Process for the purification of mixtures of toluenediisocyanate

The invention relates to a process for the purification of toluenediisocyanate by fractionating a crude distillation feed comprising toluenediisocyante, an organic solvent and less than 2% by weight of phosgene in a heat integrated system comprising an upstream distillation column (1), an interchanger (8) and a downstream distillation column (4) which are connected in series, whereby the vapor which is recovered from the upstream distillation column (1) is used to reboil the bottoms product of the downstream distillation column (4) or the feed to the downstream distillation column (4) in the interchanger (8), and whereby the crude distillation feed comprising less than 2% by weight of phosgene is fractionated into three product fractions P1 - P3 and optionally a fourth fraction P4, whereby P1 is a noncondensible gas stream enriched with phosgene and/or low-boilers, P2 is a solvent -enriched product, P3 is a high boiler enriched bottoms product comprising toluenediisocyanate and P4 is a toluenediisocyanate enriched stream lean in highboilers and reaction residues.