Analysis of reasons for poor color fastness of polyester fabrics after setting
For customers with high requirements for polyester color fastness, the dyeing factory will, in the actual production process, after high-temperature and high-pressure dyeing, reduction cleaning, and then After high temperature setting, the ideal color fastness is still not achieved.
The reasons are:
Thermal migration of polyester after dyeing with disperse dyes is the key to the above problems. Thermal migration is a common problem with disperse dyes. A performance that exists.
It refers to the migration of part of the dye 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 post-finishing and high-temperature setting, resulting in the accumulation and redistribution of dye on the fiber surface. Additives and The presence of 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 after finishing, high-temperature setting Especially when using silicone oil and 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 and colors will be produced. A series of problems such as deformation and decrease in fastness such as friction, washing, staining, etc. This phenomenon often manifests itself as one or more coexistences, which brings insurmountable hidden dangers and hazards to the dyeing quality.
How to deal with it?
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, xx company’s LXF type, xx’s XF type, xx’s Dainix XF/SF type and xx’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 dyes is not consistent with the sublimation fastness, high-temperature dyes have less dye sublimation under higher temperature setting, and the corresponding color light stability is also better.
3. Post-finishing adopts a gentler process. The darker the color, the more the dye will migrate. The higher the temperature, the greater the impact on migration. The larger the temperature, the higher the temperature, 150°C or lower can be used depending on the variety to ensure the setting effect, thereby avoiding or reducing 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 and low discoloration and yellowing. It has a better preventive effect on dye migration.
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 dyes are sensitive to pH, and some will turn blue to purple after high-temperature finishing when the pH is >6, and some of this color change is irreversible and cannot even be repaired. </p