Tin-based catalysts have been the work-horse catalysts for various polyurethane, silicone, and ester-based products where they promote the polymerization and/or crosslinking reactions. Both the inorganic (Sn II) and organotin (Sn IV) families form the foundation for the key commercial tin catalysts. Due to a combination of ideal reactivity and stability characteristics and the availability of a wide range of ligands, tin catalysts are the go-to products for the above-mentioned reactions. The reactivity, hydrolytic and heat stability make tin catalysts suitable for various esterification reactions. In polyurethanes, tin catalysts provide for a good balanced front-end and back reactivity owing to their ability to catalyze the various polyurethane reactions such as polymerization/gelation and crosslinking. For silicones, tin catalysts are the ideal catalyst for catalyzing a wide range of silicone condensation reactions, here acting to promote the key crosslinking reactions. Common tin catalysts include stannous octoate, stannous neodecanaote, dibutyltin dilaurate, dioctyl diacetate and dimethyltin dineodecanoate.
Bismuth and Zinc Catalysts
Bismuth and zinc catalysts find their main use in polyurethane reactions. Like tin catalysts, bismuth and zinc catalysts show a good balance in reactivity and stability characteristics. Additionally, they are considered lower toxicity alternatives in light of the recent issues with the toxicity of organotins. Bismuth catalysts have a similar reactivity profile compared to tin catalysts, where they are good at promoting polymerization/gelation reactions. Zinc catalysts are more preferential to the polyurethane crosslink reactions and are thus commonly used in combination with a polymerization/gelation catalyst such as bismuth. Common bismuth catalysts include, bismuth octoate and bismuth neodecanaote. Common zinc products include zinc octoate and zinc neodecanoate.
Overall, tin, zinc, and bismuth-based catalysts have proven to be versatile and valuable tools in the formulation of various polyurethane, silicone, and esterification end-use products. Owing to the formulation-specific reactivity/behavior of these catalysts, in addition to the wide range of available ligands and the desire for products with reduced toxicity, Reaxis continues in developing new products that supplement the current selection of our commercially available products.