JP3250584B2 - Lubricating 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 a lubricating oil composition and, more particularly, to a lubricating oil composition having very excellent oxidation stability and sludge formation preventing property.

[0002]

2. Description of the Related Art Lubricating oil compositions have been required to have good oxidation stability. Therefore, in order to improve the oxidation stability of the lubricating oil composition, 2,6-di-t-butyl-p
It is customary to add a phenolic antioxidant such as cresol or an amine antioxidant such as phenyl-α-naphthylamine to the base oil.

[0003] However, 2,6-di-t-butyl-
p-Cresol has a problem that its antioxidant performance deteriorates under high temperature conditions. On the other hand, phenyl-α-naphthylamine is an additive exhibiting excellent antioxidant performance even under high temperature conditions, but phenyl-α-naphthylamine, which is an antioxidant having low solubility in a lubricating base oil, is altered by oxidation itself. There is a problem that the material is sludge, and the filter in the lubricating oil supply circuit is blocked, and sludge is deposited on the surface of the heat exchanger to lower the heat exchange rate.

As an improvement over the disadvantages of such phenyl-α-naphthylamines, Applicants have previously described p-branched alkylphenyls having alkyl groups derived from oligomers of propylene instead of phenyl-α-naphthylamine. It has been proposed to use -α-naphthylamine (JP-A-62-181396). JP 62
Although the p-branched alkylphenyl-α-naphthylamine disclosed in JP-A-181396 is an additive having excellent oxidation stability and also excellent sludge formation prevention property, the proportion of the functional group in the molecule is small, When the same amount is added, there is a problem that the antioxidant ability is weaker than that of phenyl-α-naphthylamine.

Accordingly, a large amount of lubricating oil, such as gas turbine oil, compressor oil, and hydraulic oil, for which oxidation stability at high temperatures is important, must be added in a large amount. Although excellent, when such a large amount was added, sludge formation due to alteration of the additive was also concerned.

[0006]

Accordingly, a lubricating oil having very excellent oxidative stability and excellent sludge formation preventing property, which can be applied to an apparatus in which oxidative stability at high temperatures is particularly important. Has been awaited from the viewpoint of extending the life of lubricating oil. An object of the present invention is to provide a lubricating oil composition having both excellent oxidation stability and sludge formation prevention properties.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted various studies to overcome the above-mentioned problems, and as a result, have found that p-branched alkylphenyl-α-naphthylamine and phenyl-
By blending α-naphthylamine in a specific amount and in a specific ratio in a lubricating base oil, a lubricating oil composition having good oxidation stability and excellent sludge formation prevention properties can be obtained by a synergistic effect of the both. And completed the present invention.

That is, the present invention relates to (A) a p-branched alkylphenyl-α-naphthylamine represented by the following general formula (I) (Chemical Formula 2) based on the total amount of the lubricating base oil: 0.3 to 3.0% by weight,

Embedded image [In the formula (I), R represents an alkyl group having 8 to 16 carbon atoms derived from an oligomer of an olefin having 3 or 4 carbon atoms. And (B) 0.05 to 1.0% by weight of phenyl-α-naphthylamine, and the weight ratio of the components (A) and (B) is 3: 1 to 20: 1. It is intended to provide a lubricating oil composition characterized by the above.
Hereinafter, the contents of the present invention will be described in more detail.

The lubricating base oil used in the present invention is not particularly limited, and any lubricating base oil may be used regardless of whether it is a mineral oil or a synthetic oil as long as it is usually used as a base oil for lubricating oil.
As a mineral oil-based lubricating base oil, for example, a lubricating oil fraction obtained by atmospheric distillation and vacuum distillation of crude oil,
Mineral lubricating base oils such as paraffinic and naphthenic oils can be used, which are purified by appropriately combining solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid washing, and clay treatment. .

Examples of synthetic lubricating base oils include poly-α-olefins (polybutene, 1-octene oligomer, 1-decene oligomer, etc.), alkylbenzenes, alkylnaphthalenes, diesters (ditridecyl glutarate, di-2-ethylhexyl). Adipate, diisodecyl adipate, ditridecyl adipate, di-2-
Ethylhexyl sebacate, etc.), polyester (such as trimellitate), polyol ester (such as trimethylolpropane caprylate, trimethylolpropaneperargonate, pentaerythritol 2-ethylhexanoate, pentaerythritol pelargonate), polyoxyalkylene glycol , Polyphenyl ether, silicone oil, perfluoroalkyl ether and the like. In addition, these base oils may be used alone or in combination of two or more.

The viscosity of the lubricating base oil used in the present invention is arbitrary, but usually the viscosity at 40.degree.
1000 cSt is preferably used, and 5-800
Those of cSt are more preferably used.

The component (A) which is an essential additive in the lubricating oil composition of the present invention is a p-type compound represented by the above general formula (I).
Branched alkylphenyl-α-naphthylamine. In the formula (I), R represents an alkyl group having 8 to 16 carbon atoms derived from an oligomer of an olefin having 3 or 4 carbon atoms.

Specific examples of the olefin having 3 or 4 carbon atoms include propylene, 1-butene, 2-butene and isobutylene. In the present invention, the olefin is more excellent in preventing sludge formation of the compound. Propylene or isobutylene is preferred, and propylene is more preferred.

R is a branched alkyl group having 8 to 16 carbon atoms derived from an oligomer of these olefins, and is preferably a branched alkyl group having 8 to 15 carbon atoms because of its superior antioxidant properties and sludge formation preventing properties. It is preferably an alkyl group.

More specifically, R represents a branched octyl group derived from an isobutylene dimer, a branched nonyl group derived from a propylene trimer,
A branched dodecyl group derived from a tetramer, a branched dodecyl group derived from a tetramer of propylene, or a 5
A branched pentadecyl group derived from a monomer is more preferable, and a branched dodecyl group derived from a propylene tetramer or a branched pentadecyl group derived from a pentamer of propylene is particularly preferable.

In the present invention, when the number of carbon atoms of R is less than 8, it is liable to precipitate itself as sludge by oxidation, while when the number of carbon atoms is more than 16, the proportion of the functional group in the molecule becomes small. And the antioxidant ability is weakened, which is not preferable. Further, when R has 8 to 16 carbon atoms,
Even when the alkyl group is a linear alkyl group or a branched alkyl group other than the one derived from an oligomer of an olefin having 3 or 4 carbon atoms, the alkyl group itself is liable to precipitate as sludge in oil by oxidation. Therefore, it is not preferable.

[0017] The p-branched alkylphenyl-α- of the present invention
As naphthylamine, a commercially available product may be used, and it can be easily synthesized using phenyl-α-naphthylamine and an olefin oligomer as raw materials. This p-
A method for synthesizing a branched alkylphenyl-α-naphthylamine is disclosed in Japanese Patent Application Laid-Open No. 62-181 filed by the present applicant.
No. 396 discloses details thereof.

The content of the component (A) in the lubricating oil composition of the present invention is from 0.3 to 3.0% by weight, preferably from 0.5 to 2.0% by weight, based on the total amount of the composition. (A)
When the content of the component is less than 0.3% by weight, a synergistic effect with the component (B) with respect to the oxidation stability and the sludge formation-preventing property cannot be obtained, while the amount of the component (A) is 3% by weight. If the amount exceeds the above range, the effect of improving the oxidation stability corresponding to the compounding amount cannot be obtained, which is economically disadvantageous, and therefore is not preferable.

On the other hand, another essential additive (B) in the lubricating oil composition of the present invention is phenyl-α-naphthylamine represented by the following general formula (II). .

[0020]

Embedded image

The content of the component (B) in the lubricating oil composition of the present invention is 0.05 to 1.0 based on the total amount of the composition.
%, Preferably 0.1 to 0.5% by weight.
When the content of the component (B) is less than 0.05% by weight, it relates to the oxidation stability and the sludge formation preventing property (A).
On the other hand, if the synergistic effect with the component is not obtained, and if the blending amount of the component (B) exceeds 1.0% by weight, there is a possibility that the component itself may precipitate as sludge due to oxidation.

In the lubricating oil composition of the present invention, not only the individual contents of the components (A) and (B) but also the weights of the contents of the components (A) and (B) are determined. It is very important that the ratio be in the range of 3: 1 to 20: 1, preferably 4: 1 to 10: 1. (A) component and (B)
By setting the weight ratio of the contents of the components to this range, a lubricating oil composition having both oxidation stability and anti-sludge formation due to a synergistic effect of both components can be obtained. When the content of the component (A) is less than 3 parts by weight with respect to 1 part by weight of the component (B), the component (B) itself may settle as sludge by oxidation, while the content of the component (A) Is (B) component 1
When the amount exceeds 20 parts by weight with respect to the parts by weight, the effect of improving the oxidation stability due to the combined use of the component (B) is not obtained, which is not preferred.

In order to further enhance the excellent oxidation stability of the lubricating oil composition of the present invention, known antioxidants other than the present invention may be added alone or in combination of two or more, if necessary. May be.

Examples of such antioxidants include, for example, 2,6-di-t-butylphenol, 2,6
-Di-t-butyl-p-cresol, 2,6-di-t-
Butyl-4-ethylphenol, 2,2 ^'- methylenebis (4-methyl -6-t-butylphenol), 2,2
^'- methylenebis (4-ethyl -6-t-butylphenol), ^4,4' - methylenebis (2,6-di -t- butylphenol), 4,4 ^'- bis (2,6-di -t-
Phenolic antioxidants such as butylphenol); diphenylamine, linear or symmetrical or asymmetrical dialkylamine having a branched alkyl group (specifically p C4-12, p ^'- dioctyl diphenylamine,
p, p ^'- di-nonyl diphenylamine, p, ^p' - amine antioxidants such as didodecyl diphenyl amine, etc.); triphenyl phosphate, tricresyl phosphate, phosphorus, such as tris (di -t- butyl phenyl) phosphite Antioxidants; sulfur antioxidants such as alkyl disulfide and aryl disulfide; zinc di-2
A zinc thiophosphate-based antioxidant such as -ethylhexyldithiophosphate; a phenothiazine-based antioxidant such as a dialkylphenothiazine; and the like.

The addition amount of these other antioxidants is optional, but the total content is usually 0.01 to 5% by weight, preferably 0.1 to 5% by weight, based on the total amount of the composition.
It is desirable to add so that it may become 2 weight%. Further, in order to further enhance the excellent performance of the lubricating oil composition of the present invention, known lubricating oil additives may be added alone or in combination of two or more as necessary.

Specific examples of such lubricating oil additives include extreme pressure agents such as tricresyl phosphate, triphenyl phosphate and zinc dithiophosphate, rust inhibitors such as petroleum sulfonate and dinonylnaphthalene sulfonate, and benzoic acid. Metal deactivators such as triazole, tolyltriazole, mercaptobenzothiazole, alkaline earth metal sulfonates, alkaline earth metal phenates, alkaline earth metal salicylates, metal detergents such as alkaline earth metal phosphonates, succinic esters,
Ashless dispersants such as benzylamine, defoamers such as silicone, viscosity index improvers such as polymethacrylate, olefin copolymer, polyisobutylene, and polystyrene;
Pour point depressants and the like.

The amount of these lubricating oil additives to be added is arbitrary, but usually, the content of the viscosity index improver is 1 to 30% by weight, and the content of the antifoaming agent is usually based on the total amount of the composition. The content is 0.0005 to 1% by weight, the content of the metal deactivator is 0.005 to 1% by weight, and the content of other additives is 0.1 to 15% by weight. It is desirable to add so that it becomes.

The lubricating oil composition of the present invention is preferably used as a lubricating oil, such as a gas turbine oil, a compressor oil, or a hydraulic oil, in which oxidation stability at high temperatures is particularly important. Gasoline engine oils such as oil and two-cycle engine oils; Diesel engine oils such as land diesel engine oil and marine diesel engine oil; Turbine oils such as additive turbine oil and marine turbine oil; Automotive gear oils, industrial gear oils, Gear oils such as automatic transmission oils; vacuum pump oils; refrigerator oils; metal working oils such as cutting oils, grinding oils, plastic working oils, heat treatment oils, electric discharge machining oils; sliding guide surface oils (machine tool oils); Further, it is also suitably used for rust prevention oil, heat medium oil, grease and the like.

[0029]

EXAMPLES Hereinafter, the content of the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these contents. Example 1 A lubricating oil composition according to the present invention was prepared according to the composition shown in Table 1. The composition was subjected to the following performance evaluation tests, and the results are shown in Table 1.

[Oxidation stability test] JIS-K-2514
Rotating cylinder oxidation stability test method (RBO specified in
T). That is, in the test, 50 g of a sample and 5 ml of distilled water were taken in a sample vessel containing a copper catalyst, and after setting in a pressure vessel, oxygen was injected to 620 kPa and 1
The oxidation test was performed at 50 ° C., and the time from the maximum pressure until a pressure drop of 172 kPa occurred was defined as the oxidation life of the sample oil.

[Sludge Formation Prevention Test] The sample oil was circulated at 7 MPa and 120 ° C. using a piston pump by a high-temperature pump circulation test facility shown in FIG. 1, before and after a line filter (3 μm) set in a circulation system. The differential pressure rise was monitored. Differential pressure without sludge is about 35kP
The differential pressure gradually increases as the sludge is collected. The operation time until the differential pressure became 200 kPa was measured in this manner, and the measured operation time was used as a measure of the sludge formation prevention property. In addition, it shows that the larger the numerical value of this operation time is, the more excellent the sludge generation preventing property is.

Examples 2 to 8 The lubricating oil compositions according to the present invention were prepared in the same manner as in Example 1 with the compositions shown in Table 1, and the same performance evaluation tests were performed. The results are shown in Table 1.

(Comparative Examples 1 and 2) For comparison, a lubricating oil composition was prepared according to the composition shown in Table 2 when the component (B) was not used, and the same performance test was carried out. It was shown to.

(Comparative Examples 3 and 4) According to the composition shown in Table 2,
A lubricating oil composition was prepared for the case where the component (A) was not used, and the same performance test was carried out. The results are shown in Table 2.

(Comparative Examples 5 and 6) According to the composition shown in Table 2,
A lubricating oil composition was prepared for the case where the weight ratio of the component (A) to the component (B) was out of the range of the present invention, and the same performance test was performed. The results are shown in Table 2.

The lubricating base oil, component (A) and component (B) used in Examples and Comparative Examples are as follows. Lubricating base oil A: Paraffin-based highly solvent refined mineral oil (kinematic viscosity: 32.15 mm ² / s (@ 40 ° C.)) B: 1-decene oligomer (kinematic viscosity: 30.31 mm ² /
s (＠ 40 ° C.)) (A) Component A: N-branched dodecylphenyl-α-naphthylamine (having a dodecyl group derived from propylene tetramer) B: N-branched octylphenyl-α-naphthylamine (Having an octyl group derived from isobutylene dimer) (B) Component A: phenyl-α-naphthylamine

[0037]

[Table 1]

[0038]

[Table 2]

As is evident from the results of the examples, the lubricating oil compositions according to the present invention (Examples 1 to 8) have an excellent performance of having extremely good oxidation stability and preventing sludge formation. I have. On the other hand, the compositions of Comparative Examples 1 and 2 using only the component (A) have the same anti-sludge formation properties as the compositions of Examples, but are inferior in oxidation stability. Moreover, Comparative Example 2 is (A)
Oxidation stability did not reach the level of Example 1 even though the components were added twice as much as in Example 1 and Comparative Example 1.

Further, the compositions of Comparative Examples 3 and 4 using only the component (B) are significantly inferior in oxidation stability and sludge formation preventing property as compared with the compositions of Examples. Moreover, in Comparative Example 4, the oxidation stability did not reach the level of Example 1 even though the component (B) was added twice as much as in Example 1 and Comparative Example 3, and sludge formation was prevented. The property is worse than Comparative Example 3. on the other hand,
When the weight ratio of the component (A) to the component (B) is less than the range of the present invention (Comparative Example 5), sludge generation is equivalent to that of the composition of the example, but oxidation stability is inferior. ing. When the weight ratio of the component (A) to the component (B) exceeds the range of the present invention (Comparative Example 6), the oxidation stability is greatly improved, but the sludge formation prevention property is significantly deteriorated.
It is not practical.

[0041]

As described above, the lubricating oil composition of the present invention comprises:
(A) p-branched alkylphenyl having a specific structure
A lubricating oil composition comprising α-naphthylamine and (B) phenyl-α-naphthylamine in a specific amount and a specific ratio, respectively, in a lubricating base oil, and is extremely excellent due to a synergistic effect of the components (A) and (B). It has excellent oxidation stability and at the same time has excellent anti-sludge formation properties. Since the lubricating oil composition of the present invention can be applied to a device in which oxidation stability at high temperatures is particularly important, the lubricating oil composition has high industrial utility value.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a high-temperature pump circulation test facility.

Claims (1)

(57) [Claims] The present invention relates to: (A) a p-branched alkylphenyl-α-naphthylamine represented by the following general formula (I) based on the total amount of a composition based on a lubricating base oil:
0.3-3.0% by weight, [In the formula (I), R represents an alkyl group having 8 to 16 carbon atoms derived from an oligomer of an olefin having 3 or 4 carbon atoms. And (B) 0.05 to 1.0% by weight of phenyl-α-naphthylamine, and the weight ratio of the components (A) and (B) is 3: 1 to 20: 1. A lubricating oil composition comprising: