Views: 4 Author: Site Editor Publish Time: 2022-08-01 Origin: Site
The quality of cotton determines the quality of yarn and fabric to a certain extent. The types and contents of impurities and defects in raw cotton are not only related to the economic benefits of both the supply and demand, but also related to the yarn spinning process and product quality. If raw cotton impurities and defects are not properly handled, it will cause huge losses to textile enterprises. Therefore, the impurity and defect inspection of raw cotton are of great significance to improve the primary processing of seed cotton, improve the service performance of raw cotton, determine the spinning process and improve the quality of products. The influence of raw cotton quality on yarn quality is discussed below.
Strip evenness refers to the thickness evenness of the cross section in the length direction of the yarn. The evenness of the yarn strip plays a decisive role in the evenness of the cloth strip, and the evenness of the cloth strip is the main basis for textile rating. The yarn is even, the cloth surface is smooth, the grain is clear, the shadow is less, the feel is comfortable, then the textile quality is also high, the knitted fabric is higher than the woven fabric on the evenness of the strip. In particular, details and slub yarn defects may cause breakage and obvious defects in textiles. If you want a good appearance of the fabric, the evenness of the yarn is better.
The main influences of the following factors on yarn evenness in raw cotton are as follows:
(1) staple fiber content and length uniformity. Because the fiber length is the main basis to determine the spinning process and equipment. Spinning process parameters such as roller spacing, pressure, draft multiple and twist have significant influence on yarn length. The content of staple fiber is closely related to length uniformity. Generally, the content of staple fiber is high, and the uniformity of length uniformity is poor, so the length uniformity and staple fiber content have great influence on the uniformity of yarn length. In the process of spinning, the drafting mechanism can not effectively control the fibers of different lengths, resulting in some fibers out of control and long floating time, which is the main part of the planktonic fibers. The more planktonic fibers, the more uneven the drafting. If the textile factory uses different origin of cotton, length difference is very big, in addition to considering short fiber content, but also must pay attention to the length of the fiber, reduce the length difference between the cotton, because the mixed cotton length uniformity is poor, roller distance and other technological parameters need to be readjust.
(2) Moisture return rate. The moisture return of raw cotton also has a great influence on the spinning of textile mills. As we all know, cotton fiber after water absorption, transverse expansion, strength increases, elasticity becomes poor, flexibility increases, friction between each other increases, the ability to produce static electricity and resistance are reduced; On the contrary, cotton fiber after water loss, transverse contraction, strength decreases, elasticity becomes good, friction between the reduction, the ability to produce static electricity and resistance are increased. The moisture return rate of raw cotton is high, the cotton block is not easy to open loose, the cotton rolls are easy to bond layer by layer, and the uneven cotton rolls are increased. The carding machine has low efficiency in removing impurities, the cotton NetEase sags, and the evenness of the strips is poor. The MOISTURE RETURN RATE OF COTTON STRIP IS high, AND THE SOFTNESS OF COTTON fiber IS increased, which is conducive to the control OF the roller on the fiber, and the fiber is easy to straighten and parallel in the drafting process, and can increase the binding force between the fibers, reduce flying flowers, and improve the evenness of the strip. However, if the moisture return rate of the tampon is too high, it is easy to wind around the roller, roller, leather ring and other parts. The moisture return rate of raw cotton is too low, the fiber is easy to be interrupted and damaged in the textile process, the increase of short fiber, the increase of static electricity, in the roller, roller, leather ring and other parts of the "dry winding" phenomenon.
(3) the fineness. Research shows that fiber is fine, and the fineness of the overall difference is small, to improve the evenness of evenness is better, but the fineness is often controlled by the maturity and fineness of too fine maturity is generally poor, strength and low grades, fibers in carding process is easy to fracture form linter, also form the nep, indirect influence the homogeneous degree of the yarn evenness.
Influence on the knotting and impurity in the yarn
The defect and impurity of raw cotton are the main reasons that affect the knot and impurity of yarn. There are seven kinds of raw cotton defects, such as cable silk, cotton knot, sterile seed, broken seed, fibrous seed chip, soft seed skin and stiff piece.
Impurities and defects of raw cotton can be divided into three categories:
The first kind is easy to remove, the boll sheet, sediment and cottonseed which has little influence on the yarn and cotton knot and impurities;
The second type is the impurities that are easy to be broken and not easy to be removed from the impurities, such as sterile seeds, broken seeds and fibrous seed chips, which have a great impact on the quality of the gauze.
The third category is not easy to eliminate, and great harm to the quality of gauze defects, such as soft seed epidermis, rigid pieces, yellow root, etc. Belt of raw cotton fiber mote, soft seed epidermis, the harm of neps and other defects mainly short fibers in yarn twist twist into yarn, mote, nep, soft seed epidermis reveal surface of finished products, such as causing nep and impurity increases, the formation of thick section, a dry deterioration, increase of yarn hairiness, beheaded increased, especially the nep, suction color differences with the normal yarn, grey cloth dyeing is good, And the cotton knot around can not absorb dyeing, the formation of "white star", produce color difference, seriously affect the quality of printing and dyeing cloth. The above defects need to be eliminated in the cotton carding process due to the high adhesion between fibers and fibers, among which the cotton knobs and fibrous seed chips are difficult to be eliminated even after the carding process, which seriously affects the quality of high-grade products.
Effect on yarn breakage rate
There are mainly two kinds of cotton spinning, ring spinning and air spinning, and the reasons for the breakage are very different. The breakage of ring spinning is mainly caused by the strength of the yarn less than the tension of the air ring, while the breakage of air spinning is mainly caused by the gathering of dust particles in the textile condensation groove.
The impurity content of raw cotton fiber has a greater influence on air flow spinning than ring spinning. The impurity content and the size of dust particles in cotton sliver have a great influence on the performance of air flow yarn and the working state of air flow spinning machine. The impurity particles suspended in the carding air into the spinning cup, with the spinning cup rotating centrifugal force, these particles are easy to precipitate in the inner wall of the spinning cup under the action of centrifugal force, once deposited, in addition to the yarn belt out, can only stop manual removal. If the impurity particles focus on a certain point in the condensing tank, for example, a larger particle stuck in the condensing tank, it is easy to cause breakage.
The influence of different fiber and color fiber on textile
Great harm color different fibers and fiber quality of cotton gauze, heterosexual fiber mixed in the cotton fiber and color, because they have the fibre properties - thin, long, light, not only in the process of spinning processing is difficult to remove, but in removing impurity such as carding process may be pulled or opening into shorter, finer fibers, some were broken and become numerous fibrous tiny defect, spinning, These defects form yarn defects, which can easily cause yarn breakage and reduce production efficiency. Weaving, because the defect is much attached to yarn appearance, on the machine is easy to produce yarn with each other, a huge increase in the false hanged, approved by, the shrinkage defect, such as bleaching, due to the different fiber dyeing properties, and mixed with different fibers and color fiber cotton yarn, grey cloth, dyeing, appear all sorts of color, exposure to cloth, forming defects, seriously affected the appearance quality of the cloth.
Problems to be improved in practical work
In practice, it is found that cotton knot, cable thread and stiff piece without broken seed shell have no benefit to spinning, and the textile factory has long included cotton knot, cable thread and stiff piece without broken seed shell in the impurities. In view of the fact that the damage of cotton knotted, cable silk and stiff pieces without broken seed shell on textiles is the same as that of impurities and there is no essential difference, in order to unify the standard, further improve the international competitiveness of Chinese cotton inspection methods and standards and the guiding significance in practical work, promote the improvement of the quality of Chinese raw cotton and facilitate the use of textile industry, It is suggested that wire, cotton knot and rigid piece without broken seed shell should be included in the definition of impurities. The inspection method should be consistent with the defect inspection method, and all of them should be tested in 10g test sample. In this way, it can better guide the textile factory to calculate the cotton consumption correctly, reduce the cost, reduce the defect of finished products and improve the quality of products.