The condensation of disperse dyes in dyeing will lead to color spots, color spots and cylinder contamination. How to prevent the condensation of disperse dyes in dyeing
1、 Production principle of disperse dye condensation:
Generally, the particle diameter of disperse dye is about 1pm, the diameter of polyester single fiber is about 15pm, and the gap between single fibers is about 5um. Under normal circumstances, dye particles can freely pass through the gap between single fibers. If condensation occurs, the diameter of dye particles may exceed 5um, which will be blocked outside the gap between single fibers and it is difficult to complete the dyeing reaction.when the condensed dye stays on the fabric and its length exceeds 100um, it becomes a visible spot (dye spot).
2、 Causes of dispersion dye coagulation:
There are many reasons for dye condensation, generally due to the following reasons:
- Operation reason: incomplete chemical materials;
- Polyester raw material: there are many polyester oligomers;
- Dyeing water: the hardness is high, which is affected by metal ions in the water;
- The heating rate is too fast in the dyeing process.
- Polyester spinning oil residue
3、 How to avoid dye condensation?
In order to prevent dye condensation and strengthen the dispersion of dyes, the usual way is to add dispersants. With the help of dispersant, disperse dyes can form a dispersed homogeneous phase in the dye and complete the dyeing effect.
In order to keep dye particles in a good suspension and dispersion state in the dyeing process, a large number of anionic surfactants, such as diffusing agent NNO, sodium lignosulfonate and so on, are added to commercial dyes. However, in the high temperature and high pressure dyeing bath, the diffusing agent NNO is easy to be resolved from the surface of disperse dye crystal particles, and the dye particles will further agglomerate and adhere to the cloth surface, resulting in color spots and dyeing defects. To solve this problem, we can start from the following two aspects:
- Choose dispersant with good thermal stability. Such as the condensation of phenol or sodium naphthol sulfonate with formaldehyde, etc.
- Add other surfactants to the dyeing bath to increase the stability of the dyeing bath. Generally, non-ionic or anionic surfactants can be added. Although the cloud point of non-ionic surfactants is mostly below 100 ℃, and the cloud point of penetrant JFC is only about 50 ℃, due to the existence of anionic surfactants, the cloud point will be improved and can also be used for high-temperature dyeing. As long as the selection of varieties and dosage is appropriate, it can not only play a good dispersion role, but also slow down the dyeing and achieve the leveling effect
