JPH10130673A - Lube base oil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lube base oil which is low in cost, is resistant to high- temp. degradation, hardly produces tar even when degraded, and is excellent esp. in heat resistance by using an arom. carboxylic ester obtd. by using a monohydric alcohol mainly comprising 3,5,5-trimethylhexanol as the alcohol component. SOLUTION: This lube base oil comprises an arom. carboxylic ester obtd. by the complete esterification of at least one arom. carboxylic acid and a 4-18C monohydric alcohol contg. at least 50mol% 3,5,5-trimethylhexanol. Phthalic, isophthalic, terephthalic, and trimellitic acids are esp. recommended as the arom. carboxylic acid. The further use of benzoic, trimesic, and pyromellitic acids can give lube base oils having various viscosities. Pref., 3,5,5- trimethylhexanol is used alone as the monohydric alcohol since a lube base oil exhibiting esp. remarkable chemical and physical characteristics is obtd. in comparison with ones obtd. by using other alcohols.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lubricating base oil, and more particularly, to an inexpensive ester-based synthetic lubricating base oil having excellent heat resistance and low tar properties.

[0002]

2. Description of the Related Art Lubricating oil is obtained by adding various additives to a base oil and performs lubrication, sealing, cooling, rust prevention and the like of sliding parts of a machine. In recent years, with high speed, high load, high efficiency, energy saving, maintenance free, low cost, etc. of machinery, lubricating oil has high heat resistance and long life, wide operating temperature range, Even if it is deteriorated, the amount of tar generated is small, which is advantageous for maintenance, and furthermore, the performance of low cost is required.

At present, mineral oil, which is a petroleum fraction, occupies most of the amount used as a base oil for lubricating oils. Accordingly, various synthetic oils have been used as base oils.

[0004] Synthetic oils include synthetic hydrocarbons such as poly-α-olefins, polybutenes, alkylbenzenes, and alkylnaphthalenes, esters, polyalkylene glycols, phenyl ethers, silicone oils and the like. Compared to oil, it has the advantages of longer life (good heat resistance), wide operating temperature range (low pour point, high viscosity index), good lubricity, and low volatility. Ester-based base oils are generally more expensive than mineral-based base oils even though they have an excellent balance of physical properties compared to other synthetic base oils. The fact is that it is. Therefore, if it is possible to provide an inexpensive ester having performance equal to or higher than that of a conventional ester base oil, it will be possible to meet the demands of the industry.

[0005] Conventionally, ester-based synthetic lubricating oil base oils include aliphatic diesters synthesized from aliphatic dibasic acids such as adipic acid and sebacic acid and oxo alcohols, and phthalic acid, trimellitic acid and oxo alcohols. There are known aromatic carboxylic esters and polyol esters synthesized from neopentyl polyols such as pentaerythritol and trimethylolpropane and monovalent carboxylic acids.

[0006] Aliphatic diesters such as di (2-ethylhexyl) adipate and diisodecyl adipate are well known as plasticizers for vinyl chloride resins. It is blended in grease base oils, engine oils, metal working oils, etc. for low-temperature applications or high-speed rotating bearings. However, heat resistance is by no means high among esters.

The chemical structure of di (2-ethylhexyl) phthalate or diisononyl phthalate (alcohol component is 3,
Aromatic diesters such as monomethyloctanol and dimethylheptanol, unlike 5,5-trimethylhexanol, are produced in large quantities at low cost as plasticizers for vinyl chloride resins, like aliphatic diesters. However, it is hardly used as a lubricating base oil except for some uses such as compressor oil.
The reason for this is that aromatic carboxylic acid esters generally have the drawback of having a higher pour point and a lower viscosity index than aliphatic diesters and polyol esters.

At present, the main stream of ester base oils is polyol esters. Generally, polyol esters are superior to aliphatic diesters and aromatic carboxylic esters in thermal stability and oxidative stability particularly at high temperatures. Therefore, in recent years, as the use conditions of lubricating oil have become severe, various fields such as jet engine oil, gas turbine oil, compressor oil, chain oil, hydraulic oil, gear oil, bearing oil, grease base oil, etc. Has also come to be used favorably.

However, the use conditions are becoming more severe, and the problem is that even polyol esters are deteriorated at high temperatures to increase the acid value and to generate tar components (sludge, varnish and coke). It has become like. In general, polyol esters are more expensive than aliphatic diesters and aromatic carboxylic esters.

[0010]

DISCLOSURE OF THE INVENTION The present invention is inexpensive and has little deterioration at high temperatures equivalent to or higher than that of conventional polyol esters. An object of the present invention is to provide a base oil for lubricating oil which is excellent in quality.

[0011]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, have found that an aromatic carboxylic acid ester having a specific structure exhibits a predetermined effect. Thus, the present invention has been completed.

That is, the lubricating base oil according to the present invention comprises: 1) one or more aromatic carboxylic acids and 2) 3,5,5-trimethylhexanol at 50 mol%.
It is characterized by comprising an aromatic carboxylic acid ester obtained by completely esterifying the monohydric alcohol having 4 to 18 carbon atoms contained above.

The aromatic carboxylic acid ester of the present invention includes:
Conventionally well-known compounds are also included. For example,
Di (3,5,5-trimethylhexyl) phthalate is a general-purpose compound as a phthalic acid-based plasticizer, like di (2-ethylhexyl) phthalate. However, while di (2-ethylhexyl) phthalate, diisodecyl phthalate, tri (2-ethylhexyl) trimellitate, tri (isodecyl) trimellitate and the like are used as compressor oils, the aromatic oil of the present invention is used. Carboxylic esters are not used as lubricating base oils. Japanese Patent Publication No. 57-56520 describes various phthalic esters and trimellitic esters as base oils which are excellent as synthetic lubricants for reciprocating air compressors. However, the esters in this patent include various alcohols (5 to 18 carbon atoms).
It is described that the same effect can be obtained in terms of oxidative stability and heat resistance using any of the alcohols.

However, the present inventors have conducted various studies and found that an aromatic carboxylic acid ester using 3,5,5-trimethylhexanol as an alcohol component is replaced with an aromatic carboxylic acid ester using another alcohol or Shows outstanding chemical properties (oxidative stability and low tar properties) and physical properties (viscosity index and pour point) suitable for lubricating base oils compared to general polyol esters
Has been newly found.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The ester of the present invention (hereinafter referred to as "the present ester") is prepared by subjecting a predetermined acid component and an alcohol component to an esterification catalyst under an ordinary method, preferably in an atmosphere of inert gas such as nitrogen. An ester compound prepared by completely esterifying under heating or stirring with or without a catalyst.

The aromatic carboxylic acids according to the present invention include:
Benzoic acid, phthalic acid, 4-t-butylphthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, trimesic acid, pyromellitic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, 2,2′-bis (carboxyphenyl) propane, Examples thereof include aromatic carboxylic acids such as dicarboxydiphenyl ether and dicarboxydisulfide or anhydrides thereof, and the aromatic carboxylic acids and lower alcohol esters having 1 to 4 carbon atoms such as methanol and ethanol.

Among these aromatic carboxylic acids, phthalic acid,
Isophthalic acid, terephthalic acid, trimellitic acid are industrially available at low cost and are particularly recommended.
If trimesic acid or pyromellitic acid is used, lubricating base oils having various viscosities can be obtained.

The alcohol component of the present ester is a linear or branched aliphatic monohydric alcohol having 4 to 18 carbon atoms (provided that 3,5,5-trimethylhexanol contains at least 50 mol%). More specifically, in addition to 3,5,5-trimethylhexanol, n-
Butyl alcohol, isobutyl alcohol, n-amyl alcohol, isoamyl alcohol, n-hexanol, isohexanol, n-heptanol, isoheptanol, n-octanol, isooctanol, 2-ethylhexanol, n-nonanol, isononanol,
n-decanol, isodecanol, n-undecanol, isoundecanol, n-dodecanol, isododecanol, n-tridecanol, isotridecanol,
n-tetradecanol, isotetradecanol, n-pentadecanol, isopentadecanol, n-hexadecanol, isohexadecanol, n-heptadecanol, isoheptadecanol, n-octadecanol, Isooctadecanol and the like are exemplified. It is also possible to use lower alkyl esters such as acetates of these alcohols instead of these alcohols.

The aliphatic monohydric alcohol component constituting the aromatic carboxylic acid ester of the present invention contains 3,5,5-trimethylhexanol in an amount of 50 mol% or more, and the content is preferably 70 mol% or more. , And even 3,
5,5-Trimethylhexanol alone is preferred. 50
If the amount is less than mol%, a decrease in heat resistance and a tendency to generate tar are recognized. The alcohol used in combination has 4 carbon atoms.
Among them, a linear or branched aliphatic monohydric alcohol having 18 to 18 carbon atoms, among them, a linear monohydric alcohol having 8 to 14 carbon atoms is recommended.

The alcohol component of the present ester is 3,
One or two other than 5,5-trimethylhexanol
When more than one alcohol is mixed, the heat resistance is 3,5
Although the heat resistance is lower than that of the ester of 5-trimethylhexanol alone, the viscosity index can be improved and the pour point can be further lowered.

The 3,5,5-trimethylhexyl ester of an aromatic carboxylic acid has oxidation stability equal to or higher than that of a conventionally known ester lubricating base oil. Therefore, the life of the lubricating oil is extended, and the replacement period can be lengthened. Furthermore, tar and coke (carbide) when deteriorated
It is also a feature that the amount of is very small. If tar or coke is generated, it accumulates in the vicinity of the sliding portion and the lubricating oil is not spread, causing wear and squeaking noise. In addition, the necessity of disassembling and cleaning the machine causes a problem in maintenance.

The base oil of the lubricating oil is required to have an appropriate viscosity index and pour point (-10 ° C. or lower). Phthalates and trimellitates for plasticizers generally known have low viscosity index, high pour point, or have any drawbacks such as low heat resistance. It has not only chemical properties but also physical properties as a lubricating base oil.

In carrying out the esterification reaction, the alcohol component is, for example, 1.0 to 1.0 mol equivalent to the acid component.
1.5 molar equivalents, preferably about 1.05 to 1.2 molar equivalents are used.

Examples of the esterification catalyst include Lewis acids, alkali metals, and sulfonic acids. Specific examples of the Lewis acid include aluminum derivatives, tin derivatives, and titanium derivatives, and alkali metals include sodium alkoxide. , Potassium alkoxide and the like,
Further, examples of the sulfonic acids include p-toluenesulfonic acid, methanesulfonic acid, and sulfuric acid. The amount of use is, for example, 0.1 to the total weight of the raw materials acid and alcohol.
About 1 to 1.0% by weight is used.

The esterification temperature is from 150 to 230
The reaction is usually completed in 3 to 30 hours.

After the completion of the esterification reaction, excess raw material is distilled off under reduced pressure or normal pressure. Subsequently, the ester can be purified by a conventional purification method, for example, liquid-liquid extraction, distillation under reduced pressure, adsorption purification such as activated carbon treatment, or the like.

Among the thus obtained esters, di (3,5,5-trimethylhexyl) phthalate, di (3,5,5-trimethylhexyl) isophthalate and tri (3,5,5) trimellitate are particularly preferred. -Trimethylhexyl), tri (3,5,5-trimethylhexyl) trimesate and tetra (3,5,5-trimethylhexyl) pyromellitic acid are recommended.

The present ester is an aliphatic diester or aromatic carboxylic acid ester conventionally used as a base oil for a lubricating oil [eg, diheptyl phthalate, di (2-ethylhexyl) phthalate, isononyl phthalate, phthalate) Oxidation stability is higher than that of diisodecyl acid, ditridecyl phthalate, tri (2-ethylhexyl) trimellitate, and triisodecyl trimellitate]. Furthermore, it is more stable to oxidation at a higher temperature than neopentyl polyol ester, and hardly deteriorates. Accordingly, fields where mineral oils and polyol esters are currently used, such as automobile engine oils, two-cycle engine oils, jet engine oils, gas turbine oils, ceramic gas turbine oils, compressor oils, chain oils, hydraulic oils, gears Can be used for oil, bearing oil, grease base oil, etc.

Further, the lubricating base oil according to the present invention comprises mineral oil, poly-α-olefin, polybutene, alkylbenzene,
One or more compounds selected from the group consisting of hydrocarbon oils such as alkylnaphthalenes, esters other than the present ester (hereinafter referred to as "combination esters"), polyalkylene glycols, phenyl ethers and silicone oils are appropriately used in combination. To give a mixed base oil. The proportion of the present ester in the mixed base oil is 5% by weight or more, and a suitable mixing ratio varies depending on the type of oil used in combination.

The mineral oil has a viscosity of 3 to 30 mm2 / s
(100 ° C.) is suitable.

As the α-olefin oligomer, a 3 to 10-mer of linear α-olefin having 8 to 12 carbon atoms is recommended.

As the alkylbenzene and the alkylnaphthalene, those having an alkyl group of a straight-chain type or a branched type and having an average molecular weight of 200 to 1,000 are recommended.

When a hydrocarbon oil is used in combination, the proportion of the present ester is suitably from 5 to 40% by weight, preferably from 10 to 30% by weight, based on the whole mixed base oil. If such a mixed base oil is used, the additive solubility of the lubricating oil, rubber swelling property,
Good oxidation stability is obtained.

Examples of the concomitant ester include conventional aliphatic esters, aromatic carboxylic acid esters and polyol esters. When the present ester is used in combination with the concomitant ester, the proportion of the present ester is at least 20% by weight. Desirably, 50% by weight or more is appropriate. Thus, the use of the combined ester can improve the high-temperature stability of the entire ester.

Examples of the polyalkylene glycol include propylene oxide or a copolymer of ethylene oxide and propylene oxide, and those having a viscosity at 40 ° C. in the range of 10 to 4,000 mm 2 / s are recommended.

When the present ester is mixed with these polyalkylene glycols, the ratio of the present ester to the whole mixed base oil is suitably from 50 to 95% by weight, preferably from 70 to 90% by weight. The high temperature stability can be improved by the mixing.

As the phenyl ether, monoalkyl diphenyl ether, dialkyl diphenyl ether,
Examples thereof include polyphenyl ethers such as [bis (m-phenoxyphenyl) ether] and m-bis [(m-phenoxyphenoxy) benzene]. When this ester and phenyl ether are used as a mixture, they are used in the entire mixed base oil. The proportion of the present ester is at least 10% by weight, preferably at least 50% by weight. By the mixing, the oxidation stability and lubricity of the entire base oil can be improved, and the cost can be reduced.

Examples of the silicone oil include dimethyl silicone and phenyl silicone. When the present ester and silicone oil are used as a mixture, the proportion of the present ester to the whole mixed base oil is 10% by weight or more, preferably 50% by weight. The above is appropriate. The mixing makes it possible to improve lubricity and solubility of additives, and to reduce costs.

In order to improve the performance of the lubricating base oil according to the present invention, an antioxidant, an antiwear agent, a detergent / dispersant, a viscosity index improver, a pour point depressant, a metal deactivator, a metal Additives such as corrosion inhibitors, rust inhibitors, thickeners, defoamers, etc.
Seeds or two or more kinds can be appropriately blended. Although not particularly limited as long as the predetermined effect is obtained, specific examples of the formulation are shown below.

Examples of the antioxidant include hindered phenol-based compounds, aromatic amine-based compounds, sulfur-based compounds, phosphite-based compounds, and zinc dithiophosphate-based compounds. Is added.

Examples of the antiwear agent include organic sulfur-based, organic phosphorus-based, zinc dithiophosphate-based and long-chain fatty acid-based compounds, and are usually added in an amount of 0.05 to 5% by weight based on the base oil.

Examples of the detergent and dispersant include compounds such as basic sulfonates, superbasic sulfonates, basic phenates, salicinates, phosphonates, succinimides, benzylamines, succinates, and copolymer-based polymers. It is added in an amount of 2 to 10% by weight based on the base oil.

Examples of the viscosity index improver include polyalkyl methacrylates, ethylene-propylene copolymers,
A styrene-butadiene copolymer-based compound is exemplified, and is usually added in an amount of 1 to 20% by weight based on the base oil.

Examples of the pour point depressant include polymethacrylate compounds and alkylated naphthalene compounds, which are usually added in an amount of 0.1 to 2% by weight based on the base oil.

Examples of the metal deactivator and corrosion inhibitor include benzotriazole-based and thiadiazole-based compounds, which are usually added in an amount of 0.01 to 0.4% by weight based on the base oil.

Examples of the rust preventive include sulfonate compounds, carboxylic acid compounds, organic amine soap compounds, and sorbitan partial ester compounds.
3% by weight is added.

The thickener is used in grease, and includes soap-based and non-soap-based compounds, and is usually added in an amount of 5 to 20% by weight based on the base oil.

Examples of the antifoaming agent include silicone compounds such as polydimethyl silicone, and are usually added on the order of 10 ppm to the base oil.

[0049]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the examples. The physical and chemical properties of the lubricating oil in each example were evaluated by the following methods.

The kinematic viscosity and viscosity index of the lubricating base oil are determined according to JIS.
The measurement was performed according to K2283. The viscosity index is an index indicating the relationship between temperature and viscosity, and the larger the value, the better.
Usually, aliphatic diester or polyol ester is 100
, But some conventional aromatic carboxylic acid esters are close to zero.

The pour point of the lubricating base oil is JIS K226
The measurement was performed based on No. 9. The pour point is a temperature immediately before the fluidity is lost when the lubricating oil is cooled. The lower the pour point, the lower the temperature at which the lubricating oil can be used. The aromatic carboxylic acid ester of the present invention has a pour point (-10 ° C or lower) that can be used as a lubricating base oil.

The acid value of the lubricating base oil and the composition is determined according to JIS K
The measurement was performed based on 0070.

The oxidation stability test of a lubricating oil is usually performed by adding an additive such as an antioxidant. This ester and the comparative oil were also subjected to the oxidation stability test by blending the same additives.

Oxidation stability test For each ester of the examples or comparative examples, phenyl-
0.7% by weight of 1-naphthylamine, 0.7% by weight of p, p'-dioctyldiphenylamine, 2.0% by weight of tricresyl phosphate and 0.1% by weight of benzotriazole are added and dissolved to form an additive oil (hereinafter referred to as "the composition"). Was referred to as “added oil”). Next, 33mm inside diameter, 8 height
0.1 g of the above-mentioned additive oil and steel, aluminum and copper wires each cut to a length of 2 mm are placed in a 5 mm glass test tube, and the stopper of the stopper is closed. I attached.
The test tube was placed in an oven and heated at 204 ° C. for 24 or 72 hours. Thereafter, the acid value of the added oil was measured and compared with the acid value before the oxidation test, and the increase value of the acid value was measured. Further, the color of the added oil after the test was observed. In addition, 20 times the amount of hexane was added and dissolved in the added oil, and the insoluble portion was defined as tar (% by weight).

When a lubricating oil is oxidized at a high temperature, a carboxylic acid is formed and the acid value increases. Since carboxylic acid is a precursor of tar, the increase in acid value should be as low as possible. According to the oxidation stability test method, the lubricating oil changes its color in the order of red, brown, and black when deteriorated at high temperatures. The brown and black additive oils have a large increase in the acid value or a remarkably large tar content, which is a measure of deterioration. If the lubricating oil is deteriorated and tar is generated, there arises a problem that the proper viscosity required for lubrication cannot be maintained or the lubricating oil is deposited on the sliding portion and cannot be spread. Therefore, the smaller the generation of tar content, the better.

Example 1 296 g (2 mol) of phthalic anhydride and 634 g of 3,5,5-trimethylhexanol were placed in a 2-liter four-necked flask equipped with a stirrer, a thermometer, and a water fraction receiver equipped with a condenser.
(4.4 mol) and a metal catalyst, and 200
The temperature was raised to ° C. The esterification reaction was carried out for about 5 hours while the generated water was taken into a water fractionation receiver with the amount of water theoretically produced as a target. After completion of the reaction, excess alcohol was removed by distillation, neutralized with an aqueous solution of sodium hydroxide, and then washed with water until neutral. Then, it is treated with activated carbon and further filtered to obtain di (3,5,5-trimethylhexyl) phthalate.
795 g (yield 95%) of (ester A) was obtained. Table 1 shows the types and compositions of the raw materials used. Also, ester A
Table 2 shows the kinematic viscosities (40 ° C., 100 ° C.), viscosity index, and pour point.

Further, an oxidation stability test (heating for 72 hours) of the added oil comprising the ester A was carried out by the above method. Table 2 shows the results. It can be seen that ester A has a significantly lower increase in acid value than conventionally well-known ester-based lubricating oils shown in Comparative Examples described later. Furthermore,
Even when heated at high temperatures, it remains red.

Examples 2 to 6 Esters BF were synthesized in the same manner as in Example 1 using the aromatic carboxylic acids and alcohols shown in Table 1. The kinematic viscosity, viscosity index and pour point are shown in Table 2.
Further, the oxidative stability of an additive oil prepared by blending the same additive as in Example 1 with the ester was evaluated in the same manner as in Example 1. Table 2 shows the obtained results. Ester B ~
F indicates the same effect as in the first embodiment.

Examples 7 to 11 Using the aromatic carboxylic acids and alcohols shown in Table 1, esters G to K were synthesized in the same manner as in Example 1. The kinematic viscosity, viscosity index and pour point are shown in Table 2.
Further, the oxidative stability of an additive oil prepared by blending the same additive as in Example 1 with the ester was evaluated in the same manner as in Example 1. Table 2 shows the obtained results. When alcohols shown in Table 1 are selected in addition to 3,5,5-trimethylhexanol as the alcohol component, esters A to F
Although the oxidative stability is slightly inferior to the above, an ester having a good viscosity index and good fluidity can be obtained. The use of these esters enables lubrication in a wide temperature range from low to high temperatures.

Comparative Examples 1 to 8 Esters a to h were synthesized in the same manner as in Example 1 using the acids and alcohols shown in Table 1. The kinematic viscosity, viscosity index and pour point are shown in Table 2. Further, the oxidative stability of an additive oil prepared by blending the same additive as in Example 1 with the ester was evaluated in the same manner as in Example 1. Table 2 shows the obtained results.

The esters a and b shown in Comparative Examples 1 and 2 are aliphatic diesters generally used as plasticizers or lubricating base oils at present. These have lower oxidation stability and higher tar content than the esters of the examples.

The alcohol component of ester c shown in Comparative Example 3 was 3,5,5-trimethylhexanol, while the acid component was an aliphatic dicarboxylic acid. Oxidation stability is lower as compared to the esters of the examples.

The esters d to h shown in Comparative Examples 4 to 8 are aromatic carboxylate esters generally used as plasticizers at present. These have a lower viscosity index and lower oxidative stability than the esters of the examples.

Comparative Examples 9 to 10 Esters i and j were synthesized in the same manner as in Example 1 using the acids and alcohols shown in Table 1. The kinematic viscosity, viscosity index and pour point are shown in Table 2. Further, the oxidative stability of an additive oil prepared by blending the same additive as in Example 1 with the ester was evaluated in the same manner as in Example 1. Table 2 shows the obtained results.

Esters i and j shown in Comparative Examples 9 and 10
Is a polyol ester commonly used as a lubricating base oil. The esters of the examples have remarkably high oxidative stability as compared with these polyol esters, and produce less tar components.

Comparative Example 11 Ester k shown in Comparative Example 11 is a commercially available polyol ester used as a jet engine oil base oil.
The kinematic viscosity, viscosity index and pour point are shown in Table 2. Also,
The oxidative stability of an additive oil prepared by blending the ester with the same additive as in Example 1 was evaluated in the same manner as in Example 1. Table 2 shows the obtained results. The esters of the examples have higher oxidation stability than the ester k.

Comparative Example 12 An ester 1 was synthesized in the same manner as in Example 1 using the acids and alcohols shown in Table 1. Its kinematic viscosity,
Table 2 shows the viscosity index and pour point. Further, the oxidative stability of an additive oil prepared by blending the same additive as in Example 1 with the ester was evaluated in the same manner as in Example 1. Table 2 shows the obtained results.

The ester 1 shown in Comparative Example 12 contains 3,5,5-trimethylhexanol in the alcohol component, but has a low content (20 mol%), so that it is inferior in oxidation stability and also produces a tar component. .

Example 12 Refined paraffinic mineral oil (viscosity = 11.1 mm2 / s, 10
0 ° C., hereinafter abbreviated as “mineral oil”. ) A mixed base oil consisting of 80 parts by weight and 20 parts by weight of ester A was prepared and subjected to an oxidation stability test. At this time, the test time was set to 24 hours in consideration of the oxidation stability of the combined oil type (mineral oil). Table 3 shows the obtained results.

Example 13 Decene-1 oligomer (viscosity = 5.60 mm2 / s, 10
0 ° C., hereinafter abbreviated as “PAO”. Example 1) A mixed base oil composed of 80 parts by weight and 20 parts by weight of ester A was prepared, and the oxidation stability of the added oil prepared by applying the mixed base oil was determined in Example 1.
Evaluation was performed in the same manner as in Example 2. Table 3 shows the obtained results.

Example 14 A mixed base oil composed of 60 parts by weight of alkylbenzene (viscosity = 8.6 mm2 / s, 40 ° C., average molecular weight 250, abbreviated as “AB”) and 40 parts by weight of ester B was prepared.
The oxidative stability of the added oil prepared by applying the mixed base oil was evaluated in the same manner as in Example 12. The obtained result is the third
It is shown in the table.

Example 15 Polyalkylene glycol (viscosity = 631 mm2 / s, 1
00 ° C., hereinafter abbreviated as “PAG”. ) A mixed base oil composed of 10 parts by weight and 90 parts by weight of ester C was prepared, and the oxidative stability of the added oil prepared by applying the mixed base oil was evaluated in the same manner as in Example 12. Table 3 shows the obtained results.

Example 16 Alkyl diphenyl ether (viscosity = 106 mm2 / s,
40 ° C., 13 mm 2 / s, 100 ° C., hereinafter abbreviated as “ADE”. ) A mixed base oil composed of 40 parts by weight and 60 parts by weight of ester C was prepared, and the oxidative stability of the added oil prepared by applying the mixed base oil was evaluated in the same manner as in Example 12.
Table 3 shows the obtained results.

Example 17 The oxidative stability of a test oil prepared by applying an equal weight mixture of ester A and f was evaluated in the same manner as in Example 12.
Table 3 shows the obtained results.

Example 18 The oxidative stability of an additive oil prepared by using a mixed base oil consisting of 70 parts by weight of ester A and 30 parts by weight of ester i was evaluated in the same manner as in Example 12. Table 3 shows the obtained results.

Example 19 The oxidation stability of an additive oil prepared by using a mixed base oil consisting of 80 parts by weight of ester B and 20 parts by weight of ester i was evaluated in the same manner as in Example 12. Table 3 shows the obtained results.

Comparative Example 13 The oxidation stability of an additive oil prepared by applying a mineral oil was determined in Example 1.
Evaluation was performed in the same manner as in Example 2. Table 3 shows the obtained results.

Comparative Example 14 The oxidation stability of an additive oil prepared by applying PAO was evaluated in the same manner as in Example 12. Table 3 shows the obtained results.

Comparative Example 15 The oxidation stability of an additive oil prepared by applying AB was determined in Example 1.
Evaluation was performed in the same manner as in Example 2. Table 3 shows the obtained results.

Comparative Example 16 The oxidation stability of an additive oil prepared by applying PAG was evaluated in the same manner as in Example 12. Table 3 shows the obtained results.

Comparative Example 17 The oxidation stability of an additive oil prepared by applying ADE was evaluated in the same manner as in Example 12. Table 3 shows the obtained results.

Comparative Example 18 The oxidation stability of an additive oil prepared by applying ester f was evaluated in the same manner as in Example 12. Table 3 shows the obtained results.

Comparative Example 19 The oxidative stability of an additive oil prepared by applying ester i was evaluated in the same manner as in Example 12. Table 3 shows the obtained results.

Comparative Example 20 The oxidation stability of an additive oil prepared by applying ester j was evaluated in the same manner as in Example 12. Table 3 shows the obtained results.

As is clear from Examples 12 to 19 and Comparative Examples 13 to 20, the lubricating base oil of the present invention was prepared by mixing other base oils to form a mixed base oil, Oxidation stability is further improved, and the production of tar can be reduced.

[0086]

[Table 1]

[0087]

[Table 2]

[0088]

[Table 3]

[0089]

The lubricating base oil according to the present invention is inexpensive and has excellent oxidation stability and low tar properties as compared with various conventional base oils. Applicable to jet engine oil, gas turbine oil, ceramic gas turbine oil, compressor oil, chain oil, hydraulic oil, gear oil, bearing oil, grease base oil, etc., and is exposed to high temperatures of 150 ° C or higher, especially 200 ° C or higher It can function satisfactorily even under conditions.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C10N 40:12 40:25 40:30 40:32

Claims (6)

[Claims] 1. 1) One or more aromatic carboxylic acids and 2) 3,5,5-trimethylhexanol in 50 mol%
A lubricating base oil comprising an aromatic carboxylic acid ester obtained by completely esterifying the monohydric alcohol having 4 to 18 carbon atoms contained above. 2. A monohydric alcohol component of an aromatic carboxylic acid ester other than 3,5,5-trimethylhexanol is n-octanol, 2-ethylhexanol, n-octanol,
1 selected from the group consisting of nonanol, n-decanol, n-undecanol, isoundoundanol, n-dodecanol, n-tridecanol, and n-tetradecanol
The lubricating base oil according to claim 1, which is a seed or two or more kinds. 3. The lubricating base oil according to claim 1, wherein the monohydric alcohol component of the aromatic carboxylic acid ester is 3,5,5-trimethylhexanol alone. 4. The acid component of the aromatic carboxylic acid ester,
The lubricating oil base according to any one of claims 1 to 3, wherein the lubricating oil base is at least one selected from the group consisting of phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, trimesic acid, and pyromellitic acid. oil. 5. An aromatic carboxylic acid ester comprising di (3,5,5-trimethylhexyl) phthalate, di (3,5,5-trimethylhexyl) isophthalate and tri (3,5,5) trimellitate. -Trimethylhexyl), tri (3,5,5-trimethylhexyl) trimesate and tetra (3,5,5-trimethylhexyl) pyromellitic acid
The lubricating base oil according to claim 1, wherein the lubricating base oil is at least one member selected from the group consisting of: 6. The aromatic carboxylic acid ester content is 5%.
The lubricating base oil according to any one of claims 1 to 5, which is not less than% by weight.