JP2010209129A - Grease composition and rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grease composition which uses together as a viscosity improver a thickener and a gelling agent, and moreover which is contrived to give a lower torque as well as to suppress a grease leakage by curtailing still more the content of the viscosity improver. <P>SOLUTION: The grease composition is a lubricant composition including a base oil and a viscosity improver of a mixture of a gelling agent and a thickener, wherein this grease composition is such that the gelling agent is an amino acid-based gelling agent or a benzylidene sorbitol derivative, and comprises a mixture having a ratio (a gelling agent:a thickener) of (50-95):(5-50), and besides contains 1-10 mass%, based on the whole amount, of a total of the gelling agent and the thickener. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a grease composition and a rolling bearing in which the grease composition is enclosed.

  Conventionally, a grease composition obtained by curing a base oil with a thickener has been used for lubrication of rolling bearings, but as a consistency of the grease composition, a general NLGI No. To obtain a hardness of 2, a thickener is required in an amount of 10 to 30% by mass based on the total amount of grease. In the grease composition, since the stirring resistance increases as the amount of the thickener increases, the torque increases, and the torque stability is disadvantageous.

  From such a problem, a thickener and a gelling agent are mixed and used as a thickener to reduce the content thereof, and in Patent Document 1 (gelling agent: thickener). The ratio is 5-50: 50-95. However, the viscosity of the gelling agent is greatly reduced due to shearing and is effective in reducing the torque. However, since the flow-restoration reversibility is poor, grease leakage is likely to occur. Therefore, the mixing ratio of the thickener in the thickener is as high as 50% or more, and the content of the thickener, that is, the total amount of the gelling agent and the thickener cannot be reduced so much. Excess amount is needed.

JP 58-21929 A

  Therefore, the present invention aims to further reduce the torque by reducing the thickener content in a grease composition using a thickener and a gelling agent in combination as a thickener, and to suppress grease leakage. To do.

In order to achieve the above object, the present invention provides the following lubricant composition and rolling bearing.
(1) A lubricant composition comprising a base oil and a mixture of a gelling agent and a thickener as a thickener, wherein the gelling agent is an amino acid gelling agent or a benzylidene sorbitol derivative, (Greasing agent: thickening agent) ratio: 50 to 95: 5 to 50, and a total of 1 to 10% by mass of the gelling agent and thickening agent is contained. object.
(2) An inner ring, an outer ring, and a plurality of rolling elements disposed between the inner ring and the outer ring so as to be freely rollable, and encapsulating the lubricant composition according to (1) above. Rolling bearing.

  The grease composition of the present invention is obtained by using a thickener in which an amino acid-based gelling agent or benzylidene sorbitol derivative having a high gelling performance and a thickener are mixed so that the gelling agent is 50% by mass or more. In addition, the content of the thickener can be greatly reduced to achieve further low torque, and further grease leakage can be reduced.

  In addition, the rolling bearing of the present invention in which the grease composition is encapsulated also has a low torque, little grease leakage, and a long life.

It is sectional drawing which shows an example of the rolling bearing which concerns on this invention. It is a graph which shows the relationship between gelling agent content and the relative leakage rate or relative torque which were obtained in the Example.

  The present invention will be described in detail below with reference to the present invention.

[Grease composition]
The grease composition of the present invention contains a base oil and a thickener composed of a mixture of a gelling agent and a thickener.

  As the gelling agent, an amino acid gelling agent or a benzylidene sorbitol derivative is used. Any compound can be used as long as the base oil can be gelled, and various compounds can be used. As amino acid-based gelling agents, N-2-ethylhexanoyl-L-glutamic acid dibutylamide, N-lauroyl-L-glutamic acid -Α, γ-n-dibutylamide is preferred, and as the benzylidene sorbitol derivative, dibenzylidene sorbitol, ditrilidene sorbitol and asymmetric dialkylbenzylidene sorbitol are preferred.

  The thickener is not particularly limited as long as it can gel the base oil, and organic and inorganic thickeners can be used. Specifically, metal soap such as lithium soap (lithium 12-hydroxystearate, lithium stearate), calcium soap, aluminum soap, magnesium soap, sodium soap, or a composite soap thereof, urea compound (aromatic, alicyclic) , Aliphatic), bentonite, silica, carbon black and the like, and lithium soaps and urea compounds are preferred.

  The mixing ratio of the gelling agent and the thickener in the thickener is (gelator: thickener) ratio of 50 to 95: 5 to 50. When the thickener is less than 5% by mass, the action of the gelling agent becomes dominant, and the recoverability after repeated shearing becomes poor. On the other hand, if the thickener exceeds 50% by mass, the change in viscosity due to the shear characteristic of the gelling agent is suppressed, resulting in insufficient torque reduction, and the effect of improving the acoustic life cannot be obtained. Considering these, the preferred (gelator: thickener) ratio is 60: 40-80: 20.

  Moreover, content of a thickener is 1-10 mass% of grease whole quantity. If the content is less than 1% by mass, the base oil cannot be held well in a gel state, and grease leakage increases. On the other hand, if the content exceeds 10% by mass, the viscosity does not drop significantly even if shearing is applied, so the effect of reducing torque cannot be obtained, the effect of improving the acoustic life is reduced, and the initial consistency becomes too hard. Also inconvenient to fat. Considering these, the more preferable content of the thickener is 3 to 8% by mass.

  On the other hand, if base oil is gelatinized by the said thickener, there will be no restriction | limiting in particular. The base oil to be used is not particularly limited, and any oil (mineral oil-based, synthetic oil-based or natural oil-based lubricant) that is usually used as a base oil for a lubricating oil can be used. Specifically, as mineral oil-based lubricating oil, mineral oil is refined by appropriately combining vacuum distillation, oil removal, solvent extraction, hydrocracking, solvent dewaxing, sulfuric acid washing, clay refining, hydrorefining, etc. Synthetic oil base oils include hydrocarbon oils, aromatic oils, ester oils, ether oils, etc., and natural oil base oils include beef tallow, lard, soybean oil, rapeseed oil, rice bran Oils and oils such as coconut oil, palm oil, and palm kernel oil, or hydrides thereof can be used.

  In order to further improve the various performances of the grease composition, various additives may be mixed as desired. 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. 1 or 2 types of additives used in lubrication, such as agents, phosphorus-based, extreme pressure agents such as zinc dithiophosphate, 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. 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.

  There is no limitation on the method for producing the grease composition. For example, when lithium soap is used as a thickener, the gelling agent and lithium soap are added to the base oil so as to have the above mixing ratio, and the gelling agent and After stirring and completely dissolving while heating to a temperature at which lithium soap dissolves, it is poured into a pre-cooled aluminum vat, cooled with running water and cured into a gel, and the cured product is kneaded with three rolls. . When a urea compound is used as a thickener, a urea compound is synthesized by reacting an amine with an isocyanate in a base oil, and a gelling agent is added thereto so as to have the above mixing ratio. The mixture is stirred while being heated to the dissolution temperature, cooled and kneaded. Further, a grease containing only a gelling agent and a grease containing only a thickening agent may be mixed so that the gelling agent and the thickening agent have the above mixing ratio.

[Rolling bearings]
In the present invention, the type and structure of the bearing are not limited as long as the above-described grease composition is enclosed, but a bearing provided with a non-contact type seal is preferable in order to promote torque reduction by the grease composition. FIG. 1 is a cross-sectional view showing an example thereof. The illustrated ball bearing includes an inner ring 1 having an inner ring raceway surface 1a on an outer peripheral surface and an outer ring 2 having an outer ring raceway surface 2a on an inner peripheral surface. The balls 3 are arranged as rolling elements and are held by the cage 4. The bearing space formed by the inner ring 1, the outer ring 2 and the balls 3 is filled with the above grease composition (not shown) and sealed with a non-contact type seal 5.

  In order to prevent leakage of the grease composition, it is preferable to apply an oil repellent treatment to the seal surface of the non-contact type seal 5 and the seal facing surface of the inner ring 1. The oil-repellent treatment may be performed by a known method. For example, the oil-repellent treatment may be obtained by applying a coating solution obtained by adding a coupling agent to a water / alcohol mixed solution and drying it.

  Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited thereto.

(Examples 1-4, Comparative Examples 1-4)
(1) Preparation of Test Grease As shown in Table 1, a test grease was prepared by blending a gelling agent and / or a thickener with a base oil.

(2) Flow-recovery reversibility test The test grease is placed in a rotation-revolution stirrer (shear conditions: rotation: 1370 r / min, revolution: 1370 r / min, 3 min) and stirred to impart shear to mix consistency. After measuring, the mixture was allowed to stand at 40 ° C. for 3 hours, and the immiscible consistency was measured again. This was defined as 1 cycle and repeated 3 cycles. The results are also shown in Table 1. When the immiscibility penetration after shearing is 350 or more (the penetration consistency having no yield stress), the initial immiscibility penetration and the immiscibility penetration after 3 cycles are determined. A difference of +15 or less was accepted.

(3) Bearing torque test After starting rotation under the following conditions, the average value of the torque for 295 seconds to 305 seconds was used as the torque value. And the relative torque value which made the torque value of the comparative example 1 1 was calculated | required. The results are shown in Table 1, and a relative torque value of 0.9 or less was accepted.
Test conditions Test bearing: NSK Ltd. rolling bearing “6305 (inner diameter φ25 mm, outer diameter φ62 mm, width 17 mm, with non-contact type rubber seal)”
Rotational speed: 5000min ^-1
Axial load: 294N
Radial load: 29.4N
Test temperature: Room temperature Measurement time: 295 to 305 seconds after starting rotation

(4) Bearing leakage test The grease leakage rate was calculated from the weight difference before and after the rotation for 20 hours under the following conditions. And the relative leak rate which made the leak rate of the comparative example 1 1 was calculated | required. The results are shown in Table 1, and a relative leakage rate of 1.2 or less was accepted.
Test conditions Test bearing: NSK Ltd. rolling bearing “6305 (inner diameter φ25 mm, outer diameter φ62 mm, width 17 mm, with non-contact type rubber seal)”
Rotational speed: 5000min ^-1
Axial load: 98N
Radial load: 98N
Test temperature: 80 ° C

(5) Bearing acoustic durability test)
The evaluation was carried out under the following conditions, and the evaluation was performed by measuring the rotating Anderon value (H.B.) with an NSK grease noise tester, and obtaining the time (acoustic life) until it rose 3 from the Anderon value before the test. And the relative acoustic lifetime which made the acoustic lifetime of the comparative example 1 1 was calculated | required. The results are shown in Table 1, and a relative acoustic life of 1.3 or more was considered acceptable.
Test conditions: Test bearing: NSK Ltd. rolling bearing “608 (inner diameter φ8 mm, outer diameter φ22 mm, width 7 mm, with non-contact type rubber seal)”
Rotation speed: 1800min ^-1
Axial load: 29.4N
Test temperature: 80 ° C

  As shown in Table 1, in Examples 1 to 4, the viscosity is greatly reduced by shearing, and the restorability after repeated shearing is excellent. Thereby, torque is low, grease leakage is reduced, and sound durability is also good.

  On the other hand, Comparative Example 2 uses only a urea compound as the thickener, so that the change in viscosity due to shearing is small, and the amount of thickener is large, so the torque is quite high and the acoustic durability is poor. Further, Comparative Example 3 uses only a gelling agent as a thickening agent, so that the viscosity change due to shearing is good, but the flow-restoration reversibility is poor and grease leakage is very large. Since it becomes difficult to form an oil film with progress, acoustic durability is also deteriorated. In Comparative Example 4, although a gelling agent and a thickening agent are used in combination as a thickener, the viscosity change due to shearing is small because the mixing ratio of the thickening agent exceeds 50% by mass, and the torque is reduced. In addition, the effect of improving sound durability is small.

(6) Verification of mixing ratio of gelling agent 12-hydroxylithium stearate is used as a thickener, N-2-ethylhexanoyl-L-glutamic acid dibutylamide is used as a gelling agent, and the total content of both is A test grease was prepared by adding to the polyol ester (33 mm ² / s @ 40 ° C.) at a constant 6 mass% of the total amount and changing the mixing ratio. Then, the above (2) bearing torque test and (3) bearing leakage test were performed, and the relative leakage rate and relative torque for the test grease of gelling agent: thickening agent = 50: 50 were determined.

  The results are shown in FIG. 2, and grease leakage and torque increase are reduced when the gelling agent is in the range of 50 to 95 mass%.

1 Inner ring 2 Outer ring 3 Ball 4 Cage 5 Seal

Claims (2)

A lubricant composition comprising a base oil and a mixture of a gelling agent and a thickener as a thickener,
The gelling agent is an amino acid-based gelling agent or a benzylidene sorbitol derivative, and is mixed at a ratio of (gelling agent: thickener) of 50 to 95: 5, and the gelling agent and the thickener are A lubricant composition comprising 1 to 10% by mass of the total amount in total.   A rolling bearing comprising: an inner ring; an outer ring; and a plurality of rolling elements disposed between the inner ring and the outer ring so as to be freely rollable, wherein the lubricant composition according to claim 1 is enclosed. .

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