Lubricant base oil

Abstract

To provide a lubricant base oil having an excellent low-temperature flowing property, a high viscosity index, and an excellent wear resistant property.SOLUTION: There is provided a lubricant base oil containing one or more esters, wherein a wear scar diameter measured on a four-ball friction tester is 0.55 mm or less, a kinematic viscosity is 11.0 mm2 / s or less at 40°C, and a viscosity index is 120 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to lubricating base oils. [Background technology]

[0002] Lubricating oils are used at a variety of viscosities depending on the application and the equipment or machinery in which they are used, and they are also used at a variety of temperatures, from low to high. Traditionally, mineral oils have been the primary lubricating oil because they are inexpensive and readily available. However, due to their poor heat resistance and low viscosity index, synthetic lubricating oils such as synthetic hydrocarbons and organic acid esters, which have high viscosity indexes and excellent heat resistance, are preferred over mineral oils in applications with strict performance requirements.

[0003] Known examples of the organic acid esters include monoesters obtained by reacting aliphatic monocarboxylic acids with monohydric alcohols (hereinafter referred to as "monoesters"), diesters obtained by reacting aliphatic dibasic acids with monohydric alcohols (hereinafter referred to as "aliphatic dibasic acid diesters"), esters obtained by reacting polyhydric alcohols with aliphatic carboxylic acids (hereinafter referred to as "polyol esters"), and complex esters obtained by reacting polyhydric alcohols, polybasic acids, and aliphatic monocarboxylic acids (and / or aliphatic monohydric alcohols) (hereinafter referred to as "polyol-type complex esters").

[0004] However, the conditions under which lubricating oils are used and the required properties such as heat resistance, low-temperature fluidity, high viscosity index, and metal compatibility are becoming increasingly strict. Conventional organic acid esters do not seem to have a good balance of these required properties, and further improvements are desired. As a lubricating oil that combines these required properties in a well-balanced manner, for example, Patent Document 1 discloses a lubricating oil containing an aliphatic dihydric alcohol complex ester obtained by esterification reaction of an aliphatic saturated monocarboxylic acid, a specific diol, and a dicarboxylic acid.

[0005] However, in recent years, efforts have been made to improve energy conservation and fuel efficiency in devices and machines used in industrial fields such as automobiles, home appliances, electronic information devices, industrial machinery, etc. The lubricating oils used in these devices and machines are required to have improved wear resistance in order to suppress energy loss due to viscous friction. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] WO2004 / 087847 issue Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in view of the above-mentioned prior art, and has as its object to provide a lubricating base oil that has excellent low-temperature fluidity, a high viscosity index, and excellent wear resistance. [Means for solving the problem]

[0008] The present inventors have conducted research aimed at further improving the wear resistance of lubricating oils containing one or more esters, and as a result have found that lubricating base oils that satisfy specific conditions for wear scar diameter in a four-ball friction tester, kinematic viscosity at 40°C, and viscosity index will be lubricating base oils that have excellent low-temperature fluidity, a high viscosity index, and excellent wear resistance, and have completed the present invention.

[0009] That is, the present invention relates to a lubricating base oil containing one or more esters, wherein the lubricating base oil has a wear scar diameter of 0.55 mm or less as measured by a four-ball friction tester and a kinematic viscosity at 40°C of 11.0 mm. 2 / s or less and a viscosity index of 120 or more.

[0010] The lubricating base oil of the present invention has a wear scar diameter of 0.50 mm or less in a four-ball friction tester and a kinematic viscosity of 10.7 mm at 40°C. 2 / s or less and a viscosity index of 140 or more. The lubricating base oil of the present invention may also contain mineral oil. Furthermore, in the lubricating base oil of the present invention, the blending ratio (mass ratio) of the mineral oil to the one or more esters is preferably 90:10 to 0:100. Additionally, in the lubricating base oil of the present invention, the blending ratio (mass ratio) of the mineral oil to the one or more esters is preferably 60:40 to 0:100. In the lubricating base oil of the present invention, the one or more esters are preferably obtained by esterifying (A) an aliphatic linear monocarboxylic acid, (B) an aliphatic dicarboxylic acid, and (C) an aliphatic dihydric alcohol. In the lubricating base oil of the present invention, the one or more esters are preferably obtained by esterifying (A) a linear monocarboxylic acid having 8 carbon atoms, (B) an aliphatic dicarboxylic acid having 6 to 10 carbon atoms, and (C) 3-methyl-1,5-pentanediol. [Effects of the Invention]

[0011] The lubricating base oil of the present invention satisfies specific conditions for wear scar diameter in a four-ball friction tester, kinematic viscosity at 40°C, and viscosity index, and therefore exhibits excellent low-temperature fluidity, a high viscosity index, and excellent wear resistance. DETAILED DESCRIPTION OF THE INVENTION

[0012] The lubricating base oil of the present invention has a wear scar diameter of 0.55 mm or less as measured with a four-ball friction tester. If the wear scar diameter exceeds 0.55 mm, the wear resistance of the lubricating base oil of the present invention will be insufficient. In the lubricating base oil of the present invention, the upper limit of the wear scar diameter is preferably 0.50 mm. In the present invention, the wear scar diameter is the wear scar diameter (mm) measured in accordance with JPI-5S-32-90 (standard of the Japan Petroleum Institute) using a high-speed four-ball wear tester (manufactured by Shinko Engineering Co., Ltd.) under the conditions of 75°C, 1200 rpm rotation speed, 20 kg load, and 60 minutes.

[0013] The lubricating base oil of the present invention has a kinematic viscosity of 11.0 mmHg at 40°C.2 / s or less. Kinematic viscosity at 40°C is 11.0mm 2 If the kinematic viscosity exceeds 10.7 mm / s, the low-temperature fluidity of the lubricating base oil of the present invention will not be improved. 2 / s is preferred. In the present invention, the kinematic viscosity at 40°C means the kinematic viscosity measured in accordance with JIS K2283:2000.

[0014] The lubricating base oil of the present invention has a viscosity index of 120 or more. A viscosity index of 120 or more can improve the viscosity-temperature characteristics of a lubricating oil composition using the lubricating base oil of the present invention, and can also improve fuel economy and wear resistance. The viscosity index of the lubricating base oil of the present invention is preferably 140 or more. In the present invention, the viscosity index can be calculated from a value measured in accordance with JIS K2283:2000.

[0015] <One or more esters> The lubricating base oil of the present invention, which satisfies the above-mentioned wear scar diameter, 40° C. kinematic viscosity and viscosity index measured with a four-ball friction tester, contains one or more esters. The one or more esters include, for example, the following three types: (1) An ester compound prepared by esterifying (A) an aliphatic linear monocarboxylic acid, (B) an aliphatic dicarboxylic acid, and (C) an aliphatic dihydric alcohol in accordance with a conventional method, preferably under an inert gas atmosphere such as nitrogen, with heating and stirring in the presence or absence of an esterification catalyst (hereinafter, an ester synthesized by such a method is also referred to as a complex ester). (2) An ester compound prepared by esterifying (B) an aliphatic dicarboxylic acid and (D) an aliphatic monohydric alcohol in accordance with a conventional method, preferably under an inert gas atmosphere such as nitrogen, with heating and stirring in the presence or absence of an esterification catalyst (hereinafter, an ester synthesized by such a method may also be referred to as an aliphatic dicarboxylic acid diester). (3) An ester compound prepared by esterifying (A) an aliphatic linear monocarboxylic acid and (C) an aliphatic dihydric alcohol in accordance with a conventional method, preferably under an inert gas atmosphere such as nitrogen, with heating and stirring in the presence or absence of an esterification catalyst (hereinafter, an ester synthesized by such a method is also referred to as a diol-type diester).

[0016] Examples of the (A) aliphatic linear monocarboxylic acid component (hereinafter also referred to as (A) component) related to the one or more esters include (a1) aliphatic linear saturated monocarboxylic acids having 4 to 18 carbon atoms, preferably 4 to 12 carbon atoms, and more preferably 7 to 10 carbon atoms.

[0017] Specific examples of the component (a1) include n-butanoic acid, n-pentanoic acid, n-hexanoic acid, n-heptanoic acid, n-octanoic acid, n-nonanoic acid, n-decanoic acid, n-undecanoic acid, n-dodecanoic acid, n-tridecanoic acid, n-tetradecanoic acid, n-pentadecanoic acid, n-hexadecanoic acid, n-heptadecanoic acid, and n-octadecanoic acid. Among these, aliphatic linear saturated monocarboxylic acids having 4 to 9 carbon atoms are preferred because they have excellent low-temperature fluidity and low low-temperature viscosity, and specific examples include n-butanoic acid, n-pentanoic acid, n-hexanoic acid, n-heptanoic acid, n-octanoic acid, and n-nonanoic acid. Furthermore, from the viewpoint of excellent heat resistance, aliphatic linear saturated monocarboxylic acids having 8 to 12 carbon atoms are preferred, and specific examples thereof include n-octanoic acid, n-nonanoic acid, n-decanoic acid, n-undecanoic acid, and n-dodecanoic acid. Furthermore, aliphatic linear saturated monocarboxylic acids having 7 to 10 carbon atoms are preferred in that they have a very high viscosity index, good heat resistance, and low-temperature fluidity, and specifically, n-heptanoic acid, n-octanoic acid, n-nonanoic acid, and n-decanoic acid are preferred. These may be used alone or in suitable combination of two or more for esterification.

[0018] The aliphatic dicarboxylic acid (B) (hereinafter also referred to as component (B)) of the acid component related to the one or more esters is an aliphatic dicarboxylic acid having 2 to 10 carbon atoms, preferably 6 to 10 carbon atoms, and specific examples thereof include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. Among these, aliphatic dicarboxylic acids having 6 to 10 carbon atoms are preferred because they have excellent heat resistance and low-temperature fluidity. Specific examples include adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid, with adipic acid, azelaic acid, and sebacic acid being particularly preferred. These may be used alone or in suitable combination of two or more for esterification.

[0019] Examples of the (C) aliphatic dihydric alcohol (hereinafter also referred to as component (C)) used in producing the one or more esters include linear aliphatic dihydric alcohols and aliphatic dihydric alcohols having one or two branches.

[0020] Examples of the linear aliphatic dihydric alcohol include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol. Examples of the aliphatic dihydric alcohol having one or two branches include 1,2-propanediol, 2-methyl-1,3-propanediol, 1,3-butanediol, 2-methyl-1,4-butanediol, 1,4-pentanediol, 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,5-hexanediol, 2-methyl-1,6-hexanediol, 3-methyl-1,6-hexanediol, 1,6-heptanediol, 2-methyl-1,7-heptanediol, 3-methyl Examples include 1,7-heptanediol, 4-methyl-1,7-heptanediol, 1,7-octanediol, 2-methyl-1,8-octanediol, 3-methyl-1,8-octanediol, 4-methyl-1,8-octanediol, 1,8-nonanediol, 2-methyl-1,9-nonanediol, 3-methyl-1,9-nonanediol, 4-methyl-1,9-nonanediol, 5-methyl-1,9-nonanediol, 2-ethyl-1,3-hexanediol, and 2,4-diethyl-1,5-pentanediol. These may be used alone or in suitable combinations of two or more for esterification.

[0021] Among these, aliphatic dihydric alcohols having one or two branches are preferred, and aliphatic dihydric alcohols having 4 to 9 carbon atoms are particularly preferred, in view of their excellent low-temperature fluidity. Specifically, 2-methyl-1,3-propanediol, 1,3-butanediol, 2-methyl-1,4-butanediol, 1,4-pentanediol, 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,5-hexanediol, 2-methyl-1,6-hexanediol, 3-methyl-1,6-hexanediol, 1,6-heptanediol, 2-methyl-1,7-heptanediol, 3-methyl-1,7-heptanediol, 4-methyl-1,7-heptanediol, 1,7-octanediol, 2-methyl-1,8-octanediol, 3-methyl-1,8-octanediol, 4-methyl-1,8-octanediol, and 1,8-nonanediol are preferred. Among these, aliphatic dihydric alcohols having one branch (particularly a methyl group) are preferred because they have excellent heat resistance and low-temperature fluidity, more preferably aliphatic dihydric alcohols having 3 to 10 carbon atoms, and particularly preferably aliphatic dihydric alcohols having 4 to 6 carbon atoms. Specifically, 2-methyl-1,3-propanediol, 1,3-butanediol, 2-methyl-1,4-butanediol, 1,4-pentanediol, 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, and 1,5-hexanediol are preferred, and 3-methyl-1,5-pentanediol is particularly preferred.

[0022] <Esterification reaction> In the esterification of the above-mentioned components, the ratio of the acid components (A) and (B) used is preferably (A):(B)=98:2 to 40:60 (equivalent ratio), and it is particularly preferred that the components (A) and (B) be used at an (A):(B) ratio of 95:5 to 70:30 (equivalent ratio) in order to obtain one or more esters with an excellent balance between heat resistance and low-temperature fluidity. The term "equivalent" here refers to the ratio of the number of moles of carboxyl groups in each component to the total number of moles of carboxyl groups contained in components (A) and (B) used in the esterification reaction. For example, if 3 moles (MA = 3) of monocarboxylic acid (component (A)) and 1 mole (MB = 2) of dicarboxylic acid (component (B)) are used, the equivalent ratio of components (A) to (B) is (A):(B) = 3:2 = 60:40.

[0023] During the above esterification, the acid component consisting of components (A) and (B) is used in an amount of, for example, 1.0 to 1.5 equivalents per equivalent of the aliphatic dihydric alcohol of component (C), which is the alcohol component, and preferably 1.01 to 1.1 equivalents per equivalent of the alcohol component. That is, the acid component is used so that the number of moles of —COOH groups in the acid component is 1.0 to 1.5, preferably 1.01 to 1.1, and more preferably 1.01 to 1.05, per mole of —OH groups in the alcohol component.

[0024] In the above esterification reaction, it is preferable to use an esterification catalyst. Examples of the esterification catalyst include Lewis acids, alkali metals, sulfonic acids, etc. Specific examples of Lewis acids include aluminum derivatives, tin derivatives, and titanium derivatives. Specific examples of alkali metals include sodium alkoxides and potassium alkoxides. Specific examples of sulfonic acids include paratoluenesulfonic acid, methanesulfonic acid, and sulfuric acid. The amount used is, for example, about 0.1 to 1.0% by mass based on the total mass of the raw materials, the acid component (A) and the acid component (B) and the alcohol component (C). Among the above catalysts, the above Lewis acids are preferred.

[0025] The esterification reaction is preferably carried out in the presence of an inert gas at a reaction temperature of usually 150 to 250° C., preferably 160 to 230° C., for a reaction time of usually 3 to 30 hours. The esterification reaction can be carried out without a solvent, but if necessary, the water produced may be removed by azeotropic distillation from the system using a water-entraining agent such as benzene, toluene, xylene, cyclohexane, etc. When a water-entraining agent is used, the amount used is preferably 1 to 20% by mass, particularly 1 to 10% by mass, based on the total mass of the raw materials (component (A) and component (B) as acid components and component (C) as alcohol component).

[0026] After the esterification reaction is completed, excess raw materials are distilled off under reduced pressure or normal pressure. Subsequently, the one or more esters can be purified using conventional purification methods, such as neutralization, washing with water, liquid-liquid extraction, vacuum distillation, and the use of an adsorbent such as activated carbon. In particular, it is preferable to subject the esterification reaction product obtained by the above esterification reaction to alkali washing, either directly or after distilling off the unreacted acid (or the water-entraining agent, if used). This removes the remaining unreacted acid, impurities having a terminal carboxyl group, catalyst, etc., and allows one or more esters having excellent metal compatibility, heat resistance, etc. to be obtained.

[0027] Examples of the cleaning liquid used in the alkaline cleaning include aqueous solutions of alkalis such as alkali metal hydroxides, such as sodium hydroxide, potassium hydroxide, and lithium hydroxide, and alkali metal carbonates, such as sodium carbonate. The concentration of the solution is not particularly limited, but is preferably about 0.5 to 20% by mass. The amount of the aqueous alkaline solution used is preferably equal to or in excess of the total acid value of the reaction product after completion of the reaction. After the alkali washing, the product is preferably washed with water until it becomes neutral. In this way, one or more of the above esters can be obtained. The one or more esters can also be obtained by known transesterification. In place of these saturated aliphatic monocarboxylic acids, lower alkyl esters having 1 to 4 carbon atoms, such as methyl esters and ethyl esters, can also be used.

[0028] <Mineral oil> The lubricating base oil of the present invention may contain mineral oil. By containing a mineral oil in addition to one or more of the above-mentioned esters, the lubricating base oil of the present invention can be improved in particular in anti-wear properties and low-temperature fluidity. As the mineral oil, mineral oils (including GTL base oils) generally used as base oils in the field of lubricants can be used. Examples of the mineral oil include solvent refined oils or hydrotreated oils obtained by treating lubricating oil fractions obtained as distillates by vacuum distillation of residual oil from atmospheric distillation units of paraffinic, intermediate or naphthenic crude oils through one or more of various refining processes selected arbitrarily, such as solvent refining, solvent extraction, hydrocracking, hydroisomerization, solvent dewaxing, hydrorefining and clay treatment; mineral oils obtained by treating deasphalted oil obtained by solvent deasphalting of residual oil from vacuum distillation through the above-mentioned refining processes; mineral oils obtained by isomerization of wax components; and mixed oils thereof. Highly refined mineral oils are referred to as highly refined base oils.

[0029] Examples of the GTL base oil include lubricating oil fractions separated from liquid products obtained by the GTL process using natural gas or the like as a raw material, and lubricating oil fractions obtained by hydrocracking produced wax.

[0030] Specific examples of commercially available mineral oils include Nexbase 3020, Nexbase 3030 (manufactured by Neste), Super Oil M10, Super Oil M12, Super Oil M22, Super Oil N22, Super Oil M32, Super Oil N32, Super Oil M46, Super Oil N46, and Super Oil T46 (all manufactured by Nippon Oil Corporation), Diana Freshia S10, Diana Freshia S32, Diana Freshia P32, Diana Freshia N28, and Diana Freshia U46 (all manufactured by Idemitsu Kosan Co., Ltd.), Process 123 (manufactured by Showa Shell Sekiyu K.K.), Celeo 10, Celeo SP10, Celeo NH46, and Neutral 150 (all manufactured by Japan Energy Co., Ltd.), Solvent Neutral 60, Solvent Neutral 60LP, Solvent Neutral 100, and Solvent Neutral 60LP. Examples of suitable oils include Solvent Neutral 130, Solvent Neutral 100LP, Flexon 848, Terra 611, Terra 624, Plastoll 65, Plastoll 155, Plastoll J150, and Flexon 642 (all manufactured by Exxon Mobil Corporation), Kurisef Oil H22, Kurisef Oil F22, Kurisef Oil H46, and Kurisef Oil F46 (all manufactured by Nippon Oil Corporation), Cosmo Pure Safety 10, Cosmo Pure Safety 10W, Cosmo Pure Spin RC, Cosmo Pure Spin C, Cosmo Pure Spin W, Cosmo Pure Spin TK, Cosmo Neutral 100, Cosmo Neutral 150, Cosmo Pure Spin G, Cosmo Pure Spin 46N, Cosmo Pure Safety 22, Cosmo Pure Safety 32, and Cosmo Pure Safety 46 (all manufactured by Cosmo Oil Co., Ltd.). These can be used alone or in combination of two or more.

[0031] The viscosity index of the mineral oil used in the present invention is preferably 80-160, and more preferably 110-160.

[0032] The mineral oil used in the present invention preferably has a kinematic viscosity at 100°C of 1.5 to 40 mm 2 / s range.

[0033] In the lubricating base oil of the present invention, the blending ratio (mass ratio) of the mineral oil to the one or more esters is appropriately adjusted depending on the type of the one or more esters and the type of mineral oil used, but for example, the mass ratio of mineral oil to one or more esters is preferably 90:10 to 0:100. By containing the mineral oil and one or more esters in such a blending ratio, the lubricating base oil of the present invention can have excellent low-temperature fluidity, a high viscosity index, and excellent wear resistance. The blending ratio (mass ratio) of the mineral oil to the one or more esters is more preferably 60:40 to 0:100. By including the mineral oil and the one or more esters in such a blending ratio, for example, the wear scar diameter and low-temperature fluidity measured using the lubricating base oil of the present invention can be improved.

[0034] The lubricating base oil of the present invention can be used in combination with or added to other conventionally known base oils (hereinafter referred to as "combined base oils") and lubricating oil additives within the range in which the effects of the present invention are achieved.

[0035] The combined base oil is used to replace a portion of the lubricating base oil of the present invention. When the combined base oil is used, the amount of the combined base oil is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, based on the total mass of the lubricating base oil of the present invention and the combined base oil.

[0036] Examples of the base oil to be used in combination include animal and vegetable oils, the mineral oils and one or more organic acid esters other than the above-mentioned esters, polyalkylene glycols, polyvinyl ethers, polyphenyl ethers, alkylphenyl ethers, silicone oils, etc. Such base oils to be used in combination may be used alone or in appropriate combination of two or more.

[0037] Examples of the animal and vegetable oils include beef tallow, lard, palm oil, coconut oil, rapeseed oil, castor oil, and sunflower oil.

[0038] Examples of organic acid esters other than the mineral oil and one or more esters mentioned above include fatty acid monoesters and polyol esters. Examples of the fatty acid monoester include monoesters obtained from a linear or branched aliphatic monocarboxylic acid having 5 to 22 carbon atoms and a linear or branched saturated or unsaturated aliphatic alcohol having 3 to 22 carbon atoms. Examples of the polyol ester include polyol esters obtained from neopentyl-type polyols such as neopentyl glycol, trimethylolpropane, pentaerythritol, ditrimethylolpropane, and dipentaerythritol, and linear and / or branched saturated or unsaturated fatty acids having 3 to 22 carbon atoms. Examples of esters other than those mentioned above include ester compounds of polymerized fatty acids such as dimer acids and hydrogenated dimer acids, or hydroxy fatty acids such as condensed castor oil fatty acids and hydrogenated condensed castor oil fatty acids with linear or branched saturated or unsaturated aliphatic alcohols having 3 to 22 carbon atoms.

[0039] The polyalkylene glycol may be, for example, a ring-opening polymer of an alcohol and a linear or branched alkylene oxide having 2 to 4 carbon atoms. Examples of the alkylene oxide include ethylene oxide, propylene oxide, and butylene oxide, and a polymer using one of these or a copolymer using a mixture of two or more of these can be used. Compounds in which the hydroxyl groups at one or both ends are etherified or esterified can also be used. The kinematic viscosity (40°C) of the polymer is usually 5 to 1000 mm 2 / s, preferably 5 to 500 mm 2 / s.

[0040] The polyvinyl ether is a compound obtained by polymerization of a vinyl ether monomer, and examples of the monomer include methyl vinyl ether, ethyl vinyl ether, 2-propyl vinyl ether, 1-butyl vinyl ether, 2-methyl-1-propyl vinyl ether, 2-butyl vinyl ether, 2-methyl-2-propyl vinyl ether, 1-pentyl vinyl ether, 1-hexyl vinyl ether, 2-methoxyethyl vinyl ether, and 2-ethoxyethyl vinyl ether.

[0041] Examples of the polyphenyl ether include compounds having a structure in which the meta positions of two or more aromatic rings are linked by an ether bond or a thioether bond. Specific examples include bis(m-phenoxyphenyl)ether, m-bis(m-phenoxyphenoxy)benzene, and thioethers in which one or more oxygen atoms of these ethers have been substituted with sulfur (commonly known as C-ethers).

[0042] Examples of the alkyl phenyl ether include compounds in which polyphenyl ether is substituted with a linear or branched alkyl group having 6 to 18 carbon atoms, and alkyl diphenyl ethers substituted with one or more alkyl groups are particularly preferred.

[0043] Examples of the silicone oil include dimethyl silicone, methylphenyl silicone, and modified silicones such as long-chain alkyl silicone and fluorosilicone.

[0044] Among these base oils for use in combination, when the above-mentioned mineral oil and one or more organic acid esters other than esters are used in combination, heat resistance and lubricity may be improved.

[0045] In order to further improve the performance of the lubricating base oil of the present invention, known lubricating oil additives such as antioxidants, metal detergents, ashless dispersants, oiliness agents, antiwear agents, extreme pressure agents, metal deactivators, rust inhibitors, viscosity index improvers, pour point depressants, and antifoaming agents can be blended singly or in appropriate combinations of two or more within the range in which the effects of the present invention are achieved.

[0046] The present specification discloses the following: The present disclosure (1) provides a lubricating base oil containing one or more esters, which has a wear scar diameter of 0.55 mm or less in a four-ball friction tester and a kinematic viscosity of 11.0 mm at 40°C. 2 / s or less and a viscosity index of 120 or more. This disclosure (2) is a material having a wear scar diameter of 0.50 mm or less in a four-ball friction tester and a kinematic viscosity of 10.7 mm at 40°C. 2 / s or less and a viscosity index of 140 or more. The present disclosure (3) is the lubricating base oil according to the present disclosure (1) or (2), further containing a mineral oil. The present disclosure (4) is the lubricating base oil according to the present disclosure (3), in which the blending ratio (mass ratio) of the mineral oil to the one or more esters is 90:10 to 0:100. The present disclosure (5) is the lubricating base oil according to the present disclosure (4), in which the blending ratio (mass ratio) of the mineral oil to the one or more esters is 60:40 to 0:100. The present disclosure (6) is the lubricating base oil according to any one of the present disclosures (1) to (5), wherein the one or more esters are obtained by esterifying (A) an aliphatic linear monocarboxylic acid, (B) an aliphatic dicarboxylic acid, and (C) an aliphatic dihydric alcohol. The present disclosure (7) is the lubricating base oil according to any one of the present disclosures (6), wherein the one or more esters are obtained by esterifying (A) a linear monocarboxylic acid having 8 carbon atoms, (B) an aliphatic dicarboxylic acid having 6 to 10 carbon atoms, and (C) 3-methyl-1,5-pentanediol. [Example]

[0047] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring the various properties in the examples are as follows. Reagents were used for compounds not specifically mentioned.

[0048] [Compound used] Mineral oil 1: Nexbase 3030 (manufactured by Neste) Mineral oil 2: Nexbase 3020 (manufactured by Neste) One or more esters [Table 1]

[0049] (Production Example 1) A 1-liter four-neck flask equipped with a stirrer, thermometer, and a water distillation receiver with a condenser was charged with 393 g (2.7 mol) of n-octanoic acid, 61 g (0.3 mol) of sebacic acid, 177 g (1.5 mol) of 3-methyl-1,5-pentanediol, xylene (5% by mass based on the total amount of acid and alcohol), and tin oxide catalyst (0.2% by mass based on the total amount of acid and alcohol). The mixture was heated to 230 °C under reduced pressure in a nitrogen atmosphere [n-octanoic acid:sebacic acid = 9:1 (equivalent ratio)]. The esterification reaction was carried out for approximately 7 hours while removing the distilled water in the water distillation receiver, aiming for the theoretical amount of water (54 g). After the reaction was completed, excess acid and xylene were removed by distillation (conditions: 200°C, 50 mmHg or less). The reaction mixture was then neutralized with an excess amount of aqueous caustic soda solution relative to the total acid value after the reaction was completed, and washed with water until neutral to obtain a crude esterification reaction product. The crude esterification reaction product was then treated with activated carbon and filtered to obtain 395 g of a complex ester (Ester 1) obtained from 3-methyl-1,5-pentanediol / n-octanoic acid / sebacic acid.

[0050] (Production Example 2) A complex ester (Ester 2) of 3-methyl-1,5-pentanediol / n-octanoic acid / adipic acid (270 g) was obtained in the same manner as in Production Example 1, except that 277 g (1.9 mol) of n-octanoic acid was used and 19 g (0.1 mol) of azelaic acid was used instead of sebacic acid [n-octanoic acid:azelaic acid = 9.5:0.5 (equivalent ratio)].

[0051] (Production Example 3) A complex ester (Ester 3) (257 g) obtained from 3-methyl-1,5-pentanediol / n-octanoic acid / adipic acid was obtained in the same manner as in Production Example 1, except that 415 g (2.9 mol) of n-octanoic acid was used and 22 g (0.2 mol) of adipic acid was used instead of sebacic acid [n-octanoic acid:adipic acid=9.5:0.5 (equivalent ratio)].

[0052] (Production Example 4) A 255 g complex ester (Ester 4) obtained from 3-methyl-1,5-pentanediol / n-octanoic acid / adipic acid was obtained in the same manner as in Production Example 1, except that 262 g (1.8 mol) of n-octanoic acid was used and 30 g (0.2 mol) of adipic acid was used instead of sebacic acid [n-octanoic acid:adipic acid=9:1 (equivalent ratio)].

[0053] (Production Example 5) A single ester (Ester 5) obtained from isodecanol / adipic acid (401 g) was obtained in the same manner as in Production Example 1, except that 380 g (2.4 mol) of isodecanol was used instead of 3-methyl-1,5-pentanediol and 146 g (1.0 mol) of adipic acid was used as the acid component.

[0054] (Production Example 6) In the same manner as in Production Example 1, except that 446 g (2.4 mol) of n-undecanoic acid was used as the acid component, 512 g of a single ester (Ester 6) obtained from 3-methyl-1,5-pentanediol / n-undecanoic acid was obtained.

[0055] (a)Kinematic viscosity at 40℃ Based on JIS K2283 (2000), kinematic viscosity (mm 2 / s) was measured and evaluated according to the following criteria. ◎: 10.7 mm 2 / s or less 〇:10.7mm 2 / s over 11.0mm 2 / s or less ×:11.0mm 2 More than / s

[0056] (b) Viscosity index The calculation was performed in accordance with JIS K2283 (2000) and evaluated according to the following criteria. ◎: Viscosity index is 140 or more ○: Viscosity index is 120 or more but less than 140 ×: Viscosity index less than 120

[0057] (c) Wear scar diameter (wear resistance) In accordance with JPI-5S-32-90, a high-speed four-ball wear tester (manufactured by Shinko Engineering Co., Ltd.) was used to conduct the test at a rotation speed of 1200 rpm, a load of 20 kg, and a test time of 60 minutes. The wear scar diameter (mm) was measured and evaluated according to the following criteria. ◎: Wear scar diameter is 0.50mm or less ○: Wear scar diameter is over 0.50 mm and 0.55 mm or less ×: Wear scar diameter exceeds 0.55 mm

[0058] (Overall review) ◎: 2 or more ◎, no × 〇: 1 or less ◎, no × ×: 1 or more ×

[0059] Examples and Comparative Examples Tables 2 to 8 show the kinematic viscosities and wear scar diameters of lubricating oils composed of mineral oil 1 and one or more esters (esters 1 to 6) obtained in Production Examples 1 to 6 in the ratios (mass ratios) shown in Tables 2 to 8.

[0060] [Table 2] [Table 3] [Table 4] [Table 5] [Table 6] [Table 7] [Table 8]

[0061] As shown in Tables 2 to 8, the lubricating oils according to the examples had a wear scar diameter of 0.55 mm or less in a four-ball friction tester and a kinematic viscosity of 11.0 mm at 40°C. 2 / s or less and a viscosity index of 120 or more, which indicates that it has excellent low-temperature fluidity, and its high viscosity index makes it excellent in wear resistance. As shown in Comparative Examples 1 and 14, it is clear that lubricating base oils containing mineral oil alone are inferior in low-temperature fluidity, viscosity index and wear resistance. As shown in Comparative Examples 2 to 13, the wear scar diameter measured by the four-ball friction tester was 0.55 mm or less and the kinematic viscosity at 40°C was 11.0 mm. 2 It can be seen that when Esters 5 and 6 are used, which do not satisfy both the requirements of a viscosity index of 120 or more and a viscosity of 1 / s or less, the low-temperature fluidity, viscosity index, and wear resistance are not all excellent, whether the esters are used alone or in combination with mineral oil.

[0062] The lubricating base oil of the present invention has excellent low-temperature fluidity, a high viscosity index, and excellent wear resistance, and therefore can be used in a wide range of applications, such as hydraulic oil, metalworking oil, cutting oil, compressor oil, refrigeration oil, gear oil, bearing oil, chain oil, grease base oil, industrial lubricant, and textile oil. [Industrial Applicability]

[0063] The present invention provides a lubricating base oil that has excellent low-temperature fluidity, a high viscosity index, and excellent wear resistance.

Claims

1. 1. A lubricating base oil containing one or more esters, Wear scar diameter measured by a four-ball friction tester is 0.55 mm or less and kinematic viscosity at 40°C is 11.0 mm ２ / s or less and a viscosity index of 120 or more.

2. Wear scar diameter measured by a four-ball friction tester is 0.50 mm or less and kinematic viscosity at 40°C is 10.7 mm ２ 2. The lubricating base oil according to claim 1, wherein the viscosity of the lubricating base oil is 1 / s or less and the viscosity index is 140 or more.

3. The lubricating base oil according to claim 1 or 2, further comprising a mineral oil.

4. The lubricating base oil according to claim 3, wherein the blending ratio (mass ratio) of the mineral oil to the one or more esters is 90:10 to 0:

100.

5. The lubricating base oil according to claim 4, wherein the blending ratio (mass ratio) of the mineral oil to the one or more esters is 60:40 to 0:

100.

6. 3. The lubricating base oil according to claim 1, wherein the one or more esters are obtained by esterifying (A) an aliphatic linear monocarboxylic acid, (B) an aliphatic dicarboxylic acid, and (C) an aliphatic dihydric alcohol.

7. 7. The lubricating base oil according to claim 6, wherein the one or more esters are obtained by esterifying (A) a linear monocarboxylic acid having 8 carbon atoms, (B) an aliphatic dicarboxylic acid having 6 to 10 carbon atoms, and (C) 3-methyl-1,5-pentanediol.

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