Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic -co- compound
Reexamination Certificate
2001-10-11
2003-07-29
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic -co- compound
Reexamination Certificate
active
06599868
ABSTRACT:
This invention relates to lubricating oil compositions exhibiting improved crankcase cleanliness, particularly lubricating oil compositions suitable for engines which burn fuel containing asphaltene components, such as medium or slow speed diesel engines, such as 4-stroke trunk piston or 2-stroke cross-head marine engines.
Manufacturers commonly design marine diesel engines to use a variety of diesel fuels, ranging from good quality light distillate fuel with low sulfur and asphaltene content to poorer quality intermediate or heavy fuel such as “Bunker C” or residual fuel oil with generally higher sulfur and asphaltene content. Lubricants used in such engines are often contaminated with asphaltene components from the fuel. This leads to severe engine cleanliness problems in service (sometimes referred to as “black paint”), a problem which is particularly widespread in 4-stroke trunk piston engines where dirty cam boxes, deposits in piston scraper rings and sludge coatings on crankcase walls are found. Further, the lubricant handling system, for example, the heaters, filters and centrifuges, may function less well. The problem is not confined to 4-stroke engines; 2-stroke cross-head engines can also be affected.
EP-A-0662,508 and EP-A-0 708 171 describe ways of dealing with the above problem, but using compounds that contain metal salts. This constitutes a problem in view of industry trends and needs towards using lubricating oil compositions with reduced ash, ie low metal, content.
EP-A-0731,158 describes a lubricating oil composition suitable for use in low or medium speed diesel engines comprising a fuel oil with a residual oil content characterised in that the lubricating oil composition further comprises a “black paint” reducing amount of the product obtained by the reaction at elevated temperature of a hydrocarbyl-substituted succinic anhydride with either serine or an aminosalicylic acid. Such products are imides with free carboxy and hydroxy groups, eg, in the case of the aminosalicylic acid derivative, made as described in U.S. Pat. No. 5,266,081.
The present invention provides a way of solving the above problem using an ash-free chemistry and one that is remote from that described in EP-A-0 731 158, and that enables formulators to improve the cost-effectiveness of their lubricants,
It has now been found that compounds having a certain structural feature are able to effectively suspend asphaltenes in marine lubricating oil compositions and thereby improve crankcase cleanliness.
Accordingly, a first aspect of the present invention is a marine engine lubricating oil composition for a slow or medium speed diesel engine comprising a major amount of an oil of lubricating viscosity that contains a minor amount of a fuel oil with a residual fuel content and, admixed therewith, a minor amount of at least one oil-soluble or oil-dispersible ashless organic compound having at least two adjacent, substitutable carbon atoms being either part of an aromatic moiety or being connected by a double bond, each of said carbon atoms carrying an O— or O— and N-containing functional group, both groups being derived from a carboxy group.
A second aspect of the invention is the use of the compound defined in the first aspect in a lubricating oil composition to suspend asphaltene components in the composition when used in a slow or medium speed diesel engine, such as a cross-head or trunk piston engine.
A third aspect of the invention is a method of lubricating a slow or medium speed diesel engine, such as a cross-head or trunk piston engine, comprising supplying to the engine the lubricating oil composition of either the first or second aspects.
The features of the invention will now be discussed in more detail.
Marine Engines
The lubricating oil compositions of the present invention may be suitable for use in a 4-stroke trunk piston diesel engine such as having an engine speed of 200 to 2,000, e.g. 400 to 1,000, rpm, and a brake horse-power (BHP) per cylinder of 50 to 3,000 preferably 100 to 2,000. It may also be suitable for use in a 2-stroke cross-head diesel engine such as having a speed of 40 to 200, preferably 60 to 120, rpm and a BHP per cylinder of 500 to 10,000. Engines used for auxiliary power generation applications or in land-based power generation applications are also suitable. Preferably, the engine is a 4-stroke trunk piston diesel engine. As used herein, “slow speed diesel engine” refers to a 2-stroke cross-head diesel engine, and “medium speed diesel engine” refers to a 4-stroke trunk piston diesel engine.
Lubricating Oil
The oil of lubricating viscosity (sometimes referred to as lubricating oil) may be any oil suitable for the lubrication of a cross-head engine or a trunk piston engine. The lubricating oil may suitably be an animal, a vegetable or a mineral oil. Suitably the lubricating oil is a petroleum-derived lubricating oil, such as a naphthenic base, paraffinic base or mixed base oil. Alternatively, the lubricating oil may be a synthetic lubricating oil. Suitable synthetic lubricating oils include synthetic ester lubricating oils, which oils include diesters such as di-octyl adipate, di-octyl sebacate and tri-decyl adipate, or polymeric hydrocarbon lubricating oils, for example liquid polyisobutene and poly-alpha olefins. Commonly, a mineral oil is employed. The lubricating oil may generally comprise greater than 60, typically greater than 70, mass % of the composition, and typically have a kinematic viscosity at 100° C. of from 2 to 40, for example from 3 to 15, mm
2
s
−1−
, and a viscosity index of from 80 to 100, for example from 90 to 95.
Another class of lubricating oils is hydrocracked oils, where the refining process further breaks down the middle and heavy distillate fractions in the presence of hydrogen at high temperatures and moderate pressures. Hydrocracked oils typically have kinematic viscosity at 100° C. of from 2 to 40, for example from 3 to 15, mm
2
s
−1
and a viscosity index typically in the range of from 100 to 110, for example from 105 to 108.
Base oils which are solvent-extracted, de-asphalted products from vacuum residuum generally having a kinematic viscosity at 100° C. of from 28 to 36 mm
2
s
−1
are also suitable for use in the present invention. They are typically used in a proportion of less than 30, preferably less than 20, more preferably less than 15, most preferably less than 10, such as less than 5, mass %, based on the mass of the composition.
Ashless Compounds
The compounds of the present invention are ashless organic compounds, that is they do not contain any metals and, after combustion leave little or no ash.
Adjacent, substitutable carbon atoms refers to carbon atoms that can carry a substituent comprising a functional group and that are either bonded directly to one another as members of a chain or a ring, or are bonded via an unsubstitutable bridge atom.
Without wishing to be bound by any theory, it is believed that the significance of the adjacent carbon atoms is that they enable the compound to chelate, thereby increasing its ability to dissolve those contaminants present in residual fuel. Also, the significance of the presence of O and/N atoms, where present, on the functional groups is to facilitate interaction with O— and N-based functionalities known to be present on the surface of ashphaltenes.
The aromatic moiety, when employed, may be a hydrocarbon or may include in its ring or rings atoms other than carbon and hydrogen such as one or more of oxygen, nitrogen and sulfur. The moiety may be monocyclic or polycyclic, including fused polycyclic. Preferred examples of the aromatic moiety are benzene, when the functional groups are in the ortho position with respect to one another, and naphthalene, when the functional groups are in the 1- and 8-positions respectively.
The functional groups may, for example, be ester groups. The functional groups may carry hydrocarbyl groups which preferably contain from 1 to 20, such as 1 to 16, such as 2 to 10, carbon atoms. The hydrocarbyl group may be aryl, alkyl o
Aries Alan
Briffett Neil E.
Dunn Adrian
Infineum International Ltd.
McAvoy Ellen M.
LandOfFree
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