Preparation method of colored para-aramid polymer and colored para-aramid fiber

Abstract

The present application relates to a kind of preparation method of colored para-aramid polymer and colored para-aramid fiber.The preparation method described in the present application includes the following steps: para-phenylenediamine, NMP-CaCl2 Mixed solvent and copper chloride are mixed uniformly to obtain mixed system;A portion of terephthaloyl chloride is added to the mixed system to obtain prepolymer liquid;The rest of terephthaloyl chloride is added to the prepolymer liquid to obtain polymer;By neutralization, washing, drying, obtain colored para-aramid polymer.The present application realizes the intrinsic coloration of polymer by adding copper chloride in the initial stage of polymerization, and the color adjustment from yellow to black can be realized by adjusting the amount of copper chloride added, the process window is wide, and the cost is low.The colored para-aramid fiber obtained by dry jet wet spinning with the above colored polymer as raw material is uniformly colored, high in color fastness, and maintains good mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of aromatic polyamide polymer technology, and in particular to a method for preparing a colored para-aramid polymer and colored para-aramid fibers. Background Technology

[0002] Poly(p-phenylene terephthalamide) (PPTA, aramid 1414) is a polymer formed by low-temperature polycondensation of p-phenylenediamine (PPD) and terephthaloyl chloride (TPC). It is known as one of the world's three major high-performance fibers. Due to its excellent properties such as light weight, high modulus, high strength, impact resistance, high temperature resistance, and corrosion resistance, it is widely used in bulletproof and explosion-proof, aerospace, automobile manufacturing, high-strength ropes, communication engineering and other fields.

[0003] However, the highly regular molecular chains, high crystallinity, and strong surface inertness of PPTA, while endowing it with excellent mechanical properties, also make it extremely difficult for dye molecules to diffuse into the fiber interior under traditional dyeing processes, resulting in very challenging dyeing. Currently, the mainstream para-aramid products on the market are still predominantly yellow, greatly limiting their application expansion in civilian and specialty fields. How to effectively control the color of para-aramid without significantly sacrificing its intrinsic mechanical properties is key to broadening its application scenarios.

[0004] To address the difficulty of dyeing para-aramid fibers, existing technologies have proposed several solutions: Chinese patent document CN103498214A discloses a carrier dyeing method that roughens the surface of the finished fiber by mechanically combing it to increase the contact area with the dye, thereby promoting dye uptake. However, this method is a fiber post-processing step, and the mechanical combing process can easily cause physical damage to the para-aramid molecular chains, leading to a significant decrease in key mechanical properties such as tensile strength and modulus, making it difficult to meet the requirements of high-end applications. Chinese patent document CN121344803A discloses a solution dyeing method that disperses pigments in concentrated sulfuric acid and combines them with the spinning solution for spinning. However, due to the poor compatibility between the pigments and the para-aramid matrix, and the extremely high requirements for pigment dispersibility in the concentrated sulfuric acid system, uneven dispersion or agglomeration is very likely to occur, resulting in uneven fiber color and potentially creating stress defects, which adversely affects the mechanical properties of the fiber. Chinese patent document CN105696104A discloses a method for coloring using oxidized p-phenylenediamine during the final polymerization stage. However, this method requires the addition and mixing of oxidant and monomer within a very short time when the polymerization system is about to gel or has just gelled. The process window is too narrow, the operation is difficult, and the reaction process is difficult to control precisely due to the difficulty in achieving micro-uniform mixing at high viscosity, resulting in poor batch stability and making it difficult to achieve large-scale stable industrial production.

[0005] Therefore, it is of great significance to develop a simple and controllable process for preparing para-aramid fibers that can impart stable and uniform color to the fibers while maintaining their excellent mechanical properties. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing colored para-aramid polymers and colored para-aramid fibers. Para-aramid polymers with diverse and uniform colors can be prepared by simple process adjustments, and colored para-aramid fibers with high color fastness and good mechanical properties can be spun.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] The first aspect of this invention provides a method for preparing a colored para-aramid polymer, comprising the following steps:

[0009] (1) Mix p-phenylenediamine, NMP-CaCl2 mixed solvent and copper chloride evenly to obtain a mixed system;

[0010] (2) Add a portion of terephthaloyl chloride to the resulting mixture to obtain a prepolymer solution;

[0011] (3) Add the remaining terephthaloyl chloride to the obtained prepolymer solution and react to obtain the polymer;

[0012] (4) Neutralize, wash and dry the polymer to obtain a colored para-aramid polymer.

[0013] In some embodiments of the present invention, in step (1), the mass ratio of copper chloride to p-phenylenediamine is 1:4 to 1:110.

[0014] In some embodiments of the present invention, in step (1), the temperature of the mixing process and the resulting mixed system is 30~65°C.

[0015] In some embodiments of the present invention, in step (1), the content of CaCl2 in the NMP-CaCl2 mixed solvent is 7wt%~8wt%.

[0016] In some embodiments of the present invention, in step (2), the portion of terephthaloyl chloride accounts for 20% to 35% of the total molar amount of terephthaloyl chloride.

[0017] In some embodiments of the present invention, in step (2), the reaction temperature is controlled below 5°C during the preparation of the prepolymer solution.

[0018] In some embodiments of the present invention, in step (3), the ratio of the total molar amount of terephthaloyl chloride to the molar amount of p-phenylenediamine is 0.990~1.005:1.

[0019] In some embodiments of the present invention, in step (3), the reaction temperature is controlled below 50°C during polymer preparation.

[0020] A second aspect of the present invention provides a colored para-aramid polymer, wherein the colored para-aramid polymer is prepared by the above-described preparation method.

[0021] A third aspect of the present invention provides a method for preparing colored para-aramid fibers, comprising the following steps:

[0022] (1) The spinning solution is prepared by dissolving the above-mentioned colored para-aramid polymer or the blend of the above-mentioned colored para-aramid polymer and the uncolored poly(p-phenylene terephthalamide) polymer in concentrated sulfuric acid.

[0023] (2) Colored aramid fibers were prepared by using a dry-jet wet spinning process to prepare the spinning solution.

[0024] In some embodiments of the present invention, the content of the colored para-aramid polymer in the blend is 2wt% to 3wt%.

[0025] In some embodiments of the present invention, the solid content of the spinning solution is 19.3wt% to 19.8wt%.

[0026] In some embodiments of the present invention, the dry-jet wet spinning process includes forming nascent filaments by passing the spinning solution through a spinneret, then solidifying them in a coagulation bath, and finally washing, neutralizing, drying, and oiling the solidified fibers before winding them into a product.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1. This invention utilizes the catalytic oxidation of amino groups by adding copper chloride as an additive in the initial stage of polymerization and coordinating with a specific reaction temperature. This allows for the in-situ generation of coloring functional groups on the PPTA molecular chain through the catalytic oxidation of amino groups by Cu ions, thereby preparing intrinsically colored PPTA polymers. The polymer color can be precisely controlled (from yellow to yellowish-brown, coffee, reddish-brown, dark brown, or black) simply by adjusting the amount of copper chloride added. The process is simple to operate.

[0029] 2. The copper chloride used in this invention is inexpensive, which greatly reduces the preparation cost of colored aramid polymers compared to using expensive special color-developing monomers.

[0030] 3. Using the colored PPTA polymer of this invention for spinning fundamentally solves the problem of uneven pigment dispersion in traditional pigment blending spinning because the dyeing functional groups are uniformly dispersed at the molecular level. The colored PPTA polymer can be uniformly dispersed in concentrated sulfuric acid, resulting in colored aramid fibers with uniform coloring, high color fastness, and good mechanical properties comparable to those of natural-colored aramid fibers. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating the preparation process of the colored para-aramid polymer and colored para-aramid fiber of the present invention.

[0032] Figure 2 These are photographs of the polymers prepared in Examples 1-5 and Comparative Example 1 of the present invention, wherein (a)-(e) correspond to Examples 1-5 respectively, and (f) corresponds to Comparative Example 1. Detailed Implementation

[0033] The following details the preparation method of a colored para-aramid polymer and the colored para-aramid fiber according to the present invention.

[0034] The first aspect of this invention provides a method for preparing a colored para-aramid polymer, comprising the following steps:

[0035] (1) Mix p-phenylenediamine, NMP-CaCl2 mixed solvent and copper chloride evenly to obtain a mixed system;

[0036] (2) Add a portion of terephthaloyl chloride to the resulting mixture to obtain a prepolymer solution;

[0037] (3) Add the remaining terephthaloyl chloride to the obtained prepolymer solution and react to obtain the polymer;

[0038] (4) Neutralize, wash and dry the polymer to obtain a colored para-aramid polymer.

[0039] This invention utilizes Cu by adding copper chloride. 2+ The catalytic oxidation of amino groups converts some of the amino groups on the p-phenylenediamine monomer into coloring functional groups. In the subsequent polymerization reaction, these coloring functional groups are introduced into the PPTA molecular backbone as copolymer units, thereby achieving intrinsic coloring of the polymer at the molecular level. This fundamentally solves the problem of uneven pigment dispersion in traditional pigment blending and spinning.

[0040] In some embodiments of the present invention, in step (1), the mass ratio of copper chloride to p-phenylenediamine is 1:4 to 1:110, which can be 1:4 to 1:6, 1:6 to 1:8, 1:8 to 1:10, 1:10 to 1:15, 1:15 to 1:20, 1:20 to 1:50, 1:50 to 1:80, 1:80 to 1:100, or 1:100 to 1:110. In some specific embodiments of the present invention, the ratio can be, for example, 1:4, 1:8, 1:19, 1:32, 1:88, 1:110, etc. By adjusting the amount of copper chloride added, the color of the resulting polymer can be controlled, achieving a transformation from yellow to yellowish-brown, coffee, reddish-brown, dark brown, and even black. For example, when the mass ratio is 1:32, a coffee-colored polymer can be obtained; when the mass ratio is 1:8, a dark brown polymer can be obtained; and when the mass ratio is 1:4, a black polymer can be obtained. If the amount of copper chloride used is too high, such as a mass ratio exceeding 1:4, it may lead to excessive oxidation of the amino groups in the reaction system, affecting the molecular weight of the final polymer and making it unusable for subsequent spinning.

[0041] In some embodiments of the present invention, in step (1), the temperature of the mixing process and the resulting mixed system is 30~65℃, which can be 30~35℃, 35~40℃, 40~45℃, 45~50℃, 50~55℃, 55~60℃, or 60~65℃. In some specific embodiments of the present invention, it can be, for example, 30℃, 45℃, 55℃, 60℃, 65℃, etc. A suitable temperature is beneficial to the complete dissolution and uniform dispersion of p-phenylenediamine and copper chloride in the solvent system. If the temperature is too low, the copper chloride will not dissolve sufficiently, the catalytic oxidation effect will be weakened, and the polymer color will be lighter; if the temperature is too high, it may lead to rapid oxidation or even over-oxidation of the monomer, affecting the molecular weight and color stability of the final polymer.

[0042] In some embodiments of the present invention, in step (1), the content of CaCl2 in the NMP-CaCl2 mixed solvent is 7wt%~8wt%, which can be 7wt%~7.2wt%, 7.2wt%~7.4wt%, 7.4wt%~7.6wt%, 7.6wt%~7.8wt%, or 7.8wt%~8wt%.

[0043] In some embodiments of the present invention, in step (2), the portion of terephthaloyl chloride accounts for 20% to 35% of the total molar amount of terephthaloyl chloride, which can be 20% to 22%, 22% to 24%, 24% to 28%, 28% to 30%, 30% to 32%, 32% to 34%, or 34% to 35%. In some specific embodiments of the present invention, it can be, for example, 20%, 26%, 31%, 35%, etc. The monomer is added in steps to better control the heat of reaction and the polymerization rate. The portion of terephthaloyl chloride accounts for 20% to 35% of the total molar amount of terephthaloyl chloride, so that a certain length of molecular chain is formed in the prepolymerization stage, laying the foundation for the subsequent final polymerization reaction.

[0044] In some embodiments of the present invention, during step (2), the reaction temperature is controlled below 5°C during the preparation of the prepolymer solution. The reaction temperature can be -10 to -5°C, -5 to 0°C, or 0 to 5°C, preferably 0 to 5°C. In some specific embodiments of the present invention, the temperature can be, for example, -10°C, -8°C, -2°C, 0°C, 4°C, 5°C, etc. Controlling the reaction temperature below 5°C is beneficial for controlling the reaction rate in the prepolymerization stage, preventing local overheating that could lead to explosive polymerization or side reactions, thereby ensuring a narrower molecular weight distribution of the polymer and facilitating the uniform embedding of dyeing functional groups into the molecular chain.

[0045] In some embodiments of the present invention, in step (3), to ensure that the polymer has a sufficiently high molecular weight to meet the spinning requirements, the total monomer ratio needs to be precisely controlled. Preferably, the ratio of the total molar amount of terephthaloyl chloride to the molar amount of p-phenylenediamine is 0.990~1.005:1, which is beneficial for obtaining a polymer with a narrow molecular weight distribution and controllable end groups. This ratio can be 0.990-0.995:1, 0.995-1:1, or 1-1.005:1. In some specific embodiments of the present invention, for example, it can be 0.990:1, 0.998:1, 1.001:1, 1.003:1, or 1.005:1.

[0046] In some embodiments of the present invention, during step (3), the reaction temperature is controlled below 50°C during polymer preparation. The reaction temperature can be 10~15°C, 15~20°C, 20~25°C, 25~30°C, 30~35°C, 35~40°C, 40~45°C, or 45~50°C, preferably 20~50°C. In some specific embodiments of the present invention, the temperature can be, for example, 20°C, 25°C, 32°C, 44°C, 50°C, etc.

[0047] A second aspect of the present invention provides a colored para-aramid polymer, wherein the colored para-aramid polymer is prepared by the above-described preparation method.

[0048] In some embodiments of the present invention, the color of the colored para-aramid polymer is yellowish-brown, coffee-colored, reddish-brown, dark brown, or black.

[0049] A third aspect of the present invention provides a method for preparing colored para-aramid fibers, comprising the following steps:

[0050] (1) The spinning solution is prepared by dissolving the above-mentioned colored para-aramid polymer or the blend of the above-mentioned colored para-aramid polymer and the uncolored poly(p-phenylene terephthalamide) polymer in concentrated sulfuric acid.

[0051] (2) Colored aramid fibers were prepared by using a dry-jet wet spinning process to prepare the spinning solution.

[0052] In some embodiments of the present invention, the content of the colored para-aramid polymer in the blend is 2wt% to 3wt%, which can be 2wt% to 2.2wt%, 2.2wt% to 2.4wt%, 2.4wt% to 2.6wt%, 2.6wt% to 2.8wt%, or 2.8wt% to 3wt%. In some specific embodiments of the present invention, it can be, for example, 2wt%, 2.1wt%, 2.5wt%, 2.9wt%, 3wt%, etc.

[0053] In some embodiments of the present invention, the specific logarithmic viscosity of the uncolored poly(p-phenylene terephthalamide) polymer is preferably 6.0 to 7.0 dL / g.

[0054] In some embodiments of the present invention, the mass concentration of the concentrated sulfuric acid is 98%~100%, and can be 98.0%~98.5%, 98.5%~99.0%, 99.0%~99.5%, or 99.5%~100%. In some specific embodiments of the present invention, for example, it can be 98% or 100%.

[0055] In some embodiments of the present invention, the solid content of the spinning solution is 19.3wt%~19.8wt%, and can be 19.3wt%~19.4wt%, 19.4wt%~19.5wt%, 19.5wt%~19.6wt%, 19.6wt%~19.7wt%, or 19.7wt%~19.8wt%. In some specific embodiments of the present invention, it can be, for example, 19.3wt%, 19.5wt%, 19.7wt%, 19.8wt%, etc.

[0056] In some embodiments of the present invention, the dry-jet wet spinning process includes forming nascent filaments by passing the spinning solution through a spinneret, then solidifying them in a coagulation bath, and finally washing, neutralizing, drying, and oiling the solidified fibers before winding them into a product.

[0057] The following detailed description of specific embodiments of the present invention, in conjunction with preferred embodiments, further illustrates the relevant details. When numerical ranges are given in the embodiments, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range, as well as any value between the two endpoints, may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by those skilled in the art. In addition to the specific methods, devices, and materials used in the embodiments, the present invention can be implemented using any prior art methods, devices, and materials similar to or equivalent to those described in the embodiments of the present invention, provided that those skilled in the art possess the prior art and the description of the present invention.

[0058] In the following examples and comparative examples, the specific logarithmic viscosity was tested by preparing a 0.5 g / dL polymer-concentrated sulfuric acid solution after the polymer was fully dried, and then testing it at 30°C using the Ubbelohde viscometer method; the mechanical properties were tested according to GB / T14344-2022; and the color fastness to washing was tested according to GB / T 5713-2013.

[0059] Example 1

[0060] The preparation method of the colored para-aramid polymer in this embodiment is as follows: Figure 1 As shown, it includes the following steps:

[0061] (1) Prepare an NMP-CaCl2 mixed solvent with a CaCl2 content of 8wt%, and then mix PPD, NMP-CaCl2 mixed solvent and copper chloride in a dissolving vessel at 65℃ to obtain an NMP mixed system; wherein the mass ratio of copper chloride to PPD is 1:110.

[0062] (2) After PPD and copper chloride are completely dissolved, the NMP mixture is transferred into the prepolymer reactor, and a portion of TPC (accounting for 35% of the total molar amount of TPC) is added. The reaction is carried out to obtain the prepolymer liquid, and the reaction temperature is controlled not to exceed 5°C.

[0063] (3) Transfer the prepolymer liquid into the final polymerization reactor, add the remaining TPC (the final molar ratio of TPC to PPD reaches 1.005:1), and obtain the polymer. During this process, control the reaction temperature to not exceed 50°C.

[0064] (4) By neutralizing, washing and drying the polymer with sodium hydroxide solution, a yellowish-brown PPTA polymer with a specific logarithmic viscosity of 6.3 dL / g was finally obtained.

[0065] The method for preparing colored para-aramid fibers in this embodiment is as follows: Figure 1 As shown, it includes the following steps:

[0066] (1) The obtained colored PPTA polymer was used as raw material and dissolved in 100% concentrated sulfuric acid to prepare a spinning solution with a solid content of 19.3 wt%.

[0067] (2) After degassing and filtration, the spinning solution is dry-spinned and wet-spun. After coagulation, washing, neutralization, drying and oiling, colored para-aramid fibers are obtained.

[0068] Example 2

[0069] The preparation method of the colored para-aramid polymer and colored aramid fiber in this embodiment is as follows: Figure 1 As shown, it includes the following steps:

[0070] (1) Prepare a mixed solvent of NMP-CaCl2 with a CaCl2 content of 7wt%, and then mix PPD, NMP-CaCl2 mixed solvent and copper chloride in a dissolving kettle at 55℃ to obtain an NMP mixed system; wherein, the mass ratio of copper chloride to PPD is 1:32.

[0071] (2) After PPD and copper chloride are completely dissolved, the NMP mixture is transferred into the prepolymer reactor, and a portion of TPC (accounting for 25% of the total molar amount of TPC) is added. The reaction is carried out to obtain the prepolymer liquid, and the reaction temperature is controlled not to exceed 5°C.

[0072] (3) Transfer the prepolymer liquid into the final polymerization reactor, add the remaining TPC (the final molar ratio of TPC to PPD reaches 1.003:1), and obtain the polymer. During this process, control the reaction temperature to not exceed 50°C.

[0073] (4) By neutralizing, washing and drying the polymer with sodium hydroxide solution, a coffee-colored PPTA polymer with a specific logarithmic viscosity of 5.8 dL / g was finally obtained.

[0074] The method for preparing colored para-aramid fibers in this embodiment is as follows: Figure 1 As shown, it includes the following steps:

[0075] (1) The obtained colored PPTA polymer was used as raw material and dissolved in 100% concentrated sulfuric acid to prepare a spinning solution with a solid content of 19.38 wt%.

[0076] (2) After degassing and filtration, the spinning solution is dry-spinned and wet-spun. After coagulation, washing, neutralization, drying and oiling, colored para-aramid fibers are obtained.

[0077] Example 3

[0078] The preparation method of the colored para-aramid polymer and colored aramid fiber in this embodiment is as follows: Figure 1 As shown, it includes the following steps:

[0079] (1) Prepare an NMP-CaCl2 mixed solvent with a CaCl2 content of 7.7wt%, and then mix PPD, NMP-CaCl2 mixed solvent and copper chloride in a dissolving vessel at 60℃ to obtain an NMP mixed system; wherein the mass ratio of copper chloride to PPD is 1:19.

[0080] (2) After PPD and copper chloride are completely dissolved, the NMP mixture is transferred into the prepolymer reactor and a portion of TPC (accounting for 29% of the total molar amount of TPC) is added. The reaction is carried out to obtain the prepolymer liquid, and the reaction temperature is controlled not to exceed 5°C.

[0081] (3) Transfer the prepolymer liquid into the final polymerization reactor, add the remaining TPC (the final molar ratio of TPC to PPD reaches 1.001:1), and obtain the polymer. During this process, control the reaction temperature to not exceed 50°C.

[0082] (4) By neutralizing, washing and drying the polymer with sodium hydroxide solution, a reddish-brown PPTA polymer with a specific logarithmic viscosity of 5.5 dL / g was finally obtained.

[0083] The method for preparing colored para-aramid fibers in this embodiment is as follows: Figure 1 As shown, it includes the following steps:

[0084] (1) The obtained colored PPTA polymer was used as raw material and dissolved in 98% concentrated sulfuric acid to prepare a spinning solution with a solid content of 19.47 wt%.

[0085] (2) After degassing and filtration, the spinning solution is dry-spinned and wet-spun. After coagulation, washing, neutralization, drying and oiling, colored para-aramid fibers are obtained.

[0086] Example 4

[0087] The preparation method of the colored para-aramid polymer and colored aramid fiber in this embodiment is as follows: Figure 1 As shown, it includes the following steps:

[0088] (1) Prepare an NMP-CaCl2 mixed solvent with a CaCl2 content of 7.4wt%, and then mix PPD, NMP-CaCl2 mixed solvent and copper chloride in a dissolving vessel at 45°C to obtain an NMP mixed system; wherein the mass ratio of copper chloride to PPD is 1:8.

[0089] (2) After PPD and copper chloride are completely dissolved, the NMP mixture is transferred into the prepolymer reactor, and a portion of TPC (accounting for 30% of the total molar amount of TPC) is added. The reaction is carried out to obtain the prepolymer liquid, and the reaction temperature is controlled not to exceed 5°C.

[0090] (3) Transfer the prepolymer liquid into the final polymerization reactor, add the remaining TPC (the final molar ratio of TPC to PPD reaches 0.998:1), and obtain the polymer. During this process, control the reaction temperature to not exceed 50°C.

[0091] (4) By neutralizing, washing and drying the polymer with sodium hydroxide solution, a dark brown PPTA polymer with a specific logarithmic viscosity of 5.3 dL / g was finally obtained.

[0092] The method for preparing colored para-aramid fibers in this embodiment is as follows: Figure 1 As shown, it includes the following steps:

[0093] (1) The obtained colored PPTA polymer was blended with the uncolored PPTA polymer with a specific logarithmic viscosity of 6.5 dL / g as raw material (the mass content of the colored PPTA polymer in the blend was 3%) and dissolved in 100% concentrated sulfuric acid to obtain a spinning solution with a solid content of 19.61 wt%.

[0094] (2) After degassing and filtration, the spinning solution is dry-spinned and wet-spun. After coagulation, washing, neutralization, drying and oiling, colored para-aramid fibers are obtained.

[0095] Example 5

[0096] The preparation method of the colored para-aramid polymer and colored aramid fiber in this embodiment is as follows: Figure 1 As shown, it includes the following steps:

[0097] (1) Prepare an NMP-CaCl2 mixed solvent with a CaCl2 content of 7.1wt%, and then mix PPD, NMP-CaCl2 mixed solvent and copper chloride in a dissolving vessel at 30°C to obtain an NMP mixed system; wherein the mass ratio of copper chloride to PPD is 1:4.

[0098] (2) After PPD and copper chloride are completely dissolved, the NMP mixture is transferred into the prepolymer reactor, and a portion of TPC (accounting for 20% of the total molar amount of TPC) is added. The reaction is carried out to obtain the prepolymer liquid, and the reaction temperature is controlled not to exceed 5°C.

[0099] (3) Transfer the prepolymer liquid into the final polymerization reactor, add the remaining TPC (the final molar ratio of TPC to PPD reaches 0.990:1), and obtain the polymer. During this process, control the reaction temperature to not exceed 50°C.

[0100] (4) By neutralizing, washing and drying the polymer with sodium hydroxide solution, a black PPTA polymer with a specific logarithmic viscosity of 4.5 dL / g was finally obtained.

[0101] The method for preparing colored para-aramid fibers in this embodiment is as follows: Figure 1 As shown, it includes the following steps:

[0102] (1) The obtained colored PPTA polymer was blended with the uncolored PPTA polymer with a specific logarithmic viscosity of 6.5 dL / g as raw material (the mass content of the colored PPTA polymer in the blend was 2%) and dissolved in 100% concentrated sulfuric acid to prepare a spinning solution with a solid content of 19.80 wt%.

[0103] (2) After degassing and filtration, the spinning solution is dry-spinned and wet-spun. After coagulation, washing, neutralization, drying and oiling, colored para-aramid fibers are obtained.

[0104] Comparative Example 1

[0105] The difference between this comparative example and Example 1 is that copper chloride is not added, and a yellow PPTA polymer with a specific logarithmic viscosity of 6.5 dL / g is finally obtained. Yellow aramid fibers are obtained by dry-jet wet spinning.

[0106] Comparative Example 2

[0107] The difference between this comparative example and Example 1 is that the mass ratio of copper chloride to PPD is increased to 1:1.7, resulting in a large black gel instead of black polymer powder, which makes it impossible to perform subsequent specific viscosity tests and spinning.

[0108] The properties of the fibers obtained in each embodiment and comparative example were tested, and the results are shown in Table 1 below.

[0109] Table 1 Performance test results of fibers obtained in each embodiment and comparative example

[0110]

[0111] Note: " / " indicates that the test was not performed.

[0112] As shown in Table 1, Examples 1-5 of this invention successfully prepared colored para-aramid fibers ranging from yellowish-brown to black. The fibers obtained in each example maintained good mechanical properties, and their colorfastness to washing reached grade 4-5, indicating excellent color fastness. The method of this invention can achieve high fastness and diverse coloring of para-aramid fibers without significantly impairing the fiber's mechanical properties.

[0113] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a colored para-aramid polymer, characterized in that, The steps include the following: (1) Mix p-phenylenediamine, NMP-CaCl2 mixed solvent and copper chloride evenly to obtain a mixed system; (2) Add a portion of terephthaloyl chloride to the resulting mixture to obtain a prepolymer solution; (3) Add the remaining terephthaloyl chloride to the obtained prepolymer solution and react to obtain the polymer; (4) Neutralize, wash and dry the polymer to obtain a colored para-aramid polymer.

2. The method for preparing the colored para-aramid polymer as described in claim 1, characterized in that, Step (1) includes one or more of the following features: (1) The mass ratio of copper chloride to p-phenylenediamine is 1:4 to 1:110; (2) The temperature of the mixing process and the resulting mixture is 30~65℃; (3) The content of CaCl2 in the NMP-CaCl2 mixed solvent is 7 wt%~8 wt%.

3. The method for preparing the colored para-aramid polymer as described in claim 1, characterized in that, Step (2) includes one or more of the following features: (1) The portion of terephthaloyl chloride accounts for 20% to 35% of the total molar amount of terephthaloyl chloride; (2) Control the reaction temperature below 5°C during the preparation of the prepolymer solution.

4. The method for preparing the colored para-aramid polymer as described in claim 1, characterized in that, Step (3) includes one or more of the following features: (1) The ratio of the total molar amount of terephthaloyl chloride to the molar amount of p-phenylenediamine is 0.990~1.005:1; (2) Control the reaction temperature below 50°C during polymer preparation.

5. A colored para-aramid polymer, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 4.

6. The colored para-aramid polymer as described in claim 5, characterized in that, The color of the colored para-aramid polymer is yellowish-brown, coffee-colored, reddish-brown, dark brown, or black.

7. A method for preparing colored para-aramid fibers, characterized in that, Includes the following steps: (1) The spinning solution is prepared by dissolving the colored para-aramid polymer of claim 5 or 6 in concentrated sulfuric acid as raw material, or by dissolving the colored para-aramid polymer of claim 5 or 6 and the uncolored poly(p-phenylene terephthalamide) polymer as raw material. (2) Colored aramid fibers were prepared by using a dry-jet wet spinning process to prepare the spinning solution.

8. The method for preparing colored para-aramid fibers as described in claim 7, characterized in that, The content of the colored para-aramid polymer in the blend is 2wt%~3wt%.

9. The method for preparing colored aramid fibers as described in claim 7, characterized in that, The solid content of the spinning solution is 19.3wt%~19.8wt%.

10. The method for preparing colored aramid fibers as described in claim 7, characterized in that, The dry-jet wet spinning process includes passing the spinning solution through a spinneret to form nascent filaments, which are then coagulated in a coagulation bath. The coagulated fibers are then washed, neutralized, dried, and oiled before being wound into a product.

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