JP2008291179A - Grease composition and roller bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grease composition prolonging lubrication life in usage under an extreme pressure condition especially and to provide a roller bearing constructed by being filled with the grease composition for prolonging its life even by use under an extreme pressure condition. <P>SOLUTION: The grease composition contains at least one kind of base oil selected from mineral oils and synthetic oils, a thickener, and a non-ionic surfactant at a ratio of 0.1-5% by mass to the total amount of grease. In the roller bearing, the grease composition is sealed in a gap, in which a plurality of rolling elements are held freely rotationally, between an inner ring and an outer ring. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a grease composition and a rolling bearing which is filled with the grease composition and is incorporated in various industrial machines, steel equipment, vehicles, electrical equipment, motors, automobile parts and the like.

  A rolling bearing incorporated in an industrial machine, a steel facility, a vehicle, an electric device, a motor, an automobile part, or the like is sealed with a grease composition in order to impart lubricity. The grease composition used varies depending on the type of bearing used. For example, roller bearings used in steel equipment, vehicles, and industrial machinery are loaded with high loads. In many cases, a grease composition to which a system compound is added is used (see, for example, Patent Document 1).

  In other devices as well, the grease composition is required to have improved durability, including wear resistance, as devices and devices become smaller and lighter and faster.

JP 2004-332768 A

  Various demands such as those described above are expected to continue to increase, and in particular, the demand for wear resistance is becoming stricter year by year, which is one of the most important issues for bearing manufacturers.

  The present invention has been made in view of such a situation, and in particular, a grease composition that brings about an increase in the lubrication life in an application used under extreme pressure conditions, and the grease composition enclosed therein. An object of the present invention is to provide a rolling bearing that has a long life even when used under extreme pressure conditions.

In order to achieve the above object, the present invention provides the following grease composition and rolling bearing.
(1) Contains at least one base oil selected from mineral oil and synthetic oil and a thickener, and contains a nonionic surfactant in a proportion of 0.1 to 5% by mass of the total amount of grease. The grease composition characterized by the above-mentioned.
(2) A rolling bearing characterized in that a plurality of rolling elements are rotatably held between an inner ring and an outer ring, and the grease composition described in (1) above is enclosed.

  In the grease composition of the present invention, the thickener is uniformly dispersed in the grease composition by the action of the nonionic surfactant, and it is possible to maintain good lubricity and to easily enter the friction surface. Protect and improve wear resistance. The rolling bearing of the present invention also has excellent wear resistance and a long life.

  Hereinafter, the present invention will be described in detail.

[Grease composition]
In the grease composition of the present invention, the base oil is selected from mineral oil and synthetic oil. Mineral oil can be used that is purified by appropriately combining vacuum distillation, oil removal, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, white clay purification, hydrorefining, and the like.

  Synthetic oils include hydrocarbon oils, aromatic base oils, ester oils, ether oils, and the like. Examples of the hydrocarbon oil include normal paraffin, isoparaffin, polybutene, polyisobutylene, 1-decene oligomer, poly-α-olefin such as 1-decene and ethylene co-oligomer, and hydrides thereof. Examples of the aromatic oil include alkylbenzenes such as monoalkylbenzene and dialkylbenzene, and alkylnaphthalenes such as monoalkylnaphthalene, dialkylnaphthalene and polyalkylnaphthalene. Examples of ester oils include dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl glutarate, and methyl acetyl cinolate, or trioctyl trimellitate. Aromatic ester oils such as tridecyl trimellitate and tetraoctyl pyromellitate, and further trimethylolpropane caprylate, trimethylolpropane verargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol verargonate, etc. Polyol ester oils, and complex ester oils that are oligoesters of polyhydric alcohols and mixed fatty acids of dibasic acids and monobasic acids are also exemplified. Examples of ether oils include polyglycols such as polyethylene glycol, polypropylene glycol, polyethylene glycol monoether, and polypropylene glycol monoether, or monoalkyl triphenyl ether, alkyl diphenyl ether, dialkyl diphenyl ether, pentaphenyl ether, tetraphenyl ether, and monoalkyl tetra And phenyl ether oils such as phenyl ether and dialkyl tetraphenyl ether.

  Other synthetic oils can also be used, and examples thereof include tricresyl phosphate, silicone oil, perfluoroalkyl ether, and the like.

Said mineral oil and synthetic oil may each be used independently, and may be used as a mixture. Further, the base oil preferably has a kinematic viscosity at 40 ° C. of 10 to 400 mm ² / s in order to prevent seizure that occurs due to generation of abnormal noise at low temperature startup and difficulty in forming an oil film at high temperatures. Is 20 to 250 mm ² / s, particularly preferably 40 to 150 mm ² / s.

  The thickener is not particularly limited as long as it has the ability to form a gel structure and retain the base oil in the gel structure. For example, metal soaps such as Li, Na, etc., metal soaps such as composite metal soaps selected from Li, Na, Ba, Ca, etc., nonmetallic soaps such as bentonite, silica gel, urea compounds, urea / urethane compounds, etc. It can be appropriately selected and used. These may be used alone or in combination.

  The blending amount of the thickener is preferably 5 to 40% by mass with respect to the total amount of the grease. If the blending amount of the thickener is less than 5% by mass, it will be difficult to maintain the grease state, and if it exceeds 40% by mass, the grease composition will be too hard to fully exhibit lubricity. It is not preferable.

  A nonionic surfactant is added to the grease composition as an essential additive. Nonionic surfactant has both hydrophilic group and lipophilic group in one molecule, and with respect to the thickener particles, the hydrophilic group is directed to the hydrophilic group of the thickener, and the lipophilic group is on the base oil side. Adsorb toward Since the surface of the thickener particles is made oleophilic in this way, it can be stably dispersed in the base oil, and the lubricating action can be stably expressed over a long period of time. It becomes easier to enter the oil film in the gap between and protect the friction surface and improve the wear resistance.

  Because of its excellent action, nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyalkylene alkyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acids. Esters, polyoxyethylene fatty acid esters and the like can be suitably used. Of these, polyoxyethylene alkyl ethers and polyoxyalkylene alkyl ethers are particularly preferred because of their high penetrating power in the thickener and the ability to disperse thickener aggregates in a monodispersed state.

  The addition amount of the nonionic surfactant is 0.1 to 5% by mass of the total amount of grease. If the addition amount is less than 0.1% by mass, the adsorption amount of the nonionic surfactant to the thickener is too small and the thickening agent becomes insufficiently lipophilic, and the addition amount exceeds 5% by mass. However, the effect is saturated, and the amount of base oil is relatively reduced and the lubricity is lowered. The addition amount of the nonionic surfactant is more preferably 0.1 to 3% by mass of the total amount of grease.

  Various additives may be mixed in the grease composition of the present invention in order to further improve various performances. Additives include antioxidants such as amines, phenols, sulfurs, zinc dithiophosphates and zinc dithiocarbamates, rust preventions such as metal sulfonates, esters, amines, metal naphthenates, succinic acid derivatives, etc. 1 or 2 types of additives used in lubrication, such as agents, phosphorus-based, extreme pressure agents such as zinc dithiophosphate and organic molybdenum, oil improvers such as fatty acids and animal and vegetable oils, metal deactivators such as benzotriazole A mixture of the above can be used. The addition amount of these additives is not particularly limited as long as the object of the present invention is not impaired.

  In addition, the grease composition is prepared by adsorbing a nonionic surfactant to the base grease obtained by reacting the thickener in the base oil in order to adsorb the nonionic surfactant to the thickener. Add a fixed amount and stir well with a kneader or roll mill. In the case of adding other additives, only the nonionic surfactant is added and stirred, and then the other additives are added and stirred. Heating is also effective when this treatment is performed.

[Rolling bearings]
The present invention provides a rolling bearing in which the grease composition is enclosed. There is no restriction | limiting in the structure of a rolling bearing, For example, the rolling bearing 1 shown in FIG. 1 can be illustrated. In the illustrated rolling bearing 1, a rolling element 13 is rotatably held by a cage 12 between an inner ring 10 and an outer ring 11, and a bearing space formed by the inner ring 10, the outer ring 11, and the rolling element 13. Is filled with the grease composition G, and the opening between the inner ring 10 and the outer ring 11 is sealed with a contact seal 14. Note that the amount of grease composition may be equal to the amount of normal grease.

  The rolling bearing of the present invention has a long service life due to the action of the grease composition, which suppresses wear even under extreme pressure conditions.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited at all by this.

[Examples 1-5, Comparative Examples 1-3]
Test greases were prepared according to the formulation shown in Table 1. In addition, the numerical value of a mixing | blending is a ratio (mass%) which occupies for the grease whole quantity. The consistency of the test grease is NLGI No. Adjusted to 2. And evaluation shown below was performed.

(1) Thickener dispersibility evaluation test The dispersibility of the thickener was evaluated from the sedimentation rate of the thickener. That is, the test grease was dispersed in hexane, and the rate at which the thickener settled in the dispersion was measured. The slower the sedimentation rate, the better the dispersibility. The results are shown in Table 1.

(2) Wear resistance test Each test grease composition was applied to four test balls (steel balls for ball bearings, manufactured by SUJ2, 12.7 mm in diameter), and these test balls were tested in accordance with ASTM D 2596. A wear resistance test was conducted under the following conditions. Of the four test balls, three test balls are arranged in an equilateral triangle shape so that they come into contact with each other. One test ball is placed in the recess formed thereby, and a load is applied to the placed test ball. It is configured to rotate in a state.
・ Surface pressure: 2.3 GPa
・ Rotation speed: 1400rpm
-Rotation time: 20 minutes And after rotating for 20 minutes, the abrasion area of the three test balls arrange | positioned under was measured with the optical microscope. The test was performed 5 times for each test grease, and the average value of the wear area was determined. The results are shown in Table 1, and are shown as relative values where the average wear area of the test grease of Comparative Example 1 is 1.

  From Table 1, it is considered that the test grease containing the specified amount of the nonionic surfactant according to the present invention has a slow sedimentation rate, and thus the thickener is well dispersed in the grease. Is excellent. On the other hand, the test grease to which no nonionic surface activity is added has a high sedimentation rate and poor wear resistance. In addition, when the addition amount of the nonionic surfactant is 0.1% by mass of the total amount of grease, the adsorption to the thickener is insufficient, and the thickener cannot be sufficiently dispersed in the base oil. As a result, sufficient wear resistance cannot be imparted.

It is sectional drawing which shows an example of the rolling bearing of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rolling bearing 10 Inner ring 11 Outer ring 12 Cage 13 Rolling body 14 Contact seal G Grease composition

Claims (2)

  It contains a base oil consisting of at least one selected from mineral oil and synthetic oil and a thickener, and contains a nonionic surfactant in a proportion of 0.1 to 5% by mass of the total amount of grease. A grease composition.   A rolling bearing characterized in that a plurality of rolling elements are rotatably held between an inner ring and an outer ring, and the grease composition according to claim 1 is enclosed.

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