Patent ID: 7304101

Claim:
A method of purifying a dispersion of ionic fluoropolymer comprising: providing a dispersion of ionic fluoropolymer in an aqueous medium, the ionic fluoropolymer comprising ionic monomeric units and non-ionic monomeric units, wherein the ionic monomeric units have at least one group represented by the formula —R 1 SO 3 − , wherein R 1 is a perfluoroalkylene group having from 1 to 15 carbon atoms, or a perfluoroalkyleneoxy or perfluoropoly(alkyleneoxy) group having from 1 to 15 carbon atoms and from 1 to 4 oxygen atoms, wherein the ionic fluoropolymer has an sulfonate equivalent weight in the range of from at least 600 grams up to and including 1200 grams, and wherein the dispersion of ionic fluoropolymer contains anionic species that are not covalently bound to the ionic fluoropolymer; contacting the dispersion of ionic fluoropolymer with an anion exchange resin having associated hydroxide ions, such that a portion of said anionic species are exchanged with hydroxide ions to provide an anion-exchanged dispersion; and separating the anion-exchanged dispersion from the anion exchange resin, wherein the anion-exchanged dispersion comprises ionic fluoropolymer, wherein the dispersion of ionic fluoropolymer contains less than 0.001 weight percent of nonionic emulsifier based on the total weight of ionic fluoropolymer.