MICELLAR PROPERTIES OF OIL-SOLUBLE SOAPS AND THEIR SIGNIFICANCE IN DETERGENCY

摘要

Oil-soluble soaps in hydrocarbon solvents have been shown to form small and approximately isodimensional micelles. Under suitable conditions, some metal carboxylates form extended structures as well. Coordinate bonding is an important factor contributing to the stability of both types of structure. Micelles are in equilibrium with nonmicellar soap in the solvent so that the system behaves as a dilute but saturated soap solution in equilibrium with a finely divided saturating phase. This situation favors rapid and extensive adsorption on polar surfaces to effect detergency or rust inhibition. The presence of micelles facilitates the dissociation of oil-soluble soaps to produce stable micellar ions and to impart a stabilizing charge to polar particles suspended in the system. The solubilization of polar molecules in oil-soluble soap micelles involves coordination and sometimes hydrogen bonding. It provides a mechanism for the segregation of corrosive acids and of acidic precursors of sludge or lacquer. Solubilization of water by such micelles promotes dissociation of ion pairs in the micelle to form micellar ions and free anions. Water solubilization also allows secondary solubilization of inorganic salts not otherwise taken up by the micelle. Addition of excess water may lead to the formation of a stable water-saturated micelle or to the separation of a soap-rich liquid-crystalline phase.