Patent ID: 7108770

Claim:
A process for the purification of toluene diisocyanate from a crude distillation feed comprising less than 2% by weight of phosgene comprising a) fractionating the crude distillation feed comprising less than 2% by weight of phosgene to remove solvent and, optionally, reaction residue to produce a crude toluene diisocyanate feed comprising less than 20% by weight of solvent and b) separating the crude toluene diisocyanate feed comprising less than 20% by weight of solvent in a divided-wall distillation column into four product fractions P1–P4 comprising: P1, a vapor phase low-boiler and solvent-enriched gas stream, P2, a low-boiler and solvent-enriched product, P3, a high-boiler-enriched bottoms product comprising toluene diisocyanate and P4, a toluene diisocyanate product stream lean in low-boiler, high-boiler and reaction residue.