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5 key points to improve the solid color rate of reactive dyes

Views: 1     Author: Site Editor     Publish Time: 2023-03-07      Origin: Site


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Although the fixing reaction rate is far greater than the hydrolysis reaction rate, if the process conditions are not controlled properly, such as the high pH value of the dyeing liquid or the temperature is too high, it will promote the hydrolysis of the dye, the solid color rate decreases, the floating color on the dye fabric increases, and the aggravation will increase Later treatment burden, and increase the cost of dyeing, increase the burden of seal and dyeing wastewater, etc. Therefore, improving the solid color of active dyes is an important issue in active dye dyeing.

01 dye directability

The prerequisite for fixing is the dye -dye -dye fiber products. The directability of dyes is the main factor affecting the upper dye rate. Under normal circumstances, active dye solid color rate increases with the increase in directability.

When the directability of the dye is low, the solidarity rate increases rapidly with the increase in directability. When the direct as high as a certain extent, the increase in solidarity rate is not obvious.

This is because the dye diffusion performance with high direct directivity makes the dye on the fiber surface, so the dye that is too high in directability will not only improve the solid color rate, but it will reduce the dye dye, and cause hydrolyzed dyes to be difficult to wash easily. It affects dyeing fastness.

Active dye is generally small, which is one of the reasons that lead to a low solid color rate of active dyes. Therefore, to improve the directability of active dyes, it is not advisable to use too high temperature and pH value, because as the dyeing temperature is improved, the directability of active dyes decreases, as shown in the figure below.

At the same time, under the condition of higher pH values, the degree of ionization of cellulose fiber has increased, and the dye anion is rejected. As a result, the dye adsorption is reduced.

02 dyeing pH value and temperature

The main factors that affect the reactivity of active dyes are the dye temperature and pH value. Under normal circumstances, the temperature of the dye liquid is increased, the pH value is increased, and the dye reactivity is enhanced (including the reaction with the fiber and the response to the water).

Due to the increase in temperature, the response rate of dyes increases; the pH value is increased, the degree of fibrous puffing is increased, and the diffusion rate of dyes increases, which is conducive to the response of dyes and fibers. However, the pH value is too high, [cell-o-]/[oh-] ratio decreases, which is not conducive to the reaction between dyes and fibers. And too high temperature and pH value will also accelerate dye hydrolysis and reduce solidification. Therefore, in order to ensure the normal fixing color of the dye, try to make the dye less hydrolyzed, and the solid temperature and pH value should be reasonably determined according to the reactionability of the dye itself. Generally, the pH value is controlled at 10-11.

03 dyeing time

The active dye dyeing dyeing and fixing color two stages, extending the time of the upper dyeing stage, can fully diffuse, penetrate the dyes, improve the upper dyeing rate, and help even dye. However, after the active dye is fixed, the dye and the fiber have a covalent bonding, and the dyes have become part of the fiber and cannot be dyed again. Therefore, the effect of extending color fixing time has little effect on uniform dyeing. For those dyes with weak response, extending color fixing time can make the dye fixed color more fully, which is conducive to improving the color solid rate. For dyes with poor alkali resistance in dyes, prolonged color fixation time can also cause hydrolysis of solid dyes.

04 Added electrolyte

In the process of dyeing on the active dye, adding an appropriate amount of neutral electrolyte promoting dyeing is conducive to improving the color solid rate. This is because the addition of neutral electrolytes can reduce the potential potential on the fiber surface, increase the directability of the dye, and increase the color fixation rate. The principle and influencing factors are similar to direct dye dyes.

05 staining bath ratio

The direct directivity of active dyes is small. When using exhausted dyes, the small bath ratio is conducive to increasing the upper dyeing rate of dyes, and it can increase the chance of dye and fiber reaction, reduce hydrolysis of dyes, and increase the color solid rate.

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