WO2021060415A1 - Lubricating oil composition - Google Patents

Abstract

Provided is a lubricating oil composition that reduces torque losses over a broad temperature range. The lubricating oil composition comprises a base oil and poly(meth)acrylate, wherein the poly(meth)acrylate content as the resin fraction is 0.1-2.0 mass% with reference to the total amount of the lubricating oil composition. The lubricating oil composition has a kinematic viscosity at 100°C of 4.0 mm²/s to 7.5 mm²/s, a Noack evaporation loss of not more than 15.0 mass%, a ratio (KV₄₀/KV₁₀₀) between the kinematic viscosity at 40°C KV₄₀ and the kinematic viscosity at 100°C KV₁₀₀ of not more than 3.95, and a ratio (HTHS₈₀/KV₁₀₀) between the HTHS viscosity at 80°C HTHS₈₀ and the kinematic viscosity at 100°C KV₁₀₀ of not more than 0.96.

Description

Lubricating oil composition

The present invention relates to a lubricating oil composition.

In recent years, from the viewpoint of effective utilization of petroleum resources and _{reduction of CO 2} emissions, fuel efficiency of vehicles such as automobiles has been strongly demanded. Therefore, there is an increasing demand for fuel efficiency of lubricating oil compositions used in the engines of vehicles such as automobiles.
As one of the methods for reducing fuel consumption, there is a method of reducing the viscous resistance by lowering the viscosity of the lubricating oil composition.

For example, Patent Document 1 describes a lubricating oil composition which maintains the HTHS viscosity at 150 ° C. and has low kinematic viscosities at 40 ° C. and 100 ° C. and low HTHS viscosity at 100 ° C., resulting in excellent fuel efficiency. ing.

Japanese Unexamined Patent Publication No. 2014-196518

The lubricating oil composition used in the engine is used in a wide temperature range from about −20 ° C., which is the temperature before starting the engine in winter, to about 100 ° C. after starting the engine.
Here, the demand for fuel efficiency is increasing year by year. Therefore, in order to achieve further fuel efficiency, it is required to reduce the torque loss caused by the rotation of the engine in the above-mentioned wide temperature range.
Patent Document 1 examines torque loss at 80 ° C. However, Patent Document 1 does not consider any torque loss in a wide temperature range including the above-mentioned lower temperature.

The present invention has been made in view of such a demand, and an object of the present invention is to provide a lubricating oil composition that reduces torque loss in a wide temperature range.

The present inventors have found through diligent studies that a lubricating oil composition satisfying a specific requirement can solve the above-mentioned problems, and have completed the present invention.

That is, the present invention relates to the following [1] to [12].
[1] Containing a base oil and a poly (meth) acrylate,
The content of the poly (meth) acrylate in terms of resin content is 0.1% by mass or more and 2.0% by mass or less based on the total amount of the lubricating oil composition.
A lubricating oil composition that satisfies the following requirements (1) to (4).
-Requirement (1): The kinematic viscosity at 100 ° C. is 4.0 mm ² / s or more and 7.5 mm ² / s or less.
-Requirement (2): Noack evaporation amount is 30% by mass or less.
-Requirement (3): The ratio of 40 ° C. kinematic viscosity KV ₄₀ to 100 ° C. kinematic viscosity KV _{100 (KV 40} / KV ₁₀₀ ) is 3.95 or less.
-Requirement (4): The ratio of 80 ° C. HTHS viscosity HTHS ₈₀ to 100 ° C. kinematic viscosity KV _{100 (HTHS 80} / KV ₁₀₀ ) is 0.96 or less.
[2] The poly (meth) acrylate contains a structural unit derived from a macromonomer (α) and a structural unit derived from a monomer (A1) represented by the following general formula (a1).

[In the above general formula (a1), R ¹¹ is a hydrogen atom or a methyl group.
R ¹² represents a single bond, -O-, or -NH-.
R ¹³ represents a linear alkylene group having 2 to 4 carbon atoms or a branched chain alkylene group having 2 to 4 carbon atoms. m1 represents an integer from 0 to 20. When m1 is an integer of 2 or more, the plurality of R ^13s may be the same or different, and the (R ¹³ O) _m1 portion may be a random copolymerization or a block copolymerization.
R ¹⁴ is a non-cyclic alkyl group having 4 to 5 carbon atoms or a group having 6 to 8 carbon atoms having a cyclic alkyl group. ]
The macromonomer (α) has a (meth) acryloyl group at one end and has a structural unit derived from a monomer (α1) selected from butadiene and hydrogenated butadiene.
The lubricating oil composition according to the above [1], which contains the comb-shaped polymer (A) in which the content of the structural unit derived from the monomer (A1) is 75 mol% or more based on the total structural unit.
[3] The lubricating oil composition according to the above [2], wherein the acyclic alkyl group having 4 to 5 carbon atoms has a tertiary carbon.
[4] The lubricating oil composition according to the above [2] or [3], wherein the comb-shaped polymer (A) further contains a structural unit derived from the monomer (A2) represented by the following general formula (a2). ..

[In the above general formula (a2), R ²¹ is a hydrogen atom or a methyl group.
R ²² represents a single bond, -O-, or -NH-.
R ²³ represents a linear alkylene group having 2 to 4 carbon atoms or a branched chain alkylene group having 2 to 4 carbon atoms. m2 represents an integer from 1 to 20. When m2 is an integer of 2 or more, the plurality of R ^23s may be the same or different, and the (R ²³ O) _m2 portion may be a random copolymerization or a block copolymerization.
R ²⁴ is a linear alkyl group having 1 to 12 carbon atoms or a branched chain alkyl group having 1 to 12 carbon atoms. ]
[5] The comb-shaped polymer (A) further contains a structural unit derived from an alkyl (meth) acrylate (A3) having a linear alkyl group having 10 to 30 carbon atoms or a branched chain alkyl group having 10 to 30 carbon atoms. The lubricating oil composition according to any one of the above [2] to [4].
[6] The content of the structural unit derived from the alkyl (meth) acrylate (A3) having the linear alkyl group having 10 to 30 carbon atoms or the branched chain alkyl group having 10 to 30 carbon atoms is based on all the structural units. The lubricating oil composition according to the above [5], which is 0.1 mol% or more and 10 mol% or less.
[7] The content of the structural unit derived from the monomer (A1) is 75 mol% or more based on the total amount of the structural unit of the comb polymer (A).
The lubricating oil composition according to the above [2] or [3], further comprising a structural unit derived from the monomer (A2) represented by the following general formula (a2).

[In the above general formula (a2), R ²¹ is a hydrogen atom or a methyl group.
R ²² represents a single bond, -O-, or -NH-.
R ²³ represents a linear alkylene group having 2 to 4 carbon atoms or a branched chain alkylene group having 2 to 4 carbon atoms. m2 represents an integer from 1 to 20. When m2 is an integer of 2 or more, the plurality of R ^23s may be the same or different, and the (R ²³ O) _m2 portion may be a random copolymerization or a block copolymerization.
R ²⁴ is a linear alkyl group having 1 to 12 carbon atoms or a branched chain alkyl group having 1 to 12 carbon atoms. ]
[8] The lubricating oil composition according to any one of the above [2] to [7], wherein the mass average molecular weight (Mw) of the comb-shaped polymer (A) is 300,000 or more and 1.5 million or less.
[9] The lubricating oil composition according to any one of the above [2] to [8], wherein the molecular weight distribution (Mw / Mn) of the comb-shaped polymer (A) is 1.2 or more and 3.7 or less. ..
[10] The above [2] to [9], wherein the glass transition temperature (Tg) of the homopolymer composed of the structural unit derived from the monomer (A1) represented by the general formula (a1) is 20 ° C. or higher. The lubricating oil composition according to any one of the above.
[11] The lubricating oil composition according to any one of the above [1] to [10], which is used for an internal combustion engine of an automobile.
[12] The lubricating oil composition according to any one of the above [1] to [10], which is used for an internal combustion engine of an automobile equipped with a hybrid mechanism.

According to the present invention, it is possible to provide a lubricating oil composition that reduces torque loss in a wide temperature range.

Hereinafter, a mode for carrying out the present invention will be described in detail.

In the present specification, with respect to a preferable numerical range (for example, a range such as content), the lower limit value and the upper limit value described stepwise can be combined independently. For example, a description of a lower limit value of "preferably 10 or more, more preferably 30 or more, still more preferably 40 or more" and an upper limit value of "preferably 90 or less, more preferably 80 or less, still more preferably 70 or less". From the description of the above, as a suitable range, for example, a range in which a lower limit value and an upper limit value independently selected such as "10 or more and 70 or less", "30 or more and 70 or less", and "40 or more and 80 or less" are combined is selected. You can also do it. Further, from the same description, for example, it is possible to simply select a range in which either the lower limit value or the upper limit value such as "40 or more" or "70 or less" is defined. Further, for example, "preferably 10 or more and 90 or less, more preferably 30 or more and 80 or less, still more preferably 40 or more and 70 or less", "preferably 10 to 90, more preferably 30 to 80, still more preferably 40 to 40 to". The same applies to the preferable range that can be selected from the description such as "70". In the description of the numerical range in the present specification, for example, the description "10 to 90" is synonymous with "10 or more and 90 or less". It should be noted that the numerical values of "greater than or equal to", "less than or equal to", "less than", and "super" regarding the description of the numerical range can also be arbitrarily combined.

In the present specification, "kinematic viscosity at 40 ° C" is also referred to as "40 ° C kinematic viscosity". Similarly, "kinematic viscosity at 100 ° C." is also referred to as "100 ° C. kinematic viscosity".

In the present specification, "(meth) acrylate" means both "acrylate" and "methacrylate", and the same applies to other similar terms. For example, "(meth) acryloyl group" indicates both "acryloyl group" and "methacryloyl group".

In the present specification, the mass average molecular weight (Mw) and the number average molecular weight (Mn) of each component are values in terms of standard polystyrene measured by a gel permeation chromatography (GPC) method, and specifically, Examples. Means the value measured by the method described in.

Hereinafter, aspects of the present invention will be described in detail.

[Aspects of lubricating oil composition]
The lubricating oil composition of the present invention contains a base oil and a poly (meth) acrylate, and the content of the poly (meth) acrylate in terms of resin content is 0.1 mass based on the total amount of the lubricating oil composition. % Or more and 2.0% by mass or less, and satisfy the following requirements (1) to (4).
-Requirement (1): The kinematic viscosity at 100 ° C. is 4.0 mm ² / s or more and 7.5 mm ² / s or less.
-Requirement (2): Noack evaporation amount is 30.0% by mass or less.
-Requirement (3): The ratio of 40 ° C. kinematic viscosity KV ₄₀ to 100 ° C. kinematic viscosity KV _{100 (KV 40} / KV ₁₀₀ ) is 3.95 or less.
-Requirement (4): The ratio of 80 ° C. HTHS viscosity HTHS ₈₀ to 100 ° C. kinematic viscosity KV _{100 (HTHS 80} / KV ₁₀₀ ) is 0.96 or less.
When the lubricating oil composition of the present invention satisfies the requirements (1) to (4), it is possible to obtain a lubricating oil composition that reduces torque loss in a wide temperature range.

<Requirement (1)>
The lubricating oil composition of the present invention has a kinematic viscosity at 100 ° C. of 4.0 mm ² / s or more and 7.5 mm ² / s or less.
When the lubricating oil composition of the present invention satisfies the requirement (1), the amount of Noack evaporation can satisfy the requirement (2), and the viscosity of the lubricating oil composition is lowered, so that fuel efficiency is excellent.
If the kinematic viscosity at 100 ° C. ^{is less than 4.0 mm 2} / s, the amount of Noack evaporation cannot satisfy the requirement (2), and the loss of the lubricating oil composition due to evaporation increases. Further, when the kinematic viscosity at 100 ° C. ^{is more than 7.5 mm 2} / s, the viscosity of the lubricating oil composition cannot be lowered, so that the fuel efficiency becomes insufficient.
^{Further, the lubricating oil composition of the present invention has a kinematic viscosity of 5.0 mm 2} / s or more at 100 ° C. from the viewpoint that the amount of Noack evaporation satisfies the requirement (2) and the viscosity of the lubricating oil composition is further lowered. 7.4mm is preferably from ² / s, more preferably not more than 5.5 mm ² / s or more 7.3 mm ² / s, more preferably not more than 6.0 mm ² / s or more 7.2 mm ² / s.

<Requirement (2)>
The lubricating oil composition of the present invention has a Noack evaporation amount of 30.0% by mass or less.
When the lubricating oil composition of the present invention satisfies the requirement (2), the loss of the lubricating oil composition due to evaporation can be reduced.
If the amount of Noack evaporation exceeds 30.0% by mass, the amount of loss of the lubricating oil composition due to evaporation increases.
The amount of Noack evaporation is measured according to ASTM D 5800.
From the viewpoint of further reducing the amount of loss of the lubricating oil composition due to evaporation, the lubricating oil composition of the present invention preferably has a Noack evaporation amount of 25.0% by mass or less, more preferably 20.0% by mass or less.

<Requirements (3), Requirements (4)>
As specified in the requirement (3), the lubricating oil composition of the present invention has a ratio (KV ₄₀ / KV _{100 ) of 40 ° C. kinematic viscosity KV 40} to 100 ° C. kinematic viscosity KV _{100 of} 3.95 or less. ..
Further, as specified in the requirement (4), the lubricating oil composition of the present invention has a ratio (HTHS ₈₀ / KV _{100 ) of 80 ° C. HTHS viscosity HTHS 80} to 100 ° C. kinematic viscosity KV _{100 of} 0.96 or less. Is.
The 40 ° C. kinematic viscosity KV ₄₀ and the 100 ° C. kinematic viscosity KV ₁₀₀ can be measured in accordance with JIS K2283: 2000.
80 ° C. HTHS viscosity HTHS ₈₀ can be measured according to JPI-5S-36-03.
If at least one of the requirements (3) and (4) is not satisfied, the torque loss cannot be reduced in a wide temperature range.

Regarding the requirement (3), the lubricating oil composition of the present invention has a ratio of _{40 ° C. kinematic viscosity KV 40} to 100 ° C. kinematic viscosity KV _{100 (KV 40} / KV _{100) from the viewpoint of reducing torque loss in a wide temperature range.} ) Is 3.95 or less, preferably 3.93 or less, more preferably 3.90 or less, and further preferably 3.86 or less. Further, from the viewpoint of reducing torque loss in a wide temperature range, the ratio of _{40 ° C. kinematic viscosity KV 40} to 100 ° C. kinematic viscosity KV _{100 (KV 40} / KV ₁₀₀ ) is preferably 3.70 or more, which is more preferable. Is 3.75 or more, more preferably 3.78 or more, and even more preferably 3.83 or more.

Regarding the requirement (4), the lubricating oil composition of the present invention has a ratio of _{80 ° C. HTHS viscosity HTHS 80} to 100 ° C. kinematic viscosity KV _{100 (HTHS 80} / KV _{100) from the viewpoint of reducing torque loss in a wide temperature range.} ) Is 0.96 or less. Further, in the lubricating oil composition of the present invention, the ratio of _{80 ° C. HTHS viscosity HTHS 80} to 100 ° C. kinematic viscosity KV _{100 (HTHS 80} / KV ₁₀₀ ) is preferable from the viewpoint of reducing torque loss in a wide temperature range. Is 0.90 or more, more preferably 0.92 or more, still more preferably 0.93 or more, and even more preferably 0.95 or more.
Further, the lubricating oil composition of the present invention has a ratio of _{100 ° C. HTHS viscosity HTHS 100} to 100 ° C. kinematic viscosity KV _{100 (HTHS 100} /) from the viewpoint of reducing torque loss and improving fuel efficiency in a wide temperature range. KV ₁₀₀ ) is preferably 0.64 or less, more preferably 0.63 or less.

The lubricating oil composition of the present invention contains a base oil and a poly (meth) acrylate.
When the lubricating oil composition contains a base oil and a poly (meth) acrylate and satisfies a predetermined condition, torque loss can be reduced in a wide temperature range and fuel efficiency can be improved. Here, the wide temperature range means an effective temperature range assumed in the engine of a vehicle such as an automobile.
The effective temperature range shall mean a temperature range of 30 ° C. to 100 ° C.

The content of the poly (meth) acrylate in the lubricating oil composition in terms of resin content is 0.1% by mass or more and 2.0% by mass or less, preferably 0.3, based on the total amount of the lubricating oil composition. It is by mass% or more and 1.9% by mass or less, and more preferably 0.5% by mass or more and 1.8% by mass or less.

[Base oil]
The base oil is not particularly limited, and any mineral oil or synthetic oil conventionally used as a base oil for lubricating oil can be appropriately selected and used.
As the mineral oil, for example, the lubricating oil distillate obtained by vacuum distillation of the atmospheric residual oil obtained by atmospheric distillation of crude oil is subjected to solvent removal treatment; at least one treatment of solvent extraction or hydrocracking. At least one dewaxing treatment for solvent dewaxing or catalytic dewaxing; hydrorefining treatment; one or more treatments, preferably all treatments, and refined oils or mineral oil-based waxes of the opposite sex Examples thereof include oil produced by refining. Of these, oils treated by hydrorefining are preferred.
Examples of the synthetic oil include polyα-olefins such as copolymers such as polybutene, α-olefin homopolymer, and ethylene-α-olefin copolymer; various types such as polyol ester, dibasic acid ester, and phosphoric acid ester. Esters; various ethers such as polyphenyl ethers; polyglycols; alkylbenzenes; alkylnaphthalene; GTL base oils produced by hydroisomerizing and dewaxing residual WAX (gast liquid wax) in the GTL process. Be done.
These base oils may be used alone or in combination of two or more.

No particular limitation is imposed on the viscosity of the base oil, 100 ° C. kinematic viscosity is preferably 2.0mm ² /s~6.0mm ² / s, more preferably 2.0mm ² /s~5.5mm ² / s, more preferably from 2.0mm ² /s~5.0mm ² / s. When the 100 ° C. kinematic viscosity is 2.0 mm ² / s or more, evaporation loss can be easily suppressed, ^{and when it is 6.0 mm 2} / s or less, power loss due to viscous resistance is suppressed, and a fuel efficiency improving effect can be obtained. ..
The viscosity index of the base oil is preferably 50 or more, more preferably 80 or more, still more preferably 100 or more, and even more preferably 105 or more. When the viscosity index of the base oil is in this range, it becomes easy to improve the viscosity characteristics of the lubricating oil composition.
The values of the kinematic viscosity and the viscosity index of the base oil at 100 ° C. are measured and calculated by the methods described in Examples described later.

[Poly (meth) acrylate]
The poly (meth) acrylate preferably contains the comb-shaped polymer (A) described below.
The poly (meth) acrylate of one aspect of the present invention may consist only of the comb-shaped polymer (A). That is, the poly (meth) acrylate of one aspect of the present invention may contain the comb-shaped polymer (A) in an amount of 100% by mass based on the total amount (100% by mass) of the poly (meth) acrylate.

Hereinafter, the comb-shaped polymer (A) will be described in detail.

<Aspects of comb-shaped polymer (A): macromonomer (α), monomer (A1)>
The comb-shaped polymer (A) preferably contains a structural unit derived from the macromonomer (α) and a structural unit derived from the monomer (A1) represented by the following general formula (a1).

[In the above general formula (a1), R ¹¹ is a hydrogen atom or a methyl group.
R ¹² represents a single bond, -O-, or -NH-.
R ¹³ represents a linear alkylene group or a branched chain alkylene group having 2 to 4 carbon atoms. m1 represents an integer from 0 to 20. When m1 is an integer of 2 or more, the plurality of R ^13s may be the same or different, and the (R ¹³ O) _m1 portion may be a random copolymerization or a block copolymerization.
R ¹⁴ is a non-cyclic alkyl group having 4 to 5 carbon atoms or a group having 6 to 8 carbon atoms having a cyclic alkyl group. ]
The macromonomer (α) has a (meth) acryloyl group at one end and has a structural unit derived from a monomer (α1) selected from butadiene and hydrogenated butadiene.

Here, from the viewpoint of facilitating both of the above requirements (3) and (4), in the above general formula (a1), R ¹⁴ is a carbon having an acyclic alkyl group or a cyclic alkyl group having 4 to 5 carbon atoms. It is preferably a group of numbers 6-8. The carbon number of the group having a cyclic alkyl group means the total number of carbon atoms contained in the group having a cyclic alkyl group.
From the viewpoint of making it easier to satisfy both the above requirements (3) and (4) and more easily satisfying the above requirement (4), R ¹⁴ in the general formula (a1) has 6 carbon atoms having a cyclic alkyl group. ~ 8 groups are preferred.

The acyclic alkyl group having 4 to 5 carbon atoms preferably has a tertiary carbon or a quaternary carbon from the viewpoint of making it easier to satisfy both the above requirements (3) and (4), and preferably has a tertiary carbon. Is more preferable.
Specific examples of the acyclic alkyl group having 4 to 5 carbon atoms include n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, neopentyl group, isopentyl group, sec-pentyl group, and the like. Examples thereof include a tert-pentyl group and a 3-pentyl group. Among these, from the viewpoint of making it easier to satisfy both the above requirements (3) and (4), an isobutyl group, a sec-butyl group, a tert-butyl group, a neopentyl group, an isopentyl group, a sec-pentyl group, and a tert-pentyl group. Groups are preferred, isobutyl groups are more preferred.

Specific examples of the group having a cyclic alkyl group having 6 to 8 carbon atoms include a cyclohexyl group, a methylcyclohexyl group, an ethylcyclohexyl group, a dimethylcyclohexyl group, a cyclohexylmethyl group, a methylcyclohexylmethyl group, a cyclohexylethyl group and the like. Be done. Among these, a cyclohexyl group is preferable from the viewpoint of facilitating both of the above requirements (3) and (4) and further facilitating the above requirement (4).

^{In the general formula (a1), R 11} is preferably a methyl group from the viewpoint of facilitating both of the above requirements (3) and (4).
From the same viewpoint, ^{it is preferable that R 12} is −O− independently of each other.
That is, the monomer (A1) preferably has an acryloyl group or a methacryloyl group as a polymerizable functional group, and more preferably has a methacryloyl group.
From the same viewpoint, m1 is preferably 0 to 5, more preferably 0 to 2, and even more preferably 0.

Here, from the viewpoint of facilitating both of the above requirements (3) and (4), the content of the structural unit derived from the monomer (A1) is preferably 75 mol% or more, more preferably 76 mol% or more. , More preferably 77 mol% or more.
The upper limit of the content of the constituent unit derived from the monomer (A1) is not particularly limited as long as the solubility of the lubricating oil composition in the base oil can be ensured, but is preferably 90 mol% or less. , More preferably 87 mol% or less, still more preferably 85 mol% or less.

The structural unit derived from the monomer (A1) contained in the comb-shaped polymer (A) may be one kind alone or two or more kinds. For example, by preparing a comb-shaped polymer (A) containing a plurality of structural units having different ^{R 14s} in the general formula (a1), it is easy to adjust the HTHS viscosity within a desired range.

Next, the macromonomer (α) preferably has a (meth) acryloyl group at one end and has a structural unit derived from a monomer (α1) selected from butadiene and hydrogenated butadiene.
That is, the polymer having a structural unit derived from the monomer (α1) in the macromonomer (α) corresponds to the above-mentioned “high molecular weight side chain”. In the present invention, the above-mentioned "macromonomer" means a high molecular weight monomer having a polymerizable functional group, and the polymerizable functional group is a (meth) acryloyl group. That is, the main chain of the comb-shaped polymer (A) has a structural unit derived from the (meth) acryloyl group, which is a polymerizable functional group of the macromonomer (α). From the viewpoint of facilitating the satisfaction of both the above requirements (3) and (4), the polymerizable functional group is preferably a methacryloyl group.

The number average molecular weight (Mn) of the macromonomer (α) is preferably 300 or more, more preferably 500 or more, still more preferably 1,000 or more, still more preferably 2,000 or more, still more preferably 4,000 or more. Is. Further, it is preferably 100,000 or less, more preferably 50,000 or less, still more preferably 20,000 or less, still more preferably 10,000 or less.

The macromonomer (α) has, for example, one or more repeating units represented by the following general formulas (bi) to (biii) in addition to the structural unit derived from the monomer (α1). You may be.
When the macromonomer (α) is a copolymer, the form of copolymerization may be a block copolymer or a random copolymer.

In the above general formula (bi), R ^b1 represents a linear alkylene group or a branched chain alkylene group having 1 to 10 carbon atoms. Specifically, methylene group, ethylene group, 1,2-propylene group, 1,3-propylene group, pentylene group, hexylene group, heptylene group, octylene group, nonylene group, decylene group, 2-ethylhexylene group and the like. Can be mentioned.
In the above general formula (b-ii), R ^b2 represents a linear alkylene group or a branched chain alkylene group having 2 to 4 carbon atoms. Specific examples thereof include an ethylene group, a 1,2-propylene group, a 1,3-propylene group, a 1,2-butylene group, a 1,3-butylene group and a 1,4-butylene group.
In the above general formula (b-iii), R ^b3 represents a hydrogen atom or a methyl group.
Further, R ^b4 represents a linear or branched-chain alkyl group having 1 to 10 carbon atoms. Specifically, methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group. , Isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, tert-pentyl group, isohexyl group, tert-hexyl group, isoheptyl group, tert-heptyl group, 2-ethylhexyl group, isooctyl group, isononyl Groups, isodecyl groups and the like can be mentioned.
When each of a plurality of repeating units represented by the above general formulas (bi) to (biii) is provided, R ^b1 , R ^b2 , R ^b3 , and R ^b4 may be the same. , May be different from each other.

Further, from the viewpoint of facilitating both of the above requirements (3) and (4), the content of the structural unit derived from the macromonomer (α) in the comb-shaped polymer (A) is based on the total structural unit of the comb-shaped polymer (A). It is preferably 0.1 mol% to 5 mol%, more preferably 0.3 mol% to 3 mol%, and further preferably 0.5 mol% to 2 mol%.

Further, the constituent unit derived from the macromonomer (α) contained in the comb-shaped polymer (A) may be one kind alone or two or more kinds.

<Aspect of comb-shaped polymer (A): monomer (A2)>
The comb polymer (A) preferably further contains a structural unit derived from the monomer (A2) represented by the following general formula (a2).

[In the above general formula (a2), R ²¹ is a hydrogen atom or a methyl group.
R ²² represents a single bond, -O-, or -NH-.
R ²³ represents a linear alkylene group or a branched chain alkylene group having 2 to 4 carbon atoms. m2 represents an integer from 1 to 20. When m2 is an integer of 2 or more, the plurality of R ^23s may be the same or different, and the (R ²³ O) _m2 portion may be a random copolymerization or a block copolymerization.
R ²⁴ is a linear alkyl group having 1 to 12 carbon atoms or a branched chain alkyl group having 1 to 12 carbon atoms. ]

The comb-shaped polymer (A) further contains a structural unit derived from the monomer (A2) represented by the above general formula (a2), whereby the comb-shaped polymer (A) to the base oil contained in the lubricating oil composition can be prepared. The viscosity index can be improved more easily. Therefore, the content of the structural unit derived from the monomer (A1) represented by the general formula (a1) in the comb-shaped polymer (A) and the content derived from the monomer (A2) represented by the general formula (a2). By appropriately adjusting the content of the constituent unit of the above, the effect of the present invention can be more easily exerted. Specifically, the ratio [(A1) / (A2)] of the content of the structural unit derived from the monomer (A1) to the content of the structural unit derived from the monomer (A2) is a molar ratio. It is preferably 5.0 to 15.0, more preferably 6.0 to 13.0, and even more preferably 7.0 to 12.0.

^{In the general formula (a2), R 21} is preferably a methyl group from the viewpoint of facilitating both of the above requirements (3) and (4).
From the same viewpoint, ^{it is preferable that R 22} is −O− independently of each other.
That is, the monomer (A2) preferably has an acryloyl group or a methacryloyl group as a polymerizable functional group, and more preferably has a methacryloyl group.
From the same viewpoint, m2 is preferably 1 to 5, more preferably 1 to 2, and even more preferably 1.
From the same viewpoint, R ²³ is preferably a linear alkylene group having 2 to 3 carbon atoms, and more preferably a linear alkylene group having 2 carbon atoms.
From the same viewpoint, R ²⁴ is preferably a linear alkyl group having 1 to 12 carbon atoms, more preferably a linear alkyl group having 2 to 8 carbon atoms, having 2 to 6 carbon atoms It is more preferably a straight chain alkyl group, and even more preferably an n-butyl group.

The content of the structural unit derived from the monomer (A2) in the comb polymer (A) is preferably 0 mol% to 15 mol%, more preferably 3 mol, based on all the structural units of the comb polymer (A). % To 15 mol%, more preferably 5 mol% to 12 mol%.

Further, the structural unit derived from the monomer (A2) contained in the comb-shaped polymer (A) may be one kind alone or two or more kinds.

<Aspect of comb-shaped polymer (A): monomer (A3)>
The comb polymer (A) preferably further contains a structural unit derived from an alkyl (meth) acrylate (A3) having a linear alkyl group having 10 to 30 carbon atoms or a branched chain alkyl group having 10 to 30 carbon atoms.

By further containing the structural unit derived from the monomer (A3), the comb-shaped polymer (A) can easily improve the solubility in the base oil, and the effect of the present invention can be more easily exhibited.
From the viewpoint of facilitating the satisfaction of both the above requirements (3) and (4), the alkyl (meth) acrylate (A3) is preferably an alkyl methacrylate.
The alkyl group of the alkyl (meth) acrylate (A3) has preferably 10 to 24 carbon atoms, more preferably 11 to 22 carbon atoms, and even more preferably 12 to 20 carbon atoms. Further, the alkyl group is preferably a linear alkyl group.

The content of the structural unit derived from the alkyl (meth) acrylate (A3) having an alkyl group having 10 to 30 carbon atoms is preferably 0 mol% or more and 30 mol% or less, more preferably 3 on the basis of all structural units. It is mol% or more and 25 mol% or less, more preferably 5 mol% or more and 20 mol% or less.

Further, the constituent unit derived from the monomer (A3) in the comb-shaped polymer (A) may be one kind alone or two or more kinds.

<Aspect of comb-shaped polymer (A): other monomer>
The total content of the structural unit derived from the macromonomer (α) and the structural unit derived from the monomer (A1) in the comb polymer (A) is preferably 76 mol% or more, more preferably 77 mol% or more, and further. It is preferably 78 mol% or more.
Further, the comb-shaped polymer (A) may contain one or more structural units selected from the structural unit derived from the monomer (A2) and the structural unit derived from the monomer (A3). In this case, the total content of the structural unit derived from the macromonomer (α), the structural unit derived from the monomer (A1), the structural unit derived from the monomer (A2), and the structural unit derived from the monomer (A3). The amount is preferably 85 mol% to 100 mol%, more preferably 90 mol% to 100 mol%, still more preferably 95 mol% to 100 mol%.
The comb-shaped polymer (A) contains a macromonomer (α), a monomer (A1), a monomer (A2), and a monomer (A3) within a range that does not significantly impair the effects of the present invention. ) May contain structural units derived from other monomers.
Examples of the other monomer include one or more selected from styrene, N-alkyl (meth) acrylamide and the like.

<Physical characteristics of comb-shaped polymer (A)>
(Mass average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of comb-shaped polymer (A))
The comb-shaped polymer (A) preferably has a mass average molecular weight (Mw) of 300,000 or more and 1.5 million or less from the viewpoint of facilitating both of the above requirements (3) and (4).
Here, from the viewpoint of making it easier to satisfy both the above requirements (3) and (4), the mass average molecular weight (Mw) of the comb-shaped polymer (A) is preferably 300,000 or more and 900,000 or less, more preferably 400,000. It is 850,000 or less, more preferably 500,000 or more and 800,000 or less, and even more preferably 590,000 or more and 800,000 or less.

Further, from the viewpoint of facilitating both of the above requirements (3) and (4), the molecular weight distribution (Mw / Mn) of the comb-shaped polymer (A) is preferably 1.2 or more and 3.7 or less, more preferably 1. It is .2 or more and 2.0 or less, more preferably 1.25 or more and 1.95 or less, and even more preferably 1.30 or more and 1.90 or less.
In this specification, the mass average molecular weight (Mw) and the number average molecular weight (Mn) of the comb-shaped polymer (A) can be measured by the methods described in Examples described later.

(Glass transition temperature of homopolymer of constituent unit derived from monomer (A1))
The comb-shaped polymer (A) contains a structural unit derived from the monomer (A1) represented by the above general formula (a1).
Here, the glass transition temperature (Tg) of the homopolymer composed of the structural unit derived from the monomer (A1) represented by the general formula (a1) is based on the HTHS viscosity of the lubricating oil composition in the effective temperature range. From the viewpoint of facilitating adjustment in a low range, the glass transition temperature (Tg) is preferably 20 ° C. or higher, more preferably 30 ° C. or higher, still more preferably 40 ° C. or higher, still more preferably 50 ° C. or higher.
In the present specification, the glass transition temperature (Tg) of the homopolymer can be measured by differential scanning calorimetry (DSC) or dynamic viscoelasticity measurement (DMA).

<Synthesis method of comb-shaped polymer (A)>
The comb polymer (A) can be obtained, for example, by radical polymerization of the macromonomer (α) and the monomer (A1). The comb-shaped polymer (A) is preferably selected from the monomer (A2), the monomer (A3), and other monomers together with the macromonomer (α) and the monomer (A1). It can be obtained by radical polymerization with one or more kinds of monomers.

As the polymerization method, conventionally known methods such as a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, a reverse phase suspension polymerization method, a thin film polymerization method, and a spray polymerization method can be used. Of these, the solution polymerization method is preferable.
When the comb polymer (A) is produced by solution polymerization, the comb polymer (A) can be obtained by radical polymerization of the macromonomer (α) and the monomer (A1) in a solvent using a polymerization initiator. it can. Preferably, in a solvent, a polymerization initiator is used to select from the monomer (A2), the monomer (A3), and other monomers along with the macromonomer (α) and the monomer (A1). The comb-shaped polymer (A) can be obtained by radical polymerization with one or more kinds of monomers.

The solvent may be any solvent in which the monomer dissolves, and is, for example, an aromatic hydrocarbon solvent such as toluene, xylene, alkylbenzene having 9 to 10 carbon atoms; pentane, hexane, heptane, cyclohexane, octane and the like. An aliphatic hydrocarbon solvent having 5 to 18 carbon atoms; an alcohol solvent having 3 to 8 carbon atoms such as 2-propanol, 1-butanol, 2-butanol, and 1-octanol; and a ketone solvent such as methyl isobutyl ketone and methyl ethyl ketone. Solvents; amide solvents such as N, N-dimethylformamide and N-methylpyrrolidone; ester solvents such as ethyl acetate, propyl acetate and butyl acetate; ether solvents such as diethyl ether, methyl tert-butyl ether and tetrahydrofuran; and described below. Solvent oil or synthetic oil; etc. can be used. Among these, mineral oil or synthetic oil described later is preferable, and mineral oil is more preferable.

Examples of the polymerization initiator include one or more selected from the group consisting of an azo-based initiator, a peroxide-based initiator, a redox-based initiator, and an organic halogen compound initiator. Among these, one or more selected from the azo-based initiator and the peroxide-based initiator is preferable, one or more selected from the azo-based initiator and the organic peroxide-based initiator is more preferable, and the organic peroxide is further preferable. preferable.
Examples of the azo-based polymerization initiator include 2,2'-azobis (isobutyronitrile) (abbreviation: AIBN), 2,2'-azobis (2-methylbutyronitrile) (abbreviation: AMBN), 2, 2'-azobis (2,4-dimethylvaleronitrile) (abbreviation: ADVN), 4,4'-azobis (4-cyanovaleric acid) (abbreviation: ACVA) and salts thereof (eg, hydrochloride, etc.), dimethyl 2, Examples thereof include 2'-azobisisobutyrate, 2,2'-azobis (2-amidinopropane) hydrochloride, 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propionamide] and the like. ..
Examples of the peroxide-based initiator include inorganic peroxides and organic peroxides.
Examples of the inorganic peroxide include hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate and the like.
Examples of the organic peroxide include benzoyl peroxide, di-tert-butyl peroxide, cumene hydroperoxide, succinate peroxide, di (2-ethoxyethyl) peroxydicarbonate, and tert-butylperoxypivalate. , Tert-Hexylperoxypivalate, tert-butylperoxyneoheptanoate, tert-butylperoxyneodecanoate, tert-butylperoxy2-ethylhexanoate, tert-butylperoxyisobutyrate, tert-Amilperoxy2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy2-ethylhexanoate, dibutylperoxytrimethyl adipate, 2,2-bis (4,5-di-) Examples thereof include tert-butylperoxycyclohexyl) propane and laurylperoxide.
Examples of the redox-based initiator include reducing agents such as alkali metal sulfites or sulfites (for example, ammonium sulfite, ammonium persulfate, etc.), ferrous chloride, ferrous sulfate, ascorbic acid, and alkali metals. Examples thereof include those composed of a combination with an oxidizing agent such as sulfite, ammonium persulfate, hydrogen peroxide, and organic peroxide.

Here, in the radical polymerization, a known chain transfer agent may be used, if necessary, for the purpose of adjusting physical properties such as the molecular weight of the comb-shaped polymer (A).
Examples of the chain transfer agent include secondary alcohols such as mercaptans, thiocarboxylic acids and isopropanol, amines such as dibutylamine, hypophosphates such as sodium hypophosphate, chlorine-containing compounds and alkylbenzene compounds. ..
Examples of the mercaptans include alkyl groups having 2 to 20 carbon atoms such as n-butyl mercaptan, isobutyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, sec-butyl mercaptan, tert-butyl mercaptan, and tert-dodecyl mercaptan. Examples thereof include alkyl mercaptan compounds having mercaptan compounds; hydroxyl group-containing mercaptan compounds such as mercaptoethanol and mercaptopropanol; and the like.
Examples of thiocarboxylic acids include thioglycolic acid and thioapple acid.

The amount of the polymerization initiator and chain transfer agent used can be appropriately selected in consideration of the physical characteristics of the desired polymer (for example, adjustment of the molecular weight, etc.).
Examples of the polymerization control method include an adiabatic polymerization method and a temperature control polymerization method. The reaction temperature during polymerization is preferably 30 to 140 ° C, more preferably 50 to 130 ° C, and even more preferably 70 ° C to 120 ° C.
Further, in addition to the method of initiating polymerization by heat, a method of initiating polymerization by irradiating radiation, an electron beam, ultraviolet rays, or the like can also be adopted. A temperature-controlled polymerization method is preferable, and a temperature-controlled solution polymerization method is more preferable.
When the copolymerization is carried out, either random addition polymerization or alternate copolymerization may be used, and either graft copolymerization or block copolymerization may be used.
The obtained polymer may be further dissolved and diluted in a diluent for use from the viewpoint of facilitating dissolution in the base oil contained in the lubricating oil composition.
As the diluent, a solvent that can be used during the above-mentioned polymerization can be used, preferably mineral oil or synthetic oil, and more preferably mineral oil. These diluents may be used alone or in combination of two or more from the above-mentioned ones.

<Other ingredients>
The lubricating oil composition according to one aspect of the present invention further contains other components other than the poly (meth) acrylate and the base oil, if necessary, as long as the effects of the present invention are not impaired. May be good.
Examples of other components include commonly used additives for lubricating oils, and examples of the additives for lubricating oils include metal-based detergents, abrasion-resistant agents, ashless dispersants, and polymers other than the above-mentioned polymers. From the group consisting of viscosity index improvers, extreme pressure agents, pour point lowering agents, antioxidants, defoamers, surfactants, anti-emulsifiers, friction modifiers, oiliness improvers, rust inhibitors and metal inactivating agents. One or more selected types can be mentioned.
These lubricant additives may be used alone or in combination of two or more.

The content of each of these additives for lubricating oil can be appropriately adjusted within a range that does not impair the effects of the present invention. The content of each of the additives for lubricating oil is, for example, preferably 0.001 to 15% by mass, more preferably 0.005 to 12% by mass, based on the total amount (100% by mass) of the lubricating oil composition. More preferably, it is 0.01 to 11% by mass.
When these additives for lubricating oil other than the poly (meth) acrylate are contained, the total content thereof is preferably more than 0% by mass and 30% by mass based on the total amount (100% by mass) of the lubricating oil composition. % Or less, more preferably 0.001 to 25% by mass, still more preferably 0.001 to 20% by mass, still more preferably 0.001 to 15% by mass.

(Metal-based cleaning agent)
Examples of the metal-based cleaning agent include organic acid metal salt compounds containing metal atoms selected from alkali metals and alkaline earth metals, and specifically, metal atoms selected from alkali metals and alkaline earth metals. Examples thereof include metal salicylates, metal phenates, and metal sulfonates containing.
In addition, in this specification, "alkali metal" refers to lithium, sodium, potassium, rubidium, cesium, and francium.
The "alkaline earth metal" refers to beryllium, magnesium, calcium, strontium, and barium.
As the metal atom contained in the metal-based cleaning agent, sodium, calcium, magnesium, or barium is preferable, and calcium is more preferable, from the viewpoint of improving the cleanliness at high temperature.

The metal salicylate is preferably a compound represented by the following general formula (3), the metal phenate is preferably a compound represented by the following general formula (4), and the metal sulfonate is preferably the following general formula (5). ) Is preferable.

In the above general formulas (3) to (5), M is a metal atom selected from alkali metals and alkaline earth metals, and sodium, calcium, magnesium, or barium is preferable, and calcium is more preferable. Further, ^ME is an alkaline earth metal, and calcium, magnesium, or barium is preferable, and calcium is more preferable. q is the valence of M, which is 1 or 2. R ³¹ and R ³² are independently hydrogen atoms or hydrocarbon groups having 1 to 18 carbon atoms. S represents a sulfur atom. r is an integer of 0 or more, preferably an integer of 0 to 3.
Hydrocarbon groups that can be selected as R ³¹ and R ³² include, for example, 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-forming carbon atoms, and a ring-forming carbon. Examples thereof include an aryl group having 6 to 18, an alkylaryl group having 7 to 18 carbon atoms, and an arylalkyl group having 7 to 18 carbon atoms.

These metal-based cleaning agents may be used alone or in combination of two or more. Among these, at least one selected from calcium salicylate, calcium phenate, and calcium sulfonate is preferable from the viewpoint of improving cleanliness at high temperature and from the viewpoint of solubility in base oil.

These metal-based cleaning agents may be any of a neutral salt, a basic salt, a hyperbasic salt, and a mixture thereof.
The total base value of the metal-based cleaning agent is preferably 0 to 600 mgKOH / g.
When the metal-based cleaning agent is a basic salt or a hyperbasic salt, the total base value of the metal-based cleaning agent is preferably 10 to 600 mgKOH / g, more preferably 20 to 500 mgKOH / g. ..
In this specification, the term "base value" refers to JIS K2501: 2003 "Petroleum products and lubricating oil-neutralization value test method". It means the base value by the perchloric acid method measured according to.

When a metal-based cleaning agent is contained as the other component, the content of the metal-based cleaning agent is preferably 0.01 to 10% by mass based on the total amount (100% by mass) of the lubricating oil composition.
The metal-based cleaning agent may be used alone or in combination of two or more. The suitable total content when two or more kinds are used is also the same as the above-mentioned content.

(Abrasion resistant agent)
Examples of the abrasion resistant agent include sulfur-containing compounds such as zinc dialkyldithiophosphate (ZnDTP), zinc phosphate, disulfides, olefins sulfide, oils and fats sulfide, sulfide esters, thiocarbonates, thiocarbamates, and polysulfides. Phosphate esters, phosphoric acid esters, phosphonic acid esters, and phosphorus-containing compounds such as amine salts or metal salts thereof; thio-sulfuric acid esters, thiophosphoric acid esters, thiophosphonic acid esters, and these. Sulfur and phosphorus-containing abrasion resistant agents such as amine salts or metal salts of the above can be mentioned.
Among these, zinc dialkyldithiophosphate (ZnDTP) is preferable.
When an abrasion resistant agent is contained as another component, the content of the abrasion resistant agent is preferably 0.05 to 5.0% by mass based on the total amount (100% by mass) of the lubricating oil composition.
The wear resistant agent may be used alone or in combination of two or more. The suitable total content when two or more kinds are used is also the same as the above-mentioned content.

(Ashes-free dispersant)
Examples of the ashless dispersant include succinate imide, benzylamine, succinate ester, and boron-modified products thereof, and alkenyl succinate imide and boron-modified alkenyl succinate imide are preferable.

Examples of the alkenyl succinate imide include alkenyl succinate monoimide represented by the following general formula (i) and alkenyl succinate bisimide represented by the following general formula (ii).
The alkenyl succinate imide is a compound represented by the following general formula (i) or (ii), and one or more selected from alcohols, aldehydes, ketones, alkylphenols, cyclic carbonates, epoxy compounds, organic acids and the like. May be used as a modified alkenyl succinate imide reacted with.
Examples of the boron-modified alkenyl succinate imide include boron-modified products of compounds represented by the following general formulas (i) or (ii).

In the general formulas (i) and (ii), ^RA , ^RA1 and ^RA2 have independent mass average molecular weights (Mw) of 500 to 3,000 (preferably 1,000 to 3,000). It is an alkenyl group, preferably a polybutenyl group or a polyisobutenyl group.
R ^{B, R B1} and ^{R B2} are each independently an alkylene group having 2 to 5 carbon atoms.
x1 is an integer of 1 to 10, preferably an integer of 2 to 5, and more preferably 3 or 4.
x2 is an integer of 0 to 10, preferably an integer of 1 to 4, and more preferably 2 or 3.

The ratio [B / N] of the boron atom to the nitrogen atom constituting the boron-modified alkenyl succinate imide is preferably 0.5 or more, more preferably 0.6 or more, and further preferably 0.6 or more from the viewpoint of improving cleanliness. It is 0.8 or more, more preferably 0.9 or more.
When an ash-free dispersant is contained as the other component, the content of the ash-free dispersant is preferably 0.1 to 20% by mass based on the total amount (100% by mass) of the lubricating oil composition. ..

(Extreme pressure agent)
Examples of extreme pressure agents include sulfur-based extreme pressure agents such as sulfides, sulfoxides, sulfones, and thiophosphinates, halogen-based extreme pressure agents such as chlorinated hydrocarbons, and organometallic extreme pressure agents. Be done. Further, among the above-mentioned wear resistant agents, a compound having a function as an extreme pressure agent can also be used.
These extreme pressure agents may be used alone or in combination of two or more.
When an extreme pressure agent is contained as another component, the content of the extreme pressure agent is preferably 0.1 to 10% by mass based on the total amount (100% by mass) of the lubricating oil composition.

(Antioxidant)
As the antioxidant, any known antioxidant that has been conventionally used as an antioxidant for lubricating oil can be appropriately selected and used. For example, an amine-based antioxidant or a phenol-based antioxidant can be used. Examples thereof include antioxidants, molybdenum-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, and the like.
Examples of the amine-based antioxidant include diphenylamine and diphenylamine-based antioxidants such as alkylated diphenylamine having an alkyl group having 3 to 20 carbon atoms; α-naphthylamine, phenyl-α-naphthylamine, and alkyl having 3 to 20 carbon atoms. Examples include naphthylamine-based antioxidants having a group such as substituted phenyl-α-naphthylamine; and the like.
Examples of the phenolic antioxidant include 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, and 2,6-di-tert-butyl-4-ethylphenol. Monophenolic antioxidants such as isooctyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate and octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate Agents; diphenolic antioxidants such as 4,4'-methylenebis (2,6-di-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol); hinderedphenols Antioxidants; etc.
Examples of the molybdenum-based antioxidant include a molybdenum amine complex formed by reacting molybdenum trioxide and / or molybdic acid with an amine compound.
Examples of the sulfur-based antioxidant include dilauryl-3,3'-thiodipropionate and the like.
Examples of the phosphorus-based antioxidant include phosphite and the like.
These antioxidants can be contained alone or in any combination of two or more, and are preferably phenolic antioxidants and / or amine-based antioxidants.
When an antioxidant is contained as the other component, the content of the antioxidant is preferably 0.05 to 7% by mass based on the total amount (100% by mass) of the lubricating oil composition.

(Pour point depressant)
Examples of the flow point lowering agent include an ethylene-vinyl acetate copolymer, a condensate of chlorinated paraffin and naphthalene, a condensate of chlorinated paraffin and phenol, and a polymethacrylate type (PMA type; polyalkyl (meth)). (Acrylate, etc.), polyvinyl acetate, polybutene, polyalkylstyrene, etc., and polymethacrylate-based polymethacrylates are preferably used. These pour point lowering agents may be used alone or in combination of two or more.
When a pour point lowering agent is contained as another component, the content of the pour point lowering agent is preferably 0.01 to 10% by mass based on the total amount (100% by mass) of the lubricating oil composition.

(Defoamer)
Examples of the defoaming agent include silicone oils such as dimethylpolysiloxane, fluorosilicone oils and fluoroalkyl ethers. These antifoaming agents may be used alone or in combination of two or more.
When a defoaming agent is contained as another component, the content of the defoaming agent is preferably 0.005 to 5% by mass, more preferably 0.%, based on the total amount (100% by mass) of the lubricating oil composition. It is 005 to 0.5% by mass.

(Surfactant or emulsifier)
Examples of the surfactant or anti-emulsifier include polyalkylene glycol-based nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether and polyoxyethylene alkyl naphthyl ether. These surfactants or anti-emulsifiers can be contained alone or in any combination of two or more.
When a surfactant or an anti-emulsifier is contained as the other component, the content of the surfactant or the anti-emulsifier is independently based on the total amount (100% by mass) of the lubricating oil composition, preferably 0.01. ~ 3% by mass.

(Friction modifier)
Examples of the friction modifier include molybdenum-based friction modifiers such as molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and amine salts of molybthenoic acid; alkyl groups or alkenyl groups having 6 to 30 carbon atoms are contained in the molecule. Ash-free friction modifiers such as aliphatic amines, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, and aliphatic ethers having at least one; fats and oils, amines, amides, sulfide esters, phosphate esters, phosphite esters. , Phosphate ester amine salt and the like.
When a friction modifier is contained as another component, the content of the friction modifier is preferably 0.05 to 4% by mass based on the total amount (100% by mass) of the lubricating oil composition.

(Oil improver)
Examples of the oiliness improver include aliphatic saturated or unsaturated monocarboxylic acids such as stearic acid and oleic acid; polymerized fatty acids such as dimer acid and hydrogenated dimer acid; hydroxy fatty acids such as ricinoleic acid and 12-hydroxystearic acid; lauryl alcohol. , Fatty acid saturated or unsaturated monoalcohols such as oleic acid; aliphatic saturated or unsaturated monoamines such as stearylamine and oleylamine; aliphatic saturated or unsaturated monocarboxylic acid amides such as laurate amide and oleic acid amide; glycerin, Partial esters of polyvalent alcohols such as sorbitol and aliphatic saturated or unsaturated monocarboxylic acids; and the like.
When an oily improver is contained as the other component, the content of the oily improver is preferably 0.01 to 5% by mass based on the total amount (100% by mass) of the lubricating oil composition.

(anti-rust)
Examples of the rust preventive include fatty acids, alkenyl succinic acid half esters, fatty acid sequels, alkyl sulfonates, polyhydric alcohol fatty acid esters, fatty acid amines, oxidized paraffins, and alkyl polyoxyethylene ethers.
When a rust preventive is contained as another component, the content of the rust preventive is preferably 0.01 to 3% by mass based on the total amount (100% by mass) of the lubricating oil composition.

(Metal inactivating agent)
Examples of the metal inactivating agent include benzotriazole-based compounds, tolyltriazole-based compounds, thiazizol-based compounds, imidazole-based compounds, pyrimidine-based compounds and the like.
When the metal inactivating agent is contained as the other component, the content of the metal inactivating agent is preferably 0.01 to 5% by mass based on the total amount (100% by mass) of the lubricating oil composition. ..

[Physical characteristics]
<40 ° C. kinematic viscosity (KV ₄₀ ), 80 ° C. kinematic viscosity (KV ₈₀ ), 100 ° C. kinematic viscosity (KV ₁₀₀ )>
_{The 40 ° C. kinematic viscosity (KV 40} ) of the lubricating oil composition according to one aspect of the present invention is preferably 50 mm ² / s or less, more preferably 40 mm ² / s or less, and further preferably 30 mm ² / s. It is as follows.
_{The 80 ° C. kinematic viscosity (KV 80} ) of the lubricating oil composition according to one aspect of the present invention is preferably 40 mm ² / s or less, more preferably 30 mm ² / s or less, and further preferably 20 mm ² / s. It is as follows.
100 ° C. The kinematic viscosity of the lubricating oil composition which is one embodiment of the present invention _{(KV 100)} is not more than 7.5 mm ² / s, or less preferably 7.4 mm ² / s, more preferably 7.3mm ^{It is 2} / s or less ^{, more preferably 7.1 mm 2} / s or less, and even more preferably 7.0 mm ² / s or less.
_{The 40 ° C. kinematic viscosity (KV 40} ), 80 ° C. kinematic viscosity (KV ₈₀ ), and 100 ° C. kinematic viscosity (KV ₁₀₀ ) of the lubricating oil composition according to one aspect of the present invention are measured according to JIS K2283: 2000. it can.

<Viscosity index>
The viscosity index of the lubricating oil composition according to one aspect of the present invention is preferably 238 or more, more preferably 240 or more, still more preferably 241 or more. The viscosity index of the lubricating oil composition is preferably 300 or less, more preferably 290 or less, and even more preferably 280 or less.
The viscosity index of the lubricating oil composition of one aspect of the present invention can be measured and calculated in accordance with JIS K2283: 2000.

<80 ° C. HTHS viscosity (HTHS ₈₀ ), 100 ° C. viscosity HTHS viscosity (HTHS ₁₀₀ ), 150 ° C. HTHS viscosity (HTHS ₁₅₀ )>
_{The 80 ° C. HTHS viscosity (HTHS 80} ) of the lubricating oil composition according to one aspect of the present invention is preferably 6.7 mPa · s or less, more preferably 6.6 mPa · s or less, and further preferably 6. It is 5 mPa · s or less.
_{The 100 ° C. viscosity HTHS viscosity (HTHS 100} ) of the lubricating oil composition according to one aspect of the present invention is preferably 4.4 mPa · s or less, and more preferably 4.3 mPa · s or less.
_{The 150 ° C. HTHS viscosity (HTHS 150} ) of the lubricating oil composition according to one aspect of the present invention is preferably 2.0 mPa · s or more. _{The 150 ° C. HTHS viscosity (HTHS 150} ) of the lubricating oil composition of one aspect of the present invention is preferably less than 2.6 mPa · s, more preferably less than 2.5 mPa · s, and even more preferably 2. It is less than .4 mPa · s, more preferably less than 2.3 mPa · s, and even more preferably 2.2 mPa · s or less.
_{The 80 ° C. HTHS viscosity (HTHS 80} ), 100 ° C. HTHS viscosity (HTHS ₁₀₀ ), and 150 ° C. HTHS viscosity (HTHS ₁₅₀ ) of the lubricating oil composition according to one aspect of the present invention conform to ASTM D4683 and are TBS high temperature. using viscometer (Tapered Bearing Simulator viscometer), it can be measured at a shear rate of ¹⁰ 6 / s.

[Permanent Shear Stability Index (PSSI)]
PSSI indicates the decrease in viscosity due to shearing derived from the polymer as a percentage, and can be calculated by the calculation formula specified in ASTM D6022-06 (2012).
As a specific method for obtaining PSSI, the method described in Examples described later can be used.
The PSSI value is preferably 6 or less, and more preferably 2 or less, from the viewpoint of fuel efficiency.

[Fuel efficiency]
Fuel efficiency can be evaluated by the average drive torque improvement rate described in Examples described later. As a method of obtaining the average drive torque improvement rate, the method described in Examples described later can be used.
From the viewpoint of fuel efficiency, the lubricating oil composition according to one aspect of the present invention has an average drive torque improvement rate of preferably 0.2 or more, more preferably 0.3 or more.

[Manufacturing method of lubricating oil composition]
The method for producing a lubricating oil composition, which is one aspect of the present invention, includes a step of blending the base oil and the poly (meth) acrylate. Further, in the production method, the base oil and poly are required. Other components other than (meth) acrylate may be further blended.
Each of the base oil, the poly (meth) acrylate, and the other components is the same as that described for the lubricating oil composition, and the preferred embodiments thereof are also the same, and the lubricating oil composition obtained by the production method is also the same. Since the objects are also as described above, their description is omitted.
In the production method, the base oil, the poly (meth) acrylate, and other components added as necessary may be blended by any method, and the method is not limited.

[Use of lubricating oil composition]
The lubricating oil composition of the present invention can exhibit excellent fuel efficiency when used in an effective temperature range.
Therefore, the lubricating oil composition of the present invention is preferably used as an engine oil, and more preferably used as a gasoline engine oil.
Examples of an engine suitable for use of the lubricating oil composition of the present invention include an engine for vehicles such as automobiles, but an engine for automobiles is preferable, and a gasoline engine for automobiles is more preferable. Further, it can be suitably used for an automobile engine equipped with a hybrid mechanism.
The lubricating oil composition according to one aspect of the present invention is suitable for use as a lubricating oil composition for internal combustion engines (engine oil for internal combustion engines) used in automobiles and the like, but is also applicable to other uses. Can be done.

[engine]
The present invention also provides an engine containing the above-mentioned lubricating oil composition of the present invention.
As described above, examples of the engine include an engine for a vehicle such as an automobile, but an engine for an automobile is preferable, and a gasoline engine for an automobile is more preferable. An automobile engine equipped with a hybrid mechanism is also preferable.
The lubricating oil composition of the present invention can exhibit excellent fuel efficiency even when used in an effective temperature range. Therefore, according to the engine of the present invention, excellent fuel efficiency can be exhibited in the effective temperature range.

[Engine lubrication method]
The present invention also provides an engine lubrication method for lubricating an engine using the above-mentioned lubricating oil composition of the present invention.
As described above, examples of the engine include an engine for a vehicle such as an automobile, but an engine for an automobile is preferable, and a gasoline engine for an automobile is more preferable. An automobile engine equipped with a hybrid mechanism is also preferable.
The lubricating oil composition of the present invention can exhibit excellent fuel efficiency even when used in an effective temperature range. Therefore, according to the engine lubrication method of the present invention, excellent fuel efficiency can be imparted to the engine in the effective temperature range.

The present invention will be specifically described with reference to the following examples, but the present invention is not limited to the following examples.

[Various physical property values]
Various physical property values of each component used in Examples and Comparative Examples and the obtained lubricating oil composition were measured by the following methods.

<40 ° C. kinematic viscosity (KV ₄₀ ), 80 ° C. kinematic viscosity (KV ₈₀ ), 100 ° C. kinematic viscosity (KV ₁₀₀ ), and viscosity index>
The 40 ° C. kinematic viscosity (KV ₄₀ ), 80 ° C. kinematic viscosity (KV ₈₀ ), 100 ° C. kinematic viscosity (KV ₁₀₀ ), and viscosity index of the lubricating oil composition were measured and calculated in accordance with JIS K2283: 2000.

<80 ° C. HTHS Viscosity (HTHS ₈₀ ), 100 ° C. HTHS Viscosity (HTHS ₁₀₀ ), and 150 ° C. HTHS Viscosity (HTHS ₁₅₀ )>
Conforming to ASTM D4683, using TBS hot viscometer (Tapered Bearing Simulator Viscometer), at a shear rate of ¹⁰ 6 / s, 80 ℃ HTHS viscosity _(HTHS 80) of the lubricating oil composition, 100 ° C. Viscosity HTHS viscosity (HTHS ₁₀₀ ) and 150 ° C. HTHS viscosity (HTHS ₁₅₀ ) were measured or calculated.

[Viscosity ratio]
Each viscosity ratio of the lubricating oil composition was calculated by dividing the obtained kinematic viscosity or HTHS viscosity at each temperature by the kinematic viscosity at a predetermined temperature.

[Mass average molecular weight (Mw), number average molecular weight (Mn), molecular weight distribution (Mw / Mn)]
"1515 Isocratic HPLC Pump" and "2414 Differential Refractometer (RI) Detector" manufactured by Waters, one column "TSKgradecon SuperHZ-L" manufactured by Tosoh, and two "TSKSuperMultipore HZ-M" The book was attached in this order from the upstream side, measured under the conditions of measurement temperature: 40 ° C., mobile phase: tetrahydrofuran, flow velocity: 0.35 mL / min, and sample concentration 1.0 mg / mL, and determined by standard polystyrene conversion.

[Noack evaporation amount]
Measured according to ASTM D 5800 (Noack test: 250 ° C., 1 hour).

[Permanent Shear Stability Index (PSSI)]
PSSI indicates the decrease in viscosity due to shearing derived from the polymer as a percentage, and was calculated by the following formula defined by ASTM D6022-06 (2012).

In the calculation formula, Kv ₀ is a value of 100 ° C. kinematic viscosity of the mixture (before shearing) in which the polymer is added to the base oil. Kv ₁ is a value of 100 ° C. kinematic viscosity (after shearing) measured in accordance with ASTM D-6278 for a mixture of base oil plus polyalkyl (meth) acrylate. Kv _oil is the value of the kinematic viscosity of the base oil at 100 ° C., and Kv ₀ is adjusted to 7.5 mm ² / s.

[Manufacturing example]
The raw materials used in this production example are shown below.

<Macromonomer (α)>
(One-ended methacrylicated hydrogenated polybutadiene)
As the monomer (α1), one-ended methacrylicated hydrogenated polybutadiene (Kraton Liquid (registered trademark) L-1253, manufactured by Kuraray Co., Ltd.) having a structural unit derived from hydrogenated butadiene having a methacrylate at one end is used. There was. The mass average molecular weight is about 7,000 and the number average molecular weight is about 6,800.

<Polymer (A1)>
(N-Butyl methacrylate, manufactured by Alfa Aesar)
In the above general formula (a1), R ¹¹ is a methyl group, R ¹² is —O—, m1 = 0, and R ¹⁴ is an n-butyl group. The glass transition temperature (Tg) of the homopolymer is 20 ° C. (catalog value). In the following description, it is also referred to as "nC4MA".
(Isobutyl methacrylate, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.)
In the above general formula (a1), R ¹¹ is a methyl group, R ¹² is —O—, m1 = 0, and R ¹⁴ is an isobutyl group. The glass transition temperature (Tg) of the homopolymer is 53 ° C. (catalog value). In the following description, it is also referred to as "iC4MA".
(Cyclohexyl methacrylate, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.)
In the above general formula (a1), R ¹¹ is a methyl group, R ¹² is —O—, m1 = 0, and R ¹⁴ is a cyclohexyl group monomer. The glass transition temperature (Tg) of the homopolymer is 80 ° C. (catalog value). In the following description, it is also referred to as "cC6MA".
(N-hexyl methacrylate, manufactured by Aldrich)
In the above general formula (a1), R ¹¹ is a methyl group, R ¹² is —O—, m1 = 0, and R ¹⁴ is an n-hexyl group. The glass transition temperature (Tg) of the homopolymer is 10 ° C. (catalog value). In the following description, it is also referred to as "nC6MA".

<Polymer (A2)>
(Butylethyl methacrylate, manufactured by Kyoeisha Chemical Co., Ltd.)
Light ester BO was used. In the light ester BO, in the above general formula (a2), R ²¹ is a methyl group, R ²² is −O—, R ²³ is a linear alkylene group having 2 carbon atoms, and m2 = 1. R ²⁴ is a monomer having ₉ n—C ₄ H groups. In the following description, it is also referred to as "BOEMA".

<Polymer (A3)>
It was a mixture of n-dodecyl methacrylate and n-tridecyl methacrylate (C12 / C13 = 45/55%), and light ester L-7 (manufactured by Kyoeisha Chemical Co., Ltd.) was used. In the following description, it is also referred to as "nC1213MA".

<Radical polymerization initiator>
-Pertetra A: 2,2-bis (4,5-di-tert-butylperoxycyclohexyl) propane (manufactured by NOF CORPORATION)

<Base oil for polymerization solvent>
Mineral oil with 100 ° C. kinematic viscosity: 4.2 mm ² / s and viscosity index: 123 was used.

The above raw materials were used in the formulations shown in Table 1, and polymers 1, 2, 3 and 4 were polymerized as the comb-shaped polymer (A).

(1) Production Example 1 (Polymer 1)
7.70 g of macromonomer (α), 5.60 g of n-butoxyethyl methacrylate, nC1213MA in a 4-port separable flask equipped with a thermometer, Dimroth condenser, vacuum seal stirring blade, nitrogen inlet and nitrogen outlet. 11.20 g, n-butyl methacrylate (45.50 g), base oil for polymerization solvent (23.7 g), and pertetra A (0.40 g) were charged and subjected to nitrogen substitution. The mixture was heated and stirred under a nitrogen stream (nitrogen gas: 50 mL / min) at a bath temperature of 95 to 105 ° C. After 2 hours, 46.3 g of a base oil for a polymerization solvent was added, and the mixture was reacted for 7 hours. Next, 70 g of the base oil for a polymerization solvent was added, and the mixture was further heated and stirred for 1 hour. The mixture was left to stand overnight, heated and stirred at a bath temperature of 95 to 105 ° C. for 3 hours, and 140 g of a base oil for a polymerization solvent was added. After heating and stirring for 1 hour, 350 g of a base oil for a polymerization solvent was added, and the mixture was heated and stirred for 2 hours. Under reduced pressure (0.02 MPa or less), the bath temperature was raised to 120 to 130 ° C., and the unreacted monomer was distilled off over 2 hours to obtain polymer 1.

(2) Production Example 2 (Polymer 2)
4.95 g of macromonomer (α) and 3.60 g of n-butoxyethyl methacrylate in a 4-port separable flask equipped with a thermometer, a Dimroth condenser, a vacuum seal stirring blade, a nitrogen inlet, and a nitrogen outlet. 7.20 g of nC1213MA, 29.25 g of isobutyl methacrylate, 15 g of base oil for a polymerization solvent, and 0.26 g of pertetra A were charged, and nitrogen substitution was performed with the charged composition. The mixture was heated and stirred under a nitrogen stream (nitrogen gas: 50 mL / min) at a bath temperature of 95 to 105 ° C. After 1 hour, 30 g of a base oil for a polymerization solvent was added. Further, after 3 hours, 135 g of the base oil for a polymerization solvent was added, and the mixture was stirred for 2 hours. Then, the bath temperature was cooled to 75 to 85 ° C., 150 mL of tetrahydrofuran was added, and the mixture was heated and stirred at 65 to 70 ° C. for 2 hours. The mixture was left to stand overnight, heated and stirred at 65 to 70 ° C. for 8 hours, 225 g of a base oil for a polymerization solvent was added, and tetrahydrofuran was distilled off using Dean Stark while raising the bath temperature to 120 to 130 ° C. .. Further, the unreacted monomer was distilled off under reduced pressure (0.02 MPa or less) at 120 to 130 ° C. over 2 hours to obtain a polymer 2.

(3) Production Example 3 (Polymer 3)
Regarding the charged composition of Production Example 2, isobutyl methacrylate was changed to cyclohexyl methacrylate, the charged amount of pertetra A was changed to 0.23 g, and the polymer 3 was obtained in the same manner as in Production Example 2.

(4) Production Example 4 (Polymer 4)
Regarding the charged composition of Production Example 2, isobutyl methacrylate was changed to n-hexyl methacrylate, the charged amount of pertetra A was changed to 0.22 g, and nitrogen substitution was performed. The mixture was heated and stirred under a nitrogen stream (nitrogen gas: 50 mL / min) at a bath temperature of 95 to 105 ° C. After 2 hours, 30 g of a base oil for a polymerization solvent was added, and the mixture was reacted for 7 hours. The mixture was left to stand overnight, further heated and stirred at a bath temperature of 95 to 105 ° C. for 3 hours, and 135 g of a base oil for a polymerization solvent was added. Under reduced pressure (0.02 MPa or less), the bath temperature was raised to 120 to 130 ° C., and the unreacted monomer was distilled off over 2 hours to obtain a polymer 4.

(5) Comb-shaped polymer A
It is a comb-shaped polymer containing 74 mol% of n-butyl methacrylate, 11 mol% of butoxyethyl methacrylate, 14 mol% of nC1213MA, and 1 mol% of macromonomer (α).
(6) Comb-shaped polymer B
It is a comb-shaped polymer containing 85 mol% of n-butyl methacrylate, 14 mol% of nC1213MA, and 1 mol% of macromonomer (α).

[Examples 1 to 3, Comparative Examples 1 to 3]
Polymers 1 to 4 or comb-shaped polymers A to B and a base oil were blended in the formulation shown in Table 1 to obtain lubricating oil compositions of Examples 1 to 3 and Comparative Examples 1 to 3.
The content in Table 1 is the content in terms of resin content. The glass transition temperature (Tg) in Table 1 is the glass transition temperature of the homopolymer of the monomer (A1).

<Base oil>
100N mineral oil (Classification in API base oil category: Group III, 40 ° C. kinematic viscosity: 19.6 mm ² / s, 100 ° C. kinematic viscosity: 4.2 mm ² / s, viscosity index: 122)

<Additives for other lubricating oils>
Flow point depressants, phenolic antioxidants, amine antioxidants, boron-free succinic acid imides, boron-containing succinate imides, metal inactivating agents, defoamers, metal cleaning agents, etc.

[Evaluation of fuel efficiency]
An engine having the following specifications was filled with a lubricating oil composition, a motoring torque test was performed under the test conditions shown below, and the torque (dB) at a predetermined rotation speed was measured. In addition, the average drive torque improvement rate was obtained by calculating the average value of the torque at each engine speed at each oil temperature. The torque values of each Example and Comparative Example were calculated as values when the rate of change with respect to the torque value of Comparative Example 1 was set to 0 in Comparative Example 1. The results are shown in Table 1.
-Test conditions-
・ Equipment used: Engine motoring equipment ・ Engine: Water-cooled 1,500CC in-line 4-cylinder engine for four-wheeled vehicles ・ Valve type: DOHC (roller)
-Engine speed: 1,500 rpm, 2,000 rpm, and 2,500 rpm
-Oil pan Oil temperature: 60 ° C, 80 ° C, and 100 ° C

As can be seen from Table 1, the lubricating oil compositions of Examples 1 to 3 satisfying all the configurations of the present invention have a high average drive torque improvement rate and are excellent in fuel efficiency.
On the other hand, the lubricating oil compositions of Comparative Examples 1 and 2 have the evaluation results of the motoring torque tests at 60 ° C., 80 ° C., and 100 ° C., and the average drive torque improvement rate, all of which are the lubrications of Examples 1 to 3. It is lower and inferior to the oil composition. Further, the lubricating oil composition of Comparative Example 3 had an evaluation result of −0.62% in the motoring torque test at 60 ° C. and 1,500 rpm, which was the same as the evaluation result of the lubricating oil composition of Examples 1 to 3. It is low and inferior in comparison. That is, the lubricating oil compositions of Comparative Examples 1 to 3 that do not satisfy at least one of the requirements (1) to (4) of the present invention cannot reduce the torque loss and reduce the torque loss in a wide temperature range. It can be seen that the effect of making it is not obtained.

Claims (12)

1. Contains base oil and poly (meth) acrylate,
   The content of the poly (meth) acrylate in terms of resin content is 0.1% by mass or more and 2.0% by mass or less based on the total amount of the lubricating oil composition.
   A lubricating oil composition that satisfies the following requirements (1) to (4).
   -Requirement (1): The kinematic viscosity at 100 ° C. is 4.0 mm ² / s or more and 7.5 mm ² / s or less.
   -Requirement (2): Noack evaporation amount is 30% by mass or less.
   -Requirement (3): The ratio of 40 ° C. kinematic viscosity KV ₄₀ to 100 ° C. kinematic viscosity KV _{100 (KV 40} / KV ₁₀₀ ) is 3.95 or less.
   -Requirement (4): The ratio of 80 ° C. HTHS viscosity HTHS ₈₀ to 100 ° C. kinematic viscosity KV _{100 (HTHS 80} / KV ₁₀₀ ) is 0.96 or less.
2. The poly (meth) acrylate contains a structural unit derived from a macromonomer (α) and a structural unit derived from a monomer (A1) represented by the following general formula (a1).
   

   

   
   [In the above general formula (a1), R ¹¹ is a hydrogen atom or a methyl group.
   R ¹² represents a single bond, -O-, or -NH-.
   R ¹³ represents a linear alkylene group having 2 to 4 carbon atoms or a branched chain alkylene group having 2 to 4 carbon atoms. m1 represents an integer from 0 to 20. When m1 is an integer of 2 or more, the plurality of R ^13s may be the same or different, and the (R ¹³ O) _m1 portion may be a random copolymerization or a block copolymerization.
   R ¹⁴ is a non-cyclic alkyl group having 4 to 5 carbon atoms or a group having 6 to 8 carbon atoms having a cyclic alkyl group. ]
   The macromonomer (α) has a (meth) acryloyl group at one end and has a structural unit derived from a monomer (α1) selected from butadiene and hydrogenated butadiene.
   The lubricating oil composition according to claim 1, wherein the content of the structural unit derived from the monomer (A1) is 75 mol% or more based on all the structural units, and the comb-shaped polymer (A) is contained.
3. The lubricating oil composition according to claim 2, wherein the acyclic alkyl group having 4 to 5 carbon atoms has a tertiary carbon.
4. The lubricating oil composition according to claim 2 or 3, wherein the comb-shaped polymer (A) further contains a structural unit derived from the monomer (A2) represented by the following general formula (a2).
   

   

   
   [In the above general formula (a2), R ²¹ is a hydrogen atom or a methyl group.
   R ²² represents a single bond, -O-, or -NH-.
   R ²³ represents a linear alkylene group having 2 to 4 carbon atoms or a branched chain alkylene group having 2 to 4 carbon atoms. m2 represents an integer from 1 to 20. When m2 is an integer of 2 or more, the plurality of R ^23s may be the same or different, and the (R ²³ O) _m2 portion may be a random copolymerization or a block copolymerization.
   R ²⁴ is a linear alkyl group having 1 to 12 carbon atoms or a branched chain alkyl group having 1 to 12 carbon atoms. ]
5. 2. The comb-shaped polymer (A) further contains a structural unit derived from an alkyl (meth) acrylate (A3) having a linear alkyl group having 10 to 30 carbon atoms or a branched chain alkyl group having 10 to 30 carbon atoms. The lubricating oil composition according to any one of 4 to 4.
6. The content of the structural unit derived from the alkyl (meth) acrylate (A3) having the linear alkyl group having 10 to 30 carbon atoms or the branched chain alkyl group having 10 to 30 carbon atoms is 30 mol% based on the total structural unit. The lubricating oil composition according to claim 5, which is as follows.
7. The content of the structural unit derived from the monomer (A1) is 75 mol% or more based on the total amount of the structural unit of the comb polymer (A).
   The lubricating oil composition according to claim 2 or 3, further comprising a structural unit derived from the monomer (A2) represented by the following general formula (a2).
   

   

   
   [In the above general formula (a2), R ²¹ is a hydrogen atom or a methyl group.
   R ²² represents a single bond, -O-, or -NH-.
   R ²³ represents a linear alkylene group having 2 to 4 carbon atoms or a branched chain alkylene group having 2 to 4 carbon atoms. m2 represents an integer from 1 to 20. When m2 is an integer of 2 or more, the plurality of R ^23s may be the same or different, and the (R ²³ O) _m2 portion may be a random copolymerization or a block copolymerization.
   R ²⁴ is a linear alkyl group having 1 to 12 carbon atoms or a branched chain alkyl group having 1 to 12 carbon atoms. ]
8. The lubricating oil composition according to any one of claims 2 to 7, wherein the mass average molecular weight (Mw) of the comb-shaped polymer (A) is 300,000 or more and 1.5 million or less.
9. The lubricating oil composition according to any one of claims 2 to 8, wherein the molecular weight distribution (Mw / Mn) of the comb-shaped polymer (A) is 1.2 or more and 3.7 or less.
10. According to any one of claims 2 to 9, the glass transition temperature (Tg) of the homopolymer composed of the structural unit derived from the monomer (A1) represented by the general formula (a1) is 20 ° C. or higher. The lubricating oil composition described.
11. The lubricating oil composition according to any one of claims 1 to 10, which is used for an internal combustion engine of an automobile.
12. The lubricating oil composition according to any one of claims 1 to 10, which is used for an internal combustion engine of an automobile equipped with a hybrid mechanism.