Dimersäure- und Estersulfonate / Sulphonates derived from dimer acids and esters

Abstract

Several fatty acids, dimer acids - especially unsaturated ones - and some of their derivatives were sulphonated in a batch reactor with liquid sulphur trioxide or chlorosulphonic acid. The main raw materials were stearic and oleic acids and dimers of the latter, they were used as free carboxylic acids or as methyl, 2-ethylhexyl or n-decyl esters. Sulphonation products were neutralized with various alkaline or organic bases, leading to anionic surfactants; several of these have not yet been reported in the literature. Three physical-chemical properties of these sulphonates, related to their adsorption at the air-water interface or to their aggregation, were investigated: surface tension decrease, foaming power and critical micelle concentration (c. m. c.). Due to the presence of several hydrocarbon chains, solubility and c. m. c. are much higher than expected for sulphonates with such a high number of carbon atoms. The surface tension decrease of unsaturated dimer products is very favourable but sodium sulphonate of oleic acid n-decyl ester, also studied in this work, shows the most remarkable decrease. The foaming power of sulphonated unsaturated dimers is about half that of the corresponding sulphonated monomers. According to the physical-chemical properties of sulphonated quasisaturated dimers and to the evolution of these properties with surfactant structure, sulphonated unsaturated dimer acids and esters perform better than similar saturated sulphonates