The role of Yuanming powder and industrial salt in dyeing

Yuanming powder and industrial salt are both salts composed of strong acids and bases, which are easily soluble in water. They all have a certain promoting effect in dyeing, but there are also some differences in their specific principles and application characteristics. The following is a detailed introduction:

The role of Yuanming powder in dyeing

Principle of dyeing promotion: Sodium sulfate, also known as Yuanming powder, plays a major role in promoting the dye to dye fibers through the electrolyte effect during the dyeing process. For some water-soluble dyes such as direct dyes and reactive dyes, adding elemental powder to the dye solution will increase the electrolyte concentration, reduce the solubility of dye molecules in water, and promote more aggregation and migration of dye molecules to the fiber surface, thereby increasing the adsorption capacity and dyeing rate of the dye on the fiber.

Improving dyeing rate: Yuanming powder can effectively increase the dyeing rate of dyes, allowing more dyes to bind with fibers and achieve deeper and more vivid dyeing effects. Especially for some dyes or fibers with low dye uptake, adding sodium silicate powder can significantly improve the dyeing effect and reduce dye waste.

Stable dyeing process: It can also stabilize the properties of the dye solution to a certain extent, prevent the dye from precipitating or aggregating during the dyeing process, and ensure the uniformity and stability of the dyeing process. By adjusting the electrolyte balance of the dye solution, Yuanming powder helps to evenly adsorb the dye on the fiber surface, reducing the occurrence of color differences and spots.

The role of industrial salt in dyeing

The promoting effect is similar to that of Yuanming powder: the main component of industrial salt is sodium chloride, which also plays a promoting role in dyeing. Its principle is similar to that of Yuanming powder, which increases the electrolyte concentration in the dye solution, reduces the solubility of the dye, promotes the aggregation and adsorption of the dye onto the fiber surface, and thus improves the dye uptake speed and rate.

Adjusting dyeing depth: By controlling the amount of industrial salt added, the dyeing depth can be adjusted within a certain range. Appropriately increasing the amount of industrial salt usually increases the depth of dyeing, but excessive use may lead to uneven dyeing, decreased color fastness, and other problems, which need to be adjusted reasonably according to the specific dye and fiber types as well as dyeing process requirements.

Both Yuanming powder and industrial salt can be used as dyeing agents for direct dyes, sulfur dyes, reducing dyes, reactive dyes, and soluble reducing dyes when dyeing cotton fibers, which can adjust the dye uptake rate of the fibers. It can also be used as a retarder for dyeing wool and acrylic fibers with acidic and cationic dyes, to reduce the speed of dye adsorption on fibers and achieve uniform dyeing requirements. Their promotion mechanisms for dyes and fibers are basically the same. Due to the low coloring rate of direct dyes, the dyes are not easily absorbed by the fibers. After dyeing, there are more residual dyes in the foot water. Adding elemental powder or industrial salt can reduce the solubility of dyes in water, promote the combination of dyes and fibers, and increase the dye uptake rate. This can reduce the amount of dye used and deepen the color of the dye. As for their dosage, it depends on the coloring rate of the dye and the depth of the desired color to be dyed. They should not be added too much or too quickly, as too much can cause the dye to precipitate and cause stains on the fabric surface. Too fast, dye coloring is fast and prone to unevenness. Therefore, both should be dissolved in water before use and filtered before being added to the dye bath. But it should be noted that it cannot be added before final staining. Before solid dyeing, the concentration of the dye solution is relatively high. If the fiber is dyed too quickly by adding Yuanming powder or industrial salt dye, uneven dyeing may occur. Usually, after dyeing for a period of time, Yuanming powder or industrial salt is added, which can be added midway or several times. Practice has proven that when using Yuanming powder as a dye promoter, the dyed color is more vivid and bright, while when using industrial salt as a dye promoter, its effect is poor. This is related to the purity of industrial salt. Because in general industrial salt, in addition to containing a large amount of calcium and magnesium ions, it also contains a small amount of iron ions, and some dyes can be affected by iron ions, causing a dull color. Some people also believe that industrial salt is cheap and do not plan to use Yuan Ming powder. Practice has proven that when dyeing light and medium colors, it is best to use Yuan Ming powder, while for dyeing dark colors, industrial salt can be used.

When dyeing with reactive dyes, the addition of salt substances can promote dye uptake. The principle is that both fibers and dyes are negatively charged in the solution, creating a repulsive force between them. After adding neutral electrolyte salts, the cations ionized by the salt are adsorbed on the surface of the fiber and wrapped around it. When the dye anions approach the fiber surface, the repulsive force is greatly reduced. Adding an appropriate amount of salt to the dye bath can reduce the energy resistance caused by Coulomb force and improve the dye uptake rate.

The mechanism by which Yuanming powder and industrial salt are used as dyeing retardants for acidic dyes such as silk and wool is that both wool and silk belong to the category of egg fibers. Fiber molecules contain - NH2 groups. When dyed with acid dyes in acidic solution, the hydrogen ion H+in the acid solution quickly diffuses into the fiber and binds with · NH2+· NH3+, causing the fiber to carry a positive charge while the pigment ion of the acid dye carries a negative charge D -. Due to the different charges between the fiber and the dye, ion bonding occurs to synthesize · NH3 · D. When Yuanming powder or industrial salt is added to the dye solution, the negatively charged sulfate ions SO42- of Yuanming powder and the negatively charged hydrogen ions of industrial salt can compete with the pigment ions D of the dye to preferentially dye the positions of - NH3+ions in the fiber, and combine with them to form NH3CI or (: NH3) 2SO4. At high temperatures, D - replaces the positions of SO42- or C1-, allowing the dye to dye and achieve a slow dyeing effect.

Yuanming powder can also be used as a white color protectant in the production of printing and dyeing silk fabrics (or colored silk fabrics). During the refinement of printing or dyeing silk fabrics, the dye may be peeled off, causing contamination of the ground color or other fabrics. Adding Yuanming powder can reduce the solubility of the dye, thus preventing dye peeling and contamination of the ground color. Industrial salt can also be used as a base for Nafto dye to increase absorption. Adding a certain amount of industrial salt to the base bath when dyeing cotton yarn with Naftuo can greatly increase the absorption of AS phenols. Industrial salt can also be used as a sulfonation medium or sodium cation, and as an activator and pancreatic enzyme activator in the exchange resin. Using Yuanming powder does not have this effect.

The above introduces the mechanism and difference of action between Yuanming powder and industrial salt in printing and dyeing. As for the difference in dosage, the relationship between the two is: 5 parts of industrial salt=6 parts of anhydrous Yuanming powder=12 parts of crystalline Yuanming powder. 100 parts anhydrous elemental powder ≈ 100 parts industrial salt~227 parts crystalline elemental powder. Because the molecular formula of crystalline sodium sulfate is Na2SO4 · 10H20 with a molecular weight of 322.19, while the molecular formula of anhydrous sodium sulfate is Na2SO4 with a molecular weight of 142.04, that is, anhydrous sodium sulfate is 2.27 times that of crystalline sodium sulfate. Therefore, the dosage of anhydrous sodium sulfate and industrial salt is basically the same. If crystalline elemental powder is used, its dosage should be twice that of anhydrous elemental powder or twice that of the field.

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