Patent ID: 7786313

Claim:
A process for the preparation of mixtures comprising at least one diketopyrrolopyrrole pigment of formula 3 and at least one diketopyrrolopyrrole pigment of formula 4 wherein R 1 is phenyl R 2 is hydrogen, R 6 is hydrogen, R 7 is a linear C 12 -C 24 alkyl, X is —S— or —O—, by reacting a succinic acid ester with at least one unsubstituted or substituted aromatic nitrile of formula wherein R 1 and R 2 are as defined in formula 3 and 4, which process comprises carrying out the reaction in the presence of at least one nitrile of formula wherein R 6 , X and R 7 are as defined in formula (4), wherein the amount of the compound of formula (2) is from 1 to 10 mole %, based on the total amount of nitriles in the reaction mixture.