JPH0524957B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field of the Invention) The present invention relates to a novel synthetic lubricating oil, and more particularly, a synthetic lubricating oil consisting of a monoalkylnaphthalene mixture having a specific structure, or having this as a main component.
This invention relates to a new synthetic lubricating oil with particularly excellent oxidation stability. (Background of the Invention) Lubricating oils are generally required to withstand long-term use. Therefore, highly refined mineral oil mixed with an appropriate antioxidant, if necessary, is usually used as a lubricating oil. However, mineral oil has a limited oxidation stability, and it is difficult to use it for a long period of time in an environment with severe temperature conditions.
Therefore, as lubricating oils with better oxidation stability, ester-based synthetic lubricating oils such as diesters and polyol esters, and hydrocarbon-based synthetic oils such as polyα-olefins and alkylbenzenes have been developed and are now widely used. However, although these conventionally known synthetic lubricating oils are said to have higher oxidation stability than mineral oils, their oxidation stability has not been satisfactory. As a result of repeated research aimed at developing synthetic lubricating oils with higher oxidation stability, the present inventors have discovered that synthetic lubricating oils whose main component is a monoalkylnaphthalene mixture with a specific structure are different from known synthetic lubricating oils. They found that it has significantly higher oxidation stability in comparison, and completed the present invention. (Objective of the Invention) The object of the present invention is to provide a synthetic lubricating oil having particularly excellent oxidation stability. (Structure of the Invention) The synthetic lubricating oil of the present invention is made from a monoalkylnaphthalene mixture having a secondary alkyl group having 6 to 24 carbon atoms and having an α-substituted/β-substituted molar ratio of 1.0 or more. It is characterized by the fact that it consists of this or that it consists of this as a main component. Hereinafter, the content of the present invention will be explained in more detail. The alkylnaphthalene mixture that constitutes or is the main component of the synthetic lubricating oil of the present invention is monoalkylnaphthalene, the number of carbon atoms in the alkyl group is 6 to 24, and the alkyl group is a secondary alkyl group. It is necessary that the following four points be satisfied: the molar ratio of α-substituted product/β-substituted product is 1.0 or more. The use of an alkylnaphthalene mixture that does not meet the requirements for any one of the above four points is undesirable because it has inferior oxidation stability and physical properties as a lubricating oil compared to the alkylnaphthalene mixture used in the present invention. . In the monoalkylnaphthalene mixture used in the present invention, the secondary alkyl group has 6 to 24 carbon atoms.
However, from the viewpoint of the physical properties of the lubricating oil to be obtained, a carbon number of 8 to 18 is more preferable. In addition, from the viewpoint of oxidative stability, the secondary alkyl group of the monoalkylnaphthalene mixture in the present invention is one in which both of the two alkyl groups bonded to the secondary carbon bonded to the naphthalene ring are linear chains. and the mixture has the general formula

[expression] and

[Formula] [In the formula, R ₁ , R ₂ , R ₃ and R ₄ are alkyl groups, and the total number of carbon atoms of R ₁ and R ₂ and the total number of carbon atoms of R ₃ and R ₄ are both 5 to 23. ] In the formula represented by the formula, it is preferable that R ₁ , R ₂ , R ₃ and R ₄ are each a straight-chain alkyl group. Preferred secondary alkyl groups of monoalkylnaphthalene include, for example, 1-methylheptyl group, 1-ethylhexyl group, 1-propylpentyl group, 1-methyloctyl group, 1-ethylheptyl group, and 1-ethylheptyl group. Propylhexyl group, 1-butylpentyl group, 1-methylnonyl group, 1-ethyloctyl group, 1-propylheptyl group, 1-butylhexyl group, 1-methyldecyl group, 1-ethylnonyl group, 1-propyloctyl group, 1 -butylheptyl group, 1-pentylhexyl group, 1-methylundecyl group, 1-ethyldecyl group, 1-propylnonyl group, 1-butyloctyl group, 1-pentylheptyl group, 1-methyldodecyl group, 1-
Ethylundecyl group, 1-propyldecyl group, 1
-butylnonyl group, 1-pentyloctyl group, 1
-hexylheptyl group, 1-methyltridecyl group, 1-ethyldodecyl group, 1-propylundecyl group, 1-butyldecyl group, 1-pentylnonyl group, 1-hexyloctyl group, 1-methyltetradecyl group, 1 -ethyltridecyl group, 1-propyldodecyl group, 1-butylundecyl group, 1-
pentyldecyl group, 1-hexylnonyl group, 1-
Heptyl octyl group, 1-methylpentadecyl group, 1-ethyltetradecyl group, 1-propyltridecyl group, 1-butyldodecyl group, 1-pentylundecyl group, 1-hexyldecyl group, 1-heptylnonyl group, 1 -methylhexadecyl group, 1
-Ethylpentadecyl group, 1-propyltetradecyl group, 1-butyltridecyl group, 1-pentyldodecyl group, 1-hexylundecyl group, 1-heptyldecyl group, 1-octylnonyl group, 1-methylheptadecyl group , 1-ethylhexadecyl group, 1-propylpentadecyl group, 1-butyltetradecyl group, 1-pentyltridecyl group, 1-
Examples include hexyldodecyl group, 1-heptylundecyl group, and 1-octyldecyl group. The monoalkylnaphthalene mixture in the present invention can be obtained by mixing various single monoalkylnaphthalenes. It can also usually be obtained in one step by a Friedel-Crafts alkylation reaction. Monoalkylnaphthalenes include α-substituted products in which an alkyl group is substituted at the α-position of the naphthalene ring, and β-substituted products in which the alkyl group is substituted at the β-position. It is important that the molar ratio of the substituent is 1.0 or more, preferably 1.0 to 2.0. If this molar ratio is less than 1.0, it is not preferable because the oxidation stability as a lubricating oil deteriorates. As mentioned above, when the alkylnaphthalene mixture used in the present invention is synthesized in one step by Friedel-Crafts alkylation reaction, primary or secondary alkyl halides having 6 to 24 carbon atoms, alcohols, or Use of a monoolefin having 6 to 24 carbon atoms, and the presence of metal halides such as aluminum chloride, zinc chloride, and iron chloride, and acidic catalysts such as sulfuric acid, phosphoric acid, phosphorus pentoxide, boron fluoride, acid clay, and activated clay. It can be obtained by reacting with naphthalene at a reaction temperature of 0 to 250°C. In general, as the alkyl source, monoolefins having 6 to 24 carbon atoms are preferred from the viewpoint of easy availability of raw materials, and linear monoolefins, particularly linear α-olefins, are more preferred. When naphthalene and the above-mentioned alkyl source are reacted in the presence of an acidic catalyst, carbon cations are usually transferred during the reaction. A mixture of alkylnaphthalenes is formed. The production ratio of the α-substituted product and the β-substituted product varies depending on the alkyl source used, the type of catalyst, reaction conditions such as reaction temperature and reaction time, etc., but the monoalkylnaphthalene mixture used in the present invention is When attempting to obtain it by reaction, this α-substituted product/β
- The molar ratio of the substituents produced must be 1.0 or more. The synthetic lubricating oil consisting of the monoalkylnaphthalene mixture according to the present invention or having it as a main component has excellent properties such as particularly good oxidation stability as well as the various properties required of ordinary lubricating oils even when used alone. , known lubricating oil additives commonly used in the synthetic lubricating oil of the present invention as necessary;
For example, antioxidants, detergent dispersants, viscosity index improvers, pour point depressants, oil agents, anti-wear agents, extreme pressure agents, corrosion inhibitors, metal deactivators, rust inhibitors,
Antifoaming agents, emulsifiers, demulsifiers, bactericidal agents, coloring agents, etc. may be added. For details on these various additives, please refer to
For example, it is described in "Journal of the Japan Society of Lubricating Oils, Volume 15, No. 6" or "Additives for Petroleum Products" edited by Toshio Sakurai (Saiwai Shobo). In addition, the synthetic lubricating oil of the present invention has a high oxidation rate. Within a range that does not impair stability, mineral oil or known synthetic lubricating oil may be mixed in an amount of 75% by weight or less, preferably 50% by weight or less, particularly preferably 25% by weight or less.According to the present invention Single monoalkylnaphthalene mixtures or synthetic lubricating oils containing monoalkylnaphthalene mixtures as a main component are, for example, gasoline engine oils, diesel engine oils, turbine oils, gear oils, hydraulic oils, compressor oils, metal processing oils, sliding guideway oils, and bearings. It can be used for oils, etc. (Examples of the Invention) The contents of the present invention will be explained in more detail with reference to Examples and Comparative Examples. Example 1 1-Decene of naphthalene was reacted using activated clay as a catalyst, and the following C ₁₀ − with the composition and properties shown in
A monoalkylnaphthalene mixture () was obtained (α
-substituted product/β-substituted product = 1.33 (molar ratio)). [Composition] α-(1-methylnonyl)naphthalene 19 mol%, α-(1-ethyloctyl)naphthalene
16 mol%, α-(1-propylheptyl)naphthalene
12 mol%, α-(1-butylhexyl)naphthalene
10 mol%, total amount of α-substituted substances: 57 mol%, β-(1-methylnonyl)naphthalene 12 mol%, β-(1-ethyloctyl)naphthalene
11 mol%, β-(1-propylheptyl)naphthalene
10 mol%, β-(1-butylhexyl)naphthalene
10 mol%, total amount of β-substituted products: 43 mol%, [Properties] Viscosity: 11.93 cSt, @40℃, Pour point: -45℃ or less, Boiling point: 160-170℃/1mmHg This C ₁₀ monoalkylnaphthalene mixture ()
In order to evaluate the oxidation stability of , a high temperature oxidation test was conducted under the following conditions using test equipment specified in IP-280. Test temperature: 170℃, oxygen flow rate: 3/hr, catalyst: copper wire 1mmφ x 80cm, oxidation stability evaluation
The oxidation test life was defined as the time when the value reached 1.0 mgKOH/g. The results are shown in Table 1. Example 2 A C ₈ -monoalkylnaphthalene mixture () having the composition and properties shown below was prepared in the same manner as in Example 1 except that 1-octene was used instead of 1-decene.
was obtained (α-substituted product/β-substituted product = 1.44 (molar ratio)). [Composition] α-(1-methylheptyl)naphthalene
29 mol%, α-(1-ethylhexyl)naphthalene
17 mol%, α-(1-propylpentyl)naphthalene
13 mol%, total amount of α-substituted substances: 59 mol%, β-(1-methylheptyl)naphthalene
17 mol%, β-(1-ethylhexyl)naphthalene
12 mol%, β-(1-propylpentyl)naphthalene
12 mol%, total amount of β-substituted substances: 41 mol%, [Properties] Viscosity: 10.54 cSt, @40°C, Pour point: -45°C or lower Boiling point: 140-150°C/1 mmHg This C ₈ -monoalkylnaphthalene mixture ()
The oxidation stability was evaluated in the same manner as in Example 1, and the results are shown in Table 1. Example 3 A C ₁₆ -monoalkylnaphthalene mixture () having the composition and properties shown below was obtained (α-substituted/ β-substituted = 1.63
(molar ratio)). [Composition] α-(1-methylpentadecyl)naphthalene
18 mol%, α-(1-ethyltetradecyl)naphthalene
10 mol%, α-(1-propyltridecyl)naphthalene
7 mol%, α-(1-butyldodecyl)naphthalene
5 mol%, α-(1-pentylundecyl) Naphthalene α-(1-hexyldecyl) Naphthalene α-(1-heptylnonyl) Naphthalene 22 mol%, Total amount of α-substituted substances: 62 mol%, β-(1 -methylpentadecyl)naphthalene
12 mol%, β-(1-ethyltetradecyl)naphthalene
7 mol%, β-(1-propyltridecyl)naphthalene
4 mol%, β-(1-butyldodecyl)naphthalene
4% mol, β-(1-pentylundecyl) Naphthalene β-(1-hexyldecyl) Naphthalene β-(1-heptylnonyl) Naphthalene 13 mol%, Total amount of β-substituted substances: 38% mol, [Properties] Viscosity: 27.03cSt, @40℃, Pour point: -45℃ or lower Boiling point: 214-224℃/1mmHg, This C ₁₆ -monoalkylnaphthalene mixture ()
The oxidation stability was evaluated in the same manner as in Example 1, and the results are shown in Table 1. Comparative Examples 1 to 4 1-decene oligomer with an average molecular weight of 500, which has been conventionally used as a synthetic lubricating oil (Comparative Example 1),
The oxidation stability of dioctyl sebacate (Comparative Example 2), pentaerythritol tetracapriate (Comparative Example 3) and diisopropylnaphthalene (Comparative Example 4) was evaluated in the same manner as in Example 1, and the results are shown in Table 1. It was shown to. Comparative Example 5 By changing the reaction conditions of Example 1, a C ₁₀ -monoalkylnaphthalene mixture () having the composition shown below was obtained (α-substituted product/β-substituted product =
0.61 (molar ratio)). The oxidation stability was evaluated in the same manner as in Example 1, and the results are shown in Table 1. [Composition] α-(1-methylnonyl)naphthalene 13 mol%, α-(1-ethyloctyl)naphthalene
11 mol%, α-(1-propylheptyl)naphthalene
8 mol%, α-(1-butylhexyl)naphthalene
6 mol%, total amount of α-substituted substances: 38 mol%, β-(1-methylnonyl)naphthalene 22 mol%, β-(1-ethyloctyl)naphthalene
16 mol%, β-(1-propylheptyl)naphthalene
10 mol%, β-(1-butylhexyl)naphthalene
14 mol%, total amount of β-substituted products: 62 mol%, Comparative Example 6 By changing the reaction conditions of Example 2, a C ₈ -monoalkylnaphthalene mixture () having the composition shown below was obtained (α- Substituted product/β-substituted product=
0.28 (molar ratio)). The oxidation stability was evaluated in the same manner as in Example 1, and the results are shown in Table 1. [Composition] α-(1-methylheptyl)naphthalene
10 mol%, α-(1-ethylhexyl)naphthalene
7 mol%, α-(1-propylpentyl)naphthalene
5 mol%, total amount of α-substituted substances: 22 mol%, β-(1-methylheptyl)naphthalene
42 mol%, β-(1-ethylhexyl)naphthalene
20 mol%, β-(1-propylpentyl)naphthalene
16 mol%, total amount of β-substituted substances: 78 mol%,

[Table] As is clear from the oxidation test life results in Table 1, the synthetic lubricating oil comprising the monoalkylnaphthalene mixture according to the present invention exhibits very high high temperature oxidation stability. On the other hand, compounds such as poly-α-olefins, diesters, polyesters, and alkylnaphthalenes, which are conventionally said to have excellent oxidation stability, have significantly inferior oxidation test lives to those of the present invention.Also, even monoalkylnaphthalene mixtures It can be seen that when the molar ratio of α-substituted product/β-substituted product is less than 1.0, the results of the oxidation test life are inferior to those of the monoalkylnaphthalene mixture used in the present invention.

Claims (1)

[Scope of Claims] 1 Consists of a monoalkylnaphthalene mixture having a secondary alkyl group having 6 to 24 carbon atoms and having an α-substituted product/β-substituted product molar ratio of 1.0 or more, or Synthetic lubricating oil characterized by its main component. 2. The synthetic lubricating oil according to claim 1, wherein the monoalkylnaphthalene mixture has an α-substituted/β-substituted molar ratio of 1.0 to 2.0.