Dyeing Behaviors Of Polyamide/Cationic Dyeable Polyamide Mixture

Cationic dyeable polyamide (CD-PA) fibers containing sulfonate groups within thepolymer structure can be dyed with cationic dyes. The fabrics in new style can beachieved by the interweaving of CD-PA with ordinary polyamide (PA), and by theprocess of appropriate dyeing and finishing. The researches on the dyeing propertiesand methods of PA/CD-PA mixture will provide both a theoretical basis and a guidelinefor its practical dyeing and finishing process. In this paper, the dyeing behaviors andfixation methods of PA/CD-PA mixture were investigated, and the interaction betweenacid and cationic dyes was also discussed. The major results of these researches wereconcluded as follows:(a) Dyeing properties of acid, reactive and cationic dyes: The acid, reactive andcationic dyeing was greatly affected by pH, and the suitable pH of dye bath was allabout5. Acid and cationic dyes exhibited good building-up properties on this mixture,but had fast rates of initial uptake. The staining of reactive dyes on CD-PA wasdependant on their structures; the dyes containing less sulfonate groups stained moreseriously on CD-PA. The color fastness of acid and reactive dyes was good while that ofcationic dyes to light and washing was poor.(b) Interaction between acid and cationic dyes during one-bath dyeing: Theinteraction became stronger as the concentration of acid and cationic dyes increased,and varied with the dyes used. The interaction between acid and ordinary cationic dyeswas much stronger than that between acid dyes and cationic dyes in dispersed form. Thecomplex of acid and cationic dyes was obviously solubilized by the nonionic dispersant,which effectively reduce the negative effect of this interaction on dyeing.(c) One-bath dyeing with acid and cationic dyes: The influence of pH on acid andcationic dyeing in one bath was similar to that on acid or cationic dyeing in separatebath. The initial uptake rate of ordinary cationic dyes applied using one-bath dyeingtechniques was slower than that of cationic separate dyeing, but the dyeing rate of acid dyes was faster than that of acid separate dyeing. The dyeing rates of acid dyes andcationic dyes in dispersed form in one bath were close to those of acid or cationicdyeing in separate bath. When acid and cationic dyes were applied in one bath, somecolor fastness was unsatisfactory.(d) One-bath dyeing with reactive and cationic dyes: Reactive dyes showedslightly higher exhaustion and fixation when applied together with ordinary cationicdyes in one bath, obviously lower exhaustion and fixation when applied together withcationic dyes in dispersed form. Reactive dyes mainly fixed onto PA fibers, anddisplayed the effect of stain on CD-PA fibers. Compared to cationic separate dyeing, theexhaustion of cationic dyes and the apparent color depth of CD-PA decreased during theone-bath dyeing of reactive and cationic dyes. The mixture dyed with reactive andcationic dyes in one bath showed good color fastness to rubbing and light, but poorcolor fastness to washing.(e) Fixing treatment of dyed mixture: The fixing effect was evaluated using thedesorption of dyes from the dyed mixture. The desorption of cationic dyes withoutfixing was higher under acidic condition than under alkaline, neutral and nonionicauxiliary condition, and increased with increasing temperature of desorption bath. Thedesorption of acid dyes without fixing was high in alkaline condition, and very lowunder other conditions. Both the anionic and cationic fixing agents were able to restrainthe desorption of acid and cationic dyes, but the anionic fixing agent was more effective.The desorption of acid dyes decreased and the color fastness of acid dyes was improvedas the amount of anionic fixing agent and the temperature of fixing increased. Aftercationic dyes were fixed with anionic fixing agent, their color fastness to light andwashing was slightly improved, but that to rubbing decreased obviously.