Relationship between colour fastness and colour strength of polypropylene fabrics dyed in supercritical carbon dioxide: effect of chemical structure in 1,4‐bis(alkylamino)anthraquinone dyestuffs on dyeing performance

Abstract

A series of 1,4‐bis(alkylamino)anthraquinone dyestuffs were applied for supercritical fluid dyeing of unmodified polypropylene fabric, which is known to be difficult to dye in a conventional aqueous system. A marked tendency was shown that the dyeability improved as the carbon number of alkyl substituents on the anthraquinone chromophore increased. By evaluating the build‐up curves of the dyestuff, it was found that the carbon number of optimum alkyl chain length for 1,4‐bis(alkylamino)anthraquinone was 8–12. From the relationship between the build‐up curve and the colour fastness, it was concluded that the upper limit of dyeing depth for good colour fastness was 40 mmol/kg of fibre.