Process for the preparation of aromatic (di)chlorosulphonic acids and (di)bromosulphonic acids

A process for the preparation of an aromatic (di)chlorosulphonic acid or (di)bromosulphonic acid by reacting an aromatic sulphonic acid with a halogenating agent selected from the group consisting of chlorine and bromine, said chlorine and bromine being in elemental form or in the form of a compound which releases chlorine or bromine under the process conditions, wherein the reaction is carried out without the use of a catalyst and in a melt, consisting essentially of the aromatic sulphonic acid at a temperature of 40.degree.-200.degree. C.,

• wherein the aromatic sulphonic acid reacted is an aromatic sulphonic acid or mixture of aromatic sulphonic acids of the formula ##STR4## in which R.sub.1 denotes hydrogen, straight-chain or branched C.sub.1 -C.sub.20 -alkyl, C.sub.3 -C.sub.8 -cycloalkyl, benzyl, substituted benzyl, phenyl, substituted phenyl, straight-chain or branched C.sub.1 -C.sub.20 -alkoxy, benzyloxy, substituted benzyloxy, phenoxy, substituted phenoxy, nitro or cyano,
• R.sub.2 represents hydrogen, methyl or ethyl and
• R.sub.3 represents hydrogen, methyl, ethyl, fluorine, chlorine or bromine, where furthermore R.sub.1 and R.sub.2 together can denote a fused benzene ring or substituted benzene ring, a fused aromatic or non-aromatic 5- or 6-membered heterocycle, or trimethylene or tetramethylene.