How to solve the problem of dye color change?

In the dyeing of polyester and its blended knitted fabrics, printing and dyeing workers put forward the problem of the use of dyes, mainly the discoloration of disperse dye polyester. For example, the hue of disperse red FB changes to purple, and the hue of disperse dark blue H-GL changes to brown. Disperse Red FB has a bright hue and good dyeability, but when metal ions such as copper and iron are present in the dye bath, it will combine with the dye to form a metal complex structure, making the dyed shade bluish and purple, and poor dyeability.

In addition, certain metal ions in the dye bath can trigger redox reactions under acidic and high temperature environments, destroying the structure of the dye, and directly causing no coloration.

The solution is:

(1) Add a chelating dispersant to the dye bath to complex the metal ions in the water so that it does not affect the structure of the dye.

(2) Disperse red ACE with similar hue can be used instead, the latter is more stable than the former.

Disperse dark blue H-GL is (CI. Disperse Blue 79). Because of its deep dyeing and sublimation fastness, it has been used for a long time, but occasionally the problem of large color light deviation occurs. This is mainly caused by the special sensitivity of Disperse Dark Blue H-GL to the pH value of the dyeing bath. Usually the pH value of the dyeing bath is controlled at 4.5～5, and the pH value is greater than 7, and the color light will change greatly, from reddish to brown, or even change. It is khaki with a great drop in depth. Preventive measures: the amount of acetic acid for dyeing must be accurate, and the dyeing bath ratio must be strictly controlled.

The problem of color change of dyes is not only a problem of single dyes, but also has a certain relationship with the combination of dyes used in color matching. Low-temperature dyes do not require high pH, and can even be dyed in alkaline, while high-temperature individual dyes are particularly sensitive to pH; the other two types of dyes are very different from the requirements of dyeing temperature, and they are not suitable for color matching.

Attention should also be paid to the effect of additives on the change of dye shade. The leveling agent, anti-wrinkle agent, moisture wicking finishing agent, fixing agent, silicone oil softener and other auxiliary agents added in the dyeing process of knitted fabrics must ensure that they have no effect on the shade and color depth of the fabric. Pioneer experiments are generally done, and then used in mass production. Properly adjusting the setting temperature can also reduce or avoid the color change of the fabric.