JP2006016453A - Lubricating oil composition for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricating oil composition for internal combustion engines having low friction and its durability even at a low phosphorus content, exhibiting excellent oxidation stability and causing little deterioration of a seal rubber used as a constitution element of the internal combustion engine. <P>SOLUTION: The lubricating oil composition for internal combustion engines is produced by compounding a lubricant base oil with (A) 0.04-0.10 mass% (based on the total composition) zinc dialkyldithiophosphate in terms of phosphorus concentration, (B) 0.05-4.0 mass% phenyl-α-naphthylamine, (C) 0.02-0.15 mass% molybdenum dithiocarbamate-based friction lowering agent in terms of molybdenum and (D) 0.01-0.5 mass% one or more sulfur-containing compounds selected from thiazole compounds, thiadiazole compounds, dithiocarbamate compounds, dihydrocarbyl polysulfide compounds and sulfurized ester compounds in terms of sulfur concentration. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lubricating oil composition for an internal combustion engine. More specifically, the present invention has excellent oxidation resistance against nitrogen oxide gas, can maintain excellent fuel economy over a long period of time, and deteriorates seal rubber that is a constituent element of an internal combustion engine. The present invention relates to a lubricating oil composition for an internal combustion engine that is difficult.

  Lubricating oil compositions for internal combustion engines are required to have many performances such as wear resistance, oxidation stability, and clean dispersibility. In recent years, in order to suppress global warming due to an increase in carbon dioxide in the atmosphere, it has become an important issue to reduce the fuel consumption of automobiles, and the lubricating oil composition for internal combustion engines is also strongly required to have fuel efficiency. It has become. Lubricating oil compositions for internal combustion engines are usually constituted by blending additives such as viscosity index improvers, detergent dispersants, antioxidants and antiwear agents with base oils refined from petroleum. In order to improve the fuel economy of the lubricating oil composition for internal combustion engines, there is a method of adjusting the base oil and viscosity index improver to lower the viscosity and lowering the friction resistance by reducing the stirring resistance and shear resistance by the lubricating oil. . However, in a part where boundary lubrication is mainly used, such as a valve system composed of cams, tappets, etc., the friction does not decrease even when the viscosity of the lubricating oil is lowered. For this reason, friction modifiers have been incorporated into recent lubricating oil compositions for internal combustion engines. It is important that friction reduction is maintained not only at the beginning of use but also after long-term use, and it is pointed out that it is necessary to select various additives together with the friction reducing agent. In the conventional lubricating oil composition for internal combustion engines, MoDTC is blended with a specific lubricating base oil as a friction modifier, and ZDTP and a phenolic antioxidant are blended to improve the maintenance of low friction. (For example, refer to Patent Document 1). Some lubricant base oils contain ZDTP and an ashless organic polysulfide compound together with MoDTC to improve the durability of low friction (for example, see Patent Document 2). In addition, alkaline earth metal salicylate, ZDTP, specific polybutenyl succinimide, phenolic antioxidant, viscosity index improver and specific sulfur compound are blended with a specific lubricating base oil together with MoDTC to reduce friction. Some have improved maintainability (see, for example, Patent Document 3). In addition, there are some lubricant base oils that contain MoDTC or MoDTP together with alkyldiphenylamine or alkylated phenyl-α-naphthylamine to reduce friction and improve thermal oxidation stability in an air atmosphere ( For example, see Patent Document 4).

In response to the environment of automobiles, in addition to reducing carbon dioxide by reducing fuel consumption, it is also required to reduce harmful substances in exhaust gas such as nitrogen oxides. A catalyst is installed in the middle of the tube. In the internal combustion engine, a small amount of lubricating oil enters the combustion chamber, and the combustion product is mixed into the exhaust gas. At this time, the components contained in the lubricating oil poison the catalyst and reduce its activity. The three-way catalyst installed in gasoline engine-equipped vehicles is installed to detoxify nitrogen oxides, etc., and is known to be poisoned by phosphorus. From the viewpoint of preventing catalyst poisoning, internal combustion engines It has also been newly required to reduce the phosphorus content in lubricating oil compositions. ZDTP having an antioxidant function, an anti-wear function and an anti-corrosion function has been blended as a main additive in the lubricating oil composition for internal combustion engines for more than half a century (for example, see Non-Patent Document 1). In addition, ZDTP has been reported to be an additive necessary for the Mo-containing friction modifier to exhibit low friction (see, for example, Non-Patent Document 2). A reduction in the phosphorus content means a reduction in the ZDTP content, and a simple reduction in the phosphorus content is nothing but a decrease in low friction and oxidation stability.
It is said that the above-mentioned nitrogen oxide gas is also mixed with lubricating oil and promotes air oxidation, and Patent Document 1 improves maintainability of low friction even in an atmosphere containing such nitrogen oxide gas. This is a technology that was developed as one of the problems, and as mentioned above, the blending of phenolic antioxidants is one of its features.
Furthermore, as a result of blending various kinds of compounding agents in the lubricating oil as described above, certain adverse effects may occur due to the synergistic effect of the composition of the lubricating base oil or the compounding agent itself, for example, This is an effect of, for example, promoting the deterioration of a seal rubber, for example, a fluororubber seal material, which is used in an engine and may come into contact with lubricating oil. Therefore, consideration of the influence on the seal rubber is also considered as one of the problems.
That is, it is desired to develop a lubricating oil composition for an internal combustion engine that overcomes these problems as described above, maintains low friction for a long period of time, and has excellent oxidation stability.
JP-A-8-209177 (page 5-7, Table 1-3) JP-A-8-73878 (page 4-8, Table 1-6) JP-A-9-3463 (page 8-11, Table 1) JP-A-6-313183 (page 5-9, Table 1-2) Edited by Toshio Sakurai, “New Version Petroleum Product Additives”, Koshobo, July 25, 1986, p. 419-421 Masayoshi Muraki et al., “Tribologists Vol. 41, No. 10” (Japan Society for Tribologists), October 15, 1996, p. 62-69

  The present invention is an internal combustion engine lubricating oil that has excellent low friction and maintainability even with a low phosphorus content, has excellent oxidation stability, and does not easily deteriorate seal rubber that is a constituent element of an internal combustion engine. A composition is provided.

  As a result of intensive studies to solve the above problems, the present inventors have found that a lubricating oil composition for an internal combustion engine having a specific configuration is excellent in low friction and maintenance properties and has excellent oxidation stability. In addition, the present inventors have found that the seal rubber is hardly deteriorated and have completed the present invention.

That is, the first of the present invention, to the lubricating base oil, based on the total amount of the lubricating oil composition for internal combustion engines,
(A) 0.04 to 0.10% by mass of zinc dialkyldithiophosphate in terms of phosphorus concentration,
(B) 0.05 to 4.0% by mass of phenyl-α-naphthylamine,
(C) Molybdenum dithiocarbamate friction reducer 0.02 to 0.15% by mass in terms of molybdenum, and (D) from the group consisting of thiazole compound, thiadiazole compound, dithiocarbamate compound, dihydrocarbyl polysulfide compound, sulfurized ester compound 0.01 to 0.5% by mass of one or more selected sulfur-containing compounds selected in terms of sulfur concentration,
Is a lubricating oil composition for an internal combustion engine, wherein
The second aspect of the present invention is the first aspect of the present invention,
(E) Lubricant for internal combustion engines, characterized in that 0.02 to 0.5 mass% of alkaline earth metal salicylate is blended in terms of alkaline earth metal concentration based on the total amount of the lubricating oil composition for internal combustion engines. It is an oil composition.
According to a third aspect of the present invention, in any one of the first to second aspects of the present invention, at least one of the sulfur-containing compounds (D) is a dithiocarbamate compound. It is.
The fourth of the present invention, in the fourth one of the present invention, kinematic viscosity at 100 ° C. of the lubricating base oils 2~6mm ² / s,% _{C A} is 2 or less,% _{C N} 25 And the viscosity index is 105 or more,
Further, (F) an internal combustion engine comprising a viscosity index improver in such an amount that a kinematic viscosity at 100 ° C. as a lubricating oil composition for an internal combustion engine is 4.6 to 11 mm ² / s. Lubricating oil composition.
A fifth aspect of the present invention is the internal combustion engine lubricating oil composition according to the fourth aspect of the present invention, wherein the blended viscosity index improver is a dispersed and / or non-dispersed polymethacrylate.
According to a sixth aspect of the present invention, in any one of the first to fifth aspects of the present invention, the phenyl-α-naphthylamine of (B) is (Np-alkyl) phenyl-α-naphthylamine. It is a lubricating oil composition for internal combustion engines.
A seventh aspect of the present invention is the internal combustion engine according to any one of the first to fifth aspects of the present invention, wherein the alkyl group of (B) phenyl-α-naphthylamine is a branched alkyl group having 8 to 16 carbon atoms. Lubricating oil composition.
An eighth aspect of the present invention is the lubricating oil composition for an internal combustion engine according to any one of the first to seventh aspects of the present invention, which is used for lubricating an internal combustion engine equipped with a three-way catalyst for exhaust gas purification. is there.

  The lubricating oil composition for an internal combustion engine of the present invention has low friction properties both when it is new and when it is deteriorated. That is, if this lubricating oil is used, the fuel efficiency of the engine can be maintained over a long period of time. In addition, this lubricating oil is excellent in oxidation stability and hardly deteriorates the seal rubber of the engine.

Hereinafter, the contents of the present invention will be described in more detail.
As the lubricating base oil in the lubricating oil composition for an internal combustion engine of the present invention, any mineral oil, wax isomerized oil, synthetic oil or a mixture of two or more kinds used as a base oil for ordinary lubricating oils is used. can do.
Specifically, as mineral oil, for example, a lubricating oil fraction obtained by subjecting crude oil to atmospheric distillation and reduced pressure distillation is subjected to solvent removal, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrogenation. Paraffinic and naphthenic oils, normal paraffins, and the like purified by appropriately combining purification, sulfuric acid washing, purification treatment such as clay treatment, and the like can be used.

As wax isomerate oil, natural wax such as petroleum slack wax obtained by dewaxing hydrocarbon oil or a mixture of carbon monoxide and hydrogen with a suitable synthetic catalyst at high temperature and high pressure, so-called Fischer Tropu (Fischer Tropsch) Those prepared by hydroisomerizing a wax raw material such as synthetic wax produced by a synthesis method can be used. When slack wax is used as a wax raw material, slack wax contains a large amount of sulfur and nitrogen, and these are not necessary for lubricating base oils. It is desirable to use a wax having a reduced content as a raw material.
The synthetic oil is not particularly limited, but poly-α-olefin (1-octene oligomer, 1-decene oligomer, ethylene-propylene oligomer, etc.) and hydrides thereof, isobutene oligomer and hydrides thereof, isoparaffin, alkylbenzene, Alkyl naphthalene, diester (ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate, etc.), polyol ester (trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol 2) -Ethylhexanoate, pentaerythritol pelargonate, etc.), polyoxyalkylene glycol, dialkyl diphenyl ether, and polyphenyl ether Tell the like can be used.

The kinematic viscosity of these lubricating base oils is not particularly limited and is arbitrary, but usually the kinematic viscosity at 100 ° C. is preferably 1 to 10 mm ² / s, more preferably ² to 8 mm ² / s, still more preferably. is 2 to 6 mm ² / s, particularly preferably 3.5~4.5mm ² / s. The viscosity index of the lubricating base oil is not particularly limited and is arbitrary, but is preferably 105 or higher, more preferably 115 or higher, and still more preferably 120 or higher because of excellent fuel economy performance. Moreover, the aromatic component of the lubricating base oil is not particularly limited, since it is excellent in maintenance of fuel efficiency performance, in% C _A, preferably 5 or less, more preferably 3 or less, more preferably 2 or less It is. Furthermore, naphthenic component of the lubricating base oil is not particularly limited, in% _{C N,} preferably 5 to 25 or less, more preferably 10 to 22, particularly preferably 15 to 20. % If C _N is 25 or less, since a large effect on the sealing rubber, additives configuration of the present invention are useful,% effect on the sealing rubber is reduced to C _N by 10 or more. Incidentally,% _{C A} and% _{C N} in the present invention exhibit% _{C A} and% _{C N} is determined by the method prescribed in ASTM D3238.
Further, the NOACK evaporation amount of the lubricating base oil is not particularly limited, but is preferably 20% by mass or less, and preferably 16% by mass or less, because it is excellent in maintainability of fuel saving performance. The content is particularly preferably 5% by mass or less, more preferably 5% by mass or more, more preferably 10% by mass or more, and particularly preferably 12% by mass or more from the viewpoint of excellent fuel economy and low-temperature viscosity characteristics. 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 compound, phosphorus compound, or metal component in the composition is sent to the exhaust gas purification device together with the lubricating base oil. There is a possibility of accumulation, which not only deteriorates fuel economy, but is also unfavorable because there is a concern about an adverse effect on exhaust gas purification performance. Here, the NOACK evaporation amount is a value obtained by measuring the evaporation amount of the lubricating oil measured in accordance with ASTM D 5800.

  In the lubricating oil composition for an internal combustion engine of the present invention, zinc dialkyldithiophosphate is blended as the essential component (A). The blending amount of the component (A) is 0.02 to 0.10% by mass, preferably 0.04 to 0.09% by mass in terms of phosphorus concentration, based on the total amount of the lubricating oil composition for internal combustion engines. It is preferable to set it as 0.08 mass% or less at the point which can suppress the poisoning of an original catalyst more. When the blending amount of the component (A) is less than 0.02% by mass, the low friction property is insufficient, and when it exceeds 0.10% by mass, the poisoning of the three-way catalyst is accelerated. Therefore, each is not preferable.

式（５）中、Ｒ^８、Ｒ^９、Ｒ^１０及びＲ^１１はそれぞれ同一であっても異なっていてもよい炭素数２〜１８、好ましくは３〜８の直鎖又は分岐アルキル基を示し、具体的にはエチル基、プロピル基、ブチル基、ペンチル基、ヘキシル基、ヘプチル基、オクチル基、ノニル基、デシル基、ウンデシル基、ドデシル基、トリデシル基、テトラデシル基、ペンタデシル基、ヘキサデシル基、ヘプタデシル基、オクタデシル基などが挙げられ、これらは直鎖でも分岐でもよい。これらは第１級アルキル基、第２級アルキル基、第３級アルキル基のいずれでもよいが、低摩擦性に優れることから第２級アルキル基であることが好ましい。Ｒ^８、Ｒ^９、Ｒ^１０及びＲ^１１を導入する際にα−オレフィンの混合物を原料とする場合があるが、この場合、（Ａ）成分としては異なる構造のアルキル基を有するジアルキルジチオリン酸亜鉛の混合物となる。かかる混合物も無論、本発明の（Ａ）成分として使用できる。 Examples of the essential component (A) zinc dialkyldithiophosphate include compounds represented by the following general formula (5).

In formula (5), R ⁸ , R ⁹ , R ¹⁰ and R ¹¹ each represent a linear or branched alkyl group having 2 to 18 carbon atoms, preferably 3 to 8 carbon atoms, which may be the same or different, Specifically, 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, pentadecyl group, hexadecyl group, heptadecyl group Group, octadecyl group and the like, and these may be linear or branched. These may be any of a primary alkyl group, a secondary alkyl group, and a tertiary alkyl group, but a secondary alkyl group is preferred because of excellent low friction properties. When introducing R ⁸ , R ⁹ , R ¹⁰ and R ¹¹ , a mixture of α-olefins may be used as a raw material. In this case, the component (A) is a zinc dialkyldithiophosphate having an alkyl group having a different structure. A mixture of Of course, such a mixture can also be used as the component (A) of the present invention.

式（１）中、Ｒ^１は水素原子又は炭素数１〜２４の直鎖又は分岐のアルキル基を示す。Ｒ^１としては、具体的には例えば、水素原子又はメチル基、エチル基、プロピル基、イソプロピル基、各種ブチル基、各種ペンチル基、各種ヘキシル基、各種ヘキシル基、各種ヘプチル基、各種オクチル基、各種ノニル基、各種デシル基、各種ウンデシル基、各種ドデシル基、各種トリデシル基、各種テトラデシル基、各種ペンタデシル基、各種ヘキサデシル基、各種ヘプタデシル基、各種オクタデシル基、各種ノナデシル基、各種エイコシル基、各種ヘンエイコシル基、各種ドコシル基、各種トリコシル基、各種テトラコシル基などが挙げられる。 The lubricating oil composition for an internal combustion engine of the present invention contains phenyl-α-naphthylamine as the essential component (B), and this compound is represented by the following general formula (1).

In formula (1), R ¹ represents a hydrogen atom or a linear or branched alkyl group having 1 to 24 carbon atoms. Specific examples of R ¹ include a hydrogen atom or a methyl group, an ethyl group, a propyl group, an isopropyl group, various butyl groups, various pentyl groups, various hexyl groups, various hexyl groups, various heptyl groups, various octyl groups, Various nonyl groups, various decyl groups, various undecyl groups, various dodecyl groups, various tridecyl groups, various tetradecyl groups, various pentadecyl groups, various hexadecyl groups, various heptadecyl groups, various octadecyl groups, various nonadecyl groups, various eicosyl groups, various heneicosyls Groups, various docosyl groups, various tricosyl groups, various tetracosyl groups and the like.

As the component (B) of the present invention, in the above formula (1), R ¹ is preferably an alkyl group having 8 to 16 carbon atoms, and more preferably a branched alkyl group having 8 to 16 carbon atoms. Further, when R ¹ is a branched alkyl group having 8 to 16 carbon atoms, these alkyl groups are branched nonyl groups, branched dodecyl groups, branched pentadecyl groups, branched octadecyl groups, butenes derived from propylene oligomers, A branched octyl group, a branched dodecyl group, or a branched hexadecyl group derived from an isobutylene oligomer is particularly preferable.
Moreover, as long as it is a compound represented by the said General formula (1) as a (B) component of this invention, it can be used also with the form of the mixture of various phenyl-alpha-naphthylamine.
Specific examples of the compound represented by the formula (1) include phenyl-α-naphthylamine.
As the component (B) of the present invention, in the above formula (1), the substitution position of R ¹ is arbitrary, and specific examples include an ortho position, a meta position, and a para position, with the para position being particularly preferred. From this viewpoint, a particularly preferred compound in which R1 is in the para position is (Np-alkyl) phenyl-α-naphthylamine.

式（３）中、Ｒ^７は炭素数８〜１６のアルキル基であり、さらに炭素数３又は４のオレフィンのオリゴマーから誘導される炭素数８〜１６の分岐アルキル基であることが特に好ましい。ここでいう炭素数３又は４のオレフィンとしては、具体的にはプロピレン、１-ブテン、２−ブテン及びイソブチレンが挙げられるが、潤滑油基油に対するそれ自身の酸化生成物の溶解性に優れる点から、プロピレン又はイソブチレンが好ましい。
具体的な、上記式（３）で表される（Ｎ−ｐ−アルキル）フェニル−α−ナフチルアミンとしては、プロピレンの４量体から誘導された分岐ドデシル基を有する、ｐ−ドデシルフェニル−α―ナフチルアミン等が例示される。 The more preferred (Np-alkyl) phenyl-α-naphthylamine as the component (B) of the present invention is represented by the following general formula (3).

In formula (3), R ⁷ is an alkyl group having 8 to 16 carbon atoms, and more preferably a branched alkyl group having 8 to 16 carbon atoms derived from an olefin oligomer having 3 or 4 carbon atoms. Specific examples of the olefin having 3 or 4 carbon atoms include propylene, 1-butene, 2-butene, and isobutylene, and the solubility of the oxidation product itself in the lubricating base oil is excellent. From the above, propylene or isobutylene is preferred.
As specific (Np-alkyl) phenyl-α-naphthylamine represented by the above formula (3), p-dodecylphenyl-α- having a branched dodecyl group derived from a tetramer of propylene. Examples include naphthylamine.

  The blending amount of the component (B) in the lubricating oil composition for internal combustion engines of the present invention is 0.05 to 4% by mass, preferably 0.1 to 3% by mass, more preferably based on the total amount of the lubricating oil composition for internal combustion engines. Is 0.5-2 mass%. When the blending amount of the component (B) is less than 0.01% by mass, the effect of adding the component (B) does not appear. Therefore, it is not preferable respectively.

式（２）中、Ｒ^２、Ｒ^３、Ｒ^４及びＲ^５はそれぞれ同一でも異なっていてもよく、アルキル基、アルケニル基、アリール基、アルキルアリール基、アリールアルキル基などの炭化水素基を示し、特にアルキル基が好ましい。Ｒ^２、Ｒ^３、Ｒ^４及びＲ^５の具体例としては、エチル基、プロピル基、ブチル基、ペンチル基、ヘキシル基、ヘプチル基、オクチル基、ノニル基、デシル基、ウンデシル基、ドデシル基、トリデシル基、テトラデシル基、ペンタデシル基、ヘキサデシル基、ヘプタデシル基、オクタデシル基などの炭素数２〜１８、好ましくは８〜１３のアルキル基（これらアルキル基は直鎖でも分岐でもよく、また第１級アルキル基、第２級アルキル基、第３級アルキル基のいずれでもよい）；ブテニル基、ペンテニル基、ヘキセニル基、ヘプテニル基、オクテニル基、ノネニル基、デセニル基、ウンデセニル基、ドデセニル基、トリデセニル基、テトラデセニル基、ペンタデセニル基、ヘキサデセニル基、ヘプタデセニル基、オクタデセニル基などの炭素数４〜１８、好ましくは８〜１８のアルケニル基（これらアルケニル基は直鎖でも分枝でもよく、また二重結合の位置も任意である）；ブチルフェニル基、ノニルフェニル基などのアルキルアリール基（これらアルキルアリール基のアルキル部分は直鎖でも分岐でもよく、アルキル部分のアリール基上の置換位置は任意である）などが挙げられる。Ｒ^２、Ｒ^３、Ｒ^４及びＲ^５としてアルキル基を導入する際に、α−オレフィンの混合物を原料とする場合があるが、この場合、（Ｃ）成分としては異なる構造のアルキル基を有するモリブデンジチオカーバメートの混合物となる。かかる混合物も本発明の（Ｃ）成分として使用することができる。また、Ｘ^１、Ｘ^２、Ｘ^３及びＸ^４は個別に硫黄原子または酸素原子を示す。 The lubricating oil composition for internal combustion engines of the present invention is blended with a molybdenum dithiocarbamate friction reducing agent as component (C) as an essential component, which is represented by the following general formula (2).

In formula (2), R ² , R ³ , R ⁴ and R ⁵ may be the same or different and each represents a hydrocarbon group such as an alkyl group, an alkenyl group, an aryl group, an alkylaryl group or an arylalkyl group. In particular, an alkyl group is preferable. Specific examples of R ² , R ³ , R ⁴ and R ⁵ include ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, Tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group and other alkyl groups having 2 to 18, preferably 8 to 13 carbon atoms (these alkyl groups may be linear or branched, and primary alkyl Group, secondary alkyl group or tertiary alkyl group); butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, undecenyl group, dodecenyl group, tridecenyl group, tetradecenyl group Group, pentadecenyl group, hexadecenyl group, heptadecenyl group, octadecenyl group, etc. An alkenyl group having a prime number of 4 to 18, preferably 8 to 18 (the alkenyl group may be linear or branched, and the position of the double bond is arbitrary); an alkylaryl group such as a butylphenyl group or a nonylphenyl group (The alkyl part of these alkylaryl groups may be linear or branched, and the substitution position on the aryl group of the alkyl part is arbitrary). When an alkyl group is introduced as R ² , R ³ , R ⁴ and R ⁵ , a mixture of α-olefins may be used as a raw material. In this case, the component (C) has an alkyl group having a different structure. It becomes a mixture of molybdenum dithiocarbamate. Such a mixture can also be used as the component (C) of the present invention. X ¹ , X ² , X ³ and X ^{4 each} independently represent a sulfur atom or an oxygen atom.

Preferred examples of the component (C) molybdenum dithiocarbamate include molybdenum diethyldithiocarbamate, molybdenum dipropyldithiocarbamate, molybdenum dibutyldithiocarbamate, molybdenum dipentyldithiocarbamate, molybdenum dipentyldithiocarbamate, molybdenum dihexyldithiocarbamate, and molybdenum dioctyldithiocarbamate. , Molybdenum sulfide didecyl dithiocarbamate, Molybdenum didodecyl dithiocarbamate, Molybdenum ditridecyl dithiocarbamate, Molybdenum di (butylphenyl) dithiocarbamate, Molybdenum di (nonylphenyl) dithiocarbamate, Sulfide oxymolybdenum Diethyldithiocarbamate, Sulfide oxymolybdenum dipropyldithio Carbamate, sulfur Oxymolybdenum dibutyldithiocarbamate, sulfurized oxymolybdenum dipentyldithiocarbamate, sulfurized oxymolybdenum dihexyldithiocarbamate, sulfurized oxymolybdenum dioctyldithiocarbamate, sulfurized oxymolybdenum didecyldithiocarbamate, sulfurized oxymolybdenum didodecyldithiocarbamate, sulfurized oxymolybdenum ditridecyldithiocarbamate Examples thereof include oxymolybdenum di (butylphenyl) dithiocarbamate and sulfurized oxymolybdenum di (nonylphenyl) dithiocarbamate.
In the present invention, the oxidation resistance against nitrogen oxide gas is excellent, and excellent fuel economy can be maintained over a long period of time, and the properties such as solubility in a lubricating base oil and storage stability are also included in the above (2 ) In the formula, it is preferable that all of R ^{2 to} R ⁵ are not the same, and it is a mixture of a linear or branched alkyl group having 8 to 13 carbon atoms and a linear or branched alkyl group having 13 carbon atoms. More preferably, the compound represented by the formula (2) is particularly preferably an asymmetric type.

  The blending amount of the component (C) in the lubricating oil composition for internal combustion engines of the present invention is 0.02 to 0.15% by mass, preferably 0.0. It is 04-0.12 mass%. When the blending amount of the component (C) is less than 0.02% by mass, a sufficient friction reducing effect cannot be obtained. When the blending amount exceeds 0.15% by mass, the friction is reduced to meet the blending amount. Since the effect cannot be obtained, each is not preferable.

In the lubricating oil composition for internal combustion engines of the present invention, as component (D) which is an essential component, thiazole compounds, thiadiazole compounds, dithiocarbamate compounds, dithiols shown as (D-1) to (D-5) below, respectively. One or more sulfur-containing compounds selected from the group consisting of hydrocarbyl polysulfide compounds and sulfurized ester compounds are blended.
(D-1) thiazole compound (D-2) thiadiazole compound (D-3) dithiocarbamate compound (D-4) dihydrocarbyl polysulfide compound (D-5) sulfurized ester compound

式（６）、（７）中、Ｒ^1２及びＲ^１４はそれぞれ水素原子または炭素数１〜３０の炭化水素基を表し、Ｒ^１３は炭素数１〜４のアルキル基を表し、ａ及びｃは０〜３の整数を表し、ｂは０〜３の整数を表す。
これらの中でも、上記一般式（７）で表されるベンゾチアゾール化合物が特に好ましい。ここで、Ｒ^１２、Ｒ^１４としては、例えば、アルキル基、シクロアルキル基、アルキルシクロアルキル基、アルケニル基、アリール基、アルキルアリール基、及びアリールアルキル基を挙げることができる。
上記アルキル基としては、具体的には、メチル基、エチル基、プロピル基、ブチル基、ペンチル基、ヘキシル基、ヘプチル基、オクチル基、ノニル基、デシル基、ウンデシル基、ドデシル基、トリデシル基、テトラデシル基、ペンタデシル基、ヘキサデシル基、ヘプタデシル基、オクタデシル基等のアルキル基（これらアルキル基は直鎖でも分枝でもよい）を挙げることができる。
上記シクロアルキル基としては、具体的には、シクロペンチル基、シクロヘキシル基、シクロヘプチル基等の炭素数５〜７のシクロアルキル基を挙げることができる。
上記アルキルシクロアルキル基としては、具体的には、メチルシクロペンチル基、ジメチルシクロペンチル基、メチルエチルシクロペンチル基、ジエチルシクロペンチル基、メチルシクロヘキシル基、ジメチルシクロヘキシル基、メチルエチルシクロヘキシル基、ジエチルシクロヘキシル基、メチルシクロヘプチル基、ジメチルシクロヘプチル基、メチルエチルシクロヘプチル基、ジエチルシクロヘプチル基等の炭素数６〜１１のアルキルシクロアルキル基（アルキル基のシクロアルキル基への置換位置も任意である）を挙げることができる。
上記アルケニル基としては、具体的には、ブテニル基、ペンテニル基、ヘキセニル基、ヘプテニル基、オクテニル基、ノネニル基、デセニル基、ウンデセニル基、ドデセニル基、トリデセニル基、テトラデセニル基、ペンタデセニル基、ヘキサデセニル基、ヘプタデセニル基、オクタデセニル基等のアルケニル基（これらアルケニル基は直鎖状でも分枝状でもよく、また二重結合の位置も任意である）を挙げることができる。
上記アリール基としては、具体的には、フェニル基、ナフチル基等のアリール基を挙げることができる。
上記アルキルアリール基としては、具体的には、トリル基、キシリル基、エチルフェニル基、プロピルフェニル基、ブチルフェニル基、ペンチルフェニル基、ヘキシルフェニル基、ヘプチルフェニル基、オクチルフェニル基、ノニルフェニル基、デシルフェニル基、ウンデシルフェニル基、ドデシルフェニル基等の炭素数７〜１８のアルキルアリール基（アルキル基は直鎖でも分枝でもよく、またアリール基への置換位置も任意である）を挙げることができる。
上記アリールアルキル基としては、具体的には、ベンジル基、フェニルエチル基、フェニルプロピル基、フェニルブチル基、フェニルペンチル基、フェニルヘキシル基等の炭素数７〜１２のアリールアルキル基（これらにおけるアルキル基は直鎖状でも分枝状でもよい）を挙げることができる。
（Ｄ−１）チアゾール化合物としては、具体的にはアルキルチアゾール、アルキルメルカプト、アルキルベンゾチアゾール、アルキルメルカプトベンゾチアゾール等が例示される。 Here, as the (D-1) thiazole compound, a compound represented by the following general formula (6) or (7) is preferably used.

In formulas (6) and (7), R ¹² and R ¹⁴ each represent a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, R ¹³ represents an alkyl group having 1 to 4 carbon atoms, and a and c are The integer of 0-3 is represented, b represents the integer of 0-3.
Among these, the benzothiazole compound represented by the general formula (7) is particularly preferable. Here, examples of R ¹² and R ¹⁴ include an alkyl group, a cycloalkyl group, an alkylcycloalkyl group, an alkenyl group, an aryl group, an alkylaryl group, and an arylalkyl group.
Specific examples of the alkyl group include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, Examples thereof include alkyl groups such as tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, and octadecyl group (these alkyl groups may be linear or branched).
Specific examples of the cycloalkyl group include cycloalkyl groups having 5 to 7 carbon atoms such as a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group.
Specific 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, and a methylcycloheptyl group. Group, a dimethylcycloheptyl group, a methylethylcycloheptyl group, a diethylcycloheptyl group and the like, and an alkylcycloalkyl group having 6 to 11 carbon atoms (the substitution position of the alkyl group to the cycloalkyl group is also optional). .
Specific examples of the alkenyl group include butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, An alkenyl group such as a heptadecenyl group and an octadecenyl group (these alkenyl groups may be linear or branched, and the position of the double bond is also optional).
Specific examples of the aryl group include aryl groups such as a phenyl group and a naphthyl group.
Specific 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, C7-C18 alkylaryl groups such as a decylphenyl group, an undecylphenyl group, a dodecylphenyl group, etc. (the alkyl group may be linear or branched, and the substitution position on the aryl group is arbitrary) Can do.
Specific 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 (alkyl groups in these groups). May be linear or branched).
Specific examples of the (D-1) thiazole compound include alkyl thiazole, alkyl mercapto, alkyl benzothiazole, alkyl mercapto benzothiazole and the like.

式（８）、（９）中、Ｒ^１５、Ｒ^１６、Ｒ^１７及びＲ^１８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の炭化水素基を表し、ｄ、ｅ、ｆ及びｇは同一でも異なっていてもよく、それぞれ０〜８の整数を表す。Ｒ^１５、Ｒ^１６、Ｒ^１７及びＲ^１８としては、例えば、アルキル基、シクロアルキル基、アルキルシクロアルキル基、アルケニル基、アリール基、アルキルアリール基、及びアリールアルキル基を挙げることができる。 (D-2) As the thiadiazole compound, a compound represented by the following general formula (8) or (9) is preferably used.

In the formulas (8) and (9), R ¹⁵ , R ¹⁶ , R ¹⁷ and R ¹⁸ may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, d, e, f and g may be the same or different and each represents an integer of 0 to 8. Examples of R ¹⁵ , R ¹⁶ , R ¹⁷ and R ¹⁸ include an alkyl group, a cycloalkyl group, an alkylcycloalkyl group, an alkenyl group, an aryl group, an alkylaryl group, and an arylalkyl group.

Specific examples of the alkyl group include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, Examples thereof include alkyl groups such as tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, and octadecyl group (these alkyl groups may be linear or branched).
Specific examples of the cycloalkyl group include cycloalkyl groups having 5 to 7 carbon atoms such as a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group.
Specific 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, and a methylcycloheptyl group. Group, a dimethylcycloheptyl group, a methylethylcycloheptyl group, a diethylcycloheptyl group and the like, and an alkylcycloalkyl group having 6 to 11 carbon atoms (the substitution position of the alkyl group to the cycloalkyl group is also optional). .
Specific examples of the alkenyl group include butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, An alkenyl group such as a heptadecenyl group and an octadecenyl group (these alkenyl groups may be linear or branched, and the position of the double bond is also optional).
Specific examples of the aryl group include aryl groups such as a phenyl group and a naphthyl group.
Specific 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, C7-C18 alkylaryl groups such as a decylphenyl group, an undecylphenyl group, a dodecylphenyl group, etc. (the alkyl group may be linear or branched, and the substitution position on the aryl group is arbitrary) Can do.
Specific 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 (alkyl groups in these groups). May be straight chain or branched).
Specific examples of the (D-2) thiadiazole compound include 2,5-bis (linear or branched alkylthio) -1,3,4-thiadiazole, 2,5-bis (linear or branched). -Like alkyldithio) -1,3,4-thiadiazole, 2- (linear or branched alkylthio) -5-mercapto-1,3,4-thiadiazole, 2- (linear or branched alkyldithio)- Examples are 5-mercapto-1,3,4-thiadiazole and mixtures thereof.

式（１０）、（１１）中、Ｒ^１９、Ｒ^２０、Ｒ^２１、Ｒ^２２、Ｒ^２３、Ｒ^２４及びＲ^２５はそれぞれ同一でも異なっていてもよい炭素数１〜１８、好ましくは１〜１０の直鎖又は分岐アルキル基を表す。上記アルキル基としては、具体的には、メチル基、エチル基、プロピル基、ｎ−ブチル基、イソブチル基、ペンチル基、イソペンチル基、ヘキシル基、ヘプチル基、オクチル基、２−エチルヘキシル基、ノニル基、デシル基、トリデシル基及びオクタデシル基などが挙げられる。アルキル基を導入する際にα−オレフィンの混合物を原料とする場合があるが、この場合、複数種のアルキル基を有するアルキルチオカルバミル化合物が挙げられる。
また、式（１０）中、基（Ｘ^５）はＳ、Ｓ−Ｓ、Ｓ−ＣＨ_２−Ｓ、Ｓ−（ＣＨ_２）_２−Ｓ、Ｓ−（ＣＨ_２）_３−Ｓ、あるいはS−Zn−Sなどの基を表す。
上記（Ｄ−３）のジチオカーバメート化合物の好ましい例としては、具体的に、メチレンビス（ジブチルジチオカーバメート）、ビス（ジメチルチオカルバミル）モノスルフィド、ビス（ジメチルチオカルバミル）ジスルフィド、ビス（ジブチルチオカルバミル）シスルフィド、ビス（ジペンチルチオカルバミル）ジスルフィド、ビス（ジオクチルチオカルバミル）ジスルフィド、亜鉛ジペンチルジチオカーバメートなどを挙げることができる。本発明においては、メチレンビス（ジブチルジチオカーバメート）が特に好ましい。 (D-3) As the dithiocarbamate compound, a compound represented by the following general formula (10) or (11) is preferably used.

In formulas (10) and (11), R ¹⁹ , R ²⁰ , R ²¹ , R ²² , R ²³ , R ²⁴ and R ²⁵ may be the same or different and each has 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms. Represents a linear or branched alkyl group. Specific examples of the alkyl group include methyl, ethyl, propyl, n-butyl, isobutyl, pentyl, isopentyl, hexyl, heptyl, octyl, 2-ethylhexyl, and nonyl groups. Decyl group, tridecyl group, octadecyl group and the like. When introducing an alkyl group, a mixture of α-olefins may be used as a raw material. In this case, an alkylthiocarbamyl compound having a plurality of types of alkyl groups may be mentioned.
In the formula (10), the group (X ⁵ ) is S, S—S, S—CH ₂ —S, S— (CH ₂ ) ₂ —S, S— (CH ₂ ) ₃ —S, or S—. Represents a group such as Zn-S.
Preferable examples of the dithiocarbamate compound (D-3) are specifically methylene bis (dibutyldithiocarbamate), bis (dimethylthiocarbamyl) monosulfide, bis (dimethylthiocarbamyl) disulfide, bis (dibutylthio). And carbamyl) sisulfide, bis (dipentylthiocarbamyl) disulfide, bis (dioctylthiocarbamyl) disulfide, zinc dipentyldithiocarbamate and the like. In the present invention, methylene bis (dibutyldithiocarbamate) is particularly preferred.

式（１２）中、Ｒ^２６及びＲ^２７は同一でも異なっていてもよく、それぞれ炭素数１〜２２の直鎖又は分岐のアルキル基、アルケニル基、あるいは炭素数６〜２０のアリール基、アルキルアリール基またはアリールアルキル基を示し、ｈは１〜５、好ましくは1〜２の整数を表す。ここでいうアルキル基は第１級アルキル基、第２級アルキル基、第３級アルキル基を含む。
Ｒ^２６及びＲ^２７の具体例としては、メチル基、エチル基、プロピル基、ブチル基、ブチル基、、ペンチル基、ヘキシル基、ヘプチル基、オクチル基、ノニル基、デシル基、ドデシル基、シクロヘキシル基、フェニル基、ナフチル基、トリル基、キシリル基、ベンジル基、フェネチル基などを挙げることができる。 (D-4) As the dihydrocarbyl polysulfide compound, a compound represented by the following general formula (12) is preferably used.

In the formula (12), R ²⁶ and R ²⁷ may be the same or different and are each a linear or branched alkyl group having 1 to 22 carbon atoms, an alkenyl group, an aryl group having 6 to 20 carbon atoms, or an alkylaryl. Group represents an arylalkyl group, and h represents an integer of 1 to 5, preferably 1 to 2. The alkyl group here includes a primary alkyl group, a secondary alkyl group, and a tertiary alkyl group.
Specific examples of R ²⁶ and R ²⁷ include methyl group, ethyl group, propyl group, butyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group, cyclohexyl group. , Phenyl group, naphthyl group, tolyl group, xylyl group, benzyl group, phenethyl group and the like.

R ²⁶ and R ²⁷ are preferably an alkyl group having 3 to 18 carbon atoms derived from propylene or isobutene, or an aryl group, alkylaryl group or arylalkyl group having 6 to 8 carbon atoms. For example, isopropyl group, branched hexyl group derived from propylene dimer, branched nonyl group derived from propylene trimer, branched dodecyl group derived from propylene tetramer, propylene pentamer Branched pentadecyl group derived from propylene, branched octadecyl group derived from propylene hexamer, tert-butyl group, branched octyl group derived from isobutene dimer, branched form derived from isobutene trimer Alkyl groups such as dodecyl group and branched hexadecyl group derived from isobutene tetramer ( These alkyl groups include all branched isomers); alkylaryl groups such as phenyl group, tolyl group, ethylphenyl group, xylyl group (the alkyl part of these alkylaryl groups may be linear or branched, And an arylalkyl group such as a benzyl group and a phenylethyl group (the substitution position of the phenyl group is arbitrary).
R ²⁶ and R ²⁷ are more preferably a C 3-18 alkyl group derived from propylene or isobutene, and particularly preferably a C 6-15 alkyl group.

  Specific examples of the dihydrocarbyl polysulfide compound (D-4) include dibutyl polysulfide, dihexyl polysulfide, dioctyl polysulfide, dinonyl polysulfide, didecyl polysulfide, didodecyl polysulfide, ditetradecyl polysulfide, dihexadecyl polysulfide, dioctadecyl. Polysulfide, dieicosyl polysulfide, diphenyl polysulfide, dibenzyl polysulfide, diphenethyl polysulfide, polypropenyl polysulfide, polybutenyl polysulfide and mixtures thereof, and the like, and polypropenyl polysulfide, polybutenyl polysulfide and mixtures thereof are particularly preferred preferable. As used herein, polypropenyl polysulfide, polybutenyl polysulfide, or a mixture thereof is an olefinic hydrocarbon such as propylene, isobutene, a dimer to tetramer of these monomers, or a mixture of these monomers or polymers. It can be obtained by sulfiding with elemental sulfur, sulfur halide (for example, sulfur monochloride or sulfur dichloride), hydrogen sulfide and a mixture thereof.

  (D-5) The sulfurized ester compound is a compound obtained by subjecting an ester compound to sulfuration treatment. Specifically, for example, beef tallow, lard, fish fat, rapeseed oil, soybean oil and other animal and vegetable oils; unsaturated fatty acids (oleic acid) , Linoleic acid or fatty acids extracted from the above-mentioned animal and vegetable oils and fats) and unsaturated fatty acid esters obtained by reacting various alcohols; and mixtures thereof obtained by sulfiding by any method Is mentioned.

  The blending amount of the component (D) in the lubricating oil composition for internal combustion engines of the present invention is 0.01 to 0.4% by mass, preferably 0.0. It is 03-0.3 mass%. When the blending amount of component (D) is less than 0.01% by mass, the effect of adding component (D) does not appear. On the other hand, when it exceeds 0.4% by mass, it causes rust or corrosion during deterioration. Each of these is not preferable because a strong acid tends to be generated.

式（３）中、Ｒ^６は直鎖または分岐のアルキル基、アルケニル基、アリール基、アルキルアリール基、アリールアルキル基、カルボキシル基などの炭化水素基を表し、ａは１〜２の整数を表し、Ｍ^１はカルシウム又はマグネシウムを表す。Ｒ^６としては特にアルキル基が好ましい。アルキル基の炭素数は１２〜３０、好ましくは１４〜１８であることが望ましく、具体的にはドデシル基、トリデシル基、テトラデシル基、ペンタデシル基、ヘキサデシル基、ヘプタデシル基、オクタデシル基、ノナデシル基、イコシル基、ヘンイコシル基、ドコシル基、トリコシル基、テトラコシル基、ペンタコシル基、ヘキサコシル基、ヘプタコシル基、オクタコシル基、ノナコシル基、トリアコンチル基などが挙げられ、これらは直鎖でも分岐でもよい。アルキル基を導入する際にα−オレフィンの混合物を原料とする場合があるが、この場合（Ｅ）成分としては異なる構造のアルキル基を有する中性アルカリ土類金属サリシレートの混合物となる。かかる混合物も使用することができる。
例えば、具体的な中性アルカリ土類金属サリシレートとしては、炭素数１４〜１８の直鎖又は分枝α−オレフィン混合物から誘導されるアルキル基を有するカルシウムモノアルキルサリシレート及び／又はカルシウムジアルキルサリシレート等が例示される。
ここで、モノアルキルサリシレートにおけるアルキル基としては、エチレン重合体のような直鎖α−オレフィンを原料とする場合、いわゆるソフト型のアルキルサリシレートとなり、３−アルキルサリシレートと５−アルキルサリシレートが約２：１の割合で生成する。しかし、実際にはその反応条件や反応比率、立体障害等により約３：２の割合となり、その他の化合物として４−アルキルサリシレートが含まれる。ここで、サリシレートに付加するアルキル基は、第２級のアルキル基（１−アルキル−アルキル基）である。また、アルキル基の原料として分枝α−オレフィンを使用する場合、いわゆるハード型のアルキルサリシレートとなり、５−アルキルサリシレートがほぼ１００％となる。また、これらを分離あるいは濃縮させ、所望の構造を有するアルキルサリシレートを主成分とさせることも可能である。
本発明においては、摩耗防止性、溶解性、貯蔵安定性の点で上記のうち、ソフト型のアルキルサリシレートを使用することが好ましく、少なくとも３位にアルキル基を有するサリシレートが主成分となるように調整することが好ましく、その構成としては、モノアルキルサリシレートを主成分として得る場合は、３−アルキルサリシレートが４５〜１００モル％、好ましくは５０〜９０モル％、より好ましくは５５〜８０モル％であり、５−アルキルサリシレートが０〜４０モル％、より好ましくは１０〜３５モル％、さらに好ましくは２０〜３０モル％である。なお３，５−ジアルキルサリシレートは、原料となるα−オレフィンの反応比率により、０〜１００モル％となりうるが、摩耗防止性、低摩擦性、低温流動性、溶解性、貯蔵安定性、水分存在下での酸化安定性の観点から、好ましくは３〜５０モル％であり、より好ましくは６〜３０モル％であり、３−アルキルサリシレートと３，５−ジアルキルサリシレートの合計量が好ましくは５０モル％以上、より好ましくは５５モル％以上、さらに好ましくは６０モル％以上とすることが望ましい。
また、（Ｅ）成分として好ましい過塩基性アルカリ土類金属サリシレートは、炭酸カルシウム、炭酸マグネシウムなどのアルカリ土類金属炭酸塩やホウ酸カルシウム、ホウ酸マグネシウムなどのアルカリ土類金属ホウ酸塩によって前記中性アルカリ土類金属サリシレートを過塩基化することによって得られるものである。
例えば、具体的な過塩基性アルカリ土類金属サリシレートとしては、炭酸カルシウムで過塩基化された、炭素数１４〜１８の直鎖α−オレフィン混合物から誘導されるアルキル基を有するカルシウムモノアルキルサリシレート及び／又はカルシウムジアルキルサリシレートが例示される。 The lubricating oil composition for internal combustion engines of the present invention is an optional component in order to further enhance the low friction property, but it is preferable to add an alkaline earth metal salicylate as the component (E). Alkaline earth metal salicylates include neutral alkaline earth metal salicylates or overbased alkaline earth metal salicylates. The alkaline earth metal is preferably calcium, magnesium or a mixture thereof.
The neutral alkaline earth metal salicylate preferable as the component (E) is a salt obtained by neutralizing a hydrocarbon group-substituted salicylic acid with an equivalent amount of an alkaline earth metal hydroxide, and is represented by the general formula (3). It is done.

In formula (3), R ⁶ represents a hydrocarbon group such as a linear or branched alkyl group, alkenyl group, aryl group, alkylaryl group, arylalkyl group, carboxyl group, and a represents an integer of 1 to 2. , M ¹ represents calcium or magnesium. R ⁶ is particularly preferably an alkyl group. It is desirable that the alkyl group has 12 to 30 carbon atoms, preferably 14 to 18 carbon atoms, specifically, dodecyl group, tridecyl group, 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, triacontyl group and the like, which may be linear or branched. When the alkyl group is introduced, a mixture of α-olefins may be used as a raw material. In this case, the component (E) is a mixture of neutral alkaline earth metal salicylates having alkyl groups having different structures. Such mixtures can also be used.
For example, specific neutral alkaline earth metal salicylates include calcium monoalkyl salicylates and / or calcium dialkyl salicylates having an alkyl group derived from a linear or branched α-olefin mixture having 14 to 18 carbon atoms. Illustrated.
Here, as the alkyl group in the monoalkyl salicylate, when a linear α-olefin such as an ethylene polymer is used as a raw material, a so-called soft alkyl salicylate is obtained, and 3-alkyl salicylate and 5-alkyl salicylate are about 2: 1 is generated. In practice, however, the ratio is about 3: 2 due to the reaction conditions, reaction ratio, steric hindrance, and the like, and 4-alkyl salicylate is included as another compound. Here, the alkyl group added to the salicylate is a secondary alkyl group (1-alkyl-alkyl group). Further, when a branched α-olefin is used as a raw material for the alkyl group, a so-called hard alkyl salicylate is obtained, and the 5-alkyl salicylate is almost 100%. It is also possible to separate or concentrate them so that an alkyl salicylate having a desired structure is the main component.
In the present invention, it is preferable to use a soft-type alkyl salicylate among the above from the viewpoint of wear prevention, solubility and storage stability, so that the salicylate having an alkyl group at least at the 3-position is the main component. In the case of obtaining monoalkyl salicylate as a main component, it is preferable to adjust 3-alkyl salicylate in an amount of 45 to 100 mol%, preferably 50 to 90 mol%, more preferably 55 to 80 mol%. The 5-alkyl salicylate is 0 to 40 mol%, more preferably 10 to 35 mol%, and still more preferably 20 to 30 mol%. In addition, 3,5-dialkyl salicylate can be 0 to 100 mol% depending on the reaction ratio of the α-olefin used as a raw material, but it is antiwear, low friction, low temperature fluidity, solubility, storage stability, presence of moisture. From the viewpoint of oxidation stability below, it is preferably 3 to 50 mol%, more preferably 6 to 30 mol%, and the total amount of 3-alkyl salicylate and 3,5-dialkyl salicylate is preferably 50 mol. % Or more, preferably 55 mol% or more, more preferably 60 mol% or more.
The preferred overbased alkaline earth metal salicylate as component (E) is an alkaline earth metal carbonate such as calcium carbonate or magnesium carbonate or an alkaline earth metal borate such as calcium borate or magnesium borate. It is obtained by overbasing a neutral alkaline earth metal salicylate.
For example, specific overbased alkaline earth metal salicylates include calcium monoalkyl salicylates having an alkyl group derived from a C14-18 linear α-olefin mixture overbased with calcium carbonate, and Examples thereof include calcium dialkyl salicylates.

(E) Although there is no restriction | limiting in particular in the base number (JIS K2501 perchloric acid method) of a component, It is preferable that it is 50-350 mgKOH / g, and it is further more preferable that it is 150-350 mgKOH / g on a dilution oil mixing | blending base.
The blending amount of the component (E) in the lubricating oil composition for internal combustion engines of the present invention is 0.02 to 0.5% by mass, preferably in terms of alkaline earth metal concentration, based on the total amount of the lubricating oil composition for internal combustion engines. Is 0.05 to 0.4 mass%, more preferably 0.1 to 0.3 mass%. When the blending amount of component (E) is less than 0.02%, the effect of reducing friction due to blending of component (E) does not appear. On the other hand, when the blending amount exceeds 0.5% by weight, Since an effect equivalent to each other cannot be obtained, each is not preferable.

  The lubricating oil composition for internal combustion engines of the present invention is an optional component, but in order to further improve fuel economy by improving viscosity characteristics, a viscosity index improver (hereinafter referred to as “component (F)”). It is preferable to blend. Specifically, the component (F) includes a so-called non-dispersed polymethacrylate such as a copolymer of one or more monomers selected from various methacrylates or a hydride thereof, or further a nitrogen compound. So-called dispersed polymethacrylates copolymerized with various methacrylic acid esters; non-dispersed or dispersed olefin copolymers copolymerized with α-olefins such as propylene, 1-butene and 1-pentene; grafts of polymethacrylates and olefin copolymers Copolymers or hydrides thereof; or mixtures of polymethacrylates and olefin copolymers or hydrides thereof.

As the component (F) to be blended in the lubricating oil composition for internal combustion engines of the present invention, it is excellent in the effect of improving the viscosity characteristics in a practical range of low to medium temperatures, and therefore, non-dispersed polymethacrylate, dispersed polymethacrylate, or a mixture thereof Is preferably used.
The weight average molecular weights of polymethacrylates, olefin copolymers or their hydrides, and graft copolymers of polymethacrylates and olefin copolymers or their hydrides are usually 50,000 to 1,000,000, 10,000 to 500,000, 50, respectively. , 1,000 to 1,000,000.
Component (F) is used in an amount such that the kinematic viscosity at 100 ° C. of the lubricating oil composition for internal combustion engines of the present invention is 4.6 to 11 mm ² / s, preferably 5.6 to 9.3 mm ² / s. Added. Usually, such an amount is 0.1 to 10% by mass based on the total amount of the lubricating oil composition for an internal combustion engine.

For the purpose of further improving the performance of the lubricating oil composition for an internal combustion engine of the present invention, if necessary, an ashless dispersant, a hydroxyphenyl-substituted fatty acid ester, a metal detergent other than the component (E), You may mix | blend arbitrary amounts with various additives represented by an antiwear agent and friction reducing agents other than (C) component, antioxidant, corrosion inhibitor, and an antifoamer individually or in combination of several types.
As an ashless dispersant that can be used in combination with the lubricating oil composition for an internal combustion engine of the present invention, any compound that is usually used as an ashless dispersant for lubricating oil can be used. For example, an alkyl group having 40 to 400 carbon atoms. Alternatively, a nitrogen-containing compound having at least one alkenyl group in the molecule or a derivative thereof, or a modified product of alkenyl succinimide may be used.
The alkyl group or alkenyl group may be linear or branched, but specific examples include an olefin oligomer such as propylene, 1-butene and isobutylene, and a co-oligomer of ethylene and propylene. Examples thereof include branched alkyl groups and branched alkenyl groups.
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.

In addition, as a derivative of the nitrogen-containing compound mentioned as an example of the ashless dispersant, specifically, for example, a nitrogen-containing compound as described above, a monocarboxylic acid having 2 to 30 carbon atoms (fatty acid, etc.), oxalic acid, By reacting a polycarboxylic acid having 2 to 30 carbon atoms such as phthalic acid, trimellitic acid, pyromellitic acid, etc. to neutralize a part or all of the remaining amino group and / or imino group, or amidation, So-called acid-modified compounds; so-called boron-modified compounds in which boric acid is allowed to act on the nitrogen-containing compounds as described above to neutralize or amid some or all of the remaining amino groups and / or imino groups; A sulfur-modified compound obtained by allowing a sulfur compound to act on such a nitrogen-containing compound; and a nitrogen-containing compound as described above in combination with two or more kinds of modifications selected from acid modification, boron modification, and sulfur modification. Sexual compounds.
In the lubricating oil composition for an internal combustion engine of the present invention, one or two or more compounds arbitrarily selected from these can be used in any amount, but usually the content is It is desirable that the amount is 1 to 12% by mass based on the total amount of the lubricating oil composition for an internal combustion engine.

Examples of hydroxyphenyl substituted fatty acid esters include 2,2′-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], tridecyl-3- (3,5-di -Tert-butyl-4-hydroxyphenyl) propionate, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octyl-3- (3,5-di- tert-butyl-4-hydroxyphenyl) propionate, octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, octyl-3- (3-methyl-5-tert-butyl-4- And hydroxyphenyl) propionate.
In the lubricating oil composition for an internal combustion engine of the present invention, one or two or more compounds arbitrarily selected from these can be used in any amount, but usually the content is It is desirable that the amount is 0.01 to 10% by mass, preferably 0.1 to 5% by mass, based on the total amount of the lubricating oil composition for an internal combustion engine.
As the metallic detergent other than the component (E) that can be used in combination with the lubricating oil composition for an internal combustion engine of the present invention, any compound usually used as a metallic detergent for lubricating oil can be used. Alkali metal or alkaline earth metal sulfonates, phenates, carboxylates, naphthenates, and the like can be used alone or in combination of two or more. Examples of the alkali metal include sodium and potassium, and examples of the alkaline earth metal include calcium and magnesium. As a specific metal detergent, calcium or magnesium sulfonate or phenate is preferably used. In addition, the total base number and addition amount of these metal detergents can be arbitrarily selected according to the required performance.

As the antiwear agent that can be used in combination with the lubricating oil composition for internal combustion engines of the present invention, any compound that is usually used as an antiwear agent for lubricating oils can be used. For example, phosphoric acid monoesters, phosphorus Acid diesters, phosphoric acid triesters, phosphorous acid monoesters, phosphorous acid diesters, phosphorous acid triesters, and salts of these esters with amines or alkanolamines can be used.
The blending amount of these antiwear agents is not particularly limited, but it is usually preferably 0.05 to 1% by mass based on the total amount of the lubricating oil composition for internal combustion engines.

As the friction reducing agent other than the component (C) that can be used in combination with the lubricating oil composition for an internal combustion engine of the present invention, any compound that is usually used as a friction modifier for lubricating oil can be used. An amine compound, a fatty acid ester, a fatty acid amide, a fatty acid metal salt having at least one alkyl group or alkenyl group of -30, in particular, a linear alkyl group or linear alkenyl group having 6 to 30 carbon atoms in the molecule, (C) Examples include organic molybdenum compounds other than the components.
Examples of the amine compound include linear or branched, preferably linear aliphatic monoamines having 6 to 30 carbon atoms, linear or branched, preferably linear aliphatic polyamines, or fatty acids thereof. An alkylene oxide adduct of a group amine can be exemplified. Examples of fatty acid esters include esters of linear or branched, preferably linear, fatty acids having 7 to 31 carbon atoms with aliphatic monohydric alcohols or aliphatic polyhydric alcohols. Examples of fatty acid amides include amides of linear or branched, preferably linear fatty acids having 7 to 31 carbon atoms, and aliphatic monoamines or aliphatic polyamines. Examples of the fatty acid metal salt include an alkaline earth metal salt (magnesium salt, calcium salt, etc.) or zinc salt of a linear or branched, preferably linear fatty acid having 7 to 31 carbon atoms.
In the present invention, one kind or two or more kinds of compounds arbitrarily selected from these friction modifiers can be blended in any amount, but the blending amount is usually determined by the lubrication for internal combustion engines. It is desirable that the content is 0.01 to 5.0 mass%, preferably 0.03 to 3.0 mass%, based on the oil composition.

Examples of antioxidants that can be used in combination with the lubricating oil composition for internal combustion engines of the present invention include antioxidants such as bisphenol compounds, monophenol compounds, and diphenylamine compounds, and are used in a range that does not significantly impair the effects of the present invention. can do.
As the corrosion inhibitor that can be used in combination with the lubricating oil composition for internal combustion engines of the present invention, any compound that is usually used as a corrosion inhibitor for lubricating oils can be used. For example, benzotriazole-based, tolyltriazole-based And imidazole compounds. One or two or more compounds arbitrarily selected from these can be blended in any amount, but the blending amount is usually 0.01 based on the total amount of the lubricating oil composition for internal combustion engines. It is desirable that the content be ˜1% by mass.

  As the antifoaming agent that can be used in combination with the lubricating oil composition for an internal combustion engine of the present invention, any compound that is usually used as a defoaming agent for lubricating oil can be used. For example, dimethyl silicone, fluorosilicone, etc. Examples include silicones. One or two or more compounds arbitrarily selected from these can be blended in any amount, but the blending amount is usually 0.001 based on the total amount of the lubricating oil composition for internal combustion engines. It is desirable that it is -0.05 mass%.

The above-described lubricating oil composition of the present invention is suitably used for lubricating an internal combustion engine equipped with a three-way catalyst for exhaust gas purification. Here, the three-way catalyst is a catalyst that is mounted on an exhaust device such as an internal combustion engine in order to detoxify sulfur or carbon oxide as well as nitrogen oxide gas by oxidation / reduction action. Often used in gasoline engines.
The three-way catalyst is a catalyst that renders the nitrogen oxide gas harmless. However, when such nitrogen oxide gas is mixed in the lubricating oil atmosphere, a tendency to promote air oxidation of the lubricating oil is recognized. As a result, it is difficult to maintain a low coefficient of friction after oxidative degradation.
However, the lubricating oil composition of the present invention can easily maintain a low coefficient of friction after oxidative degradation even in an atmosphere containing such a nitrogen oxide gas.

Furthermore, heat-resistant rubber / sealant is often used for sealing in internal combustion engines, and silicone rubber, nitrile rubber, fluorine rubber, and the like are often used as such a sealing material.
The sealing material may come into contact with the lubricating oil, so that in some cases, the lubricating oil may affect the sealing material. However, the lubricating oil of the present invention has little effect on the sealing rubber, especially on the fluororubber. For example, it is less likely to degrade the strength and cause a decrease in strength.
Therefore, it is suitably used as a lubricating oil for an internal combustion engine using a rubber / sealing material, particularly a fluoro rubber / sealing material.

Hereinafter, the content 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.
According to the composition shown in Table 1, a lubricating oil composition for internal combustion engines (Examples 1 to 6) according to the present invention and a composition for comparison (Comparative Examples 1 to 5) according to the composition shown in Table 2 were prepared. The friction coefficient of the oil / deteriorated oil, the insoluble content of the deteriorated oil, and the seal rubber immersion test were performed.
(Deterioration test)
The deterioration test of the sample oil was performed by an oxidation test by blowing a nitrogen oxide (NOx) -containing gas. A gas having a NOx concentration of 0.12% by volume was blown into a 200 mL sample oil heated to 140 ° C. to cause deterioration. The sample oil deteriorated to 48 h was used as a deteriorated oil for friction test. Moreover, the n-pentane insoluble matter of the sample oil deteriorated to 144 h was measured and used as an index of oxidation stability.
(Friction test)
The friction characteristics of the new oil and the deteriorated oil for friction test were evaluated with an SRV reciprocating friction tester manufactured by Optimol. The test conditions are a load of 400 N, a frequency of 50 Hz, an amplitude of 1.5 mm, and an oil temperature of 110 ° C.
(Seal rubber immersion test)
Fluororubber was immersed in sample oil heated to 150 ° C. for 168 hours. Tensile tests of fluoro rubber immersed in the compositions prepared in Examples and Comparative Examples are performed, and the tensile strength change rate is calculated by comparing these results with the tensile test results of fluoro rubber before immersion, and these are used as seal rubber. It was used as an index of suitability. The fluororubber is F585 manufactured by NOK Corporation.

（式１３中、Ｒはｓｅｃ−ブチル基またはｓｅｃ−ヘキシル基を示す。）
３）プロピレンの４量体から誘導された分岐ドデシル基を有する、ｐ−ドデシルフェニル−α―ナフチルアミン。
４）Ｐ，Ｐ’−ジ−イソオクチルジフェニルアミン。
５）４，４’−メチレンビス（２，６−ジターシャリーブチルフェノール）。
６）次式で表されるモリブデンジチオカーバメート。モリブデン含有量４．８質量％。

（式１４中、Ｒは炭素数８または１３のアルキル基であり、すべてのＲが同一ではない非対象構造を有する。ＸはＯまたはＳを示す。）
７）メチレンビス（ジブチルジチオカーバメート）。
８）炭酸カルシウムで過塩基化された、炭素数１４〜１８の直鎖α−オレフィン混合物から誘導される第２級アルキル基を有するカルシウムサリシレート混合物（３−アルキルサリシレート５３モル％、４−アルキルサリシレート５モル％、５−アルキルサリシレート３３モル％、３，５−ジアルキルサリシレート８モル％、５−アルキル−４−ヒドロキシイソフタレート１モル％）。過塩素酸法塩基価（ＪＩＳ Ｋ２５０１） １６７ｍｇＫＯＨ／ｇ、Ｃａ含有量６質量％。
９）炭酸カルシウムで過塩基化されたカルシウムスルホネート。
過塩素酸法塩基価（ＪＩＳ Ｋ２５０１）３００ｍｇＫＯＨ／ｇ、Ｃａ含有量１２．５質量％。
１０）ポリブテニルコハク酸イミド（ビスタイプ、ポリブテニル基の数平均分子量１，０００、窒素含有量１．６質量％）
１１）ホウ酸変性ポリブテニルコハク酸イミド（ビスタイプ、ポリブテニル基の数平均分子量１，０００、窒素含有量１．６質量％、ホウ素含有量０．５質量％
１２）重量平均分子量３５０，０００の分散型ポリメタクリレート系粘度指数向上剤。
１３）重量平均分子量３５０，０００の非分散型ポリメタクリレート系粘度指数向上剤。
１４）１００℃の動粘度：単位ｍｍ^２／ｓ
１５）単位：質量％ 1) Hydrocracked mineral oil. Kinematic viscosity at 100 ° C .: 4.2 mm ² / s,% C _A : 0.4,% C _N : 20, viscosity index 122, NOACK evaporation: 14.5% by mass.
2) Zinc dialkyldithiophosphate represented by the following formula (13). Phosphorus content 7.2 mass%.

(In formula 13, R represents a sec-butyl group or a sec-hexyl group.)
3) p-dodecylphenyl-α-naphthylamine having a branched dodecyl group derived from a propylene tetramer.
4) P, P′-di-isooctyldiphenylamine.
5) 4,4'-methylenebis (2,6-ditertiary butylphenol).
6) Molybdenum dithiocarbamate represented by the following formula. Molybdenum content 4.8% by mass.

(In formula 14, R is an alkyl group having 8 or 13 carbon atoms, and all R's are not identical, and X represents O or S.)
7) Methylenebis (dibutyldithiocarbamate).
8) Calcium salicylate mixture having a secondary alkyl group derived from a linear α-olefin mixture having 14 to 18 carbon atoms and overbased with calcium carbonate (53 mol% of 3-alkyl salicylate, 4-alkyl salicylate) 5 mol%, 5-alkyl salicylate 33 mol%, 3,5-dialkyl salicylate 8 mol%, 5-alkyl-4-hydroxyisophthalate 1 mol%). Perchloric acid method base number (JIS K2501) 167 mgKOH / g, Ca content 6 mass%.
9) Calcium sulfonate overbased with calcium carbonate.
Perchloric acid method base number (JIS K2501) 300 mgKOH / g, Ca content 12.5 mass%.
10) Polybutenyl succinimide (bis type, polybutenyl group number average molecular weight 1,000, nitrogen content 1.6 mass%)
11) Boric acid-modified polybutenyl succinimide (bis type, polybutenyl group number average molecular weight 1,000, nitrogen content 1.6% by mass, boron content 0.5% by mass)
12) A dispersed polymethacrylate viscosity index improver having a weight average molecular weight of 350,000.
13) A non-dispersed polymethacrylate viscosity index improver with a weight average molecular weight of 350,000.
14) Kinematic viscosity at 100 ° C .: unit mm ² / s
15) Unit: mass%

(About Examples 1-6)
As is apparent from the results in Table 1, Examples 1 to 6 of the lubricating oil composition for internal combustion engines according to the present invention not only have a low coefficient of friction in the new oil state, but also have low friction even after deterioration. You can see that it is kept. Moreover, generation | occurrence | production of the n-pentane insoluble matter after deteriorating to 144 h is very little, and it turns out that it has the outstanding oxidation stability. In addition, it can be seen that the strength of the fluororubber after immersion at a high temperature is small and that the seal rubber is hardly deteriorated even in actual use.

(About Comparative Example 1)
As is clear from the results in Table 2, Comparative Example 1 in which diphenylamine was blended instead of the component (B) according to the present invention has low friction in the new oil state, but has low friction after deterioration. It disappears, and the low friction maintenance property is insufficient.
(Comparative Example 2)
As is clear from the results in Table 2, Comparative Example 2 in which phenol was blended in place of the component (B) according to the present invention had a new oil state and low friction after deterioration, but the strength of the fluororubber The decrease rate is large and the seal rubber compatibility is insufficient.
(Comparative Example 3)
As is clear from the results of Table 2, Comparative Example 3 not containing the component (D) according to the present invention has low friction in the new oil state, but has lost low friction after deterioration. , Low friction maintenance is insufficient.
(Comparative Example 4)
As is clear from the results in Table 2, Comparative Example 4 in which the component (B) according to the present invention is not blended has a large amount of n-pentane insoluble matter in a deteriorated state and has insufficient oxidation stability.
(Comparative Example 5)
As is clear from the results in Table 2, Comparative Example 5 in which the component (C) according to the present invention is not blended has insufficient low friction from the new oil state.

Claims (8)

Based on the total amount of the lubricating oil composition for internal combustion engines,
(A) 0.04 to 0.10% by mass of zinc dialkyldithiophosphate in terms of phosphorus concentration,
(B) 0.05 to 4.0% by mass of phenyl-α-naphthylamine represented by the following general formula (1),

(In formula (1), R ¹ represents a hydrogen atom or a linear or branched alkyl group having 1 to 24 carbon atoms)
(C) Molybdenum dithiocarbamate friction reducer represented by the following general formula (2) 0.02 to 0.15% by mass in terms of molybdenum,

(In the formula (2), R ² , R ³ , R ⁴ and R ⁵ may be the same or different and each represents a hydrocarbon group, and X ¹ , X ² , X ³ and X ⁴ are individually (Indicates sulfur or oxygen atoms)
And (D) one or two or more sulfur-containing compounds selected from the group consisting of thiazole compounds, thiadiazole compounds, dithiocarbamate compounds, dihydrocarbyl polysulfide compounds, and sulfurized ester compounds, 0.01 to 0 in terms of sulfur concentration .5% by mass,
A lubricating oil composition for an internal combustion engine, comprising: Furthermore, (E) The alkaline earth metal salicylate represented by the following general formula (3) is blended in an amount of 0.02 to 0.5 mass% in terms of alkaline earth metal concentration based on the total amount of the lubricating oil composition for an internal combustion engine. The lubricating oil composition for an internal combustion engine according to claim 1, wherein

(In Formula (3), R ⁶ represents a hydrocarbon group, a represents an integer of 1 to 2, and M ¹ represents calcium or magnesium.)   The lubricating oil composition for an internal combustion engine according to any one of claims 1 to 2, wherein at least one of the sulfur-containing compounds (D) is a dithiocarbamate compound. Kinematic viscosity at 100 ° C. of the lubricating base oils 2~6mm ² / s,% _{C A} is 2 or less,% _{C N} is 25 or less and the viscosity index is 105 or more,
Further, (F) a viscosity index improver is blended in such an amount that the kinematic viscosity at 100 ° C. as the lubricating oil composition for an internal combustion engine is 4.6 to 11 mm ² / s. The lubricating oil composition for internal combustion engines in any one of 1-3.   The lubricating oil composition for an internal combustion engine according to claim 4, wherein the blended viscosity index improver is a dispersed and / or non-dispersed polymethacrylate. The phenyl-α-naphthylamine of (B) represented by the general formula (1) is (Np-alkyl) phenyl-α-naphthylamine represented by the following general formula (4). The lubricating oil composition for an internal combustion engine according to any one of claims 1 to 5.

(In formula (4), R ⁷ represents a linear or branched alkyl group having 8 to 16 carbon atoms)   The lubricating oil composition for internal combustion engines according to any one of claims 1 to 6, wherein the alkyl group of (B) phenyl-α-naphthylamine is a branched alkyl group having 8 to 16 carbon atoms.   The lubricating oil composition for an internal combustion engine according to any one of claims 1 to 7, wherein the lubricating oil composition is for lubricating an internal combustion engine equipped with a three-way catalyst for exhaust gas purification.