Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Heavy metal or aluminum in an organic phosphorus compound...
Reexamination Certificate
2002-01-23
2003-12-02
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Heavy metal or aluminum in an organic phosphorus compound...
C508S372000, C508S377000, C508S378000, C508S435000
Reexamination Certificate
active
06656887
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to lubricating oil compositions, and more particularly to lubricating oil compositions which contain the metal salt or amine salt of thiophosphate or of phosphate and are decreased in sulfur content and excellent in the ability to maintain the total base number of lubricating oil composition.
2. Description of the Prior Art
Zinc dialkyldithiophosphate (ZDTP) has excellent anti-wear and anti-oxidation properties and thus has been used as an essential additive in lubricating oils for such as internal combustion engines or hydraulic oils and in every sort of lubricating oils.
On the other hand, sulfur-based additives such as zinc dialkyldithiocarbamate(ZDTC) or others are used in lubricating oil to keep anti-wear property instead of ZDTP_as disclosed in Japanese Patent Laid-Open Publication Nos. 52-704, 62-253691, 63-304095, and 6-41568 and Published Japanese Translation Nos. 62-501572, 62-501917, and 1-500912. The lubricating oils disclosed in these publications contain a large quantity of sulfur similarly to those containing ZDTP. Such lubricating oils are poor in oxidation stability and tend to be acceleratingly decreased in total base number of the composition.
After an extensive research and study on the ability to maintain the base number of lubricating oils containing a large amount of sulfur in the process of the degradation, it was found that the oxidation or thermal decomposition of a compound containing sulfur-based additives, such as ZDTP results in the formation of sulfuric acid which significantly decreases the total base number of the composition and deteriorates the high-temperature detergency at a temperature exceeding 300° C. It was also found that when recent low-sulfurized gasolines and gas oils, or alternative fuels such as LPG and natural gas are used as fuel particularly in an internal combustion engine, the decomposition of the sulfur-based additive such as ZDTP itself significantly affects the total base number maintaining properties and high-temperature detergency of the lubricating oil. Therefore, it becomes necessary to optimize the wear inhibitor such as ZDTP so as to obtain a longer drain-interval oil than conventional oils while keeping the anti-wear properties thereof. Furthermore, organic molybdenum compounds such as molybdenum dithiocarbamate and molybdenum dithiophosphate are found to be most effective in order to impart fuel efficiency and thus have been used. However, since these compounds contain a large amount of sulfur, they can not improve the total base number maintaining properties and high-temperature detergency and thus fail to obtain both long drain properties and fuel efficiency.
The object of the present invention is to provide a lubricating oil composition which can maintain or enhance anti-wear properties even though decreased in the amount of conventional ZDTP or containing no ZDTP at all and which has excellent long drain properties by suppressing the decrease of the total base number resulting from the deterioration of the lubricating oil. Another object of the present invention is to provide a lubricating oil composition with high-temperature detergency and fuel efficiency and low sulfur content.
After an extensive research and study made so as to solve the foregoing problems, the present invention was achieved by finding that the use of specific phosphorus-containing compounds represented by formulae (1) and/or (2) described hereinafter can produce a lubricating oil composition which can suppress the decrease of the base number resulting from the deterioration of the lubricating oil while maintaining anti-wear properties which are substantially equivalent to or better than those of ZDTP and are excellent in high-temperature detergency and fuel efficiency.
BRIEF SUMMARY OF THE INVENTION
According to the present invention, there is provided a lubricating oil composition which comprises a lubricating base oil and (A) at least one compound selected from the group consisting of compounds represented by the formula
wherein R
1
, R
2
, R
3
and R
4
are each independently hydrogen or a hydrocarbon group having 1 to 30 carbon atoms, X
1
, X
2
, X
3
and X
4
are each independently oxygen or sulfur, but at least one of them is oxygen, and Y
1
is a metal atom; and compounds represented by the formula
wherein R
11
and R
12
are each independently hydrogen or a hydrocarbon group having 1 to 30 carbon atoms, X
11
and X
12
are each independently oxygen or sulfur, but at least one of them is oxygen, U is a monovalent metal ion, an ammonium ion or a proton, and k
1
is an integer of 1 to 20.
REFERENCES:
patent: 4179384 (1979-12-01), Mann
patent: 4529526 (1985-07-01), Inoue et al.
patent: 4925596 (1990-05-01), Maeda et al.
patent: 5093016 (1992-03-01), Colombo
patent: 5352374 (1994-10-01), Habeeb et al.
patent: 5415793 (1995-05-01), Nassry et al.
patent: 6187723 (2001-02-01), Holt et al.
patent: 06-041568 (1994-02-01), None
Smalheer et al, “Lubricant Additives”, pp. 1-11, 1967.
Igarashi Jinichi
Koizumi Takeo
Yagishita Kazuhiro
Akin Gump Strauss Hauer & Feld, L.L.C.
McAvoy Ellen M.
Nippon Mitsubishi Oil Corporation
LandOfFree
Lubricating oil compositions does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Lubricating oil compositions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Lubricating oil compositions will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3160896