Lubricating oil composition

Abstract

The problem is to provide a lubricating oil composition that can well exhibit sludge inhibition and wear resistance as evaluated by scuffing resistance and seizure resistance over a long period of time. The problem is solved by forming a lubricating oil composition comprising a base oil (A), a hindered phenol antioxidant (B), one or more imide compounds (C) selected from a monoimide compound (C1) and a bisimide compound (C2), and an extreme pressure agent (D), wherein the hindered phenol antioxidant (B) is 2,6-di-tert-butylphenol, the monoimide compound (C1) is one or more selected from alkenyl succinic acid monoimide compounds and alkyl succinic acid monoimide compounds, and the bisimide compound (C2) is one or more selected from alkenyl succinic acid bisimide compounds and alkyl succinic acid bisimide compounds.

Description

Technical Field

[0001] The present invention relates to lubricating oil compositions. Background Art

[0002] Hydraulic equipment installed in construction machinery such as hydraulic excavators, cranes, wheel loaders, and bulldozers is required to operate under high pressure, high temperature, high speed, and high load.

[0003] Therefore, lubricating oil compositions used as power transmission media in hydraulic equipment for construction machinery are required to have wear resistance and oxidation stability that do not impair the performance of the hydraulic equipment even when used for a long period of time under high pressure, high temperature, high speed, and high load.

[0004] In particular, lubricating oil compositions used in hydraulic equipment with an operating pressure of 30 MPa or more tend to suffer from early deterioration in oxidation stability and lubrication performance, and tend to cause disadvantages such as sludge generation and malfunction.

[0005] For example, Patent Document 1 proposes a hydraulic oil composition containing an amine antioxidant, a phenolic antioxidant, and a phosphate ester in a polyolefin having a predetermined kinematic viscosity at a predetermined ratio as a hydraulic oil composition for use in hydraulic equipment such as construction machinery having a working pressure of 30 MPa or more.

[0006] Patent Document 1 describes that the hydraulic oil composition has excellent oxidation stability and lubrication performance under high pressure, can effectively prevent early degradation and sludge generation under high pressure, and can be used for a long time.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent document 1: Japanese Patent Application Publication No. 09-111277. Summary of the invention

[0010] Problems to be solved by the invention

[0011] In recent years, hydraulic equipment has been directed to high performance such as high pressure, small size, high speed, and high precision. Therefore, the performance requirements for lubricating oil compositions used in hydraulic equipment have become more stringent. Therefore, people expect further high performance of lubricating oil compositions used in hydraulic equipment.

[0012] From this viewpoint, in recent years, the ISO hydraulic oil standard has adopted the "FZG scratch test" (ISO-14635) that specifies lubricity such as wear resistance.

[0013] In addition, if a large amount of sludge is generated in hydraulic equipment, it may cause valve spring abutment pins and wear of hydraulic pumps. In order to further improve the performance of lubricating oil compositions for hydraulic equipment, it is required to suppress the amount of sludge generated to a very small amount over a long period of time.

[0014] Furthermore, due to the improvement in performance of hydraulic equipment, seizure and the like may be more likely to occur. In order to further improve the performance of lubricating oil compositions for hydraulic equipment, it is also required to be able to exhibit excellent seizure resistance for a long period of time.

[0015] That is, in view of the recent situation that hydraulic equipment is directed towards higher performance, lubricating oil compositions for use in hydraulic equipment are required to have excellent performance in suppressing the amount of sludge generated to an extremely small amount for a long period of time (hereinafter also referred to as "sludge suppression property"), and to be able to exhibit good wear resistance evaluated by scuffing resistance, seizure resistance, etc. for a long period of time.

[0016] However, in Patent Document 1, such a study has not been fully conducted.

[0017] An object of the present invention is to provide a lubricating oil composition that can exhibit good sludge inhibition performance and wear resistance as evaluated by scuffing resistance and seizure resistance over a long period of time.

[0018] Solutions to Solve Problems

[0019] The present inventors have made intensive studies and have found that a lubricating oil composition containing a specific phenolic antioxidant and two specific imide compounds can solve the above-mentioned problems.

[0020] That is, the present invention relates to the following [1].

[0021] [1] A lubricating oil composition comprising a base oil (A), a hindered phenol antioxidant (B), at least one imide compound (C) selected from a monoimide compound (C1) and a bisimide compound (C2), and an extreme pressure agent (D), wherein the hindered phenol antioxidant (B) is 2,6-di-tert-butylphenol, the monoimide compound (C1) is at least one selected from an alkenyl succinic acid monoimide compound and an alkyl succinic acid monoimide compound, and the bisimide compound (C2) is at least one selected from an alkenyl succinic acid bisimide compound and an alkyl succinic acid bisimide compound.

[0022] Effects of the Invention

[0023] According to the present invention, it is possible to provide a lubricating oil composition that can exhibit sludge inhibition properties and wear resistance as evaluated by scuffing resistance and seizure resistance well over a long period of time. DETAILED DESCRIPTION

[0024] In this specification, for a preferred numerical range (e.g., a range of content, etc.), the lower limit and upper limit values ​​described in stages can be independently combined. For example, according to the description of "preferably 10 to 90, more preferably 30 to 60", the "preferable lower limit (10)" and the "more preferably upper limit (60)" can also be combined to set to "10 to 60".

[0025] In addition, in this specification, the numerical values ​​of Examples are numerical values ​​that can be used as upper limits or lower limits.

[0026] In addition, in this specification, the numerical range described as "AA to BB" means "AA or more and BB or less" unless otherwise specified.

[0027] [Embodiments of the Lubricating Oil Composition of the Present Invention]

[0028] The lubricating oil composition of the present invention comprises a base oil (A), a hindered phenol antioxidant (B), one or more imide compounds (C) selected from a monoimide compound (C1) and a bisimide compound (C2), and an extreme pressure agent (D), wherein the hindered phenol antioxidant (B) is 2,6-di-tert-butylphenol, the monoimide compound (C1) is one or more selected from an alkenyl succinic acid monoimide compound and an alkyl succinic acid monoimide compound, and the bisimide compound (C2) is one or more selected from an alkenyl succinic acid bisimide compound and an alkyl succinic acid bisimide compound.

[0029] The present inventors have conducted intensive studies to provide a lubricating oil composition that can exhibit good sludge inhibition performance and wear resistance as evaluated by scuffing resistance and seizure resistance over a long period of time.

[0030] First, from the viewpoint of sludge inhibition, the combined use of a phenolic antioxidant and an imide compound is considered. However, it is believed that the imide compound can improve the sludge inhibition, but on the other hand, it becomes a major factor that reduces the performance of the extreme pressure agent and reduces the wear resistance of the lubricating oil composition. In addition, it is believed that the extreme pressure agent imparts wear resistance to the lubricating oil composition, but on the other hand, it becomes a major factor that causes sludge generation.

[0031] Taking these points into consideration, the present inventors believe that it is important to solve at least the following two points in order to achieve the object of the present invention.

[0032] (1) To suppress the performance degradation of the extreme pressure agent caused by using the extreme pressure agent and the imide compound in combination.

[0033] (2) Suppressing the generation of sludge caused by the addition of extreme pressure agents.

[0034] From the above viewpoints, the present inventors further conducted intensive studies.

[0035] As a result, it was found that a lubricating oil composition containing 2,6-di-tert-butylphenol (hereinafter also referred to as "DTBP") in which the methyl group of the cresol skeleton of DBPC is replaced with a hydrogen atom, instead of 2,6-di-tert-butyl-p-cresol (hereinafter also referred to as "DBPC") which is a phenolic antioxidant conventionally used in lubricating oil compositions for hydraulic equipment and the like, has a function of suppressing sludge generation caused by the addition of an extreme pressure agent and greatly improving sludge inhibition.

[0036] Furthermore, by using a monoimide compound and a bisimide compound in combination as the imide compound, it is possible to suppress the reduction in performance of the extreme pressure agent caused by using the extreme pressure agent and the imide compound together, and to fully exert the performance of the extreme pressure agent.

[0037] Based on these results, the present inventors further conducted intensive studies and thus completed the present invention.

[0038] It should be noted that the reason why the above-mentioned effects of the present invention are achieved is not clear, but it is estimated that the reasons are as follows, for example.

[0039] That is, it is presumed that DTBP, in which the methyl group of the cresol skeleton of DBPC is replaced with a hydrogen atom, becomes more likely to be retained in the lubricating oil composition than DBPC by polymerizing (e.g., dimerizing) in the lubricating oil composition, and can fully exert its performance as an antioxidant, and the dispersibility of the extreme pressure agent is improved by the monoimide compound, and the reaction site of the extreme pressure agent is easily formed on the metal surface by the bisimide compound, thereby exerting the effect of the present invention.

[0040] In the following description, the “base oil (A)”, “hindered phenol-based antioxidant (B)”, “imide compound (C)”, and “extreme pressure agent (D)” are also referred to as “component (A)”, “component (B)”, “component (C)”, and “component (D)”, respectively.

[0041] The lubricating oil composition of one embodiment of the present invention may be composed only of "component (A)", "component (B)", "component (C)", and "component (D)", but may contain other components besides "component (A)", "component (B)", "component (C)", and "component (D)" within a range not impairing the effects of the present invention.

[0042] In one embodiment of the present invention, the total content of "component (A)", "component (B)", "component (C)", and "component (D)" is preferably 70.0% by mass or more, more preferably 75.0% by mass or more, further preferably 80.0% by mass or more, and even more preferably 85.0% by mass or more, based on the total amount of the lubricating oil composition, from the viewpoint of more easily exerting the effects of the present invention.

[0043] The upper limit of the total content of component (A), component (B), component (C), and component (D) may be adjusted by taking into account components other than component (A), component (B), component (C), and component (D), and is preferably 99.0% by mass or less, more preferably 98.0% by mass or less, and even more preferably 97.0% by mass or less, based on the total amount of the lubricating oil composition.

[0044] The upper and lower limits of these numerical ranges may be arbitrarily combined. Specifically, it is preferably 70.0% to 99.0% by mass, more preferably 75.0% to 98.0% by mass, further preferably 80.0% to 98.0% by mass, and further preferably 85.0% to 97.0% by mass.

[0045] Hereinafter, the base oil (A), the hindered phenol-based antioxidant (B), the imide compound (C), the extreme pressure agent (D), and other components will be described in detail.

[0046] <<Base oil (A)>>

[0047] The lubricating oil composition of the present invention contains a base oil (A).

[0048] As the base oil (A), one or more selected from mineral oils and synthetic oils conventionally used as base oils for lubricating oils can be used without particular limitation.

[0049] Examples of the mineral oil include atmospheric residues obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate base crude oil, or cycloparaffinic crude oil; distillates obtained by vacuum distillation of these atmospheric residues; and mineral oils obtained by subjecting the distillates to one or more refining treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrofining.

[0050] Examples of synthetic oils include poly-α-olefins such as α-olefin homopolymers and α-olefin copolymers (e.g., α-olefin copolymers having 8 to 14 carbon atoms such as ethylene-α-olefin copolymers); isoparaffins; various esters such as polyol esters and dibasic acid esters; various ethers such as polyphenylene ether; polyalkylene glycols; alkylbenzenes; alkylnaphthalenes; GTL base oils obtained by isomerizing wax produced from natural gas using the Fischer-Tropsch process (Gas To Liquids WAX); and the like.

[0051] The base oil (A) may be a mineral oil alone or in combination of two or more mineral oils, or a synthetic oil alone or in combination of two or more synthetic oils. Alternatively, one or more mineral oils and one or more synthetic oils may be used in combination.

[0052] From the viewpoint of further improving the oxidation stability of the lubricating oil composition, the base oil (A) is preferably at least one selected from the group consisting of base oils classified as Group 2, Group 3 and Group 4 of the base oil classification of the American Petroleum Institute (API), and more preferably at least one selected from the group consisting of base oils classified as Group 2 and Group 3.

[0053] The kinematic viscosity of the base oil (A) at 40°C (hereinafter also referred to as “40°C kinematic viscosity”) is preferably 10 mm 2 / s~150mm 2 / s, preferably 15 mm 2 / s~100mm 2 / s, more preferably 20mm 2 / s~80mm 2 / s.

[0054] The kinematic viscosity of the base oil (A) at 40°C is 10 mm 2 / s or more, a lubricating oil composition having a high flash point and excellent lubrication performance can be easily obtained.

[0055] In addition, the kinematic viscosity of the base oil (A) at 40°C is 150 mm 2 When the viscosity is below 0.1 / s, the viscous resistance at low temperature will not become so large, making it easy for the machine to operate well.

[0056] The viscosity index of the base oil (A) is preferably 80 or more, more preferably 90 or more, further preferably 100 or more, and further preferably 110 or more. When the viscosity index of the base oil (A) is within the above range, viscosity changes due to temperature changes can be suppressed, an oil film can be easily formed at high temperatures, and wear resistance can be easily improved.

[0057] When the base oil (A) is a mixed base oil containing two or more base oils, the 40° C. kinematic viscosity and viscosity index of the mixed base oil are preferably within the above ranges.

[0058] In this specification, the 40° C. kinematic viscosity and the viscosity index refer to values ​​measured or calculated in accordance with JIS K 2283:2000.

[0059] In the lubricating oil composition of one embodiment of the present invention, the content of the base oil (A) is preferably 80.0% by mass or more, more preferably 83.0% by mass or more, and further preferably 85.0% by mass or more, based on the total amount of the lubricating oil composition, from the viewpoint of making it easier to exert the effect of the present invention. In addition, it is preferably 98.0% by mass or less, more preferably 97.0% by mass or less, and further preferably 96.0% by mass or less. The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, it is preferably 80.0% by mass to 98.0% by mass, more preferably 83.0% by mass to 97.0% by mass, and further preferably 85.0% by mass to 96.0% by mass.

[0060] <<Hindered phenol antioxidant (B)>>

[0061] The lubricating oil composition of the present invention contains a hindered phenol antioxidant (B), and the hindered phenol antioxidant (B) is 2,6-di-tert-butylphenol.

[0062] When the lubricating oil composition does not contain 2,6-di-tert-butylphenol, it is not possible to achieve excellent sludge inhibition properties.

[0063] It should be noted that according to the research of the present inventors, when 2,6-di-tert-butyl-p-cresol in which the hydrogen atom at the 4-position (para-position) of the phenyl group of 2,6-di-tert-butylphenol is replaced with a methyl group, excellent sludge inhibition cannot be achieved. In other words, it is presumed that the effect of the present invention is achieved by the subtle difference in the structure of the phenolic antioxidant (i.e., the presence or absence of a methyl group).

[0064] (Content of hindered phenol antioxidant (B))

[0065] In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of forming a lubricating oil composition with better sludge inhibition, the content of the hindered phenol antioxidant (B) is preferably 0.40% by mass or more, more preferably 0.50% by mass or more, further preferably 0.60% by mass or more, further preferably 0.65% by mass or more, further more preferably 0.70% by mass or more, based on the total amount of the lubricating oil composition. In addition, it is preferably 2.0% by mass or less, more preferably 1.5% by mass or less, further preferably 1.2% by mass or less, further preferably 1.0% by mass or less, further more preferably 0.90% by mass or less. The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, it is preferably 0.40% by mass to 2.0% by mass, more preferably 0.50% by mass to 1.5% by mass, further preferably 0.60% by mass to 1.2% by mass, further preferably 0.65% by mass to 1.0% by mass, further more preferably 0.70% by mass to 0.90% by mass.

[0066] <<Imide compound (C)>>

[0067] The lubricating oil composition of the present invention contains one or more imide compounds (C) selected from monoimide compounds (C1) and bisimide compounds (C2). When the lubricating oil composition does not contain the imide compound (C), the sludge inhibition property cannot be excellent. On the other hand, as described above, by containing the imide compound (C) in the lubricating oil composition, there is a problem of reducing the performance of the extreme pressure agent (D). In the present invention, in view of the above problem, as the imide compound (C), one or more imide compounds (C) selected from monoimide compounds (C1) and bisimide compounds (C2) are used.

[0068] This provides a lubricating oil composition that is excellent in wear resistance and that fully volatilizes the extreme pressure agent (D) without reducing the performance of the extreme pressure agent (D).

[0069] The monoimide compound (C1) is at least one selected from alkenyl succinic acid monoimide compounds and alkyl succinic acid monoimide compounds.

[0070] In addition, the bisimide compound (C2) is one or more selected from the group consisting of alkenyl succinic acid bisimide compounds and alkyl succinic acid bisimide compounds.

[0071] In the following description, the “monoimide compound (C1)” is also simply referred to as the “component (C1)”. In addition, the “bisimide compound (C2)” is also simply referred to as the “component (C2)”.

[0072] Hereinafter, the monoimide compound (C1) and the bisimide compound (C2) will be described in detail.

[0073] (Monoimide compound (C1) and bisimide compound (C2))

[0074] The monoimide compound (C1) is one or more selected from alkenyl succinic acid monoimide compounds and alkyl succinic acid monoimide compounds. As the alkenyl succinic acid monoimide compound and the alkyl succinic acid monoimide compound, for example, a compound represented by the following general formula (c1) is preferred. In addition, the bisimide compound (C2) is one or more selected from alkenyl succinic acid bisimide compounds and alkyl succinic acid bisimide compounds. As the alkenyl succinic acid bisimide compound and the alkyl succinic acid bisimide compound, for example, a compound represented by the following general formula (c2) is preferred.

[0075] [Chemical formula 1]

[0076]

[0077] [Chemical formula 2]

[0078]

[0079] In the above general formula (c1), R c11 is alkenyl or alkyl, R c12 is an alkylene group having 1 to 6 carbon atoms, and n1 is an integer of 1 to 20. When n1 is 2 or more, a plurality of R c12 It can be the same or different.

[0080] In the above general formula (c2), R c21 and R c24 are each independently alkenyl or alkyl, R c22 and R c23 Each independently represents an alkylene group having 1 to 6 carbon atoms, and n2 represents an integer from 0 to 20. When n2 is 2 or more, the plurality of R c22 It can be the same or different.

[0081] Can be used as R c11 , R c21 , and R c24 The selected alkenyl or alkyl group preferably has a mass average molecular weight (Mw) of 500 or more, more preferably 1000 or more, further preferably 2000 or more, further preferably 3000 or more, and further more preferably 4000 or more, from the viewpoint of improving the solubility in the base oil (A) and making it easier to exert the effect of the present invention. In addition, it is preferably 10000 or less, more preferably 90000 or less, and further preferably 8000 or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 500 to 10000, more preferably 1000 to 10000, further preferably 2000 to 10000, further preferably 3000 to 9000, and further more preferably 4000 to 8000.

[0082] As available as R c11 , R c21 , and R c24 The alkenyl group to be selected includes polybutenyl, polyisobutenyl, and ethylene-propylene copolymers, and the alkyl group includes those obtained by hydrogenating these. The polybutenyl group is preferably a group obtained by polymerizing a mixture of 1-butene and isobutylene or high-purity isobutylene. Among them, the alkenyl group is preferably a polybutenyl group and isobutylene, and the alkyl group includes those obtained by hydrogenating a polybutenyl group and an isobutylene group.

[0083] In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of more easily exerting the effects of the present invention, R c11 , R c21 , and R c24The selected group is preferably an alkenyl group, and among the alkenyl groups, a polybutenyl group is more preferred.

[0084] As available as R c12 , R c22 , and R c23 The alkylene group having 1 to 6 carbon atoms is preferably a methylene group; various ethylene groups such as 1,1-ethylene and 1,2-ethylene; various propylene groups such as 1,3-propylene, 1,2-propylene and 2,2-propylene; various butylene groups; various pentylene groups; and various hexylene groups, from the viewpoint of improving the solubility in the base oil (A) and making it easier to exhibit the effects of the present invention.

[0085] In addition, from the same point of view, it can be regarded as R c12 , R c22 , and R c23 The number of carbon atoms in the selected alkylene group is preferably 2 to 5, more preferably 2 to 4, and even more preferably 2 or 3.

[0086] From the viewpoint of improving the solubility in the base oil (A) and making it easier to exhibit the effects of the present invention, n1 in the general formula (c1) is preferably 2 to 15, more preferably 3 to 10, further preferably 3 to 5, and even more preferably 3 or 4.

[0087] From the viewpoint of improving the solubility of the component (C2) represented by the general formula (c2) in the base oil and making it easier to exert the effects of the present invention, n2 in the general formula (c2) is preferably 1 to 15, more preferably 2 to 10, further preferably 2 to 5, and further preferably 3 or 4.

[0088] Alkenyl succinic acid monoimide, alkyl succinic acid monoimide, alkenyl succinic acid bisimide, or alkyl succinic acid bisimide can be generally produced by reacting alkenyl succinic anhydride obtained by reacting polyolefin with maleic anhydride or alkyl succinic anhydride obtained by hydrogenating the alkenyl succinic anhydride with polyamine. The monoimide and bisimide can be produced by changing the reaction ratio of alkenyl succinic anhydride or alkyl succinic anhydride to polyamine.

[0089] As the olefin monomer forming the polyolefin, at least one selected from α-olefins having 2 to 8 carbon atoms may be used in mixture, and a mixture of isobutylene and 1-butene may be preferably used.

[0090] On the other hand, examples of the polyamine include monodiamines such as ethylenediamine, propylenediamine, butylenediamine, and pentamethylenediamine; and polyalkylenepolyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, di(methylethylene)triamine, dibutylenetriamine, tributylenetetramine, and pentamethylenehexamine.

[0091] (Total content of monoimide compound (C1) and diimide compound (C2))

[0092] In the lubricating oil composition of one embodiment of the present invention, the total content of the monoimide compound (C1) and the bisimide compound (C2) is preferably 0.10% by mass or more, more preferably 0.13% by mass or more, further preferably 0.15% by mass or more, and further preferably 0.17% by mass or more, based on the total amount of the lubricating oil composition, from the viewpoint of making it easier to exert the effect of the present invention. In addition, it is preferably 0.50% by mass or less, more preferably 0.40% by mass or less, further preferably 0.35% by mass or less, and further preferably 0.30% by mass or less. The upper limit and lower limit of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 0.10% to 0.50% by mass, more preferably 0.13% to 0.40% by mass, further preferably 0.15% to 0.35% by mass, and further preferably 0.17% to 0.30% by mass.

[0093] (Content ratio of the monoimide compound (C1) to the diimide compound (C2) [(C1) / (C2)])

[0094] In the lubricating oil composition of one embodiment of the present invention, the content ratio [(C1) / (C2)] of the monoimide compound (C1) to the bisimide compound (C2) is preferably greater than 0, more preferably 1 / 3 or more, and further preferably 2 / 3 or more in terms of mass ratio, from the viewpoint of making it easier to exert the effect of the present invention. In addition, it is preferably less than 2 / 1, and more preferably less than 3 / 2. The upper limit and lower limit of these numerical ranges may be combined arbitrarily. Specifically, it is preferably greater than 0 to 2 / 1, more preferably 1 / 3 to 3 / 2, and further preferably 2 / 3 to 3 / 2.

[0095] <<Extreme pressure agent (D)>>

[0096] The lubricating oil composition of the present invention contains an extreme pressure agent (D).

[0097] When the lubricating oil composition does not contain the extreme pressure agent (D), it cannot be a lubricating oil composition excellent in wear resistance.

[0098] Here, in the lubricating oil composition of one embodiment of the present invention, the extreme pressure agent (D) preferably includes one or more selected from phosphorus-based extreme pressure agents (D1) and sulfur-phosphorus-based extreme pressure agents (D2).

[0099] In the following description, the “phosphorus-based extreme pressure agent (D1)” is also simply referred to as the “component (D1)”. In addition, the “sulfur-phosphorus-based extreme pressure agent (D2)” is also simply referred to as the “component (D2)”.

[0100] In the lubricating oil composition of one embodiment of the present invention, the content of one or more components selected from “component (D1)” and “component (D2)” is preferably 80% by mass to 100% by mass, more preferably 85% by mass to 100% by mass, further preferably 90% by mass to 100% by mass, and even more preferably 95% by mass to 100% by mass, based on the total amount of the extreme pressure agent (D), from the viewpoint of obtaining a lubricating oil composition having excellent wear resistance.

[0101] Hereinafter, the “phosphorus-based extreme pressure agent (D1)” and the “sulfur-phosphorus-based extreme pressure agent (D2)” will be described in detail.

[0102] (Phosphorus-based extreme pressure agent (D1))

[0103] The lubricating oil composition of one embodiment of the present invention preferably contains a phosphorus-based extreme pressure agent (D1). By containing the phosphorus-based extreme pressure agent (D1) in the lubricating oil composition, it is easy to impart excellent wear resistance to the lubricating oil composition. In addition, by using the phosphorus-based extreme pressure agent (D1) in combination with the component (B) and the components (C1) and (C2), the reduction in sludge inhibition caused by the addition of the phosphorus-based extreme pressure agent (D1) can be improved, while the performance of the phosphorus-based extreme pressure agent (D1) can be fully utilized.

[0104] In this specification, the phosphorus-based extreme pressure agent (D1) refers to an extreme pressure agent containing phosphorus atoms and having extreme pressure performance. An extreme pressure agent containing both phosphorus atoms and sulfur atoms is not classified as a phosphorus-based extreme pressure agent (D1) but is classified as a sulfur-phosphorus-based extreme pressure agent (D2).

[0105] As the phosphorus-based extreme pressure agent (D1), preferably phosphate compounds such as phosphate esters, acidic phosphate esters, phosphites, and hydrogen phosphites, and amine salts of the phosphate ester compounds are listed. More specifically, preferably, the following phosphate esters represented by the general formula (d1-1), the acidic phosphate esters represented by the general formula (d1-2), the phosphites represented by the general formula (d1-3), and the hydrogen phosphites represented by the general formulas (d1-4) and (d1-5) are listed as examples of the phosphorus-based extreme pressure agent (D1).

[0106] The phosphorus-based extreme pressure agent (D1) may be used alone or in combination of two or more.

[0107] [Chemical formula 3]

[0108]

[0109] In the general formulas (d1-1) to (d1-5), R d11 , R d21 , R d31 , R d41 , and R d51Each independently represents a hydrocarbon group having a carbon number of 1 to 30. As the hydrocarbon group, from the viewpoint of obtaining more excellent wear resistance, preferably an alkyl group, an alkenyl group, an aryl group, an arylalkyl group, etc. are mentioned.

[0110] R d11 , R d21 , R d31 , R d41 , and R d51 In the case of an alkyl group, from the viewpoint of obtaining more excellent wear resistance and in consideration of availability, the carbon number is preferably 2 to 20, more preferably 2 to 10. The alkyl group may be linear, branched or cyclic, and in consideration of availability, linear or branched is preferred.

[0111] R d11 , R d21 , R d31 , R d41 , and R d51 In the case of an alkenyl group, from the viewpoint of obtaining more excellent wear resistance and in view of easy availability, the carbon number is preferably 2 to 20, more preferably 2 to 10. The alkenyl group may be linear, branched or cyclic, and is preferably linear or branched.

[0112] R d11 , R d21 , R d31 , R d41 , and R d51 In the case of an aryl group, the carbon number is preferably 6 to 20, more preferably 6 to 15, from the viewpoint of obtaining more excellent seizure resistance and abrasion resistance and in consideration of easy availability.

[0113] R d11 , R d21 , R d31 , R d41 , and R d51 In the case of an arylalkyl group, the carbon number is preferably 6 to 20, more preferably 6 to 15, from the viewpoint of obtaining more excellent seizure resistance and abrasion resistance and in consideration of easy availability.

[0114] Multiple R d11 , R d31 , and R d51 can be the same or different from each other. In addition, R d21 and R d41 When there are multiple ones, they may be the same or different from each other.

[0115] In the general formula (d1-2), m2 represents 1 or 2, and in the general formula (d1-4), m4 represents 1 or 2.

[0116] Examples of the phosphoric acid ester represented by the general formula (d1-1) include triphenyl phosphate, tricresyl phosphate, benzyl diphenyl phosphate, ethyl diphenyl phosphate, tributyl phosphate, ethyl dibutyl phosphate, tert-butylphenyl diphenyl phosphate, di-tert-butylphenyl monophenyl phosphate, cresyl diphenyl phosphate, dicresyl monophenyl phosphate, ethyl phenyl diphenyl phosphate, diethylphenyl monophenyl phosphate, triethylphenyl phosphate, trihexyl phosphate, tri(2-ethylhexyl) phosphate, tridecyl phosphate, trilauryl phosphate, trimyristyl phosphate, tripalmityl phosphate, tristearyl phosphate, and trioleyl phosphate.

[0117] Examples of the acidic phosphate ester represented by the general formula (d1-2) include mono(di)ethyl phosphate, mono(di)n-propyl phosphate, mono(di)2-ethylhexyl phosphate, mono(di)butyl phosphate, mono(di)oleyl phosphate, mono(di)isodecyl phosphate, mono(di)lauryl phosphate, mono(di)stearyl phosphate, and mono(di)isostearyl phosphate.

[0118] Examples of the phosphite represented by the general formula (d1-3) include triethyl phosphite, tributyl phosphite, triphenyl phosphite, tricresyl phosphite, tri(nonylphenyl) phosphite, tri(2-ethylhexyl) phosphite, tridecyl phosphite, trilauryl phosphite, triisooctyl phosphite, diphenylisodecyl phosphite, tristearyl phosphite, and trioleyl phosphite.

[0119] Examples of the hydrogen phosphite represented by general formula (d1-4) and (d1-5) include mono(di)ethyl hydrogen phosphite, mono(di)n-propyl hydrogen phosphite, mono(di)n-butyl hydrogen phosphite, mono(di)2-ethylhexyl hydrogen phosphite, mono(di)lauryl hydrogen phosphite, mono(di)oleyl hydrogen phosphite, mono(di)stearyl hydrogen phosphite, and mono(di)phenyl hydrogen phosphite.

[0120] In addition, as the amine salt of the phosphate compound such as the above-mentioned phosphate ester, acidic phosphate ester, phosphite ester, hydrogen phosphite ester, etc., preferably, amine salts formed from these phosphate compounds and amines are listed. Here, as the amine used in the formation of the amine salt, primary amines, secondary amines, tertiary amines, polyalkylene amines, etc. can be listed, and as the primary amine, secondary amine, tertiary amine, amines represented by the following general formula (d1-6) can be listed.

[0121] [Chemical formula 4]

[0122]

[0123] In the general formula (d1-6), R d61represents a hydrocarbon group having 1 to 30 carbon atoms. When the hydrocarbon group is an alkyl group, it may be a hydroxyalkyl group in which at least one of the hydrogen atoms in the alkyl group is substituted with a hydroxy group.

[0124] R d61 Preferred are alkyl groups having 6 to 18 carbon atoms, alkenyl groups having 6 to 18 carbon atoms, aryl groups having 6 to 18 ring carbon atoms, arylalkyl groups having 7 to 18 carbon atoms, or hydroxyalkyl groups having 6 to 18 carbon atoms, and more preferred are alkyl groups having 6 to 18 carbon atoms.

[0125] In addition, m6 is 1, 2 or 3. When m6 is 1, a primary amine is formed. When m6 is 2, a secondary amine is formed. When m6 is 3, a tertiary amine is formed.

[0126] Examples of the polyalkyleneamine include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexethyleneheptamine, heptaethyleneoctamine, tetrapropylenepentamine, and hexadiethyleneheptamine.

[0127] Among them, from the viewpoint of imparting better wear resistance to the lubricating oil composition, it is preferred to use one or more selected from phosphoric acid esters and amine salts of acidic phosphoric acid esters, and it is preferred to use phosphoric acid esters alone or in combination with amine salts of phosphoric acid esters and acidic phosphoric acid esters.

[0128] The phosphoric acid ester is preferably a compound represented by the above-mentioned general formula (d1-1), and more preferably a compound represented by the following general formula (d1-1a).

[0129] [Chemical formula 5]

[0130]

[0131] In the above general formula (d1-1a), R d71 ~R d73 Each of p1 to p3 is independently an integer of 0 to 5.

[0132] In the compound represented by the above general formula (d1-1a), from the viewpoint of more easily exerting the effect of the present invention, R d71 ~R d73 Each independently is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, and still more preferably an alkyl group having 1 to 4 carbon atoms.

[0133] In addition, p1 to p3 are each independently preferably an integer of 0 to 1.

[0134] Here, when the phosphoric acid ester is used alone, it is preferred that one or two of p1 to p3 are 0, and the rest are 1. In this case, R d71 ~R d73 The alkyl group selected is preferably tert-butyl.

[0135] In addition, the amine salt of the acidic phosphate ester is preferably an amine salt of the acidic phosphate ester formed from the acidic phosphate ester represented by the general formula (d1-2) and the amine represented by the general formula (d1-6). In this case, the acidic phosphate ester represented by the general formula (d1-2) is preferably an alkyl group having 2 to 10 carbon atoms, more preferably an alkyl group having 2 to 8 carbon atoms, and further preferably an alkyl group having 3 to 6 carbon atoms.

[0136] (Sulfur-phosphorus extreme pressure agent (D2))

[0137] The lubricating oil composition of one embodiment of the present invention preferably contains a sulfur-phosphorus extreme pressure agent (D2). By containing the sulfur-phosphorus extreme pressure agent (D2) in the lubricating oil composition, it is easy to impart excellent wear resistance to the lubricating oil composition. In addition, by using the sulfur-phosphorus extreme pressure agent (D2) in combination with the component (B) and the components (C1) and (C2), the reduction in sludge inhibition caused by the addition of the sulfur-phosphorus extreme pressure agent (D2) can be improved, while the performance of the sulfur-phosphorus extreme pressure agent (D2) can be fully exerted.

[0138] Examples of the sulfur-phosphorus extreme pressure agent (D2) include monothiophosphates, dithiophosphates, trithiophosphates, amine salts of monothiophosphates, amine salts of dithiophosphates, monothiophosphites, dithiophosphites, trithiophosphites, and the like. Among them, dithiophosphites are preferred.

[0139] Here, from the viewpoint of imparting further excellent wear resistance to the lubricating oil composition, among the dithiophosphates, dithiophosphates having a carboxyl group at the terminal are preferred.

[0140] Specific examples of the dithiophosphate having a carboxyl group at the terminal include compounds represented by the following general formula (d2).

[0141] [Chemical formula 6]

[0142]

[0143] In the above general formula (d2), R d71 represents a linear or branched alkylene group having 1 to 8 carbon atoms, R d72 and R d73 Each independently represents a hydrocarbon group having 3 to 20 carbon atoms.

[0144] From the viewpoint of improving solubility in the base oil, R d71Preferably, it is a linear or branched alkylene group having 1 to 8 carbon atoms, more preferably a linear or branched alkylene group having 2 to 4 carbon atoms, and still more preferably a branched alkylene group. Specifically, preferably, -CH2CH2-, -CH2CH(CH3)-, -CH2CH(CH2CH3)-, CH2CH(CH3)CH2-, and -CH2CH(CH2CH2CH3)- are listed, more preferably -CH2CH(CH3)-, -CH2CH(CH3)CH2-, and still more preferably -CH2CH(CH3)-.

[0145] In addition, from the viewpoint of improving the extreme pressure performance and improving the solubility in the base oil, R d72 and R d73 It is preferably a linear or branched alkyl group having 3 to 8 carbon atoms, and more preferably a linear or branched alkyl group having 4 to 6 carbon atoms. Specifically, it is preferably selected from propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, isopentyl, hexyl, 2-ethylbutyl, 1-methylpentyl, 1,3-dimethylbutyl, and 2-ethylhexyl, and among them, isobutyl and tert-butyl are more preferred.

[0146] The sulfur-phosphorus extreme pressure agent (D2) may be used alone or in combination of two or more.

[0147] (Content of extreme pressure agent (D))

[0148] In the lubricating oil composition of one embodiment of the present invention, the content of the extreme pressure agent (D) is preferably 0.20% by mass or more, more preferably 0.30% by mass or more, and further preferably 0.40% by mass or more, based on the total amount of the lubricating oil composition. In addition, it is preferably 2.0% by mass or less, more preferably 1.7% by mass or less, and further preferably 1.5% by mass or less. The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, it is preferably 0.20% by mass to 2.0% by mass, more preferably 0.30% by mass to 1.7% by mass, and further preferably 0.40% by mass to 1.5% by mass.

[0149] When the content of the extreme pressure agent (D) is at least the above lower limit, a lubricating oil composition having excellent wear resistance is easily obtained. When the content of the extreme pressure agent (D) is at most the above upper limit, sludge generation due to the extreme pressure agent (D) is easily suppressed.

[0150] (Content of phosphorus-based extreme pressure agent (D1))

[0151] In the lubricating oil composition of one embodiment of the present invention, the content of the phosphorus-based extreme pressure agent (D1) is preferably 0.30% by mass or more, more preferably 0.35% by mass or more, and further preferably 0.40% by mass or more, based on the total amount of the lubricating oil composition. In addition, it is preferably 1.5% by mass or less, more preferably 1.2% by mass or less, and further preferably 1.0% by mass or less. The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, it is preferably 0.30% by mass to 1.5% by mass, more preferably 0.35% by mass to 1.2% by mass, and further preferably 0.40% by mass to 1.0% by mass.

[0152] When the content of the phosphorus-based extreme pressure agent (D1) is at least the above lower limit, a lubricating oil composition having excellent wear resistance is easily obtained. When the content of the phosphorus-based extreme pressure agent (D1) is at most the above upper limit, sludge generation caused by the phosphorus-based extreme pressure agent (D1) is easily suppressed.

[0153] From the same viewpoint, the phosphorus atom content derived from the phosphorus-based extreme pressure agent (D1) is preferably 200 to 1400 mass ppm, more preferably 300 to 900 mass ppm, and even more preferably 500 to 700 mass ppm based on the total amount of the lubricating oil composition.

[0154] Here, as the phosphorus-based extreme pressure agent (D1), it is preferred to use a phosphoric acid ester alone or a phosphoric acid ester compound and an amine salt of an acidic phosphoric acid ester in combination.

[0155] When a phosphoric acid ester is used alone as the phosphorus-based extreme pressure agent (D1), the content of the phosphoric acid ester is preferably in the same range as the above-mentioned content of the phosphorus-based extreme pressure agent (D1).

[0156] When a phosphate ester compound and an amine salt of an acidic phosphate ester are used in combination as the phosphorus-based extreme pressure agent (D1), the total content of the phosphate ester compound and the amine salt of an acidic phosphate ester is preferably in the same range as the above content of the phosphorus-based extreme pressure agent (D1).

[0157] In addition, when a phosphoric acid ester compound and an amine salt of an acidic phosphoric acid ester are used in combination as a phosphorus-based extreme pressure agent (D1), the content of the phosphoric acid ester compound is preferably 0.20% by mass or more, more preferably 0.30% by mass or more, and further preferably 0.35% by mass or more, based on the total amount of the lubricating oil composition. In addition, it is preferably 1.4% by mass or less, more preferably 1.2% by mass or less, and further preferably 0.9% by mass or less. The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, it is preferably 0.20% by mass to 1.4% by mass, more preferably 0.30% by mass to 1.2% by mass, and further preferably 0.35% by mass to 0.9% by mass. In addition, the content of the amine salt of the acidic phosphoric acid ester is preferably 0.003% by mass or more, more preferably 0.005% by mass or more, and further preferably 0.007% by mass or more. In addition, it is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, and further preferably 0.03% by mass or less. The upper limit and lower limit of these numerical ranges may be arbitrarily combined. Specifically, it is preferably 0.003% by mass to 0.1% by mass, more preferably 0.005% by mass to 0.05% by mass, and even more preferably 0.007% by mass to 0.03% by mass.

[0158] In addition, when a phosphate compound and an amine salt of an acidic phosphate are used in combination as a phosphorus-based extreme pressure agent (D1), the content ratio of the phosphate compound to the amine salt of the acidic phosphate [(phosphate compound) / (amine salt of an acidic phosphate)] is preferably 50 / 1 or more, more preferably 60 / 1 or more, and further preferably 70 / 1 or more in terms of mass ratio. In addition, it is preferably 100 / 1 or less, more preferably 95 / 1 or less, and further preferably 90 / 1 or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 50 / 1 to 100 / 1, more preferably 60 / 1 to 95 / 1, and further preferably 70 / 1 to 90 / 1.

[0159] (Content of sulfur-phosphorus extreme pressure agent (D2))

[0160] In the lubricating oil composition of one embodiment of the present invention, the content of the sulfur-phosphorus extreme pressure agent (D2) is preferably 0.01% by mass or more, and more preferably 0.02% by mass or more, based on the total amount of the lubricating oil composition. In addition, it is preferably 0.20% by mass or less, more preferably 0.10% by mass or less, and further preferably 0.07% by mass or less. The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, it is preferably 0.01% by mass to 0.20% by mass, more preferably 0.02% by mass to 0.10% by mass, and further preferably 0.02% by mass to 0.07% by mass.

[0161] When the content of the sulfur-phosphorus extreme pressure agent (D2) is at least the above lower limit, a lubricating oil composition having excellent wear resistance can be easily obtained. When the content of the sulfur-phosphorus extreme pressure agent (D2) is at most the above upper limit, sludge generation caused by the sulfur-phosphorus extreme pressure agent (D2) can be easily suppressed.

[0162] From the same viewpoint, the phosphorus atom content derived from the sulfur-phosphorus extreme pressure agent (D2) is preferably 7 to 250 mass ppm, more preferably 15 to 150 mass ppm, and even more preferably 20 to 70 mass ppm, based on the total amount of the lubricating oil composition.

[0163] From the same viewpoint, the sulfur atom content derived from the sulfur-phosphorus extreme pressure agent (D2) is preferably 15 to 500 mass ppm, more preferably 25 to 250 mass ppm, and even more preferably 30 to 150 mass ppm, based on the total amount of the lubricating oil composition.

[0164] (Content ratio of phosphorus-based extreme pressure agent (D1) and sulfur-phosphorus-based extreme pressure agent (D2) [(D1) / (D2)])

[0165] In the lubricating oil composition of one embodiment of the present invention, the content ratio [(D1) / (D2)] of the phosphorus-based extreme pressure agent (D1) to the sulfur-phosphorus-based extreme pressure agent (D2) is preferably 20 / 3 or more, more preferably 30 / 3 or more, and further preferably 40 / 3 or more in terms of mass ratio, from the viewpoint of making it easier to exert the effect of the present invention. In addition, it is preferably 80 / 3 or less, more preferably 70 / 3 or less, and further preferably 60 / 3 or less. The upper limit and lower limit of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 20 / 3 to 80 / 3, more preferably 30 / 3 to 70 / 3, and further preferably 40 / 3 to 60 / 3.

[0166] (Other extreme pressure agents (D'))

[0167] In the lubricating oil composition of one embodiment of the present invention, the extreme pressure agent (D) is not limited to one or more extreme pressure agents selected from phosphorus-based extreme pressure agents (D1) and sulfur-phosphorus-based extreme pressure agents (D2), and other extreme pressure agents (D') may be used.

[0168] Examples of other extreme pressure agents (D′) include organic metal-based extreme pressure agents and sulfur-based extreme pressure agents.

[0169] Examples of the organometallic extreme pressure agent include at least one selected from organic molybdenum compounds such as molybdenum dialkyldithiocarbamate (MoDTC) and molybdenum dialkyldithiophosphate (MoDTP), and organic zinc compounds such as zinc dialkyldithiocarbamate (ZnDTC) and zinc dialkyldithiophosphate (ZnDTP).

[0170] Examples of the sulfur-based extreme pressure agent include one or more selected from sulfurized oils and fats, sulfurized fatty acids, sulfurized esters, sulfurized olefins, monosulfides, polysulfides, dialkyl polysulfides, thiadiazole compounds, alkylthiocarbamoyl compounds, thiocarbamate compounds, thioterpene compounds, and dialkylthiodipropionate compounds.

[0171] However, from the viewpoint of more easily exhibiting the effects of the present invention, it is preferred that the content of the organometallic extreme pressure agent and the sulfur-based extreme pressure agent be small.

[0172] Specifically, the content of the organometallic extreme pressure agent and the sulfur-based extreme pressure agent is preferably less than 0.1% by mass, more preferably less than 0.01% by mass, even more preferably less than 0.001% by mass, based on the total amount of the lubricating oil composition, and it is even more preferred that the organometallic extreme pressure agent and the sulfur-based extreme pressure agent are not contained.

[0173] <Amine antioxidant (E)>

[0174] The lubricating oil composition of one embodiment of the present invention preferably further contains an amine antioxidant (E). By containing the amine antioxidant (E), the sludge inhibition property of the lubricating oil composition can be easily further improved.

[0175] The amine antioxidant (E) that can be used in the lubricating oil composition of one embodiment of the present invention is not particularly limited, but is preferably a compound represented by the following general formula (e1), for example.

[0176] [Chemical formula 7]

[0177]

[0178] [In the above general formula (e1), Ar 1 and Ar 2 Each is independently an aryl group having 6 to 24 carbon atoms selected from the group consisting of phenyl, alkyl-substituted phenyl, aralkyl-substituted phenyl, naphthyl, and alkyl-substituted alkyl-substituted naphthyl.]

[0179] In addition, the amine antioxidant (E) is more preferably one selected from phenyl-α-naphthylamines represented by the following general formula (e1-1) and diphenylamines represented by the following general formula (e1-2).

[0180] [Chemical formula 8]

[0181]

[0182] [In the above general formula (e1-1), R e11 It is a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.]

[0183] [Chemical formula 9]

[0184]

[0185] (In the above general formula (e1-2), R e21 and R e22 Each of them is independently selected from a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, and an aralkyl group having 7 to 18 carbon atoms.

[0186] In the phenyl-α-naphthylamines represented by the above general formula (e1-1), R e11 Preferably, it is a hydrogen atom or an alkyl group having 1 to 12 carbon atoms. e11 Preferably, it is arranged in the opposite position.

[0187] In addition, among the diphenylamines represented by the general formula (e1-2), R e21 and R e22 Each of them is independently selected from a hydrogen atom, an alkyl group having 4 to 12 carbon atoms, and an α,α-dimethylbenzyl group. In addition, it is more preferred that they are all arranged in the para position.

[0188] Specific amine antioxidants are not particularly limited, and examples thereof include dioctyldiphenylamine, phenyl-α-naphthylamine, diphenylamine, dinonyldiphenylamine, monobutylphenylmonoctylphenylamine, p-tert-octylphenyl-1-naphthylamine, and 4,4′-bis(α,α-dimethylbenzyl)diphenylamine.

[0189] In addition, as the amine antioxidant (E), diamines can also be used in addition to the above, and specific examples include N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, and N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine.

[0190] The amine antioxidant (E) may be used alone or in combination of two or more.

[0191] (Content of amine antioxidant (E))

[0192] In the lubricating oil composition of one embodiment of the present invention, the content of the amine antioxidant (E) is preferably 0.02% by mass or more, more preferably 0.05% by mass or more, and further preferably 0.08% by mass or more, based on the total amount of the lubricating oil composition, from the viewpoint of making it easier to exert the effect of the present invention. In addition, it is preferably 0.20% by mass or less, more preferably 0.16% by mass or less, further preferably 0.14% by mass or less, and further preferably 0.12% by mass or less. The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, it is preferably 0.02% by mass to 0.20% by mass, more preferably 0.05% by mass to 0.16% by mass, further preferably 0.08% by mass to 0.14% by mass, and further preferably 0.08% by mass to 0.12% by mass.

[0193] <Content ratio of hindered phenol antioxidant (B) and amine antioxidant (E) [(B) / (E)]>

[0194] In the lubricating oil composition of one embodiment of the present invention, the content ratio [(B) / (E)] of the hindered phenol antioxidant (B) to the amine antioxidant (E) is preferably 6 / 1 or more, more preferably 6.5 / 1 or more, and further preferably 7 / 1 or more in terms of mass ratio, from the viewpoint of making it easier to exert the effect of the present invention. In addition, it is preferably 10 / 1 or less, more preferably 9.5 / 1 or less, and further preferably 9 / 1 or less. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 6 / 1 to 10 / 1, more preferably 6.5 / 1 to 9.5 / 1, and further preferably 7 / 1 to 9 / 1.

[0195] <Sorbitan fatty acid esters (F)>

[0196] The lubricating oil composition of one embodiment of the present invention preferably further contains a sorbitan fatty acid ester (F). By using the sorbitan fatty acid ester (F) and the imide compound (C) together, the ringing phenomenon (hereinafter also referred to as "ringing phenomenon") between the hydraulic cylinder and the sealing material can be suppressed without impairing the effect of the present invention.

[0197] Sorbitan fatty acid ester (F) is an ester compound of sorbitan and fatty acid. Sorbitan fatty acid ester (F) may be a partial ester or a full ester, and is preferably a partial ester from the viewpoint of not impairing the effect of the present invention and being easy to suppress the ringing phenomenon. That is, sorbitan fatty acid ester (F) preferably includes one or more selected from sorbitan fatty acid monoester, sorbitan fatty acid diester, and sorbitan fatty acid triester.

[0198] Specifically, the total content of one or more selected from sorbitan fatty acid monoesters, sorbitan fatty acid diesters, and sorbitan fatty acid triesters is preferably 80% to 100% by mass, more preferably 85% to 100% by mass, further preferably 90% to 100% by mass, and further preferably 95% to 100% by mass, based on the total amount of the sorbitan fatty acid ester (F).

[0199] As the fatty acid constituting the sorbitan fatty acid ester (F), preferably a fatty acid having 14 to 22 carbon atoms, more preferably a fatty acid having 16 to 20 carbon atoms, can be mentioned. The carbon number of the fatty acid also includes the carbon atom of the carboxyl group (-COOH) of the fatty acid. In addition, the fatty acid may be linear or branched, and is preferably linear.

[0200] If the fatty acid is exemplified, linear saturated fatty acids such as palmitic acid and stearic acid, and linear unsaturated fatty acids such as oleic acid and elaidic acid can be cited. They can be used alone or in combination of two or more. Among them, from the viewpoint of not damaging the effect of the present invention and being easy to suppress the ringing phenomenon, it is preferred to use a linear unsaturated fatty acid, and oleic acid is more preferred. That is, the sorbitan fatty acid ester (F) more preferably includes one or more selected from sorbitan monooleate, sorbitan dioleate, and sorbitan trioleate, more preferably includes one or more selected from sorbitan monooleate and sorbitan dioleate, and further preferably includes sorbitan monooleate.

[0201] (Content of sorbitan fatty acid ester (F))

[0202] From the viewpoint of not impairing the effect of the present invention and facilitating the suppression of the ringing phenomenon, the content of the sorbitan fatty acid ester (F) is preferably 0.02% by mass or more, more preferably 0.05% by mass or more, and further preferably 0.08% by mass or more, based on the total amount of the lubricating oil composition. In addition, it is preferably 0.50% by mass or less, more preferably 0.30% by mass or less, further preferably 0.20% by mass or less, and further preferably 0.15% by mass or less. The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, it is preferably 0.02% by mass to 0.50% by mass, more preferably 0.05% by mass to 0.30% by mass, further preferably 0.08% by mass to 0.20% by mass, and further preferably 0.08% by mass to 0.15% by mass.

[0203] <Content ratio of imide compound (C) and sorbitan fatty acid ester (F) [(C) / (F)]>

[0204] In the lubricating oil composition of one embodiment of the present invention, from the viewpoint of not impairing the effect of the present invention and facilitating the suppression of the cylinder ringing phenomenon, the content ratio [(C) / (F)] of the imide compound (C) and the sorbitan fatty acid ester (F) is preferably 1 / 3 or more, more preferably 1 / 2 or more, and further preferably 2 / 3 or more in terms of mass ratio. In addition, it is preferably 7 / 2 or less, more preferably 6 / 2 or less, and further preferably 5 / 2 or less. The upper and lower limits of these numerical ranges may be arbitrarily combined. Specifically, it is preferably 1 / 3 to 7 / 2, more preferably 1 / 2 to 6 / 2, and further preferably 2 / 3 to 5 / 2.

[0205] <Other additives>

[0206] The lubricating oil composition of one embodiment of the present invention may contain lubricating oil additives other than the component (B), the component (C), and the component (D) within a range that does not impair the effects of the present invention.

[0207] Examples of the lubricating oil additive include a viscosity index improver, a pour point depressant, a rust inhibitor, a metal inactivator, a defoaming agent, and an antioxidant other than components (B) and (E).

[0208] These lubricating oil additives may be used alone or in combination of two or more.

[0209] In this specification, in consideration of handling properties and solubility in the base oil (A), additives such as a viscosity index improver and a defoaming agent may be in the form of a solution diluted and dissolved in a part of the base oil (A). In this case, in this specification, the content of additives such as a defoaming agent and a viscosity index improver described later refers to the content calculated as the effective component (calculated as the resin component) excluding the diluent oil.

[0210] (Viscosity Index Improver)

[0211] Examples of the viscosity index improver include polymers such as non-dispersed polymethacrylate, dispersed polymethacrylate, olefin copolymers (e.g., ethylene-propylene copolymers), dispersed olefin copolymers, and styrene copolymers (e.g., styrene-diene copolymers, styrene-isoprene copolymers).

[0212] When the lubricating oil composition of one embodiment of the present invention contains a viscosity index improver, the content of the viscosity index improver in terms of resin component is preferably 0.01 to 10% by mass, more preferably 0.02 to 7% by mass, and even more preferably 0.03 to 5% by mass, based on the total amount of the lubricating oil composition.

[0213] (Pour Point Depressant)

[0214] Examples of the pour point depressant include polymethacrylates having a mass average molecular weight of about 50,000 to 150,000. When the lubricating oil composition of one embodiment of the present invention contains a pour point depressant, the content of the pour point depressant is preferably 0.01 to 5% by mass, more preferably 0.02 to 2% by mass, based on the total amount of the lubricating oil composition.

[0215] Examples of the rust inhibitor include metal sulfonates, alkylbenzene sulfonates, dinonylnaphthalene sulfonates, organic phosphites, organic phosphates, organic sulfonic acid metal salts, organic phosphate metal salts, alkenyl succinic acid esters, and alkenyl succinic acid polyol esters.

[0216] When the lubricating oil composition of one embodiment of the present invention contains a rust inhibitor, the content of the rust inhibitor is preferably 0.01 to 10.0% by mass, more preferably 0.03 to 5.0% by mass, based on the total amount of the lubricating oil composition.

[0217] (Metal Inerting Agent)

[0218] Examples of the metal inactivating agent include benzotriazole compounds, tolyltriazole compounds, thiadiazole compounds, imidazole compounds, and pyrimidine compounds.

[0219] When the lubricating oil composition of one embodiment of the present invention contains a metal inactivator, the content of the metal inactivator is preferably 0.01 to 5.0% by mass, more preferably 0.03 to 3.0% by mass, based on the total amount of the lubricating oil composition.

[0220] (Defoaming agent)

[0221] Examples of the defoaming agent include silicone-based defoaming agents, fluorine-based defoaming agents such as fluorine silicone oil and fluoroalkyl ether, and polyacrylate-based defoaming agents.

[0222] When the lubricating oil composition of one embodiment of the present invention contains a defoaming agent, the content of the defoaming agent in terms of resin component is preferably 0.0001 to 0.20 mass %, more preferably 0.0005 to 0.10 mass %, based on the total amount of the lubricating oil composition.

[0223] (Antioxidants other than ingredients (B) and (E))

[0224] Examples of antioxidants other than components (B) and (E) include phenolic antioxidants other than component (B), metal-based antioxidants, and sulfur-based antioxidants.

[0225] Here, in the lubricating oil composition of one embodiment of the present invention, from the viewpoint of obtaining a lubricating oil composition with more excellent sludge inhibition, the content of DBPC in the phenolic antioxidant other than component (B) is preferably small. From the viewpoint of obtaining a lubricating oil composition with more excellent sludge inhibition, the content of DBPC is preferably less than 0.60% by mass, more preferably less than 0.10% by mass, further preferably less than 0.01% by mass, based on the total amount of the lubricating oil composition, and it is further preferred that DBPC is not contained.

[0226] In addition, from the viewpoint of more easily exhibiting the effects of the present invention, the content of the metal-based antioxidant and the sulfur-based antioxidant is preferably small.

[0227] Specifically, the content of the metal-based antioxidant and the sulfur-based antioxidant is preferably less than 0.1% by mass, more preferably less than 0.01% by mass, even more preferably less than 0.001% by mass, based on the total amount of the lubricating oil composition, and it is even more preferred that the metal-based antioxidant and the sulfur-based antioxidant are not contained.

[0228] [Various physical properties of lubricating oil composition]

[0229] <40℃ Kinematic Viscosity>

[0230] The 40° C. kinematic viscosity of the lubricating oil composition of one embodiment of the present invention is preferably 10 mm 2 / s or more, more preferably 15mm 2 / s or more, more preferably 20mm 2 / s or more. In addition, preferably 150mm 2 / s or less, more preferably 100mm 2 / s or less, more preferably 80mm 2 / s or less. The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, 10 mm is preferred. 2 / s~150mm 2 / s, preferably 15 mm 2 / s~100mm 2 / s, more preferably 20mm 2 / s~80mm 2 / s.

[0231] The kinematic viscosity of the lubricating oil composition at 40°C is 10 mm 2 / s or more, a lubricating oil composition having a high flash point and excellent lubrication performance can be easily obtained.

[0232] In addition, the kinematic viscosity of the base oil (A) at 40°C is 150 mm 2When the viscosity is below 0.1 / s, the viscous resistance at low temperature will not become so large, making it easy for the machine to operate well.

[0233] <Viscosity Index>

[0234] The viscosity index of the lubricating oil composition according to one embodiment of the present invention is preferably 80 or more, more preferably 90 or more, even more preferably 100 or more, and even more preferably 110 or more.

[0235] <Sludge inhibition>

[0236] In the lubricating oil composition of one embodiment of the present invention, the micropore value calculated by measuring in accordance with SAE-ARP-785-63 after the high-pressure piston pump test described in the examples described above is carried out in accordance with JCMAS P045 for 2000 hours is preferably 10 mg / 100 mL or less, more preferably 5.0 mg / 100 mL or less, further preferably 4.0 mg / mL or less, and further preferably 3.5 mg / 100 mL.

[0237] The lubricating oil composition of the present invention has an extremely low micropore value after a high-pressure piston pump test is performed for a long period of 2,000 hours, and is extremely excellent in sludge inhibition.

[0238] <Abrasion resistance>

[0239] (Abrasion resistance)

[0240] In the lubricating oil composition of one embodiment of the present invention, the grade value measured by the FZG scratch test described in the examples described below according to ASTM D5182-97 (2014) after the high-pressure piston pump test described in the examples described below for 2000 hours according to JCMAS P045 is preferably 10 or higher.

[0241] The lubricating oil composition of the present invention has a high grade value in the FZG scratch test after a high-pressure piston pump test for a long period of 2000 hours, and is extremely excellent in scratch resistance.

[0242] (Bite resistance)

[0243] In the lubricating oil composition of one embodiment of the present invention, the seizure load measured by the SRV (vibration friction wear) test described in the examples described below according to ASTM D7421 after the high-pressure piston pump test described in the examples described below for 2000 hours according to JCMAS P045 is preferably 1500 N or more, more preferably 1600 N or more.

[0244] The lubricating oil composition of the present invention has a high seizure load in a SRV (suspension vibration wear) test after a high-pressure piston pump test for a long period of 2000 hours, and is extremely excellent in seizure resistance.

[0245] [Method for producing lubricating oil composition]

[0246] The method for producing the lubricating oil composition of the present invention is not particularly limited.

[0247] For example, a method for producing a lubricating oil composition according to one embodiment of the present invention includes the step of mixing a base oil (A), a hindered phenol-based antioxidant (B), one or more imide compounds (C) selected from a monoimide compound (C1) and a bisimide compound (C2), and an extreme pressure agent (D), wherein the hindered phenol-based antioxidant (B) is 2,6-di-tert-butylphenol, the monoimide compound (C1) is one or more selected from alkenyl succinic acid monoimide compounds and alkyl succinic acid monoimide compounds, and the bisimide compound (C2) is one or more selected from alkenyl succinic acid bisimide compounds and alkyl succinic acid bisimide compounds.

[0248] There are no particular restrictions on the method for mixing the above-mentioned components, and examples thereof include a method having a step of blending component (B), component (C), and component (D) in base oil (A). Component (B), component (C), and component (D) may be blended into base oil (A) at the same time, or may be blended separately. The same applies to other components other than component (B), component (C), and component (D). It should be noted that each component may be blended after being added with diluent oil or the like to form a solution (dispersion). It is preferred that each component is blended and then stirred and uniformly dispersed by a known method.

[0249] [Application of lubricating oil composition]

[0250] The lubricating oil composition of the present invention has excellent sludge suppression and wear resistance even after long-term use under high pressure conditions. Therefore, the lubricating oil composition of the present invention can be used for one or more hydraulic equipment selected from construction machinery, general industrial machinery, and generators. Preferably, among these hydraulic equipment, the lubricating oil composition can be suitably used for hydraulic equipment having an operating pressure of 30 MPa or more.

[0251] Therefore, according to the present invention, the following method of use can be provided.

[0252] ・A method of using the lubricating oil composition of the present invention in hydraulic equipment.

[0253] A method of using the lubricating oil composition of the present invention in one or more hydraulic equipment selected from the group consisting of construction machinery, general industrial machinery, and generators.

[0254] A method of using the lubricating oil composition of the present invention in a hydraulic device having an operating pressure of 30 MPa or more and selected from the group consisting of construction machinery, general industrial machinery, and generators.

[0255] It should be noted that the above-mentioned construction machinery includes, for example, cranes such as mobile cranes, fixed cranes, and frame cranes; excavation machinery such as hydraulic excavators, small excavators, and wheeled hydraulic excavators; land preparation machinery such as bulldozers; loading machinery such as wheel loaders; transport machinery such as rough terrain transporters; compaction machinery such as vibrating rollers; dismantling machinery such as crushers; foundation machinery such as pile drivers and digging machines; concrete / asphalt machinery such as concrete pump trucks; aerial work vehicles, paving machinery, shield machines, tunnel boring machines, snowplows, etc.

[0256] Examples of the general industrial machines include vehicles, machine tools, gear devices, transport devices, air conditioners, and mining equipment.

[0257] [One embodiment of the present invention provided]

[0258] In one embodiment of the present invention, the following [1] to [8] are provided.

[0259] [1] A lubricating oil composition comprising:

[0260] A base oil (A), a hindered phenol antioxidant (B), one or more imide compounds (C) selected from a monoimide compound (C1) and a bisimide compound (C2), and an extreme pressure agent (D), wherein the hindered phenol antioxidant (B) is 2,6-di-tert-butylphenol, the monoimide compound (C1) is one or more selected from alkenyl succinic acid monoimide compounds and alkyl succinic acid monoimide compounds, and the bisimide compound (C2) is one or more selected from alkenyl succinic acid bisimide compounds and alkyl succinic acid bisimide compounds.

[0261] [2] The lubricating oil composition according to [1], further comprising an amine antioxidant (E).

[0262] [3] The lubricating oil composition according to [2], wherein the content ratio of the hindered phenol antioxidant (B) to the amine antioxidant (E) [(B) / (E)] is 6 / 1 to 10 / 1 by mass ratio.

[0263] [4] The lubricating oil composition according to any one of [1] to [3], wherein the content ratio of the monoimide compound (C1) to the bisimide compound (C2) [(C1) / (C2)] is greater than 0 and less than 2 / 1 in terms of mass ratio.

[0264] [5] The lubricating oil composition according to any one of [1] to [4], wherein the content of 2,6-di-tert-butyl-p-cresol is less than 0.60 mass % based on the total amount of the lubricating oil composition.

[0265] [6] The lubricating oil composition according to any one of [1] to [5], wherein the extreme pressure agent (D) comprises at least one selected from a phosphorus-based extreme pressure agent (D1) and a sulfur-phosphorus-based extreme pressure agent (D2).

[0266] [7] The lubricating oil composition according to any one of [1] to [6], further comprising a sorbitan fatty acid ester (F).

[0267] [8] The lubricating oil composition according to any one of [1] to [7], which is used as a hydraulic oil. Example

[0268] The present invention will be specifically described with reference to the following examples, but the present invention is not limited to the following examples.

[0269] [Measurement methods of various physical properties]

[0270] The raw materials used in the examples and comparative examples and the properties of the lubricating oil compositions of the examples and comparative examples were measured in the following manner.

[0271] (1) Kinematic viscosity and viscosity index

[0272] The measurement and calculation were performed in accordance with JIS K2283:2000.

[0273] (2) Base number

[0274] The measurement was conducted by a perchloric acid method in accordance with JIS K-2501-9:2003.

[0275] [Examples 1 to 2, Comparative Examples 1 to 3]

[0276] The base oils and various additives shown below were fully mixed in the blending amounts (mass %) shown in Table 1 to prepare lubricating oil compositions.

[0277] The details of the base oils and various additives used in Examples 1 and 2 and Comparative Examples 1 to 3 are shown below.

[0278] <Base oil (A)>

[0279] The mixed base oil of mineral oil belonging to category 2 and mineral oil belonging to category 3 in API classification, that is, the base oil used in Example 1 and Comparative Examples 1 and 2, had a kinematic viscosity of 46 mm at 40°C. 2 / s, and the viscosity index was 120. In addition, the 40°C kinematic viscosity of the base oil used in Example 2 and Comparative Example 3 was 68 mm 2 / s, viscosity index is 150.

[0280] In addition, the 40 degreeC kinematic viscosity and the viscosity index were measured and calculated according to JIS K2283:2000.

[0281] <Hindered phenol antioxidant (B)>

[0282] As the hindered phenol antioxidant (B), 2,6-di-tert-butylphenol (DTBP) was used.

[0283] <Phenolic antioxidants (B')>

[0284] As a phenolic antioxidant (B′) of a comparative example, 2,6-di-tert-butyl-p-cresol (DBPC) was used.

[0285] <Imide compound (C)>

[0286] As the monoimide compound (C1), a polybutenyl succinic acid monoimide compound having a polybutenyl mass average molecular weight (Mw) of 6300, a nitrogen atom content of 1.75% by mass, and a base value of 40.0 mgKOH / g was used.

[0287] As the bisimide compound (C2), a polybutenyl succinic acid bisimide compound having a polybutenyl mass average molecular weight (Mw) of 1000, a nitrogen atom content of 1.15% by mass, and a base value of 19.5 mgKOH / g was used.

[0288] The mass average molecular weight of the polybutenyl group is a value evaluated as a mass average molecular weight (Mw) calculated in terms of standard polystyrene by measuring the mass average molecular weight (Mw) of polybutene, which is a raw material of the polybutenyl group, under the following conditions.

[0289] ・SEC device: HLC-8220GPC manufactured by Tosoh

[0290] ・Column: TSKguardcolumn HXL-H made by Tosoh + TSKgel GMH-XL 2 pieces + G2000H-XL 1 piece

[0291] ・Solvent: Tetrahydrofuran (special grade without stabilizer, manufactured by Wako Pure Chemical Industries, Ltd.)

[0292] ・Detector: Differential refractive index (RI) detector, UV detector

[0293] ・Concentration: 0.1w / v%, injection volume: 100μL

[0294] ・Flow rate: 1.0mL / min

[0295] ・Column temperature: 40℃

[0296] ・Standard reagent for calibration curve: TSK standard polystyrene manufactured by Tosoh

[0297] ・Analysis software: GPC-8020model2.

[0298] <Extreme pressure agent (D)>

[0299] (Phosphorus-based extreme pressure agent (D1))

[0300] Phosphate compound 1: a mixture of tert-butylphenyl diphenyl phosphate and di-tert-butylphenyl monophenyl phosphate

[0301] Phosphate compound 2: Tritolyl phosphate

[0302] Amine salt of acidic phosphate ester: VANLUBE 672 manufactured by Vanderbilt Chemicals

[0303] (Sulfur-phosphorus extreme pressure agent (D2))

[0304] A compound represented by the following formula (d2-1) (IRGALUBE 353 manufactured by BASF) was used.

[0305] [Chemical formula 10]

[0306]

[0307] The compound represented by the above formula (d2-1) is a compound wherein in the above general formula (d2), R d71 -CH2CH(CH3)-, R d72 and R d73 It is an isobutyl compound.

[0308] <Amine antioxidant (E)>

[0309] Monobutylphenyl monooctylphenylamine (manufactured by BASF, IRGANOX L-57) was used.

[0310] Monobutylphenyl monooctylphenylamine is in the above general formula (e1-2), R e21 and R e22 A compound in which one of the groups is butyl and the other is octyl.

[0311] <Sorbitan fatty acid esters (F)>

[0312] Sorbitan monooleate.

[0313] <Other additives>

[0314] ・Metal inert agent: Benzotriazole

[0315] ・Defoaming agent: Silicone defoaming agent

[0316] ・Viscosity index improver: Polymethacrylate with a mass average molecular weight (Mw) of 40,000

[0317] ・Pour point depressant: Polymethacrylate with a mass average molecular weight (Mw) of 69,000.

[0318] In Example 1 and Comparative Example 3, 0.02 wt % of a metal inactivator, 0.10 wt % of a silicone defoamer in terms of resin component, 10 wt % of a viscosity index improver, and 0.30 wt % of a pour point depressant were added.

[0319] In Example 2, Comparative Example 1, and Comparative Example 2, 0.02 wt % of a metal inactivator, 0.10 wt % of a silicone defoamer in terms of resin component, 2.0 wt % of a viscosity index improver, and 0.30 wt % of a pour point depressant were added.

[0320] [evaluate]

[0321] The lubricating oil compositions of Examples 1 to 2 and Comparative Examples 1 to 3 were evaluated for oxidation degradation and reduction in wear resistance when used for a long period of time under high pressure.

[0322] First, the lubricating oil compositions of Examples 1 to 2 and Comparative Examples 1 to 3 were subjected to a high-pressure piston pump test for 2000 hours in accordance with JCMAS P045 using a high-pressure piston pump test apparatus (pump: BOSCH-REXROTH A2F10) under the conditions of a pump pressure of 35 MPa, a reagent oil temperature of 80° C., and an air blowing amount of 1.0 L / h, to obtain reagent oils of lubricating oil compositions that are expected to be used under high pressure for a long period of time.

[0323] Furthermore, the reagent oil was subjected to evaluation of the micropore value, FZG scratch test, and SRV (scratch vibration) test.

[0324] <Evaluation of micropore value>

[0325] According to SAE-ARP-785-63, the precipitate in 300 mL of the reagent oil was collected by filtration, and the mass of the precipitate per 100 mL of the reagent oil was calculated as the "micropore value".

[0326] The lower the "micropore value", the less the amount of sludge generated, and it can be said that the lubricating oil composition has better sludge suppressing properties.

[0327] In this example, a case where the pore value was 10 mg / 100 mL or less was considered acceptable.

[0328] <FZG scratch test>

[0329] According to ASTM D5182-97 (2014), using type A gears, under the conditions of reagent oil temperature of 90°C, speed of 1450 rpm, and operation time of 15 minutes, the load is increased step by step as specified to obtain the load level when galling occurs. The higher the value of this level, the better the galling resistance.

[0330] In this embodiment, a level of 10 or higher is regarded as a pass.

[0331] <SRV (Vibration Friction Wear) Test>

[0332] The seizure load (N) was measured according to ASTM D7421. The seizure load is measured by increasing the load by 100N at a time under the friction conditions of 120°C, 50Hz, and 2.0mm amplitude, and measuring the load (N) at which seizure occurs and the friction coefficient increases greatly. The larger the seizure load value, the better the seizure resistance.

[0333] In the present example, the case where the seizure load was 1500 N or more was considered as acceptable.

[0334] The results are shown in Table 1.

[0335] [Table 1]

[0336] .

[0337] From Table 1, we can know the following.

[0338] It is found that the lubricating oil compositions of Examples 1 and 2 have small micropore values ​​and excellent sludge suppression properties. In addition, they are excellent in scuffing resistance and seizure resistance, and therefore, are also excellent in wear resistance.

[0339] In contrast, it is found that when the hindered phenol antioxidant (B) and the monoimide compound (C1) are not contained, as in the lubricating oil compositions of Comparative Examples 1 and 2, the micropore value becomes large and the sludge inhibition property is poor. In addition, it is found that either the scratch resistance or the seizure resistance is poor and the wear resistance is poor.

[0340] In addition, the lubricating oil composition of Comparative Example 3, which had the same composition as Example 1 except that the monoimide compound (C1) was not contained and the content of the bisimide compound (C2) was 0.20 mass %, showed that although the micropore value was small and the sludge inhibition property was excellent, the seizure resistance and wear resistance were poor.

Claims

1. A lubricating oil composition for use as a hydraulic oil, the lubricating oil composition comprising: Base oil (A), Hindered phenol antioxidant (B), an imide compound (C) comprising a monoimide compound (C1) and a bisimide compound (C2), and an extreme pressure agent (D), The content of the base oil (A) is 80.0% to 98.0% by mass based on the total amount of the lubricating oil composition. The content of the hindered phenol antioxidant (B) is 0.40 mass % to 2.0 mass % based on the total amount of the lubricating oil composition. The hindered phenol antioxidant (B) is 2,6-di-tert-butylphenol, The monoimide compound (C1) is at least one selected from alkenyl succinic acid monoimide compounds and alkyl succinic acid monoimide compounds, The bisimide compound (C2) is one or more selected from alkenyl succinic acid bisimide compounds and alkyl succinic acid bisimide compounds, The total content of the monoimide compound (C1) and the bisimide compound (C2) is 0.13% by mass to 0.50% by mass based on the total amount of the lubricating oil composition. The content ratio (C1) / (C2) of the monoimide compound (C1) to the bisimide compound (C2) is 1 / 3 to 3 / 2 in terms of mass ratio, The content of the extreme pressure agent (D) is 0.20% to 2.0% by mass based on the total amount of the lubricating oil composition.

2. The lubricating oil composition according to claim 1, wherein It also contains an amine antioxidant (E).

3. The lubricating oil composition according to claim 2, wherein: The content ratio (B) / (E) of the hindered phenol antioxidant (B) to the amine antioxidant (E) is 6 / 1 to 10 / 1 in terms of mass ratio.

4. The lubricating oil composition according to any one of claims 1 to 3, wherein The content of 2,6-di-tert-butyl-p-cresol is less than 0.60 mass % based on the total amount of the lubricating oil composition.

5. The lubricating oil composition according to any one of claims 1 to 3, wherein The extreme pressure agent (D) includes at least one selected from phosphorus-based extreme pressure agents (D1) and sulfur-phosphorus-based extreme pressure agents (D2).

6. The lubricating oil composition according to any one of claims 1 to 3, wherein It also contains sorbitan fatty acid esters (F).

7. The lubricating oil composition according to any one of claims 1 to 3, wherein The base oil (A) is at least one selected from mineral oils and synthetic oils.

8. The lubricating oil composition according to any one of claims 1 to 3, wherein The kinematic viscosity of the base oil (A) at 40°C is 10 mm 2 / s~150mm 2 / s.

9. The lubricating oil composition according to any one of claims 1 to 3, wherein The kinematic viscosity of the base oil (A) at 40°C is 15 mm 2 / s~100mm 2 / s.

10. The lubricating oil composition according to any one of claims 1 to 3, wherein The kinematic viscosity of the base oil (A) at 40°C is 20 mm 2 / s~80mm 2 / s.

11. The lubricating oil composition according to any one of claims 1 to 3, wherein The viscosity index of the base oil (A) is 80 or more.

12. The lubricating oil composition according to any one of claims 1 to 3, wherein The viscosity index of the base oil (A) is 90 or more.

13. The lubricating oil composition according to any one of claims 1 to 3, wherein The base oil (A) has a viscosity index of 100 or more.

14. The lubricating oil composition according to any one of claims 1 to 3, wherein The base oil (A) has a viscosity index of 110 or more.

15. The lubricating oil composition according to any one of claims 1 to 3, wherein The content of the base oil (A) is 83.0% by mass to 97.0% by mass based on the total amount of the lubricating oil composition.

16. The lubricating oil composition according to any one of claims 1 to 3, wherein The content of the base oil (A) is 85.0% by mass to 96.0% by mass based on the total amount of the lubricating oil composition.

17. The lubricating oil composition according to any one of claims 1 to 3, wherein The content of the hindered phenol antioxidant (B) is 0.50% by mass to 1.5% by mass based on the total amount of the lubricating oil composition.

18. The lubricating oil composition according to any one of claims 1 to 3, wherein The content of the hindered phenol antioxidant (B) is 0.60% by mass to 1.2% by mass based on the total amount of the lubricating oil composition.

19. The lubricating oil composition according to any one of claims 1 to 3, wherein The content of the hindered phenol antioxidant (B) is 0.65% by mass to 1.0% by mass based on the total amount of the lubricating oil composition.

20. The lubricating oil composition according to any one of claims 1 to 3, wherein The content of the hindered phenol antioxidant (B) is 0.70% by mass to 0.90% by mass based on the total amount of the lubricating oil composition.

21. The lubricating oil composition according to any one of claims 1 to 3, wherein The monoimide compound (C1) is a compound represented by the following general formula (c1): In the above general formula (c1), R c11 is alkenyl or alkyl, R c12 is an alkylene group having 1 to 6 carbon atoms, n1 is an integer of 1 to 20, and when n1 is 2 or more, a plurality of R c12 It can be the same or different.

22. The lubricating oil composition according to claim 21, wherein In the above general formula (c1), R c11 The mass average molecular weight is 500-10000.

23. The lubricating oil composition according to claim 21, wherein In the above general formula (c1), R c11 The mass average molecular weight is 4000-8000.

24. The lubricating oil composition according to claim 21, wherein In the above general formula (c1), R c11 It is a polybutene group.

25. The lubricating oil composition according to any one of claims 1 to 3, wherein The aforementioned bisimide compound (C2) is a compound represented by the following general formula (c2): In the above general formula (c2), R c21 and R c24 are each independently alkenyl or alkyl, R c22 and R c23 Each independently represents an alkylene group having 1 to 6 carbon atoms, n2 represents an integer from 0 to 20, and when n2 is 2 or more, the plurality of R c22 It can be the same or different.

26. The lubricating oil composition according to claim 25, wherein In the above general formula (c2), R c21 and R c24 The mass average molecular weight is 500-10000.

27. The lubricating oil composition according to claim 25, wherein In the above general formula (c2), R c21 and R c24 The mass average molecular weight is 4000-8000.

28. The lubricating oil composition according to claim 25, wherein In the above general formula (c2), R c21 and R c24 It is a polybutene group.

29. The lubricating oil composition according to any one of claims 1 to 3, wherein The total content of the monoimide compound (C1) and the bisimide compound (C2) is 0.13% by mass to 0.40% by mass based on the total amount of the lubricating oil composition.

30. The lubricating oil composition according to any one of claims 1 to 3, wherein The total content of the monoimide compound (C1) and the bisimide compound (C2) is 0.15% by mass to 0.35% by mass based on the total amount of the lubricating oil composition.

31. The lubricating oil composition according to any one of claims 1 to 3, wherein The total content of the monoimide compound (C1) and the bisimide compound (C2) is 0.17% by mass to 0.30% by mass based on the total amount of the lubricating oil composition.

32. The lubricating oil composition according to any one of claims 1 to 3, wherein The content ratio (C1) / (C2) of the monoimide compound (C1) and the bisimide compound (C2) is 2 / 3 to 3 / 2 in terms of mass ratio.

33. The lubricating oil composition according to claim 5, wherein: The content of one or more selected from the group consisting of the phosphorus-based extreme pressure agent (D1) and the sulfur-phosphorus-based extreme pressure agent (D2) is 80% by mass to 100% by mass based on the total amount of the extreme pressure agent (D).

34. The lubricating oil composition according to claim 5, wherein: The phosphorus-based extreme pressure agent (D1) is selected from one or more of the following: a phosphate ester represented by the general formula (d1-1), an acidic phosphate ester represented by the general formula (d1-2), a phosphite ester represented by the general formula (d1-3), and a hydrogen phosphite ester represented by the general formulas (d1-4) and (d1-5), In the general formulas (d1-1) to (d1-5), R d11 , R d21 , R d31 , R d41 , and R d51 Each independently represents a hydrocarbon group having 1 to 30 carbon atoms.

35. The lubricating oil composition according to claim 34, wherein The aforementioned hydrocarbon group is selected from an alkyl group, an alkenyl group, an aryl group or an arylalkyl group.

36. The lubricating oil composition according to claim 34, wherein The aforementioned phosphate ester is a compound represented by the following general formula (d1-1a), In the above general formula (d1-1a), R d71 ~R d73 Each of p1 to p3 is independently an alkyl group having 1 to 12 carbon atoms, and each of p1 to p3 is independently an integer of 0 to 5.

37. The lubricating oil composition according to claim 5, wherein: The aforementioned sulfur-phosphorus extreme pressure agent (D2) is selected from one or more of monothiophosphates, dithiophosphates, trithiophosphates, amine salts of monothiophosphates, amine salts of dithiophosphates, monothiophosphites, dithiophosphites and trithiophosphites.

38. The lubricating oil composition according to claim 37, wherein The aforementioned phosphorodithioate is a phosphorodithioate having a carboxyl group at the terminal.

39. The lubricating oil composition according to claim 38, wherein The aforementioned dithiophosphate having a carboxyl group at the terminal is a compound represented by the following general formula (d2): In the above general formula (d2), R d71 represents a linear or branched alkylene group having 1 to 8 carbon atoms, R d72 and R d73 Each independently represents a hydrocarbon group having 3 to 20 carbon atoms.

40. The lubricating oil composition according to claim 39, wherein In the above general formula (d2), R d71 It is -CH2CH2-, -CH2CH(CH3)-, -CH2CH(CH2CH3)-, CH2CH(CH3)CH2-, or -CH2CH(CH2CH2CH3)-.

41. The lubricating oil composition according to claim 39, wherein In the above general formula (d2), R d72 and R d73 is propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, isopentyl, hexyl, 2-ethylbutyl, 1-methylpentyl, 1,3-dimethylbutyl, or 2-ethylhexyl.

42. The lubricating oil composition according to any one of claims 1 to 3, wherein The content of the extreme pressure agent (D) is 0.30% by mass to 1.7% by mass based on the total amount of the lubricating oil composition.

43. The lubricating oil composition according to any one of claims 1 to 3, wherein The content of the extreme pressure agent (D) is 0.40% by mass to 1.5% by mass based on the total amount of the lubricating oil composition.

44. The lubricating oil composition according to claim 5, wherein: The content of the phosphorus-based extreme pressure agent (D1) is 0.30% by mass to 1.5% by mass based on the total amount of the lubricating oil composition.

45. The lubricating oil composition according to claim 5, wherein: The content of the phosphorus-based extreme pressure agent (D1) is 0.35% by mass to 1.2% by mass based on the total amount of the lubricating oil composition.

46. ​​The lubricating oil composition according to claim 5, wherein: The content of the phosphorus-based extreme pressure agent (D1) is 0.40% by mass to 1.0% by mass based on the total amount of the lubricating oil composition.

47. The lubricating oil composition according to claim 5, wherein: The content of the sulfur-phosphorus extreme pressure agent (D2) is 0.01% to 0.20% by mass based on the total amount of the lubricating oil composition.

48. The lubricating oil composition according to claim 5, wherein: The content of the sulfur-phosphorus extreme pressure agent (D2) is 0.02% to 0.10% by mass based on the total amount of the lubricating oil composition.

49. The lubricating oil composition according to claim 5, wherein: The content of the sulfur-phosphorus extreme pressure agent (D2) is 0.02% to 0.07% by mass based on the total amount of the lubricating oil composition.

50. The lubricating oil composition according to claim 5, wherein: The content ratio (D1) / (D2) of the phosphorus-based extreme pressure agent (D1) and the sulfur-phosphorus-based extreme pressure agent (D2) is 20 / 3 to 80 / 3 in terms of mass ratio.

51. The lubricating oil composition according to claim 5, wherein: The content ratio (D1) / (D2) of the phosphorus-based extreme pressure agent (D1) and the sulfur-phosphorus-based extreme pressure agent (D2) is 30 / 3 to 70 / 3 in terms of mass ratio.

52. The lubricating oil composition according to claim 5, wherein: The content ratio (D1) / (D2) of the phosphorus-based extreme pressure agent (D1) and the sulfur-phosphorus-based extreme pressure agent (D2) is 40 / 3 to 60 / 3 in terms of mass ratio.

53. The lubricating oil composition according to claim 2 or 3, wherein: The amine antioxidant (E) is a compound represented by the following general formula (e1): Ar 1 -NH-Ar 2 (e1) In the above general formula (e1), Ar 1 and Ar 2 Each is independently an aryl group having 6 to 24 carbon atoms selected from the group consisting of phenyl, alkyl-substituted phenyl, aralkyl-substituted phenyl, naphthyl, and alkyl-substituted alkyl-substituted naphthyl.

54. The lubricating oil composition according to claim 2 or 3, wherein: The amine antioxidant (E) is selected from the group consisting of phenyl-α-naphthylamines represented by the following general formula (e1-1) and diphenylamines represented by the following general formula (e1-2). In the above general formula (e1-1), R e11 is a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, In the above general formula (e1-2), R e21 and R e22 Each is independently selected from a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, and an aralkyl group having 7 to 18 carbon atoms.

55. The lubricating oil composition according to claim 2 or 3, wherein: The content of the amine antioxidant (E) is 0.02% by mass to 0.20% by mass based on the total amount of the lubricating oil composition.

56. The lubricating oil composition according to claim 2 or 3, wherein: The content of the amine antioxidant (E) is 0.05% by mass to 0.16% by mass based on the total amount of the lubricating oil composition.

57. The lubricating oil composition according to claim 2 or 3, wherein: The content of the amine antioxidant (E) is 0.08% by mass to 0.14% by mass based on the total amount of the lubricating oil composition.

58. The lubricating oil composition according to claim 2 or 3, wherein: The content of the amine antioxidant (E) is 0.08% by mass to 0.12% by mass based on the total amount of the lubricating oil composition.

59. The lubricating oil composition according to claim 6, wherein: The content of the sorbitan fatty acid ester (F) is 0.02% by mass to 0.50% by mass based on the total amount of the lubricating oil composition.

60. The lubricating oil composition according to claim 6, wherein: The content of the sorbitan fatty acid ester (F) is 0.05% by mass to 0.30% by mass based on the total amount of the lubricating oil composition.

61. The lubricating oil composition according to claim 6, wherein: The content of the sorbitan fatty acid ester (F) is 0.08% by mass to 0.20% by mass based on the total amount of the lubricating oil composition.

62. The lubricating oil composition according to claim 6, wherein: The content of the sorbitan fatty acid ester (F) is 0.08% by mass to 0.15% by mass based on the total amount of the lubricating oil composition.

63. The lubricating oil composition according to any one of claims 1 to 3, wherein The composition further contains one or more selected from a viscosity index improver, a pour point depressant, a rust inhibitor, a metal inertizing agent, a defoaming agent, and an antioxidant other than components (B) and (E).

64. The lubricating oil composition according to any one of claims 1 to 3, which has a kinematic viscosity of 10 mm at 40°C. 2 / s~150mm 2 / s.

65. The lubricating oil composition according to any one of claims 1 to 3, which has a kinematic viscosity of 15 mm at 40°C. 2 / s~100mm 2 / s.

66. The lubricating oil composition according to any one of claims 1 to 3, which has a kinematic viscosity of 20 mm at 40°C. 2 / s~80mm 2 / s.

67. The lubricating oil composition according to any one of claims 1 to 3, which has a viscosity index of 80 or more.

68. The lubricating oil composition according to any one of claims 1 to 3, which has a viscosity index of 90 or more.

69. The lubricating oil composition according to any one of claims 1 to 3, which has a viscosity index of 100 or more.

70. The lubricating oil composition according to any one of claims 1 to 3, which has a viscosity index of 110 or more.

71. The lubricating oil composition according to any one of claims 1 to 3, wherein The micropore value of the reagent oil obtained by the following high-pressure piston pump test is 10 mg / 100 mL or less as measured by the following micropore value evaluation. High-pressure piston pump test: According to JCMAS P045, a high-pressure piston pump test was carried out for 2000 hours using a high-pressure piston pump test apparatus under the conditions of a pump pressure of 35 MPa, a reagent oil temperature of 80°C, and an air blowing amount of 1.0 L / h to obtain a reagent oil of a lubricating oil composition that is assumed to be used for a long time under high pressure, wherein the pump is BOSCH-REXROTHA2F10. Evaluation of pore value: According to SAE-ARP-785-63, the precipitate in 300 mL of reagent oil was collected by filtration, and the mass of the precipitate per 100 mL of reagent oil was calculated as the "pore value".

72. The lubricating oil composition according to claim 71, wherein The aforementioned micropore value is 5.0 mg / 100 mL or less.

73. The lubricating oil composition according to claim 71, wherein The aforementioned micropore value is 4.0 mg / 100 mL or less.

74. The lubricating oil composition according to claim 71, wherein The aforementioned micropore value is 3.5 mg / 100 mL or less.

75. The lubricating oil composition according to any one of claims 1 to 3, wherein For the reagent oil obtained from the following high-pressure piston pump test, the grade value measured by the following FZG scratch test is 10 or above. High-pressure piston pump test: According to JCMAS P045, a high-pressure piston pump test was carried out for 2000 hours using a high-pressure piston pump test apparatus under the conditions of a pump pressure of 35 MPa, a reagent oil temperature of 80°C, and an air injection amount of 1.0 L / h to obtain a reagent oil of a lubricating oil composition that is assumed to be used for a long time under high pressure, wherein the pump is BOSCH-REXROTHA2F10. FZG scratch test: According to ASTM D5182-97 (2014), an A-type gear was used, and under the conditions of a reagent oil temperature of 90°C, a rotation speed of 1450 rpm, and an operating time of 15 minutes, the load was increased stepwise as specified to obtain the level of load when scratching occurred.

76. The lubricating oil composition according to any one of claims 1 to 3, wherein For the reagent oil obtained from the following high-pressure piston pump test, the seizure load measured by the following vibration friction and wear test is 1500N or more, High-pressure piston pump test: According to JCMAS P045, a high-pressure piston pump test was carried out for 2000 hours using a high-pressure piston pump test apparatus under the conditions of a pump pressure of 35 MPa, a reagent oil temperature of 80°C, and an air blowing amount of 1.0 L / h to obtain a reagent oil of a lubricating oil composition that is assumed to be used for a long time under high pressure, wherein the pump is BOSCH-REXROTHA2F10. Vibration friction and wear test: According to ASTM D7421, the seizure load N was measured. For the seizure load, under the friction conditions of temperature 120°C, frequency 50 Hz, and amplitude 2.0 mm, the load was increased by 100 N each time, and the load N at the time when seizure occurred and the friction coefficient increased greatly was measured.

77. The lubricating oil composition according to claim 76, wherein The aforementioned seizure load is 1600N or more.

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