JP7699368B2 - synthetic lubricant - Google Patents

Description

The present invention relates to synthetic lubricants and lubricant compositions that are useful as major components of various lubricants and lubricant compositions. In particular, the present invention relates to synthetic lubricants that have relatively good lubricity from room temperature to high temperatures up to about 100°C and have a viscosity index of 180 or more, and lubricant compositions that contain the synthetic lubricants.

In recent years, improved lubricant performance and properly adjusted lubricating performance are required for devices and machines used in various industrial fields such as automobiles, home appliances, electronic devices, and industrial machinery. In other words, not only are there improvements to conventional devices, such as faster devices and machines and smaller devices, but there is also a growing need for lubricating performance that can withstand harsher operating conditions and that is properly adjusted for each device or machine developed in various fields.

Lubricants are usually made up of base oil and additives according to the application. Base oil is the base material that determines the basic properties of the lubricant, and can be mineral oil, synthetic oil, etc.
Mineral oils are refined from petroleum lubricating oil fractions, and are generally inexpensive and have been widely used from the past to the present (see Non-Patent Document 1). However, mineral oils have poor heat resistance, are easily oxidized and deteriorated, and have poor durability. Furthermore, due to variations in molecular structure, it is becoming more difficult to obtain lubricating performance that is highly suited to each device or machine. In order to improve heat resistance and durability, various additives are sometimes blended, but depending on the type and application of the device or machine, there are cases where the blending of additives is restricted.

In contrast, synthetic oils are produced through a highly advanced and complex process, with as few impurities as possible removed, and are said to have relatively high heat resistance and lubricating performance with little variation. Although synthetic oils are more expensive than mineral oils, to date, hydrocarbon-based, ester-based, ether-based, silicone-based, fluorine-based, and other types have been developed and used depending on the application and mode of use (see Non-Patent Document 1).

As mentioned above, synthetic oils have relatively high heat resistance and provide lubricating performance with little variation, but in recent years, there has been an increasing demand for further energy and fuel savings in the operation of equipment and machinery, and there is a demand for synthetic oils that have a much smaller change in viscosity in response to temperature changes than conventional synthetic oils, i.e., synthetic oils with a significantly higher viscosity index.

However, currently, for example, PAO (poly-α-olefin) synthetic oils used in automobiles and the like have a viscosity index of only about 120 to 140. Furthermore, most ester-based synthetic oils have a viscosity index of about 120 to 150. For ether-based synthetic oils, those having a relatively high viscosity index are, for example, the synthetic oils described in Patent Document 1, which have a kinetic viscosity at 100° C. of 4.5 to 6.5 mm ² /s and a viscosity index of 120 to 140. Furthermore, among the polyether-based synthetic oils described in Non-Patent Document 2, those having a kinetic viscosity at 100° C. of less than 10.0 ^{mm 2} /s have a kinetic viscosity of 4.5 to 7.0 mm ² /s and a viscosity index of around 170.

Patent No. 6800441

“Quality properties of base oils used in the manufacture of various lubricants,” Juntsu Net 21, https://www.juntsu.co.jp/qa/qa0111.php Oil Chemistry, 29(9), 1980, pp.336-343. Tribologist, 65(5), 2018, pp.332-337.

As described above, there are no known synthetic ether oils that have a kinematic viscosity at 100° C. of 4.0 to 10.0 mm ² /s and a viscosity index of 180 or greater, which are sufficient lubricating properties for use in high-temperature lubrication applications.

On the other hand, regarding oligomers among silicone-based synthetic oils, Non-Patent Document 3 states that the viscosity index of the 1,5-didodecyltrisiloxane compound is 232. This value is significantly higher than the value (186) of a linear alkane with 26 carbon atoms. This suggests that the introduction of a siloxane moiety into the alkyl chain of a synthetic oil molecule may increase the viscosity index of the compound. However, such a compound has not been known until now.

The present invention has been made against the background of the conventional techniques and their problems as described above, and has an object to provide a novel compound that can be used for producing a synthetic lubricating oil having a kinetic viscosity at 100°C of 5.0 to 10.0 ^mm2 /s and a viscosity index of 180 or more.

The present inventors have conducted various tests and research to find a solution to the above problems, and as a result have discovered that a synthetic oil comprising a compound represented by the following formula (1) exhibits lubricating performance with a kinetic viscosity at 100°C of 5.0 to 10.0 ^mm2 /s and a viscosity index of 180 or more.

（式中、Ｒ^１は、炭素数３～２０の直鎖状又は分岐状炭化水素基であり、互いに同一であっても良いし、異なっていてもよい。Ｒ^２は、炭素数３～１２の直鎖状又は分岐状の２価の炭化水素基であり、互いに同一であっても良いし、異なっていてもよい。Ｒ^３は、水素原子又は炭素数１～１２の直鎖状若しくは分岐状炭化水素基である。ｎは１または２である。） The present invention has been completed based on the above-mentioned findings under the above-mentioned problems, and provides the following inventions in this case.
One aspect of the present invention is
<1> The compound represented by the following formula (1):

(In the formula, R ¹ is a linear or branched hydrocarbon group having 3 to 20 carbon atoms and may be the same as or different from each other. R ² is a linear or branched divalent hydrocarbon group having 3 to 12 carbon atoms and may be the same as or different from each other. ^{R 3} is a hydrogen atom or a linear or branched hydrocarbon group having 1 to 12 carbon atoms. n is 1 or 2.)

Another aspect of the present invention is a method for producing a
<2> The present invention relates to a synthetic lubricant comprising the compound according to <1>.
In one embodiment, the synthetic lubricating oil of the present invention comprises
<3> The synthetic lubricating oil according to <2>, characterized in that the kinetic viscosity at 100° C. is 5.0 to 10.0 ^{mm 2} /s and the viscosity index is 180 or more.
Another aspect of the present invention is a method for producing a
<4> A lubricating oil composition comprising the synthetic lubricating oil according to <2> or <3>.
In one embodiment, the lubricating oil composition of the present invention comprises
<5> A lubricating oil composition comprising the synthetic lubricating oil according to <2> or <3> as a base oil.

The compound of the present invention can provide a synthetic lubricating oil having lubricating properties with a kinematic viscosity at 100° C. of 5.0 to 10.0 ^{mm 2} /s and a viscosity index of at least 180. The synthetic lubricating oil can be suitably used in environments ranging from room temperature to high temperatures at least slightly above 100° C.

（式中、Ｒ^１は、炭素数３～２０の直鎖状又は分岐状炭化水素基であり、互いに同一であっても良いし、異なっていてもよい。Ｒ^２は、炭素数３～１２の直鎖状又は分岐状の２価の炭化水素基であり、互いに同一であっても良いし、異なっていてもよい。Ｒ^３は、水素原子又は炭素数１～１２の直鎖状若しくは分岐状炭化水素基である。ｎは１または２である。） The compound of the present invention is represented by the general formula (1):

(In the formula, R ¹ is a linear or branched hydrocarbon group having 3 to 20 carbon atoms and may be the same as or different from each other. R ² is a linear or branched divalent hydrocarbon group having 3 to 12 carbon atoms and may be the same as or different from each other. ^{R 3} is a hydrogen atom or a linear or branched hydrocarbon group having 1 to 12 carbon atoms. n is 1 or 2.)

In formula (1), R ¹ , R ² and R ³ may be selected from groups having an appropriate number of carbon atoms or a combination of a plurality of carbon atoms, preferably selected according to the required range of kinetic viscosity at 100° C. when the compound represented by formula (1) is used as a synthetic lubricant.
The above ^R1 is preferably a linear or branched alkyl group having 5 to 15 carbon atoms, and more preferably a linear alkyl group having 6 to 12 carbon atoms. Specific examples include a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, and a dodecyl group.

The above ^R2 is preferably a linear or branched divalent hydrocarbon group having 3 to 10 carbon atoms, and more preferably a linear alkylene group having 3 to 8 carbon atoms. Specific examples include a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, a heptamethylene group, and an octamethylene group.

The above ^R3 is preferably a hydrogen atom or a linear or branched alkyl group having 1 to 10 carbon atoms, and more preferably a hydrogen atom or a linear alkyl group having 1 to 8 carbon atoms.

The compound of the present invention may be produced by any method, but for example, it can be produced in accordance with the synthesis method disclosed in J. Am. Chem. Soc., 121(15), 1999, 3693-3703. The following formula (I) shows one embodiment of the method for producing the compound of the present invention. For example, the compound represented by the following general formula (2) can be produced by reacting 1,3-dialkenyloxy-4-alkylbenzene (compound 2) with 1-alkyl-1,1,3,3-tetramethyldisiloxane (compound 3).

（式（２）中、Ｒ^１は、炭素数３～２０の直鎖状又は分岐状炭化水素基である。Ｒ^２は、炭素数３～１２の直鎖状又は分岐状の２価の炭化水素基である。Ｒ^３は、水素原子又は炭素数１～１２の直鎖状若しくは分岐状炭化水素基である。Ｒ^４は、炭素数１～１０の直鎖状又は分岐状の２価の炭化水素基である。）

(In formula (2), R ¹ is a linear or branched hydrocarbon group having 3 to 20 carbon atoms. R ² is a linear or branched divalent hydrocarbon group having 3 to 12 carbon atoms. R ³ is a hydrogen atom or a linear or branched hydrocarbon group having 1 to 12 carbon atoms. ^{R 4} is a linear or branched divalent hydrocarbon group having 1 to 10 carbon atoms.)

The above compound 2 can be produced, for example, by reacting 4-alkylresorcinol with bromoalkene as shown in the following formula (II) in accordance with the synthesis method disclosed in Bioorg. & Med. Chem. Lett., 25 (2015) 1274-1278.

（式中、Ｒ^３は、水素原子又は炭素数１～１２の直鎖状若しくは分岐状炭化水素基である。Ｒ^４は、炭素数１～１０の直鎖状又は分岐状の２価の炭化水素基である。）

(In the formula, ^R3 is a hydrogen atom or a linear or branched hydrocarbon group having 1 to 12 carbon atoms. ^R4 is a linear or branched divalent hydrocarbon group having 1 to 10 carbon atoms.)

The above compound 3 can be produced, for example, by reacting 1,1,3,3-tetramethyldisiloxane with 1-alkene as shown in the following formula (III) in accordance with the synthesis method disclosed in Polymer, 83 (2016) 20-26.

（式中、Ｒ^１は、炭素数３～２０の直鎖状又は分岐状炭化水素基である。Ｒ^５は、炭素数１～１８の直鎖状又は分岐状炭化水素基である。）
なお上記式（Ｉ）の例では、１－アルキル－１，１，３，３－テトラメチルジシロキサン（化合物３）を用いているが、当該化合物３に代えて１－アルキル－１，１，３，３，５，５－ヘキサメチルトリシロキサンを用いることもできる。１－アルキル－１，１，３，３，５，５－ヘキサメチルトリシロキサンは、Ｐｏｌｙｍｅｒ，８３（２０１６）２０－２６に開示された合成法に準じて、１，１，３，３，５，５－ヘキサメチルトリシロキサンと１－アルケンとを反応させることにより製造することができる。

(In the formula, ^R1 is a linear or branched hydrocarbon group having 3 to 20 carbon atoms. ^R5 is a linear or branched hydrocarbon group having 1 to 18 carbon atoms.)
In the example of formula (I) above, 1-alkyl-1,1,3,3-tetramethyldisiloxane (compound 3) is used, but 1-alkyl-1,1,3,3,5,5-hexamethyltrisiloxane can also be used in place of compound 3. 1-Alkyl-1,1,3,3,5,5-hexamethyltrisiloxane can be produced by reacting 1,1,3,3,5,5-hexamethyltrisiloxane with a 1-alkene in accordance with the synthesis method disclosed in Polymer, 83 (2016) 20-26.

One aspect of the present invention provides a synthetic lubricant comprising the above compound. The synthetic lubricant of the present invention may be used as a lubricant as is, or may be used as a base oil (50 wt% or more of the lubricant composition) of a lubricant composition. It may also be used as an additive component (e.g., 1 to 49 wt% of the lubricant composition) for the purpose of improving the high-temperature lubrication properties of mineral oils and other synthetic oils.

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

[Reference example 1]
<Synthesis of 1,3-bis(5-hexenyloxy)-4-hexylbenzene (Compound 2a: R ³ =hexyl, R ⁴ =tetramethylene) (Formula II)>
Under a nitrogen atmosphere, 200 mL of dimethylformamide was added to a mixture of 4-hexylresorcinol (23.11 g, 119.0 mmol), 6-bromo-1-hexene (50.31 g, 308.5 mmol), and cesium carbonate (130.0 g, 399.0 mmol), and the mixture was stirred at 80° C. for 22 hours. Hexane/dichloromethane (3/1, 400 mL) was added to the reaction mixture, followed by water (250 mL). The organic layer was washed with water, dried over anhydrous sodium sulfate, and then concentrated under reduced pressure. The residue was purified by silica gel column chromatography (elution: hexane/dichloromethane=3/1) to obtain 41.52 g (115.8 mmol, yield 97%) of compound 2a (colorless liquid).
^1H NMR ( _CDCl3 , 600MHz) 0.89 (t, 3H, J=7.0Hz), 1.26-1.38 (m, 6H), 1.50-1.63 (m, 6H), 1.76-1 .84 (m, 4H), 2.10-2.18 (m, 4H), 2.53 (t, 2H, J=8.0Hz), 3.93 (t, 2H, J=6.2Hz), 3 .94 (t, 2H, J=6.5Hz), 4.96-5.00 (m, 2H), 5.01-5.08 (m, 2H), 5.80-5.87 (m, 2H) , 6.39 (dd, 1H, J = 8.2, 2.4Hz), 6.42 (d, 1H, J = 2.4Hz), 7.00 (d, 1H, J = 8.2Hz, 1H).
^13C NMR ( _CDCl3 , 150MHz) 14.14, 22.68, 25.40, 25.48, 28.80, 28.85, 29.28, 29.71, 30.23, 31.81, 33.41, 33.48, 67.54, 67.79, 99.69, 104.28, 114.66, 114.71, 123.84, 129.80, 138.60, 138.64, 157.71, 158.33.

[Reference example 2]
<Synthesis of 1-hexyl-1,1,3,3-tetramethyldisiloxane (Compound 3a: R ¹ =hexyl) (Formula III)>
Under a nitrogen atmosphere, a solution of 1-hexene (16.75 g, 199.0 mmol) in toluene (30 mL) was added dropwise to a solution of 1,1,3,3-tetramethyldisiloxane (107.5 g, 800.3 mmol) and Karstedt's catalyst (97 mg, 19.0-21.5 wt % as Pt) in toluene (90 mL). The mixture was stirred at room temperature for 21 hours, and the reaction mixture was concentrated under reduced pressure. The residue was purified by distillation to obtain 28.59 g (130.9 mmol, 66% yield) of compound 3a (colorless liquid, bp. 85-88°C/37 hPa).
^1H NMR ( _CDCl3 , 600MHz) 0.05 (s, 6H), 0.16 (d, 6H, J=2.8Hz), 0.50-0.60 (m, 2H), 0 .88 (t, 3H, J=7.1Hz), 1.22-1.38 (m, 8H), 4.68 (sept, 1H, J=2.8Hz).
^13C NMR ( _CDCl3 , 150MHz) 0.05, 0.92, 14.15, 18.15, 22.62, 23.16, 31.63, 33.09.
²⁹ Si NMR (CDCl ₃ , 119 MHz) -6.9, 10.0.

[Reference example 3]
<Synthesis of 1-nonyl-1,1,3,3-tetramethyldisiloxane (Compound 3b: R ¹ =nonyl) (Formula III)>
Under a nitrogen atmosphere, a solution of 1-nonene (20.00 g, 158.4 mmol) in toluene (25 mL) was added dropwise to a solution of 1,1,3,3-tetramethyldisiloxane (84.98 g, 632.6 mmol) and Karstedt's catalyst (89 mg, 19.0-21.5 wt % as Pt) in toluene (75 mL). The mixture was stirred at room temperature for 21 hours, and the reaction mixture was concentrated under reduced pressure. The residue was purified by distillation to obtain 29.78 g (114.3 mmol, 72% yield) of compound 3b (colorless liquid, bp. 96-97°C/13 hPa).
^1H NMR ( _CDCl3 , 600MHz) 0.06 (s, 6H), 0.16 (d, 6H, J=2.8Hz), 0.50-0.56 (m, 2H), 0. 88 (t, 3H, J=7.1Hz), 1.20-1.38 (m, 14H), 4.68 (sept, 1H, J=2.8Hz).
^13C NMR ( _CDCl3 , 150MHz) 0.06, 0.92, 14.13, 18.15, 22.71, 23.19, 29.40, 29.58, 31.94, 33.42.
²⁹ Si NMR (CDCl ₃ , 119 MHz) -6.9, 10.0.

[Reference example 4]
<Synthesis of 1-dodecyl-1,1,3,3-tetramethyldisiloxane (Compound 3c: R ¹ =dodecyl) (Formula III)>
Under a nitrogen atmosphere, a solution of 1-dodecene (19.31 g, 114.7 mmol) in toluene (20 mL) was added dropwise to a solution of 1,1,3,3-tetramethyldisiloxane (80.63 g, 600.2 mmol) and Karstedt's catalyst (106 mg, 19.0-21.5 wt % as Pt) in toluene (65 mL). The mixture was stirred at room temperature for 18 hours, and the reaction mixture was concentrated under reduced pressure. The residue was purified by distillation to obtain 13.39 g (44.24 mmol, 39% yield) of compound 3c (colorless liquid, bp. 123-126°C/12 hPa).
^1H NMR ( _CDCl3 , 600MHz) 0.06 (s, 6H), 0.16 (d, 6H, J=2.8Hz), 0.50-0.56 (m, 2H), 0. 88 (t, 3H, J=7.0Hz), 1.20-1.35 (m, 20H), 4.67 (sept, 1H, J=2.8Hz).
^13C NMR ( _CDCl3 , 150MHz) 0.06, 0.92, 14.14, 18.15, 22.71, 23.19, 29.38, 29.39, 29.62, 29.68, 29.71, 29.73, 31.95, 33.42.
²⁹ Si NMR (CDCl ₃ , 119 MHz) -6.9, 10.0.

[Example 1]
<Synthesis of 1,3-bis[6-(3-hexyl-1,1,3,3-tetramethyldisiloxanyl)hexyloxy]-4-hexylbenzene (Compound 1a: R ¹ =hexyl, R ² =hexamethylene, R ³ =hexyl) (Formula I)>
Under a nitrogen atmosphere, a solution of 1,3-bis(5-hexenyloxy)-4-hexylbenzene (compound 2a, 14.36 g, 40.05 mmol) in toluene (30 mL) was added to a solution of 1-hexyl-1,1,3,3-tetramethyldisiloxane (compound 3a, 22.00 g, 100.7 mmol) and Karstedt's catalyst (85 mg, 19.0 to 21.5 wt % as Pt) in toluene (85 mL), and the mixture was stirred at room temperature for 18 hours. The reaction mixture was passed through a short column (silica gel, elution: toluene), and the solution was concentrated under reduced pressure. The residue was purified by silica gel column chromatography (elution: hexane/toluene = 7/1 to 6/1), and 24.90 g (31.30 mmol, yield 78%) of compound 1a (colorless liquid) was obtained.
^1H NMR ( _CDCl3 , 600MHz) 0.02-0.05 (m, 24H), 0.47-0.55 (m, 8H), 0.86-0.92 (m, 9H), 1.22-1.57 (m, 36H), 1.72-1.81 (m, 4H), 2.52 (t, 2H, J=7 .6Hz), 3.91 (t, 2H, J = 6.4Hz), 3.92 (t, 2H, J = 6.6Hz), 6.38 (dd, 1H, J=2.4, 8.2Hz), 6.42 (d, 1H, J=2.4Hz), 6.98 (d, 1H, 8.2Hz).
^13C NMR ( _CDCl3 , 150MHz) 0.38, 0.39, 0.40, 0.41, 14.14, 14.16, 18.38, 18.39, 18.44, 22.63, 22.67, 23.26, 23.28, 25.85, 25.94, 29.27, 29. 32, 29.36, 29.69, 30.20, 31.66, 31.80, 33.12, 33.16, 33.20, 67.80, 68.05, 99.66, 104.24, 123.77, 129.74, 157.77, 158.38.
²⁹ Si NMR (CDCl ₃ , 119 MHz) 7.20, 7.38, 7.40.

[Example 2]
<Synthesis of 1,3-bis[6-(3-nonyl-1,1,3,3-tetramethyldisiloxanyl)hexyloxy]-4-hexylbenzene (Compound 1b: R ¹ =nonyl, R ² =hexamethylene, R ³ =hexyl) (Formula I)>
Under a nitrogen atmosphere, a solution of 1,3-bis(5-hexenyloxy)-4-hexylbenzene (compound 2a, 14.43 g, 40.24 mmol) in toluene (30 mL) was added to a solution of 1-nonyl-1,1,3,3-tetramethyldisiloxane (compound 3b, 26.11 g, 100.2 mmol) and Karstedt's catalyst (86 mg, 19.0 to 21.5 wt % as Pt) in toluene (85 mL), and the mixture was stirred at room temperature for 20 hours. The reaction mixture was passed through a short column (silica gel, elution: toluene), and the solution was concentrated under reduced pressure. The residue was purified by silica gel column chromatography (elution: hexane and hexane/toluene = 6/1), and 27.58 g (31.35 mmol, 78% yield) of compound 1b (colorless liquid) was obtained.
^1H NMR ( _CDCl3 , 600MHz) 0.02-0.05 (m, 24H), 0.45-0.58 (m, 8H), 0.88 (t, 9H, J=7.1Hz), 1.20-1.59 (m, 48H), 1.71-1.83 (m, 4H), 2.52 (t, 2H, J= 7.7Hz), 3.91 (t, 2H, J = 6.3Hz), 3.92 (t, 2H, J = 6.5Hz), 6.38 (dd , 1H, J=2.3, 8.2Hz), 6.41 (d, 1H, J=2.3Hz), 6.98 (d, 1H, 8.2Hz).
^13C NMR ( _CDCl3 , 150MHz) 0.38, 0.39, 0.40, 14.14, 14.15, 18.38, 18.39, 18.43, 22.67, 22.71, 23.26, 23.28, 23.30, 25.85, 25.94, 29.27, 29.33, 29.36 , 29.41, 29.44, 2959, 29.70, 30.20, 31.80, 31.94, 33.17, 33.20, 33.46, 67.79, 68.05, 99.65, 104.22, 123.77, 129.74, 157.76, 158.38.
²⁹ Si NMR (CDCl ₃ , 119 MHz) 7.20, 7.39, 7.41.

[Example 3]
<Synthesis of 1,3-bis[6-(3-dodecyl-1,1,3,3-tetramethyldisiloxanyl)hexyloxy]-4-hexylbenzene (Compound 1c: R ¹ =dodecyl, R ² =hexamethylene, R ³ =hexyl) (Formula I)>
Under a nitrogen atmosphere, a solution of 1,3-bis(5-hexenyloxy)-4-hexylbenzene (compound 2a, 12.40 g, 34.58 mmol) in toluene (25 mL) was added to a solution of 1-dodecyl-1,1,3,3-tetramethyldisiloxane (compound 3c, 27.33 g, 90.30 mmol) and Karstedt's catalyst (94 mg, 19.0 to 21.5 wt % as Pt) in toluene (80 mL), and the mixture was stirred at room temperature for 20 hours. The reaction mixture was passed through a short column (silica gel, elution: toluene), and the solution was concentrated under reduced pressure. The residue was purified by silica gel column chromatography (elution: hexane and hexane/toluene = 6/1), and 26.02 g (27.00 mmol, yield 78%) of compound 1c (colorless liquid) was obtained.
^1H NMR ( _CDCl3 , 600MHz) 0.02-0.05 (m, 24H), 0.45-0.60 (m, 8H), 0.88 (t, 9H, J=7.2Hz), 1.18-1.60 (m, 60H), 1.72-1.82 (m, 4H), 2.53 (t, 2H, J= 7.7Hz), 3.91 (t, 2H, J = 6.4Hz), 3.92 (t, 2H, J = 6.6Hz), 6.38 (dd , 1H, J=2.4, 8.2Hz), 6.42 (d, 1H, J=2.4Hz), 6.99 (d, 1H, 8.2Hz).
^13C NMR ( _CDCl3 , 150MHz) 0.39, 0.40, 0.41, 0.42, 14.14, 14.15, 18.38, 18.39, 18.44, 22.68, 22.72, 23.27, 23.29, 23.31 , 25.86, 25.95, 29.29, 29.33, 29.37, 29.39 , 29.44, 29.65 , 29.69, 29.71, 29.73 , 29.76 , 30.21, 31.81, 31.95, 33.17, 33.21, 33.47 , 67.79, 68.05, 99.65, 104.21, 123.76, 129.74, 157.77, 158.38.
²⁹ Si NMR (CDCl ₃ , 119 MHz) 7.20, 7.39, 7.41.

[Example 4]
<Kinematic Viscosity and Viscosity Index of Compounds 1a to 1c>
For the compounds 1a to 1c produced in Examples 1 to 3, the kinetic viscosity was measured according to the method of JIS K 2283. Also, the viscosity index was calculated according to the method of JIS K 2283. The kinetic viscosities and viscosity indexes of the compounds 1a to 1c at 40° C. and 100° C. are shown in Table 1.

[Comparative Example]
<Kinematic Viscosity and Viscosity Index of Compounds 4a to 4c>
The kinematic viscosity and viscosity index of 1,3-dialkyloxy-4-hexylbenzenes 4a to 4c represented by the following formulas are shown in Table 2 (Patent Document 1, etc.).

In compounds 4a to 4c, the longer the alkoxy chain, the higher the viscosity index tends to be. However, compound 4c is solid at room temperature, so there are concerns about its lubricating performance. Therefore, although extending the alkoxy chain is effective in improving the viscosity index, the upper limit of the viscosity index of synthetic oils that can fully demonstrate lubricating performance is around 140.

In the synthetic lubricating oil of the present invention, the viscosity index is significantly higher than that of the comparative compound by introducing a siloxane moiety, such as compound 1a, into the chain of the alkoxy group of compound 4b, etc. Furthermore, when a disiloxane moiety is introduced, the kinetic viscosity at 100°C is almost unchanged, or increases by about 10%. Therefore, this synthetic oil can be used suitably in environments from room temperature to high temperatures slightly above 100°C, instead of the synthetic oil of the comparative example. Furthermore, the viscosity index of this synthetic oil (180 or higher) is significantly higher than that of mineral oils such as those currently used for refinement and synthetic oil PAO (viscosity index 120 to 140). Therefore, it is believed that this synthetic oil can contribute to further improving the performance and extending the life of equipment and further energy saving in equipment operation.

The synthetic lubricating oil of the present invention has a kinematic viscosity at 100°C of 5.0 to 10.0 ^mm2 /s and a viscosity index of 180 or more, and therefore can be suitably used as it is or as a base oil for a lubricating oil composition in environments ranging from room temperature to high temperatures at least slightly above 100°C.

Claims (3)

A synthetic lubricating oil comprising a compound represented by the following formula (1), having a kinetic viscosity at 100° C. of 5.0 to 10.0 ^{mm 2} /s and a viscosity index of 180 or more:

(In the formula, ^R1 is selected from the group consisting of hexyl, nonyl, and dodecyl, R2 ^is hexamethylene, and R3 ^is hexyl . n is 1 or 2.) A lubricating oil composition comprising the synthetic lubricating oil of claim 1. A lubricating oil composition based on the synthetic lubricating oil according to claim 1.