Defect-free ultrahigh flux asymmetric membranes
AssigneeBoard of Regents, The University of Texas System
InventorsIngo Pinnau, William J. Koros
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Abstract
Defect-free, ultrahigh flux integrally-skinned asymmetric membranes having extremely thin surface layers (<0.2 .mu.m) comprised of glassy polymers are disclosed. The membranes are formed by casting an appropriate drope followed by forced convective evaporation of solvent to obtain a dry phase separated asymmetrical structure. The structure is then washed in a precipitation liquid and dried.
Claims20
A method for producing integral-asymmetric membranes having a defect-free layer to separate fluid mixtures, said method comprising:
- forming a film or a fiber of a polymer solution;
- evaporating solvent from said film or fiber by forced convection to obtain a defect-free, phase separated asymmetrical structure;
- contacting said defect-free, phase separated asymmetrical structure with a precipitation liquid to obtain a final phase inverted asymmetrical structure by polymer precipitation;
- and
- drying said final phase inverted asymmetrical structure to obtain a membrane with an apparent skin thickness of less than about 0.2 micron and a selectivity for separating fluid mixtures greater than 80% of the theoretical value for defect-free films of said polymer.
An ultrahigh flux asymmetric membrane having an apparent skin thickness of less than about 0.2 micron and a selectivity for separating fluid mixtures greater than 80% of the theoretical value for defect-free films of said polymer, said membrane being prepared by:
- forming a film or a fiber of a polymer solution;
- evaporating solvent from said film or fiber by forced convection to obtain a defect-free, phase separated asymmetrical structure;
- contacting said defect-free, phase separated asymmetrical structure with a precipitation liquid to obtain a final phase inverted asymmetrical structure;
- and
- drying said final phase inverted asymmetrical structure to obtain a membrane with an apparent skin thickness of less than about 0.2 micron and a selectivity for separating fluid mixtures greater than 80% of the theoretical value for defect-free films of said polymer.
A method for producing integral-asymmetric membranes having a defect-free layer to separate fluid mixtures, said method comprising:
- forming a film or a fiber of a polymer solution, said solution including a primary solvent, a secondary solvent, and a non-solvent;
- evaporating solvent from said film or fiber by forced convection to obtain a defect-free, phase separated asymmetrical structure;
- contacting said defect-free, phase separated asymmetrical structure with a precipitation liquid to obtain a final phase inverted asymmetrical structure;
- and
- drying said final phase inverted asymmetrical structure to obtain a membrane with an apparent skin thickness of less than about 0.2 micron and a selectivity for separating fluid mixtures greater than 80% of the theoretical value for defect-free films of said polymer.
Dependencies are inferred from the claim text.