Hollow fiber membranes having a skinned surface on one diameter, and a porous
surface on the opposite diameter arm produced from perfluorinated thermoplastic
polymers by extruding a heated solution of the polymer having a lower critical
solution temperature directly into a cooling bath to form the porous membrane by
liquid-liquid phase separation. Extrusion can be conducted either vertically or
horizontally. The hollow fiber membranes are useful as ultrafiltration membranes
and as membrane contactors.
