Process for preparing fluoropolymer dispersions

A process to remove fluorinated anionic surfactants from fluoropolymer dispersions comprising the following steps:

• a) addition to the fluoropolymer dispersion of one or more non fluorinated anionic surfactants;
• b) contact of the dispersion with an anionic exchanger;
• c) separation of the dispersion from the anionic exchanger and recovery of the dispersion fluorinated anionic surfactant free,
• wherein in step a), the non fluorinated anionic surfactant is added in an amount from 1% to 10% by weight based on the fluoropolymer dispersion weight, and
• wherein the non fluorinated anionic surfactants are selected from the group consisting of:
• surfactants having the following general formula:
• Y′—(P1)n—CH(Y)—(P2)n′—Y″ (1),
• wherein Y, Y′ and Y″ are anionic or nonionic groups, with the proviso that at least one of Y, Y′ or Y″ is an anionic group and at least one of the remaining of Y, Y′ or Y″ is a nonionic group, P1 and P2, equal or different, are linear or branched, when possible, alkylene groups, optionally containing one or more unsaturations, when possible, having a number of carbon atoms from 1 to 10, and n and n′, equal or different, are zero or 1;
• and
• surfactants having the following general formula:
• T-(O)n6—[(CH2)n3—CH2CH2O]n4—(CH2)n5—X (2),
• wherein T=C4-18 alkyl, or aryl wherein one or more hydrogen atoms are substituted with C4-18 aliphatic chains, n3 and n6, equal to or different from each other, are integers equal to 0 or 1, n4 is an integer from 0 to 50, n5 is an integer from 0 to 10, and X is an anionic group selected from COO−, SO3−, with the proviso that when n5=0, X=SO3−.