A friction-reducing lubricating oil suitable for minimal lubrication and preparation method thereof

Abstract

The invention discloses a friction-reducing lubricating oil suitable for minimal lubrication and a preparation method thereof, belonging to the technical field of lubricating oils. Molybdenum disulfide is first nucleated and grown on the surface of porous cerium oxide nanosphere powder to form a cerium oxide molybdenum disulfide composite. Modified silicon dioxide and tannic acid are then prepolymerized to form silicon dioxide prepolymer powder. Composite temperature-sensitive microcapsules are obtained using the cerium oxide molybdenum disulfide composite as a core material and the silicon dioxide prepolymer powder and N-isopropylacrylamide polymer as a shell. The composite temperature-sensitive microcapsules are then mixed with other raw materials to prepare the composite temperature-sensitive microcapsules. During a cutting operation, frictional heat between a tool and a workpiece causes the temperature to rise, causing the polymer chains of the outer shell of the composite temperature-sensitive microcapsules in the friction-reducing lubricating oil to shrink, thereby releasing the cerium oxide molybdenum disulfide composite inside. The controllable release of the internal core material is achieved by utilizing the temperature sensitivity of the composite temperature-sensitive microcapsule shell polymer and changes in external temperature during operation.

Description

Technical Field

[0001] The invention belongs to the technical field of lubricating oils, and in particular relates to a friction-reducing lubricating oil suitable for minimal lubrication and a preparation method thereof. Background Art

[0002] Minimum quantity lubrication (MQL) technology has seen rapid development in recent years in the fields of high-speed machining and energy conservation and environmental protection. Its core principle is to achieve efficient lubrication with a small amount of lubricant, thereby reducing environmental impact and improving machining efficiency. The core principle is to mix compressed gas with a very small amount of lubricating oil to form micron-sized droplets or a suspended oil mist. This is then sprayed at high speed onto the cutting area to achieve lubrication, cooling, and chip removal. For example, research has shown that the addition of stearic acid to a base oil creates de-wettability, allowing the micro-lubricant to be distributed in droplet form, thereby enhancing lubrication efficiency.

[0003] The Chinese invention patent application with publication number CN109810761B discloses a degradable trace lubricant and its preparation method, which has good extreme pressure and anti-wear properties, rust resistance, and good biodegradability. It can fully or partially replace traditional extreme pressure anti-wear agents containing chlorine, sulfur, and phosphorus in the degradable trace lubricant. A small amount of degradable trace lubricant can meet the lubrication and cooling, extreme pressure and anti-wear, and rust prevention requirements of metal processing.

[0004] Micro-lubricants have problems with insufficient oil film strength and poor extreme pressure capability. Especially during cutting operations, the friction between the tool and the workpiece will generate a large amount of frictional heat. At the same time, the pressure will increase when the tool face contacts the cutting surface. Under high temperature and high pressure conditions, the oil film of the anti-friction lubricant is more likely to break, and the friction surface cannot be effectively isolated, resulting in direct contact between metal micro-protrusions, exacerbating wear. Summary of the Invention

[0005] The object of the present invention is to provide a friction-reducing lubricant suitable for minimal lubrication and a preparation method thereof. Molybdenum disulfide is generated on the surface of porous cerium oxide nanosphere powder to obtain a cerium oxide molybdenum disulfide composite. Modified silicon dioxide powder containing amino groups, tannic acid, and N-isopropylacrylamide are polymerized to form a shell. Composite temperature-sensitive microcapsules are prepared using the cerium oxide molybdenum disulfide composite as a core material. The composite temperature-sensitive microcapsules are then mixed with other raw materials to prepare the anti-friction lubricant. The problem that the oil film is easily broken and the lubrication effect cannot be achieved under high temperature and high pressure conditions is solved, and the composite temperature-sensitive microcapsules release the core material for lubrication under high temperature and high pressure conditions.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing a friction-reducing lubricating oil suitable for minimal lubrication comprises the following steps:

[0008] Step 1: Using ammonium molybdate tetrahydrate as a molybdenum source and thiourea as a sulfur source, molybdenum disulfide is generated on the surface of porous cerium oxide nanosphere powder to obtain a cerium oxide molybdenum disulfide composite.

[0009] Step 2: Grafting a silane coupling agent containing amino groups onto the surface of silica powder to obtain modified silica powder, and then polymerizing the modified silica powder and tannic acid to obtain silica prepolymer powder.

[0010] Step 3: Using the cerium oxide molybdenum disulfide composite as the core material, silica prepolymer powder and N-isopropylacrylamide are polymerized to form a shell to obtain a composite thermosensitive microcapsule, and then elaeistolic acid, octyldodecanol, phosphorus pentasulfide, ammonium phosphomolybdate, triethanolamine, castor oil maleate and the composite thermosensitive microcapsule are mixed to prepare a friction-reducing lubricant suitable for minimal lubrication.

[0011] Furthermore, porous cerium oxide nanosphere powder is prepared by the following steps:

[0012] Cerium nitrate hexahydrate powder, deionized water, propionic acid and ethylene glycol are added to a reactor, reacted for 3-4 hours at 180-190° C., a pressure of 45-50 MPa and a rotation speed of 500-800 r / min, cooled to room temperature, filtered, washed and dried to obtain porous cerium oxide nanosphere powder.

[0013] Furthermore, the usage ratio of cerium nitrate hexahydrate powder, deionized water, propionic acid and ethylene glycol is 20-30 g: 20-35 mL: 20-30 mL: 400-450 mL.

[0014] Furthermore, the cerium oxide molybdenum disulfide composite is prepared by the following steps:

[0015] Add ammonium molybdate tetrahydrate, thiourea, polyvinyl pyrrolidone and deionized water into a reaction kettle and mix them evenly. Then add porous cerium oxide nanosphere powder and keep the reaction at 180°C and 500-800 r / min for 16-18 hours. Cool to room temperature, filter, wash and dry to obtain a cerium oxide molybdenum disulfide complex.

[0016] Furthermore, the usage ratio of ammonium molybdate tetrahydrate, thiourea, polyvinyl pyrrolidone, deionized water and porous cerium oxide nanosphere powder is 25-30g: 50-60g: 100-150g: 2.5-3.5L: 15-20g.

[0017] Further, the silica prepolymer powder is prepared by the following steps:

[0018] Add modified silica powder and a 0.5 mol / L tannic acid aqueous solution into a reactor, perform ultrasonic dispersion for 15-20 minutes, adjust the pH value to 8-9 with sodium hydroxide, react for 6 hours at 50-60°C and 300-500 r / min, filter, wash, and freeze-dry to obtain silica prepolymer powder.

[0019] Furthermore, the usage ratio of the modified silicon dioxide powder and the tannic acid aqueous solution is 0.5-1 g: 50-60 mL.

[0020] Furthermore, the composite thermosensitive microcapsules are prepared by the following steps:

[0021] The cerium oxide molybdenum disulfide complex and a 0.08 mol / L N-isopropylacrylamide solution were mixed evenly and then transferred to a high-gravity rotating packed bed. A 0.368 mol / L ammonium persulfate aqueous solution was added in a nitrogen atmosphere and reacted for 10-15 minutes. Silica prepolymer powder was added and reacted for 2-3 hours. The mixture was rapidly cooled, filtered, washed, and freeze-dried to obtain composite thermosensitive microcapsules.

[0022] Furthermore, the usage ratio of the cerium oxide molybdenum disulfide composite, the N-isopropylacrylamide solution, the ammonium persulfate aqueous solution and the silicon dioxide prepolymer powder is 5-6 g: 4.9-5 L: 50-60 mL: 0.5-1 g.

[0023] Furthermore, the mass ratio of elaeisolic acid, octyldodecanol, phosphorus pentasulfide, ammonium phosphomolybdate, triethanolamine, castor oil maleate and composite thermosensitive microcapsule is 10-12:8-9:0.5-0.6:1.5-2:1-1.5:80-90:20-30.

[0024] Beneficial effects of the present invention:

[0025] 1. The friction-reducing lubricant suitable for minimal lubrication in the present invention is prepared by first nucleating and growing molybdenum disulfide on the surface of porous cerium oxide nanosphere powder to form a cerium oxide-molybdenum disulfide composite. Modified silica and tannic acid are then prepolymerized to form a silica prepolymer powder. Composite thermosensitive microcapsules are then prepared using the cerium oxide-molybdenum disulfide composite as a core material and the silica prepolymer powder and N-isopropylacrylamide polymer as a shell. The microcapsules are then mixed with other raw materials to form composite thermosensitive microcapsules. During cutting, frictional heat between the tool and the workpiece causes the temperature to rise, causing the polymer chains of the outer shell of the composite thermosensitive microcapsules in the friction-reducing lubricant to contract, releasing the cerium oxide-molybdenum disulfide composite within. This controlled release of the core material is achieved by utilizing the temperature sensitivity of the composite thermosensitive microcapsule shell polymer and changes in the external temperature during cutting. Simultaneously, the high pressure generated on the friction surface during cutting accelerates the outflow of the core material. The cerium oxide-molybdenum disulfide composite forms a continuous lubricating film when rubbing against the metal surface, isolating the metals from direct contact, and providing excellent lubrication under high temperature and high pressure conditions.

[0026] 2. The cerium oxide molybdenum disulfide composite of the present invention is prepared by first using hexahydrate cerium nitrate powder as a cerium source to obtain nano-scale porous cerium oxide nanosphere powder with a positive surface charge, and then hydrolyzing ammonium molybdate tetrahydrate to produce MoO4 2- It carries a negative charge and attracts the positive charge on the surface of the porous cerium oxide nanosphere powder. Then, with thiourea as the sulfur source, under high temperature and high pressure conditions, the molybdenum disulfide generated by the reaction will nucleate and grow on the surface of the porous cerium oxide nanosphere powder to form a cerium oxide molybdenum disulfide complex, which can load a large amount of molybdenum disulfide on the surface of the porous cerium oxide nanosphere. Molybdenum disulfide has a layered structure of sulfur-molybdenum-sulfur. The single layers are connected by weak van der Waals forces, and interlayer slip is very likely to occur, thus showing a good lubrication effect. Cerium oxide can inhibit the oxidation of molybdenum disulfide, which not only improves the lubrication effect but also delays the oxidation time.

[0027] 3. In the present invention, the silica prepolymer powder is first grafted with a silane coupling agent containing an amino group on the surface of nano-scale silica powder. Since the surface of tannic acid is rich in hydroxyl groups, the amino groups and the hydroxyl groups on the surface of tannic acid form a hydrogen bond network, and silica and tannic acid are reacted and polymerized. Then, under the action of an initiator, ammonium persulfate, the silica prepolymer powder and N-isopropylacrylamide are hydrogen-bonded to form a cross-linked network, and the cerium oxide molybdenum disulfide complex is coated inside. The polymer shell formed by the silica prepolymer powder and N-isopropylacrylamide has a higher strength. This is because the high strength of silica itself increases the mechanical strength of the composite thermosensitive microcapsule shell, thereby realizing the dual response function of temperature and pressure. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] Example 1: This example provides a friction-reducing lubricating oil suitable for minimal lubrication, which is prepared by the following steps:

[0030] S1: 20 g of cerium nitrate hexahydrate powder, 20 mL of deionized water, 20 mL of propionic acid, and 400 mL of ethylene glycol were added to a reactor, reacted at 180°C, a pressure of 45 MPa, and a rotation speed of 500 r / min for 3 h, cooled to room temperature, and centrifuged for 10 min. The filter cake was washed three times with deionized water and ethanol, and dried at 80°C to constant weight to obtain porous cerium oxide nanosphere powder.

[0031] S2: 25g of ammonium molybdate tetrahydrate, 50g of thiourea, 100g of polyvinylpyrrolidone and 2.5L of deionized water were added to the reactor and stirred at 300r / min for 1h. Then 15g of porous cerium oxide nanosphere powder was added and ultrasonicated for 15min. The reaction was kept at 180℃ and 500r / min for 16h. The surface of the porous cerium oxide nanosphere powder was positively charged. MoO4 was produced after the hydrolysis of ammonium molybdate tetrahydrate. 2- With negative charge, positive and negative charges attract each other, MoO4 2- It will preferentially bind to the surface of the porous cerium oxide nanosphere powder, and then use thiourea as a sulfur source to make molybdenum disulfide nucleate and grow on the surface of the porous cerium oxide nanosphere powder under high temperature and high pressure conditions. After cooling to room temperature, it is centrifuged at 8000r / min. The filter cake is washed alternately with deionized water and anhydrous ethanol for 3 times, and vacuum dried at 60°C for 12h to obtain a cerium oxide molybdenum disulfide complex.

[0032] S3: Add 10 mL of deionized water, 10 mL of silane coupling agent KH-550 and 130 mL of anhydrous ethanol to the reactor, hydrolyze at 500 r / min for 30 min, then add 15 g of silica powder with a particle size of 10-30 nm, 15 mL of deionized water and 75 mL of anhydrous ethanol, adjust the pH value to 5 with glacial acetic acid, react at 60°C and 500 r / min for 8 h, graft the amino-containing KH-550 onto the silica to form a Si-O-Si bond, cool to room temperature, vacuum filter, wash the filter cake twice with deionized water and anhydrous ethanol respectively, dry at 70°C for 12 h, and grind to obtain modified silica powder.

[0033] S4: 0.5 g of modified silica powder and 50 mL of 0.5 mol / L tannic acid aqueous solution as a cross-linking agent were added to a reactor, ultrasonically dispersed for 15 min, adjusted to pH 8 with sodium hydroxide, and reacted at 50°C and 300 r / min for 6 h. The phenolic hydroxyl groups of tannic acid and the amino groups of modified silica formed a hydrogen bond network. The mixture was centrifuged and filtered. The filter cake was washed with deionized water until it became neutral and freeze-dried to obtain silica prepolymer powder.

[0034] S5: 5g of cerium oxide molybdenum disulfide complex and 4.9L of 0.08mol / L N-isopropylacrylamide solution were added to the reactor and mixed evenly, and then transferred to a high-gravity rotating packed bed. Nitrogen was passed for 30min at 70℃ and 2000r / min to deoxygenate, and then 50mL of 0.368mol / L ammonium persulfate aqueous solution was added and reacted for 10min. 0.5g of silica prepolymer powder was added and reacted for 2h. With tannic acid as an intermediate, silica prepolymer powder and N-isopropylacrylamide formed a cross-linked network on the surface of the cerium oxide molybdenum disulfide complex in the form of hydrogen bonds to form a shell. The cerium oxide molybdenum disulfide complex was wrapped in the shell, quenched in an ice-water bath, centrifuged, washed twice with deionized water, and freeze-dried to obtain composite thermosensitive microcapsules.

[0035] S6: Add 10g of elaioic acid and 8g of octyldodecanol into a reactor, slowly add 0.5g of phosphorus pentasulfide while stirring, react at 130°C and 500r / min for 2h, then add 1.5g of ammonium phosphomolybdate, react for 3h, reduce the pressure to remove moisture and ammonia, add 1g of triethanolamine at 90°C, mix well, cool to room temperature, add 80g of castor oil maleate and 20g of composite temperature-sensitive microcapsules, mix well, and obtain a friction-reducing lubricant suitable for minimal lubrication.

[0036] Example 2: This example provides a friction-reducing lubricating oil suitable for minimal lubrication, which is prepared by the following steps:

[0037] S1: 25 g of cerium nitrate hexahydrate powder, 27 mL of deionized water, 25 mL of propionic acid, and 425 mL of ethylene glycol were added to a reactor. The mixture was reacted at 185°C, a pressure of 47 MPa, and a rotation speed of 650 r / min for 3.5 h. The mixture was cooled to room temperature and centrifuged for 12 min. The filter cake was washed four times with deionized water and ethanol, and dried at 85°C to constant weight to obtain porous cerium oxide nanosphere powder.

[0038] S2: 27.5g of ammonium molybdate tetrahydrate, 55g of thiourea, 125g of polyvinylpyrrolidone and 3L of deionized water were added to the reactor and stirred at 400r / min for 1.25h. Then 17.5g of porous cerium oxide nanosphere powder was added and ultrasonicated for 17.5min. The reaction was kept at 180℃ and 650r / min for 17h. The surface of the porous cerium oxide nanosphere powder was positively charged. MoO4 2- With negative charge, positive and negative charges attract each other, MoO4 2- It will preferentially bind to the surface of the porous cerium oxide nanosphere powder, and then use thiourea as a sulfur source to make molybdenum disulfide nucleate and grow on the surface of the porous cerium oxide nanosphere powder under high temperature and high pressure conditions. After cooling to room temperature, it is centrifuged at 8000r / min. The filter cake is washed alternately with deionized water and anhydrous ethanol for 4 times, and vacuum dried at 70°C for 13h to obtain a cerium oxide molybdenum disulfide complex.

[0039] S3: Add 12.5 mL of deionized water, 12.5 mL of silane coupling agent KH-550 and 140 mL of anhydrous ethanol to the reactor, hydrolyze at 650 r / min for 35 minutes, then add 17.5 g of silica powder with a particle size of 10-30 nm, 17.5 mL of deionized water and 87.5 mL of anhydrous ethanol, adjust the pH value to 5 with glacial acetic acid, react at 70°C and 650 r / min for 10 hours, graft the amino-containing KH-550 onto the silica to form a Si-O-Si bond, cool to room temperature, vacuum filter, wash the filter cake twice with deionized water and anhydrous ethanol respectively, dry at 75°C for 12 hours, and grind to obtain modified silica powder.

[0040] S4: 0.7 g of modified silica powder and 55 mL of 0.5 mol / L tannic acid aqueous solution as a cross-linking agent were added to a reactor, ultrasonically dispersed for 17 minutes, adjusted to pH 8 with sodium hydroxide, and reacted at 55°C and 400 r / min for 6 hours. The phenolic hydroxyl groups of tannic acid and the amino groups of modified silica formed a hydrogen bond network. The mixture was centrifuged and filtered. The filter cake was washed with deionized water until it was neutral and freeze-dried to obtain silica prepolymer powder.

[0041] S5: 5.5 g of cerium oxide molybdenum disulfide complex and 5 L of 0.08 mol / L N-isopropylacrylamide solution were added to the reactor and mixed evenly, then transferred to a high-gravity rotating packed bed, and nitrogen was passed for 30 min at 75°C and 2500 r / min to deoxygenate, and then 55 mL of 0.368 mol / L ammonium persulfate aqueous solution was added and reacted for 12 min. 0.7 g of silica prepolymer powder was added and reacted for 2.5 h. With tannic acid as an intermediate, silica prepolymer powder and N-isopropylacrylamide formed a cross-linked network on the surface of the cerium oxide molybdenum disulfide complex in the form of hydrogen bonds to form a shell. The cerium oxide molybdenum disulfide complex was wrapped in the shell, quenched in an ice-water bath, centrifuged, washed 3 times with deionized water, and freeze-dried to obtain composite thermosensitive microcapsules.

[0042] S6: Add 11 g of elaeistolic acid and 8.5 g of octyldodecanol into a reactor, slowly add 0.55 g of phosphorus pentasulfide while stirring, and react at 135°C and 650 r / min for 2 h. Then add 1.75 g of ammonium phosphomolybdate and react for 3.5 h. Reduce the pressure to remove moisture and ammonia, add 1.25 g of triethanolamine at 95°C, mix well, cool to room temperature, add 85 g of castor oil maleate and 25 g of composite temperature-sensitive microcapsules, mix well, and obtain a friction-reducing lubricant suitable for minimal lubrication.

[0043] Example 3: This example provides a friction-reducing lubricating oil suitable for minimal lubrication, which is prepared by the following steps:

[0044] S1: 30 g of cerium nitrate hexahydrate powder, 35 mL of deionized water, 30 mL of propionic acid, and 450 mL of ethylene glycol were added to a reactor, reacted at 190°C, a pressure of 50 MPa, and a rotation speed of 800 r / min for 4 h, cooled to room temperature, and centrifuged for 15 min. The filter cake was washed five times with deionized water and ethanol, and dried at 90°C to constant weight to obtain porous cerium oxide nanosphere powder.

[0045] S2: 30g of ammonium molybdate tetrahydrate, 60g of thiourea, 150g of polyvinylpyrrolidone and 3.5L of deionized water were added to the reactor and stirred at 500r / min for 1.5h. Then 20g of porous cerium oxide nanosphere powder was added and ultrasonicated for 20min. The reaction was kept at 180℃ and 800r / min for 18h. The surface of the porous cerium oxide nanosphere powder was positively charged. MoO4 2- With negative charge, positive and negative charges attract each other, MoO4 2-It will preferentially bind to the surface of the porous cerium oxide nanosphere powder, and then use thiourea as a sulfur source to make molybdenum disulfide nucleate and grow on the surface of the porous cerium oxide nanosphere powder under high temperature and high pressure conditions. After cooling to room temperature, it is centrifuged at 8000r / min. The filter cake is washed alternately with deionized water and anhydrous ethanol for 5 times, and vacuum dried at 80°C for 14h to obtain a cerium oxide molybdenum disulfide complex.

[0046] S3: Add 15 mL of deionized water, 15 mL of silane coupling agent KH-550 and 150 mL of anhydrous ethanol into the reactor, hydrolyze at 800 r / min for 40 min, then add 20 g of silica powder with a particle size of 10-30 nm, 20 mL of deionized water and 100 mL of anhydrous ethanol, adjust the pH value to 6 with glacial acetic acid, react at 80°C and 800 r / min for 12 h, graft the amino-containing KH-550 onto the silica to form a Si-O-Si bond, cool to room temperature, vacuum filter, wash the filter cake with deionized water and anhydrous ethanol three times respectively, dry at 80°C for 12 h, and grind to obtain modified silica powder.

[0047] S4: 1 g of modified silica powder and 60 mL of 0.5 mol / L tannic acid aqueous solution as a cross-linking agent were added to a reactor, ultrasonically dispersed for 20 min, adjusted to pH 9 with sodium hydroxide, and reacted at 60°C and 500 r / min for 6 h. The phenolic hydroxyl groups of tannic acid and the amino groups of modified silica formed a hydrogen bond network. The mixture was centrifuged and filtered. The filter cake was washed with deionized water until it became neutral and freeze-dried to obtain silica prepolymer powder.

[0048] S5: 6 g of cerium oxide molybdenum disulfide complex and 5.1 L of 0.08 mol / L N-isopropylacrylamide solution were added to the reactor and mixed evenly, then transferred to a high-gravity rotating packed bed, and nitrogen was passed for 30 min at 80°C and 3000 r / min to deoxygenate, and then 60 mL of 0.368 mol / L ammonium persulfate aqueous solution was added and reacted for 15 min. 1 g of silica prepolymer powder was added and reacted for 3 h. With tannic acid as an intermediate, silica prepolymer powder and N-isopropylacrylamide formed a cross-linked network on the surface of the cerium oxide molybdenum disulfide complex in the form of hydrogen bonds to form a shell. The cerium oxide molybdenum disulfide complex was wrapped in the shell, quenched in an ice-water bath, centrifuged, washed 4 times with deionized water, and freeze-dried to obtain composite thermosensitive microcapsules.

[0049] S6: Add 12g of elaioic acid and 9g of octyldodecanol into a reactor, slowly add 0.6g of phosphorus pentasulfide while stirring, react at 140°C and 800r / min for 2h, then add 2g of ammonium phosphomolybdate, react for 4h, reduce the pressure to remove moisture and ammonia, add 1.5g of triethanolamine at 100°C, mix well, cool to room temperature, add 90g of castor oil maleate and 30g of composite temperature-sensitive microcapsules, mix well, and obtain a friction-reducing lubricant suitable for minimal lubrication.

[0050] Comparative Example 1: Based on Example 1, the composite temperature-sensitive microcapsules in step S6 are removed, and the remaining steps remain unchanged to prepare a friction-reducing lubricating oil suitable for minimal lubrication.

[0051] Comparative Example 2: Based on Example 1, tannic acid was used instead of silica prepolymer powder in step S5, and the other steps remained unchanged to prepare a friction-reducing lubricating oil suitable for minimal lubrication.

[0052] Comparative Example 3: Based on Example 1, the cerium oxide molybdenum disulfide composite prepared in step S2 is used in place of the composite temperature-sensitive microcapsules in step S6, and the remaining steps remain unchanged to prepare a friction-reducing lubricating oil suitable for minimal lubrication.

[0053] The anti-friction lubricating oils suitable for minimal lubrication prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests:

[0054] Friction coefficient: Referencing SH / T 0762-2005, Determination of friction coefficient of lubricating oil (four-ball method), the test equipment used was a lever four-ball friction tester manufactured by Jinan Hengke Testing Equipment Co., Ltd. The four test steel balls, upper and lower ball fixtures, and oil cup were soaked in n-heptane for 1 minute. The test was then cleaned in an ultrasonic cleaner for 10 seconds and rinsed repeatedly with acetone. Once the required equipment was clean and dry, three clean test steel balls were installed and lubricating oil was added to cover the tops of the balls by at least 3 mm. The oil cup was installed in the testing machine and a test load of 392 N was slowly applied, avoiding impact. The heater was turned on to heat the test oil to 75 ± 2°C. The motor was then started, rotating the steel balls at 600 rpm for 60 minutes. The test was repeated three times and the average value was calculated.

[0055] Wear resistance: The test was conducted using a lever-type four-ball friction tester manufactured by Jinan Hengke Testing Equipment Co., Ltd., with a load of 392N and a speed of 1200r / min. The test was conducted under these conditions for 60 minutes. After the test, the three fixed balls in the oil box were cleaned with acetone and observed using an optical reading microscope. The average wear spot diameter (WSD) of the three fixed balls was used to determine the wear resistance of the lubricant.

[0056] Oxidation: The anti-friction lubricating oils suitable for minimal lubrication prepared in Examples 1-3 and Comparative Examples 1-3 were placed in an oxidation tube, heated to 95°C in a heating bath, and oxidized by a constant pressure of dry air for 3-12 hours. After oxidation, the samples were removed from the heating bath and cooled to room temperature. The viscosity increase at 100°C and the sedimentation value of the samples before and after oxidation were measured.

[0057] Table 1 Anti-friction lubricant performance test list

[0058]

[0059] As can be seen from Table 1, the friction coefficient and wear spot diameter in Examples 1-3 are the smallest, the friction coefficient and wear spot diameter in Comparative Example 1 are the largest, the friction coefficient and wear spot diameter in Comparative Example 2 are slightly lower than those in Comparative Example 1, and the friction coefficient and wear spot diameter in Comparative Example 3 are lower than those in Comparative Example 2. In step S6 of Comparative Example 1, the composite temperature-sensitive microcapsules are removed, which shows that the anti-friction lubricating oil with the addition of composite temperature-sensitive microcapsules has a good lubricating effect under high temperature and high pressure conditions. In step S5 of Comparative Example 2, tannic acid is used instead of the silica prepolymer powder, and in step S6 of Comparative Example 3, the cerium oxide molybdenum disulfide composite prepared in step S2 is used instead of the composite temperature-sensitive microcapsules, which shows that the cerium oxide molybdenum disulfide composite has an effect of enhancing the lubrication of the anti-friction lubricating oil under high temperature and high pressure conditions, and the addition of silica to the composite temperature-sensitive microcapsules also plays a certain enhancing role.

[0060] The 100°C viscosity growth value and precipitation value in Examples 1-3 are the lowest, and the 100°C viscosity growth value and precipitation value in Comparative Example 1 are the highest. In Comparative Example 1, the composite temperature-sensitive microcapsules are removed in step S6, indicating that the anti-oxidation performance of the anti-friction lubricant with the addition of the composite temperature-sensitive microcapsules is the best. In step S5 of Comparative Example 2, tannic acid is used instead of silica prepolymer powder, and its anti-oxidation performance is reduced, indicating that the silica prepolymer powder plays a certain role in the anti-oxidation of the anti-friction lubricant. In step S6 of Comparative Example 3, the cerium oxide molybdenum disulfide composite prepared in step S2 is used instead of the composite temperature-sensitive microcapsules, indicating that the anti-oxidation performance of the cerium oxide molybdenum disulfide composite without shell coating is reduced, but the anti-oxidation performance is better than that of the lubricant without the addition of the composite temperature-sensitive microcapsules.

[0061] It should be noted that, in this document, terms such as "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0062] While the embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes, modifications, substitutions, and alterations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a friction-reducing lubricating oil suitable for minimal lubrication, characterized in that: The steps include: Step 1: using ammonium molybdate tetrahydrate as a molybdenum source and thiourea as a sulfur source, molybdenum disulfide is generated on the surface of porous cerium oxide nanosphere powder to obtain a cerium oxide molybdenum disulfide composite; Step 2: Grafting a silane coupling agent containing an amino group onto the surface of the silica powder to obtain a modified silica powder, and then polymerizing the modified silica powder with tannic acid to obtain a silica prepolymer powder; Step 3: Using a cerium oxide molybdenum disulfide composite as a core material, silica prepolymer powder and N-isopropylacrylamide are polymerized to form a shell to obtain a composite thermosensitive microcapsule, and then eleostearic acid, octyldodecanol, phosphorus pentasulfide, ammonium phosphomolybdate, triethanolamine, castor oil maleate and the composite thermosensitive microcapsule are mixed to prepare a friction-reducing lubricant suitable for minimal lubrication; The composite thermosensitive microcapsules described in step 3 are prepared specifically by the following steps: The cerium oxide molybdenum disulfide complex and a 0.08 mol / L N-isopropylacrylamide solution were mixed evenly and then transferred to a high-gravity rotating packed bed. A 0.368 mol / L ammonium persulfate aqueous solution was added in a nitrogen atmosphere and reacted for 10-15 minutes. Silica prepolymer powder was added and reacted for 2-3 hours. The mixture was rapidly cooled, filtered, washed, and freeze-dried to obtain composite thermosensitive microcapsules. The silica prepolymer powder is specifically prepared by the following steps: Add modified silica powder and a 0.5 mol / L tannic acid aqueous solution into a reactor, perform ultrasonic dispersion for 15-20 minutes, adjust the pH value to 8-9 with sodium hydroxide, react for 6 hours at 50-60°C and 300-500 r / min, filter, wash, and freeze-dry to obtain silica prepolymer powder.

2. The method for preparing a friction-reducing lubricating oil suitable for minimal lubrication according to claim 1, characterized in that: The porous cerium oxide nanosphere powder in step 1 is prepared specifically by the following steps: Cerium nitrate hexahydrate powder, deionized water, propionic acid and ethylene glycol are added to a reactor, reacted for 3-4 hours at 180-190° C., a pressure of 45-50 MPa and a rotation speed of 500-800 r / min, cooled to room temperature, filtered, washed and dried to obtain porous cerium oxide nanosphere powder.

3. The method for preparing a friction-reducing lubricating oil suitable for minimal lubrication according to claim 2, characterized in that: The usage ratio of the cerium nitrate hexahydrate powder, deionized water, propionic acid and ethylene glycol is 20-30 g: 20-35 mL: 20-30 mL: 400-450 mL.

4. The method for preparing a friction-reducing lubricating oil suitable for minimal lubrication according to claim 1, characterized in that: The cerium oxide molybdenum disulfide composite in step 1 is specifically prepared by the following steps: Add ammonium molybdate tetrahydrate, thiourea, polyvinyl pyrrolidone and deionized water into a reaction kettle and mix them evenly. Then add porous cerium oxide nanosphere powder and keep the reaction at 180°C and 500-800 r / min for 16-18 hours. Cool to room temperature, filter, wash and dry to obtain a cerium oxide molybdenum disulfide complex.

5. The method for preparing a friction-reducing lubricating oil suitable for minimal lubrication according to claim 4, characterized in that: The usage ratio of the ammonium molybdate tetrahydrate, thiourea, polyvinyl pyrrolidone, deionized water and porous cerium oxide nanosphere powder is 25-30g: 50-60g: 100-150g: 2.5-3.5L: 15-20g.

6. The method for preparing a friction-reducing lubricating oil suitable for minimal lubrication according to claim 1, characterized in that: The usage ratio of the modified silicon dioxide powder and the tannic acid aqueous solution is 0.5-1 g: 50-60 mL.

7. The method for preparing a friction-reducing lubricating oil suitable for minimal lubrication according to claim 1, characterized in that: The usage ratio of the cerium oxide molybdenum disulfide composite, N-isopropylacrylamide solution, ammonium persulfate aqueous solution and silicon dioxide prepolymer powder is 5-6g: 4.9-5L:50-60mL:0.5-1g.

8. The method for preparing a friction-reducing lubricating oil suitable for minimal lubrication according to claim 1, characterized in that: The mass ratio of elaeuric acid, octyldodecanol, phosphorus pentasulfide, ammonium phosphomolybdate, triethanolamine, castor oil maleate and composite thermosensitive microcapsule is 10-12:8-9:0.5-0.6:1.5-2:1-1.5:80-90:20-30.

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