| 摘要 |
TITLE A METHOD OF CASTING A POROUS MEMBRANE OF POLYMERIC MATERIAL INVENTORS Thomas A. Tweddle Oleh Kutowy André Tremblay A method of casting porous membranes of polymeric material is provided wherein the membrane has at least one of the following: a more homogeneous active skin layer for separation purposes with a lower molecular weight cut off, a more homogenous active skin layer with a sharper molecular weight cut off curve, a relatively thinner active skin layer with a relatively greater flux for a given separation of a substance from a solution thereof, and relatively fewer imperfections throughout the active skin layer. The method comprises casting a layer of a casting solution (e.g. polysulfone in N-methyl pyrrolidinone) on to a support, to provide a cast layer of the casting solution thereon with an exposed skin, then progressively submerging the cast layer in a gelation liquid (iced water) at a relative velocity of at least 15 cm/second, whereby the exposed skin is gently scrubbed with gelation liquid to continuously remove outwardly diffusing solvent therefrom and dissipate exothermic heat, thus causing gelation of at least a stable, more homogeneous active skin layer, with build-up of a solvent boundary layer between the exposed surface of the layer and the gelation liquid minimized. |
