GB1456615A - Process for preparing a propylene-tetrafluoroethylene copolymer - Google Patents

Abstract

1456615 Propylene-tetrafluoroethylene copolymers ASAHI GLASS CO Ltd 12 Nov 1974 48939/74 Heading C3P A process for preparing a propylene and tetrafluoroethylene copolymer comprises copolymerizing propylene and tetrafluoroethylene in an aqueous medium at 0-50‹ C. in the presence of a redox catalyst comprising (1) a water-soluble inorganic persulphate, (2) a watersoluble thiosulphate or a bisulphite and (3) a water-soluble iron salt. The copolymers produced have a number average molecular weight of at least 80,000 but not more than 300,000 and a Mooney viscosity of at least 40 but less than 150. Preferred persulphates, thiosulphates and bisulphites are the ammonium and alkali metal salts. The water-soluble iron salt may be ferrous sulphate, ferric sulphate, ferrous nitrate, ferric nitrate, ferrous chloride, ferric chloride, ammonium ferrous sulphate or ammonium ferric sulphate. The molar ratio persulphate/thiosulphate or bisulphite/iron salt may be 0À1-2/ 1À0/0À005-0À5. The copolymerization reaction may be carried out at a pressure of 100 kg/cm.<SP>2</SP> (gauge) or less, at a pH of 7-11, and in the presence of a water-miscible organic solvent. Another comonomer may be added to the gaseous mixture of propylene and tetrafluoroethylene. The copolymerization reaction velocity is improved by adding the iron salt in an activator solution containing a water-soluble pyrophosphate, such as sodium, potassium or ammonium pyrophosphate, and a reducing sugar, such as dextrose, fructose, glucose or sorbose. Preferably the inorganic persulphate and thiosulphate are charged to the aqueous medium first and then the activator solution composed of iron salt, pyrophosphate and a reducing sugar is added. Various additives may be added to the aqueous medium, e.g. as emulsifiers polyfluorocarboxylic or polyfluorochlorocarboxylic acids and salts thereof, and phosphates and sulphates of polyfluoroalcohols. The copolymer may be cross-linked by adding a conventional peroxy cross-linking agent and heating or by subjecting the copolymer to highenergy ionizing radiation. Cross-linking may be promoted by adding allyl compounds, sulphur, amines, maleimides, methacrylates, divinyl compounds, sulphur, amines, maleimides, methacrylates, divinyl compounds or oxime compounds. During the cross-linking reaction fillers such as magnesium oxide, lead oxide, carbon black and silica, pigments, antioxidants and stabilizer. The specific examples describe the preparation of propylene-tetrafluoroethylene copolymers varying the conditions of polymerization except Example 14 which describes the preparation of a copolymer of tetrafluoroethylene, propylene and ethylene. Example 12 describes the vulcanization of a propylenetetrafluoroethylene copolymer with 2,2<SP>1</SP>-bis-(tbutyl-peroxy)-p-diisopropyl benzene, triallylisocyanurate, magnesium oxide and carbon black.