WO2024116789A1

WO2024116789A1 - Lubricating oil composition

Info

Publication number: WO2024116789A1
Application number: PCT/JP2023/040521
Authority: WO
Inventors: 佳奈子鮫島; 正実金丸; 清和片山; 省二朗棚瀬; 幸太大場; 貴浩阪口; 潤小比類巻; 行敏藤浪
Original assignee: 出光興産株式会社
Priority date: 2022-12-02
Filing date: 2023-11-10
Publication date: 2024-06-06
Also published as: JP2024080513A

Abstract

Provided is a lubricating oil composition including a base oil (a) and a base oil (b), wherein the mass ratio [(a)/(b)] of the base oil (a) to the base oil (b) is 50/50 to 95/5. The base oil (a) is a metallocene catalyst–based poly-α-olefin having a kinematic viscosity at 100°C of 40-130 mm²/s. The base oil (b) is a base oil having a kinematic viscosity at 100°C of 1-30 mm²/s. The lubricating oil composition has a high viscosity index and excellent low-temperature fluidity, and particularly, can suitably be used as gear oil used in wind power generators that are utilized in harsh environments with large temperature variation.

Description

Lubricating Oil Composition

The present invention relates to a lubricating oil composition.

In recent years, in order to reduce the burden on the environment and the use of fossil fuels, which are at risk of depletion, demand for wind power generation, which utilizes renewable energy, is expected to increase further in the future.
Wind power generation utilizes wind force by converting the kinetic energy of the wind into power using a propeller or other rotor that rotates when exposed to the wind, and this power is then used to drive a generator to convert it into electrical energy.
In wind power generation, because the rotation speed of the rotor is slow, a gearbox is used in consideration of the power generation efficiency of the generator. Various types of gearboxes are known, among which planetary gear type power transmission devices are widely used.
Such planetary gear type power transmission devices require high-performance gear oil, and are also required to be able to operate for long periods of time without maintenance, with less frequent oil changes.
In response to these demands, lubricant base oils and additives are being investigated.
For example, Patent Document 1 discloses a lubricating oil composition containing at least one lubricating base oil selected from mineral oils and synthetic oils, and a copolymer of an olefin having a molecular weight of 1,200 to 50,000 and an alkyl methacrylate, for the purpose of reducing the amount of sludge generated, improving the viscosity index, and improving the extreme pressure properties.

JP 2013-249461 A

It is preferable that general machine lubricating oils have little change in viscosity at high and low temperatures and exhibit stable lubricating performance. In particular, wind power generators are used in harsh environments with large temperature changes, so gear oils used in wind power generators are required to be stable against large temperature changes. In particular, it is desirable to reduce the increase in viscosity at low temperatures.
Therefore, there has been a demand for lubricating oils with high viscosity index and good low temperature fluidity.
An object of the present invention is to provide a lubricating oil composition which has a high viscosity index and excellent low-temperature fluidity.

As a result of extensive research into solving the above problems, the inventors discovered that a lubricating oil composition containing a metallocene-catalyzed poly-α-olefin with a specific kinetic viscosity and a base oil with a specific kinetic viscosity in a specific ratio can solve the above problems.

That is, the present invention relates to the following <1> to <9>.
<1> A lubricating oil composition comprising the following base oil (a) and the following base oil (b), wherein the mass ratio of base oil (a) to base oil (b) [(a)/(b)] is 50/50 to 95/5.
Base oil (a): metallocene-catalyzed poly-α-olefin having a 100°C kinematic viscosity of 40 to 130 ^mm2 /s Base oil (b): base oil having a 100°C kinematic viscosity of 1 to 30 ^mm2 /s <2> The lubricating oil composition according to the above <1>, wherein the base oil (a) is the following base oil (a1), and the mass ratio of the base oil (a1) to the base oil (b) [(a1)/(b)] is 80/20 to 95/5.
Base oil (a1): metallocene catalyst-based poly-α-olefin having a 100°C kinematic viscosity of 40 to 50 ^mm2 /s. <3> The lubricating oil composition according to the above <2>, wherein the base oil (b) is at least one selected from the group consisting of the following base oil (b1) and the following base oil (b2).
Base oil (b1): nonmetallocene catalyst-based poly-α-olefin having a 100°C kinematic viscosity of 1 to 10 ^mm2 /s Base oil (b2): ester having a 100°C kinematic viscosity of 10 to 15 ^mm2 /s <4> The lubricating oil composition according to the above <2>, wherein the base oil (b) is the following base oil (b3), and the mass ratio of the base oil (a1) to the base oil (b3) [(a1)/(b3)] is 90/10 to 95/5.
Base oil (b3): nonmetallocene catalyst-based poly-α-olefin having a 100°C kinematic viscosity of 5 to ¹⁰ mm2/s. <5> The lubricating oil composition according to the above <3>, wherein the base oil (b) is base oil (b2), or base oil (b2) and base oil (b1), and the mass ratio of base oil (b2) to base oil (b1) [(b2)/(b1)] is 80/20 to 100/0.
<6> The lubricating oil composition according to the above <1>, wherein the base oil (a) is the following base oil (a2), the base oil (b) is the following base oil (b2) and the following base oil (b4), the mass ratio of the base oil (a2) to the base oil (b) [(a2)/(b)] is 50/50 to 70/30, and the mass ratio of the base oil (b2) to the base oil (b4) [(b2)/(b4)] is 25/75 to 60/40.
Base oil (a2): metallocene-catalyzed poly-α-olefin having a 100°C kinetic viscosity of 120 to 130 ^mm2 /s Base oil (b2): ester having a 100°C kinetic viscosity of 10 to 15 ^mm2 /s Base oil (b4): non-metallocene-catalyzed poly-α-olefin having a 100°C kinetic viscosity of 1 to 30 ^mm2 /s <7> The lubricating oil composition according to any one of the above <1> to <6>, further comprising 1 to 30 mass% of at least one additive selected from the group consisting of extreme pressure agents, antiwear agents, ashless detergent-dispersants, antioxidants, rust inhibitors, metal deactivators and pour point depressants.
<8> The lubricating oil composition according to any one of the above <1> to <7>, which has a kinematic viscosity at 40° C. of 288 to 352 mm ² /s.
<9> A gear oil for wind power generation, comprising the lubricating oil composition according to any one of <1> to <8> above.

The present invention provides a lubricating oil composition that has a large viscosity index and excellent low-temperature fluidity. This lubricating oil composition is suitable as a gear oil for wind power generation.

[Lubricating Oil Composition]
The lubricating oil composition of the present invention is a lubricating oil composition comprising the following base oil (a) and the following base oil (b), wherein the mass ratio of base oil (a) to base oil (b) [(a)/(b)] is 50/50 to 95/5.
Base oil (a): a metallocene catalyst-based poly-α-olefin having a 100° C. kinetic viscosity of 40 to 130 mm ² /s. Base oil (b): a base oil having a 100° C. kinetic viscosity of 1 to 30 mm ² /s.

The lubricating oil composition of the present invention is obtained by blending the following base oil (a) and the following base oil (b), and has a mass ratio of base oil (a) to base oil (b) [(a)/(b)] of 50/50 to 95/5. By blending base oil (a) and base oil (b) in the above ratio, it is possible to obtain a lubricating oil composition having a high viscosity index and excellent low-temperature fluidity.
Base oil (a): metallocene catalyst-based poly-α-olefin having a 100°C kinematic viscosity of 40 to 130 ^mm2 /s Base oil (b): base oil having a 100°C kinematic viscosity of 1 to 30 ^mm2 /s The components, composition, characteristics, etc. of the lubricating oil composition of the present invention will be described in detail below.

[Base oil (a)]
The lubricating oil composition of the present invention contains a base oil (a) which is a metallocene-catalyzed poly-α-olefin having a 100° C. kinematic viscosity of 40 to 130 mm ² /s.
The base oil (a) is a metallocene-catalyzed poly-α-olefin, and the term "metallocene-catalyzed poly-α-olefin" refers to a poly-α-olefin polymerized using a metallocene catalyst as a polymerization catalyst.
Metallocene catalyst-based poly-α-olefins have the characteristics of a narrow composition distribution, fewer components with low regularity, and a narrow molecular weight distribution, compared to poly-α-olefins polymerized using a conventional catalyst as a polymerization catalyst (non-metallocene catalyst-based poly-α-olefins). The lubricating oil composition of the present invention has these characteristics, and by containing a metallocene catalyst-based poly-α-olefin having a specific kinetic viscosity as a main component, it is believed that a lubricating oil composition having a large viscosity index and excellent low-temperature fluidity can be obtained.

The base oil (a) preferably satisfies the following formula (1).
(Pour point (°C))≦0.01×(40°C kinematic viscosity (mm ² /s))−56 (1)

The base oil (a) preferably has a kinematic viscosity at 40° C. of 350 to 450 mm ² /s and a pour point of −50° C. or lower.
The base oil (a) preferably satisfies the following formula (2).
(Pour point (°C))≦0.28 × (viscosity index) −102 (2)

The base oil (a) preferably contains structural units derived from 1-octene and structural units derived from 1-dodecene.
The total ratio of the constituent units derived from 1-octene and the constituent units derived from 1-dodecene in the base oil (a) is preferably 90 to 100 mol %.

When base oil (a) contains constituent units derived from 1-octene and constituent units derived from 1-dodecene, the molar ratio of the constituent units derived from 1-octene to the constituent units derived from 1-dodecene in base oil (a) is preferably 3:7 to 7:3, more preferably 4:6 to 6:4, and even more preferably 4.5:5.5 to 5.5:4.5.

The preferred physical properties of the base oil (a) vary depending on the type and content of the base oil (b).
The composition will be described below with reference to the composition numbers given in "Composition of the lubricating oil composition".
In the lubricating oil composition (1), the lubricating oil composition (1-1), the lubricating oil composition (1-2), and the lubricating oil composition (1-1-1), the base oil (a) is preferably the base oil (a1).
The base oil (a1) is a metallocene-catalyzed poly-α-olefin having a 100° C. kinematic viscosity of 40 to 50 mm ² /s.
The 100° C. kinematic viscosity of the base oil (a1) is from 40 to 50 mm ² /s, preferably from 43 to 50 mm ² /s, more preferably from 45 to 50 mm ² /s, and even more preferably from 45 to 49 mm ² /s.
The base oil (a1) has a kinematic viscosity at 40° C. of preferably 300 to 500 mm ² /s, more preferably 350 to 450 mm ² /s, and even more preferably 380 to 420 mm ² /s.
If the 100° C. kinetic viscosity and the 40° C. kinetic viscosity are within the above ranges, the evaporation loss is small and the power loss due to the viscous resistance is not large, which is preferable.

In the lubricating oil composition (2), the base oil (a) is preferably the base oil (a2).
The base oil (a2) is a metallocene catalyst-based poly-α-olefin having a 100° C. kinematic viscosity of 120 to 130 mm ² /s.
The 100° C. kinematic viscosity of the base oil (a2) is from 120 to 130 mm ² /s, preferably from 122 to 130 mm ² /s, more preferably from 125 to 130 mm ² /s, and further preferably from 127 to 130 mm ² /s.
The base oil (a2) has a 40° C. kinematic viscosity of preferably 800 to 1800 mm ² /s, more preferably 1000 to 1500 mm ² /s, and even more preferably 1100 to 1400 mm ² /s.
If the 100° C. kinetic viscosity and the 40° C. kinetic viscosity are within the above ranges, the evaporation loss is small and the power loss due to the viscous resistance is not large, which is preferable.

<Method for producing base oil (a)>
There are no limitations on the method for producing the base oil (a) so long as it is a poly-α-olefin polymerized using a metallocene catalyst as the polymerization catalyst, but it is preferable to obtain it by the following method.
Specifically, it is preferable to obtain the catalyst mixture by a production method including a step 1 of mixing a metallocene compound (A), an ionic compound (B) capable of reacting with the metallocene compound to convert it into a cation, an organometallic compound (C), a plurality of raw material monomers (D) differing in the number of carbon atoms by two or more, and a component (E) which is at least one selected from alcohols (E1), phenols (E2) and ether compounds (E3) to obtain a catalyst mixture, and a step 2 of polymerizing an α-olefin containing the plurality of raw material monomers (D) using the catalyst mixture.
This is explained in detail below.

(Step 1)
Step 1 is a step of obtaining a catalyst mixture by mixing a metallocene compound (A), an ionic compound (B) capable of reacting with the metallocene compound to be converted into a cation, an organometallic compound (C), a plurality of raw material monomers (D) each having a carbon number differing by two or more, and a component (E) which is at least one selected from alcohols (E1), phenols (E2) and ether compounds (E3).

[Metallocene Compound (A)]
Examples of the metallocene compound (A) include an unbridged metallocene compound, a single-bridged metallocene compound, and a double-bridged metallocene compound. A double-bridged metallocene compound is preferred, and a double-bridged metallocene compound represented by the following general formula (I) is more preferred.

(In the formula, R ^a and R ^b each independently represent a linking group represented by the following general formula -[L ^c (R ^1c ) (R ^2c )] _n -. X ¹ and X ² each independently represent a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 20 carbon atoms, or an organic group having 1 to 20 carbon atoms containing one or more atoms selected from a halogen atom, a silicon atom, an oxygen atom, a sulfur atom, a nitrogen atom, and a phosphorus atom. M represents a transition metal of Groups 4 to 6 of the periodic table. n is an integer of 1 to 3. R ¹ and R ² each independently represent a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 20 carbon atoms, or a halogen-containing hydrocarbon group having 1 to 20 carbon atoms. ^{L c} represents an atom of Group 14 of the periodic table.)

In formula (I), ^X1 and ^X2 each independently represent a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 20 carbon atoms, or an organic group having 1 to 20 carbon atoms containing one or more atoms selected from a halogen atom, a silicon atom, an oxygen atom, a sulfur atom, a nitrogen atom, and a phosphorus atom.
M represents a transition metal of Groups 4 to 6 of the periodic table, and is preferably zirconium, titanium, or hafnium.
R ^a and R ^b are each independently a linking group represented by -[L ^c (R ^1c ) (R ^2c )] _n -, and are preferably -C(R ^1c ) (R ^2c )-, -Si(R ^1c ) (R ^2c )-, -C(R ^1c ) (R ^2c )-C(R ^1c ) (R ^2c )- or -Si(R ^1c ) (R ^2c )-Si(R ^1c ) (R ^2c )-.
n is an integer from 1 to 3.
R ^1c and R ^2c each independently represent a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 20 carbon atoms, or a halogen-containing hydrocarbon group having 1 to 20 carbon atoms, preferably a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms, and more preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
^Lc represents an atom of Group 14 of the periodic table, and is preferably a carbon atom or a silicon atom.

Specific examples of the doubly bridged metallocene compound represented by the general formula (I) include (1,1'-ethylene)(2,2'-ethylene)biscyclopentadienyl zirconium dichloride, (1,1'-dimethylsilylene)(2,2'-dimethylsilylene)biscyclopentadienyl zirconium dichloride, (1,1'-dimethylsilylene)(2,2'-ethylene)biscyclopentadienyl zirconium dichloride, (1,1'-dimethylsilylene)(2,2'-ethylene)biscyclopentadienyl zirconium dichloride, (1,1'-isopropylidene)(2,2'- Examples of such compounds include dichlorides such as (1,1'-isopropylidene)(2,2'-isopropylidene)bis(3-methylcyclopentadienyl)zirconium dichloride, as well as dimethyl, diethyl, dihydro, diphenyl and dibenzyl forms of the above compounds, with (1,1'-dimethylsilylene)(2,2'-dimethylsilylene)biscyclopentadienylzirconium dichloride being preferred.
Further, compounds in which zirconium in the above compounds is replaced with titanium or hafnium can be mentioned.
The metallocene compound (A) may be used alone or in combination of two or more kinds.

[Ionic Compound (B)]
The ionic compound (B) is not limited as long as it is an ionic compound capable of reacting with the metallocene compound (A) to be converted into a cation. The ionic compound (B) is preferably a compound represented by the following general formula (V) or a compound represented by the following general formula (VI), and more preferably a compound represented by the following general formula (V).
([L ¹ −R ³ ] ^k+ ) _a ([Z] ⁻ ) _b ... (V)
([L ² ] ^k+ ) _a ([Z] ⁻ ) _b ... (VI)

In general formula (V), ^L1 represents a Lewis base, and ^R3 represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or a hydrocarbon group having 6 to 20 carbon atoms selected from an aryl group, an alkylaryl group, and an arylalkyl group.

Specific examples of ^L1 include amines such as ammonia, methylamine, aniline, dimethylamine, diethylamine, N-methylaniline, diphenylamine, N,N-dimethylaniline, trimethylamine, triethylamine, tri-n-butylamine, methyldiphenylamine, pyridine, p-bromo-N,N-dimethylaniline, p-nitro-N,N-dimethylaniline, phosphines such as triethylphosphine, triphenylphosphine, diphenylphosphine, thioethers such as tetrahydrothiophene, esters such as ethyl benzoate, nitriles such as acetonitrile, benzonitrile, etc. Specific examples of ^R3 include a hydrogen atom, a methyl group, an ethyl group, a benzyl group, a trityl group, etc.

In general formula (VI), ^L2 represents ^M1 , ^R4R5M2 , ^R63C or ^R7M2 . ^R4 and ^R5 each independently represent a ^{cyclopentadienyl} group, a substituted ^{cyclopentadienyl} group, an indenyl group or a fluorenyl group, ^R6 represents an alkyl group having 1 to ₂₀ carbon atoms or a hydrocarbon group having 6 to 20 carbon atoms selected from an aryl group, ^an alkylaryl group and an arylalkyl group. ^R7 represents a macrocyclic ligand such as tetraphenylporphyrin or phthalocyanine.
M ¹ includes an element of Groups 1 to 3, 11 to 13, and 17 of the periodic table, and M ² represents an element of Groups 7 to 12 of the periodic table.

Here, specific examples of R ⁴ and R ⁵ include a cyclopentadienyl group, a methylcyclopentadienyl group, an ethylcyclopentadienyl group, and a pentamethylcyclopentadienyl group. Specific examples of R ⁶ include a phenyl group, a p-tolyl group, and a p-methoxyphenyl group, and specific examples of R ⁷ include tetraphenylporphyrin and phthalocyanine. Specific examples of M ¹ include Li, Na, K, Ag, Cu, Br, I, and I ₃ , and specific examples of M ² include Mn, Fe, Co, Ni, and Zn.

In formulae (V) and (VI), k is the ionic valence of [L ¹ -R ³ ] and [L ² ] and is an integer of 1 to 3, a is an integer of 1 or more, and b=(k×a).
[Z] ^- represents a non-coordinating anion [Z ¹ ] ^- or [Z ² ] ^- .
[Z ¹ ] ^- represents an anion in which a plurality of groups are bonded to an element, that is, [M ³ G ¹ G ² ... G ^f ] ^- . Here, M ³ represents an element of Groups 5 to 15 of the periodic table, preferably an element of Groups 13 to 15 of the periodic table. G ¹ to G ^f each represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, a dialkylamino group having 2 to 40 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an alkylaryl group having 7 to 40 carbon atoms, an arylalkyl group having 7 to 40 carbon atoms, a halogen-substituted hydrocarbon group having 1 to 20 carbon atoms, an acyloxy group or an organic metalloid group having 1 to 20 carbon atoms, or a heteroatom-containing hydrocarbon group having 2 to 20 carbon atoms. Two or more of G ¹ to G ^f may form a ring. f represents an integer of [(the valence of the central metal M ³ ) + 1].
[Z ² ] ⁻ represents a conjugate base of a single Brønsted acid or a combination of a Brønsted acid and a Lewis acid having a logarithm of the reciprocal of the acid dissociation constant (pKa) of −10 or less, or a conjugate base of an acid generally defined as a superacid. A Lewis base may be coordinated.

Here, in [Z ¹ ] ^- , that is, [M ³ G ¹ G ² ... G ^f ] ^- , specific examples of M ³ include B, Al, Si, P, As, Sb, etc., and preferably B and Al. Specific examples of G ¹ and G ² to G ^f include dialkylamino groups such as dimethylamino and diethylamino, alkoxy groups or aryloxy groups such as methoxy, ethoxy, n-propoxy, and phenoxy, hydrocarbon groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-octyl, n-eicosyl, phenyl, p-tolyl, benzyl, 4-t-butylphenyl, and 3,5-dimethylphenyl, halogen atoms such as fluorine, chlorine, bromine, Examples of iodine and heteroatom-containing hydrocarbon groups include a p-fluorophenyl group, a 3,5-difluorophenyl group, a pentachlorophenyl group, a 3,4,5-trifluorophenyl group, a pentafluorophenyl group, a 3,5-bis(trifluoromethyl)phenyl group, and a bis(trimethylsilyl)methyl group. Examples of organic metalloid groups include a pentamethylantimony group, a trimethylsilyl group, a trimethylgermyl group, a diphenylarsine group, a dicyclohexylantimony group, and a diphenylboron group.

Specific examples of non-coordinating anions, that is, the conjugate base [Z ² ] ⁻ of a single Bronsted acid or a combination of a Bronsted acid and a Lewis acid having a pKa of −10 or less, include trifluoromethanesulfonate anion (CF ₃ SO ₃ ) ⁻ , bis(trifluoromethanesulfonyl)methyl anion, bis(trifluoromethanesulfonyl)benzyl anion, bis(trifluoromethanesulfonyl)amide, perchlorate anion (ClO ₄ ) ⁻ , trifluoroacetate anion (CF ₃ COO) ⁻ , hexafluoroantimony anion (SbF ₆ ) ⁻ , fluorosulfonate anion (FSO ₃ ) ⁻ , chlorosulfonate anion (ClSO ₃ ) ⁻ , fluorosulfonate anion/antimony 5-fluoride (FSO ₃ /SbF ₅ ) ⁻ , fluorosulfonate anion/arsenic 5-fluoride (FSO ₃ /AsF ₅ ) ⁻ , trifluoromethanesulfonic acid/5-antimony fluoride (CF ₃ SO ₃ /SbF ₅ ) ^{− ,} and the like.

The ionic compound (B) is preferably a tetraphenylborate which may have a substituent, and more specifically, triethylammonium tetraphenylborate, tri-n-butylammonium tetraphenylborate, trimethylammonium tetraphenylborate, tetraethylammonium tetraphenylborate, methyl(tri-n-butyl)ammonium tetraphenylborate, benzyl(tri-n-butyl)ammonium tetraphenylborate, dimethyldiphenylammonium tetraphenylborate, triphenyl(methyl)ammonium tetraphenylborate, trimethylanilinium tetraphenylborate, methylpyridinium tetraphenylborate, benzylpyridinium tetraphenylborate, methyl(2-cyanopyridinium)tetraphenylborate, ammonium tetrakis(pentafluorophenyl)borate, triethylammonium tetrakis(pentafluorophenyl)borate, tri-n-butylammonium tetrakis(pentafluorophenyl)borate, triphenylammonium tetrakis(pentafluorophenyl)borate, tetra-n-butylammonium tetrakis(pentafluorophenyl)borate, tetraethylammonium tetrakis(pentafluorophenyl)borate, benzyl(tri-n-butyl)ammonium tetrakis(pentafluorophenyl)borate, methyldiphenylammonium tetrakis(pentafluorophenyl)borate, triphenyl(methyl)ammonium tetrakis(pentafluorophenyl)borate, methylanilinium tetrakis(pentafluorophenyl)borate, tetrakis(pentafluorophenyl)borate Dimethylanilinium, trimethylanilinium tetrakis(pentafluorophenyl)borate, methylpyridinium tetrakis(pentafluorophenyl)borate, benzylpyridinium tetrakis(pentafluorophenyl)borate, methyl(2-cyanopyridinium)tetrakis(pentafluorophenyl)borate, benzyl(2-cyanopyridinium)tetrakis(pentafluorophenyl)borate, methyl(4-cyanopyridinium)tetrakis(pentafluorophenyl)borate, triphenylphosphonium tetrakis(pentafluorophenyl)borate, dimethylanilinium tetrakis[bis(3,5-ditrifluoromethyl)phenyl]borate, ferrocenium tetraphenylborate, silver tetraphenylborate, trityl tetraphenylborate, tetraphenylphosphonium tetrakis[bis(3,5-ditrifluoromethyl)phenyl]borate, Examples of the ionic compound (B) include manganese tetraphenylporphyrin borate, ferrocenium tetrakis(pentafluorophenyl)borate, (1,1'-dimethylferrocenium tetrakis(pentafluorophenyl)borate, decamethylferrocenium tetrakis(pentafluorophenyl)borate, silver tetrakis(pentafluorophenyl)borate, trityl tetrakis(pentafluorophenyl)borate, lithium tetrakis(pentafluorophenyl)borate, sodium tetrakis(pentafluorophenyl)borate, manganese tetraphenylporphyrin tetrakis(pentafluorophenyl)borate, silver tetrafluoroborate, silver hexafluorophosphate, silver hexafluoroarsenate, silver perchlorate, silver trifluoroacetate, and silver trifluoromethanesulfonate. Among these, the ionic compound (B) is preferably dimethylanilinium tetrakis(pentafluorophenyl)borate.
The ionic compound (B) may be used alone or in combination of two or more kinds.

[Organometallic Compound (C)]
The organometallic compound (C) is preferably at least one selected from the group consisting of organoaluminum compounds and organozinc compounds, and more preferably an organoaluminum compound (C1).
As the organoaluminum compound, a compound represented by the general formula (VII) is used.
(R ⁸ ) _v AlQ _3-v ... (VII)
(In the formula, ^R8 is an alkyl group having 1 to 10 carbon atoms, Q is a hydrogen atom, an alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms or a halogen atom, and v is an integer of 1 to 3 or 1.5.)
As the organozinc compound, a compound represented by the general formula (VIII) is used.
(R ⁹ ) _u ZnP _2-u ... (VIII)
(In the formula, ^R9 represents an alkyl group having 1 to 10 carbon atoms, P represents an alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms or a halogen atom, and u represents an integer of 1 or 2.)

Specific examples of organoaluminum compounds represented by the general formula (VII) include trimethylaluminum, triethylaluminum, tri-normal propylaluminum, triisopropylaluminum, tri-normal butylaluminum, triisobutylaluminum, triheptylaluminum, trioctylaluminum, diisobutylaluminum hydride, diethylaluminum hydride, dimethylaluminum chloride, diethylaluminum chloride, methylaluminum dichloride, ethylaluminum dichloride, dimethylaluminum fluoride, and ethylaluminum sesquichloride, with triisobutylaluminum being preferred.

Specific examples of the organozinc compound represented by the general formula (VIII) include dimethylzinc, diethylzinc, dibutylzinc, and dioctylzinc.
The organometallic compound (C) may be used alone or in combination of two or more kinds.

In this production method, the molar ratio of the metallocene compound (A) to the ionic compound (B) is preferably 10:1 to 1:100, more preferably 2:1 to 1:10. The molar ratio of the metallocene compound (A) to the organometallic compound (C) is preferably 1:1 to 1:10,000, more preferably 1:10 to 1:1,000. The ionic compound (B) and the organometallic compound (C) can each be used alone or in combination of two or more kinds. When using two or more kinds in combination, it is preferable from the viewpoint of catalytic activity that the total ratio of the two or more kinds is within the above range.

[Multiple raw material monomers (D) having two or more different carbon atoms]
The multiple raw material monomers (D) used in step 1 are α-olefins having different carbon numbers of 2 or more, and are included in the α-olefins polymerized in step 2.
By using α-olefins with carbon numbers differing by 2 or more in this step, the resulting poly-α-olefin-containing lubricating oil composition has excellent low-temperature fluidity. Although the reason why the poly-α-olefin-containing lubricating oil composition obtained by using α-olefins with carbon numbers differing by 2 or more in obtaining the catalyst mixture has excellent low-temperature fluidity is not clear, it is believed that the excellent low-temperature fluidity is due to the random arrangement of structural units derived from multiple raw material monomers at the molecular terminals of the poly-α-olefin.

The multiple raw material monomers (D) are preferably α-olefins having 3 to 30 carbon atoms, more preferably α-olefins having 6 to 20 carbon atoms, and even more preferably α-olefins having 8 to 14 carbon atoms. Specifically, the multiple raw material monomers (D) include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-icosene, 1-henicosene, and 1-hexene. Examples of the 1-octene include 1-octene, 1-docosene, 1-tricosene, 1-tetracosene, 1-pentacosene, 1-hexacosene, 1-heptacosene, 1-octacosene, 1-nonacosene, and 1-triacontene. At least two selected from the group consisting of 1-octene, 1-nonene, 1-decene, 1-undecene, and 1-dodecene are preferred, and 1-octene (D1) and 1-dodecene (D2) are more preferred.
When the multiple raw material monomers (D) include 1-octene (D1) and 1-dodecene (D2), the ratio [D1/D2] of 1-octene (D1) to 1-dodecene (D2) used in step 1 is preferably 3:7 to 7:3, more preferably 4:6 to 6:4, and even more preferably 4.5:5.5 to 5.5:4.5, in terms of molar ratio.

The multiple raw material monomers (D) have a carbon number difference of 2 or more between the first raw material monomer and the second raw material monomer, and the difference in the carbon number between the first raw material monomer and the second raw material monomer is 2 or more, preferably 3 or more, and more preferably 4 or more. The difference in the carbon number between the first raw material monomer and the second raw material monomer is preferably 6 or less, more preferably 5 or less, and even more preferably 4.

At least two kinds of the raw material monomers (D) are used, but three or more kinds may be used, and preferably two kinds.
The raw material monomers (D) may be used as they are in the polymerization reaction, but it is more preferable to treat them with an adsorbent such as activated alumina or molecular sieve before use, since this removes impurities and improves activity.

In step 1, the ratio [D/A] of the total of the multiple raw material monomers (D) to the metallocene compound (A) is, in molar ratio, preferably 1 to 1000, more preferably 40 to 300. By setting the amount of the multiple raw material monomers (D) used within the above range, the low-temperature fluidity of the resulting poly-α-olefin-containing lubricating oil composition can be improved.
The amount of the multiple raw material monomers (D) used in step 1 is preferably 0.1 to 30 volume %, more preferably 0.5 to 20 volume %, even more preferably 0.5 to 15 volume %, still more preferably 0.6 to 12 volume %, and even more preferably 0.6 to 10 volume %, based on the catalyst mixture obtained in step 1. By setting the amount of the multiple raw material monomers (D) used within the above range, the low-temperature fluidity of the resulting lubricating oil composition containing the poly-α-olefin can be improved.

[Component (E)]
The component (E) in step 1 is at least one selected from the group consisting of alcohols (E1), phenols (E2) and ether compounds (E3), and is preferably an alcohol (E1).
By using the (E) component, particularly the alcohols (E1), the low-temperature fluidity of the obtained poly-α-olefin-containing lubricating oil composition can be further improved. The reason for this is unclear, but is thought to be as follows. It is presumed that activated and inactivated forms coexist in the catalyst solution in step 1, but it is thought that in the catalyst solution to which alcohols (E1) have been added, the alcohols act on the activated form structure to form a protective structure, thereby suppressing the generation of inactivated forms and contributing to improved catalyst activity. By becoming an activated form with this protective structure, it becomes easier for multiple raw material monomers having different molecular weights to act on each other, and it becomes easier for the structural units derived from multiple raw material monomers to be randomly arranged, and it is thought that the obtained poly-α-olefin-containing lubricating oil composition has excellent low-temperature fluidity.

(Alcohols (E1))
The alcohol (E1) is preferably an alcohol having 1 to 20 carbon atoms, more preferably an alcohol having 1 to 8 carbon atoms, and even more preferably an alcohol having 1 to 6 carbon atoms. Specific examples of the alcohol include methyl alcohol, ethyl alcohol, 1-propyl alcohol, 2-propyl alcohol, 1-butyl alcohol, 2-butyl alcohol, isobutyl alcohol, tertiary butyl alcohol, 1-pentyl alcohol, 2-pentyl alcohol, 3-methyl-1-butyl alcohol, 1-hexyl alcohol, cyclohexyl alcohol, 1-heptyl alcohol, 1-octyl alcohol, 2-ethylhexyl alcohol, triphenylmethanol, 1,2-ethanediol, 1,2-propanediol, benzyl alcohol, α-methylbenzyl alcohol, and the like, and is preferably tertiary butyl alcohol. The alcohol (E1) may be used alone or in combination of two or more kinds.

(Phenols (E2))
The phenol (E2) is preferably a phenol having 6 to 20 ring carbon atoms, more preferably a phenol having 6 to 14 ring carbon atoms, and even more preferably a phenol having 6 to 12 ring carbon atoms. Specific examples of the phenol include phenol, catechol, cresol, naphthol, 4-phenylphenol, thymol, and bisphenol A. The phenol (E2) may be used alone or in combination of two or more.

(Ether compound (E3))
When the ether compound (E3) is represented by the general formula R ¹⁰ -O-R ¹¹ , R ¹⁰ and R ¹¹ are each independently a hydrocarbon group having 1 to 20 carbon atoms, or a halogen-containing hydrocarbon group having 1 to 20 carbon atoms, and the total number of carbon atoms of R ¹⁰ and R ¹¹ is preferably 8 or less.

Specific examples of the ether compound include dimethyl ether, diethyl ether, dipropyl ether, dibutyl ether, diamyl ether, dioctyl ether, didecyl ether, methyl normal butyl ether, methyl isobutyl ether, methyl tertiary butyl ether, ethyl normal butyl ether, ethyl isobutyl ether, ethyl tertiary butyl ether, methyl phenyl ether, chloromethyl methyl ether, chloromethyl ethyl ether, bromomethyl methyl ether, 2,2-dichloroethyl methyl ether, 2-chloroethyl methyl ether, 2-bromoethyl methyl ether, 2-chloroethyl ethyl ether, α,α-dichloromethyl methyl ether, 1-chloro-2,2,2-trifluoroethyl difluoromethyl ether, 2-chloro-1,1,2-trifluoroethyl difluoromethyl ether, difluoromethyl-2,2,2-trifluoroethyl ether, 2-chloro-1,1,2-trifluoroethyl methyl ether, 2,2-dichloro-1,1-difluoroethyl methyl ether, 2-bromo-1,1,2-trifluoroethyl ethyl ether, 2-chloro-1, 1,2-trifluoroethyl ether, ethyl-1,1,2,2-tetrafluoroethyl ether, heptafluoropropyl-1,2,2,2-tetrafluoroethyl ether, n-butyl-1,1,2,2-tetrafluoroethyl ether, 4-bromophenyl trifluoromethyl ether, tetrahydrofurfuryl chloride, 2-bromofuran, 3-bromofuran, perfluoro-2-butyltetrahydrofuran, bis(4-fluorophenyl)ether, 2-bromoethyl ether, 2-chloroethyl ether, 1,2-dichloroethyl ether, pentafluoro 2,3,5,6-pentafluoroanisole, 2,4,6-tribromoanisole, 2,3,4-trichloroanisole, 2,4,6-trichloroanisole, 2,4,5-trifluoroanisole, 2-bromo-4-fluoroanisole, 4-bromo-2-fluoroanisole, 2,4-dibromoanisole, α,4-dichloroanisole, 2,3-dichloroanisole, 2,4-difluoroanisole, 2-bromoanisole, 2-chloroanisole, 2-fluoroanisole, 2-iodoanisole, benzyl-3-bromopropyl ether, etc. The ether compound (E3) may be used alone or in combination of two or more kinds.
As the component (E), one or more of the following compounds selected from (E1) to (E3) can be used alone or in combination.

The ratio (usage ratio) of the metallocene compound (A) to the component (E) [A/E] is preferably 10:1 to 1:100, more preferably 1:1 to 1:50, and even more preferably 1:1 to 1:30, in terms of molar ratio. The ratio of the organometallic compound (C) to the component (E) is preferably less than 1, and the molar ratio of the organometallic compound (C) to the component (E) is preferably 10:9 to 1000:1. The alcohol (E1) that is the component (E) is generally added in large quantities as a terminator after the polymerization reaction. Surprisingly, in this production method, activity can be improved by adding a small amount of the component (E) before polymerization.

〔solvent〕
In step 1, a solvent may be further mixed, and it is preferable to mix a solvent from the viewpoint of uniformly mixing each component of the catalyst mixture.
The solvent that can be used in step 1 is preferably at least one selected from the group consisting of aromatic hydrocarbons, alicyclic hydrocarbons, aliphatic hydrocarbons, and halogenated hydrocarbons, and more preferably aromatic hydrocarbons. Examples of aromatic hydrocarbons include benzene, toluene, xylene, and ethylbenzene, and are preferably toluene or xylene, and more preferably toluene.
Examples of the alicyclic hydrocarbon include cyclopentane, cyclohexane, and methylcyclohexane.
Aliphatic hydrocarbons include pentane, hexane, heptane, octane, and the like.
Examples of halogenated hydrocarbons include chloroform and dichloromethane.
The solvent may be used alone or in combination of two or more kinds.

The amount of the solvent used is not particularly limited, but is preferably an amount that results in a concentration of the metallocene compound (A) of 0.1 to 10 mmol/L, more preferably an amount that results in a concentration of 0.5 to 5 mmol/L, and even more preferably an amount that results in a concentration of 1 to 3 mmol/L.

〔mixture〕
Step 1 is the step of mixing the above components to obtain a catalyst mixture.
In step 1, mixing is preferably carried out at 50° C. or lower for 30 minutes or longer.
The temperature when the above components are mixed is preferably 50° C. or lower, more preferably 40° C. or lower, and even more preferably 30° C. or lower. The lower limit is preferably 0° C. or higher, and more preferably 10° C. or higher.
The time for mixing the above components is preferably 30 minutes or more, more preferably 30 minutes to 10 hours, and even more preferably 1 to 7 hours.
That is, in step 1, mixing is preferably performed for 30 minutes or more at 50° C. or lower. By setting the mixing temperature and time within the above ranges, the obtained poly-α-olefin-containing lubricating oil composition has excellent low-temperature fluidity.

(Step 2)
Step 2 is a step of polymerizing an α-olefin containing the plurality of raw material monomers (D) using the catalyst mixture.

In this production method, an α-olefin is polymerized to obtain a poly-α-olefin, and therefore the α-olefin used in step 2 is a raw material for the poly-α-olefin.
The α-olefin used in step 2 contains the plurality of raw material monomers (D).

[α-Olefin]
The α-olefin used in step 2 is preferably an α-olefin having 3 to 30 carbon atoms, more preferably an α-olefin having 6 to 20 carbon atoms, and even more preferably an α-olefin having 8 to 14 carbon atoms. Specifically, the multiple raw material monomers (D) include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-icosene, 1-henicosene, and the like. Examples of the 1-octene include 1-octene, 1-docosene, 1-tricosene, 1-tetracosene, 1-pentacosene, 1-hexacosene, 1-heptacosene, 1-octacosene, 1-nonacosene, and 1-triacontene. At least two selected from the group consisting of 1-octene, 1-nonene, 1-decene, 1-undecene, and 1-dodecene are preferred, and 1-octene (D1) and 1-dodecene (D2) are more preferred.
When the α-olefin used in step 2 contains 1-octene (D1) and 1-dodecene (D2), the ratio [D1/D2] of 1-octene (D1) to 1-dodecene (D2) used in step 2 is preferably 3:7 to 7:3, more preferably 4:6 to 6:4, and even more preferably 4.5:5.5 to 5.5:4.5, in terms of molar ratio.
The ratio of the multiple raw material monomers (D) in the α-olefin used in step 2 is preferably 70 to 100 mol %, more preferably 80 to 100 mol %, even more preferably 90 to 100 mol %, and still more preferably 95 to 100 mol %. The α-olefin used in step 2 may be composed only of the multiple raw material monomers (D), or may be composed only of 1-octene (D1) and 1-dodecene (D2).

The α-olefin used in step 2 contains the plurality of raw material monomers (D) and therefore at least two types are used, but three or more types may be used, and two types are preferred.
The α-olefin used in step 2 may be used as it is in the polymerization reaction, but it is more preferable to treat it with an adsorbent such as activated alumina or molecular sieve before use, since this removes impurities and improves activity.

In step 2, the amount of α-olefin used as the raw material is preferably 200 kg or more, more preferably 300 kg or more, even more preferably 400 kg or more, and even more preferably 500 kg or more. By increasing the reaction scale, the effect of the reactor wall on the catalytic activity is reduced, and it is believed that the resulting lubricating oil composition containing poly-α-olefin will have better low-temperature fluidity.

〔polymerization〕
In step 2, the polymerization method is not particularly limited, and any method such as bulk polymerization, solution polymerization, suspension polymerization, slurry polymerization, and gas phase polymerization may be used.
The polymerization temperature is preferably 0 to 200°C, more preferably 30 to 150°C, even more preferably 40 to 120°C, and still more preferably 80 to 120°C.
The ratio of the catalyst to the raw material α-olefin, that is, the molar ratio of the α-olefin used in step 2 to the metallocene compound (A) used in step 1 [α-olefin/metallocene compound (A)], is preferably 1 to 10 ⁸ , more preferably 100 to 10 ⁶ .
The polymerization time is preferably 5 minutes to 20 hours, and the reaction pressure is preferably 0 to 0.2 MPaG.

In step 2, from the viewpoint of productivity, the polymerization is preferably performed without a solvent, but a solvent may be used. The solvent that can be used in step 2 is preferably at least one selected from the group consisting of aromatic hydrocarbons, alicyclic hydrocarbons, aliphatic hydrocarbons, and halogenated hydrocarbons, and more preferably aromatic hydrocarbons. Examples of aromatic hydrocarbons include benzene, toluene, xylene, and ethylbenzene, and toluene or xylene is preferable, and toluene is more preferable.
Examples of the alicyclic hydrocarbon include cyclopentane, cyclohexane, and methylcyclohexane.
Aliphatic hydrocarbons include pentane, hexane, heptane, octane, and the like.
Examples of halogenated hydrocarbons include chloroform and dichloromethane.
The solvent may be used alone or in combination of two or more kinds.

In step 2, when polymerizing α-olefins, it is preferable to add hydrogen because the activity is improved by adding hydrogen. When hydrogen is used, the hydrogen partial pressure is preferably 0.2 MPaG or less, and more preferably 0.1 MPaG or less. The lower limit of the hydrogen partial pressure is 0.01 MPaG.

Step 2 is a step of polymerizing an α-olefin using the catalyst mixture, and in step 2, it is preferable to mix the α-olefin with an organoaluminum compound (C2), and then mix the catalyst mixture to polymerize the α-olefin. The organoaluminum compound (C2) used here is the same as the organoaluminum compound (C1) used in step 1, and the preferred compounds are also the same. It is more preferable that the organoaluminum compound (C2) and the organoaluminum compound (C1) are the same compound.
Furthermore, in step 2, it is more preferable to mix the α-olefin with the organoaluminum compound (C2), then mix the catalyst mixture, and then raise the temperature to 80° C. or higher to polymerize the α-olefin. The preferred polymerization temperature is as described above, and is preferably 80 to 120° C.

In step 2, the molecular weight of the α-olefin polymer can be adjusted by adjusting the type, amount of each catalyst component used, reaction amount, polymerization temperature, and solvent.
The polymerization in step 2 is preferably carried out in a reaction vessel having a capacity of 700 L or more, more preferably in a reaction vessel having a capacity of 800 L or more, and more preferably in a reaction vessel having a capacity of 1000 L or more. It is believed that by increasing the reaction scale, the effect of the reactor wall on the catalytic activity is reduced, and the obtained lubricating oil composition containing the poly-α-olefin has better low-temperature fluidity.

It is preferable to remove the monomer and oligomer components after step 2. Methods for removing the monomer and oligomer components include, for example, distillation.

[Hydrogenation step]
The α-olefin polymer obtained in step 2 may be used as it is as a lubricant, a lubricant base oil, or an additive for a lubricant, but it is preferable to further carry out hydrogenation.
Hydrogenation can improve stability.
The reaction conditions for the hydrogenation step may be general hydrogenation reaction conditions, but the preferred conditions are as follows.
In this hydrogenation step, a commonly used gas phase hydrogenation method can be used. When a precious metal catalyst such as palladium or platinum is used as the catalyst, the reaction temperature is preferably 60 to 100°C and the hydrogen pressure is preferably 0.1 to 1 MPa. When a nickel-based catalyst is used, the reaction temperature is preferably 100 to 250°C and the hydrogen pressure is preferably 1 to 20 MPa. In either system, the amount of catalyst is preferably 0.05 to 50 mass% relative to the polymer obtained in step 2, and the reaction time is preferably 2 to 48 hours. The hydrogenation reaction proceeds quickly by using the hydrogenation catalyst, but even after the significant absorption of hydrogen has subsided, additional operations such as increasing the temperature or pressure may be performed in order to completely hydrogenate the remaining trace amounts of raw material.

[Base oil (b)]
The lubricating oil composition of the present invention contains a base oil (b) having a 100° C. kinematic viscosity of 1 to 30 mm ² /s.
The base oil (b) may be a metallocene-catalyzed poly-α-olefin, but is preferably at least one selected from the group consisting of non-metallocene-catalyzed poly-α-olefins and esters. The type of suitable base oil (b) varies depending on the type (100° C. kinematic viscosity) of the base oil (a).
The term "non-metallocene catalyst-based poly-α-olefin" refers to a poly-α-olefin polymerized using a catalyst other than a metallocene catalyst as a polymerization catalyst, and refers to a poly-α-olefin polymerized using a conventional catalyst as a polymerization catalyst.

<Nonmetallocene Catalyst-Based Poly-α-Olefins>
The nonmetallocene catalyst-based poly-α-olefin is preferably a poly-α-olefin obtained by using one or more α-olefins having 8 to 12 carbon atoms.
The non-metallocene catalyst-based poly-α-olefin is a poly-α-olefin polymerized using a catalyst other than a metallocene catalyst as a polymerization catalyst, preferably a poly-α-olefin polymerized using a cationic catalyst or a Ziegler catalyst as a polymerization catalyst, and more preferably a poly-α-olefin polymerized using a cationic catalyst.
By mixing nonmetallocene-catalyzed poly-α-olefins having a more diverse structure than metallocene-catalyzed poly-α-olefins with metallocene-catalyzed poly-α-olefins in the lubricating oil composition of the present invention, a lubricating oil having excellent low-temperature fluidity can be obtained. Furthermore, the nonmetallocene-catalyzed poly-α-olefins improve the solubility of various additives in the lubricating oil composition of the present invention, and the lubricating oil composition is also excellent in terms of the expression of the additives' functions. This is because nonmetallocene-catalyzed poly-α-olefins have the characteristic of being more diverse in structure than metallocene-catalyzed poly-α-olefins.
The viscosity index of the nonmetallocene catalyst-based poly-α-olefin is preferably at least 80, more preferably at least 100, and even more preferably at least 130. If the viscosity index is within the above range, the viscosity change due to the change in temperature is small.
The pour point of the nonmetallocene catalyst-based poly-α-olefin is preferably −25° C. or lower, more preferably −30° C. or lower, and even more preferably −40° C. or lower. If the pour point is within the above range, the lubricating oil composition of the present invention containing it will have sufficient fluidity even in a low-temperature environment.
The kinematic viscosity and viscosity index are values measured in accordance with JIS K 2283, and the pour point is a value measured in accordance with JIS K 2265.

The preferred physical properties of the base oil (b) vary depending on the type and content of the base oil (a).
The composition numbers are described in the <Composition of the lubricating oil composition> described later. Among the base oils (b), suitable nonmetallocene catalyst-based poly-α-olefins include base oils (b3), (b1) and (b4).

In the lubricating oil composition (1-2), the base oil (b) is preferably the base oil (b3).
The base oil (b3) is a nonmetallocene catalyst-based poly-α-olefin having a 100° C. kinematic viscosity of 5 to 10 mm ² /s.
The 100° C. kinematic viscosity of the base oil (b3) is from 5 to 10 mm ² /s, preferably from 5 to 9 mm ² /s, more preferably from 5 to 8 mm ² /s, and even more preferably from 5 to 7 mm ² /s.
The 40° C. kinematic viscosity of the base oil (b3) is preferably 25 to 50 mm ² /s, more preferably 25 to 40 mm ² /s, even more preferably 25 to 35 mm ² /s, and still more preferably 30 to 35 mm ² /s.
If the 100° C. kinetic viscosity and the 40° C. kinetic viscosity are within the above ranges, the evaporation loss is small and the power loss due to the viscous resistance is not large, which is preferable.

In the lubricating oil compositions (1-1) and (1-1-1), the use of base oil (b1) is optional, but it is preferable to use base oil (b1) as base oil (b).
The base oil (b1) is a nonmetallocene catalyst-based poly-α-olefin having a 100° C. kinematic viscosity of 1 to 10 mm ² /s.
The 100°C kinematic viscosity of the base oil (b1) is 1 to 10 mm ² /s, preferably 3 to 10 mm ² /s, more preferably 5 to 10 mm ² /s, even more preferably 5 to 9 mm ² /s, still more preferably 5 to 8 mm ² /s, and even more preferably 5 to 7 mm ² /s.
The 40°C kinematic viscosity of the base oil (b1) is preferably 10 to 50 mm ² /s, more preferably 20 to 50 mm ² /s, even more preferably 25 to 50 mm ² /s, still more preferably 25 to 40 mm ² /s, even more preferably 25 to 35 mm ² /s, and even more preferably 30 to 35 mm ² /s.
If the 100° C. kinetic viscosity and the 40° C. kinetic viscosity are within the above ranges, the evaporation loss is small and the power loss due to the viscous resistance is not large, which is preferable.

In the lubricating oil composition (2), the base oil (b) is preferably base oil (b4).
The base oil (b4) is a nonmetallocene catalyst-based poly-α-olefin having a 100° C. kinematic viscosity of 1 to 30 mm ² /s.
The 100°C kinematic viscosity of base oil (b4) is 1 to 30 mm ² /s, preferably 1 to 20 mm ² /s, more preferably 1 to 10 mm ² /s, even more preferably 3 to 10 mm ² /s, still more preferably 5 to 10 mm ² /s, even more preferably 5 to 9 mm ² /s, even more preferably 5 to 8 mm ² /s, and even more preferably 5 to 7 mm ² /s.
The 40°C kinematic viscosity of the base oil (b4) is preferably 10 to 300 mm ² /s, more preferably 10 to 150 mm ² /s, even more preferably 10 to 50 mm ² /s, still more preferably 20 to 50 mm ² /s, even more preferably 25 to 50 mm ² /s, even more preferably 25 to 40 mm ² /s, even more preferably 25 to 35 mm ² /s, and even more preferably 30 to 35 mm ² /s.
If the 100° C. kinetic viscosity and the 40° C. kinetic viscosity are within the above ranges, the evaporation loss is small and the power loss due to the viscous resistance is not large, which is preferable.

<Ester>
The ester may be a known ester such as a diester, an aromatic ester, a polyol ester, etc. A polyol ester is preferred, and at least one selected from the group consisting of a partial ester of a polyol and a complete ester of a polyol is more preferred.
By using an ester in the lubricating oil composition of the present invention, the fluidity of the lubricating oil composition of the present invention is improved, and the lubricating oil composition is excellent in that a low pour point can be obtained. This is because the ester has the characteristic of excellent low-temperature fluidity. By mixing an ester with a poly-α-olefin, particularly a metallocene catalyst-based poly-α-olefin, the lubricating oil composition of the present invention has even better low-temperature fluidity.
The polyol used as a raw material for the polyol ester is not particularly limited, but an aliphatic polyol is preferable. Examples of the polyol include dihydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, and neopentyl glycol; trihydric alcohols such as glycerin, trimethylolethane, and trimethylolpropane; and tetrahydric or higher polyhydric alcohols such as diglycerin, triglycerin, pentaerythritol, dipentaerythritol, mannitol, and sorbitol.

The hydrocarbon group constituting the carboxylic acid portion of the polyol ester is preferably an alkyl or alkenyl group having 6 to 30 carbon atoms, more preferably an alkyl or alkenyl group having 12 to 24 carbon atoms, and examples thereof include various hexyl groups, octyl groups, decyl groups, dodecyl groups, tetradecyl groups, hexadecyl groups, heptadecyl groups, octadecyl groups, hexenyl groups, octenyl groups, decenyl groups, dodecenyl groups, tetradecenyl groups, hexadecenyl groups, and octadecenyl groups.
The alkyl group and alkenyl group may be either linear or branched.

Specific examples of complete esters of polyols include, but are not limited to, neopentyl glycol esters such as neopentyl glycol dilaurate, neopentyl glycol dimyristate, neopentyl glycol dipalmitate, neopentyl glycol distearate, and neopentyl glycol diisostearate; trimethylolpropane esters such as trimethylolpropane trilaurate, trimethylolpropane trimyristate, trimethylolpropane tripalmitate, trimethylolpropane tristearate, and trimethylolpropane triisostearate; glycerin esters such as glycerin trilaurate, glycerin tristearate, and glycerin triisostearate; and dipentaerythritol esters such as dipentaerythritol hexalaurate.

The partial ester of the polyol is not particularly limited as long as it has at least one remaining hydroxyl group.
Specific examples of the partial ester of the polyol include partial esters of neopentyl glycol, such as neopentyl glycol monolaurate, neopentyl glycol monomyristate, neopentyl glycol monopalmitate, neopentyl glycol monostearate, and neopentyl glycol monoisostearate; partial esters of trimethylolpropane, such as trimethylolpropane mono- or dilaurate, trimethylolpropane mono- or dimyristate, trimethylolpropane mono- or dipalmitate, trimethylolpropane mono- or distearate, and trimethylolpropane mono- or diisostearate; partial esters of glycerin, such as glycerin mono- or dilaurate, glycerin mono- or distearate, and glycerin mono- or diisostearate; and partial esters of dipentaerythritol, such as dipentaerythritol pentalaurate, but are not limited thereto.

As the polyol ester, those represented by the following general formula (B2) are preferred from the viewpoint of anti-foaming properties, etc.
(R ¹ -COO-) _n L ... (B2)
(In the formula, R ¹ is a hydrocarbon group having 6 to 30 carbon atoms, n is an integer from 2 to 6, and L is an n-valent hydrocarbon group or an n-valent hydrocarbon group containing an ether bond.)
The above R ¹ is preferably an alkyl or alkenyl group having 8 to 18 carbon atoms.
It is preferred that n is 3 or 4.
L is preferably an n-valent hydrocarbon group having 3 to 10 carbon atoms, or an n-valent hydrocarbon group containing an ether bond. Here, the term "hydrocarbon group containing an ether bond" refers to two hydrocarbon groups bonded via an ether bond (-O-).
Preferred specific examples of the ester when L is an n-valent hydrocarbon group having 3 to 10 carbon atoms include neopentyl glycol esters such as neopentyl glycol dilaurate and neopentyl glycol dimyristate, etc. Preferred specific examples of the ester when L is a hydrocarbon group containing an ether bond include dipentaerythritol esters such as dipentaerythritol hexalaurate and dipentaerythritol pentalaurate, etc.

In the lubricating oil composition of the present invention, the polyol ester may be used alone or in combination of two or more kinds.

The preferred physical properties of the base oil (b) vary depending on the type and content of the base oil (a).
The composition numbers are given in the <Composition of the lubricating oil composition> described later. Among the base oils (b), a suitable ester is base oil (b2).

In the lubricating oil composition (1-1-1) and the lubricating oil composition (2), the base oil (b) is preferably the base oil (b2).
In the lubricating oil compositions (1-1) and (1-2), the use of base oil (b2) is optional, but it is preferable to use base oil (b2) as base oil (b).
The base oil (b2) is an ester having a 100° C. kinematic viscosity of 10 to 15 mm ² /s.
The 100° C. kinematic viscosity of the base oil (b2) is from 10 to 15 mm ² /s, preferably from 11 to 15 mm ² /s, more preferably from 12 to 15 mm ² /s, and even more preferably from 12 to 14 mm ² /s.
The 40° C. kinematic viscosity of the base oil (b2) is preferably 50 to 200 mm ² /s, more preferably 60 to 150 mm ² /s, even more preferably 70 to 130 mm ² /s, and still more preferably 80 to 120 mm ² /s.
If the 100° C. kinetic viscosity and the 40° C. kinetic viscosity are within the above ranges, the evaporation loss is small and the power loss due to the viscous resistance is not large, which is preferable.

[Other base oils]
The lubricating oil composition of the present invention may contain base oils other than the above-mentioned base oil (a) and base oil (b) as long as the effects of the present invention are not impaired.
The other base oils are not particularly limited in type, and can be either mineral oils or synthetic oils.Here, the mineral oils can be any of various types known in the art, such as paraffin-based mineral oils, intermediate-based mineral oils, naphthene-based mineral oils, and the like.Specific examples include light neutral oils, medium neutral oils, heavy neutral oils, and bright stocks, which are obtained by solvent refining or hydrogen refining.
As the synthetic oil, various conventionally known oils can be used, such as polybutene, phosphate ester, polyphenyl ether, alkylbenzene, alkylnaphthalene, polyoxyalkylene glycol, neopentyl glycol, silicone oil, trimethylolpropane, pentaerythritol, and further hindered ester. These base oils can be used alone or in combination of two or more, and mineral oil and synthetic oil can be used in combination.

[Additive]
The lubricating oil composition of the present invention may further contain various additives within the range that does not impair the effects of the present invention. Various additives can be used appropriately depending on the application of the lubricating oil composition, etc.
The lubricating oil composition of the present invention preferably further contains 1 to 30 mass % of at least one additive selected from the group consisting of extreme pressure agents, antiwear agents, ashless detergent-dispersants, antioxidants, rust inhibitors, metal deactivators and pour point depressants.
The content of the additives in the lubricating oil composition of the present invention is preferably 1 to 30 mass %, more preferably 1 to 20 mass %, even more preferably 1 to 10 mass %, still more preferably 1 to 5 mass %, even more preferably 1 to 4 mass %, and even more preferably 2 to 4 mass %.

Examples of the extreme pressure agent include sulfur-based extreme pressure agents, phosphorus-based extreme pressure agents, extreme pressure agents containing sulfur and metal, and extreme pressure agents containing phosphorus and metal. These extreme pressure agents can be used alone or in combination of two or more. The extreme pressure agent may be any agent that contains sulfur atoms and/or phosphorus atoms in the molecule and can exhibit load resistance and wear resistance.
The amount of the extreme pressure agent blended is preferably 0.01 to 20 mass %, and more preferably 0.01 to 10 mass %, based on the total amount of the lubricating oil composition, from the standpoint of blending effect and economy.

Examples of anti-wear agents include sulfur-containing compounds such as zinc dialkyldithiophosphate (ZnDTP), zinc phosphate, disulfides, sulfurized olefins, sulfurized oils and fats, sulfurized esters, thiocarbonates, thiocarbamates, and polysulfides; phosphorus-containing compounds such as phosphites, phosphates, phosphonates, and amine salts or metal salts thereof; and sulfur- and phosphorus-containing anti-wear agents such as thiophosphites, thiophosphates, thiophosphonates, and amine salts or metal salts thereof.
The amount of the anti-wear agent blended is preferably 0.01 to 20 mass %, more preferably 0.01 to 10 mass %, based on the total amount of the lubricating oil composition, from the viewpoints of blending effect and economy.

Examples of the ashless detergent-dispersant include succinimides, boron-containing succinimides, benzylamines, boron-containing benzylamines, succinic acid esters, fatty acids, and mono- or di-carboxylic acid amides such as succinic acid.

The antioxidant is preferably at least one selected from the group consisting of amine-based antioxidants, phenol-based antioxidants, and sulfur-based antioxidants. These antioxidants can be used alone or in combination of two or more.
Examples of the amine-based antioxidant include monoalkyldiphenylamine-based compounds such as monooctyldiphenylamine and monononyldiphenylamine; dialkyldiphenylamine-based compounds such as 4,4'-dibutyldiphenylamine, 4,4'-dipentyldiphenylamine, 4,4'-dihexyldiphenylamine, 4,4'-diheptyldiphenylamine, 4,4'-dioctyldiphenylamine and 4,4'-dinonyldiphenylamine; polyalkyldiphenylamine-based compounds such as tetrabutyldiphenylamine, tetrahexyldiphenylamine, tetraoctyldiphenylamine and tetranonyldiphenylamine; and naphthylamine-based compounds such as α-naphthylamine, phenyl-α-naphthylamine, butylphenyl-α-naphthylamine, pentylphenyl-α-naphthylamine, hexylphenyl-α-naphthylamine, heptylphenyl-α-naphthylamine, octylphenyl-α-naphthylamine and nonylphenyl-α-naphthylamine.

Examples of the phenol-based antioxidant include monophenol-based compounds such as 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and diphenol-based compounds such as 4,4'-methylenebis(2,6-di-tert-butylphenol) and 2,2'-methylenebis(4-ethyl-6-tert-butylphenol).
Examples of the sulfur-based antioxidant include thioterpene compounds such as 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino)phenol, a reaction product of phosphorus pentasulfide with pinene, and dialkyl thiodipropionates such as dilauryl thiodipropionate and distearyl thiodipropionate.
The amount of the antioxidant contained in the lubricating oil composition of the present invention is preferably 0.1 mass% or more, more preferably 0.2 mass% or more, even more preferably 0.3 mass% or more, and even more preferably 0.4 mass% or more, based on the total amount of the lubricating oil composition. It is preferably 20 mass% or less, and may be 3 mass% or less.

Examples of the rust inhibitor include metal sulfonates and succinic acid esters.
From the viewpoint of the blending effect, the blending amount of the rust inhibitor is preferably 0.01 to 20 mass %, more preferably 0.05 to 5 mass %, based on the total amount of the lubricating oil composition.

Examples of metal deactivators include benzotriazole and thiadiazole. From the viewpoint of blending effect, the preferred blending amount of the metal deactivator is preferably 0.01 to 20 mass % based on the total amount of the lubricating oil composition, and more preferably 0.01 to 1 mass %.

As a pour point depressant, polymethacrylate with a weight average molecular weight of 50,000 to 150,000 can be used.

The lubricating oil composition of the present invention may also contain a lubricating oil additive package as an additive. The lubricating oil additive package contains at least one additive selected from the group consisting of extreme pressure agents, antiwear agents, ashless detergent-dispersants, antioxidants, rust inhibitors, metal deactivators, and pour point depressants. The lubricating oil additive package may be appropriately selected depending on the application of the lubricating oil composition of the present invention, but when the lubricating oil composition is used in gear oil, it is preferable to use a gear oil additive package.
The additives contained in the lubricating oil additive package are preferably at least one selected from the group consisting of extreme pressure agents, antiwear agents, ashless detergent-dispersants, antioxidants, rust inhibitors, metal deactivators, and pour point depressants, and more preferably at least one selected from the group consisting of extreme pressure agents, antiwear agents, metal deactivators, pour point depressants, and antioxidants. The lubricating oil additive package may further contain additives other than the above additives.
The content of the lubricating oil additive package in the lubricating oil composition of the present invention is preferably 1 to 30 mass %, more preferably 1 to 20 mass %, even more preferably 1 to 10 mass %, still more preferably 1 to 5 mass %, even more preferably 1 to 4 mass %, and even more preferably 2 to 4 mass %.

<Composition of Lubricating Oil Composition>
The present invention relates to a lubricating oil composition comprising the following base oil (a) and base oil (b), in which the mass ratio of base oil (a) to base oil (b) [(a)/(b)] is 50/50 to 95/5. By setting the types and kinematic viscosities of base oil (a) and base oil (b) and the contents of each within specific ranges, the effects of the present invention can be further enhanced, and a lubricating oil composition with a high viscosity index and excellent low-temperature fluidity can be obtained.
Base oil (a): a metallocene catalyst-based poly-α-olefin having a 100° C. kinetic viscosity of 40 to 130 mm ² /s. Base oil (b): a base oil having a 100° C. kinetic viscosity of 1 to 30 mm ² /s.

The mass ratio of base oil (a) to base oil (b) in the lubricating oil composition of the present invention [(a)/(b)] is 50/50 to 95/5. By setting the mass ratio of base oil (a) to base oil (b) within a specific range, the effects of the present invention can be further enhanced, and a lubricating oil composition having a large viscosity index and excellent low-temperature fluidity can be obtained.
The total content of the base oil (a) and the base oil (b) in the lubricating oil composition of the present invention is preferably 70 mass% or more, more preferably 80 mass% or more, even more preferably 90 mass% or more, even more preferably 95 mass% or more, and even more preferably 96 mass% or more. There is no upper limit, and the lubricating oil composition of the present invention may consist of only the base oil (a) and the base oil (b), but the total content of the base oil (a) and the base oil (b) in the lubricating oil composition of the present invention is preferably 100 mass% or less, more preferably less than 100 mass%, even more preferably 99 mass% or less, and even more preferably 98 mass% or less.
The components of the preferred lubricating oil compositions are described below. For convenience, the lubricating oil compositions having each component are numbered as lubricating oil composition (1), lubricating oil composition (1-1), lubricating oil composition (2), etc.

(Lubricating Oil Composition (1))
Lubricating oil composition (1) is a lubricating oil composition of the present invention in which base oil (a) is base oil (a1) described below, and the mass ratio of base oil (a1) to base oil (b) [(a1)/(b)] is 80/20 to 95/5. Lubricating oil composition (1) is a lubricating oil composition having a larger viscosity index and more excellent low-temperature fluidity than the other lubricating oil compositions of the present invention.
Base oil (a1): metallocene catalyst-based poly-α-olefin having a 100° C. kinematic viscosity of 40 to 50 mm ² /s

That is, the lubricating oil composition (1) is a lubricating oil composition containing the following base oil (a1) and the following base oil (b), in which the mass ratio of base oil (a1) to base oil (b) [(a1)/(b)] is 80/20 to 95/5.
Base oil (a1): metallocene catalyst-based poly-α-olefin having a 100° C. kinetic viscosity of 40 to 50 mm ² /s Base oil (b): base oil having a 100° C. kinetic viscosity of 1 to 30 mm ² /s

(Lubricating Oil Composition (1-1))
The lubricating oil composition (1) is further preferably a lubricating oil composition (1-1).
The lubricating oil composition (1-1) is a lubricating oil composition in which the base oil (b) is at least one selected from the group consisting of the following base oil (b1) and the following base oil (b2). The lubricating oil composition (1-1) is a lubricating oil composition having a larger viscosity index and more excellent low-temperature fluidity than the lubricating oil compositions (1).
Base oil (b1): nonmetallocene catalyst-based poly-α-olefin having a 100° C. kinetic viscosity of 1 to 10 mm ² /s Base oil (b2): ester having a 100° C. kinetic viscosity of 10 to 15 mm ² /s

That is, the lubricating oil composition (1-1) contains the following base oil (a1) and the following base oil (b), wherein the mass ratio of the base oil (a1) to the base oil (b) [(a1)/(b)] is 80/20 to 95/5, and the base oil (b) is at least one selected from the group consisting of the following base oil (b1) and the following base oil (b2).
Base oil (a1): metallocene catalyst-based poly-α-olefin having a 100° C. kinetic viscosity of 40 to 50 mm ² /s Base oil (b1): non-metallocene catalyst-based poly-α-olefin having a 100° C. kinetic viscosity of 1 to 10 mm ² /s Base oil (b2): ester having a 100° C. kinetic viscosity of 10 to 15 mm ² /s

The mass ratio of base oil (a1) to base oil (b) in lubricating oil composition (1-1) [(a1)/(b)] is 80/20 to 95/5. By setting the mass ratio of base oil (a1) to base oil (b) within a specific range, the effects of the present invention can be further enhanced, and a lubricating oil composition with a large viscosity index and excellent low-temperature fluidity can be obtained.

(Lubricating Oil Composition (1-2))
The lubricating oil composition (1) is further preferably a lubricating oil composition (1-2).
The lubricating oil composition (1-2) is a lubricating oil composition in which the base oil (b) is the following base oil (b3) and the mass ratio of the base oil (a1) to the base oil (b3) [(a1)/(b3)] is 90/10 to 95/5 among the lubricating oil compositions (1). The lubricating oil composition (1-2) is a lubricating oil composition having a higher viscosity index and better low-temperature fluidity than the lubricating oil compositions (1). The lubricating oil composition (1-2) is also included in the lubricating oil composition (1-1), and the lubricating oil composition (1-2) is a lubricating oil composition having a higher viscosity index and better low-temperature fluidity than the lubricating oil compositions (1-1).
Base oil (b3): nonmetallocene catalyst-based poly-α-olefin having a 100° C. kinematic viscosity of 5 to 10 mm ² /s

That is, the lubricating oil composition (1-2) is a lubricating oil composition containing the following base oil (a1) and the following base oil (b3), in which the mass ratio of the base oil (a1) to the base oil (b3) [(a1)/(b3)] is 90/10 to 95/5.
Base oil (a1): metallocene catalyst-based poly-α-olefin having a 100° C. kinetic viscosity of 40 to 50 mm ² /s. Base oil (b3): non-metallocene catalyst-based poly-α-olefin having a 100° C. kinetic viscosity of 5 to 10 mm ² /s.

In the lubricating oil composition (1-2), the content of the base oil (a1) is preferably 90 to 95 mass%, more preferably 90 to 94 mass%, even more preferably 90 to 93 mass%, still more preferably 90 to 92 mass%, and even more preferably 91 to 92 mass%, based on the total amount of the lubricating oil composition (1-2).
In the lubricating oil composition (1-2), the content of the base oil (b3) is preferably 5 to 9 mass%, more preferably 5 to 8 mass%, even more preferably 5 to 7 mass%, and still more preferably 5 to 6 mass%.

The mass ratio of base oil (a1) to base oil (b3) in lubricating oil composition (1-2) [(a1)/(b3)] is 90/10 to 95/5, preferably 91/9 to 95/5, more preferably 92/8 to 95/5, even more preferably 93/7 to 95/5, and even more preferably 94/6 to 95/5. By setting the mass ratio of base oil (a1) to base oil (b3) in the above range, the effects of the present invention can be further enhanced, and a lubricating oil composition with a high viscosity index and excellent low-temperature fluidity can be obtained.

(Lubricating oil composition (1-1-1))
The lubricating oil composition (1-1) is further preferably a lubricating oil composition (1-1-1).
The lubricating oil composition (1-1-1) is a lubricating oil composition in which the base oil (b) is base oil (b2), or base oil (b2) and base oil (b1), and the mass ratio of the base oil (b2) to the base oil (b1) [(b2)/(b1)] is 80/20 to 100/0.
That is, the lubricating oil composition (1-1-1) contains the following base oil (a1) and base oil (b2), and does not contain base oil (b1) or contains base oil (b1), in which the mass ratio of base oil (a1) to the sum of base oil (b1) and base oil (b2) [(a1)/((b1)+(b2)]] is 80/20 to 95/5, and the mass ratio of base oil (b2) to base oil (b1) [(b2)/(b1)]] is 80/20 to 100/0.
Base oil (a1): metallocene catalyst-based poly-α-olefin having a 100° C. kinetic viscosity of 40 to 50 mm ² /s Base oil (b1): non-metallocene catalyst-based poly-α-olefin having a 100° C. kinetic viscosity of 1 to 10 mm ² /s Base oil (b2): ester having a 100° C. kinetic viscosity of 10 to 15 mm ² /s

In the lubricating oil composition (1-1-1), the content of base oil (a1) is preferably 80 to 95 mass%, more preferably 82 to 92 mass%, and even more preferably 83 to 89 mass%, based on the total amount of the lubricating oil composition (1-1-1). When the base oil (b) does not contain base oil (b1), the content of base oil (a1) is even more preferably 83 to 87 mass%, and even more preferably 83 to 86 mass%, based on the total amount of the lubricating oil composition (1-1-1). When the base oil (b) contains base oil (b1), the content of base oil (a1) is even more preferably 84 to 89 mass%, and even more preferably 84 to 87 mass%, based on the total amount of the lubricating oil composition (1-1-1).

In the lubricating oil composition (1-1-1), the content of the base oil (b) is preferably 5 to 20 mass%, more preferably 8 to 18 mass%, and even more preferably 9 to 16 mass%. When the base oil (b) does not contain the base oil (b1), the content of the base oil (b) is more preferably 10 to 16 mass%, and even more preferably 11 to 15 mass%, based on the total amount of the lubricating oil composition (1-1-1). When the base oil (b) contains the base oil (b1), the content of the base oil (b) is more preferably 9 to 15 mass%, and even more preferably 10 to 14 mass%, based on the total amount of the lubricating oil composition (1-1-1).
In the lubricating oil composition (1-1-1), the content of the base oil (b2) is preferably 5 to 20 mass%, more preferably 7 to 18 mass%, and even more preferably 9 to 16 mass%. When the base oil (b) does not contain the base oil (b1), the content of the base oil (b2) is more preferably 10 to 16 mass%, and even more preferably 11 to 15 mass%, based on the total amount of the lubricating oil composition (1-1-1). When the base oil (b) contains the base oil (b1), the content of the base oil (b2) is more preferably 8 to 14 mass%, and even more preferably 9 to 13 mass%, based on the total amount of the lubricating oil composition (1-1-1).
In the lubricating oil composition (1-1-1), the content of the base oil (b1) is preferably 0 to 5 mass %, more preferably 0 to 3 mass %, and even more preferably 0 to 2 mass %.

The mass ratio [(a1)/(b)] of the base oil (a1) to the base oil (b) in the lubricating oil composition (1-1-1) is 80/20 to 95/5, preferably 82/18 to 92/8, and more preferably 84/16 to 91/9. When the base oil (b) does not contain the base oil (b1), the mass ratio [(a1)/(b)] of the base oil (a1) to the base oil (b) in the lubricating oil composition (1-1-1) is more preferably 84/16 to 89/11, and even more preferably 85/15 to 88/12. When the base oil (b) contains the base oil (b1), the mass ratio [(a1)/(b)] of the base oil (a1) to the base oil (b) in the lubricating oil composition (1-1-1) is more preferably 86/14 to 91/9, and even more preferably 87/13 to 90/10. By setting the mass ratio of base oil (a1) to base oil (b) within the above range, the effects of the present invention can be further enhanced, and a lubricating oil composition with a large viscosity index and excellent low-temperature fluidity can be obtained.

The mass ratio [(a1)/(b2)] of the base oil (a1) to the base oil (b2) in the lubricating oil composition (1-1-1) is preferably 85/15 to 95/5, more preferably 85/15 to 93/7, and even more preferably 85/15 to 92/8. When the base oil (b) does not contain the base oil (b1), the mass ratio [(a1)/(b2)] of the base oil (a1) to the base oil (b2) in the lubricating oil composition (1-1-1) is even more preferably 85/15 to 89/11, and even more preferably 85/15 to 88/12. When the base oil (b) contains the base oil (b1), the mass ratio of the base oil (a1) to the base oil (b2) in the lubricating oil composition (1-1-1) [(a1)/(b2)] is more preferably 86/14 to 92/8, and even more preferably 88/12 to 91/9. By setting the mass ratio of the base oil (a1) to the base oil (b2) in the above range, the effects of the present invention can be further enhanced, and a lubricating oil composition having a large viscosity index and excellent low-temperature fluidity can be obtained.
The mass ratio [(a1)/(b1)] of the base oil (a1) to the base oil (b1) in the lubricating oil composition (1-1-1) is preferably 95/5 to 100/0, more preferably 97/3 to 100/0, and even more preferably 98/2 to 100/0. When the base oil (b) contains the base oil (b1), it is even more preferably 98/2 to 99/1. By setting the mass ratio of the base oil (a1) to the base oil (b1) in the above range, the effects of the present invention can be further enhanced, and a lubricating oil composition having a large viscosity index and excellent low-temperature fluidity can be obtained.

The mass ratio of base oil (b2) to base oil (b1) in the lubricating oil composition (1-1-1) [(b2)/(b1)] is 80/20 to 100/0, preferably 85/15 to 100/0, and more preferably 87/13 to 100/0. When base oil (b) contains base oil (b1), it is even more preferably 87/13 to 95/5. By setting the mass ratio of base oil (b2) to base oil (b1) within a specific range, the effects of the present invention can be further enhanced, and a lubricating oil composition with a large viscosity index and excellent low-temperature fluidity can be obtained.

(Lubricating Oil Composition (2))
Lubricating oil composition (2) is a lubricating oil composition of the present invention in which base oil (a) is base oil (a2) described below, base oil (b) is base oil (b2) described below and base oil (b4) described below, the mass ratio of base oil (a2) to base oil (b) [(a2)/(b)] is 50/50 to 70/30, and the mass ratio of base oil (b2) to base oil (b4) [(b2)/(b4)] is 25/75 to 60/40. Lubricating oil composition (2) is a lubricating oil composition having a larger viscosity index and better low-temperature fluidity than the lubricating oil compositions of the present invention.
Base oil (a2): metallocene catalyst-based poly-α-olefin having a 100° C. kinetic viscosity of 120 to 130 mm ² /s Base oil (b2): ester having a 100° C. kinetic viscosity of 10 to 15 mm ² /s Base oil (b4): non-metallocene catalyst-based poly-α-olefin having a 100° C. kinetic viscosity of 1 to 30 mm ² /s

That is, the lubricating oil composition (2) comprises the following base oil (a2), base oil (b2), and base oil (b4), in which the mass ratio of the base oil (a2) to the base oil (b) [(a2)/(b)] is 50/50 to 70/30, and the mass ratio of the base oil (b2) to the base oil (b4) [(b2)/(b4)] is 25/75 to 60/40.
Base oil (a2): metallocene catalyst-based poly-α-olefin having a 100° C. kinetic viscosity of 120 to 130 mm ² /s Base oil (b2): ester having a 100° C. kinetic viscosity of 10 to 15 mm ² /s Base oil (b4): non-metallocene catalyst-based poly-α-olefin having a 100° C. kinetic viscosity of 1 to 30 mm ² /s

In the lubricating oil composition (2), the content of the base oil (a2) is preferably 50 to 70 mass%, more preferably 53 to 68 mass%, even more preferably 55 to 67 mass%, still more preferably 57 to 65 mass%, and even more preferably 58 to 64 mass%, based on the total amount of the lubricating oil composition (2).
In the lubricating oil composition (2), the content of the base oil (b) is preferably 25 to 45 mass%, more preferably 27 to 43 mass%, even more preferably 28 to 42 mass%, still more preferably 30 to 40 mass%, and even more preferably 34 to 38 mass%.
In the lubricating oil composition (2), the content of the base oil (b2) is preferably 10 to 20 mass%, more preferably 10 to 19 mass%, even more preferably 11 to 18 mass%, still more preferably 12 to 17 mass%, and even more preferably 13 to 16 mass%.
In the lubricating oil composition (2), the content of base oil (b4) is preferably from 15 to 25 mass %, more preferably from 17 to 23 mass %, and even more preferably from 18 to 22 mass %.

The mass ratio of base oil (a2) to base oil (b) in the lubricating oil composition (2) [(a2)/(b)] is 50/50 to 70/30, preferably 53/47 to 70/30, more preferably 55/45 to 70/30, even more preferably 57/43 to 70/30, and even more preferably 60/40 to 70/30. By setting the mass ratio of base oil (a2) to base oil (b) within the above range, the effects of the present invention can be further enhanced, and a lubricating oil composition having a large viscosity index and excellent low-temperature fluidity can be obtained.
The mass ratio of the base oil (a2) to the base oil (b2) in the lubricating oil composition (2) [(a2)/(b2)] is preferably 70/30 to 90/10, more preferably 73/27 to 90/10, even more preferably 75/25 to 87/13, even more preferably 77/23 to 85/15, and even more preferably 80/20 to 85/15. By setting the mass ratio of the base oil (a2) to the base oil (b2) in the above range, the effects of the present invention can be further enhanced, and a lubricating oil composition having a large viscosity index and excellent low-temperature fluidity can be obtained.
The mass ratio of base oil (a2) to base oil (b4) in the lubricating oil composition (2) [(a2)/(b4)] is preferably 65/35 to 85/15, more preferably 70/30 to 83/17, even more preferably 73/27 to 81/19, and even more preferably 75/25 to 80/20. By setting the mass ratio of base oil (a2) to base oil (b4) within the above range, the effects of the present invention can be further enhanced, and a lubricating oil composition having a large viscosity index and excellent low-temperature fluidity can be obtained.
The mass ratio of base oil (b2) to base oil (b4) in the lubricating oil composition (2) [(b2)/(b4)] is 25/75 to 60/40, preferably 35/15 to 50/50, more preferably 45/55 to 50/50, and even more preferably 40/60 to 45/55. By setting the mass ratio of base oil (b2) to base oil (b4) within a specific range, the effects of the present invention can be further enhanced, and a lubricating oil composition having a large viscosity index and excellent low-temperature fluidity can be obtained.

<Characteristics of the lubricating oil composition>
The 40°C kinematic viscosity of the lubricating oil composition of the present invention is preferably 288 to 352 mm ² /s. That is, it is preferable that the ISO viscosity grade corresponds to ISO VG320. When the 40°C kinematic viscosity of the lubricating oil composition of the present invention is in the above range, it becomes suitable as a gear oil for wind power generation. The 40°C kinematic viscosity of the lubricating oil composition of the present invention is more preferably 290 to 350 mm ² /s, even more preferably 300 to 340 mm ² /s, and even more preferably 310 to 330 mm ² /s.

[Gear oil for wind power generation]
The gear oil for wind power generation of the present invention is a gear oil for wind power generation that contains the lubricating oil composition described above. That is, the gear oil for wind power generation of the present invention is a gear oil for wind power generation that contains a lubricating oil composition that contains the following base oil (a) and the following base oil (b), and in which the mass ratio of base oil (a) to base oil (b) [(a)/(b)] is 50/50 to 95/5.
The gear oil for wind power generation of the present invention may be a gear oil for wind power generation containing a lubricating oil composition containing 50 to 95 mass % of the following base oil (a) and 5 to 50 mass % of the following base oil (b).
Base oil (a): a metallocene catalyst-based poly-α-olefin having a 100° C. kinetic viscosity of 40 to 130 mm ² /s. Base oil (b): a base oil having a 100° C. kinetic viscosity of 1 to 30 mm ² /s.

The gear oil for wind power generation of the present invention is a gear oil for wind power generation that contains the above-mentioned lubricating oil composition, and preferred lubricating oil compositions are also as described above.
The gear oil for wind power generation of the present invention contains the lubricating oil composition in an amount of preferably 80 mass% or more, more preferably 90 mass% or more, even more preferably 95 mass% or more, and even more preferably 99 mass% or more. There is no upper limit to the content, but it is preferably 100 mass% or less, and may be 100 mass%, and the gear oil for wind power generation of the present invention may consist only of the lubricating oil composition.
The gear oil for wind power generation of the present invention contains the lubricating oil composition, and therefore has a high viscosity index and excellent low-temperature fluidity. Therefore, the gear oil for wind power generation of the present invention is stable even when used in harsh environments with large temperature changes, and can reduce viscosity increase, especially at low temperatures.

Next, the present invention will be described in more detail using examples, but the present invention is not limited to these examples.

The physical properties of the base oils were evaluated by the following methods, and the results are shown in Table 1.
(1) Kinematic Viscosity at 100°C, Kinematic Viscosity at 40°C, and Viscosity Index Kinematic viscosity was measured in accordance with JIS K 2283:2000. Viscosity index was calculated from kinematic viscosity in accordance with JIS K 2283:2000. The higher the viscosity index, the smaller the viscosity change due to temperature, and the better the lubricant. Therefore, the higher the viscosity index, the more suitable it is for applications where temperature changes are large during use, such as gear oil for wind power generation.
(2) Pour point: Measured according to JIS K 2269: 1987. The lower the pour point temperature, the better the low-temperature fluidity.
(3) -30°C Viscosity Measured in accordance with ASTM D2983-09 with a set temperature of -30°C. The smaller the -30°C viscosity, the better the low-temperature fluidity.

The base oils and additives used in the examples and comparative examples are shown below.
[Base oil (a-1) (metallocene catalyst-based poly-α-olefin)]
Production Example 1 (Production of Base Oil (a-1) (Metallocene Catalyst-Based Poly-α-Olefin))
(Step 1)
A 30 L stainless steel vessel was charged with 18.9 kg of toluene that had been dehydrated to a water content of 10 ppm or less under a nitrogen atmosphere, 1.2 kg of triisobutylaluminum (C1) (20% toluene solution), 0.0440 kg of tertiary butyl alcohol (E1), 30 mmol of (1,1'-dimethylsilylene)(2,2'-dimethylsilylene)-bis(cyclopentadienyl)zirconium dichloride (A), 36 mmol of N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate (B), 0.586 kg of 1-octene (D1), and 0.880 kg of 1-dodecene (D2), and the mixture was stirred at room temperature (25°C) for 2 hours to obtain a catalyst mixture.

(Step 2)
A stainless steel reaction vessel with an internal volume of 1.2 m ³ (1200 L) was thoroughly dried and purged with nitrogen, after which 230 kg of 1-dodecene (D2) and 345 kg of 1-octene (D1) were introduced, followed by 0.19 kg of triisobutylaluminum (C1) (20% toluene solution), and the temperature was raised to 95° C. Hydrogen at 0.2 MPaG was introduced, and the catalyst mixture obtained in step 1 was continuously introduced at a rate of 0.4 kg per hour. After the start of introduction of the catalyst mixture, the internal temperature was maintained at 103° C. to carry out the reaction. A small amount of the reaction liquid was withdrawn during the reaction, and the conversion was measured, and the reaction was stopped when the conversion reached 90%.
Distillation was carried out under reduced pressure of 50 Pa and 250° C. to remove residual monomers, etc., to obtain poly-α-olefin.

(Hydrogenation process)
A nickel catalyst was added in an amount of 0.25% by mass to the α-olefin polymer obtained in step 2, and the mixture was reacted under hydrogen of 0.4 MPa at 150° C. for 6 hours. After the reaction was completed, the catalyst component was removed by filtration to obtain a colorless and transparent hydrogenated poly-α-olefin (base oil (a-1)).
The resulting hydrogenated poly-α-olefin (base oil (a-1)) had a 100° C. kinetic viscosity of 46.7 mm ² /s and a 40° C. kinetic viscosity of 399.9 mm ² /s.

[Base oil (a-2) (metallocene catalyst-based poly-α-olefin)]
Production Example 2 (Production of Base Oil (a-2) (Metallocene Catalyst-Based Poly-α-Olefin))
A colorless and transparent hydrogenated poly-α-olefin (base oil (a-2)) was obtained in the same manner as in Production Example 1, except that the amount of tertiary butyl alcohol (E1) was changed from 0.0440 kg to 0.0264 kg.
The resulting hydrogenated poly-α-olefin (base oil (a-2)) had a 100° C. kinetic viscosity of 129.2 mm ² /s and a 40° C. kinetic viscosity of 1267.6 mm ² /s.

[Base oil (c) (non-metallocene catalyst-based poly-α-olefin)]
A poly-α-olefin (decene oligomer) obtained by polymerizing 1-decene using a cationic catalyst as a polymerization catalyst.
The nonmetallocene catalyst-based poly-α-olefin (base oil (c)) had a kinematic viscosity at 100° C. of 103.1 mm ² /s, a kinematic viscosity at 40° C. of 1,263.2 mm ² /s, and a viscosity index of 172.

[Base oil (b-1) (nonmetallocene catalyst-based poly-α-olefin)]
A poly-α-olefin (decene oligomer) obtained by polymerizing 1-decene using a cationic catalyst as a polymerization catalyst.
The nonmetallocene catalyst-based poly-α-olefin (base oil (b-1)) had a 100° C. kinematic viscosity of 5.9 mm ² /s, a 40° C. kinematic viscosity of 30.6 mm ² /s, and a viscosity index of 138.

[Base oil (b-2) (ester)]
Polyol ester obtained by reacting trimethylolpropane with saturated fatty acid. The polyol ester (base oil (b-2)) had a 100° C. kinetic viscosity of 13.1 mm ² /s, a 40° C. kinetic viscosity of 100.5 mm ² /s, and a viscosity index of 128.

[Additive]
All examples and comparative examples used the same gear oil additive package, which included extreme pressure agents, antiwear agents, metal deactivators, pour point depressants, and antioxidants.

The lubricating oil compositions obtained in the examples have the same 40°C and 100°C kinetic viscosities as the lubricating oil compositions of the comparative examples, but have a higher viscosity index, a very low pour point, and excellent low-temperature fluidity compared to the lubricating oil compositions of the comparative examples. This shows that the lubricating oil composition of the present invention has a high viscosity index and excellent low-temperature fluidity, and can be particularly suitably used as a gear oil for wind turbines used in harsh environments with large temperature changes.

Claims

A lubricating oil composition comprising the following base oil (a) and the following base oil (b), wherein the mass ratio of base oil (a) to base oil (b) [(a)/(b)] is 50/50 to 95/5:
Base oil (a): a metallocene catalyst-based poly-α-olefin having a 100° C. kinetic viscosity of 40 to 130 mm 2 /s. Base oil (b): a base oil having a 100° C. kinetic viscosity of 1 to 30 mm 2 /s.
The lubricating oil composition according to claim 1, wherein the base oil (a) is the following base oil (a1), and the mass ratio of the base oil (a1) to the base oil (b) [(a1)/(b)] is 80/20 to 95/5.
Base oil (a1): a metallocene catalyst-based poly-α-olefin having a 100° C. kinematic viscosity of 40 to 50 mm 2 /s
The lubricating oil composition according to claim 2, wherein the base oil (b) is at least one selected from the group consisting of the following base oil (b1) and the following base oil (b2):
Base oil (b1): nonmetallocene catalyst-based poly-α-olefin having a 100° C. kinetic viscosity of 1 to 10 mm 2 /s Base oil (b2): ester having a 100° C. kinetic viscosity of 10 to 15 mm 2 /s
The lubricating oil composition according to claim 2, wherein the base oil (b) is the following base oil (b3), and the mass ratio of the base oil (a1) to the base oil (b3) [(a1)/(b3)] is 90/10 to 95/5.
Base oil (b3): nonmetallocene catalyst-based poly-α-olefin having a 100° C. kinematic viscosity of 5 to 10 mm 2 /s
The lubricating oil composition according to claim 3, wherein the base oil (b) is base oil (b2), or base oil (b2) and base oil (b1), and the mass ratio of base oil (b2) to base oil (b1) [(b2)/(b1)] is 80/20 to 100/0.
The lubricating oil composition according to claim 1, wherein the base oil (a) is the following base oil (a2), the base oil (b) is the following base oil (b2) and the following base oil (b4), the mass ratio of the base oil (a2) to the base oil (b) [(a2)/(b)] is 50/50 to 70/30, and the mass ratio of the base oil (b2) to the base oil (b4) [(b2)/(b4)] is 25/75 to 60/40.
Base oil (a2): metallocene catalyst-based poly-α-olefin having a 100° C. kinetic viscosity of 120 to 130 mm 2 /s Base oil (b2): ester having a 100° C. kinetic viscosity of 10 to 15 mm 2 /s Base oil (b4): non-metallocene catalyst-based poly-α-olefin having a 100° C. kinetic viscosity of 1 to 30 mm 2 /s
The lubricating oil composition according to any one of claims 1 to 6 further contains 1 to 30 mass % of at least one additive selected from the group consisting of extreme pressure agents, antiwear agents, ashless detergent-dispersants, antioxidants, rust inhibitors, metal deactivators, and pour point depressants.
The lubricating oil composition according to any one of claims 1 to 7, having a kinematic viscosity at 40°C of 288 to 352 mm 2 /s.
A gear oil for wind power generation comprising the lubricating oil composition according to any one of claims 1 to 8.