Solubilization-emulsification processes in nonionic surfactant-water-liquid triglyceride systems
Miller, Clarence A.
Doctor of Philosophy
Liquid triglycerides, the major component of cooking oils, have been found difficult to remove from synthetic fabrics during washing. The relatively strong adhesion force between triglycerides and fabric and their high molecular volumes make detergency mechanisms which work well for other soils and cotton fabrics relatively ineffective with surfactants commonly used in washing products. It is likely that a process for effective triglyceride removal would involve a solubilization-emulsification mechanism. Intermediate phases such as microemulsions or liquid crystals form at the surface of contact between surfactant solution and soil. These intermediate phases solubilize the soil and are subsequently emulsified into the washing bath. Because secondary alcohol ethoxylate surfactants have double tails of varying lengths, the hydrocarbon portion of surfactant films should be more disordered than for linear alcohol ethoxylates used in previous work and hence more capable of solubilizing triglyceride molecules. Equilibrium phase behavior of systems containing water, triolein, and secondary alcohol ethoxylates showed that a D or microemulsion phase which solubilized significant amounts of triolein formed at temperatures as low as 25$\sp\circ$C. In previous work with pure linear alcohol ethoxylates and triolein the D phase had formed only at temperatures above about 55$\sp\circ$C, which are undesirably high for washing synthetic fabrics. Based on the earlier studies, formation of the D phase would be expected to promote soil removal from synthetic fabrics by a solubilization-emulsification mechanism. Even for a rather hydrophilic secondary alcohol ethoxylate surfactant, slightly below its cloud point, solubilization rate and capacity are much greater than those for comparable linear ethoxylates, and complete solubilization of oils rich in triolein is possible. Liquid triglycerides typically occur as mixtures with long chain polar compounds such as alcohols or fatty acids. Contacting experiments for alcohol-rich oils revealed a mechanism involving spontaneous emulsification which provides a means for soil removal different from that found previously in other systems. Newly developed fiber contacting experiments with drops initially attached to individual polyester fibers confirmed that little oil remained on the fibers when the emulsification was extensive.