Regulations (Preambles to Final Rules) - Table of Contents|
| Record Type:||Occupational Exposure to 4,4' Methylenedianiline (MDA)|
| Title:||Section 4 - IV. Physical Properties, Manufacture, and Uses of MDA|
IV. Physical Properties, Manufacture, and uses of MDA
Methylenedianiline (CAS 101-77-9) (MDA) is a light brown, or tan, crystalline solid with a faint amino-like odor. MDA is slightly soluble in water and very soluble in alcohol and benzene. MDA is produced commercially by the condensation of aniline and formaldehyde. Crude MDA (40-60 percent MDA) is a liquid or a hard wax-like substance. Purified (99 percent) MDA is in the form of either light yellow crystalline flakes or white granules.
Ninety-eight percent of the MDA produced is used directly in the manufacture of methylenediphenyl diiosocyanate (MDI). The remaining two percent is used as a precursor for the manufacture of plastic fibers, antioxidants, dyestuff intermediates, corrosion preventatives, and special polymers.
The MDI is produced in two grades, monomeric (pure) and polymeric. Ninety percent of the crude MDA is used to produce polymeric MDI, and another 8 percent of the crude MDA is converted to monomeric MDI. MDI is used to produce flexible and rigid polyurethane foams, elastomers, coatings, thermoplastic resins, foundry core binders, adhesives, sealants, and spandex fibers.
The remaining MDA is produced in the pure form for other uses: epoxy resin curing agents, wire coating applications, polyurethane co-reactants, in pigments and dyes, and defense applications.
There are eleven principal industry sectors where workers are potentially exposed to MDA. These sectors are: (1) MDA Production for MDI Synthesis/MDA Sale and Import; (2) Reprocessing; (3) Filament Winding; (4) Potting and Encapsulation; (5) Molding/Bonding of Tools and Specialty Small Parts; (6) Wire Coating; (7) Application of Coatings; (8) Intermediate for TGMDA and PACM-20 Production; (9) Polyurethane Curing; (10) Advanced Composite Materials Production; and (11) Use of PMR-15 Pre-preg Materials. There are also seven other industrial sectors where MDA was once used and may still be used on a limited basis. These minor sectors are: (1) Coatings (Polybismalimides) of Printed Circuit Boards and Fabrication of Airplane Parts; (2) Dyes and Pigments; (3) Quiana Yarn; (4) Intermediate for Pharmaceuticals, Herbicides, etc.; (5) Rubber Processing; (6) Anti-Oxidants; and (7) Ketamine Production. Maintenance workers have been separately identified from each of these sectors for purposes of analysis. Occupational exposure to MDA also occurs in the Construction and Maritime industries.
There are six firms which produce MDA for MDI production, MDA for sale, or which import MDA. MDA is manufactured by 6 companies at 7 locations in four states: Dow Chemical Co.(LaPorte, Texas); BASF (Geismar, La); E.I. Dupont (Belle, WV); Mobay Chemical (New Martinsville, WV and Baytown, TX); Rubicon Chemical (Geismar, La); and Uniroyal Chemicals division of Avery (Naugtuck, Ct). Three of these companies, Mobay, Rubicon, and Dow account for over 90 percent of the MDA production. It is estimated that approximately 600 million pounds of MDA are produced for MDI conversion, 4,474,000 pounds are produced domestically for sale, and an additional 1.8 million pounds are imported. In addition, it is estimated that the percentage of MDA in the product made domestically ranges from 40-70 percent while the percentage in the imported product is approximately 98 percent.
|Regulations (Preambles to Final Rules) - Table of Contents|