Fiber material composed of acid-modified homopolymers or copolymers of acrylonitrile (PAC fibers) which has been obtained by a wet spinning process, has not been dried and is still in a swollen condition (gel form), can be dyed advantageously and in fast colors by means of soluble dyes, the molecule of which contains several groups, namely more than one quaternary grouping and/or a strongly basic grouping carrying no charge, which exert a basic action towards the acid groups of the fiber substance. The chromophore of this colorant can belong to the category of monoazo or diazo dyes, methine, azamethine or diazamethine dyes or naphthalactam dyes. In accordance with the invention, after substantially removing the non-aqueous spinning solvent by washing, the spun material, as a moist gel, is dyed continuously or discontinuously from an aqueous dyebath; the fibers can be stretched before the dye is applied, during the dyeing process itself or immediately afterwards. By virtue of their special nature, the dyes of the type designated above, which have a strong fixing action, produce optimum fixing rates when dyeing PAC gels and, in the subsequent production stages, do not cause any noticeable soiling, as a result of dye which has bled out, on components of machines and operating baths, such as stretching or after-treatment baths. Investigations of penetration of the fiber by the dye, of the fixing rate and of the resulting fastness properties, such as fastness to wet processing, have shown no disadvantages compared with conventional dyes.
展开▼
