Common factors of reactive dyed flowers
Common factors of reactive dyed flowers
Color and flower is a common quality problem in the production process of printing and dyeing enterprises. The key to improve the rate of genuine products is to make a reasonable dyeing process and pay attention to the problem prone links. It is the key point for printing and dyeing enterprises to create profit and stabilize customer base under the pressure of energy conservation and emission reduction as well as various costs.
Cellulose, polyester and nylon are the three most common textile fibers in the market. However, the dyeing of cellulose with reactive dyes is relatively complex, and there are many points to be paid attention to in dyeing. In the process of dyeing and finishing, each step must be done well in order to obtain good quality. Next, we will discuss the factors that cause the colored flowers in the process of reactive dyeing and the conventional methods to avoid them.
First, scouring.
Because of its natural fiber structure, cotton fiber must be strictly refined to ensure relatively uniform water absorption and dye uptake in the dyeing process. The so-called successful preprocessing is half the success. The pretreatment must ensure enough amount of scouring agent, alkalinity, treatment time and temperature. The addition of additives should be batch and step-by-step, and the effect of adding hydrogen peroxide at 70 ℃ is the best. In case of cloth wrapping, cylinder blocking and other problems, it is necessary to keep the temperature for a period of time. Ensure that the fiber has enough and uniform hair effect to ensure the uniformity of dyeing.
2、 The scouring water stain is not clear, and the grey cloth is easy to be dyed with alkali
After pretreatment, water washing must be sufficient, and acid pickling can be carried out to ensure that the pH value of cloth surface is neutral. Otherwise, under the alkaline condition, especially under the condition of uneven alkaline, it will cause the dyeing and coloring speed to be too fast to form colored flowers.
3、 The residual oxygen treatment of cloth surface after boiling is not clean
Reactive dyes are easy to be oxidized, and the residual of hydrogen peroxide, especially the uneven residual of hydrogen peroxide, will destroy the attached reactive dyes and make them discolored. As a result, the color flowers and the color light are inaccurate. At present, it is generally used to remove the residual hydrogen peroxide with deaerator, to ensure the deaeration time and to do a good oxygen content test after deaeration can avoid such risks.
4、 Unevenness of chemical materials and insufficient dissolution of dyes cause color and flower
Mix well and adjust the temperature of chemical materials properly. Different types of reactive dyes have different solubility and different nano temperature properties. Generally, the temperature of reactive dyestuff should not exceed 60 ℃, otherwise the high temperature is easy to cause rapid hydrolysis of dyes. Because the dye molecules of Cuilan and Yanlan are large, the temperature of the compound can be increased properly. In addition, it is necessary to strengthen the filtration, and add a high-density filter screen at the feed inlet to prevent the undissolved dye particles from directly entering the dye vat and contacting the cloth surface.
5、 Speed of adding salt and alkali
Salt alkali is the key to control the dye adsorption rate and fixation rate. If the feeding speed is too fast, the difference of pH value in the dye solution will lead to uneven coloring, which will lead to colored flowers. Therefore, in the process of dyeing, especially when dyeing lighter or more sensitive colors, salt alkali must be added slowly step by step. After each feeding, it needs to be fully rotated every 10-15 minutes before the next operation. In the process of making cotton or light color, the method of adding 1 / 10 alkali in advance can be adopted to avoid the sharp change of pH value in the later stage and the generation of color flowers.
Six. Bath ratio
Due to the limitation of energy conservation and emission reduction, many factories now reduce the bath ratio to reduce the cost and reduce the pressure of sewage treatment. Especially for the air cylinder, because the bath is too small, it is more strict than the process requirements. Be sure to operate strictly without carelessness.
Seven. Soaping
After dyeing, the water can not be washed clearly. When soaping, the pH is too high and the temperature rises too fast, which will also cause color flowers. At this time, it is necessary to wash the residual alkali as much as possible before soaping, control the heating rate and ensure the soaping time. Acid soap can also be used to neutralize part of the alkali while soaping.
8、 Water washing is not clear, resulting in color and flower
If the residual liquid after soaping is not completely washed, the concentration of the residual liquid in the cloth surface will be different after the cloth is discharged. If it is not dried in time, it will cause color spots, which is often called wind seal. Therefore, at least one water wash is needed to remove the residual liquid after soaping.
Nine. Add color
Adding color is a common thing in dyestuffs, but the amount of dye used is often small. It's like dyeing a light color. Because there are a lot of salt and alkali in the original cylinder, which will increase the coloring rate, it is more important to control the feeding speed. If necessary, the method of removing part of the dye solution and adding water to reduce the salt and alkali concentration can be carried out under the condition of satisfying the color depth. Sometimes the risk of adding color with reactive dyes is too great when the color light difference is not big, so disperse dyes can be selected for fine adjustment. Due to the slow coloring of disperse dyes, cotton fabrics will only cause less staining. Therefore, the disperse dye can be used for fine adjustment when the color light is slightly different and the color is not bright.