Lubricant and lubricant composition

Abstract

Disclosed is a lubricant that contains a deep eutectic solvent which is a mixture of one or more kinds selected from among nonionic hydrogen bond donors and one or more kinds selected from among nonionic hydrogen bond acceptors. With respect to the deep eutectic solvent, it is preferable that the proton dissociation energy of the hydrogen bond donor is − 400 kcal / mol or more, and the proton affinity energy of the hydrogen bond acceptor is − 180 kcal / mol or less.

Description

Lubricants and lubricant compositions

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

[0002] In recent years, research has been conducted into the application of ionic liquids composed of cations and anions to various applications, taking advantage of their excellent thermal stability (non-volatility, flame retardancy), high ionic density (high ionic conductivity), large heat capacity, and low viscosity. For example, Patent Document 1 proposes using ionic liquids as lubricating base oils.

[0003] International Publication No. 2005 / 035702

[0004] However, the ionic liquid disclosed in Patent Document 1 is unable to sufficiently inhibit metal corrosion. Because lubricants such as lubricating base oils often come into contact with metal surfaces, lubricants that are less likely to corrode metals are desired.

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

[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 for a lubricant composition. [3] The lubricant according to [1] above, used as an additive for a lubricant composition. [4] A lubricant composition containing the lubricant according to [1] above.

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

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

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

[0010] The present inventors conducted extensive research 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, the present inventors conducted various studies and discovered that there are deep eutectic solvents that are prone to corroding metals. Therefore, as a result of further extensive research, the present inventors discovered that a deep eutectic solvent that is a mixed product of one or more nonionic hydrogen bond donors and one or more nonionic hydrogen bond acceptors is less likely to corrode metals. After further extensive research, they completed the present invention. Below, each component contained in the lubricant of this embodiment will be described in detail.

[0011] <Deep eutectic solvent> A deep eutectic solvent is a mixture product obtained by mixing a hydrogen bond donor and a hydrogen bond acceptor. The melting point of a deep eutectic solvent is lower than the melting points of the hydrogen bond donor and hydrogen bond acceptor that constitute the deep eutectic solvent due to eutectic melting point depression. The melting point of a deep eutectic solvent may be lower than the melting points of the hydrogen bond donor and hydrogen bond acceptor that constitute the deep eutectic solvent. From the viewpoint of handling as a lubricant, it is preferably a liquid at 100°C, more preferably a liquid at 60°C, and even more preferably a 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 this embodiment, at least one (preferably both) of the melting points of the nonionic hydrogen bond donor and the nonionic hydrogen bond acceptor that constitute 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. The upper limit of these melting points is not particularly limited, but from the viewpoint of ease of generating a deep eutectic solvent, it is preferably 300° C. or less, more preferably 250° C. or less, and even more preferably 200° C. or less. One deep eutectic solvent may be used alone, or two or more deep eutectic solvents may be used in combination.

[0012] Here, the deep eutectic solvent contained in the lubricant of this embodiment is characterized in that it is a mixed product of one or more nonionic hydrogen bond donors and one or more nonionic hydrogen bond acceptors. That is, it is characterized in that both the hydrogen bond donors and the hydrogen bond acceptors are nonionic substances. When the deep eutectic solvent is a mixed product of one or more nonionic hydrogen bond donors and one or more nonionic hydrogen bond acceptors, it can be made less susceptible to metal corrosion. Deep eutectic solvents in which at least one of the hydrogen bond donors and hydrogen bond acceptors is a zwitterionic substance or ionic substance having a betaine structure or the like are prone to metal corrosion. Ionic liquids composed of cationic and anionic species are also prone to metal corrosion.

[0013] In this embodiment, the nonionic hydrogen bond donor has a proton dissociation energy of preferably -400 kcal / mol or more, more preferably -390 kcal / mol or more, and even more preferably -385 kcal / mol or more, from the viewpoint of facilitating the generation of a deep eutectic solvent by making it easier to donate hydrogen for forming a deep eutectic solvent. The proton dissociation energy is typically -320 kcal / mol or less. Furthermore, in this embodiment, the nonionic hydrogen bond acceptor has a proton affinity energy of preferably -180 kcal / mol or less, more preferably -190 kcal / mol or less, and even more preferably -195 kcal / mol or less, from the viewpoint of facilitating the generation of a deep eutectic solvent by making it easier to accept hydrogen for forming a deep eutectic solvent. The proton affinity energy is typically -280 kcal / mol or more.

[0014] In this specification, the term "proton dissociation energy" refers to 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 symbols in the above formula (1) have the following meanings: E(D−H ＋ ): Total energy value after structural optimization of hydrogen bond donor E(D-) + E(H ＋ ): The sum of the total energy of the hydrogen bond donor when it is divided into the proton and the other parts. Note that D means the hydrogen bond donor after removing the proton, and H means a hydrogen atom.

[0015] In addition, in this specification, the term "proton affinity energy" refers to the energy required for a proton to bond 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 symbols in the above formula (2) have the following meanings: E(A-H ＋): Total energy value when a proton is added to the hydrogen bond acceptor and structural optimization is performed. E(A) + E(H ＋ ): The sum of the total energy of the proton and other parts of the structure optimized by adding a proton to the hydrogen bond acceptor. Note that A represents the hydrogen bond acceptor, and H represents a hydrogen atom.

[0016] The proton dissociation energy and proton affinity energy can be calculated using general-purpose quantum chemistry calculation software (e.g., Gaussian 16 manufactured by Gaussian Corporation). Specifically, first, the total energy is minimized for 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. Next, the counterpoise method is used to calculate the bond energy between the compound (molecule) to be calculated and the proton, thereby allowing the calculation.

[0017] A preferred combination of a nonionic hydrogen bond donor and a nonionic hydrogen bond acceptor is a combination of two compounds selected from the group consisting of amines, amides, carbamides, azoles, organic acids, ketones, phosphine oxides, sulfoxides, sulfones, alcohols, sugars, and amino acids, and derivatives thereof. Among these, a combination of two compounds selected from the group consisting of amines, amides, organic acids, ketones, phosphine oxides, sulfoxides, and alcohols, and derivatives thereof, is preferred. Compounds that can be used as nonionic hydrogen bond donors or nonionic hydrogen bond acceptors are described in detail below.

[0018] (Definition) In the following description, the term "hydrocarbon group" refers to a group composed of carbon and hydrogen. The hydrocarbon group may have a chain structure, a cyclic structure, or a structure containing both a chain structure and a cyclic structure. Typical examples of hydrocarbon groups 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; alicyclic 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 prefixed with "aliphatic," "alicyclic," and "aromatic" refer to compounds having the above-mentioned aliphatic hydrocarbon group, the above-mentioned alicyclic hydrocarbon group, and the above-mentioned aromatic hydrocarbon group, respectively.

[0019] In the following description, the number of carbon atoms in the compounds exemplified as nonionic hydrogen bond donors and nonionic hydrogen bond acceptors means a value including the number of carbon atoms in 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, alicyclic amines, aromatic amines, and heterocyclic amines. The heterocyclic amine may be a heterocyclic alicyclic amine or a heterocyclic aromatic amine. The amine may be a derivative having one or more substituents added thereto. 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, and a hydroxyl group. When an amine derivative has a hydroxyl group, the derivative may also be classified as an alcohol, but in this specification, it is classified as an amine. When an amine derivative has a carboxyl group, the derivative may also be classified as an organic acid, but in this specification, it is classified as an amine. When an amine derivative has a carbonyl group, the derivative may also be classified as a ketone, but in this specification, it is classified as an amine.

[0021] Here, in this embodiment, from the viewpoint of ease of generating a deep eutectic solvent, etc., the amine is preferably a heterocyclic aromatic amine or an aromatic amine. Examples of heterocyclic aromatic amines include heterocyclic aromatic amines having 4 to 30 carbon atoms. The number of carbon atoms in heterocyclic aromatic amines is preferably 6 to 25, more preferably 7 to 20, and even more preferably 8 to 15. Examples of heterocyclic aromatic amines 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 (preferably having 8 to 15 carbon atoms) are preferred, and indole is more preferred.

[0022] Examples of aromatic amines include aromatic amines having 6 to 30 carbon atoms. The number of carbon atoms in the aromatic amine is preferably 10 to 30, more preferably 16 to 30, and even more preferably 16 to 25. Examples of aromatic amines 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 amines 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 amides, alicyclic amides, and aromatic amides. Here, the amide may be a derivative having one or more substituents added thereto. 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, and a hydroxyl group. Note that when an amide derivative has a hydroxyl group, the derivative may also be classified as an alcohol, but in this specification, it is classified as an amide. Furthermore, when an amide derivative has a carboxyl group, the derivative may also be classified as an organic acid, but in this specification, it is classified as an amide. Furthermore, when an amide derivative has a carbonyl group, the derivative may also be classified as a ketone, but in this specification, it is classified as an amide. Furthermore, when an amide derivative has an amino group, the derivative can also be classified as an amine, but in this specification it is classified as an amide.

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

[0026] The amides 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 is an organic acid capable of forming 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 having one or more substituents added thereto. Examples of the substituent include hydrocarbon groups, alkoxy groups (preferably having 1 to 10 carbon atoms), polyether groups, carbonyl groups, halogen groups, nitro groups, nitroso groups, thioether groups, thiocarbonyl groups, and hydroxyl groups. Note that when a derivative of an organic acid has a hydroxyl group, the derivative may also be classified as an alcohol, but in this specification, it is classified as an organic acid. Furthermore, when a derivative of an organic acid has a carbonyl group, the derivative may also be classified as a ketone, but in this specification, it is classified as an organic acid. Here, in this embodiment, fatty acids and aromatic acids are preferred as organic acids, from the perspective of ease of forming a deep eutectic solvent.

[0028] The fatty acid preferably includes a fatty acid 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 even 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, and hexadecanoic acid. Among these, dodecanoic acid is preferred.

[0029] The aromatic acid is preferably an aromatic acid having 7 to 30 carbon atoms. The number of carbon atoms in the aromatic acid is preferably 7 to 20, more preferably 7 to 16, and even more preferably 7 to 12. Examples of the aromatic acid include benzoic acid and phenylpropionic acid. Of these, benzoic acid is preferred.

[0030] The organic acids 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. Examples include ketones having a hydrocarbon group, such as aliphatic ketones, alicyclic ketones, and aromatic ketones. Ketones also include lactones, such as aromatic lactones and aromatic lactones having a hydrocarbon group. Here, the ketone may be a derivative having one or more substituents added thereto. 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, and a hydroxyl group. Note that when a ketone derivative has a hydroxyl group, the derivative may also be classified as an alcohol, but in this specification, it is classified as a ketone. Here, in this embodiment, alicyclic ketones and aromatic lactones are preferred as the ketone, from the perspective of ease of forming a deep eutectic solvent.

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

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

[0034] The ketones 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 is a phosphine oxide that can form a deep eutectic solvent with the other component. An example is trihydrocarbylphosphine oxide. The three hydrocarbon groups possessed by the trihydrocarbylphosphine oxide are preferably each independently the above-mentioned 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), and a polyether group. Here, in this embodiment, from the viewpoint of ease of forming a deep eutectic solvent, the phosphine oxide is preferably a trialkylphosphine oxide.

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

[0037] The phosphine oxides 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 is capable of forming a deep eutectic solvent with the other component. An example is dihydrocarbyl sulfoxide. The two hydrocarbon groups possessed by the dihydrocarbyl sulfoxide are each independently the above-mentioned aliphatic hydrocarbon group, alicyclic hydrocarbon group, or aromatic hydrocarbon group. 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), and a polyether group. In this embodiment, from the viewpoint of ease of forming a deep eutectic solvent, the sulfoxide is preferably a dialkyl sulfoxide or a diaryl sulfoxide. The two alkyl groups possessed by the dialkyl sulfoxide each independently have preferably 1 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, even more preferably 3 to 18 carbon atoms, and even more preferably 4 to 16 carbon atoms. A preferred example of such a dialkyl sulfoxide is didodecyl sulfoxide. The number of carbon atoms in the two aryl groups in the diaryl sulfoxide is each independently preferably 6 to 30, more preferably 6 to 20, and even more preferably 6 to 10. A preferred example of such a diaryl sulfoxide is diphenyl sulfoxide.

[0039] The sulfoxides 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. An example is dihydrocarbyl sulfone. The two hydrocarbon groups possessed by the dihydrocarbyl sulfone are each independently the above-mentioned aliphatic hydrocarbon group, alicyclic hydrocarbon group, or aromatic hydrocarbon group. Here, the sulfone may be a derivative to which one or more substituents have been added. Examples of the substituent include a hydrocarbon group, an alkoxy group (preferably having 1 to 10 carbon atoms), a polyether group, etc. Note that when a sulfone derivative has a hydroxyl group, the derivative may 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 a deep eutectic solvent, etc., the sulfone is preferably a dialkyl sulfone or a diaryl sulfone. The carbon number of the two alkyl groups possessed by the dialkyl sulfone is preferably 1 to 30, more preferably 2 to 20, even more preferably 3 to 18, and even more preferably 4 to 16. A preferred example of such a dialkyl sulfoxide is dioctyl sulfone. The number of carbon atoms in the two aryl groups of the diaryl sulfone is each independently preferably 6 to 30, more preferably 6 to 20, and even more preferably 6 to 10. A preferred example of such a diaryl sulfone is diphenyl sulfone.

[0041] The sulfones 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 is an alcohol that can form a deep eutectic solvent with the other component. Examples include aliphatic alcohols, alicyclic alcohols, and aromatic alcohols. The alcohol may be a monoalcohol, a diol, or a polyol such as a triol. Here, the alcohol may be a derivative having one or more substituents added thereto. Examples of the substituent include a hydrocarbon group, an alkoxy group, a polyether group, a halogen group, a nitroso group, a thioether group, and a thiocarbonyl group. Among these, from the viewpoint of ease of forming a deep eutectic solvent, alicyclic alcohols, aromatic alcohols, aromatic alcohols having a nitro group (hereinafter also referred to as "nitroaromatic alcohols"), and aromatic alcohols having a halogen group (hereinafter "halogen aromatic alcohols") are preferred.

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

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

[0045] The nitroaromatic alcohol preferably includes a nitroaromatic alcohol having 6 to 30 carbon atoms. The number of carbon atoms in 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 (i.e., a nitroaromatic alcohol having a nitrophenol skeleton and having 6 to 30 carbon atoms). A preferred example of the nitroaromatic alcohol is 4-nitrophenol.

[0046] The halogenated aromatic alcohol preferably includes a halogenated aromatic alcohol having 6 to 30 carbon atoms. The number of carbon atoms in the halogenated aromatic alcohol is preferably 6 to 20, more preferably 6 to 18. Here, the halogenated aromatic alcohol is preferably a compound having a halogenated phenol skeleton (i.e., a halogenated aromatic alcohol having a halogenated phenol skeleton and having 6 to 30 carbon atoms). The halogen is preferably chlorine. A preferred halogenated aromatic alcohol is 4-chlorocresol.

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

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

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

[0050] (Sugars) The sugars used in this embodiment are not particularly limited as long as they are capable of forming a deep eutectic solvent with the other component. Examples include monosaccharides, disaccharides, and oligosaccharides. Specific examples of sugars include sucrose, glucose, fructose, lactose, maltose, cellobiose, arabinose, ribose, ribulose, galactose, rhamnose, raffinose, xylose, mannose, and trehalose. One type of sugar may be used alone, or two or more types may be used in combination.

[0051] (Amino Acid) The amino acid used in this embodiment is not particularly limited as long as it is an amino acid that 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, a β-amino acid, a γ-amino acid, or a δ-amino acid. Specific examples of amino acids include γ-aminobutyric acid, alanine, β-alanine, glutamic acid, aspartic acid, asparagine, lysine, arginine, proline, and threonine. One type of amino acid may be used alone, or two or more types may be used in combination.

[0052] <Combination of Hydrogen Bond Donor and Hydrogen Bond Acceptor> Examples of combinations of hydrogen bond donors and hydrogen bond acceptors include the following. Hydrogen bond donor: Contains one or more compounds selected from the group consisting of amines, amides, organic acids, alcohols, and derivatives thereof. In this embodiment, it is preferable to use, among these compounds, compounds having a proton dissociation energy of -400 kcal / mol or more. Specifically, it is preferable to use, among these compounds, one or more compounds selected from the group consisting of heterocyclic aromatic amines, aromatic amines, aromatic amides, fatty acids, aromatic acids, alicyclic alcohols, and aromatic alcohols. 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 acceptor: Contains one or more compounds selected from the group consisting of ketones, phosphine oxides, alcohols, sulfoxides, and derivatives thereof. In this embodiment, it is preferable to use, among these compounds, compounds 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 preferred. 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. Note that "different compounds" means that, for example, compounds classified as alcohols have different structures. For example, L-menthol and thymol are both compounds classified as alcohols, but thymol has a higher proton dissociation energy and is less stable 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, a deep eutectic solvent can be produced.

[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 compound listed first is the hydrogen bond donor, and the compound listed second is the hydrogen bond acceptor. (1) "Heteroaromatic amine" and "alicyclic ketone" (2) "Heteroaromatic amine" and "aromatic lactone" (3) "Heteroaromatic amine" and "trialkylphosphine oxide" (4) "Heteroaromatic amine" and "alicyclic alcohol" (5) "Heteroaromatic 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 preferred combinations of hydrogen bond donors and hydrogen bond acceptors include the following (1A) to (27A), in which the first compound is the hydrogen bond donor and the second compound is the hydrogen bond acceptor. (1A) "C4-30 heterocyclic aromatic amine" and "C5-30 alicyclic ketone" (2A) "C4-30 heterocyclic aromatic amine" and "C5-30 aromatic lactone" (3A) "C4-30 heterocyclic aromatic amine" and "trialkylphosphine oxide (alkyl group has 1-30 carbon atoms)" (4A) "C4-30 heterocyclic aromatic amine" and "C5-30 alicyclic alcohol" (5A) "C4-30 heterocyclic aromatic amine" and "C6-30 aromatic alcohol" (6A) "C6-30 aromatic amine" and "C5-30 alicyclic ketone" (7A) "C6-30 aromatic amine" and "C5-30 aromatic lactone" (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 alcohol having 6 to 30 carbon atoms" and "trialkylphosphine oxide (the alkyl group has 1 to 30 carbon atoms)" (15A) "Aromatic diol having 6 to 30 carbon atoms" and "trialkylphosphine oxide (the alkyl group has 1 to 30 carbon atoms)" (16A) "Alicyclic alcohol having 5 to 30 carbon atoms" and "alicyclic ketone having 5 to 30 carbon atoms" (17A) "Alicyclic alcohol having 5 to 30 carbon atoms" and "trialkylphosphine oxide (the alkyl group has 1 to 30 carbon atoms)" (18A) "Aromatic alcohol having 6 to 30 carbon atoms" and "alicyclic alcohol having 5 to 30 carbon atoms"(19A) "Aromatic alcohol having 6 to 30 carbon atoms" and "alicyclic ketone having 5 to 30 carbon atoms" (20A) "Aromatic alcohol having 6 to 30 carbon atoms" and "aromatic lactone having 5 to 30 carbon atoms" (21A) "Aromatic alcohol having 6 to 30 carbon atoms" and "trialkylphosphine oxide (the alkyl group has 1 to 30 carbon atoms)" (22A) "Aromatic alcohol having 6 to 30 carbon atoms" and "trialkylphosphine oxide (the alkyl group has 1 to 30 carbon atoms)" (23A) "Halogenated aromatic alcohol having 6 to 30 carbon atoms" and "alicyclic alcohol having 5 to 30 carbon atoms" (24A) "Halogenated aromatic alcohol having 6 to 30 carbon atoms" and "alicyclic ketone having 5 to 30 carbon atoms" (25A) "Halogenated aromatic alcohol having 6 to 30 carbon atoms" and "trialkylphosphine oxide (the alkyl group has 1 to 30 carbon atoms)" (26A) "Heterocyclic aromatic amine having 4 to 30 carbon atoms" and "diaryl sulfoxide (the number of carbon atoms in the aryl group is 6 to 30)" (27A) "Aromatic alcohol having 6 to 30 carbon atoms" and "diaryl sulfoxide (the number of carbon atoms in the aryl group is 6 to 30)"

[0056] More preferred combinations of hydrogen bond donors and hydrogen bond acceptors include the following (1B) to (27B), in which the first listed compound is the hydrogen bond donor and the second listed compound is the hydrogen bond acceptor. (1B) "A compound having 8 to 15 carbon atoms and an indole skeleton" and "an alicyclic ketone having 8 to 12 carbon atoms and a bicyclic structure" (2B) "A compound having 8 to 15 carbon atoms and an indole skeleton" and "a compound having 9 to 12 carbon atoms and a coumarin skeleton" (3B) "A compound having 8 to 15 carbon atoms and an indole skeleton" and "a trialkylphosphine oxide (the alkyl group has 4 to 16 carbon atoms)" (4B) "A compound having 8 to 15 carbon atoms and an indole skeleton" and "a compound having 8 to 12 carbon atoms and a cyclohexanol skeleton" (5B) "A compound having 8 to 15 carbon atoms and an indole skeleton" and "aromatic alcohol having 6 to 30 carbon atoms" (6B) "A compound having 16 to 25 carbon atoms and a phenylnaphthylamine skeleton" and "an alicyclic ketone having 8 to 12 carbon atoms and a bicyclic structure" (7B) "C16-25 compound having a phenylnaphthylamine skeleton" and "C9-12 compound having a coumarin skeleton" (8B) "C16-25 compound having a phenylnaphthylamine skeleton" and "trialkylphosphine oxide (the alkyl group has 4-16 carbon atoms)" (9B) "C8-15 compound having an acetanilide skeleton" and "trialkylphosphine oxide (the alkyl group has 4-16 carbon atoms)" (10B) "C8-16 fatty acid" and "trialkylphosphine oxide (the alkyl group has 4-16 carbon atoms)" (11B) "C8-16 fatty acid" and "C8-12 compound having a cyclohexanol skeleton" (12B) "C7-12 aromatic acid" and "trialkylphosphine oxide (the alkyl group has 4-16 carbon atoms)" (13B) "Nitroaromatic alcohol having a phenol skeleton and 6 to 30 carbon atoms" and "alicyclic ketone having a bicyclic structure and 8 to 12 carbon atoms" (14B) "Nitroaromatic alcohol having a phenol skeleton and 6 to 30 carbon atoms" and "trialkylphosphine oxide (alkyl group has 4 to 16 carbon atoms)"(15B) "A compound having 6 to 18 carbon atoms and a benzenediol skeleton" and "a trialkylphosphine oxide (the alkyl group has 4 to 16 carbon atoms)" (16B) "A compound having 8 to 12 carbon atoms and a cyclohexanol skeleton" and "an alicyclic ketone having 8 to 12 carbon atoms and a bicyclic structure" (17B) "A compound having 8 to 12 carbon atoms and a cyclohexanol skeleton" and "a trialkylphosphine oxide (the alkyl group has 4 to 16 carbon atoms)" (18B) "A compound having 6 to 18 carbon atoms and a phenol skeleton" and "a compound having 8 to 12 carbon atoms and a cyclohexanol skeleton" (19B) "A compound having 6 to 18 carbon atoms and a phenol skeleton" and "an alicyclic ketone having 8 to 12 carbon atoms and a bicyclic structure" (20B) "A compound having 6 to 18 carbon atoms and a phenol skeleton" and "a compound having 9 to 12 carbon atoms and a coumarin skeleton" (21B) "C6-18 compound having a phenol skeleton" and "trialkylphosphine oxide (the alkyl group has 4-16 carbon atoms)" (22B) "C6-18 compound having a phenol skeleton" and "trialkylphosphine oxide (the alkyl group has 4-16 carbon atoms)" (23B) "C6-30 halogenated aromatic alcohol having a halogenated phenol skeleton" and "C8-12 compound having a cyclohexanol skeleton" (24B) "C6-30 halogenated aromatic alcohol" and "C8-12 alicyclic ketone having a bicyclic structure" (25B) "C6-30 halogenated aromatic alcohol" and "trialkylphosphine oxide (the alkyl group has 4-16 carbon atoms)" (26B) "C8-15 compound having an indole skeleton" and "diaryl sulfoxide (the aryl group has 6-10 carbon atoms)" (27B) "Compounds having a phenol skeleton and 6 to 18 carbon atoms" and "diaryl sulfoxides (aryl groups having 6 to 10 carbon atoms)"

[0057] More preferred combinations of hydrogen bond donors and hydrogen bond acceptors include the following (1C) to (27C), in which the first listed compound is the hydrogen bond donor and the second 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-dibutylhydroxytoluene and trioctylphosphine oxide (23C) 4-chlorocresol and L-menthol (24C) 4-chlorocresol and camphor (25C) "4-chlorocresol" and "trioctylphosphine oxide" (26C) "indole" and "diphenyl sulfoxide" (27C) "thymol" and "diphenyl sulfoxide"

[0058] <Ratio of Hydrogen Bond Donor to Hydrogen Bond Acceptor> From the viewpoint of ease of preparation of the deep eutectic solvent, the deep eutectic solvent contained in the lubricant of this embodiment preferably has a molar ratio of hydrogen bond donor to hydrogen bond acceptor [hydrogen bond donor:hydrogen bond acceptor] of 1:0.4 to 1:2.5, more preferably 1:0.5 to 1:2.0, and even more preferably 1:0.6 to 1:1.6.

[0059] [Method for Producing Lubricant] The lubricant of this embodiment can be produced by mixing one or more nonionic hydrogen bond donors with one or more nonionic hydrogen bond acceptors to form a deep eutectic solvent. Preferred embodiments of the nonionic hydrogen bond donors and nonionic hydrogen bond acceptors are as described above. The blending ratio of the one or more nonionic hydrogen bond donors to the one or more nonionic hydrogen bond acceptors [hydrogen bond donor:hydrogen bond acceptor] is preferably 1:0.4 to 1:2.5, more preferably 1:0.5 to 1:2.0, and even more preferably 1:0.6 to 1:1.6, in molar ratio.

[0060] [Physical Properties of Lubricant] The lubricant of the present 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 ~ 600 mm ２ / s, more preferably 2 mm ２ / s ~ 300 mm ２ / s, more preferably 3 mm ２ / s ~ 100 mm ２ In this specification, the 40°C kinematic viscosity of a lubricant refers to a value measured in accordance with the "Testing method for kinematic viscosity of petroleum products" specified in JIS K2283:2000.

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

[0063] <Metal Corrosion> In a metal corrosiveness test using the method described in the Examples below, the lubricant of the present embodiment preferably shows no discoloration or only slight discoloration to brown or black, and more preferably shows no discoloration.

[0064] [Uses of Lubricant] The lubricant of this embodiment is preferably used, for example, as a base material for a lubricant composition. The lubricant of this embodiment is also preferably used, for example, as an additive for a lubricant composition. Therefore, this embodiment also provides the following aspects (1) and (2). (1) A method of using the lubricant of this embodiment as a base material for a lubricant composition. (2) A method of using the lubricant of this embodiment as an additive for a lubricant composition.

[0065] [Lubricant Composition] The lubricant composition of this embodiment contains the lubricant. The lubricant composition of this embodiment may be composed only of the lubricant, or may contain other components in addition to the lubricant. Examples of other components include base materials other than the lubricant and lubricant additives other than the lubricant.

[0066] <Base Material> The base material may be one or more selected from the group consisting of mineral oils and synthetic oils, which are base materials generally used in lubricant compositions. Examples of the mineral oil include atmospheric residue obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate crude oil, and naphthenic crude oil; distillate obtained by vacuum distillation of these atmospheric residues; and mineral oil obtained by subjecting the distillate to one or more refining treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining. Examples of synthetic oils include poly-α-olefins 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); isoparaffins; various esters such as polyol esters and dibasic acid esters; various ethers such as polyphenyl ether; polyalkylene glycols; alkylbenzenes; alkylnaphthalenes; and GTL base oils obtained by isomerizing wax produced from natural gas by the Fischer-Tropsch process or the like (GTL wax (GasToLiquidsWAX)).

[0067] <Lubricant Additives> The lubricant composition of this embodiment may further contain a lubricant additive. Lubricant additives commonly used in lubricant compositions can be appropriately selected. Examples of the lubricant additive include one or more additives selected from the group consisting of antioxidants, detergents, dispersants, friction modifiers, antiwear agents, extreme pressure agents, corrosion inhibitors, metal deactivators, rust inhibitors, antifoaming agents, viscosity index improvers, pour point improvers, demulsifiers, thickeners, and gelling agents. 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 diluent oil such as the lubricant or another base material, taking into account handling properties and solubility in the base material. The lubricant composition of this embodiment may also be a lubricating oil composition. Furthermore, when the lubricant composition contains a thickener, the lubricant composition may be a grease composition. That is, this embodiment also provides a grease composition containing the lubricant and a thickener. Furthermore, when the lubricant composition contains a gelling agent, the lubricant composition may be a gel-like composition. That is, this embodiment also provides a gel composition containing the lubricant and gelling agent.

[0068] The content of the base material in the lubricant composition is preferably 60% by mass or more, more preferably 65% ​​by mass, and even more preferably 70% by mass or more. 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, even more preferably 70% by mass to 100% by mass, still more preferably 80% by mass to 100% by mass, even more preferably 90% by mass to 100% by mass, and even more preferably 95% by mass to 100% by mass, based on the total amount of the base material. It is even more preferable that the entire amount of the base material is the lubricant. The total content of the lubricant additives 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. Furthermore, when the lubricant is used as an additive, the content of the lubricant is preferably 0.01 mass % to 20 mass %, more preferably 0.05 mass % to 15 mass %, and even more preferably 0.1 mass % to 10 mass %, based on the total amount of the lubricant composition.

[0069] [Uses of Lubricant Composition] The lubricant composition of this embodiment can be applied to various fields. For example, it is suitable for internal combustion engines such as engines, torque transmission devices such as fluid couplings, automatic transmissions (ATs), and continuously variable transmissions (CVTs), bearings (slide bearings, rolling bearings, oil-impregnated or wetted bearings, fluid bearings), compression devices such as compressors, chains, gears, hydraulic devices, vacuum pumps, watch parts, hard disks, aerospace equipment such as aircraft and satellites, sealing devices, and motor equipment. It can also be applied to rolling devices such as ball screws and rolling guideways, rotation transmission devices with built-in clutches, power steering devices, reciprocating compressors, and turbochargers. The lubricant composition of the present embodiment is also suitable as a metal processing oil (for cutting, pressing, forging, etc.), a mold release agent, a heat treatment agent, a heat transfer medium, a coolant, a rust inhibitor, a buffer agent such as a damper, or an electrically conductive lubricant where electrical conductivity is required.

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

[0071] [Methods for measuring various physical properties] The methods for measuring various physical properties in the present examples are as follows. (1) Kinematic viscosity: Measured in accordance with the "Testing method for kinematic viscosity of petroleum products" specified in JIS K2283:2000. (2) 50% mass loss temperature: Using a differential thermal analyzer, the temperature was increased at a rate of 10°C / min, and the temperature at which the mass was reduced by 50% from the initial mass was measured. It can be said that the higher the 50% mass loss temperature, the more excellent the evaporation resistance and heat resistance.

[0072] [Production Examples 1 to 52] The first component and the second component were placed in a beaker in the molar ratios shown in Table 3 and stirred at room temperature (25°C) using a stirring rod. After liquefaction, the mixture was stirred at room temperature for 1 hour using a stirrer to produce a deep eutectic solvent. However, in cases where it took time for the entire amount to become liquid, the mixture was heated to 40°C to 50°C to promote liquefaction, and after the entire amount became liquid, the mixture was returned to room temperature and stirred at room temperature for 1 hour to produce a deep eutectic solvent.

[0073] The three states (visually confirmed), melting points (literature values), and 50% mass loss temperatures at room temperature of the raw materials (first component and second component) used in Production Examples 1 to 52 are shown in Table 1. The proton dissociation energies and proton affinity energies of the raw materials (first component and second component) used in Production Examples 1 to 52 are shown in Table 2. All of the raw materials shown in Table 1 are nonionic substances.

[0074] [Method for Calculating Proton Dissociation Energy and Proton Affinity Energy of Raw Materials] Using Gaussian 16, a general-purpose quantum chemistry calculation program manufactured by Gaussian Corporation, structural optimization calculations were performed on the hydrogen bond donor and hydrogen bond acceptor under the following conditions. The bond energies between the parent compound and the proton (proton dissociation energy of the hydrogen bond donor, proton affinity energy of the hydrogen bond acceptor) were then calculated. <Structural Optimization Calculations for Hydrogen Bond Donor and Hydrogen Bond Acceptor> All calculations were performed using DFT (density functional theory). The 6-31+G** and B3LYP functionals were used as basis functions, and Grimme's D3 dispersion force correction was used to optimize the structural parameters of each isolated molecule, such as bonds, angles, and dihedral angles, assuming a vacuum state, so as to minimize the total energy of the molecule. <Binding Energy Calculation> Using Boys' Counterpoise method, the proton dissociation energy was calculated by dividing the parent compound into protons and other moieties, with the protons having a charge of +1 and a multiplicity of 1, and the moieties other than the protons having a charge of -1 and a multiplicity of 1, resulting in overall electrical neutrality. The proton affinity energy was calculated by adding a proton to the parent compound, optimizing the structure so that the overall compound had a charge of +1 and a multiplicity of 1, and then dividing the parent compound into protons and other moieties, with the protons having a charge of +1 and a multiplicity of 1, and the moieties other than the protons having a charge of 0 and a multiplicity of 1, resulting in binding energy.

[0075]

[0076]

[0077] Table 3 shows the first component, second component, and their ratio (first component:second component (molar ratio)) used in Production Examples 1 to 52. Table 3 also shows the three states (visually confirmed) at room temperature, the kinematic viscosity, and the 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]

[0079] [Preparation of Ionic Liquids 1 to 6] The following ionic liquids 1 to 6 were prepared as comparative compounds.

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

[0081] <Ionic Liquid 2> 1,3-dimethylimidazolium dimethyl phosphate (Tokyo Chemical Industry Co., Ltd.)

[0082] <Ionic Liquid 3> 1-ethyl-3-methylimidazolium tetrafluoroborate (Tokyo Chemical Industry Co., Ltd.)

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

[0084] <Ionic Liquid 5> 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (Tokyo Chemical Industry Co., Ltd.)

[0085] <Ionic Liquid 6> 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (Merck)

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

[0087] Comparative Production Example 1: Production of Ionic Substance-Containing Deep Eutectic Solvent 1 Malic acid (first component) and N,N,N-trimethylglycine (second component) were placed in a beaker in a molar ratio of 1:1 (first component:second component) and stirred at 80°C using a stirring rod. After liquefaction, the mixture was stirred at 80°C using a stirrer for 1 hour to produce Ionic Substance-Containing Deep Eutectic Solvent 1. N,N,N-trimethylglycine is a zwitterionic substance having a betaine structure.

[0088] Comparative Production Example 2: Production of Ionic Substance-Containing Deep Eutectic Solvent 2 In Comparative Production 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 Ionic Substance-Containing Deep Eutectic Solvent 2.

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

[0090] Comparative Production Example 4: Production of Ionic Substance-Containing Deep Eutectic Solvent 4 In Comparative Production 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 Ionic Substance-Containing Deep Eutectic Solvent 4. Choline chloride is an ionic substance.

[0091] [Examples A1 to A27, Comparative Examples A1 to A10] The deep eutectic solvents produced from nonionic substances 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, ionic liquids 1 to 6, and ionic substance-containing deep eutectic solvents 1 to 4 were used as samples to carry out the following evaluations.

[0092] <Evaluation 1: Metal Corrosion Resistance Test> A sample was applied to an iron substrate (iron content of 96% by mass or more), and after leaving it to stand at room temperature for 96 hours, the appearance of the iron substrate was observed. Metal corrosion resistance was evaluated based on the following criteria: - Evaluation A: No discoloration (no corrosion). - Evaluation B: Slight traces of discoloration were observed (slight corrosion). - Evaluation C: Brown or black discoloration was observed (corrosion was observed). - Evaluation D: Rust-like deterioration was observed (corrosion was observed). In this example, evaluations A and B were considered to be acceptable. The results are shown in Tables 4 and 5.

[0093]

[0094]

[0095] Tables 4 and 5 reveal the following: As shown in Examples A1 to A27, deep eutectic solvents produced from nonionic substances are less likely to corrode metals. In contrast, when 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 were used, metals were more likely to be corroded.

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

[0097] <Evaluation 2: Frictional Characteristics Test> A ball-on-disk type reciprocating friction tester (Bauden-Leben type) was used, and the load was 7.5 N, the temperature was 100°C, and the sliding speed was 15 mm ２The test was conducted under conditions of 1 / s and an amplitude of 15 mm, with 1,200 reciprocating strokes, and the average coefficient of friction was measured. SUJ2 (φ=10 mm, G20) was used for the ball, and SUJ2 (Rz≦1.0 μm) was used for the disk. The smaller the coefficient of friction, the better the lubrication. Conversely, the larger the coefficient of friction, the better the power transmission. The results are shown in Table 6.

[0098]

Claims

1. A lubricant comprising a deep eutectic solvent which is a mixture 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 claim 1, wherein the hydrogen bond donor has a proton dissociation energy of -400 kcal / mol or more, and the hydrogen bond acceptor has a proton affinity energy of -180 kcal / mol or less.

3. The lubricant according to claim 2, wherein 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, carbamides, azoles, organic acids, ketones, phosphine oxides, sulfoxides, sulfones, alcohols, sugars, and amino acids, and derivatives thereof.

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

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

6. Dynamic viscosity at 40°C is 1mm ２ / s ~ 600mm ２ The lubricant according to any one of claims 1 to 5, wherein 7. The lubricant according to any one of claims 1 to 6, which is used as a base material for a lubricant composition.

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

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

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