JPH1046177A - Lubricating oil composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricating oil composition, usable especially for an internal combustion engine, which not only shows low friction characteristics even under greatly varying sliding conditions as in an internal combustion engine and the like, but also is capable of maintaining low friction characteristics for a long period of time even in the presence of nitrogen oxides gas. SOLUTION: This lubricating oil composition comprises a base oil for a lubricating oil compounded with 100 to 2,000ppm in terms of the amount of molybdenum (Mo) of an organic molybdenum compound, 80 to 2,000ppm in terms of the amount of sulfur (S) of an organomonosulfide compound and 80 to 1,500ppm in terms of the amount of sulfur (S) of an organopolysulfide compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a lubricating oil composition, and more particularly to a lubricating oil composition having excellent low friction properties under a wide range of sliding conditions and maintaining low friction properties for a long period of time even in the presence of a nitrogen oxide gas. The present invention relates to a lubricating oil composition which has made it possible to achieve the above-mentioned, and more particularly to a lubricating oil composition suitable as a lubricating oil for an internal combustion engine.

[0002]

2. Description of the Related Art Lubricating oil is used in drive system devices such as an internal combustion engine, an automatic transmission, a shock absorber, and a power steering in order to facilitate the operation. In particular, lubricating oils for internal combustion engines mainly include piston rings and cylinder liners,
Smooth lubrication is required for various sliding surfaces under different conditions, such as crankshafts and connecting rod bearings, and valve mechanisms including cams and valve lifters. It is essential to have.

[0003] Furthermore, with the recent improvement in performance of the internal combustion engine such as lower fuel consumption, higher output, and severe operating conditions, more advanced lubricating oil performance is required. On the other hand, when a part of the combustion gas in the internal combustion engine leaks into the crankcase as blow-by gas from between the piston and the cylinder, the combustion gas contains a considerably high concentration of nitrogen oxide gas. This deteriorates the lubricating oil for the internal combustion engine together with the oxygen in the blow-by gas. With the recent increase in the performance of internal combustion engines, the concentration of nitrogen oxide gas leaking into the crankcase also tends to increase, so as a lubricant for internal combustion engines, a low friction coefficient is provided under a wide range of sliding conditions, and It is extremely important that a low friction coefficient can be maintained for a long period of time.

[0004] In an internal combustion engine, a friction modifier is conventionally added to a lubricating oil as a measure to reduce friction loss and fuel consumption due to a large energy loss in a friction portion involving the lubricating oil. As the friction modifier, for example, an organic molybdenum compound, a fatty acid ester, an alkylamine and the like are generally used. As an example of a lubricating oil composition using an organic molybdenum compound, for example, JP-A-59-122
597, and according to this publication,
There has been proposed a lubricating oil composition using (a) sulfurized oxymolybdenum organophosphorothioate and / or molybdenum dithiocarbamate in combination with (b) zinc dithiophosphate. However, the lubricating oil composition obtained here has a low coefficient of friction in the early stage of use, and although a friction reducing effect can be obtained, the effect can be reduced over a long period of use, especially in the presence of nitrogen oxide gas. The difficulty is that it is difficult to maintain.

On the other hand, according to Japanese Patent Application Laid-Open No. H8-73878, it is considered that a low coefficient of friction can be maintained for a long period of time because (a) molybdenum dithiocarbamate and (b) zinc dithiophosphate and (c) An engine oil composition using a combination of ash-based organic polysulfides is disclosed. However, this lubricating oil composition
There is a problem that the coefficient of friction is high in the region where the sliding speed under reciprocating friction is low, and it is of sufficient quality to be applied to all conditions as a lubricant for internal combustion engines of automobiles whose sliding conditions fluctuate widely. I can't say that.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in consideration of the above-described development of conventional low friction lubricating oils,
To provide a lubricating oil composition that maintains low friction even when the sliding conditions are greatly changed in an internal combustion engine and has low friction over a long period of time, especially even in the presence of nitrogen oxide gas. Is the subject.

[0007]

Means for Solving the Problems Accordingly, the present inventors have:
In order to solve the above problems, as a result of intensive studies, by combining an organic molybdenum compound with an organic monosulfide compound and an organic polysulfide compound, the friction coefficient under a wide range of sliding conditions is low, and for a long time. Finding that low friction can be maintained by use,
The present invention has been completed based on these findings.

That is, according to the present invention, an organic molybdenum compound is added to a lubricating base oil in an amount of 100% molybdenum (Mo).
ppm to 2,000 ppm, 80 ppm to 2,000 ppm of organic monosulfide as sulfur (s) and 80 ppm of organic polysulfide as sulfur (s)
The present invention relates to a lubricating oil composition containing up to 1,500 ppm.

Further, in a preferred embodiment of the present invention, a mineral oil and / or a synthetic oil is used as a lubricating base oil, and a) the following general formula [I]:

[0010]

Embedded image And / or the following general formula [II]

[0011]

Embedded image (In the above general formulas [I] and [II], R _{1 to} R
₈ is a hydrocarbon group, X ₁ , X ₂ , Y ₁ and Y ₂
Is an oxygen atom or a sulfur atom. ) Is defined as a molybdenum (Mo) amount of 100 p.
pm~2,000ppm, b) the following general formula [III] ~ [VI] R 9 -S-R 10 [III] OHC-R 11 -S-R 12 -CHO [IV] R 9 OOC-R 11 - SR ₁₂ -COOR ₁₀ [V]

[0012]

Embedded image (In the above general formulas [III] to [VI], R _{9 to} R _9
14 is a hydrocarbon group, which may be the same or different. ) Is 100 ppm to 1,800 as sulfur (s) amount.
ppm, and c) the following general formulas [VII] to [XII] R ₁₅ -Sx-R ₁₆ [VII] R ₁₅ OOC-R ₁₇ -Sx-R ₁₈ -COOR ₁₆ [VIII]

[0013]

Embedded image

[0014]

Embedded image _{OHC-R 17 -Sx-R 18} -CHO [XI]

[0015]

Embedded image (In the above general formulas [VII] to [XII], R ₁₅ to
R ₂₀ is a hydrocarbon group, and x is an integer of 2 or more. ), A lubricating oil composition comprising at least one selected from the group consisting of organic polysulfide compounds represented by the formula (1) in an amount of 100 ppm to 1,200 ppm as sulfur (s) can be provided.

Hereinafter, the present invention will be described in detail.

The lubricating base oil used in the lubricating oil composition of the present invention is not particularly limited, and those conventionally used as lubricating base oils, for example, mineral base oils,
Any of the synthetic base oils or a mixed base oil thereof can be used. As a mineral base oil, for example, a lubricating oil fraction obtained by vacuum distillation of a normal distillation residue of a paraffinic, intermediate or naphthenic crude oil is subjected to solvent refining, hydrogenation treatment, hydrorefining, catalytic dewatering. Wax, solvent dewaxing, mineral oil obtained by processing in a refining process such as clay treatment, after subjecting the vacuum distillation residue to solvent deasphalting, mineral oil obtained by processing the deasphalted oil in the above refining process, or Mineral oil or the like obtained by isomerization of the wax component or a mixed oil thereof can be used. In the above solvent purification, aromatic extraction solvents such as phenol, furfural and N-methyl-pyrrolidone are used, and propane, MEK / toluene and the like are used as solvents for solvent dewaxing. On the other hand, as synthetic base oils, for example, polyol esters such as poly-α-olefin oligomer, polybutene, alkylbenzene, trimethylolpropane ester, pentaerythritol ester, polyoxyalkylene glycol, polyoxyalkylene glycol ester, polyoxyalkylene glycol ether , Dibasic acid esters, phosphoric acid esters, silicone oils and the like. Each of these base oils may be used alone, or two or more may be used in combination.

The base oil used in the lubricating oil composition of the present invention has a viscosity at 100 ° C. of 3 mm ² / s or more.
Those having a range of 20 mm ² / s are preferred, and hydrocracked oils and wax isomerized oils having an aromatic component (% C _A ) of 3% by weight or less, a sulfur content of 50 ppm or less and a nitrogen content of 50 ppm or less are particularly preferred. is there.

The organic molybdenum compound as a friction modifier incorporated in the lubricating oil composition of the present invention includes, for example,
The following general formula [I]

[0020]

Embedded image Oxymolybdenum dithiocarbamate (may be abbreviated as MoDTC) represented by the following formula: and a general formula [II]

[0021]

Embedded image In addition, oxymolybdenum sulfide organophosphorothioate represented by the following formula (may be abbreviated as MoDTP) can be employed.

In the above general formulas [I] and [II], R _{1 to} R ₈ may be the same or different from each other and are each a hydrocarbon group having 1 to 30 carbon atoms. Examples of the hydrocarbon group include a linear or branched alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; a cycloalkyl group having 4 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; An aryl group or an arylalkyl group can be exemplified. Particularly, an alkyl group having 3 to 20 carbon atoms is preferable. For example, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl Pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group and the like, and their branched alkyl groups.
Preferred are 18 alkyl groups. Also, an alkenyl group having 4 to 18 carbon atoms can be used. X ₁ and X ₂ are an oxygen atom or a sulfur atom, and Y ₁ and Y ₂ are an oxygen atom or a sulfur atom.

Accordingly, as a typical example of the sulfurized oxymolybdenum dithiocarbamate represented by the above general formula [I],
Oxymolybdenum sulfide dithiocarbamate, oxymolybdenum isopropyl dithiocarbamate,
Oxymolybdenum butyl dithiocarbamate, oxymolybdenum isobutyl dithiocarbamate, oxymolybdenum pentyl dithiocarbamate, oxymolybdenum isopentyl dithiocarbamate, oxymolybdenum hexyl dithiocarbamate, oxymolybdenum sulfide 2-ethylbutyl dithiocarbamate,
Oxymolybdenum sulfide heptyl dithiocarbamate, oxymolybdenum octyl dithiocarbamate, oxymolybdenum 2-ethylhexyl dithiocarbamate, oxymolybdenum 2-propylpentyl dithiocarbamate, oxymolybdenum nonyl dithiocarbamate, oxymolybdenum 2-propylhexyl dithiocarbamate, Oxymolybdenum sulfide decyl dithiocarbamate, oxymolybdenum sulfide 2-methyldodecyl dithiocarbamate, oxymolybdenum sulfide hexadecyl dithiocarbamate, oxymolybdenum sulfide octadecyl dithiocarbamate, oxymolybdenum sulfide 2-methyloctadecyl dithiocarbamate, etc. Compounds that have As the oxymolybdenum sulfide organophosphorothioate [II], oxymolybdenum propyl phosphorodithioate, oxymolybdenum butyl phosphorodithioate, oxymolybdenum butenyl phosphorodithioate, oxymolybdenum pentyl phosphorodithioate, oxysulfide Molybdenum hexyl phosphorodithioate, oxymolybdenum heptyl phosphorodithioate, oxymolybdenum octyl phosphorodithioate, oxymolybdenum sulfide 2-ethylhexyl phosphorodithioate, oxymolybdenum decyl phosphorodithioate, oxymolybdenum decyl phosphodeoxysulfide Rodithioate, oxymolybdenum octadecyl phosphorodithioate, oxymolybdenum oleyl phosphorodisulfide It can be exemplified benzoate, etc. or a compound having these branched alkyl or alkenyl group.

Each of these compounds can be used alone, or two or more of them can be arbitrarily mixed and used.

The above organic molybdenum compound is converted to molybdenum (Mo) in an amount of 100 based on the total weight of the lubricating oil composition.
ppm to 2,000 ppm, preferably 200 ppm
It is blended into the base oil at a rate of １，1,500 ppm. If the compounding amount is less than 100 ppm, a sufficient friction reducing effect cannot be obtained. On the other hand, if it exceeds 2,000 ppm, not only the friction reducing effect according to the compounding amount cannot be obtained, but also corrosion is caused.

The organic monosulfide compound used in the lubricating oil composition of the present invention has a bond in which one sulfur atom is present alone without being adjacent to another sulfur atom in the molecule. Organic compounds represented by the general formulas [III] to [VI] can be used.

R ₉ -SR ₁₀ [III] OHC-R ₁₁ -SR ₁₂ -CHO [IV] R ₉ OOC-R ₁₁ -SR ₁₂ -COOR ₁₀ [V]

[0028]

Embedded image In the general formulas [III] to [VI], R ₉ and R ₁₀ are a chain or cyclic hydrocarbon group, and may be the same or different from each other. For example, a linear or branched alkyl group having 1 to 20 carbon atoms;
20 linear or branched alkenyl groups;
And an aryl group of 0. Preferred hydrocarbon groups are an alkyl group and an aryl group, and specifically, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl Group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group,
Examples thereof include a linear alkyl group such as an eicosyl group and the like, or a branched alkyl group thereof. However, the present invention is not limited to these. If the average number of carbon atoms of the two hydrocarbon groups is in the range of 1 to 20, one of the two hydrocarbon groups may further include one hydrocarbon group. Long chain alkyl groups can also be used. Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, a biphenyl group, and a naphthyl group. The aryl group may be a group having an alkyl group having 1 to 14 carbon atoms bonded thereto. Specific examples of the esterified alkyl group include methyl oleate, methyl stearate, triglyceride oleate, methyl ester of vegetable oil, glycerin ester of vegetable oil, glycerin ester of animal oil, methyl ester of animal oil, and the like. Can be used.

R ₁₁ and R ₁₂ are chain or cyclic hydrocarbon groups, which may be the same or different, and are hydrocarbon groups having two binding sites. Particularly, an alkyl group having 1 to 18 carbon atoms is preferable. R ₁₃ and R ₁₄
Is a chain hydrocarbon group, and is preferably the same alkyl group as described above.

Therefore, preferred specific examples of the organic monosulfide compound include dialkyl monosulfide,
For example, dimethyl monosulfide, diethyl monosulfide, di-n-propyl monosulfide, di-n
-Butyl monosulfide, di-n-pentyl monosulfide, di-n-hexyl monosulfide, di-n
-Cetyl monosulfide, di-n-octyl monosulfide, di-n-nonyl monosulfide, di-n-
In addition to decyl monosulfide, di-n-tridecyl monosulfide, di-n-hexadecyl monosulfide, di-n-octadecyl monosulfide and the like, diaryl monosulfides such as diphenyl monosulfide, dibenzyl monosulfide, and dioleic acid Examples thereof include methyl monosulfide, methyl distearate methyl monosulfide, di (trioleic acid glyceride) monosulfide and the like, and monosulfides having a branched alkyl group thereof.

The amount of the organic monosulfide compound is as follows:
80 ppm to 1,800 pp in terms of sulfur (s)
m, preferably from 100 ppm to 1,500 ppm. 80 ppm of organic monosulfide compound
If not reached, the effect of reducing the coefficient of friction in the region where the sliding speed is low under reciprocating friction is not sufficient, and
If it exceeds 000 ppm, not only the effect of reducing friction corresponding to the increase in the amount is not exhibited, but also the occurrence of corrosion becomes severe, which causes a practical problem.

The organic polysulfide compound used in the lubricating oil composition of the present invention is an organic compound having a bond in which two or more sulfur atoms are adjacent to each other in the molecule, and has the following general formulas [VII] to [VII]. XII] R ₁₅ -Sx-R ₁₆ [VII] R ₁₅ OOC-R ₁₇ -Sx-R ₁₈ -COOR ₁₆ [VIII]

[0033]

Embedded image

[0034]

Embedded image _{OHC-R 17 -Sx-R 18} -CHO [XI]

[0035]

Embedded image It is represented by

In the above general formulas [VII] to [XII], R ₁₅ and R ₁₆ are linear or cyclic hydrocarbon groups, which may be the same or different and have 1 to 1 carbon atoms. 20 aliphatic hydrocarbon groups or aromatic hydrocarbon groups. Particularly, an alkyl group, an alkenyl group, an aryl group, an esterified alkyl group and the like are preferable.
As the alkyl group, specifically, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group,
Heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group,
It is a linear alkyl group such as a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, an eicosyl group, or a branched alkyl group thereof. However, the present invention is not limited to these, and a longer-chain alkyl group can be used. Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, a biphenyl group, and a naphthyl group. The aryl group may be a group having an alkyl group having 1 to 14 carbon atoms bonded thereto. As the esterified alkyl group, specifically, methyl oleate group, methyl stearate group, triglyceride oleate group, methyl ester group of vegetable oil,
A glycerin ester group of a vegetable oil, a glycerin ester group of an animal oil, a methyl ester group of an animal oil, and the like can be used. R ₁₇ and R ₁₈ are chain or cyclic hydrocarbon groups, which may be the same or different, and are hydrocarbon groups having two binding sites. In particular, carbon number 1
Preferred are 18 alkylene groups. R ₁₉ and R ₂₀ are chain hydrocarbon groups, and are preferably the same alkyl groups as described above. In the general formulas [VII] to [XII], x is an integer of 2 or more, preferably about 2 to 6.

Accordingly, preferred organic polysulfides include, specifically, dialkyl disulfide, dialkyl trisulfide and other dialkyl polysulfides, diphenyl disulfide, diphenyl trisulfide and other diphenyl polysulfides, dibenzyl disulfide, polyolefin polysulfide and bisalkyl Examples thereof include polysulfanyl thiadiazole, sulfurized olefin, sulfurized fish oil, sulfurized whale oil, and sulfurized pinene. In particular, dialkyl disulfides,
Diphenyl disulfide, bisalkyl polysulfanyl thiadiazole and the like are preferred. Examples of the dialkyl disulfide include dimethyl disulfide, diethyl disulfide, di-n-propyl disulfide, di-n-butyl disulfide, di-n-pentyl disulfide, di-n-hexyl disulfide, and di-disulfide. n-cetyl disulfide, di-n-octyl disulfide, di-n-nonyl disulfide, di-n-decyl disulfide, di-n-tridecyl disulfide, di-n-hexadecyl disulfide, di- In addition to n-octadecyl disulfide, methyl dioleate, methyl disulfide disulfate, di (glyceride trioleate) disulfide and the like, diaryl disulfide such as diphenyl disulfide, dibenzyl disulfide and the like, and these Disulfides or the like having a branched alkyl group can be exemplified.

The amount of the organic polysulfide compound is as follows:
80 ppm to 1,500 ppm in terms of sulfur (s)
And preferably 100 ppm to 1,200 ppm. If the amount is less than 80 ppm, the effect on reducing friction is insufficient, while if it exceeds 1,500 ppm, corrosion wear may increase.

The total sulfur content of the organic monosulfide compound and the organic polysulfide compound is 16%.
0 ppm to 3,500 ppm, preferably 20 ppm
0 ppm to 2,500 ppm.

In the lubricating oil composition of the present invention, zinc dithiophosphate (ZnDTP) and zinc dithiocarbamate (ZnDTC) represented by the following general formulas [XIII] and [XIV] may be used as antiwear agents. it can.

[0041]

Embedded image

[0042]

Embedded image In the above general formulas [XIII] and [XIV], R
_{21 to} R ₂₄ are a hydrogen atom or a hydrocarbon group having 1 to 26 carbon atoms, and the hydrocarbon group is a first group having 1 to 26 carbon atoms.
Primary (primary) or secondary (secondary) alkyl group; alkenyl group having 2 to 26 carbon atoms;
A cycloalkyl group having 6; an aryl group having 6 to 26 carbon atoms;
An alkylaryl group or an arylalkyl group; or a hydrocarbon group containing an ester bond, an ether bond, an alcohol group or a carboxyl group. R _{21 to} R ₂₄ are preferably an alkyl group having 2 to 12 carbon atoms, and 8 to 18 carbon atoms.
And an alkylaryl group having 8 to 18 carbon atoms, which may be the same or different from each other.

Each of ZnDTP and ZnDTC can be used alone or in combination. The proportion of ZnDTP and ZnDTC is 0.1% based on the total weight of the lubricating oil composition.
% To 7% by weight, preferably 1% to 5% by weight.

Further, the lubricating oil composition of the present invention may contain various additives conventionally used in lubricating oils, such as other friction modifiers and metal detergents, as long as the object of the present invention is not impaired. In addition, other wear agents, ashless dispersants, antioxidants, viscosity index improvers, pour point depressants, defoamers, rust inhibitors, corrosion inhibitors and the like can be appropriately compounded.

Other friction modifiers include, for example, polyhydric alcohol partial esters, amines, amides, sulfide esters and the like.

Examples of the metal detergent include calcium sulfonate, calcium phenate, calcium salicylate, magnesium sulfonate, magnesium phenate, and magnesium salicylate. These are usually used at a ratio of 0.05 to 5% by weight.

As other antiwear agents, for example, phosphates, phosphites and the like can be mentioned, and these are usually used at a ratio of 0.05 to 5% by weight.

Examples of the ashless dispersant include succinimide-based, succinamide-based, benzylamine-based, and ester-based dispersants, and may be boronated. These are usually used at a ratio of 0.5 to 7% by weight.

Examples of the antioxidant include amine antioxidants such as alkylated diphenylamine, phenyl-α-naphthylamine and alkylated-α-naphthylamine; 2,6-di-t-butyl-4-methylphenyl;
Examples include phenolic antioxidants such as 4,4'-methylenebis (2,6-di-t-butylphenol), which are usually used at a ratio of 0.05 to 4% by weight.

Examples of the viscosity index improver include polymethacrylates, polyisobutylenes, ethylene-propylene copolymers, styrene-butadiene hydrogenated copolymers, and the like. Used in percentages.

Examples of the pour point depressant include polyalkyl methacrylate, chlorinated paraffin-naphthalene condensate, and alkylated polystyrene.

Examples of the antifoaming agent include dimethylpolysiloxane and polyacrylic acid.

Examples of the rust preventive include fatty acids, alkenyl succinic acid partial esters, fatty acid soaps, alkyl sulfonates, fatty acid polyhydric alcohol esters, fatty acid amines, paraffin oxides, and alkyl polyoxyethylene ethers.

Examples of the corrosion inhibitor include benzotriazole and benzimidazole.

[0055]

DETAILED DESCRIPTION OF THE INVENTION Mineral oil (kinematic viscosity 3 mm ² / s to 20
mm ² / s @ 100 ° C.) as a lubricating base oil, and oxymolybdenum sulfide-N, N-di (2-ethylhexyl) dithiocarbamate as a molybdenum (Mo) amount of 300 pp.
m to 1,500 ppm, diphenyl monosulfide as sulfur (s) amount of 300 ppm to 1,800 ppm, and diphenyl disulfide as sulfur (s) amount of 4
The present invention provides a lubricating oil composition containing from 00 ppm to 1,000 ppm, and further containing an effective amount of an antiwear agent, a metal detergent, an ashless dispersant, an antioxidant, a viscosity index improver, and a pour point depressant. .

[0056]

The present invention will be described in more detail with reference to examples and comparative examples.

A 150-neutral oil (5.3 mm ² / s @ 100 ° C.) was used as a lubricating base oil, and the following additives were used as additives. 1) Organic molybdenum compound C ₈ MoDTC: oxymolybdenum sulfide-N, N-di (2′-ethylhexyl) dithiocarbamate C ₈ MoDTP: Oxymolybdenum sulfide (2-ethylhexyl) phosphorodithioate 2) Organic monosulfide compound C ₈ MS: di-n-octyl monosulfide DPMS: diphenyl monosulfide 3) Organic polysulfide compound C ₈ DS: di-n-octyl disulfide DPDS: diphenyl disulfide The additives shown in Tables 1 and 2 are added to the above base oil. To prepare a lubricating oil composition. With respect to the obtained lubricating oil composition, the friction characteristics of the new oil and the used oil after the NOx oxidation test were evaluated by the following measurement methods. 1) Friction property evaluation method For the new oil and the used oil, a friction coefficient was measured under the following test conditions using a reciprocating friction tester shown in FIG. As the friction coefficient, the value after 20 minutes of the test time was used.

In the friction test, as shown in FIG. 1, an oil film of test oil was formed on a disk, a cylinder was placed on the disk, a predetermined load was applied, and the cylinder was vibrated in a horizontal direction by a predetermined width. Material is DIN100C for both cylinder and disk
R ₆ (HRc62, JISSUJ2 equivalent) was used. Test conditions Conditions Article 1 reviews 2 load, N 400 400 Oil temperature, ° C. 80 80 frequency, Hz 50 50 amplitude, mm 0.5 2.0 (average sliding speed m / s) (0.025) ( 0.1) Time, minutes 20 20 The used oil was obtained after the NOx oxidation test under the following conditions, and was subjected to the above-described friction test similarly to the new oil to evaluate the friction characteristics. NOx oxidation test conditions oil temperature, ° C. 0.99 processing time, h 5 nitrogen oxide gas, NO ₂ concentration vol% 1 Gas flow amount, l / h 3 Examples 1-10 Examples 1-10 are as shown in Table 1 And a low-friction lubricating oil composition according to the present invention.

In Examples 1 to 3, C ₈ MoDTC was used as an organic molybdenum compound using 150 neutral oil as a base oil.
1 shows a low friction lubricating oil composition obtained by using (oxymolybdenum sulfide-N, N-di (2-ethylhexyl) dithiocarbamate) in combination with an organic monosulfide compound and an organic polysulfide compound.

In Examples 4 to 6, C ₈ M was used as the organic molybdenum compound instead of C ₈ MoDTC of Examples 1 to 3.
The present invention provides a low-friction lubricating oil composition using oDTP (oxymolybdenum sulfide (2-ethylhexyl) phosphorothioate) in combination with an organic monosulfide compound and an organic polysulfide compound.

[0061] Furthermore, examples 7-10, organic molybdenum compounds, said C ₈ MoDTC and C ₈ MoDT
1 shows a low-friction lubricating oil composition using P in combination with an organic monosulfide compound and an organic polysulfide compound. Comparative Examples 1 to 9 In Comparative Examples 1 to 6, as shown in Table 2, an organic molybdenum compound alone or an organic molybdenum compound and an organic monosulfide compound and an organic polysulfide compound were used, but the compounding amount was out of the range of the present invention. 1 shows a lubricating oil composition. Comparative Example 1 is a lubricating oil composition using only C ₈ MoDTC as the organic molybdenum compound and not using any of the organic monosulfide compound and the organic polysulfide compound. As a result, although the same amount of C ₈ MoDTC was blended, the friction coefficient was high for both the new oil and the used oil because the above-mentioned sulfur compound was not blended. Have been. Comparative Example 2
Uses C ₈ MS as an organic monosulfide compound and C ₈ DS as an organic polysulfide compound, but the compounding amount of C ₈ MS is 50 pp as sulfur (s) amount.
m and the lubricating oil composition outside the range of the compounding amount of the organic monosulfide compound of the present invention, wherein the organic monosulfide compound and the organic polysulfide compound are used together, but the compounding amount of the organic monosulfide compound is It is shown that the friction coefficient under the condition 1 increases when the amount is less than the predetermined amount. On the other hand, from Comparative Example 3, it is observed that when the amount of the organic polysulfide compound is less than the predetermined amount, the friction coefficient of Condition 2 increases. Comparative Example 4 shows C ₈ M
A lubricating oil composition using C ₈ MoDTP instead of oDTC, but having a predetermined amount of DPDS of 40 ppm, and has a very high friction coefficient under condition 2. Comparative Example 5
6 shows a lubricating oil composition in which the compounding amount of the organic molybdenum compound is less than a predetermined amount, and the friction coefficient of the new oil and the used oil is remarkably high.

In Comparative Examples 7 and 8, C ₈ MoDTC was used as the organic molybdenum compound in the same amount as in Example 1, but only the organic monosulfide compound (C ₈ MS) was used and the organic polysulfide compound was used in combination. 1 shows a lubricating oil composition that did not exist.

Comparative Example 8 illustrates a lubricating oil composition using only an organic polysulfide compound (C ₈ DS) and not using an organic monosulfide compound in combination.
All of them have high friction coefficients, and it is understood that the combined use of an organic monosulfide compound and an organic polysulfide compound is indispensable for obtaining a friction reducing effect.

On the other hand, according to Comparative Example 9, a lubricating oil composition using both an organic monosulfide compound (C ₈ MS) and an organic polysulfide compound (C ₈ DS) but lacking an organic molybdenum compound was exemplified. It is clear that a sufficient friction reducing effect cannot be obtained unless an organic molybdenum compound is used.

[0065]

[Table 1]

[0066]

[Table 2]

[0067]

According to the present invention, there is provided a lubricating oil composition comprising an organic molybdenum compound, an organic monosulfide compound and an organic polysulfide compound as essential components, each of which is blended in a specific amount. It has excellent low friction under a wide range of sliding conditions, and exhibits oxidation resistance even in the presence of a nitrogen oxide gas, and can maintain low friction. Therefore, the lubricating oil composition of the present invention is suitable as a lubricating oil for an internal combustion engine, an automatic transmission, a shock absorber, a power steering, and the like, particularly, an internal combustion engine.

[Brief description of the drawings]

FIG. 1 is a basic conceptual diagram of a friction tester used for measuring a friction coefficient of a lubricating oil composition of the present invention.

[Explanation of symbols]

 1 cylinder 2 disc

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Claims (1)

[Claims] 1. A lubricating base oil comprising an organic molybdenum compound in an amount of 100 ppm to 2,000 as molybdenum (Mo).
ppm, the organic monosulfide compound is 80 ppm to 2,000 ppm as sulfur (s) amount, and the organic polysulfide compound is 80 ppm to 80 ppm as sulfur (s) amount.
A lubricating oil composition containing 1,500 ppm.