Desizing is for starched woven fabric, in order to facilitate weaving, most of the woven fabric needs to be woven after starching.

When it comes to desizing, it is necessary to mention the three major sizes in the textile sizing industry: starch and derivatives, polyvinyl alcohol (PVA), and acrylic size. PVA has been phased out due to environmental issues, and most of the starch used now is used in combination with acrylic slurry.

Four commonly used desizing methods: hot water desizing, alkali desizing, enzyme desizing, oxidation desizing. Now the most used are enzyme desizing and alkali desizing, and enzyme desizing (amylase) is mainly for starch slurry. The quality of the desizing effect is generally evaluated by the desizing grade. Among the three sizes, acrylic slurry is easier to remove, while starch slurry and PVA have simple and rapid test methods (such as iodine/potassium iodide method).

Insufficient desizing will affect the color rate of the dye when dyeing, or cause the feel of the fabric to deteriorate.

Sizing basics

Sizing is a very important process, sizing machine production one minute, the loom runs a shift, it can be seen that the quality of sizing is good or bad, the weaving process to achieve high quality, high yield, low consumption has a close relationship. Therefore, in the sizing process, the selection of sizing material, the performance of sizing and sizing machinery, technological conditions and operation technology are all important, and a little neglect will cause a disaster in the whole plant.

Before weaving, the warp must be starched with slurry to increase the wear resistance of the warp and the strength of the single yarn, so that the weaving can proceed smoothly, this process is called sizing.

For unstarched warp yarn, the head and tail of many fibers are exposed to the surface of the yarn, forming hair, and the binding force between the fibers is not strong enough. In the weaving process, due to thousands of repeated stretching (caused by opening, beating, winding), friction (warp and warp, warp and weft, warp and reed, warp stop and back beam and other components) and bending mechanical action, warp will become loose, hair, resulting in broken, affecting loom production efficiency and fabric quality. Therefore, the warp needs to be starched.

The sizing task is to make the slurry adsorb on the surface of the yarn and form a smooth and tough film after drying, so that the hair is attached and the surface is smooth, so as to improve the wear resistance of the yarn. In addition, some slurry is soaked into the interior of the yarn, so that the fibers adhere to each other, increase the holding force between the fibers, and improve the breaking strength of the warp. Practice has proved that the warp strength after sizing is 10% ~ 30% higher than that before sizing.

Proper increase of warp strength can reduce the break of warp on the loom, but too much increase will make the yarn brittle, hard and easy to break, and the process performance will be reduced. Appropriately increasing the strength of the warp (strengthening), maximizing the elasticity of the warp (maintaining elongation), reducing the hair of the warp and reducing the coefficient of friction (reducing friction) are the basic requirements of sizing. Wear-resisting and feathering are particularly important for the new shuttleless loom.

The performance change of warp yarn after sizing, under certain conditions, depends on the proportion of slurry to yarn "coating" and "soaking" during sizing. The ideal sizing should be part of the slurry soaked into the inside of the yarn, filling the space between the fibers, as a solid foundation of the slurry film; Some of the slurry forms a smooth, tough film on the surface of the yarn. If the penetration amount is too little, the slurry film is not resistant to friction and easy to fall off, but if the penetration amount is too much, the elastic loss of the yarn is too large, and it is easy to produce a broken end.

Sizing is a very important process. It is one of the most important factors to reduce warp breakage during weaving and improve product quality. If the sizing work is slightly negligent, it will seriously affect the weaving production; On the contrary, if the sizing is properly handled, the poor quality warp can also be improved to a certain extent. Weaving workers have a saying: "sizing a minute, cloth machine a class." It shows the importance of the sizing process in the weaving process, and the workers call the sizing process "tiger mouth".

Usually single yarn must be starched, depending on the type of warp, density and yarn, cotton single yarn starch sizing rate is generally 7% ~ 17%, mixed sizing rate is 4% ~ 12%, chemical sizing rate is 2.5% ~ 9%. Strand sizing and otherwise depends on the specific situation. Special strands, such as 14texX2, generally do not need to be starched or only dehydrated and shafted. For example, corduroy fabric with large weft density (669 /10cm) (due to repeated mechanical action) and thin special strands with low strength, such as 9.5texX2, the sizing rate is generally mastered at about 2%.

The sizing process is divided into two parts: mixing the sizing (making the sizing, boiling the sizing) and sizing (making the sizing stick to the warp and dry, and then winding the warp to the pulp shaft).