To dye polyester/nylon/cotton fabrics, the traditional two-bath and two-step overdying process is changed to a one-bath and one-step dyeing process. There are two key points in the process. First, qualified disperse dyes must be used to dye polyester and neutral dyes to dye brocade. Thermosetting reactive dyes are used to dye cotton; the second is to apply polyester and nylon composite leveling agents. The dyeing effect of this process is good, and the advantages of “high quality, high efficiency, energy saving, and emission reduction” are particularly prominent.
1 Preface
Polyester/nylon/cotton fabric combines the advantages of three fibers. The fabric surface is crisp, durable and comfortable. It occupies an important position in today’s clothing fabrics.
Polyester/nylon/cotton fabrics are usually dyed using the two-bath and two-step overdying method. That is, polyester and brocade are dyed with disperse dyes or disperse/neutral dyes, and then cotton fibers are over-dyed with reactive dyes. This process has the disadvantages of high energy consumption, high pollution emissions, high output, and poor efficiency.
The one-bath and one-step dyeing process is obviously in line with the dyeing and finishing concept of “energy saving, emission reduction, and efficiency improvement”.
2 Key points of the one-bath and one-step dyeing process
2.1 Selection of dyeing temperature
Nylon has poor heat resistance. After testing, the upper limit of the temperature that nylon can withstand under high-temperature and humid conditions is 120°C. Above this temperature, nylon will obviously “paper” (i.e., lose elasticity, yellow, harden, and become brittle), and even Lose practical value. This determines that the dyeing temperature of polyester/nylon/cotton fabrics can only be 120°C.
2.2 Selection of dyes
Polyester/nylon/cotton are three types of fibers with different dyeing properties, so the three dyes should be dyed with compatible dyeing properties.
(1) Dyeing cotton fiber components
Obviously, low-temperature reactive dyes dyed at 40°C, medium-temperature reactive dyes dyed at 60°C, and high-temperature reactive dyes dyed at 80°C are not suitable for this process. After testing, it is suitable to use thermosetting reactive dyes to dye cotton. The reason is: thermosetting reactive dyes are fixed by temperature rather than alkali agents. They need to be dyed in a neutral salt bath at 100 to 130°C. The dyeing conditions required for nylon with neutral dyes and nylon with disperse dyes are similar. , can realize one-bath operation.
(2) Dyed nylon components
Disperse dyes can dye both polyester and nylon. The biggest advantage of nylon dyed with disperse dyes is that it has excellent level dyeing and covering properties, which are inferior to other fuels. However, it also has many shortcomings such as poor light fastness, poor washing fastness, poor dyeing depth effect, and poor color purity. Therefore, dyeing nylon with a single disperse dye is not ideal from the overall effect.
The experimental results show that neutral dyes are effective in dyeing nylon. There are four reasons:
① Nylon is dyed with neutral dyes, and its fastness to sunlight and washing is particularly excellent.
② Neutral dyes have good heat resistance. Compared with dyeing at 120℃, the color yield tends to be higher. Therefore, it can be dyed under high temperature and high pressure (120°C) conditions.
③ When dyeing nylon with neutral dyes, there are no special requirements for pH. It can be dyed under weakly acidic (pH=5~6) conditions or neutral dyes. The latter has excellent leveling effect, but the color yield is slightly reduced, but not significantly.
④ When neutral dyes are used to dye nylon in a neutral bath, the presence of electrolytes has a dyeing effect and has no adverse effects on the neutral dyes used to dye nylon. Therefore, nylon dyeing with neutral dyes is completely adapted to the conditions of cotton fiber dyeing with thermosetting reactive dyes.
(3) Dyed polyester components
Of course, disperse dyes must be used to dye polyester, but disperse dyes suitable for this process should meet the following conditions:
① It should be of low temperature type (E type) or medium temperature type (SE type). Because the dyeing temperature of this process is 120°C, E-type or SE-type disperse dyes (which have a relatively simple molecular structure, relatively small molecular weight, and easy diffusion) can obtain a relatively high dye uptake rate.
② The dyeing amount of nylon should be low. This is because the colorability of nylon is poor. During the high-temperature dyeing process, less disperse dye remains on the nylon (mainly neutral dyes), and the color fastness of the dyed product is good.
③ The stability of hot water medium should be better. Because this process is dyed in a neutral bath, only disperse dyes with good stability in hot water can have stable color and good color presentation.
④ Thermal cohesion should be small. Because this process is dyeing in the presence of a dielectric, the dielectric has the effect of reducing the dispersion stability of disperse dyes, and it is easy to cause dyeing defects due to excessive agglomeration of dyes.
2.3 Selection of additives
When dyeing polyester/nylon/cotton fabrics using the one-bath one-step process, a composite leveling agent (high-temperature dispersion leveling agent 1.5g/L nylon leveling agent 1.5g/L) should be used for dyeing.
This is because:
(1) The polyester and brocade components in polyester/nylon/cotton fabrics are ultra-fine composite yarns with a large specific surface area, which adsorb dyes quickly and are prone to uneven color absorption and color flowers. Experiments show that adding a composite leveling agent can moderately reduce the dye adsorption rate and ensure that the dye is evenly adsorbed by the fiber.
(2) Disperse dyes have a tendency of thermal aggregation under high temperature and high pressure conditions. The presence of dielectric will increase the thermal aggregation of dyes, which can easily affect the level dyeing effect and dyeing effect.�Adverse effects on fastness. Apply l. 5 g/L high-temperature dispersion leveling agent can effectively prevent dyeing defects.
(3) Nylon has a low glass transition temperature (47~50℃) and swells easily in water. Neutral dyes can form ionic bonds with the amino groups (-N+H3) in the nylon and with the amide groups (-NHC0- ) can form hydrogen bonds and can generate strong van der Waals forces with nylon macromolecules. Therefore, neutral dyes have a high affinity for nylon and dye quickly. They are easy to absorb uneven color and easily expose warp and weft defects of nylon. Applying an appropriate amount of nylon leveling agent can effectively improve the leveling effect of nylon. Experiments show that using composite leveling agents for dyeing will not have obvious negative effects on polyester dyed with disperse dyes and nylon dyed with neutral dyes.
Table 1 Effect of compound leveling agent on the color yield of polyester dyed with disperse dyes
|
Leveling agent Relative color depth (%) |
High temperature dispersion leveling agent 1 g/L |
High temperature dispersion leveling agent 1 g/L Nylon leveling agent 1g/L |
|
Dispersed Golden SE-3R |
100 |
99.15, good leveling |
|
Disperse Red E-FB |
100 |
98.98, good leveling |
|
Disperse Blue E-4R |
100 |
97.01, level dyeing is good |
|
Dispersed ruby S-2GFL |
100 |
95.47, level dyeing is good |
Note: Dye 1% (omf), 98% acetic acid 0.5 ml/L, sodium hexametaphosphate 1. 5 g/L, 2°C/min temperature rise, 120°C incubation and dyeing for 30 minutes. (High-temperature dispersion leveling agent and nylon leveling agent are provided by Hangzhou Meigao Huayi Company)
Table 2 Effect of compound leveling agent on the color yield of nylon dyed with neutral dyes
|
Leveling agent color depth (%) |
Nylon leveling agent 1 g/L |
Nylon leveling agent 1 g/L High temperature leveling agent 1 g/L |
|
Neutral Yellow S-2G |
100 |
99. O2, the leveling effect is remarkable |
|
Neutral red S-GN |
100 |
97.70, level dyeing |
|
Neutral Brown S-GR |
100 |
100.12, the leveling effect is obvious |
|
Neutral Navy S-B |
100 |
98.99, level dye |
Note: The conditions are the same as above.
This shows that high-temperature disperse dyes and nylon leveling agents used in the same bath have good compatibility and can exert their respective leveling functions without mutual resistance or interference.
2.4 Process setting
Take the actual dyeing process as an example.
(1) Color: Lotus red
(2) Fabric:
(3) Prescription:
Dispersed golden SE-3R 0.05% (omf)
Disperse Red E-FB l%
Disperse Blue E-4R 0.3%
Neutral red S-GN 0.5%
Reactive Yellow NF-GR 0.07%
Reactive Red NF-38 1.9%
Reactive Blue NF-MG 0.37%
Sodium hexametaphosphate 1.5 g/L
Nylon leveling agent 1.5 g/L
High temperature dispersion leveling agent 1.5 g/L
Table salt 20g/L
pH buffer OT l. 5 g/L
(4) Technology (omitted)
(5) Tips
① The dyes should be separated into chemical materials. Disperse dyes should be dissolved in warm water of 50-55℃, neutral dyes should be dissolved in hot water of 90-95℃, and reactive dyes should be dissolved in warm water of 50-60℃.
② The polyester and nylon components in polyester, nylon and cotton fabrics are ultrafine fibers, which have the characteristics of large specific surface area and fast color absorption. Therefore, the dyeing temperature should be low rather than high, and the heating rate should be slow rather than fast.
③ When the temperature is raised to 65℃, dyeing needs to be kept warm for a period of time. There are two reasons: First, the glass transition temperature of nylon is low (47~50℃).As the temperature increases above 65°C, dyeing will accelerate sharply, and it is easy to absorb uneven color; secondly, thermosetting reactive dyes, when the dyeing temperature is below 70°C, the fixation reaction is not obvious, so the dye migration effect is significant. When the dyeing temperature is higher than 70°C, the fixation reaction of the dye will occur rapidly, and the dye migration effect will be significantly smaller. Therefore, heat preservation dyeing at 65°C for a period of time is very beneficial to level dyeing and thorough dyeing of nylon and cotton fibers.
④ E-type and SE-type disperse dyes have relatively simple molecular structures and relatively small molecular weights. Therefore, color absorption is relatively rapid above 105 ℃, and color unevenness is likely to occur (especially polyester microfiber is prominent). Therefore, heating up to 105°C and then holding it for dyeing for a period of time will help the ultra-fine polyester absorb color evenly.
3 Conclusion
Appropriately selected disperse dyes, neutral dyes, and thermosetting reactive dyes have good adaptability to the same bath. Taking advantage of the color specificity and color directionality of the three dyes, polyester/nylon/cotton fabrics can be dyed into a uniform color using the one-bath and one-step method. The process has high efficiency, low energy consumption, less pollutant discharge and very significant economic benefits.
Author: Cui Haoran of Changzhou Xinhao Printing and Dyeing
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