Plasma treatment and benzyl alcohol carrier-based meta-aramid fiber dyeing method

Abstract

The invention relates to the technical field of fabric dyeing, and discloses a meta-aramid fiber dyeing method based on plasma treatment and a benzyl alcohol carrier. The PMIA is subjected to surface activation pretreatment by adopting a plasma physical modification technology, and then the benzyl alcohol is adopted as a swelling agent for cationic dye dyeing, so that the dyeing property of the PMIA is improved while the thermodynamic property is not influenced, and the prepared dyed meta-aramid fiber is good in dyeing property and does not influence the thermal stability and mechanical property of the fiber; a new thought is provided for effective application of the meta-aramid fabric.

Description

Technical Field

[0001] This invention relates to the field of fabric dyeing technology, specifically to a method for dyeing meta-aramid fibers based on plasma treatment and benzyl alcohol as a carrier. Background Technology

[0002] Meta-aramid (poly(m-phenylene isophthalamide), or PMIA), is a high-performance synthetic fiber with excellent mechanical properties, high-temperature resistance, and corrosion resistance. It is widely used in defense, fire protection, and aerospace industries. The PMIA molecular structure consists of alternating benzene rings and amide bonds (—CONH—), exhibiting high regularity, high crystallinity, and strong chemical inertness. However, the dense crystalline structure of PMIA severely hinders dye molecules from penetrating the fiber or binding with it, making it difficult to achieve ideal color depth and thus greatly limiting the application of PMIA in the textile and apparel industry.

[0003] To address the challenges of PMIA dyeing, scholars both domestically and internationally have conducted extensive research on carrier dyeing and surface-modified dyeing methods. Regarding carrier dyeing, Sheng et al. investigated the effect of synergistic treatment with DMAc and NaCl on the dyeing performance of PMIA. The results showed that the color depth of the fabric dyed with cationic dyes significantly increased with increasing DMAc and NaCl concentrations. Zhuo et al., combining experimental and molecular simulation methods, systematically explored the mechanism of action of DMSO and NaCl on the dyeing behavior of PMIA. Their study found that when the DMSO mass fraction was 50% and the NaCl concentration was 50 g / L, the dyed PMIA fabric not only maintained good mechanical properties but also achieved a high color depth (K / S value of 16.0) and dye uptake rate (72.3%). Besides carrier dyeing, researchers have also explored various surface modification methods to improve the dyeing performance of PMIA. Dong et al. used UV / O3 treatment to increase the surface roughness of fibers and introduced polar functional groups such as carboxyl and hydroxyl groups on the surface, thereby significantly enhancing the affinity of PMIA for cationic dyes. Amesimeku et al. applied ultrasonic-microwave synergistic radiation technology, which promoted the diffusion and adsorption of dye molecules through cavitation effect and instantaneous heating, effectively improving the adsorption and diffusion of dyes on the fiber surface and enhancing the dyeing depth and uniformity of PMIA. Sun Zhuangzhuang et al. used NaOH pretreatment to induce partial cleavage of amide bonds, generating new polar functional groups, thereby improving the dyeing ability of PMIA. Although the above methods have improved the dyeing effect of aramid to some extent, there are still many problems, such as large carrier usage, high cost, harsh processing conditions and difficulty in recycling, which can easily cause secondary pollution to the environment. At the same time, chemical modification methods often destroy the main chain structure of the fiber, resulting in a decrease in its original thermal stability and mechanical strength. In addition, the long processing time, complex operation process, high requirements for equipment conditions, and lack of stable process window are not conducive to large-scale and continuous application. Furthermore, although some methods can improve surface dyeability, they are difficult to solve the problem of effective penetration of dye molecules into the fiber interior, and the overall dyeing depth is still limited, which restricts its promotion and application in functional and high-end apparel fields.

[0004] Therefore, it is necessary to develop a green, low-loss, and high-efficiency dyeing strategy that can improve the dye uptake and binding fastness while maintaining the structural integrity and heat resistance of the aramid fiber as much as possible. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for dyeing meta-aramid based on plasma treatment and benzyl alcohol carrier. The method uses plasma physical modification technology to perform surface activation pretreatment on PMIA, and then uses benzyl alcohol as a swelling agent for cationic dyeing. The aim is to improve the dyeing performance of PMIA without affecting its thermodynamic properties.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for dyeing meta-aramid fibers based on plasma treatment and benzyl alcohol as a carrier includes the following steps: Step (1): Wash the PMIA fabric with acetone and water in sequence, and then dry it to obtain the dried PMIA fabric. Step (2): The dried PMIA fabric is subjected to plasma treatment. After the treatment is completed, it is taken out to obtain the plasma-treated PMIA fabric. Step (3): The PMIA fabric after plasma treatment is impregnated with benzyl alcohol aqueous solution. After impregnation, the PMIA fabric after benzyl alcohol treatment is obtained. Step (4): The PMIA fabric treated with benzyl alcohol is dyed with dye. After dyeing, the dyed PMIA fabric is obtained.

[0007] Preferably, in step (2), the plasma treatment conditions are: treatment in air plasma at 200-250 V and 0.4-0.5 A for 5-25 min.

[0008] Preferably, in step (3), the concentration of benzyl alcohol in the aqueous solution is 5-12 wt%.

[0009] Preferably, in step (3), the ratio of the plasma-treated PMIA fabric to the benzyl alcohol aqueous solution is 1:20-60.

[0010] Preferably, in step (3), the immersion treatment conditions are: immersion at 60-80 ℃ for 20-30 min.

[0011] Preferably, in step (4), the dye is a cationic dye.

[0012] Furthermore, the cationic dye includes any one of cationic blue SD-BL, cationic red 46, and cationic yellow 51.

[0013] Preferably, in step (4), the concentration of the dye is 1-5% owf.

[0014] Preferably, in step (4), the staining conditions are: staining at pH 4-4.5, bath ratio 1:20-30, and temperature of 120-130 ℃ for 60-80 min.

[0015] Preferably, a dyed meta-aramid is prepared using the plasma treatment and benzyl alcohol carrier-based meta-aramid dyeing method described above.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Plasma surface pretreatment combined with benzyl alcohol swelling dyeing can effectively improve the dyeing performance of PMIA. The pretreatment method has the advantages of simple operation and short processing time. After treatment, benzyl alcohol is used as a swelling agent for dyeing, which significantly improves the dyeing performance while effectively reducing the amount of carrier and electrolyte. This maximizes the preservation of the original thermal stability and mechanical properties of PMIA, providing a new technical path for the industrialization of dyeing and finishing of aramid fibers.

[0017] 2. Plasma surface modification can improve the surface roughness of PMIA and introduce polar functional groups on the fiber surface, thereby enhancing the surface energy and dye affinity. At a treatment time of 20 min, the fiber surface roughness and active groups are optimal, resulting in the best physicochemical and dyeing properties of PMIA. Benzyl alcohol, as a swelling carrier, can further enhance the dye penetration and dyeing rate. An appropriate amount of benzyl alcohol (10%) can improve the dye migration ability within the fiber by adjusting the fiber gaps and amorphous region structure, achieving good dyeing depth and fastness while maintaining mechanical and thermal stability. Multi-factor optimization experiments showed that, as shown in Example 19, under the conditions of plasma treatment for 20 min, benzyl alcohol concentration of 10 wt%, and dye concentration of 4% owf, the K / S value of PMIA fiber increased to 19.6, the dyeing rate reached 92.4%, the fastness to dry and wet rubbing and soaping reached grade 4-5, the fastness to sunlight improved from grade 1 to grade 3, and the mechanical properties were slightly enhanced. This is because plasma treatment promotes the adsorption of dye and carrier by introducing polar groups and increasing surface energy, while the swelling effect of benzyl alcohol improves the molecular chain orientation and density; the synergistic effect of the two improves the mechanical properties of the fiber. Attached Figure Description

[0018] Figure 1 These are the XRD patterns of Examples 1-5 and Comparative Example 1 in this invention; Figure 2 These are SEM images of PMIA fibers from Examples 1-5 and Comparative Example 1 of this invention; Figure 3 These are the FTIR plots of Example 4 and Comparative Example 1; Figure 4 These are line graphs and bar graphs showing the K / S values ​​versus dyeing rates for Examples 6-10 and Comparative Example 2 of this invention; Figure 5 These are staining effect diagrams of Examples 6-10 and Comparative Example 2 in this invention; Figure 6 These are line graphs and bar graphs showing the K / S values ​​versus dyeing rates in Examples 11-16 of this invention; Figure 7These are line graphs and bar graphs showing the K / S values ​​versus dyeing rates in Examples 14 and 17-20 of this invention. Figure 8 These are staining effect diagrams of Examples 11-20 and Comparative Example 2 in this invention; Figure 9 These are staining effect diagrams of Examples 19 and 21-22 of this invention; Figure 10 These are the TG curves of Comparative Examples 1, 4, 5 and 19 of this invention; Figure 11 This is a bar chart showing the breaking strength and elongation at break of Comparative Examples 1, 4, 5 and 19 of this invention. Figure 12 This is a bar chart showing the K / S values ​​and dyeing rates of Comparative Examples 6-11 in this invention; Figure 13 This is a line graph showing the fracture strength and elongation at break of comparative examples 6-11 in this invention; Figure 14 This is a bar chart showing the K / S values ​​and dyeing rates of comparative examples 11-13 in this invention; Figure 15 This is a bar chart showing the breaking strength and elongation at break of the plasma-treated PMIA fabric prepared in Comparative Example 11 of this invention, and Comparative Examples 11-13. In the picture: Figure 2 (a) is a SEM image of PMIA fibers in Comparative Example 1; (b) is a SEM image of PMIA fibers in Example 1; (c) is a SEM image of PMIA fibers in Example 2; (d) is a SEM image of PMIA fibers in Example 3; (e) is a SEM image of PMIA fibers in Example 4; (f) is a SEM image of PMIA fibers in Example 5. Figure 8 In the example, B7 is Example 11, B8 is Example 12, B9 is Example 13, B10 and R1 are both Examples 14, B11 is Example 15, B12 is Example 16, R2 is Example 17, R3 is Example 18, R4 is Example 19, and R5 is Example 20. Figure 9 (a) is a staining effect diagram of Example 19; (b) is a staining effect diagram of Example 21; (c) is a staining effect diagram of Example 22; Figure 13 (a) is a line graph of the breaking strength of Comparative Example 6-11; (b) is a line graph of the breaking elongation of Comparative Example 6-11. Detailed Implementation

[0019] The present invention will be further illustrated below through specific embodiments. The following embodiments are specific implementations of the present invention, but the implementation of the present invention is not limited to the following embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and are included within the protection scope of the present invention.

[0020] Example 1 This embodiment discloses a plasma-based pretreatment method for meta-aramid fibers, including the following steps: Step (1): Place 2 g of PMIA fabric in acetone and ultrasonically wash for 2 h. After washing, clean the surface with deionized water and dry it in an oven at 60 ℃ to obtain the dried PMIA fabric. Step (2): Place the dried PMIA fabric in an air plasma at 200 V and 0.5 A for 5 min. After the treatment, take it out to obtain the plasma-treated PMIA fabric.

[0021] Example 2 The difference from Example 1 is that in step (2), the air plasma treatment time is changed to 10 min; other parameters and conditions are the same as in Example 1.

[0022] Example 3 The difference from Example 1 is that in step (2), the air plasma treatment time is changed to 15 min; other parameters and conditions are the same as in Example 1.

[0023] Example 4 The difference from Example 1 is that in step (2), the air plasma treatment time is changed to 20 min; other parameters and conditions are the same as in Example 1.

[0024] Example 5 The difference from Example 1 is that in step (2), the air plasma treatment time is changed to 25 min; other parameters and conditions are the same as in Example 1.

[0025] Example 6 This embodiment discloses a method for dyeing meta-aramid fibers based on plasma treatment and benzyl alcohol as a carrier, including the following steps: Step (1): The pretreated PMIA fabric prepared in Example 1 was impregnated with a 5 wt% benzyl alcohol aqueous solution. After impregnation, the benzyl alcohol-treated PMIA fabric was obtained. The immersion treatment conditions were as follows: immersion at a bath ratio of 1:20 and a temperature of 80 °C for 30 min; washing and drying conditions: washing twice with deionized water at a bath ratio of 30:1 at room temperature, 5 min each time, and then washing once more with acetone / water solution (volume ratio 1:1) to remove residual benzyl alcohol; after washing, the sample was centrifuged at 1000 rpm for 1 min to dehydrate, air-dried at room temperature for about 20 min, and then vacuum-dried at 60 °C for 3 h to constant weight; Step (2): The PMIA fabric treated with benzyl alcohol was dyed with a 40 ml mixed aqueous solution containing 0.8 g sodium chloride and 1% owf cationic blue SD-BL. After dyeing, the dyed PMIA fabric was obtained. The staining conditions were as follows: staining at pH 4.5, a liquor ratio of 1:20, and a temperature of 120 °C for 60 min.

[0026] Example 7 The difference from Example 6 is that in step (1), Example 1 is replaced with Example 2; all other parameters and conditions are the same as in Example 6.

[0027] Example 8 The difference from Example 6 is that in step (1), Example 1 is replaced with Example 3; all other parameters and conditions are the same as in Example 6.

[0028] Example 9 The difference from Example 6 is that in step (1), Example 1 is replaced with Example 4; all other parameters and conditions are the same as in Example 6.

[0029] Example 10 The difference from Example 6 is that in step (1), Example 1 is replaced with Example 5; all other parameters and conditions are the same as in Example 6.

[0030] Example 11 The difference from Example 6 is that in step (1), the concentration of benzyl alcohol is changed to 7 wt%, and Example 1 is replaced with Example 4; other parameters and conditions are the same as in Example 6.

[0031] Example 12 The difference from Example 11 is that in step (1), the concentration of benzyl alcohol is changed to 8 wt%; other parameters and conditions are the same as in Example 11.

[0032] Example 13 The difference from Example 11 is that in step (1), the concentration of benzyl alcohol is changed to 9 wt%; other parameters and conditions are the same as in Example 11.

[0033] Example 14 The difference from Example 11 is that in step (1), the concentration of benzyl alcohol is changed to 10 wt%; other parameters and conditions are the same as in Example 11.

[0034] Example 15 The difference from Example 11 is that in step (1), the concentration of benzyl alcohol is changed to 11 wt%; other parameters and conditions are the same as in Example 11.

[0035] Example 16 The difference from Example 11 is that in step (1), the concentration of benzyl alcohol is changed to 12 wt%; other parameters and conditions are the same as in Example 11.

[0036] Example 17 The difference from Example 14 is that in step (1), the concentration of cationic blue SD-BL is changed to 2%owf; other parameters and conditions are the same as in Example 14.

[0037] Example 18 The difference from Example 14 is that in step (1), the concentration of cationic blue SD-BL is changed to 3% owf; other parameters and conditions are the same as in Example 14.

[0038] Example 19 The difference from Example 14 is that in step (1), the concentration of cationic blue SD-BL is changed to 4% owf; other parameters and conditions are the same as in Example 14.

[0039] Example 20 The difference from Example 14 is that in step (1), the concentration of cationic blue SD-BL is changed to 5% owf; other parameters and conditions are the same as in Example 14.

[0040] Example 21 The difference from Example 19 is that in step (1), the dye cationic blue SD-BL is changed to cationic red 46; other parameters and conditions are the same as in Example 19.

[0041] Example 22 The difference from Example 19 is that in step (1), the dye cationic blue SD-BL is changed to cationic yellow 51; other parameters and conditions are the same as in Example 19.

[0042] Comparative Example 1 This comparative example discloses a pretreatment method for meta-aramid fibers, including the following steps: 2 g of PMIA fabric was placed in acetone and ultrasonically washed for 2 h. After washing, the surface was cleaned with deionized water and dried in an oven at 60 ℃ to obtain the pretreated PMIA fabric.

[0043] Comparative Example 2 This comparative example discloses a dyeing method for meta-aramid fibers, comprising the following steps: Step (1): Place 2 g of PMIA fabric in acetone and ultrasonically wash for 2 h. After washing, clean the surface with deionized water and dry it in an oven at 60 ℃ to obtain the pretreated PMIA fabric. Step (2): The pretreated PMIA fabric is impregnated with a 5 wt% benzyl alcohol aqueous solution. After impregnation, the PMIA fabric treated with benzyl alcohol is obtained. The immersion treatment conditions were as follows: immersion at a bath ratio of 1:20 and a temperature of 80 °C for 30 min; washing and drying conditions: washing twice with deionized water at a bath ratio of 30:1 at room temperature, 5 min each time, and then washing once more with acetone / water solution (volume ratio 1:1) to remove residual benzyl alcohol; after washing, the sample was centrifuged at 1000 rpm for 1 min to dehydrate, air-dried at room temperature for about 20 min, and then vacuum-dried at 60 °C for 3 h to constant weight; Step (3): The PMIA fabric treated with benzyl alcohol was dyed with a 40 ml mixed aqueous solution containing 0.8 g sodium chloride and 1% owf cationic blue SD-BL. After dyeing, the dyed PMIA fabric was obtained. The staining conditions were as follows: staining at pH 4.5, a liquor ratio of 1:20, and a temperature of 120 °C for 60 min.

[0044] Comparative Example 3 This comparative example discloses a dyeing method for meta-aramid fibers, comprising the following steps: The pretreated PMIA fabric prepared in Comparative Example 1 was dyed with a 40 ml mixed aqueous solution containing 0.8 g sodium chloride and 4% owf cationic blue SD-BL. After dyeing, the dyed PMIA fabric was obtained. The staining conditions were as follows: staining at pH 4.5, a liquor ratio of 1:20, and a temperature of 120℃ for 60 min.

[0045] Comparative Example 4 The difference from Comparative Example 2 is that in step (2), the concentration of benzyl alcohol is changed to 10 wt%; in step (3), the concentration of cationic blue SD-BL is changed to 4 wt%; other parameters and conditions are the same as those in Comparative Example 2.

[0046] Comparative Example 5 This comparative example discloses a dyeing method for meta-aramid fibers, comprising the following steps: The plasma-treated PMIA fabric prepared in Example 4 was dyed with 4% owf cationic blue SD-BL. After dyeing, the dyed PMIA fabric was obtained. The staining conditions were as follows: staining at pH 4.5, a liquor ratio of 1:20, and a temperature of 120 °C for 60 min.

[0047] Comparative Example 6 The difference from Comparative Example 2 is that in step (2), the 5 wt% benzyl alcohol aqueous solution was replaced with 2 mol benzyl alcohol (99% purity); in step (2), the concentration of cationic blue SD-BL was changed to 4 wt% owf; other parameters and conditions were the same as those in Comparative Example 2.

[0048] Comparative Example 7 This comparative example discloses a dyeing method for meta-aramid fibers, comprising the following steps: Step (1): Place 2 g of PMIA fabric in acetone and ultrasonically wash for 2 h. After washing, clean the surface with deionized water and dry it in an oven at 60 ℃ to obtain the dried PMIA fabric. Step (2): Place the dried PMIA fabric in an air plasma of 200 V and 0.5 A for 1 min. After the treatment, take it out to obtain the plasma-treated PMIA fabric. Step (3): The pretreated PMIA fabric is impregnated with 2 mol of benzyl alcohol. After impregnation, the PMIA fabric treated with benzyl alcohol is obtained. The immersion treatment conditions were as follows: immersion at 80 ℃ for 30 min; washing and drying conditions: washing twice with deionized water at a bath ratio of 30:1 at room temperature, 5 min each time, and then washing once more with acetone / water solution (volume ratio 1:1) to remove residual benzyl alcohol; after washing, the sample was centrifuged at 1000 rpm for 1 min to dehydrate, air-dried at room temperature for about 20 min, and then vacuum-dried at 60 ℃ for 3 h to constant weight; Step (4): The PMIA fabric treated with benzyl alcohol was dyed with a 40 ml mixed aqueous solution containing 0.8 g sodium chloride and 4% owf cationic blue SD-BL. After dyeing, the dyed PMIA fabric was obtained. The staining conditions were as follows: staining at pH 4.5, a liquor ratio of 1:20, and a temperature of 120 °C for 60 min.

[0049] Comparative Example 8 The difference from Comparative Example 7 is that in step (2), the air plasma treatment time is changed to 3 min; other parameters and conditions are the same as those in Comparative Example 7.

[0050] Comparative Example 9 The difference from Comparative Example 7 is that in step (2), the air plasma treatment time is changed to 5 min; other parameters and conditions are the same as those in Comparative Example 7.

[0051] Comparative Example 10 The difference from Comparative Example 7 is that in step (2), the air plasma treatment time is changed to 8 min; other parameters and conditions are the same as those in Comparative Example 7.

[0052] Comparative Example 11 The difference from Comparative Example 7 is that in step (2), the air plasma treatment time is changed to 10 min; other parameters and conditions are the same as those in Comparative Example 7.

[0053] Comparative Example 12 The difference from Comparative Example 7 is that in step (3), 2 mol of benzyl alcohol is replaced with 2 mol of chlorobenzene; all other parameters and conditions are the same as those in Comparative Example 7.

[0054] Comparative Example 13 The difference from Comparative Example 7 is that in step (3), 2 mol of benzyl alcohol is replaced with a mixture of 1 mol of chlorobenzene and 1 mol of benzyl alcohol; other parameters and conditions are the same as those in Comparative Example 7.

[0055] In the above embodiments and comparative examples: the PMIA fabric is a 100% meta-aramid fabric, twill weave, with a warp density of 236 threads / 10 cm, a weft density of 217 threads / 10 cm, and a weight of 160 g / m². 2 .

[0056] Experimental data and characterization To analyze the effect of different plasma pretreatment times on fiber crystallinity, XRD analysis was performed on Examples 1-5 and Comparative Example 1. The specific testing method was as follows: X-ray diffractometer (Cu) target was used at an angle of 5-80° and a scanning speed of 10° / min, and the surface crystallinity of the fabric was calculated. The results are as follows: Figure 1 As shown: Figure 1In Comparative Example 1, PMIA exhibited a distinct diffraction peak at approximately 20° 2θ, with a calculated crystallinity of 45.6%. Its highly oriented and crystalline molecular structure is precisely what makes it difficult to dye. With increasing plasma treatment time in Examples 1-5, the diffraction peak intensity gradually weakened, indicating a gradual decrease in fiber crystallinity. This demonstrates that plasma treatment can weaken the ordered arrangement of molecular chains to some extent, leading to the destruction of crystalline regions and an increase in amorphous regions. After plasma treatment, the decrease in crystallinity is more favorable for the diffusion of dye molecules and the exposure of binding sites, helping to improve the migration of fiber segments and the diffusion and penetration of dyes, providing a structural basis for subsequent dyeing performance improvement. Furthermore, the increased proportion of amorphous regions also contributes to the stable embedding of dyes within the fiber, improving the depth and persistence of dye binding.

[0057] The surface morphology of PMIA fibers in Examples 1-5 and Comparative Example 1 was observed using cold field emission scanning electron microscopy. The samples were sputter-coated with gold before testing. The surface morphology of PMIA fibers with different plasma pretreatment times is shown below. Figure 2 As shown: After plasma treatment, the surface morphology of PMIA will gradually change from smooth to rough and porous over time. Figure 2 The original surface structure of PMIA fiber in Comparative Example 1 is relatively smooth, with no obvious grooves or rough features. This indicates that the original fiber has a highly regular and dense structure, making it difficult for dyes and other molecules to penetrate. Figure 2 b and Figure 2 In Example 1 (5 min surface treatment) and Example 2 (10 min surface treatment), slight roughness and grooves appeared on the surface, indicating that the plasma initially etched the PMIA surface and may have formed a small number of active groups. Figure 2 In Example 3, where the surface treatment lasted 15 minutes, the surface roughness increased further, with more obvious cracks and groove marks appearing, making it easier to combine with dye. Figure 2 Example 4, shown in section e, involves a 20-minute surface treatment, which forms numerous micropores and grooves on the fiber surface, significantly increasing the specific surface area and allowing for full binding with dye molecules. Figure 2 In Example 5, where the surface treatment lasted 25 min, the surface roughness and porosity increased significantly, and some fibers showed obvious structural damage and excessive etching, which may be detrimental to dye adsorption.

[0058] To investigate the effect of plasma pretreatment on the surface chemical structure of PMIA fibers, FTIR analysis was performed on Examples 4 and Comparative Example 1. The specific testing method was as follows: an attenuated total reflectance Fourier transform infrared spectrometer was used, with a scanning wavenumber range of 500–4000 cm⁻¹, a resolution of 4 cm⁻¹, and a total of 64 scans. The results are as follows: Figure 3 As shown: exist Figure 3 The NH stretching vibration peaks all appeared around 3298 cm⁻¹. In Comparative Example 1, the original PMIA fiber sample showed C=O stretching vibration peaks at 1732 cm⁻¹ and 1702 cm⁻¹, respectively, corresponding to the C=C skeleton vibration peak of the amide group (-CONH-), and at 1645 cm⁻¹, the peak corresponding to the C=C skeleton vibration of the aromatic ring; all are typical characteristic absorption peaks of PMIA. After 20 min of plasma treatment, the fiber surface of Example 4 showed more pronounced NH and OH stretching vibration absorption peaks near 3300-3500 cm⁻¹, indicating an increase in the number of amino and hydroxyl groups on the surface after treatment. Furthermore, the enhanced C=O absorption peak at 1732 cm⁻¹ further indicates that plasma treatment induced a surface oxidation reaction to produce carboxyl groups, providing reaction sites for the binding of cationic dyes. The intensity of the characteristic peaks at 1702 cm⁻¹ and 1645 cm⁻¹ remained essentially unchanged, indicating that the PMIA main chain structure was basically preserved and not destroyed after plasma treatment, with only surface modification occurring. The changes in these peak intensities indicate that plasma pretreatment introduces polar groups (amino, carboxyl, and hydroxyl groups) onto the fiber surface, which enhances the interaction with cationic dyes and thus improves dyeing performance.

[0059] To further verify the effect of plasma pretreatment on the surface wettability of PMIA fibers, contact angle tests were conducted on Examples 1-5 and Comparative Example 1. The specific testing method was as follows: a KRUSS DSA25 contact angle meter was used to measure the PMIA contact angle, with deionized water as the probe solution, a droplet volume of 5 μL, a titration rate of 0.5 μL·s⁻¹, and a needle tip distance of 5 mm from the sample surface. Young–Laplace fitting was used for calculation. The water contact angles of the PMIA fibers in Examples 1-5 and Comparative Example 1 are shown in Table 1. Table 1. θ of PMIA surface and water under different pretreatment times

[0060] When the contact angle is less than 90°, the fiber is hydrophilic. The PMIA fiber in Comparative Example 1 has a contact angle of 74.2°, thus exhibiting some hydrophilicity, but the overall wettability remains limited. With increasing treatment time, the contact angle gradually decreases: to 60.4° at 5 min, further to 35.6° at 10 min, only 20.5° at 15 min, and continuing to decrease to 11.3° at 20 min. When the treatment time reaches 25 min, water droplets cannot maintain their shape on the fiber surface and spread rapidly, with the contact angle approaching 0°, exhibiting superhydrophilic characteristics. This result indicates that plasma treatment can introduce polar hydrophilic groups and alter the surface energy of PMIA fibers, thereby significantly improving the wettability of the fibers. With increasing treatment time, the hydrophilicity of the fiber surface continues to increase, ultimately achieving a transition from moderately hydrophilic to superhydrophilic.

[0061] The K / S values ​​of the dyed PMIA fabrics in Examples 6-10 and Comparative Example 2 were measured using a Datacolor 850 spectrophotometer, and the dye uptake rate was calculated using a UV spectrophotometer at the maximum absorption wavelength of the dye. The results are as follows: Figure 4 and Figure 5 As shown: Figure 4 and Figure 5 The changes in K / S value, dyeing rate, and dyeing effect after PMIA was treated with 5 wt% benzyl alcohol and dyed with 1% owf dye under different plasma pretreatment times were investigated.

[0062] from Figure 4 and Figure 5 As can be seen, when the plasma treatment time is 5-20 min, the K / S value and dye uptake of the dyed PMIA fabric gradually increase. The improvement is most significant at a treatment time of 20 min, with the K / S value increasing from 5.1 to 7.5 and the dye uptake increasing from 41.2% to 54.6% compared to the untreated PMIA in Comparative Example 2. However, at a treatment time of 25 min, both the K / S value and dye uptake decrease compared to 20 min. This indicates that plasma pretreatment for a certain period can activate the PMIA fiber surface, introducing polar groups such as oxygen-containing (-COOH, -OH, C=O) and nitrogen-containing (-NH) groups, improving its surface energy, increasing the binding sites of dye molecules, enhancing the adsorption of dye molecules to the fiber, promoting dye penetration and fixation, and maintaining the basic structural stability of the fiber. However, prolonged plasma treatment can cause excessive etching or even ablation on the PMIA surface, which is no longer conducive to dye adhesion or penetration, leading to a decrease in color intensity.

[0063] The K / S values ​​of the dyed PMIA fabrics in Examples 11-20 were measured using a Datacolor 850 spectrophotometer, and the dye uptake rate was calculated using a UV spectrophotometer at the maximum absorption wavelength of the dye. The results are as follows: Figure 6 , Figure 7 , Figure 8 As shown: Figure 6 , Figure 7 , Figure 8 The changes in K / S value, dyeing rate, and dyeing effect after PMIA staining under different benzyl alcohol and dye concentrations after plasma pretreatment for 20 min were investigated.

[0064] Figure 6 In the study, when the benzyl alcohol mass fraction was 7-12% (plasma treatment for 20 min, dye 1% owf), the K / S value reached a peak of 10.1 at 10 wt%, and the dyeing rate also reached 76.1%. Subsequently, at 12 wt%, the K / S decreased to 8.1, and the dyeing rate also decreased to 75.2%. This indicates that an appropriate benzyl alcohol concentration can optimize PMIA dyeing performance by controlling fiber swelling, but excessive benzyl alcohol will cause excessive fiber swelling and damage, resulting in a decrease in dye binding efficiency.

[0065] Figure 7 The effect of dye concentrations of 1-5% owf on the dyeing performance of PMIA was investigated under the conditions of plasma pretreatment for 20 min and benzyl alcohol mass fraction of 10%. When the dye concentration was 1%-4% owf, the K / S value and dyeing rate gradually increased, with the best effect achieved at 4% owf, where the K / S reached 19.6 and the dyeing rate reached 92.4%. However, when the dye concentration increased to 5% owf, the K / S value and dyeing rate showed a decreasing trend. This indicates that under the plasma pretreatment and the expansion effect of benzyl alcohol, an appropriate dye concentration can allow the dye to fully penetrate into the amorphous region of PMIA, improving the coloring depth of the fiber and achieving dye saturation inside the fiber. However, excessive dye forms aggregates in the dye bath, making it difficult to penetrate into the fiber interior, leading to a decrease in the K / S value. Simultaneously, competition between dye molecules for limited binding sites means that some dye is not effectively adsorbed, resulting in a decrease in the dyeing rate.

[0066] To verify the universality of the dyeing method in this invention for different color dyeing systems, the optimal example 19 was selected. Under the conditions of plasma treatment time (20 min), benzyl alcohol (10 wt%), and dye concentration (4% owf) in Example 19, cationic red 46 and cationic yellow 51 were further selected for dyeing experiments. The dyed sample images are shown below. Figure 9 As shown: Figure 9The staining depths (K / S) of the two dyes in samples b and c reached approximately 17.6 and 18.4, respectively, with staining rates of 89.3% and 91.2%. These results are consistent with... Figure 9 The results of cationic blue SD-BL in a (19.6%, 92.4%) were not significantly different, indicating that the dyeing method in the embodiments of the present invention has a significant dyeing effect on all three primary color systems, verifying the universality of the method.

[0067] Regarding color fastness, the color fastness to rubbing and washing was tested according to AATCC standards, and the color fastness to sunlight was evaluated according to GB / T 8427-2008 standards. Table 2 shows the color fastness to dry and wet rubbing, color fastness to washing, and color fastness to sunlight for Example 19 and Comparative Examples 3 and 4: Table 2 Colorfastness of PMIA fabrics dyed using different dyeing systems

[0068] As shown in Table 2, Comparative Example 4 and Example 19 both showed improved color fastness compared to the untreated directly dyed PMIA samples, indicating that both plasma treatment and benzyl alcohol dyeing improved the color fastness of the dye in the fiber to varying degrees.

[0069] The dry rubbing scores remained at 4-5, indicating that all samples exhibited excellent color fastness under dry rubbing conditions.

[0070] In terms of wet friction, the original PMIA sample was only grade 3, while the samples after plasma treatment or direct dyeing with benzyl alcohol were all improved to grade 3-4 or 4-5. This indicates that the pretreatment improved the binding strength between the dye and the fiber and reduced the dye migration or shedding in the wet state.

[0071] Regarding color fastness to washing, the treated PMIA samples were all superior to the original samples. In particular, Example 19 achieved a grade of 4-5 in the case of staining, indicating that the dye was more firmly bound to the fiber and less affected by washing. This may be due to the plasma pretreatment increasing the surface energy, while the swelling effect of benzyl alcohol promoted the dye to penetrate deeper into the amorphous region inside the fiber.

[0072] Regarding lightfastness, analysis of PMIA fabrics revealed that untreated PMIA fabrics dyed directly showed the worst performance (Grade 1), while samples dyed with benzyl alcohol alone showed a slight improvement (Grade 2). Plasma pretreatment resulted in the best effect of benzyl alcohol swelling dyeing (Grade 3). This indicates that plasma treatment enhances the penetration of benzyl alcohol through surface activation, and the combined effect of both may have created a more stable dye-fiber bond structure and a partial UV shielding effect. Overall, the lightfastness is at a moderate level. Furthermore, the increased dyeing depth in Example 19 is also a contributing factor to the improved lightfastness.

[0073] Since meta-aramid fibers are widely used in industrial protective clothing such as firefighting suits, metallurgical suits, and training uniforms, it is necessary to perform TG testing on the dyed PMIA. The specific testing method is as follows: the thermal properties of Comparative Examples 1, 4, 5, and 19 are analyzed using an SDT Q600 synchronous thermogravimetric analyzer. Test conditions: temperature range 30-800 ℃, heating rate 20 ℃ / min; test results are as follows. Figure 10 As shown.

[0074] Depend on Figure 10 It can be seen that the thermal decomposition process of PMIA can be mainly divided into three stages: The first stage occurs between 30-150 °C, and the weight loss of each sample in this stage is about 2-5%, mainly attributed to the volatilization of adsorbed moisture or residual solvent in the fiber. In this stage, the weight loss of Comparative Example 4 is slightly higher, possibly due to its more porous surface structure or increased porosity, resulting in enhanced hygroscopicity and thus more mass loss in the initial stage of heating. The second stage of thermal decomposition occurs between 150-415 °C. This stage is mainly caused by the breakage of trace impurities, small molecular chain segments, and some hydrogen bonds or weak polar bonds in the fiber.

[0075] Compared to the untreated and dyed PMIA sample of Comparative Example 1, Comparative Example 4 and Example 19 exhibited more significant mass loss (approximately 3-4%) in the 280-415 °C range. One reason may be the presence of cationic dye residue after dyeing, and the fact that benzyl alcohol is volatile or decomposes at around 300 °C, increasing the weight loss rate in this temperature range. Another reason may be the swelling effect of benzyl alcohol on the fiber surface, resulting in loose intermolecular arrangement and the introduction of volatile residues. Plasma pretreatment may also have enhanced the binding of benzyl alcohol to the fiber, leading to a more uniform distribution and less residue, partially offsetting its negative impact, thus resulting in a lower weight loss rate in Example 19.

[0076] The third stage involves the large-scale decomposition and carbonization of the main chain structure of PMIA (such as amide bonds and aromatic rings), typically starting around 415 °C. During this stage, the rate of thermal weight loss accelerates significantly, with the final char content approaching 45%. It can be observed that the thermal decomposition rates of the dyed sample treated only with benzyl alcohol (Comparative Example 4) and the plasma / benzyl alcohol-treated sample (Example 19) are faster, indicating that this type of treatment weakens the thermal stability of PMIA to some extent. This may stem from the destruction of the surface structure, the weakening of intermolecular forces, and the instability of the introduced functional groups at high temperatures. The swelling effect of benzyl alcohol has a certain impact on the thermal stability of PMIA, manifested as increased thermal weight loss in the mid-to-high temperature range. However, this effect is weakened after dyeing with benzyl alcohol following pretreatment. Plasma surface pretreatment not only alters the microstructure of the fiber, but moderate pretreatment also helps to mitigate the negative thermal effects of benzyl alcohol treatment.

[0077] Using an electronic fabric tensile tester, with a sample holding length of 200 mm, a tensile speed of 100 mm / min, and a pre-tension of 2 N, the breaking strength and elongation at break of Comparative Examples 1, 4, 5, and 19 were tested. Figure 11 The breaking strength and elongation at break of PMIA before and after staining in different systems are shown. Depend on Figure 11 It can be seen that the breaking strength of the untreated and undyed PMIA raw fibers in Comparative Example 1 is 755.7 N, and the breaking elongation is 29.7%.

[0078] In Comparative Example 5, which was directly dyed after 20 minutes of plasma treatment, the tensile strength slightly increased to 758.3 N, and the elongation at break increased to 30.5%. This indicates that moderate plasma treatment, without significantly damaging the fiber structure, may slightly enhance the mechanical properties by improving surface energy and microstructure relaxation. In Comparative Example 4, which was dyed after treatment with 10 wt% benzyl alcohol alone, the tensile strength of PMIA increased to 760.2 N, and the elongation at break increased to 31.2%. This further demonstrates that benzyl alcohol has a certain plasticizing and swelling effect on the fiber surface, which is beneficial for dispersing internal stress and improving its extensibility.

[0079] In Example 19, after plasma pretreatment for 20 min followed by staining with 10 wt% benzyl alcohol, the tensile strength of PMIA reached 765.4 N, and the elongation at break also increased to 32.3%, both higher than other samples. This indicates that plasma treatment followed by benzyl alcohol staining of PMIA improves the surface condition and internal structural orientation of the fiber without damaging the main fiber structure, making it more flexible and resilient under stress.

[0080] In conclusion, plasma treatment and benzyl alcohol dyeing not only did not weaken the mechanical properties of PMIA, but also improved its breaking strength and elongation to a certain extent, especially when dyed after treatment. These results demonstrate that while improving dyeing performance, the mechanical properties of the fiber can be maintained or even optimized, providing strong support for PMIA in applications requiring both high strength and good dyeing performance.

[0081] The dyeing properties of Comparative Examples 6-11 were analyzed. The K / S value and dye uptake of the dyed PMIA fabrics in Comparative Examples 6-11 were tested to analyze the effect of different plasma treatment times on the dyeing properties of PMIA in the comparative examples. The test results are as follows: Figure 12 As shown; like Figure 12As shown, in Comparative Example 6, the PMIA fiber without plasma treatment but after benzyl alcohol impregnation and dyeing, had a K / S value of 13.49 and a dyeing rate of 79.4%, indicating mediocre dyeing performance. With increasing plasma treatment time, both the K / S value and dyeing rate of the PMIA fiber showed a trend of first increasing and then stabilizing. In Comparative Examples 7 and 8, after plasma treatment for 1 and 3 minutes respectively, the K / S values ​​significantly increased to approximately 15.74 and 15.93, and the dyeing rates increased to approximately 80.3% and 81.5%, indicating that plasma treatment effectively improved the wettability of the fiber surface and the dye adsorption capacity. Further increasing the treatment time, in Comparative Examples 9 and 10, after plasma treatment for 5 and 8 minutes respectively, the K / S values ​​continued to increase to 16.64 and 17.18, and the dyeing rates also increased to 82.6% and 83.7%, indicating an increase in polar groups on the fiber surface and enhanced dye diffusion and binding capacity. Finally, in Comparative Example 11, which was treated with plasma for 10 min, the K / S value reached a maximum of 17.76 and the staining rate reached 86.1%, which were about 31.6% and 6.7% higher than those of the untreated sample, respectively, demonstrating the best staining performance.

[0082] The results indicate that plasma surface treatment combined with benzyl alcohol swelling can significantly improve the dyeing performance of PMIA. Furthermore, the activation level of the fiber surface gradually increases with the extension of treatment time, thereby promoting the adsorption and fixation of dye. The optimal treatment time is 10 min.

[0083] However, due to the short plasma treatment time (1-10 min) in Comparative Examples 7-11, although some polar groups (-OH, -COOH, -NH2) could be introduced onto the fiber surface to improve wettability, the degree of modification was limited; the swelling effect of benzyl alcohol was also insufficient to significantly reduce fiber crystallinity or open up enough amorphous regions, resulting in restricted diffusion of dye molecules. Even under the optimal screening conditions (10 min) in Comparative Examples 7-11, the K / S value and dyeing rate only reached 17.76 and 86.1%, respectively, which were still significantly lower than the dyeing performance (19.6 and 92.4%) of Example 19 screened in this invention.

[0084] The mechanical properties of plasma-treated PMIA fabrics prepared in Comparative Examples 1 and 7 to 11 were tested to analyze the effect of different plasma treatment times on the mechanical properties of PMIA. The test results are as follows: Figure 13 As shown: Figure 13 Figure 1 shows the tensile strength (a) and elongation at break (b) of PMIA fibers under different plasma treatment times. As can be seen from the figure, the tensile strength of the untreated and dyed raw PMIA fibers in Comparative Example 1 is approximately 755.7 N. With the extension of treatment time, the tensile strength generally shows a slight upward trend. In Comparative Example 11, the tensile strength reached 757.9 N after 10 min of plasma treatment, an increase of less than 0.3%. This result indicates that plasma treatment has a limited impact on the fiber's main structure and does not significantly alter its strength properties. Regarding elongation at break, the original untreated and undyed fiber in Comparative Example 1 had an elongation of 29.7%, which gradually increased after plasma treatment, reaching 30.3% after 10 min. Although the overall improvement was only 0.6%, the trend still showed a slight improvement in fiber toughness. This is speculated to be related to the introduction of a small number of polar groups or a slight etching effect on the fiber surface by plasma, resulting in a slightly more uniform stress distribution during stretching, thus exhibiting better ductility.

[0085] In summary, plasma treatment has no significant impact on the mechanical properties of PMIA fibers, only showing a slight increase in breaking strength and elongation. This indicates that short-term plasma treatment has little effect on the fiber backbone, with mechanical properties remaining essentially unchanged, lacking a synergistic reinforcing effect. Compared to the examples, the increase in elongation and strength from short-term plasma treatment in Comparative Examples 7-11 is insufficient, suggesting inadequate surface modification and internal structure regulation of the fibers.

[0086] Dyeing performance analysis was conducted on Comparative Examples 11, 12, and 13. The K / S values ​​and dye uptake rates of the PMIA fabrics after dyeing were tested to analyze the effect of different organic solvent treatments on the dyeing performance of PMIA in the comparative examples. The test results are as follows: Figure 14 As shown: like Figure 14 As shown, under plasma treatment for 10 min, different solvents exhibited significant differences in the dyeing performance of PMIA. In Comparative Example 12, when chlorobenzene was used alone, the K / S value of the fiber was only 7.05, and the dyeing rate was 52.5%, indicating poor dyeing effect. However, in Comparative Example 11, when benzyl alcohol was used, the K / S value and dyeing rate increased to 17.76 and 86.1%, respectively, showing better dyeing performance. This indicates that benzyl alcohol can not only effectively dissolve the dye but also interact with the fiber surface, promoting dye diffusion and binding. When Comparative Example 13 used a mixture of chlorobenzene and benzyl alcohol (1:1 mol), the K / S value and dyeing rate were 14.6 and 75.6%, respectively, which were significantly higher than chlorobenzene alone, but still significantly lower than the pure benzyl alcohol system.

[0087] The results showed that chlorobenzene, being a non-polar solvent, lacked interaction with PMIA fibers, failing to effectively swell the fibers and hindering the penetration of cationic dyes into the fiber interior. Its effect on dye diffusion was limited, resulting in extremely poor dyeing performance. In the chlorobenzene / benzyl alcohol mixture, the mixture weakened the polarity and swelling capacity of benzyl alcohol, reducing dye diffusion and, to some extent, diminishing its promoting effect. Therefore, while the K / S value (14.6) and dyeing rate (75.6%) were better than pure chlorobenzene, they were significantly worse than pure benzyl alcohol. Benzyl alcohol is a more effective carrier solvent, but in the benzyl alcohol system of Comparative Example 11, the plasma treatment time was only 10 min, resulting in insufficient surface modification of the fibers and a limited number of polar groups. Although benzyl alcohol could improve the diffusion channels within the fibers to some extent, it did not synergize with the "optimal plasma treatment time of 20 min" selected in the examples. Therefore, the dyeing performance of Comparative Example 11 was still inferior to that of Example 19.

[0088] Mechanical properties of the plasma-treated PMIA fabric prepared in Comparative Example 11, Comparative Example 11, Comparative Example 12, and Comparative Example 13 were analyzed to examine the effects of different organic solvent treatments on the mechanical properties of PMIA. The test results are as follows: Figure 15 As shown: Depend on Figure 15 It can be seen that under the condition of plasma treatment for 10 min, the effects of different solvent treatments on the mechanical properties of PMIA are different. In Comparative Example 12, the tensile strength and elongation of the chlorobenzene-treated sample are basically consistent with those of the plasma-treated PMIA fabric prepared in Comparative Example 11, indicating that chlorobenzene has a limited effect on the mechanical properties of plasma-treated PMIA. In Comparative Example 11, after treatment with benzyl alcohol, the fiber tensile strength increased slightly from 757.9 N to 759.3 N, and the tensile elongation increased from 30.3% to 30.9%, indicating that benzyl alcohol has a certain promoting effect on fiber toughness, while the strength remains basically unchanged. The performance of the sample treated with a chlorobenzene / benzenyl alcohol mixed solvent in Comparative Example 13 is between the two, showing no obvious synergistic effect.

[0089] Therefore, the main reason why different solvent treatments have different effects on the mechanical properties of PMIA is that the solvent system is not polar enough or the plasma treatment depth is not deep enough, which leads to the failure to effectively improve the stress distribution of the fiber molecular chain, thus failing to fully enhance the elongation or achieve a synergistic improvement in strength.

[0090] In summary, this invention employs a plasma surface activation-benzyl alcohol carrier-assisted dyeing method to modify and dye meta-aramid fibers. Under optimal conditions (plasma treatment time 20 min, benzyl alcohol concentration 10 wt%, dye concentration 4 owf), it exhibits superior dyeing rate and dyeing uniformity. Compared to the surface structure control method studied by SUN et al. (DOI:10.1016 / J.DYEPIG.2025.113121), this invention does not require complex chemical modification or the introduction of high-energy surfactants, is gentler, has a simpler process, and maintains the original mechanical properties of the fiber. Compared to the structure control method using a DMSO / electrolyte mixed system employed by ZHUO et al. (DOI:10.1016 / J.JCIS.2024.06.149), the benzyl alcohol system used in this invention has lower solute quantity and toxicity, is more environmentally friendly, does not require strong organic solvents or a high-salt environment, and the fiber does not undergo significant swelling or degradation. Meanwhile, plasma treatment can form active functional groups on the fiber surface, significantly improving the diffusion rate and binding fastness of dyes, thereby obtaining deeper colors and higher light fastness at lower temperatures and shorter times, with better industrial feasibility and green advantages.

[0091] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A meta-aramid dyeing process based on plasma treatment and benzyl alcohol carrier, characterized in that, The method comprises the following steps: Step (1), pretreated PMIA fabric is subjected to plasma treatment, and after the treatment, the plasma treated PMIA fabric is obtained; Step (2), the plasma treated PMIA fabric is subjected to impregnation treatment using benzyl alcohol, and after the impregnation, the benzyl alcohol treated PMIA fabric is obtained; Step (3), the benzyl alcohol treated PMIA fabric is dyed using a dye, and after the dyeing, the dyed PMIA fabric is obtained; The K / S value of the dyed PMIA fabric is 10.1-19.6, the dye-uptake is 76.1-92.4%, the dry and wet rubbing fastness and soaping fastness are grade 4-5, and the fastness to sunlight is grade 3.

2. The meta-aramid dyeing method based on plasma treatment and benzyl alcohol carrier according to claim 1, characterized in that, In step (1), the pretreated PMIA fabric is prepared by the following steps: the PMIA fabric is sequentially cleaned using acetone and water, and dried to obtain the pretreated PMIA fabric.

3. The meta-aramid dyeing method based on plasma treatment and benzyl alcohol carrier according to claim 1, characterized in that, In step (1), the plasma treatment conditions are: 5-25 min in an air plasma at 200-250 V and 0.4-0.5 A.

4. The meta-aramid dyeing method based on plasma treatment and benzyl alcohol carrier according to claim 1, characterized in that, In step (2), the concentration of benzyl alcohol in the benzyl alcohol aqueous solution is 5-12 wt%.

5. The meta-aramid dyeing method based on plasma treatment and benzyl alcohol carrier according to claim 1, characterized in that, In step (2), the bath ratio of the plasma treated PMIA fabric to the benzyl alcohol aqueous solution is 1:20-60.

6. The meta-aramid dyeing method based on plasma treatment and benzyl alcohol carrier according to claim 1, characterized in that, In step (2), the impregnation treatment conditions are: 20-30 min at 60-80 ℃.

7. The meta-aramid dyeing method based on plasma treatment and benzyl alcohol carrier according to claim 1, characterized in that, In step (3), the dye is a cationic dye.

8. The meta-aramid dyeing method based on plasma treatment and benzyl alcohol carrier according to claim 1, characterized in that, In step (3), the concentration of the dye is 1-5% o.w.f.

9. The meta-aramid dyeing method based on plasma treatment and benzyl alcohol carrier according to claim 1, characterized in that, In step (3), the dyeing conditions are: 60-80 min at 120-130 ℃, pH 4-4.5, bath ratio 1:20-30.

10. A dyed meta-aramid prepared by the method of claim 1-9.

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