Learning Points | Color fastness of reactive dyes and disperse dyes [Theory]
1, Light-fast dyeing of reactive dyes The photobleaching of reactive dyes is a very complex photooxychlorination reaction. After knowing the mechanism of photobleaching, consciously creating some obstacles to the photooxidation reaction during the design of the molecular structure of the dye, and delaying photobleaching. For example, a yellow dye containing Dole sulfonic acid group and pyrazolone, a blue dye of a phthalocyanine methyl hydrazine and a disazo chelate ring, and a metal complex-containing red dye, but still lacking a vivid red color resistance. Light fastness of reactive dyes. The light fastness of dyeings varies with the dyeing density. Fabrics dyed on the same fiber with the same dye have improved lightfastness as the dyeing concentration increases. Light-colored fabrics have low dyeing densities. The degree dropped accordingly. However, the light fastness of common dyes on printed dye colour cards is determined at a dyeing concentration of 1/1 of the standard depth (ie 1% owf or 20-30 g/l dye concentration) if the dyeing concentration is 1/1 In the case of 6,1/12 or 1/25, the light fastness will be greatly reduced. Some people have proposed using ultraviolet absorbers to improve the light fastness. This is an undesirable method. Ultraviolet light has to be used in many ways. It can only improve by half, and the cost has to be improved a lot. Therefore, only the fair use of dyes can solve the light fastness. 2. The wet rubbing fastness of reactive dyes dyeing and dyeing fabrics The reason for the difference in the wet rubbing fastness of textiles with dark dyes of reactive dyes is mainly the floating color transfer of water-soluble reactive dyes and the mechanical friction transfer of colored fiber particles. Measures to improve the dyeing of textiles with reactive dyes must be comprehensively resolved from dye selection, dyeing process, fabric type, and additive-specific additives. The fixing rate must be higher than 70%, and the difference between the final dye uptake and fixation rate is less than 15% to reduce the floating color of the dyed fabric. The dye uptake rate at one time is not higher than 75% so that the floating color can be easily removed. Also, dyes with high dye lifting power are required, that is, the amount of dye used in deep-color dyeing cannot exceed 10% of the saturated adsorption capacity of the fiber. Dyeing process is also very important, wash floating color is the key, hard water is not conducive to wash off the floating color, must be softened, it is best to use non-contact drying, functional finishing fabric damage, increase the colored fiber particles must be controlled in at the lowest limit. Finally, after the treatment with a special agent for improving the wet fastness, the wet rubbing fastness of the deep dyeing fabric with reactive dyes can be improved by 0.5-1.0. 3. Decrease in fastness due to thermal migration of disperse dyes after dyeing After dyeing, thermal migration refers to the disperse dyes dyed polyester fiber, and at high temperature treatment (stretching and setting), due to the influence of the auxiliary agent on the fabric surface, a thermal migration occurs, and the dye migrates from the fiber interior to the fiber through the expanded fiber capillary. The surface causes the dye to accumulate on the fiber surface, resulting in a series of fastnesses. This phenomenon may also occur in the long-term storage and transportation of dyed textiles and clothing. The phenomenon of redistribution of disperse dyes in polyester fibers and auxiliaries is different from that of disperse dyes. This decrease in fastness is collectively referred to as heat transfer fastness. This phenomenon has been caused by the widespread use of amino silicone oil microemulsion softeners containing a large amount of nonionic surfactants in textiles for the past 20 years. The solution is to switch to a macroemulsion type aminosilicone oil containing a small amount of emulsifier and a non-emulsifying self-emulsifying hydrophilic aminosilicone oil. At the same time, the introduction of heat-resistant migration disperse dyes in Europe, such as Foron S-WF and Dispereol XF with special structures, makes the dyes with high affinity with polyester fibers, and it is also difficult to migrate from the fiber inside at high temperatures. On the surface, it solves the decrease in fastness caused by thermal migration. Dyed Printed Scuba Fabric,Scuba Fabric,Air Layer Scuba Fabric,Digital Printed Scuba Fabric SHAOXING XIANCHENG TRADING CO.,LTD , https://www.xcxssfabric.com
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