Analysis of common problems in reactive brilliant green dyeing

Reactive emerald blue and reactive bright yellow are dyed together. The dyeing is prone to three major quality problems: first, color spots, color stains, and color flowers; second, color difference and vat difference; third, Low wet processing fastness

1. Color dots and colors

1. Excessive or premature addition of salt or soda ash will cause the dissolved dye to condense or even precipitate, causing the dye to be unevenly distributed on the surface of the fabric and within the fiber, resulting in uneven color, and even color spots and stains at conventional dyeing depths. Within the range, the amount of salt should not exceed 70g /L. Use the correct feeding sequence, that is: add dyeing auxiliaries (water softener, leveling agent) and mix evenly; raise the temperature to 40-50°C, add the dye solution and fully dissolve it; do not add salt in batches, first less and then more. The dye is added together with the salt or the salt is added first and then the dye is added. style=”margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; word-wrap: break-word !important;”> 2.Active bright yellow is sensitive to alkali. In the early stage of adding alkali, the color absorption rate is very high, and it absorbs color and fixes the color at the same time. The dye transfer property is poor. Therefore, it is easy to cause uneven color absorption and form color flowers. Therefore, the color absorption time must be sufficient, and the primary color absorption rate should be increased as much as possible to reduce the concentration of the dye solution before adding alkali for color fixation, which will help reduce the degree of dye aggregation after adding alkali. The amount of soda ash should be less, not too much, because soda ash affects the pH value. has strong buffering capacity and its concentration is in5-25g/L, pH value is 22-22.2, which is enough to meet the requirements for the bonding reaction between dye and fiber. Therefore, it is enough to keep the pH value of the residual liquid after dyeing at about 22 according to the depth of dyeing. Too much soda ash will increase the tendency of dye aggregation. The dosage of soda ash must be small first and then more, and added in batches. 1.5-2.0g/L reactive leveling agent can be added to the dye bath, which can significantly improve the dissolution state of the dye in the saline-alkali dye liquor. But the dosage should not be too much, otherwise it will reduce the dye uptake rate.

2. Color difference and cylinder difference
Reactive emerald blue and reactive bright yellow have different dependencies on various factors related to the dip-dying process. Therefore, if the dyeing process is unreasonable, or the dyeing process is not carried out according to the The execution of the process will inevitably cause the color absorption and fixation rate of active emerald blue and active bright yellow to be unstable, which will lead to fluctuations in the proportion of blue and yellow dyes on the fiber, resulting in color difference or cylinder difference. The prevention and control methods are as follows:
1.The dyeing temperature should be stable at 80-85℃. Within this temperature range, the coloring synchronization of active emerald blue and active bright yellow will be good. If the temperature is higher or lower than this, the reproducibility of dyeing will decrease. .
2.Active Cuilan and Active Bright Yellow have different dependencies on salt. When the dyeing depth is around 2% (o.w.f), the appropriate dosage of salt will be 50-60g/L. Affects the synchronization of coloring between the two.
3.The concentration of soda ash directly affects the active emerald blue and bright yellow The color absorption and color fixation rate (the impact on bright yellow is greater than that on Cuilan), the amount of soda ash must be strictly controlled, otherwise it will affect the color depth and reduce the reproducibility of dyeing.

5. Since the primary color absorption rate of reactive bright yellow is much lower than that of reactive emerald blue, and the secondary color absorption rate is much higher than that of reactive emerald blue, the depth and light of the color will be different in different dyeing periods. It is said that active emerald blue and active bright yellow are highly dependent on the dyeing time and require special attention. Therefore, on the basis of achieving a color absorption balance during the color absorption stage, appropriate heat preservation for a certain period of time is not only beneficial to level dyeing but also through dyeing. Conducive to the stability of color lightCertainly. The alkali fixation time should be sufficient to ensure that both active bright yellow and green blue can achieve relatively stable and high color yield. Reactive emerald blue has poor diffusibility and weak reactivity, and its coloring lags behind that of reactive bright yellow. Therefore, appropriately extending the dyeing time can reduce the color difference and cylinder difference.

6. Since reactive emerald blue is more direct than reactive bright yellow, it is easy to wash after dyeing. It is relatively poor, so soaping needs to be strengthened. If the soaping is insufficient or the degree of soaping is uneven, it will not only reduce the wet treatment fastness, but also cause obvious tank differences.

3. Poor fastness to wet dyeing treatments
1.Cause of occurrence.
①Reactive emerald blue has a relatively large relative molecular mass, lacks linear structure, and has poor diffusivity. Especially during the secondary color absorption process, because the adsorption rate of the dye is much higher than the diffusion rate, resulting in More dyes form overlapping accumulations on the fiber surface. In addition, reactive emerald blue has weak reactivity and low fixation rate. There is a lot of unfixed dye remaining on the fiber, and its washability is poor, resulting in wet processing fastness. Low, level dyeing effect is poor
②Because reactive yellow is very sensitive to alkali agents, in the initial stage of secondary color absorption, the “instant coloring” phenomenon is serious. In addition, the color is absorbed and fixed at the same time, and the fixed dye is harmful to the color. The diffusion of dyes adsorbed on the fiber surface but not fixed has a certain retardant effect, causing excessive floating colors and affecting wet processing fastness and leveling properties.
③Reactive emerald blue and reactive bright yellow have poor solubility stability in salt and alkali solutions. Once too much or too much salt and soda ash are added too early, agglomeration will easily occur, which will seriously affect the dye. Uniform adsorption and uniform diffusion, resulting in excessive floating colors and reduced dye fastness
2．Prevention and treatment methods.

Improve the wet treatment fastness of reactive turquoise blue and reactive bright yellow dyeing brilliant green. As far as the dyeing process is concerned, the following methods can be adopted:
①Improve the dissolution state of dyes and preventThe dye in the stain stop solution aggregates. When dyeing bright green with active green orchid and active bright yellow, it is not advisable to use the dyeing method with pre-added alkali, nor to use the dyeing method of adding salt and soda ash at the same time, otherwise it will easily cause the dye to agglomerate and precipitate (the problem of active bright yellow is prominent), thus causing Serious staining issues.
②Reduce the dye uptake rate during the dyeing process (mainly in the initial stage of alkali addition).
③ Improve the diffusion and dyeing effect of dyes and increase the fixation rate (mainly reactive emerald blue).
④ Strengthen soaping after dyeing to reduce the adhesion of floating dyes. The process of “simple soaping first and then fixing the color with fixing agent” must not be used. Because the color fixing agent is used to fix the color when there is a lot of floating color, although the washing fastness is improved, the frictionThe rubbing fastness is very poor, and it also affects the brightness and light fastness, making it difficult to repair the color after dyeing.