Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic phosphorus compound – wherein the phosphorus is...
Reexamination Certificate
2000-04-14
2003-07-01
Medley, Margaret (Department: 1714)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic phosphorus compound, wherein the phosphorus is...
C508S440000, C508S495000
Reexamination Certificate
active
06586376
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns a heat resistant lubricating oil composition, more in particular, it relates to a heat resistant and oxidation resistant lubricating oil composition comprising a polyphenyl thioether as an antioxidant or a lubricating base oil component and capable of withstanding use under a high temperature condition. Further, the present invention relates to a method of preventing oxidation of a heat resistant lubricating oil composition by using a polyphenyl thioether. Further, the present invention provides a production process thereof including a step of purifying a polyphenyl thioether as the constituent ingredient of a heat resistant lubricating oil composition.
DESCRIPTION OF THE PRIOR ART
In recent years, as the performance and the efficiency of machinery equipments and power equipments have become higher, conditions in the working circumstance of lubricating oils have become severer and high quality is required for lubricating oils capable of withstanding such conditions. For example, since jet engines, gas turbines and automobile engines such as turbo engines are operated at high speed and high temperature, high heat resistance and oxidation resistance are required for lubricating oils used in such engines.
Accordingly, as the lubricating oil used under conditions requiring, for example, high thermal oxidation stability, synthetic oils such as hindered ester and polyphenyl ethers have been known. For example, Japanese Patent Laid Open No.158079/1994 discloses a lubricating oil composition comprising an ester of a mixture of aliphatic acids and a hindered alcohol of 5 to 30 carbon atoms as the lubricating base oil, and phenol, amine or sulfur compound antioxidant blended therewith. Further, Japanese Patent Publication No. 8934/1969 discloses, as a lubricating base oil, a polyphenyl ether mixture comprising m-bis(phenylmercapto)benzene with other polyphenyl thioether and polyphenyl ether.
However, improvement for the heat resistance and the oxidation resistance by addition of a polyphenyl thioether to a heat resistant base oil such as a hindered ester and an organopolysiloxane has not been proposed at all. The amine or phenol antioxidant known so far has no effect in severe working conditions, for example, under high temperature conditions of higher than 200° C., involves a problem in view of the heat resistance and oxidation resistance such as causing remarkable change of viscosity, particularly, change of total acid number in a corrosive oxidation stability test and also forms a great amount of sludges, failing to provide a heat resistant lubricating oil of practical value.
SUMMARY OF THE INVENTION
In view of the situation for the development of the heat resistant lubricating oil as described above, a primary object of the present invention is to provide a heat resistant lubricating oil composition of high practical value excellent in heat resistance and oxidation resistance under severe working conditions, particularly, under a high temperature condition of higher than 200° C.
A secondary object of the present invention is to provide a heat resistant lubricating oil composition having excellent heat resistance and oxidation resistance under a high temperature condition, and improved wear resistance.
Further, a third object of the invention is to provide a method of preventing oxidation of a heat resistant lubricating oil composition.
Further, a fourth object of the present invention is to provide a production process including a step of purifying an ingredient of a heat resistant lubricating oil composition.
For solving the foregoing subjects, the present inventors, et. al have made earnest studies and found that addition of a specified polyphenyl thioether to be described later to a lubricating base oil is extremely useful for providing heat resistance and oxidation resistance under a high temperature condition and, further, a lubricating oil composition obtained by increasing the content of the polyphenyl thioether to an organic ester such as a polyol ester or a mixture of an organic ester and a polyphenyl ether or an organopolysiloxane can maintains high heat resistance and oxidation resistance under a high temperature condition and can improve the wear resistance.
It has been further found that a production process for a polyphenyl thioether excellent in the heat resistance and the oxidation resistance and improved with the weather resistance, particularly, UV-ray resistance can be provided. The present invention has been accomplished based on such findings.
Specifically, the present invention provides a heat resistant lubricating oil composition comprising:
(a) a lubricating base oil comprising an organic ester and/or an organopolysiloxane, or (b) a lubricating base oil comprising a mixture of a polyphenyl ether and an organic ester and/or an organopolysiloxane, incorporated with,
from 0.05% by weight to 10% by weight, based on the total weight of the lubricating oil composition, and a polyphenyl thioether represented by the following general formula [I]:
where R
1
, R
2
and R
3
which may be identical or different with each other represent each a hydrogen atom or a hydrocarbon group of 1 to 24 carbon atoms, x, y and z which are identical or different with each other represent each an integer of 1 to 4, m is 0 or an integer of 1 to 3.
The present invention further provides a heat resistant lubricating oil composition of excellent wear resistance containing, as a lubricating base oil, from 10 to 90% by weight of (a) an organic ester and/or an organopolysiloxane, or (b) an organic ester and/or an organopolysiloxane with a polyphenyl ether, and from 90 to 10% by weight of a polyphenyl thioether represented by the following general formula [1] described above.
The present invention further provides a method of preventing oxidation of a heat resistant lubricating oil composition under a high temperature condition, comprising adding a polyphenyl thioether and a free radical chain stopper to a synthetic lubricating base oil.
The present invention further provides a process for producing a heat resistant lubricating oil composition, which includes a step of purifying a polyphenyl thioether by applying heat treatment to a polyphenyl thioether as a component of the heat resistant lubricating oil composition under the presence of an alkali metal compound and/or an alkaline earth metal compound at a reduced pressure.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
Then, explanation is made to the polyphenyl thioether used as the component of the heat resistant lubricating oil composition according to the present invention.
Polyphenyl Thioether
The polyphenyl thioether has a structure in which aromatic rings are bonded with sulfur atoms and is represented by the following general formula [I]:
where R
1
, R
2
and R
3
which may be identical or different with each other represent each a hydrogen atom or a hydrocarbon group of 1 to 24 carbon atoms. A compound in which all of R
1
, R
2
and R
3
are hydrogen atoms represents polyphenyl thioether not substituted with hydrocarbon. As the hydrocarbon group, there can be mentioned, for example, a linear or branched alkyl group of 1 to 24 carbon atoms; a linear or branched alkenyl group of 2 to 24 carbon atoms, a cycloalkyl group of 6 to 24 carbon atoms; an aryl group of 6 to 24 carbon atoms. The aryl group may contain an alkyl group of 1 to 12 carbon atoms or an alkenyl group of 2 to 12 carbon atoms as a substituent. Preferred hydrocarbon group is an alkyl group of 6 to 20 carbon atoms, and those used specifically are hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group and eicosyl group, and those groups mentioned above and having branchings. Those having 8 to 18 carbon atoms are particularly preferred. The hydrocarbon group may be bonded at any position of the aromatic ring.
In the general formula &l
Kanbara Makoto
Kobori Atsuhisa
Nakamura Yoshinobu
Nakanishi Hiroshi
Onodera Ko
ExxonMobil Research and Engineering Company
Medley Margaret
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