EP0523561A1

EP0523561A1 - Lubricating oil composition

Info

Publication number: EP0523561A1
Application number: EP92111780A
Authority: EP
Inventors: Katsumi Hashimoto; Hiromichi Seiki
Original assignee: Idemitsu Kosan Co Ltd
Current assignee: Idemitsu Kosan Co Ltd
Priority date: 1991-07-17
Filing date: 1992-07-10
Publication date: 1993-01-20
Also published as: JP2966975B2; KR930002490A; JPH0517794A

Abstract

There is disclosed a lubricating oil composition comprising a base oil containing an ester compound as the essential component and a specific phosphoric compound and amine compound.

The lubricating oil composition is excellent in the antiwear property and the anti-hydrolysis property in an atmosphere of refrigerant such as fluorocarbon as well as in an atmosphere of air, and is well suited for use in refrigerators as a refrigerator oil and in hydraulic equipment as a hydraulic oil.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lubricating oil composition, more particularly, to a lubricating oil composition excellent in anti-wear property and anti-hydrolysis property, which comprises a base oil containing an ester compound as the essential component compounded with a specific phosphoric compound and amine compound.

2. Description of the Related Arts

Conventionally, various lubricating oils have been used, including a mineral lubricating oil comprising mineral oil, a chemically synthesized lubricating oil, a fatty lubricating oil comprising animal or plant oil or fat, a compounded lubricating oil comprising a mixture of mineral oil and animal or plant oil or fat, a compounded lubricating oil comprising a mixture of mineral oil and synthetic oil and the like. Of them, synthetic lubricating oils which can be chemically modified or synthesized in a variety of ways have found the wide application and particularly ester compounds have been diversified into many applications.
However, esters lubricating oils made of esters only are poor in anti-wear property, having a disadvantage that sliding members of a refrigerator compressor are liable to marked wear when the oils are used therein. To prevent this, a tricresylphosphate (TCP), a triphenylphosphite (TPP) or the like has been used as the anti-wear agent but not found as effective as initially expected. Furthermore, esters have another disadvantage that they are liable to hydrolysis in the presence of water to form fatty acids or fatty acid metal salts, causing corrosion within the operating systems or clogging of capillary tubes.
Therefore, in view of the above-mentioned circumstances, the present inventors have earnestly studied base oils containing ester compounds as the essential component for the object of developing a lubricating oil capable of achieving better performance. As the result, it has been found that said object can be achieved by mixing a specific phosphoric compound and amine compound with a base oil. The present invention has been completed on the basis of this finding.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a lubricating oil composition capable of achieving a good result and free from any problem relative to sealed tube test, excellent in the anti-wear property and the anti-hydrolysis property in an atmosphere of fluorocarbon (hereinafter referred to as "flon") and very effective as desired when used as a lubricating oil in a refrigerator.
Another object of the present invention is to provide a lubricating oil composition excellent in the anti-wear property and the anti-hydrolysis property in an atmosphere of air and markedly effective as a hydraulic oil in a hydraulic equipment or a lubricating oil.
The present invention provides a lubricating oil composition which comprises (A) a base oil containing an ester compound as the essential component, (B) at least one member selected from the group consisting of phosphoric compounds represented by the following general formulae (I), (II) and (III):

wherein R¹ and R² are independently an alkyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms or a cycloalkyl group having 3 to 30 carbon atoms; R³, R⁴ and R⁵ are independently a hydrogen atom, an alkyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms or a cycloalkyl group having 3 to 30 carbon atoms; R⁶, R⁷ and R⁸ are independently an alkylene group having 2 to 4 carbon atoms; p, q and r are each 0 to 20; R⁹, R¹⁰, R¹² and R¹³ are independently a hydrogen atom, an alkyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms or a cycloalkyl group having 3 to 30 carbon atoms; R¹¹ is an alkylene group having 2 to 4 carbon atoms; and x is 1 to 20 and (C) an amine compound represented by the following general formula (IV):

wherein R¹⁴, R¹⁵ and R¹⁶ are independently a hydrogen atom, an alkyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms or a cyloalkyl group having 3 to 30 carbon atoms provided that at least one of R¹⁴, R¹⁵ and R¹⁶ is a group other than hydrogen atom and that the number of carbon atoms per molecule totals 6 or more.

DESCRIPTION OF PREFERRED EMBODIMENTS

First of all, in the present invention, the ester compound as the essential component of the base oil (A) is a monobasic or polybasic fatty acid ester. The kinematic viscosity of the ester compound is not particularly limited but ordinarily it should be set in the range of 1 to 500 cSt (40°C), preferably 10 to 100 cSt (40°C). When the kinematic viscosity thereof is less than 1 cSt (40°C), the lubricity is poor, undesirably causing abnormal wear or seizure. When it is more than 500 cSt (40°C), the return of oil at low temperatures is disturbed, undesirably causing short oiling and thus seizure. Specific examples of the compounds meeting these properties include trimethylolpropane tri-2-ethylhexanoate, pentaerythritol tetra 2-ethylhexanoate and dioctyladipate.
Next, the phosphoric compound as component (B) to be mixed with the above base oil (A) include compounds represented by the general formula (I), (II) or (III) described above. The phosphoric compound is used singly or in combination with another one.
The ratio of the phosphoric compound as the component (B) in the lubricating oil composition is not particularly limited, and it should be selected properly according to circumstances. However, the component (B) is usually used at a ratio of 0.001 to 10% by weight, preferably 0.01 to 2% by weight based on the base oil (A) containing the ester compound as the essential component. When the ratio thereof is less than 0.001% by weight, the anti-wear effect is undesirably insufficient. On the other hand, when it is more than 10% by weight, the anti-wear effect is saturated and is not increased in proportion to the mixing ratio.
In above-mentioned general formulae (I), (II) and (III), all the symbols are the same as defined above. Namely, R¹ and R² are independently an alkyl group having 3 to 30 preferably 6 to 20 carbon atoms, (for example, hexyl group, octyl group, decyl group, lauryl group, stearyl group, oleyl group and the like), an aryl group having 6 to 30 preferably 6 to 20 carbon atoms (for example, phenyl group, tolyl group, xylyl group, nonylphenyl group, dodecylphenyl group and the like) or a cycloalkyl group having 3 to 30 preferably 5 to 15 carbon atoms (for example, cyclopentyl group, cyclohexyl group, trimethylcyclohexyl group and the like). R³, R⁴, R⁵, R⁹, R¹⁰, R¹² and R¹³ are independently a hydrogen atom, an alkyl group having 3 to 30 preferably 6 to 20 carbon atoms (for example, hexyl group, octyl group, decyl group, lauryl group, stearyl group, oleyl group and the like), an aryl group having 6 to 30 preferably 6 to 20 carbon atoms (for example, phenyl group, tolyl group, xylyl group, nonylphenyl group and the like) or a cycloalkyl group having 3 to 30 preferably 5 to 15 carbon atoms (for example, cyclopentyl group, cyclohexyl group, trimethylcyclopentyl group and the like). Further, R⁶, R⁷, R⁸ and R¹¹ are independently an alkylene group having 2 to 4 carbon atoms (for example, ethylene group, propylene group and butylene group). Meanwhile, p, q and r are each 0 to 20 (not limited to an integer but including a real number), preferably 2 to 10 and x is 1 to 20 (not limited to an integer but including a real number), preferably 1 to 10.
Specific examples of the phosphoric compounds represented by the general formula (I) include dilauryl hydrogen phosphite, dioleyl hydrogen phosphite, diphenyl hydrogen phosphite and the like. Specific examples of the phosphoric compounds represented by the general formula (II) include tris· polyoxyethylene decyletherphosphate, dipolyoxyethylene nonylphenyletherphosphate and the like. Specific examples of the phosphoric compounds represented by the general formula (III) include tetraphenyldipropylene glycol diphosphite, tetratridecyldiethylene glycol diphosphite and the like.
Furthermore, the amine compounds (C) to be mixed with the base oil (A) are those represented by the general formula (IV) described above. Herein, R¹⁴, R¹⁵ and R¹⁶ are independently a hydrogen atom, an alkyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms or a cycloalkyl group having 3 to 30 carbon atoms, preferably an alkyl group, an aryl group or a cycloalkyl group each having 6 to 24 carbon atoms provided that at least one of R¹⁴, R¹⁵ and R¹⁶ is a group other than hydrogen atom and it is essential that the number of carbon atoms per molecule totals 6 or more. As the alkyl group, any of straight chain, branched chain, saturated or unsaturated groups can be used. In view of stable solubility in the base oil, a branched chain or unsaturated alkyl group is preferable.
The ratio of the amine compound (C) in the lubricating oil composition is not particularly limited, but it should be usually 0.001 to 10% by weight, preferably 0.01 to 2% by weight based on the base oil (A). When the ratio thereof is less than 0.001% by weight, the hydrolysis preventive effect is undesirably insufficient. On the contrary, when it is more than 10% by weight, the hydrolysis preventive effect is saturated and is not increased in proportion to the mixing ratio and besides, the preventions of wear and the thermostability are adversely affected undesirably.
Specific examples of these amine compounds (C) include tri (2-ethylhexyl)amine, di(2-ethylhexyl)amine, tert-dodecylamine, tert-octadecylamine, tert-dococylamine, oleylamine, dioleylamine, isostearylamine, dimethyloleylamine, dodecylaniline, dibenzylamine, cyclohexylamine, 2-methylcyclohexylamine and cyclohexyldodecylamine.
The lubricating oil compositions of the present invention can of course be used as a lubricating oil in refrigerators using various refrigerants (flon refrigerants, alternative to flon refrigerants and the like) or as a hydraulic oil in a hydraulic equipment. They may contain an antioxidant, an oiliness agent, a copper deactivator, a defoaming agent or the like as the additive, if necessary.
The lubricating oil compositions of the present invention are capable of achieving good results and free from any problems relative to sealed tube test, excellent in the anti-wear property and the anti-hydrolysis property in an atmosphere of flon and very effective as desired when used as a lubricating oil in refrigerators.
Furthermore, the lubricating oil compositions of the present invention are excellent in the anti-wear property and the anti-hydrolysis property in an atmosphere of air, ensuring their extremely high working effect as a hydraulic oil in hydraulic equipment and other lubricating oil.
The present invention will be described in greater detail below with reference to examples and comparative examples.

EXAMPLES 1 to 6 AND COMPARATIVE EXAMPLES 1 to 8

The lubricating oil compositions were obtained by using base oils listed in Table 1 and mixing each component with the base oils at the ratios listed in Table 2. The lubricating oil compositions thus obtained were used as testing oils in following tests.
The wearing test was conducted by using a Falex testing machine and analyzing the wear amount of pins under the following condition.
Furthermore, the hydrolyzing test was conducted under the following condition in accordance with ASTM D-2619-88 governing the hydrolyzing testing procedure and the total acid number of an oil layer was determined after testing. This was followed by the sealed tube test under the following condition.

Wearing test condition

(1) Blow amount of 1,1,1,2-tetrafluoroethane (Flon 134a):
10 liters/hour

Load:

300 pounds, period: 60 minutes

Test piece material:

Pin SAE 3135 (ASTM D 2670-81 standard material)
Block AISI 1137 (ASTM D 2670-81 standard material)
(2) In an atmosphere of air

Load:

300 pounds, period: 60 minutes

Test piece material:

Pin SAE 3135 (ASTM D 2670-81 standard material)
Block AISI 1137 (ASTM D 2670-81 standard material)

Hydrolyzing test condition

Temperature:: 93°C, period: 240 hours
Catalyst:: A copper piece (13 x 51 x 1mm)
Oil:: 75g, water: 25g

Sealed tube test condition

Temperature:: 175°C, period: 720 hours
Refrigerant:: Flon 134a

Table 1

Base oil	Kind	Kinematic viscosity (40 °C)(cSt)
Ester A	Trimethylolpropane tricaprate	17
Ester B	Pentaerythritol tetracaprate	27
Ester C	Dioctyladipate	2.5

Table 3

No.	Wear amount in Wearing test (mg)	Increase in total acid number in Hydrolyzing test (mgKOH/g)	Sealed tube test	Wear amount in Wearing test ((2)Condition) (mg)
Example 1	0.1	0.1 >	Good	0.1
Example 2	0.1	0.1 >	Good	0.1
Example 3	0.1	0.1 >	Good	0.1
Example 4	0.1	0.1 >	Good	0.1
Example 5	0.1	0.1 >	Good	0.1
Example 6	0.1	0.1 >	Good	0.1
Comparative Example 1	20	2	Good	22
Comparative Example 2	15	2	Good	17
Comparative Example 3	22	2	Good	25
Comparative Example 4	18	2	Good	0.2
Comparative Example 5	19	80	Good	0.2
Comparative Example 6	0.2	85	Good	0.1
Comparative Example 7	0.2	70	Good	0.1
Comparative Example 8	21	0.1>	Good	20

As evident from Table 3, the shield tube test for the compositions of the present invention resulted in the good outcome free from any problems and finding that the compositions are excellent with a minimized wear amount and without a rise in the total acid number after hydrolysis. On the other hand, although the sealed tube test for the compositions of the comparative examples, achieved good result free from any problems as well, but led to the finding that each of the compositions lacks either of the anti-wear property or the anti-hydrolysis property.

Claims

A lubricating oil composition which comprises (A) a base oil containing an ester compound as the essential component, (B) at least one member selected from the group consisting of phosphoric compounds represented by the following general formulae (I), (II) and (III):
wherein R¹ and R² are independently an alkyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms or a cycloalkyl group having 3 to 30 carbon atoms; R³, R⁴ and R⁵ are independently a hydrogen atom, an alkyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms or a cycloalkyl group having 3 to 30 carbon atoms; R⁶, R⁷ and R⁸ are independently an alkylene group having 2 to 4 carbon atoms; p, q and r are each 0 to 20; R⁹, R¹⁰, R¹² and R¹³ are independently a hydrogen atom, an alkyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms or a cycloalkyl group having 3 to 30 carbon atoms; R¹¹ is an alkylene group having 2 to 4 carbon atoms and x is 1 to 20 and (C) an amine compound represented by the general formula (IV):
wherein R¹⁴, R¹⁵ and R¹⁶ are independently a hydrogen atom, an alkyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms or a cycloalkyl group having 3 to 30 carbon atoms provided that at least one of R¹⁴, R¹⁵ and R¹⁶ is a group other than hydrogen atom and that the number of carbon atoms per molecule totals 6 or more.
The lubricating oil composition according to Claim 1 wherein the base oil (A) has a kinematic viscosity at 40°C of 10 to 100 cSt.
The lubricating oil composition according to Claim 1 wherein the base oil (A) is a trimethylolpropane tricaprate.
The lubricating oil composition according to Claim 1 wherein the base oil (A) is a pentaerythritol tetracaprate.
The lubricating oil composition according to Claim 1 wherein the base oil (A) is a dioctyladipate.
The lubricating oil composition according to Claim 1 wherein the phosphoric compound (B) is mixed at a ratio of 0.01 to 2% by weight based on the base oil (A).
The lubricating oil composition according to Claim 1 wherein the phosphoric compound (B) is a dilaurylhydrogen phosphite.
The lubricating oil composition according to Claim 1 wherein the phosphoric compound (B) is a tripolyoxyethylene decyletherphosphate.
The lubricating oil composition according to Claim 1 wherein the phosphoric compound (B) is a tetraphenyldipropylene glycol diphosphite.
The lubricating oil composition according to Claim 1 wherein the amine compound (C) is mixed at a ratio of 0.01 to 2% by weight based on the base oil (A).
The lubricating oil composition according to Claim 1 wherein the amine compound (C) is a tert-dodecylamine.
The lubricating oil composition according to Claim 1 wherein the amine compound (C) is a tri(2-ethylhexyl)amine.
The lubricating oil composition according to Claim 1 wherein the amine compound (C) is a di(2-ethylhexyl)amine.
A refrigerator oil comprising the lubricating oil composition as set forth in Claim 1.
A hydraulic oil comprising the lubricating oil composition as set forth in Claim 1.