Nylon has a fast dyeing speed and high dye exhaustion rate, but it is prone to defects such as uneven dyeing, inconsistent colors and poor dyeing fastness. Through proofing and dyeing process tests, select a dye series with similar dyeing curves and affinity, good compatibility, and suitable for production machines, and formulate it from the aspects of temperature, liquor ratio, pH value, and the selection and dosage of leveling agent. Reasonable craftsmanship; by standardizing proofing, color matching and other operations, the difference between large and small samples is reduced and the rate of high-quality products is increased.
Foreword
Nylon is a hydrophobic fiber that contains amino and carboxyl groups. Dye with disperse dyes, acid dyes, especially weak acid dyes. Its dyeing has the characteristics of fast dyeing speed and high exhaustion rate. However, due to different spinning process specifications, the fiber structure is very different, resulting in large differences in dyeing performance and easy to produce color differences. Therefore, if you are slightly negligent when formulating the sample process, it may cause uneven dyeing, resulting in defects such as color difference, color stains, color spots, dark and light edges, stripes, color inconsistency, and poor dyeing fastness.
Therefore, when dyeing nylon, sample workers must formulate a reasonable dyeing process and strictly control the entire process to reduce the defective rate and reduce the pressure of large-scale production. Through more than ten years of practice in nylon dyeing and proofing work, the author summarizes common defects in nylon dyeing, as well as prevention and technical remedies.
Common defects and preventive and remedial measures
1. Dyeing results in colors that are inconsistent with the sample
This is caused by improper selection of dyeing materials. The dyeing saturation value of nylon is very low, so when dyeing strong colors, the competition between different dyes becomes very prominent. If the dyes selected have large differences in dye uptake and affinity, the fiber dyed colors will be very different at different dyeing times, resulting in color differences between large and small samples and poor reproducibility. The preventive and remedial measures are to choose a dye series with similar dyeing curves and affinity, good compatibility, and suitable for production machines.
Samplers are required to fully understand the dyeing properties of various dyes. When selecting dyeing materials, they must comprehensively consider the dye uptake rate, dyeing curve, level dyeing, and color. Factors such as fastness properties, and sensitivity to temperature and leveling agents.
① Fully consider the compatibility of dyes. When using several dyes for dyeing, you must choose appropriate dyes and control the amount of dyes. Generally, you should try to choose the same series of dyes from the same company. Even if you have to use dyes from different companies, you should try to choose dyes with similar dyeing curves, similar starting dyeing temperatures, and similar sensitivity to temperature and leveling agents. Try to Avoid competing contamination.
② Pay attention to the difference in dye size and sample size. Some dyes are not obvious when dyeing small samples, but are completely exposed in large-scale production. For example, when producing lake green and peacock blue, if acidic emerald blue and acidic yellow are used to combine, similar problems will arise. This is because the molecular structure of acidic emerald blue is large and the dyeing curve of acidic yellow is very different, thus causing competitive dyeing. If the acid green basket is used instead of the acid green with yellow light, the problem of competing dyes will be basically solved.
③ Pay attention to the adaptability of the machine to dyes. Dyeing machines include jet, beam and jigger dyeing machines. In the jet dyeing machine, the dye liquor is in full contact with the fabric, resulting in good level dyeing, plump product feel, good reproducibility, and small cylinder difference, but its fastness to moisture treatment is relatively poor. You can choose weak acid dyes or 1:2 metal complex acid dyes that have good fastness but slightly poor leveling properties for dyeing. The product width of the beam dyeing machine is simple to control and the color is easy to fix, but it is prone to problems such as dark and shallow layers and head and tail color differences. You can choose dyes with good leveling properties but slightly poor fastness, slightly increase the amount of leveling agent, and then strengthen the color fixation after dyeing.
2. Defects caused by unreasonable processes
Nylon dyeing has extremely high process requirements. Process conditions are important factors that affect the color and levelness of dyed products, such as temperature, liquor ratio, pH value, etc., which will all affect the quality of the product. Unreasonable craftsmanship is prone to defects such as poor level dyeing, color flowers, color willow, color difference, and poor fastness.
①Control the initial dyeing temperature and heating rate. Temperature is an important factor in controlling dyeing. The temperature will affect the degree of puffing of the fiber, the performance of the dye (solubility, dispersion, dye uptake, color, etc.) and the performance of the additives. Nylon is a thermoplastic fiber. When the temperature is low, the dyeing rate is very slow. When the temperature exceeds 50°C, the swelling of the fiber continues to increase as the temperature increases. The effect of temperature on the dye uptake rate also varies with different dyes. The dye uptake rate of level dyeing dyes gradually increases as the temperature increases; the dye uptake rate of milling-resistant dyes must be maintained when the dye bath temperature is higher than 60 After ℃, it begins to increase rapidly with the increase of temperature.
Especially in the temperature range of 65-85°C, controlling the heating rate is the key to the success of nylon dyeing. Improper control will result in fast coloring, poor dye migration, and easy dyeing. The problem of flowers being difficult to repair. If milling-resistant dyes are used to dye nylon, the initial dyeing temperature should be room temperature. In the temperature range of 65-85°C, the heating rate should be strictly controlled at about °C/min, and a leveling agent should be added to adopt a stepped heating method; then the temperature should be raised to 95 -98℃, keep warm for 45-60 minutes. In addition, the dyeing performance of this fiber also changes with the heat treatment conditions before dyeing. The dyeing rate of the fiber after dry heat setting decreases significantly.
<Phase, when matching colors, you can only choose the color preference based on the feelings of yellow, red, and cyan. The stronger the color perception, the more important the freshness and purity of the color are to the judgment of hue. Therefore, when color matching, you must first make a correct judgment and choose the correct dye.
(2) When comparing colors, pay attention to the changes in the sample and the angle of light exposure to maintain consistency.
(3) Understand the degree of drying of the sample fabric after dyeing. Excessive drying will cause the color to become irreversibly reddish; insufficient drying will affect the color saturation of the color sample. Both situations will cause color light deviation.
(4) When imitating colors, attention should be paid to the classification of varieties and color systems, and samples should be retained to accumulate data and establish a color sample library (it is better to have corresponding actual production samples).
③ Control the consistency of large and small sample processes.
(1) The pH value and heating process of the proofing dye bath should be consistent with those of mass production. Due to the cross-use of water quality and direct or indirect steam in large-scale production, the boiler steam is often alkaline and causes a high pH value in the dye bath. This problem can be solved by using a buffer or equipped with an online pH value monitor.
(2) The holding time of small sample dyeing should be consistent with that of large sample to avoid color difference due to poor dyeing penetrability.
(3) Since color fixation will also affect the color light, the color light must be adjusted after the sample is fixed before entering into the process development for mass production.
Conclusion
Influence on nylon dyeing products There are many quality factors, including equipment, technology, dyeing materials, color difference between large and small samples, and operation. Production practice has proved that by grasping the above-mentioned links, the accuracy and stability of nylon dyeing can be improved, so that the first-time success rate of sample lofting can reach more than 90%. </p
