Lubricating oil composition

Abstract

To provide a lubricating oil composition having high solubility of molybdenum dithiocarbamate, excellent in friction-reducing properties, and excellent in oxidation stability and low volatility.SOLUTION: A lubricating oil composition comprises a base oil (A), a polyol ester (B), and a molybdenum dithiocarbamate (C), wherein: the base oil (A) is one or more base oils selected from Group III base oils and Group IV base oils in the base oil classification by the American Petroleum Institute; the polyol ester (B) contains an ester of a 10C or more saturated fatty acid and neopentyl glycol; and a molybdenum atom content is 150 to 1,800 mass ppm based on the total amount of the lubricating oil composition.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] With the recent strengthening of environmental regulations, high fuel economy is being demanded of lubricating oil compositions (internal combustion oils) used in the internal combustion engines of vehicles such as automobiles. As one method for meeting such demands, various methods have been investigated for reducing the coefficient of friction by blending a friction modifier into the lubricating oil composition. For example, a method is known in which a specific ether compound is blended as a friction modifier in a lubricating oil composition to reduce the coefficient of friction (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-176668 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, organic molybdenum compounds are also known as the above-mentioned friction modifiers. Furthermore, due to environmental considerations, there has been a growing need in recent years to extend the life of internal combustion oils. For example, methods have been studied to extend the life of internal combustion oils by using, as the main component, base oils that are classified as Group III or IV in the American Petroleum Institute (API) base oil classification, which have excellent oxidation stability and low volatility. However, among the above-mentioned organic molybdenum compounds, molybdenum dithiocarbamate in particular has excellent friction-reducing properties, but has extremely low solubility in the base oils classified into the above-mentioned Groups III and IV. Therefore, when molybdenum dithiocarbamate is added to a base oil classified as Group III or IV in order to achieve both improved friction reduction and extended life of a lubricating oil composition, there is a problem in that the molybdenum dithiocarbamate is prone to precipitate during long-term storage, resulting in poor storage stability. Patent Document 1 discloses a (poly)glycerin ether having a specific structure as a friction modifier that is highly soluble in synthetic base oils, but does not consider the solubility of molybdenum dithiocarbamate in base oils. To improve various performance characteristics of internal combustion engine oils, it is necessary to combine molybdenum dithiocarbamates with base oils classified as Group III or IV. However, the solubility of molybdenum dithiocarbamates in base oils classified as Group III or IV has not yet been fully investigated.

[0005] An object of the present invention is to provide a lubricating oil composition that has high solubility of molybdenum dithiocarbamate, excellent friction-reducing properties, oxidation stability, and low evaporation properties. [Means for solving the problem]

[0006] The present inventors have conducted extensive research to solve the above problems. As a result, they found that the above-mentioned problems can be solved by a lubricating oil composition in which the base oil (A) is one or more selected from Group III base oils and Group IV base oils in the base oil classification of the American Petroleum Institute, the composition contains a polyol ester, the polyol ester contains an ester of a saturated fatty acid having 10 or more carbon atoms and neopentyl glycol, and the content of molybdenum dithiocarbamate is adjusted to a specific range. Based on the above findings, the present inventors have further conducted various studies and have completed the present invention.

[0007] According to the present invention, the following [1] is provided. [1] A lubricating oil composition containing a base oil (A), a polyol ester (B), and a molybdenum dithiocarbamate (C), The base oil (A) is at least one selected from Group III base oils and Group IV base oils according to the base oil classification of the American Petroleum Institute; the polyol ester (B) contains an ester of a saturated fatty acid having 10 or more carbon atoms and neopentyl glycol, A lubricating oil composition having a molybdenum atom content of 150 to 1800 ppm by mass based on the total amount of the lubricating oil composition. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a lubricating oil composition which has high solubility of molybdenum dithiocarbamate, excellent friction reducing properties, oxidation stability and low evaporation properties. DETAILED DESCRIPTION OF THE INVENTION

[0009] The upper and lower limits of the ranges described herein can be combined in any way. For example, when the ranges are "A to B" and "C to D," the ranges "A to D" and "C to B" are also included in the scope of the present invention. Furthermore, unless otherwise specified, the numerical range "lower limit to upper limit" described in this specification means that the range is equal to or greater than the lower limit and equal to or less than the upper limit. In this specification, the numerical values ​​in the examples are numerical values ​​that can be used as upper or lower limit values.

[0010] [Embodiments of Lubricating Oil Composition] The lubricating oil composition of this embodiment contains a base oil (A), a polyol ester (B), and a molybdenum dithiocarbamate (C), wherein the base oil (A) is one or more selected from Group III base oils and Group IV base oils in the base oil classification of the American Petroleum Institute, the polyol ester (B) comprises an ester of a saturated fatty acid having 10 or more carbon atoms and neopentyl glycol, and the molybdenum atom content is 150 to 1800 ppm by mass based on the total amount of the lubricating oil composition.

[0011] In the following description, the "base oil (A)," the "polyol ester (B)," and the "molybdenum dithiocarbamate (C)" will also be referred to as "component (A)," "component (B)," and "component (C)," respectively.

[0012] The lubricating oil composition of the present embodiment may be composed only of component (A), component (B), and component (C), but may also contain other components in addition to component (A), component (B), and component (C). In the lubricating oil composition of this embodiment, the total content of component (A), component (B), and component (C) is preferably 50 mass% or more, more preferably 60 mass% or more, even more preferably 65 mass% or more, still more preferably 70 mass% or more, even more preferably 75 mass% or more, and even more preferably 78 mass% or more, based on the total amount of the lubricating oil composition.

[0013] Each component contained in the lubricating oil composition of this embodiment will be described in detail below.

[0014] <Base oil (A)> The lubricating oil composition of this embodiment contains, as base oil (A), one or more base oils selected from those classified into Groups III and IV of the American Petroleum Institute's base oil classification. As the base oil (A), one or more types selected from the group consisting of mineral oils and synthetic oils classified into Groups III and IV of the American Petroleum Institute base oil classification, which have conventionally been used as base oils for lubricating oil compositions, can be used without particular limitation.

[0015] The base oil classified as Group III of the American Petroleum Institute's base oil classification can be any base oil classified as Group III of the American Petroleum Institute's base oil classification that has been conventionally used as a base oil for lubricating oil compositions, and can be used without any particular limitation. Examples include mineral oils obtained by vacuum distillation of atmospheric residue obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate crude oil, or naphthenic crude oil, followed by one or more refining processes such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining; GTL base oils obtained by isomerizing wax produced from natural gas by the Fischer-Tropsch process (GTL wax, Gas to Liquids Wax); and plant-derived hydrocarbon lubricating base oils (e.g., SynNova® 4 Base Oil and SynNova® 9 Base Oil manufactured by Novvi, which are hydrogenated products of the reaction product of octadecene and hexadecene).

[0016] As the base oil classified in Group IV of the American Petroleum Institute's base oil classification, any base oil classified in Group IV of the American Petroleum Institute's base oil classification that has conventionally been used as a base oil for lubricating oil compositions can be used without particular limitation.

[0017] The mineral oils may be used alone or in combination of two or more. The synthetic oils may be used alone or in combination of two or more. Furthermore, one or more mineral oils may be used in combination with one or more synthetic oils.

[0018] There are no particular restrictions on the kinematic viscosity of the base oil (A), but it is preferable to set it within the following range. The base oil (A) preferably has a kinematic viscosity at 100°C (hereinafter also referred to as "100°C kinematic viscosity") of 1.0 mm 2 / s or more 21.9mm 2 / s or less, preferably 2.0 mm 2 / s or more 16.3mm 2 / s or less, more preferably 3.8 mm 2 / s or more 12.5mm 2 / s or less.

[0019] There are no particular restrictions on the viscosity index of the base oil (A), but it is preferable that it be in the following range. The base oil (A) preferably has a viscosity index of 120 or more, more preferably 124 or more, and even more preferably 130 or more. In this specification, the 100°C kinematic viscosity and viscosity index of the base oil (A) refer to values ​​measured in accordance with JIS K2283:2000. When the base oil (A) is a mixed base oil containing two or more types of base oils, the kinematic viscosity at 100°C and viscosity index of the mixed base oil preferably fall within the above ranges.

[0020] In this embodiment, the content of base oil (A) in the lubricating oil composition is preferably 45.0 mass% or more, more preferably 50.0 mass% or more, and even more preferably 60.0 mass% or more, based on the total amount of the lubricating oil composition, and is preferably 95.0 mass% or less, more preferably 90.0 mass% or less, and even more preferably 85.0 mass% or less. The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, the content is preferably 45.0 to 95.0 mass%, more preferably 50.0 to 90.0 mass%, and even more preferably 60.0 to 85.0 mass%.

[0021] <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. The inclusion of an ester of a saturated fatty acid having 10 or more carbon atoms and neopentyl glycol in the lubricating oil composition improves the solubility of the molybdenum dithiocarbamate (C) in the lubricating oil composition. While the reason for this is unclear, it is presumed that a high level of balance is achieved between the effect of improving the solubility of the molybdenum dithiocarbamate by the polyol ester (B) having a specific structure and the effect of improving the oil solubility of the polyol ester (B) by the hydrocarbon groups of the fatty acid and the hydrocarbon groups of neopentyl glycol. Furthermore, since the fatty acid constituting the polyol ester (B) does not contain an unsaturated bond, the oxidation stability of the lubricating oil composition can be improved. Furthermore, when the fatty acid constituting the polyol ester (B) has 10 or more carbon atoms, the low volatility of the lubricating oil composition can be improved.

[0022] In this embodiment, the polyol ester (B) contains an ester of a saturated fatty acid having 10 or more carbon atoms and neopentyl glycol, as described above. Neopentyl glycol is a compound represented by the following structural formula (b1).

[0023] [ka]

[0024] As the saturated fatty acid used as the raw material for the polyol ester (B), from the viewpoint of improving the low volatility of the lubricating oil composition, saturated fatty acids having 10 or more carbon atoms are preferred, saturated fatty acids having 10 to 30 carbon atoms are more preferred, saturated fatty acids having 10 to 27 carbon atoms are even more preferred, saturated fatty acids having 10 to 24 carbon atoms are even more preferred, and saturated fatty acids having 10 to 20 carbon atoms are even more preferred. The saturated fatty acid constituting the polyol ester (B) may be either linear or branched. Furthermore, the polyol ester (B) may be a partial ester or a complete ester of neopentyl glycol, but it is preferable that it contains a complete ester of neopentyl glycol from the viewpoint of making it easier to achieve the effects of the present invention.

[0025] The saturated fatty acid used as the raw material for polyol ester (B) is not particularly limited as long as it has 10 or more carbon atoms, and specific 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 icosanoic acids, various docosanoic acids, various tetracosanoic acids, various hexacosanoic acids, various octacosanoic acids, various triacontanoic acids, etc. In this specification, the term "various" in "various decanoic acids" includes linear and branched structural isomers thereof.

[0026] In this embodiment, the content of the polyol ester (B) is, based on the total amount of the lubricating oil composition, preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.4% by mass or more, and still more preferably 0.8% by mass or more, and is preferably 35% by mass or less, more preferably 30% by mass or less, even more preferably 27% by mass or less, and still more preferably 25% by mass or less. The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, the content is preferably 0.1 to 35% by mass, more preferably 0.2 to 30% by mass, even more preferably 0.4 to 27% by mass, and still more preferably 0.8 to 25% by mass.

[0027] In this embodiment, the polyol ester (B) may contain an ester other than the ester of a saturated fatty acid having 10 or more carbon atoms and neopentyl glycol. However, from the viewpoint of easily achieving the effects of the present invention, it is preferable that the polyol ester (B) does not contain an ester other than the ester of a saturated fatty acid having 10 or more carbon atoms and neopentyl glycol. The content of esters other than esters of saturated fatty acids having 10 or more carbon atoms and neopentyl glycol in the 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, still more preferably 0.01% by mass, and even more preferably 0% by mass, based on the total amount of the polyol ester (B).

[0028] In the lubricating oil composition of this embodiment, these polyol esters (B) may be used alone or in combination of two or more.

[0029] <Base oil (A) and polyol ester (B) content ratio> In order to more easily exert the effects of the present invention, the lubricating oil composition of this embodiment preferably has a mass ratio of the base oil (A) to the polyol ester (B) [(A) / (B)] of 1.0 to 800, more preferably 2.0 to 400, and even more preferably 2.5 to 200.

[0030] <Molybdenum dithiocarbamate (C)> The lubricating oil composition of this embodiment contains molybdenum dithiocarbamate (C) and contains 150 to 1800 ppm by mass of molybdenum atoms derived from the molybdenum dithiocarbamate (C) based on the total amount of the lubricating oil composition. When the content of molybdenum atoms is 150 ppm by mass or more based on the total amount of the lubricating oil composition, sufficient friction reducing properties can be exhibited. Furthermore, when the content of molybdenum atoms is 1800 ppm by mass or less based on the total amount of the lubricating oil composition, sufficient storage stability can be exhibited. Examples of the molybdenum dithiocarbamate (C) include binuclear molybdenum dithiocarbamates containing two molybdenum atoms in one molecule, and trinuclear molybdenum dithiocarbamates containing three molybdenum atoms in one molecule.

[0031] Examples of the dinuclear molybdenum dithiocarbamate include a compound represented by the following general formula (c1) and a compound represented by the following general formula (c2).

[0032] [ka]

[0033] In the above general formulas (c1) and (c2), R 11 ~R 14each independently represents a hydrocarbon group, and these may be the same or different. X 11 ~X 18 Each independently represents an oxygen atom or a sulfur atom, and may be the same as or different from each other. However, X in formula (c1) 11 ~X 18 At least two of the groups are sulfur atoms. R 11 ~R 14 The hydrocarbon group that can be selected as the alkyl group preferably has 6 to 22 carbon atoms.

[0034] R in the above general formulas (c1) and (c2) 11 ~R 14 Examples of the hydrocarbon group that can be selected as include an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an alkylaryl group, and an arylalkyl group. Examples of the alkyl group include a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, and an octadecyl group. Examples of the alkenyl group include a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, an undecenyl group, a dodecenyl group, a tridecenyl group, a tetradecenyl group, and a pentadecenyl group. Examples of the cycloalkyl group include a cyclohexyl group, a dimethylcyclohexyl group, an ethylcyclohexyl group, a methylcyclohexylmethyl group, a cyclohexylethyl group, a propylcyclohexyl group, a butylcyclohexyl group, and a heptylcyclohexyl group. Examples of the aryl group include a phenyl group, a naphthyl group, an anthracenyl group, a biphenyl group, and a terphenyl group. Examples of the alkylaryl group include a tolyl group, a dimethylphenyl group, a butylphenyl group, a nonylphenyl group, and a dimethylnaphthyl group. Examples of the arylalkyl group include a methylbenzyl group, a phenylmethyl group, a phenylethyl group, and a diphenylmethyl group.

[0035] Among these, dialkylmolybdenum dithiocarbamate (C3) represented by the following structural formula (c3) is preferred. [ka]

[0036] In the general formula (c3), R 1 , R 2 , R 3 , and R 4 each independently represents a group of short-chain substituents (α) that are aliphatic hydrocarbon groups having 4 to 12 carbon atoms or a group of long-chain substituents (β) that are aliphatic hydrocarbon groups having 13 to 22 carbon atoms, provided that in the general formula (c3), X 1 , X 2 , X 3 , and X 4 each independently represents an oxygen atom or a sulfur atom.

[0037] Examples of the aliphatic hydrocarbon group having 4 to 12 carbon atoms that can be selected as the short-chain substituent group (α) include an alkyl group having 4 to 12 carbon atoms and an alkenyl group having 4 to 12 carbon atoms. Specific examples include butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, and dodecenyl groups, which may be linear or branched. The number of carbon atoms in the aliphatic hydrocarbon group that can be 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, from the viewpoint of making it easier to exhibit the effects of the present invention.

[0038] Examples of the aliphatic hydrocarbon group having 13 to 22 carbon atoms that can be selected as the long-chain substituent group (β) include an alkyl group having 13 to 22 carbon atoms and an alkenyl group having 13 to 22 carbon atoms. Specific examples include tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, icosyl, henicosyl, docosyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl, oleyl, nonadecenyl, icosenyl, henicosyl, and docosenyl groups. These may be linear or branched. The number of carbon atoms in the aliphatic hydrocarbon group that can be selected as the long-chain substituent group (β) is preferably 13 to 20, more preferably 13 to 16, and even more preferably 13 to 14, from the viewpoint of making it easier to exhibit the effects of the present invention.

[0039] Here, the compound (C3) represented by the general formula (c3) may contain only the short-chain substituent group (α) or the long-chain substituent group (β), or 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 the whole molecule [(α) / (β)] is 0 to 2.0. More preferably, the molar ratio of the short-chain substituent group (α) to the long-chain substituent group (β) in the whole molecule [(α) / (β)] is 0.050 to 2.0. When the molar ratio [(α) / (β)] is 0.050 or more, the friction-reducing effect is easily improved. Furthermore, when the molar ratio [(α) / (β)] is 2.0 or less, low-temperature storage stability is easily ensured. Here, from the viewpoint of making it easier to improve the friction-reducing effect, the molar ratio [(α) / (β)] is preferably 0.060 or more, and more preferably 0.070 or more. Furthermore, from the viewpoint of making it easier to ensure 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 still more preferably 1.1 or less. 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 still more preferably 0.070 to 1.1.

[0040] When compound (C3) contains both short-chain substituent group (α) and long-chain substituent group (β), the short-chain substituent group (α) and the long-chain substituent group (β) may or may not coexist in the same molecule. That is, the average molar ratio [(α) / (β)] of the short-chain substituent group (α) to the long-chain substituent group (β) in all molecules of compound (C3) represented by general formula (c3) may be in the range of 0.050 to 2.0. Therefore, when the compound (C3) contains both the short-chain substituent group (α) and the long-chain substituent group (β), the compound (C3) contains R 1 , R 2 , R 3 and R 4 may be mixed with a group of molecules (c3-1) in which all of R are short-chain substituent groups (α), 1 , R 2 , R 3 and R 4 A group of molecules (c3-2) in which all of R are long-chain substituent groups (β) may be present. 1 , R 2 , R 3 and R 4 A molecular group (c3-3) in which a part of the group is a short-chain substituent group (α) and the rest is a long-chain substituent group (β) may be mixed.

[0041] An example of the trinuclear molybdenum dithiocarbamate is a compound represented by the following general formula (c4). Mo3S k E m L n A p Q z (c4)

[0042] In the general formula (c4), k is an integer of 1 or more, m is an integer of 0 or more, and k+m is an integer of 4 to 10, preferably an integer of 4 to 7. n is an integer of 1 to 4, and p is an integer of 0 or more. z is an integer of 0 to 5, including non-stoichiometric values. Each E is independently an oxygen atom or a selenium atom, which may, for example, substitute for sulfur in the core described below. Each L is independently an anionic ligand having an organic group containing a carbon atom, the total number of carbon atoms in the organic group in each ligand is 14 or more, and each ligand may be the same or different. Each A is independently an anion other than L. Each Q is independently a neutral compound that donates an electron and is present to fill a vacant coordination position on the trinuclear molybdenum compound.

[0043] From the viewpoint of improving the friction reducing properties of the lubricating oil composition, the content of molybdenum atoms derived from the molybdenum dithiocarbamate (C) in the lubricating oil composition of this embodiment is preferably 150 ppm by mass or more, more preferably 180 ppm by mass or more, even more preferably 210 ppm by mass or more, still more preferably 240 ppm by mass or more, and even more preferably 270 ppm by mass or more, based on the total amount of the lubricating oil composition. Furthermore, from the viewpoint of improving the storage stability of the lubricating oil composition, the content is preferably 1800 ppm by mass or less, more preferably 1750 ppm by mass or less, even more preferably 1700 ppm by mass or less, still more preferably 1650 ppm by mass or less, and even more preferably 1600 ppm by mass or less. The upper and lower limits of these numerical ranges can be combined arbitrarily. Specifically, the range is preferably 150 ppm by mass to 1800 ppm by mass, more preferably 180 ppm by mass to 1750 ppm by mass, even more preferably 210 ppm by mass to 1700 ppm by mass, still more preferably 240 ppm by mass to 1650 ppm by mass, and even more preferably 270 ppm by mass to 1600 ppm by mass. In this specification, the molybdenum atom content of the lubricating oil composition is a value measured in accordance with JPI-5S-38-03.

[0044] In the lubricating oil composition of this embodiment, the molybdenum dithiocarbamate (C) may be used alone or in combination of two or more types.

[0045] <Viscosity index improver (D)> The lubricating oil composition of this embodiment preferably contains a viscosity index improver (D) in addition to components (A) to (C). Examples of viscosity index improvers include comb polymers, non-dispersant polymethacrylates (PMA), dispersant polymethacrylates, olefin copolymers (olefin copolymers (OCPs); for example, ethylene-propylene copolymers), dispersant olefin copolymers, styrene copolymers (for example, hydrogenated styrene-diene copolymers), etc. One type of viscosity index improver may be used alone, or two or more types may be used in combination.

[0046] Here, it is preferable to use a comb polymer as the viscosity index improver (D). 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. 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 usually 1.01 or more. The mass average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the viscosity index improver (D) are values ​​measured by gel permeation chromatography and calculated in terms of polystyrene.

[0047] The content of the viscosity index improver (D) is preferably 2 to 20 mass %, more preferably 4 to 15 mass %, and even more preferably 5 to 13 mass %, based on the total amount of the lubricating oil composition.

[0048] <Other additives (E)> The lubricating oil composition of this embodiment may or may not contain components other than component (A), component (B), component (C), and component (D) (hereinafter also referred to as "other additives"), provided that the effects of the present invention are not significantly impaired. Examples of the other additives (E) include metal-based detergents, dispersants, pour point depressants, antioxidants, anti-wear agents, friction modifiers other than the molybdenum dithiocarbamate (C), extreme pressure agents, rust inhibitors, antifoaming agents, oiliness improvers, metal deactivators, and demulsifiers. These may be used alone or in combination of two or more. In the lubricating oil composition of this embodiment, the total content of the other additives (E) is preferably 4.0 mass% to 14.0 mass%, more preferably 6.0 mass% to 12.0 mass%, and even more preferably 8.5 mass% to 10.0 mass%, based on the total amount of the lubricating oil composition.

[0049] [Physical properties of lubricating oil composition] <100℃ kinematic viscosity, viscosity index> The lubricating oil composition of this embodiment preferably has a kinematic viscosity at 100°C of 4.0 mmHg or less. 2 / s or more 21.9mm 2 / s, preferably less than 5.0 mm 2 / s or more 16.3mm 2 / s or less, more preferably 6.1 mm 2 / s or more 12.5mm 2 / s. The lubricating oil composition of this embodiment preferably has a viscosity index of 150 or greater, more preferably 155 or greater, and even more preferably 160 or greater. In this specification, the 100°C kinematic viscosity and viscosity index of a lubricating oil composition refer to values ​​measured in accordance with JIS K2283:2000.

[0050] <HTHS (High Temperature High Shear) Viscosity at 150°C> The HTHS viscosity at 150°C in the lubricating oil composition of this embodiment is preferably 1.4 mPa·s or more, more preferably 1.7 mPa·s or more, still more preferably 2.0 mPa·s or more, and even more preferably 2.3 mPa·s or more. Also, it is preferably 4.0 mPa·s or less, more preferably less than 3.7 mPa·s, still more preferably less than 3.0 mPa·s, and even more preferably less than 2.9 mPa·s. The upper and lower limit values of these numerical ranges can be arbitrarily combined. Specifically, it is preferably 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, still more 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. The HTHS viscosity at 150°C of the lubricating oil composition of this embodiment complies with ASTM D4683 and can be measured at a shear rate of 10 6 / s using a TBS high-temperature viscometer (Tapered Bearing Simulator Viscometer).

[0051] <Noack Evaporation Loss> The evaporation loss of the lubricating oil composition of this embodiment by the Noack method is preferably 13% by mass or less, more preferably 12% by mass or less, still more preferably 10% by mass or less based on the total amount of the lubricating oil composition. Note that the Noack evaporation loss can be measured in accordance with JPI-5S-41-2004.

[0052] <Oxidation Stability> After the lubricating oil composition of this embodiment is subjected to the ISOT test by the method described in the examples below, the ratio of the kinematic viscosity at 100°C of the lubricating oil composition before and after the test is preferably 1.20 or less, more preferably 1.15 or less, still more preferably 1.10 or less, and even more preferably 1.05 or less.

[0053] <Coefficient of friction> The lubricating oil composition of this embodiment preferably has a friction coefficient of 0.08 or less, more preferably 0.07 or less, and even more preferably 0.06 or less, measured in accordance with the SRV test described in the Examples below.

[0054] [Method of manufacturing lubricating oil composition] The method for producing the lubricating oil composition of this embodiment is not particularly limited. For example, a method for producing a lubricating oil composition of this embodiment includes a step of mixing a base oil (A), a polyol ester (B), and a molybdenum dithiocarbamate (C), The base oil (A) is at least one selected from Group III base oils and Group IV base oils according to the base oil classification of the American Petroleum Institute; the polyol ester (B) contains an ester of a saturated fatty acid having 10 or more carbon atoms and neopentyl glycol, The molybdenum atom content is adjusted to be 150 to 1800 ppm by mass based on the total amount of the lubricating oil composition. In the above steps, when additives other than components (A) to (C) are blended, the additives may be blended simultaneously with components (A) to (C) or separately. Furthermore, each component may be blended after being made into a solution (dispersion) by adding a diluent oil or the like. After blending 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.

[0055] [Uses of lubricating oil composition] The lubricating oil composition of this embodiment has high solubility of molybdenum dithiocarbamate, is excellent in friction reducing properties, oxidation stability and low evaporation properties. For this reason, the lubricating oil composition of the present embodiment is preferably used in internal combustion engines, i.e., as an internal combustion oil, more preferably in automobile engines, and even more preferably in gasoline engines, and is also suitable for use in automobile engines equipped with hybrid mechanisms. Therefore, the lubricating oil composition of this embodiment provides the following (1) to (3): (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 mechanism.

[0056] [Lubrication method using lubricating oil composition] As explained above regarding the uses 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. It is also suitable for use in automobile engines equipped with hybrid mechanisms. Therefore, the lubricating oil composition of this embodiment provides the following (5) to (8): (5) A method for lubricating an internal combustion engine using the lubricating oil composition of this embodiment. (6) A method for lubricating an automobile engine using the lubricating oil composition of this embodiment. (7) A method for lubricating a gasoline engine using the lubricating oil composition of this embodiment. (8) A method for lubricating an automobile engine equipped with a hybrid mechanism using the lubricating oil composition of this embodiment.

[0057] [One aspect of the present invention provided] In one aspect of the present invention, the following [1] to [6] are provided. [1] A lubricating oil composition containing a base oil (A), a polyol ester (B), and a molybdenum dithiocarbamate (C), The base oil (A) is at least one selected from Group III base oils and Group IV base oils according to the base oil classification of the American Petroleum Institute; the polyol ester (B) contains an ester of a saturated fatty acid having 10 or more carbon atoms and neopentyl glycol, A lubricating oil composition having a molybdenum atom content of 150 to 1800 ppm by mass based on the total amount of the lubricating oil composition. [2] The lubricating oil composition according to [1], wherein the saturated fatty acid has 10 to 30 carbon atoms. [3] The lubricating oil composition according to [1] or [2], wherein the content of esters other than the ester of a saturated fatty acid having 10 or more carbon atoms and neopentyl glycol is 5 mass% or less based on the total amount of the polyol ester (B). [4] The lubricating oil composition according to any one of [1] to [3], wherein the content of the polyol ester (B) is 30 mass % or less based on the total amount of the lubricating oil composition. [5] The lubricating oil composition according to any one of [1] to [4], further comprising a viscosity index improver. [6] The lubricating oil composition according to any one of [1] to [5], which is used as an internal combustion engine oil. [Example]

[0058] The present invention will be specifically described with reference to the following examples, although the present invention is not limited to the following examples.

[0059] [Methods for measuring various physical properties] The properties of the raw materials used in each Example and Comparative Example and the lubricating oil compositions of each Example and Comparative Example were measured according to the procedures shown below.

[0060] (1)Kinematic viscosity at 100℃, viscosity index The 100°C kinematic viscosity and viscosity index of the base oil and lubricating oil composition were measured or calculated in accordance with JIS K2283:2000. (2) HTHS viscosity at 150°C Measurement was carried out in accordance with ASTM D4683 using a TBS high temperature viscometer (Tapered Bearing Simulator Viscometer) at a temperature of 150°C and a shear rate of 106 / s. (3) Molybdenum atom content Measurements were performed in accordance with JPI-5S-38-03.

[0061] [Examples 1 to 9, Comparative Examples 1 to 6] The lubricating oil compositions having the compositions shown in Tables 1 and 2 were prepared by mixing the components below, and the following evaluations were carried out. The details of each component used in preparing the lubricating oil compositions shown in Tables 1 and 2 are described below.

[0062] <Base oil (A)> Base oil 1: Base oil classified as Group III in the American Petroleum Institute's base oil classification (kinematic viscosity at 100°C = 4.3 mm 2 / s, viscosity index 137) Base oil 2: Synthetic oil classified as Group IV in the American Petroleum Institute's base oil classification (kinematic viscosity at 100°C = 3.9 mm 2 / s, viscosity index 124) Base oil 3: Synthetic oil classified as Group IV in the American Petroleum Institute's base oil classification (100°C kinematic viscosity = 5.9 mm 2 / s, viscosity index 132)

[0063] <Polyol ester (B)> Ester 1: A diester obtained by reacting a saturated fatty acid having 18 carbon atoms with neopentyl glycol (kinematic viscosity at 100°C = 8.2 mmHg). 2 / s, viscosity index 151) Ester 2: A diester obtained by reacting a saturated fatty acid having 8 carbon atoms 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 unsaturated fatty acid having 18 carbon atoms with neopentyl glycol (kinematic viscosity at 100°C = 7.2 mmHg) 2 / s, viscosity index 196) Ester 4: A diester obtained by reacting a linear saturated fatty acid having 10 carbon atoms with neopentyl glycol (kinematic viscosity at 100°C = 2.9 mm 2 / s, viscosity index 141)

[0064] <Molybdenum dithiocarbamate (C)> A binuclear molybdenum dithiocarbamate represented by the following general formula (c3) (molybdenum atom content: 10.0 mass%, sulfur atom content: 11.5 mass%) [ka] In the above general formula (c3), R 1 , R 2 , R 3 , and R 4 are each independently selected from an isooctyl group (8 carbon atoms: short-chain substituent group) and an isotridecyl group (13 carbon atoms: long-chain substituent group), and the molar ratio of isooctyl groups to isotridecyl groups in all molecules of molybdenum dialkyldithiocarbamate is 50:50. 1 and X 2 is a sulfur atom, and X 3 and X 4 is an oxygen atom. In the table, it is written as "MoDTC."

[0065] <Viscosity index improver (D)> Comb polymer (mass average molecular weight (Mw): 260,000, molecular weight distribution (Mw / Mn): 3.1)

[0066] <Other additives (E)> Zinc dialkyldithiophosphate, metallic detergents, dispersants, antioxidants, pour point depressants, antifoaming agents

[0067] [Evaluation method] The tests described below were carried out and various evaluations were carried out.

[0068] [Evaporation loss by Noack method] Measurement was performed in accordance with JPI-5S-41 B method. A lubricating oil composition was evaluated as having excellent low volatility when the evaporation loss measured by the Noack method was 13 mass % or less based on the total amount of the lubricating oil composition.

[0069] [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 and allowed to stand at −5° C. for 5 days, after which the presence or absence of precipitation was determined when the bottle was returned to room temperature. The occurrence of precipitation was determined visually. (2) Evaluation criteria Lubricating oil compositions in which no precipitation occurred were rated as passing, and lubricating oil compositions in which precipitation occurred were rated as failing. In the evaluation results shown in Tables 1 and 2, "Evaluation A" means passing, and "Evaluation B" means failing.

[0070] [Oxidation stability] Copper and iron pieces were added to the test oil (lubricating oil composition) as catalysts, and the test oil was subjected to an ISOT test in accordance with JIS K 2514-1:2013 to forcibly degrade the test oil. The test temperature (oil temperature) was 165.5°C. 96 hours after the start of the ISOT test, the ratio of the 100°C kinematic viscosity of the test oil to that of the lubricating oil composition (new oil) before the ISOT test was measured. The smaller the ratio of kinematic viscosities at 100°C, the more excellent the oxidation stability. A lubricating oil composition having a kinematic viscosity ratio at 100°C of 1.05 or less was evaluated as having excellent oxidation stability.

[0071] [Coefficient of friction] The friction coefficient was measured using an SRV tester (manufactured by Optimol) under the following conditions when the prepared lubricating oil compositions were used. The smaller the friction coefficient, the better the friction reducing ability. The average value of the friction coefficients over the 10 minutes from 20 minutes after the start of the test to the end of the test was taken as the friction coefficient. A lubricating oil composition having a friction coefficient of 0.08 or less was evaluated as having excellent friction-reducing properties. Cylinder: SUJ-2 Standard disc: AISI52100 (Maximum height roughness (Rz): 0.45~0.65μm) Mirror disc: AISI52100 (maximum height roughness (Rz): less than 0.20 μm) Frequency: 50Hz ·Amplitude: 1.5mm Load: 400N ·Temperature: 80℃ Test duration: 30 minutes

[0072] The properties of each lubricating oil composition and the results of each test are shown in Tables 1 and 2.

[0073] [Table 1]

[0074] [Table 2]

[0075] <Evaluation results> From Tables 1 and 2, the following can be seen: It is clear that the lubricating oil compositions of Examples 1 to 9 have good storage stability and excellent solubility of molybdenum dithiocarbamate (C). Furthermore, it is clear that they are excellent in all of friction reduction, low volatility, and oxidation stability. In contrast, lubricating oil compositions that do not contain polyol ester (B), such as the lubricating oil composition of Comparative Example 2, are found to have poor storage stability and poor solubility of molybdenum dithiocarbamate (C) compared to Examples 1 to 9. Furthermore, it can be seen that lubricating oil compositions having a molybdenum atom content of less than 150 ppm, based on the total amount of the lubricating oil composition, such as the lubricating oil compositions of Comparative Examples 1 and 3, are inferior in friction-reducing properties, and that lubricating oil compositions having a molybdenum atom content of more than 1800 ppm, based on the total amount of the lubricating oil composition, such as the lubricating oil composition of Comparative Example 4, are poor in storage stability and are inferior in the solubility of the molybdenum dithiocarbamate (C). It is also found that lubricating oil compositions in which the fatty acid constituting the polyol ester (B) has less than 10 carbon atoms, such as the lubricating oil composition of Comparative Example 5, have poor low volatility, and that lubricating oil compositions in which the fatty acid constituting the polyol ester (B) is an unsaturated fatty acid, such as the lubricating oil composition of Comparative Example 6, have poor oxidation stability.

Claims

1. A lubricating oil composition comprising a base oil (A), a polyol ester (B), and a molybdenum dithiocarbamate (C), The base oil (A) is at least one selected from Group III base oils and Group IV base oils according to the American Petroleum Institute base oil classification; the polyol ester (B) contains an ester of a saturated fatty acid having 10 or more carbon atoms and neopentyl glycol, A lubricating oil composition having a molybdenum atom content of 150 to 1800 ppm by mass based on the total amount of the lubricating oil composition.

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

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

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