Analysis on Improving Yarn Quality and Application of Functional Yarn (Part 1)

Spinning is the first process in the textile industry chain. The development of high-quality and multifunctional yarn products can not only effectively broaden the application field of yarn, but also be the key to improving the added value and economic benefits of textile products.

China is the world's largest producer of yarn and textiles, and has always been committed to the research and development and production of high-quality and high-end yarns. High-quality combed yarns are developed using high-quality long-staple cotton from home and abroad for domestic and foreign companies to make high-end shirts and knitted underwear. The products are exported abroad as high-end color-spun knitted clothing yarns, and the production process is very environmentally friendly.

In recent years, as domestic consumers' requirements for textile quality continue to increase, the requirements for yarn and textiles have become increasingly stringent. In addition to bright colors and no fading, consumers also put forward higher requirements in terms of wearing comfort, moisture absorption and breathability, antibacterial and health functions. In the field of decorative home textiles, functional requirements such as flame retardancy, UV resistance, and sun resistance are also becoming increasingly prominent.

In response to the high-quality and multi-functional needs of domestic and foreign markets, Zhejiang Province and domestic textile companies have relied on the progress of textile technology and the research and development and application of functional raw materials to continuously innovate and break through, successfully producing a variety of high-quality yarns and functional yarns, meeting the diversified needs of the market and injecting new vitality into the sustainable development of the textile industry.

1. Develop high-quality functional yarns based on new technologies

1.1 Secondary combing process

In the textile field, combing technology has always been an important means to improve yarn quality. The use of combing technology to produce pure cotton yarn can effectively remove short lint, impurities and cotton knots in raw cotton, significantly improving yarn quality.

However, with the increasing quality requirements of consumers for high-count yarns for knitted apparel, it is necessary to further explore and innovate technical measures to improve product quality. For this reason, double combed low-neps ultra-soft knitting yarn came into being and is widely used in intimate underwear, infant products, fashion apparel and high-end towels, bringing consumers a more comfortable and high-quality wearing experience.

The process flow of double combed spinning is:

Cleaning and combing line - pre-drawing → drawing and winding → combing machine → drawing machine (one) → combing machine (two) → first drawing → last drawing → roving → spun yarn → winding.

After combing by two combing machines, the number of fiber neps can be reduced by 21% compared with one combing and 70% compared with raw sliver, completely removing impurities in the sliver. The AFIS short fiber rate is significantly reduced, which fully meets the stringent requirements of yarn for high-end knitting products.

(1) Some spinning companies in Zhejiang have also successfully applied the combing production process to the combing of non-cotton fibers, achieving remarkable results. For example, the waste ‘filaments’ of silk yarn are combed twice using a cotton combing machine, and used as the raw material for the production of high-quality yarns to produce filament-cotton blended yarns, which significantly increases the added value of the product.

(2) Zhejiang Jiaxing Textile Materials College successfully applied cotton combing machines to the combing of hemp fibers, producing combed hemp-cotton blended yarns. This not only retains the natural advantages of hemp fibers, but also improves the softness of hemp fibers through the combing process, making the hemp-cotton blended fabrics popular with users.

Hemp, also known as hemp, is currently the softest hemp fiber. It has the superior properties of moisture absorption and breathability, antibacterial and antibacterial properties, and shielding ultraviolet rays, and is favored by domestic and foreign consumers. However, it is slightly rougher than cotton fibers in shape, shorter in length, and less uniform. It is difficult to spin without treatment, and the yarn has more hairiness, and the finished product is prone to wrinkling.

To this end, the Textile Engineering College of Zhejiang Jiaxing University has appropriately modified the cotton combing machine, reduced the density of the combing needles, combed the hemp fibers, effectively eliminated the harmful impurities and shorter fibers in the hemp fibers, and obtained hemp fibers with high uniformity and few impurities, which were then blended with cotton fibers to produce combed hemp-cotton blended yarn using siro spinning technology.

When optimizing the blending ratio, the research team found that when the hemp blending ratio reached 40%, the number of broken ends increased during the spinning process and the uniformity of the yarn decreased. After repeated experiments, it was finally determined that 20% hemp fiber and 80% cotton fiber were blended. The clothes made of this combed hemp-cotton blended yarn not only retain the coolness and breathability of hemp, but also incorporate the softness and skin-friendliness of cotton fibers. It is popular in summer clothing and military clothing, and is favored by the international market.

1.2 Siro spinning and compact spinning technology

For a long time, traditional ring spinning has been using a single roving for feeding. The quality defects of the roving (such as uneven yarn length, coarse and fine yarn length, etc.) will be clearly revealed in the finished yarn, thus affecting the quality of the finished yarn. To this end, domestic and foreign textile machinery manufacturers and spinning companies have jointly explored and developed two new spinning technologies, Siro spinning and compact spinning, which have effectively improved the quality of yarns, especially in fine count and high-quality yarns.

(1) Siro spinning technology.

Two rovings are fed into the spun yarn drafting system. The two rovings are drafted and synthesized into yarns at the same time. The quality defects of the original roving (such as count differences, uneven yarn length, etc.) are compensated to a certain extent. Therefore, compared with traditional ring spinning, it has obvious advantages in terms of quality indicators such as yarn length uniformity and hairiness, and has achieved good application results in high-quality and high-count yarns.

(2) Compact spinning technology

A set of airflow suction devices is installed in the ring spinning drafting system, so that the coarse yarn is tightly bundled by the airflow during the drafting process, effectively avoiding the generation of free fibers. Because the fibers are subjected to negative pressure aggregation, the yarn not only eliminates the hairiness, but also the fibers are tightly held together, which significantly improves the strength and uniformity of the yarn. At present, compact spinning has become a common choice for producing high-quality yarns.

The siro compact spinning technology, which combines compact spinning and siro spinning, combines the advantages of both, and the yarn quality is even better. At present, siro compact spinning technology has been widely used in the production of high-quality high-count yarns, providing strong technical support for high-end knitting and shirt yarns.

1.3 Core-spun yarn technology

The use of coating technology on yarns can combine two or even more spinning raw materials to produce textile products of various specifications and functions. Taking polyester/cotton core-spun yarn (with polyester filament as core yarn and cotton fiber as outer yarn) as an example, the advantages of polyester being crisp, wrinkle-resistant, easy to wash and quick-dry can be perfectly combined with the characteristics of cotton fiber being hygroscopic, antistatic and skin-friendly, and it is widely used in the clothing market such as shirts, bathrobes, skirts, and sheets. The mainstream of polyester/cotton blended yarn is 65/35, and when making underwear, the blending ratio of cotton fiber can be increased to more than 50% to improve the comfort when wearing.

Core-spun yarn can also use elastic fiber as core yarn and cotton fiber as outer yarn to produce elastic core-spun yarn, which is widely used in the production of various clothing. For example, denim stretch fabric not only maintains the crispness of denim clothing, but also gives it the characteristics of flexible expansion and contraction, making it more comfortable to wear. The application of core-spun yarn in the field of casual clothing is also increasing, effectively improving the added value of products.

1.4 Two-color high-strength segment color yarn

The Textile Branch of Zhejiang Jiaxing College has successfully developed two-color high-strength segment color yarn, which is not only rich in color and novel in color matching, but also has a strong three-dimensional sense, making the fabric present a soft and full color and a strong sense of layering. Compared with traditional fancy yarn, the production process does not require complex processing technology, but is appropriately modified on the basis of the traditional ring spinning machine, and adopts a three-axis four-roller drafting form to achieve a combination of different colors in the cross-section and length direction of the yarn.

Not only does it maintain the uniformity of the yarn, but the distribution between the color segments is also very obvious, providing high-quality materials for the production of various segment color fabrics. At present, this segment color yarn has been put into mass production. The number of color segments of the segment color is controlled at 5, and the length of each color segment is within 50cm, which not only improves the strength of the segment color yarn, but also enhances the stability of the strength.

1.5 Variable twist yarn technology

Variable twist yarn is a yarn with a unique structure produced by a special spinning process. At present, the research on yarn structure in China is mostly focused on the changes in yarn thickness, color, and composition, while there is still a lack of corresponding research on the production technology of twist-changing yarns.

Zhejiang University of Arts and Sciences recently publicly released a patent for the invention of a variable-twist twisting machine for yarns. The programmable controller of the twist changing device controls the drive motor to adjust the transmission speed of the twisting system, so that the twist of the yarn in production changes. Since the twist of the yarn has a great influence on the gloss and dyeing performance of the yarn, the change of the yarn twist causes the fabric to produce special color changes after the weaving and dyeing finishing of the yarn in the later process, which can be used to process fabrics of special styles. Therefore, the variable twist technology can optimize product quality, expand the application field of products, and has a good market competitive advantage.

1.6 Asymmetric structure containing gold and silver yarn for knitting

Through the asymmetric structure design, two different colors of coarse yarn are used to spin yarns with unique style characteristics. The asymmetric structure yarn is an innovative design of yarn products based on siro spinning technology. It does not require special technical transformation and broadens the scope of siro compact spinning product development.

Since gold and silver yarns are used as the main yarns in the yarns, the bright colors of gold and silver yarns are maintained, the problem of gold and silver yarns falling off easily is solved, the wear resistance of the yarns is improved, the feel of the yarns is improved, and the fabrics made have bright metallic luster and are very decorative. They are used to decorate fabrics and are deeply loved by consumers.

1.7 Mercerization technology

At present, there are many textiles made of hemp fibers on the market. Compared with cotton fibers, hemp fibers have many excellent properties, but they also have many defects, especially the fibers are thicker, the feel is harder, the length difference is large, and the spinning difficulty is greater. In order to improve these shortcomings of hemp fibers, Zhejiang Institute of Technology has improved the surface smoothness of hemp yarns through mercerization technology, which significantly improves the rough feel of the yarns and the itching feeling when wearing, effectively improves the wearing performance of the products, and lays the foundation for expanding the application scope of hemp fiber textiles.