The color point and color difference often appear in the dyeing of reactive dyes. How can this be solved? Here to tell you!

In actual production, when the bright green and brilliant blue varieties are mixed, they will use a large amount of blue dyes. Due to the particularity of the molecular structure, Cuilan-based reactive dyes often have color problems such as color spots and chromatic aberrations in the dyeing process. Especially when the amount of the dye reaches 2.0 g/L or more, the probability of a problem is greater. Therefore, it is said to be For sensitive color. You can improve the color point in the following ways:

(1) To promote the dissolution of the dye (appropriately increase the dissolution temperature of the dye, using a co-solvent).
(2) Use high-purity accelerants.
(3) Add promotional salt in the right way. When adding, you should use clear water to dissolve the Yuan Ming powder instead of back water to dissolve (from the dye back to the addition of the barrel).

Practice has shown that excessive electrolyte in the dye bath is an important factor that causes dye molecules to aggregate. However, in the dyeing process, it is necessary to use a large number of dye-promoting salts. If water is used to dissolve Yuan Mingfen, the concentration of Yuan Mingfen will be too high, and the salting-out effect will be strengthened. As a result, a large amount of dye molecules will precipitate out of the dyeing bath and accumulate, forming a color point on the dyed fabric.

note

It is worth noting that before adding Yuan Mingfen, it should first be fully mixed in the chemical drum, and then slowly added, and the time should be 10-15 min. It should be ensured that each tube of rope-like fabric is in the dyeing machine. More than 4 cycles. Taking into account that the maximum solubility of Yuan Mingfen is 500g/L (30°C), and the volume of the chemical barrels is limited (generally not exceeding 800L). This allows the Yuan Ming powder to be quickly and uniformly diluted in the dye bath without locally excessively high electrolyte concentrations in the dye bath.

The soda ash used for the dyeing of reactive dyes is also an electrolyte, but its salting-out effect on the dyes is not as obvious as the sulphide powder, and the effect on the formation of color spots is not significant.

Usually each feeding time interval is 15-20min. Prolonging the time interval of feeding can prolong the adsorption and diffusion process of the dye. The dye molecules in the dye bath can diffuse and adsorb to the inside of the fiber more fully, thus effectively reducing the dye concentration in the dye bath, and the tendency of the dye molecules to accumulate greatly. reduce. In addition, for the dark blue dyes with low directness, the initial dyeing temperature of the dyeing can be increased to a certain extent to increase its adsorption capacity on cotton fibers. The concentration of the dye before adding the electrolyte is reduced.

For the dyeing of Fabry Blue reactive dyes, leveling agents with the dual effects of dispersing and leveling should be used. The leveling agent with strong dispersibility is very effective in preventing dye aggregation. Good levelling agent should meet the following requirements: (our leveler has the following requirements)
1 has a good slow-drying ability, has little effect on the color shade, and causes the color change to be generally 5% to 10%, or has no effect.
2 has a good chelating and dispersing ability, and has a certain role in helping the dye solution.
3 The electrolyte in the dye bath, as well as acid and alkali, can be compatible with other anionic auxiliaries.
4 low foaming or a certain degree of foam inhibition.

In the process of dyeing green jade, silicon-containing defoamers cannot be used. Because the HLB value of the antifoaming agent is generally from 1 to 3, it is more difficult to disperse such additives in water, and it is easy to form “micro-droplets”, while the Jade-blue dye molecules with larger molecular mass are easy to be “micro-droplets”. Around the gathering, a group of dye molecules is formed. Once the cloth is stained, color spots or stains will be formed. The use of anti-wrinkle agents or softeners should also be used with caution, as the compatibility of such additives in dye baths with dyes, electrolytes and bases is also a problem that should not be overlooked.

The hardness of the dyeing bath refers to the content of Ca2+ and Mg2+ in the dye bath. In the dyeing process of cotton fabrics, the main sources are: Ca2+ and Mg2+ in the dyeing water. Although the dyeing water is mostly softened, the stability of the equipment is affected by the operation. Affected by other factors, the hardness of soft water is not stable and sometimes exceeds the standard; Ca2+ and Mg2+ that natural fibers carry during the natural growth process. This part of the hardness value can not be ignored when performing sensitive coloring dyeing. Once accumulated on the surface of the fabric, Ca2+ and Mg2+ will further cause the aggregation of the dye molecules, thus forming color spots and stains on the fabric surface; when the fabric is pretreated, the used pretreatment agent will bring in Mg2+, Oxygen bleach stabilizers typically contain Mg2+. Mg2+ plays an important role in improving the decomposition stability of H2O2 and controlling the decomposition rate of H2O2, but it affects the uniformity of dyeing.

Theoretically, when the content of Ca2+ and Mg2+ is less than 20mg/kg, it can be called soft water, which can meet the requirements of general reactive dyeing. However, the dyeing of the Jade Blue dyestuff requires higher hardness of the bath. It has been found in practice that ultra-soft water with a hardness value of less than 15 mg/L or close to 0 is more favorable for the staining of sensitive colors. Therefore, it is necessary to use a suitable chelating dispersant when dyeing, which can effectively improve the hardness of the above three aspects, and provides ideal dyeing bath conditions for the turquoise dyes. However, the chelating ability of the chelating dispersant should not be too strong. Otherwise, the metal ions in some dye molecules will be “pulled out” to destroy the molecular structure of the dye, thereby affecting the dyeing performance of the dye.