The combination of reducing agents/iron as environmentally friendlier alternatives for Co-based driers in the drying of alkyd paints

In answer to the increased demand for Co-free driers for alkyd based paints, a biomimetic approach has been used to find suitable and environmentally friendly alternatives for Co-based driers for alkyd paints. This approach was chosen due to the resemblance between the mechanisms by which alkyd paints dry and lipids are oxidized in biological systems. As a consequence, the combination of iron with reducing agents was tested as drier for alkyd paints. Ascorbic acid and several ascorbic acid derivatives, in combination with iron salts, have been tested in alkyd emulsions, alkyd resins (or varnishes), and in a high gloss white paint formulation. We have found that the combination of iron salts with reducing agents forms an excellent drier, in terms of film hardness and particularly total drying time, compared to a commercial Co drier and a new Mn-based alternative. The effect of two nitrogen donor ligands, N,N-bis(2-ethyl-5-methyl-imidazol-4-ylmethyl)aminopropane (BIAP) and 2-ethyl-4-methylimidazole (Im), to the mixture reducing agent/iron was also studied in a high gloss white paint formulation. Outstanding total drying time of just 2.2 h was observed for the combination of ascorbic acid 6-palmitate, iron and imidazole