Lubricating oil composition

Abstract

To provide a lubricating oil composition capable of having a good balance of insulation, oxidation stability and extreme pressure property at a high level and also having high copper corrosion prevention properties.SOLUTION: There is provided a lubricating oil composition which comprises (A) a lubricating oil base oil, (B) an extreme pressure agent, (C) a nitrogen-containing ashless dispersant and (D) a metal-based cleaning agent, wherein the component (B) includes a specific phosphorus-based extreme pressure agent (B1) and does not include a sulfur-containing extreme pressure agent (B2) or includes the component (B2) so that the content of sulfur derived from the component (B2) is less than a specific amount, the content of phosphorus derived from the component (B1) is less than a specific amount, the component (D) is a calcium sulfonate cleaner, the mass ratio ([phosphorus] / [nitrogen]) of phosphorus derived from the component (B1) to nitrogen derived from the component (C) is within a specific range and the content of calcium derived from the component (D) is less than a specific amount.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a lubricating oil composition. [Background technology]

[0002] In recent years, electric vehicles that do not emit carbon dioxide, a greenhouse gas, have been attracting attention. Such electric vehicles usually use an electric motor as a power source for running and are equipped with a gear mechanism such as a transmission. Conventionally, different lubricating oil compositions have been used to cool and lubricate the electric motor and to lubricate the gear mechanism. However, in recent years, in order to simplify the circulation mechanism of the lubricating oil composition, it has been proposed to use the same lubricating oil composition. In particular, when an electric vehicle has a structure in which the electric motor and the transmission are integrated, it is required to use the same lubricating oil composition for lubricating the electric motor and the transmission. Under these circumstances, research has been conducted on various lubricating oil compositions for electric vehicles.

[0003] For example, Japanese Patent Application Laid-Open No. 2019-137829 (Patent Document 1) describes a lubricating oil composition comprising (A) a lubricating base oil, (B1) a phosphite ester or an amine salt thereof having at least one alkyl group having 4 to 10 carbon atoms, (C) a borate ester, (D) a sulfur-based extreme pressure agent, and (E) an organic friction modifier, wherein the lubricating oil composition has a kinematic viscosity of 1.5 to 5 mm at 100°C. 2 / s, and the phosphorus content, relative to the mass of the lubricating oil composition, is 310 to 1000 ppm, the boron content is 50 to 400 ppm, and the sulfur content is 250 to 1000 ppm.

[0004] Furthermore, Japanese Patent Laid-Open Publication No. 2020-066673 (Patent Document 2) discloses a lubricating oil composition containing a base oil (A), a neutral phosphorus-based compound (B), an acidic phosphorus-based compound (C), a sulfur-based compound (D), and a metal salt (E) selected from metal sulfonates, metal salicylates, and metal phenates, wherein the content of the acidic phosphorus-based compound (C) in terms of phosphorus atoms is 10 to 180 mass ppm based on the total amount of the lubricating oil composition, the content of the sulfur-based compound (D) in terms of sulfur atoms is 10 to 1000 mass ppm based on the total amount of the lubricating oil composition, and the content of the metal salt (E) in terms of metal atoms is 5 to 180 mass ppm based on the total amount of the lubricating oil composition.

[0005] Furthermore, in Japanese Patent Application Laid-Open No. 2021-066809 (Patent Document 3), a lubricating oil composition is disclosed that contains (A) a lubricating base oil, (B) a metal detergent, a specific (C) phosphorus-based extreme pressure agent, (D) a sulfur-based extreme pressure agent, a specific (E) ashless dispersant, and (F) a viscosity index improver having a weight average molecular weight (Mw) of 10,000 to 100,000, and that has a kinematic viscosity of 10 mm at 40°C. 2 / s super~20mm 2 / s and the boron content in the lubricating oil composition is 25 to 150 ppm by mass. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-137829 [Patent Document 2] Japanese Patent Publication No. 2020-066673 [Patent Document 3] Patent Publication No. 2021-066809 Summary of the Invention [Problem to be solved by the invention]

[0007] However, while the lubrication of the electric motors and transmissions of electric vehicles requires the simultaneous realization of high insulation properties, high oxidation stability, and high extreme-pressure properties (extreme-pressure properties based on anti-seizure properties (load-carrying properties) and anti-wear properties (wear resistance)), conventional lubricating oil compositions such as those described in Patent Documents 1 to 3 above were not necessarily sufficient in terms of achieving high levels of insulation properties, oxidation stability, and extreme-pressure properties. In recent years, to obtain higher motor output, electric motors are required to be operated at higher voltages, and gears and bearings are also required to be used under more severe conditions. Therefore, the development of lubricating oil compositions that have a good balance of high levels of insulation properties, oxidation stability, and extreme-pressure properties is desired. Furthermore, because copper is used as a material in electric motors, lubricating oil compositions used to lubricate and cool them are also required to have high corrosion prevention properties against copper (copper corrosion prevention properties).

[0008] The present invention has been made in view of the problems associated with the prior art, and has as its object to provide a lubricating oil composition that has high levels of insulating properties, oxidation stability, and extreme pressure properties in a well-balanced manner, while also having a high level of copper corrosion prevention properties. [Means for solving the problem]

[0009] As a result of intensive research conducted by the present inventors to achieve the above object, the present inventors have discovered that in a lubricating oil composition comprising (A) a lubricating base oil, (B) an extreme pressure agent, (C) a nitrogen-containing ashless dispersant, and (D) a metallic detergent, component (B) satisfies the following conditions: that component (B) contains (B1) a phosphorus-based extreme pressure agent which is at least one compound selected from the group consisting of phosphoric acid, phosphate esters, phosphites, and salts thereof; and that component (B2) does not contain a sulfur-containing extreme pressure agent, or that component (B2) is contained in such a manner that the content of sulfur derived from component (B2) is 0.01 mass % or less based on the total amount of the lubricating oil composition; and that component (B1) contains no phosphorus-based extreme pressure agent, which is at least one compound selected from the group consisting of phosphoric acid, phosphate esters, phosphites, and salts thereof; and that component (B2) contains no sulfur-containing extreme pressure agent, or contains component (B2) in such a manner that the content of sulfur derived from component (B2) is 0.01 mass % or less based on the total amount of the lubricating oil composition; The present inventors have found that by setting the phosphorus content of component (B1) to 0.050 mass% or less, based on the total amount of the lubricating oil composition; using a calcium sulfonate detergent as component (D); setting the mass ratio of phosphorus derived from component (B1) to nitrogen derived from component (C) ([phosphorus] / [nitrogen]) to 0.60 or more and 2.30 or less, based on the total amount of the lubricating oil composition, and setting the calcium content of component (D) to 200 mass ppm or less, based on the total amount of the lubricating oil composition, it is possible to obtain a lubricating oil composition that has high levels of insulating properties, oxidation stability, and extreme-pressure properties in a well-balanced manner, and that also has a high level of copper corrosion prevention, and have completed the present invention.

[0010] That is, the present invention provides the following aspects.

[0011] [1](A) Lubricant base oil, (B) extreme pressure agents, (C) a nitrogen-containing ashless dispersant, and (D) Metallic detergents A lubricating oil composition comprising: The component (B) is (B1) A mixture of alkylamine salts of phosphate esters and phosphites and (B2) a lubricating oil composition that does not contain a sulfur-containing extreme pressure agent, or that contains component (B2) so that the content of sulfur derived from component (B2) is 0.01 mass% or less based on the total amount of the lubricating oil composition, the content of phosphorus derived from the component (B1) is 0.050% by mass or less based on the total amount of the lubricating oil composition, the component (C) is a boronated succinimide having a nitrogen content of 1.2 to 2.4 mass %, the content of nitrogen derived from the component (C) is 294 ppm by mass to 600 ppm by mass based on the total amount of the lubricating oil composition; the component (D) is a calcium sulfonate detergent, the mass ratio ([phosphorus] / [nitrogen]) of phosphorus derived from the component (B1) to nitrogen derived from the component (C) is 0.60 or more and 2.30 or less, A lubricating oil composition having a calcium content derived from component (D) of 200 mass ppm or less based on the total amount of the lubricating oil composition.

[0012] [2] The lubricating base oil contains at least one selected from the group consisting of hydrotreated base oil and wax isomerized base oil, and the kinematic viscosity of the lubricating base oil at 40 ° C is 20 mm 2 / s or less of the lubricating oil composition according to [1].

[0013] [3] The lubricating oil composition according to [1] or [2], wherein the mass ratio ([sulfur] / [phosphorus]) of sulfur derived from the component (B2) to phosphorus derived from the component (B1) is 3.0 or less.

[0014] [4] The lubricating oil composition according to any one of [1] to [3], wherein the component (B1) comprises (B1-1) an alkylamine salt of a phosphoric acid ester.

[0015] [5] The lubricating oil composition according to any one of [1] to [4], which is a composition for lubricating transmissions and cooling and lubricating electric motors. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a lubricating oil composition that has a good balance of high levels of insulating properties, oxidation stability, and extreme pressure properties, and also has a high level of copper corrosion prevention properties. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention will be described in detail below with reference to preferred embodiments. In this specification, unless otherwise specified, the expression "X to Y" for numerical values ​​X and Y means "X or more and Y or less." In such an expression, when a unit is assigned only to the numerical value Y, the unit is also applied to the numerical value X.

[0018] The lubricating oil composition of the present invention comprises (A) Lubricant base oil, (B) extreme pressure agents, (C) a nitrogen-containing ashless dispersant, and (D) Metallic detergents A lubricating oil composition comprising: The component (B) is (B1) Contains a phosphorus-based extreme pressure agent which is at least one compound selected from the group consisting of phosphoric acid, phosphate esters, phosphites, and salts thereof, and (B2) a lubricating oil composition that does not contain a sulfur-containing extreme pressure agent, or that contains component (B2) so that the content of sulfur derived from component (B2) is 0.01 mass% or less based on the total amount of the lubricating oil composition, the content of phosphorus derived from the component (B1) is 0.050% by mass or less based on the total amount of the lubricating oil composition, the component (D) is a calcium sulfonate detergent, the mass ratio ([phosphorus] / [nitrogen]) of phosphorus derived from the component (B1) to nitrogen derived from the component (C) is 0.60 or more and 2.30 or less, the content of calcium derived from component (D) is 200 ppm by mass or less based on the total amount of the lubricating oil composition; It is characterized by the following.

[0019] [Component (A): Lubricant base oil] The lubricating oil composition of the present invention contains a lubricating base oil as component (A). The lubricating base oil used as component (A) is not particularly limited, and known lubricating base oils (mineral base oils, synthetic base oils, or mixed base oils thereof, etc.) can be used. For example, the lubricating base oils described in International Publication No. 2020 / 095968 can be used appropriately. The lubricating base oil used as component (A) may consist of one type of base oil, or may be a mixed base oil containing two or more types of base oils.

[0020] The lubricating base oil used as component (A) can be at least one selected from Group II base oils, Group III base oils, Group IV base oils, and Group V base oils, as classified by the API (American Petroleum Institute). Of these, Group II base oils and Group III base oils are more preferred, as they offer better oxidation stability, corrosion resistance, and insulating properties (volume resistivity), as well as the potential for improving the fuel economy of electric vehicles (hereinafter, the API base oil classification groups will be simply referred to as "API groups").

[0021] Furthermore, the lubricating base oil used as component (A) is preferably a mineral base oil. Suitable examples of such mineral base oils include paraffinic or naphthenic mineral base oils obtained by subjecting lubricating oil fractions obtained by atmospheric and vacuum distillation of crude oil to one or more refining methods, such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and clay treatment, in appropriate combination. Among these mineral base oils, hydrorefined base oils and wax isomerized base oils are particularly preferred as component (A) because they can achieve greater effects in terms of oxidation stability, corrosion resistance, insulating properties (volume resistivity), and low power consumption. These mineral base oils may be used alone or in combination of two or more in any ratio.

[0022] Furthermore, the kinematic viscosity at 40°C of the lubricating base oil used as component (A) (in the case of a mixed base oil containing two or more base oils, the mixed base oil) is 20 mm 2 / s or less, and 5 to 18 mm 2 / s is more preferable, and 8 to 12 mm 2 / s is even more preferable. By setting the kinematic viscosity of the lubricating base oil at 40°C to the above upper limit or less, it is possible to obtain higher performance (effects) in terms of low-temperature viscosity characteristics and fuel economy performance compared to when the kinematic viscosity exceeds the above upper limit. Furthermore, by setting the kinematic viscosity of the lubricating base oil at 40°C to the above lower limit or more, it is possible to improve the oil film formation performance at lubricated parts, further improve extreme pressure properties based on anti-seizure and anti-wear properties, and further improve the electrical insulation properties of new oil compared to when the kinematic viscosity is below the lower limit. In this specification, the kinematic viscosity of the base oil or composition at 40°C or 100°C means the kinematic viscosity at each temperature (40°C or 100°C) specified in JIS K 2283-2000.

[0023] The kinematic viscosity at 100°C of the lubricating base oil used as component (A) (in the case of a mixed base oil containing two or more base oils, the mixed base oil) is 2.0 to 4.0 mm 2 / s, and 2.0 to 2.7 mm 2 / s is more preferable. By setting the kinematic viscosity at 100°C of the lubricating base oil to the above upper limit or less, it is possible to obtain higher performance (effects) in terms of low-temperature viscosity characteristics and fuel economy performance compared to when the kinematic viscosity exceeds the above upper limit. Furthermore, by setting the kinematic viscosity at 100°C of the lubricating base oil to the above lower limit or more, it is possible to improve the oil film forming performance at lubricated parts, further improve extreme pressure properties based on anti-seizure and anti-wear properties, and further improve the electrical insulation properties of new oil compared to when the kinematic viscosity is below the lower limit.

[0024] The viscosity index of the lubricating base oil used as component (A) (when the base oil is a mixed base oil containing two or more base oils, the mixed base oil) is preferably 95 or higher, more preferably 120 or higher. By adjusting the viscosity index of the lubricating base oil to be equal to or higher than the lower limit, the viscosity-temperature characteristics and thermal and oxidation stability of the lubricating oil composition are improved, making it possible to further reduce the coefficient of friction and further improve wear resistance. The viscosity index of component (A) is more preferably 120 to 160, as this provides greater benefits in terms of fuel economy. In this specification, the "viscosity index" of the base oil or composition refers to the viscosity index measured in accordance with JIS K 2283-2000.

[0025] Furthermore, the sulfur content of the lubricating base oil used as component (A) (in the case of a mixed base oil containing two or more base oils, the mixed base oil) is preferably 10 ppm by mass or less (more preferably 8 ppm by mass or less, even more preferably 5 ppm by mass or less, and particularly preferably 4 ppm by mass or less). When the sulfur content is below the upper limit, it is possible to further improve oxidation stability compared to when the sulfur content exceeds the upper limit.

[0026] Furthermore, the pour point of the lubricating base oil used as component (A) (in the case of a mixed base oil containing two or more base oils, the mixed base oil) is not particularly limited, but is preferably -12°C or lower. When the pour point is below the upper limit, the low-temperature fluidity of the final lubricating oil composition can be further improved compared to when the pour point exceeds the upper limit. Furthermore, from the viewpoint of enabling a higher viscosity index, the pour point is more preferably -22°C or lower. In this specification, "pour point" refers to the pour point measured in accordance with JIS K 2269-1987.

[0027] Furthermore, the flash point of the lubricating base oil used as component (A) (in the case of a mixed base oil containing two or more base oils, the mixed base oil) is preferably 160°C or higher (more preferably 190°C or higher). Furthermore, by setting the flash point at or above the lower limit, safety during use at high temperatures tends to be improved compared to when the flash point is below the lower limit. In this specification, "flash point" refers to the flash point measured in accordance with JIS K 2265-4-2007 (Cleveland Open Method).

[0028] [Component (B): extreme pressure agent] The lubricating oil composition of the present invention contains an extreme pressure agent as component (B). The extreme pressure agent used as component (B) is (B1) Contains a phosphorus-based extreme pressure agent which is at least one compound selected from the group consisting of phosphoric acid, phosphate esters, phosphites, and salts thereof, and The lubricating oil composition does not contain a sulfur-containing extreme pressure agent (B2), or contains the component (B2) so that the content of sulfur derived from the component (B2) is 0.01 mass% or less based on the total amount of the lubricating oil composition. The condition that the component (B1) is contained; and the lubricating oil composition does not contain the component (B2), or contains the component (B2) in such a manner that the content of sulfur derived from the component (B2) is 0.01% by mass or less based on the total amount of the lubricating oil composition; It satisfies both of the above.

[0029] In this way, component (B) contains component (B1) as an essential component, but by using component (B1), it is possible to exhibit high load-bearing performance and wear resistance even if no sulfur-containing extreme pressure agent (component (B2)) is used or even if the amount of sulfur-containing extreme pressure agent (component (B2)) used is very small (such that the amount of sulfur is 0.01 mass % or less, based on the total amount of the lubricating oil composition), and it is also possible to more efficiently achieve high levels of insulating properties.

[0030] The phosphorus-based extreme pressure agent used as component (B1) is at least one compound selected from the group consisting of phosphoric acid, phosphate esters, phosphites, and salts thereof. Note that the term "phosphorus-based extreme pressure agent" as used herein excludes phosphorus-based extreme pressure agents containing sulfur atoms (so-called "sulfur-phosphorus-based extreme pressure agents"). (In this specification, phosphorus-based extreme pressure agents containing sulfur atoms correspond to sulfur-containing extreme pressure agents described below.)

[0031] The phosphate ester usable for component (B1) is not particularly limited, and any known phosphate ester usable as an extreme pressure agent can be used as appropriate. Note that the term "phosphate ester" as used herein encompasses acidic phosphate esters.That is, examples of such phosphate esters include tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, triundecyl phosphate, tridodecyl phosphate, tritridecyl phosphate, tritetradecyl phosphate, tripentadecyl phosphate, trihexadecyl phosphate, triheptadecyl phosphate, trioctadecyl phosphate, tri In addition to oleyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, xylenyl diphenyl phosphate, etc., so-called acidic phosphate esters (e.g., monobutyl acid phosphate, monopentyl acid phosphate, monohexyl acid phosphate, monoheptyl acid phosphate, monooctyl acid phosphate, monononyl acid phosphate, monodecyl acid phosphate, monoundecyl acid phosphate, monoalkyl acid phosphates such as monododecyl acid phosphate, monotridecyl acid phosphate, monotetradecyl acid phosphate, monopentadecyl acid phosphate, monohexadecyl acid phosphate, monoheptadecyl acid phosphate, monooctadecyl acid phosphate, and monooleyl acid phosphate; dibutyl acid phosphate, dipentyl acid phosphate, dihexyl acid phosphate, and diheptyl acid phosphate; and dialkyl acid phosphates such as dioctyl acid phosphate, dinonyl acid phosphate, didecyl acid phosphate, diundecyl acid phosphate, didodecyl acid phosphate, ditridecyl acid phosphate, ditetradecyl acid phosphate, dipentadecyl acid phosphate, dihexadecyl acid phosphate, diheptadecyl acid phosphate, dioctadecyl acid phosphate, and dioleyl acid phosphate.

[0032] Furthermore, the phosphite ester that can be used for component (B1) is not particularly limited, and any known phosphite that can be used as an extreme pressure agent can be appropriately used, such as dibutyl phosphite, dipentyl phosphite, dihexyl phosphite, diheptyl phosphite, dioctyl phosphite, dinonyl phosphite, didecyl phosphite, diundecyl phosphite, didodecyl phosphite, dioleyl phosphite, diphenyl phosphite, dicresyl phosphite, tributyl phosphite, tripentyl phosphite, trihexyl phosphite, triheptyl phosphite, trioctyl phosphite, and torinonyl phosphite. Examples of such phosphite esters include dialkyl phosphites having two alkyl groups, and more preferably dialkyl hydrogen phosphites having two alkyl groups each having 4 to 12 carbon atoms.

[0033] Furthermore, the salts of phosphoric acid, phosphate ester, and phosphite ester usable in component (B1) can be any known extreme pressure agent and can be used appropriately, without any particular limitation. Examples include salts obtained by neutralizing some or all of the remaining acidic hydrogen atoms in phosphoric acid, phosphate ester, or phosphite ester through the action of a metal base, or a nitrogen-containing compound such as ammonia, a hydrocarbon group having 1 to 8 carbon atoms, or an amine compound containing only a hydroxyl group-containing hydrocarbon group in the molecule.

[0034] The phosphorus-based extreme pressure agent (component (B1)) preferably contains (B1-1) an alkylamine salt of a phosphoric acid ester. There are no particular limitations on the component (B1-1), and any known alkylamine salt of a phosphoric acid ester that can be used as an extreme pressure agent can be used as appropriate. Suitable examples of such alkylamine salts of a phosphoric acid ester include salts obtained by reacting a phosphoric acid ester with an amine compound having an alkyl group in the molecule to neutralize some or all of the remaining acidic hydrogen (salt (reaction product) of a phosphoric acid ester and the amine compound).

[0035] The phosphate ester used to form component (B1-1) can be any of the above-mentioned phosphate esters, and is not particularly limited. However, acidic phosphate esters are preferred, and monoalkyl acid phosphates and / or dialkyl acid phosphates are more preferred.

[0036] Such monoalkyl acid phosphates and dialkyl acid phosphates include those represented by the following formula (1):

[0037] [ka]

[0038] [In formula (1), R a is a hydrocarbon group (more preferably an alkyl group) having 2 to 22 carbon atoms (more preferably 8 to 18 carbon atoms), and n is an integer of 1 or 2.] In other words, it is preferable to use the compound represented by the formula (1) as the phosphate ester used to form the component (B1-1).

[0039] Furthermore, as the amine compound used to form the alkylamine salt of a phosphoric acid ester, monoalkylamines, dialkylamines, and trialkylamines can be suitably used. Examples of such amine compounds include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, octadecylamine, oleylamine, tetracosylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, diundecylamine, didodecylamine, and ditridecylamine. Examples of such amine compounds include decylamine, ditetradecylamine, dipentadecylamine, dihexadecylamine, diheptadecylamine, dioctadecylamine, dioleylamine, ditetracosylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, triundecylamine, tridodecylamine, tritridecylamine, tritetradecylamine, tripentadecylamine, trihexadecylamine, triheptadecylamine, trioctadecylamine, trioleylamine, and tritetracosylamine. These amine compounds may be used alone or in combination of two or more. Examples of such amine compounds include compounds represented by the following formula (2):

[0040] [ka]

[0041] [In formula (2), R b , R c and R d are each independently a hydrogen atom or a monovalent alkyl group (provided that R b , R c and Rd At least one of the groups is a monovalent alkyl group. It is preferable that R in the formula (2) is a compound represented by the formula b , R c and R d The monovalent alkyl group that can be selected as may be linear or branched. The number of carbon atoms in such a monovalent alkyl group is not particularly limited, but may be 1 or more, 3 or more, 5 or more, 7 or more, 9 or more, or 11 or more, and may be 20 or less, 18 or less, 16 or less, or 14 or less. The compound represented by formula (2) can be prepared by the process of forming a monoalkylamine (R b , R c and R d a compound in which one of the groups is a monovalent alkyl group (particularly preferably an alkyl group having 8 to 18 carbon atoms) and the others are hydrogen atoms), and / or a dialkylamine (R b , R c and R d It is preferable that two of the groups are monovalent alkyl groups (particularly preferably alkyl groups having 8 to 18 carbon atoms), and the remaining groups are hydrogen atoms).

[0042] From the viewpoint of obtaining higher effects in terms of abrasion resistance, seizure resistance, insulation properties (volume resistivity), and oxidation stability, the component (B1-1) is preferably a salt of the compound represented by formula (1) and the compound represented by formula (2). The component (B1-1) can be used alone or in combination of two or more.

[0043] Furthermore, examples of the phosphorus-based extreme pressure agent (component (B1)) include: The component (B1-1), a component other than the component (B1-1) (hereinafter, for convenience, referred to as "component (B1-2)") consisting of at least one compound selected from the group consisting of phosphoric acid, the phosphate esters, the phosphite esters, and salts thereof; A mixture of the above is more preferred. The component (B1-2) contained in such a mixture is more preferably a phosphite ester, from the viewpoint of obtaining higher effects in terms of abrasion resistance, seizure resistance, insulation properties (volume resistivity), and oxidation stability. That is, it is preferred to use a mixture of (B1-1) an alkylamine salt of a phosphate ester and a phosphite ester as the component (B1).

[0044] Furthermore, when the component (B1) is a mixture of the components (B1-1) and (B1-2), the mass ratio of the phosphorus derived from the component (B1-1) to the phosphorus derived from the component (B1-2) ([P derived from component (B1-1)] / [P derived from component (B1-2)]) is preferably 0.4 to 2.5 (more preferably 0.4 to 2.0). When this mass ratio of phosphorus is equal to or greater than the lower limit, a higher effect in terms of seizure resistance can be obtained compared to when it is below the lower limit. On the other hand, when it is equal to or less than the upper limit, a higher effect in terms of electrical insulation can be obtained compared to when it exceeds the upper limit.

[0045] Furthermore, the component (B) does not contain a sulfur-containing extreme pressure agent (B2), or contains the component (B2) so that the content of sulfur derived from the component (B2) is 0.01 mass % (100 mass ppm) or less based on the total amount of the lubricating oil composition.

[0046] When the component (B) contains the sulfur-containing extreme pressure agent (component (B2)), the sulfur-containing extreme pressure agent is not particularly limited, and any known sulfur-containing extreme pressure agent can be used as appropriate. Examples of such sulfur-containing extreme pressure agents include sulfur-based extreme pressure agents such as dithiocarbamate, zinc dithiocarbamate, molybdenum dithiocarbamate (MoDTC), disulfide, polysulfide, sulfurized olefin, and sulfurized oils and fats; and sulfur-phosphorus-based extreme pressure agents such as thiophosphites, dithiophosphites, trithiophosphites, thiophosphates, dithiophosphates, trithiophosphates, amine salts thereof, and derivatives thereof.

[0047] When the component (B) contains the sulfur-containing extreme pressure agent (component (B2)), the content of sulfur derived from the component (B2) must be 0.01% by mass (100 ppm by mass) or less (more preferably 80 ppm by mass or less, even more preferably 60 ppm by mass or less, particularly preferably 50 ppm by mass or less, and most preferably 20 ppm by mass or less) based on the total amount of the lubricating oil composition. When the content of the component (B2) is below the upper limit, it becomes possible to obtain high oxidation stability and high copper corrosion prevention properties compared to when the content exceeds the upper limit. Note that, from the viewpoint of further improving copper corrosion prevention properties and insulating properties (volume resistivity value), it is preferable that the component (B) does not contain the sulfur-containing extreme pressure agent (B2).

[0048] The method for producing component (B) is not particularly limited, and any known method can be used as appropriate. Component (B) may also be a commercially available product.

[0049] [Component (C): Nitrogen-containing ashless dispersant] The lubricating oil composition of the present invention contains a nitrogen-containing ashless dispersant (an ashless dispersant containing nitrogen) as component (C).

[0050] Component (C) is not particularly limited, and any known nitrogen-containing ashless dispersant can be used as appropriate. From the viewpoint of further improving corrosion resistance and oxidation stability, component (C) is preferably an ashless dispersant having a nitrogen-containing functional group as the dispersing group.

[0051] Suitable examples of ashless dispersants having such nitrogen-containing functional groups as dispersing groups include succinimide, benzylamine, polyamines, and derivatives thereof, which have hydrocarbon groups (e.g., alkyl groups, alkenyl groups) having 40 to 400 carbon atoms.

[0052] Furthermore, the component (C) is not particularly limited, but from the viewpoint of further improving corrosion resistance and oxidation stability, it is more preferable that the component (C) be at least one succinimide-based ashless dispersant selected from the group consisting of succinimides having a hydrocarbon group (e.g., an alkyl group or an alkenyl group) having 40 to 400 carbon atoms and derivatives of the succinimides (modified compounds of succinimides).

[0053] The succinimide having a hydrocarbon group having 40 to 400 carbon atoms is not particularly limited, but may be any of the succinimides represented by the following formulas (3) and (4):

[0054] [ka]

[0055] [In formulas (3) and (4), R 1 and R 2 each independently represents an alkyl group having 40 to 400 carbon atoms (more preferably 60 to 350) or an alkenyl group having 40 to 400 carbon atoms (more preferably 60 to 350), and n represents an integer of 0 to 5.] In addition, in such formulas (3) and (4), R 1 an alkyl or alkenyl group that may be selected as R 2The alkyl or alkenyl group that can be selected as R is preferably a branched alkyl or alkenyl group (polyisobutenyl group) derived from an oligomer of isobutene called polyisobutylene, or a polybutenyl group. 1 and R 2 The alkyl or alkenyl group that can be selected as the group preferably has a weight-average molecular weight of 800 to 1500 (more preferably 950 to 1400). Furthermore, n in formula (3) is preferably an integer of 1 to 5 (more preferably 2 to 4). On the other hand, n in formula (4) is preferably an integer of 0 to 4 (more preferably 1 to 4, even more preferably 1 to 3). Among the compounds represented by formulas (3) and (4), the compound represented by formula (4) (bis-isomer) is more preferred from the viewpoint of further improving corrosion resistance and oxidation stability. The method for producing such succinimide is not particularly limited, and may include, for example, a method in which the succinimide is produced as a condensation reaction product by reacting at least one selected from the group consisting of alkylsuccinic acids, alkenylsuccinic acids, and anhydrides thereof, each having an alkyl or alkenyl group having 40 to 400 carbon atoms, with a polyamine.

[0056] The succinimide derivative (modified succinimide compound) is not particularly limited, and any known modified succinimide compound that can be used as an ashless dispersant can be appropriately used. For example, (i) a compound modified with an oxygen-containing organic compound (at least one selected from monocarboxylic acids having 1 to 30 carbon atoms such as fatty acids, polycarboxylic acids having 2 to 30 carbon atoms (for example, oxalic acid, phthalic acid, trimellitic acid, pyromellitic acid, etc.), anhydrides of these acids, ester compounds of these acids, alkylene oxides having 2 to 6 carbon atoms, and hydroxy(poly)oxyalkylene carbonates) (ii) boron-modified compounds (compounds obtained by reacting the above-mentioned succinimide with boric acid to neutralize or amidate some or all of the remaining amino groups and / or imino groups (so-called boronated succinimide)); (iii) phosphoric acid-modified compounds (compounds obtained by reacting the above-mentioned succinimide with phosphoric acid to neutralize or amidate some or all of the remaining amino groups and / or imino groups).

[0057] Furthermore, as the "succinimide-based ashless dispersant" suitable as the component (C), from the viewpoint of further improving corrosion resistance and oxidation stability, boron-modified compounds of the succinimide (boronated succinimide) are more preferred.

[0058] The "succinimide ashless dispersant" suitable as component (C) preferably has a nitrogen content of 1.0 to 4.8 mass% (more preferably 1.2 to 2.4 mass%). By setting the nitrogen content within this range, it is possible to more efficiently achieve high levels of corrosion resistance and oxidation stability. Furthermore, when a "boronated succinimide" is used as the succinimide ashless dispersant, the boron content in the boronated succinimide is preferably 0.01 to 5.0 mass% (more preferably 0.2 to 2.2 mass%).

[0059] Furthermore, the "succinimide-based ashless dispersant" suitable as component (C) preferably has a weight-average molecular weight of 1,000 to 9,000 (more preferably 1,000 to 5,000). By ensuring that the weight-average molecular weight of the succinimide-based ashless dispersant is at or above the lower limit, it becomes possible to further improve the electrical insulating properties of both the fresh oil and the composition after oxidative degradation. By ensuring that the weight-average molecular weight of the succinimide-based ashless dispersant is at or below the upper limit, it becomes possible to further improve the electrical insulating properties of the composition after oxidative degradation.

[0060] Furthermore, the "succinimide-based ashless dispersant" suitable for component (C) preferably has a total base number (TBN) of 20 to 80 mgKOH / g (more preferably 30 to 60 mgKOH / g). If the total base number value is within this range, even greater effects in terms of corrosion resistance and oxidation stability tend to be obtained.

[0061] The method for producing component (C) is not particularly limited, and any known method can be used as appropriate. Component (C) may also be a commercially available product.

[0062] [Component (D): Metallic detergent] The lubricating oil composition of the present invention contains a metallic detergent as component (D). In the present invention, the metallic detergent used as component (D) is a calcium sulfonate detergent.

[0063] Examples of such calcium sulfonate detergents (component (D)) include calcium sulfonates, which are calcium salts of alkyl aromatic sulfonic acids, basic salts of the calcium sulfonates, and overbased salts of the calcium sulfonates. Examples of such alkyl aromatic sulfonic acids include so-called petroleum sulfonic acids and synthetic sulfonic acids. Examples of petroleum sulfonic acids include those obtained by sulfonating alkyl aromatic compounds from the lubricating oil fraction of mineral oil, and mahogany acid, a by-product produced during the production of white oil. Examples of synthetic sulfonic acids include those obtained by sulfonating alkylbenzenes with linear or branched alkyl groups, which are obtained by recovering by-products from alkylbenzene production plants, which are used as detergent raw materials, or by alkylating benzene with polyolefins. Other examples of synthetic sulfonic acids include those obtained by sulfonating alkylnaphthalenes, such as dinonylnaphthalene. The sulfonating agent used to sulfonate these alkyl aromatic compounds is not particularly limited, and examples include fuming sulfuric acid and sulfuric anhydride. The weight-average molecular weight of such alkyl aromatic sulfonic acids is preferably 300 to 1500, more preferably 400 to 1300. The basic salt or overbased salt of calcium sulfonate is not particularly limited, and known salts can be used as appropriate. Examples include calcium sulfonates (over)based with calcium carbonate, calcium borate, or the like. The method for preparing the basic salt or overbased salt is not particularly limited, and known methods can be used as appropriate. (For example, when the overbased salt is calcium sulfonate overbased with calcium carbonate, a method of obtaining calcium sulfonate overbased with calcium carbonate by reacting calcium sulfonate with a base such as calcium hydroxide in the presence of carbon dioxide gas may be used.)

[0064] Furthermore, the component (D) preferably has a total base number (TBN) of 20 to 450 mgKOH / g (more preferably 300 to 450 mgKOH / g). If the total base number is within this range, even greater effects in terms of oxidation stability tend to be obtained.

[0065] The method for producing component (D) is not particularly limited, and any known method can be used as appropriate. Component (D) may also be a commercially available product.

[0066] [Composition of lubricating oil composition] The lubricating oil composition of the present invention contains the components (A), (B), (C), and (D). As mentioned above, the component (B) contains the component (B1) (phosphorus-based extreme pressure agent) as an essential component.

[0067] Furthermore, in the lubricating oil composition of the present invention, the content of phosphorus (P) derived from component (B1) (the total amount of phosphorus (P) derived from component (B1)) must be 0.050 mass% or less (more preferably 0.045 mass% or less, even more preferably 190 to 410 mass ppm, and particularly preferably 190 to 380 mass ppm) based on the total amount of the lubricating oil composition. When the content of phosphorus derived from component (B1) is equal to or less than the upper limit, a composition with a higher volume resistivity can be obtained compared to when the content exceeds the upper limit. Furthermore, when the content of phosphorus derived from component (B1) is equal to or greater than the lower limit, it is possible to further improve seizure resistance and wear resistance compared to when the content is less than the lower limit.

[0068] Furthermore, when the lubricating oil composition of the present invention contains a sulfur-containing extreme pressure agent (component (B2)) and the component (B2) contains phosphorus, the amount of phosphorus derived from the component (B2) is preferably 100 ppm by mass or less (more preferably 80 ppm by mass or less) based on the total amount of the lubricating oil composition. By keeping the amount of phosphorus derived from the component (B2) below the upper limit, it is possible to further improve oxidation stability and corrosion resistance.

[0069] Furthermore, in the lubricating oil composition of the present invention, the mass ratio ([phosphorus] / [nitrogen]) of the phosphorus derived from component (B1) to the nitrogen derived from component (C) must be 0.60 or more and 2.30 or less. When this mass ratio of phosphorus to nitrogen is equal to or greater than the lower limit, it is possible to achieve both high levels of extreme-pressure properties and high levels of insulating properties compared to when the mass ratio is below the lower limit, thereby achieving both extreme-pressure properties and insulating properties at high levels. On the other hand, when the mass ratio is equal to or less than the upper limit, it is possible to achieve high levels of seizure resistance and oxidation stability compared to when the mass ratio exceeds the upper limit. Furthermore, the mass ratio ([phosphorus] / [nitrogen]) of the phosphorus derived from component (B1) to the nitrogen derived from component (C) is more preferably 0.60 or more and 1.70 or less (more preferably 0.60 or more and 1.50 or less, and particularly preferably 0.60 or more and 0.75 or less), because this provides a more effective balance of high levels of seizure resistance, wear resistance, insulating properties (volume resistivity), and oxidation stability.

[0070] Furthermore, in the lubricating oil composition of the present invention, the content of calcium derived from component (D) must be 200 ppm by mass or less (more preferably 180 ppm by mass or less, and even more preferably 160 ppm by mass or less) based on the total amount of the lubricating oil composition. When the calcium content is below the upper limit, it becomes possible to obtain a higher effect in terms of insulating properties than when the calcium content exceeds the upper limit.

[0071] Furthermore, in the lubricating oil composition of the present invention, the content of component (A) is not particularly limited, but is preferably 80 to 98 mass % (more preferably 85 to 95 mass %) based on the total amount of the lubricating oil composition. When the content of component (A) is equal to or greater than the lower limit, it is possible to achieve even better oxidation stability than when the content is below the lower limit. On the other hand, when the content is equal to or less than the upper limit, it is possible to further improve the additive effect at lubricating points and achieve even better lubricity than when the content exceeds the upper limit.

[0072] As mentioned above, the lubricating oil composition of the present invention does not contain a sulfur-containing extreme pressure agent (component (B2)), or, even if it does contain a sulfur-containing extreme pressure agent (component (B2)), the amount of sulfur derived from component (B2) must be 0.01 mass % (100 ppm by mass) or less (more preferably 80 ppm by mass or less, even more preferably 60 ppm by mass or less, particularly preferably 50 ppm by mass or less, and most preferably 20 ppm by mass or less) based on the total amount of the lubricating oil composition. By keeping the amount of sulfur derived from the sulfur-containing extreme pressure agent below the above upper limit, it is possible to achieve both excellent oxidation stability and copper corrosion prevention properties.

[0073] In addition, in the lubricating oil composition of the present invention, the mass ratio ([sulfur] / [phosphorus]) of sulfur derived from component (B2) to phosphorus derived from component (B1) is preferably 3.0 or less (more preferably 2.93 or less, and even more preferably 2.2 or less). When this mass ratio of sulfur to phosphorus is equal to or less than the upper limit, it becomes possible to achieve better oxidation stability and copper corrosion prevention properties than when the mass ratio exceeds the upper limit.

[0074] Furthermore, in the lubricating oil composition of the present invention, when the component (B) contains the component (B1-1), the content of phosphorus (P) derived from the component (B1-1) is preferably 50 to 500 ppm by mass (more preferably 70 to 350 ppm by mass) based on the total amount of the lubricating oil composition. When the phosphorus content is equal to or greater than the lower limit, it is possible to more easily achieve high load-bearing capacity (seizure resistance) and wear resistance compared to when the content is below the lower limit. On the other hand, when the content is equal to or less than the upper limit, it is possible to more easily achieve high insulation (volume resistivity of 0.0020×10) compared to when the content exceeds the upper limit. 12 It is possible to achieve a resistance of Ωcm or more.

[0075] Furthermore, in the lubricating oil composition of the present invention, when component (B) contains component (B1-2), the content of phosphorus (P) derived from component (B1-2) is preferably 50 to 500 ppm by mass (more preferably 100 to 200 ppm by mass) based on the total amount of the lubricating oil composition. When the phosphorus content is equal to or greater than the lower limit, it is possible to further improve the seizure resistance and wear resistance compared to when the content is below the lower limit. On the other hand, when the content is equal to or less than the upper limit, it is possible to more efficiently obtain a composition with a high volume resistivity compared to when the content exceeds the upper limit.

[0076] Furthermore, in the lubricating oil composition of the present invention, the content of Component (C) is not particularly limited, but it is preferable that the content of nitrogen derived from Component (C) is 100 to 800 ppm by mass (more preferably 180 to 600 ppm by mass) based on the total amount of the lubricating oil composition (the upper limit of the content of nitrogen derived from Component (C) is more preferably 400 ppm by mass, and particularly preferably 200 ppm by mass). When the amount of nitrogen is equal to or greater than the lower limit, it becomes possible to further improve oxidation stability compared to when the amount is less than the lower limit. On the other hand, when the amount is equal to or less than the upper limit, it becomes easier to achieve a volume resistivity value of 0.0020×10 compared to when the amount exceeds the upper limit. 12 In the present invention, the sulfur, phosphorus, nitrogen, boron, and calcium contents in the composition and various components are values ​​measured in accordance with ASTM D4951.

[0077] The lubricating oil composition of the present invention may further contain additives in addition to the components (A) to (D). Such additives may be any known additives used in the field of lubricating oil compositions, and are not particularly limited. A suitable example is an antioxidant (E).

[0078] As such component (E), any known antioxidant in the field of lubricating oil compositions (for example, known ashless antioxidants such as amine-based antioxidants and phenol-based antioxidants) can be used appropriately, and there are no particular limitations. Among these, it is preferable to use a combination of (E1) a phenol-based antioxidant and (E2) an amine-based antioxidant.

[0079] As the component (E1), for example, a compound known as a phenolic antioxidant (for example, the compounds exemplified in WO 2020 / 095970) can be appropriately used. Examples of such phenolic antioxidants include hindered phenol compounds and bisphenol compounds.

[0080] Furthermore, as the component (E2), for example, compounds known as amine-based antioxidants, such as aromatic amine-based antioxidants and hindered amine-based antioxidants (for example, compounds exemplified in WO 2020 / 095970, etc.) can be appropriately used. Among the aromatic amine-based antioxidants, alkylated diphenylamines and alkylated phenyl-α-naphthylamines can be suitably used. Furthermore, as the hindered amine-based antioxidants, for example, compounds having a 2,2,6,6-tetraalkylpiperidine skeleton (2,2,6,6-tetraalkylpiperidine derivatives) can be suitably used. Among the amine-based antioxidants, aromatic amine-based antioxidants are more preferred, and alkylated diphenylamines are particularly preferred.

[0081] Furthermore, when the lubricating oil composition of the present invention contains the component (E), the content (total amount) of the component (E) is preferably 0.01 to 4.0 mass% (more preferably 0.01 to 2.0 mass%). When the component (E1) is contained, the content of the component (E1) is preferably 0.005 to 2.0 mass% (more preferably 0.005 to 1.0 mass%). Furthermore, when the component (E2) is contained, the content of the component (E2) is preferably 0.005 to 2.0 mass% (more preferably 0.01 to 2.0 mass%). By setting these contents within the above ranges, it is possible to further enhance the antioxidation properties while improving corrosion resistance.

[0082] Although the (E) component has been described as a suitable example of an additive that can be suitably used in the lubricating oil composition of the present invention, the additives that can be used in the lubricating oil composition of the present invention are not limited to the (E) component. Other known additives such as pour point depressants, metal deactivators, friction modifiers, dispersants other than the nitrogen-containing ashless dispersants, viscosity index improvers, rubber swelling agents, antifoaming agents, diluents, rust inhibitors, demulsifiers, colorants, corrosion inhibitors, antiwear agents, acid scavengers, etc. (for example, those described in JP 2016-3258 A, WO 2015 / 056783 A, JP 2016-160312 A, JP 2003-155492 A, WO 2017 / 073748 A, JP 2020-76004 A, etc.) can also be used as appropriate, as long as the effects of the present invention are not impaired.

[0083] Furthermore, when other additive components besides component (E) are used, the total amount (total quantity) of the other additive components is more preferably 0.5 to 2.0 mass% based on the total amount of the lubricating oil composition. When the total amount of such other additive components is equal to or greater than the lower limit, it is possible to obtain higher effects in terms of wear resistance, corrosion resistance, and oxidation stability compared to when the total amount is less than the lower limit. On the other hand, when the total amount is equal to or less than the upper limit, it is possible to obtain higher levels of insulation (volume resistivity) and higher effects in terms of low power consumption compared to when the total amount exceeds the upper limit.

[0084] The various additives that can be used in such lubricating oil compositions may be prepared and added separately for each component, or may be prepared and added as a mixture with other components, such as commercially available packages (e.g., additive packages containing rubber swelling agents, antifoaming agents, and pour point depressants).

[0085] [About the characteristics, manufacturing method, uses, etc. of lubricating oil compositions] The lubricating oil composition of the present invention has a volume resistivity of 0.0020×10 at 80°C. 12 Ωcm or more (more preferably 0.0022×10 12 Ωcm or more, more preferably 0.0024×10 12 By making the volume resistivity equal to or greater than the lower limit, it is possible to ensure a high level of insulation that exceeds the level required for use in electric vehicles. The upper limit of the volume resistivity at 80°C of the lubricating oil composition is not particularly limited, but from the viewpoint of discharge resistance, it is preferable that the upper limit is 0.10 × 10 12 The volume resistivity is preferably Ωcm. The volume resistivity is measured at an oil temperature of 80°C in accordance with the volume resistivity test specified in JIS C2101.

[0086] The lubricating oil composition of the present invention has a kinematic viscosity at 40°C of 8.0 to 18.0 mmHg 2 / s (preferably 8.0 to 14.0 mm 2 / s) are preferred. When the kinematic viscosity of the lubricating oil composition at 40°C is equal to or less than the above upper limit, it is possible to further reduce stirring resistance in a relatively low temperature range near 40°C (preferably about 20 to 60°C) compared to when the kinematic viscosity exceeds the above upper limit, and it is possible to further improve power transmission efficiency even at low temperatures such as immediately after the start of use, thereby making it possible to further improve fuel economy performance. On the other hand, when the kinematic viscosity of the lubricating oil composition at 40°C is equal to or greater than the above lower limit, the oil film forming and oil film maintaining properties of the lubricating oil composition at lubricated points are further improved in a relatively low temperature range near 40°C (preferably about 20 to 60°C), making it possible to maintain a better lubricated state, and from this perspective it is possible to further improve wear resistance, gear transmission efficiency, and power economy performance.

[0087] The lubricating oil composition of the present invention has a kinematic viscosity at 100°C of 1.8 to 4.0 mmHg 2 / s (preferably 2.2 to 3.5 mm 2 / s). When the kinematic viscosity of the lubricating oil composition at 100°C is equal to or less than the above upper limit, the lubricating oil composition can have a lower viscosity in a relatively high temperature range near 100°C compared to when the kinematic viscosity exceeds the above upper limit, and stirring resistance can be reduced, thereby enabling further improvement in power transmission efficiency and improved fuel economy performance. Furthermore, when the lubricating oil composition has a kinematic viscosity at 100°C equal to or greater than the above lower limit, the lubricating oil composition's oil film formation and oil film retention at lubricated points are improved in a relatively high temperature range near 100°C (preferably about 80 to 120°C), and the oil film can be maintained more uniformly, enabling higher levels of seizure resistance during use.

[0088] Furthermore, the lubricating oil composition of the present invention preferably has a viscosity index of at least 105 (more preferably at least 120). When the viscosity index is at least the lower limit (more preferably at least 120), it becomes possible to further improve the viscosity-temperature characteristics and anti-wear properties of the lubricating oil composition, as well as to further improve fuel economy and power economy, compared to when the viscosity index is below the lower limit (more preferably less than 120).

[0089] The method for producing the lubricating oil composition of the present invention is not particularly limited, and the lubricating oil composition may be prepared by appropriately selecting and mixing the components to be contained so as to obtain the lubricating oil composition of the present invention (so as to satisfy the above-mentioned conditions).

[0090] The lubricating oil composition of the present invention has a high level of insulating property, oxidation stability, and extreme pressure properties in a well-balanced manner, and also has a high level of copper corrosion prevention, and therefore, although its applications are not particularly limited, it can be suitably used as a composition for lubricating transmissions and for cooling and lubricating electric motors. In other words, the lubricating oil composition of the present invention can be suitably used as a lubricating oil composition for electric vehicles equipped with electric motors and transmissions. [Example]

[0091] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0092] (Ingredients used in each example) First, the base oils and additives used in the examples are shown below.

[0093] [(A) Lubricant base oil] (A1) Wax isomerized base oil [mineral oil: API Group III, kinematic viscosity at 40°C: 9.422 mm 2 / s, kinematic viscosity at 100°C: 2.676mm 2 / s, viscosity index: 125, sulfur content in base oil (sulfur content in base oil): 0 ppm by mass, pour point: -37°C, flash point: 190°C] (A2) Hydrocracked base oil [mineral oil: API Group II, kinematic viscosity at 40 ° C: 8.546 mm 2 / s, kinematic viscosity at 100°C: 2.431mm 2 / s, viscosity index: 105, sulfur content in base oil (sulfur content in base oil): 0 mass ppm, pour point: -30°C, flash point: 170°C].

[0094] [(B) Extreme pressure agent] <(B1) Phosphorus-based extreme pressure agent> (B1-1) Alkylamine salt of phosphoric acid ester [phosphoric acid ester (mixture of monoester and diester: a compound represented by the formula (1) and wherein R a is an oleyl group (formula: C 18 H 35 a compound represented by the formula (2) and an alkylamine (a compound represented by the formula (2) in which R b , R c and R d One of the groups is a dodecyl group (formula: C 12 H 25 and R b , R c and R d (compounds in which the remaining atoms are hydrogen atoms) (B1-2) Phosphite ester [Dibutyl hydrogen phosphite] <(B2) Sulfur-containing extreme pressure agent> (B2-1) Thiophosphate ester [phosphorus content: 100,000 ppm by mass, sulfur content: 190,000 ppm by mass].

[0095] [(C) Nitrogen-containing ashless dispersant] (C1) Succinimide-based ashless dispersant [boronated succinimide, nitrogen content: 2.0 mass%, boron content: 0.5 mass%, total base number (TBN): 50, succinimide type: bis-type succinimide represented by the above formula (4) (wherein R 1 and R 2is a polyisobutenyl group having a weight average molecular weight (Mw) of 1000 and n is 3).

[0096] [(D) Calcium sulfonate detergent] (D1) Calcium sulfonate detergent [base number (TBN): 400 mg KOH / g, calcium atom content: 15.0 mass %].

[0097] [(E) Antioxidant] (E1) Phenolic antioxidant [octyl 3-(4-hydroxy-3,5-diisopropylphenyl)propionate] (E2) Amine antioxidants [alkylated diphenylamines].

[0098] [(F) Other additives (performance additives)] (F1) Additive package [mixture of rubber swelling agent, antifoaming agent and pour point depressant].

[0099] (G) Calcium salicylate detergent (comparison metal detergent) (G1) Calcium salicylate detergent [Base number (TBN): 320 mg KOH / g, calcium atom content: 11.4 mass %].

[0100] (Example 1 6, Reference example 1 and Comparative Examples 1 to 7) Examples 1 to 3 were prepared using the above-mentioned components so as to obtain the compositions shown in Tables 1 and 2. 6, Reference example 1and Comparative Examples 1 to 7 were prepared, respectively. In Tables 1 and 2, "-" in the "Composition" column indicates that the component was not used. Further, in the "Composition" section in Tables 1 and 2, "in mass%" represents the mass content (mass%) relative to the total amount of lubricating base oil, "mass%" represents the mass content (mass%) relative to the total amount of lubricating oil composition, "ppm (N equivalent)" represents the mass content in terms of nitrogen atoms relative to the total amount of lubricating oil composition (ppm by mass: the nitrogen content relative to the total amount of lubricating oil composition derived from that component), "ppm (P equivalent)" represents the mass content in terms of phosphorus atoms relative to the total amount of lubricating oil composition (ppm by mass: the phosphorus content relative to the total amount of lubricating oil composition derived from that component), "ppm (S equivalent)" represents the mass content in terms of sulfur atoms relative to the total amount of lubricating oil composition (ppm by mass: the sulfur content relative to the total amount of lubricating oil composition derived from that component), and "ppm (Ca equivalent)" represents the mass content in terms of calcium atoms relative to the total amount of lubricating oil composition (ppm by mass: the calcium content relative to the total amount of lubricating oil composition derived from that component). The phosphorus, nitrogen, sulfur, and calcium contents in the composition were measured in accordance with ASTM D 4951. In Tables 1 and 2, the term "phosphorus content derived from component (B1)" indicates the mass percentage (mass%) of phosphorus derived from component (B1) contained in the lubricating oil composition, the term "sulfur content derived from component (B2)" indicates the mass percentage (mass%) of sulfur derived from component (B2) contained in the lubricating oil composition, and the term "nitrogen content derived from component (C)" indicates the mass percentage (mass%) of nitrogen derived from component (C) contained in the lubricating oil composition. In Tables 1 and 2, the notation "phosphorus derived from component (B1) / nitrogen derived from component (C)" indicates the ratio (mass ratio: [phosphorus] / [nitrogen]) of the "content of phosphorus derived from component (B1)" to the "content of nitrogen derived from component (C)," and the notation "sulfur derived from component (B2) / phosphorus derived from component (B1)" indicates the ratio (mass ratio: [sulfur] / [phosphorus]) of the "content of sulfur derived from component (B2)" to the "content of phosphorus derived from component (B1)."

[0101] [Method for evaluating the properties of the lubricating oil compositions obtained in each example] <Volume resistivity measurement> The volume resistivity of the new oil was measured for each lubricating oil composition. Here, the volume resistivity was measured in accordance with the volume resistivity test specified in JIS C2101, at an oil temperature of 80°C. The results are shown in Tables 1 and 2. Note that the volume resistivity at 80°C was 0.0020 x 10 12 If it is Ω·cm or more, it can be evaluated as having a high level of insulation.

[0102] <Falex seizure test: Seizure resistance verification test> Each lubricating oil composition was subjected to a Falex seizure test in accordance with ASTM D3233 Method A, and the load (unit: lbf) at which seizure occurred was measured. The results are shown in Tables 1 and 2. If the load at which seizure occurred was 700 lbf or more, it was determined that the seizure resistance was good.

[0103] <Falex abrasion test: Abrasion resistance confirmation test> Each lubricating oil composition was subjected to a Falex test (Falex wear resistance test) in accordance with ASTM D2670 under the conditions of an oil temperature of 80°C, a load of 390 lb, a rotation speed of 290 rpm, and a test time of 1 hour, to measure the amount of wear (mg). The results are shown in Tables 1 and 2. A wear amount of 55.0 mg or less can be considered to have good wear resistance.

[0104] <Confirmation test of copper plate corrosion resistance> Approximately 30 mL of sample was prepared from each lubricating oil composition, and a copper plate corrosion test was conducted in accordance with JIS K 2513 to evaluate copper plate corrosion resistance. That is, in accordance with JIS K 2513, a copper plate was completely immersed in approximately 30 mL of sample, and then held at an oil temperature of 150°C for 192 hours. The sample was then removed, washed, and compared with the copper plate corrosion standard to determine the corrosiveness of the sample to copper, thereby evaluating the copper corrosion inhibitory properties. The results are shown in Tables 1 and 2. Note that a copper plate corrosion standard judgment value (discoloration number) of 2 or less can be considered to have high copper corrosion inhibitory properties.

[0105] <Evaluation of oxidation stability: Test to confirm whether a strong acid value is generated after oxidation treatment> Each lubricating oil composition was subjected to oxidation treatment at an oil temperature of 165°C for 192 hours using the ISOT (Indiana Stirring Oxidation Test) method in accordance with JIS K2514-1, and the presence or absence of a strong acid number was then confirmed using the lubricating oil composition after oxidation treatment. Lubricating oil compositions that did not develop a strong acid number were evaluated as having high oxidation stability and were given a "pass" rating, while lubricating oil compositions that developed a strong acid number were evaluated as having insufficient oxidation stability and were given a "fail" rating. The results are shown in Tables 1 and 2.

[0106] [Table 1]

[0107] [Table 2]

[0108] As is clear from the results shown in Table 1, Examples 1 to 6 The lubricating oil composition obtained by (corresponding to the lubricating oil composition of the present invention) and the lubricating oil composition obtained in Reference Example 1 has a volume resistivity of 0.0020×10 12 It was found that the dielectric strength of the material was Ωcm or more, and that the material was suitable for lubricating and cooling electric motors, which require a high level of insulation. 6 The lubricating oil composition obtained by (corresponding to the lubricating oil composition of the present invention) and the lubricating oil composition obtained in Reference Example 1 It was confirmed that Examples 1 to 3 have good seizure resistance and wear resistance, and also have high extreme pressure properties based on seizure resistance and wear resistance. 6 The lubricating oil composition obtained by (corresponding to the lubricating oil composition of the present invention) and the lubricating oil composition obtained in Reference Example 1 It was found that no strong acid value was generated and the oxidation stability was high. 6 The lubricating oil composition obtained by (corresponding to the lubricating oil composition of the present invention) and the lubricating oil composition obtained in Reference Example 1It was also confirmed that the copper corrosion inhibitors in Examples 1 to 3 have a high level of corrosion prevention. 6 and Reference Example 1 The lubricating oil composition obtained in the above has high levels of insulating properties, oxidation stability and extreme pressure properties, and has a good balance of these properties, as well as high copper corrosion prevention properties.

[0109] In contrast, as is clear from the results shown in Table 2, the lubricating oil composition obtained in Comparative Example 1, in which the content of phosphorus derived from component (B1) was 0.053 mass%, had a volume resistivity of 0.0020 × 10 12 The viscosity was less than Ωcm, and the insulating properties could not be improved to a high level. Furthermore, the lubricating oil composition obtained in Comparative Example 2, in which the mass ratio (P / N) of the phosphorus content derived from component (B1) to the nitrogen content derived from component (C) was 2.68 (exceeding 2.30), did not have sufficient anti-seizure properties and could not have a high level of extreme-pressure properties. Furthermore, the lubricating oil composition obtained in Comparative Example 2 had a strong acid number and could not have a high level of oxidation stability. Furthermore, the lubricating oil compositions obtained in Comparative Examples 3 and 4, in which the mass ratio (P / N) of the phosphorus content derived from component (B1) to the nitrogen content derived from component (C) was less than 0.60, did not necessarily have sufficient extreme-pressure properties or insulating properties. Furthermore, the lubricating oil composition obtained in Comparative Example 5, which contained a sulfur-containing extreme-pressure agent in an amount such that the sulfur content was 200 ppm, had a strong acid number and could not have a high level of oxidation stability. Furthermore, the lubricating oil composition obtained in Comparative Example 6, which contained a calcium sulfonate detergent in an amount such that the calcium content was 250 ppm by mass, had a volume resistivity of 0.0020 × 10 12The electrical insulation properties were less than Ωcm, and the lubricating oil composition obtained in Comparative Example 7, which contained a calcium salicylate detergent instead of a calcium sulfonate detergent in an amount such that the calcium content was 100 ppm by mass, not only did the lubricating oil composition obtained in Comparative Example 7 not have sufficient anti-seizure properties, but also seizure occurred in the Falex wear test, making it impossible to measure the amount of wear. Thus, the lubricating oil composition obtained in Comparative Example 7, which used a calcium salicylate detergent, was unable to achieve high extreme-pressure properties. [Industrial Applicability]

[0110] As described above, the present invention makes it possible to provide a lubricating oil composition that has a good balance of high levels of insulating properties, oxidation stability, and extreme pressure properties, as well as a high level of copper corrosion prevention. Therefore, the lubricating oil composition of the present invention is particularly useful as a lubricating oil composition for electric vehicles.

Claims

1. (A) Lubricating base oil, (B) extreme pressure agents, (C) a nitrogen-containing ashless dispersant, and (D) Metallic detergents A lubricating oil composition comprising: The component (B) is (B1) A phosphorus-based extreme pressure agent which is a mixture of an alkylamine salt of a phosphate ester and a phosphite ester, and the lubricating oil composition does not contain a sulfur-containing extreme pressure agent (B2), or contains the component (B2) so that the content of sulfur derived from the component (B2) is 0.01% by mass or less based on the total amount of the lubricating oil composition; the content of phosphorus derived from the component (B1) is 0.050 mass% or less based on the total amount of the lubricating oil composition, The component (C) is a boronated succinimide having a nitrogen content of 1.2 to 2.4 mass %, the content of nitrogen derived from the component (C) is 294 ppm by mass to 600 ppm by mass based on the total amount of the lubricating oil composition; the component (D) is a calcium sulfonate detergent, a mass ratio ([phosphorus] / [nitrogen]) of phosphorus derived from the component (B1) to nitrogen derived from the component (C) is 0.60 or more and 2.30 or less, the content of calcium derived from the component (D) is 200 ppm by mass or less based on the total amount of the lubricating oil composition; A lubricating oil composition characterized by:

2. The lubricating base oil contains at least one selected from the group consisting of hydrotreated base oil and wax isomerized base oil, and the kinematic viscosity of the lubricating base oil at 40°C is 20 mm ２ 2. The lubricating oil composition according to claim 1, wherein the viscosity of the lubricating oil composition is 100 ppm or less.

3. 2. The lubricating oil composition according to claim 1, wherein the mass ratio ([sulfur] / [phosphorus]) of sulfur derived from component (B2) to phosphorus derived from component (B1) is 3.0 or less.

4. 10. The lubricating oil composition of claim 1, wherein the lubricating oil composition is a composition for lubricating transmissions and for cooling and lubricating electric motors.

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