Preparation method of wear-resistant and oxidation-resistant polyurea lubricant

Abstract

The application relates to a preparation method of a wear-resistant and oxidation-resistant polyurea lubricant, and belongs to the technical field of lubricating materials. Nickel oxide is in-situ loaded on the surface of tungsten disulfide and graphene oxide through a hydrothermal synthesis method to form a nano composite powder. The interlayer slip characteristics of the tungsten disulfide provide basic lubrication, the sheet structure of the graphene oxide provides mechanical support, and the hard phase characteristics of the nickel oxide inhibit abrasive wear. Then, the nano composite powder is modified by an ionic liquid to construct a structured solvation layer by means of electrostatic action, hydrogen bonds and van der Waals forces. The nano composite powder not only solves the problem of easy agglomeration of the nano composite powder in a polyurea lubricant matrix, but also forms a chemical adsorption film on a friction interface. In addition, microcapsule powder with poly-alpha-olefin as a core material dynamically releases and forms a liquid film in a friction process, cooperates with solid lubrication of the nano composite powder, greatly improves lubricating performance and wear resistance, and meets the long-term lubricating requirements of heavy-load machinery.

Description

Technical Field

[0001] This invention belongs to the field of lubrication materials technology, and relates to a method for preparing a wear-resistant and antioxidant polyurea lubricant. Background Technology

[0002] Polyurea materials, as a class of polymer materials generated by the reaction of isocyanates and amine compounds, possess excellent mechanical strength, outstanding high and low temperature resistance (maintaining stability in a temperature range of -50℃ to 200℃ or even wider), good chemical inertness and anti-aging properties due to the hydrogen bonding effect formed by the unique urea functional groups, and show significant advantages in lubricant modification and preparation.

[0003] By precisely designing the molecular structure of polyurea, such as controlling the ratio of soft segments (polyether, polyester, etc.) to hard segments (urea bonds, urea carbamate bonds, etc.) and selecting isocyanate monomers and amine chain extenders with different carbon chain lengths, the elastic resilience and interfacial adsorption capacity of the material can be optimized. At the same time, by combining appropriate preparation processes (such as in-situ polymerization, emulsion polymerization, etc.) and rationally compounding anti-wear additives (such as nano-metal oxides, sulfides, etc.) and antioxidants (such as hindered phenols, amines, etc.), the wear resistance and antioxidant stability of polyurea lubricants can be further improved, enabling them to form a continuous, dense and resistant lubricating film under extreme working conditions, effectively resisting oxidation erosion and frictional wear.

[0004] Chinese invention patent announcement CN108865373B discloses a composite calcium sulfonate polyurea mixed grease and its preparation method, including mineral base oil, urea thickener, composite calcium sulfonate and polyisobutylene thickener. It retains the basic characteristics of urea-based grease such as high dropping point, easy pumping, and anti-oxidation and anti-corrosion, and combines the advantages of composite calcium sulfonate-based lubricant such as good water resistance and strong extreme pressure wear resistance.

[0005] The mineral base oils in the above scheme are high-pressure hydrogenated bright oils (i.e., 150BS, 175BS, 250BS, etc.), which are essentially petroleum distillates. The small amount of unsaturated hydrocarbon bonds remaining in the molecular structure are easily attacked by oxygen at high temperatures, triggering free radical chain oxidation reactions. The transmission systems (gears, roller bearings) of equipment such as steel annealing furnaces are in a high-temperature environment for a long time and need to bear the heavy load brought by the weight of the kiln body. During the long-term service of the above-mentioned grease, intermediate products such as gum and asphalt will gradually be generated, which will then be dehydrated and dehydrogenated to form amorphous carbon deposits. In addition, the high-temperature environment will cause the calcium ions in the ash to react chemically with the carboxyl groups in the carbon deposit precursors to generate metal carboxylates that are insoluble in oil. This crosslinks and solidifies the loose carbon deposit particles, eventually forming hard and stubborn coke-like substances on the inner wall of the gearbox, bearing raceway, and pipeline inner wall, causing the problem of obstructed grease circulation. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a wear-resistant and antioxidant polyurea lubricant. The method involves stirring and refining microcapsule powder, organic amine and diisocyanate, and then mixing it with ionic liquid-modified nanocomposite powder to improve the lubrication performance and antioxidant performance of the lubricant under high temperature and extreme pressure conditions.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A method for preparing a wear-resistant and antioxidant polyurea lubricant includes the following steps:

[0009] Step 1: Nickel oxide is synthesized on tungsten disulfide and graphene oxide by hydrothermal synthesis to obtain nanocomposite powder; then modified with ionic liquid to obtain ionic liquid-modified nanocomposite powder.

[0010] Step 2: Using polyalphaolefin as the core material and urea and formaldehyde as monomers, polyurea-formaldehyde prepolymer is synthesized. Under the cross-linking action of the cross-linking agent, a shell layer is formed through a condensation reaction to obtain microcapsule powder.

[0011] Step 3: Stir and refine the microcapsule powder, organic amine and diisocyanate, and grind them to obtain the polyurea lubricant matrix; mix the polyurea lubricant matrix with the ionic liquid modified nanocomposite powder to obtain the wear-resistant and antioxidant polyurea lubricant.

[0012] Furthermore, the preparation process of the ionic liquid-modified nanocomposite powder is as follows:

[0013] The nanocomposite powder and anhydrous ethanol were added to a reaction vessel and ultrasonically dispersed for 15-20 min. Then, the ionic liquid was added dropwise and ultrasonically dispersed for 15-2 min. The mixture was then ground under a pressure of 10-15 MPa for 5-6 h and kept at 80-90℃ for 12-14 h. After cooling to room temperature, the ionic liquid-modified nanocomposite powder was obtained.

[0014] Furthermore, the ratio of nanocomposite powder, anhydrous ethanol, and ionic liquid is 0.5-1.0g: 30-40mL: 0.8-1.2g.

[0015] Furthermore, the ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate.

[0016] Furthermore, the preparation process of the nanocomposite powder is as follows:

[0017] Tungsten disulfide powder, graphene oxide powder, polyvinylpyrrolidone, nickel chloride, and distilled water were added to a reaction vessel and ultrasonically treated for 30-40 minutes. Then, ammonia water, hexadecyltrimethylammonium chloride, and KH-550 with a concentration of 25-28 wt% were added. The mixture was stirred at 20-25℃ for 2-3 hours and hydrothermally treated at 100-110℃ for 16-20 hours. After centrifugation, filtration, washing, and drying, nanocomposite powder was obtained.

[0018] Furthermore, the ratio of tungsten disulfide powder, graphene oxide powder, polyvinylpyrrolidone, nickel chloride, distilled water, ammonia, hexadecyltrimethylammonium chloride, and KH-550 used is 0.5-1.0g: 0.02-0.04g: 0.05-0.09g: 0.24-0.34g: 50-60mL: 0.2-0.4mL: 0.1-0.2g: 0.1-0.2g.

[0019] Furthermore, the preparation process of the microcapsule powder is as follows:

[0020] Urea, resorcinol, a 40wt% glyoxal aqueous solution, ammonium chloride, a 0.2wt% sodium lignosulfonate, and deionized water were added to a reaction vessel and stirred at 500-700 rpm for 10-15 min. Poly-α-olefin was added, and homogenized and sheared emulsified for 5-7 min to obtain a stable oil-in-water emulsion. The mixture was stirred at 350-450 rpm for 5-7 min, and n-octanol was added dropwise. A 37wt% formaldehyde aqueous solution was added, and the pH was adjusted to 3-4 with 1 mol / L hydrochloric acid. The temperature was slowly increased to 35-40℃ and held for 30-40 min. Then, the temperature was increased to 60-65℃ at a rate of 1℃ / min and held for 3-4 h. The mixture was then vacuum filtered, washed, and dried to obtain microcapsule powder.

[0021] Furthermore, the ratio of the amounts of urea, resorcinol, glyoxal aqueous solution, ammonium chloride, sodium lignosulfonate, deionized water, polyalphaolefin, n-octanol, and formaldehyde aqueous solution is 25-35g: 1.2-2.2g: 5-8g: 2.5-4.5g: 2-4g: 150-200mL: 75-95g: 0.8-1.0mL: 50-70g.

[0022] Furthermore, the preparation process of the polyurea lubricant matrix is ​​as follows:

[0023] Microcapsule powder is added to a reaction vessel and heated to 80-85℃. Then, organic amine and diisocyanate are added and reacted at 300-500 r / min for 40-60 min. The temperature is then raised to 100-120℃, distilled water is added, and the temperature is maintained for 20-30 min. The temperature is then raised to 180-190℃ and stirred for 15-45 min. After stirring and refining, the mixture is cooled to room temperature and ground three times with a three-roll mill to obtain the polyurea lubricant matrix.

[0024] Furthermore, the ratio of microcapsule powder, organic amine, and diisocyanate is 100-150g: 6-8g: 25-35g.

[0025] Furthermore, the organic amine is one of octadecylamine and cyclohexylamine.

[0026] Furthermore, the diisocyanate is one of hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate.

[0027] Furthermore, the preparation process of the wear-resistant and antioxidant polyurea lubricant is as follows:

[0028] The polyurea lubricant matrix and acetone solution were added to a reaction vessel, followed by the addition of ionic liquid-modified nanocomposite powder and hindered phenolic antioxidant 1010. The mixture was sonicated for 2-3 hours, and the acetone was removed under conditions of 80-85℃ and 500-700 r / min to obtain a wear-resistant and antioxidant polyurea lubricant.

[0029] Furthermore, the ratio of polyurea lubricant matrix, acetone solution, ionic liquid-modified nanocomposite powder and hindered phenolic antioxidant 1010 is 50-70g: 15-25mL: 0.5-1.0g: 0.1-0.2g.

[0030] The beneficial effects of this invention are:

[0031] 1. This invention utilizes a hydrothermal synthesis method to in-situ load nickel oxide onto the surfaces of tungsten disulfide and graphene oxide, forming a nanocomposite powder. The interlayer slip properties of tungsten disulfide provide basic lubrication, the layered structure of graphene oxide enhances mechanical support, and the hard phase properties of nickel oxide inhibit abrasive wear. After modification with ionic liquid, a structured solvation layer is constructed through electrostatic interactions, hydrogen bonds, and van der Waals forces. This not only solves the problem of easy agglomeration of nanocomposite powder in polyurea lubricant matrix but also forms a chemical adsorption film at the friction interface. In addition, microcapsule powder with polyα-olefin as the core material is dynamically released during friction and forms a liquid film, which synergizes with the solid lubrication of the nanocomposite powder, significantly improving lubrication performance and wear resistance, and meeting the long-term lubrication requirements of heavy-duty machinery.

[0032] 2. This invention endows the wear-resistant and antioxidant polyurea lubricant with excellent antioxidant stability and wide temperature range adaptability. The ionic liquid can stably inhibit the oxidation chain reaction at high temperatures and has high thermal stability, while nickel oxide has a catalytic oxygen inhibition effect. The dense sheet structure of graphene oxide can block the contact between oxygen and the matrix, slow down the oxidation rate, and form multiple antioxidant synergies with the hindered phenolic antioxidant 1010, effectively delaying the oxidative degradation of the polyurea lubricant matrix and the polyalphaolefin core material. Furthermore, the dense shell of the microcapsule powder can further prevent oxygen from directly contacting the polyalphaolefin core material, giving the lubricant good antioxidant properties.

[0033] 3. The microcapsule powder of this invention has high compressive strength and a relatively rough surface, forming an interlocking structure with the polyurea matrix. At the same time, the urea groups in the microcapsule shell form hydrogen bonds with the urea groups in the polyurea matrix, enhancing the interfacial bonding force between the two. After three-roll milling, a small amount of agglomerates are dispersed, so that the microcapsule powder is evenly dispersed in the polyurea lubricant matrix. The imidazole cation of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate binds to the negative potential points on the surface of tungsten disulfide sheets and graphene oxide in the nanocomposite powder through electrostatic interaction and van der Waals forces. The tetrafluoroborate anion forms hydrogen bonds with the hydroxyl groups on the surface of nickel oxide, which can form a structured solvation layer on the surface of nanoparticles, so that it can be evenly dispersed in the polyurea lubricant matrix. Detailed Implementation

[0034] To further illustrate the technical means and effects of the present invention in achieving the intended purpose, the following detailed description of the specific implementation methods, features and effects of the present invention, in conjunction with preferred embodiments, is provided below.

[0035] Example 1: This example provides a wear-resistant and antioxidant polyurea lubricant, which is prepared through the following steps:

[0036] S1: 0.75g tungsten disulfide powder (particle size 100nm, purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.), 0.03g graphene oxide (purity 99.99%, purchased from Henan Wanying Refractory Materials Technology Co., Ltd.), 0.07g polyvinylpyrrolidone (specification K85, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.), 0.29g nickel chloride (purchased from Jinan Shengda Chemical Co., Ltd.) and 55mL distilled water were added to a reaction vessel and ultrasonically treated for 35min. Then, 0.3mL of 26wt% ammonia water, 0.15g hexadecyltrimethylammonium chloride and 0.15g silane coupling agent KH-550 were added. The mixture was stirred at 22℃ for 2h and hydrothermally treated at 105℃ for 18h. After centrifugation and filtration, the filter cake was washed twice with distilled water and anhydrous ethanol, respectively, and dried at 82℃ for 13h to obtain nanocomposite powder.

[0037] Distilled water is used as a solvent to completely dissolve nickel chloride and ionize it into nickel ions. Polyvinylpyrrolidone (PVP) binds to the surface of tungsten disulfide via hydrogen bonds to form a steric barrier, while simultaneously forming intermolecular forces with graphene oxide sheets to jointly construct a steric barrier and inhibit tungsten disulfide aggregation. Ammonia water adjusts the pH of the system to 8, forming a stable and moderate complex with nickel ions. Hexadecyltrimethylammonium chloride enhances dispersion stability by electrostatic adsorption on the surfaces of tungsten disulfide and graphene oxide. KH-550 utilizes its amino groups to form chemical bonds with hydroxyl groups on the surfaces of tungsten dioxide and graphene oxide, as well as nickel ions, further enhancing the site-directing effect. Under hydrothermal conditions at 105℃, the complex decomposes to release nickel ions and hydrolyzes to generate nickel hydroxide, which is deposited in situ on the surface of tungsten disulfide and graphene oxide. After 18 hours of heat preservation, the nickel hydroxide dehydrates and decomposes into nickel oxide nanoparticles, which grow uniformly on the surface and edges of the tungsten disulfide sheets to form a nanocomposite powder.

[0038] S2: Add 0.75g of nanocomposite powder and 35mL of anhydrous ethanol to the reaction vessel, sonicate for 17min, then add 1.0g of ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate, purchased from the State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences), sonicate for 17min to make the nanocomposite powder and ionic liquid evenly dispersed, apply 12MPa pressure to grind for 5h, keep at 85℃ for 13h, cool to room temperature to obtain ionic liquid modified nanocomposite powder.

[0039] The imidazole cation of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate binds to the negative potential sites on the surface of tungsten disulfide sheets and graphene oxide in the nanocomposite powder through electrostatic interaction and van der Waals forces. The tetrafluoroborate anion forms hydrogen bonds with the hydroxyl groups on the surface of nickel oxide. At the same time, with the help of the solvent-mediated effect of ethanol, the ionic liquid promotes the formation of a structured solvation layer on the surface of nanoparticles.

[0040] S3: Add 30g urea, 1.7g resorcinol, 6.5g 40wt% glyoxal aqueous solution, 3.5g ammonium chloride, 3g 0.2wt% sodium lignosulfonate, and 175mL deionized water to a reactor. Stir at 600r / min for 12min. Add 85g poly-α-olefin (PAO40). Homogenize and shear emulsify at 5250r / min at 22℃ for 6min to obtain a stable oil-in-water emulsion. Stir at 400r / min for 6min. Add 0.9mL n-octanol for defoaming. Add 60g 37wt% formaldehyde aqueous solution. Adjust the pH to 3 with 1mol / L hydrochloric acid. Slowly raise the temperature to 37℃ and hold for 35min. Then raise the temperature to 62℃ at 1℃ / min and hold for 3h. Vacuum filter. Wash the filter cake alternately with deionized water, ethanol, and isopropanol. Freeze-dry for 25h to obtain microcapsule powder.

[0041] Sodium lignosulfonate was used as an anionic emulsifier. Its hydrophilic sulfonic acid groups were oriented towards the aqueous phase, while its hydrophobic groups were adsorbed onto the surface of polyalphaolefin (PAO) oil droplets. Combined with high-shear homogenization, PAO was broken into tiny droplets and formed a stable oil-in-water emulsion. Ammonium chloride enhanced the emulsion stability by adjusting the ionic strength of the aqueous phase, laying the foundation for dispersion in subsequent reactions. Next, formaldehyde aqueous solution was added. Under acidic conditions, urea and formaldehyde first underwent a hydroxymethylation reaction to generate a water-soluble polyurea-formaldehyde prepolymer. Resorcinol reacted with the prepolymer through its phenolic hydroxyl groups. The hydroxymethyl group forms an ether bond, while the glyoxal rapidly crosslinks with the amino group of the urea molecule due to its highly active aldehyde group. The two work synergistically to enhance the activity and crosslinking density of the prepolymer. At the same time, the prepolymer is oriented to adsorb onto the oil-water interface by electrostatic attraction. Subsequently, by gradient heating, the prepolymer undergoes rapid polycondensation reaction and continuous deposition and crosslinking, forming a dense and high-strength shell on the surface of the oil droplets. The polyα-olefin is then encapsulated inside the shell to form microcapsules. The addition of n-octanol eliminates bubbles during emulsification and stirring, preventing the formation of pores in the shell.

[0042] S4: Add 125g of microcapsule powder to the reaction vessel and heat to 82℃. Then add 7g of octadecylamine (industrial grade, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) and 30g of hexamethylene diisocyanate. React at 400r / min for 50min. After the reaction is complete, raise the temperature to 110℃, add 17mL of distilled water to remove excess hexamethylene diisocyanate, keep warm for 25min, raise the temperature to 185℃, and stir and refine for 30min. After stirring and refining, cool to room temperature and grind three times with a three-roll mill, controlling the grinding pressure at 0.4MPa to obtain the polyurea lubricant matrix.

[0043] The isocyanate group in hexamethylene diisocyanate undergoes an addition reaction with the amino group in octadecylamine to first generate a urea-structured prepolymer, which is then further crosslinked to form a three-dimensional network polyurea structure. The microcapsule powder is tightly encapsulated in the network structure, and its rough surface forms a mechanical interlock with the polyurea to prevent it from falling off during subsequent use, while retaining the self-lubricating function of releasing oil when the microcapsules rupture during friction.

[0044] S5: Add 60g of polyurea lubricant matrix and 20mL of acetone solution to the reactor, then add 0.75g of ionic liquid modified nanocomposite powder and 0.15g of hindered phenolic antioxidant 1010, sonicate for 2h, and volatilize the acetone at 82℃ and 600r / min to obtain wear-resistant and antioxidant polyurea lubricant.

[0045] Example 2: This example provides a wear-resistant and antioxidant polyurea lubricant, which is prepared through the following steps:

[0046] S1: 0.5g tungsten disulfide powder (particle size 100nm, purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.), 0.02g graphene oxide, 0.05g polyvinylpyrrolidone, 0.24g nickel chloride and 50mL distilled water were added to a reaction vessel and sonicated for 30min. Then, 0.2mL of 25wt% ammonia water, 0.1g hexadecyltrimethylammonium chloride and 0.1g silane coupling agent KH-550 were added. The mixture was stirred at 20℃ for 2h and hydrothermally treated at 100℃ for 16h. After centrifugation and filtration, the filter cake was washed twice with distilled water and anhydrous ethanol, respectively, and dried at 80℃ for 12h to obtain nanocomposite powder.

[0047] S2: Add 0.5g of nanocomposite powder and 30mL of anhydrous ethanol to the reaction vessel, sonicate for 15min, then add 0.8g of ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate), sonicate for 15min to make the nanocomposite powder and ionic liquid evenly dispersed, apply 10MPa pressure to grind for 5h, keep at 80℃ for 12h, cool to room temperature to obtain ionic liquid modified nanocomposite powder.

[0048] S3: Add 25g urea, 1.2g resorcinol, 5g of 40wt% glyoxal aqueous solution, 2.5g ammonium chloride, 2g of 0.2wt% sodium lignosulfonate, and 150mL deionized water to a reactor. Stir at 500r / min for 10min. Add 75g polyα-olefin (PAO40). Homogenize and shear emulsify at 5000r / min for 5min at 20℃ to obtain a stable oil-in-water emulsion. Stir at 350r / min for 5min. Add 0.8mL n-octanol for defoaming. Add 50g of 37wt% formaldehyde aqueous solution. Adjust the pH to 3 with 1mol / L hydrochloric acid. Slowly raise the temperature to 35℃ and hold for 30min. Then raise the temperature to 60℃ at 1℃ / min and hold for 3h. Vacuum filter. Wash the filter cake alternately with deionized water, ethanol, and isopropanol. Freeze-dry for 24h to obtain microcapsule powder.

[0049] S4: Add 100g of microcapsule powder to a reaction vessel and heat to 80℃. Then add 6g of octadecylamine (industrial grade, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) and 25g of hexamethylene diisocyanate (analytical grade, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.). React at 300r / min for 40min. After the reaction is complete, raise the temperature to 100℃, add 15mL of distilled water to remove excess hexamethylene diisocyanate, keep warm for 20min, raise the temperature to 180℃, and stir and refine for 15min. After stirring and refining, cool to room temperature and grind three times with a three-roll mill at a pressure of 0.4MPa to obtain the polyurea lubricant matrix.

[0050] S5: Add 50g of polyurea lubricant matrix and 15mL of acetone solution to the reactor, then add 0.5g of ionic liquid modified nanocomposite powder and 0.1g of hindered phenolic antioxidant 1010, sonicate for 2h, and volatilize the acetone at 80℃ and 500r / min to obtain wear-resistant and antioxidant polyurea lubricant.

[0051] Example 3: This example provides a wear-resistant and antioxidant polyurea lubricant, which is prepared through the following steps:

[0052] S1: 1.0 g tungsten disulfide powder (particle size 100 nm, purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.), 0.04 g graphene oxide, 0.09 g polyvinylpyrrolidone, 0.34 g nickel chloride and 60 mL distilled water were added to a reaction vessel and ultrasonically treated for 40 min. Then, 0.4 mL of 28 wt% ammonia water, 0.2 g hexadecyltrimethylammonium chloride and 0.2 g silane coupling agent KH-550 were added. The mixture was stirred at 25 °C for 3 h and hydrothermally treated at 110 °C for 20 h. After centrifugation and filtration, the filter cake was washed three times with distilled water and anhydrous ethanol, respectively, and dried at 85 °C for 14 h to obtain nanocomposite powder.

[0053] S2: Add 1.0g of nanocomposite powder and 40mL of anhydrous ethanol to the reaction vessel, sonicate for 20min, then add 1.2g of ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate), sonicate for 20min to make the nanocomposite powder and ionic liquid evenly dispersed, apply 15MPa pressure to grind for 6h, keep at 90℃ for 14h, cool to room temperature to obtain ionic liquid modified nanocomposite powder.

[0054] S3: Add 35g urea, 2.2g resorcinol, 8g of 40wt% glyoxal aqueous solution, 4.5g ammonium chloride, 4g of 0.2wt% sodium lignosulfonate, and 200mL deionized water to a reactor. Stir at 700r / min for 15min. Add 95g poly-α-olefin (PAO40). Homogenize and shear emulsify at 5500r / min for 7min at 25℃ to obtain a stable oil-in-water emulsion. Stir at 450r / min for 7min. Add 1.0mL n-octanol for defoaming. Add 70g of 37wt% formaldehyde aqueous solution. Adjust the pH to 4 with 1mol / L hydrochloric acid. Slowly heat to 40℃ and hold for 40min. Then heat to 65℃ at 1℃ / min and hold for 4h. Vacuum filter. Wash the filter cake alternately with deionized water, ethanol, and isopropanol. Freeze-dry for 26h to obtain microcapsule powder.

[0055] S4: Add 150g of microcapsule powder to the reaction vessel, heat to 85℃, then add 8g of octadecylamine and 35g of hexamethylene diisocyanate, react at 500r / min for 60min, after the reaction is complete, raise the temperature to 120℃, add 20mL of distilled water to remove excess hexamethylene diisocyanate, keep warm for 30min, raise the temperature to 190℃, stir and refine for 45min, after stirring and refining is complete, cool to room temperature, and grind 3 times with a three-roll mill, with the grinding pressure controlled at 0.5MPa, to obtain the polyurea lubricant matrix.

[0056] S5: Add 70g of polyurea lubricant matrix and 25mL of acetone solution to the reactor, then add 1.0g of ionic liquid modified nanocomposite powder and 0.2g of hindered phenolic antioxidant 1010, sonicate for 3h, and volatilize the acetone at 85℃ and 700r / min to obtain wear-resistant and antioxidant polyurea lubricant.

[0057] Example 4: This example provides a wear-resistant and antioxidant polyurea lubricant. The difference from Example 1 is that cyclohexylamine (analytical grade, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.) is used instead of octadecylamine in step S4.

[0058] Example 5: This example provides a wear-resistant and antioxidant polyurea lubricant. The difference from Example 1 is that isophorone diisocyanate is used instead of hexamethylene diisocyanate in step S4.

[0059] Example 6: This example provides a wear-resistant and antioxidant polyurea lubricant. The difference from Example 1 is that in step S4, dicyclohexylmethane diisocyanate is used instead of hexamethylene diisocyanate, and the amount is adjusted to 33g.

[0060] Comparative Example 1: This comparative example provides a wear-resistant and antioxidant polyurea lubricant, which differs from Example 1 in that base oil is used instead of microcapsule powder in step S4.

[0061] Comparative Example 2: This comparative example provides a wear-resistant and antioxidant polyurea lubricant, which differs from Example 1 in that the ionic liquid-modified nanocomposite powder is removed in step S5.

[0062] Comparative Example 3: This comparative example provides a wear-resistant and antioxidant polyurea lubricant. The difference from Example 1 is that in step S5, the nanocomposite powder prepared in step S1 is used instead of the ionic liquid-modified nanocomposite powder.

[0063] The wear-resistant and antioxidant polyurea lubricants prepared in Examples 1-6 and Comparative Examples 1-3 were subjected to performance tests:

[0064] Extreme pressure performance: The extreme pressure performance was determined according to SH / T 0202-1992 "Determination of Extreme Pressure Performance of Lubricating Grease (Four-Ball Test Method)". The test procedure was as follows: The sample was placed in a clean ball box containing three clean steel balls, which were then assembled and placed on a ball seat. Another clean steel ball was mounted on the spindle of the testing instrument. The rotational speed was set to 1770 r / min, the load was set and applied slowly, the motor was started, and the test run lasted 10 seconds. After the test, the wear trace diameters of the three balls were measured, P. B The value represents the maximum non-seize load; the higher the value, the better the lubrication performance.

[0065] Anti-wear performance: The anti-wear performance was determined according to SH / T 0202-1992 "Determination of Extreme Pressure Properties of Lubricating Grease (Four-Ball Test Method)". The test procedure is as follows: Fill the ball box with the sample, embed three clean steel balls into the box and assemble them, placing them on the ball seat. Install another clean steel ball on the spindle of the testing instrument. Set the rotation speed to 1200 r / min, the test force to 392 N, the time to 60 min, and the temperature to 75±2℃. Start the test when the set temperature is reached. After the test, measure the wear trace diameter of the three balls and record the coefficient of friction. The lower the value, the better the lubrication performance.

[0066] Antioxidant performance: The oxidation stability was determined according to SH / T 0325-1992 "Determination of Oxidation Stability of Lubricating Grease". The test procedure is as follows: 4.00±0.01g of sample was placed in each of five dishes, ensuring even distribution, and placed on a dish rack. The dish rack was placed in the oxygen bomb and the bolts were tightened to seal it. Oxygen was introduced until the pressure reached 689kPa, then the oxygen was released to remove internal air. This process was repeated four times until the oxygen pressure reached 593kPa at a temperature of 20-23℃. The oxygen bomb was allowed to stand overnight and checked for leaks. The oxygen bomb was placed in an oil bath at 99±0.5℃. When the pressure rose above 785±14kPa, oxygen was intermittently released until the pressure stabilized at 785±14kPa, and this was maintained for at least 2 hours. The oxygen bomb was then immersed in the oil bath, and the time was started, continuously oxidizing until the product specification time period (100h) was reached.

[0067] The test results are shown in the table below:

[0068] Table 1 Performance Test Overview

[0069] project Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Wear scar diameter (mm) 0.295 0.289 0.291 0.293 0.283 0.292 0.458 0.412 0.385 <![CDATA[P B Value (N) 627 621 624 625 629 619 482 526 553 Minimum coefficient of friction 0.034 0.038 0.031 0.033 0.031 0.032 0.087 0.065 0.052 Oxidation stability (100℃, 100h) Pressure drop (MPa) 0.0045 0.0042 0.0041 0.0047 0.0049 0.0041 0.0148 0.0103 0.0086

[0070] As shown in Table 1, the wear scar diameters of Examples 1-6 are smaller than those of Comparative Examples 1-3, and the maximum non-seize load (P) is smaller. BThe coefficient of friction in Examples 1-6 was higher than that in Comparative Examples 1-3, and the lowest coefficient of friction was lower than that in Comparative Examples 1-3, indicating that the lubrication performance of Examples 1-6 was better. This may be because the microcapsules ruptured during friction, releasing the poly-α-olefin core material to form a dynamic liquid lubricating film that filled the gaps at the friction interface. In the ionic liquid-modified nanocomposite powder, the interlayer slip characteristics of tungsten disulfide, the wear-resistant support of nickel oxide, and the friction-reducing effect of the ionic liquid were superimposed to form a composite lubricating film with physical lubrication, chemical adsorption, and hard phase support, which effectively reduced direct contact between friction surfaces and lowered the wear scar diameter and coefficient of friction. In contrast, Comparative Example 1 used base oil instead of microcapsules, which lacked the dynamic oil release function, and the lubricating film was easily lost. Comparative Example 2 removed the ionic liquid-modified nanocomposite powder, thus losing the multi-dimensional anti-wear synergistic effect. Comparative Example 3 did not use ionic liquid-modified nanocomposite powder, and the nanoparticles were prone to agglomeration, which could not uniformly exert the anti-wear effect, resulting in a decrease in lubrication performance.

[0071] As shown in Table 1, the oxidation stability of Examples 1-6 is higher than that of Comparative Examples 1-3, indicating that Examples 1-6 have better antioxidant performance. This may be because the high thermal stability of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate can inhibit the oxidation reaction, nickel oxide has a catalytic inhibitory effect on the oxidation of polyalphaolefins in the base oil, the sheet structure of graphene oxide can block oxidation diffusion, and the hindered phenolic antioxidant 1010 works synergistically with the above components to further delay the oxidative degradation of the polyurea matrix and polyalphaolefins. In contrast, Comparative Example 1 lacks the protection of the capsule shell, and the base oil is directly exposed and easily oxidized. Comparative Examples 2 and 3 lack the synergistic antioxidant effect of the ionic liquid-modified nanocomposite powder, resulting in significantly worse oxidation stability and a significant increase in pressure drop.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a wear-resistant and antioxidant polyurea lubricant, characterized in that, Includes the following steps: Step 1: Add tungsten disulfide powder, graphene oxide powder, polyvinylpyrrolidone, nickel chloride, and distilled water to a reaction vessel and sonicate for 30-40 min. Add ammonia water (25-28 wt%), hexadecyltrimethylammonium chloride, and KH-550. Stir at 20-25℃ for 2-3 h, and then hydrothermally treat at 100-110℃ for 16-20 h. Centrifuge, filter, wash, and dry to obtain nanocomposite powder. Add the nanocomposite powder and anhydrous ethanol to a reaction vessel and sonicate for 15-20 min. Then add ionic liquid and sonicate for 15-20 min. Apply 10-15 MPa pressure and grind for 5-6 h. Maintain at 80-90℃ for 12-14 h and cool to room temperature to obtain ionic liquid modified nanocomposite powder. Step 2: Using polyα-olefin as the core material and urea and formaldehyde as monomers, polyurea-formaldehyde prepolymer is synthesized. Under the cross-linking action of the cross-linking agent, a shell layer is formed through polycondensation reaction to obtain microcapsule powder. Step 3: Stir and refine the microcapsule powder, organic amine and diisocyanate, and grind them to obtain the polyurea lubricant matrix; mix the polyurea lubricant matrix with the ionic liquid modified nanocomposite powder to obtain the wear-resistant and antioxidant polyurea lubricant; The ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate.

2. The method for preparing a wear-resistant and antioxidant polyurea lubricant according to claim 1, characterized in that, The ratio of the nanocomposite powder, anhydrous ethanol, and ionic liquid is 0.5-1.0g: 30-40mL: 0.8-1.2g.

3. The method for preparing a wear-resistant and antioxidant polyurea lubricant according to claim 1, characterized in that, The ratio of tungsten disulfide powder, graphene oxide powder, polyvinylpyrrolidone, nickel chloride, distilled water, ammonia, cetyltrimethylammonium chloride, and KH-550 is 0.5-1.0g: 0.02-0.04g: 0.05-0.09g: 0.24-0.34g: 50-60mL: 0.2-0.4mL: 0.1-0.2g: 0.1-0.2g.

4. The method for preparing a wear-resistant and antioxidant polyurea lubricant according to claim 1, characterized in that, The preparation process of the microcapsule powder in step two is as follows: Urea, resorcinol, a 40wt% glyoxal aqueous solution, ammonium chloride, a 0.2wt% sodium lignosulfonate, and deionized water were added to a reaction vessel and stirred at 500-700 rpm for 10-15 min. Poly-α-olefin was added, and homogenized and sheared emulsified for 5-7 min to obtain a stable oil-in-water emulsion. The mixture was stirred at 350-450 rpm for 5-7 min, and n-octanol was added dropwise. A 37wt% formaldehyde aqueous solution was added, and the pH was adjusted to 3-4 with 1 mol / L hydrochloric acid. The temperature was slowly increased to 35-40℃ and held for 30-40 min. Then, the temperature was increased to 60-65℃ at a rate of 1℃ / min and held for 3-4 h. The mixture was then vacuum filtered, washed, and dried to obtain microcapsule powder.

5. The method for preparing a wear-resistant and antioxidant polyurea lubricant according to claim 4, characterized in that, The ratio of the amounts of urea, resorcinol, glyoxal aqueous solution, ammonium chloride, sodium lignosulfonate, deionized water, polyalphaolefin, n-octanol, and formaldehyde aqueous solution is 25-35g: 1.2-2.2g: 5-8g: 2.5-4.5g: 2-4g: 150-200mL: 75-95g: 0.8-1.0mL: 50-70g.

6. The method for preparing a wear-resistant and antioxidant polyurea lubricant according to claim 1, characterized in that, The preparation process of the polyurea lubricant matrix in step three is as follows: Microcapsule powder is added to a reaction vessel and heated to 80-85℃. Then, organic amine and diisocyanate are added and reacted at 300-500 r / min for 40-60 min. The temperature is then raised to 100-120℃, distilled water is added, and the temperature is maintained for 20-30 min. The temperature is then raised to 180-190℃ and stirred for 15-45 min. After stirring and refining, the mixture is cooled to room temperature and ground three times with a three-roll mill to obtain the polyurea lubricant matrix.

7. The method for preparing a wear-resistant and antioxidant polyurea lubricant according to claim 6, characterized in that, The ratio of the microcapsule powder, organic amine, and diisocyanate is 100-150g: 6-8g: 25-35g; The organic amine is one of octadecylamine and cyclohexylamine; The diisocyanate is one of hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate.

8. The method for preparing a wear-resistant and antioxidant polyurea lubricant according to claim 1, characterized in that, The preparation process of the wear-resistant and antioxidant polyurea lubricant described in step three is as follows: The polyurea lubricant matrix and acetone solution were added to a reaction vessel, followed by the addition of ionic liquid-modified nanocomposite powder and hindered phenolic antioxidant 1010. The mixture was sonicated for 2-3 hours, and the acetone was removed under conditions of 80-85℃ and 500-700r / min to obtain a wear-resistant and antioxidant polyurea lubricant. The ratio of the polyurea lubricant matrix, acetone solution, ionic liquid-modified nanocomposite powder, and hindered phenolic antioxidant 1010 is 50-70g: 15-25mL: 0.5-1.0g: 0.1-0.2g.