JP5498239B2 - Method for forming lubricating film and method for reducing power consumption of pump - Google Patents

Description

  The present invention relates to a method for forming a lubricating film and a method for reducing power consumption of a pump.

  Hydraulic equipment that transmits electric or engine energy as oil pressure is used in many industrial fields such as iron making machines, construction machines, and injection molding machines. In a pump, a control valve, a hydraulic cylinder, or the like constituting a hydraulic circuit of a hydraulic device, there is a sliding portion with metal-metal contact or metal-rubber (resin) contact. Therefore, the hydraulic fluid used for the hydraulic equipment also plays a role as a lubricant for the sliding portion.

  In general, hydraulic fluids include highly refined mineral oils such as hydrorefined mineral oils and hydrocracked mineral oils as synthetic lubricant base oils and synthetic hydrocarbon oils such as poly α-olefins to ensure thermal and oxidation stability. Etc. are used. The friction coefficient of a sliding surface is reduced by blending a friction reducing agent as an additive with these base oils (see, for example, Patent Documents 1 to 4).

Japanese Patent Laid-Open No. 4-68082 JP 2000-303086 A JP 2002-129180 A JP 2002-129181 A

  In recent years, energy conservation has become an extremely important issue as an approach to environmental problems. In order to save energy in the hydraulic equipment, it is effective to reduce the friction of the hydraulic fluid, but the hydraulic fluid containing the friction reducing agent tends to be easily worn.

  Non-zinc such as zinc antiwear agents such as zinc dithiophosphate (ZnDTP), phosphate esters and their amine salts, thiophosphates, β-dithiophosphorylated propionic acid compounds in hydraulic fluids for the purpose of preventing wear Methods for blending system antiwear agents are known. However, the effect of friction reduction and wear prevention due to the combination of the friction reducing agent and the anti-wear agent is that one effect may impair the other effect, and it is not always possible to obtain both effects universally in various systems. I couldn't say.

  The present invention has been made in view of the above circumstances, and it is possible to reduce the power consumption of the pump while sufficiently suppressing the wear of the sliding portion, and to form a lubricating film that enables energy saving in hydraulic equipment and the like. It is an object to provide a method and a method for reducing power consumption of a pump.

  As a result of intensive studies by the present inventors to solve the above problems, sliding of a pump constituting a hydraulic circuit using a lubricating oil containing a specific compound so as to be in a specific concentration range with respect to a specific element. By forming a lubricating film with a specific film thickness on the surface of the part, it is possible to reduce power consumption as input energy to a pump operated at a discharge pressure up to medium to high pressure, and also to suppress wear sufficiently Based on this finding, the present invention has been completed.

The present invention has a sliding part made of steel material, and a pump that is operated at a discharge pressure of 20 MPa or less, from at least one base oil (A) selected from mineral oil, fats and oils, and phosphorylated carboxylic acid. consisting of phosphorus and phosphorus sulfur-containing compounds containing sulfur (B), and phosphorus-containing compounds containing no sulfur phosphate esters or phosphite esters containing hydrocarbon group having 3 to 20 carbon atoms (C) And containing 0.01 to 0.05% by mass of phosphorus based on the total amount of lubricating oil, and containing 0.001 to 0.005 % by mass of sulfur derived from component (B) based on the total amount of lubricating oil The mass ratio of the sulfur content derived from the component (B) relative to the phosphorus content is 0.5 or less, and by supplying a lubricating oil containing 0.005 to 0.1 mass% of a friction modifier , on the surface of the sliding portion, washed with hexane Provides a method of forming a lubricating film, characterized in that the thickness of when Kaze燥 to form a lubricating film of 5 to 35 n m.

  According to the method for forming a lubricating film of the present invention, it is possible to form a lubricating film capable of reducing the power consumption of the pump while sufficiently suppressing the wear of the sliding portion. Thereby, energy saving can be effectively realized in a hydraulic device including a pump operated at a discharge pressure of 20 MPa or less.

  In the lubricating film forming method of the present invention, from the viewpoint of maintaining wear resistance, the mass ratio of the sulfur content derived from the component (B) to the phosphorus content contained in the lubricating oil is 0.5 or less. preferable.

  Further, from the viewpoint of satisfying both low friction and wear resistance at a high level, the lubricating oil preferably contains a friction modifier having at least one carboxyl group in the molecule.

  In the method for forming a lubricating film of the present invention, when the pump is a vane pump, the effect of low friction and excellent wear resistance can be obtained more effectively.

  The present invention is also a method for reducing the power consumption of a pump having a sliding portion made of steel and operated at a discharge pressure of 20 MPa or less, wherein the lubricating film of the present invention is formed on the surface of the sliding portion. Provided is a method for reducing power consumption of a pump, wherein a lubricating film is formed by the method.

  In the method for reducing power consumption of the pump of the present invention, the pump is preferably a vane pump from the viewpoint that the effect of the lubricating oil can be maximized.

  According to the present invention, a method of forming a lubricating film that can reduce power consumption of a pump while sufficiently suppressing wear of a sliding portion, and that can save energy in a hydraulic device, and a method of reducing power consumption of a pump Can be provided.

It is the schematic which shows the structure of a power consumption testing machine hydraulic circuit roughly. It is a figure which shows the operating condition of an electric power consumption tester. (A) is a figure which shows the internal structure of a Vickers 104C type pump, (b) is a figure which shows the measurement site | part of a cam ring.

  The method for forming a lubricating film of the present invention includes a sliding part made of steel, and a pump operated at a discharge pressure of 20 MPa or less, and at least one base oil (A) selected from mineral oil, fats and oils, and synthetic oil. A phosphorus-containing compound (B) containing phosphorus and sulfur and a phosphorus-containing compound (C) containing no sulfur, and containing 0.0001 to 0.05% by mass of the phosphorus content based on the total amount of the lubricating oil By supplying a lubricating oil containing 0.0001 to 0.01% by mass of the sulfur content derived from the component (B) based on the total amount of the lubricating oil, a lubricating film having a thickness of 50 nm or less is formed on the surface of the sliding portion. It is characterized by forming.

  Examples of the pump include a vane pump and a gear pump.

  The discharge pressure of the pump means the pressure applied to the discharge side of the pump.

  Examples of the sliding portion made of steel include a cam ring, a rotor, a vane, a shaft, a bearing, and a pressure spring.

  Next, the lubricating oil used in the present invention will be described.

  As the mineral oil, solvent degreasing, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid and sulfuric acid fractions obtained by atmospheric and vacuum distillation of crude oil Mention may be made of mineral oils such as paraffinic or naphthenic oils obtained by applying a suitable combination of one or more purification means such as washing and clay treatment. Examples of the fats and oils include beef tallow, lard, sunflower oil, soybean oil, rapeseed oil, rice bran oil, coconut oil, palm oil, palm kernel oil, and hydrogenated products thereof.

  Examples of the synthetic oil include poly α-olefins (ethylene-propylene copolymers, polybutenes, 1-octene oligomers, 1-decene oligomers, and hydrides thereof), alkylbenzenes, alkylnaphthalenes, monoesters ( Butyl stearate, octyl laurate), diester (ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sepacate, etc.), polyester (trimellitic acid ester, etc.), polyol Esters (trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate, etc.), polyoxyalkylene Recall, polyphenyl ether, dialkyl diphenyl ether, phosphate ester (tricresyl phosphate, etc.), fluorine-containing compound (perfluoropolyether, fluorinated polyolefin and the like), silicone oils and the like.

  In the lubricating oil used in the present invention, the above-mentioned base oils may be blended alone or in combination of two or more as the base oil.

  The sulfur content contained in the base oil is preferably 0.5% by mass or less, and more preferably 0.1% by mass or less.

Although the kinematic viscosity of the base oil of the lubricating oil is not particularly limited, the kinematic viscosity at 40 ° C. is usually from the viewpoint of excellent friction characteristics, cooling properties (heat removal properties), and low friction loss due to stirring resistance. Preferably it is 5-1,000 mm < ² > / s, More preferably, it is 7-500 mm < ² > / s, More preferably, it is 10-200 mm < ² > / s. The viscosity index of the base oil is not particularly limited, but is preferably 80 to 500, and more preferably 100 to 300, from the viewpoint of suppressing oil film deterioration at high temperatures. Furthermore, although the pour point is also arbitrary, from the viewpoint of pump startability in winter, the pour point is usually preferably −5 ° C. or lower, more preferably −15 ° C. or lower.

  As phosphorus sulfur containing compound (B) containing phosphorus and sulfur, the carboxylic acid compound containing sulfur and phosphorus is mentioned, for example. Such a compound is not particularly limited as long as it contains a carboxyl group, a phosphorus atom and a sulfur atom in the same molecule. However, sulfur-containing phosphorylated carboxylic acids are preferred from the standpoints of wear resistance and sludge suppression, or even frictional properties.

［式（１）中、Ｒ^１及びＲ^２は同一でも異なっていてもよく、それぞれ水素原子又は炭素数１〜３０の炭化水素基を示し、Ｒ^３は炭素数１〜２０のアルキレン基を示し、Ｒ^４は水素原子又は炭素数１〜３０の炭化水素基を示し、Ｘ^１、Ｘ^２、Ｘ^３及びＸ^４は同一でも異なっていてもよく、それぞれ酸素原子又は硫黄原子を示し、少なくとも一つは硫黄原子である。］ Examples of the phosphorylated carboxylic acid include compounds represented by the following general formula (1).

[In Formula (1), R ¹ and R ² may be the same or different, and each represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, and R ³ represents an alkylene group having 1 to 20 carbon atoms. , R ⁴ represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, and X ¹ , X ² , X ³ and X ⁴ may be the same or different and each represents an oxygen atom or a sulfur atom, and at least one One is a sulfur atom. ]

In General Formula (1), R ¹ and R ² each represent a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms. Examples of the hydrocarbon group having 1 to 30 carbon atoms include an alkyl group, an alkenyl group, a cycloalkyl group, a bicycloalkyl group, a tricycloalkyl group, an alkylcycloalkyl group, an alkylbicycloalkyl group, an alkyltricycloalkyl group, and a cycloalkylalkyl. Group, bicycloalkylalkyl group, tricycloalkylalkyl group, aryl group, alkylaryl group, arylalkyl group and the like. R ¹ and R ² may be bonded to form a divalent group represented by the following general formula (2). The two bonds of the divalent group are bonded to X ¹ and X ² , respectively.

［式（２）中、Ｒ^５及びＲ^６は同一でも異なっていてもよく、それぞれ水素原子又は炭素数１〜４のアルキル基を示し、Ｒ^５及びＲ^６の双方がメチル基であることが好ましい。］

[In the formula (2), R ⁵ and R ⁶ may be the same or different, each represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and both R ⁵ and R ⁶ are methyl groups. preferable. ]

R ¹ and R ² are each represented by the above general formula (2) in which an alkyl group, a cycloalkyl group, a cycloalkylalkyl group, a tricycloalkylalkyl group, an aryl group, an alkylaryl group, and R ¹ and R ² are bonded to each other. Such a divalent group is preferable, and an alkyl group is more preferable.

The alkyl group as R ¹ and R ² may be linear or branched. The alkyl group preferably has 1 to 18 carbon atoms. Specific examples of such alkyl groups include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl, isopentyl, hexyl, heptyl, 3-heptyl group, octyl group, 2-ethylhexyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, 2-ethylbutyl group, 1- Methylphenyl group, 1,3-dimethylbutyl group, 1,1,3,3-tetramethylbutyl group, 1-methylhexyl group, isoheptyl group, 1-methylheptyl group, 1,1,3-trimethylhexyl group and Examples include 1-methylundecyl group. Among these, a C3-C18 alkyl group is preferable and a C3-C8 alkyl group is more preferable.

Examples of the cycloalkyl group as R ¹ and R ² include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and a cyclododecyl group. Among these, a cycloalkyl group having 5 or 6 carbon atoms (cyclopentyl group and cyclohexyl group) is preferable, and a cyclohexyl group is particularly preferable.

The cycloalkylalkyl group as R ¹ and R ² is preferably a cycloalkylmethyl group, more preferably a cycloalkylmethyl group having 6 or 7 carbon atoms, and particularly preferably a cyclopentylmethyl group and a cyclohexylmethyl group.

As the bicycloalkylalkyl group as R ¹ and R ² , a bicycloalkylmethyl group is preferable, a bicycloalkylmethyl group having 9 to 11 carbon atoms is more preferable, and a decalinylmethyl group is particularly preferable.

The tricycloalkylalkyl group as R ¹ and R ² is preferably a tricycloalkylmethyl group, more preferably a tricycloalkylmethyl group having 9 to 15 carbon atoms, represented by the following formula (3) or (4). Particularly preferred are the groups

As the aryl group and alkylaryl group as R ¹ and R ² , phenyl group, tolyl group, xylyl group, ethylphenyl group, vinylphenyl group, methylphenyl group, dimethylphenyl group, trimethylphenyl group, ethylphenyl group, isopropyl Examples thereof include a phenyl group, a tert-butylphenyl group, a di-tert-butylphenyl group, and a 2,6-di-tert-butyl-4-methylphenyl group. Among these, an aryl group having 6 to 15 carbon atoms and an alkylaryl group are preferable.

R ³ represents an alkylene group having 1 to 20 carbon atoms. The number of carbon atoms of the alkylene group is preferably 1 to 10, more preferably 2 to 6, and further preferably 3 to 4. Moreover, as such an alkylene group, what is represented by following General formula (5) is preferable.

In the general formula (5), R ⁷ , R ⁸ , R ⁹ and R ¹⁰ may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms, and R ⁷ , R ⁸ , R The total number of carbon atoms of ⁹ and R ¹⁰ is 6 or less. Preferably, R ⁷ , R ⁸ , R ⁹ and R ¹⁰ may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms, and R ⁷ , R ⁸ , R ⁹ and The total number of carbon atoms of R ¹⁰ is 5 or less. More preferably, R ⁷ , R ⁸ , R ⁹ and R ¹⁰ may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 or 2 carbon atoms, and R ⁷ , R ⁸ , R ⁹ and R 10 The total of ¹⁰ carbon atoms is 4 or less. Particularly preferably, R ⁷ , R ⁸ , R ⁹ and R ¹⁰ may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 2 carbon atoms, and R ⁷ , R ⁸ , R ⁹ and R 10 The total of ¹⁰ carbon atoms is 3 or less. Most preferably, either R ⁹ or R ¹⁰ is a methyl group and the remaining three groups are hydrogen atoms.

In general formula (1) ^{R 4} in the show a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms. Examples of the hydrocarbon group include the hydrocarbon groups exemplified in the description of R ¹ and R ² . From the viewpoint of wear resistance, R ⁴ is preferably a hydrogen atom.

X ¹ , X ² , X ³ and X ⁴ in the general formula (1) may be the same or different and each represents an oxygen atom or a sulfur atom, and at least one is a sulfur atom. From the viewpoint of wear resistance, it is more preferable that two or more of X ¹ , X ² , X ³ or X ⁴ are sulfur atoms, two are sulfur atoms and the remaining two are oxygen atoms. Is more preferable. In this case, it is arbitrary which of X ¹ , X ² , X ³ or X ⁴ is a sulfur atom, but X ¹ and X ² are oxygen atoms, and X ³ and X ⁴ are sulfur atoms. It is preferable.

  As mentioned above, although each group in General formula (1) was demonstrated, since it is more excellent in abrasion resistance and a friction characteristic, (beta) -dithio phosphorylated propionic acid represented by following General formula (6) is used preferably. Is done. Furthermore, when the lubricating oil according to the present invention contains a friction modifier (especially an aliphatic carboxylic acid), the competitive adsorption effect by the friction modifier having β-dithiophosphorylated propionic acid and the adsorption effect, An excellent lubricating film can be formed due to wear.

［式（６）中、Ｒ^１、Ｒ^２はそれぞれ式（１）中のＲ^１、Ｒ^２と同一の定義内容を示し、Ｒ^７、Ｒ^８、Ｒ^９、Ｒ^１０はそれぞれ（５）中のＲ^７、Ｒ^８、Ｒ^９、Ｒ^１０と同一の定義内容を示す。］

Wherein ^(6), R 1, ^{R 2} represents a ^R 1, ^{R 2} identical definitions and their respective formulas ^{(1), R 7, R 8, R} 9, R 10 are each (5) The same definition content as R ⁷ , R ⁸ , R ⁹ , and R ¹⁰ is shown. ]

  Further, as the component (B) other than the above-mentioned carboxylic acid compound containing sulfur and phosphorus, an antiwear agent containing a phosphorus atom and a sulfur atom such as zinc dithiophosphate compound and phosphorothionate (hereinafter referred to as “containing”). Sulfur phosphorus-based antiwear agent ”).

［式中、Ｒ^１１、Ｒ^１２、Ｒ^１３及びＲ^１４は同一でも異なっていてもよく、それぞれ炭素数１以上の炭化水素基を表し、Ｘ¹及びＸ²は、それぞれ酸素原子又は硫黄原子を表す。］ Examples of the zinc dithiophosphate compound include compounds represented by the following general formula (7).

[Wherein R ¹¹ , R ¹² , R ¹³ and R ¹⁴ may be the same or different and each represents a hydrocarbon group having 1 or more carbon atoms, and X ¹ and X ² each represents an oxygen atom or a sulfur atom. Represent. ]

Examples of the hydrocarbon group represented by R ^{16 to} R ³¹ include an alkyl group having 1 to 24 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, an alkylcycloalkyl group having 6 to 11 carbon atoms, and 2 carbon atoms. -24 alkenyl group, C6-C18 aryl group, C7-C24 alkylaryl group, and C7-C12 arylalkyl group can be mentioned.

  Specific examples of the phosphorothioate include tributyl phosphorothioate, tripentyl phosphorothioate, trihexyl phosphorothionate, triheptyl phosphorothionate, trioctyl phosphorothionate, trinonyl phosphorothioate. Thionate, tridecyl phosphorothioate, triundecyl phosphorothionate, tridodecyl phosphorothionate, tritridecyl phosphorothionate, tritetradecyl phosphorothionate, tripentadecyl phosphorothionate, trihexa Decyl phosphorothioate, triheptadecyl phosphorothionate, trioctadecyl phosphorothioate, trioleyl phosphorothionate, triphenyl phosphorothionate, tricresyl phosphorothione , Trixylenyl phosphorothioate, cresyl diphenyl phosphorothioate, xylenyl diphenyl phosphorothioate, tris (n-propylphenyl) phosphorothioate, tris (isopropylphenyl) phosphorothionate, tris (N-butylphenyl) phosphorothionate, tris (isobutylphenyl) phosphorothionate, tris (s-butylphenyl) phosphorothionate, tris (t-butylphenyl) phosphorothionate, and the like. Mixtures of these can also be used.

  When the above sulfur-containing phosphorus antiwear agent is used in place of the phosphorus antiwear agent described later, lubrication is caused by a decrease in sludge suppression, an increase in friction coefficient, and a poor compatibility with materials other than steel. Defects are likely to occur.

  In addition, when a sulfur-containing phosphorus-based antiwear agent is used in the presence of a carboxylic acid compound containing sulfur and phosphorus and a phosphorus-based antiwear agent described later, the sludge suppression may be deteriorated. The content of the system wear inhibitor is preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.1% by mass or less, based on the total amount of the lubricating oil. Most preferably, no sulfur-containing phosphorus-based antiwear agent is contained.

  The blending amount of the component (B) in the lubricating oil according to the present invention is set so that the sulfur content derived from the component (B) is 0.0001 to 0.01% by mass based on the total amount of the lubricating oil, preferably 0. .0005 to 0.01% by mass, more preferably 0.001 to 0.005% by mass. These concentrations mean the elemental concentration of sulfur in the component (B) in the lubricating oil, and are calculated from the number of sulfur atoms in the compound that is the component (B), the molecular weight of the compound, and the concentration of the compound in the lubricating oil. can do. When the blending amount of the component (B) is less than the above lower limit value, the wear resistance tends to be insufficient. On the other hand, if it exceeds the upper limit value, the effect of reducing the power consumption of the pump cannot be obtained sufficiently, and energy saving tends to be difficult. This is presumably because when the sulfur content derived from the component (B) is large, a metal sulfide such as FeS is likely to be formed in the formed lubricating film, and the friction reduction is insufficient.

Of the phosphorylated carboxylic acid represented by the general formula (1), a compound in which R ⁴ is a hydrogen atom (including β-dithiophosphorylated propionic acid represented by the general formula (6)) is blended The content thereof is preferably 0.0005 to 0.05 mass%, more preferably 0.0025 to 0.05 mass%, still more preferably 0.0025 to 0.025 mass%, based on the total amount of the lubricating oil. is there. When the content is less than 0.0005% by mass, the wear resistance tends to be insufficient. On the other hand, when the content exceeds 0.05% by mass, the effect of reducing the power consumption of the pump cannot be sufficiently obtained, thereby saving energy. Tend to be difficult.

  Examples of the phosphorus-containing compound (C) that does not contain sulfur include phosphorus-based antiwear agents. Specifically, phosphoric acid esters such as phosphoric acid monoesters, phosphoric acid diesters, and phosphoric acid triesters; phosphorous acid Examples thereof include phosphites such as monoesters, phosphite diesters and phosphite triesters; salts of these phosphate esters and phosphites; and mixtures thereof. The above-described phosphate esters and phosphites are compounds containing a hydrocarbon group usually having 2 to 30 carbon atoms, preferably 3 to 20 carbon atoms.

  Specific examples of the hydrocarbon group having 2 to 30 carbon atoms include ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl. Group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, etc. (these alkyl groups may be linear or branched); butenyl group, pentenyl group, hexenyl group, heptenyl group Alkenyl groups such as octenyl group, nonenyl group, decenyl group, undecenyl group, dodecenyl group, tridecenyl group, tetradecenyl group, pentadecenyl group, hexadecenyl group, heptadecenyl group, octadecenyl group (these alkenyl groups may be linear or branched) Good, and the position of the double bond is arbitrary); C5-C7 cycloalkyl group such as pentyl group, cyclohexyl group, cycloheptyl group; methylcyclopentyl group, dimethylcyclopentyl group, methylethylcyclopentyl group, diethylcyclopentyl group, methylcyclohexyl group, dimethylcyclohexyl group, methylethylcyclohexyl group Alkylcycloalkyl groups having 6 to 11 carbon atoms such as diethylcyclohexyl group, methylcycloheptyl group, dimethylcycloheptyl group, methylethylcycloheptyl group, and diethylcycloheptyl group (the substitution position of the alkyl group to the cycloalkyl group is also arbitrary) Aryl groups such as phenyl group and naphthyl group: tolyl group, xylyl group, ethylphenyl group, propylphenyl group, butylphenyl group, pentylphenyl group, hexylphenyl group, heptyl Each alkylaryl group having 7 to 18 carbon atoms such as an phenyl group, an octylphenyl group, a nonylphenyl group, a decylphenyl group, an undecylphenyl group, a dodecylphenyl group (the alkyl group may be linear or branched, The substitution position on the aryl group is also arbitrary); each arylalkyl group having 7 to 12 carbon atoms such as benzyl group, phenylethyl group, phenylpropyl group, phenylbutyl group, phenylpentyl group, phenylhexyl group (these alkyl groups) May be linear or branched).

  Specific examples of preferable compounds as phosphorus-based antiwear agents include monoalkyl phosphates (alkyl) such as monopropyl phosphate, monobutyl phosphate, monopentyl phosphate, monohexyl phosphate, monopeptyl phosphate, monooctyl phosphate, and the like. The group may be linear or branched); mono (alkyl) aryl phosphates such as monophenyl phosphate, monocresyl phosphate; dipropyl phosphate, dibutyl phosphate, dipentyl phosphate, dihexyl phosphate, dipeptyl phosphate, Dialkyl phosphates such as dioctyl phosphate (the alkyl group may be linear or branched); di (alkyl) phosphates such as diphenyl phosphate and dicresyl phosphate Phosphoric acid trialkyl esters such as tripropyl phosphate, tributyl phosphate, tripentyl phosphate, trihexyl phosphate, tripeptyl phosphate, trioctyl phosphate (the alkyl group may be linear or branched); triphenyl phosphate Tri (alkyl) aryl esters of phosphate such as tricresyl phosphate; phosphorous such as monopropyl phosphite, monobutyl phosphite, monopentyl phosphite, monohexyl phosphite, monopeptyl phosphite, monooctyl phosphite Acid monoalkyl ester (the alkyl group may be linear or branched); mono (alkyl) aryl phosphite such as monophenyl phosphite, monocresyl phosphite; Dialkyl phosphites such as phyto, dibutyl phosphite, dipentyl phosphite, dihexyl phosphite, dipeptyl phosphite, dioctyl phosphite (the alkyl group may be linear or branched); diphenyl phosphite, dicrete Phosphorous acid di (alkyl) aryl esters such as phosphite; tripropyl phosphite, tributyl phosphite, tripentyl phosphite, trihexyl phosphite, tripeptyl phosphite, trioctyl phosphite Alkyl esters (the alkyl group may be linear or branched); tri (alkyl) aryl phosphites such as triphenyl phosphite and tricresyl phosphite; and mixtures thereof.

  Specific examples of the salts of the phosphoric acid esters and phosphite esters described above include phosphoric acid monoesters, phosphoric acid diesters, phosphorous acid monoesters, phosphorous acid diester esters, ammonia, carbon Examples include salts obtained by allowing a nitrogen-containing compound such as an amine compound containing only a hydrocarbon group of 1 to 8 or a hydroxyl group-containing hydrocarbon group in the molecule to act to neutralize part or all of the remaining acidic hydrogen. It is done.

  Specific examples of the nitrogen-containing compound include ammonia; monomethylamine, monoethylamine, monopropylamine, monobutylamine, monopentylamine, monohexylamine, monoheptylamine, monooctylamine, dimethylamine, methylethylamine, Alkylamines such as diethylamine, methylpropylamine, ethylpropylamine, dipropylamine, methylbutylamine, ethylbutylamine, propylbutylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, etc. May be branched); monomethanolamine, monoethanolamine, monopropanolamine, monobutanolamine, monopentanolamine, monohexanolamine , Monoheptanolamine, monooctanolamine, monononanolamine, dimethanolamine, methanolethanolamine, diethanolamine, methanolpropanolamine, ethanolpropanolamine, dipropanolamine, methanolbutanolamine, ethanolbutanolamine, propanolbutanolamine, dibutanol And alkanolamines such as amines, dipentanolamines, dihexanolamines, diheptanolamines, dioctanolamines (the alkanol groups may be linear or branched); and mixtures thereof.

  In addition, as the phosphorus-based antiwear agent, one of the above-described compounds may be used alone, and furthermore, a mixture of two or more compounds selected from the above in an arbitrary mixing ratio is used. May be.

  Among phosphorous antiwear agents, among phosphoric acid esters and phosphorous acid esters, phosphoric acid esters are preferable and phosphoric acid triesters are more preferable because of excellent thermal stability. The hydrocarbon group of the phosphate ester is preferably a phenyl group or an alkylphenyl group, more preferably a phenyl group or an alkylphenyl group having 1 to 10 carbon atoms, and a phenyl group or 1 to 5 carbon atoms. An alkylphenyl group having an alkyl group is more preferable, and a phenyl group or an alkylphenyl group having an alkyl group having 1 to 3 carbon atoms is particularly preferable.

  The lubricating oil according to the present invention contains 0.0001 to 0.05% by mass of the phosphorus content based on the total amount of the lubricating oil. It is preferable to contain 001-0.05 mass%, and it is still more preferable to contain 0.01-0.05 mass%. Accordingly, the content of the phosphorus-based antiwear agent described above is appropriately set according to the amount of the component (B) and the amount of other phosphorus-containing compound added as necessary. The content of the phosphorus-based antiwear agent is preferably 0.02 to 1.0 mass%, more preferably 0.05 to 0.5 mass%, based on the total amount of the lubricating oil. Even if the content exceeds 1.0% by mass, the effect of further improving the wear resistance just commensurate with the content cannot be obtained, and the oxidation stability tends to decrease. On the other hand, when the content is less than 0.02% by mass, the wear resistance due to the addition tends to be insufficient. The phosphorus content concentration means the elemental concentration of phosphorus in the lubricating oil, and can be calculated from the number of phosphorus atoms that each compound containing phosphorus has, the molecular weight of the compound, and the concentration of the compound in the lubricating oil. it can.

  In the lubricating oil according to the present invention, the mass ratio of the sulfur content derived from the component (B) to the total phosphorus content contained in the lubricating oil is 0.5 in terms of achieving both excellent energy saving characteristics and wear resistance. It is preferable to mix each additive so that it may become below, It is more preferable to mix | blend so that it may be 0.2 or less, It is still more preferable to mix | blend so that it may be 0.1 or less.

  The lubricating oil according to the present invention preferably contains a friction modifier, and more preferably contains an aliphatic carboxylic acid having at least one carboxyl group in the molecule as a friction modifier. As such a friction modifier, one kind selected from the group consisting of esters having 1 to 40 carbon atoms, amines, amides, alcohols, ethers, carboxylic acids, ketones, aldehydes and carbonates. Or 2 or more types of friction modifiers are preferable. Among them, one or two selected from the group consisting of fatty acid esters having 3 to 30 carbon atoms, more preferably 3 to 20 carbon atoms, aliphatic amines, fatty acid amides, aliphatic alcohols and aliphatic carboxylic acids. More preferably, it is a friction modifier of at least one species, and is an aliphatic carboxylic acid having 3 to 20 carbon atoms.

  Examples of the fatty acid esters include esters composed of fatty acids having 6 to 30 carbon atoms and aliphatic monohydric alcohols or aliphatic polyhydric alcohols. Specific preferred examples include glycerol monooleate, glycerol diolate, glycerol trioleate, sorbitan monooleate or sorbitan diolate.

  Examples of the aliphatic amines include aliphatic monoamines or alkylene oxide adducts thereof, aliphatic polyamines, imidazoline compounds, and derivatives thereof. Specifically, laurylamine, lauryldiethylamine, lauryldiethanolamine, dodecyldipropanolamine, palmitylamine, stearylamine, stearyltetraethylenepentamine, oleylamine, oleylpropylenediamine, oleyldiethanolamine, or N-hydroxyethyloleylimidazoline, etc. Aliphatic amine compounds, amine alkylene oxide adducts of these aliphatic amine compounds such as N, N-dipolyoxyalkylene-N-alkyl or alkenyl (6 to 28 carbon atoms), these aliphatic amine compounds having 2 carbon atoms -30 monocarboxylic acid (fatty acid, etc.), C2-C30 polycarboxylic acid such as oxalic acid, phthalic acid, trimellitic acid, pyromellitic acid and the like, and the remaining amino group and / or imino group Part of Or the so-called acid-modified compound etc. which neutralized all or amidated are mentioned. Preferable examples include N, N-dipolyoxyethylene-N-oleylamine.

  Examples of the fatty acid amides include amide compounds of fatty acids having 6 to 30 carbon atoms and ammonia or aliphatic amines. Specific examples include oleic acid amide and stearic acid amide.

  Examples of the aliphatic alcohols include monovalent or polyvalent aliphatic alcohols having 3 to 30 carbon atoms. Specifically, oleyl alcohol, ethylene glycol, propylene glycol, alkanediols such as 1,3-propanediol and 1,10-decanediol, glycerin, sorbitan, trimethylolalkanes such as trimethylolethane and trimethylolpropane. Erythritol, pentaerythritol and the like.

  Examples of the aliphatic ethers include glycerol monoalkyl ethers such as diethyl ether, didodecyl ether and glycerol monostearyl ether.

  Examples of the aliphatic carboxylic acid include oleic acid, stearic acid, and the like, which can suppress the thickening of the lubricating film and facilitate the reduction of the lubricating film thickness to 50 nm or less. An acid can be illustrated more preferably. For this reason, the present inventors have suppressed the excessive generation of sulfide (for example, FeS) due to the reaction between the phosphorus-sulfur-containing compound containing phosphorus and sulfur and the steel surface by oleic acid. I believe that.

  Each friction modifier specifically listed above can be used alone or as a mixture of two or more in use.

  The content of the friction modifier in the lubricating oil according to the present invention is preferably 0.001 to 0.5 mass%, more preferably 0.005 to 0.1 mass%, based on the total amount of the lubricating oil.

  The lubricating oil according to the present invention may further contain a sulfur-based antiwear agent. Examples of the sulfur-based antiwear agent include dihydrocarbyl polysulfide, sulfide ester, sulfide mineral oil, zinc dithiocarbamate compound, molybdenum dithiophosphate, and molybdenum dithiocarbamate.

  However, the use of sulfur-based antiwear agents causes poor lubrication due to reduced sludge suppression, increased friction coefficient, and poor compatibility with materials other than steel. The total sulfur content in the lubricating oil is preferably set within a range of 0.1% by mass or less. The addition amount of the sulfur-based antiwear agent is preferably 0.5% by mass or less, more preferably 0.1% by mass or less, and 0.05% by mass or less, based on the total amount of the lubricating oil. Is even more preferred and most preferably not added.

  Further, in the lubricating oil according to the present invention, for the purpose of further improving its performance, an antioxidant, a viscosity index improver, a cleaning dispersant, a rust inhibitor, a metal deactivator, a pour point, if necessary. Various additives typified by a depressant and an antifoaming agent may be further contained alone or in combination of several kinds.

  The lubricating oil according to the present invention may contain bis (4-dialkylaminophenyl) methane represented by the general formula (8) which is an amine-based antioxidant.

In the general formula (8), R ¹ , R ² , R ³ and R ⁴ may be the same or different and each represents a linear or branched alkyl group having 1 to 6 carbon atoms. When the number of carbon atoms in any one of R ¹ , R ² , R ³ and R ⁴ exceeds 6, the proportion of the functional group in the molecule is reduced, which may adversely affect the antioxidant effect. . Specific examples of the alkyl group represented by R ¹ , R ² , R ³ and R ⁴ include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group and the like (these alkyl groups are Linear or branched).

Among the amine-based antioxidants represented by the general formula (8), R ¹ , R ² , R ^3, and R ⁴ are each a methyl group, an ethyl group, or a carbon number because an excellent antioxidant effect can be obtained. 3-4 branched alkyl groups are preferred, with methyl or ethyl groups being most preferred.

  The lubricating oil according to the present invention can add higher antioxidant properties and sludge suppressive properties by using a phenolic antioxidant together. As the phenolic antioxidant, any alkylphenolic compound used as an antioxidant for lubricating oil can be used, and is not particularly limited. For example, hindered phenols such as alkylphenols and bisphenols The type is preferred, and those containing a sulfide group and an ester bond in the molecule are also preferably used.

  The content of the phenolic antioxidant in the lubricating oil according to the present invention is preferably 5% by mass or less, more preferably 2% by mass, and even more preferably 1.5% by mass based on the total amount of the lubricating oil. . When the content exceeds 5% by mass, sludge is generated, which is not preferable. On the other hand, the content of the phenolic antioxidant is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and further preferably 0.1% by mass or more, based on the total amount of the composition. is there. When the content of the phenolic antioxidant is less than 0.01% by mass, a sufficient improvement in the antioxidant effect cannot be expected.

  For the purpose of further improving the performance of the lubricating oil according to the present invention, if necessary, an antioxidant other than those described above, a rust inhibitor, a metal deactivator other than those described above, and an antiwear agent other than those described above. In addition, various additives represented by viscosity index improvers, pour point depressants, antifoaming agents, demulsifiers, stick-slip inhibitors, oiliness agents and the like may be contained alone or in combination.

  In addition to the amine-based antioxidant, other amine-based antioxidants may be used in combination. Other representative amine antioxidants include phenyl-α-naphthylamines represented by the following formula (9) or p, p′-dialkylated diphenylamine represented by the formula (10).

［一般式（９）において、Ｒ¹¹は水素原子又は炭素数１〜１６のアルキル基を示す。］

[In General formula (9), R < ¹¹ > shows a hydrogen atom or a C1-C16 alkyl group. ]

［一般式（１０）において、Ｒ¹²及びＲ¹³は、それぞれ個別に、炭素数１〜１６の直鎖状若しくは分枝状のアルキル基を示す。］

[In General Formula (10), R ¹² and R ¹³ each independently represent a linear or branched alkyl group having 1 to 16 carbon atoms. ]

  As for the compounding quantity of said amine antioxidant, 0.001-2.0 mass% is desirable on the basis of the composition whole quantity.

  Specific examples of rust inhibitors include amino acid derivatives, partial esters of polyhydric alcohols; esters such as lanolin fatty acid esters, alkyl succinic acid esters, and alkenyl succinic acid esters; sarcosine; polyhydric alcohol moieties such as sorbitan fatty acid esters. Esters; metal soaps such as fatty acid metal salts, lanolin fatty acid metal salts, and oxidized wax metal salts; sulfonates such as calcium sulfonate and barium sulfonate; oxidized wax; amines; phosphoric acid; It can be illustrated. Of these, amino acid derivatives are preferred because of their high rust prevention effect.

  As said amino acid derivative, the compound shown by following General formula (11) is mentioned.

In the above formula (11), A is a group represented by the following formula (12) or formula (13), and B is a C 1-12 alkyl group or a monovalent carboxylic acid represented by the following formula (14). It is a residue of an acid ester, R ¹⁴ is an alkyl group having 4 to 12 carbon atoms, and R ¹⁵ is an alkyl group having 1 to 10 carbon atoms.
^{R 17 O-CO-R 16} - (12)
R ¹⁹ O—CO—R ¹⁸ —CO— (13)
—C—CO—O—R ²⁰ (14)
(In the formulas (12) and (13), R ¹⁶ is an alkylene group having 1 to 12 carbon atoms, R ¹⁸ is an alkylene group having 1 to 10 carbon atoms, and R ¹⁷ and R ¹⁹ are each a hydrogen atom or a carbon number. (There is an alkyl group having 1 to 10. In formula (14), R ²⁰ is an alkyl group having 1 to 10 carbon atoms.)

  The lubricating oil according to the present invention can contain one or two or more compounds arbitrarily selected from these rust inhibitors, and the content thereof is usually lubricating oil. It is desirable that it is 0.001-2.0 mass% on the basis of the total amount.

  Specific examples of the metal deactivator include imidazole compounds. In the present invention, one or two or more compounds arbitrarily selected from these metal deactivators can be contained in any amount, but usually the content is the total amount of the lubricating oil. It is desirable that it is 0.0001-1 mass% on the basis.

  Examples of the cleaning dispersant include alkenyl succinimide, sulfonate, salicylate, phenate and the like. In the present invention, one or two or more compounds arbitrarily selected from these viscosity index improvers can be contained in any amount, but the content is usually the total amount of the lubricating oil. It is desirable that the content is 0.01 to 10% by mass.

  Specific examples of the viscosity index improver include a copolymer of one or more monomers selected from various methacrylates or a hydrogenated product thereof, an ethylene-α-olefin copolymer (as α-olefin). Can be exemplified by propylene, 1-butene, 1-pentene, etc.) or a hydride thereof, polyisobutylene or a hydrogenated product thereof, a hydride of a styrene-diene copolymer, and a so-called non-dispersed viscosity. An index improver etc. can be illustrated. In the lubricating oil according to the present invention, one or two or more compounds arbitrarily selected from these viscosity index improvers can be contained in any amount, but usually the content is It is desirable that it is 0.01-10 mass% on the basis of the total amount of lubricating oil.

  Specific examples of the pour point depressant include copolymers of one or more monomers selected from various acrylic esters and methacrylic esters or hydrogenated products thereof. In the lubricating oil according to the present invention, one or two or more compounds arbitrarily selected from these pour point depressants can be contained in an arbitrary amount. It is desirable that it is 0.01-5 mass% on the basis of the total amount of lubricating oil.

  In addition, specific examples of antifoaming agents include silicones such as dimethyl silicone and fluorosilicone. The lubricating oil according to the present invention may contain one or two or more compounds arbitrarily selected from these antifoaming agents in any amount, but usually the content is lubricating. It is desirable that it is 0.001-0.05 mass% on the basis of the total amount of oil.

  Examples of the demulsifier include polyoxyalkylene glycol, polyoxyalkylene alkyl ether, polyoxyalkylene alkylamide, polyoxyalkylene fatty acid ester and the like.

  Specific examples of the stick-slip preventing agent include polyhydric alcohol esters (complete esters and partial esters).

  Specific examples of the oily agent include fatty acids, esters, alcohols and the like. Usually, the content is desirably 0.01 to 0.5% by mass based on the total amount of the lubricating oil.

The kinematic viscosity of the lubricating oil according to the present invention is not particularly limited, but the kinematic viscosity at 40 ° C. is preferably from the viewpoint of excellent friction characteristics, cooling properties (heat removal properties), and low friction loss due to stirring resistance. It is 5-1,000 mm < ² > / s, More preferably, it is 7-500 mm < ² > / s, More preferably, it is 10-200 mm < ² > / s. Moreover, the viscosity index of the lubricating oil according to the present invention is not particularly limited, but is preferably 80 to 500, more preferably 100 to 300, from the viewpoint of suppressing oil film decrease at high temperature. Furthermore, although the pour point is also arbitrary, from the viewpoint of pump startability in winter, the pour point is usually preferably −5 ° C. or lower, more preferably −15 ° C. or lower.

  In the present invention, by using the above-described lubricating oil, a lubricating film having a thickness of 50 nm or less is formed on the surface of the sliding portion of the pump. The thickness of the lubricating film is closely related to energy saving performance, preferably 1 to 50 nm, more preferably 3 to 50 nm, and even more preferably 5 to 30 nm. Conventionally, for the purpose of lubrication in the sliding portion, it has been considered that a thicker oil film is better. Therefore, in a pump operated at a discharge pressure of 20 MPa or less, it is an unexpected effect for those skilled in the art that the power consumption of the pump is reduced by forming a thin lubricating film of 50 nm or less from the above-described lubricating oil. It can be said.

  Confirmation of the formed lubricating film and measurement of the film thickness are performed, for example, by cutting a sample from the sliding portion of the pump. And the thickness of a lubricating film can be measured by observing the cut-out sample with a transmission electron microscope (TEM). In addition, about a sample, it can wash | clean with nonpolar solvents, such as a heptane or hexane, and can dry an excess oil by air-drying (drying), and can evaluate a lubricating film.

  The thickness of the sample used for TEM observation is important. If the thickness is too thick, the electron beam cannot be transmitted and the lubricating film cannot be observed. For this reason, the thickness of the TEM observation sample is preferably 200 nm or less, more preferably 150 nm or less, still more preferably 120 nm or less, and particularly preferably 80 nm or less. The thickness of the TEM observation sample is preferably 30 nm or more. When the thickness is less than 30 nm, the sample tends to be easily broken and difficult to handle, or a damage layer due to ion collision described later tends to remain. When the thickness of the sample satisfies the above conditions, the lubricating film can be easily and reliably observed in the observation field.

  The sample having the thickness is preferably manufactured by a method of physically or mechanically cutting and polishing a steel material on which a lubricating film is formed. Examples of this method include an ultrathin section method, a sputtering / thinning method, and a focused ion beam method. Since the lubricating film according to the present invention is very thin and fragile, the focused ion beam method (FIB) (FIB) is used from the viewpoint that a sample for TEM observation having the above thickness can be produced in a state in which the structure is more reliably maintained. Is particularly preferred. By applying a focused ion beam (FIB) / transmission electron microscope (TEM), information on the thickness of the lubricating film can be obtained as information on the lubricating film.

An example of a method for preparing a sample for TEM observation by FIB will be described below. Typical conditions for FIB irradiation are as follows.
Ion source: Ga
Acceleration voltage: rough machining 40kV, finishing machining 10kV
Deposit: Carbon, tungsten

  When a sample for TEM observation is collected from the specimen on which the lubricating film is formed by FIB, deposit (tungsten) as a protective film is previously formed on the lubricating film surface by vapor deposition when irradiating the surface of the lubricating film with FIB. The deposit is formed by first depositing carbon on the lubricating film surface and then depositing tungsten on the carbon surface.

  Next, while observing with a scanning ion microscope, sputtering is performed by irradiating focused Ga ions to the peripheral portion (the portion where the lubricating film surface is exposed) of the region where the lubricating film surface deposit is formed. In such sputtering, first, a raised portion is formed on the surface of the lubricating film, and then the raised portion is separated from the lubricating film by irradiating the bottom of the raised portion with Ga ions and collected as a sample. A series of these operations is called “rough machining”. In the case of rough machining, Ga ions are high energy, so that a damage layer is formed by collision of Ga ions in the portion irradiated with the beam. The damaged layer is formed with a thickness of about 20 nm on the surface layer portion of the side surface of the collected raised portion, and can be removed by finishing processing described later. It is desirable to consider the thickness of the damaged layer when selecting the dimensions (particularly the thickness) of the TEM observation sample. The collected sample may be subjected to a finishing process described later as it is, but the collected sample may be further subjected to roughing.

  Next, with respect to the sample after rough processing, the acceleration voltage is made as low as possible (preferably the lowest voltage), and sputtering by Ga ion irradiation is performed over time (finishing processing). Thereby, it is possible to further reduce the thickness of the sample while suppressing the formation of a further damaged layer, and it is possible to obtain a sample suitable for TEM observation. Note that the damaged layer formed during the roughing process is removed during the finishing process.

The sample thus obtained is subjected to TEM observation and the thickness of the lubricating film is measured. Typical measurement conditions for TEM observation are as follows.
Electron gun: LaB6
Accelerating voltage: 200kV
Magnification ratio: 10,000 to 500,000 times

  The identification of the lubricating film can be determined from the difference in the contrast of the TEM observation image. In a TEM observation image, a heavier element becomes darker (black), and a lighter element becomes brighter (white). Therefore, steel materials composed of heavy elements (such as iron) become darker (black), and vapor deposition carbon, which is a lighter element (carbon), becomes brighter (whiter), so elements with intermediate weights (oxygen, phosphorus, sulfur) Etc.) has an intermediate brightness (gray). In the present embodiment, for example, the thickness of the lubricating film can be obtained from the distance between the steel material and the deposited carbon. Further, for example, by measuring the type and composition of elements constituting the lubricating film using an energy dispersive X-ray spectrometer (EDS or EDX) equipped in a transmission electron microscope (TEM), the lubricating film Can also be specified.

  Specifically, EDS analysis is continuously performed in a region where the thickness of the lubricating film is measured by TEM observation. The lubricant film can be identified by TEM observation, but can be determined by EDS analysis. That is, comparing the lubricating film with the other parts, the lubricating film contains a large amount of phosphorus and sulfur as constituent elements, and the concentration of these two elements is measured to determine whether the lubricating film is a lubricating film. be able to. As a result of the EDS analysis, it can be determined as a lubricating film if phosphorus and sulfur are contained in an amount of 0.1 mol% or more.

  In the present invention, by supplying the lubricating oil according to the present invention described above to a pump having a sliding portion made of steel and operated at a discharge pressure of 20 MPa or less, the thickness of the surface of the sliding portion is 50 nm or less. Thus, it becomes possible to reduce the power consumption of the pump while sufficiently suppressing the wear of the sliding portion. Therefore, according to the present invention, in a hydraulic device including a pump that is operated at a discharge pressure of 20 MPa or less (preferably in a range of 1 to 20 MPa), the lubricating oil according to the present invention is converted into hydraulic oil, turbine oil, compressor oil, By supplying as gear oil, sliding guide surface oil, bearing oil, etc., energy saving of hydraulic equipment can be effectively realized.

  Examples of the hydraulic equipment include an injection molding machine, a machine tool, a construction machine, an iron making facility, an industrial robot, and a hydraulic elevator.

( Reference Example 1)
[Preparation of blended oil (lubricant)]
A base oil consisting of 100% by mass of a poly α-olefin corresponding to VG32, tricresyl phosphate and dithiophosphorylated propionic acid are each 0.500% by mass and 0.010% by mass based on the total amount of the blended oil. Blended at a ratio to obtain a blended oil (lubricating oil). In addition, the sulfur (content derived from phosphorus sulfur-containing compound), phosphorus, calcium and zinc content (mass%) in the blended oil, and the mass ratio of the sulfur content (phosphorus sulfur-containing compound derived content) to the phosphorus content, respectively. Table 1 shows.

[Evaluation of energy-saving performance]
Evaluation of the energy saving performance by the lubricating film was performed using a power consumption tester having a hydraulic circuit configuration shown in FIG. The hydraulic circuit in FIG. 1 includes a Vickers 104C type pump used in ASTM D-2882-00, and a 50 m stainless steel pipe is added to the circuit. Further, the power consumption tester is provided with a control panel for controlling the inlet flow rate and inlet temperature of the Vickers 104C type pump to be kept constant.

After filling the blended oil prepared above into a predetermined oil tank, flushing operation was performed twice with one cycle of operation for 1 hour under the conditions of a flow rate of 20 L / min and a temperature of 40 ° C. Then, the Vickers 104C type pump Replace the vane and cam ring with new ones, and refill with the blended oil. “Flow rate 20 L / min, temperature 50 ° C., pump pressure 5.5 MPa” and “flow rate 25 L / min, temperature 50 ° C., pump pressure 7.2 MPa” The test machine was operated under the conditions, and the power consumption at this time was measured. The power consumption is an integrated value of power per hour at a temperature of 50 ° C. with an integrating wattmeter. The result is shown by the difference from the value based on the power consumption in Reference Example 1. When this difference is a positive value, it means that the power consumption is smaller than that of Reference Example 1 and the energy saving performance is high. When the difference is a negative value, the power consumption is larger than that of Reference Example 1 and the energy saving performance is low. Means that.

[Evaluation of wear resistance]
The above power consumption tester was operated under the operating conditions shown in FIG. The appearance of the vanes and cam rings before and after the operation was observed to check for wear and evaluated based on the following criteria. FIG. 3A shows the internal structure of the Vickers 104C type pump. In FIG. 3A, reference numeral 20 denotes a drive shaft, 22 denotes a bushing, 24 denotes a rotor, 26 denotes a vane, and 28 denotes a cam ring.
Good: Wear state is better than the standard ( Reference Example 1).
Damaged: There are scratches due to wear compared to the standard ( Reference Example 1).

[Lubrication film thickness measurement]
As shown in FIG. 3B, the sample S was cut out from the cam ring (equivalent to JIS-SUJ-2), and a sample including a lubricating film formed on the inner peripheral surface S1 of the cam ring was produced. The cam ring was washed with hexane and air-dried. From this sample, a specimen having a thickness of 100 nm was cut out according to the procedure for collecting a sample for TEM observation by the FIB described above. The FIB irradiation conditions are as follows.
Ion source: Ga
Acceleration voltage: 40 kV during rough machining, 10 kV during finishing
Deposit: Carbon and tungsten

About the specimen obtained above, the thickness of the lubricating film was measured under the following conditions using a transmission electron microscope (TEM). The thickness of the lubricating film was 20 nm.
Electron gun: LaB6
Accelerating voltage: 200kV
Shooting magnification: 200,000 times

(Examples 2-9)
Each additive was blended with the base oils shown in Tables 1 and 2 in proportions (mass%) shown in Tables 1 and 2 to obtain blended oils, respectively.

Except for using the above-mentioned blended oil, in the same manner as in Reference Example 1, energy-saving performance evaluation, wear resistance evaluation, and lubricating film thickness measurement were performed. The results are shown in Tables 1 and 2.

(Comparative Examples 1-6)
Each additive was blended with the base oil shown in Table 3 in the proportion (mass%) shown in Table 3 to obtain blended oils.

Except for using the above-mentioned blended oil, in the same manner as in Reference Example 1, energy-saving performance evaluation, wear resistance evaluation, and lubricating film thickness measurement were performed. The results are shown in Table 3. In Comparative Examples 1 and 2, it was impossible to evaluate the energy saving performance and to measure the film thickness of the lubricating film because the power consumption characteristics fluctuated greatly, which was presumed to be caused by damage on the surface of the cam ring.

Details of the base oils and additives shown in Tables 1 and 2 are as follows.
PAO: poly-α-olefin (40 ° C. kinematic viscosity: 30.6 mm ² / s, viscosity index: 124, aromatic content: 0.0 mass%).
Highly refined base oil: hydrorefined base oil obtained by hydrorefining a lubricating oil fraction obtained by subjecting crude oil to atmospheric distillation and vacuum distillation (40 ° C. kinematic viscosity: 31.6 mm ² / s, viscosity index 127, aromatic content: 0.0% by mass, sulfur content: 0.03% by mass).
Solvent refined base oil: Solvent refined base oil (40 ° C. kinematic viscosity: 30.8 mm ² / s, viscosity index: 103) obtained by solvent removal of a lubricating oil fraction obtained by atmospheric distillation and vacuum distillation of crude oil , Sulfur content: 0.28% by mass).
TCP: tricresyl phosphate (phosphorus content: 8.4% by mass).
AP: n-C8 acidic phosphate ester (phosphorus content: 11.6% by mass).
Irgalube 349: manufactured by Ciba Specialty Chemicals, amine C11-14 side chain alkyl, monohexyl and dihexyl phosphate mixture (phosphorus content 4.9% by mass, nitrogen content 2.7% by mass).
ADTP: dithiophosphorylated propionic acid (sulfur content 19.8 mass%, phosphorus content 9.3 mass%).
ADTP-2: Dithiophosphate (sulfur content 20.7 mass%, phosphorus content 9.7 mass%).
ZnDTP: zinc dialkyldithiophosphate (zinc content 3.0% by mass, sulfur content 5.75% by mass, phosphorus content 2.85% by mass).
Oleic acid: oleic acid.

20 ... Drive shaft, 22 ... Bushing, 24 ... Rotor, 26 ... Vane, 28 ... Cam ring.

Claims (6)

For a pump having a sliding part made of steel and operated at a discharge pressure of 20 MPa or less,
At least one base oil (A) selected from mineral oils, fats and oils, phosphorus- containing compounds (B) containing phosphorus and sulfur consisting of phosphorylated carboxylic acids, and hydrocarbon groups having 3 to 20 carbon atoms A phosphorous ester or phosphorous ester containing phosphorous-containing compound (C) containing no sulfur and containing 0.01 to 0.05% by mass of a phosphorus content based on the total amount of lubricating oil, the component (B) sulfur 0.001 seen 0.005 wt% including in the lubricating oil total amount of from, the mass ratio of sulfur derived from the relative phosphorus content (B) component at 0.5 or less Yes, by supplying a lubricating oil containing 0.005 to 0.1 mass% friction modifier ,
Wherein the surface of the sliding portion, and washed with hexane, the method of forming the lubricating film, wherein a thickness of when Kaze燥 to form a lubricating film of 5 to 35 n m. The method for forming a lubricating film according to claim 1, wherein the base oil (A) is poly α-olefin . The method for forming a lubricating film according to claim 1, wherein the lubricating oil contains the friction modifier made of an aliphatic carboxylic acid . The said pump is a vane pump, The formation method of the lubricating film as described in any one of Claims 1-3 characterized by the above-mentioned. A method for reducing power consumption of a pump having a sliding portion made of steel and operated at a discharge pressure of 20 MPa or less,
A method for reducing power consumption of a pump, comprising forming a lubricating film on a surface of the sliding portion by the method according to claim 1. 6. The method of reducing power consumption of a pump according to claim 5, wherein the pump is a vane pump.

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