Gas separation membrane drying with water replacement liquid

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 water replacement liquid inert to the membrane and to the membrane-wetting liquid to remove water from the membrane, and removing the replacement liquid from the membrane; the improvement which comprises contacting said wet polymeric membrane in which the polymer has a Critical Surface Tension of at least about 42 dynes per centimeter, at a temperature of about from 0° to 50° C. with a water replacement liquid consisting essentially of at least one organic solvent which is selected from the group consisting of aliphatic alcohols having 4-8 carbon atoms, aliphtic aldehydes having 3-8 carbon atoms and aliphatic ketones having 3-8 carbon atoms, carboxylic acids, carboxylic esters having 4-8 carbon atoms, aliphatic nitriles, ethers, acetals, ketals, amines, halocarbons having 1-3 carbon atoms and containing at least one hydrogen atom, and aqueous solutions thereof, said solvent having a surface tension at 20° C. of not more than about 35 dynes per centimeter, a viscosity less than about 10 centipoise, a molar volume less than about 200 cubic centimeters per mole at 20° C, a solubility for water not greater than about 20 weight percent at the contacting temperature, and a hydrogen bonding parameter of at least about 1 (calorie per cubic centimeter) 1/2 ; 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.