Membrane drying process

Claim 1

In the process for drying a semipermeable polymeric membrane that is wet with an aqueous membrane-wetting liquid by contacting the wet membrane with at least one replacement liquid to remove water from the membrane, and removing the replacement liquid from the membrane; the improvement which comprises first contacting the wet semipermeable polymeric membrane in which the polymer has a Critical Surface Tension of at least 42 dynes per centimeter with at least one replacement liquid consisting essentially of a homogeneous solution of (a) a major portion of at least one organic solvent selected from the class consisting of hydrocarbons having 4-8 carbon atoms and perchlorofluorocarbons having 1-3 carbon atoms and (b) a minor portion of at least one organic solvent substantially miscible with water having a hydrogen bonding parameter of at least about 1.5 (calories per cubic centimeter) 1/2 , wherein the components of the replacement liquid each exhibit, at 20° C, a viscosity of less than about 10 centipoise and a molar volume of less than about 200 cubic centimeters per mole; and after water has been substantially completely removed from the membrane, evaporating the replacement liquid to obtain a membrane free of water and replacement liquid.