Innovative Strategies for Emulsifying Alkyd Resins

Abstract: The emulsification of resins used in solvent-based coatings into water is a crucial strategy for developing environmentally friendlier water-based coatings. This work focuses on developing a special solvent and optimizing emulsifier compositions to reduce the viscosity of medium-in-oil alkyd resins, enabling their emulsification through phase inversion using low shear mixing equipment, and producing emulsions with particle size below 400 nm. The prototype of an environmentally friendly solvent, designed for having Hansen Solubility Parameters (HSP) close to the ones of the alkyd resins, effectively decreases the viscosity of medium-in-oil alkyd resin at 80°C, the emulsification temperature, as confirmed by rheological measurements. A small amount (5 wt%) of this solvent reduced the viscosity by approximately 60%. The emulsifier compositions include a special nonionic emulsifier designed for alkyd resin emulsification and a conventional anionic emulsifier. Interfacial tension evaluation between a model oil phase containing the emulsifier composition and water was used to select the most effective emulsifier compositions for reducing the interfacial tension, crucial for successful emulsification. The interfacial tension results indicated that compositions rich in the nonionic emulsifier could reduce the interfacial tension at 40°C from 18 mN/m to nearly 0 mN/m. Based on the interfacial tension results, three compositions rich in the nonionic emulsifier were evaluated. The emulsions had solid content around 49%, particle size between 200 - 300nm and they generated paints with drying time ranging between 3 - 5 hours.