The use of aliphatic isocyanates, particularly isophorone diisocyanate (IPDI), for manufacturing light-stable, durable polyurethanes has grown rapidly over the past 10 years. Today, IPDI and its derivatives are preferred raw materials in conventional and high-solids two-component coatings, water-based polyurethane dispersions, powder coatings, and solvent-based baking enamel systems.
A new aliphatic diisocyanate plant is well on its way toward completion, with full operation expected in January of 1996. This 20-million-pound-capacity production unit will employ a patented route for the conversion of aliphatic diamine to the isocyanate. This route uses urea and an alcohol rather than phosgene, which has been used in most commercial processes until now. The urea process eliminates chlorinated contaminants in the finished product and so offers a significant advantage over the older phosgene process.
Also, the urea process is very versatile and will efficiently convert aliphatic diamines, which can be difficult to phosgenate with good yields.
This article will review the new urea process and will …