Polysulfone porous membrane and a method of manufacturing the same

A polysulfone porous membrane comprising a mixed polymer consisting essentially of a polyarylsulfone having repeating units of the formula:

• and a polyethersulfone having repeating units of the formula:
• at a ratio of polyarylsulfone to polyethersulfone of from 9/1-1/9 by weight, said membrane being a graded porous membrane forming a mesh-like polymer network having a number of interconnected micropores from one surface to the other surface and comprising two layers wherein one layer is a dense layer having a plurality of pores with pore sizes of from 0.01 to 1 μm for performing a separation function, and a second layer is a supporting layer for supporting said dense layer and having a plurality of pores with pore sizes of from 1 to 100 μm, the sizes of said pores of the supporting layer increasing continuously from a side thereof nearest the dense layer toward a side opposite therefrom, said membrane being capable of separating particles having a size not larger than 0.5 μm, and wherein the water flux of the membrane measured under a difference of 2 Kg/cm2 is not lower than 7 L/m2.hr.mmHg.