Cotton yarn

With the improvement of people's living standard, the quality requirements of clothing and home textile products are higher and higher. Cotton yarn is the intermediate between textile fiber and fabric. It is necessary to overcome the contradiction between the quality and cost caused by the fluctuation of raw materials, and meet the quality requirements of the later process of weaving and dyeing. In the face of such market demand, the production of yarn must adapt to it, so as to occupy a place in the market. 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.

Analysis of cotton yarn quality control points

1. stability

The fluctuation of quality will eventually affect the consistency of fabric quality and cause trouble for customers' delivery. Quality index is the main reference standard for yarn stability. The mill shall organize production according to the quality standard provided by the user, and keep the index within the batch stable within the control range acceptable to the user. In case of any sign of trend change in the index, it is necessary to timely take technical measures or reasonably adjust the cotton composition. Some customers can't put forward quality requirements, so it's necessary to sample and test weave. After confirmation, formulate corresponding internal control standards before mass production. Do not blindly deliver goods, so as to avoid quality deviation and economic loss. When different batches are dyed, it's necessary to proofread again, causing trouble to the dyeing factory. Cotton spinning enterprises should try to keep the same source, processing standard and performance connection in a long time. Near raw materials, to reduce batch number, to meet the needs of large single customers, with good service to strive for long-term pleasant cooperation.

2. Heterosexual fiber

Heterosexual fiber has the characteristics of less content, great harm and uncertainty, which is difficult to be removed in processing. It can form various yarn defects and color defects on the cloth surface, reduce the production efficiency and product price, and cause great losses to the textile enterprises. From the current situation of China's cotton processing enterprises, the control of different fibers is not ideal. At present, the best way to remove different fibers in cotton mills is to manually pick, clear and install different fibers. The cleaning machine and winding drum are equipped with electronic yarn cleaner with different fiber detection function, which is supported by careful manual process control. For varieties with higher requirements for different fiber, the per capita picking volume has been reduced to more than 30 kg, and the labor force has accounted for 10-20% of the total labor force. As far as management is concerned, it is still difficult to meet the requirements of high-grade fabrics. Cloth factories still need to organize personnel to repair different fiber on fabrics, and some yarn factories send special personnel to users to repair cloth. Service team, often cause galling, pollution and broken yarn defects.

3. color difference

The main reason of color difference is the difference of fiber color and color absorption rate caused by the difference of maturity of raw cotton, and the difference of dyeing when the cotton is mixed unevenly. Therefore, cotton mill should not only test and control the average maturity of cotton fiber, but also test and control the content of immature fiber. The content of immature fiber whose maturity coefficient is less than 0.5 should be controlled within 14%. Because of the shortage of cotton resources, China's cotton comes from many countries in the world, and the performance of cotton in different regions in China is also very different. However, the development of short process blowing carding Union in China is not conducive to the better blending of cotton, and the blending effect of the winding and blowing process is more difficult to achieve uniformity, so we should choose the raw materials. As far as possible, cotton with concentrated producing area and similar performance can be used. Cotton with large performance difference can be premixed and added to achieve even blending. Enterprises with conditions can also try single mark spinning. When delivering goods to the same customer in multiple batches for a long time, the yarn mill should indicate the batch number and the prompt that can not be mixed. Some mills do not have strict batch number limit when producing the same variety, and use the production date. As the batch number of yarn, the longest time range of cotton yarn mixing should be indicated to avoid quality accident due to customer's carelessness.

4. Uneven strip

The evenness of sliver is the primary index to determine the grade of cotton yarn. The fabric with even sliver can get a good fabric appearance effect because of its smooth appearance, delicate hand feel, good dyeability (even and bright colors). Especially for those decorative light and thin fabrics, the evenness of sliver is required to be very high. The CV value of sliver can reach the level of 25% in 2001 ust bulletin, that is to say, it can meet the demand of high grade. The requirement of fabric quality. Spinning high-quality yarn with low-grade raw materials is only reflected in the improvement of some indexes, but can't really improve the grade of yarn, because the main characteristics of yarn such as coloring, strength and elongation depend on the fiber performance to a large extent. Therefore, it is an important research topic for the yarn factory to reasonably select raw materials and make economical and applicable yarn according to the yarn characteristics of fabric. Excessive emphasis on sliver drying is adopted. For example, the mechanical wave caused by the abnormal factors such as roller torsional vibration and spinning bottom loop beating caused by the excessive traction, which seriously affects the evenness value. Although the average value is improved, the evenness dispersion increases, resulting in cloth surface difference. The gauge caused by the failure of spinning front roller and front roller, etc. Due to the regularity of sliver drying, it is harmful to cloth surface.