Multi-step process for the continuous preparation of cycloaliphatic diisocyanates

摘要

Multi-level procedure for continuous production of cyclo-aliphatic diisocyanate (I) comprises reacting cycloaliphatic diamine with carbonic acid derivatives and alcohols to form cycloaliphatic diurethane and subsequent thermal splitting of the diurethane to (I), where the preparation of the diurethane is carried out in two stage, such that the light-, residue free diurethane is thermally split to release diisocyanate. Multi-level procedure for continuous production of cyclo-aliphatic diisocyanate of formula OCN-R-NCO (I) comprises reacting cycloaliphatic diamine of formula H 2N-R-NH 2 (II) with carbonic acid derivatives and alcohols of formula R 1>-OH (III) to form cycloaliphatic diurethane of formula H 2N-OC-HN-R-NH-CO-NH 2 (V) and subsequent thermal splitting of the diurethane to cycloaliphatic diisocyanate, where the preparation of the diurethane is carried out in two stage, that the light-, residue free diurethane is thermally split to release diisocyanate, a part of released diisocyanate is continuously removed from the column of apparatus, thus highly boiled components separated with alcohol are reurethanised and recycled in the process. An independent claim is also included for a multi-level procedure for continuous production of cyclo-aliphatic diisocyanate of formula (OCN-R-NCO) where both the isocyanate groups are directly bound to a cyclic hydrocarbon (between them at least 3 carbon atoms are arranged) comprises reaction of cycloaliphatic diamine with carbon dioxide derivatives and alcohols to form diurethane, and its thermal splitting, where: (a) cycloaliphatic diamine of formula (H 2N-R-NH 2) (where both nitrogen atoms are directly bound to at least a cyclic hydrocarbon and between them at least 3 carbon atoms are arranged) reacts with urea in presence of alcohols (III) of formula (R 1>-OH) and in the absence or presence of catalysts to form cycloalkylenediurea (IV) of formula (H 2N-OC-HN-R-NH-CO-NH 2) (where both the flanking nitrogen atoms of R are bonded directly to a hydrocarbon cycle and between them at least 3 carbon atoms are arranged) and simultaneous continuous removal of the emerging ammonia; (b) the resulting raw cycloalkylenediurea is converted in a second reactor to cycloalkylenediurethane compound (V) of formula (R 1>O-OC-HN-R-NH-CO-R 1>) where (III) is used as a solvent, under continuous expulsion of the released ammonia; (c) from the obtained reaction mixture, the alcohol, dialkyl carbonates and/or carbamic acid alkyl ester are separated and the alcohol is recycled into the reaction step (a); (d) optionally completely or partially separating the highly boiled residues contained in the obtained reaction mixture; (e) after the steps (c) and (d) diurethane containing reaction mixture is removed continuously by thermal splitting in the presence of a catalyst and in the absence of solvent at a temperature of 180-280 (preferably 200-260) [deg] C and under a pressure of 0.1-200 (preferably 0.2-100) mbar and a part (10-60 (preferably 15-45) wt.%) of the fed reaction mixture is constantly removed; (f) the column products are rectified into a raw diisocyanate and alcohol is separated; (g) the raw cycloaliphatic diisocyanate is removed by distillation and the pure product group is isolated; (h) the drains are removed from (e) into a valuable material and a waste stream is separated and the waste stream rich in highly boiled components, is removed and rejected from the process; (i) the valuable material stream from (h) is reacted with the alcohol from (f) in the presence or absence of catalyst within 1-150 (preferably 3-60) min, at 20-200 (preferably 50-170)[deg]C and a pressure of 0.5-20 (preferably 1-15) bar, and the molar ratio of NCO groups and OH groups amounts to 1:100 (preferably 1:10); (j) a part of the fraction of the drain of the pure distillation from (g) is continuously removed and recycled into the column reaction of (e) and/or into the urethanisied substance; (k) optionally pure distillation of the raw cycloaliphatic diisocyanate occurring with main group is led into the urethanised substances; and (l) the reurethanised stream of (i) is led back into the steps (b) and/or (c). R : 4-18C (preferably 5-15C) bivalent cyclo-aliphatic hydrocarbon; R 1>hydroxyl groups of a primary or secondary 3-8C (cyclo)aliphatic alcohol.