Patent ID: 7562778

Claim:
A composite porous membrane comprising a braid and a membrane material, wherein: the membrane material comprises a first porous layer having an inner surface, an outer surface, and a first thickness, and a second porous layer having an inner surface, an outer surface, and a second thickness, wherein the first porous layer is arranged on the outer surface of the braid and the second porous layer is arranged on the first porous layer, the first porous layer including a first dense layer with a thickness less than the first thickness, said first dense layer having an average pore diameter in the range of from 0.2 μm to 1 μm, and the second porous layer including a second dense layer with a thickness less than the second thickness, said second dense layer having an average pore diameter in a range of from 0.1 μm to 0.8 μm, and the inner surface of the second porous layer has about 1% to about 50% adhesion to the outer surface of the first porous layer, wherein said membrane has at least one of first and second dense layers located 0.1-50 μm inside from the outer surface of its respective porous layer.