Lubricating oil composition

Abstract

A lubricating oil composition comprising (A) a lubricating oil base oil, (B) an extreme pressure agent, and (C) a nitrogen-containing ashless dispersant; the lubricating oil composition has a volume resistivity of 0.0020 * 10 < 12 > [Omega] cm or more at 80 DEG C; the component (B) contains a specific phosphorus-based extreme pressure agent (B1) and does not contain a sulfur-containing extreme pressure agent (B2), or the component (B2) is contained such that the content of sulfur derived from the component (B2) is a specific amount or less; the content of phosphorus derived from the component (B1) is not more than a specific amount; the mass ratio ([phosphorus] / [nitrogen]) of the phosphorus derived from the component (B1) to the nitrogen derived from the component (C) is 0.60-2.30 (inclusive).

Description

Technical Field

[0001] The present invention relates to lubricating oil compositions. Background Art

[0002] In recent years, attention has been paid to electric vehicles that do not emit carbon dioxide, a greenhouse gas. Such electric vehicles usually use electric motors as a power source for driving and are equipped with gear mechanisms such as transmissions. In the past, different lubricating oil compositions were used for cooling and lubricating such electric motors and lubricating gear mechanisms. However, in recent years, in order to simplify the circulation mechanism of the lubricating oil composition, the use of the same lubricating oil composition has gradually been proposed. In particular, in the case where an electric vehicle has a structure that integrates the electric motor and the transmission, the same lubricating oil composition needs to be used for lubrication of the electric motor and the transmission. Under such circumstances, various lubricating oil compositions for electric vehicles have been studied.

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

[0004] In addition, Japanese Patent Application Laid-Open No. 2020-066673 (Patent Document 2) discloses a lubricating oil composition comprising 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 atom is 10 to 180 ppm by mass based on the total amount of the lubricating oil composition, the content of the sulfur compound (D) in terms of sulfur atom is 10 to 1000 ppm by mass based on the total amount of the lubricating oil composition, and the content of the metal salt (E) in terms of metal atom is 5 to 180 ppm by mass based on the total amount of the lubricating oil composition.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2019-137829

[0008] Patent Document 2: Japanese Patent Application Publication No. 2020-066673 Summary of the invention

[0009] Problems to be solved by the invention

[0010] However, for the lubrication of electric motors and transmissions of electric vehicles, it is necessary to have high insulation, high oxidation stability, and high extreme pressure (extreme pressure based on seizure resistance (load resistance) and wear resistance (wear resistance)), but the existing lubricating oil compositions described in the above-mentioned patent documents 1 to 2 have not been able to achieve high levels of insulation, oxidation stability, and extreme pressure. Furthermore, in recent years, in order to obtain higher motor output, electric motors need to be used at higher voltages, and gears and bearings need to be used under more severe conditions, and it is hoped that lubricating oil compositions with high-level balanced insulation, oxidation stability, and extreme pressure will emerge. In addition, copper is used as a material in electric motors, so the lubricating oil composition used in its lubrication and cooling also needs to have high corrosion resistance to copper (copper corrosion resistance).

[0011] The present invention has been made in view of the above-mentioned problems in the prior art, and an object of the present invention is to provide a lubricating oil composition which can have insulation properties, oxidation stability and extreme pressure properties at a high level of balance and can have a high degree of copper corrosion resistance.

[0012] Means for solving problems

[0013] The present inventors have conducted intensive studies to achieve the above-mentioned object and have found that a lubricating oil composition having insulation, oxidation stability and extreme pressure properties at a high level of balance and high copper corrosion resistance can be obtained by setting the following settings: a lubricating oil composition comprising (A) a lubricating oil base oil, (B) an extreme pressure agent and (C) a nitrogen-containing ashless dispersant, wherein the volume resistivity of the lubricating oil composition at 80° C. is 0.0020×10 12Ωcm or more; the component (B) satisfies the condition that it contains (B1) a phosphorus-based extreme pressure agent and does not contain (B2) a sulfur-containing extreme pressure agent 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 component (B1) is (B1-1) an alkylamine salt of a phosphoric acid ester or a mixture of the component (B1-1) and (B1-2) at least one compound selected from phosphoric acid, a phosphoric acid ester, a phosphite ester and salts thereof (but excluding the compound belonging to the component (B1-1)); 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; and 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.

[0014] That is, the present invention provides the following solutions.

[0015] [1] A lubricating oil composition comprising (A) a lubricating oil base oil, (B) an extreme pressure agent, and (C) a nitrogen-containing ashless dispersant,

[0016] The volume resistivity of the lubricating oil composition at 80°C is 0.0020×10 12 Ωcm or more,

[0017] The component (B) contains the phosphorus-based extreme pressure agent (B1) and does not contain the 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.

[0018] The component (B1) is an alkylamine salt of a phosphoric acid ester (B1-1), or the component (B1) is a mixture of the component (B1-1) and (B1-2) at least one compound selected from phosphoric acid, phosphoric acid esters, phosphites and salts thereof (but excluding the compounds belonging to the component (B1-1)),

[0019] 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.

[0020] 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.

[0021] [2] The lubricating oil composition according to [1], wherein the lubricating oil base oil contains at least one selected from a hydrotreated base oil and a wax isomerized base oil, and the kinematic viscosity of the lubricating oil base oil at 40° C. is 20 mm2 / s or less.

[0022] [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.

[0023] [4] The lubricating oil composition according to any one of [1] to [3], comprising (D) a calcium sulfonate scavenger such that the calcium content is 200 ppm by mass or less based on the total amount of the lubricating oil composition.

[0024] [5] The lubricating oil composition according to any one of [1] to [4], wherein the mass ratio of phosphorus derived from the component (B1) to nitrogen derived from the component (C) ([phosphorus] / [nitrogen]) is 0.60 to 1.70.

[0025] [6] The lubricating oil composition according to any one of [1] to [5], wherein 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 according to JIS K2514-1 is OL ) and the kinematic viscosity at 40°C (KV40 L ) ratio ([KV40 OL ] / [KV40 L ]) is less than 1.06.

[0026] [7] The lubricating oil composition according to any one of [1] to [6], which is a composition for lubricating a transmission and for cooling and lubricating an electric motor.

[0027] Effects of the Invention

[0028] According to the present invention, it is possible to provide a lubricating oil composition which has insulation properties, oxidation stability, and extreme pressure properties at a high level of balance and which can also have a high degree of copper corrosion resistance. DETAILED DESCRIPTION

[0029] The present invention is described in detail below according to its preferred embodiments. It should be noted that, in this specification, unless otherwise specified, for numerical values ​​X and Y, the expression "X to Y" means "above X and below Y". In this expression, when only the numerical value Y is marked with a unit, the unit also applies to the numerical value X.

[0030] The lubricating oil composition of the present invention is a lubricating oil composition comprising (A) a lubricating oil base oil, (B) an extreme pressure agent, and (C) a nitrogen-containing ashless dispersant.

[0031] The volume resistivity of the lubricating oil composition at 80°C is 0.0020×10 12 Ωcm or more,

[0032] The component (B) contains the phosphorus-based extreme pressure agent (B1) and does not contain the 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.

[0033] The component (B1) is an alkylamine salt of a phosphoric acid ester (B1-1), or the component (B1) is a mixture of the component (B1-1) and (B1-2) at least one compound selected from phosphoric acid, phosphoric acid esters, phosphites and salts thereof (but excluding the compounds belonging to the component (B1-1)),

[0034] 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.

[0035] 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.

[0036] [(A) Component: Lubricant base oil]

[0037] The lubricating oil composition of the present invention contains a lubricating base oil as component (A). The lubricating base oil used as such component (A) is not particularly limited, and a known lubricating base oil (mineral base oil, synthetic base oil, or a mixed base oil thereof, etc.) can be used. For example, the lubricating base oil described in International Publication No. 2020 / 095968 can be appropriately used. In addition, the lubricating base oil used as component (A) may be composed of one base oil, or may be a mixed base oil containing two or more base oils.

[0038] In addition, as the lubricating base oil used as the component (A), at least one selected from the group consisting of Group II base oil, Group III base oil, Group IV base oil and Group V base oil in the base oil classification according to API (American Petroleum Institute) can be preferably used. Among them, Group II base oil or Group III base oil is more preferred from the viewpoint of obtaining higher effects in terms of oxidation stability, corrosion resistance and insulation (volume resistivity) and from the viewpoint of achieving improvement in low power consumption of electric vehicles (hereinafter, the group according to the base oil classification according to API is simply referred to as "API group").

[0039] In addition, the lubricating oil base oil used as component (A) is preferably a mineral oil base oil. As such a mineral oil base oil, a paraffinic or cycloparaffinic mineral oil base oil obtained by appropriately combining solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrofining, sulfuric acid washing, clay treatment, etc., to obtain the lubricating oil fraction obtained by atmospheric distillation and vacuum distillation of crude oil can be cited as a preferred base oil. In addition, in such a mineral oil base oil, it is also from the viewpoint of being able to obtain a higher effect in terms of oxidation stability, corrosion resistance and insulation (volume resistivity) and the viewpoint of being able to achieve the improvement of low power consumption of electric vehicles, as component (A), hydrofining base oil and wax isomerization base oil are particularly preferred. In addition, these mineral oil base oils can be used alone, or two or more can be used in combination in any proportion.

[0040] Furthermore, the kinematic viscosity at 40° C. of the lubricating base oil (or, in the case of a mixed base oil containing two or more base oils) used as the component (A) is preferably 20 mm 2 / s or less, more preferably 5 to 18 mm 2 / s, more preferably 8 to 12 mm 2 / s. By making the kinematic viscosity of the lubricating base oil at 40°C below the above upper limit, higher performance (effect) can be obtained in terms of low temperature viscosity characteristics and fuel consumption performance compared to the case where the above upper limit is exceeded. In addition, by making the kinematic viscosity of the lubricating base oil at 40°C above the above lower limit, the oil film formation performance in the lubricated part is further improved compared to the case where it is below the lower limit, the extreme pressure properties based on seizure resistance and wear resistance can be further improved, and the electrical insulation of the new oil can be further improved. It should be noted that 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 K2283-2000.

[0041] The kinematic viscosity of the lubricating base oil (or the mixed base oil, if it is a mixed base oil containing two or more base oils) used as the component (A) at 100° C. is preferably 2.0 to 4.0 mm 2 / s, more preferably 2.0 to 2.7 mm 2 / s. By making the kinematic viscosity of the lubricating base oil at 100°C below the above upper limit, higher performance (effect) can be obtained in terms of low temperature viscosity characteristics and fuel efficiency performance compared to the case where the above upper limit is exceeded. In addition, by making the kinematic viscosity of the lubricating base oil at 100°C above the above lower limit, the oil film formation performance at the lubricating part is further improved compared to the case where the kinematic viscosity is below the lower limit, and the extreme pressure performance based on the seizure resistance and wear resistance can be further improved, and the electrical insulation of the new oil can also be further improved.

[0042] The viscosity index of the lubricating base oil (in the case of a mixed base oil containing two or more base oils, the mixed base oil) used as the component (A) is preferably 95 or more, and more preferably 120 or more. By setting the viscosity index of the lubricating base oil to be equal to or more than the lower limit, the viscosity-temperature characteristics and thermal and oxidation stability of the lubricating oil composition can be improved, the friction coefficient can be further reduced, and the wear resistance can be further improved. In addition, the viscosity index of the component (A) is more preferably 120 to 160 from the viewpoint of obtaining a higher effect from the perspective of fuel efficiency. It should be noted that in this specification, the "viscosity index" of the base oil or the composition means the viscosity index measured in accordance with JIS K2283-2000.

[0043] The sulfur content of the lubricating base oil (or the mixed base oil containing two or more base oils, in the case of the mixed base oil) used as the component (A) is preferably 10 mass ppm or less (more preferably 8 mass ppm or less, further preferably 5 mass ppm or less, and particularly preferably 4 mass ppm or less). When the sulfur content is below the above upper limit, the oxidation stability can be further improved compared with the case where it exceeds the above upper limit.

[0044] Furthermore, the pour point of the lubricating base oil (or the mixed base oil in the case of a mixed base oil containing two or more base oils) used as the component (A) is not particularly limited, but is preferably -12°C or lower. When such a pour point is below the upper limit, the low-temperature fluidity of the lubricating oil composition finally obtained can be further improved compared to the case where the pour point exceeds the upper limit. In addition, such a pour point is more preferably -22°C or lower from the viewpoint of being able to increase the viscosity index. It should be noted that in this specification, the so-called "pour point" means the pour point measured in accordance with JIS K2269-1987.

[0045] Furthermore, the flash point of the lubricating base oil (in the case of a mixed base oil containing two or more base oils, the mixed base oil) used as the component (A) is preferably 160°C or higher (more preferably 190°C or higher). In addition, by making such a flash point higher than the above lower limit, the safety during high temperature use tends to be further improved compared with the case where it is lower than the above lower limit. It should be noted that in this specification, the "flash point" means the flash point measured according to JIS K2265-4-2007 (Cleveland open mouth method).

[0046] [(B) ingredient: extreme pressure agent]

[0047] The lubricating oil composition of the present invention contains an extreme pressure agent as component (B). Such an extreme pressure agent used as component (B) contains a phosphorus-based extreme pressure agent (B1), and does not contain a sulfur-containing extreme pressure agent (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. That is, the extreme pressure agent as component (B) satisfies the following two conditions: a condition that the component (B1) is contained; and a condition that the component (B2) is not contained or the component (B2) is contained 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.

[0048] Thus, the component (B) contains the component (B1) as an essential component. By using the component (B1), even if the sulfur-containing extreme pressure agent (component (B2)) is not used or the amount of the sulfur-containing extreme pressure agent (component (B2)) used is very small (the amount of sulfur is 0.01% by mass or less based on the total amount of the lubricating oil composition), high load resistance and wear resistance can be exhibited, and further, the volume resistivity of the lubricating oil composition at 80°C can be more efficiently increased to 0.0020×10 12 Ωcm or more.

[0049] In addition, such a phosphorus-based extreme pressure agent used as the (B1) component is an alkylamine salt of a phosphoric acid ester (B1-1), or such a phosphorus-based extreme pressure agent used as the (B1) component is a mixture of the (B1-1) component and (B1-2) a compound selected from at least one of phosphoric acid, phosphoric acid ester, phosphite, and their salts (however, excluding the compound belonging to the (B1-1) component). In this way, the (B1) component utilizes the (B1-1) component alone, or the (B1) component is a mixture of the (B1-1) component and the (B1-2) component. In other words, the (B1) component is a phosphorus-based extreme pressure agent composed of at least one compound selected from phosphoric acid, phosphoric acid ester, phosphite, and their salts and containing the (B1-1) component as an essential component. It should be noted that the "phosphorus-based extreme pressure agent" referred to here does not include a phosphorus-based extreme pressure agent containing a sulfur atom (so-called "sulfur-phosphorus-based extreme pressure agent") (in this specification, a phosphorus-based extreme pressure agent containing a sulfur atom corresponds to a sulfur-containing extreme pressure agent described later).

[0050] The component (B1-1) contained as an essential component in such a phosphorus-based extreme pressure agent (component (B1)) is not particularly limited, and a known alkylamine salt of a phosphoric acid ester that can be used as an extreme pressure agent can be appropriately used. In addition, as such an alkylamine salt of a phosphoric acid ester, a salt (a salt (reaction product) of a phosphoric acid ester and the amine compound) obtained by allowing an amine compound having an alkyl group in the molecule to act on a phosphoric acid ester and neutralizing a part or all of the remaining acidic hydrogen can be preferably used.

[0051] As the phosphate ester used to form such a component (B1-1), known phosphate esters that can be used as phosphorus-based extreme pressure agents can be appropriately used without particular limitation. From the viewpoint of forming an alkylamine salt, acid phosphate esters are preferred, and monoalkyl acid phosphate esters and / or dialkyl acid phosphate esters are more preferred.

[0052] Examples of such monoalkyl acid phosphates and dialkyl acid phosphates include monobutyl acid phosphate, monopentyl acid phosphate, monohexyl acid phosphate, monoheptyl acid phosphate, monooctyl acid phosphate, monononyl acid phosphate, monodecyl acid phosphate, monoundecyl acid phosphate, monododecyl acid phosphate, monotridecyl acid phosphate, monotetradecyl acid phosphate, monopentadecyl acid phosphate, monohexadecyl acid phosphate, monoheptadecyl acid phosphate, monooctadecyl acid phosphate, monooleyl acid phosphate, monohexadecyl acid phosphate, monoheptadecyl acid phosphate, monooctadecyl acid phosphate, monooleyl acid phosphate, monodec ... Acid phosphate, dibutyl acid phosphate, dipentyl acid phosphate, dihexyl acid phosphate, diheptyl acid phosphate, dioctyl acid phosphate, dinonyl acid phosphate, didecyl acid phosphate, diundecyl acid phosphate, didodecyl acid phosphate, didodecyl acid phosphate, didotridecyl acid phosphate, didotetradecyl acid phosphate, didopentadecyl acid phosphate, didohexadecyl acid phosphate, didoheptadecyl acid phosphate, didooctadecyl acid phosphate, dioleyl acid phosphate, etc. Furthermore, as such monoalkyl acid phosphate and dialkyl acid phosphate, preferably, a compound represented by the following formula (1) is used. That is, as the phosphate used to form the component (B1-1), preferably, a compound represented by the formula (1) is used.

[0053]

[0054] [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.]

[0055] In addition, as the amine compound used for forming the alkylamine salt of the phosphate ester, monoalkylamine, dialkylamine, and trialkylamine can be preferably 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, ditridecylamine, ditetradecylamine, di (pentadecyl)amine, di(hexadecyl)amine, di(heptadecyl)amine, di(octadecyl)amine, di(oleyl)amine, di(cosyl)amine, trimethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, tri(undecyl)amine, tri(dodecyl)amine, tri(tridecyl)amine, tri(tetradecyl)amine, tri(pentadecyl)amine, tri(hexadecyl)amine, tri(heptadecyl)amine, tri(octadecyl)amine, tri(oleyl)amine, tri(cosyl)amine. Such amine compounds may be used alone or in combination of two or more. Such amine compounds are preferably compounds represented by the following formula (2).

[0056]

[0057] [In formula (2), R b , R c and R d Each independently is a hydrogen atom or a monovalent alkyl group (however, R b , R c and R d at least one of which is a monovalent alkyl group).]

[0058] Furthermore, R in the above formula (2) can be selected as b , R c and R d The monovalent alkyl group may be straight-chain or branched. The number of carbon atoms in such a monovalent alkyl group is not particularly limited, and 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) is preferably a monoalkylamine (R in formula (2) b , R c and R d A compound in which one of the R is a monovalent alkyl group (particularly preferably an alkyl group having 8 to 18 carbon atoms) and the other is a hydrogen atom), and / or a dialkylamine (R in formula (2) b , R cand R d A compound in which two of the groups are monovalent alkyl groups (particularly preferably alkyl groups having 8 to 18 carbon atoms), and the others are hydrogen atoms).

[0059] In addition, as the above-mentioned (B1-1) component, from the viewpoint of more effectively taking into account excellent load resistance and wear resistance and high volume resistivity, the salt of the compound represented by the above-mentioned formula (1) and the compound represented by the above-mentioned formula (2) is preferred. In addition, the above-mentioned (B1-1) component can be used alone or in combination of two or more.

[0060] In addition, the component (B1-2) in the phosphorus-based extreme pressure agent (component (B1)) that can be used together with the component (B1-1) is a compound selected from at least one of phosphoric acid, phosphoric acid esters, phosphites and salts thereof (however, excluding compounds belonging to the component (B1-1)).

[0061] There is no particular limitation on the phosphate ester that can be used in the component (B1-2), and any known phosphate ester that can be used as an extreme pressure agent can be appropriately used. Examples of such phosphate esters include, in addition to the above-mentioned monoalkyl acid phosphates and the above-mentioned dialkyl acid phosphates, 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, trioleyl phosphate, triphenyl phosphate, tritolyl phosphate, trixyl phosphate, tolyl diphenyl phosphate, and xylyl diphenyl phosphate.

[0062] In addition, there is no particular limitation on the phosphite that can be used in the component (B1-2), and known phosphites that can be used as extreme pressure agents can be appropriately used, for example, dibutyl phosphite, diamyl phosphite, dihexyl phosphite, diheptyl phosphite, dioctyl phosphite, dinonyl phosphite, didecyl phosphite, diundecyl phosphite, didodecyl phosphite, dioleyl phosphite, diphenyl phosphite, ditolyl phosphite, tributyl phosphite, tripentyl phosphite. Phosphites include trihexyl phosphite, triheptyl phosphite, trioctyl phosphite, trinonyl phosphite, tridecyl phosphite, triundecyl phosphite, tridodecyl phosphite, trioleyl phosphite, triphenyl phosphite, tritolyl 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, di(ethylhexyl) hydrogen phosphite, etc. As such phosphites, dialkyl hydrogen phosphites having two alkyl groups are preferred from the viewpoint of improving the anti-seizing performance and the anti-wear performance, and dialkyl hydrogen phosphites having two alkyl groups with a carbon number of 4 to 12 are more preferred.

[0063] In addition, the salts of phosphoric acid, phosphoric acid esters and phosphites that can be used as component (B1-2) are not particularly limited, and those that are known to be used as extreme pressure agents can be appropriately used. Among them, salts formed by allowing a metal base, ammonia, or nitrogen-containing compounds such as amine compounds containing only hydrocarbon groups with 1 to 8 carbon atoms or hydroxyl-containing hydrocarbon groups in the molecule to act on phosphoric acid, phosphoric acid esters or phosphites to neutralize part or all of the remaining acidic hydrogen.

[0064] In addition, as the component (B1), from the viewpoint of improving the seizing resistance and wear resistance, it is preferred to use a mixture of the component (B1-1) and the component (B1-2). As the component (B1-2) contained in such a mixture, from the viewpoint of achieving more effective balance between excellent seizing resistance and wear resistance as well as corrosion resistance and oxidation stability, phosphite is more preferred. That is, as the component (B1), it is preferred to use a mixture of an alkylamine salt of a phosphate ester (B1-1) and a phosphite.

[0065] In addition, when the component (B1) is a mixture of the component (B1-1) and the component (B1-2), the mass ratio of phosphorus derived from the component (B1-1) to phosphorus derived from the component (B1-2) ([P derived from the component (B1-1)] / [P derived from the component (B1-2)]) is preferably 0.4 to 2.5 (more preferably 0.4 to 2.0). When such a mass ratio of phosphorus is above the lower limit, a higher effect can be obtained in terms of sintering resistance compared to a case where the mass ratio is below the lower limit. On the other hand, when such a mass ratio of phosphorus is below the upper limit, a higher effect can be obtained in terms of electrical insulation compared to a case where the mass ratio exceeds the upper limit.

[0066] The component (B) does not contain the sulfur-containing extreme pressure agent (B2) or contains the component (B2) such 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.

[0067] In the case where the component (B) contains the sulfur-containing extreme pressure agent (component (B2)), there is no particular limitation on the sulfur-containing extreme pressure agent, and any known extreme pressure agent containing sulfur can be appropriately used. Examples of such sulfur-containing extreme pressure agents include sulfur-based extreme pressure agents such as dithiocarbamates, zinc dithiocarbamates, molybdenum dithiocarbamates (MoDTC), disulfides, polysulfides, sulfided olefins, and sulfided oils and fats; sulfur-phosphorus-based extreme pressure agents such as thiophosphites (thiophosphites), dithiophosphites (dithiophosphites), trithiophosphites (trithiophosphites), thiophosphates (thiophosphates), dithiophosphorates (dithiophosphorates), trithiophosphorates (trithiophosphorates), their amine salts, and their derivatives.

[0068] When the component (B) contains the sulfur-containing extreme pressure agent (component (B2)), the content of sulfur derived from the component (B2) needs to be 0.01 mass % (100 mass ppm) or less (more preferably 80 mass ppm or less, further preferably 60 mass ppm or less, particularly preferably 50 mass ppm or less, and most preferably 20 mass ppm or less) based on the total amount of the lubricating oil composition. When the content of the component (B2) is below the upper limit, high oxidation stability and high copper corrosion resistance can be obtained compared to the case where the content exceeds the upper limit. In addition, from the viewpoint of further improving copper corrosion resistance and insulation properties (volume resistivity value), it is preferred that the component (B) does not contain the sulfur-containing extreme pressure agent (B2).

[0069] The method for producing the component (B) is not particularly limited, and a known method can be used as appropriate. A commercially available product can be used as the component (B).

[0070] [Component (C): nitrogen-containing ashless dispersant]

[0071] The lubricating oil composition of the present invention contains a nitrogen-containing ashless dispersant (nitrogen-containing ashless dispersant) as component (C).

[0072] Such component (C) is not particularly limited, and those known as ashless dispersants containing nitrogen can be appropriately used. In addition, from the viewpoint of further improving corrosion resistance and oxidation stability, such component (C) is more preferably an ashless dispersant having a functional group containing nitrogen as a dispersing group.

[0073] Preferred examples of such ashless dispersants having a nitrogen-containing functional group as a dispersing group include succinimide, benzylamine, polyamines, and derivatives thereof having a hydrocarbon group (eg, alkyl group, alkenyl group) having 40 to 400 carbon atoms.

[0074] In addition, the component (C) is not particularly limited, but from the viewpoint of further improving corrosion resistance and oxidation stability, it is more preferably a succinimide-based ashless dispersant selected from at least one of succinimide having a hydrocarbon group (e.g., alkyl, alkenyl) having a carbon number of 40 to 400 and a derivative of the succinimide (a modified compound of succinimide).

[0075] The succinimide having a hydrocarbon group having 40 to 400 carbon atoms is not particularly limited, but is preferably a compound represented by the following formula (3) or (4).

[0076]

[0077] [In formulas (3) and (4), R 1 and R 2 Each independently represents an alkyl group having 40 to 400 (more preferably 60 to 350) carbon atoms or an alkenyl group having 40 to 400 (more preferably 60 to 350) carbon atoms, and n represents an integer of 0 to 5.]

[0078] Furthermore, in such formulas (3) and (4), R 1 An alkyl or alkenyl group and may be selected as R 2 The alkyl or alkenyl group of R is more preferably a branched alkyl or alkenyl group (polyisobutylene group) or polybutenyl group derived from an oligomer of isobutylene called polyisobutylene. 1 and R 2The alkyl or alkenyl groups preferably have a weight average molecular weight of 800 to 1500 (more preferably 950 to 1400). In addition, 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, and further preferably 1 to 3). In addition, among the compounds represented by such formulas (3) to (4), the compound (dimer) represented by formula (4) is more preferred from the viewpoint of further improving corrosion resistance and oxidation stability. Furthermore, the method for producing such succinimide is not particularly limited. For example, the following method can be used: the above-mentioned succinimide is produced as a condensation reaction product by reacting at least one selected from alkyl succinic acid, alkenyl succinic acid and their anhydrides having an alkyl or alkenyl group having a carbon number of 40 to 400 with a polyamine.

[0079] The derivatives of succinimide (modified compounds of succinimide) are not particularly limited, and known modified compounds of succinimide that can be used as ashless dispersants can be appropriately used, for example: (i) modified compounds obtained from oxygen-containing organic compounds (selected from monocarboxylic acids having 1 to 30 carbon atoms such as fatty acids, polycarboxylic acids having 2 to 30 carbon atoms (such as oxalic acid, phthalic acid, trimellitic acid, pyromellitic acid, etc.), anhydrides of these acids, ester compounds of these acids, oxyalkylenes having 2 to 6 carbon atoms, and hydroxy(poly)oxyalkylenes; (i) a compound modified by at least one of the carbonates reacting with the succinimide to neutralize or amidate a part or all of the remaining amino and / or imino groups; (ii) a boron-modified compound (a compound formed by allowing boric acid to act on the succinimide to neutralize or amidate a part or all of the remaining amino and / or imino groups (so-called borated succinimide)); (iii) a phosphoric acid-modified compound (a compound formed by allowing phosphoric acid to act on the succinimide to neutralize or amidate a part or all of the remaining amino and / or imino groups), etc.

[0080] In addition, as the "succinimide-based ashless dispersant" which is preferably used as the component (C), a boron-modified compound of succinimide (boronated succinimide) is more preferred from the viewpoint of further improving corrosion resistance and oxidation stability.

[0081] As the "succinimide-based ashless dispersant" which is preferably used as the component (C), the nitrogen content in the succinimide-based ashless dispersant is preferably 1.0 to 4.8 mass % (more preferably 1.2 to 2.4 mass %). By making such a nitrogen content within the above range, it is possible to more effectively achieve a high level of corrosion resistance and oxidation stability. In addition, when "boronated succinimide" is used as the succinimide-based 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 %).

[0082] In addition, as the "succinimide-based ashless dispersant" which is preferably used as the component (C), it is more preferable that the weight average molecular weight is 1000 to 9000 (more preferably 1000 to 5000). When the weight average molecular weight of the succinimide-based ashless dispersant is greater than the above lower limit, the electrical insulation of the new oil and the electrical insulation of the composition after oxidative degradation can be further improved. In addition, when the weight average molecular weight of the succinimide-based ashless dispersant is less than the above upper limit, the electrical insulation of the composition after oxidative degradation can be further improved.

[0083] Furthermore, as the "succinimide-based ashless dispersant" which is preferably the component (C), it is preferred that the total base number (TBN) is 20 to 80 mgKOH / g (more preferably 30 to 60 mgKOH / g). When the total base number is within the above range, a higher effect tends to be obtained in terms of oxidation stability performance.

[0084] The method for producing the component (C) is not particularly limited, and a known method can be used as appropriate. A commercially available product can be used as the component (C).

[0085] [Regarding the composition of the lubricating oil composition]

[0086] The lubricating oil composition of the present invention comprises the component (A), the component (B) and the component (C). The component (B) contains as an essential component a phosphorus-based extreme pressure agent as the component (B1) as described above. The component (B1) contains as an essential component an alkylamine salt of a phosphoric acid ester as the component (B1-1) as described above.

[0087] In the lubricating oil composition of the present invention, the mass ratio of phosphorus derived from the component (B1) to nitrogen derived from the component (C) ([phosphorus] / [nitrogen]) is required to be 0.60 or more and 2.30 or less. When the mass ratio of phosphorus to nitrogen is equal to or more than the lower limit, the extreme pressure property can be made high and the insulation property can be made high compared to the case where the mass ratio is less than the lower limit, thereby achieving both extreme pressure property and insulation property at a high level. On the other hand, when the mass ratio of phosphorus to nitrogen is equal to or less than the upper limit, the seizure resistance and oxidation stability can be made high compared to the case where the mass ratio exceeds the upper limit. In addition, the mass ratio of phosphorus derived from the component (B1) to nitrogen derived from the component (C) ([phosphorus] / [nitrogen]) is more preferably 0.60 or more and 1.70 or less (more preferably 0.60 or more and 1.50 or less, particularly preferably 0.60 or more and 1.30 or less) from the viewpoint of obtaining a higher effect in terms of achieving both high seizure resistance, wear resistance and insulation property (volume resistivity) and excellent oxidation stability.

[0088] In the lubricating oil composition of the present invention, the content of the component (A) is not particularly limited, but 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 the component (A) is equal to or greater than the lower limit, the oxidation stability can be further improved compared to a case where the content is less than the lower limit, and when the content of the component (A) is equal to or less than the upper limit, the additive effect at the lubricated part can be further improved, thereby improving the lubricity.

[0089] In the lubricating oil composition of the present invention, the content of phosphorus (P) derived from the component (B1) needs to be 0.050 mass % or less based on the total amount of the lubricating oil composition. In addition, the content of phosphorus (P) derived from the component (B1) is preferably 190 to 410 mass ppm (more preferably 190 to 380 mass ppm) based on the total amount of the lubricating oil composition. When the content of the component (B1) is equal to or greater than the lower limit, the seizure resistance and the wear resistance can be further improved compared to the case where the content is less than the lower limit. On the other hand, when the content of the component (B1) is equal to or less than the upper limit, a composition with a higher volume resistivity can be obtained compared to the case where the content exceeds the upper limit.

[0090] In addition, 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 mass ppm or less (more preferably 80 mass ppm or less) based on the total amount of the lubricating oil composition. When the amount of phosphorus derived from the component (B2) is below the upper limit, oxidation stability and corrosion resistance can be further improved.

[0091] Furthermore, the lubricating oil composition of the present invention satisfies the following conditions as described above: the lubricating oil composition does not contain a sulfur-containing extreme pressure agent (component (B2)), or even if the lubricating oil composition contains a sulfur-containing extreme pressure agent (component (B2)), the amount of sulfur derived from component (B2) is 0.01 mass % (100 mass ppm) or less (more preferably 80 mass ppm or less, further preferably 60 mass ppm or less, particularly preferably 50 mass ppm or less, and most preferably 20 mass ppm or less) based on the total amount of the lubricating oil composition. By making the amount of sulfur derived from the sulfur-containing extreme pressure agent be less than the above upper limit, both oxidation stability and copper corrosion resistance can be made excellent.

[0092] In the lubricating oil composition of the present invention, 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, the load resistance (seizing resistance) and the wear resistance can be made higher more easily than when the content is less than the lower limit. On the other hand, when the phosphorus content is equal to or less than the upper limit, the volume resistivity can be made to be 0.0020×10 12 Ωcm or more.

[0093] Furthermore, in the lubricating oil composition of the present invention, the component (B1-2) may or may not be used in the component (B), and the content of phosphorus (P) derived from the component (B1-2) may be set to, for example, 0 to 500 mass ppm based on the total amount of the lubricating oil composition. In addition, in the lubricating oil composition of the present invention, when the component (B1-2) is contained in the component (B), the content of phosphorus (P) derived from the component (B1-2) is preferably 50 to 500 mass ppm (more preferably 100 to 200 mass ppm) based on the total amount of the lubricating oil composition. When the phosphorus content is equal to or greater than the lower limit, the seizure resistance and the wear resistance can be further improved compared to the case where the phosphorus content is less than the lower limit, and when the phosphorus content is equal to or less than the upper limit, a composition with a high volume resistivity can be obtained more effectively compared to the case where the phosphorus content exceeds the upper limit.

[0094] In the present invention, the mass ratio of sulfur derived from the component (B2) to phosphorus derived from the component (B1) ([sulfur] / [phosphorus]) is preferably 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, the oxidation stability and copper corrosion resistance can be made more excellent compared to the case where the mass ratio exceeds the upper limit.

[0095] In the lubricating oil composition of the present invention, the content of the component (C) is not particularly limited, but the content of nitrogen derived from the component (C) is preferably 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 the 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, the oxidation stability can be further improved compared to the case where the amount is less than the lower limit. On the other hand, when the amount of nitrogen is equal to or less than the upper limit, the volume resistivity can be more easily reduced to 0.0020×10 12 It should be noted that in the present invention, the contents of sulfur, phosphorus, nitrogen and boron in the composition and various components are values ​​measured in accordance with ASTM D4951.

[0096] In addition, the lubricating oil composition of the present invention may further contain additives in addition to the above-mentioned components (A) to (C). As such additives, known additives used in the field of lubricating oil compositions can be appropriately used without particular limitation, and preferred additives include (D) calcium sulfonate scavengers and (E) antioxidants.

[0097] As the (D) component, for example, calcium sulfonate, which is a calcium salt of an alkyl aromatic sulfonic acid, a basic salt of the calcium sulfonate, and a high basic salt of the calcium sulfonate can be cited. As such an alkyl aromatic sulfonic acid, for example, so-called petroleum sulfonic acid and synthetic sulfonic acid can be cited. As the petroleum sulfonic acid mentioned here, petroleum sulfonic acid obtained by sulfonating the alkyl aromatic compounds of the lubricating oil fraction of mineral oil, so-called petroleum sulfonic acid produced as a by-product during the manufacture of white oil, etc. can be cited. In addition, as an example of a synthetic sulfonic acid, by-products recovered from an alkylbenzene manufacturing facility that will become a raw material for detergents or sulfonated alkylbenzenes obtained by alkylating benzene with polyolefins and having a linear or branched alkyl group can be cited. As another example of a synthetic sulfonic acid, alkylnaphthalenes such as dinonylnaphthalene can be cited as being sulfonated. In addition, as a sulfonating agent when sulfonating these alkyl aromatic compounds, there is no particular restriction, and for example, fuming sulfuric acid and sulfuric anhydride can be used. The weight average molecular weight of such an alkyl aromatic sulfonic acid is preferably 300 to 1500, more preferably 400 to 1300. In addition, there are no particular restrictions on the basic salt and the high-based salt of the calcium sulfonate, and known ones can be appropriately used, for example, calcium sulfonate (high) alkalized with calcium carbonate, calcium borate, etc. There are no particular restrictions on the preparation method of the basic salt and the high-based salt, and a known method can be appropriately used (in the case where the high-based salt is calcium sulfonate high-based with calcium carbonate, for example, a method of obtaining calcium sulfonate high-based with calcium carbonate by reacting calcium sulfonate with a base such as calcium hydroxide in the presence of carbon dioxide can be used).

[0098] The component (D) preferably has a total base number (TBN) of 20 to 450 mgKOH / g (more preferably 300 to 450 mgKOH / g). When the total base number is within the above range, a higher effect in terms of oxidation stability tends to be obtained.

[0099] In addition, when the lubricating oil composition of the present invention contains the component (D), it is preferred that the content of the component (D) is such that the content of calcium derived from the component (D) is 200 mass ppm or less (more preferably 180 mass ppm or less, and further preferably 160 mass ppm or less) based on the total amount of the lubricating oil composition. When the calcium content is below the upper limit, a higher effect can be obtained in terms of insulation properties compared to a case where the upper limit is exceeded. It should be noted that in the present invention, the calcium content in the composition and in various components is a value measured in accordance with ASTM D4951.

[0100] As the component (E), those known in the field of lubricating oil compositions (for example, known ashless antioxidants such as amine antioxidants and phenol antioxidants) can be appropriately used without particular limitation. Among them, it is preferred to use a combination of (E1) a phenol antioxidant and (E2) an amine antioxidant.

[0101] As the component (E1), for example, a compound known as a phenolic antioxidant (for example, compounds exemplified in International Publication No. 2020 / 095970) can be appropriately used. Examples of such a phenolic antioxidant include hindered phenol compounds and bisphenol compounds.

[0102] In addition, as the (E2) component, for example, compounds known as amine antioxidants such as aromatic amine antioxidants and hindered amine antioxidants (for example, compounds exemplified in International Publication No. 2020 / 095970, etc.) can be appropriately utilized. As the aromatic amine antioxidant, among them, alkylated diphenylamine and alkylated phenyl-α-naphthylamine can be preferably utilized. In addition, 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 utilized. As the amine antioxidant, aromatic amine antioxidants are more preferred, and alkylated diphenylamine is particularly preferred.

[0103] In addition, 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% by mass (more preferably 0.01 to 2.0% by mass). In addition, when the component (E1) is contained, the content of the component (E1) is preferably set to 0.005 to 2.0% by mass. Furthermore, when the component (E2) is contained, the content of the component (E2) is preferably set to 0.005 to 2.0% by mass (more preferably 0.01 to 2.0% by mass). By setting the contents within the above ranges, the oxidation resistance can be further improved and the corrosion resistance can be improved.

[0104] It should be noted that, as additives that can be preferably used in the lubricating oil composition of the present invention, the component (D) and the component (E) are exemplified as preferred additives, but the additives that can be used in the lubricating oil composition of the present invention are not limited to the components (D) and (E), and, within the range that does not impair the effects of the present invention, for example, a pour point depressant, a metal deactivator, a friction modifier, a dispersant other than the nitrogen-containing ashless dispersant, a viscosity index improver, etc. can also be appropriately used. , rubber swelling agent, defoaming agent, diluent oil, rust inhibitor, anti-emulsifier, colorant, corrosion inhibitor, wear inhibitor, acid scavenger and other known other additives (for example, additives described in JP-A-2016-3258, International Publication No. 2015 / 056783, JP-A-2016-160312, JP-A-2003-155492, International Publication No. 2017 / 073748, JP-A-2020-76004, etc.).

[0105] In addition, when other additives other than the component (D) and the component (E) are used, the total amount (total amount) of the other additives is more preferably 0.5 to 2.0% by mass based on the total amount of the lubricating oil composition. When the total amount of the other additives is equal to or greater than the lower limit, higher effects can be obtained in terms of corrosion resistance and oxidation stability compared to a case where the total amount is less than the lower limit, and when the total amount of the other additives is equal to or less than the upper limit, higher effects can be obtained in terms of seizure resistance and wear resistance compared to a case where the total amount exceeds the upper limit.

[0106] In addition, each component of various additives that can be used in such a lubricating oil composition can be prepared and added separately, or can be prepared and added in the form of a mixture with other components. As such a mixture of other components, a commercially available package (for example, an additive package containing a rubber swelling agent, a defoaming agent, a pour point depressant, etc.) can be appropriately used.

[0107] [Regarding the characteristics, preparation method, and uses of lubricating oil compositions]

[0108] The volume resistivity of the lubricating oil composition of the present invention at 80°C needs to be 0.0020×10 12 Ωcm or more. By making such a volume resistivity greater than the lower limit, it is possible to ensure a high level of insulation that is higher than the level required for use in electric vehicles. From the viewpoint of further improving the insulation, the volume resistivity of such a lubricating oil composition at 80°C is more preferably 0.0022×10 12 Ωcm or more, more preferably 0.0024×10 12The upper limit of the volume resistivity of the lubricating oil composition at 80°C is not particularly limited, but is preferably 0.10×10 12 As such a volume resistivity, a value measured by performing a volume resistivity test in accordance with JIS C2101 at an oil temperature of 80° C. is adopted.

[0109] The lubricating oil composition of the present invention preferably has a kinematic viscosity at 40°C (KV40 OL ) and the kinematic viscosity at 40°C (KV40 L ) ratio ([KV40 OL ] / [KV40 L ]) is 1.06 or less. By making the ratio of the kinematic viscosity at 40°C of the lubricating oil composition before and after the oxidation treatment ([KV40 OL ] / [KV40 L ]) is below the upper limit, thereby suppressing the increase in viscosity due to oxidative degradation compared to the case where the upper limit is exceeded, and when used in a transmission, high transmission efficiency can be exerted for a longer period of time. The ratio of the kinematic viscosity at 40°C of the lubricating oil composition before and after the oxidation treatment ([KV40 OL ] / [KV40 L ]) is more preferably 0.95 or more and 1.06 or less, and still more preferably 1.0 or more and 1.02 or less. OL ] / [KV40 L ]) is within the range, thereby tending to obtain a higher effect in terms of oxidation stability compared to the case outside the range, and when used in a transmission, a high transmission efficiency can be exerted for a longer period of time.

[0110] The lubricating oil composition of the present invention preferably has a kinematic viscosity at 40°C (KV40 L : The kinematic viscosity of the composition (new oil) which has not yet been subjected to the above-mentioned oxidation treatment is 8.0 to 18.0 mm 2 / s (more preferably 8.0 to 14.0 mm 2 / s). When the kinematic viscosity at 40°C of the lubricating oil composition is below the upper limit, the stirring resistance can be made smaller in a relatively low temperature range near 40°C (preferably about 20 to 60°C) compared to a case where the upper limit is exceeded, and the power transmission efficiency can be further improved even in a low temperature state such as immediately after use, thereby further improving the fuel consumption performance. In addition, when the kinematic viscosity at 40°C of the lubricating oil composition is above the lower limit, the oil film forming property and the oil film retaining property of the lubricating oil composition at the lubricated part are further improved in a relatively low temperature range near 40°C (preferably about 20 to 60°C), and a better lubrication state can be maintained. From this point of view, the gear transmission efficiency and the power consumption saving performance can be further improved.

[0111] The lubricating oil composition of the present invention is preferably a lubricating oil composition having a kinematic viscosity at 40°C (KV4040) after oxidation treatment at an oil temperature of 165°C for 192 hours according to the ISOT method of JIS K2514-1. OL ) is 8.0~20.0mm 2 / s (more preferably 8.0 to 18.0 mm 2 / s). In the KV40 of the lubricating oil composition OL When the KV40 of the lubricating oil composition is less than the upper limit, a higher effect can be obtained in terms of improvement of oxidation stability and improvement of transmission efficiency when used in a transmission, compared with a case where the KV40 of the lubricating oil composition exceeds the upper limit. OL When the content is not less than the above lower limit, higher wear resistance and seizure resistance can be obtained compared with the case where the content is less than the above lower limit.

[0112] The lubricating oil composition of the present invention preferably has a kinematic viscosity at 100° C. of 1.8 to 4.0 mm 2 / s (more preferably 2.2 to 3.5 mm 2 / s). When the kinematic viscosity of the lubricating oil composition at 100°C is below the upper limit, the viscosity can be lowered in a relatively high temperature range near 100°C, and the stirring resistance can be further reduced, compared with a case where the upper limit is exceeded, so that the power transmission efficiency can be further improved, and the fuel saving performance can be improved. In addition, when the kinematic viscosity of the lubricating oil composition at 100°C is above the lower limit, the oil film forming property and the oil film retaining property of the lubricating oil composition at the lubricated part are further improved in a relatively high temperature range near 100°C (preferably about 80 to 120°C), and the oil film can be more uniformly retained, so that the anti-seizing performance during use can be made higher.

[0113] In addition, the lubricating oil composition of the present invention preferably has a viscosity index of 105 or more (more preferably 120 or more). When the viscosity index is equal to or more than the lower limit (more preferably 120 or more), the viscosity-temperature characteristics and anti-wear properties of the lubricating oil composition can be further improved, and the fuel efficiency performance can be further improved, compared with the case where the viscosity index is less than the lower limit.

[0114] The method for producing the lubricating oil composition of the present invention is not particularly limited, and the lubricating oil composition of the present invention 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 conditions).

[0115] Since the lubricating oil composition of the present invention has insulation properties, oxidation stability, and extreme pressure properties at a high level of balance and has a high degree of copper corrosion resistance, its use is not particularly limited, and it can be preferably used as a composition for lubricating a transmission and cooling and lubricating an electric motor. That is, the lubricating oil composition of the present invention can be preferably used as a lubricating oil composition for electric vehicles equipped with an electric motor and a transmission.

[0116] Example

[0117] 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.

[0118] (About Components Used in Examples, etc.)

[0119] First, the base oil and additives used in each example and the like are shown below.

[0120] [(A) Lubricant base oil]

[0121] (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 mass ppm, pour point: -37°C, flash point: 190°C]

[0122] (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 the base oil (sulfur content in the base oil): 0 mass ppm, pour point: -30°C, flash point: 170°C].

[0123] [(B) Extreme pressure agent]

[0124] <(B1) Phosphorus-based extreme pressure agents>

[0125] (B1-1) Alkylamine salt of phosphoric acid ester [a mixture of a phosphoric acid ester (monoester and diester): a compound represented by the formula (1) and wherein R a Oil-based (formula: C 18 H 35 A compound of a group represented by) and an alkylamine (a compound represented by the formula (2), wherein R b , R c and R d One of them is dodecyl (formula: C 12 H 25 The group represented by b , R c and R d Other compounds in which the hydrogen atom is present)]

[0126] (B1-2) Phosphite [dibutyl hydrogen phosphite]

[0127] <(B2) Sulfur-containing extreme pressure agents>

[0128] (B2-1) Phosphorothioate [phosphorus content: 100,000 ppm, sulfur content: 190,000 mass ppm].

[0129] [(C) Nitrogen-containing ashless dispersant]

[0130] (C1) Succinimide-based ashless dispersant [boronated succinimide, nitrogen content: 2.0 mass%, boron content: 0.5 mass%, total base number (TBN): 50, type of succinimide: dimer (a dimer succinimide represented by the formula (4) (wherein R in the formula (4) is 1 and R 2 is a boron-modified compound having a weight average molecular weight (Mw) of 1000 and n is 3).

[0131] [(D) Calcium sulfonate purifier]

[0132] (D1) Calcium sulfonate scavenger [base number (TBN): 400 mgKOH / g, calcium atom content: 15.0 mass %].

[0133] [(E) Antioxidant]

[0134] (E1) Phenolic antioxidant [octyl 3-(4-hydroxy-3,5-diisopropylphenyl) propionate]

[0135] (E2) Amine antioxidant [Alkylated diphenylamine]

[0136] [(F) Other additives]

[0137] (F1) Performance additives [a mixture of rubber swellers, defoamers and pour point depressants (additive package)].

[0138] (Examples 1 to 7 and Comparative Examples 1 to 6)

[0139] The lubricating oil compositions of Examples 1 to 7 and Comparative Examples 1 to 6 were prepared using the above-mentioned components so as to have the compositions shown in Tables 1 to 2. It should be noted that, regarding the items of "Composition" in Tables 1 to 2, "-" means that the component is not used. In addition, in the items of "Composition" in Tables 1 to 2, " "mass%" indicates the content (mass%) based on mass relative to the total amount of the lubricating base oil, "mass%" indicates the content (mass%) based on mass relative to the total amount of the lubricating oil composition, "ppm (N conversion)" indicates the content (mass ppm: the nitrogen content of the component relative to the total amount of the lubricating oil composition) based on mass, "ppm (P conversion)" indicates the content (mass ppm: the phosphorus content of the component relative to the total amount of the lubricating oil composition) based on mass, "ppm (S conversion)" indicates the content (mass ppm: the sulfur content of the component relative to the total amount of the lubricating oil composition) based on mass, "ppm (Ca conversion)" indicates the content (mass ppm: the calcium content of the component relative to the total amount of the lubricating oil composition) based on mass. The contents of phosphorus, nitrogen, sulfur and calcium in the composition are values ​​measured according to ASTM D4951. In Tables 1 and 2, the term "phosphorus content derived from component (B1)" indicates the mass-based content ratio of phosphorus derived from component (B1) contained in the lubricating oil composition (mass %), the term "sulfur content derived from component (B2)" indicates the mass-based content ratio of sulfur derived from component (B2) contained in the lubricating oil composition (mass %), and the term "nitrogen content derived from component (C)" indicates the mass-based content ratio of nitrogen derived from component (C) contained in the lubricating oil composition (mass %). In addition, in Tables 1 and 2, the term "Phosphorus from component (B1) / Nitrogen from component (C)" indicates the ratio of the "phosphorus content from component (B1)" to the "nitrogen content from component (C)" (mass ratio: [phosphorus" / [nitrogen]), and the term "Sulfur from component (B2) / Phosphorus from component (B1)" indicates the ratio of the "sulfur content from component (B2)" to the "phosphorus content from component (B1)" (mass ratio: [sulfur" / [phosphorus]).

[0140] [Evaluation Methods for Properties of Lubricating Oil Compositions Obtained in Examples, etc.]

[0141] <Measurement of volume resistivity>

[0142] The volume resistivity of the new oil was measured for each lubricating oil composition. The volume resistivity was measured at an oil temperature of 80°C in accordance with the volume resistivity test specified in JIS C2101. The obtained results are shown in Tables 1 and 2. The volume resistivity at 80°C was 0.0020×10 12 When the value is Ω·cm or more, it can be evaluated that the insulation property is high.

[0143] <Falex sintering test: a test to confirm the sintering resistance>

[0144] Each lubricating oil composition was subjected to a Falex seizure test according to ASTM D3233 A method, and the load at which seizure occurred (unit: lbf) 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.

[0145] <Falex wear test: A test to confirm wear resistance>

[0146] For each lubricating oil composition, the Falex test (Falex wear resistance test) was carried out under the conditions of oil temperature 80°C, load 390 lb, rotation speed 290 rpm and 1 hour in accordance with ASTM D2670, and the wear amount (mg) was measured. The obtained results are shown in Tables 1 and 2. It should be noted that if the wear amount is 55.0 mg or less, it can be judged that the wear resistance is good.

[0147] <Confirmation test of copper plate corrosion resistance>

[0148] About 30 mL of sample was prepared from each lubricating oil composition, and the copper plate corrosion test according to JIS K2513 was carried out to evaluate the copper plate corrosion resistance. That is, according to JIS K2513, after the copper plate was completely immersed in about 30 mL of sample, it was kept at an oil temperature of 150°C for 192 hours, and then it was taken out, cleaned and compared with the copper plate corrosion standard to determine the corrosion of the sample to copper, and the copper corrosion resistance was evaluated. The obtained results are shown in Tables 1 and 2. In addition, when the judgment value (discoloration number) of the copper plate corrosion standard is 2 or less, it can be judged that the copper corrosion resistance is high.

[0149] <Evaluation of oxidation stability: Confirmation test of the presence of strong acid value after oxidation treatment>

[0150] 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 according to JIS K2514-1, and the oxidation-treated lubricating oil composition was used to confirm whether a strong acid value was generated. The lubricating oil composition that did not generate a strong acid value was evaluated as having high oxidation stability and was rated as "acceptable", while the lubricating oil composition that generated a strong acid value was evaluated as having insufficient oxidation stability and was rated as "unacceptable". The obtained results are shown in Tables 1 and 2.

[0151] <Determination of kinematic viscosity ratio>

[0152] The kinematic viscosity at 40°C (KV40) of each lubricating oil composition after oxidation treatment at an oil temperature of 165°C for 192 hours using the ISOT method according to JIS K2514-1 was determined. OL ) and the kinematic viscosity at 40°C (KV40 L ), find their ratio ([KV40 OL ] / [KV40 L ]). It should be noted that the kinematic viscosity at 40°C was a value determined in accordance with the provisions of JIS K2283-2000. The obtained results are shown in Tables 1 and 2.

[0153]

[0154]

[0155] From the results shown in Table 1, it can be seen that the volume resistivity of the lubricating oil compositions obtained in Examples 1 to 7 (corresponding to the lubricating oil compositions of the present invention) is 0.0020×10 12 Ωcm or more, suitable for lubrication and cooling of electric motors requiring a high level of insulation. In addition, it was confirmed that the lubricating oil compositions obtained in Examples 1 to 7 (equivalent to the lubricating oil compositions of the present invention) had good seizure resistance and wear resistance, and the extreme pressure resistance based on seizure resistance and wear resistance was also high. It can be further seen that the lubricating oil compositions obtained in Examples 1 to 7 (equivalent to the lubricating oil compositions of the present invention) did not produce a strong acid value and had high oxidation stability. In addition, as shown in Table 1, it was also confirmed that the lubricating oil compositions obtained in Examples 1 to 7 (equivalent to the lubricating oil compositions of the present invention) had high copper corrosion resistance. In addition, it can be seen that the lubricating oil compositions obtained in Examples 1 to 7 (equivalent to the lubricating oil compositions of the present invention) are all the ratio of the kinematic viscosity at 40°C of the lubricating oil compositions before and after the oxidation treatment ([KV40 OL ] / [KV40 L]) is 1.05 or less, and from this point of view, the oxidation stability is also high. From these results, it can be seen that the lubricating oil compositions obtained in Examples 1 to 7 have high levels of insulation, oxidation stability and extreme pressure properties, have these properties in a balanced manner, and have high copper corrosion resistance.

[0156] As shown in the results in Table 2, the lubricating oil composition obtained in Comparative Example 1, in which the content of phosphorus derived from the component (B1) was more than 0.050 mass % (0.053 mass %) based on the total amount of the lubricating oil composition, had a volume resistivity of less than 0.0020×10 12 Ωcm, and the insulation properties could not be made high. In addition, the lubricating oil composition obtained in Comparative Example 2, in which the mass ratio (P / N) of the content of phosphorus derived from the component (B1) to the content of nitrogen derived from the component (C) was a value (2.68) exceeding 2.30, had insufficient anti-seizing properties and could not make the extreme pressure properties high. In addition, the lubricating oil composition obtained in Comparative Example 2 had a strong acid value and could not make the oxidation stability high. Furthermore, the lubricating oil compositions obtained in Comparative Examples 3 and 4, in which the mass ratio (P / N) of the content of phosphorus derived from the component (B1) to the content of nitrogen derived from the component (C) was less than 0.60, were not necessarily sufficient in terms of extreme pressure properties or insulation properties. In addition, the lubricating oil composition obtained in Comparative Example 5 containing a sulfur-containing extreme pressure agent in an amount of 200 ppm of sulfur had a strong acid value and could not make the oxidation stability high. Furthermore, the volume resistivity of the lubricating oil composition obtained in Comparative Example 6, in which the alkylamine salt of the phosphate ester was not used, was less than 0.0020×10 12 Ωcm, the insulation property could not be made to a high level.

[0157] Industrial Applicability

[0158] As described above, according to the present invention, a lubricating oil composition having insulation, oxidation stability and extreme pressure properties at a high level of balance and having high copper corrosion resistance can be provided. 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 oil composition comprising (A) a lubricating oil base oil, (B) an extreme pressure agent, and (C) a nitrogen-containing ashless dispersant, The volume resistivity of the lubricating oil composition at 80°C is 0.0020×10 12 Ωcm or more, The component (B) contains the phosphorus-based extreme pressure agent (B1) and does not contain the 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 component (B1) is an alkylamine salt of a phosphoric acid ester (B1-1), or the component (B1) is a mixture of the component (B1-1) and at least one compound (B1-2) selected from phosphoric acid, phosphoric acid ester, phosphite and salts thereof, but the compound does not include the compound belonging to the component (B1-1), 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 mass ratio of phosphorus derived from the component (B1) to nitrogen derived from the component (C), that is, [phosphorus] / [nitrogen], is 0.60 or more and 2.30 or less.

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

3. The lubricating oil composition according to claim 1, wherein The mass ratio of sulfur derived from the component (B2) to phosphorus derived from the component (B1), that is, [sulfur] / [phosphorus], is 3.0 or less. 4 . The lubricating oil composition according to claim 1 , comprising (D) a calcium sulfonate scavenger such that a calcium content based on the total amount of the lubricating oil composition is 200 ppm by mass or less.

5. The lubricating oil composition according to claim 1, wherein The mass ratio of phosphorus derived from the component (B1) to nitrogen derived from the component (C), that is, [phosphorus] / [nitrogen], is 0.60 or more and 1.70 or less.

6. The lubricating oil composition according to claim 1, wherein The kinematic viscosity at 40°C, i.e., KV40, of the lubricating oil composition after oxidation treatment at an oil temperature of 165°C for 192 hours using the ISOT method according to JIS K2514-1 is OL The kinematic viscosity at 40°C, i.e., KV40, of the lubricating oil composition before the oxidation treatment is L The ratio is [KV40 OL ] / [KV40 L ] is less than 1.

06.

7. The lubricating oil composition according to claim 1, which is a composition for lubricating a transmission and for cooling and lubricating an electric motor.

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