NEWS ABOUT DYEING POLYAMIDE WITH UNCONVENTIONAL DIRECT DYE

Abstract

News about the process of dyeing a polyamide yarn with unconventional direct textile dye, which is conventional for dyeing cotton yarns have described in this study. An attempt to polyamide yarn dyeing with this type of dye in laboratory is done in order to create realistic possibilities for application in industrial conditions. Polyamide is a chemical fiber obtained from synthetically produced polymers, while direct dyes are sulphonated azo compounds: derived from benzidine and his derivates or type of amine diaminostylene and others. In the experiment, the samples of polyamide yarn with linear density of 6,6 tex (units for fineness) has used. The yarn has dyed with a direct dye of a specific structure that has a predisposition to connect to this fiber. Dyeing time with continuous mixing was 5, 10, 15, 25 and 40 minutes. Also, in dyeing solution, to achieve a certain pH solution, acetic acid is added. The applied dye is marked like a C.I. Direct Brown 2 (azo-dye). The constant bulk of solution is contained concentrations of dye 10, 30, 50, 70 and 100 mg/dm3. Samples were dyed at a temperature of 90 °C. The spectrophotometer (Cary 100 Conc UV-VIS, Varian) was used to measure the adsorption of aqueous dyed solutions and to calculate an unknown dye concentration in the solution based on the calibration curve. The degree of dye exhaustion and the amount of adsorbed dye were calculated. The degree of exhaustion at all concentrations, for different dyeing time after 40 min was 80 %. The time of length of contact between the absorbent and the adsorbent, for different concentrations of used dye, results in a higher degree of exhaustion. Noticeable is continuity in the changes in the amount of adsorbate on the adsorbent with the increase of the initial concentration and time, i.e. a bigger amount of dye in the solution or longer dyeing time contribute a higher amount of adsorbed dye per unit mass of the adsorbent. Freundlich's model in the form of nonlinear or linear isotherms proved to be the most effective in the simulating the polyamide dyeing. High functionality of the variables was detected, the coefficient of determination was 0,95. Dyeing of polyamide with direct dye expands the dye spectrum that can be dyed the polyamide yarns. Dyeing of the yarn at a higher temperature gives better results than dyeing at a lower temperature. The results of this research with achieved efficiency indicate the possibility of a different approach in the dyeing the polyamide yarn with direct dyes, in order to further development of the industrial process. For better results, it necessary to carefully select the compistion of the bath and the method od dyeing, to elaborate the phase of dyeing to achieve good dyeing of fiber. It has been shown that dzeing at a higher temperature increases adsorption of dye. It has been determined that dyeing - adsorption depends on the contact time and the initial dye concentration.