The Sorption Behavior Of A Syntan On Fibers And Its Application In Dyeing

Syntans are, typically, water-soluble anionic condensates including sulfonate groups, aromatic rings and hydroxy groups. In the field of textile, syntans are used as the fixing agents, dye-resist agents during the dyeing of wool/nylon blends and cellulose/nylon blends. The researches on their sorption and desorption properties on fibers and their applications in dyeing provide both a theoretical basis for its application and a guideline for solving the problems during practical production. In this paper, the sorption and desorption properties of a commercial syntan on wool, silk and nylon were investigated. And its applications during the dyeing of nylon/cotton blends, silk/wool blends and silk/nylon blends were also discussed. By these basic researches, the important conclusions were concluded as follows:(a)The sorption behavior of syntan: The sorption of syntan on wool, silk and nylon followed a dual sorption mechanism consisting of Nernst and Langmuir type models. Nernst and Langmuir sorption constants increased with increasing temperature, indicating that syntan sorption was endothermic. The saturation increased with the increasing temperature at acid condition or the increasing concentration of sodium sulfate at neutral condition.(b)The desorption behavior of syntan: The desorption property should be greatly dependent on syntan application temperature, pH, temperature and surfactants of desorption solution, heat setting of fiber's, etc. The research showed that the extent of syntan desorption decreased with the increase in the temperature of its application and heat setting of fibers, which was induced by the greater extent of syntan diffusion into fiber interior. The high desorption of syntan under alkaline condition would reduce the reserving effect remarkably at the fixation stage of the reactive dyeing of nylon/cellulose blends, but this character could be utilized in the stripping of syntan from dyed and syntanned nylon fibers.(c)The resist effect of syntan to the uptake of dyes by different fibers: The differences in the fiber structure caused the different resist effect of syntan to the uptake of dyes by different fibers. The syntan exhibited the excellent resist effect to the uptake of acid and reactive dyes by nylon which was induced by the compact structure of nylon. The ability of syntan to resist the uptake of the acid dyes with two sulfonate groups and large molecular weight by wool was also strong, which was primarily attributed to a decrease in the coefficient of dye diffusion within fiber interior caused by the existence of the large molecular size syntan in the scale layer of wool. But the syntan had a weak resist effect to silk dyeing due to the loose structure of silk.(d)The application of syntan to the dyeing of nylon/cotton blends: The syntan exhibited not only faster sorption rates and higher sorption quantity on nylon than on contton, but also excellent resist effect to nylon dyeing. When applied to nylon/cotton blends, the syntan imparted the resist effect to the uptake of reactive dyes by nylon component, whereas it had little influence on the dyeing of cotton component. The resist ability of the syntan to nylon was greatly influenced by the nature of the dye and the temperature of syntan application.(e) The application of syntan to the dyeing of silk/wool and silk/nylon blends: When sill/wool blends were dyed using acid dyes with two sulfonate groups and large molecular weight and silk/nylon blends were dyed to pale to medium shades using most of acid dyes, their union dyeing properties were improved because of syntan application. The mechanism of an improved in the union dyeing property was the difference in the interactions of syntan with wool, silk and nylon as well as the different resist effectiveness of syntan to the acid dyeing of wool, silk and nylon. For the dyeing of silk/wool blends using acid dyes with two sulfonate groups and large molecular weight, the syntan had the dominant resist effectiveness to wool. And for the dyeing of silk/nylon blends, the syntan had the dominant resist effectiveness to nylon and no resist effectiveness to the uptake of most of acid dyes by silk.