Rhone-poulenc Chimie

Ferenc Sagi

Gerard Collas

Jean Robin

Andre Blind

Georges Gros

Toluene diisocyanate (TDI) is separated and recovered from the residues of the production thereof, e.g., from the tars of phosgenation of an aromatic diamine, by extracting such residues with an extractant which comprises an inert gas, e.g., CO.sub.2, in either the liquid or supercritical state, optionally in the presence of a coextractant diluent, for example an ester, aromatic hydrocarbon or chlorinated aromatic hydrocarbon, or chlorinated aliphatic hydrocarbon.

Separation of toluene diisocyanate from the residues of the production

Polyisocyanates containing only trace amounts of free aromatic diisocyanates are recovered by purifying and isolating an isocyanate condensate containing free NCO groups from an impure admixture thereof, said isocyanate condensate impure admixture having been prepared by reacting a stoichiometric excess of an aromatic di- or polyisocyanate with a reactant compound containing at least two functional groups which are reactive with NCO groups, and such purification/isolation entailing extracting unreacted excess di- or polyisocyanate from said impure admixture with an inert gas, e.g., carbon dioxide, in either the liquid or supercritical state.

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Lyons, France

Ferenc Sagi