| 摘要 |
In a process for purifying a crude organic isocyanate comprising passing an inert gas through said isocyanate to remove hydrogen chloride and phosgene, distilling, in a first distillation step, the resulting degassed material to remove solvent contained therein and distilling in a second distillation step, the residue of the first distillation step to remove the organic isocyanate from residual impurities, the residue of the first distillation step is heated to a temperature in the range 150 DEG to 300 DEG C. prior to said second distillation step, whereby the concentration of the hydrolysable chloride is substantially reduced. The process may be carried out batchwise or continuosly. In examples, toluene diisocyanate is purified and nitrogen is employed as inert gas. |
