EP4310165A1

EP4310165A1 - Lubricant composition

Info

Publication number: EP4310165A1
Application number: EP22771032.4A
Authority: EP
Inventors: Masaya Kubota; Kenji Sunahara
Original assignee: Idemitsu Kosan Co Ltd
Current assignee: Idemitsu Kosan Co Ltd
Priority date: 2021-03-17
Filing date: 2022-02-24
Publication date: 2024-01-24
Also published as: JP7104200B1; CN116997640A; WO2022196274A1; JP2022143333A

Abstract

An object is to provide a lubricating oil composition having excellent low-temperature storage stability, excellent copper corrosion resistance, and a high fuel efficiency. Then, this object is achieved by using a lubricating oil composition containing a base oil (A), a molybdenum-based friction modifier (B), and a benzotriazole-based compound (C). The molybdenum-based friction modifier (B) contains a specific compound (B1), a content of the benzotriazole-based compound (C) is 0.03 mass% or less based on a total amount of the lubricating oil composition, and a kinematic viscosity at 100°C of the lubricating oil composition is 9.3 mm<sup>2</sup>/s or less.

Description

Technical Field

The present invention relates to a lubricating oil composition.

Background Art

In recent years, a lubricating oil composition used in an internal combustion engine such as an engine is required to have a further improved fuel efficiency. Therefore, along with efforts to reduce a viscosity of the lubricating oil composition, a research on a molybdenum-based friction modifier is also progressing from the viewpoint of exhibiting a higher friction reducing effect.
A friction reducing effect achieved by the molybdenum-based friction modifier such as molybdenum dithiocarbamate (hereinafter, also referred to as "MoDTC") has been known in the related art (for example, see PTL 1). In addition, PTL 2 proposes MoDTC having excellent oil solubility represented by the following general formula (1).
In the above general formula (1), R₁ to R₄ are isoalkyl groups each having C₁₁ to C₁₄. X represents an oxygen atom and/or a sulfur atom. R₁ to R₄ contain on average more than 98% of C₁₃.
PTL 2 also discloses that a lubricating oil composition prepared by blending MoDTC represented by the above general formula (1) has excellent storage stability at a low temperature (hereinafter, also referred to as "low-temperature storage stability").
At a low temperature, when cloudiness or precipitation due to the molybdenum-based friction modifier such as MoDTC occurs in the lubricating oil composition, an oil filter is clogged and the friction reducing effect based on the molybdenum-based friction modifier is lost. Therefore, it is extremely important to improve the low-temperature storage stability of the lubricating oil composition.

Citation List

Patent Literature

PTL 1: JP H07-150173 A
PTL 2: JP 2014-514407 T

Summary of Invention

Technical Problem

However, the lubricating oil composition prepared by blending MoDTC proposed in PTL 2 has excellent low-temperature storage stability, but has poor copper corrosion resistance. The lubricating oil composition having poor copper corrosion resistance has a problem that deterioration is accelerated due to copper elution into the oil caused by corrosion of a copper-based member used in the internal combustion engine such as an engine. Therefore, the lubricating oil composition is required to have excellent copper corrosion resistance in addition to excellent low-temperature storage stability.
In addition, the lubricating oil composition is required to be further improved in fuel efficiency.
Accordingly, an object of the present invention is to provide a lubricating oil composition having excellent low-temperature storage stability, excellent copper corrosion resistance, and a high fuel efficiency.
In the description herein, the "copper corrosion resistance" means that even when the copper-based members are corroded, the copper elution into the oil is unlikely to occur.

Solution to Problem

The present inventors have conducted diligent studies in order to solve the above problems. As a result, it is found that a lubricating oil composition containing a specific molybdenum-based friction modifier and a specific amount of a benzotriazole-based compound can solve the above problems, and various studies have been further repeated, and thus the present invention has been completed.
That is, the present invention relates to the following [1] to [3],

[1] A lubricating oil composition containing: a base oil (A); a molybdenum-based friction modifier (B); and a benzotriazole-based compound (C), in which
- the molybdenum-based friction modifier (B) contains a compound (B1) represented by the following general formula (b1):
- wherein R¹, R², R³, and R⁴ each independently represent a short-chain substituent group (α) which is an aliphatic hydrocarbon group having 4 to 12 carbon atoms or a long-chain substituent group (β) which is an aliphatic hydrocarbon group having 13 to 22 carbon atoms; a molar ratio [(α)/(β)] of the short-chain substituent group (α) to the long-chain substituent group (β) in all molecules of the compound (B1) is 0.10 to 0.50; and X¹, X², X³, and X⁴ each independently represent an oxygen atom or a sulfur atom,
- a content of the benzotriazole-based compound (C) is 0.03 mass% or less based on a total amount of the lubricating oil composition, and
- a kinematic viscosity at 100°C of the lubricating oil composition is 9.3 mm²/s or less.
[2] A method of using the lubricating oil composition according to the above [1] in an internal combustion engine.
[3] A method for producing a lubricating oil composition, including: a step of mixing a base oil (A), a molybdenum-based friction modifier (B), and a benzotriazole-based compound (C), in which
- the molybdenum-based friction modifier (B) contains a compound (B1) represented by the following general formula (b1):
- wherein R¹, R², R³, and R⁴ each independently represent a short-chain substituent group (α) which is an aliphatic hydrocarbon group having 4 to 12 carbon atoms or a long-chain substituent group (β) which is an aliphatic hydrocarbon group having 13 to 22 carbon atoms; a molar ratio [(α)/(β)] of the short-chain substituent group (α) to the long-chain substituent group (β) in all molecules of the compound (B1) is 0.10 to 0.50; and X¹, X², X³, and X⁴ each independently represent an oxygen atom or a sulfur atom,
- in the step, a content of the benzotriazole-based compound (C) is adjusted to be 0.03 mass% or less based on a total amount of the lubricating oil composition, and
- in the step, a kinematic viscosity at 100°C of the lubricating oil composition is adjusted to be 9.3 mm²/s or less.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a lubricating oil composition having excellent low-temperature storage stability, excellent copper corrosion resistance, and a high fuel efficiency.

Description of Embodiments

Upper limit values and lower limit values of numerical ranges described in the description herein can be freely combined as desired. For example, when "A to B" and "C to D" are described as numerical ranges, the numerical ranges "A to D" and "C to B" are also included in the scope of the present invention.
In addition, the numerical ranges "lower limit value to upper limit value" described in the description herein means the lower limit value or more to the upper limit value or less, unless otherwise specified.
In addition, in the description herein, numerical values in Examples are numerical values that can each be used as an upper limit value or a lower limit value.

[Aspect of Lubricating Oil Composition]

A lubricating oil composition according to the present embodiment contains a base oil (A), a molybdenum-based friction modifier (B), and a benzotriazole-based compound (C).
In the lubricating oil composition according to the present embodiment, the molybdenum-based friction modifier (B) contains a compound (B1) represented by the following general formula (b1).
In the general formula (b1), R¹, R², R³, and R⁴ each independently represent a short-chain substituent group (α) which is an aliphatic hydrocarbon group having 4 to 12 carbon atoms or a long-chain substituent group (β) which is an aliphatic hydrocarbon group having 13 to 22 carbon atoms. A molar ratio [(α)/(β)] of the short-chain substituent group (α) to the long-chain substituent group (β) in all molecules of the compound (B1) is 0.10 to 0.50. In addition, in the above general formula (b1), X¹, X², X³, and X⁴ each independently represent an oxygen atom or a sulfur atom.
In the lubricating oil composition according to the present embodiment, a content of the benzotriazole-based compound (C) is 0.03 mass% or less based on a total amount of the lubricating oil composition.
A kinematic viscosity at 100°C of the lubricating oil composition according to the present embodiment is 9.3 mm²/s or less.
The present inventors have conducted diligent studies in order to solve the above problems.
First, a lubricating oil composition prepared by blending a compound represented by the general formula (b1), in which R¹, R², R³, and R⁴ are each an alkyl group having 13 carbon atoms, the short-chain substituent group (α) is substantially not contained and only the long-chain substituent group (β) is substantially contained, has been investigated. As a result, it has been found that the lubricating oil composition has good low-temperature storage stability, but has poor copper corrosion resistance.
Therefore, a lubricating oil composition prepared by blending a benzotriazole-based compound as a metal deactivator in addition to this compound has been investigated. However, sufficient improvement in copper corrosion resistance is not achieved.
Then, a lubricating oil composition prepared by blending a compound represented by the general formula (b1), in which R¹, R², R³, and R⁴ are each an alkyl groups having 8 carbon atoms, the long-chain substituent group (β) is substantially not contained and only the short-chain substituent group (α) is substantially contained, has been investigated. As a result, it has been found that the lubricating oil composition has good copper corrosion resistance, but has poor low-temperature storage stability.
The present inventors have further conducted various studies based on the above study results. As a result, it has been found that the molar ratio of the short-chain substituent group (α) and the long-chain substituent group (β) in the compound (B1) represented by the general formula (b1) and the content of the benzotriazole-based compound in the lubricating oil composition are important in solving the above problems, and then various studies are repeated to complete the present invention.
In the following descriptions, the "base oil (A)", the "molybdenum-based friction modifier (B)", and the "benzotriazole-based compound (C)" are also referred to as a "component (A)", a "component (B)", and a "component (C)", respectively.
In the lubricating oil composition according to the present embodiment, a total content of the component (A), the component (B), and the component (C) is preferably 80 mass% or more, more preferably 85 mass% or more, and still more preferably 88 mass% or more, based on the total amount of the lubricating oil composition.
In the lubricating oil composition according to the present embodiment, an upper limit value of the total content of the component (A), the component (B), and the component (C) may be adjusted in relation to lubricating oil additives other than the component (A), the component (B), and the component (C), and is usually less than 100 mass%, preferably 99 mass% or less, more preferably 97 mass% or less, and still more preferably 95 mass% or less.
Upper limit values and lower limit values of these numerical ranges can be freely combined as desired. Specifically, the total content of the component (A), the component (B), and the component (C) is preferably 80 mass% to less than 100 mass%, more preferably 85 mass% to 99 mass% or less, still more preferably 88 mass% to 97 mass%, and even more preferably 88 mass% to 95 mass%.
Hereinafter, each component contained in the lubricating oil composition according to the present embodiment will be described in detail.

The lubricating oil composition according to the present embodiment contains the base oil (A).
As the base oil (A), one or more selected from a mineral oil and a synthetic oil used in the related art as base oils for lubricating oils can be used without particular limitation.
Examples of the mineral oil include: an atmospheric residual oil obtained by distilling a crude oil, such as a paraffin-based crude oil, an intermediate-base crude oil, or a naphthene-based crude oil, under an atmospheric pressure; a distillate oil obtained by distilling the atmospheric residual oil under a reduced pressure; and a mineral oil obtained by subjecting this distillate oil to one or more of solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, and the like.
Examples of the synthetic oil include: a poly-α-olefin such as an α-olefin homopolymer and an α-olefin copolymer (for example, an α-olefin copolymer having 8 to 14 carbon atoms, such as an ethylene-α-olefin copolymer); an isoparaffin; various esters such as a polyol ester and a dibasic acid ester; various ethers such as a polyphenyl ether; a polyalkylene glycol; an alkylbenzene; an alkylnaphthalene; and a gas-to-liquid (GTL) base oil obtained by isomerizing a wax (GTL wax) produced from a natural gas by a Fischer-Tropsch method or the like.
The base oil (A) is preferably a base oil classified as Group 2, 3, or 4 of the base oil category according to American Petroleum Institute (API).
As the base oil (A), a mineral oil can be used alone or a plurality of mineral oils can be used in combination, or a synthetic oil can be used alone or a plurality of synthetic oils can be used in combination. In addition, one or more mineral oils and one or more synthetic oils can be used in combination.
A kinematic viscosity at 100°C of the base oil (A) is preferably 2.0 mm²/s to 9.0 mm²/s, more preferably 3.0 mm²/s to 7.0 mm²/s, and still more preferably 4.0 mm²/s to 4.5 mm²/s.
When the kinematic viscosity at 100°C of the base oil (A) is 2.0 mm²/s or more, an evaporation loss of the lubricating oil composition is easily reduced.
In addition, when the kinematic viscosity at 100°C of the base oil (A) is 9.0 mm²/s or less, a power loss due to viscosity resistance of the lubricating oil composition can be easily reduced to achieve an effect of fuel efficiency improvement.
A viscosity index of the base oil (A) is preferably 80 or more, more preferably 90 or more, still more preferably 100 or more, and even more preferably 120 or more, from the viewpoint of a reduction in viscosity change due to a temperature change and improvement in fuel efficiency. In addition, the viscosity index is usually 200 or less.
When the base oil (A) is a mixed base oil containing two or more kinds of base oils, the kinematic viscosity at 100°C and the viscosity index of this mixed base oil are preferably within the above ranges.
In the present embodiment, the kinematic viscosity at 100°C and the viscosity index are values measured or calculated in accordance with JIS K2283:2000.
In the lubricating oil composition according to the present embodiment, from the viewpoint of easily and sufficiently securing amounts of the molybdenum-based friction modifier (B) and the benzotriazole-based compound (C) to be used, a content of the base oil (A) is preferably 97 mass% or less, more preferably 95 mass% or less, and still more preferably 93 mass% or less, based on the total amount of the lubricating oil composition. In addition, from the viewpoint of more easily exhibiting the effects of the present invention, the content of the base oil (A) is preferably 75 mass% or more, more preferably 80 mass% or more, and still more preferably 85 mass% or more, based on the total amount of the lubricating oil composition.
Upper limit values and lower limit values of these numerical ranges can be freely combined as desired. Specifically, the content of the base oil (A) is preferably 75 mass% to 97 mass%, more preferably 80 mass% to 95 mass%, and still more preferably 85 mass% to 93 mass%.

<Molybdenum-based Friction Modifier (B)>

The lubricating oil composition according to the present embodiment contains the molybdenum-based friction modifier (B).
The molybdenum-based friction modifier (B) contains a compound (B1) represented by the following general formula (b 1).
In the general formula (b1), R¹, R², R³, and R⁴ each independently represent a short-chain substituent group (α) which is an aliphatic hydrocarbon group having 4 to 12 carbon atoms or a long-chain substituent group (β) which is an aliphatic hydrocarbon group having 13 to 22 carbon atoms. A molar ratio [(α)/(β)] of the short-chain substituent group (α) to the long-chain substituent group (β) in all molecules of the compound (B1) is 0.10 to 0.50. In addition, in the above general formula (b1), X¹, X², X³, and X⁴ each independently represent an oxygen atom or a sulfur atom.
Examples of the aliphatic hydrocarbon group having 4 to 12 carbon atoms, which can be selected as the short-chain substituent group (α), include an alkyl group having 4 to 12 carbon atoms and an alkenyl group having 4 to 12 carbon atoms.
Specific examples thereof include a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, an undecenyl group, and a dodecenyl group. These may be linear or branched.
From the viewpoint of more easily exhibiting the effects of the present invention, the number of carbon atoms in the aliphatic hydrocarbon group that can be selected as the short-chain substituent group (α) is preferably 5 to 11, more preferably 6 to 10, and still more preferably 7 to 9.
Examples of the aliphatic hydrocarbon group having 13 to 22 carbon atoms, which can be selected as the long-chain substituent group (β), include an alkyl group having 13 to 22 carbon atoms and an alkenyl group having 13 to 22 carbon atoms.
Specific examples thereof include a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, an eicosyl group, a heneicosyl group, a docosyl group, a tridecenyl group, a tetradecenyl group, a pentadecenyl group, a hexadecenyl group, a heptadecenyl group, an octadecenyl group, an oleyl group, a nonadecenyl group, an icosenyl group, a heneicosenyl group, and a docosenyl group. These may be linear or branched.
From the viewpoint of more easily exhibiting the effects of the present invention, the number of carbon atoms in the aliphatic hydrocarbon group that can be selected as the long-chain substituent group (β) is preferably 13 to 20, more preferably 13 to 16, and still more preferably 13 to 14.
Here, the molar ratio [(α)/(β)] of the short-chain substituent group (α) to the long-chain substituent group (β) in all molecules of the compound (B1) represented by the general formula (b1) should be 0.10 and 0.50 as described above. When the molar ratio [(α)/(β)] is less than 0.10, the copper corrosion resistance is poor. In addition, the fuel efficiency tends to be easily degraded. When the molar ratio [(α)/(β)] is more than 0.50, the low-temperature storage stability is poor.
Here, from the viewpoint of more easily exhibiting the copper corrosion resistance and the viewpoint of more easily improving the fuel efficiency, the molar ratio [(α)/(β)] is preferably 0.15 or more, and more preferably 0.20 or more. In addition, from the viewpoint of more easily exhibiting the low-temperature storage stability, the molar ratio [(α)/(β)] is preferably 0.45 or less, more preferably 0.42 or less, and still more preferably 0.40 or less.
Upper limit values and lower limit values of these numerical ranges can be freely combined. Specifically, the molar ratio [(α)/(β)] is preferably 0.15 to 0.45, more preferably 0.20 to 0.42, and still more preferably 0.20 to 0.40.
Here, the short-chain substituent group (α) and the long-chain substituent group (β) may coexist in the same molecule or may not coexist in the same molecule. That is, an average value of the molar ratio [(α)/(β)] of the short-chain substituent group (α) to the long-chain substituent group (β) in all molecules of the compound (B1) represented by the general formula (b1) may be in the range of 0.10 to 0.50.
Therefore, the compound (B1) may contain a molecular group (B 1-1) in which R¹, R², R³, and R⁴ are all the short-chain substituent groups (α) in the general formula (b1), or may contain a molecular group (B1-2) in which R¹, R², R³, and R⁴ are all the long-chain substituent groups (β), or may contain a molecular group (B1-3) in which part of R¹, R², R³, and R⁴ is the short-chain substituent group (α) and the balance is the long-chain substituent group (β).
Here, from the viewpoint of more easily exhibiting the effects of the present invention, the compound (B1) preferably contains the molecular group (B1-3) in which part of R¹, R², R³, and R⁴ is the short-chain substituent group (α) and the balance is the long-chain substituent group (β).
The molar ratio [(α)/(β)] of the short-chain substituent group (α) to the long-chain substituent group (β) in the molecular group (B1-3) is preferably 0.3 or more, more preferably 0.5 or more, and still more preferably 0.8 or more. In addition, the molar ratio [(α)/(β)] is preferably 3.0 or less, more preferably 2.0 or less, and still more preferably 1.5 or less. Upper limit values and lower limit values of these numerical ranges can be freely combined. Specifically, the molar ratio [(α)/(β)] is preferably 0.3 to 3.0, more preferably 0.5 to 2.0, and still more preferably 0.8 to 1.5.
A content of the molecular group (B1-3) in the compound (B1) is preferably 10 mol% or more, more preferably 15 mol% or more, and still more preferably 20 mol% or more, based on the total amount of the compound (B1). In addition, the content of the molecular group (B1-3) in the compound (B1) is preferably 40 mol% or less, more preferably 35 mol% or less, and still more preferably 30 mol% or less. Upper limit values and lower limit values of these numerical ranges can be freely combined. Specifically, the content of the molecular group (B1-3) in the compound (B1) is preferably 10 mol% to 40 mol%, more preferably 15 mol% to 35 mol%, and still more preferably 20 mol% to 30 mol%.
In addition, from the viewpoint of more easily exhibiting the effects of the present invention, it is preferable that, in addition to the molecular group (B 1-3), the compound (B 1) further contains the molecular group (B 1-2) in which R¹, R², R³, and R⁴ are all the long-chain substituent groups (β).
A content of the molecular group (B 1-2) in the compound (B 1) is preferably 50 mol% or more, more preferably 55 mol% or more, and still more preferably 60 mol% or more, based on the total amount of the compound (B1). In addition, the content of the molecular group (B 1-2) in the compound (B 1) is preferably 75 mol% or less, more preferably 70 mol% or less, and still more preferably 65 mol% or less. Upper limit values and lower limit values of these numerical ranges can be freely combined. Specifically, the content of the molecular group (B1-2) in the compound (B1) is preferably 50 mol% to 75 mol%, more preferably 55 mol% to 70 mol%, and still more preferably 60 mol% to 65 mol%.
A total content of the molecular group (B 1-2) and the molecular group (B 1-3) in the compound (B1) is preferably 80 mol% or more, and more preferably 85 mol% or more, based on the total amount of the compound (B1). In addition, the total content of the molecular group (B1-2) and the molecular group (B1-3) in the compound (B1) is preferably 100 mol% or less, more preferably 95 mol% or less, and still more preferably 90 mol% or less. Upper limit values and lower limit values of these numerical ranges can be freely combined. Specifically, the total content of the molecular group (B1-2) and the molecular group (B1-3) in the compound (B1) is preferably 80 mol% to 100 mol%, more preferably 85 mol% to 95 mol%, and still more preferably 85 mol% to 90 mol%.
In the lubricating oil composition according to the present embodiment, from the viewpoint of more easily exhibiting the effects of the present invention, a content of the compound (B1) in the molybdenum-based friction modifier (B) is preferably 80 mass% to 100 mass%, more preferably 90 mass% to 100 mass%, and still more preferably 95 mass% to 100 mass%, based on the total amount of the molybdenum-based friction modifier (B).
In the lubricating oil composition according to the present embodiment, from the viewpoint of more easily exhibiting the effects of the present invention, a content of the molybdenum-based friction modifier (B) is preferably 0.30 mass% or more, more preferably 0.40 mass% or more, still more preferably 0.50 mass% or more, and even more preferably 0.60 mass% or more, based on the total amount of the lubricating oil composition. In addition, the content of the molybdenum-based friction modifier (B) is preferably 1.50 mass% or less, more preferably 1.25 mass% or less, and still more preferably 1.00 mass% or less.
Upper limit values and lower limit values of these numerical ranges can be freely combined. Specifically, the content of the molybdenum-based friction modifier (B) is preferably 0.30 mass% to 1.50 mass%, more preferably 0.40 mass% to 1.25 mass%, still more preferably 0.50 mass% to 1.00 mass%, and even more preferably 0.60 mass% to 1.00 mass%.
In the lubricating oil composition according to the present embodiment, from the viewpoint of more easily exhibiting the effects of the present invention, a content of molybdenum atoms derived from the molybdenum-based friction modifier (B) is preferably 0.04 mass% or more, more preferably 0.05 mass% or more, still more preferably 0.06 mass% or more, and even more preferably 0.07 mass% or more, based on the total amount of the lubricating oil composition. In addition, the content of molybdenum atoms derived from the molybdenum-based friction modifier (B) is preferably 0.18 mass% or less, more preferably 0.15 mass% or less, and still more preferably 0.12 mass% or less.
Upper limit values and lower limit values of these numerical ranges can be freely combined. Specifically, the content of molybdenum atoms derived from the molybdenum-based friction modifier (B) is preferably 0.04 mass% to 0.18 mass%, more preferably 0.05 mass% to 0.15 mass%, still more preferably 0.06 mass% to 0.12 mass%, and even more preferably 0.07 mass% to 0.12 mass%.

<Benzotriazole-based Compound (C)>

The lubricating oil composition according to the present embodiment contains the benzotriazole-based compound (C).
When the lubricating oil composition does not contain the benzotriazole-based compound (C), the lubricating oil composition is poor in copper corrosion resistance.
In addition, in the lubricating oil composition according to the present embodiment, the content of the benzotriazole-based compound (C) should be 0.03 mass% or less based on the total amount of the lubricating oil composition. When the content of the benzotriazole-based compound (C) is more than 0.03 mass% based on the total amount of the lubricating oil composition, the effect of improving the fuel efficiency of the lubricating oil composition is not exhibited.
Here, in the present embodiment, from the viewpoint of more easily exhibiting the effect of improving the fuel efficiency of the lubricating oil composition, the content of the benzotriazole-based compound (C) is preferably 0.02 mass% or less, and more preferably 0.015 mass% or less, based on the total amount of the lubricating oil composition. In addition, from the viewpoint of more easily improving the copper corrosion resistance, the content of the benzotriazole-based compound (C) is preferably 0.003 mass% or more, and more preferably 0.005 mass% or more, based on the total amount of the lubricating oil composition.
Upper limit values and lower limit values of these numerical ranges can be freely combined. Specifically, the content of the benzotriazole-based compound (C) is preferably 0.003 mass% to 0.02 mass%, and more preferably 0.005 mass% to 0.015 mass%.
As the benzotriazole-based compound (C), one or more kinds selected from benzotriazole-based compounds used in the related art as a metal deactivator can be used without particular limitation.
Here, in the present embodiment, from the viewpoint of more easily exhibiting the effects of the present invention, the benzotriazole-based compound (C) preferably contains a compound (C1) represented by the following general formula (c1).
In the general formula (c1), R^c1 is an alkyl group having 1 to 4 carbon atoms. This alkyl group may be linear or branched. Here, from the viewpoint of more easily exhibiting the effects of the present invention, the number of carbon atoms in this alkyl group is preferably 1 to 3, more preferably 1 to 2, and still more preferably 1.
In the general formula (c1), p is an integer of 0 to 4. When multiple R^c1's are present (that is, when p is an integer of 2 to 4), the multiple R^c1's may be same as or different from each other. Here, from the viewpoint of more easily exhibiting the effects of the present invention, p is preferably 0 to 3, more preferably 0 to 2, and still more preferably 1.
In the general formula (c1), R^c2 is a methylene group or an ethylene group. Here, from the viewpoint of more easily exhibiting the effects of the present invention, R^c2 is preferably a methylene group.
In the general formula (c1), R^c3 and R^c4 are each independently a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. This alkyl group may be linear or branched, and is preferably branched from the viewpoint of more easily exhibiting the effects of the present invention. In addition, from the viewpoint of more easily exhibiting the effects of the present invention, the number of carbon atoms in the alkyl group is preferably 2 to 14, more preferably 4 to 12, and still more preferably 6 to 10.
Here, from the viewpoint of more easily exhibiting the effects of the present invention, a content of the compound (C 1) in the benzotriazole-based compound (C) is preferably 50 mass% to 100 mass%, more preferably 60 mass% to 100 mass%, still more preferably 70 mass% to 100 mass%, even more preferably 80 mass% to 100 mass%, yet still more preferably 90 mass% to 100 mass%, and still even more preferably 95 mass% to 100 mass%, based on the total amount of the benzotriazole-based compound (C).

In the lubricating oil composition according to the present embodiment, from the viewpoint of more easily exhibiting the effects of the present invention, a content ratio [(B)/(C)] of the molybdenum-based friction modifier (B) to the benzotriazole-based compound (C) is, in mass ratio, preferably 20 or more, more preferably 30 or more, still more preferably 40 or more, even more preferably 50 or more, and yet still more preferably 60 or more. In addition, the content ratio [(B)/(C)] is preferably 120 or less, more preferably 110 or less, still more preferably 100 or less, even more preferably 90 or less, and yet still more preferably 80 or less. Upper limit values and lower limit values of these numerical ranges can be freely combined. Specifically, the content ratio [(B)/(C)] is preferably 20 to 120, more preferably 30 to 110, still more preferably 40 to 100, even more preferably 50 to 90, and yet still more preferably 60 to 80.

The lubricating oil composition according to the present embodiment may contain lubricating oil additives other than the components (B) and (C) within the range that does not impair the effects of the present invention.
Examples of the other lubricating oil additives include a viscosity index improver, a pour point depressant, a metal-based detergent, an ashless dispersant, an antioxidant, an anti-wear agent, an extreme pressure agent, a rust inhibitor, an anti-foaming agent, a demulsifier, a dissolution aid, and an ash-free friction modifier, and the viscosity index improver, the pour point depressant, the metal-based detergent, the ashless dispersant, the antioxidant, the anti-wear agent, and the extreme pressure agent are preferred.
These lubricating oil additives can be used alone or may be used in combination of two or more thereof.
Each content of these lubricating oil additives can be appropriately adjusted within the range that does not impair the effects of the present invention, and is independently usually 0.001 mass% to 15 mass%, preferably 0.005 mass% to 10 mass%, more preferably 0.01 mass% to 8 mass%, and still more preferably 0.1 mass% to 6 mass%, based on the total amount (100 mass%) of the lubricating oil composition.

(Viscosity Index Improver)

The lubricating oil composition according to the present embodiment may or may not contain a viscosity index improver.
Examples of the viscosity index improver include: a PMA-based viscosity index improver such as a non-dispersed polyalkyl (meth)acrylate and a dispersed polyalkyl (meth)acrylate; an OCP-based viscosity index improver such as an olefin-based copolymer (for example, an ethylene-propylene copolymer) and a dispersed olefin-based copolymer; and a styrene-based copolymer (for example, a styrene-diene copolymer and a styrene-isoprene copolymer).
In the description herein, the "(meth)acrylate" means acrylate or methacrylate.
A mass average molecular weight (Mw) of the viscosity index improver is preferably 5,000 or more to 1,500,000 or less. In a case of a PMA-based viscosity index improver, the mass average molecular weight (Mw) is preferably 20,000 or more and more preferably 100,000 or more, and is preferably 1,000,000 or less and more preferably 800,000 or less. In addition, in a case of an OCP-based viscosity index improver, the mass average molecular weight (Mw) is preferably 10,000 or more and more preferably 20,000 or more, and is preferably 800,000 or less and more preferably 500,000 or less.
The mass average molecular weight (Mw) of each component is a value in terms of standard polystyrene measured by gel permeation chromatography (GPC).
A structure of the viscosity index improver may be linear or branched. In addition, the viscosity index improver may be a polymer having a specific structure, such as a comb polymer that has a structure having, on the main chain, a large number of trifurcation points, from each of which a high-molecular weight side chain is started, and a star polymer that is a type of branched polymer and that has a structure having three or more linear polymer chains bonded at one point.
The viscosity index improver may be used alone or may be used in combination of two or more thereof.
In addition, the viscosity index improver contains, for example, the above-mentioned polymer as a resin component, and in consideration of the handling properties and the solubility in the above-mentioned base oil, the viscosity index improver is usually commercially available in a form of a solution obtained by diluting a polymer-containing resin component with a diluent such as a mineral oil.
When the lubricating oil composition according to the present embodiment contains a viscosity index improver, a content of the viscosity index improver in terms of a resin component is preferably 0.1 mass% to 2.6 mass%, more preferably 0.2 mass% to 1.0 mass%, and still more preferably 0.3 mass% to 0.7 mass%, based on the total amount of the lubricating oil composition.

(Pour Point Depressant)

The lubricating oil composition according to the present embodiment preferably contains a pour point depressant.
Examples of the pour point depressant include an ethylene-vinyl acetate copolymer, a condensate of chlorinated paraffin and naphthalene, a condensate of chlorinated paraffin and phenol, a polymethacrylate-based pour point depressant (PMA-based pour point depressant, such as a polyalkyl (meth)acrylate), polyvinyl acetate, polybutene, and polyalkylstyrene. The polymethacrylate-based pour point depressant is preferably used.
These pour point depressants may be used alone or may be used in combination of two or more thereof.
When the lubricating oil composition according to the present embodiment contains a pour point depressant, a content of the pour point depressant in terms of a resin component is preferably 0.01 mass% to 0.12 mass%, more preferably 0.03 mass% to 0.09 mass%, and still more preferably 0.05 mass% to 0.07 mass%, based on the total amount of the lubricating oil composition.

(Metal-based Detergent)

The lubricating oil composition according to the present embodiment preferably contains a metal-based detergent. When the lubricating oil composition contains the metal-based detergent, the formation of deposits inside the engine during high-temperature operation can be reduced and sludge accumulation can be prevented to keep the engine clean, acidic substances caused by engine oil deterioration and the like can be neutralized, and corrosion and wear can be prevented.
Examples of the metal-based detergent include an organic acid metal salt compound containing a metal atom selected from an alkali metal and an alkaline earth metal, and specific examples thereof include a metal salicylate, a metal phenate, and a metal sulfonate each containing a metal atom selected from an alkali metal and an alkaline earth metal.
In the description herein, the "alkali metal" means sodium and potassium.
In addition, the "alkaline earth metal" means magnesium, calcium, strontium, and barium.
From the viewpoint of improving the detergency at a high temperature, the metal atom contained in the metal-based detergent is preferably an alkaline earth metal, and among the alkaline earth metal, the metal atom is preferably magnesium and calcium, and more preferably calcium.
The metal salicylate is preferably a compound represented by the following general formula (d1-1), the metal phenate is preferably a compound represented by the following general formula (d1-2), and the metal sulfonate is preferably a compound represented by the general formula (d1-3).
In the general formulae (d1-1) to (d1-3), M is a metal atom selected from an alkali metal and an alkaline earth metal, and is preferably an alkaline earth metal, and more preferably magnesium or calcium.
M^E is an alkaline earth metal, and preferably magnesium or calcium.
p is a valence number of M and is 1 or 2. R^d1's are each independently a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms.
q is an integer of 0 or more, preferably an integer of 0 to 3, and more preferably 1 or 2.
Examples of the hydrocarbon group which can be selected as R^d1 include an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 18 ring carbon atoms, an aryl group having 6 to 18 ring carbon atoms, an alkylaryl group having 7 to 18 carbon atoms, and an arylalkyl group having 7 to 18 carbon atoms.
In the present embodiment, the metal-based detergent may be used alone or may be used in combination of two or more thereof. From the viewpoint of improving the detergency at a high temperature and the like the viewpoint of the solubility in a base oil and the like, the metal-based detergent is preferably one or more selected from alkaline earth metal sulfonates, more preferably one or more selected from magnesium sulfonate and calcium sulfonate, and still more preferably calcium sulfonate.
In the present embodiment, the metal-based detergent may be any of a neutral salt, a basic salt, an overbased salt, and a mixture thereof.
A base number of the metal-based detergent is preferably 0 mgKOH/g to 600 mgKOH/g.
Here, in the present embodiment, the metal-based detergent may be neutral, basic, or overbased, and is preferably basic or overbased, and more preferably overbased, from the viewpoint of improving the detergency of the lubricating oil composition. When the metal-based detergent is overbased, the base number is preferably 150 mgKOH/g or more, more preferably 200 mgKOH/g or more, and still more preferably 250 mgKOH/g or more. In addition, the base number is preferably 600 mgKOH/g or less, more preferably 500 mgKOH/g or less, and still more preferably 450 mgKOH/g or less. Upper limit values and lower limit values of these numerical ranges can be freely combined. Specifically, the base number is preferably 150 mgKOH/g to 600 mgKOH/g, more preferably 200 mgKOH/g to 500 mgKOH/g, and still more preferably 250 mgKOH/g to 450 mgKOH/g.
In the description herein, the "base number" means a value measured by a potentiometric titration method (base number/perchloric acid method) in accordance with JIS K2501:2003-9.
When the lubricating oil composition according to the present embodiment contains a metal-based detergent, a content of the metal atoms (alkali metal atom and alkaline earth metal atom) derived from the metal-based detergent is preferably 750 ppm by mass to 4,000 ppm by mass, more preferably 1,100 ppm by mass to 3,000 ppm by mass, and still more preferably 1,500 ppm by mass to 2,000 ppm by mass, based on the total amount of the lubricating oil composition.
In addition, when the lubricating oil composition according to the present embodiment contains a metal-based detergent, a content of the metal-based detergent may be adjusted such that the content of the metal atoms (alkali metal atom and alkaline earth metal atom) derived from the metal-based detergent satisfies the above range. The content of the metal-based detergent is preferably 0.5 mass% to 4.0 mass%, more preferably 0.7 mass% to 3.0 mass%, and still more preferably 1.0 mass% to 2.0 mass%, based on the total amount of the lubricating oil composition.

(Ashless Dispersant)

The lubricating oil composition according to the present embodiment preferably contains an ashless dispersant. When the lubricating oil composition contains the ashless dispersant, sludge and the like generated at a relatively low temperature can be dispersed in the oil to keep the inside of the engine clean.
Examples of the ashless dispersant include boron-free succinimides such as boron-free alkenyl succinimides, boron-containing succinimides such as boron-containing alkenyl succinimides, benzylamines, boron-containing benzylamines, succinic acid esters, and mono- or di-carboxylic acid amides represented by fatty acids or succinic acids.
These may be used alone or may be used in combination of two or more thereof.
Among these, from the viewpoint of improving the detergency inside the engine, one or more succinimides selected from the boron-free alkenyl succinimides and the boron-containing alkenyl succinimides are preferred, and combined use of the boron-free alkenyl succinimide and the boron-containing alkenyl succinimide is more preferred.
When the lubricating oil composition according to the present embodiment contains an ashless dispersant, a content of nitrogen atoms derived from the ashless dispersant is preferably 0.01 mass% to 0.10 mass%, more preferably 0.02 mass% to 0.08 mass%, and still more preferably 0.03 mass% to 0.07 mass%, based on the total amount of the lubricating oil composition.
In addition, when the lubricating oil composition according to the present embodiment contains an ashless dispersant, a content of the ashless dispersant may be adjusted such that the content of the nitrogen atoms derived from the ashless dispersant satisfies the above range. The content of the ashless dispersant is preferably 1.0 mass% to 6.0 mass%, more preferably 2.0 mass% to 5.0 mass%, and still more preferably 3.0 mass% to 4.0 mass%, based on the total amount of the lubricating oil composition.

(Antioxidant)

Examples of the antioxidant include an amine-based antioxidant, a phenol-based antioxidant, a sulfur-based antioxidant, and a phosphorus-based antioxidant.
These may be used alone or may be used in combination of two or more thereof.
Among these, it is preferable to use the amine-based antioxidant or the phenol-based antioxidant, and it is more preferable to use the amine-based antioxidant and the phenol-based antioxidant in combination.
Examples of the amine-based antioxidant include: a diphenylamine-based antioxidant such as diphenylamine and an alkylated diphenylamine having an alkyl group having 3 to 20 carbon atoms; and a naphthylamine-based antioxidant such as α-naphthylamine and an alkyl-substituted phenyl-α-naphthylamine having 3 to 20 carbon atoms.
Examples of the phenol-based antioxidant include: a monophenol-based antioxidant such as 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, and octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate; a diphenol-based antioxidant such as 4,4'-methylenebis(2,6-di-tert-butylphenol) and 2,2'-methylenebis(4-ethyl-6-tert-butylphenol); and a hindered phenol-based antioxidant.

(Anti-wear Agent or Extreme Pressure Agent)

Examples of the anti-wear agent or the extreme pressure agent include a zinc dialkyldithiophosphate (ZnDTP), zinc phosphate, zinc dithiocarbamate, a sulfur-containing compound such as a disulfide compound, a sulfurized olefin compound, sulfurized fats and oils, a sulfurized ester compound, a thiocarbonate compound, a thiocarbamate compound, and a polysulfide compound, a phosphorus-containing compound such as a phosphite ester compound, a phosphate ester compound, a phosphonate ester compound, and amine salts and metal salts thereof, and a sulfur and phosphorus-containing anti-wear agent, such as a thiophosphite ester compound, a thiophosphate ester compound, a thiophosphonate ester compound, and amine salts and metal salts thereof.
These may be used alone or may be used in combination of two or more thereof.

(Rust Inhibitor)

Examples of the rust inhibitor include a fatty acid, an alkenyl succinic acid half ester, a fatty acid soap, an alkyl sulfonate salt, a polyhydric alcohol fatty acid ester, a fatty acid amine, an oxidized paraffin, and an alkyl polyoxyethylene ether.
These may be used alone or may be used in combination of two or more thereof.

(Anti-foaming Agent)

Examples of the anti-foaming agent include a silicone oil, a fluorosilicone oil, and a fluoroalkyl ether.
These may be used alone or may be used in combination of two or more thereof.

(Demulsifier)

Examples of the demulsifier include: an anionic surfactant such as a castor oil sulfate ester salt and a petroleum sulfonate salt; a cationic surfactant such as a quaternary ammonium salt and imidazolines; polyoxyalkylene polyglycol and an ester of a dicarboxylic acid thereof; and an alkylene oxide adduct of an alkylphenolformaldehyde polycondensate.
These may be used alone or may be used in combination of two or more thereof.

(Dissolution Aid)

Examples of the dissolution aid include an ester compound such as a fatty acid ester and an aromatic-group-containing compound.
These may be used alone or may be used in combination of two or more thereof.
Here, in the lubricating oil composition according to the present embodiment, the compound (B1) contained in the molybdenum-based friction modifier (B) has excellent solubility (oil solubility) and excellent low-temperature storage stability without using a dissolution aid. Therefore, from the viewpoint of improving the solubility of the molybdenum-based friction modifier (B), an amount of the dissolution aid to be used is preferably small.
Specifically, a content of the dissolution aid is preferably less than 5 parts by mass, more preferably less than 0.5 parts by mass, and still more preferably less than 0.05 parts by mass, with respect to 100 parts by mass of the molybdenum-based friction modifier (B), and even more preferably, no dissolution aid is contained.

(Ashless Friction Modifier)

Examples of the ashless friction modifier include an ester-based friction modifier, an amine-based friction modifier, an amide-based friction modifier, and an ether-based friction modifier.
These may be used alone or may be used in combination of two or more thereof.
Here, the lubricating oil composition according to the present embodiment can have sufficiently improved fuel efficiency without using an ashless friction modifier. Therefore, a content of the ashless friction modifier is preferably small.
Specifically, the content of the ashless friction modifier is preferably less than 10 parts by mass, more preferably less than 1.0 parts by mass, still more preferably less than 0.1 parts by mass, and even more preferably less than 0.01 parts by mass, with respect to 100 parts by mass of the molybdenum-based friction modifier (B), and yet still more preferably, no ashless friction modifier is contained.

[Physical Properties of Lubricating Oil Composition]

The kinematic viscosity at 100°C of the lubricating oil composition according to the present embodiment should be 9.3 mm²/s or less. When the kinematic viscosity at 100°C of the lubricating oil composition is more than 9.3 mm²/s, the power loss due to the viscosity resistance of the lubricating oil composition makes it difficult to achieve the effect of fuel efficiency improvement.
From the viewpoint of more easily achieving the effect of fuel efficiency improvement, the kinematic viscosity at 100°C of the lubricating oil composition is preferably 8.2 mm²/s or less, more preferably 7.1 mm²/s or less, and still more preferably 6.1 mm²/s or less.
In addition, from the viewpoint of easily reducing the evaporation loss of the lubricating oil composition, the kinematic viscosity at 100°C of the lubricating oil composition is preferably 3.8 mm²/s or more, more preferably 4.0 mm²/s or more, and still more preferably 5.0 mm²/s or more.

From the viewpoint of an oil film retainability, the HTHS viscosity at 150°C (high temperature high shear viscosity) of the lubricating oil composition according to the present embodiment is preferably 1.7 mPa -s or more. In addition, from the viewpoint of improving the fuel efficiency, the HTHS viscosity at 150°C of the lubricating oil composition according to the present embodiment is preferably less than 2.9 mPa s, more preferably less than 2.6 mPa s, still more preferably less than 2.3 mPa ·s, and even more preferably less than 2.0 mPa ·s.
In the description herein, the HTHS viscosity at 150°C of the lubricating oil composition is a value measured at a shear rate of 10⁶/s under a temperature condition of 150°C using a TBS high temperature viscometer (tapered bearing simulator viscometer) in accordance with ASTM D4683.

<Low-temperature Storage Stability>

It is preferable that the lubricating oil composition according to the present embodiment does not generate cloudiness or precipitation in a low-temperature storage stability test described in Examples described later.

It is preferable that the lubricating oil composition according to the present embodiment has a discoloration number of 1 in a copper plate corrosion test described in Examples described later.
In addition, regarding the lubricating oil composition according to the present embodiment, a copper elution amount after an ISOT test described in Examples described later is preferably 90 ppm by mass or less, more preferably 70 ppm by mass or less, and still more preferably 60 ppm by mass or less, based on the total amount of the lubricating oil composition.

Regarding the lubricating oil composition according to the present embodiment, fuel efficiency improvement with respect to JASO BC (base calibration oil) (FEI% vs JASO BC) in a fuel efficiency test described in Examples described later is preferably 1.05 or more and more preferably 1.10 or more.

[Method for Producing Lubricating Oil Composition]

A method for producing the lubricating oil composition according to the present embodiment is not particularly limited.
For example, the method for producing the lubricating oil composition according to the present embodiment includes a step of mixing the base oil (A), the molybdenum-based friction modifier (B), and the benzotriazole-based compound (C).
The molybdenum-based friction modifier (B) contains a compound (B1) represented by the following general formula (b1).
[In the general formula (b1), R¹, R², R³, and R⁴ each independently represent a short-chain substituent group (α) which is an aliphatic hydrocarbon group having 4 to 12 carbon atoms or a long-chain substituent group (β) which is an aliphatic hydrocarbon group having 13 to 22 carbon atoms. A molar ratio [(α)/(β)] of the short-chain substituent group (α) to the long-chain substituent group (β) in all molecules of the compound (B1) is 0.10 to 0.50. In addition, in the above general formula (b1), X¹, X², X³, and X⁴ each independently represent an oxygen atom or a sulfur atom.]
In addition, in the step, a content of the benzotriazole-based compound (C) is adjusted to be 0.03 mass% or less based on the total amount of the lubricating oil composition.
Further, in the step, a kinematic viscosity at 100°C of the lubricating oil composition is adjusted to be 9.3 mm²/s or less.
A method of mixing the above components is not particularly limited, and examples of the method include a method including a step of blending the components (component (B), component (C), and one or more selected from the above lubricating oil additives) with the base oil (A). At this time, the above other lubricating oil additives may be blended at the same time. In addition, each component may be blended in a form of a solution (dispersion) upon addition with a diluent oil or the like. It is preferable that after blending the components, the blend is stirred and uniformly dispersed by a known method.

[Application of Lubricating Oil Composition]

The lubricating oil composition according to the present embodiment has excellent low-temperature storage stability, excellent copper corrosion resistance, and a high fuel efficiency.
Therefore, the lubricating oil composition according to the present embodiment is preferably used in an internal combustion engine, more preferably a gasoline engine, and still more preferably an automobile engine.
Therefore, the lubricating oil composition according to the present embodiment provides the following (1) to (3).

(1) A method of using the lubricating oil composition according to the present embodiment in an internal combustion engine.
(2) A method of using the lubricating oil composition according to the present embodiment in a gasoline engine.
(3) A method of using the lubricating oil composition according to the present embodiment in an automobile engine.

[Provided One Aspect of Present Invention]

According to one aspect of the present invention, the following [1] to [11] are provided.

[1] A lubricating oil composition containing: a base oil (A); a molybdenum-based friction modifier (B); and a benzotriazole-based compound (C), in which
- the molybdenum-based friction modifier (B) contains a compound (B1) represented by the following general formula (b1):
- wherein R¹, R², R³, and R⁴ each independently represent a short-chain substituent group (α) which is an aliphatic hydrocarbon group having 4 to 12 carbon atoms or a long-chain substituent group (β) which is an aliphatic hydrocarbon group having 13 to 22 carbon atoms; a molar ratio [(α)/(β)] of the short-chain substituent group (α) to the long-chain substituent group (β) in all molecules of the compound (B1) is 0.10 to 0.50; and X¹, X², X³, and X⁴ each independently represent an oxygen atom or a sulfur atom,
- a content of the benzotriazole-based compound (C) is 0.03 mass% or less based on a total amount of the lubricating oil composition, and
- a kinematic viscosity at 100°C of the lubricating oil composition is 9.3 mm²/s or less.
[2] The lubricating oil composition according to the above [1], in which the benzotriazole-based compound (C) contains a compound (C1) represented by the following general formula (c1):
wherein R^c1 is an alkyl group having 1 to 4 carbon atoms; p is an integer of 0 to 4; when multiple R^c1's are present, the multiple R^c1's may be same as or different from each other; R^c2 is a methylene group or an ethylene group; and R^c3 and R^c4 are each independently a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.
[3] The lubricating oil composition according to the above [1] or [2], in which a content of the molybdenum-based friction modifier (B) is 0.30 mass% to 1.50 mass% based on the total amount of the lubricating oil composition.
[4] The lubricating oil composition according to any of the above [1] to [3], in which a content ratio [(B)/(C)] of the molybdenum-based friction modifier (B) to the benzotriazole-based compound (C) is 20 to 120 in mass ratio.
[5] The lubricating oil composition according to any of the above [1] to [4], further comprising: one or more lubricating oil additives selected from the group consisting of a viscosity index improver, a pour point depressant, a metal-based detergent, an ashless dispersant, an antioxidant, an anti-wear agent, and an extreme pressure agent.
[6] The lubricating oil composition according to any of the above [1] to [5], in which a content of a dissolution aid is less than 5 parts by mass with respect to 100 parts by mass of the molybdenum-based friction modifier (B).
[7] The lubricating oil composition according to any of the above [1] to [6], in which a content of an ashless friction modifier is less than 10 parts by mass with respect to 100 parts by mass of the molybdenum-based friction modifier (B).
[8] The lubricating oil composition according to any of the above [1] to [7], which is used in an internal combustion engine.
[9] The lubricating oil composition according to any of the above [1] to [8], which is used in a gasoline engine.
[10] A method of using the lubricating oil composition according to any of the above [1] to [8] in an internal combustion engine.
[11] A method for producing a lubricating oil composition, including: a step of mixing a base oil (A), a molybdenum-based friction modifier (B), and a benzotriazole-based compound (C), in which
- the molybdenum-based friction modifier (B) contains a compound (B1) represented by the following general formula (b1):
- wherein R¹, R², R³, and R⁴ each independently represent a short-chain substituent group (α) which is an aliphatic hydrocarbon group having 4 to 12 carbon atoms or a long-chain substituent group (β) which is an aliphatic hydrocarbon group having 13 to 22 carbon atoms; a molar ratio [(α)/(β)] of the short-chain substituent group (α) to the long-chain substituent group (β) in all molecules of the compound (B1) is 0.10 to 0.50; and X¹, X², X³, and X⁴ each independently represent an oxygen atom or a sulfur atom,
- in the step, a content of the benzotriazole-based compound (C) is adjusted to be 0.03 mass% or less based on a total amount of the lubricating oil composition, and
- in the step, a kinematic viscosity at 100°C of the lubricating oil composition is adjusted to be 9.3 mm²/s or less.

Examples

The present invention will be described in detail with reference to the following Examples, whereas the present invention is not limited to the following Examples.

[Method of Measuring Various Physical Property Values]

Properties of raw materials used in Examples and Comparative Examples and lubricating oil compositions in Examples and Comparative Examples were respectively measured in the following manner.

(1) Kinematic viscosity and viscosity index

A kinematic viscosity at 40°C, the kinematic viscosity at 100°C, and the viscosity index of a base oil and each of the lubricating oil compositions were measured or calculated in accordance with JIS K2283:2000.

(2) HTHS viscosity at 150°C

The HTHS viscosity at 150°C of each of the lubricating oil compositions was measured at a shear rate of 10⁶/s under a temperature condition of 150°C using a TBS high temperature viscometer (tapered bearing simulator viscometer) in accordance with ASTM D4683.

(3) Molybdenum atom content

A molybdenum amount of each of the lubricating oil compositions was measured in accordance with JPI-5S-38-92 .

(4) Nitrogen atom content

A nitrogen amount of each of the lubricating oil compositions was measured in accordance with JIS K2609:1998.

(5) Mass average molecular weight (Mw)

The mass average molecular weights (Mw) of a viscosity index improver and a pour point depressant were measured using a gel permeation chromatography apparatus ("1260 Type HPLC", manufactured by Agilent Technologies, Inc.) under the following conditions, and a value measured in terms of standard polystyrene was used.

(Measurement Conditions)

Column: two columns "Shodex LF 404" sequentially connected.
Column Temperature: 35°C
Developing solvent: chloroform
Flow rate: 0.3 mL/min

[Examples 1 to 3 and Comparative Examples 1 to 8]

A base oil and additives shown below were sufficiently mixed in blending amounts (mass%) shown in Table 1 to prepare the lubricating oil compositions in Examples 1 to 3 and Comparative Examples 1 to 8.
Details of the base oil and the additives used in Examples 1 to 3 and Comparative Examples 1 to 8 are as follows.

·"100N mineral oil"
Kinematic viscosity at 100°C: 4.3 mm²/s, viscosity index: 123, API category: Group III

<Molybdenum-based Friction Modifier (B)>

·"MoDTC-1"

MoDTC-1 is a compound represented by the general formula (b1) in which the aliphatic hydrocarbon group of the short-chain substituent group (α) has 8 carbon atoms and the aliphatic hydrocarbon group of the long-chain substituent group (β) has 13 carbon atoms. In the general formula (b1), X¹, X², X³, and X⁴ are sulfur atoms. The molar ratio [(α)/(β)] of the short-chain substituent group (α) to the long-chain substituent group (β) in all molecules of MoDTC-1 is 1.0.

·"MoDTC-2"

MoDTC-2 is a compound represented by the general formula (b1) in which the short-chain substituent group (α) is substantially not contained and the long-chain substituent group (β) whose aliphatic hydrocarbon group has 13 carbon atoms is substantially contained. In the general formula (b1), X¹, X², X³, and X⁴ are sulfur atoms.

·"MoDTC-3"

MoDTC-3 is a compound represented by the general formula (b1) in which the long-chain substituent group (β) is substantially not contained and the short-chain substituent group (α) whose aliphatic hydrocarbon group has 8 carbon atoms is substantially contained. In the general formula (b1), X¹, X², X³, and X⁴ are sulfur atoms.
In Examples, a combination of MoDTC-1 and MoDTC-2 in Examples 1 to 3 and Comparative Example 5 corresponds to the compound (B1).

<Benzotriazole-based Compound (C)>

·"1-[N,N-bis(2-ethylhexyl)aminomethyl]-4-methyl-1H-benzotriazole"

This compound is represented by the following structural formula.
1-[N,N-bis(2-ethylhexyl)aminomethyl]-4-methyl-1H-benzotriazole is a compound represented by the general formula (c1) in which R^c1 is a methyl group, p is 1, R^c2 is a methylene group, and R^c3 and R^c4 are 2-ethylhexyl groups, and is a compound corresponding to the compound (C 1).

·"Viscosity index improver"

Polymethacrylate (PMA) (mass average molecular weight (Mw): 310,000, resin component: 22.7 mass%)
The polymethacrylate (PMA) was added to Example 1 and Comparative Examples 1 and 2 only. An addition amount was 1.5 mass% (resin component: 0.34 mass%, diluent oil: 1.16 mass%) based on the total amount of the lubricating oil composition.

·"Pour point depressant"

Polymethacrylate (PMA) (mass average molecular weight (Mw): 62,000, resin component: 55.0 mass%)
An addition amount was 0.1 mass% (resin component: 0.06 mass%, diluent oil: 0.04 mass%) based on the total amount of the lubricating oil composition.

·"Metal-based detergent"

Calcium sulfonate (base number: 305 mgKOH/g)
Calcium sulfonate was added such that a content of calcium atoms derived from calcium sulfonate in the lubricating oil composition was 0.16 mass%.

·"Ashless dispersant"

Succinimide (nitrogen content: 1.4 mass%)
Succinimide was added such that a content of nitrogen atoms derived from succinimide in the lubricating oil composition was 0.05 mass%.

"Others"

Amine-based antioxidant, phenol-based antioxidant, and zinc dialkyldithiophosphate (ZnDTP)

[Evaluation Method]

Tests described later were performed to evaluate the low-temperature storage stability, the copper corrosion resistance, and the fuel efficiency.

(1) Test method

Into a 100 mL glass bottle, 100 mL of each of the lubricating oil compositions in Examples 1 to 3 and Comparative Examples 1 to 8 was added to determine whether cloudiness and precipitation occurred after the lubricating oil compositions were allowed to stand at -5°C for 2 weeks.
Regarding whether the cloudiness occurred, it was determined that the cloudiness occurred when a transmittance of a visible light absorbance was 40% or less (in accordance with JIS K0115:2004: general rules for absorptiometric analysis, a measurement wavelength was 500 nm to 550 nm).
Whether the precipitation occurred was determined visually.

(2) Evaluation criteria

A lubricating oil composition in which neither the cloudiness nor the precipitation occurred was evaluated to be acceptable. A lubricating oil composition in which at least one of the cloudiness and the precipitation occurred was evaluated to be unacceptable.
<Evaluation of Copper Corrosion Resistance>

(1) Test method 1: copper plate corrosion test

A copper plate corrosion test was performed in accordance with JIS K2513:2000 (petroleum products-copper plate corrosion test method-) to evaluate the copper corrosion resistance of the lubricating oil compositions in Examples 1 to 3 and Comparative Examples 1 to 8.

(2) Test method 2: evaluation of copper elution after ISOT test

A copper piece and an iron piece were put into a test oil (each of the lubricating oil compositions in Examples 1 to 3 and Comparative Examples 1 to 8) as a catalyst, and an ISOT test in accordance with JIS K2514-1:2013 was performed at a temperature of 165.5°C for 72 hours to forcibly deteriorate the test oil. Then, a copper concentration in the forcibly deteriorated test oil was measured in accordance with JPI-5S-44-11 , and the measured copper concentration was taken as the copper elution amounts after the ISOT test.

(3) Evaluation criteria

A lubricating oil composition having a discoloration number of "1" and a copper elution amount after the ISOT test of 90 ppm by mass or less was evaluated to be acceptable.

(1) Test method

A test was performed on each of the lubricating oil compositions in Examples 1 to 3 and Comparative Examples 1 to 7 in accordance with JASO M366:2019 "gasoline engine lubricating oil for automobiles - firing fuel efficiency test method" to measure the fuel efficiency improvement (FEI% vs JASO BC) for JASO BC (base calibration oil, viscosity grade: 0W20).

(2) Evaluation criteria

A lubricating oil composition having a "FEI% vs JASO BC" of 1.05 or more was evaluated to be acceptable.
Results are shown in Table 1.
In the evaluation result shown in Table 1, "Evaluation A" means acceptable, and "Evaluation B" means unacceptable.
The following can be seen from Table 1.
It can be seen that the lubricating oil compositions in Examples 1 to 3 are excellent in all of the low-temperature storage stability, the copper corrosion resistance, and the fuel efficiency.
In addition, the following can be seen from the results shown in Comparative Examples 2 and 7.
It can be seen that a lubricating oil composition, which contains, as a molybdenum-based friction modifier, a compound substantially free of the short-chain substituent group (α) and substantially composed of the long-chain substituent group (β) (that is, a compound having a molar ratio [(α)/(β)] of 0.00) and does not contain the benzotriazole-based compound (C) (compound (C1), is poor in copper corrosion resistance and fuel efficiency (Comparative Example 2). Moreover, it can be seen that, even in the case of a lubricating oil composition, which contains the above compound as a molybdenum-based friction modifier and further contains the benzotriazole-based compound (C) (compound (C1)), the copper corrosion resistance is not sufficiently improved (Comparative Example 7).
In addition, the following can be seen from the results shown in Comparative Examples 1, 3, 4, and 6.
It can be seen that a lubricating oil composition, which contains, as a molybdenum-based friction modifier, a compound having a molar ratio [(α)/(β)] of more than 0.50 (1.00) and does not contain the benzotriazole-based compound (C) (compound (C1)), is poor in low-temperature storage stability and copper corrosion resistance (Comparative Examples 1 and 3). Moreover, it can be seen that, even in the case of a lubricating oil composition, which contains the above compound and further contains the benzotriazole-based compound (C) (compound (C1)), the copper corrosion resistance is improved and becomes good, but the low-temperature storage stability is poor (Comparative Examples 4 and 6).
In addition, as shown in Comparative Example 8, a lubricating oil composition, which contains, as a molybdenum-based friction modifier, a compound substantially free of the long-chain substituent group (β) and substantially composed of the short-chain substituent group (α), is poor in low-temperature storage stability.
In addition, as shown in Comparative Example 5, it can been seen that for a lubricating oil composition in which the content of the benzotriazole-based compound (C) (compound (C1)) is more than 0.03 mass%, even in a case of containing a compound (B1) having a molar ratio [(α)/(β)] within the range of 0.10 to 0.50 as a molybdenum-based friction modifier, the fuel efficiency is poor.

Claims

A lubricating oil composition comprising:
a base oil (A);

a molybdenum-based friction modifier (B); and

a benzotriazole-based compound (C), wherein

the molybdenum-based friction modifier (B) contains a compound (B1) represented by the following general formula (b1):

wherein R¹, R², R³, and R⁴ each independently represent a short-chain substituent group (α) which is an aliphatic hydrocarbon group having 4 to 12 carbon atoms or a long-chain substituent group (β) which is an aliphatic hydrocarbon group having 13 to 22 carbon atoms; a molar ratio [(α)/(β)] of the short-chain substituent group (α) to the long-chain substituent group (β) in all molecules of the compound (B1) is 0.10 to 0.50; and X¹, X², X³, and X⁴ each independently represent an oxygen atom or a sulfur atom,

a content of the benzotriazole-based compound (C) is 0.03 mass% or less based on a total amount of the lubricating oil composition, and

a kinematic viscosity at 100°C of the lubricating oil composition is 9.3 mm²/s or less.
The lubricating oil composition according to claim 1, wherein the benzotriazole-based compound (C) contains a compound (C1) represented by the following general formula (c1):
wherein R^c1 is an alkyl group having 1 to 4 carbon atoms; p is an integer of 0 to 4; when multiple R^c1's are present, the multiple R^c1's may be same as or different from each other; R^c2 is a methylene group or an ethylene group; and R^c3 and R^c4 are each independently a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.
The lubricating oil composition according to claim 1 or 2, wherein a content of the molybdenum-based friction modifier (B) is 0.30 mass% to 1.50 mass% based on the total amount of the lubricating oil composition.
The lubricating oil composition according to any one of claims 1 to 3, wherein a content ratio [(B)/(C)] of the molybdenum-based friction modifier (B) to the benzotriazole-based compound (C) is 20 to 120 in mass ratio.
The lubricating oil composition according to any one of claims 1 to 4, further comprising:
one or more lubricating oil additives selected from the group consisting of a viscosity index improver, a pour point depressant, a metal-based detergent, an ashless dispersant, an antioxidant, an anti-wear agent, and an extreme pressure agent.
The lubricating oil composition according to any one of claims 1 to 5, wherein a content of a dissolution aid is less than 5 parts by mass with respect to 100 parts by mass of the molybdenum-based friction modifier (B).
The lubricating oil composition according to any one of claims 1 to 6, wherein a content of an ashless friction modifier is less than 10 parts by mass with respect to 100 parts by mass of the molybdenum-based friction modifier (B).
The lubricating oil composition according to any one of claims 1 to 7, which is used in an internal combustion engine.
The lubricating oil composition according to any one of claims 1 to 8, which is used in a gasoline engine.
A method of using the lubricating oil composition according to any one of claims 1 to 7 in an internal combustion engine.
A method for producing a lubricating oil composition, comprising:
a step of mixing a base oil (A), a molybdenum-based friction modifier (B), and a benzotriazole-based compound, wherein

the molybdenum-based friction modifier (B) contains a compound (B1) represented by the following general formula (b 1):

wherein R¹, R², R³, and R⁴ each independently represent a short-chain substituent group (α) which is an aliphatic hydrocarbon group having 4 to 12 carbon atoms or a long-chain substituent group (β) which is an aliphatic hydrocarbon group having 13 to 22 carbon atoms; a molar ratio [(α)/(β)] of the short-chain substituent group (α) to the long-chain substituent group (β) in all molecules of the compound (B1) is 0.10 to 0.50; and X¹, X², X³, and X⁴ each independently represent an oxygen atom or a sulfur atom,

in the step, a content of the benzotriazole-based compound (C) is adjusted to be 0.03 mass% or less based on a total amount of the lubricating oil composition, and

in the step, a kinematic viscosity at 100°C of the lubricating oil composition is adjusted to be 9.3 mm²/s or less.