Hardness
It is generally believed that hardness below 50ppm has no effect, and 20ppm is already very good Water.
The quality of the cheese dyeing water is no better than this, but the content of copper and iron ions in the water should be paid attention to.
Usually reactive dyeing is better when it is below 50 ppm. The key is the content of metal ions, especially iron ions, which will cause changes in color and light. It is recommended to measure the conductivity of the water.
Wastewater that meets the standards is reused in bleaching and dyeing production. The main reason why products are prone to color stains is that the conductivity of the water is relatively high; when reusing bleaching and dyeing wastewater, attention should be paid to the conductivity of the wastewater. Conventional sewage treatment methods cannot effectively remove metal ions that cause high conductivity of wastewater, and must be removed through reverse osmosis membrane treatment.
If the water is too hard, water will form on the boiler wall. The calcium and magnesium ions in the water can precipitate soap. Uneven dyeing, poor fabric feel, and yellowing of the fabric. Reduce the activity of desizing enzymes, reduce the solubility of sizing materials, and are incompatible with chemicals used in finishing formulas.
As a treatment method, you can use EDTA or sodium tripolyphosphate at a trial dosage of 2g/l. It is better to purchase a special metal ion blocking agent; if the dyeing water has not been softened, Or thick cloth often contains metal ions, which often causes uneven (bad) dyeing effects. Therefore, adding chelating dispersants during the dyeing process prevents the influence of metal ions and promotes the removal effect.
However, chelating dispersants such as EDTA (ethylenediamine diacetic acid), DTPA, NTA, phosphate, gluconic acid, etc. may chelate out the metal ions in the dye, causing The light fastness decreases and the color of the legs changes. Therefore, some netizens recommend polyphosphates and polyol acids as chelating dispersants.
Example:
The water used to dye cotton in the on-site factory is groundwater, which has not been softened and filtered. A layer of dirt can clearly be seen on the yarn. Now a small amount of bleaching powder is added to the water, which has slightly improved. However, after the yarn is dyed, the bottom layer feels astringent, and the color is light or dark. The forward and reverse adjustment has been made, and the water softener has also been added. However, the effect was not obvious. After further verification, it was found that there was a water hardness difference of about 130ppm at the bottom of the pre-treatment scouring.
Reason:
The water quality is too hard, and groundwater dyes yarn. Too hard water quality and too many impurities may cause your yarn to be dyed. If the inner layer of the bobbin is dirty, the best solution is to first pump the groundwater to the ground to settle and soften the water, and then use a filter to filter the water. This way there will be no problem, but the investment will be larger.
Impurities and microorganisms
cations The non-toxic film working fluid is unstable in the river water. It flocculates with the microorganisms in the river water to produce yellow floc, which sticks to the fabric. After drying and setting, yellow spots will be formed on the fabric. Therefore, we can know why Quality problems are particularly likely to occur in May to June when the temperature is more suitable for algae reproduction, but in autumn and winter such situations rarely occur.
The quality of water has a great impact on the stability of the softening working fluid and the whiteness of the fabric after softening and finishing. Therefore, printing and dyeing factories try to use treated water during production. of water.
Some manufacturers will still experience similar situations when using water filtered by activated carbon. This is because the microorganisms are very small and activated carbon cannot completely adsorb and filter, so before water treatment Adding cationic surfactants to the sedimentation tank to flocculate with microorganisms in the water, and then filtering through activated carbon, can improve the effect of water treatment; in addition, activated carbon must be cleaned or replaced regularly.
If the above method is not feasible or cannot eliminate quality problems, it is recommended that the manufacturer use non-ionic or anionic film when algae reproduction is strong, or use non-ionic film combined with silicone oil for hand feeling. tidy.
In manufacturers that have a lot of macular spots, this does not happen when they use amino silicone oil for finishing.
Winter is not a good sign for printing and dyeing factories, as the water quality is poor.
pH value
For activity For dyeing, when the pH value is 7 to 9, the color difference of the product is normal, indicating that this pH value range has little effect on the color difference of the product, and the presence of a small amount of alkali will not change or destroy the chromogenic group of the reactive dye molecules.
When the pH value is 8.5, the soaping color fastness and wet rubbing fastness of the fabric are level 3, which cannot meet customer requirements; when the pH value further increases, the color fastness The fastness becomes worse. It can be seen that the alkalinity in the water increases, which will affect the color fastness of dyed products.
The incoming water quality of sewage reuse plants generally requires a pH value <9 to ensure that the microbial growth of the treatment system is not harmed by alkalinity and can operate normally, while the quality standards for reused water require The pH is off 85, preferably closer to 7.
Salinity
The salts in the reuse system are mainly Sodium sulfate has two sources:
(1) Added as a dye accelerator in the dyeing process;
( 2) The caustic soda and soda ash added in the bleaching and color fixing processes are converted into sodium sulfate after neutralization with sulfuric acid.
The limit salinity in the reuse system is 924mg/L, which does not affect the dyeing quality of fabrics.
Iron ions
Pretreatment Iron ions will aggregate and accelerate the decomposition of hydrogen peroxide, causing holes in the cloth surface.
Iron ions will cause the dyed fabric surface to darken and color spots will easily appear.�As for the removal method, first check the content. Generally, it does not matter if it is below 15 ppm. If it is slightly higher, chelating agent can be added.
Chloride ion
Simple Chloride ions have no effect on reactive dyeing, because some people use table salt as a dye accelerator, but it has an impact on the body of the dye vat. It depends on whether the steel of the dye vat you use is chlorine-resistant.
If it is like tap water, it contains available chlorine for bleaching and sterilization, and if it exceeds a certain standard, it will affect the dye. </p
