JP5395474B2 - Industrial hydraulic oil composition - Google Patents

Description

The present invention relates to a power-saving industrial 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 effective means for power saving, it is widely known that the kinematic viscosity is lowered, but on the other hand, improvement by reducing friction and wear by blending a specific additive has been achieved.

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).

By the way, power saving is also demanded in the hydraulic device. Recently, hydraulic oil tends to be exposed to harsher conditions such as high temperature, high pressure, high shear, etc. due to higher output, higher pressure, and smaller oil tanks.

Industrial hydraulic devices are composed of oil tanks, hydraulic pumps such as vane pumps and piston pumps, control valves for adjusting the flow rate, direction and pressure, actuators such as hydraulic cylinders and hydraulic pumps, and piping connecting them. Among these parts, in the hydraulic pump, the control valve, and the actuator, the hydraulic fluid flows through a narrow path and is exposed to a high shear condition. Reducing the viscosity at the main parts of the hydraulic system such as hydraulic pumps, control valves, and actuators is considered to be effective as one of the methods for power saving of the hydraulic system. Lowering the temporary shear viscosity under shear conditions (hereinafter sometimes referred to as “high shear viscosity”) can be expected to further contribute to power saving of the hydraulic device. At that time, in a hydraulic apparatus that is normally operated at a tank oil temperature of around 40 ° C. like an injection molding machine, it can be expected that it can contribute to power saving by reducing the high shear viscosity at 40 ° C.

Thus, in order to make high shear viscosity low, it is possible to mix | blend a suitable polymer with a base oil. However, since many of the polymers blended to reduce the high shear viscosity are likely to cause molecular cleavage under high shear, hydraulic fluids blended with such polymers have reduced permanent shear stability, There is a tendency for permanent viscosity reduction due to shear force. As a result, for example, it may be difficult to hold an appropriate oil film in a hydraulic pump or an actuator.

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

An object of the present invention is to provide an industrial hydraulic fluid composition having a low temporary shear viscosity under a high shear condition and an excellent permanent shear stability.

As a result of intensive studies to solve the above problems, the present inventor has obtained a hydrocarbon-based lubricating base oil having a specific 40 ° C. kinematic viscosity , aniline point, 15 ° C. density, and naphthene content (% CN) . Formulating a composition containing a polymethacrylate viscosity index improver having a weight average molecular weight of 84,000 to 130,000 , and setting the kinematic viscosity and viscosity index of the resulting composition at 40 ° C. to a specific range Thus, it was found that an industrial hydraulic fluid composition having a low temporary shear viscosity under high shear conditions and excellent in permanent shear stability was obtained, and the present invention was completed based on this finding.

That is, the present invention, (A) 40 ° C. kinematic viscosity 4~40mm Ri ² / s der, aniline point is 100 to 130 ° C., 15 ° C. density be 0.80~0.85g / cm ³ , naphthene (% CN) is 8-27 der Ru hydrocarbon lubricating base oil, and (B) a weight average molecular weight, containing a polymethacrylate-based viscosity index improver is 84,000～130,000 a composition, kinematic viscosity at 40 ° C. of the composition 19~51mm Ri ² / s der to provide industrial hydraulic oil composition viscosity index is characterized by 140 to 240 der Rukoto Is.

The industrial hydraulic fluid composition of the present invention has a low temporary shear viscosity under high shear conditions and is excellent in permanent shear stability. The “temporary shear viscosity” refers to a viscosity that temporarily changes under a condition where a shearing force is applied. On the other hand, irreversible changes in the chemical structure occur due to the application of shearing force, and the oil does not return to its original viscosity even when the shearing force is released, that is, it may cause a permanent decrease in viscosity. . This resistance to permanent viscosity reduction due to shear force is referred to as “permanent shear stability”. Therefore, “low temporary shear viscosity under high shear conditions and excellent permanent shear stability” means that “viscosity under low shear conditions is low, but this high shear force is It means that the viscosity after removal is the same as or close to the viscosity before applying a high shear force.
Therefore, the industrial hydraulic fluid composition of the present invention can be suitably used for industrial machines and the like as a power-saving industrial hydraulic fluid.

(1) Base oil Examples of the hydrocarbon base oil used in the industrial hydraulic fluid composition of the present invention include poly α olefins and hydrocarbon base oils other than poly α olefins. May be used alone, or two or more base oil components may be mixed. Moreover, you may mix and use hydrocarbon type base oil other than poly alpha olefin and poly alpha olefin.

The poly-α-olefin is a copolymer of α-olefin, and for example, an α-olefin having a number of carbon atoms of 6 to 18 is preferably a 10-mer or less. Particularly preferred poly-α-olefins are α-decene (carbon number 10) 2 to 4 mer, or α-dodecene (carbon number 12) 2 to 4 mer, and more than those pentamers. It contains. The average number of carbon atoms per molecule of the poly α-olefin is not particularly limited as long as it is in the above 40 ° C. kinematic viscosity range.

As a suitable production example of poly α-olefin, an α-olefin having 6 to 18 carbon atoms is synthesized by low polymerization of ethylene or thermal decomposition of wax, 2 to 9 units of this α-olefin are polymerized, and hydrogenation reaction is performed. Synthesized by doing.

Hydrocarbon base oils other than poly-alpha olefins include mineral oil base oils produced by combining crude oil fractions as appropriate, including solvent refining, hydrorefining, hydrocracking refining, and solvent removal. Examples thereof include base oils obtained by hydrotreating and hydrocracking raw materials such as slack wax by wax and wax obtained by Fischer-Tropsch synthesis.

The following method is mentioned as a preferable manufacturing method of mineral oil type | system | group lubricating base oil. 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 40 ° C. kinematic viscosity of the hydrocarbon-based lubricating base oil used in the industrial hydraulic fluid composition of the present invention is 4 to 40 mm ² / s, more preferably 8 to 35 mm ^{2 in the} JIS K2283 kinematic viscosity test method. / S, more preferably 10 to 30 mm ² / s, and particularly preferably 15 to 25 mm ² / s. When the 40 ° C. kinematic viscosity is less than 4 mm ² / s, an appropriate oil film thickness cannot be maintained, and it is difficult to obtain sufficient wear resistance. When the 40 ° C. kinematic viscosity exceeds 40 mm ² / s, it is necessary to reduce the blending amount of the viscosity index improver, which will be described later, in order to adjust the kinematic viscosity to be appropriate as the hydraulic oil, and the high shear viscosity becomes large. It becomes difficult to obtain a power saving effect. In addition, when using the base oil which mixed the some base oil component, the 40 degreeC kinematic viscosity of the base oil after mixing should just be in said range, and the 40 degreeC kinematic viscosity of each base oil component is the said range. More preferably, it is within.

The viscosity grade of the industrial hydraulic oil composition is determined by a kinematic viscosity of 40 ° C., and it is required to use a hydraulic oil of a viscosity grade suitable for each device and operating conditions. For example, hydraulic oil having a viscosity grade (hereinafter referred to as VG) of 46 is considered to be used in an apparatus and operating conditions that require higher wear resistance than hydraulic oil of VG22. Therefore, VG46, that is, a hydraulic oil having a composition having a 40 ° C. kinematic viscosity of 41.4 to 50.6 mm ² / s, and VG 32, that is, a composition having a 40 ° C. kinematic viscosity of 28.8 to 35. In the case of preparing a hydraulic oil having 2 mm ² / s, and in the case of preparing a hydraulic oil in which VG22, that is, the composition having a kinematic viscosity of 40 ° C. of 19.8 to 24.2 mm ² / s, is used. The preferred 40 ° C. kinematic viscosity of the oil is different.

For example, when preparing hydraulic oil of VG46 in the present invention, the 40 ° C. kinematic viscosity of the base oil used in the present invention is 4 to 40 mm ² / s, preferably 10 to 38 mm ² / s, more preferably 13~35mm a ² / s, particularly preferably 14~25mm ² / s.
Moreover, when preparing the hydraulic oil of VG32 in this invention, the kinematic viscosity of the base oil used by this invention becomes like this. Preferably it is 4-30 mm < ² > / s, More preferably, it is 9-28 mm < ² > / s, Especially preferably Is 11 to 25 mm ² / s.
Moreover, when preparing the hydraulic oil of VG22 in this invention, the kinematic viscosity of the base oil used by this invention becomes like this. Preferably it is 4-20 mm < ² > / s, More preferably, it is 8-18 mm < ² > / s, Especially preferably, Is 10-15 mm ² / s.

The hydrocarbon-based lubricating base oil used in the industrial hydraulic fluid composition for industrial use of the present invention may have any properties as long as the kinematic viscosity at 40 ° C. satisfies the above range, and is not particularly limited. From the viewpoint of ensuring better performance, it is preferable that the hydrocarbon base oil other than the poly-α-olefin has the following properties.

The viscosity index of the hydrocarbon-based lubricating base oil used in the industrial hydraulic fluid composition of the present invention is preferably 90 or more in the JIS K2283 kinematic viscosity test method. By setting the viscosity index to 90 or more, it is easy to obtain a viscosity index of a preferable composition described later, and as a result, it becomes easy to obtain a composition that can suppress low-temperature viscosity to a low level and suppress power consumption at low-temperature startup. Further, the viscosity index of the composition can be increased as the blending amount of the viscosity index improver that is a component of the present invention is increased. However, if the viscosity index of the base oil is high, the blending amount can be suppressed. it can. From this viewpoint, the viscosity index of the base oil is more preferably 103 or more, further preferably 105 or more, particularly preferably 110 or more, and most preferably 120 or more.

The density of the hydrocarbon-based lubricating base oil used in industrial hydraulic fluid composition of the present invention, in the JIS K2249 Density Test method (15 ° C.), a 0.80~0.85g / cm ^3. It is preferable to set the density at 15 ° C. to 0.80 or more because it tends to ensure appropriate solubility of the additive. It is preferable to set the 15 ° C. density to 0.85 g / cm ³ or less because it is easy to suppress pressure loss of piping and the like and it is easy to obtain a higher power saving effect.

Naphthene content of the hydrocarbon-based lubricating base oil used in industrial hydraulic fluid composition of the present invention (% CN), in ASTM D3238 ring analysis method, is 8-27. It is preferable to set% CN to 8 or more because it tends to ensure the solubility of the additive. By setting% CN to 27 or less, it tends to be a high viscosity index base oil.

The aniline point of the hydrocarbon-based lubricating base oil used in the industrial hydraulic fluid composition of the present invention is 100 to 130 ° C. in the JIS K2256 aniline point test method. By setting the aniline point to 100 ° C. or higher, it tends to be a high viscosity index base oil. It is preferable to set the aniline point to 130 ° C. or lower because it tends to ensure the solubility of the additive.

The industrial hydraulic fluid composition of the present invention may contain a base oil other than the base oil as long as the effects of the present invention are not impaired. The content of the base oil is based on the total amount of the base oil. Is preferably 70% by mass, more preferably 80% by mass or more, still more preferably 85% by mass or more, and particularly preferably 90% by mass or more.
In the industrial hydraulic fluid composition of the present invention, the content of the base oil is preferably 75 to 98% by mass, more preferably 77 to 97% by mass, based on the total amount of the hydraulic fluid composition. More preferably, it is 80-96 mass%, Most preferably, it is 83-95.5 mass%.

(2) Viscosity index improver The polymethacrylate viscosity index improver (hereinafter sometimes referred to as PMA viscosity index improver) used in the industrial hydraulic fluid composition of the present invention is represented by the formula (1). A non-dispersed polymethacrylate viscosity index improver obtained by polymerizing at least one monomer selected from compounds, at least one monomer selected from compounds represented by formula (1), and polarity Examples thereof include a dispersion type polymethacrylate viscosity index improver obtained by copolymerizing a monomer having a group.

(R ¹ in Formula (1) represents a hydrogen atom or a methyl group, and may be the same or different. R ² in Formula (1) is a linear or branched chain having 1 to 18 carbon atoms. Represents an alkyl group of
Specific examples of the monomer having a polar group include nitrogen atom-containing compounds such as alkyl-vinyl pyridine, N-vinyl pyrrolidone and vinyl imidazole, and esters such as polyalkylene glycol ester, maleic acid ester and fumaric acid ester. These can be used alone or in combination of two or more.

The weight average molecular weight of polymethacrylate viscosity index improver is 82,000～130,000, particularly preferably 84,000～120,000. By setting the weight average molecular weight to 80,000 or more, the high shear viscosity can be easily suppressed and a higher power saving effect tends to be obtained. By setting the weight average molecular weight to 150,000 or less, it tends to easily obtain better permanent shear stability. The weight average molecular weight is measured by gel permeation chromatography and is a value in terms of polystyrene.

The blending amount of the polymethacrylate viscosity index improver with respect to the total amount of the hydraulic oil composition is preferably 2 to 20% by mass, more preferably 3 to 18% by mass, and further preferably 4 to 15% by mass, Especially preferably, it is 4.5-12 mass%. When the blending amount is 2% by mass or more, the decrease in the temporary shear viscosity under high shear conditions is increased, and the power saving effect tends to be more easily obtained. By setting the blending amount to 20% by mass or less, it tends to easily obtain better permanent shear stability.
One of the above polymethacrylate viscosity index improvers may be used alone, or two or more thereof may be used in combination.

In addition, the industrial hydraulic fluid composition of the present invention may contain a viscosity index improver other than the polymethacrylate viscosity index improver as long as the effects of the present invention are not impaired. Examples of the viscosity index improver other than the PMA-based viscosity index improver include, for example, ethylene-propylene copolymer, polyisobutylene, styrene-diene hydrogenated copolymer, and the like, and the weight average molecular weight is less than 80,000. Examples include polymethacrylate viscosity index improvers.

(3) Other Additives Various known additives can be blended with the industrial hydraulic fluid composition of the present invention, if necessary, as long as the object of the present invention is not impaired. For example, antioxidants, extreme pressure agents, oily agents, detergents and dispersants, rust inhibitors, metal deactivators, pour point depressants, defoamers, demulsifiers 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 extreme pressure agents include phosphorous extreme pressure agents such as phosphates and phosphites, sulfur-based extreme pressure agents such as sulfurized olefins, polysulfides, sulfurized fats and oils, dithiophosphoric acid derivatives, and organometallic extreme pressure agents such as ZnDTP and ZnDTC. It is done. Particularly preferred are sulfurized olefins and dithiophosphoric acid derivatives.
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.

(4) Composition Properties The industrial hydraulic fluid composition of the present invention has a kinematic viscosity at 40 ° C. of 19 to 51 mm ² / s, more preferably 24 to 48 mm ² / s in the JIS K2283 kinematic viscosity test method. More preferably, it is 28-46 mm < ² > / s. When the 40 ° C. kinematic viscosity is less than 19 mm ² / s, an appropriate oil film thickness cannot be maintained, and sufficient wear resistance tends to be difficult to obtain. When the 40 ° C. kinematic viscosity exceeds 51 mm ² / s, the high shear viscosity increases and the power saving effect tends to be insufficient.

Viscosity index of industrial hydraulic fluid composition of the present invention, in the JIS K2283 kinematic viscosity test method is 140 to 240, the lower limit is more preferably 143 or more. By setting the viscosity index to 140 or more, it is easy to suppress the low temperature viscosity. Therefore, it is easy to suppress the power consumption at the time of low temperature start, and it is easy to obtain a higher power saving effect.

(5) Applications The industrial hydraulic fluid composition of the present invention can be applied to various industrial hydraulic fluids, but can be preferably used as a hydraulic fluid used in a hydraulic system. Furthermore, it is particularly effective for reducing power consumption in a hydraulic system such as a hydraulic pump, a hydraulic motor, a control valve, etc., where hydraulic hydraulic fluid is exposed to a sheared state.

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 industrial hydraulic fluid composition in each example and comparative example are as follows.
In addition, 40 degreeC kinematic viscosity, 100 degreeC kinematic viscosity, viscosity index are JIS
K2283 kinematic viscosity test method, density was measured by JIS K2249 density test method. % CN was determined by ASTM D3238 ring analysis. The refractive index, density, molecular weight and sulfur content necessary for calculating% CN 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.
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.

(A) Base oil (A-1) Hydrocracked mineral oil
40 ° C. kinematic viscosity: 13.2 mm ² / s, 100 ° C. kinematic viscosity: 3.2 mm ² / s, viscosity index: 106, density at 15 ° C .: 0.837 g / cm ³ ,% CN: 26, aniline point: 106 ℃
(A-2) Hydrocracked mineral oil 40 ° C. kinematic viscosity: 17.8 mm ² / s, 100 ° C. kinematic viscosity: 4.1 mm ² / s, viscosity index: 135, density at 15 ° C .: 0.825 g / cm ³ , % CN: 13, aniline point: 120 ° C

(A-3) Hydrocracked mineral oil
40 ° C. kinematic viscosity: 20.1 mm ² / s, 100 ° C. kinematic viscosity: 4.3 mm ² / s, viscosity index: 122, density at 15 ° C .: 0.834 g / cm ³ ,% CN: 20, aniline point: 115 ℃
(A-4) Hydrocracked mineral oil
40 ° C. kinematic viscosity: 46.9 mm ² / s, 100 ° C. kinematic viscosity: 7.7 mm ² / s, viscosity index: 130, density at 15 ° C .: 0.842 g / cm ³ ,% CN: 21, aniline point: 127 ℃

(A-5) Poly α-olefin base oil (2- to 5-mer of 1-decene monomer)
40 ° C. kinematic viscosity: 17.3 mm ² / s, 100 ° C. kinematic viscosity: 3.9 mm ² / s, viscosity index: 123, density at 15 ° C .: 0.820 g / cm ³ ,% CN: 8, aniline point: 120 ℃
(A-6) Polyalphaolefin base oil (2- to 5-mer of 1-decene monomer)
40 ° C. kinematic viscosity: 30.5 mm ² / s, 100 ° C. kinematic viscosity: 5.8 mm ² / s, viscosity index: 135, density at 15 ° C .: 0.827 g / cm ³ ,% CN: 9, aniline point: 127 ℃

(B) Viscosity index improver (B-1) PMA viscosity index improver: Dispersed polymethacrylate viscosity index improver (weight average molecular weight: 104,000, diluent oil content: 45 mass%)
(B-2) PMA viscosity index improver: non-dispersed polymethacrylate viscosity index improver (weight average molecular weight: 85,000, diluent oil content: 27% by mass)
(B-3) PMA viscosity index improver: non-dispersed polymethacrylate viscosity index improver (weight average molecular weight: 106,000, diluent oil content: 45 mass%)
(B-4) PMA viscosity index improver: non-dispersed polymethacrylate viscosity index improver (weight average molecular weight: 154,000, diluent oil content: 28% by mass)
(B-5) PMA viscosity index improver: Dispersed polymethacrylate viscosity index improver (weight average molecular weight: 234,000, diluent oil content: 60% by mass)
(B-6) PMA viscosity index improver: non-dispersed polymethacrylate polymer (weight average molecular weight: 35,000, diluent oil content: 40% by mass)

(C) Other additives (C-1) Extreme pressure agent 1: β-dithiophosphorylated propionic acid (C-2) Extreme pressure agent 2: Sulfurized olefin (C-3) Antioxidant: 2,6-di- tert-Butyl-p-cresol and alkylated diphenylamine

(Evaluation method)
The temporary shear viscosity (high shear viscosity) and permanent shear stability under high shear conditions of the industrial hydraulic oil composition were evaluated by the following evaluation methods.

<High shear viscosity>
With TBS viscometer, high shear viscosity (100 ° C.) at a temperature 100 ° C. · shear rate ¹⁰ 6 ^{s -1,} and to measure the high shear viscosity (0.99 ° C.) at a temperature 0.99 ° C. · shear rate ¹⁰ 6 ^{s -1} ( According to ASTM D4683).
In addition, high shear viscosity (40 ° C.) at a temperature of 40 ° C. and a shear rate of 10 ⁶ s ⁻¹ was measured using USV (Ultra Shear Viscometer, manufactured by PCS Instruments).
<Permanent shear stability test>
The ultrasonic method (JPI-5S-29 compliant, low output method) was performed, and the 40 ° C. kinematic viscosity after 30 minutes of ultrasonic irradiation was measured. The 40 ° C. kinematic viscosity reduction rate (%) was evaluated based on the 40 ° C. kinematic viscosity before ultrasonic irradiation.

(Examples 1-6)
Viscosity index improvers and other additives were blended with the base oil in the proportions (mass%) shown in the upper part of Tables 1 and 2 to prepare an industrial hydraulic fluid composition. The hydraulic fluid compositions were evaluated for viscosity index, high shear viscosity and permanent shear stability, and the results are shown in the lower part of Tables 1-2.
(Comparative Examples 1-4)
An industrial hydraulic fluid composition was prepared by blending the base oil with a viscosity index improver and other additives in the proportion (mass%) shown in the upper part of Table 3. The hydraulic fluid compositions were evaluated for viscosity index, high shear viscosity and permanent shear stability, and the results are shown in the lower part of Table 3.

Examples 1 to 6 have a higher shear viscosity at 40 ° C. than Comparative Example 1 (not including a polymethacrylate viscosity index improver) and Comparative Example 4 (containing a polymethacrylate viscosity index improver having a low weight average molecular weight). It is low, and more excellent in permanent shear stability than Comparative Examples 2 and 3 (containing a polymethacrylate viscosity index improver having a high weight average molecular weight). Moreover, Examples 1-6 have a higher viscosity index than Comparative Example 1 (not including a polymethacrylate viscosity index improver).
Therefore, all of these Examples can be expected to have a power saving effect due to a decrease in high shear viscosity, and at the same time, can be expected to have excellent permanent shear stability and low temperature startability.

Although the industrial hydraulic fluid composition of the present invention can be applied to various industrial hydraulic fluids, it can be preferably used particularly as a hydraulic fluid used in a hydraulic system. Furthermore, in a hydraulic system, in a hydraulic pump, a hydraulic motor, a control valve, etc., it is particularly effective for achieving power saving at a location where the hydraulic fluid is exposed to a sheared state.

Claims (1)

(A) 40 ° C. kinematic viscosity 4~40mm Ri ² / s der, aniline point is 100 to 130 ° C., 15 ° C. density of 0.80~0.85g / cm ^3, naphthenes (% CN ) is 8-27 der Ru hydrocarbon lubricating base oil, and (B) a weight average molecular weight of a composition containing a polymethacrylate-based viscosity index improver is 84,000～130,000, kinematic viscosity at 40 ° C. of the composition 19~51mm ² / s der is, industrial hydraulic oil composition viscosity index is characterized by 140 to 240 der Rukoto.