Aqueous synthesis of perylene pigments
A process for preparing perylene pigments of the general formula (Ia) or (Ib) or mixtures thereof, by reacting perylenetetracarboxylic acids or functional derivatives thereof with aromatic diamines, where R 1 , R 2 may be the same or different and may each independently be phenylene, naphthylene or pyridylene, where R 1 , R 2 may each be mono- or polysubstituted by C 1 -C 22 -alkyl, C 3 -C 22 -alkenyl, C 1 -C 22 -alkoxy, hydroxyl and/or halogen, X 1 , X 2 , X 3 , X 4 , X 5 , X 6 , X 7 , X 8 may be the same or different and may each independently be hydrogen or halogen, wherein the reaction is performed in the presence of a secondary or tertiary amine in an aqueous reaction medium.
1. A process for preparing a perylene pigment of the general formula (Ia) or (Ib)
or a mixture thereof, the process comprising:
reacting, in the presence of a secondary or tertiary amine in an aqueous reaction medium,
(A) a perylenetetracarboxylic acid, a perylenetetracarboxylic anhydride, a perylenetetracarbonyl chloride, or a salt of the perylenetetracarboxylic acid, with
(B) an aromatic diamine, wherein
R 1 and R 2 are independently phenylene, naphthylene, or pyridylene, and are optionally mono- or polysubstituted by C i -C 22 -alkyl, C 3 -C 22 -alkenyl, C 1 -C 22 -alkoxy, hydroxyl, halogen, or a mixture thereof, and
X 1 , X 2 , X 3 , X 4 , X 5 , X 6 , X 7 , and X 8 are independently hydrogen or halogen.
2. The process of claim 1 , wherein R 1 and R 2 are each unsubstituted phenylene.
3. The process of claim 2 , wherein the aqueous reaction medium comprises essentially no organic solvent.
4. The process of claim 1 , wherein the aqueous reaction medium comprises up to 30% by weight of an organic solvent.
5. The process of claim 4 , wherein the organic solvent is an aromatic nitrogen-containing heterocycle.
6. The process of claim 5 , wherein the aromatic nitrogen-containing heterocycle is N-methylimidazole.
7. The process of claim 1 , wherein the secondary or tertiary amine is selected from the group consisting of piperazine, N-(2-hydroxyethyl)piperazine, diethanolamine, N,N′- dimethylpiperazine, N-ethylpiperazine, N-methylcyclohexylamine, imidazole, N-methylimidazole, and pyrrolidine.
8. The process of claim 1 , wherein the reaction employs from 0.5 to 2.0 molar equivalents of a secondary or tertiary amine based on the perylenetetracarboxylic acid, the perylenetetracarboxylic anhydride, the perylenetetracarbonyl chloride, or the salt of the perylenetetracarboxylic acid.
9. The process of claim 1 , wherein the reaction is performed at a temperature in a range from 150 to 250° C.
10. The process of claim 1 , wherein the reaction is performed additionally in the presence of a surface-active substance.
11. The process of claim 1 , wherein R 1 and R 2 are each unsubstituted naphthylene.
12. The process of claim 5 , wherein the aromatic nitrogen-containing heterocycle is imidazole.
13. The process of claim 1 , wherein the secondary or tertiary amine is piperazine.
14. The process of claim 1 , wherein the secondary or tertiary amine is N-methylimidazole.
15. The process of claim 1 , wherein the secondary or tertiary amine is N-methylcyclohexylamine.
16. The process of claim 1 , wherein the secondary or tertiary amine is N,N′-dimethylpiperazine.
17. The process of claim 1 , wherein the secondary or tertiary amine is N-ethylpiperazine.
18. The process of claim 1 , wherein the secondary or tertiary amine is diethanolamine.
19. The process of claim 1 , wherein the secondary or tertiary amine is imidazole.
20. The process of claim 1 , wherein the secondary or tertiary amine is N-(2-hydroxyethyl)piperazine.
21. The process of claim 1 , wherein the secondary or tertiary amine is pyrrolidine.