How does the printing and dyeing factory solve the problem of two colors on one piece of cloth? What is the reason for color difference and dyeing defects?

During the dyeing and finishing process of textiles, there are many factors that affect the overall dyeing and finishing results. Therefore, in actual large-scale production, quality problems of one kind or another are often encountered, among which those related to color and luster are particularly frequent. The first thing that can be listed is the color difference problem. The following describes how to solve the causes of color difference dyeing defects

1. Classification of color difference

Color differences are divided into the following types:

a． Stakeout color difference (difference between large and small samples);

b. Batch color difference is further divided into color difference between batches, cylinder difference in the same batch, and tube difference in the same cylinder;

C． Other color differences include front-to-back color difference, left-middle-right color difference, discoloration color difference (color change after post-processing and post-finishing), etc.

1.1 Stake out color difference

At present, dyeing and finishing processing basically needs to be carried out according to the color specified by the customer. The requirements for the color and pattern level are very high, and some customers are almost demanding. The lofting color difference is the color difference between the small sample and the large sample. This is also a problem that must be faced and solved in the first step of mass production. It can be seen that when the dyeing method of the small sample corresponds to the large machine, the smaller the color difference will be. However, the reality is that not many of the two are highly consistent, and usually can only reach a certain degree of similarity. There is even a considerable gap in the similarity between the two for some dyeing types (such as jigger dyeing). Therefore, the success of small trials cannot be equated to the success of large-scale production. Especially in the development or trial of new products, new materials, and new processes, the methods and procedures used in small-scale tests in the laboratory may not be able to be copied to the workshop for large-scale tests, and sometimes there may be a huge gap between the two. To this end, in addition to matching appropriate and advanced supporting instruments and facilities such as small prototype machines, when conditions permit, a sample test of one piece of fabric (or 1-2 bobbins) should be carried out in the middle, and then the next step can be carried out. The big test will undoubtedly be more beneficial and safer. Because the effect of the pilot test is much closer to that of the large machine than the small test.

Accurate lofting once has always been the goal pursued in technology. Accurate lofting once is of fundamental significance to the prevention of cylinder errors. This problem is not only inseparable from the advancement of laboratory equipment and facilities, but also involves the level of technology and technical management. There is no doubt that it is also one of the key technologies of printing and dyeing enterprises, which is closely related to the widely praised “dyeing is successful in one go” ”, requiring it is even more of a prerequisite. Transforming the traditional “post-event adjustment” to “pre-emptive control and control” is the solution to the problem of setting out onceaccurate premise. At the same time, a large amount of detailed and detailed basic work is essential to grasp the evolution and rules of color throughout the entire production process.

1.2 Batch Color Difference

1.2.1 Color difference between batches

Batch color difference includes color difference between different production batches and color difference with batch nature in the same batch. Batch color difference has always been a long-standing problem in Jie color production, and it involves a wide range of areas. Its prevention and overcoming should be a systematic project.

The factors that lead to batch color difference can be summarized as follows:

a． Different origins of fiber raw materials, as well as different batches and batch numbers, have differences in dye absorption rates;

b. Different origins of dyes, auxiliaries, and chemical raw materials, as well as different batches and batch numbers, have differences in the content of their active ingredients;

c. The rationality of cylinder allocation and cylinder arrangement in planning and scheduling (different models of dyeing machines have differences in color and luster, and improper cylinder configuration and planning arrangements are also related to batch differences and cylinder differences);

d. The standardization of the execution of process conditions (determined by the quality of personnel and the level of management) is not only in the dyeing stage, but also in various production links such as pre-treatment and post-finishing.

If there is a problem with any of the above four points, it will affect the production of batch color difference. If the company’s technology and management are deficient, it is very likely that multiple influencing factors will occur concurrently, making the search for the real cause more complex and difficult.

1.2.2 Differences between cylinders in the same batch

Tank error is another common problem in batch dyeing. First of all, the preparatory stage is the prerequisite for the rationality of the blank cylinder configuration, and the biggest source of influence is the group quality of the front-line operators in the workshop, that is, whether the operation execution of the process meets the requirements, and the individual operators , each machine and each shift is highly unified.

The weighing and measuring of dyestuffs must be accurate. This is a clear and simple truth. However, in the actual work of the dye and chemical material warehouse, it is easy to make mistakes, so it needs to be equipped with procedures and systems such as review and review to provide sufficient guarantee. Even if it is equipped with a modern automatic weighing and feeding system, it cannot be absolutely guaranteed to be foolproof.It is not completely impossible for the system to malfunction or suffer human control errors after working for a long time. If maintenance and inspection management are neglected, especially on continuous production lines, the batch volume will be very large if something goes wrong.

It is also worth noting that the lofting work is also closely related to this problem. If you always need to rely on adding dye to correct the color, then the problem of cylinder difference will definitely increase.

1.2.3 Pipe difference in the same cylinder

Pipe differences occur in dyeing machines such as multi-cylinder parallel large-capacity liquid flow and jet dyeing machines. Large-capacity dyeing machines are designed to reduce or even eliminate the chance of tank differences. However, both advantages and disadvantages are that this will also bring about pipe differences. This is a formal method of equipment dyeing operation. decided. The more cylinders connected in parallel, the larger the single loading capacity of the dyeing machine will naturally be, but the more likely it is that pipe errors will occur. Therefore, in order to pursue the expansion of single dyeing capacity, it is not advisable to increase the number of cylinders in parallel too much, and it can only be done in moderation. It can be said that tube difference is essentially another form of cylinder difference in this type of dyeing machine.

Summarize the factors that cause pipe differences. Avoiding differences in the rough cloth distribution cylinder in the preliminary preparation process is the first step to prevention. Maintaining the normal operation of the equipment is more important than conventional single-cylinder dyeing machines. , and the strict and conscientious and random tracking system in blocking operations are also essential. Because the inspection and identification of tube defects, as well as the color correction and repair, are far more complicated, troublesome and inconvenient than the cylinder defects, especially for polyester, polyester-cotton, viscose and other blended fiber fabrics that need to be overdyed. Dyeing and pipe defects may occur again. If you wait until the dyeing is completed before discovering it, color correction and repair will be very costly.

1.3 Other color differences

1.3.1 Color difference before and after

The color difference between the front and back is likely to occur in the dyeing of continuous dyeing long car pad dyeing machines and large package jigger dyeing machines. This is determined by the dyeing form of the second type of equipment. It is generally not easy to occur on intermittent loose-type exhaust dyeing machines. However, if the dyeing operator blindly seeks speed and quickly heats up while adding dye, then the front and rear color differences will also occur on the loose-type exhaust dyeing machine.

In addition, when polyester fabrics are heat-set, the dyes sublimated in the setting machine are not properly removed, resulting in sublimation stains on the subsequent fabrics, especially when dark colors are changed to light colors, or the production process of complementary colors Rowing often produces what is commonly known as setting and color matching, and the dye residue in the setting machine is gradually taken away, resulting in differences in color before and after.

1.3.2 Left and right color difference

The left and right color differences mainly occur in pad dyeing and jig dyeing, and are also caused by the dyeing form and method characteristics of the equipment, so the mechanical factors are often greater than other factors.

In pad dyeing, the main problem is that the left and right pressures of the pad are uneven and the symmetry is not uniform, resulting in uneven padding rates on the left and right; or the fluid replenishing system of the pad dyeing tank fails, resulting in uneven dyeing on the left and right. The liquid concentration is uneven.

In jig dyeing, the stretch roller of the jig dyeing machine is in disrepair and deformed, and the left and right arcs are asymmetrical and uneven, which will lead to inconsistent shaving rates on the fabric. The thinner the dyed fabric and the lower the water absorbency of the fabric, the more likely it is that left and right color differences will occur when dyeing some sensitive colors in which the three primary colors are dominant. In addition, irregularities in the feeding of dyeing materials into the machine and improper adjustment of the feeding tension of thin fabrics will also cause uneven dye concentration on the left and right sides of the dye vat, resulting in color difference between the left and right sides of dyeing.

For loose dip dyeing, strictly speaking, from the form, method and principle of dyeing machine operation, there should be no reason for the left and right color difference. However, in warp knitted fabrics, the problem of color difference in the edges will also occur from time to time. Some varieties of this kind of fabrics are prone to curling. When the curling is too serious, if it cannot open by itself in the dyeing machine, it will Causes chromatic aberration in the edges. This is caused by the variety characteristics of the fabric. It is completely different in nature and reason from the left and right color differences in pad dyeing and jig dyeing. Therefore, the method to overcome it should start from the process measures of weaving and dyeing.

1.3.3 Color change

Since some dye varieties will undergo heat-sensitive discoloration to varying degrees, the dyes must be screened first. In terms of additives, fixatives, cross-linking agents, softeners, waterproof and oil-repellent agents, and coating finishing agents The post-processing and finishing auxiliaries added and processed after dyeing will more or less and unavoidably have a certain color change effect on the color after dyeing. The longer the post-treatment and post-finishing process, especially the higher the post-finishing temperature and the more additives added, the greater the possibility of color change. Even mechanical finishing processes such as raising and sanding that are not directly related to dyes, additives, chemical raw materials, etc. will affect the apparent color of the fabric and cause color difference. Of course, the color difference caused by mechanical finishing is not caused by chemical factors, but is caused by changes in the surface of the fabric, which changes the basis of light reflection, thereby affecting the color perception of human eyes, resulting in a An optical illusion. This color difference is basically unchanged in hue, but the reflection in depth is more obvious, and it also affects the color and light. Although this color difference is due to physical reasons, customersThere is still a color change in perception, so it is still necessary to control it in advance and take precautions.

“Dyeing completed” in a comprehensive sense should be the end of the final finishing process, the finished product is fully cooled, and can be used for subsequent garment production. Only when the specified color is stably reflected can the dyeing task be truly completed. . However, it is unobjective and unrealistic to require post-processing and finishing additives not to affect color change at all (at least so far). Seriously speaking, this problem should also belong to the technical work category of “setting out color difference”, and we will also encounter the problem of effect difference between large and small tests (the difference is that the focus is on color). Therefore, this requires technical solutions in proofing and lofting work. First of all, when making small samples, we must strive to imitate the links, procedures, formal methods and process conditions of large-scale production, and also correct and overcome errors in pilot and large-scale tests.

However, what needs to be straightened out is that post-processing and post-finishing additives mainly affect and act on certain intrinsic qualities of textiles (such as various color fastnesses), as well as the feel, style, characteristics and special functions. wait. When it comes to color issues, dyes have a greater role and influence than dyes. For color correction, dyes undoubtedly occupy the first position. Mastering the evolution rules of color is the prerequisite for overcoming and solving problems. Technical solutions, with prior control as the focus, are the fundamental solutions.

It is worth mentioning again that the yellowing problem of amino silicone softeners. This type of softener now accounts for a significant proportion of the use of softeners due to its superior feel and good durability. However, there are some problems that must be paid attention to in terms of performance of this type of softener. In terms of performance indicators, the higher the amino content, the better the hand feel. However, the higher the ammonia value, the greater the yellowing value. Moreover, the higher the temperature and the longer the finishing time, the more oxidative and yellowing it will become.

Although the chemical industry has been improving and improving through modification and other methods, there are still certain conflicts. Therefore, special whites and bright light colors (especially purple tones) must be chosen carefully. Work. If necessary, only part of the requirement for softness can be given up to maintain the whiteness value.

2. The relationship and impact of “prevention is better than cure” and “first-time success”

The continuous pursuit and exploration of process technology is one of the important driving forces for the improvement and development of the industry. However, every new achievement in process technology and other aspects (such as dyes, chemicals, machinery and equipment, etc.) always has a relative retention period, and in terms of time, often exhibiting certain regular phases of long and short periods of time (sometimes more and sometimes less). On the other hand, in order to enable enterprises to maximize production efficiency and benefits, according to the level of technology mastered at the current stage, in the entire production process The consumption of various resources such as raw materials, energy, and water must be both necessary, reasonable, appropriate, and efficient to the maximum extent, which has become a guiding principle, and “dyeing is successful the first time” is the application of this principle in the process. Reflection in implementation.

“Dyeing is successful the first time” means that during the entire production process, the product does not have any abnormal phenomena such as repairs and re-dying outside the set process. To achieve this level, it is a systematic project that includes extensive and comprehensive content. In addition to the corresponding comprehensive strength in technology, management, equipment configuration and other aspects, it also includes the overall quality level of the front-line staff.

There is no doubt that “successful dyeing” can not only fully improve labor production efficiency, but also make full use of raw materials, energy, water and other resources. Therefore, “successful dyeing” is not only a means to improve product quality, but also an important way to save resources, save energy, reduce emissions, and improve corporate efficiency.

The traditional quality management method is to inspect the finished products and then grade them according to the quality grading standards. But at this time, the product has been completed, and the quality status of first-class products, second-class products, and second-class products has been established, and it is objectively difficult to change and effectively remedy it. The epidemic prevention mechanism in the medical community has provided us with great inspiration. “Prevention is better than cure” is not only an important and effective means to control infectious diseases, but also has great significance in keeping production costs and resource consumption at a minimum.

“Prevention is more important than cure” is the guiding ideology of the modern quality management system, which adopts a positive and proactive approach, starting from the source, starting from the foundation, and focusing on the situation reflected in the historical records of the production archives. Take preventive measures in all links and places where problems have arisen or may arise. In the process and each stage, we try our best to prevent the reduction of the required level of semi-finished products, strive to eliminate the occurrence of various defect factors, and start from grasping the perfection of each stage, each part and the process to obtain the completeness of the result. . Therefore, it can also be said that “prevention is better than cure” is also the indispensable philosophical basis for “successful dyeing”.

3. Conclusion

There are many influencing factors that cause color difference, including raw and auxiliary materials such as fiber, gray cloth and dyeing materials.Quality differences, the status of dyeing and finishing equipment, technology, technology, management, and personnel quality, etc. Therefore, in the entire production process, from pre-preparation, pre-treatment, to dyeing, post-processing, finishing, etc., there is the basis and possibility of color difference, making color difference a quality issue that is prone to occur in dyeing and finishing production. The problem has become the first of the three major ills. Of course, measures such as color correction, repairs, and dyeing changes are still unavoidable in actual large-scale production, but these are passive remedies after all. Moreover, some textiles do not allow repairs. Therefore, for all factors that may cause color difference, we should strive to adopt a prevention-centered strategy. This is the dominant concept of dyeing and finishing production management, technical management and quality management.