Dinaphthyl ether compound and lubricating oil composition containing same

Abstract

One aspect of the present invention relates to a dinaphthyl ether compound which is expressed by formula (1). (Chemical formula 1) (In formula (1), R1 and R2 may be the same as or different from each other, and each represents a linear or branched hydrocarbon group having 6 to 32 carbon atoms; and each of m and n represents a real number of 0 or more, while satisfying 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 same. [Background technology]

[0002] Lubricating oils and lubricating oil compositions are used to reduce friction and wear between moving parts or surfaces in a variety of mechanical devices and the like.

[0003] In particular, lubricating oils, lubricating greases and the like are now being used under increasingly severe conditions, such as high temperatures, high speeds, heavy loads, and radiation exposure, and there is a demand for lubricating oil agents with even better heat resistance.

[0004] When operating conditions become high temperature and high speed, the lubricating oils and greases used for lubrication can experience temperature rises due to oil film breakdown, as well as thermal and oxidative degradation. This can accelerate the evaporation of the lubricating base oil, resulting in the formation of sludge and damage to and shortened lifespan of mechanical equipment.

[0005] For this reason, various lubricating oils and greases that can be used under high temperature conditions have been studied, and in general, improvements under high temperature conditions are largely due to the base oil, which is contained in the largest amount in the composition of the lubricating oil or grease.

[0006] A phenyl ether-based synthetic lubricating oil (Patent Document 1) containing, as an active ingredient, a polyphenyl ether having 3 to 5 phenyl groups and at least one alkyl substituent having 10 to 20 carbon atoms has been known as a heat-resistant lubricating oil. Also known as a radiation-resistant lubricating oil is a radiation-resistant lubricating oil (Patent Document 2) consisting of 0 to 70% by weight of o-(m-phenoxyphenoxy)diphenyl, 25 to 75% of m-(m-phenoxyphenoxy)diphenyl, and 75 to 25% of a monoalkyldiphenyl ether or dialkyldiphenyl ether having 10 to 20 alkyl carbon atoms.

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

[0008] [Patent Document 1] Special Publication No. 62-44797 [Patent Document 2] Special Publication No. 62-59760 Summary of the Invention

[0009] The object of the present invention is to solve the above problems, that is, to provide a compound for use as a lubricating oil having superior heat resistance and capable of being used under more severe conditions.

[0010] Means for Solving the Problems The present inventors have conducted intensive research to solve the above problems and have found that the above object can be achieved by a dinaphthyl ether compound having the following composition. Based on this finding, further investigations have led to the completion of the present invention.

[0011] That is, a dinaphthyl ether compound according to one aspect of the present invention is a compound represented by the following formula (1).

[0012] [ka]

[0013] (In formula (1), R 1 and R 2 are the same or different and are straight-chain or branched-chain hydrocarbon groups having 6 to 32 carbon atoms; m and n are each a real number of 0 or more and satisfy 1.0≦m+n≦3.0. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 shows a gas chromatography (GC) chart of the dinaphthyl ether synthesized in Example 1. [Diagram 2] FIG. 2 shows the 1H-NMR spectrum of a model compound for determining the number of hydrocarbon group substitutions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] As described above, the dinaphthyl ether compound of the present invention is a compound represented by the following formula (1).

[0016] [ka]

[0017] In formula (1), R 1 and R 2 are the same or different and are straight-chain or branched-chain hydrocarbon groups having 6 to 32 carbon atoms. Additionally, m and n are each a real number of 0 or more and satisfy 1.0≦m+n≦3.0.

[0018] The dinaphthyl ether compound of this constitution has excellent heat resistance while maintaining the same degree of lubrication as the conventional compounds described in the above-mentioned prior art, and is therefore very useful as a lubricating oil.More specifically, the dinaphthyl ether compound has low evaporation loss at high temperature and long life at high temperature, so it can be suitably used as the base oil of high temperature lubricating oil or heat-resistant grease used at higher temperature.

[0019] Therefore, according to the present invention, it is possible to provide a dinaphthyl ether compound which has superior heat resistance and can be used as a lubricating oil under severer conditions.

[0020] Hereinafter, the embodiments of the present invention will be described in detail, but the present invention is not limited to these.

[0021] The dinaphthyl ether compound of this embodiment is a compound represented by the above formula (1).

[0022] 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 Either one of R may be a hydrogen atom. 1 and R 2 Either one of the groups may be a hydrogen atom, but at least one of the groups is the above-mentioned hydrocarbon group.

[0023] If the carbon number of the hydrocarbon group is less than 6, the physical properties of the dinaphthyl ether having no hydrocarbon group will have a large effect, and it is considered that the fluidity will be poor. In addition, the molecular weight will be small, and the amount of evaporation will be large. On the other hand, if the carbon number exceeds 32, the interaction between molecules will be large, and the viscosity will become too high and exceed the generally used viscosity range. When the carbon number of the hydrocarbon group is 6 to 32, it is preferable that the heat resistance and low temperature properties are well balanced. It is more preferable that the lower limit of the carbon number of the hydrocarbon group is 16 or more, and the upper limit is 28 or less.

[0024] In this embodiment, the structure of the hydrocarbon group having 6 to 32 carbon atoms is a straight chain or a branched chain. Specifically, examples of the straight chain hydrocarbon group include alkyl groups such as a hexyl group, an octyl group, a decyl group, a dodecyl group, a tetradecyl group, a hexadecyl group, an octadecyl group, an icosyl group, a docosyl group, a tetracosyl group, a hexacosyl group, and an octacosyl group; an octene group, a decene group, a hexadecene group, a dodecene group, an octadecene group, an icosene group, a docosene group, a tetracosyl group, and an octacosyl group; to Alkylene such as lacosene group, hexacosene group, octacosene group, etc. Moto etc.Examples of the branched hydrocarbon group include 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-decyltetra ... -Dodecylhexadecyl group, 1-butyl-1-methylpentyl group, 1-butyl-1-methylheptyl group, 1-methyl-1-pentyloctyl group, 1-hexyl-1-methylnonyl group, 1-heptyl-1-methyldecyl group, 1-methyl-1-octylundecyl group, 1-decyl-1-methyltridecyl group, 1-dodecyl-1-methylpentadecyl group, 2-octyldodecene group, 2-decyltetradecene group Moto etc. The hydrocarbon group is preferably a saturated hydrocarbon group because it has excellent thermal stability. A plurality of types of the hydrocarbon group may be used at the same time. In this case, the number of carbon atoms in the hydrocarbon group is expressed as the average.

[0025] Among these hydrocarbon groups, from the viewpoint of obtaining better heat resistance, a hydrocarbon group having 12 to 32 carbon atoms is preferable, and suitable examples thereof include a 1-methylundecyl group, a 1-methyltridecyl group, a 1-methylpentadecyl group, a 1-methyl-1-octylundecyl group, a 1-decyl-1-methyltridecyl group, a 1-dodecyl-1-methylpentadecyl group, a hexadecyl group, a dodecyl group, a tetradecyl group, a 2-octyldodecyl group, a 2-decyltetradecyl group, and a 2-dodecylhexadecyl group.

[0026] In the formula (1), the hydrocarbon group may be bonded to either of the two naphthyl groups, and may be bonded to either position of the naphthyl group, so long as m and n satisfy the relationship 1.0≦m+n≦3.0. For example, when m+n is 1, R 1 and R 2 Any one of these may be a hydrogen atom.

[0027] In the compound of the above formula (1), m and n are real numbers of 0 or more, and satisfy 1.0≦m+n≦3.0. When m+n is less than 1.0, the physical properties of dinaphthyl ether without a hydrocarbon group appear, and the fluidity is considered to be poor. In addition, the molecular weight is small, so the amount of evaporation cannot be sufficiently suppressed. On the other hand, when m+n exceeds 3.0, the interaction between molecules becomes large, and the viscosity becomes too high. In this embodiment, m+n indicates the number of substitutions of linear or branched hydrocarbon groups (hereinafter, also simply referred to as the number of alkyl substitutions).

[0028] The compound of this embodiment may be, for example, a mixture of a compound in which 0≦m+n≦2.0 and a compound in which 2.0≦m+n≦3.0, etc. In the case of a mixture of compounds having a plurality of different m+n values, the value of m+n means the average value of m+n in the dinaphthyl ether compounds contained in the compound of this embodiment.

[0029] In a preferred embodiment, it is more desirable that m+n is 1 or more and 2.5 or less.

[0030] In this embodiment, the number of hydrocarbon group substitutions can be measured by the method shown in the Examples described later.

[0031] The mass average molecular weight of the dinaphthyl ether compound of this embodiment is preferably about 450 to 800. If the mass average molecular weight of the dinaphthyl ether compound is large, there is an advantage that the heat resistance is excellent. Therefore, if the mass average molecular weight is within the above range, the kinetic viscosity and pour point are not too high, and the heat resistance is excellent. On the other hand, if the mass average molecular weight is smaller than the above range, the heat resistance tends to be inferior.

[0032] The mass average molecular weight of the dinaphthyl ether compound in the present embodiment is, as shown in the examples described later, 1 It is a value measured using H-NMR. Note that, hereinafter, the mass average molecular weight is also simply referred to as "average molecular weight."

[0033] The method for producing the above-mentioned dinaphthyl ether compound is not particularly limited, but it can be obtained, for example, by the following synthesis method.

[0034] 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 to obtain dinaphthyl ether.

[0035] Next, for example, the naphthyl ether is reacted with a linear or branched olefin or the like using aluminum chloride or the like as a catalyst to obtain the dinaphthyl ether compound of this embodiment.

[0036] The present invention also includes a lubricating oil composition containing the dinaphthyl ether compound as described above.

[0037] In addition to the dinaphthyl ether compound, the lubricating oil composition of this embodiment may contain mineral oils 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, in order to further improve the performance of the lubricating oil composition or to impart further performance as necessary, within a range that does not impair 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 blended alone or in combination as necessary.

[0038] As the additive, any antioxidant generally used in lubricating oils can be used without any particular limitation. Examples of the antioxidant include phenol-based compounds, amine-based compounds, phosphorus-based compounds, and sulfur-based compounds.

[0039] Examples of the extreme pressure agent include phosphorus-based compounds and sulfur-based compounds.

[0040] Examples of the friction modifier include molybdenum compounds such as molybdenum dithiocarbamate, and fatty acid derivatives such as glycerin monostearate.

[0041] Examples of metal deactivators include benzotriazole-based, tolyltriazole-based, thiadiazole-based, and imidazole-based compounds.

[0042] Antifoaming agents include, for example, polyacrylates, styrene ester polymers, and the like.

[0043] Examples of thickeners include metal soaps (eg, lithium soaps), silica, expanded graphite, polyurea, clays (eg, hectorite or bentonite), and the like.

[0044] In the lubricating oil composition of this embodiment, when the dinaphthyl ether compound is contained as a base oil, the content thereof is preferably about 50 to 100 mass% based on the entire lubricating oil composition (total mass) from the viewpoint of ensuring heat resistance. In this case, the content of additives and the like in the lubricating oil composition is preferably about 50 to 0 mass%.

[0045] Furthermore, the dinaphthyl ether compound can be used as an additive for a lubricating oil composition. In that case, the content of the dinaphthyl ether compound is preferably about 1 to 49 mass% with respect to the entire lubricating oil composition (total mass).

[0046] The present invention also includes high temperature lubricating oils and heat resistant greases which contain the dinaphthyl ether compounds as described above.

[0047] The lubricating oil composition, high temperature lubricating oil and heat resistant grease as described above are suitably used as bearing lubricants, lubricants for impregnated bearings, grease base oils, refrigeration oils, plasticizers, etc. In particular, they can be suitably used as various lubricating oils used under high temperature conditions, such as bearing oils, hydrodynamic bearing oils, oil-impregnated bearing oils, grease base oils, oil-impregnated plastics oils, gear oils, jet engine oils, heat insulating engine oils, gas turbine oils, automatic transmission oils, vacuum pump oils, hydraulic fluids, etc.

[0048] In addition, since the above-mentioned dinaphthyl ether compounds also have excellent radiation resistance, they are considered to be suitable for use as radiation-resistant lubricating oils and radiation-resistant greases.

[0049] As described above, this specification discloses various aspects of the technology, the main technologies of which are summarized below.

[0050] A dinaphthyl ether compound according to one aspect of the present invention is a compound represented by the following formula (1).

[0051] [ka]

[0052] (In formula (1), R 1 and R 2 are the same or different and are straight-chain or branched-chain hydrocarbon groups having 6 to 32 carbon atoms; m and n are each a real number of 0 or more and satisfy 1.0≦m+n≦3.0.

[0053] This provides a compound that has superior heat resistance to conventional lubricating oils.

[0054] A lubricating oil composition according to another aspect of the present invention is characterized by containing the above-mentioned dinaphthyl ether compound.

[0055] A high temperature lubricating oil and a radiation resistant lubricating oil according to still another aspect of the present invention are characterized by containing the above-mentioned dinaphthyl ether compound.

[0056] A heat-resistant grease and a radiation-resistant grease according to yet another aspect of the present invention are characterized in that they contain the above-mentioned dinaphthyl ether compound.

[0057] The lubricating oil composition, high temperature lubricating oil and heat resistant grease according to the present invention have excellent heat resistance and are therefore suitable for use under severe conditions (particularly at high temperatures). EXAMPLES

[0058] Examples of the present invention will be described below, but the present invention is not limited to these.

[0059] [Synthesis of Compounds] Example 1: Compound 1 450g (3.12 mol) of 2-naphthol, 862g (6.24 mol) of potassium carbonate, 119g (0.62 mol) of copper iodide and 1000g of NMP were placed in a 5L four-neck flask equipped with a stirrer, a thermometer, a dropping funnel and a cooling tube, and the temperature of the reaction system was heated to 175°C after nitrogen replacement. When the temperature reached 120°C, 1292g (6.24 mol) of 1-bromonaphthalene was started to be dropped. After the dropwise addition was completed, the mixture was stirred at 175°C for 6 hours. After the reaction was completed, the mixture was naturally cooled to 90°C, and 60g of Kyoward 1000s (alkali adsorbent; manufactured by Kyowa Chemical Industry Co., Ltd.) was added and stirred for 30 minutes. Subsequently, 40g of activated clay was added, and the mixture was stirred at 90°C for 30 minutes, after which the solids were removed by vacuum filtration. The filter cake was stirred in NMP and vacuum filtration was repeated three times. The obtained filtrate was distilled under reduced pressure at 215°C to 240°C at 80 Pa to obtain 1,2-dinaphthyl ether (dinaphthyl oxide: 1,2-DNO) which is solid at room temperature as a fraction. 5% by weight of activated clay was added to the compound obtained here, and the mixture was stirred at 90°C for 30 minutes, and grease and other substances mixed in were removed by filtration under reduced pressure. The GC chart of the dinaphthyl ether is shown in Figure 1 (the measurement conditions will be described later). The purity was 94.0%. The dinaphthyl ether synthesized here was also used as a reaction material in Examples 2 to 6.

[0060] Next, 200g (0.74 mol) of dinaphthyl ether and 2.33g (0.017 mol) of anhydrous aluminum chloride were placed in a 500mL four-neck flask equipped with a stirrer, dropping funnel, and thermometer, and the anhydrous aluminum chloride was dissolved by heating to 90°C. Then, 83g (0.37 mol) of 1-hexadecene was added dropwise over 2 hours while maintaining the temperature of the reaction system at 110°C, and a substitution reaction was carried out. After the dropwise addition, stirring was continued at 110°C for 5 hours, and then the mixture was naturally cooled to 90°C. Kyoward 1000s was added in an amount 5.5 times the amount of anhydrous aluminum chloride and stirred for 30 minutes. Subsequently, activated clay was added in an amount 3.65 times the amount of anhydrous aluminum chloride, and the mixture was stirred at 90°C for 30 minutes, after which the anhydrous aluminum chloride and other by-product acidic substances were removed by vacuum filtration. The filtrate obtained here was distilled under reduced pressure at 320°C and 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)) mainly composed of a monoalkyl-substituted product. 5% by weight of activated clay was added to the compound obtained here, and the mixture was stirred at 90°C for 30 minutes, and grease and other substances that had been mixed in were removed by filtration under reduced pressure. Evaluation was performed on compound 1 from which grease and other substances had been removed. In the following Examples 1 to 7 and Comparative Examples 1 to 4, evaluation was performed after removing grease and other substances in the same manner.

[0061] Example 2: Compound 2 A 500 mL four-neck flask was used for the reaction, 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. Distillation was performed under reduced pressure at 80 Pa from 260° C. to 300° C. to obtain a monoalkyl-substituted product as a fraction. The conditions were the same as those of Example 1, but an alkyl-substituted dinaphthyl ether (compound 2: alkyl(C12)-1-(2-naphthyloxy)naphthalene (C12-1,2-DNO)) mainly composed of a monoalkyl-substituted product was obtained.

[0062] Example 3: Compound 3 A 500 mL four-neck flask was used for the reaction, and 100 g (0.37 mol) of the 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. The reaction was carried out under reduced pressure distillation at 80 Pa and 300° C. to remove unreacted raw materials and monoalkyl substitution products, etc., under the same conditions as in Example 1, to obtain an alkyl-substituted dinaphthyl ether (compound 3: dialkyl(C12)-1-(2-naphthyloxy)naphthalene (diC12-1,2-DNO)) mainly composed of dialkyl substitution products.

[0063] Example 4: Compound 4 A 500 mL four-neck flask was used for the reaction, and 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 were used. Except for this, an alkyl-substituted dinaphthyl ether (compound 4: branched alkyl(C20)-1-(2-naphthyloxy)naphthalene (bC20-1,2-DNO)) mainly composed of monoalkyl substituents was obtained under the same conditions as in Example 1.

[0064] Example 5: Compound 5 A 500 mL four-neck flask was used for the reaction, and 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 were used. Except for this, an alkyl-substituted dinaphthyl ether (compound 5: branched alkyl(C24)-1-(2-naphthyloxy)naphthalene (bC24-1,2-DNO)) mainly composed of monoalkyl substituents was obtained under the same conditions as in Example 1.

[0065] Example 6: Compound 6 A 500 mL four-neck flask was used for the reaction, and 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 were used. Under the same conditions as in Example 1, an alkyl-substituted dinaphthyl ether (compound 6: branched alkyl(C28)-1-(2-naphthyloxy)naphthalene (bC28-1,2-DNO)) mainly composed of monoalkyl substituents was obtained.

[0066] Example 7: Compound 11 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 were placed in a 2L four-neck flask equipped with a stirrer, a thermometer, a dropping funnel and a cooling tube, and the temperature of the reaction system was heated to 175°C after nitrogen replacement. When the temperature reached 120°C, 345g (1.66 mol) of 1-bromonaphthalene was added dropwise. After the dropwise addition was completed, 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 Kyoward 1000s was added and stirred for 30 minutes. Next, 15g of activated clay was added and stirred at 90°C for 30 minutes, and the solids were removed by vacuum filtration. The filter cake was stirred in NMP and vacuum filtration was repeated three times. The obtained filtrate was distilled under reduced pressure at 215 to 240°C at 80 Pa to obtain 1,1-dinaphthyl ether (1,1-dinaphthyl oxide: 1,1-DNO), which is solid at room temperature, as a fraction. 5% by weight of activated clay was added to the compound obtained here, and the mixture was stirred at 90°C for 30 minutes, and grease and other substances that had been mixed in were removed by filtration under reduced pressure. The purity was 99.6%.

[0067] 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-neck flask equipped with a stirrer, a dropping funnel, and a thermometer, and the flask was heated to 100°C to dissolve the anhydrous aluminum chloride. Then, while maintaining the temperature of the reaction system at 110°C, 32.3 g (0.01 mol) of 1-hexadecene was added. .14 mol) was added dropwise over 2 hours to carry out a substitution reaction. After the completion of the dropwise addition, stirring was continued at 110°C for 5 hours, and then the mixture was naturally cooled to 90°C, and Kyoward 1000s was added in an amount 5.5 times that of anhydrous aluminum chloride, and stirred for 30 minutes. Subsequently, activated clay was added in an amount 3.65 times that of anhydrous aluminum chloride, and the mixture was stirred at 90°C for 30 minutes, after which anhydrous aluminum chloride and other by-product acidic substances were removed by vacuum filtration. The filtrate obtained here was distilled under reduced pressure at 320°C and 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)) mainly composed of monoalkyl substitutes. 5% by weight of activated clay was added to the compound obtained here, and the mixture was stirred at 90°C for 30 minutes, and mixed grease, etc. were removed by vacuum filtration.

[0068] (Comparative Example 1: Compound 7) 200g (1.18 mol) of diphenyl ether and 1.00g (0.0075 mol) of anhydrous aluminum chloride were placed in a 500mL four-neck flask equipped with a stirrer, dropping funnel, and thermometer, and the anhydrous aluminum chloride was dissolved by heating to 90°C. Then, 186g (0.83 mol) of 1-hexadecene was added dropwise over 2 hours while maintaining the temperature of the reaction system at 100°C, and a substitution reaction was carried out. After the dropwise addition, the mixture was stirred at 100°C for 1 hour, then naturally cooled to 90°C, and Kyoward 1000s was added in an amount 5.5 times the amount of anhydrous aluminum chloride, and stirred for 30 minutes. Next, activated clay was added in an amount 3.65 times the amount of anhydrous aluminum chloride, and the mixture was stirred at 90°C for 30 minutes, after which the anhydrous aluminum chloride and other by-product acidic substances were removed by vacuum filtration. The filtrate obtained here (reaction filtrate A) was distilled under reduced pressure at 250°C to 260°C at 80 Pa 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 compound obtained here, and the mixture was stirred at 90°C for 30 minutes, and grease and other substances that had been mixed in were removed by filtration under reduced pressure.

[0069] (Comparative Example 2: Compound 8) The reaction filtrate A obtained in Comparative Example 1 was distilled under reduced pressure at 290°C and 80 Pa to remove unreacted raw materials and monoalkyl-substituted products, etc., to obtain an alkyl-substituted diphenyl ether (compound 8: dialkyl (C16) diphenyl ether (diC16-DPO)) mainly composed of dialkyl-substituted products.

[0070] (Comparative Example 3: Compound 9) 200g (0.59 mol) of o-(m-phenoxyphenoxy)diphenyl and 0.72g (0.0054 mol) of anhydrous aluminum chloride were placed in a 500mL four-neck flask equipped with a stirrer, dropping funnel, and thermometer, and the anhydrous aluminum chloride was dissolved by heating to 90°C. Then, 66g (0.29 mol) of 1-hexadecene was added dropwise over 2 hours while maintaining the temperature of the reaction system at 100°C, and a substitution reaction was carried out. After the dropwise addition, the mixture was stirred at 100°C for 1 hour, then naturally cooled to 90°C, and Kyoward 1000s was added in an amount 5.5 times the amount of anhydrous aluminum chloride, and stirred for 30 minutes. Next, activated clay was added in an amount 3.65 times the amount of anhydrous aluminum chloride, and the mixture was stirred at 90°C for 30 minutes, after which the anhydrous aluminum chloride and other by-product acidic substances were removed by vacuum filtration. The filtrate obtained here was distilled under reduced pressure at 320°C and 80 Pa to remove the reaction raw materials, etc., to obtain compound 9 (alkyl(C16)-2-(3-phenoxyphenoxy)diphenyl (C16-4P2E)) consisting mainly of monoalkyl-substituted o-(m-phenoxyphenoxy)diphenyl. 5% by weight of activated clay was added to the compound obtained here, and the mixture was stirred at 90°C for 30 minutes, and the mixed grease, etc. was removed by filtration under reduced pressure.

[0071] (Comparative Example 4: Compound 10) A 500 mL four-neck flask was used for the reaction, and 150 g (0.44 mol) of o-(m-phenoxyphenoxy)diphenyl, 1.85 g (0.014 mol) of anhydrous aluminum chloride, and 168 g (1.85 mol) of 1-hexadecene were used. Except for this, compound 10 (dialkyl(C16)-2-(3-phenoxyphenoxy)diphenyl (diC16-4P2E)) containing dialkyl-substituted o-(m-phenoxyphenoxy)diphenyl as the main component was obtained under the same conditions as in Comparative Example 3.

[0072] [ 1 H-NMR measurement conditions and calculation conditions for the number of hydrocarbon group substitutions] 1 H-NMR was measured using a nuclear magnetic resonance spectrometer JNM-ECX400 manufactured by JEOL Ltd. The measurement conditions were a temperature of 80°C and no solvent or standard substance was used.

[0073] The chemical shifts were determined by comparing the measurements of the same compound using deuterated chloroform as the solvent and TMS as the standard substance, because the peaks of deuterated chloroform and the benzene ring overlap, making it impossible to obtain accurate integral values.

[0074] Under the above conditions 1 The obtained compounds 1 to 11 were analyzed using 1 H-NMR to determine the mass average molecular weight of each compound.

[0075] The number of hydrocarbon group substitutions in compounds 1 to 11 is 1 The H-NMR spectrum was analyzed to determine the NMR spectrum of the model compound shown in Figure 2. 1 The calculation method will be explained using H-NMR spectrum.

[0076] In FIG. 2, a (chemical shift 6.5 to 7.3) indicates the peak of hydrogen in the aromatic ring. b1 (chemical shift 2.8 to 3.3) and b2 (chemical shift 2.2 to 2.7) indicate the peak of hydrogen in the benzyl position. c (chemical shift 0.5 to 1.9) indicates the peak of hydrogen in the hydrocarbon group.

[0077] These a and b 1、 Based on the integral value (ratio) of the peaks b2 and c, the number of hydrocarbon group substitutions is calculated using the following formula: Number of hydrocarbon group substitutions (m+n) = (number of hydrogen atoms in aromatic rings) × (b1+b2+c) / [(average number of hydrogen atoms in hydrocarbon groups) × a+b1+b2+c]

[0078] <Purity measurement> [Gas chromatography (GC) measurement conditions] Gas chromatography was performed using a Shimadzu GC-2010 Plus. The column was an Ultra ALLOY+-17, and the carrier gas was nitrogen gas. The measurement temperature conditions were: hold at 50°C for 2 minutes, then raise the temperature to 100°C at 25°C per minute, then raise the temperature from 100°C to 350°C at 15°C per minute, and hold at 350°C for 15 minutes.

[0079] <Evaluation test> [Measurement of evaporation amount by TG method] The amount of evaporation by the TG method was measured using an ST7200RV manufactured by Hitachi High-Technologies Corp. The carrier gas was air (200 ml / min), the sample container was an aluminum deep dish pan, the sample amount was 5 mg, the temperature was 250°C, and the amount of evaporation (%) of each compound was measured after holding for 30 and 60 minutes.

[0080] In this test, a compound that satisfies the evaluation criteria of 10% or less evaporation after 30 minutes and 15% or less evaporation after 60 minutes is considered to pass.

[0081] [Thin film heating test] 0.5 g of each of the above compounds 1 to 11 was weighed into a 50Φ concave dish made of S45C. This was left in a thermostatic chamber at 200°C, and was taken out of the chamber every 2 hours to measure the weight, and the fluidity was confirmed when the film was returned to room temperature. The time when the film lost fluidity at room temperature was defined as the thin film life. In this test, a thin film life of 25 hours or more was judged to be a pass.

[0082] [Lubricity test (SRV)] Lubricity was measured using an OPTIMOL SRV-5. The upper test piece was a 1 / 2 inch SUJ2 ball, and the lower test piece was an SK-5 plate. After a break-in period of 50 seconds at 40°C, load of 50N, and speed of 40mm / s, the main test was carried out at 40°C, load of 100N, and speed of 40mm / s for 600 seconds to measure the coefficient of friction (COF) and calculate the average COF at 100N. In this test, an average COF of 0.150 or less is considered a pass.

[0083] [Viscosity properties] 40℃ kinematic viscosity (mm 2 / s) was measured and calculated in accordance with JIS K 2283 (2000).

[0084] The above results are summarized in Tables 1 and 2.

[0085] [Table 1]

[0086] [Table 2]

[0087] (Consideration) From the results in Table 1, it was shown that the dinaphthyl ether compounds 1 to 6 and compound 11 of the examples related to the present invention all met the pass criteria for both the evaporation amount and thin film life described above. It is generally known that the kinetic viscosity increases as the number of carbon atoms in the hydrocarbon group increases, but the kinetic viscosity of the compounds of the present invention decreased as the number of carbon atoms in the hydrocarbon group increased. In addition, when comparing Examples 2 and 3 with Comparative Examples 2 and 3, the compounds of the present invention had the same molecular weight, the evaporation amount was suppressed. When comparing Examples 1 to 7 and Comparative Examples 3 and 4, which have the same number of six-membered ring structures, the evaporation amount was suppressed. Furthermore, in terms of the thin film life, which is a more stringent heat resistance evaluation, the heat resistance time was more than twice as long when comparing Examples 1 to 7 and Comparative Examples 3 and 4, which have the same number of six-membered ring structures, and an improvement in heat resistance was observed. This is thought to be because the naphthalene structure prevents polymerization reaction due to thermal oxidation.

[0088] 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 polyphenyl ether compounds of Comparative Examples 3 and 4 had a large amount of evaporation and a short thin film life, and could not obtain the same heat resistance as the compounds of the present invention.

[0089] This application is based on Japanese patent application No. 2021-020368 filed on February 12, 2021, the contents of which are incorporated herein by reference.

[0090] In order to express the present invention, the present invention has been described adequately and sufficiently through the embodiments with reference to specific examples, but it should be recognized that those skilled in the art can easily change and / or improve the above-mentioned embodiments. Therefore, unless the changes or improvements made by those skilled in the art are at a level that departs from the scope of the claims described in the claims, the changes or improvements are interpreted as being included in the scope of the claims. [Industrial Applicability]

[0091] Since the dinaphthyl ether compound of the present invention has excellent heat resistance, it can be suitably used as high-temperature lubricating oils, heat-resistant greases, etc., and has a wide range of industrial applicability.

Claims

1. A dinaphthyl ether compound represented by the following formula (1): 【Chemistry 1】 (In formula (1), R １ and R ２ are the same or different and are straight-chain or branched-chain hydrocarbon groups having 6 to 32 carbon atoms; m and n are each a real number of 0 or more, m+n is the average number of hydrocarbon group substitutions, and satisfies 1.0≦m+n≦3.0).

2. A lubricating oil composition comprising the compound of claim 1.

3. A high temperature lubricating oil comprising the compound of claim 1.

4. A heat resistant grease comprising the compound of claim 1.

5. A radiation resistant lubricating oil comprising the compound of claim 1.

6. A radiation resistant grease comprising the compound of claim 1.

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