| 摘要 |
PROBLEM TO BE SOLVED: To provide an improved method for recovering and refining toluene diisocyanate. SOLUTION: This method for refining toluene diisocyanate is provided by reboiling a bottom product of a downstream side distillation column or a feed sent to the downstream side distillation column by using steam recovered from an upstream side distillation column. An unrefined distillation feed containing≤2 wt. % phosgene is fractionated to 3 fractions of P1 to P3 and in some cases to 4th fraction P4. The P1 is a non-condensed gas stream obtained by concentrating phosgene and/or low boiling substances, P2 is a product obtained by concentrating a solvent, P3 is a bottom product obtained by concentrating high boiling substances containing toluene diisocyanate, and P4 is a stream obtained by concentrating toluene diisocyanate containing less high boiling substances and residual substances of the reaction. By the method, it is possible to reduce a total production cost by operating the recovery and refining process of toluene diisocyanate in a good energy efficiency. COPYRIGHT: (C)2004,JPO
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