METHOD OF PRE-TREATMENT BEFORE PRODUCING ISOCYANATE MIXTURE

PROBLEM TO BE SOLVED: To provide a method of pre-treatment before producing an isocyanate mixture for obtaining the isocyanate mixture reduced in the contents of metals, such as iron, affecting the reactivity of the isocyanate mixture. SOLUTION: There is provided the pre-treatment method performed before the production of the isocyanate mixture G by production processes including a reaction process for reacting an amine mixture E with phosgene F to synthesize an isocyanate mixture and a concentration process for concentrating the reaction process solution containing the isocyanate mixture, characterized by introducing an acidic substance C and pre-treating media A and B into the system of the production process, circulating them in at least one of the system of the reaction process and the system of the concentration process, and then discharging them from the production process. COPYRIGHT: (C)2010,JPO&INPIT