JPWO2008050717A1 - Lubricating oil composition for internal combustion engines - Google Patents

Abstract

A base oil, a disulfide compound represented by (A) general formula (I) R1OOC-A1-SS-A2-COOR2 (I), and general formula (II) R7OOC-CR9R10-CR11 (COOR8) -S-S-CR16 (COOR13) -CR14R15-COOR12 ..., including at least one selected from disulfide compounds represented by (II) (B) A lubricating oil composition for an internal combustion engine comprising 10 to 2000 ppm by mass of at least one selected from alkali metal or alkaline earth metal detergents as a metal amount. Such a composition has low ash content, low phosphorus content and low sulfur content, yet maintains wear resistance, excellent heat resistance, and long life that can extend the interval between lubricating oils. The lubricating oil composition.

Description

  The present invention relates to a lubricating oil composition for an internal combustion engine, particularly a lubricating oil composition suitable for an internal combustion engine such as a gasoline engine, a diesel engine, or a gas engine, and more specifically, a low ash content, a low phosphorus content, and The present invention relates to a long-life lubricating oil composition that maintains wear resistance while having a low sulfur content, is excellent in heat resistance, and can extend the interval between lubricating oils.

Lubricants for internal combustion engines are mainly used for lubrication of various sliding parts such as piston rings and cylinder liners, crankshaft and connecting rod shafts, valve mechanisms including cams and valve lifters, as well as cooling, sludge and fuel in the engine. It has functions such as dispersion of combustion products.
As described above, various kinds of performance are required for the lubricating oil for the internal combustion engine, and in addition, in recent years, advanced performance has been required with the performance enhancement, high output, and severe operation conditions of the internal combustion engine. . Therefore, various additives such as an antiwear agent, a metal detergent, an ashless dispersant, and an antioxidant are blended in the lubricating oil for internal combustion engines in order to satisfy such required performance.

In addition, as part of extending the life of lubricating oils, development of more effective antioxidants and combination techniques have been studied. Among them, zinc dialkyldithiophosphate (ZnDTP) has conventionally been used as an extreme pressure additive. It has been used a lot. This ZnDTP not only has an antioxidant action, but also has a great effect on wear prevention, and further has a corrosion prevention action, and has been widely used especially in engine oils.
However, in recent years, exhaust gas purification systems have been installed in gasoline engines due to stricter regulations on automobile exhaust gas, and in order to prevent poisoning of this three-way catalyst, gasoline has been made lead-free and engine oil has low phosphorus content. Accordingly, the use of ZnDTP has begun to be restricted. Therefore, the development of extreme pressure antiwear agents that do not contain phosphorus has become essential.

Also, in diesel engines, particulate matter (particulate matter) contained in the combustion gas discharged from diesel vehicles has become a problem, and diesel particulate removal devices (diesel particulate filters, hereinafter referred to as “DPF”) Is abbreviated as “.”). When ZnDTP is used as an extreme pressure additive in the same manner as described above, there is a risk of clogging of the filter due to the deposition of the zinc component contained in ZnDTP on the DPF, and the development of an alternative to ZnDTP is desired.
It is also desirable to reduce the phosphorus component contained in ZnDTP from the viewpoint of catalyst poisoning.

Patent Document 1 discloses a lubricating oil composition containing a thiophosphate ester, a metal salt of a phosphate ester or an amine salt, having a reduced sulfur content and excellent base number retention. Although it is possible to reduce the sulfur content as an alternative to ZnDTP, the phosphorous component and zinc component (ash content) cannot be reduced, and catalyst poisoning and DPF clogging problems remain and are still insufficient as a lubricating oil composition.
As described above, it is difficult to reduce the zinc component, the phosphorus component and the sulfur component without reducing the wear resistance and the antioxidant performance as an extreme pressure additive. In order to minimize the influence on the post-treatment process, it is desired to reduce them.

  Conventionally, it is well known that a synergistic effect can be obtained by combining a sulfur-based antioxidant and a phenol-based antioxidant. However, as the sulfur-based antioxidant, those having a monosulfide structure are mainly used, and an increase in acid value due to hydrolysis has been a problem. In addition, a sulfur compound having a polysulfide structure higher than trisulfide has a problem that it is highly corrosive to non-ferrous metals.

2002-924721

  Under such circumstances, the present invention maintains wear resistance while maintaining low ash content, low phosphorus content, and low sulfur content, is excellent in heat resistance, and further extends the renewal interval of the lubricating oil. It is an object of the present invention to provide a lubricating oil composition for an internal combustion engine having a long life.

As a result of earnest research to develop a lubricating oil composition for an internal combustion engine having the above-mentioned preferable properties, the present inventor has used the above-mentioned combination of a disulfide compound having a specific structure and a specific amount of a detergent. We have found that the objective can be achieved. The present invention has been completed based on such findings.
That is, the present invention
(1) Base oil and (A) General formula (I)
^{R 1 OOC-A 1 -S-} S-A 2 -COOR 2 ··· (I)
(In the formula, R ¹ and R ² are each independently an oxygen atom, a sulfur atom, or a C 1-30 hydrocarbyl group optionally containing a nitrogen atom, A ¹ and A ² are each independently CR; ³ R ⁴ or a group represented by CR ³ R ⁴ —CR ⁵ R ⁶ , wherein R ^{3 to} R ⁶ each independently represents a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms. Disulfide compounds and general formula (II)
^{R 7 OOC-CR 9 R 10} -CR 11 (COOR 8) -S-S-CR 16 (COOR 13) -CR 14 R 15 -COOR 12 ················・ (II)
(In the formula, R ⁷ , R ⁸ , R ¹² and R ¹³ are each independently a hydrocarbyl group having 1 to 30 carbon atoms which may contain an oxygen atom, a sulfur atom or a nitrogen atom, R ^{9 to} R ^11. And R ^{14 to} R ¹⁶ are each independently a hydrogen atom or a hydrocarbyl group having 1 to 5 carbon atoms.), And (B) an alkali metal or an alkali. A lubricating oil composition for an internal combustion engine comprising 10 to 2000 ppm by mass of at least one selected from earth metal detergents as a metal amount,
(2) The lubricating oil composition for an internal combustion engine according to (1), comprising 0.01 to 0.50% by mass of at least one selected from the disulfide compounds of component (A) as a sulfur amount,
(3) The lubricating oil composition for internal combustion engines according to (1) or (2) above, wherein the alkali metal or alkaline earth metal detergent of component (B) comprises salicylate or sulfonate, and (4) (B) The internal combustion engine lubricating oil composition according to any one of (1) to (3), wherein the component metal is Ca or Mg;
Is to provide.

  According to the present invention, although it has a low ash content, a low phosphorus content, and a low sulfur content, it has excellent wear resistance and heat resistance, and further has a long-life lubrication for an internal combustion engine that can extend the interval between lubricating oils. An oil composition can be provided.

As the base oil in the lubricating oil composition for internal combustion engines of the present invention (hereinafter sometimes abbreviated as a lubricating oil composition), mineral oil or synthetic oil can be used. There are various mineral oils and synthetic oils, and they may be appropriately selected according to the use. Examples of mineral oils include paraffinic mineral oils, naphthenic mineral oils, intermediate base mineral oils, and specific examples include light neutral oils, medium neutral oils, heavy neutral oils, bright stocks by solvent refining or hydrogenation refining. And so on.
On the other hand, as synthetic oil, for example, poly α-olefin, α-olefin copolymer, polybutene, alkylbenzene, polyol ester, dibasic acid ester, polyhydric alcohol ester, polyoxyalkylene glycol, polyoxyalkylene glycol ester, polyoxyalkylene glycol Examples include ethers and cycloalkane compounds.
These lubricating base oils can be used alone or in combination of two or more kinds, and mineral oil and synthetic oil may be used in combination.

The compound represented by the general formula (I), which is the component (A) used in the lubricating oil of the present invention, has the following structure R ¹ OOC-A ¹ -SSA ² -COOR ^2. )
It is a disulfide compound having
In the general formula (I), R ¹ and R ² each independently represent an oxygen atom, a hydrocarbyl group of a sulfur atom or a nitrogen atom to carbon atoms which may contain an 1-30, preferably 1 to 20 carbon atoms Further, a hydrocarbyl group having 2 to 18 carbon atoms, particularly 3 to 18 carbon atoms is preferable. The hydrocarbyl group may be linear, branched or cyclic. R ¹ and R ² may be the same or different, but are preferably the same for manufacturing reasons.
A ¹ and A ² are each independently a group represented by CR ³ R ⁴ or CR ³ R ⁴ —CR ⁵ R ⁶ , and R ^{3 to} R ⁶ are each independently a hydrogen atom or carbon. It is a hydrocarbyl group of number 1-20. The hydrocarbyl group preferably has 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms. A ¹ and A ² may be the same or different from each other, but are preferably the same for manufacturing reasons.

In the lubricating oil composition of the present invention, when the —S—S— bond in the general formula (I) is a bond of —S—S—S— or higher, ie, —S _x —, x is 3 The content of polysulfide higher than sulfide is preferably 30% by mass or less based on the total amount with the disulfide compound. When the content is 30% by mass or less, the corrosiveness to non-ferrous metals can be sufficiently suppressed. The content of the polysulfide compound of trisulfide or higher is more preferably 10% by mass or less, and particularly preferably 5% by mass or less.
Therefore, in the production of the disulfide compound represented by the general formula (I), it is important to adopt a method in which the by-product amount of the polysulfide compound higher than trisulfide falls within the above range. In this invention, it is preferable to manufacture according to the method shown below, for example.

That is, as a raw material, general formula (III) and / or general formula (IV)
R ¹ OOC-A ¹ -SH (III)
R ² OOC-A ² —SH (IV)
(In the formula, R ¹ and R ² , A ¹ and A ² are the same as described above.)
The oxidative coupling is performed using a mercaptoalkanecarboxylic acid ester represented by: According to such a production method, a by-product of a polysulfide compound higher than trisulfide does not substantially occur.
^{Specifically, R 1 OOC-A 1 -S} -S-A 2 -COOR 2, R 1 OOC-A 1 -S-S-A 1 -COOR 1, R 2 OOC-A 2 -S-S- A ² -COOR ² is manufactured.
As an oxidizing agent used when an α-mercaptocarboxylic acid ester is oxidized to produce a corresponding disulfide, an oxidizing agent used for producing a disulfide from mercaptan can be used. Examples of the oxidizing agent include oxygen, hydrogen peroxide, halogen (iodine, bromine), hypohalous acid (salt), sulfoxide (dimethyl sulfoxide, diisopropyl sulfoxide), manganese (IV) oxide, and the like. Among these oxidizing agents, oxygen, hydrogen peroxide, and dimethyl sulfoxide are preferable because they are inexpensive and easy to produce disulfides.

  Specific examples of the disulfide compound represented by the general formula (I) include bis (methoxycarbonylmethyl) disulfide, bis (ethoxycarbonylmethyl) disulfide, bis (n-propoxycarbonylmethyl) disulfide, and bis (isopropoxycarbonylmethyl). ) Disulfide, bis (n-butoxycarbonylmethyl) disulfide, bis (n-octoxycarbonylmethyl) disulfide, bis (n-dodecyloxycarbonylmethyl) disulfide, bis (cyclopropoxycarbonylmethyl) disulfide, 1,1-bis ( 1-methoxycarbonylethyl) disulfide, 1,1-bis (1-methoxycarbonyl-n-propyl) disulfide, 1,1-bis (1-methoxycarbonyl-n-butyl) disulfide, 1,1- (1-methoxycarbonyl-n-hexyl) disulfide, 1,1-bis (1-methoxycarbonyl-n-octyl) disulfide, 1,1-bis (1-methoxycarbonyl-n-dodecyl) disulfide, 2,2 -Bis (2-methoxycarbonyl-n-propyl) disulfide, α, α-bis (α-methoxycarbonylbenzyl) disulfide, 1,1-bis (2-methoxycarbonylethyl) disulfide, 1,1-bis (2- Ethoxycarbonylethyl) disulfide, 1,1-bis (2-n-propoxycarbonylethyl) disulfide, 1,1-bis (2-isopropoxycarbonylethyl) disulfide, 1,1-bis (2-cyclopropoxycarbonylethyl) Disulfide, 1,1-bis (2-methoxycarbonyl-n- (Lopyl) disulfide, 1,1-bis (2-methoxycarbonyl-n-butyl) disulfide, 1,1-bis (2-methoxycarbonyl-n-hexyl) disulfide, 1,1-bis (2-methoxycarbonyl-n) -Propyl) disulfide, 2,2-bis (3-methoxycarbonyl-n-pentyl) disulfide, 1,1-bis (2-methoxycarbonyl-1-phenylethyl) disulfide and the like.

Furthermore, the compound represented by the general formula (II) which is the component (A) used in the lubricating oil composition of the present invention has the following structure: R ⁷ OOC—CR ⁹ R ¹⁰ —CR ¹¹ (COOR ⁸ ) —S— S-CR ¹⁶ (COOR ¹³ ) -CR ¹⁴ R ¹⁵ -COOR ¹² (II)
It is a disulfide compound having
In the general formula (II), R ⁷ , R ⁸ , R ¹² and R ¹³ are each independently a hydrocarbyl having 1 to 30 carbon atoms which may contain an oxygen atom, a sulfur atom or a nitrogen atom. A hydrocarbyl group having 1 to 20 carbon atoms, more preferably 2 to 18 carbon atoms, and particularly 3 to 18 carbon atoms. The hydrocarbyl group may be linear, branched or cyclic.
R ⁷ , R ⁸ , R ¹² and R ¹³ may be the same or different from each other, but are preferably the same for manufacturing reasons.
Next, R ^{9 to} R ¹¹ and R ^{14 to} R ¹⁶ are each independently a hydrogen atom or a hydrocarbyl group having 1 to 5 carbon atoms. A hydrogen atom is preferable because the raw material is easily available.

In the present invention, the disulfide compound is preferably produced, for example, according to the following two methods. That is, as the first production method, as a raw material, the general formula (V) and / or the general formula (VI)
R ⁷ OOC-CR ⁹ R ¹⁰ -CR ¹¹ (COOR ⁸ ) -SH (V)
^{R 12 OOC-CR 15 R 14} -CR 16 (COOR 13) -SH ··· (VI)
(In the formula, R ^{7 to} R ¹⁶ are the same as above.)
And oxidative coupling using a mercaptoalkanedicarboxylic acid diester represented by the formula:

In particular,
^{R 7 OOC-CR 9 R 10} -CR 11 (COOR 8) -S-S-CR 16 (COOR 13) -CR 14 CR 15 -COOR 12,
^{R 7 OOC-CR 9 R 10} -CR 11 (COOR 8) -S-S-CR 11 (COOR 8) -CR 10 CR 9 -COOR 7, and ^{R 12 OOC-CR 15 R 14} -CR 16 (COOR 13 ^{) -S-S-CR 16 (} COOR 13) -CR 14 CR 15 -COOR 12 is prepared.
Examples of the oxidizing agent in this case include oxygen, hydrogen peroxide, halogen (iodine, bromine), hypohalous acid (salt), sulfoxide (dimethyl sulfoxide, diisopropyl sulfoxide), manganese (IV) oxide, and the like. Among these oxidizing agents, oxygen, hydrogen peroxide, and dimethyl sulfoxide are preferable because they are inexpensive and easy to produce disulfides.

In addition, the second production method of the disulfide compound includes, as a raw material, general formula (VII) and / or general formula (VIII).
^{HOOC-CR 9 R 10 -CR 11} (COOH) -SH ··· (VII)
HOOC-CR ¹⁴ R ¹⁵ -CR ¹⁶ (COOH) -SH (VIII)
(Wherein R ^{9 to} R ¹¹ and R ^{14 to} R ¹⁶ are the same as described above.)
And then esterifying with a monohydric alcohol comprising a hydrocarbyl group having 1 to 30 carbon atoms which may contain an oxygen atom, a sulfur atom, or a nitrogen atom. It is. Specifically, in oxidative coupling,
^{HOOC-CR 9 R 10 -CR 11} (COOH) -S-S-CR 16 (COOH) -CR 15 R 14 -COOH,
^{HOOC-CR 9 R 10 -CR 11} (COOH) -S-S-CR 11 (COOH) -CR 10 R 9 -COOH, and ^{HOOC-CR 14 R 15 -CR 16} (COOH) -S-S-CR 16 (COOH) —CR ¹⁵ R ¹⁴ —COOH is produced. In this case, the above oxidizing agents can be used.

Following oxidative coupling, general formula (IX)
R ¹⁷ —OH (IX)
(In the formula, R ¹⁷ is the same as R ⁷ described above.)
Esterify with alcohol. For the esterification, a usual method of dehydration condensation using an acid catalyst can be used. By this method, specifically,
^{R 17 OOC-CR 9 R 10} -CR 11 (COOR 17) -S-S-CR 16 (COOR 17) -CR 15 R 14 -COOR 17,
R ¹⁷ OOC-CR ⁹ R ¹⁰ —CR ¹¹ (COOR ¹⁷ ) —S—S—CR ¹¹ (COOR ¹⁷ ) —CR ¹⁰ R ⁹ —COOR ¹⁷ , and R ¹⁷ OOC—CR ¹⁴ R ¹⁵ —CR ¹⁶ (COOR ^{17 ) -S-S-CR 16 (} COOR 17) -CR 15 R 14 -COOR 17, is manufactured.

  Specific examples of the disulfide compound represented by the general formula (II) include tetramethyl dithiomalate, tetraethyl dithiomalate, tetra-1-propyl dithiomalate, tetra-2-propyl dithiomalate, and tetra-1-butyl dithiomalate. , Tetra-2-butyl dithiomalate, tetraisobutyl dithiomalate, tetra-1-hexyl dithiomalate, tetra-1-octyl dithiomalate, tetra-1- (2-ethyl) hexyl dithiomalate, tetra-1-dithiomalate 3,5,5-trimethyl) hexyl, tetra-1-decyl dithiomalate, tetra-1-dodecyl dithiomalate, tetra-1-hexadecyl dithiomalate, tetra-1-octadecyl dithiomalate, tetrabenzyl dithiomalate, dithioapple Tetra-α- (methyl) benzyl, tetra-α, α-dimethylbenzyl dithiomalate, tetra-1- (2-methoxy) ethyl dithiomalate, tetra-1- (2-ethoxy) ethyl dithiomalate, tetra-1 dithiomalate -(2-butoxy) ethyl, tetra-1- (2-ethoxy) ethyl dithiomalate, tetra-1- (2-butoxy-butoxy) ethyl dithiomalate, tetra-1- (2-phenoxy) ethyl dithiomalate, etc. Can be mentioned.

The disulfide compound represented by the general formula (I) or the general formula (II) is excellent as a load resistance and wear resistance as a sulfur-based extreme pressure additive, and is used as an additive for a lubricating oil composition. .
In the lubricating oil composition of the present invention, the disulfide compound represented by the general formula (I) may be used alone or in combination of two or more as the component (A), and the general formula (II). 1 type or 2 types or more may be included independently.
Furthermore, a mixture of at least one disulfide compound represented by the general formula (I) and at least one disulfide compound represented by the general formula (II) may be included.

  The content of the disulfide compound as the component (A) in the lubricating oil composition of the present invention is appropriately selected according to the purpose and conditions of use of the composition, but is usually 0.01 to 0. It is preferable that 50 mass% is included, More preferably, it is the range of 0.01-0.30 mass%.

Moreover, in the lubricating oil composition of this invention, it is required to contain 10-2000 mass ppm as a metal amount at least 1 type chosen from alkali metal or alkaline-earth metal type detergent as (B) component. Preferably it is 100-2000 mass ppm, More preferably, it is 200-2000 mass ppm.
By adjusting the content of the component (B) as the metal amount within the above range, the acid neutralization performance is maintained and the increase in ash is suppressed, so that the clogging of the DPF is prevented and the formation of deposits is suppressed. The oil renewal interval can be extended.

The (B) component alkali metal or alkaline earth metal detergent (hereinafter sometimes abbreviated as metal detergent) is used to improve acid neutralization performance, high temperature cleanability, wear resistance, and the like. It is preferable. There is no restriction | limiting in particular as a metallic detergent, Arbitrary metallic detergents used for lubricating oil can be used. Specifically, for example, one or more metal detergents selected from alkali metal sulfonates or alkaline earth metal sulfonates, alkali metal phenates or alkaline earth metal phenates, alkali metal salicylates, alkaline earth metal salicylates, etc. Can be mentioned. Further, examples of the alkali metal include sodium, potassium, and examples of the alkaline earth metal include magnesium, calcium, and barium. In particular, the alkaline earth metals magnesium and calcium are preferably used.
In the present invention, it is preferable to use an alkaline earth metal sulfonate and / or an alkaline earth metal salicylate in order to obtain a composition having excellent base number maintenance, high temperature cleanability, and wear resistance. . A preferable total base number is 20-600 mgKOH / g (JIS K-2501: perchloric acid method). By setting the total base number within the above range, the ability to neutralize acidic components generated by oxidation can be ensured, and an increase in ash content in the lubricating oil can be suppressed, and a large amount of deposits can be prevented from being used for a long time.

  Alkaline earth metal sulfonates are alkaline earth metal salts of various sulfonic acids, and are usually obtained by a method of carbonating alkaline earth metal salts of various sulfonic acids. Examples of the sulfonic acid include aromatic petroleum sulfonic acid, alkyl sulfonic acid, aryl sulfonic acid, alkyl aryl sulfonic acid and the like. Specifically, dodecyl benzene sulfonic acid, dilauryl cetyl benzene sulfonic acid, paraffin wax-substituted benzene sulfonic acid. And polyolefin-substituted benzenesulfonic acid, polyisobutylene-substituted benzenesulfonic acid, naphthalenesulfonic acid, and the like.

  Alkaline earth metal salicylate is an alkali metal salt of alkyl salicylic acid, usually alkylating phenol with an α-olefin having 8 to 18 carbon atoms, and then introducing a carboxyl group by a Kolbeschmitt reaction, followed by metathesis. Obtained by a carbonation method. Specific examples of the alkyl salicylic acid include dodecyl salicylic acid, dodecyl methyl salicylic acid, tetradecyl salicylic acid, hexadecyl salicylic acid, octadecyl salicylic acid, dioctyl salicylic acid and the like.

In the lubricating oil composition of the present invention, depending on the purpose of use, various additives such as other friction modifiers and antiwear agents, ashless dispersants, viscosity index improvers, pour point depressants, rust inhibitors, Metal corrosion inhibitors, antifoaming agents, surfactants, antioxidants and the like can be appropriately contained.
Examples of friction modifiers and antiwear agents include sulfur compounds such as sulfurized olefins, dialkyl polysulfides, diarylalkyl polysulfides, diaryl polysulfides, phosphate esters, thiophosphate esters, phosphite esters, alkyl hydrogen phosphites, phosphate esters. Phosphorus compounds such as amine salts and phosphite amine salts, chlorinated oils and fats, chlorinated paraffins, chlorinated fatty acid esters, chlorinated fatty acid and other chlorinated compounds, alkyl or alkenyl maleic acid esters, alkyl or alkenyl succinic acid esters Ester compounds such as alkyl or alkenyl maleic acid, organic acid compounds such as alkyl or alkenyl succinic acid, naphthenate, zinc dithiophosphate (ZnDTP), dithiocarbamic acid Lead (ZnDTC), sulfurized oxymolybdenum organo phosphorodithioate (MoDTP), and an organic metal-based compounds such as sulfurized oxymolybdenum dithiocarbamate (MoDTC).

Examples of the ashless dispersant include succinimides, boron-containing succinimides, benzylamines, boron-containing benzylamines, succinic esters, monovalent or divalent typified by fatty acids or succinic acid. Examples thereof include amides of carboxylic acids.
As the viscosity index improver, for example, polymethacrylate, dispersed polymethacrylate, olefin copolymer (for example, ethylene-propylene copolymer), dispersed olefin copolymer, styrene copolymer (for example, Examples of pour point depressants include polymethacrylate and the like.
Examples of the anticorrosive agent include alkenyl succinic acid and partial esters thereof, and examples of the metal corrosion inhibitor include benzotriazole type, benzimidazole type, benzothiazole type, thiadiazole type, etc. For example, dimethylpolysiloxane and polyacrylate are used, and as the surfactant, for example, polyoxyethylene alkylphenyl ether is used.

Examples of the antioxidant include amine-based antioxidants such as alkylated diphenylamine, phenyl-α-naphthylamine, and alkylated-naphthylamine, 2,6-di-T-butylcresol, 4,4′-methylenebis (2, And phenolic antioxidants such as 6-di-T-butylphenol).
The lubricating oil composition for an internal combustion engine of the present invention is excellent in wear resistance and heat resistance while having a low ash content, low phosphorus content and low sulfur content, and is capable of extending the renewal interval of the lubricating oil. It has a feature of life, and is mainly used for internal combustion engines. In addition, it is used for automatic transmissions, shock absorbers, drive system equipment such as power steering, automotive lubricating oil used for gears, cutting, grinding. It can be used as metal working oil used for metal working such as machining and plastic working, hydraulic oil that is power transmission fluid used for power transmission, force control, buffering, etc. in hydraulic systems such as hydraulic equipment and devices .

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
In addition, the analysis and evaluation of the lubricating oil composition prepared by the formulation described in Table 1 were performed according to the following methods.
(1) Phosphorus concentration measurement An emission spectroscopic analysis was performed by ICP (Inductively Coupled Plasma) analysis (apparatus: IRIS Advantage manufactured by JARREL ASH) to determine the mass% of phosphorus element in the sample. The measurement results are shown in Table 1.
(2) Sulfur concentration measurement Conforms to ASTM D-1552.
(3) Sulfuric acid ash Conforms to JIS K2272 “Crude oil and petroleum products—Testing method for ash and sulfated ash”.
(4) Base number (hydrochloric acid method)
This was based on the potentiometric titration method (base number / hydrochloric acid method) of “Petroleum products and lubricants—neutralization number test method” of JIS K2501.
(5) Hot tube test Sample oil 0.3 ml / hr, air 10 ml / min. Was kept flowing for 16 hours while maintaining the temperature of the glass tube at a predetermined evaluation temperature (280 ° C. to 310 ° C.). The lacquer adhering in the glass tube was compared with the color sample, and the score was given as 10 points for transparent and 0 points for black. The higher the score, the higher the performance.
(6) LFW-1 friction test Test apparatus: A friction test was performed under the following conditions using an LFW-1 friction tester, and the wear scar width of the block after the test was measured.
Block material H-60, ring material S-10, rotation speed 1400 rpm, oil temperature 80 ° C., load 30 Lbs, time 30 minutes (7) ISOT test (oxidation stability test)
The ISOT test was conducted according to JIS K-2514 “Lubricant-Oxidation stability test”. That is, an iron-copper plate was put into oil and stirred at 165.5 ° C., and the total base number after 96 hours was measured by JIS K-2501 (hydrochloric acid method).

Production Example 1 Production of bis (n-octoxycarbonylmethyl) disulfide Mercaptomethanecarboxylic acid octyl ester was oxidatively coupled according to the production method of the compound represented by the above general formula (I) to give bis (n-octoxycarbonylmethyl). ) Disulfide was produced. In this compound, the presence of polysulfide higher than trisulfide was not observed. Sulfur content 15.8 mass%.
A 100 ml eggplant flask was charged with 40.8 g of mercaptomethanecarboxylic acid octyl ester and 30.8 g of dimethyl sulfoxide, and heated in an oil bath at 120 ° C. for 8 hours. After cooling, it was dissolved in 100 ml of toluene and washed 10 times to remove unreacted dimethyl sulfoxide. Toluene under reduced pressure was distilled off to obtain 30.5 g of bis (n-octoxycarbonylmethyl) disulfide.

Production Example 2 Oil-soluble molybdenum-containing composition Polybutenyl (molecular weight 1000) succinic anhydride (PIBSA) and a mixture of polyethylene polyamine oligomers commercially available as E-100 polyethyleneamine from Huntsman Chemical Co. 250 g of bissuccinimide synthesized at a molar ratio of 0.5: 1 and 162.5 g of neutral oil were placed in a glass reactor equipped with a temperature controller, a mechanical stirrer and a water-cooled cooler. The mixture was heated to a temperature of molybdation reaction of 70 ° C. While maintaining the reaction temperature, 26.6 g of molybdenum oxide and 45.8 g of water were added to the reactor. The reactor was then maintained at a reaction temperature of 70 ° C. for 28 hours. After completion of the molybdation reaction, water was removed by distillation at a temperature of 99 ° C. and a pressure of 25 mmHg (absolute value) or less for about 30 minutes. The product contained 4.01% by weight molybdenum and 1.98% by weight nitrogen.
Examples 1-3, Comparative Example 1
A lubricating oil composition was prepared based on the formulation shown in Table 1.
About each obtained lubricating oil composition, phosphorus concentration, sulfur concentration, and sulfated ash were measured, and the hot tube test, the LFW-1 friction test, and the ISOT test were done. The measurement results and the evaluation results are shown in Table 1.

注」
＊１．１００Ｎ鉱油：水素化精製鉱油、１００℃動粘度４.５ｍｍ²/s，硫黄分０.０１質量％以下
＊２．５００Ｎ鉱油：水素化精製鉱油、１００℃動粘度１０.９ｍｍ²/s，硫黄分０.０１質量％以下
＊３．粘度指数向上剤：ポリメタクリレート（重量平均分子量；９０，０００）
＊４．流動点降下剤：ポリアルキルメタクリレート（重量平均分子量；６９，０００）
＊５．ジスルフィド：ビス（ｎ−オクトキシカルボニルメチル）ジスルフィド、硫黄含有量１５．８質量％（製造例１で調製）
＊６．金属系清浄剤：カルシウムスルホネート（塩基価３００ｍｇＫＯＨ／ｇ、カルシウム含有量；１２質量％）
＊７．ヒンダードフェノール系酸化防止剤：４，４'−メチレンビス（２，６−ジ−ｔ−ブチルフェノール）
＊８．アミン系酸化防止剤：ジアルキルジフェニルアミン（アルキル基はブチル基とオクチル基の混合物）
＊９．モリブデン系酸化防止剤：製造例２で調製した油溶性モリブデン含有組成物
＊１０．無灰分散剤：ポリブテニルコハク酸イミド（窒素含有量；０．７質量％）＊１１．無灰分散剤：ホウ素変性ポリブテニルコハク酸イミド（ホウ素含有量；０．２質量％、窒素含有量；２．１質量％）
＊１２．銅不活性剤：ベンゾトリアゾール
＊１３．消泡剤：シリコーン油

note"
* 1. 100N mineral oil: hydrorefined mineral oil, 100 ° C. kinematic viscosity 4.5 mm ² / s, sulfur content 0.01% by mass or less * 2.500 N mineral oil: hydrorefined mineral oil, 100 ° C. kinematic viscosity 10.9 mm ² / s, sulfur content of 0.01% by mass or less * 3. Viscosity index improver: polymethacrylate (weight average molecular weight; 90,000)
* 4. Pour point depressant: polyalkyl methacrylate (weight average molecular weight; 69,000)
* 5. Disulfide: bis (n-octoxycarbonylmethyl) disulfide, sulfur content 15.8% by mass (prepared in Production Example 1)
* 6. Metal detergent: calcium sulfonate (base number 300 mgKOH / g, calcium content; 12% by mass)
* 7. Hindered phenolic antioxidant: 4,4′-methylenebis (2,6-di-t-butylphenol)
* 8. Amine-based antioxidant: Dialkyldiphenylamine (alkyl group is a mixture of butyl group and octyl group)
* 9. Molybdenum-based antioxidant: oil-soluble molybdenum-containing composition prepared in Production Example 2 * 10. Ashless dispersant: polybutenyl succinimide (nitrogen content: 0.7 mass%) * 11. Ashless dispersant: Boron-modified polybutenyl succinimide (boron content; 0.2 mass%, nitrogen content; 2.1 mass%)
* 12. Copper deactivator: benzotriazole * 13. Defoamer: Silicone oil

Table 1 shows the following.
Example 1 was replaced with the disulfide compound according to the present invention based on the amount of ZnDTP sulfur in the formulation of the comparative example, and the wear resistance of Example 1 was equivalent to that of the comparative example, and the heat resistance (Hot tube test) is better than the comparative example.
In Example 2, the amount of sulfur relative to ZnDTP was reduced and replaced with the disulfide compound according to the present invention in the formulation of the comparative example, and the wear resistance and base number maintenance characteristics of Example 2 were equivalent to those of the comparative example. And heat resistance is good.
In Example 3, the amount of sulfur relative to ZnDTP in the formulation of the comparative example was reduced and replaced with the disulfide compound according to the present invention, and the sulfated ash content was adjusted to 0.6 mass% or less (Ca-based detergent increased). It is a prescription. The abrasion resistance of Example 3 is equivalent to that of the comparative example, and the heat resistance and the base number maintenance property are good.

  The formulations of Examples 1 to 3 do not contain phosphorus, which is a cause of catalyst poisoning. Furthermore, as shown in Examples 2 and 3, sulfur can cause catalyst poisoning without impairing wear resistance. The amount can be reduced. In general, an upper limit of sulfated ash representing the total amount of metal that becomes clogged with DPF is set (API standard, JASO standard, etc.). Therefore, considering the influence on the DPF, as shown in Example 3, the lubricating oil composition using the disulfide compound according to the present invention as a substitute for ZnDTP has a heat resistance (hot tube) without impairing the wear resistance. It is possible to improve the base number maintenance property after the test) and the ISOT test.

  The lubricating oil composition for an internal combustion engine of the present invention maintains wear resistance and has excellent heat resistance while having a low ash content, a low phosphorus content and a low sulfur content, and further extends the renewal interval of the lubricating oil. In addition to lubricating oil for internal combustion engines, it can be used for automatic transmissions, shock absorbers, drive systems such as power steering, automotive lubricating oils used in gears, etc., cutting, grinding, plastic working, etc. It is preferably used as a metal working oil used for metal processing, hydraulic oil that is a power transmission fluid used for operations such as power transmission, force control, and buffering in hydraulic systems such as hydraulic equipment and devices.

Claims (4)

A base oil and (A) a general formula (I)
^{R 1 OOC-A 1 -S-} S-A 2 -COOR 2 ··· (I)
(In the formula, R ¹ and R ² are each independently an oxygen atom, a sulfur atom, or a C 1-30 hydrocarbyl group optionally containing a nitrogen atom, A ¹ and A ² are each independently CR; ³ R ⁴ or a group represented by CR ³ R ⁴ —CR ⁵ R ⁶ , wherein R ^{3 to} R ⁶ each independently represents a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms. Disulfide compounds and general formula (II)
^{R 7 OOC-CR 9 R 10} -CR 11 (COOR 8) -S-S-CR 16 (COOR 13) -CR 14 R 15 -COOR 12 ················・ (II)
(In the formula, R ⁷ , R ⁸ , R ¹² and R ¹³ are each independently a hydrocarbyl group having 1 to 30 carbon atoms which may contain an oxygen atom, a sulfur atom or a nitrogen atom, R ^{9 to} R ^11. And R ^{14 to} R ¹⁶ are each independently a hydrogen atom or a hydrocarbyl group having 1 to 5 carbon atoms.), And (B) an alkali metal or an alkali. A lubricating oil composition for internal combustion engines, comprising 10 to 2000 ppm by mass of at least one selected from earth metal detergents as a metal amount.   The lubricating oil composition for an internal combustion engine according to claim 1, comprising 0.01 to 0.50 mass% with at least one selected from the disulfide compound of component (A) as a sulfur amount.   The lubricating oil composition for an internal combustion engine according to claim 1, wherein the alkali metal or alkaline earth metal detergent of the component (B) comprises salicylate and / or sulfonate.   The lubricating oil composition for an internal combustion engine according to claim 1, wherein the metal of the component (B) is Ca or Mg.