A method for preparing colored meta-aramid fibers

Abstract

This invention discloses a method for preparing colored meta-aramid fibers: (1) Under dry N2 protection, pigments treated with m-phenylenediamine and terminal amino aromatic hyperbranched polyamide are added to a solvent for dispersion, and 90%–95% isophthaloyl chloride is added for pre-condensation reaction; (2) the remaining isophthaloyl chloride is added for condensation reaction; (3) the chlorine is neutralized to obtain a meta-aramid resin solution; (4) the colored meta-aramid resin solution is used to make colored meta-aramid fibers. This invention uses terminal amino aromatic hyperbranched polyamide to treat pigments, and then combines m-phenylenediamine and isophthaloyl chloride through in-situ solution polymerization. The prepolymer can react with the terminal amino groups of the terminal amino aromatic hyperbranched polyamide adsorbed on the pigment surface, and then continue to undergo chain-growth condensation reaction, which can fundamentally and effectively prevent pigment agglomeration, thereby ensuring the mechanical properties of the fiber.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, and particularly relates to a method for preparing colored meta-aramid fibers. Background Technology

[0002] Meta-aramid fiber is a type of aromatic polyamide fiber with excellent comprehensive properties. It is one of the most widely used and highest-produced high-performance fibers, holding an important position among high-performance fibers. Meta-aramid fiber possesses excellent heat resistance, flame retardancy, acid and alkali stability, electrical insulation, and radiation resistance. It is also stable against the corrosion of reducing agents, bleaching agents, and organic solvents, making it suitable for manufacturing fire suits, fire curtains, spacesuits, aircraft decorative fabrics, and products for high-temperature and corrosive environments.

[0003] The superior performance of meta-aramid fibers stems from their unique structure. Their macromolecular backbone is composed of alternating amide bonds and aromatic rings arranged in a zigzag pattern, with numerous hydrogen bonds between molecules. The aromatic rings significantly enhance the van der Waals forces between molecules. Therefore, meta-aramid fibers are characterized by their regular structure, high crystallinity, high glass transition temperature, and lack of affinity groups. Small-molecule dyes have difficulty penetrating the fiber macromolecules, resulting in very low dye uptake using conventional dyeing methods. This problem is particularly pronounced for highly crystalline wet-spun fibers. While meta-aramid fibers are white with a metallic luster, applications such as protective and flame-retardant fibers require dyeing into vibrant colors to better meet aesthetic and comfort demands. Therefore, colored meta-aramid fibers have emerged.

[0004] Currently, there are two main methods for preparing colored meta-aramid fibers. One method involves first preparing finished or semi-finished aramid fibers, and then using post-dyeing to obtain the meta-aramid fiber product. The other method involves pre-dyeing before spinning to obtain colored meta-aramid fibers. Post-dyeing, due to the inherent characteristics of meta-aramid, requires physical or chemical treatment of the fibers, involving numerous steps, significant energy and water consumption, and varying degrees of environmental pollution. Currently, pre-spinning dyeing techniques often involve directly adding pigments or dyes to the spinning solution for dispersion before spinning. Publications CN104593898A, CN100422401C, CN102400242B, CN102839444B, and CN113882030A all employ this method. However, due to the high apparent viscosity of aramid resin, the dispersion effect of pigment particles is greatly reduced, leading to agglomeration and affecting the mechanical properties of the subsequent fibers. Another approach involves adding pigments during the aramid resin synthesis stage to improve pigment dispersion when the system viscosity is low. Methods disclosed in publications CN103726124A and CN113355764A illustrate this. However, these methods do not include appropriate surface treatment of the pigments, leading to agglomeration as viscosity increases in the later stages of the reaction, affecting the fiber's mechanical properties. If the pigments cannot be uniformly dispersed in the aramid resin, agglomeration can clog filters and spinnerets, causing fiber breakage, excessive fuzz, and impacting the fiber bundle's mechanical properties, even preventing continuous spinning for extended periods. Therefore, addressing pigment dispersion is crucial in aramid solution coloring processes. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing colored meta-aramid fibers.

[0006] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0007] A method for preparing colored meta-aramid fibers includes the following steps:

[0008] (1) Under dry N2 protection, m-phenylenediamine and self-dispersible pigment are added to a solvent for dispersion, and then the temperature is lowered to -10℃ to -15℃, and isophthaloyl chloride is added in batches at 90% to 95% of the molar amount of m-phenylenediamine for pre-condensation reaction; wherein, the self-dispersible pigment is a pigment treated with terminal amino aromatic hyperbranched polyamide.

[0009] (2) Continue to add isophthaloyl chloride, which accounts for 5% to 10% of the molar amount of m-phenylenediamine, to carry out polycondensation reaction;

[0010] (3) A neutralizing agent is slowly added to the reaction product of step (2) to neutralize the HCl generated during the polymerization process, and the viscosity is adjusted to obtain a colored meta-aramid resin solution.

[0011] (4) The colored meta-aramid resin solution is used to make colored meta-aramid fibers.

[0012] The preferred method for preparing pigments using terminal amino aromatic hyperbranched polyamide is as follows: the pigment is added to a solution or aqueous solution of terminal amino aromatic hyperbranched polyamide in dimethylacetamide (DMAc) with a mass content of 15% to 20%, ball-milled for 1 to 3 hours, ultrasonically treated for 10 to 30 minutes, filtered, and dried to obtain a self-dispersible pigment.

[0013] The above-mentioned preparation method, preferably, involves the synthesis of N,N,N',N'-tetrabutylpropionate-1-3-phenylenediamine via m-phenylenediamine and butyl acrylate, followed by reaction of N,N,N',N'-tetrabutylpropionate-1-3-phenylenediamine with ethylenediamine. The synthetic route is as follows:

[0014]

[0015] Amino-terminated aromatic hyperbranched polyamides contain a large number of highly branched polar amino groups at their ends, which are basic anchoring groups. Since most organic pigments, as well as graphene and carbon black, have weakly acidic surfaces, these basic anchoring groups have a strong adsorption capacity for these pigments. Furthermore, these basic anchoring groups are easily ionized, exhibiting good adsorption effects on inorganic pigments as well. Moreover, amino-terminated aromatic hyperbranched polyamides are suitable for various types of pigments.

[0016] Amino-terminated aromatic hyperbranched polyamides have a quasi-spherical three-dimensional structure with a large spatial structure between their branches. Therefore, the molecular size of amino-terminated aromatic hyperbranched polyamide polymers is much larger than that of other low-molecular-weight silane coupling agents. There is electrostatic repulsion between hyperbranched polyamides adsorbed on pigments, which can separate pigment particles at a large distance and prevent them from re-aggregating after collision.

[0017] Amino-terminated aromatic hyperbranched polyamides exhibit excellent compatibility with aramid resins. A large number of highly branched amino groups on the surface, combined with m-phenylenediamine and isophthaloyl chloride, are polymerized in situ. The prepolymer can react with the terminal amino groups of the amino-terminated aromatic hyperbranched polyamides adsorbed on the pigment surface, and then continue to undergo chain-growth condensation reaction. This results in a large number of aramid polymer molecules distributed on the pigment surface, which fundamentally improves the compatibility between the pigment and the aramid resin, as well as the dispersibility of the pigment in the resin.

[0018] In the above-described preparation method, preferably, the pigment includes organic pigments or inorganic pigments, wherein the organic pigment is one or more of perylene pigments, azo pigments, titanium cyanide pigments, and anthraquinone pigments, and the inorganic pigment is one or more of iron oxide red, zinc iron yellow, praseodymium yellow, cobalt blue, chrome green, cobalt green, and copper chrome black.

[0019] If organic pigments are used, DMAc is used as the solvent when paired with amino-terminated aromatic hyperbranched polyamides. If inorganic pigments are used, water is used as the solvent.

[0020] In the above preparation method, preferably, the particle size of the pigment is 700-1400 nm, and its addition amount is 3%-5% of the theoretical mass of meta-aramid polymer.

[0021] In the above preparation method, preferably, in step (1), the temperature of the pre-condensation reaction is below 30°C and the reaction time is 1.5 to 2 hours.

[0022] In the above preparation method, preferably, in step (2), the temperature of the polycondensation reaction is 50-55℃.

[0023] In the above preparation method, preferably, in step (2), the resin content in the colored meta-aramid resin solution is 14% to 18%, the specific logarithmic viscosity is 1.8 to 2.3 dL / g, and the system viscosity is 30,000 to 80,000 cP.

[0024] In the preferred embodiment of the above preparation method, step (4) involves preparing the colored meta-aramid resin solution into colored meta-aramid fiber by degassing and filtering the colored meta-aramid resin solution, then coagulating it in a coagulation bath through a spinneret, then stretching it in a hot water bath, then drying it, oiling it, and then performing a hot stretching treatment, and finally cooling, winding it, and cutting it to obtain colored meta-aramid fiber.

[0025] In the above preparation method, preferably, the degassing temperature is 40℃~50℃, the filtration accuracy is less than or equal to 15μm; the number of spinneret holes is 50~50000, the hole diameter is 0.05~0.15mm; the drying temperature is 120℃~150℃, the drying time is 1~3min; the hot stretching treatment temperature is 300℃~350℃, and the stretching ratio is 1.05~2.5.

[0026] In the above-mentioned preparation method, preferably, the coagulation bath is composed of water and dimethylacetamide, and the coagulation bath is divided into a primary coagulation bath and a secondary coagulation bath. The concentration of dimethylacetamide in the primary coagulation bath is 50% to 60%, and the coagulation bath temperature is 50℃ to 60℃; the concentration of dimethylacetamide in the secondary coagulation bath is 50% to 60%, and the coagulation bath temperature is 50℃ to 60℃; the hot water bath stretching is carried out in hot water at 70℃ to 80℃, and the stretching ratio is 1.05 to 1.25.

[0027] Compared with the prior art, the advantages of the present invention are as follows:

[0028] (1) This invention uses terminal amino aromatic hyperbranched polyamide to treat pigments. The terminal amino aromatic hyperbranched polyamide contains a large number of highly branched polar terminal amino functional groups as anchoring groups, which can effectively adsorb inorganic and organic pigments. Moreover, there is a large spatial structure between its branches, and there is electrostatic repulsion between hyperbranched polymers. Therefore, the pigments can be uniformly and stably dispersed in the dimethylacetamide continuous phase for a long time. Combined with the in-situ solution polymerization of m-phenylenediamine and isophthaloyl chloride, the prepolymer can react with the terminal amino groups of the terminal amino aromatic hyperbranched polyamide adsorbed on the pigment surface, and then continue to undergo chain growth condensation reaction, which can fundamentally and effectively prevent pigment agglomeration, thereby ensuring the mechanical properties of the fiber. As a dispersed phase, it is uniformly and stably dispersed in meta-aramid resin, which can also improve the compatibility and interfacial bonding strength between pigments and meta-aramid resin, and prevent pigments from detaching from the nascent filaments and contaminating the coagulation bath during the spinning and forming stage.

[0029] (2) The colored meta-aramid fiber prepared by the present invention and the textiles prepared from the fiber do not require subsequent dyeing, and the colors are rich and bright with good color fastness. This makes up for the shortcomings of the traditional dyeing method of meta-aramid, shortens the production process, reduces the wastewater treatment problem in the dyeing and printing process, and reduces the production cost, which has good environmental protection significance. Attached Figure Description

[0030] Figure 1 This is a diagram showing the dispersion effect of pigment in aramid resin under a 1000x optical microscope in Embodiment 1 of the present invention.

[0031] Figure 2 This is a diagram showing the dispersion effect of pigment in aramid resin under a 1000x optical microscope in Embodiment 2 of the present invention.

[0032] Figure 3 This is a diagram showing the dispersion effect of pigment in aramid resin under a 1000x optical microscope in Embodiment 3 of the present invention.

[0033] Figure 4 This is a diagram showing the dispersion effect of the pigment in aramid resin under a 1000x optical microscope in Comparative Example 1 of this invention.

[0034] Figure 5 This is a diagram showing the dispersion effect of the pigment in aramid resin under a 1000x optical microscope in Comparative Example 2 of this invention. Detailed Implementation

[0035] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0036] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0037] Unless otherwise specified, all reagents and raw materials used in this invention are commercially available products or products that can be prepared by known methods.

[0038] The amino-terminated aromatic hyperbranched polyamides used in the following examples were all prepared using the following methods:

[0039] (1) Under N2 protection, 10.8 g (0.1 mol) of m-phenylenediamine and 50 mL of acetic acid were added to a 250 mL three-necked flask. The mixture was stirred at room temperature to completely dissolve the m-phenylenediamine in the acetic acid. Then, the temperature was raised to 80 °C and 64 g of butyl acrylate was added to the three-necked flask at a dropping rate of 1 drop / s. The mixture was refluxed and cooled until the butyl acrylate was completely added. The reaction was then continued at 80 °C for 5 h.

[0040] (2) Use a vacuum pump to remove excess butyl acrylate and acetic acid from the reaction product of step (1) at 50°C to obtain the product N,N,N',N'-tetrabutyl propionate-1-3-phenylenediamine.

[0041] (3) At room temperature, add 10g (0.016mol) of N,N,N',N'-tetrabutylpropionate-1-3-phenylenediamine to a 250mL three-necked flask, heat to 100℃ to melt, and then add 6g (0.1mol) of ethylenediamine to the three-necked flask at a dropping rate of 1 drop / s using a constant pressure dropping funnel. Stir the reaction for 3h, then heat to 120℃ and react for 8h. After cooling the reaction product to room temperature, add diethyl ether and stir (ethylenediamine and diethyl ether are immiscible, while terminal amino aromatic hyperbranched polyamide is miscible with diethyl ether). After extraction, a mixture of terminal amino aromatic hyperbranched polyamide and diethyl ether can be obtained. Remove diethyl ether by rotary evaporation under reduced pressure at 80℃ to obtain terminal amino aromatic hyperbranched polyamide.

[0042] Example 1:

[0043] A method for preparing colored meta-aramid fibers according to the present invention includes the following steps:

[0044] (1) Pigment self-dispersibility modification: Perylene red organic pigment with a particle size of 700 nm to 1000 nm (the amount added is 3% of the theoretical meta-aramid polymer mass) was placed in a DMAc solution containing terminal amino aromatic hyperbranched polyamide (the mass fraction of terminal amino aromatic hyperbranched polyamide is 15%), ball-milled for 2 h and then ultrasonically treated for 15 min, filtered and dried to obtain self-dispersible perylene red pigment powder.

[0045] (2) Pre-polymerization: Under dry N2 gas protection, m-phenylenediamine was dissolved and self-dispersible pigment was added to DMAc solvent by in-situ solution polymerization. The mixture was dispersed by a high-speed disperser at a speed of 2000 r / min and ultrasonically treated for 10 min. Then, after the temperature was lowered to -10℃, isophthaloyl chloride (95% of the molar amount of m-phenylenediamine) was added in batches to carry out pre-polymerization reaction. The reaction temperature was controlled below 30℃ and the reaction was carried out for 1.5 h.

[0046] (3) Polycondensation: Gradually and slowly add isophthaloyl chloride at 5% of the molar amount of m-phenylenediamine to carry out the polycondensation reaction. During this stage, the viscosity of the system increases sharply, and the system temperature is controlled between 50℃ and 55℃.

[0047] (4) Neutralization: Calcium hydroxide was slowly added to the system after step (3) to neutralize the HCl generated during polymerization, resulting in a colored meta-aramid resin solution with a resin content of 16%, a specific logarithmic viscosity of 2.0 dL / g, and a system viscosity of approximately 58,000 cp. An optical microscope image of this colored meta-aramid resin solution is shown below. Figure 1 As shown, from Figure 1 It can be seen that the perylene red organic pigment is dispersed very evenly in the aramid resin;

[0048] (5) Fiber forming: After degassing the colored meta-aramid resin solution obtained in step (4) at 50°C, it is filtered through a 10µm filter and then enters the coagulation bath through a 100-hole spinneret with a pore size of 0.08mm. The coagulation bath consists of water and dimethylacetamide. The first coagulation bath has a DMAc concentration of 51% and a bath temperature of 50°C. The second coagulation bath has a DMAc concentration of 55% and a bath temperature of 60°C. Then, it is stretched in a hot water bath at a temperature of 76°C and a stretching ratio of 1.2. Next, it is dried at 140°C for 1 minute. After oiling, it is stretched 2.0 times at 305°C. Finally, it is wound up and cut to obtain red aramid fiber.

[0049] Example 2:

[0050] A method for preparing a colored meta-aramid resin and its fibers includes the following steps:

[0051] (1) Pigment self-dispersion modification: Zinc iron yellow inorganic pigment with a particle size of 800nm~1200nm (the amount added is 5% of the theoretical meta-aramid polymer mass) was placed in water containing terminal amino aromatic hyperbranched polyamide (the mass fraction of terminal amino aromatic hyperbranched polyamide is 18%), ball-milled for 2h and then ultrasonically treated for 15min, filtered and dried to obtain self-dispersion zinc iron yellow pigment powder.

[0052] (2) Pre-polymerization: Under dry N2 gas protection, m-phenylenediamine was dissolved and self-dispersible pigment was added to DMAc solvent by in-situ solution polymerization. The mixture was dispersed by a high-speed disperser at a speed of 2000 r / min and ultrasonically treated for 15 min. After the temperature was lowered to -10℃, isophthaloyl chloride, accounting for 90% of the molar amount of m-phenylenediamine, was added in batches to carry out pre-polymerization reaction. The reaction temperature was controlled below 30℃ and the reaction was carried out for 2 h.

[0053] (3) Polycondensation: Gradually and slowly add isophthaloyl chloride at 10% of the molar amount of m-phenylenediamine to carry out the polycondensation reaction. During this stage, the viscosity of the system increases sharply, and the system temperature is controlled between 50℃ and 55℃.

[0054] (4) Neutralization: Lithium hydroxide, a neutralizing agent, is slowly added to the system after the reaction in step (3) to neutralize the HCl generated during the polymerization process, resulting in a colored meta-aramid resin solution with a resin content of 16%, a specific logarithmic viscosity of 1.8 dL / g, and a system viscosity of 32000 cp. An optical microscope image of this colored meta-aramid resin solution is shown below. Figure 2 As shown, from Figure 2 It can be seen that the zinc iron yellow inorganic pigment is dispersed very evenly in the aramid resin;

[0055] (5) Fiber forming: After degassing the colored meta-aramid resin solution at 45°C, it is filtered through a 10µm filter and then passed through a 500-hole spinneret with a pore size of 0.07mm into a coagulation bath. The coagulation bath consists of water and dimethylacetamide. The first coagulation bath has a DMAc concentration of 55% and a bath temperature of 55°C; the second coagulation bath has a DMAc concentration of 52% and a bath temperature of 60°C. Then, it is stretched in a hot water bath at 80°C with a stretching ratio of 1.2. After drying at 120°C for 2 minutes, it is oiled and then stretched 2.0 times at 300°C. Finally, it is wound up and cut to obtain yellow aramid fibers.

[0056] Example 3:

[0057] A method for preparing a colored meta-aramid resin and its fibers includes the following steps:

[0058] (1) Pigment self-dispersibility modification: Titanium blue organic pigment with a particle size of 900 nm to 1400 nm (the amount added is 4% of the theoretical meta-aramid polymer mass) was placed in DMAc containing terminal amino aromatic hyperbranched polyamide (the mass fraction of terminal amino aromatic hyperbranched polyamide is 20%), ball-milled for 2 h and then ultrasonically treated for 15 min, filtered and dried to obtain self-dispersible titanium blue pigment powder.

[0059] (2) Prepolymerization: Under dry N2 gas protection, m-phenylenediamine was dissolved and self-dispersible pigment was added to DMAc solvent by in-situ solution polymerization. The mixture was dispersed by a high-speed disperser at a speed of 2000 r / min and ultrasonically treated for 15 min. After the temperature was lowered to -15℃, isophthaloyl chloride, accounting for 90% of the molar amount of m-phenylenediamine, was added in batches to carry out prepolymerization reaction. The reaction temperature was controlled below 30℃ and the reaction was carried out for 1.5 h.

[0060] (3) Polycondensation: Gradually and slowly add isophthaloyl chloride at 10% of the molar amount of m-phenylenediamine to carry out the polycondensation reaction. During this stage, the viscosity of the system increases sharply, and the system temperature is controlled between 50℃ and 55℃.

[0061] (4) Neutralization: Magnesium hydroxide, a neutralizing agent, is slowly added to the system after the reaction in step (3) to neutralize the HCl generated during the polymerization process, resulting in a colored meta-aramid resin solution with a resin content of 17.5%, a specific logarithmic viscosity of 2.3 dL / g, and a system viscosity of 80,000 cp. An optical microscope image of the colored meta-aramid resin solution is shown below. Figure 3 As shown, from Figure 3 As can be seen, the titanium blue organic pigment is dispersed very evenly in the aramid resin;

[0062] (5) Fiber forming: After degassing the colored meta-aramid resin solution at 50°C, it is filtered through a 10µm filter and then enters the coagulation bath through a 2000-hole spinneret with a pore size of 0.08mm. The coagulation bath consists of water and dimethylacetamide. The first coagulation bath has a DMAc concentration of 52% and a bath temperature of 60°C. The second coagulation bath has a DMAc concentration of 55% and a bath temperature of 55°C. Then, it is stretched in a hot water bath at a temperature of 75°C with a stretching ratio of 1.05. After drying at 130°C for 2 minutes, it is oiled and then stretched 1.8 times at 310°C. Finally, it is wound up to obtain blue aramid fiber.

[0063] Comparative Example 1:

[0064] The preparation method of the colored meta-aramid fiber in this comparative example includes the following steps:

[0065] (1) Pre-polymerization: Under dry N2 protection, m-phenylenediamine and perylene red organic pigment with a particle size of 700nm~1000nm (added amount is 3% of the theoretical mass of meta-aramid polymer) were dissolved in DMAc solvent by in-situ solution polymerization. The mixture was dispersed by a high-speed disperser at a speed of 2000r / min and ultrasonically treated for 10min. Then, after the temperature was lowered to -10℃, isophthaloyl chloride, accounting for 95% of the molar amount of m-phenylenediamine, was added in batches to carry out pre-polymerization reaction. The reaction temperature was controlled below 30℃ and the reaction was carried out for 1.5h.

[0066] (2) Polycondensation: Gradually and slowly add isophthaloyl chloride at 5% of the molar amount of m-phenylenediamine to carry out the polycondensation reaction. During this stage, the viscosity of the system increases sharply, and the system temperature is controlled between 50℃ and 55℃.

[0067] (3) Neutralization: Calcium hydroxide was slowly added to the system after step (2) to neutralize the HCl produced during polymerization, resulting in a colored meta-aramid resin solution with a resin content of 16%, a specific logarithmic viscosity of 2.0 dL / g, and a system viscosity of 58000 cp. An optical microscope image of this colored meta-aramid resin solution is shown below. Figure 4 As shown, from Figure 4 It can be seen that the perylene red organic pigments agglomerate severely in the aramid resin;

[0068] (4) Fiber forming: After degassing the colored meta-aramid resin solution obtained in step (3) at 50°C, it is filtered through a 10µm filter and then enters the coagulation bath through a 100-hole spinneret with a pore size of 0.08mm. The coagulation bath consists of water and dimethylacetamide. The first coagulation bath has a DMAc concentration of 51% and a bath temperature of 50°C. The second coagulation bath has a DMAc concentration of 55% and a bath temperature of 60°C. Then, it is stretched in a hot water bath at a temperature of 76°C and a stretching ratio of 1.2. Next, it is dried at 140°C for 1 minute. After oiling, it is stretched 2.0 times at 305°C. Finally, it is wound and cut to obtain aramid fibers.

[0069] Comparative Example 2:

[0070] The preparation method of the colored meta-aramid fiber in this comparative example includes the following steps:

[0071] (1) Pigment self-dispersion modification: Zinc iron yellow inorganic pigment with a particle size of 800nm~1200nm (the amount added is 5% of the theoretical meta-aramid polymer mass) was placed in water containing terminal amino aromatic hyperbranched polyamide (the mass fraction of terminal amino aromatic hyperbranched polyamide is 18%), ball-milled for 2h and then ultrasonically treated for 15min, filtered and dried to obtain self-dispersion zinc iron yellow pigment powder.

[0072] (2) Preparation of spinning resin: Under dry N2 gas protection, m-phenylenediamine was dissolved in DMAc solvent. After the temperature was lowered to -10℃, isophthaloyl chloride (90% of the molar amount of m-phenylenediamine) was added in batches to carry out pre-condensation reaction. The reaction temperature was controlled below 30℃ and the reaction was carried out for 2 hours. Then, isophthaloyl chloride (10% of the molar amount of m-phenylenediamine) was added slowly and gradually to carry out condensation reaction. During this stage, the viscosity of the system increased sharply. The system temperature was controlled between 50℃ and 55℃. Lithium hydroxide was slowly added to the system after the reaction to neutralize the HCl generated during the polymerization process, and meta-aramid resin solution was obtained.

[0073] (3) Add the self-dispersible pigment from step (1) to DMAc solvent, disperse it using a high-speed disperser at a speed of 2000 r / min, and simultaneously perform ultrasonic treatment for 15 min to obtain a dyeing solution.

[0074] (4) The meta-aramid resin solution prepared in step (2) and the dyeing solution prepared in step (3) are added to a twin-screw extruder to finally obtain a spinning resin solution. The optical microscope image of the dyed meta-aramid resin solution is shown below. Figure 5 As shown, from Figure 5 It can be seen that zinc iron yellow pigments exhibit severe agglomeration in aramid resins;

[0075] (5) Fiber forming: After degassing the spinning solution prepared in step (4) at 45°C, it is filtered through a 10µm filter and then enters the coagulation bath through a 500-hole spinneret with a pore size of 0.07mm. The coagulation bath consists of water and dimethylacetamide. The first coagulation bath has a DMAc concentration of 55% and a bath temperature of 55°C; the second coagulation bath has a DMAc concentration of 52% and a bath temperature of 60°C. Then, it is stretched in a hot water bath at 80°C with a stretching ratio of 1.2. After drying at 120°C for 2 minutes, it is oiled and then stretched 2.0 times at 300°C. Finally, it is wound up and cut to obtain yellow aramid fiber.

[0076] The mechanical properties of the aramid fibers prepared in the above embodiments and comparative examples are shown in Table 1. The linear density was tested according to "GB / T14335-2008 Test Method for Linear Density of Chemical Fibers (Short Fibers)", and the breaking strength, breaking power, breaking elongation, and modulus were all tested according to "GB / T 14337-2022 Test Method for Tensile Properties of Chemical Fibers (Short Fibers)".

[0077] Table 1. Mechanical property data of aramid fibers prepared in each example and comparative example.

[0078]

Claims

1. A process for the preparation of pigmented meta-aramid fibers, characterized in that, The method comprises the following steps: (1) under the protection of dry N2, disperse the m-phenylenediamine and the self-dispersed pigment in a solvent, then reduce the temperature to-10℃~-15℃, and then add 90%~95% of the molar amount of m-phenylenediamine to the m-phthaloyl chloride for pre-polycondensation reaction; wherein the self-dispersed pigment is a pigment treated by an amino-terminated aromatic hyperbranched polyamide; wherein the specific method for treating the pigment by the amino-terminated aromatic hyperbranched polyamide is: adding the pigment into a dimethylacetamide solution or an aqueous solution of the amino-terminated aromatic hyperbranched polyamide with a mass content of 15%~20%, then ball milling for 1~3h and ultrasonic treatment for 10~30min, and then performing suction filtration and drying to obtain the self-dispersed pigment; (2) continue to add 5%~10% of the molar amount of m-phenylenediamine to the m-phthaloyl chloride for polycondensation reaction; (3) slowly add a neutralizing agent to the reaction product of step (2) to neutralize the HCl generated in the polymerization process, and adjust the viscosity to obtain a colored meta-aramid resin solution; (4) prepare colored meta-aramid fibers from the colored meta-aramid resin solution.

2. The production method according to claim 1, wherein The pigment comprises an organic pigment or an inorganic pigment, wherein the organic pigment is one or more of a perylene pigment, an azo pigment, a titanium cyanin pigment, and an anthraquinone pigment, and the inorganic pigment is one or more of red iron oxide, zinc-iron yellow, praseodymium yellow, cobalt blue, chromium green, cobalt green, and copper-chromium black.

3. The production method according to claim 1, wherein The particle size of the pigment is 700~1400nm, and the addition amount of the pigment is 3%~5% of the mass of the theoretical meta-aramid polymer.

4. The production method according to any one of claims 1 to 3, wherein In step (1), the pre-polycondensation reaction is carried out at a temperature below 30℃, and the reaction time is 1.5~2h.

5. The production method according to any one of claims 1 to 3, wherein In step (2), the polycondensation reaction is carried out at a temperature of 50~55℃.

6. The production method according to any one of claims 1 to 3, wherein In step (3), the resin content in the colored meta-aramid resin solution is 14%~18%, the specific viscosity is 1.8~2.3dL / g, and the system viscosity is 30000~80000cP.

7. The production method according to any one of claims 1 to 3, wherein In step (4), the process for preparing the colored meta-aramid fibers from the colored meta-aramid resin solution comprises the following steps: degassing, filtering, passing through a spinneret into a coagulation bath to form a coagulated product, then performing hot water bath drawing, drying, oiling, and finally performing hot stretching treatment, and then cooling to obtain the colored meta-aramid fibers.

8. The production method according to claim 7, wherein The degassing temperature is 40℃~50℃, and the filtering precision is not higher than 15μm; the spinneret has a hole number of 50~50000 and a hole diameter of 0.05~0.15mm; the drying temperature is 120℃~150℃, and the drying time is 1~3min; the hot stretching treatment temperature is 300℃~350℃, and the stretching multiple is 1.05~2.

5.

9. The production method according to claim 7, wherein The coagulation bath is composed of water and dimethylacetamide, and the coagulation bath is divided into a first-stage coagulation bath and a second-stage coagulation bath; the concentration of dimethylacetamide in the first-stage coagulation bath is 50%~60%, and the coagulation bath temperature is 50℃~60℃; the concentration of dimethylacetamide in the second-stage coagulation bath is 50%~60%, and the coagulation bath temperature is 50℃~60℃; the hot water bath drawing is performed in hot water at 70℃~80℃, and the drawing multiple is 1.05~1.25.

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