What are the factors affecting alkaline dyes

Alkaline dyes have a high affinity for acrylic fiber. When dyeing, due to fast adsorption and slow diffusion, it is easy to produce uneven dyeing. Once uneven dyeing occurs, it is difficult to correct it by extending the dyeing time. When cationic dyes are used for dyeing, the dyeing rate should be appropriately reduced to obtain uniform dyeing results. In addition to the type of acrylic fiber, the factors affecting the dyeing rate of cationic dyes include the following:

1. Temperature

Temperature is an important factor to control level dyeing. When acrylic fiber is dyed with cationic dyes, the dye uptake is very little below 75 ℃. When the dyeing temperature reaches the glass transition temperature of the fiber (75-85 ℃), the dye uptake rate increases rapidly. Therefore, when the dyeing temperature reaches the glass transition temperature of the fiber, the temperature should be raised slowly, generally 1 ℃ every 2-4 minutes. It can also be kept warm for dyeing at 85~90 ℃ for a period of time, and then continue to heat up to boiling.

2. pH value of dyeing bath

Adding acid in the dyeing bath can inhibit the dissociation of acidic groups in acrylic fiber, reduce the number of anionic groups on the fiber, reduce the coulomb attraction between the dye and the fiber, and reduce the dyeing rate. The effect of pH value on dyeing rate is more significant for acrylic fiber containing carboxylic group, and the effect of pH value on dyeing rate of acrylic fiber containing sulfonic group is less. The pH value of the dyeing bath should be reasonably controlled during dyeing. Cationic dyes are generally not alkali resistant, and the optimal pH value for dyeing is generally 4-4.5. The pH value of the dyeing bath can be higher when dyeing dark colors, and the lower pH value should be used when dyeing light colors. The pH value of the dye bath is generally adjusted by acetic acid, which can not only reduce the pH value of the dye bath, but also improve the solubility of the dye. Adding sodium acetate in the dyeing bath at the same time can stabilize the pH value of the dyeing bath within the required range.