The application of sulphur dyes in cotton textiles is indeed economical and has good color fastness, but it often produces erythema and red strips, which require rework and affects production and cost. To solve this problem, you must pay attention to the following points:

1. Use sodium sulfide (Na2S)

Sodium sulfide is the main auxiliary agent which is indispensable for the dyeing of sulphur dyes. Sulphur dyeing must be formulated with different proportions of sodium sulfide (50%) according to the specific product. Generally, it is 1:1 with dye (100%), and can be formulated like 1:1.5. Its role is mainly to promote the dissolution and reduction of dyes.

Sometimes the sodium sulfide used is not reddish brown, it is an off-white powder, and it is also added to the dye bath. In fact, the sulfide base has been weathered in an off-white powder. In addition, it does not dissolve or reduce the dye in the dye bath. On the contrary, it will cause the dye to be prematurely oxidized into a lake. If the water is not cleaned, it will inevitably produce erythema and red strips. Dyeing rickets.

2, control the dyeing process conditions

Practice has shown that the dyeing of sulphur dyes cannot be dyed according to the theoretical so-called 80-85 ° C, especially vulcanized blue, sulfur black. After adding dye and alkali sulfide, gradually heat up to 98 ° C, heat dyeing for 15-20 min, then stop heating; while dyeing, let the temperature in the tank drop to 80-85 ° C, continue dyeing for about 20 min, and then drain Wash in the cold water and oxidize. Regardless of the removal of residual liquid (heat) and the addition of cold water, the speed should be slow and should not be too fast. The dyeing method of the first heat and the latter temperature is favorable for leveling, and is beneficial to the full dissolution and reduction of the dye, and can overcome the dyeing rickets.

3, the dye should be slowly cleaned

As already mentioned above, the dyed fabric cannot be washed in a cold water bath at once. Especially like sulfur blue, after dyeing, it should be transitioned from mild to mild, even in water containing certain reducing agent, the term is called "foot cylinder". This not only facilitates the thorough cleaning of the alkali and reducing agents on the fabric, but also facilitates sufficient color development (oxidation) of the dye on the fabric.

Of course, for some difficult-to-oxidize dyes, such as sulfide blue CV/3G, red-brown GN, dark brown, etc., in the 2-3 cylinder water bath should also add 1-2g / L sodium perborate and hydrogen peroxide to promote dyes Oxidized hair color.

4, pay attention to the dye bath is stable, solve the problem before the cylinder

Sulfur dyes are dyes with a high sulfur content, especially in black, and there are many factors that are unstable when applied. For example, when the dyeing process starts, the leuco body of the dye bath is dark green or ginger (depending on the type of dye, the leuco body is different). Before the dyeing is terminated, the leuco body in the dye bath changes, which is different from the original. It is.

Then, you can't get out of the tank. Generally, add 1/2 or 1/3 of the original amount of sodium sulfide, and then continue to dye for 10-15 minutes at about 85 °C. The leuco body of the dye bath is similar to the beginning. Then there will be another time. Otherwise, problems will occur after the cylinder is released, resulting in rework. Practice has proved that when dyeing, if adding 2-3g/L baking soda, soda ash, glucose (industrial grade) or 0.5-1g/L insurance powder and 1-2g/L urea, it can promote dye dissolution and stabilize dye bath. , significantly reduce the chance of producing erythema, red strips.

5, erythema, red strips and other rickets repair

Generally, a dilute solution of a sulfide base (about 5-10 g/L) is treated at 85-90 ° C for 20 min, and the rickets can be eliminated. When the rickets are serious, the amount of sulphate should be increased accordingly. When the amount of sodium sulfide is more than 10g/L, an appropriate amount of dye should be added to the treatment bath. Otherwise, the erythema such as erythema has been repaired, but the color may be lighter. The specific dosage and method of repair will depend on the actual situation.

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