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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.
Hydrogenated MDI (H 12 MDI or 4,4′-diisocyanato dicyclohexylmethane) is an organic compound in the class known as isocyanates. [1] More specifically, it is an aliphatic diisocyanate. It is a water white liquid at room temperature and is manufactured in relatively small quantities.
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]
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.
MDA is a common monomer in the synthesis of polymer materials. These include polyamides, [4] polyimides and polyimines. [5] MDA is also used extensively as a precursor to methylene diphenyl diisocyanate (MDI). Here, MDA is treated with phosgene to produce MDI. MDI, in turn, is a precursor to many polyurethane foams.
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)
Toluene diisocyanate (TDI) is an organic compound with the formula CH 3 C 6 H 3 (NCO) 2.Two of the six possible isomers are commercially important: 2,4-TDI (CAS: 584-84-9) and 2,6-TDI (CAS: 91-08-7). 2,4-TDI is produced in the pure state, but TDI is often marketed as 80/20 and 65/35 mixtures of the 2,4 and 2,6 isomers respectively.
Initially, the listed company only owned the methylene diphenyl diisocyanate (MDI) production line of the former Yantai synthetic leather factory. [4] It was a common practice at that time to list part of the assets instead of the whole conglomerate. The size of the listed company expanded beyond that assets, however.