1.1 Performance of soybean protein fiber
The cross-section of soybean protein fiber is dumbbell shaped, with fine pores and a skin core structure. There are obvious grooves in the longitudinal direction, with fine fineness and light specific gravity. The fiber friction coefficient is small, and the mass specific resistance is close to that of silk. The initial modulus is relatively high, the bending elastic modulus is small, and the curling recovery rate is low. The curling is flat, with good moisture absorption and conductivity.
The quality indicators of soybean protein fiber used in the experiment are as follows: fineness 1.56 dtex, length 38mm, dry strength 4.27 cN/dtex, wet strength 3.9 cN/dtex, defect 0.3mg/100g, curl count 12.5/cm, oil content 0.91%, moisture regain 6.7%.
1.2 Performance of Spandex Yarn
The main performance indicators of spandex yarn are as follows: fineness 44.4 dtex, breaking strength 43.1 cN, elongation at break 370~520%, 300% elongation stress 12.7 cN, 300% elongation elastic recovery rate 96%, boiling water shrinkage rate 20%, oil content 3.0%~9.0%.
Key Technologies for Production of Wrapped Yarn
The production difficulty of wrapped yarn is mainly reflected in the complexity of the production of soybean protein fiber yarn and the impact of wrapped yarn technology on yarn performance. In the production of soybean protein fiber yarn, the smooth development of soybean protein fiber yarn was achieved by optimizing the process and using new specialized spinning equipment. At the same time, the relationship between the linear density, draft ratio, coverage of wrapped yarn and yarn performance of spandex was determined, and the quality of 27.8 tex soybean protein/44.4 dtex spandex wrapped yarn was theoretically and practically guaranteed.
2.1 Trial production of soybean protein fiber yarn
The adhesion between soybean protein fibers is poor, the mass to resistance is high, and there is severe static electricity during spinning. In order to solve the problems of less natural crimp of soybean protein fiber, smoother fiber surface, poor cohesion between fibers, large contact friction coefficient with metal elements, and outstanding static electricity during spinning, 0.5% antistatic agent 2880 and wool oil diluted with 10 times water were used for high-pressure spraying. Pack and place for 24 hours to ensure uniform penetration and improve fiber antistatic properties. After 24 hours of dehumidification and balance in the workshop, it will be put into use.
Spinning process of soybean protein fiber yarn
FA002 cotton grabbing machine → A092AST double cotton box feeding machine → FA141 single beater coil forming machine → FA201B carding machine → FA306 drawing machine (two tracks) → FA401 roving machine → FA506 spinning machine → 1332MD winding machine
Cotton cleaning process
Soybean protein fiber has a low curl recovery rate and low blending and impurity content. Therefore, a short process is adopted, and the process should adhere to the principles of "light weight, short fixed length, more carding and less beating, more collection and less dropping, and anti sticking and rolling". The speed of the carding needle and hammer is 15-20% lower than that of spinning cotton to reduce fiber damage. The relative humidity in the workshop is relatively high, and the unevenness of the cotton roll is 1.2%, and the moisture regain is controlled at around 10%.
Carding process
The poor spinnability of soybean protein fibers is mainly reflected in the carding process, and it is important to focus on observing the condition of the doffer's cotton web. If there is a net fall, it indicates a lack of anti-static oil; If the tin cylinder is wound, it means that there is too much antistatic agent, which should be adjusted according to the situation. At the same time, it is necessary to avoid length damage during carding, increase fiber transfer rate as much as possible, and prevent repeated twisting of fibers to form cotton knots. In terms of technology, it is necessary to master the principles of "soft carding, easy transfer, light weight, low speed, and medium spacing". At the same time, it is also possible to consider installing a double rubber ring cotton guide device, using specialized needle cloth, and controlling cotton drop with low relative humidity. The main process parameters are: cylinder speed 350r/min, take-up roller speed 720r/min, cylinder cover plate spacing 0.35mm, 0.35mm, 0.30mm, 0.35mm, 0.35mm, take-up roller cover plate spacing 0.2mm, cover plate speed 175mm/min, mechanical draft multiple 94.5, tension draft multiple 1.38, dry weight 24g/5m.
Drawing process
The focus of this process is on the control of hairiness. The process adopts "medium weight, heavy pressure, large spacing, reasonable tension stretching, anti entanglement and anti blocking". The speed is controlled at a low speed, and the horn mouth is controlled at a small angle to improve the strip and resultant force.
The main process parameters of drawing are shown in Table 1
Roving process
Considering that soybean protein fibers have good elasticity and poor cohesion, in order to reduce fine yarn hairiness, the twist coefficient of the roving should be increased by 10-15% on the basis of spinning cotton, and the spinning tension should be controlled to reduce accidental stretching of the yarn.
The rubber roller should be made of domestically produced rubber rollers with high hardness and treated with WTB composite coating. The main process parameters of roving include roller spacing of 28mm and 35mm, back draft ratio of 1.18 times, total mechanical draft ratio of 8 times, designed roving twist coefficient of 74, and dry weight of 5.4g/10m.
Spinning process
Theoretical research shows that the hairiness on the surface of yarn forms in the fine yarn and grows in the package. So in practice, optimizing the spinning and winding processes is the breakthrough point to control the hairiness of soybean protein fiber yarn within the allowable range. The main process parameters of spinning are: spindle speed 12700r/min, design twist coefficient 371, back draft ratio 1.27 times, front rubber roller moving forward 3mm, front rubber roller hardness selected Shore A63 degree, small diameter yarn guide hook used to facilitate twist transmission and reduce hairiness, steel ring PG1/2 type, steel wire ring OSS type, use inner and outer pattern rubber rings to control fiber diffusion, and use nitrile rubber high-efficiency energy-saving ingot belt to reduce yarn twist unevenness. Simplification uses devices such as electric cleaning, splicing, and metal groove barrels, using a "low speed, low tension" process, and controlling the relative humidity of the workshop at 75%.
2.2 Design and development ideas for soybean spandex wrapped yarn
In the past, the production process of elastic yarn was mostly cotton or polyester cored and twisted, while the variety we developed was spandex wrapped yarn. Spandex wrapped yarn has a different appearance effect and internal quality from cored yarn and ply yarn, and the following factors were considered in the design to affect the yarn forming effect:
(1) Wrapped yarn core without twist. Wrapped yarn is sometimes also known as wrapped yarn, and one of the most obvious differences between it and cored yarn and twisted yarn is that the core yarn has no twist. The relationship between the core sheath of the spandex filament and the outer layer in the wrapped yarn is obvious, and the bonding force between the core filament and the outer fiber is lower than that of other types of elastic yarns, so its elasticity is significantly higher. Meanwhile, the hand feel of wrapped yarn is harder than that of cored yarn, and its strength is the strength of the wrapped filament or yarn, so its strength is higher than that of cored yarn of the same specification. It should be noted that the wrapped yarn is loosely wound, and the purpose of developing wrapped yarn is to fully utilize the elasticity of spandex fiber and the strength of the wrapped fiber.
(2) Consider the impact of spandex yarn specifications and elastic yarn types on weaving shrinkage.
(3) The influence of the linear density of spandex fibers. The finer the spandex fiber, the smaller the elastic elongation and retraction force, and the smaller the drawing ratio used for spandex fiber during processing. The elastic elongation and retraction of the fabric are also smaller, and the weaving shrinkage rate is also smaller.
(4) The influence of spandex fiber drawing process. The elasticity of elastic yarn is due to the stretching applied to the spandex fiber during the yarn processing, which gives it a certain degree of elasticity. The elasticity size depends on the drafting ratio E of the spandex fiber after its specification is determined. The larger the E, the greater the elasticity of the yarn, and the greater the shrinkage during weaving. Therefore, in order to meet the requirements of fabric design, the drafting characteristics of different specifications of spandex fibers should be fully considered when selecting elastic yarns. The drafting ratio of spandex yarn also affects the content of spandex in the product. The higher the drafting ratio, the lower the content of spandex in the product. This should be particularly noted when considering product costs. But we cannot blindly increase the draft ratio to reduce costs. If the draft ratio is too high, the spandex fiber is prone to breakage and processing difficulties occur. The draft ratio of 44.4dtex spandex yarn is usually 3-4 times, and this product uses 4 times.
(5) The influence of different types of elastic yarns on weaving shrinkage. Different elastic yarns exhibit varying degrees of elastic shrinkage due to their structural differences. According to the trial weaving, it is better to use wrapped yarn for high elasticity fabrics, and to use twisted yarn and cored yarn for medium and low elasticity fabrics. We conducted trial weaving on different types of yarns, and the impact of different yarn types on weaving shrinkage is shown in Table 2
(6) Wrapping process. The coverage of wrapped yarn is an important structural parameter that affects the performance of silk threads and fabrics. Coverage refers to the degree of coverage of the outer fiber on the core wire, usually expressed in terms of the number of twists per unit length of the wrapped wire. The greater the degree of coverage, the higher the number, elongation at break, and elasticity at fixed elongation of the coated wire. The strength and initial modulus of the coated wire decrease, and the drape coefficient of the fabric decreases, thereby improving the drape of the fabric. In this sense, a higher degree of coverage is better, but the larger the fabric's constant load elongation, the smaller its residual elastic deformation at constant elongation. To ensure the extensibility of elastic products, 44.4dtex spandex yarn is used as the core wire, with a spandex content of 3.5% and a coverage of 800T/m-250T/m. This product uses 650T/m.
The main performance indicators for the final selection of spandex fiber are as follows: fineness 44.4 dtex, breaking strength 43.1 cN, elongation at break 370~520%, 300% elongation stress 12.7 cN, 300% elongation elastic recovery rate 96%, boiling water shrinkage rate 20%, and oil content 3.0~9.0%.
Wrapped yarn is loosely wound, which is formed by winding at a tension less than the spinning tension. To meet the needs of weaving, the take-up rate should be increased to over 95% to ensure smooth weaving. Trial production shows that a coiling rate of around 80% makes weaving almost impossible
source:https://mp.weixin.qq.com/s/h1RV1CatUmytazX42XGK-A