Sizing refers to the process of applying sizes to warp yarns to improve their weavability. Sizing faults directly affect sizing quality, and sizing spot is one of the major faults affecting fabric surface quality, which can cause broken ends, cobweb, warp shrinkage faults of board head, increase broken ends of sizing or cloth machine and decrease the quality of cotton cloth.
Size spots are formed when the sizes are glued to the yarn. It is shown in the form of cross strip sizing, block sizing, irregular punctate sizing, and flake sizing without destroying fabric structure.
1. Transverse sizing spot: The main reason is that when sizing is on the upper and lower axles, the warp yarn speed is very slow, the stop time is too long, and the size condenses in the sizing area. After extrusion by the sizing roller, the sizing fluid with larger solid content is put into the yarn layer, which makes the moisture absorption rate of the yarn increase suddenly, and the transverse sizing spot is easy to occur at the transverse part of the yarn. With the increase of warp density, the concentration of the sizing liquid increases, and the transverse sizing spot becomes more obvious, which will also cause sizing spot defects in serious cases. What’s more, when the transverse sizing amount increases and then dries in the drying room, there will be obvious sizing on the yarn surface, which will make the yarn feel rough and even destroy the fabric structure. transverse sizing spot is easy to cause twisting and breaking.
2.Lumpy sizing spot: The slurries are stained on the yarn and pressed to form dispersed and lumpy sizing spots. There are two forms of lumpy sizing spots, one is irregular lumps between 3 cm and 4 cm, the other is lumps of different sizes with diameters between 1 cm and 10 cm.
The main reason is that the pulp pot after the machine is not thorough. Before the second start-up, the slurries adheres to the fish scale tube around the sizing pot to form a slurry block. The second is that the sizing pot slurry circulation is not smooth during the start-up process, and the sizing pot slurry circulation is not smooth around or local. This uneven slurry block or sizing skin, after entering the normal slurries, can not be fully mixed with fresh slurries, and then adheres to the yarn after squeezing by the sizing roller, which forms local sizing seriously exceeding the standard, seriously affects the stranding after drying, and destroys the structure of yarn and cloth on the spindle. The vapor pressure is unstable, the temperature of the size is too high. The boiling size splashes on the yarn after pressing, and the size patches on the yarn form sizing spots.
3. Irregular punctate sizing spot: mainly in the process of driving, the sizing pot boiled too much, the sizing liquid boiled, splashed onto the yarn surface to form a punctate uneven sizing spot.
4. Flake size spot without destroying fabric structure: Flake size spot is due to the uneven viscosity of local size, and the uneven sizing after extrusion by pressing roll. The main cause of uneven sizing is uneven exhaust steam of fish scale tube or excessive supply of size, and uneven temperature of size in the sizing pot, resulting in uneven viscosity.