When dyeing nylon fibers, the dye rarely dyes when the pH value of the dye solution is relatively high; When the pH value of the dye solution drops to a certain value, the dye begins to dye and quickly reaches saturation. The pH value continues to decrease at night without significant addition during dyeing; However, when the pH value further decreased to 3, the dye uptake increased sharply again, resulting in over equivalent adsorption. When nylon fibers are dyed under low pH conditions, they are also subjected to hydrolysis, especially after excessive adsorption. The pH value inside the fiber is lower than that in the solution, and hydrolysis accelerates. After hydrolysis, more amino groups are produced, and the accessibility of the fiber can adsorb more dyes, making it more prone to uneven dyeing. So, according to the actual situation, adjusting the pH value appropriately under light can reduce the phenomenon of discoloration.

PH value selection

Properly controlling the pH value of dyeing is also key to improving uniformity. As mentioned earlier, the dyeing performance of nylon is closely related to the pH value of the dyeing bath. Although a lower pH value is beneficial for dye uptake, the faster the uptake speed, the lower the uniformity. Therefore, it is essential to control the H value of the dye bath well. Generally, pH values can be classified as strong, weak, or neutral, as shown in Table 1.

Article source: Nylon colored yarn

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