JP2009029876A - Grease composition and rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grease composition capable of bringing a long lubrication service life at an applied place even when the grease composition is used under an extreme pressure condition, and to provide a rolling bearing using the grease composition. <P>SOLUTION: An ionic surfactant is added to the grease composition. As a result, the dispersibility of a thickening agent can be improved and consequently excellent wear resistance can be imparted to the portion to be lubricated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a grease composition and a rolling bearing excellent in wear resistance.

Rolling bearings used in various industrial machines, steel equipment, vehicles, electrical equipment, various motors, automobile parts, and the like are filled with a lubricant such as lubricating oil or grease in order to impart lubricity. The lubricant used varies depending on the type of bearing provided.In particular, roller bearings used in steel equipment, vehicles, and industrial machinery are used at high loads, so the oil film formed by the lubricant breaks. This is likely to cause wear due to poor lubrication. In Patent Document 1, wear is improved by using a sulfur-based compound for suppressing wear of vehicle grease.
JP 2004-332768 A

However, when an additive having high reactivity with a metal is used, there is a concern that it may exhibit a corrosive action depending on the environment. In addition, the above-mentioned various demands (high load resistance, wear resistance, etc.) are expected to continue to increase in the future. Particularly, the demand for wear resistance is becoming stricter year by year, which is the most important issue for bearing manufacturers. It has become one.
The present invention has been made in view of such a situation, and a grease composition capable of prolonging the lubrication life of an applied portion even when used under extreme pressure conditions, and the use of the grease composition An object of the present invention is to provide a rolling bearing.

In order to solve the above-mentioned problems, a grease composition according to claim 1 of the present invention comprises a base oil composed of at least one of mineral oil and synthetic oil, a thickener, and an anionic surfactant as an additive. An ionic surfactant selected from at least one of a cationic surfactant and an amphoteric surfactant, and the content of the ionic surfactant is 0.1 to 5 of the total amount. It is characterized by mass%.
A rolling bearing according to claim 2 of the present invention is a rolling bearing in which a plurality of rolling elements are rotatably held between an inner ring and an outer ring, and a grease composition is sealed in a bearing space in which the rolling elements are arranged. The grease composition according to claim 1 is used as the grease composition.

The operation of the grease composition according to the present invention will be described below.
[Action]
The ionic surfactant used as an additive is dissociated into a cation and an anion in solution, and an ion having an affinity for the thickener among the ions dissociated into the cation and anion is a thickener. Preferentially adsorbed on the particle surface. At this time, by selecting and blending a surfactant having a high penetrating effect with respect to the thickener, not only the surfactant is adsorbed on the surface of the thickener but also the thickener present in the grease. Aggregates can be dispersed in a monodispersed state. This is considered to be due to the following action. In other words, the ions dissociated in the solution as described above are adsorbed on the surface of the thickener, so that the thickener can have a high surface potential and the thickeners repel each other. . It is considered that this effect makes it difficult for the thickeners to agglomerate and the thickener can be stably dispersed in the oil. The thickener well dispersed in the base oil can easily enter the oil film formed between the inner and outer rings of the bearing and the rolling elements, and the friction surface of the thickener that has entered the oil film can be easily removed. The wear resistance is improved by the protective action, and good lubricity can be maintained for a long time.

  According to the grease composition of the present invention, since an additive capable of improving the dispersibility of the thickener is blended, excellent wear resistance can be imparted to the lubricated site even under extreme pressure conditions. Therefore, by enclosing it in a rolling bearing, it is possible to impart excellent wear resistance and improve durability.

Next, embodiments of the present invention will be described with reference to the drawings.
[Rolling bearings]
FIG. 1 is a partial longitudinal sectional view showing the structure of a deep groove ball bearing which is an embodiment of a rolling bearing according to the present invention.
The rolling bearing shown in FIG. 1 holds an inner ring 1, an outer ring 2, a plurality of balls (rolling elements) 3 that are disposed between the inner ring 1 and the outer ring 2, and a plurality of balls 3. The container 4 and the shields 5 and 5 attached to the seal grooves 2a and 2a of the outer ring 2 are configured. In addition, the gap surrounded by the inner ring 1, the outer ring 2, and the shields 5, 5 is filled with the grease composition 6 according to this embodiment, and is sealed in the bearing by the shield 5. The grease composition 6 lubricates the contact surfaces between the raceway surfaces of the wheels 1 and 2 and the balls 3.

In the above rolling bearing, an ionic surfactant is added to the grease composition (details of the composition will be described later) 6, so that the thickener is uniformly dispersed in the grease by the action of the ionic surfactant. To do. For this reason, the thickener can easily enter the oil film formed between the inner and outer rings of the bearing and the rolling elements, and wear is caused by the protective action of the friction surface of the thickener that has entered the oil film. And a good lubrication state can be maintained for a long time.
The rolling bearing is not limited to the deep groove ball bearing shown in FIG. 1, and may be an angular bearing or a roller bearing, and may be a thrust bearing instead of a radial bearing. Further, only a single row is shown in the figure, but a double row may be used. Further, the seal type is not limited and may be any of a shield type, a non-contact seal, and a contact seal type, and may be an open type.

Next, the grease composition of the present invention will be described in more detail.
[Base oil]
The base oil to be used is not particularly limited, and any oil that is usually used as a base oil for lubricating oil can be used. Preferably, the kinematic viscosity at 40 ° C. is preferably 10 to 400 mm ² / sec, more preferably 20 to 250 mm in order to avoid generation of abnormal noise at low temperature startup and seizure that occurs because an oil film is hardly formed at high temperature. ^A base oil of ² / sec, more preferably 40 to 150 mm ² / sec is preferred. Specific examples include mineral oil-based, synthetic oil-based or natural oil-based lubricating oils. As the mineral oil-based lubricating oil, it is possible to use a refined oil obtained by appropriately combining mineral oil under reduced pressure distillation, oil removal, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, white clay purification, hydrorefining, etc. it can. Examples of the synthetic oil base oil include hydrocarbon oils, aromatic oils, ester oils, ether oils and the like. Examples of the hydrocarbon-based 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 the ester oils include dibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, ditridecyl glutarate, and methyl acetyl ricinolate, or trioctyl trimellitate, Aromatic ester oils such as tridecyl trimellitate and tetraoctyl pyromellitate, as well as polyol esters such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate Oils, and complex ester oils which are oligoesters of polyhydric alcohols and mixed fatty acids of dibasic acids and monobasic acids are also included. Examples of the ether oil 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. Examples thereof include phenyl ether oils such as tetraphenyl ether and dialkyl tetraphenyl ether. Other synthetic lubricating base oils include tricresyl phosphate, silicone oil, perfluoroalkyl ether and the like. Examples of the natural oil-based lubricating base oil include beef tallow, lard, soybean oil, rapeseed oil, rice bran oil, coconut oil, palm oil, palm kernel oil, and other oils and hydrides thereof. These base oils can be used alone or as a mixture, and are adjusted to the above-mentioned preferable kinematic viscosity.

[Thickener]
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 soap whose metal component is Li, Na or the like, metal soap such as composite metal soap whose metal component is Li, Na, Ba, Ca or the like, benton, silica gel, urea compound, urea / urethane compound, urethane compound Non-soaps such as can be appropriately selected and used. As a compounding quantity of a thickener, it is preferable that it is 5-40 mass% with respect to the grease composition whole quantity. Here, when the blending ratio of the thickener is less than 5% by mass, it becomes difficult to maintain the grease state. On the other hand, when the blending ratio of the thickener exceeds 40% by mass, the grease composition This is not preferable because the object becomes too hard and the lubrication state cannot be sufficiently exhibited.

[Ionic surfactant]
As the ionic surfactant, an anionic surfactant, a cationic surfactant and an amphoteric surfactant can be used. Specific examples of usable ionic surfactants include anionic surfactants such as alkyl sulfate esters, polyoxyethylene alkyl ether sulfates, alkylbenzene sulfonates, fatty acid salts, and naphthalene sulfonate formalin condensates. Alternatively, the cationic surfactants such as alkylamine salts and quaternary ammonium salts, and the amphoteric surfactants include alkylbetaines and alkylamine oxides. Of these, alkyl sulfate salts and alkyl benzene sulfonates that can disperse thickener thickener agglomerates in a monodispersed state with high penetrating power are particularly preferred. A preferable addition amount of the surfactant is 0.1 to 5% by mass with respect to the total amount of the grease composition. If the amount added is less than this, the ability to disperse the thickener will be insufficient, and even if added over 5% by mass, an improvement in addition effect cannot be expected, and the amount of base oil will be relatively small so that lubrication will occur. It is not preferable because the property may be lowered. More preferably, it is 0.1-3 mass% with respect to the grease composition whole quantity.

  Furthermore, in the grease composition of the present invention, various additives may be mixed as desired 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, and succinic acid derivatives. Additives used in lubrication, such as agents, extreme pressure agents such as phosphorus-based, zinc dithiophosphate and molybdenum compounds, oiliness improvers such as fatty acids and animal and vegetable oils, metal deactivators such as benzotriazole, etc. A mixture of more than one species can be used. In addition, the addition amount of these additives will not be specifically limited if it is a grade which does not impair the objective of this invention.

[Production method]
In order to prepare the grease composition of the present invention, an ionic surfactant is added to a base grease obtained by reacting a thickener in a base oil in order to sufficiently adsorb the ionic surfactant to the thickener. It is necessary to stir well after blending a predetermined amount of the agent. When a plurality of additives are blended, first, only the ionic surfactant is added and stirred well, then the remaining additives are blended, and sufficiently stirred with a kneader or a roll mill, and uniformly dispersed. When blending the ionic surfactant and additive, heating is also effective.

[Example]
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
(Examples 1-6, Comparative Examples 1-3)
Test grease compositions were prepared with the formulations shown in Table 1. Then, using the test grease composition, the following (1) thickener dispersibility evaluation test and (2) wear resistance test were performed. The consistency of the test grease composition is NLGI No. Adjusted to 2.

(1) Thickener dispersibility evaluation test The dispersibility of the thickener was evaluated by the sedimentation rate of the thickener. The sedimentation rate is evaluated by dispersing 50 mg of the test grease in 10 ml of hexane and measuring the rate at which the thickener settles in the solution. The slower the sedimentation rate, the better the dispersibility of the thickener. did.

(2) Abrasion resistance test The abrasion resistance test was conducted using a reciprocating friction and abrasion test apparatus as shown in FIG. Specifically, a test ball 34 attached to a holder 33 is placed on a test flat plate 32 installed on a test table 31, and a grease composition to be tested is placed between the test flat plate 32 and the test ball 34. Intervened. Then, by applying a vertical load to the holder 33, the holder 33 was swung by the cam 35 while pressing the test flat plate 32 with the test ball 34. The temperature of the test flat plate 32 was kept constant by the heater 36 and the thermocouple 37 provided in the test table 31. Further, the test table 31 is provided with a load cell 38 so that the above-described oscillation can be observed.

The oscillation frequency was 10 Hz, the amplitude was 20 mm, the vertical load was 2 GPa, the film thickness of the grease composition on the test plate 32 was 1 mm, the test temperature was 60 ° C., and the test time was 10 min.
The wear resistance of the used grease composition was evaluated by the size of the diameter (wear scar diameter) perpendicular to the rocking direction that can be formed on the test plate 32 after the test. The test results are shown as the ratio of the average wear diameter after the third test, with the value of Comparative Example 1 being 1.
Tables 1 and 2 show the compositions of the grease compositions of Examples and Comparative Examples and the test results of the above (1) and (2).

The annotations in Tables 1 and 2 are as follows.
1) Base oil: ester oil (kinematic viscosity at 40 ° C. 33 mm ² / s)
2) Reaction product of 4,4'-diphenylmethane diisocyanate and p-toluidine 3) Reaction product of 4,4'-diphenylmethane diisocyanate and octylamine 4) Alkylbenzene sulfonate 5) Alkyl sulfate ester salt 6) Quaternary Ammonium salt 7) Alkylamine salt 8) Alkylbetaine

  As shown in Tables 1 and 2, it was confirmed that those containing 0.1% by mass or more of an anionic surfactant, a cationic surfactant and an amphoteric surfactant had a slow sedimentation rate. From this, it is considered that the thickener is well dispersed in the grease, and it is considered that this effect is also excellent in wear resistance. On the other hand, when the anionic surfactant, the cationic surfactant and the amphoteric surfactant are not blended, the sedimentation rate is very high and the wear resistance is low. Further, if the blending amount of the anionic surfactant, the cationic surfactant and the amphoteric surfactant is less than 0.1% by mass, the thickener cannot be sufficiently dispersed and sufficient abrasion resistance is obtained. It turns out that it cannot be obtained.

It is a figure which shows an example of a rolling bearing. It is a figure which shows a reciprocating friction wear test apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner ring 2 Outer ring 2a, 2a Seal groove 3 Ball 4 Cage 5, 5 Shield 6 Grease composition 31 Test stand 32 Test plate 33 Holder 34 Test ball 35 Cam 36 Heater 37 Thermocouple 38 Load cell

Claims (2)

A base oil consisting of at least one of mineral oil and synthetic oil, a thickener, and an additive selected from at least one of an anionic surfactant, a cationic surfactant and an amphoteric surfactant An ionic surfactant
Content of said ionic surfactant is 0.1-5 mass% of the whole quantity, The grease composition characterized by the above-mentioned. In a rolling bearing in which a plurality of rolling elements are rotatably held between an inner ring and an outer ring, and a grease composition is sealed in a bearing space in which the rolling elements are arranged.
A rolling bearing using the grease composition according to claim 1 as the grease composition.

Images