The pre-treatment process of printing and dyeing is the fundamental process in the entire production process of printing and dyeing, which plays an important role in the product quality of the subsequent processes (dyeing, printing, and finishing).
Since its establishment in the 1950s, China's pre-treatment process has been extensively studied for energy conservation and pollution reduction. From the traditional three-step process of annealing, boiling, and bleaching to the promotion and application of short process pre-treatment processes (which were reasonably reduced from three-step processes to two-step or one-step processes) in the early 1990s, especially since the 21st century, the use of environmentally friendly and energy-saving additives has been proposed Composite additives (three in one, four in one, five in one), low-temperature pre-treatment additives, and printing and dyeing pre-treatment additives are emerging in an endless variety.
The rational development and application of printing and dyeing pre-treatment additives is the fundamental direction of our research. For example, traditional scouring process aids and short process pre-treatment aids cannot be interchangeable: the latter not only wastes but also causes fabric damage when using the former, while the former not only fails to meet the requirements but also causes a large number of fabric defects when using the latter. For example, the selection of chelating dispersants must be based on one's own process, equipment, and water source conditions. Not all chelating dispersants are suitable for the application in one's own factory. For example, when using enzymes for desizing, it is important to know what enzyme is used and what size is on the fabric in order to apply the right medicine to the situation and achieve the desired results. Therefore, the reasonable development and selection of printing and dyeing pre-treatment additives (desizing agents, scouring agents, bleaching agents) is the key to product quality. The selection of pre-treatment additives is described below:
1. Desizing agent
Desizing agents are agents that remove the size from the fabric. The mechanisms of desizing agents include swelling of the size, decomposition of the size, and oxidation of the size. Depending on the size on the fabric, different desizing agents can be selected, including enzyme desizing agents, alkali desizing agents, oxygen desizing agents, and surfactant desizing agents.
1.1 Enzyme desizing agent
Enzymes are proteins produced by living organisms, but unlike general proteins, they can strongly catalyze chemical reactions of many substances and have high specificity. One enzyme can only catalyze one substance, and enzyme desizing agents have been used for decades. Amylase is a desizing agent for cotton fabrics, and there are two types of amylase: medium temperature (70 ℃) and high temperature (90 ℃), If the temperature is too high, the specific three-dimensional morphology of enzyme molecules will gradually disappear, leading to a decrease in activity. In recent years, due to the advancement of gene manipulation technology, most industrial enzymes have been produced using DNA recombinant bacteria, allowing the enzymes to be used at high temperatures. During steaming and desizing, the starch slurry can be hydrolyzed in just a few tens of seconds.
(1) The pH value of the amylase desizing bath is very important, and it is generally controlled at pH 5-7 to function. Below or above this value, the enzyme activity is greatly reduced.
(2) Be cautious when using surfactants in desizing baths: Non ionic wetting agents can be compatible with amylase, while anionic surfactants can reduce enzyme activity.
(3) Before enzyme desizing, the fabric is treated with 30 ℃ warm water to make the starch swell and improve the desizing effect. Hot water is used in the desizing bath to make the starch "gel" and accelerate the desizing reaction.
(4) Adding calcium to the desizing solution can improve α－ The stability of amylase.
(5) Redox bleach is a harmful substance of enzymes and should not be used in the same bath.
Zhejiang Chaoyu New Material Technology Co., Ltd
Suzhou Chaoyu Textile Chemical Co., Ltd
