Direct use of microemulsions

In contrast to the formation of microemulsions from aqueous surfactant systems and oily soils during the cleaning process, less basic research has been carried out on micro emulsions as a direct cleaning medium [ 80 ]. Some examples will be presented in the following sections. 

Dorfler et al [82] systematically studied the phase behaviour of quaternary systems, consisting of water, non-ionic surfactants, a co-surfactant and a hydrocarbon, with regard to possible applications in the textile-cleaning sector. As an example, Fig. 8.14 shows the 

Within certain industrial applications like gas and oil industry and ink and printing industry there is a need for cleaning when the remaining surface should be water-wet. A neutral microemulsion system based on a surfactant, a lactate ester as co-surfactant and an organic solvent like limonene is suggested by Harrison for this purpose. Butyl lactate is shown to enlarge the one-phase (Winsor IV) area in the phase diagram, for instance SDS and limonene in water [94, 95]. 

The high viscosity of certain micro emulsions is used for the adhesion of cleaner concentrates on vertical surfaces while on dilution mobile microemulsions are formed [96]. The need for this type of behaviour is especially evident when it comes to household cleaners like toilet bowl cleaners where the formulation needs to be acidic to cope with the special dirt met there, e.g. soap scum. An example of microemulsions with high viscosity for this purpose can be found in [97] which discloses acidic thickened sprayable microemulsion composition based on a balanced mixture of anionic and non-ionic surfactants, 

The synergisms of mixtures of anionic-cationic surfactant systems can be used to form middle-phase micro emulsions without adding short-chain alcohols [109, 110]. The surfactants studied were sodium dihexyl sulphosuccinate and benzethonium chloride. The amount of sodium chloride required for the middle-phase microemulsion decreased dramatically as an equimolar anionic-cationic surfactant mixture was approached. Under optimum middle-phase microemulsion conditions, mixed anionic-cationic surfactant systems solubilised more oil than the anionic surfactant alone. Upadhyaya et al. [109] proposed a model for the interaction of branched-tail surfactants (Fig. 8.16). According to this model the anionic-cationic pair allows oil to penetrate between surfactant tails and increases the oil solubilisation capacity of the surfactant aggregate. Detergency studies were conducted to test the capacity of these mixed surfactant systems to remove oil from 

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