Lubricating oil base oil

Abstract

To provide a lubricating oil base oil with excellent low-temperature stability. [Solution] A lubricating oil base oil containing an ester compound (α) of a monocarboxylic acid (a1) selected from aliphatic saturated monocarboxylic acids having 6 to 12 carbon atoms and an aliphatic saturated monohydric alcohol (b) having 2 to 8 carbon atoms, and an ester compound (β) of a monocarboxylic acid (a2) other than the monocarboxylic acid (a1) selected from aliphatic saturated monocarboxylic acids having 4 to 14 carbon atoms and the alcohol (b), wherein the content of the ester compound (β) in the lubricating oil base oil is 0.1% by mass or more and 1.0% by mass or less.

Description

Technical Field

[0001] The present invention relates to 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 such as fatty acid ester oils have been synthesized and used according to the application (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] < However, the fatty acid ester oil described in Patent Document 1 had room for improvement in terms of low-temperature stability . [[ID=3,6]]

[0005] An object of the present invention is to provide a lubricating base oil having excellent low-temperature stability.

Means for Solving the Problems

[0006] seem to have incorrect formatting in the original). I've translated it as accurately as possible while maintaining the original tag structure. Also, for 2020-139026 and . in the translation, they are just to show the parts corresponding to the original text's unclear or potentially wrong parts within the tags. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a lubricating oil base oil with excellent low-temperature stability. [Modes for carrying out the invention]

[0008] <Lubricant base oil> The lubricating oil base oil of this embodiment is A lubricating oil base oil containing an ester compound (α) of a monocarboxylic acid (a1) selected from aliphatic saturated monocarboxylic acids having 6 to 12 carbon atoms and an aliphatic saturated monohydric alcohol (b) having 2 to 8 carbon atoms, and an ester compound (β) of a monocarboxylic acid (a2) other than the monocarboxylic acid (a1) selected from aliphatic saturated monocarboxylic acids having 4 to 14 carbon atoms and the alcohol (b), The content of the ester compound (β) in the lubricating oil base oil is 0.1% by mass or more and 1.0% by mass or less. The lubricating oil base oil of this embodiment exhibits excellent low-temperature stability. The reason why the lubricating oil base oil of this embodiment exhibits this effect is not entirely clear, but it is thought that because it contains some ester compound (β), which has a slightly different molecular structure from the main component ester compound (α), the crystallization of ester compound (α) is inhibited in low-temperature environments, thereby improving the low-temperature stability of the base oil.

[0009] [Ester compounds (α)] The ester compound (α) is an ester of a monocarboxylic acid (a1), which is selected from aliphatic saturated monocarboxylic acids having 6 to 12 carbon atoms, and an aliphatic saturated monohydric alcohol (b), which has 2 to 8 carbon atoms.

[0010] The carbon number of the monocarboxylic acid (a1) is 6 or more, preferably 7 or more, more preferably 8 or more, and 12 or less, preferably 10 or less, more preferably 8 or less, from the viewpoint of improving low-temperature stability. The carbon chain of the monocarboxylic acid (a1) may be either linear or branched, but a linear chain is preferred.

[0011] The number of carbon atoms in alcohol (b) is 2 or more, preferably 4 or more, and 8 or less, preferably 4 or less, from the viewpoint of improving low-temperature stability. The carbon chain of alcohol (b) may be either linear or branched, but a linear chain is preferred.

[0012] From the viewpoint of improving low-temperature stability, the content of the ester compound (α) in the lubricating oil base oil is preferably 99.0% by mass or more and 99.9% by mass or less, more preferably 99.2% by mass or more and 99.8% by mass or less, and even more preferably 99.4% by mass or more and 99.6% by mass or less.

[0013] [Ester compounds (β)] The ester compound (β) is an ester of the alcohol (b) with a monocarboxylic acid (a2) other than the monocarboxylic acid (a1), which is selected from aliphatic saturated monocarboxylic acids having 4 to 14 carbon atoms.

[0014] The carbon number of the monocarboxylic acid (a2) is 4 or more, preferably 5 or more, more preferably 6 or more, and 14 or less, preferably 12 or less, more preferably 10 or less, from the viewpoint of improving low-temperature stability. The carbon chain of the monocarboxylic acid (a2) may be either linear or branched, but a linear chain is preferred.

[0015] The monocarboxylic acid (a2) is a carboxylic acid other than monocarboxylic acid (a1), which is selected from aliphatic saturated monocarboxylic acids having 6 to 12 carbon atoms related to the ester compound (α). For example, if the carboxylic acid (a1) related to the ester compound (α) is caprylic acid (8 carbon atoms), then monocarboxylic acid (a2) is a monocarboxylic acid selected from aliphatic saturated monocarboxylic acids having 4 to 14 carbon atoms other than caprylic acid. Also, for example, if the carboxylic acid (a1) related to the ester compound (α) is capric acid (10 carbon atoms), then monocarboxylic acid (a2) is a monocarboxylic acid selected from aliphatic saturated monocarboxylic acids having 4 to 14 carbon atoms other than capric acid.

[0016] The alcohol (b) relating to the ester compound (β) is the same as the alcohol (b) relating to the ester compound (α), so no explanation is given. The alcohol (b) relating to the ester compound (β) may be the same as or different from the alcohol (b) relating to the ester compound (α).

[0017] The content of the ester compound (β) in the lubricating oil base oil is 0.1% by mass or more and 1.0% by mass or less, preferably 0.2% by mass or more and 0.8% by mass or less, and more preferably 0.4% by mass or more and 0.6% by mass or less, from the viewpoint of improving low-temperature stability.

[0018] The mass ratio of ester compound (β) to ester compound (α) in the lubricating oil base oil (ester compound (β) / ester compound (α)) is preferably 0.0005 or higher, more preferably 0.001 or higher, even more preferably 0.002 or higher, even more preferably 0.003 or higher, and even more preferably 0.004 or higher, from the viewpoint of improving low-temperature stability. It is believed that as the value of the mass ratio of ester compound (β) to ester compound (α) in the lubricating oil base oil (ester compound (β) / ester compound (α)) increases, the intermolecular forces of the ester compound (α) in the main component of the lubricating oil base oil decrease, and low-temperature stability improves. The mass ratio of ester compound (β) to ester compound (α) in the lubricating oil base oil (ester compound (β) / ester compound (α)) is preferably 0.05 or less, more preferably 0.01 or less, even more preferably 0.008 or less, even more preferably 0.007 or less, and even more preferably 0.006 or less, from the viewpoint of improving heat resistance and low-temperature stability. It is believed that the smaller the value of the mass ratio of ester compound (β) to ester compound (α), the greater the intermolecular forces of ester compound (α) in the main component of the lubricating oil base oil, and thus the improved heat resistance.

[0019] The lubricating base oil may contain a base oil other than the ester compound (α) and the ester compound (β). Examples of the base oil other than the ester compound (α) and the ester compound (β) include mineral oil and synthetic oil. Examples of the mineral oil include distillate oil obtained by subjecting paraffinic crude oil, intermediate crude oil, or naphthenic crude oil to atmospheric distillation or subjecting the residue oil of atmospheric distillation to vacuum distillation, or refined oil obtained by refining this according to a conventional method (for example, solvent-refined oil, hydrorefined oil, dewaxed oil, clay-treated oil, etc.). Examples of the synthetic oil include esters other than the ester compound (α) and the ester compound (β), poly-α-olefin, olefin copolymer, alkylbenzene, alkylnaphthalene, polyoxyalkylene glycol, polyphenyl ether, etc.

[0020] From the viewpoint of improving low-temperature stability, the total content of the ester compound (α) and the ester compound (β) in the lubricating base oil is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably substantially 100% by mass, and even more preferably 100% by mass. In the present specification, "substantially 100% by mass" means a state containing inevitably trace amounts of impurities and the like.

[0021] <Method for producing lubricating base oil> The lubricating base oil can be prepared by subjecting the monocarboxylic acid (a1), the monocarboxylic acid (a2), and the alcohol (b) to an esterification reaction according to a known method. For example, a method of obtaining by mixing the ester compound (α) obtained by the esterification reaction of the monocarboxylic acid (a1) and the alcohol (b) and the ester compound (β) obtained by the esterification reaction of the monocarboxylic acid (a2) and the alcohol (b) at a specific ratio, and a method of obtaining by the esterification reaction of a mixed aliphatic saturated monocarboxylic acid of the monocarboxylic acid (a1) and the monocarboxylic acid (a2) at a specific ratio and the alcohol (b) are included.

[0022] The lubricating base oil can be used as the base oil for combustion lubricating oils such as gasoline engine oils, diesel engine oils, and marine engine oils; non-combustion lubricating oils such as gear oils, automatic transmission oils, hydraulic oils, fire-resistant hydraulic fluids, refrigeration oils, compressor oils, vacuum pump oils, bearing oils, insulating oils, turbine oils, sliding surface oils, rock drill oils, metalworking oils, cooling oils, plastic processing oils, heat treatment oils, and greases. In particular, the lubricating base oil is preferably used for metalworking oils.

[0023] <Metalworking oil> The metalworking oil of this embodiment contains at least the lubricating base oil. From the viewpoint of improving low-temperature stability, the content of the lubricating base oil in the metalworking oil is preferably 90% by mass or more, more preferably substantially 100% by mass or more, and still more preferably 100% by mass.

[0024] In addition to the lubricating base oil, the metalworking oil may contain additives that are commonly blended in metalworking oils. Examples of the additives include oiliness agents, extreme pressure agents, surfactants, defoamers, rust preventives, antiseptics, antioxidants, and metal deactivators. These may be used alone or in combination of two or more.

Examples

[0025] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited only to these examples. Also, various measurement and evaluation methods are as follows.

[0026] <Preparation of lubricating base oil> 〔Examples 1 to 3〕 Butyl caprylate and butyl hexanoate were mixed to have the compositions shown in Table 1 to obtain the lubricating base oils according to Examples 1 to 3, respectively.

[0027] 〔Examples 4 to 6〕 Butyl caprylate and butyl capric acid were mixed to have the compositions shown in Table 1 to obtain the lubricating base oils according to Examples 4 to 6, respectively.

[0028] 〔Examples 7 to 9〕 Butyl caprylate, butyl hexanoate, and butyl caprate were mixed to obtain the lubricating oil base oils for Examples 7 to 9, respectively, to achieve the compositions shown in Table 1.

[0029] [Comparative Example 1] Butyl caprylate was used as the lubricating oil base oil in Comparative Example 1.

[0030] [Table 1]

[0031] The ingredients listed in Table 1 are as follows: Butyl caprylate (manufactured by Tokyo Chemical Industry Co., Ltd.) Butyl hexanoate (manufactured by Tokyo Chemical Industry Co., Ltd.) Butyl caprate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0032] <Evaluation Method> [Evaluation of low-temperature stability] The low-temperature stability of each lubricating oil base oil in each example and comparative example was evaluated by placing a 5 mL sample in a screw-cap tube (No. 5) and storing it at -55°C for 3 days in a low-temperature incubator SU-662 (manufactured by ESPEC). The liquid or solid state was then visually assessed. If it was liquid, it indicated excellent low-temperature stability. The evaluation results are shown in Table 1.

[0033] The lubricating oil base oil of the present invention is expected to improve low-temperature stability without sacrificing low torque and heat resistance. Since the lubricating oil base oil of the present invention does not solidify even at low temperatures, lubricating oils containing the lubricating oil base oil of the present invention can be used as lubricants even in low-temperature environments.

Claims

1. An ester compound (α) of a monocarboxylic acid (a1) selected from aliphatic saturated monocarboxylic acids having 6 to 12 carbon atoms and an aliphatic saturated monohydric alcohol (b) having 2 to 8 carbon atoms, and A lubricating oil base oil containing an ester compound (β) of a monocarboxylic acid (a2) other than the monocarboxylic acid (a1) selected from aliphatic saturated monocarboxylic acids having 4 to 14 carbon atoms, and the alcohol (b), A lubricating oil base oil in which the content of the ester compound (β) in the lubricating oil base oil is 0.1% by mass or more and 1.0% by mass or less.

2. The lubricating oil base oil according to claim 1, wherein the content of the ester compound (α) in the lubricating oil base oil is 99.0% by mass or more and 99.9% by mass or less.

3. The lubricating oil base oil according to claim 1, wherein the mass ratio of the ester compound (β) to the ester compound (α) in the lubricating oil base oil (ester compound (β) / ester compound (α)) is 0.0005 or more and 0.05 or less.

4. A metalworking oil containing the lubricating oil base oil described in any one of claims 1 to 3.

5. The metalworking oil according to claim 4, wherein the content of the lubricating oil base oil is 90% by mass or more.

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