Process for trimerising cycloaliphatic diisocyanates
View Patent ↗The invention relates to a process for preparing polyisocyanates containing isocyanurate groups by trimerising cycloaliphatic diisocyanates using a catalyst solution comprising at least one quaternary ammonium hydroxide, characterized in that the catalyst solution is metered in such that the reaction temperature is >90° C. and ≦140° C.
1. A process for preparing a cycloaliphatic polyisocyanate containing isocyanurate groups comprising trimerizing a cycloaliphatic diisocyanate in the presence of a catalyst solution comprising at least one quaternary ammonium hydroxide in a reaction solution, wherein the catalyst solution is metered in to said reaction solution such that a reaction temperature greater than 90° C. and less than or equal to 140° C. is maintained.
2. The process of claim 1 , wherein the catalyst solution is metered in to said reaction solution such that a reaction temperature greater than 90° C. and less than or equal to 135° C. is maintained.
3. The process of claim 1 , wherein the catalyst solution is metered in to said reaction solution such that a reaction temperature greater than 90° C. and less than or equal to 120° C. is maintained.
4. The process of claim 1 , wherein the process is carried out continuously in one or more stirred tanks.
5. The process of claim 1 , wherein an isocyanate content is achieved corresponding to a degree of trimerisation of from 8 to 30%.
6. The process of claim 1 , wherein an isocyanate content is achieved corresponding to a degree of trimerisation of from 12 to 24%.
7. A continuous process for preparing a cycloaliphatic polyisocyanate containing isocyanurate groups comprising trimerizing a cycloaliphatic diisocyanate in the presence of a catalyst solution comprising at least one quaternary ammonium hydroxide in a stirred tank cascade with n stirred tanks, wherein, in at least n/2 or (n/2−0.5) tanks, the metered addition is such that the reaction temperature in at least n/2 or (n/2+0.5) tanks is greater than 90° C. and less than or equal to 140° C., where n/2 applies to an even number of tanks and (n/2−0.5) or (n/2+0.5) applies to an odd number of tanks and n is a whole number from 2 to 6.
8. The process of claim 7 , wherein an isocyanate content is achieved in the nth tank corresponding to a degree of trimerisation of from 8 to 30%.
9. The process of claim 7 , wherein an isocyanate content is achieved in the nth tank corresponding to a degree of trimerisation of from 12 to 24%.
10. The process of claim 1 , wherein the catalyst comprises from 0.001 to 2% by weight of quaternary ammonium hydroxide, based on the amount of diisocyanate.
11. The process of claim 1 , wherein the catalyst comprises from 0.005 to 1% by weight of quaternary ammonium hydroxide, based on the amount of diisocyanate.
12. The process of claim 1 , wherein the catalyst solution has a catalyst concentration of from 0.1 to 10% by weight, based on the catalyst solution.
13. The process of claim 1 , wherein the catalyst solution has a catalyst concentration of from 0.2 to 8% by weight, based on the catalyst solution.
14. The process of claim 1 , wherein the catalyst solution comprises at least one quaternary tetraalkylammonium hydroxide and/or a mixed quaternary tetraalkyl/aralkylammonium hydroxide and/or a quaternary tetraaralkylammonium hydroxide.
15. The process of claim 1 , wherein the catalyst solution comprises at least one quaternary trialkylaralkylammonium hydroxide.
16. The process of claim 14 , wherein the catalyst solution comprises at least one quaternary tetraalkylammonium hydroxide and/or one quaternary mixed tetraalkyl/aralkylammonium hydroxide, wherein the alkyl groups of said at least one quaternary tetraalkylammonium hydroxide and/or one quaternary mixed tetraalkyl/aralkylammonium hydroxide are not substituted with any hydroxyl groups.
17. The process of claim 14 , wherein the catalyst solution comprises a quaternary benzyltrialkylammonium hydroxide.
18. The process of claim 14 , wherein the catalyst solution comprises benzyltrimethylammonium hydroxide.
19. The process of claim 1 , wherein the cycloaliphatic diisocyanate comprises isophorone diisocyanate.
20. The process of claim 1 , wherein the trimerization is stopped chemically or thermally.
21. The process of claim 20 , wherein the trimerization is stopped chemically by adding an acidic compound, an acid, and/or an alkylating agent to the reaction solution.
22. The process of claim 1 , further comprising, in a downstream step, removing residual monomeric cycloaliphatic diisocyanate from the polyisocyanate by distillation.
23. The process of claim 1 , wherein the trimerization is stopped thermally.