JP5284187B2 - Hydraulic oil composition - Google Patents

Description

  The present invention relates to a power-saving hydraulic oil composition.

  In recent years, global warming has progressed, and there is an urgent need to reduce carbon dioxide emissions, which is one of the greenhouse gases. In Japan, the Law Concerning the Rational Use of Energy and the Law Concerning Promotion of Global Warming Countermeasures were revised and implemented in 2006, and factories and transportation companies have been required to reduce power consumption more than ever. I came.

As one method of reducing power consumption, power saving from the lubricating oil side used in industrial machines and transportation machines is being attempted.
As an example of power saving by using a lubricating oil, reduction of friction and wear has been proposed by adding a specific additive to the lubricating oil. For example, attempts have been made to cope with blending techniques such as phosphoric acid esters, phosphoric acid ester amine salts, fatty acid esters, carboxylic acid amides, sulfurized oxymolybdenum dithiophosphate, sulfurized oxymolybdenum dithiocarbamate (for example, Patent Documents 1 and 2). reference). Moreover, the example which aimed at reduction of pressure loss, such as piping, by using specific base oil is also mentioned (refer patent document 3).

There is also a demand for power saving in hydraulic devices. With regard to hydraulic devices, recently, it is considered that hydraulic oil is exposed to more severe conditions such as high temperature, high pressure, boundary lubrication, etc. due to higher output, higher pressure, and smaller oil tanks. Under such circumstances, it is conceivable to reduce friction and wear as one of the methods for power saving from the hydraulic oil used in the hydraulic device. In the hydraulic apparatus, there are places where the hydraulic oil is used, such as a pump and an actuator, which are exposed to a high pressure state of several gigapascals and an elastic fluid lubrication region. Therefore, it is considered that reducing friction in the elastohydrodynamic lubrication region, that is, reducing traction contributes to power saving in the hydraulic device.
Further, there are places where the hydraulic oil is exposed to the boundary lubrication region, such as the tip of the vane pump. Improving the extreme pressure property of the hydraulic oil reduces wear in this region. For example, in a vane pump, it can be expected to contribute to power saving in the hydraulic device by reducing the amount of internal leakage.
At the same time, the hydraulic oil needs to have excellent thermal oxidation stability even under high temperature conditions.

Japanese Patent Laid-Open No. 5-140556 JP 2001-040383 A JP 2004-250504 A

An object of this invention is to provide the hydraulic fluid composition which shows low traction property, the outstanding extreme pressure property, and oxidation stability.

As a result of diligent research to solve the above problems, the present inventor has found that a hydrocarbon-based lubricating base oil having a specific high-pressure viscosity contains a specific olefinic viscosity index improver, and an extreme pressure containing sulfur. A hydraulic fluid composition that exhibits low traction, excellent extreme pressure, and oxidation stability is obtained by blending the agent and adjusting the refractive index at 20 ° C. and the kinematic viscosity at 40 ° C. to a specific range. Based on this finding, the present invention has been completed.

That is, the present invention provides (A) a hydrocarbon-based lubricant base having a high-pressure viscosity of 1.0 × 10 ^{10 to} 2.0 × 10 ¹² cP at 40 ° C. and 1.7 GPa and a% CA of 5 or less by ring analysis. (B) an olefin viscosity index improver composed of a copolymer of ethylene and a monomer other than ethylene, and (C) an extreme pressure agent containing sulfur. It is a compounded composition, Comprising: The compounding quantity of the extreme pressure agent containing the sulfur of (C) component is 0.01-0.4 mass% with respect to the composition whole quantity, and in 20 degreeC of this composition A hydraulic oil composition having a refractive index of 1.453 to 1.470 and a kinematic viscosity at 40 ° C. of 19 to 51 mm ² / s is provided.

Further, in the hydraulic oil composition according to the present invention, the olefin viscosity index improver as the component (B) is a copolymer of ethylene and an olefin having 3 to 30 carbon atoms, and the refractive index thereof is 20 ° C. The hydraulic oil composition is 1.453 to 1.480 and the blending amount is 0.5 to 30% by mass with respect to the total amount of the composition.
In the above hydraulic oil composition, the extreme pressure agent containing sulfur as component (C) is at least one selected from dithiophosphoric acid derivatives represented by formula (1) and sulfurized olefins. A hydraulic fluid composition is provided.

(In Formula (1), R1 and R2 represent a C3-C18 linear or branched saturated or unsaturated aliphatic hydrocarbon group or a cyclic hydrocarbon group, and may be the same or different. R3 represents a linear or branched alkylene group having 1 to 6 carbon atoms, and R4 represents a hydrogen atom or a linear or branched saturated or unsaturated aliphatic hydrocarbon having 1 to 18 carbon atoms. Represents a group or a cyclic hydrocarbon group.)

The hydraulic oil composition of the present invention can exhibit low traction and can exhibit excellent extreme pressure properties and oxidation stability. Therefore, the hydraulic oil composition of the present invention can be suitably used for industrial machines and the like as a power-saving hydraulic oil.

The high-pressure viscosity of the hydrocarbon-based lubricating base oil used in the hydraulic oil composition of the present invention is 1.0 × 10 ^{10 to} 2.0 × 10 ¹² cP at 40 ° C. and 1.7 GPa, more preferably 2. 0 × 10 ^{10 to} 5.0 × 10 ¹¹ cP, more preferably 2.5 × 10 ^{10 to} 4.0 × 10 ¹¹ cP, and particularly preferably 3.0 × 10 ^{10 to} 2.5 × 10. ¹¹ cP, and most preferably 3.5 × 10 ^{10 to} 9.9 × 10 ¹⁰ cP. If the high-pressure viscosity is less than 1.0 × 10 ¹⁰ cP, an appropriate oil film thickness cannot be maintained, and sufficient wear prevention properties cannot be obtained, which is not preferable. When the high-pressure viscosity exceeds 2.0 × 10 ¹² cP, the traction coefficient increases and the power consumption increases, so that the power saving effect of the present application cannot be sufficiently obtained.

The high-pressure viscosity in the present application is calculated using the following Barus equation.
The Barus equation is expressed by the general formula (2).
η = η ₀ exp (αP) (2)
(In the general formula (2), η is the absolute viscosity (cP) at the pressure P, η ₀ is the absolute viscosity (cP) at atmospheric pressure, and α is the viscosity pressure coefficient.)
The viscosity-pressure coefficient α of the general formula (2) was calculated using the Ohno formula represented by the general formula (3).
^{_{α = 0.62ν 0 0.176 B 2.047 ρ}} 0.293
(3)
(In general formula (3), ν ₀ is the kinematic viscosity (mm ² / s) under atmospheric pressure, ρ is the density (g / cm ³ ) under atmospheric pressure, and B is the viscosity temperature gradient coefficient.)

（一般式（４）において、Ｔ１、Ｔ２は温度（℃）、ν_Ｔ１、ν_Ｔ２は温度Ｔ１、Ｔ２における動粘度（ｍｍ^２／ｓ）である。） Moreover, the viscosity temperature gradient coefficient B of the general formula (3) was calculated using the general formula (4) according to ASTM D341-93.

(In general formula (4), T1 and T2 are temperatures (° C.), and ν _T1 and ν _T2 are kinematic viscosities (mm ² / s) at temperatures T1 and T2.)

% CA of the hydrocarbon-based lubricating base oil used in the hydraulic oil composition of the present invention is 5 or less, preferably 3 or less, more preferably 2 or less, according to ASTM D3238 ring analysis method. When% CA exceeds 5, the traction coefficient increases and the power consumption tends to increase. Note that% CA correlates with the content of aromatic hydrocarbons, but aromatic hydrocarbons tend to have a high traction coefficient, so less is preferable. The aromatic hydrocarbon may not be substantially contained.
The naphthene content of the hydrocarbon-based lubricating base oil used in the hydraulic oil composition of the present invention is not particularly limited, but the% CN according to ASTM D3238 ring analysis method is preferably 8-27, more preferably 9-25. More preferably, it is 10-23, Most preferably, it is 10.5-20, Most preferably, it is 11-15. If% CN is less than 8, the solubility of the additive tends to decrease, and sufficient wear resistance tends to be difficult to obtain. If% CN exceeds 27, the traction coefficient increases and the power consumption tends to increase.

The refractive index of the hydrocarbon-based lubricating base oil used in the hydraulic oil composition of the present invention is not particularly limited, but the refractive index at 20 ° C. according to the JIS K0062 refractive index measurement method is preferably 1.453 to 1.473. Yes, more preferably 1.454 to 1.465, still more preferably 1.455 to 1.463, and particularly preferably 1.456 to 1.459. When the refractive index at 20 ° C. of the base oil is 1.453 or more, the refractive index at 20 ° C. of the composition tends to be easily adjusted to 1.453 or more, and good wear resistance is easily obtained. . By setting the refractive index at 20 ° C. to 1.473 or less, the refractive index at 20 ° C. of the composition tends to be easily adjusted to 1.470 or less. That is, the traction coefficient of the composition tends to be kept low, and power saving tends to be easily obtained.

The hydrocarbon-based lubricating base oil used in the present invention may be produced by any method as long as the constitution of the present invention is satisfied. For example, a crude oil lubricating oil fraction is subjected to solvent refining, hydrorefining, hydrogenation. Although the manufacturing method combined suitably, such as decomposition | disassembly refinement | purification, is mentioned, The following methods are mentioned as a preferable manufacturing method. First, bottom oil obtained by atmospheric distillation of crude oil is treated with a vacuum distillation apparatus. The vacuum gas oil thus obtained is hydrotreated and hydrocracked, and then a residue obtained by removing light and fuel components with a vacuum stripper is obtained. This residue is distilled under reduced pressure, and the resulting lubricating oil fraction is subjected to hydrodewaxing treatment and stabilization treatment. The hydrodewaxing treatment was carried out using a catalyst in which a group 6 or group 8 metal of the periodic table such as Mo, W, Ni, Pd, etc. was supported on an alumina, silica-alumina or zeolite support. Pressure 155-190
kg / cm ² G, reaction temperature 230 to 300 ° C., and LHSV 0.7 to 1.3 h ⁻¹ are preferable.

Further, a preferable method is a method in which slack wax by solvent dewaxing or wax obtained by Fischer-Tropsch synthesis is used as a raw material, and these are hydrotreated and hydrocracked.
Furthermore, the base oil of the present invention is a hydrocarbon-based lubricating oil having a high-pressure viscosity of 1.0 × 10 ^{10 to} 2.0 × 10 ¹² cP at 40 ° C. and 1.7 GPa and a% CA by ring analysis of 5 or less. The base oil of the present invention can be prepared by mixing two or more hydrocarbon-based lubricating base oils that do not correspond to the base oil. For example, a hydrocarbon-based lubricating base oil having a high pressure viscosity of 1.0 × 10 ¹³ cP at 40 ° C. and 1.7 GPa and a% CA of 7 by ring analysis, and a high pressure viscosity of 1. GPa at 40 ° C. and 1.7 GPa are 1. A preparation method in which 0 × 10 ⁹ cP and a hydrocarbon-based lubricating base oil having a% CA of 0 by ring analysis is mixed is mentioned.

As long as the above-mentioned hydrocarbon-based lubricating base oil is in the described high-pressure viscosity range, one type may be used alone, or two or more types may be used in combination.
The hydrocarbon-based lubricating base oil used in the present invention does not include a poly α-olefin base oil. Here, the poly α-olefin base oil is a base oil made of a polymer of α-olefin.
Further, the hydraulic oil composition of the present invention may contain a base oil other than the base oil as long as it does not impair the object of the present invention. The total amount is preferably 70% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

The olefin viscosity index improver used in the hydraulic oil composition of the present invention is a copolymer composed of ethylene and a monomer other than ethylene.
Examples of monomers other than ethylene that form a copolymer with ethylene include olefin hydrocarbons, diene hydrocarbons, vinyl aromatic hydrocarbons, and the like. The number of carbon atoms of these monomers other than ethylene is preferably 3 to 30, more preferably 3 to 25, still more preferably 3 to 15, particularly preferably 3 to 8, and most preferably 3. ~ 5. It is preferable that the number of carbon atoms of the monomer other than ethylene is 30 or less because the molecular weight of the viscosity index improver can be kept relatively low and shear stability can be improved.

The olefinic hydrocarbon used as a monomer other than ethylene may be linear, cyclic, or branched. Specific examples of the olefinic hydrocarbon include propylene, n-butene, i-butylene, cyclobutene, n-pentene, i-pentene, cyclopentene, n-hexene, i-hexene, n-heptene, and i-to. Puten and the like.
The diene hydrocarbon used as a monomer other than ethylene may be a chain, a ring, or a branched chain. Specific examples of the diene hydrocarbon include butadiene, cyclobutadiene, pentadiene, cyclopentadiene, hexadiene, heptadiene and the like.

Examples of vinyl aromatic hydrocarbons used as monomers other than ethylene include styrene and divinylbenzene.
Among these monomers other than ethylene, preferred are olefinic hydrocarbons, and particularly preferred are olefinic hydrocarbons having 3 to 5 carbon atoms.
The olefin-based viscosity index improver is synthesized by polymerizing monomers other than ethylene and ethylene. However, the number of monomers other than ethylene may be one, or two or more.

The molar ratio of ethylene and a monomer other than ethylene is not particularly limited, but is preferably 80:20 to 20:80, more preferably 70:30 to 30:70, and still more preferably 65:35 to 35:65. It is.
The olefin viscosity index improver may be a regular alternating polymer, a random polymer, a block polymer, or a graft polymer.

The preferred weight average molecular weight of the olefin viscosity index improver is preferably 1,000 to 130,000, more preferably 1,200 to 125,000, and still more preferably 3,000 to 100,000. Especially preferably, it is 8,000-80,000, Most preferably, it is 10,000-50,000. When the weight average molecular weight is less than 1,000, the traction coefficient tends to increase. On the other hand, even if the weight average molecular weight exceeds 130,000, the traction coefficient tends to increase. The weight average molecular weight is measured by gel permeation chromatography and is a value in terms of polystyrene.

The olefin viscosity index improver may be either a dispersion type or a non-dispersion type as long as the object of the present invention is not impaired. Here, the dispersion-type olefin viscosity index improver means a monomer having a polar group derived from a monomer in the olefin viscosity index improver, and the non-dispersion olefin viscosity index improver is an improvement in olefin viscosity index. The agent does not have a polar group. Examples of the dispersion type olefin viscosity index improver include an olefin viscosity index improver copolymerized using a nitrogen atom-containing compound or an alkyl ester as a monomer molecule other than ethylene. Specific examples of such nitrogen atom-containing compounds include alkyl-vinyl pyridine, N-vinyl pyrrolidone, vinyl imidazole and the like. Specific examples of alkyl esters include polyalkylene glycol esters, maleic acid esters, and fumaric acid esters. These can be used alone or in combination of two or more.

The refractive index of the olefin viscosity index improver is not particularly limited, but the refractive index at 20 ° C. according to the JIS K0062 refractive index measurement method is preferably 1.453 to 1.480, more preferably 1.455 to 1. .478, and more preferably 1.460 to 1.475. By setting the refractive index at 20 ° C. to 1.453 or more, the refractive index at 20 ° C. of the composition tends to be easily adjusted to 1.453 or more, and good wear resistance can be easily obtained. By setting the refractive index at 20 ° C. to 1.480 or less, the refractive index at 20 ° C. of the composition can be easily adjusted to 1.470 or less. Therefore, the traction coefficient of the composition tends to be low, and the power saving effect can be easily obtained.

The blending amount of the olefinic viscosity index improver with respect to the total amount of the hydraulic oil composition is preferably 0.5 to 30% by mass. By setting the blending amount to 0.5% by mass or more, the traction coefficient can be easily suppressed, and the power saving effect tends to be easily obtained. If the blending amount exceeds 30% by mass, an increase in effect commensurate with the increasing amount of blending amount cannot be obtained, which is not economical.
One of the above olefinic viscosity index improvers may be used alone, or two or more thereof may be used in combination.

Examples of the extreme pressure agent containing sulfur used in the hydraulic oil composition of the present invention include dithiophosphoric acid derivatives, sulfurized olefins, polysulfides, sulfurized fats and oils, sulfurized esters and the like. The extreme pressure agent containing sulfur used in the present invention is not particularly limited, but is preferably at least one selected from dithiophosphoric acid derivatives represented by the formula (1) and sulfurized olefins.
Examples of the dithiophosphoric acid derivative used in the hydraulic oil composition of the present invention include those represented by the formula (1).

 In the formula (1), R1 and R2 represent a linear or branched saturated or unsaturated aliphatic hydrocarbon group or cyclic hydrocarbon group having 3 to 18 carbon atoms, which may be the same or different. Good. Specific examples of R1 and R include n-propyl group, isopropyl group, n-butyl group, isobutyl group, pentyl group, hexyl group, octyl group, 2-ethylhexyl group, nonyl group, dodecyl group, propenyl group, A butenyl group, a phenyl group, a hexylphenyl group, etc. are mentioned.

R3 represents a linear or branched alkylene group having 1 to 6 carbon atoms. Specific examples of R3 include a methylene group, an ethylene group, a propylene group, a butylene group, an amylene group, and a hexylene group, preferably an ethylene group, a propylene group, and a butylene group.
R4 represents a hydrogen atom, or a linear or branched saturated or unsaturated aliphatic hydrocarbon group or cyclic hydrocarbon group having 1 to 18 carbon atoms. Specific examples of R4 include hydrogen, n-propyl group, isopropyl group, n-butyl group, isobutyl group, pentyl group, hexyl group, octyl group, 2-ethylhexyl group, nonyl group, dodecyl group, propenyl group, A butenyl group, a phenyl group, a hexylphenyl group, etc. are mentioned. Preferred examples include those in which R3 is a propylene group and R4 is a hydrogen atom.

Examples of the sulfurized olefin and polysulfide used in the hydraulic oil composition of the present invention include those represented by the formula (5). As will be described later, the sulfurized olefin is obtained by sulfiding olefins, and the polysulfide is different in that it is obtained by sulfiding other hydrocarbon raw materials.
R5-Sx- (R6-Sx-) n-R7 (5)
(In Formula (5), R5 and R7 are monovalent hydrocarbon groups, R6 is a divalent hydrocarbon group, x is an integer of 1 or more, and n is 0 or an integer of 1 or more. .)

In formula (5), R5 and R7 are the same or different monovalent hydrocarbon groups. R6 is a divalent hydrocarbon group. When a plurality of R6 are present, each R6 is the same or different divalent hydrocarbon group. x is an integer greater than or equal to 1, Preferably it is an integer of 1-8, and x is the same or different number in a repeating unit, respectively. X in this repeating unit is preferably an integer of 1 to 6, more preferably an integer of 2 to 4, and particularly preferably an integer of 2 to 3. If x is small, sufficient extreme pressure properties tend not to be obtained. If x is too large, sufficient thermal oxidation stability is difficult to obtain, and the amount of sludge tends to increase. n is 0 or an integer of 1 or more.

Examples of R5 and R7 include a C2-C20 linear or branched saturated or unsaturated aliphatic hydrocarbon group, or a C6-C26 aromatic hydrocarbon group. Specific examples include an ethyl group, a propyl group, a butyl group, a nonyl group, a dodecyl group, a propenyl group, a butenyl group, a benzyl group, a phenyl group, a tolyl group, and a hexylphenyl group. Examples of R6 include a C2-C20 linear or branched saturated or unsaturated divalent aliphatic hydrocarbon group, or a C6-C26 divalent aromatic hydrocarbon group. . Specific examples include an ethylene group, a propylene group, a butylene group, and a phenylene group.
Specific examples of sulfurized olefins include those obtained by sulfurizing olefins such as polyisobutylene and terpenes with sulfur or other sulfurizing agents.
Specific examples of the polysulfide compound include diisobutyl disulfide, dioctyl polysulfide, di-tert-butyl polysulfide, di-tert-benzyl polysulfide and the like.
The sulfurized ester is obtained by sulfurizing a fatty acid ester obtained by a reaction between fats and oils and various alcohols, and the chemical structure itself is not clear. Examples of the fats and oils include animal and vegetable fats and oils such as lard, beef tallow, whale oil, palm oil, coconut oil and rapeseed oil.

The blending amount of the extreme pressure agent containing sulfur used in the present invention with respect to the total amount of the hydraulic oil composition is preferably 0.01 to 0.4% by mass, more preferably 0.01 to 0.3% by mass. . If the blending amount is less than 0.01% by mass, sufficient extreme pressure performance tends to be difficult to obtain. This may also lead to a decrease in the efficiency of the hydraulic system and an increase in power consumption due to an increase in the internal leakage amount of the vane pump, for example. On the other hand, if the blending amount exceeds 0.4% by mass, it is difficult to obtain sufficient thermal oxidation stability, and the amount of sludge tends to increase.
The extreme pressure agent containing sulfur may be used alone or in combination of two or more.

The refractive index at 20 ° C. of the hydraulic oil composition of the present invention according to the JIS K0062 refractive index measurement method is 1.453 to 1.470, more preferably 1.454 to 1.468, and still more preferably 1. .455 to 1.465, particularly preferably 1.456 to 1.459. When the refractive index at 20 ° C. is less than 1.453, the wear resistance tends to decrease. When the refractive index at 20 ° C. exceeds 1.470, the traction coefficient increases, and a sufficient power saving effect cannot be obtained.

40 ° C. kinematic viscosity of the hydraulic oil composition of the present invention, in the JIS K2283 Kinematic Viscosity Test Method (40 ° C.), a 19~51mm ² / s, preferably 24~48mm ² / s, more preferably 28 ~46mm is a ² / s. When the 40 ° C. kinematic viscosity is less than 19 mm ² / s, an appropriate oil film thickness cannot be maintained, and the wear resistance tends to decrease. If the 40 ° C. kinematic viscosity exceeds 51 mm ² / s, the traction coefficient tends to increase and the power consumption tends to increase.

In the JIS K2283 kinematic viscosity test method, the viscosity index of the hydraulic oil composition of the present invention is preferably 103 or more, more preferably 110 or more, still more preferably 120 or more, and particularly preferably 130 or more. If the viscosity index is too low, the low-temperature viscosity tends to be high, and the power consumption during low-temperature starting tends to increase.

In the hydraulic oil composition of the present invention, various known additives can be blended as necessary within a range where the object of the present invention is not impaired. For example, an antioxidant, an oily agent, a detergent / dispersant, a rust inhibitor, a metal deactivator, a pour point depressant, a defoamer, a demulsifier, and the like can be mentioned.
Antioxidants include phenol-based antioxidants such as 2,6-di-tert-butyl-p-cresol, amine-based antioxidants such as alkylated diphenylamine and alkylated phenyl-α-naphthylamine, phosphonic acid esters, etc. And phosphorus-based antioxidants.

  Examples of the oily agent include higher fatty acids such as oleic acid and stearic acid, higher alcohols such as oleyl alcohol, amines such as oleylamine, and esters such as butyl stearate.

Examples of the cleaning dispersant include ashless cleaning dispersants such as alkenyl succinimides and alkenyl succinic esters, and alkaline earth metal cleaning dispersants.
Examples of the rust inhibitor include carboxylic acid, metal soap, carboxylic acid amine salt, sulfonic acid metal salt, and partial ester of polyhydric alcohol.
Examples of metal deactivators include benzotriazole and derivatives thereof, and alkyl succinic acid derivatives.
Examples of the pour point depressant include polyalkyl methacrylate, polybutene, polyalkyl styrene, polyvinyl acetate, polyalkyl acrylate and the like.

Examples of antifoaming agents include silicone oil and ester-based antifoaming agents.
Examples of the demulsifier include demulsifiers such as an anionic surfactant, a cationic surfactant, and a nonionic surfactant.
These additives may be used alone or in combination of two or more.

Next, the present invention will be described more specifically with reference to examples. In addition, this invention is not restrict | limited at all by these examples.
The base oil and additive components used in the preparation of the hydraulic oil composition in each example and comparative example are as follows.

<Method for producing hydrocarbon-based lubricating base oil>
(1) The bottom oil obtained by atmospheric distillation of the hydrocarbon-based lubricating base oil crude oil of the example was treated with a vacuum distillation apparatus, and the vacuum gas oil obtained there was hydrotreated and hydrocracked. Then, the residue which removed the light part and the fuel part with the vacuum stripper was obtained. The residue was distilled under reduced pressure, and the resulting lubricating oil fraction was subjected to hydrodewaxing treatment and stabilization treatment. The hydrodewaxing treatment is performed under the conditions of a reaction pressure of 160 to 180 kg / cm ² G, a reaction temperature of 270 to 290 ° C., and LHSV of 0.9 to 1.1 h ⁻¹ , and the base oil (A-1), (A− 2) and (A-3) were obtained.
The properties of the base oils (A-1), (A-2) and (A-3) are shown below.

(A-1) Hydrocracked mineral oil (hydrocarbon base oil)
40 ° C. kinematic viscosity: 13.2 mm ² / s, 100 ° C. kinematic viscosity: 3.2 mm ² / s, refractive index at 20 ° C .: 1.460, density at 40 ° C .: 0.820, 40 ° C., at 1.7 GPa High pressure viscosity: 1.7 × 10 ¹¹ cP,% CA: 0.9,% CN: 26.6
(A-2) Hydrocracked mineral oil (hydrocarbon-based lubricating base oil)
40 ° C. kinematic viscosity: 20.1mm ² / s, 100 ℃ kinematic viscosity: 4.3mm ² / s, a refractive index at 20 ℃: 1.463,40 density at ℃: 0.817,40 ℃, in 1.7GPa High-pressure viscosity: 2.1 × 10 ¹¹ cP,% CA: 0.6,% CN: 20.2
(A-3) Hydrocracked mineral oil (hydrocarbon base oil)
40 ° C. kinematic viscosity: 18.7mm ² / s, 100 ℃ kinematic viscosity: 4.3mm ² / s, a refractive index at 20 ℃: 1.457,40 density at ℃: 0.807,40 ℃, in 1.7GPa High-pressure viscosity: 3.8 × 10 ¹⁰ cP,% CA: 0.6,% CN: 11.5

(2) The base oil crude of the comparative example was distilled at atmospheric pressure, the residual oil after fractional distillation was fractionated under reduced pressure, and the resulting distillate was purified to paraffin-rich raffinate by a furfural solvent extraction method. Subsequently, the dewaxed oil obtained by dewaxing the raffinate was subjected to high-pressure hydrogenation. The high-pressure hydrogenation treatment was carried out under the conditions of a reaction pressure of 170 kg / cm ² G, a reaction temperature of 325 ° C., and LHSV 0.36 h ⁻¹ using a catalyst supporting Mo and Ni on an alumina support. The properties of the obtained base oil (A-4) are shown below.
(A-4) Hydrorefined mineral oil (hydrocarbon lubricant base oil)
40 ° C. kinematic viscosity: 30.8mm ² / s, 100 ℃ kinematic viscosity: 5.4mm ² / s, a refractive index at 20 ℃: 1.472,40 density at ℃: 0.842,40 ℃, in 1.7GPa High pressure viscosity: 4.6 × 10 ¹² cP,% CA: 0.4,% CN: 29.8

* 40 ° C kinematic viscosity is JIS
K2283 kinematic viscosity test method, density was measured by JIS K2249 density test method, and refractive index at 20 ° C. was measured by JIS K0062 refractive index measurement method. High pressure viscosity was calculated using the Barus equation. The viscosity pressure coefficient necessary for the calculation was calculated using the Ohno equation. The absolute viscosity can be calculated from the kinematic viscosity / density, and calculated from the measured value at 40 ° C.
% CA and% CN are ASTM
Measured by D3238 ring analysis. The refractive index, density, molecular weight and sulfur content necessary for the calculation were measured by JIS K0062 refractive index measurement method, JIS K2249 density test method, ASTM D2502 molecular weight test method, and JIS K2541 sulfur content test method.

<Viscosity index improver>
(B-1) ethylene propylene random copolymer (B-2) having a weight average molecular weight of 1,400, a refractive index of 1.461 at 20 ° C., and an ethylene / propylene molar ratio of 53:47. Ethylene-propylene random copolymer (B-3) having a refractive index of 10,000 at 20 ° C and a refractive index of 1.472 and an ethylene / propylene molar ratio of 53:47. Refractive index at a weight average molecular weight of 16,000 and 20 ° C. Ethylene propylene random copolymer (B-4) having a molar ratio of ethylene / propylene of 53:47, a weight average molecular weight of 125,000, a refractive index at 20 ° C. of 1.463, and ethylene / propylene Ethylene propylene random copolymer having a molar ratio of 55:45

(B-5) Ethylene propylene random copolymer having a weight average molecular weight of 6,500, a refractive index of 1.473 at 20 ° C., an ethylene / propylene molar ratio of 55:45, and a maleic acid modified type
(B-6) Polyisobutylene having a weight average molecular weight of 150,000 (B-7) Polymethacrylate having a weight average molecular weight of 22,000

<Extreme pressure agent>
· Sulfur-containing extreme pressure agent (C-1) β-dithiophosphorylated propionic acid (in the formula (1), R1 and R2 are isobutyl groups, R3 is a propylene group, and R4 is a hydrogen atom) )
(C-2) Sulfurized olefin (R5 and R7 in Formula (5) are unsaturated aliphatic hydrocarbon groups having 8 to 12 carbon atoms, n is 0, and x is 2 or 3)
(C-3) Polysulfide (R5 and R7 in Formula (5) are unsaturated aliphatic hydrocarbon groups having 4 to 8 carbon atoms, n is 0, and x is 2 or 3)
・ Sulfur-free extreme pressure agent (C-4) tricresyl phosphate

<Other additives>
(D) Antioxidant: 2,6-di-tert-butyl-p-cresol, alkylated diphenylamine

The weight average molecular weight was measured by gel permeation chromatography and calculated in terms of polystyrene. Gel permeation chromatography is applied to the column
Three GPC LF-804s were used, THF was used for the moving layer, and a differential refraction detector was used for the detector.
The viscosity index of the composition was measured by the JIS K2283 kinematic viscosity test method.

(Evaluation method)
The traction coefficient, thermal oxidation stability, and extreme pressure property of the hydraulic oil composition were evaluated by the following evaluation methods.

<Traction coefficient>
The traction coefficient was evaluated with a four-cylinder fatigue friction tester.
A test piece having a material SUJ-2, an outer diameter of 40 mm, a width of 10 mm, and a surface roughness of 0.08 μm or less was used, a slip ratio of 5.3%, and a maximum Hertz load of 1.7.
The test was conducted with GPa, oil temperature of 40 ° C., and test time of 5 minutes.
This test condition simulates the maximum pressure at the tip of the vane in the vane pump when the discharge pressure is 14 MPa.
<Thermal oxidation stability>
40 g of the hydraulic oil composition was placed in a glass container having an inner diameter of 2.5 cm, and the amount of sludge (mg, Millipore filter having a pore diameter of 0.8 μm) after 168 hours at 160 ° C. was evaluated.
<Extreme pressure>
A shell four-ball test (according to ASTM D2596) was carried out and evaluated by the fusion load (N).

(Examples 1-12)
A hydraulic oil composition was prepared by blending the base oil with a viscosity index improver, an extreme pressure agent, and other additives in the proportions (mass%) shown in the upper part of Tables 1 and 2. Various performances of these hydraulic oil compositions were evaluated, and the results are shown in the lower part of Tables 1 and 2.
(Comparative Examples 1-7)
A hydraulic oil composition was prepared by blending the base oil with a viscosity index improver, an extreme pressure agent, and other additives in the proportions (mass%) shown in the upper part of Tables 3 and 4. Various performances of these hydraulic oil compositions were evaluated, and the results are shown in Tables 3 and 4 below.

Examples 1 to 12 are compared to Comparative Example 1 that does not contain an olefin-based viscosity index improver, Comparative Example 2 that contains polyisobutylene as a viscosity index improver, and Comparative Example 3 that contains polymethacrylate as a viscosity index improver. Low traction coefficient. Further, the traction coefficient is very low as compared with Comparative Example 4 in which an olefinic viscosity index improver is blended with a base oil having a higher high-pressure viscosity than the base oil used in the present invention.
Examples 1-12 are excellent in thermal oxidation stability compared with the comparative example 5 with many compounding quantities of the extreme pressure agent containing sulfur, and the comparative example 7 which does not contain the extreme pressure agent containing sulfur. The extreme pressure property is excellent as compared with Comparative Example 6 in which the amount of the extreme pressure agent contained is large. Therefore, these Examples can expect a power saving effect due to low traction, and at the same time, excellent thermal oxidation stability and extreme pressure can be obtained.

The hydraulic oil composition of the present invention can be applied to various hydraulic oils, but can be preferably used as a hydraulic hydraulic oil particularly used in a hydraulic system. Furthermore, it is particularly effective in achieving power saving in a hydraulic system, such as a hydraulic pump, a hydraulic motor, and a hydraulic cylinder, where hydraulic fluid is exposed to a high pressure state, that is, an elastic fluid lubrication region.

Claims (3)

(A) Hydrocarbon base oil having a high-pressure viscosity of 1.0 × 10 ^{10 to} 2.0 × 10 ¹² cP at 40 ° C. and 1.7 GPa and a% CA of 5 or less by ring analysis (however, poly α (B) an olefinic viscosity index improver composed of a copolymer of ethylene and a monomer other than ethylene, and (C) an extreme pressure agent containing sulfur. And the compounding quantity of the extreme pressure agent containing sulfur of (C) component is 0.01-0.4 mass% with respect to the composition whole quantity, and the refractive index in 20 degreeC of this composition is 1.453. A hydraulic oil composition having a viscosity of ˜1.470 and a kinematic viscosity at 40 ° C. of 19 to 51 mm ² / s. The component (B) olefin viscosity index improver is a copolymer of ethylene and an olefin having 3 to 30 carbon atoms, and its refractive index is 1.453 to 1.480 at 20 ° C., and The hydraulic oil composition according to claim 1, wherein the blending amount is 0.5 to 30% by mass with respect to the total amount of the composition. The hydraulic oil composition according to claim 1 or 2, wherein the extreme pressure agent containing sulfur as component (C) is at least one selected from dithiophosphoric acid derivatives represented by formula (1) and sulfurized olefins. .

(In Formula (1), R1 and R2 represent a C3-C18 linear or branched saturated or unsaturated aliphatic hydrocarbon group or a cyclic hydrocarbon group, and may be the same or different. R3 represents a linear or branched alkylene group having 1 to 6 carbon atoms, and R4 represents a hydrogen atom or a linear or branched saturated or unsaturated aliphatic hydrocarbon having 1 to 18 carbon atoms. Represents a group or a cyclic hydrocarbon group.)