In production, it is common to encounter situations where polyester or polyester containing fabrics are dyed out of the vat, and the fabric surface and color light are normal, but after being processed in the next process, there are color changes or local spots and stripes, as well as a decrease in color fastness. This type of problem can be easily repaired after re repair, but in severe cases, it is difficult to meet the requirements even after repair, which has a certain impact and loss on the normal production, delivery time, quality, and efficiency of the factory. Below is a brief explanation of the causes and preventive measures for peer reference.

1、 Cause analysis

The thermal migration phenomenon of polyester after dyeing with disperse dyes is the key to the above-mentioned problems. Thermal migration is a common property of dispersed dyes, which refers to the migration of some dyes from the inside of the fibers to the surface of the fibers through fiber capillaries under the action of dry or humid air during high-temperature setting of the finishing process. This causes the accumulation and redistribution of dyes on the fiber surface, and the presence of auxiliary agents and their surfactants, including residues on the fabric surface, exacerbates their production. This thermal migration is mainly related to the structure of the dyes themselves, Moreover, the thermal mobility of dispersed dyes with different structures varies greatly, and there are also significant differences between them. Therefore, when finishing and high-temperature setting, especially when using silicone oil and antistatic agents, they contain a certain amount of surfactants. When these additives adsorb unevenly on the cloth surface, including uneven pH, a series of problems such as color splashes, color changes, and decreased fastness such as friction, washing, and staining will occur, This phenomenon is often manifested as one or several coexisting, which brings insurmountable hidden dangers and hazards to the dyeing quality.

2、 Preventive measures

1. Firstly, disperse dyes with low or similar thermal mobility should be selected. Due to the large molecular weight of these dyes and their high affinity with polyester fibers, it is difficult to migrate from the inside of the fibers to the surface. The LXF model from Longsheng Company, the XF model from BASF, the XF/SF model from Dexter, and the MS series from Annuoqi all have good thermal migration fastness.

2. The selection of color matching dyes should try to choose the same model or high-temperature type dyes. Different types of dyes have different heat transfer ratios and different sublimation fastness, and high-temperature type sublimation fastness is higher. Although the heat transfer fastness and sublimation fastness of dyes are not consistent, high-temperature type dyes have less sublimation under higher temperature setting, and the corresponding color stability is also good.

3. After finishing, a more gentle process is adopted. The darker the color, the more dye migration there is. The higher the temperature, the greater the impact on migration. While ensuring the shaping effect, a temperature of 150 ℃ or lower can be selected depending on the variety, in order to avoid or reduce dye migration.

4. The selection of finishing softeners should be made, and hydrophilic silicone oil or self-emulsifying block silicone oil without emulsifiers should be used as much as possible. This type of silicone oil has good stability, low color change and yellowing, and can effectively prevent dye migration.

5. Strengthen the reduction cleaning after dyeing, especially for dark colors. The floating color must be thoroughly cleaned to ensure its own fastness, and acidic cleaning should be used as much as possible. If alkaline insurance powder process is used, it must be neutralized. Some dyes are sensitive to pH, and some will turn blue to purple after high-temperature treatment at pH>6, and this color change is irreversible and even cannot be repaired.

In short, through the above measures and reasonable pre-treatment and dyeing processes, we believe that a series of quality issues such as color changes, color changes, and decreased fastness after finishing and shaping can be controlled within our required range.