Grease composition and rotating device

Abstract

A grease composition containing (A) a trimellitic acid ester, (B1) a phenyl alpha-naphthylamine, (B2) an alkyl diphenylamine, (C1) a succinic acid half ester, (C2) a sorbitan monoester, and (D) a urea-based thickener. The grease composition has excellent anti-stripping performance, anti-rust performance and oxidation resistance, so that the fatigue life of a rotating device and the like in which the grease is sealed can be maintained for a long period of time.

Description

Technical Field

[0001] The present invention relates to a lubricating grease composition and also to a bearing and a rotating device having the lubricating grease composition enclosed therein. Background Art

[0002] In automobiles, the demand for larger living space and further miniaturization and lightweighting of the automobile itself has forced the size of the engine compartment to be reduced. The miniaturization and lightweighting of electrical components / auxiliary equipment such as alternators, electromagnetic clutches for automotive air conditioning systems, intermediate pulleys, and electric fan motors have also been further promoted. The environments in which they are used are also diverse, for example, in tropical rainforest areas and areas close to the ocean, the high humidity and salinity of the atmosphere place high demands on rust prevention. In addition, the electrical components / auxiliary equipment themselves are required to have higher output power. In addition, due to the demand for improved quietness, the engine compartment has become more closed, which further promotes higher temperatures in the engine compartment. Therefore, parts with specifications that can withstand higher temperatures are required.

[0003] Rotating bearings are used in these electrical components / auxiliary equipment, and grease is mainly used to lubricate the rotating bearings. In order to meet the requirements of electrical components / auxiliary equipment (smaller size and weight / higher output power / rust prevention / high temperature resistance), the bearings are required to have high-speed rotation capability, high load capacity, rust prevention and high temperature resistance. Generally, in order to improve the rust resistance of the bearing, it is effective to mix a rust inhibitor into the grease. In order to improve the high temperature resistance of the bearing, it is effective to blend an antioxidant into the grease to inhibit the oxidative degradation of the grease.

[0004] On the other hand, it is reported that when the use conditions of the rolling bearing are increased to high rotation speed and high load, spalling with a white type microstructural change occurs on the rolling surface of the rolling bearing used, resulting in premature life.

[0005] In many cases, the above-mentioned electrical components / auxiliary equipment are driven by a pulley that transmits power through a belt from a power source. In this case, it is estimated that damage to the rotating bearing occurs at an early stage due to the occurrence of static electricity charging of the rotating bearing that supports the rotation of the pulley caused by the influence of static electricity generated by friction between the belt and the pulley, etc.

[0006] In order to prevent the above defects and satisfy the requirements of rust resistance and high temperature resistance of bearings at the same time, greases blended with base oils and additives such as antioxidants and rust inhibitors are considered. Grease compositions containing various additives, such as those described in Patent Document 1, have also been developed, in which trimellitic acid esters are used as base oils for the purpose of suppressing spalling.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2005-298537 Summary of the invention

[0010] Problem that the invention aims to solve

[0011] However, there is a concern that with further high rotation speeds and high loads, spalling occurring on the rotating surface of the rotating bearing will become more pronounced. In addition, some properties of the grease composition may be reduced by the addition of certain additives. Specifically, in some cases, the addition of antioxidants and rust inhibitors may reduce the anti-stripping performance of the grease composition. Therefore, it is very difficult to develop a grease composition that further suppresses spalling while also having rust resistance and oxidation resistance.

[0012] Solutions for solving problems

[0013] The present inventors have conducted intensive research on a grease composition having anti-stripping performance, anti-rust performance and oxidation resistance performance. The present inventors have found that a grease composition having anti-stripping performance, anti-rust performance and oxidation resistance performance can be obtained by combining trimellitic acid esters with specific additives, leading to the completion of the present invention.

[0014] The present invention is based on such findings, as described below.

[0015] <1>

[0016] A grease composition comprising:

[0017] (A) trimellitic acid esters,

[0018] (B1) phenyl alpha-naphthylamine,

[0019] (B2) alkyl diphenylamine,

[0020] (C1) succinic acid half ester,

[0021] (C2) sorbitan monoester, and

[0022] (D) Urea thickener.

[0023] <2>

[0024] according to <1> The grease composition described above does not contain (C3) zinc naphthenate or contains less than 2% by mass of (C3) zinc naphthenate.

[0025] <3>

[0026] according to <1> or <2> The grease composition described above does not contain (B3) zinc dialkyl dithiophosphate or contains less than 2% by mass of (B3) zinc dialkyl dithiophosphate.

[0027] <4>

[0028] according to <1> to <3> The grease composition according to any one of the preceding claims, wherein the grease composition comprises:

[0029] 50 to 95% by mass of (A) trimellitic acid ester based on the total amount of the grease composition,

[0030] 0.1 to 10% by mass of (B1) phenyl-α-naphthylamine based on the total amount of the grease composition,

[0031] 0.1 to 10% by mass of (B2) alkyl diphenylamine, based on the total amount of the grease composition,

[0032] 0.1 to 10% by mass of (C1) succinic acid half ester, based on the total amount of the grease composition,

[0033] 0.1 to 10% by mass of (C2) sorbitan monoester, based on the total amount of the grease composition, and

[0034] (D) urea thickener in an amount of 5 to 30% by mass based on the total amount of the grease composition.

[0035] <5>

[0036] A bearing and a rotating device, wherein according to <1> to <4> Any one of the greases described above is enclosed therein as a lubricant.

[0037] Effects of the Invention

[0038] The grease composition of the present invention is excellent in spalling resistance, rust resistance and oxidation resistance, and can maintain the fatigue life of a rotating device or the like in which the grease is sealed for a long time. Therefore, the grease composition of the present invention can withstand long-term use. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] [ Figure 1 ] is a cross-sectional view showing a rotating device according to one embodiment of the present invention. DETAILED DESCRIPTION

[0040] {Trimellitate}

[0041] In the grease composition of the present invention, trimellitic acid ester is used as a lubricant base oil. From the viewpoint of anti-stripping properties, it is preferred to use trimellitic acid ester represented by the following general formula (I).

[0042] [Formula 1]

[0043] Formula (I)

[0044]

[0045] In formula (I), R 1 , R 2 and R 3 is a hydrogen atom or a hydrocarbon group having 5 to 20 carbon atoms, R 1 , R 2 and R 3 can be the same as or different from each other. 1 , R 2 and R 3 They cannot all be hydrogen atoms at the same time. In addition, these hydrocarbon groups represent saturated or unsaturated, straight-chain or branched alkyl groups.

[0046] Such trimellitic acid esters are available in the market as, for example, "TRIMEX T-08" and "TRIMEX N-08" manufactured by Kao Corporation, and "ADEKA PROVER T-90" manufactured by ADEKA CORPORATION.

[0047] Preferably, the trimellitic acid esters in the present invention include the above R 1 , R 2 and R 3 By using such trimellitic acid esters, higher peeling resistance can be obtained.

[0048] From the same viewpoint, the total acid value of the trimellitic acid ester in the present invention is preferably 2 to 10 mgKOH / g. Here, the acid value of the trimellitic acid ester refers to an acid value measured in accordance with JIS K2501:2003.

[0049] When R 1 , R 2 and R 3 When it is a hydrocarbon group, the hydrocarbon group of the trimellitic acid ester of the present invention is preferably a hydrocarbon group having 7 to 15 carbon atoms, more preferably a hydrocarbon group having 8 to 11 carbon atoms, and even more preferably a hydrocarbon group having 9 to 11 carbon atoms. This is because when it is packed in a bearing as grease, it provides anti-evaporation and a stable oil film, and when it is packed in a bearing as grease, it reduces stirring heat.

[0050] As a lubricant base oil, trimellitic acid ester can be used by mixing with other lubricant base oils as appropriate. As other lubricant base oils, mineral oil, alkyl naphthalene, fluorinated oil, silicone oil, glycol oil, synthetic hydrocarbon oil, ether oil, ester oil other than trimellitic acid ester, etc. can be used. Specifically, poly α-olefin oil as a synthetic hydrocarbon oil, alkyl diphenyl ether oil and alkyl triphenyl ether oil as ether oil, and diester oil, neopentyl type polyol ester oil, these composite ester oils, etc. as ester oils can be used. These lubricant base oils combined with trimellitic acid ester can be used alone or in appropriate combination.

[0051] In the grease composition of the present invention, it is preferred that only trimellitate is contained as the lubricant base oil, and no other lubricant base oil is contained. Specifically, in the grease composition of the present invention, the content of trimellitate may be, for example, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more based on the amount of the lubricant base oil.

[0052] The kinematic viscosity of the lubricant base oil at 40°C is preferably 30 mm 2 / s or more, more preferably 40mm 2 / s or more, and even more preferably 45 mm 2 / s or more. In addition, the kinematic viscosity of the lubricant base oil at 40°C is preferably 150 mm 2 / s or less, more preferably 130mm 2 / s or less, even more preferably 100mm 2 / s or less. The specific range is preferably 30mm 2 / s~150mm 2 / s, preferably 40 mm 2 / s~130mm 2 / s, even more preferably 45mm 2 / s~100mm 2 / s.

[0053] The kinematic viscosity of the lubricant base oil at 40° C. can be measured in accordance with JIS K 2283:2000.

[0054] In the grease composition of the present invention, the content of trimellitic acid ester is preferably 50% to 95% by mass, more preferably 60% to 90% by mass, even more preferably 65% ​​to 85% by mass, and particularly preferably 70% to 85% by mass, based on the total amount of the grease composition.

[0055] {Component (B1): phenyl α-naphthylamine}

[0056] The grease composition of the present invention contains phenyl-α-naphthylamine as a first antioxidant from the viewpoint of anti-stripping property and oxidation resistance. Phenyl-α-naphthylamine is a compound having a structure represented by the following general formula (II).

[0057] [Formula 2]

[0058] Formula (II)

[0059]

[0060] In formula (II), R 10 represents a hydrogen atom or an alkyl group having 1 to 16 carbon atoms. 10 The alkyl groups represented include, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl and the like (these alkyl groups may be linear or branched).

[0061] In the grease composition of the present invention, the content of phenyl-α-naphthylamine is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, based on the total amount of the grease composition. In addition, the content is preferably 10% by mass or less, more preferably 5% by mass or less. As a specific range, the content is preferably 0.1% by mass to 10% by mass, more preferably 0.5% by mass to 5% by mass. The content of phenyl-α-naphthylamine above the lower limit achieves better oxidation resistance, and the content below the upper limit allows phenyl-α-naphthylamine to stably maintain a soluble state in the grease.

[0062] {Component (B2): alkyl diphenylamine}

[0063] The grease composition of the present invention contains alkyl diphenylamine as a second antioxidant from the viewpoint of anti-stripping property and oxidation resistance. Alkyl diphenylamine is a compound having a structure represented by the following general formula (III).

[0064] [Formula 3]

[0065] Formula (III)

[0066]

[0067] In the formula, R 11 and R 12 may be the same or different, and each represents a hydrogen atom or an alkyl group having 1 to 16 carbon atoms. 11 and R 12 They cannot all be hydrogen atoms at the same time. 11 and R 12The alkyl groups represented include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl and the like (these alkyl groups may be straight chain or branched), but branched chain alkyl groups having 3 to 16 carbon atoms are preferred.

[0068] In the grease composition of the present invention, the content of alkyldiphenylamine is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more, based on the total amount of the grease composition. In addition, the content is preferably 10% by mass or less, and more preferably 5% by mass or less. As a specific range, the content is preferably 0.1% by mass to 10% by mass, and more preferably 0.5% by mass to 5% by mass. The content of alkyldiphenylamine above the lower limit achieves better oxidation resistance, and the content below the upper limit allows the alkyldiphenylamine to stably maintain a soluble state in the grease.

[0069] In the grease composition of the present invention, the mass ratio of the content of alkyldiphenylamine to the content of phenyl-α-naphthylamine (alkyldiphenylamine / phenyl-α-naphthylamine) is preferably 0.1-10, more preferably 0.3-5, and even more preferably 0.5-2.

[0070] The present inventors have found that a synergistic effect can be obtained by adding phenyl alpha naphthylamine as a first antioxidant and further adding alkyl diphenylamine as a second antioxidant. By using these antioxidants together, better oxidation resistance can be achieved compared to when only one antioxidant is used, while these antioxidants are more stably dissolved in the grease. In addition, these antioxidants do not reduce anti-stripping properties. Therefore, the grease composition of the present invention can withstand long-term use.

[0071] (C1) Succinic acid half ester

[0072] From the viewpoint of anti-stripping property and rust prevention property, the grease composition of the present invention contains succinic acid half ester as the first rust inhibitor. Succinic acid half ester is a compound in which only one of the two carboxylic acid groups of succinic acid forms an ester bond with an alcohol or the like. The alcohol forming the ester bond includes monohydric to trihydric alcohols having 2 to 10 carbon atoms. An alkyl group or an alkenyl group or the like may be added to succinic acid, wherein the number of carbon atoms of the alkyl group or the alkenyl group is preferably 1 to 10, more preferably 2 to 5.

[0073] In the grease composition of the present invention, the content of succinic acid half ester is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, based on the total amount of the grease composition. In addition, the content is preferably 10% by mass or less, more preferably 5% by mass or less. As a specific range, the content is preferably 0.1% by mass to 10% by mass, more preferably 0.2% by mass to 5% by mass. The content of succinic acid half ester above the lower limit achieves better rust resistance, and the content below the upper limit prevents the succinic acid half ester from deteriorating in fluidity at low temperatures.

[0074] (C2) Sorbitan monoester

[0075] From the viewpoint of anti-stripping property and rust prevention property, the grease composition of the present invention contains sorbitan monoester as a second rust inhibitor. Sorbitan monoester is a compound in which sorbitan is bonded to a fatty acid to form a monoester. Sorbitan monoester includes sorbitan monooleate, sorbitan monostearate, sorbitan monopalmitate, sorbitan monolaurate, and the like.

[0076] In the grease composition of the present invention, the content of sorbitan monoester is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, based on the total amount of the grease composition. In addition, the content is preferably 10% by mass or less, more preferably 5% by mass or less. As a specific range, the content is preferably 0.1% by mass to 10% by mass, more preferably 0.5% by mass to 5% by mass. The content of sorbitan monoester above the lower limit achieves better rust resistance, and the content below the upper limit prevents the sorbitan monoester from deteriorating its fluidity at low temperatures.

[0077] In the grease composition of the present invention, the mass ratio of the content of sorbitan monoester to the content of succinic acid half ester (sorbitan monoester / succinic acid half ester) is preferably 0.1-10, more preferably 0.3-5, even more preferably 0.5-2.

[0078] The present inventors have found that by adding a succinic acid half ester as a first rust inhibitor, and further adding a sorbitan monoester as a second rust inhibitor, a synergistic effect can be obtained. By using these rust inhibitors together, better rust resistance can be achieved compared to when only one rust inhibitor is used. In addition, these rust inhibitors do not reduce anti-flaking properties. Therefore, the grease composition of the present invention can withstand long-term use.

[0079] (D) Urea thickener

[0080] The grease composition of the present invention contains a urea thickener as a thickener. As the urea thickener, for example, a diurea compound obtained by a reaction of a diisocyanate with a monoamine, a polyurea compound obtained by a reaction of a diisocyanate with a monoamine or a diamine, a urea / urethane compound obtained by a reaction of a diisocyanate with a primary amine and with a higher alcohol represented by the general formula R1-OH, or a diurethane compound obtained by a reaction of a diisocyanate with a higher alcohol, etc. can be used.

[0081] Monoamine is a compound having one amino group in one molecule. Among monoamines, primary amines are preferably octylamine, dodecylamine, hexadecylamine, octadecylamine, oleylamine, aniline, p-toluidine, cyclohexylamine, etc. Secondary amines are preferably dicyclohexylamine, etc.

[0082] Diamine is a compound having two amino groups in one molecule. Preferred diamines are ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, octanediamine, phenylenediamine, toluenediamine, xylenediamine, diaminodiphenylmethane, etc. The hydrocarbon groups of monoamines and diamines may be acyclic or cyclic hydrocarbons, and include aromatic hydrocarbons, alicyclic hydrocarbons, chain aliphatic hydrocarbons, etc. The number of carbon atoms is preferably 2 to 20, more preferably 4 to 18.

[0083] The amine used in the urea thickener of the present invention is preferably a mixed amine of an alicyclic amine (hereinafter sometimes referred to as the "first amine component") and an aromatic amine or a chain aliphatic amine or a combination thereof (hereinafter sometimes referred to as the "second amine component"). The first amine component can be used alone or in combination of two or more. The second amine component can be a single aromatic amine, a single chain aliphatic amine, or a mixture of the two.

[0084] The mixing ratio of the first amine component to the second amine component in the mixed amine is not limited, but the molar ratio of the first amine component to the second amine component (first amine component: second amine component) is preferably 99: 1 to 55: 45, more preferably 90: 10 to 75: 25. In the molar ratio, when the first amine component is a combination of two or more compounds, the molar amount of the first amine component is the molar amount of their total amount, and when the second amine component is a combination of two or more compounds, the molar amount of the second amine component is the molar amount of their total amount.

[0085] Diisocyanates are compounds in which two hydrogen atoms of a hydrocarbon are replaced by isocyanate groups. The hydrocarbon may be a non-cyclic hydrocarbon or a cyclic hydrocarbon, and may be any of an aromatic hydrocarbon, an alicyclic hydrocarbon or an aliphatic hydrocarbon. The number of carbon atoms of the hydrocarbon is preferably 4 to 20, more preferably 8 to 18. Preferred specific examples of diisocyanates may include phenylene diisocyanate, toluene diisocyanate, biphenyl diisocyanate (diphenyl diisocyanate), diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, hexane diisocyanate, etc. The diisocyanates may be used alone or in combination of two or more.

[0086] As the urea thickener of the present invention, a diurea compound represented by the following general formula (V) is preferably used.

[0087] [Formula 5]

[0088] R 20 NH-CONH-R 10 -NHCO-NHR 20 (V)

[0089] In the general formula (V), R 10 is a divalent hydrocarbon group, which may be an acyclic hydrocarbon group or a cyclic hydrocarbon group, and may be any of an aromatic hydrocarbon group, an alicyclic hydrocarbon group, and an aliphatic hydrocarbon group. 10 The number of carbon atoms in R is preferably 4 to 20, more preferably 8 to 18. 20 R may be the same or different and is a monovalent alicyclic hydrocarbon group, a monovalent chain aliphatic hydrocarbon group or a monovalent aromatic hydrocarbon group or a combination thereof. 20 The number of carbon atoms in the molecule is preferably 2 to 20, more preferably 4 to 18. 20 can be alicyclic hydrocarbon groups, and both R 20 can be an aromatic hydrocarbon group or a chain aliphatic hydrocarbon group, or two R 20 One of them may be an alicyclic hydrocarbon group, and the other may be an aromatic hydrocarbon group or a chain aliphatic hydrocarbon group. As all urea thickeners, R 20 is a combination of a monovalent alicyclic hydrocarbon group and a monovalent aromatic hydrocarbon group or a chain aliphatic hydrocarbon group, and R in all urea thickeners 20 The combined molar ratio (alicyclic hydrocarbon group:aromatic hydrocarbon group and / or chain aliphatic hydrocarbon group) is preferably 99:1 to 55:45, particularly preferably 90:10 to 75:25.

[0090] The content of the urea thickener is not limited as long as the desired penetration can be obtained, but for example, it is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more based on the total amount of the grease composition. In addition, the content of the urea thickener is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less. As a specific range, the content of the urea thickener is preferably 1% by mass to 40% by mass, more preferably 5% by mass to 30% by mass, and even more preferably 10% by mass to 25% by mass. The urea thickener may be used alone or in combination of two or more.

[0091] The grease composition may contain a thickener other than the urea thickener in addition to the urea thickener, but the content thereof is preferably 30 parts by mass or less, more preferably 10 parts by mass or less, based on 100 parts by mass of the urea thickener.

[0092] (C3) Zinc naphthenate

[0093] The grease composition of the present invention may contain zinc naphthenate as a rust preventive within a range that does not impair the effects of the present invention. If a large amount of zinc naphthenate, specifically 2% by mass or more, is contained, the anti-stripping property of the grease composition may be impaired. Therefore, the grease composition of the present invention does not contain zinc naphthenate, or even if zinc naphthenate is contained, the content is preferably less than 2% by mass, more preferably 1.0% by mass or less, and even more preferably 0.5% by mass or less.

[0094] (B3) Zinc dialkyl dithiophosphate

[0095] The grease composition of the present invention may contain zinc dialkyl dithiophosphate as an antioxidant within a range that does not impair the effects of the present invention. As zinc dialkyl dithiophosphate, a compound having a structure represented by the following general formula (VI) can be used.

[0096] [Formula 6]

[0097] Formula (VI)

[0098]

[0099] In the above general formula (VI), R 30 ~R 33 Each is independently a hydrogen atom or a linear or branched alkyl group having 1 to 24 carbon atoms, and the alkyl group may be primary, secondary or tertiary.

[0100] If zinc dialkyl dithiophosphate is contained in a large amount, specifically 2% by mass or more, the anti-stripping property of the grease composition may be impaired. Therefore, the grease composition of the present invention does not contain zinc dialkyl dithiophosphate, or even if zinc dialkyl dithiophosphate is contained, the content is preferably less than 2% by mass, more preferably 1.0% by mass or less, and even more preferably 0.5% by mass or less.

[0101] In addition, other additives may be blended into the grease composition of the present invention as required to impart various properties. For example, additives commonly used in greases, such as extreme pressure agents such as organic molybdenum, oiliness improvers such as fatty acids and animal and vegetable oils, and metal deactivators such as benzotriazole may be used alone or in a mixture of two or more. The amounts of these additives added are not limited as long as they do not impair the effects of the present invention.

[0102] The cone penetration of the grease composition of the present invention is preferably 210-310, more preferably 215-305, even more preferably 220-300, particularly preferably 230-295.

[0103] The cone penetration here refers to the working cone penetration measured according to JIS K2220.

[0104] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Figure 1 1 is a cross-sectional view in the longitudinal direction showing the structure of a ball bearing 1 according to an embodiment of a rotating device of the present invention.

[0105] Figure 1 The ball bearing 1 shown is composed of an inner ring 10, an outer ring 11, a plurality of freely arranged balls 13 for rotational movement between the inner ring 10 and the outer ring 11, a retainer 12 retaining the plurality of balls 13, and a contact seal 14 attached to the outer ring 11. A grease composition G is filled in a bearing space surrounded by the inner ring 10, the outer ring 11, and the seal 14, and is sealed in the ball bearing 1 by the seal 14. By such a grease composition G, the contact surfaces of the raceway surfaces of the two rings 10, 11 and the balls 13 are lubricated.

[0106] Example

[0107] Next, the present invention will be described by way of Examples and Comparative Examples, but the present invention is not limited to the following Examples. % means mass % unless otherwise specified.

[0108] Examples 1 to 2 and Comparative Examples 1 to 11

[0109] <Grease blending>

[0110] For each of the Examples and Comparative Examples, a test grease composition was prepared by blending a thickener, a base oil, an antioxidant, and a rust inhibitor at the blending ratios shown in Tables 1 to 3. In the tables, the numerical values ​​of the amine in the thickener represent the molar ratio of the amine that reacts with the diisocyanate compound (methylene diisocyanate), and the other numerical values ​​represent the blending ratio (%) based on the total amount of the grease composition.

[0111] The grease compositions obtained in the tests were evaluated as follows. The evaluation results are shown in Tables 1 to 3.

[0112] In addition, the kinematic viscosity of the following base oil is a value measured according to JIS K 2283:2000.

[0113] (1) Base oil

[0114] Base oil 1: trimellitate (kinematic viscosity: 75 mm 2 / s(40℃), acid value: 3.2mgKOH / g)

[0115] Base oil 2: ether base oil (kinematic viscosity: 100 mm 2 / s(40℃)

[0116] (2) Thickener

[0117] ·CHA (cyclohexylamine)

[0118] pt(p-Toluidine)

[0119] ·ODA (octadecylamine)

[0120] Amines were dissolved in base oils at molar ratios shown in Tables 1 to 3, mixed, and reacted with a diisocyanate compound (diphenylmethane diisocyanate) dissolved in the base oils to prepare urea compounds.

[0121] (3) Antioxidants and rust inhibitors

[0122] Antioxidants and rust inhibitors were added as described in Tables 1 to 3. Details of the additives are as follows.

[0123] Antioxidant 1: Phenyl α-naphthylamine

[0124] Antioxidant 2: Alkyl diphenylamine

[0125] Antioxidant 3: Zinc dialkyl dithiophosphate

[0126] Rust inhibitor 1: succinic acid half ester

[0127] Rust inhibitor 2: Sorbitan monoester

[0128] Rust inhibitor 3: zinc cyclohexane

[0129] <Evaluation>

[0130] (1) Peeling test

[0131] 1 g of the test grease composition was filled into a SUJ2 deep groove ball bearing with bearing number 6301, inner diameter 12 mm, outer diameter 37 mm, and width 12 mm, and the ball bearing was subjected to a radial load of 1225 N at room temperature for 7,000 min. -1 Rotate. When the vibration value exceeds the specified value or when the test time reaches 300 hours, stop the test. After the test, check the bearing steel to see if spalling has occurred.

[0132] (2) Rust resistance

[0133] From the test method specified in ASTM D1743, the water in which the bearings were immersed was changed to 0.1 wt % salt water, the test time was changed to 24 hours, and the test temperature was changed to 25° C. to conduct the test and exclude those in which rust occurred.

[0134] (3) Oxidative stability

[0135] Using a PDSC apparatus (DSC Q2000 manufactured by TA Instruments), 2 mg of grease was weighed in an aluminum pan, and the time until the endothermic peak appeared was measured under the conditions of 3.5 MPa of O2 and 210°C. Those with a time until the endothermic peak appeared of 200 minutes or more were acceptable.

[0136] [Table 1]

[0137]

[0138] [Table 2]

[0139]

[0140] [Table 3]

[0141]

[0142] In the grease compositions of Examples 1 and 2, no spalling was observed in the bearing steel, and the rust resistance and oxidation stability were also good.

[0143] Comparative Examples 1 and 2 using trimellitic acid esters had good anti-flaking properties, but flaking was observed in Comparative Example 3 using an ether base oil. Therefore, trimellitic acid esters are considered to be effective in improving anti-flaking properties. However, since no rust inhibitor was included in Comparative Examples 1 to 3, rust resistance was deteriorated in all cases.

[0144] In Comparative Examples 4 to 7, when Antioxidant 1, Antioxidant 2, Rust Preventive 1, or Rust Preventive 2 was added to trimellitic acid ester, no spalling was observed in the bearing steel. Therefore, it is considered that these additives have no adverse effect on spalling resistance.

[0145] On the other hand, in Comparative Examples 8 and 9, when Antioxidant 3 or Rust Preventive 3 was added to trimellitic acid ester, spalling was observed in the bearing steel. Therefore, it is considered that these additives have an adverse effect on spalling resistance.

[0146] In Comparative Example 10 in which the antioxidant 1 was contained in trimellitic acid ester but the antioxidant 2 was not contained, and Comparative Example 11 in which the antioxidant 2 was contained in trimellitic acid ester but the antioxidant 1 was not contained, compared with Examples 1 and 2, the oxidation stability of the grease itself was deteriorated.

[0147] Industrial Applicability

[0148] The grease composition of the present invention is excellent in anti-stripping, anti-rust, and oxidation resistance, and further, can maintain the fatigue life of the rotating device etc. in which the grease is sealed for a long time. Therefore, the grease composition of the present invention can withstand long-term use. Due to the properties of the grease composition of the present invention, it can be used as a grease composition for a rotating bearing of a pulley in a belt drive part such as an electrical part / auxiliary equipment.

[0149] Description of Reference Numerals

[0150] 1 ball bearing

[0151] 10 Inner Ring

[0152] 11 Outer Ring

[0153] 12 Retainer

[0154] 13 Ball

[0155] 14 Contact seals

Claims

1. A grease composition comprising: (A) trimellitic acid esters, (B1) phenyl alpha-naphthylamine, (B2) alkyl diphenylamine, (C1) succinic acid half ester, (C2) sorbitan monoester, and (D) Urea thickener. 2 . The grease composition according to claim 1 , wherein the grease composition contains no (C3) zinc naphthenate or contains less than 2% by mass of (C3) zinc naphthenate.

3. The grease composition according to claim 1 or 2, wherein the grease composition contains no (B3) zinc dialkyl dithiophosphate or contains less than 2% by mass of (B3) zinc dialkyl dithiophosphate.

4. The grease composition according to claim 1 or 2, wherein the grease composition comprises: 50% to 95% by mass of (A) the trimellitic acid ester based on the total amount of the grease composition, 0.1% to 10% by mass of (B1) phenyl-α-naphthylamine based on the total amount of the grease composition, 0.1 to 10% by mass of (B2) the alkyl diphenylamine based on the total amount of the grease composition, 0.1% to 10% by mass of (C1) the succinic acid half ester based on the total amount of the grease composition, 0.1% to 10% by mass of (C2) the sorbitan monoester based on the total amount of the grease composition, and (D) the urea thickener is present in an amount of 5 to 30% by mass based on the total amount of the grease composition.

5. The grease composition according to claim 3, wherein the grease composition comprises: 50% to 95% by mass of (A) the trimellitic acid ester based on the total amount of the grease composition, 0.1% to 10% by mass of (B1) phenyl-α-naphthylamine based on the total amount of the grease composition, 0.1 to 10% by mass of (B2) the alkyl diphenylamine based on the total amount of the grease composition, 0.1% to 10% by mass of (C1) the succinic acid half ester based on the total amount of the grease composition, 0.1% to 10% by mass of (C2) the sorbitan monoester based on the total amount of the grease composition, and (D) the urea thickener is present in an amount of 5 to 30% by mass based on the total amount of the grease composition.

6. A bearing and a rotating device, wherein the grease according to claim 1 or 2 is enclosed therein as a lubricant.

7. A bearing and a rotating device, wherein the grease according to claim 3 is enclosed therein as a lubricant.

8. A bearing and a rotating device, wherein the grease according to claim 4 is enclosed therein as a lubricant.

9. A bearing and a rotating device, wherein the grease according to claim 5 is enclosed therein as a lubricant.

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