Patent ID: 7641974

Claim:
A method for the preparation of paints for substrate coatings, comprising using aqueous dispersions of VDF-based polymers having an average particle size between 0.260 and 0.3 micrometers obtained by VDF emulsion polymerization, in the presence of a bifunctional surfactant of formula: A—R f —B (I) wherein A=—O—CFX—COOM; B=—CFX—COOM X=F, CF 3 ; M =NH 4 , alkaline metal, H; R f is: a linear or branched perfluoroalkyl chain; or a (per) fluoropolyether chain, wherein the amount of bifunctional surfactant is in the range of 0.01 to 3% by weight with respect to the VDF-based polymers and the number average molecular weight of the bifunctional surfactant of formula (I) is in the range of 600-800, and optionally in the presence of one or more fluorinated comonomers, wherein said dispersion contains other fluorinated surfactants which differ from those of formula (I) in amounts not higher than 20% by weight with respect to the total amount of surfactant of formula (I).