are hereby incorporated by reference herein asymmetric hollow fiber membrane of p84 was spun from a solution of 32 p84 9 6 tetramethylenesulfone and 1 6 acetic anhydride in n methylpyrrolidinone nmp with methods and equipment as described in u s pat nos 5 034 024 and 5 015 270 the nascent filament was extruded at a rate of 180 cm 3 hr through a spinneret with fiber channel dimensions of outer diameter 559 u03bcm and inner diameter equal to 254 u03bcm at 75 u00b0 c a fluid containing 85 nmp in water was injected into the bore of the fiber at a rate of 33 cm 3 hr the nascent fiber traveled through an air gap of 5 cm at room temperature into a water coagulant bath at 24 u00b0 c and the fiber was wound up at a rate of 52 m min the water wet fiber was washed with running water at 50 u00b0 c to remove residual solvent for about 12 hours and then sequentially exchanged with methanol and hexane as taught in u s pat nos 4 080 744 and 4 120 098 followed by vacuum drying at room temperature for 30 minutes after that the fibers were dried at 100 u00b0 c for one hour samples of fiber were formed into four test membrane modules of 52 fibers each the fiber in the modules was treated to seal defects in the separating layer with a method similar to the method described in u s pat no.