JP5068784B2 - Lubricating oil composition for internal combustion engines - Google Patents

Description

  The present invention relates to a lubricating oil composition for an internal combustion engine, and more particularly to a lubricating oil composition for an internal combustion engine that is excellent in long drain properties, high temperature cleanability, and valve system wear prevention properties.

Conventionally, in order to extend the life of lubricating oil,
(I) As a base oil, highly refined mineral base oil and / or use synthetic oils such as poly-α-olefin, polyol ester,
(Ii) As an additive, a peroxide decomposing agent such as a zinc dialkyldithiophosphate (hereinafter referred to as “ZDTP”) and a chain terminator such as a phenolic antioxidant are used in combination.
It has been done in general. Among them, ZDTP is used as an additive that is indispensable for current lubricating oils, particularly lubricating oils for internal combustion engines, as an antioxidant and antiwear agent.

  However, although sulfur-containing compounds such as ZDTP are excellent in antioxidant performance, the oxidative deterioration of the lubricating oil is accelerated by sulfuric acid released in the course of oxidation or thermal decomposition, so that the life of such a lubricating oil is increased. It has become clear that there is a limit to extending this further. In particular, in a composition containing a metal-based detergent, an ashless dispersant, or the like, consumption (deterioration) of the total base number, which is an index of acid neutralization characteristics, tends to be accelerated. Therefore, in order to obtain a long drain type lubricating oil with extremely excellent oxidation stability, it has become necessary to thoroughly review the additive additive composition centering on the antiwear agent.

  On the other hand, to exhaust gas aftertreatment devices such as three-way catalysts, oxidation catalysts, NOx occlusion reduction catalysts, or DPFs (diesel particulate filters) installed in internal combustion engines in response to recent environmental problems There is a need to mitigate the effects as much as possible, and low phosphorus, low sulfur, or low ash lubricants are also desired.

  The present applicant has found that a lubricating oil composition containing a specific phosphorus-containing antiwear agent as a lubricating oil with reduced or no use of ZDTP has long drain properties, high temperature cleanliness, low It has been found that the frictional properties are extremely excellent, and patent applications have been filed for the results (for example, Patent Document 1, Patent Document 2, etc.). However, in order to maintain the wear prevention performance of the valve train equivalent to the case where a sulfur-containing compound such as ZDTP is used, there has been a limit to the reduction in phosphorus.

  On the other hand, low phosphorus oil or non-phosphorus oil has been conventionally studied, but most of them maintain an antiwear property by using a sulfur-containing antiwear agent such as zinc dithiocarbamate instead of ZDTP (for example, Patent Documents 3 to 10). Although sulfur-containing compounds as disclosed in these can maintain wear resistance and oxidation stability to some extent as with ZDTP as described above, it is difficult to further improve long drainage and high-temperature cleanliness. Therefore, it has been desired to develop an engine oil that is low in phosphorus, low in sulfur, or substantially free of phosphorus and sulfur.

Japanese Patent Application No. 2002-015351 Japanese Patent Application No. 2001-315941 JP-A-62-253691 JP-A-6-41568 Japanese Patent Laid-Open No. 1-500912 Japanese Patent Laid-Open No. 63-304095 JP-A 63-304096 Japanese Patent Laid-Open No. Sho 62-243692 JP 62-501917 A JP 2000-63862 A

  The present invention has been made in view of the above demands, and has valve performance wear prevention performance equivalent to that of a lubricating oil containing zinc dithiophosphate, and has a long oxidation stability, base number maintenance property and the like. It is an object of the present invention to provide a lubricating oil composition for an internal combustion engine that is extremely excellent in drainability and high-temperature cleanability. Further, the present invention provides a lubrication for an internal combustion engine in which the influence on an exhaust gas purification treatment device, particularly an exhaust gas purification catalyst, is reduced as much as possible by containing substantially no phosphorus and low sulfur or substantially no sulfur. It is an object to provide an oil composition.

  As a result of intensive studies, the present inventors have found that a composition containing a boric acid ester and an ashless antioxidant in a specific lubricating base oil and not containing a metal salt of dithiophosphate can solve the above problems. As a result, the present invention has been completed.

  That is, the present invention provides a lubricating base oil composed of mineral oil and / or synthetic oil, based on the total amount of the composition, (A) boric acid ester in an amount of 0.001 to 0.5 mass% in terms of boron element and (B ) It contains 0.01 to 5% by mass of an ashless antioxidant, does not substantially contain a metal salt of dithiophosphate, and the sulfur content of the composition is 0.2% by mass or less. The lubricating oil composition for an internal combustion engine.

  In the lubricating oil composition for an internal combustion engine, it is preferable that the total aromatic content of the lubricating base oil is adjusted to 10% by mass or less and the sulfur content is adjusted to 0.05% by mass or less.

  Moreover, it is preferable that the lubricating oil composition for internal combustion engines of this invention contains 0.005-1 mass% of (C) metal type detergent in the metal element conversion amount in a composition whole quantity reference | standard.

  The metal ratio of the component (C) is preferably 3 or less.

  Furthermore, the component (C) is preferably a metallic detergent that does not contain sulfur.

  Moreover, it is preferable that the lubricating oil composition for internal combustion engines of this invention contains 0.05-0.4 mass% of (D) ashless dispersant by the nitrogen element conversion amount on the basis of the composition whole quantity.

  Moreover, it is preferable that the lubricating oil composition for internal combustion engines of this invention does not contain phosphorus substantially, and total sulfur content is 0.05 mass% or less.

  Moreover, it is preferable that the lubricating oil composition for internal combustion engines of this invention is an internal combustion engine using the fuel whose sulfur content is 50 mass ppm or less.

  The lubricating oil composition for an internal combustion engine of the present invention is substantially free of phosphorus and has low sulfur, and is excellent in wear prevention performance, oxidation stability, high temperature cleanliness, and base number maintenance of a valve system. Because it can demonstrate its performance, it can be preferably used as a lubricant for internal combustion engines such as motorcycles, automobiles, gasoline engines for power generation, marine use, diesel engines, gas engines, etc. It can be suitably used for an engine.

  Low sulfur fuel, for example, gasoline having a sulfur content of 50 mass ppm or less, light oil, kerosene, LPG, natural gas, or fuel substantially free of sulfur (hydrogen, dimethyl ether, alcohol, GTL (gas-liquid) It can be preferably used as a lubricating oil for an internal combustion engine using a fuel or the like, particularly a lubricating oil for a gasoline engine or a gas engine.

  In addition to lubricating oils for internal combustion engines, lubricating oils that require any of these performances, such as lubricating oils for drive systems such as automatic or manual transmissions, greases, wet brake oils, hydraulic fluids It can also be suitably used as a lubricating oil such as turbine oil, compressor oil, bearing oil, and refrigeration oil.

  Below, the lubricating oil composition for internal combustion engines of this invention is explained in full detail.

  There is no restriction | limiting in particular as a lubricating base oil in the lubricating oil composition for internal combustion engines of this invention, The mineral base oil and synthetic base oil used for normal lubricating oil can be used.

  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, Examples include those refined by performing one or more treatments such as solvent dewaxing, hydrorefining, etc., or base oils produced by a method of isomerizing wax isomerized mineral oil, GTL WAX (Gas Liquid Wax).

  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 , Diisodecyl adipate, ditridecyl adipate, and di-2-ethylhexyl sebacate, etc .; neopentyl glycol ester, trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, and pentaerythritol Examples thereof include polyol esters such as pelargonate; aromatic synthetic oils such as alkyl naphthalene, alkyl benzene, and aromatic esters, or mixtures thereof.

  As the lubricating base oil of the present invention, the above mineral base oil, the above synthetic base oil, or an arbitrary mixture of two or more selected from these can be used. 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 lubricating base oil of the present invention is not particularly limited in the total aromatic content, but is preferably adjusted to be 10% by mass or less, more preferably 6% by mass or less, and still more preferably 3%. It is at most 2% by mass, particularly preferably at most 2% by mass. By setting the total aromatic content of the lubricating base oil to 10% by mass or less, it is possible to obtain a lubricating oil composition for an internal combustion engine that is more excellent in oxidation stability.

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, and alkylated products thereof, compounds in which four or more benzene rings are condensed, or pyridines, quinolines, phenols, naphthols, etc. Compounds having heteroaromatics and the like are included.

  Further, the sulfur content of the lubricating base oil is not particularly limited, but is preferably adjusted to be 0.05% by mass or less, more preferably 0.01% by mass or less, and 0.005 It is particularly preferable that the content is not more than mass%. By reducing the sulfur content of the lubricating base oil, it is possible to obtain a low-sulfur lubricating oil composition that is more excellent in long draining properties and that can avoid adverse effects on the exhaust gas purification catalyst as much as possible.

The kinematic viscosity of the lubricating base oil used in the present invention is not particularly limited, but the kinematic viscosity at 100 ° C. is preferably 20 mm ² / s or less, more preferably 10 mm ² / s or less. On the other hand, the kinematic viscosity is preferably 1 mm ² / s or more, more preferably 3 mm ² / s or more, and particularly preferably 4 mm ² / s or more. If the kinematic viscosity at 100 ° C. of the lubricating base oil exceeds 20 mm 2 / ^s, and deteriorates the low-temperature viscosity characteristic, whereas, when the kinematic viscosity is less than 1 mm 2 / ^s, oil film formation at lubricating sites Insufficient lubrication results in poor lubricity and increases the evaporation loss of the lubricating base oil, which is not preferable.

The evaporation loss amount of the lubricating base oil is not particularly limited, but the NOACK evaporation amount is preferably 20% by mass or less, more preferably 16% by mass or less, and more preferably 10% by mass or less. Is particularly preferred. When the NOACK evaporation amount of the lubricating base oil exceeds 20% by mass, not only the evaporation loss of the lubricating oil is large, but also the sulfur compounds and metals in the composition may accumulate in the exhaust gas purification device together with the lubricating base oil. There is a concern about adverse effects on exhaust gas purification performance, which is not preferable. Note that the NOACK evaporation amount referred to here is based on CEC L-40-T-87, in which 60 g of a lubricating oil sample is subjected to 250 ° C. under a reduced pressure (−20 mmH ₂ O) of 20 × 9.80665 Pa from normal pressure. The amount of evaporation after holding for 1 hour was measured.

  The viscosity index of the lubricating base oil is not particularly limited, but the value is preferably 80 or more, more preferably 100 or more, and still more preferably so that excellent viscosity characteristics can be obtained from low temperature to high temperature. 120 or more. If the viscosity index is less than 80, the low-temperature viscosity characteristics deteriorate, which is not preferable.

  The component (A) in the lubricating oil composition for an internal combustion engine of the present invention is a borate ester. Boric acid esters are generally used in combination with sulfur and / or phosphorus-containing compounds as bearing corrosion inhibitors (for example, JP-A 63-304095, JP-A 63-304096, JP-A 2000- Recently, it has been found that there is an effect of increasing the coefficient of friction between metals (Japanese Patent Laid-Open No. 2002-226882).

  Examples of the boric acid ester in the present invention include compounds represented by the following general formula (1) or general formula (2), and derivatives thereof.

In the general formulas (1) and (2), R ^{1 to} R ⁶ each represent a hydrocarbon group having 1 to 30 carbon atoms, and these may be the same or different.

Specific examples of the hydrocarbon group having 1 to 30 carbon atoms include, for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, C1-C30 alkyl groups such as undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, and octadecyl group (these alkyl groups may be linear or branched) Ethenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl An alkenyl group having 2 to 30 carbon atoms such as The group may be linear or branched, and the position of the double bond is also arbitrary); a cycloalkyl group having 5 to 7 carbon atoms such as a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group; a methylcyclopentyl group, Dimethylcyclopentyl group, methylethylcyclopentyl group, diethylcyclopentyl group, methylcyclohexyl group, dimethylcyclohexyl group, methylethylcyclohexyl group, diethylcyclohexyl group, methylcycloheptyl group, dimethylcycloheptyl group, methylethylcycloheptyl group, diethylcycloheptyl group An alkylcycloalkyl group having 6 to 11 carbon atoms (the substitution position of the alkyl group to the cycloalkyl group is also arbitrary); an aryl group having 6 to 18 carbon atoms such as a phenyl group or a naphthyl group; a tolyl group, a xylyl group, Ethylphenyl group Propylphenyl group, butylphenyl group, pentylphenyl group, hexylphenyl group, heptylphenyl group, octylphenyl group, nonylphenyl group, decylphenyl group, undecylphenyl group, dodecylphenyl group, diethylphenyl group, dibutylphenyl group, and C7-C26 alkylaryl group such as dioctylphenyl group (the alkyl group may be linear or branched, and the substitution position on the aryl group is also arbitrary); benzyl group, phenylethyl group, phenylpropyl Group, phenylbutyl group, phenylpentyl group, phenylhexyl group and the like, and arylalkyl groups having 7 to 12 carbon atoms (the alkyl group may be linear or branched).

  The hydrocarbon group having 1 to 30 carbon atoms is preferably a hydrocarbon group having 2 to 24 carbon atoms, more preferably a hydrocarbon group having 3 to 20 carbon atoms, and more specifically. Is preferably an alkyl group having 1 to 30 carbon atoms or an aryl group having 6 to 24 carbon atoms, more preferably an alkyl group having 3 to 18 carbon atoms, and more preferably an alkyl group having 4 to 12 carbon atoms.

The boric acid ester represented by the general formula (1) is usually obtained by reacting 1 mol of orthoboric acid (H ₃ BO ₃ ) with 3 mol of the alcohol having 1 to 30 carbon atoms.

The boric acid ester represented by the general formula (2) is usually obtained by reacting 1 mol of orthoboric acid (H ₃ BO ₃ ) with 1 mol of the alcohol having 1 to 30 carbon atoms.

  These reaction conditions are not particularly limited, but it is particularly preferable that the reaction is usually carried out at 100 ° C. or higher because the generated moisture can be removed at the same time.

  In addition, as the derivative of component (A), for example, among organic borates described in JP-A-2002-226882, compounds containing no phosphorus or sulfur, for example, organic borate / polyamine condensates (borate esters described above) Polyamine condensate), organic borate / polyol condensate (polyol condensate of borate ester) and the like.

  Specific examples of the component (A) include triethyl borate, tri-n-propyl borate, triisopropyl borate, tri n-butyl borate, trisec-butyl borate, tritert-butyl borate, and trihexyl borate. , Trioctyl borate, tridecyl borate, tridodecyl borate, trihexadecyl borate, trioctadecyl borate, triphenyl borate, tribenzyl borate, triphenethyl borate, tritolyl borate, triethylphenyl borate, tripropylphenyl borate, tributylphenyl borate , And trinonylphenyl borate and the like. Among these, tri n-butyl borate, trioctyl borate, tridodecyl borate and the like are particularly preferable.

  In the lubricating oil composition for an internal combustion engine of the present invention, the lower limit of the content of the component (A) is 0.001% by mass in terms of boron element based on the total amount of the composition in order to exhibit wear resistance. Or more, preferably 0.01% by mass or more, particularly preferably 0.04% by mass or more. Moreover, as an upper limit of content of (A) component, it is 0.5 mass% or less normally in the amount of boron element conversions on a composition whole quantity basis, Preferably it is 0.2 mass% or less, More preferably Is 0.1% by mass or less. When the content of the component (A) exceeds the above upper limit, it is not preferable because it is difficult to obtain an anti-wear effect sufficient for the content.

  (B) component in the lubricating oil composition for internal combustion engines of this invention is an ashless antioxidant, and is generally used for lubricating oils, such as a phenolic antioxidant and an amine antioxidant. If available, it can be used.

  Examples of phenolic antioxidants include 4,4′-methylenebis (2,6-di-tert-butylphenol), 4,4′-bis (2,6-di-tert-butylphenol), 4,4 ′. -Bis (2-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4′-butylidenebis (3-methyl-6-tert-butylphenol), 4,4′-isopropylidenebis (2,6-di-tert-butylphenol), 2,2′-methylenebis (4-methyl-6) -Nonylphenol), 2,2'-isobutylidenebis (4,6-dimethylphenol), 2,2'-methylenebis (4-methyl) 6-cyclohexylphenol), 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,4-dimethyl-6-tert-butylphenol, 2, 6-di-tert-α-dimethylamino-p-cresol, 2,6-di-tert-butyl-4 (N, N′-dimethylaminomethylphenol), 4,4′-thiobis (2-methyl-6) -Tert-butylphenol), 4,4'-thiobis (3-methyl-6-tert-butylphenol), 2,2'-thiobis (4-methyl-6-tert-butylphenol), bis (3-methyl-4- Hydroxy-5-tert-butylbenzyl) sulfide, bis (3,5-di-tert-butyl-4-hydroxybenzyl) sulfide 2,2′-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], tridecyl-3- (3,5-di-tert-butyl-4-hydroxy Phenyl) propionate, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) 3) such as propionate, octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, octyl-3- (3-methyl-5-tert-butyl-4-hydroxyphenyl) propionate Preferred are methyl-5-tert-butyl-4-hydroxyphenyl substituted fatty acid esters It can be mentioned as. You may use these in mixture of 2 or more types. Of these, those not containing sulfur are particularly preferred.

  Examples of amine-based antioxidants include phenyl-α-naphthylamine, alkylphenyl-α-naphthylamine, and dialkyldiphenylamine. You may use these in mixture of 2 or more types.

  You may mix | blend the said phenolic antioxidant and amine antioxidant in combination.

  When the component (B) is contained in the lubricating oil composition for an internal combustion engine of the present invention, the content is usually 5% by mass or less, preferably 3% by mass or less, more preferably 3% by mass or less based on the total amount of the composition. 2.5% by mass or less. When the content exceeds 5% by mass, sufficient antioxidant properties corresponding to the blending amount cannot be obtained, which is not preferable. On the other hand, the content lower limit value is 0.01% by mass or more, preferably 0.1% by mass, particularly preferably 0.5% by mass or more based on the total amount of the composition in order to obtain sufficient antioxidant properties.

  The lubricating oil composition for internal combustion engines of the present invention does not substantially contain a metal salt of dithiophosphate. Examples of the metal salt of dithiophosphate include zinc dithiophosphate and salts of dithiophosphoric acid and various metals such as Group I metal, Group II metal, aluminum, lead, tin, manganese, cobalt, nickel and copper. It is done. In addition, when these do not contain substantially the metal salt of dithiophosphate here, (A) component is 0.05 mass% in conversion amount of boron elements in a composition whole quantity reference | standard. An amount that does not sufficiently exert the anti-wear performance of the valve system as compared with the composition made, and an amount that does not significantly impair the effects of the present invention, for example, 0.04% by mass or less in terms of phosphorus element based on the total amount of the composition This means that it is preferably 0.01% by mass or less, particularly preferably 0.001% by mass or less, but in essence, these are intentionally not contained at all.

  The lubricating oil composition for an internal combustion engine of the present invention can be made into a composition that is excellent in wear prevention performance of a valve train system and extremely excellent in oxidation stability by having the above-described configuration. By containing a system detergent and (D) an ashless dispersant, it is possible to obtain a composition having higher oxidation stability, excellent base number maintenance, and high temperature cleanability.

  As the component (C) in the lubricating oil composition for an internal combustion engine of the present invention, any compound used as a metallic detergent for lubricating oil can be used. Specifically, for example, alkali metal or alkaline earth Examples thereof include one or more metal detergents selected from metal sulfonate, alkali metal or alkaline earth metal phenate, alkali metal or alkaline earth metal salicylate, alkali metal or alkaline earth metal carboxylate, and the like. . Among them, it is preferable to use an alkali metal or alkaline earth metal phenate not containing sulfur, an alkali metal or alkaline earth metal salicylate, or an alkali metal or alkaline earth metal carboxylate as an essential component, particularly an alkali metal or alkaline earth. It is particularly preferable to use a metal salicylate in that a low sulfur excellent in oxidation stability, base number maintenance and high-temperature cleanability, or a lubricating oil composition containing substantially no sulfur can be obtained.

  Alkali metal or alkaline earth metal sulfonate is an alkali metal or alkaline earth metal salt of an alkyl aromatic sulfonic acid obtained by sulfonating an alkyl aromatic compound having a molecular weight of 1300 to 1500, preferably 400 to 700, particularly Magnesium salt and / or calcium salt, and calcium salt is preferably used.

  Specific examples of the alkyl aromatic sulfonic acid include so-called petroleum sulfonic acid and synthetic sulfonic acid. As the petroleum sulfonic acid here, generally used are those obtained by sulfonating an alkyl aromatic compound in a lubricating oil fraction of mineral oil, or so-called mahoganic acid produced as a by-product when white oil (liquid paraffin) is produced. As synthetic sulfonic acids, for example, sulfonated alkylbenzenes having linear or branched alkyl groups, which are obtained as a by-product from an alkylbenzene production plant, which is a raw material for detergents, or are obtained by alkylating polyolefins to benzene. Or sulfonated alkylnaphthalene such as dinonylnaphthalene is used. Further, as a sulfonating agent for sulfonating these alkyl aromatic compounds, fuming sulfuric acid or sulfuric anhydride is usually used.

  Examples of the alkali metal or alkaline earth metal phenate include alkylphenols and alkylphenols having a linear or branched alkyl group having 4 to 30 carbon atoms, preferably 6 to 18 carbon atoms (these may be primary, secondary, or tertiary). Mention may be made of alkali metal or alkaline earth metal salts, especially magnesium salts and / or calcium salts, of Mannich reactants of sulfides and alkylphenols. Among them, alkali metal or alkaline earth metal phenate containing no sulfur is particularly preferable.

  Examples of the alkali metal or alkaline earth metal salicylate include alkali metal or alkaline earth metal salts of salicylic acid having one or two hydrocarbon groups having 1 to 40 carbon atoms, particularly magnesium salts and / or calcium salts. For example, what is represented by the following general formula (3) can be mentioned.

In the general formula (3), R ¹¹ represents a hydrocarbon group having 1 to 40 carbon atoms, preferably 1 to 30 carbon atoms, preferably an alkyl group, M represents an alkaline earth metal, preferably calcium. Or magnesium, particularly preferably calcium, and n is 1 or 2.

Specific examples of R ¹¹ include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, Tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group, heicosyl group, docosyl group, tricosyl group, tetracosyl group, pentacosyl group, hexacosyl group, heptacosyl group, octacosyl group, nonacosyl group, triaconyl group These may be linear or branched, and they may also be primary alkyl groups, secondary alkyl groups or tertiary alkyl groups.

  Alkali metal or alkaline earth metal sulfonate, alkali metal or alkaline earth metal phenate, alkali metal or alkaline earth metal salicylate, etc. include the above-mentioned alkyl aromatic sulfonic acid, alkylphenol, alkylphenol sulfide, alkylphenol Mannich reaction product Alkylsalicylic acid, etc. can be directly reacted with alkaline earth metal bases such as magnesium and / or calcium alkaline earth metal oxides and hydroxides, or alkali metal salts such as sodium salts and potassium salts can be used. Further, not only neutral salts obtained by substituting with alkaline earth metal salts, but also neutral salts and excess alkaline earth metals or alkaline earth metal salts, alkaline earth metals or alkaline earth metal bases In the presence of water And basic salts obtained by heat, also include overbased salts obtained by reacting the neutral salt with a base of an alkaline earth metal in the presence of carbon dioxide or boric acid or borate.

  As the metal detergent in the present invention, the above neutral salts, basic salts, overbased salts, and mixtures thereof can be used.

  Metal-based detergents are usually commercially available in a state diluted with a light lubricating base oil or the like, and are available, but generally the metal content is 1.0 to 20% by mass, preferably Is preferably 2.0 to 16% by mass.

  In the present invention, the total base number of the component (C) is usually 0 to 500 mgKOH / g, preferably 20 to 450 mgKOH / g, and one or more selected from these can be used in combination. The total base number referred to here is JIS K 2501 “Petroleum products and lubricants—Test method for neutralization number”. Means the total base number by potentiometric titration method (base number / perchloric acid method) measured according to the above.

  In addition, the component (C) of the present invention is not particularly limited in the metal ratio, and usually 20 or less can be used alone or in combination of two or more, but preferably the metal ratio is 3 or less. It is particularly preferable to use a metal-based detergent of 1.5 or less, particularly preferably 1.2 or less, as an essential component because it is excellent in oxidation stability, base number maintenance, high-temperature cleanliness, and the like. The metal ratio here is represented by the valence of the metal element in the metal-based detergent × metal element content (mol%) / soap group content (mol%), and the metal elements include calcium, magnesium, and the like. The soap group means a sulfonic acid group, a salicylic acid group, or the like.

In the present invention, the content of component (C) is usually 1% by mass or less, preferably 0.5% by mass or less, more preferably 0.4% by mass or less, in terms of metal element. In order to further reduce the sulfated ash content of the composition to 1.0% by mass or less, the content is preferably 0.3% by mass or less. In addition, the content of the component (C) is 0.005% by mass or more, preferably 0.01% by mass or more. In order to further improve the oxidation stability, the base number maintainability, and the high temperature cleanliness, More preferably, the content is 0.05% by mass or more, and particularly 0.2% by mass or more is particularly preferable because a composition capable of maintaining the base number and the high temperature cleanliness for a longer period can be obtained. The sulfated ash referred to here is JIS K 2272 5. The value measured by the method prescribed in “Method for testing sulfated ash” is mainly due to the metal-containing additive.

  (D) As the ashless dispersant, any ashless dispersant used in lubricating oils can be used. For example, a straight-chain or branched alkyl group or alkenyl group having 40 to 400 carbon atoms is included in the molecule. Examples thereof include at least one nitrogen-containing compound or derivative thereof, or a modified product of alkenyl succinimide. One type or two or more types arbitrarily selected from these can be blended.

  The alkyl group or alkenyl group has 40 to 400 carbon atoms, preferably 60 to 350 carbon atoms. When the carbon number of the alkyl group or alkenyl group is less than 40, the solubility of the compound in the lubricating base oil decreases. On the other hand, when the carbon number of the alkyl group or alkenyl group exceeds 400, the lubricating oil composition for internal combustion engines Since the low-temperature fluidity | liquidity of a thing deteriorates, it is unpreferable respectively. The alkyl group or alkenyl group may be linear or branched, but specifically, preferred are derived from olefin oligomers such as propylene, 1-butene and isobutylene, and co-oligomers of ethylene and propylene. And a branched alkyl group and a branched alkenyl group.

Specific examples of the component (D) include the following compounds. One or two or more compounds selected from these can be used.
(D-1) A succinimide having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, or a derivative thereof (D-2) an alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule A benzylamine having at least one thereof, or a derivative thereof (D-3) a polyamine having at least one alkyl group or alkenyl group having 40 to 400 carbon atoms in the molecule, or a derivative thereof (D-1) as a succinimide More specifically, compounds represented by the following general formula (4) and general formula (5) can be exemplified.

In the general formula (4), R ²⁰ represents an alkyl group or alkenyl group having 40 to 400 carbon atoms, preferably 60 to 350, and h represents an integer of 1 to 5, preferably 2 to 4.

In the general formula (5), R ²¹ and R ²² each independently represents an alkyl group or an alkenyl group having 40 to 400 carbon atoms, preferably 60 to 350, and is preferably a polybutenyl group. i represents an integer of 0 to 4, preferably 1 to 3.

  The succinimide includes a so-called monotype succinimide represented by the general formula (4) in which succinic anhydride is added to one end of the polyamine, and a general formula in which succinic anhydride is added to both ends of the polyamine ( Although the so-called bis-type succinimide represented by 5) is included, the composition of the present invention may include any of them or a mixture thereof.

  As a method for producing these succinimides, for example, a compound having an alkyl group or an alkenyl group having 40 to 400 carbon atoms, for example, poly (iso) butene having a number average molecular weight of 700 to 3,500, preferably 900 to 2500 is mixed with maleic anhydride. It can be obtained by reacting polybutenyl succinic acid obtained by reacting at 100 to 200 ° C. with polyamine. Specific examples of the polyamine include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine.

  More specifically, examples of the (D-2) benzylamine include compounds represented by the following general formula (6).

In the general formula (6), R ²³ represents an alkyl group or alkenyl group having 40 to 400 carbon atoms, preferably 60 to 350, and j represents an integer of 1 to 5, preferably 2 to 4.

  As a method for producing this benzylamine, for example, a polyolefin such as propylene oligomer, polybutene, and ethylene-α-olefin copolymer is reacted with phenol to form alkylphenol, and then formaldehyde and polyamine (for example, diethylenetriamine, triethylene). Tetramine, tetraethylenepentamine, pentaethylenehexamine and the like) can be obtained by reacting them by Mannich reaction.

More specifically, examples of the (D-3) polyamine include compounds represented by the following general formula (7).
^{_{R 24 -NH- (CH 2 CH 2}} NH) k -H (7)
In the general formula (7), R ²⁴ represents an alkyl or alkenyl group having 40 to 400 carbon atoms, preferably 60 to 350, and k represents an integer of 1 to 5, preferably 2 to 4.

  As a method for producing this polyamine, for example, chlorinated polyolefin such as propylene oligomer, polybutene, and ethylene-α-olefin copolymer, and then polyamine (for example, ammonia, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylene). Pentamine, pentaethylenehexamine and the like) can be reacted.

  Moreover, as a derivative | guide_body of the nitrogen-containing compound quoted as an example of (D) component, C1-C30 monocarboxylic acid (fatty acid etc.), an oxalic acid, a phthalic acid, a trimellit, for example to the above-mentioned nitrogen-containing compound, for example. C2-30 polycarboxylic acid such as acid and pyromellitic acid, hydroxy (poly) alkylene carbonate, etc. are allowed to act to neutralize part or all of the remaining amino group and / or imino group, So-called boron-modified compound obtained by allowing boric acid to act on the nitrogen-containing compound described above to neutralize or amidate part or all of the remaining amino group and / or imino group; So-called phosphoric acid modification in which phosphoric acid is allowed to act on the above nitrogen-containing compound to neutralize or amidate part or all of the remaining amino group and / or imino group A sulfur-modified compound obtained by allowing a sulfur compound to act on the above-mentioned nitrogen-containing compound; and a modification obtained by combining two or more kinds of modifications selected from acid-modified, boron-modified, phosphoric acid-modified, and sulfur-modified into the aforementioned nitrogen-containing compound. Compound; and the like. Among these derivatives, the boric acid modified compound of polybutenyl succinimide is excellent in heat resistance, antioxidant property and antiwear property, and even in the lubricating oil composition for internal combustion engines of the present invention, the base number maintenance property and the high temperature cleanliness. In addition, it is effective for further improving the wear resistance.

  When the component (D) is contained in the lubricating oil composition for an internal combustion engine of the present invention, the content is usually 0.01% by mass or more in terms of nitrogen element based on the total amount of the composition, preferably 0. 0.05 mass% or more, more preferably 0.07 mass% or more, 0.4 mass% or less, preferably 0.2 mass% or less, and particularly preferably 0.16 mass% or less. When the content of the component (D) is less than 0.01% by mass in terms of nitrogen element, the effect of further improving the high-temperature cleanliness is small, whereas when it exceeds 0.4% by mass, it is for an internal combustion engine. Since the low-temperature fluidity | liquidity of a lubricating oil composition deteriorates significantly, each is unpreferable.

  In order to further improve the performance of the lubricating oil composition for an internal combustion engine of the present invention, any additive generally used in lubricating oil can be added depending on the purpose. Examples of such additives include anti-wear agents other than the component (A), friction modifiers, viscosity index improvers, corrosion inhibitors, rust inhibitors, demulsifiers, metal deactivators, antifoaming agents, And additives such as colorants.

  Antiwear agents other than component (A) include zinc dithiocarbamates, disulfides, sulfurized olefins, sulfurized fats and oils, sulfurized esters, thiocarbonates, thiocarbamates, and other sulfur-containing antiwear agents; phosphites , Phosphoric acid esters, phosphonic acid esters and their amine or metal salt phosphorus-containing antiwear agents; thiophosphites, thiophosphoric acid esters, thiophosphonic acid esters and their amine salts or metals Examples thereof include sulfur and phosphorus-containing antiwear agents such as salts. Among these, the antiwear agent containing sulfur may be contained as long as the sulfur content of the composition does not exceed 0.2% by mass by adjustment with a lubricating base oil and other sulfur-containing additives. More preferably, it is not contained. Of these, the anti-wear agent containing phosphorus is an amount equivalent to phosphorus element and does not significantly deteriorate phosphorus poisoning to the exhaust gas purification catalyst, for example, 0.04% by mass or less, preferably 0.01% by mass. % Can be contained, but it is more preferable not to contain them.

  As the friction modifier, any compound usually used as a friction modifier for lubricating oils can be used. For example, molybdenum friction modifiers such as molybdenum dithiocarbamate, molybdenum amine complex, molybdenum-succinimide complex; And an amine compound, fatty acid ester, fatty acid amide, fatty acid, fat having at least one alkyl group or alkenyl group having 6 to 30 carbon atoms, particularly a linear alkyl group or straight chain alkenyl group having 6 to 30 carbon atoms in the molecule. Ashless friction modifiers such as aliphatic alcohols and aliphatic ethers, and the like, and can usually be contained in the range of 0.1 to 5% by mass. When molybdenum dithiocarbamate is contained, the sulfur of the composition The content is 0.2% by mass or less, preferably 0.1% by mass, particularly preferably 0.05% by mass or less. It is preferred to adjust the amount and also to base oil and other additives. In these, it is especially preferable to use an ashless friction modifier by the point which does not contain sulfur or a metal.

  As the viscosity index improver, specifically, a so-called non-dispersion type viscosity index improver such as a polymer or copolymer of one or more monomers selected from various methacrylates or a hydrogenated product thereof, Alternatively, a so-called dispersed viscosity index improver obtained by copolymerizing various methacrylic acid esters containing a nitrogen compound, a non-dispersed or dispersed ethylene-α-olefin copolymer (for α-olefin, propylene, 1-butene, 1 -Pentene, etc.) or a hydrogenated product thereof, polyisobutylene or a hydrogenated product thereof, a hydrogenated product of a styrene-diene copolymer, a styrene-maleic anhydride ester copolymer, and a polyalkylstyrene.

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

  Further, among these viscosity index improvers, when an ethylene-α-olefin copolymer or a hydride thereof is used, a composition particularly excellent in shear stability can be obtained. One or two or more compounds arbitrarily selected from the above viscosity index improvers can be contained in any amount. The content of the viscosity index improver is preferably 0.1 to 20% by mass based on the composition.

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

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

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

  Examples of metal deactivators include imidazoline, pyrimidine derivatives, alkylthiadiazoles, mercaptobenzothiazoles, benzotriazoles or derivatives thereof, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bis. Examples include dialkyldithiocarbamate, 2- (alkyldithio) benzimidazole, and β- (o-carboxybenzylthio) propiononitrile.

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

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

  The lubricating oil composition for internal combustion engines of the present invention is a low-sulfur lubricating oil composition for internal combustion engines having a sulfur content of 0.2% by mass or less that does not substantially contain a metal salt of dithiophosphate. In addition, a composition containing substantially no phosphorus can be obtained by not using any phosphorus-containing antiwear agent. Further, depending on the selection of the lubricating base oil and various additives, the total sulfur content of the composition is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, and particularly preferably 0.01% by mass or less. It is also possible to obtain a low-sulfur lubricating oil composition for internal combustion engines. In particular, a lubricating oil composition for an internal combustion engine containing no more than 0.001% by mass or substantially no sulfur in consideration of the sulfur content contained in a mineral oil fraction as a diluent contained in a lubricant base oil or various additives. It is also possible to obtain

  The lubricating oil composition for an internal combustion engine of the present invention is one in which the antiwear agent does not contain a metal, and compared with the case where a metal-containing antiwear agent, for example, ZDTP is used, the sulfated ash content resulting from the metal of the composition. (Does not contain boron which does not correspond to metal) can be reduced. And, by selecting an additive containing other metals, the sulfated ash content due to the metal of the composition is preferably 1.0% by mass or less, more preferably 0.8% by mass or less, further 0.7% It is possible to make the mass% or less, and it is also suitable as a lubricating oil for an internal combustion engine for a DPF-equipped diesel vehicle.

  The lubricating oil composition for an internal combustion engine of the present invention is a lubricating oil composition for an internal combustion engine that is excellent in oxidation stability, base number maintenance, high temperature cleanliness, and valve system wear prevention by having the above-described configuration. Yes, it can be preferably used as a lubricating oil for internal combustion engines such as motorcycles, automobiles, gasoline engines for power generation, marine use, diesel engines, gas engines, etc. It is sulfur and can be used particularly suitably for an internal combustion engine equipped with an exhaust gas aftertreatment device by setting the metal-derived sulfated ash content to 0.7 mass% or less.

  Further, a low sulfur fuel, for example, gasoline, light oil, kerosene, LPG, natural gas, or sulfur content having a sulfur content of 50 ppm by mass or less, more preferably 30 ppm by mass or less, particularly preferably 10 ppm by mass or less is substantially contained. It can be particularly preferably used as a lubricating oil for an internal combustion engine using a fuel (hydrogen, dimethyl ether, alcohol, GTL (gas-liquid) fuel, etc.) not contained, particularly a gasoline engine or a gas engine.

  In addition, lubricating oils that require any of the above performances of the present invention, lubricating oils for drive systems such as automatic or manual transmissions, greases, wet brake oils, hydraulic hydraulic oils, turbine oils, compressor oils Also, it can be suitably used as a lubricating oil such as bearing oil and refrigerating machine oil.

  The contents of the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

(A) Comparison of basic performance <1. Evaluation Test Method>
As shown in Table 1, a lubricating oil composition for internal combustion engines (Example 1) and a comparative lubricating oil composition for internal combustion engines (Comparative Example 1) of the present invention were prepared.

In addition, the outline | summary of the component used for the mixing | blending of each composition was as follows.
(Base oil)
Hydrorefined mineral oil was used. The mineral oil had a total aromatic content of 5.0% by mass and a sulfur content of 0.001% by mass. The kinematic viscosity at 100 ° C. is 5.6 mm ² / s, the viscosity index is 125, and the NOACK evaporation amount is 8% by mass.
((A) borate ester)
Tributyl borate was used in the composition of Example 1. The boron content is 4.8% by mass.
((B) ashless antioxidant)
Octyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate and alkyldiphenylamine (alkyl groups: C4 and C8) were mixed and used at a mass ratio of 1: 1.
(Dithiophosphate metal salt)
Zinc dialkyldithiophosphate was used. A phosphorus content of 7.2% by mass, a sulfur content of 15.2% by mass, and a zinc content of 7.8% by mass were used. The alkyl group is a 1,3-dimethylbutyl group and has a sulfated ash content of 11.7% by mass.
((C) Metal detergent)
Calcium salicylate (containing no sulfur) was used. The metal ratio is 2.7, the calcium content is 6.0% by mass, and the sulfated ash content is 20.4% by mass.
((D) Ashless dispersant)
Polybutenyl succinimide (bis type) was used. The number average molecular weight of the polybutenyl group is 1300, and the nitrogen content is 1.5% by mass.
(Viscosity index improver and demulsifier)
An olefin (copolymer) copolymer (OCP) was used as a viscosity index improver, and a polyalkylene glycol type was used as a demulsifier.

  Performance evaluation was performed by the following test with respect to each obtained composition.

(1) High temperature cleanliness observed in hot tube test A hot tube test was performed in accordance with JPI-5S-5599. The score was 10 points for colorless and transparent (no stain) and 0 point for black opaque, and the evaluation was made with reference to a standard tube prepared in advance by 1 interval. The evaluation results are shown in Table 1. If the rating is 6 or more at 290 ° C., it is excellent in cleanliness as a lubricating oil for ordinary gasoline engines and diesel engines, but as a lubricating oil for gas engines, 300 It is preferable that excellent cleanliness even at a temperature of not lower than 0 ° C., for example, a score of “8” or higher at 300 ° C., a score of “5” or higher at 310 ° C. and a score of “2” or higher at 320 ° C.

(2) Change with time of total base number by ISOT (Lubrication Oxidation Stability for Internal Combustion Engine; Indiana Stirling Oxidation Test) Of remaining rate of total base number (hydrochloric acid method) when test oil is forcibly deteriorated in ISOT test (temperature: 165.5 ° C., air blowing amount: 10 L / Hr, catalyst: copper; iron) Changes were measured. The evaluation results are shown in Table 1. The higher the base number remaining ratio with respect to the test time, the higher the base number maintenance performance, indicating a longer drain oil that can be used for a longer time.

(3) Temporal change in total base number due to NOx absorption test When NOx gas is blown into test oil and forcedly deteriorated under conditions (150 ° C, NOx: 1198 ppm) in accordance with 1992, 10, 465 of the Japanese Tribology Conference Proceedings The time course of the total base number (hydrochloric acid method) was measured. The evaluation results are shown in Table 1. The higher the total base number remaining ratio with respect to the test time, the higher the base number maintenance performance even in the presence of NOx used in an internal combustion engine, indicating a long drain oil that can be used for a longer time.

(4) Valve system wear test JASO (Japan Automobile Engineers Association Standard) A valve wear test in accordance with M 328-95 was conducted. After 100 hours, the rocker arm pad scuff area (%), the rocker arm wear amount ( μm) and cam wear (μm) were measured. A numerical value of 10 or less for each indicates that the composition is very excellent in wear resistance of the valve train. In this test, gasoline having a sulfur content of 10 mass ppm or less was used as fuel.

<2. Evaluation test results>
As shown in Table 1, the lubricating oil composition for an internal combustion engine of the present invention (Example 1) is generally used as a long drain oil that is excellent in conventional oxidation stability, base number maintenance, high temperature cleanability, and wear resistance. Compared to a lubricating oil composition for internal combustion engines (Comparative Example 1) containing a novel zinc dialkyldithiophosphate, it exhibits extremely superior oxidation stability, base number retention at high temperatures and in the presence of NOx, and high temperature cleanliness. It can be seen that the wear resistance of the system is completely comparable.

(B) Change in properties before and after valve train wear test Example 1 and Comparative Example 1 for the test oil before and after the valve train test using gasoline having a sulfur content of 10 mass ppm or less in Example A (4) above. The total acid number increase rate, the viscosity increase rate, and the total base number residual rate of this composition were measured and compared. As a result, it was confirmed that the total acid number increase rate and the viscosity increase rate were kept low and the total base number residual rate was high in the composition of Example 1 compared to the composition of Comparative Example 1.

(C) Effect of metal ratio or the like of metal detergent on composition performance The metal ratio of calcium salicylate in Example 1 and Comparative Example 1 is changed, and calcium sulfonate is used instead of calcium salicylate. A hot tube test, an ISOT test, and a NOx absorption test were performed to evaluate oxidation stability, base number maintenance, and high temperature cleanability. The content of the metal detergent in the composition was adjusted to be the same in terms of metal element.

  (1) Instead of calcium salicylate having a metal ratio of 2.7 in the composition of Example 1, composition C1 was prepared using a calcium salicylate having a metal ratio of 3 or more, specifically 4.3. Moreover, it replaced with the calcium salicylate of metal ratio 2.7 in the composition of the comparative example 1, and prepared the composition C2 which used the calcium salicylate of metal ratio 4.3. Composition C1 exhibited superior oxidation stability, base number retention, and high temperature cleanability as compared to Composition C2. However, the composition of Example 1 showed performance superior to that of the composition C1.

  (2) On the other hand, instead of calcium salicylate having a metal ratio of 2.7 in the composition of Example 1, the metal ratio is 1.5 or less, specifically, calcium salicylate having a metal ratio of 1 or a metal ratio of 1.5 or less. The compositions C3 and C4 using calcium salicylate having a metal ratio of 1.8 to 2.3, specifically 2.1, were prepared by using both salicylate and 2.7 salicylate. In the case of the compositions C3 and C4, the oxidation stability, the base number retention, and the high temperature cleanliness superior to the composition of Example 1 were shown.

  (3) Instead of the calcium salicylate having a metal ratio of 2.7 blended in the composition of Example 1, a composition C5 using calcium sulfonate having a metal ratio of 10 (a metallic detergent containing sulfur) was prepared. Moreover, it replaced with the calcium salicylate of the metal ratio 2.7 mix | blended with the composition of the comparative example 1, and prepared the composition C6 which used the calcium sulfonate (metal-type detergent containing sulfur) of the metal ratio 10. In the case of the composition C5, the oxidation stability, the base number maintenance property, and the high temperature cleanliness superior to the composition C6 were shown, but the base number residual ratio was inferior to that of the composition of Example 1. However, in the case of the composition C7 prepared by using a calcium salicylate having a metal ratio of 1.5 or less, for example, a metal ratio of 1 as an essential component and using a calcium sulfonate of a metal ratio of 10 in comparison with the composition C5, In particular, it was confirmed that the base number maintenance ability in the presence of NOx is extremely improved.

Claims (5)

To the lubricating base oil composed of mineral oil and / or synthetic oil , the boric acid ester represented by (A) the following general formula (1) or (2) is 0.001 to 0.001 in terms of boron element, based on the total amount of the composition. 0.05% by mass and (B) 0.01 to 5% by mass of an ashless antioxidant and (C) a metal-based detergent that is an alkali metal or alkaline earth metal salicylate having a metal ratio of 3 or less, a metal element 0.005 wt% in terms of the amount of, and also contains, without including organic dithiophosphoric acid metal salts, lubricating an internal combustion engine having a sulfur content of the composition is equal to or less than 0.1 wt% Oil compositions (excluding compositions in which the amount of sulfur (S (mass%)), the amount of boron (B (mass%)) and the amount of phosphorus (P (mass%)) in the composition satisfy the following formula are excluded.
S + 5B + 3P> 0.35).

(In the general formulas (1) and (2), R ^{1 to} R ⁶ each represent a hydrocarbon group having 1 to 30 carbon atoms, and these may be the same or different.) 2. The lubricating oil composition for an internal combustion engine according to claim 1 , wherein the total aromatic content of the lubricating base oil is adjusted to 10% by mass or less and the sulfur content is adjusted to 0.05% by mass or less. . The lubricating oil composition for internal combustion engines according to claim 1 or 2, wherein (D) the ashless dispersant is contained in an amount of 0.05 to 0.4% by mass in terms of nitrogen element based on the total amount of the composition. The lubricating oil composition for an internal combustion engine according to any one of claims 1 to 3 , wherein the lubricating oil composition contains substantially no phosphorus and has a total sulfur content of 0.05% by mass or less. The lubricating oil composition for an internal combustion engine according to any one of claims 1 to 4 , wherein the lubricating oil composition is for an internal combustion engine using a fuel having a sulfur content of 50 ppm by mass or less.