Disperse dyeing of nylon 6 fiber using gemini surfactants containing ammonium cations as auxiliaries

Abstract

The dyeing behavior of the disperse dye, 1,4-diaminoanthraquinone (1,4-DAA), on nylon 6 fiber in the presence of the cationic gemini surfactants, propanediyl-α,ω-bis(dimethyldodecylammonium bromide) (DC3-12) and hexanediyl-α,ω-bis(dimethyldodecylammonium bromide) (DC6-12) as auxiliaries, was investigated, and compared with that obtained in the presence of the corresponding conventional surfactant, dodecyltrimethylammonium bromide (C12C1NBr). The dyeing rate increased in the order of C12C1NBr <DC3-12 <DC6-12, reflecting a difference in surfactant property. The extent of dye uptake altered slightly below the critical micelle concentration (CMC), but dye uptake decreased hyperbolically with an increase in surfactant concentration above the CMC. The decrease in the extent of dye uptake above the CMC is concerned with the solubilization capacity of 1,4-DAA into the micelles: the greater solubilization capacity reduced dye uptake. This result shows that the dye which is solubilized in the surfactant micelles rarely takes part in dyeing the fiber and the surfactant micelles act as a reservoir for the dye. A linear relationship was obtained between the amount of dye in the fiber and that in the dyebath, leading to the calculation of the apparent partition coefficients, K. The K values in the presence of the surfactants whose concentration was above the CMC increased in the order of C12C1NBr<DC6-12<DC3-12<<water, indicating that they were also related to solubilization capacity. On the other hand, the K values increased in the order of water <C12C1NBr<DC6-12<DC3-12 for the dyebath which contained a 1:1 molar ratio of dye:surfactant in which the surfactant concentrations were below the CMC. This result suggests that K is dependent not only on the solubilization capacity but also on the dispersing ability of the surfactant. The maximum extent of dye uptake on to nylon 6 fiber in the presence of surfactants whose concentration was above the CMC was 3.0×10 −5, 4.0×10 −5, and 3.3×10 −5 mol g −1 for DC3-12, DC6-12, and C12C1NBr, respectively, at 100 °C, whereas those obtained in a dyebath containing a 1:1 molar ratio of dye:surfactant were 4.0×10 −5, 4.2×10 −5, and 3.3×10 −5 mol g −1 for DC3-12, DC6-12, and C12C1NBr, respectively, at 100°C. This suggests that an improvement in dye uptake occurred in the presence of the gemini surfactants. Thus, it is concluded that gemini surfactants can be used to control dyeing kinetics or to improve dye uptake in the disperse dyeing of nylon.