JPH11217582A - Grease for roller bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject grease excellent in load resistant power and extreme-pressure performance, and capable of providing a long-life durability under a severe working condition by including a base oil, a thickener and specific fine particles. SOLUTION: The objective grease includes (A) a base oil (e.g. a mineral oil) preferably having 10-400 mm<2> /s, more preferably 20-250 mm<2> /s, most preferably 40-200 mm<2> /s kinetic viscosity (at 40 deg.C), (B) a thickener (e.g. diurea), (C) fine particles comprising an inorganic compound (e.g. magnesium oxide) having 0.1-2 μm mean diameter, and (D) optionally, an antioxidant, a rust-preventing agent, a metal deactivator, an oily agent, an extreme pressure agent, a clay index improver or the like. The amount of the component C formulated is preferably 0.1-15 wt.%, more preferably 0.1-10 wt.% based on the entire grease.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grease for a roller bearing, and more particularly to a roller bearing used under a heavy load such as a roll of a rolling mill, and further under a severe condition such as being exposed to water at a high temperature. It relates to a suitable grease.

[0002]

2. Description of the Related Art Roller bearings used under high loads, such as tapered roller bearings for roll necks of rolling mills in steel facilities, have a sliding surface between a flange provided on an inner ring or an outer ring and a roller end face. Since a large surface pressure is applied locally, grease that is excellent in high load performance and extreme pressure performance is sealed. In order to provide load-bearing performance and extreme pressure performance, it is common to add an extreme pressure agent to grease.
oS ₂ of a solid-state lubricant, sulfur-based, phosphorus-based, sulfur - phosphorus-based organic compounds, organic molybdenum compounds such as molybdenum dialkyldithiocarbamate (MoDTC) or dialkyl dithiophosphate, molybdenum (MoDTP), zinc dialkyldithiophosphate (ZnDTP), etc. An organic zinc compound,
Extreme pressure agents such as organic antimony compounds are known. Among them, organic extreme pressure agents have recently become mainstream because they exhibit excellent extreme pressure performance. For example, Japanese Patent Publication No. 4-34590, Japanese Patent Publication No. 3-78920, Japanese Patent Application Laid-Open No. 60-470.
No. 99 discloses MoDTC, MoDTP, and ZnDTP.
It is described that an extreme pressure agent containing an organic molybdenum compound or an organic zinc compound is particularly effective. It is also known that ashless dialkyldithiocarbamic acid is also effective.

[0003]

However, roller bearings are first required to have seizure performance, and furthermore, tapered roller bearings for roll necks of rolling mills have high temperatures or are exposed to water and water is mixed into the grease. Grease containing an organic extreme pressure agent, which has been regarded as preferable in the past, does not provide stable extreme pressure performance or load-bearing performance, leading to premature seizure. There were things. Recently, in addition to use under a higher load, use at a high speed rotation has also been demanded, and further improvement in extreme pressure performance and load resistance has been desired.

The present invention has been made in view of the above circumstances, and has excellent load-bearing performance and extreme pressure performance more than before, and has durability under severe use conditions such as mixing at high temperatures and water. It is an object of the present invention to provide a grease for a roller bearing which prolongs the life of the roller bearing.

[0005]

Means for Solving the Problems The present inventors disperse fine particles made of an inorganic compound having a specific particle size in grease, thereby making it possible to perform high-speed rotation, high load, high temperature, It has been found that the roller bearing can be provided with good seizure resistance even when used under conditions. The present invention is based on the above findings. That is, the above-described object of the present invention, a base oil, a thickener,
This is achieved by a roller bearing grease containing fine particles made of an inorganic compound having an average particle diameter of 0.1 μm to 2 μm.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the grease for a roller bearing of the present invention will be described in more detail. The grease for a roller bearing of the present invention comprises a base oil and a thickener as main components, and fine particles comprising an inorganic compound added thereto as essential components, similarly to ordinary grease. Hereinafter, each component will be described. [Base oil] There is no particular limitation, and all oils usually used as base oils for lubricating oils can be used. Preferably, the kinematic viscosity at 40 ° C. is preferably 10 to 400 to avoid an increase in starting torque due to lack of low-temperature fluidity and seizure caused by the difficulty of forming an oil film at high temperatures.
mm ² / s, particularly preferably 20 to 250 mm ² / s,
More preferably, a base oil of 40 to ²⁰⁰ mm ² / s is desirable. This kinematic viscosity can be based on a value usually measured by a glass capillary viscometer. Also,
In order to extend the bearing lubrication life, it is desirable that the ester oil, particularly the polyol ester oil, be contained in an amount of 10% by weight or more of the base oil.

[0007] Specific examples include mineral oil-based, synthetic oil-based or natural oil-based lubricating base oils. As the mineral oil-based lubricating base oil, a refined one obtained by appropriately combining mineral oil under reduced pressure distillation, solvent removal, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, clay purification, hydrorefining, and the like is used. Can be. Examples of the synthetic oil-based lubricating base oil include a hydrocarbon-based oil, an aromatic-based oil, an ester-based oil, and an ether-based oil. Examples of the hydrocarbon-based oil include normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, poly-α-olefin such as co-oligomer of 1-decene and ethylene, and hydrides thereof. Examples of the aromatic oil include alkylbenzene such as monoalkylbenzene, dialkylbenzene and polyalkylbenzene, and alkylnaphthalene such as monoalkylnaphthalene, dialkylnaphthalene and polyalkylnaphthalene. Examples of the ester-based oils include dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl glutarate, diesters such as methyl acetyl ricinolate, or trioctyl trimellitate, Aromatic ester oils such as tridecyl trimellitate and tetraoctyl pyromellitate, as well as trimethylolpropane caprylate, trimethylolpropaneperargonate, and pentaerythritol-2
Polyol esters such as -ethylhexanoate and pentaerythritol belargonate; and complex esters which are oligoesters of a polyhydric alcohol and a mixed fatty acid of dibasic acid / monobasic acid. As the ether-based oil, polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, polyglycol such as polypropylene glycol monoether, or monoalkyl triphenyl ether, alkyl diphenyl ether, dialkyl diphenyl ether, pentaphenyl ether,
And phenyl ethers such as tetraphenyl ether, monoalkyl tetraphenyl ether and dialkyl tetraphenyl ether. Other synthetic lubricating base oils include tricresyl phosphate, silicone oil, perfluoroalkyl ether oil and the like. These base oils can be used alone or as a mixture, and are adjusted to the preferable kinematic viscosity described above.

[Thickeners] Thickeners are also not particularly limited. For example, metal soaps such as aluminum, barium, calcium, lithium and sodium, composite metal soaps such as lithium complex, calcium complex and aluminum complex, and diurea , Triurea, tetraurea, urea compounds such as polyurea, or silica gel, inorganic compounds such as bentonite,
Urethane compounds, urea / urethane compounds, sodium terephthalamate compounds and the like can be used as appropriate. Among them,
By using a urea compound with excellent oxidation stability,
Lubrication performance and lubrication life at high temperature and high speed rotation can be further improved. These thickeners have their molecules or crystals connected in a chain to form a fibrous form and are uniformly dispersed in grease to form a gel structure. It is considered that the gel structure is reinforced by penetrating between the binder fibers.

[Particles Made of Inorganic Compound] (Composition) As described above, any material may be used as long as it is a material that reinforces the gel structure formed by the thickener, and there is no particular limitation. Silicon, aluminum, magnesium, titanium, zinc, Preference is given to oxides of zirconium, chromium, tungsten and boron, or carbides or nitrides thereof, and diamond. Further, in order to improve the affinity with the base oil and the urea-based thickener, those whose surfaces are modified to be lipophilic may be used.

(Particle diameter) In consideration of application to a roller bearing used under a high load such as a roll of a rolling mill, the average particle diameter is desirably at least 0.1 μm. When the average particle size is less than 0.1 μm, it hardly contributes to the improvement of load-bearing performance and extreme pressure performance aimed at by the present invention. Further, since a roll or the like of a rolling mill does not require acoustic characteristics, a large tapered roller bearing can use particles of up to 2 μm. If the average particle size exceeds 2 μm, the number of particles acting as foreign matters increases, which promotes wear of the bearing raceway and the roller surface and causes early damage to the bearing. In the present invention, the inorganic compound has an average particle size of 0.1 μm or more and 2 μm or more.
It has been found that, when the content is below, a generally good seizure prevention effect for roller bearings is exhibited. The shape is preferably as close to a spherical shape as possible, but as long as it is within the above average particle size, it may be a polyhedron (cube, rectangular parallelepiped, etc.) or extremely acicular.

[Grease composition] Since the inorganic compound fine particles also have a thickening action, the additive amount is limited to 35% by weight of the total grease with the thickener, and if the amount is more than 35%, the amount of the grease increases. It is not preferable because it adversely affects the fluidity. Within this addition range,
The ratio between the inorganic compound fine particles and the thickener is not particularly limited, but if the inorganic compound fine particles are relatively small, the effect of improving load-bearing performance and extreme pressure performance will not be sufficient, so that the inorganic compound fine particles Is preferably 0.1 to 15% by weight, particularly 0.1 to 10% by weight of the whole grease.

[Other Additives] The above-mentioned grease is formed by mixing inorganic compound fine particles and a thickener with a base oil. If necessary, the following additives may be used alone or in combination of two or more. Is also good. The compounding amount is 20% by weight or less of the whole grease as a whole. [Antioxidant] rubber, plastic,
The antioxidant, antiozonant, and antioxidant to be added to the lubricating oil and the like are appropriately selected and used. For example, the following compounds can be used. That is, phenyl-1-naphthylamine, phenyl-2-naphthylamine, diphenyl-p-phenylenediamine, dipyridylamine, phenothiazine, N-methylphenothiazine, N-ethylphenothiazine, 3,7-dioctylphenothiazine,
amine compounds such as p, p'-dioctyldiphenylamine, N, N'-diisopropyl-p-phenylenediamine, N, N'-di-sec-butyl-p-phenylenediamine; 2,6-di-tert-di A phenolic compound such as butylphenol can be used.

[Rust Inhibitor / Metal Deactivator] As the rust inhibitor, for example, the following compounds can be used. That is, an ammonium salt of an organic sulfonic acid, an alkali metal such as barium, zinc, calcium, or magnesium, an organic sulfonate or an organic carboxylate of an alkaline earth metal, a phenate, a phosphonate, or an alkyl or alkenyl such as an alkyl or alkenyl succinate. Succinic acid derivatives, partial esters of polyhydric alcohols such as sorbitan monooleate, hydroxy fatty acids such as oleoyl sarcosine, mercapto fatty acids such as 1-mercaptostearic acid or metal salts thereof, higher fatty acids such as stearic acid, Higher alcohols such as isostearyl alcohol, esters of higher alcohols and higher fatty acids, 2,5
Thiazoles such as dimercapto-1,3,4-thiadiazole and 2-mercaptothiadiazole, imidazole compounds such as 2- (decyldithio) -benzimidazole and benzimidazole, or 2,5-bis (dodecyldithio) benzimidazole Or a phosphoric acid ester such as trisnonylphenyl phosphite, a thiocarboxylic acid ester compound such as dilauryl thiopropionate, or the like. Further, nitrite and the like can also be used. As the metal deactivator, for example, a triazole-based compound such as benzotriazole or tolyltriazole can be used.

[Oiling agent] As the oiling agent, for example, the following compounds can be used. That is, fatty acids such as oleic acid and stearic acid, fatty acid alcohols such as oleyl alcohol, fatty acid esters such as polyoxyethylene stearic acid ester and polyglyceryl oleate, phosphoric acid, tricresyl phosphate, lauric acid ester and polyoxyethylene oleyl. Phosphate esters such as ether phosphoric acid can be used.

[Extreme pressure agent] The above-mentioned inorganic compound fine particles act as an extreme pressure agent. If necessary, conventionally used chlorine-based, sulfur-based, phosphorus-based, zinc dithiophosphate, organic molybdenum and the like can be used. An extreme pressure agent may be added.

[Clay index improver] As the clay index improver, for example, polymethacrylate, polyisobutylene, polystyrene and the like can be used.

[Manufacturing method] Grease is prepared by reacting a thickener in a base oil. Fine particles of an inorganic compound are preferably added during this reaction. It is also possible to obtain grease with a thickener in advance, and then mix it with inorganic compound fine particles. However, it is necessary to sufficiently stir and uniformly disperse the inorganic compound fine particles after adding the inorganic compound fine particles with a kneader or a roll. When performing this process, heating is also effective. In addition, when an additive other than the inorganic compound fine particles is added, it is preferable in the process to add the additive simultaneously with the inorganic compound fine particles. In the present invention, the amount of the grease sealed in the roller bearing may be the same as the amount applied to this type of roller bearing.

[0018]

The present invention will be described more specifically with reference to the following examples and comparative examples, but the present invention is not limited to these examples. (Examples 1 to 4, Comparative Examples 1 and 2) As shown in Tables 1 and 2, a test grease was obtained by blending a base oil, a thickener, and fine particles of an inorganic compound and passing them through a roll mill. Then, for each test grease, a high-temperature, high-speed, high-load durability test and a water injection seizure test described below were performed. (High-temperature, high-speed, high-load endurance test) Each test grease was sealed in a tapered roller bearing (call number: 30205), and continuously rotated under the conditions of an inner ring rotation speed of 8000 rpm, a bearing outer ring temperature of 150 ° C, a radial load of 100 kgf, and an axial load of 100 kgf. . Then, when the bearing outer ring temperature was 155 ° C. or the bearing torque was increased and the motor eddy current was reached, the seizure life was determined, and the time until it was measured. The test results are shown in Tables 1 and 2. (Injection seizure test) Conical bearing (Nominal number: 32)
017), each test grease was sealed, and the inner ring rotation speed was 10
Rotate at 00rpm and 0.3m every hour
One liter of water was injected into the encapsulated grease. Then, the time until burning was measured. The test results are shown in Tables 1 and 2.

[0019]

[Table 1]

[0020]

[Table 2]

From the above test results, it can be seen that by enclosing the grease containing the fine particles of the inorganic compound, the durability of the roller bearing at a high temperature, a high speed and a high load, and the durability against water injection are greatly improved.

[0022]

As described above, according to the present invention,
In addition to having better load bearing and extreme pressure than ever before, at high temperatures, in harsh usage conditions such as mixing water,
The durability life of the roller bearing can be greatly improved.

Continuation of the front page (51) Int.Cl. ⁶ Identification code FI C10N 40:02 50:10 (72) Inventor Kenichi Iso 1-5-150 Kugenuma Shinmei, Fujisawa-shi, Kanagawa Nippon Seiko Co., Ltd. (72) Invention Person Michiharu Naka 1-5-50 Kugenuma Shinmei, Fujisawa-shi, Kanagawa Nippon Seiko Co., Ltd.

Claims (1)

[Claims] 1. A base oil, a thickener, and an average particle size of 0.1.
A grease for a roller bearing, comprising fine particles of an inorganic compound having a particle size of 1 μm to 2 μm.