JP2002348585A - Viscosity index improving agent for lubricating oil and lubricating oil composition containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a viscosity index improving agent comprising a specific α-olefin/cyclic olefin copolymer giving a lubricating oil composition with excellent low-temperature characteristics in the range of all shearing rates, and to provide the lubricating oil composition containing the viscosity index improving agent. SOLUTION: This viscosity index improving agent comprises a copolymer of at least one 2-20C α-olefin and a specific cyclic olefin, having the following characteristics: (1) containing 0.1-60 mol% of the recurring unit derived from the cyclic olefin, (2) having a weight-average molecular weight converted to polystyrene of 80,000-400,000 determined by gel permeation chromatography and (3) having the ratio Mw/Mn of <=2.3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a specific viscosity index improver for a lubricating oil and a lubricating oil composition containing the viscosity index improver.

[0002]

BACKGROUND OF THE INVENTION Petroleum products generally have a so-called temperature dependence of viscosity, in which the viscosity changes greatly when the temperature changes. For example, lubricating oils and the like used in automobiles and the like preferably have low viscosity temperature dependence. Therefore, in lubricating oils, certain polymers soluble in lubricating oil bases have been used as viscosity index improvers in order to reduce the temperature dependence of viscosity. As an agent, an ethylene / α-olefin copolymer is widely used.

[0003] Lubricating oils also contain pour point depressants for the purpose of inhibiting solid wax from crystallizing at low temperatures to form a three-dimensional network and losing fluidity. By the way, among the low-temperature characteristics of lubricating oils, the viscosity at the place where the shear rate is high is determined by the compatibility of the base oil (base for lubricating oil) and the viscosity index improver. At the place where the shear rate is low, the pour point depressant Strongly influenced by It is also known that an ethylene / α-olefin copolymer having a specific composition significantly deteriorates the low-temperature properties of lubricating oils (US Pat. No. 3,697,429,
US Pat. No. 3,551,336). Therefore, in order to prevent the interaction between the pour point depressant and the ethylene / α-olefin copolymer, ethylene / α- having a non-uniform composition distribution using a specific polymerization apparatus and polymerization conditions.
An olefin copolymer has been reported (JP-A-60-1985).
228600).

Under these circumstances, the present inventors have studied and found that a specific copolymer obtained from an α-olefin and a cyclic olefin prevents interaction with a pour point depressant and has a low temperature. The present invention has been found to be a viscosity index improver that provides a lubricating oil composition having excellent low-temperature properties in all shear rate regions by adjusting the compatibility with the base oil at the time.

[0005]

An object of the present invention is to provide a lubricating oil composition having excellent low-temperature properties in any shear rate range, so as to provide a lubricating oil composition having excellent low-temperature properties.
It is an object of the present invention to provide a viscosity index improver comprising an olefin / cyclic olefin copolymer and a lubricating oil composition containing the viscosity index improver.

[0006]

SUMMARY OF THE INVENTION A viscosity index improver according to the present invention comprises at least one α-olefin having 2 to 20 carbon atoms and a cyclic olefin represented by the following general formula (I) or (II). A copolymer containing (1) a repeating unit derived from the above-mentioned cyclic olefin in the range of 0.1 to 60 mol%, and (2) a weight average molecular weight in terms of polystyrene by gel permeation chromatography of 80,000. ~
(3) Mw / Mn of 2.
It is characterized by comprising an α-olefin / cyclic olefin copolymer of 3 or less.

[0007]

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Wherein n is 0 or 1, m is 0 or a positive integer, k is 0 or 1, and R ^{1 to} R
¹⁸ and R ^a and R ^b may be the same or different and each represent a hydrogen atom, a halogen atom, a hydrocarbon group, an oxygen-containing group or a nitrogen-containing group, and R ¹⁵ and R ¹⁶ are May form a ring or polycyclic ring, and the monocyclic or polycyclic ring may have a double bond, and may be an alkylidene group at R ¹⁵ and R ¹⁶ or at R ¹⁷ and R ¹⁸ May be formed. Here, when k is 0, the respective bonds are combined to form a 5-membered ring. )

[0009]

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(Wherein p and q may be the same or different and each is 0 or a positive integer, and r and s
May be the same or different from each other, and 0, 1 or 2
And R ^{21 to} R ³⁹ may be the same or different and represent a hydrogen atom, a halogen atom, a hydrocarbon group or an alkoxy group. ). In the present invention, the above α-olefin
The cyclic olefin copolymer is composed of ethylene and 3 carbon atoms.
Is a copolymer of an α-olefin having from 20 to 20 and a cyclic olefin, and has a molar ratio of a repeating unit derived from ethylene to a repeating unit derived from an α-olefin having 3 to 20 carbon atoms (ethylene / carbon atom Α-
Olefin) is preferably in the range of 85/15 to 35/65, and the α-olefin / cyclic olefin copolymer is a copolymer of ethylene, an α-olefin having 3 to 20 carbon atoms, and a cyclic olefin. It is a polymer, ¹³ C-
It is preferable that the intensity ratio D (Sαβ / Sαα) of the peak intensity (Sαβ) indicating the ratio of αβ carbon to the peak intensity (Sαα) indicating the ratio of αα carbon determined by NMR is 0.5 or less. In addition, the above α-olefin
It is particularly preferable that the cyclic olefin copolymer is a copolymer of ethylene, propylene and a cyclic olefin.

The α-olefin / cyclic olefin copolymer is preferably produced by using a metallocene catalyst. The lubricating oil composition according to the present invention is characterized by containing the viscosity index improver, a lubricating fluid, and, if necessary, a pour point depressant.

[0012]

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the viscosity index improver and the lubricating oil composition according to the present invention will be described in detail. Viscosity index improver The viscosity index improver according to the present invention has 2 to 20 carbon atoms.
And a cyclic olefin represented by the following general formula (I) or (II).

The α-olefin having 2 to 20 carbon atoms specifically includes ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene and 3-methyl-1-butene.
Methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1
-Pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 1-octene , 1-decene, 1-
Examples thereof include linear or branched α-olefins such as dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene.

As the α-olefin, C 2 -C 2
At least one olefin selected from 10 α-olefins is preferred, a combination of ethylene and an α-olefin having 3 to 20 carbon atoms is more preferred, and a combination of ethylene and propylene is particularly preferred. Examples of the cyclic olefin include a cyclic olefin represented by the following general formula (I).

[0015]

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In the above general formula (I), n is 0 or 1, m is 0 or a positive integer, and k is 0 or 1. When k is 1, the ring represented by k is a 6-membered ring, and when k is 0, this ring is a 5-membered ring. R ^{1 to} R ¹⁸ and R ^a and R ^b may be the same or different and are a hydrogen atom, a halogen atom, a hydrocarbon group, an oxygen-containing group or a nitrogen-containing group.

Here, the halogen atom is a fluorine atom, a chlorine atom, a bromine atom or an iodine atom. Examples of the hydrocarbon group usually include an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, and an aromatic hydrocarbon group. More specifically, examples of the alkyl group having 1 to 20 carbon atoms include methyl, ethyl, propyl, isopropyl, amyl, hexyl, octyl,
Decyl, dodecyl, octadecyl and the like. These alkyl groups may be substituted with a halogen atom.

Examples of the cycloalkyl group include cyclohexyl, and examples of the aromatic hydrocarbon group include an aryl group and an aralkyl group. Specific examples include phenyl, tolyl, naphthyl, benzyl and phenylethyl. Can be Examples of the oxygen-containing group include alkoxy groups such as methoxy, ethoxy, propoxy, and phenoxy; and alkoxycarbonyl groups having 1 to 20 carbon atoms such as methoxycarbonyl and ethoxycarbonyl.

Examples of the nitrogen-containing group include an alkylamino group having 1 to 20 carbon atoms, such as dimethylamino and diethylamino, and a cyano group. Further, in the general formula (I), R ¹⁵ and R ¹⁶ , R ¹⁷ and R ¹⁸ represent R
¹⁵ and the R ^17, and R ¹⁶ and R ¹⁸ are, the R ¹⁵ and R ¹⁸ are, or in the R ¹⁶ and R ¹⁷ are respectively bonded (jointly with each other), a monocyclic or polycyclic group It may be formed, and the monocyclic or polycyclic ring thus formed may have a double bond.

[0020]

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In the above general formula (II), p and q may be the same or different from each other and are 0 or a positive integer, r and s may be the same or different from each other, and 0, 1 or 2 It is. R ^{21 to} R ³⁹ may be the same or different and are a hydrogen atom, a halogen atom, a hydrocarbon group or an alkoxy group. Here, the halogen atom, the hydrocarbon group and the alkoxy group are the same as the halogen atom, the hydrocarbon group and the alkoxy group in the general formula (I).

Where R²⁹And R³⁰Charcoal to which is bound
An element atom and R³³Is bonded to a carbon atom or R³¹Tied
The carbon atoms that are combined are directly or having 1 to 1 carbon atoms.
And 3 may be bonded via an alkylene group. Sand
Wherein the two carbon atoms are bonded via an alkylene group.
If R²⁹And R³³And or R³⁰And R ³¹
And methylene group (-CH_Two-),ethylene
Group (-CH_TwoCH_Two-) Or propylene group (-CH_TwoCH_TwoCH_Two-)of
Forms an alkylene group.

Further, when r = s = 0, R ³⁵ and R ³² or R ³⁵ and R ³⁹ may combine with each other to form a monocyclic or polycyclic aromatic ring. Specific examples of the cyclic olefin represented by the general formula (I) or (II) as described above include bicyclo-2-heptene derivatives (bicyclohept-2-ene derivatives), tricyclo-3-decene derivatives, and tricyclo-3-decene derivatives. -3-undecene derivative, tetracyclo-3-
Dodecene derivative, pentacyclo-4-pentadecene derivative, pentacyclopentadecadiene derivative, pentacyclo-3-pentadecene derivative, pentacyclo-3-hexadecene derivative, pentacyclo-4-hexadecene derivative, hexacyclo-4-heptadecene derivative, heptacyclo-5-eicocene Derivatives, heptacyclo-4-eicosene derivatives, heptacyclo-5-heneicosene derivatives, octacyclo-5-
Dococene derivatives, nonacyclo-5-pentacocene derivatives,
Nonacyclo-6-hexacocene derivative, cyclopentadiene-acenaphthylene adduct, 1,4-methano-1,4,4a, 9a-tetrahydrofluorene derivative, 1,4-methano-1,4,4a, 5,10,1
0a-hexahydroanthracene derivative and the like.

More specifically, as the cyclic olefin,
For example, norbornene, 5-methylnorbornene, 5-ethylnorbornene, 5-propylnorbornene, 5,6-dimethylnorbornene, 1-methylnorbornene, 7-methylnorbornene, 5,5,6-trimethylnorbornene, 5-phenylnorbornene, 5 -Benzyl norbornene, 5-ethylidene norbornene, 5-vinyl norbornene, 1,4,5,8-dimethano-1,2,3,4,4a, 5,8,8a-octahydronaphthalene, 2-methyl-1, 4,5,8-dimethano-1,2,3,4,4a, 5,8,8a-octahydronaphthalene, 2-ethyl-1,4,5,8-dimethano-1,2,3,4, Four
a, 5,8,8a-octahydronaphthalene, 2,3-dimethyl-1,4,
5,8-Dimethano-1,2,3,4,4a, 5,8,8a-octahydronaphthalene, 2-hexyl-1,4,5,8-dimethano-1,2,3,4,4a, 5,8,8
a-octahydronaphthalene, 2-ethylidene-1,4,5,8-dimethano-1,2,3,4,4a, 5,8,8a-octahydronaphthalene, 2
-Fluoro-1,4,5,8-dimethano-1,2,3,4,4a, 5,8,8a-octahydronaphthalene, 1,5-dimethyl-1,4,5,8-dimethano-
1,2,3,4,4a, 5,8,8a-octahydronaphthalene, 2-cyclohexyl-1,4,5,8-dimethano-1,2,3,4,4a, 5,8,8a- Octahydronaphthalene, 2,3-dichloro-1,4,5,8-dimethano-1,
2,3,4,4a, 5,8,8a-octahydronaphthalene, 2-isobutyl-1,4,5,8-dimethano-1,2,3,4,4a, 5,8,8a-octahydro Naphthalene, 1,2-dihydrodicyclopentadiene, 5-chloronorbornene, 5,5-dichloronorbornene, 5-fluoronorbornene, 5,5,6-trifluoro-6-trifluoromethylnorbornene, 5-chloromethylnorbornene, 5-methoxynorbornene, 5,6-dicarboxyl norbornene anhydrate, 5-dimethylaminonorbornene, 5-cyanonorbornene and the like.

As the cyclic olefin, a cyclic olefin represented by the above general formula (I) is preferable, and norbornene, tetracyclododecene and derivatives thereof are particularly preferable. Note that the α-olefin / cyclic olefin copolymer is the above α-olefin within a range not to impair the object of the present invention.
Other monomers other than olefins and cyclic olefins, such as linear or branched polyenes and aromatic olefins, may be copolymerized, for example, in a proportion of 1 mol% or less based on all repeating units. Preferably, the monomer is substantially free.

The α-olefin / cyclic olefin copolymer according to the present invention contains 0.1 to 60 mol%, preferably 0.2 to 40 mol%, more preferably 0.2 to 40 mol% of the repeating unit derived from the cyclic olefin. It is desirable to contain it in the range of 10 to 10 mol%. When the content of the repeating unit derived from the cyclic olefin is within the above range, when the α-olefin / cyclic olefin copolymer is used as a viscosity index improver, the molecular chain is less likely to be cut, and the heat resistance of the lubricating oil is reduced. Properties and sufficient low-temperature properties can be obtained.

The molecular weight of the α-olefin / cyclic olefin copolymer is 80,00 as a molecular weight (Mw) in terms of polystyrene determined by gel permeation chromatography.
0 to 400,000, preferably 85,000 to 320,
000, more preferably 85,000 to 260,000
It is. When the molecular weight (Mw) is within the above range, the viscosity index improving performance (thickening property imparting property) is excellent, and thus an α-olefin / cyclic olefin copolymer is required to obtain a specific lubricating oil viscosity. It is possible to obtain a lubricating oil composition which requires a small amount, does not easily jell at low temperatures, and has excellent shear stability of lubricating oil viscosity.

The measurement by gel permeation chromatography (GPC) is carried out under the conditions of a temperature of 140 ° C. and a solvent of orthodichlorobenzene. α-
The olefin / cyclic olefin copolymer has Mw / Mn (Mw: weight average molecular weight, M
n: number average molecular weight) is 2.3 or less, preferably 2.2.
Or less, more preferably 2.0 or less. It is preferable that the value of Mw / Mn is 2.3 or less, because the shear stability of the lubricating oil viscosity is good.

In the present invention, the α-olefin / cyclic olefin copolymer is preferably a copolymer of ethylene, an α-olefin having 3 to 20 carbon atoms and a cyclic olefin, and particularly, ethylene, propylene or butene. ,
It is preferably a copolymer with a cyclic olefin, and particularly preferably a copolymer of ethylene, propylene and a cyclic olefin.

When the α-olefin / cyclic olefin copolymer is a copolymer of ethylene, an α-olefin having 3 to 20 carbon atoms and a cyclic olefin, a repeating unit derived from ethylene; 3-20 carbon atoms
Is from 85/15 to 35/65, preferably 85/15 to 55, in terms of the molar ratio to the repeating unit derived from the α-olefin (ethylene / α-olefin having 3 to 20 carbon atoms).
/ 45, more preferably in the range of 85/15 to 65/35, particularly preferably in the range of 85/15 to 70/30.

When the molar ratio of the repeating unit derived from ethylene to the repeating unit derived from an α-olefin having 3 to 20 carbon atoms is within the above range, the viscosity characteristics even at a low shear rate at a low temperature (for example, as described below). MR viscosity etc.)
Is improved, and heat aging resistance is maintained. The composition of the α- olefin-cyclic olefin copolymer, "Polymer Analysis Handbook" (Japan Society for Analytical Chemistry, Polymer Analysis Research Council, ed., Kinokuniya Shoten) according to the method described in ¹³ C-
It can be measured by NMR.

In the case where the α-olefin / cyclic olefin copolymer is a copolymer of ethylene, an α-olefin having 3 to 20 carbon atoms, and a cyclic olefin,
The intensity ratio D (Sαβ / Sαα) of the peak intensity (Sαβ) indicating the ratio of αβ carbon to the peak intensity (Sαα) indicating the ratio of αα carbon determined by ¹³ C-NMR is 0.5 or less, preferably 0.1%. It is desirably 4 or less, more preferably 0.3 or less.

When the intensity ratio D (Sαβ / Sαα) is 0.5
When the following ethylene / α-olefin / cyclic olefin copolymer is contained, the lubricating oil composition can have improved low-temperature fluidity, and can also have improved high-temperature lubricating properties, Further, the lubricating oil composition is particularly excellent in the balance between the two (low-temperature fluidity and high-temperature lubricating properties).

Sαβ and Sαα determined by ¹³ C-NMR spectrum are the peak intensities of CH _{2 in} the structural unit derived from ethylene or α-olefin having 3 or more carbon atoms, respectively. it means the seed of CH _2.

[0035]

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The spectrum measured by ¹³ C-NMR is shown in JCRandall (Review Macromolecular Chemistry).
Physics, C29, 201 (1989)), and Sαβ and Sαα are measured. The intensity ratio D is calculated from the integrated value (area) ratio of each peak portion. The strength ratio D obtained in this manner is generally determined by the ratio of the occurrence of the 1,2 addition reaction of the α-olefin followed by the 2,1 addition reaction or the proportion of the 1,2 addition reaction of the α-olefin followed by the 1,2 addition reaction. It is considered a measure of the rate at which addition reactions occur. Therefore, as this intensity ratio D value increases,
This indicates that the bonding direction of the α-olefin is irregular. Conversely, a smaller D value indicates that the α-olefin bond direction is more regular.

Such an α-olefin / cyclic olefin copolymer has a large effect of improving the viscosity index when blended with a lubricating oil base, and the effect of the pour point depressant is not hindered. When this α-olefin / cyclic olefin copolymer is used as a viscosity modifier, a lubricating oil that can satisfy the low temperature characteristics of the GF-3 standard, the next-generation North American lubricating oil standard, can be obtained. Whether the lubricating oil satisfies the GF-3 standard is determined by the CC
The determination can be made by measuring S and MRV.

(Method for Producing α-Olefin / Cyclic Olefin Copolymer) The α-olefin / cyclic olefin copolymer used as the viscosity modifier for lubricating oils according to the present invention is an α-olefin / cyclic olefin copolymer having 2 to 20 carbon atoms. At least one α-olefin selected from olefins, a cyclic olefin represented by the above general formula (I) or (II), and, if necessary, another monomer are copolymerized in the presence of an olefin polymerization catalyst. Can be obtained.

As such an olefin polymerization catalyst,
A catalyst comprising a compound of a transition metal such as zirconium, hafnium and titanium, and an organic aluminum compound such as an organic aluminum compound and an organic aluminum oxy compound and / or an ionized ionic compound can be used.
In the present invention, a metallocene catalyst comprising a metallocene compound of a transition metal selected from Group 4 of the periodic table and an organic aluminum oxy compound and / or an ionized ionic compound is particularly preferably used.

When a metallocene-based catalyst is used, α becomes a viscosity modifier for lubricating oil which is excellent in shear stability and low-temperature characteristics.
-An olefin / cyclic olefin copolymer is obtained. Next, an example of a metallocene-based catalyst suitably used for producing the above-mentioned α-olefin / cyclic olefin copolymer will be described. (Metallocene compound) A metallocene compound of a transition metal selected from Group 4 of the periodic table that forms a metallocene catalyst is
Specifically, it is represented by the following general formula (a).

MLx (a) In the formula (a), M is a transition metal selected from Group 4 of the periodic table, specifically, zirconium, titanium or hafnium, and x is a number satisfying the valence of the transition metal. It is. L is a ligand coordinating to the transition metal, and at least one of these ligands L is a ligand having a cyclopentadienyl skeleton, and a ligand having this cyclopentadienyl skeleton May have a substituent.

The ligand having a cyclopentadienyl skeleton includes, for example, cyclopentadienyl group, methylcyclopentadienyl group, ethylcyclopentadienyl group, n- or i-propylcyclopentadienyl group, n-,
i-, sec- or tert-butylcyclopentadienyl group,
Hexylcyclopentadienyl group, octylcyclopentadienyl group, dimethylcyclopentadienyl group, trimethylcyclopentadienyl group, tetramethylcyclopentadienyl group, pentamethylcyclopentadienyl group, methylethylcyclopentadiene Enyl group, methylpropylcyclopentadienyl group, methylbutylcyclopentadienyl group, methylhexylcyclopentadienyl group, methylbenzylcyclopentadienyl group, ethylbutylcyclopentadienyl group, ethylhexylcyclopentadienyl group, Examples thereof include an alkyl or cycloalkyl-substituted cyclopentadienyl group such as a methylcyclohexylcyclopentadienyl group, an indenyl group, a 4,5,6,7-tetrahydroindenyl group, and a fluorenyl group.

These groups may be substituted with a halogen atom, a trialkylsilyl group or the like. Among these, an alkyl-substituted cyclopentadienyl group is particularly preferred. When the compound represented by the general formula (a) has two or more groups having a cyclopentadienyl skeleton as the ligand L, two of the groups having the cyclopentadienyl skeleton are ethylene, propylene Alkylene group such as, isopropylidene, substituted alkylene group such as diphenylmethylene, silylene group or dimethylsilylene,
It may be bonded via a substituted silylene group such as diphenylsilylene and methylphenylsilylene.

L other than the ligand having a cyclopentadienyl skeleton includes a hydrocarbon group having 1 to 12 carbon atoms, an alkoxy group, an aryloxy group, a sulfonic acid-containing group (—SO ₃ R ^a ), and halogen. An atom or a hydrogen atom (where ^Ra is an alkyl group, an alkyl group substituted with a halogen atom, an aryl group, an aryl group substituted with a halogen atom, or an aryl group substituted with an alkyl group). Can be

Examples of the hydrocarbon group having 1 to 12 carbon atoms include an alkyl group, a cycloalkyl group, an aryl group and an aralkyl group. More specifically, methyl, ethyl, n-propyl, isopropyl, Alkyl groups such as n-butyl, isobutyl, sec-butyl, t-butyl, pentyl, hexyl, octyl, decyl, dodecyl, cycloalkyl groups such as cyclopentyl and cyclohexyl, aryl groups such as phenyl and tolyl, benzyl and neophyl And aralkyl groups.

As the alkoxy group, methoxy,
Ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, t-butoxy, pentoxy, hexoxy, octoxy and the like. Examples of the aryloxy group include phenoxy, and examples of the sulfonic acid-containing group (—SO ₃ R ^a ) include methanesulfonate, p-toluenesulfonate, trifluoromethanesulfonate, and p-chlorobenzenesulfonate. .

Examples of the halogen atom include fluorine, chlorine, bromine and iodine. Examples of the metallocene compound in which M is zirconium and contains at least two ligands having a cyclopentadienyl skeleton are shown below. Bis (methylcyclopentadienyl) zirconium dichloride, bis (ethylcyclopentadienyl) zirconium dichloride, bis (n-propylcyclopentadienyl)
Zirconium dichloride, bis (indenyl) zirconium dichloride, bis (4,5,6,7-tetrahydroindenyl) zirconium dichloride and the like.

Further, there may be mentioned compounds in which zirconium metal is replaced with titanium metal or hafnium metal in the above compounds. Further, in the present invention, a compound represented by the following general formula (b) can be used as the metallocene compound. L ¹ M ¹ X ₂ (b) (where M ¹ is a metal belonging to Group 4 of the periodic table or a lanthanide series, L ¹ is a derivative of a delocalized π-bonded group,
The metal M ¹ active site has a constrained geometry, and X
Is a hydrogen atom or a halogen atom, which may be the same or different, or a hydrocarbon group containing 20 or less carbon, a silyl group containing 20 or less silicon, or 2
It is a germanyl group containing 0 or less germanium. Among the compounds represented by the general formula (b),
Compounds represented by the following general formula (c) are preferred.

[0049]

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In the formula, M ¹ is titanium, zirconium or hafnium, and X is as defined above. Cp is M
It is a substituted cyclopentadienyl group having a π bond to ¹ and having a substituent Z. Z is oxygen, sulfur, boron or an element of Group 14 of the periodic table (eg, silicon, germanium or tin); Y is a ligand containing nitrogen, phosphorus, oxygen or sulfur; May be formed.

Specific examples of the compound represented by the general formula (c) include [dimethyl (t-butylamide) (tetramethyl-η ⁵ -cyclopentadienyl) silane] titanium dichloride, [(t- Butylamide) (tetramethyl-η ⁵
-Cyclopentadienyl) -1,2-ethanediyl] titanium dichloride, [dibenzyl (t-butylamide) (tetramethyl-η ⁵ -cyclopentadienyl) silane] titanium dichloride, [dimethyl (t-butylamide) (tetramethyl -η ⁵
-Cyclopentadienyl) silane] dibenzyltitanium,
[Dimethyl (t-butylamido) (tetramethyl-eta ⁵ - cyclopentadienyl) silane] dimethyl titanium, [(t-butylamido) (tetramethyl-eta ⁵ - cyclopentadienyl) -1,2-ethanediyl] di Benzyl titanium, [(methylamide) (tetramethyl-η ⁵ -cyclopentadienyl)-
1,2-ethanediyl] dineopentyl titanium, [(phenylphosphido) (tetramethyl-η ⁵ -cyclopentadienyl) methylene] diphenyltitanium, [dibenzyl (t-butylamide) (tetramethyl-η ⁵ -cyclopenta dienyl) silane] dibenzyl titanium, [dimethyl (benzylamide) (eta ⁵ - cyclopentadienyl) silane] di (trimethylsilyl) titanium, [dimethyl (phenyl phosphide) (tetramethyl-eta ⁵ - cyclopentadienyl ) Silane] dibenzyltitanium, [(tetramethyl-η ⁵ -cyclopentadienyl) -1,2-ethanediyl] dibenzyltitanium, [2-η ^5- (tetramethyl-cyclopentadienyl)-
1-methyl-ethanolate (2-)] dibenzyltitanium, [2-
η ^5- (tetramethyl-cyclopentadienyl) -1-methyl
-Ethanolate (2-)] dimethyl titanium, [2-((4a, 4b, 8
a, 9,9a-η) -9H-fluoren-9-yl) cyclohexanolate (2-)] dimethyltitanium, [2-((4a, 4b, 8a, 9,9a-η)
-9H-Fluoren-9-yl) cyclohexanolate (2-)]
And dibenzylzil titanium.

Further, there may be mentioned compounds in which titanium metal is replaced with zirconium metal or hafnium metal in the above compounds. These metallocene compounds can be used alone or in combination of two or more. In the present invention, as the metallocene compound represented by the general formula (a), a zirconocene compound in which the central metal atom is zirconium and has a ligand having at least two cyclopentadienyl skeletons is preferably used. . As the metallocene compound represented by the general formula (b) or (c), a compound in which the central metal atom is titanium is preferably used.

Among the above metallocene compounds, a compound represented by the general formula (c) wherein the central metal atom is titanium is particularly preferably used. (Organic aluminum oxy compound) The organic aluminum oxy compound forming the metallocene catalyst may be a conventionally known aluminoxane (also referred to as alumoxane) or a benzene-insoluble organic aluminum oxy compound.

The conventionally known aluminoxane is specifically represented by the following general formula.

[0055]

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(In the above general formulas (d) and (e), R is a hydrocarbon group such as methyl, ethyl, propyl and butyl, preferably methyl and ethyl, particularly preferably methyl, and m is 2 or more. Here, this aluminoxane is an alkyloxyaluminum unit represented by the formula (OAl (R ¹ )) and a compound represented by the formula (OA).
An alkyloxyaluminum unit represented by l (R ² ) (where R ¹ and R ² can be the same hydrocarbon group as R, and R ¹ and R ² represent different groups. )
May be formed from a mixed alkyloxyaluminum unit consisting of

(Ionized Ionic Compound) The ionized ionic compound forming the metallocene catalyst is a compound capable of forming an ion pair by reacting with the above-mentioned metallocene compound. Examples can be given. Examples of the Lewis acid include a compound represented by BR ₃ (R is a phenyl group or a fluorine which may have a substituent such as a fluorine, a methyl group, and a trifluoromethyl group). Boron, triphenylboron, tris (4-fluorophenyl) boron, tris (3,5-difluorophenyl) boron, tris (4-fluoromethylphenyl) boron, tris (pentafluorophenyl) boron, tris (p-tolyl) Boron, Tris (o-tolyl) Boron, Tris (3,5-
Dimethylphenyl) boron and the like.

Examples of the ionic compound include trialkyl-substituted ammonium salts, N, N-dialkylanilinium salts, dialkylammonium salts, and triarylphosphonium salts. Specifically, the trialkyl-substituted ammonium salts include, for example, triethylammonium tetra (phenyl) boron, tripropylammonium tetra (phenyl) boron, tri (n-butyl) boron.
Ammonium tetra (phenyl) boron, trimethylammonium tetra (p-tolyl) boron, trimethylammonium tetra (o-tolyl) boron, tributylammonium tetra (pentafluorophenyl) boron, tripropylammonium tetra (o, p-dimethylphenyl)
Boron, tributylammonium tetra (m, m-dimethylphenyl) boron, tributylammonium tetra (p-
Trifluoromethylphenyl) boron, tri (n-butyl) ammoniumtetra (o-tolyl) boron and the like.

The N, N-dialkylanilinium salts include
For example, N, N-dimethylanilinium tetra (phenyl)
Boron, N, N-diethylanilinium tetra (phenyl)
Boron and N, N-2,4,6-pentamethylanilinium tetra (phenyl) boron.

Examples of the dialkylammonium salt include di (1-propyl) ammonium tetra (pentafluorophenyl) boron and dicyclohexylammonium tetra (phenyl) boron. Further, as ionic compounds, triphenylcarbenium tetrakis (pentafluorophenyl) borate, N, N-dimethylanilinium tetrakis (pentafluorophenyl)
Borate, ferrocenium tetra (pentafluorophenyl) borate and the like can also be mentioned.

In the present invention, the ionized ionic compound is α
-It is preferably used in that the composition distribution of the olefin / cyclic olefin copolymer can be controlled. The metallocene-based catalyst used when producing the α-olefin / cyclic olefin copolymer may contain an organic aluminum compound together with the organic aluminum oxy compound and / or the ionized ionic compound.

(Organoaluminum Compound) Examples of the organoaluminum compound include compounds represented by the following general formula (f). R ¹ _n AlX _3-n (f) wherein R ¹ has ¹ to 15 carbon atoms, preferably 1 to 4 carbon atoms.
Wherein X is a halogen atom or a hydrogen atom, and n is 1-3.

Examples of such a hydrocarbon group having 1 to 15 carbon atoms include an alkyl group, a cycloalkyl group and an aryl group, and specific examples include methyl, ethyl, n-propyl, isopropyl and isobutyl. , Pentyl, hexyl, octyl, cyclopentyl, cyclohexyl, phenyl, tolyl and the like. Specific examples of such an organoaluminum compound include the following compounds.

Trimethylaluminum, triethylaluminum, triisopropylaluminum, triisobutylaluminum, trioctylaluminum, tri2-
Trialkyl aluminum Nim such ethylhexyl aluminum; formula _{(i-C 4 H 9)} x Al y (C 5 H 10) z ( wherein, x, y, z are each a positive number, is z ≧ 2x Alkenyl aluminum such as isoprenyl aluminum; trialkenyl aluminum such as triisopropenyl aluminum; dialkylaluminum halides such as dimethylaluminum chloride, diethylaluminum chloride, diisopropylaluminum chloride, diisobutylaluminum chloride, dimethylaluminum bromide; methyl Alkyls such as aluminum sesquichloride, ethyl aluminum sesquichloride, isopropyl aluminum sesquichloride, butyl aluminum sesquichloride, ethyl aluminum sesquibromide Mini um sesquihalide; methyl aluminum dichloride, ethyl aluminum dichloride, alkyl aluminum dihalides such as isopropyl aluminum dichloride, ethyl aluminum dibromide;
Dialkylaluminum hydrides such as diethylaluminum hydride and dibutylaluminum hydride; alkylaluminum dihydrides such as ethylaluminum dihydride and propylaluminum dihydride.

(Polymerization method) The α-olefin / cyclic olefin copolymer used as a viscosity index improver for lubricating oils in the present invention is prepared by using an α-olefin having 2 to 20 carbon atoms in the presence of the above-mentioned metallocene catalyst. At least one α-olefin selected from -olefins, the cyclic olefin represented by the general formula (I) or (II), and, if necessary, other monomers are copolymerized in a liquid phase. In this case, a hydrocarbon solvent is generally used as the polymerization solvent, but an α-olefin such as propylene may be used.

Examples of the hydrocarbon solvent used in the polymerization include aliphatic hydrocarbons such as pentane, hexane, heptane, octane, decane, dodecane and kerosene and halogen derivatives thereof; cyclohexane, methylcyclopentane, methylcyclohexane and the like. Alicyclic hydrocarbons and their halogen derivatives; aromatic hydrocarbons such as benzene, toluene and xylene, and halogen derivatives such as chlorobenzene are used. These hydrocarbon solvents can be used alone or in combination of two or more.

An α-olefin having 2 to 20 carbon atoms,
The cyclic olefin and, if necessary, the other monomer can be copolymerized by any of a batch method and a continuous method, but is preferably copolymerized by a continuous method. It is preferred to copolymerize by a method. When the copolymerization is carried out by a continuous method, the above-mentioned metallocene catalyst is used, for example, at the following concentrations.

The concentration of the metallocene compound in the polymerization system is usually 0.00005 to 0.1 mmol / liter (polymerization volume), preferably 0.0001 to 0.05 mmol / liter.
Liters. The organoaluminum oxy compound has a molar ratio of aluminum atom to transition metal (Al / transition metal) of the metallocene compound in the polymerization system of 1 to 100.
00, preferably from 10 to 5000.

The ionized ionic compound is represented by a molar ratio of the ionized ionic compound to the metallocene compound in the polymerization system (ionized ionic compound / metallocene compound).
It is supplied in an amount of 0.5 to 30, preferably 1 to 25.
When an organoaluminum compound is used, it is generally used in an amount of about 0 to 5 mmol / L (polymerization volume), preferably about 0 to 2 mmol / L.

In the case where an α-olefin having 2 to 20 carbon atoms, a cyclic olefin and, if necessary, other monomers are copolymerized in the presence of the above-mentioned metallocene catalyst, the copolymerization reaction is carried out. , Usually at temperatures between -20 ° C and 150 ° C
° C, preferably 0 ° C to 120 ° C, more preferably 0 ° C
At １００100 ° C., the pressure exceeds 80 kg / cm
² (7.8 MPa) or less, preferably more than 0 and 50 k
It is performed under the condition of g / cm ² (4.9 MPa) or less.
The above polymerization conditions are preferably constant in the continuous polymerization method.

The reaction time (average residence time when the copolymerization is carried out by a continuous method) varies depending on conditions such as the catalyst concentration and the polymerization temperature, but is usually 5 minutes to 5 hours, preferably 10 minutes to 5 minutes. 3 hours. The α-olefin having 2 to 20 carbon atoms, the cyclic olefin and, if necessary, other monomers are polymerized in such an amount that an α-olefin / cyclic olefin copolymer having a specific composition as described above can be obtained. Supplied to the system. Further, upon copolymerization, a molecular weight regulator such as hydrogen may be used.

As described above, α having 2 to 20 carbon atoms
When an olefin, a cyclic olefin, and other monomers are copolymerized as necessary, an α-olefin / cyclic olefin copolymer is usually obtained as a polymerization solution containing the same. This polymerization solution is treated by a conventional method to obtain the α-olefin / cyclic olefin copolymer used in the present invention.

Lubricating Oil Composition The lubricating oil composition according to the present invention comprises a viscosity index improver comprising the above α-olefin / cyclic olefin copolymer, a lubricating oil base, and if necessary, a pour point depressant. Contains.
First, each component forming the lubricating oil composition according to the present invention will be described.

(Lubricating oil base) The lubricating oil base used in the present invention includes mineral oil; diesters such as poly α-olefin, polyol ester, dioctyl phthalate and dioctyl sebacate; and synthetic oil such as polyalkylene glycol. And a blend of a mineral oil or a mineral oil and a synthetic oil is preferably used.

The mineral oil is generally used after a refining step such as dewaxing, and there are several grades depending on the refining method. In general, a mineral oil containing a wax content of 0.5 to 10% is used. For example, a highly refined oil having a low pour point, a high viscosity index, and a composition mainly composed of isoparaffin produced by a hydrocracking method can be used. Also 40
Those having a kinematic viscosity at 10 ° C of 10 to 200 cSt are generally used.

(Pour point depressant) The pour point depressant used in the present invention includes alkylated naphthalene, (co) polymer of alkyl methacrylate, (co) polymer of alkyl acrylate, alkyl fumarate and acetic acid Examples include vinyl copolymers, α-olefin polymers, α-olefin and styrene copolymers, and among them, alkyl methacrylate (co) polymers and alkyl acrylate (co) polymers are preferred. Used for

(Composition) The lubricating oil composition according to the present invention comprises:
It contains the lubricating oil base, the α-olefin / cyclic olefin copolymer, and if necessary, a pour point depressant. When the lubricating oil composition contains a lubricating oil base and the α-olefin / cyclic olefin copolymer, the lubricating oil composition contains the α-olefin / cyclic olefin copolymer in an amount of, for example, 1 to 20% by weight. %, Preferably 5 to 10% by weight (the remainder is a lubricating oil base and the following compounding agents).

Such a lubricating oil composition has low temperature dependency and is excellent in low-temperature characteristics. This lubricating oil composition can be used as it is for lubricating oil applications, and the lubricating oil composition can be further blended with a pour point depressant and used for lubricating oil applications. A lubricating oil composition, a lubricating oil base, and the α-olefin / cyclic olefin copolymer,
When a pour point depressant is contained, the α-olefin / cyclic olefin copolymer is used in an amount of, for example, 0.1 to 5% by weight, preferably 0.2 to 1.5% by weight, more preferably 0.2 to 1.5% by weight.
5 to 1.5% by weight, particularly preferably 0.30 to 1.5% by weight, wherein the pour point depressant is for example 0.0%
5 to 3% by weight, preferably 0.1 to 3% by weight, more preferably 0.1 to 2% by weight, most preferably 0.2 to 2% by weight.
Desirably, it is contained in an amount of 1.5% by weight (the remainder is a lubricating oil base and the following compounding agents).

In such a lubricating oil composition, the amount of the α-olefin / cyclic olefin copolymer is 0.1% by weight.
With the above, an effect of improving viscosity is obtained, and since the α-olefin / cyclic olefin copolymer has a composition distribution, it may contain a component which inhibits the effect of the fluidity-lowering agent. When the blending amount of the olefin / cyclic olefin copolymer is 5% by weight or less, the effect of the pour point depressant is not hindered, so that the amount of the α-olefin / cyclic olefin copolymer is within the above range. In such a case, it is possible to obtain a lubricating oil composition having an excellent viscosity improving effect and having good fluidity at a low temperature.

The lubricating oil composition according to the present invention has a low viscosity temperature dependency, a small increase in pour point due to the interaction between the α-olefin / cyclic olefin copolymer and the pour point depressant, Excellent low-temperature characteristics in the speed range and excellent fuel economy. In addition, such a lubricating oil composition is excellent in high-temperature characteristics and exhibits good lubricating performance.

The lubricating oil composition according to the present invention comprises, in addition to a lubricating oil base, an α-olefin / cyclic olefin copolymer and a pour point depressant, a (co) polymer of alkyl methacrylate, hydrogenated SBR, It may contain a compounding agent having a viscosity index improving effect such as SEBS, a detergent, a rust inhibitor, a dispersant, an extreme pressure agent, an antifoaming agent, an antioxidant, a metal deactivator and the like. .

Examples of extreme pressure agents include sulfur extreme pressure agents such as sulfides, sulfoxides, sulfones, thiophosphinates, thiocarbonates, oils and fats, sulfurized oils and fats, and sulfurized olefins; phosphate esters, phosphite esters And phosphoric acid esters such as phosphoric acid ester amine salts and phosphite ester amines; and halogen compounds such as chlorinated hydrocarbons.

Examples of the antiwear agent include inorganic or organic molybdenum compounds such as molybdenum disulfide, organic boron compounds such as alkyl mercaptyl borate; graphite, antimony sulfide, boron compounds, and polytetrafluoroethylene. As a cleaning dispersant,
Calcium sulfonate, magnesium sulfonate,
Examples thereof include metal sulfonates such as barium sulfonate, thiophosphonates, phenates, salicylates, succinimides, benzylamines, and succinates.

As the antioxidant, 2,6-di-t-butyl-4-
Examples thereof include amine compounds such as methylphenol, and sulfur or phosphorus compounds such as zinc dithiophosphate. Examples of the rust preventive include carboxylic acids such as oxalic acid and salts thereof; sulfonates; esters; alcohols; phosphoric acids and salts thereof; benzotriazole and its derivatives; and thiazole compounds.

Examples of the foam inhibitor include silicone compounds such as dimethylsiloxane and silica gel dispersion, and alcohol or ester compounds. The amount of these additives varies depending on the required lubricating performance, but is usually 0.01 to 50 parts by weight, preferably 0.05 to 50 parts by weight, per 100 parts by weight of the lubricating oil composition.
30 parts by weight may be contained.

The lubricating oil composition according to the present invention can be prepared by a conventionally known method by adding an α-olefin / cyclic olefin copolymer, a pour point depressant if necessary, and another It can be prepared by mixing or dissolving a compounding agent.

[0087]

According to the viscosity index improver for lubricating oils of the present invention, a lubricating oil composition having good low-temperature characteristics and heat resistance can be obtained without hindering the effect of the pour point depressant. The lubricating oil composition according to the present invention has excellent low-temperature properties in all shear rate regions.

[0088]

EXAMPLES Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples. Composition of α-olefin / cyclic olefin copolymer Using a LA500 type nuclear magnetic resonance apparatus manufactured by JEOL Ltd., a mixed solvent of ortho-dichlorobenzene and benzene-d6 (ortho-dichlorobenzene / benzene-d6 = 3) /
1 to 4/1 (volume ratio)), 120 ° C, pulse width 45 °
The pulse was measured at a pulse repetition time of 5.5 seconds.

Viscosity at 100 ° C. (KV) Measurement was performed based on ASTM D445 . In the present embodiment, adjustment was made so that KV was about 10 mm ² / sec. The measurement was performed based on Cold Cranking Simulator (CCS) ASTM D 2602. CC
S is used for evaluating the low-temperature slidability (startability) of the crankshaft, and the smaller the value, the better the low-temperature characteristics of the lubricating oil.

The measurement was performed based on a Mini-Rotary Viscometer (MRV) ASTM D 3829, D4684. The MRV is used for evaluating the oil pump to perform pumping at a low temperature, and the smaller the value, the better the low-temperature characteristics of the lubricating oil. The measurement was performed based on the Shear Stability Index (SSI) ASTM D3945. SS
I is a measure of the loss of kinematic viscosity due to the shear force of the copolymer component in the lubricating oil under sliding and the breaking of the molecular chain. The larger the SSI, the greater the loss of kinematic viscosity. Is shown.

Low-temperature fluidity (low-temperature storage stability) The fluidity (appearance) after cooling at −18 ° C. for 2 weeks was observed and evaluated as follows. ○: Fluid ×: Gelled

[0092]

[Polymerization Example 1] [Synthesis of copolymer] A 2-liter stainless steel autoclave with stirring blades, which had been sufficiently purged with nitrogen, was placed in a stainless steel autoclave.
At 23 ° C., 900 ml of heptane and 1.7 g of norbornene were charged. In this autoclave, 5.3N-liter of propylene and 90% of hydrogen were added while rotating a stirring blade and cooling with ice.
ml was inserted. Next, the autoclave was heated to 70 ° C., and further pressurized with ethylene so that the total pressure became 6 KG. When the internal pressure of the autoclave reached 6 KG, 1.0 ml of a 1.0 mM / ml hexane solution of triisobutylaluminum was injected with nitrogen. Subsequently, triphenylcarbenium (tetrakispentafluorophenyl) borate prepared in advance is converted to a boron atom in 0.0%.
16 mM, [dimethyl (t-butylamide) (tetramethyl
-η ⁵ -cyclopentadienyl) silane] 3 ml of a toluene solution containing titanium dichloride in an amount of 0.0004 mM,
The polymerization was started by pressurizing the autoclave with nitrogen. Thereafter, the temperature of the autoclave was adjusted to 70 ° C. for 5 minutes, and ethylene was directly supplied so that the pressure became 6 kg. Five minutes after the start of the polymerization, 5 ml of methanol was inserted into the autoclave with a pump to stop the polymerization,
The autoclave was depressurized to atmospheric pressure. 3 liters of methanol was poured into the reaction solution with stirring. The polymer containing the obtained solvent was heated at 130 ° C. for 13 hours at 0.08 MPa.
It was dried at G (600 torr) to obtain 29 g of an ethylene / propylene / norbornene copolymer. Table 1 shows the properties of the obtained polymer.

[0093]

Polymerization Examples 2 and 3 Polymerization Example 1 except that the amounts of propylene, hydrogen and norbornene were changed as shown in Table 1.
The same was done. Table 1 shows the above results.

[0094]

[Table 1]

[0095]

Example 1 As a base oil, mineral oil 150 neutral (trade name, manufactured by ESSO) was 88.72% by weight, and as a viscosity index improver, the polymer obtained in Polymerization Example 1 was 0.78.
0.5% by weight of Acrube 133 (trade name, manufactured by Sanyo Kasei Co., Ltd.) as a pour point depressant,
LZ-9814, manufactured by Lubrizol Corporation) was used at 10% by weight to evaluate the performance of the lubricating oil and the fluidity at low temperatures. Table 2 shows the results.

[0096]

Comparative Example 1 and Example 2 The same procedure as in Example 1 was carried out except that the amount of the lubricating oil base and the type and amount of the polymer were changed. Table 2 shows the results.

[0097]

[Table 2]

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C10N 30:08 C10N 30:08 (72) Inventor Ryosuke Kanashige 3 Chigusa Kaigan, Ichihara-shi, Chiba Mitsui Chemicals, Inc. Association In-house F-term (reference) 4H104 CA08C CA14C EA03C EA21C LA01 LA04

Claims (7)

[Claims] A copolymer of at least one α-olefin selected from α-olefins having 2 to 20 carbon atoms and a cyclic olefin represented by the following general formula (I) or (II). (1) containing a repeating unit derived from the cyclic olefin in the range of 0.1 to 60 mol%,
(2) The weight average molecular weight in terms of polystyrene by gel permeation chromatography is 80,000 to 40.
(3) a viscosity index improver for lubricating oils, comprising (3) an α-olefin / cyclic olefin copolymer having Mw / Mn of 2.3 or less; Wherein n is 0 or 1, m is 0 or a positive integer, k is 0 or 1, and R ^{1 to} R ¹⁸ and R ^a
And R ^b may be the same or different and represent a hydrogen atom, a halogen atom, a hydrocarbon group, an oxygen-containing group or a nitrogen-containing group, and R ¹⁵ and R ¹⁶ are bonded to each other to form a monocyclic or polycyclic ring. And this monocyclic or polycyclic ring may have a double bond, and may form an alkylidene group with R ¹⁵ and R ¹⁶ or with R ¹⁷ and R ^18. You may. Here, when k is 0, the respective bonds are combined to form a 5-membered ring. ) (Where p and q may be the same or different from each other, and are 0 or a positive integer, r and s may be the same or different from each other, 0, 1 or 2, and R ²¹
To R ³⁹ may be the same or different, represent a hydrogen atom, a halogen atom, a hydrocarbon group or an alkoxy group. ). 2. The α-olefin / cyclic olefin copolymer is a copolymer of ethylene, an α-olefin having 3 to 20 carbon atoms and a cyclic olefin, and a repeating unit derived from ethylene; Α having 3 to 20 carbon atoms
The molar ratio with respect to the repeating unit derived from -olefin (ethylene / α-olefin having 3 to 20 carbon atoms) is 85.
The viscosity index improver for a lubricating oil according to claim 1, wherein the viscosity index improver is in the range of / 15 to 35/65. 3. The α-olefin / cyclic olefin copolymer is a copolymer of ethylene, an α-olefin having 3 to 20 carbon atoms and a cyclic olefin, and ¹³ C—N
The intensity ratio D (Sαβ / Sαα) of the peak intensity (Sαβ) indicating the ratio of αβ carbon to the peak intensity (Sαα) indicating the ratio of αα carbon determined by MR is 0.5 or less. Item 3. The viscosity index improver for lubricating oils according to Item 1 or 2. 4. The viscosity index improver for a lubricating oil according to claim 2, wherein the α-olefin / cyclic olefin copolymer is a copolymer of ethylene, propylene and a cyclic olefin. . 5. The viscosity index for lubricating oil according to claim 1, wherein the α-olefin / cyclic olefin copolymer is produced by using a metallocene catalyst. Enhancer. 6. A lubricating oil composition comprising the viscosity index improver according to claim 1 and a lubricating oil base. 7. A lubricating oil composition comprising the viscosity index improver according to any one of claims 1 to 5, a lubricating oil base, and a pour point depressant.