JP7551473B2 - Anti-oxidation grease composition and bearing containing same - Google Patents

Description

The present invention relates to an oxidation-resistant grease composition and a bearing containing the same.

When the concentration of gas components emitted into the atmosphere increases due to the expansion of factories and increased traffic, nitrogen oxides and hydrocarbons (volatile organic compounds) contained in the gas components can be altered by ultraviolet rays, resulting in the generation of oxidizing substances such as ozone. This phenomenon is also known as photochemical smog.
In recent years, devices (e.g., ion generators, air purifiers and air conditioners equipped with an ion generating source, etc.) and chemicals for reducing bacteria, viruses, bad odors, etc., including in the space around us, by discharging oxidizing substances such as ozone and active oxygen (oxygen radicals, hydroxyl radicals, etc.) at low concentrations into the space as cleaning components have become widespread.

When photochemical smog occurs in the atmosphere, or when low concentrations of oxidizing substances are released as cleaning components from air conditioners or the like, the oxidizing substances in that space can have a detrimental effect on surrounding objects. For example, metal parts, resin parts, grease in bearings, etc. may be oxidized, i.e., deteriorated, by the ozone or hydroxyl radicals. In particular, fans for diffusing the cleaning components and the bearings used therein are installed near oxidizing substance generators (ion generating sources, etc.), which are also cleaning components, and are therefore thought to be susceptible to exposure to oxidizing substances.

For example, Patent Document 1 discloses a grease composition that uses a thickener made of a base oil and a urea-based compound, and an amine-based antioxidant and a quinoline-based antioxidant as antioxidants, aiming to improve the oxidation resistance of the grease in order to obtain a grease that can be used at high temperatures and has a long life.

JP 2018-021140 A

The ion generating device, air conditioning device, etc., blow ozone, hydroxyl radicals, etc. into a room using a blower installed in the device, and aim to kill airborne bacteria and deodorize the room. However, there are cases where abnormal noises are confirmed after these devices are installed and operated. One of the causes of this is that the ozone and hydroxyl radicals generated from the oxidizing substance generating device (ion generating source, etc.) accelerate the deterioration of the grease sealed in the bearings installed in the blower in the device, and it has been confirmed that abnormal noises are generated in the bearings due to this deteriorated grease.
In recent years, air conditioners and the like are required to operate at low power. The blowers used in these devices are also required to operate at low power, and the bearings used in the blowers are required to be driven at low torque. Grease used in bearings for low torque purposes has generally been grease with channeling properties (the property that the grease-based lubricant in the bearing is easily pushed aside by the rolling elements), but grease with such properties has the problem of easily generating abnormal noise. On the other hand, grease with excellent acoustic properties tends to have high torque due to the churning phenomenon (the state in which the grease is constantly stirred inside the bearing when the bearing is operating). Thus, there is a demand for grease with both low torque and excellent acoustic properties.

The present invention aims to provide a grease composition that is resistant to deterioration even under the influence of oxidizing substances such as ozone and hydroxyl radicals, and that can achieve excellent acoustic properties and low torque, as well as a rolling bearing that can suppress the generation of abnormal noise and achieve low torque by applying the grease composition.

One aspect of the present invention is a composition comprising a base oil and
A urea-based thickener comprising a diurea compound represented by the following formula (1),
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 in this case, the proportion of the monovalent aliphatic hydrocarbon group relative to the total number of moles of R ₁ and R ₃ is 10% to 60%;
_R2 represents a divalent aromatic hydrocarbon group.
and an aromatic amine-based antioxidant.
The present invention also relates to a rolling bearing in which the grease composition is packed, and to the rolling bearing provided in an ion generating device or a blower of an air conditioning device.

FIG. 2 is a schematic diagram illustrating the structure of a rolling bearing according to the present invention. 1 is a schematic diagram illustrating a structure of a motor equipped with a rolling bearing according to the present invention. 1 is a schematic diagram of an ion generating device or air conditioning device having a blower equipped with a rolling bearing of the present invention. FIG. 1 is a conceptual diagram of a rotating device used in a torque test. FIG. 1 is a graph showing the results of acoustic evaluation (Anderon value) (vertical axis) of a grease composition containing a urea-based thickener, relative to the change in the blending ratio (mol %) of an aliphatic amine in the amine compound constituting the urea-based thickener (horizontal axis).

As mentioned above, it has been confirmed that abnormal noise occurs due to deterioration of the grease sealed in the bearings of the blowers in ion generating devices, air conditioning devices, and the like that emit ozone, hydroxyl radicals, etc. However, no proposal has been made so far that focuses on the bearings used in the blowers installed in such devices and aims to improve the grease composition to suppress the generation of abnormal noise.
The present inventors have investigated grease deterioration in the presence of oxidizing substances such as ozone and hydroxyl radicals, and have found that aggregates are easily formed in greases using a urea compound with a high ratio of groups derived from aliphatic amines as a thickener, which has a negative effect on the acoustic characteristics of bearings. On the other hand, they have found that the use of a urea compound having a group derived from aliphatic amines as a thickener results in a grease that can achieve low torque. They have also found that the deterioration of acoustic characteristics progresses when an aliphatic amine-based compound is used as an antioxidant blended in the grease.
One of the causes of the deterioration of the grease is believed to be that the aliphatic groups contained in the urea compound in the thickener and the aliphatic amine compound in the antioxidant are modified by oxidizing substances such as ozone and hydroxyl radicals, and some of these groups condense, causing the formation of aggregates.

The grease composition (hereinafter simply referred to as "grease composition") filled into the rolling bearing according to the present invention is characterized by being blended with a specific urea-based thickener as described below, and further characterized by being blended with a specific antioxidant. This grease composition is inhibited from deteriorating even in the presence of oxidizing substances, and achieves good acoustic properties and low torque. A specific description will be given below.

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

<Base oil>
In the grease composition of the present invention, as the base oil, synthetic oils generally used as grease base oils, such as hydrocarbon synthetic oils, ester synthetic oils and ether synthetic oils, can be used alone or in combination.
In addition, although fluorine-based base oils generally have excellent heat resistance and oxidation resistance, they have poor lubricating properties and acoustic properties, and therefore are not suitable for use in grease compositions for rolling bearings used in equipment and devices that are expected to be used indoors, such as air conditioners.

Examples of the synthetic hydrocarbon oil include normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, 1-decene ethylene oligomer and other polyalphaolefins (PAO).
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, ditridecyl phthalate, and methyl acetyl ricinoleate, aromatic ester oils such as trioctyl trimellitate, tri-2-ethylhexyl trimellitate, tridecyl trimellitate, tetraoctyl pyromellitate, and tetra-2-ethylhexyl pyromellitate, polyol ester oils such as trimethylolpropane caprylate, trimethylolpropane 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 oils.

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

<Thickener>
The grease composition used in the present invention contains a urea-based thickener as a thickener.
Urea compounds have excellent heat resistance and water resistance, and because they do not contain metal elements, they are advantageous in terms of oxidation stability, and are therefore suitably used as thickeners in applications where the application is in a high-temperature environment, etc.
As the urea-based thickener, a urea compound such as a diurea compound, a triurea compound, or a polyurea compound can be used, but in the present invention, a diurea compound is used in particular from the viewpoint of acoustic characteristics (silence).
The types of diurea compounds include aliphatic diureas, alicyclic-aliphatic diureas, and aliphatic-aromatic diureas.
As these urea-based thickeners, conventionally known urea compounds can be used.

As a urea-based thickener suitable for the present invention, a diurea compound represented by the following general formula (1) can be mentioned.
R ₁ -NHCONH-R ₂ -NHCONH-R ₃ ...(1)
In formula (1), _R1 and _R3 each independently represent a monovalent aliphatic hydrocarbon group, a monovalent alicyclic hydrocarbon group, or a monovalent aromatic hydrocarbon group, and in this case, the molar ratio of the monovalent aliphatic hydrocarbon group to the monovalent alicyclic hydrocarbon group and/or the monovalent aromatic hydrocarbon group relative to the total number of moles of _R1 and _R3 is 10% to 60%:90% to 40%.
Furthermore, _R2 represents a divalent aromatic hydrocarbon group.

The monovalent aliphatic hydrocarbon group includes a linear or branched, saturated or unsaturated alkyl group having 6 to 26 carbon atoms.
The monovalent alicyclic hydrocarbon group is, for example, a cycloalkyl group having 5 to 12 carbon atoms.
The aromatic hydrocarbon group may be a monovalent or divalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

The urea compound used as the urea-based thickener can be synthesized using an amine compound and an isocyanate compound. For example, an aliphatic-aromatic diurea compound synthesized using an aliphatic amine and an aromatic amine described below as amine raw materials and an aromatic diisocyanate, and an alicyclic-aliphatic diurea compound synthesized using an aliphatic amine and an alicyclic amine as amine raw materials and an aromatic diisocyanate can be mentioned.
In the present invention, as the amine compound used in the reaction with the isocyanate compound, an aliphatic amine can be used in a molar ratio of 10% to 60%, and an alicyclic amine and/or an aromatic amine can be used in a molar ratio of 40% to 90% (total 100%). 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 urea compound can contain a structure derived from the amine compound at a ratio of 10 to 60 mol % based on the total number of moles.

Among the amine compounds, the aliphatic amines include hexylamine, octylamine, dodecylamine, hexadecylamine, octadecylamine (stearylamine), behenylamine, oleylamine, etc. The alicyclic amines include cyclohexylamine, dicyclohexylamine, etc. The aromatic amines include aniline, p-toluidine, ethoxyphenylamine, etc.
As the isocyanate compound, aromatic diisocyanates such as phenylene diisocyanate, tolylene diisocyanate, diphenyl diisocyanate, diphenylmethane diisocyanate, dimethylbiphenyl diisocyanate, etc., and aliphatic diisocyanates such as octadecane diisocyanate, decane diisocyanate, hexane diisocyanate, etc. may be used.
In addition, when an aromatic diurea compound obtained by using only an aromatic monoamine as the amine raw material and an aromatic diisocyanate is used as a thickening agent, there is a risk of abnormal noise being generated, 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 based on the total amount of the grease composition.

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

<Other additives>
In addition to the above-mentioned essential components, the grease composition may contain additives that are usually used in grease compositions, if necessary, within the range that does not impair the effects of the present invention.
Examples of such additives include antioxidants other than those mentioned above, extreme pressure agents, metal deactivators, antifriction agents (antiwear agents), rust inhibitors (rust prevention additives), oiliness improvers, viscosity index improvers, thickeners, etc.
When these other additives are contained, the amount (total amount) of them added is usually 0.1 to 10 mass % based on the total amount of the grease composition.

Examples of antioxidants other than those mentioned above include octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 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], Examples of antioxidants include hindered phenol-based antioxidants such as 1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,2-thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxy-benzenepropionamide), and phenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and 4,4-methylenebis(2,6-di-t-butylphenol). However, many of these are solids, and there is a concern that they may recrystallize, so caution is required when using them. In addition, the use of aliphatic amine-based antioxidants such as octylamine and hexylamine is not preferred due to concerns that they may accelerate the deterioration of the grease.

Extreme pressure agents include, for example, phosphorus compounds such as phosphate esters, phosphites, and amine salts of phosphate esters; sulfur compounds such as sulfides and disulfides; chlorine compounds such as chlorinated paraffins and chlorinated diphenyls; and metal salts of sulfur compounds such as zinc dialkyldithiophosphates and molybdenum dialkyldithiocarbamates.

Examples of metal deactivators include benzotriazole-based compounds such as benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]-benzotriazole, and 1-[N,N-bis(2-ethylhexyl)aminomethyl]-4-methylbenzotriazole; thiadiazole-based compounds such as thiadiazole, 2-mercaptothiadiazole, and 2,5-bis(alkyldithio)-1,3,4-thiadiazole; benzimidazole-based compounds such as benzimidazole, 2-mercaptobenzimidazole, and 2-(decyldithio)-benzimidazole; and sodium nitrite.

Anti-wear agents include tricresyl phosphate and polymer esters.
Examples of the polymer ester include esters of aliphatic monovalent carboxylic acids and divalent carboxylic acids with 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 rust inhibitors (rust prevention additives) include, but are not limited to, zinc-based rust inhibitors, sulfonate-based rust inhibitors, carboxylic acid or carboxylate-based rust inhibitors, etc.

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 ratio, and adding other additives as desired.
In addition, a grease composition can be obtained by blending, for example, a urea-based grease (base grease) consisting of a synthetic oil (PAO, ester oil, ether oil) and a urea-based thickener, an antioxidant, and other additives as desired.
Typically, the content of the thickener in the base grease is about 10 to 30 mass %, and for example, the content of the diurea compound (urea-based thickener) in the above-mentioned urea-based grease can be about 10 to 25 mass %, or about 10 to 20 mass %.

[Rolling bearings]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the rolling bearing according to the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the present invention is not limited to the following embodiments.

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 a basic structure similar to that of a 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 center axis of a shaft (not shown) on the outer periphery side of the shaft. The outer ring 12 is a cylindrical structure arranged coaxially with the inner ring 11 on the outer periphery side of the inner ring 11. Each of the multiple rolling elements 13 is a ball arranged in a raceway in an 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 disposed within the raceway and holds the plurality of rolling elements 13. The cage 14 is an annular body that is installed coaxially with the central axis of the shaft, and has a structure that includes a plurality of pockets for holding the rolling elements 13 on one side in the direction of the central axis, with the rolling elements 13 accommodated in each pocket. The shape (crown shape, corrugated shape, 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 to seal the bearing space 16. A grease composition G is enclosed in the bearing space 16 sealed by the seal member 15. The amount of the grease composition G enclosed in the bearing space 16 is, for example, 5 to 50% of the 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 examples thereof include a steel plate shield that does not contact the outer periphery of the inner ring 11, a non-contact type rubber seal that does not contact the outer periphery of the inner ring 11, and a contact type rubber seal that contacts the outer periphery of the inner ring 11. In the present invention, any of the seal members, such as the steel plate shield, the non-contact type rubber seal, and the contact type rubber seal, can be used. Note that this figure shows an embodiment equipped with the seal member 15, but the rolling bearing of the present invention also covers an embodiment of a rolling bearing that does not have a seal member.
In the rolling bearing 10 having the above configuration, the grease composition G acts to reduce friction between the rolling elements 13 and the cage 14, and between the rolling elements 13 and the inner ring 11 through the outer ring 12. As can be seen from the configuration shown in Fig. 1, the grease composition G sealed in the rolling bearing 10 lubricates between the rolling elements 13 and the inner ring 11 through the outer ring 12 when the rolling bearing 10 rotates.

[Ion generating device or air conditioning device]
In a preferred embodiment, the rolling bearing of the present invention is provided in an ion generator or a blower of an air conditioner, and is used, for example, in the motor of the blower . The ion generator and air conditioner include so-called ozone generators and air purifiers, and may also include, but are not limited to, humidifiers, dehumidifiers, ventilators, and the like.
Furthermore, the rolling bearing of the present invention can be suitably used in blowers for devices that include an ion generation source (a source that generates ozone, hydroxyl radicals, or the like) other than the ion generating devices and air conditioning devices described above, and can also be applied to, but is not limited to, refrigerators, washer/dryers, vacuum cleaners, and the like.

As an example, an embodiment of a motor equipped with the rolling bearing of this embodiment will be described with reference to FIG. 2, but the present invention is not limited to the following embodiment.
2 is a cross-sectional view in the shaft direction of a motor equipped with the rolling bearing of this embodiment. The motor 20 has the same basic structure as a motor of the prior art, and is composed of 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.
In the motor 20, magnetic force is generated by passing current supplied from a power source (not shown) via a drive circuit through a coil 23 wound around a stator 22, which causes a rotor magnet 24 to rotate, and the rotation is transmitted to an external rotating body via a shaft 25.
In the present invention, the rolling bearing of the present invention can be suitably used as a bearing for a motor used in a blower, and in this case, the external rotating body corresponds to the impeller (not shown) of the blower.

The rolling bearing of the present invention is used in, among others, an ion generating device or a blower of an air conditioning device, which is equipped with an intake port, an ion generating source (sometimes called an ozone generating source), an exhaust port, and a blower, and has a structure in which air flows from the intake port to the exhaust port together with the generated ions, and at that time, the flow comes into contact with the blower. For example, the rolling bearing of the present invention is suitably used in, but is not limited to, an ion generating device or a blower of an air conditioning device, which are installed so as to have an intake port and an exhaust port in the same closed space. The rotation of the blower impeller (not shown) creates a negative pressure around the bearing of the motor, and air containing ions flows into the negative pressure. This exposes the grease sealed in the bearing to the ions.

An example of the ion generating device or air conditioning device is shown in a schematic diagram in Fig. 3. Note that the present invention is not limited to this diagram.
Fig. 3 is a schematic diagram of an ion generating device or air conditioning device 30, which includes a blower 31, an ion generating source 32, an air inlet 33, and an exhaust port 34. In Fig. 3, solid arrows indicate the flow of air, and dotted arrows indicate the flow of ions. The blower 31 is equipped with a motor (not shown) equipped with the rolling bearing (not shown) of the present invention.
3(a) and 3(b) are schematic diagrams of a device in which a flow path of air drawn from an intake port 33 to a blower 31 and a flow path of air discharged from the blower 31 to an exhaust port 34 are provided independently. FIG. 3(a) shows an embodiment in which an ion generating source 32 is installed in the flow path of air discharged from the blower 31 to the exhaust port 34. Ions generated from the device 32 are discharged from the exhaust port 34 together with air to the outside of the device 30. Then, ions are drawn in together with air from the intake port 33, and these are drawn into the blower 31. FIG. 3(b) shows an embodiment in which an ion generating source 32 is installed in the flow path of air drawn from the intake port 33 to the blower 31. Ions generated from the device 32 are drawn into the blower 31 together with air drawn in from the intake port 33, and these are discharged from the exhaust port 34 to the outside of the device 30.
In FIG. 3C, ions generated from an ion generating source 32 are sucked into a blower 31 together with air sucked in from an air inlet 33, and are then exhausted to the outside of the device 30 from an exhaust port .
In FIG. 3( d ), ions generated from an ion generating source 32 provided inside the device 30 are sucked into the blower 31 together with air sucked in from an air intake 33, and these are exhausted to the outside of the device 30 from an exhaust outlet 34 .

The present invention is not limited to the embodiments and specific examples described in this specification, and various changes and modifications are possible within the scope of the technical ideas described in the claims.
For example, in the above embodiment and the following examples, a ball bearing is given as an example of a rolling bearing, but the present invention is not limited thereto, and there is no restriction on application of the grease composition to other rolling bearings, such as roller bearings, needle bearings, tapered roller bearings, spherical roller bearings, thrust bearings, etc., or bearing units such as automotive axle support bearings.

The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to these examples.

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

Details of the components used in preparing the grease and their abbreviations are as follows:
(a) Base oil (a1) PAO: polyalphaolefin oil (a2) Ester oil
(a3) Ether oil (b) Thickener (b1) Urea-based thickener A diurea compound synthesized from a diisocyanate compound (aromatic diisocyanate) and one or two amines selected from the following (b1-1) to (b1-3) (the amine blending ratio (molar ratio) is shown in Table 1): (b1-1) Aliphatic amine (b1-2) Alicyclic amine
(b1-3) Aromatic amine (b2) Lithium soap thickener: lithium 12-hydroxystearate Generally, the urea-based thickener (b1) is added in an amount of 10 to 25 mass % based on the total amount of the base grease containing the urea-based thickener and base oil ((a1) to (a3)), and the lithium soap thickener (b4) is added in an amount of 10 to 20 mass % based on the total amount of the base grease containing the soap-based thickener and base oil (PAO (a1)).
(c) Additives: Antioxidants (c1) Aromatic amine-based antioxidants (c2) Aliphatic amine-based antioxidants (d) Other additives (d1) Extreme pressure additives (d2) Antirust additives Note that (d) other additives were added so that the total amount of the extreme pressure additives and antirust additives was 3 mass % relative to the total mass of each of the grease compositions of Examples 1 to 7 and Comparative Examples 1 to 7.

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. Bearing Acoustic Evaluation Acoustic evaluation of the rolling bearings after exposure to oxidizing substances was carried out according to the following procedure.
In this test, (1) a steel shielded ball bearing (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 filled in the bearing at 25% to 35% of the bearing volume. The ball bearing was placed in an oxidizing substance generator and left there for 250 hours, exposing the ball bearing (and the filled grease composition) to the oxidizing substance. The exposure conditions were as follows:
Oxidizing substances: Ozone concentration 0.1 ppm
(Detection tube: Ozone concentration is detected using a low concentration measurement detector tube manufactured by Gastec Corporation.)
Exposure time: 250 hours Pressure: 900hPa to 950hPa
・Temperature: 24℃～27℃
・Humidity: Average 85RH% (45RH% to 95RH%)

The rolling bearings exposed to the oxidizing substance were evaluated for acoustic properties (bearing acoustic evaluation) at room temperature using the following procedure. In the following explanation, the example numbers of the grease compositions will also be treated as example numbers for the performance evaluation of the rolling bearings in which they are packed.

The acoustic performance of the 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, the ball bearing after exposure to the oxidizing substance was set in a housing, a shaft was inserted into the inner diameter of the bearing, and a preload of 10 N was applied to the outer ring in the axial direction. The shaft was then connected to the rotating shaft of a test motor so that the inner ring of the ball bearing rotated. A speed type pickup was also brought into contact with the outer periphery of the outer ring of the ball bearing in the radial direction.
The bearings were then rotated at a speed of 1,800 rpm, and mechanical vibrations transmitted to the outer ring were detected to calculate the anderon value, and the maximum anderon value for 10 seconds from the start of rotation was determined. This test was carried out using four ball bearings for each test grease composition, and the average maximum anderon value was calculated and the acoustic performance was evaluated according to the following criteria (maximum anderon value measured: 50).
The M-band frequencies between 300 and 1800 Hz are said to be harsh to the ears of humans.
<Evaluation criteria>
Under the test conditions of this embodiment, when the Anderon value exceeds 1, the noise becomes noticeable, so an Anderon value of 1 or less is evaluated as being preferable.
A (good): Anderon value is 1 or less. N (bad): Anderon value is more than 1.

2. Torque Test A rotation torque test was carried out using the rotation device 60 having the configuration shown in FIG.
In this test, (2) a steel shielded ball bearing (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 filled in an amount of 25% to 35% of the bearing volume.
This ball bearing (ball bearing 61) was inserted into shaft 62 of test motor 64. After applying a preload of 3 N to the outer ring of ball bearing 61 in the axial direction with preload weight 63, shaft 62 was coupled to rotating shaft 65 of test motor 64 so that ball bearing 61 rotated on the inner ring, thereby forming rotating device 60.
The rotating device 60 was set in a thermostatic chamber (not shown) at 25° C., and the ball bearing 61 was rotated at 10,000 rpm by an external power source (not shown). The stress caused by the rotation of the outer ring of the ball bearing 61 being accompanied by the rotation of the test motor 64 was detected by a strain gauge (not shown) and converted into a rotation torque. The torque value (steady-state torque) was measured two minutes after the start of rotation and was taken as the measured value (mNm). The test was performed three times for each of the test greases of the examples and comparative examples, and the average value of each measured value was calculated.
<Evaluation criteria>
Under the test conditions of this embodiment, a measured torque value of 0.5 mNm or less is evaluated as favorable.
A: The measured torque is 0.5 mNm or less. N: The measured torque is more than 0.5 mNm.

The results are shown in Table 1. Note that the blending amounts (mass %) in the table are values relative to the total mass of the composition, and the blending ratios of the amine species of the thickener are shown in mol %.

As shown in Table 1, the grease compositions of Examples 1 to 7, which used a diurea compound with an aliphatic amine blending ratio (molar ratio) of 50% or 20% as a urea-based thickener and an aromatic amine as an antioxidant, were confirmed to have excellent acoustic properties (Anderon value: 0.35 to 0.52, where 1 or less is judged as suitable) after exposure to an oxidizing substance, regardless of the type of base oil, and to have low rotational torque (torque value: 0.22 to 0.48 mNm, where 0.5 mNm or less is judged as suitable). The grease composition of Example 1, which used PAO as the base oil, tended to have better acoustic properties (Anderon value; Example 1: 0.35, Example 5: 0.38) and rotational torque (torque value; Example 1: 0.22 mNm, Example 5: 0.48 mNm) than the grease composition using an ester oil (Example 5).

On the other hand, the grease composition using a diurea compound with an aliphatic amine blending ratio (molar ratio) of 70% (Comparative Example 1) exhibited deteriorated acoustic properties (Anderon value: 1.3), and the grease composition using a diurea compound with said blending ratio of 100% (Comparative Example 5) not only exhibited an even worse acoustic property (Anderon value: 3.8), but also exhibited an increased rotational torque value (torque value: 0.90 mNm) and deteriorated torque performance.
Furthermore, when an aliphatic amine was used as the antioxidant (Comparative Example 2, Comparative Example 3), the acoustic properties were deteriorated compared to the grease compositions using an aromatic amine (Comparative Example 1, Example 1) (Anderon value; Comparative Example 2: 3.5, Comparative Example 3: 2.8).
In Comparative Example 4, in which a lithium soap thickener was used as the thickener, the acoustic properties were excellent (Anderon value: 0.17), but the torque performance was poor (torque value: 0.58 mNm).
In addition, the grease composition (Comparative Example 6) using a diurea compound with a 100% blend ratio (molar ratio) of alicyclic amine as a thickener, and the grease composition (Comparative Example 7) using a diurea compound with a 100% blend ratio (molar ratio) of aromatic amine showed inferior acoustic properties and torque performance (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). When Comparative Example 6 and Comparative Example 7 are compared, the grease composition of Comparative Example 7, which contains a diurea compound containing only aromatic amine as an amine compound, shows a tendency to be inferior in both acoustic properties and torque performance compared to the grease composition of Comparative Example 6, which contains a diurea compound containing only alicyclic amine.

FIG. 5 shows the change in acoustic properties of the grease composition when the proportion of aliphatic amine used in the amine compound constituting the urea-based thickener (diurea compound) is changed.
FIG. 5 is a graph showing the results of acoustic evaluation (Anderon value) (vertical axis) of a grease composition containing a urea-based thickener, relative to the change in the blending ratio (mol %) of aliphatic amines (horizontal axis) in the amine compounds that constitute the urea-based thickener.
In Fig. 5, the straight line parallel to the horizontal axis indicates an Anderon value of 1.0. The grease compositions at the measurement points shown in this figure are grease compositions in which an aliphatic amine and an alicyclic amine are used as the amine compounds constituting the urea-based thickener at different blend ratios, and an aromatic amine is used as the antioxidant (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%); approximation curves calculated from the above Anderon values are also shown), or a grease composition in which the aliphatic amine ratio is 50 mol% and an aliphatic amine is used as the antioxidant (Comparative Example 3; measurement point away from the approximation curve and surrounded by a dotted line).
5, it is estimated from the approximation curve that when the blending ratio of the aliphatic amine is in the range of 10 mol % to 60 mol % (the range indicated by the dotted arrow in the figure), the anderon value is 1 or less. It is also clearly shown that when the blending ratio of the aliphatic amine is 50 mol %, the anderon value increases significantly when an aliphatic amine is used as an antioxidant.

The above results suggest that by using a urea compound containing an aliphatic amine in a ratio of 10 to 60 mol % relative to the total amount of the amine compound constituting the urea-based thickener, it is possible to provide a grease composition that suppresses the generation of abnormal noise even after exposure to an oxidizing substance and has excellent acoustic properties, and further to provide a grease composition that can also achieve low torque performance.

The above describes the best embodiment in detail, but the present invention is not limited to the above embodiment, and any modifications or improvements that can achieve the object of the present invention are included in the present invention.

G... grease composition, 10... rolling bearing, 11... inner ring, 12... outer ring, 13... rolling element, 14... cage, 15... sealing member, 16... bearing space, 30... ion generating device or air conditioning device, 31... blower, 32... ion generating source, 33... air intake, 34... exhaust port

Claims (5)

A base oil,
A urea-based thickener comprising a diurea compound represented by the following formula (1),
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 in this case, the proportion of the monovalent aliphatic hydrocarbon group relative to the total number of moles of R ₁ and R ₃ is 10% to 60%;
_R2 represents a divalent aromatic hydrocarbon group.
A rolling bearing having a grease composition filled therein, the grease composition including an aromatic amine-based antioxidant, the rolling bearing being provided in an ion generating device or an air conditioning device blower,
The ion generator or air conditioning device is equipped with an air intake port, an oxidizing substance generator, an exhaust port, and a blower, and air flows from the air intake port to the exhaust port together with the generated oxidizing substance, and the air flow is structured so that it comes into contact with the blower . The rolling bearing according to claim 1, wherein the rolling bearing is provided with a seal member. 3. The rolling bearing according to claim 1 , wherein the oxidizing substance comprises at least one substance selected from the group consisting of ions, ozone, oxygen radicals, and hydroxyl radicals. A blower comprising the rolling bearing according to any one of claims 1 to 3 . An ion generating device or an air conditioning device comprising the blower according to claim 4 .

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