Patent ID: 7666928

Claim:
A process for reducing fluorosurfactant content of a fluorosurfactant-containing aqueous fluoropolymer dispersion stabilized with nonionic surfactant comprising: reducing the fluorosurfactant content of said stabilized fluorosurfactant—containing aqueous fluoropolymer dispersion to provide a reduced surfactant dispersion; adding non-fluorinated anionic surfactant to said reduced fluorosurfactant dispersion; and concentrating said reduced fluorosurfactant dispersion by heating to a temperature within an operable temperature range for the nonionic surfactant at an operable surfactant level range which causes the dispersion to separate into upper and lower phases and recovering the lower phase as concentrated dispersion; a first portion of said non-fluorinated anionic surfactant being added to said dispersion prior to concentrating in an amount sufficient to increase said operable temperature range, said operable surfactant level range or both during concentration; and a second portion of said non-fluorinated anionic surfactant being added to said dispersion after said concentrating in an amount sufficient to control viscosity.