How to dye dark fabrics better?

For cotton fabrics, which are relatively easy to dye, the main process conditions are reasonable and the dyes are selected correctly. Generally, there is no technical problem in dyeing dark colors. Some polyester and nylon fabrics with higher requirements are generally more difficult to obtain dark colors. Such as special black polyester, etc., you need to use special dyeing methods to dye dark and light colors. The traditional dyeing methods of dark fabrics are summarized as follows:

1. Increase the dyeing temperature
Increasing the dyeing temperature can expand the fiber structure and speed up the movement of dye molecules, increasing the chance of dye diffusion to the fiber. Therefore, when dyeing dark colors, we always try to increase the dyeing temperature to improve the dyeing rate. However, one-sided increase of the dyeing temperature may affect the strength of the dyed fabric, and may also cause high-temperature discoloration or hydrolysis of certain dyes; defects such as the color point of chemical fibers; and some dyes will increase the dyeing rate with the increase of the dyeing temperature. The decrease is the desorption phenomenon; increasing the dyeing temperature also puts higher requirements on the dyeing equipment. Therefore, increasing the dyeing temperature is not scientific for improving the dyeing rate.

2. Increase the amount of dye
Some factories use dark dyed fabrics to increase the amount of dye used to obtain dark colors. For example, after the dark-colored workers found that the color was not dark after the nuclear sample was dyed, they added the amount of dye again, but the final effect was not ideal. On the contrary, due to the huge amount of dye, it is more difficult to treat the dyeing sewage. Sometimes, even if it is dyed with dark colors, the color fastness of the dyed fabric is quite poor. This is because this dyeing only increases the performance of the fabric. . Some dark fabric clothing on the market will fade after being exposed to water. Most of them are caused by this reason. This is especially obvious in printing and dyeing factories with weak technical strength.

3. Add electrolyte to promote dyeing
In the process of reactive dyes and direct dyes, electrolytes such as NaCl and Na2SO4 are often added to promote dyeing. Acidic dyes are added with glacial acetic acid HAC and H2SO4 to promote dyeing. Some methods can improve the dyeing of fabrics to a certain extent. Rate and uptake rate.

However, due to the relatively large amount of dye used in dark dyeing, the addition of dye promoters is usually more. However, the excessive addition of electrolytes will not only reduce the vividness of the dyed fabric, but also cause the quality problem due to the excessive amount of electrolyte, which may cause the aggregation of dyes. Therefore, even if the amount of dyes is large, the actual accelerator is used as a dye accelerator. There is still a certain proportion of the amount.

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