A method for preparing nanoscale liquid crystal polyarylate fibers

Abstract

The application relates to a preparation method of nanoscale liquid crystal polyarylate fibers, comprising the following steps: mixing and extruding high-molecular-weight polyarylate and low-molecular-weight polyarylate at a mass ratio of 1:(10-20), then performing melt spinning through a spinning machine to obtain nascent fibers, heating the nascent fibers to between the melting points of the high-molecular-weight polyarylate and the low-molecular-weight polyarylate in a protective atmosphere, and passing through a filter screen to obtain filter residues, wherein the filter residues are the nanoscale liquid crystal polyarylate fibers. The preparation method has the advantages of simple process, no need to use expensive equipment, high industrialization value, no need to use alkaline reagents for long-time alkali dissolution treatment, no degradation of nanofibers caused by the treatment, improved recovery rate, and high environmental protection benefit.

Description

Technical Field

[0001] This application relates to the field of liquid crystal polyester fiber technology, specifically to a method for preparing nanoscale liquid crystal polyarylate fibers. Background Technology

[0002] Liquid crystal polyaryl ester fiber (LCP) is a high-strength, high-modulus specialty fiber composed of rigid aromatic rings and flexible linking groups. Nanoscale liquid crystal polyaryl ester fiber refers to fiber materials with a diameter within 1000 nm. Its extremely fine fiber diameter results in a large specific surface area, thus exhibiting high adsorption performance. The main preparation method for nanoscale liquid crystal polyaryl ester fiber is electrospinning, but this method has low production efficiency and relies on high voltage electric fields, making large-scale production difficult. Patent CN103160953A from Wuhan Textile University discloses a short-process preparation method for thermotropic liquid crystal polyaryl ester nanofibers. Using alkali-soluble polyester as the dissolving component, thermotropic liquid crystal polyaryl ester is compounded with water-soluble polyester and spun. This allows the thermotropic liquid crystal polyaryl ester to be fully oriented along the melt flow direction within a high aspect ratio spinneret, forming nanofibers. The alkali-soluble polyester is dissolved and removed using a hot alkali solution. After separation and drying, thermotropic liquid crystal polyaryl ester nanofibers with excellent comprehensive properties are obtained. This method can prepare thermotropic liquid crystal polyarylate nanofibers in a short process. However, this method has some problems: 1. It requires a large amount of alkaline solution to dissolve the nascent fibers, causing environmental pollution, and the alkaline-soluble polyester is difficult to recover; 2. The alkaline dissolution process will lead to the degradation of the thermotropic liquid crystal polyarylate nanofibers, resulting in a low recovery rate and affecting their structural strength.

[0003] Therefore, it is necessary to provide a method for preparing nanoscale liquid crystal polyarylate fibers. Summary of the Invention

[0004] To address the issues of complex and polluting processes in the preparation of nanoscale liquid crystal polyarylate fibers (LCPs), it is necessary to provide a method for preparing LCPs.

[0005] The first aspect of this application provides a method for preparing nanoscale liquid crystal polyaryl ester fibers, comprising the following steps: mixing and extruding a high molecular weight polyaryl ester and a low molecular weight polyaryl ester in a mass ratio of 1:(5-20), then performing melt spinning through a spinning machine to obtain nascent fibers, heating the nascent fibers in a protective atmosphere to between the melting points of the high molecular weight polyaryl ester and the low molecular weight polyaryl ester, and passing them through a filter screen to obtain filter residue, wherein the filter residue is the nanoscale liquid crystal polyaryl ester fiber.

[0006] This method uses a high-quality low molecular weight polyarylate (LMW) and high molecular weight polyarylate (HMW) mixed and extruded to form a homogeneous mixture. Then, a melt spinning process is used to orient the polymer chains of the polyarylate along the flow direction to obtain highly oriented nascent fibers. During this process, LMW also acts as a plasticizer to promote the molecular chain movement of HMW. The nascent fibers are heated under a protective atmosphere to between the melting points of the two polyarylates, causing the LMW to melt and form a viscous flowing phase while the HMW component maintains a solid, highly oriented structure. The fibers are then filtered through a screen. The LMW can pass through the screen, while the HMW, which has a certain size, is trapped by the screen to form filter residue, i.e., nanoscale liquid crystal polyarylate fiber (LCP). This preparation method is simple, requires no expensive equipment, and has high industrialization value. Furthermore, it eliminates the need for prolonged alkaline dissolution treatment with alkaline reagents, avoiding degradation of the nanofibers and improving the recovery rate, while also offering significant environmental benefits.

[0007] Furthermore, the high molecular weight polyarylate and the low molecular weight polyarylate share the same monomers. Using polyarylates with identical monomers avoids phase separation due to differences in chemical structure, ensuring the formation of a homogeneous system during blending.

[0008] Furthermore, a compatibilizer is added during the mixed extrusion process. Compatibilizers, such as maleic anhydride copolymers, can prevent phase separation when the two polyarylates have significant differences in chemical structure or physical properties.

[0009] Furthermore, the mass ratio of the high molecular weight polyarylate to the low molecular weight polyarylate is 15:83. This preferred ratio balances good processing performance and production efficiency.

[0010] Furthermore, the spinneret of the spinning machine has an aspect ratio of 10-20. A high aspect ratio spinneret can prolong the shearing time of the melt within the channel, thereby further improving the orientation degree of the polyarylate molecular chains.

[0011] Furthermore, the high molecular weight polyarylate has a melting point of 270-275°C, and the low molecular weight polyarylate has a melting point of 220-230°C. The nascent fibers are heated to 245-255°C in a protective atmosphere. Within these ranges, it can be ensured that the low molecular weight polyarylate is fully melted while the high molecular weight polyarylate remains solid.

[0012] Furthermore, the temperature of the mixed extrusion is 290-310°C. This temperature ensures that the high molecular weight polyarylate fully melts and forms a homogeneous structure with the low molecular weight polyarylate, while avoiding oxidation of the polyarylate due to excessively high temperatures.

[0013] Furthermore, the parameters of the melt spinning process are: feed zone 230-250℃, melting zone 290-310℃, compression zone 290-310℃, and chamber temperature 290-310℃.

[0014] Furthermore, the filter residue is subjected to alkali dissolution treatment. Low molecular weight polyarylates have a certain degree of alkali solubility, while high molecular weight polyarylates are alkali-resistant. Since a large amount of low molecular weight polyarylates has already been removed during the filtration step (content less than 5%), only a mild alkali dissolution treatment is needed to further improve the purity of the filter residue without significantly affecting the performance of the nano-scale liquid crystal polyarylate fibers. Specifically, the alkali dissolution treatment time is 5-10 minutes, and the reagent is selected from solutions of sodium hydroxide and potassium hydroxide. Detailed Implementation

[0015] To facilitate understanding of this application, a more complete description will be provided below. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0016] 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 technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0018] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0019] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0020] Unless otherwise specified, the percentage content mentioned in this application refers to mass percentage for solid-liquid mixtures and solid-phase-solid mixtures, and volume percentage for liquid-phase-liquid mixtures.

[0021] Unless otherwise specified, all percentage concentrations mentioned in this application refer to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of that component.

[0022] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows for temperature fluctuations within the precision range controlled by the instrument.

[0023] The term "particle" as used in this application, or a substance with a defined particle size distribution, is not necessarily spherical in shape; it may be irregular and can be either primary or secondary particles. The particle size of irregular particles is calculated as the average of their maximum and minimum diameters.

[0024] Example 1: This example provides a method for preparing nanoscale liquid crystal polyarylate fibers.

[0025] Synthesis of high molecular weight polyarylate: p-hydroxybenzoic acid (PHB) and terephthalic acid (TA) are copolymerized in a molar ratio of 6:4 and then melt polycondensed to obtain the product. The intrinsic viscosity (intrinsic viscosity can be used as a measure of molecular weight) is η=4.5 dL / g, and the melting point is 272℃ (DSC test).

[0026] Synthesis of low molecular weight polyarylate: The monomers are the same as those of high molecular weight polyarylate (PHB / TA=6:4), and it is prepared by controlling the polycondensation time. The intrinsic viscosity η=1.2 dL / g and the melting point is 225℃ (DSC test).

[0027] Compatibilizer: 5-hydroxy-2-benzoxazole carboxylic acid.

[0028] Mixed extrusion: Weigh the raw materials, including high molecular weight polyarylate, low molecular weight polyarylate and compatibilizer, in a mass ratio of 15:83:2, add them to a twin-screw extruder and mix them. The extrusion temperature is 290℃ to obtain mixed granules.

[0029] Melt spinning: The above mixed particles are placed in a spinning machine for spinning, with zoned temperature control: feeding zone 220℃, melting zone 300℃, compression zone 300℃, and box temperature 300℃. Then, the nascent fibers are obtained through a spinneret with an aspect ratio of 20 (length 8mm, diameter 0.4mm). The nascent fibers are further cut into 1mm short fibers.

[0030] Heat treatment and filtration: The nascent fibers are fed into a tube furnace and heated to 255℃ in a nitrogen atmosphere (heating rate 10℃ / min), held for 10 min, and then passed through a 3μm filter screen to recover the filter residue and filtered material. The filter residue is nano-sized liquid crystal polyarylate fiber.

[0031] The filter residue was immersed in 0.5M NaOH solution (50℃) for 10 minutes to further remove the low molecular weight polyarylate on the surface of the filter residue, thus obtaining nano-sized liquid crystal polyarylate fiber.

[0032] Example 2: This example provides a method for preparing nanoscale liquid crystal polyarylate fibers.

[0033] Synthesis of high molecular weight polyarylate: p-hydroxybenzoic acid (PHB) and terephthalic acid (TA) are copolymerized in a molar ratio of 6:4 and then melt polycondensed to obtain the product. The intrinsic viscosity (intrinsic viscosity can be used as a measure of molecular weight) is η=4.5 dL / g, and the melting point is 272℃ (DSC test).

[0034] Synthesis of low molecular weight polyarylate: The monomers are the same as those of high molecular weight polyarylate (PHB / TA=6:4), and it is prepared by controlling the polycondensation time. The intrinsic viscosity η=1.2 dL / g and the melting point is 225℃ (DSC test).

[0035] Compatibilizer: 5-hydroxy-2-benzoxazole carboxylic acid.

[0036] Mixed extrusion: Weigh the raw materials, including high molecular weight polyarylate, low molecular weight polyarylate, and compatibilizer, in a mass ratio of 4:80:2, add them to a twin-screw extruder and mix them. The extrusion temperature is 290℃ to obtain mixed granules.

[0037] Melt spinning: The above mixed particles are placed in a spinning machine for spinning, with zoned temperature control: feeding zone 220℃, melting zone 300℃, compression zone 300℃, and box temperature 300℃. Then, the nascent fibers are obtained through a spinneret with an aspect ratio of 20 (length 8mm, diameter 0.4mm). The nascent fibers are further cut into 1mm short fibers.

[0038] Heat treatment and filtration: The nascent fibers are fed into a tube furnace and heated to 255℃ in a nitrogen atmosphere (heating rate 10℃ / min), held for 10 min, and then passed through a 3μm filter screen to recover the filter residue and filtered material. The filter residue is nano-sized liquid crystal polyarylate fiber.

[0039] The filter residue was immersed in 0.5M NaOH solution (50℃) for 10 minutes to further remove the low molecular weight polyarylate on the surface of the filter residue, thus obtaining nano-sized liquid crystal polyarylate fiber.

[0040] Example 3: This example provides a method for preparing nanoscale liquid crystal polyarylate fibers.

[0041] Synthesis of high molecular weight polyarylate: p-hydroxybenzoic acid (PHB) and terephthalic acid (TA) are copolymerized in a molar ratio of 6:4 and then melt polycondensed to obtain the product. The intrinsic viscosity (intrinsic viscosity can be used as a measure of molecular weight) is η=4.5 dL / g, and the melting point is 272℃ (DSC test).

[0042] Synthesis of low molecular weight polyarylate: The monomers are the same as those of high molecular weight polyarylate (PHB / TA=6:4), and it is prepared by controlling the polycondensation time. The intrinsic viscosity η=1.2 dL / g and the melting point is 225℃ (DSC test).

[0043] Compatibilizer: 5-hydroxy-2-benzoxazole carboxylic acid.

[0044] Mixed extrusion: Weigh the raw materials, including high molecular weight polyarylate, low molecular weight polyarylate and compatibilizer, in a mass ratio of 15:83:2, add them to a twin-screw extruder and mix them. The extrusion temperature is 290℃ to obtain mixed granules.

[0045] Melt spinning: The above mixed particles are placed in a spinning machine for spinning, with zoned temperature control: feeding zone 220℃, melting zone 300℃, compression zone 300℃, and box temperature 300℃. Then, the nascent fibers are obtained through a spinneret with an aspect ratio of 10 (length 4mm, diameter 0.4mm).

[0046] Heat treatment and filtration: The nascent fibers are fed into a tube furnace and heated to 255℃ in a nitrogen atmosphere (heating rate 10℃ / min), held for 10 min, and then passed through a 3μm filter screen to recover the filter residue and filtered material. The filter residue is nano-sized liquid crystal polyarylate fiber.

[0047] The filter residue was immersed in 0.5M NaOH solution (50℃) for 10 minutes to further remove the low molecular weight polyarylate on the surface of the filter residue, thus obtaining nano-sized liquid crystal polyarylate fiber.

[0048] Example 4: This example provides a method for preparing nanoscale liquid crystal polyarylate fibers.

[0049] Synthesis of high molecular weight polyarylate: p-hydroxybenzoic acid (PHB) and terephthalic acid (TA) are copolymerized in a molar ratio of 6:4 and then melt polycondensed to obtain the product. The intrinsic viscosity (intrinsic viscosity can be used as a measure of molecular weight) is η=4.5 dL / g, and the melting point is 272℃ (DSC test).

[0050] Synthesis of low molecular weight polyarylate: The monomers are the same as those of high molecular weight polyarylate (PHB / TA=6:4), and it is prepared by controlling the polycondensation time. The intrinsic viscosity η=1.2 dL / g and the melting point is 225℃ (DSC test).

[0051] Compatibilizer: 5-hydroxy-2-benzoxazole carboxylic acid.

[0052] Mixed extrusion: Weigh the raw materials, including high molecular weight polyarylate, low molecular weight polyarylate and compatibilizer, in a mass ratio of 15:83:2, add them to a twin-screw extruder and mix them. The extrusion temperature is 290℃ to obtain mixed granules.

[0053] Melt spinning: The above mixed particles are placed in a spinning machine for spinning, with zoned temperature control: feeding zone 230℃, melting zone 310℃, compression zone 310℃, and box temperature 310℃. Then, through a spinneret with an aspect ratio of 20 (length 8mm, diameter 0.4mm), nascent fibers are obtained. The nascent fibers are further cut into 1mm short fibers.

[0054] Heat treatment and filtration: The nascent fibers are fed into a tube furnace and heated to 255℃ in a nitrogen atmosphere (heating rate 10℃ / min), held for 10 min, and then passed through a 3μm filter screen to recover the filter residue and filtered material. The filter residue is nano-sized liquid crystal polyarylate fiber.

[0055] The filter residue was immersed in 0.5M NaOH solution (50℃) for 10 minutes to further remove the low molecular weight polyarylate on the surface of the filter residue, thus obtaining nano-sized liquid crystal polyarylate fiber.

[0056] Example 5: This example provides a method for preparing nanoscale liquid crystal polyarylate fibers.

[0057] Synthesis of high molecular weight polyarylate: p-hydroxybenzoic acid (PHB) and terephthalic acid (TA) are copolymerized in a molar ratio of 6:4 and then melt polycondensed to obtain the product. The intrinsic viscosity (intrinsic viscosity can be used as a measure of molecular weight) is η=4.5 dL / g, and the melting point is 272℃ (DSC test).

[0058] Synthesis of low molecular weight polyarylate: The monomers are the same as those of high molecular weight polyarylate (PHB / TA=6:4), and it is prepared by controlling the polycondensation time. The intrinsic viscosity η=1.2 dL / g and the melting point is 225℃ (DSC test).

[0059] Compatibilizer: Styrene-maleic anhydride copolymer.

[0060] Mixed extrusion: Weigh the raw materials, including high molecular weight polyarylate, low molecular weight polyarylate and compatibilizer, in a mass ratio of 15:83:2, add them to a twin-screw extruder and mix them. The extrusion temperature is 290℃ to obtain mixed granules.

[0061] Melt spinning: The above mixed particles are placed in a spinning machine for spinning, with zoned temperature control: feeding zone 220℃, melting zone 300℃, compression zone 300℃, and box temperature 300℃. Then, the nascent fibers are obtained through a spinneret with an aspect ratio of 20 (length 8mm, diameter 0.4mm). The nascent fibers are further cut into 1mm short fibers.

[0062] Heat treatment and filtration: The nascent fibers are fed into a tube furnace and heated to 255℃ in a nitrogen atmosphere (heating rate 10℃ / min), held for 10 min, and then passed through a 3μm filter screen to recover the filter residue and filtered material. The filter residue is nano-sized liquid crystal polyarylate fiber.

[0063] The filter residue was immersed in 0.5M NaOH solution (50℃) for 10 minutes to further remove the low molecular weight polyarylate on the surface of the filter residue, thus obtaining nano-sized liquid crystal polyarylate fiber.

[0064] Example 6: This example provides a method for preparing nanoscale liquid crystal polyarylate fibers.

[0065] Synthesis of high molecular weight polyarylate: p-hydroxybenzoic acid (PHB) and terephthalic acid (TA) are copolymerized in a molar ratio of 6:4 and then melt polycondensed to obtain the product. The intrinsic viscosity (intrinsic viscosity can be used as a measure of molecular weight) is η=4.5 dL / g, and the melting point is 272℃ (DSC test).

[0066] Synthesis of low molecular weight polyarylate: The monomers are the same as those of high molecular weight polyarylate (PHB / TA=6:4), and it is prepared by controlling the polycondensation time. The intrinsic viscosity η=1.2 dL / g and the melting point is 225℃ (DSC test).

[0067] Compatibilizer: 5-hydroxy-2-benzoxazole carboxylic acid.

[0068] Mixed extrusion: Weigh the raw materials, including high molecular weight polyarylate, low molecular weight polyarylate and compatibilizer, in a mass ratio of 15:83:2, add them to a twin-screw extruder and mix them. The extrusion temperature is 290℃ to obtain mixed granules.

[0069] Melt spinning: The above mixed particles are placed in a spinning machine for spinning, with zoned temperature control: feeding zone 220℃, melting zone 300℃, compression zone 300℃, and box temperature 300℃. Then, the nascent fibers are obtained through a spinneret with an aspect ratio of 20 (length 8mm, diameter 0.4mm). The nascent fibers are further cut into 1mm short fibers.

[0070] Heat treatment and filtration: The nascent fibers are fed into a tube furnace and heated to 245°C under a nitrogen atmosphere (heating rate 10°C / min), held for 10 min, and then passed through a 3μm filter screen to recover the filter residue and filtered material.

[0071] The filter residue was immersed in 0.5M NaOH solution (50℃) for 10 minutes to further remove the low molecular weight polyarylate on the surface of the filter residue, thus obtaining nano-sized liquid crystal polyarylate fiber.

[0072] Comparative Example 1: This comparative example provides a method for preparing nanoscale liquid crystal polyarylate fibers.

[0073] Synthesis of high molecular weight polyarylate: p-hydroxybenzoic acid (PHB) and terephthalic acid (TA) are copolymerized in a molar ratio of 6:4 and then melt polycondensed to obtain the product. The intrinsic viscosity (intrinsic viscosity can be used as a measure of molecular weight) is η=4.5 dL / g, and the melting point is 272℃ (DSC test).

[0074] Synthesis of low molecular weight polyarylate: The monomers are the same as those of high molecular weight polyarylate (PHB / TA=6:4), and it is prepared by controlling the polycondensation time. The intrinsic viscosity η=1.2 dL / g and the melting point is 225℃ (DSC test).

[0075] Compatibilizer: 5-hydroxy-2-benzoxazole carboxylic acid.

[0076] Mixed extrusion: Weigh the raw materials, including high molecular weight polyarylate, low molecular weight polyarylate, and compatibilizer, in a mass ratio of 83:15:2, add them to a twin-screw extruder and mix them. The extrusion temperature is 290℃ to obtain mixed granules.

[0077] Melt spinning: The above mixed particles are placed in a spinning machine for spinning, with zoned temperature control: feeding zone 220℃, melting zone 300℃, compression zone 300℃, and box temperature 300℃. Then, the nascent fibers are obtained through a spinneret with an aspect ratio of 20 (length 8mm, diameter 0.4mm). The nascent fibers are further cut into 1mm short fibers.

[0078] Heat treatment and filtration: The nascent fibers are fed into a tube furnace and heated to 255℃ in a nitrogen atmosphere (heating rate 10℃ / min), held for 10 min, and then passed through a 3μm filter screen to recover the filter residue and filtered material. The filter residue is nano-sized liquid crystal polyarylate fiber.

[0079] The filter residue was immersed in 0.5M NaOH solution (50℃) for 10 minutes to further remove the low molecular weight polyarylate on the surface of the filter residue, thus obtaining nano-sized liquid crystal polyarylate fiber.

[0080] Comparative Example 2: This comparative example provides a method for preparing nanoscale liquid crystal polyarylate fibers.

[0081] Synthesis of high molecular weight polyarylate: p-hydroxybenzoic acid (PHB) and terephthalic acid (TA) are copolymerized in a molar ratio of 6:4 and then melt polycondensed. The intrinsic viscosity (intrinsic viscosity can be used as a measure of molecular weight) is η=2.5 dL / g, and the melting point is 252℃ (DSC test).

[0082] Synthesis of low molecular weight polyarylate: The monomers are the same as those of high molecular weight polyarylate (PHB / TA=6:4), and it is prepared by controlling the polycondensation time. The intrinsic viscosity η=1.2 dL / g and the melting point is 225℃ (DSC test).

[0083] Compatibilizer: 5-hydroxy-2-benzoxazole carboxylic acid.

[0084] Mixed extrusion: Weigh the raw materials, including high molecular weight polyarylate, low molecular weight polyarylate and compatibilizer, in a mass ratio of 15:83:2, add them to a twin-screw extruder and mix them. The extrusion temperature is 290℃ to obtain mixed granules.

[0085] Melt spinning: The above mixed particles are placed in a spinning machine for spinning, with zoned temperature control: feeding zone 220℃, melting zone 300℃, compression zone 300℃, and box temperature 300℃. Then, the nascent fibers are obtained through a spinneret with an aspect ratio of 20 (length 8mm, diameter 0.4mm). The nascent fibers are further cut into 1mm short fibers.

[0086] Heat treatment and filtration: The nascent fibers are fed into a tube furnace and heated to 255℃ in a nitrogen atmosphere (heating rate 10℃ / min), held for 10 min, and then passed through a 3μm filter screen to recover the filter residue and filtered material. The filter residue is nano-sized liquid crystal polyarylate fiber.

[0087] The filter residue was immersed in 0.5M NaOH solution (50℃) for 10 minutes to further remove the low molecular weight polyarylate on the surface of the filter residue, thus obtaining nano-sized liquid crystal polyarylate fiber.

[0088] The average length and recovery rate of the nanoscale liquid crystal polyarylate fibers in the above embodiments and comparative examples were tested. The recovery rate was tested by the ratio of the mass of the product nanoscale liquid crystal polyarylate fibers to the mass of the high molecular weight polyarylate in the raw materials.

[0089] Table 1. Test results of the examples and comparative examples.

[0090] Item Average length (nm) Recovery (%) Example 1 812±68 95.3 Example 2 632±115 72.4 Example 3 950±182 93.8 Example 4 785±59 94.9 Example 5 845±71 95.1 Example 6 860±75 93.6 Comparative Example 1 1784±568 94.7 Comparative Example 2 1016±121 26.2

[0091] According to the results of the examples and comparative examples, the diameter distribution of Examples 1-6 is better than that of Comparative Examples 1-2. This is because this method uses a high-quality low molecular weight polyarylate (LMW) and high molecular weight polyarylate (HMW) mixed and extruded to form a uniform mixture. Then, through melt spinning, the polymer chains of the polyarylate are oriented along the flow direction to obtain highly oriented nascent fibers. In this process, LMW can also act as a plasticizer to promote the molecular chain movement of HMW. The nascent fibers are heated to between the melting points of the two polyarylates under a protective atmosphere, so that LMW melts to form a viscous flowing phase while the HMW component maintains a solid, highly oriented structure. At this point, the fibers are filtered through a filter screen. LMW can pass through the filter screen, while HMW, which has a certain size, is intercepted by the filter screen to form filter residue, i.e., nanoscale liquid crystal polyarylate fiber LCP. The above preparation method is simple, does not require expensive equipment, and has high industrialization value. At the same time, it does not require long-term alkaline dissolution treatment with alkaline reagents, which can avoid the degradation of nanofibers (conventional methods require long-term alkaline dissolution treatment of the entire nascent fiber), improve the recovery rate, and has high environmental benefits. Comparative Example 1 used a high proportion of high molecular weight polyarylate, resulting in poor flowability of the mixture, coarse fibers with poor dispersion, and large fiber length deviation. Comparative Example 2 used a low molecular weight high molecular weight polyarylate with a melting point close to the heat treatment temperature. Some liquid crystal polyester fibers passed through the filter screen during filtration, resulting in a low recovery rate.

[0092] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing nanoscale liquid crystal polyarylate fibers, characterized in that, The process includes the following steps: mixing and extruding a high molecular weight polyarylate and a low molecular weight polyarylate in a mass ratio of 1:(5-20), then performing melt spinning through a spinning machine to obtain nascent fibers; heating the nascent fibers in a protective atmosphere to between the melting points of the high molecular weight polyarylate and the low molecular weight polyarylate, and passing them through a filter screen to obtain filter residue, which is the nanoscale liquid crystal polyarylate fiber; The high molecular weight polyarylate has a melting point of 270-275°C, the low molecular weight polyarylate has a melting point of 220-230°C, and the nascent fiber is heated to 245-255°C in a protective atmosphere.

2. The preparation method according to claim 1, characterized in that, The high molecular weight polyarylate has the same monomer as the low molecular weight polyarylate.

3. The preparation method according to claim 1, characterized in that, A compatibilizer was added during the mixed extrusion process.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the high molecular weight polyarylate to the low molecular weight polyarylate is 15:

83.

5. The preparation method according to claim 1, characterized in that, The spinneret of the spinning machine has an aspect ratio of 10-20.

6. The preparation method according to claim 1, characterized in that, The nascent fibers are cut into short fibers with a diameter of 1-3 mm.

7. The preparation method according to claim 1, characterized in that, The temperature of the mixed extrusion is 290-310℃.

8. The preparation method according to claim 1, characterized in that, The parameters for melt spinning are: feed zone 230-250℃, melting zone 290-310℃, compression zone 290-310℃, and chamber temperature 290-310℃.

9. The preparation method according to claim 1, characterized in that, The filter residue is subjected to alkali dissolution treatment.