Ester Compounds

Abstract

To provide an ester compound useful as a lubricant base oil for power transmission (particularly, lubricant base oil for traction drive).SOLUTION: The present invention relates to an ester compound represented by general formula (1) [where R1-R5 are the same or different to represent a hydrogen atom or a C1-4 linear or branched alkyl group].SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an ester compound that can be used in a power transmission lubricant base oil (particularly, a traction drive lubricant base oil). [Background technology]

[0002] In recent years, with the advancement of the digital information society, the precision required for printers and copiers is increasing. In particular, high rotational precision, low vibration and low noise are required for the motor section, which is required for highly accurate paper feeding. When a gear system is used as the power transmission means for these rotating parts, vibration and noise are large, so a traction drive that reduces these is often used.

[0003] In addition, with the spread of industrial robots, traction drives are also used in joints that require precise movements. Other applications of traction drives include continuously variable transmissions for industrial equipment, aircraft generators, and rotor speed control for helicopters. In order to increase the amount of power transmitted, studies have been conducted on making the traction drives larger, but there is a tendency for the amount of heat generated to increase with the increase in contact area.

[0004] Lubricant base oils for traction drives preferably have a high traction coefficient to enhance power transmission performance, and alicyclic hydrocarbon compounds have been proposed, such as dicyclohexyl compounds represented by 2-methyl-2,4-dicyclohexylpentane and dimerized norbornanes (Patent Documents 1 and 2).

[0005] However, alicyclic hydrocarbon compounds such as 2-methyl-2,4-dicyclohexylpentane tend to have low flash points of 200°C or less, which is not necessarily sufficient for use in fields where heat resistance and safety are important, such as large traction drives.

[0006] Ester compounds have also been proposed as lubricant base oils for traction drives with high flash points, such as alicyclic diester compounds typified by di(cyclohexylmethyl) 1,2-cyclohexanedicarboxylate (Patent Document 3).

[0007] However, alicyclic diester compounds, such as di(cyclohexylmethyl) 1,2-cyclohexanedicarboxylate, tend to have high pour points of -20°C or higher, which are not necessarily sufficient for use in aircraft, helicopters, automobiles, and other fields where operability at low temperatures is important. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 47-7664 [Patent Document 2] Japanese Patent Application Publication No. 3-95295 [Patent Document 3] International Publication No. 2018 / 008667 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide an ester compound useful as a lubricant base oil for power transmission (particularly, a lubricant base oil for traction drives). [Means for solving the problem]

[0010] The present inventors have found that the ester compound represented by the general formula (1) has a high traction coefficient and a flash point, and has good low-temperature fluidity, and is useful as a lubricant base oil for power transmission (particularly, a lubricant base oil for traction drives). The present invention has been completed through further investigation based on this finding.

[0011] That is, the present invention provides the following ester compounds:

[0012] [Section 1] General formula (1) [ka] [In the formula, R 1 ~R 5 are the same or different and each represents a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms.] An ester compound represented by the formula:

[0013] [Section 2] R in the general formula (1) 1 ~R 5 and are the same or different and each is a hydrogen atom, a methyl group, an ethyl group, an isopropyl group, or a tert-butyl group.

[0014] [Section 3] R in the general formula (1) 1 ~R 5 and are the same or different and each is a hydrogen atom or a methyl group. Effect of the Invention

[0015] The ester compound of the present invention has the characteristics of having a high traction coefficient (60°C, 140°C) and flash point, and good low-temperature fluidity, and can therefore be suitably used as a lubricant base oil for power transmission (particularly, a lubricant base oil for traction drives). [Brief description of the drawings]

[0016] [Figure 1] 1 is an IR spectrum of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 2-methyl-cyclohexanecarboxylate obtained in Example 1. [Diagram 2] 1H-NMR spectrum of 2-methyl-cyclohexanecarboxylate 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl obtained in Example 1. [Diagram 3] IR spectrum of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 3-methyl-cyclohexanecarboxylate obtained in Example 2. [Figure 4] 1H-NMR spectrum of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 3-methyl-cyclohexanecarboxylate obtained in Example 2. [Diagram 5] IR spectrum of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 4-methyl-cyclohexanecarboxylate obtained in Example 3. [Figure 6] 1H-NMR spectrum of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 4-methyl-cyclohexanecarboxylate obtained in Example 3. [Figure 7] IR spectrum of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 3,5-dimethyl-cyclohexanecarboxylate obtained in Example 4. [Figure 8] 1H-NMR spectrum of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 3,5-dimethyl-cyclohexanecarboxylate obtained in Example 4. [Figure 9] 1 is an IR spectrum of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl cyclohexanecarboxylate obtained in Example 5. [Figure 10] 1H-NMR spectrum of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl cyclohexanecarboxylate obtained in Example 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The ester compound of the present invention is represented by the general formula (1) [ka] [In the formula, R1 ~R 5 are the same or different and each represents a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms.] and can be suitably used as a lubricating base oil for power transmission.

[0018] R in the general formula (1) 1 ~R 5 are preferably the same or different and each is a hydrogen atom, a methyl group, an ethyl group, an isopropyl group, or a tert-butyl group.

[0019] Specific examples of the ester compound represented by the general formula (1) include 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl cyclohexane carboxylate, 2-methylcyclohexane carboxylate, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 2-methylcyclohexane carboxylate, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 3-methylcyclohexane carboxylate, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 4-methylcyclohexane carboxylate, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 2-methylcyclohexane carboxylate, ,3-Dimethylcyclohexane carboxylate 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl, 2,4-Dimethylcyclohexane carboxylate 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl, 2,5-Dimethylcyclohexane carboxylate 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl, 2,6-Dimethylcyclohexane carboxylate 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl, 3,4-Dimethylcyclohexane carboxylate 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 3,5-dimethylcyclohexane carboxylate, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 2,3,4-trimethylcyclohexane carboxylate, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 2,3,5-trimethylcyclohexane carboxylate, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 2,3,6-trimethylcyclohexane carboxylate, 2-(1,3,3 -trimethylbutyl)-5,7,7-trimethyl-1-octyl, 2,4,5-trimethylcyclohexane carboxylate 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl, 2,4,6-trimethylcyclohexane carboxylate 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl, 3,4,5-trimethylcyclohexane carboxylate 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl, 2-ethylcyclohexane carboxylate 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl, 3-ethylcyclohexane carboxylate 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl, 4-ethylcyclohexane carboxylate 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl, 2-isopropylcyclohexane carboxylate 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl, 3-isopropylcyclohexane carboxylate 2-(1,3,3-trimethylbutyl) 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 4-isopropylcyclohexane carboxylate, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 2-tert-butylcyclohexane carboxylate, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 3-tert-butylcyclohexane carboxylate, 4-tert-butylcyclohexane carboxylate 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl is preferred, and in particular, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl cyclohexane carboxylate, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 2-methylcyclohexane carboxylate, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 3-methylcyclohexane carboxylate, 4-methylcyclohexane carboxylate, Preferred are 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl cyclohexane carboxylate, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 3,4-dimethylcyclohexane carboxylate, 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 3,5-dimethylcyclohexane carboxylate, and 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 4-tert-butylcyclohexane carboxylate.

[0020] The above ester compounds can be used alone or in combination as a mixture of two or more types as a lubricating oil base oil for power transmission.

[0021] The method for producing the ester compound represented by the general formula (1) is not particularly limited. For example, the ester compound represented by the general formula (1) can be produced by reacting (esterification reaction or transesterification reaction) the alcohol represented by the formula (2) with the carboxylic acid compound represented by the general formula (3) or a derivative thereof, as shown in reaction formula 1. Here, examples of the derivative of the carboxylic acid represented by the general formula (3) include highly reactive derivatives such as acid halides (e.g., acid chlorides, etc.), mixed acid anhydrides, and active esters, and lower (1 to 4 carbon atoms) alkyl esters. [ka] [In the formula, R 1 ~R 5 Same as above.] The ester compound represented by the general formula (1) can be produced, for example, by dehydration condensation of an alcohol represented by the formula (2) and a carboxylic acid compound represented by the general formula (3) in the presence of an acid catalyst (e.g., sulfuric acid, p-toluenesulfonic acid, etc.) while removing by-product water by heating. The acid catalyst can also be changed to an inorganic metal catalyst (e.g., tin oxide, etc.) or an organic titanium catalyst (e.g., tetra-n-butoxytitanium, etc.) to produce the ester compound by a similar method. The carboxylic acid compound represented by the general formula (3) can also be produced by converting the carboxylic acid compound into a highly reactive derivative such as an acid halide (e.g., acid chloride, etc.), mixed acid anhydride, or active ester, and then reacting the alcohol represented by the formula (2) in the presence of a base (e.g., triethylamine, 4?(N,N?dimethylamino)pyridine, pyridine, etc.). The alcohol represented by the formula (2) can also be produced by reacting the carboxylic acid compound represented by the general formula (3) in the presence of a condensing agent (e.g., dicyclohexylcarbodiimide, carbonyldiimidazole, etc.). Furthermore, the ester compound represented by the general formula (1) can also be produced by reacting (esterifying) the carboxylic acid compound represented by the general formula (3) with a lower (carbon number 1 to 4) alcohol (e.g., methanol, ethanol, etc.) to form a lower alkyl ester, and then subjecting the lower alkyl ester to a transesterification reaction with the alcohol represented by the formula (2). The reaction shown in the above reaction scheme 1 can be carried out according to or in accordance with known reaction conditions depending on the type of reaction.

[0022] Alternatively, the ester compound represented by general formula (1) can be produced by reacting (esterification reaction or transesterification reaction) an alcohol represented by formula (2) with an aromatic carboxylic acid or a derivative thereof represented by general formula (4) to obtain a compound represented by general formula (5), and then hydrogenating (reducing) the aromatic ring of the compound, as shown in reaction formula 2. Here, examples of the derivative of the aromatic carboxylic acid represented by general formula (4) include highly reactive derivatives such as acid halides (e.g., acid chlorides, etc.), mixed acid anhydrides, and active esters, and lower (1 to 4 carbon atoms) alkyl esters. [ka] [In the formula, R 1 ~R 5 Same as above.] The reaction of producing a compound represented by general formula (5) by reacting an alcohol represented by formula (2) with an aromatic carboxylic acid represented by general formula (4) or a derivative thereof can be carried out according to or in accordance with the reaction of producing a compound represented by general formula (1) by reacting an alcohol represented by formula (2) with a carboxylic acid compound represented by general formula (3) or a derivative thereof in the above reaction scheme 1. A known method can be adopted for the reaction of hydrogenating (reducing) the compound represented by the general formula (5). For example, the compound represented by the general formula (1) can be produced by reducing the compound represented by the general formula (5) under a hydrogen atmosphere (from room temperature to pressure) in the presence of a reduction catalyst (a transition metal such as platinum, palladium, nickel, or rhodium, or an oxide thereof, palladium / C, etc.).

[0023] The acid value of the ester compound represented by general formula (1) is preferably 0.1 mgKOH / g or less, more preferably 0.05 mgKOH / g or less. When the acid value is 0.1 mgKOH / g or less, the heat resistance of the ester compound represented by general formula (1) itself tends to be improved, and such a preferable range also has a favorable effect on improving the thermal oxidation stability of the base oil containing the ester compound represented by general formula (1). Examples of methods for reducing the acid value include a method of allowing the reaction to proceed sufficiently, a method of neutralizing with an alkaline component in a post-treatment process and washing with water (for example, a method of washing (neutralizing) with an aqueous alkaline solution and washing with water), and a method of adsorption treatment with activated alumina.

[0024] The hydroxyl value of the ester compound represented by general formula (1) is preferably 2 mgKOH / g or less, more preferably 1 mgKOH / g or less. When the hydroxyl value is 2 mgKOH / g or less, the hygroscopicity of the ester compound represented by general formula (1) itself tends to be lower and the heat resistance tends to be improved, and such a preferable range also has a favorable effect on improving the water resistance and thermo-oxidation stability of the base oil containing the ester compound represented by general formula (1). Examples of methods for reducing the hydroxyl value include a method of allowing the reaction to proceed sufficiently and a method of distilling off the raw material alcohol component in the post-treatment step under reduced pressure (for example, a method of distilling off the excess raw material alcohol that can be distilled under reduced pressure or normal pressure).

[0025] The ester compound represented by the general formula (1) can be used as a power transmission lubricant base oil (particularly, a traction drive lubricant base oil). The present invention also discloses a power transmission lubricant base oil (particularly, a traction drive lubricant base oil) containing the ester compound represented by the general formula (1).

[0026] The traction coefficient (60°C) of the power transmission lubricating base oil is usually 0.080 or more, and preferably 0.090 or more. In this specification and claims, the traction coefficient (60°C) is a value measured by the method described in the Examples below.

[0027] The traction coefficient (140°C) is usually 0.075 or more, and preferably 0.085 or more. In this specification and claims, the traction coefficient (140°C) is a value measured by the method described in the Examples below.

[0028] The low-temperature fluidity of the power transmission lubricant base oil can be evaluated, for example, by the pour point. From the viewpoint of low-temperature operability, the pour point of the lubricant base oil is usually -30°C or less, preferably -35°C or less. In this specification and claims, the pour point is a value measured by the method described in the examples below.

[0029] The flash point of the lubricating base oil for power transmission is usually 185° C. or higher, preferably 200° C. or higher, from the viewpoint of storage stability and handling. If it is lower than 185° C., there are many restrictions on handling due to ignition. In this specification and claims, the flash point is a value measured by the method described in the examples below.

[0030] Examples of the lubricating base oil for power transmission include lubricating base oil for power transmission having a traction coefficient (60°C) of 0.090 or more, a traction coefficient (140°C) of 0.085 or more, a pour point of -30°C or less, and a flash point of 185°C or more; lubricating base oil for power transmission having a traction coefficient (60°C) of 0.090 or more, a traction coefficient (140°C) of 0.075 or more, a pour point of -35°C or less, and a flash point of 185°C or more; lubricating base oil for power transmission having a traction coefficient (60°C) of 0.090 or more, a traction coefficient (140°C) of 0.075 or more, a pour point of -30°C or less, and a flash point of 200°C or more; and lubricating base oil for power transmission having a traction coefficient (60°C) of 0.080 or more, a traction coefficient (140°C) of 0.075 or more, a pour point of -35°C or less, and a flash point of 200°C or more. Further, lubricating base oils for power transmission having a traction coefficient (60°C) of 0.090 or more, a traction coefficient (140°C) of 0.085 or more, a pour point of -35°C or less, and a flash point of 185°C or more are preferred; lubricating base oils for power transmission having a traction coefficient (60°C) of 0.090 or more, a traction coefficient (140°C) of 0.085 or more, a pour point of -30°C or less, and a flash point of 200°C or more; and lubricating base oils for power transmission having a traction coefficient (60°C) of 0.090 or more, a traction coefficient (140°C) of 0.075 or more, a pour point of -35°C or less, and a flash point of 200°C or more are preferred, and lubricating base oils for power transmission having a traction coefficient (60°C) of 0.090 or more, a traction coefficient (140°C) of 0.085 or more, a pour point of -35°C or less, and a flash point of 200°C or more are particularly preferred.

[0031] A power transmission lubricating base oil containing an ester compound represented by general formula (1) has a high traction coefficient (60°C, 140°C) and flash point, and good low-temperature fluidity, and is therefore suitably used as a power transmission lubricating base oil, particularly as a lubricating base oil for traction drives.

[0032] The power transmission lubricant base oil containing the ester compound represented by the general formula (1) can contain other base oils that can be used in combination (hereinafter referred to as "combined base oils"). In other words, the power transmission lubricant base oil containing the ester compound represented by the general formula (1) includes only the ester compound represented by the general formula (1) and a mixture of the ester compound represented by the general formula (1) and the combined base oil. Hereinafter, the power transmission lubricant base oil may be referred to as "base oil".

[0033] Examples of base oils that can be used in combination include mineral oils (hydrocarbon oils obtained by refining petroleum), poly-α-olefins, polybutenes, alkylbenzenes, alkylnaphthalenes, alicyclic hydrocarbon oils, animal and vegetable oils, organic acid esters (excluding the ester compounds represented by general formula (1)), polyalkylene glycols, polyvinyl ethers, polyphenyl ethers, alkylphenyl ethers, silicone oils, etc. At least one of these can be used in combination as appropriate.

[0034] The content of the ester compound represented by general formula (1) in the power transmission lubricant base oil containing the ester compound represented by general formula (1) is usually 70 mass% or more, preferably 90 mass% or more, more preferably 95 mass% or more, and particularly preferably 98 mass% or more.

[0035] The content of the combined base oil in the power transmission lubricating base oil containing the ester compound represented by general formula (1) is usually 30 mass% or less, preferably 10 mass% or less, more preferably 5 mass% or less, and particularly preferably 2 mass% or less.

[0036] The ester compound represented by the general formula (1) can be suitably used in the power transmission lubricating oil containing the power transmission lubricating oil base oil. In order to improve the performance of the power transmission lubricating oil, it is also possible to appropriately blend at least one of additives such as antioxidants, metal detergents, ashless dispersants, oiliness agents, antiwear agents, extreme pressure agents, metal deactivators, rust inhibitors, viscosity index improvers, pour point depressants, antifoaming agents, hydrolysis inhibitors, thickeners, corrosion inhibitors, and color stabilizers into the base oil. The blending amount of these is not particularly limited as long as the effect of the present invention is achieved.

[0037] Here, in the present specification and claims, the range of the amount of additives may be specified using the expression "with respect to the base oil", such as "0.01 to 5 mass% with respect to the base oil". In this case, the "base oil" used means either a base oil consisting of only the ester compound represented by the general formula (1) or a base oil consisting of a mixture of the ester compound represented by the general formula (1) and a combined base oil. In addition, in the example of "0.01 to 5 mass% with respect to the base oil", it is synonymous with 0.01 to 5 mass parts with respect to 100 mass parts of the base oil.

[0038] A "grease" can be produced by appropriately combining a thickener with a power transmission lubricating base oil containing the ester compound represented by the general formula (1).

[0039] Examples of thickeners include metal soap-based thickeners, complex metal soap-based thickeners, and non-soap-based thickeners.

[0040] Among the above, from the viewpoints of heat resistance, water resistance, and shear stability, lithium soaps, lithium complex soaps, and urea compounds are suitable as thickeners, and urea compounds are particularly preferred.

[0041] These thickeners can be used alone or in combination of two or more kinds, and the amount added is not particularly limited as long as the desired effect is achieved.

[0042] Examples of corrosion inhibitors include sodium sulfonate and sorbitan ester, and they are usually added in an amount of about 0.1 to 3.0% by mass to the base oil.

[0043] Examples of color stabilizers include substituted hydroquinone and furfural azine, and they are usually added in an amount of about 0.01 to 0.1% by mass to the base oil.

[0044] The lubricating oil for power transmission containing the ester compound represented by general formula (1) thus obtained contains a base oil having a high traction coefficient and flash point and excellent low-temperature fluidity, as described above, and is therefore suitable as a lubricating oil for traction drives.

[0045] The power transmission lubricating oil base oil containing the ester compound represented by the general formula (1) and the ester compound represented by the general formula (1) can be added to a power transmission lubricating oil (particularly a traction drive lubricating oil) to improve the traction coefficient of the power transmission lubricating oil, and therefore can be used as a traction coefficient improver.

[0046] The lubricating oil for power transmission containing the ester compound represented by the general formula (1) has high power transmission performance, low vibration and noise generation, and a high flash point, and can be used as a lubricating oil for a traction drive, i.e., a power transmission device consisting of two or more rotating bodies. Examples of devices that use the traction drive include motors, transmissions, generators, reducers, etc. for automobiles, ships, aircraft, precision instruments, robots, etc. EXAMPLES

[0047] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The physical and chemical properties of the lubricating base oil and the lubricating oil composition in each example were evaluated by the following methods. Reagents were used for compounds not specifically mentioned.

[0048] <Compound used> Cyclohexanecarboxylic acid: Sigma-Aldrich 2-Methyl-cyclohexanecarboxylic acid: Sigma-Aldrich 3-Methyl-cyclohexanecarboxylic acid: Sigma-Aldrich 4-Methyl-cyclohexanecarboxylic acid: Sigma-Aldrich Benzoic acid: Tokyo Chemical Industry Co., Ltd., product name "Benzoic Acid" 1-Nonanoic acid: Product name "Nonanoic Acid" manufactured by Tokyo Chemical Industry Co., Ltd. 2-Hexyl-1-decanol: manufactured by Tokyo Chemical Industry Co., Ltd., product name "2-Hexyl-1-decanol" 3,5-Dimethyl-cyclohexanecarboxylic acid: Referring to JP-A-49-135950, 3,5-dimethylbenzoic acid (Tokyo Chemical Industry Co., Ltd.) was subjected to a hydrogenation reaction in the presence of a 5% by mass palladium-carbon catalyst, and the resulting crude product was purified by distillation to obtain 3,5-dimethylcyclohexanecarboxylic acid. 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanol: Nissan Chemical Co., Ltd. Product name: Fine Oxocol 180 Diisodecyl adipate: Product name "Sanso Cizer DIDA" manufactured by New Japan Chemical Co., Ltd. Mineral oil Y: NOF Corporation product name "Polybutene 0N"

[0049] (a) Acid value (AV) Measurements were performed in accordance with JIS K2501 (2003) with a detection limit of 0.01 mg KOH / g.

[0050] (b) Hydroxyl value (OHV) The measurement was performed in accordance with JIS K0070 (1992) with a detection limit of 0.1 mg KOH / g.

[0051] [Measurement of physical properties of lubricant base oil] (c) Traction coefficient The maximum traction coefficient was measured when testing was performed using the following equipment and conditions, and this was taken as the traction coefficient (60°C, 140°C). [Measurement conditions] Equipment: Ball-on-ring type friction tester (Phoenix Tribology TE54 model) Test piece shape: Upper test piece (25 mm diameter ball), lower test piece (50 mm diameter ring) Test piece material: SUJ2 Slip rate: 5% Sample temperature: 60℃, 140℃ Load: 150N <Traction coefficient (60℃) evaluation> A: 0.090 or more B: 0.080 or more and less than 0.090 C: Less than 0.080 <Traction coefficient (140℃) evaluation> A: 0.085 or more B: 0.075 or more and less than 0.085 C: Less than 0.075

[0052] (d) Low temperature fluidity test (pour point) The pour point was measured in accordance with JIS-K-2269 (1987). <Low temperature fluidity evaluation> A: -35℃ or less B: Over -35℃ and below -30℃ C: Above -30℃

[0053] (e) Flash point Measurements were performed in accordance with JIS K2265 (Cleveland open type). <Flash point evaluation> A: 200℃ or higher B: 185℃ or higher but less than 200℃ C: Less than 185℃ (f) Evaluation of power transmission lubricant base oils In the evaluation of lubricant base oils for power transmission, the traction coefficient, low temperature fluidity and flash point are evaluated as follows: if the result is C 1 or more, it is rated as unsuitable; if the result is B 2 or less (other evaluations are A), it is rated as good; and if the result is B 1 or less (other evaluations are A), it is rated as particularly good.

[0054] (g) IR spectrum The IR spectrum of the obtained ester compound was measured by the ATR method (attenuated total reflection method) using an infrared spectrometer (Spectrum 400 manufactured by PerkinElmer Japan Co., Ltd.).

[0055] (h) Proton nuclear magnetic resonance spectrum ( 1 H-NMR) The ester compound thus obtained was subjected to a nuclear magnetic resonance spectrometer (DRX-500 manufactured by Bruker). 1 H-NMR (500 MHz, deuterated chloroform) was measured.

[0056] [Example 1] In a 1-liter four-neck flask equipped with a stirrer, a thermometer, and a water fractionation receiver with a condenser, 312.8 g (2.20 mol) of 2-methyl-cyclohexane carboxylic acid, 541.0 g (2.00 mol) of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanol, 0.8 g of tin oxide, and 30 g of xylene as an entrainer were charged, and the flask was replaced with nitrogen, and then the temperature was gradually raised to 230 ° C. While adjusting the degree of vacuum so that xylene refluxed, the generated water was removed in the water fractionation receiver with the theoretical amount of generated water (36.0 g) as a target, and an esterification reaction was performed. After the reaction was completed, the remaining 2-methyl-cyclohexane carboxylic acid and xylene were removed by distillation under reduced pressure to obtain an esterified crude product. Next, the obtained esterified crude product was neutralized with 1.5 times the equivalent of an aqueous solution of caustic soda relative to the acid value, and then repeatedly washed with water until it became neutral. Magnesium sulfate was added to the obtained esterified crude product for dehydration, and the magnesium sulfate was then removed by filtration to obtain 631.5 g (1.60 mol) of 2-methyl-cyclohexanecarboxylate 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl. The acid value of the obtained ester compound was 0.01 mgKOH / g or less, and the hydroxyl value was 1 mgKOH / g or less. IR spectrum of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 2-methyl-cyclohexanecarboxylate: 1 The H-NMR spectrum was measured and is shown in Figures 1 and 2. 1 The peak at around 7.27 ppm in the H-NMR spectrum is the peak of residual protons in the solvent, deuterated chloroform.

[0057] IR(cm -1 ):2951,2866,1732,1466,1393,1378,1364,1317,1250,1172,1132,1045,1009

[0058] The physical properties of the ester compound evaluated as a power transmission lubricating base oil (A) are shown in Table 1.

[0059] [Example 2] 671.0g (1.70mol) of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 3-methyl-cyclohexane carboxylate was obtained in the same manner as in Example 1, except that 2-methyl-cyclohexane carboxylic acid was replaced with 312.8g (2.20mol) of 3-methyl-cyclohexane carboxylate. The acid value of the obtained ester compound was 0.01 mgKOH / g or less, and the hydroxyl value was 1 mgKOH / g or less. IR spectrum of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 3-methyl-cyclohexanecarboxylate: 1 The H-NMR spectrum was measured and is shown in Figures 3 and 4. 1 The peak at around 7.27 ppm in the H-NMR spectrum is the peak of residual protons in the solvent, deuterated chloroform.

[0060] IR(cm -1 ):2950,2866,1732,1458,1392,1377,1364,1247,1215,1176,1137,1089,1045,1006,969

[0061] The physical properties of the ester compound evaluated as a power transmission lubricant base oil (B) are shown in Table 1.

[0062] [Example 3] 678.8g (1.72mol) of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 4-methyl-cyclohexane carboxylate was obtained in the same manner as in Example 1, except that 312.8g (2.20mol) of 4-methyl-cyclohexane carboxylate was used instead of 2-methyl-cyclohexane carboxylate. The acid value of the obtained ester compound was 0.01 mgKOH / g or less, and the hydroxyl value was 1 mgKOH / g or less. IR spectrum of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 4-methyl-cyclohexanecarboxylate: 1 The H-NMR spectrum was measured and is shown in Figures 5 and 6. 1 The peak at around 7.27 ppm in the H-NMR spectrum is the peak of residual protons in the solvent, deuterated chloroform.

[0063] IR(cm -1 ):2950,2867,1731,1467,1456,1392,1377,1364,1246,1182,1138,1036,991

[0064] The physical properties of the ester compound evaluated as a power transmission lubricant base oil (C) are shown in Table 1.

[0065] [Example 4] 637.6g (1.56mol) of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 3,5-dimethyl-cyclohexane carboxylate was obtained in the same manner as in Example 1, except that 2-methyl-cyclohexane carboxylate was replaced with 343.7g (2.20mol) of 3,5-dimethyl-cyclohexane carboxylate. The acid value of the obtained ester compound was 0.01 mgKOH / g or less, and the hydroxyl value was 1 mgKOH / g or less. IR spectrum of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 3,5-dimethyl-cyclohexanecarboxylate: 1 The H-NMR spectrum was measured and is shown in Figures 7 and 8. 1 The peak at around 7.27 ppm in the H-NMR spectrum is the peak of residual protons in the solvent, deuterated chloroform.

[0066] IR(cm -1 ):2950,2869,1732,1458,1392,1377,1364,1280,1245,1177,1140,1104,1011,970,946

[0067] The physical properties of the ester compound evaluated as a power transmission lubricant base oil (D) are shown in Table 1.

[0068] [Example 5] The same method as in Example 1 was used except that 2-methyl-cyclohexanecarboxylic acid was replaced with 282.0 g (2.20 mol) of cyclohexanecarboxylic acid to obtain 624.3 g (1.64 mol) of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl cyclohexanecarboxylate. The acid value of the obtained ester compound was 0.01 mg KOH / g or less, and the hydroxyl value was 1 mg KOH / g or less. IR spectrum of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl cyclohexanecarboxylate: 1 The H-NMR spectrum was measured and is shown in Figures 9 to 10. 1 The peak at around 7.27 ppm in the H-NMR spectrum is the peak of residual protons in the solvent, deuterated chloroform.

[0069] IR(cm -1):2935,2860,1732,1466,1451,1392,1377,1364,1311,1274,1245,1226,1193,1167,1132, 1076, 1038, 968, 926, 894, 845, 754

[0070] The physical properties of the ester compound evaluated as a power transmission lubricant base oil (E) are shown in Table 1.

[0071] [Comparative Example 1] Table 2 shows the physical properties of diisodecyl adipate when it was evaluated as a power transmission lubricant base oil (a).

[0072] [Comparative Example 2] Table 2 shows the physical properties of mineral oil Y when it was evaluated as a power transmission lubricant base oil (b).

[0073] [Comparative Example 3] 646.7g (1.76mol) of 2-hexyl-1-decyl 3-methyl-cyclohexane carboxylate was obtained in the same manner as in Example 1, except that 2-methyl-cyclohexane carboxylic acid was replaced with 328.5g (2.31mol) of 3-methyl-cyclohexane carboxylic acid and 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octanol was replaced with 509.1g (2.10mol) of 2-hexyl-1-decanol. The acid value of the obtained compound was 0.01mgKOH / g or less, and the hydroxyl value was 1mgKOH / g or less. The physical properties of the compound evaluated as a power transmission lubricant base oil (c) are shown in Table 2.

[0074] [Comparative Example 4] 706.4g (1.72mol) of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl 1-nonanoate was obtained in the same manner as in Example 1, except that 2-methyl-cyclohexane carboxylic acid was replaced with 348.1g (2.20mol) of 1-nonanoic acid. The acid value of the obtained compound was 0.01mgKOH / g or less, and the hydroxyl value was 1mgKOH / g or less. The physical properties of the compound evaluated as a power transmission lubricant base oil (d) are shown in Table 2.

[0075] [Comparative Example 5] The same method as in Example 1 was used except that 2-methyl-cyclohexane carboxylic acid was replaced with 268.7 g (2.20 mol) of benzoic acid, and 651.8 g (1.74 mol) of 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyl-1-octyl benzoate was obtained. The acid value of the obtained compound was 0.01 mg KOH / g or less, and the hydroxyl value was 1 mg KOH / g or less. The physical properties of the compound evaluated as a power transmission lubricant base oil (e) are shown in Table 2.

[0076] [Table 1]

[0077] [Table 2]

[0078] From Table 1, it can be seen that the power transmission lubricant base oils described in Examples 1 to 5 have high traction coefficients (60°C) of 0.090 or more and traction coefficients (140°C) of 0.085 or more, pour points of -30°C or less, and high flash points of 190°C or more. [Industrial Applicability]

[0079] A power transmission lubricant base oil containing an ester compound represented by general formula (1) has a high traction coefficient, a high flash point, and good low-temperature fluidity, and can therefore be suitably used as a power transmission lubricant base oil (particularly, a traction drive lubricant base oil) for automobiles, ships, aircraft, precision instruments, and the like.

Claims

1. General formula (1) 【Chemistry 1】 [In the formula, R １ ~R ５ are the same or different and each represents a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms. An ester compound represented by the formula:

2. R represented by formula (1) １ ~R ５ and are the same or different and each is a hydrogen atom, a methyl group, an ethyl group, an isopropyl group, or a tert-butyl group.

3. R represented by formula (1) １ ~R ５ and are the same or different and each is a hydrogen atom or a methyl group.

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