Fluorhaltige Copolymere und Verfahren zu ihrer Herstellung

1,251,138. Tetrafluoroethylene/hexafluoropropene copolymers. ALLIED CHEMICAL CORP. 7 Aug., 1969 [9 Aug., 1968], No. 39569/69. Heading C3P. A granular moulding powder comprises particles of average size 25 to 600 microns of a copolymer which consists of 99.95 to 99:5 mole % tetrafluoroethylene units and 0.05 to 0.5 mole % hexafluoropropene units, and which is homogenous (i.e. does not contain molecules of tetrafluoroethylene homopolymer). The granular homogenous copolymer may be prepared by aqueous suspension polymerization in which the initial mixture of reactants consists of 99.1 to 92 mole per cent of gaseous tetrafluoroethylene and 0.9 to 8.0 mole per cent of gaseous hexafluoropropene and additional quantities of a gaseous feed consisting either of tetrafluoroethylene or of both comonomers are thereafter added to the reaction mixture while the ratio of the partial pressure of hexafluoropropene to the sum of the partial pressures of hexafluoropropene and tetrafluoroethylene is controlled to keep the mole percentages of hexafluoropropene and tetrafluoroethylene in the reaction mixture substantially constant and within the above-mentioned ranges. In the Examples tetrafluoroethylene and hexafluoropropene are copolymerized in the presence of water, H 2 SO 4 and potassium persulphate and the copolymers sintered by themselves or mixed with glass fibre or bronze powder.