Dyeing with vulcanized dyes for all cotton textiles is indeed very economical, and the color fastness is also good, but it often produces erythema and red stripes, which require rework, which affects yield and cost. To solve this problem, the following points must be paid attention to:
1. Use alkali sulfide (Na2S) well. Sulfide alkali is an indispensable main additive for dyeing sulfur dyes. When dyeing sulfur dyes, you must match different proportions of sulfide alkali (50%) according to the specific product. Generally, it is 1:1 with dyes (folded to 100%). For example, vulcanized blue can also be matched to 1:1.5. Its function is mainly to promote the dissolution and reduction of dyes. Sometimes the sulfide alkali used is not reddish-brown, but becomes an off-white powder, and is also added to the dye bath together. In fact, the sulfide alkali is in an off-white powder and has been weathered. When added in the dye bath, it will not only not function as dissolving or reducing the dye, but will instead cause the dye to oxidize too early and become a colored lake. If the water cannot be washed clean, erythema and red stripes will inevitably occur. etc.
2. Control the dyeing process conditions. Practice has proved that the impregnation of sulfurized dyes cannot be dyed at the so-called 80-85°C in theory, especially blue vulcanized and black vulcanized. After adding dye and alkali sulfide, the temperature should be gradually increased to 98℃, insulated and dyed for 15-20 minutes, and then stopped heating; while dyeing, the temperature in the cylinder should be reduced to 80-85℃, and dyed for about 20 minutes, and then drain the liquid. Wash the oxidation while in cold water. Whether the residual liquid (heat) is removed and cold water is added, the speed should be slow, not too fast. This dyeing method that is heated first and then warm is not only conducive to uniform dyeing, but also conducive to the full dissolution and reduction of dyes, and can overcome dye defects.
3. The pollutants should be cleaned slowly. As mentioned above, the dyed fabric cannot be placed in a cold water bath for cleaning at once. Especially like blue vulcanized, after dyeing, it should be transitioned from the dye bath to mild, and even cleaned in water containing a certain reducing agent. The term is “foot tank”. This not only facilitates sufficient cleaning of alkaline and reducing agents on the fabric, but also facilitates sufficient coloring (oxidation) of the dye on the fabric. Of course, for some dyes that are difficult to oxidize, such as blue sulfide CV/3G, red brown GN, dark brown, etc., 1-2g/L of sodium perborate and hydrogen peroxide should be added to promote the sufficient dye in the 2-3 tank water bath. Oxidized hair color.
4. Pay attention to the stability of the dye bath and solve the problem before leaving the tank. Vulcanized dyes are dyes with a high sulfur content, especially black, which have many unstable factors when used. If the octopus of the dye bath is dark green or ginger when the dyeing starts to dye (the octopus is different depending on the dye variety), before the dyeing is terminated, the octopus in the dye bath changes, which is different from the original one. Now. Then, you cannot leave the tank. Generally speaking, add 1/2 or 1/3 of the original amount of sulfide alkali, and then continue to dye for 10-15 minutes at about 85°C. The epithelium of the visual dye bath is similar to the beginning. Then I will give it another sip. Otherwise, problems will also occur after the cylinder is discharged, resulting in rework. Practice has proved that when dyeing, if you add 2-3g/L baking soda, soda ash, glucose (industrial grade), or 0.5-1g/L insurance powder and 1-2g/L urea, you canPromote dye dissolution, stabilize the dye bath, and significantly reduce the chance of erythema and red bars.
5. Repair of defects such as erythema, red stripes, etc. Generally, use a dilute solution of sulfide alkali (about 5-10g/L) at 85-90℃ for 20 minutes, and the defect can be eliminated. When the defect is serious, the amount of alkali sulfide should be increased accordingly. When the amount of alkali sulfide reaches more than 10g/L, an appropriate amount of dye should be added to the treatment bath, otherwise although defects such as erythema may be repaired, the color may become lighter. The specific amount and method of repair depends on the actual situation.
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