WO2017115704A1

WO2017115704A1 - Lubricating oil composition

Info

Publication number: WO2017115704A1
Application number: PCT/JP2016/088165
Authority: WO
Inventors: 八木下　和宏; 吉田　俊男
Original assignee: Ｊｘエネルギー株式会社
Priority date: 2015-12-28
Filing date: 2016-12-21
Publication date: 2017-07-06
Also published as: JP2017119789A; JP6480324B2

Abstract

The present invention provides a lubricating oil composition that contains a lubricating oil base oil, an aromatic amine antioxidant, and a cobalt carboxylate.

Description

Lubricating oil composition

The present invention relates to a lubricating oil composition.

Lubricating oil is used in various applications such as engine oil, drive system lubricating oil, turbine oil, hydraulic fluid, and grease. Lubricating oils are required to be resistant to oxidation (antioxidant properties).

Examples of antioxidants include aromatic amines, phenol compounds, zinc dialkyldithiophosphates, molybdenum compounds, etc. (see Patent Documents 1 and 2 below).

Special table 2008-514780 gazette JP-A-8-209168

However, according to the study by the present inventors, it has been found that it is difficult to maintain sufficient antioxidant properties for a long time when an aromatic amine or a phenol compound is used.

On the other hand, when zinc dialkyldithiophosphate or a molybdenum compound is used, sludge is likely to be generated.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a lubricating oil composition capable of maintaining sufficient antioxidant properties for a long time and suppressing the generation of sludge. And

In order to solve the above problems, the present invention provides a lubricating oil composition comprising a lubricating base oil, an aromatic amine-based antioxidant, and cobalt carboxylate.

In the lubricating oil composition, the sulfur content is preferably 100 ppm by mass or less in terms of sulfur atom based on the total amount of the lubricating oil composition.

According to the present invention, it is possible to provide a lubricating oil composition capable of maintaining sufficient antioxidant properties for a long time and suppressing the generation of sludge.

Hereinafter, preferred embodiments of the present invention will be described in detail.

The lubricating oil composition according to the embodiment of the present invention contains a lubricating base oil, an aromatic amine-based antioxidant, and cobalt carboxylate.

Lubricating oil base oil is not particularly limited, and those used for ordinary lubricating oil can be used. Examples thereof include mineral oil base oils, synthetic oil base oils, and mixed oils thereof.

Specifically, as the mineral base oil, the lube oil fraction obtained by distilling the atmospheric residue obtained by atmospheric distillation of the crude oil is subjected to solvent removal, solvent extraction, and hydrogenation. Examples include those refined by one or more treatments such as decomposition, solvent dewaxing, hydrorefining, etc., or base oils produced by a method of isomerizing wax isomerized mineral oil or GTL wax (gas to liquid wax). It is done. It is preferable to use highly refined base oil from the viewpoint of maintaining sufficient antioxidant properties for a long period of time, and also from the viewpoint of suppressing sludge formation.

Specific examples of synthetic oils include polybutene or hydrides thereof; poly-α-olefins such as 1-octene oligomers and 1-decene oligomers or hydrides thereof; ditridecyl glutarate, di-2-ethylhexyl. Diesters such as adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate; polyol esters such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate An aromatic synthetic oil such as alkylnaphthalene or alkylbenzene, or a mixture thereof.

The kinematic viscosity and viscosity index of the lubricating base oil are not particularly limited. For example, the kinematic viscosity at 40 ° C. of the lubricating base oil can be 5 to 500 mm ² / s, 20 to 100 mm ² / s, or 30 to 60 mm ² / s. The kinematic viscosity of the lubricating base oil at 100 ° C. can be 2 to 30 mm ² / s, 4 to 20 mm ² / s, or 6 to 10 mm ² / s. Further, the viscosity index of the lubricating base oil can be 90 or more, 105 or more, or 120 or more.

In the present invention, “kinematic viscosity at 40 ° C.”, “kinematic viscosity at 100 ° C.” and “viscosity index” mean values measured according to JIS K2283: 2000, respectively.

The total aromatic content of the lubricating base oil is not particularly limited, but is preferably 20% by mass or less, more preferably 10% by mass or less, and still more preferably 1% by mass or less. When the total aromatic content of the lubricating base oil is 5% by mass or less, the antioxidant properties of the lubricating oil composition tend to be further improved.

The “total aromatic content” as used in the present invention means an aromatic fraction content measured in accordance with ASTM D2549. This aromatic fraction includes alkylbenzene, alkylnaphthalene, anthracene, phenanthrene, and alkylated products thereof, compounds in which four or more benzene rings are condensed, or heterogeneous compounds such as pyridines, quinolines, phenols, and naphthols. An aromatic compound or the like may be included.

Examples of the aromatic amine antioxidant include alkylated diphenylamine and phenyl-α-naphthylamine.

Examples of the alkylated diphenylamine include compounds represented by the following general formula (1).

[In the formula (1), R ¹ and R ² each represent hydrogen or an alkyl group, at least one of R ¹ and R ² is an alkyl group, and when both R ¹ and R ² are alkyl groups, ¹ and R ² may be the same or different. ]

Specific examples of the alkyl group represented by R ¹ and R ² include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and undecyl. Group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group and the like (these alkyl groups may be linear or branched). Among these, a branched alkyl group having 3 to 16 carbon atoms is preferable from the viewpoint of maintaining antioxidant properties for a long period of time, and a branched chain having 3 to 16 carbon atoms derived from an olefin having 3 or 4 carbon atoms or an oligomer thereof. An alkyl group is more preferred. Specific examples of the olefin having 3 or 4 carbon atoms include propylene, 1-butene, 2-butene, and isobutylene. From the viewpoint that the antioxidant property at a high temperature can be maintained for a longer period, propylene or isobutylene is used. preferable. In addition, since superior antioxidant properties can be obtained, isopropyl group derived from propylene, tert-butyl group derived from isobutylene, branched hexyl group derived from propylene dimer, and dimer of isobutylene Branched octyl group derived from the body, branched nonyl group derived from the trimer of propylene, branched dodecyl group derived from the trimer of isobutylene, branched dodecyl derived from the tetramer of propylene Even more preferred are branched pentadecyl groups derived from a propylene or propylene pentamer, tert-butyl groups derived from isobutylene, branched hexyl groups derived from propylene dimer, isobutylene dimer Derived from branched octyl group derived, branched nonyl group derived from propylene trimer, isobutylene trimer A branched dodecyl group derived from a tetramer of a branched dodecyl or propylene are most preferred.

R ¹ and R ^{2 in} general formula (1) are preferably both alkyl groups. A compound in which both R ¹ and R ² are alkyl groups tends to be less likely to generate sludge due to oxidation of the compound itself as compared to a compound in which ^one of R ¹ and R ² is a hydrogen atom.

As the alkylated diphenylamine represented by the general formula (1), a commercially available product may be used, or a synthetic product may be used. The synthesized product uses a Friedel-Crafts catalyst and reacts diphenylamine with an alkyl halide having 1 to 16 carbon atoms and diphenylamine, or diphenylamine and an olefin having 2 to 16 carbon atoms or an olefin having 2 to 16 carbon atoms, or these It can be easily synthesized by reacting with the above oligomer. Specific examples of Friedel-Crafts catalysts include metal halides such as aluminum chloride, zinc chloride, and iron chloride; acidic catalysts such as sulfuric acid, phosphoric acid, phosphorus pentoxide, boron fluoride, acidic clay, and activated clay. Etc. can be used.

Examples of phenyl-α-naphthylamine include compounds represented by the following general formula (2).

[In the formula (2), R ³ represents hydrogen or an alkyl group. ]

The alkyl group represented by R ³ preferably has 16 or less carbon atoms from the viewpoint of antioxidant properties. When the carbon number of R ³ is 16 or less, the proportion of the functional group in the molecule increases, and the antioxidant property tends to be excellent. Specifically, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, And hexadecyl group. These alkyl groups may be linear or branched.
Among these, branched alkyl groups having 8 to 16 carbon atoms are preferable because of their excellent solubility in base oils, and branched alkyl groups having 8 to 16 carbon atoms derived from oligomers of olefins having 3 or 4 carbon atoms. Groups are more preferred. Specific examples of the olefin having 3 or 4 carbon atoms include propylene, 1-butene, 2-butene and isobutylene. Of these, propylene or isobutylene is more preferable because of its superior solubility in base oils. R ³ is derived from a branched octyl group derived from an isobutylene dimer, a branched nonyl group derived from a propylene trimer, and an isobutylene trimer because of its superior solubility in base oils. Even more preferred are branched dodecyl groups, branched dodecyl groups derived from propylene tetramers or branched pentadecyl groups derived from propylene pentamers, and branched derived from isobutylene dimers. An octyl group, a branched dodecyl group derived from a trimer of isobutylene, or a branched dodecyl group derived from a tetramer of propylene is particularly preferred.

In addition, when R ³ is an alkyl group, it can be bonded to any position of the phenyl group and may be p-position to the amino group. Furthermore, the amino group can be bonded to any position of the naphthyl group and may be in the α position.

As the phenyl-α-naphthylamine represented by the general formula (2), a commercially available product or a synthetic product may be used. The synthesized product is a reaction between phenyl-α-naphthylamine and an alkyl halide having 1 to 16 carbon atoms, or phenyl-α-naphthylamine and an olefin or carbon number having 2 to 16 carbon atoms using Friedel-Crafts catalyst. It can be easily synthesized by reacting with 2 to 16 olefin oligomers. Specific examples of Friedel-Crafts catalysts include metal halides and acidic catalysts listed in the synthesis of alkylated diphenylamine.

The aromatic amine antioxidants represented by the general formulas (1) and (2) may be used singly or in a mixture of two or more having different structures. From the viewpoint of antioxidant properties at high temperatures, it is preferable to use an alkylated diphenylamine represented by the general formula (1) and a phenyl-α-naphthylamine represented by the general formula (2) in combination. In this case, the mixing ratio of the two is arbitrary, but the mass ratio can be in the range of 1/10 to 10/1, 1/5 to 5/1, or 1/2 to 2/1.

The content of the aromatic amine antioxidant is not particularly limited, but from the viewpoint of antioxidant properties, it is preferably 0.05% by mass or more, more preferably 0.3% by mass, based on the total amount of the lubricating oil composition. % Or more, more preferably 0.5 mass% or more. Further, the content of the aromatic amine-based antioxidant is preferably 5% by mass or less, more preferably 3% by mass or less, and still more preferably 1 on the basis of the total amount of the lubricating oil composition from the viewpoint of suppressing sludge formation. It is below mass%.

Examples of the carboxylic acid constituting the cobalt carboxylate include aliphatic carboxylic acid, alicyclic carboxylic acid and aromatic carboxylic acid. These carboxylic acids may be unsubstituted or may have a substituent.

Aliphatic carboxylic acids include hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid (palmitic acid), heptadecanoic acid, octadecanoic acid ( Stearic acid) and oleic acid.

In this embodiment, cobalt carboxylate may be used alone, or a mixture of two or more different structures may be used.

Although the lubricating oil composition according to the present embodiment contains the above-described cobalt carboxylate, from the viewpoint of maintaining antioxidant properties for a long period of time, the cobalt content is based on the total amount of the lubricating oil composition. It is preferably more than 0 mass ppm and not more than 300 mass ppm, more preferably not less than 10 mass ppm and not more than 200 mass ppm, and still more preferably not less than 20 mass ppm and not more than 150 mass ppm in terms of cobalt atom. Further, the content of cobalt is preferably 300 ppm by mass or less, more preferably 200 ppm by mass or less, more preferably 150 ppm by mass in terms of cobalt atom, based on the total amount of the lubricating oil composition, from the viewpoint of suppressing sludge formation. ppm or less.

The content of sulfur is preferably 100 mass ppm or less, more preferably 50 mass ppm or less, and even more preferably 10 mass ppm or less in terms of sulfur atom, based on the total amount of the lubricating oil composition, from the viewpoint of suppressing sludge formation. It is. For the same reason, the sulfur content of the lubricating base oil contained in the lubricating oil composition is preferably 10 mass ppm or less, more preferably 7 mass ppm or less, more preferably 7 mass ppm or less in terms of sulfur atoms, based on the total amount of the lubricating oil base oil. Preferably it is 5 mass ppm or less.

In the present invention, “cobalt content” and “sulfur content” mean content (unit: mass ppm) measured by ICP elemental analysis.

The kinematic viscosity and viscosity index of the lubricating oil composition are not particularly limited. For example, the kinematic viscosity at 40 ° C. of the lubricating oil composition can be 5 to 500 mm ² / s, 20 to 100 mm ² / s, or 30 to 60 mm ² / s. The kinematic viscosity at 100 ° C. of the lubricating oil composition may be 2 to 30 mm ² / s, 4 to 20 mm ² / s, or 6 to 10 mm ² / s. The viscosity index of the lubricating oil composition can be 90 or more, 105 or more, or 120 or more.

The lubricating oil composition according to this embodiment may further contain other additives in addition to the aromatic amine antioxidant and cobalt carboxylate. Specific examples of such lubricating oil additives include antioxidants (phenolic antioxidants, etc.), ashless dispersants, metal detergents, extreme pressure agents, antiwear agents, viscosity index improvers, pour point depressants. Agents, friction modifiers, oiliness agents, corrosion inhibitors, rust inhibitors, demulsifiers, metal deactivators, seal swelling agents, antifoaming agents, colorants and the like. These additives may be used individually by 1 type, and may be used in combination of 2 or more type. Moreover, the lubricating oil composition according to this embodiment can contain an additive containing sulfur as a constituent element as long as the effects of the present invention are not impaired.

The lubricating oil composition according to the present embodiment can be used in a wide range of lubricating oil fields. Applications of the lubricating oil composition include engine oil, lubricating oil for driving systems such as an automatic transmission or a manual transmission, hydraulic working oil, turbine oil, compressor oil, and the like.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Examples 1 to 6, Comparative Examples 1 to 5]
In Examples 1 to 6 and Comparative Examples 1 to 5, lubricating oil compositions having the compositions shown in Tables 1 and 2 were prepared using the base oils and additives shown below, respectively. Tables 1 and 2 also show the copper content and sulfur content (both element conversion values) of the lubricating oil composition.
[Base oil]
Base oil 1: hydrorefined mineral oil (total aromatic content: 0.3 mass%, sulfur content: less than 10 mass ppm, 40 ° C. kinematic viscosity: 35 mm ² / s, viscosity index: 120)
[Aromatic amine antioxidants]
A-1: Octylated / Butylated diphenylamine (IRGANOX (registered trademark) L57, manufactured by BASF)
A-2: Octylated phenyl-α-naphthylamine (IRGANOX (registered trademark) L06, manufactured by BASF)
[Cobalt carboxylate]
B-1: Cobalt octoate (manufactured by DIC, cobalt content: 12% by mass)
[Sulfur-containing additive]
C-1: Dialkylthiophosphate (IRGALUBE (registered trademark) 353, manufactured by BASF, sulfur content: 18.9% by mass, phosphorus content: 9.45% by mass)
[Other additives]
D-1: 2,6-ditertiary butyl-p-cresol (DBPC)

[Oxidation stability test]
The RPVOT values of the lubricating oil compositions of Examples 1 to 6 and Comparative Examples 1 to 5 are in accordance with “6. Rotating cylinder type oxidation stability test method” of JIS K 2514 “Lubricant-Oxidation stability test method”. And measured. A large RPVOT value means that oxidation stability can be maintained for a long time. The results are shown in Tables 1-2.

[Evaluation of sludge generation]
For each of the lubricating oil compositions of Examples 1 to 6, the amount of sludge produced when the RPVOT value in the oxidation stability test reached 90% of the RPVOT value before the test (when the remaining life reached 90%) was measured. . As a result, in the lubricating oil compositions of Examples 1 to 3, 5, and 6, sludge formation was not observed when the remaining life reached 90%. In addition, in the lubricating oil compositions of Examples 4 and 7, the generation of sludge was very small when the remaining life reached 90%. Furthermore, when the lubricating oil composition of Example 4 and the lubricating oil composition of Example 7 were compared, the lubricating oil composition of Example 7 produced less sludge.

Claims

Lubricating oil composition containing a lubricating base oil, an aromatic amine-based antioxidant, and cobalt carboxylate.
The lubricating oil composition according to claim 1, wherein the sulfur content is 100 mass ppm or less in terms of sulfur atom, based on the total amount of the lubricating oil composition.