The Pre-event Phase
The UCIL factory was built in 1969 to produce the pesticide Sevin (UCC's brand name for carbaryl) using methyl isocyanate (MIC) as an intermediate. A MIC production plant was added in 1979. After the Bhopal plant was built, other manufacturers including Bayer produced carbaryl without MIC, though at a greater manufacturing cost. However, Bayer also uses the UCC process at the chemical plant once owned by UCC at Institute, West Virginia, USA.
The chemical process employed in the Bhopal plant had methylamine reacting with phosgene to form MIC, which was then reacted with 1-naphthol to form the final product, carbaryl. This "route" differed from the MIC-free routes used elsewhere, in which the same raw materials were combined in a different manufacturing order, with phosgene first reacting with naphthol to form a chloroformate ester, which was then reacted with methyl amine. In the early 1980s, the demand for pesticides had fallen, but production continued, leading to buildup of stores of unused MIC.
Read more about this topic: Bhopal Disaster
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