JP2020066645A - Lubricant base oil - Google Patents

Abstract

To provide an ester-based lubricant base oil that has a high flash point, excellent thermal stability (low sludge property) and low-temperature fluidity, and a high viscosity index.SOLUTION: The problem is solved by using, as a lubricant base oil, a mixture containing a complex ester that is obtained by esterifying (A) pentaerythritol, (B) an aliphatic dicarboxylic acid having 6 to 10 carbon atoms, (C) oleic acid, and (D) a linear or branched aliphatic monocarboxylic acid having 6 to 10 carbon atoms, at a specific molar ratio.SELECTED DRAWING: None

Description

The present invention relates to a lubricating base oil.

As the lubricating base oil, lubricating base oils having various viscosities are used depending on the use, the device used and the machine used, and the operating temperature thereof varies from low temperature to high temperature. Therefore, in order to be usable as a lubricating base oil in a wide temperature range, it is necessary to have excellent heat resistance and low temperature fluidity. Further, in order to avoid a decrease in lubricity due to a decrease in viscosity at a high temperature and a decrease in operating efficiency of an apparatus or a device due to an increase in viscosity at a low temperature, it is necessary to have a small viscosity change with temperature, that is, to have a high viscosity index.

Conventionally, mineral oil base oils have been mainly used as lubricating base oils because they are inexpensive and easily available.However, due to their poor heat resistance and low viscosity index, the viscosity index has recently been increased in applications with strict basic required properties. Synthetic hydrocarbon base oils such as synthetic hydrocarbons and organic acid esters, which have high heat resistance and are excellent in heat resistance, are mainly used.

In particular, organic acid ester-based lubricating base oils have the advantages of long life (good heat resistance), wide operating temperature range (low pour point, high viscosity index), good lubricity, low volatility, etc. Have Currently, organic acid ester-based lubricating base oils are used as jet engine lubricating base oils, gas turbine lubricating base oils, compressor lubricating base oils, mechanical chain lubricating base oils, and hydraulically operated lubricating base oils. It has also come to be used favorably in the fields of lubricant base oils for gears, lubricant base oils for bearing oils, grease base oils, and the like.

Examples of the organic acid ester-based lubricating base oil include monoesters obtained from the reaction of an aliphatic monocarboxylic acid and a monohydric alcohol (hereinafter referred to as “monoester”), reactions of an aliphatic dibasic acid and a monohydric alcohol A diester (hereinafter, referred to as "aliphatic dibasic acid diester"), an ester (hereinafter, referred to as "polyol ester") obtained from a reaction between a polyhydric alcohol and an aliphatic carboxylic acid, and a polyhydric alcohol, The complex ester (henceforth "complex ester") obtained from reaction with a polybasic acid, an aliphatic monocarboxylic acid (and / or an aliphatic monohydric alcohol), etc. are indicated (patent documents 1-11). .

However, the basic requirements for lubricating oil such as heat resistance, low temperature fluidity, and high viscosity index are becoming more and more severe, and the current organic acid ester type lubricating base oil is used as the lubricating base oil under high temperature conditions. Then, deterioration has caused problems such as an increase in acid value and generation of sludge content in terms of thermal stability. For example, lubricating oils for machine chains are used under high temperature conditions of 230 to 250 ° C. Under such a high temperature condition, when the current organic acid ester-based lubricating base oil is used, sludge is generated due to deterioration of the lubricating base oil, and a heavy load is placed on maintenance such as cleaning work. The flash point of the organic acid ester-based lubricating base oil is not so high as about 260 to 280 ° C., and when used under high temperature conditions, there is a problem that the lubricating base oil itself may burn if there is an ignition source. It was Therefore, as a lubricating base oil, an organic acid ester-based lubricating base oil having a high flash point, excellent thermal stability (low sludge property) and low-temperature fluidity, and a high viscosity index is required.

JP-A-60-161485 JP-A-4-249959 JP, 11-172267, A JP-A-3-200895 JP-A-7-224289 JP-A-3-128991 JP-A-3-128992 JP-A-3-200896 JP-A-5-331474 Japanese Patent Publication No. 7-507873 Special table 2003-501410 gazette

An object of the present invention is to provide a lubricating base oil having a high flash point, excellent thermal stability (low sludge property) and low-temperature fluidity, and a high viscosity index.

As a result of earnest studies to achieve the above object, the present inventors have found that (A) pentaerythritol, (B) aliphatic dicarboxylic acid having 6 to 10 carbon atoms, (C) oleic acid, and (D) having 6 to 10 carbon atoms. Lubricating base oil containing a complex ester obtained by esterification of a linear or branched aliphatic monocarboxylic acid with a specific molar ratio has a high flash point and thermal stability (low sludge property). ) And a low temperature fluidity and a high viscosity index of the lubricating base oil, the present invention has been completed.

That is, the present invention provides a lubricating base oil having the following items.

[Item 1]
(A) pentaerythritol, (B) aliphatic dicarboxylic acid having 6 to 10 carbon atoms, (C) oleic acid, and (D) linear or branched aliphatic monocarboxylic acid having 6 to 10 carbon atoms, and ester Which is a complex ester obtained by a chemical reaction,
The molar ratio is (A) / (B) / (C) / (D) = 10/2 to 8/4 to 29/4 to 29.
And a complex ester having an acid value of the complex ester of 10 mgKOH / g or less and a hydroxyl value of 20 mgKOH / g or less.

[Item 2]
The lubricating base oil according to [Item 1], wherein the content of the complex ester is 90% by mass or more in the lubricating base oil.

[Item 3]
The lubricant base oil according to [Claim 1] or [Claim 2], wherein the lubricant base oil is a lubricant base oil for machine chains or a grease base oil.

[Item 4]
A lubricating oil composition, comprising the lubricating base oil according to any one of [Claim 1] to [Claim 3].

[Item 5]
A lubricating oil composition comprising the lubricating base oil according to any one of [Claim 1] to [Claim 4] and an antioxidant.

[Item 6]
The lubricating oil composition according to [Item 5], wherein the antioxidant is a phenol-based antioxidant and / or an amine-based antioxidant.

The lubricating base oil of the present invention is a lubricating base oil having a high flash point, excellent thermal stability (low sludge property) and low-temperature fluidity, and a high viscosity index.

The complex ester relating to the lubricating base oil of the present invention includes pentaerythritol (A), aliphatic dicarboxylic acid (B) having 6 to 10 carbon atoms, oleic acid (C), and linear or branched chain having 6 to 10 carbon atoms. It is a complex ester obtained by esterifying a linear aliphatic monocarboxylic acid (D).

<(A) component>
As the pentaerythritol (A) relating to the complex ester relating to the lubricating base oil of the present invention, industrially available pentaerythritol can be used, and the purity of pentaerythritol is 95% or more, particularly 98%. The above is preferable.

<(B) component>
The aliphatic dicarboxylic acid (B) relating to the complex ester relating to the lubricating base oil of the present invention is an aliphatic dicarboxylic acid having 6 to 10 carbon atoms, preferably 9 to 10 carbon atoms, and specifically, adipic acid. , Pimelic acid, suberic acid, azelaic acid, sebacic acid and the like. Of these, aliphatic dicarboxylic acids having 9 to 10 carbon atoms are preferable in terms of excellent heat resistance, and specifically, azelaic acid and sebacic acid are recommended. These can be used alone or in combination of two or more kinds for esterification.

<(C) component>
The oleic acid (C) relating to the complex ester relating to the lubricating base oil of the present invention may be industrially available one containing oleic acid as a main component, and the oleic acid component is 60% by mass or more. What can be used preferably. As a component other than oleic acid, a saturated or unsaturated aliphatic monocarboxylic acid having 12 to 22 carbon atoms may be contained. Further, the more the oleic acid component is, the higher the flash point is, and the lower the pour point is. Therefore, it is more preferable that the oleic acid component is contained in 70% by mass or more.

<(D) component>
The linear or branched aliphatic monocarboxylic acid (D) relating to the complex ester of the lubricating base oil of the present invention is a linear or branched aliphatic monocarboxylic acid having 6 to 10 carbon atoms. Specific examples of the linear aliphatic monocarboxylic acid include n-hexanoic acid, n-heptanoic acid, n-octanoic acid, n-nonanoic acid and n-decanoic acid. Further, specific examples of the branched aliphatic monocarboxylic acid include isohexanoic acid, isoheptanoic acid, isooctanoic acid, 2-ethylhexanoic acid, isononanoic acid, 3,5,5-trimethylhexanoic acid, and isodecanoic acid. .

<Esterification reaction>
In the esterification, the molar ratio of the (A) component, (B) component, (C) component and (D) component used is (A) / (B) / (C) / (D) = 10 / 2 to 8/4 to 29/4 to 29, and a molar ratio of (A) / (B) / (C) / (D) = 10/3 to 7/10 to 25/8 to 24 is particularly preferable. .

In the esterification reaction of the present invention, it is preferable to use an esterification catalyst. Examples of the esterification catalyst include Lewis acids, alkali metals, sulfonic acids, and the like. Specific examples of Lewis acids include aluminum derivatives, tin derivatives, and titanium derivatives, and examples of alkali metals include sodium alkoxide and potassium. Examples include alkoxides, and examples of sulfonic acids include paratoluenesulfonic acid, methanesulfonic acid, and sulfuric acid. The amount used is, for example, about 0.05 to 1.0 mass% with respect to the total weight of the raw materials (A) component, (B) component, (C) component and (D) component. Among the above catalysts, the Lewis acid is preferable.

The esterification reaction is usually carried out at a reaction temperature of 150 to 250 ° C., preferably 160 to 230 ° C., in the presence of an inert gas. The reaction time is usually 3 to 30 hours. The esterification reaction can be carried out without a solvent, but if necessary, the produced water may be azeotropically distilled out of the system by using a water entraining agent such as benzene, toluene, xylene and cyclohexane. Good. When a water entraining agent is used, the amount used is 1 to 20% by mass, particularly 1 to 20% by mass based on the total weight of the raw materials (A) component, (B) component, (C) component and (D) component. It is preferable to use 10% by mass.

After completion of the esterification reaction, excess raw materials are distilled off under reduced pressure or normal pressure. Subsequently, the ester can be purified by a conventional purification method, for example, neutralization, water washing, liquid-liquid extraction, vacuum distillation, or an adsorbent such as activated carbon.

In particular, it is preferable to subject the esterification reaction product obtained by the esterification reaction to alkali washing as it is or after distilling off the unreacted acid (in the case of using a water entraining agent, the water entraining agent). As a result, residual unreacted acid, impurities having a carboxyl group at the terminal, catalyst, etc. are removed, and an ester having excellent metal compatibility and heat resistance can be obtained.

Examples of the cleaning liquid used for the alkali cleaning include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, and aqueous solutions of alkali such as alkali metal carbonates such as sodium carbonate, and the concentration thereof is not particularly limited. However, it is preferably about 0.5 to 20% by mass. The amount of the alkaline aqueous solution used is preferably an equivalent amount or an excess amount with respect to the acid value of the reaction product after the reaction. The product after the alkali washing is preferably washed with water until it becomes neutral. Thus, the complex ester of the lubricating base oil of the invention can be obtained.

In the lubricating base oil of the present invention, the complex ester content is preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 98% by mass or more.

<Complex ester>
The acid value of the complex ester relating to the lubricating base oil of the invention is 10 mgKOH / g or less, preferably 5 mgKOH / g or less, and particularly preferably 3 mgKOH / g or less. The lower the acid value, the better the flash point and the stability of the ester. The acid value is a value obtained by the method described in Examples below.

The complex ester relating to the lubricating base oil of the invention has a hydroxyl value of 20 mgKOH / g or less, preferably 15 mgKOH / g or less, and particularly preferably 10 mgKOH / g or less. The lower the hydroxyl value, the better the heat resistance. The hydroxyl value is a value obtained by the method described in Examples below.

Kinematic viscosity at 100 ° C. Complex ester according to the lubricating base oil of the invention, ^{8 mm} 2 / s or more 100mm preferably less than ² / s, particularly preferably less than 11 mm ² / s or more 80 mm ² / s. When the kinematic viscosity at 100 ° C. is 8 mm ² / s or more, the lubricating performance at high temperature is good, and when it is 100 mm ² / s or less, the fluidity is good and the handling is easy. The above kinematic viscosity is a value obtained by the method described in Examples below.

The viscosity index of the complex ester of the lubricating base oil of the present invention is preferably 150 or more, particularly preferably 170 or more. The higher the viscosity index, the better the viscosity-temperature characteristics. The viscosity index is a value obtained by the method described in Examples below.

The low temperature fluidity of the complex ester relating to the lubricating base oil of the present invention can be evaluated by, for example, the pour point. The pour point of the lubricating base oil is preferably 0 ° C or lower, more preferably -2.5 ° C or lower, and particularly preferably -10 ° C or lower. The lower the pour point, the better the low temperature fluidity. The pour point is a value obtained by the low temperature fluidity test described in Examples below.

The flash point of the complex ester relating to the lubricating base oil of the present invention is preferably 300 ° C or higher, and particularly preferably 310 ° C or higher. The flash point is a value obtained by the method described in Examples below.

The thermal stability (low sludge property) of the complex ester relating to the lubricating base oil of the present invention can be evaluated by, for example, the amount of sludge in a pentane insoluble matter test. As a result of the pentane insoluble matter test, a sludge amount of less than 5 mg is preferable, and a sludge amount of less than 1 mg is particularly preferable. The sludge amount is a result obtained by a pentane insoluble matter test described in Examples below.

The lubricating base oil of the present invention has a high flash point, is excellent in thermal stability (low sludge property) and low-temperature fluidity, and has a high viscosity index, so that it can be used as a lubricating base oil or a grease base oil for machine chains. It is preferably used.

The lubricating base oil of the present invention is a mineral oil (hydrocarbon oil obtained by refining petroleum), poly-α-olefin, polybutene, alkylbenzene, alkylnaphthalene, alicyclic hydrocarbon oil, synthetic obtained by the Fischer-Tropsch method. At least one of synthetic hydrocarbon oils such as isomerized hydrocarbon oils, animal and vegetable oils, organic acid esters other than the complex ester according to the present invention, and combination base oils such as polyalkylene glycol, polyvinyl ether, polyphenyl ether and alkylphenyl ether The seeds may be used in combination.

Examples of the mineral oil include solvent-refined mineral oil, hydrorefined mineral oil, and wax isomerized oil. Usually, the kinematic viscosity at 100 ° C. is 1.0 to 25 mm ² / s, preferably 2.0 to 20.0 mm ^2. Those in the range of / s are used.

Examples of the poly-α-olefin include α-olefins having 2 to 16 carbon atoms (for example, ethylene, propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, etc. ), The kinematic viscosity at 100 ° C. is 1.0 to 25 mm ² / s, and the viscosity index is 100 or more. Particularly, the kinematic viscosity at 100 ° C. is 1.5 to 20. It is preferable that the viscosity index is 0.0 mm ² / s and the viscosity index is 120 or more.

Examples of polybutene include those obtained by polymerizing isobutylene and those obtained by copolymerizing isobutylene with normal butylene, and generally include a wide range of kinematic viscosities at 100 ° C. of 2.0 to 40 mm ² / s.

Examples of the alkylbenzene include monoalkylbenzene, dialkylbenzene, trialkylbenzene, and tetraalkylbenzene having a molecular weight of 200 to 450, which is substituted with a linear or branched alkyl group having 1 to 40 carbon atoms.

Examples of the alkylnaphthalene include monoalkylnaphthalene and dialkylnaphthalene substituted with a linear or branched alkyl group having 1 to 30 carbon atoms.

Examples of animal and vegetable oils include beef tallow, lard, palm oil, coconut oil, rapeseed oil, castor oil, sunflower oil and the like.

Examples of the organic acid ester (excluding the complex ester according to the present invention) include fatty acid monoester, aliphatic dibasic acid diester, polyol ester and other esters.

As the fatty acid monoester, an ester of an aliphatic linear or branched monocarboxylic acid having 5 to 22 carbon atoms and a linear or branched saturated or unsaturated aliphatic alcohol having 3 to 22 carbon atoms Compounds.

Examples of the aliphatic dibasic acid diester include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonamethylenedicarboxylic acid, 1,10-decadecane. Examples thereof include diesters of an aliphatic dibasic acid such as methylenedicarboxylic acid or an anhydride thereof and a linear or branched saturated or unsaturated aliphatic alcohol having 3 to 22 carbon atoms.

Examples of the polyol ester include neopentyl glycol, 2,2-diethylpropanediol, 2-butyl2-ethylpropanonediol, trimethylolethane, trimethylolpropane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, and other neopentyl type structures. , 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonane Diol, 1,10-decanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, 1,3-butanediol, 2-methyl-1,4-butanediol, 1,4-pentane Diol, 2-methyl-1,5-pentanedio , 3-methyl-1,5-pentanediol, 1,5-hexanediol, 2-methyl-1,6-hexanediol, 3-methyl-1,6-hexanediol, 1,6-heptanediol, 2- Methyl-1,7-heptanediol, 3-methyl-1,7-heptanediol, 4-methyl-1,7-heptanediol, 1,7-octanediol, 2-methyl-1,8-octanediol, 3 -Methyl-1,8-octanediol, 4-methyl-1,8-octanediol, 1,8-nonanediol, 2-methyl-1,9-nonanediol, 3-methyl-1,9-nonanediol, 4-methyl-1,9-nonanediol, 5-methyl-1,9-nonanediol, 2-ethyl-1,3-hexanediol, glycerin, polyglycerin, sorbit It is possible to use a full ester of a non-neopentyl-type structure of the polyol with linear and / or branched aliphatic monocarboxylic acids, saturated or unsaturated carbon atoms 3 to 22, such as Le.

Other esters include polymerized fatty acids such as dimer acid and hydrogenated dimer acid, or hydroxy fatty acids such as condensed castor oil fatty acid and hydrogenated condensed castor oil fatty acid, and a linear or branched chain having 3 to 22 carbon atoms. Examples thereof include ester compounds with saturated or unsaturated aliphatic alcohols.

Examples of the polyalkylene glycol include ring-opening polymers of alcohol and linear or branched alkylene oxide having 2 to 4 carbon atoms. Examples of the alkylene oxide include ethylene oxide, propylene oxide, and butylene oxide, and a polymer using one of these or a copolymer using a mixture of two or more thereof can be used. Further, a compound in which the hydroxyl groups at one end or both ends are etherified or esterified can also be used. The kinematic viscosity of the polymer is 5.0 to 1,000 mm ² / s (40 ° C.), preferably 5.0 to 500 mm ² / s (40 ° C.).

The polyvinyl ether is a compound obtained by polymerizing a vinyl ether monomer, and the monomer is methyl vinyl ether, ethyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, sec-butyl vinyl ether, tert-butyl vinyl ether, n-pentyl vinyl ether. , N-hexyl vinyl ether, 2-methoxyethyl vinyl ether, 2-ethoxyethyl vinyl ether and the like. The kinematic viscosity of the polymer is 5.0 to 1,000 mm ² / s (40 ° C.), preferably 5.0 to 500 mm ² / s (40 ° C.).

Examples of the polyphenyl ether include compounds having a structure in which two or more aromatic ring meta positions are linked by an ether bond or a thioether bond. Specifically, bis (m-phenoxyphenyl) ether and m-bis ( Examples thereof include m-phenoxyphenoxy) benzene, and thioethers (commonly called C-ether) in which one or more oxygen atoms thereof are substituted with sulfur.

Examples of the alkyl phenyl ether include compounds in which polyphenyl ether is substituted with a linear or branched alkyl group having 6 to 18 carbon atoms, and alkyldiphenyl ether substituted with one or more alkyl groups is particularly preferable.

The content of the combined base oil in the lubricating base oil of the present invention is recommended to be 10% by mass or less, but it is more preferably 5% by mass or less in order to improve the balance of physical properties.

<Lubricant composition>
In order to improve the performance of the above-mentioned lubricating base oil, the lubricating oil composition of the present invention comprises a lubricating base oil (i.e., a lubricating base oil consisting only of the complex ester of the present invention, or a complex of the present invention). In addition to a lubricating base oil consisting of an ester and a base oil used in combination, an antioxidant is added.

Examples of the antioxidant include a phenol-based antioxidant, an amine-based antioxidant, a sulfur-based antioxidant and the like. Among them, phenolic antioxidants and amine antioxidants are recommended.

As the phenolic antioxidant, known ones used in this field can be used without particular limitation. Of these phenolic antioxidants, those having a total carbon number of 6 to 100, more preferably 20 to 80, are recommended.

Specifically, 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, 4,4′-methylenebis (2,6-di-tert-butylphenol), 4,4 '-Butylidene bis (3-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol) , 4,4'-isopropylidene bisphenol, 2,4-dimethyl-6-tert-butylphenol, tetrakis [methylene-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] methane, 1, 1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3 5-Trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 2,2'-dihydroxy-3,3'-di (α-methylcyclohexyl) -5 , 5'-Dimethyl-diphenylmethane, 2,2'-isobutylidene bis (4,6-dimethylphenol), 2,6-bis (2'-hydroxy-3'-tert-butyl-5'-methylbenzyl) -4-Methylphenol, 1,1'-bis (4-hydroxyphenyl) cyclohexane, 2,5-di-tert-amylhydroquinone, 2,5-di-tert-butylhydroquinone, 1,4-dihydroxyanthraquinone, 3 -Tert-butyl-4-hydroxyanisole, 2-tert-butyl-4-hydroxyanisole, 2,4-dibenzoylresorcy Nol, 4-tert-butylcatechol, 2,6-di-tert-butyl-4-ethylphenol, 2-hydroxy-4-methoxybenzophenone, 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxy. Benzophenone, 2,4,5-trihydroxybenzophenone, α-tocopherol, bis [2- (2-hydroxy-5-methyl-3-tert-butylbenzyl) -4-methyl-6-tert-butylphenyl] terephthalate, Triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenylpropionate], 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4] -Hydroxyphenyl) propionate] and the like. 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, 4,4′-methylenebis (2,6-di-tert-butylphenol), 4,4′-butylidenebis (3 -Methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4 ' -Isopropylidenebisphenol, 2,4-dimethyl-6-tert-butylphenol, tetrakis [methylene-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] methane, 1,1,3-tris (2-Methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl Cyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 2,6-di-tert-butyl-4-ethylphenol, bis [2- (2-hydroxy) -5-Methyl-3-tert-butylbenzyl) -4-methyl-6-tert-butylphenyl] terephthalate, triethyleneglycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenylpropio) Nate], 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], and more preferably 2,6-di-tert-butyl-p- Cresol, 4,4'-methylenebis (2,6-di-tert-butylphenol), 2,6-di-tert-butyl-4-ethylphene Lumpur is most preferable.

The phenolic antioxidants may be used singly or in combination of two or more, and the addition amount thereof is usually 0.01 to 5 mass% with respect to the lubricating base oil, and preferably It is 0.1 to 2 mass%.

As the amine-based antioxidant, known ones used in this field can be used without particular limitation. Among these amine-based antioxidants, those having a total carbon number of 6 to 60, more preferably 20 to 40, are recommended.

Specifically, diphenylamine, monobutyl (including linear and branched) diphenylamine, monopentyl (including linear and branched) diphenylamine, monohexyl (including linear and branched) diphenylamine, monoheptyl (linear and branched) Chain) diphenylamine, monooctyl (including straight chain and branched chain) diphenylamine, and the like, especially mono (C ₄ -C ₉ alkyl) diphenylamine (ie, one of the two benzene rings of diphenylamine is an alkyl group). , Especially those which are monosubstituted by C ₄ -C ₉ alkyl groups, ie monoalkyl-substituted diphenylamines), p, p′-dibutyl (including straight-chain and branched-chain) diphenylamine, p, p′-dipentyl Diphenylamine (including straight and branched chains), p, '-Dihexyl (including straight chain and branched chain) diphenylamine, p, p'-diheptyl (including straight chain and branched chain) diphenylamine, p, p'-dioctyl (including straight chain and branched chain) diphenylamine, p, Di (alkylphenyl) amines such as p′-dinonyl (including straight chain and branched chain) diphenylamine, especially p, p′-di (C ₄ -C ₉ alkylphenyl) amines (ie, the two benzene rings of diphenylamine). each an alkyl group, in particular C ₄ -C ₉ diphenylamine dialkyl substitution with an alkyl group is mono-substituted, those two alkyl groups are identical), di (mono-C ₄ -C ₉ alkylphenyl) an amine, which alkyl groups on one benzene ring is different from the alkyl group on the other benzene ring, di (-C ₄ -C ₉ alkyl Diphenylamines, such as those in which at least one of the four alkyl groups on the two benzene rings is different from the rest of the alkyl groups; N-phenyl-1-naphthylamine, N-phenyl-2-naphthylamine , 4-octylphenyl-1-naphthylamine, 4-octylphenyl-2-naphthylamine, and other naphthylamines; p-phenylenediamine, N-phenyl-N′-isopropyl-p-phenylenediamine, N-phenyl-N ′-( Examples thereof include phenylenediamines such as 1,3-dimethylbutyl) -p-phenylenediamine. Among these, p, p'-dioctyl (including straight chain and branched chain) diphenylamine, p, p'-dinonyl (including straight chain and branched chain) diphenylamine, and N-phenyl-1-naphthylamine are particularly preferable. In the present specification and claims, “(including straight chain and branched chain)” means that one or both of straight chain alkyl and branched chain alkyl are included.

The amine-based antioxidant is used alone or in combination of two or more, and the addition amount thereof is usually 0.01 to 5% by mass, preferably 0.1 to 5% by mass relative to the lubricating base oil. It is 2% by mass.

When a phenolic antioxidant and an amine antioxidant are used in combination, the total addition amount thereof is usually 0.01 to 5% by mass, preferably 0.1 to 5% by mass, based on the lubricating base oil. It is 2% by mass. The ratio (weight ratio) of the phenolic antioxidant and the amine antioxidant is not particularly limited and can be appropriately selected from a wide range, but preferably the phenolic antioxidant: amine antioxidant = 1 : 0.05 to 20, more preferably 1: 0.2 to 5 is recommended.

Preferred combinations of the phenol-based antioxidant and the amine-based antioxidant include 2,6-di-tert-butyl-p-cresol, 4,4′-methylenebis (2,6-di-tert-butylphenol) and 2 , 6-di-tert-butyl-4-ethylphenol, and one or more selected from the group consisting of p, p'-dioctyl (including straight chain and branched chain) diphenylamine, p, p'-dinonyl A combination of diphenylamine (including straight chain and branched chain) and one or more selected from the group consisting of N-phenyl-1-naphthylamine is exemplified.

Specifically, the following combinations are preferable. A combination of 2,6-di-tert-butyl-p-cresol and p, p'-dioctyl (including straight chain and branched chain) diphenylamine, 2,6-di-tert-butyl-p-cresol and p, p '-Dinonyl (including straight chain and branched chain) diphenylamine combination, 2,6-di-tert-butyl-p-cresol and N-phenyl-1-naphthylamine combination, 4,4'-methylenebis (2,6 -Di-tert-butylphenol) and p, p'-dioctyl (including straight chain and branched chain) diphenylamine, 4,4'-methylenebis (2,6-di-tert-butylphenol) and p, p'- Dinonyl (including straight chain and branched chain) diphenylamine combinations, 4,4'-methylenebis (2,6-di-tert-butylpheno 2) and N-phenyl-1-naphthylamine, 2,6-di-tert-butyl-4-ethylphenol and p, p'-dioctyl (including straight chain and branched chain) diphenylamine, 2,6 -A combination of di-tert-butyl-4-ethylphenol and p, p'-dinonyl (including straight chain and branched chain) diphenylamine, 2,6-di-tert-butyl-4-ethylphenol and N-phenyl- A combination of 1-naphthylamine and the like are exemplified. Among them, 4,4'-methylenebis (2,6-di-tert-butylphenol) and p, p'-dioctyl (including straight chain and branched chain) diphenylamine are more effective combinations in terms of excellent heat resistance. A combination of 4,4′-methylenebis (2,6-di-tert-butylphenol) and p, p′-dinonyl (including straight chain and branched chain) diphenylamine, 4,4′-methylenebis (2,6) -Di-tert-butylphenol) and N-phenyl-1-naphthylamine are recommended.

By blending the above-described antioxidant with the lubricating base oil of the present invention, decomposition of the lubricating base oil in the presence of air can be suppressed, so that the heat resistance of the lubricating oil composition is improved.

In order to further improve the performance of the above lubricating oil composition, a metal detergent, an ashless dispersant, an oiliness agent, an antiwear agent, an extreme pressure agent, a metal deactivator, a rust preventive agent, a viscosity index improver, a pour point. It is also possible to appropriately mix at least one additive such as a depressant and a hydrolysis inhibitor. The blending amount of these is not particularly limited as long as the effects of the present invention are exhibited, but specific examples thereof are shown below.

 Examples of the metal detergent include Ca-petroleum sulfonate, overbased Ca-petroleum sulfonate, Ca-alkylbenzene sulfonate, overbased Ca-alkylbenzene sulfonate, Ba-alkylbenzene sulfonate, and overbased Ba-alkylbenzene sulfonate. Phonates, Mg-alkylbenzene sulfonates, overbased Mg-alkylbenzene sulfonates, Na-alkylbenzene sulfonates, overbased Na-alkylbenzene sulfonates, Ca-alkylnaphthalene sulfonates, overbased Ca- Metal sulfonates such as alkylnaphthalene sulfonates, Ca-phenates, overbased Ca-phenates, Ba-phenates, metal phenates such as overbased Ba-phenates, Ca-salicylate, overbased Ca- Metal salicylates such as lysylates, Ca-phosphonates, overbased Ca-phosphonates, Ba-phosphonates, metal phosphonates such as overbased Ba-phosphonates, overbased Ca-carboxylates, etc. Can be used. When used, these metal detergents are usually added in an amount of about 1 to 10% by mass, preferably about 2 to 7% by mass, based on the lubricating base oil.

Examples of the ashless dispersant include polyalkenyl succinimide, polyalkenyl succinamide, polyalkenyl benzylamine, and polyalkenyl succinic acid ester. These ashless dispersants may be used alone or in combination, and when they are used, they are usually added in an amount of 1 to 10% by mass, preferably 2 to 7% by mass based on the lubricating base oil. desirable.

As the oiliness agent, aliphatic saturated and unsaturated monocarboxylic acids such as stearic acid and oleic acid, polymerized fatty acids such as dimer acid and hydrogenated dimer acid, ricinoleic acid, hydroxy fatty acids such as 12-hydroxystearic acid, lauryl alcohol, Aliphatic saturated and unsaturated monoalcohols such as oleyl alcohol, stearylamine, aliphatic saturated and unsaturated monoamines such as oleylamine, lauric acid amide, aliphatic saturated and unsaturated monocarboxylic acid amides such as oleic acid amide, batyl alcohol, Glycerin ethers such as chimyl alcohol and ceracyl alcohol, lauryl polyglycerin ethers, alkyl or alkenyl polyglyceryl ethers such as oleyl polyglyceryl ether, di (2-ethylhexyl) monoethanolami , Poly (alkylene oxide) alkyl or alkenyl amines such as diisotridecyl monoethanolamine adduct and the like. These oiliness agents may be used alone or in combination, and when they are used, usually 0.01 to 5% by mass, preferably 0.1 to 3% by mass is added to the lubricating base oil. It is desirable to do.

Anti-wear agents and extreme pressure agents include tricresyl phosphate, cresyl diphenyl phosphate, alkylphenyl phosphates, tributyl phosphate, dibutyl phosphate, and other phosphoric acid esters, tributyl phosphite, dibutyl phosphite, triisopropyl phosphite, etc. Phosphorus compounds such as phosphites and amine salts thereof, sulfurized fats and oils, sulfurized fatty acids such as sulfurized oleic acid, sulfur compounds such as dibenzyl disulfide, sulfurized olefins and dialkyl disulfides, Zn-dialkyldithiophosphates, Zn- Examples thereof include organometallic compounds such as dialkyldithiophosphate, Mo-dialkyldithiophosphate and Mo-dialkyldithiocarbamate. These antiwear agents may be used alone or in combination, and when they are used, they are usually used in an amount of 0.01 to 10% by mass, preferably 0.1 to 5% by mass, based on the lubricating base oil. It is desirable to add.

Examples of the metal deactivator include benzotriazole-based compounds, thiadiazole-based compounds, and gallic acid ester-based compounds. These metal deactivators may be used alone or in combination, and when they are used, they are usually used in an amount of 0.01 to 0.4% by mass, preferably 0.01 to 0.4% by mass, based on the lubricating base oil. It is desirable to add 0.2% by mass.

As the rust preventive agent, dodecenyl succinic acid half ester, octadecenyl succinic anhydride, alkyl or alkenyl succinic acid derivative such as dodecenyl succinic acid amide, sorbitan monooleate, glycerin monooleate, pentaerythritol monooleate, and the like. Partial alcohol alcohol, Ca-petroleum sulfonate, Ca-alkylbenzene sulfonate, Ba-alkylbenzene sulfonate, Mg-alkylbenzene sulfonate, Na-alkylbenzene sulfonate, Zn-alkylbenzene sulfonate, Ca-alkylnaphthalene sulfonate Examples thereof include metal sulfonates such as phonates, rosin amines, amines such as N-oleyl sarcosine, and dialkyl phosphite amine salts. These rust preventives may be used alone or in combination, and when used, they are usually used in an amount of 0.01 to 5% by mass, preferably 0.05 to 2% by mass, based on the lubricating base oil. It is desirable to add.

Examples of the viscosity index improver include olefin copolymers such as polyalkylmethacrylate, polyalkylstyrene, polybutene, ethylene-propylene copolymer, styrene-diene copolymer, and styrene-maleic anhydride copolymer. . These viscosity index improvers may be used alone or in combination, and when they are used, they are usually used in an amount of 0.1 to 15% by mass, preferably 0.5 to 7% by mass based on the lubricating base oil. % Addition is desirable.

Examples of the pour point depressant include condensates of chlorinated paraffins and alkylnaphthalenes, condensates of chlorinated paraffins and phenols, polyalkylmethacrylates, polyalkylstyrenes, polybutenes and the like which are the viscosity index improvers described above. These pour point depressants may be used alone or in combination, and when they are used, they are usually used in an amount of 0.01 to 5% by mass, preferably 0.1 to 3% by mass, based on the lubricating base oil. % Addition is desirable.

As the hydrolysis inhibitor, alkyl glycidyl ethers, alkyl glycidyl esters, alkylene glycol glycidyl ethers, alicyclic epoxies, epoxy compounds such as phenyl glycidyl ether, di-tert-butylcarbodiimide, 1,3-di- A carbodiimide compound such as p-tolyl carbodiimide can be used, and it is usually desirable to add 0.05 to 2% by mass to the lubricating base oil.

A "grease" can be prepared by appropriately combining a thickener with the lubricating base oil of the present invention.

Thickeners include soaps such as sodium soap, lithium soap, calcium soap, calcium complex soap, aluminum complex soap, lithium complex soap and the like, bentonite, silica aerogel, sodium terephthalamate, urea compound, polytetrafluoroethylene, Examples include non-soap-based materials such as boron nitride.

Examples of the metal soap-based thickeners include lithium carboxylic acid lithium salts having a hydroxyl group such as lithium-12-hydroxystearate, lithium carboxylic acid lithium salts such as lithium stearate, and mixtures thereof.

Examples of the complex metal soap thickener include a complex of a monovalent aliphatic carboxylic acid metal salt having a hydroxyl group and a divalent aliphatic carboxylic acid metal salt, and specifically, a complex lithium soap and a An example is composite aluminum soap.

Examples of the urea compound include alicyclic, aromatic, aliphatic, diurea, triurea, tetraurea, urea-urethane compounds and the like.

Among the above, as the thickener, lithium soap, lithium complex soap and urea compound are preferable, and from the viewpoint of heat resistance, the urea compound is particularly preferable.

These thickeners can be used alone or in combination of two or more kinds, and the addition amount thereof is not particularly limited as long as a predetermined effect is exhibited.

Examples of the corrosion inhibitor include sodium sulfonate and sorbitan ester, which are usually added in an amount of about 0.1 to 3.0% by mass based on the lubricating base oil.

Examples of the hue stabilizer include substituted hydroquinone, furfural azine and the like, which are usually added in an amount of about 0.01 to 0.1% by mass based on the lubricating base oil.

The present invention is described in detail below with reference to examples, but the present invention is not limited to these examples. The physical properties and chemical properties of the lubricating base oil in each example were evaluated by the following methods. Compounds not specifically mentioned used reagents.
<Compound used>
Pentaerythritol: Tokyo Chemical Industry Co., Ltd. neopentyl glycol: Tokyo Chemical Industry Co., Ltd. sebacic acid: Tokyo Chemical Industry Co., Ltd. azelaic acid: Tokyo Chemical Industry Co., Ltd. adipic acid: Tokyo Chemical Industry Co., Ltd. oleic acid: " Oleic acid D-100 "manufactured by Shin Nippon Rika Co., Ltd. (purity of oleic acid 73%)
Hexanoic acid: Tokyo Chemical Industry Co., Ltd. Capric acid: Shin Nippon Rika Co., Ltd. 2-Ethylhexanoic acid: “Octyl acid” KH Neochem Co., Ltd. Lauric acid: “Lauric acid P” Shin Nippon Rika Co., Ltd.

(A) Acid value (AV)
It was measured according to JIS K2501 (2003). The detection limit is 0.01 mgKOH / g.

(B) Hydroxyl value (OHV)
It was measured according to JIS K0070 (1992). The detection limit is 0.1 mgKOH / g.

[Measurement of physical properties of lubricating base oil]
(C) Kinematic viscosity The kinematic viscosity at 100 ° C was measured according to JIS-K-2283 (2000).
When the kinematic viscosity at 100 ° C. is in the range of 8 to 100 mm ² / s, it is evaluated as good in terms of lubricity at high temperature and fluidity in handling.
<Evaluation of kinematic viscosity at 100 ° C>
A: 11 mm ² / s or more and less than 80 mm ² / s B: 8 mm ² / s or more and less than 11 mm ² / s or 80 mm ² / s or more and less than 100 mm ² / s C: 8 mm ² / s or less than 100 mm ² / s or more

(D) Viscosity index Calculated according to JIS-K-2283 (2000).
<Evaluation of viscosity index>
A: 170 or more B: 150 or more and less than 170 C: less than 150

(E) Low temperature fluidity test (pour point)
The pour point was measured according to JIS-K-2269 (1987).
<Evaluation of low temperature fluidity>
A: -10 ° C or lower B: -10 ° C or higher and 0 ° C or lower C: 0 ° C or higher

(F) Flash point Measured according to JIS K2265 (Cleveland open type).
<Evaluation of flash point>
A: 310 ° C or higher B: 300 ° C or higher and lower than 310 ° C C: less than 300 ° C

(G) Low sludge property (pentane insoluble matter test)
It was measured according to ASTM D893. A sample of 50 g was weighed and heated at 300 ° C. for 15 minutes in the atmosphere. Then, it was cooled to room temperature and diluted with 200 g of pentane. An insoluble matter (sludge) was precipitated with a centrifuge and the supernatant was removed. After diluting again with 200 g of pentane to remove the supernatant, the remaining insoluble matter was dried and weighed.
<Evaluation of low sludge property>
A: less than 1 mg B: 1 mg or more and less than 5 mg C: 5 mg or more

(H) Evaluation of Lubricating Base Oil As the evaluation of the lubricating base oil, the results of kinematic viscosity evaluation at 100 ° C., viscosity index evaluation, low temperature fluidity evaluation, flash point evaluation and low sludge property evaluation In C, 1 or more is not suitable, B is 2 or less (other evaluation is A), good, and B is 1 or less (other evaluation is A), particularly good.

[Example 1]
In a 1-liter four-necked flask equipped with a stirrer, a thermometer, and a water content fractionation receiver with a cooling tube, 68.08 g (0.50 mol) of pentaerythritol, and sebacic acid 50 as an aliphatic dicarboxylic acid having 6 to 10 carbon atoms were added. 0.56 g (0.25 mol), oleic acid 278.59 g (1.00 mol), hexanoic acid 58.07 g (0.50 mol) esterified as a linear or branched aliphatic monocarboxylic acid having 6 to 10 carbon atoms 0.5 g of tin oxide as a catalyst and 30 g of xylene as an entrainer were charged, the inside of the flask was replaced with nitrogen, and then the temperature was gradually raised to 230 ° C. The esterification reaction was carried out while adjusting the degree of pressure reduction so that xylene was refluxed, while removing the produced water distilled out with the theoretical amount of produced water (36 g) as a target with a moisture fractionation receiver. After the reaction was completed, residual xylene was removed by distillation under reduced pressure to obtain an esterified crude product. Next, 0.5 g of activated clay was added to the obtained esterified crude product, and then the activated clay was removed by filtration to obtain 370.6 g of complex ester. The acid value of the obtained complex ester was 1.1 mgKOH / g, and the hydroxyl value was 3.4 mgKOH / g. Table 2 shows each physical property when the complex ester was evaluated as a lubricating base oil.

[Example 2]
377.0 g of complex ester was obtained in the same manner as in Example 1 except that the amount of oleic acid was changed to 208.9 g (0.75 mol) and the hexanoic acid was changed to 129.2 g (0.75 mol). . The acid value of the obtained complex ester was 1.1 mgKOH / g, and the hydroxyl value was 3.0 mgKOH / g. Table 2 shows each physical property when the complex ester was evaluated as a lubricating base oil.

[Example 3]
382.0 g of complex ester was obtained in the same manner as in Example 1 except that hexanoic acid was changed to 86.1 g (0.50 mol) of capric acid. The acid value of the obtained complex ester was 1.1 mgKOH / g, and the hydroxyl value was 3.6 mgKOH / g. Table 2 shows each physical property when the complex ester was evaluated as a lubricating base oil.

[Example 4]
368.0 g of complex ester was obtained in the same manner as in Example 1 except that sebacic acid was changed to 47.1 g (0.25 mol) of azelaic acid and the amount of oleic acid was changed to 208.9 g (0.75 mol). . The acid value of the obtained complex ester was 1.7 mgKOH / g, and the hydroxyl value was 1.9 mgKOH / g. Table 2 shows each physical property when the complex ester was evaluated as a lubricating base oil.

[Example 5]
385.0 g of complex ester was obtained in the same manner as in Example 1 except that the amount of hexanoic acid was changed to 72.1 g (0.50 mol) of 2-ethylhexanoic acid. The acid value of the obtained complex ester was 2.8 mgKOH / g, and the hydroxyl value was 16.0 mgKOH / g. Table 2 shows each physical property when the complex ester was evaluated as a lubricating base oil.

[Example 6]
Example 1 except that the amount of sebacic acid was changed to 30.3 g (0.15 mol), the amount of oleic acid was changed to 236.8 g (0.85 mol), and the hexanoic acid was changed to 146.4 g (0.85 mol) of capric acid. 385.2 g of complex ester was obtained in the same manner as in. The acid value of the obtained complex ester was 1.7 mgKOH / g, and the hydroxyl value was 1.3 mgKOH / g. Table 2 shows each physical property when the complex ester was evaluated as a lubricating base oil.

[Example 7]
Example 1 except that the amount of sebacic acid was changed to 70.8 g (0.35 mol), the amount of oleic acid was changed to 181.1 g (0.65 mol), and the hexanoic acid was changed to 112.0 g (0.65 mol) of capric acid. 350.7 g of complex ester was obtained in the same manner as in. The acid value of the obtained complex ester was 2.8 mgKOH / g, and the hydroxyl value was 2.1 mgKOH / g. Table 2 shows each physical property when the complex ester was evaluated as a lubricating base oil.

[Example 8]
Example 1 except that sebacic acid was changed to adipic acid 36.5 g (0.25 mol), the amount of oleic acid was changed to 208.9 g (0.75 mol), and hexanoic acid was changed to capric acid 129.2 g (0.75 mol). 352.9 g of complex ester was obtained by the same method as described above. The acid value of the obtained complex ester was 1.1 mgKOH / g, and the hydroxyl value was 4.3 mgKOH / g. Table 2 shows each physical property when the complex ester was evaluated as a lubricating base oil.

[Comparative Example 1]
In the same manner as in Example 1 except that the amount of oleic acid was changed to 417.9 g (1.50 mol) and hexanoic acid was omitted, 440.3 g of complex ester was obtained. The acid value of the obtained complex ester was 1.1 mgKOH / g, and the hydroxyl value was 10.7 mgKOH / g. Table 3 shows each physical property when the complex ester was evaluated as a lubricating base oil.

[Comparative Example 2]
392.3 g of complex ester was obtained in the same manner as in Example 1 except that the amount of oleic acid was changed to 208.9 g (0.75 mol) and the hexanoic acid was changed to 150.2 g (0.75 mol) of lauric acid. . The acid value of the obtained complex ester was 1.7 mgKOH / g, and the hydroxyl value was 2.4 mgKOH / g. Table 3 shows each physical property when the complex ester was evaluated as a lubricating base oil.

[Comparative Example 3]
Pentaerythritol was added to neopentyl glycol 52.1 g (0.50 mol), the amount of sebacic acid was 25.3 (0.125 mol), the amount of oleic acid was 104.5 g (0.375 mol), and the hexanoic acid was capric acid. 204.0 g of complex ester was obtained in the same manner as in Example 1 except that the amount was changed to 64.6 g (0.375 mol). The acid value of the obtained complex ester was 7.4 mgKOH / g, and the hydroxyl value was 0.0 mgKOH / g. Table 3 shows each physical property when the complex ester was evaluated as a lubricating base oil.

[Comparative Example 4]
299.1 g of complex ester was obtained in the same manner as in Example 1 except that the amount of oleic acid was changed to 258.4 g (1.5 mol) of capric acid instead of hexanoic acid. The acid value of the obtained complex ester was 1.7 mgKOH / g, and the hydroxyl value was 1.1 mgKOH / g. Table 3 shows each physical property when the complex ester was evaluated as a lubricating base oil.

For Examples 1 to 8 and Comparative Examples 1 to 4, Table 1 shows the molar ratio of each component and the acid value and hydroxyl value of the obtained complex ester.

As can be seen from Table 2, the lubricating base oils described in Examples 1 to 8 have a high kinematic viscosity at 100 ° C. of 15 mm ² / s or more and excellent lubricity at high temperatures, and are easy to handle at less than 80 mm ² / s. . Further, the viscosity index is 170 or more, and the viscosity-temperature characteristic is excellent. It has a pour point of -2.5 ° C or lower, a flash point of 300 ° C or higher, and sludge is less likely to be generated due to thermal stability, so it has an excellent performance balance and is suitable for applications such as machine chain oil.

On the other hand, the base oil described in Comparative Example 1 has a large amount of sludge and poor thermal stability. The base oil described in Comparative Example 2 has a high pour point of 5 ° C. The base oil described in Comparative Example 3 has low kinematic viscosity at 100 ° C. and flash point. The base oil described in Comparative Example 4 has a high pour point of 5 ° C.

The lubricating base oil of the present invention has a high flash point, is excellent in thermal stability (low sludge property) and low-temperature fluidity, and has a high viscosity index, and thus is good as a lubricating base oil, and particularly at a high temperature. It can be used as a lubricating base oil or a grease base oil for machine chains under conditions.

Claims (5)

(A) pentaerythritol, (B) aliphatic dicarboxylic acid having 6 to 10 carbon atoms, (C) oleic acid, and (D) linear or branched aliphatic monocarboxylic acid having 6 to 10 carbon atoms, and ester Which is a complex ester obtained by a chemical reaction,
The molar ratio is (A) / (B) / (C) / (D) = 10/2 to 8/4 to 29/4 to 29.
And a complex ester having an acid value of the complex ester of 10 mgKOH / g or less and a hydroxyl value of 20 mgKOH / g or less. The lubricating base oil according to claim 1, wherein the content of the complex ester is 90% by mass or more in the lubricating base oil. The lubricant base oil according to claim 1 or 2, wherein the lubricant base oil is a lubricant base oil for machine chains or a grease base oil. A lubricating oil composition, comprising the lubricating base oil according to claim 1. A lubricating oil composition comprising the lubricating base oil according to any one of claims 1 to 4 and an antioxidant.