JP7037282B2 - Hydraulic fluid composition and hydraulic system - Google Patents

Description

The present invention relates to hydraulic fluid compositions and hydraulic devices.

The hydraulic device is a device that transmits energy of an engine or the like as the pressure of oil (hydraulic hydraulic fluid), and is used in industrial machines such as iron making machines and construction machines. The hydraulic device includes, for example, a hydraulic pump, a control valve, a hydraulic cylinder, and the like. Since sliding portions are present in these components, the hydraulic fluid also plays a role as a lubricant for the sliding portions. Therefore, the hydraulic fluid is required to have characteristics as a lubricant such as lubricity and thermal / antioxidant properties. In addition, the hydraulic fluid gradually oxidizes and deteriorates, so it needs to be replaced regularly. In order to reduce the number of replacements, the hydraulic fluid is required to have a long life as well as a characteristic as a lubricant.

The hydraulic fluid generally contains a lubricating oil base oil and an additive selected according to the required characteristics as described above. For example, Patent Document 1 selects from 2,6-di-tert-butylphenol (A), a benzotriazole-based compound, and a sorbitan compound for the purpose of improving oxidative stability while suppressing the generation of sludge. A lubricating oil composition containing at least one compound (B) to be used is disclosed. However, even in the conventional lubricating oil composition, there is room for further improvement in terms of extending the service life.

Japanese Unexamined Patent Publication No. 2016-176027

The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a hydraulic fluid composition capable of extending the service life.

As a result of diligent studies to achieve the above object, the present inventors have combined two or more kinds of antioxidants having a specific structure to slow down the consumption rate of the antioxidants, and as a result, the antioxidants. We have found that it is possible to leave the product for a long period of time, and have completed the present invention.

The present invention relates to the hydraulic fluid composition shown in the following [1] and [2], the hydraulic device shown in the following [3] and [4], the use (application) of the composition shown in the following [5], and the following [ 6] Provides the use (application) for the production of the composition shown in.

下記式（２）で表される第２の酸化防止剤と、

［式（２）中、Ｒは酸素原子を含む基によって置換されていてもよいアルキル基を示す。］
を含有する、油圧作動油組成物。
［２］Ｒが下記式（３）で表される基である、［１］に記載の油圧作動油組成物。

［式（３）中、Ｒ^１はアルキレン基を示し、Ｒ^２はアルキル基を示す。］
［３］油圧作動油組成物が貯蔵された油貯蔵部と、油圧作動油組成物を圧送する圧送部と、圧送された油圧作動油組成物の油圧、方向又は流量を制御する制御部と、制御された油圧作動油組成物の油圧を機械的な動力に変換する変換部と、を備える油圧装置であって、
油圧作動油組成物が、
潤滑油基油と、
下記式（１）で表される第１の酸化防止剤と、

下記式（２）で表される第２の酸化防止剤と、

［式（２）中、Ｒは酸素原子を含む基によって置換されていてもよいアルキル基を示す。］
を含有する、油圧装置。
［４］Ｒが下記式（３）で表される基である、［３］に記載の油圧装置。

［式（３）中、Ｒ^１はアルキレン基を示し、Ｒ^２はアルキル基を示す。］
［５］組成物の、油圧作動油としての使用であって、組成物が、潤滑油基油と、上記式（１）で表される第１の酸化防止剤と、上記一般式（２）で表される第２の酸化防止剤と、を含有する、使用。
［６］組成物の、油圧作動油の製造のための使用であって、組成物が、潤滑油基油と、上記式（１）で表される第１の酸化防止剤と、上記一般式（２）で表される第２の酸化防止剤と、を含有する、使用。 [1] Lubricating oil Base oil and
The first antioxidant represented by the following formula (1) and

The second antioxidant represented by the following formula (2) and

[In formula (2), R represents an alkyl group that may be substituted with a group containing an oxygen atom. ]
A hydraulic fluid composition containing.
[2] The hydraulic fluid composition according to [1], wherein R is a group represented by the following formula (3).

[In the formula (3), R ¹ represents an alkylene group and R ² represents an alkyl group. ]
[3] An oil storage unit in which the hydraulic fluid composition is stored, a pumping unit for pumping the hydraulic oil composition, a control unit for controlling the hydraulic pressure, direction, or flow rate of the hydraulic fluid composition pumped. A hydraulic device comprising a converter that converts the hydraulic pressure of a controlled hydraulic fluid composition into mechanical power.
The hydraulic fluid composition,
Lubricating oil base oil and
The first antioxidant represented by the following formula (1) and

The second antioxidant represented by the following formula (2) and

[In formula (2), R represents an alkyl group that may be substituted with a group containing an oxygen atom. ]
Contains, hydraulic equipment.
[4] The hydraulic device according to [3], wherein R is a group represented by the following formula (3).

[In the formula (3), R ¹ represents an alkylene group and R ² represents an alkyl group. ]
[5] The composition is used as a hydraulic fluid, and the composition comprises a lubricating oil base oil, a first antioxidant represented by the above formula (1), and the above general formula (2). A second antioxidant, represented by, and used in.
[6] The composition is used for the production of hydraulic fluid, and the composition comprises a lubricating oil base oil, a first antioxidant represented by the above formula (1), and the above general formula. Use, which contains the second antioxidant represented by (2).

According to the present invention, there is provided a hydraulic fluid composition capable of extending the service life. Further, according to the present invention, there is provided a hydraulic actuating device using such a hydraulic hydraulic oil composition.

It is a figure which shows the hydraulic system which concerns on one Embodiment. It is a graph of the time-dependent change of the residual rate of the antioxidant of Example 1. It is a graph of the time-dependent change of the residual rate of the antioxidant of Comparative Examples 1 and 2.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

FIG. 1 is a diagram showing a hydraulic system according to an embodiment. As shown in FIG. 1, the hydraulic device 1 according to the embodiment includes an oil storage unit 2 in which a hydraulic hydraulic oil composition is stored, a pressure feeding unit 3 for pumping the hydraulic hydraulic oil composition, and a hydraulic hydraulic oil composition. Consists of a filtration unit 4 that purifies the hydraulic pressure by filtration, a control unit 5 that controls the hydraulic pressure, direction, or flow rate of the hydraulic hydraulic oil composition, and a conversion unit 6 that converts the hydraulic pressure of the hydraulic hydraulic oil composition into mechanical power. It is equipped with a hydraulic circuit.

The oil storage unit 2 is composed of, for example, a first oil tank 2A, a second oil tank 2B, and a third oil tank 2C. These oil tanks may be the same oil tank or separate oil tanks.

The pumping unit 3 is driven by, for example, an electric motor 7, and pumps the hydraulic fluid composition from the first oil tank 2A to generate hydraulic pressure. The pressure feeding unit 3 may be a hydraulic pump. The hydraulic pump is, for example, a gear pump, a screw pump, a vane pump, a plunger pump, or the like. The hydraulic pressure generated by the pumping unit 3 is, for example, 5 to 50 MPa.

The filtration unit 4 is composed of, for example, a first filter 4A and a second filter 4B. The first filter 4A is provided between the first oil tank 2A and the pumping unit 3, and filters foreign substances such as rust in the hydraulic fluid composition pumped up from the first oil tank 2A. To remove.

The control unit 5 controls the hydraulic pressure, the direction of flow, or the flow rate of the hydraulic fluid composition pumped by the pumping unit 3. The control unit 5 includes, for example, a pressure control valve 8 for controlling hydraulic pressure, a directional control valve 9 for controlling the flow direction, and a flow rate control valve 10 for controlling the flow rate.

The pressure control valve 8 adjusts the hydraulic pressure generated by the pressure feeding unit 3, for example, or when the pressure measured by the pressure gauge 11 exceeds a certain level, a part of the hydraulic fluid composition is used in the second oil tank. I escape to 2B. The pressure control valve 8 may be a relief valve, a pressure reducing valve, an unloader valve, a sequence valve, a counterbalance valve, or the like.

The directional control valve 9 is composed of, for example, an electromagnetic switching valve 12 and a check valve 13. The electromagnetic switching valve 12 is connected to a first flow path 14 and a second flow path 15 forming a flow path to the conversion unit 6, respectively, and a third oil tank 2C. The first flow path 14 is provided with, for example, a flow rate control valve 10 and a check valve 13. The second flow path 15 is directly connected to, for example, the conversion unit 6. The third oil tank 2C is connected to the electromagnetic switching valve 12 via, for example, the second filter 4B.

The electromagnetic switching valve 12 can switch the flow path of the hydraulic fluid composition pumped from the pressure feed unit 3 to the conversion unit 6 to either the first flow path 14 or the second flow path 15. There is. For example, the hydraulic fluid composition sent from the electromagnetic switching valve 12 to the first flow path 14 returns to the electromagnetic switching valve 12 from the second flow path 15 via the conversion unit 6 and returns to the electromagnetic switching valve 12, and the second filter. After the foreign matter such as rust is filtered by 4B, it is sent to the third oil tank 2C. The directional control valve 9 may be composed of a manual switching valve, a mechanical switching valve, or the like, instead of the electromagnetic switching valve 12. The check valve 13 is provided in the first flow path 14, and prevents the backflow by flowing the hydraulic fluid composition in only one direction.

The flow rate control valve 10 may be, for example, a throttle valve, a flow rate adjusting valve, or the like. These valves may include a deserration valve. The conversion unit 6 converts hydraulic pressure into power according to, for example, the flow rate controlled by the flow rate control valve 10. The conversion unit 6 may use a hydraulic cylinder, a hydraulic motor, or the like for hydraulic pressure. By controlling the flow rate of the hydraulic fluid composition by the flow rate control valve 10, the moving speed of the hydraulic cylinder, the hydraulic motor, etc. (converting unit 6) can be adjusted. The hydraulic cylinder may be a single-acting type, a double-acting type, a special type, or the like. The hydraulic motor may be a gear motor, a vane motor, a plunger motor or the like.

Next, the hydraulic fluid composition used in the hydraulic device will be described. The hydraulic fluid composition contains a lubricating oil base oil, a first antioxidant represented by the formula (1), and a second antioxidant represented by the general formula (2).

<Lubricating oil base oil>
The lubricating oil base oil is, for example, mineral oil, synthetic oil, or a mixture of both. As the mineral oil, the lubricating oil distillate obtained by atmospheric distillation and vacuum distillation of crude oil is desorbed from the solvent, extracted by the solvent, hydrolyzed and decomposed by the solvent, dewaxed by contact, dewaxed by hydrogenation, refined with sulfuric acid, and paraffin. Examples thereof include paraffin-based and naphthen-based mineral oils, normal paraffin, isoparaffin and the like, which are refined by refining treatment such as treatment alone or in combination of two or more as appropriate. One of these mineral oils may be used alone, or two or more of them may be used in combination at any ratio.

Preferred mineral oils include the following base oils.
(1) Distilled oil by atmospheric distillation of paraffin-based crude oil and / or mixed-based crude oil (2) Vacuum-distilled distillate of paraffin-based crude oil and / or atmospheric distillation residual oil of mixed-based crude oil (WVGO) )
(3) Wax obtained by dewaxing the lubricating oil and / or Fischer-Tropsch wax produced by the GTL process or the like (4) One or more mixed oils selected from the above (1) to (3). Mild Hydrocracking Treatment Oil (MHC)
(5) Mixed oil of two or more kinds of oils selected from the above (1) to (4) (6) Removal of the above (1), (2), (3), (4) or (5) Oil (DAO)
(7) Mild hydrocracking treated oil (MHC) according to (6) above.
(8) A mixed oil or the like of two or more kinds of oils selected from the above (1) to (7) is used as a raw material oil, and the raw material oil and / or the lubricating oil distillate recovered from the raw material oil is usually used. Lubricating oil obtained by refining by the refining method of

Here, as a normal refining method, a refining method used in the production of base oil can be arbitrarily adopted. Examples of the usual purification method include the following purification methods.
(A) Hydrorefining such as hydrocracking and hydrofinishing (b) Solvent refining such as full fuller solvent extraction (c) Dewaxing such as solvent dewaxing and contact dewaxing (d) White clay with acidic clay, activated clay, etc. Purification (e) Chemical (acid or alkali) purification such as washing with sulfuric acid and cleaning with caustic soda These purification methods can be used alone or in any combination and in any order.

Examples of synthetic oils include esters, ethers and hydrocarbon oils. These synthetic oils may be used alone or in combination of two or more at any ratio.

The ester may be, for example, an ester of a fatty acid (monobasic acid) and an alcohol, or an ester of a polybasic acid and an alcohol.

The fatty acid may be a saturated fatty acid or an unsaturated fatty acid. The fatty acid may be, for example, a fatty acid having 2 to 24 carbon atoms. The fatty acid may be linear or branched. Examples of the polybasic acid include dibasic acid and tribasic acid. The polybasic acid may or may not have an unsaturated bond. The number of carbon atoms of the polybasic acid may be, for example, 2 to 16. The dibasic acid may be linear or branched.

The alcohol may be a monohydric alcohol or a polyhydric alcohol. The number of carbon atoms of the monohydric alcohol may be, for example, 1 to 24, 1 to 12, or 1 to 8. The monohydric alcohol may be linear or branched. The number of hydroxyl groups contained in the polyhydric alcohol (polyol) may be, for example, 2 to 10 or 2 to 6.

Examples of the ether include polyoxyalkylene glycol, dialkyldiphenyl ether, polyphenyl ether and the like.

Examples of the hydrocarbon oil include polyα-olefins or hydrides thereof, isobutylene oligomers or hydrides thereof, isoparaffin, alkylbenzenes, alkylnaphthalene and the like.

The kinematic viscosity of the lubricating oil base oil at 40 ° C. is preferably 10 mm ² / s or more, more preferably 20 mm ² / s or more, and further preferably 30 mm ² / s or more. The kinematic viscosity of the lubricating oil base oil at 40 ° C. is preferably 150 mm ² / s or less, more preferably 100 mm ² / s or less, and further preferably 50 mm ² / s or less. The viscosity index of the lubricating oil base oil may be 80 or more, or 100 or more. The kinematic viscosity and viscosity index in the present invention mean the kinematic viscosity and viscosity index measured according to JIS K2283, respectively.

The aromatic content in the present invention is referred to as "Separation of High-Boiling Petroleum Distillates Using Gradient Elution Through Dual-Packed (Silica Gel-Alumina Gel) Adsorption Columns" in Analytical Chemistry Vol. 44, No. 6 (1972), pp. 915-919. It means a value obtained by measurement according to the described silica-alumina gel chromatographic analysis method.

The sulfur content of the lubricating oil base oil may be 10,000 mass ppm or less, 100 mass ppm or less, or 1 mass ppm or less. The sulfur content in the present invention means a value obtained by measuring by ASTM D4951 "Standard Test Method for Determination of Additive Elements inLubricating Oils by Inductively Coupled Plasma Atomic Emission Spectrometry".

<Additives for lubricating oil>
(Antioxidant)
The hydraulic fluid composition contains a first antioxidant and a second antioxidant. By combining the first and second antioxidants, it becomes possible to leave the antioxidant for a long period of time. Although the reason why such a phenomenon occurs is not clear, the present inventors have affected the difference in the chain termination rate and the self-oxidation rate of each of the antioxidants to cause the antioxidant to remain for a long period of time. I believe.

The first antioxidant is a compound represented by the formula (1), that is, 2,6-di-tert-butyl-p-cresol (DBPC).

The content of the first antioxidant is not particularly limited, but is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, still more preferably 0.5% by mass or more. When the content of the first antioxidant is 0.1% by mass or more, the consumption rate of the second antioxidant tends to be further suppressed. The content of the first antioxidant is preferably 2.0% by mass or less, more preferably 1.0% by mass or less, still more preferably 0.7% by mass or less. When the content of the first antioxidant is 2.0% by mass or less, the amount of sludge generated tends to be further suppressed.

The second antioxidant is a compound represented by the formula (2).

In formula (2), R represents an alkyl group that may be substituted with a group containing an oxygen atom. The alkyl group preferably has 1 to 25 carbon atoms, more preferably 1 to 20 carbon atoms, still more preferably 1 to 15 carbon atoms, particularly preferably 1 to 10 carbon atoms, and most preferably 1 to 5 carbon atoms.

The alkyl group as R may be, for example, a linear, branched or cyclic alkyl group. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group and a sec-pentyl group. Examples thereof include a group, a neopentyl group, an n-hexyl group, a cyclohexyl group, an n-heptyl group, an n-octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, a dodecyl group, a tetradecyl group, a hexadecyl group and an octadecyl group.

The alkyl group which may be substituted with a group containing an oxygen atom means the above-mentioned alkyl group and an alkyl group in which any hydrogen atom is substituted with a group containing an oxygen atom. In an alkyl group substituted with a group containing an oxygen atom, one or more hydrogen atoms may be substituted with a group containing an oxygen atom.

Here, the group containing an oxygen atom means a substituent containing oxygen as a constituent element. Examples of the group containing an oxygen atom include a hydroxy group (-OH), an alkoxy group (-OR ^A ), an acyl group (-CO-RB), an alkoxycarbonyl group (-CO-OR ^{C )} and the like. Note that ^RA , RB, and ^RC indicate an alkyl group, and the same alkyl groups as those exemplified in ^R can be used. Of these, the group containing an oxygen atom is preferably an alkoxycarbonyl group.

R may be a group represented by the following formula (3).

In formula (3), R ¹ represents an alkylene group and R ² represents an alkyl group.

The alkylene group as R ¹ may be, for example, a linear or branched alkylene group. Examples of the alkylene group include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group and a hexylene group. The carbon number of the alkylene group as R ¹ is preferably 1 to 6, more preferably 1 to 4, still more preferably 1 or 2, and particularly preferably 1.

As the alkyl group as R ² , the same alkyl group as that exemplified in R can be used. The number of carbon atoms of the alkyl group as ^R2 is preferably 1 to 25, more preferably 3 to 18, still more preferably 5 to 15, particularly preferably 6 to 10, and most preferably 7 to 9.

As the second antioxidant, as long as it is a compound represented by the formula (2), one type may be used alone, or two or more types may be combined at an arbitrary ratio and used as a mixture. ..

The content of the second antioxidant is not particularly limited, but is preferably 0.3% by mass or more, more preferably 0.6% by mass or more, still more preferably 0.8% by mass or more. When the content of the second antioxidant is 0.3% by mass or more, the performance of the antioxidant tends to be more easily exhibited. The content of the second antioxidant is preferably 2.0% by mass or less, more preferably 1.5% by mass or less, still more preferably 1.0% by mass or less. When the content of the second antioxidant is 2.0% by mass or less, the amount of sludge generated tends to be further suppressed.

The total content of the first antioxidant and the second antioxidant is not particularly limited, but is preferably 0.4% by mass or more, more preferably 0.9% by mass or more, still more preferably 1.3. It is mass% or more. When the total content is 0.4% by mass or more, the performance of the antioxidant tends to be more easily exhibited. The total content is preferably 4.0% by mass or less, more preferably 2.5% by mass or less, and further preferably 1.7% by mass or less. When the total content is 4.0% by mass or less, the amount of sludge generated tends to be further suppressed.

(Phosphorus-based wear inhibitor)
The hydraulic fluid composition may contain a phosphorus-based anti-wear agent, if necessary.

The phosphorus-based anti-wear agent is an anti-wear agent containing phosphorus as a constituent element. The phosphorus-based anti-wear agent is not particularly limited, and additives used in ordinary lubricating oils can be used. Specifically, phosphites, phosphate esters, amine salts thereof, metal salts thereof, derivatives thereof, etc .; zinc dialkyldithiophosphate (ZnDTP), thioaphosphate. Esters, dithiophosphates, trithiophosphates, trithiophosphates, thiophosphates (thiophosphates), dithiophosphates (dithiophosphates), trithiophosphates (trithiophosphates), amine salts thereof, Examples thereof include these metal salts and derivatives thereof. Of these, the phosphorus-based anti-wear agent is preferably neutral (triester) or acidic (monoester or diester) phosphate esters, and more preferably neutral phosphate esters. Examples of the neutral phosphate esters include tricresyl phosphate and the like.

The content of the phosphorus-based wear inhibitor may be, for example, 0.001 to 5% by mass based on the total amount of the composition. When neutral phosphoric acid esters are used, the content thereof is preferably 0.3 to 2% by mass based on the total amount of the composition. When acidic phosphoric acid esters are used, the content thereof is preferably 0.01 to 0.1% by mass based on the total amount of the composition.

(Metal inactivating agent)
The hydraulic fluid composition may contain a metal deactivating agent, if necessary.

The metal deactivating agent is not particularly limited, and additives used in ordinary lubricating oils can be used. Examples of the metal inactivating agent include benzotriazole-based compounds, thiadiazole-based compounds, and imidazole-based compounds. Of these, the metal inactivating agent is preferably a benzotriazole-based compound. Examples of the benzotriazole-based compound include N, N-bis (2-ethylhexyl)-(4 or 5) -methyl-1H-benzotriazole-1-methylamine and the like.

The content of the metal inactivating agent may be, for example, 0.001 to 2% by mass based on the total amount of the composition. When a benzotriazole-based compound or an imidazole-based compound is used, the content thereof is preferably 0.01 to 0.1% by mass based on the total amount of the composition. When a thiadiazole-based compound is used, its content is preferably 0.01 to 0.5% by mass based on the total amount of the composition.

(Other additives)
The hydraulic fluid composition may further contain any commonly used lubricant additive, depending on its purpose. Examples of such additives include viscosity modifiers, metal detergents, ashless dispersants, friction modifiers, wear inhibitors (extreme pressure agents) other than phosphorus-based wear inhibitors, first antioxidants, and first antioxidants. Examples thereof include antioxidants other than the second antioxidant, corrosion inhibitors, rust inhibitors, flow point lowering agents, antiemulsors, antifoaming agents and the like.

The viscosity modifier is specifically a non-dispersive or dispersed ester group-containing viscosity modifier, for example, a non-dispersion or dispersion poly (meth) acrylate-based viscosity modifier, a non-dispersion or dispersion-type olefin. Examples thereof include (meth) acrylate copolymer viscosity adjusters, styrene-maleine anhydride copolymer viscosity adjusters, and mixtures thereof. Among these, non-dispersive or dispersed poly (meth) acrylate viscosity adjusters. Is preferable. In particular, a non-dispersive or dispersed polymethacrylate-based viscosity modifier is preferable.

Other examples of the viscosity modifier include non-dispersive or dispersed ethylene-α-olefin copolymers or hydrides thereof, polyisobutylene or hydrides thereof, styrene-diene hydride copolymers, polyalkylstyrene and the like. be able to.

Examples of the metal-based cleaning agent include a sulfonate-based cleaning agent, a salicylate-based cleaning agent, a phenate-based cleaning agent, and any of a positive salt, a basic salt, and a hyperbasic salt with an alkali metal or an alkaline earth metal. Can also be blended. At the time of use, one kind or two or more kinds arbitrarily selected from these can be blended.

As the ashless dispersant, any ashless dispersant used for lubricating oil can be used, and for example, a mono having at least one linear or branched alkyl group or alkenyl group having 40 or more and 400 or less carbon atoms in the molecule. Alternatively, an imide biscosuccinate, a benzylamine having at least one alkyl group or alkenyl group having 40 or more and 400 or less carbon atoms in the molecule, or a polyamine having at least one alkyl group or alkenyl group having 40 or more and 400 or less carbon atoms in the molecule. Examples thereof include modified products of these boron compounds, carboxylic acids, phosphoric acids and the like. At the time of use, one kind or two or more kinds arbitrarily selected from these can be blended.

Examples of the friction modifier include ashless friction modifiers such as fatty acid ester-based, aliphatic amine-based and fatty acid amide-based materials, and metal-based friction modifiers such as molybdenum dithiocarbamate and molybdenum dithiophosphate. For example, an amine compound, an imide compound, a fatty acid ester, or a fatty acid amide having at least one alkyl group or alkenyl group having 6 to 30 carbon atoms, particularly a linear alkyl group or linear alkenyl group having 6 to 30 carbon atoms in the molecule. , Fatty acid metal salts and the like can be preferably used.

An anti-wear agent (extreme pressure agent) other than the phosphorus-based anti-wear agent can be used in combination with the phosphorus-based anti-wear agent. Examples of such an anti-wear agent (extreme pressure agent) include dithiocarbamate, zinc dithiocarbamate, molybdenum dithiocarbamate, disulfides, polysulfides, sulfurized olefins, sulfurized oils and fats and the like.

Examples of the antioxidant other than the first antioxidant and the second antioxidant include ashless antioxidants such as phenol and amines, and metal-based antioxidants such as copper and molybdenum. Specifically, for example, examples of the phenolic ashless antioxidant include 4,4'-methylenebis (2,6-di-tert-butylphenol) and 4,4'-bis (2,6-di-tert-). Butylphenol) and the like, examples of the amine-based ashless antioxidant include phenyl-α-naphthylamine, alkylphenyl-α-naphthylamine, dialkyldiphenylamine, diphenylamine and the like.

Examples of the corrosion inhibitor include benzotriazole-based, triltriazole-based, thiadiazole-based, and imidazole-based compounds.

Examples of the rust preventive include petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinic acid ester, polyhydric alcohol ester and the like.

As the pour point lowering agent, for example, a polymethacrylate-based polymer compatible with the lubricating oil base oil to be used can be used.

Examples of the anti-emulsifier include polyalkylene glycol-based nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and polyoxyethylene alkyl naphthyl ether.

Examples of the defoaming agent include silicone oil having a kinematic viscosity at 25 ° C. of 1000 mm ² / s or more and 100,000 mm ² / s or less, an alkenyl succinic acid derivative, an ester of a polyhydroxy fatty alcohol and a long-chain fatty acid, and methyl salicylate. And an ester of o-hydroxybenzyl alcohol and the like.

When these additives are contained in the lubricating oil composition, the content of each of these additives may be 0.01 to 20% by mass based on the total amount of the composition.

The kinematic viscosity of the hydraulic fluid composition at 40 ° C. is preferably 10 mm ² / s or more, more preferably 20 mm ² / s or more, still more preferably 30 mm ² / s or more, particularly preferably 30 mm 2 / s or more, from the viewpoint of durability of the hydraulic system. Is 40 mm ² / s or more. The kinematic viscosity of the hydraulic fluid composition at 40 ° C. is preferably 150 mm ² / s or less, more preferably 100 mm ² / s or less, still more preferably 75 mm ² / s or less, and particularly preferably 50 mm ² from the viewpoint of friction reduction. It is less than / s.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

[Preparation of hydraulic fluid composition]
(Example 1 and Comparative Examples 1 and 2)
As shown in Table 1, hydraulic fluid compositions of Examples 1 and Comparative Examples 1 and 2 were prepared, respectively.

<Lubricating oil base oil>
A-1: Highly refined base oil (40 ° C. kinematic viscosity: 35 mm ² / s, viscosity index: 120, total aromatic content: 0.3% by mass, sulfur content: 0% by mass)

<Additives for lubricating oil>
(Antioxidant)
B-1: 2,6-di-t-butyl-p-cresol (first antioxidant)
B-2: IRGANOX (registered trademark) L135 (manufactured by BASF, benzenepropanoic acid-3,5-bis (1,1-dimethyl-ethyl) -4-hydroxy-C7 to C9 side chain alkyl ester, the above formula (2). ), R is a group represented by the formula (3), R ¹ is a methylene group, and R ¹ is an alkyl group having 7 to 9 carbon atoms.)
(Phosphorus-based wear inhibitor)
C-1: Tricredil phosphate (metal inactivating agent)
D-1: N, N-bis (2-ethylhexyl)-(4 or 5) -methyl-1H-benzotriazole-1-methylamine (IRGAMET® 39, manufactured by BASF)

[High pressure piston pump test]
A high-pressure piston pump test was performed using the hydraulic fluid compositions obtained in Example 1 and Comparative Examples 1 and 2. The high-pressure piston pump test conforms to JCMAS P045 of the Japan Construction Machinery and Construction Association standard, and uses a hydraulic circuit equipped with a diagonal shaft type piston pump, sample oil 13L, pump pressure 35MPa, pump rotation speed 1500min ^-1 , tank oil. A circulation test was conducted at a temperature of 80 ° C. for 3000 hours. During the circulation test, the residual amount of antioxidant in the sample oil was analyzed by gas chromatography and liquid chromatography every 250 hours. The results are shown in Table 1.

FIG. 2 is a graph of changes over time in the residual rate of the antioxidant of Example 1. Further, FIG. 3 is a graph of changes over time in the residual rate of the antioxidants of Comparative Examples 1 and 2. As shown in FIG. 3, in the single system using the antioxidant B-1 or B-2 alone, the antioxidant decreased with time, and the antioxidant remained after the high pressure pump test for 3000 hours. I didn't. On the other hand, as shown in FIG. 2, in the combined system in which the antioxidants B-1 and B-2 are used in combination, the consumption rate of the antioxidant B-2 becomes slower, and the high-pressure pump test for 3000 hours is performed. Even after that, 22.2% of the antioxidants B-1 and B-2 remained. From these results, it was confirmed that the hydraulic fluid composition of the present invention can achieve a long life.

1 ... hydraulic device, 2 ... oil storage unit, 3 ... pumping unit, 5 ... control unit, 6 ... conversion unit.

Claims (2)

Lubricating oil base oil with a viscosity index of 80 or more ,
The first antioxidant represented by the following formula (1) and

The second antioxidant represented by the following formula (2) and

[In the formula (2), R represents a group represented by the following formula (3). ]

[In the formula (3), R ¹ represents an alkylene group having 1 or 2 carbon atoms, and R ² represents an alkyl group having 6 to 10 carbon atoms. ]
A hydraulic fluid composition containing. An oil storage unit in which the hydraulic fluid composition is stored, and
A pumping unit that pumps the hydraulic fluid composition and
A control unit that controls the hydraulic pressure, direction, or flow rate of the pressure-fed hydraulic fluid composition, and
A converter that converts the hydraulic pressure of the controlled hydraulic fluid composition into mechanical power,
It is a hydraulic device equipped with
The hydraulic fluid composition
Lubricating oil base oil with a viscosity index of 80 or more ,
The first antioxidant represented by the following formula (1) and

The second antioxidant represented by the following formula (2) and

[In the formula (2), R represents a group represented by the following formula (3). ]

[In the formula (3), R ¹ represents an alkylene group having 1 or 2 carbon atoms, and R ² represents an alkyl group having 6 to 10 carbon atoms. ]
Contains, hydraulic equipment.

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