Patent ID: 8840791

Claim:
A microfiltration membrane comprising (a) an asymmetric polymeric layer, (b) an isometric polymeric layer, and (c) a polymeric interface layer between the asymmetric layer and the isometric layer, the interface layer having a first portion contacting the asymmetric layer and a second portion contacting the isometric layer; wherein the membrane has a total membrane thickness; and, (i) the asymmetric layer has a region contacting the first portion of the interface layer, the region including cells having a first pore diameter; (ii) the isometric layer has a region contacting the second portion of the interface layer, the region including cells having a second pore diameter; the first pore diameter being larger than the second pore diameter; and the first portion of the interface layer comprises cells having the first pore diameter, and the second portion of the interface layer comprises cells having the second pore diameter, wherein each of the portions of the interface layer has a mixture of the cells having a first pore diameter and the cells having a second pore diameter; and, wherein the interface layer has a thickness in the range of from about 15% to about 33% of the total membrane thickness.