Dinitrotoluene toluene diisocyanates from

Formation of diamines from dinitro compounds, which are unable to interact intramolecularly, presents no problem. Very large volumes of diaminotoluene, a precursor to toluene diisocyanate, are produced by hydrogenation of dinitrotoluene over either nickel or palladium-on-carbon. Selective hydrogenation of one or the other of two nitro groups is much more of a challenge, but a number of outstanding successes have been recorded. A case in point is the hydrogenation of 2,4-dinitroaniline (11) to 4-nitro-l,2-benzenediamine (12) (2) or to 2-nitro-l,4-benzenediamine (10). 

Two other derivatives of toluene are the important explosive trinitrotoluene (TNT) and the polyurethane monomer toluene diisocyanate (TDI). TNT requires complete nitration of toluene. TDI is derived from a mixture of dinitrotoluenes (usually 80% o,p and 20% o,o) by reduction to the diamine and reaction with phosgene to the diisocyanate. TDI is made into flexible foam polyurethanes for cushioning in furniture (35%), transportation (25%), carpet underlay (20%), and bedding (10%). A small amount is used in polyurethane coatings, rigid foams, and elastomers. 

Toluene diisocyanate (TDI) is made from the reaction of 2,4-toluenediamine and phosgene. The diamine is made by reduction of dinitrotoluene, which in turn is manufactured by nitration of toluene. See Chapter 11, Section 7. 

Toluene diisocyanate is derived from a mixture of dinitrotoluenes (usually 65 to 85% o./9-dinitrotoluene and 35 to 15% o,o-dinitrotoluene) followed by reduction to the diamine and reaction with phosgene to the diisocyanate. 

Toluene Diisocyanate (TDI) Toluene diisocyanates (2,4- and 2,6 isomers) are produced from toluene diamine derived from dinitrotoluene, which is produced by the nitration of toluene with nitric/sulfuric acid mixtures. TDI is used to make flexible polyurethane foams, elastomers and coatings. 

Dinitrotoluenes are used predominantly for the manufacture of toluene diisocyanate (TDI), which is produced from the corresponding diaminotoluenes. 

Polyurethanes [351]. The production starts from toluene, which is converted by HNO3 in concentrated sulfuric acid to give a mixture of 2,4- and 2,6-dinitrotoluene (DNT). Catalytic hydrogenation with hydrogen gas gives toluene diamines (TDA). The reaction of TDA with phosgene forms toluene diisocyanate (TDI) (see Fig. 93). 

All industrial polyurethane chemistry is based on only a few types of basic isocyanates. The most significant aromatic diisocyanates are TDI and MD. TDI is derived from toluene. This is initially nitrated to dinitrotoluene, then hydrogenated to diamine, and finally phosgenated to diisocyanate. A defined mixture of isomers comprising toluene-2,4-and 2,6-diisocyanate is obtained. Approximately 1.3 million tons/year of TDI are produced world-wide, most of which is used in the production of polyurethane flexible foam materials. 

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