Production of easily dispersible, high tinctorial strength perylene-3,4,9,10-tetracarboxylic acid diimides

Claim 1

In a process for the production in pigmentary form of perylene-3,4,9,10-tetracarboxylic acid diimide or the corresponding N-alkyl diimides of one to four carbon atoms in each alkyl, the improvement for producing a pigment which has high tinctorial strength and is easily dispersible which comprises the steps of: grinding the crude pigment until the mean primary particle size is not more than 0.05 micron; introducing the ground material into a treatment medium which consists essentially of an aliphatic primary amine selected from the group consisting of ethylamine, n-propylamine, n-butylamine, n-hexylamine, ethanolamine, 1-aminopropanol, 3-aminopropanol, β-methoxyethylamine, β-ethoxyethylamine, β-butoxyethylamine, γ-methoxypropylamine, γ-ethoxypropylamine, γ-butoxypropylamine or a mixture of the same; mixing the ground pigment in said medium at a temperature of from ambient temperature to 160°C until the pigment has recrystallized; and then separating the pigment from the treatment medium.