Factors such as concentration, temperature, time, and pH are the main conditions for chemical reactions. In the process of hydrogen peroxide bleaching, the interrelationship of these factors should be clarified in order to formulate a reasonable process.
1. Concentration
The reasonable concentration required for hydrogen peroxide bleaching should be based on the principle that it can achieve a certain degree of whiteness and remove cotton seed hulls while minimizing fiber damage. Practice has proved that the relationship between fabric whiteness and hydrogen peroxide concentration is not directly proportional. When the steaming process is used, the concentration of 3-5g/L can reach a certain degree of whiteness, and the higher the concentration, the whiteness will not increase much, but it is easy to damage the fiber. Therefore, the steaming process concentration is generally 3-5g/L, and the thin fabric should be appropriately lower. The specific determination should be based on the equipment used, bleaching method, fabric thickness, desizing and scouring conditions, and liquor ratio. In order to reduce the damage to the fiber as much as possible, the concentration should be low. To obtain higher whiteness, measures should be taken in scouring.
2. Temperature
Temperature has a direct relationship with the decomposition rate of hydrogen peroxide. Under certain concentration and time conditions, the decomposition consumption of hydrogen peroxide on the fabric increases with the increase of temperature. Therefore, the bleaching effect of the fabric increases with the increase of the decomposition rate of hydrogen peroxide on the fabric. When the temperature reaches 90-100°C, hydrogen peroxide can be decomposed by 90%, and the whiteness is the best; but when the temperature is 60%, the decomposition rate is only about 50%.
3. Time
The determination of hydrogen peroxide bleaching time is related to temperature. If the cold bleaching method is used, it needs to be stacked at room temperature for about 10 hours, but the high temperature steam bleaching time can be greatly shortened. From the measurement of hydrogen peroxide consumption rate, steaming for 15 minutes has reached 70%, and steaming for 45-60 minutes, the consumption rate has reached 90%, and it is in equilibrium. It can be seen that the steaming time of 45-60 minutes is sufficient.
4. Alkali agent
In conventional bleaching, the pH value of the bleaching solution is 10.5~11, and the addition of water glass cannot meet the requirements. Therefore, an alkali agent must be added to adjust the pH value. The most commonly used alkali agent is caustic soda, and the dosage is 1-2g/L. It is an activator, which can promote the decomposition of hydrogen peroxide, so that hydrogen peroxide can generate bleaching hydrogen peroxide ions. When the pH is 10.5~11, the hydrogen peroxide decomposes at a moderate speed to achieve the purpose of bleaching. But in the short process of desizing, scouring and bleaching and scouring and bleaching, the amount of caustic soda is higher. Caustic soda not only adjusts the PH value, but also has the functions of desizing and scouring. This makes the bleach bath very unstable and accelerates the decomposition of hydrogen peroxide, which not only wastes hydrogen peroxide, but may also cause fiber degradation and make the fabric brittle. In order to control the decomposition rate of hydrogen peroxide, it has been mentioned that suitable stabilizers should be added to make the hydrogen peroxide decompose according to the process requirements and reach a balance between decomposition and stability. This is the "controlled hydrogen peroxide bleaching process with the help of stabilizers" "The use of this process can not only achieve better fabric whiteness and impurity removal, but also will not cause greater damage to the fiber
