my country's cotton ring spinning spindles have maintained sustained, rapid and stable development in recent years. According to official statistics, as of the end of 2014, domestic The number of s...
my country’s cotton ring spinning spindles have maintained sustained, rapid and stable development in recent years. According to official statistics, as of the end of 2014, domestic The number of spindles has exceeded 130 million. The overall cotton spinning equipment level has reached the internationally advanced level in the early 21st century. Spinning theory and process research are also ahead of the world. Excellent spinning technicians are concentrated in mainland China.
However, trade disputes caused by cotton yarn quality are increasing day by day. Economic losses caused by three-strand yarn, color difference, etc. have left industry insiders at a loss. What is the crux of the fluctuation in cotton yarn quality? The rapid expansion of total cotton yarn production , market competition intensifies, making cotton yarn It is always in a buyer’s market; spinning raw materials have become scarce resources and are in a seller’s market, where quality is difficult to guarantee. Market regulation has led to excessive price differences. The automation and high-speed production of weaving and dyeing enterprises have stricter requirements on the physical properties of yarns. .With the improvement of people’s living standards, the demand for services The quality requirements for decorative home textile products are also getting higher and higher. Cotton yarn is an intermediate product between textile fibers and fabrics. It must not only overcome the contradiction between quality and cost caused by fluctuations in raw materials, but also meet the quality requirements of the subsequent weaving and dyeing processes. Faced with such market demand, yarn production must adapt to it in order to be able to Occupying a place in the market. Due to the differences in fabric structure and processing equipment flow, the problems exposed by cotton yarn in the weaving and dyeing production process have different descriptions and focuses, but they can still be summarized as yarn stability, heterogeneity Fiber, color difference, unevenness, thick details, neps, woolEight aspects including feather and strength. Now we only analyze the key points of quality control of knitted and woven cotton yarn for apparel and home textiles, for your reference only.
Quality fluctuations will eventually affect the consistency of fabric quality and cause trouble to customer delivery. Quality indicators are the main reference standards for yarn stability. Spinners organize production according to the quality standards provided by users, and must maintain batch quality. The internal index is stable within the control range acceptable to the user. If there are signs of trend changes in the index, it is necessary to take timely technological measures or reasonably adjust the cotton ingredients. Some customers cannot provide quality requirements, so it is necessary to conduct sample proofing and trial weaving. Confirmed After confirmation, formulate corresponding internal control standards before mass production. Do not ship blindly to avoid quality deviations and economic losses. When dyeing with different batch numbers, you need to re-sample, which will cause trouble to the dyeing factory. Cotton spinning enterprises should try their best to maintain Obtain raw materials from the same source, consistent processing standards, and similar performance over a long period of time to reduce batch numbers, meet the needs of large orders, and strive for long-term happy cooperation with good service.
Foreign fiber has the characteristics of low content, high harm and uncertainty, and is difficult to remove during processing. It can form various yarn defects and color defects on the cloth surface, reducing production efficiency and product prices, which brings great harm to textile enterprises. Causes great losses. Judging from the current situation of my country’s cotton processing enterprises, foreign fiber control is still not ideal. At present, the best foreign fiber removal methods in cotton spinning mills are manual picking, installing foreign fiber removal machines in blowrooms, and winding configurations with foreign fiber detection Functional electronic cleaning The yarn machine is supplemented by careful and meticulous manual process control. For varieties with higher requirements for foreign fibers, the per capita picking volume has been reduced to more than 30 kilograms, and the employment has accounted for 10~20% of the total employment. Despite this, it is still difficult to manage To meet the requirements of high-end fabrics, fabric factories still have to organize personnel to repair foreign fibers on fabrics, and some yarn mills send dedicated service teams to users to repair fabrics, which often causes nap, contamination and yarn breakage defects.
The main reasons for color difference are differences in fiber color and color absorption rate caused by excessive differences in raw cotton maturity, and dyeing differences that occur when cotton is unevenly mixed. Therefore, cotton spinning mills must not only test and control the quality of cotton fibers. Average maturity, but also testing and control To control the immature fiber content, the immature fiber content with a maturity coefficient of less than 0.5 should be controlled within 14%. Generally, raw cotton with a lower maturity level can be used for bleaching blanks, while raw cotton with better maturity needs to be used for dyeing blanks. Since cotton Due to the shortage of resources, my country’s cotton sources are There are many countries in the world, and the performance of cotton in different regions of the country is also very different. The development of short-process blowroom and carding units in my country is not conducive to better mixing of cotton, and the mixing effect of the roll blowroom process is more difficult to achieve uniformity. In the raw materials When selecting products, products with concentrated production areas and comparable performance should be used as much as possible. Cotton with relatively large performance differences can be pre-mixed and combined to achieve uniform mixing. Enterprises with conditions can also try single-mark spinning. Spinners must deliver long-term multiple batches to the same customer. Indicate the batch number and the reminder that they cannot be mixed; some yarn millsWhen using one variety, there is no strict batch number limit. The production date is used as the batch number of the yarn. At this time, the long-term range of cotton yarn mixing must be indicated to avoid quality accidents due to customer inattention.
Even evenness is the primary indicator that determines the grade of cotton yarn. Fabrics made from cotton yarn with even evenness have a smooth appearance, a delicate feel, good dyeability (even and bright colors), and can produce better fabrics. Surface appearance effect. Especially those decorative light fabrics have extremely high requirements on the evenness of cotton yarn. Generally, evenness The CV value has reached the level of 25% of the 2001 USTER Gazette, which can meet the quality requirements of high-end fabrics. High-quality yarn spun from low-end raw materials is only reflected in the improvement of certain indicators, but cannot truly improve the yarn grade, because The main characteristics of yarn, such as coloring, strength and elongation, depend to a large extent on fiber properties. Therefore, according to the weaving Characteristics of physical yarns, rational selection of raw materials, and making economical and applicable yarns are important research topics for yarn mills. Overemphasis on evenness and the use of critical processes can easily lead to an increase in differences between spindles and high requirements for equipment. For example The evenness is good, but the machine failure is caused by abnormal factors such as roller torsional vibration caused by excessive drafting force, apron tapping under the spun yarn, etc. Mechanical waves seriously affect the evenness value. Although the average value is improved, the evenness dispersion increases, causing differences in the cloth surface. Regular evenness caused by the failure of the top roller and front roller of the spinning yarn has a negative impact on the cloth surface. The harm is great, and spinning machines should use non-mechanical rollers to produce high-grade cotton yarn.
Knitted fabrics require higher details and woven fabricsMaterials have higher requirements for thick places, just because the structure and yarn density of fabrics are different, and the opportunities for thick and fine details to appear are different. Thick and fine details are the main factors that affect the weaving production efficiency, and the requirements in the production process are equally important. . Long, thick, long details are average It occurs in the front spinning. When the roving weight is the same and yarns with different counts are spun, the lengths of the thick and long details are quite different. At this time, if the cutting lengths of the long and long details in the winding process are set to the same , some of the low-count yarns are long, thick, and have long details that cannot reach the designed length. The cleaning length cannot be determined by the electronic yarn clearer, which reduces the yarn defect clearance rate, and customer complaints occur from time to time. The two batches of cotton yarn are at the same level of the Uster Gazette statistical value, and the user reactions are good and bad. One of them The reason is the difference in the number of small defects, some High-end customers have tightened the thickness index of yarn defects in conventional indicators (IPI value), and assessed small yarn defects other than level 9 harmful yarn defects. These are internal control standards set by customers based on the quality of the fabric. Another reason It’s the difference in raw material performance and production process.? The yarn mill should determine the yarn defect requirements of the fabric type based on the visibility and concealment of thick and detailed details on the fabric surface. At the same time, combined with the yarn defect classification of the 100,000-meter yarn defect classification chart, the number of yarn defects in the fabric should be controlled within ten This is reflected in the 10,000-meter yarn defect classification chart.
Neps are mostly caused by poorly processed and immature fibers, especially cotton fibers damaged by pests and diseases and stiff cotton fibers. Because of their small size, they are easily entangled and adhered to yarns and cloths. They are important in the entire textile printing and dyeing process. Defects that are difficult to remove. During printing and dyeing, cotton fibers are twisted together. In the singeing process, only the cloth surface wool is burned, and the cotton fiber clumps cannot be burned. When the cotton fiber clumps are attached to the cloth surface and printed and dyed in water, their adhesion is stronger. During printing and dyeing, it blocks the color from penetrating the cloth surface. Printing and dyeing cloth drying After drying, the cellulose crystalline area in the fiber has changed under the action of chemical dyes after the cotton neps have been printed and dyed. The adhesion is reduced and falls off, and countless irregular undyed white-like small defects appear on the cloth surface, which degrades the batch quality of the printed and dyed cloth. The harm is serious and the loss is huge. As long as the quality of the raw materials is stable, the nep index is generally Relatively stable. The lightweight and slow process currently used in our country is mainly Reflected in the carding process, it is an effective measure to reduce neps; the recently launched “heavy weight, high-efficiency process” makes full use of the cohesion between fibers, so that the entangled filaments can be better stretched and can Better neps control
The harmfulness of yarn hairiness is mainly manifested in three aspects: First, the uneven distribution of hairiness on the yarn can cause weft stripe defects in woven fabrics. Yarns with more hairiness absorb color faster than yarns with less hairiness. , the yarns are of different shades after dyeing, and stripe defects are formed on the fabric when woven, resulting in downgrading of the fabric and the weaving process. Hairiness will form new neps during fabrication; secondly, when producing high-density fabrics, especially when weaving on air-jet looms, hairiness will entangle adjacent warp yarns with each other and make weft insertion difficult; thirdly, the hairiness on the yarn The hairiness falls off due to friction in various downstream processes, forming flying flowers, polluting the environment, and endangering human health. The yarn itselfThere is a lot of hairiness, which will definitely affect the pilling properties of the fabric. Especially polyester-cotton blended yarn and cotton/wool blended varieties, the requirements for pilling properties are more stringent. More than 75% of cotton yarn hairiness is shorter than 1mm and longer than 3mm. Less, less than 1% of the total hairiness. Long hairiness is mainly caused by the friction of the winding machine (especially the automatic winding machine) parts on the yarn. Self-locking safety Installing a hairiness reduction device can have obvious effects and enhance the competitive advantage of yarn. The measurement method of yarn hairiness includes the H value measured by Uster’s hairiness meter. For the same variety, the hairiness H is comparable, and the H value is relatively stable; Another method of measuring hairiness is the hairiness count method. In terms of guiding production and subsequent yarn use, the number of hairiness has more practical significance.
Modern weaving technology, whether weaving or knitting, tends to the three highs (high quality, high speed, and high efficiency). Compared with traditional equipment, the speed is doubled, and the cotton yarn is required to be strong enough to reduce breakage and ensure Production efficiency. The speed of air-jet looms is relatively fast, the process speed is generally above 500r/min, and the weft insertion rate is generally above 1300m/min. In order to obtain high-speed performance The shedding is clear, using a large tension and small shedding process. The warp yarns bear greater tension. During the shedding and beating-up processes, when the tension peak of the warp yarns overlaps with the weak warp strength ring, the probability of breakage is high. Air-jet weft insertion It is a negative free-end weft insertion. The peak value of the weft insertion tension is much larger than that of other looms. When encountering a strong weak loop, the probability of weft breakage is also very high. What really affects the efficiency and quality is the strong weak loop. Special Especially for high-count and high-density fabrics, the yarn count is fine and the strength is low. The focus is to control the two indicators of uneven strength and low strength. The low strength should reach more than 80% of the average strength. The spinning process affects the uneven strength and low strength of the yarn. Indicators have a greater impact. It is necessary to strengthen process research. It is one-sided to focus solely on backward spindles. Conclusion: Spinners and weaving and dyeing factories maintain regular communication and jointly formulate the yarn specifications for fabrics. quality standards, and constantly revise and improve them to make them more suitable for the characteristics of fabrics. Correctly choose raw materials with good processing quality and consistency to maintain relative stability of cotton distribution and production; strengthen process research, promote technological progress, and give full play to existing The efficiency of the equipment; producing and processing economic yarn that satisfies users to obtain the best economic benefits is an inevitable choice for cotton spinning enterprises to develop healthily.
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