JPS61287987A - Lubricating oil composition for high-temperature use - Google Patents

Abstract

PURPOSE:To reduce a high-temp. evaporation loss and improve a heat stability and a high-temp. cleanness, by incorporating a mineral oil and/or a synthetic oil in a mixture of a specific satd. hindered ester with an alkyl-substituted diphenyl ether. CONSTITUTION:The titled compsn. comprises 40-100wt% mixture (A) of an ester of a hindered alcohol with a 10-22C satd. or unsatd. fatty acid and an alkyl-substituted diphenyl ether (B) and 60-0wt% mineral oil and/or synthetic oil (C). Preferred hindered alcohol constituting the component A is a compd. of the formula I (wherein R1-R4 are each H, OH group, alkyl group or hydroxyl group-contg. alkyl group, provided that at least one of them is a hydroxyl group). Particularly preferred fatty acid is isostearic acid and oleic acid. The preferred component B is a compd. of the formula II (wherein R5 and R6 are each a 10-22C satd. or unsatd. alkyl group; n and m are each an integer of 0-5 satisfying the relationship 6>=n+m>=1). The titled compsn. is useful particularly as an engine oil.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention has low evaporation loss at high temperatures of 300 to 350°C, excellent thermal stability or high-temperature cleanliness, and has other properties necessary for lubricating oils, such as The present invention relates to a high-temperature lubricating oil composition that has good performance in low-temperature fluidity, viscosity-temperature characteristics, wear resistance, additive solubility, etc., and is particularly effective as an engine oil.

[Conventional technology and problems]

Conventionally, various synthetic lubricants have been known as high-temperature lubricants, and those used at high temperatures of 200°C or higher.
Examples include silicone, polyphenyl ether, and fluorine compounds. However, all of these have shortcomings in load carrying capacity, cleanliness, low temperature fluidity, etc., and they also have shortcomings in the solubility of various additives to improve these shortcomings and add other performance. Yes, its uses were limited.

On the other hand, lubricants for ceramic engines or adiabatic engines, bearing lubricants for ultra-high-temperature gas turbines, lubricants for engines with turbochargers, etc. that have recently been put into practical use can withstand high temperatures of over 200°C, especially over 300°C. A durable lubricant is required. The performance requirements for lubricants used under such conditions are (1) low evaporation loss (loss) at high temperatures, (2) low formation of deposits at high temperatures, and (3) low evaporation loss (loss) at high temperatures. ) good oxidation stability, and (4) good wear and corrosion prevention performance.

[Means for Solving the Problems] The present inventor has conducted extensive research in order to improve the drawbacks of the conventional lubricants mentioned above and to develop a lubricant that has all the required performances of a lubricant that can withstand use at high temperatures. went. As a result, certain hindered esters, alkyl-substituted diphenyl ethers,
The present invention has been completed by discovering that a lubricating oil composition consisting of mineral oil and/or synthetic oil is suitable for the purpose. Namely, the present invention consists of (A) a hindered alcohol and a carbon number of 10 to 22. esters with saturated or unsaturated fatty acids and (
B) Mixture 4 consisting of alkyl-substituted diphenyl ethers
0 to 100% by weight, and (C) mineral oil and/or synthetic oil 60%
The present invention provides a high-temperature lubricating oil composition characterized by comprising:

Component (A) of the lubricating oil composition of the present invention is an ester of a hindered alcohol and a saturated or unsaturated fatty acid having 10 to 22 carbon atoms. It is an ester consisting mainly of all esters (containing some partial esters, etc.).

Here, the hindered alcohol is a compound represented by the general formula % (in the formula, R1 to R4 each represent a hydrogen atom, a hydroxyl group, an alkyl group, or a hydroxyl group-containing alkyl group, and at least one is a hydroxyl group) Specifically, polyhydric alcohols such as trimethylolpropane, trimethylolethane, pentaerythritol, neopentyl glycol, 2-methyl-2-propyl-1,3-propanediol, and mixtures thereof Alcohol can be mentioned. In addition, although not included in the above general formula, polyhydric alcohols such as dipentaerythritol can also be mentioned.

The acid that forms the ester with this hindered alcohol must be a saturated or unsaturated fatty acid with 10 to 22 carbon atoms, and the acid with 9 carbon atoms used in general hindered esters.
The following fatty acids cannot be expected to provide sufficient performance such as evaporation loss at high temperatures. Suitable fatty acids include isostearic acid as a saturated fatty acid, and oleic acid, linoleic acid, lylunic acid and the like as unsaturated fatty acids. These fatty acids may be used alone or in the form of mixed fatty acids, and particularly preferred fatty acids include isostearic acid and oleic acid.

It goes without saying that the "isostearic acid" and "oleic acid" referred to herein are fatty acids containing highly purified isostearic acid and oleic acid, respectively, and chemically include various other fatty acids.

From the viewpoint of oxidative stability, isostearic acid is preferable to oleic acid.

Specific examples of the hindered ester which is component (A) above include trimethylolpropane triisostearate, trimethylolpropane trioleate, pentaerythritol tetraisostearate, pentaerythritol tetraoleate, neopentyl glycol diisostearate. Examples include isostearates, oleates, and their respective rylates, lylphates, and the like.

On the other hand, the alkyl-substituted diphenyl ether as component (B) of the lubricating oil composition of the present invention has the general formula (wherein R6 and R6 are each a saturated or unsaturated alkyl group having 10 to 22 carbon atoms, and n and m is an integer of O to 5 satisfying the relationship 6≧n+m≧1) is preferable.

The term "alkyl-substituted diphenyl ether" as used herein refers to at least one of the two phenyl groups of diphenyl ether.
having one or more alkyl groups as substituents,
One diphenyl ether can have 1 to 6 alkyl groups as substituents. 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-olefins, alkyl halides, and alcohols. Polyphenyl ethers have conventionally 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. . Specific examples of alkyl-substituted diphenyl ether which is component (B) include carbon atoms of 12.14 and 16.1.
Examples include alkyl-substituted diphenyl ethers obtained by reacting each α-olefin such as No. 8 or a mixed α-olefin thereof with diphenyl ether by a known method.

The molar ratio of diphenyl ether and α-olefin used is 1
The ratio is preferably in the range of 3 to 1 to 5, and it is preferable that the main component is a tri or higher alkyl substituent.

On the other hand, component (C) of the present lubricating oil composition is mineral oil or synthetic oil, and these can be used alone or in combination. Here, mineral oils that are generally known as lubricating base oils can be widely used, including paraffinic,
There are various types of naphthenes. In addition, there are various known synthetic oils, such as alkylbenzenes, polybutenes, polyα-olefins, polyalkylene glycols, diesters, polyol esters, polyphenyl ethers and their derivatives, organic phosphate esters, and organic silicate esters. etc. can be mentioned.

The above mineral oils and synthetic oils are used by mixing them into a mixture of both components (A) and (B), so when designing a high-temperature lubricating oil composition with an appropriate viscosity depending on the application, it is necessary to select an appropriate viscosity. , thermal stability, and other necessary properties. Generally, as the molecular weight of a compound increases, its viscosity also increases. , thermal stability such as evaporation loss is also improved. The viscosity range of component (C) mineral oil and synthetic oil is considered to be 1.5 to 50 centistokes as a kinematic viscosity at 100°C.
Especially those with low viscosity of 1.5 to 10 centistokes (
C) When necessary as a component, it is important to select one with good thermal stability. Preferred examples of the component (C) having a viscosity of about 4 to 7 centistics at 100°C include esters of linear or branched saturated fatty acids having 5 to 9 carbon atoms and hindered alcohols.

Particularly suitable examples of this ester include pentaerythritol tetraberargonate and trimethylolpropane tripelargonate.

As described above, the high temperature lubricating oil composition of the present invention comprises (A) an ester of a hindered alcohol and a saturated or unsaturated fatty acid having 10 to 22 carbon atoms, (B) an alkyl-substituted diphenyl ether, (C) a mineral oil and/or Alternatively, synthetic oil is used as a basic component and consists of two combinations of (A)+(B)+(C) and (8)+(B).

The blending ratio is (A) + (B) components 40 to 100% by weight, preferably 60 to 100% by weight, and (C) component 6
0-0% by weight, preferably 40-0% by weight. (^
) + component (B) is less than 40% by weight, the resulting composition will have poor thermal stability such as evaporation loss. or,
As mentioned above, the ratio of both components (A) and (B) is 95:5 to 5:95, taking into consideration the viscosity of the lubricating oil composition, thermal stability such as evaporation loss, solubility of additives, etc. can vary within the range.

In addition to the above components (A), (B), and (C), the present invention also includes
Various additives such as ashless dispersants, metal detergents, antioxidants, extreme pressure additives, viscosity index improvers, and other well-known additives are blended as needed to meet the required performance. It can be prepared by

Phenates and/or sulfonates are commonly used as metal detergents. Phenate has about 8 carbon atoms
Alkaline earth metal salts of sulfides of alkylphenols to which 30 alkyl groups have been added, preferably calcium, magnesium or barium salts. Sulfonates are alkaline earth metal salts of sulfonates of lubricating oils or synthetically alkyl-substituted aromatic compounds having a molecular weight of about 400 to 600, preferably calcium, magnesium or barium salts.

Furthermore, salicylates as alkaline earth metal salts,
Phosphonates, naphthinates, etc. can also be used. These metal detergents may be of a neutral type or an overbased type having a base number of 300 or more, and are blended in the composition in an amount of 0.5 to 20% by weight.

As the unnatural dispersant, succinimide, succinic acid ester, benzylamine, etc. to which an alkyl group or alkenyl group having 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 included in the composition in an amount of 0.5 to
Contains 15% by weight.

As the antioxidant, extreme pressure additive or antiwear agent, it is preferable to use a multifunctional zinc dihydrocarbyldithiophosphate having an alkyl group or an alkylaryl group having 3 to 18 carbon atoms, which is present in the composition. 0.1 to 3
% by weight is added. Furthermore, as antioxidants, phenol-based, amine-based, and organic sulfur compound-based antioxidants are often used.

The lubricating oil composition of the present invention itself has a higher viscosity index than conventional mineral oil systems, but if necessary, it may contain polyalkyl methacrylate, ethylene-propylene copolymer, styrene-butadiene copolymer, etc. It may also contain a viscosity index improver. Furthermore, it may contain a so-called dispersion type viscosity index improver that imparts dispersion performance.

Furthermore, the lubricating oil composition of the present invention contains, in addition to the above-mentioned additives,
Conventional common extreme pressure agents, anti-wear agents, corrosion inhibitors, rust inhibitors,
Friction modifiers and the like can also be added as appropriate.

〔Effect of the invention〕

The lubricating oil composition of the present invention thus obtained has low evaporation loss even at high temperatures of 200°C or higher, especially 300°C or higher, less deposit formation at high temperatures, and other properties required as a lubricating oil, such as It is also excellent in terms of low-temperature fluidity, viscosity-temperature characteristics, abrasion resistance, and additive solubility.

Therefore, the lubricating oil composition of the present invention can be effectively used as a lubricant for mechanical components that are exposed to high temperatures of 200° C. or higher, especially internal combustion engines, that is, as an engine oil.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Examples 1 to 10 and Comparative Reference Examples 1 to 23 As mentioned 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 evaluating the performance of Tanega compounds as lubricating oil compositions, it is appropriate to conduct the performance evaluation at the same viscosity level as much as possible.
and desirable.

The lubricating oil composition of the present invention has a kinematic viscosity of about 14 centistokes at 100°C (5AE4 according to SAP viscosity classification).
(equivalent to 0), and various physical properties and performance evaluations were performed. The results are shown in Table 1. Please refer to the second comparison reference example.
Shown in the table.

Note that the evaluation performed here was based on the following method.

(a) Viscosity and viscosity index According to "Kinematic viscosity test method for crude oil and petroleum products and method for calculating viscosity index of petroleum products" specified in JIS K 2283.

(b) Pour point According to JIS K 2269, "Pour point of crude oil and petroleum products and cloud point test method of petroleum products".

(c) Solubility of additives As shown in Examples and comparative reference examples, (A) and (B)
.

The additive puff cage was added to each composition or component selected from component (C) at a predetermined ratio, heated to about 60° C., and mixed by stirring at 500 rpm for 20 minutes. The mixture was then transferred to a glass bottle, capped and left at room temperature for one month. After 1 t month, 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 -〇 Slight turbidity or sediment - △ Severe turbidity or sediment - × (d) Thermogravimetric analysis Differential scanning calorimeter (TG-) manufactured by Rigaku Denki ■ DSCCN8
089^1) Thermogravimetric analysis was performed using the device. 1
While continuously flowing argon gas at a flow rate of 80 cc/min, measurements were taken at a heating rate of 5°C/min.
The weight loss percentage at 50°C was determined.

(e) Hot tube test The test was carried out using the 4t equipment and conditions (modified only once) as described in SAE Technical Paper Series 840262. 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 condition of the deposit formed on the inner wall of the glass capillary using a standard color scale. Evaluate (0~
This is a 10-point scale (out of 10), which evaluates the thermal stability or high-temperature cleanliness of engine oil. This hot tube test was conducted at elevated temperatures of 320°C and 330°C.

(to) Panel caulking test US Federal Test Standard (N1791 Method 3462
), the test was carried out for 3 hours under the following conditions: panel temperature 320°C, test oil temperature 100°C, repeated splashing for 15 seconds and stopping for 45 seconds. The thermal stability or high temperature cleanliness of the test oil is evaluated based on the weight of the deposit attached to the aluminum panel.

The compounds and additive packages used as components (A), (B), and (C) are as follows.

$1 = Manufactured by esterifying trimethylolpropane and isostearic acid.

Umbrella 2 Manufactured by esterifying nitrimethylolpropane and oleic acid.

Book 3: Manufactured by esterifying pentaerythritol and isostearic acid.

$4 Produced by alkylation reaction at a ratio of 3 moles of α-olefin having 14 carbon atoms to 1 mole of nidiphenyl ether.

*5 Manufactured by alkylation reaction at a ratio of 4 moles of α-olefin having 14 carbon atoms to 1 mole of nidiphenyl ether.

*6: 12 carbon atoms per mole of diphenyl ether,
This product was produced by alkylation reaction at a ratio of 5 moles of mixed α-olefin of No. 14.

117: Refined mineral oil 500 neutral oil and 150 bright stock oil mixed to 14 centistokes at 100°C.

*8: A hydrogenated α-olefin oligomer made from an α-olefin having 10 carbon atoms is blended to a concentration of 14 centistokes at 100°C.

Book 9: Pentaerythritol tetrapelargonate with Rheoloop LP3600゜mura made by Nippon Ciba Geigy O: Overbased calcium phenate, neutral calcium sulfonate, zinc dihydrocarbyl dithiophosphate (aryl type), silicone antifoam agent something that has become

*11: Packaged with succinimide, overbased calcium phenate, overbased calcium sulfonate, neutral calcium sulfonate, zinc dihydrocarbyldithiophosphate (orirol type), and silicone antifoaming agent. What I did.

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 and viscosity of additives. It also has good performance in terms of temperature characteristics and low-temperature fluidity.

Example 11 and Comparative Reference Example 24 The performance of the lubricating oil composition of the present invention was evaluated by a bench engine test using an actual engine. This test device is a Japanese-made diesel engine (4 cylinders, 2164cc, 4 cycles) installed on a bench in the test room.The test device uses diesel oil with a sulfur content of 0.45% by weight as fuel, and runs at 4000 rpm.
Tested for 00 hours. °The lubricating oil capacity of the oil pan of this engine is 5.51, and the oil temperature in the oil pan during the test was 120℃.
However, the oil that lubricates the top ring groove at the top of the piston is exposed to high temperatures of around 260°C.

The bench engine test described above was conducted on lubricating oil compositions of the present invention and conventional mineral oil-based lubricating oils containing the same additive packages in the same amounts.

The results are shown in Table 3. The lubricating oil composition and mineral oil-based lubricating oil of the present invention used here are as follows.

Book 13: Varaffinic mineral oil (same as *7) 100 parts by weight Book 14 Diborated succinimide, overbased calcium phenate, overbased calcium sulfonate,
Zinc dihydrocarbyl dithiophosphate (alkyl type)
, a packaged silicone antifoaming agent.

As is clear from Table 3, the lubricating oil composition of the present invention has less deposits in the top ring groove and top land of the piston, where the temperature is most severe than mineral oil-based lubricating oils, and has excellent thermal stability and high-temperature cleaning properties. showed his sexuality. Furthermore, no defects were observed in the wear of rings and bearings, demonstrating that the present lubricating oil composition is effective as a high-temperature lubricating oil composition in actual engines.

Claims (1)

[Claims] 1. 40 to 100% by weight of a mixture consisting of (A) an ester of a hindered alcohol and a saturated or unsaturated fatty acid having 10 to 22 carbon atoms and (B) an alkyl-substituted diphenyl ether, and (C) mineral oil. A high-temperature lubricating oil composition comprising 60 to 0% by weight of synthetic oil and/or synthetic oil. 2. Hindered alcohol has a general formula ▲ mathematical formula, chemical formula, table, etc. The composition according to claim 1, which is a compound represented by: 3. The composition according to claim 1 or 2, wherein the saturated fatty acid having 10 to 22 carbon atoms is isostearic acid, and the unsaturated fatty acid is oleic acid. 4. Alkyl-substituted diphenyl ether has the general formula ▲mathematical formula,
There are chemical formulas, tables, etc.▼ (In the formula, R_5 and R_6 are each a saturated or unsaturated alkyl group having 10 to 22 carbon atoms, and n and m are 6≧n+
The composition according to any one of claims 1 to 3, which is a compound represented by the following (an integer of 0 to 5 satisfying the relationship m≧1).