Hydrogen peroxide is a good oxidizing bleaching agent. It is used for bleaching yarns with hydrogen peroxide. It has good whiteness, pure color and no impurities in the equipment. Therefore, hydrogen peroxide is widely used. So what is the principle of hydrogen peroxide bleaching? What should I pay attention to during hydrogen peroxide bleaching?
The principle of hydrogen peroxide bleaching
Hydrogen peroxide has a good oxidizing effect, especially under purified conditions, hydrogen peroxide can make the color system of purified purified natural pigments be oxidized and destroyed during the bleaching process.
In a strong alkaline medium, the decomposition reaction of peroxygen water is: H2O2 decomposes to generate hydrogen peroxide ions (H2O2). Peroxygen water is the main component of bleaching fabrics. Peroxygen water reacts with the fiber pigment molecules to oxidize. Desizing, color reduction and bleaching. Therefore, the H2O2 bleaching process depends on the rate of decomposition of H2O2.
Analysis of hydrogen peroxide bleaching conditions.
(1) PH value of the bleaching liquid: H2O2 will not bleach under strong alkaline conditions, and if the PH value of the bleaching liquid is too high, it will damage the fiber, so the pH value of the bleaching liquid is controlled between 10-11 Ideal.
(2) Temperature: The bleaching speed of hydrogen peroxide at room temperature is relatively slow, and long-term bleaching is required; in order to increase the bleaching speed, high temperature bleaching can be carried out at a general temperature of 90~100℃.
(3) Bleaching time: the higher the temperature, the shorter the bleaching time; the lower the temperature, the longer the bleaching time.
(4) Concentration of bleaching solution: The concentration of hydrogen peroxide is 2~6g/L (the usage rate of hydrogen peroxide is 100%).
Hydrogen peroxide bleaching
Hot floatation, stacked cold floatation, cold floatation of the cylinder, floatation of the cylinder at high temperature and high pressure, double tank floatation at high temperature and high pressure, high temperature cooking floatation, high temperature cooking floatation.
Precautions for hydrogen peroxide bleaching
(1) Choose proper hydrogen peroxide concentration to achieve ideal whiteness and impurity removal rate, and to minimize fiber damage.
(2) When hydrogen peroxide bleaching water glass is used as a stabilizer, the pH value of the hydrogen peroxide bleaching solution should be between 10.5-11.
(3) Heavy metal ions such as copper and iron can catalyze the decomposition of hydrogen peroxide. Therefore, the fabric cannot be treated with heavy metal-containing materials and synthetic equipment before rinsing, and special care should be taken to avoid the formation of local brittle holes or small holes on the fabric under the effect of catalysis .
(4) In the determination of hydrogen peroxide concentration, cooking temperature and time are the main factors affecting the bleaching effect. The higher the temperature, the better the bleaching effect; the temperature is very low,
The distillation time can be extended appropriately (normally it can be distilled for 1 hour).
(5) Hydrogen peroxide can be bathed with cotton whitening agent, and sometimes it can be bathed with fluorescent whitening agent during rebleaching, so that bleaching and whitening can be performed simultaneously.
(6) Use hydrogen peroxide method to prepare bleaching liquid, hard water (hardness 50~130m/L) is suitable; if the water is soft, add 0.1g/L magnesium sulfate to make it into water glass.
(7) Water glass is used as a stabilizer for hydrogen peroxide, and it must be fully washed after distillation (the first flat washing tank can add 2~3g/L of soda ash and detergent each to prevent silicate from remaining on the fabric and affecting the luster of the fabric. And gross effect).
(8) After mercerizing the cotton fabric, the concentration of hydrogen peroxide should be appropriately reduced. At the same time, it should be noted that the mercerized fabric should not have too much alkali. When the pH value exceeds 11, it will cause the brittleness of the cotton fabric.