For fibers that are easy to dye such as cotton fabrics, the main process conditions are reasonable, and the dyes are selected correctly. Generally, there are no technical problems in dyeing dark colors. However, some polyester and nylon fabrics with relatively high requirements are generally difficult to obtain dark colors. Such as special black polyester, etc., you need to use a special dyeing method to dye dark and light colors. The traditional dark fabric dyeing methods are summarized as follows:
1. Increase the dyeing temperature
Raising the dyeing temperature can make the fiber structure bulky, accelerate the movement of dye molecules, and increase the chance of dye diffusion to the fiber. Therefore, when dyeing dark colors, we always try our best to increase the dyeing temperature to increase the dyeing rate. However, increasing the dyeing temperature one-sidedly may affect the strength of dyed fabrics, and may also cause high temperature discoloration or hydrolysis of some dyes; defects such as color spots of chemical fibers; some dyes may increase the dyeing rate with the increase of dyeing temperature. The decrease is the desorption phenomenon; increasing the dyeing temperature also puts forward higher requirements for dyeing equipment. Therefore, it is not scientific to increase the dyeing temperature to increase the dyeing rate.
2. Increase the amount of dye
Some factories dye dark fabrics, and most of them use the method of increasing the amount of dyes to obtain dark colors. For example, the dark-colored operator finds that the color is not dark after checking the sample after dyeing, and then adds the amount of dye again, but the final effect is not ideal. On the contrary, due to the huge amount of dye, the treatment of dyeing sewage is more difficult. Sometimes even if the dyed dark effect is obtained, the color fastness of the dyed fabric is quite poor. This is because this dyeing only increases the non-dyeing rate of the fabric. . The phenomenon of some dark fabrics on the market will fade when they are exposed to water, which is mostly caused by this reason, which is especially obvious in the printing and dyeing factories with weak technical force.
3. Add electrolyte to promote dyeing
In the dyeing process of reactive dyes and direct dyes, electrolytes such as NaCl and Na2SO4 are often added to promote dyeing. In acid dyeing, glacial acetic acid HAC, H2SO4, etc. are added to promote dyeing, and these methods can improve the dyeing of fabrics to a certain extent. rate and dye uptake.
However, due to the relatively large amount of dye used in dark dyeing, usually more dye accelerators are added. However, adding too much electrolyte will not only reduce the brightness of dyed fabrics, but also cause the agglomeration of dyes due to the excessive amount of electrolytes, resulting in quality problems. There is still a certain proportion of the amount.