TOUGH STABLE TETRAFLUOROETHYLENE-FLUOROALKYL PERFLUOROVINYL ETHER COPOLYMERS

1299495 Tetrafluoroethylene/perfluorovinylether copolymers EI DU PONT DE NEMOURS & CO 21 April 1970 [22 April 1969] 19111/70 Heading C3P A copolymer of tetrafluoroethylene monomer and at least one perfluorovinyl ether comonomer copolymerizable therewith which is a fluoroalkyl perfluorovinyl ether, a poly ether having the formula wherein X is F or H and n is 0 or an integer from 1 to 7 or perfluoro(3,6-dioxa-4-methyl-7-octene) sulphonyl fluoride is prepared by (a) forming a solution of the monomers and a hydrogencontaining chain transfer agent in a liquid solvent which is a perfluorinated hydrocarbon, a chlorofluoroalkane in which each carbon atom is substituted by at least one fluorine atom or a chlorofluorohydroalkane in which each carbon atom is substituted by at least one fluorine atom and in which each hydrogen atom is present in a CF 2 H radical, or a mixture of two or more of these; (b) polymerizing the monomers in the solution at a temperature of 30‹ C. to 75‹ C. and at a pressure of 15 to 1,000 p.s.i.g., the polymerization being initiated with an initiator which is active at the polymerization temperature and is soluble in the solution formed in step (a); and (c) separating the reaction mixture into a fraction containing the solvent, chain transfer agent and comonomer and a fraction containing the copolymer. Preferred copolymers contain stable -CF 2 H end groups and have a volatile index of less than 25, a per cent swelling index of less than 25 and a specific melt viscosity of 1 Î 10-4 to 100 Î 10-4 poises. In the examples tetrafluoroethylene and perfluoropropyl perfluorovinyl ether are copolymerized in the presence of 1,2,2-trichloro-1,1,2- trifluoroethane, perfluoropropionyl peroxide, methanol and cyclohexane.