JP2008081673A - Magnetic fluid lubricant - Google Patents

Abstract

Magnetism can be exhibited without containing magnetic metal fine particles, and there is no problem such as wear and settling separation, which has occurred when using a dispersed magnetic fluid containing magnetic metal fine particles, and the vapor pressure is low. The present invention provides a magnetic fluid lubricant that has a low risk of ignition, has excellent heat resistance, and can suppress generation of low-volatile components and decomposition gas during use.
A ferrofluid lubricant containing 1 to 100% by mass of a homogeneous magnetic ionic liquid.
[Selection figure] None

Description

  The present invention relates to a ferrofluid lubricant. More specifically, the present invention includes a homogeneous magnetic ionic liquid, can exhibit magnetism without containing magnetic metal fine particles, and wear and tear that have occurred during the use of dispersed magnetic fluids containing magnetic metal fine particles. This is a magnetic fluid lubricant that has no problems such as sedimentation separation, low vapor pressure, low risk of ignition, excellent heat resistance, and can suppress generation of low volatile components and decomposition gas during use. is there.

Conventionally, the surface of magnetic metal fine particles such as iron, cobalt and nickel is treated with a surfactant, and this is treated with oils such as hydrocarbon oils, ester oils, fluorinated hydrocarbon oils, silicone oils, etc. Dispersed magnetic fluids are known which are dispersed in a colloidal form in a medium such as water. Such magnetic fluids are used in the fields of semiconductor industry, computer industry, aviation industry, oil exploration industry, mining industry, for example, lubrication of bearings, sealing of rotating shafts, vibration dampers, heat conduction, audio speakers, noise control. It is used for material separation, magnetic sensors, sensors such as angle sensors and tilt sensors, and component inspection.
And research which improves the characteristic of this magnetic fluid is advanced. For example, there is a technique for producing a magnetic fluid containing metal fine particles having an average particle diameter of 7 to 12 nm at a high concentration by adding metal carbonyl to a hydrocarbon medium in which a surfactant is dissolved and heating and thermally decomposing. It is disclosed (for example, see Patent Document 1).

However, the magnetic fluid containing metal fine particles has the following problems. The metal fine particles in the magnetic fluid are attracted by an external magnetic force and move with the medium. When the magnetic force is strong, the metal fine particles uniformly dispersed in the medium are attracted to the magnetic force, and a concentration gradient of the metal fine particles is generated in the medium. As a result, a magnetic gradient is generated in the magnetic fluid. In addition, since magnetic fluid is also affected by gravity, a magnetic gradient may occur in the same manner. In addition, metal fine particles may agglomerate due to attractive force (van Desworth force) between the metal fine particles.
In order to solve such a problem, a technique for producing a magnetic fluid having a magnetic property with excellent stability has been disclosed (for example, see Patent Document 2). In this technique as well, a metal is contained in an organic medium. This is a technique for obtaining a magnetic fluid in which fine particles are dispersed, and does not essentially solve the above problem.

On the other hand, a magnetic fluid seal unit using the magnetic fluid is known. This is a sealing device that uses a magnetic fluid as a seal portion around a rotating shaft when a rotating shaft extending from the atmosphere side is driven into a sealed container whose inside is kept in a vacuum state. Such a seal using magnetic fluid has the characteristics of a magnetic fluid that can maintain the position of the particles by attracting metal fine particles in the magnetic fluid by the magnetic force of an external magnetic field such as a permanent magnet or an electromagnet. It is used.
Such a magnetic fluid seal unit may be used to seal a high temperature sealed container. For example, when the magnetic fluid seal unit is used for the purpose of vacuum sealing of a vacuum processing apparatus used in a semiconductor manufacturing process, depending on the semiconductor manufacturing conditions, the temperature of the sealed container may be increased to allow the semiconductor to be May be manufactured.
When the magnetic fluid seal unit is used for sealing such a high temperature sealed container, the heat of the outer wall of the sealed container is transmitted to the magnetic fluid seal part through the housing, and the magnetic fluid seal part is in a high temperature state.
However, the heat resistance of the magnetic fluid seal unit including the magnetic fluid seal portion is limited due to the relationship with the organic medium contained in the magnetic fluid. In order to use the magnetic fluid seal portion efficiently, the magnetic fluid seal portion It is necessary to suppress the temperature rise of the as much as possible.
For this reason, a magnetic fluid seal unit has been proposed in which a cooling medium guide passage is provided in a housing surrounding the outer periphery of the magnetic fluid seal portion to cool the magnetic fluid seal portion. However, in the conventional magnetic fluid seal unit configured to cool the magnetic fluid seal portion by providing the cooling medium guide passage, a structure or the like for supplying the cooling medium to the cooling medium guide passage must be provided. Becomes complicated. In addition, there is a problem in the reliability of the cooling structure such as cooling medium leakage.
Therefore, in the semiconductor field, development of a magnetic fluid having excellent heat resistance has been desired.
Further, when the conventional dispersion type magnetic fluid is used for various applications as a lubricant, there is also a problem that the lubricated material is easily worn due to the interposition of the magnetic metal fine particles on the friction surface.

By the way, in recent years, an organic ionic liquid composed of a cation and an anion has a series of ethylmethylimidazolium salts with different anions having excellent thermal stability and high ionic conductivity, and becomes a stable liquid even in air. (For example, see Non-Patent Document 1), and its attention has been paid to its thermal stability (non-volatile, flame-retardant), high ion density (high ion conductivity), large heat capacity, low viscosity, etc. Utilizing the characteristics, application research has been actively conducted for various uses, for example, electrolyte solutions for solar cells (see, for example, Patent Document 3), extraction separation solvents, reaction solvents, and the like.
This ionic liquid is not connected by intermolecular attractive force like molecular liquid, but is connected by strong ionic bonds, so it is difficult to volatilize, is flame retardant, and is resistant to heat and oxidation. In contrast, it is a stable liquid. Therefore, even if it has a low viscosity, it has a low evaporation property and a further excellent heat resistance.
In the field of ionic liquids, recently, 1-butyl-3-methylimidazolium iron (III) chloride has been found as a homogeneous magnetic ionic liquid. In this magnetic ionic liquid, 1-butyl-3-methylimidazolium ion, which is a typical cation, and iron (III) chloride ion, which is a typical magnetic anion, are strongly bonded by an ionic bond, and a magnetic metal It is an ionic liquid that exhibits magnetism without containing fine particles.

However, no example of using a homogeneous magnetic ionic liquid as a lubricant has been known so far.
On the other hand, as an example of using an ionic liquid as a lubricant, a lubricant is filled in a bearing gap formed between a bearing hole of a sleeve and a shaft inserted into the bearing hole, and the inner surface or the shaft surface of the bearing hole. A hydrodynamic bearing device in which an ionic liquid is added to the lubricant as a conductivity imparting agent in a liquid bearing device having a dynamic pressure generating groove in at least one of them and the sleeve and the shaft rotating relatively Is disclosed (for example, see Patent Document 4). However, this technique is obtained by adding an ionic liquid as a conductivity imparting agent to a fluid bearing lubricant, and is not a technique using a homogeneous magnetic ionic liquid as a lubricant.

JP-A-61-36907 JP 2005-123454 A Japanese Patent Laid-Open No. 2003-31270 JP 2004-183868 A “J. Chem. Soc., Chem. Commun.”, Page 965 (1992).

  Under such circumstances, the present invention can exhibit magnetism without including magnetic metal fine particles, and problems such as wear and sedimentation separation that have occurred in the past when using a dispersed magnetic fluid containing magnetic metal fine particles. In addition, the object is to provide a magnetic fluid lubricant that has low vapor pressure, low risk of ignition, excellent heat resistance, and can suppress generation of low-volatile components and decomposition gas during use. Is.

As a result of intensive studies to develop a ferrofluid lubricant having the above-mentioned preferable properties, the present inventors have found that a lubricant containing a homogeneous magnetic ionic liquid in a specific ratio is used as a ferrofluid lubricant. It was found that it can be adapted. The present invention has been completed based on such findings.
That is, the present invention
(1) A magnetic fluid lubricant containing 1 to 100% by mass of a homogeneous magnetic ionic liquid,
(2) The magnetic fluid lubricant according to (1), wherein the base oil contains 50 to 100% by mass of a homogeneous magnetic ionic liquid,
(3) The magnetic fluid lubricant according to (2) above, wherein the homogeneous ionic liquid used for the base oil has a melting point of 0 ° C. or lower.
(4) The homogeneous magnetic ionic liquid has the general formula (I)
(Z ^{p +} ) _k · (A ^q− ) _m (I)
( ^Wherein , Z ^{p +} represents a cation and an A ^q- anion, at least one of which has magnetism, and p, q, k, m, p × k and q × m are each an integer of 1 to 3. Yes, when p × k = q × m is satisfied and k or m is 2 or more, Z or A may be the same or different.
The magnetic fluid lubricant according to any one of the above (1) to (3), which is a compound represented by:

（式中、Ｒ¹〜Ｒ⁵は、それぞれ独立に水素原子、エーテル結合を有していてもよい炭素数１〜１８のアルキル基又は炭素数１〜１８のアルコキシル基を示す。）
で表されるイミダゾリウムカチオンである上記（８）に記載の磁性流体潤滑剤、及び
（１０）温度４０℃における動粘度が、５〜３００ｍｍ²／ｓである上記（１）〜（９）のいずれかに記載の磁性流体潤滑剤、
を提供するものである。 (5) In the general formula (I), the magnetic fluid lubricant according to the above (4), wherein p, k, q and m are all 1,
(6) The homogeneous magnetic ionic liquid has the general formula (II)
Z ⁺ · (MX _n ) ^- (II)
(Wherein Z ⁺ represents a cation, M represents Fe (III), X represents a halogen atom or an OH group,
n is 4. A plurality of X may be the same or different. )
The magnetic fluid lubricant according to (5) above,
(7) In the general formula (II), the magnetic fluid lubricant according to the above (6), wherein X is a halogen atom,
(8) The magnetic fluid lubricant according to the above (6) or (7), wherein, in the general formula (II), Z ⁺ is a cation having a nitrogen atom as an ion center,
(9) Z ⁺ is the general formula (III)

(In formula, R < ¹ > -R < ⁵ > shows a C1-C18 alkyl group or C1-C18 alkoxyl group which may have a hydrogen atom and an ether bond each independently.)
The ferrofluid lubricant according to (8) above, which is an imidazolium cation represented by formula (10), and (10) the kinematic viscosity at a temperature of 40 ° C. is from 5 to 300 mm ² / s. Magnetic fluid lubricant according to any one of the above,
Is to provide.

  According to the present invention, it is possible to develop magnetism even when containing a homogeneous magnetic ionic liquid and not containing magnetic metal fine particles, and the wear and sedimentation separation that has occurred during the use of dispersed magnetic fluids containing magnetic metal fine particles. In addition, there is provided a magnetic fluid lubricant that has a low vapor pressure, a low risk of ignition, excellent heat resistance, and can suppress generation of low-volatile components and decomposition gas during use. it can.

The ferrofluid lubricant of the present invention contains 1 to 100% by mass of a homogeneous magnetic ionic liquid.
In the present invention, the homogeneous magnetic ionic liquid is represented by the general formula (I)
(Z ^{p +} ) _k · (A ^q− ) _m (I)
(In the formula, Z ^{p +} represents a cation and A ^q− represents an anion, at least one of which has magnetism, and p, q, k, m, p × k, and q × m are integers of 1 to 3, respectively. When p × k = q × m is satisfied and k or m is 2 or more, Z or A may be the same or different.
The compound represented by these can be used.
As this homogeneous magnetic ionic liquid, in general formula (I), those in which p, k, q and m are all 1 are preferred. For example, general formula (II)
Z ⁺ · (MX _n ) ^- (II)
(In the formula, Z ⁺ represents a cation, M represents Fe (III), X represents a halogen atom or an OH group, and n represents 4. A plurality of X may be the same or different.)
The compound represented by these can be mentioned.
The cation represented by Z ⁺ is not particularly limited as long as it is a cation capable of forming a homogeneous magnetic ionic liquid by ionic bonding with the corresponding anion (MX _n ) ⁻ . As such Z ⁺ , for example, the general formula

（式中、Ｒ¹〜Ｒ¹²は、水素原子、エーテル結合を有していてもよい炭素数１〜１８のアルキル基及び炭素数１〜１８のアルコキシル基から選ばれる基であり、Ｒ¹〜Ｒ¹²は同一でも異なっていてもよい。）

(Wherein, R ¹ to R ¹² is a hydrogen atom, a group selected from an alkyl group and an alkoxyl group having 1 to 18 carbon atoms having 1 to 18 carbon atoms which may have an ether bond, R ¹ ~ R ¹² may be the same or different.)

The thing represented by these is preferable. Examples of the alkyl group having 1 to 18 carbon atoms which may have an ether bond of R ^{1 to} R ¹² include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec- Examples thereof include a butyl group, a tert-butyl group, various pentyl groups, various hexyl groups, various heptyl groups, various octyl groups, and 2-methoxyethyl group. Examples of the alkoxy group having 1 to 18 carbon atoms include methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, various pentoxy groups, and various heptoxy groups. Group, various octoxy groups and the like.
X is preferably a halogen atom selected from a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.
In the present invention, among the cations, a cation having a nitrogen atom as an ion center is preferable, and in particular, Z ⁺ is represented by the general formula (III).

（式中、Ｒ¹〜Ｒ⁵は前記と同じである。）

(In the formula, R ^{1 to} R ⁵ are the same as above.)

An imidazolium cation represented by the formula is preferred.
The homogeneous magnetic ionic liquid represented by the general formula (II) can be produced, for example, according to the following steps when Z ⁺ is an imidazolium cation represented by the general formula (III).

（式中、Ｘ¹はフッ素原子、塩素原子、臭素原子及びヨウ素原子から選ばれるハロゲン原子を示しＲ¹〜Ｒ⁵は前記と同じである。）
まず、イミダゾール誘導体（IV）にＲ³−Ｘ¹（Ｖ）を反応させてハロゲン化イミダゾリウム誘導体（VI）を得たのち、これにＭＸ¹ _n-1（VII）を作用させることにより、目的の均一系磁性イオン液体（II−ａ）を得ることができる。なお、前記「ハロゲン化」におけるハロゲン原子は、フッ素原子、塩素原子、臭素原子又はヨウ素原子である。

(In the formula, X ¹ represents a halogen atom selected from a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and R ^{1 to} R ⁵ are the same as described above.)
First, an imidazolium halide derivative (VI) is obtained by reacting imidazole derivative (IV) with R ³ -X ¹ (V), and then MX ¹ _n-1 (VII) is allowed to act on the imidazole derivative (IV). The homogeneous magnetic ionic liquid (II-a) can be obtained. The halogen atom in the “halogenation” is a fluorine atom, a chlorine atom, a bromine atom or an iodine atom.

Examples of the homogeneous magnetic ionic liquid represented by the general formula (II) include 1-butyl-3-methylimidazolium iron (III) chloride and 1-butyl-3-methylimidazolium iron (III) fluoride. 1-Butyl-3-methylimidazolium iron bromide (III), 1-butyl-3-methylimidazolium iron (III) iodide, 1-butyl-3-methylimidazolium cobalt (II) chloride 1-butyl-3-methylimidazolium, cobalt fluoride (II) fluoride, 1-butyl-3 cobalt acetate (II) bromide
-Methylimidazolium, 1-butyl-3-methylimidazolium cobalt (II) iodide, 1-butyl-3-methylimidazolium chloride (II) chloride, 1-butyl-3 (nickel fluoride II) -Methylimidazolium, 1-butyl-3-methylimidazolium nickel (II) bromide, 1-butyl-3-methylimidazolium nickel (II) iodide, and the like. It is not something.

In the magnetic fluid lubricant of the present invention, the homogeneous magnetic ionic liquid can be contained in the lubricant as a base oil or as an additive. When used as a base oil, the content of the homogeneous magnetic ionic liquid in the base oil is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and even more preferably 90 to 100% by mass. It is desirable to add.
When a homogeneous magnetic ionic liquid is used for the base oil, the melting point is preferably 0 ° C. or lower, more preferably −10 ° C. or lower. A homogeneous magnetic ionic liquid having such a melting point can be obtained by appropriately combining a cation and a corresponding anion, or by using a mixture of two or more homogeneous magnetic ionic liquids.

When the homogeneous magnetic ionic liquid is used as an additive in a lubricant, examples of the additive include those that function as an antistatic agent. In this case, the content of the homogeneous magnetic ionic liquid in the lubricant may be 1% by mass or more, and the upper limit is not particularly limited, but the volume resistivity of the lubricant at 25 ° C. is 1 × 10 ^10. If it is Ω · cm or less, good antistatic performance is exhibited. Therefore, when the magnetic fluid lubricant of the present invention is used for a sliding bearing of an electronic component or a magnetic component, generation of static electricity due to flow electrification of the lubricant is suppressed, and an electronic component or magnetic component (MR head of a hard disk) caused by discharge is suppressed. A hindrance can be prevented. A more preferable volume resistivity is 1 × 10 ⁹ Ω · cm or less.
The homogeneous magnetic ionic liquid is not particularly limited as long as it can be dissolved in the base oil when used as such an additive.
The homogeneous magnetic ionic liquid used in the present invention preferably has an ion concentration (cation or anion concentration) of 1 mol / dm ³ or more, more preferably 2 mol / dm ³ or more, and further preferably 3 mol / dm. ³ or more. When the ion concentration is 1 mol / dm ³ or more, the function as a magnetic fluid lubricant is sufficiently exhibited.

In the ferrofluid lubricant of the present invention, as the base oil other than the homogeneous magnetic ionic liquid, one that is miscible with the aforementioned homogeneous magnetic ionic liquid or one that can dissolve the homogeneous magnetic ionic liquid is used. it can. Examples of such base oils include polar base oils such as polyalkylene glycol type, mono-, di-, polyether-type, and phosphate ester-type.
In the ferrofluid lubricant of the present invention, various additives such as an antioxidant, an oily agent, a friction reducing agent, a rust preventive, a metal deactivator, an antifoaming agent and the like within the range in which the effects of the present invention are not impaired. A viscosity index improver etc. can be contained.

(1) Examples of antioxidants include amine-based antioxidants, phenol-based antioxidants, and sulfur-based antioxidants.
Examples of amine-based antioxidants include monoalkyl diphenylamines such as monooctyl diphenylamine and monononyl diphenylamine, 4,4′-dibutyldiphenylamine, 4,4′-dipentyldiphenylamine, and 4,4′-dihexyldiphenylamine. 4,4'-diheptyldiphenylamine, 4,4'-dioctyldiphenylamine, dialkyldiphenylamines such as 4,4'-dinonyldiphenylamine, tetrabutyldiphenylamine, tetrahexyldiphenylamine, tetraoctyldiphenylamine, polynonyldiphenylamine, etc. Alkyldiphenylamine, α-naphthylamine, phenyl-α-naphthylamine, butylphenyl-α-naphthylamine, pentylphenyl-α-naphthylamine, hexyl Butylphenyl -α- naphthylamine, heptylphenyl -α- naphthylamine, octylphenyl -α- naphthylamine, there may be mentioned naphthylamine such as nonylphenyl -α- naphthylamine, among others things dialkyl diphenylamine is preferred.

Examples of the phenol-based antioxidant include monophenols such as 2,6-di-tert-butyl-4-methylphenol and 2,6-di-tert-butyl-4-ethylphenol, 4,4′- Examples include diphenols such as methylene bis (2,6-di-tert-butylphenol) and 2,2′-methylene bis (4-ethyl-6-tert-butylphenol).
Examples of the sulfur-based antioxidant include phenothiazine, pentaerythritol-tetrakis- (3-laurylthiopropionate), bis (3,5-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- And methylamino) phenol.
These antioxidants may be used individually by 1 type, and may be used in combination of 2 or more type. Moreover, the compounding quantity is normally selected in the range of 0.01-10 mass%, preferably 0.03-5 mass% based on the total amount of the magnetic fluid lubricant.

(2) Examples of oil-based agents 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 such as ricinoleic acid and 12-hydroxystearic acid Aliphatic saturated and unsaturated monoalcohols such as fatty acids, lauryl alcohol and oleyl alcohol, aliphatic saturated and unsaturated monoamines such as stearylamine and oleylamine, aliphatic saturated and unsaturated monocarboxylic acids such as lauric acid amide and oleic acid amide Examples include amides.
These may be used singly or in combination of two or more. Further, the blending amount is usually selected in the range of 0.01 to 10% by mass, preferably 0.1 to 5% by mass, based on the total amount of the magnetic fluid lubricant.

(3) As a friction modifier, what is generally used as an oiliness agent or an extreme pressure agent can be used, and phosphoric acid ester, an amine salt of phosphoric acid ester and a sulfur-based extreme pressure agent are preferably mentioned. .
Examples of the phosphoric acid ester include phosphoric acid esters, acidic phosphoric acid esters, phosphorous acid esters, and acidic phosphorous acid esters represented by the following general formulas (VIII) to (XII).

In the general formulas (VIII) to (XII), R ^{13 to} R ¹⁵ represent an alkyl group, alkenyl group, alkylaryl group and arylalkyl group having 4 to 30 carbon atoms, and R ^{13 to} R ¹⁵ 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, di (ethylphenyl) phenyl phosphate, propylphenyl diphenyl phosphate, di (propylphenyl) phenyl phosphate, triethylphenyl phosphate, tripropyl Phenyl phosphate, butyl phenol Rudiphenyl phosphate, di (butylphenyl) phenyl phosphate, tributylphenyl phosphate, trihexyl phosphate, tri (2-ethylhexyl) phosphate, tridecyl phosphate, trilauryl phosphate, trimyristyl phosphate, tripalmityl phosphate, tristearyl phosphate, trio Examples include rail phosphate.

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 acid esters, tricresyl phosphate and triphenyl phosphate are preferred.
Furthermore, examples of amines that form amine salts with these include, for example, the general formula (XIII)
R ¹⁶ _P NH _3-P (XIII)
(In the formula, R ¹⁶ represents an alkyl group or alkenyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, an arylalkyl group having 7 to 30 carbon atoms, or a hydroxyalkyl group having 2 to 30 carbon atoms. , p is shown 1, 2 or 3. also, if R ¹⁶ is plural, R ¹⁶ 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 ¹⁶ in the general formula (XIII) may be linear, branched or cyclic.

  Examples of mono-substituted 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 monopropanolamine, etc. Examples of trisubstituted amines include tributylamine, tripentylamine, and the like. Amine, trihexylamine, tricyclohexylamine, trioctylamine, trilaurylamine, tristearylamine, trioleylamine, tribenzylamine, dioleyl monoethanolamine, dilauryl monopropanolamine, dioctyl monoethanolamine, dihexyl monopropanol Amine, dibutyl monopropanolamine, oleyl diethanolamine, stearyl dipropanolamine, lauryl diethanolamine, octyl dipropanolamine, butyl diethanolamine, benzyl diethanolamine, phenyl diethanolamine, tolyl dipropanolamine, xylyl diethanolamine, List triethanolamine, tripropanolamine, etc. It can be.

  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 lubricant base oil to exhibit the extreme pressure agent and excellent friction characteristics. Examples of such compounds include sulfurized fats and oils, sulfurized fatty acids, sulfurized esters, sulfurized olefins, dihydrocarbyl polysulfides, thiadiazole compounds, thiophosphate esters (thiophosphite, thiophosphate), 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 (XIV)
R ¹⁷ -S _q -R ¹⁸ (XIV)
(In the formula, R ¹⁷ represents an alkenyl group having 2 to 15 carbon atoms, R ¹⁸ 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 (XV)
R ¹⁹ -S _r -R ²⁰ (XV)
(In the formula, each of R ¹⁹ and R ²⁰ is 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 ¹⁹ and R ²⁰ are alkyl groups, they are referred to as alkyl sulfides.

R ¹⁹ and R ²⁰ in the general formula (XV) 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 (XVI)

（式中、Ｒ²¹及びＲ²²は、それぞれ水素原子、炭素数１〜２０の炭化水素基を示し、ｆ及びｇは、それぞれ０〜８の整数を示す。）

(In the formula, R ²¹ and R ²² each represent a hydrogen atom and a hydrocarbon group having 1 to 20 carbon atoms, and f and g each represent an integer of 0 to 8)

1,3,4-thiadiazole compounds, 1,2,4-thiadiazole compounds, 1,4,5-thiadiazole compounds represented by
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, 3,6-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-octyldithio) -1,2,3- Thiadiazole, 4,5- Scan (n- nonyldithio) -1,2,3-thiadiazole, 4,5-bis (1,1,3,3-tetramethylbutyl dithio) -1,2,3-thiadiazoles such as can be a preferably exemplified.
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 (XVII)

（式中、Ｒ²³〜Ｒ²⁶は、それぞれ炭素数１〜２０のアルキル基を示し、ｈは１〜８の整数を示す。）

(Wherein, R ²³ to R ²⁶ are each an alkyl group having 1 to 20 carbon atoms, h is an integer of 1-8.)

  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.
These friction modifiers may be used individually by 1 type, and may be used in combination of 2 or more type. The blending amount is usually selected in the range of 0.01 to 10% by mass, preferably 0.05 to 5% by mass, based on the total amount of the magnetic fluid lubricant, from the viewpoint of balance between effect and economy.

(4) Examples of the rust inhibitor include alkyl or alkenyl succinic acid derivatives such as dodecenyl succinic acid half ester, octadecenyl succinic anhydride, dodecenyl succinic acid amide, sorbitan monooleate, glycerin monooleate, pentaerythritol mono Polyhydric alcohol partial esters such as oleate, amines such as rosin amine and N-oleyl sarcosine, dialkyl phosphite amine salts and the like can be used. These may be used singly or in combination of two or more.
A preferable blending amount of these rust preventives is in the range of 0.01 to 5% by mass, particularly preferably in the range of 0.05 to 2% by mass, based on the total amount of the magnetic fluid lubricant.

(5) As the metal deactivator, for example, benzotriazole-based, thiadiazole-based, gallic acid ester-based compounds, and the like can be used.
A preferable blending amount of these metal deactivators is 0.01 to 0.4% by mass based on the total amount of the magnetic fluid lubricant, and a range of 0.01 to 0.2% by mass is particularly preferable.
(6) As an example of the antifoaming agent, liquid silicone is suitable, and methylsilicone, 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 magnetic fluid lubricant.
(7) Examples of viscosity index improvers include olefin copolymers such as polyalkyl methacrylate, polyalkyl styrene, polybutene, ethylene-propylene copolymer, styrene-diene copolymer, and styrene-maleic anhydride ester copolymer. Coalescence can be used.
A preferable blending amount of these viscosity index improvers is 0.1 to 15% by mass based on the total amount of the magnetic fluid lubricant, and a range of 0.5 to 7% by mass is particularly preferable.

In the magnetic fluid lubricant of the present invention, the kinematic viscosity at a temperature of 40 ° C. is preferably in the range of 5 to 300 mm ² / s. If this kinematic viscosity is in the above range, evaporation loss, power loss due to viscous resistance, and the like can be suppressed. A more preferable kinematic viscosity at a temperature of 40 ° C. is 5 to 150 mm ² / s.
The pour point is preferably 0 ° C. or lower, more preferably −10 ° C. or lower from the viewpoint of suppressing viscous resistance at low temperatures.
The viscosity index is preferably 80 or more, more preferably 100 or more, and still more preferably 120 or more, from the viewpoint of preventing the viscosity change with respect to temperature from becoming too large.
The 5% mass loss temperature is preferably 200 ° C. or higher, more preferably 300 ° C. or higher. The flash point is preferably 200 ° C. or higher, more preferably 250 ° C. or higher, and particularly preferably 300 ° C. or higher.
Furthermore, the acid value is preferably 1 mgKOH / g or less, more preferably 0.5 mgKOH / g or less, and still more preferably 0.3 mgKOH, from the viewpoint of preventing corrosion of a metal-based member to which the magnetic fluid lubricant of the present invention is applied. / G or less.

The ferrofluid lubricant of the present invention can exhibit magnetism even without containing magnetic metal fine particles, and does not have problems such as wear and sedimentation that have occurred in the past when using a dispersed magnetic fluid containing magnetic metal fine particles. In addition, the vapor pressure is low, the risk of ignition is low, the heat resistance is excellent, and the generation of low volatile components and decomposition gas during use can be suppressed. Therefore, the lubricant is suitably used for the following applications.
(1) For slide bearings In recent years, as the bearings for spindle motors represented by magnetic disks and optical disks, there are an increasing number of cases where slide bearings such as fluid bearings and sintered oil-impregnated bearings are used to provide quietness and durability. ing. These bearings are characterized in that the shaft and the inner surface of the bearing are separated by lubricating oil to support the load applied to the shaft and reduce the friction generated between the shaft and the bearing.
As a plain bearing using magnetic fluid, for example, a plurality of magnetic poles are circumferentially separated from each other on a bearing clearance forming surface of a bearing outer ring and a shaft fitted in the bearing outer ring via a bearing clearance. There is known a magnetic fluid bearing which is provided on the entire circumference and the other is made of a nonmagnetic material, and a magnetic fluid is held in the bearing gap by the plurality of magnetic poles.

FIG. 1 is a longitudinal sectional view of an example of the magnetic fluid bearing. A magnetic fluid bearing 1 includes a cylindrical bearing outer ring 2 and a shaft 3 fitted in the bearing outer ring 2 via a bearing gap g. Among them, a plurality of magnetic poles 4 are provided on a bearing gap forming surface 2a formed of an inner peripheral surface of the bearing outer ring 2, and a magnetic fluid 5 is placed in the bearing gap g. As the magnetic fluid 5, a fluid having lubricity is used. The plurality of magnetic poles 4 are separated from each other in both the circumferential direction and the axial direction, and are provided on the entire circumference of the bearing gap forming surface 2a.
Both the bearing outer ring 2 and the shaft 3 are made of a nonmagnetic material. Each magnetic pole 4 is provided by embedding a small piece of permanent magnet 4 </ b> A in the bearing outer ring 2. The direction of the permanent magnet 4A is determined so that the nuclear magnetic pole 4 has the same polarity (S pole in the figure) on the bearing forming surface 2a side. The size of the magnetic pole 4 on the magnetic pole forming surface 2a is preferably such that the vertical and horizontal widths are equal to the bearing gap g because the magnetic pole surface has no binding force of the magnetic fluid 5. The plurality of magnetic poles 4 may be provided on a bearing forming surface formed by the outer peripheral surface of the shaft 3 instead of being provided on the bearing forming surface 2 a of the bearing outer ring 2. In that case, a permanent magnet may be embedded in the shaft 3.
According to the magnetic fluid bearing 1 having this configuration, the magnetic fluid 5 gathers on the surface of each magnetic pole 4 and is held in the bearing gap g. Even if an external force acts on the shaft 3 and the bearing gap g becomes small at a part of the circumference, the magnetic fluid 5 held by the magnetic pole 4 does not move, and the bearing gap g is a magnetic fluid having lubricity. 5 is maintained at a constant size over the entire circumference. That is, the shaft 3 is not only in rotation but also in a non-rotating state, is not in contact with the bearing outer ring 2 and is supported at the shaft center position, and becomes a highly rigid bearing with little friction. Therefore, for example, when applied to a vibration motion unit such as a fulcrum bearing of an HDD device, support without starting friction can be performed. Further, since the magnetic fluid 5 having lubricity is always present in the bearing gap g, it is possible to have a high damping function when the vibration positioning is stopped, and to perform positioning quickly and with high accuracy.
As the magnetic fluid, the magnetic fluid lubricant of the present invention can be suitably used.

In addition, as a sintered bearing element using a magnetic fluid, a permanent magnet is disposed adjacent to a bronze-based porous sintered bearing, a permanent magnet is embedded in a porous sintered bearing, or a porous Known is a dispersion of magnetized ferromagnetic particles in a matrix alloy of a sintered bearing.
These sintered bearing elements are sintered plain bearing elements whose lubricant is a magnetic fluid, and are used for motors for audio / video equipment, scanning polygon motors, magneto-optical disks, etc. that are used at relatively high speed loads. It can be used for spindle motors. As the magnetic fluid used for such a sintered sliding bearing element, the magnetic fluid lubricant of the present invention can be suitably used.

(2) For rolling bearings Rolling bearings are used to support shafts that rotate at high speed, such as spindles of machine tools. When such a rolling bearing is used under high-speed rotation, the contact surface pressure between the rolling elements and the inner and outer rings due to centrifugal force and heat generation increase the risk of bearing damage typified by wear and seizure. End up. For this reason, with respect to rolling bearings used under such high-speed rotation, research for optimizing the lubrication conditions has been conducted by each bearing manufacturer.
Conventionally, an oil-air lubrication method, a nozzle jet lubrication method, an under-lace lubrication method, and the like are used as a lubrication method for a rolling bearing with a cooling effect. However, in these lubrication systems, a large-scale lubricant supply device using air is essential, and considering the installation area, it is difficult to reduce the size of the entire machine tool. In addition, these lubrication methods continuously consume electric power and a lubricant, so that there is a problem that operation costs are increased.
Therefore, as an energy-saving lubricant supply means that does not use air to supply the lubricant, a diaphragm attached to the lubricant oil storage chamber is vibrated by a piezoelectric element, so that a small amount of lubrication is applied to the raceway surface of the rolling bearing. Attempts have been made to spray the agent directly.
Also, as a lubrication system for bearings, a system in which grease or the like is enclosed is generally used, and attempts have been made to improve lubricity by changing the properties of the grease.

However, the method of directly injecting the lubricant using the piezoelectric element described above requires minimum maintenance and management for the supply device, and can be made more compact than the conventional method, but the bearing itself has the supply device. In some cases, it is arranged in a part where it cannot be installed or a part where power cannot be supplied, and this method cannot be applied to all bearings.
In addition, the method of encapsulating the modified grease generates a large amount of heat generated by the bearing due to the shearing of the grease, and only a small amount of the encapsulated grease contributes to lubrication. There was a problem that had to be done.
In order to solve such a problem, in a rolling bearing device in which a plurality of rolling elements are arranged to freely roll on a raceway formed between a plurality of raceway members, at least one of the raceway members or the rolling elements. One is magnetized, and a technique for arranging a magnetic fluid between them has been developed.

FIG. 2 is an axial sectional view of an example of the rolling bearing device.
This rolling bearing device is formed between an inner ring 21 having an inner ring side raceway groove 21a that is one of a plurality of raceway members, an outer ring 22 having an outer ring side raceway groove 22a that is the other raceway member, and the inner and outer rings. A plurality of balls 23 arranged on the track, a retainer 24 that holds the balls 23 in a circumferential direction so as to be freely rollable, and a seal that seals both ends of the annular space formed by the inner and outer rings. The members 25 and 25 are mainly configured.
The feature of this ball bearing is that each of the balls 23 arranged on the raceway is magnetized and a magnetic fluid (not shown) as a lubricant is arranged in the annular space of the bearing. With this configuration, the magnetic fluid stays in the vicinity of the magnetized ball 23, and the lubricant is always present in the vicinity of the surface of the ball 23. Further, even under high-speed rotation in which a high centrifugal force is applied to the bearing, the lubricant made of the magnetic fluid circulates around the magnetized ball 23, so that the contact portion between the two due to the relative rotation between the track and the ball is not affected. Oil film formation is not interrupted, and even a small amount of lubricant can reliably prevent bearing damage and the like due to oil film breakage.
The magnetic fluid lubricant of the present invention can be suitably used for the magnetic fluid used in this rolling bearing device.

(3) Sealing device A magnetic fluid sealing device is known as a long-life and clean high-performance sealing device. This magnetic fluid sealing device introduces rotational driving force into the vacuum in the manufacturing process of semiconductors and liquid crystals that require a shaft seal mechanism that can provide a clean atmosphere with less maintenance, and in various coating and etching processes. For this reason, it is widely used as a vacuum seal, a dust-proof seal for preventing oil mist from a bearing from entering a clean area, a gas seal, and the like.
A main application of the magnetic fluid seal device is a rotation introducing mechanism for transmitting rotational motion from the outside to the inside of the hermetic container. Inside the hermetic container, for example, a semiconductor-related film forming process is performed. In such a film forming process, a special environment such as film formation at a high temperature using a special reaction gas is used. Many. When the magnetic fluid seal device is used in such a special environment, it is required to operate without trouble in such an environment.

  When a thermal CVD apparatus is used for the film forming process, in the thermal CVD apparatus, the substrate processing temperature is, for example, about 700 to 1000 ° C., and the substrate holder is heated to such a high temperature. In that case, the temperature of the magnetic fluid seal device used as the rotation introducing mechanism of the substrate holder rises due to the influence of heat from the substrate holder. The conventional magnetic fluid containing metal fine particles evaporates or deteriorates at a high temperature. Therefore, when used in a high temperature environment, it is necessary to cool the magnetic fluid seal device. On the other hand, since the magnetic fluid lubricant of the present invention is extremely excellent in heat resistance, it is not necessary to cool the magnetic fluid seal device by using the magnetic fluid lubricant of the present invention in the magnetic fluid seal device. .

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 lubricant were measured according to the following methods.
(1) Kinematic viscosity It measured based on the "petroleum product kinematic viscosity test method" prescribed | regulated to JISK2283.
(2) Viscosity index It measured based on the "petroleum product kinematic viscosity test method" prescribed | regulated to JISK2283.
(3) Pour point Measured according to JIS K2269.
(4) Total acid value It measured by the potentiometric method based on the "lubricating oil neutralization test method" prescribed | regulated to JISK2501.
(5) Flash point In accordance with JIS K2265, C.I. O. It was measured by C method.
(6) 5% mass reduction temperature Using a differential thermal analyzer, the temperature was raised at a rate of 10 ° C / min, and the temperature reduced by 5% from the initial mass was measured. It can be said that the higher the 5% mass reduction temperature, the better the evaporation resistance and heat resistance.
(7) Load bearing test Based on ASTM D2783, it carried out on condition of rotation speed 1,800rpm and room temperature. The load wear index (LWI) was determined from the maximum non-seizure load (LNL) and the fusion load (WL). The larger this value, the better the load resistance.
(8) Abrasion resistance test In accordance with ASTM D 2783, the test was performed under the conditions of a load of 392 N, a rotation speed of 1,200 rpm, an oil temperature of 80 ° C., and a test time of 60 minutes. The average wear scar diameter was calculated by averaging the wear scar diameters of three 1/2 inch spheres.

Examples 1-3
Magnetic fluid lubricants having the compositions shown in Table 1 were prepared and evaluated for various properties. The results are shown in Table 1.

(note)
Magnetic ionic liquid 1: 1-butyl-3-methylimidazolium tetrachloroferrate (manufactured by Tokyo Chemical Industry Co., Ltd.), molecular weight 336.88, melting point -15 ° C
TCP: tricresyl phosphate DBDS: dibenzyl disulfide amine-based antioxidant: 4,4′-dibutyldiphenylamine

  The magnetic fluid lubricant of the present invention contains a homogeneous magnetic ionic liquid, can exhibit magnetism without containing magnetic metal fine particles, and wear that has conventionally occurred when using a dispersed magnetic fluid containing magnetic metal fine particles In addition, there are no problems such as sedimentation and sedimentation, low vapor pressure, low risk of ignition, excellent heat resistance, and the ability to suppress generation of low volatile components and decomposition gas during use. Therefore, it is suitably used as a lubricant for sliding bearings, rolling bearings, seal mechanisms and the like.

It is a longitudinal cross-sectional view of an example of the magnetic fluid bearing to which the magnetic fluid lubricant of this invention is applied. It is sectional drawing of the axial direction of an example of the rolling bearing apparatus with which the magnetic fluid lubricant of this invention is applied.

Explanation of symbols

1: Magnetic fluid bearing 2: Bearing outer ring 2a: Bearing forming surface 3: Shaft 4: Magnetic pole 4A: Permanent magnet 5: Magnetic fluid g: Bearing gap 21: Inner ring 21a: Inner ring side raceway groove 22: Outer ring 22a: Outer ring side raceway groove 23: Ball 24: Cage 25: Seal member

Claims (10)

  A magnetic fluid lubricant comprising 1 to 100% by mass of a homogeneous magnetic ionic liquid.   The ferrofluid lubricant according to claim 1, wherein the base oil contains 50 to 100% by mass of a homogeneous magnetic ionic liquid.   The magnetic fluid lubricant according to claim 2, wherein the homogeneous ionic liquid used for the base oil has a melting point of 0 ° C or lower. A homogeneous magnetic ionic liquid is represented by the general formula (I)
(Z ^{p +} ) _k · (A ^q− ) _m (I)
( ^Wherein , Z ^{p +} represents a cation and an A ^q- anion, at least one of which has magnetism, and p, q, k, m, p × k and q × m are each an integer of 1 to 3. Yes, when p × k = q × m is satisfied and k or m is 2 or more, Z or A may be the same or different.
The ferrofluid lubricant according to claim 1, which is a compound represented by the formula:   The ferrofluid lubricant according to claim 4, wherein in general formula (I), p, k, q and m are all 1. Homogeneous magnetic ionic liquid has general formula (II)
Z ⁺ · (MX _n ) ^- (II)
(In the formula, Z ⁺ represents a cation, M represents Fe (III), X represents a halogen atom or an OH group, and n represents 4. A plurality of X may be the same or different.)
The ferrofluid lubricant according to claim 5, which is represented by:   The ferrofluid lubricant according to claim 6, wherein X in the general formula (II) is a halogen atom. The ferrofluid lubricant according to claim 6 or 7, wherein, in the general formula (II), Z ⁺ is a cation having a nitrogen atom as an ion center. Z ⁺ represents the general formula (III)

(In formula, R < ¹ > -R < ⁵ > shows a C1-C18 alkyl group or C1-C18 alkoxyl group which may have a hydrogen atom and an ether bond each independently.)
The magnetic fluid lubricant according to claim 8, which is an imidazolium cation represented by the formula: The magnetic fluid lubricant according to any one of claims 1 to 9, wherein a kinematic viscosity at a temperature of 40 ° C is 5 to 300 mm ² / s.

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