Methylene diphenyl diisocyanate, most often abbreviated as MDI, is an aromatic diisocyanate. It exists in three isomers, 2,2'-MDI, 2,4'-MDI, and 4,4'-MDI. The 4,4' isomer is most practically useful, and is also known as Pure MDI. MDI is reacted with a polyol in the manufacture of polyurethane. It is the most produced diisocyanate, accounting for 61.3% of the global market in the year 2000.
There are six steps to the manufacture of pure 4,4'-MDI:
The positions of the isocyanate groups influences their reactivities. 4,4'-MDI is a symmetrical molecule and thus has two groups of equal reactivity. 2,4'-MDI is an asymmetrical molecule and thus has two groups of different reactivities. The group at the 4-position is approximately four times more reactive than the group at the 2-position.
4,4'-MDI is also used as an industrial strength adhesive, which is available to end consumers as various high-strength bottled glue preparations.
MDI is the least hazardous of the commonly available isocyanates, as it has a very low vapour pressure. This reduces its hazards during handling compared to the other major isocyanates (TDI, HDI). However, it, like the other isocyanates, is an allergen and sensitizer. Persons developing sensitivity to isocyanates may have dangerous systemic reactions to extremely small exposures, including respiratory failure. MDI should be not be heated or sprayed except with strict engineering controls and personal protective equipment. Compared to other other Isocyanic acid derived Cyanate compunds it has relatively low human toxicity. It is a reactive material and reacts with hydrogen donors, in some cases violently. Its reaction with water produces carbon dioxide which can burst containers and produce aerosols. Since it polymerizes in the presence of water, its ecological risks are low.
WIPO PUBLISHES PATENT OF BASF FOR "PROCESS FOR PURIFYING MIXTURES COMPRISING 4,4'-METHYLENE DIPHENYL DIISOCYANATE" (GERMAN, BELGIAN INVENTORS)
May 30, 2012; GENEVA, May 28 -- Publication No. WO/2012/066001 was published on May 24. Title of the invention: "PROCESS FOR PURIFYING MIXTURES...
WIPO PUBLISHES PATENT OF BASF FOR "PROCESS FOR PURIFYING MIXTURES COMPRISING 4,4'-METHYLENE DIPHENYL DIISOCYANATE" (BELGIAN, GERMAN INVENTORS)
May 27, 2012; GENEVA, May 25 -- Publication No. WO/2012/065995 was published on May 24. Title of the invention: "PROCESS FOR PURIFYING MIXTURES...
Research and Markets Offers Report: Methylene Diphenyl Diisocyanate (MDI) Industry Outlook in Mexico to 2016 - Market Size, Price Trends and Trade Balance
Jan 29, 2013; Wireless News01-29-2013Research and Markets Offers Report: Methylene Diphenyl Diisocyanate (MDI) Industry Outlook in Mexico to...