In the daily production of printing and dyeing factories, there are many factors that affect the color accuracy of finished polyester fabrics. The accuracy of laboratory proofing is undoubtedly the most important among many factors. Continuously stabilizing and improving the accuracy of laboratory proofing in printing and dyeing factories is of great significance to improving color accuracy. This article takes polyester dyed with disperse dyes as an example to illustrate this issue from aspects such as sampling equipment, dye weighing and chemical mixing, fabric weighing and preparation, and daily management of the laboratory.
Equipment
Commonly used polyester proofing equipment includes high temperature and high pressure proofing machine, glycerin proofing machine and infrared proofing machine machine; each of the three types of equipment has its own characteristics.
1. High temperature and high pressure proofing machine
The maximum working temperature of this type of proofing machine is 130°C. Adjust the heating speed and use two electric heating tubes as heat sources. It can hold up to 12 dyeing cups, and the connecting rod device drives the hook with the sample on it to move up and down to complete the proofing process. The maximum capacity of the dye cup is 300ml, and the weight of the fabric determines the liquor ratio.
The amount of dye solution added during proofing is determined by the dyeing formula. Finally, water is added to two-thirds of the height of the entire dye cup, which is about 200ml. The liquid level is too high and the liquor ratio is too different from the actual liquor ratio in production, which will affect the accuracy of the color. If the liquid level is too low, the sample may not be completely submerged by the liquid level when it rises with the hook, causing the sample to be discolored.
Commonly used dyeing cups include glass dyeing cups and stainless steel dyeing cups. The diameter of the new dyeing cup should be checked before use. If the diameter is too large, it will easily cause the cup to get stuck after dyeing. If you use too much force when taking out the cup, the glass dyeing cup may be easily damaged. Not only is it easy to cause hand injuries to the proofer, but the small broken glass can also easily cut the sealing ring between the hemispherical gland of the proofing machine and the entire proofing machine platform, affecting the next proofing.
The glass dyeing cup makes it easy to observe the state of the dye liquor and facilitates the factory inspection of new batches of dyes. When using a stainless steel dye cup to test a new batch of dye, you must pour the dye solution into the beaker before observing. Although stainless steel dye cups are not easily damaged, if the surface finish is not high, the efficiency of cleaning the dye cups will be reduced.
In addition to cleaning the small sample machine once a week, when the glass dyeing cup is damaged, all broken glass that fell into the bottom of the small sample machine must be cleaned up, otherwise it will easily cause regular cleaning of the small sample machine. The sampler’s hand was injured.
Drain all the water when cleaning, and check and clean the surface of the electric heating tube. If the scale on the surface of the electric heating tube is not cleaned for a long time, it will not only affect the heating efficiency, but also easily cause the electric heating tube to burst.
If it is found that the surface of the electric heating tube is bulging or significantly deformed during cleaning, it should be replaced in time to avoid affecting the heating speed. Every time after water is discharged from the bottom of the proofer, check whether the bottom water valve is closed tightly when adding water. If the bottom valve is not closed tightly and water leaks slightly, it will easily cause corrosion at the bottom of the small prototype or leakage of electricity, causing safety accidents. After each sample is hung on the hook, it must be fixed as necessary to avoid color stains after unhooking. If it is fixed too tightly, it may easily cause damage to the glass dyeing cup. When the sample is hung on the hook, if there are too many unsmooth wrinkles, the light-colored sample will form color flowers or color casts because the sample is not kept warm for a long time.
2. Glycerin proofing machine
After being heated, it can produce high temperature under normal pressure. It is glycerin main features. The heating principle of the glycerin proofing machine is the same as that of the high temperature and high pressure proofing machine.
Glycerin proofing machines are available in two types: 12-cup dyeing cup type and 24-pin dyeing cup type. The dye cup capacity of the glycerin proofing machine is larger than that of the high temperature and high pressure proofing machine. The adjustment of liquid level directly affects the liquor ratio of proofing. The degree of automation of glycerin proofing machine is higher than that of high temperature and high pressure proofing.
If the liquid level in the dyeing cup is too high and the liquor ratio of the dye liquor is too large, there will be a large difference between the liquor ratio of the small sample proofing and the actual large sample produced, which will affect the production process. Color accuracy.
If the liquor ratio during proofing is the same as the actual production liquor ratio, the liquor ratio in the dye cup will be too small and the liquid level will be reduced. As for the dye cup that is similar to the rotation of a wheel, the dye liquor inside the dye cup may not be completely impregnated with the sample during operation, thus affecting the levelness of the sample and affecting the proofing efficiency.
The volatilization of glycerin occurs with the evaporation of water in the glycerin heating pool. The moisture inside the glycerin mainly comes from the inside of the dye cup during proofing. The lid of the dyeing cup corresponds to the cup body one-to-one. Putting on the wrong lid or insufficient force when attaching the lid are the main reasons for the leakage of the dye cup.
Cover it and turn it upside down for a moment to determine whether the dye solution will leak out. The leakage of the dye solution not only affects the accuracy of the color of the sample, but also causes a large amount of glycerin to volatilize, filling the laboratory with the smell of glycerin and causing some samplers to feel uncomfortable. When putting the dye cup into the dye cup holder, be sure to check whether it is really stuck. If it is not clamped, a cup jam accident will occur, which will cause great damage to the small prototype. In severe cases, the motor of the small prototype may be burned or the gearbox may be damaged.
For the maintenance of the heating device of the glycerin prototype machine, refer to the maintenance method of the electric heating pipe of the high-temperature and high-pressure prototype machine. After proofing, the dye cup can be placed in a self-made glycerin recovery device for a certain period of time to allow the glycerin on the surface of the dye cup to drip into the recovery device. Consciously recycling glycerol is an effective way to save glycerol. As glycerol evaporates, the interface height of glycerol inside the proofing machine will gradually decrease. Regularly checking the interface height and replenishing glycerin at any time are the guarantee.�The resulting color error.
The automatic dripping system coupled with the automatic color matching system can bring the color management of the printing and dyeing factory to a significant level. The magnetic stirrer of the automatic dripping system can reduce the chemical strength.
pH value
The pH value of polyester dyed with disperse dyes is 4 -6. Taking the domestic high-temperature and high-pressure jet overflow J-type tank as an example, the water in the dye tank during dyeing is 4t. Adding 1000ml of glacial acetic acid can adjust the pH value of the dye liquor to between 4 and 6. Acetic acid used for laboratory proofing can be prepared by dissolving 10ml of glacial acetic acid in 1000ml of water. When proofing, add 10ml of diluted acetic acid to the dye cup to ensure that the pH value of the dye solution is between 4-6.
Fabric
1. Weighing of fabric
The moisture regain rate of polyester fabric is low. When weighing the sample, you do not need to consider too much about the impact of the moisture content of the dry fabric on the color accuracy. The electric fan must be turned off when weighing fabrics in summer. Enterprises with conditions can install air conditioners in the laboratory. The weight of the sample fabric should correspond to the concentration of the dye.
2. Obtaining fabrics
Before sampling ordinary polyester fabrics, the laboratory technician can go to the blank warehouse Cut in the middle. When cutting the gray fabric, pay attention to the batch number of the gray fabric and keep the head of the gray fabric flush so that the seam head is convenient when preparing the fabric.
Light-colored gray cloth for proofing can be pre-processed in the laboratory. Add a little washing powder to hot water and run it through the washing machine to complete the pre-treatment of the fabric sample.
The washed fabric samples should be dried in a clean oven before use. The temperature in the oven should not exceed 100°C. Polyester fabrics that require alkali reduction must be reduced before they can be sampled. At the same time, the sample fabric for weight reduction must be pre-shaped.
The sample hanging box of the intermittent alkali reduction equipment can not only be used by the shift leader in the reduction process to control the reduction feel of the fabric, but can also complete the reduction of the reduction fabric for proofing.
The control of the feel of the sample fabric can be completed by the weight reduction shift leader. The sample fabric of elastic fabric can only be obtained after reservation. The fabric is pre-shrunk and pre-shaped, and the orientation of the fibers is more uniform. This will affect the dyeing depth of the fabric. After weight reduction, the specific surface area of the fiber increases, which will improve the dyeing depth of the fabric. Stretch fabrics are pre-shrunk and pre-shaped to improve the dimensional stability of the fabric; weight-reducing fabrics require both pre-shaping and alkali weight reduction. Therefore, the accuracy of the color of this type of fabric can only be guaranteed by using the sample fabric after the reservation or reduction.
Color management
Only through the comparison of samples after dyeing in the vat It is not enough to ensure color accuracy. Most of the samples received from customers are finalized after the final product is finalized.
Thermal migration and sublimation of disperse dyes mainly occur in the setting process, which will further affect the accuracy of the color. Each shift leader in the styling process has the same responsibility for controlling color accuracy as the dye shift leader. In the process of controlling color accuracy, the responsibility of the production technical section chief should be greater than that of the dyeing workshop director and styling workshop director.
The laboratory should have a customer color filer. The laboratory shift leader, dyeing shift leader and finished product styling shift leader are the persons directly responsible for providing the color administrator with raw materials for customer color files.
Customer color files should be created. Samples from customers, color samples produced by the laboratory, large samples dyed in the dye vat, and color samples after finalization should all be retained in the customer’s color file. Accurate printing of incoming samples is the basis. Only by appropriately adjusting the dyeing formula and dyeing process according to the color produced in the large vat of the workshop, and by appropriately adjusting the shaping process according to the color after finalization, can the accuracy of the color be truly guaranteed. </p
