Novel ‘GREEN’ Sucrose Polyester Alkyds for high-Performing Low-VOC Coatings

By Neal Rogers, Delano Eslinger, Victor Arredondo

Alkyd resins have proven themselves both from a cost and performance point of view over a wide range of coatings applications such as architectural finishes, industrial metal, and agricultural/construction equipment. Since alkyd paints are solventborne, they contribute to our societal VOC emissions. Increasing concerns regarding ground level ozone and indoor air quality have spurred R&D investment to find alternative technologies or approaches directed at lowering VOC emissions without compromising performance. This has proven to be a major challenge for the industry as a whole. The key issue is reformulating solvent-borne paints to be as low as possible in VOC while still delivering—or surpassing—expected performance benchmarks.

Alkyd resins may be designed to achieve low-VOC coating formulations; however, traditional approaches invariably have compromised coat-ing performance. In one common approach, the molecular weight and viscosity of an alkyd resin must be reduced, thereby decreasing the need for solvent. In doing so, though, the paint made with it takes much longer to dry,^1,2 an undesirable feature for many applications. Another approach is to use VOC-exempt solvents, such as t-butyl acetate, acetone, and Oxsol® 100 (1-chloro-4-(trifluoromethyl) benzene).

These solvents tend to be expensive and often have odor and other performance issues. Commercial, low-VOC waterborne acrylic latex paints are available but they have performance tradeoffs that are undesirable for various coating applications, such as short open time, low gloss,² and reduced corrosion resistance when compared to solvent alkyd coatings.

For all of these reasons, solventborne alkyd coatings continue to be in demand. Sucrose polyester alkyds are a novel class of high-solids resins that offer high organic renew-able content with good application and drying characteristics while achieving much lower VOC levels than conventional alkyds.