Naphthyl phenyl ether compound and lubricating oil composition containing the same

Abstract

One aspect of the present invention relates to a naphthylphenyl ether compound represented by 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 28 carbon atoms; m and n are real numbers of 0 or more, and satisfy 1.0 ≤ m + n ≤ 3.0.

Description

Technical Field

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

[0002] Lubricating oils and lubricating oil compositions are used to reduce friction and wear between moving parts or moving surfaces of various mechanical devices, etc.

[0003] In particular, lubricating oils, greases, etc. are used under more severe conditions such as high temperature, high speed, high load, radiation, etc., and lubricating oil agents with more excellent heat resistance are required.

[0004] When the use conditions become high temperature and high speed, lubricating oils and greases used for lubrication, etc. cause temperature rise, thermal deterioration or oxidative deterioration due to insufficient oil film, thereby promoting the evaporation of the lubricating oil base oil, which results in the generation of sludge, mechanical device breakage or shortened life.

[0005] For this reason, 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 to a large extent on the base oil with the largest content in the composition of the lubricating oil and grease.

[0006] So far, radiation-resistant lubricating oils containing 75 - 25% of monoalkyl diphenyl ether or dialkyl diphenyl ether with an alkyl carbon number of 10 - 20 have been known (Patent Document 1).

[0007] In addition, as a lubricating oil having oxidation stability, a naphthyl ether compound having an alkyl group with 1 - 20 carbon atoms, a phenyl group, a monoalkylphenyl group with 7 - 26 carbon atoms, etc. has also been proposed (Patent Document 2).

[0008] The lubricating oil agent described in Patent Document 1 has excellent heat resistance and radiation resistance, but currently lubricating oil agents such as lubricating oils and greases are used under more severe conditions, so lubricating oil agents with better heat resistance are required. In addition, in Patent Document 2, the phenylnaphthyl ether compound actually used in the examples is butylphenylnaphthyl ether, and through the research of the inventors of the present invention, it is found that sufficient heat resistance cannot be obtained by using this compound.

[0009] Prior Art Documents

[0010] Patent Documents

[0011] Patent Document 1: Japanese Patent Publication Gazette Tokko Sho 62 - 59760

[0012] Patent Document 2: Japanese Patent Laid - Open Gazette Tokkai Hei 1 - 316340 Summary of the Invention

[0013] The problem to be solved by the present invention is to address the above-mentioned issues. That is, the object of the present invention is to provide a compound that can be used as a lubricating oil with more excellent heat resistance and can be used under harsher conditions.

[0014] The inventors of the present invention conducted intensive research to solve the above-mentioned problems and found that a naphthyl phenyl ether compound having the following structure can achieve the above object. Based on this insight, further research was repeatedly carried out, and thus the present invention was completed.

[0015] That is, the naphthyl phenyl ether compound according to one aspect of the present invention is a compound represented by the following formula (1).

[0016]

[0017] In formula (1), R 1 and R 2 are the same or different and are linear or branched hydrocarbon groups having 6 to 28 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

[0018] Figure 1 Shows the gas chromatography (GC) chart of the naphthyl phenyl ether synthesized in Example 1.

[0019] Figure 2 Shows the 1 1H-NMR spectrum of the model compound for determining the number of hydrocarbon group substitutions. DETAILED DESCRIPTION

[0020] As described above, the naphthyl phenyl ether compound of the present invention is a compound represented by the following formula (1).

[0021]

[0022] In formula (1), R 1 and R 2 are the same or different and are linear or branched hydrocarbon groups having 6 to 28 carbon atoms. In addition, m and n are each a real number of 0 or more, and satisfy 1.0 ≤ m + n ≤ 3.0.

[0023] The naphthyl phenyl ether compound having this structure maintains low-temperature characteristics (pour point) and lubricity equivalent to those of the conventional compounds described in the above-mentioned prior art documents, and has very excellent heat resistance. Therefore, it is very useful as a lubricating oil. More specifically, the naphthyl phenyl ether compound has a small evaporation loss at high temperatures and a long life at high temperatures, and is therefore suitable as a base oil for high-temperature lubricating oils or heat-resistant greases used at higher temperatures.

[0024] Therefore, according to the present invention, it is possible to provide a naphthylphenyl ether compound that is used as a lubricating oil having more excellent heat resistance and capable of being used under harsher conditions.

[0025] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited thereto.

[0026] The naphthylphenyl ether compound of the present embodiment is the compound represented by the above formula (1).

[0027] In formula (1), R 1 and R 2 are the same or different and are hydrocarbon groups having 6 to 28 carbon atoms. For example, when either m or n in the formula (1) is 0, either R 1 or R 2 can be a hydrogen atom. That is, either R 1 or R 2 can be a hydrogen atom, but at least one of them is the hydrocarbon group.

[0028] If the carbon number of the hydrocarbon group is less than 6, it exhibits the physical properties of naphthylphenyl ether without a hydrocarbon group and becomes easy to solidify. In addition, since the molecular weight is small, the evaporation amount increases. On the other hand, if the carbon number exceeds 28, the intermolecular interaction becomes large and the viscosity becomes too high. In addition, the hydrocarbon groups are likely to aggregate and the pour point becomes too high. When R 1 and R 2 are hydrocarbon groups having 6 to 28 carbon atoms, the naphthylphenyl ether compound of the present embodiment has excellent heat resistance, lubricity, and low-temperature fluidity.

[0029] In the present embodiment, the hydrocarbon group having 6 to 28 carbon atoms has a linear or branched structure. Specifically, as the linear hydrocarbon group, for example, alkyl groups such as hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, docosyl, tetracosyl, hexacosyl, octacosyl; alkenyl groups such as octenyl, decenyl, hexadecenyl, dodecenyl, octadecenyl, eicosenyl, docosenyl, tetracosenyl, hexacosenyl, octacosenyl; cyclohexyl and the like can be mentioned. As the branched hydrocarbon group, for example, 1-methylundecyl, 1-ethyldecyl, 1-methyltridecyl, 1-ethyldodecyl, 1-methylpentadecyl, 1-ethyltetradecyl, 1-methylheptadecyl, 1-ethyloctadecyl, 1-methylnonadecyl, 1-ethyloctadecyl, 2-ethylhexyl, 2-octyldodecyl, 2-decyltetradecyl, 2-dodecylhexadecyl, 1-butyl-1-methylpentyl, 1-butyl-1-methylheptyl, 1-methyl-1-pentyloctyl, 1-hexyl-1-methylnonyl, 1-heptyl-1-methyldecyl, 1-methyl-1-octylundecyl, 1-decyl-1-methyltridecyl, 1-dodecyl-1-methylpentadecyl, 2-octyldodecenyl, 2-decyltetradecenyl, cyclohexyl and the like can be mentioned. Since the thermal stability is excellent, the hydrocarbon group is preferably a saturated hydrocarbon group. A plurality of the hydrocarbon groups can be used simultaneously. In this case, the carbon number of the hydrocarbon group is represented by its average value.

[0030] Among these hydrocarbon groups, from the viewpoint of obtaining more excellent heat resistance, a hydrocarbon group having 12 to 24 carbon atoms is preferred, 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, 2-dodecylhexadecyl and the like.

[0031] As long as m and n satisfy 1.0 ≤ m + n ≤ 3.0 in the above-mentioned formula (1), the hydrocarbon group can be bonded to either the naphthyl group or the phenyl group, and can also be bonded to any position of the naphthyl group and the phenyl group. Further, for example, when m + n is 1, either of R 1 and R 2 can be a hydrogen atom.

[0032] In the compound of the above formula (1), m and n are each a real number of 0 or more, and satisfy 1.0 ≤ m + n ≤ 3.0. If m + n is less than 1.0, the physical properties of a naphthyl phenyl ether having no hydrocarbon group are exhibited and it is likely to solidify. In addition, since the molecular weight is small, the evaporation amount cannot be sufficiently suppressed. On the other hand, if m + n exceeds 3.0, the intermolecular interaction becomes large and the viscosity becomes too high. In the present embodiment, m + n represents the number of linear or branched hydrocarbon group substitutions (hereinafter also simply referred to as the number of alkyl substitutions).

[0033] The compound of the present embodiment may be, for example, a mixture of a compound of 0 ≤ m + n ≤ 2.0 and a compound of 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 means the average value of m + n in the naphthyl phenyl ether compound contained in the compound of the present embodiment.

[0034] In a preferred embodiment, m + n is more preferably 1 or more and 2.5 or less.

[0035] In the present embodiment, the number of hydrocarbon group substitutions can be measured by the method shown in the examples described later.

[0036] The weight average molecular weight of the naphthyl phenyl ether compound of the present embodiment is preferably about 420 to 700. If the weight average molecular weight of the naphthyl phenyl ether compound is large, there is a tendency for excellent heat resistance, but there is a risk that the kinematic viscosity is too high or the lubricity deteriorates. On the contrary, if the weight average molecular weight is small, the kinematic viscosity becomes low, but there is a tendency for poor heat resistance. If the weight average molecular weight is within the above range, it has the advantages that the kinematic viscosity and pour point are not too high and the heat resistance is excellent.

[0037] In addition, the weight average molecular weight of the naphthyl phenyl ether compound in the present embodiment is, as shown in the examples described later, a value measured by 1 1H-NMR. In addition, hereinafter, the weight average molecular weight will also be simply referred to as "average molecular weight".

[0038] The method for producing the naphthyl phenyl ether compound as described above is not particularly limited, and can be obtained, for example, by the following synthesis method.

[0039] First, 2-naphthol and N-methyl-2-pyrrolidone are mixed with potassium carbonate and copper iodide for nitrogen substitution, and bromobenzene is added dropwise thereto to obtain naphthyl phenyl ether.

[0040] Next, for example, using aluminum chloride or the like as a catalyst, the naphthyl phenyl ether is reacted with a linear or branched olefin or the like, whereby the naphthyl phenyl ether compound of the present embodiment can be obtained.

[0041] The present invention also includes a lubricating oil composition containing the naphthyl phenyl ether compound as described above.

[0042] In the lubricating oil composition of the present embodiment, in addition to the naphthyl phenyl ether compound, for the purpose of further improving its performance or for imparting more performance as needed, within the range not impairing the effects of the present invention, mineral oil can be mixed, 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 can also be mixed. In addition, various additives such as antioxidants, extreme pressure agents, friction improvers, metal deactivators, defoamers, thickeners, and colorants can be individually mixed or a combination of multiple can be mixed as needed.

[0043] As the additive, antioxidants commonly used in lubricating oils can be used without particular limitation. Examples of antioxidants include phenolic compounds, amine compounds, phosphorus compounds, sulfur compounds, and the like.

[0044] Examples of extreme pressure agents include phosphorus compounds, sulfur compounds, and the like.

[0045] Examples of friction improvers include molybdenum compounds such as molybdenum dithiocarbamate and fatty acid derivatives such as glycerol monostearate.

[0046] Examples of metal deactivators include benzotriazoles, methylbenzotriazoles, thiadiazoles, and imidazole compounds.

[0047] Examples of defoamers include polyacrylates and styrene ester polymers.

[0048] Examples of thickeners include metal soaps (such as lithium soaps), silica, expanded graphite, polyureas, clays (such as lithium montmorillonite or bentonite).

[0049] In the lubricating oil composition of the present embodiment, when the naphthyl phenyl ether compound is contained as a base oil, from the viewpoint of ensuring heat resistance, its content is preferably about 50 to 100% by mass relative to the entire lubricating oil composition (total mass). In addition, at this time, the content of additives and the like in the lubricating oil composition is preferably about 50 to 0% by mass.

[0050] Alternatively, the naphthyl phenyl ether compound can be used as an additive in the lubricating oil composition. At this time, the content of the naphthyl phenyl ether compound is preferably about 1 to 49% by mass relative to the entire lubricating oil composition (total mass).

[0051] In addition, the present invention also includes a high-temperature lubricating oil and a heat-resistant grease containing the naphthyl phenyl ether compound described above.

[0052] The lubricating oil composition, high-temperature lubricating oil, and heat-resistant grease described above are suitable for use as lubricants for bearings, lubricants for impregnated bearings, grease base oils, refrigeration oils, plasticizers, etc. They are particularly suitable for use as various lubricating oils used under high-temperature conditions, 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 working fluids, etc.

[0053] In addition, since the radiation resistance of the naphthyl phenyl ether compound described above is also excellent, it is considered to be suitable for use as a radiation-resistant lubricating oil or radiation-resistant grease.

[0054] The present specification has disclosed the technology in various ways as described above, and its main technology is summarized as follows.

[0055] The naphthyl phenyl ether compound related to one aspect of the present invention is a compound represented by the following formula (1).

[0056]

[0057] In formula (1), R 1 and R 2 are the same or different and are linear or branched hydrocarbon groups having 6 to 28 carbon atoms; m and n are real numbers of 0 or more, and satisfy 1.0 ≤ m + n ≤ 3.0.

[0058] With this configuration, a compound having more excellent heat resistance than conventional lubricating oils can be provided.

[0059] The lubricating oil composition related to another aspect of the present invention contains the above-mentioned naphthyl phenyl ether compound.

[0060] The high-temperature lubricating oil and radiation-resistant lubricating oil related to another aspect of the present invention contain the above-mentioned naphthyl phenyl ether compound.

[0061] The heat-resistant grease and radiation-resistant grease related to another aspect of the present invention contain the above-mentioned naphthyl phenyl ether compound.

[0062] The lubricating oil composition, high-temperature lubricating oil, and heat-resistant grease related to the present invention have very excellent heat resistance, and thus are suitable for use under severe conditions (especially at high temperatures).

[0063] Examples

[0064] Hereinafter, examples of the present invention will be described, but the present invention is not limited thereto.

[0065] [Synthesis of Compounds]

[0066] (Example 1: Compound 1)

[0067] Into a 5-L four-necked flask equipped with a stirrer, a thermometer, a dropping funnel, and a condenser were charged 504 g (3.50 mol) of 2-naphthol, 961 g (6.95 mol) of potassium carbonate, 135 g (0.71 mol) of copper(I) iodide, and 1500 g of N-methyl-2-pyrrolidone (hereinafter referred to as NMP). After nitrogen substitution, the mixture was heated until the temperature of the reaction system reached 175 °C. When the temperature reached 120 °C, 1120 g (7.13 mol) of bromobenzene was started to be added dropwise. After the 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, 60 g of KYOWAAD 1000s (basic adsorbent; manufactured by Kyowa Chemical Industry Co., Ltd.) was added, and the mixture was stirred for 30 minutes. Then, 40 g of activated clay was added, and after stirring at 90 °C for 30 minutes, the solid components were removed by vacuum filtration. The filter cake was stirred into NMP, and vacuum filtration was repeated three times. The obtained filtrate was subjected to vacuum distillation at 80 Pa at 165 °C to 170 °C, and 2-naphthyl phenyl ether (2-naphthyl phenyl oxide: 2-NPO), which is a solid at room temperature, was obtained as a fraction. 5 wt% 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 and the like were removed by vacuum filtration. Figure 1 The gas chromatogram (GC) of naphthyl phenyl ether is shown (measurement conditions will be described later). The purity was 98.7%. The naphthyl phenyl ether synthesized here was also used as a reaction material in Examples 2 to 6 described later.

[0068] Next, 200 g (0.91 mol) of the obtained naphthyl phenyl ether and 2.85 g (0.021 mol) of anhydrous aluminum chloride were charged into a 500 mL four-necked flask equipped with a stirrer, a dropping funnel, and a thermometer. The mixture was heated to 90 °C to dissolve the anhydrous aluminum chloride. Then, while maintaining the temperature of the reaction system at 110 °C, 102 g (0.45 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 110 °C for 5 hours, and then it was naturally cooled to 90 °C. 5.5 times the amount of KYOWAAD 1000s relative to the anhydrous aluminum chloride was added, and stirring was carried out for 30 minutes. Next, 3.65 times the amount of activated clay relative to the anhydrous aluminum chloride was added, and after stirring at 90 °C for 30 minutes, the anhydrous aluminum chloride and other by-produced acidic substances were removed by vacuum filtration. The filtrate obtained here was subjected to vacuum distillation at 260 °C under 80 Pa to remove unreacted raw materials and the like, and an alkyl-substituted naphthyl phenyl ether (Compound 1: alkyl (C16)-2-phenoxynaphthalene (C16-2-NPO)) mainly composed of a monoalkyl-substituted product was obtained. 5 wt% of activated clay was added to the obtained compound, and stirring was carried out at 90 °C for 30 minutes, and the mixed grease and the like were removed by vacuum filtration. In addition, Compound 1 after removing the grease and the like was evaluated. Hereinafter, Grease and the like were removed and evaluated in the same manner for Examples 1 to 7 and Comparative Examples 1 to 3.

[0069] (Example 2: Compound 2)

[0070] The reaction was carried out using a 500 mL four-necked flask, and 130 g (0.59 mol) of the naphthyl phenyl ether obtained in Example 1, 1.11 g (0.0083 mol) of anhydrous aluminum chloride, and 39.7 g (0.18 mol) of 1-hexadecene were used. Vacuum distillation was carried out at 300 °C under 80 Pa to remove unreacted raw materials and monoalkyl-substituted products. Except for this, under the same conditions as in Example 1, an alkyl-substituted naphthyl phenyl ether (Compound 2: dialkyl (C16)-2-phenoxynaphthalene (diC16-2-NPO)) mainly composed of a dialkyl-substituted product was obtained.

[0071] (Example 3: Compound 3)

[0072] The reaction was carried out using a 500 mL four-necked flask, and 100 g (0.45 mol) of the naphthyl phenyl ether obtained in Example 1, 1.07 g (0.0080 mol) of anhydrous aluminum chloride, and 38.2 (0.23 mol) of 1-dodecene were used. Vacuum distillation was carried out at 260 °C to 300 °C under 80 Pa, and a monoalkyl-substituted product was obtained as a fraction. Except for this, under the same conditions as in Example 1, an alkyl-substituted naphthyl phenyl ether (Compound 3: alkyl (C12)-2-phenoxynaphthalene (C12-2-NPO)) mainly composed of a monoalkyl-substituted product was obtained.

[0073] (Example 4: Compound 4)

[0074] The reaction was carried out in a 500 mL four-necked flask using 100 g (0.45 mol) of the naphthylphenyl ether obtained in Example 1, 1.93 g (0.014 mol) of anhydrous aluminum chloride, and 68.77 (0.41 mol) of 1-dodecene. In addition, under reduced pressure distillation at 300 °C and 80 Pa, an alkyl-substituted naphthylphenyl ether (Compound 4: dialkyl (C12)-2-phenoxynaphthalene (diC12-2-NPO)) mainly composed of dialkyl-substituted products was obtained under the same conditions as in Example 1.

[0075] (Example 5: Compound 5)

[0076] The reaction was carried out in a 500 mL four-necked flask using 135 g (0.61 mol) of the naphthylphenyl ether obtained in Example 1, 2.40 g (0.018 mol) of anhydrous aluminum chloride, and 85.8 (0.31 mol) of 2-octyl-1-dodecene. In addition, under the same conditions as in Example 1, an alkyl-substituted naphthylphenyl ether (Compound 5: branched alkyl (C20)-2-phenoxynaphthalene (bC20-2-NPO)) mainly composed of monoalkyl-substituted products was obtained.

[0077] (Example 6: Compound 6)

[0078] The reaction was carried out in a 100 mL four-necked flask using 33 g (0.15 mol) of the naphthylphenyl ether obtained in Example 1, 0.71 g (0.0053 mol) of anhydrous aluminum chloride, and 85.8 (0.31 mol) of 2-decyl-1-tetradecene. In addition, under the same conditions as in Example 1, an alkyl-substituted naphthylphenyl ether (Compound 6: branched alkyl (C24)-2-phenoxynaphthalene (bC24-2-NPO)) mainly composed of monoalkyl-substituted products was obtained.

[0079] (Example 7: Compound 10)

[0080] In a 2 L four-necked flask equipped with a stirrer, a thermometer, a dropping funnel, and a condenser, 250 g (1.73 moles) of 1-naphthol, 479 g (3.47 moles) of potassium carbonate, 66 g (0.35 mole) of copper iodide, and 380 g of NMP were charged. After nitrogen substitution, heating was carried out until the temperature of the reaction system reached 175 °C. When the temperature reached 120 °C, 545 g (3.47 moles) of bromobenzene was started to be dropped. After the dropping was completed, stirring was carried out at 175 °C for 6 hours. After the reaction was completed, it was naturally cooled to 90 °C, 30 g of KYOWAAD 1000s was added, and stirring was carried out for 30 minutes. Then, 20 g of activated clay was added, and after stirring at 90 °C for 30 minutes, the solid components were removed by vacuum filtration. The filter cake was stirred into NMP, and vacuum filtration was repeated 3 times. The obtained filtrate was subjected to vacuum distillation at 80 Pa at 165 °C to 170 °C, and 1-naphthyl phenyl ether (1-naphthyl phenyl oxide: 1-NPO) was obtained as a fraction. 5 wt% of activated clay was added to the compound obtained here, and stirring was carried out at 90 °C for 30 minutes, and the mixed grease, etc. was removed by vacuum filtration. The purity was 99.0%.

[0081] Next, 110 g (0.50 mole) of the above-obtained 1-naphthyl phenyl ether and 1.57 g (0.012 mole) of anhydrous aluminum chloride were charged into a 500 mL four-necked flask equipped with a stirrer, a dropping funnel, and a thermometer. It was heated to 90 °C to dissolve the anhydrous aluminum chloride, and then while maintaining the temperature of the reaction system at 110 °C, 56 g (0.25 mole) of 1-hexadecene was dropped over 1 hour, and a substitution reaction was carried out. After the dropping was completed, stirring was continued at 110 °C for 5 hours, then it was naturally cooled to 90 °C, 5.5 times the amount of KYOWAAD 1000s of anhydrous aluminum chloride was added, and stirring was carried out for 30 minutes. Then, 3.65 times the amount of activated clay of anhydrous aluminum chloride was added, and after stirring at 90 °C for 30 minutes, the anhydrous aluminum chloride and other by-produced acidic substances were removed by vacuum filtration. The filtrate obtained here was subjected to vacuum distillation at 80 Pa at 260 °C to remove unreacted raw materials, etc., and an alkyl-substituted naphthyl phenyl ether (Compound 10: alkyl (C16)-1-phenoxynaphthalene (C16-1-NPO)) mainly composed of a monoalkyl-substituted product was obtained. 5 wt% of activated clay was added to the obtained compound, and stirring was carried out at 90 °C for 30 minutes, and the mixed grease, etc. was removed by vacuum filtration.

[0082] (Comparative Example 1: Compound 7)

[0083] Into a 500 mL four-necked flask equipped with a stirrer, a dropping funnel, and a thermometer, 200 g (1.18 moles) of diphenyl ether and 1.00 g (0.0075 moles) of anhydrous aluminum chloride were charged, and 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 moles) of 1-hexadecene was added dropwise over 2 hours, and a substitution reaction was carried out. After completion of the dropwise addition, stirring was continued at 100 °C for 1 hour, then naturally cooled to 90 °C, 5.5 times the amount of KYOWAAD 1000s of anhydrous aluminum chloride was added, and stirred for 30 minutes. Next, 3.65 times the amount of activated clay of anhydrous aluminum chloride was added, stirred at 90 °C for 30 minutes, and then anhydrous aluminum chloride and other by-produced acidic substances were removed by vacuum filtration. The filtrate obtained here (reaction filtrate A) was subjected to vacuum distillation at 80 Pa from 250 °C to 260 °C, and monoalkyl-substituted diphenyl ether (Compound 7: alkyl (C16)-diphenyl ether (C16-DPO)) was obtained as a fraction. 5 wt% of activated clay was added to the compound obtained here and stirred at 90 °C for 30 minutes, and the mixed grease etc. was removed by vacuum filtration.

[0084] (Comparative Example 2: Compound 8)

[0085] The reaction filtrate A obtained in Comparative Example 1 was subjected to vacuum distillation at 80 Pa at 290 °C to remove unreacted raw materials and monoalkyl-substituted products etc., and an alkyl-substituted diphenyl ether (Compound 8: dialkyl (C16) diphenyl ether (diC16-DPO)) mainly composed of dialkyl-substituted products was obtained.

[0086] (Comparative Example 3: Compound 9)

[0087] Into a 5 L four-necked flask equipped with a stirrer, a thermometer, a dropping funnel, and a condenser, 100 g (0.67 moles) of 4-sec-butylphenyl, 275 g (1.33 moles) of 1-bromonaphthalene, 138 g (1.33 moles) of potassium carbonate, 25 g (0.13 moles) of copper iodide, and 350 g of N-methyl-2-pyrrolidone (hereinafter referred to as NMP) were charged, and nitrogen substitution was carried out. Then, stirred at 175 °C for 12 hours. After completion of the reaction, naturally cooled to 90 °C, 20 g of KYOWAAD 1000s was added, and stirred for 30 minutes. Next, 15 g of activated clay was added, stirred at 90 °C for 30 minutes, and then the solid components were removed by vacuum filtration. The filter cake was stirred into NMP, and vacuum filtration was repeated 3 times. The obtained filtrate was subjected to vacuum distillation at 80 Pa from 190 °C to 220 °C, and 4-sec-butylphenyl-1-naphthyl ether (Compound 9) was obtained as a fraction. 5 wt% of activated clay was added to the compound obtained here and stirred at 90 °C for 30 minutes, and the mixed grease etc. was removed by vacuum filtration.

[0088] [ 1 H-NMR measurement conditions and calculation conditions for the number of hydrocarbon group substitutions]

[0089] 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.

[0090] 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.

[0091] Use under the above conditions 1 The obtained compounds 1 to 10 were analyzed by H-NMR to determine the mass average molecular weight of each compound.

[0092] In addition, the number of hydrocarbon substitutions of compounds 1 to 10 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.

[0093] 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.

[0094] 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.

[0095] 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]

[0096] <Purity Determination>

[0097] [Gas chromatography (GC) measurement conditions]

[0098] 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.

[0099] <Evaluation Test>

[0100] [Determination of Evaporation Rate Based on TG Method]

[0101] The evaporation rate based on the TG method was measured using an ST7200RV manufactured by Hitachi High-Technologies Corporation. Air (200 ml / min) was used as the carrier gas, an aluminum deep dish was used as the sample container, the sample amount was 5 mg, and the evaporation rate (%) of each compound was measured when maintained at 250 °C for 30 minutes.

[0102] In this test, regarding the evaluation criteria, a compound with an evaporation rate of 27% or less after 30 minutes was regarded as qualified.

[0103] [Thin-Film Heating Test]

[0104] 0.5 g of each of the above Compounds 1 - 10 was weighed and placed in a 50Φ recessed dish made of S45C material. It was left standing in an incubator at 200 °C, taken out of the incubator every 2 hours to measure the weight, and the fluidity at room temperature was confirmed. Also, the time when fluidity was lost at room temperature was taken as the thin-film life. In this test, a thin-film life of 25 hours or more was judged as qualified.

[0105] [Lubricity Test (SRV)]

[0106] The lubricity was measured using an SRV-5 from OPTIMOL Instruments Prueftechnik GmbH. A 1 / 2-inch SUJ2 ball was used as the upper test piece, and an SK-5 plate was used as the lower test piece. After a 50-second adaptation run at a temperature of 40 °C, a load of 50 N, and a speed of 40 mm / sec, a 600-second formal test was carried out at a temperature of 40 °C, a load of 100 N, and a speed of 40 mm / sec, and the coefficient of friction (COF) was measured to obtain the average COF at 100 N. In this test, an average COF of 0.150 or less was judged as qualified.

[0107] [Fluidity]

[0108] The pour points (°C) of Compounds 1 - 10 were measured based on JIS K2269 (1987). In this test, -20 °C or lower was judged as qualified.

[0109] [Viscosity Characteristics]

[0110] The kinematic viscosity at 40 °C (mm 2 / sec) was measured and calculated according to JIS K 2283 (2000).

[0111] The above results are summarized in Tables 1 and 2.

[0112]

[0113] Table 2

[0114]

[0115] (Inspection)

[0116] According to the results in Table 1, the naphthylphenyl ether compounds 1 to 6 and compound 10 of the embodiments of the present invention all meet the qualification standards of both the evaporation amount and the film life. That is to say, it can be seen that the heat resistance is very excellent because the evaporation loss at high temperature is small and the life at high temperature is long. Generally, it is known that the evaporation amount increases as the molecular weight of the compound decreases, but in the compounds of the present invention, when Examples 1, 2 and 7 are compared with Comparative Example 2, the evaporation amount is suppressed even if the carbon number of the hydrocarbon group is the same. When Examples 2, 4, 6 and 7 are compared with Comparative Example 2, the evaporation amount is suppressed even if the molecular weight is the same. When Example 3 having the same kinematic viscosity is compared with Comparative Example 2, it can be seen that in the case of having the structure of the present invention, the friction coefficient is excellent. When Examples 1 to 7 are compared with Comparative Example 3, even if they are the same naphthyl ethers, due to the hydrocarbon group (R 1 and / or R 2 ) with different carbon numbers, Examples 1 to 7 exhibited excellent properties. Furthermore, it was confirmed that the compounds of the present invention exhibit comparable low-temperature fluidity and lubricity to compounds previously used as lubricants. While the kinematic viscosity at 40°C in the Examples was higher than that in the Comparative Examples, they were still usable as lubricants. Thus, it was confirmed that when the hydrocarbon group of the naphthylphenyl ether has 6 to 28 carbon atoms and the number of hydrocarbon group substitutions is 1.0 ≤ m + n ≤ 3.0, it exhibits both heat resistance and low-temperature fluidity and lubricity.

[0117] On the other hand, the results in Table 2 show that the conventionally used diphenyl ether compounds of Comparative Examples 1 and 2 and butylphenylnaphthyl ether of Comparative Example 3 exhibited large evaporation rates and short film life, failing to achieve heat resistance comparable to that of the compounds of the present invention. Furthermore, in all Examples and Comparative Examples 1 and 2, fluidity was reconfirmed when the ambient temperature was raised to a temperature above the pour point after pour point measurement. However, in Comparative Example 3, the film remained solid even after returning to room temperature.

[0118] It is believed that: Since NPO is solid at room temperature, R 2 The hydrocarbon group of Comparative Example 3, which has 4 carbon atoms and m+n=1, is short, so the physical properties of NPO are greatly affected, making it easy to solidify. In addition, if the carbon number of the hydrocarbon group exceeds 28, it is believed that the interaction between molecules becomes stronger, and the viscosity and pour point become too high.

[0119] This application is based on Japanese Patent Application No. 2021-020367 filed on February 12, 2021, the content of which is incorporated herein.

[0120] In order to describe the present invention, specific examples and the like are referred to in the above description, and the present invention is appropriately and sufficiently described by embodiments. However, it should be understood that those skilled in the art can easily make changes and / or improvements to the above embodiments. Therefore, as long as the modified embodiments or improved embodiments implemented by those skilled in the art do not exceed the scope of protection of the claims recited in the claims, such modified embodiments or improved embodiments can be interpreted as being included within the scope of protection of the claims.

[0121] Industrial Applicability

[0122] The naphthylphenyl ether compound of the present invention has very excellent heat resistance, and thus can be suitably used as a lubricating oil for high temperatures, a heat-resistant grease, etc., and has wide industrial applicability.

Claims

1. A lubricating oil composition, characterized in that containing a naphthyl phenyl 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 28 carbon atoms; m and n are each a real number of 0 or more, and 1.2 ≤ m + n ≤ 3.0 is satisfied.

2. The lubricating oil composition according to claim 1, characterized in that, R of the naphthyl phenyl ether compound 1 and R 2 are the same or different and are linear or branched hydrocarbon groups having 12 to 24 carbon atoms.

3. The lubricating oil composition according to claim 1 or 2, characterized in that, the weight average molecular weight of the naphthyl phenyl ether compound is 420 to 700.

Images