01 Dyeing and finishing processing and chelating dispersants
About 50% of defects in dyeing and finishing products are caused by poor water quality. Alkaline earth metals and heavy metal ions in the water Various chemical reactions will occur with other substances to cause defects. Because the desizing, scouring, bleaching and dyeing, printing, and finishing processes in the past were all carried out in water, therefore, to eliminate the root causes of defects, water quality treatment is required. To start with, chelating agents play an important and irreplaceable role.
Chelating dispersants, also known as: complexing agents, metal ion blocking agents, water softeners, etc. In dyeing plants, it can be used in many applications such as desizing, refining, bleaching, polyester alkali reduction, dyeing, soaping, drawing, silk whitening, down cleaning, equipment cleaning, water treatment, etc.
The composition of scale in dyeing plants is mainly a mixture of scale, silicon scale and dirt. Some scales are difficult to remove, such as CaCO3 scale and silicon scale (formed when H2O2 bleaching and Na2SiO3 are used as oxygen bleach stabilizers) ), etc., even need to be beaten to remove, and the remaining parts must be repeatedly cleaned with acids and alkali to remove. Some scales, such as polyester oligomers, are difficult to remove with acids and alkali. These scales mainly come from untreated water, equipment, impurities in fibers (such as pectin on cotton) and impurities in dyeing materials (such as Yuanming powder, soda ash). Due to the existence of these substances, under certain conditions, Insoluble matter is formed and deposited on equipment (such as cloth guide rollers, rollers, the bottom and wall of the dye vat, the surface of the heat transfer tube of the heat exchanger, the inner wall and outer wall of the pipe, etc.), and it will also be deposited on the textile, affecting the water absorption of the fabric. The properties, whiteness and scratches will also affect the normal operation of heat exchangers and rollers.
02 “Triple Function” of Chelating Dispersing Agent
Chelating dispersing agent is actually a water quality treatment agent. Widely used in printing and dyeing production. There are many types of chelating dispersants. An excellent chelating dispersant has strong chelating ability, good dispersion, good scale inhibition and scale dissolving effect, and good stability. It can be used in many aspects before dyeing and finishing and in the dyeing process. , plays a very important role in the color brightness, uniformity and color fastness of dyed fabrics or yarns.
Chelating dispersants act on scale through “triple effects”:
1. Chelating agents act on the ionic bonds between scale and metal surfaces. By breaking these bonds together, scale is easily removed.
2. Prevent the formation of scale through the electric double layer and steric hindrance. 3. Dispersion, inhibiting the growth and deposition of scale.
03 Application in production
1. Desizing: adding chelating dispersant in the desizing process can complex The metal ions that combine or react with the slurry improve the swellability of the sizing film, making it easy to remove the sizing film from the fabric. At the same time, they can also promote the reactivity of the desizing agent and the sizing agent, thereby greatly improving the desizing efficiency and avoiding the consequences of Defects such as uneven dyeing caused by uneven desizing.
2. Scouring: Adding chelating dispersant during the scouring process can prevent the formation of symbiotic organisms (pectin, oil wax, protein), cottonseed shells and other impurities on the cellulose. The solubility is very low. The high calcium carbonate salt and magnesium salt are beneficial to the removal of high carbonic acid content of hydrolyzate, thereby improving the wool effect, eliminating calcium spots, greatly improving the scouring effect, and improving the levelness of dyeing. If the scouring water is of a quality lower than 100×10-6 calcium and magnesium ions, a suitable chelating dispersant can be used.
Because the complexing capacity of the chelating dispersant can complex the metal ions in the water, and its dispersing effect can help disperse the reaction hydrolyzate so that it no longer sticks to the fiber, which can improve the whiteness of the fiber. Degree and gross effect. If the water quality is very poor, the hardness is very high or other heavy metal ions are present, chelating agents and chelating dispersants need to be used at the same time. Therefore, each printing and dyeing factory should select appropriate chelating agents and chelating dispersants according to the water quality of the factory, and adjust them according to the changes in water quality in each season to achieve twice the result with half the effort.
3. Bleaching: Adding chelating dispersant in the bleaching process can prevent the bleaching cloth from turning yellow, serve as a stabilizer for hydrogen peroxide bleaching, and promote washing after bleaching.
Prevent yellowing
The whiteness of bleaching cloth mainly depends on suitable bleaching conditions: the whiteness of bleach has previously been It is believed that sodium chlorite is the best, sodium hypochlorite has the worst whiteness, and hydrogen peroxide is somewhere in between. However, if sodium hypochlorite is used for high-temperature bleaching in an acidic medium, the whiteness can also reach the level of sodium chlorite. Experiments have shown that the presence of manganese ions is the main reason for the yellowing of bleaching cloth. When the concentration of manganese ions reaches 0.3×10-6, the bleaching cloth will turn yellow, and the degree of yellowing increases sharply as the ion concentration increases. . Therefore, using chelating agents that can effectively complex manganese ions is the key to overcoming the yellowing of bleached cloths.
Used as oxygen bleach stabilizer
At present, most of the domestically used organic phosphonate chelating agents are used as oxygen bleach stabilizers, while abroad, a variety of organic chelating agents are used as oxygen bleach stabilizers. Combination of phosphonate and chelating agent. It is worth mentioning that chelating agents have different stability constants and complexing abilities at different pH values. If used in high-alkali media, high-alkali-resistant chelating agents should be used as oxygen bleach stabilizers.
Promote post-bleaching washing
Impurities after scouring and bleaching are easily adsorbed on the fibers and are difficult to wash off, especially after cold rolling and stacking scouring and bleaching. Because of its high dosage of additives and small liquor ratio, impurities are more likely to be adsorbed on the fiber. It must be washed thoroughly several times to obtain a high wool effect. If a chelating dispersant is added to the washing liquid, the washing effect can be greatly improved and the fiber can be reduced. The number of washes can also improve the wool effect. Because of chelationThe addition of additives not only prevents calcium and magnesium ions from combining with impurities in the water to form insoluble precipitates, but also dissolves and disperses impurities due to hydrogen bonding, preventing back-sticking and achieving good results.
4. Reactive dye dyeing
Adding chelating dispersants in the reactive dye dyeing process is a better way to solve uneven dyeing, because hard water not only causes Significantly reduces the solubility of reactive dyes, affects dyeing performance, and can also cause dye aggregation to cause uneven dyeing. One calcium ion in hard water may combine with two sulfonic acid groups, causing the two dye molecules to bridge into one large molecule, which reduces the diffusion performance and causes uneven dyeing. At present, domestic reactive dye leveling agents are generally chelating dispersants or dispersants with phenol as the backbone.
5. Reactive dye printing
Adding chelating dispersant in the reactive dye printing process can not only improve the solubility of the dye, but also greatly improve the oxidation property , makes the color brighter, increases the coloring amount, and also helps with washing. Because the solubility of the dye directly affects the dyeing process, the oxidant anti-dye salt S added to the printing paste has a very small solubility. After the printing is dried, it becomes a solid on the surface of the fabric and exerts its oxidation ability during steaming. Very small. For example, in the presence of chelating dispersant, the solubility is improved, the oxidation is improved, and the color is obviously bright. At the same time, the insoluble calcium alginate salt generated by hard water in the color paste is avoided, causing washing difficulties.
6. Soaping
Adding chelating dispersant in the soaping process can significantly improve the soaping effect and the dye fastness. Bright color. Because after dyeing or printing, soaping is required to fully remove unfixed dyes, auxiliaries, chemicals and pastes in order to obtain the best dye fastness. Soaping agents are generally anionic and nonionic surfactants. Adding chelating dispersants to the soaping solution can complex calcium and magnesium ions in the water, preventing the calcium and magnesium ions from forming insoluble calcium soap or magnesium soap with the soaping agent. Improve the soaping effect, and at the same time use the gravity of hydrogen bonds to dissolve and disperse washed impurities to prevent re-contamination. </p
