Procédé de préparation de fluorélastomères contenant du fluorure de vinylidène

Verfahren zur Herstellung Vinylfluorid enthaltender Fluorelastomere

Process for making vinylidene fluoride containing fluoroelastomers

Abstract

Making a fluoroelastomer by feeding to an aqueous polymerization medium in a reactor about 25-75% by weight of the total monomers, vinylidene fluoride, at least one other fluorine-containing ethylenically unsaturated monomer containing at least as many fluorine atoms as carbon atoms and copolymerizable with vinylidene fluoride, an inorganic free-radical initiator, a chain transfer agent added in an amount sufficient to maintain a concentration in the aqueous polymerization medium of from about 0.5 f 10 -3 to 5 x 10 -3 moles per 100 grams of total monomers, and from about 0.02-2% by weight, based on the weight of the aqueous medium, of a surfactant which is a compound having the formula: where n is an integer of from 2-8 or mixtures thereof and M is an alkali metal cation, hydrogen or ammonium, maintaining the pH of the aqueous polymerization medium within a range of from about 2.5-5, continuously removing a portion of the resulting fluoroelastomer latex from the polymerization reactor and adding to said portion a mineral acid or a carboxylic acid containing no more than 5 carbon atoms and having a pK of less than about 4.2 to lower the pH to about 2 or below and a water-soluble salt of an alkaline earth meral to coagulate the fluoroelastomer and recovering the fluoroelastomer from the latex.

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Patent Citations (3)

    Publication numberPublication dateAssigneeTitle
    EP-0072659-A1February 23, 1983E.I. Du Pont De Nemours And CompanyKontinuierliches Polymerisationsverfahren
    FR-2286153-A1April 23, 1976Ugine KuhlmannProcede de polymerisation ou de copolymerisation en emulsion du fluorure de vinylidene
    US-3069401-ADecember 18, 1962Du PontCopolymers of hexafluoropropylene vinylidene fluoride and aliphatic, chain transfer agents

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