METHOD FOR PRODUCING LUBRICATING OIL COMPOSITION, AND LUBRICATING OIL COMPOSITION

Abstract

This method for producing a lubricating oil composition includes: a step of dissolving fullerenes in a base oil mainly composed of a multiply alkylated cyclopentane oil or an ionic liquid containing an imide as a negative ion to obtain a fullerene solution; and a step of producing fullerenes adduct by subjecting the above-described fullerene solution to a heat treatment in a non-oxidizing atmosphere.

Claims

1. A method for producing a lubricating oil composition, comprising: a step of dissolving fullerenes in a base oil mainly composed of a multiply alkylated cyclopentane oil or an ionic liquid containing an imide as a negative ion configured to obtain a fullerene solution; and a step of producing fullerene adducts by subjecting the fullerene solution to a heat treatment in a non-oxidizing atmosphere.

2. The method for producing a lubricating oil composition according to claim 1, wherein an oxygen gas partial pressure in the non-oxidizing atmosphere is less than or equal to 10 pascals.

3. The method for producing a lubricating oil composition according to claim 1, wherein a temperature of the heat treatment is 80° C. to 300° C.

4. The method for producing a lubricating oil composition according to claim 1, wherein the heat treatment is performed until a concentration of fullerenes in the fullerene solution is 0.1 to 0.7 with respect to a concentration of fullerenes before the heat treatment.

5. The method for producing a lubricating oil composition according to claim 1, wherein the fullerene dissolved in the base oil is C.sub.60 or C.sub.70 or a mixture thereof.

6. The method for producing a lubricating oil composition according to claim 1, wherein a temperature of the heat treatment in the step of producing fullerene adducts is higher than or equal to an upper limit usage temperature of the base oil, and the difference between the temperature of the heat treatment and the upper limit usage temperature is within 200° C.

7. The method for producing a lubricating oil composition according to claim 1, the method further comprising: a step of removing an insoluble component using a membrane filter or a centrifugal separator after performing the step of obtaining the fullerene solution.

8. The method for producing a lubricating oil composition according to claim 1, wherein a heat treatment time in the step of producing fullerene adducts is 5 minutes to 24 hours.

9. The method for producing a lubricating oil composition according to claim 1, wherein the concentration of the fullerene in the fullerene solution is 1 mass ppm to 1,000 mass ppm.

10. The method for producing a lubricating oil composition according to claim 1, the method further comprising: an adjustment step of reducing a concentration of oxygen molecules before the step of producing fullerene adducts, wherein the adjustment step and the step of producing fullerene adducts are continuously performed, and wherein, in the adjustment step, the fullerene solution is placed into an airtight metal container and the inside of the metal container is substituted with an inert gas.

11. The method for producing a lubricating oil composition according to claim 1, the method further comprising: an adjustment step of reducing a concentration of oxygen molecules before the step of producing fullerene adducts, wherein the adjustment step and the step of producing fullerene adducts are continuously performed, and wherein, in the adjustment step, the fullerene solution is placed into an airtight metal container and the inside of the metal container is decompressed.

12. The lubricating oil composition comprising: a base oil mainly composed of a multiply alkylated cyclopentane oil or an ionic liquid containing an imide as a negative ion; and fullerene adducts obtained by adding a component derived from the base oil to fullerenes.

Description

EXAMPLES

[0083] Hereinafter, examples of the present invention will be described. The present invention is not limited to the following examples.

Example 1

(Preparation of Lubricating Oil Composition)

[0084] 0.001 g of a fullerene raw material (manufactured by Frontier Carbon Corporation, Nanom™ Purple ST C.sub.60) and 10 g of tris(2-octyldodecyl) cyclopentane (manufactured by Nye Lubricants, Synthetic Oil 2001A) which is a MAC oil as a base oil A were mixed with each other and stirred for 36 hours using a stirrer at room temperature. The obtained mixture was filtered with a 0.1 μm mesh membrane filter, and the obtained filtrate was used as a fullerene solution. The concentration of the fullerene in the fullerene solution was 100 ppm.

[0085] Next, the fullerene solution was placed into a 25 mL eggplant flask and covered with a three-way cock. Next, the three-way cock was opened, an injection needle was inserted thereinto, and nitrogen gas having a purity of 99.99 volume % (the partial pressure of gases other than nitrogen at normal pressure is 10 pascals or less) was allowed to flow at 60 mL/min for 10 minutes. Next, the three-way cock was closed and the eggplant flask was filled with nitrogen gas. That is, the eggplant flask was filled with nitrogen gas.

[0086] Next, about 0.01 mL of the fullerene solution was sampled from the inside of the eggplant flask every 5 minutes using an injector while heat-treating the fullerene solution by immersing the eggplant flask in an oil bath at 120° C., and the concentration of the fullerene was measured through high-performance liquid chromatography (HPLC) to calculate the fullerene residual ratio. 15 minutes after the start of the measurement, the fullerene residual ratio became 0.2, and therefore, the eggplant flask was taken out of the oil bath and cooled to room temperature to obtain a lubricating oil composition. The concentration of the fullerene in the lubricating oil composition was measured, and the result was 15 ppm. Therefore, the fullerene residual ratio was found to be 0.15.

[0087] Regarding the above-described measurement of the concentration of the fullerene, the concentration thereof was detected at an absorbance (wavelength of 309 nm) using a high-performance liquid chromatograph (manufactured by Agilent Technologies, 1200 series), a column YMC-Pack ODS-AM (150 mm×4.6) manufactured by YMC CO., LTD., and a 1:1 (volume ratio) mixture of toluene and methanol as a development solvent to quantitatively determine the amount of fullerene in a sample such as a lubricating oil composition. In addition, a calibration curve was created from the above-described fullerene raw material.

[0088] In addition, the obtained lubricating oil composition and the fullerene solution before a heat treatment were subjected to a component analysis with a molecular weight of 720 to 2,000 using a mass spectrometer (manufactured by Agilent Technologies, LC/MS, 6120). As a result, in the lubricating oil composition, signal intensity peaks of m/z=750, 764, 766, 778, 780, 792, 794, 796, 808, 806, 820, and 834 were newly confirmed compared to the fullerene solution (with a main peak of 720) before a heat treatment. From this, it was confirmed that the lubricating oil composition contained fullerene adducts.

(Evaluation of Abrasion Resistance)

[0089] The abrasion resistance of the obtained lubricating oil composition was evaluated using friction test (manufactured by Anton Paar, Ball-On-Disc Tribometer).

[0090] First, the material of a substrate and a ball was a high carbon chromium bearing steel material SUJ2, and the diameter of the ball was 6 mm. The lubricating oil composition was applied to one main surface of the substrate, and the substrate was heated to 100° C. Next, the ball was slid on the one main surface of the substrate via the lubricating oil composition so that the ball drew a concentric orbit. The sliding speed of the ball on the one main surface of the substrate was set to 15 cm/sec, and the load of the ball on the one main surface of the substrate was set to 20 N. The worn area on the ball surface when the sliding distance of the ball on the one main surface of the substrate was 400 m in total was observed with an optical microscope, the diameter of the worn area was measured, and the numerical value was regarded as an abrasion resistance. It can be said that the smaller the diameter of the worn area, the better the abrasion resistance. The results are shown in Table 1.

(Evaluation of Stability)

[0091] Components volatilized from the lubricating oil composition under high vacuum were measured using a temperature-programmed desorption gas analyzer (manufactured by Rigaku Corporation, TPD type V). The amount of desorbed gas of 0.02 g of the lubricating oil composition was measured at an atmospheric pressure of 10.sup.−4 pascals. In order to eliminate the influence of molecules having a molecular weight smaller than that of carbonic dioxide gas (molecular weight of 44), an integrated value of peaks of molecular weights of 46 to 200 was obtained as an amount of desorbed gas.

[0092] An integrated value of signal intensity due to trimethylbenzene (TMB) (manufactured by Tokyo Chemical Industry Co., Ltd.) was regarded as 1 (reference value), in a case where the measurement was performed in the same manner described above on a sample obtained by adding TMB as a volatile component to the base oil A so that the content of TMB was 1 mass ppm. And a ratio of an integrated value of peaks of signal intensity due to the above-described desorbed gas from the lubricating oil composition to the reference value was obtained as a degree of desorbed gas. It can be said that the smaller the degree of desorbed gas, the better the stability under high vacuum. The degree of desorbed gas was measured at two points, one before an abrasion resistance test of the lubricating oil composition and the other after the abrasion resistance test thereof. The results are shown in Table 1.

Comparative Example 1

[0093] A lubricating oil composition was obtained in the same manner as in Example 1 except that the above-described fullerene solution was not heated. The obtained lubricating oil composition was subjected to a component analysis with a molecular weight of 720 to 2,000 using a mass spectrometer (manufactured by Agilent Technologies, LC/MS, 6120). As a result, the peak of a fullerene adduct could not be detected, and it was confirmed that there was no fullerene adduct in the lubricating oil composition of Comparative Example 1. The results of the degree of desorbed gas and the abrasion resistance of the obtained lubricating oil composition are shown in Table 1.

Comparative Example 2

[0094] A lubricating oil composition was obtained in the same manner as in Example 1 except that fullerenes were not added to the base oil A and the base oil A was not heated. That is, the obtained lubricating oil composition was composed of only the base oil A in Comparative Example 2. The results of the degree of desorbed gas and the abrasion resistance of the obtained lubricating oil composition are shown in Table 1.

TABLE-US-00001 TABLE 1 Degree of desorbed gas of lubricating oil composition Composition Diameter Before After of lubricating Heat [μm] of abrasion abrasion oil composition treatment rubbing surface resistance test [−] resistance test [−] Example 1 Base oil A + Nitrogen 175 0.4 0.9 FLN Comparative Base oil A + None 210 0.4 1.5 Example 1 FLN Comparative Base oil A None 240 0.1 2.1 Example 2 Example 2 Base oil B + Nitrogen 270 0.2 0.6 FLN Comparative Base oil B + None 330 0.2 1.1 Example 3 FLN Comparative Base oil B None 360 0.1 1.3 Example 4 Example 3 Base oil A + 120° C., 175 0.2 0.7 FLN Vacuum Example 4 Base oil A + Nitrogen + 180 0.4 1.1 FLN 1% oxygen Example 5 Base oil A + Air 200 0.4 1.3 FLN Example 6 Base oil A + 85° C., 190 0.2 0.8 FLN Vacuum Example 7 Base oil A + 105° C., 185 0.2 0.8 FLN Vacuum Example 8 Base oil A + 210° C., 185 0.2 0.8 FLN Vacuum Example 9 Base oil A + 260° C., 200 0.2 1 FLN Vacuum Example 10 Base oil C + Nitrogen 275 0.2 0.6 FLN Comparative Base oil C + None 340 0.2 1.2 Example 5 FLN

[0095] As shown in Table 1, in Example 1, when the fullerene solution was obtained by adding fullerenes to a base oil A and was heat-treated in a nitrogen atmosphere, the diameter of the worn area was 175 μm, and the degassing degrees of the lubricating oil composition before and after the abrasion resistance test were respectively 0.4 and 0.9. Therefore, it was found that the abrasion resistance and the stability under high vacuum in Example 1 were excellent.

[0096] On the other hand, in Comparative Example 1, when the above-described fullerene solution was not heat-treated, the diameter of the worn area was 210 and the abrasion resistance was inferior to that of Example 1. In addition, the degassing degrees of the lubricating oil composition before and after the abrasion resistance test were respectively 0.4 and 1.5, and the stability under high vacuum after the abrasion resistance test was inferior to that of Example 1.

[0097] In addition, in Comparative Example 2, when no fullerene was added to a base oil A and the base oil A was not heat-treated, the diameter of the worn area was 240 μm, and the abrasion resistance was greatly inferior to that of Example 1. In addition, the degassing degrees of the lubricating oil composition before and after the abrasion resistance test were respectively 0.1 and 2.1, and the stability under high vacuum after the abrasion resistance test was greatly inferior to that of Example 1.

Example 2

[0098] A lubricating oil composition was obtained in the same manner as in Example 1 except that 1-decyl-3-methyl-imidazolium-bis(trifluoromethanesulfonyl) imide (manufactured by Tokyo Chemical Industry Co., Ltd.), which is an imide-based ionic liquid, was used as a base oil B. The obtained lubricating oil composition was subjected to a component analysis with a molecular weight of 720 to 2,000 using a mass spectrometer, and as a result, it was confirmed that there was fullerene adducts. The results of the degree of desorbed gas and the abrasion resistance of the obtained lubricating oil composition are shown in Table 1.

Comparative Example 3

[0099] A lubricating oil composition was obtained in the same manner as in Example 2 except that the fullerene solution was not heated. The obtained lubricating oil composition was subjected to a component analysis with a molecular weight of 720 to 2,000 using a mass spectrometer, and as a result, it was confirmed that no fullerene adduct is found. The results of the degree of desorbed gas and the abrasion resistance of the obtained lubricating oil composition are shown in Table 1.

Comparative Example 4

[0100] A lubricating oil composition was obtained in the same manner as in Example 2 except that fullerenes were not added to the above-described base oil B and the above-described base oil B was not heated. That is, the obtained lubricating oil composition was composed of only the base oil B in Comparative Example 4. The results of the degree of desorbed gas and the abrasion resistance of the obtained lubricating oil composition are shown in Table 1.

[0101] In Example 2, when the fullerene solution was obtained by adding fullerenes to a base oil B and was heat-treated in a nitrogen atmosphere, the diameter of the worn area was 270 μm. On the other hand, the diameter of the worn area in Comparative Example 3 where heat treatment was not performed was 330 μm, and the diameter of the worn area in Comparative Example 4 where no fullerene was added was 360 μm. In addition, the degassing degrees of the lubricating oil composition before and after the abrasion resistance test were respectively 0.2 and 0.6 in Example 2, 0.2 and 1.1 in Comparative Example 3, and 0.1 and 1.3 in Comparative Example 4. Comparing the results of Example 2, Comparative Example 3, and Comparative Example 4, the results showed that both the abrasion resistance and the degree of desorbed gas were favorable in a case where fullerenes were added to a base oil B and heating was performed, but both the abrasion resistance and the degree of desorbed gas were inferior in a case where no heat treatment was performed or in a case where only a base oil B was incorporated. This showed that the base oil B, which is an ionic liquid, also has the same tendency as that of the base oil A which was a MAC oil.

Example 3

[0102] A lubricating oil composition was obtained in the same manner as in Example 1 except that oxygen contained in the fullerene solution was removed by bringing the eggplant flask into a vacuum state with a vacuum pump instead of filling the eggplant flask with nitrogen gas. The results of the degree of desorbed gas and the abrasion resistance of the obtained lubricating oil composition are shown in Table 1.

Example 4

[0103] A lubricating oil composition was obtained in the same manner as in Example 1 except that nitrogen gas containing 1 volume% of oxygen gas was allowed to flow instead of filling the eggplant flask with nitrogen gas. The results of the degree of desorbed gas and the abrasion resistance of the obtained lubricating oil composition are shown in Table 1.

Example 5

[0104] A lubricating oil composition was obtained in the same manner as in Example 1 except that air was allowed to flow instead of filling the eggplant flask with nitrogen gas.

[0105] The results of the degree of desorbed gas and the abrasion resistance of the obtained lubricating oil composition are shown in Table 1.

[0106] The diameter of the worn area was 175 μm in Example 3, 180 μm in Example 4, and 200 μm in Example 5. In addition, the degassing degrees of the lubricating oil composition before and after the abrasion resistance test were respectively 0.2 and 0.7 in Example 3, 0.4 and 1.1 in Example 4, and 0.4 and 1.3 in Example 5. Comparing the results of Examples 1 and 3 to 5, it was found that the lower the concentration of oxygen gas in the heat treatment step, the better the abrasion resistance and the degassing degree.

Example 6

[0107] A lubricating oil composition was obtained in the same manner as in Example 3 except that the fullerene solution was heat-treated at 85° C. The results of the degree of desorbed gas and the abrasion resistance of the obtained lubricating oil composition are shown in Table 1.

Example 7

[0108] A lubricating oil composition was obtained in the same manner as in Example 3 except that the fullerene solution was heat-treated at 105° C. The results of the degree of desorbed gas and the abrasion resistance of the obtained lubricating oil composition are shown in Table 1.

Example 8

[0109] A lubricating oil composition was obtained in the same manner as in Example 3 except that the fullerene solution was heat-treated at 210° C. The results of the degree of desorbed gas and the abrasion resistance of the obtained lubricating oil composition are shown in Table 1.

Example 9

[0110] A lubricating oil composition was obtained in the same manner as in Example 3 except that the fullerene solution was heat-treated at 260° C. The results of the degree of desorbed gas and the abrasion resistance of the obtained lubricating oil composition are shown in Table 1.

[0111] The diameter of the worn area was 190 μm in Example 6, 185 μm in Examples 7 and 8, and 200 μm in Example 9. In addition, the degassing degrees of the lubricating oil composition before and after the abrasion resistance test were respectively 0.2 and 0.8 in Examples 6 to 8 and 0.2 and 1.0 in Example 9. Comparing the results of Examples 3 and 6 to 9, the improvement in abrasion resistance was best when the heat treatment temperature was 120° C., then 105° C. and 210° C., then 85° C., and then 260° C.

Example 10

[0112] A lubricating oil composition was obtained in the same manner as in Example 1 except that 1-butyl-4-methyl-pyridinium-bis(fluorosulfonyl) imide, referred to as base oil C, which is an imide-based ionic liquid, was used as a base oil. The obtained lubricating oil composition was subjected to a component analysis with a molecular weight of 720 to 2,000 using a mass spectrometer, and as a result, it was confirmed that there were fullerene adducts. The results of the degree of desorbed gas and the abrasion resistance of the obtained lubricating oil composition are shown in Table 1.

Comparative Example 5

[0113] A lubricating oil composition was obtained in the same manner as in Example 10 except that the fullerene solution was not heat-treated. The obtained lubricating oil composition was subjected to a component analysis with a molecular weight of 720 to 2,000 using a mass spectrometer, and as a result, it was confirmed that there was no fullerene adduct. The results of the degree of desorbed gas and the abrasion resistance of the obtained lubricating oil composition are shown in Table 1.

[0114] The diameter of the worn area was 275 μm in Example 10 and 340 μm in Comparative Example 5. In addition, the degassing degrees of the lubricating oil composition before and after the abrasion resistance test were respectively 0.2 and 0.6 in Example 10 and 0.2 and 1.2 in Comparative Example 5. Comparing the results of Example 10 and Comparative Example 5, the results showed that both the abrasion resistance and the degree of desorbed gas were favorable in a case where fullerenes were added to a base oil C and heating was performed, but both the abrasion resistance and the degree of desorbed gas were inferior in a case where no heating was performed. This showed that the base oil C also has the same tendency as that of the base oil A or the base oil B.

INDUSTRIAL APPLICABILITY

[0115] The lubricating oil composition of the present invention is useful for devices and equipment used in high altitude regions or outer space, or under high vacuum, and is significantly useful for long-term suppression of damage or abrasion of metal parts under vacuum in, for example, sliding portions of devices or equipment mounted on aircraft, spacecrafts, rockets, probes, space stations, and satellites.