Lubricating oil composition

Abstract

To provide a lubricating oil composition capable of highly suppressing oxidative deterioration while using a component different from a component conventionally used as an antioxidant.SOLUTION: The lubricating oil composition comprises a lubricating base oil; [In formula (1), R1 each independently represents hydrogen or the like, R2 each independently represents hydrogen or the like, R3 each independently represents hydrogen or the like, and n represents an integer of 1 or more and 5 or less.]. The lubricating oil composition according to claim 1, further comprising a base oil.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Lubricating oil compositions have been used in various mechanical devices having moving parts in order to reduce the friction and wear of the components constituting the moving parts and to improve the energy saving and life of the devices.In such lubricating oil compositions, the lubricating base oil, which is an essential component, is oxidized and deteriorated when it comes into contact with air, so that in order to suppress the oxidized deterioration, it is common to use a combination of the lubricating base oil and an antioxidant.

[0003] Generally, phenol-based antioxidants and amine-based antioxidants are used as such antioxidants (for example, JP 2023-049434 A (Patent Document 1) describes amine-based antioxidants and phenol-based antioxidants as antioxidants to be blended in lubricating oil compositions).

[0004] In the field of lubricating oil compositions, from the viewpoint of designing appropriate compositions for various applications, etc., there is a demand for the development of new compositions that can prevent oxidative degradation of lubricating base oils while utilizing components different from those conventionally used as antioxidants. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2023-049434 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the problems associated with the prior art, and has as its object to provide a lubricating oil composition that is capable of suppressing oxidative degradation of a lubricating base oil while utilizing a component that is different from components that have conventionally been used as antioxidants. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to achieve the above-mentioned object, and as a result have found that by making a lubricating oil composition contain a lubricating base oil and a pyridine imine compound represented by the following general formula (1), it is possible to suppress oxidative degradation of the composition, and have thus completed the present invention.

[0008] That is, the present invention provides the following aspects.

[0009] [1] a lubricating base oil; The following general formula (1):

[0010] [ka]

[0011] [In formula (1), R 1 each independently represents one selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 8 carbon atoms, R 2 each independently represents one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, and an aryl group which may have at least one substituent selected from the group consisting of an alkyl group and an alkoxy group and which has a total of 6 to 12 carbon atoms including the carbon atoms of the substituent; R 3 each independently represents one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, and an alkoxy group having 1 to 8 carbon atoms; n is an integer between 1 and 5. a pyridine imine compound represented by the formula: A lubricating oil composition comprising:

[0012] [2] The pyridine imine compound is represented by the following general formulas (2) to (3):

[0013] [ka]

[0014] [R in formulas (2) to (3)] 1 , R 2 and R 3 are R in the formula (1) 1 , R 2 and R 3 is equivalent to.] The lubricating oil composition according to [1], wherein the compound is at least one selected from the group of compounds represented by the formula:

[0015] [3] In the formula representing the pyridine imine compound, R 1 are all hydrogen atoms, and R 2 are each independently one selected from the group consisting of a methyl group, a phenyl group, and a p-methoxyphenyl group, and R 3 is each independently one selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, a methoxy group, and an ethoxy group.

[0016] [4] The lubricating oil composition according to any one of [1] to [3], further comprising a zinc salt.

[0017] [5] The lubricating oil composition according to [4], wherein the zinc salt is at least one selected from the group consisting of zinc chloride, zinc acetate, zinc 2-ethylhexanoate, and zinc naphthenate.

[0018] In the present invention, the pyridine imine compound is used to exert high antioxidant performance. Here, pyridine diimine compounds can form complexes with various transition metals, and in particular, complexes of these compounds with iron, cobalt, etc. are known to exhibit excellent effects on olefin polymerization and oligomerization. However, until now, the technical idea of ​​using such pyridine diimine compounds as antioxidants in lubricating oil compositions has not been disclosed in the literature. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a lubricating oil composition that is capable of highly inhibiting oxidative degradation while utilizing components that are different from components that have conventionally been used as antioxidants. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will be described in detail below with reference to preferred embodiments. In this specification, unless otherwise specified, the expression "X to Y" for numerical values ​​X and Y means "X or more and Y or less." In such an expression, when a unit is assigned only to the numerical value Y, the unit also applies to the numerical value X.

[0021] The lubricating oil composition of the present invention comprises: a lubricating base oil; The following general formula (1):

[0022] [ka]

[0023] [In formula (1), R 1 each independently represents one selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 8 carbon atoms, R 2each independently represents one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, and an aryl group which may have at least one substituent selected from the group consisting of an alkyl group and an alkoxy group and which has a total of 6 to 12 carbon atoms including the carbon atoms of the substituent; R 3 each independently represents one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, and an alkoxy group having 1 to 8 carbon atoms; n is an integer between 1 and 5. a pyridine imine compound represented by the formula: In this way, the lubricating oil composition of the present invention utilizes a pyridine imine compound to combat oxidative deterioration of the lubricating base oil.

[0024] <Pyridine imine compounds> The pyridine imine compound according to the present invention is a compound represented by the general formula (1). 1 The compound may contain (5-n) of these R (n is an integer (natural number) of 1 to 5). 1 When R is present in a compound, 1 each independently represents at least one selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 8 carbon atoms (R 1 If there are multiple (n is 3 or less), R 1 may be the same or different).

[0025] Such an R 1 The alkyl group that can be selected as R has a carbon number of 1 to 8 (more preferably 1 to 6, even more preferably 1 to 4, particularly preferably 1 to 3, and most preferably 1 to 2). When the carbon number is equal to or less than the upper limit, a higher effect can be obtained in terms of solubility in base oil and ease of synthesis compared to when the carbon number exceeds the upper limit. In addition, such R 1The alkyl group having 1 to 8 carbon atoms that can be selected as R may be any of linear, branched, and cyclic, and is not particularly limited, but from the viewpoint of ease of synthesis, linear alkyl groups and / or branched alkyl groups are preferred. 1 From the viewpoint of ease of compound synthesis, each of the groups is preferably a hydrogen atom, a methyl group, an ethyl group, a propyl group, or an isopropyl group, more preferably a hydrogen atom, a methyl group, an ethyl group, or a propyl group, even more preferably a hydrogen atom, a methyl group, or an ethyl group, particularly preferably a hydrogen atom or a methyl group, and most preferably a hydrogen atom.

[0026] Furthermore, R in formula (1) 2 The compound contains n Rs (n is an integer (natural number) between 1 and 5). 2 each independently represents at least one selected from the group consisting of a hydrogen atom; an alkyl group having 1 to 8 carbon atoms; and an aryl group which may have at least one substituent selected from the group consisting of an alkyl group and an alkoxy group and which has a total of 6 to 12 carbon atoms including the carbon atoms of the substituent (R 2 If there are multiple (n is 2 or more), R 2 may be the same or different).

[0027] Such an R 2 The alkyl group that can be selected as R has a carbon number of 1 to 8 (more preferably 1 to 6, even more preferably 1 to 4, particularly preferably 1 to 3, and most preferably 1 to 2). When the carbon number is equal to or less than the upper limit, it is possible to obtain a higher effect in terms of solubility in base oil and ease of synthesis compared to when the carbon number exceeds the upper limit. In addition, such R 2The alkyl group having 1 to 8 carbon atoms that can be selected as may be any of linear, branched, and cyclic alkyl groups, and is not particularly limited. However, from the viewpoint of ease of synthesis, a linear alkyl group is preferred, and among these, a methyl group, an ethyl group, or a propyl group is more preferred, a methyl group or an ethyl group is even more preferred, and a methyl group is particularly preferred.

[0028] Such an R 2 The aryl group that can be selected as the aryl group is an aryl group that may have at least one substituent selected from the group consisting of an alkyl group and an alkoxy group and has a total carbon number of 6 to 12 (more preferably 6 to 8), including the carbon number of the substituent. By setting the carbon number of such an aryl group to the above upper limit or less, it is possible to make the resulting compound excellent in solubility in base oil and easy to synthesize.

[0029] In addition, R in such formula (1) 2 From the viewpoint of ease of synthesis, each of R is preferably independently a linear alkyl group; or an aryl group which may have at least one substituent selected from the group consisting of alkyl groups and alkoxy groups and which has a total of 6 to 12 carbon atoms including the carbon atoms of the substituent; among these, methyl, ethyl, propyl, phenyl, or p-alkoxyphenyl groups having a total of 6 to 8 carbon atoms are preferred, methyl, ethyl, phenyl, or p-methoxyphenyl groups are more preferred, methyl, phenyl, or p-methoxyphenyl groups are even more preferred, methyl or p-methoxyphenyl groups are particularly preferred, and methyl groups are most preferred. Note that from the viewpoint of ease of availability of raw materials during production, etc., R in the above formula (1) is 2 A preferred example of the group is a hydrogen atom.

[0030] In addition, R in the formula (1) 3The alkyl group that can be selected as R has a carbon number of 1 to 8 (more preferably 1 to 6, even more preferably 1 to 4, particularly preferably 1 to 3, and most preferably 1 to 2). When the carbon number is equal to or less than the upper limit, a higher effect can be obtained in terms of ease of availability of raw materials compared to when the carbon number exceeds the upper limit. 3 The alkyl group having 1 to 8 carbon atoms that can be selected as the alkyl group is not particularly limited and may be any of linear, branched, and cyclic groups. From the viewpoint of easy availability of raw materials, among these, a methyl group, an ethyl group, a propyl group, and an isopropyl group are more preferable, and a methyl group is particularly preferable.

[0031] In addition, R in the formula (1) 3 The alkoxy group that can be selected as R has a carbon number of 1 to 8 (more preferably 1 to 6, even more preferably 1 to 4, particularly preferably 1 to 3, and most preferably 1 to 2). When the carbon number is equal to or less than the upper limit, a higher effect can be obtained in terms of ease of availability of raw materials compared to when the carbon number exceeds the upper limit. 3 The alkoxy group having 1 to 8 carbon atoms that can be selected as is not particularly limited, but from the viewpoint of easy availability of raw materials, among them, a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a butoxy group, or an isobutoxy group is more preferable, a methoxy group, an ethoxy group, or a propoxy group is even more preferable, and a methoxy group is particularly preferable.

[0032] In addition, R in the formula (1) 3 From the viewpoint of availability of raw materials, each of the groups is more preferably a hydrogen atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, or a methoxy group, and particularly preferably a hydrogen atom, a methyl group, an isopropyl group, or a methoxy group.

[0033] In addition, R in the formula (1) 3is a substituent other than a hydrogen atom, the substitution position of the group on the benzene ring is arbitrary. However, since the 2nd, 4th, and 6th positions of the benzene ring have a large electronic influence on the adjacent nitrogen atom, if you want to increase the electron density, the substituent R 3 is particularly preferably an electron-donating substituent such as an alkyl group or an alkoxy group.

[0034] In the formula (1), n ​​is an integer of 1 to 5 (here, a natural number), preferably an integer of 1 to 3, more preferably 1 or 2. Note that n is R 1 (In formula (1), the substituent other than the formula: -CR 2 The number of groups containing the structure represented by =N-) bonded (R 1 The number of substituents other than those on the pyridine ring is shown. 1 The substitution position of the substituent other than the formula: -CR on the pyridine ring is not particularly limited and can be any position. However, when a zinc salt is used as described later, it is possible to enhance the interaction with zinc, so it is preferable to use a substituent of the formula: -CR at the 2-position or at the 2-position and the 6-position of the pyridine. 2 A group containing a structure represented by =N- (R 1 It is particularly preferred to place a substituent other than

[0035] Furthermore, a suitable example (a suitable embodiment) of the pyridine imine compound represented by the general formula (1) is not particularly limited, but for example, the compound represented by the formula (1), n ​​is 1 or 2, and R 1 are all hydrogen atoms, and R 2 are each independently one selected from the group consisting of a methyl group, a phenyl group, and a p-methoxyphenyl group (more preferably a methyl group), and R 3 are each independently one selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, a methoxy group and an ethoxy group.

[0036] The pyridine imine compound represented by the general formula (1) includes compounds represented by the following general formulas (2) to (3):

[0037] [ka]

[0038] It is preferable that the compound R in the formulas (2) to (3) is at least one selected from the group of compounds represented by the formulas (2) to (3). 1 , R 2 and R 3 are R in the formula (1) 1 , R 2 and R 3 and the preferred examples thereof are also the same. Therefore, for example, 1 are all hydrogen atoms, and R 2 are each independently one selected from the group consisting of a methyl group, a phenyl group, and a p-methoxyphenyl group, and R 3 are each independently one selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, a methoxy group and an ethoxy group.

[0039] Furthermore, examples of such pyridine imine compounds represented by general formula (1) include those represented by the following formulae (a) to (m):

[0040] [ka]

[0041] Compounds represented by the following formula (1) can be mentioned as preferred compounds.

[0042] The method for producing such a pyridineimine compound represented by general formula (1) may be any known synthesis method that can be appropriately applied to produce the structure represented by general formula (1), and is not particularly limited. For example, a compound represented by the following general formula (4):

[0043] [ka]

[0044] [R in formula (4)] 1 , R 2 and n are R in the formula (1), 1 , R 2 and n.] (e.g., 2-formylpyridine, 2-acetylpyridine, 2,6-diacetylpyridine, 2-formylpyridine, 2,6-diphenylpyridine, 2,6-di(4-methoxyphenyl)pyridine, etc.) and a carbonyl compound represented by the following general formula (5):

[0045] [ka]

[0046] [R in formula (5)] 3 is R in the formula (1) 3 is equivalent to.] Preferably, the carbonyl compound is synthesized by a condensation reaction with an aniline compound represented by the formula (e.g., 2,4-dimethylaniline, 2,6-diisopropylaniline, 4-methoxy-2-methylaniline, 2,6-dimethylaniline, etc.). A suitable synthesis method using such a condensation reaction is, for example, dissolving the carbonyl compound and the aniline compound in a solvent such as toluene, ethanol, THF, or DMF and then subjecting them to a condensation reaction under heating and reflux conditions. An acid catalyst may be used as needed, taking into consideration the types of the carbonyl compound and the aniline compound. To efficiently promote the condensation reaction under heating and reflux conditions, it is preferable to use a dehydration apparatus such as a Dean-Stark apparatus. When using such a synthesis method, the product may precipitate as a precipitate depending on the compatibility between the produced compound and the solvent used. In such a case, the precipitate can be filtered and then washed with an appropriate solvent, enabling efficient purification. In addition, when the produced compound is soluble in the solvent used in the synthesis, it may be purified by means of recrystallization using an appropriate solvent, separation by column chromatography, etc. As described above, the method for purifying the produced compound is not particularly limited, and known methods such as purification by recrystallization can be appropriately used depending on the type of compound, etc.

[0047] In addition, in the present invention, by combining the pyridineimine compound with the lubricating base oil, it is possible to suppress oxidative degradation of the composition, but since this makes it possible to further enhance the oxidative degradation suppression effect of the composition, it is preferable to contain a zinc salt together with the pyridineimine compound in the lubricating base oil.In this way, it is preferable that the lubricating oil composition of the present invention further contains a zinc salt.Note that the reason why a higher effect is obtained in terms of suppressing oxidative degradation when a zinc salt is contained in this way is not necessarily clear, but the inventors have found through research that an even higher level of oxidative degradation suppression effect can be obtained when a zinc salt is used in combination with the pyridineimine compound in the composition.

[0048] Furthermore, such zinc salts are preferably at least one compound selected from the group consisting of zinc fatty acid zinc, zinc halide, zinc nitrate, zinc sulfate, zinc oxide, zinc sulfide, and zinc phosphate.

[0049] The fatty acid zinc salt used as such a zinc salt is not particularly limited, and the fatty acid may be either saturated or unsaturated. Examples of such fatty acid zinc salts that can be used include zinc formate, zinc acetate, zinc propionate, zinc butanoate, zinc hexanoate, zinc adipate, zinc octanoate, zinc 2-ethylhexanoate, zinc benzoate, zinc cyclopentanoate, zinc cyclohexanoate, and zinc naphthenate. The number of carbon atoms in such fatty acids is not particularly limited, but is preferably 1 to 30 (more preferably 8 to 20). By keeping the carbon number within the above range, it is possible to improve solubility, particularly in hydrocarbon base oils.

[0050] Examples of zinc halides used as the zinc salt include zinc fluoride, zinc chloride, zinc bromide, and zinc iodide.

[0051] As such, suitable examples of the zinc salt include zinc fluoride, zinc chloride, zinc bromide, zinc iodide, zinc nitrate, zinc sulfate, zinc oxide, zinc sulfide, zinc phosphate, zinc acetate, zinc propionate, zinc butanoate, zinc hexanoate, zinc adipate, zinc octanoate, zinc 2-ethylhexanoate, zinc benzoate, zinc cyclohexanoate, and zinc naphthenate. Among these, zinc halides and zinc fatty acids are preferred in terms of availability, with zinc chloride, zinc acetate, zinc 2-ethylhexanoate, and zinc naphthenate being more preferred, and zinc acetate, zinc 2-ethylhexanoate, and zinc naphthenate being even more preferred in terms of solubility in base oil.

[0052] Furthermore, when using such a zinc salt, the lubricating oil composition of the present invention preferably contains a complex that is a reaction product of the pyridineimine compound and the zinc salt, from the viewpoint of obtaining higher antioxidant performance. Thus, in the lubricating oil composition of the present invention, the pyridineimine compound may be contained in the form of a zinc complex (in other words, the pyridineimine compound may be contained as a ligand of the zinc complex). Such a complex can be easily prepared by mixing the pyridineimine compound and the zinc salt in a base oil, and the preparation conditions for the complex are not particularly limited. Compared to conventionally known antioxidants, the use of such a complex makes it possible to suppress oxidative degradation over a long period of time even with a relatively small amount. The inventors speculate that this is because conventionally known antioxidants basically prevent oxidation through equivalent reactions, whereas the present invention prevents oxidative degradation by catalytically decomposing oxidizing active species.

[0053] Furthermore, when using the zinc salt together with the pyridine imine compound in this manner, from the viewpoint of efficiently preparing a complex (zinc complex) that is a reaction product of the pyridine imine compound and the zinc salt and utilizing each component in the form of a complex, it is preferable to mix (stir) the pyridine imine compound and the zinc salt at a temperature of 0 to 250°C (more preferably 10 to 200°C) for about 1 minute to 72 hours. Such mixing (stirring) enables the two to react efficiently, making it possible to efficiently prepare the complex. This reaction may also be carried out by adding both to a lubricating base oil and mixing (stirring) under the above conditions.

[0054] <Lubricant base oil> The lubricating base oil is not particularly limited, and any base oil known in the field of lubricating oil compositions can be used as appropriate. For example, a mineral base oil, a synthetic base oil, or a mixture thereof can be used.

[0055] Examples of the mineral oil base oil include paraffinic mineral oils, normal paraffinic base oils, isoparaffinic base oils, and naphthenic base oils, which are obtained by refining a lubricating oil fraction obtained by atmospheric distillation and / or vacuum distillation of crude oil, through one or a combination of two or more refining processes selected from solvent deasphalting, solvent extraction, hydrocracking, hydroisomerization, solvent dewaxing, catalytic dewaxing, solvent refining, hydrorefining, chemical washing, clay treatment, and the like; and mixtures of two or more of these.

[0056] Further, examples of the mineral oil-based base oil include base oils obtained by using any of the following (1) to (8) as a stock oil, refining the stock oil and / or a lubricating oil fraction recovered from the stock oil by a predetermined refining method, and recovering the lubricating oil fraction. (1) Distillates obtained by atmospheric distillation of paraffinic and / or mixed crude oils (2) Vacuum distillate (WVGO) from atmospheric residue of paraffinic and / or mixed crude oils (3) Waxes obtained by lubricating oil dewaxing processes (slack wax, etc.), and / or synthetic waxes obtained by the Fischer-Tropsch (FT) process, Gas-to-Liquid (GTL) process, etc. (FT wax, GTL wax, etc.) (4) Mild hydrocracking oil selected from the raw oils (1) to (3), and / or a mild hydrocracking oil of a mixture of two or more selected from the raw oils (1) to (3). (5) A mixed oil of two or more kinds selected from the raw material oils (1) to (4) (6) Deasphalted oil (DAO) of feedstock (1), (2), (3), (4) or (5) (7) Mild hydrocracking oil (MHC) of raw oil (6) (8) A mixed oil of two or more kinds selected from the raw material oils (1) to (7).

[0057] Preferred examples of the above-mentioned predetermined refining method include hydrorefining such as hydrocracking and hydrofinishing; solvent refining such as furfural solvent extraction; dewaxing such as solvent dewaxing and catalytic dewaxing; clay refining using acid clay or activated clay; and chemical (acid or alkali) washing such as sulfuric acid washing and caustic soda washing. One of these refining methods may be used alone, or two or more may be used in combination. When two or more refining methods are combined, the order in which they are used is not particularly limited and can be selected as appropriate.

[0058] Particularly preferred examples of mineral base oils include the following base oils (9) or (10) obtained by subjecting a stock oil selected from the above (1) to (8) or a lubricating oil fraction recovered from the stock oil to a predetermined treatment. (9) A hydrocracked base oil obtained by hydrocracking a feedstock oil selected from the above (1) to (8) or a lubricating oil fraction recovered from the feedstock oil, and subjecting the resulting product or the lubricating oil fraction recovered from the product by distillation or the like to a dewaxing treatment such as solvent dewaxing or catalytic dewaxing, or by distilling the dewaxing treatment followed by distillation. (10) A hydroisomerized base oil obtained by hydroisomerizing a feedstock oil selected from the above (1) to (8) or a lubricating oil fraction recovered from the feedstock oil, and then subjecting the resulting product or a lubricating oil fraction recovered from the product by distillation or the like to a dewaxing treatment such as solvent dewaxing or catalytic dewaxing, or by distilling the dewaxing treatment followed by distillation (it is more preferable to use a base oil produced by subjecting the dewaxing process to a catalytic dewaxing process).

[0059] In obtaining the mineral base oil (9) or (10) above, a solvent refining treatment and / or hydrofinishing treatment step may be further carried out at an appropriate stage, if necessary.

[0060] The mineral base oil may be a Group I base oil (hereinafter sometimes referred to as "API Group I base oil"), a Group II base oil (hereinafter sometimes referred to as "API Group II base oil"), or a Group III base oil (hereinafter sometimes referred to as "API Group III base oil"), or a blended base oil obtained by combining these. API Group I base oils are mineral base oils having a sulfur content of more than 0.03 mass% and / or a saturates content of less than 90 mass%, and a viscosity index of 80 or greater but less than 120. API Group II base oils are mineral base oils having a sulfur content of 0.03 mass% or less, a saturates content of 90 mass% or greater, and a viscosity index of 80 or greater but less than 120. API Group III base oils are mineral base oils having a sulfur content of 0.03 mass% or less, a saturates content of 90 mass% or greater, and a viscosity index of 120 or greater. API Group I base oils are typically produced through a solvent refining process, while API Group II and Group III base oils are typically produced through a hydrocracking process. In this specification, viscosity index refers to a viscosity index measured in accordance with JIS K 2283-2000. In this specification, the "sulfur content in the lubricating base oil" refers to a value measured in accordance with JIS K 2541-2003. In this specification, the "saturates content in the lubricating base oil" refers to a value measured in accordance with ASTM D 2007-93.

[0061] The synthetic base oil may be an API Group IV base oil (poly-α-olefin base oil, hereinafter sometimes referred to as "API Group IV base oil"), an API Group V base oil (hereinafter sometimes referred to as "API Group V base oil"), or a mixed base oil obtained by combining these.

[0062] Examples of API Group IV base oils include oligomers and cooligomers of α-olefins having 2 to 32 carbon atoms (preferably 6 to 16 carbon atoms) and their hydrogenated products, such as ethylene-propylene copolymers, polybutene, 1-octene oligomers, and 1-decene oligomers, as well as their hydrogenated products.

[0063] Preferred examples of the API Group V base oil include ester-based base oils such as monoesters (e.g., butyl stearate, octyl laurate, 2-ethylhexyl oleate, etc.); diesters (e.g., ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate, etc.); polyesters (e.g., trimellitic esters, etc.); and polyol esters (e.g., trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate, etc.). Other examples of conventional API Group V base oils include aromatic synthetic base oils such as alkylbenzenes, alkylnaphthalenes, dialkyldiphenyl ethers, and polyphenyl ethers.

[0064] <About additives> Any lubricating oil base oil containing the pyridine imine compound may be used, and depending on the application, etc., known additives used in the field of lubricating oil compositions can be appropriately used within the scope that does not impair the effects of the present invention. Such additives are not particularly limited, but examples thereof include antioxidants, ashless dispersants, metal detergents, friction modifiers, antiwear agents, extreme pressure agents, viscosity index improvers, pour point depressants, corrosion inhibitors, rust inhibitors, metal deactivators, demulsifiers, antifoaming agents, and colorants. In addition, as such additives, for example, WO 2017 / 073748, JP 2020-76004 A, WO 2020 / 095970 A, JP 2022-158124 A, JP 2022-090378 A, JP 2023-45023 A, etc. Various additives described in such publications can be appropriately used. In the present invention, the pyridineimine compound (and the zinc salt used in combination as needed) is basically used as an antioxidant to prevent oxidative deterioration by the pyridineimine compound. Therefore, from the viewpoint of oxidation prevention, the composition may be in a form that does not particularly contain other antioxidants (for example, aromatic amine antioxidants, hindered amine antioxidants, phenolic antioxidants, etc.).

[0065] Such additives are not particularly limited, but examples thereof include known ashless dispersants such as succinimide-based ashless dispersants; known metal-based detergents such as alkali or alkaline earth metal alkyl salicylates, alkali or alkaline earth metal alkylbenzene sulfonates, and alkali or alkaline earth metal alkylphenates; known friction modifiers such as oiliness agent-based friction modifiers, organic molybdenum compounds, organic boron compounds such as alkyl mercaptyl borates, graphite, molybdenum disulfide, antimony sulfide, boron compounds, and polytetrafluoroethylene; known sulfur-based additives (known extreme pressure agents) such as metal thiocarbamate salts (e.g., salts of various metals such as Mo, Zn, Pb, and Sb), and disulfides; metal dithiophosphate salts (e.g., salts of various metals such as Zn, Pb, Sb, and Mo), and diazonium compounds. Examples of suitable additives include known antiwear agents such as known phosphorus-based and phosphorus-sulfur-based additives, such as metal alkyl phosphates (e.g., salts of various metals such as Zn, Pb, Sb, and Mo), phosphate esters, phosphites, and amine salts of phosphoric acid partial esters; known viscosity index improvers, such as dispersant or non-dispersant poly(meth)acrylates (dispersant or non-dispersant polyalkyl(meth)acrylates), non-dispersant or dispersant ethylene-α-olefin copolymers and hydrogenated products thereof, polyisobutylene and hydrogenated products thereof, hydrogenated products of styrene-diene copolymers, styrene-maleic anhydride ester copolymers, and polyalkylstyrenes; known pour point depressants, such as polymethacrylate polymers and ethylene vinyl acetate; and known metal deactivators, such as tolyltriazole or its derivatives.

[0066] <About the composition> In the lubricating oil composition of the present invention, the content of the lubricating base oil is not particularly limited, but is preferably 70% by mass or more (more preferably 80% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more) based on the total amount of the composition. When the content of such lubricating base oil is equal to or greater than the lower limit, a more excellent effect can be obtained in terms of the dissolution stability of the additives when the additives are used, compared to when the content is less than the lower limit.

[0067] The content of the pyridine imine compound (compound represented by the general formula (1)) is preferably 1.0 micromol to 10 millimol (more preferably 2.0 micromol to 1 millimol, and even more preferably 3.0 micromol to 500 micromol) per gram of the lubricating base oil. By setting the content of the pyridine imine compound at or above the lower limit, a higher level of antioxidant performance can be obtained, while by setting the content at or below the upper limit, an even higher effect can be obtained in terms of obtaining high antioxidant performance economically.

[0068] The content of the pyridineimine compound used as the antioxidant is preferably 1 ppm by mass to 10% by mass (more preferably 2 ppm by mass to 9% by mass, and even more preferably 3 ppm by mass to 8% by mass) based on the total amount of the composition. By setting the content of the pyridineimine compound relative to the total amount of the composition to be equal to or greater than the lower limit, a higher level of antioxidant performance can be obtained, while by setting the content to be equal to or less than the upper limit, an even higher effect can be obtained in terms of obtaining high antioxidant performance economically.

[0069] When a zinc salt is contained in the lubricating oil composition of the present invention, the content of the zinc salt is preferably 1.0 micromol to 10 millimol (more preferably 2.0 micromol to 1 millimol, and even more preferably 3.0 micromol to 500 micromol) per gram of the lubricating base oil. The content of the zinc salt is preferably 0.1 to 10 moles per mole of the pyridineimine compound, and the molar ratio of the zinc salt to the pyridineimine compound ([zinc salt]:[pyridineimine compound]) is preferably 1:0.3 to 1:3. By using such a content, a complex can be efficiently formed between the pyridineimine and the zinc salt, thereby further enhancing the ability to inhibit oxidative degradation.

[0070] Furthermore, when the lubricating oil composition of the present invention contains the other additives (antioxidants, ashless dispersants, metallic detergents, friction modifiers, antiwear agents, extreme pressure agents, viscosity index improvers, pour point depressants, corrosion inhibitors, rust inhibitors, metal deactivators, demulsifiers, antifoaming agents, colorants, etc.), the amount used may be appropriately determined depending on the intended use of the composition, as long as it does not impair the effects of the present invention. For example, when one or more of an ashless dispersant, a viscosity index improver, and a pour point depressant are used as the additive, the content thereof may be 0.01 to 20 mass% of the total composition. Furthermore, when a metallic detergent is used as the additive, the content thereof may be 0.001 to 5.0 mass% of the total composition in terms of metal element. Furthermore, when the additives include one or more of a friction modifier, an antiwear agent, and an extreme pressure agent, the content thereof may be 0.05 to 5.0 mass% of the total composition. When the additives include one or more of a corrosion inhibitor, a rust inhibitor, and an anti-emulsifier, the content thereof may be 0.005 to 5 mass% of the total composition. When the additives include a metal deactivator, the content thereof may be 0.005 to 1 mass% of the total composition. When the additives include an anti-foaming agent, the content thereof may be 0.0001 to 0.1 mass% of the total composition. [Example]

[0071] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0072] <About lubricant base oil> The lubricating base oils used in the following examples will be described. For convenience, the lubricating base oils will be referred to by the abbreviations listed below in the following examples. (1) Polyα-olefin (manufactured by INEOS, trade name: Durasyn 164, abbreviation: PAO, API Group IV base oil) (2) Tetraester of pentaerythritol with 2-ethylhexanoic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., abbreviated name: ester base oil, API Group V base oil).

[0073] <Pyridine imine compounds> The pyridine imine compounds used in the following Examples will be described. The pyridine imine compounds used in the following Examples were prepared in Synthesis Examples 1 to 4. The chemical formulas of the compounds prepared in the Synthesis Examples are as follows:

[0074] [ka]

[0075] (Synthesis Example 1) The pyridine imine compound represented by formula (k) (hereinafter referred to as "pyridine imine compound (k)" for convenience) was synthesized as follows. First, dry toluene (60 ml) was introduced into a 100 ml recovery flask under a nitrogen atmosphere. Then, 4-methoxy-2-methylaniline (2.0893 g, 15.3 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.), 2,6-diacetylpyridine (1.2429 g, 7.6 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.), and a catalytic amount (2 mg) of paratoluenesulfonic acid were added to obtain a mixed solution. Next, the mixed solution in the recovery flask was heated with stirring using a Dean-Stark water separator, and this heating and refluxing process was carried out for 24 hours to obtain a reaction solution. The reaction solution was then concentrated to dryness to obtain a crude solid (2.8241 g). Next, 2 g of the crude solid was weighed out and washed with absolute ethanol (30 ml). The ethanol-insoluble solid was then filtered off and washed with ethanol. The remaining solid was then thoroughly dried to obtain pyridine imine compound (k) in a 50% yield. The structure of the obtained compound was identified by NMR measurement, and it was confirmed that the obtained solid was indeed pyridine imine compound (k). The results of the NMR measurement are shown below.

[0076] (NMR measurement results) 1 H-NMR(500MHz,1,2-CD2Cl4):2.13(S,6H),2.36(s,6H),3.01(s,6H),6.63(d,J=7Hz,2H ),6.76 and 6.76(d,J=7Hz,2H),6.81 and 6.82(s,2H),7.89(dd,J=8Hz,1H),8.38(d,J=7Hz,2H) 13 C-NMR (500MHz, 1,2-CD2Cl4):16.3,18.1,55.4,111.2,115.9,119.2,122.0,129.2,136.6,142.9,155.4,155.8,167.0.

[0077] (Synthesis Example 2) The pyridine imine compound represented by formula (j) (hereinafter referred to as "pyridine imine compound (j)" for convenience) was synthesized as follows. First, dry toluene (60 ml) was introduced into a 100 ml recovery flask under a nitrogen atmosphere, and then 2,6-diisopropylaniline (1.063 g, 6 mmol), 2,6-diacetylpyridine (0.4575 g, 2.8 mmol), and a catalytic amount (2 mg) of paratoluenesulfonic acid were added to obtain a mixed solution. Next, the mixed solution in the recovery flask was heated with stirring using a Dean-Stark water separator, and a heating reflux process was carried out for 10 hours to obtain a reaction solution. Next, the obtained reaction solution was allowed to cool to room temperature, and the toluene was removed using an evaporator to obtain a solid. Then, ethanol (40 ml) was added to the obtained solid, and solids insoluble in ethanol were filtered off. Next, the remaining solid (insoluble matter) was washed again with ethanol and then dried to obtain pyridinediimine compound (j) in a yield of 75%. The compound obtained was quantified by gas chromatography-mass spectrometry (GC-MS), and a peak at MS401 was confirmed. The structure of the compound obtained was identified by NMR measurement, and it was confirmed that the solid obtained was indeed pyridineimine compound (j). The results of the NMR measurement are shown below.

[0078] (NMR measurement results) 1H-NMR(500MHz,1,2-C2D2Cl4):1.17, 1.18 (d, J=5.6Hz,24H),2.27(s,6H),2.77(qq,J=5.6Hz,2H),7.09(dd,J=6.4Hz,2H),7.17(d,J=6.4Hz,4H),7.93(t,J=6.5Hz,1H),8.49(d,J=6.5Hz,2H) 13 C-NMR:17.0,22.7,23.2,28.2,122.0,122.8,123.3,135.5, 136.6,146.5,155.0,166.6.

[0079] (Synthesis Example 3) The pyridine imine compound represented by formula (i) (hereinafter referred to as "pyridine imine compound (i)" for convenience) was synthesized as follows. First, dry toluene (60 ml) was introduced into a 100 ml recovery flask under a nitrogen atmosphere, and then 2,4-dimethylaniline (0.350 g, 3 mmol), 2,6-diacetylpyridine (0.2357 g, 1.5 mmol), and a catalytic amount (2 mg) of paratoluenesulfonic acid were added to obtain a mixture. Next, the mixture in the recovery flask was heated with stirring using a Dean-Stark water separator, and the heating and refluxing process was carried out for 10 hours to obtain a reaction solution. Next, the obtained reaction solution was allowed to cool to room temperature, and the toluene was removed using an evaporator to obtain a solid. Then, ethanol (40 ml) was added to the obtained solid, and the solid insoluble in ethanol was filtered off. Next, the remaining solid (insoluble matter) was washed again with ethanol and dried, obtaining pyridine imine compound (i) in a 10% yield. The compound thus obtained was quantified by GC-MS, and a peak at MS369 was confirmed. The structure of the compound thus obtained was identified by NMR measurement, and it was confirmed that the solid obtained was indeed pyridine imine compound (i). The results of the NMR measurement are shown below.

[0080] (NMR measurement results) 1H-NMR(600MHz, CDCl3):2.10(s,6H),2.34(s,6H),2.35(s,6H),6.59(d, J=6.4Hz,2 H), 7.01(d,J=6.4Hz,2H),7.06(s,2H),7.88(t,J=6.5Hz,1H),8.38(d,J=6.5Hz,2H) 13 C-NMR:16.2, 17.7, 20.8, 118.1, 122.1, 126.9, 127.1, 131.1, 132.9,136.7,147.3, 155.5, 166.9.

[0081] (Synthesis Example 4) The pyridine imine compound represented by formula (e) (hereinafter referred to as "pyridine imine compound (i)" for convenience) was synthesized as follows. First, dry toluene (20 ml) was introduced into a 100 ml recovery flask under a nitrogen atmosphere, followed by the addition of 2-acetylpyridine (Tokyo Chemical Industry Co., Ltd., 1.452 g), 4-methoxy-2-methylaniline (1.4608 g), and a catalytic amount (2 mg) of paratoluenesulfonic acid to obtain a mixture. Next, the mixture in the recovery flask was heated with stirring using a Dean-Stark water separator, and refluxed for 8 hours to obtain a reaction solution. The reaction solution was then concentrated and purified using a silica gel column (solvent: hexane-isopropyl alcohol) to obtain pyridine imine compound (e) in a 78% yield. The structure of the resulting compound was identified by NMR analysis, confirming that the resulting solid was indeed pyridine imine compound (e). The NMR results are shown below.

[0082] (NMR measurement results) 1 H-NMR (600MHz, CDCl3):2.12(s,3H),2.33(s,3H),3.78(s,3H),6.60(d,J=8.4Hz,1H),6.74(d,J=8.4Hz,1H),6.80 (s,1H),7.33(dd,J=4.8Hz,6.6Hz,1H),7.76(dd,J=6.6Hz,7.8Hz,1H),8.30(d,J=7.8Hz,1H),8.65(d,J=4.8Hz,1H) 13 C-NMR:16.4, 18.1, 55.4, 111.4,115.9,119.2,121.6,127.1,129.0, 136.3,143.1,148.5,156.1,156.9,167.1

[0083] <Evaluation test of antioxidant performance of compositions obtained in each example> The lubricating oil compositions obtained in each example were used, and tests were conducted using an oxidation stability tester RapidOxy (manufactured by Anton Paar) as the measuring device, employing the following measurement procedures (conditions), to evaluate the antioxidant performance of the lubricating oil compositions.

[0084] [Measurement procedure for evaluation test] First, a predetermined amount of lubricating oil composition (approximately 2.5 g for the systems using PAO (Examples 1 to 5 and Comparative Example 1), approximately 5 g for the systems using ester base oil (Examples 6 to 7 and Comparative Example 2)) was placed in a glass dish for the measuring device and precisely weighed out to serve as a sample (the precisely weighed mass of the lubricating oil composition (sample mass) is listed for each Example in Tables 1 and 2). Next, the glass dish containing the sample (lubricating oil composition for testing) was placed in the measuring device and sealed, and the device was then filled with pure oxygen (G2 grade) at room temperature (25°C) at a pressure of 700 kPa. After pressurizing the device by introducing pure oxygen (G2 grade) in this way, the test was started once the pressure inside the device had stabilized. The temperature inside the device was raised to 150°C and maintained at 150°C, and the time from the start of the test until the pressure inside the device reached a pressure 10% lower than the maximum pressure was measured (the time was measured with the point at which the pressure reached 10% lower than the maximum pressure as the end point). In this measurement, the longer the measurement time, the higher the antioxidant performance can be evaluated. For the sample of the lubricating oil composition obtained in Example 6, the pressure did not decrease significantly even after a relatively long time had passed, so the test was terminated at the point when the pressure reached 3.0% lower than the maximum pressure (30,789 seconds (8.55 hours) after the start of the test). The antioxidant performance was deemed to be sufficiently high. The measurement results are shown in Tables 1 and 2.

[0085] Example 1 PAO (10.9196 g) was mixed with the pyridine imine compound (k) (23.9 mg) obtained in Synthesis Example 1 and zinc naphthenate (Tokyo Chemical Industry Co., Ltd., zinc content: 8% by mass, 27.1 mg) to obtain a mixture. The mixture was then heated to 100°C with a heat gun and stirred for 2 minutes to completely dissolve each component in the PAO, thereby obtaining a lubricating oil composition containing PAO, pyridine imine compound (k), and zinc naphthenate. From the heating conditions of the mixture, it is clear that a complex of zinc and pyridine imine compound (k) (a reaction product of pyridine imine compound (k) and zinc naphthenate) is formed in the lubricating oil composition, and at least a portion of the pyridine imine compound (k) is contained as a ligand of the complex (it is considered clear that at least a portion of the pyridine imine compound (k) and zinc naphthenate are contained in the form of a complex). The content of pyridineimine compound (k) per 1 g of PAO was 5.5 μmol / g, and the molar ratio of pyridineimine compound (k) to zinc naphthenate in the composition ([compound (k)]:[zinc naphthenate]) was 1.8:1.0.

[0086] Example 2 A lubricating oil composition containing PAO, pyridine imine compound (k), and zinc naphthenate was obtained using the same method as in Example 1, except that the amount of PAO used was changed to 20.0285 g, the amount of pyridine imine compound (k) obtained in Synthesis Example 1 used to 24.1 mg, and the amount of zinc naphthenate used to 48.8 mg. Note that, based on the heating conditions of the mixture, etc., it is clear that a complex of zinc and pyridine imine compound (k) (a reaction product of pyridine imine compound (k) and zinc naphthenate) is formed in the lubricating oil composition, and at least a portion of the pyridine imine compound (k) is contained as a ligand of the complex (it is considered clear that at least a portion of the pyridine imine compound (k) and zinc naphthenate are contained in the form of a complex). The content of pyridineimine compound (k) per 1 g of PAO was 3.0 μmol / g, and the molar ratio of pyridineimine compound (k) to zinc naphthenate in the composition ([compound (k)]:[zinc naphthenate]) was 1.0:1.0.

[0087] Example 3 A lubricating oil composition containing PAO and pyridineimine compound (k) was obtained in the same manner as in Example 1, except that zinc naphthenate was not used, the amount of PAO used was changed to 9.6199 g, and the amount of pyridineimine compound (k) obtained in Synthesis Example 1 used was changed to 11.51 mg. The content of pyridineimine compound (k) per 1 g of PAO was 3.0 μmol / g.

[0088] Example 4 A lubricating oil composition containing PAO, pyridineimine compound (i), and zinc naphthenate was obtained in the same manner as in Example 1, except that the amount of PAO used was changed to 9.5025 g, 21.2 mg of pyridineimine compound (i) obtained in Synthesis Example 3 was used instead of pyridineimine compound (k), and the amount of zinc naphthenate was changed to 25.8 mg. From the heating conditions of the mixture, it is clear that a complex of zinc and pyridineimine compound (i) (a reaction product of pyridineimine compound (i) and zinc naphthenate) is formed in the lubricating oil composition, and at least a portion of the pyridineimine compound (i) is contained as a ligand of the complex (it is considered clear that at least a portion of pyridineimine compound (i) and zinc naphthenate are contained in the form of a complex). The content of pyridineimine compound (i) per 1 g of PAO was 6.0 μmol / g, and the molar ratio of pyridineimine compound (i) to zinc naphthenate in the composition ([compound (i)]:[zinc naphthenate]) was 1.8:1.0.

[0089] Example 5 A lubricating oil composition containing PAO, pyridineimine compound (e), and zinc naphthenate was obtained in the same manner as in Example 1, except that the amount of PAO used was changed to 8.0082 g, 9.8 mg of the pyridineimine compound (e) obtained in Synthesis Example 4 was used instead of the pyridineimine compound (k), 19.4 mg of zinc naphthenate was used, and the mixture was not heated with a heat gun. From the heating conditions of the mixture, it is clear that a complex of zinc and pyridineimine compound (e) is formed in the lubricating oil composition, and at least a portion of the pyridineimine compound (e) is contained as a ligand of the complex (it is considered clear that at least a portion of the pyridineimine compound (e) and zinc naphthenate are contained in the form of a complex). The content of pyridineimine compound (e) per 1 g of PAO was 5.1 μmol / g, and the molar ratio of pyridineimine compound (e) to zinc naphthenate in the composition ([compound (e)]:[zinc naphthenate]) was 1.7:1.0.

[0090] (Comparative Example 1) The PAO was used as is and considered a comparative lubricating oil composition.

[0091] [Table 1]

[0092] Example 6 The pyridine imine compound (k) (23.4 mg) obtained in Synthesis Example 1 and zinc naphthenate (Tokyo Chemical Industry Co., Ltd., zinc content: 8% by mass, 45.5 mg) were added to an ester base oil (17.7525 g) to obtain a mixture, which was then heated to 100°C with a heat gun and stirred for 2 minutes to completely dissolve each component in the ester base oil, thereby obtaining a lubricating oil composition containing the ester base oil, the pyridine imine compound (k), and zinc naphthenate. It is clear from the heating conditions of the mixture, etc., that a complex of zinc and the pyridine imine compound (k) is formed in the lubricating oil composition, and at least a portion of the pyridine imine compound (k) is contained as a ligand of the complex (it is considered clear that at least a portion of the pyridine imine compound (k) and zinc naphthenate are contained in the form of a complex). The content of pyridineimine compound (k) per 1 g of PAO was 3.3 μmol / g, and the molar ratio of pyridineimine compound (k) to zinc naphthenate in the composition ([compound (k)]:[zinc naphthenate]) was 1.1:1.0.

[0093] Example 7 A lubricating oil composition containing an ester base oil, pyridineimine compound (j), and zinc naphthenate was obtained in the same manner as in Example 6, except that the amount of ester base oil used was changed to 11.3022 g, 34.3 mg of the pyridineimine compound (j) obtained in Synthesis Example 2 was used instead of the pyridineimine compound (k), and the amount of zinc naphthenate used was changed to 28.5 mg. From the heating conditions of the mixture, it is clear that a complex of zinc and pyridineimine compound (j) is formed in the lubricating oil composition, and at least a portion of the pyridineimine compound (j) is contained as a ligand of the complex (it is considered clear that at least a portion of the pyridineimine compound (j) and zinc naphthenate are contained in the form of a complex). The content of pyridineimine compound (j) per 1 g of PAO was 6.3 μmol / g, and the molar ratio of pyridineimine compound (j) to zinc naphthenate in the composition ([compound (j)]:[zinc naphthenate]) was 2.0:1.0.

[0094] (Comparative Example 2) The ester base oil was used as is and considered a comparative lubricating oil composition.

[0095] [Table 2]

[0096] Based on the results shown in Tables 1 and 2, by comparing Examples and Comparative Examples using the same type of base oil (PAO or ester-based base oil) (Comparison of Examples 1 to 5 with Comparative Example 1, and Comparison of Examples 6 and 7 with Comparative Example 2), it was clear that when the pyridineimine compound represented by the general formula (1) was used, oxygen was not consumed for a long period of time compared to when the base oil was used alone, and it was found that the antioxidant performance of the composition could be improved. As shown in Table 2, in Example 6, the test was terminated at 8.55 hours, and the pressure at that time was 3.0% lower than the maximum pressure. Furthermore, by comparing Examples 1 and 2 with Example 3, it was confirmed that even higher antioxidant performance could be obtained by using a zinc salt (zinc naphthenate) together with the pyridineimine compound represented by the general formula (1). [Industrial Applicability]

[0097] As explained above, according to the present invention, it is possible to provide a lubricating oil composition that can highly inhibit oxidative degradation while utilizing components different from those conventionally used as antioxidants. Therefore, the lubricating oil composition of the present invention is useful as a composition for lubricating the moving parts of various mechanical devices having moving parts (e.g., internal combustion engines, etc.).

Claims

1. a lubricating base oil; The following general formula (1): 【Chemistry 1】 [In formula (1), R １ each independently represents one selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 8 carbon atoms, R ２ each independently represents one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, and an aryl group which may have at least one substituent selected from the group consisting of an alkyl group and an alkoxy group and which has 6 to 12 carbon atoms in total, including the carbon atoms of the substituent; R ３ each independently represents one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, and an alkoxy group having 1 to 8 carbon atoms; n represents an integer of 1 or more and 5 or less. a pyridine imine compound represented by the formula: A lubricating oil composition comprising:

2. The pyridine imine compound is represented by the following general formulas (2) to (3): 【Chemistry 2】 [R in formulas (2) to (3)] １ , R ２ and R ３ are R in the formula (1). １ , R ２ and R ３ is equivalent to the above.] 2. The lubricating oil composition according to claim 1, wherein the compound is at least one selected from the group consisting of compounds represented by the formula:

3. In the formula representing the pyridine imine compound, R １ are all hydrogen atoms, and R ２ are each independently one selected from the group consisting of a methyl group, a phenyl group, and a p-methoxyphenyl group, and R ３ 3. The lubricating oil composition according to claim 2, wherein each of the groups independently represents one selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, a methoxy group, and an ethoxy group.

4. 10. The lubricating oil composition of claim 1, further comprising a zinc salt.

5. The lubricating oil composition according to claim 4, wherein the zinc salt is at least one selected from the group consisting of zinc chloride, zinc acetate, zinc 2-ethylhexanoate, and zinc naphthenate.

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