LOW VISCOSE LUBRICANT COMPOSITION WITH IMPROVED DURABILITY AND NVH PERFORMANCE

Abstract

A low-viscosity lubricating oil composition with improved durability and NVH (noise, vibration, and harshness) performance is provided. The durability and NVH performance of the low-viscosity lubricating oil can be further enhanced by a suitable combination of mineral and / or synthetic oil and a viscosity index improver.

Description

BACKGROUND(a) Technical field

[0001] The present disclosure relates to a low-viscosity lubricating oil composition with improved durability and NVH performance (noise, vibration and harshness), wherein the durability and NVH performance can be improved by a suitable combination of mineral oil and / or synthetic oil and a viscosity index improver. (b) Description of the known technique

[0002] As extreme weather events linked to climate change become more frequent worldwide, individual countries and national coalitions are striving to mitigate climate change by announcing plans to reduce carbon emissions and achieve carbon neutrality. As part of this plan, the share of electric vehicles in new car sales is being increased to reduce carbon dioxide emissions in the transport sector, and sales of electric vehicles have recently increased significantly.

[0003] The design of electric vehicle drive units is gradually changing from a conventional, separate motor and transmission to an integrated motor-transmission system. Consequently, the demands placed on the lubricants used in the integrated system are also increasing compared to the conventional separate design. While in a conventional separate transmission, the lubricant is applied only to the reduction gear section, making extreme pressure performance and wear resistance essential for effective protection, the integrated system requires additional performance characteristics such as motor cooling capacity, material compatibility with electrical components, reduced drag losses, and similar considerations.

[0004] Reducing the viscosity of a lubricant applied to an integrated engine-transmission component can improve energy efficiency by lowering the internal resistance of the engine, thus reducing energy consumption due to friction, and by dissipating heat generated during engine operation more effectively, thereby improving drive efficiency. However, there are limitations: reducing the viscosity also reduces the thickness of the lubricating oil film relative to the viscosity, which can negatively impact durability and NVH performance.

[0005] Since additives added to liquid lubricants along with the base oil to improve various performance characteristics, such as performance and durability under extreme pressure, prevention of oil oxidation, prevention of contamination, prevention of deposits, friction reduction, etc., generally have a high viscosity, it is difficult to improve durability and NVH performance by adding large quantities of them to low-viscosity oil. Therefore, it is necessary to develop a lubricant composition capable of overcoming these limitations and also achieving improved energy efficiency at low viscosity.

[0006] The explanations in this background section merely provide background information on the present disclosure and do not represent prior art. SUMMARY

[0007] The present disclosure was made in an effort to solve problems that have arisen in the known technology. One objective of the present disclosure is to provide a lubricating oil composition that improves, in a balanced manner, the performance under extreme pressure and the wear resistance required for conventional lubricating oil compositions, as well as the cooling performance, compatibility with electrical components, and the like.

[0008] Another objective of the present disclosure is to provide a lubricating oil composition that is applied to an integrated engine-transmission part, thereby improving energy efficiency compared to conventional techniques and preventing deterioration in durability and NVH performance.

[0009] The purposes of this disclosure are not limited to those mentioned above. The purposes of this disclosure should be more clearly understood through the following description and can be achieved through the means described in the claims and their combinations.

[0010] One aspect of the present disclosure provides a lubricating oil composition comprising a lubricating base oil containing mineral oil, a viscosity index improver, and an additive. Furthermore, the lubricating base oil may contain mineral oil and synthetic oil.

[0011] In one embodiment, the lubricating oil composition can contain 50 to 80 wt.% of the mineral oil, 1 to 10 wt.% of the viscosity index improver and 10 to 20 wt.% of the additive, based on the total weight thereof.

[0012] If the lubricating base oil of the lubricating oil composition contains mineral oil and synthetic oil, the lubricating oil composition may contain 50 to 80 wt.% of the mineral oil, 10 to 40 wt.% of the synthetic oil, 1 to 10 wt.% of the viscosity index improver and 8 to 20 wt.% of the additive, based on the total weight thereof.

[0013] In one embodiment, the lubricating oil composition can have a kinematic viscosity at 100°C in a range of 2.8 to 4.0 cSt.

[0014] In one embodiment, the mineral oil can contain highly refined mineral oil having an aromatic component content of 0.1 wt.% or less.

[0015] In one embodiment, the mineral oil can have a kinematic viscosity at 100°C in a range of 2.0 to 4.0 cSt.

[0016] In one embodiment, the mineral oil can have a viscosity index (VI) equal to or greater than 100.

[0017] In one embodiment, the synthetic oil can contain a polyalphaolefin (PAO)-based synthetic oil.

[0018] In one embodiment, the synthetic oil can have a kinematic viscosity at 100°C in the range of 2.0 to 3.0 cSt.

[0019] In one embodiment, the viscosity index improver may contain poly(alkyl methacrylate).

[0020] In one embodiment, the weight-average molecular weight (Mw) of the viscosity index improver can be in a range of 10,000 to 50,000.

[0021] In one embodiment, the additive may contain at least one detergent, an antioxidant, an anti-wear agent, a dispersant, a friction modifier, a corrosion inhibitor, or a combination thereof.

[0022] The detergent may contain at least one of a sulfonate detergent, a phenate detergent, a salicylate detergent, or a combination thereof.

[0023] The antioxidant may also contain at least one of hindered phenols, aromatic amines, or a combination thereof.

[0024] In one embodiment, the lubricating oil composition may further contain at least one pour point depressant, an antifoaming agent, or a combination thereof. BRIEF DESCRIPTION OF THE DRAWING Fig. Figure 1 is a diagram showing the results of the analysis of lubricating oil compositions according to Example 3 and the comparative examples 6 to 8 using a mini traction machine (MTM). DETAILED DESCRIPTION

[0025] The above and further tasks, features, and advantages of the present disclosure should be more clearly understood from the following embodiments in conjunction with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed herein and can be modified in various ways. These embodiments serve to thoroughly explain the disclosure and to adequately convey the spirit of the present disclosure to those possessing normal technical knowledge.

[0026] In the drawings, the same reference numerals refer to identical or similar elements. For the sake of clarity in this disclosure, the dimensions of the structures are shown larger than their actual sizes. Although terms such as "first," "second," and the like may be used here to describe different elements, these elements are not limited by these terms. These terms are used only to distinguish one element from another. For example, a "first" element discussed below could be referred to as a "second" element without this altering the scope of the present invention. Similarly, the "second" element could also be referred to as a "first" element. The singular forms used here also include the plural forms, unless the context clearly indicates otherwise.

[0027] It should be further understood that the terms "comprise," "contain," "exist," and the like, when used in this specification, specify the presence of certain features, integers, steps, operations, elements, components, or combinations thereof, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof. When an element, such as a layer, film, area, or plate, is described as being "on" another element, it may be located directly on top of the other element, or there may be elements intervening. When an element, such as a layer, film, area, or plate, is described as being "under" another element, it may be located directly beneath the other element, or there may be elements intervening.

[0028] Unless otherwise stated, all numbers, values, and / or representations expressing the amounts of components, reaction conditions, polymer compositions, and mixtures used herein are to be understood as approximations that include various measurement uncertainties arising, among other things, in determining these values, and should therefore be modified in all cases by the term "approximately." Where a numerical range is given in this description, it is continuous and includes all values ​​from the minimum value of the range to its maximum value, unless otherwise stated. Furthermore, where such a range refers to integer values, all integer values, including the minimum value up to the maximum value, are included, unless otherwise stated.

[0029] When a range for a variable is described in this specification, it is to be understood that the variable includes all values, including the described endpoints, within the specified range. For example, the range "5 to 10" includes all subranges such as 6 to 10, 7 to 10, 6 to 9, 7 to 9, etc., as well as individual values ​​of 5, 6, 7, 8, 9, and 10, and also includes all values ​​between valid integers within the specified range, such as 5.5, 6.5, 7.5, 5.5 to 8.5, 6.5 to 9, etc. The range "10% to 30%" includes subranges such as 10% to 15%, 12% to 18%, 20% to 30%, etc., as well as all integers with values ​​from 10%, 11%, 12%, 13%, etc., up to 30%, and also includes every value between valid integers within the specified range, such as 10.5%, 15.5%, 25.5%, etc.

[0030] In the present disclosure, each of the formulations such as “A or B”, “at least one of A and B”, “at least one of A or B”, “A, B or C”, “at least one of A, B and C”, “at least one of A, B or C” and “at least one of A, B or C or a combination thereof” may include any or all possible combinations of the elements listed in the corresponding formulation.

[0031] A lubricating oil composition according to one aspect of the present disclosure may contain a lubricating base oil containing mineral oil and / or synthetic oil, a viscosity index improver, and an additive. In particular, the lubricating oil composition may contain 50 to 80 wt.% of the mineral oil, 1 to 10 wt.% of the viscosity index improver, and 10 to 20 wt.% of the additive, based on the total weight thereof. If the lubricating base oil of the lubricating oil composition contains both mineral oil and synthetic oil, the lubricating oil composition may also contain 50 to 80 wt.% of the mineral oil, 10 to 40 wt.% of the synthetic oil, 1 to 10 wt.% of the viscosity index improver, and 8 to 20 wt.% of the additive, based on the total weight thereof.

[0032] The lubricating oil composition according to an embodiment of the present disclosure is able to improve the NVH performance of a vehicle when applied to a vehicle part, in particular an integrated motor-transmission part installed in an electric vehicle, by combining the components in suitable quantities as described above.

[0033] The kinematic viscosity of the lubricating oil composition for electric vehicles can also be related to the energy efficiency of electric vehicles. Kinematic viscosity is a measure of the resistance to flow of a fluid over time under temperature conditions at which a fluid flows, particularly at temperatures equal to or higher than room temperature. The lower the kinematic viscosity, the lower the friction in the lubricating oil composition, which can improve energy efficiency. If the lubricating oil composition according to an embodiment of the present disclosure is applied to existing parts of internal combustion engines, the "energy efficiency" described above and the "energy efficiency" used below can be understood as "fuel efficiency."

[0034] In one embodiment, the lubricating oil composition can have a kinematic viscosity at 100°C of 2.8 to 4.0 cSt. The lubricating oil composition according to one embodiment of the present disclosure has a kinematic viscosity at 100°C of 2.8 to 4.0 cSt, such that when the lubricating oil composition is applied to an integrated engine-gearbox component and the like, its internal resistance can decrease, thereby reducing energy consumption and heat generation due to friction.

[0035] If the kinematic viscosity at 100°C is less than 2.8 cSt, the oil film may become too thin when the lubricating oil composition is applied to an integrated motor-transmission component or similar, because the viscosity is too low, which impairs performance under extreme pressure. Conversely, if the kinematic viscosity at 100°C exceeds 4.0 cSt, the effect of improving energy efficiency compared to conventional lubricating oil compositions for electric vehicles may be negligible.

[0036] The individual components of the lubricating oil composition are described in more detail below. mineral oil

[0037] Mineral oil is a general term for oils obtained from mineral raw materials such as petroleum, coal, tar, shale oil, and the like, and is commonly used as a lubricating oil to reduce friction between machine parts. The mineral oil according to one embodiment of the present disclosure is not particularly limited as long as it is commonly used in a lubricating oil composition. However, it is advantageous if highly refined mineral oil is included. Highly refined mineral oil can be defined as mineral oil that is refined to such an extent that it has an aromatic component content of 0.1 wt.% or less.

[0038] The aromatic component contained in mineral oil is a material that oxidizes readily at high temperatures. Therefore, when highly refined mineral oil with a low aromatic component content, as described in the present disclosure, is used, the lubricating oil composition can exhibit higher oxidation stability. Since impurities are generally removed during the manufacturing process of highly refined mineral oil, the performance of the mineral oil can be improved and its service life extended.

[0039] Mineral oil with a viscosity index (VI) of 100 or more can also be used. The lubricating oil composition according to one embodiment of the present disclosure can exhibit higher thermal stability because it contains mineral oil with a viscosity index of 100 or more.

[0040] The term "viscosity index" refers to the relationship between the viscosity of an oil (e.g., mineral oil, synthetic oil, etc.) and its temperature. A higher number indicates a smaller change in viscosity due to temperature fluctuations. Generally, the higher the viscosity index, the more stable the oil is under heat, which can increase its lifespan and usability. The viscosity index can be determined using a well-known engineering equation or a program that calculates this equation.

[0041] In one embodiment, the lubricating oil composition can contain mineral oil having a kinematic viscosity at 100°C of 2.0 to 4.0 cSt. The lubricating oil composition according to one embodiment of the present disclosure can achieve a kinematic viscosity at 100°C of 2.8 to 4.0 cSt if it contains 50 to 80 wt.% mineral oil having a kinematic viscosity at 100°C of 2.0 to 4.0 cSt. Synthetic oil

[0042] Synthetic oil is an oil that consists of artificially modified or synthetic compounds and can be produced from crude oil, chemically modified petroleum components, or other raw materials.

[0043] The synthetic oil according to one embodiment of the present disclosure can be used without special restriction as long as it is commonly used in a lubricating oil composition. For example, synthetic hydrocarbon oils, ester oils, phenyl ethers, polyethylene glycol, and the like can be used. In particular, polyalphaolefin (PAO)-based synthetic oil is used.

[0044] Polyalphaolefin-based synthetic oil, which is a representative synthetic oil, is produced by oligomerization of linear alpha olefin, which is formed during ethylene polymerization and is commonly used in automotive and industrial lubricating oils.

[0045] The polyalphaolefin-based synthetic oil according to an embodiment of the present disclosure consists exclusively of isoparaffin and therefore has a higher viscosity index than the mineral oil, better flowability at low temperatures, a narrow molecular weight distribution, low evaporation loss, and better thermal oxidation stability and friction properties.

[0046] The lubricating oil composition according to an embodiment of the present disclosure can exhibit superior friction properties due to the use of a lubricating base oil containing highly refined mineral oil and polyalphaolefin-based synthetic oil, thereby achieving an effect of improving the energy efficiency and NVH performance of a vehicle to which the lubricating oil composition is applied.

[0047] In one embodiment, the lubricating oil composition can contain synthetic oil having a kinematic viscosity at 100°C of 2.0 to 3.0 cSt. The lubricating oil composition according to one embodiment of the present disclosure can achieve a kinematic viscosity at 100°C of 2.8 to 4.0 cSt if it contains 10 to 40 wt.% synthetic oil having a kinematic viscosity at 100°C of 2.0 to 3.0 cSt. Viscosity index improvers

[0048] A viscosity index improver is added to improve the viscosity index of a lubricating oil composition and serves to increase the viscosity index of the lubricating oil composition, reduce viscosity at low temperatures and improve energy efficiency.

[0049] When a viscosity index improver is added to a lubricating oil composition, the extent to which the viscosity index is improved can be proportional to the polarity of the polymer used as the viscosity index improver. However, since the solubility of the polymer in the lubricating oil composition decreases with increasing polymer polarity, it is important to optimize the viscosity index and solubility by increasing the polymer polarity within a range in which the viscosity index improver dissolves.

[0050] Furthermore, the viscosity index increases proportionally to the molecular weight of the viscosity index improver, but the performance at extreme pressure tends to be inversely proportional to its molecular weight, so that the viscosity index and the performance at extreme pressure of the lubricating oil composition can be improved by optimizing the molecular weight.

[0051] In one embodiment, the viscosity index improver according to one embodiment of the present disclosure includes an olefin copolymer, a hydrogenated styrene-diene compound, and poly(alkyl methacrylate). The viscosity index improver contains, for example, poly(alkyl methacrylate).

[0052] The viscosity index improver containing poly(alkyl methacrylate) exhibits excellent low-temperature performance and shear stability. In particular, its high viscosity index allows it to form a specific oil film, preventing wear on integrated engine and transmission components at high temperatures and improving vehicle energy efficiency by reducing the viscosity of the lubricating oil at low temperatures. Furthermore, its high shear stability prevents the viscosity index improver from breaking down during prolonged use under demanding conditions, thus enhancing durability and service life.

[0053] Furthermore, according to one embodiment of the present disclosure, the viscosity index improver serves to improve performance at extreme pressure by optimizing the polarity and molecular weight of the polymer, and the weight-average molecular weight (Mw) of the viscosity index improver can fall in the range of 10,000 to 50,000 g / mol. If the weight-average molecular weight of the viscosity index improver exceeds 50,000 g / mol, the durability of the lubricating oil composition may also decrease due to a reduction in performance at extreme pressure.

[0054] The lubricating oil composition according to one embodiment of the present disclosure contains 1 to 10 wt.% of the viscosity index improver, which contains poly(alkyl methacrylate). If the amount of the viscosity index improver is less than 1 wt.%, the viscosity index may be low, which reduces friction performance, wear performance, and also energy efficiency. Conversely, if the amount of the viscosity index improver exceeds 10 wt.%, the viscosity may become excessively high due to the thickening effect, which reduces energy efficiency and can lead to fracture due to shearing of the viscosity index improver. Additive

[0055] The lubricating oil composition according to one embodiment of the present disclosure contains an additive to improve its performance. The additive can be used without particular restriction as long as it is typically used in the art to improve the performance of the lubricating oil composition and may, for example, contain at least one of a detergent, an antioxidant, an anti-wear agent, a dispersant, a friction modifier, a corrosion inhibitor, or a combination thereof (e.g., any one selected from the group consisting of a detergent, an antioxidant, an anti-wear agent, a dispersant, a friction modifier, a corrosion inhibitor, and combinations thereof).The additive is used, for example, in the form of a package in which two or more, selected from the detergent, the antioxidant, the anti-wear agent, the dispersant, the friction modifier, and the corrosion inhibitor, are mixed and combined in a specific ratio.

[0056] The additive can also be added in a quantity (in wt.%) that corresponds to the remainder after the addition of the lubricating base oil and the viscosity index improver, based on the total weight of the lubricating oil composition. For example, the lubricating oil composition can contain 8 to 40 wt.%, 10 to 40 wt.%, 8 to 20 wt.%, or 10 to 20 wt.% of the additive.

[0057] The detergent serves to inhibit the growth of deposits when such deposits form due to the oxidation of the lubricating oil composition and may, for example, contain at least one of a sulfonate detergent, a phenate detergent, a salicylate detergent, or a combination thereof (e.g., any one selected from the group consisting of a sulfonate detergent, a phenate detergent, a salicylate detergent, and combinations thereof).

[0058] In particular, the sulfonate detergent may contain hyperbasic calcium sulfonate, magnesium sulfonate, barium sulfonate, and the like, and the phenate detergent may contain calcium phenate, sodium phenate, barium phenate, and the like. Furthermore, the salicylate detergent may contain calcium salicylate and the like.

[0059] The antioxidant serves to prevent the lubricating oil composition from reacting with atmospheric oxygen and forming corrosive acids or sludge. Antioxidants are generally divided into chain reaction inhibitors, peroxide decomposers, and inactivators. Examples of chain reaction inhibitors can include inhibited phenols such as 2,6-di-tert-butyl paracresol, or aromatic amines such as dioctyldiphenylamine and phenylalphanaphthalene. For example, 2,6-di-tert-butyl paracresol is used.

[0060] An anti-wear agent is an additive used to prevent wear by forming a solid lubricating film through the adsorption of a polar organic compound onto a metal surface and its subsequent reaction with that surface. Anti-wear agents include, for example, organophosphorus and active sulfur types. Organophosphorus anti-wear agents are commonly used. When dissolved in lubricating oil, active sulfur anti-wear agents pose a corrosion risk to non-ferrous metals such as copper, brass, and bronze due to the dissolved sulfur.

[0061] The dispersant can serve to disperse sludge that may occur in the lubricating oil composition and to evenly distribute soot or other small insoluble particles in the lubricating oil composition, suppress the formation of sludge deposits, and neutralize acids. When the dispersant of the present disclosure is used in a mixture of a low-molecular-weight dispersant and a high-molecular-weight dispersant, the dispersion of by-products can be improved.

[0062] The friction modifier is an additive that improves lubrication performance by producing a low coefficient of friction during sliding between metals. According to one embodiment of the present disclosure, the additive may contain an alcohol-based friction modifier to improve friction reduction performance at low temperatures.

[0063] The corrosion inhibitor is an additive that suppresses the formation of rust caused by oxygen in the air and water, and can be designed to optimize corrosion protection performance when used in a mixture of inactive sulfur-based and non-sulfur-based corrosion inhibitors.

[0064] Furthermore, according to one embodiment of the present disclosure, the lubricating oil composition may include at least one of a pour point depressant, an antifoaming agent, or a combination thereof (e.g., any one selected from the group consisting of a pour point depressant, an antifoaming agent, and combinations thereof).

[0065] A pour point depressant is an additive that lowers the pour point. When wax forms in lubricating oil at low temperatures, the pour point depressant adsorbs onto the wax and prevents it from clumping, thus lowering the pour point of the lubricating oil composition. Any commercially available pour point depressant can be used.

[0066] The antifoaming agent can also be used to suppress foaming by altering the surface tension of the lubricating oil composition. Any commonly used antifoaming agent can be employed.

[0067] Therefore, according to one embodiment of the present disclosure, the lubricating oil composition is a low-viscosity lubricating oil having a kinematic viscosity at 100°C of 2.8 to 4.0 cSt, which, however, is able to prevent a deterioration of durability and NVH performance in low-viscosity lubricating oil by suitably combining highly refined mineral oil and polyalphaolefin-based synthetic oil and adding poly(alkyl methacrylate) having a suitable molecular weight as a viscosity index improver.

[0068] Furthermore, in the lubricating oil composition according to an embodiment of the present disclosure, not only the performance under extreme pressure and wear resistance required for conventional lubricating oil compositions, but also cooling performance, compatibility with electrical parts and the like can be improved in a balanced manner.

[0069] A better understanding of the present revelation can be obtained through the following examples and comparisons. However, these examples are not to be understood as limiting the technical spirit of the present revelation. Examples 1 to 3 and comparative examples 1 to 8

[0070] To produce a low-viscosity lubricating oil composition according to an embodiment of the present disclosure, individual lubricating oil compositions were obtained by mixing components in the amounts specified in Tables 1 and 2 below. Examples 1 to 3 are shown in Table 1, and comparative examples 1 to 8 are listed in Table 2. The individual components used here are as follows. It is noted that the additive to the lubricating oil composition is added such that the sum of the proportions of the components is 100 wt.%. [Components]

[0071] The mineral oil used was highly refined mineral oil, commercially available from S-OIL. aramcoULTRA 2: Highly refined mineral oil with a kinematic viscosity at 100°C of approximately 2 cSt aramcoULTRA 3: Highly refined mineral oil with a kinematic viscosity at 100°C of approximately 3 cSt aramcoULTRA 4: Highly refined mineral oil with a kinematic viscosity at 100°C of approximately 4 cSt

[0072] A polyalphaolefin-based synthetic oil, commercially available from ExxonMobil and INEOS, was used.

[0073] PAO 2: Polyalphaolefin-based synthetic oil with a kinematic viscosity at 100°C of approximately 2 cSt

[0074] PAO 3.5: Polyalphaolefin-based synthetic oil with a kinematic viscosity at 100°C of approximately 3.5 cSt

[0075] PAO 4: Polyalphaolefin-based synthetic oil with a kinematic viscosity at 100°C of approximately 4 cSt

[0076] 3) A modified poly(alkyl methacrylate)-based viscosity index improver (VISCOPLEX series), commercially available from Evonik, was used as the viscosity index improver.

[0077] Low molecular weight: Polymethacrylate with a weight-mean molecular weight (Mw) of 10,000 to 50,000 g / mol, SSI (Shear Stability Index) 9 (KRL Shear Stability Tester, 20 hours (Test Standard: CEC L-45-A-99))

[0078] High molecular weight: Polymethacrylate with a weight-mean molecular weight (Mw) of more than 50,000 g / mol, SSI (shear stability index) 26 (KRL shear stability tester, 20 hours (test standard: CEC L-45-A-99))

[0079] 4) The additive used was an additive package for lubricating oil for an integrated engine-transmission from INFINIUM (including a detergent, a friction modifier, an anti-wear agent, an antioxidant and the like).

[0080] 5) A pour point depressant of the PAMA (poly(alkyl methacrylate)) type, which is commercially available from Evonik, was used.

[0081] 6) A silicone-type antifoaming agent, commercially available from Evonik, was used. [Table 1] Component (wt%) Example 1 2 3 Highly refined mineral oil aramcoULTRA 2 70 40 30 aramcoULTRA 3 40 30 aramcoULTRA 4 10 Synthetic oil PAO 2 20 PAO 3.5 PAO 4 Viscosity index improvers Low molecular weight 2 3 2 High molecular weight Liquid lubricant additive package 10-20 10-20 10-20 Pour point depressants 0,1 0,1 0,1 Antifoaming agent 0,2 0,2 0,2 In total 100 100 100 [Table 2] Component (wt%) Comparative example 1 2 3 4 5 6 7 8 Highly refined mineral oil aramcoULTRA 2 60 85 40 65 65 70 aramcoULTRA 3 65 75 40 20 aramcoULTRA 4 15 20 Synthetic oil PAO 2 PAO 3.5 20 PAO 4 10 15 Viscosity index improvers Low molecular weight 4 2 2 2 High molecular weight 7 2 3 Liquid lubricant additive package 10-20 10-20 10-20 10-20 10-20 10-20 10-20 10-20 Pour point depressants 0,2 0,1 0,1 0,1 0,1 0,1 0,1 0,1 Antifoaming agent 0,2 0,2 0,2 0,2 0,2 0,2 0,2 0,2 In total 100 100 100 100 100 100 100 100 Test example

[0082] To evaluate the required performance under extreme pressure, wear resistance, cooling capacity, compatibility with electrical components, etc., various property tests were performed on Examples 1 to 3 and Comparative Examples 1 to 8. The property test procedures are as follows, and the test results are presented in Tables 3 to 7 below and in Fig. Figure 1 is shown. For illustration, Table 7 shows the results of the comparison examples described in Tables 4 to 6 in a table. [Test procedure]

[0083] The kinematic viscosity at 40°C and the kinematic viscosity at 100°C of the lubricating oil composition were measured according to ASTM D445.

[0084] The low-temperature viscosity of the lubricating oil composition at -40°C was measured according to ASTM D2983 (Brookfield low-temperature viscosity).

[0085] The wear resistance of the lubricating oil composition was measured according to ASTM D5182 (scavenging load measurement method, FZG (Research Center for Gears and Transmissions) visual method).

[0086] The performance of the lubricating oil composition under extreme pressure was measured according to ASTM D2783 (4-ball).

[0087] The friction properties of the lubricating oil composition were measured with the MTM (Mini Traction Machine) at 40°C and an SRR (Slide-to-Roll Ratio) of 30%.

[0088] The transmission efficiency of the lubricating oil composition was measured using an electric dynamometer. [Table 3] Evaluation Items Example 1 2 3 Kinematic viscosity @ 40°C 12,17 14,27 12,25 @ 100°C 3,254 3,634 3,263 Viscosity index 141 145 140 FZG 10 12 - 4-ball LNSL (last non-seizure load), kgf 63 - - LWI (load wear index), kgf 20,47 - - weld point, kgf 200 - - MTM - - 0,0487 Transmission efficiency - FTP75 (Federal Test Procedure) conditions 97,71 Transmission efficiency - representative efficiency 97,52 - - [Table 4] Evaluation Items Example Comparative example 1 1 2 3 4 Kinematic viscosity @ 40°C 12,17 22,23 17,95 14,71 10,19 @ 100°C 3,254 5,399 4,287 3,792 2,781 Viscosity index 141 193 152 157 118 4-ball LNSL, kgf 63 50 80 63 50 LWI, kgf 20,47 25 27,63 20,47 16,27 weld point, kgf 200 200 200 200 160 Transmission efficiency - FTP75 conditions 97,71 97,62 97,67 97,65 - Transmission efficiency - representative efficiency 97,52 97,43 97,43 97,43 - [Table 5] Evaluation Items Example 2 Comparative example 5 Kinematic viscosity @ 40°C 14,27 14,43 @ 100°C 3,634 3,816 Viscosity index 145 167 FZG 12 11 [Table 6] Evaluation Items Example 3 Comparative example 6 Comparative example 7 Comparative example 8 Kinematic viscosity @ 40°C 12,25 12,28 12,25 12,39 @ 100°C 3,263 3,264 3,268 3,278 Viscosity index 140 140 141 139 MTM 0,0487 0,0534 0,0503 0,0522 [Table 7] Evaluation Items Comparative example 1 2 3 4 5 6 7 8 Kinematic viscosity @ 40°C 22,23 17,95 14,71 10,19 14,43 12,28 12,25 12,39 @ 100°C 5,399 4,287 3,792 2,781 3,816 3,264 3,268 3,278 Viscosity index 193 152 157 118 167 140 141 139 FZG 11 4-ball LNSL, kgf 50 80 63 50 LWI, kgf 25 27,63 20,47 16,27 weld point, kgf 200 200 200 160 MTM 0,0534 0,0503 0,0522 Transmission efficiency - FTP75 conditions 97,62 97,67 97,65 Transmission efficiency - representative efficiency 97,43 97,43 97,43

[0089] Comparing the results of Example 1 with the results of comparison examples 1 to 3, as shown in Table 4, confirms that the transfer efficiency is better the lower the kinematic viscosity at 100 °C.

[0090] In comparison example 2, which contained some PAO, the transmission efficiency was also slightly better than in comparison example 3, which did not contain PAO and had a lower kinematic viscosity, suggesting that the addition of PAO improves energy efficiency due to its better frictional properties.

[0091] The lower the viscosity, the lower the performance measured by the 4-ball BP test at extreme pressure. For example 4, with a kinematic viscosity of 2.781 cSt at 100°C, improved energy efficiency was expected due to the low kinematic viscosity, but the performance level at extreme pressure was lower than that of example 1. Accordingly, a viscosity of approximately 2.8 to 4.0 cSt was confirmed as suitable for improving energy efficiency and maintaining durability.

[0092] When comparing the kinematic viscosity, viscosity index and wear resistance of Example 2 and Comparative Example 5 using Table 5, it was confirmed that the use of poly(alkyl methacrylate) with a molecular weight of 10,000 to 50,000 (low molecular weight polymethacrylate) as a viscosity index improver results in better durability.

[0093] The results from Table 6 and Fig. 1, which show the friction properties of the lubricating oil compositions according to Example 3 and the comparative examples 6 to 8, which were mixed under the condition that the same kinematic viscosity is maintained at 100°C, show that the friction properties in Example 3 were best using PAO 2 as the polyalphaolefin-based synthetic oil.

[0094] In comparative example 6, where only highly refined mineral oil was used, the friction properties were inferior, which negatively impacted NVH performance, necessitating the use of a polyalphaolefin-based synthetic oil with improved friction properties. The results from example 3 and comparative examples 7 and 8 demonstrate that when using the product with a kinematic viscosity of 2 cSt at 100°C as a polyalphaolefin-based synthetic oil, the friction properties were superior to those achieved with products of 3.5 and 4 cSt.

[0095] As can be seen from the foregoing, a lubricating oil composition according to an embodiment of the present disclosure is a low-viscosity lubricating oil having a kinematic viscosity at 100°C of 2.8 to 4.0 cSt, which, however, is able to prevent a deterioration of durability and NVH performance in low-viscosity lubricating oil by suitably combining highly refined mineral oil and polyalphaolefin-based synthetic oil and adding poly(alkyl methacrylate) having a suitable molecular weight as a viscosity index improver.

[0096] The low-viscosity lubricating oil composition according to an embodiment of the present disclosure is able to reduce energy consumption due to friction by lowering the internal resistance of a motor and to improve drive efficiency by dissipating the heat generated during motor operation more effectively, ultimately improving energy efficiency.

[0097] The effects of this revelation are not limited to the foregoing. It is to be assumed that the effects of this revelation include all effects that can be derived from the description of this revelation.

[0098] Since the embodiments of the present disclosure have been described above, those who have ordinary technical knowledge should recognize that various modifications and variations are possible by changing, deleting or adding components without deviating from the scope and spirit of the present disclosure as described in the attached claims, which should also be considered to be included in the legal scope of the present disclosure.

Claims

[1] Lubricant oil composition, comprising: a lubricating base oil containing mineral oil; a viscosity index improver; and an additive. [2] Lubricating oil composition according to claim 1, wherein, based on the total weight of the lubricating oil composition, 50 to 80% by weight of the mineral oil; 1 to 10 wt% of the viscosity index improver; and comprises 10 to 20 wt.% of the additive. [3] Lubricating oil composition according to claim 1, wherein the lubricating base oil comprises the mineral oil and synthetic oil. [4] Lubricating oil composition according to claim 3, which, based on the total weight of the lubricating oil composition, 50 to 80% by weight of the mineral oil; 10 to 40 wt.% of the synthetic oil; 1 to 10 wt% of the viscosity index improver; and comprises 9 to 20 wt.% of the additive. [5] Lubricating oil composition according to claim 3, wherein the synthetic oil comprises a polyalphaolefin (PAO)-based synthetic oil. [6] Lubricating oil composition according to claim 3, wherein the synthetic oil has a kinematic viscosity at 100°C in the range of 2.0 to 3.0 cSt. [7] Lubricating oil composition according to claim 1, wherein the lubricating oil composition has a kinematic viscosity at 100°C in the range of 2.8 to 4.0 cSt. [8] Lubricating oil composition according to claim 1, wherein the mineral oil comprises highly refined mineral oil having an aromatic component content of 0.1 wt.% or less. [9] Lubricating oil composition according to claim 1, wherein the mineral oil has a kinematic viscosity at 100°C in the range of 2.0 to 4.0 cSt. [10] Lubricating oil composition according to claim 1, wherein the mineral oil has a viscosity index (VI) equal to or greater than 100. [11] Lubricating oil composition according to claim 1, wherein the viscosity index improver comprises poly(alkyl methacrylate). [12] Lubricating oil composition according to claim 1, wherein a weight-average molecular weight (Mw) of the viscosity index improver is in the range of 10000 to 50 000 g / mol. [13] Lubricating oil composition according to claim 1, wherein the additive comprises at least one of a detergent, an antioxidant, an anti-wear agent, a dispersant, a friction modifier, a corrosion inhibitor, or a combination thereof. [14] Lubricating oil composition according to claim 13, wherein the detergent comprises at least one of a sulfonate detergent, a phenate detergent, a salicylate detergent, or a combination thereof. [15] Lubricating oil composition according to claim 13, wherein the antioxidant comprises at least one of hindered phenols, aromatic amines, or a combination thereof. [16] Lubricating oil composition according to claim 1, wherein the lubricating oil composition further comprises at least one of a pour point depressant, an antifoaming agent or a combination thereof.

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