Modal fiber is a new type of high wet modulus cellulose fiber with very excellent properties (see Table 1). It combines the softness of cotton, the hygroscopicity of viscose, and the luster of silk. It is a biodegradable fiber. It has been favored by consumers. However, this type of fabric is prone to fluffing and pilling, which greatly reduces the wearing performance. In order to solve this problem, we conducted many experiments using Modal/cotton (50/50) blended knitted fabrics, and explored some production experience to improve pilling.
1 Factors affecting pilling
Pilling refers to the phenomenon where the fluff attached to the surface of the fabric or the short fibers on the leaking yarn are tangled into small balls. The process of pilling includes: (1) the initial generation of high-density loose fluff; (2) the fluff tends to curl and become entangled with each other; (3) the entanglements become tight and adhere to the surface of the fabric. The difficulty of pilling is related to the structure and properties of fibers, yarns and fabrics.
1.1 Characteristics of Modal fiber
The macromolecule polymerization degree of Modal fiber is between 2500-4000, which is about 300 times smaller than cotton. The amorphous zone is slightly higher than cotton, and the fiber dry modulus is low. These macromolecular characteristics determine that it has good hygroscopic swelling properties and is soft. , smooth. However, the wet modulus is high, the movement between fibers in water increases, the friction factor increases, and it is prone to serious fibrillation tendency, which is manifested as easy pilling.
1.2 Influence of spinning process
Modal fiber has good uniformity, few impurities, high looseness and poor cohesion. The fiber undergoes blow cleaning, carding, and drawing, and is especially affected by the roller tension during the spinning process, which has an important impact on the formation of yarn hairiness. Although the process parameters have been adjusted, some hairiness still leaks out on the yarn surface.
1.3 Influence of knitted fabric structure
The organizational structure of knitted fabrics has a greater impact on pilling. If the coil lengths are the same, when there are fewer knitting points per unit area, the probability of fluffing and pilling is greater.
1.4 Influence of dyeing and finishing processing
Dyeing and finishing processing play a decisive role in the final performance of the entire fabric. Practice has proven that certain processes such as mercerization and continuous bleaching have greater wet friction and mechanical stretching forces on the fabric, which will increase the pilling of Modal fiber.
2Measures to reduce pilling
2.1 Spinning process
During the spinning process, the fibers in the twisting triangle area undergo repeated internal and external transfer due to uneven stress, causing the head end, tail end or middle part of most fibers to protrude from the yarn body, forming hairiness. In order to reduce hairiness, textile mills, according to their own conditions, rationally allocate cotton, optimize processes, and adopt advanced textile technology to the best of their ability to control the generation of hairiness.
2.1.1 Cotton ratio
Most of the hairiness in ring spinning yarn is caused by leakage at the head and tail ends of the fibers. The more fibers in the yarn cross section, the shorter the fiber length, the more short velvet, and the probability and quantity of hairiness will also increase. Therefore, when blending cotton, various factors such as fiber fineness, length, and curl must be comprehensively considered to lay the foundation for selecting the ratio of excellent raw materials before spinning.
2.1.2 Principles of pre-spinning process
The presence of fiber hooks in the sliver will increase the amount of yarn hairiness. Therefore, in each pre-spinning process, we should strive to improve the straightness, parallelism and separation of fibers as a principle, try to eliminate short lint and reduce the generation of new short lint.
2.1.3 Spinning yarn
Yarn hairiness is mainly produced in the spinning process, so it is necessary to control the increase of hairiness in this process. You can use “appropriate large twist, small back area draft multiple, large back area roller gauge, small jaw gauge, medium The process principles of “pressure, low speed, medium hardness rubber roller” are used to improve the yarn quality.
2.1.4 Winding
Due to serious friction and collision between the yarn and machine parts during the winding process, the tail ends of some fibers are separated from the yarn and hairiness is regenerated. Therefore, the process of “low winding tension, slow winding speed, and metal grooved drum” is generally used in the winding process. At the same time, it is necessary to keep the winding channel smooth, burr-free, and in good mechanical operating condition.
2.2 Knitting process
The organizational structure of knitted fabrics has a great influence on pilling. Tightly structured tissues are less prone to pilling than loose tissues. Figure 1 shows the relationship between the longitudinal and transverse density product (total density) of weft plain knitted fabric and 1+1 rib knitted fabric and the mass of the wool ball. It can be seen that as the total density of knitted fabrics increases, the quality of the wool balls decreases significantly. Because when tightly knitted fabrics interact with external objects, the existing hairiness will not easily slide to the surface of the fabric due to the greater frictional resistance between fibers, so the pilling phenomenon can be reduced. It can be deduced from this: (1) Fine gauge knitted fabrics are less prone to pilling than coarse gauge knitted fabrics; (2) Weft knitted fabrics have less pilling than rib knitted fabrics; (3) The cloth surface is relatively flat and smooth The fabric is less prone to pilling than the fabric with uneven surface. Therefore, the probability of pilling can be reduced by selecting the weave structure of knitted fabrics.
2.3 Dyeing and finishing process
2.3.1 Singeing
Singeing is a good way to reduce hairiness and pilling. However, it is more difficult to singe knitted fabrics than woven fabrics, and after the gray fabric is processed, the strength decreases, the hand feels hard, and the dyed variety is not bright, which has serious consequences for the superior physical properties and wearability of Modal/cotton blended knitted fabrics. negative impact, so it is better to choose this process carefully.
2． 3.2 Process parameter adjustment
After the dyeing and finishing process is determined, parameters such as bath ratio and time can be appropriately adjusted, that is, the bath ratio can be appropriately increased or the process curve can be improved to shorten the time. These are also helpful in reducing the occurrence of pilling.
2.3.3 Use of additives
Anti-pilling agents can be added during the bleaching process. Softeners are added during the dyeing process to reduce the wet friction between yarns and between the fabric and the dyeing machine. At the same time, it can control the fiber leakage from the end of the yarn, thereby reducing the chance of pilling.
2.3.4 Hairiness application method
The hairiness adhesion method uses mechanical and physical and chemical methods to make hairiness tightly adhere to the surface of the fabric to achieve the purpose of reducing feathers and reducing pilling. Specifically, resin additives or chemical adhesives are used to make the hairiness fall down and fixed on the surface of the yarn after rolling.
2.3.5 Application of biological enzymes
Using cellulose softening enzyme to treat Modal/cotton blended knitted fabrics can improve the smoothness of the fabric surface. However, it has no effect on improving the pilling properties because the endonuclease in the cellulase component can enter the inside of the cotton fiber but not the inside of the Modal fiber, so the hairiness of the Modal fiber is not removed. , during future use, it leaks back to the outer end of the yarn due to friction, and then curls into a ball.
2.3.6 Influence of equipment
The production of Modal/cotton blended knitted fabrics is also selective in equipment, and it is generally best to use loose processing.
3Conclusion
Through the above methods, pilling can be improved to a certain extent; at the same time, reducing pilling is also a systematic project, and comprehensive measures should be taken from fiber production, spinning, weaving and other production processes to solve the problem.
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