| 摘要 |
1,161,955. Polymers containing difluoroketene units. E.I. DU PONT DE NEMOURS & CO. 12 Jan., 1968 [13 Jan., 1967], No. 1912/68. Heading C3P. A fluorocarbon polymer containing at least 0À1 mole per cent difluoroketene units of formula -CF 2 -C(O)-, is prepared by reacting a finely divided fluorocarbon polymer starting material containing alkyl trifluorovinyl ether units of formula -CF 2 -CF(OR)-, where R is an alkyl group, with a Lewis acid in the liquid state which is sulphur trioxide, aluminium trichloride or titanium tetrachloride in an inert liquid medium, whereby sufficient of the ether units are converted to difluoroketene units to provide at least 0À1 mole per cent difluoroketene units in the polymer, the presence of the liquid medium being optional when sulphur trioxide or titanium tetrachloride is used as the Lewis acid. The fluorocarbon polymer is either a homopolymer consisting substantially of difluoroketene units or a copolymer containing at least 0À1 mole per cent -CF 2 C(O) units, the remainder being units derived from perfluoro - 2 - methylene - 4 - methyl - 1,3 - dioxolane (PMD) and/or an alkyl trifluorovinyl ether and/or a perfluorinated hydrocarbon. The fluorocarbon polymer starting material is either a homopolymer consisting substantially wholly of alkyl trifluorovinyl ether units or a copolymer consisting of alkyl trifluorovinyl ether units and units derived from PMD and/or a perfluorinated hydrocarbon. The liquid medium is any medium consisting of a perfluorocarbon, a perchlorofluorocarbon or any mixture thereof. In the examples, methyl trifluorovinyl ether, tetrafluoroethylene, PMD and n-butyl trifluorovinyl ether are homopolymerized and copolymerized in the presence of CCl 2 FCClF 2 , perfluoropropionyl peroxide and (C 2 F 5 COO) 2 and the polymers treated with sulphur trioxide, aluminium trichloride and titanium tetrachloride in CCl 2 FCClF 2 . The polymer starting materials may be reduced in particle size by shearing in a blender, optionally in the presence of a fluorinated cyclic ether of formula C 8 F 16 O.
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