Patent ID: 7048855

Claim:
A method for making a semipermeable polymeric membrane of sheet formation integrally bonded to a polymeric fibrous support which allows excellent permeate flow in the plane thereof and thus finds use in cross flow filtration, which method comprises: providing a fibrous support having a thickness of between about 0.4 mm and about 2 mm and of similar properties throughout, treating an upper surface of said fibrous support to change its character and create an upper surface support region of a different character between about 1 micron and 0.3 mm thick and having a mean pore size of between about 1 micron to 300 microns by melt-blowing particles of polymer thereonto or by wet-laying a layer of polymeric fibers thereonto, casting a layer of a liquid solution containing a membrane-forming polymer in a solvent onto said upper surface of said fibrous support, and removing said solvent to gel said layer and form a semipermeable membrane, whereby the resultant arrangement of a semipermeable membrane integrally bonded to a fibrous support exhibits sufficiently low resistance to liquid flow in the plane thereof to allow its use in membrane cartridges for cross flow filtration without association with an auxiliary permeate carrier.