Grease composition, and bearing and rolling device in each of which said grease composition is sealed

Abstract

A grease composition which contains a base oil (A), a urea-based thickening agent (B), a fatty acid copper salt (C), and one or more ester compounds (D) that are selected from among a succinate ester and a sorbitan ester, wherein the base oil (A) contains a trimellitic acid ester or an alkyl diphenyl ether.

Description

Grease composition, and bearings and rolling devices containing the grease composition.

[0001] The present invention relates to a grease composition, and to a bearing and rolling device containing the grease composition. This application claims priority under Japanese Patent Application No. 2025-004978, filed in Japan on January 14, 2025, the contents of which are incorporated herein by reference.

[0002] In automobiles, the demand for increased passenger space and smaller, lighter vehicles necessitates a reduction in engine compartment size. Further miniaturization and weight reduction of electrical components and auxiliary equipment such as alternators, electromagnetic clutches for car air conditioners, intermediate pulleys, and electric fan motors are also being pursued. Furthermore, the operating environments are diverse; for example, in tropical rainforest regions and areas near the ocean, high humidity and salinity in the atmosphere necessitate increased corrosion resistance. In addition, electrical components and auxiliary equipment themselves are required to have higher output. Moreover, the demand for improved quietness is leading to increased sealing of engine compartments, further exacerbating the high temperatures within the engine compartment. Therefore, components with specifications capable of withstanding even higher temperatures are required.

[0003] Rolling bearings are used in these electrical components and auxiliary equipment, and grease is primarily used to lubricate these rolling bearings. To meet the demands of electrical components and auxiliary equipment (miniaturization, weight reduction, high output, corrosion resistance, and high temperature resistance), bearings are required to be able to rotate at high speeds, withstand heavy loads, and possess corrosion resistance and high temperature resistance. Generally, adding a rust inhibitor to the grease is effective in improving the corrosion resistance of bearings. Adding an antioxidant to the grease is effective in suppressing the oxidative degradation of the grease in order to improve the high temperature resistance of bearings.

[0004] On the other hand, when rolling bearings are used under high-speed rotation and high-load conditions, delamination accompanied by a change in white structure occurs on the rolling surface of the bearings, and there have been reports of cases where the bearings reach the end of their lifespan prematurely. Furthermore, the above-mentioned electrical components and auxiliary equipment are often driven by pulleys to which power is transmitted by a belt from a power source. It is presumed that the static electricity generated by the friction between the belt and the pulley in this process causes the rolling bearings that support the rotation of the pulleys to become charged, leading to premature damage to the rolling bearings.

[0005] To prevent the above-mentioned problems and simultaneously satisfy the rust prevention and high-temperature resistance requirements of the bearings, a grease is being considered that is a blend of a base oil and additives such as antioxidants and rust inhibitors. Patent Document 1 discloses a grease composition containing various additives, in which trimellitic acid ester is used as the base oil for the purpose of suppressing peeling.

[0006] Japanese Patent Publication No. 2005-298537

[0007] However, with further increases in rotational speed and load, there are concerns that delamination on the rolling surface of rolling bearings will become even more pronounced. Furthermore, the addition of certain additives can sometimes degrade specific properties of the grease composition. Specifically, the addition of antioxidants and rust inhibitors can reduce the delamination-preventing properties of the grease composition. Therefore, developing a grease composition that further suppresses delamination while also possessing rust prevention and oxidation resistance is extremely difficult.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a grease composition that has excellent peeling prevention, rust prevention, and oxidation resistance, as well as a bearing and rolling device containing the grease composition.

[0009] To solve the above problems, the present invention employs the following configurations: [1] A grease composition comprising a base oil (A), a urea-based thickener (B), copper fatty acid (C), and one or more ester compounds (D) selected from succinic acid esters and sorbitan esters, wherein the base oil (A) comprises trimellitic acid ester or alkyl diphenyl ether. [2] The grease composition according to [1], wherein the base oil (A) comprises trimellitic acid ester. [3] The grease composition according to [1] or [2], wherein the urea-based thickener (B) comprises one or more urea-based compounds selected from diurea compounds obtained by the reaction of diisocyanate and amine, polyurea compounds, and urea-urethane compounds. [4] The grease composition according to [3], wherein the amine comprises an alicyclic amine. [5] The grease composition according to [3], wherein the amine comprises an alicyclic amine and a chain-like aliphatic amine. [6] The grease composition according to any one of [1] to [5], wherein the copper fatty acid (C) comprises branched-chain copper fatty acid. [7] A bearing and rolling device characterized by containing the grease composition according to any one of [1] to [6] as a lubricant.

[0010] According to the present invention, it is possible to provide a grease composition that has excellent peeling prevention, rust prevention, and oxidation resistance, as well as a bearing and rolling device containing the grease composition.

[0011] This is a cross-sectional view showing a rolling device according to one embodiment of the present invention.

[0012] (Grease Composition) The grease composition of this embodiment contains a base oil (A), a urea-based thickener (B), copper fatty acid (C), and one or more ester compounds (D) selected from succinic acid esters and sorbitan esters.

[0013] The consistency of the grease composition of the present embodiment is preferably 210 or more, more preferably 215 or more, still more preferably 220 or more, and particularly preferably 230 or more. The consistency of the grease composition of the present embodiment is preferably 310 or less, more preferably 305 or less, still more preferably 300 or less, and particularly preferably 295 or less. For example, the consistency of the grease composition of the present embodiment is preferably 210 or more and 310 or less, more preferably 215 or more and 305 or less, still more preferably 220 or more and 300 or less, and particularly preferably 230 or more and 295 or less. When the consistency of the grease composition of the present embodiment is within the above preferable range, the grease characteristics are further improved. The consistency in this specification means the mixed consistency measured in accordance with JIS K2220:2013.

[0014] <Base oil (A)> The kinematic viscosity of the base oil (A) at 40°C is preferably 30 mm ２ / s or more, more preferably 40 mm ２ / s or more, still more preferably 45 mm ２ / s or more. The kinematic viscosity of the base oil (A) at 40°C is preferably 150 mm ２ / s or less, more preferably 130 mm ２ / s or less, still more preferably 110 mm ２ / s or less. For example, the kinematic viscosity of the base oil (A) at 40°C is preferably 30 mm ２ / s or more and 150 mm ２ / s or less, more preferably 40 mm ２ / s or more and 130 mm ２ / s or less, still more preferably 45 mm ２ / s or more and 110 mm ２ / s or less.

[0015] When the kinematic viscosity of the base oil (A) of the grease composition of the present embodiment at 40°C is within the above preferable range, the lubricity is further improved.

[0016] The kinematic viscosity at 40°C in this specification means a value measured in accordance with JIS K2283:2000 "Crude oil and petroleum products - Test method for kinematic viscosity and method for calculating viscosity index".

[0017] The base oil (A) contains trimellitic acid ester (A1) (hereinafter also referred to as "(A1) component") and / or alkyldiphenyl ether (A2) (hereinafter also referred to as "(A2) component").

[0018] <<Trimellitic acid ester (A1)>> From the viewpoint of improving the anti-separation property, the compound represented by the following general formula (1) is preferable as the (A1) component.

[0019] [In the formula, R １ 、R ２ and R ３ are a hydrogen atom or a hydrocarbon group having 5 to 20 carbon atoms, and R １ 、R ２ and R ３ may be the same as or different from each other. However, R １ 、R ２ and R <unk> ３ shall not all be hydrogen atoms. ]

[0020] The hydrocarbon groups in R １ 、R ２ and R ３ are saturated or unsaturated linear or branched alkyl groups. The hydrocarbon groups in R １ 、R ２ and R ３ are preferably hydrocarbon groups having 7 to 15 carbon atoms, more preferably hydrocarbon groups having 8 to 11 carbon atoms, and even more preferably hydrocarbon groups having 9 to 11 carbon atoms from the viewpoint of ensuring evaporation resistance, ensuring a stable oil film when enclosed in a bearing as grease, and suppressing the stirring heat when enclosed in a bearing as grease.

[0021] Commercially available products of the compound represented by the general formula (I) include "Trimex T-08" and "N-08" manufactured by Kao Corporation, "Adeka Puruber T-90" manufactured by Asahi Denka Kogyo Co., Ltd., and the like.

[0022] The grease composition of this embodiment may use one kind of component (A1) alone, or may use a mixture of a plurality of components (A1). The content of the component (A1) is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 65% by mass or more, and particularly preferably 70% by mass or more with respect to the total amount of the grease composition of this embodiment. The content of the component (A1) is preferably 95% by mass or less, more preferably 90% by mass or less, and still more preferably 85% by mass or less with respect to the total amount of the grease composition of this embodiment. For example, the content of the component (A1) is preferably 50% by mass or more and 95% by mass or less, more preferably 60% by mass or more and 90% by mass or less, still more preferably 65% by mass or more and 85% by mass or less, and particularly preferably 70% by mass or more and 85% by mass or less with respect to the total amount of the grease composition of this embodiment.

[0023] When the content of the component (A1) is within the above preferred range, the anti-separation property is further improved.

[0024] ≪Alkyldiphenyl ether (A2)≫ As the component (A2), a compound represented by the following general formula (2) is preferable from the viewpoint of improving the anti-separation property.

[0025] [In the formula, R ３ and R ４ are each independently an alkyl group. n and m are integers from 0 to 5. When n and m are 2 or more, the plurality of alkyl groups in R ３ and R ４ may be the same or different from each other.]

[0026] The alkyl group in R ３ and R ４ is preferably a linear alkyl group having 8 to 20 carbon atoms, and more preferably a linear alkyl group having 12 to 14 carbon atoms.

[0027] The grease composition of this embodiment may use one type of component (A2) alone, or may use a mixture of multiple components (A2). The content of component (A2) is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 65% ​​by mass or more, and particularly preferably 70% by mass or more, based on the total amount of the grease composition of this embodiment. The content of component (A2) is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less, based on the total amount of the grease composition of this embodiment. For example, the content of component (A2) is preferably 50% by mass or more and 95% by mass or less, more preferably 60% by mass or more and 90% by mass or less, even more preferably 65% ​​by mass or more and 85% by mass or less, and particularly preferably 70% by mass or more and 85% by mass or less, based on the total amount of the grease composition of this embodiment.

[0028] (A2) When the content of component is within the above preferred range, the peeling prevention properties are further improved.

[0029] The grease composition of this embodiment may contain base oils other than those described above for components (A1) and (A2). Other base oils that can be used include mineral oil, alkylnaphthalene, fluorine oil, silicone oil, glycol oil, synthetic hydrocarbon oil, ether oil other than alkyldiphenyl ether, ester oil other than trimellitic acid ester, etc. Specifically, as synthetic hydrocarbon oils, poly-α-olefin oil, etc. can be used; as ether oils, alkyltriphenyl ether oil, etc. can be used; and as ester oils, diester oil, neopentyl-type polyol ester oil, or complex ester oils thereof can be used.

[0030] In the grease composition of this embodiment, the total content of the above-mentioned components (A1) and (A2) is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more, based on the total amount of base oil (A). The grease composition of this embodiment preferably contains only the above-mentioned components (A1) and / or (A2) as the base oil (A).

[0031] The content of component (A) is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 65% ​​by mass or more, and particularly preferably 70% by mass or more, based on the total amount of the grease composition of this embodiment. The content of component (A) is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less, based on the total amount of the grease composition of this embodiment. For example, the content of component (A) is preferably 50% by mass or more and 95% by mass or less, more preferably 60% by mass or more and 90% by mass or less, even more preferably 65% ​​by mass or more and 85% by mass or less, and particularly preferably 70% by mass or more and 85% by mass or less, based on the total amount of the grease composition of this embodiment.

[0032] <Urea-based thickener (B)> Urea-based thickener (B) (hereinafter also referred to as "component (B)") includes diurea compounds obtained by the reaction of diisocyanate with monoamine, polyurea compounds obtained by the reaction of diisocyanate with monoamine or diamine, and diisocyanate with primary amine and general formula R １ Urea urethane compounds obtained by reaction with a higher alcohol represented by -OH, or diurethane compounds obtained by reaction of diisocyanate with a higher alcohol, can be used.

[0033] A monoamine is a compound having one amino group in one molecule. Preferred primary amines among monoamines include octylamine, dodecylamine, hexadecylamine, octadecylamine, oleylamine, aniline, paratoluidine, and cyclohexylamine, with octadecylamine and cyclohexylamine being more preferred. A preferred secondary amine is dicyclohexylamine. A diamine is a compound having two amino groups in one molecule. Preferred diamines include ethylenediamine, propanediamine, butanediamine, hexanediamine, octanediamine, phenylenediamine, tolylenediamine, xylenediamine, and diaminodiphenylmethane. The hydrocarbon groups of monoamines and diamines may be acyclic or cyclic hydrocarbons, including aromatic hydrocarbons, alicyclic hydrocarbons, and chain-like aliphatic hydrocarbons. The number of carbon atoms is preferably 2 to 20, and more preferably 4 to 18.

[0034] The amine used in the urea thickener preferably contains an alicyclic amine, more preferably a mixed amine of an alicyclic amine (hereinafter also referred to as the "first amine component") and an aromatic amine or a chain-like aliphatic amine or a combination thereof (hereinafter also referred to as the "second amine component"), and even more preferably a mixed amine of an alicyclic amine and a chain-like aliphatic amine.

[0035] There are no particular restrictions on the mixing ratio of the first amine component to the second amine component in the mixed amine, but it is preferable that the molar ratio (first amine component: second amine component) of the first amine component to the second amine component be 99:1 to 55:45, and more preferably 90:10 to 75:25. In this molar ratio, if the first amine component is a combination of two or more compounds, the molar amount of the first amine component is the total molar amount of those compounds, and if the second amine component is a combination of two or more compounds, the molar amount of the second amine component is the total molar amount of those compounds.

[0036] A diisocyanate is a compound in which two hydrogen atoms of a hydrocarbon are replaced by an isocyanate group. The hydrocarbon may be an acyclic or cyclic hydrocarbon, and may be an aromatic hydrocarbon, an alicyclic hydrocarbon, or an aliphatic hydrocarbon. The number of carbon atoms in the hydrocarbon is preferably 4 to 20, more preferably 8 to 18. Preferred specific examples of diisocyanates include phenylenediisocyanate, tolylenediisocyanate, biphenyldiisocyanate (diphenyldiisocyanate), diphenylmethanediisocyanate, octadecanediisocyanate, decanediisocyanate, and hexanediisocyanate. Diisocyanates may be used individually or in combination of two or more.

[0037] As a urea-based thickener, it is preferable to use a diurea compound represented by the following general formula (V).

[0038] [In the formula, R １０ R is a divalent hydrocarbon group. ２０ Each of these is independently a monovalent alicyclic hydrocarbon group, a monovalent linear aliphatic hydrocarbon group, or a monovalent aromatic hydrocarbon group, or a combination thereof.

[0039] In general formula (V), R １０ R is a divalent hydrocarbon group, which may be an acyclic hydrocarbon group or a cyclic hydrocarbon group, and may be any of aromatic hydrocarbon groups, alicyclic hydrocarbon groups, or aliphatic hydrocarbon groups. １０ The number of carbon atoms is preferably 4 to 20, more preferably 8 to 18.

[0040] R ２０ These may be the same or different, and are monovalent alicyclic hydrocarbon groups, monovalent linear aliphatic hydrocarbon groups, or monovalent aromatic hydrocarbon groups, or a combination thereof. ２０ The number of carbon atoms is preferably 2 to 20, more preferably 4 to 18. In one molecule, there are two R ２０ Both may be alicyclic hydrocarbon groups, and the two R ２０ Both R may be aromatic hydrocarbon groups or linear aliphatic hydrocarbon groups, and the two R２０ One of them may be an alicyclic hydrocarbon group, and the other may be an aromatic hydrocarbon group or a chain-like aliphatic hydrocarbon group. The urea thickener as a whole is R ２０ This is a combination of a monovalent alicyclic hydrocarbon group and a monovalent aromatic hydrocarbon group or a chain-like aliphatic hydrocarbon group, and the R of the urea thickener as a whole ２０ The molar ratio of the combined groups (alicyclic hydrocarbon groups: aromatic hydrocarbon groups and / or linear aliphatic hydrocarbon groups) is preferably 99:1 to 55:45, and particularly preferably 90:10 to 75:25.

[0041] The grease composition of this embodiment may use component (B) alone or a mixture of multiple components (B). The content of component (B) is preferably 1.0% by mass or more, more preferably 5.0% by mass or more, and even more preferably 10% by mass or more, based on the total amount of the grease composition of this embodiment. The content of component (B) is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less, based on the total amount of the grease composition of this embodiment. For example, the content of component (B) is preferably 1.0% by mass or more and 40% by mass or less, more preferably 5.0% by mass or more and 30% by mass or less, and even more preferably 10% by mass or more and 25% by mass or less, based on the total amount of the grease composition of this embodiment.

[0042] (B) If the content of component (B) is above the preferred lower limit above, problems such as reduced seizure life due to grease leakage and contamination of surrounding mechanisms will be less likely to occur. If the content of component (B) is below the preferred upper limit above, the fluidity and lubricity of the grease will be better, resulting in better seizure life, torque, and pressure feeding when sealing bearings.

[0043] <Copper Fatty Acid (C)> Examples of fatty acids in copper fatty acid (C) (hereinafter also referred to as "component (C)") include fatty acids having 1 to 25 carbon atoms, and these fatty acids may be linear or branched, and may be saturated or unsaturated. Among these fatty acids, fatty acids having 6 to 24 carbon atoms are preferred, and fatty acids having 8 to 18 carbon atoms are more preferred.

[0044] Preferred specific examples of the fatty acid include linear saturated fatty acids such as n-hexanoic acid, n-heptanoic acid, n-octanoic acid (caprylic acid), n-nonanoic acid, n-decanoic acid (capric acid), n-undecanoic acid, n-dodecanoic acid (lauric acid), n-tridecanoic acid, n-tetradecanoic acid (myristic acid), n-pentadecanoic acid, n-hexadecanoic acid (palmitic acid), n-heptadecanoic acid, n-octadecanoic acid (stearic acid), n-eicosanoic acid (arachidic acid), docosanoic acid (behenic acid), and tetracosanoic acid (lignoceric acid); isoheptanoic acid, isooctanoic acid, isono Examples include branched-chain saturated fatty acids such as nanic acid, isodecanoic acid, neodecanoic acid, isoundecanoic acid, isododecanoic acid, isotridecanoic acid, isotetradecanoic acid, isopentadecanoic acid, isohexadecanoic acid, isoheptadecanoic acid, isooctadecanoic acid, and isoeicosanoic acid; unsaturated fatty acids such as 9-tetradecenoic acid (myristoleic acid), 9-hexadecenoic acid (palmitoleic acid), 9-octadecenoic acid (oleic acid), eicosenoic acid, and linoleic acid (9,12-octadecadienoic acid); and naturally derived fatty acids containing one or more of these fatty acids (e.g., beef tallow, coconut oil).

[0045] Among the above, the fatty acid in component (C) is preferably a branched-chain fatty acid having 8 to 18 carbon atoms, more preferably a branched-chain fatty acid having 8 to 16 carbon atoms, and even more preferably a branched-chain fatty acid having 8 to 12 carbon atoms.

[0046] The grease composition of this embodiment may use component (C) alone or a mixture of multiple components (C). The content of copper atoms derived from component (C) is preferably 10 ppm by mass or more, more preferably 100 ppm by mass or more, and even more preferably 200 ppm by mass or more, based on the total amount of the grease composition of this embodiment. The content of copper atoms derived from component (C) is preferably 5,000 ppm by mass or less, more preferably 4,000 ppm by mass or less, and even more preferably 3,000 ppm by mass or less, based on the total amount of the grease composition of this embodiment. For example, the content of copper atoms derived from component (C) is preferably 10 ppm by mass or more and 5,000 ppm by mass or less, more preferably 100 ppm by mass or more and 4,000 ppm by mass or less, and even more preferably 200 ppm by mass or more and 3,000 ppm by mass or less, based on the total amount of the grease composition of this embodiment.

[0047] If the copper atom content derived from component (C) is above the preferred lower limit above, the delamination life suppression effect is further improved. If the copper atom content derived from component (C) is below the preferred upper limit above, the oxidation stability is further improved, and the seizure life is further improved.

[0048] <Ester Compound (D)> The grease composition of this embodiment contains one or more ester compounds (D) (hereinafter also referred to as "component (D)") selected from succinate ester (D1) (hereinafter also referred to as "component (D1)") and sorbitan ester (D2) (hereinafter also referred to as "component (D2)").

[0049] <<Succinate Ester (D1)>> The (D1) component includes succinate half-esters and succinate full-esters. Succinate half-esters are compounds in which only one of the two carboxylic acid groups of succinic acid forms an ester bond with an alcohol or the like. Examples of alcohols that form an ester bond include monovalent to trivalent alcohols having 2 to 10 carbon atoms. Succinic acid may also have an alkyl group or alkenyl group added to it, and the number of carbon atoms of the alkyl group or alkenyl group is preferably 6 to 24, and more preferably 8 to 16.

[0050] In the grease composition of this embodiment, the content of component (D1) 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. Furthermore, it is preferably 10% by mass or less, and more preferably 5% by mass or less. Specifically, the range is more preferably 0.1% by mass or more and 10% by mass or less, and even more preferably 0.2% by mass or more and 5% by mass or less. By having a content of component (D1) above the lower limit, better rust prevention can be obtained. By having a content of component (D1) below the upper limit, a decrease in fluidity at low temperatures can be prevented.

[0051] The grease composition of this embodiment may use one type of (D1) component alone, or may use a mixture of multiple (D1) components. The content of (D1) component is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more, based on the total amount of the grease composition of this embodiment. The content of (D1) component is preferably 10% by mass or less, more preferably 5.0% by mass or less, and even more preferably 1.0% by mass or less, based on the total amount of the grease composition of this embodiment. For example, the content of (D1) component is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.2% by mass or more and 5.0% by mass or less, and even more preferably 0.3% by mass or more and 1.0% by mass or less, based on the total amount of the grease composition of this embodiment.

[0052] If the content of component (D1) is above the preferred lower limit above, rust prevention is further improved. If the content of component (D1) is below the preferred upper limit above, the decrease in fluidity at low temperatures can be better prevented.

[0053] <<Sorbitan Ester (D2)>> Examples of (D2) components include sorbitan monoesters, diesters, triesters, and tetraesters. Specifically, examples of (D2) components include sorbitan monoesters, diesters, triesters, tetraesters, and mixtures thereof.

[0054] The grease composition of this embodiment may use one type of (D2) component alone, or may use a mixture of multiple (D2) components. The content of (D2) component is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, based on the total amount of the grease composition of this embodiment. The content of (D2) component is preferably 10% by mass or less, more preferably 5.0% by mass or less, and even more preferably 3.0% by mass or less, based on the total amount of the grease composition of this embodiment. For example, the content of (D2) component is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.3% by mass or more and 5.0% by mass or less, and even more preferably 0.5% by mass or more and 3.0% by mass or less, based on the total amount of the grease composition of this embodiment.

[0055] If the content of component (D2) is above the preferred lower limit mentioned above, rust prevention is further improved. If the content of component (D2) is below the preferred upper limit mentioned above, the decrease in fluidity at low temperatures can be better prevented.

[0056] The grease composition of this embodiment preferably contains both component (D1) and component (D2) described above. When component (D1) and component (D2) are used in combination, the synergistic effect of these components makes it possible to further improve rust prevention without reducing peeling prevention.

[0057] In the grease composition of this embodiment, the mass ratio of sorbitan ester content to succinate ester content (sorbitan ester / succinate ester) is preferably 0.1 or more and 10 or less, more preferably 0.3 or more and 5 or less, and even more preferably 0.5 or more and 2 or less.

[0058] <Optional Components> The grease composition of this embodiment may contain optional components other than the base oil components (A), (B), (C), and (D) described above. These optional components may be additives commonly used in greases, such as extreme pressure agents like organic molybdenum, oiliness improvers like fatty acids and animal / vegetable oils, and metal deactivators like benzotriazole, either alone or in a mixture of two or more. The content of these optional components is not particularly limited as long as it does not impair the effects of the present invention.

[0059] The following description of this embodiment will be made in detail with reference to the attached drawings. Figure 1 is a longitudinal cross-sectional view showing the structure of a ball bearing 1, which is one embodiment of the rolling device according to the present invention.

[0060] The ball bearing 1 in Figure 1 consists of an inner ring 10, an outer ring 11, a plurality of balls 13 that are rotatably disposed between the inner ring 10 and the outer ring 11, a cage 12 that holds the plurality of balls 13, and a contact-type seal 14 attached to the outer ring 11. The bearing space surrounded by the inner ring 10, the outer ring 11 and the seal 14 is filled with a grease composition G and sealed inside the ball bearing 1 by the seal 14. The contact surfaces between the raceway surfaces of both rings 10 and 11 and the balls 13 are lubricated by this grease composition G.

[0061] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0062] <Formulation of Grease Compositions> The grease compositions of Examples 1 to 3 and Comparative Examples 1 to 3 were prepared by blending base oil (A), component (B), component (C), and component (D) in the proportions shown in Table 1. The values ​​in Table 1 represent the proportion (mass%) of each component relative to the total amount of the grease composition.

[0063] (1) Base oil (A) A1-1: trimellitic acid ester (kinematic viscosity: 75 mm) ２ / s (40℃) A2-1: Dialkyldiphenyl ether having an alkyl group with 12 carbon atoms and an alkyl group with 14 carbon atoms (kinematic viscosity: 72 mm) ２ / s (40℃)

[0064] (2) Urea-based thickeners (B) B-1: Diurea compound (a diurea compound obtained by the reaction of diphenylmethane-4,4'-diisocyanate with cyclohexylamine and octadecylamine (CHA:ODA = 80:20)) B-2: Diurea compound (a diurea compound obtained by the reaction of diphenylmethane-4,4'-diisocyanate with cyclohexylamine and paratoluidine (CHA:paratoluidine = 80:20))

[0065] (3) Copper fatty acid (C) C-1: Copper neodecanoate c-1: Bismuth fatty acid

[0066] (4) Ester compounds (D) D1-1: Succinate ester D2-1: Sorbitan ester

[0067] (5) Other additives d-1: Zinc naphthenate (rust inhibitor)

[0068] [Evaluation of peeling prevention properties] ・White peeling test: A deep groove ball bearing with bearing designation number: 6301, inner diameter: Φ12 mm, outer diameter: Φ37 mm, width: 12 mm, material: SUJ2 was filled with 1 g of each example grease composition and subjected to a radial load of 1225 N at room temperature (25°C) for 7000 min. －１ The bearings were rotated. If the vibration value exceeded the specified value (8G), the bearing was deemed unsuccessful at that point (judged to have delaminated). Bearings that reached 700 hours of testing without delamination were deemed successful. After the test, the presence or absence of delamination of the bearing steel was checked. The results are shown in Table 1 according to the following criteria: A: No delamination B: Delamination present

[0069] [Evaluation of rust prevention] Based on the test method specified in ASTM D1743-73, the water used to immerse the bearing was changed to 0.1 mass% salt water, the test time was changed to 24 hours, and the test temperature was changed to 25°C. The number of rust spots was then checked. The following criteria are shown in Table 1. A: No corrosion was observed. B: Corrosion was observed, with three or fewer initial-stage corrosion spots that were clearly visible to the naked eye. C: Corrosion was observed, with the size of the corrosion being larger than that of evaluation B, or with four or more corrosion spots.

[0070]

[0071] As shown in Table 1, the grease composition of the example exhibited superior peel prevention, rust prevention, and oxidation resistance compared to the grease composition of the comparative example.

[0072] While preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Additions, omissions, substitutions, and other modifications are possible without departing from the spirit of the invention. The present invention is not limited by the foregoing description, but only by the scope of the appended claims.

[0073] 1 Ball bearing 10 Inner ring 11 Outer ring 12 Cage 13 Balls 14 Contact type seal

Claims

1. A grease composition comprising a base oil (A), a urea-based thickener (B), copper fatty acid (C), and one or more ester compounds (D) selected from succinic acid esters and sorbitan esters, wherein the base oil (A) comprises trimellitic acid ester or alkyl diphenyl ether.

2. The grease composition according to claim 1, wherein the base oil (A) comprises a trimellitic acid ester.

3. The grease composition according to claim 1 or 2, wherein the urea-based thickener (B) comprises one or more urea-based compounds selected from diurea compounds, polyurea compounds, and urea-urethane compounds obtained by the reaction of diisocyanate and amine.

4. The grease composition according to claim 3, wherein the amine includes an alicyclic amine.

5. The grease composition according to claim 3, wherein the amine comprises an alicyclic amine and a chain-like aliphatic amine.

6. The grease composition according to claim 1 or 2, wherein the copper fatty acid (C) comprises branched-chain copper fatty acid.

7. A bearing and rolling device characterized by containing the grease composition described in claim 1 or 2 as a lubricant.

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