Analysis of The Causes of Color Spots in Acrylic Fiber Dyeing And Solutions

Causes of color spots

1. Improper dye selection

Dyeing acrylic fiber is different from dyeing other fibers. If the dye is not selected properly, it is difficult to achieve the effect of leveling dyeing even by adding more leveling agents or improving dyeing conditions. Therefore, cationic dyes should be selected with the same compatibility value, and the difference in the compatibility value of the dyes in the formula should be less than 0.5.

Cationic dyes are particularly suitable for dyeing acrylic fibers, with Tiankun's Skyzon®Cationic dyes standing out for its exceptional performance. Skyzon dyes offer excellent compatibility and stability, effectively preventing color spots and uneven dyeing. They deliver uniform, vibrant colors, making them the ideal choice for acrylic fiber dyeing.

2. Improper selection and dosage of leveling agents

⑴Acrylic fiber leveling agents are divided into two categories: slow dyeing leveling agents and transfer dyeing leveling agents

a. Slow dyeing leveling agents are also called blocking agents. The slow dyeing principle of slow dyeing leveling agents is as follows: during dyeing, the slow dyeing agent takes the dyeing seat first. As the temperature gradually rises, the slow dyeing agent is replaced by the dye and combined with the fiber to achieve the purpose of leveling dyeing.

Precautions for using slow dyeing agents:

①If the amount is small, the leveling effect is not good and it is easy to cause color spots. If the amount is too much, it will also cause color spots.

②Because the key temperature for dyeing most acrylic fibers is around 90℃. If the dosage of PAN is appropriate, it can be dyed at a uniform speed at 90℃ for 20 minutes. If it is excessive, it will cause the dyeing temperature to rise and the dyeing speed to accelerate, thus causing color flowers.

③ Taking cationic leveling agent as an example, generally speaking, the dosage for dark colors is 1g/l, and the dosage for medium and light colors is 0.2-0.5g/l.

b. Migration leveling agent: It has the performance of migration and migration, and can migrate dyes from dark colors to light colors.

3. Differences in raw materials

The dyeing properties of acrylic fibers produced by domestic companies are different. For example, the acrylic fibers of Shanghai Jinshan Chemical Plant are fast in coloring, while the acrylic fibers of Lanzhou Petrochemical are slow in coloring, which brings great difficulties to the dyeing factory.

4. Improper control of temperature rise

Generally speaking, acrylic fibers start to be colored at 80℃, and the key stage of coloring is between 87-92℃. During this period, the temperature must be raised slowly, with a speed of 1℃/3 minutes---1℃/6 minutes. It is best to keep warm at 90℃ for 20 minutes.

5. Changes in pH value

When dyeing acrylic, the pH value should be kept between 3.5 and 5.5. When the pH value is low, the dyeing speed is slow and it is not easy to dye. But if the pH value is too low, the dyeing fastness is poor. When the pH value is high, the dyeing speed is fast and the color is high. But when the pH is too high, it is easy to dye. If the pH is higher than 6, it may also cause discoloration. Generally speaking, the pH value of dyeing acrylic is kept at around 4.5. Acetic acid is used to dye acrylic. In order to ensure that the pH value tends to be stable during the whole dyeing process, sodium acetate is added to the dye bath as a pH buffer so that the dyeing process does not change with the pH fluctuation and achieves a uniform dyeing effect. The general dosage of sodium acetate is 0.5g/l.

6. Influence of water quality

Soft water should be used for dyeing acrylic, and the total hardness value should be below 75PPM. If the hardness of the water is high, it will cause dyeing. Some dyeing factories often have the phenomenon of dyeing, which may be caused by excessive water hardness.

In summary, dyeing acrylic is more difficult than dyeing other fibers. When formulating the process, there are many factors to consider. How to formulate an optimal dyeing process? It is recommended that the laboratory make multiple samples to determine the process.

Normal temperature

This heating process is a more common dyeing process. Customers can make appropriate adjustments according to the types of dyed cloth and yarn. For example:

① The cloth with a small gram weight should be heated up slowly, and the cloth with a large gram weight can be heated up faster.

② The high-count yarn should be heated up slowly, and the low-count yarn can be heated up faster.

③ Dark colors can be heated up faster, and light colors can be heated up slower

④ Dark colors should be kept warm at 98℃ for a longer time, 45 minutes to 60 minutes, but light colors only need to be kept warm for 15 minutes.

Treatment after dyeing:

① Color correction of acrylic fiber

Dye 3% of the original formula

AN 1.5-3% (O.W.F.)

HAC 2-3%

98℃ × 60 minutes

② Color stripping of acrylic fiber

AN 3-5% (O.W.F.) or PAN 2-3%

HAC 2-3%

98℃ × 60 minutes

③ Color stripping of severe color flowers

Sodium chlorite or sodium hypochlorite 2g/L PH 3-4

60-98℃ Treatment for 30 minutes.

If you want to know more about dyeing solutions, please contact: info@tiankunchemical.com