Chemical Modification of Cotton to Enhance its Dyeability

The dyeing of cotton can be problematic to the dyeing industry when dyeing with different dye classes because a significant amount of dyes find their way into effluents. Cotton dyed with different class of dyes suffers from washing-off, wash-fastness, light-fastness, rubfastness and ring-dyeing problems. A method to increase the substantivity for the cotton fiber is to create a positive charge on the fiber. For this purpose the cotton fiber was pretreated with cationising agents Servon XRK and NMM derivative. Servon XRK and NMM derivative were used as part of EU Frame Work V. Servon XRK (3-chloro-2-hydroxy-N, N, N-trimethyl-l-propanaminium chloride) and NMM derivative [4-(3-chloro-2- hydroxypropyl)-4-methylmorpholin-4-ium chloride)] were applied to cotton by pad-batch method. In this research vat dyes, acid dyes, azoic colourants and reactive dyes have been used. The dyeings from vat dyes gave improved colour yield values when applied to the Servon XRK and NMM modified cotton fabrics as compared to the unmodified cotton fabrics. The dyeings from anthraquinone vat dyes (Cl Vat Violet 1, Cl Vat Red 13 and Cl Vat Green 1) on modified (Servon XRK and NMM) cotton fabric absolutely did not lose any colour in wash-off liquor as the dyeings from anthraquinone vat dyes (Cl Vat Violet 1, Cl Vat Red 13 and Cl Vat Green 1) on the unmodified cotton fabric gave a significant amount of colour in wash-off liquor. Vat dyes on the modified cotton fabric gave overall better dyeing results than on the unmodified cotton fabric. Disulphonated acid dyes Cl Acid Red 13 and Cl Acid Red 17 gave better wash-fastness results than monosulphonated (Cl Acid Red 88) and trisulphonated (Cl Acid Red 18 and Cl Acid Red 27). The light-fastness results were better for the dyeings from trisulphonated acid dyes than the monosulphonated and disulphonated acid dyes. The dyeings from Cl Acid Blue 193 gave good dyeing results than the dyeings from Cl Acid Violet 92. The overall dyeing results are better for the dyeings obtained by the application o f Naphthol AS to the Servon XRK modified cotton fabric by pad-dry and pad-batch-dry methods followed by coupling than the corresponding dyeings on the unmodified cotton fabric. Sumifix Supra Blue BRF and Sumifix Supra Red 3BF applied on the Servon XRK modified cotton fabric gave improved dyeing results than applying on unmodified cotton fabric. Reactive dyes co-applied with NMM have given overall better results than when applied without NMM.