JP2013209569A - Lubricating oil composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricating oil composition exhibiting a maximum friction reducing effect by optimizing a base oil and an additive other than a friction modifier used for a lubricating oil composition, especially for a lubricating oil for an internal combustion engine.SOLUTION: In a lubricating oil composition, a base oil (A), in which a sulfur content is 0.03 mass% or more and the mass ratio of an aromatic content (%C) to the sulfur content [%C(mass%)/sulfur content (mass%)] is 30 or less, contains 3 mass% or less of a metal salicylate-based cleaning agent (B) as an amount of an alkali metal or an alkaline earth metal on the basis of the total amount of the composition.

Description

  The present invention relates to a lubricating oil composition, and more particularly, to a lubricating oil composition that is suitably used for applications such as a lubricating oil for an internal combustion engine.

  In order to improve fuel economy, the lubricating oil composition for internal combustion engines often includes an organic molybdenum compound, particularly molybdenum dithiocarbamate (MoDTC), as a friction modifier (see, for example, Patent Documents 1 to 3 below). . However, since MoDTC has low maintainability of its effect and contains a metal component, it may poison the exhaust gas treatment catalyst. Therefore, a friction modifier that replaces MoDTC is required.

  Therefore, in particular, as a friction modifier that does not affect the exhaust gas treatment catalyst, an amphiphilic molecule having a polar site and an oil-soluble site, that is, an oil-soluble surfactant-type ashless friction modifier has been attempted. ing. However, although the ashless friction modifiers developed so far have some effect, no ashless friction modifier has been found that can achieve the same or better performance as MoDTC.

  On the other hand, various additives are added to the lubricating oil composition for internal combustion engines in order to improve high temperature cleanliness and acid neutralization (see, for example, Patent Documents 4 to 5 below). However, these additives generally work in the direction of increasing friction and inhibit the fuel saving effect.

Japanese Patent Laid-Open No. 06-336592 Japanese Patent Laid-Open No. 06-336593 International Publication No. 2009/104682 JP 2004-0667808 A Japanese Patent Laid-Open No. 2003-277782

  Under such circumstances, the present invention maximizes the friction reduction effect by optimizing the base oil and additives other than the friction modifier used in the lubricating oil composition, particularly the lubricating oil for internal combustion engines. An object of the present invention is to provide a lubricating oil composition.

  As a result of intensive studies to achieve the above object, the present inventors have maximized the friction reduction effect by optimizing the sulfur content and aromatic content of the base oil and specific metal detergents. The present inventors have found that a lubricating oil composition can be obtained, and have completed the present invention.

That is, the present invention
_A base oil having a sulfur content of 0.03 mass% or more and a mass ratio of aromatic content (% C _A ) to sulfur content [% C _A (mass%) / sulfur content (mass%)] of 30 or less. (A)
A lubricating oil composition containing 3% by mass or less of a metal salicylate detergent (B) as an amount of alkali metal or alkaline earth metal based on the total amount of the composition.

  In a preferred example of the lubricating oil composition of the present invention, the average number of carbon atoms in the soap chain of the metal salicylate detergent (B) is 10 or more.

  In another preferred embodiment of the lubricating oil composition of the present invention, the metal salicylate detergent (B) is an overbased calcium carbonate salicylate.

  The lubricating oil composition of the present invention is preferably a lubricating oil for an internal combustion engine.

  Moreover, this invention is a method of improving the fuel-saving property of an internal combustion engine using said lubricating oil composition.

  According to the present invention, there is provided a lubricating oil composition, particularly a lubricating oil composition for an internal combustion engine, which can sufficiently reduce friction under boundary lubrication conditions and mixed lubrication conditions without a friction modifier, and is excellent in fuel efficiency. It becomes possible to do.

Hereinafter, preferred embodiments of the present invention will be described in detail. The lubricating oil composition of the present invention has a sulfur content of 0.03 mass% or more, and a mass ratio of aromatic content (% C _A ) to sulfur content [% C _A (mass%) / sulfur content (mass%). )] Is contained in a base oil (A) of 30 or less in an amount of 3% by mass or less of the metal salicylate detergent (B) as an amount of alkali metal or alkaline earth metal based on the total amount of the composition.

  The base oil (A) of the lubricating oil composition of the present invention has a sulfur content of 0.03% by mass or more, preferably 0.1% by mass or more, and more preferably 0.2% by mass or more. Preferably, it is more preferably 0.3% by mass or more, particularly preferably 0.4% by mass or more, and most preferably 0.5% by mass or more. The base oil (A) preferably has a sulfur content of 1.2% by mass or less, more preferably 1% by mass or less, and even more preferably 0.8% by mass or less. It is especially preferable that it is 0.7 mass% or less. When the sulfur content of the base oil (A) is 0.03% by mass or more, friction is reduced, and when used as a lubricating oil for an internal combustion engine, a lubricating oil composition having an excellent fuel economy effect is obtained. Can do. However, if the sulfur content of the base oil (A) exceeds 1.2% by mass, the oxidation stability of the lubricating oil composition is deteriorated and sludge is likely to be generated, which is not preferable.

  The “sulfur content” in the present invention means JIS K 2541-4 “radiation type excitation method” (usually in a range of 0.01 to 5% by mass) or JIS K 2541-5 “bomb type mass method, attached. (Standard), inductively coupled plasma emission method "(usually 0.05% by mass or more).

The base oil (A) of the lubricating oil composition of the present invention has an aromatic content (% C _A ) and a sulfur content mass ratio [% C _A (mass%) / sulfur content (mass%)] of 30 or less. , Preferably 15 or less, more preferably 12 or less, and preferably 5 or more, more preferably 7 or more. When the% C _A / sulfur content of the base oil (A) is 30 or less, the effect of reducing friction is increased, and when it is less than 5, the influence of sulfur is excessively increased, and conversely, the friction coefficient may be increased. is there.

Moreover, the range of about% _{C A} of the base oil (A), the above-mentioned aromatic content (% _{C A)} and a sulfur content mass ratio of [% _{C A} (wt%) / sulfur (wt%)] If satisfied, there is no particular limitation, but from the viewpoint of oxidation stability, it is preferably 20 or less, more preferably 15 or less, and particularly preferably 10 or less. Incidentally,% _{C A} is determined by a method in accordance with ASTM D 3238 (n-d- M ring analysis).

The base oil (A) of the lubricating oil composition of the present invention has a sulfur content of 0.03% by mass or more, and a mass ratio of aromatic content (% C _A ) to sulfur content [% C _A (% by mass) / Sulfur content (mass%)] should just be 30 or less. Accordingly, the base oil (A) contains, for example, at least one mineral base oil containing sulfur as shown below, either alone or one or more of other mineral oil base oils or synthetic base oils. Can be configured.

  Specifically, as the mineral base oil, a lubricating oil fraction obtained by distillation under reduced pressure of atmospheric residual oil obtained by atmospheric distillation of crude oil, solvent removal, solvent extraction, hydrocracking , Purified by performing one or more treatments such as solvent dewaxing, hydrorefining and the like.

  Examples of base oils that hardly contain sulfur include base oils and synthetic base oils produced by a method of isomerizing wax isomerized mineral oil, GTL WAX (gas-trimmed wax).

  Specific examples of the synthetic base oil include polybutene or hydrides thereof; poly-α-olefins such as 1-octene oligomers and 1-decene oligomers or hydrides thereof; ditridecyl glutarate, di-2-ethylhexyl. Diesters such as adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate; neopentyl glycol ester, trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargo Examples thereof include polyol esters such as nates; aromatic synthetic oils such as alkylnaphthalenes, alkylbenzenes, and aromatic esters, or mixtures thereof.

The kinematic viscosity of the base oil (A) is not particularly limited, but the kinematic viscosity at 100 ° C. is preferably 20 mm ² / s or less, more preferably 15 mm ² / s or less, particularly preferably 10 mm. ² / s or less. On the other hand, the kinematic viscosity at 100 ° C. of the base oil (A) is preferably 1 mm ² / s or more, more preferably 2 mm ² / s or more. When the kinematic viscosity at 100 ° C. of the base oil (A) exceeds 20 mm ² / s, the low-temperature viscosity characteristics deteriorate, while when the kinematic viscosity at 100 ° C. is less than 1 mm ² / s, Insufficient oil film formation is inferior in lubricity, and the evaporation loss of the lubricating base oil is increased, which is not preferable.

  Further, the viscosity index of the base oil (A) is not particularly limited and is usually 200 or less, but the viscosity index is preferably 80 or more so that excellent viscosity characteristics from low temperature to high temperature can be obtained. , More preferably 100 or more, and particularly preferably 120 or more. When the viscosity index of the base oil (A) is less than 80, the low temperature viscosity characteristics tend to deteriorate. The viscosity index of the base oil (A) is preferably 160 or less.

  The lubricating oil composition of the present invention contains a metal salicylate detergent (B). Here, the metal salicylate detergent (B) is preferably a metal salicylate represented by the following general formula (1) and / or a (over) basic salt thereof.

In the general formula (1), R ¹ represents an alkyl group or an alkenyl group, M represents an alkali metal or an alkaline earth metal, preferably calcium or magnesium, calcium is particularly preferable, and n is 1 or 2. is there.

  The metal salicylate detergent (B) is preferably an alkali metal or alkaline earth metal salicylate having one alkyl group or alkenyl group in the molecule and / or a (over) basic salt thereof. .

  The method for producing the alkali metal or alkaline earth metal salicylate is not particularly limited, and a known method for producing a monoalkyl salicylate can be used. For example, phenol is used as a starting material and alkylated with olefin. Then, monoalkyl salicylic acid obtained by carboxylation with carbon dioxide gas or the like, or monoalkyl salicylic acid obtained by alkylation using an equivalent amount of the above olefin using salicylic acid as a starting material, alkali metal or alkaline earth metal The above alkaline earth metal salicylates can be obtained by reacting metal bases such as oxides and hydroxides of the above or by once replacing alkali metal salts such as sodium salts and potassium salts with alkaline earth metal salts. .

  The metal salicylate detergent (B) used in the lubricating oil composition of the present invention includes not only the neutral salt obtained as described above, but also these neutral salt and excess alkali metal or alkaline earth metal. Basic salts obtained by heating a salt, alkali metal or alkaline earth metal base (a hydroxide or oxide of an alkali metal or alkaline earth metal) in the presence of water, carbon dioxide, boric acid or boron Also included are overbased salts obtained by reacting a neutral salt with a base such as an alkali metal or alkaline earth metal hydroxide in the presence of an acid salt.

  In the lubricating oil composition of the present invention, the content of the metal salicylate detergent (B) is 3% by mass or less as the amount of alkali metal or alkaline earth metal based on the total amount of the composition, preferably 0.05 to 2% by mass, more preferably 0.05-1.5% by mass, even more preferably 0.05-0.8% by mass, especially 0.05-0.5% by mass, most preferably 0. 0.05 to 0.25%. If the content of the metal salicylate-based detergent (B) based on the total amount of the composition is less than 0.05% by mass as the amount of alkali metal or alkaline earth metal, the friction reducing effect is not sufficiently exhibited, which is not preferable. When it exceeds 3 mass%, the friction reduction effect will fall.

  The metal salicylate detergent (B) used in the lubricating oil composition of the present invention preferably has a metal ratio of usually 1.0 to 30. Metal salicylate detergents with a metal ratio of less than 1.0 may have acid and may be corrosive, while metal salicylate detergents with a metal ratio of 30 or more are unstable and precipitate. Since it may occur, it is not preferable. Here, the metal ratio of the metal salicylate detergent (B) is represented by the valence of the metal element in the salicylate detergent x metal element content (mol%) / soap group content (mol%), An element means calcium, magnesium or the like, and a soap group means a salicylic acid group or the like.

In the general formula (1), R ¹ preferably has 10 to 40 carbon atoms, more preferably 14 to 30 carbon atoms, and still more preferably 20 or more carbon atoms. R ¹ is preferably an alkyl group, more preferably a secondary alkyl group. When the carbon number of R ¹ is less than 10, a sufficient friction reducing effect cannot be obtained, and when the carbon number of R ¹ exceeds 40, the fluidity at low temperatures is deteriorated as a lubricating oil composition, which is not preferable. .

  The metal salicylate detergent (B) used in the lubricating oil composition of the present invention preferably has an average number of carbon atoms in the soap chain alkyl chain of 10 or more. If the carbon number of the alkyl chain of the soap group is 10 or more on average, a sufficient friction reducing effect can be obtained.

  As the metal salicylate detergent (B) used in the lubricating oil composition of the present invention, an overbased calcium carbonate salicylate is preferred. The overbased calcium carbonate salicylate is obtained by overbasing a neutral calcium salicylate obtained by neutralizing a hydrocarbon group-substituted salicylic acid with an equivalent calcium base such as calcium hydroxide or calcium oxide with calcium carbonate. Is.

  In addition to the metal salicylate detergent (B) described above, the lubricating oil composition of the present invention includes a sulfonate detergent, a phenate, in order to further improve its acid neutralization properties, high temperature cleanability and wear resistance. Metal detergents such as a system detergent and a carboxylate detergent can be added. Here, examples of the metal detergent other than the metal salicylate detergent (B) include, for example, alkali metal sulfonate or alkaline earth metal sulfonate, alkali metal phenate or alkaline earth metal phenate, alkali metal carboxylate or alkaline earth. And the like, or a mixture thereof.

  More specifically, the alkali metal or alkaline earth metal sulfonate is, for example, an alkali metal of an alkyl aromatic sulfonic acid obtained by sulfonating an alkyl aromatic compound having a molecular weight of 100 to 1500, preferably 200 to 700. Salts or alkaline earth metal salts, particularly magnesium salts and / or calcium salts are preferably used. Specific examples of the alkyl aromatic sulfonic acids include so-called petroleum sulfonic acids and synthetic sulfonic acids.

  More specifically, the alkali metal or alkaline earth metal phenate is an alkylphenol having at least one linear or branched alkyl group having 4 to 30 carbon atoms, preferably 6 to 18 carbon atoms, Alkali metal salts or alkaline earth metal salts of alkylphenol sulfide obtained by reacting elemental sulfur or Mannich reaction product of alkylphenol obtained by reacting this alkylphenol with formaldehyde, particularly magnesium salt and / or calcium salt are preferably used. It is done.

  More specifically, the alkali metal or alkaline earth metal carboxylate is an alkylbenzoic acid having at least one linear or branched alkyl group having 4 to 30 carbon atoms, preferably 6 to 18 carbon atoms. Alkali metal salts or alkaline earth metal salts, particularly magnesium salts and / or calcium salts are preferably used.

  In addition, metal detergents are usually marketed in a state diluted with a light lubricating base oil or the like, and are available, but generally the metal content is 1.0 to 20% by mass. It is desirable to use 2.0 to 16% by mass. The total base number of the metal detergent is usually 0 to 500 mgKOH / g, preferably 20 to 450 mgKOH / g. The total base number referred to here is JIS K2501 “Petroleum products and lubricating oils—Test method for neutralization number”. It means the total base number measured by the perchloric acid method based on

  The lubricating oil composition of the present invention preferably further contains an ashless dispersant. As the ashless dispersant, any ashless dispersant used in lubricating oils can be used. For example, at least one linear or branched alkyl group or alkenyl group having 40 to 400 carbon atoms is included in the molecule. Examples thereof include nitrogen-containing compounds or derivatives thereof, modified products of alkenyl succinimide, benzylamine, polyamine and the like. One type or two or more types arbitrarily selected from these can be blended in the lubricating oil composition of the present invention.

  The carbon number of the alkyl group or alkenyl group of the alkenyl succinimide is preferably 40 to 400, more preferably 60 to 350. When the carbon number of the alkyl group or alkenyl group is less than 40, the solubility of the compound in the lubricating base oil tends to decrease. On the other hand, when the carbon number of the alkyl group or alkenyl group exceeds 400, the lubricating oil The low temperature fluidity of the composition tends to deteriorate. This alkyl group or alkenyl group may be linear or branched, but specifically, preferred are derived from olefin oligomers such as propylene, 1-butene and isobutylene, and co-oligomers of ethylene and propylene. And a branched alkyl group or a branched alkenyl group.

  The lubricating oil composition of the present invention may contain either monotype or bistype succinimide, or may contain both.

  The method for producing succinimide is not particularly limited. For example, an alkyl succinic acid or alkenyl succinic acid obtained by reacting a compound having an alkyl group or alkenyl group having 40 to 400 carbon atoms with maleic anhydride at 100 to 200 ° C. It can be obtained by reacting with a polyamine. Specific examples of the polyamine include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine.

More specifically, examples of the benzylamine include compounds represented by the following general formula (2).

In the general formula (2), R ² represents an alkyl group or an alkenyl group having 40 to 400 carbon atoms, preferably 60 to 350, and p represents an integer of 1 to 5, preferably 2 to 4.

  Although the manufacturing method of the said benzylamine is not specifically limited, For example, after making polyolefin, such as a propylene oligomer, a polybutene, and an ethylene-alpha-olefin copolymer, react with phenol to make alkylphenol, this is made into formaldehyde and It can be obtained by reacting polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine by Mannich reaction.

More specifically, examples of the polyamine include compounds represented by the following general formula (3).
R ³ —NH— (CH ₂ CH ₂ NH) _q —H (3)

In the general formula (3), R ³ represents an alkyl group or alkenyl group having 40 to 400 carbon atoms, preferably 60 to 350 carbon atoms, and q represents an integer of 1 to 5, preferably 2 to 4.

  The method for producing the polyamine is not particularly limited. For example, after chlorinating a polyolefin such as a propylene oligomer, polybutene, and an ethylene-α-olefin copolymer, ammonia, ethylenediamine, diethylenetriamine, triethylene is added thereto. It can be obtained by reacting polyamines such as tetramine, tetraethylenepentamine, and pentaethylenehexamine.

  Moreover, as a derivative of the nitrogen-containing compound mentioned as an example of the ashless dispersant, specifically, for example, the above-mentioned nitrogen-containing compound is a monocarboxylic acid having 1 to 30 carbon atoms (fatty acid, etc.), oxalic acid, phthalic acid, So-called acid modification in which a part or all of the remaining amino group and / or imino group is neutralized or amidated by the action of a polycarboxylic acid having 2 to 30 carbon atoms such as trimellitic acid or pyromellitic acid Compound: A so-called boron-modified compound obtained by allowing boric acid to act on the aforementioned nitrogen-containing compound to neutralize or amidate part or all of the remaining amino group and / or imino group; And a modified compound obtained by combining two or more kinds of modifications selected from acid modification, boron modification, and sulfur modification with the above-mentioned nitrogen-containing compound. Among these derivatives, boron-modified compounds of alkenyl succinimides are excellent in heat resistance and antioxidant properties, and are effective in further improving base number maintenance and high temperature cleanliness in the lubricating oil composition of the present invention. .

  When the ashless dispersant is contained in the lubricating oil composition of the present invention, the content is usually 0.01 to 20% by mass, preferably 0.1 to 10% by mass, based on the total amount of the lubricating oil composition. is there. When the content of the ashless dispersant in the lubricating oil composition is less than 0.01% by mass, the effect on the base number retention at high temperatures is small. On the other hand, when the content exceeds 20% by mass, the lubricating oil composition Since low temperature fluidity deteriorates significantly, each is not preferable.

  Moreover, it is preferable that the lubricating oil composition of the present invention further contains a chain termination type antioxidant. By containing the chain termination type antioxidant, the antioxidant property of the lubricating oil composition is further improved, and therefore, the base number maintainability and the high temperature cleanability in the present invention can be further improved.

  As said chain termination type | mold antioxidant, what is generally used for lubricating oils, such as a phenolic antioxidant, an amine antioxidant, and a metal antioxidant, can be used. Further, the phenolic antioxidant and the amine antioxidant may be used in combination.

  When the chain-stopping antioxidant is contained in the lubricating oil composition of the present invention, the content is usually 5.0% by mass or less, preferably 3.0% by mass or less, based on the total amount of the lubricating oil composition. Yes, more preferably 2.5% by mass or less. When the content of the chain terminating antioxidant exceeds 5.0% by mass, it is not preferable because sufficient antioxidant properties corresponding to the content cannot be obtained. On the other hand, the content of the chain-stopping antioxidant is preferably 0.1% by mass or more based on the total amount of the lubricating oil composition in order to further improve the base number maintainability and the high temperature cleanability in the lubricating oil deterioration process. More preferably, it is 1% by mass or more.

  In order to further improve the performance of the lubricating oil composition of the present invention, any additive commonly used in lubricating oils can be added depending on the purpose. Examples of such additives include wear inhibitors, friction modifiers, viscosity index improvers, corrosion inhibitors, rust inhibitors, demulsifiers, metal deactivators, antifoaming agents, and colorants. An agent etc. can be mentioned.

  As the antiwear agent, phosphorus compounds and sulfur compounds can be used. A typical example of the phosphorus compound is zinc carbyl dithiophosphate, but other phosphates and phosphites containing no sulfur and metal salts thereof are also preferably used. Examples of sulfur compounds include disulfides, sulfurized olefins, sulfurized oils and fats, dithiophosphate metal salts (zinc salts, molybdenum salts, etc.), dithiocarbamic acid metal salts (zinc salts, molybdenum salts, etc.), dithiophosphate esters and derivatives thereof ( Reaction products with olefin cyclopentadiene, (methyl) methacrylic acid, propionic acid, etc .; in the case of propionic acid, those added to the β-position are preferred), sulfur-containing compounds such as trithiophosphates and dithiocarbamates. These can usually be contained in the range of 0.005 to 5% by mass as long as the performance of the lubricating oil composition of the present invention is not significantly impaired. From the viewpoint of low sulfur and long drain properties, The content in terms of sulfur is preferably 0.1% by mass or less, and more preferably 0.05% by mass or less.

  As the friction modifier, any compound usually used as a friction modifier for lubricating oils can be used. For example, molybdenum disulfide, molybdenum dithiocarbamate as long as the composition does not affect the exhaust gas treatment apparatus. Molybdenum friction modifiers such as molybdenum dithiophosphate and molybdenum amine complex can be used. In addition, an amine compound, a fatty acid ester, a fatty acid amide, a fatty acid, having at least one alkyl group or alkenyl group having 6 to 30 carbon atoms, in particular a linear alkyl group or linear alkenyl group having 6 to 30 carbon atoms in the molecule, Examples also include ashless friction modifiers such as aliphatic alcohols, aliphatic ethers, hydrazides (such as oleyl hydrazide), semicarbazides, ureas, ureidos, biurets, and the like. The content of these friction modifiers is usually 0.1 to 5% by mass.

  Specifically, the viscosity index improver is a so-called non-dispersed viscosity index improver such as a polymer or copolymer of one or more monomers selected from various methacrylic esters or a hydrogenated product thereof. Or a so-called dispersed viscosity index improver obtained by copolymerizing various methacrylic acid esters containing a nitrogen compound, a non-dispersed or dispersed ethylene-α-olefin copolymer (the α-olefin includes propylene, 1-butene 1-pentene, etc.) or a hydride thereof, polyisobutylene or a hydrogenated product thereof, a hydride of a styrene-diene copolymer, a styrene-maleic anhydride ester copolymer, and a polyalkylstyrene.

  The molecular weight of the viscosity index improver is preferably selected in consideration of shear stability. Specifically, the number average molecular weight of the viscosity index improver is usually 5,000 to 1,000,000, preferably 100,000 to 900,000 in the case of dispersed and non-dispersed polymethacrylates, for example. In the case of polyisobutylene or a hydride thereof, usually 800 to 5,000, preferably 1,000 to 4,000, and in the case of an ethylene-α-olefin copolymer or a hydride thereof, usually 800 to 500. 3,000, preferably 3,000 to 200,000 are used.

  In addition, among the above viscosity index improvers, when an ethylene-α-olefin copolymer or a hydride thereof is used, a lubricating oil composition particularly excellent in shear stability can be obtained. The lubricating oil composition of the present invention may contain one or two or more compounds arbitrarily selected from the above viscosity index improvers in any amount. The content of the viscosity index improver is usually 0.1 to 20% by mass based on the lubricating oil composition.

  Examples of the corrosion inhibitor include benzotriazole, tolyltriazole, thiadiazole, and imidazole compounds.

  Examples of the rust preventive include petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinic acid ester, and polyhydric alcohol ester.

  Examples of the demulsifier include polyalkylene glycol nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl naphthyl ether, and the like.

  Examples of the metal deactivator include imidazoline, pyrimidine derivatives, alkylthiadiazole, mercaptobenzothiazole, benzotriazole or derivatives thereof, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5- Examples thereof include bisdialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, and β- (o-carboxybenzylthio) propiononitrile.

  Examples of the antifoaming agent include silicone, fluorosilicone, and fluoroalkyl ether.

  When these additives are contained in the lubricating oil composition of the present invention, the content is based on the total amount of the lubricating oil composition, and 0.005 to 5% by mass for each of the corrosion inhibitor, rust inhibitor, and demulsifier. The metal deactivator is usually selected in the range of 0.005 to 1% by mass, and the defoamer is usually selected in the range of 0.0005 to 1% by mass.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

  In the following examples and comparative examples, the friction reduction effect was measured using a TE77 reciprocating friction tester manufactured by Phoenix Tribology (where the test plate material was BS4659, the shape was 58 mm long x 38 mm wide x 4 mm thick). Yes, the material of the test cylinder pin is EN1A, the shape is 6 mm in diameter × 16 mm in length), the stroke is 15 mm, 20 Hz, the oil temperature is 150 ° C., and the load is 300 N for 30 minutes, the stroke is 15 mm, 1 Hz, Evaluation was made by measuring the friction coefficient at an oil temperature of 150 ° C. and a load of 200 N.

  Table 1 shows the properties of the base oils used in the examples and comparative examples, and Table 2 shows the characteristics of the metal salicylate detergents used in the examples and comparative examples. In Tables 3 to 6, the amount of base oil is the content ratio in the base oil, while the amount of salicylate is the content based on the total amount of the composition.

[Examples 1-6 and Comparative Examples 1-2]
A lubricating oil composition having the composition shown in Table 3 was prepared, and the coefficient of friction was measured.

  Table 3 shows the influence of the sulfur content of the base oil according to Examples 1 to 6 and Comparative Examples 1 and 2. From Table 3, it can be seen that when the sulfur content of the base oil is 0.03% by mass or more, the friction coefficient becomes small.

[Examples 3, 7, 8 and Comparative Example 3]
A lubricating oil composition having the composition shown in Table 4 was prepared, and the coefficient of friction was measured.

Table 4 shows the influence of the ratio of the aromatic content (% C _A ) and the sulfur content (S) of the base oil according to Examples 3, 7, 8 and Comparative Example 3. From Table 4, it can be seen that when the% C _A / S of the base oil is 30 or less, the friction coefficient becomes small.

[Examples 6, 9, and 10, Comparative Examples 1, 4 to 7]
A lubricating oil composition having the composition shown in Table 5 was prepared, and the coefficient of friction was measured.

  Table 5 shows the influence of the calcium amount of the lubricating oil composition according to Examples 6, 9, and 10 and Comparative Examples 1 and 4 to 7. From Examples 6, 9, 10 and Comparative Example 4 in Table 5, it can be seen that when the sulfur content of the base oil is 0.03% by mass or more, the smaller the amount of calcium in the lubricating oil composition, the lower the friction coefficient.

[Examples 6 and 11]
A lubricating oil composition having the composition shown in Table 6 was prepared, and the coefficient of friction was measured.

  Table 6 shows the influence of the alkyl chain length of the metal salicylate detergent (B) according to Examples 6 and 11. From Table 6, it can be seen that the longer the alkyl chain length of the metal salicylate detergent (B), the higher the friction reducing effect.

  The lubricating oil composition of the present invention can be used as a general lubricating oil, but is preferably used for gasoline engines, diesel engines, gas engines, etc. for motorcycles, automobiles, power generation, cogeneration, etc. It is also useful for various engines for ships and outboard motors.

  Further, the lubricating composition of the present invention comprises a lubricating oil that requires a reduction in friction, for example, a lubricating oil for a drive system such as an automatic or manual transmission, grease, wet brake oil, hydraulic hydraulic oil, turbine oil, It can also be suitably used as a lubricating oil such as compressor oil, bearing oil, and refrigerator oil.

Claims (5)

_A base oil having a sulfur content of 0.03 mass% or more and a mass ratio of aromatic content (% C _A ) to sulfur content [% C _A (mass%) / sulfur content (mass%)] of 30 or less. (A)
A lubricating oil composition containing the metal salicylate detergent (B) in an amount of 3% by mass or less as the amount of alkali metal or alkaline earth metal based on the total amount of the composition.   The lubricating oil composition according to claim 1, wherein the average number of carbon atoms in the soap chain of the metal salicylate detergent (B) is 10 or more.   The lubricating oil composition according to claim 1 or 2, wherein the metal salicylate detergent (B) is an overbased calcium carbonate salicylate.   The lubricating oil composition according to any one of claims 1 to 3, wherein the lubricating oil composition is an internal combustion engine lubricating oil.   The method to improve the fuel-saving property of an internal combustion engine using the lubricating oil composition as described in any one of Claims 1-3.