A Base Oil Composition and Use Thereof in the Manufacture of a Fluid for an Electric Vehilcle

Abstract

The present invention provides a base oil composition formulated using a plurality of poly-α-olefins 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: a first poly-α-olefin of 50-90%, a second poly-α-olefin of 1-20%, and a third poly-α-olefin of 5-25%; the first poly-α-olefin and the second poly-α-olefin are metallocene poly-α-olefins, and the third poly-α-olefin is a non-metallocene poly-α-olefin; and the three poly-α-olefins 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, wherein the cooling and lubricating effects are achieved by means of direct contact with gears, bearings, and / or electrical windings of the electric drive 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 as compared to commercially available products.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to the field of synthetic lubricant technology, and more particularly to a base oil composition formulated with a plurality of poly-α-olefins, as well as a fluid for an electric vehicle manufactured with such base oil composition.BACKGROUND OF THE INVENTION

[0002] With the continuous development of the technology of the drive motors for new energy vehicles, the drive motors are increasingly moving towards high torque density and high power density, which are closely related to the heat dissipation method of the motors. Efficient heat dissipation can improve the continuous power and torque of the motors. For the cooling system of the drive motors of new energy vehicles, water is a good cooling medium, which has a high specific heat and thermal conductivity, and is inexpensive, non-toxic, non combustible, and has no explosion risk. However, due to water pressure leakage at the joints and sealing points of the water cooling system, there is a risk of short circuits, electric leakage, and insulation damage, which make direct cooling impossible.

[0003] Therefore, for an electric vehicle, direct cooling fluids are urgently needed to improve cooling efficiency. Oil itself, due to its local non-magnetic, non-flammable, non-conductive, and good thermal conductivity, has no impact on the motor magnetic circuit and has higher heat dissipation efficiency. The advantages of oil cooling over water cooling include good insulation performance, higher boiling point of engine oil than water, and lower pour point than water, making the coolant less prone to freezing at low temperatures and less prone to boiling at high temperatures. The cooling effect of oil cooled motors on flat wire winding motors with larger exposed end areas is more obvious, and they can actively cool the internal rotor components; at the same time, it is beneficial for the integration of the motor and gearbox, improving the lubrication and cooling effect of the bearings, and heating the gearbox oil when the ambient temperature is low to improve the lubrication and stirring efficiency. From the perspective of the entire drive system, oil cooled motors have certain technological advantages over water cooled ones, and oil cooling has become the mainstream development direction of electric vehicles.

[0004] An electric vehicle typically includes one or more motors that use a controlled three-phase AC power source for propulsion. The current mainstream design structure of an electric vehicle is a two-in-one electric drive system that integrates motors and reducers, or a three-in-one electric drive system that integrates motors, reducers, and motor controllers, in order to achieve goals such as compact structure, low weight, and high power. Among them, in order to reduce the harmful effects of friction, electric vehicle fluids are circulated in a two-in-one or three-in-one electric drive system. At the same time, such fluids can significantly improve the cooling effect of the motor, while also taking into account the cooling of the motor stator and even rotor.

[0005] Electric vehicle fluids usually use oil to directly contact the gears, bearings, and / or electrical windings of the electric drive system. In addition to cooling the motor, they also play a role in lubrication and friction reduction. This direct contact electric vehicle fluid can not only effectively reduce the operating temperature of the motor, but also reduce the complexity of the core components of the motor, lower corresponding costs, and improve the output efficiency of the motor.

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

[0007] Heat dissipation performance: Oil products require a low viscosity design to ensure good thermal conductivity of the fluid, in order to meet the cooling and heat dissipation requirements of electric drive systems under high temperature conditions.

[0008] Electrical characteristics: Oil products require high dielectric strength to meet insulation requirements.

[0009] Corrosion resistance and material compatibility: Oil products need to have high chemical stability to effectively avoid corrosion of wiring harnesses, while ensuring compatibility with non-metallic materials such as insulation paint, insulation paper, seals, and sleeves on the motor.

[0010] Oxidation stability: Oil products need to have excellent oxidation stability to prevent high-temperature thermal oxidation and reduce the formation of sludge paint films.

[0011] Friction assistance and shearing stability: For high input torque of motor speed above 12000 rpm, the oil itself should have high shear stability, providing good lubrication protection for gear bearings and other components. Meanwhile, it is necessary to meet the lubrication requirements of the reducer. Specifically, the fluid can provide anti-wear bearing features for high-speed rotating gear teeth, input and output bearings under low viscosity, greatly reducing wear.

[0012] To meet the above requirements, the oil needs to use high-performance fully synthetic lubricating oils, especially those made of poly-α-olefins (PAO) as the main component. Poly-α-olefins are an important type of lubricating oil base material with excellent lubrication performance, especially high viscosity index, low pour point, and excellent low-temperature performance. As showed in the present invention, the overall performance of the base oil and electric vehicle fluid, especially for viscosity index, oxidation stability, friction resistance, shearing stability, heat transfer effect and dielectric strength, can be improved by combined use of poly-α-olefins having different kinematic viscosities.SUMMARY OF THE INVENTION

[0013] The present invention provided a base oil which is formulated with poly-α-olefins having different kinematic viscosities, and an electric vehicle fluid prepared using such base oil. The electric vehicle fluid has higher viscosity index, oxidation stability, friction resistance, shearing stability, dielectric strength and heat transfer effect, and lower evaporation loss as compared to commercially available products.

[0014] The purposes of the present invention are achieved through the technical matters of the following aspects.

[0015] In the first aspect, the present invention provided a base oil composition, comprising the following components in percentage by mass:

[0016] a first poly-α-olefin of 50-90%;

[0017] a second poly-α-olefin of 1-20%; and

[0018] a third poly-α-olefin of 5-25%.

[0019] Preferably, the composition comprises the following components in percentage by mass:

[0020] the first poly-α-olefin of 60-80%;

[0021] the second poly-α-olefin of 5-15%; and

[0022] the third poly-α-olefin of 10-20%.

[0023] Further preferably, the composition comprises the following components in percentage by mass:

[0024] the first poly-α-olefin of 70-75%;

[0025] the second poly-α-olefin of 8-10%; and

[0026] the third poly-α-olefin of 12-16%.

[0027] Wherein, kinematic viscosity at 100° C. of the first poly-α-olefin is 3-10 mm2 / s, preferably 3-8 mm2 / s, further preferrably 3-6 mm2 / s, and further preferrably 3-4 mm2 / s.

[0028] In an embodiment, the first poly-α-olefin is a metallocene poly-α-olefin;

[0029] wherein, the metallocene poly-α-olefin is a product obtained from polymerization reaction of C4-C20 linear α-olefins in a non-metallocene catalyst system.

[0030] Furthermore, the metallocene catalyst system comprises at least one metallocene catalyst, wherein the metallocene catalyst is an inorganic-organic complex containing at least one cyclopentadienyl or cyclopentadienyl derivative as a ligand and at least one IVB transition element as a central atom.

[0031] In an embodiment, the first poly-α-olefin undergoes hydrogenation saturation treatment.

[0032] In an embodiment, the first poly-α-olefin has a viscosity index of 110-150, and preferably 120~150, and more preferably 120-140.

[0033] The first poly-α-olefin is a low viscosity metallocene poly-α-olefin, which plays a role in ensuring fluidity and low-temperature performance in base oil compositions, and also has effects of higher viscosity index, shear stability, heat transfer performance, and dielectric strength.

[0034] Wherein, the second poly-α-olefin has a kinematic viscosity at 100° C. of 100-1000 mm2 / s, preferably 100-500 mm2 / s, and further preferably 100-300 mm2 / s. In an embodiment, the second poly-α-olefin has a viscosity index of 200-300, preferably 200-260; and further preferably 200-240.

[0035] In an embodiment, the second poly-α-olefin is a metallocene poly-α-olefin.

[0036] The second poly-α-olefin is a high viscosity metallocene poly-α-olefin, which has a high viscosity index and is used as viscosity index improvers in the base oil composition, while also has an effect of increasing viscosity.

[0037] Wherein, the third poly-α-olefin has a kinematic viscosity at 100° C. of 1-8 mm2 / s, preferably 1-5 mm2 / s, more preferably 1-3 mm2 / s, and further preferably 1.5-2.5 mm2 / s.

[0038] In an embodiment, the third poly-α-olefin is a non-metallocene poly-α-olefin;

[0039] wherein, the non-metallocene poly-α-olefin is a product obtained from polymerization reaction of C4-C20 linear α-olefins in a non-metallocene catalyst system.

[0040] 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, which is formed by a ligand without a cyclopentadienyl structure and a transition metal or rare earth metal element, the non-metallocene inorganic-organic complex having a metal center comprising transition metals of Group IIIB to Group VIII and rare earth metal elements coordinated with a ligand containing heteroatoms such as N, O, S, P, such as α-diimine metal organic compounds, β-diimine metal organic compounds, β-diketoimine metal organic compounds, amidine based metal organic compounds, and P-containing metal organic compounds; a homogeneous Lewis acid catalyst, such as AlCl3, AlBr3, TiCl3, SiCl3, BiCl3, FeCl3, BF3, and BF3—ROH; a heterogeneous Lewis acid catalyst, containing the homogeneous Lewis acid catalyst and an inorganic porous material, the inorganic porous material being selected from one or more of mesoporous carbon, carbon nanotubes, activated carbon fibers, acetylene black, carbon black, expanded graphite, and graphene; a Ziegler Natta catalyst, composed of Et3Al and TiCl4; and a chromium based catalyst, such as chromium oxide, chromium halides, chromium phosphates, chromium sulfates, chromium nitrates, and chromium oxalates.

[0041] In an embodiment, the first poly-α-olefin undergoes hydrogenation saturation treatment.

[0042] In an embodiment, the third poly-α-olefin has a viscosity index of 60-120, preferably 80-120, and further preferably 80-100.

[0043] The third poly-α-olefin is a low viscosity non-metallocene poly-α-olefin, and, due to the absence of using metallocene catalysts for preparation, has a certain branching structure in the molecules, lower pour points, and better low-temperature performance for improving low-temperature performance in base oil compositions.

[0044] In the second aspect, the present invention provided a method of manufacturing the base oil composition, comprising: taking the second poly-α-olefin to be mixed evenly with the first poly-α-olefin and the third poly-α-olefin, and stirring the mixture to become clear and transparent.

[0045] In the third aspect, the present invention provided a use of the base oil composition, wherein the base oil composition is used in lubricants and / or heat transfer fluids.

[0046] In the fourth aspect, the present invention provided a fluid composition for an electric vehicle, wherein the fluid composition is consisting essentially of a base oil 95-99 wt %.

[0047] Wherein, the base oil is the base oil composition, and the functional additive including but are not limited to an antioxidant, detergent dispersant, ash-free extreme pressure agent, antifoaming agent, and extreme pressure anti-wear agent, or combination thereof.

[0048] Furthermore, the functional additives can be added selectively or in combination.

[0049] In an embodiment, the antioxidant is TH-1135, with a chemical name of 3,5-di-tert-butyl-4-hydroxyphenylpropanoic acid isooctyl ester.

[0050] In an embodiment, the detergent dispersant comprises T154A or T154B, wherein T154A is polyisobutylene succinimide and T154B is boronized polysuccinimide dispersant.

[0051] In an embodiment, the ash-free extreme pressure agent comprises ADDITIN RC8210 or RC8213, having a chemical composition of thiadiazole derivative.

[0052] In an embodiment, the antifoaming agent is Xingxing No. 1 composite antifoaming agent, having a chemical composition with the combination of polydimethylsiloxane and alkyl acrylate polymer.

[0053] In an embodiment, the extreme pressure anti-wear agent comprises T304, Irgalaube TPPT, or Irgalaube 353, wherein T304 is butyl phosphite, Irgalaube TPPT is triphenylthiophosphate, and Irgalaube 353 is dithiophosphate.

[0054] In an embodiment, the average wear scar diameter of the four ball test of the fluid composition is less than 0.4 mm, and preferably less than 0.3 mm.

[0055] In an embodiment, the fluid composition has a kinematic viscosity at 100° C. of 3-8 mm2 / s, preferably 4-8 mm2 / s, and further preferably 4-6.5 mm2 / s.

[0056] In an embodiment, the fluid composition has a viscosity index of no less than 150, and preferably no less than 160.

[0057] In an embodiment, the fluid composition has a pour point of below −60° C.

[0058] In an embodiment, the fluid composition has an evaporation loss of less than 25 wt %.

[0059] In an embodiment, the fluid composition has an oxidation resistance (RBOT) of higher than 900 min, and preferably higher than 1000 min.

[0060] In an embodiment, he fluid composition has an acid value of less than 0.5 (mg KOH / g).

[0061] In an embodiment, the fluid composition has a relative viscosity loss in the KRL test of less than 1.0%, and preferably less than 0.5%.

[0062] In an embodiment, the fluid composition has a dielectric strength of greater than 28 kV, and preferably greater than 32 kV.

[0063] In the fifth aspect, the present invention method of manufacturing the fluid composition for an electric vehicle, the method comprising: adding the functional additive to the base oil, mixing evenly, and stirring to become clear and transparent to obtain the fluid composition.

[0064] In an embodiment, the base oil is heated at a temperature of 30-50° C. while mixing.

[0065] In an embodiment, the stirring rate is 80-120 r / min.

[0066] In an embodiment, the stirring time is 0.5-1 h.

[0067] In the sixth aspect, the present invention provided a use of the fluid composition for an electric drive system.

[0068] In the seventh aspect, the present invention provided a use of the fluid composition for an electric drive system which is for a powertrain.

[0069] In the eighth aspect, the present invention provided a use of the fluid composition for the powertrain of an electric vehicle.

[0070] The technologies of the present invention have the following beneficial effects.

[0071] The base oil composition of the present invention contains two metallocene poly-α-olefins with different kinematic viscosities and a non-metallocene poly-α-olefin. The base oil composition can balance low-temperature performance, lubrication and friction-reduction property, heat transfer ability, and shear stability. Compared with commercially available products, the electric vehicle fluid formulated from the base oil composition of the invention not only has a comparably lower pour point, higher flash point, and excellent heat transfer performance, but also has higher viscosity index, oxidation stability, friction resistance, mechanical shear stability and dielectric strength, and lower evaporation loss, and thus has better comprehensive indicators and can be used as a high-quality electric vehicle fluid to replace current commercially available products.BRIEF DESCRIPTION OF THE DRAWINGS

[0072] FIG. 1 is a schematic diagram of the principle of the four ball anti-friction test.

[0073] FIG. 2 shows the test image of the wear scar diameter of the electric vehicle fluid in Example 1.

[0074] FIG. 3 shows the test image of the wear scar diameter of the electric vehicle fluid in Example 2.

[0075] FIG. 4 shows the test image of the wear scar diameter of the electric vehicle fluid in Example 3.

[0076] FIG. 5 shows the test image of the wear scar diameter of the electric vehicle fluid in Control 3.DETAILED DESCRIPTION OF THE EMBODIMENTS

[0077] The following detailed descriptions are illustrative and aim to provide further explanation for the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by an ordinary technician in the art.

[0078] It should be noted that the terms used herein are only for describing specific embodiments, and are not intended to limit the embodiments of the present invention. As used here, unless otherwise explicitly stated in the context, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms “comprising” and / or “including” are used herein, they indicate the existence of features, steps, operations, devices, components, and / or their combinations.

[0079] The examples below are presented only for the purpose of explaining the present invention and do not limit the scope of the invention. If the specific experimental conditions are not specified in the examples, they are usually based on conventional conditions or conditions recommended by the company which sales the products. The materials such as reagents used in the examples can be purchased through commercial channels unless otherwise specified.Examples 1-5 and Controls 1-4

[0080] Table 1 shows the properties of the poly-α-olefins with different kinematic viscosities used in Examples 1-5 and Controls 1-4.

[0081] Table 2 shows the formulations of Examples 1-5 and Controls 1-4, while the kinematic viscosity index of these formulations at 100° C. is about 4.5 mm2 / s. The functional additives in Examples 1-5 and Controls 1-4 include:

[0082] Thickener, Evonik VISCOPLEX 3-510, having a chemical name of polymethyl methacrylate (PMA); antioxidant TH-1135, with chemical name of 3,5-di-tert-butyl-4-hydroxyphenyl propanoic acid isooctyl ester; cleaning dispersants T154A and T154B, wherein T154A is polyisobutylene succinimide, and T154B is boronized polysuccinimide dispersant; ashless extreme pressure agent ADDITIN RC8213, having a chemical composition of thiadiazole derivative; Xinxing No. 1 composite anti foaming agent, having a chemical composition of the combination of polydimethylsiloxane and alkyl acrylate polymer; extreme pressure and wearing resistance agent including T304, Irgalaube TPPT or Irgalaube 353, wherein T304 is butyl phosphite, Irgalaube TPPT is triphenyl thiophosphate, and Irgalaube 353 is dithiophosphate.TABLE 1KinematicKinematicPourviscosity @viscosity @ViscositypointNameComposition100° C.(mm2 / s)40° C. (mm2 / s)index° C.mPAO3.5Metallocene3.5214.23130<−60poly-α-olefinsmPAO150Metallocene1591657212 −24poly-α-olefinsPAO2Non-metallocene1.674.9989<−60poly-α-olefinsPAO4Non-metallocene3.8516.75124<−60poly-α-olefins.mPAO2Metallocene1.986.07126 −55poly-α-olefinsTABLE 2Ex. Ex. Ex. Ex. Ex. Contr. Contr. Contr. Formula12345123mPAO3.575.073.672.872.374.431.074.372.4PAO213.614.715.2.15.514.017.9015.2mPAO1509.09.39.69.89.29.99.80PAO40000038.800mPAO200000013.50VISCOPLEX 000000010.03-510Irgamet 390.050.050.050.050.050.050.050.05T154A0001.61.6001.6T154B1.61.61.6001.61.60T3040.20.20.20.10.10.20.20.1Irgalube TPPT0.10.10.10.20.20.10.10.2T11350.10.10.10.10.10.10.10.1RC82130.20.20.20.20.20.20.20.2Irgalube 3530.050.050.050.050.050.050.050.05Xinxing #1 0.10.10.10.10.10.10.10.1composite anti-foaming agentControl 4 is of the BYD BOT383 electric vehicle fluid, which has a kinematic viscosity at 100° C. of 4.535 mm2 / s.

[0084] Method for preparing the electric vehicle fluid compositions of Examples 1-5 and Controls 1-4 are as follows:

[0085] Taking the poly-α-olefins with different viscosities, mixing evenly and stirring to become clear and transparent to obtain the base oil composition, and then starting to heat with addition of various functional additives to the base oil under 40° C. heating conditions, mixing evenly, and stirring at 120 r / min for 0.5 hours to obtain a clear and transparent electric vehicle fluid.Effect Verification

[0086] Testing methods and standards:

[0087] Kinematic viscosity and viscosity index: The kinematic viscosity of the electric vehicle fluid was tested using the GB / T 265 standard, and the corresponding viscosity index was calculated using the GB / T 1995 standard.

[0088] Pour point: The pour point of the electric vehicle fluid was tested using the GB / T 3535 standard.

[0089] Flash point: The flash point of the electric vehicle fluid was tested using the Cleveland open cup method of the GB / T 3536 standard.

[0090] Density: The density of the electric vehicle fluid at 100° C. and 40° C. was tested using the method of the standard ASTM D 1298-1999.

[0091] Copper corrosion resistance: The copper corrosion resistance of the electric vehicle fluid was tested for 24-hours at 100° C. using the standard GB / T 5096, and the corresponding corrosion level was recorded.

[0092] Liquid phase corrosion: The liquid phase corrosion of the electric vehicle fluid was tested using the standard GB / T 11143 (Method A).

[0093] Oxidation resistance: The oxidation stability of the electric vehicle fluid was tested using the method of Rotating Oxygen Bomb (RBOT) according to the standard SH / T 0193. The oxidation stability of the sample was expressed in minutes (min) based on time of the oxygen bomb test; the longer the oxygen bomb test time, the higher the oxidation stability.

[0094] Specific heat capacity: The specific heat capacity of the electric vehicle fluid was measured using the differential scanning calorimetry (DSC) of the method of the standard ASTM E1269-2011, with testing temperatures of 40° C. and 60° C.

[0095] Thermal conductivity: The thermal conductivity of the electric vehicle fluid was tested at 40° C. using the liquid thermal conductivity method of the standard ASTM D 2717-2009.

[0096] Heat transfer optimal value (FOM): The heat transfer optimal value (FOM) of the electric vehicle fluid at 40° C. was calculated using the evaluation formula in section 4.9.1 of the standard YD / T 3982-2021. The FOM value was used to evaluate the carrying heat or heat transfer performance of the electric vehicle fluid under forced turbulence conditions; the higher the FOM value, the stronger the heat transfer performance of the fluids.

[0097] The equation of FOM is:FOM=ρ0.8⁢κ0.6⁢Cp0.4⁢μ-0.4wherein, ρ is fluid density, κ is thermal conductivity of the fluids, Cp is the specific heat capacity of the fluids, μ is kinematic viscosity of the fluids.Acid value: The acid value of the electric vehicle fluid was determined using the potassium hydroxide ethanol solution titration method according to the standard ASTM D664.

[0099] Dielectric strength: The dielectric strength of the electric vehicle fluid was measured using the dielectric strength test method in section 5.1 of the standard YD / T 3982-2021.

[0100] Viscosity shear stability: The viscosity shear stability of the electric vehicle fluid was measured using a tapered roller bearing testing machine in accordance with the standard NB / SH / T 0845-2010. After 20 hours of testing, the kinematic viscosity of the electric vehicle fluid before and after the test was recorded at 100° C., and the relative viscosity loss Ry (%) was calculated. The viscosity shear stability of different samples was characterized by Rv. The lower the Rv, the higher the viscosity shear stability.

[0101] The equation for Rv is:Rv=VS-VEVS×1⁢0⁢0⁢%wherein, VS is the kinematic viscosity of the electric vehicle fluid sample at 100° C. before the experiment, and VE is the kinematic viscosity of the electric vehicle fluid sample at 100° C. after the experiment.Wear resistance: The wear resistance of the electric vehicle fluid was tested using a four ball testing machine in accordance with the standard NB / SH / T 0189-2017. The schematic diagram is shown in FIG. 1, where three lower steel balls with a diameter of 12.7 mm were clamped in an oil box and immersed in the electric vehicle fluid sample. Another upper steel ball with the same diameter was placed on top of three lower steel balls, and a specified load was applied. Under the action of experimental force, the upper steel ball formed three-point contact with three lower steel balls. When the sample of the electric vehicle fluid was heated to the specified test temperature, the top ball rotated at the specified speed. After the experiment, the wear scar diameter of the steel ball was measured. The smaller the wear scar diameter, the better the wearing resistance performance of the sample. The average of the wear scar diameters of three lower steel balls was taken to evaluate the wearing resistance performance of the electric vehicle fluid.

[0103] Four ball test conditions: load of 392 N (40 kgf); spindle speed of 1200 r / min; test time of 60 minutes; test temperature of 75° C.

[0104] After the experiment, the wear scar diameter of the steel ball was measured, wherein the smaller the wear scar diameter, the better the wearing resistance performance of the sample. The average of the wear scar diameters of three lower steel balls was taken to evaluate the wearing resistance performance of the electric vehicle fluid.

[0105] Friction and friction coefficient: In the above four ball test, during the 60 minute test, the testing machine automatically records the friction force f (in units of GF) at regular intervals. The force arm length of the testing machine is 3 inches (7.62 cm), and the dimensionless friction coefficient u at each time point is calculated using the following equation based on the recorded friction force f.u=0.0⁢1⁢7⁢0⁢fPwherein, u is friction coefficient at each time point, f is friction force, and P is test load.Based on the above, the average friction coefficient u of each electric vehicle fluid sample can be obtained by adding up the friction coefficient u at each time point and calculating the average value. The lower the average friction coefficient, the stronger the anti friction performance of the corresponding electric vehicle fluid sample; thus the friction coefficient between steel balls can better to reduced.

[0107] Evaporation loss: The NOACK evaporation loss measurement method of standard ASTM D5800 is used to test the electric vehicle fluid for 24 hours at 100° C., and the corresponding evaporation loss percentage (mass fraction) is recorded.

[0108] Low temperature Brinell viscosity: The Brinell viscosity at −26 and −40° C. of the electric vehicle fluid was determined using the method of lubricant low temperature viscosity (Brockfeldt Viscometer Method) according to the standard GB / T 11145-2014.

[0109] Anti-foaming performance: The anti-foaming performance of the electric vehicle fluid was tested using the standard GB / T 12579, wherein the foam volume (foam tendency) that has just been introduced into the air at different temperatures and the foam volume (foam stability) that has been left standing for 5 min were recorded respectively.

[0110] The specific results of the above tests are shown in Table 3 below.TABLE 3Testing itemsEx. 1Ex. 2Ex. 3Ex. 4Ex. 5Contr. 1Contr. 2Contr. 3Contr. 4Kinematic viscosity4.5444.5644.5954.5524.5834.4874.5764.4784.535(mm2 / s, 100° C.)Kinematic viscosity18.85218.93519.06718.89619.16520.33919.14318.37419.581(mm2 / s, 40° C.)Viscosity index165166167165164137163166152Density 100° C. g / cm30.76680.76720.76700.76600.76590.76460.76760.77150.7821Density 40° C., g / cm30.80530.80520.80500.80480.80480.80560.80640.81460.8204Flash point, ° C.198.9199.8198.8198.2198.3199.2199.5199.8201.4Pour point, ° C.<−60<−60<−60<−60<−60<−60<−60<−60−53Noack evaporation loss, wt %24.423.723.924.524.624.323.624.427.6Low temperature Brinell554546572569577548894468562viscosity, −26° C., cpsLow temperature Brinell260425782667264526862596315824832633viscosity, −40° C., cpsCopper corrosion (100° C.),1a1a1a1a1a1a1a1a1agradeLiquid phase corrosionNoNoNoNoNoNoNoNoNo(Method A)rustrustrustrustrustrustrustrustrustFoam24° C.,5 / 05 / 05 / 05 / 05 / 05 / 05 / 05 / 05 / 0propertymL / mL(foam93.5° C.,5 / 05 / 05 / 05 / 05 / 05 / 05 / 05 / 05 / 0tendency / mL / mLfoamAfter 24° C.,5 / 05 / 05 / 05 / 05 / 05 / 05 / 05 / 05 / 0stability)mL / mLOxidation resistance 11931356110211361088102710781219858(RBOT), minAcid value, mg KOH / g0.4230.3150.4680.4470.4730.4890.4750.4430.733KRL shearVS, mm2 / s4.5444.5644.5954.5524.5834.4874.5764.4784.535stability testVE, mm2 / s4.5324.5534.5824.5394.5714.4314.5604.3594.268(20 h shear)Rv, %0.2640.2410.2830.2860.2621.2480.3502.6575.887Average wear scar diameter0.2490.2620.2310.2840.2710.3240.2690.4360.457(mm)Average friction coefficient u0.1110.0980.1080.1060.1090.1210.1160.1180.115Specific heat capacity 2.0122.0552.0872.0762.0342.0212.0652.0892.117(40° C.), kJ / (kg · K)Specific heat capacity 2.0432.0862.1282.1052.0692.0542.0972.1102.122(60° C.), kJ / (kg · K)Thermal conductivity0.1950.1930.1890.1860.1880.1800.1900.1830.184coefficient 40° C., W / (m · K)Heat transfer merit (FOM,0.1290.1290.1280.1270.1260.1190.1280.1280.12740° C.)Dielectric strength, kV34.834.534.334.034.231.233.933.725.8

[0111] Analysis: Table 3 shows that the use of PAO4 in Control 1 to replace some mPAO3.5 in Examples 1-5 as the base oil component significantly reduces the viscosity index, shear stability, heat transfer performance, and dielectric strength of the prepared electric vehicle fluid. This is due to the differences in preparation methods and molecular structures between PAO and mPAO. mPAO is prepared using metallocene catalysts, while PAO is prepared using non-metallocene catalysts. Metallocene catalysts have a single active center that can precisely control the molecular structure of mPAO, while non-metallocene catalysts have diverse active centers, making it difficult to control stereoselectivity and resulting in more diverse molecular structures. Specifically, PAO molecules extend side chains of varying lengths in a disordered manner on the main chain, while mPAO molecules have a comb like structure with uniform side chain lengths, and, as a base oil component, can provide higher viscosity index, shear stability, friction resistance, heat transfer performance, and dielectric strength.

[0112] The use of mPAO2 in Control 2 to replace PAO2 in Examples 1-5 as the base oil component resulted in a significant decrease in the low-temperature performance of the prepared electric vehicle fluid, particularly in the increased low-temperature Brinell viscosity at −26 and −40° C. This indicates a decrease in the flowability of the electric vehicle fluid at extreme low temperatures, due to the presence of numerous branched chain structures and varying lengths of branches, as well as high content of isomeric alkanes in PAO2, and, as a base oil component, it is beneficial to improve the flowability of the electric vehicle fluid at extreme low temperatures.

[0113] The use of PMS thickener of COPLEX 3-510 in Control to replace mPAO150 in Examples 1-5 resulted in a slight improvement in the low-temperature performance of the electric vehicle fluid. This is reflected in the relatively lower low-temperature Brinell viscosity at −26 and −40° C., but the shear stability and anti friction performance of Control 3 were significantly reduced compared to Examples 1-5. This indicates that adding VISCOPLEX 3-510 to the formula can improve the flowability of the electric vehicle fluid at extreme low temperatures, but also reduce the shear stability and anti friction performance of the electric vehicle fluid.

[0114] Compared with the commercially available products of Control 4, Examples 1-5 not only have comparable low pour point, high flash point, and excellent heat transfer performance, but also have higher viscosity index, oxidation stability, friction resistance, shearing stability, dielectric strength and heat transfer effect, and lower evaporation loss. The comprehensive indicators of Examples 1-5 are superior to that of commercially available products, and can replace high-quality electric vehicle fluid products currently on the market.

[0115] It should be noted that although particular embodiments and examples have been described herein in detail, the above description has been done by way of example for purposes of illustration only, and is not intended to be limiting with respect to the scope of the invention. In particular, it is contemplated by a person of skills in the art that various substitutions, alterations, and modifications may be made to the invention without departing from the scope of the invention as claimed.

Claims

1. A fluid composition for an electric vehicle, wherein the fluid composition is consisting essentially of a base oil 95-99 wt %, and a functional additive 1-5 wt %; wherein the functional additive comprises an antioxidant, detergent dispersant, ash-free extreme pressure agent, antifoaming agent, and extreme pressure anti-wear agent, or combination thereof, and wherein the base oil is a base oil composition, comprising the following components in percentage by mass:a first poly-α-olefin of 50-90%;a second poly-α-olefin of 1-20%; anda third poly-α-olefin of 5-25%;wherein, the first poly-α-olefin and the second poly-α-olefin are metallocene poly-α-olefins, and the third poly-α-olefin is a non-metallocene poly-α-olefin, and the first poly-α-olefin has a viscosity index of 110-150 and a kinematic viscosity at 100° C. of 3-10 mm2 / s, the second poly-α-olefin has a viscosity index of 200-300 and a kinematic viscosity at 100° C. of 100-1000 mm2 / s, and the third poly-α-olefin has a viscosity index of 60-120 and a kinematic viscosity at 100° C. of 1-8 mm2 / s;wherein, the metallocene poly-α-olefins are products obtained from polymerization reaction of C4-C20 linear α-olefins in a metallocene catalyst system; the non-metallocene poly-α-olefins are products obtained from polymerization reaction of C4-C20 linear α-olefins in a non-metallocene catalyst system.

2. The fluid composition for an electric vehicle according to claim 1, wherein the base oil composition comprises the following components in percentage by mass:the first poly-α-olefin of 60-80%;the second poly-α-olefin of 5-15%; andthe third poly-α-olefin of 10-20%.

3. (canceled)4. The fluid composition for an electric vehicle according to claim 1, wherein the metallocene catalyst system comprises at least one metallocene catalyst, wherein the metallocene catalyst is an inorganic-organic complex containing at least one cyclopentadienyl or cyclopentadienyl derivative as a ligand and at least one IVB transition element as a central atom.5-6. (canceled)7. The fluid composition for an electric vehicle according to claim 1, whereinthe antioxidant is TH-1135, with a chemical name of 3,5-di-tert-butyl-4-hydroxyphenylpropanoic acid isooctyl ester.

8. (canceled)9. A method of manufacturing the fluid composition for an electric vehicle of any one of claims 1-13, the method comprising: mixing evenly the second poly-α-olefin with the first poly-α-olefin and the third poly-α-olefin, and stirring the mixture to become clear and transparent, adding the functional additive to the base oil, mixing evenly, and stirring until becoming clear and transparent to obtain the fluid composition.

10. A use of the fluid composition for an electric vehicle of any one of claims 1-13, wherein the use is for an electric drive system.

11. The fluid composition for an electric vehicle according to claim 2, wherein the base oil composition comprises the following components in percentage by mass:the first poly-α-olefin of 70-75%;the second poly-α-olefin of 8-10%; andthe third poly-α-olefin of 12-16%.

12. The fluid composition for an electric vehicle according to claim 1, wherein 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 cyclopentadienyl structure and a transition metal or rare earth metal element, wherein the non-metallocene inorganic-organic complex having a metal center comprising transition metals of Group IIIB to Group VIII and rare earth metal elements coordinated with a ligand containing heteroatoms such as N, O, S, P.

13. The fluid composition for an electric vehicle according to claim 1, wherein the non-metallocene catalyst comprises an α-diimine metal organic compound, β-diimine metal organic compound, β-diketoimine metal organic compound, amidine based metal organic compound, or P-containing metal organic compound.

14. The fluid composition for an electric vehicle according to claim 1, wherein the non-metallocene catalyst is a homogeneous Lewis acid catalyst; a non-heterogeneous Lewis acid catalyst, containing the homogeneous Lewis acid catalyst and an inorganic porous material; a Ziegler Natta catalyst composed of Et3Al and TiCl4; or a chromium based catalyst.

15. The fluid composition for an electric vehicle according to claim 1, wherein, the first poly-α-olefin and / or the third poly-α-olefin undergoes hydrogenation saturation treatment.

16. The fluid composition for an electric vehicle according to claim 1, wherein the detergent dispersant comprises T154A or T154B, wherein T154A is polyisobutylene succinimide and T154B is boronized polysuccinimide dispersant.

17. The fluid composition for an electric vehicle according to claim 1, wherein the ash-free extreme pressure agent comprises ADDITIN RC8210 or RC8213, having a chemical composition of thiadiazole derivative.

18. The fluid composition for an electric vehicle according to claim 1, wherein the antifoaming agent is No. 1 composite antifoaming agent, having a chemical composition of a combination of polydimethylsiloxane and alkyl acrylate polymer.

19. The fluid composition for an electric vehicle according to claim 1, wherein the extreme pressure anti-wear agent comprises T304, Irgalaube TPPT, or Irgalaube 353, wherein T304 is butyl phosphite, Irgalaube TPPT is triphenylthiophosphate, and Irgalaube 353 is dithiophosphate.

20. The method of claim 9, wherein, the base oil is heated at a temperature of 30-50° C. while mixing.

21. The method of claim 9, wherein the rate of stirring is 80-120 r / min.

22. The method of claim 9, wherein the time of stirring is 0.5-1 h.

23. The use of claim 10, wherein the electric drive system is for a powertrain.

24. The use of claim 10, wherein the powertrain is for an electric vehicle.

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