JP2018141054A - A lubricant base oil for a shaft bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lubricant base oil for a shaft bearing that has a low viscosity index and a high viscosity index and has good low-temperature fluidity and vapor pressure resistance.SOLUTION: The lubricant base oil for a shaft bearing comprises an alicyclic dicarboxylic acid diester compound represented by the following general formula (I) (Rand Rin the formula are the same or different and represent linear alkyl groups having 8 to 12 carbon atoms.).SELECTED DRAWING: None

Description

The present invention relates to a lubricating base oil for bearings.

Technical background

In motors mounted on HDDs (hard disk drives) and the like, ball bearings and roller bearings were used as bearings. However, in recent years, fluid bearings have been developed in response to demands for motor miniaturization, low vibration and low noise. As hydrodynamic bearings, hydrodynamic bearings and sintered oil-impregnated bearings have been put into practical use.

The hydrodynamic bearing supports the rotating shaft by the oil film pressure of the lubricating oil interposed in the gap between the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve, and has a dynamic pressure groove on at least one of the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve. The sliding surface of the rotating shaft is levitated and supported by a lubricating oil film formed by the dynamic pressure effect. The sintered oil-impregnated bearing is provided with a lubricating oil on a porous body made of sintered metal or the like. Alternatively, a self-lubricating function is provided by impregnation with lubricating grease.

Spindle motors equipped with fluid dynamic bearings have been used with higher performance AV / OA devices and the widespread use of portable devices. In recent years, there has been a strong demand for higher speeds and smaller sizes. There is a request. In order to meet the demand for lowering the torque, a lubricating base oil having a relatively low viscosity has been selected. Low-viscosity lubricant base oils include synthetic hydrocarbon base oils such as poly-α-olefins, ester base oils such as aliphatic dibasic acid diesters, neopentyl polyol esters, and fatty acid monoesters. Lubricating base oils for fluid bearings used have been proposed (Patent Documents 1 to 8).

Among them, ester-based lubricating base oils that are low in viscosity, excellent in viscosity characteristics, low-temperature fluidity, and the like are often used as lubricating base oils for fluid bearings.

However, when an ester-based lubricating base oil with good low-temperature fluidity is used at high temperatures, the lubricating base oil itself gradually evaporates, which may cause problems when the spindle motor is used at high temperatures. It was.

Japanese National Patent Publication No. 11-514778 Japanese National Patent Publication No. 11-51479 JP 2000-500908 A JP 2003-119482 A International Publication WO2004 / 018595 Pamphlet JP 2004-084839 A JP 2005-290256 A JP 2008-007741 A

An object of the present invention is to provide a lubricating base oil for bearings that has a low viscosity, a high viscosity index, and good evaporation resistance while maintaining good low-temperature fluidity.

As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that a specific alicyclic dicarboxylic acid diester compound has a low viscosity and a high viscosity index, and has good low-temperature fluidity and evaporation resistance. It discovered that it was a lubricating oil base oil, and came to complete this invention.

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

[Claim 1]
General formula (1)
[Wherein, R ¹ and R ² are the same or different and represent a linear alkyl group having 8 to 12 carbon atoms. ]
A lubricating base oil for bearings containing an alicyclic dicarboxylic acid diester compound represented by:

[Section 2]
[Item 1], wherein R ¹ and R ^{2 of the} alicyclic dicarboxylic acid diester compound represented by the general formula (1) are the same or different and are linear alkyl groups having 8 to 10 carbon atoms. Lubricating base oil for bearings.

[Section 3]
The bearing lubricant base oil according to [Item 1] or [Item 2], wherein the bearing lubricant base oil is a hydrodynamic bearing lubricant base oil or a sintered oil-impregnated lubricant base oil.

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

[Section 5]
[Claim 4] The lubricating oil composition for bearings according to [Item 4], wherein the antioxidant is a phenol-based antioxidant and / or an amine-based antioxidant.

The lubricating base oil containing the alicyclic dicarboxylic acid diester compound of the present invention is a lubricating base oil for bearings having a low viscosity and a high viscosity index and good low temperature fluidity and evaporation resistance.

The lubricating base oil for bearings of the present invention has the following general formula (1):
[Wherein, R ¹ and R ² are the same or different and represent a linear alkyl group having 8 to 12 carbon atoms. ]
It contains the alicyclic dicarboxylic acid diester compound represented by these.

R ¹ and R ² in the general formula (1) are the same or different and are each a linear alkyl group having 8 to 12 carbon atoms, preferably a linear alkyl group having 8 to 10 carbon atoms. Groups are preferred.

Specific examples of R ¹ and R ² include an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, and an n-dodecyl group. Among these, an n-octyl group, an n-nonyl group, and an n-decyl group are preferable, and an n-nonyl group and an n-decyl group are particularly preferable.

The production method of the alicyclic dicarboxylic acid diester compound according to the present invention is not particularly limited to the production method as long as the target product is obtained. For example, a predetermined 1,3-cyclohexanedicarboxylic acid (or 1,3-cyclohexanedicarboxylic acid lower alkyl ester) and a predetermined alcohol component [linear aliphatic saturated alcohol having 8 to 12 carbon atoms] according to a conventional method. Prepared by an esterification reaction (or transesterification reaction) with heating and stirring in the presence or absence of an esterification catalyst (or transesterification catalyst), preferably in an inert gas atmosphere such as nitrogen Inactivation of isophthalic acid (or lower alkyl ester of isophthalic acid) and a predetermined alcohol component [linear aliphatic saturated alcohol having 8 to 12 carbon atoms], preferably nitrogen, etc. In a gas atmosphere, heating or stirring with or without an esterification catalyst (or transesterification catalyst) is performed. After etherification reaction (or transesterification reaction), in accordance with a conventional method the benzene ring, in a hydrogen atmosphere, a method of preparing by reacting nuclear hydrogenation in the presence of a hydrogenation catalyst, such as is also illustrated.

Specific examples of the linear aliphatic saturated alcohol having 8 to 12 carbon atoms include 1-octanol, 1-nonanol, 1-decanol, 1-undecanol and 1-dodecanol. Among these, 1-octanol, 1-nonanol and 1-decanol are preferable, and 1-nonanol and 1-decanol are particularly preferable.

The above linear aliphatic saturated alcohols can be used alone or in combination of two or more.

In the esterification reaction of the 1,3-cyclohexanedicarboxylic acid and the alcohol component, the alcohol component is, for example, 2 to 5 mol, preferably 2.01 to 1 mol of 1,3-cyclohexanedicarboxylic acid. It is preferably used in a range of 3 mol, particularly 2.02 to 2.5 mol (in other words, 1 to 2.5 equivalents, preferably 1.005 to 1 equivalent to 1 equivalent of 1,3-cyclohexanedicarboxylic acid). 0.5 equivalent, particularly preferably in the range of 1.01 to 1.25 equivalent).

Examples of the catalyst used in the esterification reaction include mineral acids, organic acids, Lewis acids and the like. More specifically, examples of the mineral acid include sulfuric acid, hydrochloric acid, and phosphoric acid, examples of the organic acid include p-toluenesulfonic acid and methanesulfonic acid, and examples of the Lewis acid include aluminum derivatives, tin derivatives, and titanium. Derivatives, lead derivatives, and zinc derivatives are exemplified, and one or more of these can be used in combination.

Among them, p-toluenesulfonic acid, tetraalkyl titanate having 3 to 8 carbon atoms, titanium oxide, titanium hydroxide, fatty acid tin having 3 to 12 carbon atoms, tin oxide, tin hydroxide, zinc oxide, zinc hydroxide, Lead oxide, lead hydroxide, aluminum oxide and aluminum hydroxide are particularly preferred. The amount used thereof is, for example, 0.01 to 5.0% by weight, preferably 0.01 to 4.0% by weight, particularly 0.01%, based on the total weight of the acid component and alcohol component which are raw materials for ester synthesis. It is recommended to use ~ 3.0% by weight.

The reaction temperature is, for example, 100 to 250 ° C. Usually, the esterification reaction is completed in 3 to 30 hours.

1,3-cyclohexanedicarboxylic acid, which is an acid component of the raw material of the ester, is not particularly limited, and those produced by known methods, commercially available products, reagents and the like can be used.

The transesterification reaction means an ester exchange reaction between the above alcohol component and 1,3-cyclohexanedicarboxylic acid lower alkyl ester acid. In performing the transesterification reaction, the alcohol component is, for example, 1,3 -Preferably it is 2.00-5.00 mol with respect to 1 mol of cyclohexane dicarboxylic acid lower alkyl esters, More preferably, it is 2.01-3.00 mol, It is especially 2.02-2.50 mol. Recommended.

Examples of the catalyst used in the transesterification reaction include Lewis acids and alkali metals. More specifically, examples of the Lewis acid include aluminum derivatives, tin derivatives, titanium derivatives, lead derivatives, and zinc derivatives. Examples of alkali metals include sodium alkoxide, potassium alkoxide, sodium hydroxide, and potassium hydroxide. It is possible to use one or more of these in combination.

Among them, tetraalkyl titanate having 3 to 8 carbon atoms, titanium oxide, titanium hydroxide, sodium alkoxide having 1 to 4 carbon atoms, sodium hydroxide, fatty acid tin having 3 to 12 carbon atoms, tin oxide, tin hydroxide, oxidation Zinc, zinc hydroxide, lead oxide, lead hydroxide, aluminum oxide and aluminum hydroxide are particularly preferred. The amount used is, for example, 0.01 to 5.0% by weight, preferably 0.02 to 4.0% by weight, particularly 0.03%, based on the total weight of the acid component and alcohol component which are raw materials for ester synthesis. It is recommended to use ~ 3.0% by weight.

Examples of the transesterification temperature include 100 to 250 ° C, and the reaction is usually completed in 3 to 30 hours.

The 1,3-cyclohexanedicarboxylic acid lower alkyl ester, which is the acid component of the raw material of this ester, is not particularly limited, and those produced by a known method, commercially available products, reagents and the like can be used.

Specific examples of 1,3-cyclohexanedicarboxylic acid lower alkyl esters include dimethyl 1,3-cyclohexanedicarboxylate, diethyl 1,3-cyclohexanedicarboxylate, di (isopropyl) 1,3-cyclohexanedicarboxylate, 1, And dibutyl 3-cyclohexanedicarboxylate.

In the esterification reaction or transesterification reaction, it is possible to use an entrainer or entraining agent such as benzene, toluene, xylene, and cyclohexane in order to promote the distillation of water or lower alcohol produced by the reaction.

In addition, when oxygen-containing organic compounds such as oxides, peroxides, and carbonyl compounds are produced by oxidative degradation of raw materials, produced esters and organic solvents (water entraining agents) during esterification or transesterification, heat resistance and weather resistance Adversely affect From the viewpoint of suppressing the adverse effects and safety, it is desirable to carry out the reaction under normal or reduced pressure in an inert gas atmosphere such as nitrogen gas or in an inert gas stream. After completion of the esterification reaction or transesterification reaction, excess raw material alcohol is usually distilled off under reduced pressure or normal pressure.

The reaction crude product of the alicyclic dicarboxylic acid diester compound obtained by the above reaction is usually purified by subsequent post-treatment. For example, treatment methods employed in this technical field such as catalyst deactivation treatment (neutralization treatment, base treatment, acid treatment, etc.), water washing treatment, liquid-liquid extraction, distillation (decompression, dehydration treatment), adsorption purification treatment, etc. Can be purified alone or in appropriate combination.

The base used for the base treatment is not particularly limited as long as it is a basic compound, and examples thereof include sodium hydroxide and sodium carbonate.

Examples of the adsorbent used for the adsorption purification treatment include activated carbon, activated clay, activated alumina, hydrotalcite, silica gel, silica alumina, zeolite, magnesia, calcia, and diatomaceous earth. They can be used alone or in combination of two or more.

Although the said process may be performed at normal temperature, it can also be performed by heating to about 40-95 degreeC.

As another method, isophthalic acid dialkyl ester [linear alkyl group having 8 to 12 carbon atoms] obtained by esterification reaction or transesterification reaction is prepared by hydrogenating the benzene ring in a hydrogen atmosphere according to a conventional method. A method of preparing by nuclear hydrogenation reaction in the presence of a fluorination catalyst is also exemplified.

As the hydrogenation catalyst, base metals such as iron, cobalt, nickel, copper and zinc, and noble metals such as rhodium, ruthenium, platinum and palladium can be used as the catalyst.

Base metals are not limited to zero-valent metals, but include inorganic compounds such as nitrates, sulfates, acetates, chlorides, bromides, oxides, hydroxides, acetylacetonate compounds, amine compounds, phosphine compounds, and carbonyl compounds. And the like.

Furthermore, in addition to the base metal, it can also be used as a modified catalyst to which one or more of boron, magnesium, aluminum, silicon, calcium, titanium, chromium, manganese, palladium, silver, tin, barium, molybdenum and the like are added.

The base metal catalyst can be used as it is, but is usually used as a sponge metal type catalyst or a carrier-supported type catalyst.

As the sponge metal type catalyst, those conventionally known or commercially available can be widely used, and examples thereof include a sponge nickel catalyst, a sponge cobalt catalyst, a sponge copper catalyst, a sponge iron catalyst, and a sponge zinc catalyst. A catalyst and a sponge cobalt catalyst are preferable, and a sponge nickel catalyst is particularly preferable from the viewpoint of high selectivity.

It is preferable to use the sponge metal type catalyst after the water is replaced with a suitable solvent from the water-containing state after development. The solvent used for replacing water is not particularly limited as long as it is compatible with water and does not adversely affect the hydrogenated product.

Conventionally supported or commercially available catalysts can be widely used as the carrier-supported catalyst, and examples thereof include a stabilized nickel catalyst, a sulfur-resistant nickel catalyst, a flake nickel catalyst, and a supported cobalt catalyst. Among these, a stabilized nickel catalyst and a sulfur-resistant nickel catalyst are preferable.

Examples of the carrier used for the carrier-supported catalyst include diatomaceous earth, pumice, activated carbon, graphite, silica gel, alumina, magnesium oxide, zirconium oxide, titanium oxide, zeolite, calcium carbonate, barium sulfate, and the like. Alumina and the like are preferable. These carriers can be used alone or in combination of two or more.

The supported amount of the base metal component of the carrier-supported catalyst is not particularly limited, but is usually about 1 to 90% by weight, preferably 20 to 80% by weight, as the base metal content, with respect to the total weight of the catalyst.

The method for producing these carrier-supported catalysts is not particularly limited, and can be easily produced by a conventionally known method such as an impregnation method or a coprecipitation method. Usually, a commercially available product can be used as it is or after being subjected to a suitable activation treatment such as a reduction treatment before use.

The form of these base metal catalysts is not particularly limited, and is suitably selected and used in the form of a powder, a molded catalyst, etc. according to the selected reaction method. The powdered catalyst is usually used for a batch or continuous suspension bed hydrogenation reaction, and the shaped catalyst is used for a fixed bed continuous hydrogenation reaction. Moreover, as a shaping | molding catalyst, although suitably selected by the magnitude | size of the reactor to be used, the column shape of diameter 2-6mm and height 2-8mm is preferable normally.

The amount of the base metal catalyst used in the hydrogenation reaction is usually in the range of 0.1 to 50% by weight, preferably 0.5 to 20% by weight, particularly preferably 1 to 10% by weight, based on the raw material. Is recommended. Within this range, the hydrogenation reaction can be carried out at an economically advantageous and sufficient reaction rate.

As the noble metal, conventionally known metals can be widely used. Specifically, various kinds of metals such as zero-valent metals, nitrates, sulfates, acetates, chlorides, bromides, oxides and hydroxides are contained. Examples include various metal-containing organic substances such as inorganic compounds and acetylacetonate compounds, and various metal-containing complex compounds such as amine complexes, phosphine complexes, and carbonyl compounds. These may be used alone or in combination of two or more as catalysts.

The noble metal catalyst can be used as it is, but usually it is preferably used as a carrier-supported catalyst. The carrier-supported catalyst may be a conventionally known or commercially available catalyst. Specifically, diatomaceous earth, pumice, carbon (graphite, activated carbon, etc.), silica gel, alumina, hydrotalcite, barium sulfate, magnesium sulfate, zeolite, Examples thereof include calcium carbonate and a mixture thereof. Of these, a carbon-supported catalyst is particularly preferable in terms of reactivity and selectivity.

The amount of the noble metal component supported on the carrier-supported catalyst is not particularly limited, but is usually about 0.1 to 10% by weight, preferably 0.5 to 5% by weight as the noble metal, based on the total weight of the catalyst. If the supported amount is less than 0.1% by weight, the activity per weight of the catalyst is lowered, and it is necessary to use a large amount of the catalyst, which is disadvantageous in terms of equipment and economy. In addition, a precious metal catalyst exceeding 10% by weight is not preferable because an improvement in the reaction rate commensurate with the amount of the supported precious metal cannot be obtained.

The amount of the noble metal catalyst used is not particularly limited, but is 0.01 to 5% by weight, more preferably 0.05 to 2% by weight as the noble metal with respect to the raw material.

The form of these noble metal catalysts is not particularly limited, and is suitably selected from powder form, tablet form and the like according to the selected reaction method. Specifically, a powder catalyst is suitably used for batch or continuous suspension bed reactions, and a tablet catalyst is suitably used for fixed bed reactions.

The reaction temperature of the hydrogenation reaction varies depending on the type of catalyst, the amount of catalyst, the hydrogen pressure, etc., and cannot be generally specified, but is preferably in the range of 50 to 280 ° C., particularly preferably 70 to 250 ° C. The hydrogen partial pressure during the hydrogenation reaction can be selected from a wide range, but is preferably in the range of 0.5 to 20 MPa, particularly preferably in the range of 1 to 10 MPa. The reaction time varies depending on the type of catalyst, the amount of catalyst and various conditions, but is usually about 1 to 12 hours.

As the reaction format, either a batch reaction or a continuous reaction may be used, and either a fluidized bed or a fixed bed can be selected.

After completion of the hydrogenation reaction, the catalyst is separated and removed by a known method such as filtration or centrifugation, and then the post-treatment step of the “esterified crude product” described above is performed as necessary. A dicarboxylic acid diester compound can be obtained.

The acid value of the alicyclic dicarboxylic acid diester compound is preferably 0.1 mgKOH / g or less, more preferably 0.05 mgKOH / g or less. When the acid value is 0.1 mgKOH / g or less, the heat resistance of the obtained alicyclic dicarboxylic acid diester compound tends to be further improved. In such a preferable range, the improvement of the heat-resistant oxidation stability of the lubricating oil of the present invention is more positively affected. As a method of reducing the acid value, a method of sufficiently advancing the reaction, a method of neutralizing and washing with an alkali component in a post-treatment step (a step of washing with the above alkaline aqueous solution (neutralization) and washing with water) And the like.

Specific examples of the alicyclic dicarboxylic acid diester compound represented by the general formula (1) include 1,3-cyclohexanedicarboxylic acid di (n-octyl), 1,3-cyclohexanedicarboxylic acid di (n-nonyl). ), 1,3-cyclohexanedicarboxylic acid di (n-decyl), 1,3-cyclohexanedicarboxylic acid (n-octyl) (n-nonyl), 1,3-cyclohexanedicarboxylic acid (n-octyl) (n-decyl) ), 1,3-cyclohexanedicarboxylic acid (n-octyl) (n-undecyl), 1,3-cyclohexanedicarboxylic acid (n-octyl) (n-undecyl), 1,3-cyclohexanedicarboxylic acid (n-octyl) (N-dodecyl), 1,3-cyclohexanedicarboxylic acid (n-nonyl) (n-decyl), 1,3-cyclohexanedica Examples include boronic acid (n-nonyl) (n-undecyl), 1,3-cyclohexanedicarboxylic acid (n-nonyl) (n-dodecyl), 1,3-cyclohexanedicarboxylic acid (n-decyl) (n-undecyl). It is done. Among them, 1,3-cyclohexanedicarboxylic acid di (n-octyl), 1,3-cyclohexanedicarboxylic acid di (n-nonyl), 1,3-cyclohexanedicarboxylic acid di (n-decyl), 1,3-cyclohexane Dicarboxylic acid (n-nonyl) (n-decyl) is preferable, and 1,3-cyclohexanedicarboxylic acid di (n-nonyl) and 1,3-cyclohexanedicarboxylic acid di (n-decyl) are particularly preferable.

The above alicyclic dicarboxylic acid diester compounds can be used alone or in combination of two or more.

The bearing lubricant base oil of the present invention is a bearing lubricant base oil containing the alicyclic dicarboxylic acid diester compound represented by the general formula (1).

The kinematic viscosity of the bearing lubricating base oil of the present invention (40 ° C.) is preferably in the range of 8~25mm ² / s, more preferably in the range of 10 to 20 mm ² / s. When the kinematic viscosity at 40 ° C. is less than 8 mm ² / s, a tendency to decrease the lubricating performance is recognized, and when it exceeds 25 mm ² / s, a tendency to increase the energy loss is recognized. In addition, the said kinematic viscosity is a value obtained by the method described in the postscript Example.

The viscosity index of the lubricating base oil for bearings of the present invention is preferably 140 or more, more preferably 150 or more. The higher the viscosity index, the better the viscosity-temperature characteristics. In addition, the said viscosity index is a value obtained by the method described in the postscript Example.

The low temperature fluidity of the lubricating base oil for bearings of the present invention can be evaluated by, for example, the pour point by a low temperature fluidity test. The pour point of the lubricating base oil of the present invention is preferably −5.0 ° C. or lower, more preferably −7.5 ° C. or lower. The lower the pour point, the better the low temperature fluidity. The pour point is a value obtained by a low temperature fluidity test described in Examples below.

The evaporation resistance of the lubricating base oil for bearings of the present invention can be evaluated using, for example, the temperature when the weight is reduced by 5% using a TG-DTA apparatus as an index. In the present invention, the temperature of 5% weight loss is preferably 265 ° C. or higher, more preferably 275 ° C. or higher. The higher the temperature of 5% weight loss, the better the evaporation resistance. The temperature of 5% weight loss is a value obtained by the evaporation resistance test described in Examples below.

The lubricating base oil for bearings of the present invention is suitably used as a lubricating base oil for hydrodynamic bearings or sintered oil-impregnated bearings.

The lubricating base oil for bearings of the present invention includes mineral oil (hydrocarbon oil obtained by refining petroleum), poly-α-olefin, polybutene, alkylbenzene, alkylnaphthalene, alicyclic hydrocarbon oil, and fisher as combined base oil. Synthetic hydrocarbon oils such as isomerized oils of synthetic hydrocarbons obtained by the Tropsch method, animal and vegetable oils, organic acid esters other than the alicyclic dicarboxylic acid diester compounds, polyalkylene glycols, polyvinyl ethers, polyphenyl ethers, alkylphenyl ethers In addition, at least one of combination base oils such as silicone oil can be used in combination as appropriate.

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. ) And a copolymer having a kinematic viscosity at 100 ° C. of 1.0 to 25 mm ² / s and a viscosity index of 100 or more, particularly a kinematic viscosity at 100 ° C. of 1.5 to 20 Those having a viscosity index of 120 mm or more at 0.0 mm ² / s are preferable.

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 those having a kinematic viscosity at 100 ° C. of 2.0 to 40 mm ² / s.

Examples of the alkyl benzene include monoalkyl benzene, dialkyl benzene, trialkyl benzene, and tetraalkyl benzene having a molecular weight of 200 to 450, which are substituted with a linear or branched alkyl group having 1 to 40 carbon atoms.

Examples of the alkyl naphthalene include monoalkyl naphthalene and dialkyl naphthalene 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 include fatty acid monoesters, aliphatic dibasic acid diesters, aliphatic dihydric alcohol diesters, polyol esters, and other esters.

The fatty acid monoester is 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. Is mentioned.

Aliphatic dibasic acid diesters 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-deca A full ester 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 may be mentioned.

Examples of the aliphatic dihydric alcohol diester and polyol ester include neopentyl glycol, 2,2-diethylpropanediol, 2-butyl-2-ethylpropandiol, trimethylolethane, trimethylolpropane, pentaerythritol, ditrimethylolpropane, diester Polyols of neopentyl structure such as pentaerythritol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octane Diol, 1,9-nonanediol, 1,10-decanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, 1,3-butanediol, 2-methyl-1,4-butane Diol, 1,4-pentanediol, -Methyl-1,5-pentanediol, 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, 2 Non-neopentyl-type polyols such as 4-diethyl-1,5-pentanediol, glycerin, polyglycerin, sorbitol and the like, and linear and / or branched saturated or unsaturated fatty acids having 3 to 22 carbon atoms It is possible to use full esters.

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 linear or branched chain having 3 to 22 carbon atoms. And esters with saturated or unsaturated fatty alcohols.

Examples of the polyalkylene glycol include a ring-opening polymer of alcohol and a linear or branched alkylene oxide having 2 to 4 carbon atoms. Examples of the alkylene oxide include ethylene oxide, propylene oxide, and butylene oxide. A polymer using one of these or a copolymer using a mixture of two or more can be used. A compound in which one or both hydroxyl groups are etherified can also be used. The kinematic viscosity of the polymer is preferably 5.0 to 1000 mm ² / s (40 ° C.), more preferably 5.0 to 500 mm ² / s (40 ° C.).

Polyvinyl ether is a compound obtained by polymerization of vinyl ether monomers, and monomers include 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 preferably 5.0 to 1000 mm ² / s (40 ° C.), more preferably 5.0 to 500 mm ² / s (40 ° C.).

Examples of polyphenyl ether include compounds having a structure in which meta positions of two or more aromatic rings are connected by an ether bond or a thioether bond. Specifically, bis (m-phenoxyphenyl) ether, m-bis ( m-phenoxyphenoxy) benzene, and thioethers (commonly referred to as C-ether) in which one or more of these oxygens 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 alkyl diphenyl ether substituted with one or more alkyl groups is particularly preferable.

Examples of the silicone oil include dimethyl silicone and methylphenyl silicone, and modified silicones such as long-chain alkyl silicone and fluorosilicone.

The content of the combined base oil in the lubricating base oil for bearings of the present invention is recommended to be 30% by weight or less, preferably 20% by weight or less, and particularly preferably 10% by weight or less.

The lubricating oil composition for bearings of the present invention is a composition containing the lubricating base oil for bearings of the present invention and an antioxidant.

Antioxidants include 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, , 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′-isobutylidenebis (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-dibenzoylresorcinol, -Tert-butylcatechol, 2,6-di-tert-butyl-4-ethylphenol, 2-hydroxy-4-methoxybenzophenone, 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 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-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) Propionate], diphenylamine, monobutyl (linear and branched) Diphenylamine (including chain), monopentyl (including linear and branched) diphenylamine, monohexyl (including linear and branched) diphenylamine, monoheptyl (including linear and branched), diphenylamine, monooctyl (linear and branched) Monoalkyldiphenylamines, such as diphenylamine, including mono (C ₄ -C ₉ alkyl) diphenylamine (ie, one of the two benzene rings of diphenylamine is mono-substituted with an alkyl group, particularly a C ₄ -C ₉ alkyl group). I.e. monoalkyl substituted diphenylamine), p, p'-dibutyl (including linear and branched) diphenylamine, p, p'-dipentyl (including linear and branched) diphenylamine, p, p'-dihexyl (including linear and branched) diphenylamine p, p'-diheptyl (including linear and branched) diphenylamine, p, p'-dioctyl (including linear and branched) diphenylamine, p, p'-dinonyl (including linear and branched) diphenylamine Di (alkylphenyl) amines such as p, p′-di (C ₄ -C ₉ alkylphenyl) amine (ie, each of the two benzene rings of diphenylamine is an alkyl group, particularly a C ₄ -C ₉ alkyl group, in a diphenylamine dialkyl substitution monosubstituted, those two alkyl groups are identical), a di (mono-C ₄ -C ₉ alkylphenyl) amine, the alkyl groups on one benzene ring different from the alkyl group on the other benzene ring, di-a (di -C ₄ -C ₉ alkylphenyl) amine, 4 on the two benzene rings Tsunoa Diphenylamines such as those in which at least one of the kill groups is different from the remaining alkyl groups; N-phenyl-1-naphthylamine, N-phenyl-2-naphthylamine, 4-octylphenyl-1-naphthylamine, 4-octylphenyl- Naphthylamines such as 2-naphthylamine; phenylene such as p-phenylenediamine, N-phenyl-N′-isopropyl-p-phenylenediamine, N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine Examples include diamines. Among these, in particular, p, p′-dioctyl (including linear and branched) diphenylamine, p, p′-dinonyl (including linear and branched) diphenylamine, N-phenyl-1-naphthylamine, and thiodipropion Examples thereof include thiodipropionic acid esters such as di (n-dodecyl) acid and di (n-octadecyl) thiodipropionate, and sulfur compounds such as phenothiazine.
Of these, phenol-based antioxidants and / or amine-based antioxidants are preferably recommended. These antioxidants can be used alone or in appropriate combination of two or more. The content of the antioxidant is usually 0.01 to 5% by weight, preferably 0.05 to 3% by weight, based on the lubricating base oil.

Here, in the present specification and claims, it is added by using the expression “to the lubricating base oil”, such as “0.01 to 5% by weight based on the lubricating base oil”. The range of the amount of the agent may be specified. The “lubricating base oil” used in this case is a bearing consisting of a lubricating base oil for bearings consisting only of the alicyclic dicarboxylic acid diester compound according to the present invention or a mixture of an alicyclic dicarboxylic acid diester compound and a combined base oil. It is used in the meaning of any lubricating base oil. In addition, in the example of “0.01 to 5% by weight with respect to the lubricating base oil”, it has the same meaning as 0.01 to 5 parts by weight with respect to 100 parts by weight of the lubricating base oil.

In order to improve the performance of the lubricating oil composition for bearings of the present invention, a metal detergent, an ashless dispersant, an oily agent, an antiwear agent, an extreme pressure agent, a metal deactivator, a rust inhibitor, At least one of additives such as a viscosity index improver, a pour point depressant, an antifoaming agent, a hydrolysis inhibitor, a thickener, a corrosion inhibitor, and a hue stabilizer can be appropriately blended. Although these compounding quantities are not specifically limited as long as there exists an effect of this invention, The specific example is shown below.

Metal detergents include Ca-petroleum sulfonate, overbased Ca-petroleum sulfonate, Ca-alkyl benzene sulfonate, overbased Ca-alkyl benzene sulfonate, Ba-alkyl benzene sulfonate, over-based Ba-alkyl benzene sulfonate. Phonate, Mg-alkylbenzenesulfonate, overbased Mg-alkylbenzenesulfonate, Na-alkylbenzenesulfonate, overbased Na-alkylbenzenesulfonate, Ca-alkylnaphthalenesulfonate, overbased Ca- Metal sulfonates such as alkyl naphthalene sulfonates, Ca-phenates, overbased Ca-phenates, Ba-phenates, overbased Ba-phenates and other metal phenates, Ca-salicylate, overbased Ca- Metal salicylates such as resylate, Ca-phosphonates, overbased Ca-phosphonates, Ba-phosphonates, overbased Ba-phosphonates and other metal phosphonates, overbased Ca-carboxylates, etc. Can be used. When a metal detergent is used, it is usually desirable to add about 1 to 10% by weight, preferably about 2 to 7% by weight, based on the lubricating base oil.

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

Examples of oily agents include aliphatic saturated and unsaturated monocarboxylic acids such as stearic acid and oleic acid, polymerized fatty acids such as dimer acid and hydrogenated dimer acid, hydroxy fatty acids such as ricinoleic acid and 12-hydroxystearic acid, lauryl alcohol, Aliphatic saturated and unsaturated monoalcohols such as oleyl alcohol, aliphatic saturated and unsaturated monoamines such as stearylamine and oleylamine, aliphatic saturated and unsaturated monocarboxylic amides such as lauric acid amide, oleic acid amide, batyl alcohol, Glycerol ethers such as chimyl alcohol and ceralkyl alcohol, alkyl or alkenyl polyglyceryl ethers such as lauryl polyglyceryl ether and oleyl polyglyceryl ether, di (2-ethylhexyl) monoethanolamine , Poly (alkylene oxide) alkyl or alkenyl amines such as diisotridecyl monoethanolamine adduct and the like. These oil agents may be used alone or in combination, and when used, they are usually 0.01 to 5% by weight, preferably about 0.1 to 3% by weight, based on the lubricating base oil. It is desirable to add.

Antiwear / extreme pressure agents include tricresyl phosphate, cresyl diphenyl phosphate, alkylphenyl phosphates, phosphate esters such as tributyl phosphate, dibutyl phosphate, tributyl phosphate, dibutyl phosphate, triisopropyl phosphate, etc. Phosphorous esters of these and their amine salts such as phosphorus, sulfurized fats and oils, sulfurized fatty acids such as sulfurized oleic acid, sulfur such as dibenzyl disulfide, sulfurized olefin, dialkyl disulfide, Zn-dialkyldithiophosphate, 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 used, usually 0.01 to 10% by weight, preferably about 0.1 to 5% by weight, based on the lubricating base oil. It is desirable to add.

Examples of the metal deactivator include benzotriazole-based, thiadiazole-based, and gallic acid ester-based compounds. These metal deactivators may be used alone or in combination, and when used, they are usually 0.01 to 0.4% by weight, preferably 0.01 to 0%, based on the lubricating base oil. It is desirable to add about 2% by weight.

Antirust agents include alkyl or alkenyl succinic acid derivatives such as dodecenyl succinic acid half ester, octadecenyl succinic anhydride, dodecenyl succinic acid amide, sorbitan monooleate, glycerin monooleate, pentaerythritol monooleate Partial alcohol ester, Ca-petroleum sulfonate, Ca-alkyl benzene sulfonate, Ba-alkyl benzene sulfonate, Mg-alkyl benzene sulfonate, Na-alkyl benzene sulfonate, Zn-alkyl benzene sulfonate, Ca-alkyl naphthalene sulphate Examples thereof include metal sulfonates such as phonates, amines such as rosinamine and N-oleylsarcosine, dialkyl phosphiteamine salts, and the like. These rust inhibitors may be used alone or in combination, and when used, they are usually 0.01 to 5% by weight, preferably about 0.05 to 2% by weight, based on the lubricating base oil. It is desirable to add.

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

Examples of the pour point depressant include a condensate of chlorinated paraffin and alkylnaphthalene, a condensate of chlorinated paraffin and phenol, polyalkyl methacrylate, polyalkylstyrene, polybutene and the like as the viscosity index improvers described above. These pour point depressants may be used alone or in combination, and when used, they are usually 0.01 to 5% by weight, preferably 0.1 to 3% by weight, based on the lubricating base oil. It is desirable to add a certain amount.

As the antifoaming agent, liquid silicone is suitable, and when it is used, the amount added is usually about 0.0005 to 0.01% by weight based on the lubricating base oil.

Hydrolysis inhibitors include alkyl glycidyl ethers, alkyl glycidyl esters, alkylene glycol glycidyl ethers, cycloaliphatic epoxies, epoxy compounds such as phenyl glycidyl ether, di-tert-butylcarbodiimide, 1,3-di- A carbodiimide compound such as p-tolylcarbodiimide can be used, and is usually about 0.05 to 2% by weight based on the lubricating base oil.

A “grease” can be obtained by appropriately combining a thickener with the lubricating base oil for bearings of the present invention.

Thickeners include soaps such as sodium soap, lithium soap, calcium soap, calcium complex soap, aluminum complex soap, lithium complex soap, bentonite, silica airgel, sodium terephthalate, urea compound, polytetrafluoroethylene, Non-soap type such as boron nitride is exemplified.

Examples of the metal soap thickener include an aliphatic carboxylic acid lithium salt having a hydroxyl group such as lithium-12-hydroxystearate, an aliphatic carboxylic acid lithium salt such as lithium stearate, or a mixture 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. Specifically, a complex lithium soap or A composite aluminum soap is exemplified.

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

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

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

Examples of the corrosion inhibitor include sodium sulfonate and sorbitan ester, and usually about 0.1 to 3.0% by weight is added to the lubricating base oil.

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

As described above, the lubricating base oil for bearings of the present invention thus obtained has a low viscosity, a high viscosity index and good evaporation resistance while maintaining good low-temperature fluidity. Suitable as a lubricating base oil.

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. The measuring method of each characteristic in an Example and a comparative example is as follows. Reagents were used for compounds not specifically mentioned.

<Compound>
Raw material 1,3-cyclohexanedicarboxylic acid (Tokyo Chemical Industry Co., Ltd.)
・ Hexahydrophthalic anhydride: “Licacid HH” (manufactured by Shin Nippon Chemical Co., Ltd.)
・ 1,4-Cyclohexanedicarboxylic acid: “Licacid CHDA” (manufactured by Shin Nippon Chemical Co., Ltd.)
1-octanol: “Conol 10WS” (manufactured by Shin Nippon Rika Co., Ltd.)
・ 1-Nonanol (manufactured by Tokyo Chemical Industry Co., Ltd.)
・ 1-Decanol (manufactured by Tokyo Chemical Industry Co., Ltd.)
Ester compound, diisodecyl adipate: "Sansosizer DIDA" (manufactured by Shin Nippon Chemical Co., Ltd.)
-Dibasic acid sebacate (2-ethylhexyl): “Sansosizer DOS” (manufactured by Shin Nippon Rika)
Antioxidant / Phenolic Antioxidant 4,4′-Methylenebis (2,6-di-tert-butylphenol) (manufactured by Tokyo Chemical Industry Co., Ltd.) Hereinafter abbreviated as “MBDBP”.
Amine-based antioxidant p, p′-dioctyldiphenylamine: “VANLUBE 81” (manufactured by Vanderbilt Chemicals, LLC), hereinafter abbreviated as “DODPA”.

[Alicyclic dicarboxylic acid diester compound]
<Acid value (AV)>
The measurement was performed according to JIS K2501 (2003).

<Analysis by gas chromatography (GC)>
The composition analysis of the alicyclic dicarboxylic acid diester compound was performed by gas chromatography (GC).
[Measurement condition]
Equipment: GC-2014 manufactured by Shimadzu Corporation
Column: TC-5 manufactured by GL Science Co., Ltd. 30mx0.25mmx0.25μm
Column temperature: 60 to 300 ° C. (temperature increase rate 10 ° C./min)
Injection temperature / detector temperature: 305 ° C / 305 ° C
Detector: FID
Carrier gas: helium gas linear velocity: 27.4 cm / sec
Sample: 1% by weight acetone solution injection volume: 1 μl
Quantification: Quantification was performed using di (2-ethylhexyl) phthalate as an internal standard substance.

[Measurement of physical properties of lubricating base oil]
<Measuring method of kinematic viscosity and viscosity index>
Based on JIS K2283 (2000), the kinematic viscosity at 40 ° C. and 100 ° C. was measured, and the viscosity index was calculated from the obtained measured values.

<Measurement method of low temperature fluidity test (pour point)>
The pour point was measured according to JIS K2269 (1987).

<Evaporation resistance test>
About 10 mg of lubricating base oil for bearings is precisely weighed (to the third decimal place) and set in a TG-DTA device (device name: EXSTAR 6000 series, TG / DTA6200 manufactured by SII Nano Technology). Under the measurement conditions, the temperature when the weight decreased by 5% from the initial weight (temperature at which the weight decreased by 5%) was used as an index of evaporation resistance. It is evaluated that the evaporation resistance is excellent when the temperature of 5% weight loss is 265 ° C. or higher.
[Measurement condition]
Temperature increase rate: 10 ° C./min Flowing nitrogen amount: 200 ml / min Measurement start temperature: 50 ° C.

[Example 1]
In a 1 liter four-necked flask equipped with a stirrer, thermometer, and water fraction receiver with condenser, 1.26 mol of 1,3-cyclohexanedicarboxylic acid, 2.77 mol of 1-octanol as a raw alcohol, 20 g of xylene, ester After 0.15 g of tin oxide was charged as a catalyst for conversion and the atmosphere in the flask was replaced with nitrogen, the temperature was gradually raised to 220 ° C. Esterification reaction is carried out by adjusting the degree of pressure reduction so that xylene is refluxed while removing the produced water distilled off with the water fractionator with the theoretical amount of water produced (45.4 g) as the target. The reaction was continued until 0.5 mgKOH / g or less. After completion of the reaction, xylene and the remaining raw material alcohol were removed by distillation to obtain an esterified crude product. Next, after neutralizing with an aqueous solution of caustic soda equivalent to twice the acid value of the obtained esterified crude product, washing with water was repeated until the washing water became neutral. Activated carbon was added to the obtained esterified crude product and subjected to adsorption purification treatment, followed by filtration to obtain 1,3-cyclohexanedicarboxylic acid di (n-octyl). The obtained alicyclic dicarboxylic acid diester compound had an acid value of 0.01 mgKOH / g or less. As a result of GC analysis, the purity was 98.6% by weight. Table 1 shows physical properties when the alicyclic dicarboxylic acid diester compound (hereinafter referred to as “1,3-CH / n-C ₈ ”) was evaluated as a lubricating base oil for bearings.

[Example 2]
1,3-cyclohexanedicarboxylic acid di (n-nonyl) was obtained in the same manner as in Example 1 except that 1-octanol was changed to 2.77 mol of 1-nonanol. The obtained alicyclic dicarboxylic acid diester compound had an acid value of 0.01 mgKOH / g or less. As a result of GC analysis, the purity was 99.4% by weight. Table 1 shows the physical properties when the alicyclic dicarboxylic acid diester compound (hereinafter referred to as “1,3-CH / n-C ₉ ”) was evaluated as a lubricating base oil for bearings.

[Example 3]
Di (n-decyl) 1,3-cyclohexanedicarboxylate was obtained in the same manner as in Example 1 except that 1-octanol was changed to 2.77 mol of 1-decanol. The obtained alicyclic dicarboxylic acid diester compound had an acid value of 0.01 mgKOH / g or less. As a result of GC analysis, the purity was 98.4% by weight. Table 1 shows physical properties when the alicyclic dicarboxylic acid diester compound (hereinafter referred to as “1,3-CH / n-C ₁₀ ”) was evaluated as a lubricating base oil for bearings.

[Example 4]
An alicyclic dicarboxylic acid diester compound was obtained in the same manner as in Example 1 except that 1-octanol was changed to 1.39 mol of 1-nonanol and 1.39 mol of 1-decanol. The obtained alicyclic dicarboxylic acid diester compound had an acid value of 0.01 mgKOH / g or less. Moreover, as a result of GC analysis, it was as follows.
1,3-cyclohexanedicarboxylic acid di (n-nonyl): 21.3% by weight
1,3-cyclohexanedicarboxylic acid (n-nonyl) (n-decyl): 50.5% by weight
1,3-cyclohexanedicarboxylic acid di (n-decyl): 27.7% by weight
Table 1 shows the physical properties when the alicyclic dicarboxylic acid diester compound (hereinafter referred to as “1,3-CH / n—C ₉ , C ₁₀ ”) was evaluated as a lubricating base oil for bearings.

[Example 5]
A bearing lubricating oil composition was prepared by mixing 100 parts by weight of 1,3-CH / n-C ₁₀ as a lubricating base oil for bearings and 0.5 part by weight of MBDBP as an antioxidant at 60 ° C. Table 1 shows the physical properties when the bearing lubricating oil composition was evaluated.

[Example 6]
A bearing lubricating oil composition was prepared by mixing 100 parts by weight of 1,3-CH / n-C ₁₀ as a lubricating base oil for bearings and 0.5 part by weight of DODPA as an antioxidant at 60 ° C. Table 1 shows the physical properties when the bearing lubricating oil composition was evaluated.

[Example 7]
A bearing lubricating oil composition is prepared by mixing 100 parts by weight of 1,3-CH / n-C ₁₀ as a lubricating base oil for bearings and 0.5 parts by weight of MBDBP and 0.5 parts by weight of DODPA as antioxidants at 60 ° C. did. Table 1 shows the physical properties when the bearing lubricating oil composition was evaluated.

[Comparative Example 1]
1.26 mol of hexahydrophthalic anhydride, 1.77 mol of 1-octanol as raw material alcohol, 20 g of xylene, esterification in a 1 liter four-necked flask equipped with a stirrer, thermometer, and water fractionator with a condenser After 0.15 g of tin oxide was charged as a catalyst and the inside of the flask was purged with nitrogen, the temperature was gradually raised to 220 ° C. The esterification reaction is carried out by adjusting the degree of pressure reduction so that xylene is refluxed while removing the produced water distilled off with the moisture fraction receiver with the theoretical amount of water produced (22.7 g) as the target. The reaction was continued until 0.5 mgKOH / g or less. After completion of the reaction, xylene and the remaining raw material alcohol were removed by distillation to obtain an esterified crude product. Next, after neutralizing with an aqueous solution of caustic soda equivalent to twice the acid value of the obtained esterified crude product, washing with water was repeated until the washing water became neutral. Activated carbon was added to the resulting esterified crude product and subjected to adsorption purification treatment, followed by filtration to obtain 1,2-cyclohexanedicarboxylic acid di (n-octyl). The obtained alicyclic dicarboxylic acid diester had an acid value of 0.01 mgKOH / g or less. As a result of GC analysis, the purity was 98.6% by weight. Table 2 shows physical properties when the alicyclic dicarboxylic acid diester (hereinafter referred to as “1,2-CH / n-C ₈ ”) was evaluated as a lubricating base oil for bearings.

[Comparative Example 2]
Di (n-decyl) 1,2-cyclohexanedicarboxylate was obtained in the same manner as in Comparative Example 1 except that 1-octanol was changed to 2.77 mol of 1-decanol. The obtained alicyclic dicarboxylic acid diester had an acid value of 0.01 mgKOH / g or less. As a result of GC analysis, the purity was 98.5% by weight. Table 2 shows physical properties when the alicyclic dicarboxylic acid diester (hereinafter referred to as “1,2-CH / n-C ₁₀ ”) was evaluated as a lubricating base oil for bearings.

[Comparative Example 3]
Di (n-octyl) 1,4-cyclohexanedicarboxylate was obtained in the same manner as in Example 1, except that the hexahydrophthalic anhydride was changed to 1.26 mol of 1,4-cyclohexanedicarboxylic acid. The obtained alicyclic dicarboxylic acid diester had an acid value of 0.01 mgKOH / g or less. As a result of GC analysis, the purity was 98.6% by weight. Table 2 shows the physical properties when the alicyclic dicarboxylic acid diester (hereinafter referred to as “1,4-CH / n-C ₈ ”) was evaluated as a lubricating base oil for bearings.

[Comparative Example 4]
Table 2 shows each physical property value when diisodecyl adipate (DIDA) was evaluated as a lubricating base oil for bearings.

[Comparative Example 5]
Table 2 shows each physical property value when di (2-ethylhexyl) sebacate (DOS) was evaluated as a lubricating base oil for bearings.

As can be seen from Table 1, the lubricating base oil for bearings described in Examples 1 to 7 has a low viscosity, a viscosity index of 140 or more, a low pour point of −7.5 ° C. or less, and an index of evaporation resistance. A certain 5% weight loss temperature is as high as 265 ° C or higher.

On the other hand, as can be seen from Table 2, the lubricating base oils described in Comparative Examples 1 and 3 to 5 have a low 5% weight loss temperature of 260 ° C. or lower, and the lubricating base oil described in Comparative Example 2 is 5 The temperature of% weight loss is as high as 265 ° C. or higher, but the viscosity index is as low as 122.

From the above, the alicyclic dicarboxylic acid diester compound according to the present invention achieves low viscosity, high viscosity index and excellent low-temperature fluidity, and at the same time has excellent evaporation resistance and is suitable for lubricating base oil for bearings. Can be used.

The bearing lubricant base oil of the present invention has a low viscosity, a high viscosity index, and good evaporation resistance while maintaining good low-temperature fluidity. Can be used. In particular, it is suitably used as a lubricating base oil for hydrodynamic bearings or sintered oil-impregnated bearings.

Claims (4)

General formula (1)
[Wherein, R ¹ and R ² are the same or different and represent a linear alkyl group having 8 to 12 carbon atoms. ]
A lubricating base oil for bearings containing an alicyclic dicarboxylic acid diester compound represented by: The bearing lubricant base oil according to claim 1, wherein the bearing lubricant base oil is a hydrodynamic bearing lubricant base oil or a sintered oil-impregnated bearing lubricant base oil. A bearing lubricating oil composition comprising the bearing lubricating base oil according to claim 1 or 2 and an antioxidant. The lubricating oil composition for bearings according to claim 3, wherein the antioxidant is a phenol-based antioxidant and / or an amine-based antioxidant.