JP2016138241A - Grease for rolling bearing, rolling bearing, rolling bearing device and information recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide grease for rolling bearing for HDD which reduces out gas amount.SOLUTION: There is provided grease for rolling bearing of an information recording and reproducing device 1 containing a base oil, a thickener and at least one antioxidant selected from an amine-based antioxidant (A) represented by the formula (1) and a phenolic antioxidant (B) represented by the formula (2). (1), (2), where Rand Rare a C1 to 12 alkyl group or a H atom, at least one of Rand Ris a C1 to C12 alkyl group, Rand Rare a C1 to 8 alkyl group, Ris a C1 to 8 alkylene group, n is an integer of 1 to 6, Xis a residue in which n hydroxyl groups are removed from C1-24 aliphatic m valent alcohol, m is an integer of 1 to 6 and n or more, but the C number of the aliphatic m valent alcohol of Xis 2 to 24 when n is 5 or 6.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a grease for a rolling bearing, a rolling bearing, a rolling bearing device, and an information recording / reproducing device.

  2. Description of the Related Art An information recording / reproducing apparatus such as a hard disk drive (HDD) is known as a device for recording and reproducing various types of information magnetically or optically on a disk. The information recording / reproducing apparatus generally includes a swing arm provided with a head gimbal assembly (magnetic head) for recording / reproducing a signal on a disk at a tip, a rolling bearing device serving as a fulcrum of rotation of the swing arm, and a swing arm. And an actuator to be rotated. Signals can be recorded and reproduced by rotating the swing arm and moving the magnetic head to a predetermined position on the disk.

  A rolling bearing device generally includes two rolling bearings in which a plurality of spherical rolling elements are provided between an inner ring and an outer ring, and a shaft inserted inside the rolling bearing. The outer ring rotates around the shaft axis by the rolling of the plurality of rolling elements, and accordingly, the swing arm connected to the outer ring rotates. Since the rolling bearing is required to operate stably for a long period of time, grease is used for the purpose of smoothing the movement of the rolling conductor between the inner ring and the outer ring.

  The rolling bearing grease of the information recording / reproducing apparatus can reduce the torque of the rolling bearing and can provide excellent torque smoothness (property that the torque is uniform in the rotation direction of the rolling bearing). It is required to increase the durability of the bearing. In addition, if outgas from the grease accumulates in the gap between the magnetic head and the disk, a problem occurs in reading and writing of the information recording / reproducing apparatus. Therefore, it is also important that the rolling bearing grease has a small outgas amount.

  With the recent increase in the density of HDDs and the increasing demand for server applications, the operating range and operating speed of HDD swing arms and the ambient temperature in which HDDs are used have become widespread. Along with this, the grease provided in the rolling bearing device, which is a pivot point of the swing arm, is also exposed to various changing temperatures and lubrication conditions while using the HDD.

  As a rolling bearing grease for an information recording / reproducing apparatus used in such an environment, for example, Patent Document 1 discloses a base oil containing mineral oil and poly-α-olefin (hereinafter referred to as “PAO”), and a thickener. A grease that includes (a urea compound or the like) and an extreme pressure agent (such as an organic phosphorus compound) and has excellent torque stability and durability is disclosed. Patent Document 2 discloses a grease that contains a base oil composed of PAO, a thickener composed of a diurea compound, and a metal carbamate, and can reduce outgas.

Japanese Patent Application Laid-Open No. 2003-239954 JP 2013-174334 A

The outgas generated from the grease is considered to be a major cause of operation failure by attaching the magnetic head and the disk. Therefore, before the shipment, it is confirmed that the outgas amount of the rolling bearing device is within a predetermined range.
In addition to the outgas at the initial stage before the use of such an HDD, the present inventors have caused the grease to be oxidized and deteriorated due to various changes in temperature during use of the HDD, thereby generating outgas. It has come to a conclusion that the reliability has been greatly affected, and a highly reliable HDD can be obtained by suppressing this oxidative degradation. Moreover, since the lubrication failure occurs when the grease is deteriorated by oxidation, the durability of the rolling bearing including the grease is also affected. Therefore, it is desired to suppress the oxidative deterioration of grease from the viewpoint of obtaining an HDD having excellent durability.
However, the techniques of Patent Document 1 and Patent Document 2 have not been fully satisfactory in the effect of reducing outgas. Further, Patent Documents 1 and 2 do not consider the oxidative deterioration of grease during use of the HDD.

An object of this invention is to provide the grease for rolling bearings which is excellent in the reduction effect of an outgas amount. It is another object of the present invention to provide a rolling bearing grease that can satisfactorily suppress oxidative deterioration during use of an information recording / reproducing apparatus and has excellent durability.
It is another object of the present invention to provide a rolling bearing, a rolling bearing device, and an information recording / reproducing device using the rolling bearing grease.

（（１）式中、Ｒ^１及びＲ^２は、それぞれ独立して、炭素数１〜１２のアルキル基又は水素原子である。ただし、Ｒ^１及びＲ^２の少なくとも一方は、炭素数１〜１２のアルキル基である。）

（（２）式中、Ｒ^１１及びＲ^１２は、それぞれ独立して炭素数１〜８のアルキル基であり、Ｒ^１３は、炭素数１〜８のアルキレン基であり、ｎは、１〜６の数である。Ｘ^１は、炭素数１〜２４の脂肪族ｍ価アルコールからｎ個の水酸基が除かれた残基であり、前記ｍは、１〜６であり、かつｎ以上の数である。ただし、ｎが５又は６のとき、前記Ｘ^１の脂肪族ｍ価アルコールの炭素数は２〜２４である。） The rolling bearing grease of the present invention comprises a base oil, a thickener, an amine-based antioxidant (A) represented by the following general formula (1), and a phenol-based oxidation represented by the following general formula (2). And at least one antioxidant selected from the inhibitor (B).

(In formula (1), R ¹ and R ² are each independently an alkyl group having 1 to 12 carbon atoms or a hydrogen atom, provided that at least one of R ¹ and R ² has 1 to 12 carbon atoms. The alkyl group of

(In formula (2), R ¹¹ and R ¹² are each independently an alkyl group having 1 to 8 carbon atoms, R ¹³ is an alkylene group having 1 to 8 carbon atoms, and n is 1 to 6). X ¹ is a residue obtained by removing n hydroxyl groups from an aliphatic m-valent alcohol having 1 to 24 carbon atoms, and m is 1 to 6 and is a number of n or more. (However, when n is 5 or 6, the number of carbon atoms of the aliphatic m-valent alcohol represented by X ¹ is 2 to 24.)

The rolling bearing grease of the present invention preferably contains the amine-based antioxidant (A) and the phenol-based antioxidant (B).
The rolling bearing grease of the present invention preferably contains more amine-based antioxidant (A) on a mass basis than the phenol-based antioxidant (B).
In the rolling bearing grease of the present invention, the base oil includes refined mineral oil classified as Group III in the base oil category defined by the American Petroleum Institute, and the flash point of the refined mineral oil is 240 ° C. or higher. Preferably, it is 250 degreeC or more.
In the rolling bearing grease of the present invention, it is preferable that the base oil contains a mixture of 3 to 5 monomers of an α-olefin having 8 to 12 carbon atoms.
The rolling bearing grease of the present invention is preferably used for a rolling bearing of an information recording / reproducing apparatus.
The rolling bearing grease of the present invention is preferably used for a rolling bearing of an electronic device manufacturing apparatus.

The rolling bearing of the present invention includes the rolling bearing grease of the present invention.
The rolling bearing device of the present invention includes a shaft and the rolling bearing of the present invention.
The information recording / reproducing apparatus of the present invention includes the rolling bearing device of the present invention.

The rolling bearing grease of the present invention is excellent in reducing the outgas amount. Furthermore, the grease can satisfactorily suppress oxidative deterioration during use of the information recording apparatus. Furthermore, the grease has excellent durability in rolling bearings.
In the rolling bearing, the rolling bearing device, and the information recording / reproducing device of the present invention, the amount of outgas from the rolling bearing grease is reduced. Furthermore, the oxidation deterioration of the grease during use of the information recording / reproducing apparatus is suppressed, and the durability is excellent.

It is the perspective view which showed an example of the information recording / reproducing apparatus of this invention. It is the longitudinal cross-sectional view which showed the rolling bearing apparatus periphery in the information recording / reproducing apparatus of FIG. It is sectional drawing which showed the rolling bearing apparatus of FIG. It is the top view which showed the rolling bearing in the rolling bearing apparatus of FIG. It is AA sectional drawing of the rolling bearing of FIG. It is the perspective view which showed the retainer of the rolling bearing of FIG. It is a graph which shows the result of having measured the time-dependent change of the evaporation loss in 85 degreeC. It is a graph which shows the result of having measured the time-dependent change of the evaporation loss in 100 degreeC. It is a graph which shows the result of having measured the time-dependent change of the evaporation loss in 130 degreeC.

[Grease for rolling bearings]
The rolling bearing grease of the present invention (hereinafter also simply referred to as “grease”) includes a base oil, a thickener, a specific amine-based antioxidant (A), and a specific phenol-based antioxidant (B). And at least one antioxidant selected from the group consisting of

<Antioxidant>
The antioxidants included in the present invention include a specific amine-based antioxidant (A) (hereinafter also simply referred to as “component (A)”) and a specific phenol-based antioxidant (B) (hereinafter simply referred to as “ (It is also referred to as “component (B).”).
The grease of the present invention contains at least one antioxidant selected from the component (A) and the component (B), so that the outgas amount is reduced. Furthermore, it is possible to satisfactorily suppress oxidative deterioration caused by various temperature changes during use of the information recording / reproducing apparatus using the grease of the present invention. Accordingly, not only the initial stage immediately after the start of use of the information recording / reproducing apparatus and the state where the use (drive) of the information recording / reproducing apparatus is interrupted (that is, the stage where the temperature is low) but also the state where the information recording / reproducing apparatus is being used (that is, the stage where the temperature is high). ), The outgas amount can be reduced. Furthermore, lubrication failure due to oxidative degradation of grease can be suppressed, and durability can be enhanced.

（（１）式中、Ｒ^１及びＲ^２は、それぞれ独立して、炭素数１〜１２のアルキル基又は水素原子である。ただし、Ｒ^１及びＲ^２の少なくとも一方は、炭素数１〜１２のアルキル基である。） ≪ (A) component≫
The component (A) is an amine antioxidant represented by the following general formula (1).

(In formula (1), R ¹ and R ² are each independently an alkyl group having 1 to 12 carbon atoms or a hydrogen atom, provided that at least one of R ¹ and R ² has 1 to 12 carbon atoms. The alkyl group of

R ¹ and R ² in the general formula (1) are each independently an alkyl group having 1 to 12 carbon atoms, and an alkyl group having 4 to 12 carbon atoms is more preferable. The alkyl group may be linear or branched. Examples of the alkyl group include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, n-pentyl group, i-pentyl group, neopentyl group, t-pentyl group, 2-methylbutyl group, n-hexyl group, i-hexyl group, 3-methylpentyl group, ethylbutyl group, n-heptyl group, 2-methylhexyl group, n-octyl group, i-octyl group, 2-ethylhexyl group, 3-methylheptyl group, 1,1,3,3-tetramethylbutyl group, n-nonyl group, i-nonyl group, 1-methyloctyl group, ethylheptyl group, n-decyl group, 1 -Methylnonyl group, n-undecyl group, 1,1-dimethylnonyl group, n-dodecyl group and the like can be mentioned.
The alkyl group represented by R ¹ and R ² can be bonded to any position of the phenyl group, but is preferably p-position with respect to the amino group.

  Examples of the component (A) include monooctyldiphenylamine, monononyldiphenylamine, di (4-butylphenyl) amine, di (4-hexylphenyl) amine, di (4-octylphenyl) amine, and di (4-nonylphenyl). ) Amines and the like. Among these, di (4-octylphenyl) amine is preferable. As the component (A), a reaction product of N-phenylbenzeneamine and 2,4,4-trimethylpentene may be used.

As the component (A), one type may be used alone, or two or more types may be used in combination.
Although content of (A) component is not specifically limited, 0.05-2 mass% is preferable with respect to the gross mass of grease, and 0.1-1 mass% is more preferable. When the content of the component (A) is in the above preferred range, the outgas amount can be easily reduced. Furthermore, it becomes easy to suppress the oxidative deterioration of grease. This makes it easier to suppress outgassing even during use of the information recording / reproducing apparatus. Therefore, it becomes easy to reduce the total amount of outgas from the production of the rolling bearing to its use. Furthermore, it becomes easy to suppress poor lubrication due to oxidative degradation of grease, and it becomes easy to improve durability.

（（２）式中、Ｒ^１１及びＲ^１２は、それぞれ独立して炭素数１〜８のアルキル基であり、Ｒ^１３は、炭素数１〜８のアルキレン基であり、ｎは、１〜６の数である。Ｘ^１は、炭素数１〜２４の脂肪族ｍ価アルコールからｎ個の水酸基が除かれた残基であり、前記ｍは、１〜６であり、かつｎ以上の数である。ただし、ｎが５又は６のとき、前記Ｘ^１の脂肪族ｍ価アルコールの炭素数は２〜２４である。） ≪ (B) component≫
The component (B) is a phenolic antioxidant represented by the following general formula (2).

(In formula (2), R ¹¹ and R ¹² are each independently an alkyl group having 1 to 8 carbon atoms, R ¹³ is an alkylene group having 1 to 8 carbon atoms, and n is 1 to 6). X ¹ is a residue obtained by removing n hydroxyl groups from an aliphatic m-valent alcohol having 1 to 24 carbon atoms, and m is 1 to 6 and is a number of n or more. (However, when n is 5 or 6, the number of carbon atoms of the aliphatic m-valent alcohol represented by X ¹ is 2 to 24.)

In General Formula (2), R ¹¹ and R ¹² are each independently an alkyl group having 1 to 8 carbon atoms, preferably an alkyl group having 2 to 6 carbon atoms, and more preferably an alkyl group having 3 to 5 carbon atoms. . The alkyl group may be linear or branched. Examples of the alkyl group include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, n-pentyl group, i-pentyl group, neopentyl group, t-pentyl group, 2-methylbutyl group, n-hexyl group, i-hexyl group, 3-methylpentyl group, ethylbutyl group, n-heptyl group, 2-methylhexyl group, n-octyl group, i-octyl group, Examples include 2-ethylhexyl group, 3-methylheptyl group, 1,1,3,3-tetramethylbutyl group and the like. Among the alkyl groups, a t-butyl group is preferable, and both R ¹¹ and R ¹² are preferably a t-butyl group.

R ¹³ is an alkylene group having 1 to 8 carbon atoms, preferably an alkylene group having 1 to 3 carbon atoms. The alkylene group may be linear or may have a branched chain. Examples of the alkylene group include methylene group, ethylene group, n-propylene group, 1,2-propylene group, n-butylene group, 1,2-butylene group, n-hexylene group, n-heptylene group, and n-octylene group. Etc. Among the alkylene groups, an ethylene group is preferable.
n is a number of 1-6, and 1-4 are preferable.

X ¹ is a residue obtained by removing n hydroxyl groups from an aliphatic m-valent alcohol having 1 to 24 carbon atoms, and m is 1 to 6. That, ^{X 1} is a residue is removed are n hydroxyl groups from an aliphatic 1-6 monohydric alcohol having 1 to 24 carbon atoms.
Examples of the aliphatic 1-6 valent alcohol having 1 to 24 carbon atoms in X ¹ include methanol, ethanol, n-propanol, i-propanol, n-butanol, t-butanol, n-pentanol, and 2-methylbutanol. 3-methylbutanol, 2,2-dimethylpropanol, n-hexanol, 2-methylpentanol, 2-ethylbutanol, 2,3-dimethylbutanol, n-heptanol, 2-methylhexanol, 3-methylhexanol, 5 -Monohydric alcohols such as methylhexanol, n-octanol, 2-ethylhexanol, n-nonanol, 3,5,5-trimethylhexanol, decyl alcohol, 2,4,6-trimethylheptanol, neopentyl glycol, trimethylol Ethane, trimethylol pro Hindered alcohols such as bread, pentaerythritol, ditrimethylolpropane, dipentaerythritol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol And polyhydric alcohols such as glycerin, diglycerin, triglycerin, sorbitol and mannitol. Among these, monohydric alcohol and hindered alcohol are preferable.

（（３）式中、Ｒ^２１及びＲ^２２は、それぞれ独立して炭素数１〜８のアルキル基であり、Ｒ^２３は、炭素数１〜８のアルキレン基であり、Ｘ^２は、炭素数１〜２４の脂肪族１〜６価アルコールから１個の水酸基が除かれた残基である。） Examples of the component (B) include phenolic antioxidants represented by the following general formulas (3) to (8).

(In the formula (3), R ²¹ and R ²² are each independently an alkyl group having 1 to 8 carbon atoms, R ²³ is an alkylene group having 1 to 8 carbon atoms, and X ² is the number of carbon atoms. This is a residue obtained by removing one hydroxyl group from 1 to 24 aliphatic 1 to 6-valent alcohols.)

In formula (3), R ²¹ and R ²² are the same as R ¹¹ and R ^{12 in} formula (2), respectively. R ²³ in the formula (3) is the same as R ¹³ in the formula (2).
(3) As X < ² > in a formula, a C1-C24 monovalent | monohydric aliphatic hydrocarbon group is mentioned.
The aliphatic hydrocarbon group may be linear or branched, and may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. Further, the aliphatic hydrocarbon group may or may not have an ether bond between carbons. Furthermore, the aliphatic hydrocarbon group may be substituted with a hydroxy group or may not be substituted.
X ² is preferably a monovalent saturated aliphatic hydrocarbon group having 1 to 24 carbon atoms, and more preferably a monovalent saturated aliphatic hydrocarbon group having 1 to 18 carbon atoms.

（（４）式中、Ｒ^３１及びＲ^３２は、それぞれ独立して炭素数１〜８のアルキル基であり、Ｒ^３３は、炭素数１〜８のアルキレン基であり、Ｘ^３は、炭素数１〜２４の脂肪族２〜６価アルコールから２個の水酸基が除かれた残基である。）

(In the formula (4), R ³¹ and R ³² are each independently an alkyl group having 1 to 8 carbon atoms, R ³³ is an alkylene group having 1 to 8 carbon atoms, and X ³ is the number of carbon atoms. (It is a residue obtained by removing two hydroxyl groups from 1 to 24 aliphatic divalent to hexavalent alcohols.)

R ³¹ and R ³² in the formula (4) are the same as R ¹¹ and R ¹² in the formula (2), respectively. R ³³ in the formula (4) is the same as R ¹³ in the formula (2).
(4) As X < ³ > in a formula, a C1-C24 bivalent aliphatic hydrocarbon group is mentioned.
The aliphatic hydrocarbon group may be linear or branched, and may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. Further, the aliphatic hydrocarbon group may or may not have an ether bond between carbons. Furthermore, the aliphatic hydrocarbon group may be substituted with a hydroxy group or may not be substituted.
X ³ is preferably a divalent saturated aliphatic hydrocarbon group having 1 to 24 carbon atoms which may have an ether bond between carbons, and 2 to 18 carbon atoms which may have an ether bond between carbons. The divalent saturated aliphatic hydrocarbon group is more preferable.

（（５）式中、Ｒ^４１及びＲ^４２は、それぞれ独立して炭素数１〜８のアルキル基であり、Ｒ^４３は、炭素数１〜８のアルキレン基であり、Ｘ^４は、炭素数１〜２４の脂肪族３〜６価アルコールから３個の水酸基が除かれた残基である。）

(In the formula (5), R ⁴¹ and R ⁴² are each independently an alkyl group having 1 to 8 carbon atoms, R ⁴³ is an alkylene group having 1 to 8 carbon atoms, and X ⁴ is a carbon number. It is a residue obtained by removing three hydroxyl groups from 1 to 24 aliphatic tri- or hexahydric alcohols.)

In the formula (5), R ⁴¹ and R ⁴² are the same as R ¹¹ and R ¹² in the formula (2), respectively. R ⁴³ in the formula (5) is the same as R ¹³ in the formula (2).
(5) ^{X 4} in the formula include the trivalent aliphatic hydrocarbon group having 1 to 24 carbon atoms.
The aliphatic hydrocarbon group may be linear or branched, and may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. Further, the aliphatic hydrocarbon group may or may not have an ether bond between carbons. Furthermore, the aliphatic hydrocarbon group may be substituted with a hydroxy group or may not be substituted.
X ⁴ is preferably a trivalent saturated aliphatic hydrocarbon group having 1 to 24 carbon atoms which may have an ether bond between carbons, and 3 to 18 carbon atoms which may have an ether bond between carbons. The trivalent saturated aliphatic hydrocarbon group is more preferable.

（（６）式中、Ｒ^５１及びＲ^５２は、それぞれ独立して炭素数１〜８のアルキル基であり、Ｒ^５３は、炭素数１〜８のアルキレン基であり、Ｘ^５は、炭素数１〜２４の脂肪族４〜６価アルコールから４個の水酸基が除かれた残基である。）

(In the formula (6), R ⁵¹ and R ⁵² are each independently an alkyl group having 1 to 8 carbon atoms, R ⁵³ is an alkylene group having 1 to 8 carbon atoms, and X ⁵ is a carbon number. (This is a residue obtained by removing four hydroxyl groups from 1 to 24 aliphatic 4- to 6-valent alcohols.)

In formula (6), R ⁵¹ and R ⁵² are the same as R ¹¹ and R ^{12 in} formula (2), respectively. R ⁵³ in the formula (6) is the same as R ¹³ in the formula (2).
(6) As X < ⁵ > in a formula, a C1-C24 tetravalent aliphatic hydrocarbon group is mentioned.
The aliphatic hydrocarbon group may be linear or branched, and may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. Further, the aliphatic hydrocarbon group may or may not have an ether bond between carbons. Furthermore, the aliphatic hydrocarbon group may be substituted with a hydroxy group or may not be substituted.
X ⁵ is preferably a C 1-24 tetravalent saturated aliphatic hydrocarbon group which may have an ether bond between carbons, and may have 4-18 carbon atoms which may have an ether bond between carbons. The tetravalent saturated aliphatic hydrocarbon group is more preferable.

（（７）式中、Ｒ^６１及びＲ^６２は、それぞれ独立して炭素数１〜８のアルキル基であり、Ｒ^６３は、炭素数１〜８のアルキレン基であり、Ｘ^６は、炭素数２〜２４の脂肪族５〜６価アルコールから５個の水酸基が除かれた残基である。）

(In formula (7), R ⁶¹ and R ⁶² are each independently an alkyl group having 1 to 8 carbon atoms, R ⁶³ is an alkylene group having 1 to 8 carbon atoms, and X ⁶ is a carbon number. It is a residue obtained by removing 5 hydroxyl groups from 2 to 24 aliphatic 5 to 6 alcohols.)

( ⁶¹ ) R ⁶¹ and R ⁶² in the formula are the same as R ¹¹ and R ¹² in the formula (2), respectively. R ⁶³ in the formula (7) is the same as R ¹³ in the formula (2).
(7) As X < ⁶ > in a formula, a C1-C24 pentavalent aliphatic hydrocarbon group is mentioned.
The aliphatic hydrocarbon group may be linear or branched, and may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. Further, the aliphatic hydrocarbon group may or may not have an ether bond between carbons. Furthermore, the aliphatic hydrocarbon group may be substituted with a hydroxy group or may not be substituted.
X ⁶ is preferably a pentavalent saturated aliphatic hydrocarbon group having 2 to 24 carbon atoms which may have an ether bond between carbons, and 5 to 18 carbon atoms which may have an ether bond between carbons. The pentavalent saturated aliphatic hydrocarbon group is more preferable.

（（８）式中、Ｒ^７１及びＲ^７２は、それぞれ独立して炭素数１〜８のアルキル基であり、Ｒ^７３は、炭素数１〜８のアルキレン基であり、Ｘ^７は、炭素数２〜２４の脂肪族６価アルコールから６個の水酸基が除かれた残基である。）

(In the formula (8), R ⁷¹ and R ⁷² are each independently an alkyl group having 1 to 8 carbon atoms, R ⁷³ is an alkylene group having 1 to 8 carbon atoms, and X ⁷ is a carbon number. This is a residue obtained by removing 6 hydroxyl groups from 2 to 24 aliphatic hexavalent alcohols.)

In formula (8), R ⁷¹ and R ⁷² are the same as R ¹¹ and R ^{12 in} formula (2), respectively. R ⁷³ in the formula (8) is the same as R ¹³ in the formula (2).
(8) X ⁷ in the formula includes a C1-C24 hexavalent aliphatic hydrocarbon group.
The aliphatic hydrocarbon group may be linear or branched, and may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. Further, the aliphatic hydrocarbon group may or may not have an ether bond between carbons.
X ⁷ is preferably a C 2-24 hexavalent saturated aliphatic hydrocarbon group that may have an ether bond between carbons, and 6 to 18 carbon atoms that may have an ether bond between carbons. The hexavalent saturated aliphatic hydrocarbon group is more preferable.

  Examples of the component (B) include octyl 3- (4-hydroxy-3,5-di-t-butylphenyl) propionate and 3- (4-hydroxy-3,5-di-t-butylphenyl) propion. Decyl acid, dodecyl 3- (4-hydroxy-3,5-di-t-butylphenyl) propionate, stearyl 3- (4-hydroxy-3,5-di-t-butylphenyl) propionate, 3- ( 4-Hydroxy-3,5-di-t-butylphenyl) oleyl propionate, benzenepropanoic acid, 3,5-bis (1,1-dimethylethyl) -4-hydroxy C7-C9 side chain alkyl ester, tetramethylene Bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], hexamethylene bis [3- (3,5-di-t-butyl-4-hydro Cyphenyl) propionate], pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 3- (4-hydroxy-3,5-di-t-butylphenyl) propionic acid A glycerol monoester etc. are mentioned. Among these, benzenepropanoic acid, 3,5-bis (1,1-dimethylethyl) -4-hydroxy C7-C9 side chain alkyl ester, pentaerythritol tetrakis [3- (3,5-di-t-butyl- 4-hydroxyphenyl) propionate] is preferred.

As the component (B), one type may be used alone, or two or more types may be used in combination.
Although content of (B) component is not specifically limited, 0.05-2 mass% is preferable with respect to the gross mass of grease, and 0.1-1 mass% is more preferable. When the content of the component (B) is in the above preferred range, outgassing is easily suppressed. Furthermore, it becomes easy to suppress the oxidative deterioration of grease, and it becomes easy to suppress the generation of outgas even during use of the information recording / reproducing apparatus. Therefore, it becomes easy to reduce the total amount of outgas from the production of the rolling bearing to its use. Furthermore, it becomes easy to suppress poor lubrication due to oxidative degradation of grease, and it becomes easy to improve durability.

From the viewpoint that the effects of the present invention can be more easily obtained, it is preferable to use the component (B) among at least one kind of antioxidant selected from the component (A) and the component (B). Moreover, it is preferable to have both (A) component and (B) component. The component (A) is excellent in the antioxidant effect at a relatively high temperature exceeding 100 ° C., and the component (B) is particularly excellent in the antioxidant effect at room temperature to about 100 ° C. The rolling bearing of the information recording / reproducing apparatus has a wide swing arm operating range and operating speed, and a wide range of environmental temperatures, and the grease provided in the bearing is exposed to variously changing temperatures. By having both the component (A) and the component (B), it is possible to reliably prevent the oxidative deterioration of the grease even when exposed to such variously changing temperatures.
When the component (A) and the component (B) are both present, the total content of the component (A) and the component (B) is preferably 0.1 to 4% by mass relative to the total mass of the grease. 2-2 mass% is more preferable. Further, the mass ratio of the component (A) to the component (B) [the mass contained in the component (A) / the mass contained in the component (B)] is preferably 9/1 to 5/5, and 8/2 to 5/5. Is more preferable, and 8/2 to 6/4 is more preferable.
When it is in the above preferable range, the outgas amount can be further reduced.

<Base oil>
Although it does not specifically limit as base oil mix | blended with the grease of this invention, Mineral oil, synthetic oil, etc. are mentioned.

As said mineral oil, the well-known mineral oil used as a base oil can be used, For example, naphthenic mineral oil, paraffinic mineral oil, hydrogenated mineral oil, solvent refined mineral oil, highly refined mineral oil, etc. are mentioned.
One kind of mineral oil may be used alone, or two or more kinds may be used in combination. For example, a plurality of mineral oils having different kinematic viscosities may be mixed and adjusted to the target kinematic viscosity (average kinematic viscosity).

  As the mineral oil, a refined mineral oil classified into Group III (GrIII) in the API (American Petroleum Institute, American Petroleum Institute) base oil category is preferable because a grease having a smaller outgas amount and excellent heat resistance can be obtained. Examples of the refined mineral oil include paraffinic mineral oil obtained by further highly hydrorefining a lubricating oil fraction obtained by atmospheric distillation of crude oil. The refined mineral oil classified into Group III preferably has a flash point of 240 ° C. or higher, more preferably 250 ° C. or higher. Such refined mineral oil has a high degree of refinement and can further reduce the amount of outgas. As this reason, it is estimated that the low molecular weight component which causes an outgas is reduced.

As the synthetic oil, known synthetic oils used as base oils can be used. For example, polyalphaolefin (PAO), aliphatic hydrocarbon oils such as polybutene, aromatic hydrocarbon oils such as alkylbenzene and alkylnaphthalene, polyol esters And ester oils such as phosphoric acid esters, ether oils such as polyphenyl ether, polyalkylene glycol oils, silicone oils, and fluorine oils.
One of these synthetic oils may be used alone, or two or more thereof may be used in combination.

As the synthetic oil, it is preferable to use PAO. As the PAO, known PAO used as a base oil can be used without limitation. For example, α-olefins (1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-octene, Pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicocene, 1-docosene, etc.) as a raw material, or a mixture of the 3 to 5 mer. Among these, as PAO, the amount of outgas is reduced, evaporation loss at high temperature is reduced, oxidative deterioration is suppressed, and an appropriate viscosity is obtained. A mixture of pentamers is preferred. A suitable viscosity range of this mixture is, for example, 27 to 54 mm ² / s (cSt) at 40 ° C. As for the C3-C12 α-olefin 3-5 mer, one kind may be used alone, or two or more kinds may be used in combination.
One type of PAO may be used alone, or two or more types may be used in combination. For example, a plurality of PAOs having different kinematic viscosities may be mixed and adjusted to the target kinematic viscosity (average kinematic viscosity).

  As the base oil, mineral oil and PAO are preferably used in combination. In this case, it is preferable that the ratio of the mineral oil is 10 to 40% by mass with respect to 100% by mass of the base oil. Moreover, it is preferable that the content rate of the said PAO is larger than the content rate of the said mineral oil in the said base oil.

Moreover, it is preferable to make the kinematic viscosity ν ₁ of mineral oil at 40 ° C. higher than the kinematic viscosity ν ₂ of PAO at 40 ° C. When the kinematic viscosity ν ₁ of the mineral oil is higher than the kinematic viscosity ν _{2 of} PAO, the heat resistance of the mineral oil is easily increased. As a result, the amount of outgas from mineral oil decreases, and as a result, the amount of outgas from base oil is likely to be reduced. Further, the PAO having a kinematic viscosity ν ₂ lower than the kinematic viscosity ν _{1 of the} mineral oil is combined, so that the kinematic viscosity ν of the base oil is lowered. Therefore, the grease is easily supplied to the portion where the rolling element of the rolling bearing is rolling, and the lubricating effect by the grease is easily obtained.
The kinematic viscosity of the oil in the present invention means a value measured at 40 ° C. according to JIS K2283.
When a plurality of similar base oils having different kinematic viscosities are mixed, the kinematic viscosity of the mixture is considered as the kinematic viscosity of the base oil contained in the grease of the present invention.

The ratio ν ₁ / ν ₂ of the kinematic viscosity [nu ₁ of mineral oil on the kinematic viscosity [nu ₂ of the PAO, from the viewpoint of easily further reduced outgassing, preferably 1.3 or more, more preferably 1.5 or more. Further, the ratio ν ₁ / ν ₂ is preferably 4 or less, and more preferably 2 or less, from the viewpoint of reducing the torque of the rolling bearing.

The kinematic viscosity ν _{1 of the} mineral oil is preferably 40 mm ² / s or more, more preferably 45 mm ² / s or more, from the viewpoint that the outgas amount can be more easily reduced. Further, the kinematic viscosity [nu ₁ of mineral oil, from the viewpoint of easily grease or base oil is supplied to the rolling surface of the rolling bearing, is preferably from 80 mm ² / s, more preferably at most 60 mm ² / s.

The kinematic viscosity ν _{2 of} PAO is preferably 20 mm ² / s or more, more preferably 30 mm ² / s or more, from the viewpoint that the outgas amount can be more easily reduced. Further, the kinematic viscosity [nu ₂ of the PAO, from the viewpoint of the rolling elements of the rolling bearing is likely grease or base oil is supplied to the rolling surface is preferably not more than 60 mm ² / s, more preferably at most 40 mm ² / s.

Kinematic viscosity ν at 40 ° C. of the base oil is preferably ^{25~45mm 2 / s, 30~40mm 2 /} s is more preferable. If the kinematic viscosity ν of the base oil is equal to or higher than the lower limit value, the outgas amount can be more easily reduced. If the kinematic viscosity ν of the base oil is equal to or less than the above upper limit value, grease or base oil is easily supplied to the rolling contact surface of the rolling bearing and stable use at low temperatures is required (for example, even at a low temperature of −30 ° C.). Even in in-vehicle applications where stable operation is required, the operation is likely to be performed with low torque. In particular, when the ratio of mineral oil to 100% by mass of the base oil is 30% by mass or less, the outgas amount can be easily reduced if the kinematic viscosity ν at 40 ° C. of the base oil is 25 mm ² / s or more.

<Thickener>
The thickener serves to keep the grease semi-solid.
As the thickener, a known thickener generally used for rolling bearing grease can be used without limitation. As an example, known thickeners used in grease for rolling bearings of information recording / reproducing apparatuses include, for example, urea compounds, lithium soap, calcium soap, various complex soaps, silica gel, polytetrafluoroethylene, and organic bentonite. Can be mentioned. Especially, as a thickener, a urea compound is preferable from the point which is excellent in heat resistance, and the diurea compound which has two urea bonds in 1 molecule is more preferable.

Examples of the diurea compound include an aliphatic diurea compound whose end is an aliphatic group, an alicyclic diurea compound whose end is an alicyclic group, and an aromatic diurea compound whose end is an aromatic group.
Specific examples of the diurea compound include compounds obtained by reaction of diisocyanates (phenylene diisocyanate, tolylene diisocyanate, etc.) and monoamines (octylamine, dodecylamine, stearylamine, aniline, p-toluidine, etc.).
Examples of the lithium soap include lithium stearate and lithium 12-hydroxystearate.
One thickener may be used alone, or two or more thickeners may be used in combination.

<Other ingredients>
The grease of the present invention may contain components other than those described above as necessary.
As other components, known components that are usually used in grease can be used, and examples thereof include additives such as extreme pressure agents, rust inhibitors, oiliness improvers, and metal deactivators.

Examples of extreme pressure agents include organic molybdenum compounds (such as molybdenum dithiocarbamate and molybdenum dithiophosphate), organic fatty acid compounds (such as oleic acid, naphthenic acid, and succinic acid), and organic phosphorus compounds (such as trioctyl phosphate and triphenyl phosphate). Triphenyl phosphate, triethyl phosphate, etc.), phosphate ester, zinc dithiocarbamate, antimony dithiocarbamate and the like.
One extreme pressure agent may be used alone, or two or more extreme pressure agents may be used in combination.

Examples of the rust preventive include alkali metal salts or alkaline earth metal salts of organic sulfonic acids (calcium sulfonate, magnesium sulfonate, barium sulfonate, etc.) and polyhydric alcohols (sorbitan monooleate, etc.). Examples include partial esters.
One type of rust inhibitor may be used alone, or two or more types may be used in combination.

  In addition, antioxidant other than (A) component and (B) component may be contained in the grease of this invention. However, from the viewpoint of easily obtaining the effects of the present invention, it is preferable that no antioxidant other than the component (A) and the component (B) is included.

<Ratio of each component>
The ratio of the base oil to 100% by mass of the grease of the present invention is preferably 75 to 93% by mass, and more preferably 80 to 90% by mass. If the ratio of the base oil is equal to or more than the lower limit value, grease or base oil is likely to be supplied to the rolling surface of the rolling bearing. If the ratio of the base oil is equal to or less than the above upper limit value, the grease is semi-solid and difficult to leak and scatter.

  10-40 mass% is preferable and, as for the ratio of the mineral oil with respect to 100 mass% of base oils, 20-30 mass% is more preferable. If the ratio of mineral oil is equal to or greater than the lower limit, it becomes easy to obtain a grease having a good balance between durability and torque smoothness. If the ratio of mineral oil is not more than the above upper limit value, it becomes easy to obtain a grease with a sufficiently reduced outgas amount.

  50-90 mass% is preferable and, as for the ratio of PAO with respect to 100 mass% of base oils, 60-80 mass% is more preferable. If the PAO ratio is equal to or greater than the lower limit, it is easy to obtain a grease with a sufficiently reduced outgas amount. If the PAO ratio is less than or equal to the above upper limit value, it becomes easy to obtain a grease having a good balance between durability and torque smoothness.

  The total ratio of mineral oil and PAO to 100% by mass of the base oil is preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more. If the ratio of the total of mineral oil and PAO is more than the said lower limit, it will become easy to obtain a low torque grease. The upper limit of the total ratio of the mineral oil and PAO is 100% by mass.

In the grease of the present invention, it is preferable that the proportion of PAO is larger than the proportion of mineral oil in the base oil because it is easy to achieve both a reduction in the amount of outgas and excellent durability.
The mass ratio of PAO to mineral oil in the base oil (PAO / mineral oil) is preferably 1.25 to 9, and more preferably 1.5 to 4. When the mass ratio is equal to or greater than the lower limit value, the outgas amount is easily reduced. When the mass ratio is less than or equal to the upper limit value, durability and torque smoothness are easily improved.

  The ratio of the thickener to 100% by mass of the grease of the present invention is preferably 7 to 20% by mass, and more preferably 10 to 15% by mass. When the proportion of the thickener is equal to or more than the lower limit value, it is easy to obtain a grease that hardly leaks and hardly scatters. When the ratio of the thickener is equal to or less than the upper limit value, grease or base oil is easily supplied to the rolling surface of the rolling bearing.

The ratio of the extreme pressure agent to 100% by mass of the grease of the present invention is preferably 0.2 to 4% by mass, and more preferably 0.5 to 2% by mass.
The ratio of the rust inhibitor to 100% by mass of the grease of the present invention is preferably 0.2 to 4% by mass, and more preferably 0.5 to 2% by mass.

[Information recording / playback device]
The rolling bearing, the rolling bearing device, and the information recording / reproducing device of the present invention can adopt known modes except for using the grease of the present invention. Hereinafter, an example of the rolling bearing, the rolling bearing device, and the information recording / reproducing device of the present invention will be described.
An information recording / reproducing apparatus 1 according to the present embodiment is an apparatus that performs writing on a disk (magnetic recording medium) D by a perpendicular recording method. As shown in FIG. 1, the disk D, the swing arm 2, and the light guide A waveguide 3, a laser light source 4, a head gimbal assembly (HGA) 5, a rolling bearing device 6, an actuator 7, a spindle motor (rotation drive unit) 8, a control unit 9, and a housing 10 are provided. Yes.

The housing 10 accommodates each component in the information recording / reproducing apparatus 1.
The housing 10 has a rectangular bottom 10a in plan view, a peripheral wall (not shown) erected from the periphery of the bottom 10a, and a lid (not shown) that is detachably fixed to the top of the peripheral wall and closes the opening. And comprising. In the housing 10, each component is accommodated inside the peripheral wall portion on the bottom portion 10a. In FIG. 1, the peripheral wall portion and the lid are omitted for convenience.
The material of the housing 10 is not specifically limited, For example, metal materials, such as aluminum, are mentioned.

  A spindle motor 8 is attached to the approximate center of the bottom 10 a of the housing 10. Further, the center hole formed at the center of the disk D is fitted into the spindle motor 8 so that the three disks D are detachably mounted. The spindle motor 8 can rotate the disk D in a fixed direction around the rotation axis L1.

  An actuator 7 is attached to one corner of the bottom 10 a of the housing 10 so as to be located outside the disk D. A swing arm 2 extending toward the disk D is connected to the actuator 7. A rolling bearing device 6 is provided on the base end side portion of the swing arm 2. By driving by the actuator 7, the swing arm 2 is rotated in a horizontal plane around the rotation axis L <b> 2 of the rolling bearing device 6.

The swing arm 2 includes a base portion 2a connected to the actuator 7 and an arm portion 2b extending from the base portion 2a toward the disk D. The swing arm 2 can be obtained, for example, by integrally forming the base portion 2a and the arm portion 2b by cutting or the like.
The base 2a has a substantially rectangular parallelepiped shape, and is rotatably supported by the rolling bearing device 6 so as to surround the rolling bearing device 6.

The arm portion 2b has a flat plate shape and has a tapered shape that tapers from the base end portion toward the tip end portion. The arm portion 2b extends from the front surface (surface opposite to the corner portion) 2d opposite to the rear surface 2c to which the actuator 7 is attached in the base portion 2a in the surface direction (horizontal plane direction) of the upper surface of the base portion 2a. It is provided as follows.
In the swing arm 2 of this example, the three arm portions 2b are provided in the height direction (vertical direction) of the base portion 2a so that the disk D is sandwiched between the arm portions 2b. In other words, the arm portions 2b and the disk D are alternately arranged in the height direction, and the arm portion 2b is moved in a direction parallel to the disk surface (the surface of the disk D) D1 by driving the actuator 7. It is supposed to be.

  A head gimbal assembly 5 is provided at the tip of the arm portion 2 b in the swing arm 2. A laser light source 4 is provided on the side surface of the base 2 a of the swing arm 2. An optical waveguide 3 that connects the laser light source 4 and the head gimbal assembly 5 is provided on the base 2 a and the arm 2 b of the swing arm 2. Thus, light can be supplied from the laser light source 4 to the head gimbal assembly 5 through the optical waveguide 3.

The head gimbal assembly 5 includes a suspension 5a and a slider 5b attached to the tip of the suspension 5a.
The slider 5b has a near-field light generating element. Near-field light is generated from the near-field light generating element when light is guided from the laser light source 4 to the slider 5b. By using the near-field light, various information can be recorded on or reproduced from the disk D.
The near-field light generating element is configured by, for example, an optical minute aperture, a protrusion formed in a nanometer size, or the like.

  The head gimbal assembly 5 is moved in a direction parallel to the disk surface D1 together with the arm portion 2b of the swing arm 2 by driving the actuator 7. The swing arm 2 and the head gimbal assembly 5 are retracted from the disk D by driving the actuator 7 when the rotation of the disk D is stopped.

  The control unit 9 is connected to the laser light source 4. In the control unit 9, the light beam supplied to the slider 5 b of the head gimbal assembly 5 can be controlled by a current modulated according to information.

<Rolling bearing device>
2 and 3, the rolling bearing device 6 includes a shaft 20, a sleeve 21 installed coaxially with the shaft 20 outside the shaft 20, and 2 installed between the shaft 20 and the sleeve 21. Two rolling bearings 22.

The shaft 20 is a cylindrical rod-shaped member and is erected from the bottom 10 a of the housing 10. The central axis of the shaft 20 is the rotation axis L2 when the swing arm 2 rotates.
A flange portion 20b having a diameter larger than that of the main body portion 20a and a reduced diameter portion 20c having a diameter smaller than that of the main body portion 20a are sequentially provided toward the base end of the shaft 20 on the bottom 10a side of the housing 10. ing. A male screw 20d is formed on the outer peripheral surface of the reduced diameter portion 20c.
By inserting the reduced diameter portion 20c of the shaft 20 into the hole 10b provided in the bottom portion 10a of the housing 10, and screwing the female screw 10c formed on the inner peripheral surface of the hole 10b and the male screw 20d of the reduced diameter portion 20c. The shaft 20 is erected on the bottom 10 a of the housing 10. At this time, the shaft 20 is positioned in the height direction by the lower surface of the flange portion 20 b being in contact with the bottom portion 10 a of the housing 10.

The sleeve 21 is a member formed in a cylindrical shape. The inner diameter of the sleeve 21 is substantially the same as the outer diameter of the flange portion 20b.
The sleeve 21 is installed so as to surround the shaft 20 from the outside in the radial direction, and its inner peripheral surface is separated from the outer peripheral surface of the shaft 20 at a predetermined interval. The central axis of the shaft 20 and the central axis of the sleeve 21 coincide with each other.
The sleeve 21 is directly press-fitted into the mounting hole 2e formed in the base 2a of the swing arm 2, is press-fitted through an elastic body such as a metal ring formed in a corrugated shape, or is an adhesive fit. By being combined, the swing arm 2 is combined integrally.

  A spacer portion 21 a that protrudes inward over the entire circumference in the circumferential direction is formed at the center in the height direction on the inner circumferential surface of the sleeve 21. Between the shaft 20 and the sleeve 21, two rolling bearings 22 are installed above and below the spacer portion 21a, respectively, and the distance between the two rolling bearings 22 is maintained at a predetermined distance.

<Rolling bearing>
The two rolling bearings 22 provided in the rolling bearing device 6 are the same.
As shown in FIGS. 3 to 6, the rolling bearing 22 includes an inner ring 30, an outer ring 31, a retainer 32, a plurality of rolling elements 33, and two shield plates 34.

The inner ring 30 is a cylindrical member.
The inner ring 30 has an inner diameter that allows the shaft 20 to be inserted. In the present embodiment, the inner diameter of the inner ring 30 is slightly larger than the outer diameter of the shaft 20. The shaft 20 is inserted into the inner ring 30 and the inner ring 30 is fixed to the shaft 20 with an adhesive or the like.
The inner diameter of the inner ring 30 may be the same as or slightly smaller than the outer diameter of the shaft 20 as long as it can be installed on the shaft 20. In this case, the shaft 20 is press-fitted and fixed to the inner ring 30.

In the rolling bearing 22, a so-called inner ring preload in which the inner ring 30 is fixed to the shaft 20 in a state where a preload is applied to the inner ring 30 in the axial direction relative to the shaft 20 can be employed. Thereby, the rolling bearing 22 can be made highly rigid, and the resonance frequency (resonance point) of the rolling bearing device 6 can be increased. Therefore, the rolling bearing device 6 can cope with higher speed rotation.
The rolling bearing 22 may employ so-called outer ring preload in which the outer ring 31 is fixed to the sleeve 21 in a state in which a preload is applied to the outer ring 31 in the axial direction relative to the shaft 20.

A concave inner ring rolling surface 30 a that guides the rolling of the rolling elements 33 is formed over the entire circumference of the inner ring 30 at an axial intermediate portion of the outer circumferential surface of the inner ring 30. The inner ring rolling surface 30a has an arcuate cross section when cut along a plane passing through the central axis of the inner ring 30.
Examples of the material of the inner ring 30 include metal materials such as stainless steel. The inner ring 30 can be manufactured, for example, by forging or machining.

The outer ring 31 is a cylindrical member that is larger in diameter than the inner ring 30 and is similar to the inner ring 30.
The outer ring 31 is fixed to the inside of the sleeve 21, and is installed outside the inner ring 30 in a state of being separated from the inner ring 30. The inner ring 30 and the outer ring 31 are installed on the same axis so that their central axes coincide with the central axis of the shaft 20.

A concave outer ring rolling surface 31 a that guides the rolling of the rolling element 33 is provided at the intermediate portion in the axial direction on the inner circumferential surface of the outer ring 31 so as to face the inner ring rolling surface 30 a of the inner ring 30. It is formed all around. The outer ring rolling surface 31a has an arcuate cross section when cut along a plane passing through the central axis of the outer ring 31.
Examples of the material of the outer ring 31 include metal materials such as stainless steel. The inner ring 30 can be manufactured, for example, by forging or machining.

As shown in FIG. 6, the retainer 32 is formed from an annular main body portion 32 a and an upper portion of the main body portion 32 a, and seven pairs of claw portions 32 b that rise in an arc shape so as to approach each other toward the tip. , 32c. The seven pairs of claw portions 32 b and 32 c are provided at equal intervals in the circumferential direction of the retainer 32. A ball pocket B having a substantially circular shape when viewed from the front is formed inside the paired claw portion 32b and claw portion 32c so as to hold the rolling element 33 in a rollable manner.
The number of pairs of claws, that is, the number of ball pockets B is not limited to seven, but may be six or less, or may be eight or more.

The inner diameter of the retainer 32 is larger than the outer diameter of the inner ring 30, and the outer diameter of the retainer 32 is smaller than the inner diameter of the outer ring 31. In a state where the retainer 32 is installed between the inner ring 30 and the outer ring 31, the rolling elements 33 are held in the respective ball pockets B so as to be able to roll. Thus, the rolling element 33 is disposed between the inner ring rolling surface 30a of the inner ring 30 and the outer ring rolling surface 31a of the outer ring 31 in a state where the inner ring 30 and the outer ring 31 and the retainer 32 do not interfere with each other.
The retainer 32 can rotate around the central axis L2 in a state where the rolling elements 33 are held in the ball pockets B so as to be able to roll.
The material of the retainer 32 is not particularly limited, and examples thereof include resins such as polyamide resin.

  A grease pocket G having a shallower depth than the ball pocket B is formed between the pair of claw portions 32 b and 32 c at the upper portion of the retainer 32 and the pair of claw portions 32 b and 32 c adjacent thereto. That is, in the retainer 32, ball pockets B and grease pockets G are alternately formed in the circumferential direction by a plurality of pairs of claw portions 32b and 32c.

When the rolling element 33 is rotated together with the retainer 32 in a state where the grease of the present invention is disposed in the grease pocket G and the rolling element 33 is disposed in the ball pocket B, the inner ring 30 and the outer ring 31 are rotated from the grease pocket G. Grease oozes out between the moving body 33 and a lubricating effect by the grease is obtained.
By using the grease for the rolling bearing 22 using the grease pocket G, the amount of grease used can be reduced. As a result, it becomes easy to suppress an increase in the torque of the rolling bearing 22 due to an excessive amount of grease, and it becomes easy to obtain a sufficient cleanliness required for reading and writing to the disk D.

The rolling element 33 in this example is spherical. The rolling element 33 is disposed in the ball pocket B of the retainer 32 between the inner ring rolling surface 30a of the inner ring 30 and the outer ring rolling surface 31a of the outer ring 31, and is disposed on the inner ring rolling surface 30a and the outer ring rolling surface 31a. It is designed to roll along. The respective rolling elements 33 are evenly arranged in the circumferential direction by the retainer 32.
Although the number of rolling elements 33 is seven in this example, it may be determined according to the number of ball pockets B in the retainer 32, and may be six or less, or may be eight or more.
Examples of the material of the rolling element 33 include metal materials such as bearing steel.

  The shield plate 34 is an annular plate member that blocks the upper and lower sides of the annular space formed between the inner ring 30 and the outer ring 31. The shield plates 34 are installed above and below the retainer 32 and the plurality of rolling elements 33 between the inner ring 30 and the outer ring 31. Each shield plate 34 is fixed to the outer ring 31 in a state where the outer peripheral edge of the shield plate 34 enters the annular groove 40 for engagement formed in the outer ring 31.

(Action mechanism)
In the information recording / reproducing apparatus 1, the grease of the present invention is disposed in the grease pocket G of the retainer 32 in the rolling bearing 22. When the swing arm 2 is rotated by driving the actuator 7, the grease disposed in the grease pocket G passes through the side surfaces of the inner ring 30, the outer ring 31 and the retainer 32, and is supplied between the inner ring 30 and the outer ring 31 and the rolling element 33. The lubricating effect of grease is exhibited.
Since the information recording / reproducing apparatus 1 uses the grease of the present invention, the amount of outgas is sufficiently reduced. Therefore, outgas hardly accumulates in a gap between the head gimbal assembly and the disk D, and reading and writing can be performed stably. Further, excellent durability can be ensured, and a low torque and excellent torque smoothness can be maintained for a long period of time.

(Other embodiments)
The rolling bearing, rolling bearing device, and information recording / reproducing device of the present invention are not limited to those described above as long as the grease of the present invention is used.
For example, the information recording / reproducing apparatus 1 including the rolling bearing 22 and the rolling bearing device 6 uses near-field light, but a general HDD including a rolling bearing and a rolling bearing device using the grease of the present invention may be used. It may be an optical disk D device or the like.
Further, the use of the grease of the present invention is not limited to the information recording / reproducing apparatus, and can be applied to, for example, an electronic device manufacturing apparatus that is required to reduce dust generation and outgas from the grease. Examples of the electronic device manufacturing apparatus include a semiconductor manufacturing apparatus, a liquid crystal manufacturing apparatus, and a printed board manufacturing apparatus.
Furthermore, the grease of the present invention can be used not only for rolling bearings but also as grease sealed in, for example, linear guides and ball screws.

Further, the rolling bearing device may not include a sleeve. Specifically, for example, an annular spacer ring is provided between two rolling bearings that are spaced apart from each other in the axial direction outside the shaft, and the sleeve is provided with an annular spacer ring that keeps the distance between the rolling bearings at a predetermined distance. There may be no rolling bearing device. In this case, the outer ring of the rolling bearing can be directly press-fitted or adhesively fitted into the mounting hole formed in the base of the swing arm.
Further, the rolling element in the rolling bearing may be a cylindrical roller.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following description.
The raw materials used in this example are as follows.
The kinematic viscosities of mineral oil, PAO and base oil in this example were measured at 40 ° C. according to JIS K2283 using a Canon-Fenske viscometer.

<(A) component>
A-1: Di (4-octylphenyl) amine.
<(B) component>
B-1: Benzenepropanoic acid, 3,5-bis (1,1-dimethylethyl) -4-hydroxy C7-C9 side chain alkyl ester.
B-2: Pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate].

<(A ′) component, (A) component comparison component>
A′-1: bis sebacate (1,2,2,6,6-pentamethyl-4-piperidyl).
<(B ′) component, (B) component comparison component>
B′-1: 2,6-di-tert-butyl-p-cresol.

[Measurement of outgas amount]
For each of the following samples, the outgas amount was measured as follows. The results are shown in Table 1.

<Measurement sample>
Reference sample: Refined mineral oil (classified as Group III in the API base oil category).
Kinematic viscosity ν ₁ = 47 mm ² / s).
Sample 1: A reference sample added with 0.2% by mass (based on the total mass) of A-1.
Sample 2: 0.2% by mass (based on the total mass) of B-1 added to the reference sample.
Sample 3: 0.2% by mass (relative to the total mass) of B-2 added to the reference sample.
Sample 4: 0.1% by mass of A′-1 and 0.1% by mass of zinc diamyldithiocarbamate (Zn-DTC) (based on the total mass), respectively, added to the reference sample.
Sample 5: A sample obtained by adding 0.2% by mass (relative to the total mass) of B′-1 to a reference sample.

(Measurement method of outgas amount)
Each sample (4.5-5.5 mg) was evenly coated on a 15 mm square aluminum foil with a glass rod to obtain a measurement sample. The measurement sample was heated in an oven at 85 ° C. for 3 hours with 5 μL (100 ng) of a standard reagent (hexadecane), and the generated gas was adsorbed to a collection tube. Next, the collection tube was installed in a heat desorption apparatus (TD-100) and heated to 320 ° C., and the gas generated from the collection tube was sent to a gas chromatograph mass spectrometer (GC-MS). In GC-MS, chromatogram data is obtained by a temperature profile that is held at 40 ° C. for 2 minutes, heated to 280 ° C. over 20 minutes at 12 ° C./minute, and held at 280 ° C. for 20 minutes. Component identification was performed using the library. The outgas amount was calculated in terms of standard reagent based on the chromatogram peak (corresponding to 100 ng) of the standard reagent (hexadecane).

As shown in Table 1, in Samples 1 to 3 containing the component (A) or the component (B), the outgas amount was reduced as compared with the reference sample. On the other hand, the sample 4 containing the component (A ′) has the same amount of outgas as the reference sample, and the sample 5 containing the component (B ′) has an increased amount of outgas compared to the reference sample.
That is, from the results in Table 1, it was confirmed that the amount of outgas could be reduced by adding the component (A) or the component (B) to the base oil.

[Examples 1-2]
Each grease of Examples 1-2 was prepared as follows. Moreover, about each obtained grease of Examples 1-2, the measurement of the outgas amount, the oxidation stability test, the durability test, and the grease bump test were performed as follows. The results are shown in Table 2.

<Example 1>
Refined mineral oil (classified as group III in the API base oil category and having a flash point of 250 ° C. or higher. Kinematic viscosity ν ₁ = 47 mm ² / s) and PAO (MIX; α-olefin having 8, 10, 12 carbon atoms) 3 to 5 mer mixture (kinematic viscosity ν ₂ = 30 mm ² / s) was mixed at a mass ratio of 3: 7 to obtain a base oil (kinematic viscosity ν = 34 mm ² / s).
Next, the base oil and an alicyclic diurea compound (thickener) were used to make a grease, and A-1, B-1 and a rust inhibitor were added and mixed to prepare a grease of Example 1. The ratio of each component is 85.8% by mass of base oil, 12.5% by mass of thickener, 0.5% by mass of A-1, and 0.2% of B-1 with respect to 100% by mass of grease. The mass% and the rust preventive agent were 1.0 mass%.

<Example 2>
In addition to A-1, B-1 and a rust preventive agent, the grease of Example 2 was prepared in the same manner as Example 1 except that an extreme pressure agent was further added and mixed. The proportion of each component is 84.8% by mass of base oil, 12.5% by mass of thickener, 0.5% by mass of A-1 and 0.2% of B-1 with respect to 100% by mass of grease. The mass%, the rust inhibitor was 1.0 mass%, and the extreme pressure agent was 1.0 mass%.

[Reference Example 1]
With respect to the rolling bearing grease α of a commercially available information recording / reproducing apparatus, the measurement of the outgas amount, the oxidation stability test, the durability test, and the grease bump test were performed as follows. The results are shown in Table 2. Grease α contains a urea compound as a thickener.

(Measurement of outgas amount)
Except that the grease (4.5 to 5.5 mg) of Examples 1 and 2 and Reference Example 1 was uniformly applied on a 15 mm square aluminum foil with a glass rod, the above (outgas amount) The amount of outgas of each grease was measured in the same manner as in (1).

(Oxidation stability test)
In accordance with JIS K2220, a sample pressurized to 755 kPa with an oxygen cylinder was heated to 99 ° C., and the pressure drop after 100 hours was measured.
This test is mainly for evaluating the oxidation stability when the grease is used for a long time. The smaller the value, the better the oxidation stability.

(An endurance test)
The rolling bearing device 6 illustrated in FIGS. 3 to 6 is manufactured, the grease of each example is disposed in the grease pocket G of the retainer 32, and the continuous operation is performed under the following operating conditions, and the continuous operation with respect to the initial torque before the continuous operation is performed. The torque fluctuation range (hash) was measured as the ratio of the subsequent torque.
≪Operating conditions≫
Operating frequency: 30Hz
Operating angle: 10deg
Operating time: 100 hours Operating environment temperature: 80 ° C

(Grease bump test)
The rolling bearing device 6 illustrated in FIGS. 3 to 6 is manufactured, the grease of each example is placed in the grease pocket G of the retainer 32, the continuous operation is performed under the following operating conditions, and the torque immediately after the continuous operation is measured. Evaluation was made according to the following criteria.
≪Operating conditions≫
Operating frequency: 15Hz
Operating angle: 5deg
Operating time: 50 hours Operating environment temperature: Room temperature << Evaluation criteria >>
○: The torque immediately after the continuous operation hardly changes compared to the initial torque before the continuous operation.
X: The torque immediately after the continuous operation changes greatly compared to the initial torque before the continuous operation.

As shown in Table 2, the greases of Examples 1 and 2 containing the component (A) and the component (B) had a small outgas amount and excellent oxidation stability. In Examples 1 and 2, the torque variation was small in both the durability test and the grease bump test, and excellent durability was exhibited.
On the other hand, the rolling bearing grease α of a commercially available information recording / reproducing apparatus cannot sufficiently reduce the amount of outgas, and has insufficient oxidation stability. Further, the grease α had a large torque fluctuation range in the durability test, and the durability was inferior to that of Examples 1 and 2. Furthermore, in the grease bump test, the torque after continuous operation increased up to 6 times compared with the torque before continuous operation. This is considered to be caused by oxidation-degraded grease collecting at the edge of the operation range in the continuous operation to form a bump, or by intense wear at the edge of the operation range in the continuous operation.

  Furthermore, the tendency of oxidation deterioration when the grease of Example 2 and the commercially available grease α were held at 130 ° C. was observed by FT-IR. As a result, the grease α was confirmed to have a tendency to oxidatively deteriorate after 1000 hours, whereas the grease of Example 2 showed no tendency to oxidatively deteriorate after 2000 hours.

<Samples 6 to 41>
An evaluation oil containing the base oil and antioxidant shown in Table 3 was prepared. It added so that content of antioxidant might be 0.2 mass% with respect to the total mass of a base oil and antioxidant. When two kinds of antioxidants were used in combination, they were added so that the total amount was 0.2% by mass.
The refined mineral oils GrIII and PAO (MIX) in Table 3 are the same as those used in Example 1.
“Refined mineral oil GrIII + PAO (MIX)” in Table 3 is a mixture of mineral oil and PAO at a mass ratio of 3: 7, and is the same as the base oil of Example 1.
ADE in Table 3 is alkyl diphenyl ether, and its kinematic viscosity ν ₂ is 100 mm ² / s (40 ° C.).
The PE in Table 3 is pentaerythritol, and its kinematic viscosity ν ₂ is 120 mm ² / s (40 ° C.).
PAO (decene) in Table 3 is a 3 to 5 mer mixture (kinematic viscosity ν ₂ = 30 mm ² / s (40 ° C.)) using an α-olefin having 10 carbon atoms as a raw material.
A-1 and B-1 in Table 3 are the same as the antioxidant used in Example 1. “(A-1) + (B-1)” is a mixture of the two antioxidants, and the mixing ratio is 1: 1 on a mass basis.
A′-1 and B′-1 in Table 3 are the same as those used in Samples 4 and 5.

Looking at Table 3 in a column, P1-A to P6-A, P1-E to P6-E, and P1-F to P6-F are samples according to comparative examples that contain an antioxidant as a comparative component (comparative product). ).
Looking at Table 3 in a column, P1-B to P6-B, P1-C to P6-C, and P1-D to P6-D are in accordance with the examples including the specific antioxidants included in the present invention. Sample (practical product).

  The outgas amount was measured in the same manner as Samples 1-5. The results are shown in Tables 4-9.

(Confirmation of oxidation degradation)
Each sample shown in Table 3 was placed in a beaker (size outer diameter × height: 30 mm × 40 mm) in 5 g, and each beaker was allowed to stand in a constant temperature bath at 100 ° C. After 240 hours, samples in each beaker were measured by FT-IR every 24 hours to evaluate the presence or absence of oxidative degradation. The elapsed time (unit: time (h)) at which oxidative degradation was first confirmed is shown in parentheses below the sample name in Table 10. In addition, about the sample which was not measured, "-" was described in the parenthesis.

(Measurement of evaporation loss)
In a petri dish having an outer diameter of 41 mm (inner diameter of 37 mm) and a height of 8 mm (storage height of 5 mm), 5 g of the grease of Example 2 and Reference Example 1 was put, and the surface was smoothed at 85 ° C., 100 ° C., Each petri dish was allowed to stand in a thermostat set to each temperature of 130 ° C. Each petri dish was taken out at regular intervals, its weight was measured, and evaporation loss (mass%) was calculated from the amount of change. The measurement was stopped when oxidative deterioration became apparent.
The results of the evaporation loss of each grease are shown in FIG. 7 (85 ° C.), FIG. 8 (100 ° C.), and FIG. 9 (130 ° C.) as graphs with elapsed time on the horizontal axis and evaporation loss on the vertical axis. The smaller the evaporation loss, the more stable the grease. As is apparent from the graph, the evaporation loss of Example 2 was smaller than that of Reference Example 1 at any temperature condition.

DESCRIPTION OF SYMBOLS 1 Information recording / reproducing apparatus 2 Swing arm 3 Optical waveguide 4 Laser light source 5 Head gimbal assembly 6 Rolling bearing apparatus 7 Actuator 8 Spindle motor 9 Control part 10 Housing 20 Shaft 21 Sleeve 22 Rolling bearing 30 Inner ring 31 Outer ring 32 Retainer 33 Rolling element 34 Shield Plate B Ball pocket G Grease pocket

Claims (11)

Base oil,
A thickener,
At least one antioxidant selected from the amine-based antioxidant (A) represented by the following general formula (1) and the phenol-based antioxidant (B) represented by the following general formula (2);
A rolling bearing grease characterized by comprising:

(In formula (1), R ¹ and R ² are each independently an alkyl group having 1 to 12 carbon atoms or a hydrogen atom, provided that at least one of R ¹ and R ² has 1 to 12 carbon atoms. The alkyl group of

(In formula (2), R ¹¹ and R ¹² are each independently an alkyl group having 1 to 8 carbon atoms, R ¹³ is an alkylene group having 1 to 8 carbon atoms, and n is 1 to 6). X ¹ is a residue obtained by removing n hydroxyl groups from an aliphatic m-valent alcohol having 1 to 24 carbon atoms, and m is 1 to 6 and is a number of n or more. (However, when n is 5 or 6, the number of carbon atoms of the aliphatic m-valent alcohol represented by X ¹ is 2 to 24.)   The rolling bearing grease according to claim 1, comprising the amine-based antioxidant (A) and the phenol-based antioxidant (B).   The rolling bearing grease according to claim 1 or 2, wherein the amine-based antioxidant (A) is contained in a larger amount on a mass basis than the phenol-based antioxidant (B).   The said base oil contains refined mineral oil classified into the group III in the base oil category which American Petroleum Institute defines, and the flash point of the said refined mineral oil is 240 degreeC or more, Rolling bearing grease according to any one of the above.   The base oil includes refined mineral oil classified as Group III in the base oil category defined by the American Petroleum Institute, and the flash point of the refined mineral oil is 250 ° C or higher. Rolling bearing grease according to any one of the above.   The rolling stock grease according to any one of claims 1 to 5, wherein the base oil contains a mixture of 3 to 5 carbon atoms of an α-olefin having 8 to 12 carbon atoms.   The rolling bearing grease according to claim 1, wherein the grease is used for a rolling bearing of an information recording / reproducing apparatus.   The rolling bearing grease according to claim 1, wherein the grease is for a rolling bearing of an electronic device manufacturing apparatus.   A rolling bearing comprising the rolling bearing grease according to claim 1.   A rolling bearing device comprising a shaft and the rolling bearing according to claim 9.   An information recording / reproducing apparatus comprising the rolling bearing device according to claim 10.

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