US Patent 7931154 Plasma separation membrane

A process for manufacturing of an asymmetric hollow fiber membrane, comprising the steps of extruding a polymer solution through the outer ring slit of a hollow fiber spinning nozzle, simultaneously extruding a center fluid through the inner bore of the hollow fiber spinning nozzle, into a precipitation bath, whereby the polymer solution contains 10 to 26 wt-% of polysulfone (PSU), polyethersulfone (PES) or polyarylethersulfone (PAES), 8 to 15 wt-% polyvinylpyrrolidone (PVP) and 60 to 80 wt-% N-alkyl-2-pyrrolidone (NAP), the center fluid contains 60 to 70 wt-% N-alkyl-2-pyrrolidone (NAP) and 30 to 40 wt-% water, and the precipitation bath contains 70 to 82 wt-% N-alkyl-2-pyrrolidone (NAP) and 18 to 30 wt-% water.