Mobay Chemical Corporation, based in Pittsburgh, Pennsylvania, was a joint venture of Monsanto Company and Bayer to market polyurethanes in the United States. Founded in 1954, Bayer bought out Monsanto's shares in the company in the 1970s.
Mobay, along with Miles Laboratories, was a member of Bayer's menagerie of companies in the US while Bayer did not own the US rights to its name.
After a first failed attempt of appearing under the Bayer USA Inc. name in the US, Bayer consolidated its US operations under the Miles name in 1992.
Mobay was one of the suppliers of the dioxin-contaminated 2,4,5-T used to produce the Agent Orange sprayed in Operation Ranch Hand (1962-1972).
In April 1990, Mobay and Occidental Chemical Corporation refused to supply the Department of Defense with thionyl chloride, a chemical needed for the production of sarin. The US government considered filing suit against Mobay and Occidental for violating Title III of the Defense Production Act of 1950, which gives the government the power to requisition supplies for warfare.