Hoechst Aktiengesellschaft

Rolf Hengel

Reinhard Albert Sulzbach

Gernot Lohr

Bernd Felix

Gerhard Beyer

Heinz Notzon

Willibald Hofmeister

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

In the suspension polymerization of tetrafluoroethylene a mixture of tetrafluoroethylene and an inert gas is charged under pressure before starting the polymerization, the total pressure being 5 to 50 bar and the concentration of tetrafluoroethylene in this mixture being 30 to 70 mol %. Said concentration is kept within this range by an appropriate feed of tetrafluoroethylene during the polymerization. The granular PTFE powder obtained is distinguished by an improved grain structure and grindability.

Process for the preparation of tetrafluoroethylene polymer in aqueous

A molding is produced by thermoplastic shaping of at least one partially crystalline polymer which comprises, exclusively, polymerized units of vinylidene fluoride and other fluorine-containing monomers which contain only one C.dbd.C double bond, contains 20 to 50% by weight of polymerized units of vinylidene fluoride and has a melt index of at least 1 g/10 min at 250.degree. C. and 11 kg load, without addition of substances which contain polymerizable double bonds, and the molding is subsequently treated with a minimum dose of 50 kGY of ionizing rays at a minimum dose rate of 2 Gy/s. Moldings are thus obtained in a simple manner which have good mechanical and chemical properties and exhibit no discoloration.

Molding made from a vinylidene fluoride copolymer and process for its

Concentrated, aqueous, colloidal dispersions of copolymers of vinylidene fluoride with other fluoroolefinic compounds containing, as the dispersion stabilizer, ammonium salts of a carboxylic acid having 10 to 14 carbon atoms, preferably ammonium laurate, are described.

Concentrated, aqueous dispersions of vinylidene fluoride polymers and a

For the electrolysis of sodium chloride, the use of cation exchanger membranes is described which are composed of recurring units of ##STR1## and have an ion exchange capacity of 1.55 to 1.74 m-equivalents/g of dry polymer in the H.sup.+ form and a longitudinal expansion, during the hydrolysis of the ester form, of between 3.2 and 6.0%. A considerable decrease in the energy consumption is obtained with membranes of this type.

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Burgkirchen, Germany

Rolf Hengel