阅读说明：本技术 润滑油组合物 (Lubricating oil composition ) 是由 薄田洋平 福水崇裕 新吉隆利 床樱大辅 于 2020-04-09 设计创作，主要内容包括：本发明的润滑油组合物含有：润滑油基油；(A)2～10质量％的重均分子量50,000以下的聚(甲基)丙烯酸酯；(B)以P量计为0.01～0.06质量％的通式(1)的亚磷酸酯；(C)0.01～0.2质量％的噻二唑化合物；和(D)以Ca量计为0.005～0.03质量％的水杨酸钙清洁剂,该润滑油组合物的40℃运动粘度为4.0～20.0mm<Sup>2</Sup>/s,100℃运动粘度为1.8～5.2mm<Sup>2</Sup>/s,硫含量[S]与磷含量[P]的比[S]/[P]为2.2～4.0。(R<Sup>1</Sup>和R<Sup>2</Sup>独立地为通式(2)所示的碳原子数5～20的基团。)(R<Sup>3</Sup>为碳原子数2～17的直链烃基,R<Sup>4</Sup>为碳原子数2～17的直链烃基。)<Image he="140" wi="700" file="DDA0002443744640000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>(The lubricating oil composition of the present invention contains: a lubricant base oil; (A)2 to 10 mass% of a poly (meth) acrylate having a weight average molecular weight of 50,000 or less; (B) 0.01 to 0.06 mass% of a phosphite ester of the general formula (1) in terms of P amount; (C)0.01 to 0.2 mass% of a thiadiazole compound; and (D) 0.005 to 0.03 mass% of a calcium salicylate detergent based on Ca, the lubricating oil composition having a kinematic viscosity at 40 ℃The degree of the alloy is 4.0-20.0 mm 2 The viscosity at 100 ℃ is 1.8-5.2 mm 2 S, sulfur content [ S ]]With phosphorus content [ P]Ratio of (S)]/[P]2.2 to 4.0. (R) 1 And R 2 Independently a group having 5 to 20 carbon atoms represented by the general formula (2). ) (R) 3 Is a linear alkyl group having 2 to 17 carbon atoms, R 4 Is a linear alkyl group having 2 to 17 carbon atoms. ))

1. A lubricating oil composition characterized by containing:

a lubricant base oil comprising 1 or more kinds of mineral base oils, 1 or more kinds of synthetic base oils, or a mixture thereof, and the lubricating oilThe kinematic viscosity of the oil base oil at 40 ℃ is 5.0 to 15.0mm²(s) a kinematic viscosity at 100 ℃ of 1.7 to 3.5mm²/s；

(A) A poly (meth) acrylate viscosity index improver having a weight-average molecular weight of 50,000 or less, the content of which is 2 to 10% by mass based on the total amount of the composition;

(B) a phosphite ester compound represented by the following general formula (1), the content of which is 0.01 to 0.06 mass% in terms of phosphorus amount, based on the total amount of the composition;

(C) a thiadiazole compound in an amount of 0.01 to 0.2% by mass based on the total amount of the composition; and

(D) calcium salicylate detergent in an amount of 0.005 to 0.03 mass% in terms of calcium based on the total amount of the composition,

the lubricating oil composition has a kinematic viscosity at 40 ℃ of 4.0 to 20.0mm²/s，

The kinematic viscosity of the lubricating oil composition at 100 ℃ is 1.8-5.2 mm²/s，

The ratio [ S ]/[ P ] of the sulfur content [ S ] to the phosphorus content [ P ] in the lubricating oil composition is 2.2 to 4.0, wherein the unit of the sulfur content [ S ] is mass%, the unit of the phosphorus content [ P ] is mass%,

in the general formula (1), R¹And R²Each independently represents a group having 5 to 20 carbon atoms represented by the following general formula (2),

in the general formula (2), R³Is a linear alkyl group having 2 to 17 carbon atoms, R⁴Is a linear alkyl group having 2 to 17 carbon atoms.

2. The lubricating oil composition of claim 1, wherein:

the lubricating oil composition contains (E) a tolyltriazole metal deactivator and/or a benzotriazole metal deactivator in an amount of 0.001 to 0.1% by mass based on the total amount of the composition.

3. The lubricating oil composition according to claim 1 or 2, wherein:

the lubricating oil composition contains (F) a succinimide ashless dispersant in an amount of 0.1 mass% or less in terms of nitrogen amount based on the total amount of the composition, or does not contain (F) a succinimide ashless dispersant,

the component (F) is a condensation reaction product of an alkyl or alkenyl succinic acid having an alkyl or alkenyl group having 40 to 400 carbon atoms or an acid anhydride thereof and a polyamine, and/or a derivative thereof.

4. The lubricating oil composition according to any one of claims 1 to 3, wherein:

the component (A) is poly (methyl) acrylate with the weight average molecular weight of 10,000-50,000.

5. The lubricating oil composition according to any one of claims 1 to 4, wherein:

the content of the component (A) is 3-10% by mass based on the total amount of the composition.

6. The lubricating oil composition according to any one of claims 1 to 5, wherein:

the content of the component (A) is 5-10% by mass based on the total amount of the composition.

7. The lubricating oil composition according to any one of claims 1 to 6, wherein:

the component (A) is non-dispersed poly (meth) acrylate.

8. The lubricating oil composition according to any one of claims 1 to 7, wherein:

the lubricating oil composition is used for lubrication of an electric motor or lubrication of the electric motor and a transmission in an automobile having the electric motor.

9. A method of lubricating an electric motor, comprising:

lubricating an electric motor of an automobile having the electric motor with the lubricating oil composition according to any one of claims 1 to 8.

10. A method of lubricating an electric motor and a transmission, characterized by:

lubricating an electric motor and a transmission of an automobile having the electric motor and the transmission with the lubricating oil composition according to any one of claims 1 to 8.

Technical Field

The present invention relates to a lubricating oil composition, and more particularly to a lubricating oil composition suitable for lubricating an electric motor.

Background

In recent years, from the viewpoint of energy efficiency and environmental suitability, attention has been paid to electric vehicles using an electric motor as a power source for running, and hybrid vehicles using an electric motor and an internal combustion engine in combination as a power source for running. The motor generates heat as it operates, but the motor includes heat-labile components such as coils and magnets. Therefore, in these automobiles using an electric motor as a power source for running, a means for cooling the electric motor is provided. As a means for cooling the motor, air cooling, water cooling, and oil cooling are known. Among these, the oil cooling system can obtain a high cooling effect by causing oil to flow inside the motor and causing heat generating parts (e.g., coils, cores, magnets, etc.) in the motor to directly contact a cooling medium (oil). In an oil-cooled motor, lubrication and cooling of the motor are performed simultaneously by circulating oil (lubricating oil) inside the motor. Electrical insulation is required for lubricating oil (motor oil) of a motor.

An automobile using an electric motor as a power source for running generally includes a transmission having a gear mechanism. Since the lubricating oil for lubricating a gear mechanism is required to have seizure resistance and fatigue resistance, various additives are blended.

Disclosure of Invention

Technical problem to be solved by the invention

The motor and transmission are typically lubricated using different lubricating oils. If the motor and the transmission (gear mechanism) can be lubricated using the same lubricating oil, the lubricating oil circulation mechanism can be simplified. Recently, an electric drive unit in which an electric motor and a transmission (gear mechanism) are integrated as an integrated device has been proposed. In order to lubricate such an electric drive unit, it is preferable to lubricate the motor and the transmission (gear mechanism) with the same lubricating oil from the viewpoint of reduction in size and weight.

However, even if the electrical insulation of the new oil is improved for use in lubrication of the motor, the electrical insulation of the composition that is deteriorated by oxidation due to use is not sufficient in the conventional transmission oil. Further, when the conventional motor oil is used for lubrication of a transmission (gear mechanism), seizure resistance and fatigue resistance are insufficient.

Further, motor oil is required to have not only electrical insulation but also corrosion resistance to copper used as a motor material.

The technical problem to be solved by the invention is as follows: provided is a lubricating oil composition having a good balance among electrical insulation properties, seizure resistance, copper corrosion resistance and fatigue resistance of a composition after oxidative deterioration.

Technical solution for solving technical problem

A first aspect of the present invention is a lubricating oil composition containing: lubricating oil base oil, the lubricating oil base oilThe oil is 1 or more kinds of mineral oil base oil, 1 or more kinds of synthetic base oil or a mixture thereof, and has a kinematic viscosity at 40 ℃ of 5.0 to 15.0mm²(s) a kinematic viscosity at 100 ℃ of 1.7 to 3.5mm²S; (A) a poly (meth) acrylate viscosity index improver having a weight-average molecular weight of 50,000 or less, the content of which is 2 to 10% by mass based on the total amount of the composition; (B) a phosphite ester compound represented by the following general formula (1), the content of which is 0.01 to 0.06 mass% in terms of phosphorus amount, based on the total amount of the composition; (C) a thiadiazole compound in an amount of 0.01 to 0.2% by mass based on the total amount of the composition; and (D) a calcium salicylate detergent in an amount of 0.005 to 0.03 mass% in terms of calcium based on the total amount of the composition, wherein the lubricating oil composition has a kinematic viscosity at 40 ℃ of 4.0 to 20.0mm²(s) the kinematic viscosity at 100 ℃ of the lubricating oil composition is 1.8 to 5.2mm²S, sulfur content in lubricating oil composition](unit: mass%) relative to the phosphorus content [ P ] in the lubricating oil composition](unit: mass%) ratio [ S%]/[P]2.2 to 4.0.

(in the general formula (1), R¹And R²Each independently represents a group having 5 to 20 carbon atoms represented by the following general formula (2). )

(in the general formula (2), R³Is a linear alkyl group having 2 to 17 carbon atoms, R⁴Is a linear alkyl group having 2 to 17 carbon atoms. )

In the present specification, "phosphorous acid" means an oxyacid H of phosphorus having an oxidation number of + III₃PO₃. The phosphite compound represented by the general formula (1) generally has tautomerism, and in the present specification, any tautomer of the compound represented by the general formula (1) belongs to the component (B).

A second aspect of the present invention is a lubrication method, including: the lubricating oil composition according to the first aspect of the present invention is used for lubricating an electric motor or an electric motor and a transmission of an automobile equipped with the electric motor.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the first aspect of the present invention, a lubricating oil composition having a good balance among electrical insulation properties, seizure resistance, copper corrosion resistance and fatigue resistance of a composition after oxidative degradation can be provided.

The lubricating oil composition according to the first aspect of the present invention can be preferably used in the lubricating method according to the second aspect of the present invention.

Detailed Description

Hereinafter, the present invention will be described in detail. In the present specification, unless otherwise specified, the expression "a to B" as to the numerical values a and B means "a to B inclusive". In this expression, only in the case where the numerical value B marks a unit, the unit is also applied to the numerical value a. In addition, the words "or" and "or" mean a logical or without special mention. In the present specification, the element E₁And E₂"E" of₁And/or E₂"such expression means" E₁Or E₂Or a combination thereof ", with respect to the element E₁、…、E_N(N is an integer of 3 or more)' E₁、…、E_N－1And/or E_N"such expression means" E₁、…、E_N－1Or E_NOr a combination thereof.

In addition, in the present specification, the contents of respective elements of calcium, magnesium, zinc, phosphorus, sulfur, boron, barium and molybdenum in the oil were determined by inductively coupled plasma emission spectrometry (intensity ratio method) according to JPI-5S-38-2003. The content of nitrogen in the oil was measured by a chemiluminescence method according to JIS K2609.

< lubricating oil base oil >

As the lubricating base oil in the lubricating oil composition of the present invention (hereinafter, also referred to as "lubricating oil composition" or simply "composition"), 1 or more kinds of mineral base oils, 1 or more kinds of synthetic base oils, or a mixed base oil thereof can be used. In one embodiment, an API base oil classification group II base oil (hereinafter, also referred to as "API group II base oil" or simply as "group II base oil") an API base oil classification group III base oil (hereinafter, also referred to as "API group III base oil" or simply as "group III base oil"), an API base oil classification group IV base oil (hereinafter, also referred to as "API group IV base oil" or simply as "group IV base oil") or an API base oil classification group V base oil (hereinafter, also referred to as "API group V base oil" or simply as "group V base oil") or a mixed base oil thereof can be preferably used, and a group II base oil, a group III base oil or a group IV base oil or a mixed base oil thereof can be more preferably used. The API group II base oil is a mineral oil base oil having a sulfur content of 0.03 mass% or less, a saturation content of 90 mass% or more, and a viscosity index of 80 or more and less than 120. The API group III base oil is a mineral oil base oil having a sulfur content of 0.03 mass% or less, a saturation content of 90 mass% or more, and a viscosity index of 120 or more. The API group IV base oil is a polyalphaolefin base oil. The API group V base oil is a base oil other than the above groups I to IV, and is preferably an ester base oil.

Examples of the mineral base oil include a paraffin-based or naphthene-based mineral base oil obtained by appropriately combining 1 or 2 or more kinds of refining methods such as solvent deasphalting, solvent extraction, hydrogenolysis, solvent dewaxing, contact dewaxing, hydrorefining, sulfuric acid washing, and clay treatment with a lubricating oil fraction obtained by atmospheric distillation and vacuum distillation of crude oil. The API group II base oils and group III base oils are typically produced via a hydro-decomposition process. Further, WAX-isomerized base oils, base oils produced by a method of isomerizing GTL WAX (gas-to-liquid WAX), and the like can also be used.

Examples of the API group IV base oil include ethylene-propylene copolymers, polybutenes, 1-octene oligomers, 1-decene oligomers, and hydrogenated products thereof.

Examples of API group V base oils include: monoesters (e.g., butyl stearate, octyl laurate, 2-ethylhexyl oleate, etc.); diesters (e.g., ditridecylglutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyladipate, di-2-ethylhexyl sebacate, etc.); polyesters (e.g., trimellitate esters, etc.); polyol esters (e.g., trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate, etc.) and the like.

The lubricant base oil may be composed of 1 type of base oil, or may be a mixed base oil containing 2 or more types of base oils. In the blended base oil containing 2 or more types of base oils, the API classifications of these base oils may be the same or different from each other. The content of the API group V base oil is preferably 0 to 20 mass%, more preferably 0 to 15 mass%, even more preferably 0 to 10 mass%, and particularly preferably substantially no API group V base oil, based on the total amount of the lubricating oil base oil. When the content of the ester-based base oil is not more than the above upper limit, the oxidation stability of the lubricating oil composition can be improved.

The kinematic viscosity of the lubricant base oil (whole base oil) at 100 ℃ is 1.7 to 3.5mm²(ii) s, preferably 2.2 to 3.0mm²And s. When the kinematic viscosity of the lubricating base oil at 100 ℃ is not higher than the upper limit value, fuel economy can be improved. When the kinematic viscosity of the lubricating base oil at 100 ℃ is not less than the lower limit, the electrical insulation property, seizure resistance and fatigue resistance of the new oil can be improved. And in the present specification, "kinematic viscosity at 100 ℃" means kinematic viscosity at 100 ℃ specified by ASTM D-445.

The kinematic viscosity of the lubricant base oil (whole base oil) at 40 ℃ is 5.0 to 15.0mm²(ii) s, preferably 7.0 to 12.0mm²And s. When the kinematic viscosity of the lubricant base oil at 40 ℃ is not higher than the above upper limit, fuel economy can be improved. When the kinematic viscosity of the lubricating base oil at 40 ℃ is not less than the lower limit, the electrical insulation property, seizure resistance and fatigue resistance of the new oil can be improved. And in the present specification, "kinematic viscosity at 40 ℃" means kinematic viscosity at 40 ℃ specified by ASTM D-445.

The viscosity index of the lubricant base oil (whole base oil) is preferably 100 or more, more preferably 105 or more, and in one embodiment may be 110 or more, 120 or more, and 125 or more. When the viscosity index of the lubricating base oil is not less than the lower limit, the viscosity-temperature characteristics, thermal oxidation stability, and wear resistance of the lubricating oil composition can be improved, and the friction coefficient can be reduced. And in the present specification, the viscosity index means a viscosity index measured in accordance with JIS K2283-1993.

From the viewpoint of oxidation stability, the sulfur content in the lubricant base oil (whole base oil) is preferably 0.03 mass% (300 mass ppm) or less, more preferably 50 mass ppm or less, particularly preferably 10 mass ppm or less, and may be 1 mass ppm or less.

The content of the lubricant base oil (whole base oil) in the lubricant oil composition is preferably 50 to 95% by mass, more preferably 70 to 95% by mass, based on the total amount of the composition.

(A) a poly (meth) acrylate viscosity index improver

The lubricating oil composition of the present invention contains (a) a poly (meth) acrylate viscosity index improver (hereinafter, also referred to as "component (a)") having a weight average molecular weight of 50,000 or less. As the component (a), 1 kind of poly (meth) acrylate compound may be used alone, or 2 or more kinds of poly (meth) acrylate compounds may be used in combination. And in the present specification "(meth) acrylate" means "acrylate and/or methacrylate".

As the component (a), those which are used as a viscosity index improver for poly (meth) acrylate used in a lubricating oil and have a weight average molecular weight of 50,000 or less can be used without particular limitation. As the component (a), any of non-dispersible poly (meth) acrylate and dispersible poly (meth) acrylate may be used, or they may be used in combination, and it is preferable to use a non-dispersible poly (meth) acrylate viscosity index improver. In the present specification, "dispersed poly (meth) acrylate" means a poly (meth) acrylate compound having a functional group containing a nitrogen atom, and "non-dispersed poly (meth) acrylate" means a poly (meth) acrylate compound having no functional group containing a nitrogen atom. By using a non-dispersible poly (meth) acrylate viscosity index improver as the component (a), the seizure resistance can be further improved.

(A) The weight average molecular weight of the component (A) is 50,000 or less, preferably 10,000 to 50,000, more preferably 20,000 to 50,000. When the weight average molecular weight of the component (a) is not more than the upper limit, the seizure resistance can be improved. When the weight average molecular weight of the component (a) is not less than the lower limit, not only the electrical insulation property of the fresh oil but also the fatigue resistance can be further improved. And in the present specification, "weight average molecular weight" means a weight average molecular weight in terms of standard polystyrene measured by Gel Permeation Chromatography (GPC).

The content of the component (A) in the lubricating oil composition is 2 to 10 mass%, preferably 3 to 10 mass%, more preferably 5 to 10 mass% based on the total amount of the composition. When the content of the component (a) is not less than the lower limit, the seizure resistance and the electrical insulation property of the composition after oxidation deterioration can be improved. Further, the fuel economy can be improved by setting the content of the component (a) to the upper limit or less.

< (B) phosphite ester Compound

The lubricating oil composition of the present invention contains a phosphite ester compound represented by general formula (1) (hereinafter, also referred to as component (B)). As the component (B), can use 1 kind of phosphite compounds alone, can also be combined with more than 2 kinds of phosphite compounds.

In the general formula (1), R¹And R²Each independently represents a group having 5 to 20 carbon atoms represented by the following general formula (2).

In the present specification, "phosphorous acid" means an oxyacid H of phosphorus having an oxidation number + III₃PO₃. The phosphite compound represented by the general formula (1) generally has tautomerism, and in the present specification, any tautomer of the compound represented by the general formula (1) belongs to the component (B).

In the general formula (2), R³The hydrocarbon group is a linear hydrocarbon group having 2 to 17 carbon atoms, preferably an ethylene group or a propylene group, and in one embodiment, an ethylene group. R⁴Is a linear hydrocarbon group having 2 to 17 carbon atoms, preferably a linear hydrocarbon group having 2 to 16 carbon atoms, more preferably a linear hydrocarbon group having 2 to 10 carbon atoms.

By using a phosphite compound having the above structure as the component (B), sintering resistance and fatigue resistance can be improved.

As R¹And R²As preferable examples thereof, 3-thiopentyl, 3-thiohexyl, 3-thioheptyl, 3-thiooctyl, 3-thiononyl, 3-thiodecyl, 3-thioundecyl and 4-thiohexyl groups are cited.

The content of the component (B) in the lubricating oil composition is 0.01 to 0.06 mass%, preferably 0.02 to 0.05 mass%, and more preferably 0.02 to 0.04 mass% in terms of phosphorus amount based on the total amount of the lubricating oil composition. When the content of the component (B) is not more than the above upper limit, the electrical insulation property of the fresh oil, the electrical insulation property of the composition after oxidation degradation, and the seizure resistance can be improved. Further, the content of the component (B) is not less than the lower limit, whereby the seizure resistance and the fatigue resistance can be improved.

(C) thiadiazole Compound

The lubricating oil composition of the present invention may further contain (C) a thiadiazole compound (hereinafter, also referred to as "component (C)"). As the component (C), 1 kind of thiadiazole compound may be used alone, or 2 or more kinds of thiadiazole compounds may be used in combination.

Examples of the component (C) include 1,3, 4-thiadiazole represented by the following general formula (3), 1,2, 4-thiadiazole compound represented by the following general formula (4), and 1,2, 3-thiadiazole compound represented by the following general formula (5).

(in the general formulae (3) to (5), R⁵And R⁶The same or different, each independently represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms; a and b may be the same or different and each independently represents an integer of 0 to 8. )

Among the above-mentioned thiadiazole compounds, a thiadiazole compound having a hydrocarbyl disulfide group represented by any one of the above-mentioned general formulae (3) to (5) can be particularly preferably used.

The content of the component (C) in the lubricating oil composition is 0.01 to 0.2 mass% based on the total amount of the lubricating oil composition. When the content of the component (C) is not less than the lower limit, the corrosion resistance of copper can be improved. When the content of the component (C) is not more than the above upper limit, the electrical insulation properties of the virgin oil and the electrical insulation properties of the composition after oxidation degradation can be improved.

(D) calcium salicylate detergents

The lubricating oil composition of the present invention contains (D) a calcium salicylate detergent (hereinafter, also simply referred to as "component (D)"). As the component (D), calcium salicylate, or an alkaline salt or an overbased salt thereof can be used. As the component (D), 1 kind of calcium salicylate detergent may be used alone, or 2 or more kinds of calcium salicylate detergents may be used in combination. Examples of the calcium salicylate include compounds represented by the following general formula (6).

In the general formula (6), R⁷Each independently represents an alkyl group or an alkenyl group having 14 to 30 carbon atoms. c represents 1 or 2, preferably 1. The component (D) may be a mixture of a compound having c ═ 1 and a compound having c ═ 2. Wherein, in case c is 2, R⁷Combinations of different groups are possible.

A preferred embodiment of the calcium salicylate detergent includes calcium salicylate of the general formula (6) above in which c is 1, and an alkaline salt or an overbased salt thereof.

The method for producing calcium salicylate is not particularly limited, and a known method for producing monoalkyl salicylate can be used. For example, calcium salicylate can be obtained by reacting monoalkylsalicylic acid obtained by alkylating phenol as a starting material with an olefin and then carboxylating the same with carbon dioxide or the like, or monoalkylsalicylic acid obtained by alkylating salicylic acid as a starting material with an equivalent amount of the above olefin with a metal base such as an oxide or hydroxide of calcium, or by forming an alkali metal salt such as a sodium salt or a potassium salt of the monoalkylsalicylic acid or the like first and then metal-exchanging the same with a calcium salt.

The method for obtaining the overbased calcium salicylate is not particularly limited, and for example, the overbased calcium salicylate can be obtained by reacting calcium salicylate with a calcium base such as calcium hydroxide in the presence of carbon dioxide.

(D) The base number of the component (A) is not particularly limited, but is preferably 50 to 350mgKOH/g, more preferably 100 to 350mgKOH/g, and particularly preferably 150 to 350 mgKOH/g. When the base number of the component (D) is not less than the lower limit, the electrical insulation property of the composition after oxidation deterioration can be further improved. Also, in the present specification, the base number means a base number measured by a perchloric acid method in accordance with JIS K2501. In addition, the metal-based detergent is generally obtained by a reaction in a diluent such as a solvent or lubricating oil base oil. Therefore, metal-based detergents are commercially distributed in a state diluted with a diluent such as lubricating oil-based oil. In the present specification, the base number of the metal-based detergent means the base number in a state where the diluent is contained.

The content of the component (D) in the lubricating oil composition is 0.005 to 0.03 mass%, preferably 0.005 to 0.02 mass%, based on the total amount of the lubricating oil composition, in terms of the amount of calcium. When the content of the component (D) is not more than the above upper limit, the electrical insulation properties of the fresh oil and the electrical insulation properties of the composition after oxidation degradation can be improved. Further, when the content of the component (D) is not less than the lower limit, fatigue resistance can be improved.

The lubricating oil composition may contain only a calcium salicylate detergent as the metal detergent, or may further contain 1 or more metal detergents (e.g., a calcium sulfonate detergent, a calcium phenate detergent, etc.) other than the calcium salicylate detergent. The total content of the metal-based detergent in the lubricating oil composition is preferably 0.005 to 0.03 mass% in terms of metal. When the total content of the metal-based detergent in the lubricating oil composition is not more than the above upper limit, the electrical insulation properties of the fresh oil can be improved, and the electrical insulation properties of the composition after oxidative degradation can be further improved. The ratio of salicylate to the total soap base of the metal-based detergent, that is, the ratio of the mass of the salicylate-based detergent in terms of organic acid in the total soap base to the mass of the metal-based detergent in terms of organic acid in the total soap base, is preferably 65 to 100% by mass, and more preferably 90 to 100% by mass. The contribution of the salicylate to the total content of the metal-based detergent is not less than the lower limit, whereby the fatigue resistance can be further improved. In the present specification, the soap base of the metal-based detergent means a conjugate base of an organic acid constituting a soap component of the metal-based detergent (e.g., an alkyl salicylate anion in a salicylate detergent, e.g., an alkyl benzenesulfonate anion in a sulfonate detergent, e.g., an alkyl phenolate anion in a phenate detergent). In general, in the field of lubricating oils, as the metal-based detergent, an organic acid metal salt (for example, alkali or alkaline earth metal alkyl salicylate, alkali or alkaline earth metal alkyl benzene sulfonate, alkali or alkaline earth metal alkali phenate, or the like) capable of forming micelles (micelles) in a base oil, or a mixture of the organic acid metal salt and a basic metal salt (for example, hydroxide, carbonate, borate, or the like of alkali or alkaline earth metal constituting the organic acid metal salt) can be used. Such an organic acid generally contains at least 1 lipophilic group such as at least 1 polar group having bronsted acidity (for example, a carboxyl group, a sulfo group, a phenolic hydroxyl group, etc.) and a linear or branched alkyl group (for example, a linear or branched alkyl group having 6 or more carbon atoms) capable of forming a salt with a metal base in one molecule.

< (E) benzotriazole/tolyltriazole-based metal deactivator >)

In a preferred embodiment, the lubricating oil composition may further contain a tolyltriazole-based metal deactivator and/or a benzotriazol-based metal deactivator (hereinafter, also referred to as "(E) component"). As the component (E), a tolyltriazole-based metal deactivator and/or a benzotriazol-based metal deactivator used in a lubricating oil can be used without particular limitation. As the component (E), 1 kind of compound may be used alone, or 2 or more kinds of compounds may be used in combination.

The lubricating oil composition may contain no component (E), and when the lubricating oil composition contains the component (E), the content thereof is preferably 0.001 to 0.1% by mass, more preferably 0.001 to 0.075% by mass, and particularly preferably 0.001 to 0.05% by mass. When the content of the component (E) is not less than the lower limit, the corrosion resistance of copper can be further improved. When the content of the component (E) is not more than the above upper limit, the electrical insulation property and the abrasion resistance of the virgin oil can be improved, and the seizure resistance and the electrical insulation property of the composition after oxidation degradation can be further improved.

(F) succinimide ashless dispersant

In a preferred embodiment, the lubricating oil composition may further contain (F) a succinimide-based ashless dispersant (hereinafter, also referred to as "component (F)"). (F) The component (B) may contain a boronized succinimide ashless dispersant, a non-boronized succinimide ashless dispersant, or a combination thereof. Among them, the component (F) preferably contains a boronated succinimide ashless dispersant from the viewpoint of oxidation stability.

As the component (F), for example, succinimide having at least 1 alkyl group or alkenyl group in the molecule or a derivative thereof can be used. Examples of the succinimide having at least 1 alkyl group or alkenyl group in the molecule include compounds represented by the following general formula (7) or (8).

In the general formula (7), R⁸Represents an alkyl group or alkenyl group having 40 to 400 carbon atomsAnd d represents an integer of 1 to 5, preferably 2 to 4. R⁸The number of carbon atoms of (C) is preferably 60 to 350.

In the general formula (8), R⁹And R¹⁰Each independently represents an alkyl group or an alkenyl group having 40 to 400 carbon atoms, and may be a combination of different groups. e represents an integer of 0 to 4, preferably 1 to 4, and more preferably 1 to 3. R⁹And R¹⁰The number of carbon atoms of (C) is preferably 60 to 350.

By R in the general formulae (7) and (8)⁸～R¹⁰The number of carbon atoms of (a) is not less than the above lower limit, and good solubility in the lubricating base oil can be obtained. On the other hand, by R⁸～R¹⁰The number of carbon atoms of (b) is not more than the above upper limit, and the low temperature fluidity of the lubricating oil composition can be improved.

Alkyl or alkenyl (R) in the general formulae (7) and (8)⁸～R¹⁰) The polymer may be linear or branched. Preferred examples thereof include oligomers of olefins such as propylene, 1-butene and isobutylene, and branched alkyl groups or branched alkenyl groups derived from a co-oligomer of ethylene and propylene. Among them, a branched alkyl group or alkenyl group derived from an oligomer of isobutylene conventionally called polyisobutylene, and a polybutenyl group are most preferable.

Alkyl or alkenyl (R) in the general formulae (7) and (8)⁸～R¹⁰) The preferred number average molecular weight of the copolymer is 800 to 3500, preferably 1000 to 3500.

The succinimide having at least 1 alkyl group or alkenyl group in the molecule includes a so-called mono-type succinimide represented by the general formula (7) in which succinic anhydride is added only to one end of a polyamine chain, and a so-called bis-type succinimide represented by the general formula (8) in which succinic anhydride is added to both ends of a polyamine chain. The lubricating oil composition may contain either of a mono-type succinimide and a bis-type succinimide, or may contain both of them as a mixture. (F) The content of the bis-succinimide or a derivative thereof in the component (F) is preferably 50 mass% or more, and more preferably 70 mass% or more, based on the total amount (100 mass%) of the component (F).

The preparation method of the succinimide having at least 1 alkyl group or alkenyl group in the molecule is not particularly limited. The succinimide can be obtained, for example, as a condensation reaction product by reacting an alkyl or alkenyl succinic acid having an alkyl or alkenyl group having 40 to 400 carbon atoms or an acid anhydride thereof with a polyamine. The condensation product may be used as it is or may be converted into a derivative to be described later. The condensation product of the polyamine and the alkyl or alkenyl succinic acid or the acid anhydride thereof may be a bis-type succinimide in which both ends of the polyamine chain are imidized (see general formula (8)), a mono-type succinimide in which only one end of the polyamine chain is imidized (see general formula (7)), or a mixture thereof. The alkenyl succinic anhydride having an alkenyl group having 40 to 400 carbon atoms can be obtained by, for example, reacting an olefin having 40 to 400 carbon atoms with maleic anhydride at 100 to 200 ℃. Further, the alkenyl succinic anhydride is subjected to a hydrogenation reaction to obtain an alkyl succinic anhydride having an alkyl group with 40 to 400 carbon atoms. Examples of the polyamine include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and mixtures thereof, and a polyamine raw material containing 1 or more selected from these can be preferably used. The polyamine raw material may or may not contain ethylenediamine, and from the viewpoint of improving the performance of the dispersant as a condensation product or a derivative thereof, the content of ethylenediamine in the polyamine raw material is preferably 0 to 10% by mass, more preferably 0 to 5% by mass, based on the total amount of polyamines. The succinimide obtained as a condensation reaction product of a mixture of an alkyl or alkenyl succinic acid having an alkyl or alkenyl group having 40 to 400 carbon atoms or an acid anhydride thereof and 2 or more kinds of polyamines is a mixture of compounds having different d or e in the general formula (7) or (8).

As the succinimide derivative, a boron-modified compound (boronated succinimide) obtained by reacting boric acid with the succinimide to neutralize or amidate a part or all of the remaining amino groups and/or imino groups can be preferably used.

(F) The weight average molecular weight of the component (A) is 1000 to 20000, more preferably 2000 to 20000, still more preferably 3000 to 15000, and particularly preferably 4000 to 9000. When the weight average molecular weight of the component (F) is not less than the lower limit, the electrical insulation properties of the fresh oil can be improved, and the electrical insulation properties of the composition after oxidative deterioration can be further improved. When the weight average molecular weight of the component (F) is not more than the upper limit, the electrical insulation property of the composition after oxidative deterioration can be further improved.

The lubricating oil composition may contain no component (F), and when the lubricating oil composition contains component (F), the content thereof is preferably 0.1 mass% or less, more preferably 0.01 to 0.08 mass%, and still more preferably 0.03 to 0.08 mass% in terms of nitrogen, based on the total amount of the lubricating oil composition. When the content of the component (F) is not less than the lower limit, the electrical insulation property of the fresh oil can be improved. When the content of the component (F) is not more than the above upper limit, the electrical insulation properties of the fresh oil can be improved, and the electrical insulation properties of the composition after oxidative degradation can be further improved.

(G) antioxidant

In a preferred embodiment, the lubricating oil composition may further contain (G) an antioxidant (hereinafter, also referred to as "(G) component"). As the component (G), 1 kind of compound may be used alone, or 2 or more kinds of compounds may be used in combination. As the component (G), known antioxidants such as amine antioxidants and phenol antioxidants can be used without particular limitation.

Examples of the amine-based antioxidant include an aromatic amine-based antioxidant and a hindered amine-based antioxidant. Examples of the aromatic amine antioxidant include aromatic primary amine compounds such as alkylated α -naphthylamine; and aromatic secondary amine compounds such as alkylated diphenylamine, phenyl- α -naphthylamine, alkylated phenyl- α -naphthylamine, phenyl- β -naphthylamine, and the like. As the aromatic amine-based antioxidant, alkylated diphenylamine, alkylated phenyl- α -naphthylamine, or a combination thereof can be preferably used.

Examples of the hindered amine antioxidant include 2,2,6, 6-tetraalkylpiperidine derivatives. As the 2,2,6, 6-tetraalkylpiperidine derivative, a 2,2,6, 6-tetraalkylpiperidine derivative having a substituent at the 4-position is preferable. In addition, 2,6, 6-tetraalkylpiperidine skeletons may be bonded via a substituent at the respective 4-position. The N-position of the 2,2,6, 6-tetraalkylpiperidine skeleton may be unsubstituted, or the N-position may be substituted with an alkyl group having 1 to 4 carbon atoms. The 2,2,6, 6-tetraalkylpiperidine skeleton is preferably a 2,2,6, 6-tetramethylpiperidine skeleton.

Examples of the substituent at the 4-position of the 2,2,6, 6-tetraalkylpiperidine skeleton include acyloxy (R)¹¹COO-), alkoxy (R)¹¹O-), alkylamino (R)¹¹NH-), acylamino (R)¹¹CONH-), etc. R¹¹Preferably a hydrocarbon group having 1 to 30 carbon atoms, more preferably 1 to 24 carbon atoms, and still more preferably 1 to 20 carbon atoms. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, a cycloalkyl group, an alkylcycloalkyl group, an aryl group, an alkylaryl group, and an arylalkyl group.

Examples of the substituent in which 2,2,6, 6-tetraalkylpiperidine skeletons are bonded via a substituent at the 4-position include an alkylenebis (carbonyloxy) group (-OOC-R)¹²-COO-), hydrocarbylidenediamino (-HN-R)¹²-NH-), hydrocarbylidene bis (carbonylamino) -group (-HNCO-R¹²-CONH-), etc. R¹²Preferably a C1-30 alkylene group, more preferably an alkylene group.

The substituent at the 4-position of the 2,2,6, 6-tetraalkylpiperidine skeleton is preferably an acyloxy group. Examples of the compound having an acyloxy group at the 4-position of the 2,2,6, 6-tetraalkylpiperidine skeleton include esters of 2,2,6, 6-tetramethyl-4-piperidinol and carboxylic acids. Examples of the carboxylic acid include a linear or branched aliphatic carboxylic acid having 8 to 20 carbon atoms.

Examples of the phenolic antioxidant include 4, 4' -methylenebis (2, 6-di-t-butylphenol); 4, 4' -bis (2, 6-di-tert-butylphenol); 4, 4' -bis (2-methyl-6-tert-butylphenol); 2, 2' -methylenebis (4-ethyl-6-tert-butylphenol); 2, 2' -methylenebis (4-methyl-6-tert-butylphenol); 4, 4' -butylidenebis (3-methyl-6-tert-butylphenol); 4, 4' -isopropylidenebis (2, 6-di-tert-butylphenol); 2, 2' -methylenebis (4-methyl-6-nonylphenol); 2, 2' -isobutylidene bis (4, 6-dimethylphenol); 2, 2' -methylenebis (4-methyl-6-cyclohexylphenol); 2, 6-di-tert-butyl-4-methylphenol; 2, 6-di-tert-butyl-4-ethylphenol; 2, 4-dimethyl-6-tert-butylphenol; 2, 6-di-tert-butyl-4- (N, N' -dimethylaminomethyl) phenol; 4, 4' -thiobis (2-methyl-6-tert-butylphenol); 4, 4' -thiobis (3-methyl-6-tert-butylphenol); 2, 2' -thiobis (4-methyl-6-tert-butylphenol); bis (3-methyl-4-hydroxy-5-tert-butylbenzyl) sulfide; bis (3, 5-di-tert-butyl-4-hydroxybenzyl) sulfide; 3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid esters; 3-methyl-5-tert-butyl-4-hydroxyphenol fatty acid esters, and the like. Examples of the 3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate include octyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate; decyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate; dodecyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate; tetradecyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate; hexadecyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate; octadecyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate; pentaerythritol-tetrakis [ 3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ]; 2, 2' -thio-diethylenebis [ 3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], and the like.

The lubricating oil composition may contain no component (G), and when the lubricating oil composition contains an amine antioxidant as component (G), the content thereof is preferably 0.005 mass% or more and 0.15 mass% or less, more preferably 0.005 mass% or more and 0.12 mass% or less, in terms of nitrogen, based on the total amount of the lubricating oil composition. When the content of the amine-based antioxidant is not more than the above upper limit, the electrical insulation of the fresh oil can be improved, and the electrical insulation of the composition after oxidative deterioration can be further improved.

When the lubricating oil composition contains a phenol antioxidant as the component (G), the content thereof is preferably 0.1 mass% or more and 1.5 mass% or less, more preferably 0.1 mass% or more and 1.0 mass% or less, based on the total amount of the lubricating oil composition. When the content of the phenolic antioxidant is not more than the above upper limit, the electrical insulation of the fresh oil can be improved, and the electrical insulation of the composition after oxidative deterioration can be further improved.

< other additives >

In one embodiment, the lubricating oil composition may further contain 1 or more additives selected from the group consisting of a pour point depressant other than the component (a), an anti-wear agent or an extreme pressure agent other than the component (B), a friction modifier, an anti-corrosion agent other than the components (C) and (E), a metal deactivator other than the components (C) and (E), an anti-rust agent, an anti-emulsifier, an antifoaming agent, and a colorant.

As the pour point depressant other than the component (a), for example, a known pour point depressant such as a polymer which does not belong to the component (a) can be used without particular limitation. The lubricating oil composition may contain no pour point depressant, and when the lubricating oil composition contains a pour point depressant, the content thereof is preferably 1 mass% or less, more preferably 0.5 mass% or less, based on the total amount of the composition. When the content is not more than the above upper limit, the electrical insulation of the fresh oil can be improved, and the electrical insulation of the composition after oxidative deterioration can be further improved. The lower limit of the content is not particularly limited, and may be 0.1 mass% or more in one embodiment.

Examples of the anti-wear agent or the extreme pressure agent other than the component (B) include sulfur-containing compounds such as disulfides, olefin sulfides, oil and fat sulfides, and dithiocarbamate compounds, and phosphorus-containing anti-wear agents other than the component (B). Examples of the phosphorus-containing anti-wear agent other than the component (B) include phosphoric acid, thiophosphoric acid, dithiophosphoric acid, trithiophosphoric acid, and their full esters or partial esters; phosphorous acid, thiophosphoric acid, dithiophosphorous acid, trithiophosphorous acid, monoesters thereof, diesters thereof (excluding the substances represented by the general formula (1)) and triesters thereof. The lubricating oil composition may contain no wear preventive agent other than the component (B), and when the lubricating oil composition contains a wear preventive agent other than the component (B), the content thereof is preferably 10 mass% or less, more preferably 5 mass% or less, based on the total amount of the composition. When the content is not more than the above upper limit, the electrical insulation of the fresh oil can be improved, and the electrical insulation of the composition after oxidative deterioration can be further improved. The lower limit of the content is not particularly limited, and may be 1% by mass or more in one embodiment.

The lubricating oil composition may or may not contain a phosphorus-containing wear preventive agent other than the component (B), and the total phosphorus content in the lubricating oil composition is preferably 0.06% by mass or less. When the total phosphorus content in the lubricating oil composition is not more than the above upper limit, the electrical insulation properties of the fresh oil can be improved, and the electrical insulation properties of the composition after oxidative deterioration can be further improved. In one embodiment, the content of the phosphorus-containing anti-wear agent other than the component (B) in the lubricating oil composition is preferably 0.05% by mass or less, more preferably 0.03% by mass or less, and still more preferably 0.02% by mass or less in terms of phosphorus content, based on the total amount of the composition. When the content of the phosphorus-containing anti-wear agent other than the component (B) is not more than the above upper limit, the electrical insulation of the fresh oil can be improved, and the electrical insulation of the composition after oxidation degradation can be further improved.

As the friction modifier, for example, 1 or more friction modifiers selected from the group consisting of organic molybdenum compounds and ashless friction modifiers can be used. The lubricating oil composition may contain no friction modifier, and when the lubricating oil composition contains a friction modifier, the content thereof is preferably 2% by mass or less, more preferably 1% by mass or less, based on the total amount of the composition. When the content is not more than the above upper limit, the electrical insulation of the fresh oil can be improved, and the electrical insulation of the composition after oxidative deterioration can be further improved. The lower limit of the content is not particularly limited, and may be 0.01 mass% or more in one embodiment.

Examples of the organomolybdenum compound include sulfur-containing organomolybdenum compounds and organomolybdenum compounds containing no sulfur as a constituent element. As examples of the sulfur-containing organomolybdenum compound, molybdenum dithiocarbamate compounds; a molybdenum dithiophosphate compound; molybdenum compounds (for example, molybdic acids such as molybdenum oxide such as molybdenum dioxide and molybdenum trioxide, molybdic acids such as orthomolybdic acid, paramolybdic acid, and (poly) molybdic sulfide, metal salts and ammonium salts of these molybdic acids, molybdenum sulfides such as molybdenum disulfide, molybdenum trisulfide, molybdenum pentasulfide, and molybdenum polysulfide, molybdic sulfide, metal salts or amine salts of molybdic sulfide, and molybdenum halides such as molybdenum chloride) complex compounds with sulfur-containing organic compounds (for example, alkyl (thio) xanthates, thiadiazoles, mercaptothiadiazoles, thiocarbonates, tetrahydrocarbylthiurams disulfide, bis (di (thio) hydrocarbyl dithiophosphonate) disulfides, organic (poly) sulfides, sulfide esters, and the like) or other organic compounds); and sulfur-containing organic molybdenum compounds such as coordination compounds of sulfur-containing molybdenum compounds such as molybdenum sulfide and molybdic acid sulfide and alkenylsuccinimide. Wherein, the organic molybdenum compound can be a mononuclear molybdenum compound, and can also be a polynuclear molybdenum compound such as a dinuclear molybdenum compound or a trinuclear molybdenum compound. Examples of the organic molybdenum compound containing no sulfur as a constituent element include a molybdenum-amine complex, a molybdenum-succinimide complex, a molybdenum salt of an organic acid, a molybdenum salt of an alcohol, and the like.

The lubricating oil composition may contain or not contain a metal-containing additive (e.g., an organomolybdenum compound, zinc dialkyldithiophosphate, or the like) other than the metal-based detergent, and the total content of metal elements in the lubricating oil composition is preferably 0.03 mass% or less in terms of metal amount with respect to the total amount of the composition as a reference. When the total content of the metal elements in the lubricating oil composition is not more than the above upper limit, the electrical insulation properties of the fresh oil and the electrical insulation properties of the composition after oxidative deterioration can be further improved. In one embodiment, the total content of the metal-containing additive other than the metal-based detergent in the lubricating oil composition is preferably 0.010 mass% or less, more preferably 0.0075 mass% or less, and still more preferably 0.0050 mass% or less in terms of metal when the total amount of the composition is taken as a reference. When the total content of the metal-containing additive other than the metal-based detergent is not more than the above upper limit, the electrical insulation properties of the virgin oil and the electrical insulation properties of the composition after oxidative degradation can be further improved.

As the ashless friction modifier, a known oily friction modifier can be used without particular limitation. Examples of the ashless friction modifier include compounds having 6 to 50 carbon atoms containing 1 or more hetero elements selected from an oxygen atom, a nitrogen atom and a sulfur atom in the molecule. More specifically, an ashless friction modifier such as an aliphatic amine compound, an aliphatic imide compound, a fatty acid ester, an aliphatic amide, an aliphatic hydrazide, a metal salt of an aliphatic acid, an aliphatic alcohol, an aliphatic ether, and an aliphatic urea compound, which has an alkyl group or alkenyl group having at least 1 carbon atom number of 6 to 30, preferably a linear or branched alkyl group or alkenyl group having 6 to 30 carbon atoms in the molecule, can be preferably used.

As the anticorrosive agents other than the components (C) and (E), for example, known anticorrosive agents such as imidazole-based compounds can be used without particular limitation. The lubricating oil composition may contain no anticorrosive agent other than the components (C) and (E), and when the lubricating oil composition contains an anticorrosive agent other than the components (C) and (E), the content thereof is preferably 1 mass% or less, more preferably 0.5 mass% or less. When the content is not more than the above upper limit, the electrical insulation of the fresh oil can be improved, and the electrical insulation of the composition after oxidative deterioration can be further improved. The lower limit of the content is not particularly limited, and may be 0.01 mass% or more in one embodiment.

Examples of the metal deactivators other than the component (C) and the component (E) include, but are not particularly limited to, known metal deactivators such as imidazoline, pyrimidine derivatives, mercaptobenzothiazole, 2- (alkyldithio) benzimidazole, and β - (o-carboxybenzylthio) propionitrile. The lubricating oil composition may contain no metal deactivator other than the components (C) and (E), and when the lubricating oil composition contains a metal deactivator other than the components (C) and (E), the content thereof is preferably 1% by mass or less, more preferably 0.5% by mass or less. When the content is not more than the above upper limit, the electrical insulation of the fresh oil can be improved, and the electrical insulation of the composition after oxidative deterioration can be further improved. The lower limit of the content is not particularly limited, and may be 0.01 mass% or more in one embodiment.

As the rust inhibitor, for example, known rust inhibitors such as petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenylsuccinate, and polyol ester can be used without particular limitation. The lubricating oil composition may contain no rust inhibitor, and when the lubricating oil composition contains a rust inhibitor, the content thereof is preferably 1% by mass or less, more preferably 0.5% by mass or less. When the content is not more than the above upper limit, the electrical insulation of the fresh oil can be improved, and the electrical insulation of the composition after oxidative deterioration can be further improved. The lower limit of the content is not particularly limited, and may be 0.01 mass% or more in one embodiment.

As the anti-emulsifier, for example, a known anti-emulsifier such as a polyalkylene glycol nonionic surfactant such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, or polyoxyethylene alkyl naphthyl ether can be used without particular limitation. The lubricating oil composition may contain no demulsifier, and when the lubricating oil composition contains a demulsifier, the content thereof is preferably 5% by mass or less, more preferably 3% by mass or less. When the content is not more than the above upper limit, the electrical insulation of the fresh oil can be improved, and the electrical insulation of the composition after oxidative deterioration can be further improved. The lower limit of the content is not particularly limited, and may be 1% by mass or more in one embodiment.

As the defoaming agent, for example, known defoaming agents such as silicone, fluorinated alkyl ether, and the like can be used. The lubricating oil composition may contain no defoaming agent, and when the lubricating oil composition contains a defoaming agent, the content thereof is preferably 0.5% by mass or less, more preferably 0.1% by mass or less. When the content is not more than the above upper limit, the electrical insulation of the fresh oil can be improved, and the electrical insulation of the composition after oxidative deterioration can be further improved. The lower limit of the content is not particularly limited, and may be 0.0001% by mass or more in one embodiment.

As the colorant, for example, a known colorant such as an azo compound can be used.

< lubricating oil composition >

Operation of lubricating oil composition at 100 ℃The dynamic viscosity is 1.8-5.2 mm²And/s, in one embodiment, may be 2.8 to 5.2mm²And s. When the kinematic viscosity of the composition at 100 ℃ is not more than the above upper limit, the fuel economy can be improved. Further, when the kinematic viscosity at 100 ℃ of the composition is not less than the lower limit, the seizure resistance, the abrasion resistance, the fatigue resistance, the electrical insulation of the virgin oil, and the electrical insulation of the composition after the oxidative deterioration can be improved.

The kinematic viscosity of the lubricating oil composition at 40 ℃ is 4.0-20.0 mm²And/s, in one embodiment, may be 10.2 to 18.3mm²And s. When the kinematic viscosity of the composition at 40 ℃ is not more than the above upper limit, the fuel economy can be improved. Further, when the kinematic viscosity at 40 ℃ of the composition is not less than the lower limit, the seizure resistance, the abrasion resistance, the fatigue resistance, the electrical insulation of the virgin oil, and the electrical insulation of the composition after the oxidative deterioration can be improved.

The ratio [ S ]/[ P ] of the sulfur content [ S ] (unit: mass%) to the phosphorus content [ P ] (unit: mass%) in the lubricating oil composition is 2.2 to 4.0, and in one embodiment, may be 2.25 to 4.0. When the ratio [ S ]/[ P ] is not more than the above upper limit, seizure resistance, electrical insulation of the virgin oil, and electrical insulation of the composition after oxidative deterioration can be improved. Further, the ratio [ S ]/[ P ] is not less than the lower limit, whereby the seizure resistance and the copper corrosion resistance can be improved.

In one embodiment, the volume resistivity of the oxidation-degraded oil of the lubricating oil composition at 80 ℃ is preferably 1.0X 10⁹Omega cm or more. In the present specification, the volume resistivity of the oxidation-degraded oil is: an oxidized deteriorated oil obtained by subjecting a fresh oil to an Oxidation treatment at 165 ℃ for 150 hours by the ISOT method (Indiana Stirling Oxidation Test) defined in JIS K2514-1 was measured for volume resistivity at 80 ℃ in accordance with the volume resistivity Test defined in JIS C2101.

In one embodiment, the functional group is a group having a non-phenolic OH group (which may be part of another functional group (e.g., carboxyl group, phosphoric group, etc.)), or a salt thereof, > NH group, or-NH group₂A total content of compounds having a content of a group (hereinafter, also referred to as an "O/N-based active hydrogen-containing group") (hereinafter, also referred to as an "O/N-based active hydrogen-containing compound") not contributing to a poly (meth) acrylate (e.g., (a) component, etc.), a phosphite diester compound having no O/N-based active hydrogen-containing group in an alcohol residue (e.g., (B) component, etc.), a thiadiazole compound (component ((C)), a metal-based detergent (e.g., (D) component, a metal salicylate detergent, a metal sulfonate detergent, a metal phenate detergent, etc.), a benzotriazole or tolyltriazole compound ((E) component), a succinimide-based friction modifier ((F) component), and either an amine-based antioxidant or a phenol-based antioxidant ((G) component), based on the total amount of the lubricating oil composition, the total amount of the oxygen element and the nitrogen element is preferably 0 to 500 mass ppm, in one embodiment 0 to 300 mass ppm, and in another embodiment 0 to 150 mass ppm. Examples of such an O/N-based active hydrogen compound include: phosphoric acid (which may form salts) and partial esters thereof; phosphorous acid (which may form a salt) and partial esters thereof (wherein a phosphorous diester having an alcohol residue not having the above-mentioned O/N-based active hydrogen-containing group is not an O/N-based active hydrogen compound); nitrogen-containing oily agent-based friction modifiers having an N-H bond (for example, primary aliphatic amines, secondary aliphatic amines, primary fatty acid amides, secondary fatty acid amides, aliphatic ureas having an N-H bond, fatty acid hydrazides, etc.); nitrogen-containing oily agents having a hydroxyl group (e.g., amides of fatty acids and primary or secondary alkanolamines, amides of primary or secondary aliphatic amines and aliphatic hydroxy acids, etc.); nitrogen-containing oil-based friction modifiers having a carboxyl group (which can form a salt) (e.g., N-acylated amino acids); an oily agent-based friction modifier having a hydroxyl group (e.g., glycerol monooleate), an oily agent-based friction modifier having a carboxyl group (which may form a salt) (e.g., a fatty acid metal salt, etc.), and the like. In the case where both of oxygen and nitrogen are contained in one O/N-based active hydrogen compound, both of the oxygen element amount and the nitrogen element amount from the compound contribute regardless of whether each oxygen atom of the compound is bonded to a hydrogen atom or not and whether each nitrogen atom of the compound is bonded to a hydrogen atom or notThe total content (total amount of oxygen and nitrogen) of the O/N active hydrogen compound. When the total content of the O/N-based active hydrogen compound is not more than the upper limit value, the electrical insulation properties of the new oil can be improved, and the electrical insulation properties of the oxidation-degraded oil can be further improved.

(use)

The lubricating oil composition of the present invention has the electrical insulation properties, seizure resistance, copper corrosion resistance and fatigue resistance of the composition after oxidative degradation in a good balance, and therefore can be preferably used as a motor oil, a transmission oil, a common lubricating oil for a motor and a transmission (gear mechanism), or a lubricating oil for an electric drive unit having a motor and a transmission (gear mechanism). In one embodiment, the lubricating oil composition of the present invention can be preferably used for lubrication of an electric motor in an automobile having the electric motor, or lubrication of an electric motor and a transmission (gear mechanism) in an automobile having the electric motor and the transmission.