JP5188309B2 - Flame retardant gear oil composition - Google Patents

Description

  The present invention relates to a flame retardant gear oil composition.

In recent years, as machine technology has been developed more and more, equipment has been operated under high speed, high temperature and high load conditions. Lubricating oil used in such locations must assume contact with high temperature parts. In some cases, the use of lubricating oil or filling work is performed under severe conditions such as the origin of fire. Therefore, it is desired that the lubricating oil used in such a part is more flame-retardant and does not continue to burn even if ignited, that is, has excellent self-extinguishing properties.
For this reason, studies have been made for the purpose of improving the flame retardancy of lubricating oils. For example, in order to improve the flame retardancy of hydraulic fluids, attempts have been made to incorporate water-containing systems, fatty acid esters, phosphate esters, and the like. (For example, refer to Patent Documents 1 to 3).
On the other hand, improvement in flame retardancy has also been studied for gear oil (see, for example, Patent Document 4).
JP-A-2-214795 JP-A-3-21697 JP-A-11-269480 JP-A-6-264087

However, since the gear oil is required to have excellent lubricity, a higher viscosity than that of the hydraulic fluid is required. For this reason, it is difficult to obtain the viscosity required for gear oil only with the phosphoric acid ester and the like.
Moreover, although improvement of the flame retardance in gear oil is examined, there are few examples put into practical use and the further improvement is requested | required about the flame retardance and self-extinguishing property in gear oil.

  The present invention has been made in view of such circumstances, has flame retardancy and self-extinguishing properties that can be used in various applications that may be ignited, and has thermal oxidation stability and extreme pressure properties. Another object of the present invention is to provide a flame retardant gear oil composition which is excellent in the above.

  As a result of intensive studies to achieve the above object, the present inventors have found it difficult to use a specific condensed phosphate ester as a base oil and an extreme pressure agent containing sulfur as an extreme pressure agent. It has been found that a gear oil composition having excellent flammability and self-extinguishing properties, as well as excellent thermal oxidation stability and extreme pressure properties can be obtained. Furthermore, it discovered that extreme pressure property was improved further by mix | blending a specific extreme pressure agent as an extreme pressure agent containing sulfur. That is, in the present invention, the following gear oil composition is provided.

<1> A gear oil composition containing a base oil and an extreme pressure agent,
As said base oil, 20 mass% or more of condensed phosphate ester represented with the following general formula (1) is contained with respect to the said base oil whole quantity,
As the extreme pressure agent, containing 0.2 to 10% by mass of an extreme pressure agent containing sulfur with respect to the total amount of the gear composition,
And the kinematic viscosity in 40 degreeC of the said gear oil composition is 50-1000 mm < ² > / s, The gear oil composition characterized by the above-mentioned.

In general formula (1), R ¹ , R ² , R ⁴ and R ⁵ are each independently a hydrocarbon group having 1 to 22 carbon atoms, R ³ is a hydrocarbon group having 1 to 6 carbon atoms, R ⁶ and R ⁷ Each independently represents a hydrogen atom or a hydrocarbon group having 1 to 15 carbon atoms, and n is an integer of 1 to 5.
<2> In the general formula (1), R ¹ , R ² , R ⁴ and R ⁵ are aromatic hydrocarbon groups having 6 to 15 carbon atoms, R ³ is a hydrocarbon group having 3 carbon atoms, R ⁶ and R Each of ⁷ represents a hydrogen atom, and n is an integer of 1 to 4, wherein the gear oil composition according to <1>.
<3> The gear according to <1> or <2>, wherein the sulfur-containing extreme pressure agent is at least one extreme pressure agent selected from sulfurized olefins and sulfur-phosphorus. Oil composition.
<4> As the base oil, a 40 ° C. kinematic viscosity is 1 to 2000 mm ² / s, and further contains a phosphorus-containing lubricant base oil other than the condensed phosphate ester represented by the general formula (1). the features <1> to formic ya oil composition according to any one of <3>.
<5> The phosphorus-containing lubricating base oil other than the condensed phosphate represented by the general formula (1) is at least one selected from the group represented by the following general formula (2). <4> The gear oil composition according to <4> .
(R ⁸ O) (R ⁹ O) (R ¹⁰ O) P (O) _a (2)
(In General Formula (2), R ⁸ , R ⁹ and R ¹⁰ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 24 carbon atoms, and a is 0 or 1.)

  ADVANTAGE OF THE INVENTION According to this invention, the gear oil composition which is excellent in a flame retardance and self-extinguishing property, and excellent in thermal oxidation stability and extreme pressure property which can be used for the various uses with the possibility of ignition is provided.

Hereinafter, the gear oil composition according to the present invention will be specifically described.
1. Base oil (1) Condensed phosphate ester The gear oil composition according to the present invention comprises, as a base oil, a condensed phosphate ester represented by the following general formula (1) (hereinafter, "condensed phosphate ester according to the present invention"). Or simply “condensed phosphate ester”).

In general formula (1), R ¹ , R ² , R ⁴ and R ⁵ are each independently a hydrocarbon group having 1 to 22 carbon atoms, preferably 2 to 18 carbon atoms, more preferably 6 to 15 carbon atoms. Is a hydrocarbon group. If R ¹ , R ² , R ⁴ and R ⁵ have too many carbon atoms, the self-extinguishing properties and flame retardancy tend to decrease, and if too small, the fluidity, which is the inherent performance of the lubricating oil, tends to decrease. .

In addition, examples of the hydrocarbon group represented by R ¹ , R ² , R ^4, and R ⁵ include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group.
From the viewpoint of thermal oxidation stability, an aromatic hydrocarbon group having 6 to 15 carbon atoms is preferred. Specific examples of the aromatic hydrocarbon group include phenyl group, methylphenyl group, ethylphenyl group, propylphenyl group, isopropylphenyl group, n-butylphenyl group, sec-phenylbutyl group, tert-butylphenyl group, dimethylphenyl group. Group, diethylphenyl group, dipropylphenyl group, diisopropylphenyl group, dibutylphenyl group, trimethylphenyl group, triethylphenyl group, tripropylphenyl group, triisopropylphenyl group, tributylphenyl group, etc., but thermal oxidation stability From this viewpoint, a phenyl group is particularly preferable.

In general formula (1), R ³ is a hydrocarbon group having 1 to 6 carbon atoms, preferably a hydrocarbon group having 2 to 4 carbon atoms, and more preferably a hydrocarbon group having 3 carbon atoms. R ³ tends to fail to obtain a predetermined self-extinguishing property and flame retardancy even if the number of carbon atoms is too large or too small.
Examples of R ³ include an ethylene group, a propylene group, a butylene group, and a phenylene group.

In general formula (1), R ⁶ and R ⁷ are each independently a hydrogen atom or a hydrocarbon group having 1 to 15 carbon atoms, preferably a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms, particularly preferably This is the case for hydrogen atoms. When the number of carbon atoms in R ⁶ and R ⁷ is too large, there is a tendency that predetermined self-extinguishing properties and flame retardancy cannot be obtained.
The hydrocarbon group represented by R ⁶ and R ⁷ may be an aromatic hydrocarbon group, an alicyclic hydrocarbon group, or an aliphatic hydrocarbon group, and may be either a straight chain or a branched chain. Specific examples of the aliphatic hydrocarbon group include a methyl group, an ethyl group, a propyl group, a butyl group, an octyl group, an isodecyl group, a dodecyl group, and a tridecyl group. Specific examples of the aromatic hydrocarbon group include a phenyl group, a xylyl group, an ethylphenyl group, a propylphenyl group, and a butylphenyl group.

  In general formula (1), n is an integer of 1-5, Preferably it is 1-4, More preferably, it is 1-3. If n is too much or too little, the fluidity, which is the original performance of the lubricating oil, tends to decrease. From the viewpoint of fluidity, a mixture of condensed phosphates having different n is preferable.

Further, the condensed phosphate ester blended in the gear oil composition of the present invention preferably has a kinematic viscosity at 40 ° C. of 100 to 5000 mm ² / s, more preferably 200 to 4000 mm ² / s, and particularly preferably 500. -3000mm < ² > / s. When the kinematic viscosity of the condensed phosphate compound blended as the base oil is too small, the flame retardancy and the self-extinguishing property tend to be low, and the kinematic viscosity required for the gear oil may not be adjusted appropriately. If the kinematic viscosity of the condensed phosphate ester is too large, the fluidity is deteriorated, the kinematic viscosity when the gear oil composition is made tends to increase, and the stirring resistance tends to increase, and the force required to drive the gear Tend to be larger.

  Moreover, the compounding quantity of the condensed phosphate ester mix | blended with the gear oil composition of this invention is 20 mass% or more with respect to the base oil whole quantity, Preferably it contains 40 mass% or more. If the blending amount is too small, flame retardancy and self-extinguishing properties are not sufficient, and thermal oxidation stability tends to be lowered. On the other hand, there is no particular upper limit on the amount of the condensed phosphate ester, and 100 mass% of the total amount of the base oil may be the condensed phosphate ester.

(2) Phosphorus-containing lubricant base oil other than condensed phosphate ester If the condensed phosphate ester of the general formula (1) alone is difficult to be within the kinematic viscosity range of the gear oil composition of the present invention as the base oil, Lubricating base oils other than the condensed phosphate ester of the general formula (1) can also be blended. As such a lubricating base oil, those which do not lower the flame retardancy and self-extinguishing properties are desirable, and from such a viewpoint, it is preferable to use a phosphorus-containing lubricating base oil. When the phosphorus-containing lubricating base oil is blended, the blended amount of the condensed phosphate ester of the general formula (1) is 20 to 80% by weight, preferably 40 to 80% by weight, and the rest is phosphorus. It is preferable to use a contained lubricating base oil. It should be noted that a base oil other than the phosphorus-containing base oil can be included as long as it is a trace amount that does not adversely affect the characteristics of the gear oil according to the present invention (for example, a reduction in flame retardancy).

Examples of the phosphorus-containing lubricant base oil that can be blended include phosphine, phosphinite, phosphonite, phosphite, phosphine oxide, phosphinate, phosphonate, phosphate, acid phosphate, thiophosphate, and the like.
Among these, the phosphorus-containing lubricant base oil that may be blended as the base oil in the gear oil composition of the present invention is at least one selected from the group represented by the following general formula (2). Phosphoric acid compounds are preferred.
(R ⁸ O) (R ⁹ O) (R ¹⁰ O) P (O) _a (2)
In general formula (2), R < ⁸ >, R < ⁹ > and R < ¹⁰ > represent a hydrogen atom or a C1-C24 hydrocarbon group each independently, and a is 0 or 1.

In General Formula (2), when the carbon number of the hydrocarbon group represented by R ⁸ , R ⁹ and R ¹⁰ is 24 or less, the fluidity of the base oil is further improved. From the viewpoint of improving fluidity, the number of carbon atoms of the hydrocarbon groups R ⁸ , R ⁹ and R ¹⁰ is preferably 1-18, more preferably 2-15. Moreover, the total amount of carbon atoms of R ⁸ , R ⁹ and R ¹⁰ is preferably 4 to 45, more preferably 6 to 40.

In the general formula (2), the hydrocarbon group represented by R ⁸ , R ⁹ and R ¹⁰ may be any of an aromatic hydrocarbon group, an alicyclic hydrocarbon group, and an aliphatic hydrocarbon group. Is preferably an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a combination thereof, more preferably an aromatic hydrocarbon group, or a combination of an aliphatic hydrocarbon group and an aromatic hydrocarbon group Group, particularly preferably an aromatic hydrocarbon group.

  Specific examples of the phosphorus-containing lubricant base oil represented by the general formula (2) include cresyl diphenyl phosphate, tricresyl phosphate, trixyl phosphate, phenyl isopropyl phosphate, butyl phenyl phosphate and the like.

The dynamic viscosity of the phosphorus-containing lubricating base oil is 1 to 2000 mm ² / s at 40 ° C., preferably ² to 1000 mm ² / s, and more preferably 5 to 600 mm ² / s. If the kinematic viscosity of the phosphorus-containing lubricant base oil to be blended is too low, the prescribed flame retardancy and self-extinguishing properties tend not to be obtained, and the kinematic viscosity required as gear oil may not be adjusted appropriately. is there. On the other hand, if the kinematic viscosity of the phosphorus-containing lubricant base oil to be added is too high, the kinematic viscosity of the gear oil composition tends to be too high and the stirring resistance tends to increase, which is necessary for driving the gear. Tend to increase.

  The amount of the phosphorus-containing lubricating base oil that can be blended in the gear oil composition of the present invention can be appropriately selected according to the required characteristics, but the kinematic viscosity of the gear oil composition defined in the present invention is appropriately set. From the viewpoint of easy adjustment, it is preferably 10 to 80% by mass, more preferably 20 to 60% by mass, based on the total amount of base oil.

2. Extreme Pressure Agent Containing Sulfur The gear oil composition of the present invention contains an extreme pressure agent containing sulfur as the extreme pressure agent.
Examples of the extreme pressure agent containing sulfur include a sulfur-based extreme pressure agent and a sulfur-phosphorus-based extreme pressure agent.

(1) Sulfur-based extreme pressure agent Examples of the sulfur-based extreme pressure agent include hydrocarbon sulfides and sulfurized fats and oils.
Examples of the hydrocarbon sulfide include hydrocarbon sulfides represented by the following general formula (3) or general formula (4).

In the general formula (3) and the general formula (4), R ¹¹ represents a monovalent hydrocarbon group (for example, a linear or branched saturated or unsaturated group having 2 to 20 carbon atoms such as an alkyl group or an alkenyl group). Represents a saturated aliphatic hydrocarbon group or an aromatic hydrocarbon group having 6 to 26 carbon atoms, and R ¹² represents a divalent hydrocarbon group (for example, a linear or branched saturated or 2 to 20 carbon atom) An unsaturated aliphatic hydrocarbon group or an aromatic hydrocarbon group having 6 to 26 carbon atoms).
Moreover, in General formula (3) and General formula (4), b is an integer greater than or equal to 1, Each b may be the same or different in a repeating unit, and c represents 0 or an integer greater than or equal to 1.

Specific examples of the monovalent hydrocarbon group represented by R ¹¹ include ethyl group, propyl group, butyl group, nonyl group, dodecyl group, propenyl group, butenyl group, phenyl group, tolyl group, hexylphenyl group, A benzyl group etc. are mentioned.
Specific examples of the divalent hydrocarbon group represented by R ¹² include an ethylene group, a propylene group, a butylene group, and a phenylene group.

  Specific examples of these hydrocarbon sulfides include polysulfide compounds such as diisobutyl disulfide, dioctyl polysulfide, di-tert-butyl polysulfide, di-tert-nonyl polysulfide and dibenzyl polysulfide, and polyisobutylene and terpenes. Sulfurized olefins obtained by sulfurizing sulfur such as sulfur, and reaction products of isobutylene and sulfur, which are presumed to have the following general formula (5) or general formula (6) Is mentioned.

  In general formula (5), b and c are the same as b and c in general formula (3).

  In general formula (6), b and c are the same as b and c in general formula (4).

On the other hand, the sulfurized fats and oils include reaction products of fats and fats.
Here, as fats and oils, animal and vegetable fats and oils such as lard, beef tallow, whale oil, palm oil, coconut oil, rapeseed oil and the like can be mentioned.
In the present invention, the above sulfur compounds and the like can be used as a sulfur-based extreme pressure agent, but it is more preferable to use a sulfurized olefin from the viewpoint of improving extreme pressure.

(2) Sulfur-phosphorus extreme pressure agent Examples of the sulfur-phosphorus extreme pressure agent include those obtained by combining the above-mentioned sulfur extreme pressure agent and phosphorus extreme pressure agent, and sulfur-phosphorus compounds. It is done.
Phosphorus extreme pressure agents combined with sulfur extreme pressure agents include phosphates, phosphites, and derivatives thereof. The phosphate and phosphite may be any of mono, di and triester, and the alcohol residue thereof is an alkyl group having 4 to 30 carbon atoms such as butyl, octyl, lauryl, stearyl or oleyl group, carbon such as phenyl group, etc. Examples include an aryl group having 6 to 30 carbon atoms, an alkyl-substituted aryl group having 7 to 30 carbon atoms such as methylphenyl and octylphenyl groups. Specific examples of the phosphorus extreme pressure agent include tributyl phosphate, monooleyl phosphate, dioctyl phosphate, dioleyl phosphite, diphenyl phosphite, tricresyl phosphite and the like. Examples of these derivatives include the above monoesters, ie, acid phosphates and amine salts of acid phosphites, and examples thereof include stearylamine salts, oleylamine salts, and coconutamine salts.

  Examples of the sulfur-phosphorus compound include thiophosphite, thiophosphate, and derivatives thereof. The thiophosphite may be mono, di, or trithiophosphite. The thiophosphate may be mono, di, tri, or tetrathiophosphate. Thiophosphite and thiophosphate may be mono-, di- or triester, and the alcohol residue thereof is an alkyl group having 4 to 30 carbon atoms such as butyl, octyl, lauryl, stearyl or oleyl group, or phenyl group. And aryl groups having 6 to 30 carbon atoms such as alkyl substituted aryl groups having 7 to 30 carbon atoms such as methylphenyl and octylphenyl groups. Examples of specific compounds include tributyl thiophosphate, monooleyl thiophosphate, dioctyl thiophosphate, tricresyl thiophosphate, and the like. Examples of these amine salts include stearylamine salts, oleylamine salts, and coconut amine salts. Examples of the derivatives of thiophosphite and thiophosphate include amine salts, metal salts, reaction products with fatty acids, and the like with the above acid thiophosphite and acid thiophosphate, and dithiophosphoric acid represented by the following general formula (7) An ester compound or the like can also be used.

In general formula (7), R ¹³ and R ¹⁴ each represent a hydrocarbon group having 2 to 20 carbon atoms, and may be the same or different. R ¹⁵ represents a divalent aliphatic hydrocarbon having 1 to 17 carbon atoms, and may be linear or branched. X represents hydrogen or a carboxyl group.

The content of the extreme pressure agent containing sulfur must be 0.2 to 10% by mass with respect to the total amount of the gear oil composition of the present invention. More preferably, it is 0.2-8 mass%, Most preferably, it is 0.2-5 mass%, More preferably, it is 0.5-3 mass%, Most preferably, it is 0.8-2 mass% is there. If the content of the extreme pressure agent is less than 0.2% by mass, the extreme pressure performance required as a gear oil composition cannot be obtained, and if it exceeds 10% by mass, it contributes to flame retardancy and self-extinguishing properties. The content of the condensed phosphate ester is relatively lowered, and the flame retardancy and the self-extinguishing property are lowered.
The above-mentioned extreme pressure agent containing sulfur can be used singly or in combination of two or more.

3. Other Additives The gear oil composition of the present invention can contain various additives as needed.
Examples of additives include metal detergents such as alkaline earth metal sulfonates, alkaline earth metal phenates, alkaline earth metal salicylates; alkenyl succinimides, alkenyl succinimide boronated modified products, benzylamine, alkylpolyamines Dispersants such as zinc, phosphorus, sulfur, amine, ester, and other antiwear agents; polymethacrylate, ethylene propylene copolymer, styrene-isoprene copolymer, styrene-isoprene copolymer Various viscosity index improvers such as hydride or polyisobutylene; alkylphenols such as 2,6-di-tert-butyl-p-cresol, 4,4′-methylenebis- (2,6-di-t-butylphenol), etc. Bisphenols, n-octadecyl-3- (4′-hydroxy) -3 ', 5'-di-tert-butylphenol) propionate and other antioxidants such as phenolic compounds, aromatic amine compounds such as naphthylamines and dialkyldiphenylamines; carboxylic acids such as stearic acid, dicarboxylic acids, metals Various rust inhibitors such as soaps, carboxylic acid amine salts, heavy sulfonic acid metal salts, carboxylic acid partial esters of polyhydric alcohols; various corrosion inhibitors such as benzotriazole and benzimidazole; various antifoaming agents such as silicone oil Is mentioned. An additive can be used individually by 1 type or in combination of 2 or more types.

4). The kinematic viscosity of the gear oil composition kinematic viscosity invention of the gear oil composition, in JIS K2283 Kinematic Viscosity Test Method (40 ° C.), a 50 to 1000 mm ² / s, there preferably 50~800mm ² / s More preferably, it is 100-600 mm < ² > / s, Most preferably, it is 150-500 mm < ² > / s. When the 40 ° C. kinematic viscosity of the gear oil composition is less than 50 mm ² / s, flame retardancy and self-extinguishing properties tend to be low, and lubricity required for gear oil tends to be low. On the other hand, when the 40 ° C. kinematic viscosity of the gear oil composition exceeds 1000 mm ² / s, the stirring resistance tends to increase, and the force required to drive the gear tends to increase.

5. Applications The gear oil composition of the present invention can be used in various applications where there is a possibility of ignition and flame retardancy is required. For example, it can be used for bearings and gears of industrial machines, metal processing, particularly preferably for gear parts of rolling mills, conveyor belt conveyors, turbines of power plants, construction machines, machine tools, ships and the like. In addition, although the composition of this invention is used suitably for gear oil, it can also be used for industrial lubricating oils, such as hydraulic oil, turbine oil, and compressor oil.

Next, the present invention will be described more specifically with reference to examples. In addition, this invention is not restrict | limited at all by these examples.
In Table 1 (Examples 1 to 10) and Table 2 (Comparative Examples 1 to 5), the base oil is blended in mass% with respect to the entire base oil, and the additive is blended in mass% with respect to the entire composition. Was prepared.
The base oils and additives used for preparing the compositions in each Example and each Comparative Example are as follows.

<Base oil>
-Condensed phosphate ester: (trade name; “CR-741” manufactured by Daihachi Chemical Co., Ltd. In the general formula (1), R ¹ , R ² , R ⁴ and R ⁵ are each an aromatic hydrocarbon group having 6 carbon atoms. , R ³ is a hydrocarbon group having 3 carbon atoms, R ⁶ and R ⁷ are each a hydrogen atom, and n is a mixture of 1 to ^{3. The} 40 ° C. kinematic viscosity of this condensed phosphate ester is 1300 mm ² / s. .)
Phosphate ester: trixyl phosphate, 40 ° C. kinematic viscosity: 46 mm ² / s
Mineral oil A: 40 ° C. kinematic viscosity: 100 mm ² / s
Mineral oil B: 40 ° C. kinematic viscosity: 460 mm ² / s

<Additives>
(C-1) Sulfurized olefin (19% sulfur content)
(C-2) Acid phosphate amine salt (C-3) β-dithiophosphorylated propionic acid (in general formula (7), R ¹³ and R ¹⁴ are isobutyl groups, R ¹⁵ is carbon number 2 and X is a carboxyl group)
(C-4) Sulfurized ester (sulfur content 15%)

<Additives>
・ Antioxidant: Octylated diphenylamine

  The 40 ° C. kinematic viscosity was measured by the JIS K2283 kinematic viscosity test method.

-Combustion test-
After soaking the sample in half of medical gauze (100% cotton material, 7cm x 15cm), ignite from the side without the sample, and whether to continue combustion (flame retardant and self-extinguishing) It was evaluated with.
◎: No combustion ○: Combustion is completed in less than 30 seconds (with self-extinguishing)
X: Burned and continued for more than 30 seconds (no self-extinguishing)

-Thermal oxidation stability test-
The test was performed under the condition of no water mixing in TOST in accordance with JIS K 2514.4. The evaluation was performed by measuring the acid value increase after the 500 hr test at 90 ° C. and based on the following criteria.
○: Increase in acid value is less than 2.0 mgKOH / g.
X: An acid value increase is 2.0 mgKOH / g or more.

-Extreme pressure test-
It was carried out by the Timken method according to JIS K 2519.
○: OK load resistance value of 60 Lb or more Δ: OK load resistance value of 50 to less than 60 Lb ×: OK load resistance value of less than 50 Lb

Claims (5)

A gear oil composition containing a base oil and an extreme pressure agent,
As said base oil, 20 mass% or more of condensed phosphate ester represented with the following general formula (1) is contained with respect to the said base oil whole quantity,
As the extreme pressure agent, containing 0.2 to 10% by mass of an extreme pressure agent containing sulfur with respect to the total amount of the gear composition,
And the kinematic viscosity in 40 degreeC of the said gear oil composition is 50-1000 mm < ² > / s, The gear oil composition characterized by the above-mentioned.


(In the general formula (1), R ¹ , R ² , R ⁴ and R ⁵ are each independently a hydrocarbon group having 1 to 22 carbon atoms, R ³ is a hydrocarbon group having 1 to 6 carbon atoms, R ⁶ and R 5 ⁷ represents a hydrogen atom or a C1-C15 hydrocarbon group each independently, and n is an integer of 1-5.) In the general formula (1), R ¹ , R ² , R ⁴ and R ⁵ are aromatic hydrocarbon groups having 6 to 15 carbon atoms, R ³ is a hydrocarbon group having 3 carbon atoms, and R ⁶ and R ⁷ are respectively The gear oil composition according to claim 1, which represents a hydrogen atom, and n is an integer of 1 to 4.   The gear oil composition according to claim 1 or 2, wherein the sulfur-containing extreme pressure agent is at least one extreme pressure agent selected from sulfurized olefins and sulfur-phosphorus. . The base oil has a kinematic viscosity at 40 ° C. of 1 to 2000 mm ² / s, and further contains a phosphorus-containing lubricant base oil other than the condensed phosphate ester represented by the general formula (1). formic ya oil composition according to any one of claims 1 to 3. The phosphorus-containing lubricant base oil other than the condensed phosphate ester represented by the general formula (1) is at least one selected from the group represented by the following general formula (2). The gear oil composition according to claim 4 .
(R ⁸ O) (R ⁹ O) (R ¹⁰ O) P (O) _a (2)
(In General Formula (2), R ⁸ , R ⁹ and R ¹⁰ each independently represent a hydrogen atom or a hydrocarbon group having 1 to 24 carbon atoms, and a is 0 or 1.)