JPH08165485A - Lubricating oil composition for internal combustion engine - Google Patents

Abstract

PURPOSE: To obtain a lubricating oil composition for internal combustion engine improving an oxidative deterioration life, capable of reducing of maintenance according to prolongation of oil charge interval and suitable as an engine oil for a co-generation system, etc., by mixing a base oil of a lubricating oil with a specific antioxidant and a specific ester. CONSTITUTION: The objective composition is composed of a base oil of a lubricating oil, (A) a hindered phenolic-based antioxidant, or an amine-based antioxidant such as a dialkyldiphenylamine-based or a naphthylamine-based and (B) an ester derived from a substituted hydroxyaromatic carboxylic acid such as a compound expressed by the formula (Ar is a multifunctional aromatic nucleus; R is an organic group; (m) and (p) are each 1-3; (n) is 1-4) and a hydroxy compound such as an alkyl-substituted aromatic alcohol. Preferably, the objective composition contains a phosphoric acid ester-based antioxidant as an antioxidant together with the component A, and mixing amounts of the component A and B to whole amount of the composition are respectively 0.2-10wt.% and 0.1-20wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricating oil composition for an internal combustion engine, and more particularly, to a gas engine heat pump which has a significantly improved oxidative deterioration life and which can reduce maintenance due to extension of the oil change interval. The present invention relates to a lubricating oil composition for an internal combustion engine, which is preferably used as an engine oil for a cogeneration system.

[0002]

2. Description of the Related Art In recent years, for air conditioning of houses and buildings,
Gas engine heat pump system and cogeneration
System has been developed and put into practical use.
In general, natural gas and liquefied petroleum gas
Gas engines that use (LPG) as fuel have been used
There is. However, with the spread of such systems,
Since the number of maintenance and inspection work is increasing, the inspection is simple.
Improvement of maintenance such as standardization and extension of maintenance work intervals
Is an important issue.
An engine oil with excellent longevity that can extend the oil change interval is desired.
Have been. By the way, lubrication for gas engine heat pumps
Due to the structure of the equipment and the high combustion temperature, oil is
-High concentration of NO in bypass gas_XRapid contact with
Therefore, there is a problem that
Oxidation stability, especially NO resistance _XImproves oxidizability, oil change interval
Is being considered. Oxidation stability of lubricating oil
As a method for improving the property, for example, for lubricating oil,
The base oil and additives that are the constituent base materials have excellent oxidative stability.
The method of selecting the
Methods such as selecting additives that are effective in suppressing
There is. However, conventional technology is still quite satisfactory
Oxidative stability is not obtained, and
The actual situation is that the oil change interval has not yet been reached.
It

[0003]

SUMMARY OF THE INVENTION In such a situation, the present invention provides a gas engine heat pump for a gas engine heat pump or a cogeneration system, in which the oxidative deterioration life is significantly improved and maintenance can be reduced with the extension of the oil change interval. An object of the present invention is to provide a lubricating oil composition for an internal combustion engine, which is preferably used as an engine oil for automobiles.

[0004]

The inventors of the present invention have conducted extensive studies to develop a lubricating oil composition for an internal combustion engine having the above-mentioned preferable properties, and as a result, have found that a specific antioxidant and a substituted hydroxyaromatic carvone are used. It has been found that the object can be achieved by combining the acid ester with a lubricating base oil. The present invention has been completed based on such findings. That is, the present invention relates to a lubricating base oil, and (A) at least one antioxidant selected from hindered phenol-based and amine-based, or this antioxidant and a phosphonate-based antioxidant. A combination of
And (B) a lubricating oil composition for an internal combustion engine, which comprises an ester obtained from a substituted hydroxyaromatic carboxylic acid and a hydroxy compound. Further, a preferred embodiment of the present invention is based on the total amount of the composition, based on the total amount of the composition, 0.2 to 10% by weight of the component (A) and the component (B).
A lubricating oil composition for an internal combustion engine, containing 0.1 to 20% by weight.

As the base oil in the lubricating oil composition for internal combustion engines of the present invention, mineral oil or synthetic oil is usually used. There are no particular restrictions on the type of mineral oil or synthetic oil, etc., but the kinematic viscosity at 100 ° C is usually 1.5 to 40 mm.
Those in the range of ² / sec are used. Here, examples of the mineral oil include paraffin-based mineral oil, intermediate-based mineral oil, and naphthene-based mineral oil obtained by ordinary refining methods such as solvent refining and hydrogenation refining. Examples of synthetic oils include polybutene, polyolefin [α
-Olefin homopolymers and copolymers], various esters (for example, polyol esters, dibasic acid esters, phosphoric acid esters, etc.), various ethers (for example,
Polyphenyl ether, etc.), alkylbenzene, alkylnaphthalene, etc.

In the present invention, the mineral oil may be used alone or in combination of two or more as the base oil. Further, the above synthetic oils may be used alone or in combination of two or more. Furthermore, one or more mineral oils and one or more synthetic oils may be used in combination. In the composition of the present invention, as the component (A), at least one antioxidant selected from the group consisting of hindered phenols and amines, or a combination thereof with a phosphonate ester antioxidant is used. To be

Examples of the hindered phenolic antioxidants include 4,4'-methylenebis (2,6-di-
t-butylphenol); 4,4'-bis (2,6-di-t-butylphenol); 4,4'-bis (2-methyl-6-t-butylphenol); 2,2'-methylenebis (4- Ethyl-6-t-butylphenol); 2,
2'-methylenebis (4-methyl-6-t-butylphenol); 4,4'-butylidenebis (3-methyl-6)
-T-butylphenol); 4,4'-isopropylidene bis (2,6-di-t-butylphenol); 2,
2'-methylenebis (4-methyl-6-nonylphenol); 2,2'-isobutylidenebis (4,6-dimethylphenol); 2,2'-methylenebis (4-methyl-6-cyclohexylphenol); 2 , 6-di-t-
Butyl-4-methylphenol; 2,6-di-t-butyl-4-ethylphenol; 2,4-dimethyl-6-t
-Butylphenol; 2,6-di-t-α-dimethylamino-p-cresol; 2,6-di-t-butyl-4-
(N, N'-dimethylaminomethylphenol); 4,
4'-thiobis (2-methyl-6-t-butylphenol); 4,4'-thiobis (3-methyl-6-t-butylphenol); 2,2'-thiobis (4-methyl-6)
-T-butylphenol); bis (3-methyl-4-hydroxy-5-t-butylbenzyl) sulfide; bis (3,5-di-t-butyl-4-hydroxybenzyl)
Sulfide; n-octadecyl-3- (4-hydroxy-3,5-di-t-butylphenyl) propionate;
2,2'-thio [diethyl-bis-3- (3,5-di-
t-butyl-4-hydroxyphenyl) propionate] and the like. Among these, bisphenol type and ester group-containing phenol type are particularly preferable.

Examples of amine antioxidants include monooctyldiphenylamine; monoalkyldiphenylamines such as monononyldiphenylamine, 4,
4,4'-dibutyldiphenylamine;4,4'-dipentyldiphenylamine;4,4'-dihexyldiphenylamine;4,4'-diheptyldiphenylamine;
4'-dioctyldiphenylamine;4,4'-dinonyldiphenylamine and other dialkyldiphenylamines; tetrabutyldiphenylamine; tetrahexyldiphenylamine; tetraoctyldiphenylamine; tetranonyldiphenylamine and other polyalkyldiphenylamines and naphthylamines; Include α-naphthylamine; phenyl-α-naphthylamine; further butylphenyl-α-naphthylamine; pentylphenyl-α-naphthylamine; hexylphenyl-α-naphthylamine; heptylphenyl-α-naphthylamine; octylphenyl-α-naphthylamine;
Examples thereof include alkyl-substituted phenyl-α-naphthylamine such as nonylphenyl-α-naphthylamine. Among these, dialkyldiphenylamine type and naphthylamine type are preferable.

Further, the phosphonate type antioxidant is preferably, for example, a phosphonate ester having a hindered phenol structure, and examples thereof include 3,5-di-t-butyl-4-hydroxybenzylphosphonate dialkyl. . As the alkyl group,
Usually, those having 1 to 18 carbon atoms can be used, but the number of carbon atoms is 1
Those of -9 are preferred. This 3,5-di-t-butyl-
Specific examples of 4-hydroxybenzylphosphonate dialkyl include 3,5-di-t-butyl-4-hydroxybenzylphosphonate diethyl; 3,5-di-t-butyl-4-hydroxybenzylphosphonate dipropyl and the like. . In the present invention, as the component (A), the hindered phenol-based antioxidants may be used alone or in combination of two or more, and one or more amine-based antioxidants may be used. You may use it in combination. Further, one or more hindered phenol antioxidants and one or more amine antioxidants may be used in combination. Further, one or more hindered phenol-based antioxidants and / or one or more amine-based antioxidants and one or more phosphonate-based antioxidants may be used in combination.

In the composition of the present invention, the antioxidant as the component (A) is preferably blended in a proportion of 0.2 to 10% by weight based on the total amount of the composition. This amount is 0.2
If it is less than 10% by weight, the effect of suppressing oxidative deterioration is not sufficiently exerted, and if it exceeds 10% by weight, the improvement of the effect is not recognized for its amount, which is rather economically disadvantageous. From the viewpoints of the effect of suppressing oxidative deterioration and economical efficiency, the preferable blending amount is 0.
It is in the range of 5 to 5% by weight. In the lubricating oil composition for internal combustion engines of the present invention, an ester obtained from a substituted hydroxyaromatic carboxylic acid and a hydroxy compound is used as the component (B). Examples of the substituted hydroxyaromatic carboxylic acid which is the acid component of the above ester include compounds represented by the general formula (I)

[0011]

Embedded image

[Wherein, Ar is a polyvalent aromatic nucleus, R is an organic group, p is an integer of 1 to 3, n is an integer of 1 to 4, and m is 1 to 3]
When the number of Rs is plural, the plural Rs may be the same or different. ] The compound represented by these can be mentioned. In the general formula (I), Ar
Indicates a polyvalent aromatic nucleus. Examples of the polyvalent aromatic nucleus include those derived from benzene, naphthalene, anthracene, phenanthrene, indene, fluorene, biphenyl and the like. Among these, those derived from benzene and naphthalene are particularly preferable.
In addition to the hydroxyl group, the organic group (R), and the carboxyl group, Ar may also have a halogen atom, a nitro group,
A mercapto group or the like may be substituted.

R is an organic group such as a hydrocarbon group, an alkoxy group and a dialkylamino group, and a hydrocarbon group is particularly preferable. When there are a plurality of Rs, the plurality of Rs may be the same or different. The hydrocarbon group is not particularly limited, and is a chain hydrocarbon group such as an alkyl group or an alkenyl group, a cyclic hydrocarbon group such as a cycloalkyl group or a cycloalkenyl group, or an aromatic carbon group such as a phenyl group or a naphthyl group. It may be any of hydrogen groups, but is preferably a chain hydrocarbon group such as an alkyl group or an alkenyl group. These hydrocarbon groups may be substituted with another hydrocarbon group such as a lower alkyl group, a cycloalkyl group or a phenyl group.
Further, the hydrocarbon group includes those substituted with a non-hydrocarbon group as long as it retains substantially hydrocarbon-like properties. Examples of the non-hydrocarbon group include a nitro group, an amino group, a halo group, a hydroxyl group, a lower alkoxy group, a lower alkylmercapto group, an oxo group, a thio group and an interrupting group (for example, -NH-, -O-, -S
-) And the like.

Examples of the hydrocarbon group include propyl group, butyl group, isobutyl group, pentyl group, hexyl group, 1-methylhexyl group, 2,3,5-trimethylheptyl group, octyl group, 3-ethyloctyl group. Group, 4-ethyl-5-methyloctyl group, nonyl group, decyl group, dodecyl group, 2-methyl-4-ethyldodecyl group, hexadecyl group, octadecyl group, eicosyl group, docosyl group, tetracontyl group, 4-hexenyl group , 2-ethyl-4-hexenyl group, 6-octenyl group, 3-cyclohexyloctyl group, phenylnonyl group, nitrododecyl group, 3-aminononyl group, chlorohexadecyl group, (2
-Nitroethyl) octyl group, (3-aminocyclohexyl) nonyl group, 4- (p-chlorophenyl) octyl group, 4-butoxyhexadecyl group, and further an olefin polymer (for example, polyethylene, polypropylene, polyisobutylene, ethylene- Hydrocarbon groups derived from propylene copolymer, polychloroprene, chlorinated olefin polymer, oxidized ethylene-propylene copolymer, etc.).

Preferred among the above hydrocarbon groups are:
A linear or branched alkyl group, preferably having 6 carbon atoms
To 7,000, more preferably a hydrocarbon group having 8 to 225 carbon atoms. Specific examples of preferable R include hexyl group, 1-methylhexyl group, 2,3,5-
Trimethylheptyl group, octyl group, 3-ethyloctyl group, 4-ethyl-5-methyloctyl group, nonyl group,
Decyl group, dodecyl group, 2-methyl-4-ethyldodecyl group, hexadecyl group, octadecyl group, eicosyl group, docosyl group, tetracontyl group and other linear or branched alkyl groups, olefin polymers (for example, polyethylene, polypropylene, Examples thereof include linear or branched alkyl groups derived from polyisobutylene, ethylene-propylene copolymer, and the like.

On the other hand, as the alcohol component of the ester, a hydroxy compound having 2 to 80 carbon atoms is preferably used. The hydroxy compound may be an aliphatic alcohol, an aromatic alcohol, a monohydric alcohol or a polyhydric alcohol. The aliphatic alcohol has, for example, 2 carbon atoms.
-24 linear or branched monohydric alcohols, specifically hexanol, octanol, decanol, dodecanol, tetradecanol, hexadecanol, octadecanol, oleyl alcohol, linolenyl alcohol, lauryl alcohol , Myristyl alcohol, cetyl alcohol, stearyl alcohol, behenyl alcohol, etc., relatively high-grade synthetic monohydric alcohols of the type produced by the oxo process (for example, 2-ethylhexyl alcohol), types formed by aldol condensation, Organoaluminum-catalyzed relatively higher synthetic monohydric alcohols of the type formed by oligomerization of α-olefins (eg, ethylene, propylene, etc.) and subsequent oxidation, as well as cyclopentanol, cyclohexene. SANOL, cycloalkyl alcohols, etc., or polyhydric alcohols such as cyclododecanol, specifically, ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, heptylene glycol, 2
-Ethyl-1,3-trimethylene glycol, neopentyl glycol, diethylene glycol, relatively high-grade polyethylene glycol and polypropylene glycol,
Tripropylene glycol, dibutylene glycol, dipentylene glycol, dihexylene glycol, diheptylene glycol, and the general formula HOCH ₂ (C
HOH) _n CH ₂ OH (eg, glycerol, sorbitol, mannitol, etc.) Can be mentioned.

Examples of aromatic alcohols include monohydric alcohols such as phenol, alkylphenol, naphthol, and alkylnaphthol, catechol, alkylcatechol, sulfurized alkylphenol, dihydric alcohols such as methylene-bridged alkylphenol, trihydroxybenzene, and trihydroxybenzene. Examples include trihydric alcohols such as hydroxyalkylbenzene. The alcohol component of the ester is preferably an aromatic alcohol, and particularly preferably an alkyl-substituted aromatic alcohol such as alkylphenol, alkylcatechol and trihydroxyalkylbenzene from the viewpoint of the performance of the obtained ester. Here, the alkyl group is preferably one having 1 to 24 carbon atoms, preferably 6 to 20 carbon atoms, and the alkyl group may be linear or branched, and about 1 to 3 on the aromatic ring. It may be substituted, but one substituted is preferable. In the present invention, specific examples of the ester used as the component (B) include:

[0018]

Embedded image

And the like. The ester as the component (B) may be used as it is, or may be treated with a boron compound to contain boron. here,
Examples of the boron compound include boric acid, boric anhydride, boron halide, boric acid ester, boric acid amide, and boric oxide.

In the lubricating oil composition of the present invention, the ester as the component (B) may be used alone or in combination of two or more kinds. Further, the blending amount is usually selected in the range of 0.1 to 20% by weight based on the total amount of the composition. If this amount is less than 0.1% by weight, the effect of suppressing oxidative deterioration will not be fully exerted, and if it exceeds 20% by weight, the effect will not be improved for that amount, and the viscosity at low temperatures will be rather rather. It causes inconvenience such as rising. From the viewpoints of the effect of suppressing oxidative deterioration, economy and viscosity, the preferable blending amount is in the range of 0.1 to 15% by weight. By blending a hindered phenol-based or amine-based antioxidant and a substituted hydroxyaromatic carboxylic acid ester, it is possible to improve the stability and extend the life of the oil agent while satisfying the detergency. Furthermore, when a phosphonate-based antioxidant is added, it is thermally stable and, in addition, it has an effect of improving the oxidative life and improving the lubricity.

In the composition of the present invention, if necessary, various additives other than the above, such as an ashless dispersant, a metal detergent, a friction modifier, and the like, are added as long as the object of the present invention is not impaired. An antiwear agent, a viscosity index improver, a pour point depressant, a rust preventive, a metal corrosion inhibitor, a defoaming agent, a surfactant, an oiliness agent and the like can be appropriately added. Here, as the ashless dispersant, for example, succinimides, boron-containing succinimides, benzylamines, boron-containing benzylamines, succinic acid esters, monovalent compounds represented by fatty acid or succinic acid, or Examples thereof include amides of divalent carboxylic acids. Examples of the metal-based detergent include neutral metal sulfonates, neutral metal phenates, neutral metal salicylates,
Neutral metal phosphonate, basic sulfonate, basic phenate, basic salicylate, basic phosphonate,
Examples include overbased sulfonates, overbased phenates, overbased salicylates, and overbased phosphonates.

Examples of friction modifiers and antiwear agents include sulfur compounds such as sulfurized fats and oils, sulfurized olefins, dialkylpolysulfides, diarylalkylpolysulfides, diarylpolysulfides, phosphoric acid esters, thiophosphoric acid esters, phosphorous acid esters, alkyl hydrogens. Phosphite, phosphate amine salt,
Phosphorous compounds such as amine salts of phosphites, chlorinated oils and fats, chlorinated paraffins, chlorinated fatty acid esters, chlorinated compounds such as chlorinated fatty acids, alkyl or alkenyl maleic acid esters, alkyl or alkenyl succinic acid esters Compounds, organic acid compounds such as alkyl or alkenyl maleic acid, alkyl or alkenyl succinic acid, naphthenates, zinc dithiophosphate (ZnDTP), zinc dithiocarbamate (ZnDTC), sulfurized oxymolybdenum organophosphorodithioate (MoDTP) Examples thereof include organometallic compounds such as oxymolybdenum dithiocarbamate sulfide (MoDTC).

Examples of the viscosity index improver include polymethacrylate, dispersion-type polymethacrylate, olefin-based copolymer (eg ethylene-propylene copolymer, etc.), dispersion-type olefin-based copolymer, styrene-based copolymer. Examples of the pour point depressant include polymethacrylate and the like (eg, styrene-diene hydrogenated copolymer). Examples of rust preventives include alkenyl succinic acid and its partial esters, and examples of metal corrosion inhibitors include benzotriazole-based, benzimidazole-based, benzothiazole-based, and thiadiazole-based antifoaming agents. For example, dimethylpolysiloxane, polyacrylate, etc. are used, and as the surfactant, for example, polyoxyethylene alkylphenyl ether, etc. are used. INDUSTRIAL APPLICABILITY The lubricating oil composition for an internal combustion engine of the present invention is suitably used particularly for a gas engine that uses natural gas, liquefied petroleum gas (LPG) or the like as a fuel.

[0024]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Examples 1 to 4 and Comparative Examples 1 to 4 Lubricating oil compositions having the component compositions shown in Table 1 were prepared and their performances were evaluated according to the methods shown below. The results are shown in Table 1. <Performance Evaluation> (1) IP-ISOT (Induction Period-Lubricant Oxidation Stability Test for Internal Combustion Engine) It was carried out using the apparatus and test method described in Japanese Patent Application No. 6-63217. A 250 ml sample was placed in a container and kept at 175.0 ° C. together with a coiled copper / iron catalyst while blowing 3 liters / hour of oxygen. In this state, the oxidation lifetime (hr) of the sample is evaluated by the time until the sample temperature rises sharply. Other conditions are ISOT
(Lubricant oxidation stability test for internal combustion engine, JIS K-25
It is the same as 14). (2) TFOUT (Thin-film Oxygen
Uptake Test) A sample (1.5 g) was added under a pressure-filled oxygen atmosphere of 6.3 kg / cm ² to obtain 0.03 g of water, 0.06 g of metal catalyst, and 0.06 g of fuel catalyst.
And hold at 160 ° C. In this state, the oxidation life (min) of the sample is evaluated by the time until the enclosed oxygen pressure drops sharply. Other conditions are ASTM
Same as D-4742.

[0025]

[Table 1]

[0026]

[Table 2]

[Note] 1) Base oil: 100 N (100 neutral oil) and 150
Mixed oil with N, kinematic viscosity at 100 ° C. 5.1 mm ² / sec 2) Hindered phenol: 4,4′-methylenebis (2,6-di-t-butylphenol) 3) Dialkyldiphenylamine: 4,4′- Dioctyldiphenylamine 4) Naphthylamine derivative: Phenyl-α-naphthylamine 5) Phosphonate: 3,5-di-t-butyl-4
-Hydroxybenzylphosphonate diethyl 6) ester-1: dodecylsalicylic acid dodecylphenyl ester 7) ester-2: dodecylsalicylic acid ethylene glycol ester 8) metal-based detergent: Ca-based detergent, base number 250 mgK
OH / g 9) Ashless dispersant: Mixture of succinimide and boron-containing succinimide 10) ZnDTP: zinc dialkyldithiophosphate VII: olefin copolymer PPD: polymethacrylate 11) sulfur: olefin sulfide

[0028]

INDUSTRIAL APPLICABILITY The lubricating oil composition for an internal combustion engine of the present invention has a significantly improved oxidative deterioration life, and the oil-refreshing interval is extended by about 2 to 5 times as compared with normal gasoline engine oil or diesel engine oil. can do. Therefore, it is suitably used as an engine oil for a gas engine heat pump or a cogeneration system, which can reduce the maintenance due to the extension of the oil change interval.

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Claims (7)

[Claims] 1. A lubricating base oil comprising (A) at least one antioxidant selected from hindered phenols and amines, and (B) a substituted hydroxyaromatic carboxylic acid and a hydroxy compound. A lubricating oil composition for an internal combustion engine, comprising the obtained ester. 2. A combination of (A) at least one antioxidant selected from hindered phenol-based and amine-based antioxidants with a phosphonate-based antioxidant for a lubricating base oil, and (B) A lubricating oil composition for an internal combustion engine, which comprises an ester obtained from a substituted hydroxyaromatic carboxylic acid and a hydroxy compound. 3. The lubricating oil composition for an internal combustion engine according to claim 1, wherein the amine-based antioxidant is a dialkyldiphenylamine-based and / or naphthylamine-based antioxidant. 4. The lubricating oil composition for an internal combustion engine according to claim 1, wherein the component (B) is an ester obtained from a substituted hydroxyaromatic carboxylic acid and an alkyl-substituted aromatic alcohol. 5. The substituted hydroxyaromatic carboxylic acid in the component (B) has the general formula (I): [In the Formula, Ar is a polyvalent aromatic nucleus, R is an organic group, p is 1-3.
, N is an integer of 1 to 4, m is an integer of 1 to 3,
When there are a plurality of Rs, the plurality of Rs may be the same or different. ] The lubricating oil composition for internal combustion engines of Claim 1, 2 or 4 represented by these. 6. The blending amount of the component (A) and the component (B) is
Based on the total amount of the composition, 0.2 to 10% by weight and 0.1, respectively.
The lubricating oil composition for an internal combustion engine according to claim 1 or 2, which is 1 to 20% by weight. 7. The lubricating oil composition for an internal combustion engine according to claim 1, which is used in a gas engine.