JP2010095691A - Power saving gear oil composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gear oil composition, being excellent in power saving and low-temperature fluidity, and having a good extreme-pressure property. <P>SOLUTION: The gear oil composition contains a poly-α-olefin, whose kinematic viscosity at 40°C is 10-100 mm<SP>2</SP>/s, as a base oil for a lubricating oil, and an olefin-based viscosity index-improving agent including a copolymer, whose weight-average molecular weight is 4,000-150,000, of ethylene and a monomer other than ethylene and an extreme pressure agent containing sulfur are blended in the composition, the blending amount of the extreme pressure agent containing sulfur being 0.2-10 mass% based on the total amount of the composition, and a kinematic viscosity of the composition at 40°C being 50-1,000 mm<SP>2</SP>/s. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power-saving gear oil composition.

  In recent years, global warming has progressed, and there is an urgent need to reduce carbon dioxide emissions, which is one of the greenhouse gases. In Japan, the Law Concerning the Rational Use of Energy and the Law Concerning the Promotion of Global Warming Countermeasures were revised and implemented in 2006, and factories, transporters, etc. are now required to reduce power consumption more than ever. I came.

As one method of reducing power consumption, power saving from the lubricating oil side used in industrial machines and transportation machines is being attempted. Under such circumstances, power savings are also being studied for industrial gear oils used in bearings and gears of industrial machinery. Attempts have been made to cope with blending techniques such as carbamate (for example, see Patent Documents 1 and 2).
By the way, various machines are required to reduce power consumption at the start-up in addition to during normal operation, and this is addressed by improving low-temperature fluidity. Similarly, improvement in low temperature fluidity is required for gear oil.
Furthermore, when saving power and improving low-temperature fluidity, it is naturally necessary to have sufficient extreme pressure, which is the basic performance of gear oil.

JP-A-6-220475 Japanese Unexamined Patent Publication No. Hei 7-197068

An object of this invention is to provide the gear oil composition which showed the outstanding power saving effect, and also has extreme pressure property.

As a result of earnest research to solve the above problems, the present inventor blended a specific olefinic viscosity index improver with a lubricating base oil of a specific polyalphaolefin, and further contains an extreme pressure containing sulfur. Based on this finding, a gear oil composition having excellent power saving and low-temperature fluidity and excellent extreme pressure can be obtained by adding and mixing the agent to a specific composition. The present invention has been completed.

That is, the present invention contains a polyalphaolefin having a kinematic viscosity at 40 ° C. of 10 to 100 mm ² / s as a lubricating base oil and a monomer other than ethylene and ethylene having a weight average molecular weight of 4,000 to 150,000. A composition in which an olefin viscosity index improver comprising a copolymer and an extreme pressure agent containing sulfur are blended, and the blending amount of the extreme pressure agent containing sulfur is based on the total amount of the composition The gear oil composition is characterized by being 0.2 to 10% by mass and having a kinematic viscosity at 40 ° C. of 50 to 1000 mm ² / s.
Moreover, this invention provides the gear oil composition whose said olefin type viscosity index improver is a copolymer of ethylene and a C3-C30 olefin in the said gear oil composition.

Further, the present invention provides the gear oil composition, wherein the sulfur-containing extreme pressure agent is at least one selected from sulfurized olefins and sulfur-phosphorus extreme pressure agents represented by the following general formula (5). A gear oil composition is provided.

(In the formula, R ³ and R ⁴ represent a linear or branched saturated or unsaturated aliphatic hydrocarbon group or cyclic hydrocarbon group having ^{3 to} 18 carbon atoms, which may be the same or different. R ⁵ represents a linear or branched alkylene group having 1 to ⁶ carbon atoms, R ⁶ represents hydrogen or a linear or branched saturated or unsaturated aliphatic hydrocarbon group having 1 to 18 carbon atoms, Represents a cyclic hydrocarbon group.)
The present invention also provides a gear oil composition in which 0.001 to 1.0% by mass of a molybdenum compound is added to the total amount of the composition in terms of molybdenum amount in the gear oil composition. It is.

The gear oil composition of the present invention uses a poly-α-olefin having a specific kinematic viscosity as a lubricating base oil, and is further combined with a specific olefin viscosity index improver and an extreme pressure agent containing a specific amount of sulfur. Therefore, it is excellent in power saving property, low-temperature fluidity, and good extreme pressure.

(Base oil)
The poly α-olefin base oil used as the base oil of the lubricating oil composition of the present invention has a kinematic viscosity at 40 ° C. of 10 to 100 mm ² / s according to JIS K2283 kinematic viscosity test method, preferably 15 to 100 mm ² / s. , more preferably from 20 to 80 mm ² / s, particularly preferably 25~75mm ² / s. When the 40 ° C. kinematic viscosity is less than 10 mm ² / s, the kinematic viscosity of the lubricating oil composition of the present invention cannot be satisfied unless more olefin-based viscosity index improver is blended. When the 40 ° C. kinematic viscosity exceeds 100 mm ² / s, in order to satisfy the kinematic viscosity of the lubricating oil composition of the present invention, the amount of the olefin-based viscosity index improver must be reduced, and as a result, excellent Power saving cannot be obtained.

The poly α-olefin, 40 ° C. and that kinematic viscosity mixture of two or more poly α-olefin is 10 to 100 mm ² / s, 40 ° C. kinematic viscosity of 2 or more which are not included in 10 to 100 mm ² / s Or a mixture of two or more polyα olefins having a kinematic viscosity of 40 ° C. of 10 to 100 mm ² / s and a poly α olefin having a kinematic viscosity of 40 ° C. of 10 to 100 mm ² / s. Even if it exists, the 40 degreeC kinematic viscosity after mixing should just be adjusted to 10-100 mm < ² > / s.

The poly-α-olefin is an α-olefin polymer and is not particularly limited as long as it satisfies the above 40 ° C. kinematic viscosity. preferable. Particularly preferred poly α-olefins are dimer and hexamer of α-decene (carbon number 10) 2-6 mer, or α-dodecene (carbon number 12) 2-6 mer. Contains more than the body.
As a suitable production example of poly α-olefin, synthesis is performed by synthesizing α-olefin having 6 to 18 carbon atoms by low polymerization of ethylene or thermal decomposition of wax, polymerizing 2 to 9 units of this α-olefin, and performing hydrogenation reaction. Is done.
The average number of carbon atoms per molecule of the polyα-olefin is not particularly limited as long as it is in the above-mentioned 40 ° C. kinematic viscosity range, but is preferably 12 to 65, more preferably 15 to 60, and still more preferably 18 ~ 55.

In the lubricating oil composition of the present invention, a small amount of other base oil may be mixed with the poly-α-olefin as the base oil. The content of the poly α olefin is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more, based on the total amount of all base oils. It is preferably 98% by mass or more.
In the gear oil composition of the present invention, the blending amount of the total base oil is the blending of olefinic viscosity index improver, sulfur-containing extreme pressure agent, molybdenum compound added as necessary, and other additives. The total amount of the base oil and the total amount of the base oil may be adjusted to be 100% by mass, preferably 30 to 98.8% by mass, and 42 to 96.8% by mass with respect to the total amount of the composition. More preferably, 55-94.8 mass% is further more preferable, and 67-92.5 mass% is especially preferable.

(Olefin viscosity index improver)
The olefin viscosity index improver used in the hydraulic oil composition of the present invention is a copolymer composed of ethylene and a monomer other than ethylene.
Examples of monomers other than ethylene that form a copolymer with ethylene include olefin hydrocarbons, diene hydrocarbons, vinyl aromatic hydrocarbons, and the like. The number of carbon atoms of these monomers other than ethylene is preferably 3 to 30, more preferably 3 to 25, still more preferably 3 to 15, particularly preferably 3 to 8, and most preferably 3. ~ 5. It is preferable that the number of carbon atoms of the monomer other than ethylene is 30 or less because the molecular weight of the viscosity index improver can be kept relatively low and shear stability can be improved.

The olefinic hydrocarbon used as a monomer other than ethylene may be linear, cyclic, or branched. Specific examples of the olefinic hydrocarbon include propylene, n-butene, i-butylene, cyclobutene, n-pentene, i-pentene, cyclopentene, n-hexene, i-hexene, n-heptene, and i-to. Puten and the like.
The diene hydrocarbon used as a monomer other than ethylene may be a chain, a ring, or a branched chain. Specific examples of the diene hydrocarbon include butadiene, cyclobutadiene, pentadiene, cyclopentadiene, hexadiene, heptadiene and the like.

Examples of vinyl aromatic hydrocarbons used as monomers other than ethylene include styrene and divinylbenzene.
Among these monomers other than ethylene, preferred are olefinic hydrocarbons, and particularly preferred are olefinic hydrocarbons having 3 to 5 carbon atoms.
The olefin-based viscosity index improver is synthesized by polymerizing monomers other than ethylene and ethylene. However, the number of monomers other than ethylene may be one, or two or more.

The molar ratio of ethylene and a monomer other than ethylene is not particularly limited, but is preferably 80:20 to 20:80, more preferably 70:30 to 30:70, and still more preferably 65:35 to 35:65. It is.
The olefin viscosity index improver may be a regular alternating polymer, a random polymer, a block polymer, or a graft polymer.
The preferred weight average molecular weight of the olefin viscosity index improver is 1,000 to 150,000, more preferably 1,200 to 100,000, still more preferably 1,500 to 55,000, and particularly preferably. Is from 3,000 to 30,000, most preferably from 5,000 to 25,000. By setting the weight average molecular weight to 1,000 or more, predetermined traction characteristics tend to be easily obtained. By setting the weight average molecular weight to 150,000 or less, viscosity reduction under shear tends to be suppressed. The weight average molecular weight is measured by gel permeation chromatography and is a value in terms of polystyrene.

As long as the object of the present invention is not impaired, the olefin viscosity index improver may be either a dispersion type or a non-dispersion type (one having a monomer-derived polar group is a dispersion type and does not have a polar group) Things are called non-dispersive). That is, a dispersion type in which nitrogen atom-containing compounds and alkyl esters are used as monomer molecules other than ethylene may be used. Specific examples of such nitrogen atom-containing compounds include alkyl-vinyl pyridine, N-vinyl pyrrolidone, vinyl imidazole and the like. Specific examples of alkyl esters include polyalkylene glycol esters, maleic acid esters, and fumaric acid esters. These can be used alone or in combination of two or more.

However, when the molar ratio of the monomer having a dispersing group in the olefin-based viscosity index improver to the other monomer exceeds 25, the traction coefficient of the mixture of the base oil and the olefin-based viscosity index improving agent Tends to increase and power consumption tends to increase. Therefore, the molar ratio of the monomer having a dispersing group and the other monomer is preferably 0: 100 to 25:75, and more preferably 0: 100 to 10:90.

The blending amount of the olefin viscosity index improver is preferably 1 to 60% by mass, more preferably 3 to 50% by mass, and further preferably 5 to 40% by mass with respect to the total amount of the gear oil composition. It is particularly preferably 7 to 30% by mass. By setting the lower limit of the amount to be 1% by mass or more, it tends to easily obtain a power saving effect. If the blending amount exceeds 60% by mass, it is not economical.
One of the above olefinic viscosity index improvers may be used alone, or two or more thereof may be used in combination.

(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 extreme pressure agent. From the viewpoint of wear resistance, sulfurized olefins and sulfur- It is preferable to mix a phosphorus extreme pressure agent.

(I) Sulfur-based extreme pressure agent Examples of the sulfur-based extreme pressure agent include hydrocarbon sulfides, sulfurized fats and oils, and sulfurized esters.
As said hydrocarbon sulfide, the hydrocarbon sulfide represented by General formula (1) or General formula (2) is mentioned.

In General Formula (1) and General Formula (2), R ¹ is a monovalent hydrocarbon group (for example, a linear or branched saturated or unsaturated aliphatic hydrocarbon group having 2 to 20 carbon atoms (for example, , An alkyl group or an alkenyl group), or an aromatic hydrocarbon group having 6 to 26 carbon atoms), and R ² is a divalent hydrocarbon group (for example, linear or branched saturated or 2 to 20 carbon atoms) An unsaturated aliphatic hydrocarbon group or an aromatic hydrocarbon group having 6 to 26 carbon atoms).

Moreover, in general formula (1) and general formula (2), b is an integer greater than or equal to 1, and 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 ¹ 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 ² include an ethylene group, a propylene group, a butylene group, and a phenylene group.

  Specific examples of these hydrocarbon sulfides include (1) polysulfide compounds such as diisobutyl disulfide, dioctyl polysulfide, di-tert-butyl polysulfide, di-tert-nonyl polysulfide, dibenzyl polysulfide, and the like (2) polysulfide compounds. Sulfurized olefins obtained by sulfurizing olefins such as isobutylene and terpenes with sulfides such as sulfur, and (3) a reaction product of isobutylene and sulfur having the chemical formulas of general formula (3) and general formula (4). Examples of such compounds are envisioned.

一般式（３）中、ｂ及びｃは、一般式（１）におけるｂ及びｃと同じである。

In general formula (3), b and c are the same as b and c in general formula (1).

一般式（４）中、ｂ及びｃは、一般式（２）におけるｂ及びｃと同じである。
上記硫化油脂としては、油脂と硫黄の反応生成物が挙げられる。
ここで、油脂としては、ラード、牛脂、鯨油、パーム油、ヤシ油、ナタネ油などの動植物油脂が挙げられる。
硫化エステルは、油脂と各種アルコールとの反応により得られる脂肪酸エステルを硫化することにより得られ、化学構造そのものは明確でない。油脂としてラード、牛脂、鯨油、パーム油、ヤシ油、ナタネ油などの動植物油脂などが挙げられる。

In general formula (4), b and c are the same as b and c in general formula (2).
Examples of the sulfurized fats and oils include reaction products of fats and sulfur.
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.
The sulfurized ester is obtained by sulfurizing a fatty acid ester obtained by a reaction between fats and oils and various alcohols, and the chemical structure itself is not clear. Examples of the fats and oils include animal and vegetable fats and oils such as lard, beef tallow, whale oil, palm oil, coconut oil and rapeseed oil.

(Ii) Sulfur-phosphorus extreme pressure agent Examples of the sulfur-phosphorus extreme pressure agent include those prepared by combining the above 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 triesters, 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.

Specific examples of the sulfur-phosphorus compound 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 thiophosphite and thiophosphate derivatives include amine salts, metal salts, and reaction products with fatty acids with the above acid thiophosphites and acid thiophosphates, and dithiophosphoric acids represented by the following general formula (5) An ester compound or the like can also be used.

In the general formula (5), R ³ and R ^{4 each} represent a linear or branched saturated or unsaturated aliphatic hydrocarbon group or cyclic hydrocarbon group having ^{3 to} 18 carbon atoms, and may be the same. May be different. Specifically, n-propyl group, isopropyl group, n-butyl group, isobutyl group, pentyl group, hexyl group, octyl group, 2-ethylhexyl group, nonyl group, dodecyl group, propenyl group, butenyl group, phenyl Group, hexylphenyl group and the like.

R ⁵ represents a linear or branched alkylene group having 1 to 6 carbon atoms, and specifically includes a methylene group, an ethylene group, a propylene group, a butylene group, an amylene group, and a hexylene group, preferably an ethylene group. , Propylene group, butylene group.
R ⁶ represents a hydrogen atom or a linear or branched, saturated or unsaturated aliphatic hydrocarbon group or cyclic hydrocarbon group having 1 to 18 carbon atoms. Specifically, hydrogen atom, n-propyl group, isopropyl group, n-butyl group, isobutyl group, pentyl group, hexyl group, octyl group, 2-ethylhexyl group, nonyl group, dodecyl group, propenyl group, butenyl Group, phenyl group, hexylphenyl group and the like. Preferable examples include those in which R ⁵ is a propylene group and R ⁶ is a hydrogen atom.

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. This content is more preferably 0.2 to 8% by mass, still more preferably 0.2 to 5% by mass, and particularly preferably 0.5 to 3% by mass. If the content is less than 0.2% by mass, it tends to be difficult to obtain the extreme pressure performance required as a gear oil composition, and even if it exceeds 10% by mass, an effect commensurate with the addition amount cannot be obtained.
The above-mentioned extreme pressure agent containing sulfur can be used singly or in combination of two or more.

(Molybdenum compound)
The gear oil composition of the present invention can further enhance the power saving effect by further containing 0.001 to 1.0% by mass of a molybdenum compound in terms of molybdenum based on the total amount of the gear composition. The content of the molybdenum compound in terms of molybdenum is preferably 0.005 to 0.3% by mass, more preferably 0.01 to 0.2% by mass.
Examples of the molybdenum compound include amine molybdate, molybdenum dithiophosphate, molybdenum dithiocarbamate, and the like.

The amine molybdate can be obtained by reducing molybdenum trioxide, molybdic acid, or an alkali salt thereof with a reducing agent and then reacting with amines. The amines used here may be any of primary amines, secondary amines, and tertiary amines. As an example, primary amines have an alkyl group having 4 to 24 carbon atoms. Examples of secondary amines include monoalkylamines, dialkylamines having an alkyl group having 1 to 24 carbon atoms, and tertiary amines include trialkylamines having an alkyl group having 1 to 24 carbon atoms. . Among these, a particularly preferable amine in terms of oil solubility of the product is a secondary amine, and a dialkylamine having an alkyl group having 6 to 24 carbon atoms is preferable. As for carbon number of the alkyl group in dialkylamine, 8-20 are more preferable, and 10-16 are more preferable.

（式中、Ｒ^７〜Ｒ^１０は炭素数６〜１８の炭化水素基であり、それぞれ同一であってもよいし、異なってもよい。Ｘ及びＹは、硫黄原子又は酸素原子を示す。） Examples of molybdenum dithiocarbamate include compounds having the structure of general formula (6).

(In formula, R < ⁷ > -R < ¹⁰ > is a C6-C18 hydrocarbon group, and may be the same respectively, and may differ. X and Y show a sulfur atom or an oxygen atom.)

（式中、Ｒ^７〜Ｒ^１０は炭素数６〜１８の炭化水素基であり、それぞれ同一であってもよいし、異なってもよい。Ｘ及びＹは、硫黄原子又は酸素原子を示す。）
上記モリブデン化合物の中で、最も好ましいものはモリブデン酸アミンである。 Examples of molybdenum dithiophosphate include compounds having the structure of general formula (7).

(In formula, R < ⁷ > -R < ¹⁰ > is a C6-C18 hydrocarbon group, and may be the same respectively, and may differ. X and Y show a sulfur atom or an oxygen atom.)
Of the molybdenum compounds, the most preferred is an amine molybdate.

(Other additives)
In the gear oil composition of the present invention, various known additives can be blended as necessary within a range that does not impair the object of the present invention. For example, an antioxidant, an oily agent, a detergent / dispersant, a rust inhibitor, a metal deactivator, a pour point depressant, a defoamer, a demulsifier, and the like can be mentioned.
Antioxidants include phenol-based antioxidants such as 2,6-di-tert-butyl-p-cresol, amine-based antioxidants such as alkylated diphenylamine and alkylated phenyl-α-naphthylamine, phosphonic acid esters, etc. And phosphorus-based antioxidants.

Examples of the oily agent include higher fatty acids such as oleic acid and stearic acid, higher alcohols such as oleyl alcohol, amines such as oleylamine, and esters such as butyl stearate.
Examples of the cleaning dispersant include ashless cleaning dispersants such as alkenyl succinimides and alkenyl succinic esters, and alkaline earth metal cleaning dispersants.
Examples of the rust inhibitor include carboxylic acid, metal soap, carboxylic acid amine salt, sulfonic acid metal salt, and partial ester of polyhydric alcohol.

Examples of metal deactivators include benzotriazole and derivatives thereof, and alkyl succinic acid derivatives.
Examples of the pour point depressant include polyalkyl methacrylate, polybutene, polyalkyl styrene, polyvinyl acetate, polyalkyl acrylate and the like.
Examples of antifoaming agents include silicone oil and ester-based antifoaming agents.
Examples of the demulsifier include demulsifiers such as an anionic surfactant, a cationic surfactant, and a nonionic surfactant.
These additives may be used alone or in combination of two or more.

(Properties of gear oil composition)
40 ° C. The kinematic viscosity of the gear oil composition of the present invention, in the JIS K2283 Kinematic Viscosity Test Method (40 ° C.), a 50 to 1000 mm ² / s, preferably 60~700mm ² / s. When the 40 ° C. kinematic viscosity is less than 50 mm ² / s, an appropriate oil film thickness cannot be maintained, and extreme pressure properties tend to decrease. When the 40 ° C. kinematic viscosity exceeds 1000 mm ² / s, power consumption tends to increase.

The gear oil composition of the present invention has a viscosity index of preferably 100 or more, more preferably 110 or more, still more preferably 120 or more, and particularly preferably 130 or more in the JIS K2283 kinematic viscosity test method. If the viscosity index is too low, the low-temperature viscosity tends to be high, and the power consumption during low-temperature starting tends to increase.

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.
The base oil and additive components used in the preparation of the compositions in each Example and Comparative Example are as follows.
The 40 ° C. kinematic viscosity was measured by the JIS K2283 kinematic viscosity test method.

(A) Base oil (A-1) Polyalphaolefin (A-2) having a kinematic viscosity of 30.5 mm ² / s composed of 2 to 5 mer of 1-decene monomer and 2 of 1-decene monomer A polyα-olefin (A-3) having a kinematic viscosity of 47.3 mm ² / s composed of a ˜5-mer and a 2-6 mer of 1-decene monomer, and a kinematic viscosity of 40 ° C. of 62.5 mm ² / Alpha polyolefin (A-4) which is 2 to 7-mer of 1-decene monomer, polyalphaolefin (A-5) which is 400 mm < ² > / s and is 40 mm dynamic viscosity is 31 mm ² / s pentaerythritol ester (Kao Lube 262 manufactured by Kao Corporation)
(A-6) Hydrorefined mineral oil having a kinematic viscosity at 40 ° C. of 83 mm ² / s

(B) Viscosity index improver (B-1) Ethylene / propylene copolymer (B-2) having a weight average molecular weight of 16,000 and an ethylene / propylene molar ratio of 53:47 The weight average molecular weight is 5,000. An ethylene / propylene copolymer (B-3) having a molar ratio of ethylene / propylene of 53:47, polyisobutylene (B-4) having a weight average molecular weight of 150,000, and a poly having a weight average molecular weight of 22,000 The methacrylate weight average molecular weight was measured by gel permeation chromatography and calculated in terms of polystyrene. In gel permeation chromatography, three Shodex GPC LF-804 were used for the column, THF was used for the moving layer, and a differential refraction detector was used for the detector.

(C) Extreme pressure agent (C-1) Sulfurized olefin (sulfur content 19% by mass)
(C-2) Amine salt of acid phosphate (C-3) β-dithiophosphorylated propionic acid (in formula (5), R ³ and R ⁴ are isobutyl groups, R ⁵ is a propylene group, R ⁶ is a hydrogen atom What is)
(C-4) Sulfurized ester (D) Molybdenum compound (D-1) Mo acid amine (Mo content: 4.4% by mass, reaction product of molybdic acid with ditridecylamine)

(Evaluation methods)
The viscosity index, extreme pressure property, and power saving effect of the gear oil composition were evaluated by the following evaluation methods.
<Viscosity index>
The viscosity index was measured by the JIS K2283 kinematic viscosity test method.

<Extreme pressure>
Extreme pressure was evaluated by a load bearing test. The load resistance test was based on German Industrial Standard (DIN) DIN 51354-2 using an FZG gear tester. Specifically, after applying a load conforming to the standard to the gear, the test is performed until the speed reaches 21,700 at a gear rotation speed of 1,440 rpm. This is one stage. Hereinafter, the load stage was raised stepwise, and the total area of wear scratches (scuffing, scoring) on the 16 tooth surfaces of the pinion at the end of each stage was measured, and less than 20 mm ² was accepted. The "FZG gear test failure stage" described in each table is the final stage that has failed (for example, those with 11 FZG gear test failure stages are acceptable up to 10 stages, and not at the 11th stage. Indicates that it passed.) Therefore, the higher the numerical value of the FZG gear test pass stage, the higher the extreme pressure property. The test was conducted up to 12 stages, and those that passed the 12th stage were shown as 12+.

<Power saving effect>
In the FZG test specified in ASTM D 5182, the power consumption at 3 ° C. at 50 ° C. and 1450 rpm was compared with the power consumption of two types of industrial gear oil (Cosmo Gear SE220) specified in JIS K 2219. evaluated.
◎: Power saving effect 2.5% or more ○: Power saving effect 1.5% to less than 2.5% △: Power saving effect 0.5% to less than 1.5% ×: Power saving effect 0.5 %Less than

(Examples 1-7)
A gear oil composition was prepared by blending the base oil with a viscosity index improver, an extreme pressure agent containing sulfur, and other additives in the proportions (mass%) shown in the upper part of Table 1. Various performances of these gear oil compositions were evaluated, and the results are shown in the lower part of Table 1.
(Comparative Examples 1-6)
A gear oil composition was prepared by blending a base oil with a viscosity index improver, an extreme pressure agent, and other additives in the proportions (mass%) shown in the upper part of Table 2. Various performances of these gear oil compositions were evaluated, and the results are shown in the lower part of Table 2.

The gear oil composition of the present invention can be used in various applications. For example, it can be used for bearings and gears of industrial machines, metal processing, particularly preferably rolling mills, conveyor belt conveyors, turbines of power plants, construction machines, machine tools, ships and the like.

Claims (4)

From a copolymer of ethylene having a kinematic viscosity at 40 ° C. of 10 to 100 mm ² / s as a lubricating base oil and a weight average molecular weight of 4,000 to 150,000 and a monomer other than ethylene A composition in which an olefin viscosity index improver and sulfur-containing extreme pressure agent are blended, and the amount of the sulfur-containing extreme pressure agent is 0.2 to 10 with respect to the total amount of the composition. A gear oil composition having a mass% and a kinematic viscosity at 40 ° C. of 50 to 1000 mm ² / s. The gear oil composition according to claim 1, wherein the olefin viscosity index improver is a copolymer of ethylene and an olefin having 3 to 30 carbon atoms. The gear oil according to claim 1 or 2, wherein the sulfur-containing extreme pressure agent is at least one selected from sulfurized olefins and a sulfur-phosphorus extreme pressure agent represented by the following general formula (5). Composition.

(In the formula, R ³ and R ⁴ represent a linear or branched saturated or unsaturated aliphatic hydrocarbon group or cyclic hydrocarbon group having ^{3 to} 18 carbon atoms, which may be the same or different. R ⁵ represents a linear or branched alkylene group having 1 to ⁶ carbon atoms, R ⁶ represents hydrogen or a linear or branched saturated or unsaturated aliphatic hydrocarbon group having 1 to 18 carbon atoms, Represents a cyclic hydrocarbon group.) The gear oil composition according to any one of claims 1 to 3, wherein the molybdenum compound is further blended in an amount of 0.001 to 1.0 mass% with respect to the total amount of the composition in terms of molybdenum amount.