There are many factors that affect the quality of dyed products, mainly factors such as equipment, dyeing materials, processes (processes, formulas, conditions) and operations. Dyeing defects sometimes occur by chance, so when analyzing the factors that cause quality problems in dyed products When identifying the reasons, we must consider and analyze from all aspects to find out the real cause of the problem in order to solve the problem and avoid recurrence of quality problems. On the basis of summarizing experience, we can control product quality.
Factors affecting color contrast and level dyeing
1. Equipment factors and equipment selection
In order to obtain high-quality dyeing products, In addition to selecting different dyes according to different fibers and different fabrics and formulating reasonable dyeing processes, there must also be suitable dyeing equipment. With the continuous development of production and the continuous improvement of technological level, dyeing machinery has become increasingly advanced, but the quality problems caused by the equipment cannot be completely avoided.
The main influence of equipment on color light is the driving stability of the equipment, such as vehicle speed, drying conditions, temperature rise and fall speed, pressure control, etc. Stable equipment process control can ensure stable dyeing shade and reproducibility from the equipment.
Equipment factors are more important for level dyeing. In order to ensure level dyeing, the following requirements are put forward for equipment:
✔The process adaptability must be strong. It must be able to meet the requirements for level dyeing on process parameters such as equipment temperature, pressure, speed, processing time, and adjustments to changes in chemical media such as dyes and chemicals, so that the dyeing and finishing equipment can adapt to new processes and new technologies to ensure the evenness of dyed fabrics. dyeability and other quality requirements.
✔High degree of automation. The main process parameters are automatically detected and automatically adjusted as much as possible to achieve precise control, reduce leveling defects caused by human factors, meet the requirements for process repeatability, and ensure the stability of quality.
✔One machine can be used for multiple purposes, adapting to various processing requirements. The equipment in printing and dyeing plants is always limited, and dyeing and finishing products change with market demand. Therefore, it is necessary to enhance the adaptability of the equipment and ensure that the equipment can meet the level dyeing properties of different types of fabrics while reducing equipment investment. and other quality requirements.
✔The fabric runs at low tension or loose in the equipment. Tension is one of the factors that affects level dyeing. High tension or uneven tension can easily cause level dyeing quality problems. Therefore, it is required to operate the equipment in a loose or low tension or uniform tension as much as possible during the operation of the equipment.
The color matching and levelness of dyed products not only involve the formulated processes and operations, but are also closely related to the dyeing and finishing equipment. The selected dyeing and finishing equipment must meet the dyeing and finishing process requirements, be able to adapt to the requirements of multiple varieties of dyeing, and be able to process high-quality products. The equipment must be safe, durable, economical, high-speed, efficient, continuous, automated, low energy consumption, and able to prevent pollution. In a word, the equipment must ensure the quality of dyeing and finishing products.
2. Formulation of process formula
Whether the process formula is reasonable is directly related to the dyeing quality. The main basis for formulating the process formula is:
⑴ The performance of the fiber and the structure and specifications of the fabric. The structures and properties of various fibers are different, so the dyes used are also different. For example, cotton fiber is suitable for dyeing with reactive, direct, reducing, sulfur and other dyes, and the fiber is resistant to alkali but not acid. The properties of polyester are different. When formulating the dyeing process of polyester-cotton blended fabrics, the respective properties of the two fibers must be considered. The formula of the same fiber fabric with different specifications must also change.
⑵ Color and use of dyed objects.
⑶ Performance of dyes and chemicals.
⑷ Equipment performance and product adaptability.
⑸ Dyeing and finishing methods.
⑹ Quality requirements and cost requirements for dyeing and finishing.
Whether the process formula is reasonable or not directly affects whether the processed products can meet the quality requirements. For example, if cationic dyes are used to dye acrylic fibers, if the compatibility of the cationic dyes and the dyeing saturation value of the acrylic fibers are not considered, and the formula is unreasonable, the required color cannot be dyed, nor can the requirements for shade, leveling, etc. be met. After the formula is formulated, if any unreasonableness is found, it must be adjusted according to the specific requirements of production.
3. Process conditions
Process conditions are important factors that affect the color and levelness of dyed products, such as temperature, time, pH value, etc. Each condition directly affects the quality of the product.
⑴Temperature:
The temperature is related to the degree of puffing of the fiber and the performance of the dye (solubility, dispersion property, dyeing rate, dyeing rate, color light, etc.), which is related to the performance of the additive. Each fiber product and each dye has its own optimal dyeing temperature. Improper temperature or heating rate control will seriously affect the color and levelness of the dyed product. For example, when dyeing wool with weak acid black BR, the maximum dyeing temperature is 80-95℃, while the maximum dyeing temperature of acid navy blue GGR is 95-100℃. Another example is when cationic dyes are used to dye acrylic fiber. The heating rate must be strictly controlled. If the temperature rises too fast, it can easily cause dyeing.
⑵ Time:
The determination of dyeing time is related to the diffusion and combination of dye on the fiber. Sufficient time must be allowed for dyeing , allowing the dye to fully absorb, spread,, the additives added should also be selected to ensure that the additives at least will not have a negative impact on the light fastness.
4. Other fastnesses
The levels of perspiration fastness, chlorine bleaching fastness and sublimation fastness mainly depend on the structure of the dye itself. For example, in reactive dyes, the bond between some dyes and fibers is easy to break under acidic conditions, so the perspiration fastness is poor. Reactive dyes based on pyrazolone have poor oxygen bleaching fastness. Those with phthalocyanine structure are better; reactive dyes with bromoamino acid structure are prone to smoke fading. Fastness is also closely related to the structural condition of the dye and fiber, the concentration of the color, the physical state of the dye on the fiber, the dyeing process, fiber properties and other factors. </p
