In this paper we report, the reaction parameters playing a vital role in the preparation and applications of industrially important N-methylaniline blocked polyisocyanates.

ϵ‐Caprolactam blocked‐polyisocyanate is a commercially valuable raw material used mainly in the single‐package polyurethane coatings. In this study, kinetics of forward (blocking) and the reverse (deblocking) reactions of ϵ‐caprolactam‐blocked polyisocyanate catalysed by DABCO ‐ a tertiary amine, bismuth neodecanoate, calcium(II) 2‐ethylhexanoate – both non‐tin organometallics and a tin catalyst were studied using a hot stage FT‐IR spectrophotometer. It was found that calcium(II) 2‐ethylhexanoate showed highest catalytic activity in the forward reaction whereas this catalyst showed lowest activity in the reverse reaction. DABCO and bismuth neodecanoate showed same catalytic activity and that activity was high compared to that of tin(II) 2‐ethylhexanoate in the forward reaction whereas only DABCO showed high activity in the reverse reaction. As these reactions were carried out adapting neat condition, the rate constants obtained were used to construct the double Arrhenius plots for this thermally reversible reaction. All the double Arrhenius plots showed intersection, from the intersection point, equilibrium temperature and equilibrium rate constants of these reactions were determined. Compared to uncatalysed reaction, DABCO reduced the deblocking temperature 25 °C and shifted the equilibrium temperature 6 °C. The data such as time required for 60% conversion into product, deblocking temperature and equilibrium temperature reported in this paper are vital in the manufacturing and in the application of ϵ‐caprolactam‐blocked polyisocyanate.

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