JP2021161295A - Lubricant composition - Google Patents

Abstract

To provide a lubricant composition that contains at least a certain amount of a base oil excluding a hetero atom-containing base oil, and has an excellent viscosity index.SOLUTION: A lubricant composition contains a component (A): a copolymer satisfying specific requirements (A), a component (B): a hetero atom-containing base oil (x), and a component (C): a base oil (y) excluding the hetero atom-containing base oil (x). The content of the component (C) is 55 mass% or more relative to 100 mass% of the total amount of the lubricant composition.SELECTED DRAWING: None

Description

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, drive system oils such as automatic transmission fluid (ATF), stepless transmission oil (CVTF), and shock absorber oil (SAF), and lubricating oil compositions used as internal combustion engine oil, hydraulic hydraulic oil, and the like have been used. Various characteristics are required depending on the application.
For example, with regard to fuel saving of automobiles, the weight of automobiles has been reduced, the engine has been improved, and the automobile itself has been improved. Improvement of lubricating oil such as addition of additives is also important. However, since the lubricating oil is used in a wide temperature range, simply reducing the viscosity causes the oil film at the lubricating portion to become thinner under high temperature conditions, resulting in increased wear and seizure due to contact between the members. It causes such a problem. 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 example, a method of adding a viscosity index improver to improve the temperature dependence of viscosity is generally used for a lubricating oil used in a wider temperature range from a high temperature range to a low temperature range.
For example, Patent Document 1 describes a copolymer containing a specific essential constituent monomer at a specific content and an ester oil base oil having a ^{kinematic viscosity of 1.0 to 2.5 mm 2 / s at 100 ° C.} A viscosity index improver composition containing the above-mentioned viscosity index improver composition and a lubricating oil composition containing the viscosity index improver are disclosed.
Further, for example, Patent Document 2 describes an improvement in the viscosity index for a hydrocarbon-based synthetic base oil, which comprises a copolymer that satisfies a specific solubility parameter and contains a specific essential constituent monomer in a specific content. A lubricating oil composition containing an agent, the viscosity index improver, and a hydrocarbon-based synthetic base oil is disclosed.

JP-A-2017-57378 Japanese Unexamined Patent Publication No. 2015-38194

As described above, various viscosity index improvers have been used and studied to improve the viscosity index of the lubricating oil composition as a method for improving the temperature dependence of the viscosity of the lubricating oil composition.
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 viscosity index improver composition containing a copolymer containing a similar constituent monomer and a mineral base oil with a mineral base oil. In some cases, it is disclosed that the viscosity index is low. Therefore, Patent Document 1 has not studied to obtain a lubricating oil composition containing a lubricating oil base oil other than the ester oil base oil as a main component, such as a mineral base oil, and having a good viscosity index.
On the other hand, in Patent Document 1, a viscosity index improver for a hydrocarbon-based synthetic base oil is studied, but further improvement is required for the viscosity index of the obtained lubricating oil composition.
Here, as described above, the lubricating oil composition is used in various applications, and as the base oil used in the lubricating oil composition, a base oil other than a heteroatomic oil-containing base oil such as an ester oil base oil (for example, , Hydrocarbon-based base oil) are also used in many lubricating oil compositions.
As described above, the lubricating oil composition containing a base oil (for example, a hydrocarbon-based base oil) other than the heteroatomic oil-containing base oil such as an ester oil base oil as a main component has been used so far. The effect of the combination of the lubricating oil base oil and the viscosity index improver on the viscosity index, and the optimum viscosity index improver for improving the viscosity index of the lubricating oil composition have been thoroughly examined. However, there was room for further consideration.
From such a viewpoint, it is an object of the present invention to provide a lubricating oil composition containing a certain amount or more of a base oil other than the heteroatom-containing base oil and having a good viscosity index.

As a result of diligent studies, the present inventors have found that the copolymer (A) satisfying a specific requirement obtained by polymerizing in a polymerization solvent containing a heteroatom-containing base oil (x) is a heteroatom-containing base oil (x). It has been found that the viscosity index of a lubricating oil composition containing a base oil (y) other than) above a certain content can be improved. 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): A (meth) acrylate (a) having a linear alkyl group having 4 or less carbon atoms in the side chain which is a monomer (a), and a side chain which is a monomer (b). Mass average molecular weight obtained by polymerizing a constituent monomer containing (meth) acrylate (b) having a branched alkyl group having 4 or more carbon atoms in a polymerization solvent containing a heteroatom-containing base oil (x). A copolymer (A) having (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 copolymer (A), wherein 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 the 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 the above [1], wherein the heteroatom-containing base oil (x) is at least one selected from the group consisting of esters, ethers, and amides.
[3] 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. The lubricating oil composition according to [1] or [2].
[4] The lubricating oil composition according to any one of [1] to [3] above, wherein the component (C) is a hydrocarbon-based base oil.
[5] 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 any one of.
[6] The lubricating oil composition according to any one of [1] to [5] above, 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 the 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 are independent carbon atoms. .n indicating the number 2-18 alkyl groups may, when the .n is 2 or more represents an integer of 0 to 20, ^{R 2} existing in plural numbers may be the same or different.)

[8] 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 [7].
[9] The solubility parameter (SP value) of the component (A) is 9.20 (cal / cm ³ ) ^1/2 or more and 9.60 (cal / cm ³ ) ^1/2 or less. 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 mass average molecular weight (Mw) of the component (A) is 200,000 or less.
[11] The above-mentioned [1] to [10], wherein the content of the component (A) in the lubricating oil composition is 8% by mass or more and 20% by mass or less based on 100% by mass of the total amount of the lubricating oil composition. The lubricating oil composition according to any one.
[12] The lubrication according to any one of [1] to [11] above, wherein the permanent shear stability index (PSSI) measured by an ultrasonic test conforming to JASO M 347-95 is less than 5.0. Oil composition.
[13] The following component (A) used in combination with a base oil (y) other than the heteroatom-containing base oil (x).
Component (A): (Meta) acrylate (a) having a linear alkyl group having 4 or less carbon atoms in the side chain which is a monomer (a), and carbon atoms in the side chain which is a monomer (b). Mass 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 a 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
The 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 used by blending with a base oil (y) other than the heteroatom-containing base oil (x).
Component (A): (Meta) acrylate (a) having a linear alkyl group having 4 or less carbon atoms in the side chain which is a monomer (a), and carbon atoms in the side chain which is a monomer (b). Mass 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 a 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
The 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] above, wherein the following components (A) and (B) are blended with the following component (C).
Component (A): (Meta) acrylate (a) having a linear alkyl group having 4 or less carbon atoms in the side chain which is a monomer (a), and carbon atoms in the side chain which is a monomer (b). Mass 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 a 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
The copolymer (A), wherein 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] Of the component (C), the viscosity index improver composition according to the above [14] is blended with the base oil (y) other than the hetero atom-containing base oil (x) which is the 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 the above [1] to [12] or the lubricating oil composition obtained by the production method according to the above [15] or [16]. Method.
[18] A drive system 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].
[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 hydraulically actuated 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 base oil other than the heteroatom-containing base oil in a certain amount or more and having a good viscosity index.

Hereinafter, preferred embodiments of the present invention will be described in detail.
[Lubricating oil composition]
The lubricating oil composition according to the embodiment of the present invention contains the following components (A) to (C), and the content of the component (C) is 55% by mass based on 100% by mass of the total amount of the lubricating oil composition. % Or more.
Component (A): (Meta) acrylate (a) having a linear alkyl group having 4 or less carbon atoms in the side chain which is a monomer (a), and carbon atoms in the side chain which is a monomer (b). Mass 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 a 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
The copolymer (A), wherein 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 100% by mass of the total amount of the lubricating oil composition does not contain the components (A) and (B), the lubricating oil has an excellent viscosity index. Difficult to obtain composition.

Hereinafter, in the present specification, with respect to a preferable numerical range (for example, a range such as content), the lower limit value and the upper limit value described stepwise can be combined independently. For example, a description of a lower limit value of "preferably 10 or more, more preferably 30 or more, still more preferably 40 or more" and an upper limit value of "preferably 90 or less, more preferably 80 or less, still more preferably 70 or less". From the description of the above, as a suitable range, for example, a range in which a lower limit value and an upper limit value independently selected such as "10 or more and 70 or less", "30 or more and 70 or less", and "40 or more and 80 or less" are combined is selected. You can also do it. Further, from the same description, for example, it is possible to simply select a range in which one of the lower limit value and the upper limit value such as "40 or more" or "70 or less" is defined. Further, for example, "preferably 10 or more and 90 or less, more preferably 30 or more and 80 or less, still more preferably 40 or more and 70 or less", "preferably 10 to 90, more preferably 30 to 80, still more preferably 40 to 40 to". The same applies to the preferable range that can be selected from the description such as "70". In the description of the numerical range in the present specification, for example, the description "10 to 90" is synonymous with "10 or more and 90 or less".
Further, in the present specification, the “hydrocarbon group” means a group composed of only a carbon atom and a hydrogen atom. "Hydrocarbon groups" include "aliphatic groups" composed of straight or branched chains, "aliphatic groups" having one or more saturated or unsaturated carbon rings having no aromaticity, benzene rings, etc. Includes "aromatic groups" having one or more aromatic rings exhibiting the aromaticity of.
Further, in the present specification, the “ring-forming carbon number” represents the number of carbon atoms among the atoms constituting the ring itself of the 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 carbons forming the ring.
Further, in the present specification, for example, "(meth) acrylate" means both "acrylate" and "methacrylic acid", and "(meth) acrylic acid" means "acrylic acid" and "methacrylic acid". Both are shown, and so are other similar terms.

Further, in the present specification, "PSSI" means "Permanent Shear Stability Index". Generally, the PSSI indicates the ability to resist the decomposition of a polymer (polyalkyl (meth) acrylate). However, in the present specification, unless otherwise specified, the above-mentioned "PSSI" refers to the "PSSI of the lubricating oil composition" described in the present specification, and is used as an index indicating the shear stability of the lubricating oil composition. I am using it. The PSSI of the lubricating oil composition described herein is basically due to the stability of the copolymer (A), which is the component (A), to shearing. Here, the dispersed state of the copolymer (A) or the shearing force substantially applied to the copolymer (A) is a heteroatom-containing base oil (x) which is a component (B) contained in the lubricating oil composition. ) And the base oil (y) other than the heteroatom-containing base oil (x) which is the component (C). That is, it is considered that it also changes depending on the composition of the lubricating oil composition. As a result, it is considered that the degree of decomposition of the copolymer (A) is changed even when the same shearing force is applied to the entire lubricating oil composition, and as a result, the same copolymer (A) is produced. It is considered that the PSSIs of the lubricating oil compositions contained therein are different due to the difference in the composition. 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 a value measured and calculated by the method described in Examples, and the smaller the PSSI, the more stable the lubricating oil composition is with respect to shearing. Therefore, it is difficult for the viscosity to decrease due to shearing.
Hereinafter, each component contained in the lubricating oil composition will be described.

<Component (A): Copolymer (A)>
The copolymer (A) (hereinafter, also simply referred to as “component (A)”) contained in the lubricating oil composition is a linear alkyl group having 4 or less carbon atoms in the side chain which is the monomer (a). A constituent monomer containing (meth) acrylate (a) having (meth) acrylate (a) having a A copolymer obtained by polymerizing in a polymerization solvent containing an 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 "constituting monomer" refers to a monomer as a raw material constituting the copolymer (A) according to one aspect of the present invention, and polymerizes the polymer described later. The polymerization initiator and / or chain transfer agent used at the time of preparation is not included in the monomer.
Further, as will be described later, the component (A) is used by blending with a base oil (y) other than the heteroatom-containing base oil (x), and is used as a base oil other than the heteroatom-containing base oil (x). The viscosity index of the lubricating oil composition containing y) can be improved.
That is, the component (A) according to the embodiment of the present invention is used by blending with a base oil (y) other than the heteroatom-containing base oil (x).

(Polymerization solvent)
The component (A) is polymerized in a polymerization solvent, and the polymerization solvent contains a heteroatom-containing base oil (x).
Here, when the polymerization solvent for polymerizing the component (A) does not contain the heteroatom-containing base oil (x), the viscosity index of the obtained lubricating oil composition cannot be sufficiently improved.
The reason is not clear, but it can be considered as follows.
When the polymerization solvent contains a heteroatom-containing base oil (x) and when the polymerization solvent does not contain a heteroatom-containing base oil (x), there is some degree of molecular state in the molecular structure of the obtained copolymer. Differences are believed to exist. Then, for example, when the polymerization solvent does not contain the heteroatom-containing base oil (x), the molecular structure of the obtained copolymer contains a base oil (y) other than the heteroatom-containing base oil (x). It is considered that a polymer containing a large amount of a partial structure having poor compatibility or a structure having poor compatibility with a base oil (y) other than the 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 obtained lubricating oil composition cannot be sufficiently improved, or , It is considered that a problem such as white turbidity and incompatibility occurs.
Further, for example, when the polymerization solvent does not contain the heteroatom-containing base oil (x), for example, the molecular structure of the obtained copolymer can be obtained in the lubricating oil composition, even if it does not cause white turbidity. It is considered that the structure contains many structures whose viscosity index cannot be sufficiently improved.
On the other hand, the molecular structure of the copolymer which is the component (A) polymerized in the polymerization solvent containing the hetero atom-containing base oil (x) includes, for example, a base oil (y) other than the hetero atom-containing base oil (x). It is considered that there are few structures that are inferior in compatibility with) and / or many molecular structures that are more compatible with. Further, for example, it is considered that the molecular structure of the copolymer as the component (A) contains many molecular structures capable of sufficiently improving the viscosity index of the obtained lubricating oil composition. Be done.

As described above, even if the monomer composition is the same, it can be obtained when the polymerization solvent contains the hetero atom-containing base oil (x) and when the polymerization solvent does not contain the hetero atom-containing base oil (x). It is considered that there is some difference in the molecular structure of the copolymer or the molecular state in the polymerization solvent. However, for example, in order to identify the difference in the molecular structure by a known analysis method, extremely complicated analysis such as isolation and purification and establishment of a method for defining the structure of a polymer is required.
Further, a component (A) obtained by polymerizing in a polymerization solvent containing a hetero atom-containing base oil (x) and a hetero atom-containing base oil (a hetero atom-containing base oil) having the same monomer composition as the component (A). It is considered that a certain number or more of molecules having a common molecular structure are contained in the copolymer obtained by polymerizing in a polymerization solvent containing no x), and the monomer composition and the like are determined. Except for this, it is expected that confirmation of differences from the molecular structure of the polymer (arrangement of structures derived from each monomer and binding mode) will take even longer.
Further, for example, when the above difference is in the molecular state in the polymerization solvent (for example, the difference in the spatial spread of the molecule, etc.), the difference is confirmed at the time of isolation and purification. It becomes difficult to do. For example, as will be described later, in the comparative example of the present invention, the heteroatom-containing base oil (x) is added to the copolymer obtained by polymerizing in a polymerization solvent that does not contain the heteroatom-containing base oil (x). It has been confirmed that even when the lubricating oil composition is prepared by adding x), the viscosity index of the obtained lubricating oil composition cannot be sufficiently improved.
Therefore, at present, the component (A) obtained by polymerizing in a polymerization solvent containing a heteroatom-containing base oil (x) and the component (A) have the same monomer composition as the component (A) but contain a heteroatom. As mentioned above, it is considered that there are some differences between the copolymer obtained by polymerizing in a polymerization solvent that does not contain the base oil (x), but the molecular structure and characteristics of the component (A) are simply described. The reality is that it is not possible to specify and define the differences.

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 "heteroatom" refers to an atom other than carbon and hydrogen, and examples thereof include a nitrogen atom, an oxygen atom, and a sulfur atom.
Examples of the base oil (x) include 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 obtained lubricating oil composition. , More preferably one or more selected from the group consisting of esters, ethers, and amides, and even more preferably one or more selected from the group consisting of esters and ethers.

Examples of the ester include various esters such as monoester, diester, and polyester.
Examples of the monoester include decyl decanoate and 2-ethylhexyl caprylate.
Examples of the diester include bis (2-ethylhexyl) sebacate and dibutyl adipate.
Examples of the polyester include a complete ester or a partial ester of a trivalent or higher valent alcohol such as trimethylolpropane and a carboxylic acid such as myristic acid, palmitic acid, stearic acid and oleic acid. The polyester is preferably a complete ester of one or more selected from a complete ester of trimethylolpropane and a partial ester of trimethylolpropane, more preferably a complete ester of trimethylolpropane and one or more selected from stearic acid and oleic acid. And one or more selected from partial esters of trimethylol propane and one or more selected from stearic acid and oleic acid, more preferably complete with one or more selected from trimethylol propane and one or more selected from stearic acid and oleic acid. Esters can be mentioned.
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 are preferable, and decanoic acid. One or more selected from the group consisting of decyl, bis-sebacate (2-ethylhexyl), and trimethylolpropane ester is more preferable, and one or more selected from the group consisting of decyl decanoate and bis-sebacate (2-ethylhexyl). Is more preferable.

Examples of the ether include bis (2-ethylhexyl) ether and polyvinyl ether. As the polyvinyl ether, a 3 to pentamer of polyvinyl ether is preferable.

Examples of the amide include N, N-di (2-ethylhexyl) -2-ethylhexaneamide 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, still more preferably 7.93 (cal / cm 3) cm ³ ) ^1/2 or more 9.00 (cal / cm ³ ) ^1/2 or less, more preferably 7.94 (cal / cm ³ ) ^1/2 or more 8.80 (cal / cm ³ ) ^1/2 It is as follows.
Here, the solubility parameter (SP value) is a value (δ) defined by the regular solution theory introduced by Hildebrand, for example, “Property of Polymers, Third complete revised edition”, D.I. W. Van Krevelen, Elsevier Science Publishing Company, Amsterdam, 1990 Chapter 7 is a parameter that can be used to determine the compatibility of resins.
Various methods for calculating the SP value have been proposed, and for example, it can be obtained by using the method proposed by Fedors (Polym. Eng. Sci. 1974, Vol. 14, p147), the following formula (I).
δ = (ΣE _coh / ΣV) ^1/2 ... (I)
Here, δ represents the solubility parameter (cal / cm ³ ) ^1/2 , _Ecoh represents the aggregation energy density (cal / mol), V represents 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 that make up the monomer. _{Numerical values of Ecoch} and V for each atomic group are listed in Table 7.3 and the like of the above-mentioned "Properties of Polymers, Third completely reviewed edition".

The viscosity of the base oil (x) is not particularly limited, but as will be described later, when it is used as it is as the component (B) of the lubricating oil composition, the kinematic viscosity at 100 ° C. is preferably 0.5 to 0.5 to 1. 6.0 mm ² / s, more preferably 0.7~5.5mm ² / s, more preferably from 1.0 to 5.0 mm ² / s. When the 100 ° C. kinematic viscosity is 0.5 mm ² / s or more, the flash point becomes high, and when it is 6.0 mm ² / s or less, the power loss due to the viscous resistance is suppressed and the fuel efficiency is improved. Is obtained.

Further, 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 the polymerization solvent may contain (hereinafter, also simply referred to as “base oil (y)”) is the same as the component (C) described later. Since the above can be used and the preferred embodiment thereof is the same, the description thereof is omitted here.

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, 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.
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 100% by mass of the total amount of the polymerization solvent. More preferably 1% by mass or more, further 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. Hereinafter, it is even more preferably 5% by mass or less.

(Monomer (a): (meth) acrylate (a) having a linear alkyl group having 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 and ethyl. Examples thereof include (meth) acrylate, n-propyl (meth) acrylate, and 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 further preferably methyl methacrylate. be.
In addition, the monomer (a) may be used alone or in combination of two or more of the above-mentioned ones.

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 obtained lubricating oil composition, the content of the monomer (a) is preferably 52% by mass or more, more preferably 53% by mass or more, still more preferably 54% by mass. % Or more, and preferably 62% by mass or less, more preferably 60% by mass or less, still more preferably 58% by mass or less.

(Monomer (b): (meth) acrylate (b) having a branched alkyl group having 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). It is a (meth) acrylate to be produced.

（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 the 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 are independent carbon atoms. .n indicating the number 2-18 alkyl groups may, when the .n is 2 or more represents an integer of 0 to 20, ^{R 2} existing in plural numbers may be the same or different.)

The preferred embodiments and the like indicated by each reference numeral in the general formula (1) are shown below.
R ¹ preferably represents a methyl group from the viewpoint of improving the viscosity index.
Examples of the linear or branched alkylene group having 2 to 4 carbon atoms represented by R ² include an ethylene group, a propane-1,2-diyl group, a propane-1,3-diyl group, a butane-1,2-diyl group, and a butane group. Examples thereof include a -1,3-diyl group, a butane-1,4-diyl group, a butane-2,2-diyl group, and preferably an ethylene group or a propane-1,2-diyl group.
n is preferably an integer of 0 to 5, more preferably an integer of 0 to 2, and even more preferably 0, from the viewpoint of the solubility of the obtained component (A) in the base oil.
when n is 2 or more, R ⁶ where there are two or more may be the same or different and the general formula (1) in the - (R 2 ^-O-) aspect of the coupling parts to each other, represented by n May be a random join or a block join.
R ³ and R ⁴ independently represent an alkyl group having 4 to 18 carbon atoms, more preferably an alkyl group having 6 to 18 carbon atoms, and further 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, and is preferably a linear alkyl group.
Further, as an example of a preferable embodiment 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 an alkyl having 4 to 18 carbon atoms. It represents a group, more preferably 6 to 16 alkyl groups, even more preferably 8 to 14 alkyl groups. Then, R ⁴ preferably represents an alkyl group having 6 to 18 carbon atoms, more preferably an alkyl group having 8 to 18 carbon atoms, and further preferably an alkyl group having 10 to 16 carbon atoms.

Examples of specific examples of the compound represented by the general formula (1) include 2-hexyldecyl methacrylate, 2-decyltetradecyl methacrylate, 2-dodecyl hexadecyl methacrylate, 2-tetradecyl octadecyl methacrylate and the like. Can be mentioned.
The compound represented by the general formula (1) is preferably 2-decyltetradecyl methacrylate, 2-dodecyl hexadecyl methacrylate, or 2-tetradecyl octadecyl methacrylate, more preferably 2 in the specific examples. -Decil tetradecyl methacrylate, or 2-tetradecyl octa-octadecyl methacrylate, more preferably 2-tetradecyl octa-octadecyl methacrylate.
In addition, the compound represented by the general formula (1), which is a suitable monomer (b), may be used alone or in combination of two or more of the above-mentioned compounds.

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 obtained lubricating oil composition, the content of the monomer (a) is preferably 38% by mass or more, more preferably 40% by mass or more, still more preferably 42% by mass. % Or more, and preferably 48% by mass or less, more preferably 47% by mass or less, still more preferably 46% by mass or less.

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

The content of each of the monomers can be calculated from, for example, the blending amount of each monomer, and in the present specification, the molecule in the component (A) polymerized by the constituent monomer. If the conversion rate of the constituent monomer is 98% or more, the content of the constituent unit derived from each monomer based on 100% by mass of the total amount of the constituent units excluding the terminal constituent units in the structure is the constituent monomer. It can be considered that the total amount of each monomer is the same as the blending amount of each monomer based on 100% by mass. The "conversion rate" is the conversion rate of all the constituent monomers used.
Here, in the present specification, the "molecular structure" in the description "based on 100% by mass of the total amount of the structural units excluding the terminal structural units in the molecular structure" refers to the component (A) which is one aspect of the present invention. Refers to the 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 or not the component (A) present in the viscosity index improver composition or the lubricating oil composition, which will be described later, satisfies the above constitution, for example, by separating the rubber film from the lubricating oil composition. The polymer component is taken out, ^{the structural unit derived from each raw material is specified by 13} C-NMR, and the content of each structural unit is confirmed by using thermal decomposition GC-FID. , Can be confirmed.

(Other monomers)
The component (A), which is one aspect of the present invention, is a single amount of the constituent monomers other than the monomers (a) and (b) as long as the effects of the present invention are not impaired. It may include the body.
Examples of the monomers other than the monomers (a) and (b) include alkyl (meth) acrylates other than the monomers, functional group-containing monomers and the like.
Examples of the alkyl (meth) acrylate other than the monomer include a (meth) acrylate having a linear alkyl group having 5 or more carbon atoms in the side chain (for example, a linear alkyl having 5 or more carbon atoms and 36 or less carbon atoms in the side chain). (Meta) acrylate having a group), (meth) acrylate having an alicyclic alkyl group and the like can be mentioned.
Examples of the functional group-containing monomer include known amino group-containing monomers, quaternary ammonium base-containing monomers, nitrile group-containing monomers, nitro group-containing monomers, and hydroxy group-containing monomers. Examples include carboxy group-containing monomers.
When the polymer according to one aspect of the present invention contains these other monomers, the other monomers may be used alone or in combination of two or more.

When the constituent monomer contains the other monomer, the total content of the other monomer is preferably 0.01% by mass or more based on 100% by mass of the total amount of the constituent monomer. , 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, still more preferably less than 2% by mass, still more preferable. Is 1% by mass or less.

(Physical characteristics of component (A), etc.)
The 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 obtained lubricating oil composition cannot be sufficiently improved.
The mass average molecular weight (Mw) of the component (A) is preferably 200,000 or less from the viewpoint of suppressing a decrease in the shear stability of the component (A) in the obtained lubricating oil composition.
From this point of view, the mass average molecular weight (Mw) of the component (A) is preferably 34,000 or more, more preferably 35,000 or more, still more preferably 40,000 or more, still more preferably 42,000. The above, and more preferably 100,000 or less, still more preferably 70,000 or less, still more preferably 60,000 or less.
The molecular weight distribution (Mw / Mn) of the 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. The lower limit value thereof is not particularly limited, but is preferably 1.01 or more, more preferably 1.10 or more, still more preferably 1.20 or more, still more preferably 1.30 or more.
The mass average molecular weight (Mw) is measured by the method described in Examples described later.
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 obtained lubricating oil composition, the solubility parameter (SP value) of the 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, still more preferably 9.37 (cal / cm 3). 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, by using the following formula (II).
SP value of component (A) = Σ ([δx] x [component x]) ... (II)
^{Here, [δx] represents 1/2 the SP value (cal / cm 3} ) of the monomer x calculated by the formula (I) proposed by Fedors described above, and [constituent amount x] is a component (constituent amount x). When all the constituent monomers constituting A) are 1, it represents the content ratio (maximum value 1) of the monomer x in the total constituent units. Σ means to sum all the monomers constituting the polymer.
Here, for example, in the case where the component (A) is a copolymer composed of the monomer (a) and the monomer (b), the SP value of the component (A) can be calculated as follows. can.
SP value of the copolymer composed of the monomer (a) and the monomer (b) = ([δa] × [component a]) + ([δb] × [component b])
^{[Δa] represents the SP value (cal / cm 3} ) ^1/2 of the monomer (a) calculated by the formula (I) proposed by Fedors described above, and [constituent amount a] is the component (A). ) Is represented by the content ratio of the monomer (a) in the total constituent monomers. ^{[Δb] represents the SP value (cal / cm 3} ) ^1/2 of the monomer (b) calculated by the formula (I) proposed by Fedors described above, and [constituent amount b] is the component (A). ) Is represented by the content ratio of the monomer (b) in all the constituent monomers. In this case, [constituent amount a] + [constituent amount b] = 1.

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

(Polymerization method of component (A))
The component (A) can be obtained by radically polymerizing each of the above-mentioned monomers in the above-mentioned polymerization solvent containing the base oil (x).
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. You can get it by doing.

Examples of the polymerization initiator include one or more selected from the group consisting of an azo-based initiator, a peroxide-based initiator, a redox-based initiator, and an organic halogen compound initiator. The polymerization initiator used in the component (A) is preferably one or more selected from an azo-based initiator and a peroxide-based initiator, and more preferably one selected from an azo-based initiator and an organic peroxide. As described above, more preferably, an azo-based initiator can be used.
Examples of the azo-based polymerization initiator include 2,2'-azobis (isobutyronitrile) (abbreviation: AIBN), 2,2'-azobis (2-methylbutyronitrile) (abbreviation: AMBN), 2, 2'-azobis (2,4-dimethylvaleronitrile) (abbreviation: ADVN), 4,4'-azobis (4-cyanovaleric acid) (abbreviation: ACVA) and salts thereof (eg, hydrochloride, etc.), dimethyl 2, Examples thereof include 2'-azobisisobutyrate, 2,2'-azobis (2-amidinopropane) hydrochloride, 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propionamide] and the like. ..

Examples of the peroxide-based initiator include inorganic peroxides and organic peroxides.
Examples of the inorganic peroxide include hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate and the like.
Examples of the organic peroxide include benzoyl peroxide, di-tert-butyl peroxide, cumene hydroperoxide, succinate peroxide, di (2-ethoxyethyl) peroxydicarbonate, and tert-butylperoxypivalate. , Tert-Hexylperoxypivalate, tert-butylperoxyneoheptanoate, tert-butylperoxyneodecanoate, tert-butylperoxy2-ethylhexanoate, tert-butylperoxyisobutyrate, Examples thereof include tert-amylperoxy2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy2-ethylhexanoate, dibutylperoxytrimethyladipate, and lauryl peroxide.

Redox-based initiators include reducing agents such as alkali metal sulfite or persulfate (for example, ammonium sulfite, ammonium bicarbonate, etc.), ferrous chloride, ferrous sulfate, ascorbic acid, and alkali metal persulfate. Examples thereof include those composed of a combination with an oxidizing agent such as a salt, ammonium persulfate, hydrogen peroxide, and an organic peroxide.
Further, as described above, when the conversion rate of the constituent monomer does not reach 98% during the polymerization of the component (A), for example, by further adding a polymerization initiator to the polymerization system, the above conversion The conversion rate can be increased up to the rate.

In the radical polymerization, a known chain transfer agent may be used, if necessary, for the purpose of adjusting the physical properties of the copolymer such as molecular weight.
Examples of the chain transfer agent include secondary alcohols such as mercaptans, thiocarboxylic acids and isopropanol, amines such as dibutylamine, hypophosphites such as sodium hypophosphite, chlorine-containing compounds and alkylbenzene compounds. ..
Examples of the mercaptans include alkyl groups having 2 to 20 carbon atoms such as n-butyl mercaptan, isobutyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, sec-butyl mercaptan, tert-butyl mercaptan, and tert-dodecyl mercaptan. Examples thereof include alkyl mercaptan compounds having mercaptan compounds; hydroxyl group-containing mercaptan compounds such as mercaptoethanol and mercaptopropanol; and the like.
Examples of thiocarboxylic acids include thioglycolic acid and thioapple acid.
The amount of the polymerization initiator and chain transfer agent used can be appropriately selected in consideration of the physical characteristics of the desired copolymer (for example, adjustment of the molecular weight).

Examples of the polymerization control method include an adiabatic polymerization method and a temperature control polymerization method. The reaction temperature during polymerization is preferably 30 to 140 ° C, more preferably 50 to 130 ° C, and even more preferably 70 ° C to 120 ° C.
Further, in addition to the method of initiating polymerization by heat, a method of initiating polymerization by irradiating radiation, an electron beam, ultraviolet rays, or the like can also be adopted. A temperature-controlled solution polymerization method is preferred.
The copolymerization mode may be either random addition polymerization or alternate copolymerization, and may be either graft copolymerization or block copolymerization.

Further, 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 according to one aspect of the present invention is made of the copolymer (A), but is further lubricated by being dissolved and diluted in a diluent to obtain a viscosity index improver composition. It is preferable because it can be easily dissolved in the base oil contained in the oil composition.
The diluent used for the viscosity index improver is a diluent containing at least a heteroatom-containing base oil (x), and the heteroatom-containing base oil (x) used as a diluent contains the above-mentioned component (A). Since the same base oil (x) as described in the column of the polymerization solvent at the time of polymerization can be used and the preferred embodiment thereof is also the same, the description thereof is omitted here.
Further, in the case where the base oil (x) is used as the polymerization solvent used when polymerizing the above-mentioned component (A) as the diluent used for the viscosity index improver, the base oil used as the polymerization solvent is used. When (x) is added to the viscosity index improver as it is, the base oil (x) used as the polymerization solvent can be regarded as one kind of the base oil (x) contained in the viscosity index improver.
Further, as the diluent used for the viscosity index improver, it is preferable that at least the base oil (x) used at the time of polymerization of the component (A) is contained as it is.
That is, the viscosity index improver according to one aspect of the present invention contains the component (A) and the heteroatom-containing base oil (x).
These diluents may be used alone or in combination of two or more from the above-mentioned ones.
When the viscosity index improver composition comprises the copolymer (A) and a diluent, the content of the copolymer (A) is preferably 100% by mass based on the total amount of the viscosity index improver composition. It is 5 to 80% by mass, more preferably 20 to 80% by mass, and even more preferably 30 to 70% by mass.
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 described above. The same as the heteroatom-containing base oil (x) described in the column of the polymerization solvent for polymerizing the above-mentioned component (A) can be used, and the preferred embodiment thereof is also the same. Omit.
The base oil (x) to be the component (B) may be used alone or in combination of two or more from the above-mentioned ones.
The component (B) contained in the lubricating oil composition is a case where the base oil (x) is used as the polymerization solvent used when polymerizing the above-mentioned component (A), and the base oil used as the polymerization solvent ( 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, when the viscosity index improver composition according to one aspect of the present invention contains a base oil (x) as a diluent, the base oil (x) used as the diluent can be used as it is for lubrication. 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 of the component (A) as it is as the component (B), and the viscosity containing the component (A). 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 the polymerization solvent of the component (A) is used as the component (B) as it is. It is preferable to contain it.
Further, for example, when preparing a viscosity index improver composition containing the component (A), a new base oil (x) can be added to dilute the viscosity index improver composition. Even in such a case, if the lubricating oil composition contains as it is the base oil (x) added when preparing the viscosity index improver composition as the component (B), at least the component (A) It is preferable to use a viscosity index improver composition containing the base oil (x) used as the polymerization solvent of the above as the component (B) as it is.

Further, from the viewpoint of further improving the viscosity index of the obtained lubricating oil composition, the content of the component (B) in the lubricating oil composition is based on 100% by mass of the total amount of the lubricating oil composition, preferably 1% by mass. The above is more preferably 3% by mass or more, further preferably 6% by mass or more, and from the viewpoint of suppressing an increase in PSSI of the obtained lubricating oil composition, it is preferably 35% by mass or less, more preferably 25% by mass. % Or less, more preferably 15% by 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-based base oil.
The hydrocarbon-based base oil is not particularly limited, and any of mineral oils and synthetic oils (excluding component (B)) conventionally used as base oils for lubricating oils can be appropriately selected. Can be used.
As the mineral oil, for example, the lubricating oil distillate obtained by distilling the atmospheric residual oil obtained by atmospheric distillation of crude oil under reduced pressure is subjected to solvent removal treatment; at least one treatment of solvent extraction or hydrocracking. At least one dewaxing treatment of solvent dewaxing or catalytic dewaxing; hydrorefining treatment; one or more treatments, preferably all treatments, and refined oils or mineral oil-based waxes of the opposite sex Examples thereof include oil produced by distilling. Of these, oils treated by hydrorefining are preferred.
Examples of the synthetic oil include polyα-olefins such as polybutenes, α-olefin homopolymers, and copolymers such as ethylene-α-olefin copolymers; alkylbenzenes; alkylnaphthalene; or residue WAX (gastou) in the GTL process. Examples thereof include GTL base oils produced by hydrogenation isomerization and dewaxing of liquid wax).
Further, as the hydrocarbon-based base oil, at least one selected from a base oil classified into Group II of the American Petroleum Institute (API) base oil category and a base oil classified into Group III is more preferable. ..
These base oils may be used alone or in combination of two or more of the above-mentioned ones.

The component (C) contained in the lubricating oil composition is a case where the base oil (y) is used as the polymerization solvent used when polymerizing the above-mentioned component (A), and the group used as the polymerization solvent. When the oil (y) is added to the lubricating oil composition as it is, 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, when the viscosity index improver composition according to one aspect of the present invention contains a base oil (y) as a diluent, the base oil (y) used as the diluent can be used as it is for lubrication. 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 the 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 obtained lubricating oil composition cannot be sufficiently improved, and the PSSI of the obtained lubricating oil composition is sufficiently increased. Cannot be suppressed.
Further, from the viewpoint of suppressing an increase in PSSI of the obtained lubricating oil composition, the content of the component (C) is preferably 60% by mass or more, more preferably 60% by mass or more, based on 100% by mass of the total amount of the lubricating oil composition. 70% by mass or more, more preferably 75% by mass or more, still more preferably 78% by mass or more, and preferably 97% by mass or less, more preferably 95% by mass or less, still more preferably 90% by mass or less. 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, and further preferably ^{2 to 10 mm 2.} / S, more preferably 2-5 mm ² / s. When the 100 ° C. kinematic viscosity is 2 mm ² / s or more, the evaporation loss is small, ^{and when it is 30 mm 2} / s or less, the power loss due to the viscous resistance is suppressed, and the fuel consumption improving effect can be obtained.
The viscosity index of the component (C) is preferably 50 or more, more preferably 80 or more, still more preferably 100 or more, and even more preferably 105 or more. When the viscosity index of the base oil is in this range, it becomes easy to improve the viscosity characteristics of the lubricating oil composition.
The kinematic viscosity and viscosity index values at 100 ° C. are measured by the methods described in Examples described later.

Further, from the viewpoint of further improving the viscosity index of the obtained lubricating oil composition, the difference between the value of the solubility parameter (SP value) of the component (B) and the value of the solubility parameter (SP value) of the component (C). Is an absolute value, 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. More than 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 .15 (cal / cm ³ ) ^1/2 or more and 0.60 (cal / cm ³ ) ^1/2 or less.

<Other ingredients>
The lubricating oil composition according to one aspect of the present invention contains, as necessary, other components other than the above-mentioned component (A), component (B), and component (C) as long as the effects of the present invention are not impaired. It may be further contained.
Examples of other components include commonly used additives for lubricating oils, and examples of the additives for lubricating oils include metal-based cleaning agents, abrasion-resistant agents, ashless dispersants, and the above-mentioned component (A). Consists of other viscosity index improvers, extreme pressure agents, flow point lowering agents, antioxidants, defoamers, surfactants, anti-emulsifiers, friction modifiers, oiliness improvers, rust preventives and metal deactivators. One or more species selected from the group can be mentioned.
Further, a compound having a plurality of functions as the above-mentioned additive for lubricating oil (for example, a compound having a function as an abrasion resistant agent and an extreme pressure agent) may be used.
Lubricating oil additives other than these components (A) may be used alone or in combination of two or more.

The content of each of the additives for lubricating oil other than these components (A) can be appropriately adjusted within a range that does not impair the effects of the present invention. In the lubricating oil composition of one aspect of the present invention, when these additives for lubricating oil other than the component (A) are contained, the content of each of the additives for lubricating oil other than the component (A) is set. 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 further preferably 0.01 to 8% by mass.
Further, when the lubricating oil composition of one aspect of the present invention contains these additives for lubricating oil other than the component (A), the total content thereof is the total amount (100% by mass) of the lubricating oil composition. By reference, 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.

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

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

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

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

In one aspect of the present invention, these metal-based cleaning agents may be any of a neutral salt, a basic salt, a hyperbasic salt, and a mixture thereof.
The total base value of the metal-based cleaning agent is preferably 0 to 600 mgKOH / g.
In one aspect of the present invention, when the metal-based cleaning agent is a basic salt or a hyperbasic salt, the total base value of the metal-based cleaning agent is preferably 10 to 600 mgKOH / g, more preferably. It is 20 to 500 mgKOH / g.
In this specification, the term "base value" refers to 7. of JIS K2501: 2003 "Petroleum products and lubricating oil-neutralization value test method". It means the base value by the perchloric acid method measured according to.

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

(Abrasion resistant agent)
Abrasion resistant agents include, for example, sulfur-containing compounds such as zinc dialkyldithiophosphate (ZnDTP), zinc phosphate, disulfides, olefins sulfide, oils and fats sulfide, sulfide esters, thiocarbonates, thiocarbamates, and polysulfides. Phosphoric acid esters, phosphoric acid esters, phosphonic acid esters, and phosphorus-containing compounds such as amine salts or metal salts thereof; thioaroic acid esters, thiophosphate esters, thiophosphonic acid esters, and these. Examples of sulfur and phosphorus-containing abrasion resistant agents such as amine salts or metal salts of the above.
Among these, zinc dialkyldithiophosphate (ZnDTP) is preferable.
When the lubricating oil composition of one aspect of the present invention contains an abrasion resistant agent as another component, the content of the abrasion resistant agent is preferably 0 based on the total amount (100% by mass) of the lubricating oil composition. .05 to 5.0% by mass.
The wear resistant agent may be used alone or in combination of two or more. The suitable total content when two or more kinds are used is also the same as the above-mentioned content.

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

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

In the general formula ^{(i), (ii),} R A, R A1 and ^{R A2} are each independently, weight 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 to 10, preferably an integer of 2 to 5, and more preferably 3 or 4.
x2 is an integer of 0 to 10, preferably an integer of 1 to 4, more preferably 2 or 3.

In one aspect of the present invention, the ratio [B / N] of the boron atom and the nitrogen atom constituting the boron-modified alkenyl succinimide is preferably 0.5 or more, more preferably 0, from the viewpoint of improving cleanliness. It is 6.6 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 ash-free dispersant as another component, the content of the ash-free 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)
The viscosity index improver is a polymer other than the component (A), and is, for example, a PMA-based polymer such as a non-dispersive polyalkyl (meth) acrylate or a dispersed polyalkyl (meth) acrylate; an olefin-based copolymer ( For example, ethylene-propylene copolymers, etc.), OCP-based polymers such as dispersed olefin-based copolymers; styrene-based copolymers (eg, styrene-diene copolymers, styrene-isoprene copolymers, etc.) and the like. (Hereinafter, it is also referred to as "other viscosity index improver").
These other viscosity index improvers preferably have a mass average molecular weight (Mw) of 5,000 or more and 1,500,000 or less, and in the case of PMA type, preferably 20,000 or more, more preferably 100, It is 000 or more, preferably 1,000,000 or less, and more preferably 800,000 or less. Further, in the case of the 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.
The mass average molecular weight (Mw) is measured, for example, by the method described in Examples described later.
The structure of the other viscosity index improver may be a straight chain or a branched chain. In addition, a comb-shaped polymer having a structure having many three-pronged bifurcation points in the main chain having high molecular weight side chains, and a type of branched polymer in which three or more chain polymers are bonded at one point. It may be a polymer having a specific structure such as a star-shaped polymer having a structure.

Further, as the other viscosity index improver, as described above, a polymer having a structure having a large number of three-pronged branch points having linear side chains in the main chain (hereinafter, referred to as “comb-shaped polymer”) is contained. You may. As such a comb-shaped polymer, for example, a polymer having at least a structural unit derived from a macromonomer having a polymerizable functional group such as a metaacryloyl group, an acryloyl group, an ethenyl group, a vinyl ether group, and an allyl group is preferable. Here, the structural unit corresponds to a "linear side chain".
More specifically, various vinyls such as alkyl (meth) acrylates, nitrogen atom-containing systems, halogen element-containing systems, hydroxyl group-containing systems, aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons. A copolymer having a side chain containing a structural unit derived from the macromonomer having a polymerizable functional group is preferably used 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 preferably 100,000 or less, more preferably 50,000 or less, still more preferably. It is 10,000 or less.
Further, 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, and from the viewpoint of improving fuel efficiency. 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, still more preferably 5 or less, and the lower limit is not particularly limited, but is preferably 1.01 or more, more preferably 1. It is 0.05 or more, more preferably 1.10 or more, and even more preferably 1.50 or more.

The monomer constituting the polyalkyl (meth) acrylate is an alkyl (meth) acrylate, preferably 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 million or less, and more preferably 30,000 or more and 500,000 or less. By setting the mass average molecular weight of the polyalkyl (meth) acrylate within this range, it becomes easy to adjust the SSI value to 30 or less.
The mass average molecular weight (Mw) is measured by the method described in Examples described later.

These other viscosity index improvers may be used alone or in combination of two or more.
Further, the other viscosity index improver contains, for example, the above-mentioned polymer other than the component (A) as a resin component, but as described above, it usually has handleability and solubility in the above-mentioned base oil. In consideration, the resin component containing the polymer is often marketed in the state of a solution diluted with a diluent such as mineral oil.
In this case, when another viscosity index improver is used, the content of the viscosity index improver is preferably 0, based on the total amount (100% by mass) of the lubricating oil composition as the content 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, 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 above-mentioned wear resistant agents, 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 known antioxidant that has been conventionally used as an antioxidant for lubricating oils can be appropriately selected and used. For example, an amine-based antioxidant or a phenol-based antioxidant can be used. Examples thereof include antioxidants, molybdenum-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, and the like.
Examples of the amine-based antioxidant include diphenylamine and diphenylamine-based antioxidants such as alkylated diphenylamine having an alkyl group having 3 to 20 carbon atoms; α-naphthylamine, phenyl-α-naphthylamine, and alkyl having 3 to 20 carbon atoms. Examples include naphthylamine-based antioxidants having a group such as substituted phenyl-α-naphthylamine; and the like.
Examples of the phenolic antioxidant include 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, and the like. Monophenolic antioxidants such as isooctyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate and octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate Agents; diphenolic antioxidants such as 4,4'-methylenebis (2,6-di-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol); hinderedphenols Antioxidants; etc.
Examples of the molybdenum-based antioxidant include a molybdenum amine complex formed by reacting molybdenum trioxide and / or molybdic acid with an amine compound.
Examples of the sulfur-based antioxidant include dilauryl-3,3'-thiodipropionate and the like.
Examples of the phosphorus-based antioxidant include phosphite and the like. When a phosphorus-based antioxidant is used, it is preferable that the amount satisfies the suitable phosphorus atom content of the lubricating oil composition described later.
In one aspect of the present invention, these antioxidants can be contained alone or in any combination of two or more, preferably phenolic antioxidants and / or amine-based antioxidants.
In the lubricating oil composition of one aspect of the present invention, when an antioxidant is contained as another component, the content of the antioxidant is preferably 0 based on the total amount (100% by mass) of the lubricating oil composition. .05-7% by mass.

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

(Defoamer)
Examples of the defoaming agent include silicone oils such as dimethylpolysiloxane, fluorosilicone oils and fluoroalkyl ethers. These antifoaming agents may be used alone or in combination of two or more.
When the lubricating oil composition of one aspect of the present invention contains a defoaming agent as another component, the content of the defoaming agent is preferably 0 based on the total amount (100% by mass) of the lubricating oil composition. .05 to 5% by mass.

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

(Friction modifier)
Examples of the friction modifier include molybdenum-based friction modifiers such as molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and amine salts of molybthenoic acid; alkyl groups or alkenyl groups having 6 to 30 carbon atoms are contained in the molecule. Ash-free friction modifiers such as aliphatic amines, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, and aliphatic ethers having at least one; fats and oils, amines, amides, sulfide esters, phosphoric acid esters, phosphite esters. , Phosphate ester amine salt and the like.
When a friction modifier is contained as another component in the lubricating oil composition of one aspect of the present invention, the content of the friction modifier is preferably 0 based on the total amount (100% by mass) of the lubricating oil composition. .05-4% by mass.

(Oil improver)
Examples of the oiliness improver include aliphatic saturated or unsaturated monocarboxylic acids such as stearic acid and oleic acid; polymerized fatty acids such as dimer acid and hydrogenated dimer acid; hydroxy fatty acids such as ricinoleic acid and 12-hydroxystearic acid; lauryl alcohol. Fatty acid saturated or unsaturated monoalcohols such as oleyl alcohol; aliphatic saturated or unsaturated monoamines such as stearylamine and oleylamine; aliphatic saturated or unsaturated monocarboxylic acid amides such as lauric acid amide and oleic acid amide; glycerin, Partial esters of polyvalent alcohols such as sorbitol and aliphatic saturated or unsaturated monocarboxylic acids; and the like.
When the lubricating oil composition of one aspect of the present invention contains an oily improving agent as another component, the content of the oily improving agent is preferably 0 based on the total amount (100% by mass) of the lubricating oil composition. It is 0.01 to 5% by mass.

(anti-rust)
Examples of the rust preventive agent include fatty acids, alkenyl succinic acid half esters, fatty acid sicken, alkyl sulfonates, polyhydric alcohol fatty acid esters, fatty acid amines, oxidized paraffins, alkyl polyoxyethylene ethers and the like.
When the lubricating oil composition of one aspect of the present invention contains a rust preventive as another component, the content of the rust preventive is preferably 0 based on the total amount (100% by mass) of the lubricating oil composition. It is 0.01 to 3% by mass.

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

<Characteristics of lubricating oil composition, etc.>
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, and even more preferably 3 to 6 mm 2 / s.
40 ° C. The kinematic viscosity of the lubricating oil composition is preferably 8 to 20 mm ² / s, more preferably 9~18mm ² / s, more preferably 10~16mm ² / s.
The viscosity index of the lubricating oil composition is preferably 330 or more, more preferably 340 or more, still more preferably 350 or more, still more preferably 360 or more.
Each of the above kinematic viscosities and viscosity indexes is a value measured by the method described in Examples described later.

Further, the PSSI of the lubricating oil composition evaluated by the method described in 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. It is less than 0.0, 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, for example, 0 or more.

[Manufacturing method of lubricating oil composition]
In the method for producing a lubricating oil composition according to an embodiment of the present invention, the following components (A) and (B) are blended with the following component (C).
Component (A): (Meta) acrylate (a) having a linear alkyl group having 4 or less carbon atoms in the side chain which is a monomer (a), and carbon atoms in the side chain which is a monomer (b). Mass 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 a 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
The copolymer (A), wherein 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)
Further, in the production method, if necessary, other components other than the component (A) and the component (B) may be further added to the component (C).
Each of the component (A), the component (B), the component (C) and the other components is the same as that described for the lubricating oil composition, and the preferred embodiments thereof are also the same. Since the obtained lubricating oil composition is also as described above and the preferred embodiment thereof is the same, the description thereof will be omitted.
In the production method, the component (A) and the component (B), and other components added as needed, may be blended with respect to the component (C) in any order and method, and the method is limited. However, as described above, the component (B) may contain the base oil (x) used as the polymerization solvent of the component (A) as it is as the component (B), and has a viscosity containing the component (A). The component (B) added when preparing the index improver composition may be blended with the component (C) as it is, or may be newly blended when preparing the lubricating oil composition.
Then, 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 of the component (A) described above is used as a component. It is preferable to add it to the component (C) as it is as (B).
Further, for example, as described above, when preparing the viscosity index improver composition containing the 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 as the component (B) when preparing the viscosity index improver composition 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 a solvent as it is as the component (B).

[Use of lubricating oil composition]
As described above, the lubricating oil composition according to the embodiment of the present invention has an excellent viscosity index.
Therefore, the lubricating oil composition according to the embodiment of the present invention includes, for example, gear oil (manual transmission oil, differential oil, etc.), automatic transmission oil (automatic transmission oil, etc.), stepless transmission oil (belt CVT oil, etc.). Toroidal CVT oil, etc.), power steering oil, shock absorber oil, electric motor oil, and other drive system oils; internal combustion engine (engine) oils for gasoline engines, diesel engines, and gas engines; hydraulic hydraulic oils; Lubricating oil that can be suitably used for various purposes such as turbine oil; compressor oil; fluid bearing oil; rolling bearing oil; etc. Can be suitably used as.
Among these, the lubricating oil composition according to the embodiment of the present invention is more suitable as a lubricating oil composition used in a wider temperature range because of its characteristic of having a good viscosity index. Gears, automatic transmissions, stepless transmissions, shock absorbers, power steering, electric motors installed in transportation equipment such as automobiles such as two-wheeled vehicles and four-wheeled vehicles, trains, ships, and airplanes, generators, and various machine tools. Lubricating oil for drive system equipment such as motors; Lubricating oil for internal combustion engines such as gasoline engines, diesel engines, gas engines; Used for hydraulic machinery such as construction machinery and hydraulic operating equipment such as hydraulic systems such as various hydraulic equipment It can be more preferably used as a hydraulic hydraulic oil.

[Lubrication method using lubricating oil composition]
As described in the above-mentioned applications, as a lubrication method using the lubricating oil composition according to the embodiment of the present invention, the lubricating oil composition is preferably filled in the apparatus used in each of the above-mentioned applications. , A method of lubricating between each part related to each device can be mentioned.
Then, as a lubrication method using the lubricating oil composition according to the embodiment of the present invention, more preferably, the lubricating oil composition is used, for example, an automobile such as a two-wheeled vehicle or a four-wheeled vehicle, a train, a ship, an airplane, or the like. Drive system equipment such as gears, automatic transmissions, stepless transmissions, shock absorbers, power steering, electric motors, etc. installed in transportation equipment, generators, and various machine tools; gasoline engines, diesel engines, gas engines, etc. Internal engine; hydraulic hydraulic oil used for hydraulic machinery such as construction machinery and hydraulic systems such as various hydraulic equipment; A method of lubricating between each part related to the engine can be mentioned.

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

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

[Flood-operated equipment using lubricating oil composition]
Another embodiment of the present invention includes a hydraulically actuated device using the lubricating oil composition, and the hydraulically actuated device includes, for example, a hydraulic machine such as a construction machine or a flood control device of various hydraulic facilities. The system etc. can be mentioned.

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

In the present specification, each component used in each Example and each Comparative Example, and each physical property of the copolymer, the viscosity index improver composition, and the lubricating oil composition obtained in each Example and each Comparative Example. The measurement of was obtained according to the procedure shown below.
<Dynamic 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 in accordance with 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" and "2414 Differential Refractometer (RI) Detector" manufactured by Waters, one column "TSKgradecollect SuperHZ-L" manufactured by Tosoh, and two "TSKSuperMultipore HZ-M". The book was attached in this order from the upstream side, measured under the conditions of measurement temperature: 40 ° C., mobile phase: tetrahydrofuran, flow velocity: 0.35 ml / min, and sample concentration 1.0 mg / ml, and determined by standard polystyrene conversion.

<Appearance of Viscosity Index Improver Composition and Lubricating Oil Composition>
The appearances of the viscosity index improver composition and the lubricating oil composition were collected in screw vials having a capacity of 100 mL and visually observed.

<PSSI of lubricating oil composition>
The PSSIs of the lubricating oil compositions obtained in Examples 1 to 14 and Comparative Examples 1 to 8 indicate the decrease in viscosity of the lubricating oil composition derived from the copolymer due to shearing as a percentage, and ASTM D6022-06. It was calculated by the following formula specified in (2012).

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

<Evaluation of thermal stability of lubricating oil composition>
Hot tube tests were 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., the lubricating oil compositions of Examples 15 to 19 and Comparative Example 8 were placed in the glass tube at 0.3 mL / hour with air. Was continuously run at 10 mL / min for 16 hours. After that, the following evaluation was performed.
(1) Hot tube test score After the above hot tube test, the lacquer adhering to the glass tube was compared with the color sample, and a score of 11 was given as 10 points for colorless and transparent and 0 points for black. .. The higher the transparency, the higher the score, indicating that the cleanliness and stability at high temperatures are high.
(2) Deposit amount 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. The smaller the deposit amount, the higher the cleanliness and stability at high temperature.

[Polymerization of copolymers and preparation of viscosity index improver composition and lubricating oil composition]
In the following description, and the abbreviations of each component shown 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, a mixed triester of trimethylolpropane and 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": 3 to pentamer of polyvinyl ether (PVE) (100 ° C. kinematic viscosity = 2.3 mm ² / s, SP value = 8.80 (cal / cm ³ ) ^1/2 )
<Amids>
"AM-1": N, N-di (2-ethylhexyl) -2-ethylhexaneamide (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]
In a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, and a nitrogen blowing tube, ES-1 as a base oil (x) was used as a polymerization solvent, and mineral oil was added in the amounts shown in Table 1 below. I prepared it.
In another glass beaker, each of the monomers shown in Table 1 below was charged as a monomer in the blending amount shown in Table 1 below, and ADVN was set to 0 with respect to 100 parts by mass of the total amount of the monomers. A monomer-containing solution was prepared by charging 5.5 parts by mass, 0.2 parts by mass of AMBN, and 0.4 parts by mass of DM, and mixing and dissolving them at room temperature (23 ° C.).
The obtained monomer-containing solution was charged into the dropping funnel of the reaction vessel, nitrogen was replaced in the gas phase portion in the reaction vessel, and then the monomer-containing solution in the dropping funnel was placed in the dropping funnel at 85 ° C. for 1 hour in a closed state. The whole amount was dropped at a constant rate. From the end of the dropping, until the conversion of all the blended monomers reaches 98%, the mixture is aged at 85 ° C., then the temperature is raised to 120 to 130 ° C., and the temperature is reduced under reduced pressure (0.027). The unreacted monomer was removed at ~ 0.040 MPa) over 30 minutes to obtain a viscosity index improver composition (VII-1) containing the 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).
Each property of the obtained copolymer (A1), viscosity index improver composition (VII-1), and lubricating oil composition (L-1) was evaluated by the above-mentioned method. The obtained results are shown in Table 1 below.

[Examples 2 and 3]
The copolymers (A2) and (A3) and the viscosity index improver composition (VII-) are the same as in Example 1 except that the monomers are blended so as to have the compositions shown in Table 1 below. 2) and (VII-3), and lubricating oil compositions (L-2) and (L-3) were prepared, respectively.
Each property of each obtained copolymer, each viscosity index improver composition, and each lubricating oil composition was evaluated by the above-mentioned method. The obtained results are shown in Table 1 below.

[Examples 4 to 8]
The copolymer (A4) was used 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. ~ (A8), viscosity index improver compositions (VII-4) to (VII-8), and lubricating oil compositions (L-4) to (L-8) were prepared, respectively.
Each property of each obtained copolymer, each viscosity index improver composition, and each lubricating oil composition was evaluated by the above-mentioned method. The obtained results are shown in Table 1 below.

[Example 9]
The composition of the copolymer (A9) and the viscosity index improver is the same as in Example 1 except that the mixed base oil in which the base oil (x) and the mineral oil are blended in the composition shown in Table 1 below is used as the polymerization solvent. A product (VII-9) and a lubricating oil composition (L-9) were prepared.
The properties of the obtained copolymer (A9), viscosity index improver composition (VII-9), and lubricating oil composition (L-9) were evaluated by the above-mentioned methods. The obtained results are shown in Table 1 below.

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

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

[Examples 12 to 14]
The blending amount of the copolymer (A1), ES-1 which is the base oil (x) shown in Table 2 below, and mineral oil in the obtained lubricating oil composition is set to the blending amount shown in Table 2 below. Lubricating oil compositions (L-12) to (L-14) are 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 property of the obtained lubricating oil compositions (L-12) to (L-14) was evaluated by the above-mentioned method. The obtained results are shown in Table 2 below.

[Comparative Examples 1 and 2]
A copolymer (in the same manner as in Example 1), except that the base oil (x) was not used as the polymerization solvent, mineral oil was used, and the monomers were blended so as to have the composition shown in Table 3 below. X1) and (X2), viscosity index improver compositions (Y-1) and (Y-2), and lubricating oil compositions (CL-1) and (CL-2) were prepared, respectively.
Each property of each obtained copolymer, each viscosity index improver composition, and each lubricating oil composition was evaluated by the above-mentioned method. The obtained results are shown in Table 3 below.

[Comparative Example 3]
A copolymer (in the same manner as in Example 1), except that a mineral oil was used instead of the base oil (x) as the polymerization solvent and a monomer was blended so as to have the composition shown in Table 3 below. X3) and a viscosity index improver composition (Y-3) were prepared.
The obtained viscosity index improver composition (Y-3), base oil (x) ES-1, and mineral oil are used as the copolymer (X3), ES-1, and mineral oil in the obtained lubricating oil composition. The lubricating oil composition (CL-3) was prepared by blending so that the blending amount of the above was the blending amount shown in Table 3 below.
Each property of the obtained copolymer (X3), viscosity index improver composition (Y-3), and lubricating oil composition (CL-3) was evaluated by the above-mentioned method. The obtained results are shown in Table 3 below.

[Comparative Example 4]
Using the base oil (x) shown in Table 3 below, a monomer was blended so as to have the composition shown in Table 3 below, and the copolymer (X4) and the viscosity index were obtained in the same manner as in Example 1. An improver composition (Y-4) and a lubricating oil composition (CL-4) were prepared.
The properties of the obtained copolymer (X4), viscosity index improver composition (Y-4), and lubricating oil composition (CL-4) were evaluated by the above-mentioned methods. The obtained results are shown in Table 3 below.

[Comparative Example 5]
Except for the fact that the base oil (x) shown in Table 3 below was used, the monomer was blended so as to have the composition shown in Table 3 below, and the blending 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.
Each property of the obtained copolymer (X5) and the viscosity index improver composition (Y-5) was evaluated by the above-mentioned method. The obtained results are shown in Table 3 below.
Next, when the obtained viscosity index improver composition (Y-5) was blended in the mineral oil, a gradually cloudy gel was formed, and the lubricating oil composition (CL-8) could be prepared. There wasn't. Therefore, except for the appearance, each property of the lubricating oil composition (CL-5) could not be evaluated.

[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 obtained lubricating oil composition are the blending amounts shown in Table 3 below. The obtained viscosity index improver composition (Y-1), ES-1, and mineral oil were blended to prepare a lubricating oil composition (CL-6).
Each property of the obtained lubricating oil composition (CL-6) was evaluated by the above-mentioned method. The obtained results are shown in Table 3 below.

[Comparative Example 7]
It was 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 obtained lubricating oil composition were the blending amounts shown in Table 3 below. A viscosity index improver composition (VII-1) and ES-1 were blended to prepare a lubricating oil composition (CL-7) containing no mineral oil.
Each property of the obtained lubricating oil composition (CL-7) was evaluated by the above-mentioned method. The obtained results are shown in Table 3 below.

[Comparative Example 8]
The copolymer (X6), the viscosity index improver composition (Y-6), and the viscosity index improver composition (Y-6), and the same as in Example 10 except that the monomers were blended so as to have the compositions shown in Table 3 below. Lubricating oil compositions (CL-8) were prepared respectively.
Each property of the obtained copolymer, viscosity index improver composition, and lubricating oil composition was evaluated by the above-mentioned method. The obtained results are shown in Table 3 below.

From the results shown in Tables 1 to 3 above, the following can be seen.
As in Comparative Example 1, a lubricating oil composition obtained by dissolving a viscosity index improver composition (Y-1) containing a copolymer (X1) polymerized using mineral oil as a polymerization solvent in mineral oil. It can be seen that (CL-1) is inferior in viscosity index to the lubricating oil composition (L-1) obtained in Example 1. It is considered that this is due to the fact that the copolymer (X1) has been separated into white turbidity in the mineral oil, as shown by the result of the appearance.
The monomer composition used in Example 1 and Comparative Example 1 is the same, and the difference is that in Example 1, a copolymer polymerized using a hetero atom-containing base oil (x) as a polymerization solvent is used. The point is that the viscosity index improver composition contained therein 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, as in Comparative Example 1. It 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 composition obtained in each example.
Further, the lubricating oil composition (CL-3) obtained in Comparative Example 3 is a viscosity index improver composition containing a copolymer (X3) polymerized using mineral oil as a polymerization solvent, as in Comparative Example 1. A lubricating oil composition obtained by dissolving (Y-3) in mineral oil and a hetero atom-containing base oil (x), but the viscosity index is inferior to that of the lubricating oil compositions obtained in each example. You can see that.
Further, also in the lubricating oil composition (CL-4) obtained in Comparative Example 4, the composition of the monomer in the obtained copolymer (X4) is composed of the content of the monomer (a). It is probable that the viscosity index could not be sufficiently improved because the requirements of 50% by mass or more and 65% by mass or less were not satisfied based on 100% by mass of the total amount of the polymer.
Further, the composition of the monomer in the copolymer (X5) obtained in Comparative Example 5 is 37% by mass or more based on the content of the monomer (b) being 100% by mass based on the total amount of the constituent monomers. However, it 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 the polymerization solvent is dissolved in the mineral oil, it contains a hetero atom. In the lubricating oil composition (CL-6) obtained by blending the base oil (x), the copolymer (X1) is separated into white turbidity in the mineral oil, as shown in the appearance results, and the viscosity index is also shown. Could not be improved sufficiently.
Further, 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 used as a heteroatom-containing base oil (x) instead of a mineral oil. The lubricating oil composition (CL-7) obtained by blending with the above, but in the case of the lubricating oil composition (CL-7) containing only the hetero atom-containing base oil (x) as the lubricating oil base oil, it is carried out. It was found that the viscosity index was significantly reduced as compared with the lubricating oil composition (L-1) obtained in Example 1.
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 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). The lubricating oil composition (L-10) obtained in Example 10 It can be seen that the viscosity index is inferior to that of. This is because the composition of the monomer in the copolymer (X6) obtained in Comparative Example 8 is 50% by mass based on the content of the monomer (a) being 100% by mass of the total amount of the constituent monomers. Since it is less than, it is probable that the viscosity index could not be sufficiently improved.
On the other hand, as in Examples 1 to 14, a viscosity index improver containing copolymers (A1) to (A11) polymerized using a polymerization solvent containing a hetero atom-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 a good viscosity index.

Further, the copolymers (A1), (A4), (A6), (A8) and (A10) obtained in Examples 1, 4, 6, 8 and 10, respectively, and Comparative Example 3 were obtained. 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) had the composition shown in Table 4 below. When preparing the lubricating oil compositions shown in Table 4 below, the viscosity index improver compositions (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 prepared by blending them with mineral oil, respectively.
The lubricating oil compositions shown in Table 4 below were evaluated for thermal stability using the method described above.
The obtained results 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 deposit amount as compared with the lubricating oil compositions obtained in Comparative Example 9. Was confirmed.
Therefore, it was confirmed that the lubricating oil composition according to the embodiment of the present invention is also excellent in thermal stability.

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

Claims (14)

Component (A): (Meta) acrylate (a) having a linear alkyl group having 4 or less carbon atoms in the side chain which is a monomer (a), and carbon atoms in the side chain which is a monomer (b). Mass 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 a 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
The copolymer (A), wherein 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 the component (C) is 55% by mass or more based on 100% by mass of the total amount of the lubricating oil composition. The lubricating oil composition according to claim 1, wherein the heteroatom-containing base oil (x) is at least one 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 the component (C) is a hydrocarbon-based base oil. 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. The lubricating oil composition according to any one of claims 1 to 5, wherein the 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 the 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 are independent carbon atoms. .n indicating the number 2-18 alkyl groups may, when the .n is 2 or more represents an integer of 0 to 20, ^{R 2} existing in plural numbers 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. The lubricating oil composition according to item 1. Any of claims 1 to 8, wherein the solubility parameter (SP value) of the component (A) is 9.20 (cal / cm ³ ) ^1/2 or more and 9.60 (cal / cm ³ ) ^{1/2 or less.} The lubricating oil composition according to item 1. The lubricating oil composition according to any one of claims 1 to 9, wherein the mass average molecular weight (Mw) of the component (A) is 200,000 or less. The item according to any one of claims 1 to 10, wherein the content of the 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. Lubricating oil composition. The lubricating oil composition according to any one of claims 1 to 11, wherein the permanent shear stability index (PSSI) measured by an ultrasonic test according to JASO M 347-95 is less than 5.0. The following component (A) used in combination with a base oil (y) other than the heteroatom-containing base oil (x).
Component (A): (Meta) acrylate (a) having a linear alkyl group having 4 or less carbon atoms in the side chain which is a monomer (a), and carbon atoms in the side chain which is a monomer (b). Mass 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 a 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
The 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 used by blending with a base oil (y) other than the heteroatom-containing base oil (x).
Component (A): (Meta) acrylate (a) having a linear alkyl group having 4 or less carbon atoms in the side chain which is a monomer (a), and carbon atoms in the side chain which is a monomer (b). Mass 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 a 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
The 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.