Crease problem:
The boiling, bleaching and dyeing processing of knitted fabrics are generally carried out in overflow tanks. During the entire processing process, the fabrics remain in a rope-like state, and the fibers are continuously bent and deformed in the dyeing machine. The original hydrogen bonds are constantly destroyed, and new hydrogen bonds are constantly formed. Sometimes the newly formed hydrogen bonds cannot be fully restored, so chicken paw prints and dead creases are formed on the surface of the fabric.
In a single-sided fabric structure, the tension of the two yarns is asymmetrical, and it is difficult for the fabric to recover after being wrinkled in one direction for a long time. Therefore, in various structures, plain weave, sweatshirt , single pique, etc. are more likely to have fine wrinkles. The generation of fine wrinkles is also closely related to the yarn count and twist. The smaller the yarn count, the higher the twist, and the greater the possibility of reversal and untwisting of the yarn. This is reflected in the problem of fine wrinkles on the cloth surface.
The general dyeing and finishing process is:
Preparing cloth → sewing → dropping into vat and boiling and bleaching → dyeing → soaping → Fix color→soften→out of the vat→dehydration→dry the cloth with a shock wave machine or air dryer, and fine wrinkles are mainly formed in the dye vat, dehydrator, and fabric stacker…
According to its formation conditions, improvements are mainly made from the following aspects:
1. Pre-shaping
Improving fiber through pre-shaping Proximity and orientation, the fiber microstructure and morphology change when the fabric is heat-set. When the fabric is set, the fabric is fully stretched and set under the action of high temperature. The fiber shape is fixed, which reduces the chance of changes in the dye vat, and has Helps reduce creases.
2. Eliminate internal stress before lowering the cylinder
After loosening the cloth Fully relax the cloth in the stacking truck. The gray cloth is generally stored in the warehouse, and the relative humidity in the warehouse is low. If the cloth is stacked together in a very dry state for a long time, it is easy to produce indentations. After loosening the cloth, it should be placed in the workshop. Places with high humidity regain moisture, and the fibers swell to a certain extent when moisture regains, and the internal stress is partially eliminated; it is eliminated through the J-shaped groove. After loosening the cloth, let it pass through the J-shaped groove freely, and at the same time, it is squeezed by the pressure roller or drafted by the roller. The original hydrogen bonds are changed, which is conducive to eliminating internal stress; the creases on the fabric surface are reduced through open-width stretching and superheating. Knitted gray fabrics are generally cylindrical, and the fabric surface can be fully stretched through the fabric guide ring. At the same time, Spray wet steam or superheat water to reduce creases. When superheating water, a certain amount of penetrant and smoothing agent can be added to fully moisten the cloth.
3. Boiling, bleaching and dyeing
Pay attention to the cloth capacity of the dye vat , when discharging dye, it should generally be reduced by 10 to 15% according to the regulations of the dye vat. It must not be overloaded. When the amount of cloth is too large, the fabric will be seriously stressed in the cloth storage tank and cannot be stretched at the nozzle, and it is easy to form indentations.
Pay attention to the heating and cooling rate. When the heating or cooling rate is too fast, the temperature of the cloth body is likely to be uneven. When it is concentrated on one point of the fiber, the fiber will have different degrees of coldness and heat, and the shrinkage will be uneven. Especially when the temperature is lowered, it is easy to be suddenly cooled locally, and the shape of the plastic fibers is solidified, forming wrinkles that are difficult to eliminate. Therefore, after a high-temperature process, the temperature is generally lowered to 70°C for drainage at a rate of 1 to 1.5/min, or cold water overflows directly after the high-temperature process, and the temperature is lowered before complete drainage;
Lubricants are added to the dye bath to reduce friction between fabrics and between fabrics and machinery, thereby reducing the chance of wrinkles. However, the selection of smoothing agents must take into account stability, compatibility with processing procedures, etc. problems and avoid other problems caused by improper lubricant selection.
Choose more advanced machinery, increase the width of the cloth storage trough, and reduce the height of the lifting drum, which will help reduce the pressure on the cloth body. When using an air cylinder, the fabric will be at the nozzle After being fully blown open by high-pressure gas, the fibers get a “rest” from the tense state, which is conducive to the elimination of internal stress.
4. Drying method
When the fabric is dehydrated and dried , the fabric is dehydrated in a high centrifugal force dewatering machine. If the time is too long, it is easy to produce wrinkles that are difficult to eliminate. Many dyeing factories are gradually adopting the method of open-width water-drying, which not only improves the drying efficiency, but also helps to solve the wrinkle problem. solution. After padding, the cylindrical fabric can be widened through the guide ring and then dried using a shock wave machine. The open-width fabric can be widened and dried using a needle chain.
5. Cloth stacking method
The weight of cloth stacking on the cloth truck It should not be too large and the time should not be too long, especially when storing wet cloth. Generally, the amount of cloth per vehicle should not exceed 300Kg, and the storage out of the cylinder should not exceed 6 hours.
The problem is the result of the entire process. It cannot be solved by adding an additive. It is related to the fiber, the fabric structure, the processing technology, and the processing. It is related to the equipment. After creases appear, generally minor creases can be solved by widening and shaping with a setting machine. Stubborn ones can be returned to the tank for washing water, and the temperature can be gradually raised to 85°C and then repaired in a process test where the temperature is gradually cooled to 50°C. Or it can be reshaped by adding steam shrinkage in an industrial polishing dryer. The dyeing factory can perform repairs according to their own equipment and crease conditions. </p
