Problems and prevention of dip dyeing of cotton/brocade interwoven fabrics
Flash color
On the surface, the flash phenomenon is caused by the inconsistent colors and hues of cotton fibers and nylon fibers, that is, uneven hues. The fundamental reason is that some cotton dyes have different effects on the dyes. Caused by competitive dyeing of nylon.
In actual production, dyeing primary colors and secondary colors can make full use of competitive dyeing characteristics to dye cotton fibers and nylon with purer colors, flatter colors, and better effects. However, it is difficult to dye three-color combinations (such as military green, iron gray, and brown) to the same hue on two fibers at the same time, and the color flash phenomenon is serious. This is the most difficult problem encountered in the dyeing of cotton/brocade interwoven fabrics. , which can be solved from the following three aspects.
1.Dye
Generally, dyes used to dye cotton (such as reactive dyes and direct dyes) have certain competitive dyeing properties for nylon. Choosing new dyes that do not stain nylon can solve the problem of competitive dyeing.
2. Auxiliary
In order to prevent competing dyeing of nylon, you can use a special anti-dyeing agent for cotton/nylon interwoven fabric dyeing.
3. Craftsmanship
Reactive dye dyeing generally fixes color when the pH value is above ll. The optimal dyeing pH value of acid dyes usually used for dyeing nylon is 5.5 to 6.0. That is, dyeing under acidic conditions. The two completely opposite process conditions cause the reactive dyes that have been dyed on the cotton fiber to be stripped to varying degrees while dyeing the nylon, which brings great difficulties to the imitation color. Choose neutral dyes with milder dyeing conditions instead of acid dyes. The pH value of neutral dye dyeing is around 6.5, which has less impact on reactive dyes, so that dyeing three colors such as army green, iron gray, and brown can get better results. Homogenous effect.
Colored Flowers
Cotton/nylon interwoven fabrics are dyed in medium and dark colors using the reactive/acidic two-bath method. Generally, cotton is dyed first and then nylon is dyed. According to the characteristics of the process, the stage of producing colored flowers can be divided into two stages: dyeing cotton colored flowers and dyeing brocade colored flowers.
1. Prevention and control of colored flowers during cotton dyeing stage
①Pre-processing
The main reason why cotton/brocade interwoven fabrics are not scouring through pre-treatment is the main reason for cotton dyeing. Preprocessing generally uses the following three methods:
1. Pre-treatment of jigger dyeing machine: large liquid volume, high padding temperature, low tension, less likely to produce wrinkles, and better scouring effect. However, it should be noted that unless the materials are in place, the temperature in the tank should not rise rapidly to avoid wrinkles and defects in the nylon yarn. The temperature must be gradually raised to above 95°C from the first pass to the second pass; after stabilizing, the number of processing passes must be more than eight. After unwinding, it must be fully washed on a flat washing machine to ensure the scouring effect.
(ii) Cold stack pre-treatment: its temperature is low, the reaction conditions are mild, and the treatment effect is not as good as that of the jigger. However, if the liquid volume is increased, the stacking process is extended and the short steaming process is added, the scouring effect can be improved. Short steaming must be strictly controlled and is not suitable for crawler box steaming, otherwise it will cause stacking and wrinkles.
(3) Pre-treatment of overflow dyeing machine: This is a traditional treatment method with ideal effect, but the process must be strictly controlled. The temperature must be gradually raised at a rate of 1°C/min; the valves at the front and rear of the overflow dyeing machine must be controlled moderately, and the cloth speed cannot be too fast. Otherwise, the cotton fibers on the surface of the cotton/brocade interwoven fabric will rub against the inner wall of the dye vat and cause fuzzing on the dyed cloth surface. Uneven.
2Dye
Due to the different affinity of different dyes to the fiber, the dyeing rate of the dye on the fiber is different. If coupled with improper control of various process conditions, color flowers and vat differences will occur. Therefore, when formulating the dyeing process, the performance of the dye must be fully considered, and dyes with good dye compatibility should be used for color matching as much as possible, and leveling agents should be added at the same time.
①Operations during the dyeing process
Due to improper operation, such as improper nozzle size, improper adjustment of the front and rear water flow valve switches, etc., the fabric cannot flow smoothly in the cylinder, causing the fabric to become clogged, resulting in uneven dyeing on the fabric. Therefore, the operator adjusts the mechanical equipment according to the tissue specifications of the fabric and formulates reasonable parameters to ensure that the fabric runs smoothly in the cylinder.
②Prevention and control of colored flowers during the brocade dyeing stage
(1) The alkali on the cloth is uneven
The uneven alkali on the cloth surface causes the acid dye on the cloth surface to be dyed inconsistently and cause stains. In response to this situation, in actual production, before dyeing nylon, use 2 to 3g/L detergent to neutralize and wash it to make the pH value of the cloth surface uniform and weakly acidic, thereby avoiding color stains caused by uneven alkali loading. .
㈡pH value
The pH value has a great influence on the dyeing rate of acid dyes. When the pH value is less than 3, nylon will hydrolyze and its strength will decrease. In actual production, if the pH value is controlled too high, if it is greater than 6, the dye will be dyed slowly, taking a long time, and is insufficient; if the pH value is less than 5, the dye will be dyed quickly, and uneven dyeing will easily occur. Therefore, controlling the pH value at 5.5 to 6.0 can ensure uniform dyeing. Adding 0.5~1.5g/L dye stabilizer can reduce the fluctuation of pH value.
3.Temperature
The temperature of the dye bath is directly proportional to the dyeing rate of acid dyes. The higher the temperature, the faster the dyeing rate. Especially when the temperature reaches above 80℃, the dyeing rate will increase.The speed will be faster and it is easy to produce colored flowers. In view of the temperature characteristics, a heat preservation stage is added during mass production. The light color is 50~60℃ and the heat preservation period is 15~20 minutes. The appropriate heating rate is 1℃/min.
4. Chelating dispersant
If the water quality is good, no chelating dispersant can be added; if the water quality is poor, 0.5~1.5g/L chelating dispersant can be added.
5. Leveling agent
When dyeing, leveling dye must be added. 0 5~2g/L. Nylon leveling agent is a zwitterionic and amphiphilic leveling agent. It can be combined with nylon to eliminate the difference in nylon fiber affinity, and has good nylon dyeing horizontal strip coverage performance. It can also be combined with dyes to have good slow dyeing and migration effects without affecting the final color yield. Nylon leveling agent pre-scouring process can be used for color-striped fabrics, and it can be used to repair colored fabrics and fabrics with serious color differences by dyeing migration.
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