Development of Acrylic Yarn Yarn and its Process Research
1.1 Plain spandex fiber
1.1.1 Structural characteristics
Acrylic fiber, also known as polypropylene eye fiber, is a fiber made of polypropylene eye as the main raw material (containing more than 85% of acrylic eye), copolymerized with the second and third monomer.
Acrylic fiber cross-section varies with the different spinning methods, wet spinning fiber cross-section is basically round, dry spinning is peanut-shaped. The surface of the fiber is rough and bark-like, the original fiber structure can be seen in the optical or electron microscope, and there are tiny holes. acrylic fiber macromolecule is not very regular helical conformation, does not have a true crystalline structure, so there is no strict crystallization zone and amorphous zone, the thermal elasticity of acrylic fiber is a reflection of its structure.
1.1.2 Properties
Acrylic fiber strength 1.76 ~ 3.80 N/dtex, elongation at break 25% ~ 46%, wet strength is 85% ~ 95% of dry strength, Acrylic initial modulus is lower than polyester and higher than nylon, generally 35.2 ~ 61.6 cN/dtex, elongation elasticity is better than man-made fiber and cotton, hemp but worse than wool, the residual elongation of multiple stretching is larger, therefore Therefore, the cuffs and collars of Acrylic knitted fabrics are easily deformed.
The moisture absorption rate of Acrylic fiber is low, and the moisture return rate under standard conditions is 1.2% ~ 2.0%, and the moisture return rate varies slightly from species to species. the dry and wet moisture return rates of Acrylic fiber are close to each other, so the difference in tensile properties between dry and wet states is small, but because of its poor moisture absorption, it is easy to accumulate static electricity when processing and is easily stained when wearing.
In addition, Acrylic also has a small specific gravity, fluffy appearance, soft feel, excellent warmth, mildew, mothproof, colorful and other characteristics, and has good light, heat and radiation resistance, coupled with its unique elasticity and warmth similar to wool, so it has the name of “artificial wool”. The commonly used Acrylic staple fiber has two types: wool and cotton, which can be blended with wool and widely used in the manufacture of wool yarn, blankets and artificial fur.
1.2 High shrinkage eye fiber
The fiber with boiling water shrinkage rate of about 20% is called general shrinkage fiber, while the fiber with boiling water shrinkage rate of 35% ~45% is called high shrinkage fiber.
High shrinkage Acrylic fiber is to make use of the thermal elasticity of Acrylic, the silk bundle after drying, heat setting, curling treatment above its glass transition temperature and then heat drawing and stretching, and then cooling rapidly under tension, so that the fiber is fixed with large internal stress. This fiber latent shrinkage after heat, generally known as high shrinkage Acrylic fiber. Its boiling water shrinkage rate can be more than 30%.
The yarn blended with wool or other chemical fibers, which has a strong sense of hairiness, can be used to weave wool blankets or artificial fur. The textured yarn spun by using the heat shrinkage of Acrylic has good fluffiness and strong sense of hairiness, which is widely used in artificial fur and imitation cashmere industries and has good promotion prospects.
2 Yarn varieties
2.1 Common Acrylic Yarn
Cotton type Acrylic Yarn is particularly soft to the touch, some of them can be comparable to cashmere, which can be used for high-grade knitted garment fabrics, high-grade thermal underwear, high-grade socks and other products.
Medium-length Acrylic yarn, with soft and smooth handfeel, good luster, uniform strip, strong plush feeling, both cotton and wool style, and high fastness, good abrasion resistance, is the ideal yarn for developing imitation wool fabric in knitting industry, and has a good market. Its traditional spinning method is mostly done by using wool spinning equipment, but it is limited by the high cost of spinning. Using the existing cotton spinning equipment, by adjusting the process parameters, spinning medium-length pure Acrylic Yarn can greatly reduce the spinning cost.
2.2 Bulky Acrylic Yarn
The high shrinkage Acrylic fiber and no secondary heat stretching of low shrinkage fiber in a certain proportion (generally high shrinkage Acrylic fiber 40% -45%, low shrinkage fiber 55% -60%) for mixed spinning, the spun yarn will be above 100C for thermal relaxation treatment (steam or boiling water treatment). At this time, the high-shrinkage Acrylic fibers shrink along the length to become the core of the yarn, while the low-shrinkage fibers are squeezed to the surface in the shape of a circle, making the yarn puffy and soft. This yarn is called Bulky Acrylic Yarn.
Bulky Acrylic Yarn has the unique style of soft and fluffy hand feeling and similar to wool yarn, widely used in fleece, underwear, outerwear knitted sweater towels, towels and decorative fabrics.
2.3 Blended Yarn Acrylic and wool blended yarn
Because of good fluffiness and strong sense of wool shape, it has been widely used in woolen yarn, woolen blanket, the manufacture of artificial fur and other fields.
Blending fine denier Acrylic with cotton fibers with a large moisture return rate, as cotton fibers are coarser and easier to present on the outside of the finished yarn, can improve the moisture absorption properties of the fabric. In addition, blending a certain percentage of cotton can make up for the lack of strength of fine denier Acrylic fiber, so that the roving and spinning process can be carried out smoothly and prevent the phenomenon of winding rollers and skin rollers. This blended yarn has the advantages of good luster, good handfeel and less wrinkles after washing, and the yarn blended with some hemp by 45/55 has the advantages of good moisture absorption, breathability and stiffness of hemp, but also improves the disadvantages of poor dyeing performance of linen fiber, which is ideal for summer fabric knitting.
The use of high contraction Acrylic and rabbit hair to develop rabbit eye blended yarn, through the contraction of Acrylic, can strengthen the curl winding of ghost hair, so that the fiber is not easy to slip off, which is conducive to the protection of free hair, reduce free hair shedding. It can produce finished products such as rabbit fur sweaters, outerwear, scarves, hats, gloves and cashmere knitted fleece.
The products woven with medium-length Acrylic, wool and rabbit fleece fiber blended yarn not only have the characteristics of Acrylic fabric with fluffy structure, light weight, soft hand, good warmth, comfortable wearing and bright color, etc., but also further improve the appearance and feel of the fabric due to the blending of wool and rabbit fleece fiber, which makes the fabric feel woolen, full hand and feel more luxurious; the wool and fleece-free fiber The moisture recovery rate is higher than Acrylic, which enhances the moisture absorption and breathability of the fabric and makes the fabric more comfortable to wear.
In addition, Acrylic and other natural fibers and synthetic fibers, especially new fibers for blending, can develop more products suitable for market needs.
2.4 New type of spinning Acrylic Yarn
Rotor spinning machine production of low-twist Acrylic OE yarn, its structure is fluffy, uniform dry, for knitting pile fabric, its fabric pile surface is rich, thick, rich pile.
Since the structure of air-jet Acrylic Yarn is wrapped yarn, the hairiness is less than that of ring yarn, so the knitted fabric produced by air-jet Acrylic Yarn has less pilling.
Vortex spun Acrylic Yarn has special advantages as a yarn for village cushions in the knitted fleece industry. Vortex spinning yarn has the characteristics of loose and disorderly fiber internal structure arrangement, small degree and low strength, and high resilience compared with the traditional ring spinning yarn, so it gives full play to these advantages as a padding yarn in knitted fleece production.
3 Spinning process
Acrylic species is mainly short fiber, can be pure spinning, can also be mixed with wool or other fibers, made of wool fabric. In the raw material matching, consider the requirements of fiber length and fineness ratio, that is, length (inches) / fineness (denier) 1, more suitable for processing on the cotton spinning set.
Acrylic in the processing process is very sensitive to changes in temperature and humidity, outdoor conditions and raw materials change, the workshop must be timely adjustment of temperature and humidity, otherwise there will be sticky roll, around the flowers and other problems.
Most of the combing and rough combing wool spinning equipment can process Acrylic fiber very well. The following is an analysis of the key production process of each process when processing Acrylic Yarn in cotton spinning equipment.
3.1 Opening and Clearing Process
According to the characteristics of Acrylic fiber, such as fluffy, elongation, less impurity and light specific gravity, the process principle of “more loosening and less beating, more combing and less falling, proper mixing, anti-winding and anti-adhesive” can be adopted in the production.
In order to reduce the number of fiber strikes, the process can skip six silver simple cotton opener and a porcupine type cotton opener. Porcupine openers can be used on the fully enclosed dust frame to reduce the fall of cotton. In the cotton feeder, the appropriate enlargement of the V-shaped curtain on the spacing, in order to prevent the cotton box Acrylic flip and the formation of fiber mass. The quantification of cotton roll should not be too large, and the fixed length of cotton roll should not be too long, otherwise it will affect the forming and carding process, at the same time, in order to prevent the sticky roll, the coarse yarn strip should be clamped on when forming the roll.
3.2 Carding process
According to the characteristics of Acrylic fiber fluffy, elastic, easy to tangle, and in order to reduce fiber damage as much as possible, the process can take the principle of “light quantification, heavy pressure, large spacing”. acrylic fiber holding force is poor, so the pressure of the cotton roller than the spinning of cotton to increase the appropriate to enhance the cotton grip.
3.3 parallel process
The reasonable configuration of the parallel process is the key to improve the quality of Acrylic Yarn. Production of leather silver pressurization than when spinning cotton increased by 20%30%, in order to make the grip force and drafting force to adapt to reduce the unevenness of the yarn.
The process of drawing machine, can use the first channel small two large drafting times configuration, and the drafting times of the back area of the first channel is larger than the second channel head channel drafting times small, is conducive to improve the uniformity of the strip, the second channel drafting times large is conducive to improve the straightness of Acrylic fiber parallelism improve Acrylic Yarn strength.
3.4 Roving process
If the coefficient is too large, the unevenness of roving twist strength will increase, and when drawing on the spinning machine, the drawing force will increase, and even the drawing force will not fit with the holding force, and the strip will slip under the roller jaws, leading to hard head or deterioration of the strip.
3.5 Spinning process
The process principle of “low twist coefficient, suitable draft multiplier in the back area, large spacing, heavy pressure” is adopted on the spinning machine.
The twist factor of the yarn is one of the more important indicators of the quality of the knitted product. The twist factor is chosen to be low in order to adapt to the need for soft and elastic yarns for knitted underwear.
The center distance of the middle and rear rollers is enlarged to improve the distribution of the friction boundary in the drafting zone, so as to effectively control the pulmonary fibers and improve the yarn quality. In the case of suitable coefficient of roving and larger center distance of the rear area of the yarn, the rear area of the yarn drafting machine should be appropriately small, so that the roving by the rear area of the yarn drafting machine after the residual twist and into the short and long double skin ring drafting area, in order to reduce the yarn details of the weight of the wire mass than the same number (count) of cotton yarn appropriate weight.
3.6 Winding simple process
Due to the serious phenomenon of static electricity of bladder, the formation of the simple sub difficult, easy to appear the size of the head, spider web and other phenomena, the following measures can be taken: (1) reduce the speed of the groove Jane machine; (2) appropriate to increase the weight of the tension washer; (3) the use of metal groove cylinder.
(1) Acrylic Yarn has the unique excellent characteristics of extremely wool-like yarn, with soft hand, good expansion, good elasticity, good dyeing performance, bright colors, and strong warmth retention. Therefore, it is widely used in the manufacture of underwear, outerwear, knitted sweaters, blankets, artificial furs, towels and decorative fabrics, etc. It has a broad development prospect.
(2) Using Acrylic fiber and other fiber blends can give full play to the advantages of two or more fibers to develop diversified and high value-added products.
- Because Acrylic fiber has the characteristics of fluffy, light specific gravity static electricity phenomenon, etc., in the production should take appropriate process configuration to control. It is worth mentioning that processing medium-length Acrylic fiber on cotton spinning equipment can greatly reduce the spinning cost of enterprises.
