Dinaphthyl ether compound and lubricating oil composition containing the same

Abstract

One aspect of the present invention relates to a dinaphthyl ether compound represented by formula (1). #imgabs0# In formula (1), R 1 and R 2 are the same or different and are linear or branched hydrocarbon groups having 6 to 32 carbon atoms; m and n are real numbers greater than or equal to 0, and satisfy 1.0≤m+n≤3.0.

Description

Technical Field

[0001] The present invention relates to a dinaphthyl ether compound and a lubricating oil composition containing the dinaphthyl ether compound. Background Art

[0002] Lubricating oils and lubricating oil compositions are used to reduce friction and wear between movable parts or movable surfaces in various mechanical devices.

[0003] In particular, lubricants such as oils and greases are used under harsher conditions such as high temperature, high speed, high load, and radiation, and require lubricants with superior heat resistance.

[0004] When operating conditions become high temperature and high speed, the lubricating oil and grease used for lubrication will cause temperature rise, thermal degradation or oxidative degradation due to insufficient oil film, thereby promoting the evaporation of the lubricating oil base oil, which will lead to sludge formation, damage to mechanical devices or shortened service life.

[0005] To this end, various lubricating oils and greases that can be used under high temperature conditions have been studied. Generally speaking, the improvement under high temperature conditions depends largely on the base oil, which is the most abundant component in the composition of the lubricating oil and grease.

[0006] Phenylene ether-based synthetic lubricants containing polyphenylene ether as an active ingredient, wherein the polyphenylene ether has 3 to 5 phenyl groups and at least one alkyl substituent having 10 to 20 carbon atoms, are known as heat-resistant lubricants (Patent Document 1). Furthermore, radiation-resistant lubricants containing 0 to 70% by weight of o-(m-phenoxyphenoxy)biphenyl, 25 to 75% of m-(m-phenoxyphenoxy)biphenyl, and 75 to 25% of a monoalkyl diphenyl ether or dialkyl diphenyl ether having an alkyl group having 10 to 20 carbon atoms are known as radiation-resistant lubricants (Patent Document 2).

[0007] The lubricating oils described in Patent Documents 1 and 2 have excellent heat resistance and radiation resistance. However, lubricating oils such as lubricating oils and greases are currently used under increasingly severe conditions, and there is a demand for lubricating oils having even better heat resistance.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Publication No. 62-44797

[0011] Patent Document 2: Japanese Patent Publication No. 62-59760 Summary of the Invention

[0012] The present invention aims to solve the above-mentioned problems. Specifically, the present invention aims to provide a compound that can be used as a lubricating oil having better heat resistance and can be used under more severe conditions.

[0013] The present inventors have conducted intensive studies to solve the above-mentioned problems and have found that the above-mentioned objects can be achieved by a dinaphthyl ether compound having the following structure. Based on this finding, the inventors have conducted further studies and have completed the present invention.

[0014] That is, the dinaphthyl ether compound according to one aspect of the present invention is a compound represented by the following formula (1).

[0015]

[0016] In formula (1), R 1 and R 2 are the same or different and are linear or branched hydrocarbon groups having 6 to 32 carbon atoms; m and n are real numbers greater than or equal to 0, and satisfy 1.0≤m+n≤3.0. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This figure shows a gas chromatography (GC) chart of the dinaphthyl ether synthesized in Example 1.

[0018] Figure 2 The model compound used to determine the number of hydrocarbon substitutions 1 H-NMR spectrum. DETAILED DESCRIPTION

[0019] As described above, the dinaphthyl ether compound of the present invention is a compound represented by the following formula (1).

[0020]

[0021] In formula (1), R 1 and R 2 are the same or different and are linear or branched hydrocarbon groups having a carbon number of 6 to 32. m and n are each a real number of 0 or greater and satisfy 1.0≤m+n≤3.0.

[0022] The dinaphthyl ether compound having this structure maintains lubricity comparable to that of the conventional compounds described in the aforementioned prior art documents while exhibiting exceptionally excellent heat resistance, making it extremely useful as a lubricant. More specifically, the dinaphthyl ether compound exhibits minimal evaporation loss at high temperatures and a long lifespan at high temperatures, making it suitable as a base oil for high-temperature lubricating oils or heat-resistant greases used at even higher temperatures.

[0023] Therefore, according to the present invention, it is possible to provide a dinaphthyl ether compound that can be used as a lubricating oil having more excellent heat resistance and that can be used under more severe conditions.

[0024] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited thereto.

[0025] The dinaphthyl ether compound of the present embodiment is a compound represented by the above formula (1).

[0026] In formula (1), R 1 and R 2 are the same or different and are hydrocarbon groups having 6 to 32 carbon atoms. For example, when either m or n in the formula (1) is 0, R 1 and R 2 Any one of them may be a hydrogen atom. 1 and R 2 Any one of them may be a hydrogen atom, but at least one of them is the hydrocarbon group.

[0027] If the hydrocarbon group has fewer than 6 carbon atoms, the physical properties of the dinaphthyl ether, lacking the hydrocarbon group, are significantly affected, resulting in poor fluidity. Furthermore, due to the low molecular weight, evaporation increases. On the other hand, if the carbon number exceeds 32, intermolecular interactions increase, resulting in excessively high viscosity, exceeding the viscosity range for normal use. A hydrocarbon group with a carbon number of 6 to 32 is preferred, as it offers a good balance between heat resistance and low-temperature properties. More preferably, the lower limit of the hydrocarbon group's carbon number is 16 or greater, and the upper limit is 28 or less.

[0028] In this embodiment, the structure of the hydrocarbon group having 6 to 32 carbon atoms is a straight chain or branched chain. Specifically, examples of the straight chain hydrocarbon group include alkyl groups such as hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, docosyl, tetracosyl, hexacosyl, and octacosyl; alkylene groups such as octenyl, decenyl, hexadecenyl, dodecenyl, octadecenyl, eicosyl, docosenyl, tetracosenyl, hexacosenyl, and octacosenyl; and cyclohexyl. As the hydrocarbon group of branched chain, for example 1-methyl undecyl, 1-ethyl decyl, 1-methyl tridecyl, 1-ethyl dodecyl, 1-methyl pentadecyl, 1-ethyl tetradecyl, 1-methyl heptadecyl, 1-ethyl octadecyl, 1-methyl nonadecyl, 1-ethyl octadecyl, 2-ethyl hexyl, 2-octyl dodecyl, 2-decyl tetradecyl, 2-dodecyl hexadecyl, 1-butyl-1-methyl pentyl, 1-butyl-1-methyl heptyl, 1-methyl-1-pentyl octyl, 1-hexyl-1-methyl nonyl, 1-heptyl-1-methyl decyl, 1-methyl-1-octyl undecyl, 1-decyl-1-methyl tridecyl, 1-dodecyl-1-methyl pentadecyl, 2-octyl dodecenyl, 2-decyl tetradecenyl, cyclohexyl etc. can be enumerated. Due to excellent thermal stability, the hydrocarbon group is preferably a saturated hydrocarbon group. The hydrocarbon group can use multiple types simultaneously. At this time, the carbon number of the hydrocarbon group is represented by its average.

[0029] Among these hydrocarbon groups, hydrocarbon groups having 12 to 32 carbon atoms are preferred from the viewpoint of obtaining better heat resistance, and suitable examples include 1-methylundecyl, 1-methyltridecyl, 1-methylpentadecyl, 1-methyl-1-octylundecyl, 1-decyl-1-methyltridecyl, 1-dodecyl-1-methylpentadecyl, hexadecyl, dodecyl, tetradecyl, 2-octyldodecyl, 2-decyltetradecyl, and 2-dodecylhexadecyl.

[0030] The hydrocarbon group mentioned above can be bonded to any of the two naphthyl groups in the formula (1) as long as m and n satisfy 1.0≤m+n≤3.0, and can also be bonded to any position of the naphthyl group. In addition, for example, when m+n is 1, R 1 and R 2 Any one of may be a hydrogen atom.

[0031] In the compound of the above formula (1), m and n are real numbers greater than 0, and satisfy 1.0≤m+n≤3.0. It is believed that if m+n is less than 1.0, the physical properties of a dinaphthyl ether without a hydrocarbon group are exhibited and the fluidity becomes poor. In addition, due to the small molecular weight, the evaporation amount cannot be fully suppressed. On the other hand, if m+n exceeds 3.0, the interaction between molecules becomes greater and the viscosity becomes too high. In this embodiment, m+n represents the number of linear or branched hydrocarbon group substitutions (hereinafter also referred to as the alkyl group substitution number).

[0032] The compound of this embodiment may be, for example, a mixture of a compound where 0 ≤ m + n ≤ 2.0 and a compound where 2.0 ≤ m + n ≤ 3.0. As described above, in the case of a mixture of compounds having a plurality of different m + n values, the value of m + n refers to the average value of m + n in the dinaphthyl ether compounds contained in the compound of this embodiment.

[0033] In a preferred embodiment, m+n is more preferably 1 or more and 2.5 or less.

[0034] In the present embodiment, the number of hydrocarbon group substitutions can be measured by the method described in the Examples below.

[0035] The dinaphthyl ether compound of this embodiment preferably has a mass average molecular weight of approximately 450 to 800. A high mass average molecular weight of the dinaphthyl ether compound offers the advantage of excellent heat resistance. Therefore, if the mass average molecular weight is within this range, the kinematic viscosity and pour point are not excessively high, and the heat resistance is excellent. On the other hand, if the mass average molecular weight is below this range, the heat resistance tends to deteriorate.

[0036] In addition, the mass average molecular weight of the dinaphthyl ether compound in this embodiment is as shown in the examples described later. 1 The value measured by H-NMR. In addition, the mass average molecular weight is hereinafter also simply referred to as "average molecular weight".

[0037] The method for producing the above-mentioned dinaphthyl ether compound is not particularly limited, and the compound can be obtained, for example, by the following synthesis method.

[0038] First, 2-naphthol and N-methyl-2-pyrrolidone (hereinafter referred to as NMP) are mixed with potassium carbonate and copper iodide to perform nitrogen substitution, and 1-bromonaphthalene is added dropwise thereto to obtain dinaphthyl ether.

[0039] Next, the naphthyl ether is reacted with a linear or branched olefin or the like using aluminum chloride or the like as a catalyst, thereby obtaining the dinaphthyl ether compound of the present embodiment.

[0040] The present invention also includes a lubricating oil composition containing the dinaphthyl ether compound described above.

[0041] The lubricating oil composition of this embodiment may contain, in addition to the dinaphthyl ether compound, a mineral oil, and synthetic oils such as α-olefin oligomers, polyol esters, diesters, polyalkylene glycols, silicone oils, modified silicone oils, alkyl diphenyl ether oils, multiple alkylate cyclopentane oils, and silahydrocarbon oils, to further enhance performance or impart further properties as needed, without impairing the effects of the present invention. Furthermore, various additives such as antioxidants, extreme pressure agents, friction modifiers, metal deactivators, defoamers, thickeners, and colorants may be mixed alone or in combination, as needed.

[0042] As the additive, antioxidants generally used in lubricating oils can be used without particular limitation. Examples of the antioxidant include phenolic compounds, amine compounds, phosphorus compounds, and sulfur compounds.

[0043] Examples of the extreme pressure agent include phosphorus compounds and sulfur compounds.

[0044] Examples of the friction modifier include molybdenum compounds such as molybdenum dithiocarbamate and fatty acid derivatives such as glycerol monostearate.

[0045] Examples of the metal deactivator include benzotriazole-based, tolyltriazole-based, thiadiazole-based, and imidazole-based compounds.

[0046] Examples of the defoaming agent include polyacrylates and styrene ester polymers.

[0047] Examples of the thickener include metal soaps (eg, lithium soaps), silica, expanded graphite, polyurea, and clays (eg, hectorite and bentonite).

[0048] In the lubricating oil composition of this embodiment, when the dinaphthyl ether compound is included as a base oil, its content is preferably approximately 50 to 100% by mass relative to the total mass of the lubricating oil composition from the perspective of ensuring heat resistance. Furthermore, in this case, the content of additives and the like in the lubricating oil composition is preferably approximately 50 to 0% by mass.

[0049] The dinaphthyl ether compound may also be used as an additive to a lubricating oil composition. In this case, the content of the dinaphthyl ether compound is preferably about 1 to 49% by mass relative to the entire lubricating oil composition (total mass).

[0050] Furthermore, the present invention also includes high-temperature lubricating oil and heat-resistant grease containing the above-mentioned dinaphthyl ether compound.

[0051] The lubricating oil composition, high-temperature lubricating oil, and heat-resistant grease described above are suitable for use as bearing lubricants, lubricants for impregnated bearings, grease base oils, refrigerator oils, plasticizers, and the like. They are particularly suitable for use as various lubricating oils used under high-temperature conditions, such as bearing oils, fluid bearing oils, oil-containing bearing oils, grease base oils, oil-containing plastic oils, gear oils, jet engine oils, heat-insulating engine oils, gas turbine oils, automatic transmission oils, vacuum pump oils, and hydraulic fluids.

[0052] Furthermore, since the dinaphthyl ether compound as described above is also excellent in radiation resistance, it is considered to be suitably usable as a radiation-resistant lubricating oil and a radiation-resistant grease.

[0053] As described above, this specification discloses various types of technologies, and the main technologies are summarized as follows.

[0054] The dinaphthyl ether compound according to one aspect of the present invention is a compound represented by the following formula (1).

[0055]

[0056] In formula (1), R 1 and R 2 are the same or different and are linear or branched hydrocarbon groups having 6 to 32 carbon atoms; m and n are real numbers greater than or equal to 0, and satisfy 1.0≤m+n≤3.0.

[0057] This configuration makes it possible to provide a compound having better heat resistance than conventional lubricating oils.

[0058] Another aspect of the present invention provides a lubricating oil composition containing the above-mentioned dinaphthyl ether compound.

[0059] Still another aspect of the present invention provides a high-temperature lubricating oil and a radiation-resistant lubricating oil containing the above-mentioned dinaphthyl ether compound.

[0060] Still another aspect of the present invention provides a heat-resistant grease and a radiation-resistant grease containing the above-mentioned dinaphthyl ether compound.

[0061] The lubricating oil composition, high-temperature lubricating oil, and heat-resistant grease according to the present invention have very excellent heat resistance and are therefore suitable for use under severe conditions (particularly high temperatures).

[0062] Example

[0063] Hereinafter, examples of the present invention will be described, but the present invention is not limited thereto.

[0064] [Synthesis of Compounds]

[0065] (Example 1: Compound 1)

[0066] A 5-liter four-necked flask equipped with a stirrer, thermometer, dropping funnel, and cooling tube was charged with 450 g (3.12 mol) of 2-naphthol, 862 g (6.24 mol) of potassium carbonate, 119 g (0.62 mol) of copper iodide, and 1000 g of NMP. After nitrogen substitution, the reaction system was heated until the temperature reached 175°C. When the temperature reached 120°C, 1292 g (6.24 mol) of 1-bromonaphthalene was added dropwise. After the addition was complete, the mixture was stirred at 175°C for 6 hours. After the reaction was completed, the mixture was cooled to 90°C, 60 g of KYOWAAD 1000s (alkaline adsorbent; manufactured by Kyowa Chemical Industry Co., Ltd.) was added, and the mixture was stirred for 30 minutes. Next, 40 g of activated clay was added, and after stirring at 90°C for 30 minutes, the solids were removed by vacuum filtration. The filter cake was stirred into NMP, and the vacuum filtration was repeated three times. The resulting filtrate was subjected to vacuum distillation at 80 Pa at 215°C to 240°C, yielding 1,2-dinaphthyl ether (dinaphthyl oxide: 1,2-DNO), a solid at room temperature, as a fraction. 5% by weight of activated clay was added to the resulting compound, and the mixture was stirred at 90°C for 30 minutes. Contaminated grease and other substances were removed by vacuum filtration. Figure 1 The GC chart of dinaphthyl ether is shown in FIG. 1 (the measurement conditions will be described later). The purity is 94.0%. The dinaphthyl ether synthesized here was also used as a reaction material in Examples 2 to 6 described later.

[0067] Next, 200 g (0.74 mol) of dinaphthyl ether and 2.33 g (0.017 mol) of anhydrous aluminum chloride were placed in a 500 mL four-necked flask equipped with a stirrer, dropping funnel, and thermometer. The mixture was heated to 90°C to dissolve the anhydrous aluminum chloride. Then, while maintaining the reaction system at 110°C, 83 g (0.37 mol) of 1-hexadecene was added dropwise over 2 hours to carry out a substitution reaction. After the addition, stirring was continued at 110°C for 5 hours, then the mixture was naturally cooled to 90°C. KYOWAAD 1000s (5.5 times the amount of anhydrous aluminum chloride) was added and stirred for 30 minutes. Subsequently, activated clay (3.65 times the amount of anhydrous aluminum chloride) was added. After stirring at 90°C for 30 minutes, the anhydrous aluminum chloride and other by-products, such as acidic substances, were removed by vacuum filtration. The filtrate obtained here was subjected to vacuum distillation at 320°C under 80 Pa to remove unreacted raw materials, etc., to obtain an alkyl-substituted dinaphthyl ether (Compound 1: Alkyl (C16)-1-(2-naphthyloxy)naphthalene (C16-1,2-DNO)) containing a monoalkyl substituent as the main component. 5% by weight of activated clay was added to the compound obtained here, and the mixture was stirred at 90°C for 30 minutes. Grease and other substances that had been mixed in were removed by vacuum filtration. Furthermore, Compound 1 was evaluated after the removal of grease and other substances. Examples 1 to 7 and Comparative Examples 1 to 4 were also evaluated by similarly removing grease and other substances.

[0068] (Example 2: Compound 2)

[0069] The reaction was carried out in a 500 mL four-necked flask, and 120 g (0.44 mol) of the dinaphthyl ether obtained in Example 1, 1.05 g (0.0078 mol) of anhydrous aluminum chloride, and 37 g (0.22 mol) of 1-dodecene were used. The mixture was subjected to reduced pressure distillation at 80 Pa and a temperature of 260° C. to 300° C., thereby obtaining a monoalkyl substituted product as a fraction. In addition, under the same conditions as in Example 1, an alkyl-substituted dinaphthyl ether (Compound 2: Alkyl (C12)-1-(2-naphthyloxy)naphthalene (C12-1,2-DNO)) containing the monoalkyl substituted product as the main component was obtained.

[0070] (Example 3: Compound 3)

[0071] The reaction was carried out in a 500 mL four-necked flask, and 100 g (0.37 mol) of dinaphthyl ether obtained in Example 1, 1.57 g (0.012 mol) of anhydrous aluminum chloride, and 56 g (0.33 mol) of 1-dodecene were used. Unreacted raw materials and monoalkyl substituents were removed by vacuum distillation at 80 Pa and 300° C. In addition, under the same conditions as in Example 1, an alkyl-substituted dinaphthyl ether (Compound 3: dialkyl (C12)-1-(2-naphthyloxy)naphthalene (diC12-1,2-DNO)) containing a dialkyl substituent as the main component was obtained.

[0072] (Example 4: Compound 4)

[0073] The reaction was carried out using a 500 mL four-necked flask, and using 135 g (0.50 mol) of the dinaphthyl ether obtained in Example 1, 2.46 g (0.019 mol) of anhydrous aluminum chloride, and 70 g (0.25 mol) of 2-octyl-1-dodecene. In addition, under the same conditions as in Example 1, an alkyl-substituted dinaphthyl ether having a monoalkyl substituent as the main component (Compound 4: branched alkyl (C20)-1-(2-naphthyloxy)naphthalene (bC20-1,2-DNO)) was obtained.

[0074] (Example 5: Compound 5)

[0075] The reaction was carried out using a 500 mL four-necked flask, and using 30 g (0.11 mol) of the dinaphthyl ether obtained in Example 1, 0.53 g (0.0040 mol) of anhydrous aluminum chloride, and 19 g (0.060 mol) of 2-decyl-1-tetradecene. In addition, under the same conditions as in Example 1, an alkyl-substituted dinaphthyl ether having a monoalkyl substituent as the main component (Compound 5: branched alkyl (C24)-1-(2-naphthyloxy)naphthalene (bC24-1,2-DNO)) was obtained.

[0076] (Example 6: Compound 6)

[0077] The reaction was carried out using a 500 mL four-necked flask, and using 30 g (0.11 mol) of the dinaphthyl ether obtained in Example 1, 0.61 g (0.0046 mol) of anhydrous aluminum chloride, and 22 g (0.060 mol) of 2-dodecyl-1-hexadecene. In addition, under the same conditions as in Example 1, an alkyl-substituted dinaphthyl ether having a monoalkyl substituent as the main component (Compound 6: branched alkyl (C28)-1-(2-naphthyloxy)naphthalene (bC28-1,2-DNO)) was obtained.

[0078] (Example 7: Compound 11)

[0079] A 2L four-necked flask equipped with a stirrer, thermometer, dropping funnel, and cooling tube was charged with 120g (0.83 mol) of 1-naphthol, 230g (1.66 mol) of potassium carbonate, 32g (0.17 mol) of copper iodide, and 300g of NMP. After nitrogen substitution, the reaction system was heated until the temperature reached 175°C. Once the temperature reached 120°C, 345g (1.66 mol) of 1-bromonaphthalene was added dropwise. After the addition was complete, the mixture was stirred at 175°C for 6 hours. After the reaction was completed, the mixture was naturally cooled to 90°C, 20g of KYOWAAD 1000s was added, and the mixture was stirred for 30 minutes. Next, 15g of activated clay was added, and after stirring at 90°C for 30 minutes, the solid content was removed by vacuum filtration. The filter cake was stirred into NMP, and the vacuum filtration was repeated three times. The resulting filtrate was subjected to vacuum distillation at 80 Pa at 215°C to 240°C, yielding 1,1-dinaphthyl ether (1,1-dinaphthyl oxide: 1,1-DNO), a solid at room temperature, as a fraction. 5% by weight of activated clay was added to the resulting compound, stirred at 90°C for 30 minutes, and grease and other contaminants were removed by vacuum filtration. The purity was 99.6%.

[0080] Next, 77.7 g (0.29 mol) of dinaphthyl ether and 1.13 g (0.0085 mol) of anhydrous aluminum chloride were placed in a 500 mL four-necked flask equipped with a stirrer, dropping funnel, and thermometer. The mixture was heated to 100°C to dissolve the anhydrous aluminum chloride. Then, while maintaining the reaction system at 110°C, 32.3 g (0.14 mol) of 1-hexadecene was added dropwise over 2 hours to carry out a substitution reaction. After the addition, stirring was continued at 110°C for 5 hours, then the mixture was naturally cooled to 90°C. KYOWAAD 1000s (5.5 times the amount of anhydrous aluminum chloride) was added and stirred for 30 minutes. Subsequently, activated clay (3.65 times the amount of anhydrous aluminum chloride) was added. After stirring at 90°C for 30 minutes, the anhydrous aluminum chloride and other by-products, such as acidic substances, were removed by vacuum filtration. The filtrate obtained here was subjected to vacuum distillation at 320°C under 80 Pa to remove unreacted raw materials, etc., to obtain an alkyl-substituted dinaphthyl ether (Compound 11: alkyl (C16)-1-(1-naphthyloxy)naphthalene (C16-1,1-DNO)) containing a monoalkyl substituent as the main component. 5% by weight of activated clay was added to the obtained compound, and the mixture was stirred at 90°C for 30 minutes. Grease and other contaminants were then removed by vacuum filtration.

[0081] (Comparative Example 1: Compound 7)

[0082] 200 g (1.18 mol) of diphenyl ether and 1.00 g (0.0075 mol) of anhydrous aluminum chloride were placed in a 500 mL four-necked flask equipped with a stirrer, dropping funnel, and thermometer. The mixture was heated to 90°C to dissolve the anhydrous aluminum chloride. Then, while maintaining the temperature of the reaction system at 100°C, 186 g (0.83 mol) of 1-hexadecene was added dropwise over 2 hours to carry out a substitution reaction. After the addition was completed, stirring was continued at 100°C for 1 hour, then naturally cooled to 90°C, and KYOWAAD 1000s in an amount 5.5 times that of the anhydrous aluminum chloride was added, followed by stirring for 30 minutes. Subsequently, activated clay in an amount 3.65 times that of the anhydrous aluminum chloride was added. After stirring at 90°C for 30 minutes, the anhydrous aluminum chloride and other by-products, such as acidic substances, were removed by vacuum filtration. The resulting filtrate (reaction filtrate A) was subjected to vacuum distillation at 80 Pa and 250°C to 260°C to obtain a monoalkyl-substituted alkyl diphenyl ether (Compound 7: alkyl (C16) diphenyl ether (C16-DPO)) as a fraction. 5% by weight of activated clay was added to the resulting compound, and the mixture was stirred at 90°C for 30 minutes. Grease and other contaminants were removed by vacuum filtration.

[0083] (Comparative Example 2: Compound 8)

[0084] The reaction filtrate A obtained in Comparative Example 1 was subjected to reduced pressure distillation at 290°C under 80 Pa to remove unreacted raw materials and monoalkyl substituted products, thereby obtaining an alkyl-substituted diphenyl ether (Compound 8: dialkyl (C16) diphenyl ether (diC16-DPO)) containing a dialkyl substituted product as the main component.

[0085] (Comparative Example 3: Compound 9)

[0086] 200 g (0.59 mol) of o-(m-phenoxyphenoxy)biphenyl and 0.72 g (0.0054 mol) of anhydrous aluminum chloride were placed in a 500 mL four-necked flask equipped with a stirrer, dropping funnel, and thermometer. The mixture was heated to 90°C to dissolve the anhydrous aluminum chloride. Then, while maintaining the temperature of the reaction system at 100°C, 66 g (0.29 mol) of 1-hexadecene was added dropwise over 2 hours to carry out a substitution reaction. After the addition was completed, stirring was continued at 100°C for 1 hour, then the mixture was naturally cooled to 90°C. KYOWAAD 1000s in an amount 5.5 times that of the anhydrous aluminum chloride was added, and stirring was continued for 30 minutes. Subsequently, activated clay in an amount 3.65 times that of the anhydrous aluminum chloride was added. After stirring at 90°C for 30 minutes, the anhydrous aluminum chloride and other acidic by-products were removed by vacuum filtration. The filtrate obtained here was subjected to vacuum distillation at 320°C under 80 Pa to remove unreacted raw materials, etc., to obtain Compound 9 (alkyl (C16)-2-(3-phenoxyphenoxy)biphenyl (C16-4P2E)), which is mainly composed of monoalkyl-substituted o-(m-phenoxyphenoxy)biphenyl. 5% by weight of activated clay was added to the obtained compound, and the mixture was stirred at 90°C for 30 minutes. Contaminated grease, etc., was then removed by vacuum filtration.

[0087] (Comparative Example 4: Compound 10)

[0088] The reaction was carried out using a 500 mL four-necked flask, 150 g (0.44 mol) of o-(m-phenoxyphenoxy)biphenyl, 1.85 g (0.014 mol) of anhydrous aluminum chloride, and 168 g (1.85 mol) of 1-hexadecene. In addition, under the same conditions as in Comparative Example 3, compound 10 (dialkyl (C16)-2-(3-phenoxyphenoxy)biphenyl (diC16-4P2E)) having dialkyl-substituted o-(m-phenoxyphenoxy)biphenyl as the main component was obtained.

[0089] [ 1 H-NMR measurement conditions and calculation conditions for the number of hydrocarbon group substitutions]

[0090] 1 H-NMR was measured using a nuclear magnetic resonance apparatus JNM-ECX400 manufactured by JEOL Ltd. The measurement conditions were a temperature of 80° C. and no solvent or standard substance was used.

[0091] Chemical shifts were determined by comparing the same compound using deuterated chloroform as a solvent and TMS as a standard substance. This is because the peaks of deuterated chloroform and the benzene ring overlap, making it impossible to obtain an accurate integral value.

[0092] Use under the above conditions 1 The obtained compounds 1 to 11 were analyzed by H-NMR to determine the mass average molecular weight of each compound.

[0093] In addition, the number of hydrocarbon substitutions of compounds 1 to 11 was analyzed by 1 Specifically, the H-NMR spectrum was used. Figure 2 The model compounds shown 1 The calculation method is explained using H-NMR spectroscopy.

[0094] exist Figure 2 In the figure, a (chemical shift 6.5-7.3) represents the peak of hydrogen in the aromatic ring, b1 (chemical shift 2.8-3.3) and b2 (chemical shift 2.2-2.7) represent the peaks of hydrogen in the benzyl position, and c (chemical shift 0.5-1.9) represents the peak of hydrogen in the hydrocarbon group.

[0095] The number of hydrocarbon group substitutions was calculated by the following formula based on the integrated values ​​(ratios) of the peaks a, b1, b2, and c.

[0096] Number of hydrocarbon group substitutions (m+n) = (number of hydrogen atoms in the aromatic ring) × (b1+b2+c) / [(average number of hydrogen atoms in the hydrocarbon group) × a+b1+b2+c]

[0097] <Purity Determination>

[0098] [Gas chromatography (GC) measurement conditions]

[0099] Gas chromatography was performed using a Shimadzu GC-2010 Plus. The column used was an Ultra ALLOY+-17, and nitrogen was used as the carrier gas. The measurement temperature conditions were: hold at 50°C for 2 minutes, then increase at 25°C / min to 100°C, then increase from 100°C to 350°C at 15°C / min, and then hold at 350°C for 15 minutes.

[0100] <Evaluation Test>

[0101] [Measurement of evaporation amount by TG method]

[0102] The evaporation amount was measured by the TG method using a Hitachi High-Technologies Corporation ST7200RV. Air (200 ml / min) was used as the carrier gas, an aluminum deep dish was used as the sample container, and the sample amount was 5 mg. The evaporation amount (%) of each compound was measured after holding the sample at 250°C for 30 minutes and 60 minutes.

[0103] In this test, compounds that satisfy the evaluation criteria of evaporation amount of 10% or less after 30 minutes and 15% or less after 60 minutes are considered to pass.

[0104] [Thin film heating test]

[0105] Weigh 0.5g of each of Compounds 1-11 and place them in a 50Ø concave dish made of S45C material. Place the dish in a 200°C thermostat. Remove the dish from the thermostat every two hours and measure its weight to confirm its fluidity upon return to room temperature. The time it takes to lose fluidity at room temperature is considered the film life. In this test, a film life of 25 hours or more is considered acceptable.

[0106] [Lubricity test (SRV)]

[0107] Lubricity was measured using an SRV-5 from Optimol Instruments Prueftechnik GmbH. A 1 / 2-inch SUJ2 ball was used for the upper test piece, and an SK-5 plate was used for the lower test piece. After a 50-second acclimatization run at 40°C, a load of 50N, and a speed of 40mm / second, a full test was conducted at 40°C, a load of 100N, and a speed of 40mm / second for 600 seconds. The coefficient of friction (COF) was measured, and the average COF at 100N was calculated. In this test, an average COF of 0.150 or less was considered acceptable.

[0108] [Viscosity characteristics]

[0109] The kinematic viscosity at 40°C (mm) was measured and calculated according to JIS K 2283 (2000). 2 / Second).

[0110] The above results are summarized in Tables 1 and 2.

[0111]

[0112] Table 2

[0113]

[0114] (Inspection)

[0115] The results in Table 1 indicate that the dinaphthyl ether compounds 1 to 6 and compound 11 of the examples of the present invention all meet the aforementioned standards for both evaporation rate and film life. While kinematic viscosity generally increases with increasing carbon number in the hydrocarbon group, the kinematic viscosity of the compounds of the present invention decreases with increasing carbon number in the hydrocarbon group. Furthermore, a comparison of Examples 2 and 3 with Comparative Examples 2 and 3 shows that the compounds of the present invention exhibit reduced evaporation rates even with equivalent molecular weights. A comparison of Examples 1 to 7 with Comparative Examples 3 and 4, which have the same number of six-membered ring structures, also shows reduced evaporation rates. Furthermore, regarding film life, a more stringent evaluation of heat resistance, a comparison of Examples 1 to 7 with Comparative Examples 3 and 4, which have the same number of six-membered ring structures, shows that the heat resistance time is more than doubled, confirming improved heat resistance. This is believed to be due to the naphthalene structure inhibiting polymerization reactions caused by thermal oxidation.

[0116] On the other hand, according to the results shown in Table 2, the conventionally used diphenyl ether compounds of Comparative Examples 1 and 2 and the polyphenylene ether compounds of Comparative Examples 3 and 4 had large evaporation amounts and short film life, and failed to achieve heat resistance comparable to that of the compounds of the present invention.

[0117] This application is based on Japanese patent application No. 2021-020368 filed on February 12, 2021, and the contents are incorporated into this application.

[0118] In order to describe the present invention, the present invention has been appropriately and fully described in the above description with reference to specific examples and embodiments. However, it should be understood that those skilled in the art can easily modify and / or improve the above embodiments. Therefore, as long as the modified embodiments or improved embodiments implemented by those skilled in the art do not depart from the scope of protection of the claims set forth in the claims, such modified embodiments or improved embodiments should be construed as being included within the scope of protection of the claims.

[0119] Industrial applicability

[0120] The dinaphthyl ether compound of the present invention has extremely excellent heat resistance and can therefore be suitably used as a high-temperature lubricating oil, a heat-resistant grease, and the like, and has wide industrial applicability.

Claims

1. A dinaphthyl ether compound, characterized in that: A dinaphthyl ether compound represented by the following formula (1), In formula (1), R 1 and R 2 are the same or different and are linear or branched hydrocarbon groups having 6 to 32 carbon atoms; m and n are real numbers greater than or equal to 0, and satisfy 1.0≤m+n≤3.

0.

2. A lubricating oil composition, characterized in that Containing the compound according to claim 1.

3. A high temperature lubricating oil, characterized in that Containing the compound according to claim 1.

4. A heat-resistant grease, characterized in that Containing the compound according to claim 1.

5. A radiation-resistant lubricating oil, characterized in that Containing the compound according to claim 1.

6. A radiation-resistant grease, characterized in that Containing the compound according to claim 1.

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