C - Chemistry – Metallurgy – 07 – C
Patent
C - Chemistry, Metallurgy
07
C
C07C 263/06 (2006.01) C07C 265/14 (2006.01)
Patent
CA 2508471
Disclosed is a multistage process for continuous and phosgene-free preparation of a (cyclo)aliphatic diisocyanate, which comprises (1) reacting a (cyclo)aliphatic diamine with (i) urea or a urea derivative and (ii) an alcohol, while simultaneously removing formed ammonia, to form a (cyclo)aliphatic diurethane in a reaction mixture which also contains low, medium and high boiler by-product components: (2) removing the alcohol and the low and medium boiler components from the reaction mixture to obtain the (cyclo)aliphatic diurethane also containing the high boiler component; (3) thermally cleaving the (cyclo)aliphatic diurethane without a solvent in the presence of a catalyst in an apparatus, to release the desired (cyclo)aliphatic diisocyanate while leaving a cleavage residue containing the uncleaved (cyclo)aliphatic diurethane and the high boiler component; (4) discharging a portion of the cleavage residue from the apparatus, re-urethanizing it with the alcohol and then removing the high boiler component; and (5) recycling the (cyclo)aliphatic diurethane formed in step (4) to the step (1), (2) or (3). The process ensures good plant availability and good process yield, by avoiding viscous deposits promoted by the high boiler components.
Kohlstruk Stephan
Kreczinski Manfred
Michalczak Hans-Werner
Degussa Ag
Fetherstonhaugh & Co.
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