JP2020132644A - Grease composition and rolling bearing - Google Patents

Abstract

To provide a grease composition that can prevent early peeling on the rolling surface due to hydrogen embrittlement even in severe environment, and to provide a rolling bearing in which the grease composition is encapsulated.SOLUTION: The grease composition 7 is a grease composition containing a base oil, a thickener and a compounding agent, and in which the compounding agent is a metal organic structure composed of a metal ion and an organic compound coordinated to the metal ion, is contained by 0.1 to 10 mass% for the entire grease composition, and the metal organic structure has a porous structure and a density of 0.5 g/cmor less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a grease composition and a rolling bearing in which the grease composition is encapsulated, and more particularly to a rolling bearing used for an electric component of an automobile and an auxiliary machine.

In recent years, in response to demands for miniaturization, weight reduction, and quietness improvement of automobiles, the electrical components and auxiliary machinery parts have been miniaturized, lightened, and sealed in the engine room. On the other hand, there is an increasing demand for high output and high efficiency in the performance of the equipment itself, and in the electrical equipment and auxiliary equipment in the engine room, there is a method to compensate for the decrease in output caused by miniaturization by rotating at high speed. It has been taken. As a result, the usage conditions such as rapid acceleration / deceleration, high temperature, and high rotation are severe.

Under such conditions, premature peeling with a peculiar microstructure change may occur on the rolling surface of the rolling bearing. This peeling is different from normal peeling due to metal fatigue, and is considered to be hydrogen brittleness caused by hydrogen generated by decomposition of grease or the like. For example, it is considered that grease is decomposed to generate hydrogen, which invades the steel of the rolling bearing, resulting in premature exfoliation due to hydrogen brittleness.

As a method for suppressing such a peculiar exfoliation phenomenon accompanied by a white adipose tissue change that occurs at an early stage, for example, a method of adding a passivator to a grease composition (see Patent Document 1) or bismuth dithiocarbamate is added. (See Patent Document 2) has been proposed. In addition, since the rolling surface of the rolling bearing is made of iron-based metal bearing steel, aluminum, silicon, titanium, tungsten, molybdenum, chromium, cobalt, etc. are added to the grease composition in consideration of mutual solubility with iron. A method of blending the metal powder of the above has also been proposed (see Patent Document 3).

Japanese Patent No. 2878749 Japanese Unexamined Patent Publication No. 2005-421102 Japanese Unexamined Patent Publication No. 2008-266424

In recent years, the conditions for using rolling bearings are becoming more and more severe in automobile electrical equipment and auxiliary equipment. In such a harsh environment, the conventional method of adding a passivator or bismuth dithiocarbamate as in Patent Document 1 and Patent Document 2 has become insufficient as a measure to prevent the peeling phenomenon. ing. Further, even when a metal powder having a mutual solubility with iron or more is used as in Patent Document 3, it may not be possible to sufficiently intervene in the sliding surface depending on the particle size or the like, and the effect may not be obtained. As described above, the prior art is still insufficient as a measure to prevent the peeling phenomenon.

The present invention has been made in view of such circumstances, and a grease composition capable of preventing premature peeling on a rolling surface due to hydrogen brittleness even in a harsh environment, and a rolling bearing formed by encapsulating the grease composition. For the purpose of provision.

The grease composition of the present invention is a grease composition containing a base oil, a thickener and a compounding agent, and the compounding agent is a metal-organic structure composed of a metal ion and an organic compound coordinated to the metal ion. It is a metal-organic framework (hereinafter, also referred to as MOF), and is characterized in that it is contained in an amount of 0.1 to 10% by mass based on the entire grease composition. In the present invention, the MOF is a crystalline structure having a polymer structure formed by combining metal ions and a crosslinkable organic compound connecting them.

The metal-organic framework has a porous structure and has a density of 0.5 g / cm ³ or less.

The metal organic structure is (a) a structure in which the metal ion is aluminum (Al) ion and the organic compound is terephthalic acid, and (b) the metal ion is zinc (Zn) ion and the organic compound. A structure in which the compound is 2-methylimidazole, or (c) the metal ion is a copper (Cu) ion or an iron (Fe) ion, and the organic compound is 1,3,5-benzenetricarboxylic acid. It is a feature.

The grease composition further contains zinc alkyl dithiophosphate (ZnDTP), an organic sulfonate, and an amine-based antioxidant as additives, and these additives are added to the entire grease composition, respectively. It is characterized by containing 0.1 to 10% by mass.

The base oil is at least one oil selected from synthetic hydrocarbon oils, ether oils, and ester oils.

The thickener is characterized by containing at least one urea compound selected from an aliphatic diurea compound, an alicyclic diurea compound and an aromatic diurea compound.

The rolling bearing of the present invention is characterized in that the grease composition of the present invention is sealed therein.

The grease composition of the present invention is a grease composition containing a base oil, a thickener and a compounding agent, and the compounding agent is a MOF composed of a metal ion and an organic compound coordinated to the metal ion. Here, MOF is a material having a porous coordination network structure having a high surface area far exceeding that of activated carbon or zeolite by the interaction of a metal and an organic compound. Since the MOF has a function of occluding gas, the MOF can occlude the hydrogen gas generated by the decomposition of the grease composition in the rolling bearing, and the invasion of hydrogen into the rolling bearing can be suppressed. As a result, it is considered that early peeling can be suppressed.

Since the MOF has a porous structure and a density of 0.5 g / cm ³ or less, the porosity is high and the storage of hydrogen gas is further excellent.

The MOF is (a) a structure in which the metal ion is an Al ion and the organic compound is a terephthalic acid, (b) a structure in which the metal ion is a Zn ion and the organic compound is 2-methylimidazole, or (c). ) Since the metal ion is Cu ion or Fe ion and the organic compound is 1,3,5-benzenetricarboxylic acid, the above effect can be more exerted.

Further, since ZnDTP, an organic sulfonate, and an amine-based antioxidant are contained in a predetermined amount as additives, the organic sulfonate, which is a rust preventive, can form an adsorption film on the metal surface, or can be used as an extreme pressure agent. By forming a film with a certain ZnDTP, the invasion of hydrogen into the steel is suppressed, and in combination with these effects, premature peeling due to hydrogen brittleness can be further prevented.

Since the rolling bearing of the present invention is formed by encapsulating the grease composition of the present invention, premature peeling on the rolling surface due to hydrogen brittleness can be prevented, and the life of the rolling bearing can be extended.

It is sectional drawing of an example of the rolling bearing of this invention.

The grease composition of the present invention contains a base oil, a thickener, and a compounding agent, and the compounding agent is a metal-organic structure. The MOF forms a porous structure by utilizing the coordination bond between the metal ion and the organic compound. The density of MOF is preferably 0.7 g / cm ³ or less, and more preferably 0.5 g / cm ³ or less.

The specific surface area of the powder of the metal-organic framework is determined by the BET method or the Langmuir method. For example, it is preferable that a BET specific surface area of MOF is 500~3000m ² / g, more preferably 1000~2500m ² / g. It is preferable that as the Langmuir specific surface area of MOF is 1000~3500m ² / g, more preferably 1000~2500m ² / g. Since MOF has a high specific surface area based on a uniform skeletal structure, it has an excellent ability to store hydrogen gas. By appropriately combining the organic moiety (organic compound) and the inorganic moiety (metal ion), it is possible to adjust the characteristics such as pore diameter, pore structure, and surface function.

The average particle size of the particles of the metal-organic framework is not particularly limited, and is, for example, 50% average particle size (D50) in the range of 3 to 100 μm. The 50% average particle size is preferably 3 to 50 μm, more preferably 3 to 20 μm. The 50% average particle size is measured using a known particle size distribution measuring device (for example, a laser diffraction type particle size distribution measuring device).

Examples of the metal ions constituting the metal organic structure include Mg ions, Al ions, Cr ions, Mn ions, Fe ions, Co ions, Ni ions, Cu ions, Zn ions, Pd ions, and Cd ions. .. Among these, Al ion, Fe ion, Cu ion and Zn ion are more preferable. The Cu ion is more preferably divalent Cu ion, and the Fe ion is further preferably divalent Fe ion.

The organic compound constituting the metal-organic framework may be any organic ligand capable of forming a coordinate bond with the above-mentioned metal ion, and examples thereof include compounds containing a nitrogen atom or an oxygen atom in the molecular structure. Specifically, dicarboxylic acids such as fumaric acid, isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and 3,5-pyridinedicarboxylic acid. , 1,3,5-benzenetricarboxylic acid, 4,4', 4''-(benzene-1,3,5-triyl) tricarboxylic acids such as tribenzoic acid, 1,2,4,5-benzenetetracarboxylic acid Examples thereof include tetracarboxylic acids such as acids, 4,4'-bipyridine, imidazole, benzimidazole, triazole, 1,4-ethylene piperazine, and 1,2-di (4-pyridyl) ethylene.

The organic compound may have a hydroxyl group, an amino group, a methoxy group, a methyl group, a nitro group, a methylamino group, a dimethylamino group, a cyano group, a halogen group or the like as another substituent in the skeleton. .. For example, 2-methylimidazole or the like can be used as the organic compound in which the methyl group is substituted.

The method for producing MOF is not particularly limited, and a known method can be used. Specifically, it is obtained by mixing each solution of a metal ion and an organic compound under normal temperature and pressure by a diffusion method or a stirring method. By adjusting the mixing speed, the size of the crystal to be produced can be adjusted. Further, a commercially available product may be used as the MOF.

Preferred embodiments of the MOF include (a) a structure in which the metal ion is an Al ion and the organic compound is a terephthalic acid, and (b) a structure in which the metal ion is a Zn ion and the organic compound is 2-methylimidazole. Alternatively, (c) the metal ion is a Cu ion or Fe ion, and the organic compound is a 1,3,5-benzenetricarboxylic acid. Examples of these commercially available products include: Basolite (registered trademark) A100, Z1200, C300, and F300 manufactured by Sigma-Aldrich. As shown in Examples described later, the structure (b) or the structure (c) is preferable because it is superior in extending the life of the rolling bearing.

The content of MOF in the grease composition of the present invention is 0.1 to 10% by mass with respect to the entire grease composition. If it is less than 0.1% by mass, early peeling due to hydrogen brittleness may not be sufficiently prevented. The content of MOF is preferably 0.1 to 5% by mass, and more preferably 0.2 to 3% by mass.

The base oil used in the present invention is not particularly limited as long as it is usually used for rolling bearings. Examples thereof include mineral oils such as paraffin-based mineral oils and naphthenic mineral oils, synthetic hydrocarbon oils such as polyα-olefin oil (PAO oil) and alkylbenzene oils, ester oils, ether oils, silicone oils and fluorine oils. These base oils may be used alone or in combination of two or more. Among these, synthetic oils are preferable, and at least one oil selected from synthetic hydrocarbon oils, ether oils, and ester oils is particularly preferable.

PAO oil is more preferable as the synthetic hydrocarbon oil. PAO oils are α-olefins or mixtures of isomerized α-olefin oligomers or polymers. Specific examples of the α-olefin include 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1 -Nonadecene, 1-eicosene, 1-dodecene, 1-tetradodecene and the like are mentioned, and a mixture thereof is usually used.

Ester oils include diester oils such as dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecylglutarate, and methyl acetylsinolate, trioctyl remeritate, and tridecyl. Aromatic ester oils such as trimellitate and tetraoctylpyromerite, polyol ester oils such as trimethylolpropane caprilate, trimethylolpropane verargonate, pentaerythritol-2-ethylhexanoate and pentaerythritol verargonate, Examples thereof include carbonic acid ester oil and phosphoric acid ester oil.

Examples of the ether oil include polyphenyl ether oil, alkyl diphenyl ether oil, alkyl triphenyl ether oil, and alkyl tetraphenyl ether oil. Examples of the alkyl diphenyl ether oil include monoalkyl diphenyl ether oil, dialkyl diphenyl ether oil, and polyalkyl diphenyl ether oil.

A more preferable embodiment of the base oil is an oil containing an alkyldiphenyl ether oil as an essential component in an amount of 50% by mass or more based on the total base oil. Alkyl diphenyl ether oil has excellent acid value stability and high temperature durability. In particular, it is more preferable that the base oil is a mixed oil of an alkyl diphenyl ether oil and a synthetic hydrocarbon oil, and the mixing ratio thereof is an alkyl diphenyl ether oil: synthetic hydrocarbon oil: = (60:40) to (80: 80:) in terms of mass ratio. 20) is particularly preferable.

The kinematic viscosity of the base oil (in the case of a mixed oil, the kinematic viscosity of the mixed oil) is preferably 20 to 150 mm ² / s at 40 ° C. It is more preferably 20 to 100 mm ² / s, and even more preferably 50 to 80 mm ² / s.

The thickener of the grease composition of the present invention is not particularly limited, and general ones usually used in the field of grease can be used. For example, soap-based thickeners such as metal soaps and composite metal soaps, and non-soap-based thickeners such as Benton, silica gel, urea compounds, and urea-urethane compounds can be used. Examples of the metal soap include sodium soap, calcium soap, aluminum soap, lithium soap and the like, and examples of the urea compound and the urea / urethane compound include a diurea compound, a triurea compound, a tetraurea compound, other polyurea compounds and a diurethane compound. Among these, it is preferable to use a urea compound which is excellent in heat resistance and durability, and also has excellent intervening property and adhesion to the rolling surface.

The urea compound is obtained by reacting a polyisocyanate component with a monoamine component. Examples of the polyisocyanate component include phenylenediocyanate, tolylene diisocyanate, diphenyl diisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decan diisocyanate, and hexane diisocyanate. Further, as the monoamine component, an aliphatic monoamine, an alicyclic monoamine and an aromatic monoamine can be used. Examples of the aliphatic monoamine include hexylamine, octylamine, dodecylamine, hexadecylamine, octadecylamine, stearylamine, and oleylamine. Examples of the alicyclic monoamine include cyclohexylamine. Examples of aromatic monoamines include aniline and p-toluidine.

Among these urea compounds, a diurea compound using an aromatic diisocyanate as a polyisocyanate component, for example, an aromatic diurea compound using an aromatic monoamine as a monoamine component, or an aliphatic monoamine is used because it is particularly excellent in heat resistance and durability. It is preferable to use the existing aliphatic diurea compound and the alicyclic diurea compound using the alicyclic monoamine.

The grease composition of the present invention may further contain other additives as long as the object of the present invention is not impaired. For example, extreme pressure agents such as organic zinc compounds and organic molybdenum compounds, antioxidants such as amine-based, phenol-based and sulfur-based compounds, anti-wear agents such as sulfur-based and phosphorus-based compounds, sulfonates and polyhydric alcohol esters. Examples thereof include rust preventives such as, friction reducing agents such as graphite, and oily agents such as esters and alcohols.

In the grease composition of the present invention, it is preferable that ZnDTP, an organic sulfonate, and an amine-based antioxidant are further contained as additives. The blending ratio of these is preferably 0.1 to 5% by mass with respect to the entire grease composition. It is more preferably 0.1 to 3% by mass, and even more preferably 0.5 to 3% by mass. Since the organic sulfonate forms a dense rust preventive film on the metal surface, contact between hydrogen gas and steel can be suppressed. Further, ZnDTP is used as an antioxidant, an extreme pressure agent, and an anti-wear agent, and since ZnDTP also forms a film on the metal surface, contact between hydrogen gas and steel can be suppressed.

ZnDTP is represented by the following formula (1). Examples of commercially available ZnDTP products include Kikurub Z112 manufactured by ADEKA CORPORATION.

（式中、Ｒは炭素原子数１〜２４のアルキル基または炭素原子数６〜３０のアリール基である。Ｒは、好ましくは、炭素原子数３〜２１の一級アルキル基である。）

(In the formula, R is an alkyl group having 1 to 24 carbon atoms or an aryl group having 6 to 30 carbon atoms. R is preferably a primary alkyl group having 3 to 21 carbon atoms.)

Examples of the organic sulfonate include various metal salts and amine salts of alkyl aromatic sulfonic acids such as alkylbenzene sulfonic acid and alkylnaphthalene sulfonic acid, and petroleum-based sulfonic acids obtained by sulfonated the aromatic component of the petroleum distillate component. Etc. can be used. Examples of the metal constituting the metal salt include barium, calcium, zinc, sodium, lithium and magnesium. Examples of the amine constituting the amine salt include ethylamine and trimethylamine. These organic sulfonates may be used alone or in combination of two or more.

Among the organic sulfonates, metal salts are preferable, and alkaline earth metal salts (particularly calcium salts) are more preferably used as essential components. A more preferred embodiment is the combined use of an alkaline earth metal salt and another organic sulfonic acid metal salt. Specifically, the combined use of an organic sulfonic acid calcium salt and an organic sulfonic acid zinc salt can be mentioned.

As the amine-based antioxidant, known amine-based antioxidants such as alkyldiphenylamine such as octylated diphenylamine and N-phenyl-1-naphthylamine can be used.

A base grease can be obtained by blending a thickener such as a urea compound with the above-mentioned base oil. A base grease containing a urea compound as a thickener is prepared by reacting a polyisocyanate component with a monoamine component in a base oil. The mixing ratio of the thickener in the base grease is 5 to 40% by mass, preferably 10 to 25% by mass.

The miscibility of the grease composition of the present invention (JIS K 2220) is preferably in the range of 200 to 350. If the consistency is less than 200, oil separation may be small and lubrication may be poor. On the other hand, when the consistency exceeds 350, the grease is soft and easily flows out of the bearing, which is not preferable.

The grease composition of the present invention is used for lubrication of rolling parts. For example, in rolling bearings and gears, and their components, they are used by being sealed in the parts to be lubricated. In particular, as the rolling bearing, it is preferable that the rolling bearing is used for an alternator, an electromagnetic clutch for a car air conditioner, a fan coupling device, an intermediate pulley, an electric component of an automobile such as an electric fan motor, and an auxiliary machine. The assumed operating temperature of the grease composition of the present invention is, for example, 150 ° C. or higher, particularly 180 ° C. or higher. The operating temperature range is, for example, 150 to 200 ° C., particularly 180 to 200 ° C. It can be suitably used even in a high temperature atmosphere as described above and under harsh conditions such as sudden acceleration / deceleration.

Further, the grease composition used in a high temperature environment is also required to have ignition resistance and the like. In the steel industry and the like, lubricants with excellent ignition resistance are used in the bearings of equipment used in high temperature conditions. For example, a grease composition in which a water-absorbent polymer is added to a lubricant and contains water is known (Reference: Japanese Patent Application Laid-Open No. 2002-146376), but rust may occur because it contains water. In addition, if the water evaporates in a high temperature environment, a sufficient effect may not be obtained. On the other hand, one aspect of the grease composition of the present invention has excellent ignition resistance because it contains a predetermined MOF as an additive, as shown in a test example described later. Therefore, the grease composition of the present invention containing a predetermined amount of MOF as an additive is also suitable for use in a high temperature environment.

A rolling bearing in which the grease composition of the present invention is sealed will be described with reference to FIG. FIG. 1 is a cross-sectional view of a deep groove ball bearing. In the rolling bearing 1, an inner ring 2 having an inner ring rolling surface 2a on the outer peripheral surface and an outer ring 3 having an outer ring rolling surface 3a on the inner peripheral surface are arranged concentrically with the inner ring rolling surface 2a and the outer ring rolling surface 3a. A plurality of rolling elements 4 are arranged between the two rolling elements 4. The rolling element 4 is held by the cage 5. Further, the openings 8a and 8b at both ends in the axial direction of the inner and outer rings are sealed by the sealing member 6, and the above-mentioned grease composition 7 is sealed at least around the rolling element 4. The inner ring 2, the outer ring 3, and the rolling element 4 are made of an iron-based metal material, and the grease composition 7 is lubricated by interposing the rolling surface with the rolling element 4.

In the rolling bearing 1, the iron-based metal material constituting the bearing member such as the inner ring 2, the outer ring 3, the rolling element 4, and the cage 5 is an arbitrary material generally used as the bearing material, for example, high carbon chromium. Bearing steel (SUJ1, SUJ2, SUJ3, SUJ4, SUJ5, etc .; JIS G 4805), carburized steel (SCr420, SCM420, etc .; JIS G 4053), stainless steel (SUS440C, etc .; JIS G 4303), high-speed steel (M50, etc.) , Cold rolled steel and the like. Further, the sealing member 6 may be made of metal or a rubber molded body alone, or may be a composite of a rubber molded body and a metal plate, a plastic plate, or a ceramic plate. A composite of a rubber molded body and a metal plate is preferable from the viewpoint of durability and ease of fixing.

In FIG. 1, a ball bearing is illustrated as a bearing, but the rolling bearings of the present invention include cylindrical roller bearings, tapered roller bearings, self-aligning roller bearings, needle roller bearings, thrust cylindrical roller bearings, and thrust tapered roller bearings other than the above. , Thrust needle roller bearings, thrust self-aligning roller bearings, etc.

The present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these examples.

In the examples, the commercially available products shown in Table 1 were used as the MOF. Table 1 shows the organic compounds, metal ions, density, D50, and specific surface area of each MOF. As the MOF in Table 1, those of the Basolite (registered trademark) series manufactured by Sigma-Aldrich were used.

Example 1 to Example 4, Comparative Example 1
After obtaining the base grease at the blending ratios shown in Table 2, a predetermined amount of each additive was added to obtain a test grease composition. The obtained grease composition was sealed in a rolling bearing and the rapid acceleration / deceleration test shown below was performed. The test method and test conditions are shown below.

<Rapid acceleration / deceleration test>
0.86 g of grease composition was sealed in a rolling bearing for inner ring rotation (inner ring, outer ring, steel ball is bearing steel SUJ2, model number: 6203 LLU (with seal)) that supports the rotating shaft, and a rapid acceleration / deceleration test was performed. As the rapid acceleration / deceleration test conditions, the operating conditions were set at room temperature (25 ° C.) and the rotation speed was 0 to 18000 min ^-1 . Then, the time until abnormal peeling occurred in the bearing (peeling time, h) was measured. The results are also shown in Table 2.

As shown in Table 2, each example containing MOF was able to prolong the time until early exfoliation as compared with Comparative Example 1. In this test, the best result was obtained when C300 was used as the MOF. In this way, by adding the MOF having a function of occluding the gas to the grease composition, the MOF occludes the hydrogen gas generated by the decomposition of the grease composition and suppresses the invasion of hydrogen into the bearing member. As a result, premature peeling is suppressed.

<Ignition test>
In order to confirm the ignition resistance effect of MOF, an ignition test was carried out using a test lubricant composition in which base oil and MOF were mixed. The lubricant composition was obtained by blending in the blending ratios shown in Table 3. Each lubricant composition was allowed to stand on an aluminum pan, and the presence or absence of ignition in an atmosphere with an oxygen pressure of 3.5 MPa and a temperature of 220 ° C. was confirmed. The results are also shown in Table 3.

As shown in Table 3, Test Example 3 containing no MOF (100% base oil) ignited. In addition, although Test Examples 4 to 5 also contained MOF, ignition occurred. On the other hand, Test Examples 1 and 2 containing Z1200 or A100 as MOF did not ignite. The detailed mechanism by which MOF prevents ignition is unknown, but since MOF has the function of occlusion of gas, by temporarily occlusion of oxygen, it is not a momentary oxidation reaction like ignition, but a gentle reaction. It is thought that an oxidation reaction occurs. In this ignition test, it is considered that Z1200 and A100 were particularly suitable for oxygen occlusion.

Since the grease composition of the present invention can prevent premature peeling on the rolling surface due to hydrogen brittleness, it can be suitably used as a lubricant for rolling bearings used under harsh conditions such as high temperature, high speed, and rapid acceleration / deceleration.

1 Rolling bearing 2 Inner ring 3 Outer ring 4 Rolling element 5 Cage 6 Sealing member 7 Grease composition 8a, 8b Openings

Claims (7)

A grease composition containing a base oil, a thickener and a compounding agent.
The compounding agent is a metal-organic structure composed of metal ions and an organic compound coordinated to the metal ions, and is characterized by being contained in an amount of 0.1 to 10% by mass based on the entire grease composition. Grease composition. The grease composition according to claim 1, wherein the metal-organic framework has a porous structure and a density of 0.5 g / cm ³ or less. The metal organic structure is (a) a structure in which the metal ion is an aluminum ion and the organic compound is terephthalic acid, and (b) the metal ion is a zinc ion and the organic compound is 2-methylimidazole. The structure according to claim 1 or 2, wherein the metal ion is copper ion or iron ion, and the organic compound is 1,3,5-benzenetricarboxylic acid. Grease composition. The grease composition further contains zinc alkyl dithiophosphate, an organic sulfonate, and an amine-based antioxidant as additives, and each of these additives is 0.1 with respect to the entire grease composition. The grease composition according to any one of claims 1 to 3, wherein the grease composition contains 10% by mass. The grease composition according to any one of claims 1 to 4, wherein the base oil is at least one oil selected from synthetic hydrocarbon oils, ether oils, and ester oils. The one according to any one of claims 1 to 5, wherein the thickener contains at least one urea compound selected from an aliphatic diurea compound, an alicyclic diurea compound and an aromatic diurea compound. Grease composition. A rolling bearing in which a grease composition is sealed.
A rolling bearing according to any one of claims 1 to 6, wherein the grease composition is the grease composition according to any one of claims.

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