JP7597461B2 - Lubricant composition, its manufacturing method and machine - Google Patents

Description

The present invention relates to a lubricant composition, its manufacturing method, and a mechanical device.

Silicone oil is used in a variety of fields as a very useful oil because it has excellent heat and oxidation resistance, chemical resistance, low temperature characteristics, viscosity temperature characteristics, shear resistance, electrical properties, and high vacuum properties.

Patent Document 1 discloses a heat-resistant silicone composition that is made by dissolving or dispersing one or more types of fullerene in silicone oil at a ratio of 0.001 to 5% by weight, and that is characterized by a viscosity increase rate of 60% or less in a 24-hour accelerated test at 250°C.

Patent Document 2 discloses a silicone grease composition that contains a thickener, a silicone oil as a base oil, and a friction modifier as an additive, and that improves high friction properties without reducing wear resistance, with the friction modifier containing a sulfur-nitrogen additive.

Patent Document 3 proposes a lubricant composition consisting of a silicone oil containing an aromatic nucleus and a fluorine-containing aromatic compound.

Patent documents 4 and 5 are examples in which silicone oil is not used, but fullerene is used.

Patent Document 4 proposes an additive composition for engine oil, which is characterized by using mineral oil, poly-α-olefin oil, phenyl ether oil, and ester oil as a lubricating base oil, using _C60 and/or _C70 as fullerene, and blending an organic solvent, a viscosity index improver, a friction modifier, and a detergent dispersant.

Patent Document 5 proposes a release agent composition that contains a nanocarbon material and a surfactant in a liquid medium.

Patent Document 6 discloses a method for producing methanofullerenes such as di-tert-butyl malonate polyadducts as fullerene derivatives.

Patent Document 7 discloses a diethyl malonate polyadduct and a di-tert-butyl malonate polyadduct as fullerene derivatives, and suggests a use thereof as a resist underlayer film forming composition.

JP 2005-206761 A JP 2018-16725 A Japanese Patent Application Publication No. 10-168471 JP 2008-266501 A Patent No. 5635999 Patent No. 4916117 Patent No. 5757286

However, although silicone oil has the excellent properties mentioned above, its lubricity is poor, so its use as a lubricant is limited. Furthermore, lubricity improvers such as extreme pressure additives and anti-wear agents are not very effective in silicone oil, making it difficult to improve its lubricity. Also, fullerenes are not soluble in silicone oil, so it is difficult to apply fullerenes to silicone oil.

The object of the present invention is to provide a silicone oil lubricant composition with improved lubricating performance, a method for producing the same, and a machine device.

To solve the above problems, the present invention provides the following means.

（上記一般式（１）中、Ｒ^１及びＲ^２はアルコキシ基を表わし、ＦＬＮはフラーレン骨格を表し、ｎは１以上の整数を表わす。）
で表される化合物である、
潤滑剤組成物。
［２］ 前記ｎは、１～５である前項［１］に記載の潤滑剤組成物。
［３］ 前記Ｒ^１及びＲ^２は、ｔｅｒｔ－ブトキシ基である前項［１］または［２］に記載の潤滑剤組成物。
［４］ 前記基油を構成する分子構造の一部を有する付加基が前記フラーレン誘導体に付加した付加体を更に含む前項［１］～［３］のいずれかに記載の潤滑剤組成物。
［５］ さらに、増ちょう剤を含むグリース組成物である前項［１］～［４］のいずれかに記載の潤滑剤組成物。
［６］ 前記増ちょう剤がリチウム石けんである前項［５］に記載の潤滑剤組成物。
［７］ 基油にフラーレン誘導体を溶解する溶解工程を有し、
前記基油はシリコーン油であり、
前記フラーレン誘導体は前記式（１）で表される化合物である、
潤滑剤組成物の製造方法。
［８］ 非酸化性雰囲気下、溶解工程で得られたフラーレン誘導体の溶液中で、前記基油を構成する分子構造の一部を有する付加基を、前記フラーレン誘導体に付加する付加反応工程を更に含む前項［７］に記載の潤滑剤組成物の製造方法。
［９］ 前記非酸化性雰囲気中の酸素分圧が、１０パスカル以下である前項［８］に記載の潤滑剤組成物の製造方法。
［１０］ 付加反応工程は、前記溶液中のフラーレン誘導体の濃度が、付加反応工程前のフラーレン誘導体の濃度に対して０．１～０．７倍となるまで行なわれる前項［８］または［９］に記載の潤滑剤組成物の製造方法。
［１１］ 付加反応工程の処理時間が、５分以上２４時間以下である前項［８］～［１０］のいずれかに記載の潤滑剤組成物の製造方法。
［１２］ 付加反応工程が、溶解工程で得られたフラーレン誘導体の溶液を熱処理する工程である前項［８］～［１１］のいずれかに記載の潤滑剤組成物の製造方法。
［１３］ 熱処理の温度が、前記基油の使用上限温度を超え、且つ前記使用上限温度＋２５０℃以下の範囲、または、２００～３５０℃の範囲である前項［１２］に記載の潤滑剤組成物の製造方法。
［１４］ 付加反応工程が、溶解工程で得られたフラーレン誘導体の溶液に放射線照射を行う工程であり、前記放射線が紫外線又は電離放射線である前項［８］～［１１］のいずれかに記載の潤滑剤組成物の製造方法。
［１５］ 前記放射線が、波長１９０ｎｍ～３６５ｎｍの紫外線である前項［１４］に記載の潤滑剤組成物の製造方法。
［１６］ 付加反応工程で照射される放射線のエネルギーが、前記フラーレン誘導体の溶液１ｍＬあたり１Ｊ～１００Ｊである前項［１４］または［１５］に記載の潤滑剤組成物の製造方法。
［１７］ フラーレン誘導体を含む溶液から不溶成分を除去する不溶成分除去工程を更に有する前項［８］～［１６］のいずれかに記載の潤滑剤組成物の製造方法。
［１８］ 前項［１］～［６］のいずれかに記載の潤滑剤組成物を摺動部に使用した機械装置。
［１９］ 前記摺動部が真空下で摺動する前項［１８］に記載の機械装置。
［２０］ 前項［５］または［６］に記載の潤滑剤組成物を摺動部に使用した機械装置。
［２１］ 前記摺動部が摩擦板である前項［２０］に記載の機械装置。
[1] A composition comprising a base oil and a fullerene derivative,
The base oil is a silicone oil,
The fullerene derivative is represented by the following general formula (1):

(In the above general formula (1), ^R1 and ^R2 represent an alkoxy group, FLN represents a fullerene skeleton, and n represents an integer of 1 or more.)
The compound represented by the formula:
Lubricant composition.
[2] The lubricant composition according to the above item [1], wherein n is 1 to 5.
[3] The lubricant composition according to the above item [1] or [2], wherein R ¹ and R ² are tert-butoxy groups.
[4] The lubricant composition according to any one of the above items [1] to [3], further comprising an adduct in which an additional group having a part of the molecular structure constituting the base oil is added to the fullerene derivative.
[5] The lubricant composition according to any one of the above items [1] to [4], which is a grease composition further comprising a thickener.
[6] The lubricant composition according to the above item [5], wherein the thickener is a lithium soap.
[7] A dissolving step of dissolving a fullerene derivative in a base oil,
The base oil is a silicone oil,
The fullerene derivative is a compound represented by formula (1).
A method for producing a lubricant composition.
[8] The method for producing the lubricant composition according to the above item [7], further comprising an addition reaction step of adding an additional group having a part of a molecular structure constituting the base oil to the fullerene derivative in a solution of the fullerene derivative obtained in the dissolving step under a non-oxidizing atmosphere.
[9] The method for producing a lubricant composition according to the above [8], wherein the oxygen partial pressure in the non-oxidizing atmosphere is 10 Pa or less.
[10] The method for producing a lubricant composition according to the above item [8] or [9], wherein the addition reaction step is carried out until the concentration of the fullerene derivative in the solution becomes 0.1 to 0.7 times the concentration of the fullerene derivative before the addition reaction step.
[11] The method for producing a lubricant composition according to any one of the above items [8] to [10], wherein the treatment time of the addition reaction step is 5 minutes or more and 24 hours or less.
[12] The method for producing a lubricant composition according to any one of the above items [8] to [11], wherein the addition reaction step is a step of heat-treating the solution of the fullerene derivative obtained in the dissolving step.
[13] The method for producing a lubricant composition according to the above item [12], wherein the heat treatment temperature exceeds the upper limit use temperature of the base oil and is in the range of the upper limit use temperature + 250°C or less, or in the range of 200 to 350°C.
[14] The method for producing a lubricant composition according to any one of the above items [8] to [11], wherein the addition reaction step is a step of irradiating the solution of the fullerene derivative obtained in the dissolving step with radiation, and the radiation is ultraviolet radiation or ionizing radiation.
[15] The method for producing a lubricant composition according to the above [14], wherein the radiation is ultraviolet light having a wavelength of 190 nm to 365 nm.
[16] The method for producing a lubricant composition according to the above [14] or [15], wherein the energy of the radiation irradiated in the addition reaction step is 1 J to 100 J per mL of the solution of the fullerene derivative.
[17] The method for producing a lubricant composition according to any one of items [8] to [16], further comprising an insoluble component removing step of removing insoluble components from the solution containing the fullerene derivative.
[18] A mechanical device using the lubricant composition according to any one of the above items [1] to [6] in a sliding part.
[19] The mechanical device according to the above item [18], wherein the sliding part slides under a vacuum.
[20] A mechanical device using the lubricant composition according to the above item [5] or [6] in a sliding part.
[21] The mechanical device according to the above item [20], wherein the sliding portion is a friction plate.

The present invention provides a lubricant composition having excellent lubricating properties and based on silicone oil, a method for producing the same, and a machine device using the same.

The lubricant composition, its manufacturing method, and machine device according to the embodiment of the present invention will be described below. Note that this embodiment is specifically described to provide a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified. Modifications, additions, omissions, substitutions, etc. are possible within the scope of the gist of the present invention.

(Lubricant composition)
The lubricant composition according to the present embodiment contains a base oil and a fullerene derivative, the base oil being a silicone oil, and the fullerene derivative being a compound represented by the formula (1). Such a lubricant composition is generally called a lubricating oil composition, but when it contains a thickener as an additive, which will be described later, it is called a grease composition.

(Base oil)
The base oil contained in the lubricant composition of this embodiment is silicone oil.It is preferable that the base oil does not contain volatile components, in terms of use in vacuum or reduced pressure environment and long-term stability.The vapor pressure of the base oil is preferably 1 Pa or less at 25°C, more preferably 0.1 Pa or less, and particularly preferably 0.01 Pa or less.

Examples of silicone oils include dimethyl silicone oil, methylphenyl silicone oil (phenyl modified silicone oil), methylhydrogen silicone oil, polyether modified silicone oil, aralkyl modified silicone oil, fluoroalkyl modified silicone oil, alkyl modified silicone oil, fatty acid ester modified silicone oil, etc. Preferred examples include dimethyl silicone oil and methylphenyl silicone oil. Furthermore, silicone oils that are a mixture of two or more of these may also be used.

(Fullerene derivatives)
The fullerene derivative contained in the lubricant composition of this embodiment is a compound represented by the above formula (1).

The type of fullerene skeleton in the fullerene derivative may be, for example, _C60 , _C70 , or higher fullerene. From the viewpoint of availability of the raw fullerene, a derivative having a fullerene skeleton of _C60 or _C70 is preferred, and a derivative having _{a C60} is more preferred. The fullerene derivative may also be a mixture of these fullerene skeleton parts. In this case, it is preferred that the main component is a derivative having a fullerene skeleton of _C60 . The fullerene derivative may be a commercially available product, or may be obtained by the method of Patent Document 6 or 7 or the method of the Examples described below.

In the formula (1), n is an integer of 1 or more, and is preferably 2 or more from the viewpoint of the solubility of the fullerene derivative in the base oil. In addition, n can be increased as the size of the fullerene skeleton increases, but is preferably set to 5 or less from the viewpoint of the stability of the fullerene skeleton.

From the viewpoint of solubility of the fullerene derivative in the base oil, the alkoxy group in the formula (1) has a carbon number of 2 to 24, and more preferably a carbon number of 3 to 8. Note that R ¹ and R ² in the formula (1) may be different alkoxy groups or may be the same, but from the viewpoint of ease of production, they are preferably the same.

The fullerene derivative concentration in the lubricant composition can be selected as desired as long as it is less than the saturated solubility in the base oil. The concentration is preferably 0.001 μmol/g or more from the viewpoint of improving the lubricating properties with respect to the base oil, and more preferably 0.01 μmol/g or more from the viewpoint of long-term use in a harsh environment in which the fullerene derivative is consumed by cosmic rays or oxygen molecules remaining in a vacuum, and even more preferably 0.1 μmol/g or more. In addition, the concentration is preferably less than the saturated solubility in the usage environment from the viewpoint of preventing precipitation of the fullerene derivative, and from the economic viewpoint, it is more preferably 1 μmol/g or less, and even more preferably 0.1 μmol/g or less. These upper and lower limits can be combined as desired depending on the purpose. In addition, when an adduct described later is present, each of the above concentrations represents the total concentration of the fullerene derivative and the adduct.

(adduct)
The lubricant composition of this embodiment may contain an adduct (sometimes simply referred to as "adduct" in this embodiment) in which a part of the molecular structure constituting the base oil is added to the fullerene derivative. The adduct is formed by subjecting a solution of a fullerene derivative to a heat treatment or radiation irradiation described below, which cleaves a part of the molecular structure constituting the base oil, resulting in the generation of a highly reactive molecule (hereinafter referred to as "cleaved molecule"), which is then added to the fullerene derivative. Compared with a fullerene derivative that is not an adduct (sometimes simply referred to as "fullerene derivative" in this embodiment), the adduct has improved lubricating properties as shown in the examples described below, and has higher solubility in base oil, so that it can be used in a wider variety of environments without worrying about precipitation. Therefore, the solubility can be improved by forming an adduct without increasing n in the formula (1).

(Additives)
The lubricant composition of the present embodiment may contain additives within a range that does not impair the effect of the lubricant composition. Examples of additives include commercially available antioxidants, viscosity index improvers, extreme pressure additives, detergent dispersants, pour point depressants, corrosion inhibitors, solid lubricants, oiliness improvers, rust inhibitors, antiemulsifiers, antifoaming agents, hydrolysis inhibitors, thickeners, etc. These additives may be used alone or in combination of two or more.

Examples of antioxidants include butylhydroxytoluene (BHT), butylhydroxyanisole (BHA), and dialkyldiphenylamine.

Examples of viscosity index improvers include polyalkylstyrene and styrene-diene copolymer hydride additives.

Examples of extreme pressure additives include dibenzyl disulfide, allyl phosphate, allyl phosphite, amine salts of allyl phosphate, allyl thiophosphate, and amine salts of allyl thiophosphate.

Examples of detergent dispersants include benzylamine succinic acid derivatives, alkylphenol amines, and the like.
Examples of pour point depressants include chlorinated paraffin-naphthalene condensates, chlorinated paraffin-phenol condensates, polyalkylstyrenes, and the like.

Examples of demulsifiers include alkylbenzene sulfonates.

Examples of corrosion inhibitors include dialkylnaphthalene sulfonates.

Examples of thickeners include soap-based thickeners such as lithium soap and lithium complex soap, urea-based thickeners such as diurea, inorganic thickeners such as organo-clay and silica, and organic thickeners such as polytetrafluoroethylene and melamine cyanurate. Among these, silica, lithium soap, lithium complex soap, and urea compounds are preferred, and lithium soap is more preferred. As the lithium soap, lithium stearate or lithium 12-hydroxystearate is preferred, and lithium stearate is even more preferred.

(Method of producing lubricant composition)
The method for producing the lubricant composition of the present embodiment includes a dissolving step of dissolving the fullerene derivative in the base oil to obtain a solution of the fullerene derivative. Furthermore, it is preferable to provide a step of removing volatile components from the fullerene derivative, for example, by leaving the fullerene derivative in an environment at 100° C. and 10 Pascal or less, prior to the dissolving step.

The dissolution in the dissolution step can be carried out by any method selected, and is preferably carried out by, for example, mechanical stirring or ultrasonic irradiation. If the base oil is a low-viscosity liquid at room temperature, stirring may be carried out at room temperature. On the other hand, if the base oil is a high-viscosity liquid or solid at room temperature, it is preferable to heat it to a low-viscosity liquid state and dissolve it by stirring.

The concentration of the fullerene derivative can be adjusted by the amount of fullerene derivative dissolved in the dissolving step. Alternatively, it is preferable to adjust the concentration to a higher concentration than desired (but less than the saturated solubility) in the dissolving step, and then dilute with base oil in one of the subsequent steps to adjust to the desired concentration, from the viewpoint of reducing the amount of solution to be handled. When performing the removal step described below, it is preferable to perform the dilution after the removal step, since this makes it easier to adjust the concentration more accurately. The concentration of the fullerene derivative can be measured by a method using ultraviolet absorption spectrum or high performance liquid chromatography (HPLC) as described in the examples.

(Removal process)
The solution of the fullerene derivative obtained in the dissolving step may contain insoluble components. In this case, it is preferable to remove these insoluble components. That is, the manufacturing method of the lubricant composition may further include a removing step of removing insoluble components from the solution of the fullerene derivative after the dissolving step. The method of removing insoluble components can be selected arbitrarily, and examples thereof include a method of filtering using a membrane filter, a method of sedimentation removal using a centrifuge, and a method of using both of these methods in combination.

The solution of the fullerene derivative obtained in the dissolving step may be used as the lubricant composition as it is, but it is preferable to carry out the addition reaction step described below and further process the solution of the fullerene derivative to obtain the lubricant composition.

(Addition reaction process)
The adduct is obtained by subjecting the solution of the fullerene derivative to heat treatment or radiation irradiation in a non-oxidizing atmosphere in which the oxygen partial pressure is reduced, etc. That is, the method for producing the lubricant composition may further include, after the dissolving step, an addition reaction step of heat treating the solution of the fullerene derivative in a non-oxidizing atmosphere to generate the adduct. Also, after the dissolving step, the method may further include an addition reaction step of irradiating the solution of the fullerene derivative with radiation in a non-oxidizing atmosphere to generate the adduct.

The adduct may be obtained by performing either or both of the heat treatment and the radiation exposure, or by performing both simultaneously.

The adduct obtained by this process has a structure in which an additional group having a part of the molecular structure constituting the base oil is added to the fullerene derivative.

The change of the fullerene derivative into an adduct can be confirmed by performing mass spectrometry on the solution of the fullerene derivative before and after the treatment. For example, when a derivative with a fullerene skeleton of _C60 is used, the solution of the fullerene derivative before the heat treatment or radiation treatment has peaks of m/z=1148, 1362, 1576, and 1790 corresponding to the fullerene derivatives with n=2, 3, 4, and 5. In contrast, in the lubricant composition after the treatment, the peaks of 1148, 1362, 1576, and 1790 are reduced, and multiple peaks of the adduct appear. As the main peaks, peaks 1148+N, 1148+2N, 1362+N, 1362+2N, 1576+N, 1576+2N, 1790+N, and 1790+2N, etc., corresponding to the fullerene derivative to which multiple alkyl groups with different chain lengths are added, can be confirmed. N is a natural number equal to or less than the molecular weight of the molecules constituting the base oil. This is believed to be due to the addition of two molecules of alkyl radicals generated by the cleavage of the base oil to the fullerene derivative.

In addition, since the molecules of the base oil are not necessarily cleaved at specific positions, the adducts do not usually become a single type of molecule, making their analysis difficult. Therefore, the progress of the reaction to produce the adducts can be determined by measuring the concentration of the remaining fullerene derivative and using the remaining rate represented by the following formula as a guide.
(Residual rate)=[Concentration of fullerene derivative after treatment]/[Concentration of fullerene derivative before treatment]
In the above formula, the treatment refers to one or both of a heat treatment and radiation exposure. When determining the residual rate during the treatment, the above "fullerene derivative concentration after the treatment" may be read as "fullerene derivative concentration during the treatment."
The concentration of the adduct produced may be estimated by the following formula:
[Adduct concentration] = [Fullerene derivative concentration before treatment] - [Fullerene derivative concentration after treatment]

The residual ratio calculated by the above formula is preferably 0.1 to 0.7, and more preferably 0.2 to 0.5. When the residual ratio is 0.1 to 0.7, the lubricating properties of the lubricant composition are more stable from the beginning of use, friction wear of the sliding parts of mechanical devices is suppressed, and the generation of volatile components due to base oil deterioration is easily suppressed.

Therefore, in this embodiment, it is preferable to monitor the fullerene derivative concentration of the fullerene derivative solution during the addition reaction process, and perform the process until the fullerene derivative concentration becomes 0.1 to 0.7 relative to the concentration of the fullerene derivative before the heat treatment or radiation irradiation treatment. In addition, it is preferable to set the processing time of the heat treatment or radiation irradiation treatment to 5 minutes to 24 hours, which makes it easier to operate the heat treatment or radiation treatment. For example, the processing time can be shortened by increasing the heat treatment temperature or the radiation irradiation intensity, and conversely, the processing time can be lengthened by decreasing the heat treatment temperature or the radiation irradiation intensity. In addition, in radiation irradiation, for example, a method of irradiating radiation with a relatively high radiation intensity for a short time (approximately 0.1 seconds to 3 minutes) 2 to 10 times, by adjusting the number of irradiations, is also preferable, as it is easy to operate, to set the fullerene derivative concentration in the range.

Usually, a solution of a fullerene derivative is handled in the air. Therefore, the oxygen gas concentration in the solution is in equilibrium with the oxygen gas in the air. In addition, oxygen molecules react with the cleavage molecules, suppressing the formation of adducts. Therefore, it is preferable to remove as many oxygen molecules as possible from the solution of the fullerene derivative, and perform the heat treatment or radiation treatment in a non-oxidizing atmosphere. The non-oxidizing atmosphere in the heat treatment step or radiation irradiation is a gas phase in equilibrium with the solution of the fullerene derivative, and the oxygen partial pressure in the non-oxidizing atmosphere is preferably 10 Pascals or less, more preferably 5 Pascals or less, and even more preferably 2 Pascals or less. It may be 1 Pascal or less or 0.1 Pascal or less. In addition, an inert gas atmosphere as described below is preferably used as an example of a non-oxidizing atmosphere. The following two methods are specific examples of heat treatment, and the following one method is specific example of radiation irradiation.

Heat treatment The heat treatment is preferably performed at a temperature exceeding the upper limit of the use temperature of the base oil. Exceeding the upper limit of the use temperature of the base oil makes it easier for cleaved molecules to occur. Furthermore, as the temperature increases, more cleaved molecules are generated, and as a result, the heat treatment time can be shortened. From the viewpoint of heat treatment time that is easy to operate, the heat treatment temperature in this heat treatment is preferably in the range of exceeding the upper limit of the use temperature of the base oil and not exceeding the upper limit of the use temperature of the base oil + 250 ° C. The upper limit of the use temperature of the base oil can be known from the catalog of the base oil manufacturer. If the upper limit of the use temperature of the base oil is unknown, the heat treatment temperature is preferably 200 ° C. or more and 350 ° C. or less, and more preferably 250 ° C. or more and 300 ° C. or less, as a guideline. The heat treatment time is preferably 5 minutes to 24 hours from the viewpoint of operability, and may be 5 minutes to 30 minutes, 30 minutes to 1 hour, 1 hour to 5 hours, or 5 hours to 24 hours from the viewpoint of the above, depending on the circumstances of the equipment that can be handled.

The method for creating a non-oxidizing atmosphere can be selected arbitrarily, but for example, a solution of the fullerene derivative is placed in an airtight metal container such as stainless steel, and the container is then sealed. Next, the inside of the container is replaced with an inert gas such as nitrogen gas or argon gas, or the solution of the fullerene derivative in the container is bubbled with an inert gas. In this way, the solution of the fullerene derivative is brought into equilibrium with the inert gas, and the oxygen partial pressure is set to 10 Pa or less.

Alternatively, a method of creating a non-oxidizing atmosphere can be to reduce the pressure inside an airtight container. For example, by reducing the pressure inside the container to 10 Pascals or less, the partial pressure of oxygen in the gas phase can be reduced to 10 Pascals or less, usually 2 Pascals or less. In this way, a non-oxidizing atmosphere can be created inside the container by reducing the pressure, and the container can be heated while maintaining this state, thereby heat-treating the solution of the fullerene derivative.

The fullerene derivative solution can be heated by any method. For example, it can be heated from the outside in an oil bath, irradiated with infrared rays, or irradiated with microwaves.

Radiation Irradiation Treatment The radiation used in the radiation irradiation treatment is radiation having energy that generates cleaved molecules. Specifically, it is ultraviolet light or ionizing radiation, and preferably ultraviolet light. More preferably, ultraviolet light with a wavelength of 190 nm or more and 365 nm or less, even more preferably, ultraviolet light with a wavelength of 250 nm or more and 360 nm or less, and particularly preferably, ultraviolet light with a wavelength of 330 nm or more and 350 nm or less. For example, a C-C single bond is cleaved by ultraviolet light with a wavelength of 341 nm or less. In addition, when radiation irradiation treatment is performed at room temperature, thermal vibrations are superimposed, so that a C-C single bond is cleaved even by ultraviolet light with a wavelength slightly longer than 341 nm. Therefore, by irradiating with ultraviolet light with a wavelength of 190 nm or more and 365 nm or less, cleaved molecules can be sufficiently generated. In addition, as long as cleaved molecules can be generated, low-energy radiation has a limited number of bond sites in the base oil molecule that are cleaved. Therefore, it is relatively easy to obtain large cleaved molecules that retain the partial shape of the original base oil molecule, and it is considered that the affinity of the resulting adduct with the base oil is improved.

As with the heat treatment, radiation irradiation is preferably performed in a non-oxidizing atmosphere. However, when irradiating with radiation, a radiation source such as an ultraviolet lamp is inserted into the container, or the container is irradiated from outside, so that at least a part of the container is made of a material that is transparent to the radiation used. For example, when irradiating with ultraviolet light, the stainless steel container is replaced in whole or in part with a material that is transparent to ultraviolet light, such as quartz glass.

The amount of energy of the radiation irradiated in the radiation irradiation process is preferably 1 J or more and 100 J or less, more preferably 1.5 J or more and 60 J or less, and even more preferably 2 J or more and 20 J or less per 1 mL of the fullerene derivative solution. Within this range, the concentration range of the fullerene derivative after the treatment obtained from the above formula, i.e., the residual rate, can be easily adjusted to 0.1 or more and 0.7 or less. As described above, the irradiation may be performed, for example, only once, or may be performed multiple times by dividing the irradiation into two or more times. When the irradiation is divided into multiple times, the irradiation conditions for each time may be the same or different, but it is preferable that the total energy amount of the irradiated radiation is within the above range. The number of irradiations may be, for example, in the range of 1 to 10 times or in the range of 2 to 5 times. It is also preferable to check the residual rate every time irradiation is performed, and repeat the irradiation one or more times until the desired residual rate is obtained.

In the case of ultraviolet irradiation, a normal low pressure mercury lamp, UV ozone lamp, ultraviolet LED, excimer lamp, xenon lamp, etc. can be used. As the amount of ultraviolet irradiation, the energy density (mW/cm ² ) of the ultraviolet irradiation light is measured in advance using an ultraviolet photometer, and then the irradiation time (seconds) and irradiation area (cm ² ) are specified. By these, the energy amount (J) of the ultraviolet ray to be irradiated can be determined. The irradiation time may be selected within a range that is easy to handle, and is preferably, for example, 5 minutes or more and 24 hours or less. Alternatively, in cases where a lamp or shutter equipment that is easy to blink such as an LED can be used, the irradiation time may be 0.1 seconds to 1 hour, 0.2 seconds to 30 minutes, 0.3 seconds to 3 minutes, 0.5 seconds to 60 seconds, or 1 second to 30 seconds.

(Addition of additives)
The additives may be added in any of the above steps. However, when the removal step is performed, from the viewpoint of ease of handling of the fullerene derivative solution, it is preferable to add additives containing unnecessary components such as thickeners or additives having a thickening effect after the removal step, and it is preferable to add them as late as possible. Also, when the addition reaction step is performed, it is preferable to add the additives after the addition reaction step from the viewpoint of avoiding the effects of heat and radiation on the additives.
The amount of the additives added may be adjusted according to the desired effect of the additives. For example, the amount of the thickener added is preferably about 5 to 20 mass% of the resulting grease composition, but it is more preferable to adjust the amount added using the consistency of the grease composition as an index.

The lubricant composition of this embodiment not only has excellent lubricating properties such as reduced frictional resistance and wear resistance, but also has a low vapor pressure. Furthermore, the generation of volatile components associated with base oil deterioration is suppressed, and an increase in the vapor pressure of the lubricant composition can be suppressed.

The lubricant composition of this embodiment can be used for various purposes, but is particularly suitable for use in mechanical devices in which the lubricant composition is used in sliding parts that slide under vacuum. Such mechanical devices are suitable for use in vacuum containers and in outer space.

In addition, when the grease composition of this embodiment (lubricant composition containing a thickener) is used, the friction coefficient is unlikely to decrease even at high temperatures (140°C), as shown in the examples described below, so it can be preferably used, for example, for friction plates of devices such as clutches, brakes, or torque limiters.

The above describes in detail the preferred embodiment of the present invention, but the present invention is not limited to a specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[Synthesis Example]
In a reaction vessel, 9.80 g of di-t-butyl malonate (manufactured by Tokyo Chemical Industry Co., Ltd.) was added under a nitrogen stream, and 150 ml of 1,2,4-trimethylbenzene and 6.50 g of diazabicyclo-7-undecene were added and the temperature was maintained at 4°C while stirring. Furthermore, a solution in which 10.9 g of iodine (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in 130 ml of 1,2,4-trimethylbenzene was added dropwise to this solution so as to maintain the temperature at 11°C. After the dropwise addition, the temperature was returned to room temperature. Then, a solution in which 5.00 g of fullerene (manufactured by Frontier Carbon Co., Ltd., nanom (registered trademark) mix ST. A fullerene mixture mainly composed of C ₆₀ ) was dissolved in 350 ml of 1,2,4-trimethylbenzene was added while stirring. Thereafter, a solution of 6.90 g of diazabicyclo-7-undecene diluted with 5 ml of 1,2,4-trimethylbenzene was slowly dropped into the reaction solution while stirring, and after dropping, the reaction was stirred at room temperature for 7 hours. The reaction solution obtained was washed four times with a saturated aqueous sodium sulfite solution. The organic layer was washed twice with 100 ml of dilute sulfuric acid (1N), washed three times with 200 ml of pure water, and the organic layer was distilled under reduced pressure to obtain 9.4 g of a reddish brown solid. Furthermore, the solid was separated and purified using a mixed solvent of hexane and ethyl acetate by silica gel column chromatography, and dried at 100° C. under high vacuum to obtain a fullerene derivative (a mixture of compounds in which 1 to 5 malonic acid di-t-butyl esters were added to fullerene).
[Example 1]
(Preparation of Lubricant Composition)

0.001 g of the fullerene derivative obtained in the synthesis example was mixed with 10 g of silicone oil (KF-96-100, manufactured by Shin-Etsu Chemical Co., Ltd.; hereinafter, sometimes referred to as "silicone oil A") as a base oil. The resulting mixture was stirred at room temperature for 36 hours using a stirrer. This was then filtered through a membrane filter with a pore size of 0.1 μm to obtain a solution of the fullerene derivative. The fullerene derivative concentration of the resulting solution of the fullerene derivative was measured and found to be 0.1 μmol/g. The resulting solution of the fullerene derivative was used as a lubricant composition.

The concentration of the fullerene derivative was measured using an ultraviolet absorption spectrograph (Shimadzu Corporation UV2400PC series). Specifically, the amount of fullerene derivative in a sample such as a lubricant composition was quantified by measuring absorbance (wavelength 295 nm) in a stone cell using this device. A calibration curve was also created using the fullerene derivative.

(Evaluation of friction resistance and abrasion resistance)
The average friction resistance and wear resistance of the obtained lubricant composition were evaluated using a friction and wear tester (ball-on-disk tribometer, manufactured by Anton Paar).
First, a substrate and a ball were prepared, and the materials were high carbon chromium bearing steel SUJ2. The diameter of the ball was 6 mm. A lubricant composition was applied to one main surface of the substrate, and the substrate was heated to 25°C. Next, the substrate was rotated so that the ball drew a circular orbit on the one main surface of the substrate through the lubricant composition, and the fixed ball was slid. The speed of the ball on the one main surface of the substrate was 0.55 cm/sec, and the load of the ball on the one main surface of the substrate was 5 N. The rubbing surface (circular) of the ball surface when the sliding time of the ball on the one main surface of the substrate was 30 minutes was observed with an optical microscope. The diameter of the rubbing surface formed on the ball was measured, and this value was taken as the wear resistance. It can be said that the smaller the diameter of the rubbing surface, the better the wear resistance. The evaluation results of the average friction resistance and wear resistance are shown in Table 1.

(Evaluation of seizure resistance)
The resulting lubricant composition was evaluated for seizure resistance using a friction and wear tester (ball-on-disk tribometer, manufactured by Anton Paar).
First, a substrate and a ball were prepared, and the materials were high carbon chromium bearing steel SUJ2. The diameter of the ball was 6 mm. A lubricant composition was applied to one main surface of the substrate, and the substrate was kept at a constant temperature of 30°C. Next, the substrate was rotated and the fixed ball was slid on one main surface of the substrate through the lubricant composition so that the ball drew a circular orbit on the substrate. The ball was moved at a speed of 0.55 cm/sec on one main surface of the substrate, and the load shown in Table 1 was applied to the one main surface of the substrate by the ball. When the sliding time of the ball was operated for 30 minutes, the seizure resistance was judged to be good, and when it was not, the seizure resistance was judged to be poor. The results are shown in Table 1.

(Stability Evaluation)
A temperature programmed desorption gas analyzer (manufactured by Rigaku Corporation, TPD type V) was used to measure the presence or absence of components volatilizing from the lubricant composition under high vacuum. The degree of desorption of gas was measured at an atmospheric pressure of 10 ⁻⁵ Pascal for 0.01 g of the lubricant composition. The degree of desorption of gas was determined as the integrated value of the peak with a molecular weight of 46 or more and 200 or less in order to eliminate the influence of molecules with a molecular weight smaller than that of carbon dioxide gas (molecular weight 44). As a comparative product, a similar measurement was performed using silicone oil A to which 1 ppm by mass of trimethylbenzene (TMB) (manufactured by Tokyo Chemical Industry Co., Ltd.) was added as a volatile component. In the MAC oil to which TMB was added, a peak due to TMB was detected. The integrated value of this peak was set to 1 (reference value). The ratio of the integrated value of the peak due to the desorbed gas of the measured lubricant composition to this reference value was set to the degree of desorption of gas. It can be said that the smaller the degree of desorption of gas, the better the stability under high vacuum.

The degree of gas release was measured at two points, before and after the wear resistance test. In the wear resistance test, the metals come into direct contact and heat is generated, which causes the molecular chains of the base oil to break and deteriorate. As a result of the deterioration, some of the broken molecules are detected as volatile components by the above method. In other words, in lubricating oils with poor wear resistance, the deterioration of the base oil progresses, resulting in a large amount of gas release components, which is undesirable. The results are shown in Table 1.

[Comparative Example 1]
An attempt was made to obtain a lubricant composition in the same manner as in Example 1, except that fullerene (nanom (registered trademark) mix ST, manufactured by Frontier Carbon Corp.) was used instead of the fullerene derivative. However, fullerene did not dissolve in silicone oil A, and a lubricant composition containing fullerene was not obtained.

[Comparative Example 2]
A lubricant composition was obtained in the same manner as in Example 1, except that no fullerene derivative was added to the silicone oil A. The obtained lubricant composition was measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

From Table 1, it can be seen that the lubricant composition of Example 1 is superior in average friction resistance, seizure resistance, and wear resistance compared to that of Comparative Example 2, and also has a low degree of gas desorption after the wear resistance test, and is excellent in stability under high vacuum.

[Example 2]
The solution of the fullerene derivative obtained in Example 1 (lubricant composition of Example 1) was irradiated with ultraviolet light to obtain a lubricant composition. The obtained lubricant composition was measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

The ultraviolet irradiation in Example 2 was carried out according to the following procedure: First, 3 ml of the above-mentioned fullerene derivative solution was placed in a quartz cell with a septum cap (Tokyo Glass Instruments Co., Ltd., S15-UV-10).
Next, two injection needles were inserted into the septum cap of the quartz cell, and nitrogen gas with a purity of 99.99% by volume or more (partial pressure of gas other than nitrogen at normal pressure was 10 Pa or less) was flowed from one side at 60 mL per minute for 10 minutes. Next, the solution of the fullerene derivative placed in the quartz cell was intermittently irradiated with ultraviolet light.

For ultraviolet irradiation, an ultraviolet irradiation device (Omnicure S2000, manufactured by Sanei Tech Co., Ltd.) was used. Specifically, the filter was set to 250 nm to 450 nm in the near ultraviolet range, the irradiation area was set to ² cm2, the output was adjusted to 1 W/ ^cm2 while measuring with an ultraviolet illuminance meter (wavelength 230 nm to 390 nm), the irradiation timer was set to 1 second, and the settings were made so that an energy of 2 J (0.7 J per mL of fullerene derivative solution) could be irradiated in one irradiation.

Next, after each UV irradiation, about 0.1 ml of the fullerene derivative solution was extracted from the inside of the quartz cell using a syringe, and the fullerene derivative concentration was measured using the UV spectrum to determine the residual ratio. After eight UV irradiations (5.3 J per mL of fullerene derivative solution), the residual ratio was 0.25. For this reason, the UV irradiation was stopped, and the contents were removed from the quartz cell to obtain a lubricant composition. The fullerene derivative concentration of this lubricant composition was measured to be 0.030 μmol/g, and the residual ratio was 0.30. The results are shown in Table 1.

As shown in Table 1, the lubricant composition of Example 2 exhibited better average friction resistance, wear resistance, and gas release rate than those of Example 1. In particular, the increase in gas release rate before and after the wear resistance test was small, and the composition was found to have better stability under high vacuum.

In addition, the fullerene derivative solution before UV irradiation and the lubricant composition obtained after UV irradiation were subjected to component analysis of molecular weights of 720 to 5000 using a mass spectrometer (Agilent Technologies, LC/MS, 6120). In the fullerene derivative solution before UV irradiation, the main peaks of the fullerene derivative were 934, 1054, 1148, 1268, 1362, 1484, 1576, 1696, 1790, 1910, etc., and several other peaks thought to be due to the base oil were observed. In the lubricant composition, the above-mentioned peaks became smaller, and many new peaks were confirmed. From these, it was confirmed that fullerenes and the generated fullerene adducts were present in the fullerene derivative solution (lubricant composition) after UV irradiation. In other examples and comparative examples, the fullerene derivative solutions before and after heat treatment or radiation treatment were also analyzed in the same manner. As a result, no adducts were found in the fullerene derivative solution before heat treatment or radiation treatment, but adducts were found after these treatments.

[Example 3]
Instead of irradiating with ultraviolet light, a solution of the fullerene derivative in a quartz cell was immersed in an oil bath at 250° C. and heated. A lubricant composition was obtained in the same manner as in Example 2, except that heating was used instead of irradiating with ultraviolet light. The obtained lubricant composition was measured and evaluated in the same manner as in Example 2. The results are shown in Table 1.

During the heating of Example 3, about 0.1 ml of the fullerene derivative solution was extracted from the inside of the quartz cell using a syringe every 5 minutes, and the fullerene derivative concentration was measured using UV spectrum to determine the fullerene residual rate. 15 minutes after the start of the measurement, the fullerene residual rate reached 0.2. For this reason, the quartz cell was removed from the oil bath and cooled to room temperature to obtain a lubricant composition. The fullerene derivative concentration of the lubricant composition was measured to be 0.015 μmol/g, and the residual rate was 0.15.

As shown in Table 1, the lubricant composition of Example 3, which was subjected to heat treatment as an additional reaction step, also showed excellent average friction resistance, wear resistance, and gas release rate, similar to that of Example 2, which was subjected to ultraviolet irradiation. In addition, because these have excellent wear resistance, it is presumed that the decomposition of the base oil is less likely to occur and the amount of volatile components produced is suppressed.

[Example 4]
A lubricant composition was obtained in the same manner as in Example 2, except that a low-pressure mercury UV lamp (manufactured by Sen Special Light Sources, model UVL20PH-6, containing ultraviolet rays of 185 nm in the far ultraviolet range and 254 nm in the near ultraviolet range as light wavelength components) was used as a radiation source, and irradiation was performed for 20 seconds. Here, the irradiation area was 5 cm ² and the output was 0.2 W/cm ^2. That is, the lubricant composition was irradiated with 20 J of ultraviolet rays (7 J per mL of fullerene derivative solution) by irradiation for 20 seconds. The fullerene derivative concentration in the lubricant composition was measured to be 0.022 μmol/g, and the residual rate was 0.22. The obtained lubricant composition was measured and evaluated in the same manner as in Example 2. The results are shown in Table 1.

[Example 5]
A lubricant composition was obtained in the same manner as in Example 1, except that X-ray irradiation was performed for 480 seconds using an X-ray irradiation device (Torec Corporation, RIX-250C-2) as a radiation source. The fullerene derivative concentration in the obtained lubricant composition was measured to be 0.020 μmol/g, and the residual rate was 0.20. The obtained lubricant composition was measured and evaluated in the same manner as in Example 2. The results are shown in Table 1.

Comparing Example 5 with Example 4, the wear resistance and the degree of gas release after the wear resistance test were superior to Example 5. Comparing Example 4 with Example 2, the wear resistance and the degree of gas release after the wear resistance test were superior to Example 4.
From these findings, it was found that in radiation treatment, it is preferable to use low-energy radiation that produces adducts, that is, near-ultraviolet rays.

[Example 6]
A lubricant composition was obtained in the same manner as in Example 1, except that silicone oil (KF-50-100, manufactured by Shin-Etsu Chemical Co., Ltd.; hereinafter, sometimes referred to as "silicone oil B") was used as the base oil. The obtained lubricant composition was measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 3]
An attempt was made to obtain a lubricant composition in the same manner as in Example 6, except that fullerene (manufactured by Frontier Carbon Corp., nanom (registered trademark) mix ST) was used instead of the fullerene derivative. However, fullerene did not dissolve in silicone oil B, and a lubricant composition containing fullerene was not obtained.

[Comparative Example 4]
A lubricant composition was obtained in the same manner as in Example 6, except that no fullerene derivative was added to the silicone oil B. The obtained lubricant composition was measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Example 7]
A lubricant composition was obtained in the same manner as in Example 3, except that silicone oil B was used as the base oil. The fullerene derivative concentration in the lubricant composition was measured to be 0.012 μmol/g, and the residual ratio was 0.12. The obtained lubricant composition was measured and evaluated in the same manner as in Example 2. The results are shown in Table 1.

[Example 8]
A lubricant composition was obtained in the same manner as in Example 4, except that silicone oil B was used as the base oil. The fullerene derivative concentration in the lubricant composition was measured to be 0.035 μmol/g, and the residual ratio was 0.35. The obtained lubricant composition was measured and evaluated in the same manner as in Example 2. The results are shown in Table 1.

The results of the comparison between Example 6 and Comparative Example 4 showed a similar tendency to the results of the comparison between Example 1 and Comparative Example 2 described above. Furthermore, the results of the comparison between Examples 7 and 8 and Example 6 showed a similar tendency to the results of the comparison between Examples 2 and 3 and Example 1 described above.

[Example 9]
Lithium stearate was added to the lubricant composition of Example 1 to a concentration of 20% by mass, and the mixture was heated, dissolved, mixed, and then rapidly cooled to obtain a base grease. The lubricant composition of Example 1 was added while processing the mixture in a mill, and the consistency was adjusted to 300 to obtain a grease composition. The consistency was measured according to the method of JIS K2220:2013. The friction coefficient of the obtained grease composition was measured under the following conditions to obtain the friction coefficient ratio. The results are shown in Table 2.
(Measurement of Friction Coefficient Ratio)
The friction coefficient of the grease composition was measured by the friction test method using a micro clutch tester (JCMAS P 047 4) in the Japan Construction Mechanization Association's Construction Machinery Hydraulic Oil - Friction Property Test Method (JCMAS P 047:2004), under the following test conditions:

Test conditions:
Sample oil: Grease composition obtained in Example 9 or Comparative Example 5 Clutch disc facing material: SD1795-S Plate material: SS400
Sample oil temperature: 40°C, 140°C
Surface pressure: 392 kPa
Sliding speed: 30 mm/s Friction time: 5 min
The friction coefficient ratio was determined by dividing the friction coefficient measured at a sample oil temperature of 140° C. by the friction coefficient measured at a sample oil temperature of 40° C. In addition, the presence or absence of wear marks on the disks was confirmed.

[Comparative Example 5]
A grease composition was obtained in the same manner as in Example 9, except that the lubricant composition of Comparative Example 2, which did not contain a fullerene derivative, was used instead of the lubricant composition of Example 1. The results are shown in Table 2.

The lubricant composition of the present invention can be used for various applications of silicone oils, but is particularly suitable for use in mechanical devices in which the lubricant composition is used in sliding parts that slide under vacuum. Examples of such mechanical devices include devices and equipment used in vacuum vessels, high altitude regions, or outer space, and more specifically, examples of such devices include vacuum metallurgy devices that perform forging and joining, vacuum chemical devices that perform chemical reactions, vacuum thin film formation and processing devices that perform deposition and sputtering, analytical devices such as electron microscopes, vacuum test devices that perform bending, tensile, and compression tests, aircraft, rockets, and artificial satellites.

In addition, the grease composition of the present invention can be used for various applications of silicone grease, but can also be preferably applied to the above-mentioned machinery.Furthermore, it can be preferably applied to machinery that uses friction plates, such as wet clutches and wet brakes.For example, the wet clutch device can be the lock-up clutch mounted on the torque converter of AT vehicles, and the wet brake device can be the multi-plate disc brake that applies braking force to the rotating shaft of a turning device of agricultural machinery, construction machinery, etc.

Claims (21)

Contains a base oil and a fullerene derivative,
The base oil is a silicone oil,
The fullerene derivative is represented by the following general formula (1):

(In the above general formula (1), ^R1 and ^R2 represent an alkoxy group, FLN represents a fullerene skeleton, and n represents an integer of 1 or more.)
The compound represented by the formula:
Lubricant composition. The lubricant composition according to claim 1, wherein n is 1 to 5. 3. The lubricant composition according to claim 1, wherein R ¹ and R ² are tert-butoxy groups. The lubricant composition according to any one of claims 1 to 3 further comprises an adduct in which an additional group having a part of the molecular structure constituting the base oil is added to the fullerene derivative. The lubricant composition according to any one of claims 1 to 4, which is a grease composition further comprising a thickener. The lubricant composition according to claim 5, wherein the thickener is lithium soap. A dissolving step of dissolving a fullerene derivative in a base oil,
The base oil is a silicone oil,
The fullerene derivative is represented by the following general formula (1):

(In the above general formula (1), R1 ^and R2 ^represent an alkoxy group, FLN represents a fullerene skeleton, and n represents an integer of 1 or more.)
The compound represented by the formula:
A method for producing a lubricant composition. The method for producing a lubricant composition according to claim 7 further comprises an addition reaction step of adding an additional group having a part of the molecular structure constituting the base oil to the fullerene derivative in a solution of the fullerene derivative obtained in the dissolving step under a non-oxidizing atmosphere. The method for producing a lubricant composition according to claim 8, wherein the oxygen partial pressure in the non-oxidizing atmosphere is 10 Pascals or less. The method for producing a lubricant composition according to claim 8 or 9, wherein the addition reaction step is carried out until the concentration of the fullerene derivative in the solution becomes 0.1 to 0.7 times the concentration of the fullerene derivative before the addition reaction step. The method for producing a lubricant composition according to any one of claims 8 to 10, wherein the processing time of the addition reaction step is 5 minutes or more and 24 hours or less. The method for producing a lubricant composition according to any one of claims 8 to 11, wherein the addition reaction step is a step of heat-treating the solution of the fullerene derivative obtained in the dissolving step. The method for producing a lubricant composition according to claim 12, wherein the heat treatment temperature exceeds the upper limit of the use temperature of the base oil and is in the range of the upper limit of the use temperature + 250°C or less, or in the range of 200 to 350°C. The method for producing a lubricant composition according to any one of claims 8 to 11, wherein the addition reaction step is a step of irradiating the solution of the fullerene derivative obtained in the dissolving step with radiation, and the radiation is ultraviolet radiation or ionizing radiation. The method for producing a lubricant composition according to claim 14, wherein the radiation is ultraviolet light having a wavelength of 190 nm to 365 nm. The method for producing a lubricant composition according to claim 14 or 15, wherein the energy of the radiation irradiated in the addition reaction step is 1 J to 100 J per mL of the fullerene derivative solution. The method for producing a lubricant composition according to any one of claims 8 to 16 further comprises an insoluble component removal step of removing insoluble components from the solution containing the fullerene derivative. A mechanical device in which the lubricant composition according to any one of claims 1 to 6 is used in the sliding parts. The mechanical device according to claim 18, wherein the sliding part slides under vacuum. A mechanical device in which the lubricant composition according to claim 5 or 6 is used in the sliding parts. The mechanical device according to claim 20, wherein the sliding part is a friction plate.