Lubricating oil composition, its manufacturing method and machinery

Abstract

To provide a lubricant composition having a low vapor pressure in which an increase in vapor pressure due to deterioration of a base oil is suppressed, a production method of the same, and a mechanical device using the lubricant composition.SOLUTION: The lubricant composition used comprises a base oil and a fullerene derivative, wherein the base oil is a multiplex alkylcyclopentane oil or an ionic liquid, and the fullerene derivative is a compound represented by the following general formula (1).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a lubricating oil composition, a method for producing the same, and a mechanical device. [Background technology]

[0002] High vacuum (10 -1 Pa~10 -5 Lubricating oil compositions that can be used under these atmospheric pressures (MPa) are required to have properties different from those of ordinary lubricating oil compositions, such as having a low vapor pressure and being substantially free of volatile components.

[0003] Patent Document 1 proposes a lubricating oil composition using a low vapor pressure perfluoroalkyl ether (PFAE), tris(2-octyldodecyl)cyclopentane, or the like as a base oil.

[0004] Patent Document 2 proposes an antistatic lubricating oil composition containing a lithium compound such as lithium bis(trifluoromethanesulfonyl)imide, and an antistatic substance selected from ionic liquids composed of a nitrogen onium cation and a weakly coordinating fluorine-containing organic anion or a weakly coordinating fluorine-containing inorganic anion.

[0005] Patent Document 3 proposes a semi-solid lubricating oil composition that is made of an ionic liquid that has a low vapor pressure and electrical conductivity sufficient to prevent static electricity.

[0006] Patent Document 4 describes a lubricating oil composition having heat resistance and antioxidant properties, which has (a) a vapor pressure of 1×10 at 25° C. -4 A lubricating oil composition has been proposed that contains (a) at least one base oil selected from the group consisting of fluorine-free synthetic oils and ionic liquids at a viscosity of 0.05 Pa or less, and (b) at least one selected from the group consisting of fullerene compounds and carbon particles by-produced during the production of fullerenes.

[0007] Patent Document 5 discloses a method for producing methanofullerenes such as di-tert-butyl malonate polyadducts as fullerene derivatives.

[0008] Patent Document 6 discloses a diethyl malonate polyadduct and a di-tert-butyl malonate polyadduct as fullerene derivatives, and proposes a use thereof as a resist underlayer film forming composition. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 10-140169 [Patent Document 2] JP 2005-89667 A [Patent Document 3] JP 2005-154755 A [Patent Document 4] JP 2005-336309 A [Patent Document 5] Patent No. 4916117 [Patent Document 6] Patent No. 5757286 Summary of the Invention [Problem to be solved by the invention]

[0010] Patent Documents 1 to 4 propose lubricating oil compositions that can be used under vacuum. However, it is expected that the physical properties of the lubricating oil compositions will change in the harsh environment of outer space, where they are exposed to high-energy rays such as cosmic rays. Therefore, these proposals are not sufficient to maintain stable lubricating performance for a long period of time. More specifically, the change in the physical properties of the lubricating oil composition occurs because the molecules of the base oil constituting the lubricating oil composition are gradually cleaved, and the molecular chain of the base oil becomes shorter. In particular, in a lubricating oil composition used under high vacuum, the vapor pressure of the lubricating oil composition increases due to the generation of components with small molecular weights. This increase in vapor pressure causes various problems as described below. This series of changes in the base oil is called "base oil deterioration." In addition to high energy rays, base oil deterioration can also be caused by heat generated by friction and wear when extreme force is applied to a sliding part.

[0011] Due to the increase in vapor pressure caused by base oil deterioration, some of the base oil may evaporate and be lost during use, resulting in a decrease in lubricating oil from the sliding parts. This may result in wear on the sliding parts and cause seizure. In addition, when some of the base oil evaporates, the lubricating oil may also scatter and adhere to parts of the machinery other than the sliding parts, contaminating the machinery.

[0012] An object of the present invention is to provide a lubricating oil composition having a low vapor pressure in which an increase in vapor pressure due to base oil deterioration is suppressed, a method for producing the same, and a mechanical device using said lubricating oil composition. [Means for solving the problem]

[0013] In order to solve the above problems, the present invention provides the following means.

[0014] [1] A composition comprising a base oil and a fullerene derivative, The base oil is a multi-alkylcyclopentane oil or an ionic liquid; The fullerene derivative is represented by the following general formula (1): [ka] (In the above general formula (1), R 1 and R 2 represents an alkoxy group having 2 to 24 carbon atoms, FLN represents a fullerene skeleton, and n represents an integer of 1 or more. The compound represented by the formula: Lubricating oil composition. [2] The lubricating oil composition according to the above item [1], wherein n is 1 to 5. [3] R 1 and R 2 The lubricating oil composition according to the above item [1] or [2], wherein is a tert-butoxy group. [4] The lubricating oil 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] A dissolving process for dissolving a fullerene derivative in a base oil; The base oil is a multi-alkylcyclopentane oil or an ionic liquid; The fullerene derivative is a compound represented by the formula (1). A method for producing a lubricating oil composition. [6] A method for producing a lubricating oil composition according to the preceding item [5], further comprising 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. [7] The method for producing a lubricating oil composition according to the above item [6], wherein the oxygen gas partial pressure in the non-oxidizing atmosphere is 10 Pa or less. [8] The method for producing a lubricating oil composition according to the above item [6] or [7], 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. [9] The method for producing a lubricating oil composition according to any one of the above items [6] to [8], wherein the treatment time of the addition reaction step is from 5 minutes to 24 hours.

[10] The method for producing a lubricating oil composition according to any one of [6] to [9] above, wherein the addition reaction step is a step of heat-treating the solution of the fullerene derivative obtained in the dissolving step.

[11] The method for producing a lubricating oil composition according to the above item

[10] , wherein the temperature of the heat treatment is higher than the upper limit use temperature of the base oil and is in the range of the upper limit use temperature +200°C or less.

[12] The method for producing a lubricating oil composition according to any one of items [6] to [9], 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.

[13] The method for producing a lubricating oil composition according to the above item

[12] , wherein the radiation is ultraviolet light having a wavelength of 190 nm to 365 nm.

[14] The method for producing a lubricating oil composition according to the above item

[12] or

[13] , wherein the energy of the radiation irradiated in the addition reaction step is 1 J to 100 J per 1 mL of the solution of the fullerene derivative.

[15] The method for producing a lubricating oil composition according to any one of items [6] to

[14] above, further comprising an insoluble component removing step of removing insoluble components from the solution containing the fullerene derivative.

[16] A machine using the lubricating oil composition according to any one of the above items [1] to [4] in a sliding part that slides under vacuum. Effect of the Invention

[0015] According to the present invention, there are provided a lubricating oil composition having a low vapor pressure in which an increase in vapor pressure due to base oil deterioration is suppressed, a method for producing the same, and a vacuum device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The lubricating oil composition, its manufacturing method, and machinery according to the embodiment of the present invention will be described below. Note that the present embodiment is specifically described to better understand 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.

[0017] (Lubricating oil composition) The lubricating oil composition according to this embodiment contains a base oil and a fullerene derivative, the base oil being a multiple alkylcyclopentane oil or an ionic liquid, and the fullerene derivative being a compound represented by formula (1) above.

[0018] (Base oil) The base oil contained in the lubricating oil composition of this embodiment is an ionic liquid such as a multiple alkylcyclopentane oil or Dialkylpiperidin bis(trifluoromethanesulfonyl)imide, and preferably has a low vapor pressure. The base oil preferably does not contain any volatile components. Specifically, the vapor pressure of the base oil at 25°C is preferably 1 Pa or less, more preferably 0.1 Pa or less, and particularly preferably 0.01 Pa or less.

[0019] The molecule of multiply alkylated cyclopentane oil (hereinafter sometimes referred to as "MAC oil") has a structure in which multiple alkyl groups are bonded to a cyclopentane ring. The total number of carbon atoms of these alkyl groups is preferably 48 to 112. The total number of carbon atoms may be, for example, 48 to 60, 48 to 80, or 70 to 112. The number of carbon atoms of each alkyl group may be the same or different. The number of alkyl groups bonded to the cyclopentane ring can also be selected arbitrarily, and may be, for example, 1 to 5, 2 to 4, or 3 to 4. More specific examples include tris(2-octyldodecyl)cyclopentane in which three alkyl groups with 20 carbon atoms are bonded, and tetra(dodecyl)cyclopentane in which four alkyl groups with 12 carbon atoms are bonded, and further include mixtures thereof.

[0020] Ionic liquids are ionic compounds consisting of an anion moiety and a cation moiety, and those which are liquid at room temperature to 80° C. are particularly preferred because they are easy to use. Examples of the anion moiety include bis(trifluoromethanesulfonyl)imide, bis(fluorosulfonyl)imide, diethylphosphate, dicyanamide, hexafluorophosphate, tetrafluoroborate, and halides. Examples of the cation moiety include lithium, cyclohexyltrimethylammonium, ethyldimethylphenylethylammonium, methyltrioctylammonium, 1-aryl-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-butyl-2,3-diethylimidazolium, 3,3'-(butane-1,4-dyl)bis(1vinyl-3-imidazolium), 1-decyl-3-methylimidazolium, 1-butyl-4-methylpyridium, 4-ethyl-4-methylmorpholinium, tetrabutylphosphonium, tributyl(2-methoxyethyl)phosphonium, trihexyl(tetradecyl)phosphonium, butyl-1-methylpiperidium, 1-butylpyridium, 1-butyl-methylpyrrolidinenium, and tributylsulfonium. Specific examples of ionic liquids include compounds obtained by appropriately combining these compounds in the cation portion and the anion portion. The compounds in the cation portion and the anion portion to be combined do not have to be of one type each. In other words, one or more of each compound may be combined with each other.

[0021] (Fullerene derivatives) The fullerene derivative contained in the lubricating oil composition of this embodiment is a compound represented by the above formula (1).

[0022] The types of fullerene skeletons in fullerene derivatives include, for example, C 60 Or C 70 From the viewpoint of availability of the raw material fullerene, the fullerene skeleton portion is preferably C 60 Or C 70 Derivatives of C are preferred. 60 More preferred are derivatives of the formula: In addition, the fullerene derivative may be a mixture of these fullerene skeleton parts with different structures. In this case, the fullerene skeleton part is C 60 As the fullerene derivative, a commercially available product may be used, but it may also be obtained by the method of Patent Document 5 or 6 or the method of the Examples described below.

[0023] In the formula (1), n ​​is an integer of 1 or more, and from the viewpoint of the solubility of the fullerene derivative in the base oil, it is preferably 2 or more. In addition, n can be increased as the size of the fullerene skeleton increases, but is preferably 5 or less from the viewpoint of the stability of the fullerene skeleton.

[0024] The alkoxy group in the formula (1) has 2 to 24 carbon atoms, and preferably has 3 to 8 carbon atoms, from the viewpoint of the solubility of the fullerene derivative in the base oil. 1 and R 2 may be different alkoxy groups or may be the same, but from the viewpoint of ease of production, they are preferably the same.

[0025] The fullerene derivative concentration in the lubricating oil composition can be selected arbitrarily as long as it is less than the saturation 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, and even more preferably 0.1 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. In addition, the concentration is preferably less than the saturation solubility in the usage environment from the viewpoint of preventing precipitation of the fullerene derivative, and more preferably 1 μmol / g or less, and even more preferably 0.1 μmol / g or less from the economic viewpoint. These upper and lower limits can be arbitrarily combined according to the purpose. In addition, each of the concentrations represents the total concentration of the fullerene derivative and the adduct when the adduct described later exists.

[0026] (adduct) The lubricating oil 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 the 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 to 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 the base oil, so that it can be used in a wider variety of environments without worrying about precipitation. Therefore, if it is an adduct, the solubility can be improved even if n in the formula (1) is not large.

[0027] (Additives) The lubricating oil composition of the present embodiment can contain additives that are substantially free of volatile components, within a range that does not impair the effect of the lubricating oil 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, etc. These additives may be used alone or in combination of two or more.

[0028] Examples of the antioxidant include butylhydroxytoluene (BHT), butylhydroxyanisole (BHA), and dialkyldiphenylamine.

[0029] Examples of the viscosity index improver include hydrogenated additives of polyalkylstyrene and styrene-diene copolymers.

[0030] Examples of the extreme pressure additive include dibenzyl disulfide, allyl phosphate, allyl phosphite, amine salts of allyl phosphate, allyl thiophosphate, and amine salts of allyl thiophosphate.

[0031] Examples of the detergent dispersant include benzylamine succinic acid derivatives, alkylphenol amines, and the like. Examples of the pour point depressant include chlorinated paraffin-naphthalene condensates, chlorinated paraffin-phenol condensates, polyalkylstyrenes, and the like.

[0032] The demulsifier may, for example, be an alkylbenzene sulfonate.

[0033] The corrosion inhibitor may, for example, be a dialkylnaphthalene sulfonate.

[0034] (Method of producing lubricating oil composition) The method for producing the lubricating oil composition of this embodiment includes a dissolving step of dissolving a fullerene derivative in a base oil to obtain a solution of the fullerene derivative. The base oil is the above-mentioned polyalkylcyclopentane oil or ionic liquid, and the fullerene derivative is a compound represented by the above-mentioned formula (1). 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.

[0035] The dissolution in the dissolution step can be carried out by any method, and is preferably carried out by, for example, mechanical stirring, ultrasonic irradiation, etc. When the base oil is a low-viscosity liquid at room temperature, stirring may be carried out at room temperature. On the other hand, when the base oil is a high-viscosity liquid or solid at room temperature, it is preferable to heat the base oil to a low-viscosity liquid state and then stir and dissolve the base oil.

[0036] The concentration of the fullerene derivative can be adjusted by the amount of the 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 a 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 a removal step described later is performed, it is preferable to perform the dilution after the removal step, since this makes it easier to adjust the concentration to a more accurate level. 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.

[0037] (Removal process) The solution of the fullerene derivative obtained in the dissolving step may contain insoluble components. In that case, it is preferable to remove these insoluble components. That is, the method for producing the lubricating oil composition may further include a removing step of removing insoluble components from the solution of the fullerene derivative obtained in the dissolving step or any of the steps thereafter. The method for removing the insoluble components can be selected arbitrarily, and examples thereof include a method of filtering using a membrane filter, a method of sedimentation and removal using a centrifuge, and a method of using both of these methods in combination.

[0038] The solution of the fullerene derivative obtained in the dissolving step may be used as the lubricating oil composition as it is, but it is preferable to further process the solution of the fullerene derivative by carrying out the addition reaction step described below to obtain the lubricating oil composition.

[0039] (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 lubricating oil 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 in a non-oxidizing atmosphere to generate the adduct.

[0040] The adduct may be obtained by carrying out either or both of the heat treatment and the radiation exposure, or by carrying out both simultaneously.

[0041] The adduct obtained by this step 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.

[0042] The conversion 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, if the fullerene skeleton is C 60 When the derivative is used, in the solution of the fullerene derivative before heat treatment or radiation treatment, peaks of m / z=1148, 1362, 1576, and 1790 corresponding to the fullerene derivatives with n of 2, 3, 4, and 5 are confirmed. In contrast, in the lubricating oil composition after treatment, the peaks of 1148, 1362, 1576, and 1790 are reduced, and multiple peaks of adducts appear. As main peaks, peaks 1148+N, 1148+2N, 1362+N, 1362+2N, 1576+N, 1576+2N, 1790+N, and 1790+2N 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 considered to be due to the addition of two molecules of alkyl radicals generated by the cleavage of the base oil to the fullerene derivative.

[0043] 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]

[0044] 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 lubricating oil composition are more stably exhibited from the beginning of use, friction wear of the sliding parts of mechanical devices is suppressed, and the generation of volatile components due to deterioration of the base oil is easily suppressed.

[0045] Therefore, in this embodiment, it is preferable to monitor the fullerene derivative concentration in the fullerene derivative solution during the addition reaction step, and perform the reaction until the fullerene derivative concentration is 0.1 to 0.7 relative to the concentration of the fullerene derivative before the heat treatment or radiation irradiation treatment. In addition, the heat treatment or radiation irradiation treatment is preferably performed for a treatment time of 5 minutes to 24 hours, which makes it easier to operate the heat treatment or radiation treatment. For example, the heat treatment temperature or radiation irradiation intensity can be increased to shorten the treatment time, and conversely, the heat treatment temperature or radiation irradiation intensity can be decreased to lengthen the treatment time. In addition, in radiation irradiation, for example, a method of irradiating radiation with a relatively high radiation intensity for a short time (about 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.

[0046] 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 cleavage molecules to suppress the formation of adducts. Therefore, it is preferable to remove oxygen molecules from the solution of the fullerene derivative as much as possible and perform heat treatment or radiation treatment under a non-oxidizing atmosphere. The non-oxidizing atmosphere in the heat treatment step or radiation irradiation is preferably 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 the non-oxidizing atmosphere. The following two methods are specific examples of the heat treatment, and the following one method is specific examples of the radiation irradiation.

[0047] 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 + 200 ° 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 150 ° C. or more and 300 ° C. or less, and more preferably 200 ° C. or more and 250 ° 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, etc., from the viewpoint of the above, depending on the circumstances of the equipment that can be handled.

[0048] The method of creating a non-oxidizing atmosphere can be selected arbitrarily, but for example, a solution of a fullerene derivative is placed in an airtight metal container such as stainless steel, and then the container is 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.

[0049] Alternatively, a method of creating a non-oxidizing atmosphere may 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, the inside of the container is reduced in pressure to create a non-oxidizing atmosphere, and the container is heated while maintaining this state, whereby the solution of the fullerene derivative can be heat-treated.

[0050] The fullerene derivative solution can be heated by any method selected from the above, for example, by heating from the outside in an oil bath or the like, by irradiating with infrared rays, or by irradiating with microwaves.

[0051] Radiation 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 CC single bond is cleaved by ultraviolet light with a wavelength of 341 nm or less. In addition, when the radiation irradiation treatment is performed at room temperature, thermal vibrations are superimposed, so that a CC single bond is cleaved even by ultraviolet light having 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 a large cleaved molecule that retains 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.

[0052] The radiation irradiation treatment is preferably carried out in a non-oxidizing atmosphere, as in the heat treatment. 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 transmits the radiation used. For example, when irradiating with ultraviolet light, the stainless steel container is entirely or partially replaced with a material that transmits ultraviolet light, such as quartz glass.

[0053] The amount of energy of radiation irradiated in the radiation irradiation treatment 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 solution of the fullerene derivative. In this range, the concentration range of the fullerene derivative after the treatment obtained from the above formula, that is, 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.

[0054] 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. The amount of ultraviolet irradiation is measured in advance using an ultraviolet photometer to determine the energy density (mW / cm) of the ultraviolet irradiation light. 2 ) and then measure the exposure time (seconds) and exposure range (cm 2 ) is specified. From these, the energy amount (J) of the ultraviolet light 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 lamps that easily blink, such as LEDs, or shutter equipment 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.

[0055] According to the lubricating oil composition of the present embodiment, not only is it excellent in wear resistance, but it can also have a low vapor pressure, and furthermore, the generation of volatile components accompanying base oil deterioration can be suppressed, and the vapor pressure of the lubricating oil composition can be suppressed from increasing.The lubricating oil composition of the present embodiment can be used for various applications, and is particularly preferably applied to mechanical devices that use the lubricating oil composition in the sliding parts that slide under vacuum.Such mechanical devices are suitable for use in vacuum containers and in outer space.

[0056] Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims. EXAMPLES

[0057] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0058] [Synthesis example] In a reaction vessel, 9.80 g of di-t-butyl malonate (manufactured by Tokyo Chemical Industry Co., Ltd.) was placed under a nitrogen stream, and 150 ml of 1,2,4-trimethylbenzene and 6.50 g of diazabicyclo-7-undecene were further added and the temperature was maintained at 4°C while stirring. Furthermore, a solution of 10.9 g of iodine (manufactured by Tokyo Chemical Industry Co., Ltd.) 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 addition, the temperature was returned to room temperature. Thereafter, fullerene (nanom (registered trademark) mix ST.C, manufactured by Frontier Carbon Corporation) was added. 60 A fullerene mixture mainly composed of. A solution of 5.00g of 1,2,4-trimethylbenzene dissolved in 350ml of 1,2,4-trimethylbenzene was added to the reaction solution while stirring. After that, a solution of 6.90g of diazabicyclo-7-undecene diluted with 5ml 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 solution of sodium sulfite. The organic layer was washed twice with 100ml of dilute sulfuric acid (1N), washed three times with 200ml of pure water, and the organic layer was distilled under reduced pressure to obtain 9.4g of a reddish brown solid. Furthermore, the product was separated and purified using a silica gel column chromatograph with a mixed solvent of hexane and ethyl acetate, 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).

[0059] [Example 1] (Preparation of Lubricating Oil Composition) About 0.001 g of the fullerene derivative obtained in the synthesis example was mixed with 10 g of MAC oil, tris(2-octyldodecyl)cyclopentane (manufactured by Nye Lubricants, synthetic oil 2001A, referred to as "MAC oil A" in Table 1), as a base oil. The resulting mixture was stirred at room temperature for 36 hours using a stirrer. Next, the mixture was 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 obtained solution of the fullerene derivative was measured and found to be 0.1 μmol / g. The obtained solution of the fullerene derivative was used as a lubricating oil composition.

[0060] The concentration of the fullerene derivative was measured using an ultraviolet absorption spectrograph (Shimadzu Corporation UV2400PC series). Specifically, the amount of the fullerene derivative in the sample such as the lubricating oil composition was quantified by measuring absorbance (wavelength 295 nm) in a stone cell using this device. Also, a calibration curve was created using the fullerene derivative.

[0061] (Evaluation of wear resistance) The wear resistance of the obtained lubricating oil composition was 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 lubricating oil composition was applied to one main surface of the substrate, and the substrate was kept at a constant temperature of 25°C. Next, the substrate was rotated and the fixed ball was slid on one main surface of the substrate through the lubricating oil composition so that the ball drew a circular orbit on the substrate. The speed of the ball on one main surface of the substrate was 0.55 cm / sec, and the load of the ball on 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 results are shown in Table 1.

[0062] (Evaluation of seizure resistance) The resulting lubricating oil compositions were 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 lubricating oil 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 lubricating oil 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 main surface of the substrate by the ball. When the ball slid 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.

[0063] (Stability evaluation) Using a thermal desorption analyzer (Rigaku Corporation, TPD type V), the presence or absence of components volatilizing from the lubricating oil composition under high vacuum was measured. -5 The degree of gas desorption in Pascal was measured. In order to eliminate the influence of molecules with a molecular weight smaller than that of carbon dioxide (molecular weight 44), the degree of gas desorption was taken as the integrated value of the peaks with a molecular weight of 46 to 200. As a comparative product, a similar measurement was performed using a MAC oil 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 taken as 1 (reference value). The ratio of the integrated value of the peak due to the measured desorbed gas of the lubricating oil composition to this reference value was taken as the degree of gas desorption. It can be said that the smaller the degree of gas desorption, the better the stability under high vacuum.

[0064] 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 generate heat, 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, and the amount of gas release components increases, which is not preferable. The results are shown in Table 1.

[0065] [Comparative Example 1] A lubricating oil composition was obtained 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. The results of the wear resistance and gas release rate of the obtained lubricating oil composition are shown in Table 1.

[0066] [Comparative Example 2] Except for not adding a fullerene derivative to the MAC oil, a lubricating oil composition was obtained in the same manner as in Example 1. The results of the wear resistance and gas release rate of the obtained lubricating oil composition are shown in Table 1.

[0067] As can be seen from Table 1, the lubricating oil composition of Example 1 had similar seizure resistance to those of Comparative Examples 1 and 2, but had a smaller diameter of the friction surface and was therefore superior in wear resistance. In addition, the degree of gas desorption from the lubricating oil composition before the wear resistance test was low, indicating that the composition had excellent stability under high vacuum.

[0068] Comparing Example 1 and Comparative Example 1, the wear resistance and seizure resistance were comparable, but Example 1 was superior to Comparative Example 1 in the degree of gas release before and after the wear resistance test.

[0069] Comparing Example 1 and Comparative Example 2, the degree of gas release was excellent to the same extent, but the wear resistance and seizure resistance were reduced in Comparative Example 2, and the degree of gas release after the wear resistance test was significantly inferior. This shows that adding a fullerene derivative to MAC oil improves the wear resistance and seizure resistance, and as a result, the amount of gas release is suppressed.

[0070] [Example 2] The solution of the fullerene derivative obtained in Example 1 (the lubricating oil composition of Example 1) was irradiated with ultraviolet light to obtain a lubricating oil composition. The obtained lubricating oil composition was measured for wear resistance, seizure resistance, and gas release rate in the same manner as in Example 1. The results are shown in Table 1.

[0071] 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% or more by volume (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 fullerene derivatives placed in the quartz cell was intermittently irradiated with ultraviolet light.

[0072] 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, and the irradiation range was 2 cm. 2 While measuring with an ultraviolet illuminometer (wavelength 230 nm-390 nm), the output was set to 1 W / cm 2 The irradiation timer was set to 1 second, and settings were made so that an energy of 2 J (0.7 J per mL of fullerene derivative solution) could be applied in one irradiation.

[0073] 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 1 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 lubricating oil composition. The fullerene derivative concentration of this lubricating oil composition was measured to be 0.025 μmol / g, and the residual ratio was 0.25. The results are shown in Table 1.

[0074] As shown in Table 1, the lubricating oil composition of Example 2 exhibited better wear resistance and gas release rate than those of Example 1. Furthermore, there was little increase in the gas release rate before and after the wear resistance test, indicating that the composition had better stability under high vacuum.

[0075] In addition, the fullerene derivative solution before UV irradiation and the lubricating oil 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 were fullerene derivative peaks 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 addition to the above-mentioned peaks, the lubricating oil composition was newly confirmed to have the main peaks of m / z=1843, 1963, 2057, 2177, 2271, 2393, 2485, 2605, 2752, 2872, 2966, 3086, 3180, 3302, 3394, 3514, etc. From these findings, it was confirmed that the fullerene derivative and the resulting adduct were present in the solution (lubricating oil composition) of the fullerene derivative after ultraviolet irradiation. Note that in other Examples and Comparative Examples, the solutions of the fullerene derivative before and after the heat treatment or radiation treatment were similarly analyzed. As a result, no adduct was confirmed in the solution of the fullerene derivative before the heat treatment or radiation treatment, but the adduct was confirmed after these treatments.

[0076] [Example 3] A lubricating oil composition was obtained in the same manner as in Example 2, except that instead of irradiating ultraviolet rays, the solution of the fullerene derivative contained in a quartz cell was immersed in an oil bath at 200° C. and heated. The results of the wear resistance, seizure resistance and gas release rate of the obtained lubricating oil composition are shown in Table 1.

[0077] In the heating of Example 3, about 0.1 ml of the fullerene derivative solution was extracted from the inside of the quartz cell every 5 minutes using a syringe, and the fullerene derivative concentration was measured using UV spectrum to determine the residual ratio. The residual ratio reached 0.2 15 minutes after the start of measurement. For this reason, the quartz cell was removed from the oil bath and cooled to room temperature to obtain a lubricating oil composition. The fullerene derivative concentration of the lubricating oil composition was measured to be 0.015 μmol / g, and the residual ratio was 0.15.

[0078] As shown in Table 1, the lubricating oil composition of Example 3, which was subjected to heat treatment as an addition reaction step, also exhibited excellent wear resistance and gas release rate, similar to that of Example 2, which was subjected to ultraviolet irradiation. In addition, it is presumed that because these have excellent wear resistance, decomposition of the base oil is unlikely to occur, and the amount of volatile components produced is suppressed.

[0079] [Example 4] A lubricating oil 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 the radiation source, and irradiation was performed for 20 seconds. 2 , output is 0.2W / cm 2 That is, the lubricating oil composition was irradiated with 20 J of ultraviolet light (7 J per 1 mL of fullerene derivative solution) for 20 seconds. The fullerene derivative concentration in the lubricating oil composition was measured and found to be 0.022 μmol / g, with a residual rate of 0.22. The results of the wear resistance, seizure resistance, and gas release rate of the obtained lubricating oil composition are shown in Table 1.

[0080] [Example 5] A lubricating oil composition was obtained in the same manner as in Example 2, except that an X-ray irradiation device (Torec, RIX-250C-2) was used as a radiation source and X-ray irradiation was performed for 480 seconds. The fullerene derivative concentration of the obtained lubricating oil composition was measured and found to be 0.020 μmol / g, and the residual ratio was 0.20. The wear resistance, seizure resistance, and gas release rate of the obtained lubricating oil composition are shown in Table 1.

[0081] Comparing Example 5 and Example 4, both were irradiated with radiation, and as a result, the residual rate decreased to the same extent. However, in Example 4, the abrasion resistance and the degree of gas released after the abrasion resistance test were superior to Example 5. Also, comparing Example 4 and Example 2, both were irradiated with ultraviolet light, and as a result, the residual rate decreased to the same extent. However, in Example 2, the abrasion resistance and the degree of gas released after the abrasion 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.

[0082] [Example 6] A lubricating oil composition was obtained in the same manner as in Example 1, except that the ionic liquid 1-decyl-3-methyl-imidazolium bis(trifluoromethanesulfonyl)imide (Tokyo Chemical Industry Co., Ltd., shown as "ionic liquid A" in Table 1) was used as the base oil. The results of the wear resistance, seizure resistance and gas release rate of the obtained lubricating oil composition are shown in Table 1.

[0083] [Comparative Example 3] A lubricating oil composition was obtained in the same manner as in Example 6, except that fullerene (nanom (registered trademark) mix ST, manufactured by Frontier Carbon Corp.) was used instead of the fullerene derivative. The results of the wear resistance, seizure resistance and gas release rate of the obtained lubricating oil composition are shown in Table 1.

[0084] [Comparative Example 4] A lubricating oil composition was obtained in the same manner as in Example 6, except that no fullerene derivative was added to the ionic liquid of Example 6. The results of the wear resistance, seizure resistance and gas release rate of the obtained lubricating oil composition are shown in Table 1.

[0085] [Example 7] A lubricating oil composition was obtained in the same manner as in Example 3, except that 1-decyl-3-methyl-imidazolium bis(trifluoromethanesulfonyl)imide (manufactured by Tokyo Chemical Industry Co., Ltd.), an ionic liquid, was used as the base oil. The fullerene derivative concentration in the lubricating oil composition was measured and found to be 0.012 μmol / g, with a residual ratio of 0.12. The wear resistance and degree of gas release of the obtained lubricating oil composition are shown in Table 1. The wear resistance, seizure resistance, and degree of gas release of the obtained lubricating oil composition are shown in Table 1.

[0086] [Example 8] A lubricating oil composition was obtained in the same manner as in Example 2, except that 1-decyl-3-methyl-imidazolium bis(trifluoromethanesulfonyl)imide (manufactured by Tokyo Chemical Industry Co., Ltd.), an ionic liquid, was used as the base oil. The fullerene derivative concentration in the lubricating oil composition was measured and found to be 0.035 μmol / g, with a residual ratio of 0.35. The wear resistance and degree of gas release of the obtained lubricating oil composition are shown in Table 1. The wear resistance, seizure resistance, and degree of gas release of the obtained lubricating oil composition are shown in Table 1.

[0087] [Example 9] A lubricating oil composition was obtained in the same manner as in Example 1, except that the ionic liquid 1-butyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide (referred to as "ionic liquid B" in Table 1) was used as the base oil. The wear resistance, seizure resistance and degree of gas release of the obtained lubricating oil composition are shown in Table 1.

[0088] [Comparative Example 5] A lubricating oil composition was obtained in the same manner as in Example 9, except that fullerene (nanom (registered trademark) mix ST, manufactured by Frontier Carbon Corp.) was used instead of the fullerene derivative. The results of the wear resistance, seizure resistance and gas release rate of the obtained lubricating oil composition are shown in Table 1.

[0089] Comparing Example 9 and Comparative Example 5, Example 9 using a fullerene derivative was superior to Comparative Example 5 in the degree of gas desorption before and after the wear resistance test. [Comparative Example 6] A lubricating oil composition was obtained in the same manner as in Example 9, except that no fullerene derivative was added to the ionic liquid of Example 9. The results of the wear resistance, seizure resistance and gas release rate of the obtained lubricating oil composition are shown in Table 1.

[0090] [Example 10] A lubricating oil composition was obtained in the same manner as in Example 3, except that the ionic liquid 1-butyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide was used as the base oil. The fullerene derivative concentration in the lubricating oil composition was measured to be 0.018 μmol / g, and the residual ratio was 0.18. The wear resistance, seizure resistance, and gas release rate of the obtained lubricating oil composition are shown in Table 1.

[0091] [Example 11] A lubricating oil composition was obtained in the same manner as in Example 2, except that the ionic liquid 1-butyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide was used as the base oil. The fullerene derivative concentration in the lubricating oil composition was measured to be 0.040 μmol / g, and the residual ratio was 0.40. The wear resistance, seizure resistance, and gas release rate of the obtained lubricating oil composition are shown in Table 1.

[0092] The comparison results of Examples 10 and 11 with Example 9 showed the same tendency as the comparison results of Examples 7 and 8 with Example 6. That is, it was found that even with different ionic liquids, the ultraviolet irradiation treatment and the heat treatment are effective in terms of the wear resistance effect and the reduction of desorbed gas.

[0093] [Example 12] A lubricating oil composition was obtained in the same manner as in Example 1, except that the ionic liquid 1-butyl-4-methyl-pyridinium bis(trifluoromethanesulfonyl)imide (referred to as "ionic liquid C" in Table 1) was used as the base oil. The wear resistance, seizure resistance and gas release rate of the obtained lubricating oil composition are shown in Table 1.

[0094] [Comparative Example 7] A lubricating oil composition was obtained in the same manner as in Example 12, except that fullerene (nanom mix ST, manufactured by Frontier Carbon Corp.) was used instead of the fullerene derivative. The wear resistance, seizure resistance and degree of gas release of the obtained lubricating oil composition are shown in Table 1.

[0095] Comparing Example 12 with Comparative Example 7, Example 12 using the fullerene derivative had a better gas release rate before and after the wear resistance test. This was similar to the comparison results between Example 1 and Comparative Example 1 and the comparison results between Example 6 and Comparative Example 3. In other words, it was found that even if the base oil was different, it was effective to use a fullerene derivative from the viewpoint of reducing the gas release rate.

[0096] [Comparative Example 8] A lubricating oil composition was obtained in the same manner as in Example 13, except that no fullerene derivative was added to the ionic liquid of Example 12. The results of the wear resistance, seizure resistance and gas release rate of the obtained lubricating oil composition are shown in Table 1.

[0097] [Example 13] A lubricating oil composition was obtained in the same manner as in Example 3, except that the ionic liquid 1-butyl-4-methyl-pyridinium bis(trifluoromethanesulfonyl)imide was used as the base oil. The fullerene derivative concentration in the lubricating oil composition was measured to be 0.018 μmol / g, and the residual ratio was 0.18. The wear resistance, seizure resistance, and gas release rate of the obtained lubricating oil composition are shown in Table 1.

[0098] [Example 14] A lubricating oil composition was obtained in the same manner as in Example 2, except that the ionic liquid 1-butyl-4-methyl-pyridinium bis(trifluoromethanesulfonyl)imide was used as the base oil. The fullerene derivative concentration in the lubricating oil composition was measured to be 0.040 μmol / g, and the residual ratio was 0.40. The wear resistance, seizure resistance, and gas release rate of the obtained lubricating oil composition are shown in Table 1.

[0099] The comparison results of Example 6 and Comparative Examples 3 and 4, Example 9 and Comparative Examples 5 and 6, and Example 12 and Comparative Examples 7 and 8, in which the base oil is an ionic liquid, showed a similar tendency to the comparison results of Example 1 and Comparative Examples 1 and 2, in which the base oil is a MAC oil. Furthermore, the comparison results of Examples 7 and 8 and Example 6, Examples 10 and 11 and Example 9, and Examples 13 and 14 and Example 12, in which the base oil is an ionic liquid, showed a similar tendency to the comparison results of Examples 2 and 3 and Example 1, in which the base oil is a MAC oil. That is, it was found that this embodiment can be effectively applied even with different base oils.

[0100] [Table 1] [Industrial Applicability]

[0101] The lubricating oil composition of the present invention can be used in various applications, but is particularly preferably applicable to mechanical devices in which the lubricating oil composition is used in sliding parts that slide under vacuum.Such mechanical devices include, for example, devices and equipment used in vacuum vessels, high altitude regions or outer space, and more specifically, vacuum metallurgy devices for forging and joining, vacuum chemical devices for chemical reactions, vacuum thin film forming and processing devices for deposition and sputtering, analytical devices such as electron microscopes, vacuum test devices for bending, tensile and compression tests, aircraft, rockets, artificial satellites, etc.

Claims

1. Contains a base oil and a fullerene derivative, The base oil is a multi-alkylcyclopentane oil or an ionic liquid; The fullerene derivative is represented by the following general formula (1): [Formula 1] (In the above general formula (1), R １ and R ２ represents an alkoxy group having 2 to 24 carbon atoms, FLN represents a fullerene skeleton, and n represents an integer of 1 or more. The compound represented by the formula: Lubricating oil composition.

2. The lubricating oil composition according to claim 1, wherein n is an integer of 1 to 5.

3. The R １ and R ２ The lubricating oil composition according to claim 1 or 2, wherein is a tert-butoxy group.

4. 4. The lubricating oil composition according to claim 1, 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. A dissolving step of dissolving a fullerene derivative in a base oil, The base oil is a multi-alkylcyclopentane oil or an ionic liquid; The fullerene derivative is represented by the following general formula (1): [chemical 2] (In the above general formula (1), R 1 and R 2 represent an alkoxy group having 2 to 24 carbon atoms, 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 lubricating oil composition.

6. 6. The method for producing a lubricating oil composition according to claim 5, 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.

7. The method for producing a lubricating oil composition according to claim 6, wherein the partial pressure of oxygen gas in the non-oxidizing atmosphere is 10 Pa or less.

8. 8. The method for producing a lubricating oil composition according to claim 6 or 7, 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.

9. The method for producing a lubricating oil composition according to any one of claims 6 to 8, wherein the treatment time of the addition reaction step is from 5 minutes to 24 hours.

10. The method for producing a lubricating oil composition according to any one of claims 6 to 9, wherein the addition reaction step is a step of heat-treating the solution of the fullerene derivative obtained in the dissolving step.

11. The method for producing a lubricating oil composition according to claim 10, wherein the temperature of the heat treatment is in the range of exceeding the upper limit of use temperature of the base oil and not exceeding the upper limit of use temperature + 200°C.

12. 10. The method for producing a lubricating oil composition according to any one of claims 6 to 9, 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.

13. The method for producing a lubricating oil composition according to claim 12, wherein the radiation is ultraviolet light having a wavelength of 190 nm to 365 nm.

14. The method for producing a lubricating oil composition according to claim 12 or 13, 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.

15. The method for producing a lubricating oil composition according to any one of claims 6 to 14, further comprising an insoluble component removing step of removing insoluble components from the solution containing the fullerene derivative.

16. A mechanical device in which the lubricating oil composition according to any one of claims 1 to 4 is used in a sliding part which slides under vacuum.

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