Several points that acid dyes must pay attention to in dyeing

1. Use dyes with caution

Metal complex dyes containing copper, chromium, and nickel are dyes that have been previously made into metal complexes with dyes of a specific structure and metal complexing agents. There are 93 acid metal complex dyes. The European Union stipulates that when it is used for the dyeing of fibers, after dyeing with each of the metal complex dyes used, the amount of dye liquor that is discharged into the wastewater for treatment should be less than 7%, that is, the coloring rate of the metal complex dye should be More than 93%; at the same time, copper or nickel should not exceed 75ms/ks fiber, chromium should not exceed 50m ore ks fiber. Therefore, the selected dye requires a certain degree of purity.

2. Dyeing water

The dyeing water hardness of acid dyes is preferably 100-150 mg/kg. If the water hardness is high, 0.5-2s/L chelating agent can be added to improve the water quality and ensure dyeing. However, chelating agents such as phosphates or surfactants can destroy the integration of the dyes to varying degrees, affecting the color brightness and color fastness. Screen chelating agents when dyeing, do not blindly use.

3. Material method

Due to the inconsistent solubility of acidic complex dyes, they should be treated differently. It is generally slurried with cold water, then diluted with hot water or boiling water to dissolve. Sometimes due to the addition of fillers to commercial dyes, which make it difficult to dissolve, it is necessary to stir while cooking, until it is fully dissolved, and finally it is slowly filtered through the tank to prevent the formation of color spots (plaques).

4. Fabric treatment

Due to the presence of grease, slurries, impurities and natural pigments in the fabric. Sometimes it is necessary not only to remove the slurry, but also to go through half-bleaching before dyeing. Practice has proved that the pretreatment of pure textiles is relatively easy, while the blended textiles are difficult, but must have good penetration (wetting) before dyeing, depending on the specific variety.

5. The role of acid

Regardless of sulfuric acid, formic acid (formic acid) and acetic acid, they are all acidic and acid complex dyes. Sometimes, in order to further dye the dye (exhaustion), the amount of acid is usually added during the dyeing and later stages. However, it is necessary to dilute in advance, close the steam valve, stop heating, and slowly add people to prevent dyeing.

6. The role of Yuan Mingfen

Sometimes acid complex dyes need to be dyed at a pH of 4 or less, so Summon powder can be used as a retarder. On the contrary, if the dye bath medium PH value of 4 or more, it should not be used Yuan Mingfen, because it will increase the dye aggregation tendency, but should use non-ionic surfactants, such as Ping Ping plus O and emulsifier OP, etc. as a slow dyeing agent . The amount of use should be based on the color depth and the dyeing equipment. Too much amount will make the wool felt, feel rough, affect the exhaustion of the dye in the dye solution, in the flow machine will also increase due to foam, and affect the normal operation of the cyclic exchange system; the amount of less effect is not good.

7. Neutralization

The alkali agent is mainly used for neutralization treatment after dyeing with a strong acid medium. The purpose is to restore the ionized amino group to a non-ionized amino group after dyeing, so that the fiber is further combined with the dye. The amount can be determined based on the actual pH of the dye before neutralization. The general ammonia is 1mL/L, and the soda 2-3S/L. Treat it at a temperature of 40-50 bar for 20-30 minutes. The neutralization is completed and then fully washed.

8. End of dyeing

The temperature of washing out of the cylinder should not be too low, generally should be controlled at 50-60 °C, mainly to prevent the fabric from wrinkles, especially wool and nylon once wrinkled, it will be difficult to repair.

9. Fixing agent treatment

For fabrics with high requirements on color fastness, dyes with acid complex dyes can be dyed with 2%-6% (owf) of cationic fixing agent (powder) at a temperature of 55 T and impregnated for 30 min. Especially for silk fabrics, the general color fastness can be improved by 0.5-1.5 grades through fixing. Tests have shown that nylon fabrics do not require fixation.

10. The acid metal complex dyes are thermally sensitive to varying degrees, especially red and blue. Therefore, the temperature during the drying process should not be too high to prevent recovery after the color change.