8 Cách cải thiện độ bền xoa ướt

I. Selection of Dyes

There are numerous varieties of reactive dyes, and their qualities vary greatly. It is crucial to select dyes that meet the quality standards for dyeing.

1. Select dyes with dual reactive groups and multiple reactive groups.

The reactive dyes of triazine type form ester bonds with fibers, which have poor acid stability. The reactive dyes of vinyl sulfone type combine with fibers through ether bonds and have poor alkali stability. The dyes with two reactive groups have improved acid and alkali stability.

2. Select dyes with appropriate directness.

If the directness of reactive dyes (such as vinyl sulfone reactive dyes) is too high, their diffusion performance will be poor. The dyes will tend to accumulate on the fabric surface and will not easily diffuse and transfer into the fiber interior, which may result in excessive unfixed dyes and difficulty in thorough washing. However, the directness should not be too low either, as it would affect the fixation rate. Therefore, a moderate directness is preferable for reactive dyes. The magnitude of directness can be obtained from the data provided by the dye supplier.

3. Select dyes with high color fixation rates.

Dyes with a high fixation rate have less unfixed color. When the fixation rate is over 80%, the amount of unfixed color after dyeing is relatively small, which is conducive to the removal of unfixed color. For reactive dyes with a fixation rate less than 70% and (final dye uptake rate – fixation rate) greater than 15%, the unfixed color is difficult to remove and is not suitable for dyeing medium to dark colors.

4. Select dyes with high lifting power.

In dyeing process design, the amount of dye generally should not exceed 10% of the saturation value. Excessive dye cannot be fully absorbed, resulting in insufficient fixation and un-fixed dye adhering to the surface of the dyed material, which affects the wet rubbing fastness of the dyed material. When dyeing dark colors, it is necessary to choose dyes with high uptake rate, high fixation rate and high lifting power, such as reactive dyes with double or multiple reactive groups.

Second, choose the grey fabric with uniform yarn count and smooth surface. If pretreatment is needed, efficient pretreatment agents should be used.

Third, soft water or deionized water should be used for dyeing as much as possible to reduce the influence of calcium, magnesium and other ions in water on the dyeing process.

5. Selection of Fixing Agents

An efficient mordant should be capable of “bridging” between dyes and fibers to form compounds. When reacting with dyes, it can also react with cellulose fibers to form cross-links, enabling dyes and fibers to be closely and firmly bonded together, preventing dyes from falling off the fibers and avoiding a decline in dyeing fastness. The mordanting effect is achieved through the interaction of the mordant with the fibers in the medium and the formation of salts between the cationic groups and the anions of the dyes.

High-quality formaldehyde-free fixation agents can enhance the wet rubbing fastness of reactive dye dyed fabrics by 0.5 to 1 grade. The performance of the fixation agent is: a high-molecular compound capable of forming a film, such as polyurethane or organosilicon with -OH and -NH2 groups, and crosslinking agents to crosslink with high-molecular polymers, making it durable and quickly form a film, without color change, yellowing, or reduction in light fastness. It can make the dyed fabric feel smooth, reduce the surface friction coefficient, and maintain the fabric’s breathability and moisture permeability for wearing performance.

6. Special auxiliaries can reduce the amount of dyes used in finishing while achieving a deep and rich color effect, and the wet rubbing fastness is also improved.

7 pH Value of the Fabric Surface After Dyeing

When dyeing dark-colored cotton fabrics, a relatively high amount of alkali is used. After dyeing, thorough water washing, soaping and neutralization to remove alkali are necessary. The fabric must not carry any alkali, otherwise it will cause post-dyeing hydrolysis of the dye and a decrease in wet rubbing fastness. Generally, the pH value of the fabric surface should be controlled between 6.5 and 7.5, and must not exceed 9 or be less than 3.

8. Improving the post-dyeing fabric surface properties. Fabric finishing can be carried out by using biological enzyme polishing treatment, etc., which can increase the smoothness of the fabric surface and also enhance its wet rubbing fastness.

After reactive dyeing, it is very difficult to remove the unfixed dye. After soaping, an appropriate stripping agent can be used for stripping treatment to remove the unfixed dye completely and improve the wet rubbing fastness.