US 4,596,678 AGranted

Multiple-step process for the preparation of hexamethylene diisocyanate-1,6 and/or isomeric aliphatic diisocyanates with six carbon atoms in the alkylene residue

AssigneeBASF SE

InventorsFranz Merger, Friedrich Towae, Hans Hellbach, Gunther Isbarn, Waldemar Koehler

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Abstract

Hexamethylene diisocyanate and/or isomeric alkylene diisocyanates having 6 carbon atoms in the alkylene radical, preferably 2-methylpentamethylene 1,5-diisocyanate and/or 2-ethyltetramethylene 1,4-diisocyanate are prepared without the use of phosgene in a multiple-step process by means of (a) reacting hexamethylene 1,6-diamine and/or isomeric alkylene diamines having 6 carbon atoms in the alkylene radical with urea and alcohol in the presence of dialkyl carbonate and/or carbamic acid alkyl ester as well as, in some cases, catalysts to form hexamethylene 1,6-dialkylurethane and/or isomeric alkylene dialkylurethanes having 6 carbon atoms in the alkylene radical, (b) separation and return to reaction step (a) of alcohol, dialkyl carbonate, and/or carbamic acid alkyl ester from the reaction mixture (c) evaporation of the hexamethylene 1,6-dialkylurethane and/or isomeric alkylene dialkylurethanes having 6 carbon atoms in the alkylene radical, (d) cleavage of the vaporized diurethanes into hexamethylene diisocyanate and/or isomeric alkylene diisocyanate having 6 carbon atoms in the alkylene radical and alcohol, and (e) fractional condensation of the cleavage products.

Claims11

Dependent claims

A multiple-step process for the preparation of hexamethylene diisocyanate-1,6 and/or isomeric aliphatic diisocyanates with 6 carbon atoms in the alkylene residue wherein

(a) hexamethylenediamine-1,6 and/or isomeric alkylenediamines with 6 carbon atoms in the alkylene residue are reacted with urea and alcohol in the presence of dialkyl carbonates and in the presence of catalysts to form hexamethylene dialkylurethanes-1,6 and/or isomeric alkylene dialkyl urethanes with 6 carbon atoms in the alkylene residue, while the resulting ammonia is simultaneously removed,
(b) the alcohol, the dialkyl carbonates, and/or carbamic acid alkyl esters are removed from the resulting reaction mixture and returned to reaction step (a),
(c) the hexamethylene dialkylurethanes-1,6 and/or isomeric alkylene dialkyl urethanes with 6 carbon atoms in the alkylene residue are evaporated in an evaporator at temperatures from 200.degree. C. to 300.degree. C. and at a pressure of 0.1 mbar to 200 mbar,
(d) the vaporized diurethanes are thermally cleaved at temperatures of greater than 300.degree. C. and at a pressure of 0.1 to 200 mbar in a cleaving reactor into hexamethylene diisocyanate-1,6, and/or isomeric alkylene diisocyanates with 6 carbon atoms in the alkylene residue, and alcohol, and
(e) the cleavage products are fractionally condensed.

2 more elements

Dependencies are inferred from the claim text.