How to prevent the agglomeration of disperse dyes in dyeing?

Agglomeration in the dyeing of disperse dyes will lead to problems such as color spots, stains, and cylinder contamination. How to prevent the agglomeration of disperse dyes in dyeing, please see the following:

1. The principle of dye aggregation

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 gaps between single fibers. If aggregation occurs, the diameter of dye particles may exceed 5um, so they are blocked outside the gaps between single fibers and it is difficult to complete the dyeing reaction.

The condensed dye stays on the fabric, and when the length exceeds 100um, it becomes a visible spot (dye spot).

2. The cause of dye aggregation

There are many reasons for dye agglomeration, generally due to the following reasons:

a. Reason for operation: incomplete chemical materials;

b. Polyester raw materials: more polyester oligomers;

c. Dyeing water: the hardness is too high, and the metal ions in the water are affected;

d. The heating rate is too fast during the dyeing process.

3. How to avoid dye agglomeration

In order to prevent dye agglomeration and enhance the dispersibility of dye, the usual method is to add dispersant. With the assistance of dispersant, disperse dye can form a dispersed uniform phase in the dye to complete the dyeing effect.

In order to keep the dye particles in a good suspension and dispersion state during the dyeing process, a large amount of anionic surfactants, such as diffusing agent NNO and sodium lignosulfonate, are added to commercial dyes. However, in the high-temperature and high-pressure dyeing bath, the diffusing agent NNO and the like are easily decomposed from the surface of the disperse dye crystal particles, and the dye particles will further agglomerate and adhere to the cloth surface, causing color spots and dyeing defects. Solving this problem can start from the following two aspects:

I. Choose a dispersant with good thermal stability. Such as phenol or naphthol sulfonate sodium salt and formaldehyde condensation products.

II. Add other surfactants in the dye bath to increase the stability of the dye bath. Generally, nonionic or anionic surfactants can be added. Although the cloud point of non-ionic surfactants is mostly below 100°C, the cloud point of penetrant JFC is only about 50°C, but due to the presence of anionic surfactants, the cloud point will increase, and it can also be used for high-temperature dyeing , as long as the variety and dosage are selected properly, it can not only play a good dispersing effect, but also play a slow dyeing effect to achieve a level dyeing effect.