Color fixing process of aramid fiber

Abstract

The invention provides a color fixing process of aramid fibers, which comprises the following steps of: firstly, dipping a fabric containing the aramid fibers into a solution containing zinc oxide particles with amino groups modified on the surfaces so as to enhance the binding activity of the fiber surfaces and dyes; then the soaked fabric is transferred into a cold batch color fixing solution, a color fixing reaction is conducted through irradiation of an excitation light source, and close combination of dye and fibers is achieved through components such as water-based light-cured resin, an active oxygen catalyst and a cationic color fixing agent; after the color fixation reaction is completed, alkali liquor padding treatment is conducted on the fabric, and the color fixation and alkali activation steps are cycled till the preset chroma is achieved; and finally washing the fabric to be neutral and drying. By introducing an amino-modified zinc oxide nanoparticle pretreatment technology, the dye binding capacity of the fiber surface is remarkably improved, and the balance between high color fastness and fabric hand feeling is realized by combining an ultraviolet-excited cold batch fixation system and a multi-step circulating fixation mechanism.

Description

Technical Field

[0001] This invention relates to the field of printing and dyeing technology for aramid fibers, and specifically to a color-fixing process for aramid fibers. Background Technology

[0002] The color-fixing process for aramid fibers needs to address the difficulties in dyeing caused by their high crystallinity and low surface activity. Traditional methods often employ disperse dyes combined with chemical fixing agents. Existing technologies utilize sodium chloride and alternative alkalis for synergistic color fixing, or use the formaldehyde-free fixing agent TCD-R to enhance color fastness. Recent studies have found that structural color technology (such as spraying a thin layer of disordered nanospheres) can replace traditional dyes, generating color through the Mie scattering principle and significantly improving lightfastness. Furthermore, improvements in the environmental friendliness and functionalization of fixing agents, such as the introduction of quaternary ammonium cations and epoxy groups, can reduce water solubility and enhance antibacterial properties.

[0003] Currently, aramid dyeing still primarily uses disperse dyes, but this suffers from low dye uptake and poor color fastness. Traditional fixation processes rely on alkaline substances (such as soda ash) to adjust pH, which can easily damage fibers and makes wastewater treatment difficult. While emerging structural color technologies can achieve non-iridescent, high-lightfastness coloring, they depend on complex microsphere preparation and binder systems, resulting in high industrialization costs. Regarding fixative development, phosphorus-free and formaldehyde-free environmentally friendly products are gradually becoming more common, such as quaternary ammonium salt-epoxy systems, but wet rubbing fastness remains a weakness.

[0004] The technical challenges in color fastness lie in the contradiction between low wet rubbing fastness, poor lightfastness, and environmental friendliness. Traditional dyes have weak bonding strength with fibers and are easily detached due to hydrolysis or mechanical friction. While structural color technology offers good lightfastness, the bonding strength between the microsphere layer and the fiber is limited, and cracks easily appear at creases. The development of fixing agents requires a balance between colorfastness and flexibility; for example, excessive quaternary ammonium salts can reduce the feel of the fabric. Furthermore, environmental regulations restrict the use of phosphorus- and chlorine-containing auxiliaries, leading to the elimination of some efficient but highly polluting processes, further complicating the improvement of color fastness. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a color-fixing process for the printing and dyeing of aramid fibers.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows.

[0007] A color-fixing process for aramid fibers includes the following steps: S1, immerse a fabric containing aramid fibers in a solution of zinc oxide particles with an amino-modified surface, wherein the particle size of the zinc oxide particles is 10-100 nm. S2, the impregnated fabric is taken out and transferred to a cold-pile fixing solution and irradiated with an excitation light source to carry out a fixing reaction. The cold-pile fixing solution includes, by mass percentage, 2-20% dye, 2-5% water-based photocurable resin, 0.5-5% active oxygen catalyst, 0.1-3% cationic fixing agent, 0.01-1% surfactant, and the balance being water. S3 involves immersing the fabric that has completed the color fixation reaction in an alkaline solution. After immersion in the alkaline solution, the liquid retention rate is 30-45%. S2 and S3 are repeated until the preset color value is achieved. S4. After the fabric has been impregnated with alkaline solution, wash it with water until it is neutral, and then dry it.

[0008] Among the aforementioned technical features, aramid fibers refer to aromatic polyamide-restricted fibers, including meta-aramid and / or para-aramid, which possess high strength, high modulus, and excellent heat resistance. However, their high crystallinity and low surface activity result in poor dyeing performance. Primary or secondary amino structures are introduced onto the surface of nanoscale zinc oxide through chemical means to enhance its interaction with fibers and dyes. These interactions include, but are not limited to, amino groups, hydrogen bonds, intermolecular forces, and the physical anchoring effect of impregnation. Cold-pile fixing solution is a functional liquid system that performs the fixing reaction at room temperature or low temperature.

[0009] This invention utilizes the amino structure modified on the surface of nano zinc oxide particles. First, zinc oxide is attached to the surface of the fabric as a photoconversion site. In a cold-pile fixing solution, ultraviolet light irradiation activates the aqueous photocurable resin, causing it to undergo a cross-linking reaction with the dye molecules. At the same time, the reactive oxygen catalyst releases reactive oxygen free radicals, promoting a stronger covalent bond between the dye and the fiber. Meanwhile, the cationic fixing agent and surfactant further enhance the adhesion of the dye to the zinc oxide surface through electrostatic interaction.

[0010] Alkaline padding activates the fiber structure, increasing its affinity for dyes and promoting dye diffusion into the fiber interior during pre-drying. This step is repeated in conjunction with the color-fixing step to ensure uniform dye distribution and achieve the target color saturation. After neutral water washing to remove excess auxiliaries, the fabric is hot-air dried under suitable wind speed and temperature conditions to improve fabric smoothness and hand feel.

[0011] As a preferred technical solution, in step S1, the fabric is made by blending aramid fibers and viscose fibers in a blending ratio of 7:3 to 9:1. By introducing an appropriate amount of viscose fiber, the overall dyeing performance and hand feel of the fabric are improved. Viscose fiber has high hygroscopicity and surface activity, which can enhance the fabric's adsorption capacity for subsequent treatment solutions, thereby enhancing the deposition and fixation efficiency of dyes on the fiber surface. At the same time, its softness also helps to alleviate the stiffness caused by aramid fibers themselves, improving the fabric's processability and comfort.

[0012] As a preferred technical solution, in step S1, the amino groups modified on the surface of the zinc oxide particles are primary or secondary amino groups, which are bonded by a coupling agent. Primary or secondary amino groups possess strong polarity and reactivity, enabling them to interact with functional groups on the fiber surface or in the subsequent fixation system, promoting the directional deposition of dye molecules on the fiber.

[0013] As a preferred technical solution, in step S2, the excitation light source is an LED ultraviolet lamp with a wavelength of 365-405nm and an irradiation intensity of 100-500mW / cm². 2 The irradiation time is 30-60 minutes. The ultraviolet light in the wavelength range can match the absorption peak of the photoinitiator in the water-based photocurable resin. The irradiation intensity takes into account both the reaction rate and the risk of thermal damage to the fabric, avoiding uneven curing caused by local overheating or insufficient energy. The irradiation time of 30-60 minutes is determined based on the dynamic balance between the dye penetration depth and the degree of resin crosslinking, ensuring that the dye is fully fixed while maintaining the original physical properties of the fiber.

[0014] As a preferred technical solution, in step S2, the pH value of the cold-pile fixing solution is adjusted to 5-6 using a phosphate buffer solution, and the fixing reaction time is 12-24 hours. pH control helps maintain the charge interaction between the cationic fixing agent and the fiber surface, while avoiding damage to the aramid fiber structure from strong acids or alkalis. Using a phosphate buffer solution effectively stabilizes the system pH, preventing dye hydrolysis or uneven fixing due to pH fluctuations during the reaction. The reaction time fully considers the reaction kinetics requirements of dye penetration, resin crosslinking, and catalyst action, ensuring that dye molecules are firmly bound to the fiber.

[0015] As a preferred technical solution, in step S2, the active oxygen catalyst is sodium percarbonate or sodium perborate, and its molar ratio with the photocurable resin is 1:(1.05-1.2). This introduces a highly efficient active oxygen release system, which, in conjunction with UV excitation, promotes the oxidative cross-linking reaction between dye molecules and fibers. Sodium percarbonate or sodium perborate can stably release active oxygen free radicals in the reaction system, acting as an initiator to promote the cross-linking reaction of the photocurable resin, and also contributing to the covalent bonding between dye molecules and fiber functional groups. Limiting the molar ratio of catalyst to resin is to avoid over-oxidation or insufficient resin cross-linking due to excessive active oxygen.

[0016] As a preferred technical solution, in step S3, the number of cycles is 2-5. After each cycle, the fabric color is monitored using a colorimeter until the difference between the color and the preset dyeing color is ≤1.5. Here, through multiple cycles of color fixation and alkali activation, the deposition efficiency and distribution uniformity of the dye on the fiber surface are gradually improved, thereby achieving high-precision color control. Each cycle promotes further dye penetration and binding within the fiber, while alkali padding helps open the fiber structure and improve reactivity. Real-time monitoring of color changes using a colorimeter allows for accurate determination of the color fixation endpoint, avoiding over-treatment or insufficient color fixation.

[0017] As a preferred technical solution, in step S3, the alkaline solution is a 3-8 wt% sodium hydroxide solution. After padding, the fabric is pre-dried at 40-60°C for 10-30 minutes to activate the color-fixing reaction. This method combines a moderately alkaline environment with temperature-controlled pre-drying to enhance the fiber's reactivity and promote further bonding between dye molecules and the fiber structure.

[0018] As a preferred technical solution, in step S4, drying is carried out using hot air circulation, with an air velocity of 1-5 m / s, a hot air temperature of 60-80℃, and a hot air duration of 10-30 minutes. The hot air circulation method achieves rapid and uniform drying of the fabric, avoiding damage to fiber properties caused by high temperatures or prolonged heating, and ensuring simultaneous evaporation of moisture from the fabric surface and interior, thus guaranteeing the stability of the color-fixing layer structure.

[0019] As a preferred technical solution, in step S4, after drying, the fabric is transferred to the calendering roller group and calendered at a pressure of 0.1-0.3MPa to further improve the smoothness and gloss of the fabric surface, while enhancing the tight arrangement between fibers and improving the hand feel and appearance quality of the finished fabric.

[0020] The advantages and beneficial effects of this invention are as follows: the pretreatment of zinc oxide nanoparticles with amino modification enhances the binding active sites of the fiber surface and the dye. Combined with the ultraviolet light-excited cold pile fixing system, the water-based photocurable resin and the dye are tightly bound together. Combined with the multi-step fixing mechanism of cyclic alkali activation, the rubbing fastness and color uniformity can be effectively improved, achieving a balance between high color fastness and fabric hand feel. Attached Figure Description

[0021] Figure 1 This is a flowchart of the curing process shown in this invention. Detailed Implementation

[0022] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0023] Example 1 A color-fixing process for aramid fibers includes the following steps: S1, the fabric made by blending aramid fiber and viscose fiber at a ratio of 8:2 is immersed in a solution of zinc oxide particles with a surface modified primary amino group. The zinc oxide particles have a particle size of 30 nm, and the amino group is bonded to the zinc oxide surface by a silane coupling agent KH-550.

[0024] S2, the impregnated fabric is transferred to a cold-pile fixing solution. The fixing solution comprises, by mass percentage: 8% disperse dye, 3% waterborne polyurethane acrylate photocurable resin, 2% sodium percarbonate catalyst, 1% cationic fixing agent, 0.5% nonionic surfactant, and the balance deionized water. The pH of the fixing solution is adjusted to 5.5 using phosphate buffer. The fabric is then immersed in the fixing solution at a distance of 10 cm from the surface. A 300 mW / cm² solution is used. 2 Irradiate with a 385nm LED ultraviolet lamp for 40 minutes, then let stand; the color-fixing reaction lasts for 16 hours.

[0025] S3, after color fixing, immerse the fabric in a 5% sodium hydroxide solution to obtain a fabric with a liquid retention rate of 35%, and pre-dry the fabric in a dryer at 50°C for 20 minutes; repeat steps S2-S3 3 times until the color difference with the target is ≤1.4.

[0026] S4. Wash the fabric with water until neutral, then dry it with hot air circulation at a speed of 3 m / s, a temperature of 70°C, and a time of 20 minutes. After drying, transfer the fabric to a calender and calender it under a pressure of 0.2 MPa.

[0027] Example 2 A color-fixing process for aramid fibers includes the following steps: S1, the fabric made by blending aramid fiber and viscose fiber at a ratio of 7:3 is immersed in a solution of zinc oxide particles with secondary amino groups on the surface. The zinc oxide particles have a particle size of 60 nm and the amino groups are bonded to the zinc oxide surface by a silane coupling agent KH-792.

[0028] S2, the impregnated fabric is transferred to a cold-pile fixing solution. The fixing solution comprises, by mass percentage: 12% reactive dye, 4% water-based epoxy acrylate photocurable resin, 3.5% sodium perborate catalyst, 2% cationic fixing agent, 0.8% anionic surfactant, and the balance deionized water. The pH of the fixing solution is adjusted to 5.8 using phosphate buffer. A 200mW / cm² solution is used to fix the fabric at a distance of 12cm from the surface. 2 Irradiate with a 395nm LED ultraviolet lamp for 50 minutes, then let stand for 20 hours for color fixation reaction.

[0029] S3, after color fixing, immerse the fabric in a 6% sodium hydroxide solution to obtain a fabric with a liquid retention rate of 40%. Pre-dry the fabric in a dryer at 55°C for 15 minutes. Repeat steps S2-S3 4 times until the color difference with the target is ≤1.3.

[0030] S4. Wash the fabric with water until neutral, then dry it with hot air circulation at a speed of 2 m / s, a temperature of 65°C, and a time of 25 minutes. After drying, transfer the fabric to a calender and calender it under a pressure of 0.25 MPa.

[0031] Example 3 A color-fixing process for aramid fibers includes the following steps: S1, the fabric made by blending aramid fiber and viscose fiber at a ratio of 9:1 is immersed in a solution of zinc oxide particles with a surface modified primary amino group. The zinc oxide particles have a particle size of 15 nm and the amino group is bonded to the zinc oxide surface by a silane coupling agent KH-550.

[0032] S2, the impregnated fabric is transferred to a cold-pile fixing solution. The fixing solution comprises, by mass percentage: 5% acid dye, 2.5% water-based polyester acrylate photocuring resin, 1% sodium percarbonate catalyst, 0.5% cationic fixing agent, 0.3% amphoteric surfactant, and the balance deionized water. The pH of the fixing solution is adjusted to 5.2 using phosphate buffer. The fabric is then immersed in the fixing solution at a distance of 8 cm from the surface, using a 400 mW / cm² solution. 2 Irradiate with a 375nm LED ultraviolet lamp for 35 minutes, then let stand; the color-fixing reaction lasts for 14 hours.

[0033] S3, after color fixing, immerse the fabric in a 4% sodium hydroxide solution to obtain a fabric with a liquid retention rate of 32%. Pre-dry the fabric in a dryer at 45°C for 25 minutes. Repeat steps S2-S3 twice until the color difference with the target is ≤1.2.

[0034] S4. Wash the fabric with water until neutral, then dry it with hot air circulation at a speed of 4 m / s, a temperature of 75°C, and a time of 15 minutes. After drying, transfer the fabric to a calender and calender it under a pressure of 0.15 MPa.

[0035] Example 4 A color-fixing process for aramid fibers includes the following steps: S1, a fabric made by blending aramid fiber and viscose fiber at a ratio of 8.5:1.5 is immersed in a solution of zinc oxide particles with a surface modified secondary amino group. The zinc oxide particles have a particle size of 80 nm, and the amino group is bonded to the zinc oxide surface by a silane coupling agent KH-792.

[0036] S2, the impregnated fabric is transferred to a cold-pile fixing solution. The fixing solution comprises, by mass percentage: 15% vat dye, 4.5% water-based polyether acrylate photocurable resin, 4% sodium perborate catalyst, 2.5% cationic fixing agent, 0.7% nonionic surfactant, and the balance deionized water. The pH of the fixing solution is adjusted to 5.9 using phosphate buffer. A 150mW / cm² solution is used to fix the fabric at a distance of 15cm from the surface. 2 Irradiate with an LED ultraviolet lamp with a wavelength of 405nm for 55 minutes, then let stand; the color-fixing reaction lasts for 22 hours.

[0037] S3, after color fixing, immerse the fabric in a 7% sodium hydroxide solution to obtain a fabric with a liquid retention rate of 42%. Pre-dry the fabric in a dryer at 58°C for 12 minutes. Repeat steps S2-S3 5 times until the color difference with the target is ≤1.5.

[0038] S4. Wash the fabric with water until neutral, then dry it with hot air circulation at a speed of 1.5 m / s, a temperature of 80°C, and a time of 10 minutes. After drying, transfer the fabric to a calender and calender it under a pressure of 0.3 MPa.

[0039] Example 5 A color-fixing process for aramid fibers includes the following steps: S1, the fabric made by blending aramid fiber and viscose fiber at a ratio of 7.5:2.5 is immersed in a solution of zinc oxide particles with a surface modified primary amino group. The zinc oxide particles have a particle size of 50 nm and the amino group is bonded to the zinc oxide surface by a silane coupling agent KH-550.

[0040] S2, the impregnated fabric is transferred to a cold-pile fixing solution. The fixing solution comprises, by mass percentage: 10% disperse dye, 3.5% waterborne polyurethane acrylate photocurable resin, 2.5% sodium percarbonate catalyst, 1.5% cationic fixing agent, 0.6% anionic surfactant, and the balance deionized water. The pH of the fixing solution is adjusted to 5.0 using phosphate buffer. The fabric is then immersed in the fixing solution at a distance of 9 cm from the surface, using a 450 mW / cm² solution. 2 Irradiate with a 365nm LED ultraviolet lamp for 30 minutes, then let stand; the color-fixing reaction lasts for 18 hours.

[0041] S3, after color fixing, immerse the fabric in a 3% sodium hydroxide solution to obtain a fabric with a liquid retention rate of 38%, and pre-dry the fabric in a dryer at 42°C for 28 minutes; repeat steps S2-S3 3 times until the color difference with the target is ≤1.1.

[0042] S4. Wash the fabric with water until neutral, then dry it with hot air circulation at a speed of 4.5 m / s, a temperature of 60°C, and a time of 30 minutes. After drying, transfer the fabric to a calender and calender it under a pressure of 0.1 MPa.

[0043] Example 6 A color-fixing process for aramid fibers includes the following steps: S1, a fabric made by blending aramid fiber and viscose fiber at a ratio of 8.2:1.8 is immersed in a solution of zinc oxide particles with a surface modified secondary amino group. The zinc oxide particles have a particle size of 90 nm, and the amino group is bonded to the zinc oxide surface by a silane coupling agent KH-792.

[0044] S2, the impregnated fabric is transferred to a cold-pile fixing solution. The fixing solution comprises, by mass percentage: 18% reactive dye, 4.8% water-based epoxy acrylate photocurable resin, 4.5% sodium perborate catalyst, 2.8% cationic fixing agent, 0.9% amphoteric surfactant, and the balance deionized water. The pH of the fixing solution is adjusted to 6.0 using phosphate buffer. The fabric is then immersed in the fixing solution at a distance of 13 cm from the surface, using a 180 mW / cm² solution. 2 Irradiate with a 395nm LED ultraviolet lamp for 60 minutes, then let stand for 24 hours for color fixation.

[0045] S3, after color fixing, immerse the fabric in an 8% sodium hydroxide solution to obtain a fabric with a liquid retention rate of 44%. Pre-dry the fabric in a dryer at 60°C for 10 minutes. Repeat steps S2-S3 4 times until the color difference with the target is ≤1.5.

[0046] S4. Wash the fabric with water until neutral, then dry it with hot air circulation at a speed of 5 m / s, a temperature of 68°C, and a time of 12 minutes. After drying, transfer the fabric to a calender and perform calendering treatment under a pressure of 0.28 MPa.

[0047] Performance tests were conducted on the above embodiments. For dry / wet rubbing color fastness: tests were performed using a rubbing color fastness meter according to GB / T 3920-2008 "Textiles - Tests for Color Fastness to Rubbing". Hand feel was rated from 1 point (rough and stiff) to 5 points (soft and comfortable). Color change after washing was measured using a spectrophotometer after 5 standard washes with standard detergent at 40°C, according to GB / T 3921-2008 "Textiles - Tests for Color Fastness to Washing". The test results are shown in the table below. The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A color-fixing process for aramid fibers, characterized in that... Includes the following steps: S1, immersing a fabric containing aramid fibers in a solution of zinc oxide particles with an amino-modified surface, wherein the zinc oxide particles have a particle size of 10-100 nm. S2, the impregnated fabric is transferred to a cold-pile fixing solution and irradiated with an excitation light source to carry out a fixing reaction. The cold-pile fixing solution includes, by mass percentage, 2-20% dye, 2-5% water-based photocurable resin, 0.5-5% active oxygen catalyst, 0.1-3% cationic fixing agent, 0.01-1% surfactant and the balance water. S3 involves immersing the fabric that has completed the color-fixing reaction in an alkaline solution. After immersion, the liquid retention rate is 30-45%. S2 and S3 are repeated until the preset color value is achieved. S4. After the fabric has been impregnated with alkaline solution, wash it with water until it is neutral and then dry it.

2. The process according to claim 1, characterized in that: In S1, the fabric is made by blending aramid fiber and viscose fiber in a blending ratio of 7:3-9:

1.

3. The process according to claim 2, characterized in that: In S1, the amino groups modified on the surface of the zinc oxide particles are primary or secondary amino groups, which are bonded by a coupling agent.

4. The process according to claim 1, characterized in that: In step S2, the excitation light source is an LED ultraviolet lamp with a wavelength of 365-405nm and an irradiation intensity of 100-500mW / cm². 2 The irradiation time is 30-60 minutes.

5. The process according to claim 4, characterized in that: In S2, the pH value of the cold reactor fixing solution is adjusted to 5-6 using phosphate buffer, and the fixing reaction time is 12-24 hours.

6. The process according to claim 4, characterized in that: In S2, the active oxygen catalyst is sodium percarbonate or sodium perborate, and its molar ratio with the photocurable resin is 1:(1.05-1.2).

7. The process according to claim 1, characterized in that: In step S3, the number of cycles is 2-5 times. After each cycle, the colorimetry of the fabric is monitored by a colorimeter until the difference between the colorimetry and the preset dyeing colorimetry is ≤1.

5.

8. The process according to claim 7, characterized in that: In step S3, the alkaline solution is a sodium hydroxide solution with a concentration of 3-8 wt%. After padding, the fabric is pre-dried at 40-60°C for 10-30 minutes to activate the color-fixing reaction.

9. The process according to claim 1, characterized in that: In step S4, drying is carried out using hot air circulation with a wind speed of 1-5 m / s, a hot air temperature of 60-80℃, and a hot air time of 10-30 minutes.

10. The process according to claim 9, characterized in that: In step S4, after drying, the fabric is transferred to the calendering roller group and calendered at a pressure of 0.1-0.3 MPa.

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