Composite ionomeric membrane

摘要

A composite ionomeric membrane comprising a layer or film of a porous inert material on which a (per) fluorinated sulphonic ionomer is deposited wherein the sulphonic groups are at the end of short side chains (SSC), said ionomer having:
equivalent weight comprised between 280 and 1,700 g/eq;side chains of formula: —O—CF2—CF2—S03−M+, wherein M is hydrogen or an alkaline metal;

said membrane having in each of the two orthogonal directions xy of the plane, after dipping in demineralized water at 100° C. for 30 minutes and preliminary drying at 105° C. under vacuum for one hour, the following size variations:
in one direction, size variation lower than 25%;in the other direction, size variation lower than 20%.

主权项

1. A process for preparing a composite membrane comprising the following steps:
1) preparing a liquid dispersion, the liquid dispersion comprising a solvent and a (per) fluorinated ionomer, in acid or salified form, wherein the ionomer concentration is between 0.5% and 40% by weight; 2) depositing the dispersion obtained in 1) on the surfaces of a porous first support and removing excess dispersion to obtain a film or layer, of impregnated porous material; 3) applying a non-porous second support which is inert under the conditions of the process to one side of the film or layer of the impregnated porous material; 3a) optionally removing the solvent from the film or layer of the impregnated porous material positioned on the non-porous second support; 4) annealing the film or layer of impregnated porous material as applied to the non-porous second support at temperatures from 130° to 280° C.; and 5) detaching the film or layer of impregnated porous material from the non-porous second support to obtain a membrane.