A Novel Iron Based Catalyst for Curing Alkyd Coatings

摘要

Research has been done in the past to look for alternative oxidative driers to cobalt due to economic pressures. Many metal carboxylates have been evaluated including manganese, vanadium, and rare earth metals, often in combination with activating ligands such as 2,2'-bipyridyl. While good results have been reported in some resin systems, none offer the overall performance of cobalt. Currently there is concern in Europe that cobalt carboxylates might be classified as Category 2 carcinogens under REACH. As such, they would effectively be eliminated from use in decorative paints sold to the public. A new highly effective iron catalyst dries paints at much lower levels than cobalt with none of the color disadvantages typically associated with iron. This presentation describes the iron complex and shows supporting data in a range of coating systems including conventional, high solids, and waterborne systems. We have compared drying times, hardness, and L*a*b* color under room temperature and adverse (10 ℃, 80% relative humidity) conditions. Loss of dry and accelerated oven ageing were also conducted on select formulations. The results have shown that the new iron catalyst performance is at least comparable to cobalt based driers; better in some important areas such as adverse conditions and loss of dry. The undesired effects of strong discoloration or impact on film hardness which are often seen with other alternatives to cobalt are completely absent. Thus, the use of the new iron catalyst provides a viable alternative to the use of cobalt to dry the full range of alkyd coatings with no compromise in performance, and with the prospect of additional benefits under adverse conditions and in storage stability.