Raw materials were charged into the reactor that manufactured dihydroxydiphenylmethane by a reaction of phenol with formaldehyde at night on the previous day. By putting in the catalyst in the morning of the day, the contents were heated to the fixed 80 °C, and heating was stopped. However, the temperature continued to rise, so cooling was attempted, but a runaway reaction occurred. As a result, the internal pressure of the reactor increased and the reactor burst. One operator was injured. Although the cause cannot be specified, it is supposed that the temperature was raised too high initially, agitation was started while the temperature was rising, and vapor pressure was increased because cooling water piping was blocked, and so on.
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