JPH093463A - Engine oil composition - Google Patents

Abstract

PURPOSE: To obtain an engine oil composition, containing an alkaline earth metallic salicylate-based detergent, a zinc dialkyl dithiophosphate and a succinimide-based ashless dispersing agent, etc., in a base oil having a specific kinematic viscosity and a low total aromatic content. CONSTITUTION: This engine oil composition is obtained by blending (A) an alkaline earth salicylate-based detergent in an amount of 0.5-1.2 mass% expressed in terms of sulfuric acid ash, (B) a zinc dialkyl dithiophosphate in an amount of 0.04-0.10 mass% expressed in terms of phosphorus concentration, (C) a succinimide-based ashless dispersing agent having a polybutenyl group of 900-3500 number-average molecular weight in an amount of 0.05-0.20 mass% expressed in terms of nitrogen concentration, (D) 0.1-3.0 mass% phenolic ashless antioxidant, (E) a molybdenum dithiocarbamate-based friction reducing compound in an amount of 0.02-0.15 mass% expressed in terms of Mo, (F) an organic compound containing sulfur other than the components (B) and (E) in an amount of 0.01-0.5 mass% expressed in terms of S concentration and (G) a viscosity index improver so as to provide 5.6-12.5mm<2> /sec kinematic viscosity in a base oil having 2-8mm<2> /sec kinematic viscosity at 100 deg.C and <=15 mass% total aromatic content.

Description

Detailed Description of the Invention

[0001]

This invention relates to engine oil compositions. According to the present invention, it is possible to provide an engine oil composition capable of reducing fuel consumption over a long period of time.

[0002]

2. Description of the Related Art Fuel economy of automobiles, which has been implemented since the oil crisis, is still one of the important issues from the viewpoint of resource conservation and environmental protection. The improvement of fuel efficiency of automobiles has been achieved by reducing the weight of the vehicle body, improving combustion and reducing the friction of the engine. Engine friction reduction includes improvements in valve train structure, reduction in the number of piston rings, reduction in surface roughness of sliding members, and use of fuel-efficient engine oil. Among these, the use of fuel-efficient engine oil has become popular in the market due to its excellent cost / performance ratio. As a fuel economy measure with engine oil,
(1) Decrease the viscosity of engine oil intended to reduce friction loss under fluid lubrication conditions such as piston systems and bearings, and (2) Appropriate for reducing friction in valve trains under mixed lubrication conditions. Prescription development is needed. Generally, a friction reducing agent (FM) is added to engine oil as an additive effective for reducing friction. However, the formulation of other engine oil additives and the selection of the base oil are also important in order to fully exhibit the function of the friction reducing agent. In addition, it is necessary to have a long service life in which low fuel consumption is maintained even after long-distance running when engine oil deteriorates. However, the friction-reducing agent generally exerts an excellent effect in a fresh oil state before the engine oil deteriorates, but has a problem that the fuel economy effect is lost due to deterioration during engine operation. . Therefore, in order to overcome these problems, it is desired to develop an engine oil having excellent fuel economy and maintaining its performance for a long period of time.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides an engine oil having excellent fuel economy and long-lasting performance.

[0004]

As a result of intensive studies to solve the above problems, the inventors of the present invention have found that an engine oil composition having a specific constitution has excellent fuel economy and performance. The present invention has been completed and the present invention has been completed.

That is, according to the present invention, a base oil having a kinematic viscosity at 100 ° C. of ² to 8 mm ² / s and a total aromatic content of 15% by mass or less is used, based on the total amount of the composition, (1) alkali 0.5% earth metal salicylate-based detergent as sulfated ash
To 1.2% by mass, (2) 0.04 to 0.10% by mass of zinc dialkyldithiophosphate in terms of phosphorus concentration, and (3) a succinimide ashless dispersant having a polybutenyl group having a number average molecular weight of 900 to 3500. 0.05 to 0.05 in terms of nitrogen concentration
0.20% by mass, (4) phenol-based ashless antioxidant is 0.1-3.0% by mass, and (5) molybdenum dithiocarbamate-based friction reducing agent is 0.1% in terms of molybdenum concentration.
02 to 0.15% by mass, (6) above (2) and (5)
Sulfur-containing organic compounds other than 0.01 to 0.01 in terms of sulfur concentration
An engine oil composition comprising 0.5% by mass and (7) a viscosity index improver in an amount such that the composition has a kinematic viscosity at 100 ° C. of 5.6 to 12.5 mm ² / s. Regarding things. Hereinafter, the present invention will be described in detail.

The base oil of the engine oil composition of the present invention comprises 10
It is defined by the kinematic viscosity at 0 ° C and the total aromatic content. The kinematic viscosity of the base oil is 2-8 mm ² / s. It is important that the upper limit of the total aromatic content of the base oil is 15% by mass. A base oil having a total aromatic content exceeding the above upper limit cannot obtain a synergistic effect with each additive used in the present invention even if its kinematic viscosity is within the range specified by the present invention, It is not possible to obtain an engine oil composition having a long lasting effect of reducing friction. There is no particular limitation on the lower limit of the total aromatic content of the base oil, but when the total aromatic content is less than 2% by mass, various additives do not have sufficient solubility in the base oil. In some cases, the total aromatic content is particularly preferably 2% by mass or more.

[0007] The total aromatic content in the present invention is defined as:
Aromatic fraction measured according to ASTM D2549 (a
romatics fraction) content, and usually, this aromatic fraction includes alkylbenzene, alkylnaphthalene, anthracene, phenanthrene, and their alkylated compounds, compounds in which four or more benzene rings are condensed, or pyridines and quinolines. And compounds having a heteroaromatic group such as phenols and naphthols.

Mineral oil, synthetic oil or a mixture thereof can be used as the base oil of the present invention, but the total aromatic content is 15
In order to obtain a base oil having a mass% or less, preferably 2 to 15 mass%, mineral oil alone, a mixed oil of mineral oil and synthetic oil containing no aromatics, synthetic oil containing aromatics and containing no aromatics Use a mixture of synthetic oils. When a mixed oil of mineral oil and aromatic-free synthetic oil is used, the total aromatic content of the mixed oil is 15
The total aromatic content of the mineral oil used may be above 15% by weight, as long as it is below% by weight.

As the mineral oil referred to herein, the lubricating oil fraction obtained by distilling crude oil under atmospheric pressure and vacuum distillation is used to remove the solvent,
Examples include those purified by performing one or more treatments such as solvent extraction, hydrocracking, solvent dewaxing, and hydrorefining. Examples of the aromatic-containing synthetic oil include alkylnaphthalene and alkylbenzene.

Specific examples of aromatic-free synthetic oils include poly-α-olefins such as polybutene, 1-octene oligomer and 1-decene oligomer, or hydrides thereof; ditridecyl glutarate, di2-ethylhexyl adipate. , Diisodecyl adipate, ditridecyl adipate, diesters such as di3-ethylhexyl sebacate; trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethylhexanoate, polyol esters such as pentaerythritol pelargonate, or the like. A mixture may be mentioned.

The alkaline earth metal salicylate-based detergent (hereinafter referred to as "component (1)"), which is one of the essential components of the present invention, is a calcium salicylate-based detergent, a magnesium salicylate-based detergent or a mixture thereof. It is preferably used. Examples of the component (1) include neutral alkaline earth metal salicylates and overbased alkaline earth metal salicylates. The neutral alkaline earth metal salicylate as used herein refers to a salt obtained by neutralizing a hydrocarbon group-substituted salicylic acid with an equivalent amount of an alkaline earth metal hydroxide, and is represented by the following general formula (1). To be

[0012]

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Wherein R ¹ is a linear or branched alkyl group;
It shows a hydrocarbon group such as an alkenyl group, an aryl group, an alkylaryl group and an arylalkyl group, and an alkyl group is particularly preferable. It is desirable that the alkyl group has 12 to 30, preferably 14 to 18 carbon atoms, and specifically, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group. Group, henicosyl group, docosyl group, tricosyl group, tetracosyl group, pentacosyl group, hexacosyl group, heptacosyl group, octacosyl group, nonacosyl group, triacontyl group, and the like,
These may be linear or branched. When introducing an alkyl group, a mixture of α-olefins may be used as a raw material. In this case, the component (1) is a mixture of neutral alkaline earth metal salicylates having alkyl groups having different structures. M ¹ represents calcium or magnesium.

The overbased alkaline earth metal salicylate is a neutral alkaline earth prepared from an alkaline earth metal carbonate such as calcium carbonate or magnesium carbonate or an alkaline earth metal borate such as calcium borate or magnesium borate. It is obtained by overbasing a metal-salicylate.

Base number of component (1) (JIS K2501
There is no particular limitation on the perchloric acid method), but 60 to 350 mgK
OH / g, preferably 150-350 mgKOH / g.

The content of the component (1) in the engine oil composition of the present invention is 0.5 to 1.2% by mass as sulfated ash. If the content of the component (1) is less than 0.5% by mass, the fuel coefficient cannot be maintained because the friction coefficient becomes high after deterioration of the engine oil, and the above-mentioned 1.2.
When the content exceeds the mass%, the effect of reducing the fuel consumption of the engine oil composition is not sufficient, which is not desirable.

The sulfated ash referred to in the present invention means JIS.
Sulfated ash content measured according to K2272, that is,
It means the ash content that is obtained by adding sulfuric acid to the carbonization residue generated by burning the sample and heating it to a constant weight.

Examples of zinc dialkyldithiophosphate (hereinafter referred to as "component (2)") which is one of the essential components of the present invention include compounds represented by the following general formula (2).

[0019]

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In the formula, R ² , R ³ , R ⁴ and R ⁵ each independently represent a linear or branched alkyl group having 2 to 18 carbon atoms, preferably 3 to 8 carbon atoms, which may be the same or different. Include ethyl, propyl, butyl, pentyl,
Hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, etc. But it's okay. These may be primary alkyl groups, secondary alkyl groups or tertiary alkyl groups. R ² , R ³ ,
When introducing R ⁴ and R ⁵ , a mixture of α-olefins may be used as a raw material. In this case, the component (2) is a mixture of zinc dialkyldithiophosphate having an alkyl group having a different structure.

The content of the component (2) in the engine oil composition of the present invention is 0.04 to 0.10 mass% in terms of phosphorus concentration, based on the total amount of the engine oil composition. When the content of the component (2) is less than 0.04% by mass, the friction coefficient becomes high after deterioration of the engine oil, so that the fuel economy cannot be maintained, and the content exceeds 0.10% by mass. In this case, the poisoning of the three-way catalyst is accelerated and the exhaust gas is adversely affected, which is not desirable.

The succinimide ashless dispersant (hereinafter referred to as "component (3)"), which is one of the essential components of the present invention, is a monoimide represented by the following general formula (3) and a general formula (4). ) And those obtained by modifying these with an organic acid or boric acid.

[0023]

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[0024]

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In the formula, R ⁶ and R ⁷ are independently a polybutenyl group having a number average molecular weight of 900 to 3500, and n is a number of 2 to 5. The polybutenyl group mentioned here is obtained from polybutene obtained by polymerizing a mixture of 1-butene and isobutene.

The method for producing the component (3) is not particularly limited, but it can be obtained, for example, by reacting polybutene having a number average molecular weight of 900 to 3500 or chlorinated polybutene having a number average molecular weight of 900 to 3500 with maleic anhydride at 100 to 200 ° C. It can be obtained by reacting the obtained polybutenyl succinic acid with a polyamine. Examples of polyamines include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and the like.

The content of the component (3) in the engine oil composition of the present invention is 0.05 to 0.20 mass% in terms of nitrogen concentration, based on the total amount of the engine oil composition. When the content of the component (3) is less than 0.05% by mass, a sufficient friction reducing effect cannot be obtained, and the above 0.2
If it exceeds 0% by mass, it adversely affects the rubber sealant and is not desirable.

A preferred specific example of the phenol-based ashless antioxidant (hereinafter referred to as "component (4)"), which is one of the essential components of the present invention, will be described below. 4,4'-methylenebis (2,6- Di-tert-butylphenol), 4,4'-
Bis (2,6-di-tert-butylphenol), 4,
4'-bis (2-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert)
-Butylphenol), 2,2'-methylenebis (4-
Methyl-6-tert-butylphenol), 4,4'-butylidenebis (3-methyl-6-tert-butylphenol), 4,4'-isopropylidenebis (2,6-di-)
tert-butylphenol), 2,2′-methylenebis (4-methyl-6-nonylphenol), 2,2′-isobutylidenebis (4,6-dimethylphenol),
2,2'-methylenebis (4-methyl-6-cyclohexylphenol), 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,4 -Dimethyl-6-tert-butylphenol, 2,6-di-tert-α-dimethylamino-p
-Cresol, 2,6-di-tert-butyl-4 (N,
N'-dimethylaminomethylphenol), 4,4'-
Thiobis (2-methyl-6-tert-butylphenol), 4,4'-thiobis (3-methyl-6-tert-butylphenol), 2,2'-thiobis (4-methyl-)
6-tert-butylphenol), bis (3-methyl-4)
-Hydroxy-5-tert-butylbenzyl) sulfide, bis (3,5-di-tert-butyl-4-hydroxybenzyl) sulfide, 2,2'-thio-diethylenebis [3- (3,5-di- tert-butyl-4-hydroxyphenyl) propionate], tridecyl-3- (3,3
5-di-tert-butyl-4-hydroxyphenyl) propionate, pentaerythrityl-tetrakis [3-
(3,5-Di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-
Examples thereof include di-tert-butyl-4-hydroxyphenyl) propionate. Of course, these compounds can be mixed and used.

Regarding the content of the component (4) in the engine oil composition of the present invention, the upper limit value is 3.0% by mass, preferably 2.0, based on the total amount of the engine oil composition.
The lower limit value is 0.1% by mass, preferably 0.3% by mass, based on the total amount of the engine oil composition.
When the content of the component (4) is less than the lower limit value, the friction coefficient becomes high after deterioration of the engine oil, so that the fuel economy cannot be maintained, and when it exceeds the upper limit value,
It is not desirable because sufficient antioxidant properties cannot be obtained.

As the molybdenum dithiocarbamate-based friction reducing agent (hereinafter referred to as "component (5)"), which is one of the essential components of the present invention, those represented by the following general formula (5) can be mentioned.

[0031]

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In the formula, R ⁸ , R ⁹ , R ¹⁰ and R ¹¹ may be the same or different and each represents a hydrocarbon group such as an alkyl group, an alkenyl group, an aryl group, an alkylaryl group or an arylalkyl group. Particularly preferred is an alkyl group. Specific examples of R ⁸ , R ⁹ , R ¹⁰ and R ¹¹ include 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, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group and the like having 2 to 18 carbon atoms, preferably 8 to 13 alkyl groups (these alkyl groups may be linear or branched) Or a primary alkyl group, a secondary alkyl group or a tertiary alkyl group); an alkylaryl group such as a butylphenyl group or a nonylphenyl group (the alkyl portion of these alkylaryl groups may be linear or branched) , The position of substitution of the alkyl moiety on the aryl group is arbitrary).

When introducing an alkyl group as R ⁸ , R ⁹ , R ¹⁰ and R ¹¹ , a mixture of α-olefins may be used as a raw material. In this case, the component (5) has an alkyl group having a different structure. Of molybdenum dithiocarbamate. X ¹ , X ² , X ³ and X ⁴ each independently represent a sulfur atom or an oxygen atom.

Preferred examples of the molybdenum dithiocarbamate-based friction reducing agent of the component (5) are summarized below. Molybdenum sulfide diethyldithiocarbamate, molybdenum dipropyldithiocarbamate sulfide, molybdenum dibutyldithiocarbamate sulfide, molybdenum dipentyldithiocarbamate sulfide, molybdenum dihexyl sulfide. Dithiocarbamate, molybdenum dioctyldithiocarbamate, molybdenum didecyldithiocarbamate, molybdenum didodecyldithiocarbamate, molybdenum ditridecyldithiocarbamate, molybdenum di (butylphenyl) dithiocarbamate, molybdenum di (nonylphenyl) dithiocarbamate, oxymolybdenum sulfide Dithiocarbamate, oxymolybdenum sulfide dip Pill dithiocarbamate, oxymolybdenum dibutyl dithiocarbamate sulfide, oxymolybdenum dipentyl dithiocarbamate sulfide, oxymolybdenum dihexyl dithiocarbamate sulfide, oxymolybdenum dioctyl dithiocarbamate sulfide, oxymolybdenum didecyl dithiocarbamate sulfide oxymolybdenum didecyl dithiocarbamate, oxymolybdenum ditrisulfide Decyl dithiocarbamate, oxymolybdenum di (butylphenyl) dithiocarbamate,
Examples thereof include oxymolybdenum di (nonylphenyl) dithiocarbamate. Of course, these compounds can be mixed and used.

Regarding the content of the component (5) in the engine oil composition of the present invention, the upper limit value is 0.15% by mass, preferably 0.1% by mass in terms of molybdenum concentration, based on the total amount of the engine oil composition. %, And the lower limit is 0.02% by mass, preferably 0.04% by mass in terms of molybdenum concentration, based on the total amount of the engine oil composition. When the content of the component (5) is less than the lower limit value, a sufficient friction reducing effect cannot be obtained, and when the content exceeds the upper limit value, oil-insoluble sludge is generated during engine oil deterioration, Each is not desirable.

The sulfur-containing organic compound which is an essential component of the present invention (hereinafter referred to as “component (6)”) is a sulfur-containing organic compound excluding the zinc dialkyldithiophosphate of component (2) and the molybdenum dithiocarbamate of component (5). A compound selected from compounds. Specific examples of component (6) include sulfurized fats and oils, sulfur-crosslinked metal phenates, dihydrocarbyl polysulfides, dithiocarbamates, and mixtures thereof. Among these, sulfur-crosslinked metal phenates, polysulfides and dithiocarbamates are mentioned. Classes are preferred.

As the sulfurized fats and oils referred to herein, animals and plants having an unsaturated bond such as olive oil, castor oil, tea seed oil, bran oil, cottonseed oil, rapeseed oil, corn oil, beef tallow, beef leg oil, sperm whale oil, whale wax and the like. The compound obtained by adding sulfur to fats and oils and heating is mentioned.

Examples of the sulfur-crosslinked metal phenate include alkaline earth metal salts of sulfides of alkylphenol to which an alkyl group having 8 to 30 carbon atoms is added, represented by the following general formula (6). Represented by.

[0039]

[Chemical 6]

In the formula, R ¹² is a linear or branched alkyl group having 8 to 30 carbon atoms, preferably 9 to 20 carbon atoms, and these alkyl groups are primary alkyl groups, secondary alkyl groups or tertiary alkyl groups. Including. Specific examples of R ¹² include an octyl group,
Nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group, henicosyl group, docosyl group, tricosyl group, tetracosyl group, pentacosyl group , A hexacosyl group, a heptacosyl group, an octacosyl group, a nonacosyl group, a triacontyl group and the like, which may be linear or branched.

When the alkyl group is introduced, a mixture of α-olefins may be used as a starting material. In this case, a mixture of those having alkyl groups having different structures is used. Further, in the formula, M ² represents an alkaline earth metal such as magnesium, calcium, strontium or barium, and calcium and magnesium are particularly preferable. X is 1 to
4, preferably 1-2, and n is 1-3, preferably 1-2.

Dihydrocarbyl polysulfide means a compound represented by the following general formula (7).

[0043]

[Chemical 7]

In the formula, R ¹³ and R ¹⁴ may be the same or different and each is a linear or branched alkyl group having 1 to 22 carbon atoms, an alkenyl group, or 6 carbon atoms.
20 represents an aryl group, an alkylaryl group or an arylalkyl group, and y represents a number of 1 to 5, preferably 1 to 2. The alkyl group mentioned here includes a primary alkyl group, a secondary alkyl group or a tertiary alkyl group.

Specific examples of R ¹³ and R ¹⁴ are propyl group, butyl group, pentyl group, hexyl group, heptyl group,
Alkyl groups such as octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, eicosyl group (these alkyl groups may be linear Aryl group such as phenyl group, naphthyl group (including all isomers); tolyl group, ethylphenyl group, propylphenyl group, butylphenyl group, pentylphenyl group, hexylphenyl group, heptylphenyl group , Octylphenyl group, nonylphenyl group, decylphenyl group, undecylphenyl group, dodecylphenyl group, xylyl group, ethylmethylphenyl group, diethylphenyl group, dipropylphenyl group, dibutylphenyl group, methylnaphthyl group, ethylnaphthyl group , Propyl Alkylaryl groups such as naphthyl group, butylnaphthyl group, dimethylnaphthyl group, ethylmethylnaphthyl group, diethylnaphthyl group, dipropylnaphthyl group, dibutylnaphthyl group (the alkyl portion of these alkylaryl groups may be linear or branched, The substitution position of the alkyl moiety on the aryl group is arbitrary.);
And an arylalkyl group such as a benzyl group, a phenylethyl group and a phenylpropyl group (the alkyl portion of these arylalkyl groups may be linear or branched, and the substitution position of the aryl portion is arbitrary).

R ¹³ and R ¹⁴ in the general formula (7) are each an alkyl group having 3 to 18 carbon atoms derived from propylene or isobutene, or an aryl group having 6 to 8 carbon atoms, an alkylaryl group or an arylalkyl. It is preferably a group, and examples of these groups include an isopropyl group, a branched hexyl group derived from a propylene dimer, a branched nonyl group derived from a propylene trimer, and a propylene tetramer. Derived from branched dodecyl group, branched pentadecyl group derived from propylene pentamer, branched octadecyl group derived from propylene hexamer, tert-butyl group, derived from isobutene dimer Branched octyl group, branched dodecyl group derived from isobutene trimer, branched hexadecane derived from isobutene tetramer Alkyl groups such as phenyl groups (these alkyl groups include all branched isomers); phenyl groups, tolyl groups, ethylphenyl groups, alkylaryl groups such as xylyl groups (the alkyl moieties of these alkylaryl groups are It may be a chain or branched, and the substitution position of the alkyl moiety on the aryl group is arbitrary.); And an arylalkyl group such as a benzyl group, a phenylethyl group (the substitution position of the phenyl group is arbitrary). .

Further, R ¹³ and R ¹⁴ in the general formula (7) are preferably an alkyl group having 3 to 18 carbon atoms, particularly 6 to 15 carbon atoms derived from propylene or isobutene.

Specific examples of polysulfides include dibutyl polysulfide, dihexyl polysulfide, dioctyl polysulfide, dinonyl polysulfide, didecyl polysulfide, didodecyl polysulfide, ditetradecyl polysulfide, dihexadecyl polysulfide, dioctadecyl polysulfide, dieicosylphenyl sulfide, Examples thereof include polysulfide, dibenzyl polysulfide, diphenethyl polysulfide, polypropenyl polysulfide, polybutenyl polysulfide and a mixture thereof, and the like, but polypropenyl polysulfide, polybutenyl polysulfide and a mixture thereof are particularly preferable. As used herein, polypropenyl polysulfide, polybutenyl polysulfide, or a mixture thereof is an olefinic hydrocarbon such as propylene, isobutene, a dimer or tetramer of these monomers, or a mixture of these monomers or polymers. It can be obtained by sulfurization with sulfur, sulfur halide (for example, sulfur monochloride or sulfur dichloride), hydrogen sulfide and a mixture thereof.

Examples of dithiocarbamates include alkylthiocarbamyl compounds represented by the following general formula (8).

[0050]

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In the formula, R ¹⁵ , R ¹⁶ , R ¹⁷ and R ¹⁸ each represent a linear or branched alkyl group having 1 to 18, preferably 1 to 10 carbon atoms, which may be the same or different. Is a methyl group, ethyl group, propyl group, n-butyl group, isobutyl group, pentyl group, isopentyl group, hexyl group, heptyl group, octyl group, 2-ethylhexyl group, nonyl group, decyl group, tridecyl group and octadecyl group. Alkyl groups such as When the alkyl group is introduced, a mixture of α-olefins may be used as a raw material. In this case, the mixture is a mixture of alkylthiocarbamyl compounds having plural kinds of alkyl groups.

In the formula (Y), S, S-S, S-CH _{2
-S, S- (CH 2) 2} -S, S- (CH 2) 3 -S,
Alternatively, it represents S-Zn-S.

Specific examples of the alkyldithiocarbamyl compound of the above general formula (8) include methylenebis (dibutyldithiocarbamate), bis (dimethylthiocarbamyl) monosulfide, bis (dimethylthiocarba). Mil) disulfide, bis (dibutylthiocarbamyl) disulfide, bis (dipentylthiocarbamyl)
Examples thereof include disulfide, bis (dioctylthiocarbamyl) disulfide, zinc dipentyldithiocarbamate and the like.

Regarding the content of the component (6) in the engine oil composition of the present invention, the upper limit value is 0.5 mass% in terms of sulfur concentration, preferably 0.2 mass, based on the total amount of the engine oil composition. %, And the lower limit value is also 0.01% by mass, preferably 0.02% by mass, in terms of molybdenum concentration, based on the total amount of the engine oil composition. When the content of the component (6) is less than the above lower limit value, sufficient life extension effect of fuel economy cannot be obtained, and when it exceeds the above upper limit value, it may cause rust or corrosion during engine oil deterioration. They are not desirable because they tend to generate strong acids.

The engine oil composition of the present invention further comprises a viscosity index improver (hereinafter referred to as "component (7)") having a kinematic viscosity at 100 ° C. of 5.6 to 12.5 mm ² / s. Add an amount such that Examples of the component (7) include polymethacrylate, olefin copolymer or hydride thereof, graft copolymer of polymethacrylate and olefin copolymer or hydride thereof, or mixture of polymethacrylate and olefin copolymer or hydride thereof. The olefin copolymer referred to here is ethylene and has 3 to 1 carbon atoms.
The α-olefin copolymer of 8 is mentioned as a specific example.

The weight average molecular weights of the polymethacrylate, the olefin copolymer or its hydride, and the graft copolymer of the polymethacrylate and olefin copolymer or its hydride are usually 5 respectively.
10,000 to 1,000,000, 10,000 to 50
It is in the range of 50,000, 50,000 to 1,000,000.

As described above, the component (7) is added in such an amount that the engine oil composition of the present invention has a kinematic viscosity at 100 ° C. of 5.6 to 12.5 mm ² / s. However, usually 1 to 1 based on the total amount of the engine oil composition
It is about 0 mass%.

The engine oil composition of the present invention has excellent performance as an engine oil by itself, and particularly, low fuel consumption is maintained for a long time. The oil additive can be added to the engine oil composition of the present invention alone or in the form of a combination of several kinds.

Known additives that can be blended are, for example, detergents other than the components (1) and (6) of the present invention, such as alkaline earth metal sulfonates; organic phosphates, organic phosphites, fatty acids. , Fatty acid ester,
Antiwear agents such as aliphatic alcohols; ashless dispersants other than the component (3) of the present invention, such as long-chain alkyl polyamines and amides of long-chain fatty acids and polyamines; phenyl-α-naphthylamine, alkylphenyl-α-naphthylamine, dialkyl. Amine antioxidants such as diphenylamine;
Friction reducing agents other than the component (5) of the present invention such as molybdenum dithiophosphate, molybdenum disulfide, long-chain aliphatic amine, long-chain fatty acid, long-chain fatty acid ester, and long-chain fatty alcohol; petroleum sulfonate, alkylbenzene sulfonate, dinonyl Corrosion inhibitor such as naphthalene sulfonate, alkenyl succinic acid ester, polyhydric alcohol ester; Polyalkylene glycol nonionic surfactant such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylnaphthyl ether Representative demulsifiers;
Imidazoline, pyrimidine derivative, alkyl thiadiazole, mercaptobenzothiazole, benzotriazole or its derivative, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bisdialkyldithiocarbamate, 2- (alkyldithio) Examples include metal deactivators such as benzimidazole and β- (o-carboxybenzylthio) propionnitrile; defoaming agents such as silicone, fluorosilicone and fluoroalkyl ether.

When these additives are added to the lubricating oil composition of the present invention, the addition amount is based on the total amount of the engine oil composition, 0.0005 to 1% by mass for the defoaming agent, and metal deactivating agent. It is usually selected in the range of 0.005 to 1% by mass for the agents and 0.1 to 15% by mass for the other additives.

The engine oil composition of the present invention is used for motorcycles and 4
It can be preferably used as a lubricating oil for gasoline engines such as wheeled vehicles, land diesel engines, and marine diesel engines.

[0062]

EXAMPLES The contents of the present invention will be described more specifically below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The compositions of the engine oil compositions used in the examples and comparative examples are shown in the table. The performance of these engine oils was evaluated by a performance evaluation test shown below.

(Engine Oil Deterioration Test) The deterioration test of the sample oil was carried out using a bench engine. The engine used was an in-line 4-cylinder engine with a displacement of 2.2 dm ³ and OHC type. Operating conditions are oil temperature 100 ℃, rotation speed 3000r
pm and inspiratory pressure-300 mmHg, test time 75 h. The evaluation of the friction characteristics of the new oil of the sample oil and the deteriorated oil of the engine test was carried out by SRV reciprocating friction tester manufactured by Optimol. The test conditions are a load of 400 N, a frequency of 50 Hz, an amplitude of 1.5 mm, and an oil temperature of 80 ° C.

(Examples 1 to 4) Table 1 shows the results of performance evaluation tests of the engine oils of Examples 1 to 4 whose compositions are shown in Table 1. It can be seen from Table 1 that the engine oils of Examples 1 to 4 not only have a low coefficient of friction in the fresh oil state, but also maintain a low coefficient of friction after deterioration by the deterioration test. That is, the engine oil composition of the present invention has excellent fuel economy and is excellent in that it can maintain fuel economy even after deterioration.
Such effects of the present invention are realized only by the synergistic effect of each component. This will be described below by a comparative example.

Comparative Example 1 0.68 mass% as sulfated ash (3.5 mass% × sulfated ash content 19.5 mass% = 0.68)
Mass) Ca salicylate was replaced with 0.68 mass% (1.6 mass% x sulfated ash 42.5 mass% = 0.68 mass%) Ca sulfonate as a sulfated ash, and Example 1 was used. Identical composition [For polymers, the amount added is different because the amount added was such that the kinematic viscosity in Example 1 was close to 9.9 mm ² / s. The base oil is the balance excluding the additives. ] Was prepared, and a deterioration test was performed on the engine oil. The results of the engine oil performance evaluation test are shown in Table 1. Although new oil has a low coefficient of friction, the coefficient of friction increases after deterioration,
Fuel economy could not be maintained.

COMPARATIVE EXAMPLE 2 The same composition as in Example 1 except that Ca salicylate was not used. [The polymer was added in such an amount that the kinematic viscosity of Example 1 was close to 9.9 mm ² / s. Therefore, the amount of polymer added is different. The base oil is the balance excluding the additives. ] Was prepared, and a deterioration test was performed on the engine oil. The results of the engine oil performance evaluation test are shown in Table 1. Although new oil has a low coefficient of friction, the coefficient of friction increased after deterioration and fuel economy could not be maintained.

(Comparative Example 3) The amount of zinc dialkyldithiophosphate added was 0.09% by mass in terms of phosphorus concentration (1.25% by mass x additive phosphorus concentration 7.2% by mass = 0.09% by mass).
From 0.04% by mass (0.54% by mass × phosphorus concentration of additive 7.2% by mass = 0.04% by mass) to the same composition as in Example 1 An amount was added so that the viscosity was close to 9.9 mm ² / s. The base oil is the balance excluding the additives. ] Was prepared, and a deterioration test was performed on the engine oil. The results of the engine oil performance evaluation test are shown in Table 1. Although new oil has a low coefficient of friction, the coefficient of friction increased after deterioration and fuel economy could not be maintained.

(Comparative Example 4) The same composition as in Example 1 except that zinc dialkyldithiophosphate was not used. [The amount of polymer used should be close to the kinematic viscosity of 9.9 mm ² / s in Example 1]. Since it was added, the amount of polymer added is different. The base oil is the balance excluding the additives. ] Was prepared. The results of the engine oil performance evaluation test are shown in Table 1. The fresh oil had a high friction coefficient, and a deterioration test was conducted on this, but the friction coefficient was further increased and the fuel consumption was poor.

(Comparative Example 5) The same composition as in Example 1 except that the succinimide ashless dispersant was not used. [The polymer has a kinematic viscosity close to 9.9 mm ² / s in Example 1] However, the amount of polymer added is different. The base oil is the balance excluding the additives. ] Was prepared. The results of the engine oil performance evaluation test are shown in Table 1. The fresh oil had a high friction coefficient, and a deterioration test was conducted on this, but the friction coefficient was further increased and the fuel consumption was poor.

(Comparative Example 6) The same composition as in Example 1 except that no phenolic antioxidant was used. [The amount of the polymer is such that the kinematic viscosity is close to 9.9 mm ² / s in Example 1]. Was added. The base oil is the balance excluding the additives. ] Was prepared, and a deterioration test was performed on the engine oil. Table 1 shows the results of engine oil performance evaluation tests.
Shown in Although new oil has a low coefficient of friction, the coefficient of friction increased after deterioration and fuel economy could not be maintained.

(Comparative Example 7) The same composition as in Example 1 was used except that no molybdenum dialkyldithiocarbamate friction reducing agent was used. [The polymer has a kinematic viscosity close to 9.9 mm ² / s in Example 1] Such an amount was added. The base oil is the balance excluding the additives. ] Was prepared. The results of the engine oil performance evaluation test are shown in Table 1. In the fresh oil state, the coefficient of friction was fairly high, and the fuel economy was poor.

(Comparative Example 8) The same composition as in Example 1 was used except that the calcium sulfurized phenate was not used. [The amount of the polymer added was such that the kinematic viscosity was close to 9.9 mm ² / s in Example 1]. did. The base oil is the balance excluding the additives. ] Was prepared, and a deterioration test was performed on the engine oil. The results of the engine oil performance evaluation test are shown in Table 1. Although new oil has a low coefficient of friction, the coefficient of friction increased after deterioration and fuel economy could not be maintained.

(Comparative Example 9) Total aromatic content of 30.2%
The same composition as in Example 1 except that the base oil of Example 1 was used. [The amount of polymer added was different because the amount of the polymer added was such that the kinematic viscosity of Example 1 was close to 9.9 mm ² / s. . The base oil is the balance excluding the additives. ] Was prepared, and a deterioration test was performed on the engine oil.
The results of the engine oil performance evaluation test are shown in Table 1. Although new oil has a low coefficient of friction, the coefficient of friction increased after deterioration and fuel economy could not be maintained.

As can be seen from the comparative examples, in the present invention, it is essential to use a base oil having a specific wholly aromatic content and to combine a specific additive. It was possible to obtain an engine oil having only low fuel consumption and capable of maintaining the fuel consumption for a long period of time. Even if one kind of additive was missing, the amount added was outside the scope of the present invention. In addition, if the total aromatic content of the base oil deviates from the range of the present invention, an excellent engine oil capable of maintaining low fuel consumption for a long time cannot be obtained.

[0075]

[Table 1]

[Table 2]

[Table 3]

[0076]

The engine oil of the present invention has a low friction coefficient both in new oil and after deterioration due to the synergistic effect of each component, and has an excellent fuel economy effect.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location // C10M 129: 10 129: 54 135: 02 137: 10 139: 00 149: 06 C10N 10:04 20:00 20:02 30:06 40:25 (72) Inventor Masakuni Hirata 8 Chidori-cho, Naka-ku, Yokohama-shi, Kanagawa Nihon Sekiyu Co., Ltd.

Claims (1)

[Claims] 1. The kinematic viscosity at 100 ° C. is ² to 8 mm ² / s.
And the total aromatic content is 15% by mass or less, based on the total amount of the composition, (1) 0.5 to 1.2% by mass of the alkaline earth metal salicylate-based detergent as sulfated ash, (2) 0.04 to 0.10 mass% of zinc dialkyldithiophosphate in terms of phosphorus concentration, (3) number average molecular weight 90
A succinimide ashless dispersant having 0 to 3500 polybutenyl groups is used in an amount of 0.05 to 0.20% by mass in terms of nitrogen concentration, and (4) a phenol ashless antioxidant is used in an amount of 0.1 to 3.
0 mass% and (5) molybdenum dithiocarbamate-based friction reducing agent in the range of 0.02 to 0.1 in terms of molybdenum concentration.
5% by mass, (6) 0.01 to 0.5% by mass of a sulfur-containing organic compound other than the above (2) and (5) in terms of sulfur concentration, and (7) a viscosity index improver at 100 ° C of the composition. The engine oil composition was blended in an amount such that the kinematic viscosity at 5.6 to 12.5 mm ² / s.