Preparation of asymmetric membranes by the solvent extraction of polymer components from polymer blends
AssigneeThe Dow Chemical Company
InventorsChieh-Chun Chau, Ritchie A. Wessling
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Abstract
Asymmetric membranes are prepared by selectively treating a major surface of an incompatible polymer blend prepared by melt blending having at least one extractable polymer component and then contacting the polymer blend with a solvent to extract the extractable polymer component. The treated surface becomes the dense layer of the membrane. The major surface is treated by crosslinking, by contacting the surface with a crosslinking agent which is subsequently cured, or by contacting the surface with an agent which reacts with groups on the surface and imparts a polar character to it.
Claims20
A method of preparing an asymmetric membrane comprising the steps of:
- (a) selectively treating a major surface of a premembrane structure formed of a nonporous, incompatible polymer blend prepared by melt blending having at least one extractable polymer component, so as to render the surface resistant to solvent extraction;
- and then p1 (b) contacting the treated premembrane structure with a solvent to substantially extract the extractable polymer component to at least a preselected depth relative to a nontreated major surface of the polymer blend.
Dependencies are inferred from the claim text.