Aqueous emulsion polymerization process for producing fluoropolymers

Method of making a fluoropolymer through emulsion polymerization of one or more fluorinated monomers in an aqueous phase comprising adding to the aqueous phase a fluorinated surfactant having the formula:

• Y—Rf-Z-M
• wherein Y represents hydrogen, Cl or F;
• Rf represents a linear or branched perfluorinated alkylene having 4 to 10 carbon atoms;
• Z represents COO− or SO3− and M represents a monovalent cation;
• characterized in that at least part of said fluorinated surfactant is added to the aqueous phase as an aqueous mixture with at least one organic liquid that is not miscible with water and that is a perfluorinated or partially fluorinated aliphatic or aromatic organic liquid that contains up to a total of 12 oxygen, sulphur and/or nitrogen atoms per molecule, said aqueous mixture having droplets having an average droplet diameter of not more than 1000 nm and said mixture being added to the aqueous phase in such an amount that the total amount of said fluorinated surfactant is not more than 1% by weight unused on the weight of the aqueous phase and the total amount of said organic liquid is not more than 1% by weight based on the weight of said aqueous phase.