Factors such as concentration, temperature, time, pH value, etc. are the main factors for chemical reactions. In the process of hydrogen peroxide bleaching, it should be made clarify the interrelationship of these factors in order to develop a reasonable process.
(1)Concentration
The reasonable concentration specified by hydrogen peroxide bleaching should not only achieve a certain whiteness and remove cottonseed shell, but also minimize 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 control at 3-5g/L has reached a certain whiteness requirement, no matter how high the concentration, the whiteness does not increase much, on the contrary, it is easy to damage the fiber.
Therefore, the concentration of the steaming process is generally 3-5g L, and the thin fabric should be appropriately lower. The specific determination should be based on the use of equipment and bleaching method, the thickness of the fabric, the condition of the desizing and cooking condition, and the bath ratio are determined. In order to minimize damage to the fibers, the concentration should be low, to obtain higher whiteness, measures should be taken in cooking.
(2)Temperature
Temperature has a direct relationship to the rate of decomposition of hydrogen peroxide. Under certain concentration and time conditions, the decomposition consumption of hydrogen peroxide on the fabric increases with the increase of temperature, so the bleaching effect of the fabric is increased with the increase of the decomposition rate of hydrogen peroxide on the fabric. When the temperature reaches 90-100 °C, hydrogen peroxide can decompose 90%, and the whiteness is also 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 temperature dependent. If the cold bleaching method is used, it is necessary to stack at room temperature for about 10h, and the high-temperature steam bleaching time can be greatly shortened. From the perspective of measuring the consumption rate of hydrogen peroxide, the consumption rate has reached 70% in 15min and 90% in 45-60min, and tends to balance. It can be seen that the steaming time of 45-60min is enough.
(4) Alkaline agent
The pH value of the bleaching solution in conventional bleaching is 10.5~11, and the water glass cannot meet the requirements, so it is necessary to add alkali to adjust the PH value.
The most commonly used alkali agent is caustic soda, the dosage is 1-2g/L. It is an activator, can promote the decomposition of hydrogen peroxide, so that hydrogen peroxide generates hydrogen peroxide ions with bleaching effect, in the case of PH value of 10.5~11, hydrogen peroxide decomposition at medium speed to achieve the purpose of bleaching. However, in the short-process art of retreating and boiling and bleaching, the amount of caustic soda is higher, and caustic soda not only regulates the PH value, but also has the functions of depulting and training. This makes the bleaching bath very unstable, accelerates the decomposition of hydrogen peroxide, not only wastes hydrogen peroxide, but also may cause fiber degradation and brittle fabric. In order to control the decomposition rate of hydrogen peroxide, it has been mentioned that a suitable stabilizer should be added to make the hydrogen peroxide decompose according to the process requirements, and achieve a balance between decomposition and stability, which is the "controlled hydrogen peroxide bleaching process" with the help of stabilizers.
The use of this art can not only achieve better fabric whiteness and impurity removal effect, but also do not cause greater damage to the fiber.
