JPH08209173A - Lubricant composition - Google Patents

Abstract

PURPOSE: To obtain a lubricant compsn. which has a high abrasion resistance and an excellent persistence of low friction properties without being degraded even in the air contg. a nitrogen oxide gas by compounding a base oil with specified amts. of specific compds. CONSTITUTION: This lubricant compsn. is prepd. by compounding a base oil with a molybdenum dithiocarbamate having an 8-18C hydrocarbon group in an amt. of 200-2,000ppm (by wt.) in terms of molybdenum, a zinc dithiophosphate having an 8-18C hydrocarbon group in an amt. of 0.02-0.15wt.% in terms of phosphorus, and an antimony dialkyldithiocarbamate and/or an antimony dialkyldithiophosphate in an amt. of 0.012-0.20wt.% in terms of antimony. The molybdenum dithiocarbamate used is represented by the formula (wherein X is S or O).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel lubricating oil composition. More specifically, the present invention provides an internal combustion engine, an automatic transmission, a shock absorber, a power steering, etc., which has excellent low wear resistance and does not deteriorate even in an air atmosphere containing nitrogen oxide gas, and has low friction durability for a long period of time. The present invention relates to a lubricating oil composition which can be preferably used as a lubricating oil, especially as a lubricating oil for an internal combustion engine.

[0002]

2. Description of the Related Art Lubricating oil is used in internal combustion engines, drivetrain devices such as automatic transmissions, shock absorbers, power steering systems, gears, etc., in order to ensure smooth operation. In particular, lubricating oil for internal combustion engines is mainly used for lubrication of various sliding parts such as piston rings and cylinder liners, bearings of crankshafts and connecting rods, valve trains including cams and valve lifters, as well as cooling and combustion generation in internal combustion engines. Clean dispersion of things,
In addition, it also acts to prevent rust and corrosion. In this way, various performances are required for internal combustion engine lubricating oils,
Moreover, with the recent improvement in performance of internal combustion engines such as low fuel consumption, high output, and severe operating conditions, a high level of lubricating oil performance has been required. On the other hand, a part of the combustion gas in the internal combustion engine leaks into the crankcase as blow-by gas from between the piston and the cylinder. This combustion gas contains nitrogen oxide gas at a considerably high concentration,
This deteriorates the lubricating oil for the internal combustion engine together with oxygen in the blow-by gas. As the performance of internal combustion engines has improved in recent years, the concentration of nitrogen oxide gas leaking into the crankcase tends to increase. Therefore, the lubricating oil for an internal combustion engine satisfies the above-mentioned required performance and does not deteriorate even under an atmosphere of nitrogen oxide gas-containing air.
Various additives such as antiwear agents, metal detergents, ashless dispersants, and antioxidants are blended. As a basic function of a lubricating oil for an internal combustion engine, it is particularly important to smoothly operate the engine under all conditions to prevent wear and seizure. Although most of the lubrication part in an internal combustion engine is in a fluid lubrication state, boundary lubrication is likely to occur at valve operating systems and top and bottom dead centers of pistons. It is provided by the addition of zinc acid. In an internal combustion engine, since a large amount of energy is lost in a friction portion where lubricating oil is involved, a friction modifier is added to the lubricating oil as a measure for reducing friction loss and fuel consumption. As the friction modifier, for example, organic molybdenum compounds, fatty acid esters, alkylamines, etc. are generally used. On the other hand, it is known that an organic molybdenum compound reduces friction by being adsorbed on a metal surface and then thermally decomposed to form molybdenum disulfide which has a lubricating effect.

[0003]

Under the circumstances described above, the present invention has been earnestly studied, and as a result, the friction modifier has an effect of being added at the initial stage of use, but is oxidatively deteriorated by oxygen in the air. It is found that the effect is lost when exposed to nitrogen oxide gas, and that the effect is significantly reduced especially in the presence of nitrogen oxide gas. The purpose of the invention is to provide a lubricating oil composition that can be maintained.

[0004]

As a result of intensive studies to develop a lubricating oil composition having the above-mentioned preferable properties, the present inventor has a specific hydrocarbon group in a lubricating base oil. Molybdenum dithiocarbamate, zinc dithiophosphate having a specific hydrocarbon group, and antimony dialkyldithiocarbamate or dialkyldithiophosphate having a specific alkyl group, respectively, a lubricating oil composition prepared by blending at a specific ratio, They have found that they can meet the purpose, and have completed the present invention based on this finding. That is, the present invention relates to a lubricating base oil, (A) molybdenum dithiocarbamate having a hydrocarbon group having 8 to 18 carbon atoms, and (B) dithiophosphorus having a hydrocarbon group having 1 to 18 carbon atoms. A lubricating oil composition comprising zinc acid salt and (C) an antimony dialkyldithiocarbamate and / or an antimony dialkyldithiophosphate having an alkyl group having 2 to 18 carbon atoms,
Based on the total weight of the composition, the amount of molybdenum derived from molybdenum dithiocarbamate is 200 to 2000 ppm (weight ratio), the amount of phosphorus derived from zinc dithiophosphate is 0.02 to 0.15% by weight, The amount of antimony derived from antimony dialkyldithiocarbamate and / or antimony dialkyldithiophosphate is 0.012-0.
The lubricating oil composition is characterized by being 20% by weight.

The present invention will be described in detail below. The lubricating base oil used in the lubricating oil composition of the present invention is not particularly limited, and those conventionally used as a base oil for lubricating oil, such as mineral oil and synthetic oil, can be used. As mineral oil, raffinate obtained by solvent refining a lubricating oil raw material with an aromatic extraction solvent such as phenol or furfural, hydrotreated oil obtained by hydrotreatment, or lubricating oil fraction obtained by isomerization of wax Mineral oils such as min, eg 60 neutral oil, 100 neutral oil, 150 neutral oil, 300 neutral oil, 5
Examples include 00 neutral oil and bright stock. On the other hand, as synthetic oil, for example, poly α-
Examples thereof include olefin oligomer, polybutene, alkylbenzene, polyol ester, polyglycol ester, dibasic acid ester, phosphoric acid ester and silicone oil. These base oils may be used alone or in combination of two or more,
Further, a mixture of mineral oil and synthetic oil may be used. As the base oil used in the lubricating oil composition of the present invention, those having a viscosity at 100 ° C. in the range of 3 to 20 cSt are suitable, and among them, the aromatic component is 3% by weight or less and the sulfur content is 50 pp.
Hydrocracked oils and / or wax isomerized oils with m or less and nitrogen content of 50 ppm or less are particularly suitable.

The molybdenum dithiocarbamate to be added to the lubricating oil composition of the present invention has the general formula [1]

Embedded image (In the formula, R ¹ , R ² , R ³ and R ⁴ are each a hydrocarbon group having 8 to 18 carbon atoms, which may be the same or different, and X is S or O. ) Is used. In the general formula [1], R ¹ ,
R ² , R ³ and R ⁴ are hydrocarbon groups having 8 to 18 carbon atoms, and are linear or branched alkyl groups or alkenyl groups having 8 to 18 carbon atoms, cycloalkyl groups having 8 to 18 carbon atoms, Examples thereof include an aryl group, an alkylaryl group and an arylalkyl group. Specific examples of such compounds include 2-ethylhexyl group, n-octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, stearyl group, oleyl group. , Butylphenyl group, nonylphenyl group and the like. A preferred hydrocarbon group is a hydrocarbon group having 8 to 13 carbon atoms. The hydrocarbon groups R ¹ , R ² , R ³ and R ⁴ of molybdenum dithiocarbamate represented by the general formula [1] have 8 carbon atoms.
If it is less than 18 or more than 18, the compatibility of molybdenum dithiocarbamate in the lubricating oil composition may be insufficient. In the lubricating oil composition of the present invention,
One type of molybdenum dithiocarbamate can be used, or two or more types can be used in combination. In the lubricating oil composition of the present invention, molybdenum dithiocarbamate has an amount of molybdenum derived from molybdenum dithiocarbamate of 200, based on the total weight of the composition.
~ 2000ppm (weight ratio), preferably 30
Add 0 to 800ppm (weight ratio). When the blending amount of molybdenum dithiocarbamate is such that the amount of molybdenum derived from molybdenum dithiocarbamate is less than 200 ppm (weight ratio) based on the total weight of the composition,
The effect of improving the friction characteristics (low friction) is not sufficiently exerted, and the amount of molybdenum dithiocarbamate is more than 2000 ppm (weight ratio) based on the total weight of the composition. If so, the improvement of the effect commensurate with the increase of the blending amount is not recognized, and sludge is likely to be a cause.

The zinc dithiophosphate to be added to the lubricating oil composition of the present invention has the general formula [2]

Embedded image (However, in the formula, R ⁵ , R ⁶ , R ⁷ and R ⁸ have 1 to 1 carbon atoms.
8 hydrocarbon groups, which may be the same or different from each other. ) Is used. In the general formula [2], R ⁵ , R ⁶ , R ⁷ and R ⁸ have 1 to 10 carbon atoms.
18 hydrocarbon group, which is a linear or branched alkyl group or alkenyl group having 1 to 18 carbon atoms, 6 to 18 carbon atoms
And a cycloalkyl group, an aryl group, an alkylaryl group, or an arylalkyl group. Specific examples of such a group include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group,
Octyl group, 2-ethylhexyl group, n-octyl group,
Decyl group, undecyl group, dodecyl group, tridecyl group,
Examples thereof include a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, a stearyl group, an oleyl group, a butylphenyl group, and a nonylphenyl group. A preferred hydrocarbon group is a hydrocarbon group having 3 to 12 carbon atoms.
When the hydrocarbon groups R ⁵ , R ⁶ , R ⁷ and R ⁸ of the zinc dithiophosphate represented by the general formula [2] have more than 18 carbon atoms, the antiwear effect in the lubricating oil composition becomes insufficient. There is. In the lubricating oil composition of the present invention, zinc dithiophosphate is preferably added so that the amount of phosphorus derived from zinc dithiophosphate is 0.02 to 0.15% by weight based on the total weight of the composition. It is blended so as to be 04 to 0.12% by weight.
When the amount of zinc dithiophosphate mixed is such that the amount of phosphorus derived from zinc dithiophosphate is less than 0.02% by weight based on the total weight of the composition, abrasion resistance becomes insufficient and high Satisfactory low friction properties cannot be obtained under operating conditions of oil temperature and low speed rotation, and the amount of zinc dithiophosphate derived from zinc dithiophosphate based on the total weight of the composition is 0.
If it exceeds 15% by weight, the improvement of the effect commensurate with the increase of the compounding amount is not recognized.

The antimony dialkyldithiocarbamate to be added to the lubricating oil composition of the present invention has the general formula [3]

Embedded image (In the formula, R ⁹ and R ¹⁰ are alkyl groups having 2 to 18 carbon atoms, and they may be the same or different from each other.) And / or the general formula [ 4]

[Chemical 4] (However, in the formula, R ¹¹ and R ¹² are alkyl groups having 2 to 18 carbon atoms, and they may be the same or different from each other.) An antimony dialkyldithiophosphate is used. In general formula [3] and general formula [4],
Examples of the alkyl group having 2 to 18 carbon atoms represented by R ⁹ , R ¹⁰ , R ¹¹ and R ¹² include ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group and decyl group. A group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group or an octadecyl group, and these alkyl groups may be linear or branched. When the alkyl groups R ⁹ , R ¹⁰ , R ¹¹ and R ¹² of the antimony dialkyldithiocarbamate and antimony dialkyldithiophosphate represented by the general formulas [3] and [4] exceed 18, the lubricating oil The solubility of antimony dialkyldithiocarbamate and antimony dialkyldithiophosphate in the composition increases in the base oil, and the function of supplying sulfur to the friction surface may become insufficient.

In the lubricating oil composition of the present invention, the antimony dialkyldithiocarbamate and / or the antimony dialkyldithiophosphate is based on the total weight of the composition of the antimony dialkyldithiocarbamate and / or the antimony dialkyldithiophosphate. The amount is 0.012 to 0.20% by weight, preferably 0.02 to 0.15% by weight. The amount of antimony dialkyldithiocarbamate and / or antimony dialkyldithiophosphate is less than 0.012% by weight based on the total weight of the composition, since the amount of antimony derived from dialkyldithiocarbamate and / or antimony dialkyldithiophosphate is less than 0.012% by weight. If the amount is large, the function of supplying sulfur and antimony to the friction surface becomes insufficient,
The friction reducing effect of an internal combustion engine cannot be maintained for a long period of time, and the compounding amount of antimony dialkyldithiocarbamate and / or antimony dialkyldithiophosphate is based on the total weight of the composition. When the amount of antimony derived from antimony is more than 0.20% by weight, the improvement of the effect commensurate with the increase of the compounding amount is not recognized. In the lubricating oil composition of the present invention, the sulfur supplied from the antimony dialkyldithiocarbamate or the antimony dialkyldithiophosphate compensates for the decrease in the sulfur supply function due to the consumption of zinc dithiophosphate to form molybdenum sulfide, which forms a molybdenum sulfide film. The repair ability is enhanced, and a strong molybdenum sulfide film is formed by the synergistic effect of molybdenum sulfide and antimony trioxide formed on the friction surface.

The lubricating oil composition of the present invention contains various additives conventionally used in lubricating oils, such as other friction modifiers, metal detergents, and other additives, as long as the object of the present invention is not impaired. An antiwear agent, an ashless dispersant, an antioxidant, a viscosity index improver, a pour point depressant, a defoaming agent, a rust preventive, a corrosion inhibitor and the like can be appropriately added. Other friction modifiers include
For example, polyhydric alcohol partial ester, amine, amide, sulfurized ester and the like can be mentioned. Examples of the metal detergent include calcium sulfonate, magnesium sulfonate, calcium phenate, magnesium phenate, calcium salicylate, magnesium salicylate and the like, and these are usually used in a proportion of 0.1 to 5% by weight. . Other antiwear agents include, for example, thiophosphoric acid metal salts, sulfur compounds, phosphoric acid esters, phosphorous acid esters, etc., which are usually used in a proportion of 0.05 to 5.0% by weight. To be done. As the ashless dispersant, for example, benzylamine,
Examples thereof include a boron derivative of benzylamine, a polyalkenyl succinimide, and a boron derivative of a polyalkenyl succinimide, and these are usually 0.5 to 7
Used in percentage by weight. Examples of the antioxidant include amine-based antioxidants such as alkylated diphenylamine, phenyl-α-naphthylamine and alkylated-α-naphthylamine, 2,6-di-t-butyl-4-methylphenol, 4,4 '-Methylenebis (2,6-di-t
-Butylphenol), 4,4'-thiobis- (6-t-
(Butyl-o-cresol) and the like, and phenolic antioxidants and the like, which are usually 0.05 to 4
Used in percentage by weight. As a viscosity index improver,
For example, polymethacrylate type, polyisobutylene type,
An ethylene-propylene copolymer system, a styrene-butadiene hydrogenation copolymer system, etc. can be mentioned.
It is usually used in a proportion of 0.5 to 35% by weight. As the pour point depressant, for example, polyalkyl methacrylate,
Examples thereof include chlorinated paraffin-naphthalene condensate and alkylated polystyrene. As an antifoaming agent,
For example, dimethyl polysiloxane, polyacrylic acid, etc. can be mentioned. Examples of the rust preventive agent include fatty acids, alkenyl succinic acid partial esters, fatty acid soaps, alkyl sulfonates, fatty acid polyhydric alcohol esters, fatty acid amines, oxidized paraffin, and alkyl polyoxyethylene ethers. Examples of the corrosion inhibitor include benzotriazole and benzimidazole.

[0011]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The coefficient of friction of the lubricating oil composition was measured using a reciprocating sliding friction tester [SRV friction tester] with a frequency of 50 Hz, an amplitude of 3 mm, a load of 25 N and a temperature of 80.
It was measured at a temperature of 25 ° C. for a test time of 25 minutes. The oxidation test using nitrogen oxide gas-containing air was carried out at a temperature of 130 ° C. and a nitrogen oxide gas concentration of 1% by volume for 150 ml of test oil.
(Air 99% by volume), flow rate 2 liters / hour, test time 8
Went in time. Examples 1 to 7 and Comparative Examples 1 to 3 Examples 1 to 7 are (A) molybdenum dithiocarbamate, (B) zinc dithiophosphate, (C) antimony dialkyldithiocarbamate or antimony dialkyldithiophosphate, and other additions. A lubricating oil composition containing an agent (metal detergent, ashless dispersant, viscosity index improver).
Further, Comparative Examples 1 to 3 are lubricating oil compositions containing the component (A), the component (B) and other additives but not the component (C). Base oil (100 neutral oil, 10
The kinematic viscosity at 0 ° C. was 4.4 mm / s ² ) and a lubricating oil composition containing each type and amount of each compounding component and other additive components shown in Table 1 was prepared, and the friction coefficient immediately after adjustment was adjusted. , And in the presence of nitrogen oxide gas, the temperature was kept at 130 ° C. for 8 hours to oxidize, and the friction coefficient was measured. The results are shown in Table 1.

[0012]

[Table 1]

(Note) C ₈ -MoDTC: N, N-dioctyldithiocarbamate molybdenum C ₁₃ -MoDTC: N, N-ditridecyldithiocarbamate molybdenum C ₈ -ZnDTP (primary): di-2-ethylhexyldithiophosphorus Zinc acid salt C ₆ -ZnDTP (secondary): Zinc di-1-ethylbutyldithiophosphate SbDTC: N, N-di-2-ethylhexyl dithiocarbamate antimony SbDTP: Antimony dihexyldithiophosphate Phosphate Each of the lubricating oil compositions of the present invention has a low friction coefficient and shows good friction characteristics, and the friction coefficient remains almost unchanged even after being heated at 130 ° C. for 8 hours in the presence of nitrogen oxide gas for oxidation. It can be seen that these lubricating oil compositions have good oxidation resistance. On the other hand, the lubricating oil compositions of Comparative Examples 1 to 3 which do not contain the antimony compound as the component (C) have a low coefficient of friction immediately after preparation, but in the presence of nitrogen oxide gas, at 130 ° C. for 8 hours. It can be seen that after heating and oxidation, the friction coefficient increases and the oxidation resistance is poor.

[0014]

The lubricating oil composition of the present invention is prepared by blending molybdenum dithiocarbamate, zinc dithiophosphate and antimony dialkyldithiocarbamate and / or antimony dialkyldithiophosphate with a specific structure into a base oil. In addition to having excellent low wear properties,
Lubricating oil for internal combustion engines, automatic transmissions, shock absorbers, power steering, etc., exhibiting oxidation resistance even in the presence of nitrogen oxide gas and maintaining good friction characteristics (low friction), especially internal combustion engines Can be suitably used as a lubricating oil for
A good fuel consumption rate can be maintained.

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Claims (1)

[Claims] 1. A lubricating base oil having (A) a carbon number of 8 to
Molybdenum dithiocarbamate having 18 hydrocarbon groups, (B) zinc dithiophosphate having a hydrocarbon group having 1 to 18 carbon atoms, and (C) antimony dialkyldithiocarbamate having an alkyl group having 2 to 18 carbon atoms And / or a lubricating oil composition containing antimony dialkyldithiophosphate, which is based on the total weight of the composition,
The amount of molybdenum derived from molybdenum dithiocarbamate is 200 to 2000 ppm (weight ratio), and the amount of phosphorus derived from zinc dithiophosphate is 0.02 to 0.15% by weight.
And the amount of antimony derived from antimony dialkyldithiocarbamate and / or antimony dialkyldithiophosphate is 0.012 to 0.20% by weight.