Origin of impurities formed in a polyurethane production chain. Part 2: a route to the formation of coloured impurities

Callison, J., Betzler, F., de Cuba, K., van der Borden, W., van der Velde, K., Carr, R.H., Senn, H.M. , Farrugia, L.J., Winfield, J.M. and Lennon, D. (2012) Origin of impurities formed in a polyurethane production chain. Part 2: a route to the formation of coloured impurities. Industrial and Engineering Chemistry Research, 51(34), pp. 11021-11030. (doi: 10.1021/ie300987v)

Abstract

The quality of methylene diphenyl diisocyanate (MDI) products, which are valuable feedstocks in the industrial manufacture of polyurethanes, can be compromised by the presence of color, presumed to arise from trace impurities. One undesired branch in the synthesis chain originates with phosgenation of diaryl ureas, formed from reactions between aryl isocyanates and polyamine precursors. Subsequent key steps include, (i) breakdown of the primary compounds, substituted chloroformamidine-N-carbonyl chlorides (CCC), to give aryl isocyanide dichlorides, ArNCCl2, (ii) an apparent equilibrium connecting CCC with aryl carbodiimides, and (iii) the thermolysis of ArNCCl2 in the presence of MDI. Color formation is associated directly with the last process; it involves several events, including HCl elimination from reaction of ArNCCl2 and MDI, formation of carbon-centered radicals, and a contribution from oxidation at the methylene bridge.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Winfield, Professor John and Farrugia, Dr Louis and Senn, Dr Hans and Lennon, Professor David
• Authors: Callison, J., Betzler, F., de Cuba, K., van der Borden, W., van der Velde, K., Carr, R.H., Senn, H.M., Farrugia, L.J., Winfield, J.M., and Lennon, D.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Industrial and Engineering Chemistry Research
• ISSN: 0888-5885