How to control the washing color fastness of indigo knitted denim fabric

Since the first pair of jeans appeared in a gold mine in Texas, the cowboy style has changed from elegance to leisure, and more and more people have different styles of denim clothes. With the continuous expansion of the consumer market, the demand for multi-variety and multi-color denim fabrics is increasing. Knitted denim fabric is highly sought after by consumers because of its unique knitwear characteristics, such as elasticity, softness and breathability. How to accurately control the washing color fastness of knitted denim clothing before it is treated with white, matte and old-fashioned style has become a problem worthy of discussion. Production technology of indigo knitted denim fabric: 1. Process flow: pure cotton yarn → indigo dyeing → winding → weaving → post-treatment. 2. Production characteristics In order to ensure the minimum color difference of indigo yarn when weaving on the machine, the yarn is dyed by warp beam. In this way, all the yarns on the same shaft are dyed in the same cylinder to ensure the same color. Then the indigo yarn on the warp beam is made into packages and woven on a circular knitting machine. When designing weft knitting weave, choose the design scheme that the fabric structure is close to the appearance of traditional denim as much as possible. Generally, the front is exposed with indigo yarn, and the back is exposed with pure white cotton yarn or slightly indigo, which is closer to the style of traditional denim fabric. 3. Factors affecting the color fastness of fabrics to water washing Indigo yarns are usually dyed with vat dyes, which are insoluble in water and contain carbonyl groups in their molecular structure. When dyeing, they need to be reduced to soluble leuco with sodium hydrosulfite in alkaline medium, and the dyed fiber is oxidized to insoluble dye and fixed in the fiber. The dyeing process should go through four steps: dye reduction and dissolution, leuco dyeing, leuco oxidation and post-treatment. Knitted denim fabric is a yarn-dyed knitted fabric made of indigo cotton yarn and pure white cotton yarn. The off-machine grey cloth has not been treated after setting, so the color fastness is poor and it is easy to fade and stain. Therefore, washing has become an important factor affecting the color fastness of indigo knitted denim fabric. Through a large number of experiments, researchers have proved that the washing color fastness of indigo knitted denim fabric can be improved by strengthening the washing floating color treatment of grey cloth in the production process. (Source: Textile and Apparel Weekly)