The invention relates to a process for the preparation of perylene-3,4,9,10-tetracarboxylic acid N,N'-dialkyldiimides by reacting perylene-3,4,9,10-tetracarboxylic acid dianhydride with an alkylamine in aqueous suspension at a low temperature, in the course of which the bis-(alkylammonium) salt of perylene-3,4,9,10-tetracarboxylic acid bis-N-alkylamide is formed. The latter is reacted with a metal salt to give the corresponding sparingly soluble metal salt, which is subjected to the cyclization reaction at an elevated temperature. The pigments prepared by the process according to the invention are distinguished by high purity and are suitable for pigmenting lacquers and plastic compositions.
展开▼
