Patent ID: 7837042

Claim:
A hollow fiber membrane module comprising polysulfone type selectively permeable hollow fiber membranes which contain a polysulfone -based resin and a hydrophilic polymer as main components, wherein (A) the content of the hydrophilic polymer in the uppermost layer of the inner surface of said hollow fiber membrane is at least 1.1 times larger than the content of the hydrophilic polymer in the proximate layer of the inner surface of said hollow fiber membrane, (B) the content of the hydrophilic polymer in the uppermost layer of the outer surface of said hollow fiber membrane is at least 1.1 times larger than the content of the hydrophilic polymer in the uppermost layer of the inner surface of said hollow fiber membrane, and (C) said hollow fiber membrane module is exposed to a radioactive ray while said hollow fiber membrane module is sealed in a packaging bag, on condition that the oxygen concentration of an ambient atmosphere within the packaging bag around said hollow fiber membrane is from 0.001 to 0.1%, and that the moisture content of said hollow fiber membrane to the weight thereof is from 0.2 to 7 mass %, wherein the uppermost layer of the inner surface of said hollow fiber membrane is a layer having a depth of up to 10 nm from the inner surface of the hollow fiber membrane, and the proximate layer of the inner surface of said hollow fiber membrane is a layer having a depth of from 1,000 to 1,500 nm from the inner surface of the hollow fiber membrane.