36 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS BROOKFIELD VISCOSIMETER Figure 3 VISCOSITY OF ALKYLOLAMIDoe-WAToeR SYSTEMS 'ooo I I NINOL CONCENTRATION, •/o 0 20 40 60 80 100 Figure d• OPACITY Although clear soap or synthetic shampoos have long been the most popular type, the so-called liquid cream shampoos are gaining an increasing share of the market. These products are based mostly on lauryl sulfates (although alkylaryl sulfonates are also used) with an opacifier added, depending on whether a "flat" or pearly appearance is desired. Stearic acid, magnesium stearate, glyceryl stearates, and cetyl alcohol have all been used in this connection, but suffer from various drawbacks. Some are difficult to incorporate without separation, some are foam depressers, most do not give a uniform degree of pearl that can be readily controlled from batch to batch. A number of alkylolamides also show interesting opacifying properties, although this effect does not lend itself readily to quantitative study. It is to be expected that pearliness would be caused by the presence of elongated particles or agglomerates exhibiting optical effects related to flow birefringence, i.e., a change in reflectance when rod-sl•aped particles move through water for example, the silky appearance when a mercurous chloride precipitate is stirred. Although stearates as a class tend to show this effect, the conditions for high pearliness are apparently rather critical, and are probably connected with the type of colloidal aggregation taking place in different systems. Hydroxystearic compounds, for instance, do not pearl as much as stearates in many cases. This is also illustrated by two stearic alkylolamides called Ninol CB60 and Ninol CB10. Although these two opacifiers are quite

ALKYLOLAMIDES IN SHAMPOOS 37 10,000 1,000 100 THICI•ENING OF' LAURYL $ULF'ATI E•Y ALK, YL OL AMIDE.$ NINOL O /•NINOL AA62 COMPOSITION • ..... •,, •,, • •, , % NINOL 0 • 12 15 o/. ANIONIC 15 12 • 6 • 0 Figure 5 THICKENARYLALKALI•YLOLAMIDE5OFBYSULFONATE •0000 , If ... /r •0 . • INO• 8 ,o IO CO• I % NINOL 0 3 6 g 12 15 • • • 12 • 6 3 o Figure 6 similar in most respects, except for a small difference with regard to the alkylolamide employed, the first one exhibits excellent pearliness in lauryl sulfate and alkylaryl sulfonate solutions, whereas the second imparts a dead white with no trace of pearl. Unlike some opacifiers, these alkylolamides do not depress lathering in shampoos. DETERGENCY The detergent power of the water-soluble diethanolamides has been studied by several investigators. Barnett and Powers (2) and also La Fleur (3) report excellent grease removal from wool, and Armstrong (4) found high detergency and soil-suspending action in washing of soiled cotton. Not only are the alkylolamides alone excellent detergents, but they also greatly enhance the detergency of anionics in blends as pointed out by Vitale and Leonard (5) who found that lauric diethanolamides synergized the ability of alkylaryl sulfonates to wash soiled wool swatches. Richardson (6) states that even the water-insoluble lauric monoethanol- amides enhance the detergent efficiency of lauryl sulfates or alkylaryl sulfonates when solubilized by them. It can therefore be safely con- cluded that the lauric alkylolamides can contribute greatly to the cleaning power of shampoos. Higher members of the series, such as oleic and stearic derivatives possess much less detergency, however, and are used more for thickening, emollient, and whitening effects.