GB827308A - Copolymer of fluoroethylene - Google Patents

Abstract

Copolymers comprising 5 to 42 mol. per cent of tetrafluoroethylene and having vinylidene fluoride as the remaining major constituent are prepared by polymerizing monomer mixtures comprising 3 to 45 mol. per cent of tetrafluoroethylene in the presence of promoters. The polymerization is preferably effected by continuously introducing the monomers, at a pressure below the saturation pressure of at least one of the monomers, into a polymerization zone containing an aqueous system comprising catalysts, e.g. cumene hydroperoxide, diisopropyl benzene hydroperoxide, triisopropyl benzene hydroperoxide, tertiary-butyl hydroperoxide, methyl cyclohexane hydroperoxide, tertiary-butyl perbenzoate, perborates, persulphates, e.g. potassium persulphate, perphosphates, e.g. sodium perphosphate, percarbonates, barium peroxide, zinc peroxide and hydrogen peroxide, activators, e.g. sodium bisulphite, sodium metabisulphite, sodium thiosulphate, sodium hydrosulphate, p-toluene sulphinic acid, dextrose and levulose, accelerators, e.g. cuprous sulphate, ferrous sulphate and silver nitrate, emulsifiers, e.g. potassium stearate, potassium oleate, potassium perfluorooctanoate, 3,5,7,8 - tetrachloroundecafluorooctanoic and 3,5,6-trichloro-octafluorohexanoic acids and their potassium, sodium and ammonium salts, and buffering agents, e.g. disodium hydrogen phosphate and sodium metaborate, to maintain the pH, preferably at 7 or above. Organic solvents, e.g. hexane, iso-octane, cyclohexane, benzene, toluene, methanol, tertiarybutanol, dioxane, tetrahydrofuran and fluorotrichloromethane, may be used in addition to or instead of water. Alternatively the polymerization may be effected in bulk in the presence of catalysts, e.g. diacetyl peroxide, lauroyl peroxide, tertiary-butyl peroxide, caprylyl peroxide, trichloroacetyl peroxide, perfluoropropionyl peroxide, 3-carboxypropionyl peroxide, 3,4-dibromobutyryl peroxide, trifluoroacetyl peroxide, difluoroacetyl peroxide, perfluorononanoyl peroxide, benzoyl peroxide, p-nitrobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, 2,21-azo-bis-isobutyronitrile, 2,21-azo-bis-2,4-dimethylvaleronitrile and 2,21-azo-bis-2,3,3-trimethylbutyronitrile. The polymerization may be catalysed by actinic or ultra-violet radiation. The polymerization may be short-stopped and modifiers, e.g. chloroform, 1,1,2-trifluorotrichloroethane, carbon tetrachloride, trichloroacetyl chloride and dodecyl mercaptan, may be used or the molecular weight of the product reduced. Plasticizers, e.g. methyl-isobutyl ketone, and fillers, e.g. titanium dioxide, aluminium, copper and iron powders, mica and asbestos may be incorporated during or after polymerization. The products may be vulcanized. They may be dissolved, e.g. in methyl acetate, butyl acetate, amyl acetate, ethyl benzoate, diisobutyl ketone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, acetone, methoxy ethanol and ethoxy ethanol and coated on to metals and fabrics. They may be extruded into films and fibres for reinforcing ropes, lines, canvas and conveyer belts, or moulded into gaskets, pump and valve diaphragms and brake linings, or used to insulate electrical wires.