Patent ID: 9616393
Date: 2017-04-11
CPC Classifications: B01D

Claim:
1. A porous hollow fiber membrane for treating blood, comprising a polysulfone-based polymer and polyvinylpyrrolidone, and having a gradient porous structure in which a pore size of pores increases from an inside of the membrane toward an outside thereof in a membrane thickness direction, wherein a membrane thickness section of the porous structure has a membrane thickness of not less than 25 μm and less than 40 μm, and fibrils having a total-average thickness of 100 to 200 nm are arranged so that a ratio (To/Ti) of an average outside thickness (To) of the fibrils in a first intermediate region that is proximate an outer side of the membrane to an average inside thickness (Ti) of the fibrils in a second intermediate region that is proximate the inner side of the membrane, in the membrane thickness direction, is not less than 1 and not more than 2, the first intermediate region being spaced inwardly from the outer side of the membrane so as to be positioned within a central region of an outer portion of the membrane thickness section, the outer portion of the membrane thickness section being defined by a 15 μm width extending inwardly from the outer side of the membrane, the second intermediate region being spaced outwardly from the inner side of the membrane so as to be positioned within a central region of an inner portion of the membrane thickness section, the inner portion of the membrane thickness section being defined by a 15 μm width extending outwardly from the inner side of the membrane, wherein the membrane thickness direction, the membrane thickness section, the first intermediate region and the second intermediate region are each defined by a section taken perpendicular to a longitudinal direction of the porous hollow fiber membrane.