JP2002206094A - Lubricant composition, and bearing using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricant composition which can improve the life characteristics of a bearing, reduce the consumed electric power, and the like in a high speed spindle motor. SOLUTION: This lubricant composition contains as a base oil an oil consisting mainly of a fatty acid ester which is represented by the general formula (I) R1-COO-(AO)n-R2... (I) [R1 is a 12 to 24C saturated or unsaturated aliphatic hydrocarbon group; R2 is a 1 to 18C alkyl; A is a 1 to 8C alkylene; (n) is an average value of 1 to 4] and has a kinematic viscosity of 1 to 68 mm2/s at a temperature of 40 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricating oil composition and a bearing using the same. More specifically, the present invention provides a low-viscosity, low-evaporation, and low-hydrolysis fatty acid ester-based base oil that improves bearing life characteristics and reduces power consumption of high-speed spindle motors. And a bearing for a high-speed spindle motor using the same.

[0002]

2. Description of the Related Art Information related equipment [especially CDs, DVDs,
HDDs, laser printers (polygon mirrors, etc.) use spindle motors that have been increasing in speed every year (10,000 ~
(50,000 rotations). In response to such high speeds, fluid bearings, oil-impregnated bearings, etc. are used as spindle motor bearings. In order to improve bearing life, power consumption, and rotational accuracy, various aspects such as structures and mechanisms are used. Has been taken care of. On the other hand, oils used for these bearings are required to have extremely low viscosity in order to minimize power loss during high-speed rotation in terms of power consumption. However, when a low-polarity, low-viscosity base oil, such as a paraffinic mineral oil or a poly-α-olefin, is used, the evaporation loss of the base oil is large at a high-temperature atmosphere at a motor operating temperature or higher, and as a result, This has a significant effect on the life characteristics of the bearing itself. Therefore, as a base oil of a lubricating oil for a bearing of a high-speed spindle motor used in these information-related fields, a base oil having as low a viscosity as possible and having a small evaporation loss is required. By the way, typical slide bearings used in the high-speed spindle motor, that is, fluid bearings and sintered oil-impregnated bearings, are lubricated in a state relatively close to fluid lubrication during high-speed rotation, and contact between the shaft and the bearing is avoided. However, when starting or stopping, the oil film is not sufficiently generated, and contact between the shaft and the bearing is inevitable. In order to maintain a sufficiently low coefficient of friction even in such a state, it is effective to add a friction modifier such as a phosphoric acid ester that acts as an oily and extreme pressure agent. Therefore, as for the base oil used, in addition to low viscosity and low volatility, a stable base oil that is not easily decomposed or polymerized with respect to the added friction modifier is required.

Conventionally, rolling bearings and fluid bearings have been mainly studied for such high-speed spindle motor bearings. In many cases, a low-viscosity base oil is applied or sealed as it is to a bearing oil. (Japanese Patent Laid-Open No. 2000-17955)
No. 2). In addition, techniques using a low-evaporating oil agent (Japanese Patent Application Laid-Open Nos. 2000-156953 and 2000-638)
No. 60) is also disclosed, but since it is assumed to be used for rolling and fluid bearings, the working viscosity for maintaining the dynamic pressure and the oil film is not particularly specified. Furthermore, the fluid bearings of spindle motors used in recent information-related fields are provided with a dynamic pressure generating mechanism such as a herringbone groove in order to improve the rotational accuracy of the bearings. There is concern about friction loss and wear due to metal contact. In addition, in view of recent cost reduction, sintered oil-impregnated bearings that can be mass-produced at low cost are being adopted as bearings for spindle motors used in information-related fields. However, a lubricating oil that sufficiently satisfies the required characteristics of both the fluid bearing and the sintered oil-impregnated bearing has not been found so far.

[0004]

Under such circumstances, the present invention is used for both a fluid bearing and a sintered oil-impregnated bearing, particularly in a high-speed spindle motor, to improve the life characteristics of those bearings. It is another object of the present invention to provide a lubricating oil composition, a lubricating oil composition for a bearing, and the above-mentioned bearing using the lubricating oil composition, which can reduce power consumption.

[0005]

Means for Solving the Problems In order to achieve the above object, the present inventors first paid attention to the following matters.
In consideration of bearing life characteristics and power consumption, it is desirable that the base oil used has as low a viscosity as possible and has a low evaporating property. For this purpose, a low-viscosity polar oil agent (such as an ester) is effective. It is. Regarding measures against friction loss and wear during startup and shutdown, phosphate esters used in sintered oil-impregnated bearing oils that are always in metal contact are superior in terms of oiliness, extreme pressure, and wear resistance. It is known that it exerts an effect. However, when an acidic substance such as a phosphate ester is directly added to the base oil, the phosphate ester itself becomes an accelerating factor, and the ester base oil is easily hydrolyzed or deteriorated. Is required to have a structure that is not easily hydrolyzed. Furthermore, if the ester base oil is hydrolyzed, it is required that the fatty acids generated by the decomposition do not adversely affect the bearing used, such as metal elution and discoloration of the appearance. A base oil that can satisfy these characteristics in a well-balanced manner,
A lubricating oil composition applicable to both fluid bearings and sintered bearings can be provided.

[0006] The present inventors have focused on such a matter,
As a result of further research, it has a specific structure and viscosity range
Oil composition containing base oil mainly composed of fatty acid ester
Oil composition containing a base material, particularly the base oil, and a specific friction modifier
Things have been found to be suitable for that purpose. The present invention
Has been completed based on such knowledge. Sand
In the present invention, a base oil represented by the general formula (I) R¹-COO- (AO)_n-R^Two ... (I) (where R¹Is saturated or unsaturated having 12 to 24 carbon atoms
An aliphatic hydrocarbon group of R ^TwoIs an alkyl having 1 to 5 carbon atoms
Group, A is an alkylene group having 1 to 8 carbon atoms, and n is 1 on average.
The numbers of ~ 4 are shown. ) And at a temperature of 40 ° C.
Kinematic viscosity is 1-68mm^TwoFatty acid esthetics in the range of
Lubricating oil composition characterized by containing
Products, particularly preferably (A) the above base oil, (B) (a)
Phosphates or their amine salts, (ii) sulfur-based extreme pressure
Agents and (c) fatty acids or metal salts thereof.
At least one lubricating oil composition.
You. Further, a lubricating oil composition for bearings comprising the above composition is also used.
To provide. The present invention also provides the lubricating oil composition
It also provides a bearing characterized by using
You.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As the base oil in the lubricating oil composition of the present invention, a fatty acid ester represented by the general formula (I) R ¹ -COO- (AO) _n -R ² (I) is used. What is used as a main component is used. In the general formula (I), R ¹ has 12 to 12 carbon atoms.
Represents 24 saturated or unsaturated aliphatic hydrocarbon groups,
Examples of such a compound include an alkyl group and an alkenyl group having 12 to 24 carbon atoms. The alkyl group and the alkenyl group may be linear, branched, or cyclic, and include, for example, dodecyl, tetradecyl, hexadecyl, octadecyl, icosyl, dodecenyl, tetradecenyl, hexadecenyl, and octadenyl. And an icosenyl group. When R ¹ has less than 12 carbon atoms, when the fatty acid ester is hydrolyzed, the decomposed fatty acid adversely affects the bearing (particularly, discoloration in appearance). On the other hand, those having more than 24 carbon atoms
It is difficult to obtain, and the kinematic viscosity tends to be higher than the above range.

[0008] R^TwoHas 1 to 18 carbon atoms, preferably 1 to 1
2, more preferably 1 to 8 alkyl groups, examples of which
As a methyl group, an ethyl group, an n-propyl group,
Propyl group, n-butyl group, isobutyl group, sec-butyl
Butyl, tert-butyl and various pentyl groups.
I can do it. When the carbon number of the alkyl group is too large,
The viscosity is too high, which is not preferable. A has 1 to 8 carbon atoms
Represents an alkylene group of linear, branched, or cyclic
Deviations, such as methylene groups,
Tylene group, various propylene groups, various butylene groups, various types
Examples include a xylene group and various octylene groups. n is
The numbers 1 to 4 are shown as average values. In the present invention, this fat
The fatty acid ester has a kinematic viscosity at 40 ° C. of 1 to 68 mm.
^Two/ S. This kinematic viscosity is 1
mm^Two/ S, the viscosity is too low and sufficient lubrication performance
Not exhibited, 68mm^Two/ S faster than
It is not suitable for use in dollar motor bearings, and increases power consumption.
Great. Therefore, the preferred kinematic viscosity is 1 to 20 mm^Two
/ S, particularly 1 to 10 mm ^Two/ S range is good
Good.

It is important that the base oil has a low evaporation property and is not easily hydrolyzed. For example, it is preferable that the thin film residual oil ratio at 80 ° C. has the same performance as that of a polyα-olefin having a kinematic viscosity at a temperature of 40 ° C. of 17 mm ² / s and a flash point of 200 ° C. or higher. In order to satisfy such required properties of the base oil, the fatty acid ester is preferably one in which A is an ethylene group and n is 1 or 2, and 2-butoxyethyl oleate is particularly preferable. This can be produced by a known method, for example, by subjecting oleic acid and ethylene glycol to an esterification reaction to obtain 2-hydroxyethyl oleate, and then subjecting the hydroxyl group to butyl etherification. The base oil in the present invention is mainly composed of the above-mentioned fatty acid ester. Here, “mainly composed of a fatty acid ester” means that it is more preferable that the fatty acid ester is a base oil containing 50% by weight or more.

That is, as the base oil, one consisting of the fatty acid ester alone can be used. If the base oil has the above properties, the fatty acid ester 5
A mixture of the fatty acid ester and another base oil containing 0% by weight or more, preferably having a kinematic viscosity at 40 ° C. of 10 m
a mixture of m ² / s or more poly α- olefins can have also used. The lubricating oil composition of the present invention comprises (A) the above-described base oil, (B) (a) a phosphate ester or an amine salt thereof, (b) a sulfur-based extreme pressure agent, and (c) a fatty acid or a metal salt thereof. Those containing at least one kind of friction modifier selected from the following are preferred. The phosphoric acid ester of the component (a) or the phosphoric acid ester of the amine salt thereof in the friction modifier as the component (B) is, for example, a compound represented by the general formula (II):

[0011]

Embedded image

(Wherein, R ³ , R ⁴ and R ⁵ each represent a hydrogen atom or a hydrocarbon group having 4 to 30 carbon atoms, and they may be the same or different. One is a hydrocarbon group having 4 to 30 carbon atoms), or a phosphate represented by the general formula (II
I)

[0013]

Embedded image

(Wherein, R ⁶ , R ⁷ and R ⁸ each represent a hydrogen atom or a hydrocarbon group having 4 to 30 carbon atoms, which may be the same or different, and at least One is a hydrocarbon group having 4 to 30 carbon atoms.). In the general formulas (II) and (III), the hydrocarbon group having 4 to 30 carbon atoms out of R ^{3 to} R ⁸ includes a carbon group having 4 carbon atoms.
And straight-chain, branched or cyclic alkyl or alkenyl groups having up to 30 carbon atoms, aryl groups having 6 to 30 carbon atoms, and arylalkyl groups having 7 to 30 carbon atoms. Specific examples of such a compound include butyl, pentyl, hexyl, cyclohexyl, octyl, decyl, lauryl, myristyl, palmityl, stearyl, oleyl, icosyl, phenyl, xylyl. Benzyl group, phenethyl group and isomers thereof.

Examples of the phosphate represented by the general formula (II) include triphenyl phosphate, tricresyl phosphate, benzyl diphenyl phosphate, tributyl phosphate, cresyl diphenyl phosphate, dicresyl phenyl phosphate, and ethyl phenyl diphenyl. Phosphate, diethyl phenyl phenyl phosphate, propyl phenyl diphenyl phosphate, dipropyl phenyl phenyl phosphate, triethyl phenyl phosphate, tripropyl phenyl phosphate, butyl phenyl diphenyl phosphate, dibutyl phenyl phenyl phosphate, tributyl phenyl phosphate, trihexyl phosphate, tri (2-ethylhexyl) ) Phosphate, tridecyl phosphate, trilauryl Phosphate, trimyristyl phosphate, tripalmityl phosphate, tristearyl phosphate, trioleyl phosphate, 2-
Examples thereof include ethylhexyl acid phosphate, butyl acid phosphate, oleyl acid phosphate, tetracosyl acid phosphate, isodecyl acid phosphate, lauryl acid phosphate, tridecyl acid phosphate, stearyl acid phosphate, and isostearyl acid phosphate. Of these, tricresyl phosphate and oleyl acid phosphate are preferred from the viewpoints of abrasion resistance, low friction coefficient, sludge deposition resistance and the like.

On the other hand, examples of the phosphite represented by the general formula (III) include tributyl phosphite, triphenyl phosphite, tricresyl phosphite,
Tri (nonylphenyl) phosphite, tri (2-ethylhexyl) phosphite, tridecylphosphite,
Trilauryl phosphite, triisooctyl phosphite, diphenylisodecyl phosphite, tristearyl phosphite, trioleyl phosphite, diphenyl hydrogen phosphite or general formula (a) (R ^a O) ₂ POH (a) (wherein, R ^a represents an alkyl group or C 12-30 alkenyl group of 12 to 30 carbon atoms.), and the like dihydroxy hydrocarbyl hydrogen phosphite represented by. In the general formula (a), when the alkyl group or alkenyl group of R ^a has 12 to 30 carbon atoms, the stability is good, sludge is not easily generated, lubricity is good, and the carbon number is 14 to 22. Is preferred. General formula (a)
Examples of the dihydroxycarbyl hydrogen phosphite represented by are dibutyl hydrogen phosphite, dilauryl hydrogen phosphite, dioleyl hydrogen phosphite, distearyl hydrogen phosphite, dipalmityl hydrogen phosphite, and the like. Among them, dioleyl hydrogen phosphite is particularly preferred from the viewpoint of abrasion resistance, low friction coefficient, sludge deposition resistance and the like.

Furthermore, as the amines to form these phosphoric acid esters and amine salts, for example, the general formula _{^{(IV) R 9 m NH 3}} -m ··· (IV) ( wherein, R ⁹ is the number of carbon atoms 3-30 alkyl or alkenyl groups, 6-30 carbon aryl groups, 7-7 carbon atoms
30 arylalkyl group or a hydroxyalkyl group having 2 to 30 carbon atoms, m is an integer of 1 to 3, if R ⁹ is plural, R ⁹ may be the same or different. ), A mono-substituted amine, a di-substituted amine or a tri-substituted amine. In the general formula (IV), the alkyl group having 3 to 30 carbon atoms in R ⁹ may be linear, branched, or cyclic.

Here, examples of the monosubstituted amine include:
Butylamine, pentylamine, hexylamine, cyclohexylamine, octylamine, laurylamine,
Examples include stearylamine, oleylamine, and benzylamine.Examples of disubstituted amines include dibutylamine, dipentylamine, dihexylmian, dicyclohexylamine, dioctylamine, dilaurylamine, distearylamine, dioleylamine, Examples include benzylamine, stearyl monoethanolamine, decyl monoethanolamine, hexyl monopropanolamine, benzyl monoethanolamine, phenyl monoethanolamine, and tolyl monopropanolamine.

Examples of the tri-substituted amine include tributylamine, tripentylamine, trihexylamine, tricyclohexylamine, trioctylamine,
Trilaurylamine, tristearylamine, trioleylamine, tribenzylamine, dioleyl monoethanolamine, dilauryl monopropanolamine, dioctyl monoethanolamine, dihexyl
Monopropanolamine, dibutyl monopropanolamine, oleyl diethanolamine, stearyl
Examples include dipropanolamine, lauryl diethanolamine, octyl dipropanolamine, butyl diethanolamine, benzyl diethanolamine, phenyl diethanolamine, tolyl dipropanolamine, xylyl diethanolamine, triethanolamine, and tripropanolamine. In the present invention, the phosphoric acid esters of component (a) or amine salts thereof may be used alone or in a combination of two or more. The compounding amount is usually selected in the range of 0.01 to 10% by weight based on the total amount of the composition. If this amount is less than 0.01% by weight, when only this component (a) is blended as a friction modifier, the amount may be too small and the friction characteristics may be insufficient. When used together, the synergistic effect tends to result in insufficient improvement of the friction characteristics. On the other hand, if it exceeds 10% by weight, the above effect is not so much improved for the amount, and it is rather disadvantageous economically, which is not preferable. Therefore, the preferable amount of the component (a) is 0.05 to 5.
The range is 0% by weight.

The sulfur-based extreme pressure agent (b) has a sulfur atom in the molecule and can be dissolved or uniformly dispersed in a lubricating base oil, and exhibits extreme pressure properties and good friction characteristics. Is used. Examples of such a substance include sulfurized fats and oils, sulfurized fatty acids, sulfurized esters, sulfurized olefins, dihydrocarbyl polysulfide, thiadiazole compounds, alkylthiocarbamoyl compounds, thiocarbamate compounds, thioterpene compounds, dialkylthiodipropionate compounds, and the like. . The sulfurized fats and oils are sulfur and sulfur-containing compounds and fats and oils (lard oil,
Whale oil, vegetable oil, fish oil, etc.). The sulfur content is not particularly limited, but generally, 5 to 30% by weight is preferably used. Specific examples thereof include sulfurized lard, sulfurized rapeseed oil, sulfurized castor oil, sulfurized soybean oil, and sulfurized rice bran oil. Examples of the above sulfurized fatty acid include sulfurized oleic acid and the like, and examples of the sulfurized ester include methyl sulfurized methyl oleate and sulfide of rice bran fatty acid octyl.

Further, as the sulfurized olefin, the general formula (V) R ¹⁰ -S _a -R ¹¹ ... (V) (wherein, R ¹⁰ is an alkenyl group having 2 to 15 carbon atoms, and R ¹¹ is 2 carbon atoms) To an alkyl group or an alkenyl group of 1 to 15, and a represents an integer of 1 to 8). This compound has 2 to 15 carbon atoms.
Or a di- to tetramer thereof with a sulfurizing agent such as sulfur or sulfur chloride, and the olefin is preferably propylene, isobutene, diisobutene, or the like.

The dihydrocarbyl polysulfide is represented by the general formula (VI) R ¹² -S _b -R ¹³ ... (VI) (wherein R ¹² and R ¹³ are each an alkyl group having 1 to 20 carbon atoms or A cyclic alkyl group, an aryl group having 6 to 20 carbon atoms or an arylalkyl group having 7 to 20 carbon atoms, which may be the same or different, and b represents an integer of 1 to 8). It is a compound represented. Here, when R ¹² and R ¹³ are an alkyl group,
It is called "alkyl sulfide".

R ¹² and R ¹³ in the above formula (VI)
Specific examples of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s
ec-butyl group, tert-butyl group, various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups, various dodecyl groups, cyclohexyl groups, cyclooctyl groups, phenyl groups, naphthyl groups , A tolyl group, a xylyl group, a benzyl group and a phenethyl group. Preferred examples of the dihydrocarbyl polysulfide include dibenzyl polysulfide, various dinonyl polysulfides, various didodecyl polysulfides, various dibutyl polysulfides, various dioctyl polysulfides, diphenyl polysulfide, dicyclohexyl polysulfide, and the like. Examples of the thiadiazole compound include compounds represented by the general formulas (VII), (VIII) and (IX)

[0024]

Embedded image

(Wherein, R ¹⁴ and R ¹⁵ each represent a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and c and d each represent an integer of 0 to 8). , 4-thiadiazole, 1,2,4-thiadiazole, 1,2,
3-Thiadiazole and the like are preferably used. Preferred specific examples of such a thiadiazole compound include:
2,5-bis (n-hexyldithio) -1,3,4-thiadiazole, 2,5-bis (n-octyldithio)-
1,3,4-thiadiazole, 2,5-bis (n-nonyldithio) -1,3,4-thiadiazole, 2,5-bis (1,1,3,3-tetramethylbutyldithio)-
1,3,4-thiadiazole, 3,5-bis (n-hexyldithio) -1,2,4-thiadiazole, 3,5-
Bis (n-octyldithio) -1,2,4-thiadiazole, 3,5-bis (n-nonyldithio) -1,2,4
-Thiadiazole, 3,5-bis (1,1,3,3,-
Tetramethylbutyldithio) -1,2,4-thiadiazole, 4,5-bis (n-hexyldithio) -1,2,2
3-thiadiazole, 4,5-bis (n-octyldithio) -1,2,3-thiadiazole, 4,5-bis (n
-Nonyldithio) -1,2,3-thiadiazole, 4,
5-bis (1,1,3,3, -tetramethylbutyldithio) -1,2,3-thiadiazole and the like can be mentioned. Examples of the alkylthiocarbamoyl compound include compounds represented by general formula (X)

[0026]

Embedded image

(Wherein, R ^{16 to} R ¹⁹ each have 1 carbon atom)
And represents an alkyl group of -20, which may be the same or different, and e represents an integer of 1-8. )). Preferred specific examples of such an alkylthiocarbamoyl compound include bis (dimethylthiocarbamoyl) monosulfide, bis (dibutylthiocarbamoyl) monosulfide, bis (dimethylthiocarbamoyl) disulfide, bis (dibutylthiocarbamoyl) disulfide, and bis (dibutylthiocarbamoyl) disulfide. (Milthiocarbamoyl) disulfide and bis (dioctylthiocarbamoyl) disulfide. Further, examples of the thioterpene compound include a reaction product of phosphorus pentasulfide and pinene, and examples of the dialkylthiodipropionate compound include dilauryl thiodipropionate and distearyl thiodipropionate. Among these sulfur-based extreme pressure agents, sulfurized fats and oils, thiadiazole compounds, and dibenzyl polysulfite are preferred from the viewpoints of extreme pressure properties, friction characteristics, and thermal oxidation stability.

In the present invention, one kind of the sulfur-based extreme pressure agent (b) may be used alone, or two or more kinds thereof may be used in combination. The compounding amount is usually selected in the range of 0.01 to 10% by weight based on the total amount of the composition.
If the amount is less than 0.01% by weight, when only the component (b) is blended as a friction modifier, the amount may be too small and the friction characteristics may be insufficient. When used together, the synergistic effect tends to result in insufficient improvement of the friction characteristics. On the other hand, if it exceeds 10% by weight, the above effect is not so much improved for the amount, and it is economically disadvantageous, which is not preferable. Therefore,
The preferred amount of the component (b) is in the range of 0.05 to 5.0% by weight. Further, as the fatty acid of the component (C) fatty acid or the metal salt thereof, for example, the fatty acid may have 12 to 2 carbon atoms.
5 saturated or unsaturated long-chain fatty acids. Specific examples of the saturated or unsaturated long-chain fatty acid include lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid and the like. Among these, stearic acid and oleic acid are particularly preferable from the viewpoint of the effect.

Preferred examples of the metal salts of the above fatty acids include calcium salts, zinc salts, magnesium salts and aluminum salts. In the present invention,
As the fatty acid or the metal salt thereof as the component (c), one type may be used alone, or two or more types may be used in combination. The compounding amount is usually 0.01 to based on the total amount of the composition.
It is selected in the range of 10% by weight. This amount is 0.01% by weight
If less than the above, when only this component (c) is blended as a friction modifier, the amount may be too small and the friction characteristics may be insufficient, and when used in combination with other friction modifiers,
The improvement of the friction characteristics due to the synergistic effect tends to be insufficient. On the other hand, if it exceeds 10% by weight, the above effect is not so much improved in proportion to the amount, and it is economically disadvantageous, which is not preferable. Therefore, the preferred compounding amount of the component (c) is in the range of 0.05 to 5.0% by weight. In the lubricating oil composition of the present invention, only the component (A) may be used as the friction modifier of the component (B),
Only the component (b) may be used, or only the component (c) may be used. Alternatively, component (a), component (b) and component (c) may be used in an appropriate combination.

The lubricating oil composition of the present invention may contain various additives conventionally used in bearing lubricating oils, such as antioxidants, demulsifiers, etc., as long as the objects of the present invention are not impaired. A rust inhibitor, a metal deactivator, a detergent / dispersant, an antifoaming agent and the like can be appropriately compounded. Here, as the antioxidant, an amine antioxidant or a phenolic antioxidant is preferably used. Examples of the amine-based antioxidant include monooctyldiphenylamine; monoalkyldiphenylamines such as monononyldiphenylamine;
4,4'-dibutyldiphenylamine;4,4'-dipentyldiphenylamine;4,4'-dihexyldiphenylamine;4,4'-diheptyldiphenylamine; 4,
4′-dioctyldiphenylamine; dialkyldiphenylamines such as 4,4′-dinonyldiphenylamine; tetrabutyldiphenylamine; tetrahexyldiphenylamine; tetraoctyldiphenylamine; polyalkyldiphenylamines such as tetranonyldiphenylamine; α-naphthylamine; phenyl-α- Naphthylamine; butylphenyl-α-naphthylamine;
Examples include naphthylamines such as pentylphenyl-α-naphthylamine; hexylphenyl-α-naphthylamine; heptylphenyl-α-naphthylamine; octylphenyl-α-naphthylamine; and nonylphenyl-α-naphthylamine. Among these, dialkyldiphenylamine-based and naphthylamine-based ones are particularly preferable in terms of antioxidant life.

On the other hand, phenolic antioxidants include:
For example, 2,6-di-tert-butyl-4-methylphenol; 2,6-di-tert-butyl-4-ethylphenol, 2,6-di-tert-butyl-4- @ 4,
6-bis (octylthio) -1,3,5-triazine-
Monophenols such as 2-ylamino phenol,
Examples thereof include diphenol-based compounds such as 4,4'-methylenebis (2,6-di-tert-butylphenol); and 2,2'-methylenebis (4-ethyl-6-tert-butylphenol). One of these antioxidants may be used alone, or two or more thereof may be used in combination. The compounding amount is usually in the range of 0.01 to 5.0% by weight based on the total amount of the composition, and is preferably
It is in the range of 0.03 to 3.0% by weight.

Examples of the demulsifier include polyalkylene glycol and metal sulfonate.
Among them, it is preferable to use a polyalkylene glycol which is an EO / PO block copolymer and whose both ends are OH. Examples of the rust inhibitor include metal sulfonates, carboxylic acids, alkanolamines, amides, acid amides, metal salts of phosphoric acid esters, and the like. Among them, the use of carboxylic acids is preferred. Further, as the metal deactivator, benzotriazole and the like, and as the detergent and dispersant, metal sulfonate, metal finate, metal salicylate, metal phosphonate, succinimide, acid amide, and the like. Is methyl silicone oil,
Examples thereof include fluorosilicone oil and polyacrylate, and among them, methyl silicone oil is particularly preferable.

The lubricating oil composition of the present invention is particularly suitable for lubricating oil for bearings. The present invention also provides a bearing using the above lubricating oil composition, particularly a fluid bearing and a sintered oil-impregnated bearing of a spindle motor. The bearing of the present invention,
By using the lubricating oil composition, the shaft loss (sliding resistance, viscous resistance) is small and the durability is excellent in any state of starting, stopping, and operating the motor. The spindle motor equipped with the bearing of the present invention can be suitably used particularly for information-related equipment such as HDDs, laser printers (polygon mirror motors), CDs, and DVDs.

[0034]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Various properties of the base oil alone were measured according to the following methods. (1) Hydrolysis characteristics 75 g of sample oil, 25 g of distilled water and a weighed copper plate are put in a glass bottle and sealed. This glass bottle is put in a thermostat kept at 93 ° C., and is rotated at 5 rpm for 48 hours in a direction in which it is turned upside down once during one rotation. After the test, the weight loss of the copper plate (copper elution amount) and the discoloration state of the copper plate (copper plate corrosion) are examined. Further, the oil layer and the aqueous layer are separated, and the oil layer measures kinematic viscosity and total acid value increase, and the aqueous layer measures pH and the like. Test equipment and instruments Thermostatic layer: Use a thermostat that can be adjusted to 93 ± 0.5 ° C. 2. Rotating device: A device that can rotate at a speed of 5 rpm in a direction in which the glass bottle is once turned upside down in one rotation in a thermostat. 3. Glass bottle (sterile bottle): Pressure-resistant glass bottle. Capacity about 20
Use 0 ml. 4. Glass bottle lid: Use a polycarbonate bottle. 5. Glass bottle gasket: Use a silicone rubber gasket. (2) Viscosity index (VI) Measured according to JIS K2283. (3) Flash point Measured using a Cleveland flash point tester (COC) according to JIS K2265. Various properties of the lubricating oil composition were measured according to the following methods. (4) Thin Film Residual Oil Ratio The amount of residual oil at 80 ° C. for 24 hours was measured using a container and a constant-temperature air bath indicated in the lubricating oil thermal stability test of JIS K2540, with a sample amount of 1 g. It was expressed as a percentage and used as the residual oil ratio. During the measurement, keep air at 1
0 l / hr was poured. (5) Pendulum type oiliness test A pendulum type oiliness test was performed at room temperature in accordance with JASO M314-88, section 6.13, and the friction coefficient [μ] was measured. (6) Shell abrasion test A shell abrasion test was performed under the conditions of a rotational speed of 1200 rpm, a load of 392 N, a temperature of 80 ° C. and a time of 60 minutes, and the wear scar diameter was measured to determine the wear resistance. (7) Copper plate half-immersion test Evaluate by the Idemitsu type copper plate half-immersion test. That is, a 50 ml screw bottle having an outer diameter of 40 mm and a height of 75 mm and a lid suitable for the container are used as containers. As a test agent, oil agent 10g
1% by weight of distilled water and mixed with stirring. As the copper plate, a material defined by JIS H3100 and having a size of 13 × 51 × 1 mm is used. For this, the surface of the polishing paper is polished in advance with E2401. As a test method, a copper plate is put in the above-mentioned container, and the test agent is put in a 10 g container so that the test agent is applied to the entire copper plate. Place the copper plate on the side of the container and cover it. This is allowed to stand in a thermostat at 60 ° C. for 7 days, and the gas phase portion not in contact with the liquid surface of the copper plate is evaluated by appearance. Suitability is determined by the presence or absence of green products typified by fatty acid copper. Examples 1 to 5 and Comparative Examples 1 to 7 Lubricating oil compositions having the composition shown in Table 2 were prepared, and various properties were determined. The results are shown in Table 2. Table 1 shows the properties of the base oil used alone.

[0035]

[Table 1]

[0036]

[Table 2]

(Note) 2-butoxyethyl oleate (BEO) dioctyl adipate (DOA) diisononyl adipate (DINA) neopentyl glycol ester (NPG) trimethylolpropane ester (TMP) butyl stearate (BS) butyl oleate (BO) ) Poly α-olefin (poly (1-decene)) (PAO)

[0038]

[Table 3]

[0039]

[Table 4]

[0040]

[Table 5]

As can be seen from Table 1, BEO (2-butoxyethyl oleate) used as a base oil of the lubricating oil composition of the present invention (Examples 1 to 5) has a low viscosity, a high flash point,
It has a high viscosity index and is less susceptible to hydrolysis. Second
From the table, it can be seen that the lubricating oil composition of the present invention has low viscosity and low evaporability as compared with those of the comparative examples, has little influence on metal (copper), and satisfies each property in a well-balanced manner. . In Example 1, when dioleyl hydrogen phosphite was not blended, the friction coefficient [μ] increased from 0.92 to 0.125 in the pendulum type oiliness test, and the wear scar diameter was reduced in the shell wear test. 0.41m
from 0.5m to 0.57m. In Comparative Example 2, when no dioleyl hydrogen phosphite was blended,
In the pendulum type oiliness test, the coefficient of friction [μ] increased from 0.94 to 0.130, and in the shell abrasion test, the wear scar diameter increased from 0.45 mm to 0.59 mm.

[0042]

The lubricating oil composition of the present invention is particularly suitable as a lubricating oil for bearings, and is particularly applicable to both fluid bearings and sintered oil-impregnated bearings of high-speed spindle motors. In addition, the lubricating oil composition of the present invention has an extremely low-viscosity and low-evaporation base oil and a friction modifier, so that the shaft loss of the bearing (whether the motor is started, stopped, or operated) is reduced. Sliding resistance, viscous resistance) can be reduced, durability can be improved, and power consumption can be reduced. In particular, scanner motor for LBP, D
C main motor, DC brushless motor, or spindle motor for AV equipment, CD, DVD, HD
It is used as a high-performance motor such as a spindle motor for D, and as a bearing for various fan motors. The durability and reliability of those motors can be improved, and power consumption and maintenance costs can be reduced.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C10M 135/22 C10M 135/22 135/26 135/26 135/36 135/36 137/04 137/04 137 / 08 137/08 F16C 33/10 F16C 33/10 Z // C10N 10:04 C10N 10:04 10:06 10:06 20:02 20:02 30:00 30:00 Z 30:02 30:02 40 : 02 40:02

Claims (11)

[Claims] 1. A base oil of the general formula (I) R¹-COO- (AO)_n-R^Two ... (I) (where R¹Is saturated or unsaturated having 12 to 24 carbon atoms
An aliphatic hydrocarbon group of R ^TwoIs alkyl having 1 to 18 carbon atoms
Group, A is an alkylene group having 1 to 8 carbon atoms, and n is 1 on average.
The numbers of ~ 4 are shown. ) And at a temperature of 40 ° C.
Kinematic viscosity is 1-68mm^TwoFatty acid esthetics in the range of
Lubricating oil composition characterized by containing
object. 2. The lubricating oil composition according to claim 1, wherein A is an ethylene group and n is 1 or 2 in the general formula (I). 3. The lubricating oil composition according to claim 2, wherein the fatty acid ester is 2-butoxyethyl oleate. 4. A base oil, (B) at least one selected from (B) a phosphate ester or an amine salt thereof, (B) a sulfur-based extreme pressure agent, and (C) a fatty acid or a metal salt thereof. The lubricating oil composition according to claim 1, 2 or 3, comprising one kind. 5. The phosphoric acid ester of the component (B) (a) or the amine salt thereof is tricresyl phosphate, oleyl acid phosphate or a compound of the formula (a) (R ^a O) ₂ POH. 5. The lubrication according to claim 4, wherein the lubrication is dihydroxycarbyl hydrogen phosphite represented by (a) wherein R ^a represents an alkyl group having 12 to 30 carbon atoms or an alkenyl group having 12 to 30 carbon atoms. Oil composition. 6. The lubricating oil composition according to claim 4, wherein the sulfur-based extreme pressure agent as the component (B) (b) is a sulfurized fat or oil, a thiadiazole compound or dibenzyl polysulfide. 7. The fatty acid of component (B) (c) or the metal salt thereof, wherein the fatty acid is stearic acid or oleic acid, and the metal salt is a calcium salt, a zinc salt, a magnesium salt or an aluminum salt. Lubricating oil composition. 8. The lubricating oil composition according to claim 1, wherein the base oil is a fatty acid ester represented by the general formula (I) and having a kinematic viscosity at a temperature of 40 ° C. of 1 to 10 mm ² / s. . 9. The fatty acid ester represented by the general formula (I) containing at least 50% by weight of a fatty acid ester having a kinematic viscosity at a temperature of 40 ° C. of 1 to 10 mm ² / s and a temperature of 40 ° C. The lubricating oil composition according to claim 1, 2 or 3, which is a mixture with a poly-α-olefin having a kinematic viscosity of 10 mm ² / s or more. 10. The lubricating oil composition according to claim 1, which is a lubricating oil for bearings. 11. A bearing using the lubricating oil composition according to any one of claims 1 to 9.