JP2000119672A - Hydraulic oil for vibration dampers - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a hydraulic oil which has excellent long-term stability and satisfies the required performance for a vibration damper. SOLUTION: A hydraulic oil for a vibration damper having a viscosity index of 110 or more, a bulk modulus of 1.3 GPa or more, and a pour point of -25 ° C or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optimal hydraulic oil composition for use in an oil damper for controlling shaking of a high-rise building due to an earthquake, wind, or the like.

[0002]

2. Description of the Related Art High-rise buildings are constantly subject to wind sway, and occasionally encounter considerable sway due to an earthquake. However, in recent years, a system for actively controlling these swings has been invented and put into practical use. In particular, oil dampers are systems that can stably apply viscous damping to building structures over a wide range from small to large amplitudes.

Until now, the performance of lubricating oil for vibration dampers has not been sufficiently studied. At least little information has been made public, especially for large damping hydraulic fluids.

[0004]

SUMMARY OF THE INVENTION The present inventor has studied the performance required of a hydraulic oil for a vibration damper and found that the following points are important.

Suitable viscosity High viscosity index High bulk modulus Long-term use (stability) Non-corrosive Non-corrosive
１０００1000 mm ² / s can be used. Is the change in viscosity due to temperature. The smaller the change in viscosity over a wider temperature range, the more stable the viscosity resistance of the lubricating oil. The fluidity of a lubricating oil at a low temperature is represented by a pour point, and the pour point is preferably as low as possible. Also, from the operating principle of the damper, the higher the volume elastic modulus () of the lubricating oil, the better the response (the lower the compression ratio, the better). With regard to (1) and (2), it is necessary to consider the stability of the hydraulic oil base oil itself and the stability of additives to be blended.

[0006] By using a lubricating base oil that is well balanced in these respects, it becomes possible to exhibit the performance of the vibration damper. An object of the present invention is to provide a hydraulic oil composition that is well balanced in terms of appropriate viscosity, high viscosity index, high bulk modulus, long-term stability, and the like, so that the performance of a vibration damper can be sufficiently exhibited. It is in.

[0007]

SUMMARY OF THE INVENTION The viscosity index and bulk modulus of a liquid generally have a trade-off property. For this reason, it is necessary to select a base oil that is considered to be optimal in physical properties such as an appropriate viscosity, a high viscosity index, and a bulk modulus. Furthermore, in addition to this, it was necessary to search for a material that satisfies long-term stability and non-corrosiveness.

The present inventors have studied various liquids from such a viewpoint. As a result, poly-α-olefins, polyol esters and polyethers have relatively high viscosity index, low pour point, high bulk modulus, And it was confirmed that it was a non-corrosive fluid, and furthermore, it was possible to provide long-term stability by adding a predetermined amount of an antioxidant thereto, and completed the present invention. .

That is, according to the present invention, (1) the viscosity index is 1
10 or more, bulk modulus is 1.3 GPa or more, pour point is-
(2) The hydraulic oil for a vibration damper having a temperature of 25 ° C. or less, (2) the hydraulic oil for a damper according to (1), wherein the hydraulic oil for the damper is at least one selected from poly α-olefins, polyol esters, and polyethers. (3) The hydraulic oil for a vibration damper according to any one of (1) and (2), wherein the hydraulic oil for a damper is added with 0.01 to 2% by weight of an antioxidant. .

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hydraulic base oil The kinematic viscosity at 40 ° C. of the fluid used for the vibration damper can be 5 to 1000 mm ² / s.
Those having a range of 5 to 1000 mm ² / s can be more preferably used. Fluids in this viscosity range include mineral oils, silicone oils, fluorinated ethers, polyalphaolefins, fatty acid esters, polyethers, and the like. Table 1 shows the kinematic viscosities, viscosity indices, and pour points of these fluids (Konishi, Ueda: Basics and Applications of Lubricating Oils, Corona Co. (1992)). The bulk modulus at 37.8 ° C. and 0.1 MPa (HSSong, EEKlaus, JLDuda: Trans. ASME Se
r. F., J. of Tribology, 113 , 675 (1991). and B. Jaco
bson, P.Vinet: J. of Tribology, 109 , 709 (1987).)
Are also shown in Table 1.

[0011]

[Table 1]

Among them, poly-α-olefin is a fluid having a relatively high viscosity index, a low pour point, and a high bulk modulus. In addition, fatty acid esters such as polyol esters have high viscosity index, high bulk modulus, and excellent low-temperature fluidity, but have some problems in hydrolytic stability. However, since the damping damper is used in a state of being purged with an inert gas and can use a sealing material having excellent long-term oil tightness, it can be said that there is little practical problem. Polyether is a fluid having a relatively balanced viscosity index, low-temperature fluidity, bulk modulus, and the like.

Although mineral oil has a high bulk modulus, the base oil alone is inferior in low-temperature fluidity, and wax precipitates below the pour point. Therefore, the addition of a pour point depressant polymer or the like is necessary, which causes a problem in long-term reliability. Silicone oil such as polydimethylsiloxane has a high viscosity index, but has a low bulk modulus and is easily compressed, and therefore is not suitable as a base oil for dampers. There is also a problem of poor lubricity. Fluorinated ethers are not suitable because they generally have a low bulk modulus and are easily compressed. Although polyphenylene ether has a high bulk modulus, it is not suitable because of its low viscosity index.

From the above, it can be said that the poly-α-olefin, polyol ester and polyether which are synthetic oils can be used as a base oil for dampers. In particular, poly α
-Olefin has excellent basic performance and long-term stability,
It is considered to be most suitable because it has no corrosiveness. Specific examples of the poly-α-olefin, polyol ester, and polyether may be those known as lubricating base oils. For example, poly α-olefin is α-olefin (hydrocarbon having a double bond at a terminal such as 1-decene).
Is subjected to low polymerization and the terminal double bond is hydrogenated.
The polyol ester is a dehydration condensation reaction product of a polyhydric alcohol (neopentyl glycol, trimethylol propane, etc.) (carboxylic acids C ₃ -C ₁₃₎ and monobasic fatty acid. The polyether is obtained by ring-opening polymerization of an alkylene oxide such as ethylene oxide and alkylating the terminal OH.

The viscosity index of the base oil for a damper which can be used in the present invention is 110 to 400, preferably 110 to 200, more preferably 110 to 180 in consideration of the balance with the bulk modulus. A base oil having a viscosity index of more than 400 is not preferable because the bulk modulus becomes low. Further, when the diameter is less than 110, the viscous resistance becomes excessively large in extremely cold weather, and the vibration damping by the damper may be insufficient. Similarly, the bulk modulus is in the range of 1.3 to 2.0 GPa, preferably 1.3 to 1.8 GPa in consideration of the balance with the viscosity index. A base oil exceeding 2.0 GPa is not preferred because the viscosity index is lowered. Further, when the pressure is less than 1.3 GPa, the damping of the vibration by the damper may be insufficient. For the pour point,
It goes without saying that the lower the temperature, the better. However, from the viewpoint of availability, the temperature is preferably -25 ° C or lower, more preferably -30 ° C or lower. If the temperature exceeds -25 ° C, the damper may not operate during extremely cold weather. The hydraulic oil for vibration damper can be composed of these base oils, but it is preferable to further add an antioxidant in consideration of long-term stability.

2. Antioxidants As general antioxidants for lubricating oils, phenol-based, amine-based, zinc dialkyldithiophosphates and the like are known. Phenolic antioxidants are widely used, including industrial lubricating oils and vehicle lubricating oils, and act as radical inhibitors in oxidation reactions. As the amine-based antioxidants, phenylnaphthylamine, alkyldiphenylamine, and the like are known. The phenylnaphthylamine-based antioxidant is disadvantageous in that the hue is relatively easily deteriorated and sludge is easily formed. Zinc dialkyldithiophosphorus is famous as an additive having both antioxidant and antiwear properties. However, caution is required because it may act as an antioxidant or produce sticky sludge when hydrolyzed. As a result, phenolic antioxidants are the most suitable as an additive that exhibits excellent antioxidant properties against base oils such as poly-α-olefins and polyol esters, and that satisfies long-term reliability. I can say.

The phenolic antioxidants usable in the present invention include, for example, 2,6-di-t-butylphenol, 2-t-butyl-4-methoxyphenol, 2,4
-Dimethyl-6-t-butylphenol, 2,4-diethyl-6-t-butylphenol, 2,6-di-t-butyl-p-cresol, 2,6-di-t-butyl-4-
Ethylphenol, 2,6-di-t-butyl-4-hydroxymethylphenol, 2,6-di-t-butyl-4
-(N, N-dimethylaminomethyl) phenol, n-
Octadecyl-β- (4′-hydroxy 3 ′, 5-di-
t-butylphenyl) propionate, 2,4- (n-
(Octylthio) -6- (4-hydroxy3 ', 5'-di-t-butylanilino) -1,3,5-triazine, styrenated phenol, styrenated cresol, tocophenol, 2-t-butyl-6- ( 3'-t-butyl-
5′-methyl-2′-hydroxybenzyl) -4-methylphenyl acrylate, 2,2′-methylenebis (4
-Methyl-6-t-butylphenol), 2,2'-methylenebis (4-ethyl-6-t-butylphenol), 2,2'-methylenebis (4-methyl-6-cyclohexylphenol), 2,2'- Dihydroxy-
3,3′-di (α-methylcyclohexyl) -5,5 ′
-Dimethyldiphenylmethane, 2,2'-ethylidene-
Bis (2,4-di-t-butylphenol), 2,2 ′
-Butylidene-bis (4-methyl-6-t-butylphenol), 4,4′-methylenebis (2,6-di-t-
Butylphenol), 4,4'-butylidenebis (3-
Methyl-6-t-butylphenol), 1,6-hexanediol bis [3- (3,5-di-t-butyl-4-
Hydroxyphenyl) propionate], triethylene glycol-bis-3-(-t-butyl-4-hydroxy-5-methylphenyl) propionate, N, N'-
Bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine, N, N'-hexamethylenebis- (3,5-di-t-butyl-4-hydroxy) hydrocinnamide , 2,2'-thiobis (4
-Methyl-6-t-butylphenol), 4,4′-thiobis (3-methyl-6-t-butylphenol),
2,2-thiodiethylenebis- [3 (3,5-di-t-
Butyl-4-hydroxyphenyl) propionate],
Bis [2-t-butyl-4-methyl-6- (3-t-butyl-5-methyl-2-hydroxybenzyl) phenyl] terephthalate, 1,1,3-tris (2-methyl-4-hydroxy- 5-t-butylphenyl) butane,
1,3,5-trimethyl-2,4,6-tris (3,5
-Di-t-butyl-4-hydroxybenzyl) benzene, tris (3,5-di-t-4-hydroxybenzyl) isocyanurate, 1,3,5-tris (4-t-
Butyl-3-hydroxy-2,6-dimethylbenzyl)
Isocyanurate, tetrakis [methylene-3-
(3 ′, 5′-di-t-butyl-4-hydroxyphenyl) propionate] methane, calcium (3,5-di-t-butyl-4-hydroxybenzylmonoethylphosphonate), propyl gallate, gallic Octyl acid,
Lauryl gallate, 2,4,6-tri-t-butylphenol, 2,5-di-t-butylhydroquinone, 2,5
-Di-t-amylhydroquinone, 1,1,3-tris-
(2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris- (3,5-di-t-butyl-4-hydroxybenzyl) Benzene, 3,9-bis [2- {3- (3-t-
Butyl-4-hydroxy-5-methylphenyl) propionyloxy {-1,1-dimethylethyl] -2,8,
Examples thereof include 10-tetraoxaspiro [5,5] undecane, and one or more of these can be used.

Among these, 2,6-di-t-butyl-p-cresol, 2-t-butyl-4-methoxyphenol, 2,2'-methylenebis (4-methyl-6-t
-Butylphenol), 2,2'-methylenebis (4-
Ethyl-6-t-butylphenol), 4,4'-butylidenebis (3-methyl-6-t-butylphenol)
One or more selected from the following can be suitably used. In particular, 2,
6-Di-t-butyl-p-cresol has the least effect on the human body and is the most preferred antioxidant.

[0019]

Example: Base oil of base damping damper: 29.5 m in kinematic viscosity (40 ° C)
m ² / s, viscosity index 136, pour point -55 ° C. or lower polyα-olefin (PAO), kinematic viscosity (40 ° C.) 25.5
A mineral lubricating base oil having a mm ² / s, a viscosity index of 105, and a pour point of −15 ° C. was used for the test.

Antioxidants As antioxidants , phenolic 2,6-di-t-
Example 1 Using Butylparacresol (BHT) (Example 1) Oil obtained by adding 0.2% by mass of BHT to the above PAO was used as a vibration damper oil. This was put into the test apparatus shown in FIG. 1, and a load test was performed by reciprocating the piston. The test conditions were assumed to be a maximum earthquake, the oil pressure was set to be 3.3 × 10 ⁶ Pa at the maximum, and the number of reciprocations was 700,000. During the test, the temperature of the oil reached a maximum of 75 ° C. The properties of the oil before and after the test are shown in Table 2, but no significant change was observed.

(Table 2) Kinematic Viscosity Viscosity Total Acid Value Peroxide Oxidation Prevention mm ² / s Index mgKOH / g ppm Agent Reduction (40 ° C.)% Before Test 29.5 136 0.02 2-Test After 31.0 133 0.022 21 (Examples 2 to 4) BHT was added to PAO by 0.1, respectively.
RBOT was added according to JIS K2514 to confirm long-term stability.
The test was performed. For comparison, a similar test was performed on a mineral oil to which BHT was added at 0.6% by mass.
The results are shown in Table 3, which shows that PAO has a greater effect of adding an antioxidant than mineral oil, and is suitable as a lubricating oil used for a long period of time.

(Table 3) Example 2 Example 3 Example 4 Comparative Example 1 Base oil PAO PAO PAO Mineral oil BHT added 0.1 0.2 0.4 0.6 Amount, mass% RBOT, min 272 346 416 214

[0023]

As described above, the hydraulic oil of the present invention sufficiently satisfies the required performance for a vibration damper.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a test apparatus used in an example.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C10N 20:00 20:02 30:10 40:06 (72) Inventor Seijiro Yasutomi 3 Niisonanami, Toda City, Saitama Prefecture No. 17-35 in Japan Energy Co., Ltd. (72) Inventor Yuji Shitara 3-17-35 Niisonanami, Toda City, Saitama Prefecture F-term in Japan Energy Co., Ltd. 3J048 AA02 AC04 AD12 BE03 CB11 EA38 4H104 BA07A BB34A BB41A CB14A EA02A EA30A EB09 PA04 PA05

Claims (3)

[Claims] 1. A hydraulic oil for a vibration damper having a viscosity index of 110 or more, a bulk modulus of 1.3 GPa or more, and a pour point of -25 ° C. or less. 2. The hydraulic oil for a vibration damper according to claim 1, wherein the hydraulic oil for a damper is at least one selected from poly α-olefins, polyol esters, and polyethers. 3. The hydraulic oil for a vibration damper according to claim 1, wherein an antioxidant is added to the hydraulic oil for the damper in an amount of 0.01 to 2% by weight.