[0001]The present invention relates to a lubricating oil 10 composition for compressor oils and a method for producing the same.
Background Art [0002]
15 The rotary-type gas compressor has little vibration
compared to reciprocating-type gas compressors, and the temperature of discharge gas can be lowered by operating the compressor whilst injecting a large amount of lubricating oil into the compressor parts. Moreover, amongst the rotary-type
20 gas compressors, the oil-flooded screw compressor has become widely utilized in the industry in place of the
conventionally utilized reciprocating-type compressor, due to features such as high efficiency, compact size, low noise, long-term continuous operability, and low maintenance cost.

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Such oil-flooded screw compressors have a tendency to have a high discharge pressure and to be free-draining (preventing the formation of condensed water), and hence there is also an increased demand for heat resistance of lubricating oil for 5 compressor oil, which has a tendency to have an increased
discharge temperature overall (refer to Non-Patent Literature
1).
[0003]
Meanwhile, as global warming advances, it is an urgent
10 task to cut carbon dioxide emissions, which is one of the gases contributing to the greenhouse effect. Reducing the amount of electric power consumption has also come to be demanded for compressors, which are used in various industrial fields. In order to reduce the electric power
15 consumption amount of compressors, it is necessary to reduce the lubricating oil agitation torque of the screw member, as well as to lower the energy for circulating the lubricating oil by an oil pump. To deal with this, the viscosity of lubricating oil is usually lowered (refer to Patent
20 Literature 1). However, since viscosity also ends up becoming lowered at high temperatures due to the lowering of the base oil viscosity, oil film formation becomes difficult at high temperatures, and as a result, heat resistance has been lost. In order to find a balance between a low torque at low

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temperatures in the vicinity of the operating temperatures, and oil film formation at high temperatures, there have been investigations into the use of synthetic oil (poly-α-olefin), which has excellent temperature viscosity properties, in 5 place of the conventionally utilized mineral oil. However, there was still room for further investigation (refer to Patent Literature 2). [0004]
Patent Literature 3 discloses a lubricating oil
10 composition containing a specific lubricant base oil and a
specific ethylene-α-olefin copolymer, where this composition has a balance of these properties, and which is suitably applicable to compressor oil. [0005]
15 Moreover, Patent Literature 4 describes a method for
producing a liquid random copolymer of ethylene and α-olefin, wherein further described is that this copolymer is useful as a lubricating oil.
20 Citation List
Patent Literature
[0006]
Patent Literature 1: JP 2008-179679 A
Patent Literature 2: JP 2002-519448 A

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Patent Literature 3: JP 2016-069407 A Patent Literature 4: EP 2921509 A1
Non-Patent Literature 5 [0007]
Non-Patent Literature 1: Illustrated guide to the introductory basics of industrial lubricating oil (2011); Author/Editor: Lubricants Department, Lubricant Technology 2nd section of Idemitsu Kosan Co Ltd, published by Nikkan Kogyo 10 Shimbun, Ltd [The Daily Industrial News]
Summary of Invention Technical Problem [0008]
15 However, there was further room for improvement in
conventional lubricating oil compositions, from the perspective of providing a lubricating oil composition for compressor oils having remarkably excellent temperature viscosity properties; namely, having oil film retention
20 properties at high temperatures, as well as low-temperature viscosity properties, and further having excellent thermal and oxidation stability.
Solution to Problem

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[0009]
The present inventors keenly investigated the development of a lubricating oil composition for compressor oils having excellent performance, and as a result, 5 discovered that the aforementioned problem can be solved with a lubricating oil composition which contains, with a specific lubricant base oil, an ethylene-α-olefin (co)polymer prepared by means of a specific catalyst, and satisfies specific conditions, thus arriving at the perfection of the present 10 invention. The present invention specifically mentions the below aspect. [0010]
[1]
A lubricating oil composition for compressor oils, 15 comprising
10 to 99% by mass of a lubricant base oil (A) having the properties of the below (A1) to (A3), and
90 to 1% by mass of a liquid random copolymer (B) of ethylene and α-olefin, the liquid random copolymer (B) being 20 prepared by the below method (α) (where the total amount of the lubricant base oil (A) and the copolymer (B) is 100% by mass), the lubricating oil composition for compressor oils having the property of the below (C1). (A1) The lubricant base oil (A) has a kinematic viscosity at

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100°C of 1 to 14 mm2/s.
(A2) The lubricant base oil (A) has a viscosity index of 100 or more.
(A3) The lubricant base oil (A) has a pour point of 0°C or 5 lower.
(C1) The lubricating oil composition for compressor oils has a kinematic viscosity at 40°C of 10 to 300 mm2/s. (Method (α))
A method (α) for preparing a liquid random copolymer of 10 ethylene and α-olefin, comprising a step of carrying out
solution polymerization of ethylene and α-olefin having 3 to 20 carbon atoms, under a catalyst system comprising (a) a bridged metallocene compound represented by the following Formula 1, and 15 (b) at least one compound selected from a group consisting of (i) an organoaluminum oxy-compound, and (ii) a compound which reacts with the bridged metallocene compound to form an ion pair. [0011]

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(Formula 1)
[In Formula 1, R1, R2, R3, R4, R5, R8, R9 and R12 are respectively and independently hydrogen atom, hydrocarbon group or silicon-containing hydrocarbon group, and adjoining 5 groups are optionally connected to each other to form a ring structure,
R6 and R11, being the same, are hydrogen atom, hydrocarbon group or silicon-containing hydrocarbon group,
R7 and R10, being the same, are hydrogen atom, 10 hydrocarbon group or silicon-containing hydrocarbon group,
R6 and R7 are optionally connected to hydrocarbon having 2 to 3 carbon atoms to form a ring structure,
R11 and R10 are optionally connected to hydrocarbon having 2 to 3 carbon atoms to form a ring structure,

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R6, R7, R10 and R11 are not hydrogen atom at the same time;
Y is a carbon atom or silicon atom;
R13 and R14 are independently aryl group;
5 M is Ti, Zr or Hf;
Q is independently halogen, hydrocarbon group, an anionic ligand or a neutral ligand which can be coordinated to a lone pair of electrons; and
j is an integer of 1 to 4.] 10 [2]
The lubricating oil composition for compressors of the aforementioned [1], wherein in the metallocene compound represented by the above Formula 1, at least one among substituents (R1, R2, R3 and R4) bonded to a cyclopentadienyl 15 group is a hydrocarbon group having 4 or more carbon atoms. [0012] [3]
The lubricating oil composition for compressors of the aforementioned [1] or [2], wherein R6 and R11, being the same, 20 are hydrocarbon groups having 1 to 20 carbon atoms. [0013] [4]
The lubricating oil composition for compressors of any of the aforementioned [1] to [3], wherein in the metallocene

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compound represented by the above Formula 1, substituent (R2
or R3) bonded to the 3-position of the cyclopentadienyl group
is a hydrocarbon group.
[0014] 5 [5]
The Lubricating oil composition for compressors of the
aforementioned [4], wherein in the metallocene compound
represented by the above Formula 1, the hydrocarbon group (R2
or R3) bonded to the 3-position of the cyclopentadienyl group 10 is an n-butyl group.
[0015]
[6]
The lubricating oil composition for compressors of any
of the aforementioned [1] to [5], wherein in the metallocene 15 compound represented by the above Formula 1, substituents (R6
and R11) bonded to the 2-position and 7-position of the
fluorenyl group are all tert-butyl groups.
[0016]
[7]
20 The lubricating oil composition for compressors of any
of the aforementioned [1] to [6], wherein the compound which
reacts with the bridged metallocene compound to form an ion
pair is a compound represented by the following Formula 6.
[0017]

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pe R B—R
R ., ■■■ (Formula 6)
[In Formula 6, Re+ is H+, a carbenium cation, an oxonium
cation, an ammonium cation, a phosphonium cation, a
cycloheptyltrienyl cation, or a ferrocenium cation having a 5 transition metal, and Rf to Ri each is independently a
hydrocarbon group having 1 to 20 carbon atoms.]
[8]
The lubricating oil composition for compressors of the
aforementioned [7], wherein the ammonium cation is a 10 dimethylanilinium cation.
[0018]
[9]
The lubricating oil composition for compressors of the
aforementioned [7] or [8], wherein the catalyst system 15 further comprises an organoaluminum compound selected from a
group consisting of trimethyl aluminum and triisobutyl
aluminum.
[0019]
[10] 20 The lubricating oil composition for compressor oils of
any of the aforementioned [1] to [9], wherein the content of

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the liquid random copolymer (B) is 1 to 20% by mass. [0020]
[11]
A lubricating oil composition for compressor oils, 5 comprising
10 to 99% by mass of a lubricant base oil (A) having
the properties of the below (A1) to (A3), and
90 to 1% by mass of a liquid random copolymer of
ethylene and α-olefin, the liquid random copolymer having the 10 properties of the below (B1) to (B5) (where the total amount
of the lubricant base oil (A) and the copolymer is 100% by
mass), the lubricating oil composition for compressor oils
having the property of the below (C1).
(A1) The lubricant base oil (A) has a kinematic viscosity at 15 100°C of 1 to 14 mm2/s.
(A2) The lubricant base oil (A) has a viscosity index of 100
or more.
(A3) The lubricant base oil (A) has a pour point of 0°C or
lower. 20 (B1) The liquid random copolymer comprises 40 to 60 mol% of
ethylene units and 60 to 40 mol% of α-olefin units having 3
to 20 carbon atoms.
(B2) The liquid random copolymer has a number average
molecular weight (Mn) of 500 to 10,000 and a molecular weight

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distribution (Mw/Mn, Mw is the weight average molecular
weight) of 3 or less, as measured by Gel Permeation
Chromatography (GPC).
(B3) The liquid random copolymer has a kinematic viscosity at 5 100°C of 30 to 5,000 mm2/s.
(B4) The liquid random copolymer has a pour point of 30 to -
45°C.
(B5) The liquid random copolymer has a Bromine Number of 0.1
g / 100 g or less. 10 (C1) The lubricating oil composition for compressor oils has
a kinematic viscosity at 40°C of 10 to 300 mm2/s.
[12]
A lubricating oil composition for compressor oils
according to any of the aforementioned [1] to [11], wherein 15 the lubricant base oil (A) further satisfies the below (A4)
to (A6).
(A4) The lubricant base oil (A) has a kinematic viscosity at
100°C of 1 to 10 mm2/s.
(A5) The lubricant base oil (A) has a viscosity index of 110 20 or more.
(A6) The lubricant base oil (A) has a pour point of -10°C or
lower.
[13]
The lubricating oil composition for compressor oils

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according to any of the aforementioned [1] to [12], wherein 30 to 100% by mass of the lubricant base oil (A) is mineral oil. [0021] 5 [14]
The lubricating oil composition for compressor oils according to any of the aforementioned [1] to [12], wherein 30 to 100% by mass of the lubricant base oil (A) is a synthetic oil, poly α olefin (PAO) and/or an ester oil. 10 [0022] [15]
The lubricating oil composition for compressor oils according to any of the aforementioned [1] to [14], having a kinematic viscosity at 40°C of 20 to 100 mm2/s. 15 [0023] [16]
A rotary-type compressor oil, consisting of the lubricating oil composition for compressor oils according to any of the aforementioned [1] to [15]. 20 [0024] [17]
An oil-flooded screw compressor oil, consisting of the lubricating oil composition for compressor oils according to any of the aforementioned [1] to [15].

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[0025]
[18]
A method for producing a lubricating oil composition
for compressor oils, comprising the steps of:
5 preparing a liquid random copolymer (B) of ethylene and
α-olefin by the following method (α); and
preparing a lubricating oil composition for compressor
oils by mixing a lubricant base oil (A) in an amount of 10 to
99% by mass of the lubricating oil composition, the lubricant 10 base oil (A) having the properties of the below (A1) to (A3),
and the liquid random copolymer (B) in an amount of 90 to 1%
by mass of the lubricating oil composition (where the total
amount of the lubricant base oil (A) and the copolymer (B) is
100% by mass), the lubricating oil composition for compressor 15 oils having the property of the below (C1).
(A1) The lubricant base oil (A) has a kinematic viscosity at
100°C of 1 to 14 mm2/s.
(A2) The lubricant base oil (A) has a viscosity index of 100
or more. 20 (A3) The lubricant base oil (A) has a pour point of 0°C or
lower.
(C1) The lubricating oil composition for compressor oils has
a kinematic viscosity at 40°C of 10 to 300 mm2/s.
(Method (α))

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A method (α) for preparing a liquid random copolymer of ethylene and α-olefin, comprising a step of carrying out solution polymerization of ethylene and α-olefin having 3 to 20 carbon atoms, under a catalyst system comprising 5 (a) a bridged metallocene compound represented by the following Formula 1, and
(b) at least one compound selected from a group consisting of (i) an organoaluminum oxy-compound, and (ii) a compound which reacts with the bridged 10 metallocene compound to form an ion pair.
[0026]

R9 R5 ■■• (Formula 1)
[In Formula 1, R1, R2, R3, R4, R5, R8, R9 and R12 are respectively and independently hydrogen atom, hydrocarbon

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group or silicon-containing hydrocarbon group, and adjoining groups are optionally connected to each other to form a ring structure,
R6 and R11, being the same, are hydrogen atom, 5 hydrocarbon group or silicon-containing hydrocarbon group,
R7 and R10, being the same, are hydrogen atom, hydrocarbon group or silicon-containing hydrocarbon group,
R6 and R7 are optionally connected to hydrocarbon having
2 to 3 carbon atoms to form a ring structure,
10 R11 and R10 are optionally connected to hydrocarbon
having 2 to 3 carbon atoms to form a ring structure,
R6, R7, R10 and R11 are not hydrogen atom at the same time;
Y is a carbon atom or silicon atom;
15 R13 and R14 are independently aryl group;
M is Ti, Zr or Hf;
Q is independently halogen, hydrocarbon group, an
anionic ligand or a neutral ligand which can be coordinated
to a lone pair of electrons; and
20 j is an integer of 1 to 4.]
Advantageous Effects of Invention [0027]
The lubricating oil composition for compressor oils of

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the present invention has remarkably excellent temperature viscosity properties; namely has oil film retention properties at high temperatures, as well as excellent low-temperature viscosity properties, and further has excellent 5 thermal and oxidation stability. The lubricating oil
composition is preferably applicable to compressor oil, and particularly to rotary-type compressor oil or oil-flooded screw compressor oils.
10 Description of Embodiments
[0028]
The lubricating oil composition for compressor oils
according to the present invention (hereinafter, also
referred to merely as “lubricating oil composition”) will be 15 explained in detail below.
[0029]
The lubricating oil composition for compressor oils
according to the present invention comprises a lubricant base
oil (A), and a liquid random copolymer (B) of ethylene and α-20 olefin prepared by method (α) (may also be described in the
present specification as “ethylene-α-olefin copolymer (B)”),
the lubricating oil composition having a kinematic viscosity
at 40°C in a specific range.
[0030]

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< (A) Lubricant base oil >
The lubricant base oil (A) has the properties of (A1)
to (A3) below.
[0031] 5 (A1) The lubricant base oil has a kinematic viscosity at
100°C of 1 to 14 mm2/s
The value of this kinematic viscosity is that as
measured in accordance with the method described in JIS
K2283. The kinematic viscosity at 100°C of lubricant base oil 10 (A) is 1 to 14 mm2/s, preferably 1 to 10 mm2/s, and more
preferably 2 to 8 mm2/s. With a kinematic viscosity at 100°C
in this range, the lubricating oil composition of the present
invention is excellent in terms of balance between volatility
and temperature viscosity properties. 15 [0032]
(A2) The lubricant base oil has a viscosity index of 100 or
more
The value of this viscosity index is that as measured
in accordance with the method described in JIS K2283. The 20 viscosity index of lubricant base oil (A) is 100 or more,
preferably 110 or more, and further preferably 120 or more.
With a viscosity index in this range, the lubricating oil
composition of the present invention has excellent
temperature viscosity properties.

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[0033]
(A3) The lubricant base oil has a pour point of 0°C or lower
The value of this pour point is that as measured in accordance with the method described in ASTM D97. The pour 5 point of lubricant base oil (A) is 0°C or lower,
preferably -10°C or lower, more preferably -20°C or lower, and furthermore preferably -30°C or lower. With a pour point in this range, the lubricating oil composition of the present invention has excellent low-temperature viscosity properties.
10 [0034]
In the lubricant base oil used in the present invention, performance and quality such as viscosity properties, heat resistance and oxidation stability, will differ depending on the producing and refining methods etc.
15 of the lubricant base oil. In general, the lubricant base oil is classified broadly into a mineral oil and a synthetic oil. Moreover, the API (American Petroleum Institute) categorizes lubricant base oil into five types: Group I, II, III, IV and V. These API categories are defined in the API Publication
20 1509, 15th Edition, Appendix E, April 2002, which are as shown in Table 1. The lubricant base oil (A) may be either mineral oil or synthetic oil, and may be of any of the Groups I to V in the API categories. Details are described as follows. [0035]

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Table 1

Group Type Viscosity index *1 Saturated
hydrocarbon
portion *2 (vol%) Sulfur portion *3 (% by weight)
I Mineral oil 80 to 120 < 90 > 0.03
II Mineral oil 80 to 120 ≥ 90 ≤ 0.03
III Mineral oil ≥ 120 ≥ 90 ≤ 0.03
IV Poly-a-olefin
V Lubricant base material other than the aforementioned
*1: Measured in accordance with ASTM D445 (JIS K2283)
*2: Measured in accordance with ASTM D3238
*3: Measured in accordance with ASTM D4294 (JIS K2541)
5 *4: Mineral oils whose saturated hydrocarbon portion is less than 90 vol% and sulfur portion is less than 0.03% by weight, or whose saturated hydrocarbon portion is 90 vol% or more and sulfur portion exceeds 0.03% by weight, are included in Group I.
10 < Mineral oil >
The mineral oil is ascribed to Groups I to III of the aforementioned API categories. [0036]
The quality of the mineral oil is as mentioned above,
15 where the aforementioned respective qualities of mineral oil are obtainable depending on the refining method.
Exemplifications of the mineral oil specifically include: a lubricant base oil, in which a lubricating oil fraction obtained by reduced pressure distillation of an atmospheric

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residue which is obtainable by the atmospheric distillation of crude oil, is refined by one or more treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, hydrorefining; or a lubricant base oil of 5 wax isomerized mineral oil. [0037]
Moreover, a Gas-to-Liquid (GTL) base oil obtained by the Fisher-Tropsch method is a base oil which can also be suitably utilized as Group III mineral oil. Such GTL base oil
10 is also handled as Group III+ lubricant base oil, which are described e.g. in the following Patent Literatures: EP0776959, EP0668342, WO97/21788, WO00/15736, WO00/14188, WO00/14187, WO00/14183, WO00/14179, WO00/08115, WO99/41332, EP1029029, WO01/18156 and WO01/57166.
15 [0038]
< Synthetic oil >
The synthetic oil is ascribed to Group IV or Group V of the aforementioned API categories. [0039]
20 Poly-α-olefins, which are ascribed to Group IV, can be obtained by oligomerizing higher α-olefins with an acid catalyst such as a boron trifluoride catalyst or a chromic acid catalyst, as described in US Patent No. 3,382,291, US Patent No. 3,763,244, US Patent No. 5,171,908, US Patent No.

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3,780,128, US Patent No. 4,032,591, JP H01-163136 A, US Patent No. 4,967,032, and US Patent No. 4,926,004. Poly-α-olefins can also be obtained by processes using a catalyst system containing a complex of a transition metal such as 5 zirconium, titanium or hafnium, which includes a metallocene compound as described in patent literatures, JP S63-37102 A, JP 2005-200447 A, JP 2005-200448 A, JP 2009-503147 A and JP 2009-501836 A. Of these, a low molecular weight oligomer of at least one olefin selected from an olefin having 6 or more
10 carbon atoms can be utilized as the poly-α-olefin. If
utilizing a poly-α-olefin as the lubricant base oil (A), a lubricating oil composition having remarkably excellent temperature viscosity properties, low-temperature viscosity properties, as well as excellent heat resistance is
15 obtainable. [0040]
Poly-α-olefins are also industrially available, where those with a 100°C kinematic viscosity of 2 mm2/s to 150 mm2/s are commercially available. Among these, the use of a poly α-
20 olefin of 2 to 14 mm2/s is preferable from the perspective of obtaining a lubricating oil composition with excellent temperature viscosity properties. Examples include the NEXBASE 2000 series (made by NESTE), Spectrasyn (made by

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ExxonMobil Chemical), Durasyn (made by Ineos Oligomers), and
Synfluid (made by Chevron Phillips Chemical).
[0041]
As the synthetic oil ascribed to Group V, examples 5 include alkyl benzenes, alkyl naphthalenes, isobutene
oligomers and hydrides thereof, paraffins, polyoxy alkylene glycol, dialkyl diphenylether, polyphenylether, and esters. [0042]
Most of the alkyl benzenes and alkyl naphthalenes are
10 usually dialkyl benzene or dialkyl naphthalene whose alkyl chain length has 6 to 14 carbon atoms, where such alkyl benzenes or alkyl naphthalenes are produced by the Friedel– Crafts alkylation reaction of benzene or naphthalene with olefin. In the production of alkyl benzenes or alkyl
15 naphthalenes, the alkylated olefin to be utilized may be a
linear or branched olefin, or may be a combination of these. These production processes are described in e.g. US Patent 3,909,432. [0043]
20 Moreover, as the ester, fatty acid esters are preferred
from the perspective of compatibility with the ethylene-α-olefin copolymer (B). [0044]
Although there are no particular limitations on the

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fatty acid esters, examples include fatty acid esters consisting of only carbon, oxygen or hydrogen as mentioned below, where the examples include monoesters prepared from a monobasic acid and alcohol; diesters prepared from dibasic 5 acid and alcohol, or from a diol with a monobasic acid or an acid mixture; or polyolesters prepared by reacting a monobasic acid or an acid mixture with a diol, triol (e.g. trimethylolpropane), tetraol (e.g. pentaerythritol), hexol (e.g. dipentaerythritol) etc. Examples of these esters
10 include ditridecyl glutarate, di-2-ethyl hexyl adipate,
diisodecyl adipate, ditridecyl adipate, di-2-ethyl hexyl sebacate, tridecyl pelargonate, di-2-ethyl hexyl adipate, di-2-ethyl hexyl azelate, trimethylolpropane caprylate, trimethylolpropane pelargonate, trimethylolpropane
15 triheptanoate, pentaerythritol-2-ethyl hexanoate, pentaerythritol pelargonate, and pentaerythritol tetraheptanoate. [0045]
From the perspective of the compatibility with the
20 ethylene-α-olefin copolymer (B), an alcohol having two or
more functional hydroxyl groups is preferred as the alcohol moiety constituting the ester, and a fatty acid having 8 or more carbon atoms is preferred as the fatty acid moiety. However, a fatty acid having 20 or fewer carbon atoms, which

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is easily industrially available, is superior in terms of the manufacturing cost of the fatty acid. The effect of the present invention is also sufficiently exhibited with the use of one fatty acid constituting an ester, or with the use of a 5 fatty acid ester prepared by means of two or more acid
mixtures. Examples of fatty acid esters more specifically include a mixed triester of trimethylolpropane with lauric acid and stearic acid, and diisodecyl adipate, where these are preferable in terms of compatibility of saturated
10 hydrocarbon components such as the ethylene-α-olefin
copolymer (B), with stabilizers such as antioxidants, corrosion preventing agents, anti-wear agents, friction modifying agents, pour point lowering agents, anti-rust agents and anti-foamers mentioned below and having a polar
15 group. [0046]
When utilizing a synthetic oil, particularly a poly-α-olefin as the lubricant base oil (A), it is preferable that the lubricating oil composition of the present invention
20 contain a fatty acid ester in an amount of 5 to 20% by mass with respect to 100% by mass of the entire weight of the lubricating oil composition. By containing a fatty acid ester of 5% by mass or more, good compatibility is obtainable with lubricating oil sealing material such as resins and

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elastomers inside the internal combustion engines and industrial machinery of all types. Specifically, swelling of the lubricating oil sealing material can be suppressed. From the perspective of oxidation stability or heat resistance, 5 the amount of ester is preferably 20% by mass or less. When mineral oil is contained in the lubricating oil composition, a fatty acid ester is not necessarily required, because the mineral oil per se has a swelling suppression effect of the lubricating oil sealing agent.
10 [0047]
Synthetic oil is preferred in terms of superior heat resistance and temperature viscosity properties compared to mineral oil. In the lubricating oil composition of the present invention, a synthetic oil or mineral oil may be used
15 alone as the lubricant base oil (A), or any mixture etc. of two or more lubricating oils selected from the synthetic oil and mineral oil may be used as the lubricant base oil (A). [0048] < (B) Ethylene-α-olefin copolymer >
20 The ethylene-α-olefin copolymer (B) is a liquid random copolymer (B) of ethylene and α-olefin prepared by the following method (α). (Method (α))
A method (α) for preparing a liquid random copolymer of

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ethylene and α-olefin, comprising a step of carrying out solution polymerization of ethylene and α-olefin having 3 to 20 carbon atoms, under a catalyst system containing
(a) a bridged metallocene compound represented by the 5 following Formula 1, and
(b) at least one compound selected from a group consisting of
(i) an organoaluminum oxy-compound, and (ii) a compound which reacts with the bridged metallocene compound to form an ion pair.
10 [0049]

R9 R5 ■■• (Formula 1)
[In Formula 1, R1, R2, R3, R4, R5, R8, R9 and R12 are respectively and independently hydrogen atom, hydrocarbon group or silicon-containing hydrocarbon group, and adjoining

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groups are optionally connected to each other to form a ring structure,
R6 and R11, being the same, are hydrogen atom,
hydrocarbon group or silicon-containing hydrocarbon group,
5 R7 and R10, being the same, are hydrogen atom,
hydrocarbon group or silicon-containing hydrocarbon group,
R6 and R7 are optionally connected to hydrocarbon having 2 to 3 carbon atoms to form a ring structure,
R11 and R10 are optionally connected to hydrocarbon 10 having 2 to 3 carbon atoms to form a ring structure,
R6, R7, R10 and R11 are not hydrogen atom at the same time;
Y is a carbon atom or silicon atom;
R13 and R14 are independently aryl group;
15 M is Ti, Zr or Hf;
Q is independently halogen, hydrocarbon group, an anionic ligand or a neutral ligand which can be coordinated to a lone pair of electrons; and
j is an integer of 1 to 4.]
20 Here, the hydrocarbon group has 1 to 20 carbon atoms,
preferably 1 to 15 atoms, and more preferably 4 to 10 carbon atoms, and means for example an alkyl group, aryl group etc. The aryl group has 6 to 20 carbon atoms, and preferably 6 to 15 carbon atoms.

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[0050]
Examples of the silicon-containing hydrocarbon group include an alkyl or aryl group having 3 to 20 carbon atoms which contains 1 to 4 silicon atoms, and in more detail 5 includes trimethylsilyl group, tert-butyldimethylsilyl group, triphenylsilyl group etc. [0051]
In the bridged metallocene compound represented by Formula 1, cyclopentadienyl group may be substituted or 10 unsubstituted. [0052]
In the bridged metallocene compound represented by Formula 1,
(i) it is preferable that at least one among 15 substituents (R1, R2, R3 and R4) bonded to cyclopentadienyl group is a hydrocarbon group,
(ii) it is more preferable that at least one among
substituents (R1, R2, R3 and R4) is a hydrocarbon group having
4 or more carbon atoms,
20 (iii) it is most preferable that substituent (R2 or R3)
bonded to the 3-position of the cyclopentadienyl group is a hydrocarbon group having 4 or more carbon atoms (for example an n-butyl group). [0053]

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In case where at least two among R1, R2, R3 and R4 are substituents (that is, being not hydrogen atom), the above-mentioned substituents may be the same or be different, and it is preferable that at least one substituent is a 5 hydrocarbon group having 4 or more carbon atoms. [0054]
In the metallocene compound represented by Formula 1, R6 and R11 bonded to fluorenyl group are the same, R7 and R10 are the same, but R6, R7, R10 and R11 are not hydrogen atom at 10 the same time. In high-temperature solution polymerization of poly-α-olefin, in order to improve the polymerization activity, preferably neither R6 nor R11 is hydrogen atom, and more preferably none of R6, R7, R10 and R11 is hydrogen atom. For example, R6 and R11 bonded to the 2-position and 7-15 position of the fluorenyl group are the same hydrocarbon
group having 1 to 20 carbon atoms, and preferably all tert-butyl groups, and R7 and R10 are the same hydrocarbon group having 1 to 20 carbon atoms, and preferably all tert-butyl groups. 20 [0055]
The main chain part (bonding part, Y) connecting the cyclopentadienyl group and the fluorenyl group is a cross-linking section of two covalent bonds comprising one carbon atom or silicon atom, as a structural bridge section

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imparting steric rigidity to the bridged metallocene compound represented by Formula 1. Cross-linking atom (Y) in the cross-linking section has two aryl groups (R13 and R14) which may be the same or different. Therefore, the cyclopentadienyl 5 group and the fluorenyl group are bonded by the covalent bond cross-linking section containing an aryl group. Examples of the aryl group include a phenyl group, naphthyl group, anthracenyl group, and a substituted aryl group (which is formed by substituting one or more aromatic hydrogen (sp2-10 type hydrogen) of a phenyl group, naphthyl group or anthracenyl group, with substituents). Examples of substituents in the aryl group include a hydrocarbon group having 1 to 20 carbon atoms, a silicon-containing hydrocarbon group having 1 to 20 carbon atoms, a halogen atom etc., and 15 preferably include a phenyl group. In the bridged metallocene compound represented by Formula 1, preferably R13 and R14 are the same in view of easy production. [0056]
In the bridged metallocene compound represented by 20 Formula 1, Q is preferably a halogen atom or hydrocarbon
group having 1 to 10 carbon atoms. The halogen atom includes fluorine, chlorine, bromine or iodine. The hydrocarbon group having 1 to 10 carbon atoms includes methyl, ethyl, n-propyl, isopropyl, 2-methylpropyl, 1,1-dimethylpropyl, 2,2-

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dimethylpropyl, 1,1-diethylpropyl, 1-ethyl-1-methylpropyl, 1,1,2,2-tetramethylpropyl, sec-butyl, tert-butyl, 1,1-dimethylbutyl, 1,1,3-trimethylbutyl, neopentyl, cyclohexyl methyl, cyclohexyl, 1-methyl-1-cyclohexyl etc. Further, when 5 j is an integer of 2 or more, Q may be the same or different. [0057]
Examples of such bridged metallocene compounds (a) include:
ethylene [η5-(3-tert-butyl-5-methyl cyclopentadienyl)]
10 (η5-fluorenyl) zirconium dichloride, ethylene [η5-(3-tert-butyl-5-methyl cyclopentadienyl)] [η5-(3,6-di-tert-butyl fluorenyl)] zirconium dichloride, ethylene [η5-(3-tert-butyl-5-methyl cyclopentadienyl)] [η5-(2,7-di-tert-butyl fluorenyl)] zirconium dichloride, ethylene [η5-(3-tert-butyl-
15 5-methyl cyclopentadienyl)] (octamethyl
octahydrodibenzofluorenyl) zirconium dichloride, ethylene [η5-(3-tert-butyl-5-methyl cyclopentadienyl)] (benzofluorenyl) zirconium dichloride, ethylene [η5-(3-tert-butyl-5-methyl cyclopentadienyl)] (dibenzofluorenyl)
20 zirconium dichloride, ethylene [η5-(3-tert-butyl-5-methyl cyclopentadienyl)] (octahydrodibenzofluorenyl) zirconium dichloride, ethylene [η5-(3-tert-butyl-5-methyl cyclopentadienyl)] [η5-(2,7-diphenyl-3,6-di-tert-butyl fluorenyl)] zirconium dichloride, ethylene [η5-(3-tert-butyl-

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5-methyl cyclopentadienyl)] [η5- (2,7-dimethyl-3,6-di-tert-butyl fluorenyl)] zirconium dichloride;
ethylene [η5-(3-tert-butyl cyclopentadienyl)] (η5-fluorenyl) zirconium dichloride, ethylene [η5-(3-tert-butyl 5 cyclopentadienyl)] [η5-(3,6-di-tert-butyl fluorenyl)] zirconium dichloride, ethylene [η5-(3-tert-butyl cyclopentadienyl)] [η5-(2,7-di-tert-butyl fluorenyl)] zirconium dichloride, ethylene [η5-(3-tert-butyl cyclopentadienyl)] (octamethyl octahydrodibenzofluorenyl)
10 zirconium dichloride, ethylene [η5-(3-tert-butyl
cyclopentadienyl)] (benzofluorenyl) zirconium dichloride, ethylene [η5-(3-tert-butyl cyclopentadienyl)] (dibenzofluorenyl) zirconium dichloride, ethylene [η5-(3-tert-butyl cyclopentadienyl)] (octahydrodibenzofluorenyl)
15 zirconium dichloride, ethylene [η5-(3-tert-butyl
cyclopentadienyl)] [η5-(2,7-diphenyl-3,6-di-tert-butyl fluorenyl)] zirconium dichloride, ethylene [η5-(3-tert-butyl cyclopentadienyl)] [η5-(2,7-dimethyl-3,6-di-tert-butyl fluorenyl)] zirconium dichloride;
20 ethylene [η5-(3-n-butyl cyclopentadienyl)] (η5-
fluorenyl) zirconium dichloride, ethylene [η5-(3-n-butyl cyclopentadienyl)] [η5-(3,6-di-tert-butyl fluorenyl)] zirconium dichloride, ethylene [η5-(3-n-butyl cyclopentadienyl)] [η5-(2,7-di-tert-butyl fluorenyl)]

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zirconium dichloride, ethylene [η5-(3-n-butyl cyclopentadienyl)] (octamethyl octahydrodibenzofluorenyl) zirconium dichloride, ethylene [η5-(3-n-butyl cyclopentadienyl)] (benzofluorenyl) zirconium dichloride, 5 ethylene [η5-(3-n-butyl cyclopentadienyl)] (dibenzofluorenyl) zirconium dichloride, ethylene [η5-(3-n-butyl cyclopentadienyl)] (octahydrodibenzofluorenyl) zirconium dichloride, ethylene [η5-(3-n-butyl cyclopentadienyl)] [η5-(2,7-diphenyl-3,6-di-tert-butyl fluorenyl)] zirconium
10 dichloride, ethylene [η5-(3-n-butyl cyclopentadienyl)] [η5-(2,7-dimethyl-3,6-di-tert-butyl fluorenyl)] zirconium dichloride;
diphenylmethylene [η5-(3-tert-butyl-5-methyl cyclopentadienyl)] (η5-fluorenyl) zirconium dichloride,
15 diphenylmethylene [η5-(3-tert-butyl-5-methyl
cyclopentadienyl)] [η5-(3,6-di-tert-butyl fluorenyl)] zirconium dichloride, diphenylmethylene [η5-(3-tert-butyl-5-methyl cyclopentadienyl)] [η5-(2,7-di-tert-butyl fluorenyl)] zirconium dichloride, diphenylmethylene [η5-(3-tert-butyl-5-
20 methyl cyclopentadienyl)] (octamethyl
octahydrodibenzofluorenyl) zirconium dichloride, diphenylmethylene [η5-(3-tert-butyl-5-methyl cyclopentadienyl)] (benzofluorenyl) zirconium dichloride, diphenylmethylene [η5-(3-tert-butyl-5-methyl

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cyclopentadienyl)] (dibenzofluorenyl) zirconium dichloride, diphenylmethylene [η5-(3-tert-butyl-5-methyl cyclopentadienyl)] (octahydrodibenzofluorenyl) zirconium dichloride, diphenylmethylene [η5-(3-tert-butyl-5-methyl 5 cyclopentadienyl)] [η5-(2,7-diphenyl-3,6-di-tert-butyl
fluorenyl)] zirconium dichloride, diphenylmethylene [η5-(3-tert-butyl-5-methyl cyclopentadienyl)] [η5-(2,7-dimethyl-3,6-di-tert-butyl fluorenyl)] zirconium dichloride;
diphenylmethylene [η5-(3-tert-butyl cyclopentadienyl)]
10 (η5-fluorenyl) zirconium dichloride, diphenylmethylene [η5-(3-tert-butyl cyclopentadienyl)] [η5-(3,6-di-tert-butyl fluorenyl)] zirconium dichloride, diphenylmethylene [η5-(3-tert-butyl cyclopentadienyl)] [η5-(2,7-di-tert-butyl fluorenyl)] zirconium dichloride, diphenylmethylene [η5-(3-
15 tert-butyl cyclopentadienyl)] (octamethyl
octahydrodibenzofluorenyl) zirconium dichloride, diphenylmethylene [η5-(3-tert-butyl cyclopentadienyl)] (benzofluorenyl) zirconium dichloride, diphenylmethylene [η5-(3-tert-butyl cyclopentadienyl)] (dibenzofluorenyl) zirconium
20 dichloride, diphenylmethylene [η5-(3-tert-butyl
cyclopentadienyl)] (octahydrodibenzofluorenyl) zirconium dichloride, diphenylmethylene [η5-(3-tert-butyl cyclopentadienyl)] [η5-(2,7-diphenyl-3,6-di-tert-butyl fluorenyl)] zirconium dichloride, diphenylmethylene [η5-(3-

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tert-butyl cyclopentadienyl)] [η5- (2,7-dimethyl-3,6-di-tert-butyl fluorenyl)] zirconium dichloride;
diphenylmethylene [η5-(3-n-butyl cyclopentadienyl)] (η5-fluorenyl) zirconium dichloride, diphenylmethylene [η5-(3-n-5 butyl cyclopentadienyl)] [η5-(3,6-di-tert-butyl fluorenyl)] zirconium dichloride, diphenylmethylene [η5-(3-n-butyl cyclopentadienyl)] [η5-(2,7-di-tert-butyl fluorenyl)] zirconium dichloride, diphenylmethylene [η5-(3-n-butyl cyclopentadienyl)] (octamethyl octahydrodibenzofluorenyl)
10 zirconium dichloride, diphenylmethylene [η5-(3-n-butyl
cyclopentadienyl)] (benzofluorenyl) zirconium dichloride, diphenylmethylene [η5-(3-n-butyl cyclopentadienyl)] (dibenzofluorenyl) zirconium dichloride, diphenylmethylene [η5-(3-n-butyl cyclopentadienyl)] (octahydrodibenzofluorenyl)
15 zirconium dichloride, diphenylmethylene [η5-(3-n-butyl cyclopentadienyl)] [η5-(2,7-diphenyl-3,6-di-tert-butyl fluorenyl)] zirconium dichloride, diphenylmethylene [η5-(3-n-butyl cyclopentadienyl)] [η5-(2,7-dimethyl-3,6-di-tert-butyl fluorenyl)] zirconium dichloride;
20 di(p-tolyl) methylene [η5-(3-tert-butyl-5-methyl
cyclopentadienyl)] (η5-fluorenyl) zirconium dichloride, di(p-tolyl) methylene [η5-(3-tert-butyl-5-methyl cyclopentadienyl)] [η5-(3,6-di-tert-butyl fluorenyl)] zirconium dichloride, di(p-tolyl) methylene [η5-(3-tert-

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butyl-5-methyl cyclopentadienyl)] [η5- (2,7-di-tert-butyl fluorenyl)] zirconium dichloride, di(p-tolyl) methylene [η5-(3-tert-butyl-5-methyl cyclopentadienyl)] (octamethyl octahydrodibenzofluorenyl) zirconium dichloride, di(p-tolyl) 5 methylene [η5-(3-tert-butyl-5-methyl cyclopentadienyl)]
(benzofluorenyl) zirconium dichloride, di(p-tolyl) methylene [η5-(3-tert-butyl-5-methyl cyclopentadienyl)] (dibenzofluorenyl) zirconium dichloride, di(p-tolyl) methylene [η5-(3-tert-butyl-5-methyl cyclopentadienyl)]
10 (octahydrodibenzofluorenyl) zirconium dichloride, di(p-tolyl) methylene [η5-(3-tert-butyl-5-methyl cyclopentadienyl)] [η5-(2,7-diphenyl-3,6-di-tert-butyl fluorenyl)] zirconium dichloride, di(p-tolyl) methylene [η5-(3-tert-butyl-5-methyl cyclopentadienyl)] [η5-(2,7-dimethyl-3,6-di-tert-butyl
15 fluorenyl)] zirconium dichloride;
di(p-tolyl) methylene [η5-(3-tert-butyl cyclopentadienyl)] (η5-fluorenyl) zirconium dichloride, di(p-tolyl) methylene [η5-(3-tert-butyl cyclopentadienyl)] [η5-(3,6-di-tert-butyl fluorenyl)] zirconium dichloride, di(p-
20 tolyl) methylene [η5-(3-tert-butyl cyclopentadienyl)] [η5-(2,7-di-tert-butyl fluorenyl)] zirconium dichloride, di(p-tolyl) methylene [η5-(3-tert-butyl cyclopentadienyl)] (octamethyl octahydrodibenzofluorenyl) zirconium dichloride, di(p-tolyl) methylene [η5-(3-tert-butyl cyclopentadienyl)]

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(benzofluorenyl) zirconium dichloride, di(p-tolyl) methylene [η5-(3-tert-butyl cyclopentadienyl)] (dibenzofluorenyl) zirconium dichloride, di(p-tolyl) methylene [η5-(3-tert-butyl cyclopentadienyl)] (octahydrodibenzofluorenyl) zirconium 5 dichloride, di(p-tolyl) methylene [η5-(3-tert-butyl
cyclopentadienyl)] [η5-(2,7-diphenyl-3,6-di-tert-butyl fluorenyl)] zirconium dichloride, di(p-tolyl) methylene [η5-(3-tert-butyl cyclopentadienyl)] [η5-(2,7-dimethyl-3,6-di-tert-butyl fluorenyl)] zirconium dichloride; and
10 di(p-tolyl) methylene [η5-(3-n-butyl cyclopentadienyl)] (η5-fluorenyl) zirconium dichloride, di(p-tolyl) methylene [η5-(3-n-butyl cyclopentadienyl)] [η5-(3,6-di-tert-butyl fluorenyl)] zirconium dichloride, di(p-tolyl) methylene [η5-(3-n-butyl cyclopentadienyl)] [η5-(2,7-di-tert-butyl
15 fluorenyl)] zirconium dichloride, di(p-tolyl) methylene [η5-(3-n-butyl cyclopentadienyl)] (octamethyl
octahydrodibenzofluorenyl) zirconium dichloride, di(p-tolyl) methylene [η5-(3-n-butyl cyclopentadienyl)] (benzofluorenyl) zirconium dichloride, di(p-tolyl) methylene [η5-(3-n-butyl
20 cyclopentadienyl)] (dibenzofluorenyl) zirconium dichloride, di(p-tolyl) methylene [η5-(3-n-butyl cyclopentadienyl)] (octahydrodibenzofluorenyl) zirconium dichloride, di(p-tolyl) methylene [η5-(3-n-butyl cyclopentadienyl)] (2,7-diphenyl-3,6-di-tert-butyl fluorenyl) zirconium dichloride, di(p-

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tolyl) methylene [η5-(3-n-butyl cyclopentadienyl)] [η5-(2,7-dimethyl-3,6-di-tert-butyl fluorenyl)] zirconium dichloride. [0058]
Although compounds whose zirconium atoms were 5 substituted with hafnium atoms, or compounds whose chloro ligands were substituted with methyl groups etc. are exemplified in these compounds, the bridged metallocene compound (a) is not limited to these exemplifications. [0059]
10 As the organoaluminum oxy-compound used in the catalyst system in the present invention, conventional aluminoxane can be used. For example, linear or ring type aluminoxane represented by the following Formulas 2 to 5 can be used. A small amount of organic aluminum compound may be contained in
15 the organoaluminum oxy-compound. [0060]

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40

■Ai—04—A1R2 R

(Formula 2)

f-Al—0"}

n

(Formula 3)
■fAl—0") f-Al—O^—

Me

Rx

(Formula 4)

5

In Formulae 2 to 4, R is independently a hydrocarbon group having 1 to 10 carbon atoms, Rx is independently a hydrocarbon group having 2 to 20 carbon atoms, m and n are independently an integer of 2 or more, preferably 3 or more, more preferably 10 to 70, and most preferably 10 to 50. [0061]

Rc
RdAI—O—B—0~>

,/

R(

>d
R<

R •■• (Formula 5) In Formula 5, Rc is a hydrocarbon group having 1 to 10

10 carbon atoms, and Rd is independently a hydrogen atom,
halogen atom or hydrocarbon group having 1 to 10 carbon
atoms.

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[0062]
In Formula 2 or Formula 3, R is a methyl group (Me) of the organoaluminum oxy-compound which is conventionally referred to as "methylaluminoxane". 5 [0063]
The methylaluminoxane is easily available and has high polymerization activity, and thus it is commonly used as an activator in the polyolefin polymerization. However, the methylaluminoxane is difficult to dissolve in a saturated
10 hydrocarbon, and thus it has been used as a solution of
aromatic hydrocarbon such as toluene or benzene, which is environmentally undesirable. Therefore, in recent years, a flexible body of methylaluminoxane represented by Formula 4 has been developed and used as an aluminoxane dissolved in
15 the saturated hydrocarbon. The modified methylaluminoxane represented by Formula 4 is prepared by using a trimethyl aluminum and an alkyl aluminum other than the trimethyl aluminum as shown in US Patent 4960878 and US Patent 5041584, and for example, is prepared by using trimethyl aluminum and
20 triisobutyl aluminum. The aluminoxane in which Rx is an
isobutyl group is commercially available under the trade name of MMAO and TMAO, in the form of a saturated hydrocarbon solution. (See Tosoh Finechem Corporation, Tosoh Research & Technology Review, Vol 47, 55 (2003)).

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[0064]
As (ii) the compound which reacts with the bridged metallocene compound to form an ion pair (hereinafter, referred to as "ionic compound" as required) which is 5 contained in the present catalyst system, a Lewis acid, ionic compounds, borane, borane compounds and carborane compounds can be used. These are described in patent literatures, Korean Patent No. 10-551147 A, JP H01-501950 A, JP H03-179005 A, JP H03-179006 A, JP H03-207703 A, JP H03-207704 A, US
10 Patent 5321106 and so on. If needed, heteropoly compounds,
and isopoly compound etc. can be used, and the ionic compound disclosed in JP 2004-51676 A can be used. The ionic compound may be used alone or by mixing two or more. In more detail, examples of the Lewis acid include the compound represented
15 by BR3 (R is fluoride, substituted or unsubstituted alkyl group having 1 to 20 carbon atoms (methyl group, etc.), substituted or unsubstituted aryl group having 6 to 20 carbon atoms (phenyl group, etc.), and also includes for example, trifluoro boron, triphenyl boron, tris(4-fluorophenyl) boron,
20 tris(3,5-difluorophenyl) boron, tris(4-fluorophenyl) boron, tris(pentafluorophenyl) and boron tris(p-tolyl) boron. When the ionic compound is used, its use amount and sludge amount produced are relatively small in comparison with the organoaluminum oxy-compound, and thus it is economically

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advantageous. In the present invention, it is preferable that the compound represented by the following Formula 6 is used as the ionic compound. [0065]
Rg
+e Rf—B—Rh
R ■■■ (Formula 6) 5
In Formula 6, Re+ is H+, a carbenium cation, an oxonium cation, an ammonium cation, a phosphonium cation, a cycloheptyltrienyl cation, or a ferrocenium cation having a transition metal, and Rf to Ri each is independently an
10 organic group, preferably a hydrocarbon group having 1 to 20 carbon atoms, and more preferably an aryl group, for example, a penta-fluorophenyl group. Examples of the carbenium cation include a tris(methylphenyl)carbenium cation and a tris(dimethylphenyl)carbenium cation, and examples of the
15 ammonium cation include a dimethylanilinium cation. [0066]
Examples of compounds represented by the aforementioned Formula 6 preferably include N,N-dialkyl anilinium salts, and specifically include N,N-dimethylanilinium tetraphenylborate,
20 N,N-dimethylanilinium tetrakis (pentafluorophenyl) borate,
N,N-dimethylanilinium tetrakis (3,5-ditrifluoro methylphenyl)

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borate, N,N-diethyl anilinium tetraphenylborate, N,N-diethyl anilinium tetrakis (pentafluorophenyl) borate, N,N-diethyl anilinium tetrakis (3,5-ditrifluoro methylphenyl) borate, N,N-2,4,6-penta methylanilinium tetraphenylborate, and N,N-5 2,4,6-penta methylanilinium tetrakis (pentafluorophenyl) borate. [0067]
The catalyst system used in the present invention further includes (c) an organoaluminum compound when it is
10 needed. The organoaluminum compound plays a role of activating the bridged metallocene compound, the organoaluminum oxy-compound, and the ionic compound, etc. As the organoaluminum compound, preferably an organoaluminum represented by the following Formula 7, and alkyl complex
15 compounds of the Group 1 metal and aluminum represented by the following Formula 8 can be used. [0068]
RamAl(ORb)nHpXq … Formula 7 In Formula 7, Ra and Rb each is independently a
20 hydrocarbon group having 1 to 15 carbon atoms, preferably 1 to 4 carbon atoms, and X is a halogen atom, m is an integer of 0
The lubricating oil composition for compressor oils
10 according to the present invention contains the lubricant
base oil (A) and the ethylene-α-olefin copolymer (B), where the lubricating oil composition for compressor oils has the property of the below (C1). [0081]
15 (C1) The lubricating oil composition for compressor oils has a kinematic viscosity at 40°C of 10 to 300 mm2/s
The kinematic viscosity at 40°C (i.e. the kinematic viscosity as measured in accordance with the method described in JIS K2283) is 10 to 300 mm2/s, preferably 20 to 250 mm2/s,
20 more preferably 20 to 200 mm2/s, and furthermore preferably 20 to 100 mm2/s. If the kinematic viscosity at 40°C of the lubricating oil composition for compressor oils is much more than 300 mm2/s, the agitation torque rises when stirring the lubricating oil composition, and hence the energy

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conservation performance of the compressor worsens. However, if the kinematic viscosity at 40°C is much lower than 10 mm2/s, the oil film retention of the lubricating oil composition cannot be maintained, and hence sufficient 5 lubricity is not obtainable. [0082]
In general, the viscosity of industrial lubricating oil products is stipulated according to 40°C kinematic viscosity, and viscosity ranges are defined by JIS K2001 (in accordance
10 with ISO3448). The tolerance range is set at ±10% for each viscosity. For example, if a lubricating oil with a 40°C kinematic viscosity of 68 mm2/s is indicated as ISO VG68, the permitted range of the 40°C kinematic viscosity is 61.2 to 74.8 mm2/s. Although the optimal range differs depending on
15 the type of compressor as well as usage conditions, ISO VG32 to ISO VG220 is preferably utilized for compressor oil. When comparing performance, lubricating oil compositions of equal viscosity grades are usually compared. [0083]
20 The lubricating oil composition for compressor oils
according to the present invention preferably further has the
property (C2).
[0084]
(C2) The lubricating oil composition for compressor oils has

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a viscosity index of 120 or more
This viscosity index (i.e. as measured in accordance with the method described in JIS K2283) is preferably 120 or more, more preferably 130 or more, furthermore preferably 140 5 or more, and particularly preferably 150 or more. With a viscosity index in this range, the lubricating oil
composition has excellent temperature viscosity properties, and a balance can be found between the aforementioned energy conservation and lubricity, in a wide range of temperatures.
10 [0085]
The pour point of the lubricating oil composition for compressor oils according to the present invention (i.e. the pour point as measured by the method described in ASTM D97) is preferably -20°C or lower, preferably -30°C or lower, and
15 furthermore preferably -40°C or lower. A low pour point
indicates a lubricating oil composition with excellent low-temperature properties. [0086]
The lubricating oil composition for compressor oils of
20 the present invention contains the components in the ratio of 10 to 99% by mass of the lubricant base oil (A), and 90 to 1% by mass of the ethylene-α-olefin copolymer (B), where the total of the lubricant base oil (A) and the ethylene-α-olefin copolymer (B) is 100% by mass. The lubricating oil

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composition for compressor oils of the present invention contains the components in the ratios of: preferably 50 to 99% by mass of the lubricant base oil (A) and 50 to 1% by mass of the ethylene-α-olefin copolymer (B); more preferably 5 70 to 99% by mass of the lubricant base oil (A) and 30 to 1% by mass of the ethylene-α-olefin copolymer (B); and furthermore preferably 80 to 99% by mass of the lubricant base oil (A) and 20 to 1% by mass of the ethylene-α-olefin copolymer (B).
10 [0087]
A preferable aspect includes that 30 to 100% by mass of a lubricant base oil is a mineral oil. With a high ratio of the mineral oil in the lubricant base oil (A), there is excellent dissolvability of the below-mentioned additives, as
15 well as superior economy since the mineral oil is easily
obtained. It is more preferable for 50 to 100% by mass to be the mineral oil, and furthermore preferable for 80 to 100% by mass to be the mineral oil. Of the mineral oils, those of Group III in the API category are preferable because of
20 excellent temperature viscosity properties, and because a balance can be found between oil film retention at high temperatures and low torque at low temperatures. [0088]
Another preferable aspect includes that 30 to 100% by

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mass of a lubricant base oil is a synthetic oil, and the synthetic oil is a poly-α-olefin and/or an ester oil. It is more preferable that 50 to 100% by mass is a synthetic oil, and furthermore preferable that 80 to 100% by mass is a 5 synthetic oil. A high ratio of the synthetic oil in the
lubricant base oil (A) is preferable because of excellent heat resistance, temperature viscosity properties and low-temperature properties. [0089]
10 Moreover, additives such as extreme pressure agents,
detergent dispersants, viscosity index improving agents, antioxidants, corrosion preventing agents, anti-wear agents, friction modifying agents, pour point lowering agents, anti-rust agents and anti-foamers may be contained in the
15 lubricating oil composition for compressor oils of the present invention. [0090]
Below are exemplifications of additives which can be utilized in the lubricating oil composition of the present
20 invention, where these can be used alone, or used in combination of two or more. [0091]
The extreme pressure agent is the generic name for agents having a seizure preventing effect when metals are

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exposed to a high load condition, and although there are no particular limitations on the agent, sulfur-based extreme pressure agents such as sulfides, sulfoxides, sulfones, thiophosphinates, thiocarbonates, sulfurized oils and 5 sulfurized olefins; phosphoric acids such as phosphate
esters, phosphite esters, phosphate ester amine salts, and phosphite ester amines; and halogen-based compounds such as chlorinated hydrocarbons can be exemplified. Moreover, two or more types of these compounds may be used together.
10 [0092]
Until extreme pressure lubricating conditions are attained, hydrocarbon or other organic components constituting lubricating oil composition may become carbonized before reaching extreme pressure lubricating
15 conditions due to heating or shearing, and thus there is a possibility that a carbide film could be formed on a metal surface. Therefore, with the use of the extreme pressure agent alone, contact of a metal surface with the extreme pressure agent could be inhibited due to the carbide film,
20 and thus a possibility that a sufficient effect of the extreme pressure agent cannot be expected. [0093]
Although the extreme pressure agents may be added alone, because a saturated hydrocarbon such as the copolymer

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constitutes a main component in the lubricating oil composition for compressor oils in the present invention, from the perspective of dispersibility, it is preferable to add the agent to the lubricant base oil such as mineral oil 5 or synthetic hydrocarbon oil, together with the other
additives to be used, in a dissolved state beforehand. Specifically, more preferable is a method of selecting the so-called additive package to be added to the lubricating oil composition, in which the various components such as the
10 extreme pressure agent components are mixed in advance, and further dissolved in the lubricant base oil such as mineral oil or synthetic hydrocarbon oil. [0094]
Preferred additive packages include Anglamol-98A,
15 Anglamol-6043, Angramol 6085U and LUBRIZOL 1047U (made by LUBRIZOL), HITEC 1532 (made by AFTON CHEMICAL), HITEC 307 (made by AFTON CHEMICAL), HITEC 3339 (made by AFTON CHEMICAL), and Additin RC 9410 (made by RHEIN CHEMIE). [0095]
20 The extreme pressure agents may be used as required in
a range of 0 to 10% by mass, to 100% by mass of the lubricating oil composition. [0096]

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57
Exemplifications of the anti-wear agent include inorganic or organic molybdenum compounds such as molybdenum disulfide, graphite, antimony sulfide, and
polytetrafluoroethylene. The anti-wear agents may be used as 5 required in a range of 0 to 3% by mass with respect to 100% by mass of the lubricating oil composition. [0097]
Exemplifications of the friction modifying agent include amine compounds, imide compound, fatty acid esters,
10 fatty acid amides, and fatty acid metal salts having at least one alkyl group or alkenyl group having 6 to 30 carbon atoms, particularly linear alkyl groups or linear alkenyl groups having 6 to 30 carbon atoms, in a molecule. [0098]
15 Exemplifications of the amine compound include a
linear- or branched-, preferably linear-, aliphatic monoamine, or a linear- or branched-, preferably linear-, aliphatic polyamine having 6 to 30 carbon atoms, or alkylene oxide adducts of these aliphatic amines. Examples of the
20 imide compound include imide succinate with linear- or
branched- alkyl group or alkenyl group having 6 to 30 carbon atoms and/or compounds thereof modified by a carboxylic acid, boric acid, phosphoric acid, sulfuric acid etc. Exemplifications of the fatty acid ester include esters of a

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linear- or branched-, preferably linear-, fatty acid having 7 to 31 carbon atoms with an aliphatic monohydric alcohol or aliphatic polyhydric alcohol. Exemplifications of the fatty acid amide include amides of a linear- or branched-, 5 preferably linear-, fatty acid having 7 to 31 carbon atoms
with an aliphatic monoamine or aliphatic polyamine. Examples of fatty acid metal salts include alkaline-earth metal salts (e.g. magnesium salts and calcium salts) and zinc salts of a linear- or branched-, preferably linear-, fatty acid having 7
10 to 31 carbon atoms. [0099]
The friction modifying agents may be used as required in a range of 0.01 to 5.0% by mass with respect to 100% by mass of the lubricating oil composition.
15 [0100]
Exemplifications of the detergent dispersants include metal sulfonates, metal phenates, metal phosphonates, and imide succinate. The detergent dispersants may be used as required in a range of 0 to 15% by mass with respect to 100%
20 by mass of the lubricating oil composition. [0101]
In addition to ethylene-α-olefin copolymers (excluding the ethylene-α-olefin copolymer (B), known viscosity index improving agents such as olefin copolymers whose molecular

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weights exceed 50,000, methacrylate-based copolymers, liquid polybutene, and poly-α-olefins with a 100°C kinematic viscosity of 15 mm2/s or more can be used together as the viscosity index improving agent. The viscosity index 5 improving agents may be used as required in a range of 0 to 50% by mass with respect to 100% by mass of the lubricating oil composition. [0102]
Examples of the antioxidant include phenol-based or
10 amine-based compounds such as 2,6-di-t-butyl-4-methylphenol. The antioxidants may be used as required in a range of 0 to 3% by mass with respect to 100% by mass of the lubricating oil composition. [0103]
15 Examples of the corrosion preventing agent include
compounds such as benzotriazole, benzoimidazole, and thiadiazole. The corrosion preventing agent may be used as required in a range of 0 to 3% by mass with respect to 100% by mass of the lubricating oil composition.
20 [0104]
Examples of the anti-rust agent include compounds such as amine compounds, carboxylic acid metal salts, polyhydric alcohol esters, phosphorus compounds, and sulfonates. The anti-rust agent may be used as required in a range of 0 to 3%

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by mass with respect to 100% by mass of the lubricating oil
composition.
[0105]
Exemplifications of the anti-foamer include silicone-5 based compounds such as dimethyl siloxane and silica gel
dispersions, and alcohol- or ester-based compounds. The anti-foamer may be used as required in a range of 0 to 0.2% by mass with respect to 100% by mass of the lubricating oil composition.
10 [0106]
A variety of known pour point lowering agents may be used as the pour point lowering agent. Specifically, high molecular compounds containing an organic acid ester group may be used, and in particular, vinyl polymers containing an
15 organic acid ester group are suitably used. Examples of the
vinyl polymers containing an organic acid ester group include (co)polymers of methacrylic acid alkyl, (co)polymers of acrylic acid alkyl, (co)polymers of fumaric acid alkyl, (co)polymers of maleic acid alkyl, and alkylated naphthalene.
20 [0107]
Such pour point lowering agents have a melting point of -13°C or lower, preferably -15°C, and furthermore preferably -17°C or lower. The melting point of the pour point lowering agent is measured by means of differential scanning

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calorimetry (DSC). Specifically, a sample of about 5 mg is packed into an aluminum pan and temperature is raised to 200°C, where the temperature is maintained at 200°C for 5 minutes. This is then cooled at 10°C/minute until reaching -5 40°C, where the temperature is maintained at -40°C for 5
minutes. The temperature is then raised at 10°C/minute during which the melting point is obtained from the heat absorption curve. [0108]
10 The pour point lowering agent has a polystyrene
conversion weight average molecular weight obtainable by gel permeation chromatography in the range of 20,000 to 400,000, preferably 30,000 to 300,000, more preferably 40,000 to 200,000.
15 [0109]
A pour point lowering agent may be used as required in a range of 0 to 2% by mass with respect to 100% by mass of the lubricating oil composition. [0110]
20 In addition to the aforementioned additives, anti-
emulsifying agents, coloring agents, oiliness agents (oiliness improving agents) and the like may also be used as required. [0111]

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< Use >
The lubricating oil composition of the present invention can be suitably utilized in the compressor oil of a variety of industrial equipment machinery, and this 5 composition has remarkably excellent temperature viscosity properties; namely, oil film retention properties at high temperatures and low-temperature viscosity properties, and can greatly contribute to the energy conservation of compressors. The lubricating oil composition of the present 10 invention is suited to rotary-type compressor oils, and is particularly suited to oil-flooded screw compressor oils.
Examples
[0112]
15 The present invention is further specifically explained
based on the below Examples. However, the present invention
is not limited to these Examples.
[0113]
[Evaluation method]
20 In the below Examples and Comparative Examples etc.,
the physical properties etc. of the ethylene-α-olefin
copolymer and the compressor oil were measured by the below
methods.
[0114]

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< Ethylene content (mol%) >
Using a Fourier transform infrared spectrometer FT/IR-610 or FT/IR-6100 (made by JASCO), the absorbance ratio of the absorption in the vicinity of 721 cm-1 based on the 5 horizontal vibration of the long chain methylene group, and the absorption in the vicinity of 1155 cm-1 based on the skeletal vibration of propylene (D1155 cm-1 / D721 cm-1) was calculated, and the ethylene content (% by weight) was obtained by the calibration curve created beforehand (created 10 using the ASTM D3900 reference sample). Using the ethylene content (% by weight) thus obtained, the ethylene content (mol%) was obtained according to the following Formula. [0115]
Ethylene content (mol%)
= [ethylene content (% by weight) / 28]
[ethylene content (% by weight) / 28] + [propylene content (% by weight) / 42]
15
< B-value >
Employing o-dichloro benzene / benzene-d6 (4/1 [vol/vol%]) as a measurement solvent, the 13C-NMR spectrum was measured under the measuring conditions (100 MHz, ECX 400P, 20 made by JEOL Ltd) of temperature of 120°C, spectral width of 250 ppm, pulse repeating time of 5.5 seconds, and a pulse width of 4.7 μsec (45° pulse), or under the measuring

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conditions (125 MHz, AVANCE III Cryo-500 made by Bruker Biospin Inc) of temperature of 120°C, spectral width of 250 ppm, pulse repeating time of 5.5 seconds, and a pulse width of 5.0 μsec (45° pulse), and the B-value was calculated based 5 on the following Formula [1]. The peak attribution was
performed by reference to the aforementioned publicly-known
literature.
[0116]

10 In Formula [1], PE indicates the molar fraction
contained in the ethylene component, PO indicates the molar fraction contained in the α-olefin component, and POE indicates the molar fraction of the ethylene-α-olefin sequences of all dyad sequences.
15 [0117]
< Molecular weight distribution >
Employing the HLC-8320 GPC (gel permeation chromatography) device produced by Tosoh Corporation, the molecular weight distribution was measured as below. Four TSK
20 gel Super Multipore HZ-M columns were used as separation columns, the column temperature was 40°C, tetrahydrofuran (made by Wako Pure Chemical Industries) was used as the

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mobile phase, with a development rate of 0.35 ml/minute, a sample concentration of 5.5 g/L, a sample injection amount of 20 microliters, and a differential refractometer was used as a detector. PStQuick MP-M; made by Tosoh Corporation) was 5 used as the reference polystyrene. In accordance with
general-purpose calibration procedures, weight average molecular weight (Mw) and number average molecular weight (Mn) were calculated in terms of polystyrene molecular weight, and the molecular weight distribution (Mw/Mn) was 10 calculated from those values. [0118]
< Viscosity properties >
The 100°C kinematic viscosity, 40°C kinematic viscosity and the viscosity index were measured and calculated by the 15 method described in JIS K2283. [0119]
< Pour point >
The pour point was measured by the method described in ASTM D97. Pour points lower than -50°C were described as 20 <-50(°C). [0120]
< -40°C viscosity >

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As the low-temperature viscosity properties, in accordance with ASTM D2983, the -40°C viscosity was measured at -40°C with a Brookfield viscometer. [0121] 5 < Thermal and oxidation stability >
Regarding thermal and oxidation stability, a test was conducted in accordance with the Oxidation Stability Test of Lubricating Oil for Internal Combustion Engines (ISOT) method described in JIS K2514, and the lacquer rating was evaluated 10 72 hours after the test time. [0122] [Production of ethylene-α-olefin copolymer (B)]
Ethylene-α-olefin copolymers (B) were prepared in accordance with the Polymerization Examples below. The 15 resulting ethylene-α-olefin copolymer (B) was subjected to hydrogenation operation as required by the below process. [0123] [Polymerization Example 1]
760 ml of heptane and 120 g of propylene were charged 20 into a stainless steel autoclave with a volume of 2 L
sufficiently substituted with nitrogen, and the temperature in the system was raised to 150°C, and then 0.85 MPa of hydrogen and 0.19 MPa of ethylene were supplied to raise the total pressure to 3 MPaG. Then, 0.4 mmol of triisobutyl

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aluminum, 0.0002 mmol of diphenylmethylene [η5-(3-n-butyl cyclopentadienyl)] [η5-(2,7-di-tert-butyl fluorenyl)] zirconium dichloride, and 0.002 mmol of N,N-dimethylanilinium tetrakis (pentafluorophenyl) borate were injected with 5 nitrogen, and polymerization was started by stirring with a rotation of 400 rpm. Ethylene was then continuously supplied to keep the total pressure at 3 MPaG, and polymerization took place at 150°C for 5 minutes. Polymerization was stopped by adding a small amount of ethanol in the system, and the
10 unreacted ethylene, propylene and hydrogen were purged. The
resulting polymer solution was washed 3 times with 1000 ml of a 0.2 mol/L solution of hydrochloric acid, further washed 3 times with 1000 ml of distilled water, dried with magnesium sulfate, and the solvent was then distilled off under reduced
15 pressure. The resulting polymer was dried at 80°C under
reduced pressure for 10 hours. The resulting polymer had an ethylene content of 49.5 mol%, an Mw of 5,100, an Mw/Mn of 1.7, a B-value of 1.2, and a 100°C kinematic viscosity of 150 mm2/s.
20 [0124]
[Polymerization Example 2]
710 mL of heptane and 145 g of propylene were charged into a stainless steel autoclave with a volume of 2L sufficiently substituted with nitrogen, and the temperature

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in the system was raised to 150°C, and then 0.40 MPa of hydrogen and 0.27 MPa of ethylene were supplied to raise the total pressure to 3 MPaG. Then, 0.4 mmol of triisobutyl aluminum, 0.0001 mmol of diphenylmethylene [η5-(3-n-butyl 5 cyclopentadienyl)] [η5-(2,7-di-tert-butyl fluorenyl)]
zirconium dichloride, and 0.001 mmol of N,N-dimethylanilinium tetrakis (pentafluorophenyl) borate were injected with nitrogen, and polymerization was started by stirring with a rotation of 400 rpm. Ethylene only was then continuously
10 supplied to keep the total pressure at 3 MPaG, and polymerization took place at 150°C for 5 minutes. Polymerization was stopped by adding a small amount of ethanol in the system, and the unreacted ethylene, propylene and hydrogen were purged. The resulting polymer solution was
15 washed 3 times with 1000 ml of a 0.2 mol/L solution of
hydrochloric acid, further washed 3 times with 1000 ml of distilled water, dried with magnesium sulfate, and the solvent was then distilled off under reduced pressure. The resulting polymer was dried overnight at 80°C under reduced
20 pressure to obtain 52.2 g of an ethylene-propylene copolymer. The resulting polymer had an ethylene content of 52.9 mol%, an Mw of 8,600, an Mw/Mn of 1.8, a B-value of 1.2, and a 100°C kinematic viscosity of 600 mm2/s. [0125]

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[Polymerization Example 3]
250 mL of heptane was charged into a glass polymerization vessel with a volume of 1 L sufficiently substituted with nitrogen, and the temperature in the system 5 was raised to 50°C, and then 25 L/h of ethylene, 75 L/h of
propylene, and 100 L/h of hydrogen were continuously supplied into the polymerization vessel, and stirred with a rotation of 600 rpm. Then, 0.2 mmol of triisobutyl aluminum was charged into the polymerization vessel, and 0.023 mmol of
10 N,N-dimethylanilinium tetrakis (pentafluorophenyl) borate and 0.00230 mmol of diphenylmethylene [η5-(3-n-butyl cyclopentadienyl)] [η5-(2,7-di-tert-butyl fluorenyl)] zirconium dichloride, which were pre-mixed in toluene for 15 minutes or more, were charged into the polymerization vessel
15 to start the polymerization. Ethylene, propylene and hydrogen were then continuously supplied, and polymerization took place at 50°C for 15 minutes. Polymerization was stopped by adding a small amount of isobutyl alcohol in the system, and the unreacted monomers were purged. The resulting polymer
20 solution was washed 3 times with 100 mL of a 0.2 mol/L
solution of hydrochloric acid, further washed 3 times with 100 mL of distilled water, dried with magnesium sulfate, and the solvent was then distilled off under reduced pressure. The resulting polymer was dried overnight at 80°C under

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reduced pressure to obtain 1.43 g of an ethylene-propylene copolymer. The resulting polymer had an ethylene content of 52.4 mol%, an Mw of 13,600, an Mw/Mn of 1.9, a B-value of 1.2, and a 100°C kinematic viscosity of 2,000 mm2/s. 5 [0126]
[Polymerization Example 4]
760 ml of heptane and 120 g of propylene were charged into a stainless steel autoclave with a volume of 2 L sufficiently substituted with nitrogen, and the temperature
10 in the system was raised to 150°C, and then 0.85 MPa of
hydrogen and 0.19 MPa of ethylene were supplied to raise the total pressure to 3 MPaG. Then, 0.4 mmol of triisobutyl aluminum, 0.0002 mmol of dimethylsilyl bis(indenyl) zirconium dichloride, and 0.059 mmol of MMAO were injected with
15 nitrogen, and polymerization was started by stirring with a
rotation of 400 rpm. Ethylene was then continuously supplied to keep the total pressure at 3 MPaG, and polymerization took place at 150°C for 5 minutes. Polymerization was stopped by adding a small amount of ethanol in the system, and the
20 unreacted ethylene, propylene and hydrogen were purged. The
resulting polymer solution was washed 3 times with 1000 ml of a 0.2 mol/L solution of hydrochloric acid, further washed 3 times with 1000 ml of distilled water, dried with magnesium sulfate, and the solvent was then distilled off under reduced

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pressure. The resulting polymer was dried at 80°C under reduced pressure for 10 hours. The resulting polymer had an ethylene content of 48.5 mol%, an Mw of 5,000, an Mw/Mn of 1.8, a B-value of 1.2, and a 100°C kinematic viscosity of 150 5 mm2/s. [0127] [Polymerization Example 5]
710 mL of heptane and 145 g of propylene were charged into a stainless steel autoclave with a volume of 2L
10 sufficiently substituted with nitrogen, and the temperature in the system was raised to 150°C, and then 0.40 MPa of hydrogen and 0.27 MPa of ethylene were supplied to raise the total pressure to 3 MPaG. Then, 0.4 mmol of triisobutyl aluminum, 0.0001 mmol of dimethylsilyl bis(indenyl) zirconium
15 dichloride, and 0.029 mmol of MMAO were injected with
nitrogen, and polymerization was started by stirring with a rotation of 400 rpm. Ethylene only was then continuously supplied to keep the total pressure at 3 MPaG, and polymerization took place at 150°C for 5 minutes.
20 Polymerization was stopped by adding a small amount of
ethanol in the system, and the unreacted ethylene, propylene and hydrogen were purged. The resulting polymer solution was washed 3 times with 1000 ml of a 0.2 mol/L solution of hydrochloric acid, further washed 3 times with 1000 ml of

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distilled water, dried with magnesium sulfate, and the solvent was then distilled off under reduced pressure. The resulting polymer was dried overnight at 80°C under reduced pressure to obtain 52.2 g of an ethylene-propylene copolymer. 5 The resulting polymer had an ethylene content of 53.3 mol%, an Mw of 8,500, an Mw/Mn of 1.9, a B-value of 1.2, and a 100°C kinematic viscosity of 600 mm2/s. [0128] [Polymerization Example 6]
10 250 mL of heptane was charged into a glass
polymerization vessel with a volume of 1 L sufficiently substituted with nitrogen, and the temperature in the system was raised to 50°C, and then 25 L/h of ethylene, 75 L/h of propylene, and 100 L/h of hydrogen were continuously supplied
15 into the polymerization vessel, and stirred with a rotation of 600 rpm. Then, 0.2 mmol of triisobutyl aluminum was charged into a polymerization vessel, and 0.688 mmol of MMAO and 0.00230 mmol of dimethylsilyl bis(indenyl) zirconium dichloride, which were pre-mixed in toluene for 15 minutes or
20 more, were charged into a polymerization vessel to start the polymerization. Ethylene, propylene and hydrogen were then continuously supplied, and polymerization took place at 50°C for 15 minutes. Polymerization was stopped by adding a small amount of isobutyl alcohol in the system, and the unreacted

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monomers were purged. The resulting polymer solution was washed 3 times with 100 mL of a 0.2 mol/L solution of hydrochloric acid, further washed 3 times with 100 mL of distilled water, dried with magnesium sulfate, and the 5 solvent was then distilled off under reduced pressure. The
resulting polymer was dried overnight at 80°C under reduced pressure to obtain 1.43 g of an ethylene-propylene copolymer. The resulting polymer had an ethylene content of 52.1 mol%, an Mw of 13,800, an Mw/Mn of 2.0, a B-value of 1.2, and a
10 100°C kinematic viscosity of 2,000 mm2/s. [0129]
The copolymer obtained by Polymerization Example 1, the copolymer obtained by Polymerization Example 2, the copolymer obtained by Polymerization Example 3, the copolymer obtained
15 by Polymerization Example 4, the copolymer obtained by
Polymerization Example 5, and the copolymer obtained by Polymerization Example 6, are respectively described below as Polymer 1, Polymer 2, Polymer 3, Polymer 4, Polymer 5, and Polymer 6.
20 [0130]
[Preparation of lubricating oil composition for compressor oils]
The components used other than the ethylene-α-olefin copolymer in the preparation of the below lubricating oil

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compositions are as follows.
[0131]
Lubricant base oil;
The below lubricant base oils were used as the mineral 5 oils.
Mineral oil-A: API (American Petroleum Institute) Group
III mineral oil with a 100°C kinematic viscosity of 6.5
mm2/s, a viscosity index of 131, and a pour point of -12.5°C
(Yubase-6; made by SK Lubricants), and
10 Mineral oil-B: API (American Petroleum Institute) Group
I mineral oil with a 100°C kinematic viscosity of 6.8 mm2/s, a viscosity index of 108, and a pour point of -12.5°C (Super Oil N-32, made by JX Nippon Oil & Energy Corporation).
Moreover, the below lubricant base oils were used as 15 the synthetic oils.
Synthetic oil-A: Synthetic oil poly-α-olefin with a
100°C kinematic viscosity of 4.0 mm2/s, a viscosity index of
123, and a pour point of -50°C or lower (NEXBASE 2004; made
by Neste),
20 Synthetic oil-B: Synthetic oil poly-α-olefin with a
100°C kinematic viscosity of 5.8 mm2/s, a viscosity index of 138, and a pour point of -50°C or lower (NEXBASE 2006; made by Neste),
Synthetic oil-C: Synthetic oil poly-α-olefin with a

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100°C kinematic viscosity of 8.0 mm2/s, a viscosity index of 142, and a pour point -50°C (SpectrasynTM 8, made by ExxonMobil Chemical), and
Synthetic oil-D: Ester-based synthetic oil 5 trimethylolpropane caprylate (TMTC) with a 100°C kinematic
viscosity of 4.5 mm2/s, a viscosity index of 142, and a pour point -50°C or lower (SYNATIVETM ES TMTC, made by Cognis).
In addition to the lubricant base oil and ethylene-α-
olefin copolymer, the below types of additives were used.
10 Pour point lowering agent (PPD)-A; IRGAFLOW 720P made
by BASF
Additive package–A; HITEC-3339 made by AFTON CHEMICAL,
Additive package–B; LUBRIZOL 1047UI made by LUBRIZOL,
and
15 Antioxidant; Phenol-based antioxidant (Irganox L135
made by BASF).
< Lubricating oil composition for compressor oils >
[0132]
[Example 1]
20 Synthetic oil-A was used as the lubricant base oil (A),
and the copolymer obtained in Polymerization Example 2 (Polymer 2) was used as the ethylene-α-olefin copolymer (B). These were mixed together with an antioxidant and adjusted to 100% by mass, thereby preparing a lubricating oil composition

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for compressor oils. The addition amounts of the respective components are as shown in Table 2. The physical properties of the lubricating oil composition are shown in Table 2. [0133] 5 [Examples 2 to 16, Comparative Examples 1 to 7]
Except for changing the types of components and addition amounts to those as described in Table 2, the lubricating oil compositions for compressor oil were mixed and prepared in the same way as in Example 1. The physical 10 properties of the resulting lubricating oil compositions are shown in Table 2.

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[0134]
Table 2

Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12
Polymer 1 % by mass 39.0
Polymer 2 % by mass 11 .0 10.0 7.0 15.0 21.0 24.0
Polymer 3 % by mass 8.0 8.0 6.0 11 .0 16.0
Polymer 4 % by mass
Polymer 5 % by mass
Polymer 6 % by mass
Mineral oil - A % by mass 92.3 93.3
Mineral oil - B % by mass
Synthetic oil - A % by mass 88.8 91.8
Synthetic oil - B % by mass 88.8 91.8 84.8 88.8 78.8 83.8
Synthetic oil - C % by mass 49.8 64.8
Synthetic oil - D % by mass 10.0 10.0
Antioxidant % by mass 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2
Additive Package -A % by mass 1.2 1.2
Additive Package -B % by mass
Pour point lowering agent - A % by mass 0.5 0.5
40°C kinematic viscosity mm2/s 46 47 68 68 67 70 98 100 148 158 230 230
Viscosity index - 170 175 158 158 148 153 161 163 167 159 161 168
Pour point °C <-50 <-50 <-50 <-50 -50 < -50 -43 -45
-40°C viscosity mPa･s 9,500 9,200 22,000 20,000 44,000 38,000 75,000 76,000
ISOT Lacquer rating Adhered
substance
(thin) Adhered
substance
(thin) Adhered
substance
(thin) Adhered
substance
(thin) Adhered substance (medium) Adhered substance (medium) Adhered substance (medium) Adhered substance (medium) Adhered substance (medium) Adhered substance (medium) Adhered substance (medium) Adhered substance (medium)

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[0135]
Table 2 (continued)

Ex. 13 Ex. 14 Ex. 15 Ex. 16 Comp. Ex. 1 Comp. Ex. 2 Comp. Ex. 3 Comp. Ex. 4 Comp. Ex. 5 Comp. Ex. 6 Comp. Ex. 7
Polymer 1 % by mass 39.0
Polymer 2 % by mass 25.0
Polymer 3 % by mass 16.0 18.0
Polymer 4 % by mass 39.0
Polymer 5 % by mass 11 .0 7.0 25.0
Polymer 6 % by mass 8.0 6.0 18.0
Mineral oil - A % by mass 92.3 93.3
Mineral oil - B % by mass 59.5 73.5 80.5 59.5 73.5 80.5
Synthetic oil - A % by mass 88.8 91.8
Synthetic oil - B % by mass
Synthetic oil - C % by mass 72.8
Synthetic oil - D % by mass 10.0
Antioxidant % by mass 0.2 0.2 0.2 0.2
Additive Package -A % by mass 1.2
Additive Package -B % by mass 1.0 1.0 1.0 1.0 1.0 1.0
Pour point lowering agent - A % by mass 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5
40°C kinematic viscosity mm2/s 228 223 222 216 46 47 67 70 225 220 221
Viscosity index - 167 150 160 164 170 175 148 153 151 159 166
Pour point °C <-50 <-50
-40°C viscosity mPa･s 9,300 9,600
ISOT Lacquer rating Adhered
substance
(thin) Adhered
substance
(thin) Adhered
substance
(thin) Adhered
substance
(thin) Adhered
substance
(thick) Adhered
substance
(thick) Adhered
substance
(thick) Adhered
substance
(thick) Adhered
substance
(thick) Adhered
substance
(thick) Adhered
substance
(thick)

WE CLAIMS

A lubricating oil composition for compressor oils,
comprising 5 10 to 99% by mass of a lubricant base oil (A) having
the properties of the below (A1) to (A3), and
90 to 1% by mass of a liquid random copolymer (B) of
ethylene and α-olefin, the liquid random copolymer (B) being
prepared by the below method (α) (where the total amount of 10 the lubricant base oil (A) and the copolymer (B) is 100% by
mass), the lubricating oil composition for compressor oils
having the property of the below (C1).
(A1) The lubricant base oil has a kinematic viscosity at
100°C of 1 to 14 mm2/s. 15 (A2) The lubricant base oil has a viscosity index of 100 or
more.
(A3) The lubricant base oil has a pour point of 0°C or lower.
(C1) The lubricating oil composition for compressor oils has
a kinematic viscosity at 40°C of 10 to 300 mm2/s. 20 (Method (α))
A method (α) for preparing a liquid random copolymer of
ethylene and α-olefin, comprising a step of carrying out
solution polymerization of ethylene and α-olefin having 3 to
20 carbon atoms, under a catalyst system comprising

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(a) a bridged metallocene compound represented by the following Formula 1, and
(b) at least one compound selected from a group consisting of
(i) an organoaluminum oxy-compound, and
5 (ii) a compound which reacts with the bridged
metallocene compound to form an ion pair.

(Formula 1)
[In Formula 1, R1, R2, R3, R4, R5, R8, R9 and R12 are respectively and independently hydrogen atom, hydrocarbon 10 group or silicon-containing hydrocarbon group, and adjoining groups are optionally connected to each other to form a ring structure,
R6 and R11, being the same, are hydrogen atom, hydrocarbon group or silicon-containing hydrocarbon group,

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R7 and R10, being the same, are hydrogen atom, hydrocarbon group or silicon-containing hydrocarbon group,
R6 and R7 are optionally connected to hydrocarbon having
2 to 3 carbon atoms to form a ring structure,
5 R11 and R10 are optionally connected to hydrocarbon
having 2 to 3 carbon atoms to form a ring structure,
R6, R7, R10 and R11 are not hydrogen atom at the same time;
Y is a carbon atom or silicon atom;
10 R13 and R14 are independently aryl group;
M is Ti, Zr or Hf;
Q is independently halogen, hydrocarbon group, an
anionic ligand or a neutral ligand which can be coordinated
to a lone pair of electrons; and
15 j is an integer of 1 to 4.]
2. A lubricating oil composition for compressors according
to Claim 1, wherein in the metallocene compound represented
by the above Formula 1, at least one among substituents (R1,
20 R2, R3 and R4) bonded to a cyclopentadienyl group, is a hydrocarbon group having 4 or more carbon atoms.
3. A lubricating oil composition for compressors according
to Claim 1 or 2, wherein R6 and R11, being the same, are

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82

hydrocarbon groups having 1 to 20 carbon atoms.
4. A lubricating oil composition for compressors according
to any one of Claims 1 to 3, wherein in the metallocene
5 compound represented by the above Formula 1, substituent (R2
or R3) bonded to the 3-position of the cyclopentadienyl group is a hydrocarbon group.
5. A lubricating oil composition for compressors according
10 to Claim 4, wherein in the metallocene compound represented
by the above Formula 1, the hydrocarbon group (R2 or R3) bonded to the 3-position of the cyclopentadienyl group is an n-butyl group.
15 6. A lubricating oil composition for compressors according to any one of Claims 1 to 5, wherein in the metallocene compound represented by the above Formula 1, substituents (R6 and R11) bonded to the 2-position and 7-position of the fluorenyl group are all tert-butyl groups.
20
7. A lubricating oil composition for compressors according to any one of Claims 1 to 6, wherein the compound which reacts with the bridged metallocene compound to form an ion pair is a compound represented by the following Formula 6.

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pe R B—R
R ., ■■■ (Formula 6)
[In Formula 6, Re+ is H+, a carbenium cation, an oxonium cation, an ammonium cation, a phosphonium cation, a cycloheptyltrienyl cation, or a ferrocenium cation having a 5 transition metal, and Rf to Ri each is independently a hydrocarbon group having 1 to 20 carbon atoms.]
8. A lubricating oil composition for compressors according
to Claim 7, wherein the ammonium cation is a
10 dimethylanilinium cation.
9. A lubricating oil composition for compressors according
to Claim 7 or 8, wherein the catalyst system further
comprises an organoaluminum compound selected from a group
15 consisting of trimethyl aluminum and triisobutyl aluminum.
10. A lubricating oil composition for compressor oils
according to any one of Claims 1 to 9, wherein the content of
the liquid random copolymer (B) is 1 to 20% by mass.
20
11. A lubricating oil composition for compressor oils,

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comprising
10 to 99% by mass of a lubricant base oil (A) having
the properties of the below (A1) to (A3), and
90 to 1% by mass of a liquid random copolymer of 5 ethylene and α-olefin, the liquid random copolymer having the
properties of the below (B1) to (B5) (where the total amount
of the lubricant base oil (A) and the copolymer is 100% by
mass), the lubricating oil composition for compressor oils
having the property of the below (C1). 10 (A1) The lubricant base oil (A) has a kinematic viscosity at
100°C of 1 to 14 mm2/s.
(A2) The lubricant base oil (A) has a viscosity index of 100
or more.
(A3) The lubricant base oil (A) has a pour point of 0°C or 15 lower.
(B1) The liquid random copolymer comprises 40 to 60 mol% of
ethylene units and 60 to 40 mol% of α-olefin units having 3
to 20 carbon atoms.
(B2) The liquid random copolymer has a number average 20 molecular weight (Mn) of 500 to 10,000 and a molecular weight
distribution (Mw/Mn, Mw is the weight average molecular
weight) of 3 or less, as measured by Gel Permeation
Chromatography (GPC).
(B3) The liquid random copolymer has a kinematic viscosity at

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100°C of 30 to 5,000 mm2/s.
(B4) The liquid random copolymer has a pour point of 30 to -45°C.
(B5) The liquid random copolymer has a Bromine Number of 0.1 5 g / 100 g or less.
(C1) The lubricating oil composition for compressor oils has a kinematic viscosity at 40°C of 10 to 300 mm2/s.
12. A lubricating oil composition for compressor oils
10 according to any one of Claims 1 to 11, wherein the lubricant
base oil (A) further satisfies the below (A4) to (A6).
(A4) The lubricant base oil (A) has a kinematic viscosity at
100°C of 1 to 10 mm2/s.
(A5) The lubricant base oil (A) has a viscosity index of 110
15 or more.
(A6) The lubricant base oil (A) has a pour point of -10°C or
lower.
13. A lubricating oil composition for compressor oils
20 according to any one of Claims 1 to 12, wherein 30 to 100% by mass of the lubricant base oil (A) is mineral oil.
14. A lubricating oil composition for compressor oils
according to any one of Claims 1 to 12, wherein 30 to 100% by

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mass of the lubricant base oil (A) is a synthetic oil, poly α olefin (PAO) and/or an ester oil.
15. A lubricating oil composition for compressor oils
5 according to any one of Claims 1 to 14, having a kinematic viscosity at 40°C of 20 to 100 mm2/s.
16. A rotary-type compressor oil, consisting of the
lubricating oil composition for compressor oils according to
10 any one of Claims 1 to 15.
17. An oil-flooded-screw compressor oil, consisting of the
lubricating oil composition for compressor oils according to
any one of Claims 1 to 15.
15
18. A method for producing a lubricating oil composition
for compressor oils, comprising the steps of:
preparing a liquid random copolymer (B) of ethylene and α-olefin by the following method (α); and 20 preparing a lubricating oil composition for compressor oils by mixing a lubricant base oil (A) in an amount of 10 to 99% by mass of the lubricating oil composition, the lubricant base oil (A) having the properties of the below (A1) to (A3), and the liquid random copolymer (B) in an amount of 90 to 1%

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by mass of the lubricating oil composition (where the total
amount of the lubricant base oil (A) and the copolymer (B) is
100% by mass), the lubricating oil composition for compressor
oils having the property of the below (C1). 5 (A1) The lubricant base oil (A) has a kinematic viscosity at
100°C of 1 to 14 mm2/s.
(A2) The lubricant base oil (A) has a viscosity index of 100
or more.
(A3) The lubricant base oil (A) has a pour point of 0°C or 10 lower.
(C1) The lubricating oil composition for compressor oils has
a kinematic viscosity at 40°C of 10 to 300 mm2/s.
(Method (α))
A method (α) for preparing a liquid random copolymer of 15 ethylene and α-olefin, comprising a step of carrying out
solution polymerization of ethylene and α-olefin having 3 to
20 carbon atoms, under a catalyst system comprising
(a) a bridged metallocene compound represented by the
following Formula 1, and 20 (b) at least one compound selected from a group consisting of (i) an organoaluminum oxy-compound, and (ii) a compound which reacts with the bridged
metallocene compound to form an ion pair.

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(Formula 1)
[In Formula 1, R1, R2, R3, R4, R5, R8, R9 and R12 are respectively and independently hydrogen atom, hydrocarbon group or silicon-containing hydrocarbon group, and adjoining 5 groups are optionally connected to each other to form a ring structure,
R6 and R11, being the same, are hydrogen atom, hydrocarbon group or silicon-containing hydrocarbon group,
R7 and R10, being the same, are hydrogen atom, 10 hydrocarbon group or silicon-containing hydrocarbon group,
R6 and R7 are optionally connected to hydrocarbon having 2 to 3 carbon atoms to form a ring structure,
R11 and R10 are optionally connected to hydrocarbon having 2 to 3 carbon atoms to form a ring structure,

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R6, R7, R10 and R11 are not hydrogen atom at the same
time;
Y is a carbon atom or silicon atom;
R13 and R14 are independently aryl group;

5

M is Ti, Zr or Hf;

Q is independently halogen, hydrocarbon group, an anionic ligand or a neutral ligand which can be coordinated to a lone pair of electrons; and
j is an integer of 1 to 4.]