JP2010254767A - Lubricant composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricant composition excellent in low frictional coefficient and abrasion resistance. <P>SOLUTION: This lubricant composition comprises a base oil of a mineral oil and/or a synthetic oil, a zinc dialkyldithiophosphate represented by formula (1) (wherein R<SP>1</SP>, R<SP>2</SP>, R<SP>3</SP>and R<SP>4</SP>are each 2 to 18C, preferably 3 to 11C, primary alkyl, or a 3 to 18C, preferably 3 to 10C, secondary alkyl), and an organic molybdenum compound in an amount of at least ≥300 ppm in terms of molybdenum, wherein the alkyl group of the zinc dialkyldithiophosphate has a secondary alkyl group/primary alkyl group ratio of 60:40 to 10:90. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a lubricating oil composition that reduces friction generated in lubricated portions such as bearings, gears, engines, and transmissions, and suppresses wear.

  Lubricating oil compositions having excellent friction and wear characteristics are required for bearings, gears, and the like of machinery equipment in automobiles, steel, railways, and other industries. In particular, it is important for lubrication applications such as automobile engines, transmissions, constant velocity joints of automobiles in which rolling friction and sliding friction are mixed, and ball screws used in drive units of injection molding machines and electric press machines. Also, wear resistance is an important characteristic in engine oils and the like.

  Conventionally, by combining organic molybdenum with an imide compound composed of a boron addition product of polybutenyl succinimide and polybutenyl succinimide, alkaline earth metal sulfonate, and alkaline earth metal salicylate in a certain range, it is low as engine oil. It has been shown to be fuel efficient. (Patent Document 1)

JP 2000-34491 A

  The organomolybdenum compound is a friction modifier and has a lower friction reduction effect than the ashless friction modifier, especially in the boundary lubrication region. Not only engine oil, but also lubricating oil for drive systems and industrial machinery. Used in addition to. The organomolybdenum compound is soluble in oil and does not precipitate, but it is considered to decompose on the friction surface and form a so-called molybdenum disulfide film on the metal surface. It has been found that it may interact with other additives that coexist in

  In engine oils, the presence of this organomolybdenum compound and zinc dialkyldithiophosphate added as an antiwear and antioxidant agent may cause interaction and increase friction or decrease wear resistance. Occur.

In the present invention, an organomolybdenum compound and zinc dialkyldithiophosphate are used in a coexisting state with respect to the base oil. The alkyl group of zinc dialkyldithiophosphate contains a secondary alkyl group and a primary alkyl group. It is intended.
In addition, the above-mentioned organomolybdenum compound is at least 300 ppm or more in terms of molybdenum, and the alkyl group of zinc dialkyldithiophosphate has a ratio of secondary alkyl group to primary alkyl group of 60:40 to 10:90. It is to make.

  According to the present invention, even when the amount of the organomolybdenum compound is reduced and the amount of zinc dialkyldithiophosphate added is reduced, it is possible to achieve good low friction on the friction surface and improve wear resistance. It can be planned. In addition, a lubricating oil composition can be obtained economically with a decrease in the amount of organic molybdenum compound used.

As the base oil of the grease of the present invention, synthetic oils such as mineral oil, ester oil, ether oil and hydrocarbon oil, animal and vegetable oils, or mixed oils thereof are used.
In particular, base oils belonging to Group 1, Group 2, Group 3, Group 4, etc. in the API (American Petroleum Institute) base oil category can be used alone or in combination.

For Group 1 base oils, for example, paraffin obtained by applying a combination of refining means such as solvent refining, hydrorefining, and dewaxing to a lubricating oil fraction obtained by atmospheric distillation of crude oil. There are mineral oils.
For Group 2 base oils, for example, paraffinic mineral oils obtained by appropriately combining refining means such as hydrocracking and dewaxing for lubricating oil fractions obtained by atmospheric distillation of crude oil There is. Group 2 base oils refined by hydrorefining methods such as the Gulf Company method have a total sulfur content of less than 10 ppm and an aroma content of 5% or less, and can be suitably used in the present invention.

  Group 3 base oil and Group 2 plus base oil include, for example, a paraffinic mineral oil produced by advanced hydrorefining and a dewaxing process for a lubricating oil fraction obtained by atmospheric distillation of crude oil. There are base oils refined by the ISODEWAX process for converting and dewaxing the produced wax to isoparaffins, and base oils refined by the mobile WAX isomerization process, and these can also be suitably used in the present invention.

  Specific examples of synthetic oils include, for example, polyolefins, polyalkylene glycols such as polyethylene glycol and polypropylene glycol, diesters such as di-2-ethylhexyl sebacate and di-2-ethylhexyl adipate, trimethylolpropane ester and pentaerythritol ester. Polyol esters, perfluoroalkyl ethers, silicone oils, polyphenyl ethers and the like.

  The polyolefin includes polymers of various olefins or hydrides thereof. Any olefin may be used, and examples thereof include ethylene, propylene, butene, and α-olefins having 5 or more carbon atoms. In the production of polyolefin, one of the above olefins may be used alone, or two or more may be used in combination. Particularly preferred are polyolefins called poly α-olefins (PAO), which are Group 4 base oils.

  GTL (Gas Liquid) synthesized by the Fischer-Tropsch method, which is a natural gas liquid fuel technology, has an extremely low sulfur content and aromatic content compared to mineral oil base oil refined from crude oil. Is extremely high, so that it has excellent oxidation stability and very low evaporation loss, and can be suitably used as the base oil of the present invention.

Representative examples of animal and vegetable oils include castor oil and rapeseed oil.
The various oils described above can be used alone or in combination as a base oil, but the above are merely examples, and the present invention is not limited thereby.

The zinc dialkyldithiophosphate used in the present invention comprises a zinc dialkyldithiophosphate mixture consisting of a primary zinc dialkyldithiophosphate and a secondary zinc dialkyldithiophosphate.
Specific examples of the zinc dialkyldithiophosphate include those represented by the following general formula (1).

In the above formula ^{(1), R 1, R} 2, R 3 and R ⁴ are each independently 2 to 18 carbon atoms, preferably primary alkyl group or a C 3-18 having 4 to 12 carbon atoms, Preferably, it represents a secondary alkyl group having 3 to 10 carbon atoms.
In the present invention, the primary alkyl group having 2 to 18 carbon atoms refers to a group represented by the following general formula (2).
(Chemical formula 2)
R ⁶ —CH ₂ — (2)

The formula (2) in, R ⁶ is 1 to 17 carbon atoms, preferably a straight-chain or branched alkyl group having 3 to 11 carbon atoms. Specific examples of R ⁶ include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group. Examples thereof include alkyl groups such as a group, pentadecyl group, hexadecyl group, and heptadecyl group (the alkyl group may be linear or branched).

上記式（３）中、Ｒ⁷及びＲ⁸は、それぞれ個別に、炭素数１〜１６、好ましくは炭素数１〜８であり、かつＲ⁷とＲ⁸の合計炭素数が２〜１７、好ましくは２〜９である直鎖又は分岐アルキル基を示す。Ｒ⁷及びＲ⁸としては、具体的には、それぞれ個別に、直鎖又は分岐の、メチル基、エチル基、プロピル基、ブチル基、ペンチル基、ヘキシル基、ヘプチル基、オクチル基、ノニル基、デシル基、ウンデシル基、ドデシル基、トリデシル基、テトラデシル基、ペンタデシル基、ヘキサデシル基等が例示できる。 In the present invention, the secondary alkyl group having 3 to 18 carbon atoms refers to a group represented by the following general formula (3).

In the above formula (3), R ⁷ and R ⁸ are each independently 1 to 16 carbon atoms, preferably 1 to 8 carbon atoms, and the total number of carbon atoms in R ⁷ and R ⁸ are 2 to 17, preferably Represents a linear or branched alkyl group which is 2-9. The R ⁷ and R ^8, specifically, individually, linear or branched, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, heptyl group, octyl group, nonyl group, Examples include a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, and a hexadecyl group.

In general, specific examples of the primary alkyl dithiophosphate zinc include zinc diisopropyl dithiophosphate, zinc diisobutyl dithiophosphate, zinc diisodecyl dithiophosphate, and the like.
Examples of the secondary alkyl dithiophosphate zinc include, for example, zinc mono or di-sec-butyl dithiophosphate, zinc mono or di-sec-pentyl dithiophosphate, zinc mono or di-4-methyl-2-pentyl dithiophosphate, and the like. There is.

  In the zinc dialkyldithiophosphate in the present invention, the secondary alkyl group and the primary alkyl group coexist, but the ratio of the secondary alkyl group to the primary alkyl group is 60:40 to 10:90. Well, more preferably 50:50 to 10:90.

Examples of the organic molybdenum compound include molybdenum phosphate, molybdenum amine complex, molybdenum dialkyldithiocarbamate, molybdenum dialkyldithiophosphate, and the like. Usually, molybdenum dialkyldithiocarbamate and molybdenum dialkyldithiophosphate are preferably used.
Preferable examples of the molybdenum dialkyldithiocarbamate include those represented by the following formula (4).
(Chemical formula 4)
^{(R 1 R 2 N-CS} -S) 2 Mo 2 OmSn --- (4)

(In the formula (4), R ¹ and R ² each independently represent an alkyl group having 1 to 24 carbon atoms, preferably 3 to 18 carbon atoms, m is 0 to 3, n is 4 to 1, m + n = 4.)

  Specific examples of the molybdenum dialkyldithiocarbamate include, for example, molybdenum diethyldithiocarbamate, molybdenum dipropyldithiocarbamate, molybdenum dibutyldithiocarbamate, molybdenum dipentyldithiocarbamate, molybdenum dihexyldithiocarbamate, molybdenum dioctyldithiocarbamate, molybdenum didecyldithiocarbamate, Molybdenum didodecyldithiocarbamate, oxymolybdenum diethyldithiocarbamate, oxymolybdenum dipropyldithiocarbamate, oxymolybdenum dibutyldithiocarbamate, oxymolybdenum dipentyldithiocarbamate, oxymolybdenum dihexyldithiocarbamate, oxymolybdenum dioctyldithiocarbamate, didecyldithio Carbamate oxymolybdenum, didodecyl dithiocarbamate oxymolybdenum, and mixtures thereof and the like.

Moreover, what is represented by following formula (5) is mentioned as a preferable example of the above-mentioned molybdenum dialkyldithiophosphate.
(Chemical formula 5)
^{[R 1 O (R 2 O)} PS-S) 2 Mo 2 OmSn --- (5)
(In the formula (5), R ¹ and R ² each independently represent an alkyl group having 1 to 24 carbon atoms, preferably 3 to 18 carbon atoms, m is 0 to 3, n is 4 to 1, m + n = 4.)

  Specific examples of the molybdenum dialkyldithiophosphate include, for example, molybdenum diethyldithiophosphate, molybdenum dipropyldithiophosphate, molybdenum dibutyldithiophosphate, molybdenum dipentyldithiophosphate, molybdenum dihexyldithiophosphate, molybdenum dioctyldithiophosphate, molybdenum didecyldithiophosphate, Molybdenum didodecyldithiophosphate, oxymolybdenum diethyldithiophosphate, oxymolybdenum dipropyldithiophosphate, oxymolybdenum dibutyldithiophosphate, oxymolybdenum dipentyldithiophosphate, oxymolybdenum dihexyldithiophosphate, oxymolybdenum dioctyldithiophosphate, oxymolybdenum disildithiophosphate, Examples thereof include oxymolybdenum didosyldithiophosphate.

The above organic molybdenum compound coexists with the above zinc dialkyldithiophosphate, but this organic molybdenum compound is blended in the total amount of the lubricating oil composition in an amount of at least 300 ppm, preferably 500 ppm or more in terms of molybdenum amount. .
Similarly, the zinc dialkyldithiophosphate is blended in an amount of 900 ppm or more in terms of phosphorus in the total amount of the lubricating oil composition.
When a large amount of the zinc dialkyldithiophosphate is blended, the risk of being discharged simultaneously with the exhaust when used as an engine oil increases, so it is preferable to blend it in as small an amount as possible. In addition, the organomolybdenum compound is effective in a smaller amount than the above blending amount, and if it is blended in a large amount, an increase in cost is caused. Therefore, it is preferable to blend the smallest possible amount.

  As described above, the organomolybdenum compound and zinc dialkyldithiophosphate are mixed in the lubricating oil composition. The ratio of secondary alkyl groups to primary alkyl groups in the zinc dialkyldithiophosphate is 60 as described above. : 40 to 10:90. When the ratio of the secondary alkyl group exceeds 60 mol%, the friction coefficient cannot be lowered effectively, and when the ratio of the primary alkyl group exceeds 90 mol%, the wear resistance performance decreases. As such, it is often undesirable.

  If necessary, the lubricating oil composition of the present invention includes an amine-based or phenol-based antioxidant, an extreme-pressure additive such as sulfurized olefin or sulfurized fat or oil, or an extreme pressure / abrasion resistance such as phosphite or phosphate. Viscosity modifiers such as sulfonates, salicylates and phenates, thickeners such as polybutenes and polymethacrylates, solids such as molybdenum disulfide and boron nitride Lubricants, dispersants such as succinimide, metal deactivators, pour point depressants, antifoaming agents, and other known various additives can be blended.

Examples of the present invention will be described below, but the present invention is not limited thereto.
Lubricating oil compositions were prepared from the base oils and additives shown below according to the composition (% by mass) shown in Table 1, and the SRV frictional wear test shown below was conducted.

[1] Base oil [1-1] Base oil A:
A base oil of Group 3, kinematic viscosity of 100 ° C. is the kinematic viscosity of ^{4.32mm 2 / s, 40 ℃ 20.3mm} 2 / s, a viscosity index (VI) is 121.
[1-2] Base oil B:
A base oil of Group 1, the kinematic viscosity of 100 ° C. is the kinematic viscosity of ^{11.5mm 2 / s, 40 ℃ 103.6mm} 2 / s, viscosity index (VI) include the 98.
[1-3] Base oil C:
Group 1 base oil with a kinematic viscosity at 100 ° C. of 31.2 mm ² / s, a kinematic viscosity at 40 ° C. of 472.6 mm ² / s, and a viscosity index (VI) of 96.

[2] Additive [2-1] Zinc dithiophosphate (indicated in the table; primary ZnDTP (A)):
Olonaite OLOA262 (trade name) was used.
[2-2] Zinc dithiophosphate (indicated in the table; secondary ZnDTP (B)):
Olona 269R (trade name) manufactured by Oronite was used.
[2-3] Molybdenum dithiocarbamate (indicated in the table; Mo-DTC):
Adeka SAKURA-LUBE515 (trade name) was used.
[2-4] DI subpackage: GF-2 equivalent product containing the following components.
Lubrizol Lz74; 1% (Ca sulfonate),
Lubrizol Lz52; 3.5% (Ca sulfonate),
Infineum Infineum C9266; 5.0% (PIB succinimide),
Ciba Specialty Chemicals Inc. Irganox L135; 1% (phenolic antioxidant),
[2-5] Viscosity index improver: VII
Oronite PARATON8941

[SRV friction and wear test]
A sliding friction test between cylinders / disks was performed using a SRV friction tester under the conditions of a load of 400 N, a frequency of 50 Hz, an amplitude of 1.5 mm, and an oil temperature of 90 ° C. The lower the friction coefficient, the better the friction reduction effect of the engine and the better the fuel efficiency. Here, the friction coefficient and the wear scar width (amount of wear) 30 minutes after the start of the test were measured.

(Test results)
Table 1 shows the composition of the examples and comparative examples and the SRV friction and wear test results.

[Discussion]
As shown in Table 1, when the molybdenum contents of Examples 1 to 3 are 500 ppm and the ratio of secondary-ZnDTP / primary-ZnDTP is 50/50, 25/75, 10/90, the friction coefficient is low, The amount of wear is small and good results are obtained.
On the other hand, even if the molybdenum content in Comparative Examples 1 to 3 is 500 ppm, the ratio of secondary ZnDTP / primary ZnDTP in Comparative Example 1 is 100/0, but the wear amount is small, but the friction coefficient is large. In Comparative Example 2, the ratio of secondary ZnDTP / primary ZnDTP of 5/95 and that of Comparative Example 3 of 0/100 are both low in friction coefficient but large in wear.

Claims (7)

The base oil of mineral oil and / or synthetic oil contains a zinc dialkyldithiophosphate represented by the following formula 1 and an organomolybdenum compound, and the alkyl group of the zinc dialkyldithiophosphate contains a secondary alkyl group and a primary alkyl group. A lubricating oil composition characterized by that.

(R ¹ , R ² , R ³ and R ⁴ each independently represent a primary alkyl group having 2 to 18 carbon atoms or a secondary alkyl group having 3 to 18 carbon atoms.)   2. The organomolybdenum compound is contained in an amount of at least 300 ppm in terms of molybdenum amount, and the alkyl group of the zinc dialkyldithiophosphate has a ratio of secondary alkyl group to primary alkyl group of 60:40 to 10:90. The lubricating oil composition described in 1.   The organic molybdenum compound is contained in an amount of 500 ppm or more in terms of molybdenum, and the alkyl group of the zinc dialkyldithiophosphate has a ratio of secondary alkyl group to primary alkyl group of 50:50 to 10:90. The lubricating oil composition described.   The lubricating oil composition according to any one of claims 1 to 3, wherein the zinc dialkyldithiophosphate is contained in an amount of 900 ppm or more in terms of phosphorus amount.   The lubricating oil composition according to any one of claims 1 to 4, wherein the alkyl group of the zinc dialkyldithiophosphate has 3 to 8 carbon atoms.   The lubricating oil composition according to any one of claims 1 to 5, wherein the organic molybdenum compound is molybdenum dialkyldithiocarbamate and / or molybdenum dialkyldithiophosphate.   The metal detergent, ashless dispersant, antioxidant, antiwear agent, extreme pressure agent, rust inhibitor, metal deactivator, pour point depressant, viscosity modifier and antifoaming agent. The lubricating oil composition according to any one of 1 to 6.