What are the commonly used desizing methods

There are many commonly used desizing methods, including enzyme, alkali, acid and oxidant desizing, etc. The appropriate desizing method can be selected according to the variety of the original fabric, the composition of the slurry, the desizing requirements and the factory equipment. After desizing, it must be washed with hot water in time, because impurities such as starch decomposition products will re-condensate on the fabric, which will seriously hinder the subsequent processing.

Enzymatic desizing

Enzyme is a biological catalyst, a protein secreted by animals, plants or microorganisms (bacteria, molds), and has a specific catalytic effect on the decomposition of certain substances.

The catalytic efficiency of the enzyme is high, the action conditions are moderate, and severe conditions such as high temperature and high pressure are not required, and the action is fast. However, enzymes have specificity, that is, an enzyme can only catalyze one or a class of chemical substances.

Desizing principle:

Enzymes are a class of proteins with special catalytic ability, which have specific catalytic effects on the decomposition of certain substances.

Features:

The process is simple and the operation is convenient.

The starch slurry is sufficiently removed without damaging the fibers.

No desizing effect on chemical slurry;

It cannot remove the oil in the slurry and the natural impurities on the original cloth.

Alkali desizing

This method is used for PVA-based mixed pulp (containing starch) and PA pulp.

Desizing principle:

Under the action of hot caustic soda, starch and chemical pulp will be strongly expanded, and the adhesion with fibers will become loose, from gel state to sol state, and the solubility of chemical pulp in hot alkali increases. Wash off, and at the same time, hot caustic soda solution can remove some natural impurities, especially suitable for cotton cloth with more cottonseed husks. Most of the alkali used for desizing is scouring or mercerizing waste alkali, which is low in cost and does not damage fibers, so this process is widely used in printing and dyeing plants. The desizing rate of alkali desizing is about 50~70%, and the remaining pulp can only be further removed during scouring.

Acid desizing

It is mostly used for cotton desizing, and is rarely used alone. It needs to be used in combination with other desizing methods. Such as alkaline-acid desizing or enzyme-acid desizing.

Desizing principle:

Under proper conditions, dilute sulfuric acid has no decomposition effect on PVA and PA slurries, but can hydrolyze starch gradually, convert it into a product with higher water solubility, and finally be washed away by water.

Oxidizer Desizing

Oxidant desizing is mainly used for desizing of PVA and its mixed pulp.

Desizing principle:

Strong oxidants such as perhydrochloric acid, hydrogen peroxide, sodium bromite, etc. It has the effect of breaking and explaining the macromolecules of the slurry for various sizes, so that it can be easily washed off the fabric.