Hoechst Aktiengesellschaft

Gerhard Beyer

Reinhard Albert Sulzbach

Rolf Hengel

Gerhard Wolfel

Eduard Wess

The aqueous dispersions from the polymerization of fluorinated thermoplastics can be worked up to a high value product (e.g., substantially purified of cations resulting from the polymerization) in a continuous manner, if the cations are first removed from the aqueous dispersion, the dispersion is then compressed and decompressed through small openings, thereby being coagulated, the coagulated phase is washed on a filter and partially dewatered, subsequently broken up to give a free-flowing product and this is dried to the desired residual moisture content. Qualitatively high value products, which can be directly fed to a melt extruder, are thus obtained with high throughputs.

Process for working up aqueous dispersions of fluorinated thermoplastic

The invention describes a sealing material from polytetrafluoroethylene fibers, whose staple length is in the range of from 1 to 20 mm. They are intimately mixed with graphite; oil and finely divided polytetrafluoroethylene being advantageously added. The portion of PTFE fibers is at least 50% by weight, the portion of graphite is from 10 to 30% by weight, and the portion of finely divided PTFE is from 5 to 15% by weight. As PTFE fibers there are also used those which have been obtained by machining sintered PTFE resin. The sealing material is formed into tablets or half-rings. The seals prepared are marked by their applicability at uncommonly high pressures.

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Burgkirchen, Germany

Gerhard Beyer