Practice of improving the dyeing fastness of cotton fabrics

Reactive dyes and vat dyes are the two most commonly used dyes in the dyeing of cotton fabrics. Generally, the vat dye is used for the light color, and the reactive dye is used for the medium dark color, so that the quality and cost can be better balanced. However, in the production practice, due to the dye itself or process control, there is still a problem that the color fastness of the final product is unqualified. For example, if the reactive dye is mainly expressed in the light fastness of the light-colored fabric and the rubbing fastness of the dark fabric; the vat dye is mainly expressed in the blue-resistant chlorine fastness and the wet ironing fastness of the M gray. on. The following is a discussion on the improvement and improvement of the color fastness of cotton dyed fabrics.
l reactive dye dyeing fastness
1.1 Light fastness The color fastness of dyes depends mainly on the dye matrix structure. The light fastness of reactive dyes often originates from the red components in the three primary colors. Since the matrix structure is mostly azo, the light fastness is relatively low, so that the combination of the three primary colors will produce asynchronous fading in the light fastness test, resulting in visual additive fading. Therefore, the development of high light fastness red reactive dyes has been a hot spot.
1.1.1 Light fastness to red reactive dyes In order to improve the light fastness of red reactive dyes, the molecular structure of the dyes needs to be improved. One is to introduce a hydroxyl group in the ortho position of the azo group, and use its coordination ability to form a stable chelate ring with heavy metal copper (Cu) to improve light fastness. Such dyes have c. I. Reactive Red 23 (Rimasol Red 3B, Domestic Red KN-5B) and C. I. Reactive Red 49 (domestic red KN-B). The other is to use the "azo-based protection technology" in the dye synthesis process, that is, in the ortho position of the azo group, a strong electron-withdrawing group, such as a sulfonic acid group, is used to reduce the azo group by utilizing its electron-withdrawing effect. The nitrogen cloud electron cloud density increases the light stability of the azo group. Such dyes have C. I. Reactive Red 194 (domestic red M-2BE, B-2BF) and C. 1. Reactive Red 223 (domestic brilliant red M-GE) and so on.
In fact, when the above dyes are used to dye dark colors, the performance is acceptable, but when used for dyeing light colors, the performance is not satisfactory. Desma Red Red 3B is a high light fastness dye with a light fastness of 5 to 6 at a standard depth of l/l2. Since the dye molecules contain copper, which is a heavy metal element, the perspiration fastness is poor, and the leveling property is also problematic, which limits the application.
In recent years, major dye manufacturers at home and abroad have successively developed a new generation of high light fastness reactive red dyes, such as Hunter's Norwich Clone Red C-2BL and Taiwan Shuiguang's Reactive Red LF-2B. DyStar's Lihua Real Fast Red CA and other dyes do not contain heavy metal atoms in the matrix structure, but through special molecular design, the dye can meet the requirements of light fastness and light fastness. Table 1-3 lists the light fastness and light fastness data of three dyes of Norwich Clone Red C-2BL, Everbright Red LF-2B and Lihua Real Fast Red CA.

Note: Mizuno Test Method 10 is a test method of Japan Mizuno Co., Ltd., which is rated by a gray card of level 5.

Huntsman and DyStar have also recently launched Norwegian Crimson CD and Remasol Super Magenta RGB reactive dyes. The former is blue-red, the latter is yellow-red, both with high lifting power and high fixing rate, and has excellent light fastness and perspiration fastness at moderate dyeing depth (see Table 4). .

1.1.2 Selection of dyes Compared with ordinary reactive red dyes, high light fastness reactive red dyes are high-grade dyes and are expensive to use. Therefore, it is recommended to be used only for the dyeing of medium-light fabrics. For the dyeing of dark fabrics, since the light fastness increases with the increase of the dye concentration on the fabric, the light fastness can be achieved by using ordinary dyes.
The high light fastness red commodity dyes produced by different dye manufacturers also have different force scores. According to the padding test, the color of GF-2B is slightly lower when the amount of dye is the same; the color of Lihua Real Fast Red CA and Norwich Clone Red C-2BL are basically the same; Red CD and Remasu Super Magenta RGB get the deepest color. Therefore, when dyeing light color, Yongguang Red LF-2B, Novo Clone Red C-2BL and Lihua Real Fast Red CA are selected. When dyeing medium color, Novi Clone Crimson CD and Remasu Super Magenta RGB are obvious. The advantages.