What is desizing?

Desizing purpose

During the weaving process, the warp yarns are subject to greater tension and friction, and are prone to breakage. In order to reduce warp breakage and improve weaving efficiency and grey fabric quality, warp yarns need to be sizing before weaving. The fibers in the yarns are cohesive and cohesive, and a firm sizing film is formed on the surface of the yarns, making the yarns compact and comfortable. Smooth, thereby increasing the breaking strength and abrasion resistance of the yarn.

The sizing rate is related to fiber quality, yarn count, density, and loom type, generally 4% to 8%. The thread fabric can be unsized or the general rate is below 1%, and the sizing rate of tight fabrics (such as poplin) can reach 8%~14%. In recent years, the warp sizing rate of high-speed looms has exceeded 14%.

The pulp used can be divided into natural pulp (starch, sodium alginate), modified pulp (soluble starch, carboxymethyl cellulose), synthetic pulp (polyvinyl alcohol PVA, polyacrylate PA).

The existence of the size on the original cloth is not conducive to the subsequent scouring and bleaching processing. Desizing process is the basis of fabric pre-treatment. This process can remove most of the pulp on the original fabric to facilitate the scouring and bleaching process, and can also remove some natural impurities.

Desizing methods for common fabrics

Cotton fabrics: The commonly used desizing methods mainly include enzyme desizing, alkali desizing, oxidizing desizing and acid desizing.

Viscose fabric: Desizing is the key point of viscose fabric pretreatment, viscose grey fabric is generally starch sizing, so BF7658 amylase is mostly used for desizing, and the desizing process is the same as that of cotton fabric.

Tencel: Tencel itself has no impurities, and starch or modified starch-based sizing is applied during the weaving process, which can be desizing by enzyme or alkaline-oxygen one-bath method.

Soy Protein Fiber Fabric: Desizing with Amylase

Polyester fabric (desizing scouring): Polyester itself does not contain impurities, but there is a small amount of oligomers (about 3% or less) in the process of synthesis, so it does not require strong pretreatment like cotton fibers. Generally, desizing and refining are carried out in one bath, the purpose is to remove the oil agent added during fiber weaving, the slurry added during weaving, coloring dyes, and the travel notes and dust stained during transportation and storage.

Polyester-cotton blended and interwoven fabrics: The sizing of polyester-cotton fabrics is mostly a mixed size of PVA, starch and CMC, and the desizing method generally adopts hot alkali desizing or oxidizing desizing.

Spandex-containing elastic woven fabrics: The physical and chemical properties of spandex should be considered in the pretreatment, and the damage to the spandex should be minimized to keep the elastic fabric relatively stable. The desizing method generally adopts enzymatic desizing (open width relaxation treatment).