| abstract |
The present invention relates to a process for the preparation of a mixture comprising at least two structurally different diketopyrrolopyrrole pigments of formula n n n n n n n n n n whereinn nA 1 and A 2 are each independently of the other an aromatic or heteroaromatic radical, by reacting a succinic acid ester with at least one unsubstituted or substituted aromatic or heteroaromatic nitrile, which process comprises carrying out the reaction in the presence of at least one compound of formulan n n n n n n n n n n whereinn nA is an aromatic or heteroaromatic radical, R 3 is hydrogen, halogen, methyl, methoxy, —CF 3 or —CN, R 4 is a linear or, from C 3 upwards, optionally branched C 1 -C 30 alkyl, C 6 -C 10 aryl or C 6 -C 24 aralkyl radical, X is —S—, —O—, —CR 5 R 5 ′—, —COO—, —CONR 5 —, —SO—, SO 2 —, —SO 2 NR 5 — or —NR 5 — and R 5 and R 5 ′ are each independently of the other hydrogen or a linear or, from C 3 upwards, optionally branched C 1 -C 30 alkyl, C 6 -C 10 aryl or C 6 -C 24 aralkyl radical,n nto the use of such a mixture in the colouring of organic material and in cosmetics, and also to novel diketopyrrolopyrrole pigment mixtures. |