Additive composition and lubricating oil composition

Abstract

The present invention provides an additive composition that can impart excellent wear resistance when blended into a lubricating oil composition, and a lubricating oil composition containing the additive composition. [Solution] The copolymer contains two or more selected from the group consisting of copolymer (XA), copolymer (XB), and copolymer (XC), wherein the copolymer (XA) contains a structural unit (a) derived from a monomer (A) having a polymerizable functional group and an aromatic group having 6 to 12 ring carbon atoms and an electron-withdrawing group; the copolymer (XB) contains a structural unit (b) derived from a monomer (B) having a polymerizable functional group and an aromatic group having 6 to 12 ring carbon atoms and an electron-donating group; and the copolymer (XC) contains a structural unit (c) derived from a monomer (C) having a polymerizable functional group and an unsubstituted aromatic group having 6 to 12 ring carbon atoms.

Description

[Technical Field]

[0001] The present invention relates to an additive composition and a lubricating oil composition. [Background technology]

[0002] One of the typical additives for lubricating oil compositions is an anti-wear agent, and examples of commonly used anti-wear agents include phosphorus-based compounds such as phosphate esters, sulfur-based compounds such as sulfurized olefins, and sulfur-phosphorus-based compounds such as thiophosphate esters. However, phosphorus and sulfur are highly corrosive elements. Therefore, there is a need to develop new anti-wear agents that do not contain phosphorus or sulfur. In recent years, polymer compounds have been studied as such new anti-wear agents (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-041407 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the polymeric compound proposed in Patent Document 1, which contains only structural units derived from alkyl acrylate and structural units derived from hydroxyalkyl acrylate, has insufficient abrasion resistance.

[0005] Therefore, an object of the present invention is to provide an additive composition that can exhibit excellent anti-wear properties and a lubricating oil composition containing the additive composition. [Means for solving the problem]

[0006] According to the present invention, the following [1] to [3] are provided. [1] Contains two or more selected from the group consisting of copolymer (XA), copolymer (XB), and copolymer (XC), The copolymer (XA) contains a structural unit (a) derived from a monomer (A) having a polymerizable functional group and an aromatic group having 6 to 12 ring carbon atoms and an electron-withdrawing group, The copolymer (XB) contains a structural unit (b) derived from a monomer (B) having a polymerizable functional group and an aromatic group having 6 to 12 ring carbon atoms and an electron-donating group, The copolymer (XC) contains a structural unit (c) derived from a monomer (C) having a polymerizable functional group and an unsubstituted aromatic group having 6 to 12 ring carbon atoms, The additive composition, wherein the copolymer (XA), the copolymer (XB), and the copolymer (XC) each independently further contain the following structural unit (d) and the following structural unit (e): Structural unit (d): a structural unit derived from a monomer (D) having a (meth)acryloyl group and a linear or branched alkyl group having 1 to 30 carbon atoms Structural unit (e): a structural unit derived from a monomer (E) having a (meth)acryloyl group and a polar group [2] A lubricating oil composition comprising the additive composition according to [1] above and a lubricating base oil. [3] A method for producing a lubricating oil composition, comprising the step of mixing the additive composition according to [1] above with a lubricating base oil. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an additive composition that can exhibit excellent anti-wear properties, and a lubricating oil composition containing the additive composition. DETAILED DESCRIPTION OF THE INVENTION

[0008] The upper and lower limits of the ranges described herein can be combined in any way. For example, if the ranges are "A to B" and "C to D," the ranges "A to D" and "C to B" are also included in the scope of the present invention. Furthermore, unless otherwise specified, the numerical range "lower limit to upper limit" described in this specification means that the range is equal to or greater than the lower limit and equal to or less than the upper limit. In this specification, the numerical values ​​in the examples are numerical values ​​that can be used as upper or lower limit values.

[0009] As used herein, "(meth)acrylate" means acrylate or methacrylate, and similar meanings apply to other similar terms.

[0010] In this specification, the term "number of ring carbon atoms" refers to the number of carbon atoms among the atoms constituting the ring itself of a compound having a structure in which atoms are bonded in a ring. When the ring is substituted with a substituent, the carbon atoms contained in the substituent are not included in the number of ring carbon atoms. The same applies to the "number of ring carbon atoms" described below unless otherwise specified. For example, a benzene ring has 6 ring carbon atoms. Furthermore, when the benzene ring is substituted with, for example, an alkyl group as a substituent, the number of carbon atoms of the alkyl group is not included in the number of ring carbon atoms of the benzene ring. Therefore, the number of ring carbon atoms of a benzene ring substituted with an alkyl group is 6.

[0011] [Embodiments of the additive composition] The additive composition of the present embodiment contains two or more selected from the group consisting of copolymer (XA), copolymer (XB), and copolymer (XC). The copolymer (XA) contains a structural unit (a) derived from a monomer (A) having a polymerizable functional group and an aromatic group having 6 to 12 ring carbon atoms and an electron-withdrawing group. The copolymer (XB) contains a structural unit (b) derived from a monomer (B) having a polymerizable functional group and an aromatic group having 6 to 12 ring carbon atoms and an electron-donating group. The copolymer (XC) contains a structural unit (c) derived from a monomer (C) having a polymerizable functional group and an unsubstituted aromatic group having 6 to 12 ring carbon atoms. The copolymer (XA), the copolymer (XB), and the copolymer (XC) each independently further contain the following structural unit (d) and the following structural unit (e). Structural unit (d): a structural unit derived from a monomer (D) having a (meth)acryloyl group and a linear or branched alkyl group having 1 to 30 carbon atoms Structural unit (e): a structural unit derived from a monomer (E) having a (meth)acryloyl group and a polar group The copolymers (XA), (XB) and (XC) are different from each other.

[0012] The additive composition of this embodiment may contain the copolymer (XA), the copolymer (XB), and the copolymer (XC) in the following combinations (1) to (4). (1) Combination of copolymer (XA) and copolymer (XB) (2) Combination of copolymer (XA) and copolymer (XC) (3) Combination of copolymer (XB) and copolymer (XC) (4) Combination of copolymer (XA), copolymer (XB), and copolymer (XC)

[0013] As a result of investigations aimed at solving the above problems, the present inventors have found that the combination of the copolymers (1) to (4) above can exhibit excellent abrasion resistance. The reason for this is not clear, but it is presumed that the combination of the copolymers (1) to (4) above enhances the electronic interaction between the aromatic rings of each copolymer, which contributes to the wear resistance. From the viewpoint of improving wear resistance, the additive composition of this embodiment preferably contains at least copolymer (XA) and copolymer (XB). In this case, it is presumed that the "aromatic group having an electron-withdrawing group" contained in copolymer (XA) and the "aromatic group having an electron-donating group" contained in copolymer (XB) tend to enhance electronic interactions between copolymer molecules, resulting in extremely excellent wear resistance. Therefore, among the combinations (1) to (4) above, combination (1) or (4) above is preferred, and combination (1) above is more preferred.

[0014] Copolymer (XA), copolymer (XB) and copolymer (XC) will be described in detail below.

[0015] <Copolymer (XA)> The copolymer (XA) contains the following structural unit (a), the following structural unit (d), and the following structural unit (e). Structural unit (a): a structural unit derived from a monomer (A) having a polymerizable functional group and an aromatic group having 6 to 12 ring carbon atoms and an electron-withdrawing group. Structural unit (d): a structural unit derived from a monomer (D) having a (meth)acryloyl group and a linear or branched alkyl group having 1 to 30 carbon atoms Structural unit (e): a structural unit derived from a monomer (E) having a (meth)acryloyl group and a polar group

[0016] The copolymer (XA) may be composed only of the structural unit (a) derived from the monomer (A), the structural unit (d) derived from the monomer (D), and the structural unit (e) derived from the monomer (E), but may also contain structural units other than the structural units (a), (d), and (e) as long as the effects of the present invention are not significantly impaired. The total content of the structural units (a), (d), and (e) in the copolymer (XA) is preferably 70 mol% to 100 mol%, more preferably 80 mol% to 100 mol%, even more preferably 90 mol% to 100 mol%, and still more preferably 95 mol% to 100 mol%, based on all structural units in the copolymer (XA). Copolymer (XA) is a copolymer different from copolymer (XB) and copolymer (XC). Therefore, copolymer (XA) preferably contains less than 5 mol % of structural units (b) and (c) in total, based on the total amount of copolymer (XA), more preferably less than 3 mol %, even more preferably less than 1 mol %, and even more preferably does not contain structural units (b) and (c).

[0017] (Monomer (A), structural unit (a)) The monomer (A) used in this embodiment has a polymerizable functional group and an aromatic group having 6 to 12 ring carbon atoms and an electron-withdrawing group. The structural unit (a) derived from the monomer (A) interacts with one or more structural units selected from the structural unit (b) derived from the monomer (B) contained in the copolymer (XB) and the structural unit (c) derived from the monomer (C) contained in the copolymer (XC) (preferably the structural unit (b) derived from the monomer (B) contained in the copolymer (XB)), thereby exhibiting excellent abrasion resistance. The monomer (A) may be used alone or in combination of two or more types. Therefore, the copolymer (XA) may contain either one type of structural unit (a) derived from the monomer (A) alone or two or more types.

[0018] Examples of the polymerizable functional group possessed by the monomer (A) include an acryloyl group, a methacryloyl group, and a vinyl group. Among these, an acryloyl group and a methacryloyl group are preferred, and an acryloyl group is more preferred. When the polymerizable functional group possessed by the monomer (A) is an acryloyl group, the flexibility of the copolymer (XA) can be improved. Therefore, while introducing a large amount of structural unit (e) containing a polar group to bring out multipoint adsorption, the polar group can be oriented toward the inside of the copolymer (XA) to facilitate the exertion of oil solubility.

[0019] Examples of the aromatic group having 6 to 12 ring carbon atoms include a phenyl group and a naphthyl group, and from the viewpoint of improving the effects of the present invention, a phenyl group is preferred.

[0020] The electron-withdrawing group contained in the aromatic group having 6 to 12 ring carbon atoms may be a substituent that more easily withdraws electrons from the atom to which it is bonded than a hydrogen atom in the aromatic group. Examples of such a substituent include a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom), a group containing a halogen atom, a nitro group, a cyano group, and a sulfo group. From the viewpoint of improving the effects of the present invention, among these, a group having a halogen atom is preferred, a group having a fluorine atom is more preferred, and a trifluoromethyl group is even more preferred.

[0021] -Monomer (A1), structural unit (a1)- In this embodiment, from the viewpoint of improving the effects of the present invention, the monomer (A) preferably contains a monomer (A1) represented by the following general formula (a-1): In other words, the structural unit (a) preferably contains a structural unit (a1) derived from the monomer (A1). Y a -L a -Ar a -(SA) na (a-1)

[0022] In the above general formula (a-1), Y a represents a polymerizable functional group, and L a represents a direct bond or a linker, and Ar a represents an aromatic group having 6 to 12 ring carbon atoms, and SA represents Ar a represents an electron-withdrawing group as a substituent of the formula (I), and na is an integer of 1 or more.

[0023] Y a Examples of the polymerizable functional group that can be selected as include an acryloyl group, a methacryloyl group, or a vinyl group, preferably an acryloyl group or a methacryloyl group, and more preferably an acryloyl group.

[0024] L a Examples of linkers that can be selected as the linker include divalent aliphatic hydrocarbon groups having 1 to 4 carbon atoms, such as methylene, ethylene, n-propylene, and n-butylene groups; divalent groups having 6 to 10 carbon atoms and a cyclic structure, such as phenylethylene and phenylene groups; -O-; oxyalkylene groups (the alkylene group preferably has 1 to 4 carbon atoms); and polyoxyalkylene groups (the alkylene group preferably has 1 to 4 carbon atoms).

[0025] Ar a Examples of the aromatic group having 6 to 12 ring carbon atoms that can be selected as include a phenyl group and a naphthyl group, and a phenyl group is preferred.

[0026] Examples of electron-withdrawing groups that can be selected as SA include halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, iodine atoms), groups having a halogen atom, nitro groups, cyano groups, sulfo groups, etc. Among these, groups having a halogen atom are preferred, groups having a fluorine atom are more preferred, and trifluoromethyl groups are even more preferred.

[0027] na is Ar a represents the number of substituents that the group has, and is an integer of 1 or more. The upper limit of na is Ar a is determined by the number of hydrogen atoms and is the number of ring carbon atoms minus 1. In addition, na is preferably 1, 2, or 3, more preferably 1 or 2, and even more preferably 1.

[0028] -Content of structural unit (a1)- In this embodiment, from the viewpoint of improving abrasion resistance and the like, the content of the structural unit (a1) is preferably 50 mol % to 100 mol %, more preferably 60 mol % to 100 mol %, even more preferably 70 mol % to 100 mol %, still more preferably 80 mol % to 100 mol %, and even more preferably 90 mol % to 100 mol %, based on all structural units of the structural unit (a).

[0029] (Monomer (D), structural unit (d)) The monomer (D) used in this embodiment has a (meth)acryloyl group and a linear or branched alkyl group having 1 to 30 carbon atoms. The structural unit (d) derived from the monomer (D) mainly functions to impart oil solubility (solubility in mineral oil) to the copolymer (XA). The monomer (D) may be used alone or in combination of two or more types. Therefore, the copolymer (XA) may contain either one type of structural unit (d) derived from the monomer (D) alone or two or more types.

[0030] -Monomer (D1), structural unit (d1)- In this embodiment, from the viewpoint of improving the effects of the present invention, the monomer (D) preferably contains a monomer (D1) represented by the following general formula (d-1): That is, the structural unit (d) preferably contains a structural unit (d1) derived from the monomer (D1). [ka]

[0031] In the above general formula (d-1), R d1 is a hydrogen atom or a methyl group, that is, the monomer (D1) has an acryloyl group or a methacryloyl group as a polymerizable functional group. R d1 Monomers in which is a hydrogen atom or a methyl group are easily available and have excellent polymerizability. Here, in this embodiment, R d1 is preferably a hydrogen atom. That is, the monomer (D) preferably has an acryloyl group. When the (meth)acryloyl group of the monomer (D) is an acryloyl group, the flexibility of the copolymer (XA) can be improved. Therefore, while multipoint adsorption can be achieved by introducing a large amount of structural unit (e) containing a polar group, the polar group can be oriented inward of the copolymer (XA) to facilitate the exertion of oil solubility.

[0032] In the above general formula (d-1), R d2 represents a linear or branched alkyl group having 1 to 30 carbon atoms. When the number of carbon atoms in the alkyl group is within the above range, the oil solubility (solubility in mineral oil) of the copolymer (XA) can be easily improved.

[0033] R d2 Examples of the straight-chain alkyl group that can be selected as aryl include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-hexyl group, an n-octyl group, an n-decyl group, an n-dodecyl group, an n-tetradecyl group, an n-hexadecyl group, an n-octadecyl group, an n-icosyl group, an n-docosyl group, and an n-tetracosyl group. R d2Examples of branched alkyl groups that can be selected include an isopropyl group, an isooctyl group, a tert-octyl group, a 2-ethylhexyl group, an isononyl group, an isodecyl group, and an isooctadecyl group.

[0034] In order to ensure the oil solubility of the copolymer (XA), the number of carbon atoms in the alkyl group is preferably 6 or more, more preferably 8 or more, and even more preferably 10 or more. Also, the number of carbon atoms is preferably 24 or less, more preferably 22 or less, and even more preferably 20 or less.

[0035] The structural unit (d1) derived from the monomer (D1) may contain one type alone, or may contain two or more types. For example, R d2 a structural unit (d1) derived from a monomer (D1) having 1 to 4 carbon atoms (preferably 1 to 3, more preferably 1 or 2, and even more preferably 1), and R d2 and a structural unit (d1) derived from a monomer (D1) having 6 to 30 carbon atoms (preferably 6 to 24, more preferably 8 to 22, and even more preferably 10 to 20). In this case, the oil solubility of the copolymer (XA) can be more easily ensured, and the addition of the copolymer (XA) can more easily exert the effect of improving the viscosity index of the lubricating oil composition.

[0036] -Content of structural unit (d1)- In this embodiment, from the viewpoint of improving abrasion resistance and the like, the content of the structural unit (d1) is preferably 50 mol% to 100 mol%, more preferably 60 mol% to 100 mol%, even more preferably 70 mol% to 100 mol%, still more preferably 80 mol% to 100 mol%, and even more preferably 90 mol% to 100 mol%, based on all structural units of the structural unit (d).

[0037] (Monomer (E) and Structural Unit (e)) The monomer (E) used in this embodiment has a (meth)acryloyl group and a polar group. The structural unit (e) derived from the monomer (E) is responsible for making the copolymer (XA) a multi-point adsorption type copolymer, and is presumed to contribute to improving the wear resistance. The monomer (E) may be used alone or in combination of two or more types. Therefore, the copolymer (XA) may contain either one type of structural unit (e) derived from the monomer (E) alone or two or more types. The polar group contained in the monomer (E) is not particularly limited, but examples thereof include a nitrogen atom-containing group, a hydroxyl group, and a carboxyl group.

[0038] Examples of monomers having a (meth)acryloyl group and a nitrogen atom-containing group include amide group-containing acrylic monomers, primary amino group-containing acrylic monomers, secondary amino group-containing acrylic monomers, tertiary amino group-containing acrylic monomers, nitrile group-containing acrylic monomers, urea group-containing acrylic monomers, and urethane group-containing acrylic monomers. Examples of amide group-containing acrylic monomers include (meth)acrylamide; monoalkylamino(meth)acrylamides such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, Nn-butyl(meth)acrylamide, and N-isobutyl(meth)acrylamide; N-methylaminoethyl(meth)acrylamide, N-ethylaminoethyl(meth)acrylamide, N-isopropylamino-n-butyl(meth)acrylamide, Nn-butylamino-n-butyl(meth)acrylamide, and N-isobutylamino-n-butyl(meth)acrylamide. monoalkylaminoalkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, and N,N-di-n-butyl(meth)acrylamide; dialkylaminoalkyl(meth)acrylamides such as N,N-dimethylaminoethyl(meth)acrylamide, N,N-diethylaminoethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, and N,N-di-n-butylaminobutyl(meth)acrylamide; and the like. Examples of the primary amino group-containing acrylic monomer include aminoalkyl(meth)acrylates having an alkyl group with 2 to 6 carbon atoms, such as aminoethyl(meth)acrylate. Examples of the secondary amino group-containing acrylic monomer include monoalkylaminoalkyl(meth)acrylates such as tert-butylaminoethyl(meth)acrylate and methylaminoethyl(meth)acrylate. Examples of tertiary amino group-containing acrylic monomers include dialkylaminoalkyl(meth)acrylates such as dimethylaminoethyl(meth)acrylate and diethylaminoethyl(meth)acrylate. An example of the nitrile group-containing acrylic monomer is (meth)acrylonitrile. Examples of urea group-containing acrylic monomers include 2-isocyanatoethyl (meth)acrylate. Examples of the urethane group-containing acrylic monomer include monofunctional urethane acrylate.

[0039] Examples of the monomer having a (meth)acryloyl group and a hydroxyl group include hydroxyl group-containing acrylic monomers. Examples of hydroxyl group-containing acrylic monomers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 2- or 3-hydroxypropyl (meth)acrylate; and mono- or di-hydroxyalkyl-substituted (meth)acrylamides such as N,N-dihydroxymethyl (meth)acrylamide, N,N-dihydroxypropyl (meth)acrylamide, and N,N-di-2-hydroxybutyl (meth)acrylamide.

[0040] Examples of the monomer having a (meth)acryloyl group and a carboxyl group include carboxyl group-containing acrylic monomers. Examples of carboxyl group-containing acrylic monomers include (meth)acrylic acid and carboxyalkyl (meth)acrylates such as carboxyethyl (meth)acrylate.

[0041] -Monomer (E1), structural unit (e1)- In this embodiment, from the viewpoint of improving the effects of the present invention and facilitating the improvement of the adsorption properties of the copolymer (XA), the monomer (E) preferably contains a monomer (E1) represented by the following general formula (e-1): That is, the structural unit (e) preferably contains a structural unit (e1) derived from the monomer (E1). [ka]

[0042] In the above general formula (e-1), R e1is a hydrogen atom or a methyl group. That is, the monomer (E1) has an acryloyl group or a methacryloyl group as a polymerizable functional group. R e1 Monomers in which is a hydrogen atom or a methyl group are easily available and have excellent polymerizability. Here, in this embodiment, R e1 is preferably a hydrogen atom. That is, the monomer (E) preferably has an acryloyl group. When the (meth)acryloyl group of the monomer (E) is an acryloyl group, the flexibility of the copolymer (XA) can be improved. Therefore, while multipoint adsorption can be achieved by introducing a large amount of structural units (e) containing polar groups, the polar groups can be oriented inward of the copolymer (XA) to facilitate the exertion of oil solubility.

[0043] In the above general formula (e-1), R e2 represents an alkylene group having 2 to 4 carbon atoms. When the number of carbon atoms in the alkylene group is within the above range, the copolymer (XA) has an appropriate polarity, and while the oil solubility is appropriately ensured, it is also easy to ensure appropriate adsorption to metals. Here, from the viewpoint of more easily ensuring appropriate oil solubility and appropriate adsorption to metals, the alkylene group preferably has 2 to 3 carbon atoms, and more preferably 2 carbon atoms.

[0044] m1 represents an integer of 1 to 10. When m1 is an integer of 2 or more, a plurality of R e2 may be the same or different. e2 ) m1 The bonding mode between the moieties represented by the formula (I) may be random bonding or block bonding, but from the viewpoint of ease of polymerization, random bonding is preferred. When m1 is within the above range, the copolymer (XA) has an appropriate polarity, and while the oil solubility is appropriately ensured, it is also easy to ensure appropriate adsorption to metals. Here, m1 is preferably 1 to 6, more preferably 1 to 4, even more preferably 1 to 2, and even more preferably 1, from the viewpoint of more easily ensuring appropriate oil solubility and appropriate adsorption to metals.

[0045] -Content of structural unit (e1)- In this embodiment, from the viewpoint of improving abrasion resistance and the like, the content of the structural unit (e1) is preferably 50 mol % to 100 mol %, more preferably 60 mol % to 100 mol %, even more preferably 70 mol % to 100 mol %, still more preferably 80 mol % to 100 mol %, and even more preferably 90 mol % to 100 mol %, based on all structural units of the structural unit (e).

[0046] <Copolymer (XB)> The copolymer (XB) contains the following structural unit (b), the following structural unit (d), and the following structural unit (e). Structural unit (b): a structural unit derived from a monomer (A) having a polymerizable functional group and an aromatic group having 6 to 12 ring carbon atoms and an electron-donating group. Structural unit (d): a structural unit derived from a monomer (D) having a (meth)acryloyl group and a linear or branched alkyl group having 1 to 30 carbon atoms Structural unit (e): a structural unit derived from a monomer (E) having a (meth)acryloyl group and a polar group

[0047] In the present embodiment, the copolymer (XB) may be composed only of the structural unit (b) derived from the monomer (B), the structural unit (d) derived from the monomer (D), and the structural unit (e) derived from the monomer (E), but may also contain structural units other than the structural units (b), (d), and (e) as long as the effects of the present invention are not significantly impaired. In this embodiment, the total content of the structural units (b), (d), and (e) in the copolymer (XB) is preferably 70 mol % to 100 mol %, more preferably 80 mol % to 100 mol %, and even more preferably 90 mol % to 100 mol %, based on all structural units in the copolymer (XB). Copolymer (XB) is a copolymer different from copolymer (XA) and copolymer (XC). Therefore, copolymer (XB) preferably contains less than 5 mol % of structural units (a) and (c) in total, based on the total amount of copolymer (XB), more preferably less than 3 mol %, even more preferably less than 1 mol %, and even more preferably does not contain structural units (a) and (c).

[0048] (Monomer (B), structural unit (b)) The monomer (B) used in this embodiment has a polymerizable functional group and an aromatic group having 6 to 12 ring carbon atoms and an electron-donating group. The structural unit (b) derived from the monomer (B) exhibits excellent abrasion resistance due to electronic interaction with one or more structural units selected from the structural unit (a) derived from the monomer (A) contained in the copolymer (XA) and the structural unit (c) derived from the monomer (C) contained in the copolymer (XC) (preferably the structural unit (a) derived from the monomer (A) contained in the copolymer (XA)). The monomer (B) may be used alone or in combination of two or more types. Therefore, the copolymer (XB) may contain either one type of structural unit (b) derived from the monomer (B) alone or two or more types.

[0049] Examples of the polymerizable functional group possessed by the monomer (B) include an acryloyl group, a methacryloyl group, and a vinyl group. Among these, an acryloyl group and a methacryloyl group are preferred, and an acryloyl group is more preferred. When the polymerizable functional group possessed by the monomer (B) is an acryloyl group, the flexibility of the copolymer (XB) can be improved. Therefore, while introducing a large amount of structural unit (e) containing a polar group to bring out multipoint adsorption, the polar group can be oriented toward the inside of the copolymer (XB) to facilitate the exertion of oil solubility.

[0050] Examples of the aromatic group having 6 to 12 ring carbon atoms include a phenyl group and a naphthyl group, and from the viewpoint of improving the effects of the present invention, a phenyl group is preferred.

[0051] The electron-donating group contained in the aromatic group having 6 to 12 ring carbon atoms may be a substituent that more easily donates electrons to the atom to which it is bonded than the hydrogen atom in the aromatic group. Examples of such a substituent include a hydroxyl group, a thiol group, an alkoxy group, an amino group, and an alkyl group. Of these, alkyl groups having 1 to 10 carbon atoms and alkoxy groups having 1 to 10 carbon atoms are preferred from the viewpoint of improving the effects of the present invention.

[0052] -Monomer (B1), structural unit (b1)- In this embodiment, from the viewpoint of improving the effects of the present invention, it is preferable that the monomer (B) contains a monomer (B1) represented by the following general formula (b-1): That is, it is preferable that the structural unit (b) contains a structural unit (b1) derived from the monomer (B1). Y b -L b -Ar b -(SB) nb (b-1)

[0053] In the general formula (b-1), Y b represents a polymerizable functional group, and L b represents a direct bond or a linker, and Ar b represents an aromatic group having 6 to 12 ring carbon atoms, and SB represents Ar b represents an electron-donating group as a substituent of the formula (I), and nb is an integer of 1 or more.

[0054] Y b Examples of the polymerizable functional group that can be selected as include an acryloyl group, a methacryloyl group, or a vinyl group, preferably an acryloyl group or a methacryloyl group, and more preferably an acryloyl group.

[0055] L bExamples of linkers that can be selected as the linker include divalent aliphatic hydrocarbon groups having 1 to 4 carbon atoms, such as methylene, ethylene, n-propylene, and n-butylene groups; divalent groups having 6 to 10 carbon atoms and a cyclic structure, such as phenylethylene and phenylene groups; -O-; oxyalkylene groups (the alkylene group preferably has 1 to 4 carbon atoms); and polyoxyalkylene groups (the alkylene group preferably has 1 to 4 carbon atoms).

[0056] Ar b Examples of the aromatic group having 6 to 12 ring carbon atoms that can be selected as include a phenyl group and a naphthyl group, and a phenyl group is preferred.

[0057] Examples of electron-donating groups that can be selected as SB include a hydroxy group, a thiol group, an alkoxy group, an amino group, an alkyl group, etc. Among these, an alkyl group having 1 to 10 carbon atoms (preferably a linear or branched alkyl group having 1 to 8 carbon atoms, more preferably a linear or branched alkyl group having 1 to 6 carbon atoms, and even more preferably a branched alkyl group having 3 to 6 carbon atoms) and an alkoxy group having 1 to 10 carbon atoms (preferably having 1 to 6 carbon atoms, more preferably having 1 to 4 carbon atoms, and even more preferably having 1 to 3 carbon atoms) are preferred.

[0058] nb is Ar b represents the number of substituents that the group has, and is an integer of 1 or more. The upper limit of nb is Ar b is determined by the number of hydrogen atoms and is the number of ring carbon atoms minus 1. In addition, nb is preferably 1, 2, or 3, and more preferably 1 or 2.

[0059] -Content of structural unit (b1)- In this embodiment, from the viewpoint of improving abrasion resistance and the like, the content of the structural unit (b1) is preferably 50 mol % to 100 mol %, more preferably 60 mol % to 100 mol %, even more preferably 70 mol % to 100 mol %, still more preferably 80 mol % to 100 mol %, and even more preferably 90 mol % to 100 mol %, based on all structural units of the structural unit (b).

[0060] (Monomer (D), structural unit (d)) The structural unit (d) derived from the monomer (D) contained in the copolymer (XB) is the same as the structural unit (d) derived from the monomer (D) used in the copolymer (XA), and preferred embodiments are also as explained in the section on the copolymer (XA), so further explanation is omitted. The structural unit (d) derived from the monomer (D) contained in the copolymer (XB) may be the same as or different from the structural unit (d) derived from the monomer (D) contained in the copolymer (XA).

[0061] (Monomer (E), structural unit (e)) The structural unit (e) derived from the monomer (E) contained in the copolymer (XB) is the same as the structural unit (e) derived from the monomer (E) used in the copolymer (XA), and preferred embodiments are also as explained in the section on the copolymer (XA), so further explanation is omitted. The structural unit (e) derived from the monomer (E) contained in the copolymer (XB) may be the same as or different from the structural unit (e) derived from the monomer (E) contained in the copolymer (XA).

[0062] <Copolymer (XC)> The copolymer (XC) contains the following structural unit (c), the following structural unit (d), and the following structural unit (e). Structural unit (c): a structural unit derived from a monomer (A) having a polymerizable functional group and an unsubstituted aromatic group having 6 to 12 ring carbon atoms Structural unit (d): a structural unit derived from a monomer (D) having a (meth)acryloyl group and a linear or branched alkyl group having 1 to 30 carbon atoms Structural unit (e): a structural unit derived from a monomer (E) having a (meth)acryloyl group and a polar group

[0063] The copolymer (XC) may be composed only of the structural unit (c) derived from the monomer (C), the structural unit (d) derived from the monomer (D), and the structural unit (e) derived from the monomer (E), but may also contain structural units other than the structural units (c), (d), and (e) as long as the effects of the present invention are not significantly impaired. The total content of the structural units (c), (d), and (e) in the copolymer (XC) is preferably 70 mol% to 100 mol%, more preferably 80 mol% to 100 mol%, even more preferably 90 mol% to 100 mol%, and still more preferably 95 mol% to 100 mol%, based on all structural units in the copolymer (XC). Copolymer (XC) is a copolymer different from copolymer (XA) and copolymer (XB). Therefore, copolymer (XC) preferably contains less than 5 mol % of structural units (a) and (b) in total, based on the total amount of copolymer (XC), more preferably less than 3 mol %, even more preferably less than 1 mol %, and even more preferably does not contain structural units (a) and (b).

[0064] (Monomer (C), structural unit (c)) The monomer (C) used in this embodiment has a polymerizable functional group and an unsubstituted aromatic group having 6 to 12 ring carbon atoms. The structural unit (c) derived from the monomer (C) exhibits excellent abrasion resistance due to electronic interaction with one or more structural units selected from the structural unit (a) derived from the monomer (A) contained in the copolymer (XA) and the structural unit (b) derived from the monomer (B) contained in the copolymer (XB) (preferably the structural unit (a) derived from the monomer (A) contained in the copolymer (XA)). The monomer (C) may be used alone or in combination of two or more types. Therefore, the copolymer (XC) may contain either one type of structural unit (c) derived from the monomer (C) alone or two or more types.

[0065] Examples of the polymerizable functional group possessed by the monomer (C) include an acryloyl group, a methacryloyl group, and a vinyl group. Among these, an acryloyl group and a methacryloyl group are preferred, and an acryloyl group is more preferred. When the polymerizable functional group possessed by the monomer (C) is an acryloyl group, the flexibility of the copolymer (XB) can be improved. Therefore, while introducing a large amount of structural unit (e) containing a polar group to bring out multipoint adsorption, the polar group can be oriented toward the inside of the copolymer (XC) to easily exhibit oil solubility.

[0066] Examples of the aromatic group having 6 to 12 ring carbon atoms include a phenyl group and a naphthyl group, and from the viewpoint of improving the effects of the present invention, a phenyl group is preferred.

[0067] -Monomer (C1), structural unit (c1)- In this embodiment, from the viewpoint of improving the effects of the present invention, the monomer (C) preferably includes a monomer (C1) represented by the following general formula (c-1): In other words, the structural unit (c) preferably includes a structural unit (c1) derived from the monomer (C1). Y c -L c -Ar c (c-1)

[0068] In the above general formula (c-1), Y c represents a polymerizable functional group, and L c represents a direct bond or a linker, and Ar c represents an aromatic group having 6 to 12 ring carbon atoms.

[0069] Y c Examples of the polymerizable functional group that can be selected as include an acryloyl group, a methacryloyl group, or a vinyl group, preferably an acryloyl group or a methacryloyl group, and more preferably an acryloyl group.

[0070] L cExamples of linkers that can be selected as the linker include divalent aliphatic hydrocarbon groups having 1 to 4 carbon atoms, such as methylene, ethylene, n-propylene, and n-butylene groups; divalent groups having 6 to 10 carbon atoms and a cyclic structure, such as phenylethylene and phenylene groups; -O-; oxyalkylene groups (the alkylene group preferably has 1 to 4 carbon atoms); and polyoxyalkylene groups (the alkylene group preferably has 1 to 4 carbon atoms).

[0071] Ar c Examples of the aromatic group having 6 to 12 ring carbon atoms that can be selected as include a phenyl group and a naphthyl group, and a phenyl group is preferred.

[0072] -Content of structural unit (c1)- In this embodiment, from the viewpoint of improving abrasion resistance and the like, the content of the structural unit (c1) is preferably 50 mol% to 100 mol%, more preferably 60 mol% to 100 mol%, even more preferably 70 mol% to 100 mol%, still more preferably 80 mol% to 100 mol%, and even more preferably 90 mol% to 100 mol%, based on all structural units of the structural unit (c).

[0073] (Monomer (D), structural unit (d)) The structural unit (d) derived from the monomer (D) contained in the copolymer (XC) is the same as the structural unit (d) derived from the monomer (D) used in the copolymers (XA) and (XB), and preferred embodiments are also as explained in the section on the copolymer (XA), so further explanation will be omitted. The structural unit (d) derived from the monomer (D) contained in the copolymer (XC) may be the same as or different from the structural unit (d) derived from the monomer (D) contained in the copolymer (XA) and the copolymer (XB).

[0074] (Monomer (E), structural unit (e)) The structural unit (e) derived from the monomer (E) contained in the copolymer (XC) is the same as the structural unit (e) derived from the monomer (E) used in the copolymers (XA) and (XB), and preferred embodiments are also as explained in the section on the copolymer (XA), so further explanation will be omitted. The structural unit (e) derived from the monomer (E) contained in the copolymer (XC) may be the same as or different from the structural unit (e) derived from the monomer (E) contained in the copolymer (XA) and the copolymer (XB).

[0075] <Content and content ratio of each structural unit in each copolymer> In the following description, copolymer (XA), copolymer (XB), and copolymer (XC) will also be collectively referred to as each copolymer.

[0076] (Content of structural units (a), (b), and (c)) In the present embodiment, the content of the structural unit (a) derived from monomer (A) in copolymer (XA) (based on all structural units of copolymer (XA)), the content of the structural unit (b) derived from monomer (B) in copolymer (XB) (based on all structural units of copolymer (XB)), and the content of the structural unit (c) derived from monomer (C) in copolymer (XC) (based on all structural units of copolymer (XC)) are each independently preferably 7 mol % to 30 mol %, more preferably 8 mol % to 28 mol %, even more preferably 10 mol % to 26 mol %, and still more preferably 10 mol % to 25 mol %, from the viewpoint of achieving a good balance in the content of each structural unit and making it easier to improve the effects of the present invention.

[0077] (Content of structural unit (d)) In this embodiment, the content of the structural unit (d) derived from the monomer (D) is preferably 43 mol% to 84 mol%, more preferably 50 mol% to 80 mol%, and even more preferably 55 mol% to 76 mol%, based on all structural units of each copolymer. By ensuring that the content of the structural unit (d) derived from the monomer (D) is within the above range, the oil solubility of each copolymer can be appropriately maintained while maintaining a good balance between the contents of each structural unit, making it easier to further improve the effects of the present invention.

[0078] (Content of structural unit (e)) In this embodiment, the content of the structural unit (e) derived from the monomer (E) is preferably 9 mol% to 50 mol%, more preferably 10 mol% to 40 mol%, and even more preferably 12 mol% to 30 mol%, based on all structural units of each copolymer. By ensuring that the content of the structural unit (e) derived from the monomer (E) is within the above range, the oil solubility of each copolymer is appropriate, while the content of each structural unit is well balanced, making it easier to further improve the effects of the present invention.

[0079] (Ratio of structural units (e) and (d)) In this embodiment, from the viewpoint of more easily ensuring appropriate oil solubility and appropriate adsorption to metals, the content ratio of the structural unit (e) to the structural unit (d) in each copolymer [(e) / (d)] is, in molar ratio, preferably 0.15 to 0.50, more preferably 0.20 to 0.45, even more preferably 0.23 to 0.40, and still more preferably 0.25 to 0.35.

[0080] <Mass average molecular weight of each copolymer> The mass average molecular weight of the copolymer (XA), the copolymer (XB), and the copolymer (XC) is each independently preferably from 5,000 to 30,000, more preferably from 10,000 to 30,000, and even more preferably from 20,000 to 30,000. In this specification, the mass average molecular weight is a value measured by the method described in the examples below.

[0081] <Content ratio of each copolymer> When the additive composition of the present embodiment contains copolymer (XA), the ratio of the content of copolymer (XA) to the content of one or more copolymers selected from copolymer (XB) and copolymer (XC) (preferably copolymer (XB)) [content of (XA) / total content of (XB) and (XC)] is preferably 20 / 80 to 80 / 20, more preferably 30 / 70 to 70 / 30, and even more preferably 40 / 60 to 60 / 40, in molar ratio. Furthermore, when the additive composition of the present embodiment contains copolymer (XB), the ratio of the content of copolymer (XB) to the content of one or more copolymers selected from copolymer (XA) and copolymer (XC) (preferably copolymer (XA)) [content of (XB) / total content of (XA) and (XC)] is preferably 20 / 80 to 80 / 20, more preferably 30 / 70 to 70 / 30, and even more preferably 40 / 60 to 60 / 40, in molar ratio.

[0082] [Method of manufacturing additive composition] The method for producing the additive composition of this embodiment includes a step (S) of producing two or more copolymers selected from the group consisting of copolymer (XA), copolymer (XB), and copolymer (XC). The copolymer (XA) can be produced by polymerizing the following monomers (A), (D), and (E). Monomer (A): A monomer having a polymerizable functional group and an aromatic group having 6 to 12 ring carbon atoms and an electron-withdrawing group. Monomer (D): A monomer having a (meth)acryloyl group and a linear or branched alkyl group having 1 to 30 carbon atoms. Monomer (E): A monomer having a (meth)acryloyl group and a polar group The copolymer (XB) can be produced by polymerizing the following monomers (B), (D), and (E). Monomer (B): A monomer having a polymerizable functional group and an aromatic group having 6 to 12 ring carbon atoms and an electron-donating group. Monomer (D): A monomer having a (meth)acryloyl group and a linear or branched alkyl group having 1 to 30 carbon atoms. Monomer (E): A monomer having a (meth)acryloyl group and a polar group The copolymer (XC) can be produced by polymerizing the following monomers (C), (D), and (E). Monomer (C): A monomer having a polymerizable functional group and an unsubstituted aromatic group having 6 to 12 ring carbon atoms. Monomer (D): A monomer having a (meth)acryloyl group and a linear or branched alkyl group having 1 to 30 carbon atoms. Monomer (E): A monomer having a (meth)acryloyl group and a polar group

[0083] The step (S) for producing each copolymer will be described in detail below.

[0084] <Steps (S) for producing each copolymer> The method for producing each copolymer (polymerization method) is not particularly limited, and the copolymers can be produced by any of known methods, such as emulsion polymerization, suspension polymerization, and solution polymerization. From the viewpoint of the use of each copolymer in the present embodiment, for example, blending the additive composition into a lubricating oil composition, it is preferable to employ a solution polymerization method in which a solvent that dissolves in the lubricating base oil is used as the solvent for producing each copolymer (polymerization method).

[0085] (solution polymerization method) The solution polymerization method is carried out, for example, by charging raw material monomers, a solvent, and an initiator into a reactor, replacing the atmosphere in the reactor with nitrogen, and then stirring and reacting for 2 to 10 hours at 60 to 100° C. Monomers other than the raw material monomers may also be charged into the reactor as desired. The raw material monomers are monomer (A), monomer (D), and monomer (E) when copolymer (XA) is produced, monomer (B), monomer (D), and monomer (E) when copolymer (XB) is produced, and monomer (C), monomer (D), and monomer (E) when copolymer (XC) is produced.

[0086] The solvent used in the solution polymerization method is not particularly limited, but it is preferable to use, for example, esters such as polyol esters, dibasic acid esters, hindered esters, and monoesters. These may be used alone or in combination of two or more.

[0087] Examples of initiators used in the solution polymerization method include azo initiators such as 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis-(N,N-dimethyleneisobutylamidine) dihydrochloride, 1,1'-azobis(cyclohexyl-1-carbonitrile), and 2,2'-azobis(2,4-dimethylvaleronitrile); 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; and hydrogen peroxide-Fe. 2+ redox initiators; and other existing radical initiators. Examples of chain transfer agents used in solution polymerization include mercaptans, thiocarboxylic acids, secondary alcohols such as isopropanol, amines such as dibutylamine, hypophosphites such as sodium hypophosphite, chlorine-containing compounds, and alkylbenzene compounds.

[0088] The molecular weight of each copolymer can be controlled by a known method, for example, by adjusting the reaction temperature, reaction time, amount of initiator, amount of each monomer, type of solvent, use of a chain transfer agent, etc.

[0089] <Content of copolymer in additive composition> In order to more easily achieve the effects of the present invention, the additive composition of this embodiment preferably contains two or more copolymers selected from the group consisting of copolymer (XA), copolymer (XB), and copolymer (XC) in a total amount of 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, still more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more, based on the total amount of the additive composition. Furthermore, taking into consideration the purity of the copolymers, the total amount of two or more copolymers selected from the group consisting of copolymer (XA), copolymer (XB), and copolymer (XC) is usually less than 99% by mass, based on the total amount of the additive composition. From the viewpoint of ease of handling, the additive composition of the present embodiment may be diluted with a dilution solvent. As the dilution solvent, it is preferable to use the same solvent as the polymerization solvent.

[0090] <Modifications of the Additive Composition> The additive composition of the present embodiment may further contain a copolymer (X) different from the copolymers (XA), (XB), and (XC), in addition to two or more selected from the group consisting of the copolymers (XA), (XB), and (XC). Examples of copolymer (X) include copolymers containing two or more selected from the group consisting of the structural unit (a), the structural unit (b), and the structural unit (c), the structural unit (d), and the structural unit (e). Preferred embodiments of each structural unit are as described above. Copolymer (X) may contain the structural unit (a), the structural unit (b), and the structural unit (c) in the following combinations (5) to (8). (5) Combination of structural unit (a) and structural unit (b) (6) Combination of structural unit (a) and structural unit (c) (7) Combination of structural unit (b) and structural unit (c) (8) Combination of structural unit (a), structural unit (b), and structural unit (c) Of the combinations (5) to (8) above, the combination (5) or (8) above is preferred, and the combination (5) above is more preferred. The copolymer (X) may be composed only of two or more members selected from the group consisting of the structural unit (a), the structural unit (b), and the structural unit (c), the structural unit (d), and the structural unit (e), but may also contain structural units other than these as long as the effects of the present invention are not significantly impaired. The total content of the structural units (a), (b), (c), (d), and (e) in the copolymer (X) is preferably 70 mol% to 100 mol%, more preferably 80 mol% to 100 mol%, even more preferably 90 mol% to 100 mol%, and still more preferably 95 mol% to 100 mol%, based on all structural units in the copolymer (X). The preferred embodiments of each structural unit are as described above.

[0091] (Content of structural units (a), (b), and (c)) In copolymer (X), the total content of two or more structural units selected from the content of structural unit (a) derived from monomer (A), the content of structural unit (b) derived from monomer (B), and the content of structural unit (c) derived from monomer (C) is preferably 7 mol % to 30 mol %, more preferably 8 mol % to 28 mol %, even more preferably 10 mol % to 26 mol %, and still more preferably 10 mol % to 25 mol %, based on all structural units in copolymer (X), from the viewpoint of achieving a good balance between the contents of each structural unit and making it easier to improve the effects of the present invention.

[0092] (Ratio of structural unit (a) to structural units (b) and (c)) When copolymer (X) contains structural unit (a), the ratio of the content of structural unit (a) to the content of one or more types selected from structural units (b) and (c) (preferably structural unit (b)) [content of (a) / total content of (b) and (c)] is preferably 20 / 80 to 80 / 20, more preferably 30 / 70 to 70 / 30, and even more preferably 40 / 60 to 60 / 40, in molar ratio.

[0093] (Ratio of structural unit (b) to structural units (a) and (c)) When copolymer (X) contains structural unit (b), the ratio of the content of structural unit (b) to the content of one or more types selected from structural units (a) and (c) (preferably structural unit (a)) [content of (b) / total content of (a) and (c)] is preferably 20 / 80 to 80 / 20, more preferably 30 / 70 to 70 / 30, and even more preferably 40 / 60 to 60 / 40, in molar ratio.

[0094] (Content of structural unit (d)) In the copolymer (X), the content of the structural unit (d) derived from the monomer (D) is preferably 43 mol% to 84 mol%, more preferably 50 mol% to 80 mol%, and even more preferably 55 mol% to 76 mol%, based on all structural units of the copolymer (X). By ensuring that the content of the structural unit (d) derived from the monomer (D) is within the above range, the oil solubility of the copolymer (X) is appropriate, while the content of each structural unit is well balanced, making it easier to further improve the effects of the present invention.

[0095] (Content of structural unit (e)) In the copolymer (X), the content of the structural unit (e) derived from the monomer (E) is preferably 9 mol % to 50 mol %, more preferably 10 mol % to 40 mol %, and even more preferably 12 mol % to 30 mol %, based on all structural units of the copolymer (X). By ensuring that the content of the structural unit (e) derived from the monomer (E) is within the above range, the oil solubility of the copolymer (X) is appropriate, while the content of each structural unit is well balanced, making it easier to further improve the effects of the present invention.

[0096] (Ratio of structural units (e) and (d)) In order to more easily ensure appropriate oil solubility and appropriate adsorption to metals in copolymer (X), the content ratio of structural unit (e) to structural unit (d) [(e) / (d)], in molar ratio, is preferably 0.15 to 0.50, more preferably 0.20 to 0.45, even more preferably 0.23 to 0.40, and still more preferably 0.25 to 0.35.

[0097] <Uses of the additive composition> The additive composition of this embodiment exhibits excellent antiwear properties and is therefore useful as an antiwear agent. Thus, in this embodiment, there is provided a method of using the additive composition as an anti-wear agent. Furthermore, the additive composition of this embodiment can exhibit excellent anti-wear properties, particularly when blended into a lubricating oil composition. Therefore, in this embodiment, a method of using the additive composition by blending it with a lubricating oil composition is provided.

[0098] [Lubricating oil composition] The lubricating oil composition of this embodiment contains an additive composition containing two or more selected from the group consisting of copolymer (XA), copolymer (XB), and copolymer (XC), and a lubricating base oil. In order to maximize the additive effect of the additive composition, the total content of two or more selected from the group consisting of copolymer (XA), copolymer (XB), and copolymer (XC) is preferably adjusted to 0.1 mass% or more, more preferably 0.2 mass% or more, and even more preferably 0.3 mass% or more, based on the total amount of the lubricating oil composition. Also, the total content of two or more selected from the group consisting of copolymer (XA), copolymer (XB), and copolymer (XC) is preferably adjusted to 10 mass% or less, more preferably 5 mass% or less, and even more preferably 3 mass% or less, based on the total amount of the lubricating oil composition. The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, the range is preferably 0.1 to 10% by mass, more preferably 0.2 to 5% by mass, and even more preferably 0.3 to 3% by mass.

[0099] <Lubricant base oil> The lubricating base oil may be any base oil commonly used in lubricating oil compositions without any particular limitations, and specifically may be one or more selected from the group consisting of mineral oils and synthetic oils. The kinematic viscosity of lubricating base oil at 100°C is 1mm 2 / s~50mm 2 / s, and preferably in the range of 2 mm 2 / s~30mm 2 / s, and more preferably in the range of 3 mm 2 / s~20mm 2 The viscosity index of the lubricating 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 base oil are values ​​measured or calculated in accordance with JIS K2283:2000.

[0100] Specific examples of lubricating base oils are listed below. Examples of mineral oils include distillate oils obtained by atmospheric and / or vacuum distillation of paraffin-based crude oils, intermediate-based crude oils, or naphthene-based crude oils; refined oils obtained by refining the distillate oils according to conventional methods; etc. Refining methods for obtaining refined oils include, for example, solvent dewaxing, hydroisomerization, hydrofinishing, clay treatment, etc. Examples of synthetic oils include hydrocarbon oils, aromatic oils, ester oils, ether oils, etc. Furthermore, as synthetic oils, GTL (Gas to Liquids) obtained by isomerizing wax (GTL wax, Gas to Liquids Wax) produced from natural gas by the Fischer-Tropsch process or the like may be used.

[0101] <Other additives> The lubricating oil composition of this embodiment may contain other additives such as antioxidants, oiliness agents, detergents and dispersants, viscosity index improvers, rust inhibitors, metal deactivators, extreme pressure agents, friction modifiers, and antifoaming agents, as long as the effects of the additive composition are not impaired. Furthermore, antiwear agents other than the above-mentioned copolymers (XA), (XB), and (XC) may also be contained as other additives. These may be used alone or in combination of two or more. In addition, in this embodiment, there is also provided an additive composition (additive package for lubricating oil composition) containing two or more copolymers selected from the group consisting of copolymer (XA), copolymer (XB), and copolymer (XC), as well as one or more other additives selected from antioxidants, oiliness agents, detergent-dispersants, viscosity index improvers, rust inhibitors, metal deactivators, antifoaming agents, and anti-wear agents other than the above-mentioned copolymers (XA), (XB), and (XC).

[0102] <Method of manufacturing lubricating oil composition> The method for producing the lubricating oil composition of this embodiment is not particularly limited, but may include, for example, a step of mixing the additive composition described above with a lubricating base oil. In this case, other additives may be added as necessary.

[0103] <Physical properties of lubricating oil composition> (Kinematic viscosity) The lubricating oil composition of this embodiment preferably has a kinematic viscosity at 100°C of 1.0 mm 2 / s~50mm 2 / s, more preferably 2.0 mm 2 / s~30mm 2 / s, more preferably 3.0 mm 2 / s~20mm 2 / s. The kinematic viscosity of the lubricating oil composition is a value measured in accordance with JIS K2283:2000.

[0104] (wear resistance) The lubricating oil composition of this embodiment preferably has an average wear scar diameter of 0.40 mm or less, more preferably 0.39 mm or less, and even more preferably 0.38 mm or less, as determined by the ball-on-disk test (load 200 N) described in the Examples below. Furthermore, the lubricating oil composition of this embodiment preferably has an average wear scar diameter of 0.46 mm or less, more preferably 0.45 mm or less, and even more preferably 0.44 mm or less, as determined by the ball-on-disk test (load 250 N) described in the Examples below.

[0105] [Uses of lubricating oil composition] The lubricating oil composition of this embodiment has excellent wear resistance because it contains the additive composition of this embodiment. Therefore, the lubricating oil composition of this embodiment can be suitably used for various applications, including, for example, gear oils (manual transmission oils, differential oils, etc.), automatic transmission oils (automatic transmission oils, etc.), continuously variable transmission oils (belt CVT oils, toroidal CVT oils, etc.), dual clutch transmission oils (DCT oils), power steering oils, shock absorber oils, and drive system oils such as electric motor oils; oils for internal combustion engines (engines) such as gasoline engines, diesel engines, and gas engines; hydraulic oils; turbine oils; compressor oils; fluid bearing oils; rolling bearing oils; refrigeration oils, etc., and can be suitably used as a lubricating oil composition that is filled into equipment used in each of these applications and lubricates the components associated with the equipment.

[0106] [Lubrication method using lubricating oil composition] A preferred lubrication method using the lubricating oil composition of this embodiment is a method in which the lubricating oil composition is filled into equipment used for each of the above-mentioned applications and lubricates the components of each of the equipment.

[0107] [One aspect of the present invention provided] According to one aspect of the present invention, the following [1] to

[10] are provided. [1] Contains two or more selected from the group consisting of copolymer (XA), copolymer (XB), and copolymer (XC), The copolymer (XA) contains a structural unit (a) derived from a monomer (A) having a polymerizable functional group and an aromatic group having 6 to 12 ring carbon atoms and an electron-withdrawing group, The copolymer (XB) contains a structural unit (b) derived from a monomer (B) having a polymerizable functional group and an aromatic group having 6 to 12 ring carbon atoms and an electron-donating group, The copolymer (XC) contains a structural unit (c) derived from a monomer (C) having a polymerizable functional group and an unsubstituted aromatic group having 6 to 12 ring carbon atoms, The additive composition, wherein the copolymer (XA), the copolymer (XB), and the copolymer (XC) each independently further contain the following structural unit (d) and the following structural unit (e): Structural unit (d): a structural unit derived from a monomer (D) having a (meth)acryloyl group and a linear or branched alkyl group having 1 to 30 carbon atoms Structural unit (e): a structural unit derived from a monomer (E) having a (meth)acryloyl group and a polar group [2] The additive composition according to the above [1], which contains at least the copolymer (XA) and the copolymer (XB). [3] The additive composition according to the above [1] or [2], wherein the electron-withdrawing group is a functional group containing a fluorine atom. [4] The additive composition according to [3] above, wherein the electron-withdrawing group is a trifluoromethyl group. [5] The additive composition according to any one of the above [1] to [4], wherein the electron-donating group is an alkyl group having 1 to 10 carbon atoms or an alkoxy group having 1 to 10 carbon atoms. [6] The additive composition according to any one of the above [1] to [5], wherein the mass average molecular weight of the copolymer (XA), the copolymer (XB), and the copolymer (XC) is each independently 5,000 to 30,000. [7] The additive composition according to any one of the above [1] to [6], which is used as an anti-wear agent. [8] The additive composition according to any one of the above [1] to [7], which is blended into a lubricating oil composition. [9] A lubricating oil composition comprising the additive composition according to any one of the above [1] to [8] and a lubricating base oil.

[10] A method for producing a lubricating oil composition, comprising the step of mixing the additive composition according to any one of the above [1] to [8] with a lubricating base oil. [Example]

[0108] The present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples.

[0109] [Methods for measuring various physical properties] Various physical properties of the raw materials used in the examples were measured by the following methods. (1)Kinematic viscosity, viscosity index The 40°C kinematic viscosity, 100°C kinematic viscosity and viscosity index of the lubricating base oil and lubricating oil composition were measured or calculated in accordance with JIS K2283:2000. (2) Mass average molecular weight One Tosoh Corporation column, "TSKguardcolumn SuperHZ-L," and two Tosoh Corporation columns, "TSKSuperMultipore HZ-M," were attached to a Waters "1515 Isocratic HPLC Pump" and a "2414 Refractive Index (RI) Detector," in that order from the upstream side. Measurements were performed under the following conditions: measurement temperature: 40°C, mobile phase: tetrahydrofuran, flow rate: 0.35 mL / min, sample concentration: 1.0 mg / mL, and the results were calculated in terms of standard polystyrene.

[0110] [Manufacturing Examples 1 to 5] Each copolymer was produced according to Production Examples 1 to 5 described below.

[0111] <Monomers used> (Monomer (A)) 4-(Trifluoromethyl)benzyl acrylate: In the above general formula (c-1), Y is an acryloyl group, L is an oxymethylene group, and Z is a phenyl group, and this is a monomer having a trifluoromethyl group, which is an electron-withdrawing group, as a substituent (substitution position: para position, represented as "p-CF3" in Table 1). 4-(Trifluoromethyl)benzyl acrylate was synthesized by the following method. -Synthesis method- 4-(Trifluoromethyl)benzyl alcohol and triethylamine were dissolved in tetrahydrofuran and cooled to 0°C. Acryloyl chloride dissolved in tetrahydrofuran was added dropwise thereto using a dropping funnel over 30 minutes. After the dropwise addition was complete, the mixture was stirred at room temperature to 40°C for 6 hours. After the reaction was complete, water and ethyl acetate were added and the aqueous layer was separated. The organic layer was dried over anhydrous sodium sulfate, and the anhydrous sodium sulfate was filtered off and the solvent was distilled off. The residue was then purified by silica gel column chromatography to obtain 4-(trifluoromethyl)benzyl acrylate. (Monomer (B)) 4-Methoxybenzyl acrylate: In the above general formula (c-1), Y is an acryloyl group, L is an oxymethylene group, and Z is a phenyl group, and this is a monomer having a methoxy group, which is an electron-donating group, as a substituent (substitution position: para position, represented as "p-OMe" in Table 1). 4-Methoxybenzyl acrylate was synthesized by the same method as in the synthesis method described in the Monomer (A) column, except that 4-(trifluoromethyl)benzyl alcohol was replaced with 4-methoxybenzyl alcohol. 3,5-Dimethoxybenzyl acrylate: In the above general formula (c-1), Y is an acryloyl group, L is an oxymethylene group, and Z is a phenyl group. This is a monomer having two electron-donating methoxy groups as substituents (substitution positions: meta positions (3rd and 5th positions), represented as m-(OMe) in Table 1). 3,5-Dimethoxybenzyl acrylate was synthesized by the same method as in the synthesis method described in the Monomer (A) column, except that 4-(trifluoromethyl)benzyl alcohol was changed to 3,5-dimethoxybenzyl alcohol. 4-tert-Butylbenzyl acrylate: In the above general formula (c-1), Y is an acryloyl group, L is an oxymethylene group, Z is a phenyl group, and this is a monomer having a tert-butyl group, which is an electron-donating group, as a substituent (substitution position: para position, represented as "p-tBu" in Table 1). 4-tert-Butylbenzyl acrylate was synthesized by the same method as in the synthesis method described in the Monomer (A) column, except that 4-(trifluoromethyl)benzyl alcohol was replaced with 4-tert-butylbenzyl alcohol. (Monomer (C)) "Benzyl acrylate": A monomer in which, in the above general formula (c-1), Y is an acryloyl group, L is an oxymethylene group, and Z is a phenyl group (shown as "unsubstituted" in Table 1). (Monomer (D)) "Dodecyl acrylate": In the above general formula (a-1), R a1 is a hydrogen atom, and R a2 is a compound in which the alkyl group is an n-dodecyl group (a straight-chain alkyl group with 12 carbon atoms). (Monomer (E)) 2-Hydroxyethyl acrylate: A monomer containing an acryloyl group and a hydroxyl group as a polar group. The structural formula is shown below. [ka]

[0112] <Production Example 1: Production of Copolymer (XA)-1> A reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, and a nitrogen inlet tube was charged with 5.4 g (24 mmol) of monomer (A), 21.7 g (90 mmol) of monomer (D), 3.0 g (26 mmol) of monomer (E), and 20 g of bis(2-ethylhexyl) sebacate as a solvent. Next, the atmosphere in the reaction vessel was replaced with nitrogen, and 0.25 g (0.4 mmol) of azobisisobutyronitrile and 0.2 g (0.4 mmol) of dodecyl mercaptan were added as initiators. The mixture was then slowly heated with stirring, and reacted at 80°C for 3 hours and at 100°C for 1 hour. After the reaction was completed, unreacted monomer was distilled off under reduced pressure to obtain copolymer (XA)-1. The mass average molecular weight of the copolymer (XA)-1 was 25,000. The ratio (molar ratio) of the monomers in the copolymer (XA)-1 was monomer (A):monomer (D):monomer (E)=17:65:18.

[0113] <Production Example 2: Production of Copolymer (XB)-1> A reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, and a nitrogen inlet tube was charged with 4.6 g (24 mmol) of 4-methoxybenzyl acrylate as monomer (B), 21.7 g (90 mmol) of monomer (D), 3.0 g (26 mmol) of monomer (E), and 20 g of bis(2-ethylhexyl) sebacate as a solvent. Next, the atmosphere in the reaction vessel was replaced with nitrogen, and 0.25 g (0.4 mmol) of azobisisobutyronitrile and 0.2 g (0.4 mmol) of dodecyl mercaptan were added as initiators. The mixture was then slowly heated with stirring, and reacted at 80°C for 3 hours and at 100°C for 1 hour. After the reaction was completed, unreacted monomers were distilled off under reduced pressure to obtain copolymer (XB)-1. The mass average molecular weight of the copolymer (XB)-1 was 24,000. The ratio (molar ratio) of the monomers in the copolymer (XB)-1 was monomer (B):monomer (D):monomer (E)=17:65:18.

[0114] <Production Example 3: Production of Copolymer (XB)-2> A reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, and a nitrogen inlet tube was charged with 5.2 g of 3,5-dimethoxybenzyl acrylate as monomer (B), 21.7 g (90 mmol) of monomer (D), 3.0 g (26 mmol) of monomer (E), and 20 g of bis(2-ethylhexyl) sebacate as a solvent. Next, the atmosphere in the reaction vessel was replaced with nitrogen, and 0.25 g (0.4 mmol) of azobisisobutyronitrile and 0.2 g (0.4 mmol) of dodecyl mercaptan were added as initiators. The mixture was then slowly heated with stirring, and reacted at 80°C for 3 hours and at 100°C for 1 hour. After the reaction was completed, unreacted monomers were distilled off under reduced pressure to obtain copolymer (XB)-2. The mass average molecular weight of the copolymer (XB)-2 was 23,000. The ratio (molar ratio) of the monomers in the copolymer (XB)-2 was monomer (B):monomer (D):monomer (E)=17:65:18.

[0115] <Production Example 4: Production of Copolymer (XB)-3> A reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, and a nitrogen inlet tube was charged with 5.2 g (24 mmol) of 4-tert-butylbenzyl acrylate as monomer (B), 21.7 g (90 mmol) of monomer (D), 3.0 g (26 mmol) of monomer (E), and 20 g of bis(2-ethylhexyl) sebacate as a solvent. Next, the atmosphere in the reaction vessel was replaced with nitrogen, and 0.25 g (0.4 mmol) of azobisisobutyronitrile and 0.2 g (0.4 mmol) of dodecyl mercaptan were added as initiators. The mixture was then slowly heated with stirring, and reacted at 80°C for 3 hours and at 100°C for 1 hour. After the reaction was completed, unreacted monomers were distilled off under reduced pressure to obtain copolymer (XB)-3. The mass average molecular weight of the copolymer (XB)-3 was 24,000. The ratio (molar ratio) of the monomers in the copolymer (XB)-3 was monomer (B):monomer (D):monomer (E)=17:65:18.

[0116] <Production Example 5: Production of Copolymer (XC)-1> Into a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, and a nitrogen inlet tube, 3.9 g (24 mmol) of monomer (C), 21.7 g (90 mmol) of monomer (D), 3.0 g (26 mmol) of monomer (E), and 20 g of bis(2-ethylhexyl) sebacate as a solvent were charged. Next, the atmosphere in the reaction vessel was replaced with nitrogen, and 0.25 g (0.4 mmol) of azobisisobutyronitrile and 0.2 g (0.4 mmol) of dodecyl mercaptan were added as initiators. The mixture was then slowly heated with stirring, and reacted at 80°C for 3 hours and at 100°C for 1 hour. After the reaction was completed, unreacted monomer was distilled off under reduced pressure to obtain copolymer (XC)-1. The mass average molecular weight of the copolymer (XC)-1 was 27,000. The ratio (molar ratio) of the monomers in the copolymer (XC)-1 was monomer (C):monomer (D):monomer (E)=17:65:18.

[0117] [Examples 1 to 7 and Comparative Examples 1 to 10] The lubricating base oil and each of the copolymers produced in Production Examples 1 to 5 were mixed in the following combinations to prepare the following lubricating oil compositions, which were then subjected to the evaluation of wear resistance described below. (Combination of Copolymers in Each Lubricating Oil Composition) Lubricating oil composition 1: Copolymer (XA)-1 and copolymer (XB)-1 Lubricating oil composition 2: Copolymer (XA)-1 and copolymer (XB)-2 Lubricating oil composition 3: Copolymer (XA)-1 and copolymer (XB)-3 Lubricating oil composition 4: Copolymer (XA)-1 and copolymer (XC)-1 ·Lubricating oil composition 1': Copolymer (XA)-1 ·Lubricating oil composition 2': Copolymer (XB)-1 ·Lubricating oil composition 3': Copolymer (XB)-2 ·Lubricating oil composition 4': Copolymer (XB)-3 ·Lubricating oil composition 5': Copolymer (XC)-1

[0118] The lubricant base oil is mineral oil (kinematic viscosity at 100°C: 5.3 mm 2 / s, viscosity index: 104, API classification: Group II). The content of the lubricating base oil in the lubricating oil composition was 99 mass % based on the total amount of the lubricating oil composition.

[0119] Each copolymer produced in Production Examples 1 to 5 was dissolved in bis(2-ethylhexyl) sebacate, a polymerization solvent (hereinafter also referred to as "solvent"), and blended into a lubricating base oil. The mixing ratio of the copolymer to bis(2-ethylhexyl) sebacate was 1:1 (mass ratio). The content of each copolymer (including solvent) in the lubricating oil composition was 1 mass % based on the total amount of the lubricating oil composition, and therefore the content of each copolymer (content of each copolymer excluding solvent) in the lubricating oil composition was 0.5 mass % based on the total amount of the lubricating oil composition. However, when two copolymers were blended, as in lubricating oil compositions 1 to 4, the content of each copolymer (the content of each copolymer excluding the solvent) was 0.25 mass% based on the total amount of the lubricating oil composition, and the total content of the blended copolymers (the total content of each copolymer excluding the solvent) was 0.5 mass% based on the total amount of the lubricating oil composition.

[0120] <Wear resistance evaluation (ball-on-disk test)> Using a high-speed reciprocating friction tester TE77 (manufactured by Phoenix Tribology), the lubricating oil composition was introduced between the test plate and the test ball, and the test ball was moved under the following conditions to perform the test. After the test, the wear scar diameter of the test ball was measured. The measurement was performed once, and the average values ​​of the vertical and horizontal wear scar diameters were calculated. Test plate Material: SUJ2, Shape: Length 58mm x Width 38mm x Thickness 3.9mm Test ball: Material: SUJ2, diameter 10mm ·Lubricating conditions: oil bath, oil amount 3mL Load: 50N (5 minutes) → 100N (5 minutes) → 150N (5 minutes) → 200N (5 minutes) ·Temperature: 100℃ ·Amplitude: 10mm Frequency: 10Hz The smaller the wear scar diameter, the more excellent the wear resistance of the lubricating oil composition. The results are shown in Table 1. Table 2 shows the results of the above ball-on-disk test under the following load conditions. Load: 50N (5 minutes) → 100N (5 minutes) → 150N (5 minutes) → 200N (5 minutes) → 250N (5 minutes)

[0121] [Table 1]

[0122] [Table 2]

[0123] From Table 1, we can see the following: It can be seen that when copolymers are blended in specific combinations as in Examples 1 to 4, the abrasion resistance is improved compared to when a copolymer is blended alone as in Comparative Examples 1 to 5. Furthermore, the results shown in Table 2 show that similar results are obtained when the load is increased to 250N.

Claims

1. Contains two or more selected from the group consisting of copolymer (XA), copolymer (XB), and copolymer (XC), The copolymer (XA) contains a structural unit (a) derived from a monomer (A) having a polymerizable functional group and an aromatic group having 6 to 12 ring carbon atoms and an electron-withdrawing group, The copolymer (XB) contains a structural unit (b) derived from a monomer (B) having a polymerizable functional group and an aromatic group having 6 to 12 ring carbon atoms and an electron-donating group, The copolymer (XC) contains a structural unit (c) derived from a monomer (C) having a polymerizable functional group and an unsubstituted aromatic group having 6 to 12 ring carbon atoms, The additive composition, wherein the copolymer (XA), the copolymer (XB), and the copolymer (XC) each independently further contain the following structural unit (d) and the following structural unit (e): Structural unit (d): a structural unit derived from a monomer (D) having a (meth)acryloyl group and a linear or branched alkyl group having 1 to 30 carbon atoms Structural unit (e): a structural unit derived from a monomer (E) having a (meth)acryloyl group and a polar group

2. The additive composition according to claim 1, comprising at least the copolymer (XA) and the copolymer (XB).

3. 3. The additive composition according to claim 1, wherein the electron-withdrawing group is a functional group containing a fluorine atom.

4. 4. The additive composition of claim 3, wherein the electron-withdrawing group is a trifluoromethyl group.

5. 5. The additive composition according to claim 1, wherein the electron-donating group is an alkyl group having 1 to 10 carbon atoms and an alkoxy group having 1 to 10 carbon atoms.

6. The additive composition according to any one of claims 1 to 5, wherein the mass average molecular weight of the copolymer (XA), the copolymer (XB), and the copolymer (XC) is each independently 5,000 to 30,000.

7. The additive composition according to any one of claims 1 to 6, which is used as an anti-wear agent.

8. The additive composition according to any one of claims 1 to 7, which is blended into a lubricating oil composition for use.

9. A lubricating oil composition comprising the additive composition according to any one of claims 1 to 8 and a lubricating base oil.

10. A method for producing a lubricating oil composition, comprising the step of mixing the additive composition according to any one of claims 1 to 8 with a lubricating base oil.

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