diisocianat

Diisocianati are organic compounds containing two isocyanate groups (-NCO) per molecule. They are highly reactive intermediates used mainly to manufacture polyurethanes, where -NCO groups react with polyols to form urethane linkages.

The most important diisocyanates are toluene diisocyanate (TDI), methylene diphenyl diisocyanate (MDI, often as polymeric MDI), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI). Their structures may be aromatic or aliphatic, which influences the properties of the resulting polymers.

Production typically occurs by phosgenation of diamines (for example, TDI from toluenediamine; MDI from methylenediamine derivatives). Polymeric diisocyanates are mixtures of oligomers that extend functionality.

In use, diisocyanates react with polyols to form polyurethanes, with amines to form polyureas, and with water to yield amines and carbon dioxide, contributing to foam formation during processing. They are key components of foams, coatings, adhesives, elastomers, and sealants.

Health and safety: diisocyanates are respiratory sensitizers and irritants; exposure can trigger asthma and dermatitis. Handling requires adequate ventilation, protective equipment, and medical surveillance where indicated. Regulatory frameworks enforce exposure limits and restrict use.

Environmental considerations: diisocyanates are reactive and can hydrolyze in the environment; releases should be managed to minimize exposure.