GB746616A - Sulphonation method - Google Patents

Abstract

A benzene-soluble thermoplastic alkenyl aromatic resin is sulphonated by reacting with sulphuric trioxide at temperatures between - 20 DEG and 40 DEG C. while dissolved in a liquid mixture of from 20 to 80 per cent by weight of sulphur dioxide and from 80 to 20 per cent by weight of at least one polychlorinated aliphatic hydrocarbon selected from methylene and ethylene chlorides, carbon tetrachloride, tetrachloroethylene and methylchloroform. Polymers of styrene, a -methyl and ar-methyl styrenes, ar-dimethyl and ar-methyl-a -methyl styrenes and ar-chlorostyrenes and copolymers thereof with up to 10 per cent by weight of butenes, di-isobutylene, or pentenes may be used. In the sulphonation, which may be continuous or batchwise, the resin solution, which may contain 5 per cent by weight or less of the resin, is stirred, preferably at - 15 DEG to 0 DEG C., while a 5 per cent or less solution of sulphur trioxide in a similar solvent is added and the reaction carried out under a pressure sufficient to maintain the liquid state. The sulphonated resin precipitates in granular form, is washed, e.g. with diethyl ether and filtered, or obtained as the sodium salt by the addition of sodium hydroxide.