<unk> , most often abbreviated as<unk> , is an aromatic diisocyanate. It exists in three isomers, 2,2'-MDI, 2,4'-MDI, and 4,4'-MDI. The 4,4' isomer is most practically useful, and is also known as Pure<unk> .<unk>  is reacted with a polyol in the manufacture of polyurethane. It is the most produced diisocyanate, accounting for 61.3% of the global market in the year 2000.
Methylene diphenyl diisocyanate
Toluene diisocyanate
Methyl isocyanate
Toluene
Coal tar
Vinyl chloride
Dimethyl phthalate
Cadmium oxide