Peroxide-curable fluoroelastomers and chlorofluoroelastomers having bromine and iodine curesites and the preparation

Claim 1

A continuous emulsion polymerization process for preparing a peroxide-curable fluoroelastomer in which a substantial number of chain ends are terminated by iodo groups, which comprises copolymerizing (a) up to 3 weight percent, based on the total weight of the components (a) and (b) of polymer repeat units selected from the group consisting of fluoroolefins and fluorovinyl ethers, said units containing bromine and being present in an amount to provide 0.1-1.0 weight percent bromine in the fluoroelastomer; (b) at least 97 weight percent, based on the total weight of components (a) and (b), of: (1) polymer repeat units of vinylidene fluoride and polymer repeat units of one or more fluoroolefins compolymerizable therewith, said fluoroolefins containing 2-8 carbon atoms, and at least as many fluorine atoms as carbon atoms, and optionally, polymer repeat units provided by perfluoroalkyl perfluorovinyl ethers, or (2) 32-60 mole percent of polymer repeat units of tetrafluoroethylene, 20-40 mole percent of polymer repeat units of perfluoroalkyl perfluorovinyl ether and 10-40 mole percent of polymer repeat units of ethylene the polymerization being carried out in the presence of a radical generating source and an iodinated compound represented by the formula RI n wherein R is a radical of 1-8 carbon atoms and selected from the group consisting of fluorocarbons and chlorofluorocarbons, and n is 1 or 2.