Base oil composition and use thereof in preparation of fluid for electric vehicle

Abstract

A base oil composition compounded using a plurality of polyalphaolefins and a fluid for an electric vehicle prepared from the base oil composition. The base oil composition comprises the following components in percentage by mass: 50-90 wt% of a first polyalphaolefin, 1-20 wt% of a second polyalphaolefin, and 5-25 wt% of a third polyalphaolefin; the first polyalphaolefin and the second polyalphaolefin are metallocene polyalphaolefins, and the third polyalphaolefin is a non-metallocene polyalphaolefin; and the three polyalphaolefins have different kinematic viscosities. The fluid for an electric vehicle prepared from the base oil composition is used for a two-in-one or three-in-one electric driving system; the cooling and lubricating effects are achieved by means of direct contact with gears, bearings and / or electrical windings of the electric driving system; and the fluid for an electric vehicle has higher viscosity index, oxidation stability, friction resistance, shearing stability, dielectric strength, and heat transfer effect, and lower evaporation loss.

Description

Base oil composition and its application in preparing electric vehicle fluid Technical Field

[0001] The present invention belongs to the technical field of synthetic lubricating oils, and in particular relates to a base oil compounded with multiple polyalphaolefins, and an electric vehicle fluid prepared using the base oil. Background Art

[0002] With the continuous advancement of drive motor technology for new energy vehicles, drive motors are increasingly moving towards higher torque and power densities. These are closely related to the motor's heat dissipation methods. Efficient heat dissipation can improve the motor's continuous power and torque. Water is an excellent cooling medium for the cooling systems of new energy vehicle drive motors. It has high specific heat and thermal conductivity, is inexpensive, non-toxic, non-combustible, and poses no explosion hazard. However, water-cooling system joints and sealing points can suffer from water pressure leakage, which can cause short circuits, electrical leakage, and insulation burnout, making direct cooling impossible.

[0003] Therefore, electric vehicles currently urgently need direct cooling fluids to improve cooling efficiency. Oil, due to its local non-magnetic, non-flammable, non-conductive, and good thermal conductivity, has no effect on the motor's magnetic circuit and offers higher heat dissipation efficiency. Oil cooling offers advantages over water cooling in terms of excellent insulation properties, a higher boiling point than water, and a lower freezing point, making the coolant less likely to freeze at low temperatures and less likely to boil at high temperatures. Oil-cooled motors are particularly effective for flat-wire windings with larger exposed end areas, actively cooling internal rotor components. They also facilitate integration between the motor and transmission, improving bearing lubrication and cooling, and heating the transmission oil to enhance lubrication and stirring efficiency at low ambient temperatures. From a drive system perspective, oil-cooled motors offer certain technical advantages over water cooling, and oil cooling has become the mainstream development direction for electric vehicles.

[0004] Electric vehicles typically include one or more electric motors, powered by a controlled three-phase AC power supply. Current mainstream electric vehicle designs utilize a two-in-one electric drive system, integrating a motor and a reducer, or a three-in-one electric drive system, integrating a motor, a reducer, and a motor controller. These systems aim to achieve compactness, low weight, and high power. To mitigate the harmful effects of friction, electric vehicle fluid is circulated within these two-in-one or three-in-one electric drive systems. This fluid significantly improves motor cooling, both for the stator and even the rotor.

[0005] EV fluids typically come into direct contact with the gears, bearings, and / or electrical windings of the electric drive system. Besides cooling the motor, they also lubricate and reduce friction. This direct contact not only effectively lowers the motor's operating temperature but also reduces the complexity of core motor components, saving costs and improving output efficiency.

[0006] Based on the above considerations, the requirements for oil used in electric vehicle fluids are as follows:

[0007] Heat dissipation performance: The oil needs to be designed with low viscosity to ensure good thermal conductivity of the fluid, thereby meeting the cooling and heat dissipation requirements of the electric drive system under high temperature conditions.

[0008] Electrical properties: The oil needs to have a high dielectric strength to meet the insulation requirements.

[0009] Corrosion resistance and material compatibility: The oil needs to have high chemical stability to effectively avoid corrosion to the wiring harness, while ensuring compatibility with non-metallic materials such as insulating paint, insulating paper, seals, and casing on the motor.

[0010] Anti-oxidation performance: The oil needs to have excellent oxidation stability to prevent high-temperature thermal oxidation and reduce the formation of sludge and varnish.

[0011] Anti-friction performance and shear stability: To meet the high input torque of motor speeds exceeding 12,000 rpm, the oil itself must have high shear stability to provide excellent lubrication and protection for components such as gears and bearings. It must also meet the lubrication requirements of the reducer. Specifically, the fluid, at low viscosity, must provide anti-wear and load-bearing properties for the high-speed rotating gear teeth and input and output bearings, significantly reducing wear.

[0012] To meet these requirements, high-performance fully synthetic lubricants are needed, particularly those with polyalphaolefins (PAO) as their primary ingredient. PAOs are an important class of lubricant basestocks, offering exceptional lubricity, particularly high viscosity index, low pour point, and excellent low-temperature performance. By combining PAOs of varying kinematic viscosities, the overall performance of the base oil and EV fluids can be improved, particularly in terms of viscosity index, oxidation stability, anti-friction performance, shear stability, heat transfer, and dielectric strength, thereby meeting the requirements of EV fluids.

[0013] Summary of the Invention

[0014] To address the challenges of existing technologies, the present invention provides a base oil for use with polyalphaolefins of varying kinematic viscosities, as well as an electric vehicle fluid utilizing this base oil. Compared to commercially available products, the electric vehicle fluid of the present invention exhibits a higher viscosity index, oxidation stability, anti-friction properties, shear stability, dielectric strength, heat transfer performance, and lower evaporation losses.

[0015] To achieve the above objectives and other related objectives, the present invention is achieved through the following technical solutions.

[0016] In a first aspect, a base oil composition comprises the following components by mass percentage:

[0017] The first poly-alpha olefin mass fraction is 50-90%

[0018] The mass fraction of the second poly-alpha olefin is 1 to 20%

[0019] The third polyalphaolefin has a mass fraction of 5 to 25%;

[0020] Preferably, the composition comprises the following components by mass percentage:

[0021] The first poly-alpha olefin mass fraction is 60-80%

[0022] The second poly-alpha olefin mass fraction is 5 to 15%

[0023] The third polyalphaolefin accounts for 10 to 20% by mass;

[0024] Preferably, the composition comprises the following components by mass percentage:

[0025] The first poly-alpha olefin mass fraction is 70-75%

[0026] The mass fraction of the second poly-alpha olefin is 8-10%

[0027] The mass fraction of the third poly-alpha olefin is 12 to 16%.

[0028] Wherein, the kinematic viscosity of the first polyalphaolefin at 100°C is 3 to 10 mm 2 / s, preferably, the kinematic viscosity of the first poly-alpha olefin at 100°C is 3 to 8 mm 2 / s, more preferably, the kinematic viscosity of the first poly-alpha olefin at 100°C is 3 to 6 mm 2 / s, more preferably, the kinematic viscosity of the first poly-alpha olefin at 100°C is 3-4 mm 2 / s.

[0029] Preferably, the first polyalphaolefin is a metallocene polyalphaolefin.

[0030] The metallocene polyalphaolefin is a product obtained by polymerization of C4-C20 linear alpha-olefins in the presence of a metallocene catalyst system.

[0031] Furthermore, the metallocene catalyst system comprises at least one metallocene catalyst, which is an inorganic-organic complex containing at least one cyclopentadienyl or cyclopentadienyl derivative as a ligand and at least one Group IVB transition element as a central atom.

[0032] Preferably, the first polyalphaolefin is hydrosaturated.

[0033] Preferably, the viscosity index of the first poly-alpha olefin is 110-150, more preferably, the viscosity index of the first poly-alpha olefin is 120-150, and even more preferably, the viscosity index of the first poly-alpha olefin is 120-140.

[0034] The first polyalphaolefin is a low-viscosity metallocene polyalphaolefin, which plays a role in the base oil composition in ensuring fluidity and low-temperature performance. In addition, it can also provide a higher viscosity index, shear stability, heat transfer performance and dielectric strength.

[0035] The kinematic viscosity of the second polyalphaolefin at 100°C is 100-1000 mm 2 / s, preferably, the kinematic viscosity of the second poly-alpha olefin at 100°C is 100-500 mm 2 / s, more preferably, the kinematic viscosity of the second poly-alpha olefin at 100°C is 100-300 mm 2 / s.

[0036] Preferably, the viscosity index of the second poly-alpha olefin is 200-300, more preferably, the viscosity index of the second poly-alpha olefin is 200-260, and even more preferably, the viscosity index of the second poly-alpha olefin is 200-240.

[0037] Preferably, the second polyalphaolefin is a metallocene polyalphaolefin.

[0038] The second polyalphaolefin is a high-viscosity metallocene polyalphaolefin, which has a relatively high viscosity index. It is used as a viscosity index improver in the base oil composition and also plays a role in viscosity increase.

[0039] Wherein, the kinematic viscosity of the third polyalphaolefin at 100°C is 1 to 8 mm 2 / s, preferably, the kinematic viscosity of the third polyalphaolefin at 100°C is 1 to 5 mm 2 / s, and more preferably, the kinematic viscosity of the third polyalphaolefin at 100°C is 1 to 3 mm 2 / s, and more preferably, the kinematic viscosity of the third polyalphaolefin at 100°C is 1.5 to 2.5 mm 2 / s.

[0040] Preferably, the third polyalphaolefin is a non-metallocene polyalphaolefin.

[0041] The non-metallocene polyalphaolefin is a product obtained by polymerization of C4-C20 linear alpha-olefins in a non-metallocene catalyst system.

[0042] Furthermore, the non-metallocene catalyst system comprises at least one non-metallocene catalyst, wherein the non-metallocene catalyst comprises: a non-metallocene inorganic-organic complex formed by a ligand without a cyclopentadiene structure and a transition metal or a rare earth metal element, wherein the metal center comprises a transition metal and a rare earth metal element from Group IIIB to Group VIII, coordinated with a ligand containing heteroatoms such as N, O, S, and P, such as an α-diimine metal organic compound, a β-diimine metal organic compound, a β-diketoimine metal organic compound, an amidine metal organic compound, and a P-containing metal organic compound; a homogeneous Lewis acid catalyst; S acid catalysts, such as AlCl3, AlBr3, TiCl3, SiCl3, BiCl3, FeCl3, BF3 and BF3-ROH; heterogeneous Lewis acid catalysts, composed of the above homogeneous Lewis acid catalysts and inorganic porous substances, wherein the inorganic porous substances are selected from one or more of mesoporous carbon, carbon nanotubes, activated carbon fibers, acetylene black, carbon black, expanded graphite, and graphene; Ziegler-Natta catalysts, composed of Et3Al and TiCl4; chromium-based catalysts, such as chromium oxide, chromium halides, chromium phosphates, sulfates, nitrates, oxalates, etc.

[0043] Preferably, the third polyalphaolefin is subjected to a hydrogenation saturation treatment.

[0044] Preferably, the viscosity index of the third poly-alpha olefin is 60-120, more preferably, the viscosity index of the third poly-alpha olefin is 80-120, and even more preferably, the viscosity index of the third poly-alpha olefin is 80-100.

[0045] The third polyalphaolefin is a low-viscosity non-metallocene polyalphaolefin. Since it is not prepared using a metallocene catalyst, there is a certain branching structure in the molecule, a lower pour point, and better low-temperature performance, which plays a role in improving the low-temperature performance in the base oil composition.

[0046] In a second aspect of the present invention, the method for preparing the above-mentioned base oil comprises: uniformly mixing the second polyalphaolefin, the first polyalphaolefin, and the third polyalphaolefin, and stirring until the mixture is clear and transparent, thereby obtaining the base oil.

[0047] The third aspect of the present invention is the use of the above base oil in lubricants and / or heat transfer fluids.

[0048] Preferably, the above base oil is used in electric vehicle fluid.

[0049] The fourth aspect of the present invention is an electric vehicle fluid composition, which is mainly composed of the following components, with the percentage of each component being: base oil 95-99%, functional additives 1-5%.

[0050] The base oil is the base oil mentioned above, and the functional additives include but are not limited to: one or a combination of antioxidants, detergent dispersants, ashless extreme pressure agents, antifoaming agents and extreme pressure antiwear agents.

[0051] Furthermore, the functional additives may be added one by one or in combination.

[0052] Preferably, the antioxidant is antioxidant TH-1135, whose chemical name is 3,5-di-tert-butyl-4-hydroxyphenylpropionate.

[0053] Preferably, the detergent dispersant includes T154A or T154B, wherein T154A is polyisobutylene succinimide and T154B is a boronated polysuccinimide dispersant.

[0054] Preferably, the ashless extreme pressure agent includes ADDITIN RC8210 or RC8213, the chemical composition of which is a thiadiazole derivative.

[0055] Preferably, the antifoaming agent is Xinxing No. 1 composite antifoaming agent, the chemical composition of which is a compound of polydimethylsiloxane and alkyl acrylate polymer.

[0056] Preferably, the extreme pressure anti-wear agent includes T304, Irgalube TPPT or Irgalube 353, wherein T304 is dibutyl phosphite, Irgalube TPPT is triphenylthiophosphate, and Irgalube 353 is dithiophosphate.

[0057] Furthermore, the average wear spot diameter of the electric vehicle fluid composition in a four-ball test is less than 0.4 mm. Preferably, the average wear spot diameter of the electric vehicle fluid composition in a four-ball test is less than 0.3 mm.

[0058] Furthermore, the kinematic viscosity of the electric vehicle fluid composition at 100°C is 3 to 8 mm 2 / s, preferably, the kinematic viscosity of the electric vehicle fluid composition at 100°C is 4 to 8 mm 2 / s, and more preferably, the kinematic viscosity of the electric vehicle fluid composition at 100°C is 4 to 6.5 mm 2 / s;

[0059] Furthermore, the viscosity index of the electric vehicle fluid composition is not less than 150, preferably, the viscosity index of the electric vehicle fluid composition is not less than 160;

[0060] Furthermore, the pour point of the electric vehicle fluid composition is lower than -60°C;

[0061] Furthermore, the evaporation loss of the electric vehicle fluid composition is less than 25 wt%;

[0062] Furthermore, the electric vehicle fluid composition has an oxidation resistance (RBOT) higher than 900 min, preferably, the electric vehicle fluid composition has an oxidation resistance (RBOT) higher than 1000 min;

[0063] Furthermore, the electric vehicle fluid composition has an acid value of less than 0.5 (mg KOH / g);

[0064] Furthermore, the relative viscosity loss of the electric vehicle fluid composition in a KRL test is less than 1.0%. Preferably, the relative viscosity loss of the electric vehicle fluid composition in a KRL test is less than 0.5%.

[0065] Furthermore, the dielectric strength of the electric vehicle fluid composition is greater than 28 kV. Preferably, the dielectric strength of the electric vehicle fluid composition is greater than 32 kV.

[0066] A fifth aspect of the present invention: A method for preparing the above-mentioned electric vehicle fluid composition comprises: adding functional additives to base oil, mixing uniformly, and stirring until clear and transparent to obtain the electric vehicle fluid.

[0067] Preferably, the base oil is heated during the mixing process, and the heating temperature is 30-50°C.

[0068] Preferably, the stirring rate is 80-120 r / min.

[0069] Preferably, the stirring time is 0.5 to 1 h.

[0070] A sixth aspect of the present invention is an electric drive system using the electric vehicle fluid composition.

[0071] A seventh aspect of the present invention is a powertrain using the above electric drive system.

[0072] An eighth aspect of the present invention is an electric vehicle using the above-mentioned powertrain.

[0073] The above technical solution proposed by the present invention has the following beneficial technical effects:

[0074] The base oil composition proposed in this invention is composed of a blend of two metallocene polyalphaolefins (MPA) with different kinematic viscosities and a non-MPA. It balances low-temperature performance, lubrication and friction reduction, heat transfer, and shear stability. Compared to commercially available products, electric vehicle fluids formulated from this base oil composition not only have a comparable low pour point, high flash point, and excellent heat transfer, but also exhibit a higher viscosity index, oxidation stability, anti-friction performance, mechanical shear stability, high dielectric strength, and lower evaporation loss. These comprehensive indicators surpass those of commercially available products, making it a suitable alternative to current high-quality electric vehicle fluids. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 is a schematic diagram of the principle of the anti-friction four-ball test.

[0076] FIG2 is a test image of the wear spot diameter of the electric vehicle fluid in Example 1.

[0077] FIG3 is a test image of the wear spot diameter of the electric vehicle fluid in Example 2.

[0078] FIG4 is a test image of the wear spot diameter of the electric vehicle fluid in Example 3.

[0079] FIG5 is a test image of the wear spot diameter of the electric vehicle fluid in comparative example 3. DETAILED DESCRIPTION

[0080] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0081] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0082] The present invention will be further described with reference to specific examples. The following examples are intended only to illustrate the present invention and are not intended to limit its contents. Experimental conditions not specified in the examples are generally based on conventional conditions or those recommended by the sales company. Materials and reagents used in the examples are commercially available unless otherwise specified.

[0083] Examples 1-5, Comparative Examples 1-4

[0084] Table 1 below shows the properties of polyalphaolefins of different kinematic viscosities used in Examples 1-5 and Comparative Examples 1-4.

[0085] Table 2 shows the formulations of Examples 1-5 and Comparative Examples 1-4. The kinematic viscosity of these formulations at 100°C is 4.5 mm 2 / s, wherein the functional additives in Examples 1-5 and Comparative Examples 1-4 include:

[0086] The tackifier, Evonik VISCOPLEX 3-510, has a chemical structure of polymethacrylate (PMA), the antioxidant TH-1135, whose chemical name is 3,5-di-tert-butyl-4-hydroxyphenylpropionate, the detergent dispersants T154A and T154B, T154A is polyisobutylene succinimide, T154B is a boronated polysuccinimide dispersant, the ashless extreme pressure agent ADDITIN RC8213, whose chemical composition is a thiadiazole derivative, the Xinxing No. 1 composite antifoaming agent, whose chemical composition is a combination of polydimethylsiloxane and alkyl acrylate polymer, and the extreme pressure and anti-wear agents include T304, Irgalube TPPT or Irgalube353, among which T304 is dibutyl phosphite, Irgalube TPPT is triphenylthiophosphate, and Irgalube 353 is dithiophosphate.

[0087] Table 1

[0088] Table 2

[0089] Comparative Example 4 is BYD BOT383 electric vehicle fluid, which has a kinematic viscosity of 4.535 mm at 100°C. 2 / s.

[0090] The preparation methods of the electric vehicle fluid compositions of Examples 1-5 and Comparative Examples 1-4 are as follows:

[0091] Polyalphaolefins of different viscosities were mixed evenly and stirred until clear and transparent to obtain a base oil composition. At the same time, heating was turned on. Various functional additives were added to the base oil at 40°C and mixed evenly. The mixture was stirred at a stirring speed of 120 r / min for 0.5 h to obtain a clear and transparent electric vehicle fluid.

[0092] Effect verification

[0093] Relevant test methods and standards:

[0094] Kinematic viscosity and viscosity index: The kinematic viscosity of electric vehicle fluids is tested using the GB / T 265 standard, and the corresponding viscosity index is calculated using the GB / T 1995 standard;

[0095] Pour point: GB / T 3535 standard is used to test the pour point of electric vehicle fluids;

[0096] Flash point: The flash point of electric vehicle fluids is tested using the Cleveland open cup method according to standard GB / T 3536;

[0097] Density: The density of electric vehicle fluids at 100°C and 40°C is tested using the standard ASTM D 1298-1999 method;

[0098] Copper sheet corrosion: Test the electric vehicle fluid at 100°C for 24 hours using the GB / T 5096 standard and record the corresponding corrosion level.

[0099] Liquid phase corrosion: GB / T 11143 (Method A) is used to test the liquid phase corrosion of electric vehicle fluids.

[0100] Oxidation resistance: The rotating oxygen bomb test (RBOT) according to standard SH / T 0193 is used to test the oxidation stability of electric vehicle fluids. The oxidation stability of the sample is expressed in minutes based on the oxygen bomb test time. The longer the oxygen bomb test time, the higher the oxidation stability.

[0101] Specific Heat Capacity: Specific heat capacity of electric vehicle fluids was determined using differential scanning calorimetry (DSC) according to ASTM E1269-2011, with test temperatures at 40°C and 60°C.

[0102] Thermal conductivity: Electric vehicle fluids were tested at 40°C using ASTM D 2717-2009, Standard Test Method for Thermal Conductivity of Liquids.

[0103] Figure of Merit (FOM): The FOM value of electric vehicle fluid at 40°C is calculated using the figure of merit (FOM) evaluation formula in 4.9.1 of standard YD / T 3982-2021. The FOM value is used to evaluate the heat carrying or heat transfer performance of electric vehicle fluid under forced turbulent conditions. The higher the FOM value, the stronger the heat transfer performance of the fluid.

[0104] Among them, the calculation formula of FOM is expressed as: FOM=ρ 0.8 κ 0.6 C p 0.4 μ -0.4

[0105] Where ρ is the fluid density, κ is the thermal conductivity of the fluid, and Cp is the specific heat capacity of the fluid, and μ is the kinematic viscosity of the fluid.

[0106] Acid value: The acid value of electric vehicle fluid is determined by the potassium hydroxide ethanol solution titration method according to standard ASTM D664;

[0107] Dielectric strength: The dielectric strength test method in 5.1 of standard YD / T 3982-2021 is used to determine the dielectric strength of electric vehicle fluid.

[0108] Viscosity shear stability: The viscosity shear stability of electric vehicle fluid samples was measured using a tapered roller bearing testing machine according to the NB / SH / T 0845-2010 standard. After 20 hours of testing, the kinematic viscosity of the electric vehicle fluid samples at 100°C before and after the test was recorded, and the relative viscosity loss R was calculated. v (%), by R v Characterize the viscosity shear stability of different samples, R v The lower the viscosity, the higher the shear stability. v The calculation formula is:

[0109] Among them, V S is the kinematic viscosity of the electric vehicle fluid sample at 100°C before the test, V E is the kinematic viscosity of the electric vehicle fluid sample at 100°C after the test.

[0110] Anti-friction: The wear resistance of EV fluid samples was tested using a four-ball testing machine according to the NB / SH / T 0189-2017 standard. Figure 1 shows a schematic diagram of this test. Three lower steel balls, each with a diameter of 12.7 mm, were clamped in an oil chamber and submerged in the EV fluid sample. An upper steel ball of the same diameter was placed on top of the three lower steel balls. A specified load was applied, creating three-point contact between the upper and lower steel balls. When the EV fluid sample was heated to the specified test temperature, the top ball rotated at a specified speed. After the test, the diameter of the wear spot on the lower steel ball was measured. The smaller the wear spot diameter, the better the sample's wear resistance. The average of the wear spot diameters of the three lower steel balls was used to evaluate the wear resistance of the EV fluid sample.

[0111] The four-ball test conditions are: load: 392N (40kgf); spindle speed: 1200r / min; test time: 60min; test temperature: 75°C.

[0112] After the test, the wear spot diameter of the lower steel ball was measured. The smaller the wear spot diameter, the better the wear resistance of the sample. The average value of the wear spot diameters of the three lower steel balls was taken to evaluate the wear resistance of the electric vehicle fluid sample.

[0113] Friction and Coefficient of Friction: In the four-ball test described above, the friction force f (in gf) was automatically recorded by the testing machine at intervals during the 60-minute test. The force arm length of the testing machine was 3 inches (7.62 cm). The dimensionless coefficient of friction u at each time point was calculated from the recorded friction force f using the following formula.

[0114] Where u is the friction coefficient at each time point, f is the friction force, and P is the test load.

[0115] On this basis, the average friction coefficient u of each EV fluid sample is calculated by summing up the friction coefficients at each time point. A lower average friction coefficient indicates a stronger friction-reducing performance of the corresponding EV fluid sample, and is more capable of reducing the friction coefficient between the steel balls.

[0116] Evaporation loss: The NOACK evaporation loss test method of standard ASTM D5800 was used to test the electric vehicle fluid at 100°C for 24 hours, and the corresponding evaporation loss percentage (mass fraction) was recorded.

[0117] Low-temperature Brookfield viscosity: The Brookfield viscosity of electric vehicle fluids at -26 and -40°C is measured in accordance with GB / T 11145-2014 Determination of low-temperature viscosity of lubricants (Brokefeldt viscometer method).

[0118] Anti-foaming performance: The anti-foaming performance of electric vehicle fluids is tested using the GB / T 12579 standard. The foam volume immediately after air is introduced (foam tendency) and the foam volume after standing for 5 minutes (foam stability) are recorded at different temperatures.

[0119] The specific results of the above test are shown in Table 3:

[0120] Table 3

[0121] Analysis: As shown in Table 3 above, Comparative Example 1 uses PAO4 to replace some of the mPAO3.5 in Examples 1-5 as the base oil component. The electric vehicle fluid prepared in this manner has a significantly lower viscosity index, and there are also certain declines in shear stability, heat transfer performance, and dielectric strength. This is due to differences in the preparation methods and molecular structures of PAO and mPAO. mPAO is prepared using a metallocene catalyst, while PAO is prepared using a non-metallocene catalyst. Metallocene catalysts have a single active center, which allows for precise control of the molecular structure of mPAO. Non-metallocene catalysts have diverse active centers, making stereoselectivity difficult to control and having a more diverse molecular structure. This is specifically manifested in the fact that PAO molecules have side chains of varying lengths extending from the main chain in a disordered manner, while mPAO molecules have a comb-like structure with uniform side chains. As a base oil component, they can provide a higher viscosity index, shear stability, friction resistance, heat transfer performance, and dielectric strength.

[0122] Comparative Example 2 uses mPAO2 instead of PAO2 in Examples 1-5 as the base oil component. The low-temperature performance of the electric vehicle fluid prepared in this way is significantly reduced, especially in the increase of low-temperature Brookfield viscosity at -26 and -40°C, which indicates that the fluidity of the electric vehicle fluid is reduced at extremely low temperatures. This is because PAO2 has more branched structures, inconsistent branch lengths, and a high content of isoparaffins. As a base oil component, it is beneficial to improve the fluidity of the electric vehicle fluid at extremely low temperatures.

[0123] Comparative Example 3 uses the PMA tackifier VISCOPLEX 3-510 in place of the mPAO150 in Examples 1-5. The resulting EV fluid exhibits slightly improved low-temperature performance, as evidenced by relatively lower Brookfield viscosities at -26°C and -40°C. However, the shear stability and anti-friction properties of Comparative Example 3 are significantly lower than those of Examples 1-5. This demonstrates that the addition of VISCOPLEX 3-510 to the formulation improves the fluidity of the EV fluid at extremely low temperatures, but also reduces its shear stability and anti-friction properties.

[0124] Compared to the commercially available product in Comparative Example 4, Examples 1-5 not only have comparable low pour points, high flash points, and excellent heat transfer properties, but also exhibit higher viscosity index, oxidation stability, anti-friction properties, shear stability, high dielectric strength, and low evaporation loss. Their comprehensive performance surpasses that of commercially available products, making them suitable alternatives to high-quality electric vehicle fluids currently on the market.

[0125] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent replacements for parts thereof. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention. Although the above describes the specific implementation methods of the present invention, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that, based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present invention.

Claims

1. A base oil composition, characterized in that: The composition comprises the following components by mass percentage: The first poly-alpha olefin has a mass fraction of 50-90% The second poly-alpha olefin mass fraction is 1-20% The third polyalphaolefin has a mass fraction of 5 to 25%; The first polyalphaolefin and the second polyalphaolefin are metallocene polyalphaolefins, the third polyalphaolefin is a non-metallocene polyalphaolefin, the first polyalphaolefin has a viscosity index of 110 to 150, and a kinematic viscosity of 3 to 10 mm at 100°C. 2 / s, the viscosity index of the second poly-alpha olefin is 200-300, and the kinematic viscosity at 100°C is 100-1000mm 2 / s, the viscosity index of the third poly-alpha olefin is 60-120, and the kinematic viscosity at 100°C is 1-8 mm 2 / s.

2. The base oil composition according to claim 1, characterized in that The composition comprises the following components by mass percentage: The first poly-alpha olefin mass fraction is 60-80% The second poly-alpha olefin mass fraction is 5-15% The mass fraction of the third polyalphaolefin is 10 to 20%; Preferably, the composition comprises the following components by mass percentage: The first poly-alpha olefin mass fraction is 70-75% The second poly-alpha olefin mass fraction is 8-10% The mass fraction of the third poly-alpha olefin is 12-16%.

3. The base oil composition according to claim 1 or 2, characterized in that: The kinematic viscosity of the first polyalphaolefin at 100° C. is 3 to 8 mm 2 / s, and more preferably, the kinematic viscosity of the first poly-alpha olefin at 100°C is 3 to 6 mm 2 / s, and more preferably, the kinematic viscosity of the first poly-alpha olefin at 100°C is 3 to 4 mm 2 / s; and / or, The kinematic viscosity of the second poly-alpha olefin at 100° C. is 100 to 500 mm 2 / s, and more preferably, the kinematic viscosity of the second poly-alpha olefin at 100°C is 100-300 mm 2 / s; and / or, The kinematic viscosity of the third polyalphaolefin at 100° C. is 1 to 5 mm 2 / s, and more preferably, the kinematic viscosity of the third poly-alpha olefin at 100°C is 1 to 3 mm 2 / s, and more preferably, the kinematic viscosity of the third poly-alpha olefin at 100°C is 1.5-2.5 mm 2 / s; and / or, The viscosity index of the first poly-alpha olefin is 120 to 150. More preferably, the viscosity index of the first poly-alpha olefin is 120～140； and / or, The viscosity index of the second poly-alpha olefin is 200 to 260, and more preferably, the viscosity index of the second poly-alpha olefin is 200 to 240; and / or, The viscosity index of the third poly-alpha olefin is 80-120, and more preferably, the viscosity index of the third poly-alpha olefin is 80-100.

4. The base oil composition according to claim 1 or 2, characterized in that: Metallocene polyalphaolefin is a product obtained by polymerization of C4-C20 linear alpha-olefins under a metallocene catalyst system; further, the metallocene catalyst system comprises at least one metallocene catalyst, and the metallocene catalyst is an inorganic-organic complex containing at least one cyclopentadienyl or cyclopentadienyl derivative as a ligand and at least one Group IVB transition element as a central atom; The non-metallocene polyalphaolefin is a product obtained by polymerization of C4-C20 linear alpha-olefins under a non-metallocene catalyst system; further, the non-metallocene catalyst system comprises at least one non-metallocene catalyst, wherein the non-metallocene catalyst comprises: a non-metallocene inorganic-organic complex, formed by a ligand without a cyclopentadiene structure and a transition metal or a rare earth metal element, wherein the metal center comprises a transition metal and a rare earth metal element from group IIIB to group VIII, and coordinated with the ligand is a ligand containing heteroatoms such as N, O, S, and P, such as an α-diimine metal organic compound, a β-diimine metal organic compound, a β-diketoimine metal organic compound, an amidine metal organic compound, organic compounds and P-containing metal organic compounds; homogeneous Lewis acid catalysts, such as AlCl3, AlBr3, TiCl3, SiCl3, BiCl3, FeCl3, BF3 and BF3-ROH; heterogeneous Lewis acid catalysts, composed of the above homogeneous Lewis acid catalysts and inorganic porous substances, wherein the inorganic porous substances are selected from one or more of mesoporous carbon, carbon nanotubes, activated carbon fibers, acetylene black, carbon black, expanded graphite, and graphene; Ziegler-Natta catalysts, composed of Et3Al and TiCl4; chromium catalysts, such as chromium oxide, chromium halide, chromium phosphate, sulfate, nitrate, oxalate, etc.; Preferably, the first polyalphaolefin and / or the third polyalphaolefin is / are subjected to hydrogenation and saturation treatment.

5. A method for preparing a base oil composition according to any one of claims 1 to 4, comprising: The second poly-alpha olefin is mixed evenly with the first poly-alpha olefin and the third poly-alpha olefin, and stirred until clear and transparent to obtain the product.

6. Use of the base oil composition according to any one of claims 1 to 4 in lubricants and / or heat transfer fluids; preferably, use of the above base oil in electric vehicle fluids.

7. An electric vehicle fluid composition, mainly composed of the following components, based on the total weight, the percentage of each component is: base oil 95-99%, functional additives 1-5%; wherein, The base oil is the base oil composition according to any one of claims 1 to 4, and the functional additives include: one or more combinations of antioxidants, detergent dispersants, ashless extreme pressure agents, antifoaming agents and extreme pressure antiwear agents; Preferably, the antioxidant is antioxidant TH-1135, the chemical name of which is 3,5-di-tert-butyl-4-hydroxyphenylpropionate isooctyl ester; Preferably, the cleaning dispersant includes T154A or T154B, wherein T154A is polyisobutylene succinimide and T154B is a boronated polysuccinimide dispersant; Preferably, the ashless extreme pressure agent includes ADDITIN RC8210 or RC8213, whose chemical composition is a thiadiazole derivative; Preferably, the antifoaming agent is Xinxing No. 1 composite antifoaming agent, the chemical composition of which is a compound of polydimethylsiloxane and alkyl acrylate polymer; Preferably, the extreme pressure anti-wear agent includes T304, Irgalube TPPT or Irgalube 353, wherein T304 is dibutyl phosphite, Irgalube TPPT is triphenyl thiophosphate, and Irgalube 353 is dithiophosphate.

8. The electric vehicle fluid composition according to claim 7, wherein the average wear spot diameter of the fluid composition in a four-ball test is less than 0.4 mm, and preferably, the average wear spot diameter of the fluid composition in a four-ball test is less than 0.3 mm; Furthermore, the kinematic viscosity of the fluid composition at 100°C is 3 to 8 mm 2 / s, preferably, the kinematic viscosity of the fluid composition at 100°C is 4 to 8 mm 2 / s, and more preferably, the kinematic viscosity of the fluid composition at 100°C is 4 to 6.5 mm 2 / s; Further, the viscosity index of the fluid composition is not less than 150, preferably, the viscosity index of the fluid composition is not less than 160; Further, the pour point of the fluid composition is below -60°C; Further, the evaporation loss of the fluid composition is less than 25 wt%; Further, the oxidation resistance (RBOT) of the fluid composition is higher than 900 min, preferably, the oxidation resistance (RBOT) of the fluid composition is higher than 1000 min; Further, the acid value of the fluid composition is lower than 0.5 (mg KOH / g); Further, the relative viscosity loss of the fluid composition in a KRL test is less than 1.0%, preferably, the relative viscosity loss of the fluid composition in a KRL test is less than 0.5%; Furthermore, the dielectric strength of the fluid composition is greater than 28 kV, and preferably, the dielectric strength of the fluid composition is greater than 32 kV.

9. The method for preparing the electric vehicle fluid composition according to claim 7 or 8, comprising: Add the functional additives to the base oil, mix evenly, and stir until clear and transparent to obtain the electric vehicle fluid; preferably, the base oil is heated during the above mixing process, and the heating temperature is 30-50°C; preferably, the stirring rate is 80-120r / min; preferably, the stirring time is 0.5-1h.

10. An electric drive system using the electric vehicle fluid composition according to claim 7 or 8, preferably, a powertrain using the electric drive system, preferably, an electric vehicle using the powertrain.

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