Optimised emulsifiers for more sustainable water-borne alkyd coatings

 
The industry's shift from solventborne to waterborne coatings is driven by the need to reduce volatile organic compounds (VOCs) and lower the overall environmental impact of coatings. Demand for greener products has positioned alkyd resins, known for their high biobased content derived from vegetable oils, as a critical component in eco-friendly formulations. However, transitioning alkyds to waterborne forms while meeting VOC regulations requires the use of emulsifiers to achieve stable oil-in-water emulsions that maintain good performance in the formulated coatings. This study introduces a range of emulsifiers, both fossil-based and biobased, specifically tailored for medium to long oil alkyds. The emulsification process was optimized using the phase inversion method, with a focus on key parameters including alkyd viscosity, degree of neutralization, emulsification temperature, rate of water addition, and mixing techniques. The optimization of these factors proved to be essential for achieving a successful phase inversion and producing a long-term stable waterborne emulsion with desirable appearance and application properties. Both fossil-based and biobased emulsifiers were rigorously tested against industry benchmarks using several industrially relevant resins, demonstrating comparable performance in key parameters such as emulsion stability, particle size distribution, viscosity, and electrolyte resistance. Achieving robust formulations requires not only the careful selection of emulsifiers but also determining their optimal addition levels. The study further demonstrated that by leveraging 100% renewable polyols as drop-in replacements for fossil-based polyols, it is possible to significantly increase the renewable content of the final product while achieving identical, high-level performance. A central aspect of this research was exploring the relationship between the emulsifiers hydrophobicity and hydrophilicity -both non-ionic and ionic-and the ionic strength of the ionic emulsifiers in relation to the alkyd resin. Understanding and optimizing these interactions proved essential for forming stable waterborne emulsions. Successfully emulsified alkyds were formulated into paint, resulting in coatings with good sagging resistance, superior levelling, enhanced hardness, high gloss, and optimal drying times. This work provides practical guidelines for optimizing the selection of both fossil-based and biobased alkyd emulsifiers, as well as processing conditions, to develop high-performance, sustainable waterborne alkyd coatings.