Why should synthetic fiber be starched? What is the mechanism of sizing? What problems should we pay attention to?

Synthetic fiber filament is composed of multiple single fiber composite, such as 165dtex/48f, that is, by 48 single fibers combined into 165dtex composite filament, in the production process, the silk under the stress state to pass the winding, and twisting, whole and other processes, and in the weaving process, to experience the guide roller, heddle, reed repeated conflicts, Silk thread conflict to more than 10,000 times, and water jet loom weaving speed is generally 500~700r/min, high speed conflict monofilaments are very simple, not only affect the weaving power, severe will lead to weaving, and the quality of the product significantly decreased, to this end, to non-twist or low-twist synthetic filament sizing, After sizing, the warp yarn can withstand the conflicts in the processing process and smoothly weave, and ensure the quality of the product.

The sizing mechanism is: after sizing, the sizing material forms a layer of sizing film around the wire body to resist the conflict of various devices; The slurry penetrates between the single fibers and sticks to each single fiber, improving the bunching and strength of the complex filament, so as to ensure that the mission of the following process is smoothly completed. Because of the large hairiness, the sizing of staple fiber yarn requires the material to be mainly covered, and the sizing of synthetic fiber filament should be mainly soaked and supplemented by covering. Because the moisture regain of synthetic fibers is low, such as the standard moisture regain of polyester fibers is 0.4%, and nylon is 4%, they are hydrophobic fibers, that is, they are not water-friendly, so their sizing is not as simple as viscose silk, it must meet two conditions: That is, the viscosity of the slurry should be particularly good, and the slurry can stick the single fiber to each other between the penetration of the single fiber to ensure that the bunching property is met, and an outstanding slurry film is formed around the silk body to ensure its outstanding wear resistance. When pasting, it is necessary to ensure that there is a certain distance between the pasting wires to prevent the multiple wires after each pasting from sticking to each other and not weaving.

When sizing, the sizing material preparation and sizing process should be strictly controlled. At present, the domestic slurry is multi-acrylic, and the quality has generally passed, but a strict choice should be made, especially its viscosity and concentration should meet the requirements, and blind purchase should be avoided. In order to prevent the antistatic agent on the silk from being removed during the pulping process, an appropriate amount of antistatic agent should be added to the slurry. In order to maintain the softness of the silk thread, a certain amount of softening agent can be added, and an appropriate amount of impregnating agent and defoamer can also be added. In the pulping process, the prescribed pulping operation procedures should be strictly followed to make the slurry meet the production requirements.

In the production, it is necessary to effectively according to the sizing process requirements, to achieve "seven fixed", that is, fixed slurry viscosity, fixed slurry concentration, fixed slurry temperature, fixed slurry line speed, fixed slurry wire elongation, fixed slurry wire moisture recovery (fixed drying cylinder or drying chamber temperature), and fixed sizing rate. Viscosity is to show the degree of viscosity of the paste is good or bad, and the concentration is to show how much solid glue the paste contains, generally speaking: the two into filaments, but because of the different quality of the paste, even if it is the same concentration of the paste, its viscosity is not the same, so strictly speaking, the two must be controlled, and in daily production, often some people only control the viscosity, and some people only control the concentration. The higher the viscosity and concentration of the paste, the higher the strength and surface wear resistance of the filament, and the lower the elasticity, the simpler the filament is, and the more the pulp falls, so it should be controlled correctly. The sizing line speed is too fast, the production power is high, but the quality of the pulp silk is poor because the silk strip is not soaked and the coating is poor. In the sizing, because of the pull of the roller, the sizing roller and the drying cylinder, it generally shows an extended state, but the polyester, nylon and other synthetic fibers are heat shrinkable fibers, and the silk body will shrink through the pulp trough, the drying cylinder and the hot drying chamber, so the sizing rate of the synthetic fiber is generally the stretch and shrink offset, the elongation is about 0, the pulp extension is large, the silk body is elongated, the strength is inevitably affected, simple break, and so on. However, the pulp elongation is small, and the silk body is subjected to the machine tension during weaving, which will be stretched and destroy the slurry film, and the fiber is simple. The moisture return rate of the pulp is high, the silk body is simply sticky, the shrinkage of the silk strip is uneven, the lifting warp and the hardness are insufficient, and the crack axis will occur when the severity is severe, but the moisture return rate is low, the simple static electricity will occur, resulting in the fiber hair, and because the pulp film is hard and brittle, the serous fluid in the silk body has good penetration and good sizing quality. However, if the sizing rate is too high, the sizing will occur, and even cannot be woven, and the sizing rate is small, the silk fiber is simple hair. Therefore, it is necessary to find out the best pulp process from the production practice and implement it effectively, which is an important measure to ensure the pulp quality and product quality.