Patent ID: 7165682

Claim:
A defect free semipermeable composite membrane having a burst pressure of 10 to 500 psi and a pure water permeability of 1–500 gfd/psi 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, braided 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 middle 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 and coats the middle layer to provide a defect free membrane, said barrier layer consisting of 8–60% of at least one hydrophobic polymer, 1–40% of at least one hydrophilic polymer, 1–20% of an inorganic additive, 1–20% percent other organic additive, and solvent, wherein the middle layer provides binding between the support layer and the barrier layer.