Patent ID: 7217742

Claim:
A process for preparing sulphonic fluorinated ionomers comprising radical crosslinking of: A) crosslinkable sulphonic fluorinated ionomers, having equivalent weight 380–1300 g/eq and comprising: from 48% to 85% by moles of monomeric units deriving from tetrafluoroethylene (TFE); from 15% to 47% by moles of fluorinated monomeric units containing sulphonyl groups —SO 2 F; from 0.01% to 5% by moles of monomeric units deriving from a bis-olefin of formula: wherein: m=2–10; R 1 , R 2 , R 5 , R 6 , equal to or different from each other, are H or C 1–C 5 alkyl groups; B) a fluorinated compound as crosslinking radical initiator; C) a fluorinated bis-olefin of structure (I) as cross-linking agent; wherein the radical crosslinking is carried out at a temperature in the range of 250° C.–310° C.