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Methylene diphenyl diisocyanate (MDI) is an aromatic diisocyanate. Three isomers are common, varying by the positions of the isocyanate groups around the rings: 2,2′-MDI, 2,4′-MDI, and 4,4′-MDI. The 4,4′ isomer is most widely used, and is also known as 4,4′-diphenylmethane diisocyanate. [3] This isomer is also known as Pure MDI.
The global market for diisocyanates in the year 2000 was 4.4 million tonnes, of which 61.3% was methylene diphenyl diisocyanate (MDI), 34.1% was toluene diisocyanate (TDI), 3.4% was the total for hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), and 1.2% was the total for various others. [18]
More specifically, it is an aliphatic diisocyanate. It is a water white liquid at room temperature and is manufactured in relatively small quantities. It is also known as 4,4'-methylenedi(cyclohexyl isocyanate) or methylene bis(4-cyclohexylisocyanate) [2] and has the formula CH 2 [(C 6 H 10)NCO] 2.
4,4′-Methylenedianiline (MDA) is an organic compound with the formula CH 2 (C 6 H 4 NH 2) 2. It is a colorless solid, although commercial samples can appear yellow or brown. It is a colorless solid, although commercial samples can appear yellow or brown.
A diisocyanate, often 4,4’-methylenediphenyldiisocyanate (MDI), is reacted with trimellitic anhydride (TMA). The product achieved at the end of this process is a high molecular weight, fully imidized polymer solution with no condensation byproducts, since the carbon dioxide gas byproduct is easily removed.
Skeletal formula of 4,4'-methylene diphenyl diisocyanate (4,4'-MDI, Pure MDI). Created using ACD/ChemSketch 10.0 and Inkscape. Date: 5 October 2007: Source: Own work: Author: Fvasconcellos 16:37, 6 October 2007 (UTC) Permission (Reusing this file)
The two highest doses used in this study were 1.0 and 6.0 mg per cubic meter for 6 hours each day, 5 days each week for 2 years. The duration-adjusted exposure levels for these two high concentrations are equivalent to 11 ppb and 70 ppb, 24 hours/day for two years.
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