CONTINUOUS PROCESS FOR PRODUCTION OF FLUOROELASTOMERS

摘要

1434999 Copolymerizing vinylidene fluoride E I DU PONT DE NEMOURS & CO 21 Nov 1973 [22 Nov 1972] 54073/73 Heading C3P A process for the continuous copolymerization of vinylidene fluoride and at least one other polymerizable unsaturated fluorinated monomer to a polymeric product having a broad molecular weight distribution which comprises (a) introducing monomers, water and watersoluble free radical generator to a first reactor at such flow rate that the residence time is sufficient to form a high molecular weight product, (b) withdrawing product from the first reactor at a rate equal to the rate at which monomer is introduced thereto, (c) introducing the high molecular weight product, further fluorinated monomers and a chain transfer agent to a second reactor, the residence time in said second reactor being sufficient to produce a low molecular weight product and (d) continuously withdrawing polymeric product from the second reactor. The comonomers may be fluoro- or chlorofluoroolefins, fluorinated vinyl esters, derivatives of perfluoroacrylic acid or fluorinated alkyl vinyl ethers. The water-soluble initiator may be ammonium or an alkali metal persulphate, optionally with a reducing agent, e.g. sodium bisulphite. The chain transfer agent may be an ester, alcohol, ketone, mercaptan, hydrocarbon or halogenated hydrocarbon. Emulsion stabilizers and dispersing agents may be added to the first reactor. Examples describe the copolymerization of vinylidene fluoride with (1) hexafluoropropylene in the presence of ammonium persulphate with the addition of diethyl malonate to the second reactor, and (2) hexafluoropropylene and tetrafluoroethylene in the presence of ammonium persulphate and sodium sulphite with the addition of ammonium persulphate and diethyl malonate to the second reactor.