Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic -co- compound
Reexamination Certificate
2001-11-20
2003-12-09
Howard, Jacqueline V. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic -co- compound
C508S586000
Reexamination Certificate
active
06660697
ABSTRACT:
This invention relates to a lubricating oil composition suitable for a medium speed 4-stroke trunk piston compression-ignited (diesel) marine enigne.
The term “marine” does not restrict the engines to those used in water-borne vessels; as is understood in the art, it also includes those for auxiliary power generation applications and for main propulsion stationary land-based engines of the above types for power-generation.
Lubricating oil compositions (or lubricants) for trunk piston engines are known and may be referred to as trunk piston engine oils or TPEO's. They are known to include, as additives to improve their performance, ashless dispersants and overbased detergents.
EP-A-0-662 508 describes use of a composition that includes a hydrocarbyl-substituted phenate concentrate having a TBN greater than 300, and at least one of a hydrocarbyl-substituted salicylate and a hydrocarbyl-substituted sulphonate. Thee composition also includes a dispersant to minimise deposit formation in various parts of the engine.
EP-A-0-662 508 teaches the need for several additives, thus increasing cost in a cost-sensitive environment. It has now surprisingly been found that a dispersant-free or low dispersant TPEO, wherein the metal detergent is a complex detergent, provides excellent performance in the area of piston cleanliness.
Accordingly, a first aspect of the invention is a lubricating oil composition for a medium speed 4-stroke trunk piston compression-ignited (diesel) marine engine, comprising an admixture of:
(A) an oil of lubricating viscosity, in a major amount; and
(B) an oil-soluble overbased metal detergent additive, in a minor amount, in the
form of a complex wherein the basic material of the detergent is stabilised by more than one surfactant;
the composition being substantially dispersant-free or containing 1, or less than 1, preferably less than 0.5, mass % based on the mass of the compositions, of a dispersant; and the composition having a TBN in the range of 3.5 to 100, preferably 8 to 100.
A second aspect of the present invention is the use of additive (B) as defined in the first aspect of the invention in a lubricating oil composition that is dispersant-free or contains 1, or less than 1, preferably less than 0.5, mass % of a dispersant, to control piston undercrown deposits when the composition is used in a medium speed 4-stroke trunk piston compression-ignited marine engine.
A third aspect of the present invention is a method of lubricating a medium speed 4-stroke trunk piston compression-ignited marine engine which comprises supplying to the engine the lubricating oil composition according to the first aspect of the invention.
“Major amount” means in excess of 50 mass % of the composition.
“Minor amount” means less than 50 mass % of the composition, both in respect of the stated additive and in respect of the total mass % of all the additives present in the composition, reckoned as active ingredient of the additive or additives.
“Comprises or comprising” or cognate words is or are taken to specify the presence of stated features, steps, integers or components, but does not preclude the presence or addition of one or more other features, steps, integer components or groups thereof.
“TBN” (Total Base Number) is as measured by ASTM D2896, and the viscosity index is as defined by ASTM D2270.
The features of the invention will now be discussed in more detail below.
Marine Diesel Engines
The lubricating oil composition of the present invention may be suitable for use in a 4-stroke trunk piston engine 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 5,000 such as up to 3,000, preferably 100 to 2,000 or to 3,000.
Lubricating Oil Composition
The TBN of the lubricant composition is, as stated, in the range of from 3.5 to 100, preferably 8 to 100, and more preferably 10 to 60. Preferably, the viscosity index of the lubricant composition is at least 90, more preferably at least 95, and at most 140 such as 120, preferably 110. A preferred viscosity index range is from 95 to 115.
The lubricant composition may, for example, have a kinematic viscosity at 100° C. (as measured by ASTM D445) of at least 9, preferably at least 13, more preferably in the range of from 14 to 24, for example from 14 to 22, mm
2
s
−1
.
In use of the composition, it often becomes contaminated with fuel, such as residual fuel, in minor amounts, leading to cleanliness problems arising from presence of asphaltene components in the fuel. The present invention may alleviate the problem.
(A) Oil of Lubricating Viscosity
The oil of lubricating viscosity (sometimes referred to as lubricating oil) may be any oil suitable for the lubrication of 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 tridecyl 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 for 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 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 typically in the range of from 100 to 110, for example from 105 to 108.
The term ‘brightstock’ as used herein refers to 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
and 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.
The compositions are either totally free of dispersants, substantially free of dispersants or contain 1, or less than 1, preferably less than 0.5, mass % of dispersant. More preferably, the compositions include less than 0.4, more preferably less than 0.3, more preferably less than 0.2, even more preferably less than 0.1 and most preferably less than 0.01, mass % of dispersant. A dispersant is an additive for a lubricating composition whose primary function is to hold solid and liquid contaminants in suspension, thereby passivating them and reducing engine deposits at the same time as reducing sludge depositions. Thus, for example, a dispersant maintains in suspension oil-insoluble substances that result from oxidation during use of the lubricating oil, thus preventing sludge flocculation and precipitation or deposition on metal parts of the engine.
The composition preferably includes less than 0.015%, preferably less than 0.011%, more preferably less than 0.007%, even more preferably less than 0.004%, and most preferably less than 0.0004%, by mass of nitrogen.
A noteworthy class of dispersants are “ashless”, meaning a non-metallic organic material that forms substantially no ash on combustion, in contrast to metal-containing, hence ash-forming, materials. Ashless dispersants comprise a long chain hydrocarbon with a polar head, the polarity being derived from inclusion of, e.g. an O, P or N atom. The hydrocarbon is an oleophilic group that confers oil-solubility, having for example 40 to 500 carbon atoms. Thus, ashless dispersants may comprise an oil-soluble polymeric hydro
Chambard Laurent
Dunn Adrian
Garner Terence
Howard Jacqueline V.
Infineum International Ltd.
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