Nylon/cotton fabrics are usually dyed using the two-bath overdying method, that is, nylon is dyed with neutral, acidic or disperse dyes, and then cotton is dyed with medium-temperature reactive dyes. The advantage of using the two-bath overdying method is that the colors (shades, shades) of nylon and cotton fibers can compensate for each other during the overdying process, and the color of the cloth surface is easier to adjust and control; the disadvantages are that the process is time-consuming, the processing output is low, and energy is It consumes a lot of water, discharges a lot of sewage, and has poor economic benefits.
Brand/cotton or cotton/nylon fabrics can be dyed lightly using disperse/thermosetting reactive dyes in one bath. For colors, neutral/thermosetting reactive dyes can be used to dye medium colors in one bath, and neutral/high temperature reactive dyes can be used to dye dark colors in one bath. Practice has proved that the dyeing effect of the one-bath method is equivalent to that of the traditional two-bath overdying method, and it has outstanding advantages of “energy saving, emission reduction, and efficiency improvement”.
Brand/cotton fabrics were once dyed using a one-bath and two-step method of neutral dyes and medium-temperature reactive dyes. That is, under the condition of adding electrolyte, first dye in a neutral bath at 85°C, then cool to 60°C and add alkali to fix the color, and then wash with water and clean.
However, this dyeing method has three major disadvantages: First, when neutral dyes are dyed at 85°C, the dye uptake rate of nylon is about 10% lower than that at 95~98°C. 15%, which cannot reach the highest exhaust dyeing rate;
The second is that the medium-temperature reactive dye absorbs color at higher temperatures, which stains nylon heavily, and the color of the nylon component is poor. It is difficult to control;
Thirdly, the color (shade, depth) reproducibility of this dyeing process is poor, and the vat difference is prominent, so this dyeing method has been eliminated. After research, nylon/cotton fabrics can be dyed with disperse dyes and thermosetting reactive dyes in one bath and one step to dye light colors, neutral dyes and thermosetting reactive dyes in one bath and one step to dye medium colors, neutral dyes and high temperature reactive dyes One-bath, two-step dyeing for darker colors.
One-bath and one-step method for disperse/thermosetting reactive dyes
Dyeing light-colored nylon/cotton fabrics
Disperse dyes for nylon dyeing have good level dyeing properties and have good covering properties for the differences in dyeing quality of nylon itself. Dyeing defects such as “warp willow” and “weft stall” will occur. When dyeing light colors, it will not expose the shortcomings of disperse dyes such as poor dyeing ability and poor color fastness to nylon. Practice has proved that it is feasible to choose some disperse dyes with good light fastness, good coloring performance and pure color to dye nylon to light colors.
1. Adaptability of disperse/(thermosetting) reactive dyes in the same bath dyeing
1.1 Dyeing temperature
Although nylon is a hydrophobic fiber, its glass transition temperature is much lower than that of polyester, only 47~ 50℃. Moreover, the hygroscopic swelling property is greater than that of polyester, so nylon dyed with disperse dyes can obtain relatively high color yield under boiling temperature and normal pressure (100°C) conditions, and the color is pure and reproducible. If dyed under high temperature and high pressure (120°C), the color depth will be improved, but the purity of the color will be reduced. When the dyeing temperature is > 120°C, nylon will become “papery” again, with a stiff feel, loss of elasticity, reduced strength, and serious yellowing (Table 1).
Note: (1) Prescription: dye 2% (owf), sodium hexametaphosphate 1.5g/L, high temperature uniform Dye 1.5g/L, 98% acetic acid 0.5mL/L. (2) Process: Liquor ratio 1: 20, heating rate 4℃/min, rotation speed 45r/min, insulation dyeing at different dyeing temperatures listed in the table. (3) Detection: Datacolor SF 600X colorimeter detection, the relative color depth of dyeing at 100℃ is 100% relative comparison.
Thermoset reactive dyes have good heat resistance. They can achieve dyeing balance by keeping the dye at 100-120℃ for a sufficient time. The dye uptake rate is stable and the color depth does not change significantly.
If the dyeing temperature is lower than 100℃, the color will become significantly lighter. This indicates that the reaction between the dye and the cotton fiber is insufficient. If the dyeing temperature is higher than 120°C, the color will also be lighter by about 5% (this is related to the increased solubility of the dye caused by the high dyeing temperature). This shows that the most suitable dyeing temperature for cotton dyed with thermosetting reactive dyes is 100~120℃. It can be seen that disperse dyes and thermosetting reactive dyes are compatible with bath-dyed nylon/cotton fabrics under boiling temperature and normal pressure (100°C) conditions (Table 2).
Note (1) Prescription: dye 1% (owf), chelating agent 1.5g/L, buffer 07 1.5g /L, salt 40g/L. (2) Process: Liquor ratio 1:30, heating rate 2.5°C/min, heat preservation and dyeing for 40 minutes at different dyeing temperatures listed in the table, washing and soaping. (3) Detection: The color depth of dyeing at 100℃ is 100%, and the relative color depth is detected by Datacolor SF 600X colorimeter.
1.2 Dye bath pH value
The 100℃ dyeing of nylon with disperse dyes has two major characteristics:
① The dyeing of nylon with disperse dyes completely relies on the hydrogen bonding, van der Waals attraction and dipole attraction between the dye and the fiber macromolecules. , unlike direct, neutral, acidic and other anionic dyes, which mainly rely on the ionic bonding between the dye and the amino group on the nylon, so the dependence of disperse dyes on nylon dyeing bath pH is very small. After testing, there is no significant change in the dyeing effect within the pH range of 4 to 8.
② Dying nylon with disperse dyes at 100°C is completely different from dyeing polyester at a high temperature of 130°C. It has good hydrolysis resistance and stability. In the dye bath pH range of 6 to 8The dye has good adaptability to process conditions and can be used to dye brocade/cotton fabrics in one bath and one step.
Neutral/high-temperature reactive dye one-bath two-step method
Dye brocade/cotton fabrics in dark colors
Adaptation of neutral/high-temperature reactive dyes in the same bath dyeing
1. Dyeing temperature
The molecular structure of high-temperature reactive dyes is larger and is bilateral, with two monochlorine s-Triazine active group. Therefore, it has greater directness, relatively weak reactivity and relatively low diffusivity to cotton fibers, and is most suitable for high temperature (80~100℃) color absorption and high temperature (80℃) color fixation (Table 11) (Note: High-temperature color absorption has no obvious effect on the color depth, but it can effectively improve the leveling and dyeing effect).
Note: dye 1. 5% (owf), sodium hexametaphosphate 1.5g/L, salt 40g/L, Soda ash 20g/L, mercerized cotton cloth, circular motion dyeing machine, liquor ratio 1:30, color absorption 40min, color fixation 40min, soaping twice.
Due to the good heat resistance and stability of high-temperature reactive dyes, it is completely possible to use one-bath and two-step dyeing in a neutral salt bath at 100°C, and then lower the temperature to 80°C to fix the color. Dyeing method, dye brocade/cotton fabrics in the same bath with neutral dyes.
2. Dye bath pH value
Neutral dyes (referring to 2:1 complex dyes, except compound dyes) dye nylon. The pH value of the dye bath with darker color and better level dyeing is 5 to 8, that is, neutral bath dyeing can be done. (See Table 9). When dyeing cotton with high-temperature reactive dyes, the color absorption is carried out in a neutral salt bath. The two are dyed in the same bath. Since the color absorption process of high-temperature reactive dyes is the process of dyeing nylon with neutral dyes, there is no conflict in pH between the two. When the color absorption is completed and alkali is added to fix the color, the dyeing of the nylon with the neutral dye has been completed and is basically not affected by the alkali agent.
Practice has shown that in the process of adding alkali to reactive dyes to fix the color, the floating dyes on the surface of nylon (including the floating dyes of neutral dyes and the staining of reactive dyes) are more effective. Strong cleaning effect. However, due to the high affinity of neutral dyes for nylon, good color fastness, and the presence of a large amount of electrolytes, the impact on the color depth of nylon is not very obvious.
3. Nylon leveling agent
Neutral dyes dye nylon, which have high affinity, fast coloring, slow diffusion, and poor dye migration. In addition, there are obvious physical and chemical differences in the microstructure of nylon, which can easily cause uneven color absorption, so exhaust dyeing When dyeing, in addition to adopting low-temperature dyeing, slow heating, mid-way heat preservation, neutral bath dyeing and other measures, 1 to 2g/L nylon leveling agent needs to be applied. Experiments show that the use of nylon leveling agent has no significant impact on the color absorption rate, color fixation rate and color purity when dyeing cotton with high-temperature reactive dyes.
4. Electrolyte
High temperature Cotton dyed with reactive dyes, like cotton dyed with medium-temperature or heat-setting reactive dyes, must be dyed with electrolytes, because without the application of electrolytes to promote dyeing, the color depth will decrease by 40% to 50% (Table 12).
Note: (1) Prescription: dye 1% (owf), sodium hexametaphosphate 1.5g/L, salt O ~60g/L, soda ash 20g/L. (2) Process: Liquor ratio 1:25. Color absorption in 80°C neutral salt bath for 30 minutes, followed by alkali fixation for 40 minutes, water washing and soaping twice. (3) Detection: The relative color depth of 60g/L salt is 100%, and the Datacolor SF 600X colorimeter is used for detection.
Neutral dyes are used to dye nylon in a neutral bath, and the electrolyte has an obvious effect on promoting dyeing and deepening (Table 10). Therefore, neutral dyes and high-temperature reactive dyes are used for neutral bath-dyed nylon/cotton fabrics, and the presence of electrolytes has the same effect on both. From the above analysis, it can be seen that it is technologically feasible to dye brocade/cotton fabrics with neutral dyes and high-temperature reactive dyes in one bath and two steps.
</p
