Common spandex-containing textiles can be divided into the following categories, namely nylon/spandex, polyester/spandex, cellulose fiber/spandex and wool (or silk)/spandex blends or interweaves. Among them, for fabrics interwoven with nylon, wool or silk and spandex, acid dyes, neutral dyes, etc. are often used for dyeing. If spandex is modified with tertiary amine, spandex and the above-mentioned fibers can be dyed in darker colors and have better wet fastness. However, the dyeing rates and dyeing saturation values of spandex and these fibers are different, and the color fastness is often poor. The degree is also different. In order to obtain better same-color effects, dyes must be carefully selected. Commonly used dyes and dyeing processes for spandex-containing textiles are introduced below.
1. Dyeing of nylon and spandex blends or interwoven fabrics
Commonly used dyes for nylon are acid and neutral dyes. These dyes can also be used to dye spandex, but the fastness is poor, especially acid dyes. Therefore, the fastness of blended fabrics dyed with these dyes is always worse than that of pure nylon fabrics.
For this purpose, dyes with good fastness should be selected, such as Ciba’s Lanaset dye, and some domestic neutral dyes can also be used. In addition, the levelness of these dyes is poor, so it is important to develop a reasonable dyeing process, especially controlling the pH value of the dye bath and post-dyeing washing and color fixation. And because nylon absorbs acidic dyes quickly, retarder should be used for this reason, and the starting temperature of dyeing should also be lower, so that the two fibers can have better same-color effects. If it is unmodified spandex, the color of the spandex is light under normal conditions and the wet fastness is very low, so other dyes or dyeing methods need to be used for dyeing.
Ciba Company introduces the dyeing process using Lanaset or Erionyl A dyes as shown in Figure 2-18. As can be seen from the figure, because this type of dye has poor level dyeing, the pH value should be slightly higher when starting dyeing, preferably 8 to 8.5, and the dyeing speed should be slow to achieve good level dyeing; acetic acid should be added later Buffer solution to lower the pH value of the dye bath so that the dye can be fully dyed (after dyeing for 30 minutes, add acid during boiling dyeing). The application of Lanaset dye to dye light colors has good color fastness without the need for fixation treatment, and the reproducibility is good.
For dyeing dark-colored varieties, the pH value of the dye bath should be lower and adjusted to pH = 6 to 6.5 with acetic acid, and the dye bath should be washed thoroughly with water after dyeing. For particularly dark varieties, such as black or navy blue, post-dyeing treatment can be done with a color-fixing agent, such as the anionic color-fixing agent Cibafix PAS, or twice the color-fixing treatment, that is, using the cationic color-fixing agent Cibafix ECO is treated in the final water bath, or it can be treated with softener in the final padding process, and then dried. The process of twice solidification is shown in Figure 2-19. The two fixatives cannot be used in the same bath, otherwise precipitation will occur.
2. Dyeing of polyester and spandex blends or interwoven fabrics
Although polyester fabrics containing spandex can be dyed with disperse dyes, the dyeing temperatures of the two fibers are quite different. Polyester needs to be dyed at high temperature and high pressure at 130°C to have good dye uptake and improvement. Under such conditions, spandex is easily damaged and shrinks greatly. At this time, the dyeing temperature should be lowered. Therefore, the first contradiction is that disperse dyes damage the dyeing rate and improvement of polyester and spandex; the second contradiction is that under normal conditions, disperse dyes will stain spandex and reduce the color fastness of the product. To this end, various companies have developed some dyes and supporting auxiliaries. The dyes developed have the following characteristics:
(1) High dye fastness on polyester.
(2) It has good lifting properties and dye uptake rate for polyester, and can be dyed at lower temperatures.
(3) It stains spandex lightly and is easy to remove by restorative cleaning.
In order to solve the contradiction between dyeing temperature and the selection of suitable dyes, some dye accelerators were developed, which are actually some carriers, that is, carrier (environmentally friendly) dyeing was used. For example, Ciba’s Univadine PB is suitable for Terasil W dyes and can be dyed at 120 to 130°C for 60 minutes, 125°C for 45 minutes, or 130°C for 15 to 30 minutes, thereby shortening the dyeing time. . For another example, when dyeing with Foron RD series dyes, apply the dye accelerator Dilatin POE (liq.) and dye at 120°C for 45 minutes.
In addition, the wet fastness of most disperse dyes on spandex is very low, and washing must be strengthened after dyeing to remove staining on the spandex surface. Sometimes in order to obtain textiles with good fastness, anti-staining additives need to be added during dyeing to prevent the disperse dye from staining the spandex. At this time, the spandex is basically not dyed.
Research has found that selecting disperse dyes with appropriate structures and applying special additives can not only improve the dyeing rate of spandex with disperse dyes, but also improve the dye fastness. After dyeing, reduction cleaning must be carried out, especially to remove the disperse dye stained on the spandex. The temperature of reduction cleaning is 70-80℃. In addition to insurance powder and caustic soda, detergent builders can also be added, such as Cibapon OS and Sandopur PU, etc. These builders can reduce the re-staining of spandex by disperse dyes. The schematic diagram of their effects is shown in Figure 2-20.
Cibapon OS can reduce the equilibrium adsorption amount of disperse dyes to spandex. If it is restored and cleaned,If the temperature is higher than 80℃, it is best to use a reducing agent with good stability, such as a reducing agent used for discharge printing. Anti-pollution agents have affinity and solubilizing effects on dyes. Most of them are compounds of surfactants, some of which are non-ionic and some of which are amphoteric, such as weak cationic and non-ionic. The performance of products of different companies is also different. same.
3. Dyeing of blends or interweaves of cellulose fiber and spandex
There are more and more varieties of cellulose fiber and spandex blended fabrics, including blends or interweaves of cotton, Lyocell, etc. with spandex. The cellulose fibers can be dyed with commonly used dyes, such as reactive dyes, vat dyes, direct dyes, etc. These dyes cannot dye unmodified spandex. If spandex needs to be dyed, a small amount of disperse dyes are usually added, but only light colors can be dyed.
If the concentration of disperse dye is too high, the wet fastness of dyeing will be low, so washing after dyeing should be strengthened. In addition, when cellulose fiber is dyed with the above-mentioned dyes, it should not be treated under high temperature and strong alkali for a long time to prevent damage to the spandex. If cellulose fibers are mainly dyed with reactive dyes, in order to obtain good dyeing effects, the reactive dyes must be carefully selected. They should have good dye migration properties before alkali fixation, especially for dyeing regenerated cellulose fibers such as Lyocell. Because the dye absorbs quickly on this type of fiber. Overseas, it is recommended to use dyes such as Cibacron LS. It not only has good dye migration properties, but also can be dyed with low salt and is less sensitive to changes in liquor ratio. Weak oxidant Lyoprint RG can be added during dyeing to prevent the dye from being damaged by reduction at high temperatures. In addition, attention should be paid to the pH value during color fixation. A high pH value is not conducive to leveling dyeing and can easily damage spandex.
If the spandex content is small, a small amount of selected disperse dyes are often added to the cellulose fiber dyeing bath for one-bath dyeing. At this time, it is best to use special additives. In fact, in the presence of special additives, using reactive/disperse dyes for one-bath dyeing can not only obtain good same-color properties and good dyeing fastness, but also domestic reactive dyes also have good level dyeing properties. If modified acid dyes can dye spandex, acid dyes can be used to dye spandex in separate baths or in one bath with other dyes.
4. Dyeing of wool and spandex blends or interwoven fabrics
Wool and spandex blends or interwoven fabrics are a type of textile with particularly good elasticity. Before scouring, the fabric can be treated in a 40-45°C solution for 20 minutes to fully relax, which is very beneficial to the reproducibility of spandex processing. In addition, the fabric should be prevented from being stretched by large tension during processing; the temperature should be lower during heat setting, processing at 175-180°C for 45-60 seconds; and the door width and overfeeding should be controlled. For dyeing, use dyes with high migration properties, such as Neolan dyes, which have good levelness and dye fastness. Blended or interwoven fabrics of polyester/wool/spandex fibers need to be dyed with disperse dyes. On the one hand, they cannot be dyed at high temperatures to prevent damage to the spandex and wool. Therefore, disperse dye accelerators should be added during dyeing.
For example, adding Univadine PS during dyeing can reduce the dyeing temperature to below 120°C, and can also reduce the staining of wool and spandex by disperse dyes. On the other hand, you cannot use caustic soda for high-temperature reduction cleaning to reduce wool damage. At this time, you can use a weak alkali (use ammonia to adjust the pH to around 8.5) at 45-50°C, and treat it with a stable reducing agent for 20 minutes. You can also add Cibapon OS is used to reduce the staining of spandex by disperse dyes and improve wet fastness. Studies have shown that polyester can be dyed at 100-125°C by using special additives, and these additives can also promote the dyeing of wool and spandex with disperse dyes, achieving the effect of dyeing multiple fibers with one disperse dye in one bath. . For example, in the presence of a solubilizer, ultrafine polyester and wool dyed with disperse dyes can be dyed into dark colors at 100°C, and all fastnesses are good, but disperse dyes must be selected.
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