Catalysis of Blocked Isocyanate-Hydroxyl-Terminated Polybutadiene Cure Reaction

Abstract

The catalytic activity of three tertiary amines and three organotin compounds in the cure reaction of blocked isocyanate with hydroxylterminated polybutadiene was investigated. It was found that the steric factor determines the catalytic activity of the compound. The tin compounds showed higher catalytic activities than the amine compounds. The deblocking catalytic activity of the amine and tin compounds was confirmed by the identification of isocyanate functionality using infrared spectroscopy. The synergistic effect of amine and tin mixed catalysts systems in the deblocking reaction was reported for the first time.

Reactions of phenolic ester alcohol with aliphatic isocyanates?transcarbamoylation of phenolic to aliphatic urethane: A13C-NMR study

“…24 For example, Muramatsu et al 25 reported that the deblocking reactions are related to the electron densities of these compounds and, therefore, can be predicted using computer-based simulation. Endo and co-workers 26 reported the transesterification of poly(N-acylurethanes) using various diols and triols at ambient temperatures.…”

“…37 Amine and tin catalysts reportedly bring about synergistic effects in the deblocking reactions of phenol-blocked isocyanates. 24 Perhaps, the transcarbamoylation reaction of 4 using DBTDL and residual DABCO catalysts may be accelerated by such synergistic effects. This could be confirmed by allowing the transcarbamoylation reaction of 11, which has a similar structure but no residual catalyst present.…”

“…23,24,32 They are (1) an elimination-addition mechanism and (2) a substitution-type mechanism. Most of the deblocking reactions reported in the literature are thought to involve the elimination-addition § Many transcrabamoylation reactions are enzyme catalyzed.…”

“…The effect of different catalysts on the deblocking reactions of blocked isocyanates was discussed in the literature. 19a, 24 It has been reported that the DSC scans of several phenol-blocked urethanes, derived from MDI, show endothermic transitions due to deblocking reactions. 41 Anagnostou and Jaul 42 also reported the deblocking reactions of several blocked isocyanates of MDI using different blocking groups, such as caprolactam, MEKO, and benzotriazole, using DSC and IR spectroscopy.…”

Catalysis of poly(urethane imidine) copolymer formation from amine‐blocked isocyanate and bisphthalide

“…In a continuation of a previous report, here we report the effect of metal alkoxides, metal phenoxides, tertiary amines, and organotin compounds on the preparation of poly(urethane imidine) copolymer with N ‐methyl aniline‐blocked prepolymer and bisphthalide. Metal alkoxides and phenoxides catalyze the blocked isocyanate–anhydride reaction,22 whereas tertiary bases and organotin compounds are known for their deblocking catalytic activity 23, 24. Studying the sensitivity of the blocked isocyanate–phthalide reaction against these two groups of compounds is the subject of this report.…”