Amine monomers and their use in preparing interfacially synthesized membranes for reverse osmosis and nanofiltration

Water permeable reverse osmosis membranes are prepared by interfacially polymerizing on a microporous support an essentially monomeric polyamine reactant having at least two amine functional groups per reactant molecule, and an essentially monomeric amine-reactive polyfunctional aromatic or cycloaliphatic acyl halide having on the average at least about 2 acyl halide groups per reactant molecule. The polymerization is optionally carried out in the presence of a monomeric amine salt, which increases the flux rate of the resulting membrane. Preferred polyamine compounds of the generic formula, which are novel per se, include 3,5-diaminobenzoyl piperazine, 4-aminobenzoyl piperazine, 3-aminobenzoyl piperazine, isophthaloyl piperazine, and terephthaloyl piperazine.