Patent ID: 7521513
Filing Date: 2009-04-21
Classification: C08F

Abstract:
1. A semi-batch emulsion polymerization process for the production of a fluoroelastomer, said fluoroelastomer having at least 58 weight percent fluorine, comprising: (A) charging a reactor with a quantity of an aqueous solution substantially free of surfactant; (B) charging said reactor with a quantity of a monomer mixture comprising i) from 25 to 75 weight percent, based on total weight of the monomer mixture, of a first monomer, said first monomer selected from the group consisting of vinylidene fluoride and tetrafluoroethylene, and ii) between 75 and 25 weight percent, based on total weight of said monomer mixture, of one or more additional copolymerizable monomers, different from said first monomer, wherein said additional monomer is selected from the group consisting of fluorine-containing olefins, fluorine-containing vinyl ethers, hydrocarbon olefins and mixtures thereof; (C) initiating polymerization to form a fluoroelastomer dispersion while maintaining said reaction medium at a pH between 1 and 7, at a pressure between 0.5 and 10 MPa, and at a temperature between 25° C. and 130° C.; and (D) charging said reactor, after polymerization has begun, with a quantity of a hydrocarbon anionic surfactant of the formula R-L-M wherein R is an alkyl group having between 6 and 17 carbon atoms, L is selected from the group consisting of —ArSO