Lubricating oil base oil

Abstract

Since the lubricant base oil of the present invention has excellent low-temperature fluidity, hydrolysis stability, heat resistance, and lubricity, it can exhibit good performance over a long period even in various environments, contributing to the extension of the service life of lubricating oils. 【Means for solving the problem】 The kinematic viscosity at 40°C of a diester compound having 18 to 26 carbon atoms represented by the following general formula (1) is 6.0 mm 2 / s or more and 30.0 mm 2 / s or less, and a lubricant base oil in which the raw material of the diester compound contains a raw material derived from biomass. [Chemical formula 1] JPEG2026104831000007.jpg19156 [In the formula, k represents an integer of 2 to 8, and R 1 ~R 4 may be the same or different and each represents an alkyl group having 1 to 11 carbon atoms.]

Description

[Technical Field]

[0001] This invention relates to a lubricating oil base oil. [Background technology]

[0002] Lubricants are used in a variety of viscosities depending on their application and the equipment or machinery they are used in, and their operating temperatures also vary widely, from low to high temperatures. Therefore, in order for a lubricant base oil to be usable in various environments and a wide temperature range, it must have excellent low-temperature fluidity, heat resistance, lubricity, and hydrolysis stability.

[0003] For example, Patent Document 1 provides a low-viscosity fluid bearing oil with excellent low-temperature fluidity, evaporation resistance, and viscosity index, using an ester made from a dicarboxylic acid having 6 to 10 carbon atoms and a straight-chain or branched alcohol having 6 to 9 carbon atoms as the base oil. However, because it is necessary to contain a predetermined amount of diester using a linear alcohol, the low-temperature fluidity was not sufficient. Furthermore, while Patent Document 1 describes the use of a combination of a linear alcohol and a β-branched alcohol in its examples, esters using such combinations have poor hydrolysis stability and are therefore unsuitable for applications where moisture contamination is expected. In addition, it uses petrochemical-derived raw materials, which are harmful to the environment, and furthermore, its use as a fluid bearing oil for HDDs has only been shown, with no known use as a lubricant for automobiles or industrial machinery.

[0004] Furthermore, for example, Patent Document 2 provides a monoester with 18 or more carbon atoms having one or more branched structures and a natural origin index of 100% as a lubricating oil base oil. However, monoesters with a single branched structure have poor low-temperature fluidity and are unsuitable for applications such as automotive use in cold climates. Furthermore, because it is a monoester, it has poor heat resistance, and its viscosity is too low, resulting in poor lubrication and the problem of seizing due to oil film breakdown at high temperatures.

[0005] Furthermore, for example, Patent Document 3 provides a diester using a dicarboxylic acid and a monoalcohol as a bearing oil with excellent lubricity and heat resistance, but because it uses petrochemical-derived raw materials, it is not an environmentally friendly compound. Although it is stated that a linear structure can also be used, it has poor low-temperature fluidity and is unsuitable for automotive applications. In addition, it has poor hydrolysis stability and is unsuitable for applications where moisture contamination is expected. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2012-172118 [Patent Document 2] Japanese Patent Publication No. 2023-32093 [Patent Document 3] Japanese Patent Application Publication No. 11-172267 [Overview of the project] [Problems that the invention aims to solve]

[0007] In recent years, driven by the trend towards carbon neutrality, there has been a growing demand for lubricants made from biomass-derived raw materials to reduce environmental impact. In addition, there is a demand for lower viscosity lubricants from an energy-saving perspective. However, with conventional lubricants, lower viscosity has been accompanied by a decrease in low-temperature fluidity, lubricity, and heat resistance, which has been a challenge.

[0008] In other words, to reduce environmental impact, it is preferable to use biomass-derived raw materials and low-viscosity base oils as lubricating oil base oils. However, no base oils were known that were low-viscosity with a high natural origin index and possessed properties such as low-temperature fluidity, hydrolysis stability, heat resistance, and lubricity.

[0009] The present invention has been made in view of the above-described prior art, and has excellent low-temperature fluidity, hydrolysis stability, heat resistance, and lubricity, so that it can exhibit good performance in various environments for a long time, and aims to provide a lubricating base oil that contributes to the extension of the service life of lubricating oil.

Means for Solving the Problems

[0010] As a result of intensive studies, the inventors of the present invention have found that by controlling the kinematic viscosity at 40°C of a lubricating base oil containing a biomass-derived raw material and containing a diester compound having a specific structure within a predetermined range, all of the above-described problems can be solved, and the present invention has been completed.

[0011] That is, in the present invention, the kinematic viscosity at 40°C of a diester compound having 18 to 26 carbon atoms represented by the following general formula (1) is 6.0 mm 2 , 2 , , , 2 , , 2 , / s or more and 30.0 mm 2 / s or less, and the raw material of the above diester compound contains a biomass-derived raw material, which is a lubricating base oil.

Chemical Formula

[0012] In the lubricating base oil of the present invention, it is preferable that the kinematic viscosity at 40°C is 7.0 mm 2 / s or more and 12.0 mm 2 / s or less. [[ID=3�]] Further, in the lubricating base oil of the present invention, it is preferable that the kinematic viscosity at 100°C is 2.0 mm 2 / s or more and 6.0 mm 2 / s or less. Further, in the lubricating base oil of the present invention, it is preferable that the pour point is -30°C or lower. Furthermore, in the lubricating oil base oil of the present invention, the raw materials for the diester compound are a biomass-derived α-branched alcohol and a dicarboxylic acid, and the biomass-derived α-branched alcohol is preferably 2-octanol. Furthermore, in the lubricating oil base oil of the present invention, the dicarboxylic acid is preferably succinic acid, adipic acid, suberic acid, azelaic acid, or sebacic acid. Furthermore, in the lubricating oil base oil of the present invention, the dicarboxylic acid is preferably adipic acid, azelaic acid, or sebacic acid. Furthermore, in the lubricating oil base oil of the present invention, it is preferable that the naturally derived index (ISO 16128) of the above-mentioned diester compound is 70% or more. [Effects of the Invention]

[0013] The present invention provides a lubricating oil base oil that exhibits excellent low-temperature fluidity, hydrolysis stability, heat resistance, and lubricity, and can demonstrate good performance over the long term in various environments, thereby contributing to the extended lifespan of lubricating oils. [Modes for carrying out the invention]

[0014] <Diester compounds> In the lubricating oil base oil of the present invention, the diester compound represented by formula (1) is a diester compound having 18 to 26 carbon atoms and a branched structure at the 1-position, obtained by esterifying an α-branched alcohol with a dicarboxylic acid. Here, "a diester compound having a branched structure at position 1, obtained by esterifying an α-branched alcohol with a dicarboxylic acid" refers, for example, to the diester compound of formula (2) below, which consists of 2-octanol and adipic acid, in which side chains are attached to both of the two carbon atoms at position 1 indicated by the arrows. [ka] On the other hand, a diester compound obtained by esterifying a β-branched alcohol with a dicarboxylic acid, for example, a diester compound of formula (3) below consisting of 2-ethylhexanol and adipic acid, has a structure in which side chains are attached to both of the two carbon atoms at position 2 indicated by the arrows. [ka] By having 18 to 26 carbon atoms in the above-mentioned diester compound, the lubricating oil base oil of the present invention is made low-viscosity and exhibits excellent heat resistance and low-temperature fluidity. Furthermore, by using an α-branched alcohol, the above-mentioned diester compound has a branched structure at position 1, resulting in excellent hydrolysis stability of the lubricating oil base oil of the present invention.

[0015] In the lubricating oil base oil of the present invention, the diester compound contains raw materials derived from biomass. The raw materials for the above diester compound are preferably an α-branched alcohol and a dicarboxylic acid derived from biomass. By esterifying the α-branched alcohol and the dicarboxylic acid derived from biomass, a diester compound having a branched structure at position 1 can be obtained using biomass-derived raw materials.

[0016] The above biomass-derived α-branched alcohol is a secondary alcohol, and specifically, 2-octanol is preferred. By using 2-octanol as a raw material, diester compounds having 18 to 26 carbon atoms and a branched structure at the 1st position can be suitably obtained.

[0017] The carboxylic acid is preferably succinic acid, adipic acid, suberic acid, azelaic acid, or sebacic acid. By using these carboxylic acids and 2-octanol as the above biomass-derived α-branched alcohol as raw materials, a diester compound having 18 to 26 carbon atoms and a branched structure at the 1st position can be obtained. Among the carboxylic acids mentioned above, adipic acid, azelaic acid, or sebacic acid are more preferred.

[0018] The diester compound obtained from the above-mentioned raw materials preferably has a natural origin index (ISO 16128) of 70% or more from the perspective of reducing environmental impact. The diester compound satisfying such a natural origin index (ISO 16128) can be obtained by esterifying the above-mentioned biomass-derived 2-octanol and carboxylic acid as raw materials. When using the above-mentioned biomass-derived 2-octanol as a raw material, the carboxylic acid may be derived from biomass or petrochemicals, and may be appropriately selected and used within the range satisfying the above natural origin index. For example, by esterifying biomass-derived 2-octanol and petrochemical-derived adipic acid as raw materials, a diester compound with a natural origin index of 70% or more can be obtained.

[0019] The specific method of esterification using the above-mentioned biomass-derived 2-octanol and carboxylic acid as raw materials is not particularly limited, and a conventionally known esterification method using an alcohol and a dicarboxylic acid can be used.

[0020] The lubricating base oil of the present invention has a kinematic viscosity at 40°C of 6.0 mm 2 / s or more and 30.0 mm 2 / s or less. The lubricating base oil of the present invention satisfying such a kinematic viscosity at 40°C has a low viscosity and excellent energy-saving properties. The above kinematic viscosity at 40°C is preferably 7.0 mm 2 / s or more and 12.0 mm 2 / s or less.

[0021] Also, the lubricating base oil of the present invention preferably has a kinematic viscosity at 100°C of 2.0 mm 2 / s or more and 6.0 mm 2 / s or less. The lubricating base oil of the present invention satisfying such a kinematic viscosity at 100°C has excellent lubricity. The above kinematic viscosity at 100°C is more preferably 2.1 mm 2 / s or more and 4.0 mm 2 / s or less.

[0022] The kinematic viscosity at 40°C and 100°C of the lubricating oil base oil of the present invention can be adjusted by including a diester compound obtained from the above-mentioned biomass-derived α-branched alcohol and dicarboxylic acid as raw materials, and by mixing it with a known lubricating oil base oil within a range that does not affect the low-temperature fluidity, hydrolysis stability, heat resistance, and lubricity of the lubricating oil base oil of the present invention. The above-mentioned lubricating oil base oil is not particularly limited, but examples include mineral oil, hydrocarbon oils such as poly-α-olefin, polybutene, alkylbenzene, and alkylnaphthalene, esters other than the diester compounds according to the present invention, polyalkylene glycol, phenyl ether, and silicone oil.

[0023] The lubricating oil base oil of the present invention has excellent low-temperature fluidity, and specifically, it is preferable that its pour point is -30°C or lower. If the pour point is higher than -30°C, the low-temperature fluidity of the lubricating oil base oil of the present invention may be insufficient.

[0024] The lubricating oil base oil of the present invention may be appropriately blended with one or more additives such as antioxidants, anti-wear agents, detergent dispersants, viscosity index improvers, pour point depressants, metal deactivators, metal corrosion inhibitors, rust inhibitors, and defoamers to improve its performance. While not particularly limited as long as the desired effects are achieved, specific formulation examples are shown below.

[0025] Examples of the above-mentioned antioxidants include hindered phenol-based, aromatic amine-based, sulfur-based, phosphite-based, and zinc dithiophosphate-based compounds, which are typically added in an amount of 0.1 to 5% by mass relative to the lubricating oil base oil of the present invention.

[0026] Examples of the above-mentioned wear-resistant agents include organic sulfur-based, organic phosphorus-based, zinc dithiophosphate-based, and long-chain fatty acid-based compounds, which are typically added in an amount of 0.05 to 5% by mass to the lubricating oil base oil of the present invention.

[0027] Examples of the above-mentioned detergent dispersants include compounds such as basic sulfonates, ultrabasic sulfonates, basic phenates, salicinates, phosphonates, succinimides, benzylamines, succinic acid esters, and copolymer polymers, and are typically added in an amount of 2 to 10% by mass relative to the lubricating oil base oil of the present invention.

[0028] Examples of the viscosity index improvers mentioned above include polyalkyl methacrylate-based, ethylene-propylene copolymer-based, and styrene-butadiene copolymer-based compounds, which are typically added in an amount of 1 to 20% by mass to the lubricating oil base oil of the present invention.

[0029] Examples of the above-mentioned pour point depressants include polymethacrylate-based and alkylated naphthalene-based compounds, which are typically added in an amount of 0.1 to 2% by mass relative to the lubricating oil base oil of the present invention.

[0030] Examples of the above-mentioned metal deactivators and corrosion inhibitors include benzotriazole-based and thiadiazole-based compounds, which are typically added in an amount of 0.01 to 0.4% by mass relative to the lubricating oil base oil of the present invention.

[0031] Examples of the above-mentioned rust inhibitors include sulfonate-based, carboxylic acid-based, organic amine soap-based, and sorbitan partial ester-based compounds, which are typically added in an amount of 0.05 to 3% by mass relative to the lubricating oil base oil of the present invention.

[0032] Examples of the above-mentioned defoaming agents include silicone compounds such as polydimethylsilicone, which are typically added to the lubricating oil base oil of the present invention at a concentration of 1 to 20 ppm.

[0033] The lubricating oil base oil of the present invention can be obtained by mixing the diester compound having 18 to 26 carbon atoms and a branched structure at the 1st position, as described above, with additives added as needed. By appropriately adding the known lubricating oil base oil described above, the kinematic viscosity at 40°C can be increased to 6.0 mm. 2 / s or more 30.0mm 2 It can be adjusted to / s or less.

[0034] This specification discloses the following: This disclosure (1) is, The kinematic viscosity at 40°C of a diester compound with 18 to 26 carbon atoms represented by the following general formula (1) is 6.0 mm². 2 / s or more 30.0mm 2 The lubricating oil base oil is characterized by having a viscosity of 0.5 / s or less and the raw material for the diester compound containing a biomass-derived raw material. [ka] [In the formula, k represents an integer from 2 to 8, R 1 ~R 4 These may be the same or different characters, and each represents an alkyl group having 1 to 11 carbon atoms. This disclosure (2) provides a kinematic viscosity at 40°C of 7.0 mm². 2 / s or more 12.0mm 2 The lubricating oil base oil described in this disclosure (1) is less than or equal to / s. This disclosure (3) provides a kinematic viscosity at 100°C of 2.0 mm 2 / s or more 6.0mm 2 The lubricating oil base oil described in (1) or (2) of this disclosure is less than or equal to / s. Disclosure (4) is a lubricating oil base oil according to any of Disclosures (1) to (3), wherein the pour point is -30°C or lower. Disclosure (5) is a lubricating oil base oil according to any one of Disclosures (1) to (4), characterized in that the raw materials for the diester compound are a biomass-derived α-branched alcohol and a dicarboxylic acid, and the biomass-derived α-branched alcohol is 2-octanol. Disclosure (6) is a lubricating oil base oil according to Disclosure (5), wherein the dicarboxylic acid is succinic acid, adipic acid, suberic acid, azelaic acid, or sebacic acid. Disclosure (7) is a lubricating oil base oil according to Disclosure (6), wherein the dicarboxylic acid is adipic acid, azelaic acid, or sebaciic acid. Disclosure (8) is a lubricating oil base oil according to any of Disclosures (1) to (7), wherein the natural origin index (ISO 16128) of the diester compound is 70% or more. [Examples]

[0035] The present invention will be further described in detail below with reference to examples, but the present invention is not limited to these examples. Compounds not specifically mentioned were commercially available or reagents.

[0036] <Compound used> (Carboxylic acid) • Succinic acid (manufactured by Shandong Lanzian Biotechnology Co., Ltd., Bio-based) • Adipic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) • Azelaic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) • Sebacic acid (manufactured by Tokyo Chemical Industry Co., Ltd., sebacic acid) (alcohol) • 2-Octanol (manufactured by Ogura Synthetic Industries Co., Ltd., 2-octanol) n-heptanol (manufactured by Tokyo Chemical Industry Co., Ltd., 1-heptanol) • 2-Ethylhexanol (manufactured by Tokyo Chemical Industry Co., Ltd., 2-ethylhexanol) • 2-Hexyldecanol (manufactured by Shin Nippon Rika Co., Ltd., N-JECOL 160BR)

[0037] <Evaluation of physical properties> (a) Naturally derived index The calculations were performed in accordance with ISO 16128 and evaluated according to the following criteria. ◎: 100% ○: 70% or more but less than 100% ×: Less than 70% (b) Kinematic viscosity In accordance with JIS-K-2283(2000), the kinematic viscosity at 40°C and 100°C was measured and evaluated according to the following criteria. ·40℃ kinematic viscosity ◎: 6.0 (mm) 2 / s) or more 15.0(mm) 2 Less than / s 〇: 15.0 (mm) 2 / s) or more 30.0(mm) 2 Less than / s ×: 6.0 (mm)2 Less than / s, or 30.0 (mm 2 / s) or more ·Kinematic viscosity at 100℃ ◎: 2.0 (mm) 2 / s) or more 4.0(mm) 2 Less than / s 〇: 4.0(mm) 2 / s) or more 6.0(mm) 2 Less than / s ×: 2.0 (mm) 2 Less than / s, or 6.0 (mm 2 / s) or more

[0038] (c) Viscosity index The calculations were performed in accordance with JIS-K-2283(2000) and evaluated according to the following criteria. ◎: 120 or more ○: 90 or more and less than 120 ×: Less than 90

[0039] (d) Low-temperature fluidity test (pour point) In accordance with JIS-K-2269 (1987), the pour point was measured using an automatic pour point / cloud point measuring device (manufactured by Tanaka Scientific Instruments Co., Ltd., device name: MPC-6) and evaluated according to the following criteria. ◎: Below -40℃ ○: Above -40℃ and below -30℃ ×: Above -30℃

[0040] (e) Heat resistance test (evaporation rate) 50 g of the sample was weighed into a test tube and left to stand in a 150°C constant temperature bath for 500 hours. The evaporation rate before and after the test was calculated using the following formula (1) and evaluated according to the following criteria. ([Weight before 500 hours of standing at 150°C (g)] - [Weight after 500 hours of standing at 150°C (g)]) / [Weight before 500 hours of standing at 150°C (g)] × 100 ... (1) ◎: Less than 15.0% ○: 15.0% or more and less than 65.0% ×: 65.0% or more

[0041] (f) Lubricity test (wear mark diameter) In accordance with JPI-5S-32-90, a high-speed four-ball abrasion tester (manufactured by Shinko Seiki Co., Ltd.) was used to test the material under the conditions of a rotation speed of 1200 rpm, a load of 40 kg, and a time of 60 minutes. After testing, the diameter of the abrasion marks (mm) was measured and evaluated according to the following criteria. ◎: Less than 0.8mm ○: 0.8mm or more and less than 1.0mm ×: 1.0mm or larger

[0042] (g) Hydrolysis stability test (acid value increase) 5 g of the sample was weighed into a pressure vessel, 10% by mass of distilled water was added, and the mixture was left to stand in a 150°C constant temperature bath for 14 hours. The change in acid value before and after the test was calculated using the following formula (2) and evaluated according to the following criteria. [Acid value after standing at 150°C for 14 hours (mgKOH / g)] - [Acid value before standing at 150°C for 14 hours (mgKOH / g)] ... (2) ◎: Less than 3.5 mg KOH / g ○: 3.5 mg KOH / g or more and less than 4.0 mg KOH / g ×: 4.0 mg KOH / g or more

[0043] [Example 1] In a 1-liter four-necked flask equipped with a stirrer, thermometer, and a water distillation receiver with a condenser, 172.37 g (1.46 mol) of succinic acid, 418.20 g (3.21 mol) of 2-octanol, xylene (10% by mass of the total amount of raw materials), and tetra-n-butoxytitanium (0.1% by mass of the total amount of raw materials) were charged. 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 distilled product water using the water distillation receiver. After the reaction was complete, xylene and excess alcohol were removed by distillation to obtain the crude esterified product. Next, the obtained crude esterified product was neutralized with 2 equivalents of a caustic soda aqueous solution relative to its acid value, and then repeatedly washed with water until the washing water became neutral. Furthermore, the obtained esterified crude was adsorbed with activated carbon, and then the activated carbon was removed by filtration to obtain diester compound (1). The obtained diester compound (1) was evaluated as a lubricating oil base oil, and the results are shown in Table 1.

[0044] [Example 2] Diester compound (2) was obtained in the same manner as in Example 1, except that 197.17 g (1.35 mol) of adipic acid was used instead of succinic acid. The obtained diester compound (2) was evaluated as a lubricating oil base oil, and the results are shown in Table 1.

[0045] [Example 3] Diester compound (3) was obtained in the same manner as in Example 1, except that 228.05 g (1.21 mol) of azelaic acid was used instead of succinic acid. The obtained diester compound (3) was evaluated as a lubricating oil base oil, and the results are shown in Table 1.

[0046] [Example 4] Diester compound (4) was obtained by the same method as in Example 1, except that 236.99 g (1.17 mol) of sebacic acid was used instead of succinic acid. The obtained diester compound (4) was evaluated as a lubricating oil base oil, and the results are shown in Table 1.

[0047] [Comparative Example 1] Diester compound (5) was obtained in the same manner as in Example 1, except that 236.07 g (1.25 mol) of azelaic acid was used instead of succinic acid in Example 1, and 174.89 g (1.51 mol) of n-heptanol and 196.01 g (1.51 mol) of 2-ethylhexanol were used instead of 2-octanol. The obtained diester compound (5) was evaluated as a lubricating oil base oil, and the results are shown in Table 1.

[0048] [Comparative Example 2] Monoester compound (6) was obtained by the same method as in Example 1, except that 130.46 g (1.60 mol) of lauric acid and 250.00 g (1.92 mol) of 2-octanol were used instead of succinic acid. The obtained monoester compound (6) was evaluated as a lubricating oil base oil, and the results are shown in Table 1.

[0049] [Comparative Example 3] Diester compound (7) was obtained in the same manner as in Example 1, except that 197.17 g (1.35 mol) of adipic acid was used instead of succinic acid in Example 1, and n-octanol was used instead of 2-octanol. The obtained diester compound (7) was evaluated as a lubricating oil base oil, and the results are shown in Table 1.

[0050] [Comparative Example 4] Diester compound (8) was obtained in the same manner as in Example 1, except that 197.17 g (1.35 mol) of adipic acid was used instead of succinic acid, and 2-ethylhexanol was used instead of 2-octanol. The obtained diester compound (8) was evaluated as a lubricating oil base oil, and the results are shown in Table 1.

[0051] [Comparative Example 5] Diester compound (9) was obtained in the same manner as in Example 1, except that 147.71 g (0.78 mol) of azelaic acid was used instead of succinic acid in Example 1, and 388.15 g (1.60 mol) of 2-hexyldecanol was used instead of 2-octanol. The obtained diester compound (9) was evaluated as a lubricating oil base oil, and the results are shown in Table 1.

[0052] [Table 1] In Table 1, the overall evaluation was rated as "◎" if there were no "×" marks, and as "×" if there was even one "×" mark.

[0053] The lubricating oil base oils used in Examples 1, 3, and 4 were low-viscosity base oils with a 100% naturally derived index, while the lubricating oil base oil used in Example 2 was a low-viscosity base oil with a 70% naturally derived index. Both demonstrated excellent performance in evaluating various physical properties and received an overall excellent evaluation. On the other hand, the lubricating oil base oil in Comparative Example 1 used dicarboxylic acid, β-branched alcohol, and linear alcohol as raw materials for the diester compound, resulting in poor low-temperature fluidity and hydrolysis stability, as well as a low naturally derived index, and thus an overall evaluation of ×. The lubricating oil base oil in Comparative Example 2 uses 2-octanol as a raw material, but the resulting compound is a monoester with a single branched structure, resulting in poor low-temperature fluidity and heat resistance, as well as poor lubricity due to its excessively low viscosity. Therefore, the overall evaluation was a failure. The lubricating oil base oil in Comparative Example 3 uses dicarboxylic acid as a raw material, but because the alcohol is a linear monoalcohol, it has poor low-temperature fluidity, heat resistance, and hydrolysis stability, resulting in an overall evaluation of "X". The lubricating oil base oil in Comparative Example 4 uses dicarboxylic acid and β-branched alcohol as raw materials, but because it is petrochemical-derived, its natural origin index is 0%, making it unsuitable for the environment. Furthermore, its hydrolysis stability is poor, resulting in an overall evaluation of "X". The lubricating oil base oil used in Comparative Example 5 utilizes biomass-derived dicarboxylic acid and branched alcohol, but its high viscosity resulted in poor energy efficiency, leading to an overall evaluation of "X". [Industrial applicability]

[0054] The lubricating oil base oil of the present invention possesses excellent low-temperature fluidity, hydrolysis stability, heat resistance, and lubricity, enabling it to exhibit good performance over the long term in various environments and contributing to the extended lifespan of lubricants such as engine oil, gear oil, hydraulic fluid, shock absorber oil, insulating oil, metalworking oil, cooling oil, grease, chain oil, turbine oil, bearing oil, multi-purpose oil, and sliding surface oil.

Claims

1. The kinematic viscosity at 40°C of a diester compound having 18 to 26 carbon atoms, represented by the following general formula (1), is 6.0 mm². ２ / s or more 30.0mm ２ / s or less, A lubricating oil base oil characterized in that it contains a biomass-derived raw material as the raw material for the diester compound. 【Chemistry 1】 [In the formula, k represents an integer from 2 to 8, R １ ~R ４ Each of these may be the same or different, and represents an alkyl group having 1 to 11 carbon atoms.

2. The kinematic viscosity at 40°C is 7.0 mm². ２ / s or more 12.0mm ２ The lubricating oil base oil according to claim 1, wherein the value is less than or equal to / s.

3. kinematic viscosity at 100°C is 2.0 mm ２ / s or more 6.0mm ２ The lubricating oil base oil according to claim 1 or 2, wherein the value is less than or equal to / s.

4. The lubricating oil base oil according to claim 1 or 2, wherein the pour point is -30°C or lower.

5. The raw materials for the aforementioned diester compound are biomass-derived α-branched alcohol and dicarboxylic acid. The lubricating oil base oil according to claim 1 or 2, characterized in that the biomass-derived α-branched alcohol is 2-octanol.

6. The lubricating oil base oil according to claim 5, wherein the dicarboxylic acid is succinic acid, adipic acid, suberic acid, azelaic acid, or sebacic acid.

7. The lubricating oil base oil according to claim 6, wherein the dicarboxylic acid is adipic acid, azelaic acid, or sebaciic acid.

8. The lubricating oil base oil according to claim 1 or 2, wherein the naturally derived index (ISO 16128) of the diester compound is 70% or more.

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