INFLUENCE OF EMULSIFIER ON THE FORMATION OF ALKYD EMULSIONS

In traditional alkyd paints, the alkyd is dissolved in an organic solvent such as mineral spirit. For health and environmental reasons there is an increasing interest in water-borne alkyd paints. Alkyd emulsions are therefore an interesting alternative. The alkyd emulsion should have a good colloidal stability at a low concentration of surfactant. A high concentration of surfactant gives undesired properties of the paint film, such as water sensitivity. In this paper the influence of emulsification temperature and emulsifier concentration on the formation of alkyd emulsions has been investigated. The temperature dependence observed with both anionic and non-ionic emulsifiers is related to the change in viscosity of the alkyd with temperature. In the case of non-ionic emulsifiers, an additional effect is seen due to the change in hydrophilic-lipophilic balance (HLB) of the surfactant with temperature. A concentration corresponding to a close packing of the non-ionic surfactant on the surface of the droplets is needed to obtain a stable emulsion when non-ionic surfactants are used. In the case of anionic emulsifiers, stable emulsions can be obtained at low concentrations giving a very low packing density at the surface.