JPH10251680A - Engine oil composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an engine oil composition undergoing less deterioration or evaporation at high temperatures and having excellent hydrolysis stability, low temperature properties and a good viscosity index by mixing a hydrocarbon oil with an aromatic dicarboxylic acid ester and additives. SOLUTION: This composition comprises component A, component B (B1 and/or B2) and component C in such amounts that the ratio B/(A+B)=5-80wt.%, and 0.05-15 pts.wt. component C is present per 100 pts.wt. total of components A and B. Component A is a hydrocarbon oil. Component B1 is an aromatic dicarboxylic acid diester obtained by esterifying an aromatic dicarboxylic acid represented by the formula (wherein A is a 1-4C alkyl; and n is 0 or 1-4) or its anhydride with a 6-18C linear and/or branched aliphatic monohydrid alcohol. Component B2 is an aromatic dicarboxylic acid compound ester comprising the three components including the acid component and the alcohol component used in component B1 and a 2-10C aliphatic dihydric alcohol. Component C comprises a viscosity index improver and/or a pour point depressant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an engine oil composition, and more particularly to an engine oil composition having excellent heat resistance and low temperature fluidity.
Further, the present invention relates to an engine oil composition excellent in economic efficiency.

[0002]

2. Description of the Related Art In recent years, from the viewpoints of environmental problems and resource saving, there has been an increasing demand for engine oils having a long life, a long replacement period, and low fuel consumption. In order to prolong the life of the engine oil, it is important that the oxidation stability is high and the oil loss due to evaporation is small, and in order to save fuel, the change in viscosity of the engine oil from high to low temperature is small (viscosity (High index) and low viscosity at low temperature (about −30 ° C.) and good startability. In order to improve the performance of the engine oil, it is important to improve the performance of the base oil which accounts for the majority of the engine oil.

[0003] For the purpose of improving the performance of engine oils, engine oils using synthetic hydrocarbon base oils such as poly-α-olefins as base oils have been further upgraded to higher grades. Engine oils and the like using mixed base oils containing esters have been developed.

[0004] Esters generally have a longer lifespan (good heat resistance), a wide operating temperature range (low pour point, high viscosity index), good lubricity, and good volatility compared to hydrocarbon base oils. Has advantages such as low. In the case of a mixed base oil of an ester and a hydrocarbon oil, in addition to the performance of the ester described above, effects of improving the rubber sealability and improving the solubility of sludge (engine oil degraded deposits) in the engine oil are obtained. Therefore, an ester is mixed with the hydrocarbon oil at a specific ratio, and various additives are further blended to obtain an engine oil.

However, unlike mineral oils and poly-α-olefins which have been conventionally used as base oils, esters are hydrolyzed upon contact with water to produce acids and alcohols. The acid generated by the hydrolysis causes corrosion of the metal and generation of a polymerization deterioration product such as sludge, varnish, and coke. Therefore, when using an ester for the purpose of extending the replacement period of the engine oil, it is important to select an ester having excellent heat resistance and hydrolysis stability.

At present, esters mixed with a hydrocarbon base oil as an engine oil base oil include aliphatic dibasic acids such as adipic acid and sebacic acid and aliphatic dibasic acids synthesized from monohydric alcohols. Esters and polyol esters synthesized from neopentyl polyols such as pentaerythritol and trimethylolpropane and monovalent carboxylic acids are well known.

Aliphatic dibasic esters such as dioctyl adipate, diisodecyl adipate or ditridecyl adipate have been used as plasticizers for vinyl chloride resins, but have been viewed as lubricating base oils including engine oils. In this case, it is particularly excellent in low-temperature fluidity and viscosity index, and is blended with engine oil, grease base oil for low-temperature use or high-speed rotating bearings, metal working oil, and the like, in addition to engine oil. However, heat resistance is by no means high among esters.

[0008] Polyol esters are more expensive than aliphatic dibasic acid esters, but they are superior in heat stability and oxidative stability especially at high temperatures, in addition to low-temperature fluidity. It is mentioned. Therefore, as a high performance engine oil base oil, synthetic hydrocarbons (poly-α
-Olefins) and polyol esters are the most common. In addition, polyol esters are not limited to engine oils such as automobiles, but are used under severe conditions such as jet engine oils, gas turbine oils, compressor oils, chain oils, hydraulic oils, gear oils, bearing oils, and grease base oils. It is also used favorably in fields such as oil.

[0009] However, it has been required to have better oxidation stability, lower evaporation and hydrolysis stability than engine oils using a mixed base oil of a synthetic hydrocarbon and a polyol ester. Also, engine oils containing polyol esters are more expensive than mineral oil-based engine oils, which is a factor preventing their spread.

On the other hand, aromatic diesters such as di (2-ethylhexyl) phthalate and diisodecyl phthalate, which are known as plasticizers, are used in some applications such as compressor oil, in contrast to aliphatic dibasic acid esters. Except for the above, it is not used as a lubricating base oil such as engine oil. The reason is that the aromatic diester generally has a higher pour point and volatility and a lower viscosity index than the aliphatic dibasic acid ester and the polyol ester.

As described above, a high-performance engine oil having good heat resistance, oxidation stability, low volatility and hydrolysis stability and using an inexpensive ester base oil has not yet been found.

[0012]

DISCLOSURE OF THE INVENTION The present invention is inexpensive and has little deterioration or evaporation at high temperatures equivalent to or higher than that of an engine oil containing a conventional polyol ester, and has excellent hydrolysis stability. It is an object of the present invention to provide an engine oil composition having good low-temperature properties and a viscosity index.

[0013]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, have found that a composition comprising a hydrocarbon oil, an aromatic dicarboxylic acid ester having a specific structure and a specific additive. It has been found that the product has a predetermined effect as an engine oil, and based on such knowledge, the present invention has been completed.

That is, the engine oil composition according to the present invention comprises:
In an engine oil composition containing the following A component, B component (B-1 component and / or B-2 component) and C component, the weight ratio of the B component to the total amount of the A component and the B component is as follows. 5 to 80% by weight, and the weight ratio of the component C to the total amount of 100 parts by weight of the component A and the component B is 0.05 to 1
It is characterized by being 5 parts by weight. Component A: One or more hydrocarbon oils. Component B-1: an aromatic dicarboxylic acid represented by the general formula (1) or an anhydride thereof and a straight-chain having 6 to 18 carbon atoms and / or
Alternatively, one or more aromatic dicarboxylic acid diesters obtained by esterifying a branched aliphatic monohydric alcohol. Component B-2: an aromatic dicarboxylic acid represented by the general formula (1) or an anhydride thereof, a straight chain having 6 to 18 carbon atoms and / or
Or a branched aliphatic monohydric alcohol, and having 2 to 2 carbon atoms
One or more aromatic dicarboxylic acid complex esters obtained by esterifying three components of 10 aliphatic dihydric alcohols. Component C: One or more additives comprising a viscosity index improver and / or a pour point depressant.

Embedded image Wherein A is an alkyl group having 1 to 4 carbon atoms, and n is 0
Or it is an integer of 1-4. ]

Examples of the hydrocarbon oil used in the present invention include hydrorefined mineral oil or solvent-refined mineral oil having a viscosity index of 100 or more, wax isomerized oil, poly-α-olefin, polybutene, alkylbenzene, alkylnaphthalene and the like. In view of viscosity, viscosity index, oxidative stability and fluidity at low temperatures, hydrorefined mineral oil, wax isomerized oil, poly-α
-Olefins are preferred.

The hydrorefined mineral oil or wax isomerized oil preferably has a kinematic viscosity at 100 ° C. of 3 to 30 [mm ² / s] and a viscosity index of 100 or more, more preferably 120 or more.

The poly-α-olefin is preferably a compound having 2 carbon atoms.
To 16-alpha-olefins (e.g., ethylene, propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, etc.) The kinematic viscosity at 100 ° C is 2 to 30 [mm ² / s], the viscosity index is 100 or more,
The kinematic viscosity at 00 ° C is 3 to 10 [mm ² / s] and the viscosity index is 12
Those having 0 or more are preferable.

The aromatic dicarboxylic acid diester (hereinafter referred to as “(B-1) ester”) or the aromatic dicarboxylic acid complex ester (hereinafter referred to as “(B-2) ester”) according to the present invention, (B-1) The ester and the (B-2) ester are collectively referred to as “the present ester”). The predetermined acid component and the alcohol component are prepared by a conventional method, preferably under an inert gas atmosphere such as nitrogen, in the presence of an esterification catalyst or An ester compound prepared by completely esterifying with heating and stirring without a catalyst.

The aromatic dicarboxylic acid which is a component of the present ester is a phthalic acid derivative which may have an alkyl substituent having 1 to 4 carbon atoms or an anhydride thereof, and more specifically, phthalic acid. From isophthalic acid, terephthalic acid, 3-methylphthalic acid, 4-methylphthalic acid, dimethylphthalic acid, trimethylphthalic acid, tetramethylphthalic acid, ethylphthalic acid, propylphthalic acid, butylphthalic acid, t-butylphthalic acid and their anhydrides One or more selected ones are exemplified, but phthalic acid, phthalic anhydride, isophthalic acid, and terephthalic acid are industrially inexpensive and readily available, and are particularly recommended.

Examples of the aliphatic monohydric alcohol which is a constituent component of the present ester include linear and / or branched aliphatic monohydric alcohols having 6 to 18 carbon atoms. -Hexanol, isohexanol, n-heptanol, isoheptanol, n-octanol, isooctanol, 2-ethylhexanol, n-nonanol, isononanol, 3,5,5-trimethylhexanol, n-decanol, isodecanol, n-undecanol , Isoundecanol, n-dodecanol, isododecanol, n-tridecanol, isotridecanol, n-tetradecanol, isotetradecanol,
Examples thereof include n-pentadecanol, isopentadecanol, n-hexadecanol, isohexadecanol, n-heptadecanol, isoheptadecanol, n-octadecanol, and isooctadecanol. Monohydric alcohols industrially obtained as "oxo alcohols" include a mixture of a linear component and a branched component, or a complex mixture having different numbers of carbon atoms, and these can also be used. It is also possible to use a lower alkyl ester such as an acetate ester instead of these alcohols.

(B-2) The aliphatic dihydric alcohol which is a component of the ester includes a linear or branched aliphatic dihydric alcohol having 2 to 10 carbon atoms, such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,7-heptanediol, 1,8-
Octanediol, 2,2-diethyl-1,3-propanediol, 1,9-nonanediol, 2-butyl-2
-Ethyl-1,3-propanediol, 1,10-decanediol and the like.

(B-1) The ester alone preferably has a viscosity index of 50 or more, more preferably 100 or more, and preferably does not precipitate crystals at a low temperature of about 0 ° C. Such a (B-1) ester has a straight-chain component and a branched component as its constituent alcohol, and in particular, a straight-chain alcohol and a branched-chain alcohol having 8 to 12 carbon atoms are mixed (the branched-chain alcohol). It is recommended that the content is 20 to 80 mol%). If the content of the branched alcohol is less than 20 mol%, crystals tend to be easily precipitated, and if it exceeds 80 mol%, the viscosity index tends to be low.

Among the above esters (B-1), diundecyl phthalate (mixture of n-undecanol and isoundecanol) using "oxo alcohol" having 11 carbon atoms as an alcohol component is particularly recommended. In addition, particularly as an aromatic dicarboxylic acid diester having excellent heat resistance,
Di (3,5,5-trimethylhexyl) phthalate is recommended.

On the other hand, the ester (B-2) can be obtained by subjecting a mixture of an aromatic dicarboxylic acid and an aliphatic monohydric alcohol and an aliphatic dihydric alcohol to an esterification reaction. Further, it can also be obtained by subjecting (B-1) an ester as a raw material, adding a dihydric alcohol, and subjecting to ester exchange.

(B-2) When producing an ester, the ratio of monohydric alcohol to dihydric alcohol is as follows: monohydric alcohol: dihydric alcohol = 95: 5 to 50:50 (equivalent%)
Is recommended, and particularly preferably 95: 5 to 70:30 (equivalent%). If the dihydric alcohol is less than 5%, it tends to be difficult to obtain an appropriate viscosity, and if it exceeds 50 equivalent%, a large amount of a high molecular weight polymer is generated, which greatly affects the fluidity.

The present ester has higher heat resistance than the aliphatic dibasic acid ester conventionally blended as an engine oil base oil, and further has a neopentyl polyol ester (for example, neopentyl glycol, trimethylolpropane or pentane). (Ester of erythritol and a monovalent monocarboxylic acid having 7 to 10 carbon atoms) and has excellent heat resistance and is extremely stable against hydrolysis.

When the present ester is mixed with a hydrocarbon oil to form a mixed base oil, the amount of the present ester is 5 to 80% by weight based on the total mixed base oil. If the compounding amount is less than 5%, the effect of adding the ester is not seen, and if it exceeds 80%,
Both are inferior in heat resistance and also cause precipitation of crystals at low temperatures and swelling of the rubber material.

Some of the present esters alone precipitate crystals at a low temperature of about 0 ° C. Therefore, the present ester is combined with a hydrocarbon oil to form a mixed base oil, and further, a viscosity index improver and / or a pour point depressant are blended to obtain an engine oil composition. The composition becomes a composition having good heat resistance and low-temperature viscosity equal to or higher than that of the current polyol ester.

Examples of the viscosity index improver as an additive according to the present invention include polyalkyl methacrylates, alkyl methacrylate-propylene copolymers, alkyl methacrylate-ethylene copolymers, polyisobutylene, polyalkylstyrene, ethylene-propylene copolymers, Examples thereof include styrene-butadiene copolymer-based compounds and styrene-maleic anhydride copolymer-based compounds, which are usually added in an amount of 1 to 20% by weight based on the base oil.

Examples of the pour point depressant as an additive according to the present invention include polyalkyl methacrylate, polyalkyl acrylate, condensate of chlorinated paraffin and naphthalene, condensate of chlorinated paraffin and phenol, polybutene and polyalkyl. Styrene, polyvinyl acetate and the like are mentioned, and usually 0.1 to 1% is added to the base oil.

Among the above additives, polyalkyl methacrylate is particularly preferable because it has a pour point depressing effect in addition to the effect of improving the viscosity index.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION In order to improve the performance of an engine oil composition according to the present invention, in addition to additives of a viscosity index improver and a pour point depressant, an antioxidant, an antiwear agent and a friction agent are added. Conditioner, ashless dispersant, metal detergent, metal deactivator,
One or more of additives such as a metal corrosion inhibitor, a rust inhibitor, a thickener, and an antifoaming agent can be appropriately compounded. It is not particularly limited as long as it has the predetermined effect,
Specific examples of the formulation are shown below.

As antioxidants, 2,6-di-t-butylparacresol, 4,4'-methylenebis (2,6
-Di-t-butylphenol), N-phenyl-α-naphthylamine, p, p′-
Aromatic amines such as dioctyldiphenylamine, 4,
Sulfur-based such as 4'-thiobis (6-t-butyl-3-methylphenol) and phenothiazine, phosphite-based,
Examples include zinc dialkyldithiophosphate-based compounds and zinc dialkyldithiocarbamate-based compounds, which are usually added in an amount of 0.1 to 5% by weight based on the base oil.

Examples of the antiwear agent include organic sulfur-based compounds such as olefin polysulfide, sulfurized oils and fats, and dialkyl polysulfides; organic phosphorus-based compounds such as chlorinated paraffins, alkyl and allyl phosphates; and alkyl and allyl phosphites; dialkyldithiophosphates. Examples thereof include zinc-based, zinc dialkyldithiocarbamate-based, and long-chain fatty acid-based compounds, which are usually added in an amount of 0.05 to 10% by weight based on the base oil.

Examples of the friction modifier include fatty acids such as stearic acid and oleic acid, alcohols such as stearyl alcohol and oleyl alcohol, amines such as oleylamine, and organic molybdenum such as molybdenum dithiocarbamate. 0.1 to 5.0% by weight based on

Examples of the metal detergent include metal sulfonate, basic metal sulfonate, overbased metal sulfonate, metal phenate, basic metal phenate, overbased metal phenate, metal thiopyrophosphonate, metal phosphonate, salicylate, carboxylate and the like. For example, 2 to 10% by weight is usually added to the base oil.

Examples of the ashless detergent / dispersant include polyalkenyl succinimide, polyalkenyl succinamide, polyalkenyl benzylamine, polyalkenyl succinate and the like. Usually, 2 to 10% by weight based on the base oil is added. You.

Examples of the metal deactivator and corrosion inhibitor include thiadiazole-based compounds such as benzotriazole and 2,5-bis (n-dodecyldithio) -1,3,4-thiazol. 0.01 to
About 0.4% by weight is blended.

Examples of the rust preventive include sulfonate compounds, carboxylic acid compounds, organic amine soap compounds and sorbitan partial ester compounds, and 0.05 to 3% by weight based on the base oil is usually used. It is.

Examples of the antifoaming agent include silicone compounds such as polydimethyl silicone, and are usually added in an amount of about 1 to 100 ppm based on the base oil.

[0041]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the examples. still,
Prior to the examples, the physical properties of each ester and hydrocarbon oil used in the examples were evaluated by the following methods. In addition, the physical properties of the engine oil composition were similarly evaluated by the following methods.

[Kinematic viscosity and viscosity index] JIS K22
The measurement was carried out based on No. 83. The viscosity index is an index indicating the relationship between temperature and viscosity, and the larger the value, the better. An oil having good temperature-viscosity characteristics is a standard having a viscosity index of 100 or more.

[Pour point] The pour point was measured according to JIS K 2269. The pour point is a temperature immediately before the fluidity is lost when the lubricating oil is cooled. The lower the value, the lower the temperature at which the lubricating oil can be used, which is preferable as an engine oil base oil and a composition.

[Acid value] The measurement was carried out based on JIS K0070.

[Heat Resistance Test] 1) [Oxidation Starting Temperature] Each ester was heated from room temperature to 350 ° C. using TG-DTA (manufactured by Mac Science), and the temperature at which a peak appeared during oxidation or decomposition was measured. Then, the oxidation start temperature was obtained. The oxidation start temperature is an index of the temperature at which deterioration starts,
The higher the number, the better.

2) [Oxidation stability test] With respect to each ester, 0.7% by weight of phenyl-1-naphthylamine, 0.7% by weight of p, p'-dioctyldiphenylamine, 2.0% by weight of tricresyl phosphate and A sample oil was prepared by adding and dissolving 0.1% by weight of benzotriazole. Then, into a glass test tube having an inner diameter of 33 mm and a height of 85 mm, 0.1 g of the above-described additive oil and steel, aluminum, and copper wires each cut into a length of 2 mm were put, and a stopper was put on the stopper. A stopper was attached to prevent it from opening. The test tube was placed in an oven and heated at 204 ° C. for 30 hours. Thereafter, the acid value of the sample oil was measured and compared with the acid value before the heating test, and the increase in the acid value was examined. The increase in acid value should be as low as possible.

3) [Panel coking test] The panel coking test was performed according to FED. TEST METHO
D STD. 791b-3462, using the same sample oil used in the oxidation stability test. The coking value is the amount of coke adhering to the aluminum plate in mg when the test was performed at 316 ° C. for 8 hours, and the smaller the value, the better. If coke (carbide) is generated, there arises a problem that an appropriate viscosity required for lubrication cannot be maintained, and that coke is deposited on a sliding portion and lubricating oil cannot be distributed.

4) [Volatile test] 3.0 g of the same sample oil used in the oxidation stability test was placed in a glass petri dish, and the weight of the added oil was measured after heating at 204 ° C for 6.5 hours. And the amount of volatilization was determined as a percentage by weight with respect to the weight before heating, and defined as the volatility. Volatility also affects the timing of oil change, and the smaller the value, the more difficult it is to volatilize, which is preferable as an engine oil.

[Hydrolysis test] 2.0 g of each ester was placed in a Pyrex glass test tube (inner diameter 6.5 mm).
4 cm each of iron, copper, and aluminum wires and 0.2 g of distilled water were put therein and sealed. The acid value after heating at 175 ° C. for 20 hours was measured, and the rise value was determined from the acid value before and after the test.

[Measurement of Low Temperature Viscosity]
After cooling to 30 ° C., the viscosity was measured using a Brookfield viscometer.

[Hot Tube Test] A sample oil was prepared by adding 0.8 parts by weight of commercially available zinc di (sec-alkyl) dithiophosphate to both 100 parts by weight of the engine oil composition. 290 ° C
3 ml / sample oil in a 2 mm inner diameter glass tube
h, The air was kept flowing at a rate of 10 ml / h for 16 hours.
After the test, the lacquer adhering to the glass tube and the color sample were compared, and a score was given as 10 points for transparent and 0 points for black. The higher the score, the better the durability.

[Hydrolysis Stability Test] An engine oil composition was placed in a Pyrex glass test tube (inner diameter 6.5 mm).
0g, iron, copper, aluminum wire 4cm each, distilled water 0.2
g and sealed. The acid value after heating at 200 ° C. for 20 hours was measured, and the rise value was determined from the acid value before and after the test.

Ester A 148.0 g of phthalic anhydride was placed in a 1-liter four-necked flask equipped with a stirrer, a thermometer, and a water fraction receiver equipped with a cooling tube.
(1.0 mol), undecanol (linear: branched = 46:
(54 mol ratio) 378.4 g (2.2 mol) and a metal catalyst were charged, and the temperature was raised to 200 ° C. under reduced pressure. 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, an activated carbon treatment was carried out, followed by filtration, and di (n-undecyl, isoundecyl) phthalate (ester A) 440.8
g (93% yield). Table 1 shows the types and compositions of the raw materials used. Further, the kinematic viscosity of the ester A (40 ° C., 10
0 ° C.), viscosity index, pour point, volatility, heat resistance test, caulking value, and hydrolysis stability test results are shown in Table 2 below.

Ester A has a higher oxidation initiation temperature and lower acid value rise than hydrocarbon oils, aliphatic diesters, and polyol esters. Another characteristic is that the amount of generated coke is small. On the other hand, it has a low volatility and has the same or higher volatility as the polyol ester. Further, they have remarkably high stability to hydrolysis as compared with aliphatic diesters and polyol esters.

Esters BI Using the acids and alcohols shown in Table 1, the esters A
Compounds B to I were synthesized by the same operation as described above. The kinematic viscosity, viscosity index and pour point of the results of the kinematic viscosity, viscosity index, pour point, volatility, heat resistance test, caulking value and hydrolysis stability test are shown in Table 2. As with the ester A, all of the esters have excellent heat resistance, a small amount of coke generated, and high hydrolysis stability.

Esters a to c Esters a to c were synthesized in the same manner as for ester A using the acids and alcohols shown in Table 1. Table 2 shows the results of the kinematic viscosity, viscosity index, pour point, volatility, heat resistance test, caulking value and hydrolysis stability test.

Esters a and b are the most common aliphatic diesters currently compounded in plasticizers or engine oil base oils. These esters have lower heat resistance than the present esters A to I and have a large amount of coke generated,
Poor hydrolysis stability.

The ester c is a polyol ester generally used as an ester to be blended in an engine oil base oil. The polyol ester is slightly inferior in heat resistance and inferior in hydrolytic stability as compared with the present esters A to I.

Ester d Ester d is a commercially available polyol ester used as jet engine oil base oil. Table 2 shows the results of the kinematic viscosity, viscosity index, pour point, volatility, heat resistance test, caulking value and hydrolysis stability test. The polyol ester is slightly inferior in heat resistance and inferior in hydrolytic stability as compared with the present esters A to I.

Mineral oil Table 2 shows the results of kinematic viscosity, viscosity index, pour point, volatilization, heat resistance test, caulking value and hydrolysis stability test of refined paraffinic mineral oil (hereinafter abbreviated as "mineral oil"). Show.

Results of kinematic viscosity, viscosity index, pour point, volatilization, heat resistance test, coking value and hydrolysis stability test of poly-α-olefin decene-1-oligomer (hereinafter abbreviated as “PAO”) The second
It is shown in the table.

Mineral oil and PAO, which are hydrocarbon oils, have higher volatility and are more easily oxidized than the present ester. It also produces too much coke when degraded as seen in panel coking tests. If the present ester having high heat resistance is mixed with the hydrocarbon oil, the heat resistance of the whole mixed base oil is improved.

Example 1 To 100 parts by weight of a base oil obtained by mixing PAO and ester A at a weight ratio of 80:20, 7 parts by weight of a commercially available methacrylate-based viscosity index improver / pour point depressant as an additive was added. Parts were blended to give an engine oil composition. The kinematic viscosity, viscosity index, pour point, low temperature viscosity (−30 ° C.), hot tube test and hydrolysis stability test of the engine oil composition were performed. Table 3 shows the results.

Examples 2 to 9 A commercially available polyalkylmethacrylate-based viscosity index improver was added as an additive to 100 parts by weight of a base oil obtained by mixing PAO with esters B to I at a weight ratio of 80:20. A sample oil was prepared by mixing 7 parts by weight of a pour point depressant. The kinematic viscosity, pour point, low-temperature viscosity (−30 ° C.), hot tube test and hydrolysis stability test of each composition were performed in the same manner as in Example 1. Table 3 shows the results.

Comparative Examples 1-4 PAO and esters ad were mixed at a weight ratio of 80:20 to 100 parts by weight of a base oil, and a commercially available methacrylate-based viscosity index improver / pour point depressant was added to 7 parts by weight. The sample oil was blended in parts by weight. Kinematic viscosity, pour point, low temperature viscosity (-3
0 ° C.), a hot tube test and a hydrolysis stability test were performed in the same manner as in Example 1. Table 3 shows the results.

Comparative Example 5 Kinematic viscosity, pour point, low temperature viscosity (−30) of a base oil obtained by mixing PAO and ester A at a weight ratio of 80:20.
C), a hot tube test and a hydrolysis stability test were performed in the same manner as in Example 1. Table 3 shows the results.

Comparative Example 6 A sample oil was prepared by mixing 7 parts by weight of a commercially available methacrylate viscosity index improver and pour point depressant with 100 parts by weight of ester A. The kinematic viscosity, pour point and low temperature viscosity of the sample oil (-30
C), a hot tube test and a hydrolysis stability test were performed in the same manner as in Example 1. Table 3 shows the results.

Comparative Example 7 Kinematic viscosity, pour point, low temperature viscosity (-30 ° C.) of ester A,
A hot tube test and a hydrolysis stability test were performed in the same manner as in Example 1. Table 3 shows the results.

As can be seen from Comparative Example 7, when the present ester is kept at a low temperature of about −30 ° C., the viscosity becomes very high or crystals are precipitated (especially when the ester has a viscosity index of more than 100). This tendency is observed.) In some cases, it is difficult to use it alone as engine oil. Also, a combination of the present ester and a hydrocarbon oil (Comparative Example 5) or a combination of the present ester and a pour point depressant (or a viscosity index improver) (Comparative Example 6) tends to precipitate crystals at low temperatures. As shown in Examples 1 to 9, engine oil compositions comprising a combination of the present ester, a hydrocarbon oil, and a viscosity index improver (pour point depressant) are currently in practical use as in Comparative Examples 1 to 4. It exhibits similar or better performance than certain engine oil compositions.

[0070]

[Table 1]

[0071]

[Table 2]

[0072]

[Table 3]

[0073]

The engine oil composition according to the present invention has excellent heat resistance and hydrolysis stability as compared with conventionally known engine oils, and can be supplied at a low cost, so that it can be supplied to automobile engines (gasoline engines, diesel engines). It can be applied to two-cycle engine oil, gear oil, etc., and is extremely useful in practice.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C10M 107: 10 101: 02 109: 02 105: 36 105: 46 145: 14) C10N 20:04 30:02 30:08 40: 25 60:02 (72) The inventor Takashi Takahashi 13th Yoshishima Yakuracho, Fushimi-ku, Kyoto, Kyoto New Japan Rika Co., Ltd. Inside

Claims (7)

[Claims] 1. The following A component, B component (B-1 component and / or
Or B-2 component) and the C component, the amount of B relative to the total amount of the A component and the B component
An engine oil composition wherein the weight ratio of the components is 5 to 80% by weight, and the weight ratio of the component C to the total amount of the component A and the component B is 100 to 100 parts by weight. Component A: One or more hydrocarbon oils. Component B-1: an aromatic dicarboxylic acid represented by the general formula (1) or an anhydride thereof and a straight-chain having 6 to 18 carbon atoms and / or
Alternatively, one or more aromatic dicarboxylic acid diesters obtained by esterifying a branched aliphatic monohydric alcohol. Component B-2: an aromatic dicarboxylic acid represented by the general formula (1) or an anhydride thereof, a straight chain having 6 to 18 carbon atoms and / or
Or a branched aliphatic monohydric alcohol, and having 2 to 2 carbon atoms
One or more aromatic dicarboxylic acid complex esters obtained by esterifying three components of 10 aliphatic dihydric alcohols. Component C: One or more additives comprising a viscosity index improver and / or a pour point depressant. Embedded image Wherein A is an alkyl group having 1 to 4 carbon atoms, and n is 0
Or it is an integer of 1-4. ] 2. The method according to claim 1, wherein the hydrocarbon oil is a poly-α-olefin,
The engine oil composition according to claim 1, which is a hydrorefined mineral oil or a wax isomerized oil. 3. The monohydric alcohol constituting the aromatic dicarboxylic acid diester is a mixed alcohol of a linear alcohol and a branched alcohol, and the proportion of the branched alcohol in the mixed alcohol is 20 to 80 mol%. The engine oil composition according to claim 1 or claim 2. 4. The aliphatic monohydric alcohol constituting the aromatic dicarboxylic acid diester is a mixed alcohol of n-undecanol and isoundecanol.
The engine oil composition according to any one of claims 1 to 4. 5. The engine oil composition according to claim 1, wherein the aliphatic monohydric alcohol constituting the aromatic dicarboxylic acid diester is 3,5,5-trimethylhexanol. 6. The aliphatic dihydric alcohol constituting the aromatic dicarboxylic acid complex ester is one or selected from ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol and 1,6-hexanediol. The engine oil composition according to claim 1 or 2, wherein the composition is two or more types. 7. The engine oil composition according to claim 1, wherein the additive is a polyalkyl methacrylate having a molecular weight of 10,000 to 300,000.