OILY SOIL REMOVAL FROM A POLYESTER SUBSTRATE BY AQUEOUS NON-IONIC SURFACTANT SYSTEMS

Pure mineral oil soils are removed from polyester substrates by the roll-up mechanism in nonionic surfactant systems, and the process is little affected by hardness ions or builder addition. For a given surfactant system, roll-up and removal efficiency increase with temperature until the cloud point of the nonionic is reached, whereafter a further increase in temperature decreases the rate of roll-up. In general, lower ethoxylated surfactants perform better than higher ethyxylates at low temperature, but the trend is gradually reversed as the temperature is increased. For a given degree of ethoxylation, secondary alcohol ethoxylates are more effective at rolling up mineral oil soils than their primary counterparts. Addition of a small amount of oleic acid to mineral oil soils facilitates the roll-up process (by lowering the oil/water interfacial tension) and minimizes the differences in performance among the various types of unbuilt nonionic surfactants. However, addition of highly alkaline electrolytic builders with these soils promotes oil removal by emulsification, presumably because of charge neutralization and/or transfer of the fatty acid into the aqueous phase. Conditions of high pH and low electrolyte strength inhibit the removal of 5.0% oleic acid in mineral oil soils, as exemplified by studies with added triethanolamine, ammonia, and very diluted NaOH. However, addition of divalent hardness ions to such systems promotes coarse emulsification of the soil, as does addition of relatively high concentrations of monovalent cation salts. A tentative explanation of this phenomenon is proposed. Ionic strength has little effect on the removal of 5.0% oleic acid/mineral oil soils below pH 7, as rapid roll-up is obtained regardless of added electrolytes. Similarly, ionic strength (or pH) has little effect on the removal of mineral oil containing polar, but nonionizing soils such as oleyl alcohol, as rapid rollup is achieved under a number of conditions. © 1979 The American Oil Chemists' Society.