Lubricant and lubricant composition

Abstract

To provide a lubricant hardly corroding metal.SOLUTION: The lubricant contains a deep eutectic solvent which is a mixed product of one or more species selected from nonionic hydrogen bond donors and one or more species selected from nonionic hydrogen bond receptors. It is preferable for the deep eutectic solvent to have proton dissociation energy of the hydrogen bond donor of - 400 kcal / mol or greater and proton affinity energy of the hydrogen bond receptor of -180 kcal / mol or below.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to lubricants and lubricant compositions.

Background Art

[0002] In recent years, ionic liquids composed of cations and anions have been studied for various applications by taking advantage of their excellent thermal stability (low volatility, non-flammability), high ion density (high ionic conductivity), large heat capacity, and low viscosity. For example, Patent Document 1 proposes using an ionic liquid as a lubricating base oil.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the ionic liquid disclosed in Patent Document 1 cannot sufficiently suppress metal corrosion. Since lubricants such as lubricating base oils often come into contact with metal surfaces, a lubricant that is less likely to corrode metal is desired.

[0005] Therefore, an object of the present invention is to provide a lubricant that is less likely to corrode metal.

Means for Solving the Problems

[0006] According to the present invention, the following [1] to [4] are provided. [1] A lubricant containing a deep eutectic solvent that is a mixed product of one or more selected from nonionic hydrogen bond donors and one or more selected from nonionic hydrogen bond acceptors. [2] The lubricant according to [1] above, used as a base material of a lubricant composition. [3] The lubricant described in [1] above, which is used as an additive for the lubricant composition. [4] A lubricant composition containing the lubricant described in [1] above.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a lubricant that is less likely to corrode metals.

Modes for Carrying Out the Invention

[0008] The upper and lower limit values of the numerical ranges described in this specification can be arbitrarily combined. For example, when the numerical ranges "A to B" and "C to D" are described, the numerical ranges "A to D" and "C to B" are also included in the scope of the present invention. In addition, the numerical range "lower limit value to upper limit value" described in this specification means, unless otherwise specified, that it is greater than or equal to the lower limit value and less than or equal to the upper limit value. In addition, in this specification, the numerical values in the examples are numerical values that can be used as the upper limit value or the lower limit value.

[0009] [Aspects of the Lubricant] The lubricant of the present embodiment contains a deep eutectic solvent that is a mixed product of one or more selected from nonionic hydrogen bond donors and one or more selected from nonionic hydrogen bond acceptors.

[0010] The inventors of the present invention conducted intensive studies to solve the above problems. As a result, they came up with the idea of using a deep eutectic solvent as a lubricant instead of an ionic liquid. However, based on this idea, during various studies conducted by the inventors of the present invention, they found that there are also deep eutectic solvents that are likely to corrode metals. Therefore, as a result of further intensive studies by the inventors of the present invention, they found that a deep eutectic solvent that is a mixed product of one or more selected from nonionic hydrogen bond donors and one or more selected from nonionic hydrogen bond acceptors is less likely to corrode metals. Through further repeated studies, the present invention was completed. Hereinafter, each component contained in the lubricant of the present embodiment will be described in detail.

[0011] <Deep eutectic solvent> A deep eutectic solvent is a mixed product obtained by mixing a hydrogen bond donor and a hydrogen bond acceptor. The melting point of the deep eutectic solvent is lowered than the melting point of each of the hydrogen bond donor and the hydrogen bond acceptor constituting the deep eutectic solvent due to the eutectic melting point depression. The melting point of the deep eutectic solvent only needs to be lower than the melting point of the hydrogen bond donor and the melting point of each of the hydrogen bond acceptors constituting the deep eutectic solvent. From the viewpoint of handling as a lubricant, it is preferably liquid at 100 ° C, more preferably liquid at 60 ° C, and even more preferably liquid at room temperature or near room temperature. In this specification, room temperature means 25 ° C, and near room temperature means 25 ± 5 ° C. In the present embodiment, at least one (preferably both) of the melting point of the nonionic hydrogen bond donor and the melting point of the nonionic hydrogen bond acceptor constituting the deep eutectic solvent is preferably above 50 ° C, more preferably above 80 ° C, and even more preferably above 100 ° C from the viewpoint of improving the evaporation characteristics of the deep eutectic solvent and the like. The upper limit of these melting points is not particularly limited, but from the viewpoint of ease of generating the deep eutectic solvent and the like, it is preferably 300 ° C or lower, more preferably 250 ° C or lower, and even more preferably 200 ° C or lower. The deep eutectic solvent may be used alone or in combination of two or more.

[0012] Here, the deep eutectic solvent contained in the lubricant of the present embodiment is characterized in that it is a mixed product of one or more selected from nonionic hydrogen bond donors and one or more selected from nonionic hydrogen bond acceptors. That is, the hydrogen bond donor and the hydrogen bond acceptor are both nonionic substances. Since the deep eutectic solvent is a mixed product of one or more selected from nonionic hydrogen bond donors and one or more selected from nonionic hydrogen bond acceptors, it is possible to make it difficult to corrode metals. Deep eutectic solvents in which at least one of the hydrogen bond donor and the hydrogen bond acceptor is an zwitterionic substance or an ionic substance having a betaine structure or the like are likely to corrode metals. Ionic liquids composed of cationic species and anionic species are also likely to corrode metals.

[0013] In the present embodiment, from the viewpoint of facilitating the donation of hydrogen for forming a deep eutectic solvent and making it easier to generate a deep eutectic solvent, the nonionic hydrogen bond donor preferably has a proton dissociation energy of -400 kcal / mol or more, more preferably -390 kcal / mol or more, still more preferably -385 kcal / mol or more. The proton dissociation energy is usually -320 kcal / mol or less. Further, in the present embodiment, as a nonionic hydrogen bond acceptor that easily accepts hydrogen for forming a deep eutectic solvent and makes it easier to generate a deep eutectic solvent, the proton affinity energy is preferably -180 kcal / mol or less, more preferably -190 kcal / mol or less, still more preferably -195 kcal / mol or less. The proton affinity energy is usually -280 kcal / mol or more.

[0014] In this specification, the "proton dissociation energy" means the energy required for a proton to dissociate from a hydrogen bond donor, and is a value calculated by the following formula (1). (Proton dissociation energy) = E(D-H + ) - {E(D-) + E(H + )} ···· (1) The meanings of the symbols in the above formula (1) are as follows. · E(D-H + ): Total energy value after structural optimization of the hydrogen bond donor · E(D-) + E(H + ): Sum of the total energies of each part when the hydrogen bond donor is divided into a proton and other parts Here, D means the hydrogen bond donor excluding the proton, and H means a hydrogen atom.

[0015] In addition, in this specification, the "proton affinity energy" means the energy required for a proton to bind to a hydrogen bond acceptor, and is a value calculated by the following formula (2). (Proton affinity energy) = E(A-H + ) - {E(A) + E(H + )} ···· (2) The meanings of the symbols in the above formula (2) are as follows. · E(A-H + ): The total energy value when a proton is added to a hydrogen bond acceptor and structural optimization is performed · E(A) + E(H + ): The sum of the total energies of each part when a proton is added to a hydrogen bond acceptor and the optimized structure is divided into a proton and other parts Here, A means a hydrogen bond acceptor, and H means a hydrogen atom.

[0016] The proton dissociation energy and the proton affinity energy can be calculated using general-purpose quantum chemistry calculation software (for example, Gaussian16 manufactured by Gaussian, etc.). Specifically, first, the total energy is minimized with respect to all bond lengths, angles, and dihedral angles of the compound (molecule, specifically, an isolated molecule in a vacuum state) to be calculated to obtain a stable structure. Then, by utilizing the Counterpoise method and calculating the binding energy of the compound (molecule) to be calculated with a proton, it can be calculated.

[0017] Examples of the combination of a nonionic hydrogen bond donor and a nonionic hydrogen bond acceptor preferably include a combination of two selected from the group consisting of amines, amides, ureas, azoles, organic acids, ketones, phosphine oxides, sulfoxides, sulfones, alcohols, sugars, and amino acids, and derivatives thereof. Among these, a combination of two selected from the group consisting of amines, amides, organic acids, ketones, phosphine oxides, sulfoxides, and alcohols, and derivatives thereof is preferable. Hereinafter, the compounds that can be used as nonionic hydrogen bond donors or nonionic hydrogen bond acceptors will be described in detail.

[0018] (Definition) In the following description, the "hydrocarbon group" means a group consisting of carbon and hydrogen. The hydrocarbon group may have a chain structure, a cyclic structure, or a structure including both a chain structure and a cyclic structure. Typical examples of the hydrocarbon group include aliphatic hydrocarbon groups such as an alkyl group having 1 to 30 carbon atoms and an alkenyl group having 1 to 30 carbon atoms; cycloaliphatic hydrocarbon groups such as a cycloalkyl group having 5 to 30 carbon atoms, an alkylcycloalkyl group having 6 to 30 carbon atoms, a cycloalkylalkyl group having 6 to 30 carbon atoms, a cycloalkenyl group having 5 to 30 carbon atoms, an alkylcycloalkenyl group having 6 to 30 carbon atoms, and a cycloalkenylalkyl group having 6 to 30 carbon atoms; and aromatic hydrocarbon groups such as an aryl group having 6 to 30 carbon atoms, an arylalkyl group having 7 to 30 carbon atoms, and an alkylaryl group having 7 to 30 carbon atoms. In the following description, compounds with the prefixes "aliphatic", "cycloaliphatic", and "aromatic" mean compounds having the above-mentioned aliphatic hydrocarbon group, cycloaliphatic hydrocarbon group, and aromatic hydrocarbon group, respectively.

[0019] In the following description, the number of carbon atoms of the compounds exemplified as nonionic hydrogen bond donors and nonionic hydrogen bond acceptors means the value including the number of carbon atoms of the substituents.

[0020] (Amine) The amine used in this embodiment is not particularly limited as long as it can form a deep eutectic solvent with the other component. Examples include aliphatic amines, cycloaliphatic amines, aromatic amines, heterocyclic amines, etc. The heterocyclic amine may be a heterocyclic cycloaliphatic amine or a heterocyclic aromatic amine. Note that the amine may be a derivative with one or more substituents added. Examples of the substituent include a hydrocarbon group, an alkoxy group (preferably having 1 to 10 carbon atoms), a polyether group, a carboxyl group, a carbonyl group, a halogen group, a nitro group, a nitroso group, a thioether group, a thiocarbonyl group, a hydroxyl group, and the like. When the amine derivative has a hydroxyl group, although the derivative can also be classified as an alcohol, in this specification, it is classified as an amine. When the amine derivative has a carboxyl group, although the derivative can also be classified as an organic acid, in this specification, it is classified as an amine. When the amine derivative has a carbonyl group, although the derivative can also be classified as a ketone, in this specification, it is classified as an amine.

[0021] Here, in this embodiment, from the viewpoint of ease of generating the deep eutectic solvent and the like, the amine is preferably a heterocyclic aromatic amine or an aromatic amine. Examples of the heterocyclic aromatic amine include heterocyclic aromatic amines having 4 to 30 carbon atoms. The number of carbon atoms of the heterocyclic aromatic amine is preferably 6 to 25, more preferably 7 to 20, and still more preferably 8 to 15. Examples of the heterocyclic aromatic amine having 4 to 30 carbon atoms include compounds having a pyrrole skeleton, compounds having a pyridine skeleton, compounds having an indole skeleton, compounds having a quinoline skeleton, compounds having an isoquinoline skeleton, and compounds having a carbazole skeleton. Among these, compounds having an indole skeleton (the number of carbon atoms is preferably 8 to 15) are preferred, and indole is more preferred.

[0022] Examples of the aromatic amine include aromatic amines having 6 to 30 carbon atoms. The number of carbon atoms of the aromatic amine is preferably 10 to 30, more preferably 16 to 30, and still more preferably 16 to 25. Examples of the aromatic amine having 6 to 30 carbon atoms include compounds having a phenylamine skeleton, compounds having a naphthylamine skeleton, compounds having a phenylnaphthylamine skeleton, and compounds having an anthraceneamine skeleton. Among these, compounds having a phenylnaphthylamine skeleton (preferably having 16 to 25 carbon atoms) are preferred, and N-phenyl-1-naphthylamine is more preferred.

[0023] The amine may be used alone or in combination of two or more.

[0024] (Amide) The amide used in this embodiment is not particularly limited as long as it can form a deep eutectic solvent with the other component. Examples include amides having a hydrocarbon group such as aliphatic amide, alicyclic amide, and aromatic amide. Here, the amide may be a derivative to which one or more substituents are added. Examples of the substituent include a hydrocarbon group, an alkoxy group (preferably having 1 to 10 carbon atoms), a polyether group, a carboxyl group, a carbonyl group, a halogen group, an amino group, a nitro group, a nitroso group, a thioether group, a thiocarbonyl group, a hydroxyl group, and the like. When the derivative of the amide has a hydroxyl group, the derivative can also be classified as an alcohol, but in this specification, it is classified as an amide. When the derivative of the amide has a carboxyl group, the derivative can also be classified as an organic acid, but in this specification, it is classified as an amide. When the derivative of the amide has a carbonyl group, the derivative can also be classified as a ketone, but in this specification, it is classified as an amide. When the derivative of the amide has an amino group, the derivative can also be classified as an amine, but in this specification, it is classified as an amide.

[0025] Here, in this embodiment, from the viewpoint of ease of forming a deep eutectic solvent, etc., aromatic amide is preferred as the amide. Examples of the aromatic amide include aromatic amides having 7 to 30 carbon atoms. The number of carbon atoms of the aromatic amide is preferably 7 to 25, more preferably 7 to 20, and still more preferably 7 to 15. Examples of the aromatic amide having 7 to 30 carbon atoms include compounds having a benzamide skeleton and compounds having an acetanilide skeleton. Among these, compounds having an acetanilide skeleton (the number of carbon atoms is preferably 8 to 15) are preferred, compounds having an acetanilide skeleton and a hydroxyl group (the number of carbon atoms is preferably 8 to 15) are more preferred, and 4'-hydroxyacetanilide is still more preferred.

[0026] The amide may be used alone or in combination of two or more.

[0027] (Organic acid) The organic acid used in this embodiment is not particularly limited as long as it can form a deep eutectic solvent with the other component. Examples include organic acids having a hydrocarbon group such as fatty acids, alicyclic acids, and aromatic acids. Here, the organic acid may be a derivative to which one or more substituents are added. Examples of the substituent include a hydrocarbon group, an alkoxy group (preferably having 1 to 10 carbon atoms), a polyether group, a carbonyl group, a halogen group, a nitro group, a nitroso group, a thioether group, a thiocarbonyl group, a hydroxyl group, and the like. When the derivative of the organic acid has a hydroxyl group, the derivative can also be classified as an alcohol, but in this specification, it is classified as an organic acid. When the derivative of the organic acid has a carbonyl group, the derivative can also be classified as a ketone, but in this specification, it is classified as an organic acid. Here, in this embodiment, from the viewpoint of ease of forming a deep eutectic solvent, fatty acids and aromatic acids are preferred as the organic acid.

[0028] Examples of the fatty acid preferably include fatty acids having 2 to 30 carbon atoms. The number of carbon atoms of the fatty acid is preferably 2 to 20, more preferably 6 to 18, and still more preferably 8 to 16. Examples of the fatty acid include octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, etc. Among these, dodecanoic acid is preferred.

[0029] As the aromatic acid, preferably aromatic acids having 7 to 30 carbon atoms are exemplified. The number of carbon atoms of the aromatic acid is preferably 7 to 20, more preferably 7 to 16, and still more preferably 7 to 12. Examples of the aromatic acid include benzoic acid, phenylpropionic acid, etc. Among these, benzoic acid is preferred.

[0030] The organic acid may be used alone or in combination of two or more.

[0031] (Ketone) The ketone used in this embodiment is not particularly limited as long as it can form a deep eutectic solvent with the other component. Exemplarily, ketones having a hydrocarbon group such as aliphatic ketones, alicyclic ketones, and aromatic ketones are included. Further, as the ketone, lactones such as aromatic lactones and aromatic lactones having a hydrocarbon group are also included. Here, the ketone may be a derivative to which one or more substituents are added. Examples of the substituent include a hydrocarbon group, an alkoxy group (preferably having 1 to 10 carbon atoms), a polyether group, a carboxyl group, a halogen group, a nitro group, a nitroso group, a thioether group, a thiocarbonyl group, a hydroxyl group, etc. When the derivative of the ketone has a hydroxyl group, the derivative may be classified as an alcohol, but in this specification, it is classified as a ketone. Here, in this embodiment, from the viewpoint of ease of forming the deep eutectic solvent, etc., alicyclic ketones and aromatic lactones are preferred as the ketone.

[0032] Examples of the alicyclic ketone include alicyclic ketones having 5 to 30 carbon atoms. The number of carbon atoms of the alicyclic ketone is preferably 8 to 20, more preferably 8 to 16, and still more preferably 8 to 12. In addition, the alicyclic ketone is preferably an alicyclic ketone having a bicyclic structure (preferably having 8 to 12 carbon atoms). Examples of such an alicyclic ketone include camphor.

[0033] Examples of the aromatic lactone include aromatic lactones having 5 to 30 carbon atoms. The number of carbon atoms of the aromatic lactone is preferably 9 to 20, more preferably 9 to 16, and still more preferably 9 to 12. In addition, the aromatic lactone is preferably a compound having a coumarin skeleton (preferably having 9 to 12 carbon atoms). Examples of such an aromatic lactone include coumarin.

[0034] The ketone may be used alone or in combination of two or more.

[0035] (Phosphine oxide) The phosphine oxide used in this embodiment is not particularly limited as long as it can form a deep eutectic solvent with the other component. Examples include trihydrocarbylphosphine oxide. The three hydrocarbon groups of the trihydrocarbylphosphine oxide are preferably each independently the above aliphatic hydrocarbon group, alicyclic hydrocarbon group, or aromatic hydrocarbon group. Here, the phosphine oxide may be a derivative to which one or more substituents are added. Examples of the substituent include a hydrocarbon group, an alkoxy group (preferably having 1 to 10 carbon atoms), a polyether group, and the like. Here, in this embodiment, from the viewpoint of ease of forming the deep eutectic solvent, etc., the phosphine oxide is preferably trialkylphosphine oxide.

[0036] The number of carbon atoms of the three alkyl groups of the trialkylphosphine oxide is each independently preferably 1 to 30, more preferably 2 to 20, still more preferably 3 to 18, and even more preferably 4 to 16. Examples of such a trialkylphosphine oxide include trioctylphosphine oxide.

[0037] The phosphine oxide may be used alone or in combination of two or more.

[0038] (Sulfoxide) The sulfoxide used in this embodiment is not particularly limited as long as it can form a deep eutectic solvent with the other component. Examples include dihydrocarbyl sulfoxide. The two hydrocarbon groups of the dihydrocarbyl sulfoxide are each independently the above aliphatic hydrocarbon group, alicyclic hydrocarbon group, or aromatic hydrocarbon group. Here, the sulfoxide may be a derivative to which one or more substituents are added. Examples of the substituent include a hydrocarbon group, an alkoxy group (preferably having 1 to 10 carbon atoms), a polyether group, and the like. Here, in this embodiment, from the viewpoint of ease of forming the deep eutectic solvent, etc., the sulfoxide is preferably a dialkyl sulfoxide or a diaryl sulfoxide. The carbon number of the two alkyl groups of the dialkyl sulfoxide is each independently preferably 1 to 30, more preferably 2 to 20, still more preferably 3 to 18, and even more preferably 4 to 16. Examples of such a dialkyl sulfoxide preferably include dodecyl sulfoxide. The carbon number of the two aryl groups of the diaryl sulfoxide is each independently preferably 6 to 30, more preferably 6 to 20, and still more preferably 6 to 10. Examples of such a diaryl sulfoxide preferably include diphenyl sulfoxide.

[0039] The sulfoxide may be used alone or in combination of two or more.

[0040] (Sulfone) The sulfone used in this embodiment is not particularly limited as long as it can form a deep eutectic solvent with the other component. For example, dihydrocarbyl sulfone can be mentioned. The two hydrocarbon groups of the dihydrocarbyl sulfone are each independently the above aliphatic hydrocarbon group, alicyclic hydrocarbon group, or aromatic hydrocarbon group. Here, the sulfone may be a derivative with one or more substituents added. Examples of the substituent include a hydrocarbon group, an alkoxy group (preferably having 1 to 10 carbon atoms), a polyether group, and the like. When the derivative of the sulfone has a hydroxyl group, the derivative can also be classified as an alcohol, but in this specification, it is classified as a sulfone. Here, in this embodiment, from the viewpoint of ease of forming the deep eutectic solvent, etc., dialkyl sulfone or diaryl sulfone is preferred as the sulfone. The carbon number of the two alkyl groups of the dialkyl sulfone is each independently preferably 1 to 30, more preferably 2 to 20, still more preferably 3 to 18, and even more preferably 4 to 16. As such a dialkyl sulfoxide, for example, dioctyl sulfone is preferably mentioned. The carbon number of the two aryl groups of the diaryl sulfone is each independently preferably 6 to 30, more preferably 6 to 20, and still more preferably 6 to 10. As such a diaryl sulfone, for example, diphenyl sulfone is preferably mentioned.

[0041] The sulfone may be used alone or in combination of two or more.

[0042] (Alcohol) The alcohol used in this embodiment is not particularly limited as long as it can form a deep eutectic solvent with the other component. For example, aliphatic alcohol, alicyclic alcohol, aromatic alcohol, etc. can be mentioned. The alcohol may be a monoalcohol, a diol, or a polyol such as a triol. Here, the alcohol may be a derivative with one or more substituents added. Examples of the substituent include a hydrocarbon group, an alkoxy group, a polyether group, a halogen group, a nitroso group, a thioether group, a thiocarbonyl group, and the like. Among these, from the viewpoint of ease of generating the deep eutectic solvent, it is preferably an alicyclic alcohol, an aromatic alcohol, an aromatic alcohol having a nitro group (hereinafter also referred to as "nitroaromatic alcohol"), or an aromatic alcohol having a halogen group (hereinafter also referred to as "halogen aromatic alcohol").

[0043] Examples of the alicyclic alcohol preferably include alicyclic alcohols having 5 to 30 carbon atoms. The number of carbon atoms of the alicyclic alcohol is preferably 6 to 20, more preferably 6 to 16, and still more preferably 8 to 12. Here, the alicyclic alcohol is preferably a compound having a cyclohexanol skeleton (the number of carbon atoms is preferably 8 to 12). A preferred alicyclic alcohol includes L-menthol.

[0044] Examples of the aromatic alcohol preferably include aromatic alcohols having 6 to 30 carbon atoms. The number of carbon atoms of the aromatic alcohol is preferably 6 to 20, and more preferably 6 to 18. Here, the aromatic alcohol is preferably a compound having a phenol skeleton (the number of carbon atoms is preferably 6 to 18) or a compound having a benzene diol skeleton (the number of carbon atoms is preferably 6 to 18). Preferred aromatic monoalcohols include thymol and tert-butylhydroxytoluene, which is an aromatic monoalcohol having a hindered structure. A preferred aromatic diol includes tert-butylhydroquinone, which is an aromatic diol having a hindered structure.

[0045] As the nitroaromatic alcohol, preferably a nitroaromatic alcohol having 6 to 30 carbon atoms can be mentioned. The number of carbon atoms of the nitroaromatic alcohol is preferably 6 to 20, more preferably 6 to 18. Here, the nitroaromatic alcohol is preferably a compound having a nitrophenol skeleton (that is, a nitroaromatic alcohol having 6 to 30 carbon atoms having a nitrophenol skeleton). As a preferable nitroaromatic alcohol, 4-nitrophenol can be mentioned.

[0046] As the haloaromatic alcohol, preferably a haloaromatic alcohol having 6 to 30 carbon atoms can be mentioned. The number of carbon atoms of the haloaromatic alcohol is preferably 6 to 20, more preferably 6 to 18. Here, the haloaromatic alcohol is preferably a compound having a halogenated phenol skeleton (that is, a haloaromatic alcohol having 6 to 30 carbon atoms having a halogenated phenol skeleton). The halogen is preferably chlorine. As a preferable haloaromatic alcohol, 4-chlorocresol can be mentioned.

[0047] The alcohol may be used alone or in combination of two or more.

[0048] (Urea) The urea used in this embodiment is not particularly limited as long as it can form a deep eutectic solvent with the other component. Examples include urea and the like. Here, the urea may be a derivative to which one or more substituents are added. The urea may be used alone or in combination of two or more.

[0049] (Azole) The azole used in this embodiment is not particularly limited as long as it can form a deep eutectic solvent with the other component. Examples include pyrazole, imidazole, thiazole, oxazole, isoxazole, and the like. Here, the azole may be a derivative to which one or more substituents are added. The azole may be used alone or in combination of two or more.

[0050] (Sugar) The sugar used in this embodiment is not particularly limited as long as it can form a deep eutectic solvent with the other component. Examples include monosaccharides, disaccharides, oligosaccharides, and the like. Specific examples of the sugar include sucrose, glucose, fructose, lactose, maltose, cellobiose, arabinose, ribose, ribulose, galactose, rhamnose, raffinose, xylose, mannose, trehalose, and the like. The sugar may be used alone or in combination of two or more.

[0051] (Amino acid) The amino acid used in this embodiment is not particularly limited as long as it can form a deep eutectic solvent with the other component. The amino acid may be a non-naturally occurring amino acid or a naturally occurring amino acid. For example, the amino acid may be an α-amino acid, β-amino acid, γ-amino acid, or δ-amino acid. Specific examples of the amino acid include γ-aminobutyric acid, alanine, β-alanine, glutamic acid, aspartic acid, asparagine, lysine, arginine, proline, threonine, and the like. The amino acid may be used alone or in combination of two or more.

[0052] <Combination of hydrogen bond donor and hydrogen bond acceptor> Examples of the combination of the hydrogen bond donor and the hydrogen bond acceptor include the following embodiments. It contains one or more selected from the group consisting of hydrogen bond donors: amines, amides, organic acids, and alcohols, and derivatives thereof. In this embodiment, among these compounds, it is preferable to use a compound having a proton dissociation energy of -400 kcal / mol or more. Specifically, one or more selected from the group consisting of heterocyclic aromatic amines, aromatic amines, aromatic amides, fatty acids, aromatic acids, alicyclic alcohols, and aromatic alcohols are preferable. The preferred embodiments of heterocyclic aromatic amines, aromatic amines, aromatic amides, fatty acids, aromatic acids, alicyclic alcohols, and aromatic alcohols are as described above. Hydrogen bond acceptors: It contains one or more selected from the group consisting of ketones, phosphine oxides, alcohols, and sulfoxides, and derivatives thereof. In this embodiment, among these compounds, it is preferable to use a compound having a proton affinity energy of -180 kcal / mol or less. Specifically, one or more selected from the group consisting of alicyclic ketones, aromatic lactones, trialkylphosphine oxides, alicyclic alcohols, aromatic alcohols, and diaryl sulfoxides are preferable. The preferred embodiments of alicyclic ketones, aromatic lactones, trialkylphosphine oxides, alicyclic alcohols, aromatic alcohols, and diaryl sulfoxides are as described above.

[0053] Here, the hydrogen bond donor and the hydrogen bond acceptor are different compounds from each other. Note that "different compounds from each other" means that even if a compound is classified as an alcohol, for example, it has a different structure from other compounds. For example, L-menthol and thymol are both compounds classified as alcohols, but thymol has a higher proton dissociation energy and lower stability than L-menthol. Therefore, when L-menthol and thymol are mixed, thymol acts as a hydrogen bond donor and L-menthol acts as a hydrogen bond acceptor. As a result, even when alcohols are mixed with each other, a deep eutectic solvent can be formed.

[0054] <Preferred Combinations of Hydrogen Bond Donors and Hydrogen Bond Acceptors> More preferred combinations of hydrogen bond donors and hydrogen bond acceptors include the following (1) to (22). In the following (1) to (22), the previously listed compound is the hydrogen bond donor and the subsequently listed compound is the hydrogen bond acceptor. (1) "Heterocyclic Aromatic Amine" and "Alicyclic Ketone" (2) "Heterocyclic Aromatic Amine" and "Aromatic Lactone" (3) "Heterocyclic Aromatic Amine" and "Trialkylphosphine Oxide" (4) "Heterocyclic Aromatic Amine" and "Alicyclic Alcohol" (5) "Heterocyclic Aromatic Amine" and "Aromatic Alcohol" (6) "Aromatic Amine" and "Alicyclic Ketone" (7) "Aromatic Amine" and "Aromatic Lactone" (8) "Aromatic Amine" and "Trialkylphosphine Oxide" (9) "Aromatic Amide" and "Trialkylphosphine Oxide" (10) "Fatty Acid" and "Trialkylphosphine Oxide" (11) "Fatty Acid" and "Alicyclic Alcohol" (12) "Aromatic Acid" and "Trialkylphosphine Oxide" (13) "Aromatic Alcohol" and "Alicyclic Ketone" (14) "Aromatic Alcohol" and "Trialkylphosphine Oxide" (15) "Alicyclic Alcohol" and "Alicyclic Ketone" (16) "Alicyclic Alcohol" and "Trialkylphosphine Oxide" (17) "Aromatic Alcohol" and "Alicyclic Alcohol" (18) "Aromatic Alcohol" and "Alicyclic Ketone" (19) "Aromatic Alcohol" and "Aromatic Lactone" (20) "Aromatic Alcohol" and "Trialkylphosphine Oxide" (21) "Aromatic Alcohol" and "Diaryl Sulfoxide" (22) "Heterocyclic aromatic amine" and " diaryl sulfoxide"

[0055] More preferable combinations of a hydrogen bond donor and a hydrogen bond acceptor include the following (1A) to (27A). In the following (1A) to (27A), the previously listed compound is the hydrogen bond donor and the subsequently listed compound is the hydrogen bond acceptor. (1A) "Heterocyclic aromatic amine having 4 to 30 carbon atoms" and "alicyclic ketone having 5 to 30 carbon atoms" (2A) "Heterocyclic aromatic amine having 4 to 30 carbon atoms" and " aromatic lactone having 5 to 30 carbon atoms" (3A) "Heterocyclic aromatic amine having 4 to 30 carbon atoms" and "trialkylphosphine oxide (the alkyl group has 1 to 30 carbon atoms)" (4A) "Heterocyclic aromatic amine having 4 to 30 carbon atoms" and "alicyclic alcohol having 5 to 30 carbon atoms" (5A) "Heterocyclic aromatic amine having 4 to 30 carbon atoms" and " aromatic alcohol having 6 to 30 carbon atoms" (6A) "Aromatic amine having 6 to 30 carbon atoms" and "alicyclic ketone having 5 to 30 carbon atoms" (7A) "Aromatic amine having 6 to 30 carbon atoms" and " aromatic lactone having 5 to 30 carbon atoms" (8A) "Aromatic amine having 6 to 30 carbon atoms" and "trialkylphosphine oxide (the alkyl group has 1 to 30 carbon atoms)" (9A) "Aromatic amide having 7 to 30 carbon atoms" and "trialkylphosphine oxide (the alkyl group has 1 to 30 carbon atoms)" (10A) "Fatty acid having 2 to 30 carbon atoms" and "trialkylphosphine oxide (the alkyl group has 1 to 30 carbon atoms)" (11A) "Fatty acid having 2 to 30 carbon atoms" and "alicyclic alcohol having 5 to 30 carbon atoms" (12A) "Aromatic acid having 7 to 30 carbon atoms" and "trialkylphosphine oxide (the alkyl group has 1 to 30 carbon atoms)" (13A) "Nitroaromatic alcohol having 6 to 30 carbon atoms" and "alicyclic ketone having 5 to 30 carbon atoms" (14A) "Nitroaromatic alcohols with 6 to 30 carbon atoms" and "Trialkylphosphine oxides (alkyl groups having 1 to 30 carbon atoms)" (15A) "Aromatic alcohols with 6 to 30 carbon atoms" and "Trialkylphosphine oxides (alkyl groups having 1 to 30 carbon atoms)" (16A) "Cycloaliphatic alcohols with 5 to 30 carbon atoms" and "Cycloaliphatic ketones with 5 to 30 carbon atoms" (17A) "Cycloaliphatic alcohols with 5 to 30 carbon atoms" and "Trialkylphosphine oxides (alkyl groups having 1 to 30 carbon atoms)" (18A) "Aromatic alcohols with 6 to 30 carbon atoms" and "Cycloaliphatic alcohols with 5 to 30 carbon atoms" (19A) "Aromatic alcohols with 6 to 30 carbon atoms" and "Cycloaliphatic ketones with 5 to 30 carbon atoms" (20A) "Aromatic alcohols with 6 to 30 carbon atoms" and "Aromatic lactones with 5 to 30 carbon atoms" (21A) "Aromatic alcohols with 6 to 30 carbon atoms" and "Trialkylphosphine oxides (alkyl groups having 1 to 30 carbon atoms)" (22A) "Aromatic diols with 6 to 30 carbon atoms" and "Trialkylphosphine oxides (alkyl groups having 1 to 30 carbon atoms)" (23A) "Halogenated aromatic alcohols with 6 to 30 carbon atoms" and "Cycloaliphatic alcohols with 5 to 30 carbon atoms" (24A) "Halogenated aromatic alcohols with 6 to 30 carbon atoms" and "Cycloaliphatic ketones with 5 to 30 carbon atoms" (25A) "Halogenated aromatic alcohols with 6 to 30 carbon atoms" and "Trialkylphosphine oxides (alkyl groups having 1 to 30 carbon atoms)" (26A) "Aromatic alcohols with 6 to 30 carbon atoms" and "Diaryl sulfoxides (aryl groups having 6 to 30 carbon atoms)" (27A) "Heterocyclic aromatic amines with 4 to 30 carbon atoms" and "Diaryl sulfoxides (aryl groups having 6 to 30 carbon atoms)"

[0056] More preferable combinations of a hydrogen bond donor and a hydrogen bond acceptor include the following (1B) to (27B). In the following (1B) to (27B), the previously listed compound is the hydrogen bond donor and the subsequently listed compound is the hydrogen bond acceptor. (1B) "A compound having 8 to 15 carbon atoms with an indole skeleton" and "An alicyclic ketone having 8 to 12 carbon atoms with a bicyclic structure" (2B) "A compound having 8 to 15 carbon atoms with an indole skeleton" and "A compound having 9 to 12 carbon atoms with a coumarin skeleton" (3B) "A compound having 8 to 15 carbon atoms with an indole skeleton" and "Trialkylphosphine oxide (the alkyl group has 4 to 16 carbon atoms)" (4B) "A compound having 8 to 15 carbon atoms with an indole skeleton" and "A compound having 8 to 12 carbon atoms with a cyclohexanol skeleton" (5B) "A compound having 8 to 15 carbon atoms with an indole skeleton" and "An aromatic alcohol having 6 to 30 carbon atoms" (6B) "A compound having 16 to 25 carbon atoms with a phenylnaphthylamine skeleton" and "An alicyclic ketone having 8 to 12 carbon atoms with a bicyclic structure" (7B) "A compound having 16 to 25 carbon atoms with a phenylnaphthylamine skeleton" and "A compound having 9 to 12 carbon atoms with a coumarin skeleton" (8B) "A compound having 16 to 25 carbon atoms with a phenylnaphthylamine skeleton" and "Trialkylphosphine oxide (the alkyl group has 4 to 16 carbon atoms)" (9B) "A compound having 8 to 15 carbon atoms with an acetanilide skeleton" and "Trialkylphosphine oxide (the alkyl group has 4 to 16 carbon atoms)" (10B) "A fatty acid having 8 to 16 carbon atoms" and "Trialkylphosphine oxide (the alkyl group has 4 to 16 carbon atoms)" (11B) "A fatty acid having 8 to 16 carbon atoms" and "A compound having 8 to 12 carbon atoms with a cyclohexanol skeleton" (12B) "An aromatic acid having 7 to 12 carbon atoms" and "Trialkylphosphine oxide (the alkyl group has 4 to 16 carbon atoms)" (13B) "Nitroaromatic alcohols with 6 to 30 carbon atoms having a phenol skeleton" and "alicyclic ketones with 8 to 12 carbon atoms having a bicyclic structure" (14B) "Nitroaromatic alcohols with 6 to 30 carbon atoms having a phenol skeleton" and "trialkylphosphine oxides (alkyl groups having 4 to 16 carbon atoms)" (15B) "Compounds with 6 to 18 carbon atoms having a phenol skeleton" and "trialkylphosphine oxides (alkyl groups having 4 to 16 carbon atoms)" (16B) "Compounds with 8 to 12 carbon atoms having a cyclohexanol skeleton" and "alicyclic ketones with 8 to 12 carbon atoms having a bicyclic structure" (17B) "Compounds with 8 to 12 carbon atoms having a cyclohexanol skeleton" and "trialkylphosphine oxides (alkyl groups having 4 to 16 carbon atoms)" (18B) "Compounds with 6 to 18 carbon atoms having a phenol skeleton" and "compounds with 8 to 12 carbon atoms having a cyclohexanol skeleton" (19B) "Compounds with 6 to 18 carbon atoms having a phenol skeleton" and "alicyclic ketones with 8 to 12 carbon atoms having a bicyclic structure" (20B) "Compounds with 6 to 18 carbon atoms having a phenol skeleton" and "compounds with 9 to 12 carbon atoms having a coumarin skeleton" (21B) "Compounds with 6 to 18 carbon atoms having a phenol skeleton" and "trialkylphosphine oxides (alkyl groups having 4 to 16 carbon atoms)" (22B) "Compounds with 6 to 18 carbon atoms having a benzenediol skeleton" and "trialkylphosphine oxides (alkyl groups having 4 to 16 carbon atoms)" (23B) "Halogenated aromatic alcohols with 6 to 30 carbon atoms having a halogenated phenol skeleton" and "compounds with 8 to 12 carbon atoms having a cyclohexanol skeleton" (24B) "Halogenated aromatic alcohols with 6 to 30 carbon atoms" and "alicyclic ketones with 8 to 12 carbon atoms having a bicyclic structure" (25B) "Halogenated aromatic alcohols with 6 to 30 carbon atoms" and "trialkylphosphine oxides (alkyl groups having 4 to 16 carbon atoms)" (26B) "Compound with 6 to 18 carbon atoms having a phenol skeleton" and "Diaryl sulfoxide (the carbon number of the aryl group is 6 to 10)" (27B) "Compound with 8 to 15 carbon atoms having an indole skeleton" and "Diaryl sulfoxide (the carbon number of the aryl group is 6 to 10)"

[0057] More preferable combinations of a hydrogen bond donor and a hydrogen bond acceptor include the following (1C) to (27C). In the following (1C) to (27C), the previously listed compound is the hydrogen bond donor, and the subsequently listed compound is the hydrogen bond acceptor. (1C) "Indole" and "Camphor" (2C) "Indole" and "Coumarin" (3C) "Indole" and "Trioctylphosphine oxide" (4C) "Indole" and "L-Menthol" (5C) "Indole" and "Thymol" (6C) "N-Phenyl-1-naphthylamine" and "Camphor" (7C) "N-Phenyl-1-naphthylamine" and "Coumarin" (8C) "N-Phenyl-1-naphthylamine" and "Trioctylphosphine oxide" (9C) "4'-Hydroxyacetanilide" and "Trioctylphosphine oxide" (10C) "Dodecanoic acid" and "Trioctylphosphine oxide" (11C) "Dodecanoic acid" and "L-Menthol" (12C) "Benzoic acid" and "Trioctylphosphine oxide" (13C) "4-Nitrophenol" and "Camphor" (14C) "4-Nitrophenol" and "Trioctylphosphine oxide" (15C) "tert-Butylhydroquinone" and "Trioctylphosphine oxide" (16C) "L-Menthol" and "Camphor" (17C) "L-Menthol" and "Trioctylphosphine oxide" (18C) "Thymol" and "L-menthol" (19C) "Thymol" and "camphor" (20C) "Thymol" and "coumarin" (21C) "Thymol" and "trioctylphosphine oxide" (22C) "tert-Butylhydroxytoluene" and "trioctylphosphine oxide" (23C) "4-Chlorocresol" and "L-menthol" (24C) "4-Chlorocresol" and "camphor" (25C) "4-Chlorocresol" and "trioctylphosphine oxide" (26C) "Thymol" and "diphenyl sulfoxide" (27C) "Indole" and "diphenyl sulfoxide"

[0058] <Content ratio of hydrogen bond donor and hydrogen bond acceptor> From the perspective of ease of adjusting the deep eutectic solvent, etc., the content ratio [hydrogen bond donor: hydrogen bond acceptor] of the hydrogen bond donor and the hydrogen bond acceptor in the deep eutectic solvent contained in the lubricant of this embodiment is preferably 1:0.4 to 1:2.5, more preferably 1:0.5 to 1:2.0, and still more preferably 1:0.6 to 1:1.6 in molar ratio.

[0059] [Manufacturing method of lubricant] The lubricant of this embodiment can be manufactured by mixing one or more selected from nonionic hydrogen bond donors and one or more selected from nonionic hydrogen bond acceptors to generate a deep eutectic solvent. Preferred embodiments of the nonionic hydrogen bond donor and the nonionic hydrogen bond acceptor are as described above. Moreover, the blending ratio [hydrogen bond donor: hydrogen bond acceptor] of one or more selected from nonionic hydrogen bond donors and one or more selected from nonionic hydrogen bond acceptors is preferably 1:0.4 to 1:2.5, more preferably 1:0.5 to 1:2.0, and still more preferably 1:0.6 to 1:1.6 in molar ratio.

[0060] [Physical properties of the lubricant] The lubricant of this embodiment preferably satisfies the following physical properties.

[0061] [Kinematic viscosity at 40°C] The lubricant of this embodiment preferably has a kinematic viscosity at 40°C of 1 mm 2 / s to 600 mm 2 / s, more preferably 2 mm 2 / s to 300 mm 2 / s, even more preferably 3 mm 2 / s to 100 mm 2 / s. In this specification, the kinematic viscosity at 40°C of the lubricant means the value measured in accordance with the "Test Method for Kinematic Viscosity of Petroleum Products" specified in JIS K2283:2000.

[0062] [Temperature at 50% mass loss] From the viewpoint of improving evaporation resistance and heat resistance, the lubricant of this embodiment preferably has a temperature at 50% mass loss of 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher. In this specification, the temperature at 50% mass loss of the lubricant means the value measured by the method described in the examples below.

[0063] [Metal corrosiveness] In the metal corrosiveness test of the lubricant of this embodiment by the method described in the examples below, it is preferably such that there is no discoloration or only slight discoloration to brown or black, and more preferably there is no discoloration.

[0064] [Uses of the lubricant] The lubricant of this embodiment is preferably used, for example, as a base material of a lubricant composition. Also, the lubricant of this embodiment is preferably used, for example, as an additive of a lubricant composition. Therefore, in this embodiment, the following aspects (1) and (2) are also provided. (1) A method of use in which the lubricant of this embodiment is used as a base material of a lubricant composition. (2) Method of using the lubricant of the present embodiment as an additive for a lubricant composition.

[0065] [Lubricant composition] The lubricant composition of the present embodiment contains the lubricant. The lubricant composition of the present embodiment may be composed only of the lubricant, or may contain other components other than the lubricant. Examples of other components include a base material and additives for lubricants.

[0066] [Base material] Examples of the base material include one or more selected from the group consisting of mineral oil and synthetic oil, which are base materials generally used in lubricant compositions. Examples of mineral oil include atmospheric residue obtained by atmospheric distillation of crude oil such as paraffinic crude oil, intermediate-base crude oil, and naphthenic crude oil; distillate oil obtained by vacuum distillation of these atmospheric residues; and mineral oil obtained by subjecting the distillate oil to one or more purification treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining. Examples of synthetic oil include polyalphaolefins such as α-olefin homopolymers and α-olefin copolymers (for example, α-olefin copolymers having 8 to 14 carbon atoms such as ethylene-α-olefin copolymers); isoparaffin; various esters such as polyol esters and dibasic acid esters; various ethers such as polyphenyl ether; polyalkylene glycol; alkylbenzene; alkylnaphthalene; and GTL base oil obtained by isomerizing wax (GTL wax (GasToLiquidsWAX)) produced from natural gas by the Fischer-Tropsch method or the like.

[0067] [Additives for lubricants] The lubricant composition of this embodiment may further contain an additive for lubricants. As the additive for lubricants, additives for lubricants generally used in lubricant compositions can be appropriately selected. For example, one or more selected from the group consisting of antioxidants, detergents, dispersants, friction modifiers, antiwear agents, extreme pressure agents, corrosion inhibitors, metal deactivators, rust preventives, antifoaming agents, viscosity index improvers, pour point improvers, demulsifiers, thickeners, and gelling agents can be mentioned. In addition, additives such as pour point depressants, viscosity index improvers, and antifoaming agents may be in the form of a solution diluted and dissolved in a part of the diluent oil such as the lubricant or other base materials in consideration of handleability and solubility in the base material. Here, the lubricant composition of this embodiment may be a lubricating oil composition. Also, when the lubricant composition contains a thickener, the lubricant composition may be a grease composition. That is, in this embodiment, a grease composition containing the lubricant and the thickener is also provided. Also, when the lubricant composition contains a gelling agent, the lubricant composition may be a gel composition. That is, in this embodiment, a gel composition containing the lubricant and the gelling agent is also provided.

[0068] The content of the base material in the lubricant composition is preferably 60% by mass or more, more preferably 65% by mass, still more preferably 70% by mass or more. Here, when the lubricant is used as the base material, the content of the lubricant in the base material is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 100% by mass, still more preferably 70% by mass to 100% by mass, even more preferably 80% by mass to 100% by mass, still more preferably 90% by mass to 100% by mass, still more preferably 95% by mass to 100% by mass, and most preferably the entire amount of the base material is the lubricant. The total content of the additives for lubricants is preferably 0.01% by mass to 40% by mass, more preferably 0.1% by mass to 35% by mass based on the total amount of the lubricant composition. When the lubricant is used as an additive, the content of the lubricant is preferably 0.01% by mass to 20% by mass, more preferably 0.05% by mass to 15% by mass, and still more preferably 0.1% by mass to 10% by mass based on the total amount of the lubricant composition.

[0069] [Use of the lubricant composition] The lubricant composition of the present embodiment can be applied to various fields. For example, it is suitable for internal combustion engines such as engines, torque transmission devices typified by fluid joints and automatic transmissions (AT: Automatic Transmission) or continuously variable transmissions (CVT: Continuously Variable Transmission), bearings (sliding bearings, rolling bearings, oil-impregnated or impregnated bearings, fluid bearings), compression devices such as compressors, chains, gears, hydraulic devices, vacuum pumps, watch parts, hard disks, aerospace equipment such as aircraft and artificial satellites, sealing devices, and motor equipment. It is also applicable to rolling devices such as ball screws and rolling guide surfaces, rotation transmission devices with built-in clutches, power steering devices, reciprocating compressors, and turbochargers. The lubricant composition of the present embodiment is further suitable as a metalworking oil (such as cutting, pressing, and forging), mold release agent, heat treatment agent, heat medium, coolant, rust inhibitor, buffer such as a damper, or an energized lubricant that requires conductivity.

Examples

[0070] The present invention will be specifically described by the following examples, but the present invention is not limited to the following examples.

[0071] [Measurement methods for various physical property values] The measurement methods for various physical property values in this example are as described below. (1) Kinematic viscosity It was measured in accordance with the "Test Method for Kinematic Viscosity of Petroleum Products" specified in JIS K2283:2000. (2) Temperature at 50% mass loss Using a differential thermal analyzer, the temperature was raised at a rate of 10 °C / min, and the temperature at which the mass decreased by 50% from the initial mass was measured. Note that the higher the 50% mass reduction temperature, the better the evaporation resistance and heat resistance.

[0072] [Production Examples 1 to 52] The first component and the second component were put into a beaker in the molar ratio shown in Table 2 and stirred using a stirring rod at room temperature (25 °C). After liquefaction, stirring was continued using a stirrer at room temperature for 1 hour to produce a deep eutectic solvent. However, for those that took time to become completely liquid, they were heated to 40 °C to 50 °C to promote liquefaction, and after returning to room temperature after the whole amount became liquid, they were stirred at room temperature for 1 hour to produce a deep eutectic solvent.

[0073] Table 1 shows the three states (visual confirmation) at room temperature, melting points (literature values), and 50% mass reduction temperatures of the raw materials (first component and second component) used in Production Examples 1 to 52. Table 2 also shows the proton dissociation energy and proton affinity energy of the raw materials (first component and second component) used in Production Examples 1 to 52. Note that all the raw materials shown in Table 1 are nonionic substances.

[0074] [Calculation method for proton dissociation energy and proton affinity energy of raw materials] Using Gaussian16 manufactured by Gaussian, a general-purpose quantum chemistry calculation program, as the calculation program, the structural optimization calculation of the hydrogen bond donor and hydrogen bond acceptor was performed under the following conditions, and then the binding energy between the parent compound and the proton (proton dissociation energy of the hydrogen bond donor, proton affinity energy of the hydrogen bond acceptor) was calculated. [Structural optimization calculation of hydrogen bond donor and hydrogen bond acceptor] All calculations were performed by DFT (density functional theory). At that time, the 6-31+G** basis function and the B3LYP functional were used, and the Grimme's D3 dispersion force correction was used to optimize the structural parameters such as the bond, angle, and dihedral angle of each isolated molecule assuming a vacuum state so that the total energy of the molecule was minimized. <Calculation of Binding Energy> Using Boys' Counterpoise method, the proton dissociation energy was calculated by dividing the parent compound into a proton and other sites. The proton had a charge of +1 and a multiplicity of 1, and the other sites had a charge of -1 and a multiplicity of 1, making the overall charge electrically neutral. The proton affinity energy was calculated by adding a proton to the parent compound, optimizing the structure with a total charge of +1 and a multiplicity of 1, then dividing it into a proton and other sites. The proton had a charge of +1 and a multiplicity of 1, and the other sites had a charge of 0 and a multiplicity of 1, and the binding energy was calculated.

[0075]

Table 1

[0076]

Table 2

[0077] The first component, the second component, and their ratios (first component: second component (molar ratio)) used in Production Examples 1 to 52 are shown in Table 3. Also shown in Table 3 are the three states (visual confirmation) at room temperature, kinematic viscosity, and 50% mass loss temperature of the produced deep eutectic solvents. In Table 3, the "first component" is the "hydrogen bond donor", and the "second component" is the "hydrogen bond acceptor".

[0078]

Table 3

[0079] [Preparation of Ionic Liquids 1 to 6] As comparative example compounds, the following ionic liquids 1 to 6 were prepared.

[0080] <Ionic Liquid 1> 1-Butylpyridinium bis(trifluoromethanesulfonyl)imide (manufactured by Tokyo Chemical Industry Co., Ltd.)

Chem.

[0081] <Ionic Liquid 2> 1,3-Dimethylimidazolium Dimethyl Phosphate (manufactured by Tokyo Chemical Industry Co., Ltd.)

Chem.

[0082] <Ionic Liquid 3> 1-Ethyl-3-methylimidazolium Tetrafluoroborate (manufactured by Tokyo Chemical Industry Co., Ltd.)

Chem.

[0083] <Ionic Liquid 4> Triethyl(octyl)phosphonium Bis(trifluoromethanesulfonyl)imide (manufactured by Tokyo Chemical Industry Co., Ltd.)

Chem.

[0084] <Ionic Liquid 5> 1-Butyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)imide (manufactured by Tokyo Chemical Industry Co., Ltd.)

Chem.

[0085] <Ionic Liquid 6> 1-Butyl-1-methylpyrrolidinium Tris(pentafluoroethyl)trifluorophosphate (manufactured by Merck KGaA)

Chem.

[0086] [Preparation of Deep Eutectic Solvents Containing Ionic Substances 1 to 4] As comparative example compounds, deep eutectic solvents containing ionic substances 1 to 4 were prepared according to the following Comparative Preparation Examples 1 to 4.

[0087] [Comparative Preparation Example 1: Preparation of Deep Eutectic Solvent Containing Ionic Substance 1] Malic acid (first component) and N,N,N-trimethylglycine (second component) were charged into a beaker at a molar ratio of 1:1 (first component: second component), and stirred using a stirring rod at 80 °C. After liquefaction, stirring was continued using a stirrer at 80 °C for 1 hour to produce a deep eutectic solvent containing ionic substance 1. Note that N,N,N-trimethylglycine is an amphoteric ionic substance having a betaine structure.

[0088] [Comparative Preparation Example 2: Preparation of Deep Eutectic Solvent Containing Ionic Substance 2] In Comparative Preparation Example 1, the first component was changed to glycerin, and the molar ratio was changed to 1:0.5 (first component: second component) to produce a deep eutectic solvent containing ionic substance 2.

[0089] [Comparative Preparation Example 3: Preparation of Deep Eutectic Solvent Containing Ionic Substance 3] In Comparative Preparation Example 1, the first component was changed to dodecanoic acid, and the second component was changed to tetrabutylammonium chloride to produce a deep eutectic solvent containing ionic substance 3. Note that tetrabutylammonium chloride is an ionic substance.

[0090] [Comparative Preparation Example 4: Preparation of Deep Eutectic Solvent Containing Ionic Substance 4] In Comparative Preparation Example 1, the first component was changed to glycerin, the second component was changed to choline chloride, and the molar ratio was changed to 1:0.69 (first component: second component) to produce a deep eutectic solvent containing ionic substance 4. Note that choline chloride is an ionic substance.

[0091] [Examples A1 to A27, Comparative Examples A1 to A10] Using the deep eutectic solvents made from nonionic substances, ionic liquids 1 to 6, and ionic substance-containing deep eutectic solvents 1 to 4 obtained in Production Examples 3, 4, 6, 10, 11, 13, 14, 15, 17, 19, 20, 22, 23, 25, 28, 31, 32, 35, 39, 43, 46, 47, 48, 49, 50, 51, and 52 as samples, the following evaluations were carried out.

[0092] <Evaluation 1: Metal Corrosion Resistance Test> The sample was applied to an iron substrate (iron content 96 mass% or more), allowed to stand at room temperature for 96 hours, and then the appearance of the iron substrate was observed. Based on the criteria shown below, the metal corrosion resistance was evaluated. · Evaluation A: No discoloration (no corrosion). · Evaluation B: Slight traces of discoloration are observed (slight corrosion). · Evaluation C: There is a brown or black discoloration (corrosion). · Evaluation D: There is rust-like deterioration (corrosion). In this example, Evaluations A and B were considered to pass. The results are shown in Tables 4 and 5.

[0093]

Table 4

[0094]

Table 5

[0095] From Tables 4 and 5, the following can be seen. As shown in Examples A1 to A27, it can be seen that the deep eutectic solvents made from nonionic substances are less likely to corrode metals. On the other hand, when using ionic liquids 1 to 6 of Comparative Examples A1 to A6 and ionic substance-containing deep eutectic solvents 1 to 4 of Comparative Examples A7 to A10, it can be seen that metals are likely to be corroded.

[0096] [Examples B1 to B14, Reference Examples B1 to B2] Using the deep eutectic solvents produced in Production Examples 3, 6, 13, 15, 19, 20, and 35 from nonionic substances, or lubricant compositions in which a friction reducer was blended in the deep eutectic solvent (the blending amount of the friction reducer was 1.0% by mass based on the total amount of the lubricant composition) as samples, the following evaluations were carried out. In addition, poly-α-olefin (PAO) was used as Reference Example B1, and a composition in which 1.0% by mass of a friction reducer was blended in poly-α-olefin was also examined as Reference Example B2. The friction reducer was the trioctylamine salt of oleyl phosphate.

[0097] <Evaluation 2: Friction Characteristic Test> Using a ball-on-disk type reciprocating friction tester (Baudend Levene type), a test was carried out under the conditions of a load of 7.5 N, a temperature of 100 °C, a sliding speed of 15 mm 2 / s, and an amplitude of 15 mm. The sliding was repeated 1200 times to measure the average coefficient of friction. As the ball, SUJ2 (φ = 10 mm, G20) was used, and as the disk, SUJ2 (Rz ≤ 1.0 μm) was used. It can be said that the smaller the coefficient of friction, the better the lubricity. Conversely, the larger the coefficient of friction, the better the power transmission property. The results are shown in Table 6.

[0098]

Table 6

Claims

1. A lubricant containing a deep eutectic solvent that is a mixed product of one or more selected from nonionic hydrogen bond donors and one or more selected from nonionic hydrogen bond acceptors.

2. The hydrogen bond donor has a proton dissociation energy of -400 kcal / mol or more, The hydrogen bond acceptor has a proton affinity energy of -180 kcal / mol or less. The lubricant according to claim 1.

3. The combination of the hydrogen bond donor and the hydrogen bond acceptor is a combination of two selected from the group consisting of amines, amides, ureas, azoles, organic acids, ketones, phosphine oxides, sulfoxides, sulfones, alcohols, sugars, and amino acids, and derivatives thereof. The lubricant according to claim 2.

4. The hydrogen bond donor includes one or more selected from the group consisting of amines, amides, organic acids, and alcohols, and derivatives thereof, The hydrogen bond acceptor includes one or more selected from the group consisting of ketones, phosphine oxides, alcohols, and sulfoxides, and derivatives thereof, The hydrogen bond donor and the hydrogen bond acceptor are different compounds from each other. The lubricant according to claim 2 or 3.

5. The molar ratio of the hydrogen bond donor to the hydrogen bond acceptor [the hydrogen bond donor: the hydrogen bond acceptor] is in the range of 1:0.4 to 1:2.

5. The lubricant according to any one of claims 1 to 4.

6. The lubricant according to any one of claims 1 to 5, having a kinematic viscosity at 40 °C of 1 mm ２ / s to 600 mm ２ / s.

7. The lubricant according to any one of claims 1 to 6, used as a base material of a lubricant composition.

8. The lubricant according to any one of claims 1 to 6, used as an additive of a lubricant composition.

9. A lubricant composition containing the lubricant according to any one of claims 1 to 8.

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