Patent ID: 6939581

Claim:
An impregnation process of a porous support, formed by a polymer compound inert under use conditions, carried out by using colloidal dispersions in water of thermoplastic (per)fluorinated ionomeric polymers containing functional groups convertible into —SO 3 H, said aqueous dispersions of thermoplastic (per)fluorinated ionomeric polymers obtained by polymerization in emulsion of the following monomers: (A) one or more (per)fluorinated monomers, containing at least one ethylene unsaturation, (B) one or more (per)fluorinated comonomers containing functional groups convertible into the above acid groups, and (C) 0.01 to 5% by moles of a bis-olefin of formula (R 1 R 2 )C═CH—(CF 2 ) m —CH═C(R 5 R 6 ), (I) wherein; m is an integer from 2 to 10; R 1 , R 2 , R 5 , and R 6 are equal to or different from each other, and are H or C 1 -C 5 alkyl groups, said process comprising the following steps: 1) preparation of an aqueous colloidal dispersion of thermoplastic (per)fluorinated polymers by polymerization in emulsion of at least the following monomers: (A) one or more (per)fluorinated monomers, containing at least one ethylene unsaturation; (B) one or more (per)fluorinated comonomers containing functional groups convertible into the above acid groups; and (C) 0.01 to 5% by moles of a bis-olefin of formula; (R 1 R 2 )C═CH—(CF 2 ) m CH═C(R 5 R 6 ) (I) 2) a) concentration or dilution of the dispersion obtained in 1) having a solid content in the latex greater than 20% by weight; and b) optional addition of surfactants to obtain a dispersion surface tension lower than 40 mN/m; 3) impregnation of the porous support with the latex obtained in 2b); 4) thermal treatment at a temperature of 20° C. higher than the glass transition temperature of the thermoplastic ionomeric polymers and lower or equal to 200° C.; 5) a) ionomer crosslinking when the equivalent weight is lower than 650 g/eg, and b) conversion of the functional groups of the thermoplastic ionomeric polymers into the corresponding salts, by contacting the membrane with a basic aqueous solution, at temperatures comprised between 60° C. and the boiling temperature of the aqueous solution, and subsequent washings by immersion of the membrane in deionized water at room termperature, until obtaining an almost neutral pH of the washing waters; 6) optionally, membrane treatment by immersion at room temperature in an acid aqueous solution of an inorganic strong acid, and subsequent washings by immersion in deonized water up to an about neutral pH of the washing waters.