- Nov 10, 2017 -
Due to the development of denim varieties, different types of denim also have different requirements for yarn quality. But the cotton indigo denim still occupy a large share, this kind of denim is coarse and high density fabric, requiring smooth surface, clear weave, straight lines, uniform color, three-dimensional feeling, which has higher requirements for the quality of yarn, its basic requirements are:
1, the yarn must have good levelness and penetration. In order to obtain better dyeing properties, cotton fiber should be selected with better maturity and less impurities. If the maturity of cotton fibers or fibers contain dead cotton, causing serious uneven dyeing effect, light will lead to warp dyeing, flower color dyeing or class.
2, yarn must have a certain strength and elasticity. In order to obtain the stable weaving state of denim in weaving, the larger tension is required and the tension should be stretched several times during the weaving process. Therefore, the warp yarn has higher strength and good elasticity, taking 58.3tex yarn as an example. The breaking strength of yarn dyed with rope dyed yarn should be 12.5 ~ 13.5CN/tex, and the breaking strength of the yarn dyed with flake dyeing should be 11.5 ~ 12.5CN/tex.
3, yarn evenness, less yarn defects. Denim yarn evenness and yarn defects are more stringent than warp yarns. When the yarn evenness is uneven or the slub yarn defects are more, the yarn strength is lower and the strength unevenness is large, which seriously affects the fabric style and appearance quality of denim. When the weft and slub are serious, the visible white mark on the fabric surface can be formed, which is harmful to the special style of "blue in the white" of the denim cloth. Taking 58.3tex as an example, the evenness of CV% should be less than 13%.
4, less yarn hairiness. Mao Yu will make the sizing and warping process difficult to separate yarn, broken ends increase, Mao Yu will also lead to weaving warp opening is not clear, affecting the cloth style.
5, less yarn connection and small. Denim usually uses 3/1 right twill weave structure, the knot of the warp is easy to appear on the cloth surface, forming a black dot or white dot which is inconsistent with the fabric color, causing the defect. For the knot and defect of weft yarn, it is not as obvious as the warp knot and easy to expose, but affects the appearance quality of the finished product, but too much knot will cause the white star defect of fabric surface dispersion. Rotor spinning is one of the advantages of rotor spinning because of its large capacity and less knot than ring spinning. 6, the yarn weight unevenness and weight deviation is small. Denim in the international market and the variety of price mainly depends on the fabric weight per unit area, thus to strictly control the yarn weight deviation, reduce weight unevenness, or otherwise lead to the final product is not up to the standard weight loss caused by drop. The national standard stipulates that the monthly weight deviation of 100 meters should be less than + 0.5, and the uneven weight of 100 meters should be controlled within 2%.
7, in order to make denim has higher strength and good elasticity, using rotor spinning for denim fabric yarn, twist twist coefficient is higher than ring yarn 20 ~ 30%, in 450-470 twist / meter, weft twist coefficient can be lower than warp, but not less than 390 twist / meter.