Lubricating oil composition

Abstract

The present invention addresses the problem of providing a lubricant oil composition which has a small viscosity, and in which the friction coefficient thereof can be kept at a low level and the variation in the friction coefficient can be reduced. The problem can be solved by a lubricant oil composition comprising a base oil (P) and a copolymer (X), in which the copolymer (X) contains the following constituent units (a) to (c): constituent unit (a): a constituent unit derived from a monomer (A) having a (meth)acryloyl group and a linear or branched alkyl group having 6 to 24 carbon atoms; constituent unit (b): a constituent unit derived from a monomer (B) having a (meth)acryloyl group and a polar group; and constituent unit (c): a constituent unit derived from a monomer (C) having a polymerizable functional group and a cyclic structure group. The copolymer (X) has a mass average molecular weight (Mw) of 5,000 to 50,000, the content of the copolymer (X) in terms of resin content is 0.10% by mass to 2.5% by mass relative to the whole amount of the lubricant oil composition, and the 100°C dynamic viscosity is 8.2 mm2 / s or less.

Description

[Technical Field]

[0001] This invention relates to a lubricating oil composition. [Background technology]

[0002] In recent years, from the perspective of reducing environmental impact, there has been a demand for improved fuel efficiency in vehicles such as automobiles. One method for improving fuel efficiency is to reduce the viscosity of the lubricating oil composition, thereby reducing stirring losses and the viscous resistance of the oil film, and thus reducing energy loss (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2004-137317 [Overview of the project] [Problems that the invention aims to solve]

[0004] Incidentally, the viscosity of the lubricating oil composition strongly influences the formation of the oil film. Higher viscosity results in a thicker oil film, while lower viscosity results in a thinner oil film. As viscosity decreases, oil film breakdown becomes more likely, and the boundary lubrication region increases. Therefore, if the viscosity of the lubricating oil composition is reduced to the extent necessary to improve fuel efficiency, the coefficient of friction will increase. From the perspective of ensuring good lubrication, it is desirable to maintain a low coefficient of friction without increasing it, even when the viscosity of the lubricating oil composition is reduced to the extent necessary to reduce fuel consumption.

[0005] Furthermore, as the boundary lubrication region increases, the frequency of direct contact between parts (e.g., metal parts) in the lubricated area increases. Therefore, even if the average value of the friction coefficient can be kept low for the entire lubricated area, at a microscopic level, there may be areas where the friction coefficient is prone to increasing or where the friction coefficient is already increasing. Consequently, when measuring the friction coefficient with a vibration friction and wear tester (SRV tester), the variation in the friction coefficient may become large. Large variations in the coefficient of friction can cause vibration and noise in mechanisms and other components equipped with the aforementioned parts; therefore, it is desirable to minimize variations in the coefficient of friction as much as possible.

[0006] Therefore, the object of the present invention is to provide a lubricating oil composition that can maintain a low coefficient of friction while having low viscosity, and can also suppress variations in the coefficient of friction. [Means for solving the problem]

[0007] The inventors of the present invention conducted diligent research to solve the above problems. As a result, they discovered that a lubricating oil composition containing a copolymer with constituent units derived from multiple specific monomers can solve the above problems, leading to the completion of the present invention.

[0008] In other words, the present invention relates to the following [1]. [1] Contains a base oil (P) and a copolymer (X), The copolymer (X) comprises the following constituent units (a) to (c): • Constituent unit (a): A constituent unit derived from monomer (A) having a (meth)acryloyl group and a linear or branched alkyl group having 6 to 24 carbon atoms. • Constituent unit (b): Constituent unit derived from monomer (B) having a (meth)acryloyl group and a polar group • Constituent unit (c): A constituent unit derived from a monomer (C) having a polymerizable functional group and a cyclic structural group. The copolymer (X) has a mass-average molecular weight (Mw) of 5,000 to 50,000. The content of the copolymer (X) on a resin basis is 0.10% to 2.5% by mass on a total basis of the lubricating oil composition. The kinematic viscosity at 100°C is 8.2 mm². 2 A lubricating oil composition with a viscosity of / s or less. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a lubricating oil composition that can maintain a low coefficient of friction while having low viscosity, and can also suppress variations in the coefficient of friction. [Modes for carrying out the invention]

[0010] The upper and lower limits of the numerical ranges described herein can be combined in any way. For example, if the numerical ranges "A to B" and "C to D" are described, the numerical ranges "A to D" and "C to B" are also included within the scope of the present invention. Furthermore, unless otherwise specified, the numerical range "lower limit to upper limit" described herein means that the value is greater than or equal to the lower limit and less than or equal to the upper limit. Furthermore, in this specification, the numerical values ​​in the examples are values ​​that can be used as upper or lower limits.

[0011] In this specification, "(meth)acrylate" means acrylate or methacrylate, and the same applies to other similar terms.

[0012] In this specification, "ring-forming carbon number" refers to the number of carbon atoms among the atoms that constitute the ring itself in a compound with a structure in which atoms are bonded in a ring. If the ring is substituted by a substituent, the carbon atoms in the substituent are not included in the ring-forming carbon number. The same applies to "ring-forming carbon number" as described below unless otherwise specified. For example, a benzene ring has 6 ring-forming carbon atoms. Furthermore, if a benzene ring is substituted with a substituent, such as an alkyl group, the carbon atoms of the alkyl group are not included in the ring-forming carbon number of the benzene ring. Therefore, the ring-forming carbon number of a benzene ring substituted with an alkyl group is 6.

[0013] In this specification, "ring-forming atom number" refers to the number of atoms that constitute the ring itself in a compound with a structure in which atoms are bonded in a ring. Atoms that do not constitute a ring (for example, hydrogen atoms that terminate the bonds of atoms that constitute a ring) and atoms included in substituents when the ring is substituted by substituents are not included in the ring-forming atom number. The same applies to "ring-forming atom number" as described below unless otherwise specified. For example, the ring-forming atom number of a pyridine ring is 6. In addition, the number of hydrogen atoms bonded to the pyridine ring, or atoms that constitute a substituent, are not included in the number of pyridine ring-forming atoms. Therefore, the ring-forming atom number of a pyridine ring to which hydrogen atoms or substituents are bonded is 6.

[0014] [Aspects of lubricating oil composition] The lubricating oil composition of this embodiment contains a base oil (P) and a copolymer (X). The copolymer (X) contains the following constituent units (a) to (c). • Constituent unit (a): A constituent unit derived from monomer (A) having a (meth)acryloyl group and a linear or branched alkyl group having 6 to 24 carbon atoms. • Constituent unit (b): Constituent unit derived from monomer (B) having a (meth)acryloyl group and a polar group • Constituent unit (c): A constituent unit derived from a monomer (C) having a polymerizable functional group and a cyclic structural group. Copolymer (X) has a mass-average molecular weight (Mw) of 5,000 to 50,000. The content of copolymer (X) in terms of resin content is 0.10% to 2.5% by mass, based on the total amount of the lubricating oil composition. Furthermore, the kinematic viscosity of the lubricating oil composition at 100°C is 8.2 mm². 2 It is less than or equal to / s.

[0015] The inventors diligently conducted research to solve the above problems. As a result, they found that a lubricating oil composition containing copolymer (X) has a kinematic viscosity of 8.2 mm at 100°C. 2 Despite the low viscosity (below / s), we found that the coefficient of friction was kept low, and the variation in the coefficient of friction was also suppressed. The reason why copolymer (X) exhibits these effects is presumed to be as follows: (1) Appropriate oil solubility is ensured by including the above constituent unit (a). (2) By including the above constituent unit (b), a multi-point adsorption type copolymer is formed. (3) The inclusion of the above-mentioned structural unit (c) generates intermolecular interactions due to the cyclic structural group. As a result, when the copolymer (X) is adsorbed onto the surfaces of two opposing members, a moderate repulsive force is generated between the members, resulting in a friction reduction effect. (4) By adjusting the mass-average molecular weight (Mw) of the copolymer (X) to a certain range, the copolymer (X) can easily penetrate between the two opposing members, and the friction-reducing effect of the copolymer (X) can be fully exerted.

[0016] In the following explanation, "base oil (P)" and "polymer (X)" will also be referred to as "component (P)" and "component (X)," respectively.

[0017] In the lubricating oil composition according to this embodiment, the total content of component (P) and component (X) is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more, based on the total amount of the lubricating oil composition. In the lubricating oil composition according to this embodiment, the upper limit of the total content of component (P) and component (X) can be adjusted in relation to other lubricating oil additives, and is usually less than 100% by mass, preferably 99% by mass or less, more preferably 97% by mass or less, and even more preferably 95% by mass or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, preferably they are 70% by mass to less than 100% by mass, more preferably 75% by mass to 99% by mass or less, even more preferably 80% by mass to 97% by mass, and even more preferably 80% by mass to 95% by mass.

[0018] The components included in the lubricating oil composition according to this embodiment will be described in detail below.

[0019] [Base oil (P)] The lubricating oil composition of this embodiment contains a base oil (P). As the base oil (P), one or more types selected from mineral oils and synthetic oils that have been conventionally used as lubricating oil base oils can be used without particular limitation.

[0020] Examples of mineral oils include atmospheric residue obtained by atmospheric distillation of crude oil such as paraffinic crude oil, intermediate crude oil, and naphthenic crude oil; distillate obtained by vacuum distillation of the atmospheric residue; and mineral oil obtained by subjecting the distillate to one or more refining treatments such as solvent dewaxing, solvent extraction, hydrotrining, hydrocracking, advanced hydrocracking, solvent dewaxing, catalytic dewaxing, and hydroisomerization dewaxing.

[0021] Examples of synthetic oils include poly-α-olefins such as α-olefin homopolymers and α-olefin copolymers (e.g., 8-14 carbon olefin copolymers such as ethylene-α-olefin copolymers); isoparaffins; various esters such as polyol esters and dibasic acid esters; various ethers such as polyphenyl ethers; polyalkylene glycols; alkylbenzenes; alkylnaphthalenes; and GTL base oils obtained by isomerizing waxes (GTL waxes, Gas To Liquids Wax) produced from natural gas by the Fischer-Tropsch process, etc.

[0022] In this embodiment, the base oil (P) used is preferably a base oil classified as Group II or III of the API (American Petroleum Institute) base oil category.

[0023] As the base oil (P), one type selected from mineral oils may be used alone, or two or more types may be used in combination. Alternatively, one type selected from synthetic oils may be used alone, or two or more types may be used in combination. Furthermore, one or more types of mineral oil and one or more types of synthetic oil may be used in combination.

[0024] The kinematic viscosity and viscosity index of the base oil (P) are preferably within the following ranges, with the upper limit being from the viewpoint of achieving good fuel efficiency, and the lower limit being from the viewpoint of reducing the loss of the lubricating oil composition due to evaporation and ensuring oil film retention. The kinematic viscosity of base oil (P) at 100 °C is 2.0 mm 2 / s to 7.0 mm 2 / s is preferable, and 2.0 mm 2 / s to 6.0 mm 2 / s is more preferable, and 2.0 mm 2 / s to 5.0 mm 2 / s is even more preferable. The viscosity index of base oil (P) is preferably 80 or more, more preferably 90 or more, and even more preferably 100 or more. The kinematic viscosity at 100 °C and the viscosity index are values measured or calculated in accordance with JIS K 2283:2000. Further, when base oil (P) is a mixed base oil containing two or more kinds of base oils, it is preferable that the kinematic viscosity and the viscosity index of the mixed base oil are within the above ranges.

[0025] In the lubricating oil composition of the present embodiment, although the content of base oil (P) is not particularly limited, from the viewpoint of more easily exerting the effects of the present invention, based on the total amount of the lubricating oil composition, it is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. Also, it is preferably less than 98.5% by mass, more preferably 97% by mass or less, and even more preferably 95% by mass or less. The upper limit value and the lower limit value of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 60% by mass to less than 98.5% by mass, more preferably 70% by mass to 97% by mass, and even more preferably 80% by mass to 95% by mass.

[0026] [Copolymer (X)] Copolymer (X) contains the following structural units (a) to (c). · Structural unit (a): A structural unit derived from monomer (A) having a (meth)acryloyl group and a linear or branched alkyl group having 6 to 24 carbon atoms · Structural unit (b): A structural unit derived from monomer (B) having a (meth)acryloyl group and a polar group · Structural unit (c): A structural unit derived from monomer (C) having a polymerizable functional group and a cyclic structural group

[0027] In this embodiment, the copolymer (X) may consist only of constituent units (a) derived from monomer (A), constituent units (b) derived from monomer (B), and constituent units (c) derived from monomer (C). However, it may also contain other constituent units other than constituent units (a), (b), and (c) as long as the effects of the present invention are not impaired. In this embodiment, the total content of constituent units (a), (b), and (c) in copolymer (X) 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 the total constituent units of copolymer (X).

[0028] The monomers (A) through (C) will be explained in detail below.

[0029] <Monomer (A), constituent unit (a)> The monomer (A) used in this embodiment has a (meth)acryloyl group and a linear or branched alkyl group having 6 to 24 carbon atoms. The constituent unit (a) derived from monomer (A) plays a primary role in the copolymer (X) in providing oil solubility (solubility in mineral oil). Furthermore, monomer (A) may be used alone or in combination of two or more types. Therefore, copolymer (X) may contain one or more constituent units (a) derived from monomer (A). In this specification, monomer (A) is not included in monomer (B) and monomer (C). Therefore, constituent unit (a) derived from monomer (A) is also not included in constituent unit (b) derived from monomer (B) and constituent unit (c) derived from monomer (C).

[0030] (Monomer (A1), constituent unit (a1)) In this embodiment, from the viewpoint of making it easier to exhibit the effects of the present invention, it is preferable that monomer (A) includes monomer (A1) represented by the following general formula (a-1). That is, it is preferable that constituent unit (a) includes constituent unit (a1) derived from monomer (A1). [ka]

[0031] In the above general formula (a-1), R a1 This is a hydrogen atom or a methyl group. That is, monomer (A1) has an acryloyl group or a methacryloyl group as a polymerizable functional group. R a1 Monomers in which substituents other than hydrogen atoms and methyl groups are difficult to obtain, and because such monomers have low reactivity, polymerization of them is also difficult. Furthermore, from the perspective of making it easier to improve wear resistance, R a1 It is preferable that the polymerizable functional group of monomer (A1) is a hydrogen atom. In other words, it is preferable that the polymerizable functional group of monomer (A1) is an acryloyl group.

[0032] In the above general formula (a-1), R a2 This represents a linear or branched alkyl group having 6 to 24 carbon atoms. If the alkyl group has fewer than 6 carbon atoms, or if the alkyl group has more than 24 carbon atoms, it becomes difficult to ensure the oil solubility of copolymer (X).

[0033] R a2 Examples of linear alkyl groups having 6 to 24 carbon atoms that can be selected include n-hexyl group, n-octyl group, n-decyl group, n-dodecyl group, n-tetradecyl group, n-hexadecyl group, n-octadecyl group, n-icosyl group, n-docosyl group, and n-tetracosyl group. Examples of branched alkyl groups having 6 to 24 carbon atoms include isooctyl, tert-octyl, 2-ethylhexyl, isononyl, isodecyl, and isooctadecyl groups.

[0034] Here, from the viewpoint of more easily ensuring the oil solubility of the poly(meth)acrylate copolymer (X), the number of carbon atoms in the alkyl group is preferably 7 or more, more preferably 8 or more. Furthermore, it is preferably 22 or less, more preferably 20 or less.

[0035] The constituent unit (a1) derived from monomer (A1) may consist of one type alone or two or more types. In this specification, monomer (A1) is not included in monomer (B) and monomer (C). Therefore, the constituent unit (a1) derived from monomer (A1) is also not included in the constituent unit (b) derived from monomer (B) and the constituent unit (c) derived from monomer (C).

[0036] (Content of constituent unit (a1)) In this embodiment, the content of constituent unit (a1) is preferably 50 mol% to 100 mol%, more preferably 60 mol% to 100 mol%, even more preferably 70 mol% to 100 mol%, even more preferably 80 mol% to 100 mol%, and still more preferably 90 mol% to 100 mol%, based on the total constituent units of constituent unit (a).

[0037] <Monomer (B), constituent unit (b)> The monomer (B) used in this embodiment has a (meth)acryloyl group and a polar group. The constituent unit (b) derived from monomer (B) is thought to play a role in making the copolymer (X) a multi-point adsorption type copolymer, thereby contributing to improved wear resistance. Furthermore, monomer (B) may be used alone or in combination of two or more types. Therefore, copolymer (X) may contain one or more constituent units (b) derived from monomer (B). In this specification, monomer (B) is not included in monomer (A) and monomer (C). Therefore, the constituent unit (b) derived from monomer (B) is also not included in the constituent unit (a) derived from monomer (A) and the constituent unit (c) derived from monomer (C).

[0038] (Monomer (B1), constituent unit (b1)) In this embodiment, from the viewpoint of making it easier to exhibit the effects of the present invention and from the viewpoint of suppressing clouding of the lubricating oil composition, monomer (B) preferably contains monomer (B1) having one or more groups selected from the group consisting of nitrogen atom-containing groups, hydroxyl groups, and carboxyl groups as polar groups. That is, constituent unit (b) preferably contains a (meth)acryloyl group and constituent unit (b1) derived from monomer (B1) having these polar groups.

[0039] • A monomer having a (meth)acryloyl group and a nitrogen atom-containing group 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.

[0040] 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. Examples include monoalkylaminoalkyl(meth)acrylamides such as mid; dialkylamino(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; and 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.

[0041] Examples of primary amino group-containing acrylic monomers include aminoalkyl (meth)acrylates having an alkyl group with 2 to 6 carbon atoms, such as aminoethyl (meth)acrylate.

[0042] Examples of secondary amino group-containing acrylic monomers include monoalkylaminoalkyl(meth)acrylates such as tert-butylaminoethyl(meth)acrylate and methylaminoethyl(meth)acrylate.

[0043] Examples of tertiary amino group-containing acrylic monomers include dialkylaminoalkyl(meth)acrylates such as dimethylaminoethyl(meth)acrylate and diethylaminoethyl(meth)acrylate.

[0044] Examples of nitrile group-containing acrylic monomers include (meth)acrylonitrile. Examples of urea-containing acrylic monomers include 2-isocyanatoethyl (meth)acrylate. Examples of urethane group-containing acrylic monomers include monofunctional urethane (meth)acrylates.

[0045] • A monomer having a (meth)acryloyl group and a hydroxyl group Examples of monomers 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.

[0046] • A monomer having a (meth)acryloyl group and a carboxyl group Examples of monomers 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.

[0047] • Preferred acrylic monomers Among the acrylic monomers mentioned above, from the viewpoint of making it easier to exhibit the effects of the present invention, one or more selected from dialkylaminoalkyl(meth)acrylamide, hydroxyalkyl(meth)acrylate, and carboxyalkyl(meth)acrylate are preferred, with hydroxyalkyl(meth)acrylate being more preferred. The number of carbon atoms in the alkyl group of these monomers is preferably 1 to 6, more preferably 1 to 4.

[0048] The constituent unit (b1) derived from the monomer (B1) may consist of one type alone or two or more types. In this specification, monomer (B1) is not included in monomer (A) and monomer (C). Therefore, the constituent unit (b1) derived from monomer (B1) is also not included in the constituent unit (a) derived from monomer (A) and the constituent unit (c) derived from monomer (C).

[0049] (Content of constituent unit (b1)) In this embodiment, the content of constituent unit (b1) is preferably 50 mol% to 100 mol%, more preferably 60 mol% to 100 mol%, even more preferably 70 mol% to 100 mol%, even more preferably 80 mol% to 100 mol%, and still more preferably 90 mol% to 100 mol%, based on the total constituent units of constituent unit (b).

[0050] (Monomer (B2), constituent unit (b2)) In this embodiment, from the viewpoint of making it easier to exhibit the effects of the present invention and from the viewpoint of suppressing clouding of the lubricating oil composition, it is preferable that the content of constituent units (b2) derived from monomers (B2) having a polyoxyalkylene group as a polar group is low. Specifically, the content of constituent units (b2) derived from monomer (B2) having a (meth)acryloyl group and a polyoxyalkylene group is preferably less than 5 mol%, more preferably less than 1 mol%, even more preferably less than 0.1 mol%, and most preferably no constituent units (b2) are present, based on the total constituent units of constituent unit (b).

[0051] Examples of monomers (B2) having a (meth)acryloyl group and a polyoxyalkylene group include polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol monomethyl ether acrylate, and lauryl alcohol ethylene oxide adduct (meth)acrylate. Furthermore, a polyoxyalkylene group has, for example, 2 to 4 carbon atoms in its alkylene chain, and a degree of polymerization of 2 or more (for example, 2 to 50).

[0052] <Monomers (C) having polymerizable functional groups and cyclic structural groups> The monomer (C) used in the present invention has a polymerizable functional group and a cyclic structural group. It is presumed that the constituent unit (c) derived from the monomer (C) plays a role in the copolymer (X) in exhibiting a friction-reducing effect. Specifically, it is presumed that the intermolecular interactions due to the cyclic structural group of the constituent unit (c) generate an appropriate repulsive force between the two opposing members when the copolymer (X) is adsorbed onto their surfaces, thereby exhibiting a friction-reducing effect. Furthermore, monomer (C) may be used alone or in combination of two or more types. Therefore, copolymer (X) may contain one or more constituent units (c) derived from monomer (C). In this specification, monomer (C) is not included in monomer (A) and monomer (B). Therefore, the constituent unit (c) derived from monomer (C) is also not included in the constituent unit (a) derived from monomer (A) and the constituent unit (b) derived from monomer (B).

[0053] The polymerizable functional group of monomer (C) is not particularly limited as long as it can form a copolymer (X) with monomer (A) and monomer (B), but preferably, an acryloyl group, a methacryloyl group, or a vinyl group is included. Furthermore, from the viewpoint of making it easier to improve wear resistance, the polymerizable functional group is preferably an acryloyl group or a methacryloyl group, and more preferably an acryloyl group.

[0054] (Monomer (C1), constituent unit (c1)) In this embodiment, from the viewpoint of making it easier to exhibit the effects of the present invention, it is preferable that monomer (C) includes monomer (C1) having one or more cyclic structures selected from the group consisting of (I) to (III) below as the cyclic structure in the cyclic structural group. (I) Aromatic rings with 6 to 14 carbon atoms forming the ring. (II) Alicyclic rings with 3 to 14 carbon atoms forming a ring (III) Heterocycles containing one or more heteroatoms selected from the group consisting of nitrogen and oxygen atoms, with a ring-forming atom number of 3 to 14. In other words, it is preferable that the constituent unit (c) includes a constituent unit (c1) derived from a monomer (C1) having a polymerizable functional group and one or more cyclic structures selected from the group consisting of (I) to (III) below.

[0055] (I) Aromatic rings with 6 to 14 carbon atoms forming the ring. Examples of aromatic rings with 6 to 14 carbon atoms that form a ring include benzene, naphthalene, anthracene, and phenanthrene. Furthermore, from the viewpoint of making it easier to exhibit the effects of the present invention, the number of ring-forming carbon atoms in the aromatic ring is preferably 6 to 10. Specifically, the aromatic ring is preferably benzene.

[0056] (II) Alicyclic rings with 3 to 14 carbon atoms forming a ring Examples of alicyclic rings with 3 to 14 carbon atoms include monocyclic saturated alicyclic rings such as cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclodecane, and cyclododecane; monocyclic unsaturated alicyclic rings such as cyclopropene, cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, cyclodecene, and cyclododecene; polycyclic saturated alicyclic rings such as norbornane and adamantane; and polycyclic saturated alicyclic rings such as norbornene and adamantene. Furthermore, from the viewpoint of making it easier to exhibit the effects of the present invention, the number of ring-forming carbon atoms in the alicyclic ring is preferably 5 to 14, more preferably 5 to 10. Furthermore, from the viewpoint of making it easier to exhibit the effects of the present invention, the alicyclic ring is preferably a monocyclic saturated alicyclic ring or a monocyclic unsaturated alicyclic ring, and more preferably a monocyclic saturated alicyclic ring. Specifically, the alicyclic ring is preferably cyclohexane or cyclohexene, and more preferably cyclohexane.

[0057] (III) A heterocycle containing one or more heteroatoms selected from the group consisting of nitrogen and oxygen atoms, with a ring-forming atom number of 3 to 14. As heterocycles with 3 to 14 carbon atoms that include one or more heteroatoms selected from the group consisting of nitrogen and oxygen atoms, monocyclic heterocycles include saturated 3-membered heterocycles such as aziridine, oxirane, diaziridine, oxaziridine, and dioxirane; unsaturated 3-membered heterocycles such as azirine, oxilen, and diazirine; saturated 4-membered heterocycles such as azetidine, oxetane, diazetidine, and dioxetane; unsaturated 4-membered heterocycles such as azeto, oxetone, diazeto, and dioxetone; saturated 5-membered heterocycles such as pyrrolidine, tetrahydrofuran, imidazolidine, pyrazolidine, oxazolidine, isoxazolidine, and dioxolane; and pyrrole and fura. Examples include unsaturated five-membered heterocycles such as imidazole, pyrazole, oxazole, isoxazole, triazole, furazan, oxadiazole, dioxazole, tetrazole, oxatetrazole, and pentazole; saturated six-membered heterocycles such as piperidine, tetrahydropyran, piperazine, morpholine, dioxane, hexahydro-1,3,5-triazine, and trioxane; unsaturated six-membered heterocycles such as pyridine, pyran, diazine, oxazine, dioxin, triazine, tetrazine, and pentazine; saturated seven-membered heterocycles such as azepane, oxepan, and diazepane; and unsaturated seven-membered heterocycles such as azepine, oxepin, and diazepine. Examples of polycyclic heterocyclic structures include 1H-pyrrolidine, indidine, isoindole, indole, indazole, purine, 4H-quinolidine, isoquinoline, quinoline, phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, pteridine, carbazole, β-carbolin, phenanthidine, acridine, perimidine, phenanthroline, phenazine, and phenoxazine. Furthermore, from the viewpoint of making it easier to exhibit the effects of the present invention, the number of ring-forming atoms in the heterocycle is preferably 5 to 14, more preferably 5 to 10.

[0058] ·Substituents The cyclic structures described in (I) to (III) above may be unsubstituted or may have substituents. The substituents are not particularly limited as long as they are within the range in which the effects of the present invention are achieved, but examples include organic groups having 1 to 30 carbon atoms, and such organic groups may have at least one of a nitrogen atom and an oxygen atom. Specifically, examples include groups selected from the group consisting of alkyl groups having 1 to 30 carbon atoms (preferably 1 to 16, more preferably 1 to 8, and even more preferably 1 to 4), alkoxy groups having alkyl groups having 1 to 30 carbon atoms (preferably 1 to 16, more preferably 1 to 8, and even more preferably 1 to 4), amino groups, cyano groups, nitro groups, alkylcarbonyloxy groups having alkyl groups having 1 to 30 carbon atoms (preferably 1 to 16, more preferably 1 to 8, and even more preferably 1 to 4), hydroxyl groups, alkyl-substituted carbonyl groups, and carboxyl groups. The substituents may be further substituted with any of the substituents mentioned above. Furthermore, from the viewpoint of making it easier to exhibit the effects of the present invention, it is preferable that the cyclic structures (I) to (III) described above are unsubstituted.

[0059] Preferred embodiment of monomer (C1) From the viewpoint of making it easier to exhibit the effects of the present invention, the monomer (C1) is preferably a monomer represented by the following general formula (c-1). YL 1-Z (c-1) In the above general formula (c-1), Y represents a polymerizable functional group, and L 1 represents a direct bond or linker, and Z represents a cyclic structural group having the cyclic structure described in (I) to (III) above.

[0060] Examples of polymerizable functional groups that can be selected as Y include acryloyl groups, methacryloyl groups, or vinyl groups. From the viewpoint of further improving abrasion resistance, it is preferable that the polymerizable functional group be an acryloyl group.

[0061] L 1 Examples of linkers that can be selected include divalent aliphatic hydrocarbon groups having 1 to 4 carbon atoms, such as methylene groups, ethylene groups, n-propylene groups, and n-butylene groups; divalent groups having 6 to 10 carbon atoms and a cyclic structure, such as phenylethylene groups 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).

[0062] Examples of cyclic structural groups that can be selected as Z include monovalent cyclic structural groups obtained by removing one hydrogen atom from any of the cyclic structures described in (I) to (III) above. Furthermore, from the viewpoint of making it easier to improve wear resistance, it is preferable that the cyclic structural group is a monovalent cyclic structural group obtained by removing one hydrogen atom from the cyclic structure described in (I) or (II) above. Among the above (I), an aromatic ring with 6 to 10 ring-forming carbon atoms is preferred. Among the above (II), it is preferable that the ring is a monocyclic saturated alicyclic ring or a monocyclic unsaturated alicyclic ring, and more preferably a monocyclic saturated alicyclic ring. The number of ring-forming carbon atoms is preferably 6 or more and 10 or less.

[0063] Examples of preferred compounds as monomers (C1) include benzyl acrylate, cyclohexyl acrylate, and styrene.

[0064] The constituent unit (c1) derived from the monomer (C1) may consist of one type alone or two or more types. In this specification, monomer (C1) is not included in monomer (A) and monomer (B). Therefore, the constituent unit (c1) derived from monomer (C1) is also not included in the constituent unit (a) derived from monomer (A) and the constituent unit (b) derived from monomer (B).

[0065] (Content of constituent unit (c1)) In this embodiment, the content of constituent unit (c1) is preferably 50 mol% to 100 mol%, more preferably 60 mol% to 100 mol%, even more preferably 70 mol% to 100 mol%, even more preferably 80 mol% to 100 mol%, and still more preferably 90 mol% to 100 mol%, based on the total constituent units of constituent unit (c).

[0066] <Content of constituent unit (a)> In this embodiment, the content of constituent units (a) derived from monomer (A) is preferably 43 mol% or more, more preferably 50 mol% or more, and even more preferably 55 mol% or more, based on the total constituent units of copolymer (X), from the viewpoint of making it easier to exhibit the effects of the present invention. Furthermore, in order to make the effects of the present invention easier to exert by ensuring the content of constituent units (b) derived from monomer (B) and constituent units (c) derived from monomer (C), and balancing the content of each constituent unit, the content of constituent units (a) derived from monomer (A) is preferably 84 mol% or less, more preferably 80 mol% or less, and even more preferably 76 mol% or less, based on the total constituent units of copolymer (X). The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, preferably 43 mol% to 84 mol%, more preferably 50 mol% to 80 mol%, and even more preferably 55 mol% to 76 mol%.

[0067] In this specification, the content ratio of each constituent unit in copolymer (X) is usually equal to the ratio (compounding ratio) of each monomer constituting copolymer (X).

[0068] <Content of constituent unit (b)> In this embodiment, the content of constituent units (b) derived from monomer (B) is preferably 9 mol% or more, more preferably 10 mol% or more, and even more preferably 12 mol% or more, based on the total constituent units of copolymer (X), from the viewpoint of making it easier to exhibit the effects of the present invention. Furthermore, in order to make the effects of the present invention easier to exert by ensuring the content of constituent units (a) derived from monomer (A) and constituent units (c) derived from monomer (C), and balancing the content of each constituent unit, the content of constituent units (b) derived from monomer (B) is preferably 50 mol% or less, more preferably 40 mol% or less, even more preferably 30 mol% or less, and even more preferably 25 mol% or less, based on the total constituent units of copolymer (X). The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, preferably 9 mol% to 50 mol%, more preferably 10 mol% to 40 mol%, and even more preferably 12 mol% to 30 mol%.

[0069] <Content of constituent unit (c)> In this embodiment, the content of constituent units (c) derived from monomer (C) is preferably 7 mol% or more, more preferably 8 mol% or more, and even more preferably 10 mol% or more, based on the total constituent units of copolymer (X), from the viewpoint of making it easier to exhibit the effects of the present invention. Furthermore, in order to make the effects of the present invention easier to exert by ensuring the content of constituent units (a) derived from monomer (A) and constituent units (b) derived from monomer (B), and balancing the content of each constituent unit, the content of constituent units (c) derived from monomer (C) is preferably 30 mol% or less, more preferably 28 mol% or less, even more preferably 26 mol% or less, and even more preferably 25 mol% or less, based on the total constituent units of copolymer (X). The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, preferably 7 mol% to 30 mol%, more preferably 8 mol% to 28 mol%, even more preferably 10 mol% to 26 mol%, and even more preferably 10 mol% to 25 mol%.

[0070] <Content ratio of each component> (Content ratio of constituent unit (b) to constituent unit (a)) In the copolymer (X) of this embodiment, from the viewpoint of making it easier to exhibit the effects of the present invention, the content ratio of constituent unit (b) to constituent unit (a) [(b) / (a)] is preferably 0.15 or more, more preferably 0.20 or more, and even more preferably 0.25 or more in molar ratio. Also, it is preferably 0.50 or less, more preferably 0.45 or less, and even more preferably 0.40 or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 0.15 to 0.50, more preferably 0.20 to 0.45, and even more preferably 0.25 to 0.40.

[0071] (Content ratio of constituent unit (c) to constituent unit (a)) In the copolymer (X) of this embodiment, from the viewpoint of making it easier to exhibit the effects of the present invention, the content ratio of constituent unit (c) to constituent unit (a) [(c) / (a)] is preferably 0.10 or more, more preferably 0.20 or more, and even more preferably 0.30 or more in molar ratio. Also, it is preferably 0.48 or less, more preferably 0.46 or less, and even more preferably 0.45 or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 0.10 to 0.48, more preferably 0.20 to 0.46, even more preferably 0.30 to 0.45, and even more preferably 0.30 to 0.45.

[0072] <Other monomers> Copolymer (X) may contain, in addition to the above-mentioned constituent units (a), (b), and (c), other monomer-derived constituent units, to the extent that they do not impede the effects of the present invention. Examples of such other monomers include functional group-containing monomers other than monomers (A), (B), and (C). Examples of such other functional group-containing monomers include functional group-containing (meth)acrylates other than monomers (A), (B), and (C). However, from the viewpoint of making it easier to exhibit the effects of the present invention, the copolymer (X) contains, more preferably less than 30 mol%, more preferably less than 20 mol%, even more preferably less than 10 mol%, even more preferably less than 1 mol%, and still more preferably less than 0.1 mol%, based on the total number of constituent units.

[0073] <Properties and polymerization mode of copolymer (X)> (Mass average molecular weight (Mw), molecular weight distribution (Mw / Mn)) The copolymer (X) of this embodiment must have a mass-average molecular weight (Mw) of 5,000 to 50,000. If the mass-average molecular weight (Mw) of the copolymer (X) is less than 5,000, it becomes difficult to improve wear resistance. Furthermore, if the mass-average molecular weight (Mw) of copolymer (X) exceeds 50,000, its oil solubility may be poor. In addition, it becomes difficult for copolymer (X) to penetrate the gap between the two components, making it difficult to achieve the wear-resistant improvement effect. Here, from the viewpoint of making it easier to exhibit the effects of the present invention and to make it easier to improve solubility in lubricating oil base oil, preferably it is 5,500 or more, more preferably 6,000 or more, even more preferably 7,000 or more, even more preferably 8,000 or more, still more preferably 9,000 or more, even more preferably 10,000 or more, even more preferably 13,000 or more, even more preferably 16,000 or more, and even more preferably 18,000 or more. Also, preferably it is 45,000 or less, more preferably 40,000 or less, and even more preferably 35,000 or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, preferably 5,500 to 45,000, more preferably 6,000 to 45,000, even more preferably 7,000 to 45,000, even more preferably 8,000 to 45,000, still more preferably 9,000 to 45,000, even more preferably 10,000 to 45,000, even more preferably 13,000 to 45,000, even more preferably 16,000 to 40,000, and even more preferably 18,000 to 35,000.

[0074] Furthermore, the molecular weight distribution (Mw / Mn) of the copolymer (X) in this embodiment is preferably 1.30 or higher, more preferably 1.50 or higher, and even more preferably 1.70 or higher, from the viewpoint of making it easier to exhibit a friction reduction effect. Also, the molecular weight distribution (Mw / Mn) is usually 4.0 or lower, preferably 3.0 or lower, and more preferably 2.5 or lower. The mass-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) are values ​​measured or calculated by the method described in the examples below.

[0075] (Modulation pattern) The polymerization method of copolymer (X) in this embodiment is not particularly limited and may be block copolymerization, random copolymerization, or block / random copolymerization.

[0076] [Method for producing copolymer (X)] The method for producing copolymer (X) is not particularly limited, but may include, for example, a step (S) of polymerizing the monomers (A) to (C) listed below to produce copolymer (X). • Monomer (A): A monomer having a (meth)acryloyl group and a linear or branched alkyl group having 6 to 24 carbon atoms. • Monomer (B): A monomer having a (meth)acryloyl group and a polar group. • Monomer (C): A monomer having a polymerizable functional group and a cyclic structural group.

[0077] The process (S) for producing copolymer (X) will be described in detail below.

[0078] <Process (S) for manufacturing copolymer (X)> The method for producing copolymer (X) (polymerization method) is not particularly limited and can be produced by applying any known method. Examples of such methods include emulsion polymerization, suspension polymerization, and solution polymerization. Here, from the viewpoint of the application of copolymer (X) in the present invention, that is, its use as an additive composition for lubricating oil, it is preferable to employ a solution polymerization method using a solvent that dissolves in the lubricating oil base oil as the polymerization method.

[0079] (Solution polymerization method) Solution polymerization is carried out, for example, by charging monomers (A), (B), and (C), along with a solvent and an initiator, purging the reactor with nitrogen, and then reacting with stirring at 60°C to 100°C for 2 to 10 hours. Other monomers besides monomers (A), (B), and (C) may also be optionally charged into the reactor.

[0080] The solvent used in the solution polymerization method is not particularly limited, but it is preferable to use esters such as polyol esters, dibasic acid esters, hindered esters, and monoesters. These may be used individually or in combination of two or more types.

[0081] Initiators used in solution polymerization include, for example, azo-based initiators such as 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis-(N,N-methylene isobutylamidine) dihydrochloride, 1,1'-azobis(cyclohexyl-1-carbonnitrile), 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+Examples include 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.

[0082] The molecular weight of copolymer (X) can be controlled by known methods. For example, the molecular weight of copolymer (X) can be controlled by the reaction temperature, reaction time, amount of initiator, amount of each monomer, type of solvent, and use of chain transfer agent.

[0083] The copolymer (X) may be diluted with a diluent solvent for ease of handling. It is preferable to use the same diluent solvent as the polymerization solvent described above.

[0084] (Amount of monomer (A) added) In the manufacturing method of this embodiment, the amount of monomer (A) added is preferably 57% by mass or more, 65% by mass or more, and more preferably 70% by mass or more, based on the total amount of monomer added, from the viewpoint of easily adjusting the content of the constituent unit (a) described above. Furthermore, it is preferably 90% by mass or less, more preferably 87% by mass or less, and even more preferably 85% by mass or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, they are preferably 57% to 90% by mass, 65% to 87% by mass, and more preferably 70% to 85% by mass. The preferred compounds for monomer (A) are as described above.

[0085] (Amount of monomer (B) added) In the manufacturing method of this embodiment, the amount of monomer (B) added is preferably 5% by mass or more, more preferably 6% by mass or more, and even more preferably 7% by mass or more, based on the total amount of monomer added, from the viewpoint of easily adjusting the content of the constituent unit (b) described above. Furthermore, it is preferably 38% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and even more preferably 15% by mass or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 5% by mass to 38% by mass, more preferably 6% by mass to 20% by mass, and even more preferably 7% by mass to 15% by mass. The preferred compounds for monomer (B) are as described above.

[0086] (Amount of monomer (C) added) In the manufacturing method of this embodiment, the amount of monomer (C) added is preferably 5% by mass or more, more preferably 6% by mass or more, and even more preferably 7% by mass or more, based on the total amount of monomer added, from the viewpoint of easily adjusting the content of the constituent unit (c) described above. Furthermore, it is preferably 27% by mass or less, more preferably 23% by mass or less, and even more preferably 20% by mass or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 5% by mass to 27% by mass, more preferably 6% by mass to 23% by mass, and even more preferably 7% by mass to 20% by mass. The preferred compounds for monomer (C) are as described above.

[0087] <Content of copolymer (X)> In the lubricating oil composition of this embodiment, the content of copolymer (X) in terms of resin content must be 0.10% to 2.5% by mass on a basis of the total amount of the lubricating oil composition. If the content of copolymer (X) in terms of resin content is less than 0.10% by mass, the effects of the present invention will not be exhibited. Furthermore, if the content of copolymer (X) in terms of resin content exceeds 2.5% by mass, the effect obtained will be small relative to the amount of copolymer (X) added. From the viewpoint of maximizing the effects of the present invention with an appropriate amount of additive, the content of copolymer (X) in terms of resin content is preferably 0.15% by mass or more, more preferably 0.20% by mass or more. Also preferably 2.0% by mass or less, more preferably 1.8% by mass or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 0.15% by mass to 2.0% by mass, more preferably 0.20% by mass to 1.8% by mass.

[0088] [Molybdenum-based friction modifier (M)] The lubricating oil composition of this embodiment preferably further contains a molybdenum-based friction modifier (M). The inclusion of a molybdenum-based friction modifier (M) in the lubricating oil composition further improves its friction-reducing effect. In particular, the friction-reducing effect can be effectively demonstrated in environments with high temperatures.

[0089] Any compound containing molybdenum atoms can be used as the molybdenum-based friction modifier (M). Examples of molybdenum-based friction modifiers (M) include molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and molybdenum amine complexes. These may be used individually or in combination of two or more. Among these, from the viewpoint of reducing the intermetallic friction coefficient and obtaining excellent fuel efficiency, one or more selected from the group consisting of molybdenum dithiocarbamate (MoDTC) and molybdenum amine complexes are preferred. Examples of molybdenum dithiocarbamate (MoDTC) include dinuclear molybdenum dithiocarbamate containing two molybdenum atoms in one molecule, and trinuclear molybdenum dithiocarbamate containing three molybdenum atoms in one molecule.

[0090] In other words, in this embodiment, the molybdenum-based friction modifier (M) preferably contains one or more selected from the group consisting of dinuclear molybdenum dithiocarbamate, trinuclear molybdenum dithiocarbamate, and molybdenamine complexes. The following provides a detailed explanation of these molybdenum-based friction modifiers.

[0091] <Binuclear molybdenum dithiocarbamate> Examples of dinuclear molybdenum dithiocarbamate include the compound represented by the following general formula (1) and the compound represented by the following general formula (2).

[0092] [ka]

[0093] In the above general formulas (1) and (2), R 11 ~R 14 Each of these independently represents a hydrocarbon group, which may be the same as or different from one another. X 11 ~X 18 Each of these independently represents either an oxygen atom or a sulfur atom, and they may be the same or different from each other. However, X in formula (1) 11 ~X 18 At least two of them are sulfur atoms. R 11 ~R 14 The number of carbon atoms in the hydrocarbon group that can be selected is preferably 6 to 22.

[0094] In the above general formulas (1) and (2), R 11 ~R 14 Examples of hydrocarbon groups that can be selected include alkyl groups, alkenyl groups, cycloalkyl groups, aryl groups, alkylaryl groups, and arylalkyl groups. Examples of the alkyl group include hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl groups. Examples of such alkenyl groups include hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, and pentadecenyl groups. Examples of the cycloalkyl group include cyclohexyl group, dimethylcyclohexyl group, ethylcyclohexyl group, methylcyclohexylmethyl group, cyclohexylethyl group, propylcyclohexyl group, butylcyclohexyl group, and heptylcyclohexyl group. Examples of the aryl group include phenyl, naphthyl, anthracenyl, biphenyl, and terphenyl groups. Examples of the alkylaryl group include tolyl group, dimethylphenyl group, butylphenyl group, nonylphenyl group, and dimethylnaphthyl group. Examples of the arylalkyl group include methylbenzyl group, phenylmethyl group, phenylethyl group, and diphenylmethyl group.

[0095] Among these, molybdenum dialkyldithiocarbamate (M1), represented by the following general formula (m1) (hereinafter also referred to as "compound (M1)") is preferred. [ka]

[0096] In the above general formula (m1), R 1 , R 2 , R 3 , and R 4Each independently represents either a short-chain substituent group (α) which is an aliphatic hydrocarbon group having 4 to 12 carbon atoms, or a long-chain substituent group (β) which is an aliphatic hydrocarbon group having 13 to 22 carbon atoms. However, the molar ratio [(α) / (β)] of the short-chain substituent group (α) to the long-chain substituent group (β) in the total molecule of compound (M1) is 0.10 to 2.0. Also, in the general formula (m1), X 1 , X 2 , X 3 , and X 4 Each of these independently represents either an oxygen atom or a sulfur atom.

[0097] Examples of aliphatic hydrocarbon groups having 4 to 12 carbon atoms that can be selected as the short-chain substituent group (α) include alkyl groups having 4 to 12 carbon atoms and alkenyl groups having 4 to 12 carbon atoms. Specifically, examples include butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, undecenyl group, and dodecenyl group. These may be linear or branched. Furthermore, the number of carbon atoms in the aliphatic hydrocarbon group that can be selected as the short-chain substituent group (α) is preferably 5 to 11, more preferably 6 to 10, and even more preferably 7 to 9, from the viewpoint of making it easier to exhibit the effects of the present invention.

[0098] Examples of aliphatic hydrocarbon groups having 13 to 22 carbon atoms that can be selected as the long-chain substituent group (β) include alkyl groups having 13 to 22 carbon atoms and alkenyl groups having 13 to 22 carbon atoms. Specifically, examples include tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group, henicosyl group, docosyl group, tridecenyl group, tetradecenyl group, pentadecenyl group, hexadecenyl group, heptadecenyl group, octadecenyl group, oleyl group, nonadecenyl group, icocenyl group, henicosenyl group, and dococenyl group. These may be linear or branched. Furthermore, the number of carbon atoms in the aliphatic hydrocarbon group that can be selected as the long-chain substituent group (β) is preferably 13 to 20, more preferably 13 to 16, and even more preferably 13 to 14, from the viewpoint of making it easier to exhibit the effects of the present invention.

[0099] Here, the compound (M1) represented by the general formula (m1) has a molar ratio [(α) / (β)] of short-chain substituents (α) to long-chain substituents (β) in its entire molecule between 0.10 and 2.0. When the molar ratio [(α) / (β)] is 0.10 or higher, the influence of compound (D3) on copper corrosion resistance is reduced, and the friction reduction effect is also easily improved. Furthermore, when the molar ratio [(α) / (β)] is 2.0 or lower, it becomes easier to ensure low-temperature storage stability. Here, from the viewpoint of minimizing the impact on copper corrosion resistance and making it easier to improve the friction reduction effect, the molar ratio [(α) / (β)] is preferably 0.15 or higher, more preferably 0.20 or higher. Furthermore, from the viewpoint of making it easier to ensure low-temperature storage stability, the molar ratio [(α) / (β)] is preferably 1.2 or less, more preferably 1.0 or less, even more preferably 0.80 or less, and even more preferably 0.60 or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, they are preferably 0.15 to 1.2, more preferably 0.20 to 1.0, even more preferably 0.20 to 0.80, and even more preferably 0.20 to 0.60.

[0100] Here, the short-chain substituent group (α) and the long-chain substituent group (β) may or may not coexist within the same molecule. That is, the average value of the molar ratio [(α) / (β)] of the short-chain substituent group (α) to the long-chain substituent group (β) in the entire molecule of the compound (M1) represented by the general formula (m1) is within the range of 0.10 to 2.0. Therefore, compound (M1) contains R in the general formula (m1) above. 1 , R 2 , R 3 and R 4 It is also possible that a group of molecules (M1-1) in which all are short-chain substituents (α) may be present,1 , R 2 , R 3 and R 4 It is also possible that a group of molecules (M1-2) in which all of the substituents are long chain substituents (β) may be mixed, 1 , R 2 , R 3 and R 4 A group of molecules (M1-3) may be mixed in which some of the molecules consist of short-chain substituents (α) and the remainder consists of long-chain substituents (β).

[0101] <Trinuclear molybdenum dithiocarbamate> Examples of trinuclear molybdenum dithiocarbamate include compounds represented by the following general formula (3). Mo3S k E m L n A p Q z (3)

[0102] In the general formula (3) above, k is an integer greater than or equal to 1, m is an integer greater than or equal to 0, and k+m is an integer between 4 and 10, preferably between 4 and 7. n is an integer between 1 and 4, and p is an integer greater than or equal to 0. z is an integer between 0 and 5, including non-stoichiometric values. Each of E is independently either an oxygen atom or a selenium atom, and can, for example, be substituted with sulfur in the core described later. Each L is an anionic ligand having an organic group containing carbon atoms, where the total number of carbon atoms in the organic group of each ligand is 14 or more, and the ligands may be the same or different. Each A is an anion other than L, independently of the others. Each Q is an independently electron-donating neutral compound that exists to satisfy the vacant coordination on the trinuclear molybdenum compound.

[0103] The total number of carbon atoms in the organic group of the anionic ligand represented by L is preferably 14 to 50, more preferably 16 to 30, and even more preferably 18 to 24. L is preferably a monoanionic ligand, which is a monovalent anionic ligand, and more preferably a ligand represented by the following general formulas (i) to (iv). Furthermore, the anionic ligand selected as L in the above general formula (3) is preferably a ligand represented by the following general formula (iv). Furthermore, it is preferable that all the anionic ligands selected as L in the above general formula (3) are the same, and more preferably that they are all ligands represented by the following general formula (iv).

[0104] [ka]

[0105] In the above general formulas (i) to (iv), X 31 ~X 37 , and Y are each independently an oxygen atom or a sulfur atom, and may be the same as or different from each other. In the above general formulas (i) to (iv), R 31 ~R 35 Each of these is an organic group, and they may be identical or different from one another.

[0106] Note, R 31 , R 32 , and R 33 The number of carbon atoms in each of the organic groups that can be selected is preferably 14 to 50, more preferably 16 to 30, and even more preferably 18 to 24.

[0107] R in equation (iv) 34 and R 35 The total number of carbon atoms in the two organic groups that can be selected is preferably 14 to 50, more preferably 16 to 30, and even more preferably 18 to 24. R 34 and R 35 The number of carbon atoms in each of the organic groups that can be selected is preferably 7 to 30, more preferably 7 to 20, and even more preferably 8 to 13. Note, R 34 The organic group and R 35 The organic groups may be the same as or different from each other, but it is preferable that they be different from each other. Also, R 34 The number of carbon atoms in the organic group and R 35 The number of carbon atoms in the organic groups may be the same or different, but it is preferable that they be different.

[0108] R 31 ~R 35 Examples of organic groups that can be selected include alkyl groups, aryl groups, substituted aryl groups, and hydrocarbyl groups such as ether groups. The term "hydrocarbyl" refers to a substituent having a carbon atom directly bonded to the remainder of the ligand, and within the scope of this embodiment, its properties are primarily hydrocarbyl. Examples of such substituents are listed below. 1. Hydrocarbon substituents Examples of hydrocarbon substituents include aliphatic substituents such as alkyl and alkenyl substituents, alicyclic substituents such as cycloalkyl and cycloalkenyl substituents, aromatic groups, aromatic nuclei substituted with aliphatic and alicyclic groups, and cyclic groups in which the ring is completed via another site in the ligand (i.e., any two indicated substituents may together form an alicyclic group). 2. Substituted hydrocarbon substituents Examples of substituted hydrocarbon substituents include those obtained by substituting the above-mentioned hydrocarbon substituents with non-hydrocarbon groups that do not alter the properties of hydrocarbil. Examples of non-hydrocarbon groups include halogen groups such as chloro and fluoro, amino groups, alkoxy groups, mercapto groups, alkylmercapto groups, nitro groups, nitroso groups, and sulfoxy groups.

[0109] In the general formula (3) above, the anionic ligand selected as L is preferably derived from alkylxanthogenic salts, carboxylates, dialkyldithiocarbamates, and mixtures thereof, and more preferably derived from dialkyldithiocarbamates.

[0110] In the general formula (3) above, the anion that can be selected as A may be a monovalent anion or a divalent anion. Examples of anions that can be selected as A include disulfides, hydroxides, alkoxides, amides and thiocyanates or their derivatives.

[0111] In the general formula (3) above, Q can be water, amine, alcohol, ether, phosphine, etc. Q may be the same or different, but it is preferable that it be the same.

[0112] As the trinuclear molybdenum dithiocarbamate, a compound is preferred in which, in the general formula (3), k is an integer from 4 to 7, n is 1 or 2, L is a monoanionic ligand, p is an integer that imparts electrical neutrality to a compound based on the anionic charge at A, and m and z are each 0. A compound is more preferred in which k is an integer from 4 to 7, L is a monoanionic ligand, n is 4, and p, m, and z are each 0.

[0113] Furthermore, the trinuclear molybdenum dithiocarbamate is preferably a compound having a core represented by the following formula (IV-A) or (IV-B). Each core has an effective charge (net electrical charge) of +4. These cores are surrounded by an anionic ligand and, if necessary, anions other than the anionic ligand.

[0114] [ka]

[0115] The formation of trinuclear molybdenum-sulfur compounds requires, for example, the selection of appropriate anionic ligands (L) and other anions (A) depending on the number of sulfur and E atoms present in the core; that is, the total anionic charge composed of the sulfur atom, E atom (if present), L, and A (if present) must be -4. The trinuclear molybdenum-sulfur compound may also contain cations other than molybdenum, such as (alkyl)ammonium, amine, or sodium, if the anionic charge is greater than -4. A preferred embodiment of the anionic ligand (L) and other anions (A) is a configuration having four monoanionic ligands. The molybdenum-sulfur cores, for example, the structures represented by (IV-A) and (IV-B) above, can be interconnected by one or more polydentate ligands, i.e., ligands having one or more functional groups capable of bonding to molybdenum atoms to form oligomers.

[0116] The molybdenum content in trinuclear molybdenum dithiocarbamate is preferably 2.0% by mass or more, more preferably 4.0% by mass or more, and even more preferably 5.0% by mass or more, based on the total amount of trinuclear molybdenum dithiocarbamate. Furthermore, it is preferably 9.0% by mass or less, more preferably 7.0% by mass or less, and even more preferably 6.0% by mass or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, they are preferably 2.0% to 9.0% by mass, more preferably 4.0% to 7.0% by mass, and even more preferably 5.0% to 6.0% by mass.

[0117] <Molybdenamine complex> Examples of molybdenamine complexes include molybdenamine complexes obtained by reacting a hexavalent molybdenum compound, such as molybdenum trioxide and / or molybdic acid, with an amine compound. Preferred amine compounds include alkylamines, dialkylamines, and the like. The alkylamines and dialkylamines reacted with the hexavalent molybdenum compound are not particularly limited, and examples include alkylamines and dialkylamines having an alkyl group with 1 to 30 carbon atoms.

[0118] The molybdenum content in the molybdenamine complex is preferably 4.0% by mass or more, more preferably 6.0% by mass or more, and even more preferably 7.0% by mass or more, based on the total amount of the molybdenamine complex. It is also preferably 12.0% by mass or less, more preferably 10.0% by mass or less, and even more preferably 9.0% by mass or less. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, they are preferably 4.0% to 12.0% by mass, more preferably 6.0% to 10.0% by mass, and even more preferably 7.0% to 9.0% by mass.

[0119] <Content of molybdenum-based friction modifier (M)> In the lubricating oil composition of this embodiment, the content of the molybdenum-based friction modifier (M) is preferably 0.30% by mass or more, more preferably 0.50% by mass or more, even more preferably 0.70% by mass or more, based on the total amount of the lubricating oil composition, and also preferably 3.0% by mass or less, more preferably 2.0% by mass or less, and even more preferably 1.0% by mass or less, from the viewpoint of lowering the intermetallic friction coefficient and obtaining excellent fuel efficiency. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, they are preferably 0.30% to 3.0% by mass, more preferably 0.50% to 2.0% by mass, and even more preferably 0.70% to 1.0% by mass.

[0120] In the lubricating oil composition of this embodiment, the content of molybdenum atoms derived from the molybdenum-based friction modifier (M) is preferably 0.01% by mass or more, more preferably 0.04% by mass or more, and even more preferably 0.05% by mass or more, based on the total amount of the lubricating oil composition, from the viewpoint of improving the friction reduction effect. Furthermore, from the viewpoint of reducing sulfated ash content, the molybdenum atom content derived from the molybdenum-based friction modifier (M) is preferably 0.20% by mass or less, more preferably 0.15% by mass or less, and even more preferably 0.12% by 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 in any way. Specifically, they are preferably 0.01% to 0.20%, more preferably 0.04% to 0.15%, and even more preferably 0.05% to 0.12%.

[0121] <Content ratio of dinuclear molybdenum dithiocarbamate and trinuclear molybdenum dithiocarbamate> In this embodiment, the ratio of dinuclear molybdenum dithiocarbamate to trinuclear molybdenum dithiocarbamate [(dinuclear MoDTC) / (trinuclear MoDTC)] is preferably 0.1 to 10, more preferably 0.5 to 7.0, and even more preferably 1.0 to 5.0 by mass, from the viewpoint of improving the friction reduction effect.

[0122] <Content ratio of dinuclear molybdenum dithiocarbamate and molybdenamine complex> In this embodiment, the ratio of dinuclear molybdenum dithiocarbamate to molybdenamine complex [(dinuclear MoDTC) / (MoAmn)] is preferably 0.1 to 10, more preferably 1.0 to 8.0, and even more preferably 2.0 to 6.0 by mass, from the viewpoint of improving the friction reduction effect.

[0123] [Other ingredients] The lubricating oil composition of this embodiment may contain other components besides those mentioned above, as necessary, as long as they do not impair the effects of the present invention. Examples of additives as other components include metal deactivators, viscosity index improvers, metal-based detergents, pour point depressants, antioxidants, wear inhibitors, friction modifiers other than molybdenum-based friction modifiers (M), extreme pressure agents, rust inhibitors, defoamers, oiliness improvers, and anti-emulsifiers. These may be used individually or in combination of two or more types.

[0124] (Metal deactivator) Examples of metal deactivators include benzotriazole compounds, toltriazole compounds, thiadiazole compounds, imidazole compounds, and pyrimidine compounds. These may be used individually or in combination of two or more types. Among these, the lubricating oil composition of this embodiment preferably contains a benzotriazole compound from the viewpoint of improving copper corrosion resistance.

[0125] As the benzotriazole compound, one or more benzotriazole compounds conventionally used as metal deactivators can be used without particular limitation. In this embodiment, from the viewpoint of improving copper corrosion resistance, it is preferable that the benzotriazole compound includes compound (C1) represented by the following general formula (c1). [ka]

[0126] In the above general formula (c1), R c1 This is an alkyl group having 1 to 4 carbon atoms. This alkyl group may be linear or branched. Here, from the viewpoint of improving copper corrosion resistance, the number of carbon atoms in the alkyl group is preferably 1 to 3, more preferably 1 to 2, and even more preferably 1. In the above general formula (c1), p is an integer between 0 and 4. c1 If there are multiple instances (i.e., p is an integer between 2 and 4), then multiple R c1 These may be the same or different from each other. Here, from the viewpoint of improving copper corrosion resistance, p is preferably 0 to 3, more preferably 0 to 2, and even more preferably 1. In the above general formula (c1), R c2 This is a methylene group or an ethylene group. Here, from the viewpoint of improving copper corrosion resistance, R c2 The group is preferably a methylene group. In the above general formula (c1), R c3 and R c4Each of these is independently a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. The alkyl group may be linear or branched, but it is preferably branched. The number of carbon atoms in the alkyl group is preferably 2 to 14, more preferably 4 to 12, and even more preferably 6 to 10.

[0127] In the lubricating oil composition of this embodiment, the content of the benzotriazole compound is preferably 0.03% by mass or less, more preferably 0.02% by mass or less, and even more preferably 0.015% by mass or less, based on the total amount of the lubricating oil composition, from the viewpoint of further improving the friction reduction effect. Furthermore, from the viewpoint of improving copper corrosion resistance, it is preferably 0.003% by mass or more, and more preferably 0.005% by mass or more. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 0.003% by mass to 0.03% by mass, more preferably 0.005% by mass to 0.02% by mass, and even more preferably 0.005% by mass to 0.015% by mass.

[0128] (Viscosity index improver) Examples of viscosity index improvers include polymers such as non-dispersible poly(meth)acrylate, dispersed poly(meth)acrylate, comb-shaped polymers, star-shaped polymers, olefin copolymers (e.g., ethylene-propylene copolymer, etc.), dispersed olefin copolymers, and styrene copolymers (e.g., styrene-diene copolymer, styrene-isoprene copolymer, etc.). These may be used individually or in combination of two or more types.

[0129] Here, from the viewpoint of making it easier to exhibit the effects of the present invention, the viscosity index improver is preferably a comb-shaped polymer. A comb-shaped polymer can be any polymer having a structure in which the main chain has many tridental branching points from which high molecular weight side chains protrude. As the comb-shaped polymer, a polymer having at least one structural unit derived from a macromonomer is preferred. The structural unit derived from the macromonomer corresponds to the "high molecular weight side chain" mentioned above. Note that "macromonomer" refers to a high molecular weight monomer having a polymerizable functional group, and it is preferable that the high molecular weight monomer has a polymerizable functional group at its terminal end.

[0130] The number-average molecular weight (Mn) of the macromonomer is preferably 300 or more, more preferably 400 or more, even more preferably 500 or more, and also preferably 100,000 or less, more preferably 50,000 or less, and even more preferably 20,000 or less.

[0131] The comb-shaped polymer may be a homopolymer consisting of only one type of macromonomer, or it may be a copolymer containing two or more types of macromonomers. Furthermore, the comb-shaped polymer may be a copolymer containing not only macromonomers but also other monomers. As for the specific structure of such comb-shaped polymers, a copolymer having a main chain containing structural units derived from monomers other than macromonomers, and side chains containing structural units derived from macromonomers, is preferred.

[0132] Other monomers besides macromonomers include, for example, alkyl (meth)acrylates, nitrogen atom-containing vinyl monomers, hydroxyl group-containing vinyl monomers, phosphorus atom-containing monomers, aliphatic hydrocarbon vinyl monomers, alicyclic hydrocarbon vinyl monomers, vinyl esters, vinyl ethers, vinyl ketones, epoxy group-containing vinyl monomers, halogen element-containing vinyl monomers, esters of unsaturated polycarboxylic acids, (di)alkyl fumarates, (di)alkyl maleates, aromatic hydrocarbon vinyl monomers, and the like.

[0133] The mass-average molecular weight (Mw) of the comb-shaped polymer is preferably 100,000 to 1,000,000, more preferably 200,000 to 800,000, and even more preferably 250,000 to 750,000. The molecular weight distribution (Mw / Mn) of the comb-shaped polymer is preferably 8.00 or less, more preferably 7.00 or less, even more preferably 6.00 or less, and even more preferably 3.00 or less, and usually 1.01 or more, preferably 1.05 or more, and more preferably 1.10 or more. The PSSI (Permanent Shear Stability Index) of the comb-shaped polymer is preferably 12.0 or less, more preferably 10.0 or less, even more preferably 5.0 or less, even more preferably 3.0 or less, and still most preferably 1.0 or less. Furthermore, while there is no particular lower limit for the PSSI of comb-shaped polymers, it is usually 0.1 or higher, preferably 0.2 or higher.

[0134] In this specification, the PSSI (Permanent Shear Stability Index) of a viscosity index improver represents the percentage of viscosity reduction due to shear originating from the resin component in the viscosity index improver, and is a value calculated in accordance with ASTM D6022-06. More specifically, it is a value calculated using the following formula.

number

[0135] In the above calculation formula, Kv0 is the kinematic viscosity at 100°C of the sample oil, which is prepared by diluting a viscosity index improver containing resin in mineral oil, and Kv1 is the kinematic viscosity at 100°C after passing the sample oil, which is prepared by diluting the viscosity index improver containing resin in mineral oil, through a 30-cycle high-shear diesel injector according to the procedure of ASTM D6278. oil This is the kinematic viscosity at 100°C of the mineral oil used to dilute the viscosity index improver.

[0136] The content of the comb-shaped polymer in terms of resin content is preferably 0.01 to 10% by mass, more preferably 0.05 to 5.0% by mass, and even more preferably 0.10 to 4.0% by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0137] (Metal-based cleaning agent) Examples of metal-based cleaning agents include organic acid metal salt compounds containing metal atoms selected from alkali metals and alkaline earth metals. Specifically, examples include metal salicylates, metal phenates, and metal sulfonates containing metal atoms selected from alkali metals and alkaline earth metals. In this specification, "alkali metals" refers to lithium, sodium, potassium, rubidium, and cesium. Furthermore, "alkaline earth metals" refer to beryllium, magnesium, calcium, strontium, and barium. From the viewpoint of improving cleaning performance at high temperatures, the metal atoms included in the metal-based cleaning agent are preferably sodium, calcium, magnesium, or barium, with calcium and magnesium being more preferred.

[0138] As the metal salicylate, a compound represented by the following general formula (4) is preferred; as the metal phenate, a compound represented by the following general formula (5) is preferred; and as the metal sulfonate, a compound represented by the following general formula (6) is preferred.

[0139] [ka]

[0140] In the above general formulas (4) to (6), M is a metal atom selected from alkali metals and alkaline earth metals, and sodium, calcium, magnesium, or barium are preferred, with calcium and magnesium being more preferred. E is an alkaline earth metal, preferably calcium, magnesium, or barium, with calcium and magnesium being more preferred. q is the valence of M, which is 1 or 2. R 31 and R 32 Each of these is independently a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms. S represents a sulfur atom. r is an integer of 0 or more, preferably an integer from 0 to 3. R 31 and R 32Examples of hydrocarbon groups that can be selected include C1-C18 alkyl groups, C1-C18 alkenyl groups, C3-C18 cycloalkyl groups, C6-C18 aryl groups, C7-C18 alkylaryl groups, C7-C18 arylalkyl groups, and C7-C18 arylalkyl groups. These may be used individually or in combination of two or more. Among these, it is preferable to use one or more selected from calcium salicylate, calcium phenate, calcium sulfonate, magnesium salicylate, magnesium phenate, and magnesium sulfonate, from the viewpoint of improving high-temperature cleaning and dispersibility, and from the viewpoint of solubility in base oil.

[0141] These metal-based cleaning agents may be neutral salts, basic salts, superbasic salts, or mixtures thereof. The base number of the aforementioned metal-based detergent is preferably 0 to 600 mg KOH / g. If the metal-based detergent is a basic salt or an overbasic salt, the base number of the metal-based detergent is preferably 10 to 600 mg KOH / g, more preferably 20 to 500 mg KOH / g. In this specification, "base number" refers to the base number measured by the perchloric acid method in accordance with JIS K 2501:2003 "Petroleum products and lubricating oils - Neutralization number test method" 7.

[0142] In the lubricating oil composition of this embodiment, the content of the metal-based detergent is preferably 0.01% to 10% by mass, more preferably 0.1% to 5.0% by mass, even more preferably 0.2% to 4.0% by mass, and even more preferably 0.3% to 3.0% by mass, based on the total amount (100% by mass) of the lubricating oil composition, from the viewpoint of making it easier to exhibit the effects of the present invention. Furthermore, metal-based cleaning agents may be used alone or in combination of two or more types. The optimal total content when using two or more types is the same as the content mentioned above.

[0143] In the lubricating oil composition of this embodiment, when the metal-based detergent contains a calcium-based detergent, the calcium content derived from the calcium-based detergent is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.10% by mass or more, based on the total amount (100% by mass) of the lubricating oil composition, from the viewpoint of high-temperature cleaning and dispersibility. Furthermore, from the viewpoint of reducing sulfated ash and preventing LSPI (abnormal combustion), the calcium atom content derived from the metal-based detergent is preferably 0.25% by mass or less, more preferably 0.22% by mass or less, and even more preferably 0.20% by mass or less, based on the total amount (100% by mass) of the lubricating oil composition. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, they are preferably 0.01% to 0.25%, more preferably 0.05% to 0.22%, and even more preferably 0.10% to 0.20%.

[0144] In the lubricating oil composition of this embodiment, when the metal-based detergent includes a magnesium-based detergent, the magnesium content derived from the magnesium-based detergent is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and even more preferably 0.03% by mass or more, based on the total amount (100% by mass) of the lubricating oil composition, from the viewpoint of high-temperature cleaning and dispersibility. Furthermore, from the viewpoint of reducing sulfated ash and preventing LSPI (abnormal combustion), the magnesium atom content derived from the metal-based detergent is preferably 0.20% by mass or less, more preferably 0.15% by mass or less, and even more preferably 0.07% by mass or less, based on the total amount (100% by mass) of the lubricating oil composition. The upper and lower limits of these numerical ranges can be combined in any way. Specifically, they are preferably 0.01% to 0.20%, more preferably 0.02% to 0.15%, and even more preferably 0.03% to 0.07%.

[0145] (Ashless dispersant) Examples of ashless dispersants include boron-free succinimides such as boron-free alkenyl succinimides, boron-containing succinimides such as boron-containing alkenyl succinimides, benzylamines, boron-containing benzylamines, succinic acid esters, and monovalent or divalent carboxylic acid amides represented by fatty acids or succinic acid. These may be used individually or in combination of two or more types. Among these, from the viewpoint of improving the cleanliness of the engine interior, one or more succinimides selected from boron-free alkenyl succinimides and boron-containing alkenyl succinimides are preferred, and it is more preferable to use boron-free alkenyl succinimides and boron-containing alkenyl succinimides in combination.

[0146] When the lubricating oil composition of this embodiment contains an ashless dispersant, the nitrogen atom content derived from the ashless dispersant is preferably 0.01% to 0.15% by mass, more preferably 0.02% to 0.10% by mass, and even more preferably 0.04% to 0.06% by mass, based on the total amount of the lubricating oil composition.

[0147] (Pour point depressant) Examples of pour point depressants include ethylene-vinyl acetate copolymers, condensates of chlorinated paraffin and naphthalene, condensates of chlorinated paraffin and phenol, polymethacrylates (PMA-based; polyalkyl(meth)acrylate, etc.), polyvinyl acetate, polybutene, polyalkylstyrene, etc., with polymethacrylates being preferred. These may be used individually or in combination of two or more types.

[0148] (Antioxidant) Examples of antioxidants include amine-based antioxidants and phenol-based antioxidants. Examples of amine-based antioxidants include diphenylamine antioxidants such as diphenylamine and alkylated diphenylamines having an alkyl group with 3 to 20 carbon atoms; naphthylamine antioxidants such as phenyl-α-naphthylamine, phenyl-β-naphthylamine, substituted phenyl-α-naphthylamine having an alkyl group with 3 to 20 carbon atoms, and substituted phenyl-β-naphthylamine having an alkyl group with 3 to 20 carbon atoms; and the like. Examples of phenolic antioxidants include monophenolic antioxidants such as 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, isooctyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; diphenolic antioxidants such as 4,4'-methylenebis(2,6-di-tert-butylphenol) and 2,2'-methylenebis(4-ethyl-6-tert-butylphenol); and hindered phenolic antioxidants. These may be used individually or in combination of two or more types.

[0149] (Abrasion-resistant agent) Examples of wear-resistant agents include zinc-containing compounds such as zinc dialkyldithiophosphate (ZnDTP) and zinc phosphate; sulfur-containing compounds such as disulfides, sulfurized olefins, sulfurized oils and fats, sulfurized esters, thiocarbonates, thiocarbamates, and polysulfides; phosphorus-containing compounds such as phosphite esters, phosphate esters, phosphonic acid esters, and their amine salts or metal salts; and sulfur and phosphorus-containing wear-resistant agents such as thiophosphite esters, thiophosphate esters, thiophosphonic acid esters, and their amine salts or metal salts. Among these, zinc dialkyldithiophosphate (ZnDTP) is preferred. These may be used individually or in combination of two or more types.

[0150] When the lubricating oil composition of this embodiment contains zinc dialkyldithiophosphate (ZnDTP), the phosphorus content derived from zinc dialkyldithiophosphate (ZnDTP) is preferably 0.01% to 0.15% by mass, more preferably 0.02% to 0.12% by mass, and even more preferably 0.06% to 0.09% by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0151] (Friction modifiers other than ingredient (M)) The lubricating oil composition of this embodiment may also contain friction modifiers other than component (M). Other friction modifiers besides component (M) include, for example, ashless friction modifiers such as aliphatic amines, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, and aliphatic ethers; and oils and fats, amines, amides, sulfur esters, phosphate esters, phosphite esters, and phosphate ester amine salts. These may be used individually or in combination of two or more types.

[0152] (Extreme pressure agent) Examples of extreme pressure agents include sulfur-based extreme pressure agents such as sulfides, sulfoxides, sulfones, and thiophosphinates, halogen-based extreme pressure agents such as chlorinated hydrocarbons, and organometallic extreme pressure agents. Furthermore, compounds that function as extreme pressure agents among the aforementioned wear-resistant agents can also be used. These may be used individually or in combination of two or more types.

[0153] (Rust inhibitor) Examples of rust inhibitors include fatty acids, alkenyl succinate half esters, fatty acid soaps, alkyl sulfonates, polyhydric alcohol fatty acid esters, fatty acid amines, oxidized paraffins, and alkyl polyoxyethylene ethers. These may be used individually or in combination of two or more types.

[0154] (Antifoaming agent) Examples of defoaming agents include silicone oils such as dimethylpolysiloxane, fluorosilicone oils, and fluoroalkyl ethers. These may be used individually or in combination of two or more types.

[0155] (Oil-enhancing agent) Examples of oiliness improvers include aliphatic saturated or unsaturated monocarboxylic acids such as stearic acid and oleic acid; polymerized fatty acids such as dimer acid and hydrogenated dimer acid; hydroxy fatty acids such as ricinoleic acid and 12-hydroxystearic acid; aliphatic saturated or unsaturated monoalcohols such as lauryl alcohol and oleyl alcohol; aliphatic saturated or unsaturated monoamines such as stearylamine and oleylamine; aliphatic saturated or unsaturated monocarboxylic acid amides such as lauric acid amide and oleic acid amide; and partial esters of polyhydric alcohols such as glycerin and sorbitol with aliphatic saturated or unsaturated monocarboxylic acids.

[0156] (Antiemulsifier) Examples of antiemulsifiers include anionic surfactants such as castor oil sulfates and petroleum sulfonates; cationic surfactants such as quaternary ammonium salts and imidazolines; polyalkylene glycol-based nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and polyoxyethylene alkylnaphthyl ethers; esters of polyoxyalkylene polyglycols and their dicarboxylic acids; alkylene oxide adducts of alkylphenol-formaldehyde polycondensates; and the like. These may be used individually or in combination of two or more types.

[0157] The content of the other components mentioned above can be adjusted as appropriate within a range that does not impair the effects of the present invention, but for each of them, the content is usually 0.001% to 15% by mass, and preferably 0.005% to 10% by mass, based on the total amount (100% by mass) of the lubricating oil composition. In addition, in this specification, the additive as the other component may be blended with other components in the form of a solution diluted and dissolved in a part of the above-described base oil (P) in consideration of handling properties, solubility in the base oil (P), etc. In such a case, in this specification, the above-described content of the additive as the other component means the content in terms of the active ingredient (in terms of resin content) excluding the diluent oil.

[0158] <Physical properties of the lubricating oil composition, etc.> (Kinematic viscosity, viscosity index) The lubricating oil composition according to this embodiment is required to have a kinematic viscosity at 100°C of 8.2 mm 2 / s or less. If the kinematic viscosity at 100°C of the lubricating oil composition exceeds 8.2 mm 2 / s, it becomes difficult to obtain a fuel efficiency improvement effect due to the stirring loss caused by the viscous resistance of the lubricating oil composition. From the viewpoint of making it easier to obtain the fuel efficiency improvement effect, the kinematic viscosity at 100°C of the lubricating oil composition is preferably 7.8 mm 2 / s or less, more preferably 7.1 mm 2 / s or less, still more preferably 6.1 mm 2 / s or less. Also, from the viewpoint of making it easier to suppress the evaporation loss of the lubricating oil composition, the kinematic viscosity at 100°C of the lubricating oil composition is preferably 3.8 mm 2 / s or more, more preferably 4.0 mm 2 / s or more, still more preferably 5.0 mm 2 / s or more. The lubricating oil composition according to this embodiment preferably has a viscosity index of 150 or more, more preferably 200 or more, and still more preferably 220 or more.

[0159] <HTHS viscosity at 150°C> From the perspective of oil film retention, the lubricating oil composition according to this embodiment preferably has a high-temperature high-shear (HTHS) viscosity at 150°C of 1.7 mPa·s or more, more preferably 2.0 mPa·s or more. Further, from the perspective of improving fuel efficiency, the lubricating oil composition according to this embodiment preferably has an HTHS viscosity at 150°C of less than 2.9 mPa·s, more preferably less than 2.6 mPa·s, and even more preferably less than 2.3 mPa·s. In this specification, the HTHS viscosity of the lubricating oil composition at 150°C is measured using a TBS high-temperature viscometer (Tapered Bearing Simulator Viscometer) in accordance with ASTM D4683 under the temperature condition of 150°C and a shear rate of 10 6 / s.

[0160] <Noack value> The lubricating oil composition according to this embodiment preferably has a Noack value (at 250°C for 1 hour) of 25% by mass or less, more preferably 23% by mass or less, and even more preferably 22% by mass or less. When the Noack value is within the above range, thickening of the lubricating oil composition can be suppressed, and a decrease in fuel consumption can be suppressed. Note that the Noack value is usually 0.1% by mass or more. In this specification, the Noack value is a value measured in accordance with JPI-5S-41-2004 under the conditions of 250°C for 1 hour.

[0161] <Contents of various atoms> The contents of various atoms in the lubricating oil composition of this embodiment are as described below. In this specification, the molybdenum content, calcium content, magnesium content, and phosphorus content of the lubricating oil composition are values measured in accordance with JIS-5S-38-03.

[0162] (Molybdenum content) In the lubricating oil composition of this embodiment, the molybdenum content is preferably 0.01% by mass or more, more preferably 0.04% by mass or more, and even more preferably 0.05% by mass or more, based on the total amount of the lubricating oil composition, from the viewpoint of improving the friction reduction effect. Furthermore, from the viewpoint of reducing sulfated ash, the molybdenum atom content is preferably 0.20% by mass or less, more preferably 0.15% by mass or less, and even more preferably 0.12% by 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 in any way. Specifically, they are preferably 0.01% to 0.20%, more preferably 0.04% to 0.15%, and even more preferably 0.05% to 0.12%.

[0163] (Calcium content) In the lubricating oil composition of this embodiment, the calcium content is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.10% by mass or more, based on the total amount of the lubricating oil composition, from the viewpoint of making it easier to further improve high-temperature cleaning properties. Furthermore, from the viewpoint of reducing sulfated ash and preventing LSPI (abnormal combustion), the calcium content is preferably 0.25% by mass or less, more preferably 0.22% by mass or less, and even more preferably 0.20% by 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 in any way. Specifically, they are preferably 0.01% to 0.25%, more preferably 0.05% to 0.22%, and even more preferably 0.10% to 0.20%.

[0164] (Magnesium content) In the lubricating oil composition of this embodiment, the magnesium content is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and even more preferably 0.03% by mass or more, based on the total amount of the lubricating oil composition, from the viewpoint of making it easier to further improve high-temperature cleaning properties. Furthermore, from the viewpoint of reducing sulfated ash and preventing LSPI (Low-Severity Phenomenon Incidence), the magnesium content is preferably 0.20% by mass or less, more preferably 0.15% by mass or less, and even more preferably 0.07% by 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 in any way. Specifically, they are preferably 0.01% to 0.20%, more preferably 0.02% to 0.15%, and even more preferably 0.03% to 0.07%.

[0165] (Phosphorus content) In the lubricating oil composition of this embodiment, the phosphorus content is preferably 0.01% to 0.15% by mass, more preferably 0.02% to 0.12% by mass, and even more preferably 0.06% to 0.09% by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0166] [Method for producing a lubricating oil composition] The method for producing the lubricating oil composition of this embodiment is not particularly limited. For example, the method for producing the lubricating oil composition of this embodiment includes the step of mixing a base oil (P) and a copolymer (X). The copolymer (X) comprises the following constituent units (a) to (c): • Constituent unit (a): A constituent unit derived from monomer (A) having a (meth)acryloyl group and a linear or branched alkyl group having 6 to 24 carbon atoms. • Constituent unit (b): Constituent unit derived from monomer (B) having a (meth)acryloyl group and a polar group • Constituent unit (c): A constituent unit derived from a monomer (C) having a polymerizable functional group and a cyclic structural group. The copolymer (X) has a mass-average molecular weight (Mw) of 5,000 to 50,000. The content of the copolymer (X) on a resin basis is 0.10% to 2.5% by mass on a total basis of the lubricating oil composition. The kinematic viscosity at 100°C is 8.2 mm². 2 It is less than or equal to / s. The manufacturing method may further include a step of blending one or more selected from other components as needed. There is no particular limitation on the method of mixing the components. For example, a method of blending each component into the base oil (P) can be mentioned. Further, each component may be blended after being made into a solution (dispersion) by adding a diluent oil or the like. After blending each component, it is preferable to stir and uniformly disperse them by a known method.

[0167] [Use of the lubricating oil composition] The lubricating oil composition according to the present embodiment has a low viscosity, yet has a low friction coefficient and the variation in the friction coefficient is suppressed. Therefore, the lubricity in the sliding parts of the internal combustion engine can be made good, and the generation of vibration and noise caused by the variation in the friction coefficient can also be suppressed. Therefore, the lubricating oil composition according to the present embodiment is preferably used in an internal combustion engine, more preferably used in an automobile engine, and even more preferably used in a gasoline engine. <000096​​​​​​​​​​​​​​​​​​​​(6) A method for lubricating a gasoline engine using the lubricating oil composition of this embodiment.

[0169] [Internal combustion engine containing lubricating oil composition] Other embodiments include an internal combustion engine containing the lubricating oil composition of this embodiment, preferably an internal combustion engine (engine) containing the lubricating oil composition of this embodiment as engine oil. Examples of such internal combustion engines include automobile engines, preferably gasoline engines.

[0170] [One aspect of the present invention provided] According to one aspect of the present invention, the following [1] to

[15] are provided. [1] Contains a base oil (P) and a copolymer (X), The copolymer (X) comprises the following constituent units (a) to (c): • Constituent unit (a): A constituent unit derived from monomer (A) having a (meth)acryloyl group and a linear or branched alkyl group having 6 to 24 carbon atoms. • Constituent unit (b): Constituent unit derived from monomer (B) having a (meth)acryloyl group and a polar group • Constituent unit (c): A constituent unit derived from a monomer (C) having a polymerizable functional group and a cyclic structural group. The copolymer (X) has a mass-average molecular weight (Mw) of 5,000 to 50,000. The content of the copolymer (X) on a resin basis is 0.10% to 2.5% by mass on a total basis of the lubricating oil composition. The kinematic viscosity at 100°C is 8.2 mm². 2 A lubricating oil composition with a viscosity of / s or less. [2] The lubricating oil composition according to [1] above, further comprising a molybdenum-based friction modifier (M). [3] The lubricating oil composition according to [2] above, wherein the molybdenum-based friction modifier (M) comprises one or more selected from the group consisting of dinuclear molybdenum dithiocarbamate, trinuclear molybdenum dithiocarbamate, and molybdenamine complexes. [4] The lubricating oil composition according to [3] above, wherein the binuclear molybdenum dithiocarbamate is a compound (M1) represented by the following general formula (m1). [Chemical formula] [In the general formula (m1), R 1 , R 2 , R 3 , and R 4 each independently represent a short-chain substituent group (α) which is an aliphatic hydrocarbon group having 4 to 12 carbon atoms or a long-chain substituent group (β) which is an aliphatic hydrocarbon group having 13 to 22 carbon atoms. However, the molar ratio [(α) / (β)] of the short-chain substituent group (α) to the long-chain substituent group (β) in the whole molecule of the compound (M1) is 0.10 to 2.0. Further, in the general formula (m1), X 1 , X 2 , X 3 , and X 4 each independently represent an oxygen atom or a sulfur atom.] [5] The lubricating oil composition according to [2] or [3] above, wherein the molybdenum content derived from the molybdenum-based friction modifier (M) is 0.01% by mass to 0.20% by mass based on the total amount of the lubricating oil composition. [6] The lubricating oil composition according to any one of [1] to [5] above, further containing a metal-based detergent. [7] The lubricating oil composition according to [6] above, wherein the metal-based detergent contains one or more selected from the group consisting of a calcium-based detergent and a magnesium-based detergent. [8] The lubricating oil composition according to [7] above, wherein the metal-based detergent contains the calcium-based detergent, and the calcium content derived from the calcium-based detergent is 0.01% by mass to 0.25% by mass based on the total amount of the lubricating oil composition. [9] The lubricating oil composition according to [7] or [8] above, wherein the metal-based detergent contains the magnesium-based detergent, and the magnesium content derived from the magnesium-based detergent is 0.01% by mass to 0.20% by mass based on the total amount of the lubricating oil composition.

[10] The lubricating oil composition according to any one of [1] to [9] above, further comprising an ashless dispersant.

[11] The lubricating oil composition according to

[10] above, wherein the nitrogen content derived from the ashless dispersant is 0.01% by mass to 0.15% by mass on a total basis of the lubricating oil composition.

[12] The lubricating oil composition according to any one of [1] to

[11] above, further comprising zinc dithiophosphate.

[13] The lubricating oil composition according to

[12] above, wherein the phosphorus content derived from zinc dithiophosphate is 0.01% by mass to 0.10% by mass on a basis of the total amount of the lubricating oil composition.

[14] A lubricating oil composition according to any of [1] to

[13] above, for use in an internal combustion engine.

[15] A lubricating oil composition according to any of [1] to

[13] above, for use in a gasoline engine. [Examples]

[0171] The present invention will be specifically described by the following examples, but the present invention is not limited to the following examples.

[0172] [Methods for measuring various physical properties] The properties of each raw material used in each example and comparative example, as well as the properties of each lubricating oil composition in each example and comparative example, were measured according to the following procedure.

[0173] (1)Kinematic viscosity, viscosity index The kinematic viscosity at 40°C, kinematic viscosity at 100°C, and viscosity index of the base oil and lubricating oil compositions were measured or calculated in accordance with JIS K2283:2000.

[0174] (2) HTHS viscosity at 150°C The HTHS viscosity of the lubricating oil composition at 150°C was determined in accordance with ASTM D4683, using a TBS (Tapered Bearing Simulator Viscometer) under a temperature of 150°C and a shear rate of 10 6 Measured using / s.

[0175] (3) Noack evaporation The amount of Nock evaporation of the lubricating oil composition was measured in accordance with ASTM D 5800 (Nock test: 250°C, 1 hour).

[0176] (4) Mass average molecular weight (Mw), molecular weight distribution (Mw / Mn) A Waters 1515 isocratic HPLC pump and a 2414 differential refractive index (RI) detector were used, with one TSKguardcolumn SuperHZ-L and two TSKSuperMultipore HZ-M columns from Tosoh Corporation installed in that order from upstream. Measurements were taken at a temperature of 40°C, with tetrahydrofuran as the mobile phase, a flow rate of 0.35 mL / min, and a sample concentration of 1.0 mg / mL. The results were then calculated in terms of standard polystyrene equivalents.

[0177] (5) PSSI (Shear Stability Index) PSSI represents the percentage decrease in viscosity due to shear originating from the polymer, and was calculated using the following formula specified in ASTM D6022-06 (2012).

number

[0178] (6) Molybdenum content, calcium content, magnesium content, and phosphorus content The molybdenum, calcium, magnesium, and phosphorus content of the lubricating oil composition was measured in accordance with JIS-5S-38-03.

[0179] [Manufacturing Examples 1-2] Copolymers (X)-1 and (X)-2 were produced according to the following manufacturing examples 1 and 2.

[0180] <Monomers used> (Monomer (A)) • "Dodecyl acrylate": In the above general formula (a-1), R a1 is a hydrogen atom, and R a2 It is a compound in which the group is a dodecyl group (a linear alkyl group with 12 carbon atoms).

[0181] (Monomer (B)) • "2-Hydroxyethyl acrylate": This monomer has an acryloyl group and a hydroxyl group as a polar group. Its structural formula is shown below. [ka]

[0182] (Monomer(C)) • "Benzyl acrylate": A monomer in which the polymerizable functional group is an acryloyl group and the cyclic structure is benzene. Specifically, in the above general formula (c-1), Y is an acryloyl group, and L 1 Z is a monomer where is an oxymethylene group and Z is a phenyl group.

[0183] <Manufacturing Example 1: Manufacturing of copolymer(X)-1> In a reaction vessel equipped with a stirring device, a heating and cooling device, a thermometer, a dropping funnel, and a nitrogen blowing tube, 20 g (83 mmol) of dodecyl acrylate as monomer (A) and 28 g of 2-ethylhexyl sebacate as solvent were charged. Next, the reaction vessel was purged with nitrogen, and 0.1 g (0.4 mmol) of 2,2'-azobis(2,4-dimethylvaleronitrile) and 0.13 g (0.4 mmol) of dodecylcyanomethyl trithiocarbonate were added as initiators. The mixture was then slowly heated with stirring and reacted at 75-85°C for 6 hours. After confirming that more than 96% of the dodecyl acrylate had been converted to polymer, 5 g (31 mmol) of benzyl acrylate and 0.05 g (0.2 mmol) of 2,2'-azobis(2,4-dimethylvaleronitrile) were added as monomer (C), and the mixture was reacted at 75-85°C for another 6 hours. After confirming that more than 96% of the benzyl acrylate had been converted to polymer, 3 g (26 mmol) of 2-hydroxyethyl acrylate and 0.05 g (0.2 mmol) of 2,2'-azobis(2,4-dimethylvaleronitrile) were added as monomer (B), and the reaction was continued at a temperature of 75-85°C for a further 6 hours. After the reaction was complete, copolymer (X)-1 was obtained by removing the unreacted monomer under reduced pressure.

[0184] <Manufacturing Example 2: Manufacturing of Copolymer (X)-2> In a reaction vessel equipped with a stirring device, a heating and cooling device, a thermometer, a dropping funnel, and a nitrogen blowing tube, 20 g (83 mmol) of dodecyl acrylate, 3 g (26 mmol) of 2-hydroxyethyl acrylate, 5 g (31 mmol) of benzyl acrylate, and 28 g of 2-ethylhexyl sebacate as a solvent were charged. Next, the reaction vessel was purged with nitrogen, and 0.1 g (0.4 mmol) of 2,2'-azobis(2,4-dimethylvaleronitrile) and 0.08 g (0.4 mmol) of dodecyl mercaptan were added as initiators. The mixture was then slowly heated with stirring and reacted at a temperature of 75-85°C for 6 hours. After the reaction was complete, the unreacted monomer was removed by distillation under reduced pressure to obtain copolymer (X)-2.

[0185] Table 1 shows the composition and properties of copolymers (X)-1 to (X)-2.

[0186] [Table 1]

[0187] [Examples 1-4, Comparative Examples 1-5] The following components were added in the amounts shown in Table 2 and thoroughly mixed to obtain a lubricating oil composition. Details of each component used in Examples 1-4 and Comparative Examples 1-5 are as follows.

[0188] <Base oil (P)> ·“Base oil (P1)” Mineral oil (API classification: Group III, kinematic viscosity at 40°C: 18.5 mm) 2 / s, 100℃ kinematic viscosity: 4.1mm 2 / s, Viscosity index: 125, Noack evaporation rate: 12% by mass ·“Base oil (P2)” Mineral oil (API classification: Group II, kinematic viscosity at 40°C: 9.7 mm) 2 / s, 100℃ kinematic viscosity: 2.7mm 2 / s, Viscosity index: 111, Noack evaporation rate: 43% by mass ·“Base oil (P3)” Mineral oil (API classification: Group III, kinematic viscosity at 40°C: 19.7 mm) 2 / s, 100℃ kinematic viscosity: 4.3mm 2 / s, Viscosity index: 123, Noack evaporation rate: 14% by mass ·“Base oil (P4)” Mineral oil (API classification: Group II, kinematic viscosity at 40°C: 8.0 mm) 2 / s, 100℃ kinematic viscosity: 2.3mm 2 / s, Viscosity index: 102, Noack evaporation rate: 74% by mass)

[0189] <Copolymer (X)> Copolymers (X)-1 to (X)-2, prepared in Production Examples 1 and 2, were used.

[0190] <Comparative polymer> ·“Distributed PMA” It was used to compare its effects with those of copolymer (X). This PMA has a mass-average molecular weight (Mw) of 57,000, a molecular weight distribution (Mw / Mn) of 2.19, and contains dimethylaminoethyl groups.

[0191] <Molybdenum-based friction modifier (M)> • "Dinuclear molybdenum dithiocarbamate" As a dinuclear molybdenum dithiocarbamate (hereinafter also referred to as "dinuclear MoDTC"), a compound was used in which the aliphatic hydrocarbon group of the short-chain substituent group (α) has 8 carbon atoms and the aliphatic hydrocarbon group of the long-chain substituent group (β) has 13 carbon atoms in the general formula (m1). In the general formula (m1), X 1 , X 2 , X 3 , and X 4 is a sulfur atom. The molar ratio [(α) / (β)] of short-chain substituents (α) to long-chain substituents (β) in the entire molecule of dinuclear MoDTC is 1.0. • "Molybdenum dithiocarbamate trinuclear" As the trinuclear molybdenum dithiocarbamate (hereinafter also referred to as "trinuclear MoDTC"), we used trinuclear molybdenum dithiocarbamate with a molybdenum atom content of 5.3% by mass. • "Molybdenum amine complex" Dialkylamine molybdate (molybdenum atom content: 7.9% by mass) was used as the molybdenamine complex.

[0192] <Other additives> (Viscosity index improver) ·“Comb-shaped PMA” Mass average molecular weight (Mw): 310,000, molecular weight distribution (Mw / Mn): 1.93, PSSI: 1

[0193] (Benzotriazole compounds) As a metal deactivator, we used 1-[N,N-bis(2-ethylhexyl)aminomethyl]-4-methyl-1H-benzotriazole, a benzotriazole compound. [ka] 1-[N,N-bis(2-ethylhexyl)aminomethyl]-4-methyl-1H-benzotriazole is a compound in general formula (c1), R c1 However, it is a methyl group, p is 1, and R c2 However, it is a methylene group, R c3 and R c4 However, it is a compound with a 2-ethylhexyl group.

[0194] (Additive package) This additive package conforms to API / ILSAC and SN / GF-6 standards and contains the following additives. Metal-based cleaning agents: Calcium sulfonate, magnesium sulfonate Dispersant: succinimide (nitrogen content: 1.4% by mass), boron-modified imide Anti-wear agent: ZnDTP (P content: 6.7% by mass, Zn content: 7.4% by mass) Antioxidants: Amine-based antioxidants, phenol-based antioxidants Pour point depressant

[0195] [Evaluation Method] The following tests were conducted to evaluate the reduction in the coefficient of friction and the variability of the coefficient of friction. Furthermore, a visual evaluation was conducted to confirm the solubility of the copolymer in mineral oil. Furthermore, fuel efficiency tests were conducted to evaluate the fuel-saving performance of lubricating oil compositions containing copolymers.

[0196] <Evaluation of friction coefficient reduction and friction coefficient variation> The coefficient of friction was measured using the prepared lubricating oil composition under the following conditions, using an SRV testing machine (manufactured by Optimol). Cylinder: AISI52100 • Disk: AISI52100 • Frequency: 50Hz ·Amplitude: 1.5mm • Load: 400N Temperature: 30-140℃, increasing in 10-degree increments. • Test time: 5 minutes for each temperature First, the temperature was increased in 10-degree increments from 30°C to 130°C, and the test was conducted by sliding the parts for 5 minutes at each temperature under the following conditions. During the final minute at 130°C, the coefficient of friction was measured every second, and the average value and standard deviation of the coefficient of friction during the final minute were calculated. Furthermore, the test was conducted by sliding the parts for 5 minutes at each temperature while increasing the temperature from 30°C to 140°C in 10°C increments, under the conditions described below. During the final minute at 140°C, the coefficient of friction was measured every second, and the average value and standard deviation of the coefficient of friction during the final minute were calculated.

[0197] Then, by dividing the difference between the average friction coefficient of each lubricating oil composition and the average friction coefficient of the lubricating oil composition of Comparative Example 1 by the average friction coefficient of the lubricating oil composition of Comparative Example 1, the reduction rate (%) of the average friction coefficient of each lubricating oil composition from the average friction coefficient of Comparative Example 1 was calculated. A larger reduction rate from the average value of the coefficient of friction in Comparative Example 1 indicates a superior effect in reducing the coefficient of friction. In this embodiment, a reduction rate of 10% or more was considered acceptable.

[0198] Furthermore, by dividing the difference between the standard deviation of the friction coefficient of each lubricating oil composition and the standard deviation of the friction coefficient of the lubricating oil composition of Comparative Example 1 by the standard deviation of the friction coefficient of the lubricating oil composition of Comparative Example 1, the reduction rate (%) of the standard deviation of the friction coefficient of each lubricating oil composition from the standard deviation of the friction coefficient of Comparative Example 1 was calculated. The greater the reduction rate from the standard deviation of the friction coefficient in Comparative Example 1, the more the variation in the friction coefficient is suppressed. In this embodiment, a reduction rate of 60% or more was considered acceptable.

[0199] <Exterior Evaluation> The lubricating oil composition was heated to 80°C, stirred for 30 minutes, and then allowed to stand until it reached room temperature (25°C). The appearance of the lubricating oil composition at room temperature was then visually evaluated. Compositions that showed no turbidity were rated "A," and those that showed turbidity were rated "B."

[0200] <Evaluation of fuel efficiency> In accordance with JASO M366:2019 "Lubricants for gasoline engines for automobiles - Test method for firing fuel efficiency," tests were conducted on the lubricant compositions of Example 3 and Comparative Example 5, and the improvement in fuel efficiency of the lubricant composition of Example 3 compared to the lubricant composition of Comparative Example 5 was measured.

[0201] The results are shown in Table 2.

[0202] [Table 2]

[0203] From Table 2, the following can be seen. The lubricating oil compositions of Examples 1 to 4, each containing copolymer (X)-1 to copolymer (X)-2, exhibited low friction coefficients and minimal variation in friction coefficients. Furthermore, the visual evaluation results showed no turbidity in the lubricating oil compositions, indicating good solubility of copolymer (X)-1 to copolymer (X)-2 in mineral oil. In contrast, the lubricating oil compositions of Comparative Examples 2, 4, and 5, which do not contain copolymer (X), have a higher kinematic viscosity at 100°C compared to the lubricating oil composition of Comparative Example 1. Although the coefficient of friction is kept low, it can be seen that the variation in the coefficient of friction is large in all of them. Furthermore, while the lubricating oil composition of Comparative Example 3, which contains dispersed PMA instead of copolymer (X), also has a low coefficient of friction, it can be seen that the variation in the coefficient of friction is large.

[0204] Furthermore, the fuel efficiency evaluation results show that the lubricating oil composition of Example 3, which contains copolymer (X)-2, exhibits improved fuel efficiency compared to the lubricating oil composition of Comparative Example 5, which does not contain copolymer (X).

Claims

1. It contains a base oil (P) and a copolymer (X), The copolymer (X) comprises the following constituent units (a) to (c): • Constituent unit (a): A constituent unit derived from monomer (A) having a (meth)acryloyl group and a linear or branched alkyl group having 6 to 24 carbon atoms. • Constituent unit (b): Constituent unit derived from monomer (B) having a (meth)acryloyl group and a polar group • Constituent unit (c): A constituent unit derived from a monomer (C) having a polymerizable functional group and a cyclic structural group. The copolymer (X) has a mass-average molecular weight (Mw) of 5,000 to 50,000. The content of the copolymer (X) on a resin basis is 0.10% to 2.5% by mass on a total basis of the lubricating oil composition. The kinematic viscosity at 100°C is 8.2 mm². ２ / s or less, A lubricating oil composition in which the content of constituent unit (c) is 7 mol% to 30 mol% based on the total constituent units of the copolymer (X).

2. Furthermore, the lubricating oil composition according to claim 1 contains a molybdenum-based friction modifier (M).

3. The lubricating oil composition according to claim 2, wherein the molybdenum-based friction modifier (M) comprises one or more selected from the group consisting of dinuclear molybdenum dithiocarbamate, trinuclear molybdenum dithiocarbamate, and molybdenum amine complexes.

4. The lubricating oil composition according to claim 3, wherein the binuclear molybdenum dithiocarbamate is a compound (M1) represented by the following general formula (m1). 【Chemistry 1】 [In the general formula (m1), R １ , R ２ , R ３ , and R ４ each independently represent a short-chain substituent group (α) which is an aliphatic hydrocarbon group having 4 to 12 carbon atoms or a long-chain substituent group (β) which is an aliphatic hydrocarbon group having 13 to 22 carbon atoms. However, the molar ratio [(α) / (β)] of the short-chain substituent group (α) to the long-chain substituent group (β) in the entire molecule of the compound (B1) is 0.10 to 2.

0. Further, in the general formula (b1), X １ , X ２ , X ３ , and X ４ each independently represent an oxygen atom or a sulfur atom.]

5. The lubricating oil composition according to claim 2 or 3, wherein the molybdenum content derived from the molybdenum-based friction modifier (M) is 0.01% by mass to 0.20% by mass on a basis of the total amount of the lubricating oil composition.

6. Furthermore, the lubricating oil composition according to any one of claims 1 to 5, further containing a metal-based detergent.

7. The lubricating oil composition according to claim 6, wherein the metal-based detergent comprises one or more selected from the group consisting of calcium-based detergents and magnesium-based detergents.

8. The metal-based cleaning agent includes the calcium-based cleaning agent, The lubricating oil composition according to claim 7, wherein the calcium content derived from the calcium-based detergent is 0.01% by mass to 0.25% by mass on a basis of the total amount of the lubricating oil composition.

9. The metal-based cleaning agent includes the magnesium-based cleaning agent, The lubricating oil composition according to claim 7 or 8, wherein the magnesium content derived from the magnesium-based detergent is 0.01% by mass to 0.20% by mass on a basis of the total amount of the lubricating oil composition.

10. Furthermore, the lubricating oil composition according to any one of claims 1 to 9, further containing an ashless dispersant.

11. The lubricating oil composition according to claim 10, wherein the nitrogen content derived from the ashless dispersant is 0.01% by mass to 0.15% by mass on a basis of the total amount of the lubricating oil composition.

12. Furthermore, the lubricating oil composition according to any one of claims 1 to 11 contains zinc dithiophosphate.

13. The lubricating oil composition according to claim 12, wherein the phosphorus content derived from zinc dithiophosphate is 0.01% by mass to 0.10% by mass on a basis of the total amount of the lubricating oil composition.

14. A lubricating oil composition according to any one of claims 1 to 12, for use in an internal combustion engine.

15. A lubricating oil composition according to any one of claims 1 to 12, for use in a gasoline engine.

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