Lubricating oil base oil composition

[0001] [Technical field to which the invention belongs] The present invention relates to a lubricating oil base oil composition, and more particularly to a lubricating oil base oil composition having improved low temperature flow characteristics while maintaining high temperature traction characteristics, which is suitable for a fluid composition for traction drive. .. [0002] [Conventional technology] The traction drive fluid used in an automobile traction type CVT (continuously variable transmission) must satisfy the contradictory performances of high traction coefficient even at high temperature and low viscosity even at low temperature. That is, synthetic naphthenic compounds having a high traction coefficient at high temperatures have poor low-temperature fluidity, and additives may be added to eliminate the poor low-temperature fluidity, but conversely, the traction coefficient at high temperatures tends to decrease. For example, Japanese Patent Application Laid-Open No. 2000-204386 discloses a fluid composition for a traction drive in which poly-α-olefin is added to a naphthenic synthetic lubricating oil base oil. There is a drawback that the traction coefficient at high temperature decreases. In general, it is desirable that the flash point of the lubricating oil for automobiles be maintained at 150 ° C. or higher for practical use. [0003] [Problems to be Solved by the Invention] The present invention has been made from the above viewpoint, and provides a lubricating oil-based oil composition having a flash point of 150 ° C. or higher, maintaining traction characteristics at high temperatures, and having improved low-temperature flow characteristics. It is the purpose. [0004] [Means for solving problems] As a result of intensive studies, the present inventors have found that the object of the above invention can be effectively achieved by adding a small amount of a specific ester compound to a naphthenic synthetic lubricating oil base oil, and completed the present invention. It was done. That is, the gist of the present invention is as follows. 1. (a) At least 2 rings selected from cyclohexane ring, bicyclo [2.2.1] heptane ring, bicyclo [3.2.1] octane ring, bicyclo [2.2.2] octane ring and bicyclo [3.3.0] octane ring. It is a compound possessed by 80 to 98% by mass of a naphthenic synthetic lubricating oil base oil having a flammability of 140 ° C or higher, and (b) obtained from an alcohol having a gem-type dimethyl structure and a fatty acid having a gem-type dimethyl structure. Lubricating oil base oil composition consisting of 2 to 20% by mass of fatty acid ester having 18 to 23 total carbon atoms. 2. (a) Naften-based synthetic lubricating oil The lubricating oil according to 1 above, wherein the base oil is a dimer hydride of a bicyclo [2.2.1] heptane ring compound.<u style="single">Base oil</u>Composition. 3. The lubricating oil base oil composition according to 1 or 2 above, wherein the flash point of the lubricating oil base oil composition is 150 ° C. or higher. 4. The lubricating oil base oil composition according to any one of 1 to 3 above, wherein the alcohol is 3,3,5-trimethylhexanol, 3,5,5,7,7-pentamethyloctanol or neopentyl glycol. 5. The lubricating oil base oil composition according to any one of 1 to 4 above, wherein the fatty acid is 3,5,5-trimethylcaproic acid. 6. The lubricating oil base oil composition according to any one of 1 to 5 above, wherein the lubricating oil base oil composition is a base oil composition for a fluid for traction drive. [0005] BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. First, the component (a) constituting the present invention is a naphthenic synthetic lubricating oil base oil having a flash point of 140 ° C. or higher. If the flash point is less than 140 ° C, the flash point is unlikely to be 150 ° C or higher even if the ester compound is mixed, which is not preferable. As the naphthenic synthetic lubricating oil base oil, a compound having a ring selected from a cyclohexane ring, a bicycloheptane ring and a bicyclooctane ring is preferable. Among them, it has at least two rings selected from cyclohexane ring, bicyclo [2.2.1] heptane ring, bicyclo [3.2.1] octane ring, bicyclo [2.2.2] octane ring and bicyclo [3.3.0] octane ring. Compounds are particularly preferred. [0006] Specifically, at least one selected from bicyclo [2.2.1] heptane ring compound, bicyclo [3.2.1] octane ring compound, bicyclo [3.3.0] octane ring compound, and bicyclo [2.2.2] octane ring compound. Dimeric hydrides of alicyclic compounds, and 2,4-dicyclohexyl-2-methylpentane, 2,4-dicyclohexylpentane, 2,4-dicyclohexyl-2-methylbutane, 1-decahydronaphthyl-1-cyclohexylethane It can be preferably selected from cyclohexane ring compounds such as. [0007] As a preferable method for producing the dimer hydride of the alicyclic compound, for example, the following olefins, which may be substituted with an alkyl group, may be treated in the order of dimerization, hydrogenation, and distillation. Examples of the olefin in which an alkyl group such as a methyl group, an ethyl group or a propyl group of the above-mentioned raw materials may be substituted include bicyclo [2.2.1] hepto-2-ene; vinyl-substituted or isopropenyl-substituted bicyclo [2.2. 1] Alkyl-substituted bicyclos such as hepto-2-ene [2.2.1] Hept-2-ene; methylene-substituted, ethylidene-substituted or isopropylidene-substituted bicyclos [2.2.1] Alkylidene-substituted bicyclos such as hepto-2-ene [2.2] .1] Hept-2-ene; vinyl-substituted or isopropenyl-substituted bicyclo [2.2.1] alkenyl-substituted bicyclos such as heptane [2.2.1] heptane; methylene-substituted, ethylidene-substituted or isopropylidene-substituted bicyclos [2.2.1] heptane Alkylidene-substituted bicyclo [2.2.1] heptane; bicyclo [3.2.1] octene; vinyl-substituted or isopropenyl-substituted bicyclo [3.2.1] octene and other alkenyl-substituted bicyclo [3.2.1] octene; methylene-substituted, ethylidene-substituted Alternatively, isopropylidene substituted bicyclo [3.2.1] alkylidene substituted bicyclo [3.2.1] octene such as octene; vinyl substituted or isopropenyl substituted bicyclo [3.2.1] alkenyl substituted bicyclo [3.2.1] octane; methylene substituted Alkylidene-substituted bicyclo [3.2.1] octane, bicyclo [3.2.1] octane; bicyclo [3.3.0] octene; vinyl-substituted or isopropenyl-substituted bicyclo [3.3.0] alkene, etc. Substituted bicyclo [3.3.0] octene; methylene substituted, ethylidene substituted or isopropylidene substituted bicyclo [3.3.0] Alkylidene substituted bicyclo [3.3.0] octene such as octene; vinyl substituted or isopropenyl substituted bicyclo [3.3.0] octane Alkyl-substituted bicyclos such as [3.3.0] octane; methylene-substituted, ethylidene-substituted or isopropylidene-substituted bicyclos [3.3.0] Alkylidene-substituted bicyclos such as octane [3.3.0] Octane; bicyclos [2.2.2] octene; vinyl-substituted or isopropenyl-substituted bicyclos [2.2.2] alkene-substituted bicyclos such as octene [2.2.2] octene; methylene-substituted Alkylidene-substituted bicyclos such as octene [2.2.2] octene [2.2.2] octene; vinyl-substituted or isopropenyl-substituted bicyclos [2.2.2] alkenyl-substituted bicyclos such as octane [2.2.2] octane Examples thereof include alkylidene-substituted bicyclo [2.2.2] octane such as methylene-substituted, ethylidene-substituted or isopropylidene-substituted bicyclo [2.2.2] octane. [0008] Among them, the dimer hydride of the bicyclo [2.2.1] heptane ring compound is particularly preferable, and as the corresponding raw material olefin, specifically, for example, bicyclo [2.2.1] hept-2-ene; 2- Methylenebicyclo [2.2.1] heptane; 2-methylbicyclo [2.2.1] hept-2-ene; 2-methylene-3-methylbicyclo [2.2.1] heptane; 3-methylene-2-methylbicyclo [2.2. 1] heptane; 2,3-dimethylbicyclo [2.2.1] hept-2-ene; 2-methylene-7-methylbicyclo [2.2.1] heptane; 3-methylene-7-methylbicyclo [2.2.1] heptane 2,7-Dimethylbicyclo [2.2.1] hept-2-ene; 2-methylene-5-methylbicyclo [2.2.1] heptane; 3-methylene-5-methylbicyclo [2.2.1] heptane; 2, 5-Dimethylbicyclo [2.2.1] hept-2-ene; 2-methylene-6-methylbicyclo [2.2.1] heptane; 3-methylene-6-methylbicyclo [2.2.1] heptane; 2,6-dimethyl Bicyclo [2.2.1] hept-2-ene; 2-methylene-1-methylbicyclo [2.2.1] heptane; 3-methylene-1-methylbicyclo [2.2.1] heptane; 1,2-dimethylbicyclo [2.2] .1] Hept-2-ene; 2-methylene-4-methylbicyclo [2.2.1] heptane; 3-methylene-4-methylbicyclo [2.2.1] heptane; 2,4-dimethylbicyclo [2.2.1] Hept-2-ene; 2-methylene-3,7-dimethylbicyclo [2.2.1] heptane; 3-methylene-2,7-dimethylbicyclo [2.2.1] heptane; 2,3,7-trimethylbicyclo [2.2] .1] Hept-2-ene; 2-methylene-3,6-dimethylbicyclo [2.2.1] heptane; 3-methylene-2,6-dimethylbicyclo [2.2.1] heptane; 2-methylene-3,3 -Dimethylbicyclo [2.2.1] heptane; 3-methylene-2,2-dimethylbicyclo [2.2.1] heptane; 2,3,6-trimethylbicyclo [2.2.1] hept-2-ene; 2-methylene-3-ethylbicyclo [2.2.1] heptane; 3-methylene-2-ethylbicyclo [2.2.1] heptane; 2-methyl-3 -Ethylbicyclo [2.2.1] Hept-2-ene and the like can be mentioned. [0009] The above-mentioned dimerization means not only the dimerization of the same type of olefin but also the co-dimerization of a plurality of different olefins. The dimerization of the above-mentioned olefin is usually carried out by adding a solvent as needed in the presence of a catalyst. As the catalyst used for this dimerization, an acidic catalyst is usually used. Specifically, solid acids such as active white clay, zeolite, montmorillonite, and ion exchange resin, mineral acids such as hydrofluoric acid and polyphosphoric acid, organic acids such as trifric acid, aluminum chloride, ferric chloride, and ferric chloride. Lewis acids such as tin, boron trifluoride, boron trifluoride complex, boron tribromide, aluminum bromide, gallium chloride, gallium bromide, organoaluminum compounds such as triethylaluminum, diethylaluminum chloride, ethylaluminum dichloride, etc. Can be mentioned. [0010] The amount of these catalysts used is not particularly limited, but is usually in the range of 0.1 to 100% by mass with respect to the raw material olefin. A solvent is not always required for this dimerization, but it can also be used for handling the raw material olefin or catalyst during the reaction or for adjusting the progress of the reaction. Examples of such a solvent include saturated hydrocarbons such as various pentane, various hexane, various octane, various nonane, and various decane, alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclosan, and decalin, diethyl ether, tetrahydrofuran, and the like. Examples thereof include ether compounds, halogen-containing compounds such as methylene chloride and dichloroethane, and nitro compounds such as nitromethane and nitrobenzene. [0011] The dimerization reaction is carried out in the presence of these catalysts and the like, and the reaction temperature is generally in the range of -70 to 200 ° C. Appropriate conditions are set in the temperature range depending on the type of catalyst, additives, etc., but the reaction pressure is usually normal pressure, and the reaction time is usually 0.5 to 10 hours. Next, the dimer of the raw material olefin thus obtained is hydrogenated to obtain a hydride of the target dimer. In addition, hydrogenation may be carried out for a dimer obtained by appropriately mixing dimers separately using another raw material olefin. [0012] This hydrogenation reaction is also usually carried out in the presence of a catalyst, and examples of the catalyst include catalysts for hydrogenation such as nickel, ruthenium, palladium, platinum, rhodium, and iridium. The amount of this catalyst used is usually in the range of 0.1 to 100% by mass with respect to the above dimerization product. Further, this hydrocarbon reaction proceeds in the same manner as the dimerization reaction in the absence of a solvent, but a solvent can also be used. In that case, as the solvent, various pentanes, various hexanes, various octanes, various nonans, Examples thereof include saturated hydrocarbons such as various decane and alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclosan, and decalin. [0013] The reaction temperature is usually 20 to 300 ° C, and the reaction pressure can be in the range of normal pressure to 20 MPa · G. The reaction time is usually 1 to 10 hours. The produced hydride may be mixed with a hydride produced from another raw material olefin in another step and used as the base oil as the component (a). Next, the component (b) constituting the present invention is a fatty acid ester of an alcohol having a gem-type dimethyl structure having a flash point of 150 ° C. or higher. If the flash point is less than 150 ° C, the flash point of the mixed oil tends to be less than 150 ° C, which is not preferable. The alcohol constituting the ester of the component (b) has a gem-type dimethyl structure, and is preferably a monoalcohol such as 3,3,5-trimethylhexanol or 3,5,5,7,7-pentamethyloctanol. Examples thereof include diols such as neopentyl glycol and hexylene glycol. Of these, 3,3,5-trimethylhexanol, 3,5,5,7,7-pentamethyloctanol and neopentyl glycol are preferable. [0014] The fatty acid constituting the ester of the component (b) is also preferably one having a gem-type dimethyl structure, specifically 3,5,5-trimethylcaproic acid and 3,5,5,7,7-pentamethylcaproic acid. Among them, 3,5,5-trimethylcaproic acid is particularly preferable. When the alcohol is a diol, the ester of the component (b) may be a monoester or a diester. Further, it is preferable to adjust the total carbon number of the ester of the component (b) to 18 to 23. [0015] The above lubricating oil base oil composition can be obtained by blending the component (a) and the component (b), but the ratio of the component (a) and the component (b) is the component (a) and the component (b). Based on the sum of the components, (a) component 80 to 98% by mass and (b) component 2 to 20% by mass. (b) Explaining in terms of the proportion of components, if it is less than 2% by mass, the effect of improving the low temperature fluidity is small, and if it exceeds 20% by mass, the high temperature traction coefficient of the composition decreases. It is preferably in the range of 3 to 18% by mass. Therefore, the preferable range of the component (a) is 82 to 97% by mass. [0016] The lubricating oil base oil composition of the present invention contains, if necessary, an antioxidant, a rust preventive, a cleaning dispersant, a pour point lowering agent, a viscosity index improver, an extreme pressure agent, an abrasion resistant agent, an oily agent, and a defoaming agent. , Various additives such as corrosion inhibitors can be blended in appropriate amounts. The lubricating oil base oil composition of the present invention can be used for a traction drive fluid, a transmission oil, a hydraulic hydraulic oil, a compressor oil, an electrically insulating oil, and the like, and among them, it can be preferably used for a traction drive fluid. [0017] [Example] Next, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. [Reference example 1] In a 1 liter stainless steel autoclave, 350.5 g (5 mol) of crotonaldehyde and 198.3 g (1.5 mol) of dicyclopentadiene were charged and reacted by stirring at 170 ° C. for 2 hours. After cooling the reaction solution to room temperature, 22 g of a 5 mass% ruthenium-carbon catalyst [manufactured by NE Chemcat] was added, and hydrogenation was carried out at a hydrogen pressure of 6.86 MPa · G and a reaction temperature of 180 ° C. for 4 hours. After cooling, the catalyst was separated by filtration, and the filtrate was distilled under reduced pressure to obtain 242 g of a 70 ° C / 1.20 hPa fraction. As a result of analyzing this fraction by mass spectrum and nuclear magnetic resonance spectrum, this fraction is 2-hydroxymethyl-3-methylbicyclo [2.2.1] heptane and 3-hydroxymethyl-2-methylbicyclo [2.2.1]. It was confirmed to be heptane. [0018] Next, 15 g of γ-alumina [Nichiki Kagaku Co., Ltd., N612] was placed in a flow-type atmospheric pressure reaction tube made of quartz glass with an outer diameter of 20 mm and a length of 500 mm, and the reaction temperature was 280 ° C and the weight space velocity (WHSV) was 1.07 hr.^-12-Methylene-3-methylbicyclo [2.2.1] heptane and 3-methylene-2-methylbicyclo [2.2.1] heptane 65% by mass and 2,3-dimethylbicyclo [2.2.1] 196 g of dehydration reaction product of 2-hydroxymethyl-3-methylbicyclo [2.2.1] heptane and 3-hydroxymethyl-2-methylbicyclo [2.2.1] heptane containing 28% by mass of hept-2-ene was obtained. It was. [0019] (Preparation of dimer hydride) 9.5 g of dried activated clay [Galleon Earth NS manufactured by Mizusawa Industrial Chemicals, Inc.] and 190 g of the olefin compound obtained above were placed in a 500 ml four-necked flask, and the mixture was stirred at 145 ° C for 3 hours to carry out a dimerization reaction. .. After filtering the active white clay from this reaction mixture, add 6 g of a nickel / diatomaceous earth catalyst for hydrogenation [N-113, manufactured by Nikki Kagaku Co., Ltd.] to a 1 liter autoclave, hydrogen pressure 3.92 MPa · G, reaction temperature 160 ° C, The hydrogenation reaction was carried out under the condition that the reaction time was 3 hours. After completion of the reaction, the catalyst was removed by filtration, and the filtrate was distilled under reduced pressure to obtain 116 g of a dimer hydride having a boiling point of 126 to 128 ° C. / 2.67 daPa. Table 1 shows the general properties of this dimer hydride and the measurement results of the traction coefficient. [0020] [Comparative Example 1] The base oil obtained in Reference Example 1 was blended with a dimer of 1-decene (Idemitsu PAO-5002, flash point 171 ° C) in an amount of 15% by mass based on the total amount of the composition. Table 1 shows the general properties of this composition and the measurement results of the traction coefficient. [0021] [0021] [Example 1] An ester compound (3,3,5-trimethylcaproic acid 3,5,5-trimethylhexanol ester, manufactured by Higher Alcohol Industry Co., Ltd., flash point 156 ° C) was added to the base oil obtained in Reference Example 1 to form a composition. Based on the total amount, 15% by mass was blended. Table 1 shows the general properties of this composition and the measurement results of the traction coefficient. [0022] [Reference example 2] Put 4 g of activated clay [Galleon Earth NS, manufactured by Mizusawa Industrial Chemicals, Inc.], 10 g of diethylene glycol monoethyl ether and 200 g of α-methylstyrene into a 500 ml four-necked flask equipped with a reflux condenser, agitator and a thermometer, and react. The mixture was heated to a temperature of 105 ° C and stirred for 4 hours. After completion of the reaction, the product was analyzed by gas chromatography to select a conversion of 70%, a selectivity of the target α-methylstyrene linear dimer of 95%, and a by-product α-methylstyrene cyclic dimer. It was found that the rate was 1% and the selectivity of high boiling point substances such as trimers was 4%. By hydrogenating this reaction product and distilling it under reduced pressure in the same manner as in Comparative Example 1, an α-methylstyrene linear dimer hydride having a purity of 99% by mass, that is, 125 g of 2,4-dicyclohexyl-2-methylpentane was obtained. Obtained. Table 1 shows the general properties of this dimer hydride and the measurement results of the traction coefficient. [0023] [Example 2] The ester compound (3,3,5-trimethylcaproic acid 3,5,5-trimethylhexanol ester) was added to the base oil (2,4-dicyclohexyl-2-methylpentane) obtained in Reference Example 2, manufactured by Higher Alcohol Industry Co., Ltd. ,, Flash point 156 ° C) was blended in an amount of 10% by mass based on the total amount of the composition. Table 1 shows the general properties of this composition and the measurement results of the traction coefficient. [0024] [Example 3] The ester compound (3,3,5-trimethylcaproic acid 3,5,5-trimethylhexanol ester) was added to the base oil (2,4-dicyclohexyl-2-methylpentane) obtained in Reference Example 2, manufactured by Higher Alcohol Industry Co., Ltd. ,, Flash point 156 ° C) was blended in an amount of 15% by mass based on the total amount of the composition. Table 1 shows the general properties of this composition and the measurement results of the traction coefficient. [0025] The traction coefficient in the above Examples and Comparative Examples was measured with a two-cylindrical friction tester. That is, one of the adjacent cylinders of the same size (52 mm in diameter, 6 mm in thickness, tyco type with a radius of curvature of 10 mm on the driven side, flat type without crowning on the drive side) is continuously rotated at a constant speed. A load of 98.0 N was applied to the contact portion of both cylinders by a weight, and the tangential force generated between the two cylinders, that is, the traction force was measured, and the traction coefficient was obtained. This cylinder was made of bearing steel SUJ-2 mirror finish, with an average peripheral speed of 6.8 m / s and a maximum Hertz contact pressure of 1.23 GPa. In addition, when measuring the traction coefficient at a fluid temperature (oil temperature) of 140 ° C, the oil temperature is raised from 40 ° C to 140 ° C by heating the oil tank with a heater, and the slip rate is 5%. The traction coefficient was calculated. [0026] [table 1]<img file="JP4792171B2_D0001.tif" />[0027] [Table 2]<img file="JP4792171B2_D0002.tif" />[0028] [Effect of the invention] The lubricating oil-based oil composition of the present invention has a high traction coefficient at high temperatures and excellent low-temperature flow characteristics while ensuring a flash point of 150 ° C. or higher, and is excellent in low-temperature flow characteristics, from cold regions to high-temperature regions all over the world. It can be practically used as a traction drive type CVT oil.