consumption is produced by heating polyethylene terephthalate having an intrinsic viscosity of about 0.5--0.85 at a temperature of 180.degree.-230.degree. C., preferably 200.degree.-220.degree. C., for about 4 to 12 hours. The polyethylene terephthalate must not include more than 25 ppm of ester interchange catalyst or 20 ppm of phosphorous during this heating.

Process for production of polyester polymer for food packing

A separating or anticaking agent consisting of spherical glass particles having a diameter of 3 to 30.mu. is added to polyester resin granulates to prevent agglomeration during solid state polycondensation in a plug-flow reactor. Thin-walled articles formed from the end product are characterized by high strength, high transparency, crystal clear color, good gas impermeability and a smooth surface.

Process for the solid state polycondensation of linear polyesters

An alkali metal hydrogen monoglycolphosphate is added to the reaction product of diethylene glycol and dimethyl terephthalate to arrest the ester-interchange reaction and nullify the action of the divalent metal salt catalyst. These phosphates are easy to handle and convert the catalyst to an inactive compound which does not adversely affect subsequent polycondensation of the diethylene glycol terephthalate.

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Werner Gey