JP2001172660A - Hydraulic fluid composition for shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition good in storage stability at low temperatures, exhibiting excellent friction diminishing effect or abrasion preventive effect in the lubrication of Teflon (R) resin-impregnated bushes or piston bands and excellent in maintainability of these effects as well. SOLUTION: This hydraulic fluid composition for shock absorbers is obtained by incorporating a lubricating base oil with [1] an acid phosphorous ester with 12-20C alkyl group and/or alkenyl group, [2] an aliphatic amine or alkylene oxide adduct thereof with 3-8C alkyl group and/or alkenyl group and [3] an alkylene oxide adduct of an aliphatic amine with 12-24C alkyl group and/or alkenyl group; wherein the components [1] and [2] are in mutual contact in the absence of the component [3].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic fluid composition for a shock absorber, and more particularly to a hydraulic oil composition for a shock absorber suitable for an automobile suspension system (shock absorber, active suspension, stay damper, engine damper, etc.). .

[0002]

2. Description of the Related Art Conventionally, phosphate hydraulic fluids for shock absorbers used in automobile suspension systems (shock absorbers, active suspensions, stay dampers, engine dampers, etc.) have been used to reduce friction and prevent wear. Or what added a phosphite is known. Further, in order to further enhance the friction reducing effect, those using an oily agent such as a fatty acid, an aliphatic alcohol, a fatty acid ester, an aliphatic amine, or an alkylene oxide adduct of an aliphatic amine in combination have been used (JP-A-6-12).
No. 8581, JP-A-7-224293, JP-A-7-258673, etc.). Friction and wear of the shock absorber mainly occur in the piston rod / seal, the piston rod / bush, and the piston band / cylinder. Therefore, in order to reduce the vibration of the automobile and secure ride comfort and steering performance, the hydraulic oil used for the shock absorber is required to have excellent friction reducing effect, wear preventing effect and maintaining these characteristics. In recent years, bushings impregnated with Teflon resin and molded pistons (piston bands) with carbon fiber or graphite embedded in Teflon resin have been used for the purpose of reducing friction from the material side. It has been an issue. In addition, the use of gas-filled type or variable damping force type shock absorbers having a high load applied to the friction surface has been increasing, and the use conditions of the hydraulic oil for shock absorbers have become severe. Therefore, the applicant of the present invention used a phosphite and an aliphatic amine having a specific structure and / or an alkylene oxide adduct thereof to provide a hydraulic fluid for a shock absorber having good storage stability and excellent performance. It has been found that a composition can be obtained, and a patent application (Japanese Patent Application No. Hei 4-301578, Japanese Patent Application No. Hei 6-37528,
Japanese Patent Application No. Hei 6-77840).

[0003]

In the above-described hydraulic oil composition for shock absorbers, the conventional phosphate ester and / or phosphite ester are replaced by the above-mentioned changes in the use environment of the hydraulic oil for shock absorbers. When a fatty acid, an aliphatic alcohol, or a fatty acid ester oil agent is used in combination, there is a problem that the friction surface is greatly worn and the friction reducing effect is small. Further, although a combination of a phosphate ester and / or a phosphite ester and an aliphatic amine has an initial wear-preventing effect and a friction-reducing effect, there may be a problem in maintaining the effects. The combination of a phosphate ester and / or a phosphite ester with an alkylene oxide adduct of an aliphatic amine has relatively good friction-reducing and abrasion-preventing effects. There may be a problem that a reaction product of the group III amine with the alkylene oxide adduct precipitates at a low temperature. This problem may also be observed with combinations of phosphates and / or phosphites with aliphatic amines. These deposits risk blocking the filters in the line that fills the shock absorber with hydraulic fluid. However, in order to reduce friction and wear of the Teflon resin-impregnated bush and piston band, a combination of these phosphites and an aliphatic amine and / or an alkylene oxide adduct of an aliphatic amine is very effective. Therefore, the present invention has good storage stability especially at low temperatures, exhibits excellent friction reducing effect and wear preventing effect in lubrication of Teflon resin-impregnated bushes and piston bands, and is excellent in maintaining these effects. An object of the present invention is to provide a hydraulic fluid composition for a shock absorber.

[0004]

Means for Solving the Problems The present inventors have [1] an acidic phosphite having a specific structure; [2] an aliphatic amine having a specific structure or an alkylene oxide adduct thereof; By containing an alkylene oxide adduct of an aliphatic amine having a specific structure and by giving a characteristic to the method of blending the components [1] and [2], the storage stability at low temperatures is good and excellent. The present inventors have found a hydraulic oil composition for a shock absorber having excellent performance, and have completed the present invention. That is, the hydraulic fluid composition for a shock absorber according to the present invention is used in a lubricant base oil [1].
Acidic phosphite having an alkyl group and / or alkenyl group having 12 to 20 carbon atoms, [2] an aliphatic amine having an alkyl group and / or alkenyl group having 3 to 8 carbon atoms or an alkylene oxide adduct thereof, 3] An alkylene oxide adduct of an aliphatic amine having an alkyl group and / or an alkenyl group having 12 to 24 carbon atoms, respectively, and the component [1] and the component [2] are the above [3]. They are in contact in the absence of components.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The lubricating base oil in the present invention is not particularly limited, and any lubricating base oil which is generally used as a lubricating base oil can be used regardless of whether it is a mineral oil or a synthetic oil. As a mineral oil-based lubricating base oil, for example, a lubricating oil fraction obtained by atmospheric distillation and vacuum distillation of crude oil is subjected to solvent removal, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrogen Paraffin-based, naphthenic-based oils, etc. purified by appropriately combining purification treatments such as chemical purification, sulfuric acid washing, and clay treatment can be used. In addition, as a synthetic lubricating base oil,
For example, α-olefin oligomers (polybutene, polyisobutylene, 1-octene oligomer, 1-decene oligomer, ethylene-propylene copolymer, etc.) or hydrides thereof, alkylbenzene, alkylnaphthalene, diester, (ditridecyl glutarate, di- 2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate, etc., polyol esters (trimethylolpropane caprylate, trimethylolpropaneperargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol peralgo And the like, polyoxyalkylene glycol, polyphenyl ether, silicone oil, perfluoroalkyl ether, and the like. These base oils may be used alone or in combination of two or more. The viscosity of the lubricating base oil used in the present invention is not particularly limited, and is arbitrary. However, the lower limit of the kinematic viscosity at 40 ° C. is preferably from the need to adjust to the damping force required for a general shock absorber. It is 8 mm ² / s, more preferably 10 mm ² / s. On the other hand, the upper limit of the kinematic viscosity at 40 ° C. is preferably 60 mm ² / s, more preferably 40 mm ² / s. The viscosity index of the lubricating base oil used in the present invention is not particularly limited, and is arbitrary. However, the damping action, which is the basic performance required for the shock absorber, depends on the viscosity of the hydraulic oil, and the damping force due to temperature is reduced. From the viewpoint of minimizing the change, it is desirable to use a viscosity index of preferably 80 or more, more preferably 95 or more.

The component [1] in the hydraulic fluid composition for a shock absorber according to the present invention comprises an alkyl group having 12 to 20 carbon atoms and / or
Or an acid phosphite diester or an acid phosphite monoester having an alkenyl group. Specific examples thereof include a phosphite diester represented by the following general formula (1), a phosphite monoester represented by the general formula (2), and a mixture thereof.

Embedded image

Embedded image In some cases, the acidic phosphite diester represented by the above formula (1) is a tautomer thereof in the form of the following general formula (3) or the acid phosphite diester represented by the above formula (2). Phosphorous acid monoesters may be represented by the following general formula (4), which is a tautomer thereof, but each represents the same compound.

Embedded image

Embedded image In the above formulas (1), (2), (3) and (4), R
¹ , R ² and R ³ are each independently linear or branched, or have 12 to 20 carbon atoms, preferably 16 to 1 carbon atoms.
8 represents an alkyl group or an alkenyl group. R ¹ ,
As R ² and R ³ , individually and specifically, for example, alkyl groups such as dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group and the like (these alkyl groups) Groups may be straight-chain or branched); dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl,
Alkenyl groups such as an octadecenyl group, a nonadecenyl group and an icosenyl group (these alkenyl groups may be linear or branched); As preferable examples of the component [1], specifically, for example, di-n-dodecyl hydrogen phosphite (dilauryl hydrogen phosphite), di-n-tetradecyl hydrogen phosphite (dimyristyl hydrogen) Phosphite), di-n-hexadecyl hydrogen phosphite (dipalmityl hydrogen phosphite), di-
n-octadecyl hydrogen phosphite (distearyl hydrogen phosphite), di-9-octadecenyl hydrogen phosphite (dioleyl hydrogen phosphite), di-n-icosenyl hydrogen phosphite, etc. Diester, n-dodecyl hydrogen phosphite (lauryl hydrogen phosphite), n-tetradecyl hydrogen phosphite (myristyl hydrogen phosphite),
n-hexadecyl hydrogen phosphite (palmityl hydrogen phosphite), n-octadecyl hydrogen phosphite (stearyl hydrogen phosphite), 9-octadecenyl hydrogen phosphite (oleyl hydrogen phosphite), Monoesters such as n-icosenyl hydrogen phosphite can be exemplified, and a mixture thereof can also be used. In the hydraulic fluid composition for a shock absorber according to the present invention, the content of the component [1] is not particularly limited, and is arbitrary. However, in view of the effect of reducing friction and improving the effect of preventing wear, the lower limit of the content is as follows. , Based on the total amount of the composition.
1% by weight, more preferably 0.3% by weight, while
From the viewpoint of storage stability at low temperatures, the upper limit of the content is preferably 5.0% by mass, more preferably 2.0% by mass.

The component [2] in the present invention has 3 to 3 carbon atoms.
8 is an aliphatic amine having an alkyl group and / or an alkenyl group, or an alkylene oxide adduct thereof.
Examples of the aliphatic amine include an aliphatic primary amine represented by the following general formula (5), an aliphatic secondary amine represented by the following general formula (6), and a mixture thereof.
R ⁴ —NH ₂ (5)

Embedded image In the above formulas (5) and (6), R ⁴ , R ⁵ and R ⁶ are each independently a linear or branched alkyl group having 3 to 8 carbon atoms, preferably 4 to 8 carbon atoms. Or an alkenyl group. R ⁴ , R ^5, and R ⁶ are each individually specifically, for example, an alkyl group such as a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group; Alkenyl groups such as a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, and an octenyl group (these alkenyl groups may be linear or branched). Specific examples of preferred aliphatic amines include, for example, n-
Examples thereof include aliphatic primary amines such as butylamine, n-octylamine (caprylamine), and 2-ethylhexylamine, and aliphatic secondary amines such as di (2-ethylhexyl) amine, and mixtures thereof. Can be used. The alkylene oxide adduct of an aliphatic amine used as the component [2] of the present invention is specifically an aliphatic primary amine alkylene oxide adduct represented by the following general formula (7). And an aliphatic secondary amine alkylene oxide adduct represented by the following general formula (8) and a mixture thereof.

Embedded image

Embedded image In the above formulas (7) and (8), R ⁷ , R ¹⁰ and R ¹¹ are
Each individually, straight or branched, having 3 to 8 carbon atoms;
It preferably represents an alkyl group or an alkenyl group having 4 to 8 carbon atoms. R ⁷ , R ^10, and R ¹¹ are each individually specifically, for example, an alkyl group such as a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group (the alkyl group may be linear or branched; Good); butenyl group,
Alkenyl groups such as a pentenyl group, a hexenyl group, a heptenyl group, and an octenyl group (these alkenyl groups may be linear or branched); In addition, the above (7)
In the formula and the formula (8), R ⁸ , R ⁹ and R ¹² are each independently a linear or branched C 2 to C 6, preferably C 2 to C 3, more preferably C 2 or C 3 2 represents an alkylene group. R ⁸ , R ^9, and R ¹² are each individually specifically, for example, an alkylene group such as an ethylene group, a propylene group, a butylene group, a pentylene group, and a hexylene group (the alkylene group may be linear or branched; Good). In the above formula (7), a and b are each independently 0 to 10, preferably 0 to 5, and a +
b represents a number of 1 to 10, preferably 1 to 5,
In the formula (8), c represents a number of 1 to 10, preferably 1 to 5. As preferred alkylene oxide adducts of aliphatic amines, specifically, for example,
Aliphatic primary amines such as n-butylamine, n-octylamine (caprylamine), and 2-ethylhexylamine, ethylene oxide adducts, propylene oxide adducts, butylene oxide adducts, and di (2-ethylhexyl) amines Examples thereof include an ethylene oxide adduct, a propylene oxide adduct, and a butylene oxide adduct of an aliphatic secondary amine, and a mixture thereof can also be used. It goes without saying that a mixture of an aliphatic amine and an aliphatic amine alkylene oxide adduct as exemplified above can also be used as the component [2] of the present invention. In the hydraulic fluid composition for a shock absorber of the present invention,
The content of the component [2] is not particularly limited and is optional, but the lower limit of the content is preferably 0.1% based on the total amount of the composition.
01% by mass, more preferably 0.02% by mass, while the upper limit of the content is preferably 5.0% by mass,
More preferably, the content is 2.0% by mass. If the amount is outside the above range, the effect of reducing friction and the effect of preventing wear may be poor.

[0008] The component [3] in the hydraulic fluid composition for a shock absorber of the present invention comprises an alkyl group having 12 to 24 carbon atoms and / or
Or an alkylene oxide adduct of an aliphatic amine having an alkenyl group. As the component [3], specifically, an aliphatic primary amine alkylene oxide adduct represented by the following general formula (9) or an aliphatic secondary amine represented by the following general formula (10) Examples thereof include amine alkylene oxide adducts and mixtures thereof.

Embedded image

Embedded image In the above formulas (9) and (10), R ¹³ , R ¹⁶ and R
¹⁷ is each independently a linear or branched C 1 -C 1
An alkyl group or alkenyl group having 2 to 24, preferably 14 to 22, and more preferably 16 to 18 carbon atoms is shown. R ¹³ , R ¹⁶ and R ¹⁷ are each individually specifically, for example, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, icosyl, henycosyl, docosyl Alkyl groups such as a group, tricosyl group and tetracosyl group (these alkyl groups may be linear or branched); dodecenyl group, tridecenyl group, tetradecenyl group, pentadecenyl group, hexadecenyl group, heptadecenyl group, octadecenyl group, nonadecenyl group ,
Alkenyl groups such as an icosenyl group, a henicocenyl group, a docosenyl group, a tricosenyl group, and a tetracosenyl group (these alkenyl groups may be linear or branched); In the above formulas (9) and (10), R ¹⁴ ,
R ¹⁵ and R ¹⁸ are each independently a linear or branched, having 2 to 6 carbon atoms, preferably 2 to 3 carbon atoms, more preferably represents an alkylene group having 2 carbon atoms. R ¹⁴ , R
Specific examples of ¹⁵ and R ¹⁸ are each independently an alkylene group such as an ethylene group, a propylene group, a butylene group, a pentylene group, and a hexylene group (the alkylene groups may be linear or branched). it can. In the formula (9), d and e each independently represent a number of 0 to 10, preferably 0 to 5, and d + e = 1 to 10, preferably 1 to 5, and (10) Where f is 1
10 to 10, preferably 1 to 5.
As preferred components of the component [3], specifically,
n-dodecylamine (laurylamine), n-tetradecylamine (myristylamine), n-hexadecylamine (palmitylamine), n-octadecylamine (stearylamine), 9-n-octadecenylamine (oleylamine) , Ethylene oxide adducts of aliphatic primary amines such as isostearylamine, propylene oxide adducts, butylene oxide adducts, and ethylene oxide adducts of aliphatic secondary amines such as di (n-dodecyl) amine Adducts, butylene oxide adducts and the like can be exemplified, and mixtures thereof can also be used. In the hydraulic fluid composition for a shock absorber according to the present invention, the content of the component [3] is not particularly limited and is arbitrary. However, based on the total amount of the composition, the lower limit of the content is preferably 0.01% by mass. , More preferably 0.02% by mass, while the upper limit of the content is preferably 5.0%.
%, More preferably 2.0% by mass. [3] When the content of the component is less than the above lower limit,
There is a possibility that the effect of reducing the friction and the effect of preventing abrasion by the inclusion of the component [3] may be poor. On the other hand, if the content of the component [3] exceeds the above upper limit, the storage stability at low temperatures may be poor. is there.

The hydraulic fluid composition for a shock absorber according to the present invention comprises:
Component [1], component [2] and component [3] are respectively contained, and component [1] and component [2] are component [3].
They are in contact in the absence of components. The contact temperature between the component [1] and the component [2] is preferably 10 ° C. or higher, more preferably 40 ° C. or higher, and preferably 150 ° C. or lower.
More preferably, it is 100 ° C. or lower. Contact temperature is 10
If the temperature is lower than 150 ° C, contact will not be sufficient
If the ratio exceeds the above, it is not preferable because problems such as decomposition of the components [1] and [2] occur. The contact time is not particularly limited, but is usually 30 minutes or more, preferably 60 minutes or more.
It is desirably 3 hours or less, preferably 2 hours or less. When the contact time is less than 30 minutes, the contact is not sufficiently performed, and even if the contact is performed for more than 3 hours, the performance of the obtained hydraulic fluid composition is not further improved, and thus has no meaning. In addition, the contact here is usually performed by stirring, but the stirring method and stirring conditions other than the temperature and time are not particularly limited, and any stirring method performed in the production of a known lubricating oil composition, Stirring conditions are applicable.
Specifically, for example, a method using a stirrer such as a propeller stirrer or a honeycomb mixer is preferably used. [3]
There are no particular restrictions on the conditions under which the components are contained, and any conditions under which an alkylene oxide adduct of an aliphatic amine is contained in a general lubricating oil composition can be applied.
[3] The component is usually contained by stirring, but the stirring method at this time is also optional, and any known stirring method used in producing a lubricating oil composition can be applied. Specifically, for example, a method using a stirrer such as a propeller stirrer or a Hamicam mixer is preferably used. As one method for obtaining the hydraulic fluid composition for a shock absorber of the present invention, first, the component [1] and the component [2] are added to the lubricating base oil simultaneously or separately, and then the above conditions, that is, 10 to 150 are added. A method of contacting at a temperature of ° C. and finally including the component [3] therein. As another method for obtaining the hydraulic fluid composition for a shock absorber of the present invention, first, the component [1] and the component [2] are subjected to the above-mentioned conditions, that is, 10 to 150 ° C.
After contacting at a temperature of the above, the contact product thus obtained is mixed with the component [3], and the resulting mixture is added to a lubricating base oil. As another method for obtaining the hydraulic fluid composition for a shock absorber of the present invention, first, the component [3] is added to a lubricating base oil, and then the components [1] and [2] are added under the above-mentioned conditions, ie, A method of contacting at a temperature of 10 to 150 ° C. and adding the contact substance thus obtained to a lubricating base oil can be mentioned. In these exemplified methods, the components [1] to [3] may be used individually in the form of a compound individually, or as described above, may be used in a form diluted with a solvent or lubricating oil.

In the present invention, the lubricating base oil contains components [1] to [3] as described above, and
By contacting the component [1] with the component [2] in the absence of the component [3], a hydraulic oil composition for a shock absorber having excellent performance can be obtained. Known lubricating oil additives for the purpose of further increasing, specifically, for example, an antiwear agent, an ashless detergent / dispersant, a metal-based detergent, an antioxidant, a rust inhibitor, a metal deactivator, a viscosity index improver, Pour point depressants, defoamers and the like can be used alone or in a combination of several types. Examples of the antiwear agent include zinc dithiophosphate, sulfurized fats and oils, sulfide, phosphate ester, and amine salt of phosphate ester. Examples of the ashless detergent / dispersant include succinimide, succinamide, succinate, benzylamine, and the like, and a boron-containing ashless detergent / dispersant can also be used. Examples of the metal-based detergent include alkaline earth metal sulfonates, alkaline earth metal phenates, alkaline earth metal salicylates, alkaline earth metal phosphonates, and the like. Examples of the antioxidant include amine antioxidants such as alkylated diphenylamine and phenyl-α-naphthylamine, and 2,6-di-te.
In addition to phenol-based antioxidants such as rt-butyl-p-cresol, etc., sulfur-based, zinc dithiophosphate-based, phenothiazine-based antioxidants and the like can be mentioned. Examples of the rust inhibitor include petroleum-based and dinonylnaphthalene-based sulfonates, ester-based rust inhibitors and the like. Benzotriazole-based compounds as metal deactivators,
And thiadiazole compounds. Examples of the viscosity index improver and pour point depressant include polymethacrylate, polyisobutylene, and olefin copolymer. Examples of the antifoaming agent include dimethyl silicone, fluorosilicone, and polyacrylate. The content of these additives is not particularly limited and is arbitrary. Usually, based on the total amount of the composition, the content of the defoamer is 0.0005 to 0.1% by mass, and the content of the viscosity index improver is 1 to 30% by mass, the content of the metal deactivator is 0.005 to 1% by mass, and the content of other additives is 0.
1 to 15% by mass.

The hydraulic fluid composition for a shock absorber of the present invention is suitably used particularly for a suspension system of an automobile (shock absorber, active suspension, stay damper, engine damper, etc.).

[0012]

EXAMPLES Hereinafter, the content of the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these contents.

Examples 1 to 3 and Comparative Examples 1 to 3 Various compositions according to the present invention having compositions shown in Table 1 (Examples 1 to 3)
3) A hydraulic working oil composition for a shock absorber was prepared. In this preparation, the components [1] and [2] are first added to the base oil, and the mixture is stirred at 50 ° C. for 1 hour using a propeller stirrer, and then the component [3] is contained. Let's go. A laboratory storage stability test and a real machine durability test described below were performed on each of the prepared compositions to evaluate the storage stability at low temperatures, the friction reduction effect, and the wear prevention effect. The results are shown in Table 1. Also, for comparison,
Comparative Examples 1 to 3 having the same composition ratio as Example 1 were prepared in the following mixing order. Comparative Example 1: All the components [1] to [3] are added simultaneously. Comparative Example 2: The component [1] and the component [3] are added first, and then the component [3] is added. Comparative Example 3: The component [2] and the component [3] are added first, and then the component [1] is added. A test similar to the above was performed on the composition thus prepared, and the results are shown in Table 1.

<Storage stability test> Composition 10 shown in Table 1
0 ml was placed in a screw tube with a lid and stored at −5 ° C. for one month, and the presence or absence of a precipitate was visually inspected. <Durability test of actual machine> Using a commercially available strut-type shock absorber, a durability test was performed under the following test conditions with 2 million vibrations. Test oil temperature: 80 ° C Test oil amount: 330 ml Lateral load: 200 kgf Vibration total amplitude: 50 mm Vibration speed: 0.5 m / s Friction reduction effect In the above actual machine durability test, when the number of vibrations was 0 (initial of the durability test) ) And the number of vibrations of 2,000,000 times (at the end of the durability test), and the friction coefficient on the friction surface of each shock absorber was measured. Wear prevention effect In the above-mentioned actual machine durability test, the shock absorber was disassembled after the end of the durability test, and the surfaces of the friction surfaces (cylinder, piston rod, bush, piston band, oil seal) were visually evaluated, and the results were shown in Table 1. It was shown to.
The criterion of the wear prevention effect is 6 from 0 to 5 (best: 5).
Expressed in stages.

[0015]

[Table 1]

As is clear from the results of the examples in Table 1,
Hydraulic hydraulic oil composition for shock absorber according to the present invention (Examples 1 to 5)
3) has good low-temperature storage stability, is excellent in friction reduction effect in the early stage of durability, and has excellent performance that its change with time is small. In addition, the friction surface after the end of the durability has little wear, and it can be seen that the hydraulic oil composition for shock absorbers of the present invention is excellent also in terms of the effect of preventing wear. On the other hand, Comparative Examples 1 to 3 in which the contact between the component [1] and the component [2] was not performed in the absence of the component [3].
All three compositions have a problem in low-temperature storage stability.

[0017]

In summary, according to the present invention, the storage stability at low temperatures is good, and excellent lubrication of Teflon resin-impregnated bushings and piston bands can be achieved with excellent friction reduction and wear prevention effects. A hydraulic oil composition for shock absorbers having excellent maintainability can be obtained.

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Claims (1)

[Claims] Claims: 1. A lubricating base oil having [1] 12 carbon atoms
Acidic phosphite having an alkyl group and / or an alkenyl group of from 20 to 20; [2] an aliphatic amine having an alkyl group and / or an alkenyl group having a carbon number of 3 to 8 or an alkylene oxide adduct thereof; Number 12-2
4) an alkylene oxide adduct of an aliphatic amine having an alkyl group and / or an alkenyl group, and wherein the component [1] and the component [2] are in the absence of the component [3]. A hydraulic fluid composition for a shock absorber, which is in contact with the hydraulic fluid.