GB888766A - Improvements in or relating to fluorinated copolymers, their production and cured products obtained therefrom - Google Patents

Abstract

Curable carboxyl-terminated copolymers consisting essentially of -CH2-CF2- units and one or more of the units <FORM:0888766/IV (a)/1> ; -CF2-CF2-; and -CFCl-CF2-, having a carboxyl content of 0,2 to 3,75 wt. per cent and an inherent viscosity in 1 wt. per cent acetone/30 DEG C. of 0,04 to 0,25, are obtained from a copolymer of vinylidene fluoride with one or more of perfluoropropene, tetrafluoroethylene and trifluorochloroethylene, said vinylidene fluoride copolymer having an inherent viscosity of at least 0,4 at 30 DEG C. in 0,1 wt. per cent solution in 86,1% tetrahydrofuran/13,9% dimethyl formamide, by dehydrohalogenation in an inert solvent, and in the presence of a nitrogenous base having a dissociation constant of at least 1 X 10-5 in aqueous solution at 25 DEG C., until at least two intralinear double bonds are formed, followed by heating in an inert solvent and in the presence of an oxidizing agent to cleave some or all of these intralinear double bonds, the conditions being such as will result in the product having the specified properties. Nitrogenous bases specified are n-butylamine, di- and tri-ethylamine, piperidine, cyclohexylamine, dicyclohexylamine, dimethyldodecylamine, dimethylcyclohexylamine, allylamine, diallylamine, dimethylbenzylamine, ammonia, ammonium hydroxide and quaternary ammonium hydroxides. Preferred conditions for the dehydrohalogenation step are to heat with 0,1 to 0,4 moles of N compound per 100g. polymer at 35 DEG to 70 DEG C. for 6 to 24 hours. Oxidation may be effected at 50 DEG to 70 DEG C. for 2 to 24 hours with potassium permanganate or fuming nitric acid in an inert solvent such as acetone or acetic acid. The products may be cured to form p plastic or elastic solids, e.g. by reacting the terminal carboxyl groups with polyvalent metal oxides or bases which can react with more than one molecule of acid. Elastomers are obtained when the copolymer contains 70 to 30 wt. per cent of vinylidene fluoride. The products may also be cured with compounds containing two or more epoxy groups, e.g. butadiene dioxide; diglycidyl ether; polyglycidyl ethers of glycol or erythritol; glycidyl ethers of resorcinol, hydroquinone or phloroglucinol; epoxy resins; pyromellitic dianhydride; dicyclopentadiene diepoxide; and the diglycidyl ether of tetramethyl-bis (3-hydroxypropyl) disiloxane. Specifications 589,577, 758,419 and 888,765 are referred to.