Understanding Mao Yu Problem And Its Causes, Controlling Cotton Yarn Mao Yu

With the continuous improvement of the quality requirements of textiles at home and abroad, customers have put forward higher requirements for cotton yarn hairiness. The uniformity and stability of cotton yarn hairiness in cotton mill have great influence on the production efficiency and fabric quality of the back loom, and even the quality of finished products of cotton printed and dyed fabrics. Yarn hairiness involves the whole process of raw cotton, spinning, weaving and dyeing finished products. The author discusses the causes of cotton yarn hairiness.

Mao Yu problem

Mao Yu of cotton yarn is divided into three types according to the shape of fiber stretched yarn: end Mao Yu, circle Mao Yu and floating Mao Yu; according to the direction of yarn, it can be divided into: head to Mao Yu, tail to Mao Yu, two-way Mao Yu, circle to Mao Yu and random direction. In general, the hairiness of 0.5 mm to 1 mm length accounts for 60% of the total, and the hairiness of 1 mm to 3 mm is about 35% of the total, and the hairiness of the length above 3 mm accounts for 5% of the gross hairiness.

Cotton yarn is usually formed by twisting and condensing a short fiber. It is necessary to have hairiness to stretch out the yarn. The key point is that the hairiness above 3 mm will seriously affect the production of the rear track and affect the appearance, handle and performance of the yarn and its final product. For example, the yarn is easily entangled, which causes the yarn to not pass smoothly through the stop piece, the heald eye and the reed teeth, resulting in unclear opening or broken ends. When it is used on shuttleless looms, the looms are mostly small sheds, large tension and high speed working conditions. If the yarn Mao Yu problem is serious, it will cause warp blocking breakage, and the weaving efficiency will be reduced. It can be said that controlling cotton yarn hairiness is the key to weaving production. The problem of cotton yarn hairiness will have adverse effects on the quality of cotton fabrics, but it will also fall off in the downstream processes due to friction and form flying flowers, which will cause environmental pollution problems and endanger human health.

Cause of hairiness

1 fiber properties

Cotton yarn hairiness is related to maturity, length, short staple rate and fineness of cotton fiber. Mao Yu is mostly exposed to the ends of fibers in yarn. The more the number of fibers in the yarn, the more the head and tail. Under the same conditions, the more Mao Yu number, the shorter the fiber length, the more likely to produce Mao Yu. Many scholars have shown that the torsion stiffness and flexural rigidity of cotton fibers are the most closely related mechanical properties of yarn in terms of many physical and mechanical properties. The torsion stiffness and flexural rigidity of cotton fibers are large, and the possibility of fiber ends extending out of the yarn is large.

Through tests, it is found that in the 18.22 tex cotton yarn, 2/3 of the yarn hairiness is characterized by the extension of the root end of the cotton fiber, and only about 1/6 of the cotton yarn is slightly extended. The analysis shows that the root end ratio of cotton fiber is slightly thicker and more rigid, and the root end ratio is easier to protrude the yarn body and become Mao Yu, so the end of the cotton yarn Mao Yu is mostly the root end of the cotton fiber.

It is found in production that under certain conditions, the maturity of raw cotton is high, and Mao Yu is less when spinning fine staple cotton and long staple cotton. The analysis shows that raw cotton has high maturity and good strength of cotton fiber, with relatively uniform thickness and longer length. The number of fibers in the yarn per unit length is reduced, the fiber head is reduced, and the slender fibers are susceptible to twisting torque and frictional force between fibers, so that the length of the fiber heads that may extend out of the yarn body is shortened. Therefore, the yarn is smooth and has fewer hairiness.

The index of parallelism and evenness of cotton fiber is not only related to the properties of raw cotton, but also depends on the processing technology of each spinning process. Therefore, the influence of parallelism and evenness on cotton yarn hairiness is discussed in the following spinning process.

2 pre spinning process

1) carding process. The higher the lint content is, the easier it is to produce Mao Yu. The test shows that when the general cotton's short linen removal rate is below 5%, the yarn hairiness is more, and the yarn hairiness will be reduced when the short staple removal rate is above 5%. Generally speaking, combed yarn has 30% to 40% hairiness than that of combed yarn. Through the combing process, a large number of short staple fibers of cotton were removed, and the parallelism of fiber extension was increased, so the yarn Mao Yuhui decreased.

2) coarse process. The hairiness of two yarns is less than that of a single yarn. The improvement of parallelism of fiber in two cotton strips is beneficial to reduce hairiness. It is also advantageous to stretch the fibers by drawing the back area drafting with big head and two small ones. The use of the concentric front zone drafting technology is beneficial to reduce the fiber hook in the two drawing.

The surface of roving yarn is not bright and clean, which can lead to increased hairiness in spinning process. Therefore, increasing yarn twist coefficient in roving process is beneficial to reducing cotton hairiness. In addition, the sliver passage on roving frame will cause the yarn hairiness to increase.

3 spinning process

1) spinning is the key process of spinning, and its spinning equipment has great influence on yarn hairiness. It is as follows: 1. The diameter of the steel collar is not precise, the roundness and smoothness are not good, or there are ripples, burrs, uneven and unpolished, uneven steel bars or moving around, and the vertical movement is not vertical. The increase of yarn tension and friction will result in the increase of the yarn Mao Yu. Second, the improper matching of the ring travellers and the steel collar will result in a significant increase in the yarn Mao Yu. Thirdly, the friction of the sliver and the friction of the yarn will cause Mao Yu to increase. Main performance

2) the yarn collector can close the yarn edge fibers and make the yarn structure compact and smooth, thereby reducing hairiness. But if the openings of the collectors are too small, the cotton sliver will become rough and increase the yarn hairiness.

3) the excessive encircling arc of the yarn to the guide hook will affect the twisting transmission, and the twist of the spinning section will decrease and Mao Yuhui will increase.

4) spinning spindle speed and workshop temperature and humidity conditions are also important factors affecting hairiness. The yarn hairiness increased proportions with fine spindle speed. The yarn hairiness will increase sharply when the relative humidity of the spinning workshop is less than 50%.

5) the twisting part of spinning frame is in bad condition and equipment condition; the yarn is scraped, which will damage the yarn structure and make Mao Yu increase. During the twisting process, foreign flying flowers and short linen are attached to the yarn body and some yarns will also form hairiness.

4 winding process

Winding is the last process of spinning. Winding processing can not only change the form and quality of cotton yarn, but also remove coarse and weak yarn defects. However, the poor winding process will lead to an increase in the final hairiness of cotton yarn. It has been tested that the hairiness of cotton yarn can be increased by 50% to 150% after the winding process, and some even up to 250%. This is because during the winding process, the yarn contacts with the winder parts, collide and rub, so that the fiber ends that have been wrapped in the yarn are exposed to the yarn body, forming a new Mao Yu or pulling the short hairs on the raw cotton yarn to grow into Mao Yu.

1) grooved drum. At present, there are two types of grooves used in cotton mills in China: Bakelite grooves and metal troughs. The traditional bakelite grooves have poor wear resistance. The surface of the bakelite grooves is easy to grooved. The friction of the grooves on the yarn causes the cotton yarn Mao Yu to increase.

2) winding channel. The winding channel includes tension frame S plate, porcelain column, yarn clearer detection head, guide yarn tube sleeve, Zhang Liwan and probe. Once burrs, grooves and breakage are found on these components, the cotton yarn will be subject to greater friction and static electricity during the movement process, resulting in increased yarn hairiness. Normally, the tension bowl is balanced and rotated. If the inner hole of the tension bowl is worn or polished, the yarn will remain in a stationary state for a long time. The friction of the cotton yarn will increase and the yarn hairiness will increase.

3) self stopping device. When the yarn is broken, the yarn will immediately jump out of the high speed rotating drum. Otherwise, the yarn will not jump immediately, it can not escape from the slot, and the friction of the same position with the high speed running tank will seriously damage the yarn and increase the Mao Yu. If the self stopping box is short of oil, the speed of the yarn is too fast before the start of the yarn, the impact force is too strong, the friction force is increased, the cotton yarn is damaged, and the number of hairiness is increased.

4) coordination of pagoda tube, barrel and groove. If the angle of the barrel angle deviate, that is, the angle of the pagoda tube and the slot tube is not correct, the two are not closely connected, and the big head of the pagoda tube or the small head and the groove tube have larger gaps, and the yarn will be bouncing in motion. When the diameter of the pagoda tube is large or the pressure of the ingot tube fails, the coordination between the two tubes is not tight. During the winding process, the longitudinal slip between the tube and the grooved tube will occur. The beating and slipping of yarn will lead to local friction and increase of yarn hairiness.

5) process parameters. (1) the higher the vehicle speed, the greater the friction between yarn and groove tube, the greater the yarn damage and the increase of hairiness; 2. The tension sheet weight, the tension of the winding yarn, the friction force of the components of the yarn and the winding channel, the yarn hairiness becoming longer and increasing; third, the yarn clearance is too small, the yarn is damaged by the friction with the cleaning plate, and the hairiness increases. If the volume is too large, the weight of the bobbin is large, the friction between the cheese and the grooved tube is large, and the yarn damage will increase, and the yarn hairiness will increase.