Note: Descriptions are shown in the official language in which they were submitted.
CA 02420514 2003-02-27
LUBRICATING OIL COMPOSITIONS
The present invention concerns lubricating oil compositions for lubricating
the
crankcase of engines, particularly compression-ignited engines, such as heavy
duty diesel engines, for example, engines found in road trucks.
Lubrication of the crankcase of internal combustion engines is necessary to
maintain the performance and expected life-time of the engine, for example by
keeping the engine as clean as possible.
The heavy duty trucking market employs the diesel engine as its preferred
power
source due to its excellent longevity, and specialised lubricants have been
developed to meet the more stringent performance requirements of such heavy
duty diesel engines than passenger car engines.
It has been found that viscous lubricating oil compositions tend to provide
better
engine cleanliness than less viscous lubricating oil compositions: this is
particularly evident in the OM441 LA engine test, where piston cleanliness is
assessed on two grooves on the piston.
A potential means of improving the cleanliness effect of oil compositions is
to
include detergent additives, such as calcium or magnesium sulfonate and
phenate, which are believed to improve engine cleanliness. However,
regulations aimed at reducing environmental pollution caused by exhaust gas
components, such as particulates and nitrogen oxides (NO,), are driving
lubricating oil compositions to lower sulfated ash, and therefore, to a
reduced
amount of detergents. This is because metal-containing additives, such as
metal
detergents, zinc compounds and molybdenum compounds, contribute to the
amount of sulfated ash.
It has been surprisingly found that satisfactory piston cleanliness can be
achieved for lubricating oil compositions that are less viscous and contain a
reduced amount of detergent additives.
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Accordingly, in a first aspect, the present invention provides a heavy duty
diesel
engine lubricating oil composition comprising, or made by admixing:
(A) a major amount of an oil of lubricating viscosity comprising at least 35
mass % of a Group III basestock, based on the mass of the oil of
lubricating viscosity, that contains at most 0.03 mass % of sulfur, based on
the mass of said basestock, and that has a viscosity index of 120 or
greater and has greater than or equal to 90 mass % saturates, based on
lo the mass of said basestock; and
(B) a minor amount of an additive composition comprising :
(i) a detergent composition; and
(ii) one or more other additives;
wherein the oil composition has a cold cranking simulated viscosity, measured
according to ASTM D2602, of less than 7000 mPa.s at -25 C and a sulfated ash,
measured according to ASTM D874, of less than 1.35 mass %, based on the
mass of the oil composition.
In a second aspect, the present invention provides a method of lubricating a
heavy duty diesel engine, which engine has a total displacement of at least
6.5
litres and a displacement per cylinder of at least 1.0 litre per cylinder,
which
method comprises supplying to the engine a lubricating oil composition as
defined in the first aspect.
In a third aspect, the present invention provides a combination of a heavy
duty
diesel engine, which engine has a total displacement of at least 6.5 litres
and a
displacement per cylinder of at least 1.0 litre per cylinder and a lubricating
oil
composition as defined in the first aspect.
In a fourth aspect, the present invention provides the use of an oil of
lubricating
viscosity comprising at least 35 mass % of a Group III basestock, based on the
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mass of the oil of lubricating viscosity, that contains at most 0.03 mass % of
sulfur, based on the mass of said basestock, and that has a viscosity index of
120 or greater and has greater than or equal to 90 mass % saturates, based on
the mass of said basestock, in a lubricating oil composition for improving the
piston cleanliness of an engine.
In a fifth aspect, the present invention provides a method of improving the
piston
cleanliness of an engine, particularly in the OM441 LA test, by adding to the
engine a lubricating oil composition as defined in the first aspect.
In a sixth aspect, the present invention provides a heavy duty diesel engine
lubricating oil composition giving at least 25 piston cleanliness merit points
and
not greater than 4 % boost pressure loss in the OM441 LA engine test,
according
to the CEC-L-52-T-97 procedure, which oil composition comprises, or is made by
admixing:
(A) a major amount of an oil of lubricating viscosity; and
(B) a minor amount of an additive composition comprising :
?o (i) a detergent composition; and
(ii) one or more other additives;
wherein the oil composition has a cold cranking simulated viscosity, measured
according to ASTM D2602, of less than 7000 mPa,s at -25 C and a sulfated ash,
measured according to ASTM D874, of less than 1.35 mass %, based on the
mass of the oil composition.
In this specification:
"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 of the
additives
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present in the composition, reckoned as active ingredient of the additive or
additives.
"Comprises or comprising" or cognate words are taken to specify the presence
of
stated features, steps, integers, or components, but do not preclude the
presence
or addition of one or more other features, steps, integers, components or
groups
thereof. In the instance the term "comprising" or comprises" is used herein,
the
term "consisting essentially of" and its cognate are within its scope and are
a
preferred embodiment of it, and consequently the term "consisting of" and its
io cognate are within the scope of "consisting essentially of" and are a
preferred
embodiment of it.
"TBN" is Total Base Number as measured by ASTM D2896.
is "Oil-soluble" or "oil-dispersible" does not necessarily indicate that the
additives
are soluble, dissolvable, miscible or capable of being suspended in the oil of
lubricating viscosity, in all proportions. They do mean, however, that they
are, for
example, soluble or stably dispersible in the oil to an extent sufficient to
exert
their intended effect in the environment in which the oil is employed.
Moreover,
20 the additional incorporation of other additives may also permit
incorporation of
higher levels of a particular additive, if desired.
"ppm" means parts per million, expressed by mass based on the mass of the
lubricating oil composition.
The abbreviation.SAE stands for Society of Automotive Engineers.
All percentages reported are mass % on an active ingredient basis, i.e.,
without
regard to carrier or diluent oil, unless otherwise stated.
It should be noted that the lubricating oil compositions of this invention
comprise
defined individual, i.e. separate, components that may or may not remain the
same chemically before and after mixing. Thus, it will be understood that
various
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components of the composition, essential as well as optional and customary,
may react under the conditions of formulation, storage or use, and that the
invention also provides the product obtainable or obtained as a result of any
such
reaction.
Also, it should be noted that when the specification refers to a lubricating
oil
composition having a defined amount of sulfated ash, this means that the oil
composition gives the defined amount of sulfated ash under ASTM D874.
io The features of the present invention will now be discussed in more detail.
HEAVY DUTY DIESEL ENGINES
Heavy duty diesel engines according to the present invention are preferably
used
in land-based vehicles, more preferably large road vehicles, such as large
trucks.
The road vehicles typically have a weight greater than 12 tonnes. The engines
used in such vehicles tend to have a total displacement of at least 6.5,
preferably
at least 8, more preferably at least 10, such as at least 15, litres; engines
having
a total displacement of 12 to 20 litres are preferred. Generally, engines
having a
total displacement greater than 24 litres are not considered land-based
vehicles.
The engines according to the present invention also have a displacement per
cylinder of at least 1.0 or at least 1.5, such as at least 1.75, preferably at
least 2,
litres per cylinder. Generally, heavy duty diesel engines in road vehicles
have a
displacement per cylinder of at most 3.5, such as at most 3.0; preferably at
most
2.5, litres per cylinder. The term "heavy duty" in relation to internal
combustion
engines is known in the art: see ASTM D4485 at 3.17 where heavy duty engine
operation is characterised by average speeds, power outputs and internal
temperatures that are generally close to potential maximums; therefore, a
heavy
duty diesel engine is considered to operate generally under such conditions.
As used herein, the terms 'total displacement' and `displacement per cylinder'
are
known to those skilled in the art of internal combustion engines (see "Diesel
Engine Reference Book", edited by B. Challen and R. Baranescu, second edition,
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1999, published by SAE International). Briefly, the term "displacement'
corresponds to the volume of the cylinder in the engine as determined by the
piston movement and consequently the "total displacement" is the total volume
dependent on the number of cylinders; and the term `displacement per cylinder'
is
the ratio of the total displacement to the number of cylinders in the engine.
LUBRICATING OIL COMPOSITION
The present invention particularly concerns multigrade lubricating oil
lo compositions (also known as multigrade lubricants) that tend to be less
viscous.
The SAE J300 classification defines the lubricants according to their
viscometric
properties, such as their maximum low temperature cranking and pumping
viscosities and maximum and minimum kinematic viscosities at 100 4C.
is Preferably, the lubricating oil compositions, in each aspect of the present
invention, have a low temperature cranking viscosity or cold cranking
simulated
viscosity, independently of the amount of sulfated ash, as measured by ASTM
D2602, of less than 6000 mPa.s at -30 QC, more preferably less than 6200
mPa.s at -35 C.
Preferably, the lubricating oil compositions, in each aspect of the present
invention, have a sulfated ash, independently of the cold cranking simulated
viscosity, as measured by ASTM D874, of less than 1.25 or 1.15, more
preferably
less than any of 1.05, 1.00, and 0.95, such as less than 0.90, especially less
than
2? 5 0.85, advantageously less than 0.75, mass %, based on the mass of the oil
composition. The sulfated ash can be in the range from 0 to 0.5 mass %.
In a preferred embodiment, the amount of sulfated ash, as defined above, is
derived from metal-containing additives only, more preferably the sulfated ash
is
derived from metal detergents only, such as a calcium detergent and/or a
magnesium detergent.
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Preferably, the lubricating oil compositions, in each aspect of the present
invention, have a TBN of less than 11.2 or 10.5 or 9.8, preferably less than
any
one of 9.2, 8.8 and 8.5, especially less than 7.8, advantageously less than 7.
1.
The TBN can be in the range from 2.1 to 5.5.
Preferably, the lubricating oil compositions, in each aspect of the present
invention, have a metal content, whether transition metal or alkaline earth
metal
or alkali metal, of less than 4800 or 4400 or 4000, more preferably less than
any
of 3700, 3500 and 3300, especially less than 3000, advantageously less than
io 2600, ppm. The metal content can be in the in the range from 0 to 1800 ppm.
Test methods for measuring metal content are well known to those skilled in
the
art.
In an embodiment of each aspect of the present invention, lubricating oil
compositions of the present invention have a maximum kinematic viscosity at
100
C, independently of the cold cranking simulated viscosity and the amount of
sulfated ash, of less than 21.9 mm2a; preferably less than 16.3 mm2s; such as
less than 12.5 mm2s; especially less than 9.3 mm2s. The kinematic viscosity at
100 C can be, for example, in the range of 16.3 to less than 21.9; preferably
in
the range of 12.5 to less than 16.3; more preferably in the range of 9.3 to
less
than 12.5; such as in the range of 5.6 to less than 9.3.
Accordingly, the lubricating oil compositions of the present invention are
multigrade oil compositions having a viscosmetric grade of an SAE 10W-X or an
SAE 5W-X or OW-X, where X represents any one of 20, 30, 40 and 50, preferably
X is 20 or 30 or 40, more preferably X represents 40.
The American Petroleum Institute (API), Association des Constructeur Europeen
3o d'Autombile (ACEA) and Japanese Standards Organisation (JASO) specify the
performance level required for lubricating oil compositions. Also there are
performance specifications known as Global, which contain tests and
performance levels from the ACEA, API and JASO specifications.
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Thus, a heavy duty lubricating oil composition of the present invention
preferably
satisfies at least the performance requirements of heavy duty diesel engine
lubricants, such as at least the API CG-4; preferably at least the API CH-4;
especially at least the API CI-4. In another embodiment, the lubricating oil
composition of the invention, independently of meeting the API performance
requirements, preferably satisfies, in particular relating to piston
cleanliness, at
least the ACEA E2-96; more preferably at least the ACEA E3-96;
advantageously at least the ACEA E5-99; and especially at least ACEA E4-99.
io In a further embodiment, the lubricating oil composition of the invention,
independently of meeting the API and ACEA performance requirements,
preferably satisfies the JASO DH-1 or Global DHD-1.
Oil of Lubricating Viscosity
The oil of lubricating viscosity is the major liquid constituent of a
lubricating oil
composition. The oil of lubricating viscosity includes (a) oil added to a
concentrate or additive package, and (b) any oil present in a concentrate or
additive package.
The oil of lubricating viscosity or lubricating oil can be a synthetic or
mineral oil of
lubricating viscosity selected from the group consisting of Group I, II, III,
IV and V
basestocks, and a mixture containing any two or more thereof.
Basestocks may be made using a variety of different processes including but
not
limited to distillation, solvent refining, hydrogen processing,
oligomerization,
esterification, and rerefining.
API 1509 "Engine Oil Licensing and Certification System" Fourteenth Edition,
3o December 1996 states that all basestocks are divided into five general
categories:
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Group I basestocks contain less than 90% saturates and/or greater than 0.03%
sulfur and have a viscosity index greater than or equal to 80 and less than
120;
Group Il basestocks contain greater than or equal to 90% saturates and less
than
or equal to 0.03% sulfur and have a viscosity index greater than or equal to
80
and less than 120;
Group III basestocks contain greater than or equal to 90% saturates and less
than or equal or 0.03% sulfur and have a viscosity index greater than or equal
to
io 120;
Group IV basestocks are polyalphaolefins (PAO); and
Group V basestocks include all other basestocks not included in Group I, II,
IIl or
IV.
The test methods used in defining the above groups are ASTM D2007 for
saturates; ASTM D2270 for viscosity index; and one of ASTM D2622, 4294, 4927
and 3120 for sulfur.
Group IV basestocks, i.e. polyalphaolefins (PAO), include hydrogenated
oligomers of an alpha-olefin, the most important methods of oligomerization
being free radical processes, Ziegler catalysis, cationic and Friedel-Crafts
catalysis.
Group V basestocks in the form of esters are preferred and are also
commercially available. Examples include polyol esters such as pentaerythritol
esters, trimethylolpropane esters and neopentylglycol esters; diesters; C36
dimer
acid esters; trimellitate esters, i.e. 1, 2, 4-benzene tricarboxylates; and
pthalate
3o esters, i.e. 1,2 - benzene dicarboxylates. The acids from which the esters
are
made are preferably monocarboxylic acids of the formula RCO2H where R
represents a branched, linear or mixed alkyl group. Such acids may, for
example, contain 6 to 18 carbon atoms
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The oil of lubricating viscosity of the first aspect, and preferably of the
sixth
aspect, comprises at least 35 mass % of a Group III basestock, based on the
mass of the oil of lubricating viscosity, that contains at most 0.03 mass % of
suifur, based on the mass of said basestock, and that has a viscosity index of
120 or greater and has greater than or equal to 90 mass % saturates, based on
the mass of said basestock.
Preferably, the oil of lubricating viscosity comprises said basestock in an
amount
io of at least 40, more preferably at least 45, such as at least 50,
especially in the
range of 55 to 95, advantageously from 65 to 90, for example 70 to 80 or 85,
mass %, based on the mass of the oil of lubricating viscosity. For the
avoidance
of doubt, the oil of lubricating viscosity includes the basestock that arise
from the
provision of additive components in the oil composition.
In a preferred embodiment, the defined proportion of said basestock is that
added to the concentrate or additive package.
In the instance the oil of lubricating viscosity comprises a mixture of
basestock
2o Groups, it is preferred that a Group I basestock and a Group III basestock
are
present.
In a preferred embodiment, the oil of lubricating viscosity consists
essentially of a
Group III basestock and one or more of a Group IV basestock and a Group V
basestock in the form of an ester, and optionally a minor amount of those
basestocks that arise from the provision of additive components in the oil
composition.
Additive Composition
In each aspect of the present invention, an additive composition comprises a
detergent composition and one or more other additives, which may include other
metal-containing additives, such as zinc dithiophosphates.
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A detergent composition contains a detergent. A detergent is an additive that
reduces formation of piston deposits, for example high-temperature varnish and
lacquer deposits, in engines; it has acid-neutralising properties and is
capable of
keeping finely divided solids in suspension. It is based on metal "soaps",
that is
metal salts of organic acids, also known as surfactants herein.
A detergent comprises a polar head, e.g. the metal salt of the organic acid,
with a
long hydrophobic tail for oil solubility. Therefore, the organic acids
typically have
io one or more functional groups, such as OH or COOH or SO3H; and a
hydrocarbyl
substituent.
Examples of organic acids include sulfonic acids; phenols, salicylic acids and
sulfurised derivatives thereof; and carboxylic acids.
The detergents of the present invention can comprise metal salts of an organic
acid and particles of basic inorganic salts (e.g. calcium carbonate
particles).
Thus, each or the metal detergent in the detergent composition may be neutral
or
overbased, such terms are understood by those skilled in the art.
A detergent composition comprising one or more metal salts of organic acids
may be present, for example, a mixture of metal sulfonate and metal phenate.
The detergents of the present invention may be salts of one type of organic
acid
or salts of more than one type of organic acids, for example hybrid complex
detergents. Preferably, they are salts of one type of organic acid.
A hybrid complex detergent is where the basic material within the detergent is
stabilised by more than one type of organic acid. It will be appreciated by
one
skilled in the art that a single type of organic acid may contain a mixture of
organic acids of the same type. For example, a sulfonic acid may contain a
mixture of sulfonic acids of varying molecular weights. Such an organic acid
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composition is considered as one type. Thus, complex detergents are
distinguished from mixtures of two or more separate overbased detergents, an
example of such a mixture being one of an overbased calcium salicylate
detergent with an overbased calcium phenate detergent.
The art describes examples of overbased complex detergents. For example,
International Patent Application Publication Nos. 97-46643/4/5/6 and 7
describe
hybrid complexes made by neutralising a mixture of more than one acidic
organic
compound with a basic metal compound, and then overbasing the mixture.
io Individual basic micelles of the detergent are thus stabilised by a
plurality of
organic acid types. Examples of hybrid complex detergents include calcium
phenate-salicylate-sulfonate detergent, calcium phenate-sulfonate detergent
and
calcium phenate-salicylate detergent.
is EP-A-0 750 659 describes a calcium salicylate phenate complex made by
carboxylating a calcium phenate and then sulfurising and overbasing the
mixture
of calcium salicylate and calcium phenate. Such complexes may be referred to
as "phenalates"
20 Preferred complex detergents are salicylate-based detergents, for example,
a
calcium phenate-salicylate-sulfonate detergent and "phenalates".
A detergent, whether a complex or not, can have a Total Base Number (TBN) in
the range of 15 or 60 to 600, preferably 100 to 450, more preferably 160 to
400.
For the avoidance of doubt, the detergent composition may also comprise
ashiess detergents, i.e. non-metal containing detergents.
Preferably the detergent composition comprises at least one overbased metal
3o detergent.
Group 1 and Group 2 metals are preferred as metals in the detergents; more
preferably calcium and magnesium, especially preferred is calcium.
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Preferably, the amount of alkaline earth metal in the lubricating oil
composition, in
each aspect of the invention, is less than 3200, or 3000 or 2800, more
preferably
less than any of 2500, 2400 and 2300, especially less than 2000,
advantageously
less than 1800, ppm. The alkaline earth metal content can be in the range from
0
to 1200 ppm.
Preferably, the detergent composition is present in the oil composition, in
each
aspect of the invention, in an amount, based on surfactant content, of at most
50,
io preferably at most 30, especially at most 20, millimoles of surfactant per
kilogram
of the oil composition (mmol/kg). In an embodiment, the amount of detergent
composition, based on surfactant content, in the oil composition is 10 to15
mmol/kg.
ls Means for determining the amount of surfactant are known to those skilled
in the
art. For example, a skilled person can calculate the amounts in the final
lubricating oil composition from information concerning the amount of raw
materials (e.g., organic acids) used to make the detergent(s) and from
information concerning the amount of detergent(s) used in the final oil
210 composition. Analytical methods (e.g., dialysis, metal analysis, C02
analyis,
potentiometric titration and chromatography) can also be used to determine the
amounts of surfactant.
It will be appreciated by a skilled person in the art that the methods to
determine
25 the amount of metal salts of organic acids (also known as surfactants) are
at best
approximations and that differing methods will not always give exactly the
same
result; they are, however, sufficiently precise to allow the practice of the
present
invention.
30 Co-additives
Other additives may also be present in the oil composition of the present
invention.
CA 02420514 2007-12-18
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Co-additives suitable in the present invention include viscosity index
improvers,
corrosion inhibitors, oxidation inhibitors or antioxidants, dispersants, rust
inhibitors or rust prevention agents, anti-wear agents, pour point
depressants,
demulsifiers, and anti-foaming agents.
Viscosity index improvers (or viscosity modifiers) impart high and low
temperature operability to a lubricating oil and permit it to remain shear
stable at
elevated temperatures and also exhibit acceptable viscosity or fluidity at low
io temperatures. Suitable compounds for use as viscosity modifiers are
generally
high molecular weight hydrocarbon polymers, including polyesters, such as
polymethacrylates; poly(ethylene-co-propylene) polymers and closely related
modifications (so called olefin copolymers); hydrogenated poly(styrene-co-
butadiene or -isoprene) polymers and modifications; and esterified
poly(styrene-
co-maleic anhydride) polymers. Oil-soluble viscosity modifying polymers
generally have number average molecular weights of at least 15,000 to
1,000,000, preferably 20,000 to 600,000, as determined by gel permeation
chromatography or light scattering methods. See the disclosure in Chapter 5 of
"Chemistry & Technology of Lubricants", edited by R.M. Mortier and S.T.
Orzulik,
2o First edition, 1992, Blackie Academic & Professional.
Corrosion inhibitors reduce the degradation of metallic parts contacted by the
lubricating oil composition. Thiadiazoles, for example those disciosed in US-A-
2
719 125, 2 719 126 and 3 087 932 are examples of corrosion inhibitors for
lubricating oils.
Oxidation inhibitors, or antioxidants, reduce the tendency of mineral oils to
deteriorate in service, evidence of such deterioration being, for example, the
production of varnish-like deposits on metal surfaces and of sludge, and
viscosity
increase. Suitable oxidation inhibitors include sulfurized alkyl phenols and
alkali
or alkaline earth metal salts thereof; hindered phenols; diphenylamines;
phenyl-
naphthylamines; and phosphosulfurized or sulfurized hydrocarbons.
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Other oxidation inhibitors or antioxidants which may be used in lubricating
oil
compositions include oil-soluble copper compounds. The copper may be
blended into the oil as any suitable oil-soluble copper compound. By oil-
soluble it
is meant that the compound is oil-soluble under normal blending conditions in
the
~ oil or additive package. The copper may, for example, be in the form of a
copper
dihydrocarbyl thio- or dithio-phosphate. Alternatively, the copper may be
added
as the copper salt of a synthetic or natural carboxylic acid, for example, a
C8 to
C18 fatty acid, an unsaturated acid, or a branched carboxylic acid. Also
useful
are oil-soluble copper dithiocarbamates, sulfonates, phenates, and
acetylacetonates. Examples of particularly useful copper compounds are basic,
neutral or acidic copper Cul and/or Cull salts derived from alkenyl succinic
acids
or anhydrides.
Copper antioxidants will generally be employed in an amount of from about 5 to
500 ppm by weight of the copper, in the final lubricating composition.
Dispersants maintain oil-insoluble substances, resulting from oxidation during
use, in suspension in the fluid, thus preventing sludge flocculation and
precipitation or deposition on metal parts. So-called ashiess dispersants are
organic materials which form substantially no ash on combustion, in contrast
to
metal-containing (and thus ash-forming) detergents. Borated metal-free
dispersants are also regarded herein as ashless dispersants. Suitable
dispersants include, for example, derivatives of long chain hydrocarbyl-
substituted carboxylic acids, in which the hydrocarbyl group has a number
average molecular weight tends of less than 15,000, such as less than 5000;
examples of such derivatives being derivatives of high molecular weight
hydrocarbyl-substituted succinic acid. Such hydrocarbyl-substituted carboxylic
acids may be reacted with, for example, a nitrogen-containing compound,
advantageously a polyalkylene polyamine, or with an alcohol. Particularly
preferred dispersants are the reaction products of polyalkylene amines with
alkenyl succinic anhydrides. Examples of specifications disclosing dispersants
of
the last-mentioned type are US-A-3 202 678, 3 154 560, 3 172 892, 3 024 195,
3 024 237, 3 219 666, 3 216 936 and BE-A-662 875.
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Heavy duty diesel engine lubricating oil compositions tend to have a higher
amount of nitrogen, preferably derived from a dispersant, than passenger car
engine oil compositions because more oil-insoluble substances, such as soot,
are formed in heavy duty diesel engines. Accordingly, the nitrogen content, is
preferably at least 0.06, more preferably at least 0.08, such as at least
0.10,
especially at least 0.12, mass %, based on the mass of the oil composition.
The
amount of nitrogen, preferably derived frorn the dispersant, tends not to be
more
than 0.2 mass %. The amount of nitrogen is measured according to ASTM
1o D4629.
Alternatively or in addition, dispersancy may be provided by polymeric
compounds capable of providing viscosity index improving properties and
dispersancy, such compounds are known as a multifunctional viscosity index
ls improvers. Such polymers differ from conventional viscosity index improvers
in
that they provide performance properties, such as dispersancy and/or
antioxidancy, in addition to viscosity index improvement.
Dispersant olefin copolymers and dispersant polymethacrylates are examples of
20 multifunctional viscosity index improvers. Multifunctional viscosity index
improvers are prepared by chemically attaching various functional moieties,
for
example amines, alcohols and amides, onto polymers, which polymers preferably
tend to have a number average molecular weight of at least 15,000, such in the
range from 20,000 to 600,000, as determined by gel permeation chromatography
25 or light scattering methods. The polymers used may be those described above
with respect to viscosity modifiers. Therefore, amine molecules may be
incorporated to impart dispersancy and/or antioxidancy characteristics,
whereas
phenolic molecules may be incorporated to improve antioxidant properties. A
specific example, therefore, is an inter-polymer of ethylene-propylene post
30 grafted with an active monomer such as maleic anhydride and then
derivatized
with, for example, an alcohol or amine.
CA 02420514 2007-03-12
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EP-A-24146 and EP-A-0 854 904 describe examples of dispersants and
dispersant viscosity index improvers.
Rust inhibitors selected from the group consisting of nonionic polyoxyalkylene
polyols and esters thereof, polyoxyalkylene phenols, and anionic alkyl
sulfonic
acids may be used.
Antiwear agents, as their name implies, reduce wear of metal parts. Zinc
dihydrocarbyl dithiophosphates (ZDDPs) are very widely used as antiwear
1o agents. Examples of ZDDPs for use in oil-based compositions are those of
the
formula Zn[SP(S)(OR1)(OR2)]2 wherein R1 and R2 contain from 1 to 18, and
preferably 2 to 12, carbon atoms.
Sulfur- and molybdenum-containing compounds are also examples of anti-wear
ls additives. Also suitable are ashless phosphorus- and sulfur-containing
compounds.
Pour point depressants, otherwise known as lube oil flow improvers, lower the
minimum temperature at which the fluid will flow or can be poured. Such
2o additives are well known. Foam control may be provided by an antifoamant of
the polysiloxane type, for example, silicone oil or polydimethyl siloxane.
A small amount of a demulsifying component may be used. A preferred
demulsifying component is described in EP-A-0 330 522. It is obtained by
25 reacting an alkylene oxide with an adduct obtained by reacting a bis-
epoxide with
polyhydric alcohol.
Some of the above-mentioned additives may provide a multiplicity of effects;
thus
for example, a single additive may act as a dispersant-oxidation inhibitor.
This
3o approach is well known and need not be further elaborated herein.
CA 02420514 2003-02-27
-18-
Preferably an anti-wear additive, such a metal dihydrocarbyldithiophosphate,
for
example, zinc dihydrocarbyidithiophosphate, is present in the lubricating oil
compositions of the present invention.
> When lubricating compositions contain one or more of the above-mentioned
additives, including the detergents, each additive is typically blended into
the
base oil in an amount which enables the additive to provide its desired
function.
Representative effective amounts of such additives, when used in lubricants,
are
as follows:
Additive Mass % a.i.* Mass % a.i.*
(Broad) (Preferred)
Viscosity Modifier 0.01-6 0.01-4
Corrosion Inhibitor 0.01-5 0.01-1.5
Oxidation Inhibitor 0.01-5 0.01-1.5
Friction Reducer 0.01-5 0.01-1.5
Dispersant 0.1-20 0.1-8
Dispersant Viscosity Modifier 0.01 -5 0.05-5
Detergent 0.01-6 0.01-3
Anti-wear Agent 0.01-6 0.01-4
Pour Point Depressant 0.01-5 0.01-1.5
Rust Inhibitor 0.001-0.5 0.01-0.2
Anti-Foaming Agent 0.001-0.3 0.001-0.15
Demulsifier 0.001-0.5 0.01-0.2
* Mass % active ingredient based on the final lubricating oil composition.
The additives may be incorporated into an oil of lubricating viscosity (also
known
as a base oil) in any convenient way. Thus, each additive can be added
directly
to the oil by dispersing or dissolving it in the oil at the desired level of
concentration. Such blending may occur at ambient temperature or at an
elevated temperature. Typically an additive is available as an admixture with
a
base oil so that the handling thereof is easier.
CA 02420514 2003-02-27
-19-
When a plurality of additives are employed it may be desirable, although not
essential, to prepare one or more additive packages (also known as additive
compositions or concentrates) comprising additives and a diluent, which can be
a
base oil, whereby the additives, with the exception of viscosity modifiers,
s multifuntional viscosity modifiers and pour point depressants, can be added
simultaneously to the base oil to form the lubricating oil composition.
Dissolution
of the additive package(s) into the oil of lubricating viscosity may be
facilitated by
diluent or solvents and by mixing accompanied with mild heating, but this is
not
essential. The additive package(s) will typically be formulated to contain the
io additive(s) in proper amounts to provide the desired concentration in the
final
formulation when the additive package(s) is/are combined with a predetermined
amount of oil of lubricating viscosity. Thus, one or more detergents may be
added to small amounts of base oil or other compatible solvents (such as a
carrier oil or diluent oil) together with other desirable additives to form
additive
1s packages containing from 2.5 to 90, preferably from 5 to 75, most
preferably from
8 to 60, mass %, based on the mass of the additive package, of additives on an
active ingredient basis in the appropriate proportions. The final formulations
may
typically contain 5 to 40 mass % of the additive package(s), the remainder
being
oil of lubricating viscosity.
The amount of additives in the final lubricating oil composition is generally
dependent on the type of the oil composition, for example, a heavy duty diesel
engine lubricating oil composition has 2 to 20, preferably 5 to 18, more
preferably
7 to 16, such as 8 to 14, mass % of additives, based on the mass of the oil
composition.
Thus, a method of preparing the oil composition according to the present
invention can involve admixing an oil of lubricating viscosity and one or more
additives or an additive package that comprises one or more of the additives.
A means of increasing the power output of an engine, particularly a
compression-
ignited engine, is to include a turbocharger in its assembly. The turbo-
charger
CA 02420514 2003-02-27
-20-
enables more fuel to be burnt per given cylinder size by pressurising the
intake
air so that more air is charged to the cylinder.
Turbo-chargers are typically powered by the gas expelled through the exhaust,
and this can lead to a loss of efficiency of the turbo-charger during the life-
time of
the engine because species contained in the exhaust gas deposit within the
turbo-charger. It has been also discovered that lubricating oil compositions
of the
present invention can minimise the loss of efficiency of a turbo-charger. A
method of determining the loss of efficiency is, for example, the OM441 LA
test,
io where a boost pressure loss, as a percent, is given: the higher the boost
pressure loss the greater the loss of efficiency.
CA 02420514 2003-02-27
-21-
Examples
Lubricating oil compositions, identified herein as Examples A to D and
Examples
1 to 4, were blended by methods known in the art at comparable TBN from oils
of
lubricating viscosity and additive concentrates. Examples A to D are
comparative
and Examples 1 to 4 are of the invention. Table 1 shows details of the oil of
lubricating viscosity used and the physical properties of the resulting oil
compositibns. Comparative Example A was blended to a SAE 15W40
viscometric grade, whereas comparative Examples B to D and Examples 1 to 4
io were blended to an SAE 10W40 viscometric grade.
Comparative Examples A to D and Examples 1 to 4 were tested for piston
cleanliness and boost pressure loss in the OM441 LA test, according to the CEC-
L-52-T-97 procedure. The results are also given in Table 1.
Table 1 shows that Example A, a SAE 15W40 lubricating oil composition,
provided better piston cleanliness and boost pressure loss than Example B, an
oil
composition containing the same additives as those in Example A but blended to
a SAE 10W40 viscometric grade.
Further, the results in Table 1 show that the piston cleanliness and boost
pressure loss are improved as the proportion of Group III basestock is
increased
in an SAE 10W40 oil composition (see Example B through to Example 4).
ACEA E5-99 performance specification sets a passing limit of at least 25
merits
points for piston cleanliness and at most 4 % for boost pressure loss.
Accordingly, at least about 35 mass % of a Group III basestock in an oil of
lubricating viscosity may be required to meet the limits set by ACEA E5-99 in
respect of the piston cleanliness and boost pressure loss.
CA 02420514 2003-02-27
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