Pre Processing Mercerizing Knowledge [Textile Knowledge]

Mercerization: under the condition of a certain tension, the textile can obtain the silk luster by using the role of strong caustic soda and maintaining the required size. This process is called mercerizing.

One

Mercerizing purpose

Improving fabric surface gloss and feel

Because of the expansion of fibers, the arrangement of fibers is more orderly, and the reflection of light is more regular, thus enhancing glossiness.

Improve the dye yield.

After mercerizing, the crystal area of the fiber decreased and the amorphous zone increased. Therefore, the dye was easier to enter the fiber. The color rendering rate increased by 20% compared with the non mercerized cotton fabric, and the brightness increased, while the covering power of the dead surface increased.

Improving dimensional stability

Mercerizing has a stereotyped effect, which eliminates rope wrinkles, and better meets the quality requirements of dyeing and printing on semi-finished products. The most important thing is that after the mercerization, the stability of the fabric has been greatly improved, so the shrinkage of the fabric has been greatly reduced.

Two

Principle of mercerization

The fibers undergo irreversible swelling. Na+ is highly hydrated, and a large amount of water is brought into the fiber, resulting in severe swelling of the fibers.

In the mercerizing process, natural cellulose, also called cellulose I, can produce alkali cellulose with the action of caustic soda. Alkali cellulose is very unstable. It is hydrolyzed by water and hydrated (hydrated) cellulose, then dehydrated and dried to obtain mercerized cellulose, i. e. cellulose II.

　　 The main factors affecting mercerizing effect are the concentration of alkali liquor, temperature, the time of action and the tension exerted on the fabric.

Three

Mercerizing method

Dry cloth mercerizing

Traditionally, the mercerization of cotton fabrics is usually treated with concentrated caustic soda at room temperature under dry conditions. The dry cloth mercerizing process is easy to control and the quality is stable. However, due to the requirement of drying, the energy consumption is large and the production cycle is longer.

Wet mercerizing

Wet mercerizing can save the drying process before mercerizing and save equipment and energy. Moreover, in the wet mercerizing process, due to the expansion of fiber, the alkali absorption is uniform and the product quality is better. However, wet mercerizing has a high requirement for rolling water before mercerizing, low rolling rate (50%~60%), and uniform rolling water, otherwise it will affect mercerizing effect. When the wet cloth is mercerized, the lye is easy to dilute, so the concentration of the alkali solution is high, and the consistency of the alkali liquor in the alkali bath is uniform.

Hot alkali mercerizing

The conventional mercerizing process is room temperature mercerizing (18~20 degrees). The caustic solution is thicker and less permeable. It is easy to cause "surface mercerization", and the thick and tightly woven fabric needs uniform and thorough effect. Heat and alkali permeability is good, but puffing is poor. Therefore, the mercerizing process with first hot alkali and later cold alkali is adopted. The early infiltration of hot alkali is conducive to the continuous infiltration of cold lye, so that the fabric has more alkali content, resulting in uniform and effective expansion.

Main advantages

(1) mercerization is uniform and effective.

(2) gloss, strength and dimensional stability are superior to regular mercerization.

(3) it can be combined with the scouring process to shorten the process route, reduce the cost and increase the economic efficiency (before heating, the steaming soda fabric is steamed 10 ', normal pressure).

Four

Mercerizing equipment

Commonly used mercerizing machines include cloth mercerizing, bending roll mercerizing and straight roller mercerizing machine. The cloth mercerizing machine has the best effect and the most extensive application.

1 cloth mercerizing machine

It is composed of pre rolling base tank, cloth roller, post rolling alkali bath, cloth expanding device, alkali removing box, horizontal washing machine and so on.

　　 Advantages: tension is easy to control, fabric shrinkage and alkali removal are better than its mercerizing machine. Missing: cloth parts are prone to mechanical defects, and equipment occupies a large area.

2 straight roller cloth mercerizing machine

It is composed of cloth feeding device, alkali rolling tank, heavy pressure roller, alkali removing tank, alkali removing box and horizontal washing tank.

　　 Features: double deck, high yield, uniform mercerization, no break edge, short fuselage, simple transmission and easy operation, but the expansion effect is poor (the drawback shrinkage rate is difficult to reach the national standard), which is the main drawback. Some factories in China use cloth and straight roller to solve this problem.