JP7281426B2 - lubricating oil composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a lubricating oil composition having an excellent viscosity index, a copolymer used in the lubricating oil composition, and a viscosity index improver containing the copolymer.

In recent years, lubricating oil compositions used as drive system oils such as automatic transmission oils (ATF), continuously variable transmission oils (CVTF), shock absorber oils (SAF), internal combustion engine oils, hydraulic fluids, etc. Various properties are required depending on the application.
For example, with regard to fuel efficiency of automobiles, we need to reduce the weight of automobiles, improve the engine, improve the automobile itself, reduce the viscosity of lubricating oil to prevent friction loss in drive system equipment and engines, Improvements in lubricating oils, such as the addition of additives, have also become important. However, since the lubricating oil is used in a wide temperature range, simply reducing the viscosity will thin the oil film at the lubricated part under high temperature conditions, increasing wear and seizure due to contact between members. It causes troubles such as Therefore, it is desirable that the viscosity of the lubricating oil does not change as much as possible over a wide temperature range. That is, it is desirable that the lubricating oil has a high viscosity index.
Therefore, for lubricating oils that are used over a wider temperature range, for example, from high to low temperatures, a method of adding a viscosity index improver to improve the temperature dependence of viscosity is generally used.
For example, Patent Document 1 discloses a copolymer containing a specific content of a specific essential constituent monomer, and an ester oil base oil having a kinematic viscosity at 100° C. of 1.0 to 2.5 mm ² /s. and lubricating oil compositions containing the viscosity index improver.
Further, for example, in Patent Document 2, a viscosity index improvement for a hydrocarbon-based synthetic base oil containing a copolymer that satisfies a specific solubility parameter and contains a specific content of a specific essential constituent monomer and lubricating oil compositions containing the viscosity index improver and a hydrocarbon synthetic base oil.

JP 2017-57378 A JP 2015-38194 A

As described above, various viscosity index improvers have been used and studied to improve the viscosity index of lubricating oil compositions as a method of improving the temperature dependence of the viscosity of lubricating oil compositions.
Patent Document 1 discloses that a lubricating oil composition obtained by mixing the viscosity index improver composition with an ester oil base oil has a high viscosity index. On the other hand, in Patent Document 1, a lubricating oil composition obtained by mixing a mineral base oil with a viscosity index improver composition containing a copolymer containing similar constituent monomers and a mineral base oil. In some cases, it is disclosed that the viscosity index is low. Therefore, in Patent Document 1, no study is made to obtain a lubricating oil composition containing a lubricating oil base oil other than an ester oil base oil such as a mineral base oil as a main component and having a good viscosity index.
On the other hand, in Patent Document 1, a viscosity index improver for a hydrocarbon synthetic base oil is studied, but there is a demand for further improvement in the viscosity index of the obtained lubricating oil composition.
Here, as described above, the lubricating oil composition is used in various applications, and the base oil used in the lubricating oil composition is base oil other than heteroatom oil-containing base oil such as ester oil base oil (for example, , hydrocarbon-based base oils) are mainly used in many lubricating oil compositions.
As described above, as a lubricating oil composition, a lubricating oil composition containing as a main component a base oil other than a heteroatom oil-containing base oil such as an ester oil base oil (for example, a hydrocarbon base oil) has been The effect of the combination of a lubricating base oil and a viscosity index improver on the viscosity index, and the optimum viscosity index improver for improving the viscosity index of the lubricating oil composition have not been sufficiently studied. However, there was room for further investigation.
From this point of view, an object of the present invention is to provide a lubricating oil composition containing a certain amount or more of a base oil other than a heteroatom-containing base oil and having a good viscosity index.

As a result of extensive studies, the present inventors have found that the copolymer (A) satisfying specific requirements obtained by polymerization in a polymerization solvent containing a heteroatom-containing base oil (x) is a heteroatom-containing base oil (x ) can improve the viscosity index of a lubricating oil composition containing a certain amount or more of the base oil (y). Each embodiment of the present invention has been completed based on such findings. That is, according to each embodiment of the present invention, the following [1] to [20] are provided.
[1] Component (A): (meth)acrylate (a) having a linear alkyl group having 4 or less carbon atoms in the side chain of the monomer (a), and the side chain of the monomer (b) A weight-average molecular weight obtained by polymerizing a constituent monomer containing a (meth)acrylate (b) having a branched alkyl group with 4 or more carbon atoms in a polymerization solvent containing a heteroatom-containing base oil (x) A copolymer (A) having a (Mw) of 32,000 or more,
The content of the monomer (a) is 50% by mass or more and 63% by mass or less based on 100% by mass of the total amount of the constituent monomers, and
A copolymer (A) in which the content of the monomer (b) is 37% by mass or more and 50% by mass or less based on 100% by mass of the total amount of the constituent monomers;
Component (B): heteroatom-containing base oil (x), and
Component (C): base oil (y) other than heteroatom-containing base oil (x)
contains
A lubricating oil composition in which the content of component (C) is 55% by mass or more based on 100% by mass of the total amount of the lubricating oil composition.
[2] The lubricating oil composition according to [1] above, wherein the heteroatom-containing base oil (x) is one or more selected from the group consisting of esters, ethers, and amides.
[3] The heteroatom-containing base oil (x) has a solubility parameter (SP value) of 7.90 (cal/cm ³ ) ^1/2 or more and 9.40 (cal/cm ³ ) ^1/2 or less. The lubricating oil composition according to [1] or [2].
[4] The lubricating oil composition according to any one of [1] to [3] above, wherein component (C) is a hydrocarbon base oil.
[5] The above [1] to [4], wherein the content of the heteroatom-containing base oil (x) in the polymerization solvent is 50% by mass or more and 100% by mass or less based on 100% by mass of the total amount of the polymerization solvent. ] Lubricating oil composition according to any one of.
[6] The lubricating oil composition according to any one of [1] to [5], wherein the monomer (a) is methyl methacrylate.
[7] The lubricating oil composition according to any one of [1] to [6] above, wherein the monomer (b) is a (meth)acrylate represented by the following general formula (1).

（一般式（１）中、Ｒ^１は、水素原子又はメチル基を示し、Ｒ^２は炭素数２～４の直鎖又は分岐アルキレン基を示し、Ｒ^３及びＲ^４は、それぞれ独立に、炭素数２～１８のアルキル基を示す。ｎは、０～２０の整数を示す。ｎが２以上の場合、複数存在するＲ^２は同一であっても異なっていてもよい。）

(In general formula (1), R ¹ represents a hydrogen atom or a methyl group, R ² represents a linear or branched alkylene group having 2 to 4 carbon atoms, and R ³ and R ⁴ each independently represent a carbon represents an alkyl group of numbers 2 to 18. n represents an integer of 0 to 20. When n is 2 or more, a plurality of R ² may be the same or different.)

[8] The above [1], wherein the total content of the monomer (a) and the monomer (b) is 90% by mass or more and 100% by mass or less based on 100% by mass of the total amount of the constituent monomers. The lubricating oil composition according to any one of to [7].
[9] The solubility parameter (SP value) of component (A) is 9.20 (cal/cm ³ ) ^1/2 or more and 9.60 (cal/cm ³ ) ^{1/2 or} less, above [1] to [8] The lubricating oil composition according to any one of [8].
[10] The lubricating oil composition according to any one of [1] to [9] above, wherein the weight average molecular weight (Mw) of component (A) is 200,000 or less.
[11] The content of component (A) in the lubricating oil composition is 8% by mass or more and 20% by mass or less, based on the total amount of 100% by mass of the lubricating oil composition. A lubricating oil composition according to any one of the preceding claims.
[12] The lubrication according to any one of [1] to [11], wherein the permanent shear stability index (PSSI) measured by an ultrasonic test in accordance with JASO M 347-95 is less than 5.0. oil composition.
[13] The following component (A), which is blended with the base oil (y) other than the heteroatom-containing base oil (x).
Component (A): (meth)acrylate (a) having a linear alkyl group having 4 or less carbon atoms in the side chain of monomer (a), and the number of carbon atoms in the side chain of monomer (b) Weight average molecular weight (Mw) obtained by polymerizing a constituent monomer containing (meth)acrylate (b) having 4 or more branched alkyl groups in a polymerization solvent containing heteroatom-containing base oil (x) is 32,000 or more (A),
The content of the monomer (a) is 50% by mass or more and 63% by mass or less based on 100% by mass of the total amount of the constituent monomers, and
A copolymer (A) in which the content of the monomer (b) is 37% by mass or more and 50% by mass or less based on 100% by mass of the total amount of the constituent monomers.
[14] A viscosity index improver composition containing the following component (A) and a heteroatom-containing base oil (x), which is blended with a base oil (y) other than the heteroatom-containing base oil (x).
Component (A): (meth)acrylate (a) having a linear alkyl group having 4 or less carbon atoms in the side chain of monomer (a), and the number of carbon atoms in the side chain of monomer (b) Weight average molecular weight (Mw) obtained by polymerizing a constituent monomer containing (meth)acrylate (b) having 4 or more branched alkyl groups in a polymerization solvent containing heteroatom-containing base oil (x) is 32,000 or more (A),
The content of the monomer (a) is 50% by mass or more and 63% by mass or less based on 100% by mass of the total amount of the constituent monomers, and
A copolymer (A) in which the content of the monomer (b) is 37% by mass or more and 50% by mass or less based on 100% by mass of the total amount of the constituent monomers.
[15] The method for producing a lubricating oil composition according to any one of [1] to [12], wherein the following components (A) and (B) are blended with the following component (C).
Component (A): (meth)acrylate (a) having a linear alkyl group having 4 or less carbon atoms in the side chain of monomer (a), and the number of carbon atoms in the side chain of monomer (b) Weight average molecular weight (Mw) obtained by polymerizing a constituent monomer containing (meth)acrylate (b) having 4 or more branched alkyl groups in a polymerization solvent containing heteroatom-containing base oil (x) is 32,000 or more (A),
The content of the monomer (a) is 50% by mass or more and 63% by mass or less based on 100% by mass of the total amount of the constituent monomers, and
A copolymer (A) in which the content of the monomer (b) is 37% by mass or more and 50% by mass or less based on 100% by mass of the total amount of the constituent monomers;
Component (B): heteroatom-containing base oil (x)
Component (C): base oil (y) other than heteroatom-containing base oil (x)
[16] Component (C), wherein the viscosity index improver composition according to [14] is blended with base oil (y) other than heteroatom-containing base oil (x) as component (C). A method for producing a lubricating oil composition, wherein the content is 55% by mass or more based on 100% by mass of the total amount of the lubricating oil composition.
[17] Lubrication characterized by using the lubricating oil composition according to any one of [1] to [12] or the lubricating oil composition obtained by the production method according to [15] or [16] Method.
[18] Drive system equipment using the lubricating oil composition according to any one of [1] to [12] or the lubricating oil composition obtained by the production method according to [15] or [16].
[19] An internal combustion engine using the lubricating oil composition according to any one of [1] to [12] or the lubricating oil composition obtained by the production method according to [15] or [16].
[20] A hydraulic device using the lubricating oil composition according to any one of [1] to [12] or the lubricating oil composition obtained by the production method according to [15] or [16].

According to the present invention, it is possible to provide a lubricating oil composition containing a certain amount or more of a base oil other than a heteroatom-containing base oil and having a good viscosity index.

Preferred embodiments of the present invention are described in detail below.
[Lubricating oil composition]
A lubricating oil composition that is one embodiment of the present invention contains the following components (A) to (C), and the content of component (C) is 55 mass based on the total amount of the lubricating oil composition 100% by mass. % or more.
Component (A): (meth)acrylate (a) having a linear alkyl group having 4 or less carbon atoms in the side chain of monomer (a), and the number of carbon atoms in the side chain of monomer (b) Weight average molecular weight (Mw) obtained by polymerizing a constituent monomer containing (meth)acrylate (b) having 4 or more branched alkyl groups in a polymerization solvent containing heteroatom-containing base oil (x) is 32,000 or more (A),
The content of the monomer (a) is 50% by mass or more and 63% by mass or less based on 100% by mass of the total amount of the constituent monomers, and
A copolymer (A) in which the content of the monomer (b) is 37% by mass or more and 50% by mass or less based on 100% by mass of the total amount of the constituent monomers;
Component (B): heteroatom-containing base oil (x)
Component (C): base oil (y) other than heteroatom-containing base oil (x)

When the lubricating oil composition containing 55% by mass or more of the component (C) based on the total amount of 100% by mass of the lubricating oil composition does not contain the components (A) and (B), the lubricating oil has an excellent viscosity index. Difficult to obtain compositions.

Hereinafter, in the present specification, the lower limit values and upper limit values described stepwise for preferable numerical ranges (for example, ranges of content etc.) can be independently combined. For example, the description of the lower limit "preferably 10 or more, more preferably 30 or more, more preferably 40 or more" and the upper limit "preferably 90 or less, more preferably 80 or less, more preferably 70 or less" From the description, as a suitable range, for example, "10 or more and 70 or less", "30 or more and 70 or less", "40 or more and 80 or less". can also Also, from the same description, for example, it is also possible to select a range in which either the lower limit value or the upper limit value is simply defined, such as "40 or more" or "70 or less". 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, more preferably 40 to The same applies to the preferred range that can be selected from the description such as "is 70". In addition, in the description of numerical ranges in this specification, for example, the description "10 to 90" is synonymous with "10 or more and 90 or less".
Moreover, in this specification, the term "hydrocarbon group" means a group composed only of carbon atoms and hydrogen atoms. The "hydrocarbon group" includes an "aliphatic group" composed of a straight or branched chain, an "alicyclic group" having one or more non-aromatic saturated or unsaturated carbon rings, a benzene ring, etc. includes an "aromatic group" having one or more aromatic rings exhibiting the aromaticity of
In the present specification, "the number of ring-forming carbon atoms" means the number of carbon atoms among the atoms constituting the ring itself of a compound having a structure in which atoms are cyclically bonded. When the ring is substituted with a substituent, the carbon contained in the substituent is not included in the number of ring-forming carbon atoms.
Further, in this specification, for example, "(meth)acrylate" refers to both "acrylate" and "methacrylate", and "(meth)acrylic acid" refers to both "acrylic acid" and "methacrylic acid." Both are indicated, as are other similar terms.

Moreover, in this specification, "PSSI" means "Permanent Shear Stability Index". Generally, the PSSI indicates the ability of the polymer (polyalkyl (meth)acrylate) to resist degradation. However, in this specification, unless otherwise specified, the "PSSI" refers to the "PSSI of the lubricating oil composition" described herein, and as an index showing the shear stability of the lubricating oil composition I am using The PSSI of the lubricating oil compositions described herein is primarily due to the shear stability of component (A), copolymer (A). Here, the dispersed state of the copolymer (A) or the shear force substantially applied to the copolymer (A) is the heteroatom-containing base oil (x ), and the base oil (y) other than the heteroatom-containing base oil (x), which is the component (C). That is, it is thought that it also varies depending on the composition of the lubricating oil composition. As a result, even when the same shearing force is applied to the entire lubricating oil composition, the degree of decomposition of the copolymer (A) is considered to change, and as a result, the same copolymer (A) It is considered that the PSSI is different due to the difference in the composition even between the lubricating oil compositions containing. Therefore, the PSSI of the lubricating oil composition can be considered to indicate the shear stability of the lubricating oil composition itself containing the copolymer (A). In the present specification, the PSSI of the lubricating oil composition is specifically measured and calculated by the method described in Examples, and the smaller the PSSI, the more stable the lubricating oil composition against shear. Therefore, viscosity reduction due to shearing is unlikely to occur.
Each component contained in the lubricating oil composition will be described below.

<Component (A): Copolymer (A)>
The copolymer (A) contained in the lubricating oil composition (hereinafter also simply referred to as "component (A)") has a linear alkyl group having 4 or less carbon atoms in the side chain of the monomer (a) (Meth) acrylate (a) having a, and a constituent monomer containing a (meth) acrylate (b) having a branched alkyl group having 4 or more carbon atoms in the side chain of the monomer (b), A copolymer obtained by polymerization in a polymerization solvent containing the atom-containing base oil (x) and having a mass average molecular weight (Mw) of 32,000 or more,
The content of the monomer (a) is 50% by mass or more and 63% by mass or less based on 100% by mass of the total amount of the constituent monomers, and
The content of the monomer (b) is 37% by mass or more and 50% by mass or less based on 100% by mass of the total amount of the constituent monomers.
Here, in the present specification, the "constituent monomer" refers to a monomer that is a raw material constituting the copolymer (A) that is one embodiment of the present invention, and the polymer described later is polymerized. Polymerization initiators and/or chain transfer agents used at the time of polymerization are not included in the monomers.
Further, as will be described later, the component (A) is used by blending with the base oil (y) other than the heteroatom-containing base oil (x), and the base oil other than the heteroatom-containing base oil (x) ( y) can improve the viscosity index of the lubricating oil composition.
That is, the component (A), which is one embodiment of the present invention, is used by blending with the base oil (y) other than the heteroatom-containing base oil (x).

(Polymerization solvent)
Said component (A) is polymerized in a polymerization solvent, said polymerization solvent comprising a heteroatom-containing base oil (x).
Here, if the polymerization solvent in polymerizing the component (A) does not contain the heteroatom-containing base oil (x), the viscosity index of the resulting lubricating oil composition cannot be sufficiently improved.
Although the reason is not clear, it is considered as follows.
When the polymerization solvent contains the heteroatom-containing base oil (x) and when the polymerization solvent does not contain the heteroatom-containing base oil (x), there is some difference in the molecular state in the molecular structure of the resulting copolymer. It is believed that there are differences. Then, for example, when the polymerization solvent does not contain the heteroatom-containing base oil (x), the molecular structure of the obtained copolymer includes the base oil (y) other than the heteroatom-containing base oil (x). It is thought that a polymer containing many partial structures with poor compatibility or a structure with poor compatibility with base oil (y) other than heteroatom-containing base oil (x) as a whole is produced.
In this case, the copolymer is not sufficiently compatible with the base oil (y) other than the heteroatom-containing base oil (x), and the viscosity index of the resulting lubricating oil composition cannot be sufficiently improved, or , it is thought that a problem such as cloudiness occurs and incompatibility occurs.
Also, for example, if the polymerization solvent does not contain the heteroatom-containing base oil (x), the molecular structure of the obtained copolymer may be different from that of the obtained lubricating oil composition, even if it does not cause white turbidity. It is considered that many structures are included that cannot sufficiently improve the viscosity index.
On the other hand, the molecular structure of the copolymer, which is the component (A) polymerized in the polymerization solvent containing the heteroatom-containing base oil (x), includes, for example, a base oil (y) other than the heteroatom-containing base oil (x) ) and/or contains many molecular structures with better compatibility. Further, for example, it is considered that the molecular structure of the copolymer, which is the component (A), contains many molecular structures capable of sufficiently improving the viscosity index of the resulting lubricating oil composition. be done.

As described above, even if the monomer composition is the same, when the polymerization solvent contains the heteroatom-containing base oil (x) and when the polymerization solvent does not contain the heteroatom-containing base oil (x), It is believed that there is some difference in the molecular structure of the copolymer or in the molecular state in the polymerization solvent. However, for example, if an attempt is made to identify the difference in molecular structure by a known analytical technique, extremely complicated analysis such as isolation and purification, establishment of a technique for defining the structure of macromolecules, etc. is required.
Furthermore, a component (A) obtained by polymerization in a polymerization solvent containing a heteroatom-containing base oil (x) and a heteroatom-containing base oil (x) having the same monomer composition as the component (A) A copolymer obtained by polymerization in a polymerization solvent that does not contain x) is thought to contain a certain number or more of molecules having a molecular structure common to each other. Except for this, it is expected that confirmation of differences from the molecular structure of the polymer (sequence and binding mode of the structure derived from each monomer) will take much longer.
In addition, for example, if the above difference is in the molecular state in the polymerization solvent (for example, the difference in the spatial spread of molecules, etc.), the difference is confirmed at the time of isolation and purification. difficult to do. For example, as described later, in Comparative Examples of the present invention, a copolymer obtained by polymerization in a polymerization solvent containing no heteroatom-containing base oil (x) was added to a heteroatom-containing base oil ( It has been confirmed that even when x) is added to prepare a lubricating oil composition, the viscosity index of the resulting lubricating oil composition cannot be sufficiently improved.
Therefore, at present, a component (A) obtained by polymerization in a polymerization solvent containing a heteroatom-containing base oil (x) has a monomer composition similar to that of the component (A), but has a heteroatom-containing As described above, it is considered that there is some difference between the copolymer obtained by polymerization in a polymerization solvent that does not contain the base oil (x), but the molecular structure and properties of the component (A) are simply The reality is that it is not possible to specify the differences specifically.

The heteroatom-containing base oil (x) (hereinafter also simply referred to as "base oil (x)") is a base oil composed of a compound containing a heteroatom in its molecular skeleton. Here, the term "heteroatom" refers to atoms other than carbon and hydrogen, such as nitrogen, oxygen and sulfur atoms.
Base oils (x) include, for example, alcohols, esters, ethers, amides, ketones, thioethers and the like. Among these, the base oil (x) is preferably one or more selected from the group consisting of esters, ethers, amides, ketones, and thioethers, from the viewpoint of further improving the viscosity index of the resulting lubricating oil composition. , more preferably one or more selected from the group consisting of esters, ethers and amides, more preferably one or more selected from the group consisting of esters and ethers.

Examples of the esters include various esters such as monoesters, diesters, and polyesters.
Examples of monoesters include decyl decanoate and 2-ethylhexyl caprylate.
Examples of diesters include bis(2-ethylhexyl) sebacate and dibutyl adipate.
Examples of polyesters include complete esters or partial esters of trihydric or higher polyhydric alcohols such as trimethylolpropane and carboxylic acids such as myristic acid, palmitic acid, stearic acid and oleic acid. The polyester is preferably one or more selected from full esters of trimethylolpropane and partial esters of trimethylolpropane, more preferably full esters of trimethylolpropane and one or more selected from stearic acid and oleic acid. and one or more selected from partial esters of trimethylolpropane and one or more selected from stearic acid and oleic acid, more preferably trimethylolpropane and one or more selected from stearic acid and oleic acid. esters.
Among the above esters, one or more selected from the group consisting of decyl decanoate, 2-ethylhexyl caprylate, bis(2-ethylhexyl) sebacate, dibutyl adipate, and trimethylolpropane ester is preferable, and decanoic acid More preferably one or more selected from the group consisting of decyl, bis(2-ethylhexyl) sebacate, and trimethylolpropane ester, and one or more selected from the group consisting of decyl decanoate and bis(2-ethylhexyl) sebacate is more preferred.

Examples of the ether include bis(2-ethylhexyl) ether and polyvinyl ether. As the polyvinyl ether, trimers to pentamers of polyvinyl ether are preferable.

Examples of the amide include N,N-di(2-ethylhexyl)-2-ethylhexanamide and the like.

Further, from the viewpoint of further improving the viscosity index of the obtained lubricating oil composition, the solubility parameter (SP value) of the base oil (x) is preferably 7.90 (cal/cm ³ ) ^1/2 or more and 9.40 (cal/cm ³ ) ^1/2 or less, more preferably 7.92 (cal/cm ³ ) ^1/2 or more and 9.20 (cal/cm ³ ) ^1/2 or less, more preferably 7.93 (cal/cm 3 ) cm ³ ) ^1/2 or more and 9.00 (cal/cm ³ ) ^1/2 or less, more preferably 7.94 (cal/cm ³ ) ^1/2 or more and 8.80 (cal/cm ³ ) ^1/2 It is below.
Here, the solubility parameter (SP value) is a value (δ) defined by the regular solution theory introduced by Hildebrand. W. It is a parameter that can be used to determine resin compatibility, as described by Van Krevelen, Elsevier Science Publishing Company, Amsterdam, 1990, Chapter 7.
Various methods for calculating the SP value have been proposed. For example, the method proposed by Fedors (Polym. Eng. Sci. 1974, Vol. 14, p. 147), which is the following formula (I), can be used.
δ=(ΣE _coh /ΣV) ^1/2 (I)
Here, δ is the solubility parameter (cal/cm ³ ) ^1/2 , E _coh is the cohesive energy density (cal/mol), V is the molar molecular volume (cm ³ /mol), and Σ is given for each atomic group. It means that these numerical values are summed for all the atomic groups constituting the monomer. The values of E _coh and V for each atomic group are listed in Table 7.3 of the above "Properties of Polymers, Third completely revised edition".

Further, the viscosity of the base oil (x) is not particularly limited, but as described later, when used as it is as the component (B) of the lubricating oil composition, the kinematic viscosity at 100 ° C. is preferably 0.5 to 6.0 mm ² /s, more preferably 0.7 to 5.5 mm ² /s, still more preferably 1.0 to 5.0 mm ² /s. When the kinematic viscosity at 100°C is 0.5 mm ^{2 /} s or more, the flash point is preferably high. is obtained.

Moreover, the polymerization solvent may contain a base oil (y) other than the heteroatom-containing base oil (x).
The base oil (y) other than the heteroatom-containing base oil (x) that may be contained in the polymerization solvent (hereinafter also simply referred to as "base oil (y)") is the same as the component (C) described later. can be used, and the preferred aspects are also the same, so the description here is omitted.

In addition, the content of the base oil (x) in the polymerization solvent is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass or more, based on 100% by mass of the total amount of the polymerization solvent. and preferably 100% by mass or less.
Further, when the polymerization solvent contains the base oil (y), the content of the base oil (y) in the polymerization solvent is preferably 0.1% by mass or more based on the total amount of the polymerization solvent of 100% by mass. More preferably 1% by mass or more, still more preferably 5% by mass or more, and preferably 50% by mass or less, more preferably 30% by mass or less, still more preferably 10% by mass or less, still more preferably 10% by mass Below, more preferably 5% by mass or less.

(Monomer (a): (meth)acrylate (a) having a linear alkyl group with 4 or less carbon atoms in the side chain)
Examples of the (meth)acrylate (a) having a linear alkyl group having 4 or less carbon atoms in the side chain (hereinafter also simply referred to as "monomer (a)") include methyl (meth)acrylate, ethyl (Meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate. The monomer (a) is preferably one or more selected from methyl (meth)acrylate and ethyl (meth)acrylate, more preferably methyl (meth)acrylate, and still more preferably methyl methacrylate. be.
Moreover, the monomer (a) may be used singly or in combination of two or more of the above-mentioned monomers.

Moreover, the content of the monomer (a) is 50% by mass or more and 63% by mass or less based on 100% by mass of the total amount of the constituent monomers.
If the content of the monomer (a) is less than 50% by mass or more than 63% by mass, the viscosity index of the obtained lubricating oil composition cannot be sufficiently improved.
Therefore, from the viewpoint of further improving the viscosity index of the resulting lubricating oil composition, the content of the monomer (a) is preferably 52% by mass or more, more preferably 53% by mass or more, and still more preferably 54% by mass. % or more, and preferably 62% by mass or less, more preferably 60% by mass or less, and even more preferably 58% by mass or less.

(Monomer (b): (meth)acrylate (b) having a branched alkyl group with 4 or more carbon atoms in the side chain)
The (meth)acrylate (b) having a branched alkyl group having 4 or more carbon atoms in the side chain (hereinafter also simply referred to as "monomer (b)") is preferably represented by the following general formula (1) is a (meth)acrylate that is

（一般式（１）中、Ｒ^１は、水素原子又はメチル基を示し、Ｒ^２は炭素数２～４の直鎖又は分岐アルキレン基を示し、Ｒ^３及びＲ^４は、それぞれ独立に、炭素数２～１８のアルキル基を示す。ｎは、０～２０の整数を示す。ｎが２以上の場合、複数存在するＲ^２は同一であっても異なっていてもよい。）

(In general formula (1), R ¹ represents a hydrogen atom or a methyl group, R ² represents a linear or branched alkylene group having 2 to 4 carbon atoms, and R ³ and R ⁴ each independently represent a carbon represents an alkyl group of numbers 2 to 18. n represents an integer of 0 to 20. When n is 2 or more, a plurality of R ² may be the same or different.)

Preferred aspects indicated by each symbol in the general formula (1) are shown below.
From the viewpoint of improving the viscosity index, R ¹ preferably represents a methyl group.
Linear or branched alkylene groups having 2 to 4 carbon atoms represented by R ² include ethylene group, propane-1,2-diyl group, propane-1,3-diyl group, butane-1,2-diyl group and butane. -1,3-diyl group, butane-1,4-diyl group, butane-2,2-diyl group and the like, preferably ethylene group or propane-1,2-diyl group.
n is preferably an integer of 0 to 5, more preferably an integer of 0 to 2, still more preferably 0, from the viewpoint of the solubility of the obtained component (A) in the base oil.
When n is 2 or more, the plurality of R ⁶ may be the same or different, and the mode of bonding between moieties represented by —(R ² —O—)n in general formula (1) may be random or block bound.
R ³ and R ⁴ each independently represent preferably an alkyl group having 4 to 18 carbon atoms, more preferably an alkyl group having 6 to 18 carbon atoms, and still more preferably an alkyl group having 6 to 16 carbon atoms.
R ³ and R ⁴ may be the same or different from each other, and are preferably different from each other.
The alkyl group having 2 to 18 carbon atoms represented by R ³ and R ⁴ may be either a linear or branched alkyl group, preferably a linear alkyl group.
Further, as an example of a preferred aspect of the compound represented by the general formula (1), for example, when R ³ and R ⁴ are different from each other, for example, R ³ is preferably alkyl having 4 to 18 carbon atoms groups, more preferably 6 to 16 alkyl groups, more preferably 8 to 14 alkyl groups. R ⁴ is preferably an alkyl group having 6 to 18 carbon atoms, more preferably an alkyl group having 8 to 18 carbon atoms, and still more preferably an alkyl group having 10 to 16 carbon atoms.

Specific examples of the compound represented by the general formula (1) include 2-hexyldecyl methacrylate, 2-decyltetradecyl methacrylate, 2-dodecylhexadecyl methacrylate, and 2-tetradecyloctadecyl methacrylate. are mentioned.
Among the specific examples, the compound represented by the general formula (1) is preferably 2-decyltetradecyl methacrylate, 2-dodecylhexadecyl methacrylate, or 2-tetradecyloctadecyl methacrylate, more preferably 2 -decyltetradecyl methacrylate or 2-tetradecyloctaoctadecyl methacrylate, more preferably 2-tetradecyloctaoctadecyl methacrylate.
Moreover, the compound represented by the general formula (1), which is a suitable monomer (b), may be used singly or in combination of two or more kinds selected from those mentioned above.

Moreover, the content of the monomer (b) is 37% by mass or more and 50% by mass or less based on 100% by mass of the total amount of the constituent monomers.
If the content of the monomer (b) is less than 37% by mass or more than 50% by mass, the viscosity index of the obtained lubricating oil composition cannot be sufficiently improved.
Therefore, from the viewpoint of further improving the viscosity index of the resulting lubricating oil composition, the content of the monomer (a) is preferably 38% by mass or more, more preferably 40% by mass or more, and still more preferably 42% by mass. % or more, and preferably 48% by mass or less, more preferably 47% by mass or less, and even more preferably 46% by mass or less.

Further, from the viewpoint of further improving the viscosity index of the resulting lubricating oil composition, the total content of the monomer (a) and the monomer (b) is based on the total amount of the constituent monomers of 100% by mass. , preferably 90% by mass or more and 100% by mass or less, more preferably 95% by mass or more and 100% by mass or less, still more preferably 98% by mass or more and 100% by mass or less, still more preferably 99% by mass or more and 100% by mass or less .

The content of each monomer can be calculated, for example, from the amount of each monomer blended. The content of the structural unit derived from each monomer based on the total amount of 100% by mass of the structural units excluding the terminal structural units in the structure, if the conversion rate of the structural monomer is 98% or more, the structural monomer It can be considered that the amount of each monomer is the same as the amount of each monomer based on the total amount of 100% by mass. In addition, the said "conversion rate" is the conversion rate based on all the constituent monomers used.
Here, in this specification, the "molecular structure" in the description "based on 100% by mass of the total amount of structural units excluding terminal structural units in the molecular structure" refers to component (A), which is one embodiment of the present invention. Refers to molecular structure. The "terminal structural unit in the molecular structure" refers to a structural unit derived from a polymerization initiator and/or a chain transfer agent used when polymerizing the component (A) described later.
Further, when determining whether the component (A) present in the viscosity index improver composition or the lubricating oil composition described later satisfies the above configuration, for example, from the lubricating oil composition, by rubber membrane separation, It is also possible to take out a polymer component, identify the structural unit derived from each raw material by ¹³ C-NMR, and further confirm the content of each structural unit by using pyrolysis GC-FID. , can be verified.

(Other monomers)
Component (A), which is one aspect of the present invention, includes, among the constituent monomers, in addition to the monomers (a) and (b), other monomers within a range that does not impair the effects of the present invention. It may contain a body.
Examples of monomers other than the above monomers (a) and (b) include alkyl (meth)acrylates other than the above monomers, functional group-containing monomers, and the like.
Examples of alkyl (meth)acrylates other than the monomers include (meth)acrylates having a linear alkyl group having 5 or more carbon atoms in the side chain (for example, linear alkyl groups having 5 to 36 carbon atoms in the side chain). (meth)acrylates having a group, (meth)acrylates having an alicyclic alkyl group, and the like.
The functional group-containing monomers include known amino group-containing monomers, quaternary ammonium salt-containing monomers, nitrile group-containing monomers and nitro group-containing monomers, hydroxy group-containing monomers, Carboxy group-containing monomers and the like can be mentioned.
When the polymer that is one embodiment of the present invention contains these other monomers, the other monomers may be used singly or in combination of two or more.

When the constituent monomers contain the other monomers, the total content of the other monomers is preferably 0.01% by mass or more based on 100% by mass of the total amount of the constituent monomers. , more preferably 0.05% by mass or more, still more preferably 0.01% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably less than 2% by mass, still more preferably is 1% by mass or less.

(Physical properties of component (A), etc.)
Component (A) has a mass average molecular weight (Mw) of 32,000 or more. If the mass average molecular weight (Mw) is less than 32,000, the viscosity index of the resulting lubricating oil composition cannot be sufficiently improved.
In addition, the mass average molecular weight (Mw) of component (A) is preferably 200,000 or less from the viewpoint of suppressing deterioration in shear stability of component (A) in the resulting lubricating oil composition.
From such a viewpoint, the weight average molecular weight (Mw) of component (A) is preferably 34,000 or more, more preferably 35,000 or more, still more preferably 40,000 or more, and even more preferably 42,000. and more preferably 100,000 or less, more preferably 70,000 or less, and even more preferably 60,000 or less.
Further, the molecular weight distribution (Mw/Mn) of component (A) is preferably 3.0 or less, more preferably 2.5 or less, still more preferably 2.0 or less, still more preferably 1.8 or less. Although the lower limit thereof is not particularly limited, it is preferably 1.01 or more, more preferably 1.10 or more, still more preferably 1.20 or more, and still more preferably 1.30 or more.
The mass average molecular weight (Mw) is measured by the method described in Examples below.
Moreover, the aspect of the component (A) may be, for example, any of a random addition polymer, an alternating copolymer, a graft copolymer, and a block copolymer.

Further, from the viewpoint of further improving the viscosity index of the resulting lubricating oil composition, the solubility parameter (SP value) of component (A) is preferably 9.20 (cal/cm ³ ) ^1/2 or more and 9.60 ( cal/cm ³ ) ^1/2 or less, more preferably 9.30 (cal/cm ³ ) ^1/2 or more and 9.50 (cal/cm ³ ) ^1/2 or less, more preferably 9.37 (cal/cm ³ ) ^1/2 or more and 9.42 (cal/cm ³ ) ^1/2 or less.

Here, the solubility parameter (SP value) of the component (A) can be obtained, for example, using the following formula (II).
SP value of component (A)=Σ([δx]×[constituent amount x]) (II)
Here, [δx] represents the SP value (cal/cm ³ ) ^1/2 of the monomer x calculated by the formula (I) proposed by Fedors, and [Constituent amount x] is the component ( When all constituent monomers constituting A) are set to 1, it represents the content ratio (maximum value 1) of the monomer x in all the constituent units. Σ means the sum of all the monomers constituting the polymer.
Here, for example, when the component (A) is a copolymer consisting of the monomer (a) and the monomer (b), the SP value of the component (A) can be calculated as follows. can.
SP value of copolymer consisting of monomer (a) and monomer (b) = ([δa] x [constituent amount a]) + ([δb] x [constituent amount b])
[δa] represents the SP value (cal/cm ³ ) ^1/2 of the monomer (a) calculated by the formula (I) proposed by Fedors, and [constituent amount a] is the component (A ) represents the content ratio of the monomer (a) to the total constituent monomers constituting ). [δb] represents the SP value (cal/cm ³ ) ^1/2 of the monomer (b) calculated by the formula (I) proposed by Fedors, and [constituent amount b] is the component (A ) represents the content ratio of the monomer (b) to the total constituent monomers constituting ). In this case, [configuration amount a]+[configuration amount b]=1.

Further, from the viewpoint of further improving the viscosity index of the obtained lubricating oil composition, the content of component (A) in the lubricating oil composition is preferably 2% by mass based on the total amount of the lubricating oil composition 100% by mass. Above, more preferably 5% by mass or more, more preferably 8% by mass or more, and from the viewpoint of suppressing an increase in PSSI of the obtained lubricating oil composition, preferably 20% by mass or less, more preferably 18% by mass % or less, more preferably 15 mass % or less.

(Polymerization method of component (A))
The component (A) can be obtained by radically polymerizing each of the monomers described above in a polymerization solvent containing the base oil (x) described above.
When the component (A) is produced by solution polymerization, the monomers (a) and (b) and, if necessary, other monomers are radically polymerized using a polymerization initiator in the polymerization solvent. can be obtained by doing

Examples of the polymerization initiator include one or more selected from the group consisting of azo initiators, peroxide initiators, redox initiators, and organic halogen compound initiators. The polymerization initiator used in the component (A) is preferably one or more selected from azo initiators and peroxide initiators, more preferably one selected from azo initiators and organic peroxides. As described above, an azo initiator can be used more preferably.
Examples of azo polymerization initiators 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 (for example, hydrochloride etc.), dimethyl 2, 2'-azobis isobutyrate, 2,2'-azobis(2-amidinopropane) hydrochloride, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] and the like. .

Examples of peroxide-based initiators include inorganic peroxides and organic peroxides.
Examples of inorganic peroxides include hydrogen peroxide, ammonium persulfate, potassium persulfate, and sodium persulfate.
Examples of organic peroxides include benzoyl peroxide, di-tert-butyl peroxide, cumene hydroperoxide, succinic peroxide, di(2-ethoxyethyl)peroxydicarbonate, and tert-butyl peroxypivalate. , tert-hexyl peroxypivalate, tert-butyl peroxyneoheptanoate, tert-butyl peroxyneodecanoate, tert-butyl peroxy 2-ethylhexanoate, tert-butyl peroxyisobutyrate, tert-amylperoxy 2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, dibutylperoxytrimethyladipate, lauryl peroxide and the like.

Examples of redox initiators include alkali metal sulfites or bisulfites (e.g., ammonium sulfite, ammonium bisulfite, etc.), reducing agents such as ferrous chloride, ferrous sulfate, and ascorbic acid, and alkali metal persulfates. Examples thereof include a combination with an oxidizing agent such as a salt, ammonium persulfate, hydrogen peroxide, or an organic peroxide.
Further, as described above, during the polymerization of the component (A), if the conversion rate of the constituent monomers does not reach 98%, for example, by further adding a polymerization initiator to the polymerization system, the conversion conversion can be increased up to

In the radical polymerization, if necessary, a known chain transfer agent may be used for the purpose of adjusting physical properties of the copolymer such as molecular weight.
Examples of chain transfer agents include mercaptans, thiocarboxylic acids, secondary alcohols such as isopropanol, amines such as dibutylamine, hypophosphites such as sodium hypophosphite, chlorine-containing compounds, and alkylbenzene compounds. .
Mercaptans include, for example, 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, tert-dodecyl mercaptan. Alkyl mercaptan compounds having a
Examples of thiocarboxylic acids include thioglycolic acid and thiomalic acid.
The amount of the polymerization initiator and the chain transfer agent to be used can be appropriately selected in consideration of the physical properties of the desired copolymer (for example, adjustment of molecular weight, etc.).

Polymerization control methods 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, still more preferably 70 to 120°C.
In addition to the method of initiating polymerization by heat, a method of initiating polymerization by irradiating radiation, electron beams, ultraviolet rays, or the like can also be employed. Preferred is a temperature-controlled solution polymerization method.
The mode of copolymerization may be either random addition polymerization or alternating copolymerization, or may be either graft copolymerization or block copolymerization.

Moreover, the copolymer (A), which is one aspect of the present invention, can be suitably used as a viscosity index improver for a lubricating oil composition.
The viscosity index improver, which is one aspect of the present invention, is composed of the copolymer (A), and is further dissolved and diluted in a diluent to form a viscosity index improver composition. It is preferable in that it facilitates dissolution in the base oil contained in the oil composition.
The diluent used for the viscosity index improver is a diluent containing at least the heteroatom-containing base oil (x), and the heteroatom-containing base oil (x) used as the diluent contains the component (A) described above. The same base oil (x) as described in the section on the polymerization solvent for polymerization can be used, and the preferred embodiment thereof is also the same, so the description is omitted here.
Further, the diluent used for the viscosity index improver is the base oil (x) used as the polymerization solvent in the case where the base oil (x) is used as the polymerization solvent for polymerizing the component (A) described above. When (x) is directly added to the viscosity index improver, the base oil (x) used as the polymerization solvent can be regarded as one type of base oil (x) contained in the viscosity index improver.
The diluent used for the viscosity index improver preferably contains at least the base oil (x) used in the polymerization of the component (A) as it is.
That is, the viscosity index improver, which is one aspect of the present invention, contains the component (A) and the heteroatom-containing base oil (x).
These diluents may be used singly or in combination of two or more from those mentioned above.
When the viscosity index improver composition comprises the copolymer (A) and a diluent, the content of the copolymer (A) is preferably 5 to 80% by mass, more preferably 20 to 80% by mass, still more preferably 30 to 70% by mass.
In addition, the content of the diluent is preferably 520 to 95% by mass, more preferably 20 to 80% by mass, still more preferably 30 to 70% by mass, based on 100% by mass of the total amount of the viscosity index improver composition.

<Component (B): heteroatom-containing base oil (x)>
The heteroatom-containing base oil (x) contained in the lubricating oil composition (hereinafter, the heteroatom-containing base oil (x) contained in the lubricating oil composition is also simply referred to as "component (B)") is The same heteroatom-containing base oil (x) as described in the section on the polymerization solvent when polymerizing the component (A) obtained above can be used, and the preferred embodiment thereof is also the same. omitted.
The base oil (x) to be the component (B) may be used singly or in combination of two or more of the above-mentioned base oils.
The component (B) contained in the lubricating oil composition includes the base oil (x) used as the polymerization solvent in the case where the base oil (x) is used as the polymerization solvent for polymerizing the component (A) described above ( When x) is added to the lubricating oil composition as it is, the base oil (x) used as the polymerization solvent can be regarded as one of the components (B) contained in the lubricating oil composition. Similarly, in the case where the viscosity index improver composition of one embodiment of the present invention described above contains a base oil (x) as a diluent, the base oil (x) used as the diluent is used as it is for lubricating When added to the oil composition, the base oil (x) used as the diluent can also be regarded as one of the components (B) contained in the lubricating oil composition.

Here, as described above, the component (B) may contain the base oil (x) used as the polymerization solvent for the component (A) as it is as the component (B). The component (B) added when preparing the index improver composition may be contained as it is, or may be newly added when preparing the lubricating oil composition.
From the viewpoint of workability and the viewpoint of improving the solubility of the component (A) in the lubricating oil composition, at least the base oil (x) used as a polymerization solvent for the component (A) is used as the component (B) as it is. It is preferable to contain.
Further, for example, when preparing a viscosity index improver composition containing component (A), base oil (x) can be newly added to dilute the viscosity index improver composition. Even in such a case, when the lubricating oil composition contains as it is the base oil (x) added when preparing the viscosity index improver composition as component (B), at least component (A) It is preferable to use a viscosity index improver composition containing as component (B) the base oil (x) used as the polymerization solvent in (1).

Further, from the viewpoint of further improving the viscosity index of the obtained lubricating oil composition, the content of component (B) in the lubricating oil composition is preferably 1% by mass based on the total amount of the lubricating oil composition 100% by mass. Above, more preferably 3% by mass or more, more preferably 6% by mass or more, and from the viewpoint of suppressing an increase in PSSI of the obtained lubricating oil composition, preferably 35% by mass or less, more preferably 25% by mass % or less, more preferably 15 mass % or less.

<Component (C): Base oil (y) other than heteroatom-containing base oil (x)>
The base oil (y) other than the heteroatom-containing base oil (x) contained in the lubricating oil composition (hereinafter also simply referred to as "component (C)") is preferably a hydrocarbon base oil.
The hydrocarbon-based base oil is not particularly limited, and can be appropriately selected from mineral oils and synthetic oils (excluding component (B)) conventionally used as base oils for lubricating oils. can be used
As the mineral oil, for example, the lubricating oil fraction obtained by vacuum distillation of the atmospheric residue obtained by atmospheric distillation of crude oil is subjected to at least one treatment of solvent deasphalting treatment; solvent extraction or hydrocracking. at least one dewaxing treatment of solvent dewaxing or catalytic dewaxing; hydrorefining treatment; and oils produced by decomposing. Of these, oils treated by hydrorefining are preferred.
Examples of synthetic oils include poly-α-olefins such as polybutene, α-olefin homopolymers, and copolymers such as ethylene-α-olefin copolymers; alkylbenzenes; alkylnaphthalenes; GTL base oil produced by hydroisomerization dewaxing liquid wax) and the like.
Further, the hydrocarbon base oil is more preferably at least one selected from base oils classified into Group II and base oils classified into Group III of the American Petroleum Institute (API) base oil category. .
These base oils may be used singly or in combination of two or more from those mentioned above.

In the component (C) contained in the lubricating oil composition, when the base oil (y) is used as the polymerization solvent used when polymerizing the component (A) described above, the base oil used as the polymerization solvent When the oil (y) is added as it is to the lubricating oil composition, the base oil (y) used as the polymerization solvent can be regarded as one of the components (C) contained in the lubricating oil composition. Similarly, in the case where the viscosity index improver composition of one embodiment of the present invention described above contains the base oil (y) as a diluent, the base oil (y) used as the diluent is used as it is for lubricating When added to the oil composition, the base oil (y) used as the diluent can also be regarded as one of the components (C) contained in the lubricating oil composition.

As described above, the content of component (C) is 55% by mass or more based on 100% by mass of the total amount of the lubricating oil composition. If the content of the component (C) is less than 55% by mass, the viscosity index of the resulting lubricating oil composition cannot be sufficiently improved, and the PSSI of the resulting lubricating oil composition is also sufficiently increased. cannot be suppressed by
In addition, from the viewpoint of suppressing an increase in PSSI of the obtained lubricating oil composition, the content of component (C) is preferably 60% by mass or more, more preferably 70% by mass or more, more preferably 75% by mass or more, even more preferably 78% by mass or more, and preferably 97% by mass or less, more preferably 95% by mass or less, even more preferably 90% by mass or less, and more More preferably, it is 85% by mass or less.

The viscosity of the component (C) is not particularly limited, but the kinematic viscosity at 100° C. is preferably 2 to 30 mm ² /s, more preferably 2 to 15 mm ² /s, still more preferably 2 to 10 mm ² . /s, more preferably 2 to 5 mm ² /s. When the kinematic viscosity at 100° C. is 2 mm ² /s or more, evaporation loss is small, and when it is 30 mm ² /s or less, power loss due to viscous resistance is suppressed, resulting in improved fuel efficiency.
The viscosity index of component (C) is preferably 50 or higher, more preferably 80 or higher, still more preferably 100 or higher, and even more preferably 105 or higher. When the viscosity index of the base oil is within this range, the viscosity characteristics of the lubricating oil composition can be easily improved.
The values of kinematic viscosity and viscosity index at 100° C. are measured by the methods described in Examples below.

In addition, from the viewpoint of further improving the viscosity index of the resulting lubricating oil composition, the difference between the solubility parameter (SP value) of the component (B) and the solubility parameter (SP value) of the component (C) is an absolute value of preferably 0.01 (cal/cm ³ ) ^1/2 or more and 1.20 (cal/cm ³ ) ^1/2 or less, more preferably 0.05 (cal/cm ³ ) ^1/2 1.00 (cal/cm ³ ) ^1/2 or less, more preferably 0.10 (cal/cm ³ ) ^1/2 or more and 0.80 (cal/cm ³ ) ^1/2 or less, still more preferably 0 0.15 (cal/cm ³ ) ^1/2 or more and 0.60 (cal/cm ³ ) ^1/2 or less.

<Other ingredients>
The lubricating oil composition, which is one aspect of the present invention, optionally contains other components other than the components (A), (B), and (C) within a range that does not impair the effects of the present invention. Further, it may be contained.
Other components include commonly used lubricating oil additives. Examples of the lubricating oil additives include metallic detergents, anti-wear agents, ashless dispersants, and component (A). Consisting of viscosity index improvers, extreme pressure agents, pour point depressants, antioxidants, antifoam agents, surfactants, demulsifiers, friction modifiers, oiliness improvers, rust inhibitors and metal deactivators other than One or more selected from the group can be mentioned.
A compound having multiple functions as the lubricating oil additive (for example, a compound having functions as an anti-wear agent and an extreme pressure agent) may also be used.
These lubricating oil additives other than component (A) may be used singly or in combination of two or more.

The content of each lubricating oil additive other than component (A) can be appropriately adjusted within a range that does not impair the effects of the present invention. When the lubricating oil composition of one aspect of the present invention contains these lubricating oil additives other than the component (A), the content of each of the lubricating oil additives other than the component (A) is For example, based on the total amount (100% by mass) of the lubricating oil composition, it is preferably 0.001 to 15% by mass, more preferably 0.005 to 10% by mass, and still more preferably 0.01 to 8% by mass.
Further, in the lubricating oil composition of one aspect of the present invention, when containing these lubricating oil additives other than the component (A), the total content is the total amount of the lubricating oil composition (100% by mass) On the basis, it is preferably more than 0% by mass and 30% by mass or less, more preferably 0.001 to 25% by mass, still more preferably 0.001 to 20% by mass, and even more preferably 0.001 to 15% by mass.

(Metallic detergent)
Examples of metal-based detergents 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. containing metal salicylates, metal phenates, and metal sulfonates.
In this specification, the term "alkali metal" refers to lithium, sodium, potassium, rubidium, cesium, and francium.
Also, "alkaline earth metal" refers to beryllium, magnesium, calcium, strontium, and barium.
The metal atom contained in the metallic detergent is preferably sodium, calcium, magnesium, or barium, more preferably calcium, from the viewpoint of improving detergency at high temperatures.

The metal salicylate is preferably a compound represented by the following general formula (2), the metal phenate is preferably a compound represented by the following general formula (3), and the metal sulfonate is a compound represented by the following general formula (4 ) are preferred.

In the general formulas (2) to (4), M is a metal atom selected from alkali metals and alkaline earth metals, preferably sodium, calcium, magnesium or barium, more preferably calcium. M ^E is an alkaline earth metal, preferably calcium, magnesium or barium, more preferably calcium. p is the valence of M and is 1 or 2; R ¹¹ and R ¹² are each independently a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms. S represents a sulfur atom. q is an integer of 0 or more, preferably an integer of 0-3.
Hydrocarbon groups that can be selected as R ¹¹ and R ¹² include, for example, alkyl groups having 1 to 18 carbon atoms, alkenyl groups having 1 to 18 carbon atoms, cycloalkyl groups having 3 to 18 ring carbon atoms, and ring carbon atoms. Examples include aryl groups having 6 to 18 carbon atoms, alkylaryl groups having 7 to 18 carbon atoms, and arylalkyl groups having 7 to 18 carbon atoms.

In one aspect of the present invention, these metallic detergents may be used alone or in combination of two or more. Among these, one or more selected from calcium salicylate, calcium phenate, and calcium sulfonate is preferred from the viewpoint of improving detergency at high temperatures and solubility in base oil.

In one aspect of the present invention, these metallic detergents may be neutral salts, basic salts, overbased salts and mixtures thereof.
The total base number of the metallic detergent is preferably 0 to 600 mgKOH/g.
In one aspect of the present invention, when the metallic detergent is a basic salt or an overbased salt, the total base number of the metallic detergent is preferably 10 to 600 mgKOH/g, more preferably 20 to 500 mg KOH/g.
As used herein, the term “base number” refers to 7. of JIS K2501:2003 “Petroleum products and lubricating oils—neutralization value test method”. Means the base number by the perchloric acid method measured in accordance with.

When the lubricating oil composition of one aspect of the present invention contains a metallic detergent as another component, the content of the metallic detergent is based on the total amount (100% by mass) of the lubricating oil composition, preferably It is 0.01 to 10% by mass.
In addition, the said metallic detergent may be used individually and may use 2 or more types together. The preferred total content when using two or more types is also the same as the content described above.

(Antiwear agent)
Examples of antiwear agents include sulfur-containing compounds such as zinc dialkyldithiophosphate (ZnDTP), zinc phosphate, disulfides, sulfurized olefins, sulfurized oils and fats, sulfurized esters, thiocarbonates, thiocarbamates, and polysulfides. phosphorus-containing compounds such as phosphites, phosphates, phosphonates, and their amine salts or metal salts; thiophosphites, thiophosphates, thiophosphonates, and these and sulfur- and phosphorus-containing antiwear agents such as amine salts or metal salts of
Among these, zinc dialkyldithiophosphate (ZnDTP) is preferred.
When the lubricating oil composition of one aspect of the present invention contains an anti-wear agent as another component, the content of the anti-wear agent is preferably 0 based on the total amount (100% by mass) of the lubricating oil composition. 0.05 to 5.0% by mass.
In addition, the said anti-wear agent may be used individually and may use 2 or more types together. The preferred total content when using two or more types is also the same as the content described above.

(ashless dispersant)
Examples of the ashless dispersant include succinimide, benzylamine, succinic acid ester, boron-modified products thereof, and the like, and alkenylsuccinimide and boron-modified alkenylsuccinimide are preferred.

Examples of alkenylsuccinimides include alkenylsuccinic acid monoimides represented by the following general formula (i) and alkenylsuccinic acid bisimides represented by the following general formula (ii).
The alkenylsuccinimide 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 alkenylsuccinimide reacted with.
Examples of boron-modified alkenylsuccinimides include boron-modified compounds represented by the following general formula (i) or (ii).

In the general formulas (i) and (ii), R ^A , R ^A1 and R ^A2 each independently have a mass average molecular weight (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 1-10, preferably an integer of 2-5, more preferably 3 or 4.
x2 is an integer of 0-10, preferably an integer of 1-4, more preferably 2 or 3.

In one aspect of the present invention, the ratio [B/N] of boron atoms and nitrogen atoms constituting the boron-modified alkenylsuccinimide is preferably 0.5 or more, more preferably 0, from the viewpoint of improving cleanliness. 0.6 or more, more preferably 0.8 or more, and even more preferably 0.9 or more.
When the lubricating oil composition of one aspect of the present invention contains an ashless dispersant as another component, the content of the ashless dispersant is based on the total amount (100% by mass) of the lubricating oil composition. , preferably 0.1 to 20% by mass.

(Viscosity index improver)
Viscosity index improvers include polymers other than component (A), such as PMA-based polyalkyl (meth)acrylates such as non-dispersed polyalkyl (meth)acrylates and dispersed polyalkyl (meth)acrylates; olefin-based copolymers ( ethylene-propylene copolymers, etc.), OCP systems such as dispersed olefin-based copolymers; styrene-based copolymers (e.g., styrene-diene copolymers, styrene-isoprene copolymers, etc.) (hereinafter also referred to as "other viscosity index improvers").
These other viscosity index improvers preferably have a weight average molecular weight (Mw) of 5,000 or more and 1,500,000 or less; 000 or more, preferably 1,000,000 or less, more preferably 800,000 or less. In the case of an OCP system, it is preferably 10,000 or more, more preferably 20,000 or more, and preferably 800,000 or less, more preferably 500,000 or less.
In addition, the said mass average molecular weight (Mw) is measured by the method as described in the Example mentioned later, for example.
The structure of other viscosity index improvers may be linear or branched. Also, a comb-shaped polymer having a structure with many trigeminal branch points in the main chain from which high-molecular-weight side chains come out, and a type of branched polymer in which three or more chain-like polymers are bonded at one point It may also be a polymer with a specific structure, such as a structured star polymer.

Further, as other viscosity index improvers, as described above, a polymer having a structure having many trigeminal branch points in the main chain with linear side chains (hereinafter referred to as "comb-shaped polymer") is contained. may Preferred examples of such comb-shaped polymers include polymers having at least structural units derived from macromonomers having polymerizable functional groups such as methacryloyl groups, acryloyl groups, ethenyl groups, vinyl ether groups, and allyl groups. Here, the structural unit corresponds to a "linear side chain".
More specifically, alkyl (meth)acrylates, nitrogen atom-containing systems, halogen element-containing systems, hydroxyl group-containing systems, aliphatic hydrocarbon systems, alicyclic hydrocarbon systems, aromatic hydrocarbon systems, etc. A preferred example is a copolymer having a side chain containing a structural unit derived from a macromonomer having a polymerizable functional group with respect to a main chain containing a structural unit derived from a polymer.

The number average molecular weight (Mn) of the macromonomer is preferably 200 or more, more preferably 300 or more, still more preferably 400 or more, and is preferably 100,000 or less, more preferably 50,000 or less, and still more preferably 10,000 or less.
In addition, the mass average molecular weight (Mw) of the comb-shaped polymer is preferably 1,000 or more, more preferably 5,000 or more, still more preferably 50,000 or more, from the viewpoint of improving fuel efficiency, and It is preferably 1,000,000 or less, more preferably 800,000 or less, still more preferably 700,000 or less. The molecular weight distribution (Mw/Mn) is preferably 6 or less, more preferably 5.6 or less, and still more preferably 5 or less. 0.05 or greater, more preferably 1.10 or greater, and even more preferably 1.50 or greater.

The monomer constituting the polyalkyl (meth) acrylate is an alkyl (meth) acrylate, preferably an alkyl (meth) acrylate having a linear alkyl group having 1 to 18 carbon atoms or a branched alkyl group having 3 to 34 carbon atoms. is.
The polystyrene-equivalent mass average molecular weight (Mw) of the polyalkyl (meth)acrylate is preferably 10,000 or more and 1,000,000 or less, more preferably 30,000 or more and 500,000 or less. By setting the weight average molecular weight of the polyalkyl (meth)acrylate within this range, the SSI value can be easily adjusted to 30 or less.
In addition, the said mass average molecular weight (Mw) is measured by the method as described in the Example mentioned later.

These other viscosity index improvers may be used alone or in combination of two or more.
In addition, the other viscosity index improver contains, as a resin component, for example, the above-mentioned polymer other than the component (A). Considering this, the polymer-containing resin component is often marketed in the form of a solution diluted with a diluent such as mineral oil.
In this case, when other viscosity index improvers are used, the content of the viscosity index improver is preferably 0.00%, based on the total amount (100% by mass) of the lubricating oil composition, in terms of resin content. 001% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.5% by mass or more, and preferably 5.0% by mass or less, more preferably 2.0% by mass or less, and still more preferably is 1.0% by mass or less.

(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 organic metal-based extreme-pressure agents. be done. Further, among the anti-wear agents described above, a compound having a function as an extreme pressure agent can also be used.
In one aspect of the present invention, these extreme pressure agents may be used alone or in combination of two or more.
When the lubricating oil composition of one aspect of the present invention contains an extreme pressure agent as another component, the content of the extreme pressure agent is preferably 0 based on the total amount (100% by mass) of the lubricating oil composition. .1 to 10% by mass.

(Antioxidant)
As the antioxidant, any of known antioxidants conventionally used as antioxidants for lubricating oils can be appropriately selected and used. Examples include antioxidants, molybdenum-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, and the like.
Examples of amine-based antioxidants include diphenylamine-based antioxidants such as diphenylamine and alkylated diphenylamine having an alkyl group of 3 to 20 carbon atoms; naphthylamine-based antioxidants such as substituted phenyl-α-naphthylamine having a group;
Phenolic antioxidants include, for example, 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, Monophenol antioxidants such as isooctyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate agent; diphenol antioxidants such as 4,4'-methylenebis(2,6-di-tert-butylphenol) and 2,2'-methylenebis(4-ethyl-6-tert-butylphenol); hindered phenol antioxidant; and the like.
Molybdenum-based antioxidants include, for example, molybdenum amine complexes obtained by reacting molybdenum trioxide and/or molybdic acid with an amine compound.
Examples of sulfur-based antioxidants include dilauryl-3,3'-thiodipropionate and the like.
Examples of the phosphorus antioxidant include phosphite and the like. When a phosphorus-based antioxidant is used, it is preferable that the content of the phosphorus atom satisfies the suitable phosphorus atom content of the lubricating oil composition described later.
In one aspect of the present invention, these antioxidants may be contained alone or in any combination of two or more, preferably phenolic antioxidants and/or amine antioxidants.
When the lubricating oil composition of one aspect of the present invention contains an antioxidant as another component, the content of the antioxidant is based on the total amount (100% by mass) of the lubricating oil composition, preferably 0 0.05 to 7% by mass.

(Pour point depressant)
Examples of the pour point depressant include ethylene-vinyl acetate copolymers, condensates of chlorinated paraffin and naphthalene, condensates of chlorinated paraffin and phenol, polymethacrylates (PMA; polyalkyl (meth) acrylate, etc.), polyvinyl acetate, polybutene, polyalkylstyrene, etc., and polymethacrylates are preferably used. These pour point depressants may be used alone or in combination of two or more.
In the lubricating oil composition of one aspect of the present invention, when containing a pour point depressant as another component, the content of the pour point depressant is based on the total amount (100% by mass) of the lubricating oil composition, preferably is 0.01 to 10% by mass.

(Antifoaming agent)
Antifoaming agents include, for example, 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 the lubricating oil composition of one aspect of the present invention contains an antifoaming agent as another component, the content of the antifoaming agent is based on the total amount (100% by mass) of the lubricating oil composition, preferably 0 0.05 to 5% by mass.

(Surfactant or emulsifier)
Examples of surfactants or demulsifiers include polyalkylene glycol-based nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers and polyoxyethylene alkylnaphthyl ethers. These surfactants or demulsifiers can be contained alone or in any combination of two or more.
In the lubricating oil composition of one aspect of the present invention, when a surfactant or demulsifier is contained as another component, the content of the surfactant or demulsifier is each independently the total amount of the lubricating oil composition ( 100% by mass), preferably 0.01 to 3% by mass.

(friction modifier)
Examples of friction modifiers include molybdenum-based friction modifiers such as molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and amine salts of molybdic acid; Ashless friction modifiers such as fatty amines, fatty acid esters, fatty acid amides, fatty acids, fatty alcohols, and fatty ethers having at least one; , phosphate amine salts and the like.
When the lubricating oil composition of one aspect of the present invention contains a friction modifier as another component, the content of the friction modifier is based on the total amount (100% by mass) of the lubricating oil composition, preferably 0 0.05 to 4% by mass.

(oiliness improver)
Oiliness improvers 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 , aliphatic saturated or unsaturated monoalcohols such as oleyl alcohol; aliphatic saturated or unsaturated monoamines such as stearylamine and oleylamine; aliphatic saturated or unsaturated monocarboxylic acid amides such as lauric amide and oleic amide; glycerin, partial esters of polyhydric alcohols such as sorbitol and aliphatic saturated or unsaturated monocarboxylic acids;
When the lubricating oil composition of one aspect of the present invention contains an oiliness improver as another component, the content of the oiliness improver is preferably 0 based on the total amount (100% by mass) of the lubricating oil composition. 0.01 to 5% by mass.

(anti-rust)
Examples of rust preventives include fatty acids, alkenylsuccinic acid half esters, fatty acid soaps, alkylsulfonates, polyhydric alcohol fatty acid esters, fatty acid amines, paraffin oxide, and alkyl polyoxyethylene ethers.
When the lubricating oil composition of one aspect of the present invention contains a rust inhibitor as another component, the content of the rust inhibitor is preferably 0 based on the total amount (100% by mass) of the lubricating oil composition. 0.01 to 3% by mass.

(Metal deactivator)
Examples of metal deactivators include benzotriazole-based compounds, tolyltriazole-based compounds, thiadiazole-based compounds, imidazole-based compounds, and pyrimidine-based compounds.
When the lubricating oil composition of one aspect of the present invention contains a metal deactivator as another component, the content of the metal deactivator is based on the total amount (100% by mass) of the lubricating oil composition. , preferably 0.01 to 5% by mass.

<Properties of lubricating oil composition>
The 100° C. kinematic viscosity of the lubricating oil composition is preferably 2 to 10 mm ² /s, more preferably 2.5 to 8 mm ² /s, still more preferably 3 to 6 mm ² /s.
The 40° C. kinematic viscosity of the lubricating oil composition is preferably 8 to 20 mm ² /s, more preferably 9 to 18 mm ² /s, still more preferably 10 to 16 mm ² /s.
The viscosity index of the lubricating oil composition is preferably 330 or higher, more preferably 340 or higher, even more preferably 350 or higher, and even more preferably 360 or higher.
Each of the above kinematic viscosities and viscosity indices is a value measured by the method described in the examples below.

In addition, the PSSI of the lubricating oil composition evaluated by the method described in the examples described later is preferably less than 10.0, more preferably 7, from the viewpoint of improving the shear stability of the lubricating oil composition. .0, more preferably less than 6.0, even more preferably less than 5.0, and even more preferably less than 4.5.
The lower limit of the PSSI is not particularly limited, but is 0 or more, for example.

[Method for producing lubricating oil composition]
In the method for producing a lubricating oil composition, which is one embodiment of the present invention, the following components (A) and (B) are blended with the following component (C).
Component (A): (meth)acrylate (a) having a linear alkyl group having 4 or less carbon atoms in the side chain of monomer (a), and the number of carbon atoms in the side chain of monomer (b) Weight average molecular weight (Mw) obtained by polymerizing a constituent monomer containing (meth)acrylate (b) having 4 or more branched alkyl groups in a polymerization solvent containing heteroatom-containing base oil (x) is a copolymer (A) having a value of 32,000 or more,
The content of the monomer (a) is 50% by mass or more and 63% by mass or less based on 100% by mass of the total amount of the constituent monomers, and
A copolymer (A) in which the content of the monomer (b) is 37% by mass or more and 50% by mass or less based on 100% by mass of the total amount of the constituent monomers;
Component (B): heteroatom-containing base oil (x)
Component (C): base oil (y) other than heteroatom-containing base oil (x)
Moreover, in the said manufacturing method, you may further mix|blend other components other than a component (A) and a component (B) with a component (C) as needed.
Component (A), component (B), component (C) and other components are the same as those described for the lubricating oil composition, and their preferred embodiments are also the same. The obtained lubricating oil composition is also as described above, and the preferred aspects thereof are also the same, so description thereof will be omitted.
In the production method, the components (A) and (B), and other components added as necessary, may be blended with the component (C) in any order and by any method, and the method is limited. However, as described above, the component (B) may be blended with the base oil (x) used as the polymerization solvent for the component (A) as it is as the component (B). The component (B) added during the preparation of the index improver composition may be directly blended with the component (C), or may be newly blended during the preparation of the lubricating oil composition.
From the viewpoint of workability and the viewpoint of improving the solubility of the component (A) in the lubricating oil composition, at least the base oil (x) used as the polymerization solvent for the component (A) described above is used as the component (B) is preferably blended with component (C) as it is.
Further, for example, as described above, when preparing a viscosity index improver composition containing component (A), a new base oil (x) can be added to dilute the viscosity index improver composition. . Even in such a case, when the base oil (x) added in preparing the viscosity index improver composition as the component (B) is directly blended with the component (C), at least the polymerization of the component (A) It is preferable to use a viscosity index improver composition containing the base oil (x) used as the solvent as it is as the component (B).

[Use of lubricating oil composition]
As described above, the lubricating oil composition of one embodiment of the present invention has an excellent viscosity index.
Therefore, the lubricating oil composition, which is one embodiment of the present invention, includes, for example, gear oil (manual transmission oil, differential oil, etc.), automatic transmission oil (automatic transmission oil, etc.), continuously variable transmission oil (belt CVT oil, drive system oils such as toroidal CVT oil, power steering oil, shock absorber oil, and electric motor oil; oil for internal combustion engines (engines) such as gasoline engine, diesel engine, and gas engine oil; hydraulic oil; Turbine oil; compressor oil; fluid bearing oil; rolling bearing oil; can be preferably used as.
Further, among these, the lubricating oil composition which is one embodiment of the present invention is more suitable as a lubricating oil composition used in a wider temperature range due to the characteristic that it has a good viscosity index. Gears, automatic transmissions, continuously variable transmissions, shock absorbers, power steering, electric gears mounted on automobiles such as two-wheeled vehicles, four-wheeled vehicles, transportation equipment such as trains, ships, and airplanes, generators, and various machine tools. Lubricating oils for drive system equipment such as motors; lubricating oils for internal combustion engines such as gasoline engines, diesel engines, and gas engines; Hydraulic oil; can be used more preferably.

[Lubrication method using lubricating oil composition]
As described in the applications described above, the lubricating method using the lubricating oil composition according to one embodiment of the present invention preferably includes filling the lubricating oil composition into an apparatus used in each of the applications described above. , a method of lubricating between each part related to each device.
And, as a lubricating method using the lubricating oil composition which is one embodiment of the present invention, it is more preferable to use the lubricating oil composition, for example, automobiles such as two-wheeled vehicles and four-wheeled vehicles, trains, ships, and airplanes. Driving equipment such as gears, automatic transmissions, continuously variable transmissions, shock absorbers, power steering, and electric motors mounted on transportation equipment, generators, and various machine tools; gasoline engines, diesel engines, gas engines, etc. The internal combustion engine; Hydraulic hydraulic fluid used in hydraulic equipment such as hydraulic machinery such as construction machinery and hydraulic systems such as various hydraulic equipment; There is a method of lubricating between each part related to the engine.

[Drive system equipment using lubricating oil composition]
Another embodiment of the present invention includes a drive system device using the lubricating oil composition, preferably a drive system device using the lubricating oil composition as a drive system oil. Examples of the drive system equipment include automobiles such as two-wheeled vehicles and four-wheeled vehicles, transportation equipment such as trains, ships, and airplanes, generators, and gears mounted on various machine tools, automatic transmissions, and continuously variable transmissions. machine, shock absorber, power steering, electric motor, etc.

[Internal combustion engine using lubricating oil composition]
Another embodiment of the present invention includes an internal combustion engine using the lubricating oil composition, preferably an internal combustion engine (engine) using the lubricating oil composition as an engine oil. Examples of the internal combustion engine include gasoline engines, diesel engines, gas engines, etc., which are mounted on automobiles such as two-wheeled vehicles and four-wheeled vehicles, trains, ships, and transportation equipment such as airplanes.

[Hydraulic device using lubricating oil composition]
Another embodiment of the present invention includes a hydraulic device using the lubricating oil composition. Examples of the hydraulic device include hydraulic machinery such as construction machinery and various hydraulic equipment. system and the like.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

In this specification, each component used in each example and each comparative example, and each physical property of the copolymer, viscosity index improver composition, and lubricating oil composition obtained in each example and each comparative example The measurement of is obtained according to the procedure shown below.
<Kinematic viscosity (100° C. kinematic viscosity)>
It is a value measured using a glass capillary viscometer according to JIS K2283:2000.
<Viscosity index>
It is a value calculated according to JIS K2283:2000.
<Solubility parameter (SP value)>
It is a solubility parameter calculated by the method described in the specification.

<Mass average molecular weight (Mw), number average molecular weight (Mn), Mw/Mn>
"1515 isocratic HPLC pump" manufactured by Waters, "2414 refractive index (RI) detector", one column "TSKguardcolumn SuperHZ-L" manufactured by Tosoh Corporation, and two "TSKS SuperMultipore HZ-M" Measured under the following conditions: measurement temperature: 40° C., mobile phase: tetrahydrofuran, flow rate: 0.35 ml/min, sample concentration: 1.0 mg/ml, and conversion to standard polystyrene.

<Viscosity index improver composition and appearance of lubricating oil composition>
The appearances of the viscosity index improver composition and the lubricating oil composition were each collected in a 100 mL screw vial bottle and visually observed.

<PSSI of lubricating oil composition>
The PSSI of the lubricating oil compositions obtained in Examples 1-14 and Comparative Examples 1-8 indicates the percentage shear viscosity loss of lubricating oil compositions derived from the copolymer, and is determined according to ASTM D6022-06. (2012) was calculated by the following formula.

In the formula, Kv ₀ is the value of the 100° C. kinematic viscosity of the lubricating oil composition of each example and comparative example. Kv ₁ is the value of kinematic viscosity at 100°C measured in accordance with JASO M347-95 "Automatic Transmission Oil Shear Stability Test Method" (Sonic Ultrasonic) for the lubricating oil composition of each example and comparative example. be. In addition, Kv _oil is the value of the kinematic viscosity at 100 ° C. of the base oil (in the case of a mixed base oil of base oils (x) and (y), the mixed base oil) contained in the lubricating oil composition of each example and comparative example. is.

<Thermal stability evaluation of lubricating oil composition>
A hot tube test was performed on the lubricating oil compositions of Examples 15-19 and Comparative Example 9.
(Evaluation method)
A hot tube test was performed according to JPI-5S-55-99. Specifically, in a glass tube having an inner diameter of 2 mm, while maintaining the temperature of the glass tube at 240 ° C., 0.3 mL / hour of the lubricating oil composition of Examples 15 to 19 and Comparative Example 8 was added to the glass tube. was continued to flow at 10 mL/min for 16 hours. After that, the following evaluations were performed.
(1) Hot tube test score After the hot tube test, the lacquer adhering to the glass tube was compared with a color sample, and 10 points were given for colorless and transparent, and 11 points were given for black, with 0 points. . The higher the transparency, the higher the score, indicating higher detergency and stability at elevated temperatures.
(2) Amount of Deposit After the hot tube test, the amount of increase in the mass of the glass tube before and after the test was defined as the amount of deposit adhering to the inside of the glass tube. Lower deposits indicate higher cleanliness and stability at elevated temperatures.

[Polymerization of copolymer and preparation of viscosity index improver composition and lubricating oil composition]
The abbreviations of the components in the description below and in Tables 1 to 4 below represent the following compounds, respectively.

(monomer (a))
・ “C1MA”: methyl methacrylate ・ “C12MA”: n-dodecyl methacrylate ・ “C16MA”: n-hexadecyl methacrylate (monomer (b))
- "G24MA": 2-decyltetradecyl methacrylate - "G32MA": 2-tetradecyl octadecyl methacrylate - "HEMA": hydroxyethyl methacrylate (radical polymerization initiator)
・ “ADVN”: 2,2′-azobis (2,4-dimethylvaleronitrile)
・ “AMBN”: 2,2′-azobis (2-methylbutyronitrile)
(chain transfer agent)
・ “DM”: n-dodecyl mercaptan

(Component (B): heteroatom-containing base oil (x))
<Esters>
- "ES-1": bis(2-ethylhexyl) sebacate (100°C kinematic viscosity = 3.2 mm ² /s, SP value = 8.87 (cal/cm ³ ) ^1/2 )
・ “ES-2”: decyl decanoate (100° C. kinematic viscosity = 2.0 mm ² /s, SP value = 8.62 (cal/cm ³ ) ^1/2 )
・ “ES-3”: trimethylolpropane ester (product name “Unistar (registered trademark) H-334R” manufactured by NOF Corporation, mixed triester of trimethylolpropane, lauric acid and stearic acid. 100 ° C kinematic viscosity = 4.3 mm ² /s, SP value = 9.11 (cal/cm ³ ) ^1/2 )
・ “ES-4”: 2-ethylhexyl caprylate (100° C. kinematic viscosity = 1.1 mm ² /s, SP value = 8.54 (cal/cm ³ ) ^1/2 )
・ “ES-5”: dibutyl adipate (100° C. kinematic viscosity = 1.4 mm ² /s, SP value = 9.27 (cal/cm ³ ) ^1/2 )
<Ethers>
・"ET-1": bis(2-ethylhexyl) ether (100°C kinematic viscosity = 1.0 mm ² /s, SP value = 7.95 (cal/cm ³ ) ^1/2 )
- "ET-2": tri- to pentamer of polyvinyl ether (PVE) (100°C kinematic viscosity = 2.3 mm ² /s, SP value = 8.80 (cal/cm ³ ) ^1/2 )
<Amide>
・ “AM-1”: N,N-di(2-ethylhexyl)-2-ethylhexanamide (100°C kinematic viscosity = 4.5 mm ² /s, SP value = 8.88 (cal/cm ³ ) ^{1/ 2} )

(Component (C): base oil (y) other than heteroatom-containing base oil (x))
"Mineral oil": 100°C kinematic viscosity = 2.2 mm ² /s, viscosity index = 106, API standard group II base oil. (SP value = 8.20 (cal/cm ³ ) ^1/2 )

[Example 1]
Into a reaction vessel equipped with a stirrer, a heating/cooling device, a thermometer, a dropping funnel, and a nitrogen blowing tube, ES-1, which is the base oil (x), was used as a polymerization solvent, and mineral oil was added in the amounts shown in Table 1 below. I prepared.
In another glass beaker, each monomer shown in Table 1 below was charged as a monomer in the amount shown in Table 1 below. 5 parts by mass, 0.2 parts by mass of AMBN, and 0.4 parts by mass of DM were charged, mixed and dissolved at room temperature (23° C.) to prepare a monomer-containing solution.
The obtained monomer-containing solution was charged into the dropping funnel of the reaction vessel, and the gas phase in the reaction vessel was replaced with nitrogen. The entire amount was added dropwise at a constant rate. From the end of dropping, further until the conversion rate of all the blended monomers reaches 98%, it is aged at 85 ° C., then the temperature is raised to 120 to 130 ° C., and at the same temperature under reduced pressure (0.027 0.040 MPa) to remove unreacted monomers over 30 minutes to obtain a viscosity index improver composition (VII-1) containing a copolymer (A1) shown in Table 1 below.
The obtained viscosity index improver composition (VII-1) was dissolved in mineral oil so as to have the blending amount shown in Table 1 below to prepare a lubricating oil composition (L-1).
The properties of the resulting copolymer (A1), viscosity index improver composition (VII-1), and lubricating oil composition (L-1) were evaluated by the methods described above. The results obtained are shown in Table 1 below.

[Examples 2 and 3]
Copolymers (A2) and (A3), viscosity index improver composition (VII- 2) and (VII-3), and lubricating oil compositions (L-2) and (L-3) were prepared, respectively.
The properties of each copolymer, each viscosity index improver composition, and each lubricating oil composition obtained were evaluated by the methods described above. The results obtained are shown in Table 1 below.

[Examples 4 to 8]
Copolymer (A4) was prepared in the same manner as in Example 1 except that the base oil (x) shown in Table 1 below was used and the monomers were blended so as to have the composition shown in Table 1 below. to (A8), viscosity index improver compositions (VII-4) to (VII-8), and lubricating oil compositions (L-4) to (L-8) were prepared, respectively.
The properties of each copolymer, each viscosity index improver composition, and each lubricating oil composition obtained were evaluated by the methods described above. The results obtained are shown in Table 1 below.

[Example 9]
Copolymer (A9), viscosity index improver composition A product (VII-9), and a lubricating oil composition (L-9) were prepared.
The properties of the resulting copolymer (A9), viscosity index improver composition (VII-9), and lubricating oil composition (L-9) were evaluated by the methods described above. The results obtained are shown in Table 1 below.

[Example 10]
The copolymer (A10), the viscosity index improver composition (VII-10), and the lubricating oil composition were prepared in the same manner as in Example 1, except that the DM content was changed to 0.6 parts by mass. Product (L-10) was prepared.
The properties of the resulting copolymer (A10), viscosity index improver composition (VII-10), and lubricating oil composition (L-10) were evaluated by the methods described above. The results obtained are shown in Table 1 below.

[Example 11]
Copolymer (A11), viscosity index improver composition (VII-11), and lubricating oil composition were prepared in the same manner as in Example 1, except that the amount of DM was changed to 0.15 parts by mass. Product (L-11) was prepared.
The properties of the resulting copolymer (A11), viscosity index improver composition (VII-11), and lubricating oil composition (L-11) were evaluated by the methods described above. The results obtained are shown in Table 1 below.

[Examples 12-14]
Conducted so that the blending amounts of the copolymer (A1), ES-1, which is the base oil (x) shown in Table 2 below, and mineral oil in the lubricating oil composition obtained are the blending amounts shown in Table 2 below. Lubricating oil compositions (L-12) to (L-14) were prepared by blending the viscosity index improver composition (VII-1), ES-1, and mineral oil obtained in the same manner as in Example 1. bottom.
Each characteristic of the obtained lubricating oil compositions (L-12) to (L-14) was evaluated by the methods described above. The results obtained are shown in Table 2 below.

[Comparative Examples 1 and 2]
A copolymer ( X1) and (X2), viscosity index improver compositions (Y-1) and (Y-2), and lubricating oil compositions (CL-1) and (CL-2) were prepared, respectively.
The properties of each copolymer, each viscosity index improver composition, and each lubricating oil composition obtained were evaluated by the methods described above. The results obtained are shown in Table 3 below.

[Comparative Example 3]
A copolymer ( X3), and a viscosity index improver composition (Y-3) were prepared.
The obtained viscosity index improver composition (Y-3), ES-1 which is the base oil (x), and mineral oil are added to the copolymer (X3), ES-1 and mineral oil in the obtained lubricating oil composition. A lubricating oil composition (CL-3) was prepared by blending so that the blending amount of was the blending amount shown in Table 3 below.
The properties of the resulting copolymer (X3), viscosity index improver composition (Y-3), and lubricating oil composition (CL-3) were evaluated by the methods described above. The results obtained are shown in Table 3 below.

[Comparative Example 4]
Using the base oil (x) shown in Table 3 below, the monomers were blended so as to have the composition shown in Table 3 below, and the copolymer (X4), viscosity index An improver composition (Y-4) and a lubricating oil composition (CL-4) were prepared.
The properties of the resulting copolymer (X4), viscosity index improver composition (Y-4), and lubricating oil composition (CL-4) were evaluated by the methods described above. The results obtained are shown in Table 3 below.

[Comparative Example 5]
Except that the base oil (x) shown in Table 3 below was used, the monomers were blended so that the composition shown in Table 3 below was obtained, and the amount of DM was changed to 0.2 parts by mass. A copolymer (X5) and a viscosity index improver composition (Y-5) were prepared in the same manner as in Example 1.
The properties of the resulting copolymer (X5) and viscosity index improver composition (Y-5) were evaluated by the methods described above. The results obtained are shown in Table 3 below.
Next, when the obtained viscosity index improver composition (Y-5) was blended in mineral oil, a cloudy gel gradually formed, and a lubricating oil composition (CL-8) could be prepared. I didn't. Therefore, it was not possible to evaluate each characteristic of the lubricating oil composition (CL-5) except for its appearance.

[Comparative Example 6]
In the same manner as in Comparative Example 1, the blending amounts of the copolymer (X1), the base oil (x) ES-1, and the mineral oil in the resulting lubricating oil composition were as shown in Table 3 below. The resulting viscosity index improver composition (Y-1), ES-1, and mineral oil were blended to prepare a lubricating oil composition (CL-6).
Each characteristic of the obtained lubricating oil composition (CL-6) was evaluated by the methods described above. The results obtained are shown in Table 3 below.

[Comparative Example 7]
Obtained in the same manner as in Example 1 so that the blending amounts of the copolymer (A1) and the base oil (x) ES-1 in the resulting lubricating oil composition are the blending amounts shown in Table 3 below. A mineral oil-free lubricating oil composition (CL-7) was prepared by blending the viscosity index improver composition (VII-1) and ES-1.
Each characteristic of the obtained lubricating oil composition (CL-7) was evaluated by the methods described above. The results obtained are shown in Table 3 below.

[Comparative Example 8]
A copolymer (X6), a viscosity index improver composition (Y-6), and a A lubricating oil composition (CL-8) was prepared respectively.
The properties of the resulting copolymer, viscosity index improver composition, and lubricating oil composition were evaluated by the methods described above. The results obtained are shown in Table 3 below.

The results shown in Tables 1 to 3 above reveal the following.
A lubricating oil composition obtained by dissolving, in mineral oil, a viscosity index improver composition (Y-1) containing a copolymer (X1) polymerized using mineral oil as a polymerization solvent, as in Comparative Example 1. (CL-1) is inferior to the lubricating oil composition (L-1) obtained in Example 1 in viscosity index. It is considered that this is due to the fact that the copolymer (X1) was cloudy and separated in the mineral oil, as shown by the appearance results.
The monomer compositions used in Example 1 and Comparative Example 1 were the same, and the difference was that in Example 1, a copolymer polymerized using a heteroatom-containing base oil (x) as a polymerization solvent was used. The point is that the viscosity index improver composition containing is dissolved in the same mineral oil as in Comparative Example 1 to obtain a lubricating oil composition (L-1).
Further, the lubricating oil composition (CL-2) obtained in Comparative Example 2 is also a viscosity index improver composition containing a copolymer (X2) polymerized using mineral oil as a polymerization solvent, similarly to Comparative Example 1. This is a lubricating oil composition obtained by dissolving (Y-2) in mineral oil, and it can be seen that the viscosity index is inferior to that of the lubricating oil compositions obtained in each example.
Further, the lubricating oil composition (CL-3) obtained in Comparative Example 3 is, similarly to Comparative Example 1, a viscosity index improver composition containing a copolymer (X3) polymerized using mineral oil as a polymerization solvent. A lubricating oil composition obtained by dissolving (Y-3) in a mineral oil and a heteroatom-containing base oil (x), but the viscosity index is inferior to the lubricating oil composition obtained in each example. I understand.
Further, the lubricating oil composition (CL-4) obtained in Comparative Example 4 also had a monomer composition in the obtained copolymer (X4), and the content of the monomer (a) was a constituent unit It is considered that the viscosity index could not be sufficiently improved because the requirement of 50% by mass or more and 65% by mass or less based on the total amount of 100% by mass of the polymer was not satisfied.
Further, the composition of the monomers in the copolymer (X5) obtained in Comparative Example 5 is such that the content of the monomer (b) is 37% by mass or more based on the total amount of the constituent monomers of 100% by mass. , does not satisfy the requirement of 50% by mass or less, but as described above, it gradually gels when dissolved in mineral oil, and is not worthy of evaluation.
Further, as in Comparative Example 6, when the viscosity index improver composition (Y-1) containing the copolymer (X1) polymerized using mineral oil as a polymerization solvent is dissolved in mineral oil, the heteroatom-containing In the lubricating oil composition (CL-6) obtained by also blending the base oil (x), as shown by the appearance results, the copolymer (X1) was clouded and separated in the mineral oil, and the viscosity index could not be improved enough.
In Comparative Example 7, the viscosity index improver composition (VII-1) containing the copolymer (A1) obtained in the same manner as in Example 1 was mixed with the heteroatom-containing base oil (x) instead of mineral oil. is a lubricating oil composition (CL-7) obtained by blending in, but in the case of the lubricating oil composition (CL-7) containing only a heteroatom-containing base oil (x) as a lubricating base oil, Compared with the lubricating oil composition (L-1) obtained in Example 1, it was found that the viscosity index was remarkably lowered.
Further, the lubricating oil composition (CL-8) obtained in Comparative Example 8 is a viscosity index improver containing a copolymer (X6) polymerized using ES-1 as a polymerization solvent in the same manner as in Example 10. A lubricating oil composition obtained by dissolving the composition (Y-6) in a mineral oil and a heteroatom-containing base oil (x), but the lubricating oil composition (L-10) obtained in Example 10 It can be seen that the viscosity index is inferior compared to This is because the composition of the monomers in the copolymer (X6) obtained in Comparative Example 8 is 50% by mass when the content of the monomer (a) is based on 100% by mass of the total amount of the constituent monomers. It is considered that the viscosity index could not be sufficiently improved because it was less than.
On the other hand, as in Examples 1 to 14, viscosity index improvers containing copolymers (A1) to (A11) polymerized using a polymerization solvent containing a heteroatom-containing base oil (x) as a polymerization solvent It can be seen that the lubricating oil compositions (L-1) to (L-14) obtained by dissolving the compositions (VII-1) to (VII-11) in mineral oil have good viscosity indexes.

Further, the copolymers (A1), (A4), (A6), (A8) and (A10) obtained in Examples 1, 4, 6, 8 and 10, respectively, and the copolymers obtained in Comparative Example 3 The lubricating oil compositions of Examples 15 to 19 and Comparative Example 9 were prepared so that each lubricating oil composition containing the copolymer (X3) was blended as shown in Table 4 below. When preparing the lubricating oil compositions shown in Table 4 below, the viscosity index improver compositions obtained in Examples 1, 4, 6, 8 and 10 (VII-1), (VII-4), ( VII-6), (VII-8) and (VII-10), and the viscosity index improver composition (Y-3) obtained in Comparative Example 3 were each prepared by blending with mineral oil.
Thermal stability evaluation was performed on the lubricating oil compositions shown in Table 4 below using the method described above.
The results obtained are shown in Table 4 below.

From Table 4, the lubricating oil compositions obtained in Examples 15 to 19 are all excellent in high temperature stability and have a small amount of deposits compared to the lubricating oil composition obtained in Comparative Example 9. was confirmed.
Therefore, it was confirmed that the lubricating oil composition of one embodiment of the present invention also has excellent thermal stability.

The lubricating oil composition of one embodiment of the present invention has a higher viscosity index than conventional lubricating oil compositions.
Therefore, the lubricating oil composition that is one embodiment of the present invention is, for example, as described above, a lubricating oil composition that is used in a wide temperature range such as drive system oil, lubricating oil for internal combustion engines, and hydraulic oil can be suitably used as
The same applies to the component (A) used in the lubricating oil composition of one embodiment of the present invention, and the viscosity index improver composition containing the component (A) of one embodiment of the present invention. .

Claims (14)

Component (A): (meth)acrylate (a) having a linear alkyl group having 4 or less carbon atoms in the side chain of monomer (a), and the number of carbon atoms in the side chain of monomer (b) Weight average molecular weight (Mw) obtained by polymerizing a constituent monomer containing (meth)acrylate (b) having 4 or more branched alkyl groups in a polymerization solvent containing heteroatom-containing base oil (x) is 32,000 or more (A),
The content of the monomer (a) is 50% by mass or more and 63% by mass or less based on 100% by mass of the total amount of the constituent monomers, and
A copolymer (A) in which the content of the monomer (b) is 37% by mass or more and 50% by mass or less based on 100% by mass of the total amount of the constituent monomers;
Component (B): heteroatom-containing base oil (x), and
Component (C): base oil (y) other than heteroatom-containing base oil (x)
contains
A lubricating oil composition in which the content of component (C) is 55% by mass or more based on 100% by mass of the total amount of the lubricating oil composition. 2. The lubricating oil composition of claim 1, wherein the heteroatom-containing base oil (x) is one or more selected from the group consisting of esters, ethers, and amides. The solubility parameter (SP value) of the heteroatom-containing base oil (x) is 7.90 (cal/cm ³ ) ^1/2 or more and 9.40 (cal/cm ³ ) ^1/2 or less, claim 1 or 2. The lubricating oil composition according to 2. The lubricating oil composition according to any one of claims 1 to 3, wherein component (C) is a hydrocarbon base oil. 5. Any one of claims 1 to 4, wherein the content of the heteroatom-containing base oil (x) in the polymerization solvent is 50% by mass or more and 100% by mass or less based on 100% by mass of the total amount of the polymerization solvent. The lubricating oil composition according to . A lubricating oil composition according to any one of claims 1 to 5, wherein monomer (a) is methyl methacrylate. The lubricating oil composition according to any one of claims 1 to 6, wherein the monomer (b) is a (meth)acrylate represented by the following general formula (1).

(In general formula (1), R ¹ represents a hydrogen atom or a methyl group, R ² represents a linear or branched alkylene group having 2 to 4 carbon atoms, and R ³ and R ⁴ each independently represent a carbon represents an alkyl group of numbers 2 to 18. n represents an integer of 0 to 20. When n is 2 or more, a plurality of R ² may be the same or different.) Any of claims 1 to 7, wherein the total content of the monomer (a) and the monomer (b) is 90% by mass or more and 100% by mass or less based on 100% by mass of the total amount of the constituent monomers. 1. The lubricating oil composition according to claim 1. 9. Any one of claims 1 to 8, wherein the solubility parameter (SP value) of component (A) is 9.20 (cal/cm ³ ) ^1/2 or more and 9.60 (cal/cm ³ ) ^1/2 or less. 2. The lubricating oil composition according to item 1. The lubricating oil composition according to any one of claims 1 to 9, wherein component (A) has a mass average molecular weight (Mw) of 200,000 or less. Content of component (A) in the lubricating oil composition is 2% by mass or more and 20% by mass or less based on 100% by mass of the total amount of the lubricating oil composition, according to any one of claims 1 to 10. lubricating oil composition. The lubricating oil composition according to any one of claims 1 to 11, having a Permanent Shear Stability Index (PSSI) of less than 5.0 as measured by ultrasonic testing according to JASO M 347-95. The following component (A), which is blended with the base oil (y) other than the heteroatom-containing base oil (x).
Component (A): (meth)acrylate (a) having a linear alkyl group having 4 or less carbon atoms in the side chain of monomer (a), and the number of carbon atoms in the side chain of monomer (b) Weight average molecular weight (Mw) obtained by polymerizing a constituent monomer containing (meth)acrylate (b) having 4 or more branched alkyl groups in a polymerization solvent containing heteroatom-containing base oil (x) is 32,000 or more (A),
The content of the monomer (a) is 50% by mass or more and 63% by mass or less based on 100% by mass of the total amount of the constituent monomers, and
A copolymer (A) in which the content of the monomer (b) is 37% by mass or more and 50% by mass or less based on 100% by mass of the total amount of the constituent monomers. A viscosity index improver composition containing the following component (A) and a heteroatom-containing base oil (x), which is blended with a base oil (y) other than the heteroatom-containing base oil (x).
Component (A): (meth)acrylate (a) having a linear alkyl group having 4 or less carbon atoms in the side chain of monomer (a), and the number of carbon atoms in the side chain of monomer (b) Weight average molecular weight (Mw) obtained by polymerizing a constituent monomer containing (meth)acrylate (b) having 4 or more branched alkyl groups in a polymerization solvent containing heteroatom-containing base oil (x) is 32,000 or more (A),
The content of the monomer (a) is 50% by mass or more and 63% by mass or less based on 100% by mass of the total amount of the constituent monomers, and
A copolymer (A) in which the content of the monomer (b) is 37% by mass or more and 50% by mass or less based on 100% by mass of the total amount of the constituent monomers.