In the textile industry, dyelot chromatism refers to the color difference when the same gray fabric is dyed with the same color in different dyeing vats. This is a widespread problem. The vat difference is also the color difference between the first vat of cloth in dyeing and the next vat. The color difference generally refers to the color difference of the same kind of dyed cloth, including vat difference and the color difference in the same vat.
Causes of cylinder differences
The influence of the remaining dye liquid in the dye vat
Dyeing in the dye vat causes vat differences. Mainly refers to a small amount of residual liquid after dyeing in the previous tank, and various dyes are present in the residual liquid. Because the dye uptake rate of each dye is different, during the continuous vat dyeing process, the dye is replenished more times, so the error is larger and vat differences are easy to occur.
The influence of temperature
Like other dyeings, under the condition that the dyeing process can reach a balance, the dyeing percentage will change with the dyeing process. It increases with the decrease of temperature. The temperature during dyeing is 60 degrees. If the temperature is lower than 60 degrees, it will affect the dyeing rate and make the fiber color yield too low. If it is higher than 60 degrees, the dye will be easily hydrolyzed, affecting the dyeing rate and the fiber color yield. The rate is low.
The influence of dyeing time
The longer the time, the easier the color will be, and the color will be deeper. Therefore, the length of dyeing control time of the cylinder blocker will produce cylinder differences.
The influence of electrolyte
Reactive dye molecules are relatively small, have good diffusion performance and good leveling effect , therefore when dyeing, a larger amount of electrolyte can be added to promote dyeing, effectively increasing the dyeing percentage. However, too much electrolyte can also cause dyeing instability.
The influence of alkali agent
Reactive dyes bond with cellulose molecules in alkaline medium While fixing, the dye will also undergo alkali hydrolysis. Although the reaction between dye and fiber is fast, if it is not handled well, the amount of dye hydrolysis will increase. Therefore, under the condition of ensuring good color fixation, a lower pH value should be used as much as possible, generally controlled at 10-11. Insufficient dosage of alkali agent will affect the dyeing fastness and color yield; too much dosage, the pH value will be too high High, which causes a large amount of hydrolysis of the dye and reduces the fixation rate of the dye on the fiber.
The influence of liquor ratio
The so-called liquor ratio refers to the ratio of fabric to water. When dyeing with reactive dyes, the concentration ratio of the dye in the aqueous solution and in the fiber is constant and close to a constant no matter what the conditions are. Obviously, when the amount of dye remains unchanged and other dyeing conditions are the same, a small liquor ratio is beneficial to the dyeing process.
The influence of soaping
When dyeing with reactive dyes, dyes that are not fixed due to hydrolysis, It is not easy to wash off the fiber. During post-processing, washing must be strengthened, otherwise it will affect the washing fastness and rubbing fastness of the dyed material. Causing different colors.
The weighing of materials is inaccurate
Due to different dyeing colors, different formulas are used. The materials used will definitely cause color changes, and improper operation will cause cylinder differences.
Different dyes
Different dyes refer to vat differences caused by not using the same batch of dyeing materials.
Cylinder difference caused by cloth
Use different batches of cloth because different fibers have different properties.
Measures to save vat failure
1. Semi-finished fabrics are generally desized, scoured, and oxygenated before dyeing. After bleaching and other treatments, the fabric should not contain residual oxides, alkali agents and other impurities, and the wool effect on the cloth surface should be uniform.
2. The hardness of water used for fabric dyeing and finishing must not be higher than 100PPm.
3. The dye must be fully dissolved before dyeing.
4. Strictly operate according to the process, strictly control the liquor ratio, time, temperature, addition of electrolyte, alkali, additives, etc., and dyeing and fixation solutions must maintain regulations. quantity.
5. After color fixation, it must be fully washed and soaped to remove floating color and hydrolyzed dyes in order to obtain normal color light and fastness.
Control of color light deviation during production
Within the △E range allowed by the customer, production should be uniformly controlled to +△ E or -△E deviation, if there is ±△E (chromatic light deviation of complementary colors) at the same time, it is very likely to be rejected by the customer because the cylinder difference is too large, although at this time △E is still within the range required by the customer.
In addition, the uniformity and uniqueness of color standards must be ensured during production in the dyeing workshop. The coexistence of multiple standards is extremely detrimental to truly controlling cylinder differences. Since the real sample standards will change with time and space, it is necessary to update the real color samples in a timely manner. With the development of computer technology, the use of computers for digital management of color differences can effectively solve the above problems. This is one of the development directions for enterprises to realize modern management.
Correct color adjustment method
Because the color light deviates from the standard requirements, in-machine color adjustment is often performed during the dyeing process. operations performed. The color mixing methods used by each factory are different, but a common principle is: when the color light is reddish or darker, it is advisable to use the post-soap color mixing method, because experience shows that red reactive dyes will fade over time. There is a continuous dyeing process, and the color will become more and more red; when the color is yellowish or bluish, it is advisable to use the “half-foot water” color mixing method, which will be faster and more effective; when the overall color is lighter When doing so, it is advisable to adopt the proportional “whole foot water” total addition method.
Correct cylinder allocation method
Rational cylinder allocation is also helpful in reducing cylinder differences.� Method, in principle, the fewer the number of cylinders of the same color, the better. When the number of cylinders for a color is 2 or more, the first cylinder will be dyed first and the original process will be carried out. If the color and light of the first cylinder does not match, the process formula will be adjusted before dyeing the second cylinder; and then the second cylinder will be dyed. The first cylinder is to be color-adjusted according to the color of the second cylinder, and all subsequent dyeings are to be carried out according to the second formula. Of course, when the number of tanks is only 2, dyeing and color mixing can also be performed at the same time.
It is worth noting that the capacity of the first tank should be as small as possible. After all, color mixing is a risky operation in the dyeing process. In principle, the risk should be controlled. within the minimum range. In addition, when dyeing the same color in the same dyeing machine, try to achieve the same amount of cloth each time, which is of great benefit in reducing vat differences.
Summary
In short, there are many factors that cause cylinder differences, and controlling them is a complex process. Simply put It is not objective enough to attribute it to technical or management factors. Each factory has its own set of experience methods on how to control it. In actual production, only with the joint efforts of relevant technologies and front-line managers, the probability of cylinder errors will be reduced. </p
