Abstract: In the process of dyeing cotton fabrics with reactive dyes, a variety of inorganic salts are used as leveling agents in the dyeing process. Cotton fabrics were dyed under different conditions, and the best reaction process was determined through comprehensive inspection of the dyeing effects. The results show that sodium citrate has good dyeing effect under the conditions of 300mmol/L and the dye solution PH being 9.
Author: Liu Ting Liu Liu
Reactive dyes have gradually become the main dyes for cotton fabric dyeing due to their simple molecular structure, bright color, complete chromatogram, simple dyeing process, low cost, and their ability to chemically react with fibers to form strong covalent bonds.
Despite this, since cotton fiber and dye are both negatively charged in the dye bath, the electrostatic repulsion between the two makes it difficult for the dye to be adsorbed on the fiber, which can easily lead to uneven dyeing; coupled with factors such as the hydrolysis of the reactive dye itself , leading to problems such as complex dyeing conditions during the dyeing process, low exhaustion and fixation rates, and low dye utilization. The traditional solution is to add inorganic salts during the dyeing process. Neutral electrolytes such as inorganic salts are added to inhibit the ionization of cellulose, thereby reducing the negative charge of cotton fibers and reducing the static electricity suffered by anionic dyes during the dyeing process. Repulsive force, thereby making the dye easy to dye.
There are many types of inorganic salts, and their different properties lead to differences in dyeing rates and leveling effects during the dyeing process of reactive dyes. Therefore, in this experiment, sodium chloride, sodium sorbate, sodium benzoate, and sodium citrate were used as leveling agents to promote the dyeing of cotton fabrics under different inorganic salt concentrations and dye liquor PH conditions. The best dyeing process is judged by the dyeing effect on the fabric.
01Experiment
1. Equipment and raw materials
Fabric: pure cotton knitted (Nantong Taimushi Clothing Co., Ltd.).
Reagents: sodium chloride, sodium sorbate, sodium benzoate, trisodium citrate, soda ash are all AR; reactive blue M-2GE (Hubei Liyuan Technology Co., Ltd. ).
Equipment: AL104 electronic balance oscillating dyeing machine, U-3310 UV – visible spectrophotometer.
Figure5 Dye uptake rate of each group
It can be seen from the curve in Figure 5 that under dye liquors with different PH values, the dyeing rate of the fabric ranges from 0 to 10min, then rises more slowly, and finally reaches stability at 30～50min; among them, when the dye liquor PHThe dye uptake rate is the highest when it is 9.
This may be because the PH value has a greater impact on the reaction between dyes and cellulose. Increasing the PH value of the dye liquor causes -OH in the dye liquor. As the concentration of span> increases, -OH can swell the cotton fiber under certain conditions, allowing the cotton fabric to have more space to absorb dye molecules, thereby increasing the dye uptake rate of the cotton fabric; But when PH exceeds a certain value, although the excess -OH in the solution can increase the reaction rate of the dye and cellulose fiber, it will also increase the dye’s Hydrolysis rate, resulting in a decrease in the dye uptake rate of cellulose fibers. Therefore, comprehensive consideration should be given to the PH of the dye liquor as 9.
03Conclusion
1. In the process of reactive dye dyeing of cotton fabrics, inorganic salts help improve the dye uptake rate of reactive dyes by reducing the electronegativity of the fiber surface. Under the same conditions, sodium citrate has better leveling effect.
2. Within a certain range, the dye uptake rate of reactive dyes on cotton fabrics increases greatly with the increase in the concentration of inorganic salts. However, when it reaches a certain concentration, the dye uptake rate does not show obvious decreases with the increase in the concentration of inorganic salts. Increase, considering that high concentrations of inorganic salts are not easy to degrade, so on the premise of ensuring the dyeing effect, the concentration of inorganic salts should not be too high.
3. The PH value has a great influence on the reaction between dyes and cellulose. Appropriately increasing the PH value of the dye liquor can improve the dye uptake rate of cotton fabrics; but when PH When it exceeds a certain value, the excess -OH in the solution will increase the hydrolysis rate of the dye, resulting in a decrease in the dye uptake rate of the cellulose fiber. Therefore, the dye liquor PH should be set as weakly alkaline.
It can be seen from the curve in Figure 5 that under dye liquors with different PH values, the dyeing rate of the fabric ranges from 0 to 10min, then rises more slowly, and finally reaches stability at 30～50min; among them, when the dye liquor PHThe dye uptake rate is the highest when it is 9.
This may be because the PH value has a greater impact on the reaction between dyes and cellulose. Increasing the PH value of the dye liquor causes -OH in the dye liquor. As the concentration of span> increases, -OH can swell the cotton fiber under certain conditions, allowing the cotton fabric to have more space to absorb dye molecules, thereby increasing the dye uptake rate of the cotton fabric; But when PH exceeds a certain value, although the excess -OH in the solution can increase the reaction rate of the dye and cellulose fiber, it will also increase the dye’s Hydrolysis rate, resulting in a decrease in the dye uptake rate of cellulose fibers. Therefore, comprehensive consideration should be given to the PH of the dye liquor as 9.
03Conclusion
1. In the process of reactive dye dyeing of cotton fabrics, inorganic salts help improve the dye uptake rate of reactive dyes by reducing the electronegativity of the fiber surface. Under the same conditions, sodium citrate has better leveling effect.
2. Within a certain range, the dye uptake rate of reactive dyes on cotton fabrics increases greatly with the increase in the concentration of inorganic salts. However, when it reaches a certain concentration, the dye uptake rate does not show obvious decreases with the increase in the concentration of inorganic salts. Increase, considering that high concentrations of inorganic salts are not easy to degrade, so on the premise of ensuring the dyeing effect, the concentration of inorganic salts should not be too high.
3. The PH value has a great influence on the reaction between dyes and cellulose. Appropriately increasing the PH value of the dye liquor can improve the dye uptake rate of cotton fabrics; but when PH When it exceeds a certain value, the excess -OH in the solution will increase the hydrolysis rate of the dye, resulting in a decrease in the dye uptake rate of the cellulose fiber. Therefore, the dye liquor PH should be set as weakly alkaline.
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