Mixture of alkyl-substituted diphenyl ether compounds and lubricant

Abstract

The present invention is a mixture of alkyl-substituted diphenyl ether compounds, wherein the average number of alkyl groups added is 2-3.6, the proportion of alkyl-substituted diphenyl ether compounds having 0 or 1 added alkyl groups is 1 mol% or less, the proportion of alkyl-substituted diphenyl ether compounds having 2 added alkyl groups is 25 mol% or more, and the proportion of alkyl-substituted diphenyl ether compounds represented by formula (1) is 25 mol% or less. In formula (1), R1 and R2 are alkyl groups which may be the same or different from each other.

Description

Alkyl-substituted diphenyl ether compound mixture and lubricant

[0001] The present invention relates to a mixture of alkyl-substituted diphenyl ether compounds and a lubricant. This application claims priority to Japanese Patent Application No. 2024-027640, filed February 27, 2024, and the entire contents of said Japanese Patent Application are incorporated by reference.

[0002] Lubricants used in semiconductor manufacturing are desired to have low dust generation and low vapor pressure even in a vacuum. For example, Patent Document 1 discloses a technique of this type in which a lubricant having a surface tension (25°C) of 25 mN / m or more is used, and a vapor pressure (25°C) of 1×10 －５ Patent Document 1 (JP-A 2001-152175) describes alkyl-substituted diphenyl ether as a specific example of a low-dust-generating lubricating oil.

[0003] Patent Document 2 (Japanese Patent No. 5659422) discloses a lubricating oil containing an alkyl-substituted diphenyl ether composition, which has excellent heat resistance and little evaporation loss at high temperatures. The alkyl-substituted diphenyl ether composition contained in the lubricating oil of Patent Document 2 has a hydrocarbon group with 12 or 14 carbon atoms and has an added number of alkyl groups of 3.6 to 4.0.

[0004] JP 2001-152175 A Japanese Patent No. 5659422 A

[0005] In semiconductor manufacturing, lubricants with low vapor pressure are desired to maintain a clean working environment. Conventionally, fluorine-based lubricants have been widely used as such low vapor pressure lubricants. However, in light of social demands such as PFAS regulations, lubricants to replace fluorine-based lubricants are desired. As fluorine-free lubricants, lubricants composed of alkyl-substituted diphenyl ethers are known, as shown in Patent Documents 1 and 2. Such lubricants have high heat resistance and low vapor pressure, and are therefore used as lubricants for semiconductor manufacturing. However, with the recent advancement of high-vacuum technology in semiconductor manufacturing, there is a demand for lubricants that emit even less substances into clean environments.

[0006] An object of the present invention is to provide a lubricant containing an alkyl-substituted diphenyl ether that has a low vapor pressure and generates little outgassing, and to provide an alkyl-substituted diphenyl ether mixture that constitutes such a lubricant.

[0007] In the mixture of alkyl-substituted diphenyl ether compounds according to the present disclosure, the average number of added alkyl groups is 2 to 3.6, the proportion of alkyl-substituted diphenyl ether compounds having 0 or 1 added alkyl groups is 1 mol % or less, the proportion of alkyl-substituted diphenyl ether compounds having 2 added alkyl groups is 25 mol % or more, and the proportion of alkyl-substituted diphenyl ether compounds represented by formula (1) is 25 mol % or less. (In formula (1), R １ and R ２ are alkyl groups which may be the same or different.

[0008] A lubricant containing an alkyl-substituted diphenyl ether having a low vapor pressure and low outgassing is provided, as well as a mixture of alkyl-substituted diphenyl ethers that constitute such a lubricant.

[0009] 1 is an HPLC chart of the alkyl-substituted diphenyl ether mixture of Example 2. FIG. 2 is an HPLC chart of the alkyl-substituted diphenyl ether mixture of Example 2. １ 3 is a H-NMR chart of the alkyl-substituted diphenyl ether mixture of Example 2. １３ 4 is a GC-MS chart of the alkyl-substituted diphenyl ether mixtures of Example 6 and Comparative Example 1.

[0010] [Outline of the embodiment] First, embodiments of the mixture of alkyl-substituted diphenyl ether compounds according to the present disclosure will be listed and described. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more and B or less."

[0011] In the mixture of alkyl-substituted diphenyl ether compounds according to the present disclosure, the average number of added alkyl groups is 2 to 3.6, the proportion of alkyl-substituted diphenyl ether compounds having 0 or 1 added alkyl groups is 1 mol % or less, the proportion of alkyl-substituted diphenyl ether compounds having 2 added alkyl groups is 25 mol % or more, and the proportion of alkyl-substituted diphenyl ether compounds represented by formula (1) is 25 mol % or less. (In formula (1), R １ and R ２ are alkyl groups which may be the same or different.

[0012] Alkyl-substituted diphenyl ethers used as lubricants and their base oils are usually not composed of a single compound but are mixtures of multiple diphenyl ether compounds with different numbers and positions of alkyl groups added. Previous studies (e.g., Patent Document 2) have proposed that the number and distribution of alkyl groups added to the diphenyl ether skeleton should be within a specific range.

[0013]

[0003] With the aim of further reducing the vapor pressure and outgassing of lubricants composed of alkyl-substituted diphenyl ethers, the present inventors focused on the proportions and structures of the components of the alkyl-substituted diphenyl ether mixture obtained by alkyl substitution reaction (i.e., the compounds constituting the alkyl-substituted diphenyl ether mixture). As a result of extensive investigation, they found that a mixture of alkyl-substituted diphenyl ether compounds in which the average number of added alkyl groups is within a specific range, compounds with 0 or 1 added alkyl groups and compounds with 2 added alkyl groups are present in specific proportions, and the proportion of compounds having two alkyl groups on one benzene ring of the diphenyl ether is not more than a specific amount has low vapor pressure and generates little outgassing, leading to the completion of the present invention.

[0014] In the mixture of alkyl-substituted diphenyl ether compounds, the number average molecular weight of the mixture may be 330 to 1,800.

[0015] In the mixture of alkyl-substituted diphenyl ether compounds, the alkyl groups may have an average of 6 to 28 carbon atoms.

[0016] In the mixture of alkyl-substituted diphenyl ether compounds, the alkyl-substituted diphenyl ether compound having two added alkyl groups or the alkyl-substituted diphenyl ether compound having three added alkyl groups may be present in the largest proportion.

[0017] The mixture of alkyl-substituted diphenyl ether compounds has a kinematic viscosity at 40°C of 139 mm ２ / s or less.

[0018] The mixture of alkyl-substituted diphenyl ether compounds has a vapor pressure of 1.0×10 at 25° C. －６ Pa or less.

[0019] Lubricants according to the present disclosure may contain mixtures of the alkyl-substituted diphenyl ether compounds described above.

[0020] [Specific Example of Embodiment] The mixture of alkyl-substituted diphenyl ether compounds according to the present disclosure will be described more specifically. Hereinafter, the "mixture of alkyl-substituted diphenyl ether compounds" may be referred to as an "alkyl-substituted diphenyl ether mixture" or simply as a "mixture."

[0021] [Compounds Constituting the Alkyl-Substituted Diphenyl Ether Mixture] The mixture according to the present disclosure is a mixture of alkyl-substituted diphenyl ether compounds. Here, the alkyl-substituted diphenyl ether mixture is a mixture composed of alkyl-substituted diphenyl ethers and unsubstituted diphenyl ethers. In the case of a composition containing additives such as antioxidants in addition to alkyl-substituted diphenyl ethers, the portion composed solely of alkyl-substituted diphenyl ethers corresponds to the alkyl-substituted diphenyl ether mixture. Hereinafter, alkyl-substituted diphenyl ethers may be referred to as ADE.

[0022] The alkyl-substituted diphenyl ether mixture according to the present disclosure contains multiple types of alkyl-substituted diphenyl ether compounds that differ in the number and / or position of alkyl groups added. The number of alkyl groups added to the alkyl-substituted diphenyl ether compounds is not limited, and may be from 0 to 10. The alkyl-substituted diphenyl ether mixture may contain one or more compounds selected from the group consisting of a compound with zero alkyl groups added (hereinafter sometimes referred to as a non-adduct, diphenyl ether, or diphenyl oxide (DPO)), a compound with one alkyl group added (hereinafter sometimes referred to as a monoalkyl adduct), a compound with two alkyl groups added (hereinafter sometimes referred to as a dialkyl adduct), a compound with three alkyl groups added (hereinafter sometimes referred to as a trialkyl adduct), a compound with four alkyl groups added (hereinafter sometimes referred to as a tetraalkyl adduct), and a compound with five or more alkyl groups added. The number of alkyl groups added to the alkyl-substituted diphenyl ether compound is preferably 2 to 6, more preferably 2 to 5. If the number of alkyl groups added is within this range, the mixture tends to maintain a low vapor pressure and have a low viscosity.

[0023] The number of carbon atoms in the alkyl group of the alkyl-substituted diphenyl ether compound constituting the mixture is not particularly limited, but may be 6 to 28, preferably 6 to 24, and more preferably 12 to 20. The alkyl group may be a linear alkyl group or a branched alkyl group, and the same compound may contain both a linear alkyl group and a branched alkyl group. From the viewpoint of heat resistance, the alkyl group is preferably a linear alkyl group.

[0024] Specific examples of the alkyl group include linear alkyl groups such as hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, icosyl, docosyl, and tetracosyl groups. Examples of branched alkyl groups include alkyl groups such as a 1-methylundecyl group, a 1-ethyldecyl group, a 1-methyltridecyl group, a 1-ethyldodecyl group, a 1-methylpentadecyl group, a 1-ethyltetradodecyl group, a 1-methylheptadecyl group, a 1-ethyloctadecyl group, a 1-methylnonadecyl group, a 1-ethyloctadecyl group, a 2-ethylhexyl group, a 2-octyldodecyl group, a 2-decyltetradecyl group, a 2-dodecylhexadecyl group, a 1-butyl-1-methylpentyl group, a 1-butyl-1-methylheptyl group, a 1-methyl-1-pentyloctyl group, a 1-hexyl-1-methylnonyl group, a 1-heptyl-1-methyldecyl group, a 1-methyl-1-octylundecyl group, and a 1-decyl-1-methyltridecyl group.

[0025] [Alkyl-substituted diphenyl ether mixture] The following describes the composition and physical properties of the mixture as a whole, with respect to the mixture of alkyl-substituted diphenyl ether compounds.

[0026] As described above, the alkyl-substituted diphenyl ether mixture according to the present disclosure is a mixture of alkyl-substituted diphenyl ether compounds having different numbers of added alkyl groups. The average number of alkyl groups possessed by the compounds constituting the mixture is referred to as the average number of added alkyl groups of the mixture. The average number of added alkyl groups of the alkyl-substituted diphenyl ether mixture according to the present disclosure is 2 to 3.6, preferably 2.1 to 3.3. Within this range, the alkyl-substituted diphenyl ether mixture becomes liquid at room temperature (20°C) and has physical properties suitable for use as a base oil for lubricants. The method for calculating the average number of added alkyl groups is described in detail in the Examples.

[0027] The proportion of alkyl-substituted diphenyl ether compounds having 0 or 1 added alkyl groups relative to the total amount of the mixture is 1 mol% or less, preferably 0.6 mol% or less, more preferably 0.3 mol% or less, and particularly preferably 0 mol%. By keeping the non-adducts and monoalkyl adducts at 1 mol% or less, the amount of outgassing can be reduced. In this specification, the proportion of alkyl-substituted diphenyl ether compounds is a value measured by HPLC under the conditions shown in the Examples described later.

[0028] The proportion of the alkyl-substituted diphenyl ether compound having two added alkyl groups relative to the total amount of the mixture is 25 mol % or more, preferably 30 mol % or more, and more preferably 35 mol % or more. By having the alkyl-substituted diphenyl ether compound having two added alkyl groups present in a proportion of 25 mol % or more, it is believed that low viscosity can be maintained and low torque can be achieved when used as a lubricant.

[0029] In the alkyl-substituted diphenyl ether mixture according to the present disclosure, the proportion of alkyl-substituted diphenyl ether compounds having 0 or 1 added alkyl groups is 1 mol % or less, and the proportion of alkyl-substituted diphenyl ether compounds having 2 added alkyl groups is 25 mol % or more.

[0030] The proportion of the alkyl-substituted diphenyl ether compound represented by formula (1) relative to the total amount of the mixture is 25 mol% or less, preferably 20 mol% or less, and more preferably 15 mol% or less. The alkyl-substituted diphenyl ether compound represented by formula (1) is a dialkyl adduct, a compound in which two alkyl groups are added to one of the two aromatic rings of a diphenyl ether skeleton. The dialkyl adduct is composed of a compound in which one alkyl group is substituted on each of the two aromatic rings of a diphenyl ether and a compound in which two alkyl groups are substituted on one aromatic ring. By limiting the proportion of the compound in which two alkyl groups are substituted on one aromatic ring to 25 mol% or less, the vapor pressure can be reduced. It has previously been believed that the vapor pressure of an alkyl-substituted diphenyl ether correlates with the molecular weight of the alkyl-substituted diphenyl ether compound, and that the substitution position of the alkyl groups does not affect the vapor pressure. However, the present inventors surprisingly found that if the amount of a diphenyl ether compound having the structure of formula (1) present in a mixture is small, the vapor pressure decreases even if the number-average molecular weight of the mixture is the same. (In formula (1), R １ and R ２ are alkyl groups which may be the same or different.

[0031] R in the formula (1) １ and R ２ may be the alkyl group described above, and is preferably an alkyl group having 6 to 24 carbon atoms.

[0032] Furthermore, it is preferable that the proportion of the compound represented by formula (2) among the dialkyl adducts is 15 mol % or less. The alkyl-substituted diphenyl ether compound represented by formula (2) is a dialkyl adduct in which two alkyl groups are added to one aromatic ring of the diphenyl ether skeleton, the alkyl group added to the p-position is a branched alkyl group, and the shorter alkyl group in the branched chain is longer than or equal to the butyl group. When the proportion of such a compound is 15 mol % or less, it is believed that the vapor pressure can be reduced. (In formula (2), R ３ and R ４is an alkyl group, and R ３ and R ４ The shorter alkyl chain has 4 or more carbon atoms. ５ is an alkyl group.)

[0033] R in the formula (2) ３ , R ４ , and R ５ may be the alkyl group described above, and R ５ is preferably an alkyl group having 6 to 24 carbon atoms, and R ３ and R ４ The sum of the carbon numbers of R is preferably 5 to 23. ３ may be a methyl group, an ethyl group, or a propyl group, and R ４ may be a nonyl, decyl or undecyl group.

[0034] In the mixture, it is preferable that the proportion of alkyl-substituted diphenyl ether compounds having two added alkyl groups (dialkyl adducts) or alkyl-substituted diphenyl ether compounds having three added alkyl groups (trialkyl adducts) be the greatest. Within this range, a low vapor pressure can be achieved while maintaining a low viscosity. When the non-adducts and monoalkyl adducts are 1 mol % or less in the mixture and the proportion of dialkyl adducts or trialkyl adducts is the greatest, an alkyl-substituted diphenyl ether mixture can be obtained that has a kinematic viscosity suitable for use as a lubricant, a low vapor pressure, and low outgassing.

[0035] In the alkyl-substituted diphenyl ether mixture according to the present disclosure, the average number of carbon atoms in the alkyl group (the average number of carbon atoms in one alkyl group) is preferably 6 to 28. The average number of carbon atoms in the alkyl group is a real number representing the average number of carbon atoms per alkyl group in the alkyl-substituted diphenyl ether compounds contained in the alkyl-substituted diphenyl ether mixture. The average number of carbon atoms in the alkyl group can be measured by the method shown in the Examples below.

[0036] The lower limit of the average total carbon number of the alkyl groups in the alkyl-substituted diphenyl ether mixture of the present invention is 12 or more, preferably 24 or more, and more preferably 28 or more. The upper limit of the average total carbon number of the alkyl groups in the mixture is 100 or less, preferably 80 or less, more preferably 70 or less, and even more preferably 60 or less. The "total carbon number of the alkyl groups" means the sum of the carbon numbers of the alkyl groups in one molecule of the alkyl-substituted diphenyl ether compound contained in the alkyl-substituted diphenyl ether mixture. The "average total carbon number of the alkyl groups" means the average value of the total carbon numbers of the alkyl groups of the alkyl-substituted diphenyl ether compounds contained in the alkyl-substituted diphenyl ether mixture. The average total carbon number of the alkyl groups in the alkyl-substituted diphenyl ether mixture is a real number calculated by multiplying the average carbon number of the alkyl groups by the average number of additions.

[0037] The number average molecular weight of the alkyl-substituted diphenyl ether mixture according to the present disclosure is preferably about 330 to 1800, more preferably about 500 to 1200, and even more preferably about 500 to 1000. A large number average molecular weight tends to provide excellent heat resistance, but the kinematic viscosity tends to be excessively large. A small number average molecular weight tends to provide low kinematic viscosity, but the heat resistance tends to be poor. If the number average molecular weight is within the above range, an alkyl-substituted diphenyl ether mixture having low viscosity and excellent heat resistance can be obtained. In this specification, the number average molecular weight of the alkyl-substituted diphenyl ether mixture is determined by the following formula, as shown in the examples below: １ This is a value measured using H-NMR. Note that, hereinafter, the number average molecular weight may be simply referred to as "average molecular weight."

[0038] [Physical Properties of Alkyl-Substituted Diphenyl Ether Mixture] The viscosity of the alkyl-substituted diphenyl ether mixture according to the present disclosure is not limited as long as the effects according to the present disclosure can be obtained. ２ / s, and 50 to 130 mm ２ It is preferable that the kinematic viscosity at 100°C is 3 to 16 mm / s. ２ / s, and 8 to 16 mm ２ / s. The viscosity index (VI) is also not particularly limited, but may be 100 to 135, and preferably 110 to 135. When it is in this range, a lubricant with low evaporation and low outgassing can be obtained, while having an appropriate viscosity as a lubricant over a wide temperature range. The method for measuring the kinematic viscosity will be described in detail in the Examples.

[0039] The alkyl-substituted diphenyl ether mixture according to the present disclosure has a vapor pressure (Pa) at 25°C of 1.0 x 10 －６ Pa or less, and －７ The alkyl-substituted diphenyl ether mixture according to the present disclosure has an extremely low vapor pressure, and therefore can provide a lubricant that can suppress the dispersion of droplets even in a high vacuum environment and maintain a clean environment. The method for measuring the vapor pressure at 25°C is described in detail in the Examples.

[0040] The alkyl-substituted diphenyl ether mixture according to the present disclosure preferably has little outgassing. For example, when outgassing is measured by the method described in detail in the Examples, the area of ​​the chromatogram of the relevant part is 5.0×10 ８ Preferably, it is 1.0 x 10 or less. ８ The alkyl-substituted diphenyl ether mixture according to the present disclosure has an extremely low vapor pressure, and in addition, generates little outgassing, suppresses the dispersion of droplets even in a high vacuum environment, making it possible to provide a lubricant that can maintain a clean environment.

[0041] [Production Method] The method for producing the alkyl-substituted diphenyl ether mixture described above is not particularly limited, but it can be produced, for example, by the following production method.

[0042] Using aluminum chloride as a catalyst, a Friedel-Crafts reaction of diphenyl ether with an olefin or alkyl halide produces a mixture containing alkyl-substituted diphenyl ether compounds. Purification is then carried out. Light boiling components, such as unreacted raw materials, are removed by adsorption or distillation. Further distillation is repeated to obtain a mixture of alkyl-substituted diphenyl ether compounds according to the present disclosure.

[0043] More specifically, for example, aluminum chloride is added as a catalyst to diphenyl ether, and the mixture is heated to 80 to 130°C to uniformly dissolve the catalyst in the diphenyl ether. Then, while maintaining the temperature at 80 to 125°C, 1 to 4 equivalents of α-olefin per equivalent of diphenyl ether is added dropwise over 1 to 5 hours. After the dropwise addition is complete, the mixture is aged at 80 to 110°C for 5 to 90 minutes. The reaction mixture is allowed to cool naturally until it reaches room temperature. An alkali neutralizer is added and the mixture is stirred for about 30 minutes at 80 to 90°C, after which activated clay is added and the mixture is heated and stirred for 0.5 to 3 hours at 80 to 90°C. The mixture is then allowed to cool naturally to 30°C, filtered under reduced pressure, and then distilled under reduced pressure. The mixture is then heated at about 150 to 220°C, and aged for 1.0 x 10 minutes. －２ ~1.0 x 10 －４ The distillation is carried out once or multiple times under conditions of about 1.0×10 Pa. For this distillation, a conventional distillation method such as reduced pressure (headless distillation) or molecular distillation can be used, but molecular distillation is preferred. The distillation pressure is lower than the pressures conventionally used (1.0×10 －２ ~1.0 x 10 －４ Distillation at a pressure lower than usual makes it easier to obtain a mixture of alkyl-substituted diphenyl ether compounds according to the present disclosure.

[0044] [Lubricants] The alkyl-substituted diphenyl ether mixture according to the present disclosure can be suitably used as a lubricant (lubricating oil, grease, etc.). The alkyl-substituted diphenyl ether mixture according to the present disclosure can be used alone as a lubricant or in combination with other compounds or compositions as a base oil for a lubricant. In addition to the alkyl-substituted diphenyl ether mixture according to the present disclosure, the lubricant may contain synthetic oils such as mineral oil, α-olefin oligomer, polyol ester, diester, polyalkylene glycol, silicone oil, modified silicone oil, alkyl-substituted benzene oil, multiple alkylate cyclopentane oil, and silahydrocarbon oil, for example, to further improve its performance or, if necessary, to impart additional performance, provided that the effects of the present disclosure are not impaired. Furthermore, the lubricant may contain various additives, such as antioxidants, extreme pressure agents, friction modifiers, metal deactivators, antifoaming agents, thickeners, colorants, and thickeners, either alone or in combination.

[0045] As the additive, any antioxidant commonly used in lubricants can be used without particular limitation, such as phenolic compounds, amine compounds, phosphorus compounds, and sulfur compounds.

[0046] Examples of extreme pressure agents include phosphorus-based compounds and sulfur-based compounds. Examples of friction modifiers include molybdenum-based compounds such as molybdenum dithiocarbamate and fatty acid derivatives such as glycerin monostearate. Examples of metal deactivators include benzotriazole-based, tolyltriazole-based, thiadiazole-based, and imidazole-based compounds. Examples of antifoaming agents include polyacrylates and styrene ester polymers. Examples of thickeners include inorganic compounds such as metal soaps (e.g., lithium soap), silica, graphite, and clay (e.g., hectorite or bentonite), and organic compounds such as polyurea, polyether ether ketone (PEEK), polyphenyl sulfide (PPS), melamine cyanurate (MC), PTFE, polyester, and polyacrylic acid.

[0047] When a lubricant contains an alkyl-substituted diphenyl ether mixture according to the present disclosure, its content is not particularly limited, but is preferably about 50 to 100 mass% relative to the total mass of the lubricant. In this case, the content of additives and the like in the lubricant is preferably about 0 to 50 mass%. Within this range, a lubricant with low evaporation and low outgassing can be obtained.

[0048] Furthermore, the alkyl-substituted diphenyl ether mixture according to the present disclosure can also be used as an additive for a lubricant. In this case, the content of the alkyl-substituted diphenyl ether mixture is preferably about 1 to 49 mass% of the entire lubricant (total mass). Furthermore, the alkyl-substituted diphenyl ether mixture according to the present disclosure can be used as a component of a lubricant or grease used in a high-vacuum environment.

[0049] Lubricants containing alkyl-substituted diphenyl ether mixtures are suitable for use as bearing lubricating oils, grease base oils, refrigeration oils, sealing oils, etc. In particular, they are suitable for use as various lubricating oils used in high-vacuum environments, such as bearing oils (fluid bearing oils, oil-impregnated bearing oils), grease base oils, oil-impregnated plastic oils, gear oils, jet engine oils, heat-insulating engine oils, gas turbine oils, automatic transmission oils, vacuum pump oils, hydraulic fluids, and oils for driving members (guide rails, bearings, ball screws, etc.) in semiconductor manufacturing equipment and measuring devices.

[0050] EXAMPLES The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0051] [Preparation of Alkyl-Substituted Diphenyl Ether Mixture (Crude Mixture)] Diphenyl ether (Dow Chemical Japan) and aluminum chloride were added to a flask and stirred at 85°C. Next, olefin was added dropwise to the flask, and after the addition was completed, the mixture was stirred at 95°C for 1 hour. The mixture was allowed to cool to room temperature, followed by an adsorption treatment using activated clay and Kyoward (registered trademark). Next, low-boiling substances such as unreacted skeletal compounds were removed by overhead distillation (40 to 200 Pa), yielding ADEs 1 to 6. Table 1 shows the amounts (g) and types of diphenyl ether, olefin, and aluminum chloride charged.

[0052]

[0053] [Purification of Alkyl-Substituted Diphenyl Ether Mixture (Crude Mixture)] Alkyl-substituted diphenyl ether mixtures having various alkyl substitution ratios were obtained by distilling ADEs 1 to 6 under the following conditions: The distillation conditions used below were lower pressure than conventionally employed distillation conditions.

[0054] (1) Distillation of ADE-1 ADE-1 was distilled at 170°C, 1.0 x 10 －３ The distillate was subjected to molecular distillation at 150°C and 1.0 x 10 Pa to obtain a colorless, transparent liquid from which high molecular weight components had been removed. －３ The residue was subjected to molecular distillation at 160°C and 1.0 x 10 －３ The mixture was subjected to molecular distillation at 1000 kJ / cm² / min, yielding a colorless, transparent liquid as the distillate (Comparative Example 3) and a colorless, transparent liquid as the bottoms (Example 1).

[0055] (2) Distillation of ADE-2 and ADE-3 ADE-2 and ADE-3 were mixed at 50 wt% each and distilled at 1 × 10 －２ The mixture was subjected to molecular distillation at a pressure of 100 Pa or less and 180° C., and low molecular weight components were distilled off to obtain bottoms (Example 2). The mixture before molecular distillation was designated Comparative Example 4.

[0056] (3) Distillation of ADE-4 (Material A) ADE-4 was added to 1 x 10 －２ The mixture was subjected to molecular distillation at a pressure of 100 Pa or less and 215°C to remove low molecular weight components, thereby obtaining a pale yellow transparent liquid (Material A).

[0057] (4) Distillation of ADE-5-1 (Material B) ADE-5 was distilled at 320°C and 60 Pa to obtain a yellow transparent liquid as the bottoms from which low molecular weight components had been removed. －２ The mixture was subjected to molecular distillation at 220°C and a pressure of 0.1 Pa or less to obtain a pale yellow transparent liquid (Material B) from which high molecular weight components had been removed.

[0058] (5) Distillation of ADE-5-2 ADE-5 was distilled to 1.0 × 10 －２ The mixture was subjected to molecular distillation at 150°C or less and low molecular weight components were removed, to obtain a pale yellow liquid (Example 6).

[0059] [Preparation of Evaluation Samples] Example 1: The colorless, transparent liquid obtained as bottoms in (1) above was designated as Example 1. Example 2: The bottoms obtained in (2) above was designated as Example 2. Example 3: A liquid obtained by blending Example 1 and material B in a weight ratio of 50:50 was designated as Example 3. Example 4: A liquid obtained by blending Example 1 and material B in a weight ratio of 20:80 was designated as Example 4. Example 5: A liquid obtained by blending Example 1 and material A in a weight ratio of 35:65 was designated as Example 5. Example 6: The pale yellow liquid obtained as bottoms in (5) above was designated as Example 6. Comparative Example 1: ADE-5 was designated as Comparative Example 1. Comparative Example 2: ADE-6 was designated as Comparative Example 2. Comparative Example 3: The colorless, transparent liquid obtained as a fraction in (1) above was designated as Comparative Example 3. Comparative Example 4: A mixture of ADE-2 and ADE-3 at 50 wt % each, before molecular distillation, was designated as Comparative Example 4.

[0060] Composition analysis of alkyl-substituted diphenyl ether mixtures The alkyl-substituted diphenyl ether mixtures of Examples 1 to 6 and Comparative Examples 1 to 4 were subjected to composition analysis using HPLC and NMR. The results are shown in Table 2.

[0061]

[0062] The compositions of the mixtures shown in Table 2 were measured and calculated according to the following methods. The alkyl-substituted diphenyl ether mixtures of Examples 1 to 6 and Comparative Examples 1 to 4 were analyzed for the abundance ratio (mol %) of diphenyl ether compounds with different alkyl addition numbers, the average number of alkyl groups added, and the structure of the dialkyl adducts.

[0063] [Measurement and Calculation of Diphenyl Ether Compounds with Different Addition Numbers] 1. HPLC Analysis Diphenyl ether compounds with different molecular weights were separated using HPLC. The abundance ratio (mol %) of diphenyl ether compounds with different alkyl substitution numbers was calculated from the obtained peak areas. HPLC device: 1220 InfinityLC manufactured by Agilent Technologies Developing solvent: CHCl ３ : acetonitrile = 50:50 Column: TSKgel ODS-100V 5 μm 4.6 mm × 15 cm, manufactured by Tosoh Corporation Flow rate: 1.00 mL / min Detector: UV 254 nm

[0064] Figure 1 shows the results of HPLC analysis of the mixture of Example 2. Referring to Figure 1, peaks for dialkyl adducts were observed at retention times of 3.0 to 4.3 min, trialkyl adducts at 4.3 to 6.6 min, and tetraalkyl adducts at 6.6 to 10.0 min.

[0065] 2. NMR Analysis The synthesized mixture was identified using NMR. Measurements were performed using the following equipment and conditions: NMR equipment: JNM-ECX series FT NMR equipment, 400 MHz, manufactured by JEOL Ltd. Solvent: None Temperature: 70°C Measurement conditions: １ H-NMR: Number of scans: 8 times １３ C-NMR: Number of scans: 1024 times

[0066] (a) Confirmation of the number of alkyl additions This will be explained using Example 2 as an example. １ The overall view of H-NMR is shown in Figure 2. １ From the H-NMR chart, the peak integral ratios representing hydrogen atoms bonded to the aromatic ring, hydrogen atoms bonded to the benzyl carbon of the alkyl group, and hydrogen atoms bonded to the alkyl group excluding the benzyl carbon were calculated. １The a to c shown in the H-NMR chart correspond to the following: Hydrogen bonded to the aromatic ring: a is the integral ratio from 6.5 to 7.5 ppm (a is the reference, a = 1). Hydrogen bonded to the benzyl carbon of the alkyl group: b is the integral ratio from 2.2 to 3.4 ppm. Hydrogen bonded to the alkyl group excluding the benzyl position: c is the integral ratio from 0.7 to 1.7 ppm. Also, d is the number of protons in the added alkyl chain. For example, when 1-dodecene and 1-tetradecene are added, the average of the added alkyl chains is C １３ H ２７ Therefore, d = 27. The average number of alkyls added was calculated using the following formula: Average number of alkyls added = 10 x (b + c) / (b + c + a x d)

[0067] (b) Analysis of the structure of the dialkyl adduct The dialkyl adduct in the mixture was separated by the above-mentioned HPLC. The obtained dialkyl adduct components were １３ The dialkyl adduct component separated from the mixture of Example 2 was measured by C-NMR. １３ The C-NMR chart is shown below. １３ From the C-NMR chart, the integral ratios of the peaks representing "the carbon atom adjacent to the carbon atom bonded to the oxygen atom of ADE having two alkyl groups attached to one benzene ring" and "the carbon atom adjacent to the carbon atom bonded to the oxygen atom of ADE having one alkyl group attached to each of the two benzene rings" were calculated. - Carbon atom adjacent to the carbon atom bonded to the oxygen atom of ADE having two alkyl groups attached to one of the benzene rings: A1 (158 to 160 ppm) + A3 (152 to 154 ppm) - Carbon atom adjacent to the carbon atom bonded to the oxygen atom of ADE having one alkyl group attached to each of the two benzene rings: A2 (154 to 157 ppm) - Proportion of alkyl added to one of the aromatic rings in the dialkyl adduct (S1) = (A1 + A3) / (A1 + A2 + A3) - Proportion of compound of the following general formula (1) (alkyl-substituted diphenyl ether compound having an alkyl group attached to one of the aromatic rings) in the mixture = Proportion of dialkyl adduct × (S1) (In formula (1), R １ and R ２are alkyl groups which may be the same or different.

[0068] [Analysis of physical properties of alkyl-substituted diphenyl ether mixtures] The alkyl-substituted diphenyl ether mixtures of Examples 1 to 6 and Comparative Examples 1 to 4 were subjected to measurements of vapor pressure at 25°C, kinematic viscosity (40°C and 100°C), viscosity index, and outgassing. The results are summarized in Table 2. Each measurement was performed according to the following procedure.

[0069] (a) Vapor pressure at 25°C Using a thermogravimetric simultaneous analyzer (STA7200RV manufactured by Hitachi High-Tech Science), the amount of evaporation was measured under the following conditions, and the vapor pressure of the measurement sample at 25°C was calculated using equations 1 to 3. Test container: AL deep dish pan Sample amount: 5 mg Gas flow rate: N ２ 100 mL / min Measurement temperature: Constant temperature measurement at four temperatures (varies depending on the measurement sample) Measurement time: 4 hours The measurement temperature is the lowest temperature T at which the weight loss (evaporation amount) at the end of the measurement is 3 to 20%. １ As such, T １ The three temperatures were increased by 10°C from T ２ =T １ +10°C, T ３ =T １ +20°C, T ４ =T １ The evaporation rate per unit area was calculated using Equation 1 from the slope at an evaporation rate of 2-3%. The calculated evaporation rate A was substituted into Equation 2 to obtain T １ ~T ４ The vapor pressure p was calculated at 1000 kJ / cm2. The same calculation was performed for each measurement sample.

[0070] p: vapor pressure [Pa], U: cross-sectional area of ​​sample pan [m ２ ], m: weight [kg], t: time [s], A: evaporation rate [kg・s －１ ・m －２ ] α: Coagulation coefficient (3.9×10 －５ where T is temperature [K], R is gas constant [J mol －１ ・K －１ ], M: molecular weight [g / mol －１] Note that the coagulation coefficient is 1 in an absolute vacuum, but in this measurement, a substance with a known vapor pressure was measured using this method to calculate p × α, and α was obtained by dividing the calculated value by the known vapor pressure value.

[0071] The obtained T １ ~T ４ The relationship between the reciprocal of absolute temperature and the common logarithm of vapor pressure was plotted to create an approximate curve of the points, and the vapor pressure at 25°C was extrapolated using Equation 3. P: vapor pressure [Pa], T: temperature [K], B: slope of the approximate line, C: intercept of the approximate line

[0072] (b) Kinematic Viscosity and Viscosity Index The kinematic viscosity and viscosity index (VI) of the resulting mixtures and compositions were measured in accordance with JIS K 2283.

[0073] (c) Measurement of Outgassing Amount Using a gas chromatograph mass spectrometer (GC-MS), the outgassing amount of the measurement sample was calculated from the peak area (A+B) obtained under the following conditions. * Apparatus: Gas chromatograph mass spectrometer manufactured by Agilent Technologies (5977B / MS, 7890B / GC) * Collection conditions * Collection method: Dynamic headspace method * Collection tube / purge gas: Tenax TA (manufactured by Gerstel) / inert gas * Heating temperature / heating time / collection time / purge gas amount: 150°C / 60 minutes / 10 minutes / 1000 mL * GC conditions * Injection method: Splitless * Column: DB-1 (60 m x 0.25 mm x 0.25 μm) manufactured by Agilent Technologies * Temperature range: 40°C (5 minutes) - 300°C * Heating rate: 10°C / minute A (retention time 20 to 22 minutes) indicates the outgassed component of the non-adduct. The area of ​​this portion of the chromatogram was evaluated as the amount of outgassing. B (retention time 30-36 minutes) indicates the outgassed component of the monoalkyl adduct. The area of ​​this portion of the chromatogram was evaluated as the amount of outgassing.

[0074] 4 shows the gas chromatograph mass spectrometer charts for Comparative Example 1 and Example 6. The amounts of outgassing were evaluated in the same manner for Examples 1 to 6 and Comparative Examples 1 to 4.

[0075] As shown in Table 2, all of Examples 1 to 6, which are mixtures of alkyl-substituted diphenyl ether compounds according to the present disclosure, have a vapor pressure of 1.0 × 10 at 25°C. －６ The outgassing amount is 5.0×10 ８ The kinematic viscosity at 40°C was 139 mm ２ / s or less.

[0076] In contrast, Comparative Examples 1 and 4, in which the proportion of alkyl-substituted diphenyl ether compounds having 0 or 1 added alkyl groups exceeded 1 mol %, exhibited large amounts of outgassing. Comparative Example 2, in which the average alkyl addition number was greater than 3.6 and the proportion of alkyl-substituted diphenyl ether compounds having 2 added alkyl groups was less than 25 mol %, exhibited large amounts of outgassing and a high kinematic viscosity at 40° C. Comparative Example 3, in which the proportion of the compound represented by formula (1) exceeded 25 mol %, exhibited high vapor pressure.

[0077] A comparison of Example 1 with Comparative Example 3 confirmed that the proportion of the compound represented by formula (1) affects the vapor pressure. A comparison of Examples 3 to 6 with Comparative Example 1 and a comparison of Example 2 with Comparative Example 4 suggested that the proportions of the non-adduct and monoalkyl adduct affect the amount of outgassing. A comparison of Example 2 with Comparative Example 2 suggested that when the average alkyl addition number is 3.6 or less and the proportion of the alkyl-substituted diphenyl ether compound is 25 mol% or more, the 40°C kinematic viscosity and 100°C kinematic viscosity are low, resulting in good lubricity. From the above, it was confirmed that in order to obtain a lubricant containing an alkyl-substituted diphenyl ether that has good lubricity, low vapor pressure, and little outgassing, in addition to the average alkyl addition number, the proportions of the non-adduct, monoalkyl adduct, and dialkyl adduct, and the proportion of the compound represented by formula (1), must be within predetermined ranges.

[0078] [Preparation of Lubricant (Grease)] The alkyl-substituted diphenyl ether mixture of Example 2 and a thickener were stirred in a centrifugal mixer (THINKY Corporation, Awatori Rentaro AR-100) to obtain off-white greases 1 to 6. The resulting greases were evaluated for the following physical properties. The mixing ratios of each material and the measurement results are shown in Table 3. In Table 3, blank spaces indicate that the corresponding component was not added, and "-" indicates that no measurement was performed. (Thickeners) PTFE1: Dyneon TF-9207Z manufactured by 3M PTFE2: TLP-10F-1 manufactured by Chemors Corporation PEEK: KETASPIRE KT-820 UFP manufactured by Solvay Specialty Polymers Japan Ltd. MC1: MC-4000 manufactured by Nissan Chemical Industries, Ltd. MC2: MC-6000 manufactured by Nissan Chemical Industries, Ltd. PPS: Ryton M1100 UFP manufactured by Solvay Specialty Polymers Japan Ltd. [Evaluation of Lubricant (Grease)] The consistency was measured in accordance with JIS K2220 using a consistency tester (RPM-201 manufactured by Rigo Co., Ltd.). The oil separation rate was measured in accordance with JIS K2220 Method B using a wire mesh cone filter (manufactured by Rigo Co., Ltd.). Dropping points were measured in accordance with JIS K2220 using a Mettler Toledo DP70 automatic dropping point and softening point apparatus. The coefficient of friction was measured using an Optimol SRV tester under the following conditions: average values ​​between 3000 and 3600 s. Samples were prepared by applying 0.1 g of grease to an SUJ2 disc. Stroke: 4 mm Load / frequency / time: (Run-in) 1 N / 1 Hz / 60 s, (Main operation) 10 N / 1 Hz / 3600 s Temperature: 25°C / 100°C Material and size: SUJ2 Φ10 mm ball, Φ24 x 7.9 mm disc. Vapor pressure and outgassing at 25°C were measured using the same methods as in the physical property analysis of the alkyl-substituted diphenyl ether mixture described above.

[0079]

[0080] As shown in Table 3, it was confirmed that lubricants containing the alkyl-substituted diphenyl ether mixture according to the present disclosure had good consistency and other evaluation results. Furthermore, because the vapor pressure of the base oil is low, lubricants for which the vapor pressure and outgassing amount were not measured are also presumed to have low volatility and low outgassing properties, similar to other lubricants. It was confirmed that the lubricants according to the present disclosure have the same consistency, oil separation, dropping point, and friction coefficient as conventional lubricants, and also have lower volatility and lower outgassing properties than conventional lubricants.

[0081] The present invention is intended to cover a wide range of applications, including those related to the present invention, including those related to the present invention.

[0082] The aspects of the present invention are further described with reference to the following numbered items: [1] A mixture of alkyl-substituted diphenyl ether compounds, wherein the average number of added alkyl groups is 2 to 3.6, the proportion of alkyl-substituted diphenyl ether compounds having 0 or 1 added alkyl groups is 1 mol % or less, the proportion of alkyl-substituted diphenyl ether compounds having 2 added alkyl groups is 25 mol % or more, and the proportion of alkyl-substituted diphenyl ether compounds represented by the following formula (1) is 25 mol % or less: (In formula (1), R １ and R ２are alkyl groups which may be the same or different.) [2] The mixture of alkyl-substituted diphenyl ether compounds according to [1], wherein the number average molecular weight of the mixture is 330 to 1,800. [3] The mixture of alkyl-substituted diphenyl ether compounds according to [1] or [2], wherein the average number of carbon atoms in the alkyl groups is 6 to 28. [4] The mixture of alkyl-substituted diphenyl ether compounds according to any one of [1] to [3], wherein the mixture contains the largest proportion of alkyl-substituted diphenyl ether compounds having two added alkyl groups or alkyl-substituted diphenyl ether compounds having three added alkyl groups. [5] The mixture of alkyl-substituted diphenyl ether compounds having a kinematic viscosity at 40°C of 139 mm ２ [6] The mixture of alkyl-substituted diphenyl ether compounds according to any one of [1] to [4], wherein the vapor pressure at 25°C is 1.0 x 10 / s or less. －６ [7] A lubricant comprising the mixture of alkyl-substituted diphenyl ether compounds according to any one of [1] to [6], wherein the mixture has a viscosity of 100 Pa or less.

Claims

1. A mixture of alkyl-substituted diphenyl ether compounds, wherein the average number of added alkyl groups is 2 to 3.6, the proportion of alkyl-substituted diphenyl ether compounds having 0 or 1 added alkyl groups is 1 mol% or less, the proportion of alkyl-substituted diphenyl ether compounds having 2 added alkyl groups is 25 mol% or more, and the proportion of alkyl-substituted diphenyl ether compounds represented by the following formula (1) is 25 mol% or less. (In formula (1), R １ and R ２ are alkyl groups which may be the same or different.

2. The mixture of alkyl-substituted diphenyl ether compounds according to claim 1, wherein the number average molecular weight of the mixture is 330 to 1,800.

3. The mixture of alkyl-substituted diphenyl ether compounds according to claim 1 or 2, wherein the alkyl group has an average carbon number of 6 to 28.

4. A mixture of alkyl-substituted diphenyl ether compounds according to claim 1 or 2, wherein the mixture contains the highest proportion of alkyl-substituted diphenyl ether compounds having two added alkyl groups or alkyl-substituted diphenyl ether compounds having three added alkyl groups.

5. The kinematic viscosity at 40°C is 139 mm ２ 3. The mixture of alkyl-substituted diphenyl ether compounds according to claim 1 or claim 2, wherein the alkyl-substituted diphenyl ether compound has a molecular weight of 1 / s or less.

6. The vapor pressure at 25°C is 1.0 x 10 －６ 3. The mixture of alkyl-substituted diphenyl ether compounds according to claim 1 or claim 2, wherein the viscosity of the mixture is 100 MPa or less.

7. A lubricant comprising the mixture of alkyl-substituted diphenyl ether compounds according to claim 1 or claim 2.

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