GB950084A - Improvements in or relating to fluorine containing copolymers, their production and cured products obtained therefrom - Google Patents

Abstract

Vinylidene fluoride and hexafluoropropylene are copolymerized by heating in the presence of a chain transfer agent, which is a C8 or lower aliphatic alcohol, ketone or carboxylic acid ester, and in contact with a polymerization initiator, the proportions of monomers and transfer agent being such that in the copolymer the weight ratio of -CH2-CF2- to -C3F6- units is from 70:30 to 45:55 with the radicals of the transfer agent present on average about once per molecule of copolymer, and the copolymer has an inherent viscosity from 0.025 to 0.25 at 30 DEG C. in 0.1% by weight solution in a mixture of 86.1% by weight tetrahydrofuran and 13.9% by weight dimethylformamide. The copolymers are stated to range from viscous oils to semi-solid greases at room temperature and to be capable of being cured to plastic or elastomeric products. Chain transfer agents specified are methanol, ethanol, isopropanol, 2-ethylhexanol-1, acetone, methyl ethyl or propyl ketone, ethyl acetate and hexanoate, butyl formate and amyl acetate. Copolymerization may be effected in the presence or absence of a solvent with a peroxy catalyst, e.g. acetyl, chloroacetyl, benzoyl, dicumyl or di-t-butyl peroxide or cumene hydroperoxide, with or without a reducing agent, or in aqueous emulsion with a redox catalyst e.g. ammonium persulphate and sodium bisulphate, and may be on a batch or continuous basis. The products may be cured by the conventional procedures for fluorocarbon elastomers. Specification 789,786 is referred to.ALSO:Vinylidene fluoride and hexafluoropropylene are copolymerized by heating in the presence of a chain transfer agent, which is a C8 or lower aliphatic alcohol, ketone or carboxylic acid ester, and in contact with a polymerization initiator, the proportions of monomers and transfer agent being such that in the copolymer the weight ratio of -CH2-CF2- to -C3F6- units is from 70:30 to 45:55 with the radicals of the transfer agent present on average about once per molecule of copolymer, and the copolymer has an inherent viscosity from 0.025 to 0.25 at 30 DEG C. in 0.1% by weight solution in a mixture of 86.1% by weight tetrahydrofuran and 13.9% by weight dimethylformamide. The copolymers are stated to range from viscous oils to semisolid greases at room temperature and to be capable of being cured to plastic or elastomeric products. Chain transfer agents specified are methanol, ethanol, isopropanol, 2-ethylhexanol-1, acetone, methyl ethyl or propyl ketone, ethyl acetate and hexanoate, butyl formate and amyl acetate. Copolymerization may be effected in the presence or absence of a solvent with a peroxy catalyst, e.g. acetyl, chloroacetyl, benzoyl, dicumyl or di-t-butyl peroxide or cumene hydroperoxide, with or without a reducing agent, or in aqueous emulsion with a redox catalyst e.g. ammonium persulphate and sodium bisulphate, and may be on a batch or continuous basis. Curing. The products may be cured by the conventional procedures for fluorocarbon elastomers. They may be compounded with an acid acceptor, e.g. magnesium oxide, followed by a curing agent. Examples are given of the following types of curing agents:-organic or inorganic peroxides; alkylene diamine carbamates, polythiols combined with a tertiary amine; and N,N1-diarylidene diamine. Curing is preferably effected in two temperature stages. Fillers such as carbon black may be introduced with the curing agents. Specification 789,986 is referred to.