Lubricating oil composition

Abstract

The present application provides a lubricating oil composition of molybdenum dithiocarbamate, which is high in solubility, excellent in friction reduction, and excellent in oxidation stability and low evaporation. The lubricating oil composition contains a base oil (A) selected from one or more of Group III base oil and Group IV base oil in the base oil classification of the American Petroleum Institute, a polyol ester (B) containing an ester of a saturated fatty acid having 10 or more carbon atoms and neopentyl glycol, and molybdenum dithiocarbamate (C), with the molybdenum atom content being 150 to 1800 mass ppm based on the total amount of the lubricating oil composition.

Description

Technical Field

[0001] This invention relates to lubricating oil compositions. Background Technology

[0002] With the increasing stringency of environmental regulations in recent years, lubricating oil compositions (internal combustion engine oils) used in internal combustion engines of vehicles such as automobiles are required to have high fuel economy. As one method to meet these requirements, various studies have been conducted on methods of adding friction modifiers to lubricating oil compositions to reduce the coefficient of friction.

[0003] For example, there are known methods for reducing the coefficient of friction by incorporating a specific ether compound as a friction modifier into a lubricating oil composition (see, for example, Patent Document 1).

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 9-176668. Summary of the Invention

[0005] The problem that the invention aims to solve In addition, organomolybdenum compounds are also known as the aforementioned friction modifiers.

[0006] Furthermore, due to environmental concerns, the demand for longer-life internal combustion engine oils has been increasing in recent years. For example, methods to extend the life of internal combustion engine oils have been studied by using Group III or Group IV base oils, which have excellent oxidation stability and low volatility, as the main component.

[0007] However, among the aforementioned organomolybdenum compounds, especially molybdenum dithiocarbamate, although they have excellent friction-reducing properties, their solubility in the aforementioned Group III or Group IV base oils is extremely low.

[0008] Therefore, in order to simultaneously improve the friction reduction and extend the service life of the lubricating oil composition, when molybdenum dithiocarbamate is added to base oils classified as Group III or Group IV, there is a problem that molybdenum dithiocarbamate tends to precipitate and has low storage stability during long-term storage.

[0009] Patent document 1 discloses a (poly)glycerol ether with a specific structure as a friction modifier with high solubility in synthetic base oils, but does not conduct any research on the solubility of molybdenum dithiocarbamate in base oils.

[0010] To improve the various properties of internal combustion engine oils, it is necessary to use molybdenum dithiocarbamate in combination with base oils classified as Group III or IV. However, the solubility of molybdenum dithiocarbamate in Group III or IV base oils has not been adequately studied.

[0011] The present invention provides a lubricating oil composition with high solubility of molybdenum dithiocarbamate, excellent friction reduction properties, and excellent oxidation stability and low volatility.

[0012] Methods for solving problems The inventors have conducted in-depth research to solve the above-mentioned problems.

[0013] The results showed that the lubricating oil composition, wherein the base oil (A) is selected from one or more Group III and Group IV base oils in the American Petroleum Institute's base oil classification, the composition contains a polyol ester, the polyol ester comprising an ester of saturated fatty acids with more than 10 carbon atoms and neopentyl glycol, and the content of molybdenum dithiocarbamate is adjusted to a specific range, can solve the above-mentioned problems.

[0014] Based on the above insights, the inventors conducted further research and thus completed this invention.

[0015] According to the present invention, the following [1] is provided.

[0016] [1] A lubricating oil composition comprising a base oil (A), a polyol ester (B), and molybdenum dithiocarbamate (C). The base oil (A) is selected from one or more Group III and Group IV base oils in the American Petroleum Institute's base oil classification. The polyol ester (B) comprises an ester of a saturated fatty acid with more than 10 carbon atoms and neopentyl glycol. Based on the total amount of the lubricating oil composition, the molybdenum atomic content is 150 to 1800 ppm by mass.

[0017] Invention Effects According to the present invention, a lubricating oil composition with high solubility of molybdenum dithiocarbamate, excellent friction-reducing properties, and excellent oxidation stability and low volatility can be provided. Detailed Implementation

[0018] The upper and lower limits of the numerical ranges described in this specification can be combined arbitrarily. For example, when the numerical ranges of "A to B" and "C to D" are described, the numerical ranges of "A to D" and "C to B" are also included within the scope of this invention.

[0019] Furthermore, the numerical range “lower limit to upper limit” described in this specification, unless otherwise stated, refers to the value above the lower limit and below the upper limit.

[0020] Furthermore, in this specification, the numerical values ​​of the embodiments are numerical values ​​that can be used as upper or lower limits.

[0021] [Method of Lubricating Oil Composition] The lubricating oil composition of this embodiment contains a base oil (A), a polyol ester (B), and molybdenum dithiocarbamate (C). The base oil (A) is selected from one or more Group III and Group IV base oils in the American Petroleum Institute's base oil classification. The polyol ester (B) contains esters of saturated fatty acids with more than 10 carbon atoms and neopentyl glycol. The molybdenum atom content is 150 to 1800 ppm by mass based on the total amount of the lubricating oil composition.

[0022] In addition, in the following description, “base oil (A)”, “polyol ester (B)” and “molybdenum dithiocarbamate (C)” are also referred to as “component (A)”, “component (B)” and “component (C)”, respectively.

[0023] The lubricating oil composition of this embodiment may consist only of component (A), component (B) and component (C), but may further contain other components besides component (A), component (B) and component (C).

[0024] In the lubricating oil composition of this embodiment, the total content of component (A), component (B) and component (C), based on the total amount of the lubricating oil composition, is preferably 50% by mass or more, more preferably 60% by mass or more, further preferably 65% ​​by mass or more, even more preferably 70% by mass or more, even more preferably 75% by mass or more, and even more preferably 78% by mass or more.

[0025] The components contained in the lubricating oil composition of this embodiment will be described in detail below.

[0026] <Base Oil (A)> The lubricating oil composition of this embodiment contains one or more base oils selected from Group III and Group IV base oils in the American Petroleum Institute's base oil classification as base oil (A).

[0027] As a base oil (A), one or more mineral oils and synthetic oils selected from those previously used as base oils in lubricant compositions and classified as Group III and Group IV in the American Petroleum Institute's base oil classification may be used without particular restriction.

[0028] As a base oil classified as Group III of the American Petroleum Institute (API), any base oil that has been previously used as a base oil in lubricating oil compositions and is classified as Group III of the API can be used without particular restrictions. Examples include: mineral oils obtained by vacuum distillation of the residual oil from atmospheric distillation of crude oils such as paraffinic crude oil, intermediate-base crude oil, or naphthenic crude oil, and subjected to one or more refining processes such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining; GTL base oils obtained by isomerization of waxes (Gas To Liquids Wax) produced from natural gas through processes such as the Fischer-Tropsch process; and plant-derived hydrocarbon lubricating oil base oils (e.g., hydrides of the reaction products of octadecene and hexadecene, SynNova 4 Base Oil and SynNova 9 Base Oil manufactured by Novvi Corporation).

[0029] As a base oil classified as American Petroleum Institute (API) Base Oil Classification IV, there may be no particular restrictions on using base oils that have been previously used as base oils in lubricant compositions and are classified as API Base Oil Classification IV.

[0030] Mineral oil can be used alone or in combination with two or more. Synthetic oil can also be used alone or in combination with two or more. In addition, one or more mineral oils and one or more synthetic oils can be used in combination.

[0031] There are no particular limitations on the kinematic viscosity of the base oil (A), but the following range is preferred.

[0032] The kinematic viscosity of base oil (A) at 100°C (hereinafter also referred to as "kinematic viscosity at 100°C") is preferably 1.0 mm. 2 / s or higher and 21.9mm 2 / s or less, preferably 2.0mm 2 / s or higher and 16.3mm 2 / s or less, and more preferably 3.8mm 2 / s or higher and 12.5mm 2 / s or less.

[0033] There are no particular limitations on the viscosity index of the base oil (A), but the following range is preferred.

[0034] The viscosity index of the base oil (A) is preferably 120 or higher, more preferably 124 or higher, and even more preferably 130 or higher.

[0035] In this specification, the kinematic viscosity and viscosity index of base oil (A) at 100°C refer to the values ​​measured according to JIS K2283:2000.

[0036] Furthermore, when the base oil (A) is a blended base oil containing two or more base oils, the kinematic viscosity and viscosity index of the blended base oil at 100°C are preferably within the ranges described above.

[0037] In this embodiment, the content of base oil (A) in the lubricating oil composition, based on the total amount of the lubricating oil composition, is preferably 45.0% by mass or more, more preferably 50.0% by mass or more, and even more preferably 60.0% by mass or more. Furthermore, it is preferably 95.0% by mass or less, more preferably 90.0% by mass or less, and even more preferably 85.0% by mass or less.

[0038] The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, it is preferably 45.0% to 95.0% by mass, more preferably 50.0% to 90.0% by mass, and even more preferably 60.0% to 85.0% by mass.

[0039] <Polyol Ester (B)> The lubricating oil composition of this embodiment contains a polyol ester (B), and the polyol ester (B) comprises an ester of a saturated fatty acid having 10 or more carbon atoms and neopentyl glycol. By containing an ester of a saturated fatty acid having 10 or more carbon atoms and neopentyl glycol, the lubricating oil composition can improve the solubility of molybdenum dithiocarbamate (C) in the lubricating oil composition. While the reason is unclear, it is speculated that, for example, the effect of the polyol ester (B) with a specific structure in improving the solubility of molybdenum dithiocarbamate is balanced at a high level with the effect of the hydrocarbon groups of the fatty acid and neopentyl glycol in improving the oil solubility of the polyol ester (B).

[0040] Furthermore, since the fatty acids that constitute the polyol ester (B) do not contain unsaturated bonds, the oxidative stability of the lubricating oil composition can be improved.

[0041] Furthermore, since the fatty acids constituting the polyol ester (B) have 10 or more carbon atoms, the low volatility of the lubricating oil composition can be improved.

[0042] In this embodiment, the polyol ester (B) comprises, as described above, an ester of a saturated fatty acid with 10 or more carbon atoms and neopentyl glycol.

[0043] Neopentyl glycol is a compound represented by the following structural formula (b1).

[0044] [Chemistry 1] From the viewpoint of improving the low volatility of the lubricating oil composition, saturated fatty acids that are used as raw materials for forming polyol esters (B) are preferably saturated fatty acids with 10 or more carbon atoms, more preferably saturated fatty acids with 10 to 30 carbon atoms, even more preferably saturated fatty acids with 10 to 27 carbon atoms, even more preferably saturated fatty acids with 10 to 24 carbon atoms, and even more preferably saturated fatty acids with 10 to 20 carbon atoms.

[0045] In addition, the saturated fatty acids that make up polyol esters (B) can be linear or branched.

[0046] In addition, the polyol ester (B) can be a partial ester of neopentyl glycol or a full ester of neopentyl glycol, but from the viewpoint of easily exerting the effects of the present invention, a full ester containing neopentyl glycol is preferred.

[0047] There are no particular restrictions on saturated fatty acids that are the raw materials for forming polyol esters (B), as long as they have 10 or more carbon atoms. Examples include various decanoic acids, various undecanoic acids, various dodecanoic acids, various tridecanoic acids, various tetradecanoic acids, various pentadecanoic acids, various hexadecanoic acids, various heptadecanoic acids, various octadecanoic acids, various nonadecanoic acids, various eicosanoic acids, various docosanoic acids, various hexacosanoic acids, various octacosanoic acids, and various triacontanoic acids. Furthermore, in this specification, "various" in "various decanoic acids, etc." refers to substances including linear-chain forms and their structural isomers, i.e., branched-chain forms.

[0048] In this embodiment, the content of polyol ester (B), based on the total amount of the lubricating oil composition, is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, further preferably 0.4% by mass or more, and even more preferably 0.8% by mass or more. Furthermore, it is preferably 35% by mass or less, more preferably 30% by mass or less, further preferably 27% by mass or less, and even more preferably 25% by mass or less.

[0049] The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, the preferred values ​​are 0.1% to 35% by mass, more preferably 0.2% to 30% by mass, even more preferably 0.4% to 27% by mass, and even more preferably 0.8% to 25% by mass.

[0050] Furthermore, in this embodiment, the polyol ester (B) may contain esters other than esters of saturated fatty acids with 10 or more carbon atoms and neopentyl glycol, but from the viewpoint of easily exerting the effects of the present invention, it is preferable not to contain esters other than esters of saturated fatty acids with 10 or more carbon atoms and neopentyl glycol.

[0051] The content of esters in polyol ester (B) other than esters of saturated fatty acids with more than 10 carbon atoms and neopentyl glycol, based on the total amount of polyol ester (B), is preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.1% by mass or less, even more preferably 0.01% by mass, and even more preferably 0% by mass.

[0052] In the lubricating oil composition of this embodiment, these polyol esters (B) can be used alone or in combination with two or more.

[0053] <Ratio of base oil (A) to polyol ester (B)> From the viewpoint of making it easier to achieve the effects of the present invention, the content ratio of base oil (A) to polyol ester (B) [(A) / (B)] in the lubricating oil composition of this embodiment is preferably 1.0 to 800 by mass, more preferably 2.0 to 400, and even more preferably 2.5 to 200.

[0054] <Molybdenum dithiocarbamate (C)> The lubricating oil composition of this embodiment contains molybdenum dithiocarbamate (C), and based on the total amount of the lubricating oil composition, contains 150 to 1800 ppm by mass of molybdenum atoms derived from molybdenum dithiocarbamate (C). When the molybdenum atom content is 150 ppm by mass or more based on the total amount of the lubricating oil composition, friction-reducing properties can be fully utilized. Furthermore, when the molybdenum atom content is 1800 ppm by mass or less based on the total amount of the lubricating oil composition, storage stability can be fully utilized.

[0055] Examples of molybdenum dithiocarbamate (C) include: binuclear molybdenum dithiocarbamate containing two molybdenum atoms per molecule, and triuclear molybdenum dithiocarbamate containing three molybdenum atoms per molecule.

[0056] Examples of dinuclear molybdenum dithiocarbamate include compounds represented by the following general formula (c1) and compounds represented by the following general formula (c2).

[0057] [Chemistry 2] In the above general formulas (c1) and (c2), R 11 ~R 14 Each hydrocarbon group can be represented independently; they can be the same as or different from each other.

[0058] X 11 ~X 18 The oxygen atom or sulfur atom can represent each other independently, and they can be the same or different. However, X in formula (c1) 11 ~X 18At least two of them are sulfur atoms.

[0059] As R 11 ~R 14 The number of carbon atoms in the optional hydrocarbon group is preferably 6 to 22.

[0060] As an optional form of R in the above general formulas (c1) and (c2) 11 ~R 14 Examples of such hydrocarbon groups include alkyl, alkenyl, cycloalkyl, aryl, alkylaryl, arylalkyl, etc.

[0061] Examples of such alkyl groups include hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecanyl, octadecyl, etc.

[0062] Examples of alkenyl groups include hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, and pentadecenyl.

[0063] Examples of cyclohexyl groups include cyclohexyl, dimethylcyclohexyl, ethylcyclohexyl, methylcyclohexylmethyl, cyclohexylethyl, propylcyclohexyl, butylcyclohexyl, and heptylcyclohexyl.

[0064] Examples of aryl groups include phenyl, naphthyl, anthracene, biphenyl, and terphenyl.

[0065] Examples of alkylaryl groups include tolyl, dimethylphenyl, butylphenyl, nonylphenyl, and dimethylnaphthyl.

[0066] Examples of aryl alkyl groups include methyl benzyl, phenylmethyl, phenylethyl, and diphenylmethyl.

[0067] Among them, molybdenum dialkyl dithiocarbamate (C3) represented by the following structural formula (C3) is preferred.

[0068] [Chemistry 3] In the general formula (c3), R 1 R 2 R 3 and R 4 Each group independently represents a short-chain substituent group (α) representing an aliphatic hydrocarbon group with 4 to 12 carbon atoms, or a long-chain substituent group (β) representing an aliphatic hydrocarbon group with 13 to 22 carbon atoms. However, in the general formula (c3), X 1 X 2 X 3 and X 4 Each can be used to represent an oxygen atom or a sulfur atom independently.

[0069] Examples of aliphatic hydrocarbon groups with 4 to 12 carbon atoms that can be used as short-chain substituents (α) include alkyl groups with 4 to 12 carbon atoms and alkenyl groups with 4 to 12 carbon atoms.

[0070] Specifically, examples include butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, and dodecenyl. They can be linear or branched.

[0071] Furthermore, from the viewpoint that it is easier to exert the effects of the present invention, the number of carbon atoms of the aliphatic hydrocarbon group selected as the short-chain substituent group (α) is preferably 5 to 11, more preferably 6 to 10, and even more preferably 7 to 9.

[0072] Examples of aliphatic hydrocarbon groups with 13 to 22 carbon atoms that can be used as long-chain substituents (β) include alkyl groups with 13 to 22 carbon atoms and alkenyl groups with 13 to 22 carbon atoms.

[0073] Specifically, examples include tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecanyl, octadecyl, nonadecanyl, eicosyl, dodecyl, tridecylenyl, tetradecylenyl, pentadecylenyl, hexadecylenyl, heptadecanyl, octadecylenyl, oleylenyl, nonadecanylenyl, eicosylenyl, dodecylenyl, and dodecylenyl. They can be linear or branched.

[0074] Furthermore, from the viewpoint that it is easier to exert the effects of the present invention, the number of carbon atoms of the aliphatic hydrocarbon group that can be selected as the long-chain substituent (β) is preferably 13 to 20, more preferably 13 to 16, and even more preferably 13 to 14.

[0075] Here, the compound (C3) represented by the general formula (C3) may contain only one of the short-chain substituent group (α) or the long-chain substituent group (β), or it may contain both the short-chain substituent group (α) and the long-chain substituent group (β). Preferably, the molar ratio of the short-chain substituent group (α) to the long-chain substituent group (β) in its entire molecule [(α) / (β)] is 0 to 2.0. Furthermore, it is more preferable that the molar ratio of the short-chain substituent group (α) to the long-chain substituent group (β) in its entire molecule [(α) / (β)] is 0.050 to 2.0. When the molar ratio [(α) / (β)] is 0.050 or higher, it is easier to improve the friction reduction effect. Furthermore, when the molar ratio [(α) / (β)] is 2.0 or lower, it is easier to ensure low-temperature storage stability.

[0076] Here, from the viewpoint of making it easier to improve the friction reduction effect, the molar ratio [(α) / (β)] is preferably 0.060 or more, and more preferably 0.070 or more.

[0077] Furthermore, from the viewpoint of more easily ensuring low-temperature storage stability, the molar ratio [(α) / (β)] is preferably 1.8 or less, more preferably 1.5 or less, even more preferably 1.2 or less, and even more preferably 1.1 or less.

[0078] The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, the range is preferably 0.060 to 1.8, more preferably 0.070 to 1.5, even more preferably 0.070 to 1.2, and even more preferably 0.070 to 1.1.

[0079] Here, when compound (C3) contains both short-chain substituents (α) and long-chain substituents (β), the short-chain substituents (α) and long-chain substituents (β) may or may not coexist in the same molecule. That is, as long as the average molar ratio [(α) / (β)] of the short-chain substituents (α) to the long-chain substituents (β) in the whole molecule of compound (C3) represented by the general formula (C3) is in the range of 0.050 to 2.0.

[0080] Therefore, when compound (C3) contains both short-chain substituents (α) and long-chain substituents (β), R can coexist in compound (C3). 1 R 2 R 3 and R 4 Molecules consisting entirely of short-chain substituents (α) (c3-1) can also exist in mixtures with R. 1 R 2 R 3 and R 4 Molecules consisting entirely of long-chain substituents (β) (c3-2) can also coexist with R. 1 R 2 R 3 and R 4 A portion of the molecular group consists of short-chain substituents (α), and the remainder consists of long-chain substituents (β) (c3-3).

[0081] Examples of trinuclear dithiocarbamate molybdenum include compounds represented by the following general formula (c4).

[0082] Mo3S k E m L n A p Q z (c4) In the general formula (c4), k is an integer greater than or equal to 1, m is an integer greater than or equal to 0, k+m is an integer from 4 to 10, preferably an integer from 4 to 7. n is an integer from 1 to 4, p is an integer greater than or equal to 0, and z is an integer from 0 to 5, including non-stoichiometric values.

[0083] E can be an oxygen atom or a selenium atom, for example, it can replace sulfur in the core described later.

[0084] L are each anionic ligands that independently contain organic groups with carbon atoms. The total number of carbon atoms in the organic group of each ligand is more than 14. The ligands can be the same or different.

[0085] A can be an anion other than L.

[0086] Q is an independent neutral compound for supplying electrons, existing to satisfy vacancy coordination on the trinuclear molybdenum compound.

[0087] In the lubricating oil composition of this embodiment, the content of molybdenum atoms derived from molybdenum dithiocarbamate (C) is preferably 150 ppm by mass or more, more preferably 180 ppm by mass or more, further preferably 210 ppm by mass or more, even more preferably 240 ppm by mass or more, and still more preferably 270 ppm by mass or more, based on the total amount of the lubricating oil composition, from the viewpoint of improving the friction reduction of the lubricating oil composition.

[0088] Furthermore, from the viewpoint of improving the storage stability of the lubricating oil composition, it is preferable to have a mass of 1800 ppm or less, more preferably 1750 ppm or less, even more preferably 1700 ppm or less, even more preferably 1650 ppm or less, and even more preferably 1600 ppm or less.

[0089] The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, the range is preferably 150 ppm to 1800 ppm by mass, more preferably 180 ppm to 1750 ppm by mass, even more preferably 210 ppm to 1700 ppm by mass, even more preferably 240 ppm to 1650 ppm by mass, and even more preferably 270 ppm to 1600 ppm by mass.

[0090] Furthermore, in this specification, the molybdenum atomic content of the lubricating oil composition is a value determined according to JPI-5S-38-03.

[0091] In the lubricating oil composition of this embodiment, molybdenum dithiocarbamate (C) can be used alone or in combination with two or more.

[0092] <Viscosity Index Improver (D)> In the lubricating oil composition of this embodiment, it is preferable to further contain a viscosity index improver (D) in addition to components (A) to (C).

[0093] Examples of viscosity index improvers include comb-shaped polymers, non-dispersed polymethyl methacrylate (PMA), dispersed polymethyl methacrylate, olefin copolymers (olefin copolymers (OCPs); for example, ethylene-propylene copolymers), dispersed olefin copolymers, and styrene copolymers (for example, hydrogenated styrene-diene copolymers). Furthermore, viscosity index improvers can be used alone or in combination of two or more.

[0094] Here, comb-shaped polymers are preferred as viscosity index improvers (D).

[0095] Furthermore, the mass-average molecular weight (Mw) of the viscosity index improver (D) is preferably in the range of 50,000 to 1,000,000, more preferably in the range of 100,000 to 700,000, and even more preferably in the range of 150,000 to 500,000.

[0096] Furthermore, the molecular weight distribution (Mw / Mn) of the viscosity index improver is preferably 9.0 or less, more preferably 7.0 or less, even more preferably 5.0 or less, and even more preferably 3.5 or less, and is generally 1.01 or more.

[0097] In addition, the mass-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the viscosity index improver (D) were determined by gel permeation chromatography and calculated based on polystyrene.

[0098] The content of the viscosity index improver (D), based on the total amount of the lubricating oil composition, is preferably 2% to 20% by mass, more preferably 4% to 15% by mass, and even more preferably 5% to 13% by mass.

[0099] <Other Additives (E)> The lubricating oil composition of this embodiment may contain other components (hereinafter also referred to as "other additives") besides components (A), (B), (C) and (D) without significantly impairing the effects of the present invention, or it may not contain any of them.

[0100] Other additives (E) include, for example, metal detergents, dispersants, pour point depressants, antioxidants, anti-wear agents, friction modifiers other than molybdenum dithiocarbamate (C), extreme pressure agents, rust inhibitors, defoamers, oiliness improvers, metal passivators, and demulsifiers.

[0101] They can be used individually or in combination of two or more.

[0102] In the lubricating oil composition of this embodiment, the total content of other additives (E) is preferably 4.0% to 14.0% by mass, more preferably 6.0% to 12.0% by mass, and even more preferably 8.5% to 10.0% by mass, based on the total amount of the lubricating oil composition.

[0103] [Physical Properties of Lubricating Oil Compositions] <Kinematic viscosity and viscosity index at 100℃> The kinematic viscosity of the lubricating oil composition in this embodiment at 100°C is preferably 4.0 mm. 2 / s or higher and less than 21.9mm 2 / s, more preferably 5.0mm 2 / s or higher and less than 16.3mm 2 / s, further preferably 6.1mm 2 / s or higher and less than 12.5mm 2 / s.

[0104] Furthermore, the viscosity index of the lubricating oil composition of this embodiment is preferably 150 or higher, more preferably 155 or higher, and even more preferably 160 or higher.

[0105] In this specification, the kinematic viscosity and viscosity index of the lubricating oil composition at 100°C refer to the values ​​measured according to JIS K2283:2000.

[0106] <HTHS (High Temperature High Shear) viscosity at 150°C> The HTHS viscosity of the lubricating oil composition of this embodiment at 150°C is preferably 1.4 mPa·s or more, more preferably 1.7 mPa·s or more, even more preferably 2.0 mPa·s or more, and even more preferably 2.3 mPa·s or more. Furthermore, it is preferably 4.0 mPa·s or less, more preferably less than 3.7 mPa·s, even more preferably less than 3.0 mPa·s, and even more preferably less than 2.9 mPa·s.

[0107] The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, it is preferred to be 1.4 mPa·s or more and 4.0 mPa·s or less, more preferably 1.7 mPa·s or more and less than 3.7 mPa·s, further preferably 2.0 mPa·s or more and less than 3.0 mPa·s, and even more preferably 2.3 mPa·s or more and less than 2.9 mPa·s.

[0108] The HTHS viscosity of the lubricating oil composition of this embodiment at 150°C was determined using a TBS high-temperature viscometer (tapered bearing simulator viscometer) according to ASTM D4683 at a shear rate of 10... 6The measurement was performed at / s.

[0109] <Noack Evaporation> The evaporation loss of the lubricating oil composition of this embodiment, as determined by the Noack method, is preferably 13% by mass or less, more preferably 12% by mass or less, and even more preferably 10% by mass or less, based on the total amount of the lubricating oil composition.

[0110] In addition, Noack evaporation can be determined according to JPI-5S-41-2004 Method B.

[0111] <Oxidative Stability> The ratio of the kinematic viscosity of the lubricating oil composition at 100°C before and after the ISOT test performed using the method described in the following examples is preferably 1.20 or less, more preferably 1.15 or less, even more preferably 1.10 or less, and even more preferably 1.05 or less.

[0112] <Coefficient of Friction> The lubricating oil composition of this embodiment, as the coefficient of friction determined by the SRV test described in the following examples, preferably has a coefficient of friction of 0.08 or less, more preferably 0.07 or less, and even more preferably 0.06 or less.

[0113] [Method for manufacturing lubricating oil composition] The method for manufacturing the lubricating oil composition in this embodiment is not particularly limited.

[0114] For example, the method for manufacturing the lubricating oil composition of this embodiment includes a step of mixing a base oil (A), a polyol ester (B), and molybdenum dithiocarbamate (C). The base oil (A) is selected from one or more Group III and Group IV base oils in the American Petroleum Institute's base oil classification. The polyol ester (B) comprises an ester of a saturated fatty acid with more than 10 carbon atoms and neopentyl glycol. The adjustment resulted in a molybdenum atom content of 150 to 1800 ppm by mass, based on the total amount of the lubricating oil composition.

[0115] In the above process, when additives other than components (A) to (C) are added, the additives can be added simultaneously with components (A) to (C) or separately. Alternatively, each component can be added to diluent oil or the like to prepare a solution (dispersion) before being added.

[0116] After combining the ingredients, it is preferable to stir them using a known method to ensure uniform dispersion.

[0117] Furthermore, the preferred methods for each of the above components are as described above.

[0118] [Uses of Lubricating Oil Compositions] In the lubricating oil composition of this embodiment, molybdenum dithiocarbamate has high solubility, excellent friction reduction properties, and excellent oxidation stability and low volatility.

[0119] Therefore, the lubricating oil composition of this embodiment is preferably used in internal combustion engines, i.e., as an internal combustion engine oil, more preferably in automobile engines, and even more preferably in gasoline engines. Furthermore, it is also suitable for use in automobile engines equipped with hybrid powertrains.

[0120] Therefore, the lubricating oil composition of this embodiment provides the following (1) to (4). (1) A method of using the lubricating oil composition of this embodiment in an internal combustion engine. (2) A method of using the lubricating oil composition of this embodiment in an automobile engine. (3) A method of using the lubricating oil composition of this embodiment in a gasoline engine. (4) A method of using the lubricating oil composition of this embodiment in an automobile engine equipped with a hybrid power system.

[0121] [Lubrication methods using lubricating oil compositions] As described in the description of the application of the lubricating oil composition, the lubricating oil composition of this embodiment is preferably used in internal combustion engines, more preferably in automobile engines, and even more preferably in gasoline engines. Furthermore, it is also suitable for use in automobile engines equipped with hybrid powertrains.

[0122] Therefore, the lubricating oil composition of this embodiment provides the following (5) to (8). (5) A lubrication method for an internal combustion engine using the lubricating oil composition of this embodiment. (6) A lubrication method for an automobile engine using the lubricating oil composition of this embodiment. (7) A lubrication method for a gasoline engine using the lubricating oil composition of this embodiment. (8) A lubrication method for an automobile engine equipped with a hybrid powertrain using the lubricating oil composition of this embodiment.

[0123] [The method of the present invention provided] In one aspect of the present invention, the following [1] to [6] are provided.

[0124] [1] A lubricating oil composition comprising a base oil (A), a polyol ester (B), and molybdenum dithiocarbamate (C). The base oil (A) is selected from one or more Group III and Group IV base oils in the American Petroleum Institute's base oil classification. The polyol ester (B) comprises an ester of a saturated fatty acid with more than 10 carbon atoms and neopentyl glycol. Based on the total amount of the lubricating oil composition, the molybdenum atomic content is 150 to 1800 ppm by mass.

[0125] [2] The lubricating oil composition according to [1], wherein the saturated fatty acid has 10 to 30 carbon atoms.

[0126] [3] The lubricating oil composition according to [1] or [2], wherein the content of esters other than saturated fatty acids with more than 10 carbon atoms and neopentyl glycol esters is less than 5% by mass based on the total amount of the polyol esters (B).

[0127] [4] The lubricating oil composition according to any one of [1] to [3], wherein the content of the polyol ester (B) is 30% by mass or less based on the total amount of the lubricating oil composition.

[0128] [5] The lubricating oil composition according to any one of [1] to [4] further contains a viscosity index improver.

[0129] [6] The lubricating oil composition according to any one of [1] to [5] is used as an internal combustion engine oil. Example

[0130] The present invention will be specifically described below through embodiments. However, the present invention is not limited to the following embodiments.

[0131] [Methods for determining various physical properties] The determination of the properties of each raw material used in each embodiment and each comparative example, as well as the properties of the lubricating oil compositions in each embodiment and each comparative example, was carried out according to the following guidelines.

[0132] (1) Kinematic viscosity and viscosity index at 100℃ The kinematic viscosity and viscosity index of the base oil and lubricating oil composition at 100°C were determined or calculated according to JIS K2283:2000.

[0133] (2) HTHS viscosity at 150℃ According to ASTM D4683, using a TBS high-temperature viscometer (tapered bearing simulator viscometer), at a temperature of 150°C and a shear rate of 10... 6 The measurement was performed at / s.

[0134] (3) Molybdenum atomic content The determination was performed according to JPI-5S-38-03.

[0135] [Examples 1-9, Comparative Examples 1-6] The following components were mixed to prepare a lubricating oil composition having the compositions shown in Tables 1 and 2, and the following evaluation was conducted.

[0136] The detailed descriptions of each component used to prepare the lubricating oil compositions shown in Tables 1 and 2 are as follows.

[0137] <Base Oil (A)> • Base Oil 1: Classified as Group III base oil by the American Petroleum Institute (kinematic viscosity at 100°C = 4.3 mm). 2 ( / s, viscosity index 137) • Base Oil 2: Synthetic oil classified as Group IV by the American Petroleum Institute (kinematic viscosity at 100°C = 3.9 mm). 2 ( / s, viscosity index 124) • Base Oil 3: Synthetic oil classified as Group IV by the American Petroleum Institute (kinematic viscosity at 100°C = 5.9 mm). 2 ( / s, viscosity index 132) <Polyol Ester (B)> Ester 1: A diester obtained by reacting a branched 18-carbon saturated fatty acid with neopentyl glycol (kinematic viscosity at 100°C = 8.2 mm). 2 ( / s, viscosity index 151) • Ester 2: A diester obtained by reacting a branched 8-carbon saturated fatty acid with neopentyl glycol (kinematic viscosity at 100°C = 2.0 mm). 2 ( / s, viscosity index 47) Ester 3: A diester obtained by reacting a branched, 18-carbon unsaturated fatty acid with neopentyl glycol (kinematic viscosity at 100°C = 7.2 mm). 2 ( / s, viscosity index 196) Ester 4: A diester obtained by reacting a 10-carbon straight-chain saturated fatty acid with neopentyl glycol (kinematic viscosity at 100°C = 2.9 mm). 2 ( / s, viscosity index 141) <Molybdenum dithiocarbamate (C)> • Dinuclear molybdenum dithiocarbamate represented by the following general formula (c3) (molybdenum atom content: 10.0% by mass, sulfur atom content: 11.5% by mass) [Chemistry 4] In the general formula (c3), R 1 R 2 R 3 and R 4 The molar ratio of isooctyl to isotriadecyl in the total molecule of dialkyldithiocarbamate molybdenum is 50:50, independently selected from isooctyl (8 carbon atoms: short chain substituent group) and isotriadecyl (13 carbon atoms: long chain substituent group). 1 and X 2is a sulfur atom, X 3 and X 4 is an oxygen atom.

[0138] In addition, it is denoted as "MoDTC" in the table.

[0139] <Viscosity Index Improver (D)> ·Comb polymer (weight average molecular weight (Mw): 260,000, molecular weight distribution (Mw / Mn): 3.1) <Other Additives (E)> ·Zinc dialkyldithiophosphate, metallic detergent, dispersant, antioxidant, pour point depressant, antifoaming agent [Evaluation Methods] The tests described below are carried out to perform various evaluations.

[0140] [Noack Method Evaporation Loss] The measurement is performed in accordance with JPI-5S-41-2004 Method B.

[0141] In addition, when the evaporation loss measured by the Noack method is 13 mass% or less based on the total amount of the lubricating oil composition, the lubricating oil composition is evaluated as being excellent in low volatility.

[0142] [Storage Stability] (1) Test Method 100 mL of each of the lubricating oil compositions of Examples 1 to 9 and Comparative Examples 1 to 6 was placed in a 100 mL glass bottle, allowed to stand at -5°C for 5 days, and then returned to room temperature, whereupon the presence or absence of precipitate formation was judged.

[0143] The presence or absence of precipitate formation is judged visually.

[0144] (2) Evaluation Criteria A lubricating oil composition with no precipitate formed is judged as acceptable, and a lubricating oil composition with precipitate formed is judged as unacceptable.

[0145] In addition, "Evaluation A" in the evaluation results shown in Tables 1 and 2 means acceptable, and "Evaluation B" means unacceptable.

[0146] [Oxidation Stability] A copper piece and an iron piece as catalysts are placed in the test oil (lubricating oil composition), and an ISOT test according to JIS K2514-1:2013 is performed to forcibly degrade the test oil. The test temperature (oil temperature) is set to 165.5°C. Then, for the test oil 96 hours after the start of the ISOT test, the ratio of the kinematic viscosity at 100°C relative to that of the lubricating oil composition (fresh oil) before the ISOT test is measured.

[0147] The smaller the ratio of kinematic viscosity at 100°C, the better the oxidation stability.

[0148] Furthermore, if the ratio of kinematic viscosity at 100°C is 1.05 or less, the lubricating oil composition is evaluated as having excellent oxidation stability.

[0149] [Coefficient of Friction] The coefficient of friction of the prepared lubricating oil composition was determined using an SRV testing machine (manufactured by Optimol) under the following conditions.

[0150] The smaller the coefficient of friction, the better the friction reduction performance.

[0151] Furthermore, the average friction coefficient from 20 minutes after the start of the test to 10 minutes after the end of the test is taken as the friction coefficient. If the friction coefficient is 0.08 or less, the lubricating oil composition is evaluated as having excellent friction-reducing properties.

[0152] • Cylinder: SUJ-2 • Standard plate: AISI 52100 (maximum height roughness (Rz): 0.45~0.65μm) • Mirror finish: AISI 52100 (maximum height roughness (Rz): less than 0.20μm) • Frequency: 50Hz • Amplitude: 1.5mm • Load: 400N Temperature: 80℃ • Test duration: 30 minutes The properties of each lubricating oil composition and the results of each test are shown in Tables 1 and 2.

[0153] [Table 1] .

[0154] [Table 2] .

[0155] <Evaluation Results> The following information can be obtained from Tables 1 and 2.

[0156] It is evident that the lubricating oil compositions of Examples 1-9 exhibit good storage stability and excellent solubility of molybdenum dithiocarbamate (C). Furthermore, they demonstrate superior performance in all aspects, including friction reduction, low volatility, and oxidation stability.

[0157] In contrast, the lubricating oil composition that does not contain polyol ester (B), such as the lubricating oil composition of Comparative Example 2, has poor storage stability and poor solubility of molybdenum dithiocarbamate (C) compared to Examples 1-9.

[0158] Furthermore, as with the lubricating oil compositions of Comparative Examples 1 and 3, lubricating oil compositions with a molybdenum atom content of less than 150 ppm by mass based on the total amount of the lubricating oil composition have poor friction reduction properties; as with the lubricating oil composition of Comparative Example 4, lubricating oil compositions with a molybdenum atom content of more than 1800 ppm by mass based on the total amount of the lubricating oil composition have poor storage stability and poor solubility of molybdenum dithiocarbamate (C).

[0159] In addition, as with the lubricating oil composition of Comparative Example 5, the lubricating oil composition in which the fatty acid constituting the polyol ester (B) has less than 10 carbon atoms has poor low volatility; as with the lubricating oil composition of Comparative Example 6, the lubricating oil composition in which the fatty acid constituting the polyol ester (B) is an unsaturated fatty acid has poor oxidative stability.

Claims

1. A lubricating oil composition comprising a base oil (A), a polyol ester (B), and molybdenum dithiocarbamate (C). The base oil (A) is selected from one or more Group III and Group IV base oils in the American Petroleum Institute's base oil classification. The polyol ester (B) comprises an ester of a saturated fatty acid with more than 10 carbon atoms and neopentyl glycol. Based on the total amount of the lubricating oil composition, the molybdenum atomic content is 150 to 1800 ppm by mass.

2. The lubricating oil composition according to claim 1, wherein, The saturated fatty acid has 10 to 30 carbon atoms.

3. The lubricating oil composition according to claim 1 or 2, wherein, The content of esters other than saturated fatty acids with more than 10 carbon atoms and neopentyl glycol esters is less than 5% by mass based on the total amount of the polyol esters (B).

4. The lubricating oil composition according to any one of claims 1 to 3, wherein, The content of the polyol ester (B) is less than 30% by mass based on the total amount of the lubricating oil composition.

5. The lubricating oil composition according to any one of claims 1 to 4, further comprising a viscosity index improver.

6. The lubricating oil composition according to any one of claims 1 to 5, which is used as an internal combustion engine oil.

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