Patent ID: 7297744

Claim:
A process for the preparation of pumpable fluoropolymer dispersions, free from anionic fluorinated surfactants, and with a coagulum amount <0.1% by weight referred to the polymer weight, comprising: a) step a1) adding: a nonionic surfactant having cloud point (CP) between 40° and 80° C., in an amount from 1.5% to 50% by weight on the dispersion fluoropolymer; and an electrolyte in an amount such to bring the specific conductivity of the dispersion, measured at 25° C., to values in the range 130-8,000 μS/cm; and optionally a buffer agent to have a pH between 2 and 12, to a fluoropolymer dispersion obtained by an emulsion polymerization process; step a2): heating of the dispersion obtained in step a1), under stirring, up to a temperature T c in the range CP±10° C., CP being the cloud point of the used nonionic surfactant; decanting without stirring, by operating at the temperature T c until obtaining the dispersion separation in the following aqueous phases: a lower phase wherein the concentrated fluoropolymer is in the range 40% 75% w/w, a surnatant phase not containing fluoropolymer; surnatant separation; discharge of the lower phase containing the concentrated fluoropolymer; b) step b1): adding to the discharged dispersion obtained in step a2), after surnatant separation: optionally, an electrolyte in an amount such to bring the specific conductivity of the dispersion, measured at 25° C., to values in the range 130-8,000 μS/cm; a nonionic surfactant having cloud point (CP) in the range 40°-80° C., and such to be present in the dispersion in an amount from 1.5% to 50% by weight on the dispersion fluoropolymer; optionally, a buffer agent to have a pH in the range 2-12; step b2): repeating the steps indicated in step a2); optionally c) step c1): repeating step b1) but using the dispersion obtained in step b2); step c2): repeating the steps indicated in step b2).