Lubricating oil composition

Abstract

To provide a lubricating oil composition excellent in vaporization properties and wear resistance.SOLUTION: A lubricating oil composition contains a base oil (A) including an ester oil (A1), a phenothiazine compound (B), and a non-metal thiophosphate compound (C). The ester oil (A1) preferably includes a diester oil (A11).SELECTED DRAWING: None

Description

[Technical field]

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

[0002] 2. Description of the Related Art In recent years, oil-retaining bearings formed by sintering metal powder have been widely used as bearings incorporated in devices such as automotive electrical equipment, home appliances, and office automation equipment. Oil-impregnated bearings are generally produced by forming a porous metal body from raw metal powder through various processes such as mixing, molding, sintering, and sizing, and then using an impregnation device to vacuum-impregnate the metal body with lubricating oil; they are sliding bearings that are used in a self-lubricating state. In oil-impregnated bearings, the lubricating oil composition impregnated in a porous metal body is supplied to the sliding surface between the rotating shaft and the inner surface of the bearing by the pumping action caused by the rotation of the rotating shaft, thereby providing lubrication. Not only are these bearings excellent in durability and rigidity, they also have the advantage of being able to keep production costs low.

[0003] As the base oil of the lubricating oil composition to be impregnated into the oil-impregnated bearing, various base oils are used, such as mineral oil, hydrocarbon synthetic oil, ether oil, ester oil, fluorinated oil, silicone oil, etc. Patent Document 1 proposes a lubricating oil composition for oil-impregnated bearings using ester oil as the base oil (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-210443 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, oil-impregnated bearings are generally used without lubrication, and therefore if the amount of lubricating oil composition impregnated in the oil-impregnated bearing is likely to decrease over time, the life of the oil-impregnated bearing is likely to be shortened. Therefore, the present inventors conducted extensive research into the formulation of a lubricating oil composition for oil-impregnated bearings that is less likely to evaporate, and as a result, they have discovered a formulation that makes a lubricating oil composition for oil-impregnated bearings that uses an ester oil as a base oil even less likely to evaporate, and has excellent evaporation characteristics, while also providing excellent wear resistance. Lubricating oil compositions having excellent evaporation characteristics and wear resistance are required not only for use in oil-impregnated bearings, but also for a variety of other applications.

[0006] An object of the present invention is to provide a lubricating oil composition which is excellent in evaporation characteristics and antiwear properties. [Means for solving the problem]

[0007] According to the present invention, the following [1] to [5] are provided. [1] A lubricating oil composition comprising a base oil (A) containing an ester oil (A1), a phenothiazine compound (B), and a non-metallic thiophosphate compound (C). [2] The lubricating oil composition according to the above item [1], which is used as an impregnated bearing oil. [3] A method for using the lubricating oil composition according to the above item [1] as an impregnated bearing oil. [4] An oil-impregnated bearing impregnated with the lubricating oil composition described in [1] above. [5] A method for producing a lubricating oil composition, comprising the step of mixing a base oil (A) containing an ester oil (A1), a phenothiazine compound (B), and a non-metallic thiophosphate compound (C). Effect of the Invention

[0008] According to the present invention, it is possible to provide a lubricating oil composition that is excellent in evaporation characteristics and anti-wear properties. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The upper and lower limit values ​​of the numerical ranges described in this specification can be combined in any way. For example, when "A to B" and "C to D" are described as numerical ranges, the numerical ranges "A to D" and "C to B" are also included in the scope of the present invention. In addition, unless otherwise specified, a numerical range of "lower limit value to upper limit value" described in this specification means not less than the lower limit value and not more than the upper limit value. In this specification, the numerical values ​​in the examples are numerical values ​​that can be used as upper or lower limits.

[0010] [Embodiments of the lubricating oil composition] The lubricating oil composition of the present embodiment contains a base oil (A) containing an ester oil (A1), a phenothiazine-based compound (B), and a non-metallic thiophosphate-based compound (C).

[0011] The present inventors have conducted extensive research in order to solve the above problems. As a result, the present inventors have come to the novel discovery that phenothiazine compounds have the effect of suppressing the evaporation of ester oils. Based on this finding, the present inventors conducted further intensive research and discovered that the use of a non-metallic thiophosphate ester compound can impart wear resistance to a lubricating oil composition without impairing the evaporation inhibitory effect of the ester oil provided by the phenothiazine compound. Based on these findings, the present inventors conducted further studies and completed the present invention.

[0012] In the following description, the “base oil (A)”, the “phenothiazine compound (B)”, and the “non-metallic thiophosphate ester compound (C)” will also be referred to as “component (A)”, “component (B)”, and “component (C)”, respectively.

[0013] The lubricating oil composition of the present embodiment may be composed only of component (A), component (B), and component (C), or may further contain components other than component (A), component (B), and component (C). In the lubricating oil composition of this embodiment, the total content of components (A), (B) and (C) is preferably 50 mass% or more, more preferably 60 mass% or more, even more preferably 70 mass% or more, still more preferably 75 mass% or more, and even more preferably 80 mass% or more, based on the total amount of the lubricating oil composition.

[0014] Each component contained in the lubricating oil composition of this embodiment will be described in detail below.

[0015] <Base oil (A)> The lubricating oil composition of this embodiment contains a base oil (A) that includes an ester oil (A1). Since the lubricating oil composition of the present embodiment contains the phenothiazine compound (B), the evaporation characteristics of the ester oil (A1) are improved, and the evaporation characteristics of the lubricating oil composition can be made excellent. From the viewpoint of making it easier to enjoy the effects of the present invention, the content of the ester oil (A1) in the base oil (A) is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, even more preferably 70% by mass to 100% by mass, still more preferably 80% by mass to 100% by mass, even more 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 base oil (A).

[0016] The kinematic viscosity of the base oil (A) at 100°C is preferably 2.0 mm 2 / s~30.0mm 2 / s, more preferably 2.5 mm 2 / s~25.0mm 2 / s, more preferably 3.0 mm 2 / s~22.0mm 2 / s. The viscosity index of the base oil (A) is preferably 65 or more. When a mixed oil of two or more base oils is used as the base oil (A), the kinematic viscosity and viscosity index of the mixed oil are preferably within the above ranges. The kinematic viscosity and viscosity index of the base oil (A) refer to values ​​measured and calculated in accordance with JIS K2283:2000.

[0017] In the lubricating oil composition of this embodiment, the content of base oil (A) is, based on the total amount of the lubricating oil composition, preferably 60 mass% or more, more preferably 70 mass% or more, even more preferably 75 mass% or more, still more preferably 80 mass% or more, and is preferably 99.5 mass% or less, more preferably 99.0 mass% or less, even more preferably 98.0 mass% or less.

[0018] (Ester oil (A1)) The ester oil (A1) includes a compound having an ester bond. Specific examples include diester oil (A11), polyol ester oil (A12), and aromatic ester oil (A13). The ester oil (A1) may be used alone or in combination of two or more kinds.

[0019] -Diester oil (A11)- The diester oil (A11) is an ester of a dibasic acid and an alcohol, and is preferably a compound represented by the following general formula (a-1).

[0020] [ka]

[0021] In the above general formula (a-1), R a1 and R a2 are each independently an alkyl group having 2 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms. a3 is an alkylene group having 2 to 20 carbon atoms.

[0022] R a1 and R a2Examples of the alkyl group that can be selected as the aryl group include an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an n-hexyl group, an n-octyl group, a 2-ethylhexyl group, an n-nonyl group, a 3,3,5-trimethylhexyl group, an n-decyl group, a dimethyloctyl group, an isodecyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, an n-hexadecyl group, an n-octadecyl group, and an n-icosyl group. Also, R a1 and R a2 Examples of alkenyl groups that can be selected for include ethenyl, n-propenyl, n-butenyl, n-hexenyl, n-octenyl, 2-ethylhexenyl, n-nonenyl, 3,3,5-trimethylhexenyl, n-decenyl, dimethyloctenyl, isodecenyl, n-undecenyl, n-dodecenyl, n-tridecenyl, n-tetradecenyl, n-pentadecenyl, n-hexadecenyl, n-octadecenyl, and n-icosenyl groups. The alkyl group or alkenyl group may be linear or branched. The alkyl or alkenyl group preferably has 4 to 16 carbon atoms, more preferably 5 to 14 carbon atoms, and even more preferably 6 to 12 carbon atoms, from the viewpoint of improving the effects of the present invention.

[0023] Also, R a3 Examples of the alkylene group that can be selected as the alkylene group include an ethylene group, an n-propylene group, an isopropylene group, an n-butylene group, an isobutylene group, an n-pentylene group, an n-hexylene group, an n-heptylene group, an n-octylene group, a 2-ethylhexylene group, an n-nonylene group, an n-decylene group, an n-undecylene group, an n-tridecylene group, an n-hexadecylene group, an n-octadecylene group, and an n-icosylene group. The alkylene group may be linear or branched. The alkylene group preferably has 4 to 16 carbon atoms, more preferably 6 to 13 carbon atoms, and further preferably 8 to 12 carbon atoms, from the viewpoint of improving the effects of the present invention.

[0024] The diester oil (A11) may be used alone or in combination of two or more kinds.

[0025] -Polyol ester oil (A12)- The polyol ester oil (A12) is an ester which is a condensation product of a polyol and a fatty acid. The number of carbon atoms in the polyol constituting the polyol ester oil (A12) is preferably 2-20, more preferably 2-15, and even more preferably 2-12, from the viewpoint of improving heat resistance and the like. The number of carbon atoms in the fatty acid constituting the polyol ester oil (A12) is preferably 2-20, more preferably 2-18, and even more preferably 2-16, from the viewpoint of improving heat resistance and the like.

[0026] Specific examples of polyols constituting the polyol ester oil (A12) include ethylene glycol, 1,3-propanediol, propylene glycol, 1,4-butanediol, 1,2-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 1,7-heptanediol, 2-methyl-2-propyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,8-octanediol, 1,9-nonanediol, 1,10- Examples of the polyhydric alcohols include diols such as decanediol, 1,11-undecanediol, and 1,12-dodecanediol; polyhydric alcohols such as trimethylolethane, trimethylolpropane, trimethylolbutane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, glycerin, glycerin dimer, 1,3,5-pentanetriol, sorbitol, sorbitan, adonitol, arabitol, xylitol, and mannitol; and sugars such as xylose, arabinose, ribose, rhamnose, glucose, fructose, galactose, mannose, and sorbose. Among these, trimethylolpropane, glycerin, pentaerythritol, and dipentaerythritol are preferred from the viewpoint of improving heat resistance.

[0027] Specific examples of fatty acids constituting the polyol ester oil (A12) include propionic acid, n-butanoic acid, n-pentanoic acid (valeric acid), isopentanoic acid (isovaleric acid), n-hexanoic acid (caproic acid), n-heptanoic acid, isoheptanoic acid, n-octanoic acid (caprylic acid), 2-ethylhexanoic acid, isooctanoic acid, n-nonanoic acid (pelargonic acid), isononanoic acid, n-decanoic acid (capric acid), isodecanoic acid, and n-unsodium ester. Decanoic acid, isoundecanoic acid, n-dodecanoic acid (lauric acid), isododecanoic acid, n-tridecanoic acid, isotridecanoic acid, n-tetradecanoic acid (myristic acid), n-hexadecanoic acid (palmitic acid), n-octadecanoic acid (stearic acid), isostearic acid, n-eicosanoic acid (arachic acid), 10-undecenoic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, and gadoleic acid. These fatty acids may be straight-chain or branched-chain. Furthermore, these fatty acids may be saturated fatty acids or unsaturated fatty acids.

[0028] The polyol ester oil (A12) may be used alone or in combination of two or more kinds.

[0029] -Aromatic ester oil (A13)- The aromatic ester oil (A13) is an ester having one or more ester groups bonded to an aromatic ring, and is preferably a compound represented by the following general formula (a-3).

[0030] [ka]

[0031] In the above general formula (a-3), m represents an integer of 1 to 5, preferably an integer of 2 to 4, and more preferably an integer of 3 to 4. R a31 is an alkyl group having 2 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms. a31 may be the same as each other or different from each other. R a31 The alkyl group that can be selected as R a11 and R a12 Examples of the alkyl group include those exemplified as above. R a31 The alkenyl group that can be selected as R a11 and R a12 Examples of the alkenyl groups include those exemplified as: The alkyl group and the alkenyl group may be linear or branched. The alkyl group and the alkenyl group each preferably have 4 to 16 carbon atoms, more preferably 6 to 13 carbon atoms, and even more preferably 8 to 12 carbon atoms, from the viewpoint of improving heat resistance and the like.

[0032] The aromatic ester oil (A13) may be used alone or in combination of two or more kinds.

[0033] (Preferred embodiment of ester oil (A1)) In the lubricating oil composition of this embodiment, the ester oil (A1) preferably contains a diester oil (A11). In general, esters in which a hydrogen atom is bonded to the carbon atom at the β-position on the alcohol side of the ester bond are easily decomposed when heated (Non-Patent Document 1: Tribology Series 8, Lubricating Grease and Synthetic Lubricating Oil, Saiwai Shobo Co., Ltd., First Edition, First Printing, December 25, 1983). According to the investigations of the present inventors, it has been confirmed that even in the case of an ester in which a hydrogen atom is bonded to the carbon atom at the β-position on the alcohol side of the ester bond, it is possible to improve the evaporation characteristics by the action of the phenothiazine compound (B). Therefore, according to the formulation shown in this embodiment, even when the ester oil (A1) contains an ester in which a hydrogen atom is bonded to the carbon atom at the β-position on the alcohol side of the ester bond, the evaporation characteristics of the lubricating oil composition can be excellent. Here, diester oils (A11) often have a hydrogen atom bonded to the carbon atom at the β-position on the alcohol side of the ester bond, and therefore often have poor evaporation characteristics. Therefore, the formulation shown in this embodiment (i.e., the lubricating oil composition of this embodiment) is suitable when the ester oil (A1) contains the diester oil (A11). Furthermore, the formulation shown in this embodiment is more suitable when the diester oil (A11) is a diester oil (A11x) in which a hydrogen atom is bonded to the carbon atom at the β-position on the alcohol side of the ester bond.

[0034] From the viewpoint of making it easier to enjoy the effects of the present invention, the content of the diester oil (A11) in the ester oil (A1) is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, even more preferably 70% by mass to 100% by mass, still more preferably 80% by mass to 100% by mass, even more 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 ester oil (A1). Furthermore, from the viewpoint of making it easier to enjoy the effects of the present invention, the content of the diester oil (A11x) in the ester oil (A1) is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, even more preferably 70% by mass to 100% by mass, still more preferably 80% by mass to 100% by mass, even more 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 ester oil (A1).

[0035] (Base oil (A2) other than ester-based oil (A1)) The lubricating oil composition of this embodiment may contain, as the base oil (A), one or more base oils (A2) selected from synthetic oils other than the ester oil (A1) and mineral oils.

[0036] Examples of synthetic oils other than the ester oil (A1) include polyolefins such as α-olefin homopolymers or α-olefin copolymers (for example, α-olefin copolymers having 8 to 14 carbon atoms, such as ethylene-α-olefin copolymers); isoparaffins; various ethers such as polyalkylene glycols and polyphenyl ethers; alkylbenzenes; alkylnaphthalenes; and base oils (GTL) obtained by isomerizing wax produced from natural gas by the Fischer-Tropsch process or the like (GTL wax (Gas To Liquids WAX)). These synthetic oils may be used alone or in combination of two or more.

[0037] Examples of mineral oils include atmospheric residual oils obtained by atmospheric distillation of crude oils such as paraffin-based crude oil, intermediate-based crude oil, and naphthene-based crude oil; distillate oils obtained by vacuum distillation of these atmospheric residual oils; and mineral oils obtained by subjecting the distillate oils to one or more refining treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining. These mineral oils may be used alone or in combination of two or more.

[0038] <Phenothiazine Compounds (B)> The lubricating oil composition of the present embodiment contains a phenothiazine compound (B). The phenothiazine compound (B) has the effect of improving the evaporation characteristics of the ester oil (A1), and this effect is fully exhibited even when the nonmetallic thiophosphate compound (C) is blended in the lubricating oil composition. In this specification, the term "phenothiazine compound (B)" means one or more compounds selected from the group consisting of phenothiazine (B1) and phenothiazine derivatives (B2).

[0039] (Phenothiazine (B1)) Phenothiazine (B1) is an unsubstituted phenothiazine represented by the following structural formula (b-1).

[0040] [ka]

[0041] (Phenothiazine derivative (B2)) The phenothiazine derivative (B2) is a compound in which at least one hydrogen atom of unsubstituted phenothiazine represented by the above structural formula (b-1) is substituted with a substituent, and preferably includes a compound represented by the following general formula (b-2). [ka]

[0042] In the above general formula (b-2), R b1 , R b2 , and R b3 each independently represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 11 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, an acyl group having 1 to 10 carbon atoms, a hydroxyl group, a sulfone group, a nitro group, an amino group, a carboxyl group, or a halogen. In the above general formula (b-2), p1 and p2 each independently represent an integer of 0 to 4. If p1 is 2 or more, there are multiple R b1 may be the same as each other or different from each other. In addition, if p2 is 2 or more, there are multiple R b2 may be the same as each other or different from each other.

[0043] The phenothiazine derivative (B2) may be used alone or in combination of two or more kinds.

[0044] (Preferred embodiment of phenothiazine derivative (B2)) The phenothiazine derivative (B2) preferably satisfies one or more requirements selected from the following requirements 1 to 4. - Requirement 1 - R b1 , R b2 , and Rb3 is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 11 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or an acyl group having 1 to 10 carbon atoms, from the viewpoint of improving the solubility of the phenothiazine derivative (B2) in the base oil (A). - Requirement 2 - R b1 , R b2 , and R b3 is an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or an acyl group having 1 to 10 carbon atoms, the number of carbon atoms of these substituents is preferably 4 to 10, more preferably 6 to 10, from the viewpoint of improving the solubility of the phenothiazine derivative (B2) in the base oil (A) and from the viewpoint of suppressing sludge deposition, etc. - Requirement 3 - From the viewpoint of suppressing the oxidation of the phenothiazine derivative (B2) itself, one or both of the 3- and 7-positions of the phenothiazine may be substituted with R b1 , R b2 , and R b3 The above-mentioned substituents are introduced. - Requirement 4 - From the viewpoint of inhibiting oxidation of the phenothiazine derivative (B2) itself, an acyl group having 1 to 10 carbon atoms is introduced into one or both of the 1- and 2-positions of phenothiazine, preferably both.

[0045] (Content of phenothiazine compound (B)) In the lubricating oil composition of this embodiment, the content of the phenothiazine compound (B) is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and even more preferably 0.08 mass% or more based on the total amount of the lubricating oil composition, from the viewpoint of making it easier to improve the evaporation characteristics of the lubricating oil composition. Also, the content of the phenothiazine compound (B) is preferably 5.0 mass% or less, more preferably 3.0 mass% or less, and even more preferably 2.5 mass% or less, from the viewpoint of the balance between the content of the phenothiazine compound (B) and the effect of improving the evaporation characteristics. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, the range is preferably 0.01 mass % to 5.0 mass %, more preferably 0.05 mass % to 3.0 mass %, and even more preferably 0.08 mass % to 2.5 mass %.

[0046] <Non-metallic thiophosphate compounds (C)> The lubricating oil composition of the present embodiment contains a nonmetallic thiophosphate compound (C). The nonmetallic thiophosphate compound (C) can impart wear resistance to the lubricating oil composition while fully utilizing the effect of the phenothiazine compound (B) in improving the evaporation characteristics of the ester oil (A1). The non-metal thiophosphate compound (C) may be a compound that does not contain a metal atom as a constituent atom, but contains a phosphorus atom and a sulfur atom as constituent atoms. Examples of such compounds include one or more selected from thiophosphates, thiophosphites, and amine salts thereof. Among these, from the viewpoint of improving the effects of the present invention, the nonmetallic thiophosphate ester compound (C) preferably contains a thiophosphate ester (C1). The thiophosphates (C1) include one or more selected from monothiophosphates, dithiophosphates, trithiophosphates, and the like. Among these, one or more selected from monothiophosphates and dithiophosphates are preferred. The content of the thiophosphates (C1) is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, even more preferably 70% by mass to 100% by mass, still more preferably 80% by mass to 100% by mass, even more 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 non-metal thiophosphate compound (C).

[0047] In this specification, the term "monothiophosphates" refers to thiophosphates having one sulfur atom bonded to the phosphorus atom, or derivatives thereof. Moreover, the term "dithiophosphates" refers to thiophosphates in which the number of sulfur atoms bonded to the phosphorus atom is two, or derivatives thereof. Moreover, the term "trithiophosphates" refers to thiophosphates in which the number of sulfur atoms bonded to the phosphorus atom is three, or derivatives thereof.

[0048] (Monothiophosphate triester (C1x)) From the viewpoint of improving the hydrolysis resistance of the ester oil (A1), the thiophosphates (C1) preferably contain, as monothiophosphates, one or more types selected from monothiophosphate triesters (C1x) represented by the following general formula (c-1x): [ka] [In the above general formula (c-1x), each symbol represents the following. R c1 , R c2 , and R c3 each independently represents a saturated or unsaturated aliphatic hydrocarbon group having 1 to 18 carbon atoms, an optionally substituted saturated or unsaturated alicyclic hydrocarbon group having 5 to 18 carbon atoms, or an optionally substituted aromatic hydrocarbon group having 5 to 18 carbon atoms.]

[0049] In the above general formula (c-1x), R c1 , R c2 , and R c3 The number of carbon atoms of the saturated or unsaturated aliphatic hydrocarbon group that can be selected as is more preferably 5 to 18. Specific examples of saturated aliphatic hydrocarbon groups include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, and an octadecyl group. These may be linear or branched. Examples of the unsaturated aliphatic hydrocarbon group include specific saturated aliphatic hydrocarbon groups other than the above methyl group, such as an ethylene group and a propylene group, which have at least one unsaturated bond.

[0050] In the above general formula (c-1x), R c1 , R c2 , and R c3 Specific examples of the saturated alicyclic hydrocarbon group that can be selected for include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, and a cyclodecyl group. Examples of the unsaturated alicyclic hydrocarbon group include the above-mentioned saturated alicyclic hydrocarbon groups having at least one unsaturated bond, such as a cyclopentenyl group and a cyclohexenyl group.

[0051] In the above general formula (c-1x), R c1 , R c2 , and R c3 Specific examples of aromatic hydrocarbon groups that can be selected for include aryl groups such as phenyl and naphthyl groups.

[0052] Examples of the substituent include a C1 to C6 alkyl group, a C1 to C6 alkoxy group, a C6 to C 14 and the like.

[0053] Specific examples of monothiophosphate triesters (C1x) include tributyl phosphorothioate, tripentyl phosphorothioate, trihexyl phosphorothioate, triheptyl phosphorothioate, trioctyl phosphorothioate, trinonyl phosphorothioate, tridecyl phosphorothioate, triundecyl phosphorothioate, tridodecyl phosphorothioate, tritridecyl phosphorothioate, tritetradecyl phosphorothioate, tripentadecyl phosphorothioate, trihexadecyl phosphorothioate, triheptadecyl phosphorothioate, and trioctadecyl phosphorothioate. phosphorothioate, trioleyl phosphorothioate, triphenyl phosphorothioate, tricresyl phosphorothioate, trixylenyl phosphorothioate, cresyl diphenyl phosphorothioate, xylenyl diphenyl phosphorothioate, tris(n-propylphenyl) phosphorothioate, tris(isopropylphenyl) phosphorothioate, tris(n-butylphenyl) phosphorothioate, tris(isobutylphenyl) phosphorothioate, tris(sec-butylphenyl) phosphorothioate, and tris(tert-butylphenyl) phosphorothioate.

[0054] From the viewpoint of improving the effects of the present invention and improving the hydrolysis resistance of the ester oil (A1), the content of the monothiophosphate triester (C1x) is preferably 50 mass% to 100 mass%, more preferably 60 mass% to 100 mass%, even more preferably 70 mass% to 100 mass%, still more preferably 80 mass% to 100 mass%, still more preferably 90 mass% to 100 mass%, and even more preferably 95 mass% to 100 mass%, based on the total amount of the thiophosphates (C1).

[0055] The monothiophosphate triester (C1x) may be used alone or in combination of two or more kinds.

[0056] (Monothiophosphoric acid triaryl ester (C11x)) From the viewpoint of improving the effects of the present invention and improving the hydrolysis resistance of the ester oil (A1), the monothiophosphate triester (C1x) preferably includes one or more selected from monothiophosphate triaryl esters (C11x) represented by the following general formula (c-11x):

[0057] [ka] [In the above general formula (c-11x), each symbol represents the following. R c11 , R c12 , and R c13 each independently represents an alkyl group having 1 to 3 carbon atoms. n1, n2, and n3 each independently represent an integer of 0 to 5.

[0058] In the above general formula (c-11x), R c11 , R c12 , and R c13 are each independently an alkyl group having 1 to 3 carbon atoms. Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. Each of n1, n2, and n3 independently is preferably 0 to 2, more preferably 0 to 1, and further preferably 0.

[0059] Specific examples of the monothiophosphate triaryl ester (C11x) represented by the above general formula (c-11x) include tricresylthiophosphate and triphenyl phosphorothioate.

[0060] From the viewpoint of improving the effects of the present invention and improving the hydrolysis resistance of the ester oil (A1), the content of the monothiophosphate triaryl ester (C11x) is preferably 50 mass% to 100 mass%, more preferably 60 mass% to 100 mass%, even more preferably 70 mass% to 100 mass%, still more preferably 80 mass% to 100 mass%, still more preferably 90 mass% to 100 mass%, and even more preferably 95 mass% to 100 mass%, based on the total amount of the monothiophosphate triester (C1x).

[0061] The monothiophosphate triaryl ester (C11x) may be used alone or in combination of two or more kinds.

[0062] (Dithiophosphate esters (C1y) having a carboxyl group at the end) From the viewpoint of improving abrasion resistance, the thiophosphates (C1) preferably contain, as dithiophosphates, a dithiophosphate (C1y) having a carboxyl group at its terminal. Specific examples of dithiophosphate esters having a carboxyl group at their terminals include compounds represented by the following general formula (c-1y).

[0063] [ka]

[0064] In the above general formula (c-1y), R c21 R represents a linear or branched alkylene group having 1 to 8 carbon atoms. c22 and R c23 each independently represents a hydrocarbon group having 3 to 20 carbon atoms. In the above general formula (c-1y), R c21 From the viewpoint of improving the solubility in the base oil (A), is preferably 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 even more preferably a branched alkylene group having 2 to 4 carbon atoms. Also, R c22 and R c23From the viewpoint of improving the solubility in the base oil (A) and the viewpoint of improving the wear resistance, the alkyl group is preferably a linear or branched alkyl group having 3 to 8 carbon atoms, more preferably a linear or branched alkyl group having 4 to 6 carbon atoms. Specific examples thereof include a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, an n-hexyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a 1,3-dimethylbutyl group, and a 2-ethylhexyl group. Of these, an isobutyl group and a tert-butyl group are preferred.

[0065] From the viewpoint of improving the effects of the present invention, the content of the dithiophosphate ester (C1y) having a carboxyl group at its terminal is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, even more preferably 70% by mass to 100% by mass, still more preferably 80% by mass to 100% by mass, even more 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 thiophosphates (C1).

[0066] The dithiophosphate ester (C1y) having a carboxyl group at its terminal may be used alone or in combination of two or more kinds.

[0067] (Non-metallic thiophosphate ester compound (C) content) In the lubricating oil composition of this embodiment, the content of the nonmetallic thiophosphate ester compound (C) is preferably 0.10 mass% or more, more preferably 0.50 mass% or more, and even more preferably 0.80 mass% or more based on the total amount of the lubricating oil composition, from the viewpoint of making it easier to improve the wear resistance of the lubricating oil composition. Also, the content of the nonmetallic thiophosphate ester compound (C) is preferably 5.0 mass% or less, more preferably 3.0 mass% or less, and even more preferably 2.5 mass% or less, from the viewpoint of the balance between the content of the nonmetallic thiophosphate ester compound (C) and the effect of improving the wear resistance. The upper and lower limits of these numerical ranges can be arbitrarily combined. Specifically, the range is preferably 0.10 mass % to 5.0 mass %, more preferably 0.50 mass % to 3.0 mass %, and even more preferably 0.80 mass % to 2.5 mass %.

[0068] Here, in the lubricating oil composition of this embodiment, from the viewpoint of improving the hydrolysis resistance of the ester oil (A1), the content of the dithiophosphate ester (C1y) having a carboxyl group at the end is preferably small. Specifically, the content of the dithiophosphate ester (C1y) having a carboxyl group at the end is preferably less than 0.95 mass%, more preferably less than 0.5 mass%, even more preferably less than 0.1 mass%, even more preferably less than 0.01 mass%, and even more preferably no dithiophosphate ester (C1y) having a carboxyl group at the end is contained based on the total amount of the lubricating oil composition.

[0069] <Content ratio of component (B) and component (C)> From the viewpoint of improving the effects of the present invention, the content ratio of the phenothiazine compound (B) to the nonmetallic thiophosphate compound (C) [(B) / (C)] is, in terms of mass ratio, preferably 1 / 10 to 10 / 1, more preferably 1 / 8 to 8 / 1, and even more preferably 1 / 6 to 6 / 1.

[0070] <Metal deactivator (D)> From the viewpoint of improving the hydrolysis resistance of the ester oil (A1), the lubricating oil composition of this embodiment preferably further contains a metal deactivator (D). In the following description, "metal deactivator (D)" will also be referred to as "component (D)". Examples of the metal deactivator (D) include triazole-based compounds, thiadiazole-based compounds, imidazole-based compounds, and pyrimidine-based compounds. These may be used alone or in combination of two or more.

[0071] (Benzotriazole Compounds (D1)) From the viewpoint of further improving the hydrolysis resistance of the ester oil (A1), the metal deactivator (D) preferably contains a triazole-based compound, and more preferably contains a benzotriazole-based compound (D1) represented by the following general formula (d-1): [ka]

[0072] In the above general formula (d-1), R d1 is an alkyl group having 1 to 4 carbon atoms. The alkyl group may be linear or branched. From the viewpoint of improving the hydrolysis resistance of the ester oil (A1), the alkyl group preferably has 1 to 3 carbon atoms, more preferably 1 to 2 carbon atoms, and even more preferably 1 carbon atom.

[0073] In the above general formula (d-1), q is an integer of 0 to 4. d1 When there are multiple R d1 may be the same as or different from each other. Here, from the viewpoint of improving the hydrolysis resistance of the ester oil (A1), q is preferably 0 to 3, more preferably 0 to 2, and even more preferably 1.

[0074] In the above general formula (d-1), R d2 is a methylene group or an ethylene group. From the viewpoint of improving the hydrolysis resistance of the ester oil (A1), R d2 is preferably a methylene group.

[0075] In the above general formula (d-1), R d3 and R d4 are each independently a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. The alkyl group may be linear or branched, but is preferably branched from the viewpoint of improving the hydrolysis resistance of the ester oil (A1). Furthermore, from the viewpoint of improving the hydrolysis resistance of the ester oil (A1), the alkyl group preferably has 2 to 14 carbon atoms, more preferably 4 to 12 carbon atoms, and even more preferably 6 to 10 carbon atoms.

[0076] Here, from the viewpoint of improving the hydrolysis resistance of the ester oil (A1), the content of the benzotriazole compound (D1) in the metal deactivator (D) is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, even more preferably 70% by mass to 100% by mass, still more preferably 80% by mass to 100% by mass, even more 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 metal deactivator (D).

[0077] From the viewpoint of improving the hydrolysis resistance of the ester oil (A1), the content of the metal deactivator (D) is preferably 0.01 mass % to 2.0 mass %, more preferably 0.05 mass % to 1.5 mass %, and even more preferably 0.08 mass % to 1.0 mass %, based on the total amount of the lubricating oil composition.

[0078] <Lubricant additives> The lubricating oil composition of the present embodiment may further contain lubricating oil additives other than components (B), (C) and (D) as required. Examples of such lubricating oil additives include antioxidants (e.g., amine-based antioxidants and phenol-based antioxidants), metal-based detergents, dispersants, friction modifiers, anti-wear agents other than the non-metal thiophosphate ester-based compound (C) (e.g., zinc dithiophosphate), extreme pressure agents, viscosity index improvers, pour point depressants, antifoam agents, rust inhibitors, and antistatic agents. Among these, it is preferable to contain a dispersant such as a succinimide-based dispersant and a viscosity index improver such as polymethacrylate. The lubricating oil additives may be used alone or in combination of two or more kinds.

[0079] The content of each of these lubricating oil additives can be adjusted as appropriate within a range that does not impair the effects of the present invention, but is usually 0.001 to 15 mass%, preferably 0.005 to 10 mass%, and more preferably 0.01 to 5 mass%, for each additive independently, based on the total amount (100 mass%) of the lubricating oil composition.

[0080] From the viewpoint of improving evaporation characteristics, the lubricating oil composition of this embodiment preferably contains a small amount of phenol-based antioxidant. Examples of the phenol-based antioxidant include monophenol-based antioxidants and bisphenol-based antioxidants. Examples of monophenolic antioxidants include alkyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate, such as n-octyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate, 6-methylheptyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate, and n-octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate. propionate (the alkyl group has 4 to 20 carbon atoms, and preferably 8 to 18 carbon atoms); 2,6-di-tert-butyl-4-alkylphenols (the alkyl group has 1 to 4 carbon atoms), such as 2,6-di-tert-butyl-4-methylphenol and 2,6-di-tert-butyl-4-ethylphenol; 2,4-dimethyl-6-tert-butylphenol, 2,6-di-tert-amyl-p-cresol, and the like. In addition, examples of bisphenol antioxidants include 4,4'-methylenebis(2,6-di-tert-butylphenol), 4,4'-bis(2,6-di-tert-butylphenol), 4,4'-bis(2-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-butylidenebis(3-methyl-6-tert-butylphenol), 4,4'-isopropylidenebis(2,6-di-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-nonylphenol), 2,2 '-isobutylidenebis(4,6-dimethylphenol), 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 4,4'-thiobis(2-methyl-6-tert-butylphenol), 4,4'-thiobis(3-methyl-6-tert-butylphenol), 2,2'-thiobis(4-methyl-6-tert-butylphenol), bis(3-methyl-4-hydroxy-5-tert-butylbenzyl)sulfide, bis(3,5-di-tert-butyl-4-hydroxybenzyl)sulfide, thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and the like. The content of the phenolic antioxidant is preferably less than 0.5 mass %, more preferably less than 0.1 mass %, even more preferably less than 0.01 mass %, based on the total amount of the lubricating oil composition, and even more preferably the lubricating oil composition does not contain any phenolic antioxidant.

[0081] Moreover, from the viewpoint of improving the hydrolysis resistance of the ester oil (A1), the lubricating oil composition of this embodiment preferably contains a small amount of thiocarbamate-based compounds, which correspond to anti-wear agents other than the nonmetallic thiophosphate-based compound (C). Examples of the thiocarbamate compounds include thiocarbamate compounds and dithiocarbamate compounds. Examples of the thiocarbamate compound include diethylthiocarbamic acid, methylene diethylthiocarbamate, ethylene diethyldithiocarbamate, dipropylthiocarbamic acid, methylene dipropylthiocarbamate, ethylene dipropyldithiocarbamate, dibutyldithiocarbamic acid, methylene dibutyldithiocarbamate, ethylene dibutyldithiocarbamate, dipentyldithiocarbamic acid, methylene dipentyldithiocarbamate, ethylene dipentyldithiocarbamate, methylene dihexyldithiocarbamate, and ethylene dihexyldithiocarbamate. Examples of dithiocarbamate compounds include methylene bis(diethylthiocarbamate), ethylene bis(diethyldithiocarbamate), methylene bis(dipropylthiocarbamate), ethylene bis(dipropyldithiocarbamate), methylene bis(dibutyldithiocarbamate), ethylene bis(dibutyldithiocarbamate), methylene bis(dipentyldithiocarbamate), ethylene bis(dipentyldithiocarbamate), methylene bis(dihexyldithiocarbamate), and ethylene bis(dihexyldithiocarbamate). The content of the thiocarbamate compound is preferably less than 1.0 mass%, more preferably less than 0.1 mass%, even more preferably less than 0.01 mass%, based on the total amount of the lubricating oil composition, and even more preferably the lubricating oil composition does not contain any thiocarbamate compound.

[0082] In the lubricating oil composition of this embodiment, the content of the molybdenum-based friction modifier is preferably small. Examples of the molybdenum-based friction modifiers include molybdenum dithiocarbamate (MoDTC) and molybdenum dithiophosphate (MoDTP). The content of the molybdenum-based friction modifier is preferably less than 0.5 mass %, more preferably less than 0.1 mass %, even more preferably less than 0.01 mass %, and even more preferably the lubricating oil composition does not contain any molybdenum-based friction modifier.

[0083] [Physical properties of lubricating oil composition] <Evaporation characteristics> The lubricating oil composition of this embodiment preferably has a longer evaporation life as measured by the method described in the Examples section below, specifically, preferably 10 days or more, more preferably 12 days or more, and even more preferably 14 days or more.

[0084] <Wear resistance> The lubricating oil composition of this embodiment is preferably such that the wear scar diameter measured by the method described in the Examples below is as small as possible, specifically, preferably 0.90 mm or less, more preferably 0.80 mm or less, even more preferably 0.70 mm or less, still more preferably 0.60 mm or less, and even more preferably 0.50 mm or less.

[0085] <Hydrolysis resistance (acid value, copper elution amount)> The lubricating oil composition of this embodiment preferably has a lower acid value of the oil component as measured by the method described in the Examples below. The lower the acid value, the better the hydrolysis resistance. Specifically, the acid value is preferably 5.00 mgKOH / g or less, more preferably 4.00 mgKOH / g or less, and even more preferably 3.70 mgKOH / g or less. The lubricating oil composition of this embodiment preferably has a lower copper elution amount from the oil as measured by the method described in the Examples below. The lower the copper elution amount, the better the hydrolysis resistance. Specifically, it is preferably 20 ppm by mass or less, more preferably 15 ppm by mass or less, and even more preferably 10 ppm by mass or less.

[0086] <Kinematic viscosity, viscosity index> The lubricating oil composition of this embodiment preferably has a kinematic viscosity at 100°C of 2.0 mm 2 / s~30.0mm 2 / s, more preferably 2.5 mm 2 / s~25.0mm 2 / s, more preferably 3.0 mm 2 / s~22.0mm 2 / s. The lubricating oil composition of this embodiment preferably has a viscosity index of 90 or greater. The kinematic viscosity and viscosity index of the lubricating oil composition refer to values ​​measured and calculated in accordance with JIS K2283:2000.

[0087] [Method of manufacturing lubricating oil composition] The method for producing the lubricating oil composition of this embodiment is not particularly limited. For example, the method for producing the lubricating oil composition of this embodiment includes the step of mixing a base oil (A) containing an ester oil (A1), a phenothiazine compound (B), and a non-metallic thiophosphate compound (C). The method for mixing the base oil (A) containing the ester oil (A1), the phenothiazine compound (B), and the non-metallic thiophosphate ester compound (C) is not particularly limited, and examples thereof include a method in which the phenothiazine compound (B) and the non-metallic thiophosphate ester compound (C) are blended with the base oil (A) containing the ester oil (A1). When additives other than the phenothiazine compound (B) and the nonmetallic thiophosphate compound (C) are blended, the additives may be blended simultaneously with the phenothiazine compound (B) and the nonmetallic thiophosphate compound (C) or may be blended separately. In addition, each component may be blended in the form of a solution (dispersion) by adding a diluent oil or the like. After mixing the components, it is preferable to stir them by a known method to disperse them uniformly. The preferred embodiments of each of the above components are as described above.

[0088] [Uses of lubricating oil composition] The lubricating oil composition of the present embodiment has excellent evaporation characteristics and anti-wear properties. Therefore, the lubricating oil composition of the present embodiment can be used in general applications where evaporation characteristics and wear resistance are required, and can be particularly suitably used for oil-retaining bearings incorporated in devices such as automotive electrical equipment, home appliances, and OA office equipment. Therefore, the lubricating oil composition of this embodiment provides the following (1) to (3). (1) The lubricating oil composition of the present embodiment is used as an impregnated bearing oil. (2) A method of using the lubricating oil composition of the present embodiment as an impregnated bearing oil. (3) An oil-impregnated bearing impregnated with the lubricating oil composition of the present embodiment. In addition, this embodiment also provides the following methods (4) to (6). (4) A method of blending an ester oil (A1) with a phenothiazine compound (B) to improve the evaporation characteristics of the ester oil (A1). (5) A method of blending a phenothiazine compound (B) with a diester oil (A11) to improve the evaporation characteristics of the diester oil (A11). (6) A method for improving the evaporation characteristics of a diester oil, in which a diester oil (A11) has a hydrogen atom bonded to the carbon atom at the β-position on the alcohol side of an ester bond, by blending a phenothiazine compound (B) with the diester oil.

[0089] Furthermore, the lubricating oil composition of this embodiment is not limited to use in oil-impregnated bearings, and can also be suitably used in, for example, fluid dynamic bearings of spindle motors used in electronic devices such as hard disk drives.

[0090] [One aspect of the present invention provided] In one embodiment of the present invention, the following [1] to

[11] are provided. [1] A lubricating oil composition comprising a base oil (A) containing an ester oil (A1), a phenothiazine compound (B), and a non-metallic thiophosphate compound (C). [2] The lubricating oil composition according to the above [1], wherein the ester oil (A1) comprises a diester oil (A11). [3] The lubricating oil composition according to the above [1] or [2], wherein the nonmetallic thiophosphate ester compound (C) comprises a thiophosphate ester (C1). [4] The lubricating oil composition according to the above item [3], wherein the thiophosphate esters (C1) include one or more selected from monothiophosphate triesters (C1x) represented by the following general formula (c-1x): [ka] [In the general formula (c-1x), each symbol represents the following.] R c1 , R c2 , and R c3 each independently represents a saturated or unsaturated aliphatic hydrocarbon group having 1 to 18 carbon atoms, an optionally substituted saturated or unsaturated alicyclic hydrocarbon group having 5 to 18 carbon atoms, or an optionally substituted aromatic hydrocarbon group having 5 to 18 carbon atoms.] [5] The lubricating oil composition according to the above item [4], wherein the monothiophosphate triester (C1x) comprises one or more selected from monothiophosphate triaryl esters (C11x) represented by the following general formula (c-11x): [ka] [In the general formula (c-11x), each symbol represents the following.] R c11 , R c12 , and R c13 each independently represents an alkyl group having 1 to 3 carbon atoms. n1, n2, and n3 each independently represent an integer of 0 to 5. [6] The lubricating oil composition according to any one of the above [1] to [5], further comprising a metal deactivator (D). [7] The lubricating oil composition according to any one of the above [1] to [6], wherein the content ratio of the phenothiazine compound (B) to the non-metallic thiophosphate compound (C) [(B) / (C)], in terms of mass ratio, is 1 / 10 to 10 / 1. [8] The lubricating oil composition according to any one of the above [1] to [7], which is used as an impregnated bearing oil. [9] A method for using the lubricating oil composition according to any one of the above [1] to [7], which comprises using the lubricating oil composition as an impregnated bearing oil.

[10] An oil-impregnated bearing impregnated with the lubricating oil composition according to any one of the above [1] to [7].

[11] A method for producing a lubricating oil composition, comprising the step of mixing a base oil (A) containing an ester oil (A1), a phenothiazine compound (B), and a non-metallic thiophosphate compound (C). EXAMPLES

[0091] The present invention will be described in more detail with reference to the following examples, although the present invention is not limited to the following examples.

[0092] [Methods for measuring various physical properties] The properties of the raw materials used in each Example and Comparative Example and the lubricating oil compositions in each Example and Comparative Example were measured according to the procedures described below.

[0093] (1)Kinematic viscosity, viscosity index Measurements and calculations were made in accordance with JIS K2283:2000.

[0094] [Examples 1-2, Comparative Examples 1-5] The above components were mixed to prepare lubricating oil compositions having the compositions shown in Table 1, and the following evaluations were carried out. The numerical units for the blend compositions in Table 1 are "mass %." The components used in preparing the lubricating oil compositions shown in Table 1 are described in detail below.

[0095] <Base oil (A)> Bis(2-ethylhexyl) dodecanedioate (DODN) was used. Bis(2-ethylhexyl) dodecanedioate is a base oil that corresponds to the diester oil (A11), and in the above general formula (a-1), R a1 and R a2 is a 2-ethylhexyl group, and R a3 is a decylene group (-(CH2) 10 -), which is a compound in which a hydrogen atom is bonded to the beta carbon atom on the alcohol side of the ester bond. The kinetic viscosity at 40°C is 13.9mm. 2 / s, and the kinetic viscosity at 100°C is 3.71 mm 2 / s and the viscosity index is 163.

[0096] <Phenothiazine Compounds (B)> Phenothiazine was used. Phenothiazine is an unsubstituted phenothiazine that corresponds to phenothiazine (B1).

[0097] <Non-phenothiazine Compound (B')> For comparison with the phenothiazine compound (B), the following two compounds known as antioxidants were used. Amine compounds: 4,4'-bis(α,α-dimethylbenzyl)diphenylamine Phenolic compounds: n-octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate

[0098] <Non-metallic thiophosphate compounds (C)> Triphenyl phosphorothioate (TPPT) was used. Triphenyl phosphorothioate is a compound corresponding to monothiophosphate triaryl ester (C11x), and is a compound in which n1, n2, and n3 are 0 in the above general formula (c-11x).

[0099] <Metal deactivator (D)> The benzotriazole compound represented by the following structural formula was used. The benzotriazole-based compound represented by the following structural formula is a compound corresponding to the benzotriazole-based compound (D1), and in the above general formula (d-1), R d1 is a methyl group, q is 1, and R d2 is a methylene group, and R d3 and R d4 is a compound that is a 2-ethylhexyl group. [ka]

[0100] <Other additives> Viscosity index improver: Polymethacrylate (mass average molecular weight: 300,000, resin content 19 mass%, diluent oil: diester oil (diisodecyl sebacate)) Dispersant: Succinimide dispersant (succinimide: 53% by mass, components other than succinimide: deuterated paraffin (diluent) and polybutene)

[0101] <Evaluation 1: Evaluation of evaporation characteristics> The evaporation characteristics of the lubricating oil compositions of Examples 1 and 2 and Comparative Examples 1 to 5 were evaluated according to the following procedure. The thermostatic chamber used was a thermostatic chamber equipped with a rotating disk (TST-9R model, manufactured by Yoshida Scientific Instruments Co., Ltd.) as specified in the lubricating oil thermal stability test method (JIS K 2540:2000). The sample container used was a glass container with an inner diameter of 53 mm and a depth of 56 mm. 2.0 g (±0.010 g) of the lubricating oil composition to be evaluated and 2.0 g (±0.010 g) of iron powder or copper powder were weighed into a sample container, and then placed in a thermostatic bath heated to 150°C. The samples were then removed at multiples of 24 hours and their weights were measured. The evaporation rate (wt%) was calculated from the weight before and after the test, and the time (days) until the evaporation rate began to rise sharply was defined as the evaporation life. Specifically, the coefficient of determination R 2 The number of test days when the evaporation rate became less than 0.9 was defined as the evaporation life. The longer the evaporation life, the better the evaporation characteristics of the lubricating oil composition. Conversely, the shorter the evaporation life, the poorer the evaporation characteristics of the lubricating oil composition. In this example, lubricating oil compositions with an evaporation life of 10 days or more were deemed to pass. For the lubricating oil compositions of Comparative Examples 2 to 5, no evaluation was carried out using copper powder.

[0102] <Evaluation 2: Evaluation of wear resistance> The lubricating oil compositions of Examples 1 and 2 and Comparative Example 1 were evaluated for wear resistance by the following procedure. A Shell four-ball wear test was conducted using a 0.5-inch ball made of SUJ-2 grade 20 at an oil temperature of 80°C, a rotation speed of 1200 rpm, a load of 392 N, and a test time of 60 minutes. The wear scar diameter (mm) of the fixed ball after the test was measured. The smaller the wear scar diameter, the better the wear resistance of the lubricating oil composition. Conversely, the larger the wear scar diameter, the poorer the wear resistance of the lubricating oil composition. In this example, lubricating oil compositions with a wear scar diameter of 0.90 mm or less were deemed to pass.

[0103] The results of Evaluation 1 and Evaluation 2 are shown in Table 1. In addition, "<" in Table 1 means "greater than."

[0104] [Table 1]

[0105] From Table 1, we can see the following: It is clear that the lubricating oil compositions of Examples 1 and 2 are excellent in both evaporation characteristics and wear resistance. In contrast, the lubricating oil composition of Comparative Example 1 ensures wear resistance but has poor evaporation characteristics.The lubricating oil compositions of Comparative Examples 2 to 5 all have poor evaporation characteristics.

[0106] <Evaluation 3: Evaluation of hydrolysis resistance> The lubricating oil compositions of Examples 1 and 2 and Comparative Example 1 were evaluated for hydrolysis resistance according to the following procedure. Using a rotating bomb oxidation stability tester (RBOT) and a sample container (RBOT test beaker) specified in JIS K 2514-3:2003, the lubricating oil composition to be evaluated was tested under the following conditions. After the test, the oil and water in the sample container were separated, and the acid value of the oil and the amount of copper eluted were evaluated. The acid value and the amount of copper eluted of the lubricating oil composition before the test were also measured. (Test conditions) ·Sample oil amount: 20g ·Catalyst: Copper powder 120mg Water: 1mL inside the beaker, 1mL outside the beaker Filling: Air (atmospheric pressure) ·Temperature: 150℃ Test duration: 24 hours The acid value of the oil was measured by a potentiometric method using TS1700 manufactured by Hiranuma Sangyo Co., Ltd. (HIRANUMA CORPORATION) in accordance with JIS K2501:2003. The amount of copper eluted from the oil was measured by ICP emission spectrometry using an ICPS-8100 manufactured by Shimadzu Corporation. The lower the acid value of the oil, the better the hydrolysis resistance. Conversely, the higher the acid value of the oil, the poorer the hydrolysis resistance. Furthermore, the smaller the amount of copper eluted from the oil, the better the hydrolysis resistance. Conversely, the greater the amount of copper eluted from the oil, the poorer the hydrolysis resistance. In this example, lubricating oil compositions in which the acid value of the oil after 24 hours was 5.00 mgKOH / g or less and the amount of copper eluted was 20 ppm by mass or less were deemed to pass.

[0107] The results of Evaluation 3 are shown in Table 2. In addition, ">" in Table 2 means "less than."

[0108] [Table 2]

[0109] It can be seen from Table 2 that all of the lubricating oil compositions of Examples 1 and 2 also have excellent hydrolysis resistance.

Claims

1. A lubricating oil composition comprising a base oil (A) containing an ester oil (A1), a phenothiazine compound (B), and a non-metallic thiophosphate ester compound (C).

2. 2. The lubricating oil composition according to claim 1, wherein the ester oil (A1) comprises a diester oil (A11).

3. The lubricating oil composition according to claim 1 or 2, wherein the non-metallic thiophosphate ester compound (C) comprises a thiophosphate ester (C1).

4. The lubricating oil composition according to claim 3, wherein the thiophosphate esters (C1) comprise one or more monothiophosphate triesters (C1x) represented by the following general formula (c-1x): 【Chemical 1】 [In the general formula (c-1x), each symbol represents the following.] R ｃ１ , R ｃ２ , and R ｃ３ each independently represents a saturated or unsaturated aliphatic hydrocarbon group having 1 to 18 carbon atoms, an optionally substituted saturated or unsaturated alicyclic hydrocarbon group having 5 to 18 carbon atoms, or an optionally substituted aromatic hydrocarbon group having 5 to 18 carbon atoms.]

5. The lubricating oil composition according to claim 4, wherein the monothiophosphate triester (C1x) comprises one or more selected from monothiophosphate triaryl esters (C11x) represented by the following general formula (c-11x): 【Chemistry 2】 [In the general formula (c-11x), each symbol represents the following.] R ｃ１１ , R ｃ１２ , and R ｃ１３ each independently represents an alkyl group having 1 to 3 carbon atoms. n1, n2, and n3 each independently represent an integer of 0 to 5.

6. The lubricating oil composition according to claim 1 or 2, further comprising a metal deactivator (D).

7. 3. The lubricating oil composition according to claim 1, wherein the content ratio of the phenothiazine compound (B) to the non-metallic thiophosphate ester compound (C) [(B) / (C)] is, in mass ratio, 1 / 10 to 10 / 1.

8. The lubricating oil composition according to claim 1 or 2, which is used as an impregnated bearing oil.

9. 3. A method for using the lubricating oil composition according to claim 1 or 2, wherein the lubricating oil composition is used as an impregnated bearing oil.

10. An oil-impregnated bearing impregnated with the lubricating oil composition according to claim 1 or 2.

11. A method for producing a lubricating oil composition, comprising the step of mixing a base oil (A) containing an ester oil (A1), a phenothiazine compound (B), and a non-metallic thiophosphate ester compound (C).

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