Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Heterocyclic ring compound; a heterocyclic ring is one...
Reexamination Certificate
1997-10-23
2002-04-23
Medley, Margaret (Department: 1714)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Heterocyclic ring compound; a heterocyclic ring is one...
C508S391000, C508S460000, C508S586000
Reexamination Certificate
active
06376434
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to lube oil compositions for diesel engines, and more particularly to lube oil compositions suitable for use as cylinder oils for two-cycle marine engines.
2. Description of the Related Art
Fuels used for diesel engines generally have high sulfur content, and therefore, exhaust gases from diesel engines contain large amounts of sulfur oxides (hereinafter collectively referred to as SO
x
). SO
x
reacts with moisture which is also present in exhaust gases to form sulfuric acid, which breaks an oil film of a lube oil for diesel engines and corrodes or wears components of the diesel engine. Particularly in the case of two-cycle marine engines, corrosion and wear of cylinder liners or piston rings raise serious problems. Therefore, lube oils for diesel marine engines must have properties that can effectively prevent corrosion and wear. To this end, conventional lube oils for diesel engines (hereinafter maybe referred to as diesel engine oils) have been designed to include metallic detergents/dispersants of the over based type, to thereby neutralize sulfuric acid that has been produced.
With a recent trend of increased popularity of diesel engines for land vehicles which are equipped with a unique system of circulating and recombusting exhaust gas (EGR, i.e., exhaust gas recirculation) for coping with exhaust gases, the SO
x
content of exhaust gases tends to increase. Also, in diesel marine engines, fuels of high sulfur content are widely used with an aim of cutting costs. However, this invites a tendency of increased SO
x
content as is the case with diesel engines for land vehicles.
As a conceivable measure for solving this problem, the amount of a over based metallic detergent/dispersant, which serves as a neutralizer, may be increased. However, the sole use of this approach cannot sufficiently neutralize and remove large amounts of sulfuric acid, and therefore, corrosion and wear cannot be fully prevented.
There has been tried another approach in which metallic detergents/dispersants are used in combination with a plurality of additives such as ashless dispersants to thereby promote the neutralizing effect of the metallic detergents/dispersants for acids, so as to prevent wear and corrosion of cylinder liners and piston rings. For example, Japanese Patent Application Laid-Open (kokai) No. 6-271885 discloses in its Example section additives containing Ca-salicylate and bis-type alkenylsuccinic imide. However, in order to promote the effect of neutralizing acid by use of the bis-type alkenylsuccinic imide, an amine molybdenum complex must be further added.
In this connection, the ability of diesel engine oils to prevent wear/corrosion of cylinder liners or piston rings can be assessed by measurement of the reaction rate of the lube oil to neutralize acids, because acid neutralization reaction rate is known to correlate with corrosion/wear of cylinder liners and piston rings.
The present invention has been made in view of the foregoing, and the object of the present invention is to provide a lube oil composition for diesel engines, which is endowed with excellent anticorrosion/antiwear properties even when used for diesel engines which exhaust large amounts of SO
x
.
SUMMARY OF THE INVENTION
The present inventors have conducted careful studies based on the aforementioned acid neutralization rate, and have found that when a specific type of over based alkaline earth metal compound is combined with a specific type of succinic imide compound, the object of the present invention can be effectively attained, leading to completion of the present invention.
Accordingly, the present invention is directed to a lube oil composition for diesel engines, which comprises a lube oil base having a kinematic viscosity of 8-35 mm
2
/s at 100° C.; a component (A) which is at least one compound selected from the group consisting of over based sulfonates of alkaline earth metals, over based phenates of alkaline earth metals, and salicylates of over based alkaline earth metals; and a component (B) which is a bis-type succinic imide compound having an absorption ratio, &agr;/&bgr;, of absorption peaks in an IR spectrum (wherein &agr; is the intensity of an absorption peak at 1550±10 cm
−1
and &bgr; is the intensity of an absorption peak at 1700±10 cm
−1
) of not more than 0.005.
The present invention also relates to a lube oil composition for diesel engines, which comprises component (A) in an amount of 5-40% by weight and component (B) in an amount of 0.1-3% by weight, both based on the total weight of the composition.
The present invention also relates to a lube oil composition for diesel engines, in which the total base number of the composition falls within the range from 30 to 150 mgKOH/g.
The present invention still further relates to a lube oil composition for diesel engines, wherein the concentration of the nitrogen atoms contained in the composition is 10-200 ppm by weight based on the total weight of the composition.
These and other objects, features, and advantages of the present invention will become apparent from the following description.
MODES FOR CARRYING OUT THE INVENTION
The present invention will next be described in detail.
The lube oil base of the lube oil composition of the present invention for diesel engines is a mineral oil and/or a synthetic oil having a kinematic viscosity of 8-35 mm
2
/s, preferably 10-25mm
2
/s. If the kinematic viscosity at 100° C. is higher than 35 mm
2
/s, the fuel consumption rate becomes unsatisfactory, whereas if it is less than 8, the lube oil composition evaporates considerably, both cases being not preferable. There is no particular limitation as to the pour point—which serves as an index for the low temperature fluidity—of the base oil. However, it is generally preferred that the pour point be not higher than −10° C.
Several types of mineral oils and synthetic oils are usable in the present invention, and they are suitably selected in accordance with use, etc. Examples of mineral oils include, but are not limited to, paraffin base mineral oils, naphthene-type mineral oils, and intermediate-base-type mineral oils. Specific examples of mineral oils include light neutral oils, intermediate neutral oils, heavy neutral oils, and bright stocks.
Examples of synthetic oils include, but are not limited to, poly&agr;-olefin, &agr;-olefin copolymers, polybutene, alkylbenzene, polyol esters, dibasic acid esters, polyoxyalkylene glycols, polyoxyalkylene glycol esters, and polyoxyalkylene glycol ethers.
These base oils may be used singly or in combination of two or more species, and a mineral oil and a synthetic oil may be used in combination.
Components (A) and (B) which are incorporated into the lube oil base will next be described.
Component (A)
The component (A) of the present invention is a compound selected from the group consisting of over based sulfonates, phenates, and salicylates of alkaline earth metals. These compounds have conventionally been used as metallic detergents/dispersants. Preferable total base numbers of these compounds fall within the range from 100 to 600 mgKOH/g (JIS K-2501: perchloricacid method). Total base numbers of lower than 100 mgKOH/g require increased amounts of additives, and therefore are economically disadvantageous. On the other hand, if the total base number is in excess of 600 mgKOH/g, the ash content of the lube oil increases, raising the risk of producing great amounts of deposit during long-term use.
The over based sulfonates of alkaline earth metals that are usable as component (A) may usually be obtained through carbonation of alkaline earth metal salts of a variety of sulfonic acids. Examples of usable sulfonic acids include aromatic petrosulfonic acids, alkylsulfonic acids, arylsulfonic acids, and alkyl sulfonic acids. Specific examples of preferred over based sulfonates of alkaline earth metals include dodecylbenzenesulfonic acid, dilaurylcetylbenzenesulfonic acid, paraffin-wax-substituted benzen
Idemitsu Kosan Co. Ltd.
Medley Margaret
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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