In production, it is often encountered that polyester or polyester-containing fabrics have normal color and light after being dyed out of the vat, but then the color and light do not match after finishing in the next process, resulting in discoloration or local spots, streaks, and a decrease in fastness. , such problems can be repaired if they are minor and need to be re-repaired, but cannot meet the requirements even if they are serious, which will have a certain impact and loss on the normal production, delivery, quality and efficiency of the factory. What is the reason for this?
It turned out that the thermal migration of polyester was to blame. So what is the thermal migration of polyester?
Thermal migration is a common property of disperse dyes. It means that part of the dye migrates from the inside of the fiber to the surface of the fiber through the fiber capillary due to the action of dry heat or hot and humid air during high-temperature setting, resulting in the accumulation and accumulation of the dye on the fiber surface. Redistribution, the presence of additives and surfactants including residues on the cloth will aggravate its occurrence.
Since this thermal migration is mainly related to the structure of the dye itself, and the thermal migration of disperse dyes with different structures are also different, and the differences between them are also large, so when finishing high-temperature styling, especially when using silicone oil, When antistatic, it contains a certain amount of surfactants. When these additives are unevenly adsorbed on the cloth surface, including uneven PH on the cloth surface, the above-mentioned so-called color flowers, discoloration, and decrease in fastness such as friction will occur. , washing, staining and other problems. This phenomenon often manifests itself as one or several coexistences, which brings insurmountable hidden dangers and hazards to the dyeing quality.
Solution:
1. First, choose disperse dyes with small and similar thermal migration properties. Because these dyes have larger molecular weight structures and greater affinity with polyester fibers, they are difficult to migrate from the interior of the fiber to the surface. For example, the commonly used LXF type, XF type, XF/SF type and MS series on the market have good thermal migration fastness.
2. When selecting color-matching dyes, try to use the same type or high-temperature dyes, because different types of dyes have different thermal migration ratios and different sublimation fastnesses. The high-temperature type has higher sublimation fastness, although the thermal migration fastness of the dyes is different. The strength and sublimation fastness are not consistent,
However, high-temperature dyes have less sublimation of the dye under higher temperature setting, and the stability of the corresponding color light is also better.
3. Post-finishing uses a gentler process. The darker the color, the more the dye will migrate. The higher the temperature, the greater the impact on migration. To ensure the setting effect, 150°C or lower can be used depending on the variety. temperature. In order to avoid or reduce the migration of dye, it is recommended that high temperature be used to fix the size first for this type of variety.
4. When choosing a post-finishing softener, try to use hydrophilic silicone oil or self-emulsifying block silicone oil that does not contain emulsifiers. This type of silicone oil has good stability, low color change and yellowing, and can play a better role in dye migration. Good preventive effect.
5. Strengthen the reduction cleaning after dyeing, especially for dark colors. The floating color must be fully cleaned to ensure its own fastness. At the same time, try to use acidic cleaning. If the alkaline insurance powder process is used, it must be neutralized because some parts Dyes are sensitive to pH. Some dyes will turn blue or purple after high-temperature treatment when the pH is >6, and some of this color change is irreversible and cannot even be repaired.
As long as the above measures are adopted during the production process and combined with reasonable pre-treatment and dyeing processes, I believe that a series of quality problems such as color flowers, color changes and decrease in fastness after finishing and shaping will be able to be controlled within the scope of our requirements.
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