Patent ID: 7375171

Claim:
A process for preparing a fluorine-containing elastomer vulcanizable by peroxide vulcanization, which is a batch copolymerization process conducted under conditions that the reduced temperature of the critical constant is at least 0.95 and the reduced pressure of the critical constant is at least 0.80 wherein the reduced temperature and the reduced pressure are calculated using the Peng-Robinson formula from the critical temperature, the critical pressure and the composition ratio of each of the monomers in the gaseous phase in the reaction vessel, wherein monomers comprising at least one fluoroolefin are copolymerized in the presence of water, an emulsifier and a compound having the formula: R f 1 .I x wherein R f 1 is a saturated or unsaturated fluorohydrocarbon or chlorofluorohydrocarbon group having 1 to 16 carbon atoms, and x is the number of bonds of R f 1 and an integer of 1 to 4.