Cationic Dyes Exhaustion Process

Dyeing of Special Fiber Types with Cationic Dyes by the Exhaustion Process... 

Since the objective of this work was the evaluation of the exhaustion process, for the exhaustion process different concentrations of antibacterial product were applied and their impact in dye uptake evaluated. Figure 2 compares the exhaustion of dye for cotton treated with 15% (w.o.f) and 7.5% (o.w.f.). As expected the exhaustion of dye reflects the quantity of cationic antibacterial compound in fibre, being about 20% lower when using half the amount. If the lower concentration of antibacterial is sufficient for the objective, then for hi er exhaustion some salt should be used. 

The modified cotton showed excellent dye exhaustion for all the dyes in the absence of salt. The treatment was foimd to improve the dye fixation also. The modification was also assessed through elemental analysis. This study may be further extended to viscose material after suitably modifying the treatment conditions. In another trial, 3-chloro-2-hydroxypropyltrimethylammonium chloride was used as a cationic agent to cationize cotton fabric by a pad-batch process. The cationized cotton samples were dyed with different reactive dyes containing various reactive groups. The dyeability of the cationized cotton samples with reactive dyes without salt was significantly improved due to an increase in the ionic attraction between the dye and cationized cotton. The... 

Direct dyes have an inherent substantivity for cellulose fibers. The dyebath is gradually heated and electrolyte added to promote exhaustion and diffusion. The most attractive feature is the simplicity of the dyeing process. However, a cationic after-treatment is necessary for most direct dyeings to enhance washing fastness (Cook, 1982 Shore, 1995b). The wash fastness of the apparel item, even with an aftertreate-ment, is only satisfactory for pale and some selected medium shades. Consequently direct dyes have been largely replaced by reactive dyes. 

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