Composite membranes based on interpenetrating polymer networks

Claim 1

A composite semipermeable membrane which comprises an interpenetrating polymer network of: (1) an isocyanate-capped polyether component which is obtained by reacting a polyether with an isocyanate, said isocyanate-capped polyether being physically entwined with (2) a heterocyclic nitrogen-containing component selected from the group consisting of polyvinylpyridine and mixtures of polyvinylpyridine and poly(N-vinylpyrrolidone) wherein the ratio by weight of polyvinylpyridine to poly(N-vinylpyrrolidone) ranges from about 1:1 to 4:1, said interpenetrating polymer network being supported on a porous backing support material; and (3) said component (1) being physically entwined with component (2) by means of a substituted polyurea, said polyurea being formed by curing of said membrane at a temperature in the range of from about ambient to about 100° C. in an atmosphere which possesses a relative humidity in the range of from about 20% to about 100% for a period of time sufficient to generate an amine-capped polymer by hydrolysis of a portion of said isocyanate-capped polyether, with said amine-capped polymer subsequently reacting with a portion of isocyanate groups present in said membrane to form a substituted polyurea which serves to physically entwine said component (2) in said membrane.