Synthetic detergents from animal fats. VIII. The ethenoxylation of fatty acids and alcohols

Summary A laboratory survey of the properties of a series of ethenoxylated fatty acids and alcohols containing about 10, 15, 20, 30, and 40 ethenoxy groups per molecule has brought together information on solubility, cloud point, surface and interfacial tension, detergency, and wetting, foaming and emulsifying properties. Ethenoxylated alcohols were generally more soluble and had better wetting and foaming properties than the acids. Ethenoxylated acids had generally lower surface and interfacial tension values. Both types of nonionics appeared to be excellent emulsifying agents. Most of the ethenoxylated acids and alcohols were equally effective as built detergents. Built ethenoxylated oleic acid (n=10) and built hydroxy-, dihydroxy-, phenyl-, and xylylstearic acids (n=20) were the best detergents. Nonionic surface-active agents derivable from animal fats appeared to have an optimum range in the average number of ethenoxy groups per molecule, with respect to certain properties. The optimum was in the range of about 14 to 18 for wetting properties, the foaming properties of ethenoxylated alcohols, and the interfacial tension of ethenoxylated acids. This range is about equal to the value suggested for adequate solubility [3 less than the number of carbon atoms in the parent alcohol (3)] but somewhat higher than the general rule for maximum detergency [2/3 the number of carbon atoms in the parent acid or alcohol (1,5)]. The rate of the reaction of octadecanol and stearic acid with ethylene oxide was compared. The alcohol reacted faster, in a non-specific manner. The acidity of the carboxyl group of stearic acid promoted conversion to ethylene glycol monostearate before further ethenoxylation occurred. After disappearance of the carboxylic acid the rate of the reaction of the ethenoxylated acid approached that for octadecanol. A reaction mechanism consistent with these results is proposed. Presented at the meeting of the American Oil Chemists' Society, Chicago, September 24–26, 1956. For number VII in this series see reference 14. A laboratory of the Eastern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture.