Blue dye with particularly high purity and positive triboelectric control effect

摘要

The dye base sulphate of formula (I) is produced with a residual amine content of less than 2000 ppm, as determined by HPLC, by precipitation of the dye base, made by Friedel-Crafts alkylation, substitution and hydrolysis, as the dye base sulphate and a) taken up in water and subjecting to a first steam distillation then filtered and optionally dried at 50 to 180° C., b) the pressed cake is treated with water or the optionally dried dye base sulphate is moistened with water, c) subjected to a further steam distillation and filtration and d) dried at 50 to 180° C.