Patent ID: 8123945

Claim:
A method of producing a cellulose acetate polymer for high flux, high salt rejection cellulose acetate desalination membranes by removing rod-like impurities, said method comprising the steps of: (a) mixing cellulose acetate polymer in a first solvent to produce a slurry in a vessel; (b) stirring the slurry, and thereafter permitting the slurry to settle for a time sufficient for a majority of the cellulose acetate to precipitate out of solution to form a cellulose acetate precipitate in the vessel; (c) decanting off and discarding the solvent containing impure components so as to leave the cellulose acetate precipitate behind in the vessel; (d) stirring the cellulose acetate precipitate into an excess of a further solvent; (e) repeating steps (c) and (d) two to four times; (f) adding the cellulose acetate slurry into a second solvent that results in solvent exchange of the first solvent for the second solvent; and (g) evaporating the second solvent to leave cellulose acetate polymer.