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

The dyeing behavior of the disperse dye, 1,4-diaminoanthraquinone (1,4-DAA) , on polyester fiber in the presence of two cationic gemini surfactants, pr opanediyl-alpha,omega -bis(dimethyldodecylammonium bromide) (DC3-12) and he xanediyl-alpha,omega -bis(dimethyldodecylammonium bromide) (DC6-12) as auxi liaries, was investigated, and compared with that obtained in the presence of the corresponding conventional surfactant, dodecyltrimethylammonium. bro mide (C12ClNBr). The dyeing rate in the presence of the gemini surfactants was larger than that for the conventional surfactant, reflecting a differen ce in surfactant property. Dye uptake decreased hyperbolically with increas e in surfactant concentration above the critical micelle concentration (CMC ). The observed decrease in the extent of the dye uptake above the CMC can be attributed to the solubilization capacity of 1,4-DAA into the micelles: the greater solubilization capacity reduced dye uptake. This result shows t hat dye which is solubilized within the surfactant micelles rarely takes pa rt in the dyeing of the fiber and also that the surfactant micelles act as a reservoir for the dye. A linear relationship was obtained between the amo unt of dye in the fiber and that in the dyebath, leading to the calculation of values of the apparent partition coefficients, K. The K values in the p resence of the surfactants whose concentration was above the CMC increased in the order of C12C1NBr <DC6-12 < DC3-12 < < water, indicating that they w ere also related to solubilization capacity. In contrast, the K values hard ly changed in the presence of surfactants whose concentration was below the CMC, suggesting that the K values cannot reflect the dispersing ability of the surfactants because the 1,4-DAA was dissolved in the dyebath under suc h conditions (120 degreesC). It was found that the affinity of the dye for the polyester fiber was unchanged by the addition of surfactant. Maximum dy e uptake on to the polyester fiber in the presence of the surfactants whose concentration was below the CMC was 10.3 x 10(-5), 10.8 x 10(-5), and 9.1 x 10(-5) mol g(-1) for DC3-12, DC6-12, and C12C1NBr, respectively at 130 de greesC the gemini surfactants slightly enhanced dye uptake. It is concluded that gemini surfactants can be used to control dyeing kinetics or to impro ve uptake of disperse dyes on to polyester. (C) 2001 Elsevier Science Ltd. All rights reserved.