Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic compound containing boron
Reexamination Certificate
2001-11-14
2003-04-22
Howard, Jacqueline V. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic compound containing boron
C508S291000, C508S391000, C508S375000, C508S378000, C508S574000
Reexamination Certificate
active
06551965
ABSTRACT:
The present invention relates to a lubricating oil composition for internal combustion engines, particularly two-stroke cross-head diesel engines such as marine engines. The lubricating oil composition of the present invention is highly effective under severe conditions in which cylinder liner temperatures may reach 200 to 260° C.
BACKGROUND OF THE INVENTION
For conventional two-stroke cross-head diesel internal combustion engines of large ships, a “marine cylinder lubricating oil” is used. Such lubricating oils usually contain various additives for improving durability and/or lubricating performance.
A typical lubricating oil for two-stroke cross-head diesel internal combustion engines of large ships comprises a lubricating base oil in which dissolved or dispersed are additives such as an overbased metal-containing detergent (e.g., calcium sulfonate, calcium phenate, calcium salicylate) and an ashless dispersant.
Metal-containing detergents help to neutralize acidic sulfur oxide (particularly sulfuric acid) that results from the burning of petroleum fuel such as fuel oil of grade C, which contains considerable amounts of sulfur (usually 1.0 to 4.0 wt %). Metal-containing detergents, along with ashless dispersants, also serve to disperse combustion residues, such as soot and sludge, which are produced as the fuel and the lubricating oil deteriorate and to prevent the residues from accumulating on the inner surface of the engine parts such as the pistons, piston grooves, and cylinder liner. While metal-containing detergents and ashless dispersants provide adequate heat stability and anti-wear performance under relatively moderate and high temperatures, their combination cannot give fully satisfactory performance under severe load conditions. In particular, in a two-stroke cross-head diesel engine having a large-caliber cylinder, the temperature at the top area of the cylinder liner wall (near the piston top ring groove) may rise up to 230 to 260° C., which is higher than the temperature in the conventional engine by 20% or more. Accordingly, if the lubricating oil has insufficient heat stability or gives poor anti-wear performance at such high temperatures, combustion residues produced by thermal deterioration of the lubricating oil accumulate on the top area of the piston or on the piston groove to cause wearing or scuffing on the cylinder liner.
Accordingly, there is a need for a lubricating oil composition having high heat stability and anti-wear performance at high temperatures to comply with the severe load conditions in marine two-stroke cross-head diesel engines.
SUMMARY OF THE INVENTION
The present invention relates to a lubricating oil composition for internal combustion engines, particularly two-stroke cross-head diesel engines such as marine diesel engines. The lubricating oil composition of the present invention is useful in a method of improving the heat stability and anti-wear performance of marine diesel engines operated under severe conditions where cylinder liner temperatures may reach 200 to 260° C.
In its broadest aspect, the present invention comprises a lubricating oil composition having a TBN (in terms of mg KOH/g) in the range of 40 to 100, preferably 50 to 90, and having a major amount of a base oil of lubricating viscosity having a kinematic viscosity of 22 to 300 mm
2
/s at 40° C., overbased sulfurized alkylphenate detergent or its calcium salt, an overbased alkylsulfonate detergent or its calcium salt, an ashless dispersant, and a zinc dialkyldithiophosphate and/or zinc diaryldithiophosphate, wherein the weight ratio between the overbased sulfurized alkylphenate detergent or its calcium salt and the overbased alkylsulfonate detergent or its calcium salt is in the range of 55:45 to 95:5.
In another aspect, the present invention relates to a lubricating oil additive concentrate containing a compatible organic diluent, overbased sulfurized alkylphenate detergent or its calcium salt, an overbased alkylsulfonate detergent or its calcium salt, an ashless dispersant, and a zinc dialkyldithiophosphate and/or zinc diaryidithiophosphate, wherein the weight ratio between the overbased sulfurized alkylphenate detergent or its calcium salt and the overbased alkylsulfonate detergent or its calcium salt is in the range of 55:45 to 95:5.
In a further aspect, the present invention relates to a method of improving the heat stability and anti-wear performance at high temperatures of an internal combustion engine, particularly a two-stroke cross-head diesel engine, by lubricating the engine with the lubricating oil composition of the present invention.
In still a further aspect, the present invention relates to a method of producing the lubricating oil composition of the present invention by blending a mixture of the components of the lubricating oil composition of the present invention. The resulting lubricating oil composition having improved heat stability and anti-wear performance at high temperatures in an internal combustion engine.
Among other factors, the present invention relates to the use of an overbased sulfurized alkylphenate detergent or its calcium salt, an overbased alkylsulfonate detergent or its calcium salt, an ashless dispersant and a zinc dialkyldithiophosphate and/or of a zinc diaryldithiophosphate for improving the heat stability and anti-wear performance at high temperatures of a lubricating oil composition for two-stroke cross-head diesel engines comprising a major amount of a base oil of lubricating viscosity and an effective amount of an overbased sulfurized alkylphenate detergent or its calcium salt, an overbased alkylsulfonate detergent or its calcium salt, an ashless dispersant and a zinc dialkyldithiophosphate and/or of a zinc diaryldithiophosphate, wherein the weight ratio between the overbased sulfurized alkylphenate detergent or its calcium salt and the overbased alkylsulfonate detergent or its calcium salt is in the range of 55:45 to 95:5.
DETAILED DESCRIPTION OF THE INVENTION
In its broadest aspect, the present invention involves a lubricating oil composition for internal combustion engines, particularly two-stroke cross-head diesel engines such as marine diesel engines, having improved heat stability and anti-wear performance.
The base oil of lubricating viscosity used in the lubricating oil composition of the present invention may be a mineral or a synthetic base oil having a kinematic viscosity of 22 to 300 mm
2
/s, preferably 22 to 140 mm
2
/s at 40° C. Mineral oil employable for the invention can be obtained from crude oil by distillation (under atmospheric or reduced pressure) and purification such as solvent extraction, hydrogenolysis, solvent dewaxing or hydrogenation refining. Mineral oils for use as the base oil in this invention include, for example, paraffinic, naphthenic and other oils that are ordinarily used in lubricating oil compositions.
Synthetic oils include, for example, both hydrocarbon synthetic oils and synthetic esters and mixtures thereof having desired viscosity. Useful synthetic hydrocarbon oils include liquid polymers of alpha olefins having the proper viscosity. Especially useful are the hydrogenated liquid oligomers of C
6
to C
12
alpha olefins such as 1-decene trimer. Likewise, alkyl benzenes of proper viscosity, such as didodecyl benzene, can be used. Useful synthetic esters include the esters of monocarboxylic acids and polycarboxylic acids, as well as mono-hydroxy alkanols and polyols. Typical examples are didodecyl adipate, pentaerythritol tetracaproate, di-2-ethylhexyl adipate, dilaurylsebacate, and the like. Complex esters prepared from mixtures of mono and dicarboxylic acids and mono and dihydroxy alkanols can also be used. Blends of mineral oils with synthetic oils are also useful. The overbased sulfurized alkylphenate detergent of the present invention is a metal salt of sulfurized alkylphenol having an alkyl group of about 8 to 30 carbon atoms. It may be incorporated in an amount of 5.0 to 35.0 wt %, preferably 20 to 30 wt %, based on the total amount of the lubricating oil composition. The
Fujita Hirokazu
Iwamoto Shigeru
Nagamatsu Hiroyuki
Chevron Oronite Company LLC
Howard Jacqueline V.
Lee S. G. K.
LandOfFree
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