High-elongation and easy-dyeing para-aramid monofilament and its preparation method and product

Abstract

This application provides a highly elongated, easily dyeable para-aramid monofilament, a preparation method, and a product thereof. The para-aramid monofilament comprises a plurality of para-aramid nanofibrils arranged in bundles along the length of the para-aramid monofilament. The para-aramid monofilament exhibits high elongation at break and is easily dyeable. The simple preparation method makes it suitable for industrial production and expands the application of para-aramid.

Description

Technical Field

[0001] The present application relates to the field of polymer materials, and in particular to a high-elongation, easily dyeable para-aramid monofilament, a preparation method thereof, and a product thereof. Background Art

[0002] Aramid fibers, made from aromatic polyamides, are a class of high-performance polymer materials. Common aramid fibers are primarily divided into para-aramid and meta-aramid, depending on their molecular structure. Para-aramid fibers, with their exceptional properties such as high strength, high modulus, high heat resistance, and chemical corrosion resistance, are indispensable for applications in defense, aerospace, and numerous civilian sectors. However, due to the high molecular rigidity and strong intermolecular conjugation and hydrogen bonding, para-aramid fibers exhibit poor processability. Currently, they can only be produced into para-aramid fiber products through liquid crystal spinning.

[0003] The liquid crystal spinning process primarily involves dissolving a para-aramid polymer in concentrated sulfuric acid to prepare a liquid crystal solution of a certain concentration. This solution is then converted into para-aramid fiber material via a dry-jet wet spinning process. The liquid crystal spinning process is complex and demanding, and the resulting para-aramid monofilaments exhibit limited performance and structural tunability. For example, para-aramid monofilaments produced using this process exhibit a distinct sheath-core structure, with a dense sheath and a loose core. This sheath-core structure results in a smooth and inert surface, making it difficult to composite with other materials. This makes the fiber difficult to dye, hindering its application in areas such as clothing. Furthermore, despite its high tensile strength and modulus, para-aramid monofilaments exhibit a very low elongation at break, typically less than 5%. This brittleness hinders the expansion of para-aramid's application range. Therefore, the development of high-elongation and easily dyeable para-aramid monofilaments remains a pressing need for both scientific development and industrial application. Summary of the Invention

[0004] The present application provides a high-elongation, easily dyeable para-aramid monofilament, a preparation method thereof, and a product thereof, aiming to obtain a para-aramid monofilament with high elongation at break and easy dyeing by optimizing the structure of the para-aramid monofilament.

[0005] In a first aspect, the present application provides a highly elongated and easily dyeable para-aramid monofilament, comprising a plurality of para-aramid nanofibrils, wherein the plurality of para-aramid nanofibrils are arranged in bundles along the length direction of the para-aramid monofilament.

[0006] According to the present application, the para-aramid monofilament is obtained by arranging a plurality of para-aramid nanofibrils in bundles along the length direction of the para-aramid monofilament. Due to the highly oriented bundle arrangement structure of the para-aramid nanofibrils, the structure can effectively reduce the local stress concentration of the para-aramid monofilament, so that the stress is more easily dispersed and absorbed during the stretching process, and thus the para-aramid monofilament has a higher elongation at break; in addition, although the surface of the para-aramid nanofibrils is smooth, the para-aramid monofilament obtained by the bundle arrangement is relatively rough, and the gaps between the para-aramid nanofibrils are conducive to the penetration of the dye, so the para-aramid monofilament is easier to dye.

[0007] In some embodiments, the average diameter of the para-aramid nanofibrils is 10 to 60 nm.

[0008] In some embodiments, the para-aramid monofilament satisfies at least one of the following conditions: 1) the diameter of the para-aramid monofilament is 5 to 100 μm; 2) the tensile strength of the para-aramid monofilament is 100 to 1100 MPa; 3) the elongation at break of the para-aramid monofilament is 15% to 50%.

[0009] In a second aspect, the present application provides a method for preparing high-elongation and easily dyeable para-aramid monofilament, comprising the following steps:

[0010] S10: providing para-aramid polymerization liquid;

[0011] S20: adding a second polar aprotic solvent and a polar protic solvent to the para-aramid polymer solution, stirring to obtain a dispersion containing para-aramid nanofibrils, to obtain a spinning solution, wherein the mass content of para-aramid in the spinning solution is 0.2% to 2%, and the mass content of the polar protic solvent is 1000 to 50000 ppm;

[0012] S30: performing solution spinning on the spinning solution to obtain para-aramid monofilament.

[0013] According to the present application, the method is prepared using a bottom-up strategy, by diluting the para-aramid polymer solution to an appropriate concentration and adding a trace amount of polar protic solvent to promote the in-situ precipitation of para-aramid to form a relatively stable dispersion containing para-aramid nanofibrils, which is used as a spinning solution for solution spinning. During the spinning process, the para-aramid nanofibrils are oriented along the spinning extrusion direction, and this oriented structure is solidified in a coagulation bath, thereby obtaining highly elongated and easily dyeable para-aramid monofilaments, which have a high elongation at break and are easy to dye.

[0014] In some embodiments, the step S10 specifically includes: polymerizing p-phenylenediamine monomer and terephthaloyl chloride monomer in a composite solvent to obtain a p-aramid polymer solution, wherein the composite solvent includes a first polar aprotic solvent and a solubilizing salt.

[0015] In some embodiments, the first polar aprotic solvent and the second polar aprotic solvent independently include at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

[0016] In some embodiments, the polar protic solvent includes at least one of water, methanol, and ethanol.

[0017] In some embodiments, the step S20 further includes adding an alkaline medium to the para-aramid polymerization solution, wherein the mass ratio of the alkaline medium to the para-aramid is 0.5 to 5:100.

[0018] In some embodiments, the step S30 specifically includes: filtering and degassing the spinning solution, passing the solution through a spinneret into a coagulation bath to coagulate to form a gel bundle, and washing and drying the gel bundle to obtain para-aramid monofilament.

[0019] In a third aspect, the present application provides a para-aramid fiber product, comprising the para-aramid monofilament according to any embodiment of the first aspect or the para-aramid monofilament prepared by the method according to any embodiment of the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0021] Figure 1 These are the surface SEM images and cross-sectional SEM images of the para-aramid monofilament in one embodiment of the present application.

[0022] Figure 2 These are the SEM images and tensile stress-strain curves of para-aramid monofilaments with different diameters in some embodiments of the present application.

[0023] Figure 3 These are pictures of para-aramid monofilament before and after dyeing in some examples of this application.

[0024] The above drawings illustrate specific embodiments of the present application, which will be described in more detail below. These drawings and the textual description are not intended to limit the scope of the present application in any way, but rather to illustrate the concepts of the present application to those skilled in the art by reference to specific embodiments. DETAILED DESCRIPTION

[0025] The various embodiments or implementation schemes in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments.

[0026] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with an embodiment or example is included in at least one embodiment or example of the present application. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0027] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0028] It should be noted that the monofilament in this application refers to a single filament produced from a single hole during the spinning process.

[0029] As described in the background technology above, due to the high rigidity and poor processability of para-aramid molecules, para-aramid monofilament can only be prepared using the liquid crystal spinning process. The para-aramid raw yarn prepared using the liquid crystal spinning process has a clear skin-core structure, is not easy to dye, and has a very low elongation at break.

[0030] The emergence of para-aramid nanofibrils has made it possible to prepare new para-aramid monofilaments. These can be prepared using a conventional spinning process with a para-aramid nanofibril dispersion as the raw material. However, the problem is that, on the one hand, the preparation of the para-aramid nanofibril dispersion has high solvent requirements and low production efficiency. On the other hand, the nanofibrils in the para-aramid nanofibril dispersion are in a disordered state. Therefore, during the spinning and extrusion process, the para-aramid nanofibrils will entangle and agglomerate, resulting in micron-sized para-aramid monofilaments. However, due to their disordered entangled structure, their tensile strength and elongation at break are both low. At the same time, the small gaps inside the para-aramid monofilaments are not conducive to the penetration of dyes, making them difficult to dye.

[0031] Based on this, the present application provides a high-elongation, easily dyeable para-aramid monofilament and a preparation method thereof. By optimizing the structure of the para-aramid nanofibrils in the para-aramid monofilament, a para-aramid monofilament with high elongation at break and easy dyeing is obtained. The specific embodiments of the present application are described in detail below.

[0032] In a first aspect, the present application provides a highly elongated and easily dyeable para-aramid monofilament, comprising a plurality of para-aramid nanofibrils, wherein the plurality of para-aramid nanofibrils are arranged in bundles along the length direction of the para-aramid monofilament.

[0033] According to the present application, the para-aramid monofilament is obtained by arranging a plurality of para-aramid nanofibrils in bundles along the length direction of the para-aramid monofilament. Due to the highly oriented bundle arrangement structure of the para-aramid nanofibrils, the structure can effectively reduce the local stress concentration of the para-aramid monofilament, so that the stress is more easily dispersed and absorbed during the stretching process, and thus the para-aramid monofilament has a higher elongation at break; in addition, although the surface of the para-aramid nanofibrils is smooth, the para-aramid monofilament obtained by the bundle arrangement is relatively rough, and the gaps between the para-aramid nanofibrils are conducive to the penetration of the dye, so the para-aramid monofilament is easier to dye.

[0034] It should be noted that the arrangement of a plurality of para-aramid nanofibrils in bundles along the length direction of the para-aramid monofilament means that the para-aramid nanofibrils are arranged substantially in parallel along the length direction of the para-aramid monofilament to obtain bundles of para-aramid monofilaments. Figure 1 The figure shows a scanning electron microscope (SEM) image of the surface and cross-section (fiber cross-section and fiber surface) of the para-aramid monofilament in one embodiment of the present application. It can be seen from the SEM images of the monofilament surface and cross-section that the para-aramid monofilament is obtained by arranging a plurality of para-aramid nanofibrils in a bundle shape along the length direction of the para-aramid monofilament. The orientation degree of the para-aramid nanofibrils is high, and no obvious entanglement structure appears. There are gaps between the para-aramid nanofibrils and the surface of the monomer is relatively rough.

[0035] In some embodiments, the average diameter of the para-aramid nanofibrils is 10 to 60 nm.

[0036] In some of the above embodiments, the average diameter of the para-aramid nanofibrils is specifically limited. It can be understood that, generally, the smaller the average diameter of the para-aramid nanofibrils, the better their toughness, and the corresponding para-aramid monofilament has a higher elongation at break. However, the average diameter is also limited by the preparation process, so the average diameter of the para-aramid nanofibrils can be 10 to 60 nm.

[0037] The average diameter of the para-aramid nanofibrils has a well-known meaning in the art and can be measured by methods and instruments known in the art, such as observing the cross-section of the sample to be measured using a scanning electron microscope and randomly selecting more than 20 para-aramid nanofibrils to calculate their average diameter.

[0038] In some embodiments, the diameter of the para-aramid monofilament is 5 to 100 μm. Since the elongation at break of the para-aramid monofilament is related to its diameter, the elongation at break of the para-aramid monofilament is higher in this case.

[0039] In some embodiments, the tensile strength of the para-aramid monofilament is 100-1100 MPa. Due to the rigid molecular structure of para-aramid, the dense nanofiber structure and high degree of orientation, the para-aramid fiber has a high tensile strength.

[0040] In some embodiments, the elongation at break of the para-aramid monofilament is 15% to 50%. Although para-aramid has high strength and modulus, since the para-aramid monofilament is formed by arranging a plurality of para-aramid nanofibrils in a bundle along the length of the para-aramid monofilament, unlike mutually entangled para-aramid nanofibrils, the forces between the bundled para-aramid nanofibrils are small during the stretching process, and the para-aramid nanofibrils are more likely to extend uniformly along the stretching direction, reducing stress concentration in the para-aramid monofilament. The strong hydrogen bonding between the para-aramid nanofibrils allows the nanofibers to slip without breaking when stretched. Therefore, the para-aramid fiber formed by the oriented arrangement of the nanofibers also has a high elongation at break.

[0041] Figure 2 The SEM images of para-aramid monofilaments with different diameters and the corresponding tensile stress-strain curves of some embodiments of the present application are shown in FIG. Figure 2 It can be seen that para-aramid monofilaments of different diameters have high tensile strength and elongation at break, and the smaller the diameter of the para-aramid monofilament, the higher the tensile strength and elongation at break.

[0042] In a second aspect, the present application provides a method for preparing high-elongation and easily dyeable para-aramid monofilament, comprising the following steps:

[0043] S10: providing para-aramid polymerization liquid;

[0044] S20: adding a second polar aprotic solvent and a polar protic solvent to the para-aramid polymer solution, stirring to obtain a dispersion containing para-aramid nanofibrils, thereby obtaining a spinning solution, wherein the mass content of the para-aramid in the spinning solution is 0.2% to 2%, and the mass content of the polar protic solvent is 1000 to 50000 ppm;

[0045] S30: performing solution spinning on the spinning solution to obtain para-aramid monofilament.

[0046] According to the present application, the method is prepared using a bottom-up strategy. By diluting the para-aramid polymer solution to an appropriate concentration and adding a trace amount of polar protic solvent, the para-aramid is promoted to precipitate in situ to form a relatively stable dispersion containing para-aramid nanofibrils, which is used as a spinning solution for solution spinning. During the spinning process, the para-aramid nanofibrils are arranged in bundles along the spinning extrusion direction, thereby obtaining highly elongated and easily dyeable para-aramid monofilaments, which have a high elongation at break and are easy to dye.

[0047] Specifically, in step S10, a para-aramid polymer solution is provided. This is because para-aramid polymer molecules have high rigidity and strong intermolecular conjugation and hydrogen bonding forces, making it difficult for para-aramid polymer molecules to redisperse after agglomeration. Therefore, a bottom-up strategy is adopted to provide the para-aramid polymer solution. It should be noted that the para-aramid polymer solution can be prepared according to methods known in the art and is not particularly limited.

[0048] Step S20 is the key step of the method. It is necessary to add a second polar aprotic solvent to the para-aramid polymer solution so that the mass content of para-aramid in the spinning solution is within an appropriate range to meet the requirements of solution spinning. At the same time, a trace amount of polar protic solvent needs to be added. The polar protic solvent and the polar aprotic solvent are miscible and will not separate. The polar protic solvent uniformly dispersed in the spinning solution promotes the in situ combination of para-aramid polymer molecules in the spinning solution to obtain para-aramid nanofibrils, so that para-aramid nanofibrils are uniformly dispersed in the spinning solution.

[0049] It is understandable that those skilled in the art can control the diameter of the para-aramid nanofibrils by adjusting the concentration of para-aramid and the content of polar protic solvent in the spinning solution according to actual needs, thereby obtaining para-aramid monofilaments with different properties.

[0050] Step S30 is to perform solution spinning on the spinning solution. During the spinning process, the para-aramid nanofibrils in the spinning solution are spontaneously oriented during the extrusion process, and the para-aramid nanofibrils are arranged in bundles along the spinning extrusion direction, thereby obtaining highly elongated and easily dyeable para-aramid monofilaments, which have a high elongation at break and are easy to dye.

[0051] In some embodiments, the method can produce the para-aramid monofilament as in any embodiment of the first aspect.

[0052] In some embodiments, step S10 specifically includes: polymerizing p-phenylenediamine monomer and terephthaloyl chloride monomer in a composite solvent to obtain a p-aramid polymer solution, wherein the composite solvent includes a first polar aprotic solvent and a solubilizing salt.

[0053] In some embodiments, the concentration of the p-phenylenediamine monomer may be 0.1 to 0.5 mol / L, and the molar ratio of the p-phenylenediamine monomer to the terephthaloyl chloride monomer may be 0.9 to 1.1:1.

[0054] In some embodiments, the water content in the first polar aprotic solvent is less than 300 ppm.

[0055] In some embodiments, the solubilizing salt may include at least one of calcium chloride and lithium chloride, and the mass concentration of the solubilizing salt in the composite solvent may be 3% to 8%.

[0056] It is understandable that the specific conditions for preparing the para-aramid polymer solution in step S10 are not limited to the above-mentioned embodiment, and those skilled in the art may make corresponding selections based on the preparation method of the para-aramid polymer solution in the prior art.

[0057] In some embodiments, the first polar aprotic solvent and the second polar aprotic solvent independently include at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide. Para-aramid has good dispersibility in polar aprotic solvents. Therefore, the polar aprotic solvent serves as the main solvent of the spinning solution. The first polar aprotic solvent and the second polar aprotic solvent can be the same or different, and are not limited to the aforementioned solvents. Those skilled in the art can select the appropriate polar aprotic solvent based on known polar aprotic solvents.

[0058] In some embodiments, the polar protic solvent includes at least one of water, methanol, and ethanol. Polar aprotic solvents can promote the binding and precipitation of para-aramid polymer molecules, and their polarity allows them to be miscible with polar aprotic solvents, thereby achieving corresponding effects. Therefore, polar protic solvents are not limited to the aforementioned ones, and those skilled in the art can select polar protic solvents based on known polar protic solvents in the art.

[0059] In some embodiments, step S20 further includes adding an alkaline medium to the para-aramid polymer solution, wherein the mass ratio of the alkaline medium to the para-aramid is 0.5 to 5:100. During the process of diluting the para-aramid polymer solution and forming the para-aramid nanofibrils, the appropriate addition of the alkaline medium can inhibit entanglement and agglomeration of the para-aramid nanofibrils, further improve the orientation of the para-aramid nanofibrils in the para-aramid monofilament, and thus further improve the elongation at break of the para-aramid monofilament.

[0060] In some embodiments, the alkaline medium may include but is not limited to sodium hydroxide and potassium hydroxide. Those skilled in the art may select an alkaline medium known in the art according to actual needs.

[0061] In some embodiments, solution spinning can be performed according to methods known in the art, such as dry spinning or wet spinning.

[0062] In some embodiments, step S30 specifically includes: filtering and degassing the spinning solution, passing the solution through a spinneret into a coagulation bath to coagulate to form a gel bundle, and washing and drying the gel bundle to obtain para-aramid monofilament.

[0063] In the above embodiment, the p-aramid monofilament is prepared by a wet spinning method, and the specific spinning conditions can be selected according to actual needs, so as to prepare p-aramid monofilaments of different specifications.

[0064] As an example, the coagulation bath temperature can be 0-30°C, preferably 10-25°C; the solvent in the coagulation bath can include at least one of water, acetone, ethanol, and methanol; the coagulation time can be 1-30 minutes; the spinneret orifice diameter can be 50-200 μm, and the aspect ratio can be 1-3:1; the spinning speed can be 5-50 m / min; and the drying condition can be 20-150°C for 5-20 minutes. Those skilled in the art can control the above parameters to obtain para-aramid monofilaments of different specifications.

[0065] In a third aspect, the present application provides a para-aramid fiber product, comprising a para-aramid monofilament according to any embodiment of the first aspect or a para-aramid monofilament prepared by the method according to any embodiment of the second aspect.

[0066] In some embodiments, the para-aramid fiber product may be a para-aramid yarn obtained by twisting para-aramid monofilaments, or may be a product obtained by further processing the para-aramid yarn.

[0067] In some embodiments, the para-aramid fiber product further includes a dye, which can be obtained by soaking a para-aramid monofilament in a dye solution and drying it, soaking a para-aramid yarn in a dye solution and drying it, or soaking a para-aramid fiber product in a dye solution and drying it. The dye includes, but is not limited to, rhodamine B, methylene blue, methyl orange, and the like.

[0068] As an example, the para-aramid monofilament can be immersed in a dye solution with a concentration of 0.01 to 1 mol / L and dyed for 2 to 20 minutes. The para-aramid monofilament is then taken out and dried at 20 to 150° C. for 5 to 20 minutes to obtain the dyed para-aramid monofilament.

[0069] Figure 3 The figure shows the para-aramid monofilaments after dyeing in some embodiments of the present application. The undyed para-aramid monofilaments are original yellow in color. Different colors of dyes can be used to dye the para-aramid monofilaments into different colors. It can be seen that the para-aramid monofilaments have a good dyeing effect.

[0070] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0071] Testing of tensile strength and elongation at break: Test in accordance with the provisions of "GB / T19975-2005 Test method for tensile properties of high-strength reinforced filaments".

[0072] Example 1

[0073] (1) In 1m 3 In a stirred reactor, 25 kg of calcined calcium chloride was added to 500 L of N-methylpyrrolidone with a water content of 80 ppm. The mixture was then heated to 80°C under stirring and nitrogen protection to completely dissolve the calcium chloride. The temperature was then lowered to 15°C, and 10.80 kg of p-phenylenediamine monomer was added and dissolved to a monomer concentration of 0.2 mol / L. The temperature was then further lowered to 0°C, and 20.44 kg of terephthaloyl chloride powder was slowly added to the polymerization reactor to initiate a polymerization reaction. The stirring speed was increased to 500 rpm. After the addition of terephthaloyl chloride, the mixture was reacted for 10 minutes to obtain a para-aramid (PPTA) polymerization solution.

[0074] (2) Adding a diluent 10 times the mass of the PPTA polymer solution to the polymer solution and stirring for 4 hours to obtain a gel (or dispersion) containing para-aramid nanofibrils, i.e., a spinning solution. The diluent is composed of N-methylpyrrolidone, water, and potassium hydroxide. In the spinning solution, the concentration of PPTA is 0.4wt%, the water content is 10,000ppm, and the amount of potassium hydroxide added is 1wt% of the mass of PPTA;

[0075] (3) The spinning solution is filtered and degassed before being transferred to the spinning assembly. The spinning solution passes through the spinneret and enters the coagulation bath to coagulate into a gel bundle. The spinneret orifice has a diameter of 50 μm and an aspect ratio of 2:1. The gel bundle remains in the coagulation bath for 5 minutes. The coagulation bath used is water at a temperature of 20°C and a spinning speed of 15 m / min.

[0076] (4) The gel filaments were continuously washed with deionized water and then dried at 60°C for 10 min to obtain para-aramid monofilaments.

[0077] (5) After testing, the diameter of the para-aramid monofilament is about 20 μm, the tensile strength is 430 MPa, and the elongation at break is 28%.

[0078] Example 2

[0079] (1) In 1m 3In a stirred reactor, 35 kg of calcined calcium chloride was added to 500 L of N-methylpyrrolidone with a water content of 50 ppm. The mixture was then heated to 100°C under stirring and nitrogen protection to completely dissolve the calcium chloride. The temperature was then lowered to 15°C, and 16.20 kg of p-phenylenediamine monomer was added and dissolved to a monomer concentration of 0.3 mol / L. The temperature was then further lowered to 0°C, and 30.65 kg of terephthaloyl chloride powder was slowly added to the reactor to initiate a polymerization reaction. The stirring speed was increased to 600 rpm. After the addition of terephthaloyl chloride, the mixture was reacted for 8 minutes to obtain a para-aramid (PPTA) polymer solution.

[0080] (2) Adding a diluent 10 times the mass of the PPTA polymer solution to the polymer solution and stirring for 1 hour to obtain a gel (or dispersion) containing para-aramid nanofibrils, i.e., a spinning solution. The diluent is composed of N-methylpyrrolidone, water, and potassium hydroxide. In the spinning solution, the concentration of PPTA is 0.6wt%, the water content is 10,000ppm, and the amount of potassium hydroxide added is 2wt% of the mass of PPTA;

[0081] (3) The spinning solution is filtered and degassed before being transferred to the spinning assembly. The spinning solution passes through the spinneret and enters the coagulation bath to coagulate into a gel bundle. The spinneret orifice diameter is 100 μm, and the aspect ratio is 3:1. The gel bundle remains in the coagulation bath for 10 minutes. The coagulation bath used is water / acetone at a temperature of 25°C and a spinning speed of 10 m / min.

[0082] (4) The gel filaments were continuously washed with deionized water and then dried at 60°C for 15 minutes to obtain para-aramid monofilaments.

[0083] (5) After testing, the diameter of the para-aramid fiber monofilament is about 30 μm, the tensile strength is 320 MPa, and the elongation at break is 25%.

[0084] Example 3

[0085] (1) In 1m 3 In a stirred reactor, 40 kg of calcined calcium chloride was added to 500 L of N-methylpyrrolidone with a water content of 100 ppm. The mixture was then heated to 100°C under stirring and nitrogen protection to completely dissolve the calcium chloride. The temperature was then lowered to 20°C, and 21.60 kg of p-phenylenediamine monomer was added and dissolved to a monomer concentration of 0.4 mol / L. The temperature was then further lowered to -5°C, and 40.85 kg of terephthaloyl chloride powder was slowly added to the reactor to initiate a polymerization reaction. The stirring speed was increased to 400 rpm, and the mixture was reacted for 8 minutes after the addition of terephthaloyl chloride to obtain a para-aramid (PPTA) polymer solution.

[0086] (2) Adding a diluent 20 times the mass of the PPTA polymer solution and stirring for 0.5 h to obtain a gel (or dispersion) containing para-aramid nanofibrils, i.e., a spinning solution. The diluent is composed of N-methylpyrrolidone, water, and potassium hydroxide. In the spinning solution, the concentration of PPTA is 0.4 wt%, the water content is 20,000 ppm, and the amount of potassium hydroxide added is 2 wt% of the mass of PPTA.

[0087] (3) The spinning solution is filtered and degassed before being transferred to the spinning assembly. The spinning solution passes through the spinneret and enters the coagulation bath to coagulate into a gel bundle. The spinneret orifice diameter is 200 μm, and the aspect ratio is 2:1. The gel bundle remains in the coagulation bath for 15 minutes. The coagulation bath used is a water / ethanol bath at a temperature of 25°C and a spinning speed of 25 m / min.

[0088] (4) The gel filaments were continuously washed with deionized water and then dried at 80°C for 10 min to obtain para-aramid monofilaments.

[0089] (5) After testing, the diameter of the para-aramid monofilament is about 50 μm, the tensile strength is 210 MPa, and the elongation at break is 19%.

[0090] Example 4

[0091] (1) In 1m 3 In a stirred reactor, 30 kg of calcined lithium chloride / calcium chloride (1 / 1, mass ratio) was added to 500 L of N-methylpyrrolidone with a water content of 80 ppm. The mixture was then heated to 70° C. under stirring and nitrogen protection to completely dissolve the lithium chloride / calcium chloride. The temperature was then lowered to 10° C., and 10.80 kg of p-phenylenediamine monomer was added and dissolved to a monomer concentration of 0.2 mol / L. The temperature was then further lowered to 0° C., and 20.42 kg of terephthaloyl chloride powder was slowly added to the polymerization reactor to initiate a polymerization reaction. The stirring speed was increased to 500 rpm. After the addition of terephthaloyl chloride, the mixture was reacted for 15 minutes to obtain a para-aramid (PPTA) polymerization solution.

[0092] (2) Adding a diluent 20 times the mass of the polymer solution to the PPTA polymer solution and stirring for 3 hours to obtain a gel (or dispersion) containing para-aramid nanofibrils, i.e., a spinning solution. The diluent is composed of dimethyl sulfoxide, water, and potassium hydroxide. In the spinning solution, the concentration of PPTA is 0.2wt%, the water content is 10,000ppm, and the amount of potassium hydroxide added is 1wt% of the mass of PPTA;

[0093] (3) The spinning solution is filtered and degassed before being transported to the spinning assembly. The spinning solution passes through the spinneret and enters the coagulation bath to coagulate into a gel bundle. The spinneret orifice has a diameter of 50 μm and an aspect ratio of 3:1. The gel bundle remains in the coagulation bath for 5 minutes. The coagulation bath used is water at a temperature of 25°C and a spinning speed of 5 m / min.

[0094] (4) The gel filaments were washed continuously with deionized water and then dried at 50°C for 5 minutes to obtain para-aramid monofilaments.

[0095] (5) After testing, the diameter of the para-aramid monofilament is about 8 μm, the tensile strength is 825 MPa, and the elongation at break is 40%.

[0096] Example 5

[0097] (1) In 1m 3 In a stirred reactor, 25 kg of calcined calcium chloride was added to 500 L of N-methylpyrrolidone with a water content of 80 ppm. The mixture was then heated to 80°C under stirring and nitrogen protection to completely dissolve the calcium chloride. The temperature was then lowered to 15°C, and 10.80 kg of p-phenylenediamine monomer was added and dissolved to a monomer concentration of 0.2 mol / L. The temperature was then further lowered to 0°C, and 20.44 kg of terephthaloyl chloride powder was slowly added to the polymerization reactor to initiate a polymerization reaction. The stirring speed was increased to 500 rpm. After the addition of terephthaloyl chloride, the mixture was reacted for 10 minutes to obtain a para-aramid (PPTA) polymerization solution.

[0098] (2) Adding a diluent 5 times the mass of the polymer solution to the PPTA polymer solution and stirring for 2 hours to obtain a gel (or dispersion) containing para-aramid nanofibrils, i.e., a spinning solution. The diluent is composed of dimethyl sulfoxide, water, and potassium hydroxide. In the spinning solution, the concentration of PPTA is 0.7wt%, the water content is 20,000ppm, and the amount of potassium hydroxide added is 2wt% of the mass of PPTA;

[0099] (3) The spinning solution is filtered and degassed before being transferred to the spinning assembly. The spinning solution passes through the spinneret and enters the coagulation bath to coagulate into a gel bundle. The spinneret orifice has a diameter of 150 μm and an aspect ratio of 2:1. The gel bundle remains in the coagulation bath for 5 minutes. The coagulation bath used is water / acetone at a temperature of 30°C and a spinning speed of 20 m / min.

[0100] (4) The gel filaments were continuously washed with deionized water and then dried at 60°C for 10 min to obtain para-aramid monofilaments.

[0101] (5) After testing, the diameter of the para-aramid monofilament is about 40 μm, the tensile strength is 275 MPa, and the elongation at break is 22%.

[0102] Example 6

[0103] (1) In 1m 3 In a stirred reactor, 25 kg of calcined lithium chloride / calcium chloride (3 / 2, mass ratio) was added to 500 L of N-methylpyrrolidone with a water content of 80 ppm. The mixture was then heated to 80° C. under stirring and nitrogen protection to completely dissolve the lithium chloride / calcium chloride. The temperature was then lowered to 15° C., and 10.80 kg of p-phenylenediamine monomer was added and dissolved to a monomer concentration of 0.2 mol / L. The temperature was then further lowered to 0° C., and 20.40 kg of terephthaloyl chloride powder was slowly added to the polymerization reactor to initiate a polymerization reaction. The stirring speed was increased to 500 rpm. After the addition of terephthaloyl chloride, the mixture was reacted for 15 minutes to obtain a para-aramid (PPTA) polymerization solution.

[0104] (2) Adding a diluent 10 times the mass of the polymer solution to the PPTA polymer solution and stirring for 1 hour to obtain a gel (or dispersion) containing para-aramid nanofibrils, i.e., a spinning solution. The diluent is composed of N-methylpyrrolidone, water, and potassium hydroxide. In the spinning solution, the concentration of PPTA is 0.4wt%, the water content is 20,000ppm, and the amount of potassium hydroxide added is 2wt% of the mass of PPTA;

[0105] (3) The spinning solution is filtered and degassed before being transported to the spinning assembly. The spinning solution passes through the spinneret and enters the coagulation bath to coagulate into a gel bundle. The spinneret orifice diameter is 200 μm, and the aspect ratio is 1:1. The gel bundle remains in the coagulation bath for 30 minutes. The coagulation bath used is water / methanol at a temperature of 40°C and a spinning speed of 50 m / min.

[0106] (4) The gel filaments were continuously washed with deionized water and then dried at 150°C for 20 min to obtain para-aramid monofilaments.

[0107] (5) After testing, the diameter of the para-aramid monofilament is about 100 μm, the tensile strength is 105 MPa, and the elongation at break is 16%.

[0108] (6) The para-aramid monofilament was soaked in a rhodamine B dye solution and a methylene blue dye solution (0.01 mol / L) for 15 minutes, removed from the dye solution, and dried to obtain the dyed para-aramid monofilament. The macroscopic images of the undyed para-aramid monofilament and the para-aramid monofilament before and after dyeing with rhodamine B or methylene blue dye are shown in FIG. Figure 3 shown.

[0109] According to the structure of the above embodiment, the para-aramid monofilament provided in this application has a high elongation at break and is easy to dye, and the preparation method and dyeing conditions are simple, which is suitable for industrial production applications and expands the application scenarios of para-aramid.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A high-elongation and easily dyeable para-aramid monofilament, characterized in that: The invention comprises a plurality of para-aramid nanofibrils, wherein the plurality of para-aramid nanofibrils are arranged in bundles along the length direction of the para-aramid monofilament, and the breaking elongation of the para-aramid monofilament is 15% to 50%.

2. The para-aramid monofilament according to claim 1, characterized in that The average diameter of the para-aramid nanofibrils is 10 to 60 nm.

3. The para-aramid monofilament according to claim 1, characterized in that The para-aramid monofilament satisfies at least one of the following conditions: 1) The diameter of the para-aramid monofilament is 5 to 100 μm; 2) The tensile strength of the para-aramid monofilament is 100 to 1100 MPa.

4. A method for preparing high-elongation and easily dyeable para-aramid monofilament, characterized in that: The following steps are involved: S10: providing para-aramid polymerization liquid; S20: adding a second polar aprotic solvent and a polar protic solvent to the para-aramid polymer solution, stirring to obtain a dispersion containing para-aramid nanofibrils, to obtain a spinning solution, wherein the mass content of para-aramid in the spinning solution is 0.2% to 2%, and the mass content of the polar protic solvent is 1000 to 50000 ppm; S30: performing solution spinning on the spinning solution to obtain para-aramid monofilament.

5. The method according to claim 4, characterized in that The step S10 specifically includes: Para-phenylenediamine monomer and para-terephthaloyl chloride monomer are polymerized in a composite solvent to obtain a para-aramid polymer solution, wherein the composite solvent comprises a first polar aprotic solvent and a solubilizing salt.

6. The method according to claim 5, characterized in that The first polar aprotic solvent and the second polar aprotic solvent independently include at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

7. The method according to claim 4, characterized in that The polar protic solvent includes at least one of water, methanol and ethanol.

8. The method according to claim 4, characterized in that The step S20 further includes adding an alkaline medium to the para-aramid polymerization solution, wherein the mass ratio of the alkaline medium to the para-aramid is 0.5 to 5:

100.

9. The method according to claim 4, characterized in that The step S30 specifically includes: The spinning solution is filtered and deaerated, and then passes through a spinneret into a coagulation bath to coagulate into a gel bundle, which is then washed and dried to obtain a para-aramid monofilament.

10. A para-aramid fiber product, characterized in that: The invention comprises the para-aramid monofilament according to any one of claims 1 to 3 or the para-aramid monofilament prepared by the method according to any one of claims 4 to 9.

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