JP2022104460A - Lubricating oil additive composition and lubricating oil composition - Google Patents

Abstract

To provide: a lubricating oil additive composition that is suitable as a load-withstanding additive and that is excellent in both of abrasion resistance and extreme pressure properties; and a lubricating oil composition that contains the lubricating oil additive composition.SOLUTION: The present invention discloses a lubricating oil additive composition containing a boron poly(meth)acrylate-based copolymer (X) that includes a structural unit (a) derived from a specific alkyl(meth)acrylate (A), a structural unit (b) derived from a specific hydroxyl group-containing (meth)acrylate (B), and a structural unit (c) derived from a borate ester compound (C) of the hydroxyl group-containing (meth)acrylate (B), with the structural unit (c) having a side chain with one or more hydroxyl groups bound to a boron atom.SELECTED DRAWING: None

Description

The present invention relates to an additive composition for lubricating oil and a lubricating oil composition containing the additive composition for lubricating oil.

Various additives for lubricating oil are blended in the lubricating oil for the purpose of imparting properties and performance required as the lubricating oil, or supplementing and enhancing the lubricating oil.
As one of the typical additives for lubricating oil, there is a load-bearing additive that imparts wear resistance and extreme pressure resistance to the lubricating oil. As the load-bearing additive, for example, phosphorus-based compounds such as phosphoric acid esters, subphosphate esters, and phosphonic acid esters, and sulfur-phosphorus compounds such as thiophosphate esters are widely used.

However, phosphorus and sulfur are highly corrosive elements. Therefore, in recent years, various studies have been made on polymer compounds as load-bearing additives to replace phosphorus compounds and sulfur-phosphorus compounds (see Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 2013-124266 Japanese Unexamined Patent Publication No. 6-65588

However, polymer compounds, which are being studied as load-bearing additives, are still inadequate in achieving both wear resistance and extreme pressure resistance.

Therefore, the present invention provides a lubricating oil additive composition which is suitable as a load-bearing additive and has excellent wear resistance and extreme pressure resistance, and a lubricating oil composition containing the lubricating oil additive composition. The challenge is to provide.

The present inventors have conducted diligent studies in order to solve the above problems. As a result, they have found that a borated poly (meth) acrylate-based copolymer having a specific structural unit and a specific side chain can solve the above-mentioned problems, and have completed the present invention.

［上記一般式（ａ－１）中、Ｒ^ａ１は、水素原子又はメチル基である。Ｒ^ａ２は、炭素数８～２０のアルキル基を示す。］

［上記一般式（ｂ－１）中、Ｒ^ｂ１は、水素原子又はメチル基である。Ｒ^ｂ２は、炭素数２～４のアルキレン基を示す。ｍ１は、１～１０の整数を示す。ｍ１が２以上の整数の場合の複数のＲ^ｂ２は、同一であっても異なっていてもよい。］
［２］ 上記［１］に記載の潤滑油用添加剤組成物を、耐荷重添加剤として使用する、使用方法。
［３］ 上記［１］に記載の潤滑油用添加剤組成物と、潤滑油基油と、を含有する、潤滑油組成物。
［４］ 下記一般式（ａ－１）で表されるアルキル（メタ）アクリレート（Ａ）と、下記一般式（ｂ－１）で表される水酸基含有（メタ）アクリレート（Ｂ）とを、無機ホウ酸系化合物（ｙ）の存在下で重合させて、ホウ素化ポリ（メタ）アクリレート系共重合体（Ｘ）を製造する工程（Ｓ）を含む、潤滑油用添加剤組成物の製造方法。

［上記一般式（ａ－１）中、Ｒ^ａ１は、水素原子又はメチル基である。Ｒ^ａ２は、炭素数８～２０のアルキル基を示す。］

［上記一般式（ｂ－１）中、Ｒ^ｂ１は、水素原子又はメチル基である。Ｒ^ｂ２は、炭素数２～４のアルキレン基を示す。ｍ１は、１～１０の整数を示す。ｍ１が２以上の整数の場合の複数のＲ^ｂ２は、同一であっても異なっていてもよい。］ That is, the present invention relates to the following [1] to [4].
[1] A structural unit (a) derived from the alkyl (meth) acrylate (A) represented by the following general formula (a-1) and a hydroxyl group-containing (meth) represented by the following general formula (b-1). The structural unit (b) derived from the acrylate (B) and the structural unit (c) derived from the boron esterified product (C) of the hydroxyl group-containing (meth) acrylate (B) are included in the structural unit (c). Is an additive composition for a lubricating oil containing a boronized poly (meth) acrylate-based copolymer (X) having a side chain in which one or more hydroxyl groups are bonded to a boron atom.

[In the above general formula (a-1), ^Ra1 is a hydrogen atom or a methyl group. R ^a2 represents an alkyl group having 8 to 20 carbon atoms. ]

[In the above general formula (b-1), R ^b1 is a hydrogen atom or a methyl group. R ^b2 represents an alkylene group having 2 to 4 carbon atoms. m1 represents an integer from 1 to 10. When m1 is an integer of 2 or more, the plurality of R ^b2s may be the same or different. ]
[2] A method of use in which the additive composition for lubricating oil according to the above [1] is used as a load-bearing additive.
[3] A lubricating oil composition containing the lubricating oil additive composition according to the above [1] and a lubricating oil base oil.
[4] The alkyl (meth) acrylate (A) represented by the following general formula (a-1) and the hydroxyl group-containing (meth) acrylate (B) represented by the following general formula (b-1) are inorganic. A method for producing an additive composition for a lubricating oil, which comprises a step (S) of producing a borated poly (meth) acrylate-based copolymer (X) by polymerizing in the presence of a boric acid-based compound (y).

[In the above general formula (a-1), ^Ra1 is a hydrogen atom or a methyl group. R ^a2 represents an alkyl group having 8 to 20 carbon atoms. ]

[In the above general formula (b-1), R ^b1 is a hydrogen atom or a methyl group. R ^b2 represents an alkylene group having 2 to 4 carbon atoms. m1 represents an integer from 1 to 10. When m1 is an integer of 2 or more, the plurality of R ^b2s may be the same or different. ]

According to the present invention, an additive composition for a lubricating oil, which is suitable as a load-bearing additive and has excellent wear resistance and extreme pressure resistance, and a lubricating oil composition containing the additive composition for the lubricating oil are provided. It will be possible to provide.

The upper and lower limits of the numerical range described herein can be combined arbitrarily. For example, when "AB" and "C to D" are described as numerical ranges, the numerical ranges of "A to D" and "C to B" are also included in the scope of the present invention.
Further, the numerical range "lower limit value to upper limit value" described in the present specification means that it is equal to or more than the lower limit value and equal to or less than the upper limit value unless otherwise specified.
Further, in the present specification, the numerical value of the embodiment is a numerical value that can be used as an upper limit value or a lower limit value.
In addition, in this specification, "(meth) acrylate" means acrylate or methacrylate, and has the same meaning for other similar terms.

［上記一般式（ａ－１）中、Ｒ^ａ１は、水素原子又はメチル基である。Ｒ^ａ２は、炭素数８～２０のアルキル基を示す。］

［上記一般式（ｂ－１）中、Ｒ^ｂ１は、水素原子又はメチル基である。Ｒ^ｂ２は、炭素数２～４のアルキレン基を示す。ｍ１は、１～１０の整数を示す。ｍ１が２以上の整数の場合の複数のＲ^ｂ２は、同一であっても異なっていてもよい。］ [Aspects of additive composition for lubricating oil]
The additive composition for lubricating oil of the present embodiment has a structural unit (a) derived from the alkyl (meth) acrylate (A) represented by the following general formula (a-1) and the following general formula (b-1). ), A structural unit (b) derived from the hydroxyl group-containing (meth) acrylate (B), and a structural unit (c) derived from the boron-containing (meth) acrylate (B) borate esterified product (C). The structural unit (c) contains a boronized poly (meth) acrylate-based copolymer (X) having a side chain in which one or more hydroxyl groups are bonded to a boron atom.

[In the above general formula (a-1), ^Ra1 is a hydrogen atom or a methyl group. R ^a2 represents an alkyl group having 8 to 20 carbon atoms. ]

[In the above general formula (b-1), R ^b1 is a hydrogen atom or a methyl group. R ^b2 represents an alkylene group having 2 to 4 carbon atoms. m1 represents an integer from 1 to 10. When m1 is an integer of 2 or more, the plurality of R ^b2s may be the same or different. ]

The present inventors have conducted diligent studies in order to solve the above problems. As a result, the structural unit (a) derived from the alkyl (meth) acrylate (A) represented by the general formula (a-1) and the hydroxyl group-containing (meth) represented by the general formula (b-1). Boroned poly (meth) acrylate system containing a structural unit (b) derived from the acrylate (B) and a structural unit (c) derived from the borate esterified product (C) of the hydroxyl group-containing (meth) acrylate (B). We found that the copolymer (X) is excellent in both wear resistance and extreme pressure resistance, and used the boronized poly (meth) acrylate-based copolymer (X) as an additive for lubricating oil (particularly as a load-bearing additive). ) It has been found that it can be suitably used.
The reason why the boronized poly (meth) acrylate-based polymer (X) is excellent in abrasion resistance and extreme pressure resistance is that oil solubility is ensured by containing the above-mentioned structural unit (a), and the above-mentioned structural unit (b). It is presumed that it is a multi-point adsorption type polymer by containing), and that it contains boron by containing the above-mentioned structural unit (c) and has a side chain in which one or more hydroxyl groups are bonded to a boron atom. Will be done.
According to the study by the present inventors, it is difficult for the non-borylated poly (meth) acrylate-based copolymer composed of the above-mentioned structural units (a) and (b) to have both wear resistance and extreme pressure resistance. It has been confirmed that. Further, even if the boronized poly (meth) acrylate-based copolymer does not have a side chain in which one or more hydroxyl groups are bonded to a boron atom, both wear resistance and extreme pressure resistance can be achieved. It has been confirmed to be difficult.

In the following description, the boric acid esterified product (C) of the alkyl (meth) acrylate (A), the hydroxyl group-containing (meth) acrylate (B), and the hydroxyl group-containing (meth) acrylate (B) will be referred to as “monomers (A)”, respectively. ) ”,“ Monomer (B) ”, and“ Monomer (C) ”.

In the present embodiment, the boronized poly (meth) acrylate-based copolymer (X) is a structural unit (a) derived from the monomer (A), a structural unit (b) derived from the monomer (B), and a monomer (C). It may be composed of only the constituent unit (c) from which it is derived, but it may contain other constituent units other than the constituent units (a), (b), and (c) as long as the effects of the present invention are not impaired. You may.
In the present embodiment, the total content of the structural units (a), (b), and (c) in the boring poly (meth) acrylate-based copolymer (X) is the same as that of the boronized poly (meth) acrylate-based copolymer. Based on the total structural unit of the polymer (X), it is preferably 70 mol% to 100 mol%, more preferably 80 mol% to 100 mol%, and further preferably 90 mol% to 100 mol%.

Hereinafter, the boric acid esterified product (C) of the alkyl (meth) acrylate (A), the hydroxyl group-containing (meth) acrylate (B), and the hydroxyl group-containing (meth) acrylate (B) will be described.

<Alkyl (meth) acrylate (A)>
The alkyl (meth) acrylate (A) used in this embodiment is represented by the following general formula (a-1).

The structural unit (a) derived from the alkyl (meth) acrylate (A) mainly has a function of exhibiting oil solubility in the borated poly (meth) acrylate-based copolymer (X).
The alkyl (meth) acrylate (A) may be used alone or in combination of two or more. Therefore, the boried poly (meth) acrylate-based copolymer (X) may contain one type of the structural unit (a) derived from the alkyl (meth) acrylate (A) alone, or may contain two or more types. You may.

In the above general formula (a-1), ^Ra1 is a hydrogen atom or a methyl group. That is, the alkyl (meth) acrylate (A) has an acryloyl group or a methacryloyl group as a polymerizable functional group.
It is difficult to obtain a monomer in which ^Ra1 is a substituent other than a hydrogen atom and a methyl group, and since the monomer has low reactivity, it is also difficult to polymerize them.
Here, in the present embodiment, from the viewpoint of facilitating the adjustment of the molecular weight of the borated poly (meth) acrylate-based copolymer (X), ^Ra1 is preferably a hydrogen atom. That is, the alkyl (meth) acrylate (A) preferably has an acryloyl group as a polymerizable functional group.

In the above general formula (a-1), ^Ra2 represents an alkyl group having 8 to 20 carbon atoms.
When the number of carbon atoms of the alkyl group is less than 8, and when the number of carbon atoms of the alkyl group is more than 20, it becomes difficult to secure the oil solubility of the boronized poly (meth) acrylate-based copolymer (X). ..

Examples of the alkyl group having 8 to 20 carbon atoms that can be selected as R ^a2 include an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group and a heptadecyl group. Examples thereof include an octadecyl group, a nonadecyl group, and an icosyl group. These may be linear or branched.

Here, from the viewpoint of making it easier to secure the oil solubility of the boronized poly (meth) acrylate-based copolymer (X), the number of carbon atoms of the alkyl group is preferably 10 to 18, more preferably 10 to 16, More preferably, it is 10 to 14.

<Hydroxy group-containing (meth) acrylate (B)>
The hydroxyl group-containing (meth) acrylate (B) used in this embodiment is represented by the following general formula (b-1).

The structural unit (b) derived from the hydroxyl group-containing (meth) acrylate (B) has a function of converting the borated poly (meth) acrylate-based copolymer (X) into a multi-point adsorption type polymer, and has wear resistance. It is presumed to contribute to the improvement of sex and extreme pressure.
As the hydroxyl group-containing (meth) acrylate (B), one type may be used alone, or two or more types may be used in combination. Therefore, the boried poly (meth) acrylate-based copolymer (X) may contain one type of the structural unit (b) derived from the hydroxyl group-containing (meth) acrylate (B) alone, or may contain two or more types. You may be.

In the above general formula (b-1), R ^b1 is a hydrogen atom or a methyl group. That is, the hydroxyl group-containing (meth) acrylate (B) has an acryloyl group or a methacryloyl group as a polymerizable functional group.
It is difficult to obtain a monomer in which R ^b1 is a substituent other than a hydrogen atom and a methyl group, and since the monomer has low reactivity, it is also difficult to polymerize them.
Here, in the present embodiment, R ^b1 is preferably a hydrogen atom from the viewpoint of facilitating the adjustment of the molecular weight of the borated poly (meth) acrylate-based copolymer (X). That is, the hydroxyl group-containing (meth) acrylate (B) preferably has an acryloyl group as a polymerizable functional group.

In the above general formula (b-1), R ^b2 represents an alkylene group having 2 to 4 carbon atoms.
When the number of carbon atoms of the alkylene group is 1, the polarity becomes high and the oil solubility decreases.
Further, when the alkylene group has 5 or more carbon atoms, the oil solubility is excessively improved and the adsorptivity to the metal is lowered.
Here, the carbon number of the alkylene group is preferably 2 to 3, and more preferably 2 from the viewpoint of facilitating ensuring appropriate oil solubility and appropriate adsorptivity to a metal.

m1 represents an integer from 1 to 10. When m1 is an integer of 2 or more, the plurality of R ^b2s may be the same or different. Further, the bonding mode between the portions represented by − (OR ^b2 ) _m1 may be a random bond or a block bond, but from the viewpoint of easiness of polymerization, a random bond is preferable.
When m1 is 0, the hydroxyl group-containing (meth) acrylate (B) becomes a carboxylic acid, so that the oil solubility is lowered.
Further, when m1 is an integer of 11 or more, the polarity becomes high due to the influence of the − (OR ^b2 ) − portion, and the oil solubility decreases.
Here, from the viewpoint of facilitating ensuring appropriate oil solubility, m1 is preferably 1 to 6, more preferably 1 to 4, still more preferably 1 to 2, and even more preferably 1.

<Boric acid esterified product (C) of hydroxyl group-containing (meth) acrylate (B)>
The boric acid esterified product (C) of the hydroxyl group-containing (meth) acrylate (B) used in the present embodiment is obtained by reacting, for example, the hydroxyl group-containing (meth) acrylate (B) with the inorganic boric acid-based compound (y). Can be synthesized. The structural unit (c) derived from the boric acid esterified product (C) of the hydroxyl group-containing (meth) acrylate (B) is a poly (meth) acrylate-based copolymer containing the above structural units (a) and (b). It can also be produced by reacting (x) with the inorganic boric acid-based compound (y) and boring a part of the structural unit (b).

Examples of the inorganic boric acid compound (y) include compounds represented by the following general formula (y-1).
(R ^y1 O) _n -B- (OH) _3-n (y-1)
[In the above general formula (y-1), ^Ry1 is an alkyl group having 1 or 2 carbon atoms. n is 0 or 1. ]
Specific examples of the inorganic boric acid compound (y) include orthoboric acid, monomethyl borate, monoethyl borate and the like. Among these, orthoboric acid is preferable from the viewpoint of making it easier to exert the effect of the present invention.
When n = 2, a side chain in which one or more hydroxyl groups are bonded to a boron atom is not formed in the boric acid esterified product (C) of the hydroxyl group-containing (meth) acrylate (B). In other words, a side chain in which one or more hydroxyl groups are bonded to a boron atom is not formed in the structural unit (c). Therefore, it becomes impossible to obtain an additive composition for a lubricating oil having excellent wear resistance and extreme pressure resistance.

<Requirements (α)>
The boronized poly (meth) acrylate-based copolymer (X) of the present embodiment must satisfy the requirement (α) from the viewpoint of facilitating the effect of the present invention and the solubility in the base oil. preferable. That is, the content ratio [(a) / (b)] of the structural unit (a) and the structural unit (b) is preferably 20/80 to 80/20 in terms of molar ratio.
Further, from the viewpoint of further improving the solubility of the boronized poly (meth) acrylate-based copolymer (X) in the base oil, [(a) / (b)] is more preferably 40/60. Above, more preferably 50/50 or more.
Further, from the viewpoint of further facilitating the effect of the present invention, [(a) / (b)] is more preferably 75/25 or less, still more preferably 70/30 or less.
The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is more preferably 40/60 to 75/25, and even more preferably 50/50 to 70/30.

<Requirements (β)>
The boronized poly (meth) acrylate-based copolymer (X) of the present embodiment must satisfy the requirement (β) from the viewpoint of facilitating the effect of the present invention and the solubility in the base oil. preferable. That is, the boron content of the boronized poly (meth) acrylate-based copolymer (X) is 0.10% by mass to 1.70 based on the total amount of the boronized poly (meth) acrylate-based copolymer (X). It is preferably by mass%. Further, from the viewpoint of further improving the solubility of the boronized poly (meth) acrylate-based copolymer (X) in the base oil, the boronized poly (meth) acrylate-based copolymer weight. The amount of boron in the coalescence (X) is more preferably 1.60% by mass or less, still more preferably 1.40% by mass or less, based on the total amount of the boronized poly (meth) acrylate-based copolymer (X). More preferably, it is 1.20% by mass or less.
Further, from the viewpoint of further facilitating the effect of the present invention, the boron content of the boronized poly (meth) acrylate-based copolymer (X) is the same as that of the boronized poly (meth) acrylate-based copolymer (X). Based on the total amount, it is more preferably 0.20% by mass or more, further preferably 0.60% by mass or more, and further preferably 0.80% by mass or more.
The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is more preferably 0.20% by mass to 1.60% by mass, further preferably 0.60% by mass to 1.40% by mass, and even more preferably 0.80% by mass to 1.20% by mass. Is.
The boron content of the boronized poly (meth) acrylate-based copolymer (X) is such that a predetermined amount of the boronized poly (meth) acrylate-based copolymer (X) is dissolved in an organic solvent (for example, a lubricating oil base oil). After that, based on the result of measuring the amount of boron in the organic solvent in accordance with JIS-5S-38-03 and the amount of the boronized poly (meth) acrylate-based copolymer (X) dissolved in the organic solvent. Can be calculated.

<Other monomers>
The boronized poly (meth) acrylate-based copolymer (X) is a monomer other than the above-mentioned structural units (a), (b), and (c) to the extent that the effect of the present invention is not impaired. It may contain a constituent unit of origin. Examples of the other monomer include functional group-containing monomers other than the monomers (A), (B), and (C). Examples of the other functional group-containing monomer include functional group-containing (meth) acrylates other than the monomers (A), (B), and (C).
However, from the viewpoint of making it easier to exert the effect of the present invention, the poly (meth) acrylate-based copolymer (X) has a total content of the above-mentioned structural units (a), (b), and (c). Based on the total structural unit of the boronized poly (meth) acrylate-based copolymer (X), it is preferably more than 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, and further preferably 70% by mass to 70% by mass. It is 100% by mass, more preferably 80% by mass to 100% by mass, and even more preferably 90% by mass to 100% by mass.
Further, from the viewpoint of making it easier to exert the effect of the present invention, the boronized poly (meth) acrylate-based copolymer (X) is a functional group-containing monomer other than the monomers (A), (B), and (C). The content of the structural unit derived from is preferably 50% by mass or less, more preferably less than 40% by mass, still more preferably less than 30% by mass, still more preferably less than 20% by mass, and further more preferably less than 20% by mass based on all the structural units. It is preferably less than 10% by mass.

<Physical properties of borated poly (meth) acrylate-based copolymer (X)>
(Mass average molecular weight (Mw), molecular weight distribution (Mw / Mn))
The mass average molecular weight (Mw) of the boried poly (meth) acrylate-based copolymer (X) of the present embodiment is preferably from the viewpoint of facilitating the effect of the present invention and the solubility in the base oil. Is 5,000 to 100,000, more preferably 5,000 to 50,000, and even more preferably 5,000 to 30,000.
Further, the molecular weight distribution (Mw / Mn) of the boried poly (meth) acrylate-based copolymer (X) of the present embodiment is preferably 3.0 or less from the viewpoint of facilitating the effect of the present invention. It is more preferably 2.7 or less, still more preferably 2.4 or less. The molecular weight distribution (Mw / Mn) of the poly (meth) acrylate-based copolymer (X) of the present embodiment may be 1.01 or more, 1.3 or more, and 1. It may be 4 or more.
The mass average molecular weight (Mw) and the molecular weight distribution (Mw / Mn) are values measured or calculated by the method described in Examples described later.

(Polymerization mode)
The polymerization mode of the boronized poly (meth) acrylate-based copolymer (X) of the present embodiment is not particularly limited, and may be any of block copolymerization, random copolymerization, and block / random copolymerization. Among these, random copolymerization is preferable from the viewpoint of easiness of polymerization reaction.

［上記一般式（ａ－１）中、Ｒ^ａ１は、水素原子又はメチル基である。Ｒ^ａ２は、炭素数８～２０のアルキル基を示す。］

［上記一般式（ｂ－１）中、Ｒ^ｂ１は、水素原子又はメチル基である。Ｒ^ｂ２は、炭素数２～４のアルキレン基を示す。ｍ１は、１～１０の整数を示す。ｍ１が２以上の整数の場合の複数のＲ^ｂ２は、同一であっても異なっていてもよい。］ [Manufacturing method of additive composition for lubricating oil]
The method for producing the additive composition for lubricating oil of the present embodiment is not particularly limited, and for example, the alkyl (meth) acrylate (A) represented by the following general formula (a-1) and the following general formula (b) are used. The hydroxyl group-containing (meth) acrylate (B) represented by -1) is polymerized in the presence of the inorganic boric acid-based compound (y) to obtain a boronized poly (meth) acrylate-based copolymer (X). It is preferable that the manufacturing method includes the manufacturing step (S).

[In the above general formula (a-1), ^Ra1 is a hydrogen atom or a methyl group. R ^a2 represents an alkyl group having 8 to 20 carbon atoms. ]

[In the above general formula (b-1), R ^b1 is a hydrogen atom or a methyl group. R ^b2 represents an alkylene group having 2 to 4 carbon atoms. m1 represents an integer from 1 to 10. When m1 is an integer of 2 or more, the plurality of R ^b2s may be the same or different. ]

Hereinafter, the step (S1) and the step (S2) will be described in detail.

<Process (S1)>
In the step (S1), the poly (meth) acrylate-based copolymer (x), which is a raw material for producing the boronized poly (meth) acrylate-based copolymer (X), is produced.
The method for producing the poly (meth) acrylate-based copolymer (x) (polymerization method) is not particularly limited, and the poly (meth) acrylate-based copolymer (x) is produced by applying any of the known methods. Examples of such a method include an emulsion polymerization method, a suspension polymerization method, a solution polymerization method, and the like, but from the viewpoint of convenience, it is preferable to adopt the solution polymerization method.

(Solution polymerization method)
In the solution polymerization method, for example, the monomers (A) and (B), as well as the solvent and the initiator are charged into the reactor, the inside of the reactor is replaced with nitrogen, and then the mixture is stirred at 60 ° C to 100 ° C for 2 hours to 10 hours. It is done by reacting. The reactor is optionally charged with monomers other than the monomers (A) and (B).

Examples of the solvent used in the solution polymerization method include alcohols such as methanol, ethanol, propanol, 2-propanol and butanol; hydrocarbons such as benzene, toluene, xylene and hexane; ethyl acetate, butyl acetate and isobutyl acetate. Esters such as: Esters such as acetone, methyl ethyl ketone, methyl isobutyl ketone; ethers such as methoxybutanol, ethoxybutanol, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, dioxane; mineral oil; poly-α- Examples thereof include synthetic oils such as olefins, ethylene-α-olefin copolymers, alkylbenzenes, alkylnaphthalene, polyphenyl ethers, alkyl substituted diphenyl ethers, polyol esters, dibasic acid esters, hindered esters, monoesters and GTL base oils.
These may be used individually by 1 type and may be used in combination of 2 or more type.

Examples of the initiator used in the solution polymerization method include 2,2'-azobis (isobutyronitrile), 2,2'-azobis (2-methylpropionitrile), and 2,2'-azobis (2). -Amidinopropane) dihydrochloride, 2,2'-azobis- (N, N-dimethyleneisobutyramidine) dihydrochloride, 1,1'-azobis (cyclohexyl-1-carbonitrile) and other azo initiators; Hydrogen peroxide; Organic peroxides such as benzoyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, methyl ethyl ketone peroxide, perbenzoic acid; persulfates such as sodium persulfate, potassium persulfate, ammonium persulfate; Redox initiators of hydrogen peroxide-Fe ²⁺ ; other existing radical initiators can be mentioned.

The molecular weight of the poly (meth) acrylate-based copolymer (x) (molecular weight of the borated poly (meth) acrylate-based copolymer (X)) is controlled by a known method. For example, the molecular weight of the poly (meth) acrylate-based copolymer (x) can be determined by the reaction temperature, reaction time, amount of initiator, amount of each monomer charged, type of solvent, use of chain transfer agent, etc. The molecular weight of the meta) acrylate-based copolymer (X)) can be controlled.

(Preferable embodiment in step (S1))
In the step (S1), an alkyl (meth) is obtained from the viewpoint of producing a poly (meth) acrylate-based copolymer (x) (borated poly (meth) acrylate-based copolymer (X)) that satisfies the above requirement (α). ) It is preferable to adjust the blending ratio [(A) / (B)] of the acrylate (A) and the hydroxyl group-containing (meth) acrylate (B) to 20/80 to 80/20 in terms of molar ratio.
Further, from the viewpoint of further improving the solubility of the poly (meth) acrylate-based copolymer (x) (borinated poly (meth) acrylate-based copolymer (X)) in the base oil, [(A). ) / (B)] is more preferably 40/60 or more, still more preferably 50/50 or more.
Further, from the viewpoint of further facilitating the effect of the present invention, [(A) / (B)] is more preferably 75/25 or less, still more preferably 70/30 or less.
The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is more preferably 40/60 to 75/25, and even more preferably 50/50 to 70/30.

<Process (S2)>
In the step (S2), the poly (meth) acrylate-based copolymer (x) is reacted with the inorganic boric acid-based compound (y) to produce a boronized poly (meth) acrylate-based copolymer (X). ..
As the inorganic boric acid-based compound (y), the same compounds as those described above can be used, and orthoboric acid is preferable.
The reaction between the poly (meth) acrylate-based copolymer (x) and the inorganic boric acid-based compound (y) can be allowed to proceed, for example, in a solvent at a reaction temperature of 100 ° C. to 150 ° C. The reaction time is, for example, 3 hours to 10 hours. Examples of the solvent include the same solvents as those mentioned in the above step (S1).

(Preferable embodiment in step (S2))
In the step (S2), from the viewpoint of producing the boronized poly (meth) acrylate-based copolymer (X) satisfying the above requirement (β), the hydroxyl group in the poly (meth) acrylate-based copolymer (x) It is preferable to adjust the ratio [(y) / (x)] of the number of moles to the number of moles of the inorganic boric acid-based compound (y) to 1/3 or more and less than 3/3.
Further, from the viewpoint of the solubility of the borated poly (meth) acrylate-based copolymer (X) in the base oil, [(y) / (x)] is preferably 2.9 / 3 or less, more preferably 2.9/3 or less. It is 2.7 / 3 or less, more preferably 2.5 / 3 or less.
Further, from the viewpoint of making it easier to exert the effect of the present invention, [(y) / (x)] is preferably 1.5 / 3 or more, more preferably 1.7 / 3 or more, still more preferably 2. It is 0/3 or more.
The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is more preferably 1.5 / 3 to 2.9 / 3, still more preferably 1.7 / 3 to 2.7 / 3, and even more preferably 2.0 / 3 to 2.5 / 3. Is.

<Content of Borylated Poly (Meta) Acrylate-based Copolymer (X) in Additive Composition for Lubricating Oil>
The additive composition for lubricating oil of the present embodiment is made of a boronized poly (meth) acrylate-based copolymer (X) from the viewpoint of facilitating the effect of the present invention when added to the lubricating oil base oil. The content is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, still more preferably 80% by mass or more, still more, based on the total amount of the additive composition for lubricating oil. It is preferably 90% by mass or more, more preferably 95% by mass or more. Considering the purity of the boronized poly (meth) acrylate-based copolymer (X), the content of the boried poly (meth) acrylate-based copolymer (X) is based on the total amount of the additive composition for lubricating oil. , Usually less than 99% by weight.
The additive composition for lubricating oil of the present embodiment may be diluted with a diluting solvent from the viewpoint of solubility in the lubricating oil base oil and handleability. The content of the boronized poly (meth) acrylate-based copolymer (X) in the additive composition for lubricating oil is based on the total amount of the active ingredient in the additive composition for lubricating oil, excluding the diluting solvent. Means the content for.

<Use of additive composition for lubricating oil>
The additive composition for lubricating oil of the present embodiment is excellent in both wear resistance and extreme pressure resistance. Therefore, it is useful as a load-bearing additive.
Therefore, in the present embodiment, there is provided a method of using the additive composition for lubricating oil as a load-bearing additive.

[Lubricating oil composition]
The lubricating oil composition of the present embodiment contains a lubricating oil additive composition containing a boronized poly (meth) acrylate-based copolymer (X) and a lubricating oil base oil.
As for the content of the additive composition for lubricating oil, the content of the boronized poly (meth) acrylate-based copolymer (X) is lubricated from the viewpoint of satisfactorily exerting the effect of adding the additive composition for lubricating oil. Based on the total amount of the oil composition, it is preferably 0.30% by mass or more, more preferably 0.40% by mass or more, still more preferably 0.50% by mass or more, still more preferably 0.60% by mass or more. Is adjusted to. Further, it is preferably adjusted to be 3.0% by mass or less, more preferably 2.5% by mass or less, still more preferably 2.0% by mass or less, still more preferably 1.5% by mass or less.
The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 0.30% by mass to 3.0% by mass, more preferably 0.40% by mass to 2.5% by mass, still more preferably 0.50% by mass to 2.0% by mass, and more. More preferably, it is 0.60% by mass to 1.5% by mass.
Further, the content of the additive composition for lubricating oil is the amount of boron derived from the boronized poly (meth) acrylate-based copolymer (X) from the viewpoint of satisfactorily exerting the effect of adding the additive composition for lubricating oil. However, it is preferably 20% by mass to 400% by mass, more preferably 30% by mass to 380% by mass, and further preferably 40% by mass to 350% by mass based on the total amount of the lubricating oil composition.

<Lubricating oil base oil>
As the lubricating oil base oil, a general base oil used in the lubricating oil composition can be used without particular limitation. Specifically, for example, one or more selected from the group consisting of mineral oil and synthetic oil can be mentioned.
The kinematic viscosity of the lubricating oil base oil at 100 ° C. is preferably in the range of 1 mm ² / s to 50 mm ² / s, more preferably in the range of 2 mm ² / s to 30 mm ² / s, and 3 mm ² / s. It is more preferably in the range of ~ 20 mm ² / s. Further, the viscosity index of the lubricating oil base oil is preferably 80 or more, more preferably 90 or more, and even more preferably 100 or more.
The kinematic viscosity and viscosity index of the lubricating oil base oil are values measured or calculated according to JIS K2283: 2000.

Specific examples of the lubricating oil base oil are given below.
The mineral oil may be, for example, a distillate obtained by atmospheric distillation and / or vacuum distillation of paraffin-based crude oil, intermediate-based crude oil, or naphthenic-based crude oil; refining obtained by refining the distillate according to a conventional method. Oil; etc. Examples of the refining method for obtaining refined oil include solvent dewaxing treatment, hydrogenation isomerization treatment, hydrogenation finishing treatment, and white clay treatment.
Examples of the synthetic oil include hydrocarbon oils, aromatic oils, ester oils, ether oils and the like. Further, as the synthetic oil, GTL (Gas To Liquids) obtained by isomerizing a wax (GTL wax, Gas To Liquids WAX) produced from natural gas by the Fischer-Tropsch method or the like may be used.

<Other additives>
The lubricating oil composition of the present embodiment is an antioxidant, an oily agent, a cleaning dispersant, a viscosity index improver, a rust preventive, and a metal inactivation within a range that does not impair the effect of the additive composition for lubricating oil. It may contain an agent and other additives such as an antifoaming agent. These may be used individually by 1 type and may be used in combination of 2 or more type.
Further, in the present embodiment, the boronized poly (meth) acrylate-based copolymer (X) is contained together with the additive composition for a lubricating oil containing the boronized poly (meth) acrylate-based copolymer (X). As an additive other than the additive composition for lubricating oil, it is selected from antioxidants, oily agents, cleaning dispersants, viscosity index improvers, rust preventives, metal deactivators, defoamers and the like. Additive packages for lubricating oil compositions containing one or more additives are also provided.

(Antioxidant)
As the antioxidant, an amine-based antioxidant, a phenol-based antioxidant, or the like used in conventional lubricating oil compositions can be used. These antioxidants may be used alone or in combination of two or more.
Examples of the amine-based antioxidant include monoalkyldiphenylamine-based compounds such as monooctyldiphenylamine and monononyldiphenylamine; 4,4'-dibutyldiphenylamine, 4,4'-dipentyldiphenylamine, 4,4'-dihexyldiphenylamine, 4 , 4'-Diheptyldiphenylamine, 4,4'-dioctyldiphenylamine, and 4,4'-dinonyldiphenylamine and other dialkyldiphenylamine compounds; Polyalkyldiphenylamine-based compounds; α-naphthylamine, phenyl-α-naphthylamine, butylphenyl-α-naphthylamine, pentylphenyl-α-naphthylamine, hexylphenyl-α-naphthylamine, heptylphenyl-α-naphthylamine, octylphenyl-α-naphthylamine , And naphthylamine-based compounds such as nonylphenyl-α-naphthylamine.
Examples of the phenolic antioxidant include monophenolic compounds such as 2,6-di-tert-butyl-4-methylphenol and 2,6-di-tert-butyl-4-ethylphenol; 4,4'. Examples include bisphenol compounds such as -methylenebis (2,6-di-tert-butylphenol) and 2,2'-methylenebis (4-ethyl-6-tert-butylphenol). The content of antioxidants is the lubricating oil composition. The minimum amount required to maintain the oxidative stability of the product may be added. Specifically, for example, 0.01 to 1% by mass is preferable based on the total amount of the lubricating oil composition.

(Oil-based agent)
Examples of the oily agent include fatty alcohols; fatty acid compounds such as fatty acids and fatty acid metal salts; ester compounds such as polyol esters, sorbitan esters, and glycerides; amine compounds such as aliphatic amines.
The content of the oily agent is usually 0.1 to 20% by mass, preferably 0.5 to 10% by mass, based on the total amount of the lubricating oil composition from the viewpoint of the addition effect.

(Cleaning dispersant)
Examples of the clean dispersant include metal sulfonate, metal salicylate, metal phenate, succinimide and the like.
The content of the cleaning dispersant is usually 0.01 to 10% by mass, preferably 0.1 to 5% by mass, based on the total amount of the lubricating oil composition from the viewpoint of the addition effect.

(Viscosity index improver)
Examples of the viscosity index improver include polymethacrylate, dispersed polymethacrylate, olefin-based copolymer (for example, ethylene-propylene copolymer, etc.), dispersed olefin-based copolymer, and styrene-based copolymer (for example, styrene-based copolymer). Styrene-diene hydride copolymer, etc.) and the like.
The content of the viscosity index improver is preferably 0.3 to 5% by mass based on the total amount of the lubricating oil composition.

(anti-rust)
Examples of the rust preventive include metal-based sulfonates, succinic acid esters, and alkanolamines such as alkylamines and monoisopropanolamines.
The content of the rust inhibitor is usually 0.01 to 5% by mass, preferably 0.03 to 3% by mass, based on the total amount of the lubricating oil composition from the viewpoint of the addition effect.

(Metal deactivator)
Examples of the metal deactivator include benzotriazole and thiadiazole.
The preferable content of the metal deactivator is usually 0.01 to 5% by mass, preferably 0.01 to 1% by mass, based on the total amount of the lubricating oil composition from the viewpoint of the addition effect.

(Defoamer)
Examples of the defoaming agent include methyl silicone oil, fluorosilicone oil, and polyacrylate.
The content of the defoaming agent is usually 0.0005 to 0.01% by mass based on the total amount of the lubricating oil composition from the viewpoint of the addition effect.

<Grease composition>
The additive composition for lubricating oil of the present embodiment can also be used by blending with the grease composition.
That is, in the present embodiment, it is also possible to provide a grease composition containing the above-mentioned additive composition for lubricating oil, a thickener, and a base oil for lubricating oil.

<Physical characteristics of lubricating oil composition, etc.>
(Kinematic viscosity, viscosity index)
The 100 ° C. kinematic viscosity of the lubricating oil composition of the present embodiment is preferably 1.0 mm ² / s to 50 mm ² / s, more preferably 2.0 mm ² / s to 30 mm ² / s, and further preferably 3.0 mm. It is ² / s to 20 mm ² / s.
The viscosity index of the lubricating oil composition of the present embodiment is preferably 90 or more, more preferably 100 or more, still more preferably 110 or more.
The kinematic viscosity and viscosity index of the lubricating oil composition are values measured or calculated according to JIS K2283: 2000.

(Abrasion resistance)
The lubricating oil composition of the present embodiment has a wear scar diameter of preferably 0.57 mm or less, more preferably 0.53 mm or less, still more preferably 0.50 mm or less according to the shell wear test described in Examples described later. ..

(Extreme pressure)
The lubricating oil composition of the present embodiment has a maximum non-seizure load (LNL) of preferably 490 N or more, more preferably 618 N or more, still more preferably, according to the shell four-ball test load-bearing capacity (EP) test described in Examples described later. Is 785N or more.

[Use of lubricating oil composition]
Since the lubricating oil composition of the present embodiment contains a borated poly (meth) acrylate-based copolymer (X), it is excellent in wear resistance and extreme pressure resistance.
Therefore, the lubricating oil composition of the present embodiment is, for example, gear oil (manual transmission oil, differential oil, etc.), automatic transmission oil (automatic transmission oil, etc.), stepless transmission oil (belt CVT oil, toroidal CVT oil, etc.). , Power steering oil, shock absorber oil, drive system oil such as electric motor oil; oil for internal combustion engine (engine) such as for gasoline engine, diesel engine, and gas engine; hydraulic hydraulic oil; turbine oil; compressor oil It can be suitably used for various applications such as fluid bearing oil; rolling bearing oil; etc., and is suitable as a lubricating oil composition that is filled in the equipment used in each of these applications and lubricates between the parts related to the equipment. Can be used.

[Lubrication method using lubricating oil composition]
As a lubrication method using the lubricating oil composition of the present embodiment, a method of filling the lubricating oil composition into the above-mentioned devices used for each application and lubricating between each component related to the above-mentioned devices is preferable. Can be mentioned.

［上記一般式（ａ－１）中、Ｒ^ａ１は、水素原子又はメチル基である。Ｒ^ａ２は、炭素数８～２０のアルキル基を示す。］

［上記一般式（ｂ－１）中、Ｒ^ｂ１は、水素原子又はメチル基である。Ｒ^ｂ２は、炭素数２～４のアルキレン基を示す。ｍ１は、１～１０の整数を示す。ｍ１が２以上の整数の場合の複数のＲ^ｂ２は、同一であっても異なっていてもよい。］
［２］ 前記ホウ素化ポリ（メタ）アクリレート系共重合体（Ｘ）が、さらに下記要件（α）を満たす、上記［１］に記載の潤滑油用添加剤組成物。
＜要件（α）＞
前記構成単位（ａ）と前記構成単位（ｂ）との含有比率［（ａ）／（ｂ）］が、モル比で、２０／８０～８０／２０である。
［３］ 前記ホウ素化ポリ（メタ）アクリレート系共重合体（Ｘ）が、さらに下記要件（β）を満たす、上記［１］又は［２］に記載の潤滑油用添加剤組成物。
＜要件（β）＞
前記ホウ素化ポリ（メタ）アクリレート系共重合体（Ｘ）のホウ素含有量が、前記ホウ素化ポリ（メタ）アクリレート系共重合体（Ｘ）の全量基準で、０．１０質量％～１．７０質量％である。
［４］ 前記ホウ素化ポリ（メタ）アクリレート系共重合体（Ｘ）は、質量平均分子量（Ｍｗ）が５，０００～１００，０００である、上記［１］～［３］のいずれかに記載の潤滑油用添加剤組成物。
［５］ 耐荷重添加剤として用いられる、上記［１］～［４］のいずれかに記載の潤滑油用添加剤組成物。
［６］ 上記［１］～［４］のいずれかに記載の潤滑油用添加剤組成物を、耐荷重添加剤として使用する、使用方法。
［７］ 上記［１］～［５］のいずれかに記載の潤滑油用添加剤組成物と、潤滑油基油と、を含有する、潤滑油組成物。
［８］ 下記一般式（ａ－１）で表されるアルキル（メタ）アクリレート（Ａ）と、下記一般式（ｂ－１）で表される水酸基含有（メタ）アクリレート（Ｂ）とを重合させて、ポリ（メタ）アクリレート系共重合体（ｘ）を製造する工程（Ｓ１）と、
前記ポリ（メタ）アクリレート系共重合体（ｘ）と無機ホウ酸系化合物（ｙ）とを反応させて、ホウ素化ポリ（メタ）アクリレート系共重合体（Ｘ）を製造する工程（Ｓ２）とを含む、潤滑油用添加剤組成物の製造方法。

［上記一般式（ａ－１）中、Ｒ^ａ１は、水素原子又はメチル基である。Ｒ^ａ２は、炭素数８～２０のアルキル基を示す。］

［上記一般式（ｂ－１）中、Ｒ^ｂ１は、水素原子又はメチル基である。Ｒ^ｂ２は、炭素数２～４のアルキレン基を示す。ｍ１は、１～１０の整数を示す。ｍ１が２以上の整数の場合の複数のＲ^ｂ２は、同一であっても異なっていてもよい。］
［９］ 前記工程（Ｓ１）において、前記アルキル（メタ）アクリレート（Ａ）と前記水酸基含有（メタ）アクリレート（Ｂ）との配合比率［（Ａ）／（Ｂ）］を、モル比で、２０／８０～８０／２０に調整する、上記［８］に記載の潤滑油用添加剤組成物の製造方法。
［１０］ 前記工程（Ｓ２）において、前記無機ホウ酸系化合物（ｙ）のモル数と前記ポリ（メタ）アクリレート系共重合体（ｘ）中の水酸基のモル数との比率［（ｙ）／（ｘ）］を１／３以上３／３未満に調整する、上記［８］又は［９］に記載の潤滑油用添加剤組成物の製造方法。 [Aspect of the present invention provided]
According to one aspect of the present invention, the following [1] to [10] are provided.
[1] A structural unit (a) derived from the alkyl (meth) acrylate (A) represented by the following general formula (a-1) and a hydroxyl group-containing (meth) represented by the following general formula (b-1). The structural unit (b) derived from the acrylate (B) and the structural unit (c) derived from the boron esterified product (C) of the hydroxyl group-containing (meth) acrylate (B) are included in the structural unit (c). Is an additive composition for a lubricating oil containing a boronized poly (meth) acrylate-based copolymer (X) having a side chain in which one or more hydroxyl groups are bonded to a boron atom.

[In the above general formula (a-1), ^Ra1 is a hydrogen atom or a methyl group. R ^a2 represents an alkyl group having 8 to 20 carbon atoms. ]

[In the above general formula (b-1), R ^b1 is a hydrogen atom or a methyl group. R ^b2 represents an alkylene group having 2 to 4 carbon atoms. m1 represents an integer from 1 to 10. When m1 is an integer of 2 or more, the plurality of R ^b2s may be the same or different. ]
[2] The additive composition for a lubricating oil according to the above [1], wherein the boried poly (meth) acrylate-based copolymer (X) further satisfies the following requirement (α).
<Requirements (α)>
The content ratio [(a) / (b)] of the structural unit (a) and the structural unit (b) is 20/80 to 80/20 in terms of molar ratio.
[3] The additive composition for a lubricating oil according to the above [1] or [2], wherein the boronized poly (meth) acrylate-based copolymer (X) further satisfies the following requirement (β).
<Requirements (β)>
The boron content of the boronized poly (meth) acrylate-based copolymer (X) is 0.10% by mass to 1.70 based on the total amount of the boronized poly (meth) acrylate-based copolymer (X). It is mass%.
[4] The above-mentioned [1] to [3], wherein the boried poly (meth) acrylate-based copolymer (X) has a mass average molecular weight (Mw) of 5,000 to 100,000. Lubricating oil additive composition.
[5] The additive composition for lubricating oil according to any one of the above [1] to [4], which is used as a load-bearing additive.
[6] A method of use in which the additive composition for lubricating oil according to any one of the above [1] to [4] is used as a load-bearing additive.
[7] A lubricating oil composition containing the lubricating oil additive composition according to any one of the above [1] to [5] and a lubricating oil base oil.
[8] The alkyl (meth) acrylate (A) represented by the following general formula (a-1) and the hydroxyl group-containing (meth) acrylate (B) represented by the following general formula (b-1) are polymerized. In the step (S1) of producing the poly (meth) acrylate-based copolymer (x),
A step (S2) of reacting the poly (meth) acrylate-based copolymer (x) with the inorganic boric acid-based compound (y) to produce a boronized poly (meth) acrylate-based copolymer (X). A method for producing an additive composition for lubricating oil, which comprises.

[In the above general formula (a-1), ^Ra1 is a hydrogen atom or a methyl group. R ^a2 represents an alkyl group having 8 to 20 carbon atoms. ]

[In the above general formula (b-1), R ^b1 is a hydrogen atom or a methyl group. R ^b2 represents an alkylene group having 2 to 4 carbon atoms. m1 represents an integer from 1 to 10. When m1 is an integer of 2 or more, the plurality of R ^b2s may be the same or different. ]
[9] In the step (S1), the blending ratio [(A) / (B)] of the alkyl (meth) acrylate (A) and the hydroxyl group-containing (meth) acrylate (B) is 20 in molar ratio. The method for producing an additive composition for a lubricating oil according to the above [8], which is adjusted to 80 to 80/20.
[10] In the step (S2), the ratio of the number of moles of the inorganic boric acid compound (y) to the number of moles of the hydroxyl group in the poly (meth) acrylate-based polymer (x) [(y) / (X)] is adjusted to 1/3 or more and less than 3/3, the method for producing an additive composition for a lubricating oil according to the above [8] or [9].

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

[Measurement method of various physical property values]
The measurement of each property of each raw material used in each Example and each Comparative Example and each property of the lubricating oil composition of each Example and each Comparative Example was carried out according to the procedure shown below.

(1) Dynamic Viscosity, Viscosity Index The 40 ° C. kinematic viscosity, 100 ° C. kinematic viscosity, and viscosity index of the lubricating oil composition were measured or calculated in accordance with JIS K2283: 2000.

(2) Amount of boron The amount of boron in the lubricating oil composition was measured according to JIS-5S-38-03.
The boron content of the lubricating oil additive composition is the result of measuring the boron content of the lubricating oil composition in accordance with JIS-5S-38-03, and the lubricating oil additive composition to the lubricating oil composition. It was calculated based on the addition amount (dissolution amount) of.

(3) Mass average molecular weight (Mw), molecular weight distribution (Mw / Mn)
"1515 Isocratic HPLC Pump" and "2414 Differential Refractometer (RI) Detector" manufactured by Waters, one column "TSKguardcollect 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.

[Examples 1 to 4, Comparative Examples 1 to 3]
The lubricating oil base oil and the lubricating oil additive composition shown below are sufficiently mixed in the blending amount (mass%) shown in Table 1 to obtain the lubricating oil compositions of Examples 1 to 4 and Comparative Examples 1 to 3. Each was prepared.
The details of the lubricating oil base oil and the lubricating oil additive composition used in Examples 1 to 4 and Comparative Examples 1 to 3 are as shown below.

<Lubricating oil base oil>
Mineral oil (150N) classified as Group II by API classification

<Additive composition for lubricating oil>
-Poly (meth) acrylate-based copolymer (x): Manufactured by the method described in Comparative Production Example 1.
-Boronized poly (meth) acrylate-based copolymer (X) -1: Produced by the method described in Production Example 1.
-Boronized poly (meth) acrylate-based copolymer (X) -2: Produced by the method described in Production Example 2.
-Boronized poly (meth) acrylate-based copolymer (X'): Manufactured by the method described in Comparative Production Example 2.

<Production Examples 1 and 2, Comparative Production Examples 1 and 2>
(Monomers used in Production Examples 1 and 2)
"Dodecyl acrylate": In the above general formula (a-1), R ^a1 is a hydrogen atom and Ra ² is a dodecyl group (an alkyl group having 12 carbon atoms). It was used as an alkyl (meth) acrylate (A).
"2-Hydroxyethyl acrylate": In the above general formula (b-1), R ^b1 is a hydrogen atom, R ^b2 is an ethylene group (alkylene group having 2 carbon atoms), and m1 = 1. be. It was used as a hydroxyl group-containing (meth) acrylate (B).
-Inorganic boric acid compound (C): orthoboric acid (monomer and the like used in Comparative Production Examples 1 and 2)
"1- (methacryloylethoxy) -4,4,6-trimethyl-dioxabolinan": a monomer corresponding to the compound of Reference Example 1 of JP-A-6-65588.
-"Dodecylmethacrylate": In the above general formula (a-1), R ^a1 is a methyl group and R ^a2 is a dodecyl group.
"Stearyl methacrylate": In the above general formula (a-1), R ^a1 is a methyl group and R ^a2 is a stearyl group.

(Comparative Production Example 1: Production of Poly (meth) Acrylate-based Copolymer (x))
30.3 g (126 mmоl) of dodecyl acrylate, 8.6 g (74 mmоl) of 2-hydroxyethyl acrylate, and 2-propanol as a solvent in a 200 mL four-necked flask equipped with a thermometer, a nitrogen inlet tube, and a stirrer. Was charged in 39.9 g.
Next, the inside of the flask was replaced with nitrogen, 0.17 g of 2,2'-azobis (isobutyronitrile) was added as an initiator, the temperature was slowly raised with stirring, and the mixture was refluxed at a temperature of 75 to 85 ° C. The reaction was carried out for 4 hours, and after completion of the reaction, the solvent was distilled off under reduced pressure to obtain a poly (meth) acrylate-based copolymer (x).
The mass average molecular weight (Mw) of the poly (meth) acrylate-based copolymer (x) was 12,800, and the molecular weight distribution (Mw / Mn) was 1.5.
The poly (meth) acrylate-based copolymer (x) is diluted with mineral oil so that the content of the poly (meth) acrylate-based copolymer (x) is 50% by mass, and mixed with the lubricating oil base oil. did.

(Production Example 1: Production of Boronized Poly (meth) Acrylate Copolymer (X) -1)
25 g of the poly (meth) acrylate-based copolymer (x) obtained in Comparative Production Example 1 was diluted with mineral oil in a 500 mL four-necked flask equipped with a thermometer, a nitrogen introduction tube, a toluene stark and a stirrer. 0.97 g (15.7 mmоl) of the diluted product, orthoboric acid, and 260.0 g of toluene as a solvent were charged.
The temperature was slowly raised with stirring, and the reaction was carried out for 4 hours while refluxing at a temperature of 110 to 120 ° C., and after the reaction was completed, the solvent was distilled off under reduced pressure to obtain a boronized poly (meth) acrylate-based copolymer (X). A diluted mineral oil product containing 50% by mass of -1 (50% by mass diluted mineral oil product) was obtained.
The boronized poly (meth) acrylate-based copolymer (X) -1 had a mass average molecular weight (Mw) of 12,300 and a molecular weight distribution (Mw / Mn) of 1.5. The boron content of the boronized poly (meth) acrylate-based copolymer (X) -1 was 0.29% by mass.
In Production Example 1, the ratio [(y) / (x)] of the number of moles of the hydroxyl group in the poly (meth) acrylate-based copolymer (x) to the number of moles of the inorganic boric acid-based compound (y) is 1. / 3.
Since there is almost no difference in the mass average molecular weight (Mw) of the boronized poly (meth) acrylate-based copolymer (X) -1 and the mass average molecular weight of the poly (meth) acrylate-based copolymer (x). The crosslinked structure is not formed by the reaction between the poly (meth) acrylate-based copolymer (x) and orthoboric acid, and the boron atom of the boronized poly (meth) acrylate-based copolymer (X) -1 is 1. It is a state in which the above hydroxyl groups are bonded.
The boronized poly (meth) acrylate-based copolymer (X) -1 was mixed with the lubricating oil base oil in the state of a 50% by mass diluted mineral oil.

(Production Example 2: Production of Boronized Poly (meth) Acrylate Copolymer (X) -2)
The same operation was carried out except that 1.93 g (31.2 mmоl) of orthoboric acid was charged in Production Example 1 to obtain a boronized poly (meth) acrylate-based copolymer (X) -2.
The boronized poly (meth) acrylate-based copolymer (X) -2 had a mass average molecular weight (Mw) of 12,300 and a molecular weight distribution (Mw / Mn) of 1.5. The boron content of the boronized poly (meth) acrylate-based copolymer (X) -2 was 0.57% by mass.
In Production Example 2, the ratio [(y) / (x)] of the number of moles of the hydroxyl group in the poly (meth) acrylate-based copolymer (x) to the number of moles of the inorganic boric acid-based compound (y) is 2. / 3.
Since there is almost no difference in the mass average molecular weight (Mw) of the boronized poly (meth) acrylate-based copolymer (X) -2 and the mass average molecular weight of the poly (meth) acrylate-based copolymer (x). The crosslinked structure is not formed by the reaction between the poly (meth) acrylate-based copolymer (x) and orthoboric acid, and the boron atom of the boronized poly (meth) acrylate-based copolymer (X) -2 has 1 It is a state in which the above hydroxyl groups are bonded.
The boronized poly (meth) acrylate-based copolymer (X) -2 was mixed with the lubricating oil base oil in the state of a 50% by mass diluted mineral oil.

(Comparative Production Example 2: Production of Boronized Poly (Meta) Acrylate-based Copolymer (X'))
5.3 g (20.7 mmоl) of 1- (methacryloylethoxy) -4,4,6-trimethyl-dioxabolinane in a 200 mL four-necked flask equipped with a thermometer, a nitrogen inlet tube, and a stirrer, dodecylmethacrylate. 39.2 g (154.3 mmоl), 4.4 g (13 mmоl) of stearyl methacrylate, and 48.9 g of mineral oil as a solvent were charged.
Next, the inside of the flask was replaced with nitrogen, 0.5 g of perbutyl O was added as an initiator, the temperature was slowly raised with stirring, and the reaction was carried out for 4 hours while refluxing at a temperature of 95 to 100 ° C. A mineral oil diluted product (50% by mass mineral oil diluted product) containing 50% by mass of the meta) acrylate-based copolymer (X') was obtained. The boronized poly (meth) acrylate-based copolymer (X') had a mass average molecular weight (Mw) of 155,000 and a molecular weight distribution (Mw / Mn) of 3.3. The boron content of the boronized poly (meth) acrylate-based copolymer (X') was 0.25% by mass.
The boring poly (meth) acrylate-based copolymer (X') remains diluted with the diluting solvent used in the polymerization (that is, in the state of a 50% by mass diluted mineral oil) and has a lubricating oil group. Mixed with oil.

[Evaluation method]
The tests described below were carried out to evaluate wear resistance and extreme pressure resistance.

<Shell wear test>
Using a shell wear tester, the test conditions were set to a load of 30 kg, a rotation speed of 1,200 rpm, a temperature of 80 ° C. and a test time of 30 minutes in accordance with ASTM D 4172, and the wear resistance of the lubricating oil composition. Was evaluated. The results are expressed in terms of wear mark diameter (mm) of the test hard sphere.

<Shell walk test load bearing (EP) test>
In accordance with ASTM D2783-03 (2014), the maximum non-seizure load (LNL) was measured by using a four-ball tester under the conditions of a rotation speed of 1,800 rpm and an oil temperature (room temperature: 25 ± 5 ° C.). .. The larger this value, the better the extreme pressure property.

<Evaluation criteria>
Those who meet the following criteria (I) or (II) are considered as acceptable.
-Reference (I): The wear mark diameter in the shell wear test is less than 0.50 mm, and the maximum non-seizure load (LNL) is 490 N or more.
Criteria (II): The wear scar diameter in the shell wear test is 0.50 mm or more and 0.60 mm or less, and the maximum non-seizure load (LNL) is 618 N or more.

The results are shown in Table 1. In Table 1, the numerical values in parentheses for the content of the additive composition for lubricating oil mean the content in terms of resin content.

From Table 1, the following can be seen.
From the results shown in Examples 1 to 4, a lubricating oil composition containing a boronized poly (meth) acrylate-based copolymer (X) -1 or a boronized poly (meth) acrylate-based copolymer (X) -2 is blended. Satisfies any of the above criteria (I) and (II), and is found to be excellent in wear resistance and extreme pressure resistance.
From the results shown in Comparative Example 1, the lubricating oil composition containing the poly (meth) acrylate-based copolymer (x) does not satisfy any of the above criteria (I) and (II), and has abrasion resistance and extreme pressure resistance. It can be seen that both are not compatible. Further, from the results shown in Comparative Example 2, it can be seen that by increasing the blending amount of the poly (meth) acrylate-based copolymer (x), the wear resistance is improved, but the extreme pressure resistance is significantly reduced. From the above, it can be seen that it is difficult to achieve both wear resistance and extreme pressure resistance in the lubricating oil composition containing the poly (meth) acrylate-based copolymer (x).
Further, from the results shown in Comparative Example 3, the lubricating oil composition containing the boronized poly (meth) acrylate-based copolymer (X') did not satisfy any of the above criteria (I) and (II), and was resistant to the above-mentioned criteria (I) and (II). It can be seen that both wear resistance and extreme pressure resistance have not been achieved. Since the boronized poly (meth) acrylate-based polymer (X') does not have a side chain in which at least one hydroxyl group is bonded to the boron atom, at least one hydroxyl group is bonded to the boron atom. It is probable that, as in the boronized poly (meth) acrylate-based copolymers (X) -1 and (X) -2 having a side chain, both wear resistance and extreme pressure resistance could not be achieved.

Claims (10)

The structural unit (a) derived from the alkyl (meth) acrylate (A) represented by the following general formula (a-1) and the hydroxyl group-containing (meth) acrylate (B) represented by the following general formula (b-1). ) And the structural unit (c) derived from the borate esterified product (C) of the hydroxyl group-containing (meth) acrylate (B), the structural unit (c) is a boron atom. An additive composition for a lubricating oil, which contains a boronized poly (meth) acrylate-based copolymer (X) and has a side chain having one or more hydroxyl groups bonded thereto.

[In the above general formula (a-1), ^Ra1 is a hydrogen atom or a methyl group. R ^a2 represents an alkyl group having 8 to 20 carbon atoms. ]

[In the above general formula (b-1), R ^b1 is a hydrogen atom or a methyl group. R ^b2 represents an alkylene group having 2 to 4 carbon atoms. m1 represents an integer from 1 to 10. When m1 is an integer of 2 or more, the plurality of R ^b2s may be the same or different. ] The additive composition for a lubricating oil according to claim 1, wherein the boried poly (meth) acrylate-based copolymer (X) further satisfies the following requirement (α).
<Requirements (α)>
The content ratio [(a) / (b)] of the structural unit (a) and the structural unit (b) is 20/80 to 80/20 in terms of molar ratio. The additive composition for a lubricating oil according to claim 1 or 2, wherein the boried poly (meth) acrylate-based copolymer (X) further satisfies the following requirement (β).
<Requirements (β)>
The boron content of the boronized poly (meth) acrylate-based copolymer (X) is 0.10% by mass to 1.70 based on the total amount of the boronized poly (meth) acrylate-based copolymer (X). It is mass%. The lubricating oil according to any one of claims 1 to 3, wherein the boried poly (meth) acrylate-based copolymer (X) has a mass average molecular weight (Mw) of 5,000 to 100,000. Additive composition. The additive composition for lubricating oil according to any one of claims 1 to 4, which is used as a load-bearing additive. A method of use, wherein the additive composition for lubricating oil according to any one of claims 1 to 4 is used as a load-bearing additive. A lubricating oil composition containing the lubricating oil additive composition according to any one of claims 1 to 5 and a lubricating oil base oil. The alkyl (meth) acrylate (A) represented by the following general formula (a-1) and the hydroxyl group-containing (meth) acrylate (B) represented by the following general formula (b-1) are polymerized to form a poly. The step (S1) for producing the (meth) acrylate-based copolymer (x) and
A step (S2) of reacting the poly (meth) acrylate-based copolymer (x) with the inorganic boric acid-based compound (y) to produce a boronized poly (meth) acrylate-based copolymer (X). A method for producing an additive composition for lubricating oil, which comprises.

[In the above general formula (a-1), ^Ra1 is a hydrogen atom or a methyl group. R ^a2 represents an alkyl group having 8 to 20 carbon atoms. ]

[In the above general formula (b-1), R ^b1 is a hydrogen atom or a methyl group. R ^b2 represents an alkylene group having 2 to 4 carbon atoms. m1 represents an integer from 1 to 10. When m1 is an integer of 2 or more, the plurality of R ^b2s may be the same or different. ] In the step (S1), the blending ratio [(A) / (B)] of the alkyl (meth) acrylate (A) and the hydroxyl group-containing (meth) acrylate (B) is 20/80 to the molar ratio. The method for producing an additive composition for a lubricating oil according to claim 8, which is adjusted to 80/20. In the step (S2), the ratio of the number of moles of the inorganic boric acid compound (y) to the number of moles of the hydroxyl group in the poly (meth) acrylate-based polymer (x) [(y) / (x). ] To 1/3 or more and less than 3/3, the method for producing an additive composition for a lubricating oil according to claim 8 or 9.