Pigment Synthesis and Aftertreatment

Coupling reactions, which are commonly carried out in aqueous media, afford benzimidazolone pigments, usually in the form of hard particles. Thermal after-treatment is necessary to adapt these crude products to the demands of technical application (Sec. 2.2.3). 

Subsequent finishing of the crude product typically involves heating the aqueous pigment suspension, frequently to temperatures of 100 to 150°C. The crude pigment slurry is thus heated under pressure. This technique may be varied to a certain extent. It is possible, for instance, to add or to exclusively use either water soluble or water immiscible organic solvents or to add surface-active nonionic, anionic, or cationic agents. 

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