1. Selection of dyes
There are many varieties of reactive dyes, and their quality varies greatly. Dyes that meet dyeing quality standards are crucial.
1. Choose dyes with double reactive groups and multi-reactive groups
S-triazine reactive dyes react with fibers to form ester bonds, which have poor acid resistance and stability. Vinyl sulfone dyes react with fibers to form ether bonds and have poor alkali resistance. Dyes with dual reactive groups have improved acid and alkali resistance.
2. Choose dyes with suitable substantivity
Reactive dyes ( For example, if the substantivity of vinyl sulfone-based reactive dyes is too high, the diffusion performance will be poor. The dye will easily accumulate on the surface of the fabric and will not easily diffuse and transfer into the fibers. This will easily cause floating colors and be difficult to clean, but the directness should not be too low. Fixation rate, so the substantivity of reactive dyes is preferably medium. The magnitude of substantivity can be obtained from the data provided by the dye supplier.
3. Use dyes with high fixation rate
Fixation Dyes with high dyes have less floating color, and the fixation rate is >80%. The amount of floating color after dyeing is relatively small, which is beneficial to removing floating color; the fixation rate is 15% Reactive dyes are difficult to remove floating colors and are not suitable for dyeing medium and dark colors.
4. Select dyes with high lifting power
Dyeing process design , the amount of dye should generally not exceed 10% of the dyeing saturation value. Excessive dye cannot be dyed completely, and the color fixation is insufficient. The unfixed dye attaches to the surface of the dyed object, affecting the wet rubbing fastness of the dyed object. Dark colors must be dyed Choose dyes with high exhaustion rate, high fixation rate and high lifting power, such as reactive dyes with dual reactive groups and multi-reactive groups.
2. Choose a gray fabric with uniform yarn count and smooth surface. When pretreatment is required, use a high-efficiency pretreatment agent. .
3. Soft water or deionized water should be used as much as possible for dyeing, which can reduce the impact of calcium, magnesium and other ions in the water on dyeing. Influence.
IV. Selection of color-fixing agent
High-efficiency color-fixing agent It should be able to “bridge” between the dye and the fiber to form a compound. When reacting with the dye, it can react and cross-link with the cellulose fiber, so that the dye fiber can be closely and firmly connected together to prevent the dye from falling off the fiber. Causes a decrease in color fastness. The color-fixing effect is achieved by the color-fixing agent acting on the fibers in the medium and the cationic groups forming salts with the dye anions to achieve the color-fixing effect.
Excellent formaldehyde-free fixative can improve the wet rubbing fastness of fabrics dyed with reactive dyes by 0.5-1 level. The performance of the fixing agent is: a polymer compound that can form a film, polyurethane or silicone with -OH, -NH2, and a cross-linking agent to cross-link the polymer to make it durable and fast film-forming It is non-toxic, does not change color, does not turn yellow, and does not reduce the light fastness. It can make the dyed objects feel smooth, reduce the surface friction coefficient, and maintain the breathable and moisture-permeable performance of the dyed objects.
5. Special additives can reduce the amount of dye used in finishing to obtain a deep color effect, and the wet rubbing fastness is also improved. get improved.
6. The pH value of the cloth after dyeing.
When dyeing dark-colored cotton fabrics, a higher amount of alkali is used. After dyeing, it is necessary to strengthen washing, soaping and neutralization to remove alkali. There should be no alkali on the fabric, otherwise it will cause the dye to deteriorate. It hydrolyzes after dyeing and the wet rubbing fastness decreases. Usually the pH value of the cloth is controlled at 6.5-7.5, and cannot exceed 9 or less than 3.
7. Improve the surface properties of dyed cloth. Fabric finishing can be done by biological enzyme polishing, etc. The smoothness of the cloth surface can also be improved, and its wet rubbing fastness can also be improved.
8. It is difficult to remove the floating color after dyeing with reactive dyes. Appropriate color stripping can be used after the soap is cooked. The agent is used for color stripping treatment to remove the floating color and improve the wet rubbing fastness.
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