What is Core-Spun Yarn?

Wrapped core yarn from the 1960s production, has a history of more than 40 years. The demand for core yarn is increasing, and the varieties emerge endlessly. According to relevant information, there are about 1 percent worldwide More than 10 million ingots in the production of core yarn, which is expected to increase by 200,000~300,000 per year ingots. Wrapped core yarn won the favor of the market, promising prospects, enduring, spinning edge varieties of an evergreen tree.

#1 Properties of Core-spun Yarn

Core spun yarn is a composite yarn composed of core yarn and sheath yarn. Its characteristics are that through the combination of outer fiber and core yarn, we can give full play to their respective advantages, make up for the shortcomings of both sides, take advantage of strengths and circumvent weaknesses, and optimize the structure and characteristics of the yarn. The comparison of the properties of general short fibers with filaments and their fabrics is shown in Table 1.

Table 1 Comparison of the properties of staple yarn and filament and their fabrics

It can be seen that compared with staple yarn, the filament has the advantages of uniform drying, high strength, good elongation, and elasticity, and is suitable for the backbone of wrapped core yarn. It can give full play to the characteristics of high strength, good elasticity, and special filament function. Short fiber is the outer fiber of core yarn, which can give full play to the function and apparent effect of fiber, such as the luster and beauty of new fiber, excellent water absorption, moisture absorption, heat resistance, warmth preservation, softness, anti-pilling and so on. The best combination of the two can produce general staple yarn and filament incomparable core yarn, such as elastic core yarn, high strength, high modulus, high-temperature resistance sewing core yarn, rotten core yarn, hollow-core yarn, high function-core yarn, and so on. In addition, the combination of the two fibers, the core is also often conducive to spinnability and weaving, such as stainless steel conductive fibers can not be spun due to open fire, but can be used as core yarn to make core yarn, can also play a conductive and shielding electromagnetic waves function. The core yarn is generally better than filament. The core yarn is equipped with two kinds of fiber suitable blending ratio, which can also save raw material cost and spinning cost.

#2 Classification of Core-spun Yarn

#2.1 Classification by Uses

It can be divided into core-spun yarn for sewing, core-spun yarn for burnt-out fabric, elastic fabric (including knitted fabric, woven fabric) core-spun yarn, fancy core-spun yarn (such as hollow core-spun yarn, color core-spun yarn, Siro Phil core-spun yarn, slub core-spun yarn, etc.), functional and high-performance fabric core-spun yarn, etc.

#2.2 Classification by Core Filament Yarns

Generally, it can be divided into rigid core-spun yarn and elastic core-spun yarn. The former include polyester, acrylic, vinylon (including water-soluble vinylon), nylon, etc., and the latter includes spandex, PTT fiber, PBT fiber, DOW XLA fiber, etc. Spandex is the most widely used.

#2.3 Classification by Sheath Fibers

Usually, cotton, wool, silk, hemp (including ramie, linen, hemp, etc.), color cotton and other natural fibers, viscose, Modal, Tencel®, soybean protein composite fiber, milk fiber, bamboo pulp fiber, polyester, acrylic and various Colored chemical fibers can be used for covering fibers of core-spun yarns.

#2.4 Classification by Spinning Equipment

At present, ring spinning, rotor spinning, friction spinning, air-jet spinning, etc. can be equipped with core-spun yarn spinning devices to produce various core-spun yarns. The spinning device is basically the same.

#2.5 Classification by Filament (Core Yarn) Content

The content of filament in the core-spun yarn is the main indicator of the core-spun yarn, and it has a great influence on the yarn performance and cost. Generally, the filament content below 10% is called low-proportion core-spun yarn, 10% to 40% is called medium-proportion core-spun yarn, and more than 40% is called high-proportion core-spun yarn. The content of elastic core-spun yarn is generally less than 10%, between 3% and 5%. The higher the proportion, the greater the cost; the core-spun yarn for pure polyester sewing has a core-spun yarn ratio of 50% to 60%; the core-spun yarn for burnt-out fabrics The content is 40% to 60%; the general rigid core-spun yarn content is 20% to 40%. The core yarn content cannot be too high, which is restricted. Theoretically, the covering width of the outer fiber should be greater than the circumference of the core yarn surface, otherwise, it will produce "ruth" defects.

#2.6 Classification by Spinning Yarn Density

Same as the traditional yarn classification, core-spun yarns are classified as thick tex core-spun yarns at 32 tex and above, 21 to 30 tex are called medium-tex special core-spun yarns, and 1 to 20 tex are called fine-tex core-spun yarns. The count of conventional core-spun yarn is 16 to 70 tex.

#3 The Key of Core-spun Yarn Manufacturing

#3.1 Schematic Diagram of Core-spun Yarn Production Device(Picture 1)

Picture 1 Schematic Diagram of Core-spun Yarn Production Device

#3.2 The Core Yarn Must be Positioned Correctly

The core yarn filament must be placed in the middle of the output of the front roller; due to the twisting moment, the filament position should be left to the center when spinning the Z-twist core-spun yarn, and to the right of the center when spinning the S twist.

#3.3 Properly Control Core Yarn Tension and Pre-draft Multiples

The rigid filament feeding type should be equipped with a guide tension controller, and the filament feeding tension is slightly larger than the drafting tension of the whisker. Suessen recommends 20 cN for general yarn spinning and 50 cN for compact spinning. The pre-draft ratio of the elastic filament feeding type is generally 2.5 to 4 times, which needs to be set according to the core yarn density, product strength and elasticity requirements. Generally, the higher the density of the core yarn, the higher the filament content, the better the yarn strength, and the greater the pre-draft of the core yarn. However, excessive pre-draft is likely to cause filament breakage. Actual pre-drafting will produce variations in the size of filaments of different materials, filaments with different linear densities, and filament packages; too much variation will result in differences in core-spun yarn shrinkage and elasticity, resulting in defective products. The actual pre-draft stability directly affects the stability of yarn quality and linear density. The selection of pre-draft shown in Table 2 is for reference.

Table 2 Selection of pre-drafting of elastic core-spun yarn

#3.4 Optimal Twist Coefficient

Generally, the twist coefficient of rigid core-spun yarn is about 10% larger than that of ordinary yarn. The commonly used twist coefficient ranges from 350 to 400. The twist coefficient of elastic core-spun yarn is 10% larger than that of ordinary yarn.

～20%, the general range is 350～400. If the cotton-type hollow core-spun yarn has a low twist coefficient, the combination of sheath yarn and core yarn will be loose, and the low strength will easily produce white yarn. If the twist is too high, it is easy to produce core yarn, and it is difficult to form a fuse. Too high twist is prone to weft reduction defects and textile weft skew during weaving.

#3.5 Prevent Hard Ends

When spinning core-spun yarn, the pulling tension of the core yarn increases the guiding force of the front roller. Therefore, if the front roller’s holding power is insufficient, it is easy to produce "hard ends". In view of this, the spinning process must be adjusted and the front roller must be enlarged. Roller pressure, increase the jaw gap, appropriately enlarge the front middle roller gap and other measures to reduce the drafting force and prevent the front rubber roller from slipping backwards and causing hard ends.

#3.6 Optimal Traveller

The optimization of the traveler when spinning core-spun yarn is very important. Generally, the filament has poor thermal melting and low melting point. It is easy to form thermal damage during the operation of the traveler and break the filament or wear, resulting in defective yarn and post-processing breakage. When selecting the type, the channel should be wide and smooth to prevent the channel and the wear from forming a cross and damaging the filament. The traveler exchange cycle can be appropriately shortened. It is recommended to use flat or semi-circular cross-section travellers for rigid core-spun yarns, and semi-circular cross-section travellers for elastic core-spun yarns. The former model can be 1 to 2 heavier than traditional spun yarns, and the latter should be 1 to 2 lighter than traditional yarns. number.

#3.7 Twist Fixation of Core-spun Yarn

The purpose of a fixed twist is to stabilize the twist and elasticity of the yarn and prevent kinks, uneven tension, and weft shrinkage during the weaving production process. The setting temperature is generally 85°～90°. Elastic core-spun yarn can be controlled low, and too high temperature will affect the strength and elasticity of the core-spun yarn. The setting time is related to the degree of vacuum and temperature and can be determined at discretion.

#4 Core-spun Yarn Defects and Their Preventive Measures (Table 3)

Table 3 Cored yarn defects and their countermeasures

#5 Core-spun Yarn Product Development (Table 4)

Table 4 List of Core Yarn Products

It can be seen that the core-spun yarn products are very wide. Various raw materials including natural fibers, traditional chemical fibers, new fibers, functional fibers, high-performance fibers, etc. can be applied. Aspect, and in continuous development, promising prospects.

Experts predict that fabrics with both filament and staple advantages will be popular products in the future. The core-spun yarn is a medium and high-end product. It is the edge product of various fibers such as cotton, wool, silk, and hemp. It has high technical content and high added value and is worthy of research and development and continuous innovation.