Patent ID: 8225941
Filing Date: 2012-07-24
Classification: B01D,C02F

Abstract:
1. A hollow fiber membrane for treating liquids, wherein the hollow fiber membrane comprises a polysulfone-based polymer and polyvinylpyrrolidone, and has a structure such that: (a) dense layers are formed on the inner and outer surfaces; (b) a pore diameter in the vicinity of the inner surface is smaller than a pore diameter in the vicinity of the outer surface; and (c) a porosity of the hollow fiber membrane increases from the inner surface toward a portion between the inner surface and the outer surface, the porosity being maximum at said portion and thereafter decreasing toward the outer surface, wherein the porosity at the inner surface is less than the porosity at the outer surface, and wherein a ratio of Flux 120 to Flux 30 is 0.45 or higher when filtration is performed by supplying a solution having a turbidity of 20 NTU into a hollow fiber membrane having an internal diameter of 500 to 1500 μm and a membrane thickness of 100 to 500 μm with a transmembrane pressure of 1.5 bar, the Flux 30 being flux 30 minutes after the start of the filtration, and the Flux 120 being flux 120 minutes after the start of the filtration.