JPH11189781A - Lubricant composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricant that comprises a base oil of reduced degree of hydrorefining, solvent-dewaxed base oil and Zn DTP and is long-lived nevertheless, resistant to sludge formation by thermal and oxidative deterioration. SOLUTION: Use of the lubricant containing (a) 100 pts.wt. of mineral oil and/or synthetic oil, (b) 0.05-0.3 pt.wt. of a zinc salt of dithiophosphoric acid bearing two hydrocarbon groups calculated as the weight of Zn, (c) 0.1-3 pts.wt. of a phosphorus antioxidant only or a combination thereof with a phenolic antioxidant, (d) 0.1-2 pts.wt. of a dispersant and (e) 0.1-2 pts.wt. of a thiophosphate bearing three hydrocarbon groups can inhibit the occurrence of sludge for a long period of time.

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 containing zinc dithiophosphate having a hydrocarbon group, and in particular, has excellent heat and oxidation stability and suppresses the generation of sludge for a long period of time. A possible lubricating oil composition.

[0002]

2. Description of the Related Art As lubricating oils such as hydraulic oils and transmission oils, those obtained by blending additives such as antiwear agents and antioxidants with base oils such as mineral oils and synthetic oils are used. Since such a lubricating oil is used for a long time, durability against heat and oxidation is required. Deterioration of the lubricating oil not only causes wear due to a decrease in lubricity, but also generates sludge, which may lead to blockage of the hydraulic circuit. In particular, zinc dialkyldithiophosphate (ZnDT
In the case of adding P), sludge is likely to be generated due to thermal and oxidative deterioration. Therefore, it is important to take measures to prevent the generation of sludge.

Further, in recent years, the load per unit volume of lubricating oil has been increased with higher performance, compactness, higher pressure, etc. of hydraulic equipment and transmissions. This means that the lubricating oil is used at a higher temperature and a higher pressure than before, and the use conditions of the lubricating oil are becoming stricter. For this reason, higher stability against heat and oxidation has been required.

[0004] To suppress sludge generation, phenol-based
There are a method of adding an antioxidant such as an amine to prevent thermal oxidative decomposition of ZnDTP, and a method of adding a metal or ashless dispersant to supplement and disperse the sludge component.

As antioxidants, 2,6-di-ter
It is known that t-butyl-p-cresol (DBPC) has excellent performance, and is frequently used in lubricating oils and the like. Also, JP-A-60-156644 discloses that
It is described that sterically hindered hydroxyphenylcarboxylic esters such as (3,5-di-tert-butyl-4-hydroxyphenyl) propionate are useful as stabilizers for lubricating oils and the like. Further, Japanese Patent Application Laid-Open No. 8-157854 discloses that 3-methyl-5-
A 3-methyl-5-tert-butyl-4-hydroxyphenyl group-substituted fatty acid ester such as tert-butyl-4-hydroxypropionate or 3-methyl-5-tert-butyl-4-hydroxyacetate was added. A lubricating oil composition is disclosed, which exhibits excellent antioxidant properties and anti-sludge formation properties, and that the antioxidant properties are unlikely to deteriorate even after long-term use under high-temperature conditions.

On the other hand, a method using a dispersant is disclosed in Japanese Examined Patent Publication No. 4-32878, in which a phosphorus-based extreme pressure agent and / or a sulfur-based extreme pressure agent and an alkyl methacrylate and N-vinylpyrrolidone are used as dispersants. There is disclosed a lubricating oil composition to which a polymer, a copolymer of alkyl methacrylate and morpholinoethyl methacrylate, a copolymer of ethylene, propylene and diethylaminoethyl methacrylate, and the like are added. Japanese Patent Application Laid-Open No. Hei 5-31187 discloses Z
There is disclosed a heat-resistant hydraulic oil composition to which nDTP and an alkaline earth metal salt of salicylic acid are added.

[0007]

The conventional method of adding an antioxidant and a dispersant as described above is effective in preventing the generation of sludge in a highly hydrorefined base oil.
However, in some cases, the effect is insufficient for base oils having a reduced degree of hydrorefining or for solvent dewaxing base oils due to cost reduction and the like. In addition, even when both the antioxidant and the dispersant are added, the effect of preventing sludge generation may be weak. The present invention has been made to solve this problem, and ZnDTP is used for a base oil having a reduced degree of hydrorefining or a solvent dewaxed base oil.
It is an object of the present invention to provide a long-life lubricating oil in which sludge due to thermal and oxidative deterioration hardly occurs even in a lubricating oil containing.

[0008]

Means for Solving the Problems The inventor of the present invention has made intensive studies to prevent the generation of sludge in a base oil having a reduced hydrorefining degree or a lubricating oil using a solvent dewaxed base oil. As a result, it has been found that when thiophosphate having three hydrocarbon groups is added in addition to ZnDTP, an antioxidant and a dispersant, sludge is hardly generated and can be used stably for a long period of time.

That is, the lubricating oil composition according to the present invention comprises:
(A) 100 parts by weight of a lubricating base oil composed of mineral oil and / or synthetic oil, and (b) a zinc compound of dithiophosphoric acid having two hydrocarbon groups as zinc weight of 0.005 to 0.3.
Parts by weight of (c) the phosphorus-based antioxidant alone, or 0.1 parts by weight of both the phosphorus-based antioxidant and the phenol-based antioxidant.
To 3 parts by weight, (d) 0.1 to 2 parts by weight of a dispersant, and (e) 0.1% of a thiophosphate having three hydrocarbon groups.
It contains 1 to 2 parts by weight. In particular, even if a lubricating base oil having a reduced hydrorefining degree or a solvent dewaxing lubricating base oil is used, generation of sludge can be prevented for a long period of time.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a lubricating base oil used in the present invention, known mineral oils and / or synthetic oils can be used.
For example, by a known method, neutral oil or crude stock produced from crude oil as a raw material, bright stock, distillate at normal pressure is extracted with a solvent such as furfural, and the resulting raffinate is dewaxed with a solvent such as methyl ethyl ketone. And those obtained by further purifying them under high pressure to remove impurities such as sulfur. In the present invention, in particular, even a lubricating base oil having a reduced hydrorefining degree or a solvent dewaxing lubricating base oil can be used stably for a long period of time. Can be used without any problem. Examples of the synthetic oil include poly-α-olefin, polyhydric alcohol ester, and polyalkylene glycol. When used as a hydraulic oil, the kinematic viscosity is 15 to 150 mm ² /
s (40 ° C.) is usually used.

A zinc compound of dithiophosphoric acid having two hydrocarbon groups to be added to the base oil, wherein the hydrocarbon group is a primary alkyl group having 5 to 11 carbon atoms and a secondary alkyl group having 5 to 11 carbon atoms. One or more selected from an aryl group substituted with an alkyl group having 5 to 18 carbon atoms. Of these, those with primary alkyl groups are heat and
It is preferable because it has excellent stability against oxidative deterioration. Especially,
When long-term stability of the lubricating oil is important, 5
0% or more, preferably 70% or more, more preferably 90% or more
% Or more is desirably a primary alkyl group. But,
Since zinc dithiophosphate having a secondary alkyl group is excellent in lubricity, a part of the hydrocarbon group may be a secondary alkyl group. In this case, the primary alkyl group is in the range of 50 to 90%, preferably 60 to 90%, more preferably 70 to 90%. If it is less than 50%, the long-term stability of the lubricating oil is reduced, and if it is more than 90%, the effect of improving the lubricity cannot be seen.

Although it is inevitable that dithiophosphoric acid having one hydrocarbon group is mixed as an impurity, it can be used as long as its solubility in the base oil does not pose a problem.

The addition amount of the zinc compound of dithiophosphoric acid having two hydrocarbon groups is 0.005 to 0.3 parts by weight of zinc based on 100 parts by weight of the base oil.
It is preferably from 0.01 to 0.2 parts by weight. 0.005
If the amount is less than parts by weight, lubricity may not be sufficient. When the amount exceeds 0.3 parts by weight, it is preferable in terms of lubricity, but sludge increases, which may make long-term use difficult.

As the antioxidant, a phosphorus-based antioxidant is used alone, or a mixture of a phosphorus-based antioxidant and a phenol-based antioxidant is used. The addition amount of the antioxidant is 0.1 to 3 parts by weight, particularly preferably 0.2 to 2 parts by weight, based on 100 parts by weight of the lubricating base oil. If the amount added is less than 0.1 part by weight, the antioxidant ability may not be sufficient. Also,
If the amount exceeds 3 parts by weight, not only the antioxidant ability is saturated, but also the concentration of oxidative decomposition products increases, which may cause a decrease in lubricity and the generation of sludge, which is not preferable.

As a phosphorus-based antioxidant, bis (2,4
-Di-t-butylphenyl) pentaerythritol diphosphite, phenyldiisodecylphosphite, diphenyldiisooctylphosphite, diphenyldiisodecylphosphite, triphenylphosphite, trisnonylphenylphosphite, tris-di-nonylphenylphosphite , Tris- (2,4-di-t-butylphenyl) phosphite, distearyl-pentaerythritol diphosphite, bis (nonylphenyl) pentaerythritol diphosphite, 4,4'-isopropylidene diphenol alkyl phosphite , 4,4 '
-Butylidenebis (3-methyl-6-t-butylphenyldi-tridecyl phosphite), 1,1,3-tris (2-methyl-4-di-tridecyl phosphite-5-
t-butylphenyl) butane, tetrakis (2,4-di-t-butylphenyl) -4,4'-bisphenylenediphosphite, 3,4,5,6-dibenzo-1,2-oxaphosphane- 2-oxide, trilauryltrithiophosphite, tris (isodecyl) phosphite, tris (tridecyl) phosphite, phenyldi (tridecyl) phosphite, diphenyltridecylphosphite, phenyl-bisphenol A pentaerythritol diphosphite, 3,5 -Di-t-butyl-4-hydroxybenzylphosphonic acid diethyl ester; and one or more of these can be used.

Among these, aryl phosphites,
In particular, an alkylated phenyl phosphite in which one aryl group has at least one or more, preferably two alkyl groups is preferred from the viewpoint of hydrolysis stability, and tris- (2,4-di-t-butylphenyl) Phosphite,
Tris nonyl phenyl phosphite, tris-(mono &
Di-mixed nonylphenyl) phosphite and the like can be suitably used. In addition, especially when an industrial grade reagent is used, it is unavoidable that one having one or two hydrocarbon groups is mixed. However, as long as the solubility in the base oil is not a problem, it can be used as it is.

The phenolic antioxidants usable in the present invention include, for example, 2,6-di-t-butylphenol, 2-t-butyl-4-methoxyphenol, 2,4
-Dimethyl-6-t-butylphenol, 2,4-diethyl-6-t-butylphenol, 2,6-di-t-butyl-p-cresol, 2,6-di-t-butyl-4-
Ethylphenol, 2,6-di-t-butyl-4-hydroxymethylphenol, 2,6-di-t-butyl-4
-(N, N-dimethylaminomethyl) phenol, n-
Octadecyl-β- (4′-hydroxy 3 ′, 5-di-
t-butylphenyl) propionate, 2,4- (n-
(Octylthio) -6- (4-hydroxy3 ', 5'-di-t-butylanilino) -1,3,5-triazine, styrenated phenol, styrenated cresol, tocophenol, 2-t-butyl-6- ( 3'-t-butyl-
5′-methyl-2′-hydroxybenzyl) -4-methylphenyl acrylate, 2,2′-methylenebis (4
-Methyl-6-t-butylphenol), 2,2'-methylenebis (4-ethyl-6-t-butylphenol), 2,2'-methylenebis (4-methyl-6-cyclohexylphenol), 2,2'- Dihydroxy-
3,3′-di (α-methylcyclohexyl) -5,5 ′
-Dimethyldiphenylmethane, 2,2'-ethylidene-
Bis (2,4-di-t-butylphenol), 2,2 ′
-Butylidene-bis (4-methyl-6-t-butylphenol), 4,4′-methylenebis (2,6-di-t-
Butylphenol), 4,4'-butylidenebis (3-
Methyl-6-t-butylphenol), 1,6-hexanediol bis [3- (3,5-di-t-butyl-4-
Hydroxyphenyl) propionate], triethylene glycol-bis-3-(-t-butyl-4-hydroxy-5-methylphenyl) propionate, N, N'-
Bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine, N, N'-hexamethylenebis- (3,5-di-t-butyl-4-hydroxy) hydrocinnamide , 2,2'-thiobis (4
-Methyl-6-t-butylphenol), 4,4′-thiobis (3-methyl-6-t-butylphenol),
2,2-thiodiethylenebis- [3 (3,5-di-t-
Butyl-4-hydroxyphenyl) propionate],
Bis [2-t-butyl-4-methyl-6- (3-t-butyl-5-methyl-2-hydroxybenzyl) phenyl] terephthalate, 1,1,3-tris (2-methyl-4-hydroxy- 5-t-butylphenyl) butane,
1,3,5-trimethyl-2,4,6-tris (3,5
-Di-t-butyl-4-hydroxybenzyl) benzene, tris (3,5-di-t-4-hydroxybenzyl) isocyanurate, 1,3,5-tris (4-t-
Butyl-3-hydroxy-2,6-dimethylbenzyl)
Isocyanurate, tetrakis [methylene-3-
(3 ', 5'-di-t-butyl-4-hydroxyphenyl) propionate] methane, calcium (3,5-di-t-butyl-4-hydroxybenzylmonoethylphosphonate), propyl gallate, gallic Octyl acid,
Lauryl gallate, 2,4,6-tri-t-butylphenol, 2,5-di-t-butylhydroquinone, 2,5
-Di-t-amylhydroquinone, 1,1,3-tris-
(2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris- (3,5-di-t-butyl-4-hydroxybenzyl) Benzene, 3,9-bis [2- {3- (3-t-
Butyl-4-hydroxy-5-methylphenyl) propionyloxy {-1,1-dimethylethyl] -2,8,
Examples thereof include 10-tetraoxaspiro [5,5] undecane, and one or more of these can be used.

Of these, 2,6-di-tert-butyl-p-cresol and 2,2′-methylenebis (4-methyl-6-butyl) are preferred in terms of availability and use in lubricating oils.
t-butylphenol), 2,2′-methylenebis (4
-Ethyl-6-t-butyl-4-ethylphenol),
4,4′-methylenebis (2,6-di-t-butylphenol) and the like are preferable.

The concentration ratio in the case of mixing and using a phenolic antioxidant and a phosphorus-based antioxidant is not particularly limited. Therefore, the concentration of the phenolic antioxidant should be 1
In this case, the concentration of the phosphorus-based antioxidant can be used without any problem in the range of about 0.1 to 9.

As the dispersant, known dispersants can be used. For example, a dispersion type polymethacrylate, a sulfonate, a phenate, a salicylate, a phosphonate, a phosphonate, a carboxylate, a succinimide, and the like can be given, and one or more selected from these are added and used. The amount of the dispersant added is 0.1 to 2 parts by weight, preferably 0.2 to 1 part by weight based on 100 parts by weight of the base oil.
Parts by weight. If the amount is less than 0.1 parts by weight, the dispersing effect is weakened. On the other hand, if the amount exceeds 2 parts by weight, the demulsifying property and long-term stability may decrease, which is not preferable.

The dispersion-type polymethacrylate can be obtained by copolymerization of an alkyl methacrylate monomer and a polar monomer. As the polar monomer, one or more selected from diethylaminoethyl methacrylate, 2-methyl-5-vinylpyrrolidone, N-vinylpyrrolidone, and morpholinoethyl methacrylate can be suitably used. The molar ratio between the alkyl methacrylate monomer and the polar monomer is 80:20 at which the dispersion effect is maximized.
A range of ~ 95: 5 is preferred. The molecular weight of the polymer is 50,000 to 100 in number average molecular weight.
000 can be suitably used.

The sulfonates, phenates, salicylates, phosphonates, phosphonates, carboxylate are added in the form of alkaline earth metal salts. As alkaline earth metals, calcium, magnesium, barium,
One or more selected from strontium can be used. However, at least one selected from calcium and magnesium is preferred in terms of availability. Further, the alkaline earth metal can be used by adding it in a large excess over the neutralization equivalent. Such salts are called overbased salts and have excellent ability to neutralize acidic substances such as carboxylic acids and sulfur oxides generated by oxidation.

Examples of the succinimide include monosuccinimide, bissuccinimide, and boron-containing succinimides thereof. Those having an alkenyl group can be suitably used. This alkenyl succinimide is used for dispersing insolubles, sludge, etc. generated by oxidation of organic substances.

A thiophosphate having three hydrocarbon groups, wherein the hydrocarbon group has 1 to 15 carbon atoms, preferably 9 to 14 carbon atoms, more preferably 10 to 13 carbon atoms.
One or more selected from a secondary alkyl group, a secondary alkyl group, and an aryl group having an alkyl group can be suitably used. In the case where an aryl group having an alkyl group (alkylated phenyl group) is used as the hydrocarbon group, it is preferable to have two alkyl groups from the viewpoint of hydrolysis stability. When an alkyl group is used as the hydrocarbon group, a primary alkyl group is used.
It is preferable because it has excellent stability against thermal and oxidative deterioration. In particular, when emphasis is placed on the long-term stability of the lubricating oil, it is preferable that 90% or more of the hydrocarbon groups be primary alkyl groups. However, since the secondary alkyl group is excellent in lubricity, a part of the hydrocarbon group may be a secondary alkyl group. In this case, the primary alkyl group is 50 to 90%, preferably 60 to 90%.
To 90%, more preferably 70 to 90%.
If it is less than 50%, the long-term stability of the lubricating oil decreases, and 90%
When the ratio exceeds the above, the effect of improving lubricity cannot be seen.

When two or more kinds of different hydrocarbon groups or different hydrocarbon groups are introduced, two kinds of hydrocarbon groups having the same hydrocarbon group in the molecule may be used in combination. Further, thiophosphates having different types of hydrocarbon groups or hydrocarbon groups having different carbon numbers in the molecule may be used as a mixture. For example, trialkylthiophosphates in which alkyl groups having 11 and 12 carbon atoms have substantially the same molecular number can be used.

In addition, particularly when an industrial grade reagent is used, it is unavoidable that one having one or two hydrocarbon groups in the molecule is mixed. Further, in the alkylated phenyl group, those having a different number of substitutions of the alkyl group,
It is inevitable that alkyl groups having different carbon numbers are mixed. However, as long as sludge generation preventing performance and solubility in base oil do not matter, they can be used as they are.

The addition amount of the thiophosphate having three hydrocarbon groups is 0.1 to 2 parts by weight, particularly preferably 0.2 to 1 part by weight, per 100 parts by weight of the base oil. If the amount is less than 0.1 part by weight, the effect of preventing sludge formation may not be sufficient. If it exceeds 2 parts by weight,
Not only does the sludge formation prevention effect saturate,
The concentration of oxidative decomposition products increases, which may cause a decrease in lubricity and generation of sludge, which is not preferable.

In addition to the above additives, amine antioxidants, rust inhibitors, pour point depressants, and metal deactivators conventionally used in lubricating oils as long as the object of the present invention is not impaired. An agent or the like can be appropriately added.

Examples of the amine antioxidant include p, p'-dioctyldiphenylamine, N-phenyl-N'-isopropyl-p-phenylenediamine, poly 2,2,4-trimethyl-1,2-dihydroquinoline,
6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, thiodiphenylamine, 4-amino-p
-Diphenylamine and the like, and one or more of these can be used. Examples of the metal deactivator include benzotriazole, tolyltriazole, benzotriazole derivatives having a hydrocarbon group having 2 to 10 carbon atoms, benzimidazole, and 2 to 2 carbon atoms.
Imidazole derivative having 20 hydrocarbon groups, carbon number 2
Examples thereof include thiazole derivatives having from 20 to 20 hydrocarbon groups, 2-mercaptobenzothiazole and the like, and one or more of these can be used.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to hydraulic working oils, but the present invention is not limited to these embodiments.

(Test Method) The oxidation stability test of lubricating oil
Lubricating oil oxidation stability test for internal combustion engines according to JIS K2514 (ISOT: 165.5 ° C, 48 hours, 165.5 ° C,
72 hours, copper and iron catalyst). Also,
The measurement of the pollution degree corresponding to the amount of sludge generated is based on JIS
Performed according to B9931.

(Example 1) As lubricating oils, the following (a) to
A composition comprising (e) was prepared. The test results are shown in Table 1. The pollution degree of ISOT at 165.5 ° C. for 48 hours was 2.8 mg / 100 ml, and the contamination degree at 165.5 ° C. for 72 hours was 9.4 mg / 100 ml. (A) Lubricating base oil (100 parts by weight): a solvent dewaxed base oil having a kinematic viscosity of 46 mm ² / s at 40 ° C.
6.8 mm ² / s at 100 ° C., flash point 222
° C, sulfur content: 0.15 mass%, aromatic component: 5 mass% (b) ZnDTP (0.05 parts by weight as zinc): dialkyldithiophosphorus having a primary alkyl group having 8 carbon atoms in the alkyl group Zinc acid (c) Phosphorus antioxidant (0.4 parts by weight): Tris-
(Alkylated phenyl) phosphite (Irganox L-180 manufactured by Ciba Specialty Chemicals) (d) Dispersed polymethacrylate (0.5 parts by weight): Nitrogen-dispersed polymethacrylate Vi manufactured by Lomax Co.
scoplex O-292 (number average molecular weight is about 700
(E) Trialkylthiophosphate A (0.5 parts by weight): Phoslex S-230 manufactured by Sakai Chemical Co., in which alkyl groups having 11 and 12 carbon atoms are almost equimolar.

[0033]

[Table 1]

(Example 2) To the lubricating oil of Example 1, 0.5 part by weight of 2,6-di-tert-butyl-p-cresol (DBPC), which is a phenolic antioxidant, was further added.
A lubricating oil was made. Table 1 shows the test results.
The degree of contamination at 165.5 ° C for 48 hours is 1.8 mg.
/ 100 ml, the degree of contamination at 165.5 ° C. for 72 hours was 8.4 mg / 100 ml.

Example 3 (e) Trialkylthiophosphate A in Example 1 was replaced with trialkylthiophosphate B tri (alkylated phenyl) thiophosphate: Irgalubbe manufactured by Ciba Specialty Chemicals
A lubricating oil similar to that of Example 1 was prepared except that the lubricating oil was changed to 211 °. Table 1 shows the test results.
The contamination degree at 5.5 ° C. for 48 hours is 1.8 mg / 10
0ml, 165.5 ° C, contamination degree at 72 hours is 1
It was 4.7 mg / 100 ml.

Example 4 A lubricating oil was prepared in the same manner as in Example 1 except that (d) in Example 1 was changed to an overbased Ca salicylate. The base number of the overbased Ca salicylate used was 280 mgKOH / g. The test results are shown in Table 1. The degree of contamination of the ISOT at 165.5 ° C. for 48 hours was 1.4 mg / 100 ml and 165.5.
The degree of contamination at 72 ° C. for 72 hours is 3.2 mg / 100 ml.
Met.

Example 5 A lubricating oil was prepared in the same manner as in Example 1 except that (d) in Example 1 was changed to basic Ca salicylate. The basic Ca salicylate used had a base number of 170 mgKOH / g. The test results are shown in Table 1. The degree of contamination of ISOT at 165.5 ° C. for 48 hours was 0.9 mg / 100 ml, 165.5 ° C.
The contamination degree at 72 hours was 1.0 mg / 100 ml.

Example 6 A lubricating oil was prepared in the same manner as in Example 1 except that (d) in Example 1 was changed to bissuccinimide. The test results are shown in Table 1.
The contamination degree at 65.5 ° C. for 48 hours is 2.3 mg / 1.
The degree of contamination at 00 ml, 165.5 ° C. and 72 hours is 1
It was 1.2 mg / 100 ml.

Comparative Example 1 A lubricating oil similar to that of Example 1 was prepared except that (d) and (e) of Example 1 were omitted. Table 2 shows the test results.
The degree of contamination at time is 150 mg / 100 ml, 16
The contamination degree at 5.5 ° C. for 72 hours is 400 mg / 10
It was 0 ml.

[0040]

[Table 2]

Comparative Example 2 The same lubricating oil as in Comparative Example 1 was used except that the phosphorus-based antioxidant (c) in Comparative Example 1 was changed to 2,6-di-t-butyl-p-cresol. Produced. Table 2 shows the test results.
The contamination degree at time was as good as 2.6 mg / 100 ml, but the contamination degree at 165.5 ° C. and 72 hours was 2
It was 94 mg / 100 ml.

Comparative Example 3 A lubricating oil was prepared in the same manner as in Example 1 except that (e) of Example 1 was omitted. The test results are shown in Table 2. The pollution degree of ISOT at 165.5 ° C. and 48 hours was as good as 1.6 mg / 100 ml, but the pollution degree at 165.5 ° C. and 72 hours was 385 m.
g / 100 ml.

Comparative Example 4 A lubricating oil was prepared in the same manner as in Example 1 except that (d) of Example 1 was omitted. The test results are shown in Table 2. The pollution degree of the ISOT at 165.5 ° C. for 48 hours was as good as 1.0 mg / 100 ml, but the contamination degree at 165.5 ° C. for 72 hours was 327 m.
g / 100 ml.

Comparative Example 5 A lubricating oil was prepared in the same manner as in Example 3 except that the dispersion type polymethacrylate of Example 3 was omitted. Table 3 shows the test results.
The degree of contamination at 5 ° C for 48 hours is 2.3 mg / 100m
However, the degree of contamination at 165.5 ° C. for 72 hours showed a high value of 550 mg / 100 ml.

[0045]

[Table 3]

Comparative Example 6 A lubricating oil was prepared in the same manner as in Example 4 except that the trialkylthiophosphate was not used. The test results are shown in Table 3.
The contamination degree at 5.5 ° C. for 48 hours is 1.2 mg / 10
It was as good as 0 ml, but the contamination degree at 165.5 ° C. for 72 hours was 23.5 mg / 100 ml.

Comparative Example 7 A lubricating oil similar to that of Example 5 was prepared except that the trialkylthiophosphate of Example 5 was omitted. The test results are shown in Table 3.
The contamination degree at 5.5 ° C. for 48 hours is 1.8 mg / 10
It was as good as 0 ml, but the contamination degree at 165.5 ° C. for 72 hours was 41.8 mg / 100 ml.

Comparative Example 8 A lubricating oil similar to that of Example 6 was prepared except that the trialkylthiophosphate of Example 6 was omitted. The test results are shown in Table 3.
The contamination degree at 5.5 ° C. for 48 hours is 10.5 mg / 1.
The value was as high as 00 ml, and the contamination degree at 165.5 ° C. for 72 hours was also 800 mg / 100 ml.

[0049]

According to the present invention, a lubricating oil capable of preventing the generation of sludge for a long period of time even when a lubricating base oil having a reduced degree of hydrorefining or a lubricating base oil having a solvent dewaxed is used. Manufacturable. In particular, it is suitable for hydraulic equipment and transmissions used in poor environments.

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Claims (8)

[Claims] 1. A zinc compound of dithiophosphoric acid having two hydrocarbon groups in an amount of 0.005 to 5 parts by weight based on 100 parts by weight of a lubricating base oil composed of mineral oil and / or synthetic oil.
0.3 parts by weight, 0.1 to 3 parts by weight of a phosphorus-based antioxidant,
0.1 to 2 thiophosphates having three hydrocarbon groups
A lubricating oil composition containing 0.1 parts by weight and 0.1 to 2 parts by weight of a dispersant. 2. 50% of the hydrocarbon groups of the dithiophosphoric acid
The lubricating oil composition according to claim 1, wherein the above is a primary alkyl group having 5 to 11 carbon atoms. 3. The hydrocarbon group of the thiophosphate,
The lubricating oil composition according to any one of claims 1 and 2, wherein the lubricating oil composition is at least one selected from an alkyl group having 8 to 15 carbon atoms, an aryl group, and an aryl group having an alkyl group. 4. The lubricating oil composition according to claim 1, wherein the dispersant is a dispersion type polymethacrylate. 5. A zinc compound of dithiophosphoric acid having two hydrocarbon groups in an amount of 0.005 to 5 parts by weight based on 100 parts by weight of a lubricating base oil composed of mineral oil and / or synthetic oil.
0.3 parts by weight, 0.1 to 3 parts by weight of a mixture of a phenolic antioxidant and a phosphorus-based antioxidant, 0.1 to 2 parts by weight of a thiophosphate having three hydrocarbon groups, and 0 .1 to 2 parts by weight of a lubricating oil composition. 6. 50% of the hydrocarbon groups of the dithiophosphoric acid
The lubricating oil composition according to claim 5, wherein the above is a primary alkyl group having 5 to 11 carbon atoms. 7. The hydrocarbon group of the thiophosphate,
The lubricating oil composition according to any one of claims 5 and 6, wherein the lubricating oil composition is at least one selected from an alkyl group having 8 to 15 carbon atoms, an aryl group, and an aryl group having an alkyl group. 8. The lubricating oil composition according to claim 5, wherein the dispersant is a dispersion type polymethacrylate.