DESCRIPTION Title of Invention: GREASE COMPOSITION
5 Technical Field
[0001] The present invention relates to a grease composition.
Background Art
[0002] Conventionally, a grease has been used as a lubricant in a
10 bearing, a constant velocity joint and the like with which an apparatus
such as a driving force transmission mechanism is provided. [0003] In recent years, the apparatus such as a driving force transmission mechanism has tended to be increasmgly advanced, higher in performance, higher in speed, smaller in size and longer in lifetime,
15 and a bearing, a constant velocity joint and the like have been used
under a high load condition. Therefore, in order to maintain stable lubrication characteristics for a long period of time, levels required for characteristics of a grease, in particularj stability and lubricity as basic performances have been further higher.
20 [0004] In addition, in an apparatus with a large number of bearing
systems rotated at a relatively low speed and bearing positions, the energy saving effect due to a reduction in friction is high. Then, a measure by a reduction in viscosity of a base oil for use in a grease is studied. The reduction in viscosity, however, deteriorates oil film
25 formability in a lubrication part, and thus has limitations with the
occuiTence of a lubrication failure in mind.

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[0005] From the above, a grease that is superior in stability and
lubricity and exhibits low friction characteristics is demanded.
[0006] With respect to the enhancement in stability of a gi^ease, Patent
Literature I discloses a grease in which a thickener, (A) a
5 dialkyldithiocarbamate and (B) an aromatic amine compound are added
to a base oil with a polyol ester and an alkyl phenyl ether mixed. Patent Literature 2 discloses a grease composition in which a base oil includes a polyoxyalkylene glycol ether and an additive includes a quinoline type compound and a benzotriazole type compound, Patent Literature 3
10 discloses a grease in which a base oil is a specific condensed phosphoric
acid ester and a specific thickener such as organic bentonite is blended therewith, Patent Literature 4 discloses a lubricant containing in a base oil, fluorinated calcium phosphate also having a thickening effect, Patent Literatui'e 5 discloses a lubricant composition containing a
15 thickener and trimagnesium phosphate in a base oil, Patent Literature 6
discloses a grease contairdng a thickener and a base oil including a specific poly-a-olefm and a specific ethylene-a-olefin copolymer, and Patent Literature 7 discloses a grease in which a base oil is a specific perfluoropolyether, respectively.
20 [0007] With respect to the enhancement in lubricity of a grease, Patent
Literature 8 discloses a grease containing a powdery oxymolybdenum dithiocarbamate sulfide composition of a specific structure, Patent Literature 9 discloses a conductive grease composition having good lubricity, including an ionic liquid, an alkaline eaith metal salt of a
25 higher fatty acid, and a dispersant, Patent Literature 10 discloses a
grease mixed with a particulate thickening substance whose rate of

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increase in viscosity can satisfy the condition expressed by a specific
expression, Patent Literature 11 discloses a grease containing a
thickener, a specific polj^etrafluoroethyiene resin powder and a specific
zinc dialkyldithiophosphate in a synthetic base oil, Patent Literature 12
5 discloses a gi'case in which a base oil is a perfluoropolyether and a
thickener is a specific fluororesin, and Patent Literature 13 discloses a grease composition containing a silicone oil, a polyurethane powder and synthetic mica, respectively.
10 Citation List
Patent Literature
[0008] [Patent Literature 1] Japanese Patent Application Laid-Open No.
9-3468
[Patent Literature 2] Japanese Patent Application Laid-Open No.
15 2006-249376
[Patent Literature 3] Japanese Patent Application Laid-Open No.
2010-174209
[Patent Literature 4] Japanese Patent Application Laid-Open No.
2011-21149
20 [Patent Literature 5] Japanese Patent Application Laid-Open No.
2011-57762
[Patent Literature 6] Japanese Patent Application Laid-Open No.
2011-148908
[Patent Literature 7] Japanese Patent Application Laid-Open No.
25 2011-256397
[Patent Literature 8] Japanese Patent Application Laid-Open No.

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2004-2872
[Patent Literature 9] Japanese Patent Application Laid-Open No. 2007-99826
[Patent Literature 10] Japanese Patent Application Laid-Open No.
5 2007-231207
[Patent Literature 11] Japanese Patent Application Laid-Open No. 2008-101122
[Patent Literature 12] Japanese Patent Application Laid-Open No.
2010-65171
10 [Patent Literature 13] Japanese Patent Application Laid-Open No.
2010-138320
Summary of Invention Technical Problem
15 [0009] According to studies by the present inventor, however, the
greases described in Patent Literatures 1 to 13 above cannot be said to be necessarily sufficient in terms of stability and lubiicity under severe use conditions, and have room for improvement in simultaneously satisfying these characteristics and friction characteristics.
20 [0010] The present invention has been made in view of the problems of
the prior art above, and an object thereof is to provide a grease composition that is good in stability, lubricity and friction characteristics and excellent in long-teim reliability even under severe use conditions as compared with a conventional grease.
25
Solution to Problem

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[0011] The present inventors have found that the above problems are
solved by blending a thickener, an epoxy compound and an antiwear
additive with a specific base oil in respective specific proportions to
thereby result in improvements in stability lubricity and friction
5 characteristics of a gi^ease, leading to completion of the present
invention.
[0012] That, is, the present invention provides grease compositions according to the following [1] to [10]. [1] A grease composition comprising at least one base oil selected from
10 a mineral oil and a synthetic oil, and, based on the total amoimt of the
grease composition, 2 to 35% by mass of a thickener, 0.05 to 5% by mass of an epoxy compound and 0.1 to 20% by mass of an antiwear additive. [2] The grease composition according to [1], wherein the epoxy
15 compound is at least one selected from a phenyl glycidyl ether type
epox>'^ compound, an alkyl glycidyl ether type epoxy compound, a glycidyl ester type epoxy compound, an alicycHc epoxy compound, an epoxidized aliphatic monoester and an epoxidized vegetable oil. [3] The grease composition according to [2], wherein the epoxy
20 compound is an alkyl glycidyl ether represented by the following
formula (1):
R—^O-—CH—CH2
\/ (1)
O
wherein R represents a linear or branched alkj'l group having 6 to 20
carbon atoms.
25 [4] The grease composition according to [3], wherein the epoxy

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compound is at least one selected fi:om octyl glycidyl ether,
2-ethylhexyl glycidyl ether, nonyl glycidyl ether, decyl glycidyl ether,
undecyl glycidyl ether and dodecyl glycidyl ether.
[5] The grease composition according to any one of [1] to [3], wherein
5 the antiwear additive is at least one selected from an oxygen-containing
compound, a nitrogen-containing compound, an organophosphorus compound, an organosulfur compound, an organomolybdenum compoimd, an alkaline earth metal compound and an organozinc compound.
10 [6] The gi'ease composition according to [5], wherein the
oxygen-containing compound is at least one selected from an ester, an alcohol, an ether and a carboxylic acid; the nitrogen-containing compound is at least one selected from an aliphatic amine, an aliphatic amide and an aliphatic imide; the organophosphorus compound is at
15 least one selected fi'om a phosphoric acid ester, a phosphorous acid ester
and an acidic phosphoric acid ester amine salt; the organosulfur compound is at least one selected from a sulfrde compound, and sulfiiiized fat and oil; the organomolybdenum compound is at least one selected from molybdenum dithiocarbamate and molybdenum
20 dithiophosphate; the alkaline earth metal compound is at least one
selected fi'om alkaline earth metal sulfonate salt, phenate salt and salicylate salt; and the organozinc compound is at least one selected from a zinc dialkyl, a zinc dialkyldithiophosphate and a zinc dialkyldithiocarbamate.
25 [7] The grease composition according to any one of [1] to [3], wherein
the antiwear additive is a solid lubricant.

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[8] The grease composition according to 17], wherein the solid lubricant
is at least one selected from molybdenum disulfide, graphite, a
tetrafluoroethylene resin powder and boron nitride.
[9] The grease composition according to any one of [1] to [8], wherein
5 the synthetic oil is at least one selected from a hydrocarbon oil, a
diester, a polyol ester and a polyaUcylene glycol compound.
[10] The grease composition according to any one of [1] to [8], wherein
the thickener is at least one selected fi'om lithium soaps, calcium soaps,
aluminum soaps and a urea compound.
10 [11] The grease composition according to [5], containing, as the
antiwear additive, an organomolybdenum compound and an organozinc
compound.
[12] The grease composition according to [5], containing, as the
antiwear additive, an organomolybdenum compound, an organozinc
15 compound and an organosulfur compound.
Advantageous Effects of Invention
[0013] According to the present invention, it is possible to provide a
grease composition that is good in stability, lubricity and friction
20 characteristics and excellent in long-term reliability even under severe
use conditions as compared with a conventional grease.
Description of Embodiments
[0014] Hereinafter, a preferred embodiment of the present invention is
25 described in detail.
[0015] A grease composition according to an embodiment of the
7

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present invention comprises at least one base oil selected from a mineral
oil and a synthetic oil, and based on the total amount of the gi'ease
composition, 2 to 3 5% by mass of a thickener, 0.05 to 5% by mass of an
epoxy compound and 0.1 to 20% by mass of an antiwear additive.
5 [0016] [Base oil]
As the base oil in the present embodiment, a mineral oil and/or a synthetic oil for use in a lubricating oil may be used. [0017] The mineral oil includes a paraffmic base oil, a naphtlienic base oil and a mixed base oil. These are each a refmed lubiicating oil
10 fraction obtained by subjecting a crude oil to distillation at ordinary
pressure and fiirther distillation at reduced pressure and treating the resulting lubricating oil fraction by an appropriate combination of lubricating oil-refining procedures such as solvent deasphalting, solvent extraction, hydrorefining, hydrocracking, solvent dewaxing,
15 hydrodewaxing and a clay treatment, and may be suitably used. In
particular, a step of controlling the composition corresponds to solvent extraction, hydrorefining and hydrocracking, a step of controlling low temperature chamcteristics such as a pour point corresponds to solvent dewaxing and hydrodewaxing for removal of the wax content, and a
20 clay treatment is a step of removing the niti-ogen content mainly to
enhance the stability of the base oil.
[0018] In addition, examples include a lubricating base oil such as a wax-cracked/isomerized mineral oil obtained by hydrocracking and/or isomerizing a raw material containing a wax mainly including
25 n-paraffins, such as a slack wax or GTL "WAX (gas to liquid wax)
produced by a Fischer-Tropsch process or the like. A refmed

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lubricating oil fi:action having a different property, obtained from a combination of vaiious raw materials and various refining procedures, may be used singly or in combinations of two or more, and is a suitable base oil.
5 [0019] In addition, the synthetic oil includes esters such as monoesters,
diesters and polyol esters, ethers such as polyoxyalkylene glycols, polyvinyl ethers, dialkyl diphenyl ethers and polyphenylethers, and hydrocarbon oils such as poly-a-olefms (PAO), an ethylene-a-olefm oligomer, alkylbenzenes and alkylnaphthalenes.
10 [0020] Esters are compounds having various molecular stmctures, and
each of them has particular viscosity characteristics and low temperature characteristics and is a base oil that is characterized by being high in flash point as compared with a hydrocarbon type base oil whose viscosity is the same. Esters may be each obtainable by a
15 dehydration condensation reaction of an alcohol with a carboxylic acid
such as a fatty acid, bnt, in the present invention, a suitable base oil component includes diesters of dibasic acids and monohydric alcohols, polyol esters of polyols (m particular, neopentyl polyol) and monovalent fatty acids, or complex esters of polyols, polyvalent basic acids and
20 monohydric alcohols (or monovalent fatty acids) in terms of chemical
stability.
[0021] Dibasic acids include adipic acid, azelaic acid, sebacic acid and dodecanedioic. acid, and monohydric alcohols Include, as linear monohydric alcohols, butanol, pentanol, hexanol, octanol and decanol,
25 and, as branched monohydric alcohols, 2-ethylhexanol,
3,5,54rimethylhexanol and isodecanol.

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[0022] Among monovalent fatty acids, specifically, linear fatty acids
include butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid,
octanoic acid, nonanoic acid and oleic acid, and branched fatty acids
include branched butanoic acid, branched pentanoic acid, branched
5 hexanoic acid, branched heptanoic acid, branched octanoic acid and
branched nonanoic acid. Specifically, a- and/or p-branched fatty acids include isobutanoic acid, .2-methylbutanoic acid, 2-methylpentanoic acid, 2-methylhexanoic acid, 2-ethylpentanoic acid, 2-methylheptanoic acid, 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid. As
10 monovalent fatty acids, saturated fatty acids having 4 to 18 carbon
atoms, preferably 6 to 12 carbon atoms, can be used. [0023] As polyhydric alcohols, polyhydric alcohols having 2 to 6 hydroxyl groups, polyhydric alcohols having 4 to 12 carbon atoms, are preferably used. Specifically, polyhydric alcohols include hindered
15 alcohols such as neopentyl glycol, trimethylolethane,
trimethylolpropane, trimethylolbutane, di-(trunethylolpropane), pentaeiythritol and di-(pentaerythritoi).
[0024] Ethers mclude polyalkylene glycols, polyvinyl ethers and dialkyl diphenyl ethers. Polyalkylene glycols kiclude polypropylene
20 glycol, polyethylene glycol, and a copolymer of propylene oxide and
ethylene oxide. A compound, in which the hydroxyl group at one end is etherified and the hydroxyl group at the remaining end remains as it is, is commonly used, but a compound in which the hydroxy! gi'oups at both ends ai*e etherified is preferable because of being low in
25 hygroscopicity, and the backbone thereof is more preferably an
oxypropyiene type than an oxyethyiene type high in hygroscopicity. In
10

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the present embodiment, a polyalkylene glycol compound may be
suitably used.
[0025] Among hydrocarbon oils, poly-a-olefins (PAOs) are widely
used, and are polymers of a-olefms and thus are characterized by the
5 degree of polymerization. While alkylbenzenes and alkylnaphthalenes
are used in the field of a specific lubricating oil, they are classified to a
linear type and a branched type depending on the structure of the alkyl
group and are different in terms of characteristics, and thus are used
depending on the purpose.
10 [0026] Among these base oils, a mineral oil, diesters, polyol esters, a
polyalkylene glycol compound or poly-a-olefins may be preferably
used.
[0027] In the present embodiment, one of the mineral oil or one of the
synthetic oil may be used singly. In addition, two or more selected
15 from the gt'oup consisting of the mineral oil and the synthetic oil may be
appropriately combined and blended in appropriate proportions so as to
satisfy various performances required depending on the application.
Herein, a plurality of the mineral oil type base oils and a plurality of the
synthetic oil type base oils may be each used.
20 [0028] The kinematic viscosity of the base oil at 40°C is preferably 3 to
2000 mm /s, more preferably 5 to 1000 mm /s and further preferably 8
to 500 mm^/s in order that the grease composition maintains an
appropriate viscous property.
[0029] The content of the base oil is preferably 60% by mass or more
25 and more preferably 70% by mass or more based on the total amount of
the grease composition. In addition, the content of the base oil is
11

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preferably 95% by mass or less and more preferably 90% by mass or
less based on the total amount of the composition. If the content is
within this range, lubricity is excellent and it is possible to stably
. provide a grease.
5 [0030] [Thickener]
The thickener for use in the grease composition according to the present embodiment is not particularly limited, and all thickeners usually used for a grease composition may be used. Examples of the thickener include metal soaps including lithiimi, calcium, sodium or
10 aluminum, a urea compound, an imide compound, Bentone, silica gel, a
non-soap thickener such as a fluorinated thickener typified by polytetrafluoroethylene, and furthermore an amide compound that is liquid at a temperature equal to or higher than the melting point of the compound and is a gel-like grease at room temperature. Among them,
15 . metal soaps and a urea compound are preferable. In addition, among
metal soaps, lithium soaps are particularly preferable. [0031] Lithium soaps include lithium soaps and lithium complex soaps. Lithium soaps include lithium metal soaps such as lithium 12-hydroxystearate and lithium stearate, and lithium complex soaps
20 include lithium soaps with a mixture of a monovalent carboxylic acid
and a polyvalent carboxylic acid (preferably, divalent carboxylic acid), specifically, a mixture of a reaction product of 12-hydroxystearic acid and lithium hydroxide and a reaction product of azeiaic acid and lithium hydroxide, and the like.
25 [0032] The m*ea compound includes a diurea compound, and in
particular, examples of the diurea compound include a diurea compound
12

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obtained by reacting an aromatic amine^ an aliphatic amine, an alicyclic
amine or a mixture of two or more of them with an aromatic
diisocyanate. Examples of the aromatic diisocyanate include tolyiene
diisocyanate, diphenylmethane diisocyanate and naphthalene
5 diisocyanate, examples of the aromatic amine include p-toluidine,
aniline and naphthylamine, examples of the aliphatic amine include octylaminCj nonylamine, decylamine, undecylamine, dodecylamine, tiidecyiamine and tetradecylamine, and examples of the alicyclic amine include cyclohexylamine and methylcyclohexylamine.
10 [0033] These thickeners are thickeners that are balanced in terms of
characteristics and suitable for practical use in terms of availability and cost. In the present embodiment, the thickener may be used singly or in combinations of two or more. The content of the thickener can be appropriately selected so as to be necessar)'- for achieving required
15 consistency, but is preferably 2 to 35% by mass, preferably 5 to 30% by
. mass and further preferably 5 to 25% by mass based on the total amount of the grease composition. [0034] [Epoxy compound]
The grease composition according to the present embodiment
20 comprises an epoxy compound, hi the present embodiment, the epoxy
compoimd and an antiwear additive are used in combination while the base oil and the thickener are combined, thereby enabling to enhance stability and wear resistance, and also to simultaneously satisfy these characteristics and friction characteristics. Herein, the epoxy
25 compound itself does not usually exhibit the effect of enhancing wear
resistance. In addition, the present inventor has confirmed that the
13

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grease composition according to the present embodiment is excellent in wear resistance as compared with the case where no epoxy compound is used and the antiwear additive is used singly. It is thus found that the above effect by the grease composition according to the present
5 embodiment is a synergetic effect by use of the epoxy compound and
the antiwear additive in respective specific contents in combination, and a special effect that is not exerted by a conventional grease composition. [0035] The type of the epoxy compound includes an alkyl glycidyl ether type epoxy compound, a phenyl glycidyl ether type epoxy
10 compound, a glycidyl ester type epoxy compound, an alicyclic epoxy
compoimd, an epoxidized fatty acid monoester and an epoxidized vegetable oil.
[0036] The alkyl glycidyl ether type epoxy compound specifically includes hexyl glycidyl ether, octyl glycidyl ether, 2-ethylhexyl glycidyl
15 ether, nonyl glycidyl ether, decyl glycidyl ether, undecyl glycidyl ether,
dodecyl glycidyl ether, tridecyl glycidyl ether, tetradecyl glycidyl ether, oleyl glycidyl ether, neopentyl glycol diglycidyl ether, trimethyiolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, 1,6-hexanediol diglycidyl ether, sorbitol polyglycidyl ether,
20 polyalkylene glycol monoglycidyl ether and polyalkylene glycol
diglycidyl ether.
[0037] The phenyl glycidyl ether type epoxy compound includes phenyl glycidyl ether, methylphenyl glycidyl ether, ethylphenyl glycidyl ether, propylphenyl glycidyl ether and butylphenyl glycidyl ether.
25 [0038] The glycidyl ester type epoxy compound specifically includes
phenyl glycidyl esters, alkyl glycidyl esters and alkenyl glycidyl esters,
14

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and examples Include glycidyl-2,2-dimethyl octanoate, glycidyl
benzoate, glycidyl acrylate and glycidyl methacrylate. Examples
include alkyl glycidyl esters in which the number of carbon atoms in the
alkyl gi'oup is 4 to 18, in particular, 6 to 12.
5 [0039] The alicyclic epoxy compound specifically includes
1,2-epoxycyclohexane, 1,2-epoxycyclopentane, 3,4-epoxycyclohexyl
methyl-3 ',4'-epoxycyclohexane carboxylate,
bis(3j4"epoxy-6-methyIcyclohexyl methyl)adipate,
2-(7-oxabicyclo[4,l,0]hept-3-yl)-spiro(l,3~dioxane"5,3'-[7]oxabicyclo[4
10 ,1,0]heptane, 4-(l'-methylepoxyethyl)-1,2-epoxy-2-methylcyclohexane
and 4-epoxyethyl-152-epoxycyclohexane. Examples include
derivatives of epoxycycloaUcanes having 5 to 7 carbon atoms. [0040] Epoxidized fatty acid monoesters include esters of epoxidized fatty acids having 12 to 20 carbon atoms and alcohols having 1 to 8
15 carbon atoms, or phenols or alkyl phenols, and examples include butyl,
hexyl, benzyl, cyclohexyl, methoxyethyl, octyl, phenyl and butyl phenyl esters of epoxy stearic acid.
The epoxidized vegetable oil includes an epoxy compound of a vegetable oil such as a soybean oil, a flaxseed oil or a cotton seed oil.
20 [0041] In the present embodiment, the epoxy compound incorporates a
carboxylic acid or the like produced along with degradation of the grease into the molecule to stabilize the carboxylic acid or the like, and thus suppresses production of a component that causes corrosion weai' and suppresses degradation of the additive to thereby contribute to an
25 enhancement in lubricity.
[0042] Furthermore, the present inventor has found that alkyl glycidyl
15

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ethers among the epoxy compounds exliibit a different behavior from
other types of epoxy compounds, and result in not only an enhancement
in lubricity by stabilization but also a significant increase in the effect of
the antiwear additive. In particular, an alkyl glycidyl ether represented
5 by the following formula (1) is preferable because of resulting in not
- only an enhancement m stability but also a large effect of increasing wear resistance, and fdithermore an alkyl glycidyl ether in which R in the formula (1) represents an alkyl group having 8 to 12 carbon atoms is more preferable.
R—o—CH—CH2
\ / H)
10 O
[wherein R represents a linear or branched alkyl group having 6 to 20
carbon atoms,]
[0043] PrefeiTcd alkyl glycidyl ethers include octyl glycidyl ether,
2-ethylhexyl glycidyl ether, nonyl glycidyl ether, decyl glycidyl ether,
15 undecyl glycidyl ether and dodecyl glycidyl ether,
[0044] In the present embodiment, the epoxy compound may be used singly or may be used in combinations of two.or more. [0045] The content of the epoxy compound is 0.05 to 5% by mass, preferably 0.1 to 3% by mass and more preferably 0.1 to 2% by mass
20 based on the total amount of the grease composition. If the content is
low, no effect of enhancing stability and wear resistance is exerted, and if the content is too high, chai'acteristics as the grease are not balanced, for example, an organic material in a mechanical system is swollen. [0046] [Antiwear additive]
25 The grease composition according to the present embodiment
16

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comprises an antiwear additive. A preferred antiwear additive includes an oxygen-containing compound, a nitrogen-containing compound, an organophosphorus compound, an organosulfiir compound, an organomolybdenum compound, a calcium compound and an organozinc
5 compound. In addition, a solid lubricant may also be preferably used.
Herein, the antiwear additive may be classified to an oiliness agent, an antiwear agent and an extreme pressure agent, but such classification is not necessarily critical. In addition, one antiwear additive may correspond to two or three of an oiliness agent, an antiwear agent and an
10 extreme pressure agent. The epoxy compound for use in the present
invention is excluded from the antiwear additive in the present invention.
[0047] Among the antiwear additives, the oxygen-containing compound includes higher fatty acids such as oleic acid and stearic acid, higher
15 alcohols such as oleyl alcohol, esters such as glycerol monooleate, and
ethers such as glycerol monooleyl ether. These oxygen-containing compounds are typically configured from an oxygen-containing polar group such as a hydroxy! group, a carboxylic acid group, an ether group or an ester group, and a saturated or unsaturated hydrocarbon gfoup
20 having 12 to 24 carbon atoms. It is expected in these
oxygen-containing compounds that the polar gi-oup adsorbs to the surface of a metal sliding portion and the hydrocarbon group foims an oil film to enhance wear resistance. Examples include partial esters in which a hydroxyl group remains, in particular, glycerol partial esters
25 with fatty acids having 12 to 24 carbon atoms.
[0048] In addition, the nitrogen-containing compound includes aliphatic
17

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amines such as oleylamine and dodecylamine, aliphatic amides and aliphatic imides. These nitrogen-containirig compounds are typically configured horn a nitrogen-containing polar group such as an amine group, an amide group or an imide group and a hydrocarbon group
5 having a saturated or unsaturated bond and having 12 to 24 carbon
atoms. It is expected in these nitrogen-containing compounds that the polar group adsorbs to the surface of a metal sliding portion and the hydrocarbon group forms an oil film to enhance wear resistance. In particular, examples include aliphatic amines having 12 to 24 carbon
10 atoms.
[0049] In addition, the organophosphorus compound includes phosphoric acid esters, phosphorous acid esters and an acidic phosphoric acid ester amine salt. In the present invention, it is to be noted that a compound containing nitrogen or the like, in addition to
15 phosphorus, as a constituent element^ is included in the
organophosphoms compound. The organophosphorus compound is typically one having one or more hydrocaihon groups having 6 to 24 carbon atoms. Such a hydrocarbon group includes a linear hydrocarbon group, a branched hydrocaihon group and an aromatic
20 group. The salt compound in the organophosphorus compound
includes a compound completely neutralized or a compound partially neutralized. It is expected in such an organophosphoms compound that a lubricant film of iron phosphate or the like is formed on the surface of a metal sliding portion to enhance wear resistance.
25 Examples of phosphoric acid esters include those having an aromatic
group, and typically include triaryl phosphates.
18

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[0050] The organosulfur compound includes a monosulfide compound,
a disulfide compound, a polysulfide compound, sulfurized fat and oil
and sulfurized olefms. It is expected in such an organosulfur
compound that a lubricant film of iron sulfide or the like is formed on
5 the surface of a metal sliding portion to enhance wear resistance.
Examples include diaiyi sulfides, dialkyl sulfides and dialkenyl sulfides. The sulfiir element content in the organosulfur compound can be, for example, 2 to 70% by mass, m particular, 5 to 60% by mass. [0051] The organomolybdenum compound includes molybdenum
10 dithiocai'bamate and molybdenum dithiophosphate. In the present
- invention, it is to be noted that a compound containing sulfur or the like,
in addition to molybdenum, as a constituent element, is included in the
organomolybdenum compound. It is expected in such an
organomolybdenum compound that a lubricant film made of
15 molybdenum disulfide is formed on the surface of a metal sHding
portion to enhance wear resistance. Examples include molybdenum dialkyldithiocarbamates and molybdenum dialkyldithiophosphates in which the number of carbon atoms in an alkyl group is 4 to 12. [0052] The alkaline earth metal compound includes alkalme earth metal
20 . sulfonate salt, phenate salt and salicylate salt. The alkaline earth metal
may be selected from calcium, magnesium and barium. In the present invention, it is to be noted that a compound containing sulfur or the like, in addition to the alkaline earth metal, as a constituent element is included in the alkahne eaitb metal compound. In addition, the
25 calcium compound may include a basic component such as calcium
carbonate.
19

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[0053] The organozinc compound includes organozinc compounds such
as zinc dialkyls, zinc dialkyldithiophosphates and zinc
dialicyldithiocarbamates. In the present invention, it is to be noted that
a compound containing sulfur, phosphorus or the like, in addition to
5 zinCj as a constituent element is included in the organozinc compound.
The organozinc compound typically has one or more linear, branched or aromatic hydrocarbon groups having 6 to 24 carbon atoms. Examples include zinc dialkyldithiophosphates in which the number of carbon atoms in an alkyl group is 4 to 12.
10 [0054] In addition, a solid lubricant may also be applied to the grease
being a semi-solid lubricant. The solid lubricant is an additive that is used in the form of a powder or thin film in order to prevent the surface of a sliding material from being damaged or in order to reduce friction/wear, and includes molybdenum disulfide, tungsten disulfide,
15 graphite, graphite fluoride, melamine cyanurate, a tetrafluoroethylene
(PTFE) resin powder, a polyimide resin powder, a high-denslt}'^ polyethylene resin powder, boron-nitride, a copper powder, a nickel powder, a tin powder and a silver powder.
In particular, molybdenum disulfide, graphite, a
20 tetrafluoroethylene resin powder and boron nitride may be suitably used
in the present invention.
[0055] In the present embodiment, the antiwear additive may be used
singly or may be used in combinations of two or more. The content of
, -the antiwear additive is 0.1 to 20% by mass, preferably 0.2 to 20% by
25 mass, more preferably 0.2 to 7% by mass and fiirther preferably 0.3 to
5% by mass based on the total amount of the grease composition. If
20

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the content is too low, no effect of wear-resistance is exerted, and if the content is too high, the stability of the lubricatmg oil is deteriorated. [0056] It is preferable to contain the organomolybdenum compound and the organozinc compound as the antiwear additive. The mass ratio
5 of the content of the organomolybdenum compound to the content of
the organozinc compound may be, for example, 0.2 to 10 : 1, in particular, 1 to 5 : 1. In this case, it is possible to use a lithium complex soap as the thickener. [0057] It is preferable to contain the organomolybdenum compound,
10 the organozinc compound and the organosulflir compound as fhe
antiwear additive. The mass ratio of the content of the organomolybdenum compound to the content of the organozinc compoimd may be, for example, 1 to 10 : 1, in particular, 1 to 5 : 1, and the mass ratio of the content of the organozbic compound to the content
15 of the organosulfor compound may be, for example, 0.2 to 2 : 1, in
paiticular, 0.5 to 2 : L In this case, it is possible to use a lithium soap as the thickener. It is possible to use a dialkyl sulfide having alkyl having 4 to 18, in particular, 6 to 10 carbon atoms as the organosulfiir compound.
20 [0058] [Other additives]
The grease composition according to the present embodiment may contain, in order to improve its performance, additives such as an antioxidant, an antimst agent, a metal deactivator, a corrosion inhibitor, a viscosity index improver, a pour point depressant, a detergent
25 dispersant, an emulsifier and an antifoamer that have been
conventionally used for a lubricating oil, as long as the object of the
21

FP13-0326-00
present invention is not impaired.
[0059] The antioxidant includes a phenol type compound like
di-teit-butyl-p-cresol, and an amine type compound lilce alkyl diphenyl
amines, the antirust agent includes alkenyl succinic acid esters or partial
5 esters thiereof, the metal deactivator includes benzotriazole and gallic
- acid esters, the corrosion inhibitor includes thiadiazole, the viscosity
index improver includes polymethaciylate and polyisobutyiene, the pour
point depressant includes polyalkylacrylate and polyalkylstyrene, the
detergent dispersant includes succinic imide and phosphonates, the
10 emulsifier includes a fatty acid soap and a long-chain alcohol sulfate
ester salt, and the antifoamer includes a silicone compound and a
polyester compound, respectively.
Examples
15. [0060] Hereinafter, the present invention is described in more detail
based on Examples and Comparative Examples, but the present
invention is not limited to such Examples.
[0061] [Examples 1 to 28, Comparative Examples 1 to 17]
In Examples 1 to 28 and Comparative Examples 1 to 17,
20 respective base oils, thickeners and additives shown below were used to
prepare respective grease compositions having composition shown in
Tables 1 to 6.
[0062] (A) Base oil
(A-1) Mineral oil: parafFmic refined mineral oil (kinematic
25 viscosity at 40°C: 93.3 mm /s; viscosity index: 95; poui- point; -15°C;
flash point: 260°C)
22

FP13-0326-00
(A-2) Polyol ester (POE): ester of pentaeiythritol and a mixed
acid of 2-ethylhexanoic acid and 3,5,5-trimethylhexanoic acid in a mass
ratio of 5 : 5 (kinematic viscosity at 40^C: 66.7 mm /s; viscosity index:
92; pour point: -40°C; flash point: 248°C)
5 (A-3) Polyalkylene glycol (PAG): polyoxypropylene in which
both ends were blocked by a methyl group (weight average molecular weight: 1000; kinematic viscosity at 40*^0: 46.0 mm /s; viscosity index: 190; pour point: -•45"'C; flashpoint: 218°C)
(A-4) Poly-a-olefin (PAO): polymer of 1-dodecene (kinematic
10 viscosity at 40°C: 100 mm /s; viscosity index: 140; pour point: -40^C;
flash point: 260°C)
Herein, the kinematic viscosity and the viscosity index of each of the base oils were measured according to JIS K2283, the pour point thereof was measured according to JIS K2269, and the flash point thereof was
15 measui-ed according to JIS K2265.
[0063] (B) Thickener
(B-1) Lithium soap grease: lithium 12-hydroxystearate (10% by mass) was blended and stirxed with any of the base oils, uniformly dissolved therein at about 200°C and then cooled, and additive (C or D)
20 was added thereto at about 80°C to provide a grease. This lithium
soap grease was allowed to pass through a roll mill and tested as the grease composition.
(B -2) Urea grease: one in which
diphenylmethane-4,4'-diisocyanate was dissolved in any of the base oils
25 (about 80°C) and one in which cyclohexylamine and octadecylamine
were dissolved in any of the base oils (about 80°C) were prepared (mass
23

FP13-0326-00
ratio of
diphenylmethane-4,4'-diisocyanate/cyclohexylamine/octadecylamine:
9/6/4), both- of them were mixed and stirred for reaction (160°C, 30
minutes) and cooled, and thereafter an additive (C or D) was added
5 thereto at about 80°C to provide a urea grease (5% by mass as diurea).
This urea grease was allowed to pass through a roll mill and tested as the gi'ease composition.
(B-3) Lithium complex soap grease: 12-hydroxystearic acid and
azelaic acid, and lithium hydroxide were blended and stiiTed with any of
10 the base oils in 10% by mass relative to the total amount of the grease
composition, uniformly dissolved therein at about 200°C and then cooled, and additive (C or D) was added thereto at about 80*^C to provide a grease. This lithium complex soap grease was allowed to pass through a roll mill and tested as the grease composition. 15 . [0064] (C) Epoxy compound
(C-1) 2-Ethylhexylglycidyl ether
(C-2) Dodecyl glycidyl ether
(C-3) Glycidyl-2,2-dimethyl octanoate
(C-4) 3,4-Epoxycyclohexylmethyl-3',4'-epoxycyclohexane
20 carboxylate
[0065] (X))Antiwear additive
(D-1) Oxygen-containing compound: glycerol monooleate
(D-2) Nitrogen-containing compound: oleylamine
(D-3) Organophosphorus compound: tricresyl phosphate
25 (p-4) Organosulfur compound A: dibenzyl disulfide
(D-5) Organomolybdenum compound A: molybdenum
24

FP13-0326-00
dialkyidithiophosphate [Mo element content: 8.0% by mass]
(0-6) Alkaline earth metal compound: overbasic Ca sulfonate,
[TBN (ASTM D2895): 325 mgKOHg; Ca: 12.7% by mass; S: 2% by
mass]
5 (D-^) Organozinc compound: zinc dioctyl dithiophosphate
(D-8) Solid lubricant: graphite (average particle size: 10 fim) (D-9) Organomolybdenum compound B: molybdenum dialkyldithiocai-bamate [Mo element content: 10.0% by mass]
(D-10) Organosulfur compound B: dioctyl polysulfide [sulfiir
10 element content: 39% by mass]
[0066] With respect to each of the gi-ease compositions in Examples 1
to 28 and Comparative Examples 1 to 17, the following tests were
performed.
[0067] [SRVtest]
15 A ball/disc reciprocating kinematic friction/wear test machine,
SRV test machine (Optimol Instruments, Instrument SRV), was used to perform seizure load and wear coefficient measurements according to ASTMD5706.
SUJ2 was used for materials of the ball and disc of the SRV test.
20 The test was started at a temperature of 80°C, an amplitude of 1 mm, a
frequency of 50 Hz and a load of 50 N, and the load was increased by
100 N every 2 minutes to perform the operation until seizure occurred
(the maximum load set was 2000 N).
In this test, the seizure load, and the friction coefficient at each
25 load before the seiioore can be measured. Tables 1 to 6 show the
seizure load, and the friction coefficient at a load lower than the seizm^e
25

FPi3-0326-00
load by 200 N in the test in which each of the grease compositions was
used. Herein, "Unstable" in the column "Friction coefficient" in Tables
means that the Motion coefficient vaiied between 0.08 and 0.18 and the
value could not be read.
5 [0068] [Oxidation stability test]
A sample pressurized to 755 KPa by an oxygen tank was heated
to 99''C and the pressure drop after a lapse of 100 hoxors was measured
according to the grease oxidation stability test method of JIS K2220.
The results obtained are shown in Tables 1 to 3. JIS K2220 defines
10 Class 3 grease for rolling bearing (oxidation stability is good over a
wide temperature range) as having a reduction in oxygen pressure of 49 KPa or less, and the oxidation stability of each of the grease compositions can be rated based on the definition.
26

FP13-0326~(
[0069] [Table 1]

Example Compara
tive Compara
tive Compai'a tive Example Compara five Example Compara tive
1 Example 1 Example 2 Example 3 2 Example
4 3 Example 5
Base oil
IVpe A-1 A-1 A-1 A-1 A-1 A-1 A-I A-1
Content (% by mass) Balance Balance Balance Balance Balance Balance Balance Balance
Thickener (% by
mass)
B-1 10.0 10.0 10.0 10.0 10.0 10.0 - -
B-2 - - - - - ~ 5.0 5.0
Epoxy compound (% by mass)
C-1 0.5 - 0.5 - 0.2 - - . _
C-2 - - - - ~ - 0.3 -
C-3 - - - - - - - -
C-4 - - - - -■ - - -
Antiwear additive
(% by mass)
D-1 1.0 - - 1.0 - - - -
D-2 - - - - 0.5 0.5 - -
D-3 - - - - - - 1.5 1.5
D-4 - - - - - - - -
D-5 - - - - - - - -
D-6 - - - - - - - -
D-7 - - - - - - - -
D-8 - - - -• - - - -
SRV test
Seizure load (N) 700 200 200 400 700 400 800 500
Friction coefficient 0.07 Unstable Unstable 0.10 0.08 0.11 O.IO 0.13
Oxidation stability
test
Amount of
reduction iii oxygen 35 85 38 75 39 70 25 73
pressure (KPa)
27

FP13-0326-00
[007O] [Table 2]

Compara Compara Compara Compara
Example tive Example tive Example tive Example tive
4 Example 6 5 Example
7 6 Example 8 7 Example 9
Base oil
Type A-1 A-1 A-1 A-1 A~l A-1 A-1 A-1
Content (%_ by mass) Balance Balance Balance Balance Balance Balance Balance Balance
Thickener
(%by
mass)
B-1 10.0 10.0 - - 10.0 10.0 10.0 10.0
B-2 - - 5.0 5.0 - - - -
Epoxy
compound
(%by
mass)
C-1 - - - - 2.0 - 0.2 ~
C-2 - - - - - - - -
C-3 1.0 - - - - - " -
C-4 - - 0.5 - - - - -
Antiwear
additive (%
by mass)
D-1 - - - - " .- - -
D-2 - - - - - - - -
D-3 - - - - - - - -
D-4 1.0 1.0 - - - - - -
D-5 - - 1.0 1.0 - - ■■ -
D-6 - - - - 3.0 3.0 - -
D-7. - - - - - - 0.5 0.5
D-8 - - - - . - - - -
SRVtest
Seizure load (N) 700 500 700 500 1100 700 900 500
V V
Friction 0.11 0.13 0.07 0.09 0.08 O.U 0.08 O.U
coefRcient
Oxidation
stability
test
Amount of
reduction in
oxygen 32 76 35 80 28 92 22 68
pr^sure
(KPa)
28

FP13-0326-00
[0071] [Tables]

Example Compara tive Example Compara tive Example Compara tive Example Corapam tive
8 Example 10 9 Example 11 10 Example 12 U Example 13
Base oil
Type A-1 A-1 A-2 A-2 A-3 A-3 A-1 A-1
Content (% by mass) Balance Balance Balance Balance Balance Balance Balance Balance
Thickener (% by
mass)
B-1 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0
B-2 - - - - - - - -
Epoxy compound (% by mass)
C-1 - - 0.15 - 0.1 - 0.3 -
C-2 0.3 - - - - - - -
C-3 - - - - - - - -
C-4 - - - - - - - -
Antiwear additive
(% by mass)
D-1 - - 0.2 0.2 - - - -
D-2 - - - - - - - -
D-3 - - 1.0 1.0 - - - "
D-4 - - - 0.5 0.5 - -
D-5 - - - - 0.1 0.1 1.0 1.0
D-6 2.0 2.0 - - - - 2.0 2.0
D-7 1.5 1.5 - - - ~ 1.5 1.5
D-8 1.0 1.0 - - - - - -
SRVtest
Seizure load (N) 1500 UOO UOO 700 1000 700 1500 1200
Friction coefiicient 0.07 0.10 0.07 0.10 0.07 0.10 0.06 0.09
Oxidation
stability test
Amount of
reduction in oxygen pressure (KPa) 20 60 38 75 39 70 21 65
29

FP13-0326-00
[0072] [Table 4]

Example Example Example Example Example Example Example Example
12 13 14 15 16 17 18 19
Base oil
Type A-1 A-1 A~l A-1 A-1 A-4 A-1 A-1
Content (% by Balance Balance Balance Balance Balance Balance Balance Balance
mass)
Thickener (% by
mass)
B-1 - 10.0 - - - - - -
B-3 10.0 - 10.0 10.0 10.0 10.0 10.0 10.0
Epoxy compound
(% by mass)
C-1 0.5 0.5 - ■■ - 0.5 1.0 0.5
C-2 - - 0.5 - - - - -
C-3 - - - 0.5 - - - -
C-4 - -• - - 0.5 - " -
Atitiwear additive
(% by mass)
D'5 1.0 1.0 1.0 1.0 1.0 i.O 5.0 1.0
D-7 1.0 1.0 1.0 1.0 1.0 1.0 5.0 -
D-9 1.0 1.0 i.O 1.0 1.0 1.0 5.0 -
SRVtest
Seizure load (N) 1500 1400 1400 1400 1400 1500 1700 1200
30

FP13-0326-00
[0073] [Table 5]

Example 20 Comparative Example 14 Comparative Example 15 Comparative Example 16 Comparative Example 17
Base oil
Type
Content (% by mass) A-1 Balance A-1 Balance A-1 Balance A-1 Balance A-1 Balance
Thickener (% by mass) B-1 B-3
Epoxy compo\ind (% by mass)
C-1
C-2
C-3
C-4
Antiwear additive (% by mass)
D-5 D-7 D-9 D-10 iO.O 0.5
1.0 10.0
1.0 1.0 1.0 10.0 0.5 10.0 10.0
0.5 1.0 3.0 1.0
SRVtest Seizure load (N) Fiiction coefficient 1100 800 400 - 400 800 0.07
31

FP13-0326-00
[0074] [Table 6]

Example 21 Example 22 Example 23 Example 24 Example
25 Example 26 Example 27 Example 28
Base oil
lype A"l A-1 A-1 A-1 A-1 A-2 A-1 A-l
Content (% by mass) Balance Balance Balance Balance Balance Balance Balance Balance
Thickener (% by mass) B-l 10.0 10.0 lO.O 10.0 lO.O 10.0 10.0
B-2 - lO.O - - - - - -
Epoxy
compound (% by mass) C-1 0.5 0.5 0.5 1.0 0.5
C-2 - - 0,5 - - - - -
C-3 - - - 0.5 - - - -
C-4 - - - - 0.5 - - -
Antiwear additive (% by mass) D-5 0.5 0.5 0.5 0.5 0.5 0.5 2.0
D-7 1.0 1.0 1.0 l.O 1.0 1.0 3.0 1.0
D-9 3.0 3.0 3.0 3.0 3.0 3.0 5.0 3.0
D-10 1.0 1.0 to 1.0 1.0 1.0 3.0 1.0
SRVtest
Seizure load (K) 1600 1500 1500 1500 1500 1600 1700 1400
Friction coefficient 0.04 0.05 0.05 0.05 0.05 0.04 0.04 0.04
Ittdustrial Applicability
[0075] The grease composition of the present invention is a grease that is significantly improved in teniis of stability, lubricity and Mction characteristics and that is excellent in reliability so that the initial characteristics may be maintained and the effect of weai-resistance may be kept even under severe lubrication conditions, as compared with a conventional grease. Accordingly, the grease composition of the
32

FP13-0326-00
present invention may be suitably used as a lubricant for various machines, vehicles, driving force transmission mechanisms and the like that are required to have anti-wear performance and energy saving performance.
33

WE CLAIM:-
A grease composition comprising:
at least one base oil selected from a mineral oil and a synthetic oil; and
5 based on the total amount of the grease composition,
2 to 35% by mass of a thickener;
0.05 to 5% by mass of an epoxy compound; and
0.1 to 20% by mass of an antiwear additive.
[Claim 2]
10 The grease composition according to claim 1, wherein the epoxy
compound is at least one selected from a phenyl glycidyl ether type
epoxy compound, an alkyl glycidyl ether type epoxy compound, a
glycidyl ester type epoxy compound, an alicyclic epoxy compound, an
epoxidized aliphatic monoester and an epoxidized vegetable oil.
15 [Claim 3]
The grease composition according to claim 2, wherein the epoxy compound is an alkyl glycidyl ether represented by the following formula (1):
R-—^O CH~-CH2
\/ 0)
0
20 wherein R represents a linear or branched alkyl group having 6 to 20
carbon atoms.
[Claim 4]
The grease composition according to claim 3, wherein the epoxy
compound is at least one selected from octyl glycidyl ether,
25 2-ethylhexyl glycidyl ether, nonyl glycidyl ether, decyl glycidyl ether,
34

FP13-0326-00
undecyl glycidyl ether and dodecyl glycidyl ether.
[Claim 5]
The grease composition according to any one of claims 1 to 3,
wherein the antiwear additive is at least one selected from an
5 oxygen-containing compound, a nitrogen-containing compound, an
organophosphorus compound, an organosulfiir compound, an
organomolybdenum compound, an alkaUne earth metal compound and
an organozinc compound.
[Claun 6]
10 The grease composition according to claim 5, wherein
the oxygen-containing compound is at least one selected from an ester,
an alcohol, an ether and a carboxylic acid, ,
the nitrogen-contaming compound is at least one selected from an
aliphatic amine, an aliphatic amide and an aliphatic kiude,
15 the organophosphorus compound is at least one selected fi-om a
phosphoric acid ester, a phosphorous acid ester and an acidic phosphoric
acid ester amine salt,
the organosulfur compound is at least one selected from a sulfide
compound, and sulflirized fat and oil,
20 the organomolybdenum compound is at least one selected from
molybdenum dithiocarbamate and molybdenum dithiophosphate,
the alkahne earth metal compoimd is at least one selected from alkaline
earth metal sulfonate salt, phenate salt and salicylate salt, and
the organozinc compound is at least one selected from a zinc dialkyl, a
25 zinc dialkyldithiophosphate and a zinc dialkylditliiocarbamate.
[Claim 7]
35

FP13-0326-00
The grease composition according to any one of claims 1 to 3, wherein the antiwear additive is a solid lubricant. [Claun 8]
The grease composition according to claim 7, wherein the solid
5 lubricant is at least one selected fr'om molybdenum disulfide, graphite, a
tetrafluoroethylene resin powder and boron nitride. [Claim 9]
The gi-ease composition according to any one of claims 1 to 8,
wherein the synthetic oH type is at least one selected from a
10 hydrocarbon oil, a diester, a polyol ester and a polyalkylene glycol
compound. [Claim 10]
The grease composition according to any one of claims I to 8^
wherein the thickener is at least one selected from lithium soaps,
15 calcium soaps, aluminum soaps and a ui*ea compound.
[Claim 11] , -
The grease composition according to claim 5, containing, as the
antiwear additive^ an organomolybdenum compound and an organozinc
compound.
20 [Clami 12]
The grease composition according to claim 5, containing, as the antiwear additive, an organomolybdenum compound, an organozinc compound and an organosulfru* compound.