Patent ID: 7172075

Claim:
A defect free semipermeable composite membrane comprising: (i) a support layer which provides mechanical strength and is selected from the group consisting of extruded porous material, non woven material, woven material, braiding material, knitted material, any other rigid or flexible organic or inorganic permeable material, (ii) a middle layer bonded to the support layer which covers the rough surface and defects of the support layer, said layer selected from the group consisting of an epoxy, a polyurethane, a silicone, and a combination thereof and provides binding between said support and said barrier layers; and (iii) a barrier layer which provides selective separation, said barrier layer consisting of 8â€“55% by weight of at least one hydrophobic polymer and 1â€“50% by weight of at least one hydrophilic polymers, 1â€“50% by weight of at least one polymer particle as an additive, 1â€“30% by weight of other organic and inorganic additives, and the remaining % by weight solvent, wherein the at least one polymeric particle has a particle size from 0.2 nm to 500 Î¼m, and is selected from the group consisting of cross-linked polyvinylpyrrolidone, poly(acrylonitrile-co-methacrylonitrile), crosslinked polystyrene, polyethylene, polypropylene, crosslinked sulfonated polystyrene, crosslinked poly(4-trimethylamino chloride styrene), crosslinked polyethylenimine, crosslinked poly(4-vinylpyridine), poly(4-vinylpyridine) cross-linked, methyl chloride quaternary salt, crosslinked cellulose acetate, crosslinked anion exchange resin, cation exchange resin, crosslinked sulfonated polysulfone and polyethersulfones and combinations thereof.