C - Chemistry – Metallurgy – 07 – C
Patent
C - Chemistry, Metallurgy
07
C
C07C 263/06 (2006.01) C07C 265/14 (2006.01)
Patent
CA 2478723
Disclosed is a process for continuous phosgene- free preparation of (cyclo)aliphatic diisocyanates. The process comprises: (A) reacting (i) a (cyclo)aliphatic diamine with (ii) urea or a urea derivative and (iii) an alcohol to give a (cyclo)aliphatic diurethane and by- products comprising low-boiling, middle-boiling and high- boiling fractions (B) freeing the (cyclo)aliphatic diurethane of the low, middle and high boiling fractions; (C) thermally cleaving the (cyclo)aliphatic diurethane to give the (cyclo)aliphatic diisocyanate and a cleavage residue; (D) discharging a portion of the cleavage residue and reurethanizing the portion with the alcohol, to form a reurethanization product; and (E) reintroducing the reurethanizing product into step (B). The process affords a good yield and is free from a decrease in selectivity over a long operation time.
Elm Rainer
Kohlstruk Stephan
Kreczinski Manfred
Michalczak Hans-Werner
Degussa Ag
Fetherstonhaugh & Co.
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