Dyeing properties of reactive dyes
When dyeing with reactive dyes, the dye can be dyed directly onto the cloth. At the same time, because it has good diffusion ability, it is easy for the dye to diffuse into the fiber. However, since it has not yet chemically reacted with the fiber, it is easy to wash away most of the dye with water. Therefore, an alkali agent must be used to promote the production of dye and fiber. A chemical reaction that fixes the dye to the fiber. The former is called dyeing and the latter is called fixation.
Reactive dye dyeing process
Basic process:
1. Adsorption (color absorption): The fiber absorbs the dye from the dyeing solution and diffuses it into the fiber.
2. Fixation (color fixation): The dye reacts chemically with the fiber to form a covalent bond.
3. Washing (soaping): Unfixed dye is washed away from the fiber. When dyeing, the reactive dye first dissolves in water, and the dye and water molecules enter the fiber at the same time and are adsorbed by the fiber.
Reactive dyeing problem
1. Dye problem
The main possible problem is that the dye is added directly into the tank before it is completely dissolved during feeding, resulting in the appearance of material spots. (It is best to dissolve the dye in advance before adding it to the auxiliary tank. It is best to filter the light-colored dye after it has been dissolved. Once, if the material is mixed directly in the auxiliary tank, it is generally best to use hot water. This may cause some dyes to hydrolyze faster, but the overall effect is not obvious. It is best to ensure that the dye is completely dissolved before adding Dyeing vat) In addition, you can also consider whether there is a problem with the quality of the dye itself. In this case, you must directly conduct spot checks on the incoming dye before entering the warehouse.
2. Electrolyte problem
Yuanming powder is not dissolved and added. Although this effect may not be common in general, if Yuanming powder The powder has not melted (the Yuanming powder produced by some individual manufacturers has too many impurities and is not easy to melt). If the Yuanming powder cannot be completely melted during dyeing, the Yuanming powder will cause color spots on the cloth during the dyeing process (such as In this case, it is best to use water with a higher temperature to melt the Yuanming powder. Generally, put some water in the auxiliary tank, add the Yuanming powder, and then turn on the steam. This will have a better effect.)
3. Alkali agent problem
Reactive dye dyeing generally uses soda ash as the fixing agent. Soda ash fixes slower than caustic soda, but its alkalinity is directly Release, the initial dyeing rate is still relatively high. In this case, if the alkali addition is not properly controlled during the alkali addition process, color blooming may occur, especially sensitive colors and green orchid macromolecular dyes are more likely to appear color blooming. .
4. Water quality issues
If the water hardness used for dyeing is too high, it may cause dye aggregation and color spots. This requires the dyeing factory itself to regularly test the quality of the water used. If the water hardness is high, it can be controlled by adding 0.2-1g/L chelating dispersant during the dyeing process. Chelating dispersants not only have the ability to chelate metal ions, but also have the functions of dispersing, refining, and increasing whiteness. They also block metal ions and are suitable for pre-treatment, dyeing, post-treatment and other processes. It is adaptable to the compatibility of various additives and can effectively prevent the re-adhesion of silicon slicks or other pollutants. When used in dyeing, it has certain leveling and retarding effects.
Causes and measures for color blooms
1. Color blooms caused by uneven cooking and opacity
Uneven scouring and uneven removal of impurities on the fabric will cause different moisture absorption rates in parts of the fabric, resulting in colored flowers.
Measures:
A. Inject the scouring additives quantitatively in batches, and the additives must be kept uniform. The injection effect of hydrogen peroxide is better at 60-70 degrees.
B. The cooking and heat preservation time must be strictly in accordance with the process requirements.
C. The dead cloth wrapping process should continue to be kept warm for a while.
2. If the water is not washed carefully, the residual oxygen on the cloth surface will cause color stains.
The water stains during scouring are unclear, and the gray cloth is stained with alkali. Dyeing causes stains, and the remaining oxygen on the cloth surface after boiling is not clean.
Measures:
A. After washing the water, neutralize the residual alkali with 10% glacial acetic acid and then wash the water to make the cloth surface PH7-7.5.
B. Use deoxygenase additives to complete the deoxygenation treatment. Inject glacial acetic acid quantitatively for 5 minutes in the normal procedure, raise the temperature to 50 degrees and run for 5 minutes, and inject deoxygenase quantitatively with clean water. , keep warm for 15 minutes, take water samples to measure oxygen content.
3. Uneven chemical materials and insufficient dye dissolution may cause color flowers.
Measures:
Stir with cold water first, then dissolve with warm water. According to the properties of the dye, adjust the temperature of the chemical material to normalize the reactive dye. The temperature of the material should not exceed 60 degrees. Special dyes need to be hydrated, such as brilliant blue br_v. They can be made into separate materials. They must be thoroughly stirred, diluted and filtered before use.
4. The dyeing accelerator (yuanming powder or table salt) is added too fast
Consequences:
If the speed is too fast, the surface of the rope-like fabric will contain dyeing accelerator with different concentrations, resulting in different dyeing promotion rates on the inside and outside, resulting in color flowers.
Measures:
A. The dye should be added in batches, and each addition should be slow and even.
B. Adding in batches should be less at the beginning and more at the end. Each addition should be separated by 10-15 minutes to promote uniform dyeing.
5. The color-fixing agent (alkali agent) is added too quickly.
The color-fixing agent (alkali agent) is added too fast. Too many, resulting in colored flowers.
Measures:
A. Normally, the alkali is injected quantitatively in 3 times, with the principle of less first and then more, the first dosage 1%10. The second time 3%10. The last 6%10.
B. Each addition should be slow and even.
C. The heating rate should not be too fast. Differences in the surface of the rope-like fabric will cause different color absorption rates and cause color blooming. It is strictly required to control the heating rate (1-2℃/min) to adjust the amount of steam on both sides.
6. The liquor ratio is too small, resulting in color differences and stains
Many factories now use air flow cylinder dyeing equipment, with a liquor ratio of 1: 4 or even 1:3
Measures: Control the amount of water according to process requirements.
7. Soaping colored flowers
The washing water after dyeing is unclear, the ph content is high during soaping, and the temperature rises too fast Causes colored flowers. After heating to the specified temperature, it must be kept warm for a certain period of time.
Measures:
Wash clean, neutralize some parts with acidic soaping agent, and run it in the dyeing machine for 10 minutes or so, and then heat it up. If the conditions are convenient for sensitive colors such as lake blue and colorful orchids, try to test the pH before soaping.
Of course, with the emergence of new soaping agents, there are low-temperature soaping agents on the market, which is another matter.
8. Dyeing The bath water is unclear, resulting in stains
The residual liquid after soaping is unclear, so the concentration of the residual color liquid on the surface and inside of the fabric is different. During drying Fixed on the fabric to form colored flowers.
Measures:
Wash thoroughly after dyeing to remove floating color.
9. Added color
Color difference caused by added color (cylinder difference, stripe difference)
Causes of color difference:
A. The feeding speed is different. If the dosage of dye accelerator is small, it will have an impact whether it is added in batches. If it is added at one time, the time is short, the dye accelerator is not enough, resulting in color flowers.
B. The materials are rubbed unevenly on both sides, causing stripe differences. For example, one side is darker and the other is lighter.
C. Incubation time
D. Color difference caused by different cutting and color matching techniques.
Requirements: Cut the sample and match the color using the same technique.
For example: cut the sample to match the color after being kept warm for 20 seconds, and the degree of washing after cutting is different.
E. Different liquor ratios cause color difference. Small liquor ratio: dark color Large liquor ratio: light color
F. The degree of post-processing is different. If the post-processing is sufficient, the floating color is sufficient to be removed, and the color will be lighter than if the post-processing is insufficient.
G. There is a temperature difference on both sides and in the middle, resulting in strip differences.
Add color slowly. Inject it quantitatively for at least 20 minutes. For sensitive colors, In 30-40 minutes.
Add ingredients to chase the color
1) Light color condition:
A. First, check the original process prescription and weigh the dye according to the degree of color difference and fabric weight.
B. The chasing dye must be fully dissolved, fully diluted, and filtered before use.
C. When chasing colors, add materials at room temperature. The materials should be added slowly and evenly to prevent recoloring caused by excessive operation.
2) Color depth situation
A. Strengthen soaping and sufficient post-processing.
B. Add Na2CO3 for slight decolorization.
Only by mastering the correct method can we effectively avoid the occurrence of quality problems. This requires continuous learning and exploration by the dyeing frontline workers, and they should try their best to add color to the dyeing master to create greater profits for the dyeing factory. </p
