JP2971748B2 - Engine oil composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine oil composition for an automobile, and more particularly to a long-life fuel-saving engine oil composition capable of maintaining a low engine friction loss for a long period of time. is there.

[0002]

2. Description of the Related Art With the advancement of engines, various performances such as abrasion resistance, oxidative stability, and clean dispersibility have been required for automotive engine oil compositions (hereinafter simply referred to as engine oils). ing. In recent years, in order to suppress global warming due to an increase in CO ₂ in the atmosphere, etc., it has become an important issue to reduce fuel consumption of automobiles, and fuel oil has also been strongly required for engine oils. .

[0003] Normally, engine oils are constituted by blending additives such as a detergent / dispersant, an antioxidant, an antiwear agent and a viscosity index improver with a base oil refined from petroleum. In order to improve the fuel efficiency of the engine oil, there is a method of lowering the viscosity of the engine oil by lowering the viscosity of the base oil or changing the viscosity index improver. However, in a region where the viscosity does not contribute to friction reduction, such as a boundary lubrication region, the friction cannot be reduced with the above-described ordinary engine oil. Therefore, in recent years, a friction modifier (FM) has been added to engine oil to reduce friction in a boundary lubrication region. Among the friction modifiers, as shown in JP-B-3-23595,
Molybdenum dithiocarbamate (MoDTC) and oxymolybdenum sulfide organophosphorodithioate (MoD
It is known that an organic molybdenum compound such as TP) has a high effect.

[0004]

However, these organic molybdenum compounds have been used with the use of engine oils.
It is oxidized and decreases. Therefore, even if the fuel economy is excellent at the time of the new oil, there is a problem that the fuel economy of the engine oil is lost as the operating time elapses. In order to improve this, it is conceivable to increase the amount of the organic molybdenum compound added when fresh oil is used. However, simply increasing the amount of the organic molybdenum compound is not economically preferable because the product cost increases. Further, among organic molybdenum compounds, MoDTP
Since phosphorus contains phosphorus, a deposit of a phosphorus compound may be formed on the surface of the exhaust gas catalyst and the catalytic activity may be reduced. Therefore, the amount of phosphorus cannot be increased to a certain extent.

[0005] On the other hand, since MoDTC does not contain phosphorus, even if its amount is increased, the catalytic activity does not decrease. However, MoDTC has a small friction relaxation effect, and to compensate for this, it is conceivable to use MoDTC in combination with zinc dithiophosphate (ZnDTP), which is an antiwear agent. Originally, ZnDTP is frequently used in engine oils as an antioxidant and an antiwear agent, but contains phosphorus and has an adverse effect on exhaust gas catalysts as described above. There is a problem that the effect cannot be maintained for a long time. Also, M
It has been proposed to use oDTC in combination with a sulfur-based extreme pressure agent (Japanese Patent Publication No. 5-83599). Although this combination does not adversely affect the exhaust gas catalyst, it has a serious practical problem for engine oils such as high wear of the valve train.

Accordingly, an object of the present invention is to make it possible to maintain low friction loss even when engine oil is used for a long period of time. Another object of the present invention is to make it possible to maintain low friction loss over a long period of time while maintaining the same amount of friction modifier as before. Another object of the present invention is to make it possible to maintain a low friction loss over a long period of time without adversely affecting the exhaust gas catalytic activity.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and as a result, MoDTC
By combining a predetermined polysulfide compound with ZnDTP and ZnDTP, or by combining a polysulfide compound with MoDTC and a predetermined ZnDTP, the life of fuel economy can be remarkably improved without adversely affecting the exhaust gas catalyst. Found that it was possible to maintain the friction reducing effect of oil for a long time,
The present invention has been completed.

That is, the present invention provides a base oil comprising a mineral oil and / or a synthetic lubricating oil and molybdenum dithiocarbamate in an amount of 50 to 2,000 ppm by weight of molybdenum (Mo).
The zinc dithiophosphate is used in an amount of 0.01 to 0.1 as phosphorus (P).
2% by weight, and a thiadiazole-type polysulfide compound or an ashless organic polysulfide compound having a sulfur atom group in which three or more sulfur atoms are bonded adjacent to each other in a molecular structure is defined as a sulfur (S) amount of 0.01 to 0.1%. The present invention relates to an engine oil composition characterized by containing 4% by weight, and the present invention uses a mineral oil and / or a synthetic lubricating oil as a base oil, and uses molybdenum dithiocarbamate as a molybdenum (Mo) amount of 50 to 50%. A predetermined zinc dithiophosphate having a secondary or tertiary alkyl group or an aryl group having 3 to 18 carbon atoms in an amount of 2000 ppm by weight is converted to phosphorus (P)
Ashless organic polysulfide compound in an amount of 0.01 to 0.2% by weight as sulfur (S).
The present invention relates to an engine oil composition characterized by containing 4% by weight, and to a long-life fuel-saving engine oil composition capable of maintaining a low friction loss for a long period of time.

The base oil that can be used in the present engine oil composition is a mineral oil or a synthetic oil of a lubricating oil fraction. Any base oil can be used. Specifically, as the mineral oil, a fraction obtained by vacuum distillation of a normal pressure distillation residue such as a paraffinic crude oil is subjected to a treatment such as solvent extraction with furfural or the like, hydrorefining, solvent dewaxing with MEK / toluene or the like. Base oil obtained by treating by the method, lubricating base oil obtained by treating the deasphalted oil obtained by deasphalting the residue of the vacuum distillation by the above-mentioned appropriate treatment method, slack wax The appropriate fraction of the isomerized oil obtained by hydroisomerizing
A highly refined base oil obtained by dewaxing a K / toluene solvent, a mixture thereof and the like can be used.

Examples of synthetic oils include α-olefin oligomers, diesters synthesized from dibasic acids such as adipic acid and primary alcohols, and high alcohols such as neopentyl glycol, trimethylolpropane and pentaerythritol. Examples include polyol esters, alkylbenzenes, polyoxyalkylene glycols, and mixtures thereof, which are synthesized from a basic acid. Further, it goes without saying that a mixed oil obtained by combining an appropriate mineral oil and a synthetic oil can also be used as the base oil of the present engine oil.

The molybdenum dithiocarbamate (MoDTC) used as an additive in the present invention has the following general formula (1)
It is a compound represented by these.

[0012]

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In the general formula (1), R represents a group having 4 to 4 carbon atoms.
Linear and / or branched alkyl groups having 18 and / or
Or X represents an oxygen atom or a sulfur atom, and the ratio of the oxygen atom to the sulfur atom is 1/3 to 3/1.
It is. R is preferably an alkyl group, and specific examples include a butyl group, a 2-diethylhexyl group, an isotridecyl group, and a stearyl group. The four Rs present in one molecule may be the same or different. Further, two or more MoDTCs having different Rs may be used in combination.

The amount of MoDTC added is molybdenum (M
o) It is 50 to 2000 ppm by weight, more preferably 300 to 1000 ppm by weight in terms of amount. If the addition amount is 50 ppm by weight, the effect of reducing friction is small, and even if added at 2000 ppm by weight or more, the effect of reducing friction is saturated and the cost increases.

The zinc dithiophosphate (ZnDTP) used as an additive in the present invention is a compound represented by the following general formula (2).

[0016]

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In the general formula (2), R ′ has 3 carbon atoms.
A straight-chain and / or branched alkyl group or aryl group having up to 18 groups. As R ′, an alkyl group, particularly a primary (primary) type alkyl group, is more preferable from the viewpoint of maintaining friction-reducing performance over a long period of time. Specifically, propyl, butyl, pentyl Group, hexyl group, octyl group, lauryl group and the like. Two R's present in one molecule may be the same or different. Further, two or more kinds of ZnDTPs having different R ′ may be used in combination.

The amount of ZnDTP added is 0.01 to 0.3% by weight based on the amount of phosphorus (P).
0.04 to 0.2% by weight, more preferably 0.04 to 0.2% by weight.
4 to 0.1% by weight. This added amount is 0.01% by weight
When the amount is less than the above, the wear prevention performance of the valve train is impaired. On the other hand, when the amount exceeds 0.3% by weight, the influence of the phosphorus component on the exhaust gas catalytic activity is great.

The ashless organic polysulfide compound used in the present invention has a sulfur atom group in which two or more sulfur atoms are adjacently bonded to each other in the molecular structure. Organic compound represented by the following general formula:

[0020]

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In the above general formula, R ₁ and R ₂ represent a chain, cyclic (alicyclic and aromatic) or a hydrocarbon group containing these in combination. Although unsaturated bonds may be present, saturated hydrocarbon groups are preferred. Among them, an alkyl group, an aryl group, an alkylaryl group,
Benzyl groups and alkylbenzyl groups are preferred. R ₃ and R ₄ have a binding site of 2 which is linear, cyclic (alicyclic and aromatic), or a combination thereof.
Represents a hydrocarbon group having one, and is particularly preferably an alkylene group. R ₅ and R ₆ represent a chain hydrocarbon group, and particularly preferably an alkyl group. x and y are integers of 2 or more.

More specifically, sulfurized coconut oil, sulfurized pinene oil, sulfurized soybean oil, sulfurized polyolefin, dialkyl disulfide, dialkyl polysulfide, dibenzyl disulfide, ditertiary butyl disulfide, polyolefin polysulfide, bisalkyl polysulfanyl Thiadiazole, sulfurized phenol and the like. Among these compounds, dialkyl polysulfide and dibenzyl disulfide are preferable,
Bisalkyl polysulfanyl thiadiazoles are particularly preferred.

As a lubricating oil additive, a compound containing a metal such as Ca phenate containing a polysulfide bond is used, but this is not preferred because of its high coefficient of friction. On the other hand, the above-mentioned organic polysulfide compounds are ashless containing no metal,
When used in combination with oDTC and ZnDTP, it exhibits excellent performance of maintaining a low coefficient of friction for a long period of time.

The amount of the ashless organic polysulfide compound (hereinafter referred to as polysulfide compound) is as follows:
It is added to the finished lubricating oil so as to be contained in an amount of 0.01 to 0.4% by weight based on the amount of sulfur (S).
Preferably, it is 0.1-0.3% by weight, more preferably 0.2-0.3% by weight. If it is less than 0.01% by weight, it is difficult to obtain the desired effect, and if it exceeds 0.4% by weight, there is a risk that corrosion wear will increase. It goes without saying that the above-mentioned polysulfide compounds can be used alone or in combination of two or more.

The engine oil of the present invention can further improve the overall performance by appropriately adding an engine oil additive other than those described above, if necessary, in order to ensure the performance suitable for the intended use. As such an engine oil additive,
So-called metallic detergents and dispersants such as sulfonates, phenates and salicylates of alkaline earth metals such as Ca, Mg and Ba and alkali metals such as Na; ashless such as alkenyl succinimide, succinate, succinamide and benzylamine Examples include a dispersant, a phenolic antioxidant such as bisphenol, an amine antioxidant such as diphenylamine, and a viscosity index improver such as an olefin copolymer and polymethacrylate. Further, an engine oil additive such as a pour point depressant, a rust preventive and an antifoaming agent may be appropriately added.

[0026]

EXAMPLES The present invention will be described in more detail with reference to Examples, Test Examples and Comparative Examples. Using mineral oil 1 and mineral oil 2 having the following properties as base oils, lubricating oils of Examples, Test Examples and Comparative Examples were prepared.

[0027]

[Table 1]

The following additives were used. MoDTC: a compound of the general formula (1), wherein R is a 2-ethylhexyl group. Sulfur-based additive 1: Sulfur-based additive refers to an additive having a polysulfide compound used in the present invention, and this sulfur-based additive 1 contains a thiadiazole-type polysulfide compound represented by the following formula, Is 3 in the additive
6% by weight is contained.

[0029]

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Sulfur-based additive 2: An additive containing a sulfurized oil-fat type polysulfide compound, and the sulfur content is 10.5% by weight in the additive. Sulfur-based additive 3: An additive containing dibenzyl disulfide, and the sulfur content is 25.5% by weight in the additive.

ZnDTP1: a compound of the general formula (2), wherein R ′ is a 2-ethylhexyl group and a primary type alkyl group. ZnDTP2: a compound of the general formula (2),
R ′ is a compound of an isopropyl group, a compound of an isohexyl group and a mixture of the above-mentioned compounds having both alkyl groups, wherein the alkyl group is a secondary type compound. Additive package: consisting of metal-based detergent, ashless dispersant, phenol-based antioxidant, amine-based antioxidant, viscosity index improver, rust inhibitor and defoamer.

These base oils and the respective additives were mixed at the ratios shown in Table 3 to obtain the long-life fuel-saving engine oil compositions of the present invention shown in Examples 1 to 3 and the engine oil compositions shown in the test examples. Comparative Example 1
-8 engine oil compositions were prepared. In Tables 3 and 5, each numerical value indicates the blending ratio in the unit of “% by weight”, but indicates the defoaming agent in the unit of ppm. With respect to the engine oil compositions of Examples, Test Examples and Comparative Examples thus prepared, the friction characteristics and the wear performance of the valve train were evaluated by the following methods.

(1) Friction characteristics The friction coefficient of the new oil and the deteriorated oil was measured using an SRV tester under the following conditions.

[0034]

[Table 2]

The coefficient of friction was determined from the average coefficient of friction during the last 20 minutes of the test. The deteriorated oil was obtained by simulating actual vehicle running using the following engine. That is, a bench durability test was performed in an AMA traveling mode at an oil temperature of 100 ° C. and a water temperature of 100 ° C., and after 160 hours (corresponding to 4000 km) and 400 hours (corresponding to 10,000 km), engine oil was sampled, and the friction was determined as a degraded oil. Tested.

(2) Valve train wear test For each engine oil, the Japanese Automobile Engineers Association regulations (JAS
OM328-91), a valve train wear test was performed to evaluate the scuffing of the rocker arm and the wear amount of the cam nose. The evaluation results are shown in Table 4 for Examples 1 to 3 and Test Examples 1 and 2, and in Table 6 for Comparative Examples 1 to 8. However, in Tables 4 and 6, the scuffing of rocker arms was evaluated from 0 to 1
A score between 0.0 and 10.0 indicates good and 0 indicates bad.

[0037]

[Table 3]

[0038]

[Table 4]

[0039]

[Table 5]

[0040]

[Table 6]

Example 1 and Test Examples 1 and 2 in Table 3 are engine oils using mineral oil 1 and thiadiazole-type compounds, sulfurized oil-and-fat type compounds, and dibenzyldisulfide as polysulfide compounds, respectively.
Is an engine oil obtained by replacing the mineral oil 1 of Example 1 with a more highly refined mineral oil 2, and Example 3 is an example in which a secondary type ZnDTP is used.

In Table 5, Comparative Example 1 shows an engine oil containing no polysulfide compound, Comparative Example 2 shows an engine oil containing a large amount of ZnDTP, Comparative Example 3 shows an engine oil containing no ZnDTP, and Comparative Example 4 shows a comparative example. Engine oil in which the base oil of Example 1 was replaced by highly refined mineral oil 2, Comparative Example 5 was an engine oil containing no MoDTC, and Comparative Example 6 was M
oDTC, engine oil containing no polysulfide compound, Comparative Example 7 was ZnDTP, engine oil containing no polysulfide compound, Comparative Example 8 was MoDTC, Zn
Engine oil containing no DTP.

Comparing Tables 4 and 6, the engine oils of the examples and test examples are clearly different from those of the comparative example, especially when the new oil has almost no difference in friction coefficient even after being deteriorated for 400 hours. It can be seen that the change in the coefficient of friction is small even after long-term use.

For example, comparing Example 1 with Comparative Example 1 and Example 2 with Comparative Example 4, the use of a polysulfide compound also significantly reduced the friction coefficient especially after 400 hours. Comparing Example 1 with Comparative Example 3, in Comparative Example 3, not using ZnDTP, not only the coefficient of friction after 400 hours had elapsed but also the cam nose wear increased significantly. . When Example 4 is compared with Comparative Examples 5 and 6, in Comparative Examples 5 and 6, since MoDTC was not used in combination, the friction coefficient was high from the beginning. Comparative Example 7
Since not using ZnDTP and a polysulfide compound, not only the friction coefficient after the elapse of 400 hours was high but also the cam nose wear amount was significantly increased. In Comparative Example 8, since both MoDTC and ZnDTP were not used, the friction coefficient was high from the beginning, and the cam nose wear was extremely high.

[0045]

The present invention provides an engine oil composition comprising a combination of MoDTC and ZnDTP with a predetermined ashless organic polysulfide compound, or a combination of MoDTC and a predetermined ZnDTP with a polysulfide compound, and adding a specific amount of each. Even if MoDTC or ZnDTP is not added in a particularly large amount, a low coefficient of friction can be maintained for a long-term use, so that it is filled and used in automobiles, and has a special effect on fuel saving and environmental protection. .

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C10M 135: 26 135: 28 135: 30 135: 36) C10N 10:04 10:12 30:06 40:25 (58) Field (Int.Cl. ⁶ , DB name) C10M 141/10 C10M 135/18-135/36 C10M 137/10 C10N 30:06 C10N 40:25 EPAT (QUESTEL) WPI / L (QUESTEL)

Claims (2)

(57) [Claims] 1. A mineral oil and / or synthetic lubricating oil as a base oil,
Molybdenum dithiocarbamate has a molybdenum (Mo) content of 50 to 2000 ppm by weight, and zinc dithiophosphate has a phosphorus (P) content of 0.01 to 0.
2% by weight, and a thiadiazole-type polysulfide compound or an ashless organic polysulfide compound having a sulfur atom group in which three or more sulfur atoms are bonded adjacent to each other in a molecular structure is defined as a sulfur (S) amount of 0.01 to 0.1%. An engine oil composition containing 4% by weight. 2. A mineral oil and / or synthetic lubricating oil as a base oil,
Molybdenum dithiocarbamate is molybdenum (Mo) in an amount of 50 to 2000 ppm by weight, and has the following general formula: (Wherein, R represents a secondary or tertiary alkyl group or an aryl group having 3 to 18 carbon atoms). An engine oil composition comprising 2% by weight and 0.01 to 0.4% by weight of an ashless organic polysulfide compound as sulfur (S).