Requirements for dyes in piece dyeing and scattered dyeing in grey fabrics

There are two ways of dyeing viscose in carded wool spinning mills: piece dyeing and loose dyeing in grey fabrics, and they have different requirements for dyes.

1. Piece-dyed and piece-dyed fabrics mainly refer to wool-viscose blended fabrics. Direct dyes are suitable for piece-dyeing. Direct dyes can not only dye the viscose in wool-viscose blended fabrics, but also dye both wool and viscose fibers at the same time (partly). Dyes have a dyeing effect on wool, similar to weak acid dyes), reactive dyes are generally not used for dyeing wool-viscose blended fabrics, when sulfur dyes are used for piece dyeing, first dye viscose, and then overdye wool with wool dyes. Cumbersome and rarely used.

2. For loose dyeing, the same color number can be dyed with direct dyes, reactive dyes, and sulfur dyes, respectively, but these three dyes have their own advantages and disadvantages, and one of the best processes should be selected. When choosing these three kinds of dyes, the dyeing principle and the characteristics of the dyes should be considered comprehensively. Below we discuss the considerations for choosing dyes when dyeing loose:

a. The washing fastness of direct dyes is poor, even if the color is fixed, it is not worth the reactive dyes and sulfur dyes. In the fancy woolen products, in order to prevent the phenomenon of color selling in the washing process, in principle, direct dyes cannot be used for dyeing. Dyeing with dyes, but direct dyes cannot be used for dark line dyeing.

b. The price of sulfur dyes is the lowest. When dyeing dark colors, sulfur dyes can be used to reduce costs. For light and medium colors, direct dyes and reactive dyes with convenient technology are used. . .Reactive dyes and direct dyes are more colorful than sulfur dyes. Therefore, sulfur dyes cannot be used for woolen varieties with bright colors.

c. The chromatogram of sulfur dyes is incomplete, such as bright red, etc., only reactive dyes or direct dyes can be used.

d. The fibers are brittle and damaged after dyeing with sulfur dyes. If the yarn is spun after dyeing, it is easy to break. Therefore, in the woollen mill, if spun wool and viscose blended 9^-145 yarns, it is best not to use sulfur dyes for viscose dyeing. Otherwise, the spinning and weaving efficiency is not high.

e. The performance of direct lightfast dyes and direct copper salt dyes has surpassed that of the old direct dyes. Except for a few varieties, the old direct dyes have been replaced by these two dyes.

f. Among the reactive dyes, KN reactive dyes are acid and alkali resistant, and cannot be used for viscose fiber dyeing in carded wool spinning mills to avoid hydrolysis in the washing process. It is advisable to use the same type of reactive dyes for color matching

g, K type can not color match each other. Characteristics of viscose fiber To dye viscose fiber, we must first have a sufficient understanding of the characteristics of viscose fiber. Viscose fiber is a regenerated cellulose fiber. Its chemical composition is similar to that of cotton fiber, and its performance is close to that of cotton fiber. However, the degree of polymerization and crystallinity of viscose fiber is lower than that of cotton fiber, and there are many amorphous regions in the fiber, so the hygroscopicity of viscose fiber is better than that of cotton fiber, and the wet strength is lower than that of cotton fiber.