JPH0566438B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention has low evaporation loss at high temperatures of 300 to 350°C, is excellent in thermal stability or high-temperature detergency, and has other properties necessary for lubricating oils, such as low-temperature fluidity and viscosity-temperature. The present invention relates to a high-temperature lubricating oil composition that has good performance in terms of properties, wear resistance, additive solubility, etc., and is particularly effective as an engine oil. [Prior art and problems] Conventionally, various synthetic lubricants have been known as high-temperature lubricants, and those used at high temperatures of 200°C or higher include silicones, polyphenyl ethers, fluorine compounds, etc. Can be mentioned. However, all of these have drawbacks in terms of load-bearing capacity, cleanliness, low-temperature fluidity, etc., and they also have deficiencies in the solubility of various additives used to improve these drawbacks and add other properties. , its uses were limited. On the other hand, lubricants for ceramic engines or adiabatic engines, bearing lubricants for ultra-high-temperature gas turbines, and lubricants for turbocharged engines, which have recently been put into practical use, can withstand high temperatures of over 200°C, especially over 300°C. Lubricant is required. The performance requirements for lubricants used under these conditions are (1) low evaporation loss (weight loss) at high temperatures, (2) low formation of deposits at high temperatures, (3) ) good oxidation stability, and (4) good wear and corrosion prevention performance. [Means for Solving the Problems] The present inventors have improved the drawbacks of the conventional lubricants mentioned above,
We conducted intensive research to develop a lubricant that has all the required properties for a lubricant that can withstand use at high temperatures. As a result, they discovered that a lubricating oil composition consisting of an alkyl-substituted diphenyl ether and a specific saturated hindered ester is suitable for the purpose,
The present invention has now been completed. That is, the present invention provides a saturated hindered ester of (A) 40 to 95% by weight of an alkyl-substituted diphenyl ether, and (B) a linear or branched saturated fatty acid having 5 to 9 carbon atoms and a hindered alcohol at 100°C. 60 to 5% by weight, and further contains (C) an additive containing at least calcium phenate, calcium sulfonate, and zinc dihydrocarbyldithiophosphate. It is something to do. The alkyl-substituted diphenyl ether as component (A) of the lubricating oil composition of the present invention has the general formula (In the formula, R ₁ and R ₂ are each a saturated or unsaturated alkyl group having 10 to 22 carbon atoms, and n and m are 6≧
(an integer from 0 to 5 that satisfies the relationship n+m≧1) is preferred. The alkyl-substituted diphenyl ether referred to herein is one in which at least one of the two phenyl groups of the diphenyl ether has one or more alkyl groups as a substituent, and one diphenyl ether has 1 to 6 alkyl groups. It can have a group as a substituent.
The number of carbon atoms in the alkyl group is suitably in the range of 10 to 22, and examples of the alkyl source include α-olefin, alkyl halide, and alcohol. Conventionally, polyphenyl ethers have been known as high-temperature lubricants, but these have poor low-temperature fluidity, whereas the alkyl-substituted diphenyl ethers of the present invention have both good low-temperature fluidity and thermal stability. There is. Specific examples of the alkyl-substituted diphenyl ether that is component (A) include carbon atoms of 12, 14,
Each α-olefin such as 16, 18, etc. or a mixture of these α-
Examples include alkyl-substituted diphenyl ethers obtained by reacting olefins and diphenyl ethers by a known method. Diphenyl ether and α-
The molar ratio of olefin used is preferably in the range of 1:3 to 1:5, and it is preferable that the main component is a tri- or higher alkyl substituent. On the other hand, the saturated hindered ester component (B) of this lubricating oil composition has a kinematic viscosity of 4 to 7 at 100°C.
centistokes, and has better thermal stability in this viscosity range than mineral oil, polyα-olefin, diester, etc. of the same viscosity.
Particularly preferred examples of this ester include pentaerythritol tetrapelargonate, which is an ester of pentaerythritol or trimethylolpropane with pelargonic acid, and trimethylolpropane tripelargonate. The blending ratio of components (A) and (B) in the high temperature lubricating oil composition of the present invention is 40 to 95% by weight of component (A), preferably 60% by weight.
~95% by weight, component (B) 60-5% by weight, preferably 40% by weight
~5% by weight. Here, the blending ratio of component (A) is 40
If it is less than % by weight, the resulting composition will have poor thermal stability such as evaporation loss. Furthermore, the solubility of various additives added to improve the performance of lubricating oils is generally poor. On the other hand, if the blending ratio of component (A) is more than 95% by weight, when it becomes necessary to make the viscosity of the lubricating oil composition lower than that of component (A), the viscosity of component (B) must be lowered or the viscosity of component (B) must be lowered. It becomes necessary to increase the amount used, and thermal stability such as evaporation loss is impaired. Component (C) blended into the lubricating oil composition of the present invention is an additive containing at least calcium phenate, calcium phonate, and zinc dihydrocarbyldithiophosphate. The above-mentioned phenate and fluphonate are known as metal-based detergents, but calcium phenate is a calcium salt of sulfide of alkyl phenate to which an alkyl group having about 8 to 30 carbon atoms is added, and calcium sulfone is Molecular weight approximately 400-600
Calcium salts of sulfonated lubricating oils or synthetically alkyl-substituted aromatic compounds. Zinc dihydrocarbyl dithiophosphate is a multifunctional additive known as an antioxidant, an extreme pressure additive, or an anti-wear agent, but those having an alkyl group or alkylaryl group having 3 to 18 carbon atoms are suitable. . Calcium phenate and calcium sulfonate may be neutral or overbased with a base number of 300 or more, and these may be present in the composition at a concentration of 0.5
Contains ~20% by weight. Zinc dihydrocarbyl dithiophosphate is incorporated into the composition in an amount of 0.1 to 3% by weight. In addition to the above components (A), (B), and (C), the present invention also includes various additives, such as ashless dispersants, metallic detergents, antioxidants, extreme pressure additives, It can be prepared by appropriately blending well-known additives such as viscosity index improvers depending on the required performance. As the ashless dispersant, succinimide, succinate ester, benzylamine, etc. to which an alkyl group or alkenyl group with a molecular weight of about 700 to 3000 is added are used. Furthermore, borated versions of these can also be used. These ashless dispersants are blended into the composition in an amount of 0.5 to 15% by weight. Phenol-based, amine-based, and organic sulfur compound-based antioxidants are also often used. The lubricating oil composition of the present invention itself has a higher viscosity index than conventional mineral oil systems;
If necessary, a viscosity index improver such as polyalkyl methacrylate, ethylene-propylene copolymer, and styrene-butadiene copolymer may be contained. Furthermore, it may contain a so-called dispersion type viscosity index improver that imparts dispersion performance. Furthermore, in addition to the above-mentioned additives, the lubricating oil composition of the present invention may optionally contain conventional extreme pressure agents, anti-wear agents, corrosion inhibitors, rust preventives, friction modifiers, etc. be able to. [Effects of the Invention] The lubricating oil composition of the present invention thus obtained has the following properties:
It has low evaporation loss even at high temperatures of 200°C or higher, especially 300°C or higher, has low deposit formation at high temperatures, and has other properties required as a lubricating oil, such as low-temperature fluidity, viscosity-temperature characteristics, and wear resistance. It also has excellent solubility of additives. Therefore, the lubricating oil composition of the present invention can be used as a lubricant for mechanical components that are exposed to high temperatures of 200°C or higher, especially for internal combustion engines.
That is, it is effectively used as engine oil. [Example] Next, the present invention will be explained in more detail with reference to Examples. Examples 1 to 4 and Comparative Reference Examples 1 to 9 As described above, there is an appropriate viscosity range for the lubricating oil used depending on the lubrication conditions. If the viscosity is too low, there will be more opportunities for boundary lubrication, which will also increase friction and wear. On the other hand, if the viscosity is too high, viscous resistance during fluid lubrication will increase, resulting in excessive energy consumption. Additionally, in general, as the molecular weight of a compound such as a hydrocarbon increases, the viscosity also increases, and thermal stability such as evaporation loss also improves. In view of these various circumstances, when performing performance evaluations of various compounds as lubricating oil compositions, it is appropriate and desirable to perform performance evaluations at the same viscosity level as much as possible. The lubricating oil composition of the present invention was prepared to have a kinematic viscosity of approximately 14 centistokes at 100°C (equivalent to SAE40 in SAE viscosity classification), and various physical properties and performance evaluations were conducted. Since the alkyl-substituted diphenyl ether as component (A) of the lubricating oil composition of the present invention has a high viscosity, it is necessary to adjust the viscosity without impairing thermal stability or the like. The results are shown in Table 1. Comparative reference examples are shown in Table 2. The evaluation performed here was based on the following method. (a) Viscosity and viscosity index The test was conducted according to the "Kinematic viscosity test method for crude oil and petroleum products and the method for calculating the viscosity index of petroleum products" stipulated in JIS K2283. (b) Pour point According to the "Pour point of crude oil and petroleum products and cloud point test method of petroleum products" stipulated in JIS K2269. (C) Solubility of additives As shown in the examples and comparative reference examples, the additive package of component (C) is added to each composition or component selected from components (A) and (B) at a predetermined ratio. death,
The mixture was heated to approximately 60° C. and stirred at 500 rpm for 20 minutes to mix. Then transfer the mixture to a glass bottle,
It was capped and left at room temperature for one month. 1
After several months, the solubility of the additive was determined based on the turbidity of the liquid phase and the presence or absence of sediment. No turbidity or sediment...○ Some turbidity or sediment...△ Severe turbidity or sediment...× (d) Thermogravimetric analysis Differential scanning calorimeter (manufactured by Rigaku Denki Co., Ltd.) TG-
Thermogravimetric analysis was performed using a DSC CN8089A1) instrument. While continuously flowing argon gas at a flow rate of 80 c.c. per minute, measurements were taken at a heating rate of 5°C/min, and the weight loss % at 300°C and 350°C was measured.
I asked for (E) Hot tube test Apparatus and conditions described in SAE Technical Paper Series 840262 (temperature only corrected)
It was carried out in This device maintains the temperature of a vertically erected glass capillary at a predetermined temperature, flows a small amount of test oil and air from below at a predetermined flow rate for 16 hours, and measures the state of deposits formed on the inner wall of the glass capillary using a standard color scale. Rate (0-10
(out of 10), which evaluates the thermal stability or high-temperature cleanliness of engine oil. This hot tube test was conducted at high temperatures of 320°C and 330°C. (F) Panel caulking test Tested for 3 hours using a device compliant with the U.S. Federal Test Standard (No.791Method3462) under the conditions of panel temperature 320℃, test oil temperature 100℃, and repeated splashing for 15 seconds and stopping for 45 seconds. . This test evaluates the thermal stability or high-temperature cleanliness of the test oil based on the weight of the deposit attached to the aluminum panel, and the amount of deposit must be less than 30 mg in this test. The additive packages of each compound and component (C) used here as components (A), (B) or comparative components are as follows. *1: Number of carbon atoms per mole of diphenyl ether
14 by alkylation reaction at a ratio of 3 moles of α-olefin. *2: Number of carbon atoms per mole of diphenyl ether
14 by alkylation reaction at a ratio of 4 moles of α-olefin. *3: Number of carbon atoms per mole of diphenyl ether
Produced by alkylation reaction in a ratio of 5 moles of mixed α-olefins of 12 and 14. *4: Pentaerythritol tetrapelargonate made by Nippon Ciba Geigy Co., Ltd., Rheolube
LP3600. *5: Packaged overbased calcium phenate, neutral calcium sulfonate, zinc dihydrocarbyldithiophosphate (aryl type), and silicone antifoaming agent. *6: Packaged product of succinimide, overbased calcium phenate, overbased calcium sulfonate, neutral calcium sulfonate, zinc dihydrocarbyldithiophosphate (aryl type), and silicone antifoaming agent. . *7: Rheolube made by Nippon Ciba Geigy Co., Ltd. with trimethylolpropane tripelargonate
LT2700. *8: Refined mineral oil 150 neutral oil. *9: Refined mineral oil 500% neutral oil and 150% bright stock oil mixed to 100:14 centistokes. *10: α made from α-olefin with 10 carbon atoms
- PAO40 made by Lion Co., Ltd., which is a hydrogenated olefin oligomer *11: α made from α-olefin with 10 carbon atoms
−Olefin oligomer hydrogenated product at 100℃ 14
Concocted to become centistokes.

【table】

【table】

[Table] As shown in the examples in Table 1, the lubricating oil composition of the present invention has low evaporation loss even at high temperatures of 300°C or higher, has excellent thermal stability and high-temperature detergency, and has excellent solubility of additives. It also has good performance in terms of viscosity-temperature characteristics, low-temperature fluidity, etc.

Claims (1)

[Scope of Claims] 1 (A) 40 to 95% by weight of an alkyl-substituted diphenyl ether, and (B) a saturated hindered ester of a linear or branched saturated fatty acid having 5 to 9 carbon atoms and a hindered alcohol. It consists of 5% by weight and Karana, and further
(C) A high-temperature lubricating oil composition comprising an additive containing at least calcium phenate, calcium sulfonate, and zinc dihydrocarbyldithiophosphate. 2 Alkyl-substituted diphenyl ether has the general formula (In the formula, R ₁ and R ₂ are each a saturated or unsaturated alkyl group having 10 to 22 carbon atoms, and n and m are 6≧
The composition according to claim 1, which is a compound represented by: 3. The composition according to claim 1, wherein the saturated hindered ester is an ester of pentaerythritol or trimethylolpropane and pelargonic acid.