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TDI

TDI is an important industrial chemical because of its central role in polyurethane chemistry. Global production volumes for TDI were 2.6 billion pounds in 1990, 4 billion pounds in 2008, and 4 billion pounds in 2010 and expected to grow to 5 billion pounds in 2013 [115] with an implied growth rate of about 4.5% per year. Demand is driven by the main TDI applications, which are 85% for flexible foams, 10% for coatings, and the remaining 5% spread over numerous small applications. The largest flexible foam applications are furniture, automotive seating, carpet underlay, and mattresses. China was the largest consumer of TDI in 2011 using 30% of available total volume followed by Western Europe using 17%, and then the United States using about 15% [112].

TDI is produced from toluene. As a basic feedstock, it accounts for over 50% of the price of TDI on the market. Interestingly, none of the producers of TDI are back integrated into toluene. The two largest toluene producers are Exxon and Formosa Chemical and Fiber Corporation accounting for about 9% of the total. The toluene market is not concentrated—the top 25 producers only accounting for about 45% of the total produced [116]. Toluene is produced from fuel stocks, and the level of supplier diversity and implied competition accounts for the lack of interest by TDI

World (a) capacities and (b) production of isocyanates for polyurethane polymerization [112].

FIGURE 2.48 World (a) capacities and (b) production of isocyanates for polyurethane polymerization [112].

producers to back integrate to toluene. TDI production accounts for only about 5% of toluene consumption; however, as feedstock for chemical synthesis, it is the second largest consumer of value added to toluene (the largest being conversion to benzene/ xylenes) (Fig. 2.49).

World toluene production and portion used for manufacturing TDI [116].

FIGURE 2.49 World toluene production and portion used for manufacturing TDI [116].

Another key component to making TDI and isocyanates, in general, is phosgene. It is produced by the vapor-phase reaction of carbon monoxide with chlorine. The reaction is exothermic and requires cooling to prevent the reversion of phosgene back to reactants above 200 °C:

Due to severe health and safety issues associated with exposure to phosgene, this product is almost never shipped and almost always produced in the plant where its use will occur. A significant amount of engineering optimization is expended on securing phosgene from loss of containment.

 
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