Asymmetric hollow fiber gas separation membrane

1. An asymmetric hollow fiber membrane for gas separation made of a soluble aromatic polyimide, wherein

an orientation index is 1.3 or less,

a separation coefficient α(P′O 2 /P′N 2 ) which represents a ratio of permeation rate of oxygen gas and nitrogen gas at 40° C. is 5.3 or more, and

a tensile elongation at break is 15% or more.

2. The asymmetric hollow fiber membrane for gas separation according to claim 1 , wherein an oxygen gas permeation rate P′O 2 at 40° C. is 6.0×10 −5 cm 3 (STP)/cm 2 ·sec·cmHg or more.

3. The asymmetric hollow fiber membrane for gas separation according to claim 1 , wherein the soluble aromatic polyimide comprises a repeating unit represented by general formula (1):

wherein in the general formula (1), 25 to 100 mol % of A is a tetravalent unit based on a biphenyl structure represented by formula (2):

to 70 mol % of A is a tetravalent unit based on a diphenylhexafluoropropane structure represented by formula (3):

and 0 to 30 mol % of A is a tetravalent unit based on a phenyl structure represented by formula (4):

and in general formula (1), 30 to 70 mol % of R is a divalent unit based on a diphenylene sulfone structure represented by formula (5):

wherein R1 and R2 in formula (5) are a hydrogen atom or a lower alkyl group, and

30 to 70 mol % of R is a divalent unit based on a biphenyl structure represented by formula (6):

wherein X in formula (6) is a chlorine or bromine atom and n is 1 to 3.

4. A process comprising selectively separating and collecting a particular gas from a mixed gas containing a plurality of gases with the asymmetric hollow fiber membrane for gas separation according to claim 1 .

5. A process comprising producing an oxygen-rich air or nitrogen-rich air from the air with the asymmetric hollow fiber membrane for gas separation according to claim 1 .