Monoester Compounds

Abstract

Provided are a lubricating oil base oil or grease base oil, which can impart excellent low-temperature fluidity and a high flash point as a lubricating oil base oil or grease base oil, and a lubricating oil composition or grease composition, which can suppress carbon dioxide emissions by using the lubricating oil base oil or grease base oil obtained from a biomass-derived raw material. [Solution] General formula (1) TIFF2026041597000007.tif45150 [wherein k represents 7 or 8, n represents an integer of 7 to 9, and m represents an integer of 5 to 7], the biomass degree of a monoester compound represented by the formula (I) is 80% or more, and the lubricating base oil contains the compound.

Description

[Technical Field]

[0001] The present invention relates to a monoester compound. [Background technology]

[0002] From the viewpoint of reducing environmental impact, there is an increasing demand for energy-saving lubricating oils, and it is necessary to improve energy loss due to increased viscosity at low temperatures and reduced life due to decreased viscosity and evaporation at high temperatures. Therefore, there is a demand for lubricating base oils that have low viscosity at operating temperatures and low evaporation. As such lubricating base oils, monoesters (hereinafter referred to as monoester compounds) obtained by reacting monocarboxylic acids with monohydric alcohols have been disclosed (Patent Documents 1 and 2).

[0003] Furthermore, with the growing demand for the creation of a recycling-oriented society, there is a desire to move away from petroleum-derived raw materials, and the use of biomass-derived raw materials is attracting attention. Biomass-derived raw materials are organic compounds photosynthesized from carbon dioxide and water, and when used, they are converted back into carbon dioxide and water, making them so-called carbon-neutral raw materials. Recently, the practical application of biomass chemical products made from these biomass raw materials has been progressing rapidly, and a monoester compound with a natural origin index of 100% has been disclosed as one such lubricating oil base oil (Patent Document 3).

[0004] Incidentally, lubricating oils used in electrical equipment and mechanical parts used in various industries, including automobiles, are required to maintain or improve lubricity, particularly in cold regions, even in low-temperature environments such as -40° C. For this reason, there is a demand for lubricating base oils with a high natural index that have an appropriate kinematic viscosity at the operating temperature and excellent low-temperature fluidity. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2009-185191 [Patent Document 2] Patent Publication No. 2014-139306 [Patent Document 3] Patent Publication No. 2023-32093 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide a lubricating oil base oil or grease base oil, and a lubricating oil composition or grease composition, which have a kinematic viscosity in an appropriate range as a lubricating oil base oil or grease base oil, can impart excellent low-temperature fluidity and a high flash point, and which can reduce carbon dioxide emissions by using a lubricating oil base oil or grease base oil obtained from a biomass-derived raw material. [Means for solving the problem]

[0007] In view of the current situation, the present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have found that monoester compounds having a specific structure obtained from biomass-derived raw materials are excellent as lubricating oil base oils or grease base oils, and can impart kinematic viscosity in an appropriate range, excellent low-temperature fluidity, and a high flash point, and are lubricating oil base oils or grease base oils having a specific natural origin index, thereby completing the present invention.

[0008] That is, the present invention provides a lubricating oil base oil or a grease base oil having the following features:

[0009] General formula (1) [ka] [In the formula, k represents an integer of 6 to 10, n represents an integer of 7 to 9, and m represents an integer of 5 to 7.] Monoester compounds with a biomass ratio of 80% or more.

[0010] A lubricating base oil characterized by containing the monoester compound described above.

[0011] A lubricating base oil characterized by containing a monoester compound of general formula (1) in which k is 6 or 10, n is 7, and m is 5.

[0012] A lubricating oil composition having a content of the monoester compound described above of 80 mass % or more.

[0013] A grease base oil having a content of the monoester compound described above of 80 mass % or more.

[0014] A grease composition comprising the above-described grease base oil and a thickener. [Effects of the Invention]

[0015] The lubricating base oil and grease base oil of the present invention have an appropriate kinematic viscosity at the temperature of use as a lubricating base oil and a grease base oil, excellent low-temperature fluidity, and a high flash point, so that they can impart excellent low-temperature fluidity and a high flash point to a lubricating oil composition or a grease composition, and can be suitably used as a lubricating base oil, particularly a grease base oil, having a specific natural origin index. Furthermore, by replacing the raw material of the lubricating base oil from petroleum-derived to biomass-derived, the amount of petroleum resources used can be reduced, and carbon dioxide emissions during the production of the lubricating base oil can be suppressed, thereby reducing the environmental load. DETAILED DESCRIPTION OF THE INVENTION

[0016] The lubricating base oil of the present invention is General formula (1) [ka] [In the formula, k represents an integer of 6 to 10, n represents an integer of 7 to 9, and m represents an integer of 5 to 7.] The biomass ratio of the monoester compound represented by the formula (I) is 80% or more, and the biomass ratio is 80% or more.

[0017] In the monoester compound represented by the general formula (1), if k is 5 or less, the viscosity decreases, which is not preferred, and if k is 11 or more, the viscosity increases and the low-temperature fluidity deteriorates, which is not preferred.

[0018] In the monoester compound represented by the general formula (1), n ​​of 6 or less is undesirable because the viscosity decreases, and n of 10 or more is undesirable because the viscosity increases and the low-temperature fluidity deteriorates.

[0019] In the monoester compound represented by the general formula (1), if m is 4 or less, the viscosity decreases, which is not preferred, and if m is 8 or more, the viscosity increases and the low-temperature fluidity deteriorates, which is not preferred.

[0020] Specific examples of the monoester compound represented by general formula (1) include 2-hexyldecyl caprylate, 2-heptylundecyl caprylate, 2-octyldodecyl caprylate, 2-octyldecyl caprylate, 2-hexyldodecyl caprylate, (2-hexyldodecyl)(2-octyldecyl) caprylate, 2-hexyldecyl pelargonate, 2-heptylundecyl pelargonate, 2-octyldodecyl pelargonate, 2-octyldecyl pelargonate, 2-hexyldodecyl pelargonate, (2-hexyldodecyl)(2-octyldecyl) pelargonate, 2-hexyldecyl caprate, 2-heptylundecyl caprate, 2-octyldecyl caprate, Cetyldodecyl, 2-octyldecyl caprate, 2-hexyldodecyl caprate, 2-hexyldodecyl (2-octyldecyl) caprate, 2-hexyldecyl undecanoate, 2-heptylundecyl undecanoate, 2-octyldodecyl undecanoate, 2-octyldecyl undecanoate, 2-hexyldodecyl (2-octyldecyl) undecanoate, 2-hexyldecyl laurate, 2-heptylundecyl laurate, 2-octyldodecyl laurate, 2-octyldecyl laurate, 2-hexyldodecyl (2-octyldecyl) laurate, 2-hexyldodecyl (2-octyldecyl) laurate.

[0021] Two or more monoester compounds represented by the above general formula (1) can also be used as a lubricating oil base oil or a grease base oil.

[0022] The method for producing the monoester compound represented by general formula (1) is not particularly limited, but it can be obtained, for example, by an esterification reaction or transesterification reaction between one or more monocarboxylic acids having 8 to 12 carbon atoms and one or more biomass-derived alcohols having a linear alkyl group at the 2-position. The monocarboxylic acid may be derived from petroleum or biomass, and is preferably a biomass-derived monocarboxylic acid.

[0023] Specific examples of the monocarboxylic acid include caprylic acid, pelargonic acid, capric acid, undecanoic acid, and lauric acid.

[0024] Biomass-derived caprylic acid, biomass-derived pelargonic acid, biomass-derived capric acid, biomass-derived undecanoic acid, and biomass-derived lauric acid can be commercially available biomass-derived products produced from animal or plant-derived fats and oils.

[0025] Biomass-derived alcohols having a linear alkyl group at the 2-position are also called Guerbet alcohols, and although there are no particular limitations on the method for producing Guerbet alcohols, JP 2021-095405 A discloses a method for producing high-quality Guerbet alcohols with few impurities by using biomass-derived linear alcohols as a raw material and suppressing the production of by-product esters, and one or more types of biomass-derived linear alcohols can be used as the raw material for Guerbet alcohols.

[0026] Specific examples of the biomass-derived alcohols having a linear alkyl group at the 2-position (Guerbet alcohols) include 2-hexyldecanol, 2-hexylundodecanol, 2-hexyldodecanol, 2-heptyldecanol, 2-heptylundecanol, 2-heptyldodecanol, 2-octyldecanol, 2-octylundecanol, and 2-octyldodecanol, and preferred are 2-hexyldecanol, 2-hexyldodecanol, 2-octyldecanol, and 2-octyldodecanol.

[0027] Two or more of the biomass-derived alcohols (Guerbet alcohols) having a linear alkyl group at the 2-position can also be used as raw materials for the monoester compound represented by general formula (1).

[0028] The natural origin index of monoester compounds is a value calculated in accordance with ISO 16128 and indicates the proportion of natural raw materials derived from plants, animals, algae, microorganisms such as bacteria and fungi, and minerals in the raw materials used to produce lubricating base oils.

[0029] From the viewpoints of reducing the amount of petroleum resources used and mitigating the environmental burden, the higher the natural origin index of the monoester compound represented by general formula (1), the better, as this can reduce the amount of carbon dioxide emitted during the production of the lubricating base oil or grease base oil, thereby reducing the environmental burden. From the viewpoints of simplicity and practicality, the natural origin index of the monoester compound represented by general formula (1) is preferably 80 to 100%, more preferably 90 to 100%, and particularly preferably 99 to 100%. If the natural origin index of the monoester compound represented by general formula (1) is less than 80%, the effect of reducing the amount of carbon dioxide emitted during the production of the lubricating base oil or grease base oil is small, which is not preferred.

[0030] In the lubricating base oil or grease base oil, the content of the monoester compound represented by general formula (1) is preferably 80% by mass or more, more preferably 90% by mass or more.

[0031] <Thickener> The thickener usable in the present invention is not particularly limited, but is preferably at least one selected from metal soap compounds, complex metal soap compounds, and urea compounds. The thickener may be used alone or in combination of two or more.

[0032] Examples of metal soap compounds include lithium soaps and calcium soaps, with lithium soaps being preferred. Here, the lithium soap is a soap obtained by saponifying an aliphatic carboxylic acid or ester with lithium hydroxide. Examples of lithium soaps include lithium salts of aliphatic monocarboxylic acids having 12 to 24 carbon atoms and lithium salts of aliphatic monocarboxylic acids having 12 to 24 carbon atoms and at least one hydroxy group, with lithium stearate and lithium 12-hydroxystearate being particularly preferred.

[0033] Examples of complex metal soap compounds include lithium complex soaps, calcium complex soaps, and barium complex soaps, with lithium complex soaps and barium complex soaps being preferred. Here, the lithium complex soap is a soap obtained by saponifying multiple aliphatic carboxylic acids or esters with lithium hydroxide, and the barium complex soap is a soap obtained by saponifying multiple aliphatic carboxylic acids or esters with barium hydroxide. Examples of lithium complex soaps include lithium salts of aliphatic monocarboxylic acids and aliphatic dicarboxylic acids, and lithium salts of two or more aliphatic monocarboxylic acids.

[0034] The urea compound is not particularly limited, but examples thereof include diurea compounds, triurea compounds, tetraurea compounds, polyurea compounds, etc., and diurea compounds are preferred. Examples of the diurea compound include diurea compounds represented by the following general formula (2): [ka]

[0035] In the above general formula (2), R 1represents an aromatic hydrocarbon group having 6 to 15 carbon atoms, and R 2 and R 3 are each independently an aromatic hydrocarbon group having 6 to 18 carbon atoms, a cyclohexyl group, an alkylcyclohexyl group having 7 to 12 carbon atoms, an alkyl group having 8 to 22 carbon atoms, or an alkenyl group having 8 to 22 carbon atoms.

[0036] The diurea compound represented by the general formula (2) can be obtained by reacting an amine with a diisocyanate compound by a known method. Examples of the amine include aromatic amines having 6 to 18 carbon atoms, cyclohexylamine, alkylcyclohexylamines having 7 to 12 carbon atoms, alkyl or alkylamines having 8 to 22 carbon atoms, and mixtures thereof. Examples of the diisocyanate compound include diphenylmethane-4,4'-diisocyanate, 2,4'-tolylene diisocyanate, and 2,6-tolylene diisocyanate.

[0037] The amount of thickener contained in the grease composition is preferably 1% by mass or more and 30% by mass or less, and more preferably 5% by mass or more and 20% by mass or less, relative to the total mass of the grease composition. When the thickener content is within this range, the grease composition has an appropriate hardness, is less likely to leak, and has good fluidity, resulting in excellent low-temperature properties.

[0038] The lubricating base oil of the present invention can also be a mixed base oil prepared by appropriately combining one or more compounds selected from the group consisting of mineral oil, hydrocarbon oil such as poly-α-olefin, polybutene, alkylbenzene, alkylnaphthalene, esters other than the monoester compound of the present invention (hereinafter referred to as "combined esters"), and polyalkylene glycol, phenyl ether, and silicone oil. The proportion of the monoester compound of the present invention in the mixed base oil is 5% by mass or more, and the suitable mixing ratio varies depending on the type of oil used in combination.

[0039] As mineral oil, the kinematic viscosity is 3 to 30 mm 2 / s (100℃) is appropriate.

[0040] As the α-olefin oligomer, a trimer to decamer of a linear α-olefin having 8 to 12 carbon atoms is recommended.

[0041] The alkylbenzene and alkylnaphthalene may have a straight-chain or branched alkyl group, and those having an average molecular weight of 200 to 1,000 are recommended.

[0042] When a hydrocarbon oil is used in combination, the proportion of the monoester compound of the present invention relative to the total mixed base oil is suitably 5 to 40 mass %, preferably 10 to 30 mass %. Use of such a mixed base oil results in a lubricating oil with good additive solubility, rubber swelling properties, and oxidation stability.

[0043] Examples of the co-ester include aliphatic esters other than the monoester compound of the present invention, aromatic carboxylic acid esters, and polyol esters. When the monoester compound of the present invention and the co-ester are used in combination, the proportion of the monoester compound of the present invention is suitably 20% by mass or more, preferably 50% by mass or more. By using the co-ester in this way, the high-temperature stability of the mixed base oil can be improved.

[0044] Examples of polyalkylene glycols include propylene oxide and copolymers of ethylene oxide and propylene oxide, and in particular, those having a kinematic viscosity at 40°C of 10 to 4,000 mm 2 Something in the / s range is recommended.

[0045] When the monoester compound of the present invention is mixed with these polyalkylene glycols, the proportion of the monoester compound of the present invention relative to the total mixed base oil is suitably 50 to 95 mass %, preferably 70 to 90 mass %. By mixing the polyalkylene glycol in this way, the high temperature stability of the mixed base oil can be improved.

[0046] Examples of phenyl ethers include monoalkyl diphenyl ethers, dialkyl diphenyl ethers, and polyphenyl ethers, such as bis(m-phenoxyphenyl) ether and m-bis(m-phenoxyphenoxy)benzene. When the monoester compound according to the present invention is used in combination with a phenyl ether, the proportion of the monoester compound according to the present invention relative to the total mixed base oil is preferably 10% by mass or more, and more preferably 50% by mass or more. By mixing a phenyl ether in this way, the oxidation stability and lubricity of the mixed base oil can be improved, and costs can be reduced.

[0047] Examples of silicone oils include dimethyl silicone and phenyl silicone, and when the monoester compound according to the present invention is mixed with silicone oil, the proportion of the monoester compound according to the present invention relative to the total mixed base oil is preferably 10% by mass or more, more preferably 50% by mass or more. By mixing silicone oil in this way, the lubricity of the mixed base oil and the solubility of additives can be improved, and costs can be reduced.

[0048] To improve its performance, the lubricating base oil of the present invention may be appropriately blended with one or more additives such as antioxidants, antiwear agents, detergent-dispersants, viscosity index improvers, pour point depressants, metal deactivators, metal corrosion inhibitors, rust inhibitors, and antifoaming agents. While not particularly limited as long as the desired effects are achieved, specific formulation examples are shown below.

[0049] Examples of antioxidants include hindered phenol-based, aromatic amine-based, sulfur-based, phosphite-based, and zinc dithiophosphate-based compounds, and they are usually added in an amount of 0.1 to 5 mass % based on the base oil.

[0050] Examples of anti-wear agents include organic sulfur-based, organic phosphorus-based, zinc dithiophosphate-based, and long-chain fatty acid-based compounds, and these are usually added in an amount of 0.05 to 5% by mass to the base oil.

[0051] Examples of detergent-dispersants include compounds such as basic sulfonates, superbasic sulfonates, basic phenates, salicinates, phosphonates, succinimides, benzylamines, succinic acid esters, and copolymers, and they are usually added in an amount of 2 to 10% by mass based on the base oil.

[0052] Examples of viscosity index improvers include polyalkyl methacrylate-based, ethylene-propylene copolymer-based, and styrene-butadiene copolymer-based compounds, and they are usually added in an amount of 1 to 20% by mass to the base oil.

[0053] Examples of pour point depressants include polymethacrylate-based and alkylated naphthalene-based compounds, and they are usually added in an amount of 0.1 to 2% by mass to the base oil.

[0054] Examples of metal deactivators and corrosion inhibitors include benzotriazole-based and thiadiazole-based compounds, which are usually added in an amount of 0.01 to 0.4 mass % to the base oil.

[0055] Examples of rust inhibitors include sulfonate-based, carboxylic acid-based, organic amine soap-based, and sorbitan partial ester-based compounds, and they are usually added in an amount of 0.05 to 3 mass % based on the base oil.

[0056] Examples of antifoaming agents include silicone compounds such as polydimethyl silicone, which are usually added in an amount of 1 to 20 ppm to the base oil. [Example]

[0057] 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 oils in each example were evaluated by the following methods. Reagents were used for compounds not specifically mentioned.

[0058] <Compound used> 2-Hexyldecanol: N-Jekol 160BR (manufactured by New Japan Chemical Co., Ltd.) 2-Octyldodecanol: N-Jekol 200A (manufactured by New Japan Chemical Co., Ltd.) 2-Octyldecanol / 2-Hexyldodecanol: Fine Oxocol 180T (Nissan Chemical Co., Ltd.) 1-Methylheptanol: 2-Octanol (Kokura Synthetic Industries Co., Ltd.) 2-Ethylhexanol: 2-Ethylhexanol (Tokyo Chemical Industry Co., Ltd.) Caprylic acid: "Caprylic acid" (manufactured by New Japan Chemical Co., Ltd.) Capric acid: "Capric acid" (manufactured by New Japan Chemical Co., Ltd.) Lauric acid: "Lauric acid P" (manufactured by New Japan Chemical Co., Ltd.) Myristic acid: "Myristic acid" (manufactured by New Japan Chemical Co., Ltd.) Palmitic acid: "Palmitic acid P" (manufactured by New Japan Chemical Co., Ltd.)

[0059] <Evaluation of the physical properties of monoester compounds> (a) Acid number Measurements were made in accordance with JIS-K-2501 (2003), with a detection limit of 0.01 KOHmg / g.

[0060] (b) Kinematic viscosity The kinematic viscosity was measured at 40°C and 100°C in accordance with JIS-K-2283 (2000). Kinematic viscosity at 40°C is 7 to 12 mm 2 / s range is evaluated as good in terms of lubrication performance and energy saving.

[0061] (c) Low-temperature fluidity test (pour point) The pour point was measured using an automatic pour point / cloud point measuring device (MPC-6, manufactured by Tanaka Scientific Instruments Manufacturing Co., Ltd.) in accordance with JIS-K-2269 (1987). A pour point of -30°C or below is considered to have excellent low-temperature fluidity.

[0062] (d) Flash point The flash point was measured using an automatic flash point tester (Clean Brand open type) (Yoshida Scientific Instruments Co., Ltd., device name: aco-8) in accordance with JIS-K-2265-4 (2007). A flash point temperature of 200°C or higher is considered to be excellent in flammability.

[0063] The natural origin index of monoester compounds was calculated according to ISO 16128.

[0064] (e) Evaluation of lubricant base oils The lubricating base oil was evaluated for kinematic viscosity, flash point, and low-temperature fluidity. The kinematic viscosity at 40°C was 7-12 mmHg. 2 If the / s is in the range of "Good", the flash point temperature is 200°C or higher "Good", and the pour point in the low-temperature fluidity test (pour point) is -30°C or lower "Good", the overall evaluation is good.

[0065] [Example 1] A 1-liter four-neck flask equipped with a stirrer, thermometer, and condenser-equipped water distillation receiver was charged with 200 g (1.38 mol) of caprylic acid, 330 g (1.36 mol) of 2-hexyldecanol, xylene (10% by mass relative to the total amount of raw materials), and stannous oxide catalyst (0.1% by mass relative to the total amount of raw materials). Under a nitrogen atmosphere, the temperature was gradually raised to 200 °C, and the esterification reaction was carried out for 6 hours while gradually increasing the pressure from atmospheric pressure and removing the resulting water in the water distillation receiver. After the reaction was completed, the xylene and excess carboxylic acid were removed by distillation to obtain a crude esterified product. The crude esterified product was then neutralized with 2 equivalents of aqueous caustic soda based on its acid value, and repeatedly washed with water until the wash water became neutral. The crude esterified product was then subjected to adsorption treatment with activated carbon, followed by filtration to remove the activated carbon, yielding a monoester compound. The acid value of the resulting monoester compound (1) was 0.01 KOHmg / g or less. The monoester compound (1) was evaluated as a lubricating base oil, and the results are shown in Table 1.

[0066] [Example 2] A monoester compound was obtained in the same manner as in Example 1, except that 239 g (1.39 mol) of capric acid was used instead of caprylic acid. The acid value of the obtained monoester compound (2) was 0.01 KOH mg / g or less. The monoester compound (2) was evaluated as a lubricating base oil, and the results are shown in Table 1.

[0067] [Example 3] A monoester compound was obtained in the same manner as in Example 1, except that 278 g (1.39 mol) of lauric acid was used instead of caprylic acid. The acid value of the obtained monoester compound (3) was 0.01 KOH mg / g or less. The monoester compound (3) was evaluated as a lubricating base oil, and the results are shown in Table 1.

[0068] [Example 4] A monoester compound was obtained in the same manner as in Example 1, except that 394 g (1.32 mol) of 2-octyldodecanol was used instead of 2-hexyldecanol. The acid value of the obtained monoester compound (4) was 0.01 KOHmg / g or less. The monoester compound (4) was evaluated as a lubricating base oil, and the results are shown in Table 1.

[0069] [Comparative Example 1] A monoester compound outside the present invention was obtained in the same manner as in Example 1, except that 316 g (1.39 mol) of myristic acid was used instead of caprylic acid in Example 1. The acid value of the obtained monoester compound (5) outside the present invention was 0.01 KOHmg / g or less. The monoester compound (5) outside the present invention was evaluated as a lubricating base oil, and the results are shown in Table 2.

[0070] Comparative Example 2 A monoester compound outside the present invention was obtained in the same manner as in Example 1, except that 153 g (1.18 mol) of 1-methylheptanol was used instead of 2-hexyldecanol in Example 3. The acid value of the obtained monoester compound (6) outside the present invention was 0.01 KOHmg / g or less. The monoester compound (6) outside the present invention was evaluated as a lubricating base oil, and the results are shown in Table 2.

[0071] Comparative Example 3 A monoester compound outside the present invention was obtained in the same manner as in Example 1, except that 177 g (1.36 mol) of 2-ethylhexanol was used instead of 2-hexyldecanol in Example 3. The acid value of the obtained monoester compound (7) outside the present invention was 0.01 KOHmg / g or less. The monoester compound (7) outside the present invention was evaluated as a lubricating base oil, and the results are shown in Table 2.

[0072] [Table 1]

[0073] [Table 2]

[0074] From Tables 1 and 2, it can be seen that the lubricating base oil or grease base oil of the present invention has an appropriate range of kinematic viscosity, excellent low-temperature fluidity, and a high flash point, and also has a high natural origin index, making it an excellent lubricating base oil. [Industrial Applicability]

[0075] The lubricating oil base oil or grease base oil of the present invention has an appropriate kinematic viscosity at the temperature of use, excellent low-temperature fluidity, a high flash point, and a high natural origin index. Therefore, when used as a lubricating oil base oil or grease base oil, it is possible to reduce carbon dioxide emissions, and it can be used in bearings, sliding parts, etc. of automobiles and various precision instruments.

Claims

1. General formula (1) 【Chemistry 1】 [In the formula, k represents an integer of 6 to 10, n represents an integer of 7 to 9, and m represents an integer of 5 to 7.] A monoester compound having a biomass ratio of 80% or more, represented by the formula:

2. A lubricating base oil comprising the monoester compound according to claim 1.

3. 3. The lubricating base oil of claim 2, wherein k is 6 or 10, n is 7, and m is 5 in the monoester compound of claim 1.

4. A lubricating oil composition comprising the monoester compound according to claim 1 in an amount of 80 mass % or more.

5. A grease base oil, comprising the monoester compound according to claim 1 in an amount of 80 mass% or more.

6. A grease composition comprising the grease base oil according to claim 5 and a thickener.

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