Patent ID: 7157550

Claim:
Thermoprocessable tetrafluoroethylene (TFE) copolymers in gel form obtained by adding to a polymer latex, produced by polymerization in dispersion or aqueous emulsion of TEE with one or more monomers containing at least one unsaturation of ethylene type selected from the following: C 3 –C 8 perfluoroolefins; C 2 –C 8 hydrogenated fluoroolefins, selected from vinyl fluoride (VF), vinylidene fluoride (VDF), tri-fluoroethylene, hexafluoroisobutene and (perfluoroalkyl)ethylene CH 2 =═CH—R f , wherein R f is a C 1 –C 6 perfluoroalkyl; C 2 –C 8 chloro- and/or bromo- and/or iodo-fluoroolefins; (per) fluoroalkylvinylethers (PAVE) CF 2 ═CFOR f , wherein R f is a C 1 –C 6 (per) fluoroakyl; (per) fluoro-oxyalkylvinylethers CF 2 ═CFOX, wherein X is: a C 1 –C 12 alkyl, a C 1 –C 12 oxyalkyl, or a C 1 –C 12 (per)—fluoro oxyalkyl having one or more ether groups; fluorodioxoles; non conjugated dienes selected from the following: CF 2 ═CFOCF 2 CF 2 CF═CF 2 , CFX 1 ═CX 2 OCX 3 X 4 OCX 2═ CX 1 F wherein X 1 and X 2, equal to or different from each other, are F, Cl or H; X 3 and X 4 , equal to or different from each other, are F or CF 3 , which during the polymerization cyclopolymerize; and fluorovinylethers (MOVE) of general formula: CFX Al ═CX Al OCF 2 OR Al (A-I) wherein R Al is a C 2 –C 6 linear, branched or C 5 –C 6 cyclic (per)fluoroalkyl group, or a C 2 –C 6 linear, branched (per) fluoro oxyalkyl group, containing from one to three oxygen atoms; when R Al is a fluoroalkyl or a fluorooxyalkyl group as above it can contain from 1 to 2 atoms, equal or different, selected from the following: H, Cl, Br, l; X Al ═F, H; and an acid electrolyte having pH values ≦2, washing the polymeric gel with acid aqueous solutions or neutral aqueous solutions having a pH from 1 to 7: wherein the thermoprocessable TEE copolymers contain an amount of extractable cations lower than 1 ppm and an amount of surfactant lower than 10 ppm.