After dyeing nylon fabric, the silk surface will produce horizontal stripes or longitudinal stripes of color, which are often referred to as rungs and warp willows. In addition to the causes already caused by the gray silk, improper dyeing can also cause this defect. Especially if there are slight rungs and warp threads in the gray silk, the original exposure is not obvious. Once it is dyed, the structure of the fabric will be different. If changes occur, some rungs and warp willows will be obviously exposed. Taking appropriate measures during dyeing will effectively reduce the rungs and warp willows of the fabric. If the measures are not taken properly, the rungs and warp willows of the fabric will be more serious.
The first is the improper selection of dyes. Some dyes have poor level dyeing properties on nylon fabrics, and their covering properties for weaving are not obvious. For example, rungs and warp threads often appear after dyeing with separate neutral dyes, especially when dyed with zong-colored and gray dyes. Secondly, improper PH value and temperature control during dyeing can also produce rungs and warps.
How to reduce the rungs and warp threads of the fabric?
1. The covering ability of various dyes on the warp and rungs of nylon fabrics is divided into scattered dyes>acid dyes>reactive dyes>neutral dyes>direct dyes. Therefore, when dyeing, the rationality of blending should be taken into consideration when selecting dyes. Try to choose dyes with similar dye uptake rates or complementary dyes. Especially when using neutral dyes as the main color to dye dark rice dumplings or dark gray, a certain amount of acid dye must be added to reduce the probability of warp and horizontal rails.
2. The addition of diffusing agent can also improve or solve such problems. For example, adding a diffusing agent and a leveling agent can form dye micelles, so that when the dye is dyed, the dye dissolved in the bath forms a dynamic balance with the micellar dye, so that the dye can be evenly adsorbed on the fiber and play a role in dye transfer. And achieve level dyeing.
3. The correct control of the pH value in the dye bath is also an effective measure to reduce rungs and warps. The isoelectric point of nylon fabric is 5.6. When the pH value of the dye bath is lower than the isoelectric point, it is beneficial for the dye to absorb the fiber. However, as the pH value of the dye bath decreases, the dye absorption rate accelerates, and the level dyeing property is poor. It is poor, and the covering effect on warp willows and rungs is also reduced. Ammonium sulfate is commonly used as a pH regulator. Improper dyeing heating and dyeing temperature control will also produce warps and rungs. Therefore, if the temperature rises quickly and enters high-temperature dyeing, the dye will lack time to penetrate and diffuse into the fiber. In addition, the dye migration property is poor at high temperature, resulting in warp Willows and crossbars, so the temperature needs to be gradually raised during dyeing. At high temperatures (above 70°C), the heating rate should be slow to ensure that the dye has sufficient time to adsorb, penetrate and diffuse to achieve uniform dyeing.
4. The key issue is that the quality of the bad silk woven from nylon fabrics should be good, and the raw materials, preparation process, and weaving process should be prevented from being improper. Pre-shaping can eliminate the internal stress formed during the weaving process, keep the fiber in a stable state, and provide a good raw material for dyeing. It is also an effective measure to reduce the generation of rungs and warps in the fabric during dyeing.
Process Example
Since the amino and carboxyl groups at both ends of the nylon fiber macromolecule are sensitive to light, heat and oxygen, especially For amino groups, during the process of oxidation and thermal cracking, the number of groups will decrease. Nylon fibers will also yellow at the same time. In addition, the various oils used in the fiber spinning and weaving processes of nylon fabrics may also change their properties under the action of light and oxidation, causing oil stains that are difficult to remove on the fabric surface, which will also cause “white stains” , white spots” phenomenon occurs. Therefore, it is required that nylon fabrics should be packaged in opaque packaging materials after weaving.
1. Pre-treatment of nylon and elastic fabrics
(smoothing)→(desizing)→scouring
1. Desizing of nylon woven fabric
Desizing agent 8g/L
Chelating dispersant 1g/L
Liquid caustic soda (30%) 30g/L
Continuous open-width desizing, the vehicle speed is 40m/min, use the working fluid in the first two compartments, and overflow water washes each compartment. Since nylon woven fabrics are prone to creases or chicken paw prints, it is best to use open-width equipment before the fabric is pre-shaped at high temperatures.
2. Example of scouring process
Nylon scouring agent 1-3g/L
Chelating dispersant 1-2g/L
pH around 5 (HAc adjustment), overflow machine immersion method 95℃×30min, liquor ratio 1:8, or according to the dyeing factory’s own equipment In this case, the open-width machine is used to adjust the number of sections of the feeding box and the water washing box, and the long car continuous refining and oil removal process is used.
3. Washing
Due to the increasing pressure on environmental protection, many factories only pay attention to the removal of oil and impurities from fabrics, but do not pay attention to them. The subsequent washing work will cause excessive accumulation of oil and impurities washed from the fabric. The accumulated oil bundles will cause back staining, thus forming “white spots and white stains” after dyeing. Therefore, the fabric cleaning after oil removal is refined. There are also craftsmanship details that cannot be ignored. Alkaline cleaning often requires a large amount of water. It should be noted that if the oil stains cannot be completely removed under acidic conditions, an alkaline refining process can be added.
2. Dyeing of nylon and its elastic fabrics
The dyes that can be used for nylon dyeing include acid (weakly acidic) dyes, disperse dyes, reactive dyes, Direct dyes and more. Although reactive dyes have the advantages of bright colors, good light fastness, and no heavy metal ions, their dyeing depth and cover dyeing properties are poor. Disperse dyes can only dye light colors, so the dyes currently used for nylon dyeing are stillThe phenomenon of “competition” among enterprises.
4. The influence of the choice of leveling agent on nylon dyeing. Weak acid dyes have fewer water-soluble groups than strong acid dyes, and have a higher affinity for nylon fibers. In aqueous solution Its solubility is worse than that of strong acid dyes, and its solubility and aggregation are moderate, so its wet processing fastness is better, but its dye migration and leveling properties are poor. During the fiber spinning and weaving process of nylon and its elastic fabrics, the physical and chemical structure of the fiber itself is uneven, including differences in fineness, internal stress, molecular structure orientation, etc., or differences in fiber chemical properties, such as fiber ends. Differences in the number of amino groups can also cause dyeing problems such as color bars and rungs during the dyeing process.
In addition, operational problems during the dyeing process will affect the levelness of nylon dyeing. Therefore, the selection of a good leveling agent can effectively prevent or reduce the occurrence of the above problems. There are many types of leveling agents used for nylon dyeing, including fiber-friendly anionic type, dye-loving polymer type, amphiphilic type zwitterionic type, etc. Zwitterionic leveling agents have larger molecular weights and have excellent leveling effects on weakly acidic dyes with larger molecular weights. They have higher dye migration capabilities and the ability to even out the dyeing rates of different types of acidic dyes.
Improvement of horizontal stripes and warp stripes of nylon fabrics: During the fiber spinning and weaving process of nylon and its elastic fabrics, the physical and chemical structure of the fiber itself is uneven, including differences in fineness, internal stress differences, and molecular structure orientation. Differences in density, etc., or differences in fiber chemical properties, such as differences in the number of amino groups at fiber terminals, will cause dyeing problems such as color bars and rungs during the dyeing process. Use leveling agent to pre-scouring nylon fabrics before dyeing them to improve defects such as rungs and warps caused by fiber differences.
5. Improving the wet treatment fastness of nylon fabric after dyeing. After the nylon fabric is dyed, because the acid dye has a water-soluble group, and the dye and fiber are not in a strong cohesion Due to the combination of valence bond method, the wet treatment fastness of nylon dyed medium and dark varieties is poor, and color fixation treatment is required to improve the wet treatment fastness. The special color-fixing agent for nylon can react with nylon fiber, and the color-fixing agent molecules can be cross-linked with each other to form a three-dimensional network structure, which can effectively fix the acid dye molecules in the fiber to improve its wet processing fastness.
Finishing of nylon fabrics
1. Soft finishing of nylon fabrics
As people pay more attention to clothing With the diversification of wearing requirements, nylon fabrics not only have rich changes in fabric categories and clothing styles, but also the feel and style of nylon fabrics have also changed. Some require waxy and smooth, some require soft and elastic, and some require strong drape. Yes, there are requirements for dry and fluffy ones, etc. Silicone softeners comply with the requirements of clothing trends and have gone through the development stages of methyl silicone oil, amino silicone oil, polyether modified silicone oil, and ternary copolymer silicone oil. Product performance has been continuously improved, and hand feel styles have emerged in endlessly.
2. Other functional finishing
Due to market demand, the finishing of nylon fabrics also has many functions. Sexual finishing requirements, such as moisture wicking finishing, flame retardant finishing, mite removal and deodorizing finishing, sanding finishing, as well as pre-formed antioxidant, storage anti-yellowing, etc., all require the use of corresponding additives and processes, which will not be discussed here. Let’s elaborate further.
Note
1. The choice of nylon fabric pre-treatment process directly affects the quality of nylon fabric dyeing and finishing products.
2. During the dyeing process, the control of the pH value of the dye solution is one of the key factors for the success or failure of dyeing. The lower the pH value of the dyeing solution, the faster the dyeing speed, and the worse the dye’s leveling properties and warp hiding ability. 3. The nylon leveling agent can improve the initial dyeing pH value of the dye solution and the charge of the nylon fabric, and can effectively prevent problems such as color flowers, warps, and rungs caused by too low initial dyeing pH. It has a very good leveling effect. 4. The wet treatment fastness of nylon fabrics not only requires the selected dyes to meet product requirements. Moreover, a good nylon color fixing agent has a good effect on improving the wet processing fastness. 5. The control of dyeing temperature is also one of the key factors in nylon dyeing. The dyeing heating curve and dyeing starting temperature should be determined according to the selected dyes, different colors, and different fabric structures. The heating curve generally adopts the ladder method. 6. The finishing process of nylon fabric should be determined according to different product requirements. </p
