Fluorinated copolymers for oil and water repellency treatment of various substrates

To improve the barrier effect to the grease of cationic fluorocopolymers of patent EP 542 598 resulting from the copolymerisation of at least a polyfluoromonomer, of at least an aminoalcohol (meth)acrylate and at least a vinyl monomer (in particular vinyl acetate), it is subjected to the action of hydrogen peroxide during the salification step or after it.