Interfacially synthesized reverse osmosis membrane

A sheet-like composite material comprising a microporous support layer, and, polymerized in situ thereon, a crosslinked, water permeable, interfacially polymerized polyamide desalinizing membrane comprising the interfacial condensation product of the components consisting essentially of:

• Ar(COX).sub.3, (a)
• wherein Ar represents a carbocyclic, monocyclic aromatic nucleus free of any amide-forming groups other than the COX group, and X represents halogen of atomic weight less than 130;
• up to about 50% by weight of said Ar(COX).sub.3 being replaceable with the compound Ar(COX).sub.2, wherein Ar and X are as defined previously;
• Ar'(NH.sub.2).sub.2, (b)
• wherein Ar' represents a carbocyclic, monocyclic aromatic nucleus free of any acyl halide-reactive groups other than the primary amine substituents;
• said interfacial reaction product having a crosslink density in excess of one per 100,000 polymer molecular weight, being substantially insoluble in organic liquid amide, sulfoxide, and pyrrolidone solvents and solvent blends, and having a salt rejection capability, tested with simulated seawater under 40 to 70 atmospheres pressure and 25.degree. C., of at least about 95 at 600 l/m.sup.2 d flux.

A process for the preparation of a composite reverse osmosis membrane comprising the steps of:

• (a) coating a porous support with a liquid layer comprising an aqueous solution containing, dissolved therein, an essentially monomeric, aromatic polyamine reactant having at least two primary amine substituents substituted on an aromatic nucleus comprising less than 3 aromatic rings;
• said aromatic polyamine reactant having a solubility in water of at least 0.01% by weight and being free of substituents capable of chemical interference with amide-forming reactions;
• (b) contacting the said liquid layer with an essentially monomeric, armoatic, amine-reactive reactant comprising a volatilizable polyfunctional acyl halide, said polyfunctional acyl halide being selected such that the primary amine functionality of said aromatic polyamine reactant is no more than the carboxylic acid equivalent functionality of said polyfunctional acyl halide;
• the amine-reactive acyl halide groups of said polyfunctional acyl halide being capable of condensing with primary amine functional groups to form amide linkages in less than 60 seconds under normal ambient temperature and pressure;
• the aromatic nucleus of said acyl halide comprising less than 3 aromatic rings;
• said amine-reactive reactant being at least 0.01 weight percent soluble in liquid aliphatic or liquid halogenated aliphatic solvents;
• said aromatic nucleus of said polyfunctional acyl halide being free of substituents capable of chemical interference with intermolecular amide-forming condensation reactions;
• thereby interfacially condensing said amine-reactive reactant with said polyamine reactant, for an effective amount of interfacial condensation reaction time ranging up to about 60 seconds, until a crosslinked, interfacial polyamide layer has been formed, said polyamide having a plurality of sites having the formula Ar(CONH--).sub.2 COOH, wherein Ar represents the aromatic nucleus of the polyfunctional acyl halide;
• and said polyamide having a solubility of less than 10% by weight in liquid organic amide, sulfoxide, and pyrrolidone solvents or solvent blends;
• and
• (c) drying the product of step (b) to form a composite reverse osmosis membrane having a salt rejection capability, tested with simulated sea water under 40 to 70 atmospheres pressure and 25.degree. C., of at least 85% at a flux of at least about 400 l/m.sup.2 d.