About Toluene Diisocyanate. Toluene Diisocyanate (a.k.a. TDI) is an organic compound, in the aromatic isocyanate class. It is a colorless oily liquid, with a sharp, pungent odor, soluble in acetone, benzene, and other organic solvents. TDI readily reacts with water at ambient temperature, forming insoluble urea compounds and a large amount of carbon dioxide gas. Like other isocyanates, TDI can be classified as a potential human carcinogen. The main effects of hazardous exposures are occupational asthma and other lung problems, as well as irritation of the eyes, nose, throat, and skin. It is largely produced, accounting for 34.1% of the global isocyanate market in 2000.

TDI is a key aromatic isocyanate with formula CH3C6H3(NCO)2. More specifically, 2,4-TDI and 2,6-TDI - two out of the six possible isomers - are widely used in the polymer industry, mainly in the production of flexible polyurethane foams. Industrial TDI manufacture is primarily based on toluene raw material. The most common method of preparing TDI on a commercial scale involves the nitration of toluene to dinitrotoluene (DNT), which is hydrogenated to toluene diamine (TDA) that is finally treated with phosgene. TDI is produced mainly in three forms: as an 80:20 mixture of 2,4-TDI and 2,6-TDI, referred to as TDI (80/20), as a 65:35 mixture of such isomers, known as TDI (65/35), and as pure 2,4-TDI.

Toluene Diisocyanate Handling. Contact of this product with water should be avoided during handling, storage, and transportation. TDI reacts readily with water, at room temperature, forming both an insoluble urea compound and large quantities of carbon dioxide gas, which can create a serious pressure hazard and cause container rupture. To protect TDI from atmospheric moisture, all containers should have blankets with a dry inert gas pad. Storage temperature should be above freeze point (approximately 14 °C [57 °F]) because if TDI freezes, the 2,4- and 2,6-isomers may separate. Prolonged storage of TDI at higher temperatures than 40 °C (104 °F) may cause the NCO content and viscosity to vary from product specifications. TDI is transported in railroad tank cars, tank trucks, tanks in ships, containers, and drums. They are stored in steel tanks and processed in steel equipment. For long-term storage, stainless steel is recommended.

Toluene Diisocyanate Production. Toluene Diisocyanate is typically manufactured via the reaction of phosgene and toluene diamine. Production pathways may differ by integrating toluene diamine production and also its precursor, dinitrotoluene. TDI can also be produced by a non-phosgene process in which it reacts with dimethyl carbonate. Raw materials and the respective production processes employed in the manufacturing of Toluene Diisocyanate are listed below.

Toluene Diisocyanate Uses. The uses and applications of Toluene Diisocyanate may vary according to its specification. The main forms of Toluene Diisocyanate are 100% 2,4-isomer solution and 80% or 65% 2,4-isomer solutions mixed with 2,6-isomer.