Decoction bleaching process

The purpose of the three steps of desizing, scouring, and bleaching contained in the fabric training and bleaching is different. The common point is that the impure-stained pulp, cellulose commensals and pigments on the grey fabric are removed. To achieve the purpose of improving fiber permeability. However, the division of desizing, scouring, and bleaching is not absolute. The pre-processes do the necessary preparations for the post-process while completing the main tasks. It can be said that the pre-process is the basis of the post-process, and the post-process is also often required. Make up for the deficiencies of the previous process. After the fabric is withdrawn, the slurry is conducive to the penetration of the scouring liquid. The residual slurry which has not been completely removed during the scouring process can also be further removed. The main purpose of the scouring is to remove cellulose commensals (including cotton seed hulls) and can The whiteness of fabrics is increased, but it is not possible to completely remove these symbionts after the scouring of pure cotton fabrics, and in particular, pigments and residual cotton shells must be subjected to hydrogen peroxide oxidation to remove them.This decoking process sequence is very important. Can not be arbitrarily reversed, this is a summary of people's practical experience over the years.

1. Three steps of desizing, scouring and bleaching

The three-step process of desizing, scouring and bleaching is still the most reliable process route. The most classic three-step bleaching process is as follows:

Dipping and desizing - steaming or stacking - washing - padding scouring fluid - steaming - washing - padding oxygen bleaching - steaming - washing - drying

The semi-finished products processed by the three-step process can achieve the effects of desizing, scouring and whiteness. At present, there are still printing and dyeing plants that use this process technology to ensure the quality of semi-finished products for heavy cotton fabrics and linen/cotton blended fabrics. The shortcomings are long process flow, high energy consumption, and therefore high costs.

2, boil, bleach two-step method

The general trend of process reforms handled in the past two decades is to shorten the technological process. Usually, the three-step process of desizing, scouring and bleaching is changed to a two-step process of decoction and bleaching. At present, this kind of process is a mainstream pretreatment process in printing and dyeing plants. The process is as follows:
Padding scouring fluid - steaming - washing - padding oxygen bleaching - steaming - washing - drying

This process actually combines the desizing and scouring processes into one. The two-step process can be adapted to the processing and bleaching of most fabrics. For example, medium-thickness pure cotton fabrics and polyester/cotton blended fabrics can be processed by this process. Since the process flow is short, only two processes are used. In the steam box and the two washing units, the consumption of steam and energy will certainly be lower than the traditional three-step process.

3, cold rolling reactor

The cold rolling practice bleaching process is actually a process of combining desizing, scouring, and bleaching into one step, and it can also be said to be a step-by-step process of practicing bleaching. The process is as follows:

Padding Cold Rolling Bleaching - Rolling Stacking - Washing / Steaming - Washing - Drying

Because the cold-rolling and stacking process can adapt to all kinds of fabrics for bleaching and processing. Compared with the conventional L-BOX (R-BOX) steamer steaming process, the cold-rolling process does not produce pile marks, and is more suitable for compact fabrics such as corduroy and line cards. The processing, in addition, the energy saving effect of cold rolling and stacking bleaching is quite remarkable. It is because of its many advantages that the cold-reactor process has been recognized by professionals in the printing and dyeing industry, and is now becoming more and more widely used, and the proportion of the bleaching process used has reached 50%.

The main disadvantage of the cold-rolling and stacking process is that it cannot be continuously produced, and the stacking time after dipping and padding is too long, which affects the production cycle. Process quality control will also be more difficult (not timely monitoring), because the fabric padding cold rolling after the stacking of stacking liquid 20 and then after a short steam, washing, drying out the cloth before seeing the boil The quality of the fabric. In addition, after the winding and unwinding, there will be a time difference between the front and back of the fabric on different stacking positions. This may lead to differences in the effects of different parts of the fabric before and after the fabric, which may occur after dyeing. Before and after color and other issues. Although this situation is rare in actual production, it still needs attention.

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