| abstract |
(57) [Summary] [Structure] The cross-section of a hollow fiber membrane with a membrane thickness of 50 to 500 µm has a three-dimensional mesh-like porous portion with an average pore diameter of 0.05 to 1 µm and a size of 10 to 200 µm. The void area of the membrane is in the range of 5 to 70% with respect to the total cross-sectional area of the membrane, and the inner and outer surfaces of the hollow fiber membrane have irregular or circular micropores. The three-dimensional mesh-like porous portion of the cross section of the membrane is 50% of the total thickness from the inner and outer surfaces of the hollow fiber membrane. 40 to 80 in all ranges except the one-to-one portion %, The molecular weight cutoff is in the range of 10,000 to 500,000, the tensile strength at break of the membrane is 30 kg / cm 2 or more, and the transmembrane differential pressure is 1 kg / cm 2 , A cellulose acetate hollow fiber separation membrane having a permeation rate of pure water of at least 500 liters / (m 2 · hr) at a temperature of 25 ° C and a method for producing the same. [Effect] A hollow fiber separation membrane can be obtained which can maintain a high filtration rate for a long period of time even under a low filtration pressure. |