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 C1-C4alkyl, hydroxyl and nitro, each R1 and R2, independently, represent hydrogen or, a C1-C4alkyl group, R′1 represents hydrogen, hydroxyl, C1-C4alkyl or C1-C4hydroxyalkyl, R3 represents hydrogen, C1-C4alkyl or phenyl, which is unsubstituted or substituted by one or two groups selected from C1-C4alkyl, C1-C4alkoxy, halogen, hydroxyl, —NH2, nitro, —SO3M and —CO2M and M represents hydrogen, an alkaline or alkaline earth metal, ammonium or ammonium that is mono-, di-, tri- or tetrasubstituted by C1-C4alkyl or C2-C4hydroxyalkyl 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 C1-C4alkyl and C1-C4alkoxy and R3 and 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.

Dependencies are inferred from the claim text.