| abstract |
The dye base sulfate of the formula (1), is prepared with a residual amine content of less than 2000 ppm as determined by HPLC by precipitating the dye base, prepared by Friedel-Crafts alkylation, substitution and hydrolysis, as the dye base sulfate and (a) taking up the dye base sulfate in water and subjecting it to a first steam distillation, then filtering it and drying, where appropriate, at from 50 to 180 DEG C, (b) adding water to the presscake or pasting the dye base sulfate, where it has been dried, with water, (c) subjecting it to a further steam distillation and filtration (d) and to drying at from 50 to 180 DEG C. |