JP5523885B2 - Lubricating oil composition - Google Patents

Description

  The present invention relates to a lubricating oil composition.

  Conventionally, lubricating oil has been used for internal combustion engines, automatic transmissions, greases, and the like in order to make their operations smooth. Among these lubricating oils, the lubricating oil for internal combustion engines (also referred to as “engine oil”) has high performance due to the high performance, high output, and severe operating conditions of the internal combustion engine. It is becoming required.

  In the conventional lubricating oil for internal combustion engines, various additives such as an antiwear agent, a metallic detergent, an ashless dispersant, and an antioxidant are blended in order to satisfy the above-mentioned required performance. Among them, zinc dialkyldithiophosphate (ZnDTP) has a function as an antiwear or antioxidant, and is therefore used as an indispensable additive for lubricating oil for internal combustion engines (for example, see Patent Document 1 below). ).

Japanese Patent Laid-Open No. 08-302378

  Further, in fuel-saving engine oils, in order to reduce friction loss and improve fuel consumption, it has been generally performed to add organic molybdenum compounds containing metals and sulfur such as molybdenum dithiocarbamate and molybdenum dithiophosphate. . In order to exert the friction reducing effect, a method of forming a molybdenum disulfide film on the sliding surface by using a certain amount of a compound containing sulfur and a metal such as zinc dialkyldithiophosphate (ZnDTP) is generally used. Has been done. For this reason, the conventional fuel-saving engine oil has a relatively high sulfur content, and it has been difficult to reduce the sulfur while maintaining the performance. In order to solve this problem, it was proposed that zinc dialkyl phosphate (ZP) is used in place of ZnDTP to reduce sulfur while maintaining excellent friction reduction, but there is a problem with wear prevention. It turned out to be.

  The present invention has been made in view of the above-described problems of the prior art, and provides a lubricating oil composition capable of achieving both low sulfur and excellent friction reduction while maintaining wear prevention. For the purpose.

  As a result of intensive studies to achieve the above-mentioned object, the present inventor uses a specific zinc dialkylmonothiophosphate in combination with a specific metal-based detergent instead of ZnDTP, thereby providing a ZnDTP single additive oil. The present inventors have found that the present invention exhibits the low sulfur content and excellent friction reduction property while maintaining the wear prevention property of the present invention, and have completed the following present invention.

  The present invention is a lubricating oil composition comprising a lubricating base oil, a metal salt of a phosphorus compound represented by the following general formula (1), and a metal detergent alkylated with a linear α-olefin. In this lubricating oil composition, the metal salt of the phosphorus compound is contained in an amount of 0.005% by mass to 0.12% by mass in terms of phosphorus element, based on the total amount of the lubricating oil composition.

［一般式（１）中、Ｒ^１〜Ｒ^４は炭素数１〜３０の直鎖型アルキル基であって、Ｒ^１〜Ｒ^４は互いに同一でも異なっていてもよく、Ｙは２価以上の金属原子である］

[In General Formula (1), R ^{1 to} R ⁴ are linear alkyl groups having 1 to 30 carbon atoms, R ^{1 to} R ⁴ may be the same as or different from each other, and Y is divalent or higher. Is a metal atom]

  In this invention, it is preferable that the average carbon number of the linear alkyl group of the metal salt of a phosphorus compound is 5-9.

  In the present invention, the linear alkyl group in the metal salt of the phosphorus compound is preferably a combination of a linear alkyl group having 1 to 6 carbon atoms and a linear alkyl group having 7 to 20 carbon atoms.

  According to the lubricating oil composition of the present invention, by containing a specific phosphorus compound metal salt and a specific metal-based detergent in combination, while maintaining the anti-wear property of the ZnDTP single additive oil, low sulfur and excellent It is possible to show a low friction reduction.

Hereinafter, preferred embodiments of the present invention will be described in detail.
<Lubricating oil composition>
The lubricating oil composition of the present invention comprises a lubricating base oil, a specific phosphorus compound metal salt, and a specific metal detergent.

(Lubricant base oil)
The lubricating base oil contained in the lubricating oil composition of the present invention is not particularly limited, and those used for ordinary lubricating oils can be used. Specifically, a mineral oil base oil, a synthetic oil base oil, or a mixture of two or more kinds of base oils selected from these can be used.

  Specifically, as the mineral base oil, the lube oil fraction obtained by distilling the atmospheric residue obtained by atmospheric distillation of the crude oil is subjected to solvent removal, solvent extraction, and hydrogenation. Examples include those refined by one or more treatments such as decomposition, solvent dewaxing, hydrorefining, etc., or base oils produced by isomerizing wax isomerized mineral oil, GTL wax (gas-tuly wax) it can.

  Specific examples of the synthetic oil-based lubricating oil include polybutene or a hydride thereof; poly α-olefin such as 1-octene oligomer and 1-decene oligomer or a hydride thereof; ditridecyl glutarate, di-2-ethylhexyl adipate Diesters such as diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate; polyol esters such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate; Examples thereof include aromatic synthetic oils such as alkylnaphthalene and alkylbenzene, or mixtures thereof.

The kinematic viscosity of the lubricating base oil is not particularly limited, but the kinematic viscosity at 100 ° C. of the lubricating base oil is preferably 50 mm ² / s or less, more preferably 40 mm ² / s or less, and even more preferably 20 mm ² / s or less. Particularly preferably, it is 10 mm ² / s or less. When the kinematic viscosity at 100 ° C. of the lubricating base oil exceeds 50 mm ² / s, the low-temperature viscosity characteristics tend to be insufficient. The kinematic viscosity at 100 ° C. of the lubricating base oil 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 lubricating base oil is less than 1 mm ² / s, oil film formation at the lubrication site tends to be insufficient and the lubricity tends to decrease, and the evaporation loss of the lubricating base oil The amount tends to increase. The kinematic viscosity at 100 ° C. here refers to the kinematic viscosity at 100 ° C. defined in JIS K2283.

  The viscosity index of the lubricating base oil is not particularly limited, but is preferably 80 or more from the viewpoint of low temperature viscosity characteristics. Further, from the viewpoint of obtaining excellent viscosity characteristics in a wide temperature range from low temperature to high temperature, the viscosity index of the lubricating base oil is more preferably 100 or more, further preferably 110 or more, particularly 120 or more. It is preferable that

  The sulfur content of the lubricating base oil is not particularly limited, but is preferably 0.1% by mass or less, more preferably 0.01% by mass or less, 0.005% by mass or less, Particularly preferred are those which do not substantially contain (0.001% by mass or less). The “sulfur content” in the present invention is JIS K2541-4 “radiation excitation method” (usually in the range of 0.01 to 5 mass%) or JIS K2541-5 “bomb mass method, attached. This is a value measured in accordance with the “Document (normative), inductively coupled plasma emission method” (usually 0.05% by mass or more).

  The total aromatic content of the lubricating base oil is not particularly limited, but is preferably 30% by mass or less, more preferably 15% by mass or less, still more preferably 5% by mass or less, and particularly preferably 2% by mass or less. It is. When the total aromatic content of the lubricating base oil exceeds 30% by mass, the oxidation stability tends to be insufficient. The “total aromatic content” as used in the present invention means an aromatic fraction content measured in accordance with ASTM D2549. Usually, this aromatic fraction includes alkylbenzene, alkylnaphthalene, anthracene, phenanthrene, and alkylated products thereof, compounds in which four or more benzene rings are condensed, or pyridines, quinolines, phenols, naphthols, etc. Compounds having heteroaromatics and the like are included.

((A) Metal salt of phosphorus compound)
The lubricating oil composition of the present invention contains (A) a metal salt of a phosphorus compound represented by the following general formula (1) in addition to the above lubricating base oil.

In the general formula (1), R ^{1 to} R ⁴ are linear alkyl groups having 1 to 30 carbon atoms, R ^{1 to} R ⁴ may be the same or different, and Y is divalent or higher. It is a metal atom.

In the general formula ^(1), examples of the linear alkyl group having 1 to 30 carbon atoms represented by R 1 to R ^4, for example, a methyl group, an ethyl group, n- propyl group, n- butyl radical, n -Pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n -A pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, etc. can be mentioned.

R ^{1 to} R ⁴ are preferably a linear alkyl group having 3 to 14 carbon atoms, and more preferably a linear alkyl group having 4 to 12 carbon atoms.

The number of carbon atoms of R ¹ to R ⁴ may be a one, it may also be used in combination of two or more. When combining two or more preferably has an average carbon number of ^R 1 to R ⁴ is 5-9. In particular, as R ^{1 to} R ⁴ , it is possible to use a metal salt of a phosphorus compound having an average carbon number of 5 to 9 by combining an alkyl group having 1 to 6 carbon atoms and an alkyl group having 7 to 20 carbon atoms. preferable. Note that, with the combination of the phosphorus-based compound (e.g., R ¹ to R ⁴ of the phosphorus compound and 10 carbon atoms having a R ¹ to R ⁴ of 5 carbon atoms having different alkyl group of carbon number In combination with a phosphorus compound), a mixture of phosphorus compounds having an average carbon number of 5 to 9 may be used, or one molecule of a phosphorus compound has an alkyl group having a different carbon number. Any of these may be used, or a mixture of these may be used, and in any case, two types of alkyl groups having 1 to 6 carbon atoms and 7 to 20 carbon atoms are provided, and the average carbon number is 5 as a whole. It is preferable to be set to ˜9.

  Specific examples of the metal in the metal salt include alkaline earth metals such as calcium, magnesium and barium, and heavy metals such as zinc, copper, iron, lead, nickel, silver, manganese and molybdenum. Among these, alkaline earth metals such as calcium and magnesium, molybdenum and zinc are preferable, and zinc is particularly preferable.

  In the lubricating oil composition of the present invention, the content of the metal salt of the phosphorus compound represented by the general formula (1) is 0.005% by mass or more and 0.12 in terms of phosphorus based on the total amount of the lubricating oil composition. It is necessary to be not more than mass%, preferably not less than 0.01 mass% and not more than 0.11 mass%, more preferably not less than 0.03 mass% and not more than 0.10 mass%, still more preferably 0.05 mass%. It is 0.09 mass% or less. In addition, if the content of the metal salt of the phosphorus compound represented by the general formula (1) is less than the lower limit, the wear resistance is insufficient, and if it exceeds the upper limit, the exhaust gas purification catalyst is poisoned. This is not preferable because there is a possibility.

((B) metal detergent alkylated with linear α-olefin)
In order to further improve the acid neutralization properties, high temperature cleanability and wear prevention properties of the lubricating oil composition of the present invention, in addition to the lubricating base oil and the metal salt of the phosphorus compound, (B) linear chain Contains metal detergents alkylated with α-olefins.

  The metal detergent is not particularly limited, and examples thereof include alkali metal or alkaline earth metal sulfonate, alkali metal or alkaline earth metal phenate, alkali metal or alkaline earth metal salicylate, alkali metal or alkaline earth metal phosphonate. Or a mixture thereof.

  Regardless of the type of metallic detergent, the lipophilic group must be alkylated with a linear α-olefin. It is preferable that carbon number of the linear alpha olefin to be used is 4-30, More preferably, it is 6-28, More preferably, it is 8-26, Most preferably, it is 10-24. When the carbon number is less than 4, the oil solubility may be insufficient, and when the carbon number exceeds 30, the solubility in the base oil and the low temperature viscosity may be deteriorated.

  In the case of alkali metal or alkaline earth metal sulfonate, for example, benzene is alkylated with the above linear α-olefin to give alkylbenzene, and sulfonated with a sulfonating agent such as fuming sulfuric acid or sulfuric acid to obtain alkylbenzenesulfonic acid, and then neutralized. Thus, a metal salt is obtained.

  In the case of an alkali metal or alkaline earth metal salicylate, for example, phenol or cresol is alkylated with the above linear α-olefin to form an alkylphenol, converted into an alkylsalicylic acid by the Koch reaction, and then neutralized to form a metal salt.

  In the case of alkali metal or alkaline earth metal phenate, for example, phenol is alkylated with the above-mentioned linear α-olefin to form alkylphenol, and alkylphenol sulfide obtained by reacting this alkylphenol with elemental sulfur or obtained by reacting this alkylphenol with formaldehyde. The resulting product is a Mannich reaction product of alkylphenol, which is then neutralized to form a metal salt.

  As the alkali metal or alkaline earth metal, magnesium and / or calcium are particularly preferably used.

  Alkali metal or alkaline earth metal sulfonate, alkali metal or alkaline earth metal salicylate and alkali metal or alkaline earth metal phenate include alkyl aromatic sulfonic acid, alkyl salicylic acid, alkylphenol, alkylphenol sulfide, alkylphenol mannich reaction product Directly react with a metal base such as an alkali metal or alkaline earth metal oxide or hydroxide, or once as an alkali metal salt such as a sodium salt or potassium salt, and then replace with an alkaline earth metal salt In addition to neutral salts (normal salts) obtained by, etc., these neutral salts (normal salts) and excess alkali metal or alkaline earth metal salts or alkali metals or alkaline earth metal bases (alkali metals or Alkaline earth A basic salt obtained by heating a genus hydroxide or oxide in the presence of water, or a neutral salt (normal salt) in the presence of carbon dioxide, boric acid or borate, or an alkali metal Also included are overbased salts (superbasic salts) obtained by reacting with a base such as an alkaline earth metal hydroxide.

  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 preferably 1.0% by mass. It is 20 mass% or less, More preferably, it is 2.0 mass% or more and 16 mass% or less. The base number of the metal detergent is preferably 0 mgKOH / g or more and 500 mgKOH / g or less, more preferably 20 mgKOH / g or more and 450 mgKOH / g or less. The base number referred to here is 7. JIS K2501 “Petroleum products and lubricating oils-Neutralization number test method”. Means the base number measured by the perchloric acid method according to the above.

  In the present invention, one selected from sulfonates, salicylates, phenates and the like of alkali metals or alkaline earth metals can be used alone or in combination of two or more. As the metal detergent, alkali metal or alkaline earth metal salicylate is particularly preferable in that it has a large friction reducing effect due to low ashing and is excellent in long drain properties.

  The metal ratio of the metal-based detergent is not particularly limited, and usually 20 or less can be used, but the metal-based cleaner having a metal ratio of 1 to 10 from the point that the friction reduction effect and the long drain property can be further improved. It is preferable that it consists of 1 type, or 2 or more types chosen from an agent. The metal ratio here is represented by the valence of the metal element in the metal detergent × the metal element content (mol%) / the soap group content (mol%). The metal elements are calcium and magnesium. Etc., a soap group means a sulfonic acid group, a salicylic acid group, and the like.

  The upper limit of the content of the metallic detergent in the lubricating oil composition of the present invention is not particularly limited, and is usually 0.5% by mass or less in terms of metal element based on the total amount of the composition. It is preferable to adjust it together with other additives so that the sulfated ash content of the composition is 1.0% by mass or less based on the total amount. From such a viewpoint, the content of the metal detergent is preferably 0.3% by mass or less, more preferably 0.23% by mass or less, in terms of metal element, based on the total amount of the composition. Further, the lower limit of the content of the metal detergent is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and further preferably 0.15% by mass or more. When the content of the metal detergent is less than 0.01% by mass, it is difficult to obtain long drain performance such as high temperature cleanability, oxidation stability, and base number maintenance, which is not preferable.

  The lubricating oil composition of the present invention can contain various additives shown below in addition to the components described above.

(Ashless dispersant)
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. And nitrogen-containing compounds or derivatives thereof, or modified products of alkenyl succinimides. One type or two or more types arbitrarily selected from these can be blended.

  The alkyl group or alkenyl group has 40 to 400 carbon atoms, preferably 60 to 350 carbon atoms. When the alkyl group or alkenyl group has less than 40 carbon atoms, the solubility of the compound in the lubricating base oil decreases. On the other hand, when the alkyl group or alkenyl group has more than 400 carbon atoms, the lubricating oil composition has a low temperature. Since fluidity | liquidity deteriorates, it is unpreferable respectively. The 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 and a branched alkenyl group.

Specific examples of the ashless dispersant include the following compounds. One or two or more compounds selected from these can be used.
(I) Succinimide having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, or a derivative thereof (II) At least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule A benzylamine having a derivative thereof (III) A polyamine having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, or a derivative thereof.

  More specifically, examples of the (I) succinimide include compounds represented by the following general formula (2) or (3).

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

In general formula (3), R ⁶ and R ⁷ each independently represent an alkyl or alkenyl group having 40 to 400 carbon atoms, preferably 60 to 350 carbon atoms, more preferably a polybutenyl group, and n is 0 to 4, preferably Represents an integer of 1 to 3.

  The succinimide is represented by the formula (2) in which succinic anhydride is added to one end of the polyamine, and the formula (3) in which succinic anhydride is added to both ends of the polyamine. The so-called bis-type succinimide represented by the formula (1) is included, but the lubricating oil composition of the present invention may contain only one of them or a mixture thereof.

  The production method of the succinimide is not particularly limited. For example, an alkyl 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. is a polyamine. It can obtain by making it react. Specific examples of the polyamine include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine.

  More specifically, examples of (II) benzylamine include compounds represented by the following general formula (4).

In the general formula (4), R ⁸ represents an alkyl or 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.

More specifically, examples of the (III) polyamine include compounds represented by the following general formula (5).
R ⁹ —NH— (CH ₂ CH ₂ NH) _q —H (5)
In the general formula (5), R ⁹ represents an alkyl group or alkenyl group having 40 to 400 carbon atoms, preferably 60 to 350, and q represents an integer of 1 to 5, preferably 2 to 4.

  Moreover, as a derivative of the nitrogen-containing compound mentioned as an example of the ashless dispersant, 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, trimellitic acid, A so-called acid-modified compound obtained by allowing a C2-C30 polycarboxylic acid such as pyromellitic acid to act to neutralize or amidate part or all of the remaining amino group and / or imino group; A so-called boron-modified compound in which boric acid is allowed to act on a nitrogen-containing compound to neutralize or amidate part or all of the remaining amino group and / or imino group; a sulfur compound acts on the above-mentioned nitrogen-containing compound And a modified compound in which two or more kinds of modifications selected from acid modification, boron modification, and sulfur modification are combined with the above-mentioned nitrogen-containing compound. Among these derivatives, boron-modified compounds of alkenyl succinimide are excellent in heat resistance and antioxidant properties, and are also effective in the lubricating oil composition of the present invention to further enhance base number maintenance and high temperature cleanability.

  When the ashless dispersant is contained in the lubricating oil composition of the present invention, the content is usually 0.01% by mass or more and 20% by mass or less, preferably 0.1% by mass based on the total amount of the lubricating oil composition. % To 10% by mass. When the content of the ashless dispersant is less than 0.01% by mass, the effect of maintaining the base number at high temperatures is small. On the other hand, when the content exceeds 20% by mass, the low-temperature fluidity of the lubricating oil composition is greatly increased. Since it deteriorates, it is not preferable respectively.

(Chain-stopping antioxidant)
Moreover, it is preferable that the lubricating oil composition of the present invention further contains a chain termination type antioxidant. Thereby, since the antioxidant property of a lubricating oil composition is improved more, the base number maintenance property and high temperature detergency in this invention can be improved more.

  Any chain-stopping antioxidant can be used as long as it is generally used in lubricating oils such as phenol-based antioxidants, amine-based antioxidants, and metal-based antioxidants.

  Examples of phenolic antioxidants include 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-) Chlorylphenol), 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- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, penta Erythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, octadecyl- Preferred examples include 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate and 3-methyl-5-tert-butyl-4-hydroxyphenyl substituted fatty acid esters. These may be used individually by 1 type, or may mix and use 2 or more types.

  Examples of amine-based antioxidants include phenyl-α-naphthylamine, alkylphenyl-α-naphthylamine, and dialkyldiphenylamine. These may be used individually by 1 type, or may mix and use 2 or more types.

  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 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 is preferably 0.1% by mass or more, more preferably 1% by mass based on the total amount of the lubricating oil composition in order to further improve the base number maintenance and high temperature cleanability in the process of lubricating oil deterioration. % Or more.

(General additives)
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.

  Antiwear agents include, for example, disulfides, sulfurized olefins, sulfurized oils and fats, dithiophosphate metal salts (zinc salts, molybdenum salts, etc.), alkyl phosphate metal salts (zinc salts, etc.), dithiocarbamic acid metal salts (zinc salts, molybdenum salts). Etc.), dithiophosphoric acid esters and derivatives thereof (reaction products with olefin cyclopentadiene, (methyl) methacrylic acid, propionic acid, etc., and in the case of propionic acid, those added to the β-position are preferred), trithiophosphoric acid esters, And sulfur-containing compounds such as dithiocarbamic acid esters. These can be contained in the range of 0.005% by mass or more and 5% by mass or less as long as the performance of the composition of the present invention is not significantly impaired in the range of 0.005% by mass to 5% by mass, based on the total amount of the composition. From the viewpoint of sulfurization and long drain properties, the content is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, in terms of sulfur, based on the total amount of the composition.

  As the friction modifier, any compound usually used as a friction modifier for lubricating oils can be used. For example, molybdenum friction modifiers such as molybdenum disulfide, molybdenum dithiocarbamate, molybdenum dithiophosphate, carbon number 6 An amine compound, fatty acid ester, fatty acid amide, fatty acid, fatty alcohol, fatty acid having at least one alkyl group or alkenyl group of -30, in particular, a straight-chain alkyl group or straight-chain alkenyl group having 6 to 30 carbon atoms in the molecule. Ashless friction modifiers such as group ethers, hydrazides (eg oleyl hydrazide), semicarbazides, ureas, ureidos, biurets and the like. The content of these friction modifiers is usually 0.1% by mass or more and 5% by mass or less based on the total amount of the composition.

  As the viscosity index improver, specifically, a so-called non-dispersion type viscosity index improver such as a polymer or copolymer of one or more monomers selected from various methacrylates or a hydrogenated product thereof, Alternatively, 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 (for α-olefin, propylene, 1-butene, 1 -Pentene, etc.) or a hydride thereof, polyisobutylene or a hydride thereof, a hydride of a styrene-diene copolymer, a styrene-maleic anhydride copolymer, and a polyalkylstyrene.

  The molecular weight of these viscosity index improvers needs to be 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. Is usually 800 to 5,000 in the case of polyisobutylene or a hydride thereof, preferably 1,000 to 4,000, and usually 800 to 500 in the case of an ethylene-α-olefin copolymer or a hydride thereof. 3,000, preferably 3,000 to 200,000 are used.

  Among these 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. One or two or more compounds arbitrarily selected from the above viscosity index improvers can be contained in any amount. The content of the viscosity index improver is usually 0.1% by mass or more and 20% by mass or less based on the total amount of the lubricating oil composition.

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

  Examples of the rust inhibitor 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, and polyoxyethylene alkyl naphthyl ether.

  Examples of metal deactivators include imidazoline, pyrimidine derivatives, alkylthiadiazoles, mercaptobenzothiazoles, benzotriazoles or derivatives thereof, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bis. Examples include dialkyldithiocarbamate, 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 thereof is based on the total amount of the lubricating oil composition, and 0.005% by mass or more for each of the corrosion inhibitor, rust inhibitor, and demulsifier. It is usually selected in the range of 0.005% by mass or more and 1% by mass or less for the metal deactivator, and 0.0005% by mass or more and 1% by mass or less for the antifoaming agent.

(Kinematic viscosity of the lubricating oil composition of the present invention)
Kinematic viscosity at 100 ° C. of the lubricating oil composition of the present invention is less 4.1 mm ² / s or more 21.9 mm ² / s, preferably 5.6 mm ² / s or more 16.3 mm ² / s or less, further it is preferably at most 5.6 mm ² / s or more 12.5 mm ² / s.

(Sulfur content of the lubricating oil composition of the present invention)
The sulfur content in the lubricating oil composition of the present invention is preferably 0.3% by mass or less, more preferably 0.2% by mass or less, still more preferably 0.1% by mass or less, based on the total amount of the lubricating oil composition. It is. By setting the sulfur content to the upper limit or less, a low sulfur lubricating oil composition having excellent long drain properties can be realized.

  The total phosphorus concentration in the lubricating oil composition of the present invention is preferably 0.005% by mass or more and 0.12% by mass or less in terms of phosphorus element, based on the total amount of the lubricating oil composition, and 0.03% by mass. The content is more preferably 0.11% by mass or less and more preferably 0.05% by mass or more and 0.105% by mass or less. If the phosphorus concentration in the lubricating oil composition exceeds the upper limit, the exhaust gas purification catalyst may be poisoned.

(Use of lubricating oil composition of the present invention)
Since the lubricating oil composition of the present invention can achieve both low sulfur and excellent friction reduction while maintaining wear prevention properties, gasoline engines for two-wheeled vehicles, four-wheeled vehicles, power generation, ships, etc., diesel It can be preferably used as a lubricating oil for internal combustion engines such as engines and gas engines. Other lubricants that require wear prevention and long drain performance, such as lubricants for drive systems such as automatic or manual transmissions, wet brakes, hydraulic fluids, turbine oils, compressor oils, bearing oils, refrigerator oils, etc. It can also be suitably used as a lubricating oil.

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.
(Examples 1-3, Comparative Examples 1-5)
In Examples 1 to 3 and Comparative Examples 1 to 5, a mineral oil base oil was used, and as shown in Table 1, 0.07% by mass of metal salts of various phosphorus compounds in terms of phosphorus element, and metal detergents The composition which added 0.2 mass% in conversion of the metal element was prepared. With respect to these compositions, the friction reduction effect was evaluated by the following block-on-ring test (Block on ring test), and the anti-wear property was evaluated by the KA24E valve system wear test. The results are also shown in Table 1.

(Block-on-ring test)
The block-on-ring test was performed according to ASTM D3701 and D2714, with the test conditions being a load of 445 N, an oil temperature of 100 ° C., and a sliding speed described in Table 1.

(KA24E valve system wear test)
The KA24E valve train wear test was performed according to JASO M328-95.

  From the results shown in Table 1, the compositions of Examples 1 to 3 using a straight chain dialkylmonothiophosphate zinc salt and a metal detergent alkylated with a straight chain α-olefin are branched dialkylmonothiophosphates. Comparative Example 1 using a salt, Comparative Example 2 using a zinc dialkylphosphate, Comparative Example 3 using a zinc dialkyldithiophosphate, and Comparative Examples 4 and 5 using a metal detergent alkylated with a branched olefin In comparison, the friction coefficient is low under any condition, and the fuel efficiency is excellent and the wear resistance is also excellent.

  While the present invention has been described in connection with embodiments that are presently the most practical and preferred, the present invention is not limited to the embodiments disclosed herein. However, the present invention can be modified as appropriate without departing from the spirit or concept of the invention that can be read from the claims and the entire specification, and lubricating oil compositions with such changes are also included in the technical scope of the present invention. It must be understood as a thing.

  Since the lubricating oil composition of the present invention can achieve both low sulfur and excellent friction reduction while maintaining wear prevention properties, gasoline engines for two-wheeled vehicles, four-wheeled vehicles, power generation, ships, etc., diesel It can be preferably used as a lubricating oil for internal combustion engines such as engines and gas engines. Other lubricants that require wear prevention and long drain performance, such as lubricants for drive systems such as automatic or manual transmissions, wet brakes, hydraulic fluids, turbine oils, compressor oils, bearing oils, refrigerator oils, etc. It can also be suitably used as a lubricating oil.

Claims (2)

A lubricating oil composition comprising a lubricating base oil, a metal salt of a phosphorus compound represented by the following general formula (1), and a metal detergent alkylated with a linear α-olefin,
A lubricating oil composition comprising 0.005% by mass or more and 0.12% by mass or less in terms of phosphorus element, based on the total amount of the lubricating oil composition, of the metal salt of the phosphorus compound.

[In General Formula (1), R ^{1 to} R ⁴ are linear alkyl groups having 1 to 30 carbon atoms, and R ^{1 to} R ⁴ may be the same or different from each other, and the linear alkyl group is Is a combination of a linear alkyl group having 1 to 6 carbon atoms and a linear alkyl group having 7 to 20 carbon atoms, and Y is a divalent or higher valent metal atom . ] The lubricating oil composition according to claim 1, wherein an average carbon number of the linear alkyl group of the metal salt of the phosphorus compound is 5 to 9.