In production, it is often encountered that after polyester or polyester-containing fabrics are dyed out of the vat, the fabric surface and color light are normal, but after finishing in the next process, the color light does not match, resulting in discoloration or local spots, streaks, and a decrease in fastness. Phenomenon, such minor problems can be repaired through re-repair, but severe problems cannot meet the requirements even after re-repair, which will have a certain impact and loss on the normal production, delivery time, quality and efficiency of the factory. The following is a brief explanation of its causes and preventive measures for the reference of peers.
1Cause analysis
Thermal migration of polyester after dyeing with disperse dyes is the key to the above problems. Thermal migration is a common property of disperse dyes. It refers to the effect of dry heat or hot and humid air during post-finishing and high-temperature setting. Part of the dye migrates from the inside of the fiber to the surface of the fiber through the fiber capillary, causing the dye to move on the surface of the fiber. Accumulation and redistribution, the presence of additives and surfactants, including residues on the cloth, will aggravate its occurrence. This thermal migration is mainly related to the structure of the dye itself, and the thermal migration of disperse dyes with different structures is different. They are also different, and the differences between them are also large. Therefore, when post-finishing and high-temperature styling, especially when using silicone oil and antistatic, they contain a certain amount of surfactants, and when these additives cannot be adsorbed on the cloth surface, When the pH of the cloth surface is uneven, a series of problems such as the above-mentioned so-called color flowers, color changes, and decrease in fastness such as friction, washing, and staining will occur. This phenomenon often manifests as one or several coexistences, thus It brings insurmountable hidden dangers and hazards to the dyeing quality.
2Preventive measures
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, Longsheng’s LXF type, BASF’s XF type, DyStar’s Dainix XF/SF type and Annochi’s MS series all 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 sublimation fastness and sublimation fastness are not consistent, but the sublimation of high-temperature dyes is less 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 to avoid or reduce dye migration.
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 discoloration and yellowing, and has a greater effect on dye migration. Good preventive effect.
5) Strengthen the restoration 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, and some 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.
In short, through the above measures and 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 styling can be controlled within the scope of our requirements.
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