Preparation and application of a composite yarn of melt-spun polyethylene melt-coated thermotropic liquid crystal polyarylate fiber

Abstract

The present invention relates to high-strength, high-modulus, and wear-resistant thermotropic liquid crystal polyarylate fibers and a preparation method thereof. Specifically, a melt-processable polyethylene resin is used as the coating material, and the thermotropic liquid crystal polyarylate fibers are used as the core material. Modification techniques are employed to effectively enhance the overall wear resistance of the composite fibers while retaining their original high mechanical properties. The resulting thermotropic liquid crystal polyarylate composite fibers exhibit a tensile strength exceeding 20 cN / dtex, a tensile modulus exceeding 600 cN / dtex, and a strength retention rate exceeding 80% after 10,000 friction cycles. Furthermore, the fibers exhibit a low dielectric constant (less than or equal to 2.5) and dielectric loss (less than or equal to 0.005).

Description

Technical Field

[0001] The invention belongs to the technical field of high-performance chemical fibers and relates to a high-performance thermotropic liquid crystal polymer fiber and a preparation method thereof. Background Art

[0002] Thermotropic liquid crystal polyarylate fibers, due to their exceptional mechanical properties and heat resistance, have established a significant position in the high-performance fiber market. These fibers are widely used in automotive, ropes, cables, and slings, and are also demonstrating their unique value in parachutes, particularly those used in spacecraft recovery systems.

[0003] To improve the wear resistance of thermotropic liquid crystal polyarylate fibers, researchers have adopted a variety of chemical modification strategies. First, by adjusting the monomer ratio and the use of catalysts, the molecular structure of the fiber can be optimized, thereby improving its wear resistance. For example, by increasing the molar percentage of 5-aminoindole-2-carboxylic acid, the wear resistance of the fiber can be effectively enhanced. In addition, optimizing the solid-phase polycondensation reaction is also an important means to improve the wear resistance of the fiber. By conducting the reaction under an inert gas atmosphere, fiber products with higher strength and modulus can be produced.

[0004] Surface modification techniques, such as plasma treatment and silane coupling agent treatment, are also effective methods for improving fiber wear resistance. These techniques can introduce reactive groups onto the fiber surface, enhancing adhesion between the fiber and the matrix, thereby improving wear resistance. Furthermore, the addition of inorganic fillers, such as glass fiber and boron nitride fiber, can significantly enhance fiber wear resistance.

[0005] Heat treatment is another key step in improving fiber wear resistance. Relaxation heat setting under a nitrogen atmosphere can improve the fiber's crystallinity and mechanical properties, thereby enhancing wear resistance. Furthermore, the application of UV-irradiation grafting modification technology, by introducing active groups such as acrylic acid onto the fiber surface, can also effectively improve fiber wear resistance.

[0006] The wear resistance of thermotropic liquid crystal polyarylate fibers is particularly important in the parachute industry. Parachutes used in spacecraft recovery systems must withstand extreme mechanical loads and environmental conditions, placing extremely high demands on the material's wear resistance and strength. Through the aforementioned chemical modification method, the performance of thermotropic liquid crystal polyarylate fibers has been significantly improved, enabling them to play a vital role in critical applications such as parachutes (Chinese Patent CN 111038707 B).

[0007] In summary, chemical modification has significantly enhanced the wear resistance of thermotropic liquid crystal polyarylate fibers. This not only enhances their potential for application in traditional fields but also provides a solid foundation for their development in high-end applications such as spacecraft recovery systems. With continued advancements in materials science, the performance of thermotropic liquid crystal polyarylate fibers will be further optimized, and their application range will continue to expand.

[0008] On the other hand, polyethylene materials have excellent wear resistance, especially ultra-high molecular weight polyethylene (UHMWPE) and its fibers are well-known for their excellent wear resistance, impact resistance, low friction coefficient and good chemical stability, and are widely used in multiple industries. The specific strength of UHMWPE fiber is 15 times that of steel. It has ultra-high strength, ultra-high modulus, low density and excellent chemical corrosion resistance, which makes it very ideal in areas such as bulletproof, stab-proof security protection materials and high-performance lightweight composite materials. In terms of wear resistance, UHMWPE fiber performs well, and its wear resistance is better than many other materials, including POM (polyacetal), fluororesin and PA66 nylon. The wear resistance of this material makes it very suitable for high-wear applications such as pipes, bushings, shafts, containers, etc. The wear resistance of UHMWPE increases with the increase of molecular weight, which allows it to replace metal in applications requiring high wear resistance, while also having the advantage of lightweight.

[0009] However, ultra-high molecular weight polyethylene (UHMWPE) is often processed by solution because its molecular weight is over 1 million, which is a complex process and uses high costs for organic solvents. Conventional molecular weight polyethylene can be processed by melt processing, which is more economical and environmentally friendly, and can be used as a coating layer for thermotropic liquid crystal polyarylate fibers. Therefore, combining thermotropic liquid crystal polyarylate fibers and polyethylene by melt coating is an effective way to improve the wear resistance of thermotropic liquid crystal polyarylate fibers. However, there are also many difficulties in the composite process of the two, such as the poor interfacial adhesion between polyethylene and thermotropic liquid crystal polyarylate, which all require targeted improvements and the proposal of new process solutions.

[0010] In summary, the existing technology cannot simultaneously meet people's requirements for high strength, high modulus and wear resistance of thermotropic liquid crystal polyarylate fibers. Therefore, it is necessary to develop thermotropic liquid crystal polyarylate fibers with high strength, high modulus and wear resistance to meet the needs of the downstream application market; and it is very necessary to develop new methods and new processes to fully combine polyethylene materials and thermotropic liquid crystal polyarylate materials during the development process. Summary of the Invention

[0011] The purpose of the present invention is to break the bottleneck of the existing technical solutions and provide a preparation and application of a composite yarn of melt-spun polyethylene melt-coated thermotropic liquid crystal polyarylate fiber. The present invention can be achieved through the following technical solutions:

[0012] The present invention provides a composite yarn of melt-spun polyethylene melt-coated thermotropic liquid crystal polyarylate fiber, which has a composite structure (fiber cross-sectional structure such as Figure 1 The main components are thermotropic liquid crystal polyarylate and modified polyethylene. In this composite structure, the thermotropic liquid crystal polyarylate fiber accounts for 25-95 parts by weight, and the modified polyethylene resin accounts for 5-90 parts by weight.

[0013] Preferably, the composite yarn of melt-spun polyethylene melt-coated thermotropic liquid crystal polyarylate fiber, wherein the thermotropic liquid crystal polyarylate fiber used has a tensile strength of 20-40 cN / dtex, a tensile modulus of 500-1000 cN / dtex, and a weight average molecular weight of the modified polyethylene resin of 20,000-600,000.

[0014] The present invention also provides a method for preparing a composite yarn of melt-spun polyethylene melt-coated thermotropic liquid crystal polyarylate fiber, which specifically comprises the following steps:

[0015] Step 1: Using dioxane as a solvent, (4-methoxyphenyl)(4-(trifluoromethyl)phenyl)methanone (benzophenone compound 1), thioperoxydicarbonate ([(HS)C(S)]2S2) C,C'-dioctadecyl ester (disulfide compound 2), and phenyl acrylate are mixed in a specific ratio to form a modified solution. Polyethylene resin chips are added to the modified solution, and high-purity argon gas is introduced and stirred for a period of time to form a solid-liquid mixture.

[0016] Step 2: Irradiate the solid-liquid mixture from step 2 for a period of time using an ultraviolet lamp with a wavelength of 253 nm. During the irradiation process, stirring is continued and high-purity argon gas is continuously introduced. The temperature of the solid-liquid mixture is controlled within a certain range. After stopping the ultraviolet lamp irradiation, the irradiated solid-liquid mixture is filtered and washed with dichloromethane. The mixture is then dried in an oven at a certain temperature to obtain modified polyethylene resin chips.

[0017] Step 3: preheating the thermotropic liquid crystal polyarylate fiber (including thermotropic liquid crystal polyarylate monofilament and thermotropic liquid crystal polyarylate multifilament) in air at a certain temperature, and then coating the modified polyethylene resin chips in step 2 on the surface of the thermotropic liquid crystal polyarylate fiber using a screw extruder at a certain temperature, and then cooling to obtain the thermotropic liquid crystal polyarylate composite filament.

[0018] Preferably, in step 1, the chemical structures of (4-methoxyphenyl)(4-(trifluoromethyl)phenyl)methanone (referred to as benzophenone compound 1) and thioperoxydicarbonate ([(HS)C(S)]2S2) C,C'-dioctadecyl ester (referred to as disulfide compound 2) are as follows: Figure 2As shown, the molar ratio of benzophenone compound 1, disulfide compound 2 and phenyl acrylate is 1:1:(100-300); the weight average molecular weight of the polyethylene resin chips in step 1 is between 20,000 and 500,000; the purity of argon is greater than 99.999%; the argon gas flow rate is 10-2000 ml / min; the mass ratio of polyethylene resin chips to phenyl acrylate is 1:(0.1-50), and the stirring and nitrogen flow time are the same, 5-60 minutes.

[0019] Preferably, in step 2, the argon gas flow rate is 10-2000 ml / min; the temperature of the solid-liquid mixture is controlled within the range of 10 to 60 degrees Celsius, and the UV lamp irradiation time is 3 to 48 hours. During the drying process, the oven temperature is 40-80 degrees Celsius, and the drying time is 2-10 hours.

[0020] Preferably, in step 3, the thermotropic liquid crystal polyarylate fibers (including thermotropic liquid crystal polyarylate monofilaments and thermotropic liquid crystal polyarylate multifilaments) are preheated in air at 100-130 degrees Celsius. The screw extruder is set at a temperature of 130-200 degrees Celsius.

[0021] The thermotropic liquid crystal polyarylate composite yarn obtained through steps 1 to 3 of the present invention has a tensile strength higher than 20 cN / dtex, a tensile modulus higher than 600 cN / dtex, and a strength retention rate higher than 80% after rubbing 10,000 times.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: polyethylene is used as the coating material and thermotropic liquid crystal polyarylate fiber is used as the core material. The composite yarn obtained by the melt coating method can effectively improve the wear resistance while retaining the original high mechanical properties. At the same time, the present invention also adopts a modification technology to chemically modify the polyethylene resin before coating. On the polyethylene molecular chain, under the action of benzophenone compounds and disulfide compounds, reaction sites are formed to trigger the polymerization of the monomer phenyl acrylate, and successfully graft polyphenyl acrylate. The polyethylene resin grafted with the polyphenyl acrylate molecular chain has a similar chemical structure to the main component polyarylate of the thermotropic liquid crystal polyarylate fiber. Compared with the unmodified polyethylene resin, the method provided by the present invention can effectively improve the bonding force between the polyethylene resin and the thermotropic liquid crystal polyarylate fiber, and is shown in terms of performance as having more excellent overall mechanical properties and wear resistance, and the composite yarn has a lower dielectric constant (less than or equal to 2.5) and dielectric loss (less than or equal to 0.005).

[0023] The thermotropic liquid crystal polyarylate composite yarn of the present invention can be processed and compounded with various additives, such as antioxidants, antistatic agents, flame retardants, pigments, glass fibers, and inorganic powders, depending on the product's properties. Suitable applications include fishing lines, ropes, arresting cables, parachutes, and more. DETAILED DESCRIPTION

[0024] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0025] Example 1

[0026] Step 1: Using dioxane as a solvent, (4-methoxyphenyl)(4-(trifluoromethyl)phenyl)methanone (hereinafter referred to as benzophenone compound 1), thioperoxydicarbonate ([(HS)C(S)]2S2) C,C'-dioctadecyl ester (hereinafter referred to as disulfide compound 2), and phenyl acrylate were mixed in a molar ratio of 1:1:100 to obtain a modified solution. Polyethylene resin chips with a weight-average molecular weight of 100,000 were added to the modified solution, with a mass ratio of polyethylene to phenyl acrylate of 1:10. Argon gas with a purity greater than 99.999% was introduced at a rate of 200 ml / min, and stirred for 30 minutes to obtain a solid-liquid mixture.

[0027] Step 2: The solid-liquid mixture from step 2 was irradiated with an ultraviolet lamp having a wavelength of 253 nm for 12 hours. During the irradiation process, stirring was continued and high-purity argon gas was continuously introduced at a rate of 200 ml / min. The temperature of the solid-liquid mixture was controlled at 20°C. After stopping the ultraviolet lamp irradiation, the irradiated solid-liquid mixture was filtered and washed with dichloromethane, and then dried in an oven at 60°C for 3 hours to obtain modified polyethylene resin chips.

[0028] Step 3: preheating the thermotropic liquid crystal polyarylate fiber in air at a certain temperature of 110 degrees Celsius, and then melt-coating the modified polyethylene resin chips in step 2 on the surface of the thermotropic liquid crystal polyarylate fiber using a screw extruder at 140 degrees Celsius, and cooling to obtain a thermotropic liquid crystal polyarylate composite yarn.

[0029] The prepared composite yarn contains 78 parts by weight of thermotropic liquid crystal polyarylate and 22 parts by weight of modified polyethylene resin.

[0030] Example 2

[0031] Step 1: Using dioxane as a solvent, (4-methoxyphenyl)(4-(trifluoromethyl)phenyl)methanone (hereinafter referred to as benzophenone compound 1), thioperoxydicarbonate ([(HS)C(S)]2S2) C,C'-dioctadecyl ester (hereinafter referred to as disulfide compound 2), and phenyl acrylate were mixed in a molar ratio of 1:1:150 to obtain a modified solution. Polyethylene resin chips with a weight-average molecular weight of 200,000 were added to the modified solution, with a mass ratio of polyethylene to phenyl acrylate of 1:50. Argon gas with a purity greater than 99.999% was introduced at a rate of 500 ml / min, and stirred for 40 minutes to obtain a solid-liquid mixture.

[0032] Step 2: The solid-liquid mixture from step 2 was irradiated with an ultraviolet lamp having a wavelength of 253 nm for 18 hours. During the irradiation process, stirring was continued and high-purity argon gas was continuously introduced at a rate of 500 ml / min. The temperature of the solid-liquid mixture was controlled at 25°C. After stopping the ultraviolet lamp irradiation, the irradiated solid-liquid mixture was filtered and washed with dichloromethane, and then dried in an oven at 70°C for 5 hours to obtain modified polyethylene resin chips.

[0033] Step 3: preheating the thermotropic liquid crystal polyarylate fiber in air at a certain temperature of 115 degrees Celsius, and then melt-coating the modified polyethylene resin chips in step 2 on the surface of the thermotropic liquid crystal polyarylate fiber using a screw extruder at 145 degrees Celsius, and cooling to obtain a thermotropic liquid crystal polyarylate composite yarn.

[0034] The prepared composite yarn contains 82 parts by weight of thermotropic liquid crystal polyarylate and 18 parts by weight of modified polyethylene resin.

[0035] Example 3

[0036] Step 1: Using dioxane as a solvent, (4-methoxyphenyl)(4-(trifluoromethyl)phenyl)methanone (hereinafter referred to as benzophenone compound 1), thioperoxydicarbonate ([(HS)C(S)]2S2) C,C'-dioctadecyl ester (hereinafter referred to as disulfide compound 2), and phenyl acrylate were mixed in a molar ratio of 1:1:150 to obtain a modified solution. Polyethylene resin chips with a weight-average molecular weight of 250,000 were added to the modified solution, with a mass ratio of polyethylene to phenyl acrylate of 1:80. Argon gas with a purity greater than 99.999% was introduced at a rate of 200 ml / min, and stirred for 30 minutes to obtain a solid-liquid mixture.

[0037] Step 2: The solid-liquid mixture from step 2 was irradiated with an ultraviolet lamp having a wavelength of 253 nm for 12 hours. During the irradiation process, stirring was continued and high-purity argon gas was continuously introduced at a rate of 700 ml / min. The temperature of the solid-liquid mixture was controlled at 20°C. The UV irradiation was stopped, and the irradiated solid-liquid mixture was filtered and washed with dichloromethane. The mixture was then dried in an oven at 80°C for 3 hours to obtain modified polyethylene resin chips.

[0038] Step 3: preheating the thermotropic liquid crystal polyarylate fiber in air at a certain temperature of 118 degrees Celsius, and then melt-coating the modified polyethylene resin chips in step 2 on the surface of the thermotropic liquid crystal polyarylate fiber using a screw extruder at 150 degrees Celsius, and cooling to obtain a thermotropic liquid crystal polyarylate composite yarn.

[0039] The prepared composite yarn contains 85 parts by weight of thermotropic liquid crystal polyarylate and 15 parts by weight of modified polyethylene resin.

[0040] Example 4

[0041] Step 1: Using dioxane as a solvent, (4-methoxyphenyl)(4-(trifluoromethyl)phenyl)methanone (hereinafter referred to as benzophenone compound 1), thioperoxydicarbonate ([(HS)C(S)]2S2) C,C'-dioctadecyl ester (hereinafter referred to as disulfide compound 2), and phenyl acrylate were mixed in a molar ratio of 1:1:100 to obtain a modified solution. Polyethylene resin chips with a weight-average molecular weight of 300,000 were added to the modified solution, with a mass ratio of polyethylene to phenyl acrylate of 1:150. Argon gas with a purity greater than 99.999% was introduced at a rate of 500 ml / min, and stirred for 55 minutes to obtain a solid-liquid mixture.

[0042] Step 2: The solid-liquid mixture from step 2 was irradiated with an ultraviolet lamp having a wavelength of 253 nm for 20 hours. During the irradiation process, stirring was continued and high-purity argon gas was continuously introduced at a rate of 1000 ml / min. The temperature of the solid-liquid mixture was controlled at 23°C. After stopping the ultraviolet lamp irradiation, the irradiated solid-liquid mixture was filtered and washed with dichloromethane, and then dried in an oven at 65°C for 6 hours to obtain modified polyethylene resin chips.

[0043] Step 3: preheating the thermotropic liquid crystal polyarylate fiber in air at a certain temperature of 120 degrees Celsius, and then melt-coating the modified polyethylene resin chips in step 2 on the surface of the thermotropic liquid crystal polyarylate fiber using a screw extruder at 180 degrees Celsius, and cooling to obtain a thermotropic liquid crystal polyarylate composite yarn.

[0044] The prepared composite yarn contains 89 parts by weight of thermotropic liquid crystal polyarylate and 11 parts by weight of modified polyethylene resin.

[0045] Comparative Example 1

[0046] Steps: preheat the thermotropic liquid crystal polyarylate fiber in air at 110 degrees Celsius, then use a screw extruder at 140 degrees Celsius to coat the surface of the thermotropic liquid crystal polyarylate fiber with polyethylene resin chips having a weight-average molecular weight of 100,000, and cool it to obtain a thermotropic liquid crystal polyarylate composite yarn.

[0047] The prepared composite yarn contains 78 parts by weight of thermotropic liquid crystal polyarylate and 22 parts by weight of polyethylene resin.

[0048] Comparative Example 2

[0049] Steps: preheat the thermotropic liquid crystal polyarylate fiber in air at 110 degrees Celsius, then use a screw extruder at 150 degrees Celsius to coat the surface of the thermotropic liquid crystal polyarylate fiber with polyethylene resin chips having a weight-average molecular weight of 100,000, and cool it to obtain a thermotropic liquid crystal polyarylate composite yarn.

[0050] The prepared composite yarn contains 80 parts by weight of thermotropic liquid crystal polyarylate and 20 parts by weight of polyethylene resin.

[0051] The relevant material properties of Examples 1 to 4 and Comparative Examples 1 to 2 are shown in Table 1.

[0052] Table 1

[0053]

[0054]

[0055] Note: The tensile strength, tensile modulus and dielectric constant in the table are the average values ​​of 20 samples measured under the same processing technology.

[0056] As can be seen from the above table, the tensile strength, tensile modulus, and wear resistance of the composite yarn of melt-spun polyethylene melt-coated thermotropic liquid crystal polyarylate fiber prepared by the present invention are significantly improved compared with the products obtained by the conventional method, especially the wear resistance index is significantly improved, indicating that the method of the present invention can effectively improve the performance of the fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 Schematic diagram of the cross-sectional structure of a composite yarn made of melt-spun polyethylene melt-coated thermotropic liquid crystal polyarylate fiber

[0058] Figure 2 Chemical structural formulas of benzophenone compound 1 and disulfide compound 2.

Claims

1. A composite yarn of melt-spun polyethylene melt-coated thermotropic liquid crystal polyarylate fiber, characterized in that: The fiber comprises thermotropic liquid crystal polyarylate and modified polyethylene resin, wherein the thermotropic liquid crystal polyarylate fiber accounts for 25-95 parts by weight and the modified polyethylene resin accounts for 5-90 parts by weight; The method for preparing a composite yarn of melt-spun polyethylene melt-coated thermotropic liquid crystal polyarylate fiber comprises: step (1) premixing a benzophenone compound, a disulfide compound and phenyl acrylate to obtain a modified solution, and then mixing it with polyethylene resin chips; step (2) modifying the solution in argon gas under ultraviolet light irradiation to obtain modified polyethylene resin chips; step (3) using a screw extruder to melt-coat and composite with preheated thermotropic liquid crystal polyarylate fiber, and cooling to obtain a composite yarn of melt-spun polyethylene melt-coated thermotropic liquid crystal polyarylate fiber.

2. The composite yarn of melt-spun polyethylene melt-coated thermotropic liquid crystal polyarylate fiber according to claim 1, characterized in that: In the step (1), the molar ratio of the benzophenone compound, the disulfide compound and the phenyl acrylate is 1:1:(100-300), the mass ratio of the polyethylene resin chips to the phenyl acrylate is 1:(0.1-50), and the weight average molecular weight of the polyethylene resin chips is 20,000-500,000.

3. The composite yarn of melt-spun polyethylene melt-coated thermotropic liquid crystal polyarylate fiber according to claim 1, characterized in that: The UV lamp irradiation time in step (2) is 3 to 48 hours.

4. The composite yarn of melt-spun polyethylene melt-coated thermotropic liquid crystal polyarylate fiber according to claim 1, characterized in that: The thermotropic liquid crystal polyarylate fibers described in step (3) include thermotropic liquid crystal polyarylate monofilaments and thermotropic liquid crystal polyarylate multifilaments, which are preheated in air at 100-150 degrees Celsius, and the screw extruder is set at a temperature of 130-200 degrees Celsius.

5. The composite yarn of melt-spun polyethylene melt-coated thermotropic liquid crystal polyarylate fiber according to claim 1, characterized in that: The obtained melt-spun polyethylene melt-coated thermotropic liquid crystal polyarylate fiber composite yarn has a tensile strength higher than 20 cN / dtex, a tensile modulus higher than 600 cN / dtex, a strength retention rate higher than 80% after 10,000 frictions, a dielectric constant less than or equal to 2.5, and a dielectric loss less than or equal to 0.005.

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