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Polyamide membrane with controlled surface properties

  • US 4,707,266 A
  • Filed: 04/07/1986
  • Issued: 11/17/1987
  • Est. Priority Date: 02/05/1982
  • Status: Expired due to Term
First Claim
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1. A process for preparing a surface modified, skinless, hydrophilic, microporous, alcohol-insoluble polyamide membrane with controlled pore surface properties, capable of reacting or interacting in a controlled manner with (a) particulate matter in a fluid, (b) non-particulate matter in a fluid, or (c) both (a) and (b) and that is readily wetted by water, which comprises:

  • (1) preparing a casting solution comprised of (A) a casting resin system comprised of (a) an alcohol-insoluble polyamide resin having a ratio CH2 ;

    NHCO of methylene CH2 to amide NHCO groups within the range of from about 5;

    1 to about 7;

    1, and (b) a water-soluble, membrane surface modifying polymer having functional polar groups selected from the group consisting of hydroxyl, carboxyl, and amino or a non-reacting combination thereof, and a molecular weight of 20,000 or greater, and (B) a solvent system in which said casting resin system is soluble;

    (2) inducing nucleation of said casting solution by controlled addition of nonsolvent for said casting resin system under controlled conditions of concentration, temperature, addition rate and degree of agitation to obtain a visible precipitate of casting resin system particles, thereby forming a casting composition;

    (3) spreading said casting composition on a substrate to form a thin film thereof on the substrate;

    (4) contacting and diluting the film of said casting composition with a liquid nonsolvent system for said casting resin system comprised of a mixture of solvent and nonsolvent liquids, thereby precipitating said casting resin system from said casting composition in the form of a thin, skinless, hydrophilic, surface modified, microporous, polyamide membrane with controlled surface properties;

    (5) washing said membrane to remove solvent; and

    (6) drying said membrane.

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