JP2008231203A - Lubricant composition for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricant composition for an internal combustion engine excellent in resistance of a base number relative to a combustion product of a fuel such as formic acid and acetic acid, especially retaining performance of a base number by hydrochloric acid method generated when the fuel having a carbon/hydrogen ratio (element ratio) of 0.4 or lower or the fuel containing oxygen-containing hydrocarbon compound is used for the internal combustion engine, and its means. <P>SOLUTION: The lubricant composition for the internal combustion engine uses the fuel having a carbon/hydrogen ratio (element ratio) of 0.4 or lower or the fuel containing oxygen-containing hydrocarbon compound. The lubricant composition contains (A) 0.01-0.2 mass% of a metal salt of a phosphorus-containing acid represented by the formula (a) or (b) as a phosphorus amount based on the total amount of composition, and (B) a metal-based cleaning agent in a lubricant base oil comprising a mineral oil-based base oil and/or a synthetic-based base oil. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a lubricating oil composition for an internal combustion engine using a fuel having a carbon / hydrogen ratio (element ratio) of 0.4 or less or a fuel containing an oxygen-containing hydrocarbon compound, and more specifically, combustion generation of the fuel The present invention relates to a lubricating oil composition for internal combustion engines having excellent resistance to substances (formic acid, acetic acid, etc.).

  In recent years, the environmental impact of exhaust gas is low, so the use of fuels with low C / H ratios such as hydrogen, natural gas, and liquefied petroleum gas and fuels containing oxygenated hydrocarbon compounds as fuel for internal combustion engines Is in the process of conversion. Examples of oxygen-containing fuels include alcohol fuels such as methanol and ethanol, ether fuels having methyl groups or ethyl groups such as dimethyl ether, methyl tertiary butyl ether and ethyl tertiary butyl ether, and fatty acid ester fuels such as fatty acid methyl esters or derivatives thereof. Can be mentioned. These oxygen-containing fuels are being studied for use alone or mixed with gasoline fractions, light oil fractions, and the like. However, these fuels are easier to incorporate moisture than hydrocarbon fuels such as gasoline and light oil, and because the C / H ratio is low, the fuel that contains unburned moisture is mixed with the engine oil. As a problem, there is a problem that water with a large amount generated as a combustion product or an organic acid with a small number of carbon atoms is mixed into the engine oil.

  According to the study of the present inventor, when water or an organic acid having a short carbon chain, especially formic acid or acetic acid, is mixed into an engine oil containing zinc dithiophosphate that has been used as an essential additive in the past, hydrolysis and basic components As a result, it was found that the base number of engine oil, particularly the base number of hydrochloric acid method, markedly decreased, and the resistance and life of engine oil were significantly impaired.

Various reports have been made on lubricating oils used in engines using alcohol-based fuels or dimethyl ether as oxygen-containing fuels (see, for example, Patent Documents 1 to 10). There have been few reports on how to suppress significant declines. In recent years, lubricating oil containing a specific phosphorus compound in place of zinc dithiophosphate has been found to have excellent base number maintenance for heat and NOx (Patent Document 11), but has short moisture and carbon chains. The resistance to acids is completely unknown.
JP-A-5-70786 JP-A-7-62371 JP-A-8-3173 JP-A-8-165484 JP-A-9-110800 JP-A-9-194866 Japanese Patent No. 2866703 Japanese Patent No. 2925683 JP 2007-009122 A JP-A-7-62371 JP 2002-294271 A

  The present invention has been made in view of the above circumstances, and formic acid generated when a fuel having a carbon / hydrogen ratio (element ratio) of 0.4 or less or a fuel containing an oxygen-containing hydrocarbon compound is used in an internal combustion engine. It is intended to provide a lubricating oil composition for an internal combustion engine that is excellent in resistance to a combustion product of a fuel such as acetic acid or the like, particularly a base performance of hydrochloric acid method, and its means.

  As a result of intensive studies to solve the above problems, the present inventor has found that a lubricating oil composition containing a specific phosphorus compound metal salt and a metal-based detergent is used for the combustion products (formic acid, acetic acid, etc.) of the fuel. The inventors have found that the base number and the like, particularly the hydrochloric acid method base number retention performance are excellent, and the present invention has been completed.

  That is, the first aspect of the present invention is a lubricating oil composition for an internal combustion engine using a fuel having a carbon / hydrogen ratio (element ratio) of 0.4 or less or a fuel containing an oxygen-containing hydrocarbon compound, (A) A metal salt of a phosphorus-containing acid represented by the general formula (a) or (b) is added 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. The present invention solves the above problems by providing a lubricating oil composition characterized by containing 0.01 to 0.2% by mass and (B) a metallic detergent.

［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 fuel having a carbon / hydrogen ratio (element ratio) of 0.4 or less is preferably liquefied or compressed natural gas or liquefied petroleum gas.

  In this embodiment, the fuel having a carbon / hydrogen ratio (element ratio) of 0.4 or less is preferably hydrogen.

  In this embodiment, the oxygen-containing hydrocarbon is preferably an aliphatic alcohol, an ether having a methyl group or an ethyl group, a fatty acid ester, or a mixture of a plurality of them.

  The component (B) is preferably a phenate detergent or a salicylate detergent.

  In this embodiment, the lubricating oil composition preferably contains an ashless dispersant having a weight average molecular weight of 5000 to 20000.

  The second aspect of the present invention is the first aspect of the present invention for an internal combustion engine using a fuel having a carbon / hydrogen ratio (element ratio) of 0.4 or less or a fuel containing an oxygen-containing hydrocarbon compound. The above-described problem is solved by providing a method for improving the resistance of a lubricating oil composition to a combustion product of fuel, characterized in that the lubricating oil composition is used.

  In this embodiment, in this embodiment, if the combustion product contains formic acid or acetic acid, the durability improving effect becomes more remarkable.

  The lubricating oil composition for internal combustion engines of the present invention is excellent in stability against acids such as formic acid and acetic acid. Therefore, these acids are generated as fuel combustion products, and the carbon / hydrogen ratio (element ratio) is 0.4 or less, or the fuel containing the oxygen-containing hydrocarbon compound is excellent in resistance when used in an internal combustion engine. Thus, the base number, particularly the hydrochloric acid method base number can be maintained well.

  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 for internal combustion engines of the present invention (hereinafter also simply referred to as a lubricating oil composition) is a mineral base oil and / or a synthetic base oil used in ordinary lubricating oil. Any oil can be used without 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. Although the total aromatic content may be 0% by mass, it is preferably 1% by mass or more, more preferably 5% by mass or more, and further preferably 10% by mass or more in terms of the solubility of the additive. It is preferably 20% by mass or more. When the total aromatic content of the base oil exceeds 40% by mass, oxidation stability is inferior, which is not preferable.

  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. Although 0 mass% may be sufficient as a sulfur content, Preferably it is 0.1 mass% or more, More preferably, it is 0.2 mass% or more. By including the sulfur content of the mineral oil base oil to some extent, the solubility of the additive can be sufficiently increased.

  Specific examples of synthetic base oils 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 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 copolymers of dicarboxylic acids such as dibutyl acid and α-olefins having 2 to 30 carbon atoms; aromatic synthetic oils such as alkylnaphthalene, alkylbenzene and aromatic ester, or mixtures thereof.

  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 lubricant base oil, kinematic viscosity at 100 ° C. kinematic viscosity at 2 to 8 mm ² / s and / or 100 ° C. is 8~50mm ² / s lubricating base oil It is preferable to contain.

Examples of the lubricating base oil having a kinematic viscosity of ² to 8 mm ² / s at 100 ° C. include mineral base oils and synthetic base oils such as SAE 10 to 20, and the kinematic viscosity is 3.5 mm ² / s or more, more preferably 4 mm ² / s or more, preferably 7 mm ² / s or less, more preferably 6 mm ² / s or less. The sulfur content is preferably 0 to 1% by mass, more preferably 0.05 to 0.2% by mass, and the total aromatic content is preferably 0 to 40% by mass, more preferably 15%. It is -35 mass%, More preferably, it is 20-30 mass%. Further, the viscosity index is preferably 80 or more, more preferably 90 or more, still more preferably 100 or more, and may be 120 or more, but is preferably less than 120, more preferably 110 or less.

Examples of the lubricating base oil having a kinematic viscosity at 100 ° C. of 8 to 50 mm ² / s include mineral base oils and synthetic base oils such as SAE 30 to 50 and bright stock. The thickness is preferably 9 mm ² / s or more, more preferably 10 mm ² / s or more, preferably 40 mm ² / s or less, more preferably 20 mm ² / s or less, and particularly preferably 12 mm ² / s or less. The sulfur content is preferably 0 to 1% by mass, more preferably 0.05 to 0.9% by mass, still more preferably 0.3 to 0.8% by mass, and the total aromatic content is The content is preferably 0 to 40% by mass, more preferably 15 to 35% by mass, and still more preferably 20 to 30% by mass. Furthermore, the viscosity index is preferably 80 or more, more preferably 90 or more, still more preferably 95 or more, and may be 120 or more, but is preferably less than 120, more preferably 110 or less, and particularly preferably 100 or less.

In the present invention, a lubricating base oil having a kinematic viscosity at 100 ° C. of ² to 8 mm ² / s is contained 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 blend a lubricating base oil having a kinematic viscosity at 8 ° C. of 8 to 50 mm ² / s in an amount of 50% by mass or less, preferably 10 to 30% by mass.

  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, and is about 135 to 180, such as normal paraffin, slack wax, GTL wax, or isoparaffin mineral oil obtained by isomerizing these, complex ester base oil, HVI-PAO, etc. Although about 150 to 250 such as a base oil can be used, it is preferably 120 or less, more preferably 110 or less from the viewpoint of the solubility and storage stability of the additive.

  The lubricating oil composition for internal combustion engines 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. “Hydrocarbyl” in the examples of the general formulas (a) and (b) means the hydrocarbon-containing substituent 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 used in the present invention, a zinc salt of a phosphite diester having two alkyl groups or aryl groups having 3 to 18 carbon atoms, or 3 to 18 carbon atoms. A zinc salt of a monoester of phosphoric acid having one alkyl group or aryl group, a zinc salt of a diester of phosphoric acid having two alkyl groups or two aryl groups having 3 to 18 carbon atoms, an alkyl group having 1 to 18 carbon atoms or Zinc salt of (hydrocarbyl) phosphonous acid having one aryl group, alkyl group having 1 to 18 carbon atoms or zinc salt of (hydrocarbyl) phosphonous acid monoester having two aryl groups, alkyl having 1 to 18 carbon atoms Zinc salt of (hydrocarbyl) phosphonic acid having one group or aryl group, two alkyl groups or aryl groups having 1 to 18 carbon atoms (hydrocarbyl) ) Zinc salts of phosphonic acid monoesters, and more preferred are zinc monoesters of phosphoric acid monoesters and / or phosphoric acid diesters having an alkyl group having 3 to 18 carbon atoms, preferably an alkyl group having 4 to 12 carbon atoms, Particularly preferred is a zinc salt of a phosphoric diester having an alkyl group having 3 to 18 carbon atoms, preferably an alkyl group having 4 to 12 carbon atoms.

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

  In the lubricating oil composition for an internal combustion engine 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 It is 0.02-0.15 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 anti-wear property tends to be insufficient, and even if it exceeds 0.2% by mass, it is only commensurate with the added amount. 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 10 to 400 mgKOH / g, and particularly preferably 60 to 250 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).

  As the component (B) in the present invention, the above-described sulfonate detergents and phenate detergents have excellent base number retention for organic acids having a short carbon chain such as formic acid and acetic acid, and particularly excellent retention of hydrochloric acid method base number. It is preferable to use one or two or more selected from an agent and a salicylate detergent, and among them, it is preferable to use a phenate detergent or a salicylate detergent because of its excellent retention. Most preferably, a system detergent is used. In addition, when a phenate-type detergent or a salicylate-type detergent is used, even if exposed to water or an organic acid having a short carbon chain such as formic acid or acetic acid, (A) phosphorus and metal resulting from the component, (B) The resulting metal can be maintained in a properly dispersed state in the oil, and the initial performance of the lubricating oil can be maintained for a long period of time, which is particularly preferable.

  In the present invention, the content of the metal detergent is not particularly limited, but is usually 0.1 to 30% by mass on the basis of the total amount of the composition, but preferably 0.05 to 0.3 as a metal conversion amount. % By mass, more preferably 0.10 to 0.25% by mass.

  The lubricating oil composition of the present invention is generated when used in an internal combustion engine using a fuel having a carbon / hydrogen ratio (element ratio) of 0.4 or less or a fuel containing an oxygen-containing hydrocarbon compound. It has strong resistance to fuel combustion products (formic acid, acetic acid, etc.) and is particularly excellent in retention of hydrochloric acid method base number, but in order to further improve its performance or according to other purposes, Any additive generally used in lubricating oils can be added to the lubricating oil composition of the present invention. 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 on 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 is excellent in resistance to formic acid, acetic acid and the like by adopting the above configuration, the carbon / hydrogen ratio (element ratio) generated by these acids as combustion products is 0.4 or less. Therefore, it can be suitably used for an internal combustion engine using a fuel containing any of the above or an oxygen-containing hydrocarbon compound. Here, the fuel having a carbon / hydrogen ratio (element ratio) of 0.4 or less means a fuel mainly containing hydrogen, methane, ethane, propane, butane, etc., specifically, hydrogen, liquefaction or compression. Natural gas, propane gas, liquefied petroleum gas, etc. are included. Specific examples of the fuel containing an oxygen-containing hydrocarbon compound include aliphatic alcohol fuels such as methanol, ethanol, propanol, and butanol; methyl groups or ethyl groups such as dimethyl ether, methyl tertiary butyl ether, and ethyl tertiary butyl ether. Ether fuels having fatty acid; fatty acid ester fuels such as fatty acid methyl esters or derivatives thereof; and hydrocarbon fuels containing these (gasoline, light oil, etc.). When the oxygen-containing fuel is contained in a hydrocarbon fuel (gasoline, light oil, etc.), the oxygen-containing fuel content ratio is usually 0.1 to 90% by volume based on the total amount of the oxygen-containing fuel and the hydrocarbon fuel. It is preferably used in the range of 1 to 50% by volume, particularly preferably 2 to 20% by volume. Since these compounds are compounds in which an alkyl group having a small number of carbon atoms (for example, a C1-C4 alkyl group) is bonded to oxygen, as a combustion product, not only water but also formic acid, compared to gasoline and light oil, It is considered that an organic acid having a small number of carbon atoms such as acetic acid (for example, an organic acid having about C1 to C4) is likely to be generated.

  In addition, as a lubricating oil composition of another aspect of the present invention, a primary and / or secondary alkyl group having 3 to 8 carbon atoms, preferably a secondary class having 3 to 6 carbon atoms, is added to the above-described lubricating base oil. A zinc dialkyldithiophosphate having an alkyl group as a phosphorus amount of 0.01 to 0.2% by mass, the aforementioned (B) metal-based detergent, and a succinimide-based ashless dispersant having a weight average molecular weight of 5000 to 20000 And the aforementioned octyl- (3,5-dialkyl-4-hydroxyphenyl) propionate (one alkyl group is a tertiary butyl group, and the rest is a methyl group or a tertiary butyl group, preferably a tertiary butyl group) And a lubricating oil composition for an internal combustion engine containing the aforementioned polymethacrylate pour point depressant and the aforementioned ethylene α-olefin viscosity index improver.

  The lubricating oil composition for an internal combustion engine may also be used for an internal combustion engine that uses a fuel having a carbon / hydrogen ratio (element ratio) of 0.4 or less or a fuel containing an oxygen-containing hydrocarbon compound. However, the lubricating oil composition for internal combustion engines has practically sufficient performance for hydrolysis stability using only water, and particularly the above-described overbased sulfonate as component (B). It is remarkable when it contains. Therefore, the lubricating oil composition for internal combustion engines, which is a lubricating oil composition for internal combustion engines according to another aspect of the present invention, is a fuel or oxygen-containing hydrocarbon having a hydrogen or carbon / hydrogen ratio (element ratio) exceeding 0.4. It can be suitably used for an internal combustion engine that uses a fuel that does not contain a compound or contains 20% by volume or less of an oxygen-containing hydrocarbon compound. In addition, it does not contain formic acid or acetic acid as a combustion product and does not contain water, for example, hydrogen or oxygen-containing hydrocarbon compounds, preferably 10% by volume or less, more preferably 5% by volume or less. It is useful as a lubricating oil composition for an internal combustion engine using gasoline, kerosene, light oil, especially hydrogen, gasoline, especially hydrogen.

  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.

A total of six types of lubricating oil compositions of sample oils 1 to 6 were prepared so that the kinematic viscosity at 100 ° C. was 11 mm ² / s so as to have the composition of 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.

  For these lubricating oil compositions, except for using no catalyst and adding a 10% by weight aqueous solution, this corresponds to the amount of neutralizing 1 mg KOH / g for sample oils 1 to 6 in accordance with ASTM D2619 method. A hydrolysis stability test was performed using an aqueous solution of acetic acid and formic acid or water. For the sample oils 1 to 6 after hydrolysis, the acid value, base value (hydrochloric acid method and perchloric acid method), metal content, and phosphorus content of the supernatant treated with the centrifuge were measured, and the results were obtained. The results are shown in Table 2 (hydrolysis test with aqueous acetic acid solution and aqueous formic acid solution) and Table 3 (hydrolysis test with water).

  As shown in Table 2, the retention rate of the hydrochloric acid method base number after the hydrolysis test using an acetic acid aqueous solution or a formic acid aqueous solution was compared when the other components having the same composition were compared, that is, sample oil 1 2 and sample oils 3 and 4, and sample oils 5 and 6, respectively, the sample oil using both component (A) and component (B) uses zinc dialkyldithiophosphate instead of component (A). Compared with the sample oil, the results were excellent. In particular, when a phenate-type detergent or a salicylate-type detergent was used as the component (B), a significant advantage was recognized. Even after the hydrolysis test, these sample oils have high retention ratios of calcium, phosphorus, and zinc in the oil, so that it is understood that the influence of acetic acid and formic acid is small and the resistance to these is excellent. Therefore, they are suitable for an internal combustion engine using a fuel in which acetic acid or formic acid is generated as a combustion product and a carbon / hydrogen ratio (element ratio) is 0.4 or less or a fuel containing an oxygen-containing hydrocarbon compound. It turns out that it is a lubricating oil composition.

  From Tables 2 and 3, when using dialkyldithiophosphate zinc (sample oils 2, 4, and 6), compared to using only water, acetic acid or formic acid aqueous solution was used. When it is applied to an internal combustion engine using a fuel having a carbon / hydrogen ratio (element ratio) of 0.4 or less or a fuel containing an oxygen-containing hydrocarbon compound It is clear that there are different conditions for the deterioration of the lubricating oil from the internal combustion engine using gasoline or light oil. From this point of view, it has been clarified that the resistance can be particularly improved when the components (A) and (B), particularly phenate detergent or salicylate detergent, are used in combination.

  Further, from Table 3, in a hydrolysis stability test using only water, zinc dialkyldithiophosphate (alkyl group: secondary C4 / C6), overbased calcium sulfonate, and succinic acid having a weight average molecular weight of 6500 to 20000 An imide-based ashless dispersant, octyl- (3,5-dialkyl-4-hydroxyphenyl) propionate (one alkyl group is a tertiary butyl group, and the rest is a methyl group or a tertiary butyl group), and polymethacrylate A sample oil 2, a zinc dialkyldithiophosphate (alkyl group: secondary C4 / C6), an overbase, and a lubricating oil composition for an internal combustion engine containing a system pour point depressant, an ethylene α-olefin viscosity index improver, and the like Calcium phenate and succinic acid a 6500-20000 weight average molecular weight Ashless dispersant, octyl- (3,5-dialkyl-4-hydroxyphenyl) propionate (one alkyl group is tertiary butyl group and the rest is methyl group or tertiary butyl group), polymethacrylate A sample oil 4 that is a lubricating oil composition for an internal combustion engine containing a system pour point depressant, an ethylene α-olefin viscosity index improver, and the like, and a zinc dialkyldithiophosphate (alkyl group: secondary C4 / C6), Overbased calcium salicylate, succinimide ashless dispersant having a weight average molecular weight of 6500 to 20000, octyl- (3,5-dialkyl-4-hydroxyphenyl) propionate (one alkyl group is a tertiary butyl group) And the rest is methyl or tertiary butyl) and polymethacrylate Since sample oil 6 which is a lubricating oil composition for an internal combustion engine containing a dynamic point depressant and an ethylene α-olefin viscosity index improver has better results than sample oil 1, hydrolysis stability is obtained. As an excellent lubricating oil for internal combustion engines, it is suitable as another aspect of the present invention.

  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 (8)

A lubricating oil composition for an internal combustion engine using a fuel having a carbon / hydrogen ratio (element ratio) of 0.4 or less or a fuel containing an oxygen-containing hydrocarbon compound, comprising a mineral oil base oil and / or a synthetic base (A) A metal salt of a phosphorus-containing acid represented by the general formula (a) or (b) is added to a lubricating base oil composed of an oil, based on the total amount of the composition, 0.01 to 0.2 mass as phosphorus. % And (B) a metal-based detergent.

[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 lubricating oil composition according to claim 1, wherein the fuel having a carbon / hydrogen ratio (element ratio) of 0.4 or less is liquefied or compressed natural gas or liquefied petroleum gas. The lubricating oil composition according to claim 1, wherein the fuel having a carbon / hydrogen ratio (element ratio) of 0.4 or less is hydrogen. 2. The lubricating oil composition according to claim 1, wherein the oxygen-containing hydrocarbon is an aliphatic alcohol, an ether having a methyl group or an ethyl group, a fatty acid ester, or a mixture thereof. object. The lubricating oil composition according to any one of claims 1 to 4, wherein the component (B) is a phenate detergent or a salicylate detergent. The lubricating oil composition according to any one of claims 1 to 4, comprising an ashless dispersant having a weight average molecular weight of 5000 to 20000. Use of the lubricating oil composition according to claim 1 for an internal combustion engine using a fuel having a carbon / hydrogen ratio (element ratio) of 0.4 or less or a fuel containing an oxygen-containing hydrocarbon compound. A method for improving the resistance of a lubricating oil composition to a combustion product of fuel. The method according to claim 7, wherein the combustion product contains formic acid or acetic acid.