Effects of concentration of sodium dodecyl sulfate and the washing temperature on the removal of palmitic acid as a model of fatty soil from cotton fabrics were studied. In addition, the effect of the addition of lower n-fatty alcohols (C₂C₆) to the surfactant on the removal of the fatty soil was also studied.
At the washing temperature below the melting point of palmitic acid, the removal of palmitic acid is only small in the vicinity of critical micelle concentration of sodium dodecyl sulfate but is very remarkable in the 10 times higher concentration than c.m.c. At the washing temperature higher than the melting point of palmitic acid, the removal was easy at the vicinity of the c.m.c. of sodium dodecyl sulfate.
The removal amount of palmitic acid from cotton fabrics at the higher concentration than the c.m.c. was less than the saturated solubilized amount of the soil at the same concentration. Therefore, the complete removal by the mechanism of solubilization only would be impossible. The addition of fatty alcohols to sodium dodecyl sulfate solution was effective to increase the removal of palmitic acid. The longer the alkyl chain of the alcohol was the more effective in lesser amount of the addition.