Ronald W Fox

US Patent:

43071350, Dec 22, 1981

Filed:

Apr 8, 1980

Appl. No.:

6/138397

Inventors:

Ronald L. Fox - San Diego CA

Assignee:

The United States of America as represented by the Secretary of the
Interior - Washington DC

International Classification:

B05D 310
B05D 500

US Classification:

427244

Abstract:

Asymmetric reverse osmosis membranes are made from synthetic aromatic polyimides having a relatively high predominance of polar groups in the polymer backbone. A polar/non-polar group ratio of from 2:2 to 2:7 per imidized nitrogen link is required. Such membranes can be fabricated using conventional casting equipment by providing a solution of the polyimide in a good solvent and a poor solvent, the poor solvent being compatible with solution components at poor solvent/good solvent ratios of at least 1:1 up to about 7:1, casting a film of such solution, and partially evaporating the exposed surface of the cast film for 100. +-. 30 seconds prior to gelation.

US Patent:

40269787, May 31, 1977

Filed:

Jul 17, 1975

Appl. No.:

5/596883

Inventors:

Charles R. Mungle - San Diego CA
Ronald L. Fox - San Diego CA

Assignee:

The United States of America as represented by the Secretary of the
Interior - Washington DC

International Classification:

B29D 2704
B29D 2720
B01D 3900

US Classification:

264 41

Abstract:

Asymmetric cellulose triacetate semipermeable membranes cast from a solution of cellulose triacetate having an acetyl content of at least 43 percent in a solvent mixture having a ratio of dioxane to acetone of at least about 1. 5 to 1, which solution also contains a swelling agent in the form of a low molecular weight alcohol or a low molecular weight mono- or poly-basic acid. Solvent is evaporated from one surface of the cast film to form a dense gel layer and the film is immersed in water to provide an asymmetric semipermeable membrane having a high salt-rejection capability and good flux.