JP2008280476A - Lubricant composition and rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricant composition capable of more improving abrasion resistance, durability and reduced torque and to provide a long life rolling bearing having the reduced torque and excellent abrasion resistance and durability. <P>SOLUTION: The lubricant composition is obtained by compounding a base oil with a specific urea compound and a benzylidenesorbitol derivative in the total amount of 10-30 mass%. The rolling bearing comprises the lubricant composition sealed therein. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rolling bearing incorporated in various industrial machines, various motors, automobile parts and the like, and a lubricant composition suitable for the rolling bearing.

  For example, grease and lubricating oil are used for rolling bearings incorporated in various industrial machines, various motors, and automobile parts in order to impart lubricity. Of these, grease has the advantage that it can be sealed in the bearing, and is widely used in rolling bearings. On the other hand, since grease has poor fluidity compared to an oil lubrication system that supplies lubricating oil, supply to the transfer surface is poor, and various problems may occur due to insufficient lubrication.

  From such a background, by using a thickener and a small amount of gelling agent in combination, a grease composition that exhibits fluidity when shearing / heat is applied and re-cures when shearing / heat is removed is obtained. It has been proposed (see Patent Document 1).

JP 58-219297 A

  In the grease composition described in Patent Document 1, when the rolling bearing rotates, the amount of the thickener is reduced on the bearing transfer surface and heat generation is suppressed, and the grease composition discharged from the bearing transfer surface is not subjected to shearing. Therefore, it can be hardened to prevent leakage and contamination. However, if the grease composition discharged from the bearing transfer surface does not flow into the bearing transfer surface again, even if heat generation is suppressed, wear resistance and durability are not improved due to insufficient lubrication.

  In recent years, rolling bearings incorporated in various industrial machines, various motors, and automobile parts have been further increased in speed, and in addition to further improving wear resistance and durability, lowering of torque is desired. Accordingly, an object of the present invention is to provide a lubricant composition capable of further improving these characteristics at an application site, and a rolling bearing having a low torque, excellent wear resistance and durability, and a long life.

In order to solve the above problems, the present invention provides the following lubricant composition and rolling bearing.
(1) Lubricant composition characterized in that a urea compound represented by the following general formula (1) or (2) and a benzylidene sorbitol derivative are blended in a base oil in a proportion of 10 to 30% by mass. object.

[(1) _where, C _{m H 2m + 1} and _C n _{H 2n + 1} is a straight-chain alkyl group, m + n is 16-36. Further, in _(2), C _{x H 2x + 1} and _C y _{H 2y + 1} is a linear alkyl group, x + y is 20 to 36. ]
(2) The lubricant composition as described in (1) above, wherein the base oil is an ester oil.
(3) The lubricant composition as described in (1) or (2) above, wherein the weight ratio (urea compound / benzylidene sorbitol derivative) is 0.1 to 1.0.
(4) The lubricant composition as described in any one of (1) to (3) above, wherein a grease noise count of 120 seconds by an NSK grease noise tester is 50 counts or less.
(5) A plurality of rolling elements are rotatably held between an inner ring and an outer ring, and the lubricant composition according to any one of (1) to (4) is enclosed. Rolling bearing.

  The lubricant composition of the present invention becomes oily (having no yield value) in a state where shearing force is applied, and is solidified and gelled (state where the yield value is large) when no shearing force is applied. Therefore, when encapsulated in a rolling bearing, even if it is discharged from the transfer surface, it becomes oily due to the extremely weak shear force generated by contact with the gap between the cage and the seal and the lubricant composition existing near the transfer surface, Re-supplied to the transfer surface, wear due to insufficient lubrication is suppressed, the service life is extended, and the torque is reduced.

  Hereinafter, the present invention will be described in detail.

[Lubricant composition]
The lubricant composition of the present invention is a mixture of a urea compound represented by the following general formula (1) or (2) and a benzylidene sorbitol derivative in a base oil.

In _(1), C _{m H 2m + 1} and _C n _{H 2n + 1} is a straight-chain alkyl group, m + n is 16-36. Further, in _(2), C _{x H 2x + 1} and _C y _{H 2y + 1} is a linear alkyl group, x + y is 20 to 36.

  As the base oil, ester oil is preferable because it has high affinity with urea compounds and benzylidene sorbitol derivatives and can completely dissolve them. The ester oil is not limited, but is obtained from the reaction of an aromatic tribasic acid or aromatic tetrabasic acid with a branched alcohol and a reaction of a monobasic acid with a polyhydric alcohol. Preferred examples include polyol ester oils.

  Specifically, as the aromatic ester oil, pyromellitic acid ester oil, trimesic acid ester oil, specifically trioctyl trimellitate as ester oil obtained from the reaction of aromatic tribasic acid and branched alcohol. And tridecyl trimellitate, pyromellitic ester oil obtained from a reaction of an aromatic tetrabasic acid and a branched alcohol, specifically tetraoctyl pyromellitate, and the like.

  Moreover, as a polyol ester oil, what is obtained by making the polyhydric alcohol and monobasic acid shown below react suitably is mentioned. In addition, a monobasic acid may be individual and multiple may be used. Furthermore, you may use as complex ester which is an oligoester of a polyhydric alcohol and the mixed fatty acid of a dibasic acid and a monobasic acid. Examples of the polyhydric alcohol include trimethylolpropane, pentaerythritol, dipentaerythritol, neopentyl glycol, 2-methyl-2-propyl-1,3-propanediol and the like. On the other hand, monobasic acids are mainly monohydric fatty acids having 4 to 16 carbon atoms, specifically, butyric acid, valeric acid, caproic acid, caprylic acid, enanthic acid, pelargonic acid, capric acid, undecanoic acid. , Lauric acid, mysteric acid, palmitic acid, beef tallow fatty acid, stearic acid, caproleic acid, palmitoleic acid, petrothelic acid, oleic acid, elaidic acid, asclepic acid, vaccenic acid, sorbic acid, linoleic acid, linoic acid, abinic acid, ricinol An acid etc. are mentioned.

The urea compound is obtained by reacting diisocyanate with a monoamine. As the diisocyanate, hexamethylene diisocyanate is used in the urea compound represented by the general formula (1), and 4,4′-diphenylmethane diisocyanate is used in the urea compound represented by the general formula (2). On the other hand, as the monoamine, the urea compound represented by the general formula (1) uses an aliphatic amine having linear C _m H _{2m + 1} and an aliphatic amine having linear C _n H _{2n + 1.} In the urea compound represented by), an aliphatic amine having linear C _x H _{2x + 1} and an aliphatic amine having linear C _y H _{2y + 1} are used. In addition, although m + n is 16-36 and x + y is 20-36, the higher the carbon number, the higher the affinity with a base oil, particularly ester oil, which is preferable.

  Preferred examples of the benzylidene sorbitol derivative include dibenzylidene sorbitol, ditrilidene sorbitol, asymmetric dialkyl benzylidene sorbitol, and the like.

  The benzylidene sorbitol derivative is obtained by adding NLGI No. 2-No. It has the ability to increase to about 3 hardness. Further, it has fluidity-reversibility reversibility, in which crystal particles are dispersed to exhibit fluidity when subjected to shearing, and crystal particles aggregate and no longer exhibit fluidity when not subjected to shearing. However, as the presence or absence of shearing is repeated, the structural restoration in a short time becomes difficult and softens. Therefore, by using a urea compound that has a moderate flow-reversibility reversibility, the benzylidene sorbitol fluid crystal particles crosslink the urea compound crystal particles and easily re-aggregate, so that stable fluid-restoration reversibility is achieved. Can be obtained.

  In order to effectively obtain such an action, the urea compound and the benzylidene sorbitol derivative are mixed so that the weight ratio of (benzylidene sorbitol derivative / urea compound) is 0.1 to 1.0. When the mixing ratio is less than 0.1, the benzylidene sorbitol derivative crystal particles are less likely to agglomerate, and the restoration of the thickener network structure is delayed when not subjected to shearing, and leakage from the application site is likely. On the other hand, when the mixing ratio exceeds 1, the reversibility of dispersion / aggregation is impaired and leakage tends to occur.

  Both urea compounds and benzylidene sorbitol derivatives function as thickeners. Therefore, it mix | blends so that 10-30 mass% of the lubricant composition whole quantity may occupy in total of both. When the total blending amount is less than 10% by mass, the lubricant composition is too soft from the beginning and easily leaks from the application site, the fluidity exceeding 30% by mass is low, and sufficient lubricity cannot be imparted to the application site.

  In the lubricant composition of the present invention, in a state where shearing force is applied, the network structure composed of the urea compound and the benzylidene sorbitol derivative is cut, and the crystal particles of the urea compound and the crystal particles of the benzylidene sorbitol derivative are oriented to cause a significant change in hardness. Occurs and becomes oily. On the other hand, in a state where no shear is applied, the network structure is restored to become a gel. Therefore, when encapsulated in a rolling bearing, even if a part of the lubricant composition is discharged from the transfer surface during operation, if it comes into contact with the lubricant composition existing in the gap between the cage and the seal or in the vicinity of the transfer surface, A weak shear force is applied to impart fluidity, and it is supplied again to the transfer surface. Thus, the lubricant composition has good fluidity close to that of lubricating oil, has low torque, and has good durability performance. Further, since the lubricant composition attached to the seal is in a state where no shearing force is applied, it can be gelled to prevent leakage.

  Various performances can be improved by adding an additive to the lubricant composition depending on the application. For example, when used to lubricate rolling bearings for rocking motion, antioxidants such as amines, phenols, sulfurs, zinc dithiophosphates and zinc dithiocarbamates; metal sulfonates, esters, amines, naphthenic acids Rust preventives such as metal salts and succinic acid derivatives; extreme pressure agents such as phosphorus, zinc dithiophosphate and organic molybdenum; oiliness improvers such as fatty acids and animal and vegetable oils; metal deactivators such as benzotriazole Or can be added in appropriate combination. In addition, the addition amount of these additives will not be restrict | limited especially if it is a range which does not impair the objective of this invention.

[Rolling bearings]
The present invention also provides a rolling bearing encapsulating the above-described lubricant composition. There is no limitation on the type and structure of the rolling bearing. For example, the ball bearing 1 shown in a cross-sectional view in FIG. 1 is illustrated, but a plurality of rolling elements are provided between the inner ring 10 and the outer ring 11 via a cage 12. The ball 13 is rotatably held, filled with the lubricant composition G between the inner ring 10 and the outer ring 11, and sealed with a seal member 14.

  As described above, the rolling bearing of the present invention is re-supplied to the feeding surface by the action of the lubricant composition, wear due to insufficient lubrication is suppressed, the life is extended, and the torque is reduced.

  Examples The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited thereby.

Example 1
In a first container, 4 parts of hexamethylene diisocyanate (HDI) was added and dissolved in 42 parts of pentaerythritol ester (PET) and heated to 70 ° C. In a second container, 6 parts of octylamine (C ₈ NH ₂ ) was dissolved in 45 parts of PET. And the content of the 2nd container was put into the 1st container, and it heated up gradually, stirring, and hold | maintained at 140 degreeC for 30 minutes, and synthesize | combined the urea compound. Next, 3 parts of dibenzylidene sorbitol (DBS) was added to the first container, and after sufficiently stirring and mixing, the temperature was raised to 195 ° C. to completely dissolve the urea compound and DBS. Next, the contents of the first container were poured into an aluminum bat that had been previously water-cooled, and the bat was cooled with running water to obtain a gel-like material. Then, a gel lubricant was put on a three-roll mill to obtain a test lubricant composition.

(Examples 2 to 6)
A test lubricant composition was obtained according to Example 1 using the base oil, diisocyanate, monoamine and benzylidene sorbitol derivative shown in Table 1.

(Comparative Example 1)
In PET, 4,4′-diphenylmethane diisocyanate (MDI) and cyclohexylamine (CHA) were reacted to synthesize a urea compound to obtain a test lubricant composition.

(Comparative Example 2)
DBS was added to PET to obtain a test lubricant composition.

(Comparative Example 3)
A test lubricant composition was obtained by blending 12 hydroxylithium stearate and DBS with mineral oil (MO).

(Comparative Example 4)
In MO, MDI and p-toluidine were reacted to synthesize a urea compound, and N-acylamino acid diamide was added to obtain a test lubricant composition.

(Comparative Example 5)
In PET, HDI and C ₈ NH ₂ were reacted to synthesize a urea compound to obtain a test lubricant composition.

(Comparative Example 6)
Toluene diisocyanate (TDI) and C ₈ NH ₂ were reacted in PET to synthesize a urea compound, and DBS was added to obtain a test lubricant composition.

  The following evaluation was performed for each of the above-described lubricant compositions.

(1) Relationship between presence / absence of shear and apparent viscosity Using the test lubricant composition of Example 1 and the test lubricant composition of Comparative Example 1, the initial apparent viscosity (● in the figure) and shear were 1 Apparent viscosity after receiving (▲ in the figure), apparent viscosity after receiving a shear for a specified time (■ in the figure), and apparent viscosity after further shearing (second shear) (Figure) Medium ◆) was measured. FIG. 2 shows the measurement results of the test lubricant composition of Example 1, which is oily and fluid when subjected to shearing, and has the property of returning to a gel with the original hardness when left untreated. I understand. On the other hand, FIG. 3 shows the measurement result of the test lubricant composition of Comparative Example 1. Since only the urea compound is contained, the change in the apparent viscosity is small when subjected to shearing and when left standing.

(2) Evaluation of blending penetration and immiscibility penetration For each sample lubricant composition, the difference between the blending penetration (60 W) and the immiscibility penetration (0 W) was determined. Although a result is shown in Table 1 and Table 2, 50 or more was set as the pass.

(3) Flow-recovery reversibility test Each lubricant composition was stirred with a rotation-revolution stirrer (shear conditions: rotation 1370 r / min, revolution 1370 r / min, 3 min), and the immiscible consistency was measured. Thereafter, the cycle of leaving the mixture at 40 ° C. for 3 hours and measuring the immiscible penetration was repeated 4 times. The results are shown in Tables 1 and 2, and the difference between the immiscible penetration after the first shearing and the respective immiscibility penetrations after the 2nd to 4th shearing, and the immiscibility after the first standing. And the immiscible penetration after 2nd to 4th exposure are all within ± 15, it can be regarded as having good flow-restoration reversibility. The test lubricant composition satisfies this criterion.

  FIG. 4 is a graph showing the measurement results of the test lubricant compositions of Example 1, Comparative Example 1 and Comparative Example 2. The test lubricant compositions of Comparative Example 1 and Comparative Example 2 are shown in FIG. As the stirring and leaving are repeated, the increase in the immiscibility after standing is large and the flow-restoration reversibility is lowered.

(4) Bearing torque test Single-row deep groove ball bearings with a non-contact seal (inner diameter 25 mm, outer diameter 62 mm, width 17 mm) were filled with each test lubricant composition to prepare test bearings. The test bearing was rotated for 180 seconds at a rotational speed of 3000 r / min, an axial load of 98 N, and a radial load of 98 N, and then the rotational torque was measured. The results are shown in Tables 1 and 2, but are shown as relative values with respect to Comparative Example 1. Although this torque relative value of less than 1.0 was determined to be acceptable, all of the test bearings of the examples satisfied the above criteria.

(5) Bearing leakage test Single-row deep groove ball bearings with a non-contact seal (inner diameter 25 mm, outer diameter 62 mm, width 17 mm) were filled with each test lubricant composition to prepare test bearings. The test bearing was continuously rotated for 20 hours at a rotational speed of 10000 r / min, an axial load of 98 N, and a radial load of 98 N, and the grease leakage rate was determined from the difference from the initial weight. The results are shown in Table 1. A grease leakage rate of 6% by mass or less was accepted. The test bearings of the examples all satisfy the above criteria.

  In addition, according to Example 1, test lubricant compositions were prepared by changing the weight ratio of (benzylidene sorbitol derivative / urea compound), and the grease leakage rate was determined in the same manner. The results are shown in FIG. 5 and are shown as relative values with respect to the test bearing having a (benzylidene sorbitol derivative / urea compound) weight ratio of 1. From the figure, it can be seen that when the weight ratio of (benzylidene sorbitol derivative / urea compound) is in the range of 0.1 to 1.0, grease leakage can be suppressed as much as possible.

(6) Grease noise test A single-row deep groove ball bearing with a non-contact seal (inner diameter 15 mm, outer diameter 35 mm, width 11 mm) was filled with each test lubricant composition to prepare a test bearing. Then, after rotating the test bearing for 120 seconds at a rotational speed of 1800 r / min and an axial load of 29.4 N, a pulse value greater than a prescribed value due to vibration in the bearing radial direction was measured using an NSK grease noise tester. The results are shown in Table 1 and Table 2, and the grease noise count of 120 seconds was determined to be 50 counts or less. The test bearings of the examples all satisfy the above criteria.

It is sectional drawing which shows the ball bearing which is an example of the rolling bearing of this invention. 2 is a graph showing the relationship between shear stress and apparent viscosity in the test lubricant composition of Example 1. FIG. 6 is a graph showing the relationship between shear stress and apparent viscosity in the test lubricant composition of Comparative Example 1. It is a graph which shows the result of the (3) flow-restoration reversibility test in an Example. It is a graph which shows the relationship between the weight ratio obtained in the Example (benzylidene sorbitol derivative / urea compound) and the grease leakage rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ball bearing 10 Inner ring 11 Outer ring 12 Cage 13 Ball 14 Seal member
G Lubricant composition

Claims (5)

A lubricant composition comprising a base oil and a urea compound represented by the following general formula (1) or (2) and a benzylidene sorbitol derivative in a proportion of 10 to 30% by mass in total.

[(1) _where, C _{m H 2m + 1} and _C n _{H 2n + 1} is a straight-chain alkyl group, m + n is 16-36. Further, in _(2), C _{x H 2x + 1} and _C y _{H 2y + 1} is a linear alkyl group, x + y is 20 to 36. ]   The lubricant composition according to claim 1, wherein the base oil is an ester oil.   The lubricant composition according to claim 1 or 2, wherein a weight ratio of (urea compound / benzylidene sorbitol derivative) is 0.1 to 1,0.   The lubricant composition according to any one of claims 1 to 3, wherein a grease noise count of 120 seconds by an NSK grease noise tester is 50 counts or less.   A rolling bearing characterized in that a plurality of rolling elements are rotatably held between an inner ring and an outer ring, and the lubricant composition according to any one of claims 1 to 4 is enclosed.

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