Additive composition for lubricating oil and lubricating oil composition

Abstract

The objective of this invention is to provide a lubricating oil additive composition suitable as a load-bearing additive, exhibiting excellent wear resistance, extreme pressure properties, and thermal stability, as well as a lubricating oil composition containing the lubricating oil additive composition. This objective is achieved by preparing a lubricating oil additive composition containing a poly(meth)acrylate copolymer (X), wherein the poly(meth)acrylate copolymer (X) comprises structural units (a) derived from a specific alkyl methacrylate (A), structural units (b) derived from a specific hydroxyl-containing methacrylate (B), and structural units (c) derived from a specific phosphorus-containing methacrylate (C).

Description

TECHNICAL FIELD

[0001] The present application relates to an additive composition for lubricating oil and a lubricating oil composition containing the additive composition for lubricating oil. BACKGROUND

[0002] Various lubricating oil additives are blended in lubricating oil for the purpose of imparting or supplementing properties and performances required as lubricating oil.

[0003] As one of representative lubricating oil additives, a load resistance additive which imparts wear resistance and extreme pressure resistance to lubricating oil can be cited. As the load resistance additive, low molecular weight phosphorus-based compounds such as phosphoric acid esters, phosphorous acid esters and phosphonic acid esters are widely used, for example.

[0004] However, the low molecular weight phosphorus-based compounds are capable of imparting excellent wear resistance and extreme pressure resistance to lubricating oil, on the other hand, many cases lack heat stability. In addition, among the low molecular weight phosphorus-based compounds, there are compounds excellent in heat stability, but such compounds many cases are poor in wear resistance and extreme pressure resistance.

[0005] Therefore, in recent years, as a load resistance additive instead of the low molecular weight phosphorus-based compounds, various studies on polymer-based compounds are being conducted (refer to Patent Documents 1 and 2).

[0006] PRIOR ART DOCUMENTS

[0007] PATENT DOCUMENTS

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-2747

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2014-518925 SUMMARY

[0010] PROBLEMS TO BE SOLVED BY THE INVENTION

[0011] However, the polymer-based compounds which are studied as the load resistance additive are many cases insufficient in wear resistance and extreme pressure resistance compared with the low molecular weight phosphorus-based compounds. In addition, many cases also lack heat stability.

[0012] Therefore, the object of the present application is to provide an additive composition for lubricating oil which is suitable as a load resistance additive and is excellent in wear resistance, extreme pressure resistance and heat stability, and a lubricating oil composition containing the additive composition for lubricating oil.

[0013] MEANS FOR SOLVING THE PROBLEMS

[0014] The present inventors have conducted intensive studies in order to solve the above-described problems. As a result, it has been found that a poly(meth)acrylate-based copolymer containing a plurality of structural units derived from a specific monomer can solve the above-described problems, thereby completing the present application.

[0015] That is, the present application relates to the following [1] to [4].

[0016] [1] An additive composition for lubricating oil, comprising a poly(meth)acrylate-based copolymer (X) containing a structural unit (a) derived from an alkyl (meth)acrylate (A) represented by the following general formula (a-1), a structural unit (b) derived from a hydroxyl-containing (meth)acrylate (B) represented by the following general formula (b-1), and a structural unit (c) derived from a phosphorus-containing (meth)acrylate (C) represented by the following general formula (c-1).

[0017] [Chemical Formula 1]

[0018]

[0019] [In the above-described general formula (a-1), R a1 is a hydrogen atom or a methyl group. R a2 represents an alkyl group having 8 to 20 carbon atoms.]

[0020] [Chemical Formula 2]

[0021]

[0022] [In the above-described 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 of 1 to 10. When ml is an integer of 2 or more, a plurality of R b2 may be the same or different.]

[0023] [Chemical Formula 3]

[0024]

[0025] [In the above-described general formula (c-1), R c1 is a hydrogen atom or a methyl group. R c2 represents an ethylene group. m2 represents an integer of 1 to 6. When m2 is an integer of 2 or more, a plurality of R c2 may be the same or different. n represents an integer of 1 or 2. When n = 1, at least one of a plurality of R c3 represents a hydrogen atom. When n = 2, R c3 is a hydrogen atom.]

[0026] [2] A use method which uses the additive composition for lubricating oil described in the above [1] as a load resistance additive.

[0027] [3] A lubricating oil composition which contains the additive composition for lubricating oil described in the above [1] and a lubricating oil base oil.

[0028] [4] A manufacturing method of an additive composition for lubricating oil, comprising a step (S) of manufacturing a poly(meth)acrylate-based copolymer (X) by polymerizing (meth)alkyl acrylate (A) represented by the following general formula (a-1), hydroxyl group-containing (meth)acrylate (B) represented by the following general formula (b-1), and phosphorus-containing (meth)acrylate (C) represented by the following general formula (c-1).

[0029] [Chemical Formula 4]

[0030]

[0031] [In the above general formula (a-1), R a1 is a hydrogen atom or a methyl group. R a2 represents an alkyl group having 8 to 20 carbon atoms.]

[0032] [Chemical Formula 5]

[0033]

[0034] [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 of 1 to 10. When m1 is an integer of 2 or more, a plurality of R b2 may be the same or different.]

[0035] [Chemical Formula 6]

[0036]

[0037] [In the above general formula (c-1), R c1 is a hydrogen atom or a methyl group. R c2 represents an ethylene group. m2 represents an integer of 1 to 6. When m2 is an integer of 2 or more, a plurality of R c2 may be the same or different. n represents an integer of 1 or 2. When n = 1, at least one of a plurality of R c3 represents a hydrogen atom. When n = 2, R c3 is a hydrogen atom.]

[0038] Effects of the Invention

[0039] According to the present application, it is possible to provide a lubricating oil additive composition suitable as a load-resistant additive, and excellent in wear resistance, extreme pressure resistance, and heat stability, and a lubricating oil composition containing the same. DETAILED DESCRIPTION

[0040] The upper limit value and the lower limit value of the numerical range described in the present specification can be combined arbitrarily. For example, in the case where "A to B" 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 range of the present application.

[0041] In addition, the numerical range "lower limit value to upper limit value" described in the present specification means above the lower limit value and below the upper limit value unless otherwise specified.

[0042] In addition, in the present specification, the numerical value of the examples is a numerical value that can be used as the upper limit value or the lower limit value.

[0043] Note that, in the present specification, "(meth)acrylate" means acrylate or methacrylate, and other similar terms have the same meaning.

[0044] [Form of the lubricating oil additive composition]

[0045] The lubricating oil additive composition of the present embodiment contains a poly(meth)acrylate-based copolymer (X).

[0046] The poly(meth)acrylate-based copolymer (X) contains a structural unit (a) from an alkyl (meth)acrylate (A) represented by the following general formula (a-1), a structural unit (b) from a hydroxyl group-containing (meth)acrylate (B) represented by the following general formula (b-1), and a structural unit (c) from a phosphorus-containing (meth)acrylate (C) represented by the following general formula (c-1).

[0047] [Chemical Formula 7]

[0048]

[0049] [In the above general formula (a-1), R a1 is a hydrogen atom or a methyl group. R a2 represents an alkyl group having 8 to 20 carbon atoms.

[0050] [Chemical Formula 8]

[0051]

[0052] [In the above general formula (b-1), R b1 is a hydrogen atom or a methyl group. R b2represents an alkylene group having 2 to 4 carbon atoms. m1 represents an integer of 1 to 10. When m1 is an integer of 2 or more, a plurality of R b2 may be the same or different.

[0053] [Chemical Formula 9]

[0054]

[0055] [In the above general formula (c-1), R c1 is a hydrogen atom or a methyl group. R c2 represents an ethylene group. m2 represents an integer of 1 to 6. When m2 is an integer of 2 or more, a plurality of R c2 may be the same or different. n represents an integer of 1 or 2. When n = 1, at least one of a plurality of R c3 represents a hydrogen atom. When n = 2, R c3 is a hydrogen atom.

[0056] The present inventors have conducted intensive studies in order to solve the above problems. As a result, it has been found that a poly(meth)acrylate-based copolymer (X) containing a structural unit (a) from an alkyl (meth)acrylate (A) represented by the above general formula (a-1), a structural unit (b) from a hydroxyl group-containing (meth)acrylate (B) represented by the above general formula (b-1), and a structural unit (c) from a phosphorus-containing (meth)acrylate (C) represented by the above general formula (c-1) is excellent in wear resistance, extreme pressure resistance, and thermal stability, and the poly(meth)acrylate-based copolymer (X) can be suitably used as an additive for lubricating oil (particularly, as a load-resistant additive).

[0057] The reason why the poly(meth)acrylate-based copolymer (X) is excellent in wear resistance, extreme pressure resistance, and thermal stability is that oil solubility is ensured by the inclusion of the above structural unit (a), the polymer becomes a multi-point adsorption type by the inclusion of the above structural unit (b), and a phosphoric acid group or a group from an acidic phosphate is introduced into a side chain by the inclusion of the above structural unit (c). In more detail, in a lubricating oil composition, the phosphoric acid group or the group from an acidic phosphate introduced into a side chain is protected by steric hindrance of the poly(meth)acrylate-based copolymer (X), and the thermal stability is improved. On the other hand, it is presumed that in a sliding portion, the poly(meth)acrylate-based copolymer (X) is compressed, the phosphorus of the phosphoric acid group or the group from an acidic phosphate introduced into a side chain is exposed, and thus the phosphorus reacts with a metal, and the wear resistance and the extreme pressure resistance are improved.

[0058] Note that in the following description, the alkyl (meth)acrylate (A), the hydroxyl group-containing (meth)acrylate (B), and the phosphorus-containing (meth)acrylate (C) will also be referred to as "monomer (A)", "monomer (B)", and "monomer (C)", respectively.

[0059] In the present embodiment, the poly(meth)acrylate-based copolymer (X) can be composed only of the structural unit (a) from the monomer (A), the structural unit (b) from the monomer (B), and the structural unit (c) from the monomer (C), but can also contain other structural units than the structural units (a), (b), and (c) within a range not impairing the effects of the present application.

[0060] In the present embodiment, the total content of the structural units (a), (b), and (c) in the poly(meth)acrylate-based copolymer (X) is preferably 70 to 100 mol%, more preferably 80 to 100 mol%, and further preferably 90 to 100 mol%, based on the total structural units of the poly(meth)acrylate-based copolymer (X).

[0061] Hereinafter, the (meth)acrylic acid alkyl ester (A), the hydroxyl group-containing (meth)acrylic acid ester (B), and the phosphorus-containing (meth)acrylic acid ester (C) will be described in detail.

[0062] <(Meth)acrylic acid alkyl ester (A)>

[0063] The (meth)acrylic acid alkyl ester (A) used in the present embodiment is represented by the following general formula (a-1).

[0064] [Chemical Formula 10]

[0065]

[0066] The structural unit (a) from the (meth)acrylic acid alkyl ester (A) mainly assumes a function of imparting oil solubility in the poly(meth)acrylate-based copolymer (X).

[0067] Note that the (meth)acrylic acid alkyl ester (A) can be used alone or in combination with two or more kinds. Therefore, the poly(meth)acrylate-based copolymer (X) can contain one kind of the structural unit (a) from the (meth)acrylic acid alkyl ester (A) alone, or can contain two or more kinds.

[0068] In the above general formula (a-1), R a1 is a hydrogen atom or a methyl group. That is, the (meth)acrylic acid alkyl ester (A) has an acryloyl group or a methacryloyl group as a polymerizable functional group.

[0069] R a1 Monomers having a substituent other than a hydrogen atom and a methyl group are difficult to obtain, and the reactivity of such monomers is low, and thus it is also difficult to polymerize them.

[0070] In this embodiment, R a1 is preferably a hydrogen atom. That is, the alkyl (meth)acrylate (A) preferably has an acryloyl group as a polymerizable functional group.

[0071] In the above general formula (a-1), R a2 represents an alkyl group having 8 to 20 carbon atoms.

[0072] In the case where the number of carbon atoms of the alkyl group is less than 8 or the number of carbon atoms of the alkyl group exceeds 20, it is difficult to ensure the oil solubility of the poly(meth)acrylate-based copolymer (X).

[0073] As the alkyl group having 8 to 20 carbon atoms that can be selected as R a2 , for example, there are mentioned straight-chain alkyl groups such as 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, a heptadecyl group, an octadecyl group, a nonadecyl group, and an icosyl group. They can be straight-chain or branched-chain.

[0074] Here, from the viewpoint of more easily ensuring the oil solubility of the 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, and further preferably 10 to 14.

[0075] <Hydroxyl group-containing (meth)acrylate (B)>

[0076] The hydroxyl group-containing (meth)acrylate (B) used in this embodiment is represented by the following general formula (b-1).

[0077] [Chemical Formula 11]

[0078]

[0079] It is presumed that the structural unit (b) from the hydroxyl group-containing (meth)acrylate (B) assumes a function of making the poly(meth)acrylate-based copolymer (X) a polymer of a multi-point adsorption type, and is advantageous for improvement in wear resistance and extreme pressure resistance.

[0080] Note that the hydroxyl group-containing (meth)acrylate (B) can be used alone as one kind or in combination with two or more kinds. Therefore, the poly(meth)acrylate-based copolymer (X) can contain one kind of the structural unit (b) from the hydroxyl group-containing (meth)acrylate (B) alone or two or more kinds.

[0081] In the above general formula (b-1), R b1is 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.

[0082] R b1 Monomers in which R is a substituent other than a hydrogen atom and a methyl group are difficult to obtain, and the reactivity of such monomers is low, so it is also difficult to polymerize them.

[0083] Here, in the present embodiment, R b1 is preferably a hydrogen atom. That is, the hydroxyl group-containing (meth)acrylate (B) preferably has an acryloyl group as a polymerizable functional group.

[0084] In the above general formula (b-1), R b2 represents an alkylene group having 2 to 4 carbon atoms.

[0085] In the case where the number of carbon atoms of the alkylene group is 1, the polarity becomes high and the oil solubility decreases.

[0086] In addition, in the case where the number of carbon atoms of the alkylene group is 5 or more, the oil solubility excessively increases and the adsorptivity to metals decreases.

[0087] Here, from the viewpoint of easily ensuring appropriate oil solubility and appropriate adsorptivity to metals, the number of carbon atoms of the alkylene group is preferably 2 to 3, more preferably 2.

[0088] m1 represents an integer of 1 to 10. In the case where m1 is an integer of 2 or more, the plurality of R b2 may be the same or different. In addition, -(OR b2 ) m1 The bonding mode of the moieties represented by the above formulae to each other can be random bonding or block bonding, and from the viewpoint of easiness of polymerization, random bonding is preferred.

[0089] In the case where m1 is 0, the hydroxyl group-containing (meth)acrylate (B) becomes a carboxylic acid, so the oil solubility decreases.

[0090] In addition, in the case where m1 is an integer of 11 or more, the polarity becomes high and the oil solubility decreases due to the influence of the -(OR b2 ) moiety.

[0091] Here, from the viewpoint of easily ensuring appropriate oil solubility, m1 is preferably 1 to 6, more preferably 1 to 4, further preferably 1 to 2, and still further preferably 1.

[0092] <Phosphorus-containing (meth)acrylate (C)>

[0093] The phosphorus-containing (meth)acrylate (C) used in the present application is represented by the following general formula (c-1).

[0094] [Chemical Formula 12]

[0095]

[0096] It is presumed that the structural unit (c) from the phosphorus-containing (meth)acrylate (C) assumes a function of improving wear resistance and extreme pressure by introducing a phosphoric acid group or a group from an acidic phosphoric acid ester in a side chain of the poly(meth)acrylate-based copolymer (X).

[0097] Here, phosphorus is an element that is a main cause of reduction in heat stability, and thus is not generally introduced from the viewpoint of securing heat stability. However, the present inventors and others found, from the viewpoint of improving wear resistance and extreme pressure, in the course of studying introduction of a phosphoric acid group or a group from an acidic phosphoric acid ester, that by introducing the structural unit (c) from the phosphorus-containing (meth)acrylate (C) in a polymer composed of the structural unit (a) from the alkyl (meth)acrylate (A) and the structural unit (b) from the hydroxyl group-containing (meth)acrylate (B), the problem of reduction in heat stability due to introduction of phosphorus was alleviated, and a polymer that is excellent in heat stability as a whole of the poly(meth)acrylate-based copolymer (X) and also excellent in wear resistance and extreme pressure was obtained.

[0098] Note that the phosphorus-containing (meth)acrylate (C) can be used alone as one kind or in combination with two or more kinds. Thus, the poly(meth)acrylate-based copolymer (X) can contain one kind of the structural unit (c) from the phosphorus-containing (meth)acrylate (C) alone or two or more kinds.

[0099] In the above general formula (c-1), R c1 is a hydrogen atom or a methyl group. That is, the phosphorus-containing (meth)acrylate (C) has an acryloyl group or a methacryloyl group as a polymerizable functional group.

[0100] R c1 is a hydrogen atom and a substituent other than a methyl group, the monomer is difficult to obtain, and the reactivity of the monomer is low, so it is also difficult to polymerize them.

[0101] Here, in the present embodiment, from the viewpoint of easily adjusting the molecular weight of the poly(meth)acrylate-based copolymer (X), R c1 is preferably a hydrogen atom. That is, the phosphorus-containing (meth)acrylate (C) preferably has an acryloyl group as a polymerizable functional group.

[0102] In the above general formula (c-1), R c2represents ethylene group.

[0103] In the case where the number of carbon atoms of the alkylene group is 1, the polarity becomes high and the oil solubility decreases.

[0104] Further, in the case where the number of carbon atoms of the alkylene group is 3 or more, the oil solubility excessively increases and the adsorptivity to metals decreases.

[0105] m2 represents an integer of 1 to 6. In the case where m2 is an integer of 2 or more, the plurality of R c2 may be the same or different. Further, -(OR c2 ) m2 The bonding mode of the moieties represented by the above formulae to each other can be random bonding or block bonding, and from the viewpoint of easiness of polymerization, random bonding is preferred.

[0106] In the case where m2 is 0, the polarity of the phosphorus-containing (meth)acrylate (C) becomes high, and thus the oil solubility decreases.

[0107] Further, in the case where m2 is an integer of 7 or more, the polarity becomes high and the oil solubility decreases due to the influence of the -(OR b2 ) moiety.

[0108] Here, from the viewpoint of easy assurance of appropriate oil solubility, m2 is preferably an integer of 1 to 4, more preferably an integer of 1 to 2, and further preferably 1.

[0109] n represents an integer of 1 or 2. In the case where n = 1, at least one of the plurality of R c3 represents a hydrogen atom. In the case where n = 2, R c3 is a hydrogen atom. Note that in the case where n = 1, only one of the plurality of R c3 may be a hydrogen atom. In this case, the other of the plurality of R c3 is a hydrocarbon group.

[0110] Here, in the case where n = 1, if the other of the plurality of R c3 is a hydrocarbon group, from the viewpoint of easy exertion of the effect of the present application, the hydrocarbon group is preferably a methyl group or an ethyl group.

[0111] Further, in the case where n = 1, from the viewpoint of more easy exertion of the effect of the present application, it is preferred that the plurality of R c3 are all hydrogen atoms.

[0112] Here, from the viewpoint of easy exertion of the effect of the present application, the phosphorus-containing (meth)acrylate (C) preferably contains, as a main component, a phosphorus-containing (meth)acrylate (C1) in which n = 1.

[0113] In the present specification, the "main component" means a component whose content is more than 50% by mass. That is, the content of the phosphorus-containing (meth) acrylate (C1) having n = 1 is preferably more than 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, further preferably 70% by mass to 100% by mass, more further preferably 80% by mass to 100% by mass, and still further preferably 90% by mass to 100% by mass, based on the total amount of the phosphorus-containing (meth) acrylate (C).

[0114] In addition, the content of the structural unit (c1) derived from the phosphorus-containing (meth) acrylate (C1) having n = 1 is preferably more than 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, further preferably 70% by mass to 100% by mass, more further preferably 80% by mass to 100% by mass, and still further preferably 90% by mass to 100% by mass, based on the total amount of the structural unit (c) derived from the phosphorus-containing (meth) acrylate (C).

[0115] In addition, the acid value of the phosphorus-containing (meth) acrylate (C) used in the present embodiment is more preferably 300 mgKOH / g to 600 mgKOH / g, and further preferably 350 mgKOH / g to 550 mgKOH / g, from the viewpoint of further easily improving the wear resistance and extreme pressure resistance of the poly(meth) acrylate-based copolymer (X).

[0116] In the present specification, the acid value of the phosphorus-containing (meth) acrylate (C) means a value measured by the potential difference method prescribed in 7 of JIS K 2501 2003.

[0117] <Condition (α)>

[0118] The poly(meth) acrylate-based copolymer (X) of the present embodiment preferably satisfies Condition (α) from the viewpoint of more easily exerting the effects of the present application and the solubility in base oil. That is, the ratio of the content of the above structural unit (a) to the above structural unit (b) [(a) / (b)] is preferably 20 / 80 to 80 / 20 in terms of molar ratio.

[0119] In addition, [(a) / (b)] is more preferably 40 / 60 or more, and further preferably 50 / 50 or more, from the viewpoint of more favorably solubilizing the poly(meth) acrylate-based copolymer (X) in base oil.

[0120] Further, [(a) / (b)] is more preferably 75 / 25 or less, and further preferably 70 / 30 or less, from the viewpoint of more easily exerting the effects of the present application.

[0121] The upper limit value and the lower limit value of these numerical ranges can be combined arbitrarily. Specifically, more preferably 40 / 60 to 75 / 25, further preferably 50 / 50 to 70 / 30.

[0122] <Condition (β)>

[0123] From the viewpoint of more easily exerting the effects of the present application, the poly(meth)acrylate-based copolymer (X) of the present embodiment preferably satisfies Condition (β). That is, the phosphorus content of the poly(meth)acrylate-based copolymer (X) is preferably 0.05% by mass or more and 1.0% by mass or less based on the total amount of the poly(meth)acrylate-based copolymer (X). In addition, from the viewpoint of more easily exerting the effects of the present application, it is more preferable to be 0.10% by mass or more, further preferably 0.20% by mass or more based on the total amount of the poly(meth)acrylate-based copolymer (X). In addition, it is more preferable to be 0.70% by mass or less, further preferably 0.50% by mass or less, more further preferably 0.40% by mass or less, still further preferably 0.30% by mass or less.

[0124] The upper limit value and the lower limit value of these numerical ranges can be combined arbitrarily. Specifically, more preferably 0.10% by mass to 0.70% by mass, further preferably 0.10% by mass to 0.50% by mass, more further preferably 0.20% by mass to 0.40% by mass, still further preferably 0.20% by mass to 0.30% by mass.

[0125] The phosphorus content of the poly(meth)acrylate-based copolymer (X) can be calculated based on the result of measuring the amount of phosphorus in an organic solvent according to JIS-5S-38-03 after dissolving the poly(meth)acrylate-based copolymer (X) in the organic solvent (for example, a lubricating oil base oil) in a prescribed amount, and the amount of the poly(meth)acrylate-based copolymer (X) dissolved in the organic solvent.

[0126] <Other Monomer>

[0127] The poly(meth)acrylate-based copolymer (X) can contain a structural unit derived from another monomer in addition to the above-described structural units (a), (b), and (c), within a range that does not hinder the effects of the present application. As the other monomer, a functional group-containing monomer other than monomers (A), (B), and (C) can be cited. As the other functional group-containing monomer, for example, a (meth)acrylate ester containing a functional group other than monomers (A), (B), and (C) can be cited.

[0128] In the poly(meth)acrylate-based copolymer (X), the total content of the structural units (a), (b), and (c) is preferably 50% by mass or more to 100% by mass, more preferably 60% by mass or more to 100% by mass, further preferably 70% by mass or more to 100% by mass, more further preferably 80% by mass or more to 100% by mass, and still further preferably 90% by mass or more to 100% by mass, based on the total structural units in the poly(meth)acrylate-based copolymer (X), from the viewpoint of more easily exerting the effects of the present application.

[0129] In addition, in the poly(meth)acrylate-based copolymer (X), the content of the structural units derived from the functional group-containing monomers other than the monomers (A), (B), and (C) is preferably 50% by mass or less, more preferably less than 40% by mass, further preferably less than 30% by mass, more further preferably less than 20% by mass, and still further preferably less than 10% by mass, based on the total structural units, from the viewpoint of more easily exerting the effects of the present application.

[0130] <Properties of the poly(meth)acrylate-based copolymer (X)>

[0131] (Mass average molecular weight (Mw), molecular weight distribution (Mw / Mn))

[0132] The mass average molecular weight (Mw) of the poly(meth)acrylate-based copolymer (X) of the present embodiment is preferably 5,000 to 100,000, more preferably 5,000 to 50,000, and further preferably 5,000 to 40,000, from the viewpoint of more easily exerting the effects of the present application and the solubility in base oil.

[0133] In addition, the molecular weight distribution (Mw / Mn) of the poly(meth)acrylate-based copolymer (X) of the present embodiment is preferably 3.5 or less, more preferably 3.0 or less, and further preferably 2.8 or less, from the viewpoint of more easily exerting the effects of the present application. Note that the molecular weight distribution (Mw / Mn) of the poly(meth)acrylate-based copolymer (X) of the present embodiment can be 1.01 or more, 1.3 or more, or 1.5 or more.

[0134] The mass average molecular weight (Mw) and the molecular weight distribution (Mw / Mn) are values determined or calculated using the methods described in the Examples below.

[0135] (Polymerization method)

[0136] The polymerization method of the poly(meth)acrylate-based copolymer (X) of the present embodiment is not particularly limited and can be any one of block copolymerization, random copolymerization, and block / random copolymerization. From the viewpoint of the ease of polymerization reaction, random copolymerization is preferred.

[0137] [Method for producing lubricating oil additive composition]

[0138] The method for producing a lubricating oil additive composition of the present embodiment includes a step (S) of producing a poly(meth)acrylate copolymer (X) by polymerizing an alkyl (meth)acrylate (A) represented by the following general formula (a-1), a hydroxyl group-containing (meth)acrylate (B) represented by the following general formula (b-1), and a phosphorus-containing (meth)acrylate (C) represented by the following general formula (c-1).

[0139] [Chemical Formula 13]

[0140]

[0141] [In the above general formula (a-1), R a1 is a hydrogen atom or a methyl group. R a2 represents an alkyl group having 8 to 20 carbon atoms.]

[0142] [Chemical Formula 14]

[0143]

[0144] [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 of 1 to 10. When m1 is an integer of 2 or more, the plurality of R b2 may be the same or different.]

[0145] [Chemical Formula 15]

[0146]

[0147] [In the above general formula (c-1), R c1 is a hydrogen atom or a methyl group. R c2 represents an ethylene group. m2 represents an integer of 1 to 6. When m2 is an integer of 2 or more, the plurality of R c2 may be the same or different. n represents an integer of 1 or 2. When n = 1, at least one of the plurality of R c3 represents a hydrogen atom. When n = 2, R c3 is a hydrogen atom.]

[0148] Hereinafter, the step (S) of producing a poly(meth)acrylate copolymer (X) will be described in detail.

[0149] [Step (S) of producing a poly(meth)acrylate copolymer (X)]

[0150] The method for producing the poly(meth)acrylate-based copolymer (X) (polymerization method) is not particularly limited, and any of publicly known methods can be used for the production. As such a method, for example, emulsion polymerization, suspension polymerization, solution polymerization, and the like can be given.

[0151] Here, from the viewpoint of the use of the poly(meth)acrylate-based copolymer (X) in the present application, i.e., the use as an additive composition for lubricating oil, as the method for producing the poly(meth)acrylate-based copolymer (X) (polymerization method), a solution polymerization method using a solvent in which a lubricating oil base oil is dissolved as a solvent is preferred.

[0152] (Solution polymerization method)

[0153] The solution polymerization method is performed, for example, by charging the monomers (A), (B), and (C), and a solvent and an initiator into a reactor, performing nitrogen substitution in the reactor, and stirring the mixture at 60°C to 100°C for 2 hours to 10 hours to allow the reaction to proceed. Other monomers than the monomers (A), (B), and (C) can also be charged into the reactor.

[0154] As the solvent used in the solution polymerization method, for example, alcohols such as methanol, ethanol, propanol, 2-propanol, and butanol; hydrocarbons such as benzene, toluene, xylene, and hexane; esters such as ethyl acetate, butyl acetate, and isobutyl acetate; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ethers such as methoxybutanol, ethoxybutanol, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, and dioxane; mineral oil; synthetic oils such as poly-α-olefin, ethylene-α-olefin copolymer, alkylbenzene, alkylnaphthalene, polyphenylene ether, alkyl-substituted diphenyl ether, polyol ester, dibasic acid ester, hindered ester, monoester, and GTL base oil can be given.

[0155] One of these can be used alone, or two or more of these can be used in combination.

[0156] As the initiator used in the solution polymerization method, for example, azo-based initiators such as 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis-(N,N-dimethyleneisobutylamidine) dihydrochloride, and 1,1'-azobis(cyclohexyl-1-carbonitrile); hydrogen peroxide; organic peroxides such as benzoyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, methyl ethyl ketone peroxide, and perbenzoic acid; persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate; redox initiators such as hydrogen peroxide-Fe 2+ ; and other existing radical initiators can be given.

[0157] Note that the molecular weight of the poly(meth)acrylate-based copolymer (X) can be controlled by a publicly known method. For example, the molecular weight of the poly(meth)acrylate-based copolymer (X) can be controlled by the reaction temperature, the reaction time, the amount of the initiator, the amounts of the respective monomers, the kind of the solvent, the use of a chain transfer agent, and the like.

[0158] (PREFERRED EMBODIMENT 1 IN THE STEP (S))

[0159] In the step (S), from the viewpoint of producing the poly(meth)acrylate-based copolymer (X) satisfying the above condition (a), it is preferable that the mixing ratio [(A) / (B)] of the alkyl (meth)acrylate (A) to the hydroxyl group-containing (meth)acrylate (B) is adjusted to 20 / 80 to 80 / 20 in terms of molar ratio.

[0160] Further, from the viewpoint of further improving the solubility of the poly(meth)acrylate-based copolymer (X) in base oil, the [(A) / (B)] is more preferably 40 / 60 or more, and further preferably 50 / 50 or more.

[0161] Furthermore, from the viewpoint of more easily exerting the effects of the present application, the [(A) / (B)] is more preferably 75 / 25 or less, and further preferably 70 / 30 or less.

[0162] The upper limit value and the lower limit value of these numerical ranges can be combined arbitrarily. Specifically, 40 / 60 to 75 / 25 is more preferable, and 50 / 50 to 70 / 30 is further preferable.

[0163] (PREFERRED EMBODIMENT 2 IN THE STEP (S))

[0164] In the step (S), from the viewpoint of producing the poly(meth)acrylate-based copolymer (X) satisfying the above condition (b), it is preferable that the mixing ratio [(C) / {(A)+(B)}] of the phosphorus-containing (meth)acrylate (C) to the total amount of the alkyl (meth)acrylate (A) and the hydroxyl group-containing (meth)acrylate (B) is adjusted to 0.1 / 100 to 10 / 100 in terms of molar ratio.

[0165] Further, from the viewpoint of easily further improving the wear resistance and the extreme pressure resistance of the poly(meth)acrylate-based copolymer (X), the [(C) / {(A)+(B)}] is more preferably 0.5 / 100 or more, and further preferably 1.0 / 100 or more.

[0166] Furthermore, from the viewpoint of easily further improving the heat stability of the poly(meth)acrylate-based copolymer (X), the [(C) / {(A)+(B)}] is more preferably 5.0 / 100 or less, and further preferably 3.0 / 100 or less.

[0167] The upper limit and lower limit of these numerical ranges can be combined arbitrarily. Specifically, 0.5 / 100 to 5.0 / 100 is more preferable, and 1.0 / 100 to 3.0 / 100 is further preferable.

[0168] <Content of poly(meth)acrylate-based copolymer (X) in the lubricating oil additive composition>

[0169] In the lubricating oil additive composition of the present embodiment, the content of the poly(meth)acrylate-based copolymer (X) is preferably 50% by mass or more, more preferably 60% by mass or more, further preferably 70% by mass or more, more further preferably 80% by mass or more, still further preferably 90% by mass or more, yet further preferably 95% by mass or more, based on the total amount of the lubricating oil additive composition, from the viewpoint of more easily exerting the effects of the present application when added to a lubricating oil base oil. If the purity of the poly(meth)acrylate-based copolymer (X) is taken into account, the content of the poly(meth)acrylate-based copolymer (X) is usually less than 99% by mass, based on the total amount of the lubricating oil additive composition.

[0170] Note that the lubricating oil additive composition of the present embodiment can be diluted with a dilution solvent, from the viewpoints of solubility in a lubricating oil base oil and workability. Note that the content of the poly(meth)acrylate-based copolymer (X) in the lubricating oil additive composition refers to the content based on the total amount of effective ingredients in the lubricating oil additive composition excluding the dilution solvent.

[0171] <Use of the lubricating oil additive composition>

[0172] The lubricating oil additive composition of the present embodiment is excellent in wear resistance, extreme pressure resistance, and heat stability. Therefore, it is useful as a load resistance additive.

[0173] Therefore, in the present embodiment, a method of using the lubricating oil additive composition as a load resistance additive is provided.

[0174] [Lubricating oil composition]

[0175] The lubricating oil composition of the present embodiment contains the lubricating oil additive composition containing the poly(meth)acrylate-based copolymer (X) and a lubricating oil base oil.

[0176] From the viewpoint of good exertion of the additive effect of the lubricating oil additive composition, the content of the lubricating oil additive composition is adjusted so that the content of the resin component of the poly(meth)acrylate-based copolymer (X) is preferably 0.3 to 10 mass%, more preferably 0.6 to 6.0 mass%, further preferably 1.0 to 5.0 mass%, based on the total amount of the lubricating oil composition.

[0177] In addition, regarding the content of the lubricating oil additive composition, from the viewpoint of good exertion of the additive effect of the lubricating oil additive composition, the amount of phosphorus from the poly(meth)acrylate-based copolymer (X) is preferably 10 to 300 mass ppm, more preferably 20 to 200 mass ppm, further preferably 30 to 150 mass ppm, based on the total amount of the lubricating oil composition.

[0178] < Lubricating oil base oil >

[0179] The lubricating oil base oil can be used without particular limitation as a general base oil used in the lubricating oil composition. Specifically, for example, one or more selected from the group consisting of mineral oils and synthetic oils can be mentioned.

[0180] 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, further preferably in the range of 3 mm 2 / s to 20 mm 2 / s. In addition, the viscosity index of the lubricating oil base oil is preferably 80 or more, more preferably 90 or more, further more preferably 100 or more.

[0181] The kinematic viscosity and the viscosity index of the lubricating oil base oil are values determined or calculated according to JIS K2283:2000.

[0182] Specific examples of the lubricating oil base oil are listed below.

[0183] As the mineral oil, for example, distillate oils obtained by subjecting paraffin-based, intermediate-based or naphthenic-based crude oil to atmospheric distillation and / or vacuum distillation; refined oils obtained by refining the distillate oils according to a conventional method, etc. can be mentioned. As the refining method for obtaining the refined oils, for example, solvent dewaxing treatment, hydrogen isomerization treatment, hydrogen refining treatment, clay treatment, etc. can be mentioned.

[0184] As the synthetic oil, for example, a hydrocarbon-based oil, an aromatic-based oil, an ester-based oil, an ether-based oil, and the like can be given. In addition, as the synthetic oil, a GTL (Gas To Liquids) obtained by isomerization of a wax (GTL wax, Gas To Liquids WAX) produced from natural gas by a Fischer-Tropsch method or the like can be used.

[0185] <Other additives>

[0186] The lubricating oil composition of the present embodiment can contain other additives such as an antioxidant, an oiliness agent, a detergent dispersant, a viscosity index improver, a rust preventive, a metal deactivator, and an antifoaming agent, within a range not impairing the effects of the above-described lubricating oil additive composition. They can be used alone as one kind, or two or more kinds can be used in combination.

[0187] In addition, in the present embodiment, a lubricating oil additive composition containing the poly(meth)acrylate-based copolymer (X) and a lubricating oil composition containing one or more kinds of additives selected from an antioxidant, an oiliness agent, a detergent dispersant, a viscosity index improver, a rust preventive, a metal deactivator, and an antifoaming agent, or the like, as an additive package other than the lubricating oil additive composition containing the poly(meth)acrylate-based copolymer (X) are also provided.

[0188] (Antioxidant)

[0189] As the antioxidant, an amine-based antioxidant, a phenol-based antioxidant, and the like used in the conventional lubricating oil composition can be used. These antioxidants can be used alone as one kind, or two or more kinds can be used in combination.

[0190] As the amine-based antioxidant, for example, monoalkyldiphenylamine-based compounds such as monooctyldiphenylamine and monononyldiphenylamine; dialkyldiphenylamine-based compounds such as 4,4'-dibutyldiphenylamine, 4,4'-dipentyldiphenylamine, 4,4'-dihexyldiphenylamine, 4,4'-diheptyldiphenylamine, 4,4'-dioctyldiphenylamine, and 4,4'-dinonyldiphenylamine; polyalkyldiphenylamine-based compounds such as tetrabutyldiphenylamine, tetrahexyldiphenylamine, tetraoctyldiphenylamine, and tetranonyldiphenylamine; naphthylamine-based compounds such as α-naphthylamine, phenyl-α-naphthylamine, butylphenyl-α-naphthylamine, pentylphenyl-α-naphthylamine, hexylphenyl-α-naphthylamine, heptylphenyl-α-naphthylamine, octylphenyl-α-naphthylamine, and nonylphenyl-α-naphthylamine can be given.

[0191] As the phenol-based antioxidant, for example, monophenol-based compounds such as 2, 6-di-tert-butyl-4-methylphenol and 2, 6-di-tert-butyl-4-ethylphenol; biphenol-based compounds such as 4, 4'-methylenebis (2, 6-di-tert-butylphenol) and 2, 2'-methylenebis (4-ethyl-6-tert-butylphenol) can be given.

[0192] The content of the antioxidant is only required to add the minimum amount necessary to maintain the oxidation stability of the lubricating oil composition. Specifically, for example, 0.01 to 1 mass% based on the total amount of the lubricating oil composition is preferred.

[0193] (Oily agent)

[0194] As the oily agent, aliphatic alcohols; fatty acid compounds such as fatty acids and fatty acid metal salts; ester compounds such as polyol esters, sorbitan esters, and glycerol esters; amine compounds such as aliphatic amines, and the like can be given.

[0195] From the aspect of the effect of the addition, the content of the oily agent is usually 0.1 to 20 mass% and preferably 0.5 to 10 mass% based on the total amount of the lubricating oil composition.

[0196] (Detergent dispersant)

[0197] As the detergent dispersant, metal sulfonates, metal salicylates, metal phenates, succinimides, and the like can be given.

[0198] From the aspect of the effect of the addition, the content of the detergent dispersant is usually 0.01 to 10 mass% and preferably 0.1 to 5 mass% based on the total amount of the lubricating oil composition.

[0199] (Viscosity index improver)

[0200] As the viscosity index improver, for example, polymethacrylates, dispersed polymethacrylates, olefin-based copolymers (for example, ethylene-propylene copolymers and the like), dispersed olefin-based copolymers, styrene-based copolymers (for example, styrene-diene hydrogenated copolymers and the like), and the like can be given.

[0201] The content of the viscosity index improver is preferably 0.3 to 5 mass% based on the total amount of the lubricating oil composition.

[0202] (Antirust agent)

[0203] As the antirust agent, metal sulfonates, succinates, and alkanolamines such as alkylamines and monoisopropanolamines can be given.

[0204] From the aspect of the effect of the addition, the content of the antirust agent is usually 0.01 to 5 mass% and preferably 0.03 to 3 mass% based on the total amount of the lubricating oil composition.

[0205] (Metal deactivator)

[0206] As the metal deactivator, benzotriazole and thiadiazole, etc. can be given.

[0207] From the aspect of the effect of addition, the preferable content of the metal deactivator is usually 0.01 to 5 mass% based on the total amount of the lubricating oil composition, and preferably 0.01 to 1 mass%.

[0208] (Antifoaming agent)

[0209] As the antifoaming agent, methyl silicone oil, fluorosilicone oil, and polyacrylate, etc. can be given.

[0210] From the aspect of the effect of addition, the content of the antifoaming agent is usually 0.0005 to 0.01 mass% based on the total amount of the lubricating oil composition.

[0211] <Grease composition>

[0212] The lubricating oil additive composition of the present embodiment can also be used in a grease composition.

[0213] That is, in the present embodiment, a grease composition containing the above lubricating oil additive composition, a thickening agent, and a lubricating oil base oil can also be provided.

[0214] <Physical properties, etc. of the lubricating oil composition>

[0215] (Kinematic viscosity, viscosity index)

[0216] The kinematic viscosity at 100°C 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, further preferably 3.0 mm 2 / s to 20 mm 2 / s.

[0217] The viscosity index of the lubricating oil composition of the present embodiment is preferably 90 or more, more preferably 100 or more, and further preferably 110 or more.

[0218] The kinematic viscosity and the viscosity index of the lubricating oil composition are values measured or calculated according to JIS K2283:2000.

[0219] (Wear resistance)

[0220] The wear scar diameter of the lubricating oil composition of the present embodiment obtained by the Shell wear test described in the Examples below is preferably 0.50 mm or less, more preferably 0.47 mm or less, and further preferably 0.45 mm or less.

[0221] (Extreme pressure property)

[0222] The maximum non-seizure load (LNL) of the lubricating oil composition of the present embodiment based on the Shell four-ball test load carrying capacity (EP) test described in the examples below is preferably 490 N or greater, more preferably 618 N or greater, and further preferably 785 N or greater.

[0223] In addition, the weld load (WL) based on the test is preferably 1569 N or greater, and more preferably 1961 N or greater.

[0224] (Thermal stability)

[0225] The amount of sludge produced after the ISOT test described in the examples below is preferably 5.0 mg / 100 mL or less for the lubricating oil composition of the present embodiment.

[0226] [Use of the lubricating oil composition]

[0227] The lubricating oil composition of the present embodiment is excellent in wear resistance, extreme pressure property, and thermal stability due to the presence of the poly(meth)acrylate-based copolymer (X).

[0228] Accordingly, the lubricating oil composition of the present embodiment can be suitably used, for example, in various applications typified by gear oil (manual transmission oil, differential oil, etc.), automatic transmission oil (Automatic Transmission Fluid, etc.), continuously variable transmission oil (belt CVT oil, ring CVT oil, etc.), power steering oil, shock absorber oil, and motor oil, etc. drive system oil; gasoline engine, diesel engine, and gas engine, etc. internal combustion engine (engine) oil; hydraulic working oil; turbine oil; compressor oil; fluid bearing oil; rolling bearing oil; refrigerator oil, etc., and can be suitably filled into devices used in these various applications to be used as a lubricating oil composition for lubricating the parts of the devices.

[0229] [Lubricating method using the lubricating oil composition]

[0230] As the lubricating method using the lubricating oil composition of the present embodiment, a method of filling the above-described lubricating oil composition into devices used in the above-described various applications to lubricate the parts involved in the devices can be preferably selected.

[0231] [One embodiment of the present application]

[0232] According to one embodiment of the present application, the following [1] to

[15] are provided.

[0233] [1] An additive composition for lubricating oil, which contains a poly(meth)acrylate-based copolymer (X) comprising a structural unit (a) derived from an alkyl (meth)acrylate (A) represented by the following general formula (a-1), a structural unit (b) derived from a hydroxyl group-containing (meth)acrylate (B) represented by the following general formula (b-1), and a structural unit (c) derived from a phosphorus-containing (meth)acrylate (C) represented by the following general formula (c-1).

[0234] [Chemical Formula 16]

[0235]

[0236] [In the above general formula (a-1), R a1 is a hydrogen atom or a methyl group. R a2 represents an alkyl group having 8 to 20 carbon atoms.]

[0237] [Chemical Formula 17]

[0238]

[0239] [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 of 1 to 10. When m1 is an integer of 2 or more, the plurality of R b2 may be the same or different.]

[0240] [Chemical Formula 18]

[0241]

[0242] [In the above general formula (c-1), R c1 is a hydrogen atom or a methyl group. R c2 represents an ethylene group. m2 represents an integer of 1 to 6. When m2 is an integer of 2 or more, the plurality of R c2 may be the same or different. n represents an integer of 1 or 2. When n = 1, at least one of the plurality of R c3 represents a hydrogen atom. When n = 2, R c3 is a hydrogen atom.]

[0243] [2] The additive composition for lubricating oil according to the above [1], wherein, in the above general formula (c-1), when n = 1, one of the plurality of R c3 is a hydrogen atom, and the other is a methyl group or an ethyl group.

[0244] [3] The additive composition for lubricating oil according to the above [1], wherein, in the above general formula (c-1), when n = 1, one of the plurality of R c3all are hydrogen atoms.

[0245] [4] The additive composition for lubricating oil according to any one of the above [1] to [3], wherein the above poly(meth)acrylate-based copolymer (X) further satisfies the following condition (a).

[0246] [Condition (a)]

[0247] The ratio of the content of the above structural unit (a) to the above structural unit (b) [(a) / (b)] is 20 / 80 to 80 / 20 in terms of molar ratio.

[0248] [5] The additive composition for lubricating oil according to any one of the above [1] to [4], wherein the above poly(meth)acrylate-based copolymer (X) further satisfies the following condition (b).

[0249] [Condition (b)]

[0250] The phosphorus content in the above poly(meth)acrylate-based copolymer (X) is 0.05% by mass or more and 1.0% by mass or less based on the total amount of the above poly(meth)acrylate-based copolymer (X).

[0251] [6] The additive composition for lubricating oil according to any one of the above [1] to [5], wherein the mass average molecular weight (Mw) of the above poly(meth)acrylate-based copolymer (X) is 5,000 to 100,000.

[0252] [7] The additive composition for lubricating oil according to any one of the above [1] to [7], wherein the acid value of the above phosphorus-containing (meth)acrylate (C) is 300 mgKOH / g to 600 mgKOH / g.

[0253] [8] The additive composition for lubricating oil according to any one of the above [1] to [7], which is used as a load resistance additive.

[0254] [9] A use method of using the additive composition for lubricating oil according to any one of the above [1] to [8] as a load resistance additive.

[0255]

[10] A lubricating oil composition containing the additive composition for lubricating oil according to any one of the above [1] to [8] and a lubricating oil base oil.

[0256]

[11] A method for producing an additive composition for lubricating oil, comprising a step (S) of producing a poly(meth)acrylate copolymer (X) by polymerizing (meth)alkyl acrylate (A) represented by the following general formula (a-1), hydroxyl group-containing (meth)acrylate (B) represented by the following general formula (b-1), and phosphorus-containing (meth)acrylate (C) represented by the following general formula (c-1).

[0257] [Chemical Formula 19]

[0258]

[0259] [In the above general formula (a-1), R a1 is a hydrogen atom or a methyl group. R a2 represents an alkyl group having 8 to 20 carbon atoms.]

[0260] [Chemical Formula 20]

[0261]

[0262] [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 of 1 to 10. When m1 is an integer of 2 or more, the plurality of R b2 may be the same or different.]

[0263] [Chemical Formula 21]

[0264]

[0265] [In the above general formula (c-1), R c1 is a hydrogen atom or a methyl group. R c2 represents an ethylene group. m2 represents an integer of 1 to 6. When m2 is an integer of 2 or more, the plurality of R c2 may be the same or different. n represents an integer of 1 or 2. When n = 1, at least one of the plurality of R c3 represents a hydrogen atom. When n = 2, R c3 is a hydrogen atom.]

[0266]

[12] The method for producing an additive composition for lubricating oil according to the above

[11] , wherein, in the above general formula (c-1), when n = 1, one of the plurality of R c3 is a hydrogen atom, and the other is a methyl group or an ethyl group.

[0267]

[13] The method for producing an additive composition for lubricating oil according to the above

[11] or

[12] , wherein, in the above general formula (c-1), when n = 1, the plurality of R c3 are all hydrogen atoms.

[0268]

[14] The method for producing an additive composition for lubricating oil according to any one of the above

[11] to

[13] , wherein the mixing ratio [(A) / (B)] of the (meth)alkyl acrylate (A) to the hydroxyl group-containing (meth)acrylate (B) is adjusted to 20 / 80 to 80 / 20 in terms of molar ratio in the step (S).

[0269]

[15] The method for producing an additive composition for lubricating oil according to any one of the above

[11] to

[14] , wherein the mixing ratio [(C) / {(A)+(B)}] of the phosphorus-containing (meth)acrylate (C) to the total amount of the (meth)alkyl acrylate (A) and the hydroxyl group-containing (meth)acrylate (B) is adjusted to 0.1 / 100 to 10 / 100 in terms of molar ratio in the step (S).

[0270] Examples

[0271] The present application is specifically described by the following examples, but the present application is not limited to the following examples.

[0272] [Measurement method of various physical property values]

[0273] Each raw material used in each example and comparative example and each property of the lubricating oil composition of each example and comparative example was measured according to the following gist.

[0274] (1) Kinematic viscosity, viscosity index

[0275] The 40°C kinematic viscosity, 100°C kinematic viscosity and viscosity index of the lubricating oil composition were measured or calculated according to JIS K2283:2000.

[0276] (2) Phosphorus amount

[0277] The phosphorus amount of the lubricating oil composition was measured according to JIS-5S-38-03.

[0278] The phosphorus content of the additive composition for lubricating oil was calculated based on the result of measuring the phosphorus amount of the lubricating oil composition according to JIS-5S-38-03 and the added amount (dissolved amount) of the additive composition for lubricating oil in the lubricating oil composition.

[0279] (3) Weight average molecular weight (Mw), molecular weight distribution (Mw / Mn)

[0280] A column "TSKguard column Super HZ-L" manufactured by Tosoh Corporation and two "TSK Super Multipore HZ-M" were installed in this order from the upstream side on a "1515 isocratic HPLC pump" and "2414 differential refractive index (RI) detector" manufactured by Waters Corporation, and measurement was performed under the conditions of measurement temperature: 40°C, mobile phase: tetrahydrofuran, flow rate: 0.35 ml / min, and sample concentration 1.0 mg / ml, and the polystyrene conversion was used to calculate the molecular weight.

[0281] [Examples 1 to 6, Comparative Examples 1 to 6]

[0282] The lubricating oil base oil and the lubricating oil additive composition shown below were sufficiently mixed at the compounding amounts (mass %) shown in Table 1 to prepare the lubricating oil compositions of Examples 1 to 6 and Comparative Examples 1 to 6, respectively.

[0283] The details of the lubricating oil base oils and the lubricating oil additive compositions used in Examples 1 to 6 and Comparative Examples 1 to 6 are shown below.

[0284] < Lubricating oil base oil >

[0285] Mineral oil classified as Group II in the API classification (150N)

[0286] < Lubricating oil additive composition >

[0287] • Poly(meth)acrylate-based copolymer (X)-1: manufactured by the method described in Production Example 1.

[0288] • Poly(meth)acrylate-based copolymer (X)-2: manufactured by the method described in Production Example 2.

[0289] • Poly(meth)acrylate-based copolymer (X)-3: manufactured by the method described in Production Example 3.

[0290] • Poly(meth)acrylate-based copolymer (X')-1: manufactured by the method described in Comparative Production Example 1.

[0291] • Poly(meth)acrylate-based copolymer (X')-2: manufactured by the method described in Comparative Production Example 2.

[0292] • Hydrophosphonate (P amount: 5.34 mass %)

[0293] • Acidic phosphoric ester (P amount: 6.3 mass %)

[0294] • Triaryl phosphate (P amount: 8.30 mass %)

[0295] <Manufacturing Examples 1 to 3, Comparative Manufacturing Examples 1 and 2>

[0296] (The monomers used in Manufacturing Examples 1 to 3)

[0297] • "Lauryl acrylate": a compound in which R a1 is a hydrogen atom, R a2 is lauryl group (alkyl group having 12 carbon atoms) in the above general formula (a-1). It was used as the alkyl (meth)acrylate (A).

[0298] • "2-Hydroxyethyl acrylate": a compound in which R b1 is a hydrogen atom, R b2 is ethylene group (alkylene group having 2 carbon atoms), and m1 = 1 in the above general formula (b-1). It was used as the hydroxyl group-containing (meth)acrylate (B).

[0299] • "P-1A(N)": manufactured by Kyoeisha Chemical Co., Ltd., phosphorus content = 14.3 mass%

[0300] is a mixture of a compound in which n = 1 in the above general formula (c-1) as a main component and a compound in which n = 2. Note that, in both of the compounds, R c1 is a hydrogen atom, and m2 = 1. In addition, in both of the compounds, R c3 is a hydrogen atom. It was used as the phosphorus-containing (meth)acrylate (C).

[0301] Note that the acid value of P-1A(N) (value measured by the potential difference method prescribed in 7 of JIS K 2501 2003) is 420 to 520 mgKOH / g.

[0302] (The monomers used in Comparative Manufacturing Examples 1 and 2)

[0303] • "P-1M": manufactured by Kyoeisha Chemical Co., Ltd., phosphorus content = 14.7 mass%

[0304] is a mixture of a compound in which n = 1 in the above general formula (c-1) as a main component and a compound in which n = 2. Note that, in both of the compounds, R c1 is a methyl group, and m2 = 1. In addition, in both of the compounds, R c3 is a hydrogen atom.

[0305] • "Methyl methacrylate": a compound in which R a1 is a methyl group, R a2 is a methyl group in the above general formula (a-1).

[0306] • "Lauryl methacrylate": a compound in which R a1 is a methyl group, Ra2 a compound in which R1is a dodecyl group.

[0307] • "Tetradecyl methacrylate" is a compound of the above general formula (a-1) in which R1is a tetradecyl group. a1 a methyl group, R a2 a compound in which R1is a tetradecyl group.

[0308] • "Glycidyl methacrylate": a compound having the following structure.

[0309] [Chemical Formula 22]

[0310]

[0311] (Production Example 1: Production of Poly(meth)acrylate Copolymer (X)-1)

[0312] Into a four-necked flask of 200 mL capacity equipped with a thermometer, a nitrogen introduction tube, and a stirrer, were charged dodecyl acrylate 36 g (150 mmol), 2-hydroxyethyl acrylate 11.5 g (99 mmol), P-1A(N) 0.944 g (4.8 mmol), and 2-propanol 47.6 g as a solvent.

[0313] Next, the flask was subjected to nitrogen replacement, and after addition of 2,2'-azobis(isobutyronitrile) 0.2 g as an initiator, the mixture was slowly warmed while stirring, and was reacted at a temperature of 75 to 85°C while refluxing. After completion of the reaction, the solvent was distilled off under reduced pressure to obtain poly(meth)acrylate copolymer (X)-1.

[0314] The weight average molecular weight (Mw) of poly(meth)acrylate copolymer (X)-1 was 18200, and the molecular weight distribution (Mw / Mn) was 2.1. In addition, the phosphorus content of poly(meth)acrylate copolymer (X)-1 was 0.28 mass%.

[0315] Poly(meth)acrylate copolymer (X)-1 was diluted with mineral oil so that the content of poly(meth)acrylate copolymer (X)-1 became 50 mass%, and was mixed into lubricating oil base oil.

[0316] (Production Example 2: Production of Poly(meth)acrylate Copolymer (X)-2)

[0317] The same operation was performed except that 2-propanol 95.2 g was charged as a solvent in Production Example 1, to obtain poly(meth)acrylate copolymer (X)-2.

[0318] The weight average molecular weight (Mw) of the poly(meth)acrylate-based copolymer (X)-2 was 11500, and the molecular weight distribution (Mw / Mn) was 1.9. In addition, the phosphorus content of the poly(meth)acrylate-based copolymer (X)-2 was 0.28 mass%.

[0319] The poly(meth)acrylate-based copolymer (X)-2 was diluted with mineral oil so that the content of the poly(meth)acrylate-based copolymer (X)-2 became 50 mass%, and mixed into a lubricating oil base oil.

[0320] (Production Example 3: Production of poly(meth)acrylate-based copolymer (X)-3)

[0321] The same operation was performed except that 2-propanol 23.8 g was put in as a solvent in Production Example 1, to obtain the poly(meth)acrylate-based copolymer (X)-3.

[0322] The weight average molecular weight (Mw) of the poly(meth)acrylate-based copolymer (X)-3 was 31900, and the molecular weight distribution (Mw / Mn) was 2.6. In addition, the phosphorus content of the poly(meth)acrylate-based copolymer (X)-3 was 0.28 mass%.

[0323] The poly(meth)acrylate-based copolymer (X)-3 was diluted with mineral oil so that the content of the poly(meth)acrylate-based copolymer (X)-3 became 50 mass%, and mixed into a lubricating oil base oil.

[0324] (Comparative Production Example 1: Production of poly(meth)acrylate-based copolymer (X’)-1)

[0325] Into a four-necked flask of 200 mL equipped with a thermometer, a nitrogen introduction tube, and a stirrer, were put methyl methacrylate 8.5 g (84.9 mmol), dodecyl methacrylate 25.0 g (98.3 mmol), tetradecyl methacrylate 15.0 g (53.1 mmol), P-1M 1.5 g (7.1 mmol), dodecyl mercaptan 0.5 g (2.5 mmol) as a chain transfer agent, and 2-propanol 17.5 g as a solvent.

[0326] Next, the inside of the flask was subjected to nitrogen replacement, and after adding 2,2'-azobis(2,4-dimethylvaleronitrile) 0.25 g as an initiator, the temperature was slowly increased while stirring, and the reaction was performed at a temperature of 75 to 85°C while refluxing, for 4 hours. After the end of the reaction, the solvent was distilled off under reduced pressure, whereby the poly(meth)acrylate-based copolymer (X’)-1 was obtained.

[0327] The mass average molecular weight (Mw) of the poly(meth)acrylate-based copolymer (X')-1 was 24500, and the molecular weight distribution (Mw / Mn) was 1.8. In addition, the phosphorus content of the poly(meth)acrylate-based copolymer (X')-1 was 0.44 mass%.

[0328] The poly(meth)acrylate-based copolymer (X')-1 was diluted with mineral oil so that the content of the poly(meth)acrylate-based copolymer (X')-1 became 50 mass%, and mixed into the lubricating oil base oil.

[0329] (Comparative Production Example 2: Production of poly(meth)acrylate-based copolymer (X')-2)

[0330] Into a four-necked flask having a capacity of 200 mL equipped with a thermometer, a nitrogen introduction tube, and a stirrer, were charged glycidyl methacrylate 1.6 g (11.3 mmol), dodecyl methacrylate 37.4 g (147.1 mmol), dodecyl mercaptan 0.35 g (1.7 mmol) as a chain transfer agent, and mineral oil 16.9 g as a solvent.

[0331] Next, the inside of the flask was replaced with nitrogen, and after addition of 2,2'-azobis(isobutyronitrile) 0.22 g as an initiator, the temperature was slowly raised while stirring, and the reaction was carried out at a temperature of 75 to 85°C while refluxing for 7 hours. After cooling to room temperature, dibutyl phosphate 2.49 g (11.9 mmol) and mineral oil 24.9 g as a solvent were added, the temperature was slowly raised while stirring, and the reaction was carried out at a temperature of 80 to 100°C while refluxing for 10 hours, to obtain the poly(meth)acrylate-based copolymer (X')-2 (50 mass% diluted with mineral oil).

[0332] The mass average molecular weight (Mw) of the poly(meth)acrylate-based copolymer (X')-2 was 26800, and the molecular weight distribution (Mw / Mn) was 1.8. In addition, the phosphorus content of the poly(meth)acrylate-based copolymer (X')-2 was 0.86 mass%.

[0333] The poly(meth)acrylate-based copolymer (X')-2 was mixed into the lubricating oil base oil in a state directly diluted with the dilution solvent used at the time of polymerization (i.e., in a state diluted with 50 mass% of mineral oil).

[0334] [Method of Evaluation]

[0335] The following tests were carried out to evaluate the wear resistance, extreme pressure resistance, and heat stability.

[0336] <Shell Wear Test>

[0337] The abrasion resistance of the lubricating oil composition was evaluated using a Shell abrasion tester in accordance with ASTM D 4172, with test conditions set to a load of 30 kg, a rotation speed of 1200 rpm, a temperature of 80°C, and a test time of 30 minutes. The result was expressed as the wear scar diameter (mm) of the test pin.

[0338] In this test, if the wear scar diameter was 0.50 mm or less, the abrasion resistance was judged to be good.

[0339] <Shell four-ball test load-carrying property (EP) test>

[0340] The maximum non-seizure load (LNL) and the weld load (WL) were measured in accordance with ASTM D 2783-03 (2014) using a four-ball tester at a rotation speed of 1800 revolutions / minute and an oil temperature (room temperature: 25 ± 5°C). The larger these values, the better the extreme pressure property.

[0341] In this test, if the maximum non-seizure load (LNL) was 490 N or more and the weld load (WL) was 1569 or more, the extreme pressure property was judged to be good.

[0342] <ISOT test>

[0343] The ISOT test according to JIS K 2514-1:2013 was performed on the test oil (lubricating oil composition) to which a sheet and iron chips were added as catalysts to forcibly deteriorate the test oil. The test temperature (oil temperature) was set to 150°C. Then, for the test oil 24 hours after the start of the ISOT test, the sludge amount (mg / 100 mL) was measured in accordance with JIS B 9931.

[0344] Then, the evaluation was performed according to the following criteria, and the case of "none" was judged to be good in heat stability.

[0345] • "none": sludge amount was less than 5.0 mg / 100 mL

[0346] • "little": sludge amount was 5.0 mg / 100 mL or more and less than 20.0 mg / 100 mL

[0347] • "moderate": sludge amount was 20.0 mg / 100 mL or more and less than 40.0 mg / 100 mL

[0348] • "much": sludge amount was 40.0 mg / 100 mL or more

[0349] The results are shown in Table 1. In Table 1, the values in parentheses in the content of the additive composition for lubricating oil mean the content in terms of the resin component.

[0350] [Table 1]

[0351]

[0352] The following can be known from Table 1.

[0353] As can be known from the results shown in Examples 1 to 6, the lubricating oil compositions each containing poly(meth)acrylate-based copolymer (X)-1, poly(meth)acrylate-based copolymer (X)-2, or poly(meth)acrylate-based copolymer (X-3) are excellent in wear resistance, extreme pressure resistance, and heat stability.

[0354] As can be known from the results shown in Comparative Example 1, the lubricating oil composition containing a hydrogen phosphonate as a low-molecular-weight phosphorus-based compound is insufficient in wear resistance, extreme pressure resistance, and heat stability.

[0355] As can be known from the results shown in Comparative Examples 2 and 3, the lubricating oil compositions each containing an acid phosphoric ester as a low-molecular-weight phosphorus-based compound can ensure wear resistance and extreme pressure resistance by increasing the amount of the acid phosphoric ester to be blended, but are insufficient in heat stability.

[0356] As can be known from the results shown in Comparative Example 4, the lubricating oil composition containing a triaryl phosphate as a low-molecular-weight phosphorus-based compound is insufficient in wear resistance and extreme pressure resistance.

[0357] As can be known from the results shown in Comparative Example 5, the lubricating oil composition containing poly(meth)acrylate-based copolymer (X')-1 is good in wear resistance and extreme pressure resistance, but is insufficient in heat stability.

[0358] As can be known from the results shown in Comparative Example 6, the lubricating oil composition containing poly(meth)acrylate-based copolymer (X')-2 is good in wear resistance and heat stability, but is insufficient in extreme pressure resistance.

Claims

1. An additive composition for lubricating oil, comprising a poly(meth)acrylate copolymer X, the poly(meth)acrylate copolymer X containing structural units a derived from an alkyl (meth)acrylate A represented by the following general formula (a-1), structural units b derived from a hydroxyl group-containing (meth)acrylate B represented by the following general formula (b-1), and structural units c derived from a phosphorus-containing (meth)acrylate C represented by the following general formula (c-1), the mass average molecular weight Mw of the poly(meth)acrylate copolymer X being 5,000 or greater and less than 40,000, the total content of the structural units a, b, and c in the poly(meth)acrylate copolymer X being 70 to 100 mol% based on the total structural units of the poly(meth)acrylate copolymer X, and the poly(meth)acrylate copolymer X further satisfying the following condition α, <Condition α> the ratio a / b of the content of the structural unit a to the structural unit b is 20 / 80 to 80 / 20 in terms of molar ratio.

2. The additive composition for lubricating oil according to claim 1, wherein the total content of the structural units (a), (b), and (c) in the poly(meth)acrylate copolymer X is 80 to 100 mol% based on the total structural units of the poly(meth)acrylate copolymer X.

3. The additive composition for lubricating oil according to claim 1 or 2, wherein the poly(meth)acrylate copolymer X further satisfies the following condition β. In the general formula (a-1), R a1 is a hydrogen atom or a methyl group, R a2 represents an alkyl group having 8 to 20 carbon atoms, In the 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, and m1 represents an integer of 1 to 10. When m1 is an integer of 2 or more, the plurality of R b2 are optionally the same or different, In the general formula (c-1), R c1 is a hydrogen atom or a methyl group, R c2 represents an ethylene group, m2 represents an integer of 1 to 6, and when m2 is an integer of 2 or more, the plurality of R c2 are optionally the same or different, and n represents an integer of 1 or 2, when n = 1, at least one of the plurality of R c3 represents a hydrogen atom, and when n = 2, R c3 is a hydrogen atom.

4. The additive composition for lubricating oil according to claim 1 or 2, wherein the poly(meth)acrylate copolymer X further satisfies the following condition γ.

5. The additive composition for lubricating oil according to claim 1 or 2, wherein the poly(meth)acrylate copolymer X further satisfies the following condition δ.

6. The additive composition for lubricating oil according to claim 1 or 2, wherein the poly(meth)acrylate copolymer X further satisfies the following condition ε. In the general formula (a-1), R a1 is a hydrogen atom.

7. The additive composition for lubricating oil according to claim 1 or 2, wherein the poly(meth)acrylate copolymer X further satisfies the following condition ζ. In the general formula (a-1), R a2 is an alkyl group having 10 to 18 carbon atoms.

8. The additive composition for lubricating oil according to claim 1 or 2, wherein the poly(meth)acrylate copolymer X further satisfies the following condition η. In the general formula (a-1), R a2 is an alkyl group having 10 to 16 carbon atoms.

9. The additive composition for lubricating oil according to claim 1 or 2, wherein the poly(meth)acrylate copolymer X further satisfies the following condition θ. In the general formula (a-1), R a2 is an alkyl group having 10 to 14 carbon atoms.

10. The additive composition for lubricating oil according to claim 1 or 2, wherein the poly(meth)acrylate copolymer X further satisfies the following condition ι. In the general formula (b-1), R b1 is a hydrogen atom.

11. The additive composition for lubricating oil according to claim 1 or 2, wherein, in the general formula (b-1), m1 is 1 to 6. In the general formula (b-1), R b2 is an alkylene group having 2 to 3 carbon atoms.

12. The additive composition for lubricating oil according to claim 1 or 2, wherein, in the general formula (b-1), m1 is 1 to 4. In the general formula (b-1), R b2 is an alkylene group having 2 carbon atoms.

13. The additive composition for lubricating oil according to claim 1 or 2, wherein, in the general formula (b-1), m1 is 1 to 2.

14. The additive composition for lubricating oil according to claim 1 or 2, wherein, in the general formula (b-1), m1 is 1.

15. The additive composition for lubricating oil according to claim 1 or 2, wherein, in the general formula (c-1), m2 is 1 to 4.

16. The additive composition for lubricating oil according to claim 1 or 2, wherein, in the general formula (c-1), m2 is 1 to 2.

17. The additive composition for lubricating oil according to claim 1 or 2, wherein, in the general formula (c-1), m2 is 1. ​ ​ ​ ​ In the general formula (c-1), R c1 is a hydrogen atom. ​ ​ ​ ​ ​ ​ 18. The lubricating oil additive composition of claim 1 or 2, wherein, In the general formula (c-1), when n = 1, one of the plurality of R c3 is a hydrogen atom, and the other is a methyl group or an ethyl group.

19. The lubricating oil additive composition of claim 1 or 2, wherein, In the general formula (c-1), when n = 1, each of the plurality of R c3 is a hydrogen atom.

20. The additive composition for lubricating oil according to claim 1 or 2, wherein The content of the structural unit (cl) from the phosphorus-containing (meth)acrylate ester (Cl) with n = 1 is more than 50 mass% and 100 mass% or less, based on the total amount of the structural unit (c) from the phosphorus-containing (meth)acrylate ester (C).

21. The lubricating oil additive composition of claim 1 or 2, wherein, The poly(meth)acrylate-based copolymer X also satisfies the following condition α', <Condition α'> The content ratio a / b of the structural unit a to the structural unit b is 40 / 60 to 75 / 25 in terms of molar ratio.

22. The lubricating oil additive composition of claim 1 or 2, wherein, The poly(meth)acrylate-based copolymer X also satisfies the following condition β, <Condition β> The phosphorus content in the poly(meth)acrylate-based copolymer X is 0.05 mass% or more and 1.0 mass% or less, based on the total amount of the poly(meth)acrylate-based copolymer X.

23. The lubricating oil additive composition of claim 1 or 2, wherein, The weight average molecular weight Mw of the poly(meth)acrylate-based copolymer X is 5000 to 31900.

24. The lubricating oil additive composition of claim 1 or 2, wherein, The acid value of the phosphorus-containing (meth)acrylate ester C is 300 mgKOH / g to 600 mgKOH / g.

25. The additive composition for lubricating oil according to claim 1 or 2, wherein The molecular weight distribution (Mw / Mn) of the poly(meth)acrylate-based copolymer X is 3.5 or less.

26. The additive composition for lubricating oil according to claim 1 or 2, wherein The total content of the structural units (a), (b), and (c) in the poly(meth)acrylate-based copolymer X is more than 50 mass% and 100 mass% or less, based on the total structural units of the poly(meth)acrylate-based copolymer X.

27. The additive composition for lubricating oil according to claim 1 or 2, wherein The content of the poly(meth)acrylate-based copolymer X is 50 mass% or more, based on the total amount of the additive composition for lubricating oil.

28. The additive composition for lubricating oil according to claim 1 or 2, which is used as a load resistant additive.

29. A use method of using the additive composition for lubricating oil according to any one of claims 1 to 28 as a load resistant additive.

30. A lubricating oil composition containing the additive composition for lubricating oil according to any one of claims 1 to 28 and a lubricating oil base oil.

31. The lubricating oil composition according to claim 30, wherein The content of the resin component of the poly(meth)acrylate-based copolymer X is 0.3 mass% to 10 mass%, based on the total amount of the lubricating oil composition.

32. The lubricating oil composition according to claim 30 or 31, wherein The amount of phosphorus from the poly(meth)acrylate-based copolymer X is 10 mass ppm to 300 mass ppm, based on the total amount of the lubricating oil composition.

33. The lubricating oil composition according to claim 30 or 31, wherein The lubricating oil base oil is one or more selected from the group consisting of mineral oil and synthetic oil.

34. The lubricating oil composition according to claim 30 or 31, wherein The lubricating oil base oil has a kinematic viscosity at 100°C of 1 mm 2 / s ~ 50 mm 2 / s.

35. The lubricating oil composition according to claim 30 or 31, wherein the viscosity index of the lubricating oil base oil is 80 or more.

36. The lubricating oil composition according to claim 30 or 31, wherein one or more selected from the group consisting of an antioxidant, an oiliness agent, a detergent dispersant, a viscosity index improver, a rust preventive, a metal deactivator, and an antifoaming agent are contained.

37. The lubricating oil composition of claim 30 or 31 having a kinematic viscosity at 100 °C of 1.0 mm 2 / s ~ 50 mm 2 / s.

38. The lubricating oil composition according to claim 30 or 31, which has a viscosity index of 90 or more.

39. The lubricating oil composition according to claim 30 or 31, which has a wear scar diameter of 0.50 mm or less by a Shell wear test.

40. The lubricating oil composition according to claim 30 or 31, which has a maximum non-seizure load of 490 N or more based on a load-carrying property test by a Shell four-ball test.

41. The lubricating oil composition according to claim 30 or 31, which has a weld load of 1569 N or more based on a load-carrying property test by a Shell four-ball test.

42. The lubricating oil composition according to claim 30 or 31, which has a sludge generation amount of less than 5.0 mg / 100 mL after an ISOT test.

43. A method of using a lubricating oil composition, wherein, The lubricating oil composition according to any one of claims 30 to 42 is used as a gear oil, an automatic transmission oil, a continuously variable transmission oil, a power steering oil, a shock absorber oil, a motor oil, an oil for a gasoline engine, an oil for a diesel engine, an oil for a gas engine, a hydraulic working oil, a turbine oil, a compressor oil, a fluid bearing oil, a rolling bearing oil, or a refrigerator oil.

44. A method for producing an additive composition for lubricating oil, comprising a step S of polymerizing (methyl)alkyl acrylate A represented by the following general formula (a-1), hydroxyl group-containing (methyl)acrylate B represented by the following general formula (b-1), and phosphorus-containing (methyl)acrylate C represented by the following general formula (c-1) to produce poly(meth)acrylate copolymer X, the poly(meth)acrylate copolymer X containing structural unit a derived from (methyl)alkyl acrylate A represented by the following general formula (a-1), structural unit b derived from hydroxyl group-containing (methyl)acrylate B represented by the following general formula (b-1), and structural unit c derived from phosphorus-containing (methyl)acrylate C represented by the following general formula (c-1), the mass average molecular weight Mw of the poly(meth)acrylate copolymer X being 5000 or more and less than 40000, the total content of the structural units a, b, and c in the poly(meth)acrylate copolymer X being 70 to 100 mol% based on the total structural units of the poly(meth)acrylate copolymer X, the poly(meth)acrylate copolymer X further satisfying the following condition α, <Condition α> the ratio a / b of the content of the structural unit a to the structural unit b is 20 / 80 to 80 / 20 in terms of molar ratio, In the general formula (a-1), R a1 is a hydrogen atom or a methyl group, R a2 represents an alkyl group having 8 to 20 carbon atoms, In the 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, and m1 represents an integer of 1 to 10. When m1 is an integer of 2 or more, the plurality of R b2 are optionally the same or different, In the general formula (c-1), R c1 is a hydrogen atom or a methyl group, R c2 represents an ethylene group, m2 represents an integer of 1 to 6, and when m2 is an integer of 2 or more, the plurality of R c2 are optionally the same or different, n represents an integer of 1 or 2, when n = 1, at least one of the plurality of R c3 represents a hydrogen atom, and when n = 2, R c3 is a hydrogen atom.

45. The method of manufacturing an additive composition for lubricating oil according to claim 44, wherein, In the general formula (c-1), when n = 1, one of the plurality of R c3 is a hydrogen atom, and the other is a methyl group or an ethyl group.

46. The method of manufacturing an additive composition for lubricating oil according to claim 44, wherein, In the general formula (c-1), when n = 1, each of the plurality of R c3 is a hydrogen atom.

47. The method of manufacturing an additive composition for lubricating oil according to any one of claims 44 to 46, wherein in the step S, the mixing ratio A / B of the (methyl)alkyl acrylate A to the hydroxyl group-containing (methyl)acrylate B is adjusted to 20 / 80 to 80 / 20 in terms of molar ratio.

48. The method of manufacturing an additive composition for lubricating oil according to any one of claims 44 to 46, wherein In the process S, the mixing ratio C / {A+B} of the phosphorus-containing (meth)acrylate C to the total amount of the alkyl (meth)acrylate A and the hydroxyl group-containing (meth)acrylate B is adjusted to 0.1 / 100 to 10 / 100 in terms of molar ratio. In the process S, the mixing ratio C / {A+B} of the phosphorus-containing (meth)acrylate C to the total amount of the alkyl (meth)acrylate A and the hydroxyl group-containing (meth)acrylate B is adjusted to 0.1 / 100 to 10 / 100 in terms of molar ratio.

Images