**Su Hua, Li Huamei, Qi Jin (Taixing Jinji Dye Co., Ltd., Taixing, Jiangsu 225404, China)**
**Abstract:** Reactive Turquoise KN-G is commonly known for issues such as color spots, uneven dyeing, and color blooming during the dyeing and fixation process. To address these challenges, it is essential to incorporate appropriate leveling agents and optimize the dyeing conditions. This helps in improving the color fastness and achieving a more uniform dyeing result.
**Keywords:** reactive dyes; dyeing; leveling agent; copper phthalocyanine structure; color fastness; dyeing performance
Reactive Turquoise KN-G, with its unique copper phthalocyanine structure, offers bright colors, low cost, and good dyeing performance, making it widely used in cellulose fiber dyeing. However, due to its large molecular weight, high directness, and poor diffusibility, it can be difficult to penetrate into the fiber, leading to uneven dyeing. Moreover, when soda ash is added, the dye tends to agglomerate, resulting in color spots, color flowers, and reduced color fastness.
To overcome these issues, the use of leveling agents, sodium sulfate, and alkali agents is crucial. These additives help control the dyeing rate, improve dispersion, and enhance the overall dyeing quality. By carefully selecting and using these chemicals, the problems of color points, color spots, and color blooming can be significantly minimized.
**1. Test Part**
**1.1 Test Reagents and Dyeing Materials**
Active Cuilan KN-G was obtained from Taixing Jinji Dye Co., Ltd. Sodium sulfate, soda ash, and other reagents were industrial-grade. The leveling agent JY-21 was provided by Jiangyin Auxiliary Chemical Co., Ltd.
**1.2 Test Instruments**
A translational room temperature dyeing machine (Jingjiang Dyeing Machine Manufacturing Co., Ltd.), an ALC-110.4 electronic balance (Shanghai Ruisai Scientific Instrument Co., Ltd.), a SF600 color measuring instrument (Datacolor, USA), and a Y572B friction fastness meter (Changzhou Second Textile Machinery Factory) were used for the experiments.
**1.3 Test Procedures**
**1.3.1 Alkali-Resistant Salt Stability Test**
At a concentration of 10g/L, Active Cuilan KN-G was mixed with different amounts of leveling agent JY-21 (0, 0.5, 1.0, 1.5, 2.0 g/L). Sodium sulfate (60g/L) and soda ash (20g/L) were then added at 50°C. The solution was observed for any signs of coagulation on filter paper after mixing.
**1.3.2 Dyeing Leveling Test**
The leveling effect of the agent was evaluated through various tests including dyeing rate, time-dependent dye uptake, and the influence of fixing temperature on color intensity and shade.
**Dyeing Procedure:**
At a fabric-to-bath ratio of 1:20, 2% (by weight) of active Cuilan KN-G and varying levels of JY-21 (0, 0.5, 1.0, 1.5, 2.0 g/L) were added to the dye bath along with 60g/L sodium sulfate. The cloth samples were dyed at 60°C for 30 minutes, followed by the addition of 20g/L soda ash and fixing at 80°C for 60 minutes. After washing, neutralizing, and soaping, the samples were dried and analyzed for K/S values and color fastness.
**Results and Discussion**
**2.1 Test Principle**
The circular and bulky structure of Active Cuilan KN-G leads to poor solubility and diffusion. During fixation, the addition of soda ash increases dye aggregation, causing salting out and uneven dyeing. Adding a leveling agent improves the dispersibility and controls the initial dyeing rate, leading to better leveling and higher color fastness.
**2.2 Alkali-Resistant Salt Stability**
Without the leveling agent, the dye precipitated within 8 minutes after adding sodium sulfate and soda ash. With increasing levels of JY-21, the precipitation time extended up to 2 hours. At optimal levels (1.5–2.0 g/L), no precipitation occurred, ensuring stable dye solutions.
**2.3 Dyeing Leveling Effect**
**2.3.1 Effect of Leveling Agent Amount**
As the concentration of JY-21 increased, the K/S value decreased, indicating slower dyeing and improved leveling. This helped reduce color spots and uneven dyeing.
**2.3.2 Effect of Dyeing Time**
With the leveling agent, the K/S value remained stable over time, showing a controlled dyeing process. Without it, the dyeing speed was too fast, leading to color spots and uneven distribution.
**2.3.3 Effect on Color Intensity and Fastness**
Adding the leveling agent slightly reduced the color intensity but significantly improved the soaping and rubbing fastness. The soaping fastness improved by half a grade, while the wet rubbing fastness improved by one to two grades.
**2.3.4 Effect of Fixing Temperature**
Fixing at 80°C instead of 60°C increased the color strength by 14%, with improvements in both soaping and rubbing fastness. This suggests that higher temperatures enhance dye penetration and reaction with the fiber.
**Conclusion**
The use of an appropriate amount of leveling agent (1.5–2.0 g/L) significantly improves the dyeing performance of Active Cuilan KN-G. It enhances solubility, reduces dye agglomeration, and improves color fastness. Proper control of dyeing conditions, including temperature, pH, and chemical concentrations, is essential to achieve uniform dyeing and eliminate defects like color spots and color flowers.
**References**
[1] Chen Xuan. Production Practice of Reactive Blue-KN-G Dyeing of Cotton Knitted Fabrics[J]. Dyeing and Printing, 2001, 36(3): 26–27.
[2] Miao Yuzhen. Dyeing Characteristics and Dyeing Process of Reactive Turquoise Blue G[J]. Dyeing and Printing, 2005, 31(2O): 10–14.
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