Process for preparing (cyclo)aliphatic isocyanates
View Patent ↗The present invention relates to a process for preparing (cyclo)aliphatic diisocyanates and triisocyanates corresponding to the formula R—(NCO) n (I), wherein R represents a (cyclo)aliphatic hydrocarbon group having up to 15 carbon atoms, provided that there are at least two carbon atoms between two nitrogens, n represents the number 2 or 3, by a) separately heating phosgene and a diamine or triamine corresponding to the formula R—(NH 2 ) n (II), to a temperature of 200° C. to 600° C., wherein the amine may optionally be diluted with an inert gas or with the vapors of an inert solvent, b) optionally passing the reactants over torque-producing baffles and c) continuously reacting phosgene and the amine in the gas phase in a reaction chamber without moving parts and with constrictions of the walls in the region of the reaction zone.
1. A process for preparing a (cyclo)aliphatic diisocyanate or triisocyanate corresponding to the formula
R—(NCO) n (I),
wherein
R represents a (cyclo)aliphatic hydrocarbon group having up to 15 carbon atoms, provided that there are at least two carbon atoms between two nitrogens,
n represents the number 2 or 3,
which comprises
a) separately heating phosgene and a diamine or triamine corresponding to the formula
R—(NH 2 ) n (II),
to a temperature of 200° C. to 600° C., wherein the amine may optionally be diluted with an inert gas or with the vapors of an inert solvent,
b) optionally passing the reactants over torque-producing baffles and
c) continuously reacting phosgene and the amine in the gas phase in a reaction chamber without moving parts and with constrictions of the wall in the region of the reaction zone, wherein the reaction chamber has an abrupt widening of the cross-sectional area in the direction of flow after the mixing of the reactants.
2. The process of claim 1 wherein the reaction chamber has a cascade-like and/or continuous variation in the cross-sectional area.
3. The process of claim 1 wherein the cross-sectional area of the reaction chamber widens at an angle of 80° to 90° and wherein the ratio of the cross-sectional areas of the reaction chamber before and after the widening is 3:1 to 7:1.
4. The process of claim 2 wherein the cross-sectional area of the reaction chamber widens continuously or cascade-like and the ratio of the cross-sectional areas of the reaction chamber before and after the widening is greater than 1:1 to 2:1.
5. The process of claim 1 which comprises passing the phosgene and amine over torque-producing baffles shortly before being mixed in the reactor.
6. The process of claim 1 wherein said amine is diluted with an inert gas and/or with the vapors of an inert solvent.
7. The process of claim 1 wherein said diamine comprises 1,6-diaminohexane.
8. The process of claim 1 wherein the diisocyanate comprises 1,6-diisocyanatohexane.
9. The process of claim 1 wherein the triamine comprises triaminononane.
10. The process of claim 1 wherein the triisocyanate comprises triisocyanatononane.