Sodium Sulfate for Printing and Dyeing

Chemical Formula

Na2SO4

Molecular Weight

142.04214

Stability

Stable. Incompatible with strong acids, aluminium, magnesium, strong bases. Hygroscopic.

Application

When dyeing cotton with direct dyes, sulfide dyes, vat dyes, and indocyanin dyes, sodium sulfate can be used as a dye promoter. Sodium sulfate for printing and dyeing is easily soluble in the formulated dye solution, but it is not easy to dye cotton fibers. Due to the difficulty of absorbing the dye completely, there are many residual dyes in the water. Adding sodium sulfate can reduce the solubility of dyes in water, thereby increasing the coloring power of the dyes. In this way, the amount of dye used can be reduced while the color of the dyed product deepens.

1. The amount of sodium sulfate for printing and dyeing depends on the coloring power of the dyes used and the depth of the desired color. It should not be added too much or too quickly; otherwise, the dyes in the dye solution will precipitate, causing stains on the fabric surface.

2. During the roll dyeing of cotton cloth, sodium sulfate is generally added in batches in the third to fourth passes. Due to the thick dye solution before dyeing, if added quickly, the dye will dye the fiber too quickly, resulting in unevenness. Therefore, it is advisable to dye for a period of time before adding it.

3. Before use, sodium sulfate should be thoroughly diluted with water and filtered before being added to the dye bath. It is also 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 promoter.

4. Sodium sulfate and salt are commonly used as dye promoters. Practice has proven that in direct dyeing and stir-frying dyeing, using sodium sulfate as a dye promoter can obtain bright colors. The effect of using salt is poor, which is related to the purity of salt. In addition to containing more calcium and magnesium plasma, general industrial salts also contain iron ions. Some dyes that are greatly affected by iron ions (such as Direct Turquoise Blue GL, etc.) can cause a dull color when using salt as a dye promoter.

5. Some people also believe that salt is cheaper and can be used instead of sodium sulfate. However, when dyeing light colors, using sodium sulfate is better than salt, while when dyeing dark colors, using salt is better. Whatever is appropriate should be tested before application.

6. The relationship between sodium sulfate and salt consumption is roughly as follows: 6 parts anhydrous Na2SO4 = 5 parts NaCl 12 parts hydrate Na2SO4 "10H20=5 parts NaCl.