ABSTRACT
The anionic surfactants, which include the carboxylates, sulfonates, sulfates, and to a lesser extent the phosphates, represent the most important type of surfactants (Table 1).
The soaps may be the oldest surfactant that have been used as washing and cleansing agents. They are produced from the hydrolysis of fats and oils with alkali. Commercial soaps are mostly mixtures of salts of lauric, myristic, palmitic, stearic, and oleic acids. The potassium and ammonium soaps are much more soluble in water than the sodium soaps. They precipitate in hard water because of the poor solubility of the calcium and magnesium salts. The surfactant properties of soaps comprise good wetting power, foaming power, high detergency, and soil-carrying capacity. Among others, nowadays one essential use of the soaps is in the field of body care. Here they are consumed as toiletry soaps, liquid soaps, shaving soaps, and skinprotection soaps. Because of their alkalinity and sensitivity to hard water, the soaps have lost their importance as cleaning agents in textile washing. Especially because of their reactivity with the hardness components in water, they are still applied in heavyduty detergents. Washing powders in western Europe contain some percent soap of higher fatty acids, which form calcium soaps in the washing liquid and then act as a defoaming agent. Liquid detergents are mostly formulated with large amounts of coconut fatty acids. Fatty acids and their esters are the basis for a large number of compounds that are utilized in cosmetics as skin mild anionics. Examples of those derivatives are:
sarconisate : RCONðCH3ÞCH2COONa asparginate : RCONHCHðCOONaÞCH2CH2COONa isethionate : RCOOCH2CH2SO3Na taurate : RCONðCH3ÞCH2CH2SO3Na
Ethoxylates can be transformed into polyether carboxylates by selective oxidation of the terminal primary hydroxyl group or by carboxy methylation of this hydroxyl group with sodium chloroacetate. The hydrophobic group can arise from various
adducts, from natural or synthetic sources, from linear or branched alcohols, as well as from alkyl phenols or dialkyl phenols. Normally, the degree of ethoxylation is between 2 and 10 mol ethylene oxide. The sodium salts of polyether carboxylic acids are water-soluble, mild, very resistant against water hardness, and have extremely good dispersal and emulsifying power. This is why they are appropriate for many application fields as for surfactants in detergents and cosmetics [1] or as industrial emulsifiers. Further variations can be achieved in using propylene oxide/ethylene oxide adducts instead of simple ethoxylates for carboxy methylation.
