Description [Title of the Invention] Lubricating Oil Composition [Technical Field] [0001] 5 The present invention relates to a lubricating oil composition and a gear for a wind power generator, which is filled with the lubricating oil composition. [Background Art] [0002] 10 For grease lubricating oils, gear oils, hydraulic oils, etc., various properties are required, and in recent years, as the internal combustion engines and industrial machines are made to have higher performance and higher output power or as the operation conditions become severer, higher properties of engine parts, such as higher 15 abrasion resistance, heat resistance, sludge resistance, lubricating oil consumption properties and fuel saving, have been required. The environment where the lubricating oils are used is becoming severer, while life lengthening of lubricating oils tends to be required in consideration of environmental problems, and on that account, decrease 20 in lowering of viscosity attributable to shear stress given by a gear during the operation of engine, that is, improvement in shear stability of lubricating oils has been desired. On the other hand, in order to improve energy conversion efficiency of engine or ensure favorable lubricating properties of engine in an extremely low temperature SF-2368 2 environment, temperature viscosity properties such that oil films of lubricating oils are maintained at high temperatures and fluidity of lubricating oils is rather maintained at low temperatures are regarded as important. 5 [0003] Accordingly, as grease lubricating oils, gear oils, hydraulic oils, etc., those having long life, namely, low-evaporation properties, and having favorable temperature viscosity properties are desired. [0004] 10 Particularly in wind power generators which have been paid attention as generators of renewable energy in recent years, gear boxes to convert wind force into electric power are installed at elevated spots in order to receive more stable wind force. In addition, from the viewpoint of stable supply of wind force and direction of 15 wind, they are often installed not only in the inland areas but also on the sea. On this account, maintenance of gears, that is, exchange of lubricating oils is very difficult, and as a result, higher shear stability is required for the lubricating oils. Moreover, from the viewpoint of efficiency of energy conversion from wind force into 20 electric power, favorable lubricating properties at extremely low temperatures such as -40°C, that is, high fluidity of lubricating oils in a low temperature environment is desired. [0005] Furthermore, high anti-micropitting performance is desired for SF-2368 3 gear oils for wind power generators. Micropitting is a fatigue process of gear brought about immediately before gear damage because of a cycle of excess stress in the rolling elasto-hydrodynamic lubrication (EHL) region under high load. Separation of small fragments from 5 gear tooth surface due to repeated compression stress in this high-load state is referred to as "micropitting", and for lubricating oils used for gear oils for wind power generators, high anti-micropitting performance is desired. [0006] 10 In view of the above background, developments of various synthetic lubricating oils have been made (patent literatures 1 and 2, etc.). [Prior Art Literature] [Patent Literature] 15 [0007] Patent literature 1: National Publication of International Patent No. 542524/2008 Patent literature 2: National Publication of International Patent No. 500489/2009 20 [Summary of the Invention] [Problem to be Solved by the Invention] [0008] However, particularly in the fields where high shear stability is desired, such as a field of gear oils for wind power generators, SF-2368 3 gear oils for wind power generators. Micropitting is a fatigue process of gear brought about immediately before gear damage because of a cycle of excess stress in the rolling elasto-hydrodynamic lubrication (EHL) region under high load. Separation of small fragments from 5 gear tooth surface due to repeated compression stress in this high-load state is referred to as "micropitting", and for lubricating oils used for gear oils for wind power generators, high anti-micropitting performance is desired. [0006] 10 In view of the above background, developments of various synthetic lubricating oils have been made (patent literatures 1 and 2, etc.). [Prior Art Literature] [Patent Literature] 15 [0007] Patent literature 1: National Publication of International Patent No. 542524/2008 Patent literature 2: National Publication of International Patent No. 500489/2009 20 [Summary of the Invention] [Problem to be Solved by the Invention] [0008] However, particularly in the fields where high shear stability is desired, such as a field of gear oils for wind power generators, SF-2368 6 excellent low-temperature viscosity properties and anti-micropitting performance is obtained. Inparticular, a lubricating oil composition capable of maintaining the above properties even under high-load conditions which are also referred to as "extreme pressure lubricating 5 conditions" is obtained. [Brief Description of the Drawings] [0013] Fig. 1 is a view to explain an example of a wind power generating apparatus of the present invention, and is a partially cutaway 10 sectional view of the wind power generating apparatus in the longitudinal direction, and is a perspective view of the wind power generating apparatus partially visually observed from the front side of the apparatus. Fig. 2 is an enlarged perspective view of X portion of the wind 15 power generating apparatus shown in Fig. 1, said X portion being visually observed. Fig. 3 is an enlarged perspective view of Y portion of the wind power generating apparatus shown in Fig. 1, said Y portion being visually observed. 20 Fig. 4 is a diagrammatical perspective view of a driving strung module used for driving a wind power generating apparatus. [Mode for Carrying out the Invention] [0014] Lubricating oil composition SF-2368 6 excellent low-temperature viscosity properties andanti-micropitting performance is obtained. Inparticular, a lubricating oil composition capable of maintaining the above properties even under high-load conditions which are also referred to as "extreme pressure lubricating 5 conditions" is obtained. [Brief Description of the Drawings] [0013] Fig. 1 is a view to explain an example of a wind power generating apparatus of the present invention, and is a partially cutaway 10 sectional view of the wind power generating apparatus in the longitudinal direction, and is a perspective view of the wind power generating apparatus partially visually observed from the front side of the apparatus. Fig. 2 is an enlarged perspective view of X portion of the wind 15 power generating apparatus shown in Fig. 1, said X portion being visually observed. Fig. 3 is an enlarged perspective view of Y portion of the wind power generating apparatus shown in Fig. 1, said Y portion being visually observed. 20 Fig. 4 is a diagrammatical perspective view of a driving strung module used for driving a wind power generating apparatus. [Mode for Carrying out the Invention] [0014] Lubricating oil composition SF-2368 9 and 1-octene and/or 1-dodecene, not less than 60% by mol of its constituent units are formed from 1-decene. If the (co)polymer is a copolymer of 1-decene and 1-octene, low-temperature viscosity properties are sometimes lowered, and if it is a copolymer of 1-decene 5 and 1-dodecene, shear stability is sometimes lowered. Therefore, a homopolymer of 1-decene is preferably used. [0019] The acid value of the (co) polymer (i) comprising 1-decene, as measured by JIS K2501, is preferably less than 0.1 mgKOH/g, and is 10 more preferably less than 0.05 mgKOH/g. When the acid value is in this range, the resulting lubricating oil composition is excellent in oxidation stability and heat resistance. [0020] The kinematic viscosity of the (co)polymer (i) comprising 15 1-decene at 100°C is not more than 45 nun2/s, and is preferably not more than 11 mm2/s. When the kinematic viscosity is not more than 11 mm2/s, the lubricating oil composition exhibits more excellent low-temperature viscosity properties. [0021] 20 The (co) polymer (i) comprising 1-decene may be used singly or may be used as a mixture of two or more kinds. [0022] The 1-decene (co) polymer can be prepared by a hitherto publicly known process. For example, by using a catalyst such as BF3 or AiC13 SF-2368 10 and controlling polymerization temperature, polymerization time, etc., a (co) polymer having a desired molecular weight can be obtained. Through this control of molecular weight (that is, high-molecular weight gives high viscosity, and low-molecular weight gives low 5 viscosity), the kinematic viscosity at 100°C can be adjusted. In order to adjust the acid value to less than 0.1 mgKOH/g, the resulting (co)polymer is generally subjected to hydrogenation process in a publicly known way. The processes for preparing the 1-decene (co) polymer are disclosed in U. S. Patent No. 3,149,178, No. 3, 382, 291, 10 No. 3,742,082, No. 3,780,128, No. 4,172,855, No. 4,956,122, etc. [0023] The (co)polymer (ii) having a kinematic viscosity at 100°C of not less than 35 mm2/s but not more than 1,500 mm2/s is a (co) polymer obtained by polymerizing a monomer having 8 carbon atoms, namely, 15 1-octene, and the content of the constituent units of the monomer is in the range of 90 to 100% by mot, preferably 95 to 100% by mol. In other words, this (co)polymer is a homopolymer of 1-octene or a copolymer of 1-octene and another monomer. When the content is in this range, the lubricating oil composition of the present invention 20 has properties substantially equal to those of a lubricating oil composition containing a polymer obtained by homopolymerizing 1-octene. By combining the decene (co) polymer (i) with such an octene (co) polymer (ii) in the lubricating oil composition, shear stability and low-temperature viscosity properties of the lubricating oil SF-2368 10 and controlling polymerization temperature, polymerization time, etc., a (co) polymer having a desired molecular weight can be obtained. Through this control of molecular weight (that is, high-molecular weight gives high viscosity, and low-molecular weight gives low 5 viscosity), the kinematic viscosity at 100°C can be adjusted. In order to adjust the acid value to less than 0. 1 mgKOH/g, the resulting (co)polymer is generally subjected to hydrogenation process in a publicly known way. The processes for preparing the 1-decene (co) polymer are disclosed in U.S.PPaatteennttNo. 3,149,178, No. 3,38 10 No. 3,742,082, No. 3,780,128, No. 4,172,855, No. 4,956,122, etc. [0023] The (co)polymer (ii) having a kinematic viscosity at 100°C of not less than 35 mm2/s but not more than 1, 500 mm2/s is a (co) polymer obtained by polymerizing a monomer having 8 carbon atoms, namely, 15 1-octene, and the content of the constituent units of the monomer is in the range of 90 to 100% by mol, preferably 95 to 100% by mol. In other words, this (co)polymer is a homopolymer of 1-octene or a copolymer of 1-octene and another monomer. When the content is in this range, the lubricating oil composition of the present invention 20 has properties substantially equal to those of a lubricating oil composition containing a polymer obtained by homopolymerizing 1-octene. By combining the decene (co) polymer (i) with such an octene (co) polymer (ii) in the lubricating oil composition, shear stability and low-temperature viscosity properties of the lubricating oil SF-2368 13 gear oil, industrial lubricating oil, gear oil for a wind power generator or lubricating oil for bearing, and therefore, the lubricating oil composition exhibits excellent low-temperature viscosity properties. When the kinematic viscosity is not more than 5 1,200 mm 2/s, the lubricating oil composition exhibits more excellent shear stability. [0029] A number-average molecular weight can be measured by gel permeation chromatography (GPC) calibrated by the use of a standard 10 substance (monodisperse polystyrene (PSt)) whose molecular weight is already known, and the number-average molecular weight (Mn) of the (co) polymer using 1-octene as a monomer in the present invention is in the range of preferably 500 to 15,000, more preferably 3,000 to12,000. When the number-average molecular weight is in this range, 15 the resulting lubricating oil composition is excellent in a balance between low-temperature viscosity properties and shear stability. [0030] The molecular weight distribution (Mw/Mn) of the (co)polymer comprising 1-octene in the present invention is in the range of 1.8, 20 preferably in the range of 1.1 to 1.8, more preferably in the range of 1.2 to 1.7. When the molecular weight distribution is in this range, shear stability of the resulting lubricating oil composition is excellent. [0031] SF-2368 14 The (co)polymer (ii) comprising octene may be used singly or may be used as a mixture of two or more kinds. [0032] Preparation of (co)polymer (ii) comprising octene in the present 5 invention Such a (co) polymer comprising 1-octene as above can be prepared referring to such catalysts used in the preparation of a-olefin (co) polymers as described in Japanese Patent Laid-Open Publication No. 41303/1990, Japanese Patent Laid-Open Publication No. 41305/1990, 10 Japanese Patent Laid-Open Publication No. 274703/1990, Japanese Patent Laid-Open Publication No. 274704/1990, Japanese Patent Laid-Open Publication No. 179005/1991, Japanese Patent Laid-Open Publication No. 179006/1991, Japanese Patent Laid-Open Publication No. 193796/1991, Japanese Patent Laid-Open Publication No. 69394/1992, 15 Japanese Patent Laid-Open Publication No. 17589/1993, Japanese Patent Laid-Open Publication No. 122718/1994, Japanese Patent Laid-Open Publication No. 120127/1996, Japanese Patent Laid-Open Publication No. 239414/1996, Japanese Patent Laid-Open Publication No. 08.7716/1998, Japanese Patent Laid-Open Publication No. 212194/2000, 20 WO 01/27124, WO 02/074855, WO 04/029062, EP 0881236 and EP 1416000. [0033] More specifically, in the preparation of the (co) polymer using 1-octene as a monomer, a homopolymer or a copolymer can be obtained by homopolymerizing 1-octene or copolymerizing 1-octene and the SF-2368 15 above-mentioned another a-olefin in the presence of, for example, an olefin polymerization catalyst comprising: (A) a transition metal compound (transition metal compound of a Group 4 transition metal of the periodic table, or the like), and 5 (B) at least one compound selected from: (B-1) an organometallic compound, (B-2) an organoaluminum compound, (B-3) an organoaluminum oxy-compound, and (B-4) a compound which reacts with the Group 4 transition metal 10 compound (A) to form an ion pair. [0034] The transition metal compound (A) and the compound (B) are described below in more detail. (A) Transition metal compound 15 As the transition metal compound (A) for use in the present invention, publicly known periodic table Group IV to Group VI transition metal compounds having olefin polymerizability are employable without any restriction. For example, halogenation products of transition metals of Group IV to Group VI of the periodic 20 table, alkylation products thereof, alkoxylation products thereof, and non-bridged or bridged metallocene compounds are employable. Of these, preferable are halogenation products of periodic table Group IV transition metals (more preferable are halogenations products of Group IVB transition metals), alkylation products thereof, SF-2368 16 alkoxylation products thereof, and non-bridged or bridgedmetallocene compounds. Preferred embodiments of the transition metal compound (A) are described below. [0035] Examples of the transition metal halogenation products, the transition metal alkylation products and the transition metal alkoxylation products include titanium tetrachloride, dimethyltitanium dichloride, tetrabenzyltitani.um, tetrabenzylzirconium and tetrabutoxytitanium. [0036] The non-bridgedorbridgedmetallocene compound is, for example, a compound represented by the following formula (1) which is a periodic table Group 4 transition metal compound having cyclopentadienyl skeleton. [0037] ML, (1) In the above formula, M is a transition metal atom selected from Group IV of the periodic table, preferably zirconium, titanium or. hafnium of a Group IVB transition metal. x is a valence of the transition metal and is a number of L. L is a ligand or a group coordinated to the transition metal; at least one L is a ligand having cyclopentadienyl skeleton; and L other than the ligand having cyclopentadienyl skeleton is a group or an atom selected from a halogen, a hydrogen atom, a hydrocarbon group of 1 to 10 carbon atoms, a neutral, SF-2368 17 conjugated or non-conjugated diene of 10 or less carbon atoms, an anionic ligand and a neutral ligand capable of coordination with a lone pair, two or more of said L being the same or different. [0038] 5 Examples of the ligands having cyclopentadienyl skeleton include a cyclopentadienyl group, an alkyl substituted cyclopentadienyl group, an indenyl group, an alkyl substituted indenyl group, a 4, 5, 6, 7-tetrahydroindenyl group, a fluorenyl group and an alkyl substituted fluorenyl group. These groups may be substituted 10 with halogen atoms, trialkylsilyl groups or the like. [0039] When the compound represented by the formula (1) contains two or more ligands having cyclopentadienyl skeleton, two ligands having cyclopentadienyl skeleton among them may be bonded to each other 15 through an alkylene group, a substituted alkylene group, a silylene group, a substituted silylene group or the like. (Such a compound is sometimes referred to as a "bridged metallocene compound" hereinafter, and a compound other than such a compound is sometimes referred to as a "non-bridged metallocene compound" hereinafter.) 20 Of the above compounds, preferable is, for example, a compound represented by the following formula (2). [0040] MLaXb (2) SF-2368 18 In the above formula, M is a transition metal atom selected from Group IV of the periodic table, preferably zirconium, titanium or hafnium of a Group IVB transition metal, L is a ligand coordinated to the transition metal, a is an integer of 1 or greater and is a 5 number of L, X is a group or an atom bonded to the transition metal and selected from a halogen, a hydrogen atom, a hydrocarbon group of 1 to 10 carbon atoms, a neutral, conjugated or non-conjugated diene of 10 or less carbon atoms, an anionic ligand and a neutral ligand capable of coordination with a lone pair, each X being the same or 10 different, and b is an integer of 1 or greater and is a number of X. In the formula (2) , L is a ligand coordinated to the transition metal, and at least one Lisa ligand having cyclopentadienyl skeleton. Examples of the ligands having cyclopentadienyl skeleton include a 15 cyclopentadienyl group; alkyl substituted cyclopentadienyl groups, such as methylcyclopentadienylgroup,dimethylcyclopentadionyl group, trimethylcyclopentadienyl group, tetramethylcyclopentadienyl group, pentamethylcyclopentadienyl group, ethylcyclopentadienyl group, methylethylcyclopentadienyl group, propylcyclopentadienyl group, 20 methylpropylcyclopentadienyl group, butylcyclopentadienyl group, methylbutylcyclopentadienyl group and hexylcyclopentadienyl group; an indenyl group; a 4, 5, 6, 7-tetrahydroindenyl group; and a fluorenyl group. These groups may be substituted with halogen atoms, trialkylsilyl groups or the like. SF-2368 18 In the above formula, M is a transition metal atom selected from Group IV of the periodic table, preferably zirconium, titanium or hafnium of a Group IVB transition metal, L is a ligand coordinated to the transition metal, a is an integer of 1 or greater and is a 5 number of L, X is a group or an atom bonded to the transition metal and selected from a halogen, a hydrogen atom, a hydrocarbon group of 1 to 10 carbon atoms, a neutral, conjugated or non-conjugated diene of 10 or less carbon atoms, an anionic ligand and a neutral ligand capable of coordination with a lone pair, each X being the same or 10 different, and b is an integer of 1 or greater and is a number of X. In the formula (2) , L is a ligand coordinated to the transition metal, and at least one Lisa ligand having cyclopentadienyl skeleton. Examples of the ligands having cyclopentadienyl skeleton include a 15 cyclopentadienyl group; alkyl substituted cyclopentadienyl groups, such as methylcyclopentadienylgroup, dimethylcyclopentadienylgroup, trimethylcyclopentadienyl group, tetramethylcyclopentadienyl group, pentamethylcyclopentadienyl group, ethylcyclopentadienyl group, methylethylcyclopentadienyl group, propylcyclopentadienyl group, 20 methylpropylcyclopentadienyl group, butylcyclopentadienyl group, methylbutylcyclopentadienyl group and hexylcyclopentadienyl group; an indenyl group; a 4, 5, 6, 7 -tetrahydroindenyl group; and a fluorenyl group. These groups may be substituted with halogen atoms, trialkylsilyl groups or the like. SF-2368 21 When the compound represented by the formula (2) contains two ligands having cyclopentadienyl group, this compound is more specifically represented by the following formula (3) or (4). [0047] RZ [0048] In the above formula, M is a transition metal atom selected from Group IV of the periodic table, preferably zirconium, titanium or hafnium of a Group IVB transition metal, R1, R2, R3, R4, R5, R6, 10 R7, R°, R9 and R10 are each selected from hydrogen, a hydrocarbon group and a silicon-containing hydrocarbon group and may be the same or different, neighboring substituents among R1 to R10 may be bonded to each other to form a ring, X is a group or an atom selected from a halogen, a hydrogen atom, a hydrocarbon group of 1 to 10 carbon atoms, 15 a neutral, conjugated or non-conjugated diene of 10 or less carbon atoms, an anionic ligand and a neutral ligand capable of coordination with a lone pair, each X being the same or different, and n is 1 or 2 and is a number of X. [0049] SF-2368 22 (4) [0050] In the above formula, M is a transition metal atom selected from Group IV of the periodic table, preferably zirconium, titanium 5 or hafnium of a Group IVB transition metal, R1, R2, R3, R4, R5, R6, R7 and R8 are each selected from hydrogen, a hydrocarbon group and a silicon-containing hydrocarbon group and maybe the same or different, neighboring substituents among R1 to R8 may be bonded to each other to form a ring, X is a group or an atom selected from a halogen, a 10 hydrogen atom, a hydrocarbon group of 1 to 10 carbon atoms, a neutral, conjugated or non-conjugated diene of 10 or less carbon atoms, an anionic ligand and a neutral ligand capable of coordination with a lone pair, each X being the same or different, n is 1 or 2 and is a number of X, Q is selected from carbon, silicon and germanium, and 15 Y1 and Y2 are each selected from hydrogen, a hydrocarbon group and a silicon-containing group, may be the same or different and may be bonded to each other to form a ring. In the formulas (3) and (4) , the hydrocarbon group is preferably an alkyl group of 1 to 20 carbon atoms, an arylalkyl group of 7 to 20 20 carbon atoms, an aryl group of 6 to 20 carbon atoms or an alkylaryl 23 .om selected ml, titanium R4, R5, R6, n group and Jr different, each other halogen, a a neutral, n atoms, an tion with a or 2 and is manium, and n group and and may be preferably cup of 7 to n alkylaryl 0 carbon atoms, andmay contain one or more ring structures. ;uch groups include methyl, ethyl, n-propyl, isopropyl, y1, 1,1-dimethylpropyl, 2,2-dimethylpropyl, ropyl, 1-ethyl-l-methylpropyl, amethylpropyl, sec-butyl, tert-butyl, butyl, 1,1,3-trimethylbutyl, neopentyl, thyl, cyclohexyl, 1-methyl-l-cyclohexyl, 1-adamantyl, 2-methyl-2-adamantyl, menthyl, norbornyl, benzyl, rl, 1-tetrahydronaphthyl, .etrahydronaphthyl, phenyl, naphthyl and tolyl. formulas (3) and (4), the silicon-containing hydrocarbon ferably an alkylsilyl or arylsilyl group having 1 to 4 3 and 3 to 20 carbon atoms. Examples of such groups include _y1, tert-butyldimethylsilyl and triphenylsilyl. I present invention, R1, R2, R3, R4, R5, R6, R7, Re, R9 and rmula (3) are each selected from hydrogen, a hydrocarbon silicon-containing hydrocarbon group, and they may be [ifferent. Preferred examples of the hydrocarbon groups icon-containing hydrocarbon groups include those [ascribed. Ri, R2, R3, R4, R5, R6, R7 and RB in the formula z selected from hydrogen, a hydrocarbon group and a raining hydrocarbon group, and they may be the same or SF-2368 25 X is a group or an atom selected from a halogen, a hydrogen atom, a hydrocarbon group of 1 to 10 carbon atoms, a neutral, conjugated or non-conjugated diene of 10 or less carbon atoms, an anionic ligand and a neutral ligand capable of coordination with a lone pair, and 5 each X is the same or different . Examples of the halogens are fluorine, chlorine, bromine and iodine. Examples of the hydrocarbon groups include methyl, ethyl, n-propyl, isopropyl, 2-methylpropyl, 1,1-dimethylpropyl, 2,2-dimethylpropyl, 1,1-di.ethylpropyl, 1-ethyl-l-methylpropyl, 1,1,2,2-tetramethylpropyl, sec-butyl, 10 tert-butyl, l,l-dimethylbutyl, 1,1,3-trimethylbutyl, neopentyl, cyclohexylmethyl, cyclohexyl and 1-methyl-l-cyclohexyl. Examples of the neutral, conjugated or non-conjugated dienes of 10 or less carbon atoms include s-cis- or s-trans-r4-1,3-butadiene, s-cis- or s-trans-q4-1,4-diphenyl-l,3-butadiene, s-cis- or 15 s-trans-r14-3-methyl-1,3-pentadiene, s-cis- or s-trans-r,4-1,4-dibenzyl-l,3-butadiene, s-cis- or s -trans -rI4-2, 4 -hexadiene, s-cis- or s-trans-04-1,3-pentadiene, s-cis- or s-trans-r,4-1,4-ditolyl-1,3-butadiene, and s-cis- or s-trans-q 4-1,4-bis(trimethylsilyl)-1,3-butadiene. Examples of the 20 anionic ligands include alkoxy groups, such as methoxy, tert-butoxy and phenoxy; carboxylate groups, such as acetate and benzoate; and sulfonate groups, such as mesylate and tosylate. Examples of the neutral ligands capable of coordination with a lone pair include organic phosphorus compounds, such as trimethylphosphine, SF-2368 26 triethylphosphine, triphenylphosphine and diphenylmethylphosphine; and ethers, such as tetrahydrofuran, diethyl ether, dioxane and 1,2-dimethoxyethane. Each X may be the same or different. [0056] 5 n is 1 or 2 and is a number of X. [0057] Examples of the compounds represented by the formula (3) include cyclopentadienyl trichloride, cyclopentadienylzirconium trichloride, bis(cyclopentadienyl)titanium dichloride, 10 bis(cyclopentadienyl)zirconium dichloride, bis(pentamethylcyclopentadienyl)zirconium dichloride, (cyclopentadienyl)(pentamethylcyclopentadienyl)zirconium dichloride, bis(methylcyclopentadienyl)zirconium dichloride, bis(ethylcyclopentadienyl)zirconium dichloride, 15 bis(propylcyclopentadienyl)zirconium dichloride, bis(butylcyclopentadienyl)zirconium dichloride such as bis(n-butylcyclopentadienyl)zirconium dichloride, bis(dimethlcyclopentadienyl)zirconium dichloride such as bis(1,3-dimethlcyclopentadienyl)zirconium dichloride, 20 bis(diethylcyclopentadienyl)zirconium dichloride such as bis(1,3-diethylcyclopentadienyl)zirconium dichloride, bis(methylethylcyclopentadienyl)zirconium dichloride, bis(methylpropylcyclopentadienyl)zirconium dichloride such as bis (1-methyl-3-n-propylcyclopentadienyl) zirconium dichloride, and SF-2368 27 bis(methylbutylcyclopentadienyl)zirconium dichloride such as bis(1-methyl-3-n-butylcyclopentadienyl)zirconium dichloride. Examples of the compounds represented by the formula (4) include ethylenebis(indenyl)zirconium d.ichloride, 5 ethylenebis(1-indenyl)titanium dichloride, ethylenebis(4,5,6,7-tetrahydroindenyl)zirconium dichloride, dimethylsilylenebis(methylcyclopentadienyl)zirconium dichloride, dimethylsilylenebis (dimethylcyclopentadienyl) zirconium dichloride, dimethylsilylenebis(di-tert-butylcyclopentadienyl)zirconium 10 dichloride, dimethylsilylenebis(indenyl)zirconium dichloride, dimethylsilylenebis(2-methylindenyl)zirconium dichloride, dimethylsilylenebis (2-methyl-4, 5-benzindenyl) zirconium dichloride, dimethylsilylenebis (2-methyl-4-phenylindenyl) zirconiumdichloride, dimethylsilylenebis(2-methyl-4-naphthylindenyl)zirconium 15 dichloride, dimethylethylenebis(2-methylindenyl)zirconium dichloride, dimethylethylenebis (2-methyl-4, 5-benzindenyl) zirconium dichloride, dimethyl ethyl enebi s (2-methyl-4-phenylindenyl) zirconium dichloride, dimethylethylenebis(2-methyl-4-naphthylindenyl)zirconium 20 dichloride, isopropylidene(cyclopentadienyl)(fluorenyl)zirconium dichloride, isopropylidene(cyclopentadienyl)(3,6-di-t-butylfluorenyl)zirconi um dichloride, isopropylidene(methylcyclopentadienyl)(fluorenyl)zirconium SF-2368 27 bis(methylbutylcyclopentadienyl)zirconium dichloride such as bis(1-methyl-3-n-butylcyclopentadienyl)zirconium dichloride. Examples of the compounds represented by the formula (4) include ethylenebis(indenyl)zirconium dichloride, 5 ethylenebis(1-indenyl)titanium dichloride, ethylenebis(4,5,6,7-tetrahydroindenyl)zirconium dichloride, dimethylsilylenebis(methylcyclopentadienyl)zirconium dichloride, dimethylsilylenebis (dimethylcyclopentadienyl) zirconium dichloride, dimethylsilylenebis(di-tert-butylcyclopentadienyl)zirconium 10 dichloride, dimethylsilylenebis(indenyl)zirconium dichloride, dimethylsilylenebis(2-methylindenyl)zirconium dichloride, dimethylsilylenebis (2-methyl-4, 5-benzindenyl) zirconiumdichloride, dimethylsilylenebis (2-methyl-4-phenylindenyl) zirconiumdichloride, dimethylsilylenebis(2-methyl-4-naphthylindenyl)zirconium 15 dichloride, dimethylethylenebis(2-methylindenyl)zirconium dichloride, dimethyl ethyl eneb is (2-methyl-4, 5-benzindenyl) zirconium dichloride, dime thylethylenebis(2-methyl-4-phenylindenyl)zircon.ium dichloride, dimethylethylenebis(2-methyl-4-naphthylindenyl)zirconium 20 dichloride, isopropylidene(cyclopentadienyl)(fluorenyl)zirconium dichloride, isopropylidene(cyclopentadienyl)(3,6-di-t-butylfluorenyl)zirconi um dichloride, isopropylidene(methylcyclopentadienyl)(fluorenyl)zirconium SF-2368 30 tylfluorenyl)zirconium dichloride, di(p-tert-butylphenyl)methylene(cyclopentadienyl)(2,7-dimethylfl uorenyl)zirconium dichloride, di(p-tert-butylphenyl)methylene(cyclopentadienyl)(3,6-di-tert-bu 5 tylfluorenyl)zirconium dichloride, di(p-n-butylphenyl)methylene(cyclopentadienyl)(fluorenyl)zirconi um dichloride, di(p-n-butylphenyl)methylene(cyclopentadienyl)(2,7-di-tert-butyl fluorenyl)zirconium dichloride, 10 di(p-n-butylphenyl)methylene(cyclopentadienyl)(2,7-dimethylfluor enyl)zirconium dichloride, di(p-n-butylphenyl)methylene(cyclopentadienyl)(3,6-di-tert-butyl fluorenyl)zirconium dichloride, di(m-tolyl)methylene(cyclopentadienyl)(fluorenyl)zirconium 15 dichloride, di(m-tolyl)methylene(cyclopentadienyl)(2,7-di-tert-butylfluoreny 1)zirconium dichloride, di(m-tolyl)methylene(cyclopentadienyl)(2,7-dimethylfluorenyl)zir conium dichloride, 20 di(m-tolyl)methylene(cyclopentadienyl)(3,6-di-tert-butylfluoreny 1)zirconium dichloride, di(p-tolyl)methylene(cyclopentadienyl)(fluorenyl)zirconium dimethyl, di(p-tolyl)methylene(cyclopentadienyl)(octamethyloctahydrodibenz SF-2368 31 ofluorenyl)zirconium dichloride, di(p-tert-butylpheny.l)methylene(cyclopentadienyl)(cyclopentadien yl)(octamethyloctahydrodibenzofluorenyl)zirconium dichloride, di(p-tolyl)methylene(cyclopentadienyl)(octamethyloctahydrodibenz 5 ofluorenyl)zirconium dimethyl, di(p-tert-butylphenyl)methylene(cyclopentadienyl)(2,7-di-tert-bu tylfluorenyl)zirconium dichloride, di(p-tolyl)methylene(cyclopentadienyl)(2,7-di-tert-butylfluoreny 1)zirconium dimethyl, 10 di(p-isopropylphenyl)methylene(cyclopentadienyl)(3,6-di-tert-but ylfluorenyl)zirconium dichloride, di(p-tert-butylpheyl)methylene(cyclopentadienyl)(3,6-di-tert-but ylfluorenyl)zirconium dichloride, di(4-biphenyl)methylene(cyclopentadienyl)(fluorenyl)zirconium 15 dichloride, di(4-biphenyl)methylene(cyclopentadienyl)(2,7-di-tert-bt'utylfluor enyl)zirconium dichloride, di(4-biphenyl)methylene(cyclopentadienyl)(2,7-dimethylfluorenyl) zirconium dichloride, 20 di(4-biphenyl)methylene(cyclopentadienyl)(3,6-di-tert-butylfluor enyl)zirconium dichloride, cyclopentylidene(cyclopentadienyl)(2,7-di-tent-butylfluorenyl)zi rconium dichloride, cyclohexylidene(cyclopentadienyl)(2,7-di-tert-butylfluorenyl)zir SF-2368 32 conium dichloride, adamantylidene(cyclopentadienyl)(2,7-di-tert-butylfluorenyl)zirc onium dichloride, monophenylmonomethylmethylene(cyclopentadienyl)(2,7-di-tert-buty lfluorenyl)zirconium dichloride, dimethylmethylene(cyclopentadienyl)(2,7-di-tert-butylfluorenyl)z irconium dichloride, diphenylmethylene(cyclopentadienyl)(2,7-di-tert-butylfluorenyl)z irconium dichloride, di(p-tolyl)methylene(cyclopentadienyl)(2,7-di-tert-butylfluoreny 1)zirconium dichloride, diethylmethylene(cyclopentadienyl)(2,7-di-tert-butylfluorenyl)zi rconium dichloride, cyclopentylidene(cyclopentadienyl)(3,6-di-tert-butylfluorenyl)zi rconium dichloride, cyclohexylidene(cyclopentadienyl)(3,6-di-tert-butylfluos:enyl)zir conium dichloride, adamantylidene(cyclopentadienyl)(3,6-di-tert-butylfluorenyl)zirc onium dichloride, monophenylmonomethylmethylene(cyclopentadienyl)(3,6-di-tert-buty lfluorenyl)zirconium dichloride, dimethylmethylene(cyclopentadienyl)(3,6-di-tert-butylfluorenyl)z irconium dichloride, diphenylmethylene(cyclopentadienyl)(3,6-di-tert-butylfluorenyl)z SF-2368 33 irconium dichloride, di(p-tolyl)methylene.(cyclopentadienyl)(3,6-di-tert-butylfluoreny 1)zirconium dichloride, diethylmethylene(cyclopentadienyl)(3,6-di-tert-butylfluorenyl)zi 5 rconium dichloride, cyclopentylidene(cyclopentadienyl)(octamethyloctahydrodibenzoflu orenyl)zirconium dichloride, cyclohexylidene(cyclopentadienyl)(octamethyloctahydrodibenzofluo renyl)zirconium dichloride, 10 adamantylidene(cyclopentadienyl)(octamethyloctahydrodibenzofluor enyl)zirconium dichloride, monophenylmonomethylmethylene(cyclopentadienyl)(octamethyloctahy drodibenzofluorenyl)zirconium dichloride, dimethylmethylene(cyclopentadienyl)(octamethyloctahydrodibenzofl 15 uorenyl)zirconium dichloride, diphenylmethylene(cyclopentadienyl)(octamethyloctahydrodibenzofl uorenyl)zirconium dichloride, di(p-tolyl)methylene(cyclopentadienyl)(octamethyloctahydrodibenz ofluorenyl)zirconium dichloride, 20 diethylmethylene(cyclopentadienyl)(octamethyloctahydrodibenzoflu orenyl)zirconium dichloride, cyclopentylidene(cyclopentadienyl)(octamethyltetrahydrodicyclope ntafluorenyl)zirconium dichloride, cyclohexylidene(cyclopentadienyl)(octamethyltetrahydrodicyclopen SF-2368 34 tafluorenyl)zirconium dichloride, adamantylidene(cyclopentadienyl)(octamethyltetrahydrodicyclopent afluorenyl)zirconium dichloride, 5 monophenylmonomethylmethylene(cyclopentadienyl.)(octamethyltetrah ydrodicyclopentafluorenyl)zirconium dichloride, dimethylmethylene(cyclopentadienyl)(octamethyltetrahydrodicyclop entafluorenyl)zirconium dichloride, diphehylmethylene(cyclopentadienyl)(octamethyltetrahydrodicyclop 10 entafluorenyl)zirconium dichloride, di(p-tolyl)methylene(cyclopentadienyl)(octamethyltetrahydrodicyc lopentafluorenyl)zirconium dichloride, diethylmethylene(cyclopentadienyl)(octamethyltetrahydrodicyclope ntafluorenyl)zirconium dichloride, 15 cyclopentylidene(cyclopentadienyl)(dibenzofluorenyl)zirconium dichloride, cyclohexylidene(cyclopentadienyl)(dibenzofluorenyl)zirconium dichloride, adamantylidene(cyclopentadienyl)(dibenzofluorenyl)zirconium 20 dichloride, monophenylmonomethylmethylene(cyclopentadienyl)(dibenzofluorenyl )zirconium dichloride, dimethylmethylene(cyclopentadienyl)(dibenzofluorenyl)zirconium dichloride, SF-2368 35 diphenylmethylene(cyclopentadienyl)(dibenzofluorenyl)zirconium dichloride, di(p-tolyl)methylene(cyclopentadienyl)(dibenzofluorenyl)zirconiu m dichloride, 5 diethylmethylene(cyclopentadienyl)(dibenzofluorenyl)zirconium dichloride, ethylene(cyclopentadienyl)(fluorenyl)zirconium dichloride, ethylene(cyclopen.tadienyl)(2,7-di-tert-butylfl.uorenyl)zirconium dichloride, 10 ethylene(cyclopentadienyl)(3,6-di-tert-butylfluorenyl)zirconium dichloride, ethylene(cyclopentadienyl)(octamethyltetrahydrodicyclopentafluor enyl)zirconium dichloride, ethylene(cyclopentadienyl)(octamethyloctahydrodibenzofluorenyl)z 15 irconium dichloride, propylene(cyclopentadienyl)(fluorenyl)zirconium dichloride, propylene(cyclopentadienyl)(2,7-di-tert-butylfluorenyl)zirconium dichloride, propylene(cyclopentadienyl)(3,6-di-tert-butylfluorenyl)zirconium 20 dichloride, propylene(cyclopentadienyl)(octamethyltetrahydrodicyclopentafluo renyl)zirconium dichloride, propylene(cyclopentadienyl)(octamethyloctahydrodibenzofluorenyl) zirconium dichloride, '-2368 36 ethyl)(p-tolyl)methylene(cyclopentadienyl)(octamethyloctahydro benzofluorenyl)zirconium dichloride, Methyl)(phenyl)methylene(cyclopentadienyl)(octamethyloctahydrod eenzofluorenyl)zirconium dichloride, Lethyl)(p-tolyl)methylene(cyclopentadienyl)(2,7-di-tert-butylfl renyl)zirconium dichloride, iethyl)(phenyl)methylene(cyclopentadienyl)(2,7-di-tert-butylflu 'enyl)zirconium dichloride, iethyl)(p-tolyl)methylene(cyclopentadienyl)(3,6-di-tert-butylf1 )renyl)zirconium dichloride, eethyl)(phenyl)methylene(cyclopentadienyl)(3,6-di-tert-butylflu ;enyl)zirconium dichloride, aethyl)(benzyl)methylene(cyclopentadienyl)(3,6-di-tert-butylflu ;enyl)zirconium dichloride, aethyl)(benzyl)methylene(cyclopentadienyl)(3,6-di-tert-butylflu °enyl)zirconium dichloride, nethyl)(benzyl)methylene(cyclopentadienyl)(2,7-di-tert-butylflu =enyl)zirconium dichloride, nethyl)(benzyl)methylene(cyclopentadienyl)(2,7-di-tert-butylflu ^enyl)zirconium dichloride, nethyl)(benzyl)methylene(cyclopentadienyl)(octamethyloctahydrod Denzofluorenyl)zirconium dichloride, and nethyl)(benzyl)methylene(cyclopentadienyl)(octamethyloctahydrod Denzofluorenyl)zirconium dichloride. SF-2368 [0062] [0063] (5) (6) (7) 38 SF-2368 (8) [0065] [0066] 39 5 In the polymerization examples of the present invention, the compound (6) is described as (methyl)(p-tolyl)methylene(cyclopentadienyl)(octamethyloctahydro dibenzofluorenyl)zirconium dichloride. [0067] 10 The structure of the transition metal compound obtained is determined by 270 MHz 1H-NMR (GSH-270 of JEOL Ltd.) and FD-mass spectrometry (SX-102A of JEOL Ltd.). [0068] SF-2368 (8) [0065] (9) [0066] 39 5 In the polymerization examples of the present invention, the compound (6) is described as (methyl)(p-tolyl)methylene(cyclopentadienyl)(octamethyloctahydro dibenzofluorenyl)zirconium dichloride. [0067] 10 The structure of the transition metal compound obtained is determined by 270 MHz 1H-NMR (GSH-270 of JEOL Ltd.) and FD-mass spectrometry (SX-102A of JEOL Ltd.). [0068] SF-2368 42 wherein Ra and Rb may be the same as or different from each other and are each a hydrocarbon group of 1 to 15 carbon atoms, preferably 1 to 4 carbon atoms, and m is preferably a number of 1.5<-m<_3. RamAlX23-m (14) 5 wherein Ra is a hydrocarbon group of 1 to 15 carbon atoms, preferably 1 to 4 carbon atoms, X2 is a halogen atom, and m is preferably a number of 010 101 Ex. 2 45. 44. 2 10. 3 33 326 low >10 Ex. 3 49. 7 40. 0 10. 3 2. 7 33 329 low 9. 8 >10 Ex. 4 45. 4 44. 2 10. 4 44 328 medium >10 SF-2368 [0227] Table 2 102 I Comp. Ex. 1 Comp. Ex. 2 Comp. Ex. 3 Comp Ex. 4 Comp. Ex. 5 Content of PAO (i) (% by mass) 32. 3 23. 6 34. 0 51. 2 33. 2 Content of polymer (i) (% by mass) 57. 1 66. 1 55. 7 38. 5 56. 5 Content of ester (% by mass) 10. 6 10. 3 10. 3 10. 3 10. 3 Content of extreme pressure agent (% by mass) 6. 0 2. 7 2. 7 2. 7 2. 7 Content of boron (ppm) 76 33 33 33 < 1 40°C Dynamic viscosity (mm2/s) 326 315 320 31 9 325 -30°C Viscosity (mPa-s) high medium low low medium Shear stability (dynamic viscosity decrease ratio, %) 2, 3 1 0. 4 17. 9 51 2. 3 Micropitting failure load stage > 10 > 1 0 > 1 0 > 1 0 8 SF-2368 103 [Q228] Polymerization Examples 1 to 3 are excellent in viscosity index, namely, temperature viscosity properties, as comparedwith the polymer using a monomer of 6 carbon atoms, i.e., 1-hexene, said polymer being 5 shown in Polymerization Example 4. Accordingly, it is apparent that the low-temperature viscosity properties of the lubricating oil composition of the present invention are superior to those of the lubricating oil composition containing a polymer using 1-hexene as a monomer. 10 [0229] Examples 1 to 4 (Table 1) are excellent in -30°C viscosity as compared with Comparative Example 1 (Table 2) having a boron content of more than 75 ppm. [0230] 15 Further, Examples 1 to 4 (Table 1) are excellent in shear stability as compared with Comparative Examples 2 to 4 (Table 2) in each of which a polymer using 1-decene as a monomer is contained in the lubricating oil composition. [0231] 20 Furthermore, Examples 1 to 4 (Table 1) are excellent in anti-micropitting performance as compared with Comparative Example 5 (Table 2) having a low boron content. [Description of Reference Signs] [0232] 5 10 15 SF-2368 104 1:, rotor nose 2: encasing opening 3: roller bearing 4: rotor carrier 5: azimuth bearing 8: tow bin 9: driving stage 10: driven stage 11: generator 12: sun gear 13: hollow gear 14: hollow gear 15: power transmission device casing 16: planetary gear carrier 17: vibration damping device 18: fixed rail SF-2368 105 Claims [Claim 1] A lubricating oil composition comprising the following (i) to (iii) , having a kinematic viscosity at 40°C of not less than 30 mm2/s 5 but not more than 750 mmZ/s and containing boron atoms in an amount of not less than 5 ppm but not more than 75 ppm, (i) 90to10%bymassofa (co)polymerhavingakinematicviscosity at 100°C of not more than 45 mm2/s and having an acid value of less than 0.1 mgKOH/g, not less than 60% by mol of its constituent units 10 being derived from 1-decene, (ii) 5to85%bymassofa (co)polymerhavingakinematicviscosity at 100°C of not less than 35 mm2/s but not more than 1,500 mm2/s and having a molecular weight distribution, as measured by gel permeation chromatography, of not more than 1.8, not less than 90% by mol of 15 its constituent units being derived from 1-octene, and (iii) 5 to 15% by mass of a fatty acid ester having a kinematic viscosity at 100°C of not more than 20 mm 2/s, with the proviso that the total amount of (i) to (iii) is 100% by,mass. 20 [Claim 2] The lubricating oil composition as claimed in claim 1, which further comprises one or more kinds of extreme pressure agents. [Claim 3] The lubricating oil composition as claimed in claim 1 or 2, SF-2368 106 wherein the kinematic viscosity of the lubricating oil composition at 40°C is not less than 190 mm2/s but not more than 750 mm2/s. [Claim 4] The lubricating oil composition as claimed in any one of claims 5 1 to 3, wherein the kinematic viscosity of the lubricating oil composition at 40°C is not less than 288 mm2/s but not more than 352 mm2/s, and a kinematic viscosity decrease ratio of the lubricating oil composition at 40°C after a KRL shear stability test, as measured in accordance with DIN 52350-6, is less than 10%. 10 [Claim 5] The lubricating oil composition as claimed in any one of claims 1 to 4, wherein the kinematic viscosity of the (co)polymer (ii) at 100°C is not less than 150 mm2/s but not more than 1,200 mmZ/s. [Claim 6] 15 The lubricating oil composition as claimed in any one of claims 1 to 5, wherein the kinematic viscosity of the (co)polymer comprising 1-decene at 100°C is not more than 11 mm2/s. e [Claim 7] (i) A gear for a wind power generator, which is filled with the 20 lubricating oil composition as claimed in any one of claims 1 to 6.