Hydraulic fluid composition

Abstract

The objective is to provide a hydraulic fluid composition having a high static friction coefficient and other properties. [Solution] One embodiment of the present invention is a hydraulic fluid composition. The hydraulic fluid composition comprises a base oil belonging to Gr1 and a base oil belonging to Gr3 in the API (American Petroleum Institute) base oil category, a viscosity index improver, polyisobutenyl succinic anhydride, and a thiophosphate ester derivative. The content of the polyisobutenyl succinic anhydride is 0.08 to 0.15% by mass based on the total mass of the hydraulic fluid composition, and the content of the thiophosphate ester derivative is 0.013 to 0.030% by mass based on the total mass of the hydraulic fluid composition.

Description

Technical Field

[0001] The present invention relates to a hydraulic fluid composition.

Background Art

[0002] Hydraulic equipment is used in various fields such as the construction field and the civil engineering field for reasons including that even a simple and compact device can provide a large output.

[0003] In hydraulic equipment, hydraulic systems including hydraulic actuators such as hydraulic motors and hydraulic cylinders are generally used, and the hydraulic actuators such as hydraulic motors and hydraulic cylinders are operated by pressurized hydraulic fluid that is generated by driving a hydraulic pump with an engine or the like.

[0004] As a hydraulic fluid used for such hydraulic equipment, Patent Document 1 proposes a hydraulic fluid prepared by blending an amine-based antioxidant, a phenol-based antioxidant, a phosphate ester, and a fatty acid amide or a polyhydric alcohol ester into a base oil.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0006] However, the hydraulic fluid according to the related art may not have a sufficient static friction coefficient or the like when power transmission in a multi-plate clutch or the like is taken into consideration.

[0007] Accordingly, an object of the present invention is to provide a hydraulic fluid composition having a high static friction coefficient and the like.

Means for Solving the Problems

[0008] As a result of diligent research, the inventors have found that the above-mentioned problems can be solved by using a specific base oil. That is, the present invention is as follows.

[0009] One embodiment of the present invention is a hydraulic fluid composition. The aforementioned hydraulic fluid composition comprises a base oil belonging to Gr1 and a base oil belonging to Gr3 in the API (American Petroleum Institute) base oil category, Viscosity index improver, Polyisobutenyl succinic anhydride and, It contains thiophosphate ester derivatives. The content of polyisobutenyl succinic anhydride is 0.08 to 0.15% by mass, based on the total mass of the hydraulic fluid composition. The content of the thiophosphate ester derivative is 0.013 to 0.030% by mass, based on the total mass of the hydraulic fluid composition.

[0010] The aforementioned hydraulic fluid composition is preferably for use in the hydraulic motor of a crane with a transmission. [Effects of the Invention]

[0011] According to the present invention, a hydraulic fluid composition having a high static friction coefficient and the like is provided. [Modes for carrying out the invention]

[0012] In this specification, where upper and lower limits are described separately, a numerical range combining any upper and lower limit shall be deemed to be substantially disclosed.

[0013] Unless otherwise specified, all measurements will be conducted at room temperature (25°C).

[0014] The components, manufacturing method, and uses of the composition relating to this disclosure will be described below, but the present invention is not limited to the following.

[0015] <<Ingredients>> The composition according to the present disclosure includes a base oil, a viscosity index improver, polyisobutenyl succinic anhydride, and a thiophosphate ester derivative. In addition, the composition according to the present disclosure may contain other components. Hereinafter, each component will be described.

[0016] <Base Oil> The base oil is a mixed base oil including a base oil belonging to Group I and a base oil belonging to Group III in the base oil categories of the API (American Petroleum Institute).

[0017] Examples of the base oil belonging to Group I include paraffinic mineral oils obtained by appropriately combining and applying purification means such as solvent refining, hydrorefining, and dewaxing to a lubricating oil fraction obtained by atmospheric distillation of crude oil.

[0018] Examples of the base oil belonging to Group III include paraffinic mineral oils produced by advanced hydrorefining of a lubricating oil fraction obtained by atmospheric distillation of crude oil, base oils refined by the ISODEWAX process in which wax produced in the dewaxing process is converted to isoparaffin and dewaxed, and base oils refined by the Mobile Wax isomerization process.

[0019] The content of the base oil is preferably 80% by mass or more, 90% by mass or more, or 95% by mass or more based on the total mass of the composition.

[0020] The ratio of the content of the base oil belonging to Group I to the content of the base oil belonging to Group III (Group I base oil / Group III base oil) is preferably 1.0 or more, 1.2 or more, 1.5 or more, or 1.8 or more, and is preferably 5.0 or less, 4.0 or less, 3.0 or less, or 2.5 or less.

[0021] Based on the total mass in the base oil, the total content of the base oil belonging to Gr1 and the base oil belonging to Gr3 is preferably 80 mass% or more, 90 mass% or more, 95 mass% or more, or 99 mass% or more. In other words, the content of base oils other than the base oil belonging to Gr1 or the base oil belonging to Gr3 in the base oil is preferably 20 mass% or less, 10 mass% or less, 5 mass% or less, or 1 mass% or less.

[0022] <Viscosity Index Improver> The viscosity index improver is generally a polymer base material having a viscosity index improving effect. Examples of the viscosity index improver include non-dispersible viscosity index improvers such as poly(meth)acrylates and olefin copolymers such as ethylene / propylene copolymers and styrene / diene copolymers, as well as dispersible viscosity index improvers obtained by copolymerizing these with nitrogen-containing monomers. The viscosity index improver preferably comprises PMA (polymethacrylate). The weight average molecular weight Mw of PMA is, for example, 10,000 or more, 15,000 or more, or 20,000 or more, and is 100,000 or less, 80,000 or less, or 50,000. The weight average molecular weight and the number average molecular weight are measured using GPC and calculated as polystyrene-equivalent values.

[0023] The viscosity index improver may be a comb-type polymer. A comb-type polymer is a polymer in which relatively long side chains are bonded to the polymer main chain to form a comb-like structure. Known comb-type polymers can be used. Specific examples of comb-type polymers include those containing (1) repeating units derived from polyolefin-based macromonomers and (2) repeating units derived from low-molecular-weight monomers in the main chain. Examples of low-molecular-weight monomers include styrene monomers having 8 to 17 carbon atoms, alkyl (meth)acrylates having 1 to 10 carbon atoms in the alcohol group, vinyl esters having 1 to 11 carbon atoms in the acyl group, vinyl ethers having 1 to 10 carbon atoms in the alcohol group, (di)alkyl fumarates having 1 to 10 carbon atoms in the alcohol group, (di)alkyl maleates having 1 to 10 carbon atoms in the alcohol group, and low-molecular-weight monomers selected from the group consisting of mixtures of these monomers. The viscosity index improver preferably contains a comb-type polymer, and more preferably contains comb-type PMA.

[0024] The content of the viscosity index improver is not particularly limited and is adjusted according to the viscosity grade, etc. As an example, the content of the viscosity index improver is preferably 1.00% by mass, 1.50% by mass or more, 1.65% by mass or more, or 2.00% by mass or more, based on the total mass of the composition, and is also preferably 10.00% by mass or less, 6.00% by mass or less, 5.20% by mass or less, or 3.50% by mass or less.

[0025] <Polyisobutenyl succinic anhydride> Polyisobutenyl succinic anhydride has a structure in which succinic anhydride is bonded to the terminal end of a polyisobutenyl skeleton.

[0026] The content of polyisobutenyl succinic anhydride is preferably 0.08% by mass or more, 0.10% by mass or more, or 0.11% by mass or more, based on the total mass of the composition, and preferably 0.15% by mass or less, or 0.14% by mass or less. By using such a blending ratio, a hydraulic fluid composition with a high static friction coefficient can be obtained.

[0027] <Thiophosphate ester derivatives> The thiophosphate ester derivative can be any derivative containing a thiophosphate ester structure, and may be a monoester, diester, or triester.

[0028] The thiophosphate ester derivative is preferably a monothiophosphate ester compound represented by formula 1 below or a dithiophosphate ester compound represented by formula 2 below.

[0029] [ka]

[0030] [ka]

[0031] In formulas 1 and 2, R1 and R2 are hydrogen or alkyl groups. Preferably, one or more of R1 and R2 are alkyl groups, and more preferably, R1 and R2 are alkyl groups. R3 is an alkyl group, or a group in which a carboxyl group is bonded to an alkylene group (alkylene carboxyl group). R1, R2, and R3 each preferably have 1 or more carbon atoms, 2 or more carbon atoms, or 3 or more carbon atoms, and also preferably 10 or less, 8 or less, 5 or less, or 4 or less carbon atoms.

[0032] R3 is preferably an alkylene carboxyl group. Examples of compounds having an alkylene carboxyl group as R3 in Formula 2 include 3-(O,O-diisopropyl-dithiophosphoryl)-propionic acid, 3-(O,O-diisopropyl-dithiophosphoryl)-2-methylpropionic acid, 3-(O,O-diisobutyl-dithiophosphoryl)-propionic acid, and 3-(O,O-diisobutyl-dithiophosphoryl)-2-methylpropionic acid.

[0033] The content of the thiophosphate ester derivative is preferably 0.013% by mass or more, 0.014% by mass or more, or 0.015% by mass or more, based on the total mass of the composition, and preferably 0.030% by mass or less, or 0.025% by mass or less. By using such a blending ratio, it is easy to obtain performance that balances wear resistance and copper corrosion resistance while appropriately adjusting friction.

[0034] In addition, the content of polyisobutenyl succinic anhydride (polyisobutenyl succinic anhydride / thiophosphate derivative) relative to the content of thiophosphate derivative in the oil composition is preferably 3.0 or more, 4.0 or more, or 5.0 or more, and also preferably 15.0 or less, 13.5 or less, or 12.0 or less.

[0035] <Other ingredients> The compositions relating to this disclosure may also contain other components. Examples of other components include known additives such as antioxidants, rust inhibitors, copper deactivators, anti-wear agents, extreme pressure agents, dispersants, metal-based detergents, friction modifiers, corrosion inhibitors, anti-emulsifiers, pour point depressants, and defoaming agents.

[0036] The types and amounts of other components are not particularly limited and may be adjusted as appropriate according to the physical properties required of the composition. For example, the amount of other components in the composition may be 20.00% by mass or less, 10.00% by mass or less, or 5.00% by mass or less, based on the total mass of the composition. The composition may not contain any other components.

[0037] <<Manufacturing method>> The compositions according to this disclosure can be manufactured according to known methods, and the components can be mixed as appropriate, with no particular limit on the order of mixing. The additives contained in the compositions according to this disclosure may be added to the base oil as a package containing a mixture of multiple types. Alternatively, a mixture of components such as thiophosphate derivatives and polyisobutenyl succinic anhydride may be prepared in advance by mixing them with a predetermined amount of base oil, and the composition may be manufactured by adding this mixture to the base oil.

[0038] <<Applications>> The compositions relating to this disclosure are preferably used in hydraulic fluids. Hydraulic systems to which the hydraulic fluid relating to this disclosure can be applied are not particularly limited, but examples include construction machinery, general industrial machinery, and generators.

[0039] In particular, the compositions relating to this disclosure are suitable for use as hydraulic fluids under high-load conditions and are therefore preferably applicable to construction machinery, especially hydraulic motors in cranes with transmissions.

[0040] Furthermore, the hydraulic fluid composition according to this disclosure can also be used as a conventional lubricating oil composition. In other words, the hydraulic fluid composition according to this disclosure can also be applied to applications other than hydraulic fluid (for example, machine oil, turbine oil, compressor oil, gear oil, sliding surface oil, bearing oil, calibration oil, etc.). [Examples]

[0041] <<Preparation of Composition>> The base oil was mixed with the components in the proportions (parts by mass) shown in Table 1 to obtain the compositions for each example and comparative example. The raw materials used are listed below.

[0042] • Base oil: Mixed oil containing the following base oils Gr1 base oil (KV40:24.7, KV100:4.71, VI:108): Approximately 30.1% by mass Gr1 base oil (KV40:54.1, KV100:7.71, VI:106): Approx. 38.8% by mass Gr3 base oil (KV40:18.7, KV100:4.17, VI:128): Approximately 31.1% by mass • Viscosity index improver: Non-dispersive PMA (Mw: 33,000, Mw / Mn: 1.9) • Polyisobutenyl succinic anhydride • Thiophosphate derivative: 3-(di-isobutoxy-thiophosphorylsulfanyl)-2-methylpropionic acid • Diluting oil: Mineral oil

[0043] Although not shown in Table 1, a hydraulic fluid package was added to each composition. The amount of hydraulic fluid package added was such that, when the total of the base oil, viscosity index improver, and hydraulic fluid package was set to 100% by mass, the hydraulic fluid package accounted for 0.75% by mass.

[0044] Furthermore, as additives for comparative examples, we prepared the following products: "Infineum C9330" (manufactured by Infineum International, an additive containing Ca sulfonate and mineral oil), "Infineum C9230" (manufactured by Infineum International, an ashless dispersant containing boron-modified polybutenyl succinimide and mineral oil), and "Afton Hitec611" (manufactured by ChemPoint, an additive containing alkylbenzene sulfonate calcium salt and mineral oil).

[0045] <<Rating>> <Coefficient of friction> For each example and comparative example, the friction coefficient was evaluated using an SAE No. 2 testing machine based on JCMAS P047 mod. A dynamic friction coefficient test is performed by rotating a friction material with an inertia plate attached at 800 rpm and measuring the coefficient of friction from the time the clutch is engaged until it stops. A static friction test is also performed by repeatedly measuring the coefficient of friction generated when the material is rotated at 0.7 rpm with the clutch engaged. In the static friction test after 400 cycles, the coefficient of friction 2 seconds after the start of rotation is used as the evaluation value. The evaluation results are shown in Table 1. In this evaluation test, a friction coefficient of 0.140 or higher is considered to indicate excellent performance.

[0046] <Seizure resistance> In the friction coefficient evaluation described above, lubricating oil compositions with a friction coefficient of 0.140 or higher were further evaluated for their seizure resistance. The evaluation results are shown in Table 1. Specifically, in accordance with JIS-B-1760, the load at which damage occurs on the tooth surface was evaluated using an FZG tester. The load stage was increased from 1 to 12, and the load stage at which damage occurred on the tooth surface (failing stage) was taken as the evaluation value. When no damage occurred on the tooth surface, the sample was evaluated as 12 pass. In this evaluation test, a result of 10 fail or higher (passing at least up to load stage 9) is judged to indicate excellent performance.

[0047] <Cu Corrosion Property> For the lubricating oil compositions that achieved 10 fail or higher in the aforementioned seizure resistance evaluation, a Cu corrosion property evaluation was further performed. The evaluation results are shown in Table 1. Specifically, a Cu corrosion test (100°C, 3 hours) based on JIS K2513 was conducted to evaluate the degree of discoloration (1a to 4c) on the copper plate. In this evaluation test, a discoloration classification of 1a or 1b (very slight discoloration) is judged to indicate excellent performance.

[0048] [Table 1]

[0049] As described above, it was demonstrated that the compositions according to the present examples are excellent in static friction coefficient, gear seizure resistance, Cu corrosion resistance, and the like. [Industrial Applicability]

[0050] Since the composition according to the present disclosure has a high static friction coefficient and the like, it can be applied as various hydraulic fluids, and is particularly preferably applied for the hydraulic pressure of cranes equipped with a clutch and a transmission.

Claims

1. In the API (American Petroleum Institute) base oil categories, base oils belonging to Gr1 and base oils belonging to Gr3, Viscosity index improver, Polyisobutenyl succinic anhydride and A hydraulic fluid composition containing a thiophosphate ester derivative, The content of the polyisobutenyl succinic anhydride is 0.08 to 0.15% by mass based on the total mass of the hydraulic fluid composition. A hydraulic fluid composition in which the content of the thiophosphate ester derivative is 0.013 to 0.030% by mass based on the total mass of the hydraulic fluid composition.

2. The hydraulic fluid composition according to claim 1, for use in a hydraulic motor of a crane with a transmission.

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