Novel Iron Based Driers for Alkyd Paints

Dr Ronald Hage & Philana Wesenhagen, Rahu Catalytics BV, Netherlands

Dr Franjo Gol & Dietmar Oberste (Speaker), OMG Borchers GmbH, Germany

Alkyd resins are a renewable product offering excellent durability and protection and resin producers have been successful in making products which will comply with the 2010 VOC regulations. Cobalt carboxylates are the main driers for alkyd resins in paints and inks but concerns about their possible classification as carcinogens has generated considerable interest in alternatives to cobalt. Alternatives such as manganese have been proposed but none have been found to have the all round performance of cobalt carboxylates.

Work on tomato stain removal in the detergent industry has resulted in the development of new iron based complexes [1]. The mechanism of stain bleaching catalysed by the iron complexes is analogous to the cobalt catalysed crosslinking of alkyd resins and it has been shown that these compounds can be used to replace conventional cobalt driers in both solvent and waterborne alkyd paints. Results will be presented in a range of systems – conventional, high solids and water based and under a variety of temperature/humidity conditions showing that comparable or superior drying times and film properties such as gloss and haze can be achieved using very low catalyst levels but without the problems with film discoloration typically seen in other non-cobalt systems. The technology provides a cost effective high performance alternative to cobalt. Extensive testing of the iron complex has shown no negative issues and coupled with its very low use level provides a drier system with no regulatory concerns and without the carcinogenicity concerns of cobalt.

[1] R.Hage, A. Lienke; Applications of transition-metal catalysts for bleaching textile and wood-pulp. Angew Chem, 45, 206 (2006).