SULFONATES DERIVED FROM DIMER ACIDS AND ESTERS - SOME SURFACTANT PROPERTIES

Several fatty acids, dimer acids - especially unsaturated ones - and s ome of their derivatives were sulphonated in a batch reactor with liqu id sulphur trioxide or chlorosulphonic acid. The main raw materials we re 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. S ulphonation 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 inter face or to their aggregation, were investigated: surface tension decre ase, foaming power and critical micelle concentration (c.m.c). Due to the presence of several hydro-carbon 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 produc ts is very favourable but sodium sulphonate of oleic acid n-decyl este r, 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-chem ical properties of sulphonated quasi-saturated dimers and to the evolu tion of these properties with surfactant structure, sulphonated unsatu rated dimer acids and esters perform better than similar saturated sul phonates.