SYNTHESES OF ANIONIC SURFACTANTS HAVING 2 POLYFLUOROALKYL CHAINS AND THEIR FLOCCULATION ABILITY FOR DISPERSED MAGNETITE PARTICLES IN WATER

Four anionic surfactants having two polyfluoroalkyl chains in a molecule, sodium salt of bis(1H,1H,2H,2H-heptadecafluorodecyl) 2-sulfosuccinate, CF3(CF2)7(CH2)2OCOCH2CH(SO3Na)COO(CH2)2(CF2)7CF3, sodium salt of bis(1H,1H,9H-hexadecafluorononyl) 2-sulfosuccinate, H(CF2)8CH2OCOCH2CH(SO3Na)COOCH2(CF2)8H, sodium salt of bis(1H,1H,7H-dodecafluoroheptyl) 2-sulfosuccinate, H(CF2)6CH2OCOCH2CH(SO3Na)COOCH2(CF2)6H and sodium salt of bis(1H,1H,5H-octafluoropentyl) 2-sulfosuccinate, H(CF2)4CH2OCOCH2CH(SO3Na)COOCH2(CF2)4H, were prepared from maleic anhydride, the corresponding alcohols having a polyfluoroalkyl chain and sodium hydrogensulfite. The flocculation and redispersion abilities of these surfactants against dispersed magnetite particles in water have been examined in comparison with other four anionic surfactants having a single polyfluoroalkyl chain in a molecule; sodium pentadecafluorooctanoate, CF3(CF2)6COONa, sodium 9H-hexadecafluorononanoate, H(CF2)8COONa, sodium 7H-dodecafluoroheptanoate, H(CF2)6COONa, and sodium 5H-octafluoropentanoate, H(CF2)4COONa. These abilities were estimated by measurement of the contact angle against water using pelleted surface-modified magnetite. The abilities of the surfactants having two polyfluoroalkyl chains against flocculation-redispersion were superior to those of the surfactants having one polyfluoroalkyl chain. Especially, sodium salt of bis(1H,1H,2H,2H-heptadecafluorodecyl) 2-sulfosuccinate was the most effective surface active agent for these abilities.