2,4- and 2,6-Toluene diisocyanates

Diisocyanates generally employed with polyols to produce polyurethanes are 2,4-and 2,6-toluene diisocyanates prepared from dinitro-toluenes (Chapter 10) ... 

Solubility 2,4- and 2,6-Toluene diisocyanates decompose in water and are very soluble in acetone and benzene (Lide, 1997)... 

Lind, P, Dalene, M., Sharping, G. Hagmar, L. (1996) Toxicokinetics of 2,4- and 2,6-toluene-diamine in hydrolysed urine and plasma after occupational exposure to 2,4- and 2,6-toluene diisocyanate. Occup. environ. Med., 53, 94-99... 

In the production of polyurethane elastomers, only diisocyanates are of any important use. The major diisocyanates manufactured and used are the 2,4 and 2,6-toluene diisocyanates (TDI) and 4,4 -diphenylmethane diisocyanates (MDI). See Figure 2.15. 

The toxicokinetics of TDI (2,4- and 2,6-toluene-diisocyanates) in chronically exposed workers at two... 

In Japan, Tosoh Corporation commenced construction in 2003 of a 160,000 metric tons per year plant at Nanyo, to supply Nippon Polyurethane Industry Co. Ltd, manufacturer of 170,000 metric tons per year of MDI (9d)23. Nippon also manufactures 25,000 metric tons per year of a blend of 2,4- and 2,6-toluene diisocyanates, TDI (10a and 10b), by a process that involves toluidines as intermediates24. Tosoh has since embarked on construction of a new 159 million aniline plant. Japan produced 196,000 metric tons of aniline in 2005, based on 1.1% annual growth. 

Benzene, 1,3 Jiisocyanatomethyl- CCRIS 596 Desmodur T 80 Desmodur T100 Diisocyanatotoluene 1,3-Diisocyanatomethylbenzene EINECS 247-722-4 HSDB 6003 Isocyanic acid, methyl-m-phenylene ester Methyl-m-phenylene isocyanate Methylphenylene isocyanate Mondur TD-80 Nacconate-lOO Niax iso-cyanate TDI RCRA waste number U223 Rubinale TDI Rubinate TDI 80/20 TDI TDI 80-20 Toluene-2,4-diisocyanate (mixt. with Toluene-2,6-diisocyanate) Toluene diisocyanate 2,4/2,6-Toluene diisocyanate iso-meric mixture 2,4-Toluene diisooyanate 2,4- and 2,6-Toluene diisocyanate Toluenediisocyanate (mixed isomers) Tolylene diisocyanate Tolylene isocyanate m-Tolylidene diisocyanate UN 2078. Mixture of... 

B. A. G., Development, validation and characterization of an analytical method for the quantification of hydrolysable urinary metabolites and plasma protein adducts of 2,4-and 2,6-toluene diisocyanate, 1, 5-naphthalene diisocyanate and 4,4 -methylenediphenyl diisocyanate. Biomarkers, 8, 204-217, 2003. 

Examples of toxic compounds, including some important intermediates and starting materials in the chemical industry, are shown in Figure 3.3. Many alkali fluorides, such as alkali hexafluorosilicate, alkali hydrogen difluoride, or alkali sulfuryl fluoride, are well known toxic substances. Sulfur dioxide and ammonia (ubiquitous gases) are toxic, as are chlorine, metallic mercury vapors, many organic phenol compounds, amino aromatic compounds such as aniline, and many substituted amino-benzene derivatives. Additionally, many diisocyanates are toxic, e.g., 2,4- and 2,6-toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), chloro-, bromo-, and iodoacetic acid, methyl bromide, tribromomethane (bromoform), carbon tetrachloride, and formaldehyde. Also, many natural compounds present in many plants have toxic properties, and a selection of these are listed in Table 3.4. 

Two of the most important aromatic isocyanates are 2,4-tolylene diisocyanate (TDI) and 4,4-diphenylmethane diisocyanate (MDI). TDI consists of a mixture of the 2,4-and 2,6-toluene diisocyanate isomers [37-39]. 

Polyurethanes consist of flexible polyester or polyether units (blocks) alternating with rigid urethane units (blocks) derived from a diisocyanate, commonly a mixture of 2,4- and 2,6-toluene diisocyanate ... 

Only the diisocyanates are of interest for urethane polymer manufacture and relatively few of these are employed commercially. The most important ones used in elastomer manufacture are the 2,4- and 2,6-toluene diisocyanates (TDl) 4,4 -diphenylmethane diisocyanates (MDI) and its aliphatic analogue 4,4 -dicyclohexylmethane diisocyanate (Hi2 MDI) 1,5-naphthalene diisocyanate (NDI) 1,6-hexamethylenediisocyanate (HDI) xylyene diisocyanate (XDI), isophorone diisocyanate (IPDI) and 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (TMDI). Also manufactured commercially are various monoisocyanates, including methyl, /7-propyl, /7-butyl, cyclohexyl, phenyl, and 4-chloro- and 3,4-dichlorophenyl isocyanates which are used for substituted ureas and carbamates important as herbicides and crop protection agents. 

Polyurethanes consist of flexible polyester or polyether units (blocks) alternating with rigid urethane units (blocks). The rigid urethane blocks are derived from a diisocyanate, commonly a mixture of 2,4- and 2,6-toluene diisocyanate. The more flexible blocks are derived from low-molecular-weight (MW 1000-4000) polyesters or polyethers with —OH groups at each end of the polymer chain. Polyurethane fibers are fairly soft and elastic and have found use as Spandex and Lycra, the "stretch" fabrics used in bathing suits, leotards, and undergarments. 

Typical diisocyanates include 2,4- and 2,6-toluene diisocyanate (TDI), and methylenediphenyl-4,4 -diisocyanate (MDI). Depending on whether a rigid or elastomeric flexible polyurethane is required, the diols can be either simple diols, e.g. butan-l,4-diol, or polymeric poly ether diols (e.g. poly-THF) or hydroxy-terminated polyesters. Cross-linkage is provided by the addition of small amounts of glycerol. Carbon dioxide is liberated by the presence of trace amounts of water and this is often used as the blowing agent for foams. 

Table 3.4 Rate Constants for Various Reactions of 2,4 and 2,6 Toluene Diisocyanates with Polyols...

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