Lubricating base oil

Abstract

Provided is a lubricating base oil that contains a C28-50 ester compound (A) and that has a Saybolt color as determined according to JIS K2580 of at least +20.

Description

Lubricant base oil

[0001] The present invention relates to a lubricating oil base oil, a lubricating oil composition containing the lubricating oil base oil, and a method for cooling electronic equipment using the lubricating oil composition.

[0002] Lubricating oil compositions are being considered not only for lubricating sliding mechanisms, but also as cooling media for cooling heat-generating equipment such as motors and batteries mounted in automobiles. For example, Patent Document 1 discloses a lubricating composition for cooling and / or insulating batteries or electric motors in kinetic energy regeneration systems (KERS) or hybrid vehicles.

[0003] Special table 2013-522409 publication

[0004] Incidentally, in recent years, there has been a demand for lubricating oil compositions that can cool not only motors and batteries, but also electronic devices such as computer servers. Under these circumstances, the present invention seeks a lubricating oil base oil that can prepare a lubricating oil composition that can be suitably used for cooling electronic devices.

[0005] The present invention provides a lubricating oil base oil containing an ester compound with a specific number of carbon atoms, having a Saybolt color adjusted according to JIS K2580, and a lubricating oil composition containing said lubricating oil base oil. Specifically, the invention provides the following embodiments: [1] A lubricating oil base oil containing an ester compound (A) having 28 to 50 carbon atoms, and having a Saybolt color of +20 or higher as measured according to JIS K2580. [2] The lubricating oil base oil according to [1], wherein component (A) contains an ester compound having one or more branched chain structures. [3] The lubricating oil base oil according to [1] or [2], wherein component (A) contains a saturated ester compound. [4] The lubricating oil base oil according to any one of [1] to [3], wherein component (A) contains a monoester compound. [5] The lubricating oil base oil according to [1], wherein component (A) contains a saturated monoester compound having one or more branched chain structures. [6] The kinematic viscosity of the lubricating oil base oil at 40°C is 12.0 to 60.0 mm ２[1] to [2] above, a lubricating oil base oil having a viscosity index of 140 or higher. [3] A lubricating oil base oil according to any one of the above items [1] to [2] above. [4] A lubricating oil base oil according to any one of the above items [1] to [2] above, having a thermal conductivity of 0.145 W / mK or higher at 40°C. [5] A lubricating oil base oil according to any one of the above items [1] to [2] above, having a pour point of 0°C or lower. [6] A lubricating oil base oil according to any one of the above items [1] to [2] above, having a flash point of 200°C or higher.

[11] The lubricating oil base oil according to any one of the above items [1] to

[10] , wherein the volume change rate of the test acrylic rubber, measured under conditions of 150°C for 72 hours in accordance with JIS K6258, after immersing a test acrylic rubber in the lubricating oil base oil, is 0% or more and less than 15%.

[12] The lubricating oil base oil according to any one of the above items [1] to

[11] , wherein the naturally derived index of the lubricating oil base oil, calculated in accordance with ISO 16128, is 90 to 100%.

[13] A lubricating oil composition comprising the lubricating oil base oil according to any one of the above items [1] to

[12] .

[14] The lubricating oil composition according to the above item

[13] , which substantially does not contain a viscosity index improver.

[15] The lubricating oil composition according to the above item

[13] or

[14] , which substantially does not contain an extreme pressure agent or an anti-wear agent.

[16] The lubricating oil composition according to any one of the above items

[13] to

[15] , which is used for cooling electronic equipment.

[17] A method for cooling electronic equipment, comprising using the lubricating oil composition described in any one of the above items

[13] to

[16] to cool the electronic equipment.

[0006] A lubricating oil base oil according to one preferred embodiment of the present invention is excellent in properties required for a cooling medium, such as colorless transparency, viscosity characteristics, low-temperature viscosity characteristics, cooling properties, insulating properties, high flash point, and resistance to rubber swelling, and can therefore be used to prepare a lubricating oil composition suitable for cooling electronic equipment and the like.

[0007] The numerical ranges described herein can be any combination of upper and lower limits. For example, if the numerical range is described as "preferably 30 to 100, more preferably 40 to 80," then the ranges of "30 to 80" and "40 to 100" are also included in the numerical range described herein. Similarly, if the numerical range is described as "preferably 30 or more, more preferably 40 or more, and also preferably 100 or less, more preferably 80 or less," then the ranges of "30 to 80" and "40 to 100" are also included in the numerical range described herein. In addition, for example, if the numerical range described herein is described as "60 to 100," then it means the range is "60 or more (60 or greater than 60), and 100 or less (100 or less than 100)."

[0008] [Composition of Lubricating Oil Base Oil] A lubricating oil base oil according to one aspect of the present invention contains an ester compound (A) having 28 to 50 carbon atoms, and has a Saybolt color of +20 or higher as measured in accordance with JIS K2580. Since a Saybolt color of +20 or higher can be obtained, it is possible to prepare a lubricating oil base oil that is colorless and transparent and can be used in applications where visibility is required. For example, if such a lubricating oil composition with excellent visibility is used as a cooling medium for a computer server, the status of the server can be visually confirmed even when the lubricating oil composition is filled inside the server.

[0009] From the viewpoint of providing a lubricating oil base oil that can prepare a lubricating oil composition that is excellent in colorless transparency and can be applied to applications where visibility is required, the Saybolt color of the lubricating oil base oil in one embodiment of the present invention is preferably +21 or higher, +22 or higher, +23 or higher, +24 or higher, +25 or higher, +26 or higher, +27 or higher, +28 or higher, or +29 or higher, and more preferably the maximum value of +30.

[0010] In one aspect of the present invention, the lubricating oil base oil preferably has a natural origin index of 90-100%, calculated in accordance with ISO 16128, from the viewpoint of reducing the environmental impact at the time of disposal. In this specification, the natural origin index 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 in the manufacture of the lubricating oil base oil. In other words, a lubricating oil base oil with a natural origin index of 90-100% means that 90% or more of the raw materials are derived from natural raw materials. Furthermore, if the lubricating oil base oil in one aspect of the present invention is composed of plant-derived raw materials, even if carbon dioxide is generated by combustion at the time of disposal, the plants that make up the raw materials have absorbed carbon dioxide during their growth process, so the amount of carbon dioxide in the atmosphere does not increase over the entire lifecycle, and the balance of carbon dioxide emissions can be suppressed. Furthermore, if the lubricating oil base oil has a natural origin index of 100%, it is treated as "carbon neutral," meaning that the carbon dioxide emissions are virtually zero.

[0011] The natural origin index of the lubricating oil base oil in one aspect of the present invention may be 91-100%, 92-100%, 93-100%, 94-100%, 95-100%, 96-100%, 97-100%, 98-100%, 99-100%, or 100%.

[0012] <Component (A): Ester compound> A lubricating oil base oil according to one embodiment of the present invention contains an ester compound (A) having 28 to 50 carbon atoms. A lubricating oil base oil containing component (A) is excellent in various properties (for example, viscosity characteristics, low-temperature viscosity characteristics, cooling properties, insulating properties, safety due to a high flash point, and resistance to rubber swelling, etc.), and a lubricating oil composition with excellent properties can be prepared.

[0013] The carbon number of component (A) used in one aspect of the present invention is 28 or more from the viewpoint of providing a lubricating oil base oil with excellent viscosity characteristics, high flash point, and resistance to rubber swelling, but is preferably 29 or more, 30 or more, 31 or more, 32 or more, 33 or more, or 34 or more, and is 50 or less from the viewpoint of having good viscosity characteristics, adjusting the Saybolt color, and providing a lubricating oil base oil with excellent colorless transparency, but is preferably 48 or less, 46 or less, 44 or less, 42 or less, 40 or less, 39 or less, 38 or less, 37 or less, 36 or less, 35 or less, or 34 or less.

[0014] The naturally derived index of component (A) used in one aspect of the present invention, calculated in accordance with ISO 16128, may be 90-100%, 91-100%, 92-100%, 93-100%, 94-100%, 95-100%, 96-100%, 97-100%, 98-100%, 99-100%, or 100%. From the viewpoint of providing a lubricating oil base oil that is carbon neutral, it is preferable that component (A) used in one aspect of the present invention consists only of ester compounds produced from naturally derived raw materials (carboxylic acid components, and alcohol components, diol components, or polyol components). Furthermore, the natural raw materials for the carboxylic acid component and the alcohol component, diol component, or polyol component that are the raw materials for component (A) are preferably plant-based, more preferably selected from oil palm, rapeseed, corn, castor bean, soybean, and rice, even more preferably selected from oil palm, rapeseed, corn, and castor bean, and even more preferably selected from oil palm and rapeseed.

[0015] In a lubricating oil base oil according to one aspect of the present invention, the content of component (A) may be 5% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, 45% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, 95% by mass or more, 97% by mass or more, 98% by mass or more, 99% by mass or more, or 100% by mass, based on the total amount (100% by mass) of the lubricating oil base oil.

[0016] In one aspect of the present invention, component (A) preferably contains an ester compound having 28 to 50 carbon atoms and having one or more branched chain structures, from the viewpoint of adjusting the Saybolt color and providing a lubricating oil base oil with excellent colorless transparency, and from the viewpoint of providing a lubricating oil base oil with excellent various properties (e.g., viscosity characteristics, cooling properties, insulating properties, high flash point, and rubber swelling resistance). The number of branched chain structures in component (A) is preferably one or more, but from the above viewpoint, it is more preferably 1 to 4, even more preferably 1 to 3, and even more preferably 1 to 2.

[0017] In one aspect of the present invention, component (A) used preferably contains a saturated ester compound having 28 to 50 carbon atoms, from the viewpoint of adjusting the Saybolt color and obtaining a lubricating oil base oil with excellent colorless transparency. In the lubricating oil base oil of one aspect of the present invention, from the viewpoint of the above, the content ratio of the saturated ester compound in component (A) is preferably 5% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, 45% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, 95% by mass or more, 97% by mass or more, 98% by mass or more, 99% by mass or more, or 100% by mass, based on 100% by mass of the total amount of component (A) in the lubricating oil base oil.

[0018] In a lubricating oil base oil according to one embodiment of the present invention, from the viewpoint of adjusting the Saybolt color and obtaining a lubricating oil base oil with excellent colorless transparency, the content of unsaturated ester compounds having 28 to 50 carbon atoms is preferably less than 95% by mass, less than 90% by mass, less than 85% by mass, less than 80% by mass, less than 75% by mass, less than 70% by mass, less than 65% by mass, less than 60% by mass, less than 55% by mass, less than 50% by mass, less than 40% by mass, less than 30% by mass, less than 20% by mass, less than 10% by mass, less than 5.0% by mass, less than 3.0% by mass, less than 2.0% by mass, less than 1.0% by mass, less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass, based on the total amount (100% by mass) of the lubricating oil base oil.

[0019] In one aspect of the present invention, component (A) is preferably a monoester compound having 28 to 50 carbon atoms, from the viewpoint of adjusting the Saybolt color and providing a lubricating oil base oil with excellent colorless transparency, as well as excellent insulating properties and resistance to rubber swelling. In a lubricating oil base oil according to one aspect of the present invention, from the above viewpoint, the content ratio of the monoester compound in component (A) is preferably 5% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, 45% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, 95% by mass or more, 97% by mass or more, 98% by mass or more, 99% by mass or more, or 100% by mass, based on 100% by mass of the total amount of component (A) contained in the lubricating oil base oil.

[0020] In a lubricating oil base oil according to one embodiment of the present invention, from the viewpoint of adjusting the Saybolt color to obtain a lubricating oil base oil with excellent colorless transparency, as well as excellent insulating properties and resistance to rubber swelling, it is preferable that the content of diester compounds having 28 to 50 carbon atoms is less than 95% by mass, less than 90% by mass, less than 85% by mass, less than 80% by mass, less than 75% by mass, less than 70% by mass, less than 65% by mass, less than 60% by mass, less than 55% by mass, less than 50% by mass, less than 40% by mass, less than 30% by mass, less than 20% by mass, less than 10% by mass, less than 5.0% by mass, less than 3.0% by mass, less than 2.0% by mass, less than 1.0% by mass, less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass, based on the total amount (100% by mass) of the lubricating oil base oil.

[0021] In a lubricating oil base oil according to one embodiment of the present invention, from the viewpoint of adjusting the Saybolt color to obtain a lubricating oil base oil with excellent colorless transparency and excellent insulating properties, the content of the polyester compound having 28 to 50 carbon atoms is preferably less than 95% by mass, less than 90% by mass, less than 85% by mass, less than 80% by mass, less than 75% by mass, less than 70% by mass, less than 65% by mass, less than 60% by mass, less than 55% by mass, less than 50% by mass, less than 40% by mass, less than 30% by mass, less than 20% by mass, less than 10% by mass, less than 5.0% by mass, less than 3.0% by mass, less than 2.0% by mass, less than 1.0% by mass, less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass, based on the total amount (100% by mass) of the lubricating oil base oil. In this specification, the polyester compound means a compound containing three or more ester bonds.

[0022] In one aspect of the present invention, component (A) used preferably contains one or more saturated monoester compounds (A1) having a branched chain structure and having 28 to 50 carbon atoms, from the viewpoint of adjusting the Saybolt color and providing a lubricating oil base oil with excellent colorless transparency, and from the viewpoint of providing a lubricating oil base oil with excellent various properties (for example, viscosity characteristics, cooling properties, insulating properties, high flash point, and rubber swelling resistance). In a lubricating oil base oil according to one aspect of the present invention, from the above viewpoint, the content ratio of component (A1) in component (A) is preferably 5% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, 45% by mass or more, 50% by mass or more, 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, 95% by mass or more, 97% by mass or more, 98% by mass or more, 99% by mass or more, or 100% by mass, based on 100% by mass of the total amount of component (A) contained in the lubricating oil base oil.

[0023] In one aspect of the present invention, component (A1) is preferably a compound represented by the following general formula (1), from the viewpoint of adjusting the Saybolt color and obtaining a lubricating oil base oil with excellent colorless transparency, and from the viewpoint of obtaining a lubricating oil base oil with excellent various properties (for example, viscosity characteristics, low-temperature viscosity characteristics, cooling properties, insulating properties, high flash point, rubber swelling resistance, etc.).

[0024] In the above general formula (1), R １ and R ２ Each of these is independently a linear or branched alkyl group, but from the viewpoint of producing a lubricating oil base oil with excellent properties (e.g., viscosity characteristics, low-temperature viscosity characteristics, cooling properties, insulating properties, high flash point, rubber swelling resistance, etc.), R １ and R ２ At least one of them is preferably a branched alkyl group, and at least R ２ It is more preferable that R is a branched alkyl group. １ and R ２It is more preferable that both are branched-chain alkyl groups. The branched-chain alkyl group may be an alkyl group having one or more branch points, but is preferably an alkyl group having one or two branch points, and more preferably an alkyl group having one branch point.

[0025] R １ and R ２ The total number of carbon atoms of is preferably 27 or more, 28 or more, 29 or more, 31 or more, 32 or more, or 33 or more from the viewpoint of obtaining a lubricating base oil excellent in viscosity characteristics, high flash point, and rubber swelling resistance, and has good viscosity characteristics. From the viewpoint of obtaining a lubricating base oil having adjusted Saybolt color and excellent colorless transparency, it is preferably 49 or less, 47 or less, 45 or less, 43 or less, 41 or less, 40 or less, 39 or less, 38 or less, 37 or less, 36 or less, 35 or less, 34 or less, or 33 or less.

[0026] R in the general formula (1) １ The number of carbon atoms of is preferably 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 11 or more, 12 or more, or 13 or more from the viewpoint of obtaining a lubricating base oil having increased viscosity and high flash point and further improved rubber swelling resistance, and may be further 14 or more, 15 or more, 16 or more, or 17 or more. Also, from the viewpoint of obtaining a lubricating base oil having good viscosity characteristics, adjusted Saybolt color, and excellent colorless transparency, it is preferably 44 or less, 42 or less, 40 or less, 38 or less, 36 or less, 34 or less, 32 or less, 30 or less, 28 or less, 26 or less, 24 or less, 22 or less, 20 or less, 18 or less, or 17 or less, and may be further 16 or less, 15 or less, 14 or less, or 13 or less.

[0027] R in the general formula (1) １ is preferably a group represented by the following formula (1-i). In the above formula (1-i), m is an integer of 1 or more, and R ａ is a hydrogen atom, a methyl group, an ethyl group, or an n-propyl group. * indicates the bonding position.

[0028] R in the general formula (1) ２From the viewpoint of producing a lubricating oil base oil with high viscosity and a high flash point, as well as improved resistance to rubber swelling, the number of carbon atoms is preferably 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 11 or more, 12 or more, 13 or more, 14 or more, 15 or more, or 16 or more, and may also be 17 or more, 18 or more, 19 or more, or 20 or more. Furthermore, from the viewpoint of producing a lubricating oil base oil with good viscosity characteristics, a Saybolt color, and excellent colorless transparency, the number of carbon atoms is preferably 44 or less, 42 or less, 40 or less, 38 or less, 36 or less, 34 or less, 32 or less, 30 or less, 28 or less, 26 or less, 25 or less, 24 or less, 23 or less, 22 or less, 21 or less, or 20 or less, and may also be 19 or less, 18 or less, 17 or less, or 16 or less.

[0029] R in the general formula (1) ２ It is preferable that the group is represented by the following formula (1-ii). In equation (1-ii) above, p and q are each independent integers of 0 or greater. * indicates the joining position.

[0030] <Base oils other than component (A)> In addition, the lubricating oil base oil of one embodiment of the present invention may further contain other base oils other than component (A) in a range in which the Saybolt color is +20 or higher without impairing the effects of the present invention. Examples of such other base oils include one or more selected from mineral oils and synthetic oils.

[0031] Examples of mineral oils include atmospheric residues obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate crude oil, and naphthenic crude oil; distillates obtained by vacuum distillation of these atmospheric residues; and refined oils obtained by subjecting the distillates to one or more refining treatments such as solvent delamination, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining.

[0032] Examples of synthetic oils include poly-α-olefins such as α-olefin homopolymers or α-olefin copolymers (e.g., 8-14 carbon olefin copolymers such as ethylene-α-olefin copolymers); isoparaffins; polyalkylene glycols; ester-based synthetic oils not falling under component (A), such as polyol esters, dibasic acid esters, and phosphate esters; ether-based synthetic oils such as polyphenyl ethers; alkylbenzenes; alkylnaphthalenes; synthetic oils (GTL) obtained by isomerizing wax (GTL wax (Gas To Liquids Wax)) produced from natural gas by the Fischer-Tropsch process, etc.; CTL base oils obtained by direct liquefaction methods (such as the Bergius process) in which coal is crushed, mixed with a solvent, and directly reacted with hydrogen under high temperature and pressure; and CTL base oils obtained by indirect liquefaction methods (such as the Fischer-Tropsch process) in which coal is gasified (coal gasification), and the resulting gas is separated and purified and then liquefied by a synthesis reaction with the raw materials.

[0033] In a lubricating oil base oil according to one embodiment of the present invention, from the viewpoint of adjusting the Saybolt color and obtaining a lubricating oil base oil with excellent colorless transparency, the content of hydrocarbon compounds (hydrocarbon synthetic oils) may be less than 95% by mass, less than 90% by mass, less than 85% by mass, less than 80% by mass, less than 75% by mass, less than 70% by mass, less than 65% by mass, less than 60% by mass, less than 55% by mass, less than 50% by mass, less than 40% by mass, less than 30% by mass, less than 20% by mass, less than 10% by mass, less than 5.0% by mass, less than 3.0% by mass, less than 2.0% by mass, less than 1.0% by mass, less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass, based on the total amount (100% by mass) of the lubricating oil base oil.

[0034] In a lubricating oil base oil according to one embodiment of the present invention, from the viewpoint of adjusting the Saybolt color and obtaining a lubricating oil base oil with excellent colorless transparency, the content of unsaturated ester compounds (unsaturated ester synthetic oils) may be less than 95% by mass, less than 90% by mass, less than 85% by mass, less than 80% by mass, less than 75% by mass, less than 70% by mass, less than 65% by mass, less than 60% by mass, less than 55% by mass, less than 50% by mass, less than 40% by mass, less than 30% by mass, less than 20% by mass, less than 10% by mass, less than 5.0% by mass, less than 3.0% by mass, less than 2.0% by mass, less than 1.0% by mass, less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass, based on the total amount (100% by mass) of the lubricating oil base oil.

[0035] In a lubricating oil base oil according to one embodiment of the present invention, from the viewpoint of adjusting the Saybolt color to obtain a lubricating oil base oil with excellent colorless transparency, as well as excellent insulating properties and resistance to rubber swelling, it is preferable that the content of diester compounds (diester synthetic oils) is less than 95% by mass, less than 90% by mass, less than 85% by mass, less than 80% by mass, less than 75% by mass, less than 70% by mass, less than 65% by mass, less than 60% by mass, less than 55% by mass, less than 50% by mass, less than 40% by mass, less than 30% by mass, less than 20% by mass, less than 10% by mass, less than 5.0% by mass, less than 3.0% by mass, less than 2.0% by mass, less than 1.0% by mass, less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass, based on the total amount (100% by mass) of the lubricating oil base oil.

[0036] In a lubricating oil base oil according to one embodiment of the present invention, from the viewpoint of adjusting the Saybolt color to obtain a lubricating oil base oil with excellent colorless transparency and excellent insulating properties, it is preferable that the content of polyester compounds (polyester synthetic oil) containing three or more ester bonds is less than 95% by mass, less than 90% by mass, less than 85% by mass, less than 80% by mass, less than 75% by mass, less than 70% by mass, less than 65% by mass, less than 60% by mass, less than 55% by mass, less than 50% by mass, less than 40% by mass, less than 30% by mass, less than 20% by mass, less than 10% by mass, less than 5.0% by mass, less than 3.0% by mass, less than 2.0% by mass, less than 1.0% by mass, less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass, based on the total amount (100% by mass) of the lubricating oil base oil.

[0037] In a lubricating oil base oil according to one embodiment of the present invention, the mineral oil content may be less than 95% by mass, less than 90% by mass, less than 85% by mass, less than 80% by mass, less than 75% by mass, less than 70% by mass, less than 65% by mass, less than 60% by mass, less than 55% by mass, less than 50% by mass, less than 40% by mass, less than 30% by mass, less than 20% by mass, less than 10% by mass, less than 5.0% by mass, less than 3.0% by mass, less than 2.0% by mass, less than 1.0% by mass, less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass, based on the total amount (100% by mass) of the lubricating oil base oil.

[0038] In a lubricating oil base oil according to one embodiment of the present invention, the total content of other base oils that do not fall under component (A) may be less than 95% by mass, less than 90% by mass, less than 85% by mass, less than 80% by mass, less than 75% by mass, less than 70% by mass, less than 65% by mass, less than 60% by mass, less than 55% by mass, less than 50% by mass, less than 40% by mass, less than 30% by mass, less than 20% by mass, less than 10% by mass, less than 5.0% by mass, less than 3.0% by mass, less than 2.0% by mass, less than 1.0% by mass, less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass, based on the total amount (100% by mass) of the lubricating oil base oil.

[0039] [Properties of Lubricating Oil Base Oil] The kinematic viscosity of the lubricating oil base oil according to one embodiment of the present invention at 40°C is 12.0 mm². ２ / s or more, 13.0mm２ / s or more, 14.0mm ２ / s or more, 15.0mm ２ / s or more, 16.0mm ２ / s or more, 17.0mm ２ / s or more, 18.0mm ２ / s or more, 19.0mm ２ / s or more, 20.0mm ２ / s or more, or 21.0 mm ２ It may be set to 60.0 mm or more, and when preparing a lubricating oil composition for cooling electronic equipment, from the viewpoint of improving the cooling performance of the lubricating oil composition, ２ / s or less, 55.0mm ２ / s or less, 50.0mm ２ / s or less, 45.0mm ２ / s or less, 40.0mm ２ / s or less, 35.0mm ２ / s or less, 30.0mm ２ / s or less, 28.0mm ２ / s or less, 26.0mm ２ / s or less, 24.0mm ２ / s or less, 22.0mm ２ / s or less, 20.0mm ２ / s or less, or 18.0 mm ２ It is preferable to keep it below / s.

[0040] The kinematic viscosity at 100°C of the lubricating oil base oil according to one embodiment of the present invention is 2.0 mm². ２ / s or more, 2.2mm ２ / s or more, 2.4mm ２ / s or more, 2.6mm ２ / s or more, 2.8mm ２ / s or more, 3.0mm ２ / s or more, 3.2mm ２ / s or more, 3.4mm ２ / s or more, 3.6mm ２ / s or more, 3.8mm ２ / s or more, 4.0mm ２ / s or more, 4.2mm ２ / s or more, 4.4mm ２ / s or more, or 4.6 mm ２It may be set to 20.0 mm or more, and when preparing a lubricating oil composition for cooling electronic equipment, from the viewpoint of improving the cooling performance of the lubricating oil composition, ２ / s or less, 18.0mm ２ / s or less, 16.0mm ２ / s or less, 14.0mm ２ / s or less, 12.0mm ２ / s or less, 10.0mm ２ / s or less, 9.0mm ２ / s or less, 8.0mm ２ / s or less, 7.0mm ２ / s or less, 6.0mm ２ / s or less, or 5.0 mm ２ It is preferable to set it to less than or equal to / s, and furthermore, 4.9 mm ２ / s or less, 4.8mm ２ / s or less, 4.7mm ２ / s or less, or 4.6 mm ２ It may also be set to / s or less.

[0041] The viscosity index of the lubricating oil base oil in one aspect of the present invention may be 140 or more, 145 or more, 150 or more, 155 or more, 160 or more, or 165 or more, or it may be 500 or less, 450 or less, 400 or less, 350 or less, 300 or less, 280 or less, 260 or less, 240 or less, 220 or less, 200 or less, or 180 or less. In this specification, kinematic viscosity and viscosity index mean values ​​measured or calculated in accordance with JIS K2283:2000.

[0042] The thermal conductivity of the lubricating oil base oil in one embodiment of the present invention at 40°C is preferably 0.145 W / mK or higher, 0.148 W / mK or higher, 0.150 W / mK or higher, 0.152 W / mK or higher, 0.154 W / mK or higher, 0.156 W / mK or higher, 0.158 W / mK or higher, or 0.160 W / mK or higher, from the viewpoint of providing a lubricating oil base oil that is easy to prepare into a lubricating oil composition with excellent cooling properties. In this specification, thermal conductivity refers to the value measured in accordance with ASTM D7896-14.

[0043] In one embodiment of the present invention, the pour point of the lubricating oil base oil is preferably 0°C or below, -5°C or below, -10°C or below, -12.5°C or below, -15°C or below, -17.5°C or below, -20°C or below, -25°C or below, -30°C or below, -35°C or below, -40°C or below, -45°C or below, or -50°C or below, from the viewpoint of providing a lubricating oil base oil that is easy to prepare into a lubricating oil composition that can be used over a wide temperature range. In this specification, the pour point refers to the value measured in accordance with JIS K2269.

[0044] For a lubricating oil base oil according to one embodiment of the present invention, the volume resistivity measured under test conditions of a measurement temperature of 80°C, an applied voltage of 250V, and a measurement time of 1 minute in accordance with JIS C2101 is preferably 1.0 TΩm or more, 1.2 TΩm or more, 1.4 TΩm or more, 1.6 TΩm or more, 1.8 TΩm or more, 2.0 TΩm or more, 2.2 TΩm or more, or 2.4 TΩm or more, from the viewpoint of providing a lubricating oil base oil with excellent insulating properties. Furthermore, it may be 2.6 TΩm or more, 2.8 TΩm or more, 3.0 TΩm or more, 3.2 TΩm or more, or 3.4 TΩm or more.

[0045] The flash point of the lubricating oil base oil in one embodiment of the present invention is preferably 200°C or higher, 210°C or higher, 220°C or higher, 230°C or higher, 240°C or higher, 242°C or higher, 244°C or higher, 246°C or higher, 248°C or higher, 250°C or higher, or 252°C or higher, and may also be 400°C or lower, 380°C or lower, 350°C or lower, 330°C or lower, 320°C or lower, 310°C or lower, or 300°C or lower. In this specification, the flash point refers to the value measured by the Cleveland open casing method (COC method) in accordance with JIS K2265-4 (Method for determining flash point - Part 4: Cleveland open casing method).

[0046] When a test acrylic rubber is immersed in a lubricating oil base oil according to one embodiment of the present invention and measured under conditions of 150°C for 72 hours in accordance with JIS K6258, the volume change rate of the test acrylic rubber is preferably less than 15%, 14% or less, 12% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, or 2% or less, from the viewpoint of providing a lubricating oil base oil with good resistance to rubber swelling, and may also be 0% or more, greater than 0%, or 1% or more. In this specification, the volume change rate of the test acrylic rubber is a value measured in accordance with JIS K6258, and more specifically, it means a value measured and calculated based on the method described in the examples.

[0047] [Composition of Lubricating Oil Composition] A lubricating oil composition according to one aspect of the present invention contains the lubricating oil base oil according to one aspect of the present invention described above. The lubricating oil composition according to one aspect of the present invention may further contain lubricating oil additives, specifically, one or more lubricating oil additives selected from pour point depressants, viscosity index improvers, antioxidants, extreme pressure agents, metal-based detergents, ashless dispersants, metal deactivators, friction modifiers, rust inhibitors, and defoamers. These lubricating oil additives may be used individually or in combination of two or more.

[0048] The content of each of these lubricating oil additives can be adjusted as appropriate within a range that does not impair the effects of the present invention, but on a basis of the total amount (100% by mass) of the lubricating oil composition, the content of each additive is usually 0.001 to 15% by mass, preferably 0.005 to 10% by mass, and more preferably 0.01 to 5% by mass for each additive independently.

[0049] Furthermore, the content of lubricating oil additives, including other additives (such as surfactants), may be restricted. The restricted content of lubricating oil additives may be, based on the total amount (100% by mass) of the lubricating oil composition, independently set for each additive to less than 3.0% by mass, less than 2.0% by mass, less than 1.0% by mass, less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, less than 0.0001% by mass, or less than 0.00001% by mass.

[0050] In a lubricating oil composition according to one aspect of the present invention, the content of the lubricating oil base oil according to one aspect of the present invention described above may be 50% by mass or more, 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass or more, based on the total amount (100% by mass) of the lubricating oil composition.

[0051] [Pour point depressants] Examples of pour point depressants used in one aspect of the present invention include ethylene-vinyl acetate copolymers, condensates of chlorinated paraffin and naphthalene, condensates of chlorinated paraffin and phenol, polymethacrylates, and polyalkylstyrenes. These pour point depressants may be used alone or in combination of two or more.

[0052] [Viscosity Index Improvers] Examples of viscosity index improvers used in one aspect of the present invention include polymers such as non-dispersible polymethacrylate, dispersed polymethacrylate, olefin copolymers (e.g., ethylene-propylene copolymer, etc.), dispersed olefin copolymers, and styrene copolymers (e.g., styrene-diene copolymer, styrene-isoprene copolymer, etc.). These viscosity index improvers may be used alone or in combination of two or more. The weight-average molecular weight (Mw) of the viscosity index improver used in one aspect of the present invention may be 5,000 or more, 7,000 or more, 10,000 or more, 15,000 or more, or 20,000 or more, or 1,000,000 or less, 700,000 or less, 500,000 or less, 300,000 or less, 200,000 or less, 100,000 or less, or 50,000 or less.

[0053] Furthermore, when preparing a lubricating oil composition for cooling electronic equipment, from the viewpoint of improving the cooling performance of the lubricating oil composition, the lubricating oil composition according to one embodiment of the present invention may not substantially contain a viscosity index improver. In this specification, "substantially not containing" excludes embodiments in which the target additive is added with a specific intention, and does not exclude embodiments in which it is inevitably contained. In embodiments of lubricating oil compositions that substantially do not contain a viscosity index improver, the content of the viscosity index improver may be less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, less than 0.0001% by mass, or less than 0.00001% by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0054] [Antioxidants] Examples of antioxidants used in one aspect of the present invention include amine-based antioxidants such as alkylated diphenylamine, phenylnaphthylamine, and alkylated phenylnaphthylamine; phenol-based antioxidants such as 2,6-di-t-butylphenol, 4,4'-methylenebis(2,6-di-t-butylphenol), isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate. These antioxidants may be used alone or in combination of two or more.

[0055] From the viewpoint of adjusting the Saybolt color and obtaining a lubricating oil composition that is colorless, highly transparent, and has excellent oxidation stability, it is preferable that the antioxidant in one embodiment of the present invention is a phenolic antioxidant. Furthermore, from the viewpoint of adjusting the Saybolt color and obtaining a lubricating oil composition that is colorless, highly preferable that the content of the amine antioxidant in one embodiment of the present invention be as low as possible. The content of the amine antioxidant in this embodiment may be less than 1.0% by mass, less than 0.5% by mass, less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, less than 0.0001% by mass, or less than 0.00001% by mass, based on the total amount (100% by mass) of the lubricating oil composition.

[0056] [Extreme pressure agents (wear-resistant agents)] Examples of extreme pressure agents (wear-resistant agents) used in one aspect of the present invention include sulfur-containing compounds such as zinc dithiophosphate; phosphorus-containing compounds such as phosphite esters, phosphate esters, phosphonic acid esters, and their amine salts or metal salts; and sulfur and phosphorus-containing compounds such as thiophosphite esters, thiophosphate esters, thiophosphonic acid esters, and their amine salts or metal salts. These extreme pressure agents may be used alone or in combination of two or more.

[0057] Furthermore, when preparing a lubricating oil composition for cooling electronic equipment, from the viewpoint of maintaining good insulating properties of the lubricating oil composition, the lubricating oil composition according to one embodiment of the present invention may not substantially contain extreme pressure agents or wear inhibitors, nor may it substantially contain zinc dithiophosphate. In the embodiment of the lubricating oil composition that substantially does not contain extreme pressure agents or wear inhibitors, the content of extreme pressure agents or wear inhibitors may be less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, less than 0.0001% by mass, or less than 0.00001% by mass, based on the total amount (100% by mass) of the lubricating oil composition. In embodiments of lubricating oil compositions substantially free of zinc dithiophosphate, the zinc atom content of zinc dithiophosphate may be less than 50 ppm by mass, less than 20 ppm by mass, less than 10 ppm by mass, less than 2.0 ppm by mass, less than 1.0 ppm by mass, less than 100 ppb by mass, less than 10 ppb by mass, or less than 1.0 ppb by mass, based on the total amount (100% by mass) of the lubricating oil composition. In this specification, the zinc atom content refers to the value measured in accordance with JPI-5S-38-92.

[0058] [Metal-based cleaning agents] Examples of metal-based cleaning agents used in one aspect of the present invention include metal salts such as metal sulfonates, metal salicylates, and metal phenates. The metal atoms constituting the metal salt are preferably selected from alkali metals and alkaline earth metals, more preferably sodium, calcium, magnesium, or barium, and even more preferably calcium. These metal-based cleaning agents may be used alone or in combination of two or more.

[0059] In a lubricating oil composition according to one aspect of the present invention, the metal-based detergent preferably contains one or more selected from calcium sulfonate, calcium salicylate, and calcium phenate, and more preferably contains calcium sulfonate. The calcium sulfonate content is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, even more preferably 70 to 100% by mass, and even more preferably 80 to 100% by mass, based on the total amount (100% by mass) of the metal-based detergent contained in the lubricating oil composition.

[0060] The base number of the metal-based detergent is preferably 0 to 600 mg KOH / g. However, in one embodiment of the present invention, the metal-based detergent is preferably an overbasic metal-based detergent with a base number of 100 mg KOH / g or more. The base number of the overbasic metal-based detergent is 100 mg KOH / g or more, preferably 150 to 500 mg KOH / g, and more preferably 200 to 450 mg KOH / g. In this specification, "base number" means the base number measured by the perchloric acid method in accordance with JIS K2501:2003 "Petroleum products and lubricating oils - Neutralization number test method" 9. Furthermore, the lubricating oil composition in one embodiment of the present invention may be a lubricating oil composition in which the content of the metal-based detergent is limited. In this embodiment, the content of the metal-based detergent in terms of metal atoms may be less than 1500 ppm by mass, less than 1200 ppm by mass, less than 1000 ppm by mass, less than 800 ppm by mass, less than 600 ppm by mass, less than 500 ppm by mass, less than 400 ppm by mass, less than 300 ppm by mass, less than 200 ppm by mass, less than 100 ppm by mass, less than 50 ppm by mass, less than 10 ppm by mass, less than 5.0 ppm by mass, less than 2.0 ppm by mass, less than 1.0 ppm by mass, less than 0.1 ppm by mass, less than 0.01 ppm by mass, or less than 0.001 ppm by mass, based on the total amount (100% by mass) of the lubricating oil composition. In this specification, examples of metal atoms include alkali metals such as sodium atoms, and alkaline earth metals such as calcium atoms, magnesium atoms, and barium atoms. The content of these metal atoms refers to values ​​measured in accordance with JPI-5S-38-92.

[0061] [Ashless Dispersants] Examples of ashless dispersants used in one aspect of the present invention include boron-free succinimides such as boron-free alkenyl succinimides, boron-containing succinimides such as boron-containing alkenyl succinimides, benzylamines, boron-containing benzylamines, succinic acid esters, monovalent or divalent carboxylic acid amides represented by fatty acids or succinic acid, and the like. These ashless dispersants may be used alone or in combination of two or more.

[0062] [Metal deactivators] Examples of metal deactivators used in one aspect of the present invention include benzotriazole compounds, toltriazole compounds, imidazole compounds, pyrimidine compounds, and the like. These metal deactivators may be used alone or in combination of two or more.

[0063] [Friction modifiers] Examples of friction modifiers used in one aspect of the present invention include organic molybdenum compounds such as molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDTP), and amine salts of molybdenum acid; ashless friction modifiers such as aliphatic amines, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, and aliphatic ethers having at least one alkyl group or alkenyl group with 6 to 30 carbon atoms in the molecule; and oils and fats, amines, amides, sulfur esters, etc. These friction modifiers may be used alone or in combination of two or more.

[0064] Furthermore, when preparing a lubricating oil composition for cooling electronic equipment, from the viewpoint of maintaining good insulating properties of the lubricating oil composition, the lubricating oil composition according to one embodiment of the present invention may not substantially contain a friction modifier, nor may it substantially contain an organic molybdenum compound. In the embodiment of the lubricating oil composition that substantially does not contain a friction modifier, the content of the friction modifier may be less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, less than 0.0001% by mass, or less than 0.00001% by mass, based on the total amount (100% by mass) of the lubricating oil composition. In embodiments of lubricating oil compositions substantially free of organic molybdenum compounds, the content of the organic molybdenum compound in terms of molybdenum atoms may be less than 50 ppm by mass, less than 20 ppm by mass, less than 10 ppm by mass, less than 2.0 ppm by mass, less than 1.0 ppm by mass, less than 100 ppb by mass, less than 10 ppb by mass, or less than 1.0 ppb by mass, based on the total amount (100% by mass) of the lubricating oil composition. In this specification, the molybdenum atom content refers to the value measured in accordance with JPI-5S-38-92.

[0065] [Rust Inhibitors] Examples of rust inhibitors used in one aspect of the present invention include fatty acids, alkenyl succinate half esters, fatty acid soaps, alkyl sulfonates, polyhydric alcohol fatty acid esters, fatty acid amines, oxidized paraffins, alkyl polyoxyethylene ethers, and the like. These rust inhibitors may be used individually or in combination of two or more.

[0066] [Antifoaming agent] Examples of antifoaming agents used in one aspect of the present invention include silicone oil, fluorosilicone oil, and fluoroalkyl ether. These antifoaming agents may be used individually or in combination of two or more.

[0067] [Properties and characteristics of the lubricating oil composition] The kinematic viscosity of the lubricating oil composition according to one embodiment of the present invention at 40°C is appropriately adjusted according to the application, and is 12.0 mm ２ / s or more, 13.0mm ２ / s or more, 14.0mm ２ / s or more, 15.0mm ２ / s or more, 16.0mm ２ / s or more, 17.0 mm ２ / s or more, 18.0 mm ２ / s or more, 19.0 mm ２ / s or more, 20.0 mm ２ / s or more, or 21.0 mm ２ / s or more may be used. Also, when adjusting the lubricating oil composition for cooling an electronic device, from the viewpoint of improving the cooling performance of the lubricating oil composition, 60.0 mm ２ / s or less, 55.0 mm ２ / s or less, 50.0 mm ２ / s or less, 45.0 mm ２ / s or less, 40.0 mm ２ / s or less, 35.0 mm ２ / s or less, 30.0 mm ２ / s or less, 28.0 mm ２ / s or less, 26.0 mm ２ / s or less, 24.0 mm ２ / s or less, 22.0 mm ２ / s or less, 20.0 mm ２ / s or less, or 18.0 mm ２ / s or less is preferable.

[0068] The kinematic viscosity at 100 °C of the lubricating oil composition according to one aspect of the present invention is appropriately adjusted according to the application, and is 2.0 mm ２ / s or more, 2.2 mm ２ [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​２ / s or less, 16.0mm ２ / s or less, 14.0mm ２ / s or less, 12.0mm ２ / s or less, 10.0mm ２ / s or less, 9.0mm ２ / s or less, 8.0mm ２ / s or less, 7.0mm ２ / s or less, 6.0mm ２ / s or less, or 5.0 mm ２ It is preferable to set it to less than or equal to / s, and furthermore, 4.9 mm ２ / s or less, 4.8mm ２ / s or less, 4.7mm ２ / s or less, 4.6mm ２ / s or less, or 4.5 mm ２ It may also be set to / s or less.

[0069] The viscosity index of the lubricating oil composition according to one embodiment of the present invention may be 140 or more, 145 or more, 150 or more, 155 or more, 160 or more, or 165 or more, or it may be 500 or less, 450 or less, 400 or less, 350 or less, 300 or less, 280 or less, 260 or less, 240 or less, 220 or less, 200 or less, or 180 or less.

[0070] From the viewpoint of providing a lubricating oil composition that reduces the environmental impact when disposed of, the naturally derived index of one embodiment of the present invention is preferably 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, 95% or more, or 98% or more.

[0071] From the viewpoint of providing a lubricating oil composition with excellent cooling properties, the thermal conductivity of the lubricating oil composition at 40°C is preferably 0.145 W / mK or higher, 0.148 W / mK or higher, 0.150 W / mK or higher, 0.152 W / mK or higher, 0.154 W / mK or higher, 0.156 W / mK or higher, 0.158 W / mK or higher, or 0.160 W / mK or higher.

[0072] From the viewpoint of providing a lubricating oil composition that can be used over a wide temperature range, the pour point of the lubricating oil composition according to one embodiment of the present invention is preferably 0°C or below, -5°C or below, -10°C or below, -12.5°C or below, -15°C or below, -17.5°C or below, -20°C or below, -25°C or below, -30°C or below, -35°C or below, -40°C or below, -45°C or below, or -50°C or below.

[0073] For a lubricating oil composition according to one embodiment of the present invention, the volume resistivity measured under test conditions of a measurement temperature of 80°C, an applied voltage of 250V, and a measurement time of 1 minute in accordance with JIS C2101 is preferably 1.0 TΩm or more, 1.2 TΩm or more, 1.4 TΩm or more, 1.6 TΩm or more, 1.8 TΩm or more, 2.0 TΩm or more, 2.2 TΩm or more, or 2.4 TΩm or more, from the viewpoint of obtaining a lubricating oil composition with excellent insulating properties.

[0074] The flash point of the lubricating oil composition according to one embodiment of the present invention is preferably 200°C or higher, 210°C or higher, 220°C or higher, 230°C or higher, 240°C or higher, 242°C or higher, 244°C or higher, 246°C or higher, 248°C or higher, 250°C or higher, 252°C or higher, 254°C or higher, 256°C or higher, 258°C or higher, or 260°C or higher, and may also be 400°C or lower, 380°C or lower, 350°C or lower, 330°C or lower, 320°C or lower, 310°C or lower, or 300°C or lower.

[0075] When a test acrylic rubber is immersed in a lubricating oil composition according to one embodiment of the present invention and measured under conditions of 150°C for 72 hours in accordance with JIS K6258, the volume change rate of the test acrylic rubber is preferably less than 15%, 14% or less, 12% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, or 2% or less, and may also be 0% or more, greater than 0%, or 1% or more.

[0076] [Uses of the Lubricating Oil Composition] A lubricating oil composition according to one preferred embodiment of the present invention can be used for lubrication in mechanisms such as torque converters, wet clutches, gear bearing mechanisms, oil pumps, and hydraulic control mechanisms incorporated into various devices such as electric drive units, engines, transmissions, reducers, compressors, and hydraulic systems. However, because it excels in performance required for cooling media, such as being colorless and transparent, safe, and resistant to rubber swelling, it can be suitably used for cooling electronic equipment (e.g., computer servers). Therefore, one embodiment of the present invention also provides a method for cooling electronic equipment (e.g., computer servers) using the above-described lubricating oil composition.

[0077] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited in any way by these examples. The measurement or calculation methods for various properties are as follows.

[0078] (1) Natural origin index: Calculated in accordance with ISO 16128. (2) Kinematic viscosity and viscosity index: Measured and calculated in accordance with JIS K2283:2000. (3) Density at 15°C: Measured in accordance with JIS K2249-1. (4) Thermal conductivity at 40°C: Measured in accordance with ASTM D7896-14. (5) Volume resistivity: Measured in accordance with JIS C2101 under test conditions of measurement temperature 80°C, applied voltage 250V, and measurement time 1 minute. (6) Pour point: Measured in accordance with JIS K2269. (7) Flash point: Measured in accordance with JIS K2265-4 (Method for determining flash point - Part 4: Cleveland open method) using the Cleveland open method (COC method). (8) Volume change rate of acrylic rubber: A rubber immersion test was performed in accordance with JIS K6258. Specifically, the test specimen, a test acrylic rubber (manufactured by NOK Corporation, product name "T303"), was immersed in the lubricating oil base oil to be measured under conditions of immersion temperature of 150°C and immersion time of 72 hours. The volume of the test specimen was measured before and after the test, and the volume change rate was calculated using the following formula: ・[Volume change rate (%)] = ([Volume of test specimen after test] - [Volume of test specimen before test]) / [Volume of test specimen before test] × 100 (9) Saybolt color Measured in accordance with JIS K2580.

[0079] Examples 1-2 and Comparative Examples 1-4: Lubricating oil base oils consisting of ester compounds of the types and amounts shown in Table 1 were prepared. Next, 1 part by mass of an additive mixture was added to 99 parts by mass of the lubricating oil base oil to prepare a lubricating oil composition. Various physical properties of the prepared lubricating oil base oil and lubricating oil composition were measured according to the above method. These results are shown in Tables 1-2. The details of each component used in the preparation of the lubricating oil base oil and lubricating oil composition are as follows.

[0080] <Ester compounds> ・"Octyldodecyl myristate": A 34-carbon monoester compound produced from myristic acid (derived from oil palm) and 2-octyldodecanol (derived from oil palm). R in the general formula (1) above １ = n-tridecyl group (C13 linear alkyl group), R ２= 2-octyldodecyl group (C20 branched alkyl group), natural origin index = 100%. • "Hexyldecyl isostearate": A 34-carbon monoester compound produced from isostearic acid (derived from rapeseed) and 2-hexyldecanol (derived from oil palm). R in the above general formula (1) １ = C17 branched alkyl group, R ２ = 2-hexyldecyl group (C16 branched alkyl group), natural origin index = 100%. • "2-ethylhexyl laurate": A C20 monoester compound produced from lauric acid (derived from oil palm) and 2-ethylhexanol (derived from petroleum). R in the above general formula (1) １ = n-undecyl group (C11 linear alkyl group), R ２ = 2-ethylhexyl group (C8 branched alkyl group), natural origin index = 58%. ・"Bis-2-ethylhexyl sebacate": A C26 diester compound produced from sebacate (derived from castor bean) and 2-ethylhexanol (derived from petroleum), natural origin index = 39%. ・"Trimethylolpropane triisostearate": A C60 triester compound produced from isostearic acid (derived from rapeseed) and trimethylolpropane (derived from petroleum), natural origin index = 86%. ・"Trimethylolpropane trioleate": A C60 triester compound produced from oleic acid (derived from oil palm) and trimethylolpropane (derived from petroleum), natural origin index = 86%. <Additives> ・"Additive mixture": An additive mixture obtained by diluting a pour point depressant, a phenolic antioxidant, and an antifoaming agent with diluent oil.

[0081]

[0082] Table 1 shows that the lubricating oil base oils and lubricating oil compositions prepared in Examples 1 and 2 exhibited excellent colorless transparency, resulting in good visibility, as well as superior viscosity characteristics, low-temperature viscosity characteristics, cooling properties, insulating properties, high flash point, and resistance to rubber swelling. On the other hand, the lubricating oil base oils and lubricating oil compositions prepared in Comparative Examples 1 and 2 showed poor resistance to rubber swelling. Of these, the lubricating oil base oil and lubricating oil composition prepared in Comparative Example 1 also had a low flash point, resulting in insufficient safety. Furthermore, the lubricating oil base oils and lubricating oil compositions prepared in Comparative Examples 3 and 4 had poor colorless transparency, resulting in visibility problems.

Claims

1. A lubricating oil base oil containing an ester compound (A) having 28 to 50 carbon atoms, and having a Saybolt color of +20 or higher as measured in accordance with JIS K2580.

2. The lubricating oil base oil according to claim 1, wherein component (A) comprises one or more ester compounds having a branched chain structure.

3. The lubricating oil base oil according to claim 1 or 2, wherein component (A) contains a saturated ester compound.

4. A lubricating oil base oil according to any one of claims 1 to 3, wherein component (A) contains a monoester compound.

5. The lubricating oil base oil according to claim 1, wherein component (A) comprises a saturated monoester compound having one or more branched chain structures.

6. The kinematic viscosity of the lubricating oil base oil at 40°C is 12.0 to 60.0 mm². ２ A lubricating oil base oil according to any one of claims 1 to 5, wherein the value is / s.

7. The lubricating oil base oil according to any one of claims 1 to 6, wherein the viscosity index of the lubricating oil base oil is 140 or higher.

8. The lubricating oil base oil according to any one of claims 1 to 7, wherein the thermal conductivity of the lubricating oil base oil at 40°C is 0.145 W / mK or higher.

9. The lubricating oil base oil according to any one of claims 1 to 8, wherein the pour point of the lubricating oil base oil is 0°C or lower.

10. The lubricating oil base oil according to any one of claims 1 to 9, wherein the flash point of the lubricating oil base oil is 200°C or higher.

11. The lubricating oil base oil according to any one of claims 1 to 10, wherein the volume change rate of the test acrylic rubber, measured under conditions of 150°C for 72 hours in accordance with JIS K6258, is 0% or more and less than 15%.

12. The lubricating oil base oil according to any one of claims 1 to 11, wherein the naturally derived index of the lubricating oil base oil calculated in accordance with ISO 16128 is 90 to 100%.

13. A lubricating oil composition comprising the lubricating oil base oil according to any one of claims 1 to 12.

14. The lubricating oil composition according to claim 13, which substantially does not contain a viscosity index improver.

15. The lubricating oil composition according to claim 13 or 14, which substantially does not contain an extreme pressure agent or an anti-wear agent.

16. A lubricating oil composition according to any one of claims 13 to 15, used for cooling electronic equipment.

17. A method for cooling electronic equipment, comprising using the lubricating oil composition described in any one of claims 13 to 16.

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