In recent years, as more and more customers realize that package yarn dyeing has low loss, high quality, fast delivery and good profits, orders for package yarn dyeing have grown rapidly. However, the dyeing process of polyester package yarn is complex and demanding, and there are many influencing factors that are difficult to control. A slight negligence can easily cause color stains.
1. Dyeing mechanism
Polyester cheese yarn dyeing is carried out on a high temperature and high pressure cheese yarn dyeing machine using high temperature and high pressure dyeing. Due to the tight structure of polyester fibers, disperse dyes hardly stain at low temperatures. Only when the temperature is increased to above 90°C, the dye uptake gradually increases. When it reaches above 110°C, the movement of the polymer chain segments in the amorphous region of the polyester fiber intensifies, increasing micro gaps, reducing the resistance of dye molecules to diffuse into the interior of the fiber, increasing the diffusion rate of dye molecules, and increasing the dyeing rate of disperse dyes. Increase rapidly. Satisfactory dyeing results can only be obtained at 130°C. The dye utilization rate reaches more than 90%, the color is plump, and various dye fastnesses are excellent.
Polyester bobbin yarn dyeing is to use the pressure of the main pump on the dyeing machine to make the dye liquid penetrate the yarn layer wound on the porous bobbin at a certain temperature, so that the dye molecules come into contact with the fiber molecules, and the dissolved dye It is first absorbed by the outer layer of the fiber, and then diffuses into the interior of the fiber to achieve the purpose of dyeing.
2. Factors that easily cause color flowers and their control
2.1 Pine tube
Polyester bobbin yarn needs to be loosened before dyeing. Stainless steel spring tube is the first choice for Songjian. Its advantage is that the effective penetration area is particularly large, which is very beneficial for obtaining level dyeing. It can be compressed freely and has strong adaptability to orders with different batch numbers. The winding density of the package yarn is very important. Taking into account the lift height of the pump of the dyeing machine, the appropriate winding density of the polyester package yarn is 0.33-0.39g/cubic centimeter. If the winding is too tight, it is difficult for the dye solution to penetrate the thick yarn layer, and the partial color will be lighter due to too little contact with the dye, resulting in dyeing defects such as color flowers or color circles. If the winding is too loose, the yarn will easily deform and fall off, causing mess. Yarn, difficult to get on the machine.
2.2 Pre-processing
The purpose of pre-treatment is to remove the oil stained on the polyester yarn during the pre-dyeing processes such as spinning and cone dyeing. Demeijing 3381g/L is usually used, and sodium carbonate 2g/L is added at 80°C. Process for 20 minutes under the conditions.
It must be noted that it must be cleaned after pre-treatment, otherwise it will easily cause flower stains.
2.3 Selection of dyes
High-temperature and high-pressure dyeing should try to use dyes with small molecular weight and excellent dispersion. Domestic disperse red E-4B, disperse yellow E-3RL, and disperse blue E-4R are a well-matched low-temperature dye combination. Can spell out most common chromatographic systems. Taking into account the European Community and other restrictions on the prohibition of the use of substances that may and may contain carcinogens, satisfactory dyeing results can also be obtained by using disperse yellow SE-4RL instead of E-3RL. Products with particularly high fastness requirements need to use high-temperature dispersions. Dyes, this combination often chooses Disperse Red S-5BL, Disperse Orange S-4RL, and Disperse Blue S-3BG. Most colors can be produced and the cost is relatively low. However, the amount of dispersant needs to be increased, otherwise dyes will be formed. They gather together, causing stains that are difficult to remove.
2.4 Selection of additives
The use of leveling agents is of extremely important significance in high temperature and high pressure package yarn dyeing. The leveling agent selected must have small foam, good dispersion at high temperatures, and strong dye migration. The requirements for water quality when dyeing packages are extremely high. The integrated dispersant R-DL has a strong ability to integrate Ca ions and Mg ions in the water. The usual dosage in the dye liquor is 0.5g/l, 1g/l, which can reduce The hardness of the water can increase the dispersion ability of the dye and prevent the dye from gathering on the yarn and forming dye spots.
2.5 pH value requirements
High temperature and high pressure package yarn dyeing requires the pH value of the dye bath to be controlled at 4.5-5.
2.6 Control of liquid flow
Controlling the direction of the liquid flow is a key factor in achieving level dyeing. Poor control will cause color difference between the inside and outside, and what is reflected on the fabric surface is the color gradient. The control of the liquid flow direction requires long-term exploration and depends on the pressure of the pump. Under normal circumstances, a forward cycle of 3 minutes and a reverse cycle of 4 minutes are used to make the inner and outer colors of the dyed yarn consistent.
2.7 Control of heating rate
When the dyeing temperature is below 85°C, the dye rarely stains and the temperature can be raised directly. 85℃-110℃ is the temperature area where the dyeing speed increases rapidly, and the temperature rise rate needs to be strictly controlled below 1.5℃/min. It can be slightly faster within the range of 115℃-130℃, but the heating rate still needs to be controlled at about 2℃/min.
The heat preservation time here is for medium-depth colors. Light colors can be appropriately shortened, and dark colors can be appropriately extended. The heat preservation time must be appropriate. If it is too short, ring dyeing will occur, and if it is too long, it will easily produce lint. Generally it should be controlled within 30–60min.
After dyeing, the temperature should be cooled down quickly, because oligomers will be produced during the slow cooling process, and their residues will be tar-like on the yarn surface and difficult to remove.
2.8 Restoration cleaning
Reduction cleaning is an important process after dyeing polyester package yarn. It can not only wash away the disperse dyes adsorbed on the surface of the yarn to ensure the dyeing fastness, but also remove other substances adsorbed on the surface of the yarn during the dyeing process to reduce the occurrence of dye spots.
2. ColorFlower repair
Package yarn dyeing can generally be repaired. The method of repair is to transfer the dye from dark areas to light areas by means of the transfer effect of leveling agent under high temperature conditions. Repair agent L is a low-foaming leveling agent with efficient dispersion and strong dye transfer ability. Increase the dosage to 3g/L-5g/L. Used as a repair flower, the success rate is as high as 95%. We once mixed colored yarns of different colors together, used repair agent L5g/L, added acid to adjust the pH value to about 5, and treated it at 135°C for 60 minutes. Then check the color difference between each package of yarn. The color difference is very good and difficult to distinguish.
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