10 points to note: Things to note when dyeing with reactive dyes. According to market research, reactive dyes are one of the most commonly 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 the materials, and the temperature of the mixing materials cannot be too high?
(1) First use a small amount of cold water to make the slurry to make the dye easily 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 Wrapping it up will make it difficult for the inside of the dye particles to get wet and melt. Therefore, you should first use a small amount of cold water to mix the slurry, and then use hot water to melt 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 should we add materials slowly and evenly?
This is mainly to prevent the dye from dyeing too quickly. 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 can easily cause color stains. Or striped flowers.
3. After adding the dye, why does it take a certain period of time (for example: 10 minutes) before adding salt?
Salt is a dye accelerator. When the dye reaches a certain level, it has reached saturation and it is difficult to continue dyeing. The purpose of adding salt is to break this balance, but adding salt promotes dyeing. It will take about 10-15 minutes before the dye can fully penetrate evenly, otherwise it will easily cause stripes 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 after adding salt.
There are two main reasons: A. to allow the salt to dissolve evenly in the tank and fully promote dyeing; B. to allow the dyeing to enter the dye saturation stage and reach equilibrium. Add alkali to fix the color to achieve the highest dye uptake.
6. Why does adding alkali cause “color fixation”?
Adding salt to reactive dyes can only promote dyeing, but adding alkali will stimulate the activity of reactive dyes, causing the dye and fiber to react (chemical reaction) under alkaline conditions, thereby making the dye It is fixed on the fiber, so it is called “fixed color” because of the chemical reaction of this kind of color fixation, which achieves higher fastness. Once solidified, the color print will be difficult to achieve evenly.
7. Why does alkali need to be added in stages?
The purpose of adding it in batches is to make the color fix evenly 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 ingredients?
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 is raised if the temperature exceeds 3℃, dyeing will be affected. If the temperature exceeds 5℃, stripes will appear. If the temperature exceeds 10℃, the dyeing will stop.
machine for maintenance.
c. Someone has tested that after the cylinder is steamed and rotated for 10-15 minutes, the temperature in the front, back, left, and right of the cylinder is basically uniform and equal to the surface temperature, so when adding materials, regardless of the chlorine cooking time When adding H202 or dyeing dye salt and soda ash, the steam should be turned off before adding materials.
9. Why ensure the process holding time after adding alkali?
The holding time should be calculated after the alkali is added and the temperature is raised 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 The formulation is based on how long it takes for a certain amount of dye to react. The laboratory also designs samples at this time.
10. Several types of shearing that do not follow the process regulations cause unstable quality.
The time is not up to “correct” the color shear.
Due to problems with plate making, material weighing, cloth weight, liquor ratio and other issues, color deviations will occur. Abnormalities such as color “correcting” before the time is up should be reported. The squad leader or craftsman, no matter what, shortens 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.
The board is cut early and the material replenishment is inaccurate.
Dyeing can only be stable when the process heat preservation time is reached. The earlier the shearing time, the greater the change and the more unstable. If the time is not up to shearing, (after cooking, After practicing, washing, and blow-drying, it is sent to the craftsman for color inspection. During the time between placing the order and weighing the materials, the actual heat preservation time of the vat cloth has been extended. At this time, the dyeing has also increased. The vat cloth is too dark after adding supplementary materials. It’s time to go shallow again.)
It’s no good to extend the time to cut the board.
After the insulator is sheared, the dye reaction has ended, and it is useless to dye again. On the contrary, some of the dyes that have been dyed will be re-hydrolyzed.
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