The mechanism of crease production
1. The boiling, bleaching and dyeing processing of cotton knitted fabrics are generally carried out in overflow tanks. The fabrics remain in a rope-like state, and the fibers continue to bend and deform 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, etc. are formed on the surface of the fabric. Dead crease.
2. 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, plain weave is used in various structures. , sweatshirts, etc. are more likely to have crease problems, especially on fabrics with less or larger weight.
The occurrence of creases is also closely related to the yarn count and twist. The smaller the yarn count and the higher the twist, the greater the possibility of reversing and untwisting the yarn and the easier it is. There is a crease problem.
▲J-type overflow cylinder
The main process step of crease generation – boiling and bleaching
1. The general dyeing and finishing process is: cloth preparation → seaming → lowering and boiling Bleaching → Dyeing → Soaping → Fixing → Softening → Out of the vat → Dehydration → Shock wave machine or air dryer to dry the cloth. Generally, many people think that the formation of creases is mainly in the dye vat, but our engineers have proven through rigorous experiments : In fact, most cotton knitted fabrics have formed creases during the boiling and bleaching stage, but it is not easy to observe them before dyeing.
2. According to the many years of experience of our engineers, it has been confirmed that the following types of fabrics and equipment are prone to creases during the cooking and bleaching stage:
Fabric reasons: single-sided cotton fabrics with small or large weight (eg weight 300g), especially cotton stretch fabrics (with spandex);
Equipment reason: Compared with the L-type overflow cylinder, the J-type overflow cylinder is more prone to creases due to its strong tensile force; while the air flow cylinder is less prone to creases because the fabric is fully blown open by the high-pressure gas at the nozzle , the fibers get a “rest” from the tense state, which is conducive to the elimination of internal stress to reduce crease problems;
Process reasons: Fabrics that have not been pre-shaped are more likely to have creases Problem: The fabric is shaped under high temperature, which can improve the fiber proximity and orientation. The fiber shape is fixed, which reduces the chance of changes in the dye vat and helps reduce creases.
350g pure cotton knitted flannel (no creases after dyeing)
140g pure cotton knitted jersey (no creases after dyeing)
Boiled Solution to creases
1. General method: add polyacrylamide type lubricant (such as Yuzhongbao) during bleaching and dyeing. This type The main function of the lubricant is to “reduce the friction between fabrics and between fabrics and machinery”, but it is difficult to solve the creases formed during cooking and bleaching.
2. The solution in this article: Use the following additives, processes, and operations to improve creases during cooking and bleaching. It has been confirmed by multiple customer applications that the results are satisfactory.
Auxiliaries:
A. Preferably high strength and solubility polyacrylamide bath anti-wrinkle agent JET (non-ionic), its function is to reduce the friction between fabrics and between fabrics and machinery;
B. Use a new anti-wrinkle softener RCE (non-ionic), which Its function is to give the fabric itself good softness and smoothness, as well as level dyeing properties. The combined use of the above two auxiliaries is the core of this method.
Process: Reduce the heating rate; the focus is on reducing the cooling rate, generally 1.0~1.5℃/min is better.
Operation: Before entering the cylinder, the gray fabric should be placed in a place with high humidity in the workshop to fully regain moisture. The fibers will swell to a certain extent when moisture regains, and the internal stress will be eliminated, which is beneficial to reducing creases. ; After loosening the gray fabric, let it pass through the J-shaped groove freely, and at the same time, it is squeezed by the pressure roller or stretched by the roller, which is beneficial to eliminating internal stress and reducing creases.
3. Process examples
Add refining penetrant before boiling and bleaching Wait, put the anti-wrinkle agent JET and the anti-wrinkle softener RCE in the bath without raising the temperature first, and then circulate it for 20 minutes after entering the fabric, so that the gray fabric is fully moistened and the additives fully react with the fabric fibers. If bleaching is required, caustic soda and hydrogen peroxide can be added before heating.
Reduce the heating rate; especially the cooling rate, generally 1.0~1.5℃/min is better; and the temperature must be completely cooled to 50℃ before the liquid can be drained for dyeing.
Other things to prevent creases
1. In order to prevent the occurrence of creases, it is recommended to add a polyacrylamide type lubricant – bath anti-wrinkle agent JET during dyeing, and reduce the cooling rate.
2. When dehydrating and drying cloth, you can use the method of rolling dry cloth with open width, which not only improves the efficiency of drying cloth, but also is beneficial to the drying process.Solve the scar problem.
3. When stacking cloth on the cloth truck, it is recommended that the weight should not be too large and the time should not be too long, especially when storing wet cloth.
4. If the crease problem cannot be completely solved using this solution for cotton stretch fabric (with spandex), you can consider the pre-shaping process.
5. Generally, slight creases can be solved by stretching and shaping with a setting machine. Stubborn ones can be returned to the wash water tank, gradually raising the temperature to 85°C, and then gradually cooling it to 50°C. ℃ process test and repair, or it can be reshaped by adding steam shrinkage in an industrial polishing dryer. The repair can be carried out according to the respective equipment and crease conditions. </p
