Patent ID: 8334386

Claim:
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.