Abstract

Commercial production of 4,4¢-methylenedianiline (4,4¢-MDA) is carried out by the acid-catalyzed reaction of formaldehyde with aniline. All processes produce polymeric MDA (PMDA), which consists of mixtures of isomers and oligomers of MDA. More than 99% of the manufactured PMDA products are used in reactions with phosgene to produce the corresponding isocyanates for use in polyurethanes. The resultant polymeric isocyanates (PMDI) are either sold commercially or are purified to isolate 4-4¢-methylenediphenyldiisocyanate (MDI). MDI is an important intermediate in the manufacture of spandex fibers, thermoplastic resins, and coatings, and it is used in reaction injection molding (RIM) for automotive applications. The primary use of PMDI products is in rigid foam insulation, but they are also used in semiflexible foams, foundry core binders, and particle board manufacture. Nonisocyanate uses for MDA or PMDA include epoxy curing agents, filament wound pipe, wire coatings, and military applications. MDA reacts similarly to other aromatic amines under the proper conditions. All of the toxicity data on MDA have been collected using either 4,4¢-MDA or the corresponding hydrochloride salt. Because MDA is a potentially hazardous chemical, worker exposure should be kept to a minimum. The major exposure route in workers who experience MDA poisoning is by skin contact. MDA is a suspected human carcinogen.