JPH08259982A - Lubricating fluid composition for dynamic pressure bearing - Google Patents

Abstract

PURPOSE: To obtain a lubricating fluid compsn. which is used for a dynamic pressure bearing and excellent in magnetic sealing properties, lubricity, low volatility. and high-temp. resistance by adding a specific substance to a compsn. comprising a base oil solvent and magnetic particles dispersed therein. CONSTITUTION: A lubricating fluid compsn. used as a lubricating fluid for a dynamic pressure bearing, which supports a shaft by dynamic pressure, is prepd. by dispersing magnetic particles (e.g. fine Mn-Zn ferrite particles) in a base oil solvent (e.g. a mixture of a hydrogenated poly-α-olefin, a polycarbonate, a diisodecyl adipate oil, and a trioctyl trimellitate oil). Pref. 0.5wt.% or higher, still pref. 1-5wt.%, amine-based gelation inhibitor (e.g. an alkyldiphenylamine), which is an amine-based antioxidant, is added to the base oil solvent in preparing the compsn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricating fluid composition for a dynamic pressure bearing, which is used as a lubricating fluid for a dynamic pressure bearing that supports a shaft by dynamic pressure and uses its magnetic characteristics for a sealing action. .

[0002]

2. Description of the Related Art In recent years, a dynamic pressure bearing using a magnetic lubricating fluid has been proposed for various devices, particularly for devices such as a motor for driving various rotary plates such as a polygon mirror, a magnetic disk and an optical disk at high speed. . That is, a magnetic fluid is a colloidal solution in which ferromagnetic fine particles are stably dispersed in a liquid dispersion solvent, and because the liquid itself has apparently strong magnetism, it is usually used as a sealing in combination with a ball bearing. However, a dynamic pressure bearing using a magnetic lubricating fluid is considered to be promising because it is superior to the ball bearing in high-speed rotation stability and quietness. The proposal of a dynamic pressure bearing using a magnetic fluid has been made under such a background, for example, Japanese Patent Laid-Open No. 60-88223.
The publication discloses a device in which one fluid is used as both a lubricating fluid for generating a dynamic pressure and a magnetic fluid for magnetic sealing.

However, in such a device,
The magnetic fluid composition is required to have both a low evaporation property as a seal and a low viscosity property for reducing a bearing loss. Therefore, it is necessary to actually obtain a characteristic of the magnetic fluid composition that can be adapted to it. The current situation is that it is not possible. That is, the bearing portion receives a much larger shearing force than the seal portion and is exposed to a high temperature, and at the time of starting and stopping, the metals may come into contact with each other and wear to contact the active metal surface.
Although the magnetic fluid composition is used with the greatest advantage that "high airtightness can be obtained even at high speed (-10-6 Toor)", it functions as a lubricating fluid (low wear characteristics) and life characteristics (low wear characteristics). Those having both sufficient evaporating property and high temperature resistance) have not yet been developed (from PETROTECH Vol. 13, No. 12 (1989)).

[0004]

Thus, there is a demand for a lubricating fluid composition for a dynamic pressure bearing that covers not only the sealing property but also the lubricity and life characteristics, and there is a need for a lubricating fluid for generating a dynamic pressure and a magnetic seal. In order to use a single magnetic fluid as a magnetic fluid, it is necessary to prevent deterioration over a long period of time, especially to prevent gelation. Generally, 0.1 to 0.1 of a phenolic, amine, or sulfur antioxidant is added to the lubricating oil.
It is known to add about 0.5% by weight to improve the oxidation life, but it is not known what kind of additive should be added and how to prevent gelation of magnetic fluid. . Incidentally, Japanese Patent Laid-Open No. 59-105093 discloses that
Although it is described that an antioxidant is added while paying attention to the oxidative deterioration of the magnetic fluid, there is no description about the anti-gelling measure as described above.

Therefore, an object of the present invention is to provide a lubricating fluid composition for a dynamic pressure bearing, which can prevent gelation satisfactorily for a long period of time and can improve the life reliability.

[0006]

As a result of the study by the inventors of the present application, the action of the added antioxidant is different from that of a general lubricant because of the complexity of the structure of the magnetic fluid, especially the interaction with the surfactant. It is different, and it was found that a sufficient anti-gelling effect can be obtained by adding a specific type of anti-gelling agent.
In order to obtain a sufficient gelation-preventing action as a lubricating fluid composition for dynamic pressure bearings, in particular, 1) it should dissolve in the base oil and should not be precipitated even if it is made into a magnetic fluid by adding a surfactant. It has been found that conditions are required such that the action is small, 3) the evaporation amount is small, 4) the reaction product does not precipitate.

From this point of view, the lubricating fluid composition for a dynamic pressure bearing according to the invention of claims 1 to 3 is a magnetic fluid composition obtained by dispersing magnetic fine particles in a base oil solvent. A lubricant containing an amine-based antigelling agent is used as the base oil solvent.

As the amine-based gelling agent according to the present invention, for example, an amine-based antioxidant is used, and as the amine-based antioxidant, an alkyldiphenylamine (trade name; Irganox L01 is used. , L
57, L06 etc.) and phenyl-α-naphthylamine (trade name; Irganox L05 etc.) are adopted. These alkyldiphenylamines and phenyl-α-naphthylamines are preferable in terms of evaporation characteristics and compatibility with base oils.

On the other hand, examples of the base oil solvent include poly-α.
-A base oil obtained by mixing an olefin hydride and a polyol ester oil is preferably used. This poly-α-olefin hydride can be obtained, for example, by hydrogenating a polymer obtained by polymerizing 1-decene, isobutylene or the like with a Lewis acid or the like. Some of these have a number average molecular weight of about 200 to 1,600, but those having a number average molecular weight of about 400 are preferable in view of evaporation characteristics and the like. Although the hydrogenation does not have to be performed completely, it is likely to deteriorate when the degree of hydrogenation is low.

As the polyol ester, for example, a polyhydric alcohol such as neopentyl glycol (NPG), trimethylolpropane (TMP), pentaerythritol (PE), and a long-chain or branched fatty acid having 5 to 18 carbon atoms are used. And various trimethylolpropane mixed esters in which R (R is an alkyl group) of CH ₃ CH ₂ —C— (CH ₂ OOCR) ₃ is changed within the range of C5 to C20 are used. To be More specifically, valeric acid, a mixed trimethylolpropane ester of heptanoic acid (manufactured by Nippon Steel Chemical Co., Ltd .; trade name HATCOL 2915, 2925, 2937, etc.) and trimethylolpropane with decanoic acid and heptanoic acid Mixed ester oil (manufactured by Nippon Steel Chemical Co., Ltd .; HATCOL29)
38).

In the present invention, the total blending ratio is preferably in the range of 1 to 15 parts by weight of the amine gel inhibitor to 100 parts by weight of the base oil solvent, and the viscosity is 100 cp or less,
It is preferable that the saturation magnetization is 150 gauss or more. If the amount of magnetic particles is 25 parts by weight or less, it is less than 150 gauss
If it is more than part by weight, it will affect the thickening. Further, various additives such as a rust preventive agent, a viscosity index improver, and a metal deactivator can be used in the same manner as the lubricating oil.

[0012]

According to the above-mentioned means, by using the lubricant containing the amine-based gelation inhibitor as the base oil solvent, it is possible to maintain excellent viscosity and evaporation characteristics, and especially at high temperature. It is possible to improve the physical properties of gelation, and thus it is possible to provide a composition having a long service life as a lubricating fluid for generating dynamic pressure.

In this case, as in the inventions of claims 2 and 3, the amine-based antigelling agent is added in an amount of more than 0.5% by weight and 1 to
If 5% by weight is added or if an amine antioxidant is used as the amine gelling agent as in the invention of claim 4, the above-mentioned action is further improved.

[0014]

Embodiments of the present invention will be described below. In each example of the present invention, Mn-Zn ferrite with a saturation magnetization of 250 gauss obtained by the coprecipitation method was used as the magnetic fine particles. Manganese sulfate 0.1 mol, zinc sulfate 0.4 m
ol, 0.5 mol of ferric sulfate was dissolved in 1 liter of water, the water-soluble liquid temperature was maintained at 90 ° C., and 6N sodium hydroxide was added dropwise with stirring to adjust the pH of the aqueous solution to 11,
After the colloid of Mn-Zn ferrite was generated, the solution temperature was set to 80 ° C, 250 ml of a 10% solution of sodium oleate was added to the solution while continuing to stir, and the solution was cooled to room temperature. In addition PH 6
And The aggregated colloidal particles were thoroughly washed with water and further dehydrated and dried to obtain Mn-Zn ferrite fine particles coated with oleic acid.

Then, the Mn coated with the above-mentioned oleic acid was used.
-Take 14.8 g of Zn ferrite, add 15 g of the following base oil solvent, sufficiently stir to disperse, then remove undispersed substance by centrifugation, and further add base oil to have a specific gravity of 1.16. To obtain the fluid. The thus obtained fluid had a ferrite concentration of 35 wt% and a saturation magnetization of 250 gauss.

Further, Mn-Zn as the above-mentioned magnetic fine particles
As a base oil solvent for dispersing ferrite, poly-α-olefin hydride [C30 to C40] (manufactured by Nippon Steel Chemical Co., Ltd .; Shinflude 401), polycarbonate (ROCOOR) [R is C5 to C10. Alkyl group]
(Mitsui Petrochemical Co., Ltd .; DIALCARB SR1
000 / R), diisodecyl adipate oil (Nippon Steel Chemical Co., Ltd .; HATCOL2910), trimellitic acid trioctyl ester oil (Nippon Steel Chemical Co., Ltd .; HA)
To the mixture of TCOL2920), an amine-based antioxidant as a gelling agent, specifically, alkyldiphenylamine (trade name; Irganox L57) was added. Then, by changing the alkyldiphenylamine as the antigelling agent variously as shown in Table 1 below, Examples 1 to 5 were obtained.
The lubricating fluid compositions according to Comparative Examples 1 to 4 were prepared.

[0017]

[Table 1]

Each of the obtained lubricating fluid compositions was put in a petri dish, and the dispersion stability was evaluated by confirming the appearance such as precipitation, aggregation, separation, etc., and the evaporation amount was compared by weight reduction at a temperature of 80 ° C. for 520 hours. Further, the high temperature gelling time due to oxidative deterioration when left at a temperature of 140 ° C. was compared. Regarding the viscosity, the viscosity at 25 ° C and the viscosity temperature index were compared. Table 2 shows the evaluation results.

[0019]

[Table 2]

In Table 2, first, in comparison with Comparative Example 1 in which no gelling agent was added, in Examples 3 and 4, only a small amount of an amine antioxidant as a gelling agent was added. . That is, in Example 3, 0.1% by weight of alkyldiphenylamine (L57) was added as an amine-based antioxidant (antigelling agent), and in Example 4, only 0.5% by weight of alkyldiphenylamine (L57) was added. . Thus, when only a small amount of the amine-based antioxidant (anti-gelling agent) was added, almost no improvement was observed in each property of viscosity and evaporation amount, but high temperature anti-gelling effect (antioxidant effect) As for the above, it improved slightly. It is considered that this is due to the interaction between the amine antioxidant as the amine anti-gelling agent and the surfactant. Further, when the amine-based antioxidant (antigelling agent) is added in an amount of more than 0.5% by weight, as will be described later, the viscosity, the amount of evaporation, and the high temperature antigelling properties are
It was found that both have excellent effects.

On the other hand, when a small amount of an anti-gelling agent (antioxidant) other than the amine type was added, no high temperature anti-gelling effect (antioxidant effect) was obtained.
For example, as a phenolic gelling agent (antioxidant), 2,6-di-t-butyl phenol (trade name; ethyl 701, Irganox L108, etc.) in a small amount (0.
5% by weight) of Comparative Example 4, or 4,4′-thiobis (2-t-butyl-4) as a sulfur-based antioxidant.
In Comparative Example 6 in which a small amount (0.5 wt%) of methylphenol (L115) was added, the properties of viscosity and evaporation did not significantly improve, and gelation prevention (high temperature gelation time) The characteristics of () were not improved at all.

On the other hand, in the magnetic fluid compositions of Examples 1 and 2 according to the present invention, an amine-based gelling agent, specifically, alkyldiphenylamine (L57) as an amine-based antioxidant was added to 1.0 % And 5.0% by weight, respectively. In Examples 1 and 2 according to the present invention in which a large amount of the amine-based anti-gelling agent (amine-based antioxidant) was added in this manner, the respective properties of viscosity, evaporation amount and high-temperature gelation prevention (oxidation life) were obtained. It was found that all of them exhibited preferable values, and in particular, the characteristics of the high temperature gelation prevention effect (antioxidation effect) were remarkably improved, and therefore the high temperature stability was excellent.

However, as in Comparative Example 5 or Comparative Example 7, when a large amount of anti-gelling agent other than the amine-based anti-gelling agent is added, the ferromagnetic fine particles are dispersed in the liquid dispersion solvent. However, the magnetic fluid composition itself could not be obtained.

Although the invention made by the present inventor has been specifically described based on the embodiments, the invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say. For example, as the magnetic fine particles, in addition to Mn-Zn ferrite, Ni
-Zn ferrite or magnetite can be used as well. Further, as the surfactant, any other higher fatty acid can be adopted. Further, as the amine-based gelling agent, all kinds of amine-based ones other than the antioxidant can be similarly employed.

[0025]

As described above, the lubricating fluid composition for a dynamic pressure bearing according to the invention of claim 1 contains an amine-based gelling agent, for example, a lubricant containing an antioxidant as described in claim 4. By using as a base oil solvent, while maintaining good properties of viscosity and evaporation, in particular, the physical properties of high-temperature gelation is improved, it is possible to obtain good properties with a simple structure, A lubricating fluid composition for a dynamic pressure bearing in which one fluid is used both as a lubricating fluid for generating a dynamic pressure and a fluid for a magnetic seal, and the feasibility and reliability of a motor using the same can be improved. .

Further, as in the inventions of claims 2 and 3, by adding the gelling inhibitor over a predetermined amount, it is possible to further improve the feasibility and reliability of the motor using the dynamic pressure bearing. .

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C10N 10:02 10:14 10:16 30:02 30:08 40:02 40:14 (72) Inventor Toshihiro Kobayashi 5329 Shimosuwa-cho, Suwa-gun, Nagano Sankyo Seiki Co., Ltd. (72) Inventor Kazuya Shimizu 9 Kirihara-cho, Fujisawa-shi, Kanagawa Central Research Institute, Taiho Industrial Co., Ltd. (72) Yusuke Matsumura 2-21-44, Takanawa, Minato-ku, Tokyo Within Taiho Industries Co., Ltd. (72) Inventor Katsumi Nagano 12 4-4 Tsutsujigaoka, Chita City, Aichi Prefecture (72) Inventor Masuhiro Onoyama 997-10 Higashi Ohtake, Isehara City, Kanagawa Prefecture

Claims (4)

[Claims] 1. A lubricating fluid composition for a dynamic pressure bearing, which is used as a lubricating fluid for a dynamic pressure bearing which supports a shaft by dynamic pressure, wherein magnetic particles are dispersed in a base oil solvent. A lubricating fluid composition for a dynamic pressure bearing, wherein an amine-based antigelling agent is added to the oil solvent. 2. A lubricating fluid composition for a dynamic pressure bearing, wherein the amine-based antigelling agent according to claim 1 is added in an amount of more than 0.5% by weight. 3. A lubricating fluid composition for a dynamic pressure bearing, comprising 1 to 5% by weight of the amine-based antigelling agent according to claim 1. 4. A lubricating fluid composition for a dynamic pressure bearing, wherein the amine-based antigelling agent according to claim 1, 2 or 3 is an amine-based antioxidant.