Hoechst Aktiengesellschaft

3m Innovative Properties Company

Dyneon Gmbh

Other

Reinhard Albert Sulzbach

Klaus Hintzer

Werner Schwertfeger

Gernot L&ouml;hr

Jurgen Kuhls

Konrad Von Werner

Thomas Kaiser

Herbert Fitz

Gernot Lohr

Bernd Felix

Dieter Steidl

Gernot Löhr

Robert Hartwimmer

Rolf Hengel

Stephan F&uuml;hrer

Hermann Blädel

Armin Budesheim

Gerhard Beyer

Hermann Bl&auml;del

Eduard Wess

Wilhelm Kowatsch

Hagen Kniep

Georg Oberauer

Rik A Brandenburg

Rainer Grasberger

Fluorine-containing emulsifiers can be removed from fluoropolymer dispersions by adding to the dispersion a non ionic emulsifier, removing the fluorine-containing emulsifier by contact with an anion exchanger and separating the dispersion from the anion exchanger. The resulting dispersions can be concentrated and used for coating applications.

Aqueous dispersions of fluoropolymers

Fluorine-containing emulsifiers can be removed from fluoropolymer dispersions by adding to the dispersion a nonionic emulsifier, removing the fluorine-containing emulsifier by contact with an anion exchanger and separating the dispersion from the anion exchanger. The resulting dispersions can be concentrated and used for coating applications.

Fluorinated emulsifier acids can be isolated from wastewater by firstly removing fine solids and/or material which can be converted into fine solids from the wastewater, preferably by precipitation, subsequently bringing the wastewater into contact with an anion-exchange resin and eluting the adsorbed emulsifier acids from the latter.

Method for recovering fluorinated alkanoic acids from waste waters

Non-free flowable, non-dusting molding powders with a bulk density of more than 450 g/l are obtained when a suspension polymer of tetrafluoroethylene with a content of 0.01 to 1% by weight of units of at least one perfluoro(alkyl-vinyl) ether is ground to a particle diameter of 10 to 50 &mgr;m and agglomerated in water.

Non-free flowable molding powders of modified polytetrafluoroethylenes

The process for the recovery of highly fluorinated carboxylic acids from off-gas streams, in which the off-gas is brought into contact with an alkaline washing solution of density >1.15 g/cm,so that the salt of the highly fluorinated carboxylic acid settles out as a separate phase, proceeds particularly advantageously when the alkaline washing solution is a potassium carbonate solution.

Recovery of highly fluorinated carboxylic acids from the gaseous phase

Non-free flowable, non-dusting molding powders with a bulk density of more than 450 g/l are obtained when a suspension polymer of tetrafluoroethylene with a content of 0.01 to 1% by weight of units of at least one perfluoro(alkyl-vinyl) ether is ground to a particle diameter of 10 to 50 .mu.m and agglomerated in water.

Process for non-free flowable molding powders of modified

Highly fluorinated carboxylic acids can be removed from exhaust gas streams by scrubbing with concentrated alkali solutions if these alkali solutions have a density high enough for the salt of the highly fluorinated carboxylic acid to separate out as an independent phase. An apparatus suitable therefor contains a scrubber and a separation vessel which is advantageously equipped with a conveying element, a collection vessel connected via an overflow and a circulation line for the scrubbing liquor.

Recovery of highly fluorinated carboxylic acids from the gas phase

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

Stable aqueous, colloidal dispersions, having a high shear stability, of copolymers of tetrafluoroethylene and ethylene, which may also contain at least one further comonomer, are described. Such dispersions are prepared in the presence of a mixture of perfluorooctanoic acid and perfluorononanoic or perfluorodecanoic acids or salts thereof.

Stable, aqueous, colloidal dispersions of copolymers of the

Quaterpolymers are described which are composed of the following copolymerized monomer units (in mole %):

Quaterpolymers of the tetrafluoroethylene/ethylene type

Novel granular, free-flowing, non-melt-fabricable raw polymer powders of tetrafluoroethylene polymers consisting of 0.004 to 0.075 mole % of polymerized units of a perfluoroalkyl vinyl ether and of tetrafluoroethylene units, are described. These powders have an average particle diameter of 450 to 1,400 .mu.m, a bulk density of at least 570 g/l, a powder flow index of .ltoreq.5 seconds/50 g and a grain stability of .ltoreq.5.5 seconds/50 g. They are prepared direct by suspension polymerizing TFE in the presence of the perfluoroalkyl ether, while stirring, the calculated concentration of the ether in the gas phase being kept within the range from 0.1 to 1.0% by volume in the period of time until 1.5% by weight of solid polymer have been formed, and the polymerization being carried out under a total pressure of 5 to 11 bars. A further improvement in bulk density, powder flow and grain stability is achieved if the intensity of stirring is kept at a relatively low level in a critical range, beginning at the formation of 1.5 to 3% by weight of solid polymer and extending to the formation of 8 to 12% by weight of solid polymer. The raw polymer powders which can be obtained in this manner are suitable, as such and without further pretreatment, for the production of ram-extruded articles of all types.

Raw polymer powder of a modified tetrafluoroethylene polymer having a

The separation of mixtures of hexafluoropropylene oxide and hexafluoropropylene is effected by extractive distillation in the presence of methylene chloride, whereby an excellent separating effect is achieved at a low energy consumption.

Process for the preparation of pure hexafluoropropylene oxide

An improved process for the preparation of aqueous, colloidal dispersions of copolymers comprising at most 60 mole % of units of tetrafluoroethylene, 60 to 40 mole % of units of ethylene and 0 to 15 mole % of units of at least one other .alpha.-olefinic monomer, which can be copolymerized with tetrafluoroethylene and ethylene, in the presence of manganese compounds as the catalyst is described. In this process, the emulsion polymerization is carried out in an aqueous phase in the presence (a) of a chain transfer agent of the formula X--CH.sub.2 --COOR (X=Cl, Br, COOH, COOR, COCH.sub.3, CH.sub.3, C.sub.2 H.sub.5 or C.sub.3 H.sub.7 ; and R=C.sub.1 -C.sub.4 -alkyl), and (b) of a compound which stabilizes the dispersion and has the formula ##STR1## (Y=COONH.sub.4, COOH, CH.sub.3, CH.sub.2 OH, CH.sub.2 COOH or CH.sub.2 COONH.sub.4). (b) can additionally contain an ammonium salt of an inorganic non-metal acid, for example ammonium chloride or fluoride. Terpolymers or quaterpolymers containing, in addition to tetrafluoroethylene and ethylene, preferably hexafluoropropylene and/or a 'bulky' vinyl monomer as the third and/or fourth comonomer are preferably prepared. The copolymer dispersions thus prepared have very low coagulate contents and are very stable and the copolymers have melt flow indices most appropriate to the processing operations. They can be processed to coatings and shaped articles.

Process for the preparation of aqueous, colloidal dispersions of

In a process for aftertreating thermally presintered polymers of tetrafluoroethylene the optionally comminuted powders are subjected, at temperatures below +80.degree. C., to the action of a gas jet mill. Preferred starting materials are tetrafluoroethylene polymers containing a small proportion of a modifying monomer. By the aftertreatment the bulk density and the flow index of the powders are considerably improved without a noticeable disintegration taking place. The aftertreated powders are used in the first place for the manufacture of shaped articles in extrusion devices with automatic feeding means.

Aftertreatment of thermally pretreated tetrafluoroethylene polymers and

Tetrafluoroethylene, often obtained in industrial processes in admixture with nitrogen and/or carbon monoxide can be separated practically quantitatively by absorption in aliphatic hydrocarbons or aliphatic ketones boiling at a temperature in the range of from +50 to +130.degree. C at atmospheric pressure with subsequent desorption. A separation from three component mixtures is also possible. Components boiling at a temperature below the boiling point of tetrafluoroethylene, which are absorbed together with the tetrafluoroethylene, can be separated by known methods.

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Burghausen, Germany

Reinhard Albert Sulzbach