What issues should be paid attention to when dyeing elastic fabrics
The functionality and fashionability of elastic fabrics are becoming more and more important in the fabric market, but elastic fabrics are particularly particular about the coloring process requirements. The properties of elastic fibers and their fabrics affect various processes from pretreatment to fabric finishing. The editor of this article summarizes the key factors that should be paid attention to in the dyeing and finishing of elastic fabrics, the selection of relevant products and the recommendation of process parameters, and specially shares them with friends.
Elastic fabrics and raw materials are not suitable for long-term storage. When spinning and winding, use a large amount of silicone oil and other lubricants to improve spinnability; when weaving and knitting fabrics, use more oils and auxiliaries to ensure good finishing properties. During long-term storage, degradation of these products causes the fabric to yellow until elasticity decreases. “Ambient hardening” is a potential problem that can cause lasting creases. If the storage period of the fabric exceeds 3 months, it should be sealed in an airtight and non-permeable plastic film. Elastic yarn is always woven into the fabric under a certain tension, and heat setting can avoid streaks and wrinkles during coloring, ensuring good dimensional stability. Usually heat set at 180-190℃ for 30-45 seconds. Higher temperatures cause elastic fibers to turn yellow and lose elasticity. Because silicone oil and lubricants will destroy the levelness of the dye and reduce the dyeing fastness, they should be completely removed from the elastic fabric before dyeing. The oil residue on elastic fiber blended chemical fiber fabrics and natural cotton fabrics is usually invisible before coloring, but metal complex dyes are lipophilic, that is, the oil spots on natural cotton fabrics are affinity with it at the beginning of the coloring process. When the coloring temperature rises, the oil is emulsified, but the dye remains, causing irremovable stains. Do not use cold water for rinsing after cleaning, because this will cause the emulsified oil to precipitate again, causing spots on the fabric. An effective method is to use hot water for thorough overflow rinsing and cold water for final rinsing.
During the coloring and finishing process of elastic fabrics, high mechanical stress can cause elastic loss. In order to preserve its elasticity, elastic fabrics with more than 10% elastic fiber content should be dyed on a slow-flow jet machine. Fabrics with less than 10% elastic fiber content can be dyed on an air jet machine. The wet fastness grade of polyamide and elastic fiber blended chemical fiber fabrics is lower than that of pure polyamide fiber. Experience shows that coloring with alkaline pH value is a practical method to reduce the dyeing speed of lanaset dye and improve the level dyeing. Polyester is increasingly used in elastic fabrics. This is a challenge for coloring: on the one hand, disperse dyes require high temperatures, and on the other hand, the elasticity of elastic fibers is greatly reduced when the temperature exceeds 115°C. Another obstacle in finishing such blended synthetic fabrics is that disperse dyes heavily stain the elastic fibers and their wet fastness is very low. The new dispersion accelerator cibapb allows the use of terasilw dyes at different temperatures without loss of elasticity. The recommended pb dosage depends on the required color concentration. Polyester and elastic fiber blended chemical fiber fabrics need to be thoroughly restored and cleaned after being dyed. The reduction cleaning of polyester is usually done using insurance powder, caustic soda and os at a temperature of 70℃. In order to remove disperse dyes from elastic fibers, the temperature needs to be between 80°C and 90°C. General insurance powder reacts too quickly and is therefore ineffective. If disperse dyes are to be removed from spandex, then os is the only effective product for reduction cleaning. Proper temperature, stable dispersant and good dispersant will determine the appropriate reduction cleaning.
In elastic fabrics that are blended chemical fiber fabrics with cellulose and elastic fibers, the higher the elastic fiber content, the greater the risk. Careful selection of reactive dyes that ensure easy migration before fixation of cellulose fibers is the only way to obtain good results. Compared with other reactive dyes, the use of cibacronls dyes can significantly reduce the amount of salt used; because these dyes are less sensitive to changes in liquor ratio, they are ideal for dyeing cellulose and elastic fiber blended chemical fiber fabrics. Especially for regenerated cellulose fiber, it is recommended to use the process of adding salt in batches during coloring. Dyeing regenerated cellulose fiber only requires 70% of the recommended amount of salt for ordinary cotton dyeing. Wool-like elastic fabrics gain additional functionality and good performance due to the increased elastic fiber content. A blend of elastane and wool improves its dimensional stability and wrinkle resistance. In the coloring process, piece dyeing is usually recommended. Good surface level dyeing requires dyes with good migration properties. Cibane-olan dyes are very suitable. When used with a pH value of 3.5, satisfactory dyeing fastness can be obtained even in traditional dark colors. Even trickier are fabrics where polyester, wool and elastane are blended together into synthetic fabrics. Due to the sensitivity of wool to strongly alkaline conditions, enhanced reduction cleaning is difficult to remove disperse dyes from elastic fibers. In particular, dyeing black and navy blue is more restricted. The use of disperse dye accelerator can ensure good reproducibility and reduce dyeing spots of wool and elastic fiber disperse dyes in blended chemical fiber fabrics. Under weakly alkaline conditions (ammonia adjusts the pH value to 8.5), use stable insurance powder to moderately reduce and post-process at 45-50°C for 20 minutes to ensure the improvement of wet fastness characteristics.
The pretreatment, coloring and finishing of elastic fabrics such as blended chemical fiber fabrics, such as shrinking, heat setting and cleaning, etc., depend on the fabric structure and its sensitivity to mechanical stress. Suitable machines maintain high elasticity, goodLevelness and reproducibility are particularly critical. Understanding all parameters, correct product selection and careful process adjustments will help achieve optimal performance from stretch fabrics. I hope that the fabric editor’s sharing can provide some help to my friends.
AAAKY, 7II56U65
Extendedreading:https://www.tpu-ptfe.com/post/7728.html
