Analysis | Technical points of spun yarn in warp knitting products!

The labor cost and raw material cost of the textile industry continue to increase, and the traditional knitting industry faces the challenge of transformation and upgrading. The “Twelfth Five-Year” Science and Technology Progress Outline of the Textile Industry lists the development of staple fiber warp knitting products as one of the three key contents. It is hoped that the warp knitting products will be upgraded through raw material innovation. During the “13th Five-Year Plan” period, the staple fiber yarn warp knitting Product development techniques will also continue to be studied intensively as a focus.

1 development status

Since the 1970s, companies such as DuPont have begun to study spun yarns and staple fibers with staple fibers for warp-knitted underwear and sweatshirts; Japan has developed HKS 3-M for E32. The warp knitting machine uses crystal cotton plant fiber as warp-knitted underwear; later, Karl Mayer of Germany introduced the KS4FBZ double-sided cotton terry warp knitting machine and RD6DPLM double needle bed for the spun yarn. Velvet raschel warp knitting machine. The domestic start was a little late. In the early days of the founding of the People's Republic of China, Shanghai Zhonghua No. 1 Cotton Knitting Knitting Factory used the American Aveco crochet warp knitting machine to produce warp-knitted mesh underwear fabrics, and the brushed fabrics produced by Shanghai Camel Factory with color yarns. The Z303 warp knitting machine appeared in cotton woven vest fabrics. In recent years, with the innovation and progress of technology, KARL MAYER and Changzhou Eight Textile Machinery respectively launched the ZM-SP type of spun yarn direct warping machine and GE211 warping machine to promote the spun yarn in outer clothes and underwear fabrics. Applications in decorative and industrial products, but low-cost, high-speed production has not yet been achieved.

2 technical difficulties

Warp knit fabric is an ideal product for the development trend of knitted garments. Because of its high production speed, it requires high yarn strength, elongation and smoothness uniformity. How to keep the staple fiber in the weaving process. Extensibility and breaking strength, after being subjected to high-speed running friction of warp knitting machine, the strip is evenly dried and the surface is smooth. It is the technical research focus of short fiber used in warp knitting products, and needs to be improved from raw materials, warping and weaving. The spun yarn is quickly woven on the warp knitting machine and the product quality is improved.

2.1 Raw material selection

Spinning technology uses a new type of compact spinning, which allows the fibers to be arranged neatly in the yarn, with moderate twist, smooth surface of the yarn, not easy to fluff, good breaking strength and elasticity; on the other hand, special pretreatment technology, such as joining Pretreatment auxiliaries enhance breaking strength and softness, or reduce neps and hairiness through processes such as mercerizing, waxing and singeing.

Compact yarn

2.2 warping techniques

Warp knitting with staple fiber yarns should be distinguished from chemical fiber filament warping: warping workshop temperature and humidity (RH) are controlled at 25 °C and 70%, respectively, to reduce flying flowers; reduce yarn path and avoid the difference in bending between yarns Keep the yarn tension uniform; the spacing of the yarns is suitable, the number is not too much, avoiding the excessively close yarn spacing and excessive number of yarns to increase the surface hairiness; the tension of the creel is "0", and the angle of the active winding is small. Avoid the sudden increase of the tension of the spun yarn; the warping speed is appropriate, and the excessive warping speed affects the warp tension uniformity and increases the hairiness caused by the warp yarn friction.

2.3 Weaving technology

2.3.1 Uniform tension weaving technology

The spun yarn is subjected to tension fluctuations due to the action of the yarn guiding rod, the yarn dividing crepe, the tension rod, the yarn guiding comb and the knitting needle in the warp knitting process. Among them, the tension bar has a significant influence on the tension of the equalized warp yarn in any looping stage. It is necessary to adjust the tension bar spring piece according to the number of the spun yarns of each bar to optimize the tension compensation, so that the tension bar maintains the relaxed and balanced frequency. In addition, it is necessary to ease the adjustment of the speed of the machine to avoid the violent fluctuation of the warp tension caused by the sudden change of the speed.

Warp yarn road map

2.3.2 Low friction yarn guiding technology

The surface of the spun yarn has a small friction coefficient with the yarn guiding rod and the tension rod in the yarn path, but the complicated relative friction is generated when the yarn is divided by the yarn and the yarn guiding needle, and the hairiness in the direction of the yarn is easy to be scraped. After the yarn is divided, a smooth yarn guiding rod is added to reduce the upper and lower friction between the warp yarn and the yarn dividing yarn. The hairiness of the spun yarn after the yarn is combed is more significant, and the long hair feathers are easily entangled to produce yarn breakage and flying flowers, which can be adjusted by sending The amount and the improvement of the needle pinhole structure reduce the relative friction coefficient of the yarn and the needle hole of the yarn guide, but the knitting requirement can still be satisfied for the compact spinning.

2.3.3 online clear fly technology

When the spun yarn is unwound from the pan head, the surface hairiness is easily scraped off and gathered when the yarn is twisted and guided, which affects the normal yarn feeding or adhesion to the warp yarn; on the other hand, the yarn surface during the weaving process The hairiness is easy to attach to the needle hole and the needle groove of the yarn guide. If the machine is cleaned, it will affect the normal weaving, which is time-consuming and labor-intensive. Therefore, according to the characteristics of the warp knitting of the spun yarn, the suction device for the self-stopping of the photoelectric yarn breakage is respectively arranged in the vicinity of the yarn dividing yam and the needle groove, and the hairiness of the spun yarn is cleaned in real time.