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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.
In the industrial production, MDA is produced by reaction of formaldehyde and aniline in the presence of hydrochloric acid. [3] 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).
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]
Aniline is predominantly used for the preparation of methylenedianiline and related compounds by condensation with formaldehyde. The diamines are condensed with phosgene to give methylene diphenyl diisocyanate, a precursor to urethane polymers. [7] Most aniline is consumed in the production of methylenedianiline, a precursor to polyurethanes.
English: Synthesis of from 4,4'-methylene diphenyl diisocyanate (MDI) from 4,4'-diaminodiphenylmethane and phosgene. Deutsch: ...
The production of plastics worldwide has doubled in the last two decades, according to Our World in Data. Plastic’s versatility, durability, and low weight-to-strength ratio have made it an ...
California Gov. Gavin Newsom ordered state agencies to recommend ways to reduce health harms and limit the purchase of candy, soda and other ultra-processed foods.
The reaction of (MDI) and polyol takes place at higher temperatures compared with the reaction temperature for the manufacture of PUR. At these elevated temperatures and in the presence of specific catalysts, MDI will first react with itself, producing a stiff, ring molecule, which is a reactive intermediate (a tri-isocyanate isocyanurate compound).