JP6757278B2 - Conductive lubricating oil composition - Google Patents

Description

The present invention relates to a conductive lubricating oil composition.

In recent years, precision equipment such as personal computers and other peripheral equipment have become more sophisticated and smaller. The lubricating oil composition used for the high-speed rotating portion of such a precision instrument may be required to have conductivity in order to suppress the charge of static electricity generated by the friction of the high-speed rotating portion. Examples of the lubricating oil composition imparted with conductivity include an ester-based base oil and a conductive lubricant for dynamic bearings including an anionic, cationic, amphoteric or non-ionic antistatic agent. It has been proposed (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2001-115180

However, when nonionic (nonionic) and ionic (anionic, cationic, amphoteric) antistatic agents are used, the conductivity of the lubricating oil composition depends on the amount of water contained in the lubricating oil composition. There are problems such as fluctuations in sex. Further, depending on the type of antistatic agent, the stability at high temperature is insufficient, and there is a problem that the conductivity greatly fluctuates when the lubricating oil composition is used for a long period of time.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a conductive lubricating oil composition having excellent conductivity with time.

As a result of diligent research to solve the above problems, the present inventors, when a specific base oil and a specific conductivity-imparting agent are combined, the change in conductivity is suppressed and stable for a long period of time. The present invention has been completed by finding that a conductive lubricating oil composition can be obtained. That is, the present invention is as follows.

<1> At least one lubricating oil base oil selected from the group consisting of fatty acid monoester base oil and ether ester base oil, potassium trifluoromethanesulfonate, lithium trifluoromethanesulfonate, lithium nonafluorobutanesulfonate, bis ( At least one conductivity-imparting agent selected from the group consisting of trifluoromethanesulfonyl) imide lithium, bis (trifluoromethanesulfonyl) imide potassium, and tris (trifluoromethanesulfonyl) methidolithium was added to the total mass of the composition from 0.01 to 0.01. A conductive lubricating oil composition containing 1% by mass and having a rate of change in conductivity of 10% or less after storage at 120 ° C. for 200 hours.

<2> Further, at least one antioxidant selected from the group consisting of a diphenylamine compound, an alkylated phenyl-α-naphthylamine, a hindered phenol compound, and phosphite is added at 0.05 to 2 to the total mass of the composition. The conductive lubricating oil composition according to <1>, which contains% by mass.

<3> The lubricating oil base oil is a compound represented by any of the following general formulas (1), (2), or general formula (3), according to <1> or <2>. Conductive lubricating oil composition.

[In the general formula (1), R ¹ represents a linear or branched alkyl group having 8 to 16 carbon atoms or a heteroalkyl group containing an oxygen atom, and n represents an integer of 5 to 11. ]

[In the general formula (2), R ² represents a linear or branched alkyl group having 8 to 16 carbon atoms or a heteroalkyl group containing an oxygen atom, and n represents an integer of 5 to 11. ]

[In the general formula (3), A ¹ represents a linear or branched alkylene group or a heteroalkylene group having 8 to 15 carbon atoms, and R ³ and R ⁴ independently represent 6 to 6 carbon atoms. Represents 10 linear or branched alkyl groups. ]

According to the present invention, there is provided a conductive lubricating oil composition having excellent conductivity with time.

By using such a conductive lubricating oil composition for a sliding portion and a rotating portion of a precision instrument, it is possible to achieve excellent lubricity while stably ensuring conductivity.

Hereinafter, the conductive lubricating oil composition of the present invention will be described in detail. In the present specification, "~" representing a numerical range represents a range including numerical values described as its upper limit and lower limit, respectively. Further, when the unit is described only for the upper limit value in the numerical range represented by "~", it means that the lower limit value is also the same unit.

The conductive lubricating oil composition of the present invention comprises at least one lubricating oil base oil selected from the group consisting of fatty acid monoester base oil and ether ester base oil, potassium trifluoromethanesulfonate, lithium trifluoromethanesulfonate, and nona. 0.01 at least one conductivity-imparting agent selected from the group consisting of lithium fluorobutane sulfonate, bis (trifluoromethanesulfonyl) imide lithium, bis (trifluoromethanesulfonyl) imide potassium, and tris (trifluoromethanesulfonyl) methidolithium. It contains ~ 1% by mass, and the rate of change in conductivity after storage at 120 ° C. for 200 hours is 10% or less.
The conductive lubricating oil composition of the present invention may contain components other than the above, if necessary.

As a result of diligent research to solve the above problems, the present inventors have made at least one lubricating oil base oil selected from the group consisting of fatty acid monoester base oil and ether ester base oil, and potassium trifluoromethanesulfonate. , Lithium trifluoromethanesulfonate, lithium nonafluorobutanesulfonate, bis (trifluoromethanesulfonyl) imide lithium, bis (trifluoromethanesulfonyl) imide potassium, tris (trifluoromethanesulfonyl) methidolithium, at least one conductive material selected from the group. The present invention has been completed by finding that a conductive lubricating oil composition having excellent conductivity and stability over time can be obtained by combining with a sex-imparting agent. Hereinafter, the conductive lubricating oil composition of the present invention will be specifically described.

<Conductivity imparting agent>
The conductive lubricating oil composition of the present invention comprises potassium trifluoromethanesulfonate, lithium trifluoromethanesulfonate, lithium nonafluorobutanesulfonate, bis (trifluoromethanesulfonyl) imidelithium, bis (trifluoromethanesulfonyl) imidepotassium, and tris. Contains 0.01 to 1% by mass of at least one conductivity-imparting agent selected from the group consisting of (trifluoromethanesulfonyl) methidolithium.

Among the above-mentioned conductivity-imparting agents, lithium trifluoromethanesulfonate, lithium nonafluorobutanesulfonate, bis (trifluoromethanesulfonyl) imidelithium, or bis (trifluoromethanesulfonyl) imidepotassium are preferable, and lithium nonafluorobutanesulfonate, Bis (trifluoromethanesulfonyl) imide lithium or bis (trifluoromethanesulfonyl) imide potassium is more preferable, bis (trifluoromethanesulfonyl) imide lithium or bis (trifluoromethanesulfonyl) imide potassium is more preferable, and bis (trifluoromethanesulfonyl) imide lithium. Is particularly preferable.

The content of the conductivity-imparting agent is 0.01 to 1% by mass, preferably 0.01 to 0.5% by mass, and 0.01 to 0.1% by mass with respect to the total mass of the composition. Is more preferable.
When the content of the conductivity-imparting agent is 0.01% by mass or more, the conductivity of the lubricating oil composition is improved, and when it is 1% by mass or less, the conductivity commensurate with the content can be imparted.
The conductivity-imparting agent may be contained alone or in combination of two or more. When two or more kinds are contained in combination, the total amount is preferably within the above range.

<Lubricating oil base oil>
The conductive lubricating oil composition of the present invention contains at least one lubricating oil base oil selected from the group consisting of fatty acid monoester base oils and ether ester base oils.
In the present specification, the fatty acid monoester base oil is a reaction product obtained by an esterification reaction of a monohydric alcohol and a monovalent carboxylic acid, and means an ester oil having 21 to 41 carbon atoms.
In the present specification, the ether ester base oil is a reaction product obtained by an esterification reaction of a monohydric or divalent alcohol and a monovalent carboxylic acid, and has 20 to 20 carbon atoms having at least one ether bond. Means 35 ester oils. The ether bond possessed by the ester oil is introduced by the fact that at least one of the monohydric or divalent alcohol and the monovalent carboxylic acid is a compound having an ether bond.

Examples of the lubricating oil base oil include compounds represented by the following general formula (1), general formula (2), or general formula (3).

In the general formula (1), R ¹ represents a linear or branched alkyl group having 8 to 16 carbon atoms or a heteroalkyl group containing an oxygen atom. The heteroalkyl group containing an oxygen atom represented by R ¹ may contain one oxygen atom or a plurality of oxygen atoms.
In the general formula (1), n represents an integer of 5 to 11.

In the general formula (2), R ² represents a linear or branched alkyl group having 8 to 16 carbon atoms or a heteroalkyl group containing an oxygen atom. The heteroalkyl group containing an oxygen atom represented by R ² may contain one oxygen atom or a plurality of oxygen atoms.
In the general formula (2), n represents an integer of 5 to 11.

In the general formula (3), A ¹ represents a linear or branched alkylene group or a heteroalkylene group having 8 to 15 carbon atoms. The heteroalkylene group represented by A ¹ may contain one heteroatom or may contain a plurality of heteroatoms. Examples of the hetero atom include an oxygen atom and a nitrogen atom.
In the general formula (3), R ³ and R ⁴ independently represent linear or branched alkyl groups having 6 to 10 carbon atoms.

<Antioxidant>
The conductive lubricating oil composition of the present invention preferably contains at least one antioxidant.
Antioxidants include, for example, antioxidants such as diphenylamine compounds, alkylated phenyl-α-naphthylamines, hindered phenolic compounds, and phosphite. From the viewpoint of maintaining a low rate of change in conductivity of the conductive lubricating oil composition at high temperatures, the above-mentioned antioxidant is preferably used.

Examples of the diphenylamine compound include a compound represented by the following general formula (4).

In the general formula (4), R ⁵ and R ⁶ independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 16 carbon atoms.
R ⁵ and R ⁶ may be the same or different.

Specific examples of the linear or branched alkyl group represented by R ⁵ and ^{R 6} are methyl group, ethyl group, n- propyl group, an isopropyl group, n- butyl group, isobutyl group, tert- butyl group, n-Pentyl group, Isopentyl group, Neopentyl group, tert-Pentyl group, 2-Methylbutyl group, n-Hexyl group, Isohexyl group, 3-Methylpentyl group, Ethylbutyl group, n-Heptyl group, 2-Methylhexyl group, n -Octyl group, 2-ethylhexyl group, 3-methylheptyl group, n-nonyl group, methyloctyl group, ethylheptyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tetradecyl group and the like. Be done.

R ⁵ and R ⁶ are preferably hydrogen atoms or linear or branched alkyl groups having 3 to 9 carbon atoms, and more preferably hydrogen atoms or linear or branched alkyl groups having 4 to 8 carbon atoms. is there.

The above diphenylamine compound may be contained alone or in combination of two or more.

Examples of the alkylated phenyl-α-naphthylamine include compounds represented by the following general formula (5).

In the general formula (5), R ⁷ represents a linear or branched alkyl group having 1 to 16 carbon atoms.

Specific examples of the linear or branched alkyl group represented by R ⁷ include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group and n-pentyl group. Group, isopentyl group, neopentyl group, tert-pentyl group, 2-methylbutyl group, n-hexyl group, isohexyl group, 3-methylpentyl group, ethylbutyl group, n-heptyl group, 2-methylhexyl group, n-octyl group , 2-Ethylhexyl group, 3-Methylheptyl group, n-nonyl group, methyloctyl group, ethylheptyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tetradecyl group and the like.

R ⁷ is preferably a linear or branched alkyl group having 4 to 8 carbon atoms.

Alkylated phenyl-α-naphthylamine may be contained alone or in combination of two or more.

Examples of the hindered phenol compound include compounds represented by the following general formula (6), general formula (7) or general formula (8).

In the general formula (6), R ⁸ , R ⁹ , R ¹¹ and R ¹² each independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 12 carbon atoms.
R ⁸ , R ⁹ , R ¹¹ and R ¹² may be the same or different.

Specific examples of the linear or branched alkyl groups represented by R ⁸ , R ⁹ , R ¹¹ and R ¹² include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group and isobutyl. Group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, tert-pentyl group, 2-methylbutyl group, n-hexyl group, isohexyl group, 3-methylpentyl group, ethylbutyl group, n-heptyl group, 2-Methylhexyl group, n-octyl group, 2-ethylhexyl group, 3-methylheptyl group, n-nonyl group, methyloctyl group, ethylheptyl group, n-decyl group, n-undecyl group, n-dodecyl group, etc. Can be mentioned.

R ⁸ , R ⁹ , R ¹¹ and R ¹² are preferably hydrogen atoms or linear or branched alkyl groups having 4 to 8 carbon atoms.

In the general formula (6), R ¹⁰ represents an alkylene group having 1 to 5 carbon atoms.

Specific examples of the alkylene group represented by R ¹⁰ include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group and the like.

R ¹⁰ is preferably an alkylene group having 1 to 4 carbon atoms.

In the general formula (7), R ¹³ and R ¹⁴ each independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 12 carbon atoms.
R ¹³ and R ¹⁴ may be the same or different.

Specific examples of the alkyl group of the linear or branched chain represented by R ¹³ and R ¹⁴ include the same ones as R ⁸ , R ⁹ , R ¹¹ and R ^{12 in} the general formula (6).

R ¹³ and R ¹⁴ are preferably hydrogen atoms or linear or branched alkyl groups having 4 to 8 carbon atoms.

In the general formula (7), n represents an integer of 1 to 4, and is preferably an integer of 1 to 3.

In the general formula (8), R ¹⁵ , R ¹⁶ and R ¹⁷ each independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 12 carbon atoms.
R ¹⁵ , R ¹⁶ and R ¹⁷ may be the same or different.

Specific examples of the linear or branched alkyl groups represented by R ¹⁵ , R ¹⁶ and R ¹⁷ are the same as those of R ⁸ , R ⁹ , R ¹¹ and R ^{12 in} the general formula (6). Can be mentioned.

R ¹⁵ and R ¹⁶ are preferably hydrogen atoms or linear or branched alkyl groups having 4 to 8 carbon atoms, and R ¹⁷ is preferably hydrogen atoms or linear or branched alkyl groups having 1 to 4 carbon atoms. It is the basis.

The hindered phenol compound may be contained alone or in combination of two or more.

Examples of the phosphite include a compound represented by the following general formula (9).

In the general formula (9), R ¹⁸ and R ¹⁹ each independently represent a linear or branched alkyl group having 1 to 20 carbon atoms.
R ¹⁸ and R ¹⁹ may be the same or different.

Specific examples of the linear or branched alkyl groups represented by R ¹⁸ and R ¹⁹ include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, and the like. n-Pentyl group, Isopentyl group, Neopentyl group, tert-Pentyl group, 2-Methylbutyl group, n-Hexyl group, Isohexyl group, 3-Methylpentyl group, Ethylbutyl group, n-Heptyl group, 2-Methylhexyl group, n -Octyl group, 2-ethylhexyl group, 3-methylheptyl group, n-nonyl group, methyloctyl group, ethylheptyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tetradecyl group, etc. Can be mentioned.

R ¹⁸ R ¹⁹ is preferably a linear or branched alkyl group having 2 to 6 carbon atoms.

The phosfite may be contained alone or in combination of two or more.

The content of the antioxidant is preferably 0.05 to 2.0% by mass, more preferably 0.25 to 1.5% by mass, and 0.5 to 0.5% by mass with respect to the total mass of the composition. It is more preferably 1.0% by mass.
When the content of the antioxidant is 0.05% by mass or more, the fluctuation of the conductivity of the conductive lubricating oil composition at a high temperature is further suppressed.
The antioxidant may be contained alone or in combination of two or more. When two or more kinds are contained in combination, the total amount is preferably within the above range.

In the conductive lubricating oil composition, the ratio of the antioxidant to the above-mentioned conductivity-imparting agent (antioxidant / conductivity-imparting agent) is preferably 0.05 to 200, preferably 0.5 to 150 on a mass basis. More preferred.
When the above ratio is 0.05 or more, the change in conductivity with time is suppressed, and when it is 200 or less, an effect commensurate with the amount of addition can be obtained.

<Other additives>
The conductive lubricating oil composition of the present invention further comprises general lubricating oil additives such as metal inactivating agents, rust preventives, anti-wear agents, pour point lowering agents, viscosity index improvers, and hydrolysis inhibitors. May be contained.

<Conductivity of composition>
The conductive lubricating oil composition of the present invention has a conductivity at 80 ° C. of preferably 10,000 pS / m or more, more preferably 10,000 pS / m to 100,000 pS / m. When the conductivity is 10,000 pS / m or more, the charge of the generated static electricity can be suppressed.
To measure the conductivity, a conductivity meter (for example, a handy conductivity meter 1152 manufactured by Emcee Electricals) is used to heat the temperature of the conductive lubricating oil composition to 80 ° C., and the probe of the conductivity meter is stirred while stirring. It can be done by inserting.

The conductive lubricating oil composition of the present invention has a change rate of 10% or less in conductivity after being stored at 120 ° C. for 200 hours.
The change rate of the above conductivity is more preferably 5% or less, further preferably 2.5% or less, further preferably 2% or less, further preferably 1.5% or less, and particularly preferably 1% or less.
The lower the rate of change in conductivity, the more stable the conductivity can be maintained for a long period of time.
The rate of change in conductivity can be determined by measuring the conductivity of the conductive lubricating oil composition before and after storage under the condition of 120 ° C. for 200 hours.

<Kinematic viscosity and viscosity index of composition>
The conductive lubricating oil composition of the present invention preferably has a kinematic viscosity at 40 ° C. of 6 to 15 mm ² / s, more preferably 7.5 to 13 mm ² / s. When the 40 ° C. kinematic viscosity is 6 mm ² / s or more, evaporation loss is suppressed and sufficient lubrication performance can be maintained. Further, when it is 15 mm ² / s or less, it is suppressed that the viscous torque when used in precision equipment or the like becomes large and the low temperature fluidity decreases. Therefore, it is considered that the range of kinematic viscosity of 6 to 15 mm ² / s is good from the viewpoint of low power consumption, evaporation loss and lubrication performance.
Further, the conductive lubricating oil composition of the present invention preferably has a viscosity index of 110 or more, more preferably 120 or more. When the viscosity index is 110 or more, the change in viscosity with respect to the temperature change is suppressed, and the increase in viscosity torque at low temperature is suppressed.
The 40 ° C. kinematic viscosity of the composition is a value measured by the method specified in JIS-K-2283: 2000 (ASTM D445). The viscosity index of the composition is a value measured by a method specified in JIS K 2283: 2000 (ASTM D2270)).

<Use of composition>
The conductive lubricating oil composition of the present invention can be used as a lubricating oil for motors and bearings of various precision instruments such as CD-Rs, DVD-Rs, HDDs, and watches.
In particular, by using it for the sliding portion and the rotating portion of the above-mentioned precision equipment, excellent lubrication performance is exhibited while stably ensuring conductivity.

Hereinafter, the contents of the present invention will be specifically described based on Examples, but the present invention is not limited to these Examples.

In Examples and Comparative Examples, the conductivity was measured using "Handy Conductivity Meter 1152 manufactured by Emcee Electricals". The sample placed in the light-shielding bottle was heated to 80 ° C. with a hot stirrer, and the probe of the conductivity meter was inserted while stirring to perform the measurement.
Further, the change in conductivity was evaluated by evaluating the conductive lubricating oil composition at 80 ° C. after storage under the condition of 120 ° C., which is harsher than the normal use conditions.

(Examples 1 to 4)
Each component was blended in the ratio (mass%) shown in Table 1 below to prepare a conductive lubricating oil composition of each example.
Each of the prepared compositions was stored in a constant temperature bath at 120 ° C. for 200 hours, the conductivity before and after storage was measured, and the rate of change was calculated. Each composition was stored in a constant temperature bath (DRN420DB manufactured by Advantech Co., Ltd.) in a light-shielding bottle, and the temperature was set to 120 ° C. without applying pressure or humidity. The results are shown in Table 1 below.

Details of each component in Table 1 are as follows.
(Base oil A) Decanoic acid 2-hexyldecyl ester: In the general formula (1), a compound in which R ¹ is a linear alkyl group having 10 carbon atoms and n = 7 (antioxidant A) alkylated phenyl-α- Naftylamine: A compound in which R ⁷ is a branched alkyl group having 7 carbon atoms in the general formula (5) (antioxidant B) Phosphite: In the general formula (9), R ¹⁸ and R ¹⁹ are branched chains having 4 carbon atoms. alkyl, compound (antioxidant C) alkylated diphenylamine: in the general formula (4), R ^5, R ⁶ is branched alkyl group having 7 carbon atoms (conductive agent a) bis (trifluoromethanesulfonyl) Limid lithium (conductivity-imparting agent B) Lithium trifluoromethanesulfonate (conductivity-imparting agent C) Lithium nonafluorobutane sulfonate (conductivity-imparting agent D) Bis (trifluoromethanesulfonyl) Idopotassium (other lubricating oil additives) Metal Inactivating agents, rust preventives, anti-wear agents, hydrolysis inhibitors

(Comparative Examples 1 to 3)
Each component was blended in the ratio (mass%) shown in Table 2 below to prepare a conductive lubricating oil composition of each Comparative Example.
Each of the prepared compositions was stored in a constant temperature bath at 120 ° C. for 200 hours, and the conductivity before and after storage was measured in the same manner as in Examples 1 to 4, and the rate of change was calculated. The results are shown in Table 2 below.

Details of each component in Table 2 are as follows. The base oil A, the antioxidant A, the antioxidant B, the antioxidant C, the conductivity-imparting agent A, and other lubricating oil additives were the same as those in Table 1.
(Conductivity-imparting agent E) Alkylnaphthalene sulfonate (Conductivity-imparting agent F) Phosphate-type anionic surfactant

From Tables 1 and 2, it can be seen that the conductive lubricating oil composition of the example has a low rate of change in conductivity and is excellent in conductivity with time.

The conductive lubricating oil composition of the present invention can be used as a lubricating oil for motors and bearings of various precision instruments such as CD-Rs, DVD-Rs, HDDs, and watches.

Claims (3)

At least one lubricating oil base oil selected from the group consisting of fatty acid monoester base oils and ether ester base oils,
Selected from the group consisting of potassium trifluoromethanesulfonate, lithium trifluoromethanesulfonate, lithium nonafluorobutanesulfonate, bis (trifluoromethanesulfonyl) imide lithium, bis (trifluoromethanesulfonyl) imide potassium, and tris (trifluoromethanesulfonyl) methidolithium. Contains at least one conductivity-imparting agent, 0.01 to 1% by mass, based on the total mass of the composition.
A conductive lubricating oil composition in which the rate of change in conductivity after storage at 120 ° C. for 200 hours is 10% or less. Further, at least one antioxidant selected from the group consisting of a diphenylamine compound, an alkylated phenyl-α-naphthylamine, a hindered phenol compound, and phosphite is contained in an amount of 0.05 to 2% by mass based on the total mass of the composition. The conductive lubricating oil composition according to claim 1. The conductive lubrication according to claim 1 or 2, wherein the lubricating oil base oil is a compound represented by any of the following general formulas (1), (2), or general formula (3). Oil composition.

[In the general formula (1), R ¹ represents a linear or branched alkyl group having 8 to 16 carbon atoms or a heteroalkyl group containing an oxygen atom, and n represents an integer of 5 to 11. ]

[In the general formula (2), R ² represents a linear or branched alkyl group having 8 to 16 carbon atoms or a heteroalkyl group containing an oxygen atom, and n represents an integer of 5 to 11. ]

[In the general formula (3), A ¹ represents a linear or branched alkylene group or a heteroalkylene group having 8 to 15 carbon atoms, and R ³ and R ⁴ independently have 6 to 10 carbon atoms. Represents a linear or branched alkyl group of. ]