About pre-treatment
Poor whiteness includes impure whiteness, uneven whiteness and wool effect not reaching 8-10cm/30min or more. This is related to the quality of knitted fabric gray fabric, such as low-grade cotton content. , it is often difficult to achieve good whiteness and wool effect. Of course, the most critical issues are process formulation and additive selection. In process formulation:
① The amount of H202 and NaOH must be sufficient
H202: After pre-treatment, it not only plays the role of bleaching pigments, but also has the function of removing impurities (including removing cottonseed hulls). The amount of H202 is insufficient (including decomposing too quickly), and the whiteness It is impossible to guarantee that NaOH not only provides the alkalinity (PH) required for H202 bleaching, but also cooperates with the scouring agent to achieve the greatest impurity removal effect. If the amount of NaOH is insufficient, impurity removal will be poor, and the hair effect will not meet the requirements first. Of course, the whitening effect will be poor. The degree cannot meet the requirements, so the amount of H202 and NaOH can be said to be the primary factor in ensuring whiteness and wool effect;
② Select high-quality scouring agents:
The comprehensive effects of scouring agents such as cleaning, emulsification, dispersion, and penetration must be excellent to ensure the removal of impurities and ensure whiteness and wool effect. , but the quality of scouring agents on the market is uneven. We must choose products with excellent comprehensive effects instead of just measuring penetration and solid content. Penetration is only one aspect to consider;
③ Oxygen bleach stabilizer and chelating dispersant:
These two additives are mainly used to improve water quality. It adsorbs and complexes metal ions such as Fe3+ in water to prevent the rapid and ineffective decomposition of H202 caused by metal ion catalysis. If H202 decomposes quickly and ineffectively, its whiteness and wool effect will not meet the requirements, and it will cause brittleness and even holes in the fabric. , so in order to achieve whiteness and wool effect, excellent oxygen bleaching stabilizers must be selected, and the decomposition rate of H202 must be considered during the selection. The addition of chelating dispersant not only chelates iron, etc., but also chelates and disperses various impurities in the water, so that these impurities will no longer contaminate the fabric again and cause dark whiteness and graying. Therefore, chelating dispersant not only It is necessary to consider its chelating force for metal ions and its dispersion force;
④ Process conditions:
It takes a certain amount of time and temperature for the additives to react with impurities. If the conditions are not met, the pigments and impurities will not be completely removed, and the whiteness and hair effect will not be achieved:
⑤ Washing:
Washing after scouring and bleaching is very important. It is necessary to clean and remove the impurities to ensure whiteness. and gross effect. </p
