Patent ID: 6264044
Filing Date: 2001-07-24
Classification: B01D,B32B,D06N

Abstract:
A three zone, reinforced, continuous, geometrically symmetrical, microporous membrane prepared by a process comprising the acts of:providing a porous support material;providing first, second, and third polymeric dopes, the first dope being formulated to produce a quenched polymeric layer having a pore size which differs from quenched layer pore sizes obtained from at least one of the second and third dopes;substantially impregnating the porous support material with the first polymeric dope;coating the second dope over a first side of the impregnated porous support material such that the first and second dopes intermingle at an interface between the first and second dopes;coating the third dope over a second side of the impregnated porous support material such that the first and third dopes intermingle at an interface between the dopes; andquenching the coated substantially impregnated support material thereby forming the reinforced, continuous, geometrically symmetrical three-zoned microporous membrane, the microporous membrane comprising:a middle membrane zone having a first pore size, the middle zone comprising the porous support material and a microporous polymer derived from quenching the first polymeric dope;a second membrane zone having a second pore size, the second zone comprising a microporous polymer derived from quenching the second polymeric dope upon the first side of the substantially impregnated porous support material; anda third membrane zone having a third pore size, the third zone comprising a microporous polymer derived from quenching the third polymeric dope upon the second side of the impregnated porous support material, wherein the first pore size being at least about 20% greater than at least one of the second and the third pore size.