Cotton yarn

Although there are different descriptions and emphases on the problems of cotton yarn exposed in the process of weaving and dyeing due to the difference of weaving structure and processing equipment flow, they can be summarized into eight aspects: yarn stability, heterosexual fiber, color difference, unevenness of sliver, slub, nep, hairiness and strength. This paper analyzes the quality control points of knitted and woven cotton yarn for clothing and home textile only

following LQ-0207

5. Rough and detail

Knitted fabrics have higher requirements for details and woven fabrics have higher requirements for coarseness, only because of different organizational structure and yarn density of fabrics, and different opportunities for coarseness and details to appear. Coarseness and details are the main factors affecting weaving production efficiency, and the requirements in the production process are the same and important. Long coarseness and long details are generally produced in the front spinning, when the roving quantity is the same and the number of yarns is different. There is a big difference in the length of long coarse and long detail. At this time, if the defect length of long coarse and long detail in winding process is set the same, part of the long coarse and long detail in the low count yarn cannot be detected by the electronic yarn cleaner because the length cannot reach the set removal length, which reduces the removal rate of yarn defect, and there are frequent complaints from customers. Two batches of cotton yarn with the same statistical value in Uster bulletin, users There are good and bad reactions. One of the reasons is the difference in the number of small defects. Some high-end customers have tightened the roughness index of the conventional index (IPI value) yarn defects, and examined the small yarn defects other than the grade 9 harmful yarn defects. These are the internal control standards formulated by customers according to the cloth quality. The other reason is the difference in the performance of raw materials and production process. The yarn factory should be based on the coarse and details in the cloth. At the same time, combined with the defect classification of 100000 meter defect classification chart, the quantity of fabric defect control is reflected in 100000 meter defect classification chart.

6. Neps

Neps are mostly caused by poor processing and immature fibers, especially disease and insect pests cotton and stiff petal cotton fiber. Because of its small size, it is easy to be held and adhered by yarn and cloth, which is difficult to remove in the whole textile printing and dyeing process. In the printing and dyeing process, due to the tangled cotton fiber, only the cloth surface wool is burnt in the singeing process, and the cotton fiber pellet cannot be burnt. When the cotton fiber pellet is attached to the cloth surface and dyed into the water, it is difficult to remove the defects. Its adhesion is stronger, and it blocks the color soaked cloth surface when printing and dyeing. After drying, the cellulose crystal area in the fiber changes under the action of chemical dyes after dyeing and dyeing, and its adhesion reduces and falls off, and there are numerous irregular unstained original white defects on the cloth surface, which makes the batch property of the printed and dyed cloth reduce. The damage is serious and the loss is huge. As long as the quality of raw materials is stable In general, the NEP index is relatively stable. At present, the light weight and slow speed process adopted in China is mainly reflected in the carding process, which is the most effective measure to reduce neps. The recently launched "heavy weight and high efficiency process" makes full use of the cohesive force between fibers, so that the entangled yarn can be better drawn and the neps can be better controlled.

7. Hairiness

The harmfulness of yarn hairiness is mainly manifested in three aspects: first, the uneven distribution of hairiness on the yarn can cause the weft stripe defect of woven fabric, the yarn with more hairiness has faster color absorption than that with less hairiness, the yarn will be different in depth after dyeing, the yarn with more hairiness will form stripe defect when weaving, and the hairiness will form new neps when weaving; second, in the production of high-density fabrics, especially When weaving on air-jet loom, the hairiness will make the adjacent warp yarns entangled with each other and make the weft insertion difficult. Thirdly, the hairiness on the yarn will fall off due to friction in the downstream processes, forming flying flowers, polluting the environment and endangering human health. The hairiness of the yarn itself will inevitably affect the pilling and pilling properties of the fabric. In particular, the polyester cotton blended yarn and the cotton / wool blended yarn have more strict requirements on the pilling and pilling properties. More than 75% of the hairiness of cotton yarn is shorter than 1mm, but less than 3mm, which is less than 1% of the total hairiness. The hairiness is mainly caused by the friction of the winder (especially the automatic winder) on the yarn. The installation of hairiness reduction device by self winding can have obvious effect and enhance the competitive advantage of the yarn. The measurement method of the hairiness of the yarn is the H value measured by the hairiness meter of Uster. For the same variety, the hairiness h has comparability. And H value is relatively stable; another method to measure hairiness is hairiness root count method, which has more practical significance in guiding production and subsequent yarn use.

8. Strength

Modern weaving technology, whether weaving or knitting, tends to be three high (high quality, high speed and high efficiency). Compared with traditional equipment, the speed is doubled, which requires cotton yarn to have enough strength to reduce the breakage and ensure the production efficiency. Air jet loom has a fast speed, the process speed is generally over 500r / min, and the filling rate is generally over 1300m / min. in order to obtain a clear opening at high speed, large tension and small opening are adopted. In the process of opening and beating up, when the peak tension of the warp overlaps with the weak ring of the warp strength, the probability of breaking ends is high. Air jet weft insertion is a negative free end weft insertion, and the peak tension of the weft insertion is much larger than that of other looms. When the strong weak ring is encountered, the probability of breaking the weft is also high. The real impact on efficiency and quality is the strong weak ring, especially the high count one. High density fabrics have fine count and low strength. It is important to control the strength unevenness and minimum strength. The minimum strength should be over 80% of the average strength. The spinning process has a great influence on the yarn strength unevenness and minimum strength. Therefore, it is one-sided to strengthen the process research and focus on the backward spindles. Conclusion: the yarn factory and the dyeing factory always keep in touch and work out a joint plan. The quality standard of the yarn used for fabric is revised and perfected continuously to make it more suitable for the characteristics of fabric. The cotton spinning enterprises are moving towards a sound development, which is to choose and purchase the materials with good processing quality and consistency, keep the relative stability of cotton blending and production, strengthen the technological research, promote the technological progress and give full play to the efficiency of the existing equipment, produce and process the most economical yarn satisfying the users to obtain the best economic benefit. Inevitable choice.