A study of novel bisazo reactive red dyes with good wet fastness

Three series of bisazo reactive red dyes were synthesised using 6‐amino‐1‐naphthol‐3‐sulphonic acid and its derivatives as the coupling components. The dyeing parameters and wash fastness of these dyes on knitted cotton were evaluated and the relationships between the structure and dyeing properties were investigated. It was found that the hydrophilic groups introduced into the dye molecules decrease the substantivity and fixation of the dyes, but increase the build‐up and migration properties. The defined wash‐off factor can directly reflect the wash fastness of the dyes and the build‐up property can be improved by commercialisation using certain auxiliaries. The results indicate that there is the possibility of synthesising a red reactive dye with a satisfying balance between high fixation and good wash fastness and several such dyes have been developed.