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 and (C) a nitrogen-containing ashless dispersant, 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 as to satisfy a specific condition, the mass ratio of phosphorus derived from the component (B1) to nitrogen derived from the component (C) and the mass ratio of sulfur derived from the component (B2) to phosphorus derived from the component (B1) satisfy specified conditions respectively and the ratio of the kinematic viscosity of the lubricating oil composition at 40°C before and after performing a specific oxidation treatment is a specific value or less.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In recent years, electric vehicles (EVs), which do not emit carbon dioxide, a greenhouse gas, have attracted attention. These EVs typically use an electric motor as their power source and are equipped with gear mechanisms such as a transmission. Traditionally, different lubricating oil compositions have been used for cooling and lubricating the electric motor and the gear mechanism. However, in recent years, it has been proposed to use the same lubricating oil composition to simplify the circulation mechanism. In particular, when an EV has a structure where the electric motor and transmission are integrated, the use of the same lubricating oil composition is required for the lubrication of both the electric motor and the transmission. Under these circumstances, research into various lubricating oil compositions for electric vehicles has been progressing.

[0003] For example, Japanese Patent Publication No. 2019-137829 (Patent Document 1) describes a lubricating oil composition comprising (A) a lubricating oil base oil, (B1) a phosphite ester having at least one alkyl group having 4 to 10 carbon atoms or an amine salt thereof, (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 A lubricating oil composition is disclosed, wherein the phosphorus content is 310 to 1000 ppm, the boron content is 50 to 400 ppm, and the sulfur content is 250 to 1000 ppm, relative to the mass of the lubricating oil composition.

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

[0005] Furthermore, Japanese Patent Publication No. 2021-066809 (Patent Document 3) describes a lubricating oil composition comprising (A) a lubricating oil 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, wherein the kinematic viscosity of the lubricating oil composition at 40°C is 10 mm². 2 / s super~20mm 2 A lubricating oil composition is disclosed that is in the range of / s and has a boron content of 25 to 150 ppm by mass in the lubricating oil composition. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2019-137829 [Patent Document 2] Japanese Patent Publication No. 2020-066673 [Patent Document 3] Japanese Patent Publication No. 2021-066809 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, lubrication of electric motors and transmissions in electric vehicles requires a combination of high insulation, high oxidation stability, and advanced extreme pressure resistance (extreme pressure resistance based on anti-seizure (load-bearing capacity) and anti-wear (wear resistance)). Conventional lubricating oil compositions, such as those described in the above-mentioned Patent Documents 1-3, have not always been sufficient in achieving high levels of insulation, oxidation stability, and extreme pressure resistance. In recent years, in order to obtain higher motor output, electric motors are required to be used at higher voltages, and gears and bearings are also required to be used under more severe conditions. Therefore, there is a need for a lubricating oil composition that has a good balance of high levels of insulation, oxidation stability, and extreme pressure resistance. Furthermore, since copper is used as a material in electric motors, lubricating oil compositions used for lubrication and cooling must also have high corrosion resistance to copper (copper corrosion prevention).

[0008] The present invention has been made in view of the problems of the prior art described above, and aims 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 advanced copper corrosion prevention properties. [Means for solving the problem]

[0009] The present inventors, through diligent research to achieve the above objective, have found a lubricating oil composition comprising (A) a lubricating oil base oil, (B) an extreme pressure agent, and (C) a nitrogen-containing ashless dispersant; wherein component (B) satisfies the following conditions: (B1) contains a phosphorus-based extreme pressure agent which is at least one compound selected from the group consisting of phosphoric acid, phosphate esters, phosphite esters, and salts thereof; and (B2) does not contain a sulfur-containing extreme pressure agent, or contains component (B2) such that the sulfur content derived from component (B2) is 0.01% by mass or less based on the total amount of the lubricating oil composition; the mass ratio ([phosphorus] / [nitrogen]) of phosphorus derived from component (B1) to nitrogen derived from component (C) is 0.60 or more and 2.30 or less; and the mass ratio ([sulfur] / [phosphorus]) of sulfur derived from component (B2) to phosphorus derived from component (B1) is 3.0 or less; JIS The kinematic viscosity (KV40) of the lubricating oil composition at 40°C after oxidation treatment under the conditions of an oil temperature of 165°C and 192 hours, as measured by the ISOT method in accordance with K2514-1:2013. OL ) and the kinematic viscosity (KV40) of the lubricating oil composition at 40°C before the oxidation treatment. L ) ratio ([KV40 OL ] / [KV40 L We discovered that by setting the ratio to 1.06 or less, it becomes possible to obtain a lubricating oil composition that has a good balance of high levels of insulating properties, oxidation stability, and extreme pressure properties, as well as high copper corrosion prevention properties, and thus completed the present invention.

[0010] In other words, the present invention provides the following embodiments.

[0011] [1](A) Lubricant base oil, (B) Extreme pressure agents, and (C) Nitrogen-containing ashless dispersant, A lubricating oil composition comprising, The aforementioned component (B) is, (B1) It is a mixture of alkylamine salts of phosphate esters and phosphite esters. It contains a phosphorus-based extreme pressure agent, and (B2) does not contain a sulfur-containing extreme pressure agent, or contains the (B2) component such that the sulfur content derived from the (B2) component is 0.01% by mass or less based on the total amount of the lubricating oil composition. The nitrogen content derived from component (C) is 294 ppm by mass to 600 ppm by mass based on the total amount of the lubricating oil composition. The mass ratio ([phosphorus] / [nitrogen]) of phosphorus derived from the (B1) component to nitrogen derived from the (C) component is 0.60 or more and 2.30 or less. The mass ratio ([sulfur] / [phosphorus]) of sulfur derived from the (B2) component to phosphorus derived from the (B1) component is 3.0 or less. The kinematic viscosity (KV40 OL ) at 40°C of the lubricating oil composition after oxidation treatment under the conditions of an oil temperature of 165°C for 192 hours by the ISOT method in accordance with JIS K2514-1, and L the kinematic viscosity (KV40 OL ) at 40°C of the lubricating oil composition before the oxidation treatment, L ) ([KV40 ) is 1.06 or less.

[0012] [2] The ratio ([KV40 B ) of the kinematic viscosity (KV40 The lubricating oil composition ) at 40°C of the lubricating oil base oil before the oxidation treatment to the kinematic viscosity (KV40 L ) at 40°C of L ) before the oxidation treatment ([KV40 B ) is 0.95 or more and 1.15 or less. The lubricating oil composition according to [1].

[0013] [3] The lubricating oil base oil contains at least one selected from the group consisting of a hydrorefined base oil and a wax isomerization base oil, and the kinematic viscosity of the lubricating oil base oil at 40°C is 20 mm 2 / s or less. The lubricating oil composition according to [1] or [2].

[0014] [4](D) A lubricating oil composition according to any one of [1] to [3], wherein the calcium sulfonate detergent is contained such that the calcium content is 200 ppm by mass or less based on the total amount of the lubricating oil composition.

[0015] [5] A lubricating oil composition according to any one of [1] to [4], which is a composition for lubricating a transmission and for cooling and lubricating an electric motor. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a lubricating oil composition that has a high level of balance between insulating properties, oxidation stability, and extreme pressure properties, as well as advanced copper corrosion prevention properties. [Modes for carrying out the invention]

[0017] The present invention will be described in detail below with reference to its preferred embodiments. In this specification, unless otherwise specified, the notation "X~Y" for numerical values ​​X and Y means "X or greater and Y or less". If a unit is attached only to the numerical value Y in such notation, that unit shall also apply to the numerical value X.

[0018] The lubricating oil composition of the present invention is (A) Lubricant base oil, (B) Extreme pressure agents, and (C) Nitrogen-containing ashless dispersant, A lubricating oil composition comprising, The aforementioned 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, phosphite esters and their salts, (B2) Either does not contain a sulfur-containing extreme pressure agent, or contains the (B2) component such that the sulfur content derived from the (B2) component is 0.01% by mass or less based on the total amount of the lubricating oil composition. The mass ratio ([phosphorus] / [nitrogen]) of phosphorus derived from component (B1) to nitrogen derived from component (C) is 0.60 or more and 2.30 or less. The mass ratio ([sulfur] / [phosphorus]) of sulfur derived from component (B2) to phosphorus derived from component (B1) is 3.0 or less. The kinematic viscosity (KV40) of the lubricating oil composition at 40°C after oxidation treatment under the conditions of an oil temperature of 165°C and 192 hours using the ISOT method in accordance with JIS K2514-1. OL ) and the kinematic viscosity (KV40) of the lubricating oil composition at 40°C before the oxidation treatment. L ) ratio ([KV40 OL ] / [KV40 L ]) must be 1.06 or less, It is characterized by the following:

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

[0020] Furthermore, as the lubricating oil base oil used as component (A), at least one selected from Group II, Group III, Group IV, and Group V base oils according to the API (American Petroleum Institute) classification of base oils can be suitably used. Among these, Group II or Group III base oils are more preferable from the viewpoint of obtaining a composition with higher oxidation stability, corrosion resistance, and insulation (volume resistivity), as well as from the viewpoint of improving the low energy consumption of electric vehicles (hereinafter, the groups of base oil classification according to the API will simply be referred to as "API groups").

[0021] Furthermore, mineral oil-based base oils are preferred as the lubricating oil base oil used as component (A). Suitable examples of such mineral oil-based base oils include paraffinic or naphthenic mineral oil-based base oils obtained by applying one or more refining methods, such as solvent delamination, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and clay treatment, to a lubricating oil fraction obtained by atmospheric distillation and vacuum distillation of crude oil. Among such mineral oil-based base oils, hydrorefined base oils and wax isomerized base oils are particularly preferred as component (A) from the viewpoint of obtaining compositions with higher oxidation stability, corrosion resistance, and insulation (volume resistivity), as well as from the viewpoint of improving the low energy consumption of electric vehicles. These mineral oil-based base oils may be used individually or in combination of two or more in any proportion.

[0022] Furthermore, the kinematic viscosity at 40°C of the lubricating oil base oil used as component (A) (or the mixed base oil if it is a mixed base oil containing two or more base oils) is 20 mm². 2 It is preferable that the speed be less than or equal to 5-18 mm. 2 It is more preferable that it be / s, which is 8-12mm 2 It is even more preferable that the kinematic viscosity of the lubricating oil base oil at 40°C is less than or equal to the upper limit, which makes it possible to obtain higher performance (effects) in terms of low-temperature viscosity characteristics and fuel efficiency compared to when the upper limit is exceeded. Furthermore, by setting the kinematic viscosity of the lubricating oil base oil at 40°C to or equal to the lower limit, which makes it possible to further improve the oil film formation performance at the lubrication point, as well as further improve extreme pressure performance based on seizure resistance and wear prevention, and also to further improve the electrical insulation properties of the new oil. In this specification, the kinematic viscosity of the base oil or composition at 40°C or 100°C refers to the kinematic viscosity at each temperature (40°C or 100°C) as specified in JIS K 2283-2000.

[0023] Furthermore, the kinematic viscosity at 100°C of the lubricating oil base oil used as component (A) (or the mixed base oil if it is a mixed base oil containing two or more base oils) is 2.0 to 4.0 mm². 2 It is preferable that the value be / s, and the size is 2.0 to 2.7 mm. 2 It is more preferable that the kinematic viscosity of the lubricating oil base oil at 100°C is below the upper limit, which makes it possible to obtain higher performance (effects) in terms of low-temperature viscosity characteristics and fuel efficiency compared to when it exceeds the upper limit. Furthermore, when the kinematic viscosity of the lubricating oil base oil at 100°C is above the lower limit, which makes it possible to improve the oil film formation performance at the lubrication point, improve extreme pressure performance based on seizure resistance and wear prevention, and also improve the electrical insulation properties of the new oil.

[0024] Furthermore, the viscosity index of the lubricating oil base oil used as component (A) (or the mixed base oil if it is a mixed base oil containing two or more base oils) is preferably 95 or higher, and more preferably 120 or higher. By setting the viscosity index of the lubricating oil base oil to be above the lower limit, the viscosity-temperature characteristics and thermal and oxidative stability of the lubricating oil composition can be improved, making it possible to further reduce the coefficient of friction and further improve wear resistance. In addition, the viscosity index of component (A) is more preferably 120 to 160, as this provides a greater effect from the viewpoint of fuel efficiency. In this specification, the "viscosity index" of the base oil and composition refers to the viscosity index measured in accordance with JIS K 2283-2000.

[0025] Furthermore, the sulfur content of the lubricating oil base oil used as component (A) (or the mixed base oil if it is a mixed base oil containing two or more base oils) 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 above upper limit, it is possible to further improve the oxidation stability compared to when it exceeds the above upper limit.

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

[0027] Furthermore, the flash point of the lubricating oil base oil used as component (A) (or the mixed base oil if it is a mixed base oil containing two or more base oils) is preferably 160°C or higher (more preferably 190°C or higher). In addition, setting the flash point above the aforementioned lower limit tends to improve safety during high-temperature use compared to cases where it is below the lower limit. In this specification, "flash point" means the flash point measured in accordance with JIS K 2265-4-2007 (Cleveland open flash test).

[0028] [(B) Component: 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 such 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, phosphite esters and their salts, (B2) Either the lubricant does not contain sulfur-containing extreme pressure additives, or it contains the (B2) component such that the sulfur content derived from the (B2) component is 0.01% by mass or less based on the total amount of the lubricant composition. That is, the extreme pressure additive as component (B) is The condition that it contains the aforementioned (B1) component; and, The condition is that the lubricating oil composition does not contain the aforementioned component (B2), or that it contains the aforementioned component (B2) such that the sulfur content derived from the aforementioned component (B2) is 0.01% by mass or less based on the total amount of the lubricating oil composition; It satisfies both conditions.

[0029] Thus, although component (B) contains component (B1) as an essential component, by utilizing component (B1), it becomes possible to achieve high load-bearing capacity and wear resistance even without using sulfur-containing extreme pressure agent (component (B2)) or by using only a minute amount of sulfur-containing extreme pressure agent (component (B2)) (an amount such that the amount of sulfur is 0.01% by mass or less based on the total amount of the lubricating oil composition), and furthermore, it becomes possible to achieve high insulation performance more efficiently.

[0030] The phosphorus-based extreme pressure agent used as such component (B1) is at least one compound selected from the group consisting of phosphoric acid, phosphoric acid esters, phosphite esters, and their salts. 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 the sulfur-containing extreme pressure agents described later).

[0031] The phosphate esters that can be used for such (B1) components are not particularly limited, and any known phosphate esters that can be used as extreme pressure agents can be used as appropriate. The term "phosphate ester" as used herein includes acidic phosphate esters.In other words, such phosphate esters include, for example, 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., there are also 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, etc.). Monoalkyl acid phosphates such as phosphates, monododecyl acid phosphate, monotridecyl acid phosphate, monotetradecyl acid phosphate, monopentadecyl acid phosphate, monohexadecyl acid phosphate, monoheptadecyl acid phosphate, monooctadecyl acid phosphate, monooleyl acid phosphate, dibutyl acid phosphate, dipentyl acid phosphate, dihexyl acid phosphate, and diheptyl acid phosphate. Examples of dialkyl acid phosphates include 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, dioryl acid phosphate, and diolyl acid phosphate.

[0032] Furthermore, the phosphite esters that can be used for component (B1) are not particularly limited, and any known phosphites that can be used as extreme pressure agents can be used as appropriate, for example, 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, trino Examples of such phosphites include nyl phosphite, tridecyl phosphite, triundecyl phosphite, toridodecyl phosphite, trioleyl phosphite, triphenyl phosphite, tricresyl phosphite, monolauryl hydrogen phosphite, monooleyl hydrogen phosphite, monostearyl hydrogen phosphite, monophenyl hydrogen phosphite, dibutyl hydrogen phosphite, dihexyl hydrogen phosphite, diheptyl hydrogen phosphite, di-n-octyl hydrogen phosphite, and diethylhexyl hydrogen phosphite. Among such phosphite esters, dialkyl hydrogen phosphite having two alkyl groups is preferred from the viewpoint of improving anti-seizure and anti-wear properties, and dialkyl hydrogen phosphite having two alkyl groups with 4 to 12 carbon atoms is more preferred.

[0033] Furthermore, as salts of phosphoric acid, phosphate esters, and phosphite esters that can be used for component (B1), any known salts that can be used as extreme pressure agents can be used as appropriate and are not particularly limited. For example, salts obtained by reacting phosphoric acid, phosphate esters, or phosphite esters with a metal base, or nitrogen-containing compounds 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 its molecule, can be used to neutralize some or all of the remaining acidic hydrogen.

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

[0035] Furthermore, the phosphate esters used to form such (B1-1) components can be any of the aforementioned phosphate esters as appropriate and are not particularly limited, but acidic phosphate esters are preferred, and monoalkyl acid phosphates and / or dialkyl acid phosphates are more preferred.

[0036] Examples of such monoalkyl acid phosphates and dialkyl acid phosphates are given by the following formula (1):

[0037] [ka]

[0038] [In formula (1), R a n 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. It is preferable that the compound is represented by the formula (1). That is, it is preferable to use the compound represented by formula (1) as the phosphate ester used to form the component (B1-1).

[0039] Furthermore, monoalkylamines, dialkylamines, and trialkylamines can be suitably used as amine compounds to form alkylamine salts of phosphate esters. 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 ditri 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. Such amine compounds may be used individually or in combination of two or more. Examples of such amine compounds include those shown in formula (2):

[0040] [ka]

[0041] [In formula (2), R b , R c and R d Each is independently a hydrogen atom or a monovalent alkyl group (however, R b , R c and Rd (At least one of them is a monovalent alkyl group.) It is preferable that the compound is represented by the formula (2) above. Note that R b , R c and R d The monovalent alkyl group that can be selected may be linear or branched. Furthermore, 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. Note that the compound represented in such formula (2) is a monoalkylamine (R in formula (2)). b , R c and R d A compound in which one of the atoms 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 in formula (2) b , R c and R d It is preferable that two of these are monovalent alkyl groups (particularly preferably alkyl groups having 8 to 18 carbon atoms), and the remaining atoms are hydrogen atoms.

[0042] Furthermore, the (B1-1) component is preferably a salt of the compound represented by formula (1) and the compound represented by formula (2), from the viewpoint of more efficiently achieving both excellent load-bearing capacity and wear resistance and high volume resistivity. In addition, the (B1-1) component can be used alone or as a mixture of two or more types.

[0043] Furthermore, the phosphorus-based extreme pressure agent (component (B1)) is: The above (B1-1) component and, A component other than component (B1-1) (hereinafter referred to as "component (B1-2)" for convenience), consisting of at least one compound selected from the group consisting of phosphoric acid, the phosphate ester, the phosphite ester, and salts thereof, A mixture of these is more preferable. From the viewpoint of making it easier to achieve excellent anti-seizure performance, wear resistance, corrosion resistance, and oxidation stability simultaneously, the (B1-2) component to be included in such a mixture is more preferably a phosphite ester. That is, it is preferable to use a mixture of an alkylamine salt of (B1-1) phosphate ester and a phosphite ester as the (B1) component.

[0044] Furthermore, if component (B1) is a mixture of component (B1-1) and component (B1-2), the mass ratio of phosphorus derived from component (B1-1) to phosphorus derived from 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 the mass ratio of phosphorus is above the lower limit, it is possible to obtain a higher effect in terms of anti-seizure performance compared to when it is below the lower limit, while when it is below the upper limit, it is possible to obtain an even higher effect in terms of electrical insulation compared to when it exceeds the upper limit.

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

[0046] Here, if 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 dithiocarbamates, zinc dithiocarbamates, molybdenum dithiocarbamates (MoDTC), disulfides, polysulfides, sulfurized olefins, and sulfurized oils and fats; sulfur-phosphorus-based extreme pressure agents such as thiophosphites, dithiophosphites, trithiophosphites, thiophosphates, dithiophosphates, trithiophosphates, amine salts thereof, and derivatives thereof; and so on.

[0047] If component (B) contains the sulfur-containing extreme pressure agent (component (B2)), the sulfur content derived from 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 component (B2) is below the upper limit, it is possible to obtain higher oxidation stability and higher copper corrosion prevention compared to when it exceeds the upper limit. Furthermore, from the viewpoint of further improving copper corrosion prevention and insulation (value of volume resistivity), it is preferable that component (B) does not contain the sulfur-containing extreme pressure agent (B2).

[0048] Furthermore, there are no particular restrictions on the method for producing such component (B), and known methods can be used as appropriate. In addition, commercially available products may be used as such component (B).

[0049] [(C) Component: 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] Such component (C) is not particularly limited, and any known ashless dispersant containing nitrogen can be used as appropriate. Furthermore, from the viewpoint of further improving corrosion resistance and oxidation stability, such component (C) is more preferably an ashless dispersant having a nitrogen-containing functional group as the dispersant group.

[0051] Suitable examples of ashless dispersants that use a nitrogen-containing functional group as a dispersion group include succinimide, benzylamine, polyamine, and derivatives thereof, which have a hydrocarbon group with 40 to 400 carbon atoms (e.g., alkyl groups, alkenyl groups).

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

[0053] Furthermore, the succinimide having a hydrocarbon group with 40 to 400 carbon atoms is not particularly limited, but the following formulas (3) and (4):

[0054] [ka]

[0055] [In equations (3) and (4), R 1 and R 2 Each of these 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 from 0 to 5. It is preferable that the compound is represented by formula (3) and (4). 1 A selectable alkyl group or alkenyl group, and R 2The alkyl group or alkenyl group that can be selected is more preferably a branched alkyl group or alkenyl group (polyisobutenyl group) or polybutenyl group derived from an oligomer of isobutene called polyisobutylene. 1 and R 2 The alkyl or alkenyl group that can be selected preferably has a weight-average molecular weight of 800 to 1500 (more preferably 950 to 1400). Also, n in formula (3) is preferably an integer from 1 to 5 (more preferably 2 to 4). On the other hand, n in formula (4) is preferably an integer from 0 to 4 (more preferably 1 to 4, even more preferably 1 to 3). Furthermore, among the compounds represented by such formulas (3) to (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 for example, a method may be employed in which succinimide is produced as a condensation reaction product by reacting at least one selected from the group consisting of alkyl succinic acid, alkenyl succinic acid, and their anhydrides having an alkyl or alkenyl group having 40 to 400 carbon atoms with a polyamine.

[0056] Furthermore, the derivative of succinimide (modified succinimide compound) is not particularly limited, and known modified succinimide compounds that can be used as ashless dispersants can be used as appropriate, for example, (i) a modified compound with an oxygen-containing organic compound (at least one of monocarboxylic acids having 1 to 30 carbon atoms such as fatty acids, polycarboxylic acids having 2 to 30 carbon atoms (e.g., 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) Examples include: (ii) compounds in which some or all of the remaining amino groups and / or imino groups are neutralized or amidated by reacting with succinimide; (ii) boron-modified compounds (compounds in which some or all of the remaining amino groups and / or imino groups are neutralized or amidated by reacting succinimide with boric acid (so-called boronated succinimide)); (iii) phosphoric acid-modified compounds (compounds in which some or all of the remaining amino groups and / or imino groups are neutralized or amidated by reacting succinimide with phosphoric acid).

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

[0058] As a suitable succinimide-based ashless dispersant for component (C), it is preferable that the nitrogen content in the succinimide-based ashless dispersant is 1.0 to 4.8% by mass (more preferably 1.2 to 2.4% by mass). By keeping the nitrogen content within this range, it is possible to more efficiently achieve high levels of corrosion resistance and oxidation stability. Furthermore, when using boronated succinimide as the succinimide-based ashless dispersant, it is preferable that the boron content in the boronated succinimide is 0.01 to 5.0% by mass (more preferably 0.2 to 2.2% by mass).

[0059] Furthermore, as the succinimide-based ashless dispersant suitable for component (C), a weight-average molecular weight of 1000 to 9000 (more preferably 1000 to 5000) is more preferable. By having a weight-average molecular weight of the succinimide-based ashless dispersant above the lower limit, it becomes possible to further improve the electrical insulation properties of the new oil and the composition after oxidative degradation. Also, by having a weight-average molecular weight of the succinimide-based ashless dispersant below the upper limit, it becomes possible to further improve the electrical insulation properties of the composition after oxidative degradation.

[0060] Furthermore, as a suitable succinimide-based ashless dispersant for component (C), one with a total base number (TBN) of 20 to 80 mgKOH / g (more preferably 30 to 60 mgKOH / g) is preferred. When the total base number is within the above range, an even higher effect in terms of oxidation stability tends to be obtained.

[0061] Furthermore, there are no particular restrictions on the method for producing such component (C), and known methods can be used as appropriate. In addition, commercially available products may be used as such component (C).

[0062] [Regarding the composition of the lubricating oil composition] The lubricating oil composition of the present invention contains component (A), component (B), and component (C). Component (B) contains component (B1) (phosphorus-based extreme pressure agent) as an essential component, as described above.

[0063] Furthermore, in the lubricating oil composition of the present invention, the mass ratio ([phosphorus] / [nitrogen]) of phosphorus derived from component (B1) to nitrogen derived from component (C) must be 0.60 or more and 2.30 or less. When the mass ratio of phosphorus to nitrogen is above the lower limit, it is possible to achieve a high level of both extreme pressure resistance and insulation compared to the case below the lower limit, while also achieving high insulation. On the other hand, when it is below the upper limit, it is possible to achieve a high level of anti-seizure resistance and oxidation stability compared to the case above the upper limit. Moreover, the mass ratio ([phosphorus] / [nitrogen]) of phosphorus derived from component (B1) to 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 1.30 or less) in order to obtain an even higher effect in terms of achieving both high anti-seizure resistance, wear resistance and volume resistivity and excellent oxidation stability.

[0064] Furthermore, in the lubricating oil composition of the present invention, it is preferable that the mass ratio ([sulfur] / [phosphorus]) of sulfur derived from component (B2) to phosphorus derived from component (B1) is 3.0 or less (more preferably 2.93 or less, and even more preferably 2.2 or less). When the mass ratio of sulfur to phosphorus is below the upper limit, it is possible to achieve better oxidation stability and copper corrosion prevention properties compared to when it exceeds the upper limit.

[0065] Furthermore, in the lubricating oil composition of the present invention, the content of component (A) is not particularly limited, but it is preferably 80 to 98% by mass (more preferably 85 to 95% by mass) based on the total amount of the lubricating oil composition. When the content of component (A) is above the lower limit, it is possible to further improve oxidation stability compared to when it is below the lower limit, while when it is below the upper limit, it is possible to further improve the additive effect at the lubrication point and further improve lubricity compared to when it exceeds the upper limit.

[0066] 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)) is preferably 0.050% by mass or less (more preferably 0.045% by mass or less, even more preferably 190 to 410 ppm by mass, and particularly preferably 190 to 380 ppm by mass) based on the total amount of the lubricating oil composition. When the content of phosphorus derived from component (B1) is below the upper limit, it is possible to further improve seizure resistance and wear resistance compared to when it exceeds the upper limit. When the content of phosphorus derived from component (B1) is above the lower limit, it is possible to obtain a composition with a higher volume resistivity compared to when it is below the lower limit.

[0067] Furthermore, in the lubricating oil composition of the present invention, as described above, it is necessary to satisfy the condition that it does not contain a sulfur-containing extreme pressure agent (component (B2)), or, if it contains component (B2), the sulfur content derived from component (B2) is 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. 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.

[0068] Furthermore, if the lubricating oil composition of the present invention contains a sulfur-containing extreme pressure agent (component (B2)), and component (B2) contains phosphorus, it is preferable that the amount of phosphorus derived from component (B2) is 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 component (B2) below the above upper limit, it is possible to further improve corrosion resistance and oxidation stability.

[0069] Furthermore, in the lubricating oil composition of the present invention, if component (B) contains component (B1-1), the phosphorus (P) content derived from 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 above the lower limit, it is easier to improve load-bearing capacity (seizure resistance) and wear resistance compared to when it is below the lower limit, while when it is below the upper limit, it is easier to improve insulation compared to when it exceeds the upper limit.

[0070] Furthermore, in the lubricating oil composition of the present invention, if the component (B) contains the component (B1-2), the phosphorus (P) content derived from the 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 above the lower limit, it is possible to further improve seizure resistance and wear resistance compared to when it is below the lower limit, while when it is below the upper limit, it is possible to obtain a composition with a higher volume resistivity more efficiently compared to when it exceeds the upper limit.

[0071] 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 nitrogen content derived from component (C) be 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 nitrogen content derived from component (C) is more preferably 400 ppm by mass, and particularly preferably 200 ppm by mass). When the amount of nitrogen is above the lower limit, it is possible to further improve oxidation stability compared to when it is below the lower limit, while when it is below the upper limit, it is possible to increase the volume resistivity more easily compared to when it exceeds the upper limit.

[0072] Furthermore, when using "boronated succinimide" as component (C), it is preferable that the boron content derived from component (C) is 200 ppm by mass or less (more preferably 50 ppm by mass or more and 130 ppm by mass or less) based on the total amount of the lubricating oil composition. When the amount of boron is above the lower limit, it is possible to further improve seizure resistance and oxidation stability compared to when it is below the lower limit. On the other hand, when it is below the upper limit, it is possible to suppress the increase in kinematic viscosity and obtain a higher volume resistivity compared to when it exceeds the upper limit.

[0073] In this invention, the sulfur, phosphorus, nitrogen, and boron content in the composition and various components are determined according to the values ​​measured in accordance with ASTM D4951.

[0074] Furthermore, the lubricating oil composition of the present invention may further contain additives in addition to the components (A) to (C) described above. Such additives can be any known additives used in the field of lubricating oil compositions, and are not particularly limited, but (D) calcium sulfonate detergents and (E) antioxidants are particularly suitable.

[0075] Component (D) can be, for example, calcium sulfonate, which is a calcium salt of alkyl aromatic sulfonic acid; a basic salt of the calcium sulfonate; or an overbasic salt of the calcium sulfonate. Examples of such alkyl aromatic sulfonic acid include so-called petroleum sulfonic acid and synthetic sulfonic acid. Examples of petroleum sulfonic acid include alkyl aromatic compounds obtained by sulfonating the lubricating oil fraction of mineral oil, or so-called mahogany acid, which is a by-product produced during the manufacture of white oil. An example of synthetic sulfonic acid is obtained by sulfonating alkylbenzenes having linear or branched alkyl groups, which are obtained by recovering by-products in alkylbenzene production plants that are raw materials for detergents, or by alkylating benzene with polyolefins. Another example of synthetic sulfonic acid is obtained by sulfonating alkylnaphthalenes such as dinonylnaphthalene. There are no particular restrictions on the sulfonating agent used when sulfonating these alkyl aromatic compounds; for example, fuming sulfuric acid or anhydrous sulfuric acid can be used. Furthermore, the weight-average molecular weight of such alkyl aromatic sulfonic acid is preferably 300 to 1500, and more preferably 400 to 1300. The basic salt and overbasic salt of the calcium sulfonate are not particularly limited, and known salts can be used as appropriate. For example, calcium sulfonate (over)basified with calcium carbonate or calcium borate can be used. The method for preparing the basic salt and overbasic salt is not particularly limited, and known methods can be used as appropriate (for example, if the overbasic salt is calcium sulfonate overbasified with calcium carbonate, a method may be employed in which calcium sulfonate is reacted with a base such as calcium hydroxide in the presence of carbon dioxide to obtain calcium sulfonate overbasified with calcium carbonate).

[0076] Furthermore, as such component (D), a total base number (TBN) of 20 to 450 mgKOH / g (more preferably 300 to 450 mgKOH / g) is preferred. When the total base number is within the above range, an even higher effect in terms of oxidative stability tends to be obtained.

[0077] Furthermore, when the lubricating oil composition of the present invention contains component (D), it is preferable that the amount of component (D) be such that the calcium content derived from component (D) is 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 is possible to obtain a higher effect in terms of insulating properties compared to when it exceeds the upper limit. In this invention, the calcium content in the composition and various components is determined by values ​​measured in accordance with ASTM D4951.

[0078] (E) Component can be any known ashless antioxidant in the field of lubricating oil compositions (e.g., amine-based antioxidants, phenol-based antioxidants, etc.), and is not particularly limited, but it is preferable to use a combination of (E1) a phenol-based antioxidant and (E2) an amine-based antioxidant.

[0079] For the (E1) component, for example, compounds known as phenolic antioxidants (e.g., compounds exemplified in International Publication No. 2020 / 095970) can be used as appropriate. Examples of such phenolic antioxidants include hindered phenol compounds and bisphenol compounds.

[0080] Furthermore, as the (E2) component, compounds known as amine antioxidants, such as aromatic amine antioxidants and hindered amine antioxidants (for example, compounds exemplified in International Publication No. 2020 / 095970) can be used as appropriate. Among the aromatic amine antioxidants, alkylated diphenylamine and alkylated phenyl-α-naphthylamine can be preferably used. As the hindered amine antioxidant, for example, compounds having a 2,2,6,6-tetraalkylpiperidine skeleton (2,2,6,6-tetraalkylpiperidine derivatives) can be preferably used. Among the amine antioxidants, aromatic amine antioxidants are more preferred, and alkylated diphenylamine is particularly preferred.

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

[0082] While components (D) and (E) have been described as suitable additives for use in the lubricating oil composition of the present invention, the additives usable in the lubricating oil composition of the present invention are not limited to components (D) and (E). Other known additive components (such as those described in Japanese Patent Publication No. 2016-3258, International Publication No. 2015 / 056783, Japanese Patent Publication No. 2016-160312, Japanese Patent Publication No. 2003-155492, International Publication No. 2017 / 073748, Japanese Patent Publication No. 2020-76004, etc.) can also be used as appropriate, within the limits that do not impair the effects of the present invention.

[0083] Furthermore, when using additive components other than those described in (D) and (E), it is more preferable that the total amount of the other additive components is 0.5 to 2.0% by mass based on the total amount of the lubricating oil composition. When the total amount of such other additive components is above the lower limit, it is possible to obtain a higher effect in terms of corrosion resistance and oxidation stability compared to when it is below the lower limit. On the other hand, when it is below the upper limit, it is possible to obtain a higher effect in terms of seizure resistance and wear resistance compared to when it exceeds the upper limit.

[0084] Furthermore, the various additives that can be used in such lubricating oil compositions may be prepared and added separately for each component, or they may be prepared and added as mixtures of other components. As such mixtures of other components, commercially available packaged products (for example, additive packages containing rubber swelling agents, defoaming agents, and pour point depressants) may be used as appropriate.

[0085] [Regarding the characteristics, manufacturing method, and uses of lubricating oil compositions] The lubricating oil composition of the present invention has been subjected to oxidation treatment under the conditions of an oil temperature of 165°C and 192 hours according to the ISOT method in accordance with JIS K2514-1, and its kinematic viscosity (KV40) at 40°C is the result of this oxidation treatment. OL) and the kinematic viscosity (KV40) of the lubricating oil composition at 40°C before the oxidation treatment. L ) ratio ([KV40 OL ] / [KV40 L The ratio of kinematic viscosity ([KV40)) of the lubricating oil composition before and after oxidation treatment at 40°C must be 1.06 or less. OL ] / [KV40 L By keeping the ratio of kinematic viscosity ([KV40)) below the upper limit, it becomes possible to suppress the increase in viscosity due to oxidative degradation compared to when the upper limit is exceeded, and when used in a transmission, it becomes possible to exhibit higher transmission efficiency over a longer period of time. The ratio of kinematic viscosity ([KV40)) of the lubricating oil composition at 40°C before and after such oxidation treatment OL ] / [KV40 L The ratio ([KV40 OL ] / [KV40 L By setting the range to the aforementioned range, a higher effect in terms of oxidation stability tends to be obtained compared to the case outside the aforementioned range, and when used in a transmission, it becomes possible to exhibit a higher transmission efficiency over an even longer period of time.

[0086] The lubricating oil composition of the present invention has a kinematic viscosity (KV40) at 40°C. L The kinematic viscosity of the composition (new oil) that has not undergone the aforementioned oxidation treatment is 8.0 to 18.0 mm². 2 / s (more preferably 8.0~14.0mm) 2 A lubricating oil composition of KV40 is preferred. LWhen the kinematic viscosity of the lubricating oil composition at 40°C is below the upper limit, compared to when it exceeds the upper limit, it becomes possible to further reduce the stirring resistance in a relatively low temperature range around 40°C (preferably around 20 to 60°C), thereby further improving power transmission efficiency even in low-temperature conditions such as immediately after the start of use, and thus further improving fuel efficiency. Furthermore, when the kinematic viscosity of the lubricating oil composition at 40°C is above the lower limit, the oil film formation and oil film retention properties of the lubricating oil composition at the lubrication points are further improved in a relatively low temperature range around 40°C (preferably around 20 to 60°C), making it possible to maintain a better lubrication state, and from this viewpoint, it becomes possible to further improve gear transmission efficiency and energy efficiency.

[0087] The lubricating oil composition of the present invention is the kinematic viscosity (KV40) at 40°C after oxidation treatment under the conditions of an oil temperature of 165°C and 192 hours by the ISOT method in accordance with JIS K2514-1. OL ) 8.0~20.0mm 2 / s (more preferably 8.0~18.0mm) 2 A lubricating oil composition of KV40 is preferred. OL When the value is below the upper limit, it is possible to obtain a greater effect in terms of improved oxidation stability and improved transmission efficiency when used in a transmission, compared to when it exceeds the upper limit, while the KV40 of the lubricating oil composition OL When the value is above the aforementioned lower limit, it is possible to obtain higher levels of wear resistance and seizure resistance compared to when it is below the aforementioned lower limit.

[0088] The lubricating oil composition of the present invention is the kinematic viscosity (KV40) of the lubricating oil base oil that has not undergone the oxidation treatment at 40°C. B (The kinematic viscosity of the base oil in its fresh state before the aforementioned oxidation treatment) and the kinematic viscosity of the base oil before the aforementioned oxidation treatment. The lubricating oil composition kinematic viscosity at 40°C (KV40 L : Ratio of kinematic viscosity of the composition in its fresh oil state without the aforementioned oxidation treatment) ([KV40 L ] / [KV40 BA ratio of kinematic viscosity ([KV40 L ] / [KV40 B When the ratio ([KV40 L ] / [KV40 B When ]) is equal to or greater than the lower limit, a higher effect in terms of wear resistance and seizure resistance can be obtained compared to when it is less than the lower limit.

[0089] The lubricating oil composition of the present invention has a kinematic viscosity at 100°C (kinematic viscosity of the composition that has not undergone the aforementioned oxidation treatment (new oil)) of 1.8 to 4.0 mm². 2 / s (more preferably 2.2~3.5mm) 2 A viscosity of / s is preferred. When the kinematic viscosity of the lubricating oil composition at 100°C is below the upper limit, it is possible to make it more viscous in the relatively high temperature range around 100°C compared to when it exceeds the upper limit, and the stirring resistance can be made smaller, which makes it possible to further improve power transmission efficiency and improve fuel efficiency. Furthermore, when the kinematic viscosity of the lubricating oil composition at 100°C is above the lower limit, the oil film formation and oil film retention properties of the lubricating oil composition at the lubrication point are further improved in the relatively high temperature range around 100°C (preferably around 80 to 120°C), and the oil film can be maintained more uniformly, which makes it possible to make the anti-seizure performance during use more advanced.

[0090] Furthermore, the lubricating oil composition of the present invention is preferably one having a viscosity index of 105 or higher (more preferably 120 or higher). When the viscosity index is above the lower limit (more preferably 120 or higher), it is possible to further improve the viscosity-temperature characteristics and wear prevention properties of the lubricating oil composition, as well as further improve fuel efficiency, compared to when it is below the lower limit (more preferably less than 120).

[0091] 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 × 10⁻¹⁰) 12 Ωcm or greater, more preferably 0.0024 × 10⁻⁶ 12 It is preferable that the volume resistivity is Ωcm or greater. By setting such a volume resistivity to be above the lower limit, it is possible to ensure a high level of insulation that exceeds the level required when used in electric vehicles. There is no particular upper limit to the volume resistivity of the lubricating oil composition at 80°C, but from the viewpoint of discharge resistance, 0.10 × 10 12 It is preferable that the volume resistivity is Ωcm. The value to be adopted for such volume resistivity is the value measured by performing a measurement in accordance with the volume resistivity test specified in JIS C2101 at an oil temperature of 80°C.

[0092] The method for producing the lubricating oil composition of the present invention is not particularly limited, and it may be prepared by appropriately selecting and mixing each component to be included so that the lubricating oil composition of the present invention can be obtained (so that the above conditions are met).

[0093] The lubricating oil composition of the present invention has a well-balanced combination of high levels of insulating properties, oxidation stability, and extreme pressure properties, as well as advanced copper corrosion prevention. Therefore, its applications are not particularly limited, but it can be suitably used as a lubricating oil for transmissions and as a cooling and lubricating oil for 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. [Examples]

[0094] Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[0095] (Regarding the components used in each Example, etc.) First, the base oils and additives used in each Example, etc. are shown below.

[0096] [(A) Lubricating oil base oil] (A1) Wax isomerization base oil [Mineral oil: API Group III, Kinematic viscosity at 40 °C: 9.422 mm 2 / s, Kinematic viscosity at 100 °C: 2.676 mm 2 / s, Viscosity index: 125, Sulfur content in the base oil (sulfur content in the base oil): 0 mass ppm, 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: 2.431 mm 2 / s, Viscosity index: 105, Sulfur content in the base oil (sulfur content in the base oil): 0 mass ppm, Pour point: -30 °C, Flash point: 170 °C].

[0097] [(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 above formula (1) and R in the formula a is an oleyl group (group represented by the formula: C 18 H 35 ), and an alkylamine (a compound represented by the above formula (2), where one of R b , R c and R d is a dodecyl group (group represented by the formula: C 12 H 25 ), and the other of R b , R c and R d is a hydrogen atom) salt] (B1-2) Phosphite [Dibutyl hydrogen phosphite] <(B2) Sulfur-containing extreme pressure agent> (B2-1) Thiophosphate [Phosphorus content: 100,000 ppm by mass, sulfur content: 190,000 ppm by mass].

[0098] 〔(C) Nitrogen-containing ashless dispersant〕 (C1) Succinimide-based ashless dispersant [Borated succinimide, nitrogen content; 2.0% by mass, boron content: 0.5% by mass, total base number (TBN): 50, type of succinimide: bis form (bis type succinimide represented by the above formula (4) (wherein, R in the formula (4)]] 1 and R 2 is a polyisobutenyl group with a weight average molecular weight (Mw) of 1000 and n is 3) of boron-modified compound).

[0099] 〔(D) Calcium sulfonate detergent〕 (D1) Calcium sulfonate detergent [Base number (TBN): 400 mg KOH / g, calcium atom content: 15.0% by mass].

[0100] 〔(E) Antioxidant〕 (E1) Phenolic antioxidant [Octyl 3-(4-hydroxy-3,5-diisopropylphenyl)propionate] (E2) Amine-based antioxidant [Alkylated diphenylamine].

[0101] 〔(F) Other additives (performance additives)〕 (F1) Performance additive [Mixture of rubber swelling agent, defoaming agent and pour point depressant (additive package)].

[0102] (Examples 1~ 6, Reference example 1 and Comparative Examples 1~4) Using the above-mentioned respective components, so as to have the compositions shown in Tables 1~2, Examples 1~ 6, Reference example 1Lubricant compositions for Comparative Examples 1-4 were prepared. In Tables 1-2, a "-" in the "Composition" column indicates that the component was not used. Furthermore, in the "Composition" column in Tables 1 and 2, "inmass%" represents the mass-based content (mass%) relative to the total amount of lubricating oil base oil, "mass%" represents the mass-based content (mass%) relative to the total amount of lubricating oil composition, "ppm (N equivalent)" represents the mass-based content (mass ppm: nitrogen content relative to the total amount of lubricating oil composition derived from that component) relative to the total amount of lubricating oil composition, "ppm (P equivalent)" represents the mass-based content (mass ppm: phosphorus content relative to the total amount of lubricating oil composition derived from that component) relative to the total amount of lubricating oil composition, "ppm (S equivalent)" represents the mass-based content (mass ppm: sulfur content relative to the total amount of lubricating oil composition derived from that component) relative to the total amount of lubricating oil composition, and "ppm (Ca equivalent)" represents the mass-based content (mass ppm: calcium content relative to the total amount of lubricating oil composition derived from that component) relative to the total amount of lubricating oil composition. Furthermore, in Tables 1 and 2, the phosphorus, nitrogen, sulfur, boron, and calcium content values ​​are measured in accordance with ASTM D4951. In addition, in Tables 1 and 2, the notation "(B1) phosphorus content" indicates the percentage by mass of phosphorus derived from component (B1) contained in the lubricating oil composition (mass %), the notation "(B2) sulfur content" indicates the percentage by mass of sulfur derived from component (B2) contained in the lubricating oil composition (mass %), the notation "(C) nitrogen content" indicates the percentage by mass of nitrogen derived from component (C) contained in the lubricating oil composition (mass %), and the notation "(C) boron content" indicates the percentage by mass of boron derived from component (C) contained in the lubricating oil composition (mass %).Furthermore, in Tables 1 and 2, the notation "(B1) phosphorus / (C) nitrogen" indicates the ratio (mass ratio: [phosphorus] / [nitrogen]) between the "(B1) phosphorus content" and the "(C) nitrogen content," and the notation "(B2) sulfur / (B1) phosphorus" indicates the ratio (mass ratio: [sulfur] / [phosphorus]) between the "(B2) sulfur content" and the "(B1) phosphorus content."

[0103] [Regarding the evaluation method for the properties of the lubricating oil compositions obtained in each example, etc.] <Measurement of volume resistivity> The volume resistivity of 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 × 10⁻⁶. 12 If the value is Ω·cm or higher, it can be considered to have high insulation properties.

[0104] <Falex seizure test: Test to confirm seizure resistance> For each lubricating oil composition, a Falex seizure test was performed in accordance with ASTM D3233 A, and the load at which seizure occurred (unit: lbf) was measured. The results are shown in Tables 1 and 2. A load of 700 lbf or higher indicates good seizure resistance.

[0105] <Falex abrasion test: Abrasion resistance confirmation test> For each lubricating oil composition, a Falex test (Falex wear resistance test) was performed in accordance with ASTM D2670 under the conditions of oil temperature 80°C, load 390 lb, rotation speed 290 rpm, and 1 hour, and the amount of wear (mg) was measured. The obtained results are shown in Tables 1 and 2. Note that a wear amount of 55.0 mg or less indicates good wear resistance.

[0106] <Confirmation test for copper plate corrosion resistance> Approximately 30 mL samples were prepared from each lubricating oil composition, and copper plate corrosion tests were conducted in accordance with JIS K 2513 to evaluate their resistance to copper plate corrosion. Specifically, in accordance with JIS K2513, a copper plate was completely immersed in approximately 30 mL of the sample, held at an oil temperature of 150°C for 192 hours, then removed, washed, and compared with a copper plate corrosion standard to determine the sample's corrosiveness to copper and evaluate its copper corrosion prevention capability. The results are shown in Tables 1 and 2. Note that if the judgment value (discoloration number) of the copper plate corrosion standard is 2 or less, it can be judged that the copper corrosion prevention capability is high.

[0107] <Evaluation of oxidative stability: Confirmation test to determine whether or not a strong acid value is generated after oxidation treatment> Each lubricating oil composition was subjected to oxidation treatment using the ISOT (Indiana Stirring Oxidation Test) method in accordance with JIS K2514-1, under conditions of 165°C for 192 hours. After oxidation treatment, the presence or absence of a strong acid value was checked using the treated lubricating oil composition. Lubricating oil compositions that did not develop a strong acid value were evaluated as "pass" due to high oxidation stability, while lubricating oil compositions that developed a strong acid value were evaluated as "fail" due to insufficient oxidation stability. The results are shown in Tables 1 and 2.

[0108] <Measurement of kinematic viscosity ratio> For each lubricating oil composition, the kinematic viscosity (KV40) at 40°C was determined after oxidation treatment under the conditions of an oil temperature of 165°C and 192 hours using the ISOT method in accordance with JIS K2514-1. OL ) and the kinematic viscosity (KV40) of the lubricating oil composition at 40°C before the oxidation treatment. L ) and calculate their respective ratios ([KV40 OL ] / [KV40 L The kinematic viscosity (KV40) of the base oil used in each lubricating oil composition at 40°C was determined. B (Kinematic viscosity of new oil) and the kinematic viscosity (KV40) of the lubricating oil composition at 40°C before the oxidation treatment. L ) ratio ([KV40 L ] / [KV40 BThe kinematic viscosity at 40°C was determined in accordance with the values ​​specified in JIS K 2283-2000. The results obtained are shown in Tables 1 and 2.

[0109] [Table 1]

[0110] [Table 2]

[0111] As is clear from the results shown in Table 1, Example 1 to 6 The lubricating oil composition obtained (corresponding to the lubricating oil composition of the present invention) and the lubricating oil composition obtained in Reference Example 1 The volume resistivity is 0.0020 × 10⁻⁶. 12 It was found to be suitable for lubrication and cooling of electric motors, where a high level of insulation is required, as it is greater than Ωcm. Also, Examples 1- 6 The lubricating oil composition obtained (corresponding to the lubricating oil composition of the present invention) and the lubricating oil composition obtained in Reference Example 1 It was confirmed that the material exhibits excellent seizure resistance and wear resistance, and also possesses high extreme pressure resistance based on seizure resistance and wear resistance. Furthermore, Examples 1- 6 The lubricating oil composition obtained (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 that the oxidation stability was high. Also, as shown in Table 1, Examples 1- 6 The lubricating oil composition obtained (corresponding to the lubricating oil composition of the present invention) and the lubricating oil composition obtained in Reference Example 1 It was also confirmed that it has high copper corrosion prevention properties. Furthermore, Examples 1- 6 The lubricating oil composition obtained (corresponding to the lubricating oil composition of the present invention) and the lubricating oil composition obtained in Reference Example 1 In all cases, the ratio of the kinematic viscosity of the lubricating oil composition before and after the oxidation treatment at 40°C ([KV40 OL ] / [KV40 L The ratio was 1.05 or less, and from this perspective as well, it was found that the oxidation stability was high. Based on these results, Example 1~ 6 and Reference Example 1The resulting lubricating oil composition exhibited high levels of insulation, oxidation stability, and extreme pressure resistance, demonstrating a good balance of these properties, and also possessing high copper corrosion prevention capabilities.

[0112] In contrast, as is clear from the results shown in Table 2, the lubricating oil composition obtained in Comparative Example 1, in which the mass ratio (P / N) of phosphorus content from component (B1) to nitrogen content from component (C) exceeded 2.30 (2.68), did not exhibit sufficient seizure resistance and could not achieve a high level of extreme pressure resistance. Furthermore, the lubricating oil composition obtained in Comparative Example 1 exhibited a strong acid value and could not achieve a high level of oxidation stability. Moreover, the lubricating oil compositions obtained in Comparative Examples 2 and 3, in which the mass ratio (P / N) of phosphorus content from component (B1) to nitrogen content from component (C) was less than 0.60, were not necessarily sufficient in terms of extreme pressure resistance or insulating properties. Furthermore, the lubricating oil composition obtained in Comparative Example 4, in which the sulfur content derived from the sulfur-containing extreme pressure agent exceeds 100 ppm by mass (200 ppm by mass), and the mass ratio (S / P) of sulfur derived from component (B2) to phosphorus derived from component (B1) exceeds 3.0 (4.55), generates a strong acid value, and the ratio of the kinematic viscosity at 40°C of the lubricating oil composition before and after the oxidation treatment ([KV40 OL ] / [KV40 L The coefficient of oxidation stability was 1.08, indicating that it was not possible to achieve a high level of oxidation stability. Furthermore, the lubricating oil composition obtained in Comparative Example 4 did not exhibit high levels of copper corrosion prevention. [Industrial applicability]

[0113] As described above, the present invention makes it possible to provide a lubricating oil composition that has a high level of balance between insulating properties, oxidation stability, and extreme pressure properties, as well as advanced copper corrosion prevention properties. Therefore, the lubricating oil composition of the present invention is particularly useful as a lubricating oil composition for electric vehicles, etc.

Claims

1. (A) Lubricating base oil, (B) Extreme pressure agents, and (C) Nitrogen-containing ashless dispersant, A lubricating oil composition comprising, The aforementioned component (B) is, (B1) Contains a phosphorus-based extreme pressure agent which is a mixture of an alkylamine salt of a phosphate ester and a phosphite ester, (B2) Either does not contain a sulfur-containing extreme pressure agent, or contains the (B2) component such that the sulfur content derived from the (B2) component is 0.01% by mass or less based on the total amount of the lubricating oil composition. The nitrogen content derived from component (C) is 294 ppm by mass to 600 ppm by mass based on the total amount of the lubricating oil composition. The mass ratio ([phosphorus] / [nitrogen]) of phosphorus derived from component (B1) to nitrogen derived from component (C) is 0.60 or more and 2.30 or less. The mass ratio ([sulfur] / [phosphorus]) of sulfur derived from component (B2) to phosphorus derived from component (B1) is 3.0 or less. The kinematic viscosity (KV40) at 40°C of the lubricating oil composition after oxidation treatment at an oil temperature of 165°C for 192 hours using the ISOT method in accordance with JIS K2514-1. ＯＬ ) and the kinematic viscosity (KV40) of the lubricating oil composition at 40°C before the oxidation treatment. Ｌ ) ratio ([KV40 ＯＬ ] / [KV40 Ｌ ]) must be 1.06 or less. A lubricating oil composition characterized by the following.

2. The kinematic viscosity (KV40) of the lubricating oil base oil that has not undergone the aforementioned oxidation treatment at 40°C Ｂ ) and the kinematic viscosity (KV40) of the lubricating oil composition at 40°C before the oxidation treatment. Ｌ ) ratio ([KV40 Ｌ ] / [KV40 Ｂ The lubricating oil composition according to claim 1, characterized in that ) is 0.95 or more and 1.15 or less.

3. The base oil for the lubricant contains at least one selected from the group consisting of a hydrorefined base oil and a wax isomerized base oil, and the kinematic viscosity of the base oil for the lubricant at 40 °C is 20 mm ２ / s or less, and the lubricant composition according to claim 1 is characterized thereby.

4. (D) The lubricating oil composition according to claim 1, characterized in that it contains a calcium sulfonate detergent such that the calcium content is 200 ppm by mass or less based on the total amount of the lubricating oil composition.

5. The lubricating oil composition according to claim 1, characterized in that it is a composition for lubricating a transmission and for cooling and lubricating an electric motor.

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