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Abstract

Hitherto processes proposed in recent years for preparing esters of phenol sulphonate salts by reaction between a carboxylic acid chloride and a phenol sulphonate salt place considerable emphasis upon dehydrating the reactants before they are brought into contact in an organic solvent reaction medium. The present invention avoids the problems of employing non-aqueous solvents by carrying out the reaction under aqueous conditions but with controlled alkalinity and water content, especially at a base to phenol sulphonate mole ratio of from 1.3:1 to 1.6:1 and a total water to phenol sulphonate (as the anhydrous material) of not more than 4.5:1. The reaction advantageously employs in preference only a small molar excess of carboxylic acid chloride over the phenol sulphonate and preferably has a reaction temperature controlled to below 30.degree. C., expecially 5.degree. to 20.degree. C. In a further improvement to the process, the difficulty of enhanced contamination with benzoic acid in the products can be ameliorated by employing a small but effective amount of a surfactant, especially an alcohol ethoxylate, in the reaction mixture. The process is especially well suited to making sodium benzoyl oxybenzene sulphonate from sodium phenol sulphonate dihydrate and benzoyl chloride.

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First Claim