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Abstract

A composite membrane which is substantially insoluble (and preferably swells no more than 10%) in acetonitrile, ethanol, hexane, toluene, N-methylpyrrolidone, dimethylsulfoxide, dimethylformamide, dimethylacetamide, and their mixtures with each other and/or with water, comprises a substrate made from copolymers or homopolymers of ethylenically unsaturated nitriles, the substrate having been subjected to the steps of: (1) insolubilizing the polymer by crosslinking; (2) coating with a silicone layer; and (3) crosslinking the silicone layer. Prior to step (2), the substrate is preferably treated with a pore protector in absence of curing agents and catalysts. The pore protector is e.g. a hydroxy-terminated polysiloxane, particularly a silanol-terminated polysiloxane; it prevents the pores from collapsing, when the support is dried during step (3), and prevents passage of the coating material deeply into the pores, thus also preventing an undue reduction of the flux of the finished membrane.

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First Claim