High-temperature-resistant antioxidant lubricating oil as well as preparation method and application thereof

Abstract

The invention belongs to the field of automobile lubricating oil, and discloses high-temperature-resistant antioxidant lubricating oil as well as a preparation method and application thereof. The lubricating oil is prepared from poly-alpha-olefin synthetic oil, pentaerythritol diester, a composite antioxidant, oleic acid modified nano zirconium oxide, molybdenum dithiocarbamate, high-molecular-weight polymethacrylate, an ashless dispersant, a high-temperature oxidation and corrosion inhibitor and an auxiliary additive according to a specific ratio. The preparation method comprises the key steps of base oil preheating, additive step-by-step dispersion, high-speed shearing, thermalization treatment, homogeneous filtration and the like. Through the synergistic effect of the composite antioxidant system and the modified nano material and in combination with a refined preparation process, the thermal oxidation stability, the wear resistance and the high-temperature cleanliness of the lubricating oil are remarkably improved. The product is especially suitable for a modern high-performance turbocharged gasoline engine, can effectively solve the problems of oil product oxidation, viscosity increase and part wear under high-load and high-temperature working conditions, and prolongs the service life and oil change period of the engine.

Description

Technical Field

[0001] This invention belongs to the field of automotive lubricants, and specifically discloses a high-temperature resistant and oxidation-resistant lubricant, its preparation method, and its application. Background Technology

[0002] As the "blood" of an engine, lubricating oil's performance directly determines the engine's reliability, efficiency, and service life. With the automotive industry's technological advancements towards high performance, miniaturization, and turbocharging (TGDI), modern gasoline engines are operating under increasingly demanding conditions. The thermal load and oxidative pressure on their internal lubricating oil films are rising dramatically, posing unprecedented challenges to the high-temperature resistance and oxidation resistance of lubricating oils.

[0003] However, existing commercial engine lubricants, especially those for high-performance gasoline engines, still have significant technical shortcomings when dealing with these extreme conditions: First, the thermal stability of the base oil and additive system is insufficient, making it prone to thermal decomposition and oxidative deterioration at sustained high temperatures, leading to abnormal viscosity increases, elevated acid values, and the formation of harmful deposits such as varnish and carbon deposits, which exacerbate engine wear and operating resistance; second, traditional antioxidant systems (such as single phenols or amines) have limited durability under high temperature and pressure, and their antioxidant efficacy decays rapidly, failing to provide full protection for modern long oil change intervals; third, some additive components introduced to solve high-temperature problems lack synergistic effects and may even antagonize each other, resulting in overall performance falling short of expectations, or undergoing phase separation and precipitation during long-term storage and use, affecting product stability.

[0004] The limitations of current technical solutions are prominently manifested in the following ways: First, the molecular structure of commonly used mineral base oils or simple synthetic oils has poor thermal stability, resulting in large evaporation losses at high temperatures, making it difficult to form a durable and effective lubricating film in ultra-high temperature parts such as turbocharger bearings; Second, new materials such as nano anti-wear agents, due to their high surface energy, are prone to agglomeration and sedimentation in oil, and the problem of dispersion stability has not been completely solved, which not only affects their effectiveness but may also clog oil filters; Third, excessive addition of additives to improve a certain performance (such as detergency and dispersibility) often sacrifices other properties of the oil, such as sealing compatibility or fuel economy, making it difficult to achieve a balanced formulation.

[0005] Furthermore, existing lubricant manufacturing processes often employ simple sequential mixing and stirring, making it difficult to ensure that nanoscale functional additives achieve the ideal dispersion state, thus failing to fully realize their anti-wear, thermal conductivity, and micro-repair potential. Conventional filtration precision also cannot effectively remove potential submicron-sized gel particles, raising questions about the long-term stability of the product. Therefore, the market urgently needs a fully synthetic lubricant specifically designed for high-performance gasoline engines, possessing excellent high-temperature stability, long-lasting oxidation resistance, superior anti-wear performance, and good stability, coupled with a refined manufacturing process that ensures its perfect performance. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, this invention discloses a high-temperature resistant and oxidation-resistant lubricating oil, its preparation method, and its application.

[0007] This invention includes the following technical solutions: A high-temperature resistant and oxidation-resistant lubricating oil, comprising the following raw materials by weight: Polyalphaolefin synthetic oil (PAO 6) 50-70 parts; 20-30 parts of pentaerythritol diester; 1-2 parts of diisooctyldiphenylamine; 0.5-1.5 parts of 2,6-di-tert-butyl-p-cresol; Oleic acid modified nano-zirconia 1-4 parts; 0.5-2 parts of molybdenum dithiocarbamate; High molecular weight polymethyl methacrylate (PMA) 3-8 parts; Polyisobutylene succinimide (T154) 1-3 parts; Alkylated diphenylamine (L57) 0.5-1.5 parts; 0.01-0.1 parts of polydimethylsiloxane; 0.2-0.8 parts of polymethyl methacrylate pour point depressant.

[0008] Furthermore, in the aforementioned high-temperature resistant and oxidation-resistant lubricating oil, the mass ratio of the polyalphaolefin synthetic oil (PAO 6) to pentaerythritol diester is (65-70):(25-30).

[0009] Furthermore, in the aforementioned high-temperature resistant and oxidation-resistant lubricating oil, the oleic acid-modified nano-zirconia has a particle size of 20-35 nm, and it is added to the lubricating oil by pre-preparing it with a portion of pentaerythritol diester to form a stable nano-slurry with a concentration of 20-30 wt%.

[0010] Furthermore, the aforementioned high-temperature resistant and oxidation-resistant lubricating oil has a high-temperature high-shear (HTHS) viscosity of not less than 3.5 mPa•s at 150°C; a temperature at which it loses 5% of its mass, as determined by thermogravimetric analysis (TGA), is not less than 345°C; and an oxidation induction period of not less than 180 minutes, as determined by the rotating oxygen bomb test (ASTM D2270).

[0011] This invention also discloses a method for preparing the above-mentioned high-temperature resistant and oxidation-resistant lubricating oil, comprising the following steps: (1) Base oil preheating and initial dispersion: Poly-α-olefin synthetic oil and pentaerythritol diester were added to the reactor and heated to 60±2℃. The mixture was stirred at 400-600 r / min for 10 minutes. Then, polyisobutylene succinimide, polymethacrylate pour point depressant and high molecular weight polymethacrylate were added in sequence. The temperature was raised to 70±2℃ and the speed was increased to 800-1000 r / min. The mixture was stirred for 60 minutes until it was completely dissolved and dispersed. (2) Antioxidant system addition and reaction: After the system is homogeneous, add diisooctyl diphenylamine, 2,6-di-tert-butyl-p-cresol and alkylated diphenylamine in sequence, maintain the temperature at 70-75℃ and stir at 1000 r / min for 30 minutes. (3) High-temperature shear dispersion: Add molybdenum dithiocarbamate and pre-prepared oleic acid modified nano-zirconia concentrated slurry, raise the system temperature to 85±2℃, switch to high-speed shear machine, and perform high-speed shear dispersion at a speed of 5000-6000 r / min for 90 minutes. (4) Blending and stabilization: Reduce the system temperature to below 60°C, add polydimethylsiloxane defoamer, switch to conventional stirring, and stir at a speed of 300-400 r / min for 30 minutes; (5) Post-processing: Cool the lubricating oil to room temperature (25℃), transfer it to a homogenizer, homogenize and circulate it twice under a pressure of 40-50MPa, and finally filter it through a filter bag with an absolute precision of 5μm to obtain a clear and transparent finished lubricating oil.

[0012] Furthermore, in the above preparation method, the high-speed shear dispersion in step (3) adopts a pipeline high-shear emulsifier, and the material is circulated between the reaction vessel and the emulsifier, with the number of circulations not less than 10.

[0013] Furthermore, in the above preparation method, step (3) includes a thermal treatment step after high-speed shear dispersion: the material is transferred into a sealed container and aged at a low speed of 50-100 r / min for 4-6 hours under nitrogen protection at 100-110℃, and then naturally cooled to the starting temperature of step (4).

[0014] Furthermore, in the above preparation method, the homogenization process described in step (5) is carried out under the protection of an inert gas.

[0015] The present invention also discloses the application of the above-mentioned high-temperature resistant and oxidation-resistant lubricating oil, characterized in that it is used for lubrication of high-performance gasoline direct injection (TGDI) engines equipped with turbochargers.

[0016] Furthermore, in the above applications, the lubricant is suitable for engines that meet API SP or ACEA C6 and above specifications, and is particularly used for lubricating turbocharger bearings and piston ring-cylinder liner friction pairs.

[0017] Compared with the prior art, the present invention has the following outstanding advantages: I. High-temperature antioxidant performance: Through the scientific compounding of amine and phenolic antioxidants, a highly efficient synergistic antioxidant system is formed, which can also produce a synergistic effect with nanomaterials, greatly slowing down the oxidation rate of base oil at high temperatures and effectively inhibiting the formation of harmful deposits such as paint film and carbon deposits.

[0018] II. Extreme Pressure Anti-wear Protection: By utilizing the synergistic effect of surface-modified nano-zirconia and organic molybdenum compounds, a strong protective film can be formed on the surface of the friction pair, which has both physical filling and chemical friction improvement effects, significantly reducing the wear of key components (such as turbocharger bearings and cam-tapoles).

[0019] III. High-Temperature Viscosity Stability: The unique preparation process ensures the full dispersion and stabilization of polymer and nano-additives, making them less prone to degradation or cross-linking under long-term high-temperature and high-shear conditions. The viscosity change rate is extremely low, ensuring the reliability of lubrication throughout the entire cycle.

[0020] IV. Balanced Overall Performance: The components have good compatibility. While highlighting the main properties of high-temperature oxidation resistance and wear resistance, the product also takes into account its dispersibility, detergency, and low-temperature flowability. The overall performance is comprehensive and meets the high-level specifications such as API SP. Attached Figure Description

[0021] Figure 1 Comparative test results of high-temperature oxidation induction period (OIT); Figure 2 Heat pipe deposit test results; heat pipe rating (grade). Figure 3 Heat pipe deposit test results: Deposit weight (mg); Figure 4 Four-ball wear test results: Comparison of wear scar diameter WSD (mm). Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The preparation method of oleic acid modified nano-zirconia concentrated slurry in the examples is as follows: 1) Pretreatment: 10 parts by weight of nano-zirconia powder (particle size 20-35 nm, specific surface area ≥50 m² / g) were vacuum dried at 120℃ for 2 hours to remove physically adsorbed water on the surface.

[0024] 2) Dispersion: The dried nano-zirconia powder was slowly added to 35 parts by weight of anhydrous ethanol and pre-dispersed for 30 minutes using a high-speed shear disperser (rotation speed 8000-10000 r / min) to obtain a preliminary suspension.

[0025] 3) Modification reaction: The above suspension was transferred to a three-necked flask equipped with a reflux condenser. Under continuous mechanical stirring (500 r / min), 2.5 parts by weight of oleic acid (chemically pure or higher) were added. The system temperature was raised to 75±5℃, and the reaction was maintained at this temperature at a constant rate for 4 hours. The carboxyl groups (-COOH) of the oleic acid molecules underwent an esterification reaction with the hydroxyl groups (-OH) on the surface of the nano-zirconia, thereby forming an organic coating layer on its surface.

[0026] 4) Washing and centrifugation: After the reaction is complete, cool the mixture to room temperature, transfer it to a high-speed centrifuge, and centrifuge at 10,000 r / min for 15 minutes. Discard the supernatant. Wash the precipitate with anhydrous ethanol by centrifugation several times (usually 3-4 times) until the washing solution is neutral to remove unreacted excess oleic acid.

[0027] 5) Preparation of slurry: Mix the washed modified nano-zirconia precipitate with 40 parts by weight of pentaerythritol diester (as carrier oil), and grind and disperse it for 2 hours using a basket mill or sand mill (such as Drais Perl Mill PML-H / V) under circulating water cooling until the fineness of the slurry reaches grade 7 or above of the Hegmann fineness meter, and finally obtain a stable and uniform oleic acid modified nano-zirconia concentrated slurry with a solid content of 25wt%.

[0028] 6) Storage: Seal and store the prepared concentrated slurry in a dark place for later use.

[0029] Example 1 A high-temperature resistant and oxidation-resistant lubricating oil, the preparation steps of which are as follows: (1) Raw material preparation: Weigh each component according to the following weight parts: 65 parts of poly-α-olefin synthetic oil (PAO 6), 25 parts of pentaerythritol diester, 1.5 parts of diisooctyl diphenylamine, 1.0 part of 2,6-di-tert-butyl-p-cresol, 2 parts of pre-prepared oleic acid modified nano-zirconia concentrated slurry (equivalent to 2 parts of pure nano-zirconia), 1.0 part of molybdenum dithiocarbamate, 5 parts of high molecular weight polymethyl methacrylate (PMA), 2 parts of polyisobutylene succinimide (T154), 1.0 part of alkylated diphenylamine (L57), 0.05 parts of polydimethylsiloxane, and 0.5 parts of polymethyl methacrylate pour point depressant.

[0030] (2) Base oil preheating and initial dispersion: PAO 6 base oil and pentaerythritol diester were added to a reactor equipped with a heating mantle, stirrer and thermometer. Stirring was started (500 r / min), and the temperature was raised to 60°C and maintained for 10 minutes. Then, T154 dispersant, pour point depressant and PMA viscosity index improver were added slowly in sequence. The temperature was raised to 70°C, the speed was increased to 900 r / min, and stirring was continued for 60 minutes until all additives were completely dissolved and the system was uniform and transparent.

[0031] (3) Antioxidant system addition and reaction: Keep the temperature at 72℃, add diisooctyl diphenylamine, 2,6-di-tert-butyl-p-cresol and L57 high temperature antioxidant in sequence, and stir at 1000 r / min for 30 minutes to allow the antioxidant to be fully mixed and pre-reacted.

[0032] (4) High-temperature shear dispersion: Molybdenum dithiocarbamate and oleic acid modified nano-zirconia concentrated slurry were added. The temperature was raised to 85℃ and switched to an inline high-shear emulsifier (brand: Silverson, model: L5M-A) at a speed of 5500 r / min for high-speed shear dispersion. At the same time, the material was circulated between the reactor and the emulsifier for 15 cycles, taking 90 minutes.

[0033] (5) Heat treatment: Transfer the material into a sealed aging tank with nitrogen protection, heat it to 105°C, and stir at a low speed of 80 r / min for 5 hours.

[0034] (6) Blending and stabilization: Cool the material to 60°C, add polydimethylsiloxane defoamer, switch to conventional anchor stirring, and stir at 350 r / min for 30 minutes.

[0035] (7) Post-processing: Cool the lubricating oil to room temperature (25°C), transfer it to a homogenizer (brand: GEA, model: NS2006L), homogenize and circulate it twice under a pressure of 45MPa, and finally filter it through a filter bag with an absolute precision of 5μm to obtain the finished lubricating oil.

[0036] Example 2 A high-temperature resistant and oxidation-resistant lubricating oil, the preparation steps of which are as follows: (1) Raw material preparation: Weigh each component according to the following weight parts: 60 parts of poly-α-olefin synthetic oil (PAO 6), 28 parts of pentaerythritol diester, 1.2 parts of diisooctyl diphenylamine, 0.8 parts of 2,6-di-tert-butyl-p-cresol, oleic acid modified nano-zirconia concentrated slurry (equivalent to 3 parts of pure nano-zirconia), 1.5 parts of molybdenum dithiocarbamate, 6 parts of high molecular weight polymethyl methacrylate (PMA), 1.5 parts of polyisobutylene succinimide (T154), 0.8 parts of alkylated diphenylamine (L57), 0.03 parts of polydimethylsiloxane, and 0.6 parts of polymethyl methacrylate pour point depressant.

[0037] (2) Base oil preheating and initial dispersion: The operation is the same as in Example 1, the temperature is set to 62℃, the stirring speed is 450 r / min, and after adding the additive, it is stirred at 68℃ and 850 r / min for 50 minutes.

[0038] (3) Antioxidant system addition and reaction: The operation is the same as in Example 1, with a temperature of 70℃, a rotation speed of 950 r / min, and a time of 25 minutes.

[0039] (4) High-temperature shear dispersion: The operation is the same as in Example 1, with a shear temperature of 83°C, a rotation speed of 5000 r / min, 12 cycles, and a time of 80 minutes.

[0040] (5) Heat treatment: The aging temperature is 100℃ and the aging time is 4 hours.

[0041] (6) Blending and stabilization: The operation is the same as in Example 1.

[0042] (7) Post-treatment: The homogenization pressure is 40 MPa, and the filtration accuracy is the same as in Example 1.

[0043] Example 3 A high-temperature resistant and oxidation-resistant lubricating oil, the preparation steps of which are as follows: (1) Raw material preparation: Weigh each component according to the following weight parts: 70 parts of poly-α-olefin synthetic oil (PAO 6), 22 parts of pentaerythritol diester, 1.8 parts of diisooctyl diphenylamine, 1.2 parts of 2,6-di-tert-butyl-p-cresol, oleic acid modified nano-zirconia concentrated slurry (equivalent to 1.5 parts of pure nano-zirconia), 0.8 parts of molybdenum dithiocarbamate, 7 parts of high molecular weight polymethyl methacrylate (PMA), 2.5 parts of polyisobutylene succinimide (T154), 1.2 parts of alkylated diphenylamine (L57), 0.08 parts of polydimethylsiloxane, and 0.3 parts of polymethyl methacrylate pour point depressant.

[0044] (2) Base oil preheating and initial dispersion: The operation is the same as in Example 1, the temperature is set to 58℃, the stirring speed is 550 r / min, and after adding the additive, it is stirred at 72℃ and 1000 r / min for 70 minutes.

[0045] (3) Antioxidant system addition and reaction: The operation is the same as in Example 1, with a temperature of 75℃, a rotation speed of 1050 r / min, and a time of 35 minutes.

[0046] (4) High-temperature shear dispersion: The operation is the same as in Example 1, with a shear temperature of 87°C, a rotation speed of 6000 r / min, 18 cycles, and a time of 100 minutes.

[0047] (5) Heat treatment: The aging temperature is 108℃ and the aging time is 6 hours.

[0048] (6) Blending and stabilization: The operation is the same as in Example 1.

[0049] (7) Post-treatment: The homogenization pressure is 50 MPa, and the filtration accuracy is the same as in Example 1.

[0050] Comparative Example 1 A lubricating oil, the raw materials, equipment and steps of which are basically the same as those in Example 2, the only difference being: Nanomaterials and thermal treatment are omitted. Oleic acid-modified nano-zirconia concentrated slurry is not added, and after high-speed shear dispersion in step (4), step (5) thermal treatment is skipped directly, and cooling and subsequent steps are performed.

[0051] Comparative Example 2 A lubricating oil, the raw materials, equipment and steps of which are basically the same as those in Example 2, the only difference being: Modify the antioxidant system. Replace all of the compound antioxidants (diisooctyl diphenylamine + 2,6-di-tert-butyl-p-cresol) and alkylated diphenylamine (L57) with an equal amount of the single antioxidant 2,6-di-tert-butyl-p-cresol.

[0052] Comparative Example 3 A lubricating oil, the raw materials, equipment and steps of which are basically the same as those in Example 2, the only difference being: The preparation process is simplified. The high-speed shear dispersion in step (4) and the thermal treatment in step (5) are omitted. After step (3), the molybdenum dithiocarbamate and nano-slurry are mixed by stirring with a regular stirrer (1000 r / min) for 30 minutes, and then directly cooled and filtered.

[0053] Comparative Example 4 A lubricating oil, the raw materials, equipment and steps of which are basically the same as those in Example 2, the only difference being: Use unmodified nanomaterials. Replace the oleic acid-modified nano-zirconia concentrate with an equal amount of unmodified nano-zirconia powder of the same specifications.

[0054] Comparative Example 5 Commercially available fully synthetic engine oils were selected, with API SP grade 5W-30 fully synthetic lubricant chosen as the comparison.

[0055] Test Example 1 High-temperature oxidative stability test (PDSC method) Objective: To verify the synergistic antioxidant effect brought about by the compatibility of the composite antioxidant system of the present invention with the base oil, and to evaluate the oxidation induction period of the lubricating oil at high temperature.

[0056] method: Sample preparation: Take the lubricating oil samples prepared in Example 2 and Comparative Examples 1-5.

[0057] Test conditions: A pressure differential scanning calorimeter (PDSC, model: TA Instruments Q20P) was used. 1.0 ± 0.1 mg of sample was accurately weighed into an aluminum sample crucible. Oxygen was introduced at a flow rate of 100 mL / min under an oxygen atmosphere (pressure 3.5 MPa). The test temperature was set to 210℃. The time from the start of heating to the occurrence of intense exothermic oxidation (oxidation peak) was recorded; this was the oxidation induction period (OIT, unit: minutes).

[0058] Data processing: Each sample was tested in parallel three times, and the mean ± standard deviation (SD) was taken.

[0059] The results are shown in Table 2 and Figure 1 .

[0060] Conclusion: Example 2 exhibited the longest oxidation induction period (185.2 min), demonstrating significantly superior antioxidant performance compared to the comparative examples (P<0.01). Comparative Example 2 (single antioxidant) showed the worst performance, highlighting the crucial synergistic effect of the amine-phenol composite antioxidant system. Comparative Example 1 (without nanomaterials and thermal processing) and Comparative Example 3 (simplified process) showed significantly shorter OIT, indicating the necessity of the catalytic antioxidant effect of nanomaterials and the high-speed shearing and thermal processing for additive stabilization and synergistic effect. The complete formulation and refined preparation process of this invention jointly ensure the lubricating oil's excellent long-term high-temperature antioxidant capacity.

[0061] Test Example 2 Test of high-temperature deposit formation trend (heat pipe test method) Objective: To evaluate the thermal oxidation stability and cleaning properties of lubricating oil on high-temperature metal surfaces, and to simulate the formation of carbon deposits and varnish in high-temperature areas such as piston ring grooves.

[0062] method: Sample preparation: Take the lubricating oil samples from Example 2, Comparative Example 2 (single antioxidant) and Comparative Example 5 (commercially available product).

[0063] Test conditions: Refer to the enterprise standard (or JIS K2514). Circulate the lubricating oil sample in an aluminum metal tube at a constant temperature (300℃) for a certain period of time (6 hours). After completion, remove the metal tube and allow it to cool to room temperature.

[0064] Rating: The deposits (paint film) formed on the inner wall of the metal pipe are rated by comparing them with a standard color chart using an optical rating instrument. The rating standard is 0-10, with higher grades indicating less deposits and better cleanliness. The weight of the deposits (mg) is also measured.

[0065] The results are shown in Table 3 and Figure 2-3 .

[0066] Conclusion: Example 2 showed the highest heat pipe rating (9.5) and the least amount of deposit formation (12.5 mg), significantly better than Comparative Examples 2 and 5 (P<0.01). This indicates that the composite antioxidant in the lubricating oil of this invention can effectively inhibit oxidative polymerization reactions at high temperatures, and the nanoparticles may play a role in dispersing nascent deposits, thereby keeping the high-temperature components of the engine clean and effectively preventing piston ring sticking and varnish formation.

[0067] Test Example 3 Wear resistance test (four-ball test method) Objective: To verify the synergistic anti-wear and friction-reducing effects of modified nano-anti-wear agents and organic molybdenum compounds under extreme pressure conditions.

[0068] method: Sample preparation: Take lubricating oil samples from Example 2, Comparative Example 1 (without nanomaterials) and Comparative Example 4 (without modified nanomaterials).

[0069] Test conditions: A four-ball wear tester (model: MS-10J) was used. The test conditions were: temperature 75℃, rotation speed 1200 rpm, load 392 N (40 kgf), and duration 60 minutes. After the test, the wear scar diameter (WSD, unit: mm) of the three fixed steel balls was measured using an optical microscope.

[0070] Data processing: Each sample was tested 3 times.

[0071] The results are shown in Table 4 and Figure 4 .

[0072] Conclusion: Example 2 exhibited the smallest wear scar diameter (0.36 mm) and the best wear resistance. Comparative Example 1, lacking all nano-anti-wear components, showed the worst wear resistance. Comparative Example 4, using unmodified nano-zirconia, showed better wear resistance than Comparative Example 1, but was still significantly worse than Example 2 (P<0.05). This demonstrates that oleic acid surface modification is crucial for preventing nanoparticle aggregation, promoting stable dispersion in base oils, and fully utilizing their filling and ball bearing anti-wear effects. This invention maximizes the synergistic effect of additives through material modification and refined preparation processes.

[0073] Test Example 4 High Temperature High Shear (HTHS) Viscosity Stability Test Objective: To evaluate the viscosity retention capacity of lubricating oil under high-temperature and high-shear conditions in engines (such as turbocharger bearings and piston ring-cylinder liner areas), which is a key indicator affecting fuel economy and lubrication reliability.

[0074] method: Sample preparation: Take the lubricating oil samples from Example 2 and Comparative Example 3 (simplified process).

[0075] Test conditions: Following ASTM D4683 standard, a high-temperature, high-shear viscometer (Tapered Bearing Simulator) was used. The test temperature was 150℃, and the shear rate was 10^6 s^-1. The dynamic viscosity (HTHS viscosity, unit: mPa·s) of the sample was measured under these conditions.

[0076] Aging test: The above samples were placed in an oven at 180°C and continuously bubbled with air for 72 hours of forced aging. After aging, their HTHS viscosity was measured again.

[0077] Calculation: Calculate the rate of change in HTHS viscosity before and after aging.

[0078] The results are shown in Table 5.

[0079] Conclusion: After rigorous aging, Example 2 showed only a slight increase in HTHS viscosity (3.5%), demonstrating excellent viscosity stability. In contrast, Comparative Example 3 (simplified process) showed a viscosity increase as high as 16.4%, indicating that its polymer (viscosity index improver PMA) underwent significant degradation and cross-linking under high-temperature shear and oxidation, leading to an abnormally high viscosity. This proves that the high-speed shear dispersion and thermal treatment process used in this invention can effectively stabilize the additive system, prevent performance degradation during long-term use, and ensure that the oil provides stable and reliable lubrication protection throughout the entire oil change cycle.

[0080] Test case Simulated turbocharger bearing bench test Objective: To simulate the ultra-high temperature and high speed operating conditions of turbocharger bearings and comprehensively evaluate the overall performance of lubricating oil in this critical component.

[0081] method: Sample preparation: Take the lubricating oil samples from Example 2 and Comparative Example 5 (commercially available products).

[0082] Test bench: A turbocharger was used to simulate the test bench. The lubricating oil to be tested was heated to 150°C and circulated.

[0083] Test cycle: Drive the turbine shaft at 180,000 rpm, stop and cool to room temperature every 2 hours, check and record the status, for a total of 5 cycles (10 hours).

[0084] Testing indicators: Bearing weight loss (mg): After the test, the weight loss of the floating bearing is precisely measured.

[0085] Sludge Deposition Rating: After disassembly, the sludge and varnish deposits on the bearing housing and thrust surface are rated (1-10 points, the higher the score, the cleaner the surface) by comparing them with standard pictures.

[0086] Final HTHS viscosity (150℃): Measured by taking an oil sample after the test.

[0087] The results are shown in Table 6.

[0088] Conclusion: In tests simulating extreme turbocharger operating conditions, the lubricant of this invention (Example 2) demonstrated comprehensive advantages. Its excellent oxidation and wear resistance resulted in lower bearing wear, better high-temperature cleanliness (high deposit score), and minimal viscosity change. In contrast, Comparative Example 5 (commercially available product) exhibited greater bearing wear, more deposits, and a significant increase in viscosity. This test fully demonstrates that the lubricant of this invention can provide superior protection for the most demanding component of modern high-performance gasoline engines—the turbocharger—effectively extending its service life.

[0089] Test Case Summary: Quantitative data from the above series of test cases demonstrate that the lubricant of this invention exhibits performance comprehensively superior to the comparative examples and commercially available products: High-Temperature Oxidation Resistance: The PDSC test (210℃) showed an oxidation induction period of 185.2 minutes, 47.7% longer than Comparative Example 2 (single antioxidant) and 19.5% longer than Comparative Example 5 (commercially available product). High-Temperature Cleanliness: The heat pipe test (300℃, 6h) achieved a rating of 9.5, with a deposit weight of only 12.5 mg, significantly lower than Comparative Example 2 (48.3 mg) and Comparative Example 5 (35.8 mg). Wear Resistance: The four-ball wear test showed a wear scar diameter as low as 0.36 mm, a 26.5% reduction compared to Comparative Example 1 (without nanomaterials, 0.49 mm) and a 20.0% reduction compared to Comparative Example 4 (unmodified nanomaterials, 0.45 mm). Viscosity stability: After 72 hours of forced aging at 180℃, its HTHS viscosity change rate at 150℃ was only +3.5%, while the change rate of the simplified process in Comparative Example 3 was as high as +16.4%. Turbocharger simulation test: The bearing weight loss was only 15.2mg, significantly lower than the 38.7mg of commercially available products.

Claims

1. A high-temperature resistant antioxidant lubricating oil, characterized by, The raw materials include, by weight fraction: Poly-alpha-olefin synthetic oil (PAO 6) 50-70 parts; Pentaerythritol diester 20-30 parts; Diisooctyl diphenylamine 1-2 parts; 2,6-di-tert-butyl-p-cresol 0.5-1.5 parts; Oleic acid modified nano zirconium oxide 1-4 parts; Molybdenum dithiocarbamate 0.5-2 parts; High molecular weight polymethacrylate (PMA) 3-8 parts; Polyisobutylene succinimide (T154) 1-3 parts; Alkylated diphenylamine (L57) 0.5-1.5 parts; Polydimethylsiloxane 0.01-0.1 parts; Poly-methacrylate pour point depressant 0.2-0.8 parts.

2. The high temperature resistant and oxidation stable lubricating oil as claimed in claim 1, wherein: The mass ratio of the poly-alpha-olefin synthetic oil (PAO 6) to the pentaerythritol diester is (65-70):(25-30).

3. The high temperature resistant and oxidation stable lubricating oil of claim 1, wherein: The particle size of the oleic acid modified nano zirconium oxide is 20-35 nm, and it is added to the lubricating oil in the form of a stable nano slurry with a concentration of 20-30wt% prepared in advance.

4. The high temperature oxidation resistant lubricating oil of claim 1, wherein: Its high temperature high shear (HTHS) viscosity at 150℃ is not less than 3.5 mPa•s; its temperature at 5% mass loss is not less than 345℃ by thermogravimetric analysis (TGA); and its oxidation induction period is not less than 180 minutes by rotary oxygen bomb test (ASTM D2270).

5. The method of claim 1 to 4, wherein the high-temperature oxidation resistant lubricating oil is prepared by adding the antioxidant to the base oil. 5 The method comprises the following steps: (1) Preheating and initial dispersion of base oil: poly-alpha-olefin synthetic oil and pentaerythritol diester are put into a reaction kettle, heated to 60±2℃, and stirred and mixed at a speed of 400-600 r / min for 10 minutes; then polyisobutylene succinimide, poly-methacrylate pour point depressant, and high molecular weight polymethacrylate are added in sequence, the temperature is raised to 70±2℃, the speed is increased to 800-1000 r / min, and stirring is performed for 60 minutes until complete dissolution and dispersion; (2) Addition and reaction of antioxidant system: after the system is uniform, diisooctyl diphenylamine, 2,6-di-tert-butyl-p-cresol, and alkylated diphenylamine are added in sequence, the temperature is maintained at 70-75℃, and stirring is performed at a speed of 1000 r / min for 30 minutes; (3) High temperature shear dispersion: molybdenum dithiocarbamate and pre-prepared oleic acid modified nano zirconium oxide concentrated slurry are added, the temperature of the system is raised to 85±2℃, a high speed shear machine is switched in, high speed shear dispersion is performed at a speed of 5000-6000 r / min for 90 minutes; (4) Blending and stabilization: the temperature of the system is reduced to below 60℃, polydimethylsiloxane defoaming agent is added, a conventional stirrer is switched in, and stirring is performed at a speed of 300-400 r / min for 30 minutes; (5) Post-treatment: the lubricating oil is cooled to room temperature (25℃), transferred to a homogenizer, homogenized for 2 cycles under a pressure of 40-50 MPa, and finally filtered through a filter bag with an absolute precision of 5μm to obtain clear and transparent finished lubricating oil.

6. The method of claim 4, wherein: The high speed shear dispersion in step (3) uses a pipeline type high shear emulsifier, and the material is circulated between the reaction kettle and the emulsifier for not less than 10 times.

7. The method of claim 4, wherein: In step (3), after high-speed shearing dispersion, a heat treatment step is further included: the material is transferred into a closed container, and under the protection of nitrogen, low-speed stirring is carried out at a speed of 50-100 r / min for 4-6 hours, and then natural cooling is carried out to the starting temperature of step (4).

8. The method of claim 4, wherein: The homogenization process in step (5) is carried out under the protection of inert gas.

9. Use of the high-temperature resistant antioxidant lubricating oil according to any one of claims 1 to 4, characterized in that: Lubrication for high-performance gasoline direct injection (TGDI) engines equipped with turbochargers.

10. Use according to claim 9, characterized in that: The lubricating oil is suitable for engines meeting API SP or ACEA C6 and above specification standards, and is particularly used for lubricating turbocharger bearings and piston ring-cylinder liner friction pairs. The application relates to a lubricating oil composition for high-performance gasoline direct injection (TGDI) engines equipped with a turbocharger. The lubricating oil composition is suitable for engines meeting API SP or ACEA C6 and above specification standards, and is particularly used for lubricating turbocharger bearings and piston ring-cylinder liner friction pairs.

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