Multiple-step process for the preparation of 3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate
AssigneeBASF SE
InventorsHans Hellbach, Franz Merger, Friedrich Towae
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Abstract
This invention discloses a non-phosgene process for the preparation of 3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate by the reaction of the precursor diamine with urea and an aliphatic alcohol in the presence of a dialkyl carbonate and an alkyl carbonate. The intermediate diurethane is separated from starting materials and by-products and thermally cleaved to alcohol and diisocyanate which are separated by fractional condensation of the products from the vapor state. This process gives high yields of the desired diisocyanate and lends itself particularly to continuous processing.
Claims11
A multiple-step process for the preparation of 3-isocyanatomethyl-3,5,5-trimethyl-cyclohexylisocyanate, wherein
- (a) 3-aminomethyl-3,5,5-trimethylcyclohexylamine is reacted with urea and alcohol in the presence of dialkyl carbonates and/or carbamide acid alkyl esters to form 3-alkoxycarbonylaminomethyl-3,5,5-trimethyl-1-alkoxycarbonylaminocyclohexa ne while the ammonia produced thereby is simultaneously removed,
- (b) the alcohol, the dialkyl carbonates and/or carbamic acid alkyl esters are removed and, preferably, returned to reaction step (a),
- (c) the 3-alkoxycarbonylaminomethyl-3,5,5-trimethyl-1-alkoxycarbonylaminocyclohexa ne is evaporated in an evaporator at temperatures from 200.degree. C. to 300.degree. C. and at a pressure of from 0.1 mbar to 200 mbar,
- (d) the vapors are thermally cleaved at temperatures in excess of 300.degree. C. and at a pressure of from 0.1 to 200 mbar in a cleaving reactor into 3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate and alcohol, and
- (e) the cleavage products are fractionally condensed.
Dependencies are inferred from the claim text.