Quality problems may occur during production due to factors such as gray fabrics, semi-finished products, equipment, process level and execution, quality of dyeing materials, etc. Among them, the selection and use quality of auxiliaries directly affect the quality of dyeing and finishing products. , this article mainly talks about the relationship between the common quality problems of knitted fabric dyeing and finishing products and the selection of auxiliaries.
Auxiliaries in dyeing and finishing production The role and relationship
Due to the multi-link nature of the dyeing and finishing production process, it is also a relatively independent small system project within the scope of the dyeing and finishing production enterprise.
However, some sources of quality impact will also involve enterprises in fiber raw materials, spinning, weaving, dyeing materials, equipment and other related industries. Dyeing and finishing enterprises can only inspect, detect and accept, but not Maybe the other person can control all aspects independently.
For example, different origins, production batches, and batch numbers of dyestuffs have differences in the content of their active ingredients, so it is necessary to carry out accurate testing of chemical raw materials such as dyestuffs. Especially for dyes, which have the greatest impact on color difference. Since the current GB standard stipulates that the allowable intensity error of commercial dyes is ±3%, and to truly achieve the allowable color difference error in textile dyeing and finishing, the dye intensity error is required to be reduced to within ±1%. The gap between the two is very large. Obviously, it is necessary to conduct precise testing before use to make precise improvements.
Different origins of fiber raw materials, different production batches, batch numbers, and different types of large-scale production equipment also have differences in the dye uptake rate, thus affecting the color. reproducibility and stability. In particular, the fluidity and changeability of fiber raw materials and dyeing materials are both extremely large and extremely fast.
For dyeing and finishing companies, they are all supplied from outside and cannot produce by themselves. Therefore, dyeing and finishing production must achieve “first-time success”, which not only involves a wide range of areas, but also has a deep depth, so it is a large-scale systematic project.
Auxiliary companies often encounter technical or managerial personnel from dyeing and finishing companies, asking for help or consultation to collaborate in solving certain quality problems. There are often requests for an effective leveling agent to solve the problem of color fixing agents to improve the color fastness of a certain product, or to overcome color unevenness such as color blooming when dyeing a new textile product or when dyeing in a new type of equipment; there are inquiries. The application process and key points of novel additive varieties, and some also put forward the research and development requirements and specific goals of additives that can help them achieve “first-time success”. This kind of situation also shows that everyone realizes that coordinated operations by all relevant parties are the shortest, fastest and most beneficial measures to overcome and solve problems.
The multi-faceted nature of the impact in dyeing and finishing production also determines the multi-faceted nature of the solution and processing work and its the complexity. For example, regarding the color fastness problem, we should first pay attention to the nature of the dye. Although improvements can be made with additives, there are certain limits. It is impossible to use fixing agents to raise direct dyes to the level of reactive dyes; similarly, it is also impossible to fix reactive dyes to reach the level of vat dyes.
The problem of uneven dyeing is not only caused by the dye, but also affected by various factors such as the quality and nature of the textile yarn and its fiber raw materials, or the characteristics of the weaving structure design. about. Auxiliaries can help improve dyeing levelness in a targeted manner, but they are not omnipotent. If there is a large difference in the dyeing rate between the various varieties of color-matching dyes, you must carefully choose varieties with good compatibility. This is also an important reason why dye factories provide various types of three primary color series that are divided into different application processes such as high temperature, medium temperature, and low temperature.
The problem of color unevenness affected by dyeing machinery is easily overlooked. There are also many types of dyeing machinery, and they are constantly being updated. Therefore, how to make good use of new types of machinery and equipment in dyeing and finishing production is also a topic that requires efforts.
Different types of dyeing machines adapt to different types of textiles, and the resulting color unevenness also has different manifestations. For example, normal-pressure jig dyeing machines are prone to overlapping prints and left-right color differences, high-temperature and high-pressure jig dyeing machines are prone to color spot defects, and semi-filled liquid jet dyeing machines are prone to color bloom problems.
From the perspective of dyes, disperse dyes with low water solubility are prone to color spots and stains, while reactive dyes and acid dyes with good water solubility are less likely to have this phenomenon; for acidic dyes As for dyes, weakly acidic dyes are more likely to cause blooming than strong acidic dyes; dyes with larger molecular weights have higher color yields than the same type of dyes with smaller molecular weights, but are also relatively prone to blooming problems.
For some problems caused by the way the dyeing machine operates during dyeing and the individual characteristics of dyes, the participation of different targeted auxiliary varieties is essential and becomes an integral part of the dyeing quality maintenance system. and its vital and reliable pillars.
Production requirements for highly standardized batch-to-batch stability of additives
Once the dyeing and finishing enterprise recognizes and determines certain varieties of the auxiliary enterprise, it will be selected.The choice of substitute acids and bases for strong inorganic acids should also be as gentle as possible.
5. Color variations (including color difference, lack of color samples, etc.)
Color stains are the most common and most common quality problem in the dyeing process. The causes are:
Process formulation and operation problems: Unreasonable formulation or improper operation produces color stains. flower.
Equipment problems: For example, after polyester is dyed with disperse dyes, the temperature in the oven of the heat setting machine is different, which can easily produce color differences and flakes. Insufficient pump power of the rope dyeing machine can easily cause color blooms, etc.
Dye problems: dyes are easy to aggregate, have poor solubility, poor compatibility, are too sensitive to temperature and pH, and are prone to color blooms and color differences. For example, active green orchid KN-R is easy to produce colored flowers.
Water quality problems: Poor water quality causes dyes to combine with metal ions or dyes and impurities to agglomerate, resulting in colored flowers, light colors without sample attachment, etc.
Auxiliary issues: Regarding the auxiliary issues, the auxiliaries related to color flowers mainly include penetrants, leveling agents, chelating dispersants, PH value control agents, etc. The penetrating agent’s penetrating power is not enough, which can easily lead to uneven penetration of the dye solution and color blooming, such as loose cotton dyeing, cheese dyeing, and heavy fabric dyeing. The role of the penetrating agent cannot be ignored.
Leveling agents include various types of leveling agents for polyester, cotton, wool, nylon, and acrylic. The quality of leveling agents varies. Leveling agents must take into account the dispersion of dyes. It has the effect of helping to dissolve, retarding dye transfer, assisting penetration, and even complexing of metal ions in water. Factors such as its PH suitability, foaming properties, etc. that affect the coloring rate must be taken into consideration. Leveling agents can improve Color flowers, color spots and other phenomena cannot be eliminated.
Some leveling agents are just solutions of diffusing agents, but it is not expected that the diffusing agent’s anti-dye aggregation effect is greatly reduced at high temperatures. Similarly, if the non-ionic surfactant is not suitable, the non-ionic surfactant itself will precipitate above the cloud point, adsorbing the dye and forming a tar-like substance that will stick to the fabric equipment, which will cause quality problems.
The quality of chelating dispersants is also related to leveling dyeing issues. At present, when the water quality is getting worse and worse, the help of chelating dispersing agents in leveling dyeing should be paid more attention to.
PH control is an issue that factories do not pay much attention to. In some factories, the pH of each dyeing tank is different, and in some factories, the quality of substitute acids used is different. . Some factories use pH slip agents, but do not understand the relationship between temperature and time and the pH value generated by the slip agent. Therefore, pH control is impossible, so color flowers and color differences continue to occur.
6. Color point (including white point)
Color point There are many reasons for the occurrence, such as white spots, which may be the reason why immature cotton cannot be dyed with dye, or it may be caused by solids such as soda ash staining the cloth, causing local dyeing to not be dyed.
The main causes of color spots are:
① Improper selection of dyes: dye particles are too large or can easily agglomerate to form color spots;
② Poor dye dissolution: Undissolved dye enters the dye solution and sticks to the fabric to form color spots;
③ Poor water quality: Poor water quality causes dye condensation:
④ The equipment is not clean: the tar-like material in the dye vat falls off and causes color spots;
⑤ Reasons for auxiliaries: The additives added during dyeing sometimes cause the dye to agglomerate and produce color spots; auxiliary The agent foams too much, and the foam combines with the dye to form colored foam, which stains the fabric to form color spots; the additives precipitate and combine with the dye to stain the fabric and equipment, and the agglomerates on the equipment will transfer to the fabric to form color spots.
Afterwords
Common quality problems of knitted fabric dyeing and finishing products There are many, and there are many reasons for them. Some quality problems cannot even be analyzed and it is difficult to find out. In the printing and dyeing production process, details always determine product quality. </p
