JP2022085766A - Anti-oxidation grease composition and bearing that encloses the same - Google Patents

Abstract

To provide a grease composition and a rolling bearing, wherein the grease composition is resistant to deterioration even under influence of oxidizing substances such as ozone and hydroxyl radicals, and can achieve excellent acoustic characteristics and low torque, and the rolling bearing can suppress generation of abnormal noise, and can realize low torque by applying the grease composition.SOLUTION: Provided is the grease composition comprising: a base oil; an urea-based thickener composed of a diurea compound represented by formula (1): R1-NHCONH-R2-NHCONH-R3 (in the formula, R1 and R3 each independently represent a monovalent aliphatic hydrocarbon group, a monovalent alicyclic hydrocarbon group, or a monovalent aromatic hydrocarbon group, at this time, a ratio of the monovalent aliphatic hydrocarbon group to the total number of moles of R1 and R3 is 10% to 60%, and R2 represents a divalent aromatic hydrocarbon group); and an aromatic amine-based antioxidant. Also provided is the rolling bearing encapsulated with the grease composition .SELECTED DRAWING: None

Description

The present invention relates to an oxidation resistant grease composition and a bearing in which the composition is encapsulated.

When the concentration of gas components emitted into the atmosphere rises due to the increase in the scale of factories and the increase in traffic volume of automobiles, etc., nitrogen oxides and hydrocarbons (volatile organic compounds) contained in the gas components are affected by ultraviolet rays. In response to this, it may deteriorate and produce oxidizing substances such as ozone. This phenomenon is also called photochemical smog.
In recent years, by discharging oxidizing substances such as ozone and active oxygen (oxygen radicals, hydroxyl radicals, etc.) into the space as clean components at low concentrations, bacteria, viruses, foul odors, etc., including the space around us, have been reduced. Devices for making radicals (for example, ion generators, air purifiers equipped with ion generators, air regulators, etc.) and chemicals have become widespread.

When photochemical smog is generated in the atmosphere or a low-concentration oxidizing substance is released as a cleaning component from an air conditioner or the like, the oxidizing substance in the space may adversely affect surrounding objects. For example, metal parts, resin parts, grease in bearings, and the like may be oxidized, that is, deteriorated by the ozone, hydroxyl radicals, and the like. In particular, since the blower for diffusing the cleaning component and the bearing used therein are installed near an oxidizing substance generator (ion generation source, etc.) which is also a cleaning component, it is said that they are easily exposed to the oxidizing substance. Conceivable.

For example, Patent Document 1 describes a thickener composed of a base oil and a urea-based compound, and an amine-based antioxidant as an antioxidant, with the aim of improving the oxidation resistance of the grease in order to obtain a grease having a high temperature and a long life. There is a disclosure of a grease composition using a quinoline-based antioxidant in combination.

Japanese Unexamined Patent Publication No. 2018-021140

The ion generator, the air conditioner, and the like blow ozone, hydroxyl radicals, and the like into the room by a blower installed in the device to sterilize and deodorize airborne bacteria in the room. However, there are cases where abnormal noise is confirmed after installing and operating these devices. One of the factors is the deterioration of the grease sealed in the bearing provided in the blower in the device due to ozone and hydroxy radicals generated from the above-mentioned oxidizing substance generator (ion generation source, etc.). It has been confirmed that abnormal noise is generated in the bearing due to this deteriorated grease.
Further, in recent years, an air conditioner or the like is required to operate with low electric power. The blowers used for these are also required to operate at low power, and the bearings used for the blowers are required to be driven with low torque. Until now, as the grease used for bearings for the purpose of low torque, grease having channeling characteristics (the property that the grease-based lubricant in the bearing is easily pushed away by the rolling elements) has been generally used. Grease has a problem that it tends to cause abnormal noise. On the other hand, grease having excellent acoustic characteristics tends to have a high torque due to a churn phenomenon (grease is constantly agitated inside the bearing during bearing operation). As described above, there is a demand for grease having excellent characteristics of both low torque and acoustic characteristics.

The present invention is resistant to deterioration even under the influence of oxidizing substances such as ozone and hydroxyl radicals, and is capable of achieving excellent acoustic characteristics and low torque. It is an object of the present invention to provide a rolling bearing capable of suppressing the generation of radical grease and realizing low torque.

One aspect of the present invention is a base oil and
A urea-based thickener composed of a diurea compound represented by the following formula (1), and
R ₁ -NHCONH-R ₂ -NHCONH-R ₃ ... (1)
(In the formula, R ₁ and R ₃ each independently represent a monovalent aliphatic hydrocarbon group, a monovalent alicyclic hydrocarbon group, or a monovalent aromatic hydrocarbon group, and at this time, The ratio of monovalent aliphatic hydrocarbon groups to the total number of moles of R ₁ and R ₃ is 10% to 60%.
R ₂ represents a divalent aromatic hydrocarbon group. )
It is a grease composition containing an aromatic amine-based antioxidant.
The present invention also covers rolling bearings in which the grease composition is encapsulated, and the rolling bearings provided in a blower of an ion generator or an air conditioner.

It is a schematic diagram explaining the structure of the rolling bearing of this invention. It is a schematic diagram explaining the structure of the motor provided with the rolling bearing of this invention. It is a schematic diagram of the ion generator or the air control device which has a blower provided with the rolling bearing of this invention. It is a conceptual diagram of the rotating apparatus used in the torque test. Acoustic evaluation (Anderon value) using a grease composition containing the urea-based thickener with respect to a change (horizontal axis) in the compounding ratio (mol%) of the aliphatic amine in the amine compound constituting the urea-based thickener. It is a figure which shows the result (vertical axis) of).

As described above, in an ion generator, an air conditioning device, or the like that emits ozone, hydroxyl radicals, etc., abnormal noise is generated due to deterioration of the grease sealed in the bearing provided in the blower in the device. Has been confirmed. However, until now, attention has been paid to the bearings used in the blowers installed in such devices, and no proposal has been made for an improved grease composition for suppressing the generation of abnormal noise.
The present inventors have studied grease deterioration in the presence of oxidizing substances such as ozone and hydroxy radicals, and found that greases using urea compounds having a high proportion of groups derived from aliphatic amines as thickeners. It has been found that agglomerates are likely to form, which adversely affects the acoustic properties of the bearing. On the other hand, it has been found that a grease capable of achieving low torque can be obtained by using a urea compound having a group derived from an aliphatic amine as a thickener. At the same time, it has been found that when an aliphatic amine compound is used as an antioxidant to be blended in the grease, deterioration of acoustic characteristics progresses.
As one of the causes of deterioration of the grease, the aliphatic groups contained in the urea compound of the thickener and the aliphatic amine compound of the antioxidant are denatured by oxidizing substances such as ozone and hydroxy radicals, and one of them. It is probable that the parts were condensed to cause the formation of agglomerates.

The grease composition enclosed in the rolling bearing according to the present invention (hereinafter, simply referred to as "grease composition") is characterized by containing a specific urea-based thickener as described later, and further. It is characterized by blending a specific antioxidant. This grease composition suppresses deterioration even in the presence of an oxidizing substance, and realizes good acoustic characteristics and low torque. This will be described in detail below.

[Grease composition]
First, the grease composition of the present invention will be described.

<Base oil>
In the grease composition of the present invention, synthetic oils such as hydrocarbon-based synthetic oils, ester-based synthetic oils, and ether-based synthetic oils, which are generally used as grease base oils, can be used alone or in combination as the base oil. ..
Fluorine-based base oils are generally excellent in heat resistance and oxidation resistance, but inferior in lubrication characteristics and acoustic characteristics. Therefore, in rolling bearings used for equipment / devices that are expected to be used indoors such as air conditioners, the use of fluorine-based base oil in the grease composition used for the bearings is not suitable.

Examples of the hydrocarbon-based synthetic oil include polyalphaolefins (PAOs) such as normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, and 1-decene ethylene oligomer.
Examples of the ester-based synthetic oil include diester oils such as dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecylphthalate, and methyl acetyllithinolate, and tri. Aromatic ester oils such as octyl lymericate, tri-2-ethylhexyl trimellitate, tridecyl trimellitate, tetraoctylpyromericate, tetra-2-ethylhexylpyromeritate, trimethylolpropane caprilate, trimethylolpropane Examples thereof include polyol ester oils such as pelargonate, pentaerythritol-2-ethylhexanoate and pentaerythritol pelargonate, and carbonate ester oils. Among these, aromatic ester oils can be preferably used.
Examples of the ether-based synthetic oil include alkyl ether oils such as monoalkyl diphenyl ether, dialkyl diphenyl ether, and polyalkyl diphenyl ether, and alkyl diphenyl ether oil.

The ratio of the base oil to the total amount of the grease composition of the present invention can be 70 to 90% by mass, for example, 75 to 95% by mass or 75 to 85% by mass.

<Thickener>
In the grease composition used in the present invention, a urea-based thickener is added as a thickener.
The urea compound is excellent in both heat resistance and water resistance and is advantageous in oxidative stability because it does not contain a metal element, and is suitably used as a thickener in a place of application in a high temperature environment or the like.
As the urea compound, a urea compound such as a diurea compound, a triurea compound, or a polyurea compound can be used, but in the present invention, the diurea compound is used from the viewpoint of acoustic characteristics (quietness).
Examples of the type of the diurea compound include aliphatic diurea, alicyclic-aliphatic diurea, and fat-aromatic diurea.
Conventionally known urea compounds can be used as these urea-based thickeners.

Examples of the urea-based thickener suitable for the present invention include diurea compounds represented by the following general formula (1).
R ₁ -NHCONH-R ₂ -NHCONH-R ₃ ... (1)
In the formula (1), R ₁ and R ₃ each independently represent a monovalent aliphatic hydrocarbon group, a monovalent alicyclic hydrocarbon group, or a monovalent aromatic hydrocarbon group. When, the molar ratio of the monovalent aliphatic hydrocarbon group to the monovalent alicyclic hydrocarbon group and / or the monovalent aromatic hydrocarbon group is the total number of moles of R ₁ and R ₃ . 10% to 60%: 90% to 40%.
Further, R ₂ represents a divalent aromatic hydrocarbon group.

Examples of the monovalent aliphatic hydrocarbon group include linear or branched saturated or unsaturated alkyl groups having 6 to 26 carbon atoms.
Examples of the monovalent alicyclic hydrocarbon group include a cycloalkyl group having 5 to 12 carbon atoms.
Examples of the aromatic hydrocarbon group include monovalent or divalent aromatic hydrocarbon groups having 6 to 20 carbon atoms.

The urea compound used as the urea-based thickener can be synthesized by using an amine compound and an isocyanate compound. For example, an aliphatic amine and an aromatic amine, which will be described later, are used as an amine raw material, and an aliphatic-aromatic diurea compound synthesized by this and an aromatic diisocyanate, and an aliphatic amine and an alicyclic amine are used as an amine raw material. Examples thereof include an alicyclic-aliphatic diurea compound synthesized by using an aromatic diisocyanate.
In the present invention, as the amine compound used for the reaction with the isocyanate compound, an aliphatic amine is used at a molar ratio of 10% to 60%, and an alicyclic amine and / or an aromatic amine is used in a molar ratio. It can be used at 40% to 90% (100% in total). That is, the urea-based thickener used in the present invention is a urea compound which is a reaction product of an amine compound and an isocyanate compound, and the structure derived from the amine compound is 10 to 60 mol with respect to the total number of moles thereof. Urea compounds containing structures derived from aliphatic amines can be used in% proportions.

Among the amine compounds, as the aliphatic amine, hexylamine, octylamine, dodecylamine, hexadecylamine, octadecylamine (stearylamine), behenylamine, oleylamine and the like are used. As the alicyclic amine, cyclohexylamine, dicyclohexylamine and the like are used. As the aromatic amine, aniline, p-toluidine, ethoxyphenylamine and the like are used.
As the isocyanate compound, aromatic diisocyanates such as phenylenediisocyanate, tolylene diisocyanate, diphenyldiisocyanate, diphenylmethane diisocyanate and dimethylbiphenyl diisocyanate, and aliphatic diisocyanates such as octadecane diisocyanate, decane diisocyanate and hexane diisocyanate are used.
When an aromatic diurea compound obtained by using only an aromatic monoamine and an aromatic diisocyanate as an amine raw material is used as a thickener, abnormal noise may occur, so it is better to refrain from using it.

The urea-based thickener is preferably used in an amount of 10 to 20% by mass with respect to the total amount of the grease composition.

<Antioxidant>
In the grease composition of the present invention, an antioxidant excluding the aliphatic amine-based antioxidant is used, and in particular, an aromatic amine-based antioxidant is used.
Examples of the aromatic amine-based antioxidant include, but are not limited to, diphenylamine, diarylamine, triphenylamine, phenyl-α-naphthylamine, alkylated phenyl-α-naphthylamine, phenothiazine, and alkylated phenothiazine.
The aromatic amine-based antioxidant is used in an amount of 0.1 to 10% by mass, preferably 0.1 to 5% by mass, for example 0.5 to 3% by mass, based on the total amount of the grease composition. Is preferable.

<Other additives>
Further, in addition to the above-mentioned essential components, the grease composition may contain, if necessary, additives usually used in the grease composition as long as the effects of the present invention are not impaired.
Examples of such additives include antioxidants, extreme pressure agents, metal deactivators, anti-friction agents (wear resistant agents), rust preventive agents (rust preventive additives), oiliness improvers, and viscosity indexes other than the above. Examples include improvers and thickeners.
When these other additives are included, the addition amount (total amount) is usually 0.1 to 10% by mass with respect to the total amount of the grease composition.

For example, antioxidants other than the above include octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate and pentaerythritol tetrakis [3- (3,5-di-t-butyl-). 4-Hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, 1,3 5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-) Hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,2-thio-diethylenebis [3- (3,3) 5-Di-t-butyl-4-hydroxyphenyl) propionate], N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-benzenepropionamide) and other hindered phenolic oxidations Examples thereof include an inhibitor, a phenolic antioxidant such as 2,6-di-t-butyl-4-methylphenol, and 4,4-methylenebis (2,6-di-t-butylphenol). However, many of these are solid, and there is concern about recrystallization, so caution is required when using them. In addition, aliphatic amine-based antioxidants such as octylamine and hexylamine are not preferred because they may accelerate the deterioration of grease.

The extreme pressure agent includes, for example, phosphorus compounds such as phosphate ester, phobic ester and phosphate ester amine salt, sulfur compounds such as sulfides and disulfides, and chlorine compounds such as chlorinated paraffin and chlorinated diphenyl. Examples thereof include a compound, a metal salt of a sulfur-based compound such as zinc dialkyldithiophosphate and molybdenum dialkyldithiocarbamate.

Examples of the metal deactivator include benzotriazole, 1- [N, N-bis (2-ethylhexyl) aminomethyl] -benzotriazole, 1- [N, N-bis (2-ethylhexyl) aminomethyl] -4-. Benzotriazole compounds such as methylbenzotriazole, thiazyl compounds such as thiazyl, 2-mercaptothiazol, 2,5-bis (alkyldithio) -1,3,4-thiazilazole, benzoimidazole, 2-mercaptobenzomidazole, 2 -(Decildithio) -A benzoimidazole-based compound such as benzoimidazole, sodium nitrite and the like can be mentioned.

Examples of the wear resistant agent include tricresyl phosphate and polymer esters.
Examples of the polymer ester include esters of aliphatic monovalent carboxylic acids and divalent carboxylic acids and polyhydric alcohols. Specific examples of the polymer ester include, but are not limited to, the PRIOLUBE (registered trademark) series manufactured by Croda Japan.

Examples of the rust preventive (rust preventive additive) include zinc-based rust preventives, sulfonate-based rust preventives, carboxylic acids, carboxylic acid-based rust preventives, and the like, but are not limited thereto. do not have.

The grease composition of the present invention can be obtained by mixing the base oil, the thickener, and the antioxidant in the above-mentioned predetermined ratios, and optionally adding other additives. ..
Further, for example, a urea-based grease (base grease) composed of synthetic oil (PAO, ester oil, ether oil) and a urea-based thickener, an antioxidant, and, if desired, other additives are blended to prepare a grease composition. You can also get it.
Usually, the content of the thickener in the base grease is about 10 to 30% by mass, for example, the content of the diurea compound (urea-based thickener) in the above-mentioned urea-based grease is about 10 to 25% by mass, and 10 It can be about 20% by mass.

[Rolling bearing]
Hereinafter, preferred embodiments of rolling bearings according to the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the following embodiments.

FIG. 1 is a radial cross-sectional view of a rolling bearing 10 according to a preferred embodiment of the present invention. The rolling bearing 10 has the same basic structure as the rolling bearing of the prior art, and includes an annular inner ring 11, an outer ring 12, a plurality of rolling elements 13, a cage 14, and a seal member 15.
The inner ring 11 is a cylindrical structure installed coaxially with the central axis of the shaft on the outer peripheral side of the shaft (not shown). The outer ring 12 is a cylindrical structure arranged coaxially with the inner ring 11 on the outer peripheral side of the inner ring 11. Each of the plurality of rolling elements 13 is a ball arranged in a track in the annular bearing space 16 formed between the inner ring 11 and the outer ring 12. That is, the rolling bearing 10 in this embodiment is a ball bearing.
The cage 14 is arranged in the orbit and holds a plurality of rolling elements 13. The cage 14 is an annular body installed coaxially with the central axis of the shaft, and has a plurality of pocket portions for holding the rolling elements 13 on one side in the direction of the central axis, and rolls in each pocket portion. It has a structure in which the moving body 13 is housed. The shape (crown shape, corrugation, etc.) and material (steel plate, resin, etc.) of the cage 14 are arbitrary and are not limited to a specific shape or material.
The seal member 15 is fixed to the inner peripheral surface of the outer ring 12 and extends toward the inner ring 11, and seals the bearing space 16. The grease composition G is sealed in the bearing space 16 sealed by the sealing member 15. The amount of the grease composition G enclosed in the bearing space 16 is, for example, 5 to 50% of its volume. In order to achieve both torque performance and life performance, an amount of about 25 to 35% is preferable. The seal member 15 is formed of, for example, a steel plate or rubber, and has a steel plate shield that is non-contact with the outer circumference of the inner ring 11, a non-contact rubber seal that is non-contact with the outer circumference of the inner ring 11, and a contact-type rubber seal that is in contact with the outer circumference of the inner ring 11. Can be mentioned. In the present invention, any of the steel plate shields, non-contact type rubber seals, and contact type rubber seals can be used. Although this figure is an embodiment including a seal member 15, the rolling bearing of the present invention also covers an embodiment of a rolling bearing not provided with a seal member.
In the rolling bearing 10 having the above configuration, the grease composition G acts to reduce friction between the rolling element 13 and the cage 14, and between the rolling element 13 and the inner ring 11 to the outer ring 12. .. As can be seen from the configuration shown in FIG. 1, the grease composition G enclosed in the rolling bearing 10 lubricates between the rolling element 13 and the inner ring 11 to the outer ring 12 when the rolling bearing 10 rotates.

[Ion generator or air conditioner]
In a preferred embodiment, the rolling bearing of the present invention is provided in a blower of an ion generator or an air conditioner, and is used, for example, in a motor of the blower. The ion generator and the air conditioner include, but are not limited to, a so-called ozone generator, an air purifier, and the like, and may also include a humidifier, a dehumidifier, a ventilation device, and the like.
Further, the rolling bearing of the present invention can be suitably used for a blower of a device provided with an ion generation source (a source of ozone, hydroxy radicals, etc.) in addition to the blower of the ion generator and the air conditioning device, for example, a refrigerator. It can be applied to washing / drying devices, vacuum cleaners, etc., but is not limited to these.

As an example, FIG. 2 describes an embodiment of a motor including a rolling bearing of the present embodiment, but the present invention is not limited to the following embodiments.
FIG. 2 is a cross-sectional view in the shaft direction of the motor provided with the rolling bearing of the present embodiment. The motor 20 has a basic structure similar to that of a conventional motor, and includes a housing 21, a stator 22, a coil 23, a rotor magnet 24, a shaft 25, and a rolling bearing 26 that supports the shaft 25.
The motor 20 generates a magnetic force by passing a current supplied from a power source (not shown above) through a drive circuit to a coil 23 wound around the stator 22, thereby rotating the rotor magnet 24 and rotating the shaft. The rotation is transmitted to the external rotating body through 25.
In the present invention, the rolling bearing of the present invention can be suitably used as the bearing of the motor used in the blower, and in this case, the impeller (not shown) of the blower corresponds to the external rotating body.

The rolling bearing of the present invention is provided with an intake port, an ion generation source (sometimes also referred to as an ozone generation source), an exhaust port and a blower, and air flows from the intake port to the exhaust port together with the generated ions. At that time, it is used for a blower of an ion generator or an air conditioner having a structure in which the flow comes into contact with the blower. For example, the rolling bearing of the present invention is suitably used for, but is not limited to, a blower of an ion generator or an air regulating device, which is installed so as to have an intake port and an exhaust port in the same closed space. Due to the rotation of the impeller (not shown) of the blower, the pressure around the bearing of the motor becomes negative, so that air containing ions flows into it. As a result, the grease sealed in the bearing is exposed to ions.

As an example of the ion generator or the air conditioner, a schematic diagram thereof is shown in FIG. The present invention is not limited to the present invention.
FIG. 3 is a schematic view of an ion generator or an air conditioning device 30, which includes a blower 31, an ion generator 32, an intake port 33, and an exhaust port 34. In FIG. 3, the solid arrow indicates the air flow, and the dotted arrow indicates the ion flow. The blower 31 is equipped with a motor (not shown) provided with the rolling bearing (not shown) of the present invention.
3A and 3B are devices in which the air flow path sucked into the blower 31 from the intake port 33 and the air flow path discharged from the blower 31 to the exhaust port 34 are independently provided. It is a schematic diagram. FIG. 3A shows an embodiment in which the ion generation source 32 is installed in the flow path of the air discharged from the blower 31 to the exhaust port 34. The ions generated from the device 32 are discharged to the outside of the device 30 together with the air from the exhaust port 34. Then, ions are sucked from the intake port 33 together with air, and these are sucked into the blower 31. FIG. 3B shows an embodiment in which the ion generation source 32 is installed in the flow path of the air sucked into the blower 31 from the intake port 33. The ions generated from the device 32 are sucked into the blower 31 together with the air sucked from the intake port 33, and these are discharged to the outside of the device 30 from the exhaust port 34.
Further, in FIG. 3C, the ions generated from the ion generation source 32 are sucked into the blower 31 together with the air sucked from the intake port 33, and these are discharged to the outside of the device 30 from the exhaust port 34.
Then, in FIG. 3D, the ions generated from the ion generation source 32 provided inside the device 30 are sucked into the blower 31 together with the air sucked from the intake port 33, and these are sucked into the blower 31 from the exhaust port 34 to the device 30. It is discharged to the outside.

The present invention is not limited to the embodiments and specific examples described in the present specification, and various modifications and modifications can be made within the scope of the technical idea described in the claims. ..
For example, in the above embodiment and the following embodiment, ball bearings are mentioned as rolling bearings, but the present invention is not limited to this, and other rolling bearings such as roller bearings, needle bearings, conical roller bearings, and spherical surfaces are used. It does not limit the application of the grease composition to bearing units such as roller bearings, thrust bearings, and axle support bearings of automobiles.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to this.

[Evaluation of grease composition]
The grease compositions used in Examples 1 to 7 and Comparative Examples 1 to 7 were prepared with the blending amounts shown in Table 1 below.

The details of each component used for preparing the grease and its abbreviations are as follows.
(A) Base oil (a1) PAO: Polyalphaolefin oil (a2) Ester oil
(A3) Ether oil (b) Thickener (b1) Urea-based thickener Diisocyanate compound (aromatic diisocyanate) and one or two selected from the following (b1-1) to (b1-3) Diurea compound (b1-1) aliphatic amine (b1-2) alicyclic amine synthesized from the amine (the compounding ratio (molar ratio) of the amine is shown in Table 1).
(B1-3) Aromatic amine (b2) Lithium soap thickener: Lithium 12-hydroxystearate Generally, the urea-based thickener (b1) is the urea-based thickener and the base oil ((a1) to (A3)) is added in an amount of 10 to 25% by mass based on the total amount of the base grease, and the lithium soap thickener (b4) is a soap-based thickener and a base oil (PAO (a1)). It is added in an amount of 10 to 20% by mass based on the total amount of the base grease contained.
(C) Additives: Antioxidants (c1) Aromatic amine-based antioxidants (c2) aliphatic amine-based antioxidants (d) Other additives (d1) Extreme pressure additives (d2) Anti-corrosion additives (D) Other additives include the above-mentioned extreme pressure additive and rust preventive additive for each grease composition (total mass) of Examples 1 to 7 and Comparative Examples 1 to 7. It was added so as to be by mass%.

The rolling bearings used in the following test evaluations are as follows.
(1) Ball bearing with steel plate shield (inner diameter 5 mm, outer diameter 13 mm, width 4 mm)
(2) Ball bearing with steel plate shield (inner diameter 3 mm, outer diameter 8 mm, width 3 mm)

<Test method>
1. 1. Bearing acoustic evaluation The acoustic evaluation of rolling bearings after exposure to oxidizing substances was carried out according to the following procedure.
In this test, (1) a ball bearing with a steel plate shield (inner diameter 5 mm, outer diameter 13 mm, width 4 mm) was used, and the grease compositions of Examples 1 to 7 and Comparative Examples 1 to 7 were applied thereto. Each was sealed at 25% to 35% of the bearing volume. The ball bearing was placed in an oxidizing substance generator and left for 250 hours to expose the ball bearing (and the enclosed grease composition) to the oxidizing substance. The exposure conditions are as follows.
・ Oxidizing substance: Ozone concentration 0.1ppm
(Detective tube: Ozone concentration is detected with a low concentration measurement detector tube manufactured by Gastec Co., Ltd.)
・ Exposure time: 250 hours ・ Atmospheric pressure: 900 hPa to 950 hPa
-Temperature: 24 ° C to 27 ° C
Humidity: Average 85RH% (45RH% -95RH%)

The rolling bearing exposed to an oxidizing substance was evaluated for its acoustic characteristics (bearing acoustic evaluation) at room temperature using the following procedure. In the following description, the example number of the grease composition shall be treated as the example number of the performance evaluation of the rolling bearing in which the grease composition is enclosed.

The acoustic performance of ball bearings using each test grease composition was evaluated by measuring the Anderon value in the M band (300 to 1800 Hz) using an Anderon meter.
At room temperature, set the ball bearing after exposure to the oxidizing substance in the housing, insert the shaft into the inner diameter of the bearing, apply a preload of 10 N to the outer ring from the axial direction, and then use it on the rotating shaft of the test motor. The shafts were connected so that the ball bearings could rotate inside. In addition, the speed type pickup was brought into contact with the outer circumference of the outer ring of the ball bearing in the radial direction.
Then, it was rotated at a rotation speed of 1,800 rpm, the mechanical vibration transmitted to the outer ring was detected, the Anderon value was calculated, and the maximum Anderon value in 10 seconds from the start of rotation was obtained. This test was carried out using four ball bearings for each test grease composition, the average value of the maximum Anderon value was obtained, and the acoustic performance was evaluated according to the following criteria (maximum value of Anderon value in measurement: 50).
The frequency of the M band: 300 to 1800 Hz is said to be annoying to humans.
<Evaluation criteria>
In the test conditions of this example, when the Anderon value exceeds 1, noise becomes remarkable, so 1 or less is evaluated as suitable.
A (suitable): Anderon value is 1 or less N (unsuitable): Anderon value is more than 1

2. 2. Torque test A rotary torque test was performed with the rotary device 60 having the configuration shown in FIG.
In this test, (2) a ball bearing with a steel plate shield (inner diameter 3 mm, outer diameter 8 mm, width 3 mm) was used, and the grease compositions of Examples 1 to 7 and Comparative Examples 1 to 7 were applied thereto. Each was sealed at 25% to 35% of the bearing volume.
This ball bearing (ball bearing 61) was inserted into the shaft 62 of the test motor 64. After applying a preload of 3N to the outer ring of the ball bearing 61 from the axial direction with the preload weight 63, the shaft 62 is coupled to the rotating shaft 65 of the test motor 64 so that the ball bearing 61 rotates in the inner ring. The rotating device 60 was configured.
The rotating device 60 is set in a constant temperature bath (not shown) at 25 ° C., the ball bearing 61 is rotated at a rotation speed of 10,000 rpm by an external power source (not shown), and the ball bearing 61 is rotated by the rotation of the test motor 64. The stress carried by the outer ring was detected by a strain gauge (not shown) and converted into rotational torque. The torque value (steady torque) 2 minutes after the start of rotation was measured and used as the measured value (mNm). The test greases of each Example and Comparative Example were tested three times each, and the average value of each measured value was calculated.
<Evaluation criteria>
Under the test conditions of this example, those having a measured torque value of 0.5 mNm or less are evaluated as suitable.
A: Torque measurement value is 0.5mNm or less N: Torque measurement value is over 0.5mNm

The results are shown in Table 1. In the table, the blending amount: mass% is a value with respect to the total mass of the composition, and the blending ratio of the thickener for the amine type is mol%.

As shown in Table 1, an example in which a diurea compound having an aliphatic amine compounding ratio (molar ratio) of 50% or 20% was used as the urea-based thickener, and an aromatic amine was used as an antioxidant. The grease compositions of Examples 1 to 7 are excellent in acoustic characteristics after exposure to an oxidizing substance (Anderon value: 1 or less, which is a suitable judgment, 0.35 to 0.52) regardless of the type of base oil. It was also confirmed that the rotational torque (torque value: 0.22 to 0.48 mNm, which is a suitable judgment when the torque value is 0.5 mNm or less) is also low. The grease composition of Example 1 using PAO as the base oil has acoustic characteristics (Anderon value; Example 1: 0.35, Example 5) as compared with the grease composition using ester oil (Example 5). Both Example 5: 0.38) and rotational torque (torque value; Example 1: 0.22 mNm, Example 5: 0.48 mNm) tended to be good.

On the other hand, the grease composition (Comparative Example 1) using the diurea compound in which the compounding ratio (molar ratio) of the aliphatic amine is 70% deteriorates the acoustic characteristics (Anderon value: 1.3), and the compounding ratio is adjusted. The grease composition using the diurea compound set to 100% (Comparative Example 5) not only has further deteriorated acoustic characteristics (Anderon value: 3.8), but also has a large rotational torque value (torque value: 0.90 mNm). ), The torque performance also deteriorated.
Further, when an aliphatic amine was used as an antioxidant (Comparative Example 2 and Comparative Example 3), the acoustic characteristics were deteriorated as compared with the grease composition using an aromatic amine (Comparative Example 1 and Example 1) (Anderon). Value; Comparative Example 2: 3.5, Comparative Example 3: 2.8).
In Comparative Example 4 in which the lithium soap thickener was used as the thickener, the acoustic characteristics were excellent (Anderon value: 0.17), but the torque performance was inferior (torque value: 0.58 mNm). ).
Further, as a thickener, a grease composition using a diurea compound having an alicyclic amine compounding ratio (molar ratio) of 100% (Comparative Example 6) and an aromatic amine compounding ratio (molar ratio) of 100%. In the grease composition using the diurea compound (Comparative Example 7), both the acoustic characteristics and the torque performance were inferior (Anderon value; Comparative Example 6: 1.2, Comparative Example 7: 1.5, Torque value; Comparative Example 6: 0.93 mNm, Comparative Example 7: 1.20 mNm). Comparing Comparative Example 6 and Comparative Example 7, the grease composition of Comparative Example 7 containing a diurea compound using only aromatic amine as an amine compound contained a diurea compound using only an alicyclic amine. Compared with the grease composition of Comparative Example 6, both the acoustic characteristics and the torque performance tended to be inferior.

Here, FIG. 5 shows a change in the acoustic characteristics of the grease composition when the ratio of the aliphatic amine used in the amine compound constituting the urea-based thickener (diurea compound) is changed.
FIG. 5 shows the acoustics using the grease composition containing the urea-based thickener with respect to the change (horizontal axis) of the blending ratio (mol%) of the aliphatic amine in the amine compound constituting the urea-based thickener. It is a figure which shows the result (vertical axis) of the evaluation (the Anderon value).
In FIG. 5, a straight line drawn in parallel with the horizontal axis indicates an Anderon value: 1.0. In the grease composition at the measurement points shown in this figure, aliphatic amines and alicyclic amines are used as amine compounds constituting urea-based thickeners in different blending ratios, and aromatic amines are used as antioxidants. (Comparative Example 6 (aliphatic amine ratio 0 mol%), Example 2 (20 mol%), Example 1 (50 mol%), Comparative Example 1 (70 mol%), Comparative Example 5 (100 mol%) and the approximate curve calculated from the above Anderon values are also shown), or a grease composition using an aliphatic amine as an antioxidant with an aliphatic amine ratio of 50 mol%. (Comparative Example 3, measurement point separated from the approximate curve and surrounded by a dotted line).
As shown in FIG. 5, it is estimated from the approximate curve that the Anderon value is 1 or less in the range of 10 mol% to 60 mol% of the aliphatic amine compounding ratio (dotted arrow range in the figure). It is clearly shown that even when the blending ratio of the aliphatic amine is 50 mol%, the Anderon value is significantly increased when the aliphatic amine is used as the antioxidant.

The above results are obtained by using a urea compound containing an aliphatic amine at a ratio of 10 to 60 mol% with respect to the total amount of the amine compound constituting the urea-based thickener, even after exposure to an oxidizing substance. It is suggested that it is possible to provide a grease composition in which the generation of abnormal noise is suppressed and excellent in acoustic characteristics, and further, it is possible to provide a grease composition capable of realizing low torque performance.

Although the best embodiment has been described in detail above, the present invention is not limited to the above embodiment, and modifications, improvements, etc. within the range in which the object of the present invention can be achieved are included in the present invention. be.

G ... Grease composition, 10 ... Rolling bearing, 11 ... Inner ring, 12 ... Outer ring, 13 ... Rolling element, 14 ... Cage, 15 ... Seal member, 16 ... Bearing space 30 ... Ion generator or air regulator, 31 ... Blower, 32 ... Ion source, 33 ... Intake port, 34 ... Exhaust port

Claims (5)

Base oil and
A urea-based thickener composed of a diurea compound represented by the following formula (1), and
R ₁ -NHCONH-R ₂ -NHCONH-R ₃ ... (1)
(In the formula, R ₁ and R ₃ each independently represent a monovalent aliphatic hydrocarbon group, a monovalent alicyclic hydrocarbon group, or a monovalent aromatic hydrocarbon group, and at this time, The ratio of monovalent aliphatic hydrocarbon groups to the total number of moles of R ₁ and R ₃ is 10% to 60%.
R ₂ represents a divalent aromatic hydrocarbon group. )
A grease composition containing an aromatic amine-based antioxidant. A rolling bearing in which the grease composition according to claim 1 is enclosed. The rolling bearing according to claim 2, wherein the rolling bearing includes a sealing member. The rolling bearing according to claim 2 or 3, which is provided in a blower of an ion generator or an air regulating device. The ion generator or air regulator includes an intake port, an ion generation source, an exhaust port, and a blower, and air flows from the intake port to the exhaust port together with the generated ions, and the flow comes into contact with the blower. The rolling bearing according to claim 4, which has a structure.

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