The effect of polar soil components on the phase inversion temperature and optimum detergency conditions

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Abstract
Previously reported results have shown that optimum removal of a hydrocarbon soil from polyester/cotton fabric occurs above the cloud point at the phase inversion temperature (PIT) of nonionic surfactant/water/soil systems. Through comparison of phase behavior measurements to radiotracer detergency studies using model sebum soils, i.e., cetane/oleyl alcohol and cetane/oleic acid blends, the relevance of the PIT for removal of nonpolar/polar soil mixtures has also been demonstrated. For these soils, the PIT is typically below the cloud point, and the highest level of soil removal is found between the PIT and cloud point rather than only at the PIT. This relatively temperature‐insensitive soil removal is attributed to the preferential solubilization of polar soil components which continually changes the composition of the residual soil during the washing cycle. These findings explain the long‐observed results that 4‐ to 5‐EO alcohol ethoxylates are preferred for the removal of nonpolar soils while 6‐ to 9‐EO ethoxylates are the more effective surfactants for sebum soils.