Lubricating oil base oil

Abstract

To provide a lubricating oil base oil that has low viscosity, low volatility, and excellent low-temperature stability. [Solution] A lubricating oil base oil containing a condensed ester of an alcohol compound (A) selected from the group consisting of pentaerythritol and trimethylolpropane and a carboxylic acid (B), The carboxylic acid (B) comprises an aliphatic monocarboxylic acid (B1) having 8 or fewer carbon atoms and an aliphatic monocarboxylic acid (B2) having 9 to 12 carbon atoms. The aliphatic monocarboxylic acid (B1) comprises a carbon-7 aliphatic monocarboxylic acid (B1a) and a carbon-8 aliphatic monocarboxylic acid (B1b). A lubricating oil base oil in which the mass ratio of the content of aliphatic monocarboxylic acid (B2) to the content of aliphatic monocarboxylic acid (B1) in the carboxylic acid (B) is 0.12 or more and 0.24 or less.

Description

Technical Field

[0001] The present invention relates to a lubricating base oil, a lubricating oil, and a method for producing a lubricating base oil.

Background Art

[0002] Lubricating oils are used in various fields that require friction reduction. In the past, natural fats and oils, petroleum refined products, etc. have been used, but in recent years, synthetic lubricating oils have been synthesized and used according to the application. In particular, synthetic esters are excellent in thermal stability, and specifically, organic acid esters, phosphate esters, silicate esters, etc. are exemplified.

[0003] Among the organic acid esters, from the viewpoints of 1) having a low pour point, a high viscosity index, and a wide use temperature range, 2) having a high flash point and a small evaporation amount, 3) being excellent in thermal and oxidative stability, 4) having good lubricity, 5) having a detergent-dispersant action, and 6) having biodegradability, polyol esters (condensation esters of polyhydric alcohols and carboxylic acids) are used (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, in order to further reduce friction, further reduction of the viscosity of lubricating base oils has been demanded. However, when the viscosity of lubricating base oils is reduced, the volatility increases, and there is a tendency for the consumption amount of lubricating base oils to increase. Therefore, lubricating base oils having low viscosity and low volatility are demanded. In addition, conventional lubricating base oils had room for improvement in terms of low-temperature stability.

[0006] The present invention provides a lubricating oil base oil that has low viscosity, low volatility, and excellent low-temperature stability. [Means for solving the problem]

[0007] The present invention A lubricating oil base oil containing a condensed ester of an alcohol compound (A) selected from the group consisting of pentaerythritol and trimethylolpropane and a carboxylic acid (B), The carboxylic acid (B) comprises an aliphatic monocarboxylic acid (B1) having 8 or fewer carbon atoms and an aliphatic monocarboxylic acid (B2) having 9 to 12 carbon atoms. The aliphatic monocarboxylic acid (B1) comprises a carbon-7 aliphatic monocarboxylic acid (B1a) and a carbon-8 aliphatic monocarboxylic acid (B1b). The mass ratio of the content of aliphatic monocarboxylic acid (B2) to the content of aliphatic monocarboxylic acid (B1) in the carboxylic acid (B) (content of aliphatic monocarboxylic acid (B2) / content of aliphatic monocarboxylic acid (B1)) is 0.12 or more and 0.24 or less. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a lubricating oil base oil that has low viscosity, low volatility, and excellent low-temperature stability. [Modes for carrying out the invention]

[0009] <Lubricant base oil> The lubricating oil base oil of this embodiment is A lubricating oil base oil containing a condensed ester of an alcohol compound (A) selected from the group consisting of pentaerythritol and trimethylolpropane and a carboxylic acid (B), The carboxylic acid (B) comprises an aliphatic monocarboxylic acid (B1) having 8 or fewer carbon atoms and an aliphatic monocarboxylic acid (B2) having 9 to 12 carbon atoms. The aliphatic monocarboxylic acid (B1) comprises a carbon-7 aliphatic monocarboxylic acid (B1a) and a carbon-8 aliphatic monocarboxylic acid (B1b). The mass ratio of the content of aliphatic monocarboxylic acid (B2) to the content of aliphatic monocarboxylic acid (B1) in the carboxylic acid (B) (content of aliphatic monocarboxylic acid (B2) / content of aliphatic monocarboxylic acid (B1)) is 0.12 or more and 0.24 or less. The lubricating oil base oil of this embodiment has low viscosity, low volatility, and excellent low-temperature stability.

[0010] [Condensed esters] [Alcohol compound (A)] The alcohol compound (A) comprises one or more alcohols selected from the group consisting of pentaerythritol and trimethylolpropane. From the viewpoint of achieving both low viscosity and low volatility, the alcohol compound (A) is preferably trimethylolpropane. The alcohol compound (A) may also contain alcohol compounds other than pentaerythritol and trimethylolpropane, to the extent that it does not impair the effects of the present invention.

[0011] [Carboxylic acid (B)] The carboxylic acid (B) includes the aliphatic monocarboxylic acid (B1) and the aliphatic monocarboxylic acid (B2). The carboxylic acid (B) may also include carboxylic acids other than the aliphatic monocarboxylic acid (B1) and the aliphatic monocarboxylic acid (B2) to the extent that the effects of the present invention are not impaired.

[0012] (Aliphatic monocarboxylic acid (B1)) The aliphatic monocarboxylic acid (B1) includes a carbon-7 aliphatic monocarboxylic acid (B1a) and a carbon-8 aliphatic monocarboxylic acid (B1b).

[0013] Examples of the aliphatic monocarboxylic acid (B1a) include one or more selected from the group consisting of heptanoic acid (linear fatty acid); 2-methylhexanoic acid, 3-methylhexanoic acid, 4-methylhexanoic acid, 5-methylhexanoic acid, 2,2-dimethylpentanoic acid, 2,3-dimethylpentanoic acid, 2,4-dimethylpentanoic acid, 3,3-dimethylpentanoic acid, 3,4-dimethylpentanoic acid, 4,4-dimethylpentanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid, 2,2,3-trimethylbutanoic acid, 2,3,3-trimethylbutanoic acid, 2-ethyl-2-methylbutanoic acid, and 2-ethyl-3-methylbutanoic acid. Among these, heptanoic acid is preferred from the viewpoint of achieving both low viscosity and low volatility.

[0014] Examples of the aliphatic monocarboxylic acid (B1b) include one or more selected from the group consisting of octanoic acid (linear fatty acid); 2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic acid, 5-methylheptanoic acid, 6-methylheptanoic acid, 2-ethylhexanoic acid, 3-ethylhexanoic acid, 4-ethylhexanoic acid, 2,2-dimethylhexanoic acid, 2,3-dimethylhexanoic acid, 2,4-dimethylhexanoic acid, 2,5-dimethylhexanoic acid, 3,3-dimethylhexanoic acid, 3,4-dimethylhexanoic acid, 3,5-dimethylhexanoic acid, 4,4-dimethylhexanoic acid, 4,5-dimethylhexanoic acid, 5,5-dimethylhexanoic acid, 2-propylpentanoic acid, etc. Among these, octanoic acid is preferred from the viewpoint of achieving both low viscosity and low volatility.

[0015] The mass ratio of the content of aliphatic monocarboxylic acid (B1a) to the content of aliphatic monocarboxylic acid (B1b) in the aliphatic monocarboxylic acid (B1) (content of aliphatic monocarboxylic acid (B1a) / content of aliphatic monocarboxylic acid (B1b)) is preferably 0.25 or more, more preferably 0.29 or more, from the viewpoint of low evaporation, and preferably 0.60 or less, more preferably 0.57 or less, from the viewpoint of low viscosity.

[0016] The total content of aliphatic monocarboxylic acid (B1a) and aliphatic monocarboxylic acid (B1b) in the aliphatic monocarboxylic acid (B1) is preferably 95% by mass or more, more preferably 97% by mass or more, even more preferably substantially 100% by mass, and even more preferably 100% by mass, from the viewpoint of low viscosity and low evaporation. In this specification, "substantially 100% by mass" means a state in which trace amounts of impurities are inevitably included.

[0017] (Aliphatic monocarboxylic acid (B2)) Examples of the aliphatic monocarboxylic acid (B2) include straight-chain fatty acids such as nonanoic acid, decanoic acid, and dodecanoic acid; branched fatty acids such as 2-methyloctanoic acid, 3-methyloctanoic acid, 4-methyloctanoic acid, 5-methyloctanoic acid, 6-methyloctanoic acid, 7-methyloctanoic acid, 2,2-dimethylheptanoic acid, 2,3-dimethylheptanoic acid, 2,4-dimethylheptanoic acid, 2,5-dimethylheptanoic acid, 2,6-dimethylheptanoic acid, 3,3-dimethylheptanoic acid, 3,4-dimethylheptanoic acid, 3,5-dimethylheptanoic acid, 3,6-dimethylheptanoic acid, 4,4-dimethylheptanoic acid, 4,5-dimethylheptanoic acid, 4,6-dimethylheptanoic acid, 5,5-dimethylheptanoic acid, 5,6-dimethylheptanoic acid, 6,6-dimethylheptanoic acid, 2-methyl-2-ethylhexanoic acid, 2-methyl-3-ethylhexanoic acid, 2-methyl-4-ethylhexanoic acid, 3-methyl-2-ethylhexanoic acid, 3-methyl-3-ethylhexanoic acid, 3-methyl-4-ethylhexanoic acid, 4-methyl-2-ethylhexanoic acid, 4-methyl-3-ethylhexanoic acid, 4-methyl-4-ethylhexanoic acid, 5-methyl-2-ethylhexanoic acid, 5-methyl-3-ethylhexanoic acid, 5-methyl-4-ethylhexanoic acid, 2-ethylheptanoic acid, 3-methyloctanoic acid, 3,5,5-trimethylhexanoic acid, 2-ethyl-2,3,3-trimethylbutyric acid, 2,2,4,4-tetramethylpentanoic acid, and 2,2,3,3-tetramethylpentanoic acid, 2,2,3,4-tetramethylpentanoic acid. Among these, from the viewpoint of achieving both low viscosity and low volatility, one or more selected from the group consisting of decanoic acid and dodecanoic acid are preferred, and decanoic acid is more preferred.

[0018] The mass ratio of the content of the aliphatic monocarboxylic acid (B2) to the content of the aliphatic monocarboxylic acid (B1) in the carboxylic acid (B) (content of the aliphatic monocarboxylic acid (B2) / content of the aliphatic monocarboxylic acid (B1)) is 0.12 or more, preferably 0.13 or more, from the viewpoint of low volatility, and 0.24 or less, preferably 0.21 or less, from the viewpoint of reducing viscosity.

[0019] The total content of the aliphatic monocarboxylic acid (B1) and the aliphatic monocarboxylic acid (B2) in the carboxylic acid (B) is preferably 95% by mass or more, more preferably 97% by mass or more, still more preferably substantially 100% by mass, and even more preferably 100% by mass from the viewpoints of low viscosity and low volatility.

[0020] The mass ratio of the content of the aliphatic monocarboxylic acid (B2) to the content of the aliphatic monocarboxylic acid (B1a) in the aliphatic monocarboxylic acid (B1) (content of the aliphatic monocarboxylic acid (B2) / content of the aliphatic monocarboxylic acid (B1a)) is preferably 0.30 or more from the viewpoint of low volatility, and preferably 0.60 or less from the viewpoint of viscosity reduction.

[0021] The mass ratio of the content of the aliphatic monocarboxylic acid (B2) to the content of the aliphatic monocarboxylic acid (B1b) in the aliphatic monocarboxylic acid (B1) (content of the aliphatic monocarboxylic acid (B2) / content of the aliphatic monocarboxylic acid (B1b)) is preferably 0.15 or more, more preferably 0.16 or more from the viewpoint of low volatility, and preferably 0.40 or less, more preferably 0.34 or less from the viewpoint of viscosity reduction.

[0022] The mass ratio of the content of the aliphatic monocarboxylic acid (B2) to the content of the alcohol compound (A) in the condensed ester (content of the aliphatic monocarboxylic acid (B2) / content of the alcohol compound (A)) is preferably 0.10 or more from the viewpoint of low volatility, and preferably 1.50 or less from the viewpoint of viscosity reduction.

[0023] The total content of the alcohol compound (A) and the carboxylic acid (B) in the condensed ester is preferably 95% by mass or more, more preferably 97% by mass or more, still more preferably substantially 100% by mass, and even more preferably 100% by mass from the viewpoints of low viscosity and low volatility.

[0024] The content of the condensed ester in the lubricating oil base oil is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably substantially 100% by mass, and even more preferably 100% by mass, from the viewpoint of achieving both low viscosity and low volatility, and low temperature stability.

[0025] <Method for manufacturing lubricating oil base oil> The method for producing the lubricating oil base oil of this embodiment is the method for producing the lubricating oil base oil, The reaction step comprises carrying out an esterification reaction between the alcohol compound (A) and the carboxylic acid (B), The carboxylic acid (B) contains the monocarboxylic acid (B1) and the aliphatic monocarboxylic acid (B2).

[0026] The esterification reaction in the aforementioned reaction step can be carried out using known methods.

[0027] <Lubricating oil> The lubricating oil of this embodiment contains the lubricating oil base oil. The lubricating oil may also contain other additives to the extent that it does not impair the effects of the present invention. Examples of such other additives include detergents, dispersants, antioxidants, oiliness improvers, anti-wear agents, extreme pressure agents, rust inhibitors, corrosion inhibitors, metal deactivators, viscosity index improvers, pour point depressants, defoaming agents, emulsifiers, anti-emulsifiers, mold inhibitors, and solid lubricants.

[0028] The content of the lubricating oil base oil in the lubricating oil is preferably 90% by mass or more, more preferably 95% by mass or more.

[0029] The total content of the other additives in the lubricating oil is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0030] The lubricating oil can be used as a combustion-type lubricating oil such as gasoline engine oil, diesel engine oil, and marine engine oil; and as a non-combustible lubricating oil such as gear oil, automatic transmission oil, hydraulic oil, flame-retardant hydraulic fluid, refrigeration oil, compressor oil, vacuum pump oil, bearing oil, insulating oil, turbine oil, sliding surface oil, rock drill oil, metalworking oil, plastic working oil, heat treatment oil, and grease. In particular, the lubricating oil is preferably used as a non-combustible lubricating oil. Furthermore, the lubricating oil can be used on sliding parts such as sliding bearings, surface sliding bearings such as thrust bearings, and sliding parts such as splines, and can be used in lubrication methods for the spline portion of a clutch disc, the shaft and gear inner diameter bearing portion of a transmission, the spline portion of a hub sleeve, the metal-supported portion of each part, and the spline portion of a gear shift operating system. [Examples]

[0031] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0032] <Preparation of lubricating oil base oil> [Example 1] A stirrer, thermometer, nitrogen gas inlet, and condenser were attached to a 2-liter four-necked flask. 357.0 g of heptanoic acid, 856.9 g of octanoic acid, and 214.2 g of decanoic acid were added to the flask as carboxylic acid components, and 370.0 g of trimethylolpropane was added as the alcohol component. The amount of trimethylolpropane added was set so that the carboxyl groups of the carboxylic acid components were 1.2 equivalents for every 1 equivalent of hydroxyl groups of trimethylolpropane. Next, the mixture was reacted at 240°C for 16 hours while blowing nitrogen gas into the flask, and the distilled water was removed. After the reaction was complete, excess carboxylic acid components were removed under reduced pressure of 0.06 kPa, and the mixture was steamed under reduced pressure of 0.06 kPa for 1 hour. The remaining carboxylic acid components were adsorbed with an adsorbent (Kyowa Chemical Industry Co., Ltd., product name: Kyoward 500SH), and then filtered. The resulting condensed ester was used as lubricating oil base oil 1.

[0033] [Examples 2-4 and Comparative Examples 1-9] Except for changing the type of alcohol component and the type and proportion of the carboxylic acid component as shown in Table 1, condensed esters were prepared in the same manner as in Example 1, and each of the obtained condensed esters was used as lubricating oil base oil 2 to 13. In Table 1, the amount of alcohol component used in each example was the same as in Example 1, and each carboxylic acid component was blended so that there were 1.2 equivalents of carboxyl groups for every 1 equivalent of hydroxyl groups of the alcohol component.

[0034] Table 1 shows the amounts of each raw material used in the synthesis of the above-mentioned examples and comparative examples. The raw materials listed in Table 1 are as follows: Trimethylolpropane (manufactured by Tokyo Chemical Industry Co., Ltd.) Heptanoic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) Octanoic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) Decanoic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) Dodecanoic acid (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0035] [Table 1]

[0036] <Rating> [Evaluation of viscosity] The viscosity of the lubricating oil base oil for each example and comparative example was measured using a method in accordance with JIS K2283, and the kinematic viscosity (mm²) at 40°C was determined accordingly. 2 The kinematic viscosity was evaluated by measuring the kinematic viscosity (k / second). This kinematic viscosity was measured for each lubricating oil base oil immediately after preparation.

[0037] [Evaluation of volatility] The viscosity of the lubricating oil base oils from each example and comparative example, prepared in 100 mL beakers, was weighed out at 20 g each and stored in a constant temperature bath at 150°C. Volatility was evaluated by calculating the evaporation rate of the lubricating oil base oil from the weight change of the beakers after 500 hours. The evaporation rates listed in Table 2 are the average values ​​obtained by simultaneously evaluating four identical samples.

[0038] [Evaluation of the pour point] The pour point (°C) of the lubricating oil base oil for each example and comparative example was measured using a measurement method compliant with ASTM D6749.

[0039] [Evaluation of low-temperature stability] 15g of the lubricating oil base oil according to each example and comparative example was placed in a 20mL screw-cap tube and stored in a -40°C constant temperature bath for 168 hours (7 days). The state of the liquid upon removal was then checked. Those that remained in a liquid state were marked with ○, while those that solidified or showed partial crystal precipitation were marked with ×.

[0040] The evaluation results are shown in Table 2.

[0041] [Table 2]

[0042] The results in Table 2 show that the lubricating oil base oils in Examples 1 to 4 have low viscosity, low volatility, and excellent low-temperature stability.

Claims

1. A lubricating oil base oil containing a condensed ester of an alcohol compound (A) selected from the group consisting of pentaerythritol and trimethylolpropane and a carboxylic acid (B), The carboxylic acid (B) comprises an aliphatic monocarboxylic acid (B1) having 8 or fewer carbon atoms and an aliphatic monocarboxylic acid (B2) having 9 to 12 carbon atoms. The aliphatic monocarboxylic acid (B1) comprises a carbon-7 aliphatic monocarboxylic acid (B1a) and a carbon-8 aliphatic monocarboxylic acid (B1b). A lubricating oil base oil in which the mass ratio of the content of aliphatic monocarboxylic acid (B2) to the content of aliphatic monocarboxylic acid (B1) in the carboxylic acid (B) (content of aliphatic monocarboxylic acid (B2) / content of aliphatic monocarboxylic acid (B1)) is 0.12 or more and 0.24 or less.

2. The lubricating oil base oil according to claim 1, wherein the mass ratio of the content of aliphatic monocarboxylic acid (B2) to the content of aliphatic monocarboxylic acid (B1a) in the carboxylic acid (B) (content of aliphatic monocarboxylic acid (B2) / content of aliphatic monocarboxylic acid (B1a)) is 0.30 or more and 0.60 or less.

3. The lubricating oil base oil according to claim 1, wherein the mass ratio of the content of aliphatic monocarboxylic acid (B2) to the content of aliphatic monocarboxylic acid (B1b) in the carboxylic acid (B) (content of aliphatic monocarboxylic acid (B2) / content of aliphatic monocarboxylic acid (B1b)) is 0.15 or more and 0.40 or less.

4. The lubricating oil base oil according to claim 1, wherein the mass ratio of the content of the aliphatic monocarboxylic acid (B2) to the content of the alcohol compound (A) (content of the aliphatic monocarboxylic acid (B2) / content of the alcohol compound (A)) is 0.10 or more and 1.50 or less.

5. A lubricating oil containing the lubricating oil base oil described in any one of claims 1 to 4.

6. A method for producing a lubricating oil base oil according to any one of claims 1 to 4, The reaction step comprises carrying out an esterification reaction between the alcohol compound (A) and the carboxylic acid (B), A method for producing a lubricating oil base oil, wherein the carboxylic acid (B) contains the monocarboxylic acid (B1) and the aliphatic monocarboxylic acid (B2).

Images