Ultra-high molecular weight polyethylene fiber for robot and preparation method of ultra-high molecular weight polyethylene fiber

Abstract

The invention discloses an ultra-high molecular weight polyethylene fiber for a robot and a preparation method thereof, and belongs to the technical field of polyethylene fibers.The ultra-high molecular weight polyethylene fiber for the robot is prepared from, by weight, 100 parts of ultra-high molecular weight polyethylene, 10-18 parts of inorganic filler, 5-9 parts of compatilizer, 4-10 parts of cross-linking agent and 0.5-2 parts of peroxide. 0.5-2 parts of a lubricant and 0.2-2 parts of an antioxidant; the cross-linking agent takes an N, N '-methylene bisacrylamide structure as a parent, diethyl-methoxysilane with a flexible structure and a pyrimidine ring with excellent wear resistance are introduced, and due to introduction of the diethyl-methoxysilane, cross-linking reaction sites are increased, and meanwhile, the processing performance of a cross-linked polyethylene material is improved; the bipyrimidine ring and the amido bond improve the molecular polarity and the chemical stability and improve the resistance of the polyethylene cross-linking agent to strong polarity or special solvents, so that the tolerance of the ultra-high molecular weight polyethylene fiber to oil stains and solvents contacted in a robot working environment is improved.

Description

Technical Field

[0001] This invention belongs to the field of polyethylene fiber technology, specifically relating to an ultra-high molecular weight polyethylene fiber for robots and its preparation method. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE) fiber is a high-performance fiber made from polyethylene with a relative molecular weight of over 1.5 million. It has excellent mechanical properties, low density, good weather resistance, chemical corrosion resistance, low temperature resistance, bending resistance, cut resistance, impact resistance, low electrical conductivity, high transmittance to mid-wavelength infrared, and certain water resistance. It is widely used in military equipment, aerospace, marine engineering, security protection, transportation, sports equipment, biomedicine, home textiles, and robotics.

[0003] In the field of robotics, specific applications of polyethylene fiber include: robot structural protection and wear-resistant components, robot motion transmission and execution components, and special functional applications of robots. Due to the presence of molecular chain ends and amorphous defects in UHMWPE fibers, their heat resistance is insufficient, thus limiting their application in high-temperature robot operations. Furthermore, the relatively low surface hardness of UHMWPE fibers results in poor wear resistance, which can affect the long-term accuracy of robot transmission components.

[0004] To address the inherent defects of UHMWPE fibers, current modification research mainly includes methods such as blending modification, crosslinking modification, and the construction of surface wear-resistant coatings. For example, CN119980497A modifies UHMWPE by adding a crosslinking agent with a polyene-terminated polyaromatic ring structure, resulting in polyethylene fibers with good wear resistance and heat resistance. However, this crosslinking agent contains a large number of ester bonds and ether bonds (with poor chemical stability), which leads to excessive reaction sites when it undergoes a crosslinking reaction with UHMWPE at high temperatures, causing over-crosslinking and resulting in reduced fiber mechanical properties and decreased fiber processing stability. At the same time, the large number of ester bonds and ether bonds in this crosslinking agent also leads to poor solvent corrosion resistance of the crosslinked polyethylene fibers. Summary of the Invention

[0005] To overcome the shortcomings of the existing technology, the present invention provides an ultra-high molecular weight polyethylene fiber for robots and its preparation method. By adding a flexible diethyl-methoxysilane, a pyrimidine ring with excellent wear resistance, and a crosslinking agent with a chemically stable amide bond structure, the processing performance, solvent resistance, and chemical stability of the polyethylene fiber are improved.

[0006] The technical solution for achieving the objective of this invention is as follows: A type of ultra-high molecular weight polyethylene fiber for robots, comprising the following components by weight: 100 parts ultra-high molecular weight polyethylene, 10-18 parts inorganic filler, 5-9 parts compatibilizer, 4-10 parts crosslinking agent, 0.5-2 parts peroxide, 0.5-2 parts lubricant, and 0.2-2 parts antioxidant; the structure of the crosslinking agent is shown in Formula 1. In Formula 1, R1, R2, and R3 are independently one or more of methyl, ethyl, methoxy, and ethoxy; and R1, R2, and R3 in Formula 1 contain at least one of methoxy or ethoxy.

[0007] Preferably, the crosslinking agent has the structure shown in Formula 2:

[0008] The preparation method of Formula 2 includes the following steps:

[0009] S1. Reaction of N,N′-methylenebisacrylamide with 2-chloro-1,3-pyrimidine yields N,N′-methylenebis(N-pyrimidin-2-yl)acrylamide, i.e., M1; S2.M1 reacts with chloro-diethyl-methoxysilane to obtain the crosslinking agent as described in formula (1).

[0010] S1 is specifically: N,N′-methylenebisacrylamide and 2-chloro-1,3-pyrimidine undergo an affinity substitution reaction with toluene as solvent, pd2(dba)3 as catalyst, Am-Phos as ligand, and t-BuONa as base to generate intermediate M1. S2 specifically refers to Mn2(CO). 10 (Decacarbonyldimanganese) undergoes homolytic cleavage under heating (140 °C) and air conditions to generate active monovalent manganese radical Mn(CO)5·; the active manganese radical Mn(CO)5· attacks the Si-Cl bond of chloro-diethyl-methoxysilane (Et2(MeO)SiCl), resulting in a single electron transfer and homolytic cleavage of the Si-Cl bond to generate silicon radicals Et2(MeO)Si· and Mn(CO)5Cl; the silicon radical Et2(MeO)Si· attacks the active olefin (acryloyl double bond) in the substrate, resulting in a radical addition reaction to generate a carbon radical intermediate connected to silicon; the generated carbon radical undergoes a redox reaction with manganese species (such as Mn(CO)5Cl) to regenerate the catalyst and eliminate the radical, ultimately forming a carbon-silicon bond to obtain the product shown in formula (1).

[0011] Preferably, the ligand is .

[0012] Preferably, the peroxide is at least one of tert-butyl cumene peroxide (BIPB) or dicumene peroxide (DCP).

[0013] Preferably, the antioxidant is at least one of hindered phenolic antioxidants, phosphite antioxidants, or thioether antioxidants.

[0014] Preferably, the hindered phenolic antioxidant is antioxidant 1010.

[0015] Preferably, the phosphite antioxidant is antioxidant 168.

[0016] Preferably, the lubricant is at least one of butyl stearate, calcium stearate, or zinc stearate.

[0017] Preferably, the inorganic filler includes sheet-like filler or granular filler; the sheet-like filler is at least one of molybdenum disulfide sheet, mica sheet, graphite sheet or talc sheet, and the granular filler is at least one of barium sulfate, calcium carbonate, boron carbide or silicon dioxide.

[0018] Preferably, the inorganic filler is a mixture of sheet filler and granular filler in a mass ratio of (1:2) to (1:4).

[0019] Preferably, the compatibilizer is at least one of ethylene-vinyl acetate copolymer or ethylene-vinyl acetate-maleic anhydride copolymer.

[0020] Preferably, the method for preparing ultra-high molecular weight polyethylene (UHMWPE) fiber for robots includes the following steps: after screening, UHMWPE powder is mixed with filler, crosslinking agent, compatibilizer, peroxide, lubricant and antioxidant in proportion, and the additives are uniformly distributed in the matrix by high-speed stirring; the premixed raw materials are added to a solvent and heated and stirred at 120-150°C to form a homogeneous solution of "UHMWPE-additive-solvent", and after cooling, a gel spinning solution containing additives is prepared; the solution is spun and cooled to obtain nascent gel fibers; the nascent gel fibers are extracted with an extractant to remove the solvent, dried and then hot-stretched, shaped and wound to obtain UHMWPE fiber for robots.

[0021] The second objective of this invention is to protect the application of the ultra-high molecular weight polyethylene fiber in robot structural protection and wear-resistant components, robot motion transmission and execution components, and robot special function scenarios.

[0022] Beneficial effects

[0023] This invention provides the following beneficial effects: It offers a method for preparing and applying ultra-high molecular weight polyethylene (UHMWPE) fiber for robots. By adding N,N'-methylenebisacrylamide (MBA) with diethyl-methoxysilane and pyrimidine rings to UHMWPE, the MBA structure itself exhibits good chemical stability, and the vinyl group provides high crosslinking efficiency. The free radical polymerization reaction initiated at high temperatures introduces diethyl-methoxysilane and pyrimidine rings. The introduction of diethyl-methoxysilane increases the crosslinking reaction sites and improves the processing performance of the crosslinked polyethylene material. The pyrimidine rings and amide bonds in the crosslinking agent improve molecular polarity and chemical stability, enhancing the polyethylene's resistance to highly polar or special solvents, thereby improving the UHMWPE fiber's tolerance to oil and solvents encountered in the robot's working environment. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the synthesis pathway of the crosslinking agent. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] Unless otherwise specified, the experimental methods used in the embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0027] The raw materials and equipment used in the embodiments and comparative examples are described below: Ultra-high molecular weight polyethylene: Ultra-high molecular weight polyethylene powder, molecular weight 1.5 million, grade UH150P, Daqing Petrochemical; Flake filler: mica flakes, Guanjin Mica Products Factory, Xinghua City, Jiangsu Province; Granular filler: Silica, 1250 mesh, Lingshou County Jianshi Mineral Powder Factory; Compatibilizer 1: Ethylene-vinyl acetate copolymer, Wuhan Xinyang Ruihe Chemical Technology Co., Ltd.; Compatibilizer 2: Ethylene-vinyl acetate-maleic anhydride copolymer, Arkema; Peroxide: tert-butyl cumene peroxide (BIPB), 99%, Nantong Zhonghe Chemical New Materials Co., Ltd.; Lubricant: Calcium stearate, commercially available; Antioxidant: Antioxidant B215, composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2, manufactured by Henan Wokas Biotechnology Co., Ltd. Solvent: Decahydronaphthalene, 99%, Wuhan Hongde Yuexin Pharmaceutical Technology Co., Ltd.; Extractant: Dichloromethane, commercially available; Crosslinking agent 1: Preparation method is as follows: S1. Under nitrogen protection, add 1.0 mol of N,N′-methylenebisacrylamide, 2.0 mol of 2-chloro-1,3-pyrimidine, and 1.5 L of toluene to a 3.0 L three-necked flask. Stir until the solution is clear, then add 0.03 mol of Pd2(dba)3, 0.08 mol of Am-phos, and 4.0 mol of... t -BuONa sodium tert-butoxide, the reaction solution was heated to 110~120℃ and reacted for 10h. After the reaction was completed, it was filtered with diatomaceous earth while hot. The filtrate was cooled to room temperature, washed with purified water, separated, and the organic phase was retained. The aqueous phase was then extracted with ethyl acetate, and the organic phases were combined. The organic phase was dried with anhydrous magnesium sulfate, concentrated, and subjected to column chromatography (petroleum ether / dichloromethane = 15:1) to obtain intermediate M1 with a yield of 76.5% and a purity of 99.0%.

[0028] S2. Add 0.5 mol of intermediate M1, 0.5 mol of chloro-diethyl-methoxysilane, and 0.025 mol of Mn2(CO) to a 3.0 L three-necked flask. 10 (Decacarbonyldimanganese), 0.05 mol of ligand, and 1.5 L of trifluoromethylbenzene were added. Stirring was started, and the system was heated to 140 °C and reacted for 24 h. After the reaction was complete, the mixture was cooled to room temperature. The reaction solution was concentrated and subjected to column chromatography (petroleum ether / dichloromethane = 10:1) to obtain the crosslinking agent product, with a yield of 82.3% and a purity of 99.5%. The reaction process is as follows: Figure 1 As shown; 1H NMR data of the crosslinking agent product: 1H NMR (400 MHz, CDOD3) δ 8.47 (d, J = 7.4 Hz, 4H), 7.21 (t, J = 7.5 Hz, 2H), 6.92 (d, J = 15.1 Hz, 1H), 6.71 (d, J = 15.1 Hz, 1H), 6.50 (s, 2H), 6.40 (dd, J = 16.8, 10.0 Hz, 1H), 5.96 – 5.77 (m, 2H), 3.43 (s, 3H), 0.99 – 0.73 (m, 10H).

[0029] Crosslinking agent 2: Triallyl isocyanurate, 99%, Hefei Anbang Chemical Co., Ltd.

[0030] Crosslinking agent 3: Intermediate M1 prepared in this invention.

[0031] Example

[0032] A method for preparing a type of ultra-high molecular weight polyethylene fiber for robots is as follows: ultra-high molecular weight polyethylene powder is sieved using a 60-mesh sieve to remove larger particles; ultra-high molecular weight polyethylene powder with a concentration of 10wt%, filler, crosslinking agent, compatibilizer, peroxide, lubricant and antioxidant are added to a mixing tank; and high-speed stirring is used to ensure that the additives are initially and uniformly distributed in the matrix. The premixed raw materials are added to a spinning solvent (such as decahydronaphthalene), heated and stirred at 120-150℃ to form a homogeneous solution of "ultra-high molecular weight polyethylene-additive-solvent". After cooling, a gel spinning dope containing additives is prepared. The raw solution is extruded through a spinneret and enters a low-temperature coagulation bath (0-20℃), where the solvent precipitates out, forming nascent gel fibers containing additives. The residual solvent in the fiber is removed by an extractant (dichloromethane) while the additives are retained, and then the extractant is removed by drying. In this process, the crosslinking agent is introduced into the fiber network structure by the exchange between the extractant and the spinning solvent.

[0033] Then, the fibers are stretched 20-40 times in stages at 80-120℃. At this time, the additives are aligned with the molecular chains, which synergistically improves the fiber strength, wear resistance and other properties. At the same time, during the high-ratio hot stretching process, polyethylene undergoes a cross-linking reaction with the cross-linking agent under high temperature, forming a tight cross-linking network. The diethyl-methoxysilane in the cross-linking agent increases the cross-linking reaction sites and improves the processing performance of the cross-linked polyethylene material. The pyrimidine ring and amide bond in the cross-linking agent improve the molecular polarity and chemical stability of polyethylene, and improve the resistance of the cross-linked polyethylene to strong polarity or special solvents.

[0034] The stretched fibers are heat-set (120-140℃) to eliminate internal stress. Ultra-high molecular weight polyethylene (UHMWPE) fibers for robots are prepared using the above method. The formulation of the UHMWPE fibers for robots is shown in Table 1.

[0035] Table 1. Specific components and proportions of ultra-high molecular weight polyethylene fiber for robots.

[0036] Note: "-" indicates that this component was not added.

[0037] The obtained polyethylene fibers were subjected to the following performance tests, and the results are shown in Table 2: (1) Swelling rate: Randomly cut a 50 mm long fiber segment without damage or twist deviation from the finished fiber product for robot use; put the sample into a vacuum drying oven at 60-80 ℃ and dry for 2-4 h until constant weight (the difference between two weighings is ≤0.1 mg), and record the fiber mass m0 and initial diameter / or cross-sectional area S0 before the experiment.

[0038] The sample was completely immersed in the prepared gear oil and placed in a constant temperature water bath (three temperature conditions: 25 ℃, 50 ℃, 80 ℃, simulating the equipment's rest temperature and working temperature) and sealed for 48 h.

[0039] After the soaking time is reached, quickly remove the sample and gently blot off excess oil with filter paper (do not squeeze the sample to avoid losing the oil adsorbed inside). Record the mass m1 and the diameter (or cross-sectional area S1) after soaking; the mass swelling rate Q. m =[(m1-m0) / m0]×100%, volume swelling ratio Q v =[(S1-S0) / S0]×100%.

[0040] (2) Quality retention rate: Randomly cut a 50 mm long fiber segment without damage or twist deviation from the finished fiber product for robot use; put the sample into a vacuum drying oven at 60-80 ℃ and dry for 2-4 h until constant weight (the difference between two weighings ≤ 0.1 mg), and record the fiber mass m0 before the experiment.

[0041] The sample was completely immersed in gear oil and placed in a constant temperature water bath (three temperature conditions: 25 ℃, 50 ℃, 80 ℃, simulating the equipment's rest temperature and working temperature) and sealed for 48 h.

[0042] After aging, remove the sample and gently blot away surface oil with clean filter paper (do not squeeze to avoid damaging the fiber structure). Place the treated sample back into a vacuum drying oven (at the same pretreatment temperature) and dry for 2-3 hours until constant weight. Record the mass m1 after aging. Mass retention rate (%) = (m1 / m0) × 100%. The closer the value is to 100%, the stronger the fiber's resistance to aging and resistance to mass loss.

[0043] (3) Tensile strength retention rate: Randomly cut a 300mm long fiber segment without damage or twist deviation from the finished fiber product for robot use, with the effective clamping distance set at 150mm; put the sample into a vacuum drying oven at 60-80℃ and dry it for 2-4h until constant weight (the difference between two weighings ≤0.001 g). After the sample is cooled to room temperature, use a vernier caliper with an accuracy of 0.01 mm to measure the diameter of the middle section of the sample (take the average value of 3 different positions, recorded as d0), and calculate the initial cross-sectional area (S0=π(d0 / 2)²).

[0044] The pretreated specimens were placed in a standard environment (temperature 23±2 ℃, relative humidity 50±5%) for 24 hours to eliminate processing stress and avoid environmental factors from interfering with the test results. Tensile tests were performed using a universal testing machine, and the maximum load (F0) at which the specimen broke was recorded. The initial tensile strength was calculated according to the formula: σ0=F0 / S0 (unit: MPa), and the average value of σ0 of parallel specimens was taken.

[0045] The samples from the same batch were completely immersed in gear oil and placed in a constant temperature water bath (three temperature conditions: 25 ℃, 50 ℃, 80 ℃, simulating the equipment's rest temperature and working temperature) and sealed for 48 h.

[0046] After aging is complete, remove the sample. For oil-stained aged samples, gently blot the surface oil with filter paper (do not squeeze). Then repeat the "conditioning" step.

[0047] Using the same equipment parameters and operating methods as for "measuring initial tensile strength," test the maximum breaking load (F1) of the aged specimen and calculate the tensile strength after aging: σ1 = F1 / S0 (Note: the cross-sectional area is calculated based on the initial S0 to avoid the influence of dimensional changes after aging on the results). Tensile strength retention rate (%) = (σ1 / σ0) × 100%. The higher the value, the better the retention of mechanical properties of the fiber after aging and the stronger its resistance to oil stains.

[0048] (4) Heat resistance: The heat resistance was tested in accordance with GB / T 19466.3-2004 "Differential scanning calorimetry (DSC) for plastics - Part 3: Determination of melting and crystallization temperature and enthalpy". The polyethylene fibers of the examples and comparative examples were subjected to thermogravimetric analysis. The heat resistance of the material was characterized by the temperature at which the mass loss percentage reached 10% (T10%). The higher the T10% temperature, the better the heat resistance of the material.

[0049] Table 2 Performance test results of ultra-high molecular weight polyethylene fiber for robots

[0050] As can be seen from Examples 1-6 and Comparative Examples 1, 2, and 3, the swelling rate, mass retention rate, tensile strength retention rate, and heat resistance of ultra-high molecular weight polyethylene after chemical crosslinking are significantly improved compared with uncrosslinked ultra-high molecular weight polyethylene. Furthermore, the crosslinking agent and intermediate M1 provided in this application have a more significant modification effect on polyethylene fibers modified by existing crosslinking agents (trylyl isocyanate). The pyrimidine ring and amide bond improve molecular polarity and chemical stability, and enhance the resistance of the polyethylene crosslinking agent to highly polar or special solvents. The swelling rate of ultra-high molecular weight polyethylene obtained after crosslinking agent modification is reduced, while the mass retention rate and tensile strength retention rate are significantly improved. The thermal decomposition temperature is greater than 430℃, indicating broad application prospects.

[0051] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. An ultrahigh molecular weight polyethylene fiber for a robot, characterized by, By weight, including the following components: ultra-high molecular weight polyethylene 100 parts, inorganic filler 10-18 parts, compatibilizer 5-9 parts, crosslinking agent 4-10 parts, peroxide 0.5-2 parts, lubricant 0.5-2 parts, antioxidant 0.2-2 parts; the structure of the crosslinking agent is shown as formula 1: In formula 1, R1, R2, R3 are independently one or more of methyl, ethyl, methoxy, ethoxy; and at least one of R1, R2, R3 is one of methoxy or ethoxy.

2. The ultra-high molecular weight polyethylene fiber for robots according to claim 1, characterized by The structure of the crosslinking agent is shown as formula 2: ， The preparation method of the formula 2 comprises the following steps: S1. N, N'-methylene bisacrylamide is reacted with 2-chloro-1, 3-pyrimidine to obtain N, N'-methylene bis (N-pyrimidine-2-yl) acrylamide; S2. N, N'-methylene bis (N-pyrimidine-2-yl) acrylamide is reacted with chloro-diethyl-methoxysilane to obtain the crosslinking agent shown as formula (1).

3. The ultra-high molecular weight polyethylene fiber for robots according to claim 1, characterized by The peroxide is at least one of t-butyl hydroperoxide (BIPB) or dicumyl peroxide (DCP).

4. The ultra-high molecular weight polyethylene fiber for robots according to claim 1, characterized by The antioxidant is at least one of hindered phenolic antioxidant, phosphite antioxidant or sulfide antioxidant.

5. The ultra-high molecular weight polyethylene fiber for robots according to claim 1, wherein The lubricant is at least one of butyl stearate, calcium stearate or zinc stearate.

6. The ultra-high molecular weight polyethylene fiber for robots according to claim 1, wherein The inorganic filler includes flaky filler or particulate filler; the flaky filler is at least one of molybdenum disulfide sheet, mica sheet, graphite sheet or talc sheet, and the particulate filler is at least one of barium sulfate, calcium carbonate, boron carbide or silicon dioxide.

7. The ultra-high molecular weight polyethylene fiber for robots according to claim 6, wherein The inorganic filler is a combination of flaky filler and particulate filler, and the mass ratio is (1:2)~(1:4).

8. The ultra-high molecular weight polyethylene fiber for robots according to claim 1, wherein The compatibilizer is at least one of ethylene-vinyl acetate copolymer or ethylene-vinyl acetate-maleic anhydride copolymer.

9. The method of producing an ultrahigh molecular weight polyethylene fiber for robots according to any one of claims 1 to 8, characterized by, The method comprises the following steps: after the ultra-high molecular weight polyethylene is sieved, the filler, the crosslinking agent, the compatibilizer, the peroxide, the lubricant and the antioxidant are mixed in proportion, and the preliminary uniform distribution of the additives in the matrix is ensured by high-speed stirring; the premixed raw material is added to a spinning solvent, heated and stirred at 120-150℃ to form a homogeneous solution of "ultra-high molecular weight polyethylene-additives-solvent", and a gel spinning solution containing additives is prepared after cooling; after the spinning solution is spun, the nascent gel fiber is prepared by cooling; the nascent gel fiber is extracted with an extractant to remove the solvent, dried and then heat stretched to obtain a robot ultra-high molecular weight polyethylene fiber.

10. The application of the ultra-high molecular weight polyethylene fiber according to any one of claims 1-8 in robot structure protection and wear-resistant parts, robot motion transmission and execution parts, and robot special function scenarios.

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