A regenerated ultra-high molecular weight polyethylene fiber dry yarn and a method for manufacturing the same

Abstract

The present application relates to the technical field of polyethylene materials, and particularly relates to a regenerated ultra-high molecular weight polyethylene fiber dry yarn and a preparation method thereof. The present application takes into account the processing fluidity and the mechanical skeleton integrity through the design of spherical lubrication-linear enhancement, realizes the long-term residence of the antioxidant, solves the technical bottleneck that the melt viscosity and the mechanical strength are difficult to take into account in the regeneration process of waste UHMWPE fibers, the antioxidant is easy to migrate and lose, and the weather resistance is poor, the obtained regenerated fiber has uniform diameter, stable whiteness, and the outdoor weather resistance is significantly improved, and can be widely applied to outdoor and protection fields such as mountaineering ropes, marine cables, cut-resistant gloves and the like.

Description

Technical Field

[0001] This invention relates to the field of polyethylene material technology, specifically to a recycled ultra-high molecular weight polyethylene fiber filament and its preparation method. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE) fiber, with its superior specific strength, specific modulus, and chemical resistance, is widely used in high-end fields such as bulletproof vests, marine cables, cut-resistant gloves, and aerospace composite materials. With the widespread global application of this material, a large amount of bulletproof products reaching the end of their service life and industrial waste are generated. Considering that UHMWPE material is extremely difficult to biodegrade and that incineration would cause serious carbon emissions, recycling waste UHMWPE fiber to produce high-value-added recycled fiber has significant economic benefits.

[0003] However, the recycling and regeneration of UHMWPE faces significant challenges in the engineering field, primarily due to its unique molecular structure and processing characteristics. Firstly, the extremely high molecular weight of UHMWPE (typically greater than 1.5 million) imparts extremely high melt viscosity, exhibiting a rubbery, highly elastic state rather than a viscous flow state even in the molten state. During the recycling process, to achieve spinnability, existing technologies typically require the addition of large amounts of solvents (such as white oil or dacarne) for gel spinning, or the addition of low-molecular-weight polyethylene wax or stearates as lubricants. However, while this simple physical lubrication improves flowability to some extent, it introduces a fatal flaw: low-molecular-weight lubricants cannot form effective physical entanglement with the UHMWPE macromolecular chains. They act as microscopic defects when the fibers are under stress, causing the molecular chains to easily slip, resulting in a significant decrease in the breaking strength of the recycled fibers, making it difficult to meet the requirements for load-bearing or protective applications. This constitutes the first irreconcilable contradiction between improving flowability and maintaining mechanical strength in the processing of recycled UHMWPE.

[0004] Secondly, during initial processing and long-term service, the molecular chains of waste UHMWPE fibers have been damaged by light, heat, and mechanical shear, resulting in a large number of free radicals and chain breakage defects. To ensure the service life of regenerated fibers, sufficient antioxidants and light stabilizers must be introduced. However, UHMWPE is a highly crystalline and non-polar polymer, and conventional polar small-molecule auxiliaries (such as hindered phenols and hindered amines) have extremely poor compatibility with it and are difficult to penetrate its dense crystal lattice. During high-temperature spinning or long-term outdoor use, these physically mixed auxiliaries are prone to phase separation, migrating to the fiber surface to form bloom, and being washed away by rain or mechanical friction. The non-durability of the auxiliaries causes regenerated fibers to rapidly undergo photo-oxidative aging under outdoor ultraviolet radiation, manifesting as yellowing, embrittlement, and strong precipitous degradation, severely limiting its application in outdoor fields such as climbing ropes and mooring cables. This constitutes the second contradiction between the need for auxiliaries and the matrix repulsion effect.

[0005] In summary, developing a regenerative modification technology that can significantly reduce melt viscosity without sacrificing mechanical strength, while also enabling long-term and stable retention of antioxidants in the matrix, is a key technological bottleneck that urgently needs to be addressed in the field of polymer material recycling. Summary of the Invention

[0006] In view of this, the purpose of this invention is to propose a recycled ultra-high molecular weight polyethylene fiber dry filament and its preparation method, so as to solve the problems faced in the existing recycled UHMWPE fiber preparation process, which are difficult to balance high viscosity melt flowability and mechanical skeleton integrity, and the easy migration of antioxidants leading to extremely poor outdoor weather resistance.

[0007] To achieve the above objectives, the present invention provides a method for preparing recycled ultra-high molecular weight polyethylene fiber filaments, comprising the following steps: S1: Under nitrogen atmosphere and reflux conditions, 3-mercaptopropionic acid and 4-hydroxy-2,2,6,6-tetramethylpiperidinol were esterified in the presence of anhydrous toluene and p-toluenesulfonic acid, and the resulting product was post-treated to obtain a thiolation hindered amine light stabilizer. S2: In a high-pressure reactor, after purging with high-purity nitrogen, anhydrous toluene and nickel diimide are added as catalysts, and ethylene gas is introduced to carry out a polymerization reaction. After the reaction is completed, activated diatomaceous earth is added for stirring and adsorption to obtain a clear and transparent hyperbranched polyethylene toluene solution. After purification, it is redispersed in toluene to form a homogeneous solution, and a thiol-hindered amine light stabilizer and photoinitiator-651 are added to the system. Under ultraviolet light irradiation, a thiol-ene click chemical reaction is carried out. The resulting reaction solution is precipitated and dried to obtain modified hyperbranched polyethylene powder. S3: Linear low-density polyethylene powder and 4-vinylpyridine are melt-grafted in the presence of dicumyl peroxide to obtain modified linear polyethylene. Then, the modified linear polyethylene is melt-blended with antioxidant 1010 and cooled and pulverized to obtain antioxidant masterbatch. S4: Mix the recycled ultra-high molecular weight polyethylene waste fiber with white oil and modified hyperbranched polyethylene powder, carry out the first stage of heating and swelling, then add antioxidant masterbatch, carry out the second stage of heating and blending, and continue heating to 170-180℃ until a uniform and transparent spinning melt is formed. S5: The spinning melt is homogenized and extruded through a twin-screw extruder, then spun to form gel filaments. After extraction, stretching, heat setting, and winding, recycled ultra-high molecular weight polyethylene fiber dry filaments are obtained.

[0008] Preferably, the weight ratio of 3-mercaptopropionic acid, 4-hydroxy-2,2,6,6-tetramethylpiperidinol, and p-toluenesulfonic acid in step S1 is 200-220g:340-360g:8-12g.

[0009] Preferably, the esterification reaction in step S1 is carried out at a temperature of 110-120°C for 5-7 hours.

[0010] Preferably, the ethylene gas in step S2 has a purity of 99.9% and is introduced into the reaction system after being dried and deoxygenated.

[0011] Preferably, the weight ratio of ethylene gas, nickel diimide, hindered thiolation amine light stabilizer, and photoinitiator-651 in step S2 is 4500-5000g:8-12g:450-550g:15-25g.

[0012] Preferably, the polymerization reaction in step S2 is carried out at a temperature of 20-30°C and for a time of 50-70 min.

[0013] Preferably, the reaction temperature of the thiol-ene click chemistry reaction in step S2 is 35-45°C, and the reaction time is 2-4 hours.

[0014] Preferably, the linear low-density polyethylene powder in step S3 has a melt flow index of 2 g / 10 min and a density of 920 kg / m³. 3 .

[0015] Preferably, the weight ratio of the linear low-density polyethylene powder, 4-vinylpyridine, and dicumyl peroxide in step S3 is 4500-5500g:200-300g:4-6g.

[0016] Preferably, the melt grafting reaction in step S3 is carried out in a twin-screw reactive extruder at a melting temperature of 165-175°C.

[0017] Preferably, the melt blending temperature in step S3 is 135-145°C and the time is 8-12 min.

[0018] Preferably, the recycled waste bulletproof vest fibers in step S4 need to be washed, degummed and vacuum dried until the moisture content is less than 0.05%, and then cut into short fibers with a length of 4-8 mm.

[0019] Preferably, in step S4, the temperature for the heating and swelling in the first stage is 115-125°C, and the time is 40-50 minutes.

[0020] Preferably, the temperature for the second stage of heating and blending in step S4 is 155-165°C, and the time is 10-20 min.

[0021] Preferably, the temperature of the homogenization extrusion in step S5 is 175-180°C.

[0022] Preferably, the extraction in step S5 is carried out at room temperature, with dichloromethane as the extractant.

[0023] Preferably, the specific stretching process in step S5 is a first-stage stretching (95-105℃), a second-stage stretching (115-125℃), a third-stage stretching (130-140℃), and a fourth-stage stretching (140-150℃), with the total stretching ratio controlled at 45-50 times.

[0024] Preferably, the temperature of the heat setting treatment in step S5 is 145-155℃, the treatment time is 5-8 minutes, and the relaxation rate is controlled at 3%-5%.

[0025] Furthermore, the present invention also provides a recycled ultra-high molecular weight polyethylene fiber filament.

[0026] The beneficial effects of this invention are: This invention systematically solves the rheological processing challenges and aging failure issues in the regeneration process of UHMWPE through a unique modified component design and step-by-step processing technology, as detailed below: First, by introducing hyperbranched polyethylene prepared in situ via chain-walking polymerization as a modifying unit, it can act as nano-molecular ball bearings in the dense entangled network of ultra-high molecular weight polyethylene, significantly reducing the friction coefficient between molecular chains and melt viscosity, greatly improving processing rheology, and eliminating the instability of the fine flow and the breakage phenomenon during spinning. More importantly, this invention is compounded with side-chain modified linear low-density polyethylene, which utilizes its linear long-chain structure to form deep physical entanglement and co-crystallization with the waste UHMWPE matrix, effectively repairing the decrease in entanglement density caused by the introduction of spherical molecules and rebuilding the mechanical skeleton of the fiber. This dual structural design of spherical lubrication and linear reinforcement breaks the technical curse of traditional recycling technology where waxing results in fast flow but low strength. Secondly, a dual localization and anchoring strategy was adopted. On the one hand, the thiol-ene click chemistry reaction was used to graft the thiol-hindered amine light stabilizer onto the terminal double bond of the hyperbranched polyethylene in the form of a covalent bond, thus completely eliminating the physical loss of the light stabilizer from the level of chemical bonding. On the other hand, a pyridine ring structure was introduced into the side chain of the linear carrier, and the small molecule antioxidant was firmly locked onto the polymer chain segment by using strong hydrogen bonding. This dual anchoring mechanism not only retains the chemical activity of the auxiliary agent in capturing free radicals, but also endows it with the resident stability of the macromolecule, so that the regenerated fiber can still maintain a very high strength retention rate and color stability after long-term exposure to sun and rain. Finally, a stepwise addition process was adopted to avoid competitive adsorption and local agglomeration caused by the simultaneous addition of various components, ensuring the uniformity of the microstructure of the regenerated fiber and significantly improving the whiteness uniformity and batch stability of the fiber appearance. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0028] The sources or properties of the raw materials used in the embodiments and comparative examples of this invention are as follows: Linear low-density polyethylene: Industrial grade powder, melt index 2 g / 10 min, density 920 kg / m³ 3 White oil: Industrial grade, kinematic viscosity 15 mmHg at 40°C 2 / s.

[0029] Example 1: A method for preparing recycled ultra-high molecular weight polyethylene fiber filaments, the specific steps of which are as follows: (1) In a reaction flask equipped with a water separator, 200g of 3-mercaptopropionic acid and 340g of 4-hydroxy-2,2,6,6-tetramethylpiperidinol were dissolved in 1800mL of anhydrous toluene and 8g of p-toluenesulfonic acid was added as a catalyst. The reaction was carried out under nitrogen atmosphere and refluxed at 110℃ for 5h. The solvent was removed by washing, drying and rotary evaporation to obtain a thiolation hindered amine light stabilizer. (2) In a stainless steel high-pressure reactor equipped with a mechanical stirrer, temperature sensor, and reflux condenser, the air inside the reactor was replaced three times with high-purity nitrogen to remove oxygen and moisture. Then, under a nitrogen atmosphere, 18L of anhydrous toluene and 8g of nickel diimide were added as catalysts. The mechanical stirrer was started and the speed was set to 400rpm. 4500g of ethylene gas with a purity of 99.9% after drying and deoxygenation was introduced. The reaction was carried out at a constant temperature of 20℃ for 50min. After the reaction was completed, the pressure was quickly released to terminate the polymerization. 500g of activated diatomaceous earth was added to the reaction solution, and the mixture was stirred and adsorbed for 20min. The mixture was then filtered while hot and under pressure to remove the dark-colored catalyst residue, yielding a clear and transparent hyperbranched polyethylene toluene solution. Slowly pour the mixture into 5 times its volume of methanol while stirring rapidly. A white flocculent precipitate forms. After standing and separating into layers, filter and collect the precipitate. Wash the precipitate twice with methanol to thoroughly remove residual toluene and trace impurities. Place the obtained solid product in a vacuum drying oven and dry to constant weight to obtain hyperbranched polyethylene powder. Redissolve the powder in 20 L of anhydrous toluene to form a homogeneous solution. Then add 450 g of thiol-hindered amine light stabilizer and 15 g of photoinitiator-651. The system is then heated to 35 °C and continuously irradiated with a 365 nm ultraviolet lamp for 2 h. After the reaction is complete, pour the resulting reaction solution into methanol to precipitate. After filtration and vacuum drying, the modified hyperbranched polyethylene powder is obtained. (3) 4500g of linear low-density polyethylene powder, 200g of 4-vinylpyridine and 4g of dicumyl peroxide were added to a high-speed mixer as initiators and mixed at 2000rpm for 4min. Then the mixture was added to a twin-screw reactive extruder and melt grafted at 165℃. The product was dissolved in xylene and washed with acetone to remove unreacted monomers to obtain modified linear polyethylene. Then 1800g of modified linear polyethylene and 70g of antioxidant 1010 were added to a melt blender and melt blended at 135℃ for 8min. After cooling and pulverizing, antioxidant masterbatch was obtained. (4) The recycled waste bulletproof vest fiber is washed, degummed and vacuum dried to a moisture content of less than 0.05%, cut into short fibers with a length of 4 mm, 55000 g of white oil and 14000 g of short fibers are added to the dissolving kettle, along with 1800 g of modified hyperbranched polyethylene powder. The anchor-type stirring paddle is turned on and the kettle temperature is slowly raised to 115°C and kept at that temperature for 40 min. Then the kettle temperature is raised to 155°C and 1800 g of antioxidant masterbatch is added. The temperature is kept at that temperature for 10 min. The temperature is raised to 170°C and stirred until the system completely forms a uniform and transparent spinning melt. (5) The spinning melt is transported to the twin-screw extruder by a gear pump and homogenized at 175°C. It is then precisely metered by a metering pump and fed into the spinning box and extruded through a spinneret (0.8 mm diameter, 60 holes). After passing through a 15 mm air layer, it is quenched in a 15°C water bath to form gel filaments. The gel filaments are then introduced into an extraction tank and dichloromethane is used as the extractant. The filaments are kept at room temperature for 30 minutes to remove the white oil inside the filaments. After the extraction is completed, the filaments are dried with hot air at 55°C to remove the residual dichloromethane and then enter a multi-stage hot stretching unit. The filaments are stretched sequentially at 95°C, 115°C, 130°C, and 140°C. The total stretching ratio is controlled at 45 times. Finally, the filaments are heat-set in a constant temperature oven at 145°C for 5 minutes. The relaxation rate is controlled at 3%. The filaments are then naturally cooled to room temperature and wound to obtain recycled ultra-high molecular weight polyethylene fiber filaments.

[0030] Example 2: A method for preparing recycled ultra-high molecular weight polyethylene fiber filaments, the specific steps of which are as follows: (1) In a reaction flask equipped with a water separator, 210 g of 3-mercaptopropionic acid and 350 g of 4-hydroxy-2,2,6,6-tetramethylpiperidinol were dissolved in 2000 mL of anhydrous toluene and 10 g of p-toluenesulfonic acid was added as a catalyst. The reaction was carried out under nitrogen atmosphere and refluxed at 115 °C for 6 h. The solvent was removed by washing, drying and rotary evaporation to obtain a thiolation hindered amine light stabilizer. (2) In a stainless steel high-pressure reactor equipped with a mechanical stirrer, temperature sensor and reflux condenser, the air inside the reactor was replaced three times with high-purity nitrogen to remove oxygen and moisture. Then, under a nitrogen atmosphere, 20L of anhydrous toluene and 10g of nickel diimide were added as catalysts. The mechanical stirrer was turned on and the speed was set to 500rpm. 4800g of ethylene gas with a purity of 99.9% after drying and deoxygenation was introduced. The reaction was carried out at a constant temperature of 25℃ for 60min. After the reaction was completed, the pressure was quickly released to stop the polymerization. 500g of activated diatomaceous earth was added to the reaction solution. After stirring and adsorption for 30min, the solution was filtered while hot and under pressure to remove the dark catalyst residue, and a clear and transparent hyperbranched polyethylene toluene solution was obtained. The mixture was slowly poured into 6 times its volume of methanol while stirring rapidly. A white flocculent precipitate formed. After standing and separating into layers, the precipitate was collected by filtration and washed three times with methanol to thoroughly remove residual toluene and trace impurities. The resulting solid product was dried in a vacuum drying oven to constant weight to obtain hyperbranched polyethylene powder. This powder was then redissolved in 20 L of anhydrous toluene to form a homogeneous solution. 500 g of thiol-dependent hindered amine light stabilizer and 20 g of photoinitiator-651 were added. The system was then heated to 40 °C and continuously irradiated with a 365 nm UV lamp for 3 h. After the reaction was complete, the resulting reaction solution was poured into methanol to precipitate. After filtration and vacuum drying, the modified hyperbranched polyethylene powder was obtained. (3) 5000g of linear low-density polyethylene powder, 250g of 4-vinylpyridine and 5g of dicumyl peroxide were added to a high-speed mixer and mixed at 2000rpm for 5min. Then the mixture was added to a twin-screw reactive extruder and melt-grafted at 170℃. The product was dissolved in xylene and washed with acetone to remove unreacted monomers to obtain modified linear polyethylene. Then 2000g of modified linear polyethylene and 80g of antioxidant 1010 were added to a melt blender and melt-blended at 140℃ for 10min. After cooling and pulverizing, antioxidant masterbatch was obtained. (4) The recycled waste bulletproof vest fiber is washed, degummed and vacuum dried to a moisture content of less than 0.05%, cut into short fibers with a length of 6 mm, 60,000 g of white oil and 15,000 g of short fibers are added to the dissolving kettle, along with 2,000 g of modified hyperbranched polyethylene powder. The anchor-type stirring paddle is turned on and the kettle temperature is slowly raised to 120°C and kept at that temperature for 45 min. Then the kettle temperature is raised to 160°C and 2,000 g of antioxidant masterbatch is added. The temperature is kept at that temperature for 15 min. The temperature is raised to 175°C and stirred until the system completely forms a uniform and transparent spinning melt. (5) The spinning melt is transported to the twin-screw extruder by a gear pump and homogenized at 180°C. It is then precisely metered by a metering pump and fed into the spinning box and extruded through a spinneret (0.8 mm orifice, 60 holes). After passing through a 20 mm air layer, it is quenched in a 20°C water bath to form gel filaments. The gel filaments are then introduced into an extraction tank and dichloromethane is used as the extractant. The filaments are kept at room temperature for 35 min to remove the white oil inside the filaments. After the extraction is completed, the filaments are dried with hot air at 60°C to remove the residual dichloromethane and then enter a multi-stage hot stretching unit. The filaments are stretched sequentially at first stage (100°C), second stage (120°C), third stage (135°C), and fourth stage (145°C). The total stretching ratio is controlled at 48 times. Finally, the filaments are heat-set in a constant temperature oven at 150°C for 7 min. The relaxation rate is controlled at 4%. The filaments are then naturally cooled to room temperature and wound to obtain recycled ultra-high molecular weight polyethylene fiber filaments.

[0031] Example 3: A method for preparing recycled ultra-high molecular weight polyethylene fiber filaments, the specific steps of which are as follows: (1) In a reaction flask equipped with a water separator, 220g of 3-mercaptopropionic acid and 360g of 4-hydroxy-2,2,6,6-tetramethylpiperidinol were dissolved in 2200mL of anhydrous toluene and 12g of p-toluenesulfonic acid was added as a catalyst. The reaction was carried out under nitrogen atmosphere and refluxed at 120℃ for 7h. The solvent was removed by washing, drying and rotary evaporation to obtain a thiolation hindered amine light stabilizer. (2) In a stainless steel high-pressure reactor equipped with a mechanical stirrer, temperature sensor, and reflux condenser, the air inside the reactor was replaced three times with high-purity nitrogen to remove oxygen and moisture. Then, under a nitrogen atmosphere, 22L of anhydrous toluene and 12g of nickel diimide were added as catalysts. The mechanical stirrer was turned on and the speed was set to 600rpm. 5000g of ethylene gas with a purity of 99.9% after drying and deoxygenation was introduced. The reaction was carried out at a constant temperature of 30℃ for 70min. After the reaction was completed, the pressure was quickly released to terminate the polymerization. 500g of activated diatomaceous earth was added to the reaction solution. After stirring and adsorption for 40min, the solution was filtered while hot and under pressure to remove the dark catalyst residue, resulting in a clear and transparent hyperbranched polyethylene toluene solution. The mixture was slowly poured into 8 times its volume of methanol while stirring rapidly. A white flocculent precipitate formed. After standing and separating into layers, the precipitate was collected by filtration and washed three times with methanol to thoroughly remove residual toluene and trace impurities. The resulting solid product was dried in a vacuum drying oven to constant weight to obtain hyperbranched polyethylene powder. The powder was then redissolved in 20 L of anhydrous toluene to form a homogeneous solution. 550 g of thiol-dependent hindered amine light stabilizer and 25 g of photoinitiator-651 were added. The system was then heated to 45 °C and continuously irradiated with a 365 nm UV lamp for 4 h. After the reaction was complete, the resulting reaction solution was poured into methanol to precipitate. After filtration and vacuum drying, the modified hyperbranched polyethylene powder was obtained. (3) 5500g of linear low-density polyethylene powder, 300g of 4-vinylpyridine and 6g of dicumyl peroxide were added to a high-speed mixer as initiators and mixed at 2000rpm for 6min. Then the mixture was added to a twin-screw reactive extruder and melt grafted at 175℃. The product was dissolved in xylene and washed with acetone to remove unreacted monomers to obtain modified linear polyethylene. Then 2200g of modified linear polyethylene and 90g of antioxidant 1010 were added to a melt blender and melt blended at 145℃ for 12min. After cooling and pulverizing, antioxidant masterbatch was obtained. (4) The recycled waste bulletproof vest fiber is washed, degummed and vacuum dried to a moisture content of less than 0.05%, cut into short fibers with a length of 8 mm, 65000 g of white oil and 16000 g of short fibers are added to the dissolving kettle, along with 2200 g of modified hyperbranched polyethylene powder. The anchor-type stirring paddle is turned on and the kettle temperature is slowly raised to 125°C and kept at that temperature for 50 min. Then the kettle temperature is raised to 165°C and 2200 g of antioxidant masterbatch is added. The temperature is kept at that temperature for 20 min. The temperature is raised to 180°C and stirred until the system completely forms a uniform and transparent spinning melt. (5) The spinning melt is transported to the twin-screw extruder by a gear pump and homogenized at 180°C. It is then precisely metered by a metering pump and fed into the spinning box and extruded through a spinneret (0.8 mm orifice, 60 holes). After passing through a 25 mm air layer, it is quenched in a 25°C water bath to form gel filaments. The gel filaments are then introduced into an extraction tank and dichloromethane is used as the extractant. The filaments are kept at room temperature for 40 min to remove the white oil inside the filaments. After the extraction is completed, the filaments are dried with hot air at 65°C to remove the residual dichloromethane and then enter a multi-stage hot stretching unit. The filaments are stretched sequentially at first stage (105°C), second stage (125°C), third stage (140°C), and fourth stage (150°C), with the total stretching ratio controlled at 50 times. Finally, the filaments are heat-set in a constant temperature oven at 155°C for 8 min, with the relaxation rate controlled at 5%. After natural cooling to room temperature, the filaments are wound and regenerated ultra-high molecular weight polyethylene fiber filaments are obtained.

[0032] Comparative Example 1: The difference from Example 2 is that in step (2), hyperbranched polyethylene is replaced with an equal amount of polyethylene wax (molecular weight 6000), while the rest of the steps are the same as in Example 2.

[0033] Comparative Example 2: The difference from Example 2 is that in step (4), the antioxidant masterbatch is replaced with an equal amount of linear low-density polyethylene powder, while the rest of the steps are the same as in Example 2.

[0034] Comparative Example 3: The difference from Example 2 is that in step (3), the linear low-density polyethylene powder is replaced with an equal amount of modified hyperbranched polyethylene powder, while the remaining steps are the same as in Example 2.

[0035] Comparative Example 4: The difference from Example 2 is that 4-vinylpyridine and dicumyl peroxide are not added in step (3) for reaction, while the remaining steps are the same as in Example 2.

[0036] Comparative Example 5: The difference from Example 2 is that in step (4), the modified hyperbranched polyethylene powder and antioxidant masterbatch are added all at once, while the remaining steps are the same as in Example 2.

[0037] Comparative Example 6: The difference from Example 2 is that the order in which the modified hyperbranched polyethylene powder and antioxidant masterbatch are added is replaced in step (4), while the rest of the steps are the same as in Example 2.

[0038] Tensile properties: Tested according to GB / T 19975-2005 "Test Method for Tensile Properties of High-Strength Filaments". After the fiber samples obtained from the examples and comparative examples were conditioned to moisture equilibrium under standard atmospheric conditions (temperature 20℃, relative humidity 65%) for 24 hours, they were tested using an electronic single yarn tensile tester equipped with pneumatic clamps. The spacing length was set to 500 mm, the tensile speed to 250 mm / min, and the pre-tension to 0.05 cN / dtex. Twenty filaments were randomly selected from each sample group for testing. The maximum load (cN) and elongation at break were recorded, and the breaking strength (cN / dtex) and breaking elongation (%) were calculated. The arithmetic mean was taken as the final result. Fiber whiteness and color difference uniformity test: The test was conducted according to GB / T 8424.2-2001 "Instrumental Evaluation Method for Relative Whiteness in Color Fastness Testing of Textiles". A colorimetric spectrometer was used, and the measurements were taken under D65 standard light source and 10° viewing angle conditions. The specific procedure was as follows: The fiber sample was wound around a standard whiteness plate, ensuring that the number of layers was thick enough to be opaque, creating a test sample with a smooth surface. Five different points were randomly selected from each sample for testing, and the CIE whiteness value (W) was recorded. Simultaneously, the standard deviation (SD) of the whiteness values ​​at the five test points was calculated. Melt flowability and spinning breakage rate tests: These were conducted according to GB / T 3682.1-2018 "Determination of melt mass flow rate and melt volume flow rate of thermoplastics - Part 1: Standard methods". The specific procedures were as follows: After melting the fiber samples obtained in the examples and comparative examples at 190℃, a load of 21.6 kg was applied, and the mass of melt flowing out within 10 minutes (g / 10min) was recorded. The number of breakages occurring within a continuous spinning length of 10,000 m (times / 10,000 meters) was also counted. Artificial weathering resistance: Tested according to GB / T 16422.3-2022 "Laboratory Light Source Exposure Test Methods for Plastics - Part 3: Fluorescent Ultraviolet Lamps". The equipment was an aging test chamber equipped with UVA-340 fluorescent ultraviolet lamps. Specific operations were as follows: the blackboard temperature was set to 60℃, and the irradiance to 0.76 W / m². 2 @340nm, the light cycle is 8h drying light / 4h condensation dark cycle. The fiber samples of each group are fixed on the sample holder and the exposure time is set to 720h. After the aging is completed, the samples are taken out and their breaking strength is measured again, and the strength retention rate (%) is calculated. The test results are shown in Table 1.

[0039]

[0040] Data Analysis: As can be seen from the data in Table 1, the recycled ultra-high molecular weight polyethylene fiber prepared by this invention exhibits excellent and stable comprehensive performance in multiple dimensions, including mechanical strength, appearance, color, and aging resistance. Specifically, the breaking strength of Examples 1 to 3 is consistently in the range of 33.2-34.5 cN / dtex, significantly higher than that of conventional recycled fibers. Furthermore, the breakage rate during spinning is extremely low, and the high CIE whiteness value and extremely low standard deviation further confirm that through a specific stepwise addition process, various functional additives are homogeneously dispersed in the ultra-high molecular weight matrix, avoiding stress concentration points caused by local agglomeration. This allows the recycled fiber to meet the dual requirements of strength and aesthetics for high-end outdoor products in practical applications.

[0041] As can be seen from the data in Example 2 and Comparative Example 1 in Table 1, compared with ordinary polyethylene wax, the use of modified hyperbranched polyethylene significantly improves the mechanical skeleton strength and processing rheological stability of recycled fibers, achieving a perfect balance between high strength and ease of processing. This is presumably because the hyperbranched spherical structure acts as molecular balls in the melt, greatly reducing internal friction, while the surface grafted groups impart excellent interfacial compatibility, avoiding the defects caused by the easy precipitation of ordinary wax. This indicates that functionalized topology is the core technology for solving the bottleneck of high-viscosity recycled spinning processing.

[0042] As can be seen from the data of Example 2 and Comparative Example 2 in Table 1, compared with the absence of antioxidant masterbatch, the introduction of special masterbatch enables the regenerated fiber to resist the erosion of harsh environments and achieves the extension of service life. It is speculated that this is because the highly active components in the antioxidant masterbatch build an efficient free radical capture network in the early stage of thermal processing, which effectively inhibits the chain breakage degradation cycle of the recycled material.

[0043] As can be seen from the data in Example 2 and Comparative Example 3 in Table 1, compared with only hyperbranched components, the introduction of linear polyethylene endows the regenerated fiber with excellent structural integrity and resistance to deformation, solving the mechanical imbalance problem caused by simply pursuing fluidity. It is speculated that this is because the linear long chain can form deep physical entanglement and co-crystallization with the UHMWPE matrix, reconstructing the fiber's stress skeleton. In contrast, the fully hyperbranched system suffers from molecular chain slippage due to the lack of entanglement. This indicates that the dual structural combination of linear reinforcement and spherical lubrication is a necessary condition for high-performance regeneration.

[0044] As can be seen from the data in Example 2 and Comparative Example 4 in Table 1, the introduction of the pyridine ring significantly improved the long-term retention rate and stability of the functional additives in the fiber matrix. This is presumably due to the strong hydrogen bonding between the nitrogen atom of the pyridine ring and the phenolic hydroxyl group of the antioxidant, which firmly locks the small-molecule additives onto the polymer chain, effectively overcoming the migration and blooming problems that easily occur in physical blending. This verifies the unique advantages of supramolecular assembly technology in ensuring the long-term service performance of regenerated fibers.

[0045] As can be seen from the data in Example 2 and Comparative Examples 5 and 6 in Table 1, the stepwise process significantly improved the homogeneity and microstructure consistency of the multi-component system in the ultra-high viscosity melt. This is presumably because the preferential penetration and swelling of the small-molecule hyperbranched component at low temperature pre-opens channels for the uniform entanglement of the subsequent large-molecule linear masterbatch, avoiding local agglomeration caused by competitive adsorption. This demonstrates that a scientific stepwise addition strategy is a process guarantee for maximizing the synergistic effect of each component.

[0046] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A method for preparing recycled ultra-high molecular weight polyethylene fiber filaments, characterized in that, Includes the following steps: S1: 3-Mercaptopropionic acid and 4-hydroxy-2,2,6,6-tetramethylpiperidinol were esterified in the presence of anhydrous toluene and p-toluenesulfonic acid to obtain a thiolation hindered amine light stabilizer. S2: Under a nitrogen atmosphere, using nickel diimide as a catalyst, ethylene gas is introduced to carry out a polymerization reaction. After stirring and adsorption purification, hyperbranched polyethylene is obtained. Subsequently, it undergoes a thiol-olefin click chemical reaction with a hindered thiolation amine light stabilizer and photoinitiator-651 under ultraviolet light irradiation to obtain modified hyperbranched polyethylene powder. S3: Linear low-density polyethylene powder and 4-vinylpyridine are melt-grafted in the presence of dicumyl peroxide to obtain modified linear polyethylene. Then, the modified linear polyethylene is melt-blended with antioxidant 1010 and cooled and pulverized to obtain antioxidant masterbatch. S4: Mix waste ultra-high molecular weight polyethylene fibers with white oil and modified hyperbranched polyethylene powder, carry out the first stage of heating and swelling, then add antioxidant masterbatch, carry out the second stage of heating and blending, and continue heating until a uniform and transparent spinning melt is formed. S5: The spinning melt is homogenized and extruded through a twin-screw extruder, then spun to form gel filaments. After extraction, stretching, heat setting, and winding, recycled ultra-high molecular weight polyethylene fiber dry filaments are obtained.

2. The preparation method according to claim 1, characterized in that, The weight ratio of 3-mercaptopropionic acid, 4-hydroxy-2,2,6,6-tetramethylpiperidinol, and p-toluenesulfonic acid in step S1 is 200-220g:340-360g:8-12g.

3. The preparation method according to claim 1, characterized in that, The esterification reaction in step S1 is carried out at a temperature of 110-120℃ for 5-7 hours.

4. The preparation method according to claim 1, characterized in that, The weight ratio of ethylene gas, nickel diimide, hindered thiolation amine light stabilizer, and photoinitiator-651 in step S2 is 4500-5000g:8-12g:450-550g:15-25g.

5. The preparation method according to claim 1, characterized in that, The polymerization reaction in step S2 is carried out at a temperature of 20-30°C for 50-70 min; the thiol-olefin click chemistry reaction is carried out at a temperature of 35-45°C for 2-4 h.

6. The preparation method according to claim 1, characterized in that, The weight ratio of the linear low-density polyethylene powder, 4-vinylpyridine, and dicumyl peroxide in step S3 is 4500-5500g:200-300g:4-6g.

7. The preparation method according to claim 1, characterized in that, The melt grafting reaction in step S3 is carried out in a twin-screw reactive extruder at a melt temperature of 165-175°C; the melt blending temperature is 135-145°C and the time is 8-12 min.

8. The preparation method according to claim 1, characterized in that, In step S4, the temperature for the first stage of heating and swelling is 115-125℃, and the time is 40-50 min; the temperature for the second stage of heating and blending is 155-165℃, and the time is 10-20 min.

9. The preparation method according to claim 1, characterized in that, In step S5, the homogenization extrusion temperature is 175-180℃; the extraction is carried out at room temperature with dichloromethane as the extractant; the total stretching ratio is controlled at 45-50 times; the heat setting temperature is 145-155℃, the processing time is 5-8 minutes, and the relaxation rate is controlled at 3%-5%.

10. A type of recycled ultra-high molecular weight polyethylene fiber filament, characterized in that, It is prepared according to any one of claims 1-9.

Images