JPH07258675A - Hydraulic pressure oil composition for buffer - Google Patents

Abstract

PURPOSE:To obtain the subject composition having a property for preventing corrosion of a guide bush and durability of abrasion characteristics without impairing characteristics as a buffer oil and capable of stably using for a long period even under high-temperature circumference by blending a phosphoric acid ester with calcium salicylate at a specific ratio. CONSTITUTION:This composition contains a base oil for lubricating oil consisting of a mineral oil, a synthetic oil or their mixture, (A) 0.005-1wt.% of at least one phosphorus compound selected from alkyl or alkyl-substituted or unsubstituted phenylphosphoric acid-based compounds and (B) 0.03-2wt.% of calcium salicylate. Furthermore, e.g. a compound expressed by the formula (R<3> is a 8-20C alkyl; N is OH or O-Ca-OH) is preferably used as the component B.

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 shock absorbers, and more particularly to a hydraulic fluid composition for shock absorbers having excellent corrosion resistance and durability of friction characteristics.

[0002]

2. Description of the Related Art Among suspension components of automobiles, shock absorbers are functional parts that play an important role in maneuverability, stability and riding comfort. Its structure is basically a tubular structure that utilizes the flow resistance of oil. The sliding portion between the cylinder and the piston rod is sealed to prevent mutual wear. Various shock absorbers such as a double pipe type and a gas filled type are known. In addition to the above, similar shock absorbers are also used in automobiles for supporting devices for engines, shock absorbing devices for bumpers, door checkers, and the like. Performances required for hydraulic fluids used in these shock absorbers include damping force characteristics, low temperature fluidity, wear resistance, low friction characteristics, corrosion resistance, thermal oxidation stability, seal compatibility and the like. That is, in order to satisfy these performances, at present, various additives are blended with the selected base oil to provide a hydraulic fluid composition for a shock absorber.

The shock absorbers of these automobiles are often used without being replaced until they are usually discarded until they are installed in the automobile. Further, the oil temperature of the shock absorber during normal traveling is about 40 to 80 ° C, but it may rise to about 100 to 120 ° C during traveling in midsummer. When the oil is used for a long period of time in such an environment, the oil undergoes thermal oxidative deterioration, corrodes the guide bush of the shock absorber, and increases the friction characteristics. In that case, the smooth cushioning action is impaired, which is not preferable. From such a background, development of a hydraulic fluid for a shock absorber, which is excellent in the corrosion prevention property of the guide bush and which can suppress an increase in friction characteristics, has been desired.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in order to meet the above-mentioned demands, and it is possible to effectively prevent the guide bush from being corroded and to provide a hydraulic actuation for a shock absorber having excellent friction characteristics and durability. It is intended to provide an oil composition.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have combined a base oil of mineral oil or synthetic oil with a phosphate ester and a metal type detergent. It has been found that by compounding a specific amount, it is possible to exhibit excellent prevention performance against the corrosion of the guide bush, and to maintain the friction characteristics for a long time without impairing the initial friction characteristics, The present invention has been completed based on this finding. That is, the present invention is a lubricating base oil comprising a mineral oil, a synthetic oil or a mixture thereof,
0.005 to 1% by weight of (A) alkyl or at least one selected from alkyl-substituted or unsubstituted phenylphosphate compounds as a phosphorus content, and (B) calcium salicylate at a rate of 0.03 to 2% by weight. The present invention provides a hydraulic fluid composition for shock absorbers, which is characterized by containing. Hereinafter, the present invention will be described in detail.

The base oil used in the hydraulic fluid composition for shock absorbers of the present invention is a mineral oil or a synthetic oil, and may be a mixture thereof. Suitable base oils include at least one of mineral oils and synthetic oils which have been refined by solvent refining or hydrorefining and then the wax content is further removed to improve the low temperature fluidity. Specific examples of the mineral oil include petroleum fractions and refined products thereof. Specific examples of synthetic oils include poly-α-olefin oligomers,
Examples thereof include polybutene, diester, polyol ester and polyalkylene glycol. Considering the solubility of the additives, these synthetic oils are preferably used as a mixture with mineral oils or as a mixture of synthetic oils, rather than being used alone. The viscosity of the base oil can be appropriately selected depending on the purpose. Suitable base oils have a viscosity of 5 to 50 cSt at 40 ° C. and an aniline point of 50 to 110 ° C., for example.

The hydraulic fluid composition for shock absorbers of the present invention comprises:
As the component (A), an alkyl or an alkyl-substituted or unsubstituted phenylphosphoric acid compound is used. Examples of the alkyl or alkyl-substituted or unsubstituted phenyl phosphate compound include alkyl phosphite ester, phosphonate ester, orthophosphate ester, pyrophosphate ester, acidic phosphate ester, acidic phosphate ester amine salt, and the like. There may be mentioned alkyl-substituted or unsubstituted phenyl phosphate compounds. Suitable alkyl groups of these phosphoric acid compounds are linear or branched alkyl groups having 1 to 18 carbon atoms, preferably 4 to 4 carbon atoms.
It is a linear or branched alkyl group having 18 carbon atoms, and particularly preferably a linear or branched alkyl group having 10 to 18 carbon atoms. The alkyl group includes an alkenyl group. Specific examples of the alkyl group include, for example, methyl, ethyl, propyl, butyl, hexyl, octyl,
Examples thereof include nonyl, lauryl, hexadecyl, octadecyl and oleyl groups. The same applies to the alkyl group of the alkyl-substituted phenyl group. These phosphorus compounds may be used alone or in combination of two or more.

In the hydraulic fluid composition for a shock absorber of the present invention, the alkyl component or the alkyl-substituted or unsubstituted phenylphosphoric acid compound as the component (A) is 0.00% as the phosphorus content.
5 to 1% by weight, preferably 0.008 to 0.5% by weight,
Particularly preferably, the content is 0.01 to 0.4% by weight.
The alkyl or the alkyl-substituted or unsubstituted phenylphosphoric acid compound as the component (A) contributes to the frictional characteristics, and if the blending amount is less than 0.005% by weight, the initial frictional characteristics cannot be obtained. If the amount exceeds 5% by weight, the effect is saturated and not only economically disadvantageous, but also rubber compatibility and oxidation stability are adversely affected.

Calcium salicylate is used as the component (B) in the hydraulic fluid composition for shock absorbers of the present invention. As this calcium salicylate, various salicylates can be used. Specific examples of the calcium salicylate include, for example, at least one selected from those represented by the general formula (1) of Chemical formula 1, and preferably R ₃ in the general formula (1) is an alkyl group having 8 to 28 carbon atoms. R ₃ in the general formula (1) is particularly preferably an alkyl group having 14 to 24 carbon atoms. An alkyl group having a carbon number of 29 or more is a solid and can be used by being dissolved. However, in consideration of handleability, it is preferable that the upper limit of the carbon number of R ₃ is about 24. .

[0010]

[Chemical 1]

(In the formula, R ₃ is a linear or branched alkyl group having 8 to 28 carbon atoms, and N is —OH group or —O—Ca—OH.
In the general formula (1) representing the component (B), R _{3 on} the left and right sides may be the same or different, and N on the left and right sides are also the same. May be different or different. Specific examples of R ₃ include n
-Octyl, isooctyl, 2-ethylhexyl, 3-
Methylheptyl, n-nonyl, isononyl, 1-methyloctyl, ethylheptyl, n-decyl, 1-methylnonyl, n-undecyl, n-dodecyl, n-tetradecyl, n-heptadecyl, n-octadecyl and the like can be mentioned. The substitution position of R _{3 on} the benzene ring is not particularly limited. These (B) component calcium salicylates may be used alone or in combination of two or more.

In the hydraulic fluid composition for shock absorbers of the present invention, the component (B) calcium salicylate is
0.03 to 2% by weight, preferably 0.05 to 1% by weight, particularly preferably 0.1 to 0.7% by weight.
Calcium salicylate contributes to the prevention of guide bush corrosion, and can prevent an increase in frictional characteristics due to long-term use and maintain the initial characteristics. If the content of calcium salicylate is too small, the desired effect cannot be obtained, and if it is too large, the effect is saturated and uneconomical, and the initial friction coefficient increases.

In addition to the components (A) and (B), the hydraulic fluid composition for shock absorbers of the present invention has, for example, the following components in order to maintain basic performance as a hydraulic fluid for shock absorbers:
Antioxidants, antiwear agents, dispersants, metal deactivators, friction modifiers, defoamers, viscosity index improvers, corrosion inhibitors, metallic detergents, pour point depressants and the like can be added. Examples of the antioxidant include amine-based compounds such as phenyl-α-naphthylamine and bis (alkylphenyl) amine,
2,6-di-t-butylparacresol, 4,4′-methylenebis (2,6-di-t-butylphenol),
Examples include phenolic antioxidants such as 4,4′-thiobis (2-methyl-6-t-butylphenol) and 4,4′-bis (2,6-di-t-butylphenol). As the antiwear agent, for example, zinc dithiophosphate,
Examples thereof include phosphorus compounds, sulfur compounds and chlorine compounds. Examples of the dispersant include alkenyl succinimide, polyoxyalkylene aminoamide, benzylamine and the like.

Examples of the metal deactivator include benzotriazole and thiadiazole. As the friction modifier, for example, higher fatty acids such as oleic acid, stearic acid and palmitic acid, lauryl alcohol, oleyl alcohol, higher alcohols such as cetyl alcohol, ethyl oleate, sorbitan monostearate,
Examples thereof include esters such as oleic acid monoglyceride, amines such as cetylamine and octadecylamine, and phosphate ester amine salts. As an antifoaming agent,
Examples thereof include silicone compounds such as dimethylpolysiloxane and phenylmethylsiloxane, and ester compounds such as alkenylsuccinic acid derivatives.

Examples of the viscosity index improver include polymethacrylate, polyisobutylene, ethylene / propylene copolymer, styrene / diester copolymer and the like. Examples of the metal-type detergents include alkaline earth metal sulfonates and alkaline earth metal phenates. Examples of the corrosion inhibitor include benzotriazole and alkenyl succinic acid ester.
Examples of the pour point depressant include polymethacrylate and the like. The blending amount of these various additives may be appropriately selected, but each additive other than the metallic detergent is 20% by weight or less, preferably 10% by weight or less. Since the friction coefficient may increase with a large amount of the metallic detergent, it may be appropriately added within a range in which the friction does not increase.

The hydraulic oil composition for shock absorbers of the present invention is produced by appropriately blending the above-mentioned base oils with the respective components (A) and (B) in predetermined amounts and, if necessary, various additives. can do. The method of mixing each component and the method of adding various additives are not particularly limited, and various methods can be used, and the mixing order and the addition order can also be performed in various mixing orders and addition orders. For example,
You may sequentially mix each component and various additives to the base oil,
Each component and various additives may be mixed in advance and then mixed with the base oil. The hydraulic fluid composition for shock absorbers of the present invention,
Although it can be used for various hydraulic devices, it is particularly preferably used as a hydraulic fluid for a shock absorber used for a suspension of an automobile body. Of course, it can be suitably used for an active suspension for automobiles.

[0017]

EXAMPLES Next, the present invention will be described more specifically by way of Examples and Comparative Examples. The present invention is not limited to these examples. The components used in Examples and Comparative Examples are as follows. (1) Calcium salicylate A compound having the following structure in which R _{3 in the} general formula (1) is a mixture of C _{14 to} C ₂₄ and N is an OH group.

[0018]

[Chemical 2]

The evaluation tests of Examples and Comparative Examples were carried out by the following method. (1) Measurement of Friction Force Using the hydraulic fluid compositions for shock absorbers described in the examples and comparative examples, a bench test was conducted to measure changes in friction force with time. Specifically, a double-cylinder gas shock absorber for automobiles was used to move the piciton rod up and down at high speed. In this case, the lateral load, stroke, and frequency were set to the following test conditions in order to match the actual running conditions of the automobile. Test conditions Temperature: 60 ° C. Lateral load: 60 Kgf Stroke: ± 2 mm Vibration frequency: 15 Hz A bench test was performed under the above test conditions, and after 200 hours of operation, the force required above and below the rod, that is, the frictional force, was measured. When the value was less than 3 times as large as the value before the bench test, the result was regarded as acceptable, and the value higher than that was regarded as unacceptable.

(2) Bush Immersion Test Using the hydraulic fluid compositions for shock absorbers described in Examples and Comparative Examples, a bush immersion test was conducted to evaluate the corrosion prevention property of the guide bush. After immersing the guide bush in the composition under the following conditions, the Pb concentration in the oil was measured. When the value was less than 50 ppm, it was judged as acceptable, and when it was more than 50 ppm, it was judged as unacceptable and evaluated. Test conditions Temperature: 130 ° C. Sample oil amount: 100 cc Guide bush: Made by Daido Metal Industry Co., Ltd., Product name: DU metal (Dimension: 10 × 80 × 1.5 mm) Time: 120 hr

Examples 1 to 9 Mineral oil having a viscosity of 22 cSt at 40 ° C., component (A), component (B), and other additives were mixed in the proportions shown in Table 1 for a buffer. A hydraulic fluid composition was prepared. With respect to the hydraulic fluid composition for a shock absorber, the above-mentioned evaluation test was conducted to evaluate the performance. Among the results, Examples 1 to 5 are shown in Table 1, and Examples 6 to 9 are shown in Table 2.

Comparative Examples 1 to 4 In Comparative Example 1, a hydraulic fluid composition for a shock absorber was prepared in the same manner as in Example 1 except that the calcium salicylate of Example 1 was not added, and in Comparative Example 2, A hydraulic fluid composition for a shock absorber was prepared in the same manner as in Example 2 except that the amount of calcium salicylate in Example 2 was reduced to 0.01% by weight. In Comparative Example 3, the calcium salicylate in Example 1 was added. 2. A hydraulic fluid composition for a softened container was prepared in the same manner as in Example 2 except that the compound was not added, and in Comparative Example 4, the phosphoric acid compound of Example 1 was not added, and the calcium salicylate content was 3. A hydraulic fluid composition for shock absorbers was prepared in the same manner as in Example 1 except that the content was increased to 0% by weight. With respect to the hydraulic fluid composition for a shock absorber, the above-mentioned evaluation test was conducted to evaluate the performance. The results are shown in Table 3. In Tables 1, 2 and 3, the phosphorus content of the phosphoric acid compound is shown in parentheses. The unit of the mixing ratio of each component in Tables 1 and 2 is% by weight.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3] In Table 1, Table 2 and Table 3, the composition ratio of mineral oil is indicated as balanced, which means that the sum of the numerical values of mineral oil and each component is 100% by weight. As is clear from Table 1, Table 2 and Table 3, it can be seen that the examples are excellent in the guide bush corrosion prevention property and the durability of the friction characteristics, while the comparative examples are inferior. .

[0026]

The hydraulic fluid composition for shock absorbers of the present invention comprises:
By blending the phosphoric acid ester and calcium salicylate in a specific ratio, it is possible to provide the gasido bush corrosion resistance and the durability of friction characteristics, which have not been solved in the past, without impairing various characteristics as a shock absorber oil. As described above, the hydraulic fluid composition for a shock absorber of the present invention can be stably used for a long period of time even in a high temperature environment, and is clearly industrially very useful.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication C10N 30:12 40:08 (72) Inventor Natsuto Soga 1134-2 Gongendo, Satte City, Saitama Prefecture Stock Cosmo Research Institute Co., Ltd.

Claims (1)

[Claims] 1. A lubricating base oil comprising a mineral oil, a synthetic oil or a mixture thereof, and 0.005 to at least one selected from (A) an alkyl or an alkyl-substituted or unsubstituted phenyl phosphate compound as a phosphorus content. A hydraulic fluid composition for a shock absorber, comprising 1% by weight and (B) calcium salicylate in a proportion of 0.03 to 2% by weight.