Lubricating oil, preparation method therefor, and use thereof

Abstract

Star-shaped poly-branched polyolefin. The star-shaped poly-branched polyolefin comprises a star-shaped coupling unit and M polyolefin branches connected to the star-shaped coupling unit; and the number average molecular weight of the star-shaped poly-branched polyolefin is 200-10,000 g / mol, wherein M is 2-8. By using the star-shaped poly-branched polyolefin as a base oil for a lubricating oil, a coefficient of friction is effectively reduced, particularly the coefficient of friction between components of an electric vehicle at a high sliding speed, thereby prolonging the service life of components in the vehicle. Further provided are a lubricating oil using star-shaped poly-branched polyolefin as a base oil, a preparation method therefor, and a use thereof.

Description

A lubricating oil, its preparation method and application

[0001] This application claims priority to Chinese Patent Application No. 202411585239.X, filed on November 7, 2024, entitled "A Lubricating Oil and Its Preparation Method and Application", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of chemistry, and more particularly to a lubricating oil, its preparation method, and its application. Background Technology

[0003] New energy vehicles have received widespread attention due to their environmentally friendly and energy-saving characteristics, and more and more new energy vehicles are occupying market share, showing a very broad market prospect.

[0004] Currently, the main powertrain assemblies for new energy vehicles on the market include: a combination of a water-cooled motor and a single-stage reduction gearbox for pure electric vehicles, a combination of an oil-cooled motor and a single-stage reduction gearbox, and a hybrid powertrain with an oil-cooled motor and transmission. In recent years, with the maturation of technology, oil-cooled motor technology has gradually become the mainstream technology in new energy vehicle transmission systems. Oil-cooled motor technology requires lubricating oil to provide necessary lubrication for the bearings and other rotating parts in the motor, reducing friction and wear. As the core component of lubricating oil, base oil has a crucial impact on its lubricating performance.

[0005] CN107828481A discloses a lubricating oil composition for electric vehicle transmissions. The base oil of the lubricating oil in this application is at least one of Group III hydrogenated base oil and polyalphaolefin base oil.

[0006] CN105132107B discloses a lubricating oil composition for transmissions of pure electric vehicles, wherein the base oil of the lubricating oil is one or more of PAO4, PAO10, and Group III hydrotreated base oils.

[0007] However, currently used lubricants using the aforementioned base oils do not perform satisfactorily in terms of friction coefficient at high sliding speeds. Therefore, there is an urgent need for a base oil that can significantly reduce the friction coefficient, especially reducing the friction coefficient between electric vehicle components at high sliding speeds, thereby improving the service life of automotive internal components. Summary of the Invention

[0008] The main objective of this application is to provide a star-shaped multi-branched polyolefin. Using the above-mentioned star-shaped multi-branched polyolefin as the base oil of lubricating oil can reduce the coefficient of friction, especially the coefficient of friction between electric vehicle components at high sliding speeds, thereby improving the service life of automotive internal components.

[0009] In a first aspect, this application provides a star-shaped multi-branched polyolefin, the star-shaped multi-branched polyolefin comprising a star coupling unit and M polyolefin branches connected to the star coupling unit, the number-average molecular weight of the star-shaped multi-branched polyolefin being 200 to 10000 g / mol, and M being 2 to 8.

[0010] As described above, in the star-shaped multi-branched polyolefin, each polyolefin branch independently comprises at least one structural unit from butadiene and a structural unit from isoprene.

[0011] The star-shaped multi-branched polyolefins described above, wherein each polyolefin branch comprises, by weight percentage, 25-100 wt% structural units from butadiene and 0-75 wt% structural units from isoprene.

[0012] The star-shaped branched polyolefin as described above, wherein the molecular weight distribution index of the star-shaped branched polyolefin is 1.05 to 1.6; and / or,

[0013] The degree of hydrogenation of the star-shaped branched polyolefin is 80-100%.

[0014] The star-shaped multi-branched polyolefin as described above, wherein the star-shaped coupling unit includes at least one of silicon core, tin core, lead core, titanium core, and germanium core.

[0015] The star-shaped multibranched polyolefin described above is prepared by a method comprising the following process:

[0016] An olefin monomer is polymerized and then a star coupling agent is added to undergo a coupling reaction to obtain a star coupling compound. Subsequently, the star coupling compound is hydrogenated to obtain the star-shaped multi-branched polyolefin.

[0017] This application further provides a method for preparing star-shaped multi-branched polyolefins, comprising the following steps:

[0018] 1) In a solvent, using alkyllithium as an initiator and adding a polarity modifier, olefin monomers undergo a polymerization reaction to obtain a polymer reaction solution;

[0019] 2) Add a star-shaped coupling agent to the polymerization reaction solution to carry out a coupling reaction, and obtain a star-shaped coupling reaction solution;

[0020] 3) Add a metal catalyst to the star-shaped coupling reaction solution to carry out a hydrogenation reaction to obtain a reaction solution containing star-shaped multi-branched polyolefins.

[0021] In the method for preparing star-shaped branched polyolefins as described above, the olefin monomer includes at least one selected from butadiene and isoprene; and / or,

[0022] The star-shaped coupling agent includes at least one of RCH3Cl3, RCl4, R2Cl6, and R3Cl8, wherein R includes at least one of silicon, tin, lead, titanium, and germanium.

[0023] The method for preparing star-shaped multi-branched polyolefins as described above,

[0024] The butadiene accounts for 25% to 100% of the total mass of the olefin monomers; and / or,

[0025] The isoprene accounts for 0-75% of the total mass of the olefin monomers.

[0026] In the method for preparing star-shaped branched polyolefins as described above, in step 1), the olefin monomer accounts for 5-15 wt% of the total mass of the olefin monomer and solvent; and / or,

[0027] The polarity modifier accounts for 0 to 0.5 wt% of the total mass of the polarity modifier and solvent; and / or,

[0028] In step 2), the mass of the star-shaped coupling agent accounts for 1 to 10 wt% of the total mass of the star-shaped coupling agent and the solvent.

[0029] In the preparation method of star-shaped branched polyolefins as described above, in step 1), the polymerization reaction temperature is 50–70°C, and the reaction time is 30–90 min; and / or,

[0030] In step 2), the coupling reaction is carried out at a temperature of 50–90°C for 30–90 minutes; and / or,

[0031] In step 3), the reaction temperature of the hydrogenation reaction is 50-70°C, the reaction time is 1-4 hours, and the hydrogen pressure is 1-4 MPa.

[0032] The method for preparing star-shaped multi-branched polyolefins as described above further includes, after step 3), adding an oxidant to the reaction solution containing the star-shaped multi-branched polyolefins for post-treatment to obtain the star-shaped multi-branched polyolefins.

[0033] In another aspect, this application provides a lubricating oil, wherein the base oil of the lubricating oil comprises a star-shaped multi-branched polyolefin as described above or a star-shaped multi-branched polyolefin prepared by the method for preparing star-shaped multi-branched polyolefins according to any one of claims 7-12.

[0034] The lubricating oil as described above comprises, by weight percentage, 0.5% to 8.0% viscosity index improver, 0.5% to 6.0% dispersant, 0.1% to 1.0% antioxidant, 0.1% to 4.0% anti-wear agent, 0.1% to 0.7% extreme pressure agent, 0.1% to 0.5% rust inhibitor, 0.01% to 0.3% metal deactivator, 0.1% to 0.5% detergent, 0.01% to 0.05% antifoaming agent, with the balance being the base oil.

[0035] A fourth aspect of this application provides an electric motor that includes the lubricating oil described above.

[0036] This application also provides an automobile that includes the motor described above.

[0037] The star-shaped multi-branched polyolefin provided in this application forms a product with low viscosity and a large number of branched structures by controlling the number-average molecular weight of the multi-branched polyolefin and the number of polyolefin branches connected to the star coupling unit. It is suitable as a base oil in lubricating oil, effectively reducing the coefficient of friction, especially reducing the coefficient of friction between electric vehicle components under high sliding speed, and improving the service life of automotive internal components. Attached Figure Description

[0038] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0039] Figure 1 is a line graph of the friction coefficient of the embodiments and comparative examples provided in this application.

[0040] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0042] Currently, Group III hydrogenated base oils, polyalphaolefin base oils, PAO4, and PAO10 are commonly used as base oils in lubricating oils. However, when using these base oils, there is a problem that they cannot effectively improve the coefficient of friction at high sliding speeds.

[0043] Therefore, the key issue in preparing base oils is to develop a base oil that possesses the essential physicochemical properties required by the base oil, such as low kinematic viscosity and small acid value variation, and can reduce the friction coefficient of various components in the car under high sliding speeds.

[0044] Based on this, the first aspect of this application provides a star-shaped multi-branched polyolefin, wherein the star-shaped multi-branched polyolefin includes a star coupling unit and M polyolefin branches connected to the star coupling unit, the number average molecular weight of the star-shaped multi-branched polyolefin is 200 to 10000 g / mol, and M is 2 to 8.

[0045] Star-shaped multi-branched polyolefins are obtained from olefin monomers through polymerization, coupling, and hydrogenation reactions. The star-shaped coupling unit, serving as the core of the star-shaped multi-branched polyolefin, connects to M polyolefin branches. After polymerization, the olefin monomers form polyolefin branch precursors. These precursors contain multiple double bonds. The polyolefin branch precursors, including those with multiple double bonds, are coupled to the star-shaped coupling unit and then undergo hydrogenation to form the polyolefin branches.

[0046] Based on considerations regarding base oil viscosity and reducing the coefficient of friction, this application limits the number-average molecular weight of the star-shaped branched polyolefin and the polyolefin branches on each star coupling unit. For example, the number-average molecular weight of the star-shaped branched polyolefin includes, but is not limited to, a range of 200 g / mol, 500 g / mol, 1000 g / mol, 3000 g / mol, 5000 g / mol, 7000 g / mol, 10000 g / mol, or any combination thereof. Preferably, when the number-average molecular weight of the star-shaped branched polyolefin is 200–500 g / mol, the star-shaped branched polyolefin has a more suitable viscosity for use as a base oil.

[0047] For example, the star-shaped multi-branched polyolefins provided in this application include, but are not limited to, the following structures:

[0048] In this context, A1, A2, and A3 represent different polyolefin branches. The aforementioned star-shaped multi-branched polyolefin includes one or more star-shaped coupling units C. The same or different polyolefin branches are connected to the star-shaped coupling units C to form the star-shaped multi-branched polyolefin. When there are multiple star-shaped coupling units C, these units are connected by connecting units B. Connecting units B include covalent bonds and polyolefin branches; that is, multiple star-shaped coupling units can be connected through polyolefin branches or covalent bonds. The differences in the star-shaped coupling units within the star-shaped multi-branched polyolefin are due to the use of different star-shaped coupling agents as described above.

[0049] This application restricts the polyolefin branches on each star coupling unit, which on the one hand reduces the molecular weight of the product star-shaped multi-branched polyolefin and reduces the steric hindrance between molecules, thereby reducing the viscosity of the product. On the other hand, when the polyolefin branches on each star coupling unit are within the above range, the star-shaped multi-branched polyolefin forms a sliding layer between automotive components that require lubrication, which helps to reduce the direct contact between the components and thus effectively reduces the coefficient of friction.

[0050] In the aforementioned star-shaped multi-branched polyolefins, each polyolefin branch independently comprises structural units derived from butadiene and structural units derived from isoprene. Specifically, the composition of each polyolefin branch can be the same or different. Identical composition means that each polyolefin branch has structural units from the same source and the same molecular chain length. Different composition means that each polyolefin branch has the same molecular chain length but structural units from different sources, or each polyolefin branch has different molecular chain lengths but structural units from the same source, or each polyolefin branch has both different molecular chain lengths and different structural units.

[0051] Furthermore, each polyolefin branch comprises, by weight percentage, 25–100 wt% structural units from butadiene and 0–75 wt% structural units from isoprene. This application, by defining the structural unit composition of each polyolefin branch, can further improve the viscosity and coefficient of friction of star-shaped multi-branched polyolefins.

[0052] It should be clarified that butadiene can form two main polymers, 1,4-polybutadiene and 1,2-polybutadiene, during polymerization. In this application, the mass of the 1,2-polybutadiene structural unit accounts for 7 to 25% of the total mass of the polybutadiene structural unit, and the mass of the 1,4-polybutadiene structural unit accounts for 75 to 93% of the total mass of the butadiene structural unit.

[0053] In addition, the molecular weight distribution index of the star-shaped multi-branched polyolefin in this application is 1.05 to 1.6. By controlling the molecular weight distribution index of the star-shaped multi-branched polyolefin within the above range, the flowability of the star-shaped multi-branched polyolefin can be further improved, enabling it to quickly cover all surfaces that require lubrication, thereby reducing the wear of various components when the car starts.

[0054] In another specific embodiment, in order to reduce intermolecular interaction forces and thus improve the flowability of the product, this application controls the degree of hydrogenation of the star-shaped multi-branched polyolefin to be 80-100%.

[0055] As mentioned above, the star coupling unit of a star-shaped multibranched polyolefin includes at least one of a silicon core, a tin core, a lead core, a titanium core, and a germanium core. Because these substances have different coordination abilities, star-shaped multibranched polyolefins with 2 to 8 polyolefin branches can be synthesized by using these substances as star coupling units. For example, when the star coupling agent is RCH3Cl3, such as methyl silicon trichloride, i.e., the star coupling unit is a silicon core, the star-shaped multibranched polyolefin includes 3 polyolefin branches; when the star coupling agent is RCl4, such as tin tetrachloride, i.e., the star coupling unit is a tin core, the star-shaped multibranched polyolefin includes 4 polyolefin branches. In addition, the above-mentioned substances have different electron cloud densities and spatial configurations, which will affect the growth of polymer chains. By using the above-mentioned substances as star coupling units, this application can synthesize star-shaped multi-branched polyolefins with different chain lengths and 2 to 8 polyolefin branches, which is beneficial to further reduce the viscosity of star-shaped multi-branched polyolefins and improve their ability to improve the coefficient of friction.

[0056] The above-mentioned star-shaped multi-branched polyolefins are prepared by a method including the following process:

[0057] After the olefin monomer is polymerized, a star coupling agent is added to undergo a coupling reaction to obtain a star coupling compound. Subsequently, the star coupling compound is hydrogenated to obtain a star-shaped multi-branched polyolefin.

[0058] In this application, during the polymerization reaction of olefin monomers, the mass of the added olefin monomers can be controlled to achieve star-shaped multi-branched polyolefins with low number-average molecular weights. Simultaneously, a polarity modifier is added during the polymerization process to control the molecular weight. This polarity modifier acts as a chain transfer agent, terminating the growth of the growing polymer chain by reacting with the chain ends and generating a new active center. This effectively reduces the molecular weight of the final polymer. Furthermore, increasing the concentration of the polarity modifier results in a narrower molecular weight distribution.

[0059] As mentioned above, this application also controls the molecular weight of star-shaped multi-branched polyolefins by controlling the polymerization reaction time.

[0060] Furthermore, to control the number of polyolefin branches attached to the star coupling unit, this application incorporates different star coupling agents, including at least one of RCH3Cl3, RCl4, R2Cl6, and R3Cl8, wherein R includes at least one of silicon, tin, lead, titanium, and germanium. By using the above-mentioned star coupling agents, this application can control the number of polyolefin branches attached to the star coupling unit to be 2 to 8, thereby reducing the viscosity of the star-shaped multi-branched polyolefin and improving its ability to improve the coefficient of friction.

[0061] It is understandable that an initiator is required for the polymerization reaction to occur. This application does not impose any special limitations on the initiator, as long as it can start the polymerization reaction.

[0062] A second aspect of this application provides a method for preparing the above-mentioned star-shaped multi-branched polyolefin, comprising the following steps:

[0063] 1) In a solvent, using alkyllithium as an initiator and adding a polarity modifier, olefin monomers undergo a polymerization reaction to obtain a polymer reaction solution;

[0064] 2) Add a star-shaped coupling agent to the polymerization reaction solution to carry out a coupling reaction, and obtain a star-shaped coupling reaction solution;

[0065] 3) Add a metal catalyst to the star-shaped coupling reaction solution to carry out a hydrogenation reaction to obtain a reaction solution containing star-shaped multi-branched polyolefins.

[0066] It should be noted that, to avoid the influence of moisture and air on the polymerization reaction, the polymerization reaction must be carried out in an inert atmosphere, and the reaction equipment also needs to be dehydrated and deoxygenated. For example, a stainless steel reactor (5L) can be connected to a vacuum pump and an inert gas port. The stainless steel reactor can be evacuated (vacuum degree 10-60 Pa) and then filled with an inert gas (such as nitrogen / argon) for dehydration and deoxygenation treatment, repeated at least 3 times, and then used under inert gas protection. In addition, the solvent and olefin monomer also need to be dehydrated and deoxygenated before the polymerization reaction.

[0067] Furthermore, in the above preparation method, in order to make the product synthesis more efficient and uniform, a stirring operation can be performed in each of the above steps, with a stirring speed of 100 to 500 rpm.

[0068] In step 1), this application does not impose any special limitations on the solvent, as long as it can serve as a medium for the reaction of the olefin monomers and does not react with the components in the reaction system. For example, the solvent includes at least one of cyclohexane, n-hexane, heptane, benzene, toluene, and tetrahydrofuran. This application also does not impose any special limitations on the volume of the solvent; it can be selected according to actual needs.

[0069] This application does not specifically limit the initiator alkyllithium, as long as it can initiate the polymerization reaction. For example, the alkyl group of alkyllithium is a hydrocarbon group with 2 to 20 carbon atoms, such as at least one of n-butyllithium, sec-butyllithium, tert-butyllithium, methyllithium, ethyllithium, and isopropyllithium.

[0070] This application does not impose any specific limitations on polarity modifiers, as long as they can be used to adjust the molecular weight and chain length of the polymerization reaction. For example, polarity modifiers are one or more of oxygen-containing, nitrogen-containing, sulfur-containing, and phosphorus-containing polar compounds. For instance, polarity modifiers include at least one of tetrahydrofuran, 2,2-di(5-methyl-2-tetrahydrofuranyl)propane (DMOP), tetramethylethylenediamine, N,N-dimethylformamide, N,N,N',N'-tetramethyl-p-toluidine (TMPTMA), and P-complexes.

[0071] This application does not specifically limit the olefin monomer, which includes one or more olefins. When the olefin monomer undergoes a polymerization reaction, the olefin monomer is an olefin, and the resulting polymer is a monomer. In the aforementioned monomer, the molecular chain lengths of each monomer may be the same or different.

[0072] In another embodiment, when the olefin monomer includes multiple olefins, the resulting polymer is a polymer, and the composition of the structural units in the polymer originates from the multiple olefins used as raw materials. Each polymer may have the same structural unit composition and the same molecular chain length, or different structural unit compositions and the same molecular chain length, or the same structural unit composition and different molecular chain lengths, or different structural unit compositions and different molecular chain lengths. The polymer obtained by the polymerization reaction of the olefin monomer is a polyolefin branched precursor.

[0073] In step 2), this application controls the type of star-shaped coupling agent added to form a star-shaped multi-branched polyolefin with 2 to 8 polyolefin branches. Specifically, in the coupling reaction, the polyolefin branch precursor is attached to the star-shaped coupling unit under the action of the star-shaped coupling agent to obtain a star-shaped coupling compound. In the star-shaped coupling compound, the structural formula of the polyolefin branch precursor is (B x I y ) n Where n is the average number of arms, B is the structural unit from butadiene, x is the mass percentage of butadiene structural units in the polyolefin branched precursor, I is the structural unit from isoprene, and y is the mass percentage of isoprene structural units in the polyolefin branched precursor. x and y satisfy x + y = 100 wt%, 25% ≤ x ≤ 100%, and 0% ≤ y ≤ 75%. The structure of the aforementioned polyolefin branched precursor is controlled by the composition and mass of the added olefin monomers.

[0074] It should be clarified that polyolefin branched precursors and star-shaped couplings include unsaturated carbon-carbon double bonds and saturated carbon-carbon single bonds.

[0075] In step 3), this application does not specifically limit the metal catalyst, as long as it can catalyze the hydrogenation reaction. For example, the metal catalyst includes at least one of nickel, platinum, palladium, rhodium, and ruthenium. Through the hydrogenation reaction, the unsaturated carbon-carbon double bonds of the star-shaped coupling can undergo addition to form carbon-carbon single bonds, ultimately forming a star-shaped multi-branched polyolefin.

[0076] It should be noted that, because hydrogen gas is often used in hydrogenation reactions, a high-pressure reactor is required for the hydrogenation reaction.

[0077] By using the above-described method for preparing star-shaped multi-branched polyolefins, star-shaped multi-branched polyolefins as described above can be obtained. Using the above-described product in base oil can reduce the coefficient of friction between various automotive components, especially the coefficient of friction between components at high sliding speeds.

[0078] Specifically, the olefin monomers include at least one of butadiene and isoprene. The aforementioned olefins have relatively low molecular weights, resulting in polyolefins with low viscosity and good flowability. This application utilizes the aforementioned olefin monomers to prepare star-shaped branched polyolefins, which is advantageous for obtaining star-shaped branched polyolefins with low viscosity.

[0079] In another embodiment, the star coupling agent includes at least one selected from RCH3Cl3, RCl4, R2Cl6, and R3Cl8, wherein R includes at least one selected from silicon, tin, lead, titanium, and germanium. For example, when the star coupling agent used is RCl4, such as tin tetrachloride, the star-shaped multi-branched polyolefin includes one star coupling unit; when the star coupling agent used is R2Cl6, such as hexachlorosilane, the star-shaped multi-branched polyolefin includes two star coupling units.

[0080] This application uses different star-shaped coupling agents to prepare star-shaped multi-branched polyolefins with different branched structures, which is beneficial to reduce the viscosity of star-shaped multi-branched polyolefins and improve their performance as base oils in reducing the coefficient of friction.

[0081] In another embodiment of the above-mentioned olefin monomers, butadiene accounts for 25-100% of the total mass of the olefin monomers.

[0082] In another specific embodiment, the mass of isoprene accounts for 0 to 75% of the total mass of the olefin monomer.

[0083] This application, by limiting the olefin component in the olefin monomer, facilitates the synthesis of star-shaped multi-branched polyolefins with lower molecular weight, thereby improving their flowability.

[0084] In detail, in the above-mentioned method for preparing star-shaped multi-branched polyolefins, the mass of the olefin monomer accounts for 5-15 wt% of the total mass of the olefin monomer and solvent. By controlling the mass ratio of the olefin monomer, this application is beneficial to both initiating the polymerization reaction and synthesizing star-shaped multi-branched polyolefins with lower molecular weights, thereby reducing their viscosity as base oils.

[0085] As described above, when butadiene participates in the reaction as an olefin monomer, it generates 1,2-polybutadiene and 1,4-polybutadiene. In another specific embodiment, the mass of the polarity modifier accounts for 0 to 0.5 wt% of the total mass of the polarity modifier and solvent. The polarity modifier can adjust the structural ratio of 1,2-polybutadiene and 1,4-polybutadiene in the polymerization product. For example, when the mass of the polarity modifier accounts for 0% of the total mass of the polarity modifier and solvent, the 1,2-polybutadiene structure accounts for 6%-10% of the total mass of the polybutadiene structure. As the mass of the polarity modifier increases, the mass percentage of the 1,2-polybutadiene structure gradually increases. When the mass of the polarity modifier accounts for 0.5% of the total mass of the polarity modifier and solvent, the 1,2-polybutadiene structure accounts for 15%-20% of the total mass of the polybutadiene structure.

[0086] This application does not impose any special restrictions on the mass of the initiator alkyllithium, as long as it can initiate the polymerization reaction.

[0087] This application further limits the mass ratio of polarity modifiers, the amount of alkyl lithium, and the mass ratio of star coupling agents, which is beneficial for synthesizing star-shaped multi-branched polyolefins with a number average molecular weight of 200-10000 g / mol, and thus helps to reduce their viscosity.

[0088] Furthermore, in the above-mentioned method for preparing star-shaped branched polyolefins, the polymerization reaction temperature is 50–70°C, and the reaction time is 30–90 min. For example, the polymerization reaction temperature includes, but is not limited to, a range of 50°C, 60°C, 70°C, or any combination thereof; the reaction time includes, but is not limited to, a range of 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, or any combination thereof. This application, by controlling the temperature and time of the polymerization reaction, facilitates the synthesis of star-shaped branched polyolefins with a number-average molecular weight of 200–10000 g / mol.

[0089] In another specific embodiment, the coupling reaction temperature is 50–70°C, and the reaction time is 30–90 min; for example, the coupling reaction temperature includes, but is not limited to, a range of 50°C, 60°C, 70°C, or any combination thereof; the reaction time includes, but is not limited to, a range of 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, or any combination thereof. This application, by controlling the temperature and time of the coupling reaction, facilitates the formation of star-shaped multi-branched polyolefins with the above structure.

[0090] In another specific embodiment, the hydrogenation reaction temperature is 50–70°C, the reaction time is 1–4 hours, and the hydrogen pressure is 1–4 MPa. This application uses hydrogenation to transform the star-shaped coupling into a more saturated star-shaped branched polyolefin. By controlling the reaction conditions of the hydrogenation reaction, it is beneficial to ensure the completeness of the hydrogenation reaction, thereby improving the oxidation resistance and thermal stability of the star-shaped branched polyolefin.

[0091] In the above method for preparing star-shaped multi-branched polyolefins, step 3) is followed by adding an oxidant to the reaction solution containing the star-shaped multi-branched polyolefin for post-treatment to obtain the star-shaped multi-branched polyolefin.

[0092] Specifically, this application does not impose any particular limitation on the oxidant, as long as it can deactivate the metal catalyst in the hydrogenation reaction. For example, the oxidant mentioned above includes at least one of hydrogen peroxide, potassium permanganate, nitric acid, sodium hypochlorite, oxygen, and ozone.

[0093] It is understandable that post-processing includes using solvents, deionized water, etc. to clean the product in order to obtain a relatively pure star-shaped branched polyolefin.

[0094] A third aspect of this application provides a lubricating oil whose base oil includes the star-shaped multi-branched polyolefin as described above or the star-shaped multi-branched polyolefin prepared by the method described above.

[0095] To further reduce the friction coefficient of various automotive components, this application uses the star-shaped multi-branched polyolefin as described above as the base oil for lubricating oil, which in particular reduces the friction coefficient of various automotive components under high-speed sliding and effectively improves the life of automotive components.

[0096] Furthermore, the aforementioned lubricating oil comprises, by weight percentage, 0.5% to 8.0% viscosity index improver, 0.5% to 6.0% dispersant, 0.1% to 1.0% antioxidant, 0.1% to 4.0% anti-wear agent, 0.1% to 0.7% extreme pressure agent, 0.1% to 0.5% rust inhibitor, 0.01% to 0.3% metal deactivator, 0.1% to 0.5% detergent, 0.01% to 0.05% antifoaming agent, with the balance being the base oil.

[0097] Specifically, viscosity index improvers include at least one of polymethyl methacrylate, polyisobutylene, ethylene-propylene copolymer, and polyisoprene;

[0098] The dispersant includes at least one of bis(succinimide) and mono(succinimide);

[0099] Antioxidants include at least one of the following: high molecular weight phenols containing sulfides, such as sulfide derivatives of 2,6-di-tert-butyl-4-methylphenol and 4,4'-thiobis(6-tert-butyl-3-methylphenol);

[0100] Anti-wear agents include at least one of butyl triphenyl thiophosphate, zinc dialkyl dithiophosphate, and tributyl phosphate;

[0101] Extreme pressure agents include phosphate ester amine salts, such as at least one of tributyl phosphate ester amine salt, dioctyl phosphate ester amine salt, and triphenyl phosphite ester amine salt;

[0102] Rust inhibitors include at least one of alkenyl succinate half ester, alkenyl succinic anhydride, tricresyl phosphate, and dibutyl phosphate;

[0103] Metal deactivators include triazole derivatives, such as at least one of methylbenzotriazole, benzotriazole, and mercaptobenzotriazole;

[0104] The detergent includes at least one of the following: high-alkalinity calcium salicylate, high-alkalinity calcium sulfonate, and high-alkalinity alkylphenol calcium sulfide;

[0105] Antifoaming agents include at least one of methyl silicone oil, polysiloxane, polyethylene glycol, and glyceryl monostearate.

[0106] By using the above components to prepare a lubricating oil, a lubricating oil with good lubrication performance can be obtained. In addition, the lubricating oil also has a low viscosity, which is beneficial for quickly covering the components that need lubrication during the lubrication process and achieving a better lubrication effect.

[0107] The fourth aspect of this application provides an electric motor that includes the lubricating oil described above. When the lubricating oil described above is used, the internal components of the electric motor have a low coefficient of friction, and therefore the electric motor has a long service life.

[0108] This application also provides a car that includes the motor described above. When the car uses the motor, due to the good internal lubrication of the motor, the car does not need to consume a lot of kinetic energy when starting, and the motor has a long lifespan, which can save the cost of car maintenance and improve economic efficiency.

[0109] The technical solution of this application will be further described below with reference to specific embodiments.

[0110] Example 1

[0111] The preparation method of star-shaped multi-branched polyolefin in this embodiment includes the following steps:

[0112] 1) Connect the stainless steel reactor (5L) to the vacuum pump and the inert gas port. Vacuum the stainless steel reactor (30Pa) and then fill it with inert gas (such as nitrogen / argon) to dehydrate and deoxygenate it. Repeat this process at least 3 times. The reactor is then ready for use under inert gas protection.

[0113] 2) The solvents cyclohexane, butadiene, and isoprene were respectively immersed in a column filled with conventional packing material for more than 24 hours for dehydration and deoxygenation treatment. Then, cyclohexane, butadiene, and isoprene were separately pressurized into the metering tank of a balance using an inert gas (such as nitrogen / argon). First, the solvent cyclohexane was pressurized into the above-treated polymerization reactor using an inert gas (argon). Then, 96g of butyllithium initiator was added quantitatively. The polymerization reactor was stirred at 300 rpm, and the circulating water was turned on, with the circulating water bath temperature set to 50℃.

[0114] 3) Weigh 84g butadiene and 102g isoprene. Add butadiene and isoprene into the polymerization reactor in sequence. The mass of the added olefin monomer accounts for 10wt% of the total mass of the olefin monomer and solvent. At the same time, add 3.6g of the polarity modifier tetrahydrofuran. Start the polymerization reaction at 50℃ for 60min to obtain the polymer reaction solution.

[0115] 4) Add 80g of star-shaped coupling agent to the reactor for coupling reaction. The reaction temperature is 50℃ and the reaction time is 60min to obtain the star-shaped coupling reaction solution.

[0116] 5) The above-mentioned star-shaped coupling reaction liquid was injected into a high-pressure reactor and a nickel-aluminum metal catalyst was added. The temperature was set to 50°C and the stirring speed was 300 revolutions per minute. Then, hydrogen gas was introduced into the reactor at a pressure of 3 MPa. The temperature and speed were kept constant and the reaction was carried out for 3 hours. Heating was stopped, the hydrogen pressure valve was closed, the hydrogen gas in the reactor was slowly discharged, and stirring was stopped to obtain a reaction liquid containing star-shaped multi-branched polyolefins.

[0117] 6) Add cyclohexane solvent and hydrogen peroxide to the reaction solution of the above star-shaped multi-branched polyolefin, wash repeatedly with water to remove the metal catalyst, and obtain star-shaped multi-branched polyolefin.

[0118] Among them, the number average molecular weight of star-shaped multi-branched polyolefins is 450 g / mol;

[0119] The number of polyolefin branches on the star coupling unit of the star-shaped multi-branched polyolefin is 2.4;

[0120] The star-shaped branched polyolefin contains 30 wt% structural units derived from butadiene and 40 wt% structural units derived from isoprene.

[0121] The molecular weight distribution index of star-shaped branched polyolefins is 1.3;

[0122] The degree of hydrogenation of star-shaped branched polyolefins is 100%.

[0123] Example 2

[0124] The reagents used in this embodiment are as follows:

[0125] Polymethacrylate: Evonik, number average molecular weight 1.8 × 10⁻⁶ 4 .

[0126] High molecular weight phenols: BASF L135.

[0127] Phosphate esters and amine salts: BASF.

[0128] Toluenetriazole derivative: BASF RR39.

[0129] High-alkalinity calcium salicylate: Ruifeng New Materials, with an alkalinity of 200mg KOH / g.

[0130] In this embodiment, the star-shaped multi-branched polyolefin obtained in Example 1 is used as the base oil for the preparation of lubricating oil. The specific composition of the lubricating oil in this embodiment is shown in Table 1:

[0131] Table 1

[0132] Example 3

[0133] In this embodiment, the star-shaped multi-branched polyolefin obtained in Example 1 is used as the base oil for the preparation of lubricating oil. The specific composition of the lubricating oil in this embodiment is shown in Table 2:

[0134] Table 2

[0135] Example 4

[0136] In this embodiment, the star-shaped multi-branched polyolefin obtained in Example 1 is used as the base oil for the preparation of lubricating oil. The specific composition of the lubricating oil in this embodiment is shown in Table 3:

[0137] Table 3

[0138] Example 5

[0139] In this embodiment, the star-shaped multi-branched polyolefin obtained in Example 1 is used as the base oil for the preparation of lubricating oil. The specific composition of the lubricating oil in this embodiment is shown in Table 4:

[0140] Table 4

[0141] Comparative Example 1

[0142] This comparative example is basically the same as Example 2, except that the base oil in this comparative example is replaced with Group II / III mineral base oil.

[0143] Comparative Example 2

[0144] This comparative example is basically the same as Example 2, except that the base oil in this comparative example is replaced with polyalphaolefin (PAO) synthetic oil.

[0145] Comparative Example 3

[0146] This comparative example is basically the same as Example 2, except that the base oil in this comparative example is replaced with coal-to-oil base oil.

[0147] Test case

[0148] The performance of the lubricating oils in Examples 2-5 and Comparative Examples 1-3 was tested using an oil-cooled motor gearbox transmission system. The test results are shown in Table 5.

[0149] The lubricating oils used in Examples 2-5 and Comparative Examples 1-3 were evaluated for their frictional characteristics using a Falex ring-block friction testing machine (manufactured by Falex Corporation, USA). In the experiment, a fixed steel block and a rotating steel ring rub against each other under a certain pressure. The frictional force, velocity, friction time, and coefficient of friction were measured. The Japan Automotive Standardization Organization (JASO) established an experimental method (JASO M358-2005) using the Falex ring-block friction testing machine to simulate and evaluate the frictional performance of oils, namely the LFW-1 steel-to-steel friction test high-load test method. The experimental parameters are shown in Table 6. The results of the coefficient of friction are shown in Table 7 and Figure 1.

[0150] Table 5

[0151] As shown in Table 5, the lubricating oils in Examples 2-5 and Comparative Examples 1-3 exhibit similar performance in various tests of the oil-cooled motor gearbox transmission system.

[0152] Table 6

[0153] Table 7

[0154] As shown in Table 7 and Figure 1, Example 1 achieved a sliding friction coefficient similar to that of the comparative example when the sliding speed was between 0.025 and 0.125 m / s. At a higher sliding speed of 0.25-1 m / s, the lubricating oil in Example 1 had a lower friction coefficient. Therefore, using the star-shaped multi-branched polyolefin provided in this application as the base oil of the lubricating oil can effectively reduce the friction coefficient at the sliding speed.

[0155] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A star-shaped multi-branched polyolefin, wherein, The star-shaped multi-branched polyolefin includes a star-shaped coupling unit and M polyolefin branches connected to the star-shaped coupling unit. The number-average molecular weight of the star-shaped multi-branched polyolefin is 200-10000 g / mol, and M is 2-8.

2. The star-shaped multi-branched polyolefin according to claim 1, wherein, Each of the polyolefin branches independently includes at least one structural unit from butadiene and a structural unit from isoprene.

3. The star-shaped multi-branched polyolefin according to claim 2, wherein, Each of the polyolefin branches comprises, by weight percentage, 25–100 wt% structural units from butadiene and 0–75 wt% structural units from isoprene.

4. The star-shaped multi-branched polyolefin according to any one of claims 1-3, wherein, The molecular weight distribution index of the star-shaped multi-branched polyolefin is 1.05–1.6; and / or, The degree of hydrogenation of the star-shaped branched polyolefin is 80-100%.

5. The star-shaped multi-branched polyolefin according to any one of claims 1-4, wherein, The star-shaped coupling unit includes at least one of silicon core, tin core, lead core, titanium core, and germanium core.

6. The star-shaped multi-branched polyolefin according to any one of claims 1-5, wherein, The star-shaped multi-branched polyolefin is prepared by a method comprising the following process: An olefin monomer is polymerized and then a star coupling agent is added to undergo a coupling reaction to obtain a star coupling compound. Subsequently, the star coupling compound is hydrogenated to obtain the star-shaped multi-branched polyolefin.

7. A method for preparing a star-shaped multi-branched polyolefin according to any one of claims 1-6, wherein, Includes the following steps: 1) In a solvent, using alkyllithium as an initiator and adding a polarity modifier, olefin monomers undergo a polymerization reaction to obtain a polymer reaction solution; 2) Add a star-shaped coupling agent to the polymerization reaction solution to carry out a coupling reaction, and obtain a star-shaped coupling reaction solution; 3) Add a metal catalyst to the star-shaped coupling reaction solution to carry out a hydrogenation reaction to obtain a reaction solution containing star-shaped multi-branched polyolefins.

8. The method for preparing star-shaped multi-branched polyolefins according to claim 7, wherein, The olefin monomer includes at least one selected from butadiene and isoprene; and / or The star-shaped coupling agent includes at least one of RCH3Cl3, RCl4, R2Cl6, and R3Cl8, wherein R includes at least one of silicon, tin, lead, titanium, and germanium.

9. The method for preparing star-shaped multi-branched polyolefins according to claim 8, wherein, The butadiene accounts for 25% to 100% of the total mass of the olefin monomers; and / or, The isoprene accounts for 0-75% of the total mass of the olefin monomers.

10. The method for preparing star-shaped multi-branched polyolefins according to any one of claims 7-9, wherein, In step 1), the olefin monomer accounts for 5-15 wt% of the total mass of the olefin monomer and solvent; and / or, The polarity modifier accounts for 0 to 0.5 wt% of the total mass of the polarity modifier and solvent; and / or, In step 2), the mass of the star-shaped coupling agent accounts for 1 to 10 wt% of the total mass of the star-shaped coupling agent and the solvent.

11. The method for preparing star-shaped multi-branched polyolefins according to any one of claims 7-10, wherein, In step 1), the polymerization reaction is carried out at a temperature of 50–70°C for 30–90 minutes; and / or, In step 2), the coupling reaction is carried out at a temperature of 50–90°C for 30–90 minutes; and / or, In step 3), the reaction temperature of the hydrogenation reaction is 50-70°C, the reaction time is 1-4 hours, and the hydrogen pressure is 1-4 MPa.

12. The method for preparing star-shaped multi-branched polyolefins according to any one of claims 7-11, wherein, Step 3) is followed by adding an oxidant to the reaction solution containing the star-shaped multi-branched polyolefin for post-treatment to obtain the star-shaped multi-branched polyolefin.

13. A lubricating oil, wherein, The base oil of the lubricating oil includes the star-shaped multi-branched polyolefin as described in any one of claims 1-6 or the star-shaped multi-branched polyolefin prepared by the method described in any one of claims 7-12.

14. The lubricating oil according to claim 13, wherein, The lubricating oil comprises, by weight percentage, 0.5%–8.0% viscosity index improver, 0.5%–6.0% dispersant, 0.1%–1.0% antioxidant, 0.1%–4.0% anti-wear agent, 0.1%–0.7% extreme pressure agent, 0.1%–0.5% rust inhibitor, 0.01%–0.3% metal deactivator, 0.1%–0.5% detergent, 0.01%–0.05% antifoaming agent, with the balance being the base oil.

15. An electric motor, wherein, The motor includes the lubricating oil as described in claim 13 or 14.

16. A type of automobile, wherein, The vehicle includes the motor as described in claim 15.

Images