Application of anhydrous sodium sulfate (sodium sulfate) in textile printing and dyeing industry

Yuanming powder is an inorganic salt with chemical properties very similar to table salt. It is soluble in water, and its solution is mostly neutral, soluble in glycerol but not in ethanol. It is a inorganic compound. The anhydrous substance with high purity and fine particles is called sodium sulfate. Below, we will take you to understand the specific application of sodium sulfate in the textile printing and dyeing industry.

1、 Used as a direct dye or other cotton dyeing promoter
When dyeing cotton with direct dyes, sulfide dyes, vat dyes, and printing dyes, sodium sulfate can be used as a dyeing promoter. These dyes are easily soluble in the formulated dye solution, but they are not easy to dye cotton fibers. Due to the difficulty in absorbing the dye completely, there is a lot of residual dye in the foot water. Adding sodium sulfate can reduce the solubility of dyes in water, thereby increasing their coloring power. In this way, the amount of dye used can be reduced while the resulting color deepens.

1. Before using sodium sulfate
Before using sodium sulfate, thoroughly deepen it with water and filter it before adding it to the dye bath. It is necessary to stir the dye bath while slowly adding it to prevent local dye baths from salting out due to contact with a large amount of dye promoting agents.
2. Dosage of Sodium Glutamate
It depends on the coloring power of the dye used and the depth of the desired color. It should not be added too much or too quickly, otherwise the dye in the dye solution will precipitate and cause stains on the fabric surface.
3. When cotton fabric is rolled and dyed
Yuanming powder is usually added in batches in the 3rd to 4th stages. Before dyeing, the dye solution is very thick. If added quickly, the dye will dye the fibers too quickly, which can cause unevenness. Therefore, it is advisable to dye for a period of time before adding it.
4. Sodium sulfate and table salt are commonly used dye enhancers
Practice has proven that in direct dyeing and stir frying, using sodium sulfate as a dye promoter can achieve bright colors. The effect of using table salt is poor, which is related to the purity of table salt. In general, industrial salt contains not only a large amount of calcium and magnesium plasma, but also iron ions. Some dyes that are greatly affected by iron ions (such as direct turquoise blue GL) can cause a dull color when using salt as a dye promoter. Some also believe that salt is cheaper and can be used as a substitute for sodium sulfate. But when dyeing light colors, using sodium sulfate is better than salt, while when dyeing dark colors, using salt is better.
5. The relationship between the dosage of sodium sulfate and table salt
The relationship between the dosage of sodium sulfate and table salt is roughly as follows:
6 parts anhydrous Na2SO4=5 parts NaCl
12 parts of hydrate Na2SO4 · 10H20=5 parts of NaCl
2、 Used as a direct dye silk dyeing retarder
The application of direct dyes on protein fibers is mainly found in the dyeing of silk, resulting in better dyeing fastness than general acidic dyes. Some direct dyes also have excellent discharge properties, so they are often used as discharge ground colors in silk fabric printing. Direct dyeing of silk with dyes often involves adding a small amount of sodium sulfate, but the role of sodium sulfate here is different from that of dyeing cotton, only serving as a dyeing retarder.
1. The principle behind the slow dyeing effect of direct dyeing silk with sodium sulfate is as follows:
The direct dye R SO3Na dissociates into sodium ions Na+and pigment anions R SO3- in water, as follows: RSO3Na (mutual conversion arrow in parentheses) Na+R SO3- sodium sulfate Na2SO4 dissociates into sodium ions Na+and sulfate ions SO4- in water, as follows: Na2SO4 (mutual conversion arrow in parentheses) 2Na+RSO4- In the dyeing bath, the dye anions R SO3- can be directly dyed onto silk. When sodium sulfate is added, it dissociates and produces sodium ions Na+, The scarcity of sodium ions affects the dissociation of dyes; That is to say, due to the equilibrium relationship of the ion post reaction equation, it is affected by the common ion guilt of Na+, reducing the dissociation of the dye, thus playing a slow dyeing role in silk dyeing.
2. Fabrics dyed with direct dyes are generally treated with fixing agent Y or fixing agent M (about 3-5 g/L, 30% acetic acid 1-2 g/L, temperature 60 ℃) for 30 minutes to improve the dyeing fastness of the finished product.
3、 Used as an acid dye retarder
When dyeing animal fibers such as silk and hair with acidic dyes, sulfuric acid and acetic acid are often added to promote the coloring of pigment acids, but at the same time, elemental powder is also added as a dyeing retarder.
1. When acid dyes are used for silk and wool, if sulfuric acid or acetic acid is added alone, the production and coloring of pigment acids in acid dyes are too fast, which can easily combine with the outside of the fiber and form precipitates, making it difficult to penetrate and penetrate into the inside of the fiber. Therefore, not only does it cause staining spots, but it also causes floating color and cannot withstand friction.
2. Adding sodium sulfate can alleviate the production and coloring of pigment acids, making dyeing easier and more uniform. Therefore, the simultaneous application of sodium sulfate and sulfuric acid or acetic acid can adjust the interaction and achieve better results.
3. If anhydrous sodium sulfate is used, the dosage should be halved according to the amount of crystalline sodium sulfate used.
4、 Used as a ground color protector for printing and dyeing silk fabrics during scouring
When refining printing or dyeing silk fabrics, the dye may be peeled off, causing contamination of the ground color or other similar fabrics. Adding sodium sulfate can reduce the solubility of the dye, thus avoiding the risk of staining the ground color due to dye peeling.