Precautions for dyeing with reactive dyes. According to market research, reactive dyes are one of the most widely used dyes in the market. This article mainly summarizes 10 common operating misunderstandings and solutions for your reference.
1. Why is it required to use a small amount of cold water to mix the slurry first when mixing materials, and the temperature of mixing materials cannot be too high?
(1) First use a small amount of cold water to make the slurry to make the dye easily and fully wet. If the dye is poured directly into the water, the outer layer of the dye will form a gel and the dye particles will be wrapped, making it difficult for the dye particles to soak through and dissolve. , so you should first mix the paste with a small amount of cold water, and then use hot water to dissolve it.
(2) If the temperature of the chemical material is too high, it will cause hydrolysis of the dye and reduce the dye fixation rate.
2. Why do you need to add ingredients slowly and evenly?
This is mainly to prevent the dye from dyeing too fast. If the dye is added quickly at one time, the dyeing rate will be too fast, which will make the outer layer of the fiber darker and the inner layer lighter, which may easily cause stains or streaks.
3. After adding the dye, why should the dye be dyed for a certain period of time (for example: 10 minutes) before adding salt?
Salt is a dye accelerator. When the dye is dyed to a certain extent, it has reached saturation and it is difficult to continue dyeing. The purpose of adding salt is to break this balance, but it takes about 10-15 minutes before adding salt to promote dyeing, so that the dye can Penetrate fully and evenly, otherwise it will easily cause streaks and color flowers.
4. Why should salt be added in batches?
The purpose of adding salt in stages is to promote dyeing evenly, so as not to promote dyeing too quickly and cause color blooming.
5. Why does it take a certain period of time (such as 20 minutes) to solidify the color after adding salt.
There are two main reasons: A. To allow the salt to dissolve evenly in the tank to fully promote dyeing. B. To promote dyeing and reach a saturated and balanced state, then add alkali to fix the color to achieve a high dyeing amount.
6. Why does adding alkali cause “color fixation”?
Adding salt to reactive dyes only has the effect of promoting dyeing, but adding alkali will stimulate the activity of reactive dyes, causing the dye and fiber to react (chemical reaction) under alkaline conditions, thereby fixing the dye on the fiber, so it is also called “color fixation” because This type of color fixation undergoes a chemical reaction to achieve higher fastness. Once solidified, the color print will be difficult to achieve evenly.
7. Why should alkali be added in stages?
The purpose of adding it in batches is to achieve uniform color fixation and prevent color blooming.
If added at one time, it will easily cause excessive concentration of the local residual liquid and accelerate the reaction with the fiber, which will easily cause color blooming.
8. Why must the steam be turned off first when adding materials?
a. The purpose of turning off the steam before adding materials is to reduce the stripe difference and prevent color blooming.
b. When the temperature on both sides of the controlled cylinder rises, if the temperature exceeds 3℃, dyeing will be affected. If the temperature exceeds 5℃, stripes will appear. If the temperature exceeds 10℃, dyeing will stop.
machine for repair.
c. Someone has tested that the temperature inside the cylinder is basically uniform and equal to the surface temperature after the steam is turned for 10-15 minutes. Therefore, when adding materials, whether H202 is added during chlorine boiling or home dye salt and soda ash are added during dyeing, the temperature should be the same. Turn off the steam before adding ingredients.
9. Why ensure the process holding time after adding alkali?
The holding time should be calculated after the alkali is added and the temperature rises to the process holding temperature. Only when the panels are cut according to the process holding time can the quality be guaranteed, because the holding time is determined based on how much time it takes for a certain amount of dye to react. The laboratory also does proofing at this time.
10. Several kinds of plate shearing that do not follow the process regulations cause unstable quality.
The time has not yet come for the “right” color clip.
Due to plate printing problems, material weighing problems, cloth weight and liquor ratio, etc., problems will cause color deviations. If the color has not been “corrected” before the time is up, this abnormality should be reported to the squad leader or craftsman. In any case, shorten the process and heat preservation time. , the dye reaction is not sufficient, the color does not change, the dyeing is uneven, there is no fullness, and the fastness is also a problem.
Cut the board early and replenish the material incorrectly.
Dyeing can only be stable when the process heat preservation time is reached. The earlier the cutting time, the greater the change and the more unstable. If the cutting time is not up, (after boiling, scouring, washing, and blow-drying, it will be sent to the craftsman for color inspection , between the time of placing the order and weighing the material, the actual heat preservation time of the vat cloth has been extended, and the dyeing has also increased. The vat cloth is too dark after adding the supplementary material, and it will be lightened again.)
There is no benefit in prolonging the cutting time.
When the temperature is exceeded by the insulator, the dye reaction has ended, and it is useless to dye again. Instead, some of the dyes that have been dyed will be re-hydrolyzed.
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