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Separation membrane and method of preparing and using same

  • US 4,527,999 A
  • Filed: 03/23/1984
  • Issued: 07/09/1985
  • Est. Priority Date: 03/23/1984
  • Status: Expired due to Fees
First Claim
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1. A process of preparing an asymmetric separation membrane suitable for use as a gas-permeation or reverse-osmosis separation membrane, which process comprises:

  • (a) treating a preformed dried leached high-flux, asymmetric, polymeric membrane, having a top skin surface with large pores of about 50 angstroms or more and an underlying bulk porous layer, with a posttreatment solution which comprises a volatile nonsolvent for the polymer of the membrane in the presence of a swelling agent for the polymer or a solvent for the polymer; and

    (b) drying the solution-treated, asymmetric membrane, while the membrane is under one-sided constraint, to provide for the evaoporating of the nonsolvent substantially through the top skin layer and for the differential collapsing of the pores of the top skin surface of the asymmetric membrane to a selected, smaller pore size of about 10 angstroms or less.

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