Lubricating oil composition

Abstract

To provide a lubricating oil composition which can highly suppress the oxidative deterioration of a lubricating base oil and can highly suppress the deposition of a metal with which the composition comes into contact.SOLUTION: A lubricating base oil; and at least one antioxidant selected from the group consisting of a phenol-based antioxidant and an amine-based antioxidant; wherein the lubricating base oil has the following general formula (1): wherein R1 is each independently a hydrogen atom or the like; R2 is each independently a hydrogen atom or the like; R3 is each independently a hydrogen atom or the like; and n is an integer of 1 or more and 5 or less. The lubricating oil composition contains the pyridine imine compound represented by formula (1) and at least one kind of zinc salt selected from the group consisting of fatty acid zinc, halogenated zinc, zinc nitrate, zinc sulfate, zinc oxide, zinc sulfide and zinc phosphate.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 to reduce 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 subject to oxidative degradation when in contact with air, and therefore antioxidants are generally used to suppress such oxidative degradation.

[0003] Phenol-based antioxidants and amine-based antioxidants are generally used as such antioxidants (for example, Japanese Patent Application Laid-Open No. 2023-049434 (Patent Document 1) describes amine-based antioxidants and phenol-based antioxidants as antioxidants to be blended into lubricating oil compositions). However, in lubricating oil compositions that directly use such conventional antioxidants, even if it is possible to achieve a high level of antioxidant properties, it is not possible to suppress at a high level the deposition of metals that come into contact with the composition (such as the elution of metal ions).

[0004] Generally, in the field of lubricating oil compositions, when an oxidation reaction of a base oil progresses, metals in contact with the base oil are oxidized, causing metal ions to be eluted into the lubricating oil composition, or oxidative degradation of the metals may occur, resulting in the floating of metals, metal oxides, etc. in the lubricating oil composition. Therefore, in the field of lubricating oil compositions, there is a demand for a lubricating oil composition that has a high metal deposition inhibition effect (excellent metal deposition inhibition effect), which can highly inhibit copper deposition based on the amount of copper present in the composition after oxidative degradation in the ISOT test according to JIS K2514-1:2013. [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 aims to provide a lubricating oil composition that can highly inhibit oxidative deterioration of lubricating base oils and highly inhibit deposition of metals with which the composition comes into contact. [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 a lubricating oil composition obtained by incorporating into a lubricating base oil a combination of at least one antioxidant selected from the group consisting of phenolic antioxidants and amine-based antioxidants; a pyridine imine compound represented by the following general formula (1); and at least one zinc salt selected from the group consisting of a zinc fatty acid, a zinc halide, zinc nitrate, zinc sulfate, zinc oxide, zinc sulfide, and zinc phosphate; can exhibit higher antioxidant performance, measured after oxidative degradation in the ISOT test in accordance with JIS K2514-1:2013, as determined by the amount of pentane insoluble matter in the composition after oxidative degradation, compared to a lubricating oil composition using the antioxidant alone without the pyridine imine compound and the zinc salt. The present inventors have also found that the lubricating oil composition can exhibit higher antioxidant performance, measured by the amount of pentane insoluble matter in the composition after oxidative degradation, as determined by the amount of copper present in the composition after oxidative degradation, as determined by the amount of copper present in the composition after oxidative degradation. As a result of intensive research conducted by the present inventors to achieve the above-mentioned object, they have discovered that by preparing a lubricating oil composition containing a lubricating base oil, at least one antioxidant selected from the group consisting of phenolic antioxidants and amine-based antioxidants, a pyridine imine compound represented by the following general formula (1), and the zinc salt, it is possible to highly inhibit oxidative deterioration of the lubricating base oil in the composition, and also to highly inhibit deposition of metals that come into contact with the composition during use, which led to the completion of the present invention.

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

[0009] [1] a lubricating base oil; at least one antioxidant selected from the group consisting of phenolic antioxidants and amine antioxidants; The following general formula (1):

[0010] [ka]

[0011] [In formula (1), R1 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 is an integer between 1 and 5. a pyridine imine compound represented by the formula: at least one zinc salt selected from the group consisting of zinc fatty acid zinc, zinc halide, zinc nitrate, zinc sulfate, zinc oxide, zinc sulfide, and zinc phosphate; 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 R3 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], wherein the zinc salt is at least one selected from the group consisting of zinc chloride, zinc acetate, zinc 2-ethylhexanoate, and zinc naphthenate.

[0017] In the present invention, in order to achieve high antioxidant performance and excellent metal deposition inhibition, the pyridinediimine compound and the zinc salt are used in combination with the antioxidant described above. Here, the pyridinediimine compound can form complexes with various transition metals, and in particular, its complexes with iron, cobalt, etc. are known to exhibit excellent effects in olefin polymerization and oligomerization. However, the technical idea of ​​using such a pyridinediimine compound in combination with the zinc salt and the antioxidant in a lubricating oil composition has not been reported in the field of lubricating oil compositions, and no literature describing such a matter has been found. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a lubricating oil composition that can highly inhibit oxidative deterioration of a lubricating base oil and highly inhibit deposition of metals that come into contact with the composition. DETAILED DESCRIPTION OF THE INVENTION

[0019] 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.

[0020] The lubricating oil composition of the present invention comprises: at least one antioxidant selected from the group consisting of phenolic antioxidants and amine antioxidants; The following general formula (1):

[0021] [ka]

[0022] [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 is an integer between 1 and 5. a pyridine imine compound represented by the formula: at least one zinc salt selected from the group consisting of zinc fatty acid zinc, zinc halide, zinc nitrate, zinc sulfate, zinc oxide, zinc sulfide, and zinc phosphate; Hereinafter, the components contained in the composition, such as the lubricating base oil, the antioxidant, the pyridine imine compound, and the zinc salt, will be described separately.

[0023] <Lubricant base oil> The lubricating base oil according to the present invention 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 mixed base oil thereof can be used.

[0024] 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.

[0025] 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).

[0026] 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.

[0027] 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).

[0028] 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.

[0029] 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 mixed base oil obtained by combining these. As such, the mineral base oil may be a single base oil selected from the group consisting of API Group I to III base oils, or a mixture of two or more base oils selected from the group consisting of API Group I to III base oils. Here, API Group I base oils are mineral base oils having a sulfur content of more than 0.03% by mass and / or a saturates content of less than 90% by mass and a viscosity index of 80 to less than 120. API Group II base oils are mineral base oils having a sulfur content of 0.03% by mass or less, a saturates content of 90% by mass or more, and a viscosity index of 80 to less than 120. Furthermore, 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 more, and a viscosity index of 120 or more. API Group I base oils are typically produced via a solvent refining process, while API Group II and Group III base oils are typically produced via 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.

[0030] Furthermore, such mineral base oils are not particularly limited, but from the viewpoint of making it easier to achieve desired properties (such as kinematic viscosity) depending on the application, a preferred embodiment is at least one base oil selected from API Group I base oils, API Group II base oils, and API Group III base oils (such base oils may be mixed base oils obtained by mixing two or more types of base oils).

[0031] 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.

[0032] 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.

[0033] 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.

[0034] Furthermore, from the viewpoint of the balance between various physical properties such as viscosity, viscosity index, and low-temperature characteristics and price, the lubricating base oil is preferably a mineral base oil, and among these, API Group I base oil, API Group II base oil, and API Group III base oil are preferably used. For example, the present invention is not affected by using one grade of API Group I base oil alone or by mixing it with another grade of the same Group I base oil. The use of a single grade of API Group II base oil or API Group III base oil, a mixture with another grade, or a mixture of two or more selected from the group consisting of API Group I base oil, API Group II base oil, and API Group III base oil (for example, a mixture of two or three of these is preferred) is also preferred.

[0035] <Antioxidants> The antioxidant according to the present invention is at least one selected from the group consisting of phenolic antioxidants and amine antioxidants. Thus, in the present invention, the antioxidant may be a phenolic antioxidant, an amine antioxidant, or a mixture thereof.

[0036] Such phenolic antioxidants are not particularly limited, and any known phenolic antioxidants used in the field of lubricating oil compositions can be used as appropriate. Examples of such phenolic antioxidants include 4,4'-methylenebis(2,6-di-tert-butylphenol); 4,4'-bis(2,6-di-tert-butylphenol); 4,4'-bis(2-methyl-6-tert-butylphenol); 2,2'-methylenebis(4-ethyl-6-tert-butylphenol); 2,2'-methylenebis(4-methyl-6-tert-butylphenol); 4,4'-butylidenebis(3-methyl-6-tert-butylphenol); 4,4'-isopropylidenebis(2,6-di-tert-butylphenol); 2,2'-methylenebis(4-methyl-6-nonylphenol); 2,2'-isobutylidenebis(4,6-dimethylphenol); 2,2'-methylenebis(4-methyl-6-cyclohexylphenol); 2,6-di-tert-butyl-4-methylphenol; Examples of hindered phenol compounds and bisphenol compounds include 2,6-di-tert-butyl-4-ethylphenol; 2,4-dimethyl-6-tert-butylphenol; 2,6-di-tert-butyl-4-(N,N'-dimethylaminomethyl)phenol; 4,4'-thiobis(2-methyl-6-tert-butylphenol); 4,4'-thiobis(3-methyl-6-tert-butylphenol); 2,2'-thiobis(4-methyl-6-tert-butylphenol); bis(3-methyl-4-hydroxy-5-tert-butylbenzyl)sulfide; bis(3,5-di-tert-butyl-4-hydroxybenzyl)sulfide; 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid esters; and 3-methyl-5-tert-butyl-4-hydroxyphenol fatty acid esters. In this specification, the term "hindered phenol compound" refers to a compound having a structure in which at least one hydroxyl group and at least one, preferably two, tert-butyl groups are bonded adjacent to each other on a benzene ring.Among these phenolic antioxidants, it is preferable to use hindered phenol compounds from the viewpoint of excellent antioxidant effect, and 2,6-di-tert-butyl-4-methylphenol and 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid esters are more preferable. Examples of such 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid esters include methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, ethyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, propyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, isopropyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, butyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate. Suitable examples of the phenolic antioxidant include isobutyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, hexyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, cyclohexyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, octyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, decyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, dodecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate. Commercially available phenolic antioxidants can also be used as appropriate.

[0037] The amine-based antioxidant according to the present invention is not particularly limited, and any known amine-based antioxidant used in the field of lubricating oil compositions can be used as appropriate. Suitable examples of such amine-based antioxidants include aromatic amine-based antioxidants and hindered amine-based antioxidants.

[0038] Examples of such aromatic amine antioxidants include primary aromatic amine compounds such as alkylated α-naphthylamine, and secondary aromatic amine compounds such as alkylated diphenylamine, phenyl-α-naphthylamine, alkylated phenyl-α-naphthylamine, and phenyl-β-naphthylamine. As the aromatic amine antioxidant, at least one selected from the group consisting of alkylated diphenylamine, alkylated phenyl-α-naphthylamine, and mixtures thereof can be preferably used.

[0039] Examples of hindered amine antioxidants include compounds having a 2,2,6,6-tetraalkylpiperidine skeleton (2,2,6,6-tetraalkylpiperidine derivatives). The 2,2,6,6-tetraalkylpiperidine derivatives are preferably 2,2,6,6-tetraalkylpiperidine derivatives having a substituent at the 4-position. Two 2,2,6,6-tetraalkylpiperidine skeletons may be bonded via a substituent at the 4-position. The N-position of the 2,2,6,6-tetraalkylpiperidine skeleton may be unsubstituted or may be substituted with an alkyl group having 1 to 4 carbon atoms at the N-position. The 2,2,6,6-tetraalkylpiperidine skeleton is preferably a 2,2,6,6-tetramethylpiperidine skeleton.

[0040] The substituent at the 4-position of the 2,2,6,6-tetraalkylpiperidine skeleton may be an acyloxy group (R a COO-), alkoxy group (R a O-), alkylamino group (R a NH-), acylamino group (R a CONH-), etc. In the formula of each of these groups, R a is a hydrocarbon group preferably having 1 to 30 carbon atoms, more preferably 1 to 24 carbon atoms, and even more preferably 1 to 20 carbon atoms. Examples of such hydrocarbon groups include alkyl groups, alkenyl groups, cycloalkyl groups, alkylcycloalkyl groups, aryl groups, alkylaryl groups, and arylalkyl groups.

[0041] When two 2,2,6,6-tetraalkylpiperidine skeletons are bonded via a substituent at each 4-position, the substituent may be a hydrocarbylene bis(carbonyloxy) group (-OOC-R b -COO-), hydrocarbylenediamino group (-HN-R b -NH-), hydrocarbylene bis(carbonylamino) group (-HNCO-R b -CONH-), etc. In the formula of each of these groups, R b is preferably a hydrocarbylene group having 1 to 30 carbon atoms, and more preferably an alkylene group.

[0042] The substituent at the 4-position of the 2,2,6,6-tetraalkylpiperidine skeleton is preferably an acyloxy group. An example of a compound having an acyloxy group at the 4-position of the 2,2,6,6-tetraalkylpiperidine skeleton is an ester of 2,2,6,6-tetramethyl-4-piperidinol with a carboxylic acid. Examples of the carboxylic acid include linear or branched aliphatic carboxylic acids having 8 to 20 carbon atoms.

[0043] From the viewpoints of antioxidant effect and carbon skeleton stability, such amine antioxidants are more preferably aromatic amine antioxidants, and are more preferably at least one selected from the group consisting of alkylated diphenylamines, alkylated phenyl-α-naphthylamines, and dinaphthylamines. At least one selected from the group consisting of alkylated diphenylamines and alkylated phenyl-α-naphthylamines is particularly preferred, with alkylated diphenylamines being most preferred. In such alkylated diphenylamines and alkylated phenyl-α-naphthylamines, the alkyl groups substituting the phenyl groups preferably have 1 to 20 carbon atoms (more preferably 1 to 18 carbon atoms). In such alkylated diphenylamines and alkylated phenyl-α-naphthylamines, the alkyl groups substituting the phenyl groups may be substituted at two or more positions on the phenyl group.

[0044] Furthermore, as such an amine-based antioxidant, commercially available products can be used as appropriate.

[0045] Furthermore, as the antioxidant according to the present invention, it is more preferable to use a combination of at least one phenol-based antioxidant and at least one amine-based antioxidant from the viewpoints of coloration prevention and duration of antioxidant effect.

[0046] <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 1may be the same or different).

[0047] 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 1 The 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.

[0048] 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).

[0049] Such an R 2The 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 2 The 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.

[0050] 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.

[0051] In addition, R in such formula (1) 2From 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.

[0052] In addition, R in the formula (1) 3 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 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.

[0053] 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. 3The 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.

[0054] 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.

[0055] In addition, R in the formula (1) 3 is a substituent other than a hydrogen atom, the position of the substituent on the benzene ring can be any position. 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.

[0056] 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 have a substituent of the formula: -CR at the 2-position or at the 2- and 6-positions of the pyridine. 2 A group containing a structure represented by =N- (R 1It is particularly preferred to place a substituent other than

[0057] 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.

[0058] The pyridine imine compound represented by the general formula (1) includes compounds represented by the following general formulas (2) to (3):

[0059] [ka]

[0060] 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.

[0061] As the pyridine imine compound represented by the general formula (1), for example, compounds represented by the following formulae (a) to (m) can be given as suitable examples.

[0062] [ka]

[0063] 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):

[0064] [ka]

[0065] [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):

[0066] [ka]

[0067] [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.

[0068] <Zinc salts> The zinc salt according to the present invention is 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.

[0069] Such zinc salts are divalent zinc, and are intermediate acids according to the Hard Soft Acid Base (HSAB) principle, and exhibit a favorable interaction with intermediate bases such as pyridine, making it possible to easily form complexes. For this reason, the inventors speculate that by using such zinc salts together with the pyridine imine compound, the pyridine imine compound can be coordinated as a ligand to the zinc in the zinc salt, thereby efficiently forming a complex, thereby enabling a more advanced metal deposition inhibition effect.

[0070] 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.

[0071] Examples of zinc halides used as the zinc salt include zinc fluoride, zinc chloride, zinc bromide, and zinc iodide.

[0072] Furthermore, among the zinc salts, zinc halides and zinc fatty acids are preferred in terms of availability, zinc chloride, zinc acetate, zinc 2-ethylhexanoate, and zinc naphthenate are more preferred, and zinc acetate, zinc 2-ethylhexanoate, and zinc naphthenate are even more preferred in terms of solubility in base oil.

[0073] Thus, the lubricating oil composition of the present invention contains the pyridineimine compound and the zinc salt as essential components, and in the composition, the pyridineimine compound and the zinc salt may react to form a complex. In the present invention, the pyridineimine compound and the zinc salt are preferably contained as a complex, which is a reaction product of the pyridineimine compound and the zinc salt, from the viewpoint of obtaining high oxidation degradation prevention performance and a higher metal deposition inhibition effect when used in combination with the antioxidant. That is, the lubricating oil composition of the present invention preferably contains a complex, which is a reaction product of the pyridineimine compound and the zinc salt, from the viewpoint of obtaining a higher metal deposition inhibition effect. 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.

[0074] Furthermore, when preparing a complex (zinc complex) that is a reaction product of the pyridineimine compound and the zinc salt, it is preferable to mix (stir) the pyridineimine 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, from the viewpoint of utilizing each component in the form of a complex. Such mixing (stirring) enables the two to react efficiently, thereby enabling the efficient preparation of a complex. This reaction may be carried out, for example, by adding both components to a lubricating base oil (which may be a base oil in a mixture containing other additives (a lubricating oil composition containing a general additive formulation)) and mixing (stirring) under the above conditions, or by adding both components to a general organic solvent and mixing them. In this way, the complex (zinc complex) that is a reaction product of the pyridineimine compound and the zinc salt may be prepared in the base oil during the production of the composition and used. Alternatively, the complex may be prepared separately in an organic solvent and used as the pyridineimine compound and the zinc salt.

[0075] <About additives> The lubricating oil composition of the present invention may contain the lubricating base oil, the antioxidant, the pyridineimine compound, and the zinc salt, and may appropriately use other known additives (additives other than the antioxidant, the pyridineimine compound, and the zinc salt) used in the field of lubricating oil compositions, depending on the intended use, etc., as long as the effects of the present invention are not impaired. In other words, even when the antioxidant, the pyridineimine compound, and the zinc salt are used in combination with a lubricating oil composition (a composition containing a lubricating base oil) formulated with a general additive formulation, the composition can still exhibit excellent oxidation degradation inhibitory effects and metal deposition inhibitory effects.

[0076] Such other additives are not particularly limited, but include, for example, antiwear agents, ashless dispersants, viscosity index improvers, pour point depressants, metal detergents, metal deactivators, friction modifiers, extreme pressure agents, corrosion inhibitors, rust inhibitors, demulsifiers, antifoaming agents, and colorants. In addition, as such additives, for example, WO 2017 / 073748, JP 2020-76004 A, WO 2020 / 095970, JP 2022-158124 A, JP 2022-090378 A, JP 2023-45023 A, etc. Various additives described in such publications can be appropriately used.

[0077] Furthermore, such other 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 (sulfur-containing extreme pressure agents) such as metal thiocarbamates (e.g., salts of various metals such as Mo, Zn, Pb, and Sb), and disulfides; metal dithiophosphates (e.g., salts of various metals such as Zn, Pb, Sb, and Mo), Examples of suitable additives include known antiwear agents such as dialkyl phosphate metal salts (e.g., salts of various metals such as Zn, Pb, Sb, and Mo), phosphate esters, phosphites, and amine salts of phosphoric acid partial esters, as well as known phosphorus- and phosphorus-sulfur-based additives; 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.

[0078] In addition, a suitable embodiment of the lubricating oil composition containing such other additives is not particularly limited, but for example, a composition containing a combination of antiwear agents, ashless dispersants, viscosity index improvers, pour point depressants, metal detergents, and metal deactivators as the additives. Components such as antiwear agents, ashless dispersants, viscosity index improvers, pour point depressants, metal detergents, and metal deactivators that can be suitably used as the additives will be described in more detail below.

[0079] Such antiwear agents are not particularly limited, and for example, as described above, known phosphorus-based and phosphorus-sulfur-based (sulfur-phosphorus-based) antiwear agents can be appropriately used. Examples of such antiwear agents include phosphites, thiophosphites, dithiophosphites, trithiophosphites, phosphates, thiophosphates, dithiophosphates, trithiophosphates, amine salts thereof, metal salts thereof, and derivatives thereof. Furthermore, from the viewpoint of availability and effectiveness, zinc dialkyldithiophosphate (ZnDTP) or zinc dialkylphosphate (ZnP) is preferred as the antiwear agent. Such zinc dialkyldithiophosphate (ZnDTP) or zinc dialkylphosphate (ZnP) is not particularly limited, and known agents (for example, those described in JP 2023-45023 A) can be appropriately used. Such antiwear agents may be used alone or in combination of two or more.

[0080] The ashless dispersant is not particularly limited, but for example, a succinimide-based ashless dispersant can be suitably used. Specific examples of the ashless dispersant include non-boronated succinimides, boronated succinimides, and mixtures thereof. It is more preferable that the non-boronated succinimides, boronated succinimides, and mixtures thereof have a nitrogen atom content of 0.5 to 3.0 mass%. The ashless dispersants can be used alone or in combination of two or more.

[0081] Furthermore, the viscosity index improver is not particularly limited, and known viscosity index improvers such as those described above can be used as appropriate. As such viscosity index improvers, poly(meth)acrylate-based viscosity index improvers (viscosity index improvers made of poly(meth)acrylate) are more preferred from the viewpoints of the effect of increasing the viscosity index and improving shear stability. In this specification, "(meth)acrylate" refers to acrylate and / or methacrylate. Such poly(meth)acrylate-based viscosity index improvers may be of the so-called non-dispersion type or the dispersion type. Furthermore, poly(meth)acrylates used in viscosity index improvers preferably have a weight-average molecular weight of 10,000 to 1,000,000. Furthermore, the viscosity index improvers may be used alone or in combination of two or more types.

[0082] The pour point depressant is not particularly limited, and known pour point depressants can be used as appropriate. Examples include poly(meth)acrylate polymers and ethylene-vinyl acetate copolymers (EVA: ethylene vinyl acetate). Among these pour point depressants, poly(meth)acrylate pour point depressants (those composed of poly(meth)acrylate) are more preferred from the viewpoint of improving the low-temperature pour point depressant effect and shear stability. Such poly(meth)acrylate pour point depressants may be either so-called non-dispersant or dispersant. Furthermore, the poly(meth)acrylate used as the pour point depressant preferably has a weight-average molecular weight of 10,000 to 1,000,000 from the viewpoint of improving the pour point depressant effect and shear stability.

[0083] In the viscosity index improvers and pour point depressants, the "weight average molecular weight" refers to a value determined by gel permeation chromatography (GPC) (molecular weight obtained in terms of standard polystyrene). The pour point depressants may be used alone or in combination of two or more.

[0084] As the metallic detergent, for example, known metallic detergents such as alkali or alkaline earth metal alkyl salicylates, alkali or alkaline earth metal alkyl benzene sulfonates, and alkali or alkaline earth metal alkyl phenates can be appropriately used. The alkali metal is preferably sodium or potassium, and the alkaline earth metal is preferably calcium or magnesium. The metallic detergent may be overbased with a carbonate (e.g., alkali metal carbonates such as sodium carbonate or potassium carbonate, or alkaline earth metal carbonates such as calcium carbonate or magnesium carbonate) or with a borate (e.g., alkali metal borates such as sodium borate or potassium borate, or alkaline earth metal borates such as calcium borate or magnesium borate). Calcium sulfonate detergents, calcium salicylate detergents, and calcium phenate detergents are preferred. Preferably, each of these calcium sulfonate detergents, calcium salicylate detergents, and calcium phenate detergents is overbased with calcium carbonate.

[0085] The base number of such metallic detergents can be appropriately determined depending on the application of the lubricating oil composition, and is not particularly limited, but is preferably 10 mgKOH / g or more and 650 mgKOH / g or less, more preferably 20 mgKOH / g or more and 600 mgKOH / g or less. In this specification, the base number (perchloric acid method) of metallic detergents is the value measured according to JIS K 2501:2003-9.

[0086] Furthermore, the metal deactivator is not particularly limited, and known ones (e.g., imidazoline, pyrimidine derivatives, alkyl thiadiazoles, thioalkyl thiadiazoles, mercaptobenzothiazole, benzotriazole or derivatives thereof, tolyltriazole or derivatives thereof, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bisdialkyldithiocarbamate, 2-(alkyldithio)benzimidazole, β-(o-carboxybenzylthio)propionitrile, etc.) can be used appropriately. As such metal deactivators, triazole-based metal deactivators are more preferred. Furthermore, the metal deactivators may be used alone or in combination of two or more.

[0087] The above describes a preferred embodiment of the lubricating base oil when it contains other additives, and compounds suitable as additives used in that embodiment. However, the other additives and their combinations are not limited to these, and the design can be changed as appropriate depending on the application, etc.

[0088] <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 the 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.

[0089] In the lubricating oil composition of the present invention, the content of the antioxidant is not particularly limited, but is preferably 0.1 to 5.0 mass% (more preferably 0.15 to 4.5 mass%, and even more preferably 0.2 to 4.0 mass%) based on the total amount of the composition. If the content of such antioxidant is equal to or greater than the lower limit, a more excellent effect in terms of antioxidant effect can be obtained compared to when the content is less than the lower limit, while if the content is equal to or less than the upper limit, a more excellent effect can be obtained in terms of cost-effectiveness balance compared to when the content exceeds the upper limit.

[0090] Furthermore, when the antioxidant contains a combination of the phenolic antioxidant and the amine antioxidant, the content of the phenolic antioxidant is preferably 0.1% by mass or more and 5.0% by mass or less (more preferably 0.15% by mass or more and 4.5% by mass or less, and even more preferably 0.2% by mass or more and 4.0% by mass or less) based on the total amount of the composition. When the content of such a phenolic antioxidant is equal to or more than the lower limit, a more excellent effect can be obtained in terms of antioxidant effect compared to when it is below the lower limit, while when it is equal to or less than the upper limit, a more excellent effect can be obtained in terms of cost-effectiveness balance compared to when it exceeds the upper limit.

[0091] Furthermore, when the antioxidant contains a combination of the phenolic antioxidant and the amine antioxidant, the content of the amine antioxidant is preferably 0.1% by mass or more and 5.0% by mass or less (more preferably 0.15% by mass or more and 4.5% by mass or less, and even more preferably 0.2% by mass or more and 4.0% by mass or less) based on the total amount of the composition. When the content of such an amine antioxidant is equal to or more than the lower limit, a more excellent effect can be obtained in terms of antioxidant effect compared to when it is below the lower limit, while when it is equal to or less than the upper limit, a more excellent effect can be obtained in terms of cost-effectiveness balance compared to when it exceeds the upper limit.

[0092] 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.

[0093] The content of the pyridineimine compound 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 in combination with an antioxidant. On the other hand, by setting the content to be equal to or less than the upper limit, a higher level of antioxidant performance can be obtained in combination with an antioxidant with good economic efficiency.

[0094] The content of the zinc salt is preferably 1 ppm by mass to 10% by mass (more preferably 2 ppm by mass to 8% by mass, and even more preferably 3 ppm by mass to 5% by mass) based on the total amount of the composition. The content of the zinc salt is preferably 1.0 micromoles to 10 millimoles (more preferably 1.5 micromoles to 1 millimoles, and even more preferably 2.0 micromoles to 500 micromoles) 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 setting the content in this range, a complex can be efficiently formed between the pyridineimine and the zinc salt, thereby further enhancing the ability to inhibit oxidative degradation.

[0095] Furthermore, when the lubricating oil composition of the present invention contains the other additives (ashless dispersants, metal-based 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 the effects of the present invention are not impaired.

[0096] When one or more of an ashless dispersant, a viscosity index improver, and a pour point depressant are used as the additive, the content of each of them may be 0.01 to 20 mass% of the total composition. Here, the content of the ashless dispersant is more preferably 0.1 to 10 mass% of the total composition, the content of the viscosity index improver is more preferably 0.1 to 22 mass% of the total composition, and the content of the pour point depressant is more preferably 0.1 to 1.0 mass% of the total composition.

[0097] Furthermore, when a metallic detergent is used as the additive, for example, its content may be 0.01 to 30 mass% (more preferably 0.1 to 20 mass%) based on the total amount of the composition. When the metallic detergent is used, its content in terms of metal amount is preferably 200 ppm by mass or more, more preferably 250 ppm by mass or more, based on the total amount of the lubricating oil composition. From the viewpoint of improving fuel economy and fatigue resistance, the content of the metallic detergent in terms of metal amount is preferably 600 ppm by mass or less, more preferably 550 ppm by mass or less, based on the total amount of the lubricating oil composition. Note that, in one preferred embodiment of the composition when the metallic detergent is used, the content of the metallic detergent in terms of metal amount is 200 to 600 ppm by mass, and in another preferred embodiment, the content is 250 to 550 ppm by mass. Furthermore, when the lubricating oil composition is used for lubrication of an internal combustion engine, the content of the metallic detergent in terms of metal amount is preferably 500 mass ppm or more, more preferably 1000 mass ppm or more, based on the total amount of the lubricating oil composition, from the viewpoint of improving cleaning performance and base number maintenance, while from the viewpoint of suppressing the ash content in the composition and from the viewpoint of the life of the exhaust gas aftertreatment device, it is preferably 10000 mass ppm or less, more preferably 5000 mass ppm or less, based on the total amount of the lubricating oil composition. Note that when the lubricating oil composition is used for lubrication of an internal combustion engine, a preferred embodiment of the composition in which the metallic detergent is used can be a composition in which the content of the metallic detergent in terms of metal amount is 500 to 10000 mass ppm, and another preferred embodiment can be a composition in which the content is 1000 to 5000 mass ppm.

[0098] Furthermore, when one or more of a friction modifier, an antiwear agent, and an extreme pressure agent are used as the additive, the content thereof may be 0.05 to 5.0 mass% of the total composition. Here, the content of the antiwear agent is more preferably 0.01 to 15 mass% of the total composition. When the antiwear agent contains phosphorus atoms, the content thereof, calculated as phosphorus atoms, is preferably 50 ppm by mass or more, more preferably 100 ppm by mass or more, based on the total lubricating oil composition. From the same viewpoint, the content of the antiwear agent, calculated as phosphorus atoms, is preferably 800 ppm by mass or less, more preferably 700 ppm by mass or less, based on the total lubricating oil composition. A preferred embodiment of the composition containing the antiwear agent is a composition in which the content of the antiwear agent, calculated as phosphorus atoms, is 50 to 800 ppm by mass, and another preferred embodiment is a composition in which the content is 100 to 700 ppm by mass. Furthermore, when the lubricating oil composition is used for lubrication of an internal combustion engine, the content of the antiwear agent, calculated as phosphorus atoms, is preferably 400 ppm by mass or more, more preferably 500 ppm by mass or more, based on the total amount of the lubricating oil composition, from the viewpoint of improving wear resistance, and on the other hand, from the viewpoint of reducing catalyst poisoning in an exhaust gas aftertreatment device, it is preferably 5000 ppm by mass or less, more preferably 3000 ppm by mass or less. Note that, when the lubricating oil composition is used for lubrication of an internal combustion engine, a preferred embodiment of the composition in which the antiwear agent is used can be a composition in which the content of the antiwear agent, calculated as phosphorus atoms, is 400 to 5000 ppm by mass, and another preferred embodiment can be a composition in which the content is 500 to 3000 ppm by mass.

[0099] Furthermore, when one or more of a corrosion inhibitor, a rust inhibitor, and a demulsifier are used as the additive, the content thereof may be, for example, 0.005 to 5 mass% of the total amount of the composition. When a metal deactivator is used as the additive, the content thereof may be, for example, 0.005 to 1 mass% of the total amount of the composition. Furthermore, when an antifoaming agent is used as the additive, the content thereof may be, for example, 0.0001 to 1 mass% of the total amount of the composition (more preferably, 0.001 to 0.1 mass%). [Example]

[0100] 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.

[0101] [Ingredients used in the examples] First, the lubricating base oil, antioxidant, pyridine imine compound, zinc salt, and other additives used in each example will be described.

[0102] <About lubricant base oil> In all of the following examples, a mineral base oil consisting of the following base oil (A) was used as the lubricating base oil. Base oil (A) Solvent refined mineral oil [API Group I, 350N, kinematic viscosity at 40°C: 75.2 mm 2 / s, kinematic viscosity at 100°C: 9.4mm 2 / s, viscosity index: 101, sulfur content in base oil (sulfur content in base oil): 0.46 mass%, pour point: -15°C, flash point: 260°C]

[0103] <About antioxidants> The antioxidants used in the following examples will be described. Phenolic antioxidant: Hindered phenol compound (compound name: octyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), hindered phenolic antioxidant Amine antioxidants: alkylated diphenylamine (formula: C4H9-Ph-NH-Ph-C8H 17 (wherein Ph represents a phenylene group), a diarylamine-based antioxidant.

[0104] <About pyridine imine compounds> The pyridine imine compound used in the following Examples etc. will be described below. In the following Examples etc., the pyridine imine compound (k) prepared in the following Synthesis Example 1 was used.

[0105] (Synthesis Example 1: Preparation of pyridine imine compound (k)) The following formula (k):

[0106] [ka]

[0107] A pyridine imine compound represented by the following formula (hereinafter referred to as "pyridine imine compound (k)" for convenience) was synthesized as follows.

[0108] Specifically, dry toluene (60 ml) was first introduced into a 100 ml recovery flask under a nitrogen atmosphere, followed by the addition of 4-methoxy-2-methylaniline (2.0893 g, 15.3 mmol, Tokyo Chemical Industry Co., Ltd.), 2,6-diacetylpyridine (1.2429 g, 7.6 mmol, Tokyo Chemical Industry Co., Ltd.), 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 this heating and refluxing process was carried out for 24 hours to obtain a reaction mixture. The reaction mixture was then concentrated to dryness to obtain a crude solid (2.8241 g). Next, 2 g of the resulting crude solid was weighed out and washed with absolute ethanol (30 ml). The ethanol-insoluble solid was then filtered off, and the solid was further 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.

[0109] (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.

[0110] <Zinc salt> Zinc naphthenate (zinc content 8%, manufactured by Tokyo Chemical Industry Co., Ltd.).

[0111] <Other additives> In all of the following examples, antiwear agents, ashless dispersants, viscosity index improvers, metallic detergents, and antifoaming agents were used as other additives. The compound types of the other additives used will be described below. Anti-wear agent: zinc dialkyldithiophosphate (ZnDTP, secondary alkyl type (compound containing a secondary alkyl group with 4 carbon atoms and a secondary alkyl group with 6 carbon atoms), zinc content: 7.9% by mass, phosphorus content: 7.2% by mass). Ashless dispersant: Succinimide ashless dispersant (boronated succinimide, nitrogen content: 1.44% by mass, boron content: 0.5% by mass, succinimide type: bis-form) Viscosity index improver: Poly(meth)acrylate viscosity index improver (non-dispersant polymethacrylate, Mw: 130,000) Metallic detergent: calcium salicylate [base number (TBN): 225 mg KOH / g, calcium atom content: 8.1 mass%] Antifoaming agent: Dimethyl silicone (25°C kinematic viscosity: 60,000 mm 2 / s), diluted with kerosene 1% by mass.

[0112] [Method for preparing lubricating oil composition (Example 1, Comparative Examples 1-2, and Reference Example 1)] Example 1 <First step: Preparation of basic composition> First, the antiwear agent, the ashless dispersant, the viscosity index improver, and the metallic detergent were introduced into a 2-liter beaker in this order. Next, the base oil (A) (API Group I base oil) was added to the beaker, followed by the addition of an antifoaming agent. The mixture was heated to 60 to 90°C and stirred with a mechanical stirrer for 2 hours to prepare a base composition (a base composition (composition not containing any antioxidant) prior to the addition of the antioxidant, the pyridine imine compound, and the zinc salt). The resulting base composition was confirmed to be a precipitate-free solution. The contents of each additive component (other additive components) in the base composition, based on the total mass of the composition, were: antiwear agent: 1.0 mass%, ashless dispersant: 4.0 mass%, viscosity index improver: 7.0 mass%, metallic detergent: 4.0 mass%, and antifoaming agent: 0.2 mass%, respectively.

[0113] <Second Step: Preparation of Lubricating Oil Composition> The zinc salt (zinc naphthenate), the pyridinediimine compound (k) obtained in Synthesis Example 1, the phenolic antioxidant, and the amine-based antioxidant were added to a 500-milliliter beaker, followed by the base composition (340 grams) prepared in the first step. The mixture was heated to 60-90°C and stirred with a mechanical stirrer for 2 hours to obtain a precipitate-free solution, resulting in a lubricating oil composition. The contents (mass ratios) of each component in the resulting lubricating oil composition, based on the total composition, were: zinc salt: 0.38 mass% (312 mass ppm as zinc), pyridinediimine compound (k): 0.40 mass%, phenolic antioxidant: 0.7 mass%, and amine-based antioxidant: 0.7 mass%. The zinc salt content was 4.8 μmol / g, and the pyridinediimine compound (k) content was 10.2 μmol / g per gram of lubricating base oil contained in the resulting lubricating oil composition.

[0114] (Comparative Example 1) The base composition obtained by employing the first step of Example 1 was used as it was as a comparative lubricating oil composition (a composition that did not contain the antioxidant, the pyridine imine compound, and the zinc salt).

[0115] (Comparative Example 2) A comparative lubricating oil composition (a composition containing no pyridineimine compound or zinc salt but containing an antioxidant) was obtained using the base composition obtained by employing the first step of Example 1 as the base composition used in the preparation of the lubricating oil composition, employing the same process as the second step described in Example 1, except that the zinc salt (zinc naphthenate) and the pyridinediimine compound (k) were not used. Specifically, the phenolic antioxidant and the amine-based antioxidant were introduced into a 500-milliliter beaker, and then the base composition (340 grams) was added thereto. The mixture was heated to 60 to 90°C and stirred with a mechanical stirrer for 2 hours to obtain a precipitate-free solution, thereby obtaining a comparative lubricating oil composition. In the resulting lubricating oil composition, the content (mass ratio) of each antioxidant based on the total amount of the composition was 0.7 mass% for the phenolic antioxidant and 0.7 wt% for the amine-based antioxidant, respectively.

[0116] (Reference example 1) A reference lubricating oil composition (a composition containing the pyridine imine compound and the zinc salt, but without the phenolic antioxidant and the amine antioxidant, but without the pyridine imine compound and the zinc salt) was obtained using the base composition obtained by the first step of Example 1 as the base composition used in the preparation of the lubricating oil composition, and the same process as in the second step described in Example 1 was used, except that the phenolic antioxidant and the amine antioxidant were not used. Specifically, zinc naphthenate and the pyridine diimine compound (k) obtained in Synthesis Example 1 were introduced into a 500-milliliter beaker, and then the base composition (340 grams) was added thereto. The mixture was heated to 60 to 90°C and stirred with a mechanical stirrer for 2 hours to obtain a precipitate-free solution, thereby obtaining a reference lubricating oil composition. The contents (mass ratios) of each component in the lubricating oil composition, based on the total weight of the composition, were 0.38 wt % (312 ppm by weight as zinc) for the zinc salt and 0.40 wt % for the pyridine diimine compound (k). The content of zinc salt relative to 1 g of lubricating base oil contained in the obtained lubricating oil composition was 4.8 μmol / g, and the content of pyridine diimine compound (k) was 10.2 μmol / g.

[0117] [Evaluation of the properties of the lubricating oil compositions obtained in Example 1, Comparative Examples 1 to 3, and Reference Example 1] <Oxidation Degradation Test> In order to obtain samples to be used in the tests described below, the lubricating oil compositions obtained in Example 1, Comparative Examples 1 to 3, and Reference Example 1 were each subjected to an ISOT test in accordance with JIS K2514-1:2013 (test temperature: 165.5°C, test time: 144 hours), and each lubricating oil composition was subjected to oxidative degradation and used in the tests described below.

[0118] <Antioxidation Performance Measurement Test 1 (Measurement of Pentane Insolubles)> For the lubricating oil compositions obtained in Example 1 and Comparative Examples 1 and 2, the compositions (degraded oils) after the oxidation degradation test were used to measure the pentane-insoluble content (unit: mass%) in accordance with ASTM D893-12 (note that the pentane-insoluble content (pentane-insoluble content) refers to the proportion (unit: mass%) of components in the degraded oil that are not soluble in pentane).

[0119] For this measurement, the deteriorated oil, pentane, n-butylethanolamine, and 2-propanol were first mixed in a centrifuge test tube, and the insoluble matter was separated using a centrifuge. This procedure was repeated three times. The test tube was then dried and weighed. The mass (g) of the insoluble matter was calculated from the increase in the mass of the test tube before and after the treatment, and the proportion of components that were not soluble in pentane (pentane insolubles) was calculated. The results are shown in Table 1. It can be seen that the lower the proportion (mass%) of pentane insolubles, the higher the oxidation stability.

[0120] [Table 1]

[0121] As is clear from the results shown in Table 1, the lubricating oil compositions obtained in Example 1 and Comparative Example 2, in which an antioxidant was added to the base composition, both had lower pentane-insoluble matter values ​​than the base composition itself (Comparative Example 1), confirming their high performance in preventing oxidative degradation. In particular, the lubricating oil composition obtained in Example 1, which contained the antioxidant in combination with the zinc salt and pyridine diimine compound (k), had a pentane-insoluble matter value of 0, confirming that it obtained a higher level of antioxidant performance than the lubricating oil composition obtained in Comparative Example 2, which did not contain the zinc salt and pyridine diimine compound (k) and simply utilized an antioxidant.

[0122] <Antioxidant performance measurement test 2> Regarding the lubricating oil compositions obtained in Example 1 and Comparative Example 1, using the composition before the oxidation deterioration test and the composition after the oxidation deterioration test (deteriorated oil) respectively, the kinematic viscosities of the compositions before and after the test were measured respectively, and the rate of increase in the viscosity of the composition by the oxidation deterioration test was determined. In the measurement, the kinematic viscosity (40°C kinematic viscosity) of each composition at 40°C was measured using an automatic viscometer (trade name "CAV-2000", manufactured by Cannon Instrument Company) as a measuring device in accordance with JIS K 2283-2000. The obtained results are shown in Table 2.

[0123]

Table 2

[0124] As is clear from the results shown in Table 2, the lubricating oil composition obtained in Example 1 had a change rate of 97% in the 40°C kinematic viscosity before and after the oxidation deterioration test, and no increase in viscosity was confirmed. On the other hand, the lubricating oil composition (basic composition) obtained in Comparative Example 1 without an antioxidant had a change rate of 1046% in the 40°C kinematic viscosity before and after the test, and the viscosity increased significantly. From such results, it was also found that the lubricating oil composition obtained in Example 1 has a high level of antioxidant performance.

[0125] <Measurement of Cu precipitation amount (dissolution amount)> Regarding the lubricating oil compositions obtained in Example 1, Comparative Examples 1 to 2 and Reference Example 1, using the composition before the oxidation deterioration test and the composition after the oxidation deterioration test (deteriorated oil) respectively, for each composition, in accordance with JIS K 0116 (issued in 2014), the dissolution amount of Cu (copper) as a metal component was determined by inductively coupled plasma atomic emission spectrometry. The Cu (copper) as the metal component to be measured is the metal that the composition contacts during the oxidation deterioration test (ISOT test). The obtained results are shown in Table 3.

[0126]

Table 3

[0127] The results shown in Table 3 confirm that the lubricating oil composition obtained in Example 1, compared with the lubricating oil compositions obtained in Comparative Examples 1 and 2, is able to highly inhibit the deposition of Cu, a metal component that came into contact with the composition during the oxidation degradation test. Comparing the lubricating oil composition obtained in Comparative Example 2, which did not contain the pyridine imine compound and zinc salt but contained an antioxidant, with the lubricating oil composition obtained in Reference Example 1, which did not contain the antioxidant but contained the pyridine imine compound and zinc salt, the lubricating oil composition obtained in Comparative Example 2, which utilized a conventional antioxidant, exhibited a higher metal deposition inhibition effect. The mixture of the pyridine imine compound and zinc salt alone did not necessarily achieve a high metal deposition inhibition effect compared with conventional antioxidants. In contrast, when the antioxidant, pyridine imine compound, and zinc salt were combined (Example 1), the metal deposition inhibition effect, based on the amount of Cu deposition, was significantly higher than that of the lubricating oil composition obtained in Comparative Example 2, although the reason for this is unclear. This indicates that the metal deposition inhibition effect was very excellent.

[0128] As described above, from the results shown in Tables 1 to 3, it was confirmed that the lubricating oil composition obtained in Example 1, which utilizes a combination of the antioxidant, the pyridine imine compound, and the zinc salt, is capable of highly inhibiting oxidation degradation of the lubricating base oil while also highly inhibiting deposition of metals (Cu) that come into contact with the composition into the composition. [Industrial Applicability]

[0129] As described above, the present invention provides a lubricating oil composition that can highly inhibit oxidative degradation of a lubricating base oil and highly inhibit deposition of metals that come into contact with the composition. 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; at least one antioxidant selected from the group consisting of phenolic antioxidants and amine antioxidants; 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: at least one zinc salt selected from the group consisting of zinc fatty acid zinc, zinc halide, zinc nitrate, zinc sulfate, zinc oxide, zinc sulfide, and zinc phosphate; 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. 2. The lubricating oil composition according to claim 1, 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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