METHOD OF TETRAFLUOROETHYLENE COPOLYMERS PRODUCING (VARIANTS) Russian patent published in 1997 - IPC

FIELD: chemistry of polymers. SUBSTANCE: copolymers of tetrafluoroethylene were synthesized by the following manner: 1-st variant: by polymerization of tetrafluoroethylene with one or some fluorinated comonomers with ethylene-unsaturated bonds in an aqueous emulsion in the presence of dispersers, inorganic peroxide initiating agent and chain transferring agent - asymmetric difluoroethane $$$ used at amount 0.55-30 mole% with respect to comonomers mixture. Polymerization is carried out in the presence of base or basic salt at amounts necessary to obtain copolymers with nonstable terminal carboxyl or carboxylate groups. Sodium or potassium salts can be used to make pH = 7-10 in medium. Sodium or potassium persulfate is used as peroxide initiating agent. Disperser: perfluoroalkylcarboxylic acid potassium or sodium salts or perfluoroalkoxyether acid sodium or potassium salts. Polymerization is carried out in the presence of an aqueous emulsion or microemulsion of perfluoropolyethers with terminal perfluoroalkyl groups containing perfluorinated disperser. 2-d variant: process is carried out in the presence of base or potassium or sodium basic salt at pH = 7-8 and copolymers with nonstable terminal carboxylate groups were obtained followed by their treatment at 180-300 C up to producing copolymer with stable terminal groups $$$. 3-d variant: as variant 1 up to producing copolymers with nonstable terminal carboxylate groups. Then copolymer is treated with base or potassium or sodium basic salt up to pH = 7-8 followed by thermic treatment at 180-300 C and process is carried out up to producing copolymer with stable terminal groups $$$. 4-th variant: as variant 1 but process is carried out in the presence of base or basic salt at amount necessary for pH value maintaining 7-8 and ammonia aqueous solution taken at excess with respect to stoichiometric amount necessary for conversion of nonstable terminal groups to stable $$$-groups. Asymmetric difluorethane is used at amount 0.55-10 mole% with respect to monomers mixture. Ammonium persulfate is used as an inorganic peroxide initiating agent. Ammonium basic salt is used as a base or basic salt. Disperser: perfluoroalkylcarboxylic or perfluoroalkoxyether acid ammonium salt. Polymerization is carried out in the presence of an aqueous emulsion or microemulsion of perfluoropolyethers with terminal perfluoroalkyl groups that contains perfluorinated disperser. Polymer is used for production of chemically and thermically stable copolymers of tetrafluoroethylene. EFFECT: improved method of synthesis. 14 cl, 4 tbl