Preparation method of coarse-diameter high-strength polyethylene fiber and polyethylene fiber

Abstract

The application discloses a preparation method of a coarse-diameter high-strength polyethylene fiber and the polyethylene fiber, and comprises the following steps: preparing a nano modifier, wherein the nano modifier is hyperbranched polyethylene modified nano SiO2; mixing polyethylene powder, white oil, the nano modifier and an antioxidant 1010 to form a mixed solution; subjecting the mixed solution to an extrusion step to form a gel fiber, and then allowing the gel fiber to stand to remove oil, and then subjecting the gel fiber to three-stage extraction by using an ionic liquid, drying and stretching to form the polyethylene fiber. By using the nano modifier as a raw material of the polyethylene fiber, the nano modifier is a hyperbranched modified nanoparticle, the volume steric hindrance of the nanoparticle is small, the uniformity of the nanoparticle dispersion can be ensured, the long-chain alkyl on the outside of the nanoparticle has very good compatibility with a polyethylene molecular chain, bidirectional penetration and diffusion of an extractant and a solvent are greatly promoted, the extraction process is accelerated, the residual solvent is reduced, and the mechanical property of the prepared fiber is effectively improved.

Description

Technical Field

[0001] This invention generally relates to the field of fiber preparation, and more particularly to a method for preparing coarse denier high-strength polyethylene fiber and polyethylene fiber. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE) fiber is widely used in defense, security, marine engineering, and sporting goods due to its high strength, high modulus, low density, and excellent impact and abrasion resistance. In recent years, with the continuous expansion of its applications, the consumption and proportion of UHMWPE fiber in both industrial and civilian sectors have continued to increase. Especially against the backdrop of increasing emphasis on marine resource development, the demand for UHMWPE fiber in marine cables has grown significantly.

[0003] However, existing ultra-high molecular weight polyethylene (UHMWPE) ropes are mostly made from dozens to hundreds of bundles of fine denier fibers through a braiding process. It is difficult to ensure uniform tension across all fibers during processing, leading to premature breakage of some fibers and resulting in an actual breaking strength far lower than the theoretical value. The finer the fiber diameter, the more fibers are required, and the more pronounced the tension unevenness becomes. Furthermore, ropes made from fine denier UHMWPE fibers have a loose surface structure, making them prone to the incorporation of high-hardness impurities such as mud and sand during use, causing surface fiber wear. Simultaneously, due to their large specific surface area, the heat generated by friction is difficult to dissipate quickly, leading to fiber surface softening and reduced strength, severely impacting the overall performance and service life of the rope. Therefore, developing coarse denier UHMWPE fibers is an effective way to improve rope performance. By increasing the monofilament diameter, the number of fibers required for rope making can be effectively reduced, improving stress uniformity and inhibiting the embedding of external impurities, thereby improving the mechanical properties of UHMWPE fibers and their products.

[0004] Currently, the gel spinning-super-stretching technology is widely used in industry to produce ultra-high molecular weight polyethylene (UHMWPE) fibers. The conventional process involves dissolving UHMWPE powder in a solvent to form a spinning solution, extruding it through a spinneret, and then rapidly cooling it to form gel fibers. These fibers are then extracted to remove the solvent, dried, and finally subjected to super-stretching to obtain high-strength, high-modulus fibers. However, existing processes suffer from drawbacks such as low spinning concentration and high consumption of solvents and extractants. Especially when preparing large-diameter fibers, the fiber's specific surface area is small, resulting in a long and difficult path for solvent diffusion from the core to the surface, making it difficult to fully extract the solvent within a limited time. Residual solvent can affect the subsequent hot-stretching process, reducing the final fiber strength. Summary of the Invention

[0005] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide a method for preparing coarse denier high-strength polyethylene fiber and polyethylene fiber.

[0006] In a first aspect, a method for preparing coarse denier high-strength polyethylene fiber is provided, the method comprising:

[0007] A nano-modifier was prepared, wherein the nano-modifier was hyperbranched polyethylene modified nano-SiO2.

[0008] Polyethylene powder, white oil, the nano-modifier, and antioxidant 1010 are mixed and added to a swelling reactor and reacted for a period of time to form a mixed solution; wherein, the mass of the polyethylene powder accounts for 8-12% of the total mass of the polyethylene powder and the white oil, the nano-modifier accounts for 1-2% of the mass of the polyethylene powder, and the antioxidant 1010 accounts for 0.5-1% of the mass of the polyethylene powder;

[0009] The mixed solution is extruded to form gel fibers, and the gel fibers are left to stand to extract oil. Subsequently, they are subjected to three-stage extraction with ionic liquid, drying and stretching to form polyethylene fibers.

[0010] As one possible approach, the preparation of the nano-modifier includes the following steps:

[0011] Nano-SiO2 was added to an ethanol aqueous solution and stirred until homogeneous to obtain a suspension. Then, 3-mercaptopropyltriethoxysilane was added, and glacial acetic acid was added to adjust the pH of the mixed solution to 4-5. The solution was stirred at room temperature for a predetermined time. The volume ratio of ethanol to water in the ethanol aqueous solution was 9:1.

[0012] After the reaction was completed, the mixed solution was centrifuged, washed with water and dried to obtain mercapto-based nano-SiO2;

[0013] Thiol-modified nano-SiO2 and hyperbranched polyethylene were added to toluene, along with an initiator. The mixture was stirred under a nitrogen atmosphere and reacted at 80-90°C for a set time. After the reaction was completed, the reaction solution was filtered, and the filter residue was dispersed in hot toluene and washed once. After filtration, it was thoroughly washed with anhydrous ethanol and dried to obtain hyperbranched polyethylene modified nano-SiO2.

[0014] As an example, the nano-SiO2 has a particle size of 300-500 nm, and the mass ratio of the nano-SiO2 to the 3-mercaptopropyltriethoxysilane is 1:1.

[0015] As an achievable method, the hyperbranched polyethylene is a hyperbranched polyethylene with carbon-carbon double bonds at the ends, wherein the viscosity-average molecular weight of the hyperbranched polyethylene is 600~1000 g / mol and the double bond content is 1~3 mol.

[0016] As a feasible method, the mass ratio of the thiolized nano-SiO2 to the hyperbranched polyethylene is 5:1.

[0017] The initiator is one of azobisisobutyronitrile and benzoyl peroxide, and the amount of initiator added is 0.5 to 1% of the total mass of the thiolized nano-SiO2 and the hyperbranched polyethylene.

[0018] As an example, the temperature of the swelling vessel is 110-120°C.

[0019] As an achievable method, the "forming gel fiber by extrusion of the mixed solution" specifically includes: extruding the mixed solution into a twin-screw extruder and a spinning box, wherein the temperature of the twin-screw extruder is 230-250℃;

[0020] The extruded filaments are rapidly cooled in a cold water bath to form the gel fiber, wherein the temperature of the cold water bath is 5-15℃.

[0021] As a feasible approach, in the aforementioned three-stage extraction process of ionic liquids

[0022] The ionic liquid is a mixed ionic liquid composed of 1-ethyl-3-methylimidazolium dicyanamide salt and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, wherein the mass ratio of 1-ethyl-3-methylimidazolium dicyanamide salt to 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt is 4:6.

[0023] The three-stage extraction is countercurrent extraction, and the temperature of the ionic liquid is 60~80 ℃.

[0024] As an example, the monofilament linear density of the polyethylene fiber is 40-90D.

[0025] Secondly, a method for preparing polyethylene fibers according to the above-mentioned method for preparing coarse denier high-strength polyethylene fibers is provided.

[0026] According to the technical solution provided in the embodiments of this application, by using a nano-modifier as the raw material for polyethylene fiber, which is a hyperbranched modified nanoparticle, the small steric hindrance of the particle can ensure the uniformity of nanoparticle dispersion. Furthermore, the long-chain alkyl groups on the outside of the particle have very good compatibility with the polyethylene molecular chain, fundamentally solving the problems of nanoparticle dispersion and interfacial compatibility. At the same time, the modified nanoparticles can be uniformly dispersed in the formed gel fiber, and the nanoparticles form a large number of micropores, which can greatly promote the bidirectional penetration and diffusion of the extractant and solvent in the subsequent extraction steps, accelerate the extraction process, and reduce solvent residue. The less residual solvent, the better the mechanical properties of the prepared fiber can be. Attached Figure Description

[0027] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0028] Figure 1 This is a flowchart of the polyethylene fiber preparation method in this embodiment. Detailed Implementation

[0029] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] Please refer to Figure 1 This embodiment provides a method for preparing coarse denier high-strength polyethylene fiber, including:

[0032] A nano-modifier was prepared, wherein the nano-modifier was hyperbranched polyethylene modified nano-SiO2.

[0033] Polyethylene powder, white oil, the nano-modifier, and antioxidant 1010 are mixed and added to a swelling vessel to react for a period of time to form a mixed solution. The polyethylene powder accounts for 8-12% of the total mass of the polyethylene powder and white oil, the nano-modifier accounts for 1-2% of the mass of the polyethylene powder, and the antioxidant 1010 accounts for 0.5-1% of the mass of the polyethylene powder.

[0034] The mixed solution is extruded to form gel fibers, and the gel fibers are left to stand to extract oil. Subsequently, they are subjected to three-stage extraction with ionic liquid, drying and stretching to form polyethylene fibers.

[0035] This embodiment uses a nano-modifier as the raw material for polyethylene fiber. The modifier is a hyperbranched modified nanoparticle. Due to the small steric hindrance of the particles, the uniformity of nanoparticle dispersion can be ensured. Furthermore, the long-chain alkyl groups on the outside of the particles have excellent compatibility with the polyethylene molecular chain, fundamentally solving the problems of nanoparticle dispersion and interfacial compatibility. At the same time, the modified nanoparticles can be uniformly dispersed in the formed gel fiber. The nanoparticles form a large number of micropores, which can greatly promote the bidirectional penetration and diffusion of the extractant and solvent in the subsequent extraction step, accelerate the extraction process, and reduce solvent residue. The less residual solvent, the better the mechanical properties of the prepared fiber.

[0036] This embodiment first prepares hyperbranched polyethylene-modified nano-SiO2, enabling it to be uniformly distributed in subsequent raw material mixing steps and providing better micropores. The specific steps include:

[0037] Nano-SiO2 was added to an ethanol aqueous solution and stirred until homogeneous to obtain a suspension. Then, 3-mercaptopropyltriethoxysilane was added, and glacial acetic acid was added to adjust the pH of the mixed solution to 4-5. The solution was stirred at room temperature for a predetermined time. The volume ratio of ethanol to water in the ethanol aqueous solution was 9:1.

[0038] After the reaction was completed, the mixed solution was centrifuged, washed with water and dried to obtain mercapto-based nano-SiO2;

[0039] Thiol-modified nano-SiO2 and hyperbranched polyethylene were added to toluene, along with an initiator. The mixture was stirred under a nitrogen atmosphere and reacted at 80-90°C for a set time. After the reaction was completed, the reaction solution was filtered, and the filter residue was dispersed in hot toluene and washed once. After filtration, it was thoroughly washed with anhydrous ethanol and dried to obtain hyperbranched polyethylene modified nano-SiO2.

[0040] In this embodiment, the above method is used to prepare hyperbranched polyethylene modified nano-SiO2, and its small volume steric hindrance ensures its dispersion in the fiber.

[0041] The nano-SiO2 used has a particle size of 300-500 nm, and the mass ratio of the nano-SiO2 to the 3-mercaptopropyltriethoxysilane is 1:1.

[0042] Optionally, the hyperbranched polyethylene used is hyperbranched polyethylene with carbon-carbon double bonds at the ends, wherein the viscosity-average molecular weight of the hyperbranched polyethylene is 600~1000 g / mol and the double bond content is 1~3 mol.

[0043] The above process enables the prepared hyperbranched polyethylene modified nano-SiO2 to have an outer long-chain alkyl group that is highly compatible with the polyethylene fiber molecular chain, which can fundamentally solve the problems of nanoparticle dispersion and interfacial compatibility.

[0044] In the above fiber preparation process, the mass ratio of thiolized nano-SiO2 to hyperbranched polyethylene is 5:1.

[0045] The initiator is one of azobisisobutyronitrile and benzoyl peroxide, and the amount of initiator added is 0.5 to 1% of the total mass of the thiolized nano-SiO2 and the hyperbranched polyethylene.

[0046] Polyethylene powder, white oil, nano-modifier and antioxidant 1010 are mixed in a certain proportion and added to a swelling vessel for a period of time. The temperature of the swelling vessel is set at 110-120℃ to form a mixed solution.

[0047] The mixed solution is then extruded to form gel fibers, preferably using a twin-screw extruder. Specifically, the mixed solution is fed into the twin-screw extruder and the spinning box for extrusion, wherein the temperature of the twin-screw extruder is 230-250°C.

[0048] The extruded filaments are rapidly cooled in a cold water bath to form the gel fiber, wherein the temperature of the cold water bath is 5-15℃.

[0049] The aforementioned gel fibers were left to stand for a period of time to extract oil, followed by extraction using a three-stage ionic liquid extraction process. This ionic liquid is characterized by stable performance, near non-volatile properties, easy recyclability, and environmental friendliness. Furthermore, the ionic liquid used in this embodiment is a mixed ionic liquid composed of 1-ethyl-3-methylimidazolium dicyanamide salt and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt. Using this mixed ionic liquid as the extractant and increasing the temperature of the extraction bath effectively reduces the extractant concentration, improves fluidity and diffusion rate, and increases the solubility of the white oil in the extractant. The three-stage countercurrent extraction process, with the polyethylene fibers in counter-current contact with the extractant, significantly reduces the amount of extractant used. The mixed solution is then sheared by the twin screws in a twin-screw extruder and subsequently fed into a spinning box where it is extruded through a spinneret to form monofilaments. The temperature of the twin-screw extruder is set between 230-250°C.

[0050] The three-stage extraction method used in this embodiment employs a commonly used extraction technique, which will be briefly introduced here. In this extraction technique, the fiber and the extractant move in opposite directions. The fiber, i.e., the gel fiber, enters in the first stage, passes through the second stage, and then the third stage. The extractant, i.e., the ionic liquid, enters in the third stage, passes through the second stage, and flows out from the first stage. The white oil content in the fiber gradually decreases, and the fiber with the lowest white oil content appears in the third stage, where it encounters the freshest ionic liquid. The fresh ionic liquid is added as the extractant in the final stage, reducing the amount of extractant consumed and facilitating subsequent recovery.

[0051] Optionally, the mass ratio of the above-mentioned 1-ethyl-3-methylimidazolium dicyandiamide salt and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt is 4:6.

[0052] The three-stage extraction is countercurrent extraction, and the temperature of the ionic liquid is 60~80 ℃.

[0053] The extracted gel fibers are dried and stretched, preferably using a three-stage hot stretching process, with stretching temperatures of 90℃, 110℃, and 120℃ for the first to third stages, and a total stretching ratio of 50-120 times.

[0054] The polyethylene fibers prepared by the above steps have a monofilament linear density of 40-90D. They are coarse denier fibers. The preparation process uses a three-stage extraction process with ionic liquids, which combines the non-volatility and recyclability of ionic liquids. This not only yields fibers with uniform structure, few defects, and excellent mechanical properties, but also makes the entire process green and environmentally friendly, meeting the urgent needs of specific industrial sectors for coarse denier, high-strength fibers.

[0055] Several embodiments and comparative examples are provided below: Example 1

[0056] Step (1) Preparation of hyperbranched modified nano-SiO2: 50 g of nano-SiO2 with a particle size of 300 nm was added to 0.75 L of anhydrous ethanol and stirred to obtain a uniform suspension. Then, 50 g of 3-mercaptopropyltriethoxysilane was added, and 75 mL of water was added to promote the hydrolysis of silane. The pH of the mixed solution was adjusted to 4 with glacial acetic acid and stirred at room temperature for 4 h. After the reaction was completed, the mixture was centrifuged, washed with water, and dried to obtain thiolized nano-SiO2. Hyperbranched polyethylene with a double bond content of 3 mol% and a viscosity-average molecular weight of 600 g / mol was selected. 40 g of thiolized nano-SiO2 and 8 g of hyperbranched polyethylene were added to 600 mL of toluene, and 0.45 g of azobisisobutyronitrile was added. The mixture was stirred under a nitrogen atmosphere and reacted at 90 °C for 24 h. After the reaction was completed, the mixture was filtered. 600 mL of toluene was heated to 90 °C, and the filter residue was poured into it for washing. After filtration, the mixture was thoroughly washed with anhydrous ethanol and then heated to 80 °C. Drying at ℃ yields hyperbranched polyethylene modified nano-SiO2;

[0057] Step (2) Preparation of ultra-high molecular weight polyethylene fiber: 4 kg of ultra-high molecular weight polyethylene fiber with a molecular weight of 3.0 × 10⁻⁶ 6Ultra-high molecular weight polyethylene (UHMWPE) of g / mol, 46 kg of white oil, 40 g of nano-modifier, and 20 g of antioxidant 1010 were mixed in proportion and added to a swelling kettle to swell at 110℃ for 1 h. The mixed solution was then extruded through a twin-screw extruder and a spinning box at a spinning temperature of 230~250℃. After cooling in a water bath at 10℃, gel fiber was obtained. After 72 hours of settling and oil extraction, the gel filaments were pre-stretched 2.3 times and then entered an extraction tank for tertiary extraction. The extractant consisted of 40% of a mixture of 1-ethyl-3-methylimidazolium dicyandiamide salt ([EMIM][DCA]) and 60% of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt ([BMIM][NTf2]). The extraction temperature was 70 °C. After drying, the filaments underwent hot stretching. The hot stretching process was as follows: first-stage stretching temperature 90 °C, first-stage stretching ratio 15; second-stage stretching temperature 110 °C, second-stage stretching ratio 2; third-stage stretching temperature 120 °C, third-stage stretching ratio 1.3; and a total stretching ratio of 89.7. Finally, the filaments were wound up to obtain ultra-high molecular weight polyethylene fibers with a linear density of 72 D. Example 2

[0058] Step (1) Preparation of hyperbranched modified nano-SiO2: 50 g of nano-SiO2 with a particle size of 400 nm was added to 0.75 L of anhydrous ethanol and stirred to obtain a uniform suspension. Then, 50 g of 3-mercaptopropyltriethoxysilane was added, and 75 mL of water was added to promote the hydrolysis of silane. The pH of the mixed solution was adjusted to 4.5 with glacial acetic acid and stirred at room temperature for 3.5 h. After the reaction was completed, the mixture was centrifuged, washed with water, and dried to obtain thiolized nano-SiO2. Hyperbranched polyethylene with a double bond content of 2 mol% and a viscosity-average molecular weight of 800 g / mol was selected. 40 g of thiolized nano-SiO2 and 8 g of hyperbranched polyethylene were added to 600 mL of toluene, and 0.45 g of benzoyl peroxide was added. The mixture was stirred under a nitrogen atmosphere and reacted at 90 °C for 24 h. After the reaction was completed, the mixture was filtered. 600 mL of toluene was heated to 90 °C, and the filter residue was poured into it to wash once. After filtration, the mixture was thoroughly washed with anhydrous ethanol and then heated to 80 °C. Drying at ℃ yields hyperbranched polyethylene modified nano-SiO2;

[0059] Step (2) Preparation of ultra-high molecular weight polyethylene fiber: 5.5 kg of ultra-high molecular weight polyethylene fiber with a molecular weight of 3.5 × 10⁻⁶ 6Ultra-high molecular weight polyethylene (UHMWPE) at a concentration of g / mol, 49.5 kg of white oil, 55 g of nano-modifier, and 44 g of antioxidant 1010 were mixed in a specific ratio and added to a swelling vessel for swelling at 120°C for 1 h. The mixture was then extruded through a twin-screw extruder and a spinning box at a spinning temperature of 230-250°C. After cooling in a 5°C water bath, gel fibers were formed. After 72 h of settling and oil extraction, the gel fibers were pre-stretched 2.2 times and then subjected to tertiary extraction in an extraction tank. The extractant was a mixture of 40% [EMIM][DCA] and 60% [BMIM][NTf2] at an extraction temperature of 80°C. After washing and drying, the fibers were hot-stretched. The hot-stretching process was as follows: first-stage stretching temperature of 90°C with a first-stage stretching ratio of 17; second-stage stretching temperature of 110°C with a second-stage stretching ratio of 2; and third-stage stretching temperature of 120°C with a third-stage stretching ratio of 1.31, for a total stretching ratio of 97.9. The final winding yields ultra-high molecular weight polyethylene fibers with a linear density of 66 D. Example 3

[0060] Step (1) Preparation of hyperbranched modified nano-SiO2: 50 g of nano-SiO2 with a particle size of 500 nm was added to 0.75 L of anhydrous ethanol and stirred to obtain a uniform suspension. Then, 50 g of 3-mercaptopropyltriethoxysilane was added, and 75 mL of water was added to promote the hydrolysis of silane. The pH of the mixed solution was adjusted to 5 with glacial acetic acid and stirred at room temperature for 3 h. After the reaction was completed, the mixture was centrifuged, washed with water, and dried to obtain thiolized nano-SiO2. Hyperbranched polyethylene with a double bond content of 2 mol% and a viscosity-average molecular weight of 1000 g / mol was selected. 40 g of thiolized nano-SiO2 and 8 g of hyperbranched polyethylene were added to 600 mL of toluene, and 0.45 g of benzoyl peroxide was added. The mixture was stirred under a nitrogen atmosphere and reacted at 90 °C for 24 h. After the reaction was completed, the mixture was filtered. 600 mL of toluene was heated to 90 °C, and the filter residue was poured into it to wash once. After filtration, the mixture was thoroughly washed with anhydrous ethanol and then heated to 80 °C. The nano-SiO2 modified with hyperbranched polyethylene was obtained by drying at ℃.

[0061] Step (2) Preparation of ultra-high molecular weight polyethylene fiber: 5 kg of ultra-high molecular weight polyethylene fiber with a molecular weight of 4.5 × 10⁻⁶ 6A mixture of g / mol ultra-high molecular weight polyethylene, 40.5 kg white oil, 75 g nano-modifier, and 44 g antioxidant 1010 was added to a swelling vessel and swelled at 115℃ for 1 h. The mixture was then extruded through a twin-screw extruder and spinning box at a spinning temperature of 230~250℃. After cooling in a 15℃ water bath, gel fibers were formed. After 72 h of settling and oil extraction, the gel fibers were pre-stretched 2.5 times and then subjected to tertiary extraction in an extraction tank. The extractant was a mixture of 40% [EMIM][DCA] and 60% [BMIM][NTf2] at an extraction temperature of 70℃. After washing and drying, the fibers were hot-stretched. The hot-stretching process was as follows: first-stage stretching temperature 90℃, first-stage stretching ratio 17; second-stage stretching temperature 110℃, second-stage stretching ratio 2; third-stage stretching temperature 120℃, third-stage stretching ratio 1.31; and the total stretching ratio was 104.8. The final winding yields ultra-high molecular weight polyethylene fibers with a linear density of 60 D. Example 4

[0062] Step (1) Preparation of hyperbranched modified nano-SiO2: 50 g of nano-SiO2 with a particle size of 400 nm was added to 0.75 L of anhydrous ethanol and stirred to obtain a uniform suspension. Then, 50 g of 3-mercaptopropyltriethoxysilane was added, and 75 mL of water was added to promote the hydrolysis of silane. The pH of the mixed solution was adjusted to 4.5 with glacial acetic acid and stirred at room temperature for 4 h. After the reaction was completed, the mixture was centrifuged, washed with water, and dried to obtain thiolized nano-SiO2. Hyperbranched polyethylene with a double bond content of 3 mol% and a viscosity-average molecular weight of 1000 g / mol was selected. 40 g of thiolized nano-SiO2 and 8 g of hyperbranched polyethylene were added to 600 mL of toluene, and 0.45 g of azobisisobutyronitrile was added. The mixture was stirred under a nitrogen atmosphere and reacted at 90 °C for 24 h. After the reaction was completed, the mixture was filtered. 600 mL of toluene was heated to 90 °C, and the filter residue was poured into it to wash once. After filtration, the mixture was thoroughly washed with anhydrous ethanol and then heated to 80 °C. Drying at ℃ yields hyperbranched polyethylene modified nano-SiO2;

[0063] Step (2) Preparation of ultra-high molecular weight polyethylene fiber: 5 kg of ultra-high molecular weight polyethylene fiber with a molecular weight of 3.0 × 10⁻⁶ 6A mixture of g / mol ultra-high molecular weight polyethylene, 36.7 kg white oil, 50 g nano-modifier, and 25 g antioxidant 1010 was added to a swelling vessel and swelled at 110℃ for 1 h. The mixture was then extruded through a twin-screw extruder and spinning box at a spinning temperature of 230~250℃. After cooling in a 10℃ water bath, gel fibers were formed. After 72 h of settling and oil extraction, the gel fibers were pre-stretched 2.5 times and then entered an extraction tank for tertiary extraction. The extractant was a mixture of 40% [EMIM][DCA] and 60% [BMIM][NTf2] at an extraction temperature of 60℃. After washing and drying, the fibers were hot-stretched. The hot-stretching process was as follows: first-stage stretching temperature 90℃, first-stage stretching ratio 15; second-stage stretching temperature 110℃, second-stage stretching ratio 1.8; third-stage stretching temperature 120℃, third-stage stretching ratio 1.18; and the total stretching ratio was 79.7. The final winding yields ultra-high molecular weight polyethylene fibers with a linear density of 75 D. Example 5

[0064] Step (1) is the same as in Example 1.

[0065] In step (2), 5 kg of molecules with a molecular weight of 3.0 × 10⁻⁶ are used. 6 A mixture of g / mol ultra-high molecular weight polyethylene, 36.7 kg white oil, 100 g nano-modifier, and 30 g antioxidant 1010 was added to a swelling vessel and swelled at 110℃ for 1 h. The mixture was then extruded through a twin-screw extruder and spinning box at a spinning temperature of 230~250℃. After cooling in a 10℃ water bath, gel fibers were formed. After 72 h of settling and oil extraction, the gel fibers were pre-stretched 2.5 times and then subjected to tertiary extraction in an extraction tank. The extractant was a mixture of 40% [EMIM][DCA] and 60% [BMIM][NTf2] at an extraction temperature of 65℃. After washing and drying, the fibers were hot-stretched. The hot-stretching process was as follows: first-stage stretching temperature 90℃, first-stage stretching ratio 16.5; second-stage stretching temperature 110℃, second-stage stretching ratio 2.1; third-stage stretching temperature 120℃, third-stage stretching ratio 1.3; and total stretching ratio 112.6. The final winding yielded ultra-high molecular weight polyethylene fiber with a linear density of 53 D. Example 6

[0066] Step (1) is the same as in Example 1.

[0067] In step (2), 5 kg of a molecular weight of 4.0 × 10⁻⁶ is used. 6A mixture of g / mol ultra-high molecular weight polyethylene, 57.5 kg white oil, 50 g nano-modifier, and 25 g antioxidant 1010 was added to a swelling vessel and swelled at 110℃ for 1 h. The mixture was then extruded through a twin-screw extruder and spinning box at a spinning temperature of 230~250℃. After cooling in a 10℃ water bath, gel fibers were formed. After 72 h of settling and oil extraction, the gel fibers were pre-stretched 2.5 times and then entered an extraction tank for three-stage extraction. The extractant was a mixture of 40% [EMIM][DCA] and 60% [BMIM][NTf2] at an extraction temperature of 60℃. After washing and drying, the fibers were hot-stretched. The hot-stretching process was as follows: first-stage stretching temperature 90℃, first-stage stretching ratio 16.5; second-stage stretching temperature 110℃, second-stage stretching ratio 2.1; third-stage stretching temperature 120℃, third-stage stretching ratio 1.3; and total stretching ratio 112.6. The final winding yielded ultra-high molecular weight polyethylene fiber with a linear density of 49 D. Example 7

[0068] Step (1) is the same as in Example 1.

[0069] In step (2), 5 kg of molecules with a molecular weight of 4.5 × 10⁻⁶ are used. 6 A mixture of g / mol ultra-high molecular weight polyethylene, 57.5 kg white oil, 50 g nano-modifier, and 25 g antioxidant 1010 was added to a swelling vessel and swelled at 110℃ for 1 h. The mixture was then extruded through a twin-screw extruder and spinning box at a spinning temperature of 230~250℃. After cooling in a 10℃ water bath, gel fibers were formed. After 72 h of settling and oil extraction, the gel fibers were pre-stretched 2.5 times and then entered an extraction tank for three-stage extraction. The extractant was a mixture of 40% [EMIM][DCA] and 60% [BMIM][NTf2] at an extraction temperature of 60℃. After washing and drying, the fibers were hot-stretched. The hot-stretching process was as follows: first-stage stretching temperature 90℃, first-stage stretching ratio 17; second-stage stretching temperature 110℃, second-stage stretching ratio 2.1; third-stage stretching temperature 120℃, third-stage stretching ratio 1.31; and the total stretching ratio was 116.9. The final winding yielded ultra-high molecular weight polyethylene fiber with a linear density of 48 D. Example 8

[0070] Step (1) is the same as in Example 3.

[0071] In step (2), 5 kg of molecules with a molecular weight of 3.5 × 10⁻⁶ are used. 6A mixture of g / mol ultra-high molecular weight polyethylene, 40.5 kg white oil, 75 g nano-modifier, and 44 g antioxidant 1010 was added to a swelling vessel and swelled at 115℃ for 1 h. The mixture was then extruded through a twin-screw extruder and spinning box at a spinning temperature of 230~250℃. After cooling in a 15℃ water bath, gel fibers were formed. After 72 h of settling and oil extraction, the gel fibers were pre-stretched 2.3 times and then entered an extraction tank for three-stage extraction. The extractant was a mixture of 40% [EMIM][DCA] and 60% [BMIM][NTf2] at an extraction temperature of 70℃. After washing and drying, the fibers were hot-stretched. The hot-stretching process was as follows: first-stage stretching temperature 90℃, first-stage stretching ratio 15; second-stage stretching temperature 110℃, second-stage stretching ratio 2; third-stage stretching temperature 120℃, third-stage stretching ratio 1.2; and the total stretching ratio was 82.8. The final winding yielded ultra-high molecular weight polyethylene fiber with a linear density of 73 D. Example 9

[0072] Step (1) is the same as in Example 3.

[0073] In step (2), 5 kg of molecules with a molecular weight of 3.5 × 10⁻⁶ are used. 6 A mixture of g / mol ultra-high molecular weight polyethylene, 40.5 kg white oil, 75 g nano-modifier, and 44 g antioxidant 1010 was added to a swelling vessel and swelled at 115 °C for 1 h. The mixture was then extruded through a twin-screw extruder and spinning box at a spinning temperature of 230-250 °C. After cooling in a 15 °C water bath, gel fibers were formed. After 72 h of settling and oil extraction, the gel fibers were pre-stretched 2.1 times and then subjected to tertiary extraction in an extraction tank. The extractant was a mixture of 40% [EMIM][DCA] and 60% [BMIM][NTf2] at an extraction temperature of 70 °C. After washing and drying, the fibers were hot-stretched. The hot-stretching process was as follows: first-stage stretching temperature 90 °C, first-stage stretching ratio 14.5; second-stage stretching temperature 110 °C, second-stage stretching ratio 2; third-stage stretching temperature 120 °C, third-stage stretching ratio 1.1; and total stretching ratio 67.0. The final winding yielded ultra-high molecular weight polyethylene fiber with a linear density of 79 D. Example 10

[0074] Step (1) is the same as in Example 3.

[0075] In step (2), 5 kg of molecules with a molecular weight of 3.5 × 10⁻⁶ are used. 6A mixture of g / mol ultra-high molecular weight polyethylene, 40.5 kg white oil, 75 g nano-modifier, and 44 g antioxidant 1010 was added to a swelling vessel and swelled at 115 °C for 1 h. The mixture was then extruded through a twin-screw extruder and spinning box at a spinning temperature of 230-250 °C. After cooling in a 15 °C water bath, gel fibers were formed. After 72 h of settling and oil extraction, the gel fibers were pre-stretched 1.8 times and then subjected to three-stage extraction in an extraction tank. The extractant was a mixture of 40% [EMIM][DCA] and 60% [BMIM][NTf2] at an extraction temperature of 70 °C. After washing and drying, the fibers were hot-stretched. The hot-stretching process was as follows: first-stage stretching temperature of 90 °C with a first-stage stretching ratio of 14.5; second-stage stretching temperature of 110 °C with a second-stage stretching ratio of 2; and third-stage stretching temperature of 120 °C with a third-stage stretching ratio of 1.1, for a total stretching ratio of 57.4. The final winding yielded ultra-high molecular weight polyethylene fiber with a linear density of 81 D. Example 11

[0076] Step (1) is the same as in Example 4.

[0077] In step (2), 4 kg of molecules with a molecular weight of 3.0 × 10⁻⁶ are used. 6 A mixture of g / mol ultra-high molecular weight polyethylene, 40.4 kg white oil, 40 g nano-modifier, and 30 g antioxidant 1010 was added to a swelling vessel and swelled at 115℃ for 1 h. The mixture was then extruded through a twin-screw extruder and spinning box at a spinning temperature of 230~250℃. After cooling in a 15℃ water bath, gel fibers were formed. After 72 h of settling and oil extraction, the gel fibers were pre-stretched 1.8 times and then entered an extraction tank for three-stage extraction. The extractant was a mixture of 40% [EMIM][DCA] and 60% [BMIM][NTf2] at an extraction temperature of 60℃. After washing and drying, the fibers were hot-stretched. The hot-stretching process was as follows: first-stage stretching temperature 90℃, first-stage stretching ratio 15; second-stage stretching temperature 110℃, second-stage stretching ratio 2.1; third-stage stretching temperature 120℃, third-stage stretching ratio 1.2; and total stretching ratio 94.5. The final winding yields ultra-high molecular weight polyethylene fibers with a linear density of 75 D.

[0078] Comparative Example 1

[0079] Step (1) is the same as in Example 1.

[0080] In step (2), 4 kg of molecules with a molecular weight of 3.0 × 10⁻⁶ are used. 6A mixture of g / mol ultra-high molecular weight polyethylene, 46 kg white oil, 100 g nano-modifier, and 20 g antioxidant 1010 was added to a swelling vessel and swelled at 110 °C for 1 h. The mixture was then extruded through a twin-screw extruder and spinning box at a spinning temperature of 230-250 °C. After cooling in a 10 °C water bath, gel fibers were formed. After 72 h of settling and oil extraction, the gel fibers were pre-stretched 2.3 times and then subjected to tertiary extraction in an extraction tank. The extractant was a mixture of 40% [EMIM][DCA] and 60% [BMIM][NTf2] at an extraction temperature of 75 °C. After washing and drying, the fibers were hot-stretched. The hot-stretching process was as follows: first-stage stretching temperature 90 °C, first-stage stretching ratio 15; second-stage stretching temperature 110 °C, second-stage stretching ratio 2; third-stage stretching temperature 120 °C, third-stage stretching ratio 1.3; and the total stretching ratio was 89.7. The final winding yielded ultra-high molecular weight polyethylene fiber with a linear density of 68 D.

[0081] Comparative Example 2

[0082] Step (1) is the same as in Example 1.

[0083] In step (2), 4 kg of molecules with a molecular weight of 3.0 × 10⁻⁶ are used. 6 Ultra-high molecular weight polyethylene (UHMWPE) at a concentration of g / mol, 46 kg of white oil, 40 g of nano-modifier, and 28 g of antioxidant 1010 were mixed in a specific ratio and added to a swelling vessel for swelling at 110 °C for 1 h. The mixture was then extruded through a twin-screw extruder and a spinning box at a spinning temperature of 230–250 °C. After cooling in a 10 °C water bath, gel fibers were formed. After 72 h of settling and oil extraction, the gel fibers were pre-stretched 2.3 times and then subjected to tertiary extraction in an extraction tank. The extractant was a mixture of 40% [EMIM][DCA] and 60% [BMIM][NTf2] at room temperature. After washing and drying, the fibers were hot-stretched. The hot-stretching process was as follows: first-stage stretching temperature 90 °C, first-stage stretching ratio 14; second-stage stretching temperature 110 °C, second-stage stretching ratio 2; third-stage stretching temperature 120 °C, third-stage stretching ratio 1.1; and total stretching ratio 70.8. The final winding yielded ultra-high molecular weight polyethylene fiber with a linear density of 77 D.

[0084] Comparative Example 3

[0085] Step (1) is the same as in Example 1.

[0086] In step (2), 4 kg of molecules with a molecular weight of 3.0 × 10⁻⁶ are used. 6A mixture of g / mol ultra-high molecular weight polyethylene, 46 kg white oil, 40 g nano-modifier, and 28 g antioxidant 1010 was added to a swelling vessel and swelled at 110 °C for 1 h. The mixture was then extruded through a twin-screw extruder and spinning box at a spinning temperature of 230–250 °C. After cooling in a 10 °C water bath, gel fibers were formed. After 72 h of settling and oil extraction, the gel fibers underwent a 2.3-fold pre-stretch and were then subjected to a three-stage extraction process using dichloromethane as the extractant at room temperature. After washing and drying, the fibers were hot-stretched. The hot-stretching process consisted of a first-stage stretching temperature of 90 °C with a first-stage stretching ratio of 8.5, a second-stage stretching temperature of 110 °C with a second-stage stretching ratio of 2, and a third-stage stretching temperature of 120 °C with a third-stage stretching ratio of 1.25, for a total stretching ratio of 48.8. Finally, the fibers were wound to obtain a single ultra-high molecular weight polyethylene fiber with a diameter of 82 D.

[0087] The mechanical properties and oil content of the above embodiments and comparative examples were tested using the following methods, and the test results are shown in the table below:

[0088] (1) Mechanical property test: The breaking strength of the monofilament was tested according to GB / T 4344-2008 "Test method for tensile properties of chemical fiber filaments". The tensile interval was 200 mm and the tensile speed was 200 m / min.

[0089] (2) Oil content test: The oil content of the gel fiber and the extracted fiber was tested according to GB / T 6504-2017 "Test Method for Oil Content of Chemical Fibers". The gel fiber was blotted with oil-absorbing paper to remove white oil from the fiber surface and weighed (mo). Then, it was placed in n-hexane with a bath ratio greater than 50:1 and allowed to stand for 24 h for extraction. This process was repeated three times. After drying, the fiber was removed and weighed (m1). The oil content calculation formula is as follows:

[0090]

[0091] Table 1. Results of fiber tensile strength test

[0092]

[0093] Table 2. Oil content test results of fibers after extraction

[0094]

[0095] Table 1 shows that the coarse denier ultra-high molecular weight polyethylene fiber prepared by adding hyperbranched modified nano-SiO2 for gel spinning and using a mixed ionic liquid extractant exhibits good strength, with the highest tensile breaking strength reaching 37.0 cN / dtex. However, compared to Example 1 and Comparative Example 1, the excessive addition of nanoparticles negatively impacts fiber strength. In Comparative Example 2, compared to Example 1, the extractant was not heated during extraction, resulting in poor fluidity of the ionic liquid at room temperature, poor extraction efficiency, higher white oil content in the fiber, and lower fiber strength. In Comparative Example 3, conventional dichloromethane was used for extraction. Under the same extraction conditions (i.e., without changing the extraction tank length and drawing rate), the white oil extraction in the core of the coarse denier fiber was incomplete, leading to frequent fiber breakage during hot stretching, low draw ratio, and ultimately, low fiber strength.

[0096] Therefore, the process method described in this application can ensure that the prepared fiber has good strength, and the control of various parameters such as temperature during the process can ensure that the fiber strength is guaranteed.

[0097] Table 2 shows that the oil content in the fiber after extraction is low. This is because the modified nanoparticles are uniformly dispersed in the fiber, forming micropores that facilitate the penetration and diffusion of the ionic liquid into the fiber, thus accelerating the extraction process. Simultaneously, using a mixed ionic liquid as the extractant and increasing the temperature of the extraction bath effectively reduces the viscosity of the ionic liquid, improving its fluidity and diffusion rate. The low oil content in the fiber is beneficial for subsequent hot stretching, resulting in a final product with a uniform fiber structure and good mechanical properties. Comparative Example 2 demonstrates that higher temperatures are more conducive to improving extraction efficiency. Comparative Example 4 shows that the extraction process using ionic liquid as the extractant is not suitable for dichloromethane, indicating that the extraction efficiency of ionic liquid is much higher than that of dichloromethane.

[0098] In summary, this embodiment successfully prepared coarse denier, high-strength ultra-high molecular weight polyethylene fibers with a monofilament linear density of 40-90 D. Combining the non-volatile and recyclable properties of ionic liquids, the entire process is green and environmentally friendly. The final obtained fibers have a uniform structure, few defects, and excellent mechanical properties, filling a market gap and meeting the urgent needs of specific industrial fields for coarse denier, high-strength fibers.

[0099] This application also includes a method for preparing polyethylene fiber according to the above-described method for preparing coarse denier high-strength polyethylene fiber. This fiber can be used in fields such as national defense, security protection, marine engineering, and sporting goods.

[0100] It should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" used above to indicate orientation or positional relationships are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention; the directional terms "inner" and "outer" refer to the inside or outside relative to the outline of each component itself. 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. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0101] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways, rotated 90 degrees, or in other orientations, and the spatial relative descriptions used herein will be interpreted accordingly.

[0102] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A method for preparing coarse denier high-strength polyethylene fiber, characterized in that, The polyethylene fiber has a monofilament linear density of 40-90D, and the method includes: The preparation of a nano-modifier, wherein the nano-modifier is hyperbranched polyethylene modified nano-SiO2, comprises the following steps: Nano-SiO2 was added to an ethanol aqueous solution and stirred until homogeneous to obtain a suspension. Then, 3-mercaptopropyltriethoxysilane was added, and glacial acetic acid was added to adjust the pH of the mixed solution to 4-5. The solution was stirred at room temperature for a predetermined time. The volume ratio of ethanol to water in the ethanol aqueous solution was 9:

1. After the reaction was completed, the mixed solution was centrifuged, washed with water and dried to obtain mercapto-based nano-SiO2; Thiol-modified nano-SiO2 and hyperbranched polyethylene were added to toluene, along with an initiator. The mixture was stirred under a nitrogen atmosphere and reacted at 80-90°C for a set time. After the reaction was complete, the reaction solution was filtered, and the filter residue was dispersed in hot toluene and washed once. After filtration, it was thoroughly washed with anhydrous ethanol and dried to obtain hyperbranched polyethylene-modified nano-SiO2. The hyperbranched polyethylene was hyperbranched polyethylene with carbon-carbon double bonds at the ends, wherein the viscosity-average molecular weight of the hyperbranched polyethylene was 600-1000 g / mol, and the double bond content was 1-3 mol%. Polyethylene powder, white oil, the nano-modifier, and antioxidant 1010 are mixed and added to a swelling reactor and reacted for a period of time to form a mixed solution; wherein, the mass of the polyethylene powder accounts for 8-12% of the total mass of the polyethylene powder and the white oil, the nano-modifier accounts for 1-2% of the mass of the polyethylene powder, and the antioxidant 1010 accounts for 0.5-1% of the mass of the polyethylene powder; The mixed solution is extruded to form gel fibers, and the gel fibers are left to stand to extract oil. Subsequently, they are subjected to three-stage extraction with ionic liquid, drying and stretching to form polyethylene fibers.

2. The method for preparing coarse denier high-strength polyethylene fiber according to claim 1, characterized in that, The nano-SiO2 has a particle size of 300-500 nm, and the mass ratio of the nano-SiO2 to the 3-mercaptopropyltriethoxysilane is 1:

1.

3. The method for preparing coarse denier high-strength polyethylene fiber according to claim 1, characterized in that, The mass ratio of the thiolized nano-SiO2 to the hyperbranched polyethylene is 5:

1. The initiator is one of azobisisobutyronitrile and benzoyl peroxide, and the amount of initiator added is 0.5 to 1% of the total mass of the thiolized nano-SiO2 and the hyperbranched polyethylene.

4. The method for preparing coarse denier high-strength polyethylene fiber according to claim 1, characterized in that, The temperature of the swelling vessel is 110-120℃.

5. The method for preparing coarse denier high-strength polyethylene fiber according to claim 1, characterized in that, The "forming gel fiber by extrusion of the mixed solution" specifically includes: extruding the mixed solution into a twin-screw extruder and a spinning box, wherein the temperature of the twin-screw extruder is 230-250℃; The extruded filaments are rapidly cooled in a cold water bath to form the gel fiber, wherein the temperature of the cold water bath is 5-15℃.

6. The method for preparing coarse denier high-strength polyethylene fiber according to claim 1, characterized in that, In the aforementioned three-stage extraction process of ionic liquids The ionic liquid is a mixed ionic liquid composed of 1-ethyl-3-methylimidazolium dicyanamide salt and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, wherein the mass ratio of 1-ethyl-3-methylimidazolium dicyanamide salt to 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt is 4:

6. The three-stage extraction is countercurrent extraction, and the temperature of the ionic liquid is 60~80 ℃.

7. A polyethylene fiber, characterized in that, It is prepared by the method for preparing coarse denier high-strength polyethylene fiber according to any one of claims 1-6.

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