A process for the purification of toluenediisocyanate by fractionating a
crude distillation feed containing toluenediisocyante, an organic solvent
and less than 2% by weight of phosgene in a heat integrated system having
an upstream distillation column, an interchanger and a downstream
distillation column which are connected in series. The vapor which is
recovered from the upstream distillation column is used to reboil the
bottoms product of the downstream distillation column or the feed to the
downstream distillation column in the interchanger. 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. 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.
