Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic sulfur compound – wherein the sulfur is single bonded...
Reexamination Certificate
2000-09-06
2002-09-03
Medley, Margaret (Department: 1714)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic sulfur compound, wherein the sulfur is single bonded...
C508S398000
Reexamination Certificate
active
06444625
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to marine cylinder oils containing overbased detergents for the lubrication between piston rings and cylinder walls in high output adverse environment engines, and to overbased calcium sulfonate detergents therefor.
2. Background and Discussion of Prior Art
Particularly high rates of wear occur in high output marine engines or oceangoing vessel diesel engines, and particularly when these adverse environment engines are operated on fuels containing significant amounts of sulfur and asphaltenes. The oils subject to these adverse cylinder and piston ring environments are known as marine cylinder oils or cylinder oils. It was therefore necessary for marine cylinder oils to meet diverse stringent requirements. Marine cylinder oils are, generally speaking, blends of a high viscosity base oil and a solvent neutral or paraffinic oil, with detergents such as an overbased calcium sulfonate and overbased calcium phenate.
Marine cylinder oils are consumed with each stroke at a typical rate of about 0.9 g/hphr (1.20 g/kwhr) while being subjected to a severe environment. The marine cylinder oils, unlike conventional lubricating oils, must perform extremely broad functions, including the ability to spread over the entire cylinder liner surface, the ability to resist the effects of temperature, pressure, oxygen, moisture, and combustion products, the ability to maintain an oil film between piston rings, piston and cylinder liners, and also the ability to prevent corrosive wear and resist oxidation under extreme conditions.
In addition to the foregoing stringent demands, the marine cylinder oil art greatly desired a low cost product particularly so because of the high level of consumption.
Reported test data suggests that cylinder liner wear and piston ring wear would decrease with increase in the marine cylinder oil viscosity. The art, was for the foregoing reasons, directed to additive packages for improving viscosity as well as other characteristics. Additives, however, are costly components.
Another prior art solution to achieve the requisite viscosity was to provide substantial amounts of a high viscosity lubricating base oil having a viscosity of at least about 430 to 850 mm
2
/s at 40° C. (2000 to 4000 SUS at 100° F.), in combination with the low cost, low viscosity, refined solvent neutral or paraffinic oil which has a viscosity of only about 117 mm
2
/s (500 SUS at 100° F.). The high viscosity base oil, such as a bright stock oil, however, was more costly and less stable at high temperatures than the solvent neutral oil.
The art directed to lubricating oils required overbased detergents with improved filterability and reduced viscosity, and was therefore directed away from the use of high viscosity detergents. This prior art direction is discussed in U.S. Pat. No. 5,011,618, granted Apr. 30, 1991 to Papke et al and U.S. Pat. No. 4,387,033, granted Jun. 7, 1983 to Lenack et al.
The present invention provides improved marine cylinder oil viscosity with a reduction in the amount of the high viscosity base oil, thereby, achieving cost effectiveness.
SUMMARY OF THE INVENTION
The invention is, in one aspect, a novel overbased calcium sulfonate detergent which produces clear solutions in lubricating oil, has a TBN of at least about 400 (i.e. about 400 or more), and which has a viscosity of at least 180 mm
2
/s (180 cST) at 100° C. Such calcium sulfonate detergents are particularly useful in marine cylinder oil compositions. The inventive detergents are especially useful in formulating marine cylinder oil compositions which comprise a blend of expensive high viscosity lubricating oil and lower cost low viscosity oil, where their high viscosity, when used alone or in combination with another high viscosity detergent such as an overbased calcium phenate, allows a commensurately proportional reduction of the high viscosity oil, relative to compositions prepared with prior art detergents, while maintaining a selected TBN and viscosity in finished oil composition.
Marine cylinder oil compositions formulated to specified viscosity and TBN specifications and employing a blend of two oils of substantially different viscosity constitute a further aspect of the invention. In such oils the weight percent of the higher viscosity oil in the blend is inversely commensurately proportional to the viscosity of the detergent. That is, for an amount of detergent calculated to provide a given TBN in the finished oil, the higher the detergent viscosity the lesser the amount of the higher viscosity oil is required to achieve a specified finished oil viscosity.
A method of preparing the high viscosity calcium sulfonate detergent of the invention constitutes a still further aspect of the invention.
DESCRIPTION OF THE INVENTION
The Marine Cylinder Oil
The term “substantially higher” as used hereinbefore and hereinafter in the context of the difference between viscosities of two lubricating oils in a blend means that the viscosity of the higher viscosity oil is at least about 170 mm
2
/s at 40° C. (800 SUS at 100° F.) greater than the viscosity of the lower viscosity oil.
A cost effective way to achieve a desired finished marine cylinder oil viscosity is to blend relatively substantial amounts of an inexpensive low viscosity oil, suitably one having a viscosity of 195 mm
2
/s at 40° C. (900 SUS at 100° F.) or less, with an expensive high viscosity oil, such as a bright stock oil of about 430 mm
2
/s at 40° C. (2000 SUS at 100° F.) or more. The finished marine cylinder oils may contain a detergent component which is composed of up to 100% of the overbased calcium sulfonate of the invention. Optionally, the detergent component will contain a combination of a high viscosity overbased calcium sulfonate of the invention and a high viscosity overbased calcium phenate. Insofar as the high viscosity overbased phenate is generally more costly than the high viscosity overbased sulfonate, a blend of the phenate and sulfonate provides optimization of both viscosity and economy.
The marine cylinder oil of the present invention, in an exemplary embodiment, comprises a blend of a solvent neutral paraffinic or like oil having a relatively low viscosity of no more than about 117 mm
2
/s at 40° C. (500 SUS at 100° F.), a bright stock or like oil having a relatively high viscosity of at least about 430 mm
2
/s at 40° C. (2000 SUS at 100° F.), and a detergent component comprising a high viscosity overbased calcium sulfonate detergent of the invention, optionally in combination with a calcium phenate detergent.
The marine cylinder oil compositions suitably comprises no more than about 35% by weight, and preferably no more than about 30% by weight, of the high viscosity oil, and yet achieves a desired marine cylinder oil blend viscosity of at least about 15 to 25 mm
2
/s or more at 100° C. at a specified TBN of at least about 10 and preferably at least about 50 to 90 or more. The oil composition TBN is determined by the amount of the overbased calcium sulfonate and, if used, the overbased calcium phenate used in the composition.
The overbased detergent is present in the marine cylinder oil in amounts of about 2 to 25% by weight and preferably about 10 to 20% by weight. Where a combination of detergents is used, the total detergent present in the marine cylinder oil is preferably in an amount of about 10 to 25% by weight.
The low viscosity solvent neutral oil preferably has a viscosity of no more than about 195 mm
2
/s at 40° C. (900 SUS at 100° F.), and especially suitably has a viscosity of 500 SUS at 100° F. (117 mm
2
/s at 40° C.) or less. The relatively low cost, low viscosity solvent neutral oil may be present in the marine cylinder oil in amounts greater than about 40% by weight, and preferably 80% by weight or more, where the high viscosity overbased detergent is present.
It has-been found that the marine cylinder oil of the present invention achieves a comparable viscosity to that of prior art blends but can reduce the high viscosity lubricating oil (e.g.
Eliades Theo I.
Matthews Leonard
Muir Ronald J.
Crompton Corporation
Dilworth Michael P.
Medley Margaret
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