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



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.