JPH0222799B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a synthetic lubricating oil composition, and more particularly to a synthetic lubricating oil composition with particularly excellent oxidation stability obtained by adding specific amounts of a specific alkylphenol and a nitrogen-containing compound as essential components to an alkylnaphthalene. Lubricating oils that are used in circulation are generally required to withstand long-term use. For this reason, mineral oil-based lubricating oils are usually used, which are highly refined mineral oils mixed with appropriate antioxidants, but mineral oil-based lubricating oils have limited oxidation stability and are subject to temperature conditions in the lubricated parts. Difficult to use in harsh equipment for long periods of time. Therefore, ester-based synthetic lubricating oils such as diesters and polyol esters have been developed as lubricating oils with better oxidation stability, have been commercialized, and are currently in general use. however,
Although these ester-based synthetic lubricating oils have high oxidation stability, they hydrolyze to produce acids.
The actual situation is that the range of use of sealing materials is limited because they have essential drawbacks such as swelling and high cost. Hydrogenated poly-α-olefins are also widely known as highly oxidatively stable synthetic lubricating oils, but although their oxidative stability is superior to mineral oils, it is not as good as ester-based synthetic lubricating oils. As described above, conventionally known lubricating oil compositions, even synthetic lubricating oil compositions that are said to have higher oxidative stability than mineral oils, have unsatisfactory oxidative stability and also have various drawbacks. It was hot. On the other hand, among hydrocarbons, it has long been known that naphthalene derivatives have high oxidation stability (R, G, Larsen et al., IEC, 34 , 2,
183 (1942)), and it is also known that blending α-methylnaphthalene with mineral oil improves its oxidative stability (Fuchs, IEC, 34 , 8, 927).
(1942)). Therefore, the present inventors focused on the fact that naphthalene derivatives have excellent oxidative stability, searched for naphthalene derivatives suitable for lubricating oil base oil, and created synthetic lubricating oil compositions with high oxidative stability. As a result of numerous studies on combinations of various additives, we have found that by using a specific alkylnaphthalene as a base oil and adding specific amounts of specific alkylphenols and nitrogen-containing compounds as essential components, we have created a high-grade lubricant. Has all the properties necessary for oil,
Furthermore, the present inventors have discovered that a synthetic lubricating oil composition can be obtained that has high oxidation stability that cannot be achieved with conventionally known lubricating oil compositions, leading to the completion of the present invention. An object of the present invention is to provide a synthetic lubricating oil composition that has all the physical properties required for a high-grade lubricating oil (hue, specific gravity, viscosity, flash point) and has particularly excellent oxidation stability. That is, the present invention provides the following methods: [General] formula

[expression] or

0.03 to 3.0 parts by weight of one or more alkylphenols represented by the formula [In the above formula, R ₁ is an alkyl group having 1 to 4 carbon atoms or a cycloalkyl group having 5 to 7 carbon atoms, and R ₂ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms and n
represents an integer from 1 to 4, respectively. Moreover, X is a monovalent to tetravalent group shown below. When n=1: an alkyl group, alkoxy group or hydroxyalkyl group having 1 to 4 carbon atoms, an aryl group or aralkyl group having 6 to 8 carbon atoms, or a group represented by the following general formula. −(CH ₂ −) _a COOR ₃ ,

【formula】 or

[Formula] (In the above formula, a, b and c are integers of 0 to 3,
R ₃ , R ₄ and R ₅ are the same or different carbon atoms of 10 or more
22 alkyl groups and R ₆ and R ₇ each represent the same or different alkyl groups having 1 to 4 carbon atoms. ) When n=2: C1-C4 alkylene group or alkylalkylene group, thio group (-S-)
or a dithio group (-S-S-). When n=3: a saturated aliphatic hydrocarbon group having 3 to 5 carbon atoms, an aromatic hydrocarbon group having 6 to 12 carbon atoms, or a general formula

A group represented by [Formula]. (In the above formula, d is an integer from 0 to 3, and e is an integer from 0 to 4.
indicates an integer. ) When n=4: General formula ((-CH ₂ )- _f COOCH ₂ ) ₄ C
or

A group represented by [Formula]. (In the above formula, f and g represent integers of 0 to 3.)] and [] 0.03 to 3.0 parts by weight of one or more nitrogen-containing compounds selected from the following groups (1) Benzotriazole (2) General formula

Compound represented by [Formula] [In the above formula, R ₈ and R ₉ are the same or different alkyl groups having 4 to 18 carbon atoms, and Y is

【formula】

[Formula] Also teeth

[Formula] is shown respectively. ] The present invention provides a synthetic lubricating oil composition characterized in that it contains the following as an essential component. Hereinafter, the content of the present invention will be explained in more detail. In the synthetic lubricating oil composition of the present invention, the alkylnaphthalene used as the base oil has 1 as a side chain.
It refers to an alkylnaphthalene having ~2 straight chain alkyl groups and a total number of carbon atoms in the side chain alkyl groups ranging from 12 to 36, or a mixture thereof. In addition, the alkylnaphthalene as used in the present invention includes not only an alkylated product of naphthalene but also an alkylated product of methylnaphthalene. The structure and composition of the side chain alkyl groups of alkylnaphthalenes have a great influence on the properties of the final lubricating oil composition. In the present invention, the side chain alkyl group must be linear and have a total number of carbon atoms of 12 to 36, preferably 12 to 32.
Alkylnaphthalenes in which the side chain alkyl group is branched are not preferred because the viscosity index of the lubricating oil composition becomes low. Also, the total number of carbon atoms in the side chain alkyl group is
Alkylnaphthalenes with a total carbon number of less than 12 will lower the flash point of the lubricating oil composition, while alkylnaphthalenes with a total carbon number of more than 36 will increase the pour point of the lubricating oil composition and worsen low-temperature fluidity, so these are preferred. do not have. Particularly preferred base oils for the lubricating oil composition of the present invention are monoalkylnaphthalenes/monoalkylmethylnaphthalenes having one linear alkyl group having 12 to 20 carbon atoms as a side chain;
Dialkylnaphthalene/dialkylmethylnaphthalene having two 16 straight-chain alkyl groups as side chains or a mixture thereof. Although the method for synthesizing the alkylnaphthalene referred to in the present invention is arbitrary, it is generally synthesized by alkylating naphthalene and/or methylnaphthalene with an alkylating agent. As the alkylating agent, linear α-olefins obtained by low polymerization of ethylene, thermal cracking or catalytic cracking of heavy oils and petroleum fractions can be used. Alkylation catalysts include Friedel-Crafts catalysts such as aluminum chloride, zinc chloride, iron chloride, sulfuric acid, phosphoric acid, phosphorus pentoxide,
Known catalysts such as acidic catalysts such as hydrofluoric acid, acid clay, and activated clay are used. Alkylated naphthalene can also be synthesized by separating n-paraffin from petroleum fractions such as kerosene and gas oil, and using chlorinated paraffin, which is obtained by chlorinating this as an alkylating agent. However, since it is possible to obtain an alkylnaphthalene in which the side chain alkyl group has a single carbon number or a narrow carbon number distribution, and the resulting alkylnaphthalene has an excellent hue, it is difficult to use the linear α- Alkylnaphthalenes using olefins are preferred. For example, when using monoalkylnaphthalene as the base oil of a lubricating oil composition, carbon atoms of 12 to 36,
It is desirable to use monoalkylnaphthalenes synthesized using preferably 12 to 32, particularly preferably 12 to 20, linear α-olefins as alkylating agents. On the other hand, when dialkylnaphthalene is used, it is desirable to use a dialkylnaphthalene synthesized using a linear α-olefin having 6 to 18 carbon atoms, preferably 6 to 16 carbon atoms, and particularly preferably 6 to 12 carbon atoms as an alkylating agent. . Also, straight chain α- with 2 to 36 carbon atoms
Selected from olefins and with a total carbon number of 12
Dialkylnaphthalenes synthesized using a mixture of two types of linear α-olefins of ˜38 as an alkylating agent can also be used. However, in that case, it is necessary to separate dialkylnaphthalenes whose side chain alkyl groups have a total number of carbon atoms of 12 to 38 from the reaction product mixture by any method. On the other hand, the component [] in the present invention refers to the general formula

[expression] or

One or more alkylphenols represented by the formula: In the formula, R ₁ is 1 to
4 alkyl group or a cycloalkyl group having 5 to 7 carbon atoms, specifically, for example, methyl group, ethyl group, propyl group, butyl group, cyclopentyl group, cyclohexyl group, methylcyclopentyl group, cycloheptyl group, methylcyclohexyl group. group, ethylcyclopentyl group, etc., but a butyl group, particularly a t-butyl group, and a cyclohexyl group are preferred. R ₂ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and specific examples thereof include a hydrogen atom, a methyl group, an ethyl group, a propyl group, a butyl group, and the like. n is 1 to 4, preferably 2
It is an integer of ~4. Moreover, X is selected from the following monovalent to tetravalent groups depending on the value of n. That is, when n= ₁ ,
−) _a COOR ₃ ,

[Formula] or

[Formula] (where a, b and c are integers of 0 to 3, preferably 1 to 2, R ₃ , R ₄ and R ₅ are the same or different carbon atoms of 10 to 22, preferably 14 to 20) Alkyl groups and R ₆ and R ₇
represent the same or different alkyl groups having 1 to 4 carbon atoms, respectively. As R ₃ , R ₄ and R ₅ ,
Specific examples include a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, and an eicosyl group. Furthermore, examples of R ₆ and R ₇ include a methyl group, an ethyl group, a propyl group, a butyl group, and the like. )
It is a monovalent organic group represented by When n=1, specific examples of X include methyl group, ethyl group, propyl group, butyl group, methoxy group, ethoxy group, propoxy group, butoxy group, hydroxymethyl group, hydroxyethyl group, hydroxypropyl group. , hydroxybutyl group, phenyl group, tolyl group, xylyl group, benzyl group, methylbenzyl group, phenethyl group, -CH ₂ COOC ₁₄ H ₂₉ , -
CH ₂ COOC ₁₆ H ₃₃ , −CH ₂ COOC ₁₈ H ₃₇ , −
CH ₂ COOC ₂₀ H ₄₁ , −CH ₂ CH ₂ COOC ₁₄ H ₂₉ , −
CH ₂ CH ₂ COOC ₁₆ H ₃₃ , −CH ₂ CH ₂ COOC ₁₈ H ₃₇ , −
CH ₂ CH ₂ COOC ₂₀ H ₄₁ ,

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

Examples include [Formula]. When n=2, X is an alkylene group having 1 to 4 carbon atoms, an alkylalkylene group, a thio group (-S
-) or a dithio group (-S-S-). Specifically, for example, methylene group, ethylene group, methylmethylene group, trimethylene group, propylene group (methylethylene group), dimethylmethylene group, tetramethylene group, propylmethylene group, ethylmethylmethylene group, dimethylethylene group, ethylethylene group. group, methyltrimethylene group, etc. When n=3, X is a trivalent saturated aliphatic hydrocarbon group having 3 to 5 carbon atoms, 6 to 12 carbon atoms, preferably 6
~9 trivalent aromatic hydrocarbon group or general formula

A group represented by the formula (where d is 0 to 3, preferably 2 to 3)
and c is an integer of 0 to 4, preferably 1 to 3
). Specifically, for example
CHCH ₂ CH ₂ −,

【formula】

【formula】

【formula】

【formula】

【formula】

[Formula] CHCH ₂ CH ₂ CH ₂ −, (− CH ₂ ) ₃ CH,

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

[Formula] (CH ₂ ) ₃ CCH ₃ ,

【formula】

【formula】

【formula】

[Formula] CHCH ₂ CH ₂ CH ₂ CH ₂ −,

【formula】

【formula】

【formula】

【formula】 【formula】

Examples include. When n=4, X has the general formula ((-CH ₂ )- _f
COOCH ₂ ) _4C or

It is a tetravalent organic group represented by the formula (where f and g are integers of 0 to 3, preferably 1 to 2). Specifically, for example, (CH ₂ COOCH ₂ ) ₄ C, (−
CH ₂ CH ₂ COOCH ₂ ) ₄ C,

【formula】

Examples include [Formula]. Particularly preferable compounds as the alkylphenol [ ] in the present invention include, for example, the following compounds or mixtures thereof.・When n=1 2-t-butyl-4-methylphenol, 2-
t-Butyl-4-methoxyphenol, 2,6-
Di-t-butyl-4-methylphenol, 2,6
-di-t-butyl-4-ethylphenol, 2,
6-di-t-butyl-4-hydroxymethylphenol, 2-t-butyl-4-methyl-6-phenethylphenol, n-octadecyl-3-
(4'-hydroxy-3',5'-di-t-butylphenyl)propionate, di-n-octadecyl (4'-hydroxy-3'-methyl-5'-t-butylbenzyl)malonate, 3,5- di-t-butyl-
4-Hydroxybenzyl phosphate diethyl ester.・When n=2 2,2'-methylenebis(4-methyl-6-t-
butylphenol), 2,2'-methylenebis(4
-ethyl-6-t-butylphenol), 4,
4'-methylenebis(2,6-di-t-butylphenol), 2,2'-methylenebis(4-methyl-
6-cyclohexylphenol), 1,1-bis(2'-methyl-4'-hydroxy-5'-t-butylphenyl)butane, 4,4'-thiobis(3-methyl-6-t-butylphenol), 2,2'-thiobis(4-methyl-6-t-butylphenol) ・When n=3 1,1,3-tris(2'-methyl-4'-hydroxy-5'-t-butyl)butane , 1,3,5-trimethyl-2,4,6-tris(3',5'-di-t
-butyl-4'-hydroxybenzyl)benzene,
1,3,5-trimethyl-2,4,6-tris[methylene-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]benzene, when n=4 Tetrakis[methylene -3-(3',5'-ji-t
-butyl-4'-hydroxyphenyl)propionate] methane, bis[3,3'-bis(4'-hydroxy-3'-t-butylphenyl)butanoic acid] ethylene glycol ester. is (1) benzotriazole or (2) general formula

【formula】

[Formula] or

A compound represented by [Formula] (wherein R ₈ and R ₉ are the same or different carbon atoms 4
~18 preferably represents an alkyl group of 4 to 12. ) is one or more nitrogen-containing compounds selected from the following. Specific examples of the alkyl group for R ₈ and R ₉ include butyl group, pentyl group, hexyl group, heptyl group, octyl group, 2-ethylhexyl group, nonyl group, decyl group, dodecyl group, tetradecyl group, hexadecyl group. group, octadecyl group, etc. Particularly preferable compounds as the nitrogen-containing compound [ ] in the present invention include, for example, benzotriazole 1-[bis(n-butyl)aminomethyl]benzotriazole, 1-[bis(n-butyl)aminomethyl]benzotriazole, 1-[bis(n-butyl)aminomethyl]benzotriazole,
-hexyl)aminomethyl]benzotriazole, 1-[bis(n-octyl)aminomethyl]
Benzotriazole, 1-[bis(2-ethylhexyl)aminomethyl]benzotriazole, 1
-[Bis(2-ethylhexyl)aminomethyl]
Methylbenzotriazole, 1-[bis(n-decyl)aminomethyl]benzotriazole, 1-
[bis(n-dodecyl]aminomethyl]benzotriazole, 7-[bis(n-butyl)aminomethyl]-8-hydroxyquinoline, 7-[bis(n-butyl)aminomethyl]-8-hydroxyquinoline, 7-[bis(n-butyl)aminomethyl]-8-hydroxyquinoline,
-hexyl)aminomethyl]-8-hydroxyquinoline, 7-[bis(n-octyl)aminomethyl]-8-hydroxyquinoline, 7-[bis(2-
ethylhexyl)aminomethyl]-8-hydroxyquinoline, 7-[bis(n-decyl)aminomethyl]-8-hydroxyquinoline, 7-[bis(n
-dodecyl)aminomethyl]-8-hydroxyquinoline, 1-[bis(n-butyl)aminomethyl]
Tetrazole, 1-[bis(n-hexyl)aminomethyl]tetrazole, 1-[bis(n-octyl)aminomethyl]tetrazole, 1-[bis(2-ethylhexyl)aminomethyl]tetrazole, 1-[bis(n-octyl)aminomethyl]tetrazole, 1-[bis(n-octyl)aminomethyl]tetrazole, -decyl)aminomethyl]
Examples include tetrazole, 1-[bis(n-dodecyl)aminomethyl]tetrazole, and mixtures thereof. In the synthetic lubricating oil composition of the present invention, the amount of the alkylphenol added is 0.01 to 3.0 parts by weight based on 100 parts by weight of the alkylnaphthalene in the base oil.
parts by weight, preferably 0.03 to 1.5 parts by weight. If the amount added does not reach the above range, the effect of addition will be low and high oxidation stability will not be obtained, which is not preferable. If the amount added exceeds the above range, the effect commensurate with the amount added will not be observed, and it will be economically disadvantageous. On the other hand, the amount of the nitrogen-containing compound added is as follows:
The amount is 0.01 to 3.0 parts by weight, preferably 0.03 to 0.5 parts by weight. If the amount added does not reach the above range, the effect of addition is low and oxidation stability cannot be improved, which is not preferable. If the amount added exceeds the above range, the effect commensurate with the amount added will not be observed and more sludge will be generated, which is not preferable. In the synthetic lubricating oil composition of the present invention, if necessary, further commonly used known lubricating oil additives, such as other antioxidants, detergent dispersants, viscosity index improvers, pour point depressants, Oil-based agents, anti-wear agents, extreme pressure agents, corrosion inhibitors, metal deactivators, rust inhibitors, antifoaming agents, emulsifiers, demulsifiers, bactericides, coloring agents, and the like may be added. Details of these various additives are described in, for example, the Journal of the Japan Society of Lubrication, Vol. 15, No. 6, or ``Petroleum Product Additives'' by Toshio Sakurai (Saiwai Shobo). The synthetic lubricating oil composition of the present invention can be used for lubricating oils that require oxidation stability, such as gasoline engine oil, diesel engine oil, turbine oil, gear oil, hydraulic oil, compressor oil, metal working oil, and slideway oil. , can be used as bearing oil, etc. The synthetic lubricating oil composition of the present invention employs an alkylnaphthalene having a specific structure and excellent oxidation stability as a base oil, and further adds an alkylphenol having a specific structure and a nitrogen-containing compound in combination. , it was possible to obtain high oxidation stability that could not be achieved with other conventionally known lubricating oil compositions. The use of base oils other than alkylnaphthalenes, the sole addition of alkylphenols or nitrogen-containing compounds, or the combination of other additives cannot achieve the level of oxidative stability of the synthetic lubricating oil compositions of the present invention. Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples unless the gist thereof is changed. Example 1 0.1 part by weight of 2,6-di-t-butyl-4-methylphenol and 0.05 part by weight of benzotriazole were added to 100 parts by weight of eicosylnaphthalene,
A synthetic lubricating oil composition was obtained. For this composition,
A high-temperature oxidation test was conducted under the following conditions using test equipment specified in IP-280, and the oxidation stability was evaluated. Test temperature: 170°C Oxygen flow rate: 3/hr Catalyst: Copper wire 1 mmφ x 80 cm The oxidation stability evaluation is based on the acid value of the sample oil.
The oxidation test life was defined as the time when the value reached 1.0 mgKOH/g. The results are shown in Table 1. Examples 2 to 10, Comparative Examples 1 and 2 Synthetic lubricating oil compositions were obtained by adding alkylphenols and nitrogen-containing compounds in the amounts shown in Table 1 to the alkylnaphthalenes shown in Table 1. This composition was subjected to the same high temperature oxidation test as in Example 1, and the results are shown in Table 1. For comparison, a synthetic lubricating oil composition was obtained using a synthetic base oil other than alkylnaphthalene and an additive other than the alkylphenol nitrogen-containing compound. This composition was also subjected to the same high temperature oxidation test as in Example 1, and the results are also listed in Table 1.

【table】

[Table] As is clear from the oxidation test life results in Table 1, the synthetic lubricating oil compositions of Examples 1 to 10 according to the present invention exhibit extremely high high temperature oxidation stability.
On the other hand, the compositions of Comparative Examples 1 and 2, in which an antioxidant was added to a polyol ester, which is conventionally said to have excellent oxidation stability, had significantly inferior oxidation test life to the composition of the present invention. As described above, the synthetic lubricating oil composition of the present invention has high oxidation stability that cannot be achieved by other conventionally known lubricating oil compositions.

Claims (1)

[Scope of Claims] 1. has 1 to 2 linear alkyl groups as side chains, and the total number of carbon atoms in the side chain alkyl groups is 12 to 36
[] 0.01 to 3.0 parts by weight of one or more types of alkylphenol represented by the general formula [Formula] or [Formula] [In the above formula, R ₁ is an alkyl group or a cycloalkyl group having 5 to 7 carbon atoms, R ₂ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n
represents an integer from 1 to 4, respectively. Moreover, X is a monovalent to tetravalent group shown below. When n=1: an alkyl group, alkoxy group or hydroxyalkyl group having 1 to 4 carbon atoms, an aryl group or aralkyl group having 6 to 8 carbon atoms, or a group represented by the following general formula -(CH ₂ -) aCOOR ₃ , [Formula] or [Formula] (In the above formula, a, b and c are integers of 0 to 3,
R ₃ , R ₄ and R ₅ are the same or different carbon atoms of 10 or more
22 alkyl groups and R ₆ and R ₇ each represent the same or different alkyl groups having 1 to 4 carbon atoms. ) When n=2: C1-C4 alkylene group or alkylalkylene group, thio group (-S-)
or a dithio group (-S-S-). When n=3: a saturated aliphatic hydrocarbon group having 3 to 5 carbon atoms, an aromatic hydrocarbon group having 6 to 12 carbon atoms, or a group represented by the general formula [Formula]. (In the above formula, d is an integer from 0 to 3, and e is an integer from 0 to 4.
indicates an integer. ) When n=4: General formula ((-CH ₂ )- _f COOCH ₂ ) ₄ C
Or a group represented by [Formula]. (In the above formula, f and g represent integers of 0 to 3.)] and [] 0.01 to 3.0 parts by weight of one or more nitrogen-containing compounds selected from the following group (1) Benzotriazole (2) General formula Compound represented by [Formula] [In the above formula, R ₈ and R ₉ are the same or different alkyl groups having 4 to 18 carbon atoms, and Y represents [Formula] [Formula] or [Formula], respectively. ] A synthetic lubricating oil composition characterized in that it contains the following as an essential component.