JP2007211234A - Lubricating oil composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lubricating oil composition having excellent viscosity characteristics of having good low-temperature fluidity, viscosity maintaining the rigidity even at a high-temperature region, and low viscosity at low temperature, further having low volatility at high temperature, energy-saving property and heat-resistant stability, and suitable for a compact fluid bearing or a porous substance-containing oil bearing used at high-speed rotation. <P>SOLUTION: The lubricating oil composition contains a tetraalkylsilane represented by general formula (I) (wherein, R<SP>1</SP>, R<SP>2</SP>, R<SP>3</SP>and R<SP>4</SP>are each a 2-16C linear saturated hydrocarbon, are the same or different, and are regulated so that the total of the number of the carbons may be 28-40) as a base oil, and has ≥2.0 mPa s viscosity at 100°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lubricating oil composition, and more specifically, a low-viscosity fluid having a high viscosity index, excellent low-temperature fluidity, low evaporation, energy saving, and the like, and is used at high speed rotation. The present invention relates to a lubricating oil composition suitable for a bearing and a porous oil-impregnated bearing.

Conventionally, in motors mounted on hard disk drives and the like, ball bearings and roller bearings have been used as bearings. However, due to demands for motor miniaturization, low vibration and low noise, fluid bearings and porous oil-impregnated bearings in recent years. Has been developed and put to practical use.
The hydrodynamic bearing supports the rotating shaft by the oil film pressure of the lubricating oil interposed in the gap between the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve, and the dynamic pressure is applied to at least one of the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve. A groove is provided, and the sliding surface of the rotary shaft is levitated and supported by a lubricating oil film formed by the dynamic pressure effect.
Also, a porous body made of sintered metal or the like is impregnated with lubricating oil or lubricating grease to have a self-lubricating function, and a porous oil-impregnated bearing that supports the rotating shaft. Further, the bearing surface of the porous oil-impregnated bearing A dynamic pressure type porous oil-impregnated bearing provided with a dynamic pressure groove is also used in the rotating device.
Since these do not have ball bearings, they are suitable for miniaturization and weight reduction, and are excellent in quietness and economy, and demand for personal computers, audio equipment, visual equipment, car navigation systems, etc. Has increased.
Viscosity characteristics such as low viscosity in the low temperature range, good low temperature fluidity, and low viscosity drop in the high temperature range for lubricating oils used in such fluid bearings and porous oil-impregnated bearings , And low evaporation is required.

Furthermore, in the future, it is expected that demands for high-speed processing of large-capacity information and further downsizing of devices will increase. As described above, fluid bearings and porous oil-impregnated bearings are required to rotate at higher speeds with the demand for high-speed processing of information or downsizing of equipment, and the energy loss in bearings increases as the speed increases. Become.
Furthermore, the use in harsh environments is also expanding in places where various information processors are used. In particular, a device such as a car navigation system used in a car must be able to withstand use from a cold region to a hot sun in consideration of the use environment of the car. Therefore, it is required that the lubricating oil for bearings used in vehicle equipment can be used without problems in a wide temperature range of −40 to 80 ° C.
In other words, in addition to basic performance such as lubricity, deterioration stability (lifetime), sludge generation prevention, wear prevention, and corrosion prevention, the bearing lubricant has good low temperature fluidity and high temperature range. In addition, it is desirable to have an excellent viscosity characteristic such as low viscosity reduction, low evaporation, energy saving (low power consumption), and heat resistance stability.
Conventionally, as a lubricating oil for bearings, those using poly α-olefin oil (PAO) or dioctyl sebacate (DOS) as a base oil have been used, but high-speed processing of information, downsizing of equipment, etc. Thus, polyol esters have been used in recent years.

Examples of the fluid bearing lubricating oil using a polyol ester as the base oil include (1) polyhydric alcohols such as hexamethylene glycol, neopentyl glycol, decamethylene glycol, pentaerythritol, trimethylolpropane, heptanoic acid, octane, and the like. A mixture of a polyol ester oil obtained by reacting a fatty acid having 5 to 20 carbon atoms such as acid, nonanoic acid or decanoic acid with a diester oil such as dioctyl adipate or dioctyl sebacate is used as a base oil. A fluid bearing lubricant (see, for example, Patent Document 1), a lubricant for a fluid bearing using, as a base oil, an ester of trimethylolpropane and at least two mixed acids of monovalent fatty acids having 4 to 8 carbon atoms. (See, for example, Patent Document 2).
However, the fluid bearing lubricating oil using the above-mentioned polyol ester as a base oil does not necessarily satisfy the above-mentioned required characteristics, and it has an ester bond, so that it is easily hydrolyzed and is metallic. It has problems such as the possibility of corroding the material.
On the other hand, what consists of phenyl trialkylsilane (refer patent document 3) is known as what uses tetraalkylsilane as a lubricant composition. However, there is a problem that the viscosity index is low and the low-temperature viscosity is too high, which is not suitable for a fluid bearing lubricating oil.

JP 2001-279284 A JP 2004-91524 A Japanese Patent Laid-Open No. 05-112788

  The present invention has excellent viscosity characteristics such as good low-temperature fluidity and the ability to maintain rigidity even in a high-temperature range, low-temperature viscosity, etc., low evaporation at high temperatures, energy-saving properties and An object of the present invention is to provide a lubricating oil composition having heat resistance stability and suitable for a compact fluid bearing or porous oil-impregnated bearing used at high speed rotation.

As a result of intensive studies to develop a lubricating oil composition having the above-mentioned excellent performance, the present inventors have included a specific tetraalkylsilane as a base oil and a viscosity at a temperature of 100 ° C. It has been found that lubricating oil compositions above a certain value can be adapted to that purpose. The present invention has been completed based on such findings.
That is, the present invention
(1) A lubricating oil composition comprising a tetraalkylsilane represented by general formula (I) as a base oil and having a viscosity at a temperature of 100 ° C. of 2.0 mPa · s or more,

(In the formula, R ¹ , R ² , R ³ and R ⁴ each represent a straight-chain saturated hydrocarbon group having 2 to 16 carbon atoms, and may be the same or different, and the total carbon number of R ^{1 to} R ⁴ Is 28-40.)
(2) The lubricating oil composition according to (1), which comprises a phenolic and / or amine antioxidant,
(3) The lubricating oil composition according to (1) or (2), comprising a lubricity improver and / or a conductive additive,
(4) The lubricating oil composition according to any one of (1) to (3), wherein the evaporation loss after heat treatment at a temperature of 150 ° C. is 1.5% by mass or less,
(5) The lubricating oil composition according to any one of (1) to (4), wherein the viscosity at a temperature of −20 ° C. is 150 mPa · s or less and the pour point is −50 ° C. or less.
(6) The lubricating oil composition according to any one of (1) to (5), wherein the volume resistivity is 1 × 10 ¹⁰ Ω · cm or less in the substantial absence of metal particles or metal oxide particles,
(7) Bearing oil comprising the lubricating oil composition according to any one of (1) to (6),
(8) A bearing using the bearing oil according to (7),
(9) The bearing according to (8), which is a hydrodynamic bearing, an oil-impregnated bearing, an oil-impregnated bearing or a porous oil-impregnated bearing provided with a dynamic pressure groove, and (10) The description according to (8) or (9) Information processing equipment comprising a bearing unit having a bearing of
I will provide a.

  According to the present invention, it has excellent low temperature fluidity and excellent viscosity characteristics such as low viscosity decrease even in a high temperature range, as well as low evaporation, energy saving and heat stability, and high speed rotation. And a lubricating oil composition suitable for a compact fluid bearing and a porous oil-impregnated bearing, particularly a fluid bearing.

  The lubricating oil composition of the present invention needs to be a lubricating oil composition containing a specific tetraalkylsilane as a base oil and having a viscosity at a temperature of 100 ° C. of a certain value or more. The tetraalkylsilane is a tetraalkylsilane represented by the general formula (I).

In the formula, R ¹ , R ² , R ³ and R ⁴ each represent a linear saturated hydrocarbon having 2 to 16 carbon atoms, and may be the same or different, and the total carbon number of R ^{1 to} R ⁴ is 28. It is selected from a combination of ˜40, more preferably 28˜32.
When the total number of carbon atoms is in the range of 28 to 40, as a lubricating oil composition for fluid bearings and a lubricating oil composition for porous oil-impregnated bearings, low volatility, suitability for viscosity at high to low temperatures, low pour point These are suitable for these bearings and can be suitably used as a lubricating oil for bearings.
Examples of the straight chain and saturated hydrocarbon having 2 to 16 carbon atoms include ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, and tridecyl. Group, tetradecyl group, pentadecyl group and hexadecyl group.
More specifically, the combination of R ^{1 to} R ⁴ is more specifically R ¹ is a decyl group or dodecyl group, R ² , R ³ and R ⁴ are all hexyl groups, or R ¹ and R ² are both ethyl groups, R ³ and R ⁴ may be a combination such as a dodecyl group.

In the lubricating oil composition of the present invention, other base oil is optionally added in an amount of 50% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less, as long as the effects of the present invention are not impaired. Preferably it can be made to contain in the ratio of 10 mass% or less.
Examples of other base oils include mineral oils, poly α-olefin oils, and ester oils such as diesters and polyol esters.

The lubricating oil composition of the present invention has a viscosity at a temperature of 100 ° C. of 2.0 mPa · s or more and does not cause shaft shake. When the viscosity is 2.0 mPa · s or more, the bearing has good bearing rigidity even when used at a high temperature, can sufficiently support the rotating sleeve body, and has good durability. The upper limit of the viscosity at 100 ° C. is usually about 3.5 mPa · s.
The viscosity at a temperature of −20 ° C. is preferably 150 mPa · s or less, and the driving torque at low temperature is preferably small. If the viscosity is 150 mPa · s or less, the lubricating performance can be sufficiently exhibited even in a low temperature environment. In general, the lower the viscosity at −20 ° C., the better.
The viscosity is a value measured according to JIS K2283.
Furthermore, the pour point measured according to JIS K2269 is preferably −50 ° C. or lower, and more preferably −55 ° C. or lower. When the pour point is −50 ° C. or lower, the device operates well even when used in a low temperature range.
In the lubricating oil composition of the present invention, the evaporation loss after heat treatment at a temperature of 150 ° C. for 168 hours is preferably 1.5 mass% or less. If the evaporation loss is 1.5% by mass or less, the lubricating performance can be exhibited stably for a long period of time. The evaporation loss is more preferably 1.0% by mass or less. The evaporation loss is a value measured according to JIS C2101.

In the lubricating oil composition of the present invention, various additives such as an antioxidant, a lubricity improver, a conductive additive, a rust inhibitor, a metal deactivator, as long as the effects of the present invention are not impaired. An antifoaming agent, a viscosity index improver, etc. can be contained as desired.
Examples of the antioxidant include amine-based antioxidants, phenol-based antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants.
Examples of the amine antioxidant include monoalkyl diphenylamines such as monooctyl diphenylamine and monononyl diphenylamine, 4,4-'dibutyldiphenylamine, 4,4'-dipentyldiphenylamine, 4,4'-dihexyldiphenylamine, 4, Dialkyldiphenylamines such as 4′-diheptyldiphenylamine, 4,4′-dioctyldiphenylamine, 4,4′-dinonyldiphenylamine, 4,4′-bis (α, α-dimethylbenzyl) diphenylamine, tetrabutyldiphenylamine, tetra Polyalkyldiphenylamines such as hexyldiphenylamine, tetraoctyldiphenylamine, tetranonyldiphenylamine, α-naphthylamine, phenyl-α-naphthylamine, butylphenyl-α- Examples include naphthylamines such as phthalylamine, pentylphenyl-α-naphthylamine, hexylphenyl-α-naphthylamine, heptylphenyl-α-naphthylamine, octylphenyl-α-naphthylamine, and nonylphenyl-α-naphthylamine. Among them, dialkyldiphenylamine Those are preferred.

Examples of the phenol-based antioxidant include 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, and octadecyl-3- (3,5-diphenyl). Monophenols such as -t-butyl-4-hydroxyphenyl) propionate, 4,4'-methylenebis (2,6-di-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-) And bisphenol-based compounds such as butylphenol.
Examples of the sulfur-based antioxidant include phenothiazine, pentaerythritol-tetrakis- (3-laurylthiopropionate), bis (3,5-di-tert-butyl-4-hydroxybenzyl) sulfide, thiodiethylenebis ( 3- (3,5-di-tert-butyl-4-hydroxyphenyl)) propionate, 2,6-di-tert-butyl-4- (4,6-bis (octylthio) -1,3,5-triazine -2-methylamino) phenol and the like.
Examples of phosphorus antioxidants include diethyl [[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] phosphonate.
The antioxidants may be used singly or in combination of two or more, and among them, phenol-based and / or amine-based antioxidants are preferable.
The preferable compounding quantity of these antioxidants is the range of 0.01-10 mass% on the basis of the total amount of the composition, and the range of 0.03-5 mass% is particularly preferable.

As the lubricity improver, an oily agent or a friction modifier can be used.
Examples of the oily agent include aliphatic saturated and unsaturated monocarboxylic acids such as stearic acid and oleic acid, polymerized fatty acids such as dimer acid and hydrogenated dimer acid, hydroxy fatty acids such as ricinoleic acid and 12-hydroxystearic acid, Aliphatic saturated and unsaturated monoalcohols such as lauryl alcohol and oleyl alcohol, aliphatic saturated and unsaturated monoamines such as stearylamine and oleylamine, aliphatic saturated and unsaturated monocarboxylic amides such as lauric acid amide and oleic acid amide, etc. Is mentioned.
The preferable compounding amount of these oily agents is in the range of 0.01 to 10% by mass, particularly preferably in the range of 0.1 to 5% by mass based on the total amount of the composition.

Moreover, as an example of a friction modifier, what is generally used as an extreme pressure agent can be used, Especially the phosphate salt, the amine salt of phosphate ester, and a sulfur type extreme pressure agent are mentioned.
Examples of phosphoric acid esters include phosphoric acid esters, acidic phosphoric acid esters, phosphorous acid esters, and acidic phosphorous acid esters represented by the following general formulas (II) to (VI).

In the general formulas (II) to (VI), R ^{6 to} R ⁸ represent an alkyl group, alkenyl group, alkylaryl group and arylalkyl group having 4 to 30 carbon atoms, and R ^{6 to} R ⁸ are the same or different. May be.
Examples of the phosphate ester include triaryl phosphate, trialkyl phosphate, trialkylaryl phosphate, triarylalkyl phosphate, trialkenyl phosphate, and the like, for example, triphenyl phosphate, tricresyl phosphate, benzyldiphenyl phosphate, ethyl diphenyl phosphate, Tributyl phosphate, ethyl dibutyl phosphate, cresyl diphenyl phosphate, dicresyl phenyl phosphate, 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 Examples include sulfate, dibutylphenylphenyl phosphate, tributylphenyl phosphate, trihexyl phosphate, tri (2-ethylhexyl) phosphate, tridecyl phosphate, trilauryl phosphate, trimyristyl phosphate, tripalmityl phosphate, tristearyl phosphate, trioleyl phosphate be able to.

Examples of the acidic phosphate ester include 2-ethylhexyl acid phosphate, ethyl acid phosphate, butyl acid phosphate, oleyl acid phosphate, tetracosyl acid phosphate, isodecyl acid phosphate, lauryl acid phosphate, tridecyl acid phosphate, stearyl acid phosphate , Isostearyl acid phosphate and the like.
Examples of phosphites include triethyl phosphite, tributyl phosphite, triphenyl phosphite, tricresyl phosphite, tri (nonylphenyl) phosphite, tri (2-ethylhexyl) phosphite, tridecyl phosphite, Examples include trilauryl phosphite, triisooctyl phosphite, diphenylisodecyl phosphite, tristearyl phosphite, and trioleyl phosphite.

Examples of the acidic phosphite include dibutyl hydrogen phosphite, dilauryl hydrogen phosphite, dioleyl hydrogen phosphite, distearyl hydrogen phosphite, and diphenyl hydrogen phosphite. Of the above phosphoric esters, tricresyl phosphite and triphenyl phosphate are preferred.
Furthermore, examples of amines that form amine salts with these include, for example, general formula (VII)
R ⁹ _p -NH _2-p (VII)
(In the formula, R ⁹ represents an alkyl group or alkenyl group having 3 to 30 carbon atoms, an aryl group or arylalkyl group having 6 to 30 carbon atoms, or a hydroxyalkyl group having 2 to 30 carbon atoms; or an 3. also, if R ⁹ is plural, R ⁹ may be the same or different.)
And mono-substituted amines, di-substituted amines, and tri-substituted amines. The alkyl group or alkenyl group having 3 to 30 carbon atoms in R ⁹ in the general formula (VII) may be linear, branched or cyclic.

  Examples of monosubstituted amines include butylamine, pentylamine, hexylamine, cyclohexylamine, octylamine, laurylamine, stearylamine, oleylamine, benzylamine, etc. Examples of disubstituted amines include dibutylamine, Dipentylamine, dihexylamine, dicyclohexylamine, dioctylamine, dilaurylamine, distearylamine, dioleylamine, dibenzylamine, stearyl monoethanolamine, decyl monoethanolamine, hexyl monopropanolamine, benzyl monoethanolamine , Phenyl monoethanolamine, tolyl monopropanol and the like. Examples of tri-substituted amines include tributylamine, tripentylamine. , Trihexylamine, tricyclohexylamine, trioctylamine, trilaurylamine, tristearylamine, trioleylamine, tribenzylamine, dioleyl monoethanolamine, dilauryl monopropanolamine, dioctyl monoethanolamine, dihexyl monopropanolamine , Dibutyl monopropanolamine, oleyl diethanolamine, stearyl dipropanolamine, lauryl diethanolamine, octyl dipropanolamine, butyl diethanolamine, benzyl diethanolamine, phenyl diethanolamine, tolyl dipropanolamine, xylyl diethanolamine, triyl Ethanolamine, tripropanolamine, etc. .

  Any sulfur-based extreme pressure agent may be used as long as it has a sulfur atom in the molecule and can be dissolved or uniformly dispersed in the lubricating base oil to exhibit extreme pressure properties and excellent friction characteristics. Examples of such compounds include sulfurized fats and oils, sulfurized fatty acids, sulfurized esters, sulfurized olefins, dihydrocarbyl polysulfides, thiadiazole compounds, thiophosphates (thiophosphites, thiophosphates), alkylthiocarbamoyl compounds, thiocarbamate compounds, thioterpene compounds. And dialkylthiodipropionate compounds. Here, sulfurized fats and oils are obtained by reacting sulfur and sulfur-containing compounds with fats and oils (lard oil, whale oil, vegetable oil, fish oil, etc.), and the sulfur content is not particularly limited, but generally 5 to 30 mass. % Is preferred. Specific examples thereof include sulfurized lard, sulfurized rapeseed oil, sulfurized castor oil, sulfurized soybean oil, and sulfurized rice bran oil. Examples of the sulfurized fatty acid include sulfurized oleic acid, and examples of the sulfurized ester include sulfurized methyl oleate and sulfurized rice bran fatty acid octyl.

As the sulfurized olefin, for example, the following general formula (VIII)
R ¹⁰ -S _q -R ¹¹ (VIII)
(In the formula, R ¹⁰ represents an alkenyl group having 2 to 15 carbon atoms, R ¹¹ represents an alkyl group or alkenyl group having 2 to 15 carbon atoms, and q represents an integer of 1 to 8)
The compound etc. which are represented by these can be mentioned. This compound is obtained by reacting an olefin having 2 to 15 carbon atoms or a dimer to tetramer thereof with a sulfurizing agent such as sulfur or sulfur chloride. As the olefin, propylene, isobutene, diisobutene and the like are preferable.
As dihydrocarbyl polysulfide, the following general formula (IX)
R ¹² -S _r -R ¹³ (IX)
(In the formula, 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, an alkylaryl group having 7 to 20 carbon atoms, or 7 to 20 carbon atoms. An arylalkyl group, which may be the same or different from each other, and r represents an integer of 1 to 8.
It is a compound represented by these. Here, when R ¹² and R ¹³ are alkyl groups, they are referred to as alkyl sulfides.

R ¹² and R ¹³ in the general formula (IX) are methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-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, tolyl groups, xylyl groups, benzyl groups, phenethyl groups, etc. Can be mentioned.
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.
As the thiadiazole compound, for example, the following general formula (X)

(In the formula, R ¹⁴ and R ¹⁵ each represent a hydrogen atom and a hydrocarbon group having 1 to 20 carbon atoms, and f and g each represents an integer of 0 to 8)
1,3,4-thiadiazole, 1,2,4-thiadiazole compound, 1,4,5-thiadiazole and the like are preferably used.
Examples of the thiadiazole compound include 2,5-bis (n-hexyldithio) -1,3,4-thiadiazole, 2,5-bis (n-octyldithio) -1,3,4-thiadiazole, 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) -1,2,3- Thiadiazole, 4,5- Sus (n-octyldithio) -1,2,3-thiadiazole, 4,5-bis (n-nonyldithio) -1,2,3-thiadiazole, 4,5-bis (1,1,3,3-tetra Preferable examples include methylbutyldithio) -1,2,3-thiadiazole.
Examples of the thiophosphate include alkyl trithiophosphate, aryl or alkylaryl thiophosphate, zinc dilauryl dithiophosphate, and lauryl trithiophosphate and triphenyl thiophosphate are particularly preferable.
Examples of the alkylthiocarbamoyl compound include the following general formula (XI)

(Wherein R ^{16 to} R ¹⁹ each represent an alkyl group having 1 to 20 carbon atoms, and h represents an integer of 1 to 8)
Examples of the alkylthiocarbamoyl compound include bis (dimethylthiocarbamoyl) monosulfide, bis (dibutylthiocarbamoyl) monosulfide, bis (dimethylthiocarbamoyl) disulfide, bis (dibutylthiocarbamoyl) disulfide, and bis (diamilthiocarbamoyl). Preferred examples include disulfide and bis (dioctylthiocarbamoyl) disulfide.

Further, as the thiocarbamate compound, for example, zinc dialkyldithiocarbamate, as the thioterpene compound, for example, a reaction product of phosphorus pentasulfide and pinene, and as the dialkylthiodipropionate compound, for example, dilaurylthiodipropionate. And distearyl thiodipropionate. Of these, thiadiazole compounds and benzyl sulfide are preferable from the viewpoints of extreme pressure, friction characteristics, thermal oxidation stability, and the like.
The preferable compounding amount of these friction modifiers is in the range of 0.01 to 10% by mass, particularly preferably in the range of 0.05 to 5% by mass, based on the total amount of the composition.

The lubricating oil composition of the present invention preferably has a volume resistivity of 1 × 10 ¹⁰ Ω · cm or less substantially in the absence of metal particles or metal oxide particles. When the volume resistivity is 1 × 10 ¹⁰ Ω · cm or less, the lubricating oil composition has good antistatic performance. The lower limit of the volume resistivity is not particularly limited, but is usually about 1 × 10 ⁷ Ω · cm. The volume resistivity is a value measured according to JIS C2101.
The lubricating oil composition of the present invention may contain a conductive additive in order to make the volume resistivity 1 × 10 ¹⁰ Ω · cm or less. As the conductive additive, amine derivatives, succinic acid derivatives, poly (oxyalkylene) glycols or partial esters of polyhydric alcohols, which are nonmetallic antistatic agents, are preferable. In this case, the addition amount is based on the total amount of the composition 0.01 to 10% by mass is preferable. Specifically, as the amine derivative, poly (oxyethylene) alkylamine of the following formula (XII) (wherein R ²⁰ is an alkyl group having 1 to 18 carbon atoms),

Poly (oxyethylene) alkylamide of the following formula (XIII) (wherein R ²¹ is an alkyl group having 1 to 18 carbon atoms),

Examples include a reaction condensate using polyethyleneimine such as tetraethylenepentamine (TEPE) and a fatty acid, and a reaction condensate of TEPE and stearic acid is preferable. Moreover, as a succinic acid derivative, polybutenyl succinimide etc. are mentioned preferably.
Moreover, as poly (oxyalkylene) glycol, the compound represented by the following general formula (XIV) or its mixture is preferable.
R ²² —O— (R ²³ —O) _d — (R ²⁴ —O) _e — (R ²⁵ —O) _f —R ²⁶ (XIV)
(XIV) In the formula, each of R ²² and R ²⁶ independently represents hydrogen, an alkyl group having 1 to 24 carbon atoms, a phenyl group, or an alkylaryl group having 7 to ²⁴ carbon atoms, and R ²³ , R ²⁴ and R ²⁵ each independently represents an alkylene group having 2 to 18 carbon atoms, d, e and f each independently represents a number of 0 to 50, and the total of d to f is 9 to 50. (R ²³ —O), (R ²⁴ —O) and (R ²⁵ —O) may be the same or different for each structural unit.
Of these compounds, poly (oxyethylene) alkyl ether R ²⁷ O (CH ₂ CH ₂ O) _n H (XV)
(However, R ²⁷ is the number of which .n 1-10 alkyl group having 1 to 18 carbon atoms.),
Poly (oxyethylene) alkyl phenyl ether _{^{R 28 -Q-O (CH 2}} CH 2 O) n H (XVI)
(Wherein R ²⁸ is an alkyl group having 1 to 18 carbon atoms, Q is an aromatic residue, n is a number of 1 to 10), and poly (oxyethylene) glycol fatty acid ester R ²⁹ COO (CH ₂ CH ₂ O) _n H (XVII)
(However, R ²⁹ is the number of which .n 1-10 alkyl group having 1 to 18 carbon atoms.)
Etc. are more preferable.
In addition, as partial esters of polyhydric alcohols, sorbitan fatty acid esters represented by the following formula (XVIII) such as sorbitan monooleate and sorbitandiolate

(However, R ³⁰ is .n an alkyl group having 1 to 18 carbon atoms, m is the number of each 1 to 10.),
Glycerin fatty acid ester represented by the following formula (XIX) such as glycerol monooleate and glyceroldiolate

(However, R ³¹ is .n an alkyl group having 1 to 18 carbon atoms, m is the number of each 1 to 10.),
And partial ester compounds of polyhydric alcohols such as neopentyl glycol, trimethylolpropane, pentaerythritol and fatty acids having 1 to 24 carbon atoms.

Examples of rust inhibitors include, for example, alkyl or alkenyl succinic acid derivatives such as dodecenyl succinic acid half ester, octadecenyl succinic anhydride, dodecenyl succinic acid amide, sorbitan monooleate, glycerin monoeleate, pentaerythritol monooleate. Polyhydric alcohol partial esters such as ate, amines such as rosin amine and N-oleyl sarcosine, dialkyl phosphite amine salts and the like can be used.
The preferable compounding quantity of these rust preventives is the range of 0.01-5 mass% on the composition whole quantity basis, and the range of 0.05-2 mass% is especially preferable.

As examples of the metal deactivator, for example, benzotriazole-based, thiadiazole-based, gallic acid ester-based compounds, and the like can be used.
The preferable compounding amount of these metal deactivators is 0.01 to 0.4% by mass, particularly preferably 0.01 to 0.2% by mass based on the total amount of the composition.
As an example of the antifoaming agent, liquid silicone is suitable, and for example, methyl silicone, fluorosilicone, and polyacrylate can be used.
A preferable blending amount of these antifoaming agents is 0.0005 to 0.01% by mass based on the total amount of the composition.
Examples of viscosity index improvers include olefin copolymers such as polyalkyl methacrylate, polyalkyl styrene, polybutene, ethylene-propylene copolymer, styrene-diene copolymer, styrene-maleic anhydride ester copolymer. Is possible.
A preferable blending amount of these viscosity index improvers is 0.1 to 15% by mass, particularly preferably 0.5 to 7% by mass based on the total amount of the composition.
The lubricating oil composition of the present invention comprises, for example, a hydrodynamic bearing, an oil-impregnated bearing, and a hydrodynamic groove used in a rotating device for driving magnetic disks and optical disks such as FD, MO, minidisk, compact disk, DVD, and hard disk. It is suitably used for fluid bearings such as oil-impregnated bearings and porous oil-impregnated bearings or for oil-impregnated bearings, and further for information processing equipment including these bearing units.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Various characteristics of the lubricating oil were measured according to the following methods.
(1) Viscosity Measured at −100 ° C. and −20 ° C. according to JIS K2283.
(2) Pour point Measured according to JIS K2269.
(3) Loss on evaporation In accordance with the thermal stability test of JIS C2101, the loss on evaporation was measured by heat treatment at 150 ° C. for 168 hours.
(4) Volume resistivity It measured based on JIS C2101.

Production Example 1
Trihexylsilane (commercial product) was reacted with α-olefin (1-dodecene) and then distilled to obtain trihexyldecylsilane (C30Si) having a total carbon number of 30 as a lubricating base oil.

Production Example 2
Trihexylsilane (commercial product) was reacted with α-olefin (1-decene) and distilled to obtain trihexyldecylsilane (C28Si) having a total carbon number of 28 as a lubricating oil base oil.

Production Example 3
Trihexylsilane (commercial product) was reacted with α-olefin (1-octene) and distilled to obtain trihexyloctylsilane (C26Si) having a total carbon number of 26 as a lubricating base oil.

Examples 1 and 2 and Comparative Examples 1-6
Tetraalkylsilanes obtained in Production Examples 1 to 3, commercially available mineral oils, poly α-olefins (PAO), etc., and the following base oils were used as (Note), and phenolic antioxidants [octadecyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate], amine antioxidant [4,4′-bis (α, α-dimethylbenzyl) diphenylamine], phosphorus antioxidant [diethyl [[3, 5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] phosphonate] was added in an amount of 0.5% by mass to obtain a lubricating base oil.
Table 1 shows properties of various lubricating base oils such as viscosity, pour point and evaporation loss.

(note)
C30Si: Trihexyldecylsilane C28Si: Trihexyldecylsilane C26Si: Trihexyloctylsilane Mineral oil: (hydrogenated base oil, equivalent to API classification group II)
PAO: poly α-olefin (“DURASYN 164”, manufactured by Amoco)
DOS: Dioctyl sebacate (dioctyl sebacate)
DOA: Dioctyl adipate (Dioctyl adipate)
NPG dipelargonate: Neopentyl glycol dipelargonate

As can be seen from Table 1, among the lubricating oils of the present invention, in particular, Examples 1 and 2 have a viscosity at −20 ° C. of 150 mPa · s or less, a pour point of −50 ° C. or less, and an evaporation loss of 1.5% by mass or less. Therefore, it is a preferable base oil for bearing lubricating oil.
Comparative Example 1 has a large evaporation loss, and Comparative Example 2 has an extremely high viscosity of −20 ° C.
In Comparative Examples 3 and 4, the evaporation loss is relatively small, but the viscosity at −20 ° C. is high.

  The lubricating oil composition of the present invention contains a specific tetraalkylsilane as a base oil, has a low viscosity, excellent low-temperature fluidity, low evaporation, energy saving, etc., and is used at high speed rotation. It is suitably used as a lubricant for compact fluid bearings and porous oil-impregnated bearings.

Claims (10)

A lubricating oil composition comprising a tetraalkylsilane represented by the general formula (I) as a base oil and having a viscosity at a temperature of 100 ° C of 2.0 mPa · s or more.

(In the formula, R ¹ , R ² , R ³ and R ⁴ each represent a straight-chain saturated hydrocarbon group having 2 to 16 carbon atoms, and may be the same or different, and the total carbon number of R ^{1 to} R ⁴ Is 28-40.)   The lubricating oil composition according to claim 1, comprising a phenolic and / or amine antioxidant.   The lubricating oil composition according to claim 1, comprising a lubricity improver and / or a conductive additive.   The lubricating oil composition according to any one of claims 1 to 3, wherein the evaporation loss after the heat treatment at 150 ° C for 168 hours is 1.5 mass% or less.   The lubricating oil composition according to any one of claims 1 to 4, wherein the viscosity at a temperature of -20 ° C is 150 mPa · s or less and the pour point is -50 ° C or less. The lubricating oil composition according to any one of claims 1 to 5, which has a volume resistivity of 1 × 10 ¹⁰ Ω · cm or less substantially in the absence of metal particles or metal oxide particles.   A bearing oil comprising the lubricating oil composition according to claim 1.   A bearing using the bearing oil according to claim 7.   The bearing according to claim 8, which is a hydrodynamic bearing, an oil-impregnated bearing, an oil-impregnated bearing provided with a dynamic pressure groove, or a porous oil-impregnated bearing.   An information processing device comprising a bearing unit having the bearing according to claim 8.