How to improve color fastness?

Date:Sep 22, 2020

The factors that affect the color fastness of textiles are mainly divided into internal factors and external factors. Internal factors refer to the firmness of the combination of dyes and fibers, and external factors refer to the external force applied to the product or the environmental conditions provided by external factors during use. External factors cannot be controlled, so producers must strive to improve the color fastness of the product itself.

Choice of dyestuffs:

How fast a product is, the choice of dyestuff is very important. If the choice of dyeing materials is inappropriate, no matter how good the auxiliary agent and the best dyeing process are, there is no way to dye high-quality color fastness. Only by choosing the right dye can we talk about the next step.

(1) Choose dyes according to fiber characteristics. Different types of dyes and fibers have different binding forms, and the strength of the binding bonds is also different. After the type of dye is determined, select dyes with high dyeing performance. For example, when dyeing wool fabrics, strong acid dyes can be used. The strong acid dyes of the Levat series of Tiankun Group have good dyeing performance, not only the color is not good, but the firmness of the combination is also very good. It is also a domestic strong acid dye, and different dyes have different binding fastness to wool and dyeing vividness. For example, the color fastness of wool yarn dyed with weak acid dyes is higher than that of strong acid dyes; while for pure cotton fabrics or regenerated cellulose fiber fabrics, either direct dyes or reactive dyes can be used; silk fabrics can be used except weak In addition to acid dyes and some reactive dyes, individual direct dyes can also be used.

Acid dye

(2) Choose dyes according to the color depth. After determining the major category of the dye, it is necessary to further determine which dye to use according to the color system and depth of the dyed color. *, try to choose dyes with shades close to the desired color, if there is a deviation, use other dyes to color. Second, look at the color fastness index of the selected dye itself. The color fastness of the dye itself is poor, and the half-level color fastness can be improved through the process. Third, see whether the saturation of the dye can reach the required color depth. If you choose a dye with a very low dyeing rate, even if the desired high-depth color can be temporarily achieved after processing, the combination of the dye will not be firm, and it will fall off during use or reprocessing.

(3) Select the dye according to its own color fastness grade. In the introduction of each dye, the color fastness grade of the dye is introduced. When choosing a dye, you must choose the dye according to the color fastness grade required by the product, and the dye fastness of the dyes of the matching colors should be similar. For example, the color fastness of the dye itself can only reach 2~3, or even 1~2, no matter how good the auxiliary and dyeing process are, the product with 4~5 color fastness can not be dyed. Because the color fastness of the dye mainly depends on the binding force between the dye and the fiber. If the bond between the two is not strong, no external force can make them bond firmly, even if the color is improved. , Also can not withstand the damage of external factors such as washing and friction.

(4) The dye uptake rate of the fiber. Different dyes will exhibit different dye uptake rates, and under different dyeing conditions, the dye uptake rate of the same dye is also different. Therefore, the dyeing rate must be considered when choosing dyes, otherwise there will be competition among dyes, that is, one of the dyes occupies the dyeing position of the fiber in advance, so that other dyes can only be dyed on the surface of the fiber, not evenly. It forms a strong bond with the fiber, which is destroyed first in the subsequent process or daily use. This is why some colors fade and show a completely different color system from the original color. Therefore, when selecting dyes, dyes with similar dyeing speeds under the same conditions must be selected, which is also very beneficial to the next step of the formulation process.

(5) There should be good compatibility between dyes. Different dyes in the same type of dyes have different compatibility. The greater the compatibility value, the better the ability of dyes to match colors. There must be good compatibility between the dyes of the matching colors. The colors that are not easy to fight are best to use the three primary colors. The three primary colors have the best compatibility among each type of dyes, and they are also the three dyes with the most complete and correct color matching. Therefore, it is easy to match the colors with the three primary colors for some of the more difficult strange colors. Try not to use other dyes to fight against it. It is prone to competing dyeing and dyeing flowers. 2.1.6 To minimize the number of dyes needed, when choosing dyes, first choose dyes whose shades are similar to the required colors, and then use one or two dyes to supplement the lack of shades of the main dyes, and the shades should be selected. With the dyes of the same color series, the color dyed in this way is pure, smooth, gorgeous and full. Try not to use four or five kinds of dyes for coloring. That is not easy to color, and it is not easy to handle mass dyeing. Moreover, although the color and luster are matched, the dyed shade is not bright and full, and the dye cannot be fully combined with the fiber, resulting in poor color fastness.

 Selection and use of additives:

(1) Choose suitable additives. After determining the type of dye, the choice of additives is also very important. Generally try to choose the auxiliary agent that matches with the dyestuff, if it is the common dyestuff that is used routinely, the determination of the auxiliary agent amount and usage method should be emphasized. For dark colors, the dye is not easy to be exhausted, and the auxiliary agent can be added in batches to increase the exhaustion rate, and also improve the fastness of dye adsorption to play a role in fixing the color.

(2) Minimize the amount of retarder. The amount of retarding agent that plays a role of retarding dyeing should be reduced as much as possible, otherwise it will have peeling effect. On the one hand, it will reduce the dye uptake, and on the other hand, it will weaken the binding force of the dye and the fiber, making the color fastness worse. For colors that are easy to dye, the leveling effect can be achieved through the deployment of dyes and the heating speed.

(3) Selection of fixing agent. The use of fixing agent will greatly improve the color fastness of the dye, generally at least 0.5 to 1 level, but the choice of fixing agent should also consider the fastness of the dye, rather than just look at individual items. For example, after reactive dyes are treated with cationic low-molecular-weight or polyamine-type fixing agents, the washing fastness of the fabric is 4~5, but the light fastness will decrease. When fixing, it is necessary to strictly control the amount of fixing agent, fixing temperature and fixing time.

(4) Soaping and water washing. When soaping and washing, you must wash thoroughly, and ensure the washing temperature and time, otherwise the floating color on the surface of the fabric will fade during use.

(5) Use of softener. In order to make the product plump and soft, it is necessary to add a softener. Softeners are cationic, anionic, non-ionic and silicone. Softener is a process carried out after the dyeing process is finished. The dye and softener may react further, which may reduce the color fastness. Especially when the acid dye is dyed, the silicone softener is used, and part of it will even be removed during the softening process. Dyes make the color slightly lighter. Therefore, the amount of softener used in softening treatment should be just right, otherwise, it will not only feel sticky, but also affect dyeing.