JPH06207191A - Lubricating oil composition - Google Patents

Abstract

PURPOSE:To obtain a lubricating oil composition suitable for automobile internal combustion engines, etc., being made by blending a dialkyl dithiophosphate having a specific alkyl with a lubricating base oil and giving a low friction coefficient under a driving condition at high oil temperature and low rate of rotation. CONSTITUTION:To (A) a lubricant base oil is compounded (B) a dialkyl dithiophosphate having 10-25C primary alkyl, 0.2-3wt.% dialkyl dithiophosphate containing zinc in >=50 molar % zinc based on the total zinc amount in the total dialkyl dithiophosphate based on the total amount of the composition, to obtain the objective composition. E.g. a light neutral oil, poly alpha-olefin, etc., can be used. Further, in addition to the component B, it is preferable to compound a compound selected from sulfoxymolybdenum organophosphorodithioates having 1-20C hydrocarbon and sulfoxymolybdenum dithiocarbamates having 1-20C hydrocarbon in order to make the friction characteristics of the above- mentioned composition excellent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel lubricating oil composition, and more particularly to an internal combustion engine, such as an automobile engine, which provides a low friction coefficient under a wide range of use conditions, especially at operating conditions of high oil temperature and low speed rotation. And a lubricating oil composition suitable as a lubricating oil for automobiles such as gear oil, ATF, and shock absorber oil.

[0002]

2. Description of the Related Art Conventionally, lubricating oils have been 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 (engine oil) mainly lubricates various sliding parts, such as piston rings and cylinder liners, bearings for crankshafts and connecting rods (connecting rods), valve trains including cams and valve lifters, etc. It functions to cool the engine, cleanly disperse combustion products, and prevent rust and corrosion. As described above, lubricating oils for internal combustion engines are required to have various performances, and in recent years, high performances have been required as the performances, output power, and operating conditions of internal combustion engines have become more severe. . Therefore,
In order to satisfy such required performance, the lubricating oil for internal combustion engine may be, for example, an antiwear agent, a metal detergent, an ashless dispersant,
Various additives such as antioxidants are blended. As a basic function of a lubricating oil for an internal combustion engine, it is important to operate the engine smoothly under all conditions to prevent wear and seizure. Most of the engine lubrication part is in a fluid lubrication state, but boundary lubrication is likely to occur at the valve operating system and the top and bottom dead center of the piston, and the wear prevention property under such boundary lubrication is generally zinc dithiophosphate ( ZnDTP)
And zinc dithiocarbamate (ZnDTC). By the way, in an internal combustion engine, energy loss is large in a friction portion where lubricating oil is involved.
As a measure to reduce friction loss and fuel consumption, a friction modifier (F
(M: Friction modifier), and lubricating oils in which various additives are combined are used (for example, Japanese Patent Publication No. 3-23595). Lubricating oils for internal combustion engines of automobiles are operated at various oil temperatures, rotational speeds, and loads. Therefore, in order to further improve fuel consumption, it is necessary to have excellent friction characteristics under a wide range of use conditions. Conventionally, there have been combinations of ZnDTP, succinimide, calcium sulfonate, sulfurized oxymolybdenum dithiocarbamate (MoDTC), etc. in order to lower the coefficient of friction. As the ZnDTP, those mainly having a secondary alkyl group are used. Zn having a primary alkyl group
DTP was at most about 40 mol% of the total zinc content. However, such a lubricating oil has a problem that a sufficiently low friction coefficient cannot be obtained under operating conditions of high oil temperature and low speed rotation.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a lubricating oil composition which provides a low friction coefficient under a wide range of conditions suitable for use as a lubricating oil for internal combustion engines of automobiles, especially under operating conditions of high oil temperature and low speed rotation. It is made for the purpose of providing.

[0004]

DISCLOSURE OF THE INVENTION As a result of intensive studies to develop a lubricating oil composition having the above-mentioned preferable properties, the present inventors have found that the lubricating base oil has a specific alkyl group. Zinc dialkyldithiophosphate, and optionally a sulfurized oxymolybdenum organophosphorodithioate or a sulfurized oxymolybdenum dithiocarbamate, a lubricating oil composition containing a specific proportion, respectively, found that it can meet the purpose, The present invention has been completed based on this finding. That is, the present invention provides zinc dialkyldithiophosphate having a primary alkyl group having 10 to 25 carbon atoms, based on the total weight of the composition, based on the total weight of the lubricating base oil, and the zinc content thereof is 50% of the total zinc content. A lubricating oil composition comprising 0.2 to 3.0% by weight of zinc dialkyldithiophosphate contained in an amount of at least mol%, and (A) 0.2 to 3 of the zinc dialkyldithiophosphate. 0.0% by weight, and (B) the sulfurized oxymolybdenum organophosphorodithioate having 1 to 20 carbon atoms of the hydrocarbon group and the hydrocarbon group having 1 to 20 carbon atoms.
The present invention provides a lubricating oil composition comprising 0.01 to 10% by weight of at least one selected from 20 sulfurized oxymolybdenum dithiocarbamates.

The present invention will be described in detail below. There is no particular limitation on the lubricating base oil used in the composition of the present invention, those conventionally used as the base oil of conventional lubricating oils,
For example, mineral oil or synthetic oil is used. Examples of the mineral oil include light neutral oil, medium neutral oil, heavy neutral oil, and bright stock. On the other hand, examples of the synthetic oil include poly α-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 two or more kinds may be used in combination, or a mineral oil and a synthetic base oil may be mixed and used. The base oil preferably has a kinematic viscosity at a temperature of 100 ° C. usually in the range of 3 to 20 cSt. The zinc dialkyldithiophosphate used in the lubricating oil composition of the present invention has the general formula

[0006]

[Chemical 1]

(Wherein R ¹ and R ² have 10 to 25 carbon atoms,
Dialkyldithiophosphorus having a long-chain primary alkyl group having 10 to 25 carbon atoms, preferably 12 to 20 primary alkyl groups, which may be the same or different from each other. Zinc acidate (ZnDT
P) in an amount of 50 mol% or more of the total zinc content in the zinc dialkyldithiophosphate (Zn).
It is necessary to use DTP). ZnDT having a long-chain primary alkyl group represented by the general formula [1]
If the content of P is less than 50 mol% of the total zinc content, a satisfactory low friction coefficient cannot be obtained under the operating conditions of high oil temperature and low speed rotation. Specific examples of R ¹ and R ² in the general formula [1] include lauryl group, myristyl group,
Preferable examples are long-chain primary alkyl groups such as palmityl group, stearyl group and eicosyl group. The general formula [1]
ZnDTP having a long-chain primary alkyl group represented by
One kind may be used, or two or more kinds may be used in combination. In the composition of the present invention, when the sulfurized oxymolybdenum organophosphorodithioate and the sulfurized oxymolybdenum dithiocarbamate shown below are not used together, the total Zn
The compounding amount of DTP is 0.2 to 3.0 based on the total weight of the composition.
% By weight, preferably 0.3 to 1.5% by weight. If this amount is less than 0.2% by weight, abrasion resistance will be insufficient, and a satisfactory low coefficient of friction will not be obtained under operating conditions of high temperature and low speed rotation, and if it exceeds 3.0% by weight, the amount will be insufficient. However, the improvement of the effect is not recognized. In the lubricating oil composition of the present invention, in order to further improve the friction characteristics, the ZnDTP is used as the component (A), and if desired, the component (B) has a hydrocarbon group having 1 to 20 carbon atoms.
Sulfurized oxymolybdenum organophosphorodithioate (MoDTP) and sulfurized oxymolybdenum dithiocarbamate (MoDTC) having 1 to 20 carbon atoms in the hydrocarbon group
You may mix | blend at least 1 sort (s) selected from the above. The MoDTP has the general formula

[0008]

[Chemical 2]

(In the formula, R ³ and R ⁴ are each a carbon number of 1 to
20 hydrocarbon groups, which may be the same or different from each other, and p and q each have a sum of 4
A compound represented by the following general formula) can be used, and as MoDTC, a compound represented by the general formula

[0010]

[Chemical 3]

(R ⁵ and R ⁶ in the formula are each 1 to 1 carbon atoms.
20 hydrocarbon groups, which may be the same or different from each other, and x and y each have a sum of 4
Which is a positive integer such that R ³ , R ⁴ , R ⁵ and R ⁶ in the general formulas [2] and [3] are hydrocarbon groups having 1 to 20 carbon atoms,
For example, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, a cycloalkyl group having 5 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an alkylaryl group having 7 to 20 carbon atoms, and a carbon number. 7 to 20 hydrocarbon groups such as arylalkyl groups. The alkyl group or alkenyl group may be linear or branched. Specific examples of R ¹ , R ² , R ³ , R ⁴ and R ⁵ include methyl, ethyl, propyl, butyl, pentyl, hexyl,
Octyl, 2-ethylhexyl, decyl, lauryl, myristyl, palmityl, stearyl, vinyl, allyl,
Examples thereof include propenyl, butenyl, pentenyl, octenyl, oleyl, cyclopentyl, cyclohexyl, methylcyclohexyl, phenyl, tolyl, naphthyl, benzyl and phenethyl groups. In the composition of the present invention, the component (B) MoDTP or MoDTC may be used alone or in combination of two or more.
The content of ZnDTP as the component (A) is 0.2 to 3.0% by weight based on the total weight of the composition, preferably 0.3 to 1.
MoDT of the component (B) is selected in the range of 5% by weight.
The compounding amount of P and MoDTC is 0.01 to 10% by weight, preferably 0.1 to 5.0% by weight, based on the total weight of the composition.
It is selected in the range of. If the content of ZnDTP as the component (A) is less than 0.2% by weight, abrasion resistance becomes insufficient, and a satisfactory low coefficient of friction cannot be obtained under operating conditions of high temperature and low speed rotation. If it exceeds 0% by weight, the improvement of the effect is not recognized for the amount.

On the other hand, the component (B), MoDTP or MoD
If the amount of TC is less than 0.01% by weight, the effect of improving the friction characteristics is not sufficiently exerted, and if it exceeds 10% by weight, the effect is not improved for the amount, and it causes sludge and the like. Cheap. The lubricating oil composition of the present invention contains various additives conventionally used in lubricating oils, such as metal detergents, ashless detergent dispersants, viscosity index improvers, and fluidizers, as long as the object of the present invention is not impaired. A point depressant, an antioxidant, a rust preventive, a corrosion inhibitor, an antifoaming agent, another antiwear agent, a friction modifier and the like can be appropriately added. As a metal detergent,
For example, calcium sulfonate, magnesium sulfonate, barium sulfonate, calcium phenate,
Examples thereof include barium phenate and calcium salicylate, and these are usually used in a proportion of 0.1 to 5% by weight. Examples of the ashless detergent dispersant include succinimide type, succinic acid amide type and its boron derivatives, benzylamine type, ester type and the like, and these are usually contained in a proportion of 0.5 to 7% by weight. used. Examples of the viscosity index improver include polymethacrylate-based, polyisobutylene-based, ethylene-propylene copolymer system, styrene-butadiene hydrogenated copolymer system, etc., and these are usually contained in a proportion of 0.5 to 35% by weight. used.
Examples of the antioxidant include alkylated diphenylamine, phenyl-α-naphthylamine, alkylated-α-
Amine antioxidants such as naphthylamine, 2,6-di-t-butyl-4-methylphenol, phenolic antioxidants such as 4,4'-methylenebis (2,6-di-t-butylphenol) Which is usually used in a proportion of 0.05 to 2% by weight. Examples of the rust preventive agent include alkenyl succinic acid and its partial ester, examples of the corrosion inhibitor include benzotriazole and benzimidazole, and examples of the defoaming agent include dimethylpolysiloxane and polyacrylate. These can be added appropriately.

[0013]

EXAMPLES The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto. The coefficient of friction of the lubricating oil composition (LFW
-1) and the wear scar diameter were determined as follows. (1) Friction coefficient (LFW-1) Using the tester shown in FIG. 1, the rotation speed is 200 rpm and the oil temperature is 1
An LFW-1 friction test was performed using a Falex R-type block (made of iron) and a Falex S-10 test ring (made of iron) under the conditions of 20 ° C. and a load of 80 kgf. In FIG. 1, 1 is an S-10 test ring, 2 is an R-type block, and 3 is a strain gauge. A load is applied to the R-shaped block and the resistance generated when the ring is rotated is detected by a strain gauge to calculate the friction coefficient. The test oil is immersed in about half of the ring. This friction coefficient is represented by the Sommafeld number Z shown below. Sommerfeld number Z = μN / w μ: Viscosity coefficient [Pa · s] N: Slip velocity [m / s] w: Surface pressure [Pa] LFW-1 test corresponds to the order of Z = 10 ^-8 [m] I went. (2) Wear scar diameter A shell four-ball test was conducted under the conditions of a rotation speed of 2000 rpm, an oil temperature of 100 ° C., a load of 30 kgf, and a high-chromium carbon steel (SUJ-2) having a diameter of 1/2 inch to determine the wear scar diameter. Examples 1 to 10 and Comparative Examples 1 to 3 Lubricating oil compositions containing a base oil (100N) and the additive components of the types and amounts shown in Table 1 were prepared, and the friction coefficient (LF
W-1) and wear scar diameter (shell four-ball type test) were determined.
The results are shown in Table 1.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

INDUSTRIAL APPLICABILITY The lubricating oil composition of the present invention exerts an oily effect by strongly adsorbing to the friction surface even under the operating conditions of high oil temperature and low speed rotation, and has a function of reducing the friction coefficient. ing. The lubricating oil composition is suitably used for internal combustion engines such as automobile engines, and as automobile lubricating oils such as gear oil, ATF, and shock absorber oil.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an apparatus used in a LFW-1 friction test.

[Explanation of symbols]

 1 S-test ring 2 R type block 3 Strain meter

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Claims (2)

[Claims] 1. A zinc dialkyldithiophosphate having a primary alkyl group having 10 to 25 carbon atoms, based on the total weight of the composition, based on the total weight of the lubricating base oil, in which the amount of zinc is 50 moles of the total zinc amount. % Of zinc dialkyldithiophosphate contained in an amount of 0.2 to 3.0% by weight, which is a lubricating oil composition. 2. A zinc dialkyldithiophosphate having a primary alkyl group of 10 to 25 carbon atoms (A) based on the total weight of the composition, based on the total weight of the lubricating base oil. 0.2 to 3.0% by weight of zinc dialkyldithiophosphate contained in an amount of 50 mol% or more, and (B) a sulfurized oxymolybdenum organophosphorodithioate having 1 to 20 carbon atoms in the hydrocarbon group and carbonization. Hydrogen group has 1 to 2 carbon atoms
0 to 10% by weight of at least one selected from sulfurized oxymolybdenum dithiocarbamates of 0.