Composite yarn 1—untwisted yarn
1. Introduction
As we all know, the pursuit of “softness” in products such as quilts and knitted underwear is always a major theme. In order to achieve “softness”, one of the requirements for yarns is to use as small a twist as possible. However, Too small a twist of ordinary yarn will cause difficulties in spinning and increase breakage in weaving. Therefore, in the past, achieving “softness” could only be achieved by balancing spinning and weaving. Select a compromise value for the yarn twist requirements. The emergence of untwisted yarn provides another brand-new solution to achieve “softness” for quilt, knitting and other industries. The outstanding feature of untwisted yarn products is its super “softness” and water absorption. 1.1 Definition of untwisted yarn Yarn (twistless processing): A spinning method that uses an adhesive to bond the fibers in the fiber strips to each other into yarn.
After the roving is drawn by the drafting device, the sliver is sent to the twisting drum, and the thin layer of adhesive from the tank box on the return drum is contacted. The fiber sliver is pressed by several rotating small presses. The rollers and drums are transported forward together, and one of the small pressure rollers also acts as Axial reciprocating motion twists the fiber strips into a circular cross-section, allowing each fiber to evenly contact the adhesive. The circular fiber strips are dried by the heater, and the fibers stick to each other to form yarn. The spinning speed is comparable The conventional spinning method is 2 to 4 times larger, and the yarn produced can be used for weaving. An adhesive is used to bond the fibers in the yarn sliver to each other to form a yarn. There is no twist in the yarn sliver, and the strength is obtained by the mutual adhesion between the fibers. It is a new spinning method.
1.2 Development Overview
Untwisted yarn is a new type of yarn that appeared in the late 1970s. It is characterized by the fact that the fibers constituting the yarn are arranged in parallel, and the cross-section of the yarn In ribbon form.
In the early 1980s, Texas Tech University Textile Rescarch Center (TRC) Luadfdsock, Tex introduced twistless yarn fabric to the market. Its fluffy, soft and soft luster effect was welcomed by the market.
And it has begun to be used in knitted fabrics. Because of its excellent characteristics that are different from traditional yarns, it is receiving more and more attention.
1.3 Uses of untwisted yarn
Home textile products (pajamas, bed blankets, quilts, towels, bath towels, shower caps, high-end uniforms, baby suits, pillowcases, etc.) are characterized by softness , bulky, strong sweat-absorbent, wearing cotton, warm, light, transparent and thin.
2． The yarn forming principle and method of untwisted yarn 2.1 The yarn forming principle
It is wrapped with soluble PVA (polyvinyl alcohol) filament or mulberry silk in untwisted yarn.The wrapped yarn is formed on the surface of the cotton bundle, which has good wear resistance and withstands a certain tension when weaving towels. Then after weaving into the finished product, PVA or mulberry silk is dissolved in water to make the terry loops untwisted and fluffy. The state is in the fabric.
2.2 Yarn-forming method
2.2.1 The adhesive method uses adhesive to tightly bind the fibers together through pseudo-adhesion. Fiber adhesion mixing can be done directly or during drawing. The yarn formed after the fibers are adhered and mixed on the draw frame can be directly supplied to the twistless worsted spinning machine after drying. It eliminates the four processes of traditional spinning process, namely two drawing processes, roving process and spinning process. This twistless yarn-forming method can increase yarn output 10 times compared to ring spinning. It overcomes the obstacles of high output in ring spinning and rotor spinning. Yarn can be spun directly from slivers, and some can even be spun directly from combs. Net-spun untwisted yarn, the output is large, up to 300~400 meters /min. In addition, the distance between the draft rollers can be adjusted to adapt to the spinning of fibers of different lengths, so that different types of yarns such as cotton yarn and wool yarn can be spun on the same machine. 2.2.2 Soft wrapping method The method is to use parallel spinning method to spin the first yarn. The primary yarn is composed of soluble filament fibers and untwisted parallel short fibers. The soluble filament fibers are spirally wound around the untwisted parallel short fibers. The filaments are dissolved during the finishing process, leaving only the core without Twisted short yarn. In this process, the role of the filament is only to provide the tension required during the weaving process.
2.2.3 Reverse twisting method raw materials: water-soluble vinylon thread + cotton yarn process: doubling → reverse twisting.
Process key points: The reverse twisting process is a key process for processing untwisted yarn. The number of reverse twists of the ply yarn should be equal to the twist of the spun cotton yarn and PVA yarn. Use an appropriate small spindle speed. The height of the balloon should be appropriate to increase the indoor humidity, increase the vinylon cohesion force, reduce the breakage, adjust the doubling tension and untwisting unwinding tension to solve the knotting phenomenon 3. Characteristics of untwisted yarn fabric 3.1 The main difference between untwisted yarn fabric and twisted yarn fabric 3.1.1 Fiber arrangement Untwisted yarn fabric Since the fibers in the yarn forming the fabric are arranged in parallel, the fiber has a large degree of freedom, so the fiber is It becomes a ribbon or flat shape after being extruded, which makes it have different characteristics from the fabric formed by traditional spinning methods. 3.1.2 Appearance Since the yarns in the fabric are cut in a ribbon shape Due to the above reasons, the coverage coefficient of the fabric increases, so the fabric looks thick and tight, with a good fluffy feel, and the fabric quality is lighter. The untwisted yarn fabric has a softer luster than the twisted yarn fabric. 3.1.3 Processing technology The untwisted yarn has no twist The shrinkage of the fabric makes the shrinkage of the fabric smaller than that of traditional yarn fabrics, which can greatly save raw materials; the dyeing performance of untwisted yarn fabrics is good, and a mercerized effect can be obtained. The fibers in untwisted yarn are exposed and can fully contact the dye, so the dye is easy to be dyed. Twisted yarn often needs to be mercerized to make the fibers arranged more neatly to obtain good luster, while untwisted yarn does not need this One treatment; untwisted yarn can be usedThe loft effect of the fabric creates lighter, thicker and more comfortable fabrics.
3.1.4 Disadvantages of untwisted yarn
Untwisted towels feel super soft and thick, but during use, no matter how high-end untwisted, there will be some lint loss, which It is a shortcoming caused by the workmanship that is difficult to eliminate. But we can wash it with warm water before use, which can remove most of the floating hair and improve the shedding phenomenon. 3.2 Research on the wearing performance of untwisted yarn fabrics 3.2.127.8tex untwisted polyester core cotton yarn and twisted cotton yarn , The tensile properties of twisted polyester-cotton yarn have been tested and the strength of untwisted yarn is between twisted cotton yarn and polyester-cotton yarn. We know that the strength of ordinary cotton yarn is enough to provide the tension required for spinning. This shows that the strength of untwisted yarn is enough to provide Strength required for weaving.
3.2.2 Performance test of untwisted yarn knitted fabric
Cotton/water-soluble vinylon ply yarn knitted fabric is completed on an ordinary manual flat knitting machine, and the needle number of the knitting machine is 14 Number , the fabric is plain knitted fabric, the single yarn density is 28tex, and the area density is 147g/m2.
3.2.2.1 Air permeability The air permeability experiment was conducted on the YG461 medium-pressure air permeability instrument. In order to compare the air permeability of cotton knitted fabrics and untwisted yarn knitted fabrics, the two samples used were woven under the same conditions, and their yarn and fabric specifications were also the same (28tex yarn, needle number 14, plain knitted The surface density is 147g/m2). At the same time, the cotton knitted fabric is also boiled in boiling hot water for 0·5h and then dried. The average value of 10 sets of measured data is 28tex untwisted yarn 4.284mm.s-1; 28tex twisted yarn 2.609mm.s-1. It can be seen that the air permeability of untwisted yarn knitted fabric is nearly higher than that of traditional cotton knitted fabric. 1 times, which shows that the untwisted yarn knitted fabric has good breathability. 3.2.2.2 Moisture absorption and quick-drying performance Cut two 12cm×8cm rectangular pieces of fabric from the untwisted yarn knitted fabric and cotton knitted fabric respectively, and weigh them. Number the four samples and immerse them in water for 30 minutes to ensure that they are fully infiltrated. Take them out and hold them in your hand after 0.5 hours. When they no longer drip, measure their mass with a precision physical balance and record the corresponding data. Then, hang the sample on the rack and let it dry naturally. Then measure the quality every 10 minutes and record the data of each measurement until all four samples are dried naturally. Use the experimental data obtained to calculate the average moisture content of cotton fabrics and untwisted yarn fabrics, moisture content = (wet weight – dry weight)/wet weight × 100%, and the time moisture content curve.
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