Monoalkali metal salts of perylene-3,4,9,10-tetracarboxylic acid monoanhydride and process for their manufacturing

Abstract

Perylene-3,4,9,10-tetracarboxylic acid monoanhydride mono-sodium or mono-potassium salts are obtained from neutral salts of perylene-3,4,9,10-tetracarboxylic acid, if necessary in the presence of at least one molar equivalent of sodium or potassium ions, at 20.degree. to 100.degree. C. by adding three molar equivalents of a sufficiently strong acid. The products are dye precursors, especially for asymmetric N-substituted perylenetetracarboxylic acid diimide pigments.

Dependencies are inferred from the claim text.