JP5241122B2 - Lubricating oil composition in contact with silver-containing material - Google Patents

Description

  The present invention relates to a lubricating oil composition in contact with a silver-containing material.

  In recent years, the in-cylinder pressure of an engine tends to be increased for the purpose of improving performance such as higher output and lower fuel consumption of the engine. Since engine bearings are required to improve bearing performance under high surface pressure, lead-containing materials have been widely used as sliding bearings. However, the use of lead is being restricted as an environmentally hazardous substance, and a lead-free high-performance bearing is required.

  In high-load engine bearings, the use of various lead-free materials such as aluminum materials for the overlay and lining parts is being studied. A silver-containing material is one of them. For example, in overseas railway diesel engines, a silver alloy may be used for a piston pin bearing or a turbocharger bearing. Moreover, silver containing material or silver plating material may be used also for sliding surfaces other than a bearing as a solid lubricating film other than overlay and lining (for example, refer patent documents 1-6).

  However, the use of silver-containing materials is not common in Japan, and there are few studies on compatibility with lubricating oils. For automotive engine oils, zinc dithiophosphate has been used as an essential additive for decades, but it corrodes silver and is not suitable for high-load diesel engines using silver-containing materials. It is believed that.

  Overseas, many studies have been made on lubricating oils suitable for silver-containing materials for use in railway diesel engines and the like (Patent Documents 7 to 25). For example, Patent Document 7 includes a hydrocarbon amine salt of a dialkyldithiophosphoric acid, a hydrocarbon amine salt of an acidic alkyl phosphate, and a detergent as a lubricating oil suitable for a high-load diesel engine using a silver-containing material. Zinc-free lubricating oils are disclosed, and phenate detergents are particularly suitable as detergents.

By the way, in recent years, a lubricating oil containing a specific phosphorus compound instead of zinc dithiophosphate has been studied as being significantly superior in base number maintenance and high-temperature cleanliness (see, for example, Patent Document 26). The effect on silver-containing materials has not been studied at all.
JP 2002-195266 A JP 2000-240657 A Japanese Patent Laid-Open No. 10-61727 Japanese Patent Laid-Open No. 9-257045 JP-A-7-151148 JP-A-6-264110 JP 2007-23289 A British Patent No. 1415964 Specification of Canadian Patent No. 810120 U.S. Pat. No. 2,959,546 US Pat. No. 3,267,033 US Pat. No. 3,649,373 US Pat. No. 3,775,321 U.S. Pat. No. 4,169,799 US Pat. No. 4,244,827 U.S. Pat. No. 4,278,553 U.S. Pat. No. 4,285,823 US Pat. No. 4,575,431 U.S. Pat. No. 4,717,490 US Pat. No. 4,764,296 US Pat. No. 4,820,431 US Pat. No. 5,244,591 US Pat. No. 5,302,304 US Patent Application Publication No. 2004/0259743 US Patent Application Publication No. 2005/0026791 JP 2002-294271 A

  This invention is made | formed in view of the said situation, and is providing the lubricating oil composition which can suppress corrosion of a silver containing material as lubricating oil which contacts a silver containing material.

  When the present inventors use zinc dithiophosphate, which has been concerned about silver corrosion as a phosphorus compound, together with a phenate-based detergent suitable for silver-containing materials as in Patent Document 7, there is a significant silver corrosion problem. Reaffirmed that there is. In this case, it has been found that silver corrosion cannot be prevented even by using a corrosion inhibitor such as triazole which is effective for preventing corrosion of copper or the like. And as a result of earnest examination about suppression of silver corrosion, it discovered that the lubricating oil composition containing a specific phosphorus compound can suppress silver corrosion significantly, and came to complete this invention.

  That is, the first aspect of the present invention is represented by (A) the general formula (a) or (b) on the basis of the total amount of the composition in a lubricating base oil composed of a mineral base oil and / or a synthetic base oil. A silver salt containing 0.01 to 0.2% by mass of a phosphorus-containing acid metal salt and 0.005% by mass of a metal detergent (B) as a metal amount. A lubricating oil composition that comes into contact with a contained material is provided to solve the above-mentioned problems.

［式中、Ｒ^１は炭素数１〜３０の炭化水素含有基を示し、Ｒ^２及びＲ^３は同一でも異なっていてもよく、それぞれ水素原子又は炭素数１〜３０の炭化水素含有基を示し、ｐは０又は１を示す。］

[Wherein, R ¹ represents a hydrocarbon-containing group having 1 to 30 carbon atoms, and R ² and R ³ may be the same or different, and each represents a hydrogen atom or a hydrocarbon-containing group having 1 to 30 carbon atoms. , P represents 0 or 1. ]

［式中、Ｒ^４は炭素数１〜３０の炭化水素含有基を示し、Ｒ^５及びＲ^６は同一でも異なっていてもよく、それぞれ水素原子又は炭素数１〜３０の炭化水素含有基を示し、ｑは０又は１を示す。］

[Wherein, R ⁴ represents a hydrocarbon-containing group having 1 to 30 carbon atoms, R ⁵ and R ⁶ may be the same or different, and each represents a hydrogen atom or a hydrocarbon-containing group having 1 to 30 carbon atoms. , Q represents 0 or 1. ]

  In this embodiment, the lubricating oil composition preferably has a component (B) content of 0.05 to 0.6% by mass and is used for a diesel engine having a silver-containing material.

  Moreover, in this aspect, the lubricating oil composition has a component (B) content of 0.3 to 0.6% by mass and is used for a railway vehicle diesel engine having a silver-containing material. Is preferred.

  In this embodiment, the lubricating oil composition preferably has a component (B) content of 0.05 to 0.3% by mass and is used for a gasoline engine having a silver-containing material.

In this embodiment, the lubricating base oil has a kinematic viscosity at 100 ° C. of 2 mm ² / s or more and less than 9 mm ² / s and a viscosity index of 110 to 160 and a poly α-olefin base oil having a kinematic index at 100 ° C. It is preferable to contain a poly α-olefin base oil having a viscosity of 9 to 50 mm ² / s and a viscosity index of 120 to 160.

  According to a second aspect of the present invention, there is provided a method for protecting a silver-containing material in contact with a lubricating oil, characterized in that the lubricating oil composition of the first aspect is brought into contact with the silver-containing material. To do.

  When the lubricating oil composition of the present invention is used as a lubricating oil that comes into contact with a silver-containing material in order to suppress corrosion of the silver that it contacts, the silver-containing material and a machine or device having the silver-containing material Can be protected. Therefore, it is useful as a lubricating oil for various internal combustion engines, especially a lubricating oil for diesel engines, railway diesel engines, automobile gasoline engines, and four-cycle motorcycle engines.

  Such an operation and gain of the present invention will be made clear from the best mode for carrying out the invention described below.

Hereinafter, the lubricating oil composition of the present invention will be described in detail.
The lubricating base oil used in the lubricating oil composition of the present invention (hereinafter also simply referred to as a lubricating oil composition) may be a mineral base oil and / or a synthetic base oil used in ordinary lubricating oil. Can be used without any particular limitation.

  Specifically, as the mineral base oil, the lubricating oil fraction obtained by subjecting the crude oil to atmospheric distillation obtained under reduced pressure is subjected to solvent removal, solvent extraction, hydrocracking, Produced by one or more processes such as solvent dewaxing, hydrorefining, etc., or by a method of isomerizing GTLWAX (Gas Liquid Wax) produced by wax isomerized mineral oil, Fischer-Tropsch process, etc. Lubricating oil base oil etc. can be illustrated.

  The total aromatic content of the mineral oil base oil is not particularly limited, but is preferably 40% by mass or less, and more preferably 30% by mass or less. When the total aromatic content of the base oil exceeds 40% by mass, oxidation stability is inferior, which is not preferable.

  In addition, since a sufficient silver corrosion inhibitory effect can be exhibited by using the component (A), the total aromatic content is 10% by mass or more, preferably as a mineral oil-based base oil that is more excellent in solubility and economy of additives. You may use 20 mass% or more mineral base oil. In addition, the total aromatic content is less than 10% by mass, more preferably 5% in that it is excellent in oxidation stability even under more severe conditions, and can suppress corrosion of silver by components due to deterioration of mineral oil even in long-term use. It is desirable to use a mineral base oil having a mass% or less, more preferably 2 mass% or less.

  In addition, the said total aromatic content means the aromatic fraction (aromatic fraction) content measured based on ASTMD2549. Usually, this aromatic fraction includes alkylbenzene, alkylnaphthalene, anthracene, phenanthrene, alkylated products thereof, compounds in which four or more benzene rings are condensed, and heterogeneous compounds such as pyridines, quinolines, phenols, and naphthols. Compounds having aromatics are included.

  Further, the sulfur content in the mineral oil base oil is not particularly limited, but is preferably 1% by mass or less, and more preferably 0.7% by mass or less. In addition, since a sufficient silver corrosion inhibitory effect can be exhibited by using the component (A), as a mineral oil base oil that is more excellent in solubility and economy of additives, a sulfur content is preferably 0.1% by mass or more, more preferably May use 0.2% by mass or more mineral base oil. In addition, the sulfur content is less than 0.1% by mass, more preferably 0 in that it is excellent in oxidation stability even under more severe conditions, and can suppress corrosion of silver due to components resulting from deterioration of mineral oil even in long-term use. It is desirable to use a mineral base oil of 0.05% by mass or less, more preferably 0.005% by mass or less.

  Specific examples of synthetic base oils include polybutene or hydrides thereof; polyα-olefins such as 1-octene oligomers, 1-decene oligomers, 1-dodecene oligomers or hydrides thereof; ditridecyl glutarate, dihydrates Diesters such as 2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate; trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate Polyol esters such as: dicarboxylic acids such as dibutyl maleate and copolymers of α-olefins having 2 to 30 carbon atoms; aromatic synthetic oils such as alkyl naphthalene, alkyl benzene, aromatic esters or the like A mixture etc. can be illustrated.

  The poly α-olefin or hydride thereof is particularly preferable in that it has excellent oxidation stability even under severe conditions, and can suppress silver corrosion due to components resulting from deterioration of the base oil even in long-term use. Can be used.

  In the present invention, a mineral base oil, a synthetic base oil, or an arbitrary mixture of two or more kinds of lubricating oils selected from these can be used as the lubricating base oil. Examples thereof include one or more mineral base oils, one or more synthetic base oils, a mixed oil of one or more mineral base oils and one or more synthetic base oils, and the like.

The kinematic viscosity of the lubricating base oil is not particularly limited, but the kinematic viscosity at 100 ° C. is preferably 4 to 50 mm ² / s, more preferably 6 to 40 mm ² / s, particularly preferably 8 to. 35 mm ² / s. When the kinematic viscosity at 100 ° C. of the lubricating base oil exceeds 50 mm ² / s, the low-temperature viscosity characteristic deteriorates, whereas when the kinematic viscosity is less than 4 mm ² / s, oil film formation at the lubrication site is caused. Insufficient lubrication results in poor lubricity and increases the evaporation loss of the lubricating base oil, which is not preferable.

In the lubricating oil composition of the present invention, the lubricating base oil has a kinematic viscosity at 100 ° C. of 2 mm ² / s or more and less than 9 mm ² / s and / or a kinematic viscosity at 100 ° C. of 9 to 50 mm ² / s. It is preferable to contain a lubricating base oil.

Examples of the lubricating base oil having a kinematic viscosity at 100 ° C. of 2 mm ² / s or more and less than 9 mm ² / s include mineral base oils and synthetic base oils such as SAE 10-20, and the kinematic viscosity is 3 .5mm ² / s or more, more preferably ^{4 mm} 2 / s or more, preferably not more than 8.5 mm ² / s. The sulfur content is preferably 0 to 1% by mass, more preferably 0.2% by mass or less, and the total aromatic content is preferably 0 to 40% by mass, more preferably 35% by mass or less. More preferably, it is 30% by mass or less. Further, the viscosity index is preferably 80 or more, more preferably 90 or more, still more preferably 100 or more, and 120 or more.

In addition, examples of the lubricating base oil having a kinematic viscosity at 100 ° C. of 9 to 50 mm ² / s include mineral base oils and synthetic base oils such as SAE 30 to 50 and bright stock. preferably at 10 mm ² / s or more, preferably not more than 40 mm ² / s. The sulfur content is preferably 0 to 1% by mass, more preferably 0.9% by mass or less, and still more preferably 0.8% by mass or less. The total aromatic content is preferably 0 to 40% by mass. It is 35 mass% or less, More preferably, it is 35 mass% or less, More preferably, it is 30 mass% or less. Further, the viscosity index is preferably 80 or more, more preferably 90 or more, still more preferably 95 or more, and 120 or more.

In the present invention, a lubricating base oil having a kinematic viscosity at 100 ° C. of 2 mm ² / s or more and less than 9 mm ² / s as a main component, for example, 50% by mass or more based on the total amount of the base oil, more preferably 70% by mass or more. It is particularly desirable to contain 50% by mass or less, preferably 10 to 30% by mass of a lubricating base oil having a kinematic viscosity at 100 ° C. of 9 to 50 mm ² / s at 100 ° C.

  The viscosity index of the lubricating base oil is not particularly limited, but the value is preferably 80 or more, more preferably 90 or more, and still more preferably 95 or more so that excellent viscosity characteristics can be obtained from low temperature to high temperature. It is. The upper limit of the viscosity index is not particularly limited, such as hydrocracked mineral oil, poly α-olefin base oil (for example, oligomers of α-olefins such as 1-octene, 1-decene, 1-dodecene or hydrides thereof). About 120 to 160, normal paraffin, slack wax, GTL wax, etc., or about 135 to 180 such as isoparaffin mineral oil obtained by isomerizing these, complex ester base oil or HVI-PAO base oil The thing of about 150-250 like this can also be used.

In the present invention, the kinematic viscosity at 100 ° C. is 2 mm ² / s or more in that a lubricating oil composition having a sufficient effect against silver corrosion and having excellent solubility and economical efficiency of additives can be obtained. Mineral oil base oil of less than 9 mm ² / s, total aromatic content of 20 to 40% by mass, sulfur content of 0.1 to 0.3% by mass, viscosity index of 90 to 110 and / or kinematic viscosity at 100 ° C. A mineral oil base oil having 9 to 50 mm ² / s, a total aromatic content of 20 to 40% by mass, a sulfur content of 0.3 to 0.9% by mass, and a viscosity index of 90 to 110 can be used.

Further, in the present invention, the kinematic viscosity at 100 ° C. is 2 mm ² in that it is excellent in oxidation stability even under harsher conditions and can suppress corrosion of silver due to components due to deterioration of the base oil even in long-term use. / S or more and less than 9 mm ² / s, total aromatic content is 10% by mass or less, sulfur content is 0.1% by mass or less, and viscosity index is 120-160 hydrocracking / isomerized mineral oil or poly α-olefin group Oil and / or hydrocracking / isomerism having a kinematic viscosity of 9 to 50 mm ² / s at 100 ° C., a total aromatic content of 10% by mass or less, a sulfur content of 0.1% by mass or less, and a viscosity index of 120 to 160 Chemical mineral oil or poly α-olefin base oil can be particularly preferably used.

In particular, 100 ° C. kinematic viscosity ^{2 mm} 2 / s or more ^9mm less than 2 / s at, preferably ^{7 mm} 2 / s or more ^9mm less than 2 / s, a viscosity index of 110 to 160, preferably poly α- olefin of 130 to 160 A base oil and / or a poly α-olefin base oil having a kinematic viscosity at 100 ° C. of 9 to 50 mm ² / s, preferably 30 to 50 mm ² / s and a viscosity index of 120 to 160, preferably 140 to 160. Lubricating base oil to be contained, especially the former is 50 to 95% by mass, preferably 70 to 90% by mass, and the latter is 5 to 50% by mass, preferably 10 to 30% by mass, based on the total amount of base oil. In addition to being excellent in oxidation stability, it is possible to increase the high-temperature viscosity and high-temperature shear viscosity and to increase the thickness of the oil film. It is particularly preferable because wear or corrosion wear of the receiver can be suppressed at a higher level, and wear or corrosion wear of the silver-containing material or the bearing due to deterioration of the lubricating oil can be suppressed for a long period of time.

  The lubricating oil composition of the present invention contains a metal salt of a phosphorus-containing acid represented by the general formula (a) or (b) as the component (A). As the component (A), a metal salt of a phosphorus-containing acid represented by the general formula (a) or (b) and a metal base such as a metal oxide, a metal hydroxide, a metal carbonate, or a metal chloride. It can be illustrated.

［式中、Ｒ^１は炭素数１〜３０の炭化水素基を示し、Ｒ^２及びＲ^３は同一でも異なっていてもよく、それぞれ水素原子又は炭素数１〜３０の炭化水素含有基を示し、ｐは０又は１を示す。］

[Wherein, R ¹ represents a hydrocarbon group having 1 to 30 carbon atoms, R ² and R ³ may be the same or different, and each represents a hydrogen atom or a hydrocarbon-containing group having 1 to 30 carbon atoms; p represents 0 or 1; ]

［式中、Ｒ^４は炭素数１〜３０の炭化水素基を示し、Ｒ^５及びＲ^６は同一でも異なっていてもよく、それぞれ水素原子又は炭素数１〜３０の炭化水素含有基を示し、ｑは０又は１を示す。］

[Wherein, R ⁴ represents a hydrocarbon group having 1 to 30 carbon atoms, R ⁵ and R ⁶ may be the same or different, and each represents a hydrogen atom or a hydrocarbon-containing group having 1 to 30 carbon atoms, q represents 0 or 1; ]

Specific examples of the hydrocarbon-containing group having 1 to 30 carbon atoms represented by R ^{1 to} R ⁶ in the general formulas (a) and (b) include an alkyl group, a cycloalkyl group, an alkenyl group, and an alkyl group. Particularly preferred examples include hydrocarbon groups such as substituted cycloalkyl groups, aryl groups, alkyl-substituted aryl groups, and arylalkyl groups. In addition, as this hydrocarbon containing group, if it has this hydrocarbon group, you may have 1 type, or 2 or more types chosen from sulfur, nitrogen, and oxygen in a molecule | numerator.

  As the alkyl group, for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, Alkyl groups such as pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, etc. (These alkyl groups may be linear or branched, and may be primary alkyl groups, secondary alkyl groups, or tertiary alkyl groups. Good).

  As said cycloalkyl group, C5-C7 cycloalkyl groups, such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, can be mentioned, for example. Examples of the alkylcycloalkyl group include a methylcyclopentyl group, a dimethylcyclopentyl group, a methylethylcyclopentyl group, a diethylcyclopentyl group, a methylcyclohexyl group, a dimethylcyclohexyl group, a methylethylcyclohexyl group, a diethylcyclohexyl group, a methylcycloheptyl group, Examples thereof include alkyl cycloalkyl groups having 6 to 11 carbon atoms such as dimethylcycloheptyl group, methylethylcycloheptyl group, and diethylcycloheptyl group (the substitution position of the alkyl group to the cycloalkyl group is also arbitrary).

  Examples of the alkenyl group include butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, An alkenyl group such as an octadecenyl group (these alkenyl groups may be linear or branched, and the position of the double bond is also optional).

  As said aryl group, aryl groups, such as a phenyl group and a naphthyl group, can be mentioned, for example. Examples of the alkylaryl group include tolyl group, xylyl group, ethylphenyl group, propylphenyl group, butylphenyl group, pentylphenyl group, hexylphenyl group, heptylphenyl group, octylphenyl group, nonylphenyl group, and decylphenyl. Group, an alkylaryl group having 7 to 18 carbon atoms such as undecylphenyl group and dodecylphenyl group (the alkyl group may be linear or branched, and the substitution position on the aryl group is also arbitrary). be able to.

  Examples of the arylalkyl group include arylalkyl groups having 7 to 12 carbon atoms such as benzyl group, phenylethyl group, phenylpropyl group, phenylbutyl group, phenylpentyl group, and phenylhexyl group (these alkyl groups are linear). Or may be branched.).

^R 1 above hydrocarbon group having 1 to 30 carbon atoms represented by the to R ^6, preferably an alkyl group or an aryl group having 6 to 24 carbon atoms having 1 to 30 carbon atoms, more preferably 3 carbon atoms -18, more preferably an alkyl group having 4 to 12 carbon atoms, particularly preferably an alkyl group having 6 to 10 carbon atoms.

  Examples of the phosphorus-containing acid represented by the general formula (a) include phosphorous acid monoester having one hydrocarbon-containing group having 1 to 30 carbon atoms, (hydrocarbyl) phosphonous acid; Phosphorous acid diester having two 30 hydrocarbon-containing groups, (hydrocarbyl) phosphonous acid monoester; Phosphorous acid triester having three hydrocarbon-containing groups having 1 to 30 carbon atoms, (hydrocarbyl) phosphon Acid diesters; and mixtures thereof.

  Examples of the phosphorus-containing acid represented by the general formula (b) include a phosphoric acid monoester having one hydrocarbon-containing group having 1 to 30 carbon atoms, (hydrocarbyl) phosphonic acid; Phosphoric acid diester having two hydrocarbon-containing groups, (hydrocarbyl) phosphonic acid monoester; phosphoric acid triester having three hydrocarbon-containing groups having 1 to 30 carbon atoms, (hydrocarbyl) phosphonic acid diester; and A mixture etc. are mentioned. In addition, the “hydrocarbyl” in the examples of the general formulas (a) and (b) means substitution of the hydrocarbon-containing group having 1 to 30 carbon atoms.

  Moreover, the metal salt of the phosphorus-containing acid represented by the general formula (a) or (b) is a metal oxide, a metal hydroxide, a phosphorus-containing acid represented by the general formula (a) or (b), It can be obtained by allowing a metal base such as metal carbonate or metal chloride to act to neutralize part or all of the remaining acidic hydrogen.

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

  In addition, the structure of the metal salt of the phosphorus compound differs depending on the valence of the metal or the number of OH groups of the phosphorus compound, and therefore the structure of the metal salt of the phosphorus compound is not limited at all. For example, when 1 mol of zinc oxide and 2 mol of phosphoric acid diester (compound having one OH group) are reacted, a compound having a structure represented by the following formula (c) is considered to be obtained as a main component. Is also considered to exist.

［式中、Ｒはそれぞれ独立に水素原子又は炭素数１〜３０の炭化水素含有基を示す。］

[In formula, R shows a hydrogen atom or a C1-C30 hydrocarbon containing group each independently. ]

  Further, for example, when 1 mol of zinc oxide and 1 mol of phosphoric acid monoester (a compound having two OH groups) are reacted, it is considered that a compound having a structure represented by the following formula (d) is obtained as a main component. Polymerized molecules are also thought to exist.

［式中、Ｒは水素原子又は炭素数１〜３０の炭化水素含有基を示す。］

[Wherein, R represents a hydrogen atom or a hydrocarbon-containing group having 1 to 30 carbon atoms. ]

  In the present invention, the metal salt of the phosphorus-containing acid may be used alone or in combination of two or more.

  As a more preferable specific example of the metal salt of the phosphorus-containing acid according to the present invention, a zinc salt of a phosphorous acid diester having two alkyl groups having 3 to 18 carbon atoms or two aryl groups, and an alkyl having 3 to 18 carbon atoms. Zinc salt of monoester of phosphoric acid having 1 group or aryl group, zinc salt of diester of phosphoric acid having 2 or 3 alkyl groups or 2 aryl groups, alkyl group or aryl having 1 to 18 carbon atoms Zinc salt of (hydrocarbyl) phosphonous acid having 1 group, alkyl group having 1 to 18 carbon atoms or zinc group of (hydrocarbyl) phosphonous acid monoester having 2 aryl groups, alkyl group having 1 to 18 carbon atoms Or a zinc salt of phosphonic acid having one aryl group (hydrocarbyl), two alkyl groups having 1 to 18 carbon atoms or two aryl groups (hydrocarbyl) A zinc salt of a phosphonic acid monoester, and a zinc salt of a phosphoric monoester and / or a phosphoric diester having an alkyl group having 3 to 18 carbon atoms, preferably an alkyl group having 4 to 12 carbon atoms, is more preferable. A zinc salt of a phosphoric diester having an alkyl group of 3 to 18 carbon atoms, preferably an alkyl group of 4 to 12 carbon atoms, is particularly preferable.

  As the most preferable component (A) of the present invention, in addition to the effects of the present invention, it has an alkyl group having 6 to 10 carbon atoms in that it has a good balance between solubility in lubricating base oil and wear resistance. The metal salt of phosphoric acid monoester and / or phosphoric acid diester is good, and the mass ratio (M / P) of the amount of metal (M) to the amount of phosphorus (P) is preferably 1 to 3, but phosphoric acid. The metal salt of a mixture of monoester and phosphoric acid diester is better, and the M / P value is preferably 1.2 to 2.5, more preferably 1.3 to 1.8.

  In the lubricating oil composition of the present invention, the content of the component (A) is usually 0.01 to 0.2% by mass in terms of phosphorus element based on the total amount of the composition, preferably 0.02 It is -0.15 mass%, More preferably, it is 0.04-0.12 mass%. When the content of the component (A) in terms of phosphorus element is less than 0.01% by mass, the corrosion wear resistance of the silver-containing material tends to be insufficient, and even if it exceeds 0.2% by mass The effect corresponding to the amount added may not be obtained, and the solubility may be insufficient.

  The lubricating oil composition of the present invention contains a metallic detergent as component (B). The metal detergent is not particularly limited, and is a known alkali metal or alkaline earth metal sulfonate detergent, alkali metal or alkaline earth metal phenate detergent, alkali metal or alkaline earth metal salicylate detergent, Examples thereof include alkali metal or alkaline earth metal naphthenate detergents, alkali metal or alkaline earth metal phosphonate detergents, and mixtures of two or more of these (including complex types).

  Examples of the alkali metal herein include sodium and potassium, and examples of the alkaline earth metal include calcium, magnesium, barium and the like, preferably an alkaline earth metal, and preferably calcium or magnesium. Particularly preferred. In addition, the total base number and addition amount of these metal detergents can be arbitrarily selected according to the required performance of the lubricating oil.

  The metal-based detergent includes not only a neutral metal-based detergent but also a (over) basic metal-based detergent. In the present invention, the metal-based detergent has calcium carbonate and / or calcium borate. It is preferable that it is a (over) basic metal type detergent.

  The base number of the metal detergent is not particularly limited, but is usually preferably 0 to 500 mgKOH / g, more preferably 150 to 450 mgKOH / g, and particularly preferably 200 to 400 mgKOH / g. The base number referred to here is 7. JIS K2501 “Petroleum products and lubricating oils-Neutralization number test method”. This means the base value by the perchloric acid method measured according to the above (the same shall apply hereinafter).

  In the present invention, the content of the (B) metal-based detergent is not particularly limited, but is usually 0.1 to 30% by mass on the basis of the total amount of the composition. 5 mass%, More preferably, it is 0.05-0.6 mass%.

  When the lubricating oil composition of the present invention is used as a lubricating oil in contact with a silver-containing material in a diesel engine having a silver-containing material, from the viewpoint of improving high-temperature cleanliness, acid neutralization performance, and oxidation stability performance. The content of the component (B) is more preferably 0.05 to 0.6% by mass, further preferably 0.1 to 0.3% by mass, and particularly preferably 0.15 to 0% as a metal amount. .25% by mass.

  In addition, when the lubricating oil composition of the present invention is used as a lubricating oil in contact with a silver-containing material in a railway vehicle diesel engine having a silver-containing material, the high-temperature cleanliness enough to withstand high-load operation. From the viewpoint of enhancing acid neutralization performance and oxidation stability performance, the content of the component (B) is more preferably 0.05 to 0.6% by mass, further preferably 0.3 to 0 as the metal amount. .6% by mass, particularly preferably 0.35 to 0.6% by mass.

  Further, when the lubricating oil composition of the present invention is used as a lubricating oil in contact with a silver-containing material in an automobile gasoline engine and a four-cycle two-wheeled vehicle engine having the silver-containing material, excellent high-temperature cleaning performance and acidity are obtained. From the viewpoint of enhancing the neutralization performance and oxidation stability performance and mitigating the influence on the exhaust gas aftertreatment device, the content of the component (B) is more preferably 0.05 to 0.6% by mass as the amount of metal. More preferably, it is 0.1-0.3 mass%, Most preferably, it is 0.15-0.25 mass%.

  Since the lubricating oil composition of the present invention is excellent in corrosion resistance of the silver-containing material by adopting the above-described configuration, the lubricating oil composition in contact with the silver-containing material is used as a machine or device having a silver-containing material, particularly an internal combustion engine. When used, it can prevent corrosion, corrosive wear, elution, etc. of the silver-containing material, but in order to further improve its performance or according to other purposes, the lubricating oil composition of the present invention can be used. Any additive commonly used in lubricating oils can be added. Examples of such additives include ashless dispersants, antioxidants, anti-wear agents (or extreme pressure agents) other than those described above, friction modifiers, viscosity index improvers, corrosion inhibitors, rust inhibitors, and demulsifiers. And additives such as metal deactivators, antifoaming agents, and colorants.

  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. Examples of the nitrogen-containing compound herein include succinimide, benzylamine, polyamine, Mannich base, etc., and derivatives thereof include boron compounds such as boric acid and borate, (thio ) Phosphoric acid, phosphorus compounds such as (thio) phosphate, organic acids, and derivatives obtained by reacting hydroxy (poly) oxyalkylene carbonate. In the present invention, one or two or more 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 carbon number of the alkyl group or alkenyl group is less than 40, the solubility of the compound in the lubricant base oil decreases, whereas when the alkyl group or alkenyl group exceeds 400 carbon atoms, the lubricating oil composition has a low temperature. Since fluidity | liquidity deteriorates, it is unpreferable respectively. 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 and a branched alkenyl group.

  In the present invention, the content of the ashless dispersant is not particularly limited, but is usually 0.1 to 10% by mass, preferably 1 to 8% by mass, more preferably 3 to 7% based on the total amount of the composition. % By mass. When the content of ashless dispersant is less than the above, the sulfuric acid neutralization rate tends to be insufficient, and when the content exceeds the above range, not only an effect commensurate with the content is not obtained, but also the cleanliness of the piston ring groove is deteriorated. Tend to.

  As the ashless dispersant in the present invention, mono-type and / or bis-type succinimide-based ashless dispersants, particularly bis-type succinimide-based ashless dispersants are preferable from the viewpoint of high-temperature detergency. The acid imide ashless dispersant may or may not contain boron, but preferably contains boron in terms of seizure resistance, sludge dispersibility, high temperature It is more preferable to use an ashless dispersant that does not contain boron in terms of excellent maintainability of cleaning performance and economy.

  In addition, as the ashless dispersant in the present invention, it is preferable to use a succinimide ashless dispersant having a weight average molecular weight of 3000 to 20000. When the weight average molecular weight is less than 3000, the molecular weight of the non-polar polybutenyl group is small and the sludge dispersibility is poor, and the amine portion of the polar group which may become an active site for oxidative degradation is relatively increased and oxidized. Since it is inferior in stability, it is not preferable. On the other hand, from the viewpoint of preventing deterioration of low temperature viscosity characteristics, the weight average molecular weight is preferably 20000 or less. From such a viewpoint, the weight average molecular weight of the ashless dispersant in the present invention is preferably 4000 or more, more preferably 6500 or more, preferably 15000 or less, more preferably 12000 or less. Here, the weight average molecular weight means that two columns of GHSHR-M (7.8 mm ID × 30 cm) manufactured by Tosoh Corporation are used in series with a 150-CALC / GPC apparatus manufactured by Waters, and tetrahydrofuran is used as a solvent. By means of temperature, 23 ° C., flow rate of 1 mL / min, sample concentration of 1% by mass, sample injection amount of 75 μL, and weight average molecular weight in terms of polystyrene measured with a detector differential refractometer (RI) are meant.

  Examples of the antioxidant include ashless antioxidants such as phenols and amines, and metal antioxidants. Of these, phenolic antioxidants are preferred because of their excellent anti-caking properties, bisphenol-based or phenolic antioxidants having ester bonds are preferred, and octyl-3- (3,5-ditertiarybutyl-4-hydroxy 3,5-dialkyl-4-hydroxyphenyl-substituted fatty acid esters such as phenyl) propionate and octyl-3- (3-methyl-5-tertiarybutyl-4-hydroxyphenyl) propionate (one alkyl group is tertiary) A butyl group, with the remainder being a methyl group or a tertiary butyl group) is particularly preferred.

  The content of these optional components is usually 0.1 to 5% by mass, preferably 0.5 to 2% by mass, based on the total amount of the composition.

  As the antiwear agent (or extreme pressure agent) other than the above, any antiwear agent used for lubricating oil can be used. For example, sulfur-based, phosphorus-based, sulfur-phosphorus extreme pressure agents and the like can be used. Specifically, phosphites, thiophosphites, dithiophosphites, trithiophosphites Esters, phosphate esters, thiophosphate esters, dithiophosphate esters, trithiophosphate esters, amine salts thereof, metal salts thereof, derivatives thereof, dithiocarbamates, disulfides, polysulfides, sulfurized olefins And sulfurized oils and the like.

  In the lubricating oil composition of the present invention, when these antiwear agents (or extreme pressure agents) are used, the content thereof is not particularly limited, but is usually 0.01 to 5% by mass based on the total amount of the composition. It is.

  Examples of the friction modifier include ashless friction modifiers such as fatty acid esters, aliphatic amines, and fatty acid amides, and metal friction modifiers such as molybdenum dithiocarbamate and molybdenum dithiophosphate. These contents are usually 0.01 to 5% by mass based on the total amount of the composition.

As the viscosity index improver, polymethacrylate viscosity index improver, olefin copolymer viscosity index improver, styrene-diene copolymer viscosity index improver, styrene-maleic anhydride copolymer viscosity index improver or poly Examples thereof include alkylstyrene viscosity index improvers. Among these, an olefin copolymer-based viscosity index improver or a styrene-diene copolymer-based viscosity index improver is preferable because of its superior anti-coking properties, and an ethylene-α-olefin copolymer-based viscosity index improver is particularly preferable. . The weight average molecular weight of these viscosity index improvers is usually 800 to 1,000,000, preferably 100,000 to 900,000. The PSSI of the viscosity index improver is not particularly limited, but is preferably 1 to 60, more preferably 10 to 40, and still more preferably 20 to 30. Here, PSSI (Permanent Shear Stability Index) is the following calculation using the kinematic viscosity at 100 ° C. before and after the shear stability test (ASTM D6278) and the kinematic viscosity of the base oil at 100 ° C. It means the index calculated by the formula.
PSSI (%) =
{1- (Kinematic viscosity after shearing-Kinematic viscosity of base oil) / (Kinematic viscosity before shearing-Kinematic viscosity of base oil)} × 100
Moreover, content of a viscosity index improver is 0.1-20 mass% normally on the composition whole quantity basis.

  Examples of the corrosion inhibitor include benzotriazole, tolyltriazole, thiadiazole, or 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, or 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 thereof include dialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, and β- (o-carboxybenzylthio) propiononitrile.

  Examples of antifoaming agents include silicone oil, alkenyl succinic acid derivatives, esters of polyhydroxy aliphatic alcohols and long chain fatty acids, methyl salicylate and o-hydroxybenzyl alcohol, aluminum stearate, potassium oleate, N-dialkyl-allylamine Nitroaminoalkanol, aromatic amine salt of isoamyl octyl phosphate, alkylalkylene diphosphate, metal derivative of thioether, metal derivative of disulfide, fluorine compound of aliphatic hydrocarbon, triethylsilane, dichlorosilane, alkylphenyl polyethylene glycol ether sulfide, fluoro Examples thereof include alkyl ethers.

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

The kinematic viscosity at 100 ° C. of the lubricating oil composition of the present invention containing the above components is 5.6 to 21.3 mm ² / s, preferably 5.6 to 16.3 mm ² / s. The kinematic viscosity at 100 ° C. here refers to the kinematic viscosity at 100 ° C. defined in JIS K2283.

  Since the lubricating oil composition of the present invention can suppress silver corrosion, it can be suitably used as a lubricating oil in contact with a silver-containing material. The silver-containing material is not limited as long as silver is present on the metal surface that comes into contact with the lubricating oil composition of the present invention. Not only silver but also silver alloys, silver plating, etc. The material which coat | covered the metal base material surface is mentioned. Further, even if the surface of the silver-containing material is coated with a non-silver-containing material, the coated surface is abraded during use and the silver-containing material is exposed, and comes into contact with the lubricating oil composition of the present invention. This includes cases where there is a possibility. The silver-containing material includes not only the silver-containing material used for the sliding portion but also a silver-containing material that comes into contact with the lubricating oil composition other than the sliding portion.

  Examples of silver alloys include silver-tin alloys, silver-copper alloys, silver-tin-copper alloys, silver-aluminum alloys, silver-aluminum-silicon alloys, silver-aluminum-tin alloys, silver-aluminum-copper alloys, Silver-aluminum-silicon-tin alloy, silver-aluminum-silicon-copper alloy, silver-aluminum-tin-copper alloy, silver-aluminum-silicon-tin-copper alloy, and the like. The content is preferably 1% by mass or more, more preferably 2% by mass or more, further preferably 5% by mass or more, and further preferably 10% by mass or more.

  Specific examples of the silver-containing material include a silver-tin-containing alloy containing 50 to 95 mass%, preferably 60 to 90 mass% of silver, and 5 to 50 mass%, preferably 10 to 30 mass% of silver. -A copper-containing alloy, a silver-aluminum-containing alloy containing 1 to 10% by mass, preferably 2 to 5% by mass of silver, and the like. The lubricating oil composition of the present invention is useful because the silver content on the metal surface is more likely to cause silver lead corrosion or corrosive wear.

  In addition, the lubricating oil composition of the present invention is excellent not only in silver-containing materials or silver-plated materials but also in corrosion or corrosion wear resistance against materials such as lead and copper. In addition to being useful, it is also useful for machines and devices in which a silver-containing material and a lead-containing material or a copper-containing material are in contact with a lubricating oil separately.

  Since the lubricating oil composition of the present invention suppresses corrosion of the silver-containing material with which it comes into contact, it protects a silver-containing material and a machine or apparatus having the silver-containing material when used as a lubricating oil. Can do. Therefore, it can be suitably used as a lubricating oil for various internal combustion engines, in particular, a lubricating oil for diesel engines, railway diesel engines, automobile gasoline engines, and four-cycle motorcycle engines.

  Hereinafter, the content of the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

The lubricating oil compositions of Reference Examples 1 to 3 and Comparative Example 1 were prepared so that the kinematic viscosities at 100 ° C. were 11 mm ² / s so as to have the compositions shown in Table 1. Similarly, the lubricating oil compositions of Examples 4 to 7 and Comparative Example 2 were prepared so that the kinematic viscosities at 100 ° C. were 14.5 mm ² / s so as to have the compositions shown in Table 1. The ratio of the base oil is based on the total amount of the base oil, and the amount of each additive is based on the total amount of the composition.

The obtained composition was subjected to a corrosive oxidation stability test for each test oil in accordance with Federal Test Method Standard 791 5308 Method except for the test conditions shown below, and the amount of silver dissolved in the test oil was measured. did. The results obtained are also shown in Table 1.
Test piece: Silver (0.8 mm × 25.4 mm × 25.4 mm)
Test temperature: 150 ° C
Test time: 72 hours Test oil amount: 100 g

  As is apparent from the results in Table 1, the lubricating oil compositions (Examples 1 to 7) according to the present invention using zinc alkylphosphate had a silver elution amount of 1 in the test oil after the corrosion oxidation stability test. It is less than ppm by mass, indicating that the silver corrosion resistance is extremely excellent. On the other hand, in the lubricating oil compositions (Comparative Examples 1 and 2) using zinc dithiophosphate and a phenate detergent, the silver elution amount in the test oil after the corrosion oxidation stability test significantly exceeds 100 mass ppm. Thus, it can be seen that the corrosion resistance to the silver-containing material is significantly inferior.

  In addition, the lubricating oil composition (Example 7) using a specific poly-α-olefin base oil has much higher oxidation stability than that of Example 1 using a solvent refined mineral oil, and has a high temperature viscosity, Since the high-temperature shear viscosity is also increased, the oil film can be thickened, so that not only silver corrosion due to oil deterioration can be suppressed even during long-term use, but also bearing wear or corrosion wear can be greatly improved.

  Although the present invention has been described with reference to the most practical and preferred embodiments at the present time, the present invention is not limited to the embodiments disclosed herein. However, the present invention can be changed as appropriate without departing from the spirit or concept of the invention that can be read from the claims and the entire specification. Lubricating oil compositions with such changes are also included in the technical scope of the present invention. Must be understood as.

Claims (6)

To a lubricating base oil composed of a mineral base oil and / or a synthetic base oil, based on the total amount of the composition,
(A) 0.01 to 0.2% by mass of phosphorus-containing acid metal salt represented by general formula (a) or (b) as phosphorus amount, and (B) metal detergent as metal amount 0.35 to 0.6 % by mass,
Does not contain hydrocarbon amine salts and metal salts of dialkyldithiophosphoric acids,
It is characterized by
Used in railway vehicle diesel engines with silver-containing materials,
A lubricating oil composition in contact with the silver-containing material.

[Wherein, R ¹ represents a hydrocarbon-containing group having 1 to 30 carbon atoms, and R ² and R ³ may be the same or different, and each represents a hydrogen atom or a hydrocarbon-containing group having 1 to 30 carbon atoms. , P represents 0 or 1. ]

[Wherein, R ⁴ represents a hydrocarbon-containing group having 1 to 30 carbon atoms, R ⁵ and R ⁶ may be the same or different, and each represents a hydrogen atom or a hydrocarbon-containing group having 1 to 30 carbon atoms. , Q represents 0 or 1. ] The content of the component (B) is 0.45 to 0.6% by mass as a metal amount.
The lubricating oil composition according to claim 1. In contact with the silver-containing material used in the sliding part of a diesel engine for railway vehicles,
The lubricating oil composition according to claim 1 or 2. The lubricating base oil, 100 ° C. kinematic viscosity ^{2 mm} 2 / s or more ^9mm less than 2 / s in viscosity index is a kinematic viscosity at poly α- olefin base oil and / or 100 ° C. of 110 to 160 9～50Mm The lubricating oil composition according to any one of claims 1 to 3, further comprising a poly α-olefin base oil having a viscosity index of 120/160 and ² / s. And wherein contacting the lubricating oil composition according to the silver-containing material of a diesel engine for rail vehicles in claim 1 as a lubricating oil, a diesel engine for rail vehicles which is in contact with the lubricating oil Methods for protecting silver-containing materials. A lubricating oil, wherein the lubricating oil composition according to any one of claims 1 to 4 is brought into contact with a silver-containing material used in a sliding part of a railway vehicle diesel engine as a lubricating oil, and A method for protecting a silver-containing material of a contacting diesel engine for a railway vehicle.