Patent ID: 8207235

Claim:
A process for stabilizing a semi-crystalline fluoropolymer comprising ion exchange groups, said process comprising: suspending at least one semi-crystalline fluoropolymer having ion exchange groups (polymer (I)) in at least one fluorinated organic dispersing medium (medium (M)) so as to obtain a dispersion (D) of polymer (I) in said dispersing medium (M); contacting said dispersion (D) with fluorine under irradiation with U.V. radiation so as to obtain a stabilized polymer, wherein the polymer (I) comprises: recurring units derived from at least one ethylenically unsaturated fluorinated monomer comprising at least one fluorine atom; and a substantial amount of recurring units derived from at least one ethylenically unsaturated functional monomer comprising at least one ion exchange group; wherein the polymer (I) comprises recurring units derived from at least one fluorinated functional monomer selected from the group consisting of: (M1) sulfonated perfluoroolefin of formula (M1): wherein n is an integer between 0 and 6, and X′ is selected from the group consisting of Cl, Fl, Br, I, —O − M + , wherein M + is a cation selected among H + , NH 4 + , K + , Li + , or Na + , and mixtures thereof; (M2) sulfonated perfluorovinylethers of formula (M2): wherein m is an integer between 1 and 10, and X′ is selected from the group consisting of Cl, Fl, Br, I, —O − M + , wherein M + is a cation selected among H + , NH 4 + , K + , Li + , or Na + , and mixtures thereof; (M3) sulfonated perfluoroalkoxyvinylethers of formula (M3): wherein w is an integer between 0 and 2, RF 1 and RF 2 , equal to or different from each other and at each occurrence, are independently —F, —Cl or a C 1-10 perfluoroalkyl group, optionally substituted with one or more ether oxygens, y is an integer between 0 and 6, and X′ is selected from the group consisting of Cl, Fl, Br, I, —O − M + , wherein M + is a cation selected among H + , NH 4 + , Li + , or Na + , and mixtures thereof; (M4) sulfonated aromatic (per)fluoroolefins of formula (M4): wherein Ar is a C 3-15 aromatic or heteroaromatic moiety, and X′ is selected from the group consisting of Cl, Fl, Br, I, —O − M + , wherein M + is a cation selected among H + , NH 4 + , K + , Li + , or Na + , and mixtures thereof; and (M5) mixtures thereof.