High-strength high-modulus wear-resistant thermotropic liquid crystal polyarylate fiber and preparation method thereof
By using a specific ratio of monomer and catalyst prepolymerization and solid-phase polycondensation process, combined with inorganic fillers, high-strength, high-modulus, and wear-resistant thermotropic liquid crystal polyarylate fibers were prepared, solving the problem of poor fiber wear resistance and achieving a balance between high strength and wear resistance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG YONGCHUAN JUJIA NEW MATERIAL TECH CO LTD
- Filing Date
- 2023-12-27
- Publication Date
- 2026-06-12
Smart Images
Figure BDA0004631407300000051 
Figure BDA0004631407300000101
Abstract
Description
Technical Field
[0001] This invention belongs to the field of high-performance organic fiber preparation, specifically relating to a high-strength, high-modulus, wear-resistant thermotropic liquid crystal polyarylate fiber and its preparation method. Background Technology
[0002] Thermotropic liquid crystal polyarylate is a polymer composed of rigid molecular chains. Through melt spinning, the molecular chains are highly oriented along the fiber axis, and further heat treatment (post-solid-state polymerization) yields high-strength, high-modulus fiber products. With increasingly fierce market competition, in certain fields (automotive, ropes, slings, etc.), in addition to high strength and high modulus, abrasion resistance has become a highly important indicator for thermotropic liquid crystal polyarylate fibers. However, thermotropic liquid crystal polyarylate fibers produced by existing formulation systems, due to the high orientation of the rigid molecular chains along the fiber axis, form dense crystals, resulting in low interaction forces perpendicular to the fiber axis. This often leads to the formation of fibrils due to friction, resulting in poor abrasion resistance.
[0003] To improve the abrasion resistance of thermotropic liquid crystal polyarylate fibers, existing technologies typically involve blending thermotropic liquid crystal polyarylate with other resins or adding fillers or additives to enhance the abrasion resistance of polyarylate fibers. However, to significantly improve abrasion resistance, a large amount of abrasion-resistant additives are required, which often leads to a decrease in fiber strength and modulus.
[0004] In summary, existing technologies cannot simultaneously meet the requirements for high strength, high modulus, and wear resistance of thermotropic liquid crystal polyarylate fibers. Therefore, it is necessary to develop a thermotropic liquid crystal polyarylate fiber that combines high strength, high modulus, and wear resistance to meet the needs of downstream application markets. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention provides a method for preparing high-strength, high-modulus, and wear-resistant thermotropic liquid crystal polyarylate fibers, comprising the following preparation steps:
[0006] (i) Four monomers, p-hydroxybenzoic acid, 2,6-naphthyldicarboxylic acid, 5-aminoindole-2-carboxylic acid, and 2,6-difluorohydroquinone, are mixed with an acylation reagent and a catalyst to obtain a reaction mixture; wherein, by molar percentage, the proportions of each of the four monomers are as follows: p-hydroxybenzoic acid 40-65 mol%, 2,6-naphthyldicarboxylic acid 16.7-29 mol%, 5-aminoindole-2-carboxylic acid 1.6-3.2 mol%, and 2,6-difluorohydroquinone 16.7-29 mol%;
[0007] (ii) The reaction mixture is subjected to a prepolymerization reaction to obtain a prepolymer;
[0008] (iii) Under an inert gas atmosphere, the prepolymer is subjected to a solid-state polycondensation reaction to obtain a thermotropic liquid crystal polyarylate;
[0009] (iv) The thermotropic liquid crystal polyarylate is melt-extruded through an extruder at a temperature of 300-340℃, metered by a gear pump, and supplied to the spinning assembly. The fiber filaments are sprayed out through the spinning assembly, and the fiber filaments are heat-preserved, air-cooled, stretched and shaped, separated and wound to obtain nascent fibers.
[0010] (v) Heat treatment is performed on the nascent fibers to obtain high-strength, high-modulus, wear-resistant thermotropic liquid crystal polyarylate fiber products.
[0011] In the above-mentioned method for preparing high-strength, high-modulus, wear-resistant thermotropic liquid crystal polyarylate fibers, in step (I), the molar percentage of the monomer 5-aminoindole-2-carboxylic acid is 2.0-3.0 mol%.
[0012] In the above-mentioned method for preparing high-strength, high-modulus, wear-resistant thermotropic liquid crystal polyarylate fiber, in step (I), the acylation agent is acetic anhydride, and the amount added is 1.25-1.6 times the total molar number of hydroxyl groups in the four monomers.
[0013] In the above-mentioned method for preparing high-strength, high-modulus, wear-resistant thermotropic liquid crystal polyarylate fiber, in step (I), the catalyst is N-methyl-4-aminoimidazole, and the amount added is 400-500 ppm of the total weight of the four monomers.
[0014] In the above-mentioned method for preparing high-strength, high-modulus, wear-resistant thermotropic liquid crystal polyarylate fiber, step (ii) involves prepolymerizing the reaction mixture to obtain a prepolymer, which includes: holding the reaction mixture at 120-140°C for 4-8 hours, then raising the temperature to 280-330°C and holding it for 2-4 hours, pulverizing it, and then drying it at 120-130°C for 2-3 hours to obtain the prepolymer.
[0015] In the above-mentioned method for preparing high-strength, high-modulus, wear-resistant thermotropic liquid crystal polyarylate fiber, in step (iii), the temperature of the solid-phase polycondensation reaction is 270-310℃ and the time is 12-36h.
[0016] In the above-mentioned method for preparing high-strength, high-modulus, wear-resistant thermotropic liquid crystal polyarylate fiber, in step (iv), the temperature for heat preservation is 250-280℃, and the speed for stretching and shaping is 900-1100m / min.
[0017] In the above-mentioned method for preparing high-strength, high-modulus, wear-resistant thermotropic liquid crystal polyarylate fiber, in step (v), the heat treatment temperature is 270-330℃ and the time is 12-24h.
[0018] Another objective of this invention is to provide a high-strength, high-modulus, and wear-resistant thermotropic liquid crystal polyarylate fiber, which is prepared by the above-described method for preparing high-strength, high-modulus, and wear-resistant thermotropic liquid crystal polyarylate fiber.
[0019] Among the above-mentioned high-strength, high-modulus, wear-resistant thermotropic liquid crystal polyarylate fibers, the tensile modulus of the high-strength, high-modulus, wear-resistant thermotropic liquid crystal polyarylate fibers is higher than 110 GPa, the tensile strength is higher than 20 cN / dtex, and the strength retention rate after 5000 rubs is higher than 76%.
[0020] Without compromising the effectiveness of the present invention, fibrous inorganic fillers such as glass fiber, boron nitride fiber, silicon nitride fiber, and potassium titanate fiber can be added; powdered inorganic fillers such as glass beads, calcium silicate, aluminum silicate, alumina, calcium carbonate, barium sulfate, silicon nitride, and boron nitride can be added; and plate-shaped inorganic fillers such as mica and talc can also be added.
[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: by using a specific ratio of monomers, catalysts and acetylation reagents for prepolymerization, and then through matching processes such as solid-state polycondensation, spinning and heat treatment, the resulting thermotropic liquid crystal polyarylate fiber has a tensile modulus higher than 110 GPa and a tensile strength higher than 20 cN / dtex. It also has excellent wear resistance, with a strength retention rate of more than 76% after 5000 friction tests. Based on these excellent properties, it can be used as a cord for automobile tires or as a reinforcing wear-resistant filler for automobile brake pads. It can also be used in special ropes, slings and other fields. Detailed Implementation
[0022] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.
[0023] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.
[0024] The formulations of each monomer raw material in the embodiments are shown in Table 1:
[0025] Table 1:
[0026]
[0027] The performance testing methods for the fiber products in the examples and comparative examples are as follows:
[0028] The fiber products in each embodiment and comparative example were divided into two groups: one group was tested for tensile modulus and tensile strength (as the original tensile strength), and the other group was tested for tensile strength after 5000 cycles of friction.
[0029] (1) Tensile modulus and tensile strength: Tested according to ASTM D638-10 standard.
[0030] (3) Friction Resistance Test: The fiber filaments are continuously and repeatedly placed between the wire hooks on both sides of the cohesion apparatus frame. Under constant and uniform tension, different parts of the filaments are simultaneously subjected to friction. Through the continuous friction between the blades moving back and forth at a certain speed and the filaments, the filaments split. The test parameters used in the friction test are: friction blade thickness (0.5±0.1) mm, total center distance of the upper friction blades: (35±0.2) mm, total center distance of the lower friction blades: (28±0.2) mm, friction blade edge height difference ≤0.2 mm, mass of the upper friction blade holder (300±3) g, mass of the tension weight: (200±2) g, reciprocating stroke of the friction blade holder: (90±2) mm, reciprocating speed of the friction blade holder: (120±5) times / min.
[0031] When the number of friction cycles reaches 5000, the friction test is stopped, the filament is removed, and the tensile strength is measured according to the test standard in test method (1). The tensile strength measured after 5000 friction cycles is multiplied by 100% to obtain the strength retention rate after 5000 friction cycles. The wear resistance is evaluated based on the strength retention rate. Under normal circumstances, the strength retention rate of qualified wear-resistant fiber filaments after 5000 wear resistance tests is not less than 70%.
[0032] Example 1
[0033] 1.1 According to the formula in Table 1, the four monomers were mixed with acetic anhydride (1.25 times the total molar number of hydroxyl groups in the four monomers) and N-methyl-4-aminoimidazole (400 ppm of the total weight of the four monomers). The mixture was added to a Hastelloy reactor and kept at 120°C for 8 hours. Then, the temperature was increased to 280°C at a rate of 0.8°C / min and kept at that temperature for 4 hours. Nitrogen gas of 0.5 MPa was introduced into the Hastelloy reactor to discharge the reaction product through a discharge valve with a diameter of 4 mm and 8 holes. The product was crushed, passed through a 30-mesh sieve, and dried at 120°C for 3 hours to obtain the prepolymer.
[0034] 1.2 Under a nitrogen atmosphere, the prepolymer was subjected to solid-state polycondensation at 270°C for 36 h in a rotary kiln to obtain thermotropic liquid crystal polyarylate;
[0035] 1.3 The thermotropic liquid crystal polyarylate was heated to 300°C and extruded, and then fed to the spinning assembly. The fiber filaments were sprayed out through the spinning assembly. The fiber filaments were kept at 250°C for 10 minutes, then air-cooled to room temperature, and then stretched and shaped at a speed of 900 m / min. Finally, the filaments were separated and wound to obtain the nascent fiber.
[0036] 1.4 The nascent fibers were heat-treated at 270℃ for 24h to obtain high-strength, high-modulus, wear-resistant thermotropic liquid crystal polyarylate fiber products.
[0037] Example 2
[0038] 1.1 According to the formula in Table 1, 2#, four monomers were mixed with acetic anhydride (1.3 times the total molar number of hydroxyl groups in the four monomers) and N-methyl-4-aminoimidazole (420 ppm of the total weight of the four monomers). The mixture was added to a Hastelloy reactor and kept at 130°C for 6 hours. Then, the temperature was increased to 290°C at a rate of 0.8°C / min and kept at that temperature for 3 hours. Nitrogen gas of 0.5 MPa was introduced into the Hastelloy reactor to discharge the reaction product through a discharge valve with a diameter of 4 mm and 8 holes. The product was crushed, passed through a 30-mesh sieve, and dried at 120°C for 3 hours to obtain the prepolymer.
[0039] 1.2 Under a nitrogen atmosphere, the prepolymer was subjected to solid-state polycondensation at 280°C for 30 h in a rotary kiln to obtain thermotropic liquid crystal polyarylate.
[0040] 1.3 Thermotropic liquid crystal polyarylate was heated to 310℃ and extruded, and then fed to the spinning assembly. The fiber filaments were sprayed out through the spinning assembly. The fiber filaments were kept at 260℃ for 8 minutes, then air-cooled to room temperature, and then stretched and shaped at a speed of 1000m / min. Finally, the filaments were separated and wound to obtain the nascent fiber.
[0041] 1.4 The nascent fibers were heat-treated at 280℃ for 18 hours to obtain high-strength, high-modulus, wear-resistant thermotropic liquid crystal polyarylate fiber products.
[0042] Example 3
[0043] 1.1 According to the formula in Table 1, 3#, four monomers were mixed with acetic anhydride (1.4 times the total molar number of hydroxyl groups in the four monomers) and N-methyl-4-aminoimidazole (450 ppm of the total weight of the four monomers). The mixture was added to a Hastelloy reactor and kept at 130°C for 5 hours. Then, the temperature was increased to 300°C at a rate of 0.8°C / min and kept at that temperature for 3 hours. Nitrogen gas of 0.5 MPa was introduced into the Hastelloy reactor to discharge the reaction product through a discharge valve with a diameter of 4 mm and 8 holes. The product was crushed, passed through a 30-mesh sieve, and dried at 130°C for 2 hours to obtain the prepolymer.
[0044] 1.2 Under a nitrogen atmosphere, the prepolymer was subjected to solid-state polycondensation at 290°C for 24 h in a rotary kiln to obtain thermotropic liquid crystal polyarylate;
[0045] 1.3 The thermotropic liquid crystal polyarylate was heated to 320°C and extruded, and then fed to the spinning assembly. The fiber filaments were sprayed out through the spinning assembly. The fiber filaments were kept at 260°C for 8 minutes, then air-cooled to room temperature, and then stretched and shaped at a speed of 1000 m / min. Finally, the filaments were separated and wound to obtain the nascent fiber.
[0046] 1.4 The nascent fibers were heat-treated at 300℃ for 20h to obtain high-strength, high-modulus, wear-resistant thermotropic liquid crystal polyarylate fiber products.
[0047] Example 4
[0048] 1.1 According to the formula in Table 1, acetic anhydride (1.5 times the total molar amount of hydroxyl groups in the four monomers) and N-methyl-4-aminoimidazole (480 ppm of the total weight of the four monomers) were mixed and placed in a Hastelloy reactor and kept at 120°C for 6 hours. Then, the temperature was increased to 320°C at a rate of 0.8°C / min and kept at that temperature for 3 hours. Nitrogen gas of 0.5 MPa was introduced into the Hastelloy reactor to discharge the reaction product through a discharge valve with a diameter of 4 mm and 8 holes. The product was crushed, passed through a 30-mesh sieve, and dried at 130°C for 2 hours to obtain the prepolymer.
[0049] 1.2 Under a nitrogen atmosphere, the prepolymer was subjected to solid-state polycondensation at 300°C for 18 h in a rotary kiln to obtain thermotropic liquid crystal polyarylate.
[0050] 1.3 The thermotropic liquid crystal polyarylate was heated to 330°C and extruded, and then fed to the spinning assembly. The fiber filaments were sprayed out through the spinning assembly. The fiber filaments were kept at 270°C for 6 minutes, then air-cooled to room temperature, and then stretched and shaped at a speed of 900 m / min. Finally, the filaments were separated and wound to obtain the nascent fiber.
[0051] 1.4 The nascent fibers were heat-treated at 320℃ for 15 hours to obtain high-strength, high-modulus, wear-resistant thermotropic liquid crystal polyarylate fiber products.
[0052] Example 5
[0053] 1.1 According to the formula in Table 1, 5#, four monomers were mixed with acetic anhydride (1.6 times the total molar number of hydroxyl groups in the four monomers) and N-methyl-4-aminoimidazole (500 ppm of the total weight of the four monomers). The mixture was added to a Hastelloy reactor and kept at 120°C for 8 hours. Then, the temperature was increased to 330°C at a rate of 0.8°C / min and kept at that temperature for 2 hours. Nitrogen gas of 0.5 MPa was introduced into the Hastelloy reactor to discharge the reaction product through a discharge valve with a diameter of 4 mm and 8 holes. The product was crushed, passed through a 30-mesh sieve, and dried at 130°C for 2 hours to obtain the prepolymer.
[0054] 1.2 Under a nitrogen atmosphere, the prepolymer was subjected to solid-state polycondensation reaction at 310°C for 12 h in a rotary kiln to obtain thermotropic liquid crystal polyarylate;
[0055] 1.3 The thermotropic liquid crystal polyarylate was heated to 340°C and extruded, and then fed to the spinning assembly. The fiber filaments were sprayed out through the spinning assembly. The fiber filaments were kept at 280°C for 5 minutes, then air-cooled to room temperature, and then stretched and shaped at a speed of 1100 m / min. Finally, the filaments were separated and wound to obtain the nascent fiber.
[0056] 1.4 The nascent fibers were heat-treated at 330℃ for 12 hours to obtain high-strength, high-modulus, wear-resistant thermotropic liquid crystal polyarylate fiber products.
[0057] Comparative Example 1
[0058] The difference from Example 3 is that the monomers participating in the polymerization reaction do not contain 5-aminoindole-2-carboxylic acid, and the molar content of p-hydroxybenzoic acid is 58 mol%. All other aspects are the same as in Example 3.
[0059] Comparative Example 2
[0060] The difference from Example 3 is that the polymer monomer 2,6-difluorohydroquinone is replaced with an equimolar amount of hydroquinone; all other aspects are the same as in Example 3.
[0061] Comparative Example 3
[0062] The difference from Example 3 is that the polymerization uses the following monomer formulation: 55 mol% p-hydroxybenzoic acid, 42 mol% 2-hydroxy-6-naphthoic acid, and 3 mol% 5-aminoindole-2-carboxylic acid; all other components are the same as in Example 3.
[0063] Comparative Example 4
[0064] The difference from Example 3 is that an equal amount of potassium acetate was used instead of N-methyl-4-aminoimidazolium as a catalyst during the polymerization process; all other aspects are the same as in Example 3.
[0065] The performance test results of the fibers in Examples 1-5 and Comparative Examples 1-4 are shown in Table 2:
[0066] Table 2:
[0067]
[0068] As can be seen from Table 2, the thermotropic liquid crystal polyarylate fiber obtained by adopting the technical solution of the present invention has high modulus and excellent wear resistance. The tensile modulus is higher than 110 GPa and the tensile modulus is higher than 20 cN / dtex. After 5000 friction tests, the strength retention rate is higher than 76%. It can be used as cord for automobile tires or as a reinforcing wear-resistant filler for automobile brake pads, etc. It can also be used in special ropes, slings, etc.
[0069] A comparison of the data from Examples 4-5 and Example 3 in Table 2 also shows that when the proportion of the polymer monomer 5-aminoindole-2-carboxylic acid exceeds the range of 2-3 mol%, the various performance indicators decrease. Therefore, it is better to control the proportion of 5-aminoindole-2-carboxylic acid at 2-3 mol%.
[0070] As can be seen from the comparison between Comparative Examples 1-3 and Example 3 in Table 2, when the formulation system of the present invention is broken, at least one of the performance indicators of the fiber product is significantly reduced, which may lead to the product being unable to be used normally or its service life being significantly shortened.
[0071] In addition, after the catalyst selected according to the formulation system of the present invention is replaced, the side reactions of the polymerization reaction increase significantly, the prepolymer has difficulty in being discharged from the reactor, and the color of the prepolymer is black and dark compared with the normal off-white color, making it impossible to spin normally in the spinning machine.
[0072] Due to space limitations, only test data from a few specific embodiments are given here. Those skilled in the art will understand that repeating the following tests with other embodiments of the present invention will also yield the same or similar test conclusions.
[0073] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.
Claims
1. A method for preparing high-strength, high-modulus, and wear-resistant thermotropic liquid crystal polyarylate fibers, characterized in that, Includes the following steps: (i) Four monomers, p-hydroxybenzoic acid, 2,6-naphthyldicarboxylic acid, 5-aminoindole-2-carboxylic acid, and 2,6-difluorohydroquinone, are mixed with an acylation reagent and a catalyst to obtain a reaction mixture; wherein, by molar percentage, the proportions of each of the four monomers are as follows: p-hydroxybenzoic acid 40-65 mol%, 2,6-naphthyldicarboxylic acid 16.7-29 mol%, 5-aminoindole-2-carboxylic acid 1.6-3.2 mol%, and 2,6-difluorohydroquinone 16.7-29 mol%; the acylation reagent is acetic anhydride, and the amount added is 1.25-1.6 times the total molar number of hydroxyl groups in the four monomers; the catalyst is N-methyl-4-aminoimidazole, and the amount added is 400-500 ppm of the total weight of the four monomers; (ii) The reaction mixture is subjected to a prepolymerization reaction to obtain a prepolymer; (iii) Under an inert gas atmosphere, the prepolymer is subjected to a solid-state polycondensation reaction to obtain a thermotropic liquid crystal polyarylate; (iv) The thermotropic liquid crystal polyarylate is melt-extruded through an extruder at a temperature of 300-340℃, metered by a gear pump, and fed to the spinning assembly. The fiber filaments are sprayed out through the spinning assembly, and the fiber filaments are heat-insulated, air-cooled, drawn and shaped, separated and wound to obtain nascent fibers. (v) Heat treatment is performed on the nascent fibers to obtain high-strength, high-modulus, wear-resistant thermotropic liquid crystal polyarylate fiber products.
2. A method for preparing high-strength, high-modulus, and wear-resistant thermotropic liquid crystal polyarylate fiber as described in claim 1, characterized in that, In step (a), the monomer 5-aminoindole-2-carboxylic acid has a molar percentage of 2.0-3.0 mol.
3. A method for preparing high-strength, high-modulus, and wear-resistant thermotropic liquid crystal polyarylate fiber as described in claim 1, characterized in that, In step (ii), the prepolymerization reaction of the reaction mixture to obtain the prepolymer includes: keeping the reaction mixture at 120-140℃ for 4-8 hours, then raising the temperature to 280-330℃ and keeping it at that temperature for 2-4 hours, pulverizing it, and then drying it at 120-130℃ for 2-3 hours to obtain the prepolymer.
4. A method for preparing high-strength, high-modulus, and wear-resistant thermotropic liquid crystal polyarylate fiber as described in claim 1, characterized in that, In step (iii), the solid-phase polycondensation reaction is carried out at a temperature of 270-310℃ for 12-36 hours.
5. A method for preparing high-strength, high-modulus, and wear-resistant thermotropic liquid crystal polyarylate fiber as described in claim 1, characterized in that, In step (iv), the temperature for heat preservation is 250-280℃, and the speed for stretching and shaping is 900-1100m / min.
6. A method for preparing high-strength, high-modulus, and wear-resistant thermotropic liquid crystal polyarylate fiber as described in claim 1, characterized in that, In step (v), the heat treatment temperature is 270-330℃ and the time is 12-24h.
7. A high-strength, high-modulus, wear-resistant thermotropic liquid crystal polyarylate fiber, characterized in that, It is prepared by the method of preparing high-strength, high-modulus, and wear-resistant thermotropic liquid crystal polyarylate fiber as described in any one of claims 1-6; the prepared thermotropic liquid crystal polyarylate fiber has a tensile modulus higher than 110 GPa, a tensile strength higher than 20 cN / dtex, and a strength retention rate higher than 76% after 5000 rubs.