One must fundamentally distinguish between inert catalysts and accelerators, which take part in the reaction of the isocyanate. The first group includes tertiary amines.To prevent premature polymerisation of the isocyanates one should add these to the paint that is to be cured. An amount of 0,5 %, calculated on the solids content, is nomially sufficient. Triethylamine, N-methylpiperidine, N,N- dimethylcyclohexylamine and many other similary composed amines are relatively effective.
Organo-metallic compounds can also be used, including lead and cobalt naphthenates or organo-tin compounds such as dibutyltin laurate. lf there is no objection to chemically incorporating the accelerator into the product to be cured, other amine compounds, too. can be used as reactive catalysts, e.g. methyl diethanolamine or tri-isopropanolamine.
Other compounds which may be used include urethane propolymers, particularly those with terminal hydroxyl groups.