78.7 Parts of 1-chloronaphthalene, 4.3 parts of perylene-3,4:9,10-tetracarboxylic dianhydride and 11.9 parts of o-phenylenediamine were charged in a stainless steel reactor equipped with a pitched blade turbine agitator, a circulation jacket connected to an oil supply system, a temperature measuring element and a distillation line with a condenser. After the aforementioned raw materials were charged and the agitator speed adjusted to 200 rpm, the reactor was purged with nitrogen gas, and the reactor contents were heated by raising the temperature of the jacket in about one hour to the desired reaction temperature of 240° to 245° C. The reaction was continued for an additional 6 hours at this temperature. The reactor was then cooled by cooling the jacket oil with water to about 90° C. and the reactor contents were then transferred to a Nutsche vacuum filter equipped with an agitator. The filtrate was drained by applying vacuum to the filter. The crude, wet pigment cake was reslurry washed twice using 80 parts of warm dimethylformamide, with the wash filtrate drained each time by vacuum filtration. The cake was subsequently reslurry washed nine times with alkaline methanol at room temperature to, for example, remove acidic impurities. Each alkaline methanol wash was prepared by dissolving 0.33 part of sodium hydroxide in 66 parts of methanol. The pigment cake was then reslurry washed four times with methanol (66 parts of methanol used in each wash) and dried in a vacuum dryer at 65° C. and full vacuum for 16 hours. 5.89 Parts of crude benzimidazole perylene powder were obtained.
