Lubricant composition for wet clutches

Abstract

To provide a wet clutch lubricating oil composition which has a suitable friction coefficient and is excellent in copper compatibility.SOLUTION: A wet clutch lubricating oil composition contains: a base oil; a zinc dithiocarbamate compound represented by the general formula (a); a dispersant including nitrogen. A content of the zinc dithiocarbamate compound is 0.2 mass% or more and 0.3 mass% or less based on the total amount of the lubricating oil composition and a content of the dispersant in terms of a nitrogen amount is 0.02 mass% or more and 0.03 mass% or less based on the total amount of the lubricating oil composition. In the general formula (a), R11, R12, R13, and R14 each independently represent a hydrogen atom or an alkyl group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to a lubricating oil composition for wet clutches. [Background technology]

[0002] Wet clutch mechanisms, particularly metal friction clutches, are used in automotive differentials and shaft couplings, primarily to control power transmission. Since power transmission in these wet clutch mechanisms is controlled by the sliding of the clutch, the lubricating oil used in wet clutches must have a friction coefficient above a certain level to ensure good torque transmission performance.

[0003] As such a lubricant for wet clutches, for example, Patent Document 1 describes an oleic acid ester having an alkyl group with 7 to 9 carbon atoms in the ester portion, and which can be heated at 100°C for 2 to 50 mm 2 A lubricating oil for wet clutches is disclosed, comprising a base oil having a kinematic viscosity of / s, (A) 0.1 to 10% by mass of a higher alcohol and glycerin ether with an alkyl group having 8 or more carbon atoms, relative to the total amount of lubricating oil, and (B) 0.1 to 5% by mass of a phosphate ester compound, relative to the total amount of lubricating oil.

[0004] Furthermore, Patent Document 2 contains a base oil and a viscosity index improver (A), wherein the base oil has a kinematic viscosity of 1.0 to 3.0 mm at 100°C. 2 It contains polyalphaolefin with a viscosity of / s, and the viscosity of the base oil at 100°C is 1.0 to 2.5 mm. 2 The viscosity index improver (A) is a polymethacrylate-based viscosity index improver with a weight-average molecular weight of 10,000 to 100,000, the content of the viscosity index improver (A) is 10 to 20% by mass, and the kinematic viscosity at 100°C is 4.5 to 6.0 mm². 2 A lubricating oil composition for wet clutches is disclosed, having a viscosity index of 200-280 and a viscosity of 1 / s.

[0005] Furthermore, Patent Document 3 describes a method for measuring 2 to 50 mm at 100°C. 2One or more selected from mineral oils and synthetic oils having a viscosity of / s are used as a base oil, and this contains (A) 0.1 to 10% by mass of an ether of a higher alcohol having 8 or more carbon atoms and glycerin, and (B) 0.1 to 5% by mass of a phosphate ester compound, and a lubricating oil for a wet clutch that does not contain hydrophobic silica is disclosed.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] For a lubricating oil composition used in a wet clutch mechanism, a friction coefficient of a certain level or more (that is, torque transmission performance) is required to transmit torque. In recent years, for a lubricating oil composition for a wet clutch, a performance (so-called copper compatibility) for suppressing copper corrosion when contacting a copper member is required.

[0008] That is, the problem to be solved by the present disclosure is to provide a lubricating oil composition for a wet clutch having an appropriate friction coefficient and excellent copper compatibility.

Means for Solving the Problems

[0009] The present disclosure includes the following embodiments. <1> A base oil, A zinc dithiocarbamate compound represented by the following general formula (a), A dispersant containing nitrogen, and The content of the zinc dithiocarbamate compound is 0.2% by mass or more and 0.3% by mass or less based on the total amount of the lubricating oil composition, A lubricating oil composition for a wet clutch, wherein the content of the dispersant in terms of nitrogen amount is 0.02% by mass or more and 0.03% by mass or less based on the total amount of the lubricating oil composition.

[0010]

Chemical formula

[0011] (In the general formula (a), R 11 , R 12 , R 13 , and R 14 each independently represents a hydrogen atom or an alkyl group.) <2> The ratio (Y / X) of the content (Y) of the dispersant in terms of nitrogen amount to the content (X) of the zinc dithiocarbamate compound is 0.08 or more, and the lubricating oil composition for a wet clutch according to <1>. <3> The lubricating oil composition for a wet clutch according to <1> or <2>, containing a metal deactivator in a range of 0.05% by mass or more and 0.15% by mass or less based on the total amount of the lubricating oil composition. <4> The lubricating oil composition for a wet clutch according to any one of <1> to <3>, containing a corrosion inhibitor in a range of 0.01% by mass or more and 0.1% by mass or less based on the total amount of the lubricating oil composition. <5> The lubricating oil composition for a wet clutch according to any one of <1> to <4>, containing an ether-containing friction modifier having an ether group in a range of 2.0% by mass or more and 4.0% by mass or less based on the total amount of the lubricating oil composition. <6> The lubricating oil composition for a wet clutch according to any one of <1> to <5>, containing a phosphorus-containing friction modifier containing phosphorus in a range of 0.5% by mass or more and 1.5% by mass or less based on the total amount of the lubricating oil composition. <7> The lubricating oil composition for a wet clutch according to any one of <1> to <6>, containing a pour point depressant in a range of 0.1% by mass or more and 0.5% by mass or less based on the total amount of the lubricating oil composition. <8> The aforementioned base oil is 1 mm at 100°C. 2 / s or more 5mm 2 It is a synthetic base oil having a kinematic viscosity of less than / s. <1> ~ <7> A lubricating oil composition for wet clutches according to any one of the following items. [Effects of the Invention]

[0012] According to one embodiment of the present disclosure, a lubricating oil composition for a wet clutch is provided that has an appropriate coefficient of friction and excellent copper compatibility. [Modes for carrying out the invention]

[0013] The following describes an example of an embodiment of this disclosure. These descriptions and examples are illustrative and do not limit the scope of the invention.

[0014] In this disclosure, a numerical range indicated using "~" means a range that includes the numbers written before and after "~" as the lower limit and upper limit, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples. In this disclosure, when referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, it means the total amount of all multiple components present in the composition unless otherwise specified. In this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In this disclosure, "JIS" is used as an abbreviation for Japanese Industrial Standards.

[0015] <Lubricant composition for wet clutches> A lubricating oil composition for a wet clutch according to the embodiments of this disclosure (hereinafter also simply referred to as the "lubricating oil composition") contains a base oil, a zinc dithiocarbamate compound represented by the above-mentioned general formula (a) (hereinafter also simply referred to as the "ZnDTC compound"), and a nitrogen-containing dispersant (hereinafter also simply referred to as the "nitrogen dispersant"). Furthermore, the ZnDTC compound content is 0.2% by mass or more and 0.3% by mass or less relative to the total amount of the lubricating oil composition, and the nitrogen dispersant content, calculated on a nitrogen basis, is 0.02% by mass or more and 0.03% by mass or less relative to the total amount of the lubricating oil composition.

[0016] Wet clutch mechanisms, to which lubricating oil compositions for wet clutches are applied, are used in automobile differentials and shaft couplings, as well as brakes on agricultural and construction machinery, and are primarily responsible for controlling power transmission. Lubricating oil compositions used in such wet clutch mechanisms require a certain level of friction coefficient (i.e., torque transmission performance) to transmit torque. Similarly, electronically controlled drivetrain mechanisms also require an appropriate friction coefficient. Furthermore, in recent years, lubricating oil compositions for wet clutches have been required to have the ability to suppress copper corrosion when in contact with copper components (so-called copper compatibility). As described above, lubricating oil compositions used in wet clutch mechanisms are required to have an appropriate coefficient of friction and excellent copper compatibility.

[0017] In contrast, the lubricating oil composition according to the embodiment of this disclosure contains both a ZnDTC compound represented by general formula (a) and a nitrogen dispersant, and controls the content of each within the above range. This makes it possible to achieve both an appropriate coefficient of friction and copper compatibility. For example, in both cases—when only a nitrogen dispersant is present and no ZnDTC compound is present, and when only a ZnDTC compound is present and no nitrogen dispersant is present—an appropriate coefficient of friction cannot be obtained. Furthermore, even when both are present, if the content of the ZnDTC compound exceeds the aforementioned upper limit, the copper compatibility is poor. Thus, in this disclosure, both an appropriate coefficient of friction and copper compatibility are achieved by containing a ZnDTC compound and a nitrogen dispersant, and by controlling the content of each.

[0018] Next, the components contained in the lubricating oil composition according to the embodiment of this disclosure will be described.

[0019] <Base oil> The base oil is not particularly limited, and any base oil used in lubricating oils for wet clutches can be used. Specific examples of base oils include mineral oil-based base oils and synthetic base oils (synthetic base oils).

[0020] Examples of mineral oil-based base oils include base oils classified as API (American Petroleum Institute) Group I, obtained by combining processes such as atmospheric distillation, vacuum distillation, solvent desalination, solvent extraction, hydrorefining, and solvent dewaxing from crude oil; base oils classified as API Group II, obtained by combining processes such as hydrocracking and catalytic dewaxing; and base oils classified as API Group III, obtained by combining advanced hydrotreatment processes such as hydrocracking and hydroisomerization dewaxing. The mineral oil-based base oil may be refined paraffinic mineral oil, naphthenic mineral oil, or aromatic base oil, and these base oils may be used individually or in combination.

[0021] Examples of synthetic base oils include synthetic hydrocarbons such as α-olefin oligomers (polyalphaolefins: PAO, e.g., propylene oligomer, isobutylene oligomer, 1-butene oligomer, 1-octene oligomer, 1-decene oligomer, ethylene-propylene oligomer, etc.) and isoparaffin oligomers; aromatic hydrocarbons such as alkylbenzenes and alkylnaphthalenes; esters such as di-2-ethylhexyl adipate and diisodecyl adipate; polyol esters such as trimethylolpropaneoleate and pentaerythritol-2-ethylhexanoate; polyglycols such as polyoxyalkylene glycols; polyphenyl ethers; and the like.

[0022] In lubricant compositions for wet clutches, synthetic base oils are preferred as the base oil, and among these, α-olefin oligomers (e.g., 1-decene oligomers) are more preferred. α-olefin oligomers are copolymers of α-olefins. As α-olefin oligomers, polymers or copolymers of 10-mer or less of α-olefins having 6 to 18 carbon atoms are preferred. More preferably, as α-olefin oligomers, polymers of 2-4 mers of α-decene (10 carbon atoms), polymers of 2-4 mers of α-dodecene (12 carbon atoms), copolymers of 5-mer or more containing 2-4 mers of α-decene (10 carbon atoms) as the main component, and copolymers of 5-mer or more containing 2-4 mers of α-dodecene (12 carbon atoms) as the main component are preferred.

[0023] The kinematic viscosity of the base oil at 100°C is 1 mm 2 / s or more 5mm 2 It is preferable that the speed be less than or equal to 2 mm 2 / s or more 4mm 2 It is more preferable that the kinematic viscosity is less than or equal to / s. The kinematic viscosity of the base oil at 100°C is preferably the above kinematic viscosity whether it is a base oil alone or a mixed base oil. The kinematic viscosity of the base oil at 100°C is measured in accordance with JIS K2283 (2000).

[0024] <Zinc dithiocarbamate compounds (ZnDTC compounds)> The lubricating oil composition according to the embodiments of this disclosure contains a zinc dithiocarbamate compound (ZnDTC compound) represented by the following general formula (a). By adding the ZnDTC compound together with a nitrogen dispersant, a lubricating oil composition having an appropriate coefficient of friction can be obtained.

[0025] [ka]

[0026] In general formula (a), R 11 , R 12 , R 13 , and R 14 Each of these independently represents either a hydrogen atom or an alkyl group.

[0027] R 11 , R 12 , R 13 , and R 14 The alkyl group represented by may be linear, branched, or cyclic, but it is preferably linear or branched.

[0028] The alkyl group is not particularly limited, but it is preferably having 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and even more preferably 1 to 8 carbon atoms. Examples of alkyl groups include methyl, ethyl, propyl, butyl, pentyl (amyl), hexyl, heptyl, nonyl, and decyl groups.

[0029] R 11 , R 12 , R 13 , and R 14 Each of these is preferably a hydrogen atom or a linear or branched alkyl group having 1 to 10 carbon atoms, more preferably a linear or branched alkyl group having 1 to 10 carbon atoms, and even more preferably a linear or branched alkyl group having 1 to 8 carbon atoms.

[0030] Examples of ZnDTC compounds include zinc diamyldithiocarbamate.

[0031] The content of the ZnDTC compound is preferably 0.2% by mass or more and 0.3% by mass or less, and more preferably 0.22% by mass or more and 0.28% by mass or less, based on the total amount of the lubricating oil composition. If the content of the ZnDTC compound is below the lower limit, an appropriate coefficient of friction cannot be obtained, and if it exceeds the upper limit, the copper compatibility is poor.

[0032] <Nitrogen-containing dispersants (nitrogen dispersants)> The lubricating oil composition according to the embodiments of this disclosure contains a nitrogen-containing dispersant (nitrogen dispersant). By adding a nitrogen dispersant together with a ZnDTC compound, a lubricating oil composition having an appropriate coefficient of friction can be obtained.

[0033] Examples of nitrogen dispersants include boron-containing nitrogen dispersants containing boron and nitrogen, and boron-free nitrogen dispersants containing nitrogen. A single nitrogen dispersant may be used, or two or more may be used in combination.

[0034] -B-containing nitrogen dispersant- As the boron-containing nitrogen dispersant, boron-containing nitrogen dispersants used in the lubricating oil field can be used. As the boron-containing nitrogen dispersant, boron-containing imide-based dispersants are preferred. A boron-containing imide-based dispersant refers to a dispersant that is a compound containing boron and having an imide bond. Examples of boron-containing imide-based dispersants include monoimide compounds of alkyl or alkenyl succinic acid, and boron-modified bisimide compounds thereof. Among these, boron-modified bisimide compounds of alkyl or alkenyl succinic acid are preferred as boron-containing imide-based dispersants from the viewpoint of extending the lifespan of the lubricating oil composition, wear resistance, and dispersibility.

[0035] The B-containing nitrogen dispersant may be either a low-molecular-weight compound or a polymer, but from the viewpoint of clean dispersibility, a polymer is preferred. In this disclosure, a polymer means a compound having a weight-average molecular weight (Mw) of 1,000 or more on a polystyrene basis.

[0036] From the viewpoint of clean dispersibility, the B-containing nitrogen dispersant preferably has a weight-average molecular weight (Mw) of 2,000 to 7,000.

[0037] In this disclosure, the weight-average molecular weight (Mw) is a value measured by gel permeation chromatography (GPC). The weight-average molecular weight (Mw) is measured using the following conditions: measuring instrument: Shodex GPC-101 (Showa Denko Corporation), measuring column: three Shodex GPC LF-804 (Showa Denko Corporation), detector: differential refractive detector, mobile phase: THF (tetrahydrofuran), flow rate: 1 ml / min, sample concentration: 1.0 mass% / vol, injection volume: 100 μL. The weight-average molecular weight is calculated from this measurement result using a molecular weight distribution curve prepared with monodisperse polystyrene standard samples.

[0038] -B-Non-containing nitrogen dispersant- A boron-free nitrogen dispersant refers to a dispersant that does not contain boron but contains nitrogen, and is included, for example, in ashless dispersants.

[0039] As a boron-free nitrogen dispersant, an ashless dispersant used in the lubricating oil field that does not contain boron and contains nitrogen can be used. Examples of boron-free nitrogen dispersants include compounds in which a polar group is directly bonded to the side chain of a polyolefin that does not have a polar group in its main chain, or to the side chain of a polyamine that has a polar group in its main chain. Here, examples of polar groups include alcoholic hydroxyl groups, amide groups, and ester groups.

[0040] As B-free nitrogen dispersants, for example, polyamines containing one or more alkyl or alkenyl groups in the molecule, and acid-modified versions thereof can be used. As B-free nitrogen dispersants, for example, succinimides represented by general formula (1) or general formula (2) described in paragraphs 0029 to 0032 of Japanese Patent Application Publication No. 2018-048220 (however, boron-modified products are not included) and dispersant B described in paragraph 0048 can also be suitably used. Specifically, as B-free nitrogen dispersants, boron-free polyisobutenyl succinimide compounds are preferred.

[0041] The nitrogen content of the nitrogen dispersant (total content when multiple types of nitrogen dispersants are used in combination) is 0.02% by mass or more and 0.03% by mass or less, preferably 0.022% by mass or more and 0.028% by mass or less, relative to the total amount of the lubricating oil composition. If the nitrogen dispersant content is below the lower limit, an appropriate coefficient of friction cannot be obtained, and if it exceeds the upper limit, deterioration of low-temperature viscosity characteristics can be expected.

[0042] The content of the nitrogen dispersant itself is adjusted so that the content in terms of nitrogen amount is within the above range. The content of the nitrogen dispersant is preferably 5% by mass or more and 20% by mass or less, more preferably 6% by mass or more and 15% by mass or less, and even more preferably 8% by mass or more and 12% by mass or less, based on the total amount of the lubricating oil composition.

[0043] <Content ratio of ZnDTC compound and nitrogen dispersant> In the lubricating oil composition, the ratio (Y / (X + Y)) of the content (Y) of the nitrogen dispersant in terms of nitrogen amount to the total of the content (X) of the ZnDTC compound and the content (Y) of the nitrogen dispersant in terms of nitrogen amount is preferably more than 0.05 and less than 1.00, more preferably 0.07 or more and 0.50 or less, and even more preferably 0.08 or more and 0.10 or less. By adjusting the content ratio of the ZnDTC compound and the nitrogen dispersant within the above range, it becomes easier to achieve both an appropriate friction coefficient and copper compatibility.

[0044] In the lubricating oil composition, the ratio (Y / X) of the content (Y) of the nitrogen dispersant in terms of nitrogen amount to the content (X) of the ZnDTC compound is preferably 0.08 or more, more preferably 0.085 or more and 0.120 or less, and even more preferably 0.090 or more and 0.110 or less. By adjusting the content ratio of the ZnDTC compound and the nitrogen dispersant within the above range, it becomes easier to achieve both an appropriate friction coefficient and copper compatibility.

[0045] <Metal deactivator> The lubricating oil composition according to an embodiment of the present disclosure preferably contains a metal deactivator from the viewpoint of suppressing the chemical activity of the metal and improving copper compatibility.

[0046] The metal deactivator is not particularly limited, and examples thereof include compounds such as benzotriazole and its derivatives, tolyltriazole and its derivatives, imidazole and its derivatives, pyrimidine and its derivatives. Among them, benzotriazole and its derivatives are preferable as the metal deactivator.

[0047] The content of the metal deactivator is preferably 0.05% by mass or more and 0.15% by mass or less, and more preferably 0.07% by mass or more and 0.13% by mass or less, based on the total amount of the lubricating oil composition. A metal deactivator content above the lower limit can be obtained to obtain higher copper compatibility, and a content below the upper limit can be obtained to obtain appropriate friction characteristics.

[0048] <Corrosion inhibitor> The lubricating oil composition according to the embodiments of this disclosure preferably contains a corrosion inhibitor, from the viewpoint of suppressing the occurrence of corrosion in metals and improving copper compatibility.

[0049] Corrosion inhibitors are primarily non-ferrous metal materials and are added to prevent corrosion in areas where copper-based or lead-based materials are used. Furthermore, because corrosion inhibitors suppress the catalytic activity of metals, they also indirectly function as antioxidants.

[0050] Corrosion inhibitors are compounds that exhibit a corrosion-preventive effect by forming a film on the metal surface. Examples include thiadiazole and its derivatives, indazole and its derivatives, benzimidazole and its derivatives, indole and its derivatives, etc. Among these, thiadiazole and its derivatives (hereinafter also simply referred to as "thiadiazole compounds") are preferred as corrosion inhibitors.

[0051] Examples of thiadiazole compounds include 1,3,4-thiadiazole derivatives having a structure represented by the following general formula (1-1) or general formula (1-2).

[0052] [ka]

[0053] (In general formulas (1-1) and (1-2), R 11 , R 12 and R 13 Each of these independently represents a thioalkyl group having one or more sulfur atoms.

[0054] A thioalkyl group represents an organic linking group having carbon (C) and sulfur (S). The alkyl group in a thioalkyl group may be further substituted with another substituent. The thioalkyl group may be linear, branched, or cyclic, but linear or branched is preferred. The thioalkyl group may be an aliphatic group or an aromatic group, but an aliphatic group is preferred. The thioalkyl group preferably has 3 or more carbon atoms, more preferably 6 or more carbon atoms, and particularly preferably 8 or more carbon atoms.

[0055] The thioalkyl groups shown in (a) and (b) below are preferred.

[0056] [ka]

[0057] In bases (a) and (b), R 14 and R 15 Each of these independently represents an alkyl group. The alkyl group may be further substituted by another substituent. It may be linear, branched, or cyclic, but linear or branched is preferred. The alkyl group may be an aliphatic group or an aromatic group, but it is preferred to be an aliphatic group. The alkyl group preferably has 3 or more carbon atoms, more preferably 6 or more carbon atoms, and particularly preferably 8 or more carbon atoms.

[0058] The content of the corrosion inhibitor is preferably 0.01% by mass or more and 0.1% by mass or less, and more preferably 0.02% by mass or more and 0.07% by mass or less, based on the total amount of the lubricating oil composition. A content of corrosion inhibitor above the lower limit of the above value can be obtained to obtain higher copper compatibility, and a content below the upper limit of the above value can be obtained to obtain appropriate friction characteristics.

[0059] <Ether-containing friction modifier> The lubricating oil composition according to the embodiments of this disclosure preferably contains an ether-containing friction modifier having an ether group, from the viewpoint of obtaining an appropriate coefficient of friction.

[0060] Examples of ether-containing friction modifiers include (poly)glyceryl ethers represented by general formula (2-1).

[0061] [ka]

[0062] In general formula (2-1), R 1 This represents a hydrocarbon group. Examples of hydrocarbon groups include alkyl groups, alkenyl groups, aryl groups, cycloalkyl groups, and cycloalkenyl groups. Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, secondary butyl, tertiary butyl, pentyl, isopentyl, secondary pentyl, neopentyl, tertiary pentyl, hexyl, secondary hexyl, heptyl, secondary heptyl, octyl, 2-ethylhexyl, secondary octyl, nonyl, secondary nonyl, decyl, secondary decyl, undecyl, secondary undecyl, dodecyl, secondary dodecyl, tridecyl, isotridecyl, secondary tridecyl, tetra Examples include radicyl, secondary tetradecyl, hexadecyl, secondary hexadecyl, stearyl, icosyl, docosyl, tetracosyl, triacontyl, 2-butyloctyl, 2-butyldecyl, 2-hexyloctyl, 2-hexyldecyl, 2-octyldecyl, 2-hexyldodecyl, 2-octyldodecyl, 2-decyltetradecyl, 2-dodecylhexadecyl, 2-hexadecyloctadecyl, 2-tetradecyloctadecyl, monomethyl branched-isostearyl, and the like.

[0063] Examples of alkenyl groups include vinyl, allyl, propenyl, butenyl, isobutenyl, pentenyl, isopentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tetradecenyl, and oleyl. Examples of aryl groups include phenyl, toluyl, xylyl, cumenyl, mesityl, benzyl, phenethyl, styryl, cinnamyl, benzhydryl, trityl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, dodecylphenyl, phenylphenyl, benzylphenyl, styrene-phenyl, p-cumylphenyl, α-naphthyl, and β-naphthyl groups.

[0064] Examples of cycloalkyl and cycloalkenyl groups include cyclopentyl, cyclohexyl, cycloheptyl, methylcyclopentyl, methylcyclohexyl, methylcycloheptyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, methylcyclopentenyl, methylcyclohexenyl, and methylcycloheptenyl groups.

[0065] R 1 The alkyl or alkenyl group is preferred, and an alkyl or alkenyl group having 4 to 30 carbon atoms is more preferred. Furthermore, in general formula (1), n ​​is a coefficient representing the degree of polymerization of glycerin, and is a number of 1 or more, preferably a number between 1 and 5. When n is 1 or more, n is the average value.

[0066] The content of the ether-containing friction modifier is preferably 2.0% by mass or more and 4.0% by mass or less, and more preferably 2.5% by mass or more and 3.5% by mass or less, based on the total amount of the lubricating oil composition. It is preferable that the content of the ether-containing friction modifier is above the lower limit, as this makes it easier to obtain an appropriate coefficient of friction, and preferable that it is below the upper limit, as this reduces the temperature dependence of the coefficient of friction.

[0067] <Phosphorus-containing friction modifier> The lubricating oil composition according to the embodiments of this disclosure preferably contains a phosphorus-containing friction modifier, in terms of obtaining an appropriate coefficient of friction.

[0068] Examples of phosphorus-containing friction modifiers include phosphate esters, phosphite esters, and their amine salts, represented by the general formula (2-2). Preferably, they are acidic phosphate esters and their amine salts.

[0069] [ka]

[0070] In general formula (2-2), R 2 represents a monovalent hydrocarbon group, X represents an oxygen atom or a sulfur atom, a represents 1, 2, or 3, and b represents 0 or 1. The above R 2 The monovalent hydrocarbon group represented by includes linear or branched saturated or unsaturated aliphatic hydrocarbon groups having 5 to 20 carbon atoms (e.g., alkyl groups, alkenyl groups), aromatic hydrocarbon groups having 6 to 26 carbon atoms, or cycloalkyl groups.

[0071] Specific examples of the amine salts mentioned above include compounds obtained by neutralizing acidic phosphate esters, acidic phosphite esters, acidic thiophosphate esters, and acidic dithiophosphate esters with alkylamines. Examples of acidic phosphate esters include butyl acid phosphate, 2-ethylhexyl acid phosphate, octyl acid phosphate, isodecyl acid phosphate, lauryl acid phosphate, tridecyl acid phosphate, oleyl acid phosphate, toryl acid phosphate, and di-2-ethylhexyl acid phosphate.

[0072] Examples of acidic phosphite esters include triphenyl phosphite, tri(p-cresyl) phosphite, tri(octylphenyl) phosphite, tri(nonylphenyl) phosphite, triisooctyl phosphite, toridodecyl phosphite, diphenylisodecyl phosphite, triisodecyl phosphite, tritearyl phosphite, trioleyl phosphite, di-2-ethylhexyl hydrozene phosphite, didodecyl hydrozene phosphite, dilauryl hydrozene phosphite, and dioleyl hydrozene phosphite.

[0073] Examples of acidic thiophosphate esters include dioctyl thiophosphate, trioctyl thiophosphate, toridodecyl thiophosphate, trihexadecyl thiophosphate, trioctadecenyl thiophosphate, and tri(octylphenyl) thiophosphate. Examples of acidic dithiophosphate esters include tridecyl dithioacid phosphate and di(2-ethylhexyl)dithioacid phosphate. Examples of amine salts of phosphate esters include alkylamine salts obtained by neutralizing the above-mentioned phosphate ester with an alkylamine represented by the following general formula (2-3).

[0074] [ka]

[0075] In general formula (2-3), R 3 , R 4 and R 5 Each of these independently represents a monovalent hydrocarbon group or hydrogen atom, and at least one of them is a hydrocarbon group. Specific examples of general formula (2-3) include dibutylamine, octylamine, dioctylamine, laurylamine, dilaurylamine, oleylamine, coconutamine, and beef tallowamine.

[0076] The content of the phosphorus-containing friction modifier is preferably 0.5% by mass or more and 1.5% by mass or less, and more preferably 0.6% by mass or more and 1.0% by mass or less, relative to the total amount of the lubricating oil composition. It is preferable that the content of the phosphorus-containing friction modifier is above the lower limit, as this makes it easier to obtain an appropriate coefficient of friction, and preferable that it is below the upper limit, as this reduces the temperature dependence of the coefficient of friction.

[0077] <Pour point depressant> The lubricating oil composition according to the embodiments of this disclosure preferably contains a pour point depressant, in order to suppress the crystallization of wax in the lubricating oil at low temperatures, thereby lowering the pour point and expanding the applicable temperature range of the lubricating oil.

[0078] Examples of pour point depressants include polymethacrylate, polyalkyl methacrylate, olefin copolymer, chlorinated paraffin-naphthalene condensate, and alkylated polystyrene. Among these, polymethacrylate and polyalkyl methacrylate are preferred as pour point depressants.

[0079] The weight-average molecular weight of the pour point depressant is preferably between 10,000 and 100,000. The weight-average molecular weight of the pour point depressant is a value calculated using polystyrene as the standard, measured by gel permeation chromatography.

[0080] The content of the pour point depressant is preferably 0.1% to 0.5% by mass, and more preferably 0.2% to 0.4% by mass, relative to the total amount of the lubricating oil composition. A pour point depressant content above the lower limit broadens the applicable temperature range of the lubricating oil, while a content below the upper limit provides excellent low-temperature viscosity characteristics.

[0081] <Other additives> The lubricating oil compositions according to the embodiments of this disclosure may further contain other additives. Examples of other additives include detergents and viscosity index improvers.

[0082] • Cleansing agents As a cleaning agent, a metal-type cleaning agent containing metal is preferably used. Examples of metal-type cleaning agents include alkaline earth metal salts such as alkaline earth metal sulfonates, alkaline earth metal phenates, and alkaline earth metal salicylates. Alkaline earth metal sulfonates are preferred as the metal-type cleaning agent.

[0083] Examples of alkaline earth metals included in metal-type detergents include calcium, sodium, and barium. Among these, calcium is preferred as the alkaline earth metal. As a metal-type detergent, an alkaline earth metal salt over-basicated with carbonic acid or boric acid is preferred.

[0084] The base number of the cleaning agent is determined by the perchloric acid method according to JIS K2501 (2003), preferably 150 mg KOH / g to 500 mg KOH / g, more preferably 200 mg KOH / g to 450 mg KOH / g, and even more preferably 250 mg KOH / g to 450 mg KOH / g.

[0085] From the viewpoint of improving cleanliness, the content of the cleaning agent is preferably 0.01% by mass or more and 2.0% by mass or less, and more preferably 0.05% by mass or more and 1.0% by mass or less, relative to the total amount of the lubricating oil composition.

[0086] • Viscosity index improver Examples of viscosity index improvers include non-dispersive and dispersion-type viscosity index improvers as described in JASO M355:2021.

[0087] Examples of non-dispersive viscosity index improvers include olefin copolymers. Examples of olefin copolymers include polymers such as polyisobutylene and ethylene-propylene copolymers.

[0088] Examples of dispersion-type viscosity index improvers include polymers such as polymethacrylate, random copolymers of olefins and methacrylate, block copolymers of olefins and methacrylate, and graft copolymers of polymethacrylate and olefin copolymers. Examples of polymethacrylates include polyalkyl methacrylates. Examples of random copolymers of olefins and methacrylates include random copolymers of ethylene-alkyl methacrylate, random copolymers of propylene-alkyl methacrylate, and random copolymers of isobutylene-alkyl methacrylate. Examples of olefin and methacrylate block copolymers include ethylene-alkyl methacrylate block copolymers, propylene-alkyl methacrylate block copolymers, and isobutylene-alkyl methacrylate block copolymers. Examples of graft copolymers of polymethacrylate and olefin copolymer include polymers in which the main chain is polymethacrylate and the side chains are olefin copolymers.

[0089] When the polymer (olefin copolymer, polymethacrylate, etc.) used as a viscosity index improver is an alkylated derivative having a side-chain alkyl group, the number of carbon atoms in the side-chain alkyl group is preferably 1 to 50.

[0090] In this disclosure, the viscosity index improver is a polymer with a weight-average molecular weight of 10,000 or more that contributes to improving the viscosity index, and the content of the polymer is 1% by mass or more based on the total amount of the lubricating oil composition. The weight-average molecular weight of the viscosity index improver is preferably between 50,000 and 1,000,000, and more preferably between 100,000 and 800,000. The weight-average molecular weight of the viscosity index improver is a value calculated using polystyrene as the standard, measured by gel permeation chromatography.

[0091] The viscosity index improver content is preferably 2.0% by mass or more and 15.0% by mass or less, and more preferably 4.0% by mass or more and 10.0% by mass or less, based on the total amount of the lubricating oil composition.

[0092] (Preparation method) A lubricating oil composition according to the embodiments of this disclosure can be prepared by appropriately mixing a base oil, a zinc dithiocarbamate compound (ZnDTC compound), a nitrogen-containing dispersant (nitrogen dispersant), and various additives as needed. The mixing order of these components is not particularly limited; they may be mixed sequentially with the base oil, or the various additives may be added to the base oil in advance.

[0093] (Kinematic viscosity, viscosity index) The lubricating oil composition according to the embodiments of this disclosure is not particularly limited in terms of kinematic viscosity, but considering stability at low and high temperatures and starting performance, a kinematic viscosity of 1.0 mm at 100°C is preferred. 2 / s~10.0mm 2 It is preferable that it be / s, and 3.0 mm 2 / s~8.0mm 2 It is more preferable to use / s.

[0094] Furthermore, the viscosity index of the lubricating oil composition is preferably 150 or higher, more preferably 170 or higher, and even more preferably 190 or higher.

[0095] (Application) The lubricating oil compositions according to the embodiments of this disclosure are suitably used in electronically controlled couplings incorporating wet clutches, multi-plate clutch type LSDs, wet brakes, ATs (Automatic Transmissions), CVTs (Continuously Variable Transmissions), and the like. [Examples]

[0096] Examples are described below, but this disclosure is not limited to these examples.

[0097] <Examples, Comparative Examples> A lubricating oil composition was obtained by preparing the base oil and various additives in the proportions shown in Table 1. The following evaluations were performed using each of the obtained lubricating oil compositions. The results are shown in Table 1.

[0098] <Rating> The wet clutch lubricant compositions of the examples and comparative examples were evaluated using the following test methods. In the table, a blank space indicates that the component was not included, and a "-" in the evaluation results indicates that the measurement was not performed.

[0099] -Kinematic viscosity, viscosity index (VI)- The kinematic viscosity of the wet clutch lubricant composition at 40°C and 100°C was measured using a capillary viscometer in accordance with JIS K2283 (2000), and the viscosity index (VI) was calculated.

[0100] -Copper compatibility (copper elution performance)- A copper plate was placed in a test tube, immersed in 30g of a wet clutch lubricant composition, and kept in a constant temperature bath at 150°C for 24 hours before being removed. ·exterior The copper plates after testing were evaluated for their appearance using the copper plate corrosion standard plate specified in ASTM D130. ·Elution amount The copper concentration of the wet clutch lubricant composition was measured after testing. If the copper plate corroded under the above test conditions and the elution of more than 150 ppm by mass of copper into the lubricant composition was confirmed, it indicates that the copper corroded and that the protective effect was insufficient at high temperatures. ·judgement Regarding copper compatibility, if the above-mentioned appearance judgment met criterion 1 or 2, and the above-mentioned elution amount was 150 ppm by mass or less, it was judged as "A (○)". If neither of these conditions was met, it was judged as "B (×)".

[0101] -Dynamic friction characteristics (SAE No.2)- The friction characteristics of wet friction materials were investigated using a lubricating oil composition for wet clutches, with the use of an SAE No. 2 test apparatus as defined in the Japan Automotive Standard JASO M348 "Test Method for Friction Characteristics of Automatic Transmission Oils". Specifically, tests were conducted using the cycle specified in JASO M348, and the friction characteristics of the wet friction materials were evaluated according to the following criteria. (Evaluation criteria for the frictional properties of wet friction materials) The friction disc and steel plate were observed after the test. A high-magnification, high-precision electron microscope was used for the observation. For the friction disc, it was confirmed that no clogging occurred, and for the steel plate, it was confirmed that no surface discoloration (blackening) occurred. A rating of "A (○)" was given if there was no clogging in the friction disc and no discoloration of the steel plate surface. A rating of "B (×)" was given if either of these conditions was not met.

[0102] -Static friction characteristics (LVFA)- The static friction characteristics of the lubricating oil composition for wet clutches were investigated by the following method. Life evaluation was performed according to the shudder prevention performance test method specified in JASO M349 (2020). Products that maintained a life of 400 hours or more were judged as "A (○)", and those that did not meet this criterion were judged as "B (×)".

[0103] -Measurement of low-temperature viscosity- The viscosity of the wet clutch lubricant composition was measured at -40°C using the ASTM D 2983 method.

[0104] [Table 1]

[0105] Details of the abbreviations in the table are provided below.

[0106] (Base oil) • Base oil 1: Poly-α-olefin (α-decene oligomer, PAO), kinematic viscosity at 100°C is 2 mmHg2 / s • Base oil 2: Poly-α-olefin (α-decene oligomer, PAO), kinematic viscosity at 100°C is 4 mmHg 2 / s

[0107] (Additives) • Additives: DEXRON III (GM's ATF (Automatic Transmission) ATF package-type additive for mission fluid (quality standards): Contains 0.28% by mass of phosphate ester compounds as phosphorus, and also contains anti-wear agents, antioxidants, defoamers, and dispersants. • Polymer 1: Pour point depressant, polymethacrylate (weight-average molecular weight 60,000) • Polymer 2: Viscosity index improver, polyalkyl methacrylate (weight-average molecular weight 140,000) • Polymer 3: Viscosity index improver, polyalkyl methacrylate (weight-average molecular weight 440,000) • Alkyl glyceryl ether: Ether-containing friction modifier (ether-based FM), oleyl (poly)glyceryl ether (a mixture of oleyl alcohol, monoether, and polyether in a ratio of approximately 40:30:30 by mass) • Georail Hydrozen Phosphate: Phosphorus-containing friction modifier (phosphorus-based FM), Georail Hydrozen Phosphate • Ester: Compatibilizer, diisodecyl adipate, kinematic viscosity at 40°C: 14.2 mm 2 / s • Overbasic sulfonate: Cleaning agent, overbasic calcium sulfonate, base number 300 mg / KOH • Triazole-based metal deactivators: Metal deactivators, 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole • Alkyldithiothiadiazole: Corrosion inhibitor, 2,5-bis(tertiaryoctyldithio)1,3,4-thiadiazole • Succinimide dispersant: Dispersant, boron-free succinimide, weight-average molecular weight (polystyrene equivalent) 5300, nitrogen content 1.7% by mass, boron content 0.0% by mass. • Dispersant B: Dispersant, boron-containing succinimide, weight-average molecular weight (polystyrene equivalent) 5500, nitrogen content 1.4% by mass, boron content 0.9% by mass • ZnDTC: Zinc diamyldithiocarbamate

[0108] As shown in Table 1, the wet clutch lubricant compositions of the examples, which contain a base oil, a specific zinc dithiocarbamate compound (alkyldithiothiadiazole), and a nitrogen-containing dispersant (succinimide dispersant, B-type dispersant), and in which the content of the zinc dithiocarbamate compound and the nitrogen content of the dispersant are within a specific range, are able to achieve both an appropriate coefficient of friction and copper compatibility.

[0109] In contrast, the lubricating oil compositions of Comparative Examples 1 and 2, which do not contain nitrogen-containing dispersants (succinimide dispersants, B-type dispersants), show abnormal friction material conditions after testing and fail to obtain appropriate friction characteristics. Comparative Example 3, a lubricating oil composition that does not contain nitrogen-containing dispersants (succinimide dispersants, B-type dispersants) and has a zinc dithiocarbamate compound content exceeding a specific range, exhibits abnormal friction material conditions after testing, fails to provide appropriate friction characteristics, and also has poor copper compatibility. The lubricating oil composition of Comparative Example 4, which does not contain a zinc dithiocarbamate compound, did not exhibit normal friction material conditions after testing, and therefore could not obtain appropriate friction characteristics. In Comparative Examples 5 and 6, the lubricating oil compositions, in which the content of nitrogen-containing dispersants (succinimide dispersants, B-type dispersants) is below a specific range, the friction material is not in a normal state after testing, and appropriate friction characteristics cannot be obtained.

[0110] From the above, it can be seen that the lubricating oil composition for wet clutches in this embodiment has an appropriate coefficient of friction and excellent copper compatibility.

Claims

1. Base oil and, A zinc dithiocarbamate compound represented by the following general formula (a), It contains a nitrogen-containing dispersant, The content of the zinc dithiocarbamate compound is 0.2% by mass or more and 0.3% by mass or less based on the total amount of the lubricating oil composition. A lubricating oil composition for wet clutches, wherein the content of the dispersant, calculated on a nitrogen basis, is 0.02% by mass or more and 0.03% by mass or less, relative to the total amount of the lubricating oil composition. 【Chemistry 1】 (In general formula (a), R １１ , R １２ , R １３ , and R １４ Each of these independently represents either a hydrogen atom or an alkyl group.

2. The wet clutch lubricant composition according to claim 1, wherein the ratio (Y / X) of the content of the dispersant in terms of nitrogen content (Y) to the content (X) of the zinc dithiocarbamate compound is 0.08 or more.

3. The lubricating oil composition for wet clutches according to claim 1, further comprising a metal deactivator in an amount of 0.05% by mass or more and 0.15% by mass or less based on the total amount of the lubricating oil composition.

4. The lubricating oil composition for wet clutches according to claim 1, further comprising a corrosion inhibitor in an amount of 0.01% by mass or more and 0.1% by mass or less based on the total amount of the lubricating oil composition.

5. The wet clutch lubricant composition according to claim 1, further comprising an ether-containing friction modifier having an ether group in an amount of 2.0% by mass or more and 4.0% by mass or less based on the total amount of the lubricant composition.

6. The lubricating oil composition for a wet clutch according to claim 1, further comprising a phosphorus-containing friction modifier containing phosphorus in an amount of 0.5% by mass or more and 1.5% by mass or less based on the total amount of the lubricating oil composition.

7. The wet clutch lubricant composition according to claim 1, further comprising a pour point depressant in an amount of 0.1% by mass or more and 0.5% by mass or less based on the total amount of the lubricant composition.

8. The base oil is 1 mm at 100°C. ２ / s or more 5mm ２ The wet clutch lubricant composition according to claim 1, wherein the synthetic base oil has a kinematic viscosity of 0 / s or less.

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