NOVEL PREPARATION METHODS FOR HIGHLY CONCENTRATED WATER-IN-OIL EMULSIONS

Kinetically stable water-in-oil (W/O) high-internal-phase-volume-ratio emulsions with gel-like appear ance have been formed in water/hydroge nated non-ionic surfactant/oil systems. Their visual aspect varies fro m transparent to translucent or white depending on composition variabl es and temperature. Systematic studies undertaken to characterize thes e emulsions, referred to as gel emulsions, have revealed that they for m above the hydrophilic-lipophilic balance (HLB) temperature of the co rresponding ternary system. They consist of two isotropic liquid phase s; the dispersed phase is composed of aqueous droplets and the continu ous phase is a W/O microemulsion. These emulsions can be prepared by g radual addition of the internal phase to the external phase while stir ling, the most common method for preparing highly concentrated emulsio ns. In the ternary systems water/non-ionic surfactant/hydrocarbon we f ound two new procedures for preparing gel emulsions. (a) Mixing of the three components, at their final composition, with vigorous stirring, can lead, at the appropriate temperature, to gel emulsion formation.( b) Increasing the temperature of an isotropic phase, the composition o f which is that of the final emulsion. These methods of preparation ha ve been rationalized in terms of the evolution of system properties du ring the process.