Why is the textile yarn sizing?

What are the requirements for textile sizing?

In weaving, the warp yarn has to withstand a variety of forces and undergo complex deformation. From the basic movement of the loom:

(1) During the shedding movement, the warp yarn is bent into a fold line at the heddle eyelet from the substantially straight heald line, and the elongation is proportional to the square of the height of the shed. At the same time, due to the asymmetrical length of the front and back of the shed, the warp yarn slips in the heddle eyelet, causing friction. When the upper and lower warp yarns rise and fall alternately in the shedding movement, severe friction occurs between each other.

(2) During the weft insertion movement, the shuttle of the shuttle loom relies on the shed and rubs between them, especially when entering and exiting the shed, the edge warp yarns are squeezed to a large extent, causing bending, elongation and friction. , The weft guide component of the shuttleless loom also has considerable friction on the warp yarn.

(3) During the beating-up movement, the warp at the front of the shed is rubbed by the reciprocating reed teeth. Due to the shrinkage, the squeezing friction between the reed teeth and the edge warp yarns is more severe. In the beating-up area of the cloth mouth, the back and forth movement caused by each beating-up will increase the friction between the warp yarn and the heddle eyelet.

(4) In the warp let-off and take-up movement, the warp on the weaving shaft always has a certain braking tension when it is sent out. Most of the existing let-off mechanisms are tension-regulated let-off mechanisms, and the amount of warp let-off is controlled by the sensor feedback of the warp tension. Therefore, the warp yarns with weak knots begin to break when they pass through the back beam. The take-up movement also affects the warp tension and forms a warp elastic-plastic deformation system with the let-off, beat-up and shedding.

It can be seen that the force and deformation of the warp yarn during the weaving process are mainly formed by tension (required not to cause breakage), elongation (recoverable from cyclic deformation), and friction (not to cause fuzzing, pilling, or wear).

At the same time, it is worth paying attention to the problem of hairiness. In the warp shedding, the protruding hairiness will entangle with each other, making the shedding unclear, resulting in difficult to eliminate defects such as skipping, skipping, and hanging warp. In the weft insertion of an air jet loom, the weft yarn is blocked due to the unclear opening, which is the main factor affecting the efficiency. Therefore, reducing hairiness is an important indicator.

In view of the above situation, in order to improve the weaving performance of the warp yarn, the effective method adopted in the weaving preparation project is sizing. That is, a slurry with adhesive material as the main body is applied to the warp yarn, which acts on the surface of the warp yarn to a certain depth, and after drying, it forms a sizing structure that integrates the size and the yarn.

The improvement of warp performance after sizing should be strengthening, maintaining elongation, abrasion resistance, and conforming to hairiness. Through the sizing, the filaments adhere to each other, which has a clustering property, prevents the filaments from fluffing or breakage, and can inhibit the elasticity of the filaments, which is convenient for operation. Spun warp stretch yarns and strong twisted yarns also need to be sized to suppress shrinkage before they can be produced smoothly. The ultimate goal of sizing is: good sizing axis, fewer weaving defects, low number of ends, high weaving efficiency, and improved weaving of warp yarns.

The specific requirements for textile sizing

(1) Increase yarn breaking strength. It is necessary to increase the strength appropriately, but if the increase of the sizing strength is pursued too much, it will inevitably make the yarn hard and brittle, lose its elasticity, and easily break. The reinforcement rate of pure cotton yarn is generally controlled at 25%-40%, polyester/cotton yarn 10%-25%, pure polyester yarn 10%-20%, polyester/viscose and pure viscose yarn>25%.

(2) Maintain yarn elongation at break. The elongation of raw cotton yarn is generally 7%. After sizing, it should be kept at 4%-5% to facilitate weaving. Therefore, the elongation reduction rate is ≤30%, polyester/cotton, polyester/viscose yarn ≤25%, and pure viscose yarn ≤ 35%.

(3) Improve the wear resistance rate. As the current wear resistance test has not been standardized, the wear resistance rate of various slurry formulations is also very different.

(4) Hairiness reduction rate. Using YGl7lB yarn hairiness tester and BT-2 online hairiness tester to compare yarn hairiness before and after sizing, the advanced index of hairiness reduction rate is more than 75%.

(5) Good shaft rate of weaving shaft. It is required that the sizing yarn has no broken ends, long ends, sticking, twisted ends, light sizing, fuzzing and pilling, and no edge pulling and other defects in the weaving, and the advanced level of shaft rate is more than 60%.

(6) The number of broken warps on the loom. Shuttle looms should be less than 1/(set•h), and shuttleless looms should have less than 10-15 warps for 100,000 wefts.

As a gray fabric for printing, dyeing and finishing, in addition to the requirements for weaving, it is also required to be easy to desizing, and the desizing waste liquid does not pollute the environment. Must be considered in the selection and ratio of slurry.

As a finished fabric, it is required to give the fabric a unique style and feel, and it must be appropriately adjusted in terms of the type of size, oil and sizing rate.