Photolatent alkyd curing with iron

Paint plays an important part in waterproofing metal and wood, which is vital in extending the lifetime of outdoor structures. Common paints contain several ingredients to control their (physical) properties, such as binders, pigments, fillers and diluents. Traditionally oil paints were used, with plant oils such as linseed oil as binder. Nowadays many of the binders are based on synthetic polymers such as alkyd resins: polyesters prepared by a polycondensation reaction between fatty acids derived from plant oils, a diacid and a polyol. The process of alkyd paint curing (‘drying’) relies on the formation of (conjugated) fatty acid hydroperoxides. Activation of these hydroperoxides by catalysts results in the formation of radical species which (1) can initiate the formation of new peroxide species and (2) can perform reactions leading to crosslinks, resulting in the formation of a three-dimensional network and a cured coating. In commercially available alkyd paints, cobalt-, manganese- and iron-based catalysts are applied frequently, with cobalt-based driers being particularly attractive due to their ability to produce the hardest coatings. Catalysts should however not start curing the paint during storage, and typically (volatile) inhibitors are added to prevent this. Due to legislative pressure regarding the use of cobalt-based driers and certain (volatile) inhibitors in alkyds, these compounds possibly may be banned from used in alkyd formulations in the future. Therefore, suitable alternatives need to be developed. This thesis addresses these issues, and describes new photo-latent catalytic Fe-based driers suitable to provide latent alkyd curing free from (volatile) inhibitors.