Extremely-low-viscosity electric vehicle gear oil composition and preparation method thereof

Abstract

The invention belongs to the technical field of lubricating oil preparation, and particularly relates to an extremely-low-viscosity electric vehicle gear oil composition and a preparation method thereof. The lubricating oil comprises the following raw materials in percentage by mass: 0.3%-0.5% of a pour point depressant, 0.2%-1% of a viscosity index improver, 2.0%-3.5% of a dispersing agent, 2.0%-2.5% of an antioxidant, 0.1%-0.5% of a metal deactivator, 0.1%-0.5% of a friction improver, 0.5%-1.5% of an anti-wear reagent at extreme pressure and the balance of base oil, the electric vehicle gear oil composition further comprises an anti-foaming agent, and the concentration of the anti-foaming agent in the electric vehicle gear oil composition is 100-200 ppm. The composition disclosed by the invention has excellent gear shaft protection capability, cooling and heat dissipation performance, insulating performance, good low-temperature performance and the like, meanwhile, has a relatively low friction coefficient, and can effectively improve the transmission efficiency of an electric drive system.

Description

Technical Field

[0001] This invention belongs to the field of lubricant preparation technology, specifically relating to an ultra-low viscosity electric vehicle gear oil composition and its preparation method. Background Technology

[0002] While my country's economy and technology are developing rapidly, we must also place greater emphasis on promoting environmentally friendly, energy-saving, and low-carbon new energy development. New energy vehicles are becoming a global trend in the automotive industry. Jointly promoting the development of new energy will help my country's environmental protection, energy conservation, and emission reduction efforts reach a new level.

[0003] New energy vehicles can be categorized based on their power source, including: pure electric vehicles, fuel cell vehicles, hybrid electric vehicles, hydrogen fuel cell vehicles, solar-powered vehicles, natural gas vehicles, and biofuel vehicles. The electric drive systems of pure electric vehicles can be further divided into: central drive systems, wheel-side drive systems, and hub drive systems. In a central drive system, the electric motor is located at the center of the vehicle, transmitting power to the drive wheels through a transmission system. The most common structures include electric drive reduction gearboxes and electric drive axles. The performance requirements for the fluid used in electric drive reduction gearboxes differ from those of traditional transmission fluids due to the integrated motor and the inherent differences in the gearbox itself. These differences manifest in higher demands on gear shaft protection, improved cooling and heat dissipation capabilities, enhanced anti-foaming properties, increased compatibility between the fluid and motor materials, and higher transmission efficiency.

[0004] Chinese invention patent publication number CN105670747A discloses a gear oil composed of the following raw materials in parts by weight: 93-95 parts base oil, 0.5-2.5 parts amine antioxidant, 4-6 parts extreme pressure anti-wear agent, 0.1-0.5 parts metal passivator, and 0.05-0.15 parts antifoaming agent. However, the antioxidant capacity and copper corrosion inhibition performance of the gear oil in this invention need to be further improved.

[0005] Chinese invention patent publication number CN111073744A discloses a high-temperature transmission gear oil for electric vehicles that prevents leakage and dissipates electrical current, and its preparation method. The composition and viscosity index improvers are as follows: blended base oil 70.35%-98.12%; free radical terminator 0.02-5.0%; friction improver oiliness agent 0.08-5%; metal deactivator 0.02-0.8%; high-temperature antioxidant 0.05-1.5%; dispersant 1-5%; pour point depressant 0.5-3.5%; anti-wear agent 0.2-8.8%; and antifoaming agent 0.01-0.05%. This invention's high-temperature transmission gear oil composition for electric vehicles exhibits excellent high-temperature antioxidant properties, a significantly longer oxidation induction period than various domestic and international gear oil products, and superior insulation properties.

[0006] Previously, the most commonly used oil for electric drive gearboxes by domestic new energy vehicle manufacturers was 5.2 cst oil. However, many OEMs, in order to improve vehicle transmission efficiency, hoped that oil manufacturers could develop 3.0 cst oil. According to verification by some OEMs, the decrease in oil viscosity does indeed help to further improve the transmission efficiency of vehicle electric drive systems. To adapt to market changes and demands, through the screening of base oil and viscosity index improver formulations, research on new structural single agents, and research on additive compounding technology, it is necessary to develop a high-performance, ultra-low viscosity electric drive gearbox oil and successfully pass relevant simulation and bench tests. Summary of the Invention

[0007] To address the current demand from some OEMs for ultra-low viscosity electric vehicle gear oils, this invention provides an ultra-low viscosity electric vehicle gear oil composition and its preparation method. This composition exhibits excellent gear shaft protection, cooling and heat dissipation performance, insulation properties, and good low-temperature performance, while also possessing a low coefficient of friction, effectively improving the transmission efficiency of electric drive systems.

[0008] To achieve the above-mentioned objectives of this invention, the specific technical solution adopted by this invention is as follows:

[0009] An ultra-low viscosity electric vehicle gear oil composition, by mass percentage, comprises the following raw materials: 0.3%-0.5% pour point depressant, 0.2%-1% viscosity index improver, 2.0%-3.5% dispersant, 2.0%-2.5% antioxidant, 0.1%-0.5% metal deactivator, 0.1%-0.5% friction modifier, 0.5%-1.5% extreme pressure anti-wear agent, and the balance being base oil; the raw materials also include an antifoaming agent, the concentration of which in the electric vehicle gear oil composition is 100-200 ppm.

[0010] Preferably, the base oil is a mixture of API Group II base oil and ester oil, or a mixture of PAO base oil and ester oil.

[0011] More preferably, the mass ratio of API Group II base oil to ester oil, or the mass ratio of PAO base oil to ester oil, is 65-70:20-25.

[0012] Preferably, the antioxidant is a mixture of alkylated phenyl α-naphthylamine and dinonyldiphenylamine, wherein the mass ratio of alkylated phenyl α-naphthylamine to dinonyldiphenylamine is 1:0.8-1.2.

[0013] Preferably, the metal deactivator is a dialkyl-1-(2-benzothiazolyl)-2-propane-phosphonate, with the following structure:

[0014]

[0015] Preferably, the friction modifier is a nitroborate, and the extreme pressure anti-wear agent is an aliphatic phosphate ester.

[0016] Preferably, the extreme pressure anti-wear agent is a mixture of aliphatic phosphate ester and zinc borobutylthiocarbamate.

[0017] More preferably, the mass ratio of the aliphatic phosphate ester to zinc borobutylthiocarbamate is 1:1-1.5.

[0018] Preferably, the pour point depressant is Viscoplex 1-300.

[0019] Preferably, the viscosity index improver is Viscoplex 12-095.

[0020] Preferably, the dispersant is a high molecular weight succinimide.

[0021] Preferably, the antifoaming agent is FOAM BAN 257 or FOAM BAN 204.

[0022] This invention also relates to a method for preparing the above-mentioned ultra-low viscosity electric vehicle gear oil composition, comprising the following steps:

[0023] (1) Mix antioxidant, metal deactivator, extreme pressure anti-wear agent, friction modifier and dispersant, heat and stir to obtain composite agent a;

[0024] (2) Mix the viscosity index improver, pour point depressant and base oil, heat and stir, add antifoaming agent to obtain mother liquor b;

[0025] (3) Mix the composite agent a and the mother liquor b, heat and stir to obtain the ultra-low viscosity electric vehicle gear oil composition.

[0026] Preferably, the stirring temperature in step (1) is 50℃-55℃ and the stirring time is 0.8-1.2h.

[0027] Preferably, the stirring temperature in steps (2) and (3) is 55℃-60℃ and the stirring time is 1.5-2.5h.

[0028] Preferably, the antifoaming agent in step (2) is added in two batches.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The present invention uses a dispersible polymethyl methacrylate viscosity index improver to ensure that the oil has excellent shear resistance and can effectively resist the phenomenon of oil viscosity dropping too fast under high-speed bearing conditions.

[0031] (2) The extreme pressure anti-wear agent selected in this invention has a synergistic effect with the other two, and is supplemented with a certain amount of ester oil, so that the oil has excellent extreme pressure anti-wear properties, anti-pitting properties, and excellent load-bearing capacity. The preferred mass ratio of the two is 2:3.

[0032] (3) The carefully selected antioxidant and metal deactivator of this invention not only improve the copper corrosion inhibition performance of the oil, but also effectively improve the oxidation resistance of the oil, without affecting its extreme pressure anti-wear performance. The recommended mass ratio of the two is about 4:1.

[0033] (4) Through reasonable single-agent screening and compounding, this invention ensures that the oil has excellent electrochemical performance, including good volume resistivity and breakdown voltage; the ratio of different types of base oils makes the oil have stable and excellent cooling performance, providing sufficient lubrication protection for gears and high-speed bearings while ensuring the safe and reliable operation of the motor, and further improving the vehicle transmission efficiency. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to specific embodiments. The following embodiments are not intended to limit the present invention, but only to illustrate the present invention. Unless otherwise specified, the experimental methods used in the following embodiments are generally performed under conventional conditions. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available.

[0035] The metal deactivating agent used in this invention, dialkyl-1-(2-benzothiazolyl)-2-propane-phosphonate, is synthesized via the following method and route:

[0036] (1) Ethyl acetoacetate (1.35 g, 0.01 mol) and o-aminothiophenol (1.25 g, 0.01 mol) were added to 20 mL of toluene and mixed to dissolve. The solution was added to an oil bath and reacted at 120 °C for 30 minutes. Then the reaction solution was cooled to room temperature, ethanol was added to precipitate the solid product, and the solid was filtered and collected to obtain (1-(benzothiazolyl-2-yl)propane-2-one);

[0037]

[0038] (2) Cool a mixture of 5 mL methanol and 5 mL diethyl ether to 0 °C, then add the ketone compound (5 mmol) obtained in step (1), stir to dissolve, add NaBH4 (0.3 g, 10 mmol), react for 30 minutes, quench the reaction with saturated NH4Cl solution, and extract with diethyl or dichloromethane (3 × 5 mL). Combine the extracts and dry with anhydrous Na2SO4. Filter to remove the drying agent, and rotary evaporate the filtrate to obtain an alcohol compound, yielding 1-(benzothiazolyl-2-yl)propane-2-ol;

[0039]

[0040] (3) 20 mL of dichloromethane was cooled to 0 °C, and then 4.14 g (15.8 mmol) of triphenylphosphine was added to obtain solution 1; then 2.53 g (15.8 mmol) of liquid bromine was added to 7 mL of dichloromethane, and the resulting liquid was added dropwise to solution 1, which immediately formed a white solid. After reacting at room temperature for 30 minutes, 8 mL of dichloromethane solution containing 13.6 mmol of 1-(benzothiazol-2-yl)propane-2-ol was added dropwise under ice bath conditions, and then reacted at room temperature for 1 hour. The solvent was removed by rotary evaporation, and the residue was washed several times with cyclohexane to obtain the solid product 1-(benzothiazol-2-yl)propane-2-bromine;

[0041]

[0042] (4) Add magnesium shavings (18 mmol) to 20 mL of dry tetrahydrofuran to obtain solution 2; then add bromide (15 mmol) to 5 mL of dry tetrahydrofuran, and add this solution dropwise to solution 2. Heat the resulting reaction solution at 50 °C to allow the reaction to occur, and stir the reaction for 2 hours. Subsequently, dissolve triethoxyphosphine (15 mmol) in 5 mL of tetrahydrofuran and add it dropwise to the reaction solution, and continue the reaction for 3 hours. Quench the resulting reaction solution with an appropriate amount of water, then extract with dichloromethane, dry with anhydrous Na2SO4, filter to remove the desiccant, and rotary evaporate the filtrate to obtain the metal deactivating agent.

[0043]

[0044] Example 1

[0045] An ultra-low viscosity electric vehicle gear oil composition, with raw materials listed in Table 1 based on viscosity index improver.

[0046] Table 1 Raw materials and viscosity index improvers

[0047]

[0048]

[0049] The preparation method of the ultra-low viscosity electric vehicle oil is as follows:

[0050] (1) Mix the dispersant, antioxidant, metal deactivator, extreme pressure anti-wear agent and friction modifier, heat to 52℃ and stir for 1 hour to obtain composite agent a;

[0051] (2) Mix the viscosity index improver, pour point depressant and base oil in proportion, heat to 56°C and stir for 2 hours. During this period, add the antifoaming agent in two batches according to the amount added to obtain mother liquor b.

[0052] (3) Mix the composite agent a and the mother liquor b, heat to 56°C and stir for 2 hours to obtain the final product.

[0053] Example 2

[0054] An ultra-low viscosity electric vehicle gear oil composition, with raw materials listed in Table 2 based on viscosity index improver.

[0055] Table 2 Raw materials and viscosity index improvers

[0056]

[0057]

[0058] The preparation method of the ultra-low viscosity electric vehicle oil is as follows:

[0059] (1) Mix the dispersant, antioxidant, metal deactivator, extreme pressure anti-wear agent and friction modifier, heat to 50°C and stir for 1 hour to obtain composite agent a;

[0060] (2) Mix the viscosity index improver, pour point depressant and base oil in proportion, heat to 55°C and stir for 2 hours. During this period, add the antifoaming agent in two batches according to the amount added to obtain mother liquor b.

[0061] (3) Mix the composite agent a and the mother liquor b, heat to 55°C and stir for 2 hours to obtain the final product.

[0062] Example 3

[0063] An ultra-low viscosity electric vehicle gear oil composition, with raw materials listed in Table 3 based on viscosity index improver.

[0064] Table 3 Raw materials and viscosity index improvers

[0065]

[0066] The preparation method of the ultra-low viscosity electric vehicle oil is as follows:

[0067] (1) Mix dispersant, antioxidant, metal deactivator, extreme pressure anti-wear agent and friction modifier, heat to 55℃ and stir for 1 hour to obtain composite agent a;

[0068] (2) Mix the viscosity index improver, pour point depressant and base oil in proportion, heat to 60°C and stir for 2 hours. During this period, add the antifoaming agent in two batches according to the amount added to obtain mother liquor b.

[0069] (3) Mix the composite agent a and the mother liquor b, heat to 60°C and stir for 2 hours to obtain the final product.

[0070] Comparative Example 1

[0071] The only difference between this comparative example and Example 1 is that it contains different metal deactivators. The specific raw materials and their amounts are shown in Table 4.

[0072] Table 4 Raw materials and viscosity index improvers

[0073]

[0074] Comparative Example 2

[0075] The only difference between this comparative example and Example 2 is that it contains different metal deactivators. Specific raw materials and amounts are shown in Table 5.

[0076] Table 5 Raw materials and viscosity index improvers

[0077]

[0078]

[0079] Comparative Example 3

[0080] The only difference between this comparative example and Example 3 is that it does not contain ester oils. Specific raw materials and their amounts are shown in Table 6.

[0081] Table 6 Raw materials and viscosity index improvers

[0082]

[0083] Comparative Example 4

[0084] The only difference between this comparative example and Example 1 is that the extreme pressure anti-wear agent is only an aliphatic phosphate ester, and the addition amount is 1.5%.

[0085] Table 7 Raw Materials and Viscosity Index Improvers

[0086]

[0087]

[0088] Comparative Example 5

[0089] The only difference between this comparative example and Example 1 is that the extreme pressure anti-wear agent is only zinc borobutylthiocarbamate, with an addition amount of 1.5%.

[0090] Table 8 Raw Materials and Viscosity Index Improvers

[0091]

[0092] Effect test

[0093] The main performance test results of the above embodiments and comparative products are shown in Table 9.

[0094] Table 9 Detection Data

[0095]

[0096]

[0097]

[0098] Table 9 shows that the ultra-low viscosity electric vehicle oils obtained in Examples 1-3 have good low-temperature Brinell viscosity and pour point, indicating good low-temperature performance. The 192-hour shear data shows good shear resistance, maintaining good viscosity under high-speed bearing operating conditions. Both short-cycle and long-cycle copper strip corrosion tests indicate good copper corrosion inhibition. High-speed FZG and FE8 bearing wear tests show excellent stability, indicating good mechanical properties. The DKA oxidation stability test at 170℃ shows a good antioxidant system. Breakdown voltage and volume resistivity data show excellent insulation properties throughout the formulation, ensuring safe motor operation. Thermal conductivity and specific heat capacity data indicate stable heat dissipation capabilities.

[0099] Comparative Examples 1 and 2 both contain different metal deactivators. Compared with Examples 1 and 2, in the formulation without the metal deactivator dialkyl-1-(2-benzothiazolyl)-2-propane-phosphonate, short-cycle copper corrosion still achieves a good level, but long-cycle copper corrosion is relatively poor. This indicates that dialkyl-1-(2-benzothiazolyl)-2-propane-phosphonate plays a very important role in inhibiting copper corrosion in this invention. Since there are copper wire windings in the motor, and the oil is immersed in the windings for a long time, the oil must have good copper corrosion inhibition performance to ensure the safe and reliable operation of the motor.

[0100] The difference between Comparative Example 3 and Example 3 is that it does not contain ester oil. As can be seen from the low-temperature data, the oil without ester oil has poor low-temperature performance. At the same time, since ester oil also has a certain anti-wear effect, Comparative Example 3 performed weaker in the high-speed FZG test and the FE8 bearing wear worsened. This will affect the protection of the bearing and gears by the oil during long-term operation of the equipment.

[0101] In Comparative Examples 4 and 5, only one extreme pressure anti-wear agent was used. Compared with other examples, the mechanical properties of the oil were obviously worse, the load-bearing capacity of FZG was only level 5, and the wear of FE8 bearing was also greater.

[0102] In summary, the ultra-low viscosity electric vehicle gear oil composition of this invention possesses excellent antioxidant properties, providing sufficient technical support for achieving long oil change intervals. Simultaneously, the oil exhibits good insulation and cooling properties, directly addressing the performance requirements of oil-cooled motors. Excellent load-bearing capacity and bearing wear data ensure that the oil provides effective and long-lasting lubrication protection for the gear shafts during equipment operation.

[0103] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

Claims

1. A very low viscosity electric vehicle gear oil composition, characterized in that, The raw materials of the electric vehicle gear oil composition, by weight percentage, include: 0.3%-0.5% pour point depressant, 0.2%-1% viscosity index improver, 2.0%-3.5% dispersant, 2.0%-2.5% antioxidant, 0.1%-0.5% metal deactivator, 0.1%-0.5% friction improver, 0.5%-1.5% extreme pressure anti-wear agent, and the balance being base oil; the raw materials also include an antifoaming agent, the concentration of which in the electric vehicle gear oil composition is 100-200 ppm.

2. The ultra-low viscosity electric vehicle gear oil composition according to claim 1, characterized in that, The base oil is a mixture of API Group II base oil and ester oil, or a mixture of PAO base oil and ester oil.

3. The ultra-low viscosity electric vehicle gear oil composition according to claim 2, characterized in that, The mass ratio of API Group II base oil to ester oil, or the mass ratio of PAO base oil to ester oil, is 65-70:20-25.

4. The ultra-low viscosity electric vehicle gear oil composition according to claim 1, characterized in that, The antioxidant is a mixture of alkylated phenyl α-naphthylamine and dinonyldiphenylamine, wherein the mass ratio of alkylated phenyl α-naphthylamine to dinonyldiphenylamine is 1:0.8-1.

2.

5. The ultra-low viscosity electric vehicle gear oil composition according to claim 1, characterized in that, The metal deactivator is a dialkyl-1-(2-benzothiazolyl)-2-propane-phosphonate, with the following structure:

6. The ultra-low viscosity electric vehicle gear oil composition according to claim 1, characterized in that, The friction modifier is a nitrogen borate ester, and the extreme pressure anti-wear agent is an aliphatic phosphate ester.

7. The ultra-low viscosity electric vehicle gear oil composition according to claim 1, characterized in that, The extreme pressure anti-wear agent is a mixture of aliphatic phosphate ester and zinc borobutylthiocarbamate.

8. The ultra-low viscosity electric vehicle gear oil composition according to claim 7, characterized in that, The mass ratio of the aliphatic phosphate ester to zinc borobutylthiocarbamate is 1:1-1.

5.

9. The ultra-low viscosity electric vehicle gear oil composition according to claim 1, characterized in that, The pour point depressant is Viscoplex 1-300.

10. The ultra-low viscosity electric vehicle gear oil composition according to claim 1, characterized in that, The viscosity index improver is Viscoplex 12-095.

11. The ultra-low viscosity electric vehicle gear oil composition according to claim 1, characterized in that, The dispersant is a high molecular weight succinimide.

12. The ultra-low viscosity electric vehicle gear oil composition according to claim 1, characterized in that, The antifoaming agent is either FOAM BAN 257 or FOAM BAN 204.

13. A method for preparing the ultra-low viscosity electric vehicle gear oil composition according to any one of claims 1-12, characterized in that, Includes the following steps: (1) Mix antioxidant, metal deactivator, extreme pressure anti-wear agent, friction modifier and dispersant, heat and stir to obtain composite agent a; (2) Mix the viscosity index improver, pour point depressant and base oil, heat and stir, add antifoaming agent to obtain mother liquor b; (3) Mix the composite agent a and the mother liquor b, heat and stir to obtain the ultra-low viscosity electric vehicle gear oil composition.

14. The preparation method according to claim 13, characterized in that, The stirring temperature in step (1) is 50℃-55℃, and the stirring time is 0.8-1.2h.

15. The preparation method according to claim 13, characterized in that, The stirring temperature in steps (2) and (3) is 55℃-60℃ and the stirring time is 1.5-2.5h.

16. The preparation method according to claim 13, characterized in that, In step (2), the antifoaming agent is added in two batches.

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