Abstract: A process for chlorinating a compound of the formula ##STR1## in which R.sup.1 is a C.sub.1 -alkyl radical, C.sub.1 -alkoxy radical or C.sub.1 -thioalkyl radical, andX.sup.1, X.sup.2, X.sup.3 and X.sup.4 are identical or different hydrogen or halogen, andX.sup.3 may alternatively be ##STR2## or --NCO, comprising, in an initial phase, dissolving a chlorination catalyst in the compound to be chlorinated, continuously metering this solution together with chlorine into a reaction vessel containing the compound to be chlorinated, and, after the initial phase, removing partially or fully chlorinated compounds from the reaction vessel, dissolving fresh chlorination catalyst in the removed compounds, and feeding this catalyst solution, together with chlorine, to the reaction vessel.

Abstract: The present invention relates to a process for preparation of a highly fluorinated polymer by converting a polymer containing the recurring unit R--S'--X.sub.m, in which R denotes a base unit forming the matrix, X denotes identical or different functional groups, with the exception of halogen, and S' is an aromatic or araliphatic radical with m+1 free valencies, m being at least 1, into a highly fluorinated polymer by fluorination with elementary fluorine. The process is particularly useful for the preparation of cation exchangers, such as those which contain the unit ##STR1## in which C.sub.6 F.sub.10 represents a perfluorinated cyclohexyl ring.