Disazo dyes and dye compositions for shading white paper

Abstract

The invention relates to novel dyes of the formula (1) in which D represents a phenyl or naphthalene residue which is substituted by one or two sulphonic Acid or carboxylic acid groups and, optionally, by one or two groups selected from C-Calkyl, hydroxyl and nitro, each Rand R, independently, represent hydrogen or, a C-Calkyl group, R'represents hydrogen, hydroxyl, C-Calkyl or C-Chydroxyalkyl, Rrepresents hydrogen, C-Calkyl or phenyl, which is unsubstituted or substituted by one or two groups selected from C-Calkyl, C-Calkoxy, halogen, hydroxyl, —NH, nitro, —SOM and —COM and M represents hydrogen, an alkaline or alkaline earth metal, ammonium or ammonium that is mono-, di-, tri- or tetrasubstituted by C-Calkyl or C-Chydroxyalkyl or a polyglycolammonium cation and also known dyes of formula (5), in which D′ represents a phenyl or naphthalene residue which is substituted by one or two sulphonic acid or carboxylic acid groups and, optionally, by one or two groups selected from C-Calkyl and C-Calkoxy and Rand M are as defined above, and their mixtures suitable for shading white paper, a process for shading, a process for the preparation of the novel dyes and white paper which has been treated with such shading components.