process for the production of c. i. acid red 42 with improved application properties, and use farbstoffpräparationen dyeing or printing of nitrogenous fasermaterialien

摘要

C.I. Acid Red 42, of formula (I), is prepd. by the following process:- 2-aminodiphenylsulphone is diazotised in aq. mineral acid and coupled with 2-amino-8-naphthol-6-culphonic acid at pH 0.5-3.5 maintained by adding alkali metal or alkaline earth metal of mineral acids or of 1-3C carboxylates; the suspension is heated at 40-130 degrees C, filtered at 30-100 degrees C, after which the dye is optionally washed with a 1.5-10% aq. soln. of an alkali metal salt of a strong acid to obtain the dye in free acid form with an electrolyte content 15%. The dye is used to colour natural or synthetic N contg. fibres, particularly wool and polyamides. A much purer shade with a better colour yield is obtd. and solns. and paste contg. the prepd. dye do not tend to thicken or gel or cooling.