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Fate of Methylenediphenyl Diisocyanate and Toluene Diisocyanate in the Aquatic Environment

1999; American Chemical Society; Volume: 33; Issue: 15 Linguagem: Inglês

10.1021/es981350c

1520-5851

Yoshikuni Yakabe, Karen M. Henderson, William C. Thompson, Denis Pemberton, Bernard Tury, Robert E. Bailey,

Occupational exposure and asthma

Toluene diisocyanate (TDI) and methylenediphenyl diisocyanate (MDI) are highly reactive materials used on a large scale in the production of polyurethanes. Their behavior in the aquatic environment has only been reported in general terms. This work provides a clearer understanding of their heterogeneous interaction with water to enable a better prediction of the environmental impact of a spill. The kinetics and product distribution have been studied for both stirred and unstirred reactions and have been correlated with the degree of agitation, surface area, and stoichiometry. TDI reacts rapidly, in less than 5 min, when well stirred, and MDI reacts more slowly because of its greater viscosity. However, under poorly mixed conditions, typical of an environmental spill, the reaction of both materials may take several weeks for completion because of the formation of insoluble solid polyurea crusts. This polyurea is the predominant product under all conditions except at very low loadings of diisocyanate. Under all conditions studied, only low concentrations of water-soluble products, including diamines, were formed. These results are indicative of a reaction occurring predominantly in the organic phase where the initial hydrolytic product, amine, can react further with isocyanate to produce ureas. These studies are consistent with the minimal effects noted from the accidental spillage of TDI and MDI in the environment.