Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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LUBRICATING OIL COMPOSITION
The present invention relates to improved additive and lubricating oil
compositions, such
as multigrade lubricants, particularly those demonstrating better piston
cleanliness.
Lubricating oil compositions (or lubricants) for the crankcase of internal
combustion
engines are well-known and it is also well-known for them to contain additives
(or
additive components) to enhance their properties and performance.
Environmental concerns have led to continued efforts to reduce the particulate
emissions
of vehicular internal combustion engines, particularly compression ignited
(diesel)
internal combustion engines. One technology being used to reduce particulate
emissions
of diesel engines is the particulate trap, which is to be incorporated into
all passenger car
and heavy duty diesel vehicles designed to comply with the requirements of
Euro IV
emissions legislation. When lubricant is consumed during use in the engine,
ash derived
2o from metal-containing additives in the lubricant, primarily from metal-
containing
detergents and antiwear agents, accumulate in the particulate trap. This ash
cannot be
purged without removing the trap from the engine and cleaning either via
washing or
blowing the ash from the particulate trap with compressed air. Ash allowed to
accumulate in the particulate trap may cause an increase in pressure behind
the trap (back
pressure). If this back pressure becomes severe, internal exhaust gas
recirculation may
occur with a resulting loss of fuel economy and eventual engine failure.
Because
lubricants require acid neutralization (provided by detergents), and to a
lesser extent wear
protection (provided by ZDDP), metal-containing additives that form ash upon
use in
engines cannot simply be removed. The drive to lower sulfated ash in
lubricants affects
3o at least the available detergents, particularly overbased detergents, that
can be included,
which consequently impacts on piston cleanliness, particularly in high
temperature diesel
engines. High temperature piston cleanliness in diesel engines may measured by
the
VWTDi test (according to CEC L-78-T-99 procedure). This test also provides an
indication of the degree of sticking of the piston rings (referred to as "ring-
sticking").
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Thus, the formulators have to carefully control the choice and amount of
additives and
basestock in a lubricating oil composition to achieve the required performance
whilst
satisfying the limits set by governmental and automotive bodies.
US-A-5,102,566 describes low sulphated ash lubricating oil compositions, which
contain
ashless dispersants, oil-soluble anti-oxidants and oil-soluble
dihydrocarbyldithiophosphates.
EP-A-1167497 describes a lubricating oil composition having low P content, low
sulphated ash content and low sulphur content.
EP-A-1 266 955 describes using an ester basestock to improve the piston
cleanliness
properties. While EP-A-1 087 008 describes a way of improving "ring-sticking"
performance by provision of molybdenum-containing additive components to the
lubricating oil composition.
However, Applicants have now surprisingly found that the combination of an
increased
amount of soap and an increased amount of dispersant provides improved piston
cleanliness in lubricating oil compositions having at most 1.0 mass %
sulphated ash.
Accordingly, in a first aspect, the present invention provides a lubricating
oil composition
comprising, or made by admixing, a major amount of an oil of lubricating
viscosity, and
minor amounts of (A) a dispersant additive composition and (B) a detergent
additive
composition, wherein the oil composition gives a sulfated ash content of at
most 1.0, such
3o as in the range 0.3 to 0.9, preferably 0.5 to 0.7, mass %; has a total base
number (TBN) of
4 to 9.5, such as S to 9, preferably 6 to 8.5; has at least 0.08, for example,
0.085 to 0.115,
preferably 0.09 to 0.10, mass % of nitrogen derived from the dispersant
additive
composition, based on the mass of the oil composition; and has at least 25,
especially at
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least 28 or 30, such as at most 35, millimoles (mmol) of soap per 1000 g of
the oil
composition derived from the detergent additive composition.
The data contained in the specification demonstrate that the use of the
increased amounts
of soap and dispersant unexpectedly improves the performance of lubricating
oil
compositions that give less than 1.0 mass % of ash. Further, a preferred ratio
of the
amount of (A) a dispersant additive composition, based on ppm of nitrogen, in
the
lubricating oil composition to the amount of (B) a detergent additive
composition, based
on mmol of soap per 1000g of the oil composition, in the lubricating oil
composition is
from 22:1 to 46:1, especially from 25:1 to 40:1, such as 27:1 to 30:1. This
allows for
controlling the debits associated with dispersant additives (e.g. degradation
of elastomer
seals) and detergent additives, especially salicylate-based additives (e.g.
ability to control
soot).
In a second aspect, the present invention provides a method of lubricating a
compression-
ignited internal combustion engine comprising operating the engine and
lubricating the
engine with a lubricating oil composition of the first aspect.
In a third aspect, the present invention provides a method of improving piston
cleanliness
and reducing the ring-sticking tendencies of a compression-ignited internal
combustion
engine comprising adding to the engine a lubricating oil composition of the
first aspect.
In a fourth aspect, the present invention provides a combination comprising
the crankcase
of a compression-ignited internal combustion engine, preferably having a
specific power
output of 25 kW/ litre or greater, and a lubricating oil composition of the
first aspect.
In a fifth aspect, the present invention provides the use of (1) a dispersant
additive
composition in an amount that provides at least 0.085 mass % of nitrogen and
(2) a
detergent additive composition in an amount that provides at least 25 mmol of
soap per
1000 g of the oil composition, in a lubricating oil composition, which oil
composition
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gives a sulfated ash of most 1.0 mass % and has a TBN of 4 to 9.5, to improve
the piston
cleanliness in an internal combustion engine.
In a sixth aspect, the present invention provides an additive concentrate for
preparing a
lubricating oil composition comprising an oleaginous Garner fluid, a
dispersant additive
1o composition and a detergent additive composition, in such a proportion as
to provide a
lubricating oil composition as defined in the first aspect when the oil
composition
contains 10 or 13.5 to 30, preferably 16 to 27, such as 18 to 25, mass %,
based on the
mass of the oil composition, of additives, said additives excluding viscosity
modifier and
pour point depressant additives.
The features of the invention will now be discussed in more detail as follows:
Lubricating Oil Composition
The lubricating oil compositions of the present invention are for lubricating
the crankcase
of an internal combustion engine, preferably a compression-ignited (diesel)
engine, more
preferably a compression-ignited passenger vehicle engine. Crankcase
lubricating oil
compositions for a diesel application, in particular for passenger vehicles,
have to be
specifically formulated to meet the performance requirements in such an
application.
It is preferred that lubricating oil compositions of the invention are
multigrade oil
compositions having a viscometric grade of SAE SW-X or SAE OW-X, where X
represents 20 and 30; the characteristics of the different grades can be found
in the SAE
J300 classification.
3o In another embodiment of the present invention, the lubricating oil
compositions of the
first aspect have a NOACK volatility of at most 15, such as less than 13,
preferably less
than 11, mass %, as determined according to CEC L-40-A-93. The NOACK
volatility of
the lubricating oil composition is generally not less than 4, such as not less
than 5.
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Further, the lubricating oil compositions of the invention preferably have
less than 0.09,
such as less than 0.08, preferably 0.01 to 0.07, in particular 0.03 to 0.06,
mass % of
phosphorus, preferably derived from one or more zinc dithiophosphate
additives, based
on the mass of the oil composition.
Independently of the other embodiments, the sulfur content of lubricating oil
compositions of the invention is preferably at most 0.25, more preferably at
most 0.2,
such as 0.05 to 0.15, mass %, based on the mass of the oil composition.
The lubricating oil composition may also have a molybdenum content of at most
300,
preferably in the range 10 to 200, especially 50 to 175, ppm by mass, based on
the mass
of the oil composition.
Also, a boron-containing additive may be present in the lubricating oil
composition. In
such an event, the amount of boron in the oil composition is preferably at
most 150,
2o preferably in the range 10 to 100, especially 25 to 75, ppm by mass, based
on the mass of
the oil composition.
The amount of phosphorus, sulfur, molybdenum and boron are determined
according to
method ASTM DS 185; "TBN" is Total Base Number as measured by ASTM D2896; the
amount of nitrogen is determined according to method ASTM D4629; and sulfated
ash is
measured according to method ASTM D874.
The lubricating oil composition preferably satisfies at least the performance
requirements
of ACEA B2-98, more preferably at least the ACEA B 1-98, such as at least the
ACEA
B3-98, especially at least the ACEA B4-98, for light duty diesel engines.
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 an
additive
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concentrate or additive package, and (b) any oil present in an additive
concentrate or
additive package.
The oil lubricating viscosity can be a synthetic or mineral oil selected from
the group
consisting of Group I, II, III, N and V basestocks, and any mixtures thereof.
0
Basestocks may be made using a variety of different processes including but
not limited
to distillation, solvent refining, hydrogen processing, oligomerization,
esterification, and
rerefining.
American Petroleum Institute (API) 1509 "Engine Oil Licensing and
Certification
System" Fourteenth Edition, December 1996 states that all basestocks are
divided into
five general categories:
Group I basestocks contain less than 90% saturates and/or greater than 0.03%
sulfur and
2o have a viscosity index greater than or equal to 80 and less than 120;
Group II 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 120;
Group IV basestocks are polyalphaolefins (PAO); and
3o Group V basestocks contain all other basestocks not included in Group I,
II, III or IV.
Group IV basestocks, i.e. polyalphaolefins (PAO), are generally hydrogenated
oligomers
of an alpha-olefin, the most important methods of oligomerization being free
radical
processes, Ziegler catalysis, cationic, and Friedel-Crafts catalysis.
CA 021487767 2004-11-18
Group V basestocks in the form of esters are preferred and also tend to be
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 phthalate
esters, i.e. 1,2 -
o benzene dicarboxylates. The acids from which the esters are made are
preferably
monocarboxylic acids of the formula RC02H where R represents a branched,
linear or
mixed alkyl group. Such acids may, for example, contain 6 to 18 carbon atoms.
Preferably the oil of lubricating viscosity is selected from any one of Group
I to V
basestocks and any mixture thereof, provided that the oil contains at most
0.1, such as at
most 0.05, more preferably 0.005 to 0.03, mass % of sulfur, based on the mass
of the oil.
Especially preferred is an oil of lubricating viscosity comprising a Group III
basestock,
advantageously in an amount of at least 20, such as at least 40, more
preferably in the
2o range from 55 to 90, mass %, based on the mass of the oil composition.
In a preferred embodiment, the oil of lubricating viscosity comprises a Group
1T1
basestock and a Group V basestock in the form of an ester. The amount of Group
V
basestock in the form of an ester is preferably at most 15, such as 0.5 to 15,
more
preferably 1 or 2 to 15, especially 3 to 15, more especially 3 to 10,
advantageously 3 to 8,
such as 5 to 8, mass %, based on the mass of the oil composition. Group I,
Group II or
Group N basestock or any mixture thereof may also be present, in a minor
amount, in the
oil of lubricating viscosity as a diluent or Garner fluid for the additive
components and
additive concentrates) used in preparing the lubricating oil compositions of
the invention.
More preferably, the oil of lubricating viscosity consists essentially of
Group III
basestocks and Group V basestocks in the form of an ester, but may contain
minor
amounts, such as at most 25, such as at most 20, preferably at most 10,
advantageously at
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most 5, mass %, based on the mass of the total basestock, of other basestocks,
such as
Group I, Group II or Group IV basestock or any mixture thereof.
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
l0 sulfur.
Dispersant Additive Composition
Dispersants (or dispersant additives), such as ashless (i.e. metal-free)
dispersants hold
solid and liquid contaminants, resulting from oxidation during use, in
suspension and thus
15 preventing sludge flocculation and precipitation or deposition on metal
parts; they
comprise long-chain hydrocarbons, to confer oil-solubility, with a polar head
capable of
associating with particles to be dispersed. A noteworthy group is hydrocarbon-
substituted
succinimides.
20 Generally, ashless dispersants 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. "Substantially no ash" means that
the
dispersant may give trace amounts of ash on combustion, but amounts which do
not have
practical or significant effect on the performance of the dispersant.
A dispersant additive composition may contain one or more dispersants.
The ashless, dispersants of the present invention comprise an oil soluble
polymeric long
chain backbone having functional groups capable of associating with particles
to be
3o dispersed. Typically, such dispersants have amine, amine-alcohol or amide
polar moieties
attached to the polymer backbone, often via a bridging group. The ashless
dispersant may
be, for example, selected from oil soluble salts, esters, amino-esters,
amides, imides and
oxazolines of long chain hydrocarbon-substituted mono- and polycarboxylic
acids or
anhydrides thereof; thiocarboxylate derivatives of long chain hydrocarbons;
long chain
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aliphatic hydrocarbons having polyamine moieties attached directly thereto;
and Mannich
condensation products formed by condensing a long chain substituted phenol
with
formaldehyde and polyalkylene polyamine. 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 5,000; examples of such derivatives being derivatives of high
molecular
weight hydrocarbyl-substituted succinic acid. Such hydrocarbyl-substituted
carboxylic
acids may be derivatised with, for example, a nitrogen-containing compound,
advantageously a polyalkylene polyamine or amine-alcohol or amide or ester.
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.
The dispersant may comprise a polyisobutenyl succinimide prepared using high
2o vinylidene polyisobutene (PIB), for example one in which greater than 80%
of the
terminal olefin groups have only hydrogen moieties. The total chlorine content
of the oil
composition of the present invention when such dispersants are used should be
below 50
ppm as measured by XRF.
The dispersant(s) of the present invention are preferably non-polymeric (e.g.
are mono- or
bis-succinimides).
The dispersant(s) of the present invention may optionally be borated. Such
dispersants
can be borated by conventional means, as generally taught in U.S. Patent Nos.
3,087,936,
3,254,025 and 5,430,105. Boration of the dispersant is readily accomplished by
treating
an acyl nitrogen-containing dispersant with a boron compound such as boron
oxide, boron
halide boron acids, and esters of boron acids, in an amount sufficient to
provide from
about 0.1 to about 20 atomic proportions of boron for each mole of acylated
nitrogen
composition.
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An ashless succinimide or a derivative thereof, obtainable from a
polyisobutenylsuccinic
anhydride produced from polybutene and malefic anhydride by a thermal reaction
method
using neither chlorine nor a chlorine atom-containing compound, is a preferred
dispersant.
to
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 dispersant viscosity index improver additive or a
multifunctional viscosity index improver. Such polymers differ from
conventional
15 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
dispersant viscosity index improver additives. Dispersant viscosity index
improver
2o additives are prepared by chemically attaching various functional moieties,
for example
amines, alcohols and amides, on to 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 or light scattering
methods.
The polymers used may be those described below with respect to viscosity
modifiers.
25 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 grafted with an active monomer such as malefic anhydride and
then
derivatized with, for example, an alcohol or amine. In the event a dispersant
viscosity
30 modifier is used in the present invention, the nitrogen content of the
lubricating oil
composition also includes that derived from the dispersant viscosity modifier.
An
example of a dispersant viscosity modifier is Hitec~ 5777, which is
manufactured and
sold by Ethyl Coip.
't
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EP-A-24146 and EP-A-0 854 904 describe examples of dispersants and dispersant
viscosity index improvers, which are accordingly incorporated herein.
Advantageously, the dispersant additive composition contains one or more
dispersants,
preferably a borated and non-borated dispersant.
Detergent Additive Composition
A detergent (or detergent additive) reduces formation of piston deposits, for
example
high-temperature varnish and lacquer deposits, by keeping finely divided
solids in
suspension in engines; it may also have acid-neutralising properties. A
detergent
comprises metal salts of organic acids, which are referred herein as soaps or
surfactants.
A detergent has a polar head, i.e. the metal salt of the organic acid, with a
long
hydrophobic tail for oil solubility. Therefore, the organic acids typically
have one or
more functional groups, such as OH or COOH or S03H, for reacting with a metal,
and a
hydrocarbyl substituent. A detergent may be overbased, in which case the
detergent
contains an excess of metal in relation to the stoichiometric quantity needed
for the
neutralisation of the organic acid. This excess is in the form of a colloidal
dispersion,
typically metal carbonate and/or hydroxide, with the metal salts of organic
acids in a
micellar structure.
Examples of organic acids include sulfonic acids, phenols and sulfurised
derivatives
thereof, and carboxylic acids including aromatic carboxylic acids.
Phenols may be non-sulfurized or, preferably, sulfurized. Further, the term
"phenol" as
used herein includes phenols containing more than one hydroxyl group (for
example,
alkyl catechols) or fused aromatic rings (for example, alkyl naphthols) and
phenols which
have been modified by chemical reaction, for example, alkylene-bridged phenols
and
Mannich base-condensed phenols; and saligenin-type phenols (produced by the
reaction
of a phenol and an aldehyde under basic conditions).
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Preferred phenols are of the formula
OH
/~
(R)y
where R represents a hydrocarbyl group and y represents 1 to 4. Where y is
greater than
l0 1, the hydrocarbyl groups may be the same or different.
The phenols are frequently used in sulfurized form. Details of sulfurization
processes are
known to those skilled in the art, for example, see US-A-4,228,022 and US-A-
4,309,293.
In the above formula, hydrocarbyl groups represented by R are advantageously
alkyl
groups, which advantageously contain 5 to 100, preferably 5 to 40, especially
9 to 12,
carbon atoms, the average number of carbon atoms in all of the R groups being
at least
about 9 in order to ensure adequate solubility in oil. Preferred alkyl groups
are nonyl
(e.g., tripropylene) groups or dodecyl (e.g., tetrapropylene) groups.
As indicated above, the term "phenol" as used herein includes phenols which
have been
modified by chemical reaction with, for example, an aldehyde, and Mannich base-
condensed phenols.
Aldehydes with which phenols may be modified include, for example,
formaldehyde,
propionaldehyde and butyraldehyde. The preferred aldehyde is formaldehyde.
Aldehyde-
modified phenols suitable for use in accordance with the present invention are
described
in, for example, US-A-5 259 967 and WO 01/74751.
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Mannich base-condensed phenols are prepared by the reaction of a phenol, an
aldehyde
and an amine. Examples of suitable Mannich base-condensed phenols are
described in
GB-A-2 121432.
In general, the phenols may include substituents other than those mentioned
above.
1o Examples of such substituents are methoxy groups and halogen atoms.
A preferred phenol is a sulfurised derivative thereof.
Sulfonic acids are typically obtained by sulfonation of hydrocarbyl-
substituted, especially
15 alkyl-substituted, aromatic hydrocarbons, for example, those obtained from
the
fractionation of petroleum by distillation and/or extraction, or by the
alkylation of
aromatic hydrocarbons. The alkylaryl sulfonic acids usually contain from about
22 to
about 100 or more carbon atoms. The sulfonic acids may be substituted by more
than one
alkyl group on the aromatic moiety, for example they may be dialkylaryl
sulfonic acids.
20 Preferably the sulfonic acid has a number average molecular weight of 350
or greater,
more preferably 400 or greater, especially 500 or greater, such as 600 or
greater. Number
average molecular weight may be determined by ASTM D3712.
Another type of sulfonic acid which may be used in accordance with the
invention
25 comprises alkyl phenol sulfonic acids. Such sulfonic acids can be
sulfurized.
Carboxylic acids include mono- and dicarboxylic acids. Preferred
monocarboxylic acids
are those containing 8 to 30, especially 8 to 24, carbon atoms. (Where this
specification
indicates the number of carbon atoms in a carboxylic acid, the carbon atoms)
in the
30 carboxylic groups) is/are included in that number). Examples of
monocarboxylic acids
are iso-octanoic acid, stearic acid, oleic acid, palmitic acid and behenic
acid. Iso-octanoic
acid may, if desired, be used in the form of the mixture of C8 acid isomers
sold by Exxon
Chemical under the trade name "Cekanoic". Other suitable acids are those with
tertiary
substitution at the a-carbon atom and dicarboxylic acids with 2 or more carbon
atoms
CA 02487767 2004-11-18
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separating the carboxylic groups. Further, dicarboxylic acids with more than
35 carbon
atoms, for example, 36 to 100 carbon atoms, are also suitable. Unsaturated
carboxylic
acids can be sulfurized.
A preferred type of carboxylic acid is an aromatic carboxylic acid. The
aromatic moiety
of the aromatic carboxylic acid can contain heteroatoms, such as nitrogen and
oxygen.
Preferably, the moiety contains only carbon atoms; more preferably the moiety
contains
six or more carbon atoms; for example benzene is a preferred moiety. The
aromatic
carboxylic acid may contain one or more aromatic moieties, such as one or more
benzene
rings, either fused or connected via alkylene bridges.
The carboxylic moiety may be attached directly or indirectly to the aromatic
moiety.
Preferably the carboxylic acid group is attached directly to a carbon atom on
the aromatic
moiety, such as a carbon atom on the benzene ring.
2o More preferably, the aromatic moiety also contains a second functional
group, such as a
hydroxy group or a sulfonate group, which can be attached directly or
indirectly to a
carbon atom on the aromatic moiety.
Preferred examples of aromatic carboxylic acids are salicylic acids and
sulfurised
derivatives thereof, such as hydrocarbyl substituted salicylic acid and
derivatives thereof.
Processes for sulfurizing, for example a hydrocarbyl-substituted salicylic
acid, are known
to those skilled in the art.
3o Salicylic acids are typically prepared by carboxylation, for example, by
the Kolbe-Schmitt
process, of phenoxides, and in that case, will generally be obtained, normally
in a diluent,
in admixture with uncarboxylated phenol.
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Preferred substituents for oil-soluble salicylic acids are alkyl substituents.
In alkyl-
substituted salicylic acids, the alkyl groups advantageously contain 5 to 100,
preferably 9
to 30, especially 14 to 20, carbon atoms. Where there is more than one alkyl
group, the
average number of carbon atoms in all of the alkyl groups is preferably at
least 9 to ensure
adequate oil-solubility.
to
The metal detergent may be neutral or overbased; such terms are known in the
art. A
detergent additive composition may comprise one or more detergent additives,
which can
be a neutral detergent, an overbased detergent or a mixture of both.
15 Total Base Number (TBN) of detergents range from 15 to 600.
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.
2o A hybrid complex detergent is a detergent in which the basic material, e.g.
colloidal metal
carbonate, within the detergent is stabilised by metal salts of 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
25 organic acid composition is considered as one type. Thus, complex
detergents are
distinguished from mixtures of two or more separate detergents, an example of
such a
mixture being one of an overbased calcium salicylate detergent with an
overbased
calcium phenate detergent.
3o The art describes examples of overbased complex detergents. For example,
International
Patent Application Publication Nos. WO 97/46643/4/5/6 and 7, which are
incorporated
herein in respect of the description and definition of the hybrid complex
detergents,
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.
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Individual basic material 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.
to 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"
A detergent additive composition may contain two or more detergents, for
example, an
15 alkali metal, such as sodium, detergent, and an alkaline earth metal, such
as calcium
and/or magnesium, detergent. For the avoidance of doubt, the detergent
additive
composition may also comprise an ashless detergent, i.e. a non-metal
containing
detergent, typically in the form of an organic salt of an organic acid, in
which case the
soap corresponds to the salt of the organic acid and the soap derived from
such a
20 detergent also contributes to the amount of defined soap in the lubricating
oil composition
of the present invention. The detergents are preferably metal containing and
Group 1 and
Group 2 metals are preferred as metals in the detergents, more preferably
calcium and
magnesium, especially calcium.
25 Preferably the detergent composition comprises at least one overbased metal
detergent,
irrespective of whether the detergent contains metal salts of one type of
organic acid or
metal salts of more than one type of organic acid.
Detergent additive compositions comprising, preferably consisting essentially
of, at least
30 one metal detergent based on one or more organic acids not containing
sulfur, e.g.,
carboxylic acid, salicylic acid, alkylene bridged phenols and Mannich base-
condensed
phenol, are preferred. Especially, salicylate-based detergent have been found
to
particularly effective. Therefore, s detergent additive composition comprising
only
CA 02487767 2004-11-18
-17-
metal, preferably calcium, salicylate-based detergents, whether neutral or
overbased, are
advantageous, such as an overbased calcium salicylate.
The detergent additive composition preferably contains two or more detergents,
preferably at least one detergent having a TBN greater than 150 and at least
one detergent
1o having a TBN of at most 150.
Preferably at most 35, such as 5 to 30, preferably 10 to 25, % of the mmol of
soap is
derived from one or more detergents having a TBN greater than 150.
Applicant has found that a detergent additive composition consisting of a
calcium
salicylate having a TBN of 150 to 200 and a calcium salicylate having a TBN of
at most
80 is preferred. Preferably the amount of the calcium salicylate having a TBN
of 150 to
200 in the detergent additive composition is such as to contribute at most 35,
such as 5 to
30, preferably 10 to 25, % of the mmol of soap per 1000 g of the oil
composition to the
lubricating oil composition
In another embodiment, a detergent additive composition consisting of at least
one metal
salicylate, preferably a calcium salicylate, more preferably a calcium
salicylate having a
TBN of at most 150, such as at most 100, preferably at most 80, is
particularly effective
for high temperature piston cleanliness.
In the instance where a composition comprises a detergent and one or more co-
additives,
then the detergent may be separated from the co-additives, for example, by
using dialysis
techniques and then the detergent may be analysed as described above to
determine the
metal ratio. Background information on suitable dialysis techniques is given
by Amos, R.
and Albaugh, E. W. in "Chromatography in Petroleum Analysis" Altgelt, K. H.
and
Gouw, T. H., Eds., pages 417 to 421, Marcel Dekker Inc., New York and Basel,
1979.
CA 02487767 2004-11-18
-I8-
Means for determining the amount of soap are known to those skilled in the
art. EP-A-0
876 449 describes methods for determining the number of moles of a calcium
salt of an
organic acid, which disclosure is incorporated herein.
A skilled person can also calculate the amount of soap in the final
lubricating oil
1o composition from information concerning the raw materials (e.g. amount and
type of
organic acids) used to make the detergents) and from information concerning
the amount
of detergents) used in the final oil composition. Analytical methods (e.g.
potentiometric
titration and chromatography) can also be used to determine the amounts of
soap.
It will be appreciated by a skilled person in the art that the methods to
determine the
amount of metal salts of organic acids (also known as soap) 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.
2o Additive concentrate
An additive concentrate constitutes a convenient means of handling two or more
additives
before their use, as well as facilitating solution or dispersion of the
additives in lubricant
compositions. When preparing a lubricant composition that contains more than
one type
of additive (sometimes referred to as "additive components"), each additive
may be
incorporated separately. In many instances, however, it is convenient to
incorporate the
additives as an additive concentrate (a so-called additive "package" (also
referred to as an
"adpack")) comprising two or more additives.
In the preparation of the lubricant oil compositions, it is common practice to
introduce
3o additives therefore in the form of additive concentrates) containing the
additives. When
a plurality of additives are employed it may be desirable, although not
essential, to
prepare one or more additive concentrates (also known as additive packages)
comprising
the additives, whereby several additives, with the exception generally of
viscosity
modifiers, multifuntional viscosity modifiers and pour point depressants, can
be added
CA 02487767 2004-11-18
-19-
simultaneously to the oil of lubricating viscosity to form the lubricating oil
composition.
Dissolution of the additive concentrates) into the lubricating oil may be
facilitated by
diluent or solvents and by mixing accompanied with mild heating, but this is
not
essential. The additive concentrates) will typically be formulated to contain
the
additives) in proper amounts to provide the desired concentration in the final
formulation
1o when the additive concentrates) is/are combined with a predetermined amount
of oil of
lubricating viscosity. If required, the viscosity modifiers, multifuntional
viscosity
modifiers and pour point depressants are then separately added to form a
lubricating oil
composition.
Examples of other additives include rust inhibitors, anti-wear agents, anti-
oxidants,
corrosion inhibitors, friction modifiers, pour point depressants, anti-foaming
agents,
viscosity modifiers and surfactants.
An additive concentrate may contain 1 to 90, such as 10 to 80, preferably 20
to 80, more
2o preferably 40 to 70, mass % based on active ingredient, of the additives,
the remainder
being an oleaginous carrier or diluent fluid (for example, an oil of
lubricating viscosity).
The final lubricating oil composition may typically contain 5 to 40 mass % of
the additive
concentrate(s).
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 preferably has 10 to 40, more preferably 15 to 35, such as 25 to
30, mass %
of additives (including any diluent fluid), based on the mass of the oil
composition. A
passenger car engine lubricating oil composition, for example, a gasoline or a
diesel
3o engine oil composition, tends to have a lower amount of additives, for
example 10 or 13.5
to 30, preferably 16 to 27, such as 18 to 25, mass % of additives, based on
the mass of the
oil composition. The amounts expressed above exclude viscosity modifier and
pour
point depressant additives.
CA 02487767 2004-11-18
-20-
Generally the viscosity of the additive concentrate is higher than that of the
lubricating oil
composition. Typically, the kinematic viscosity at 100 °C of the
additive concentrate is at
least 50, such as in the range 100 to 200, preferably 120 to 180, mmzs~l (or
cSt).
Thus, a method of preparing a lubricating oil composition according to the
present
invention can involve admixing an oil of lubricating viscosity and one or more
of
additives or additive concentrates that comprises two or more of additives and
then,
admixing other additive components, such as viscosity modifier, a
multifunctional
viscosity modifier and pour point depressant.
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
temperatures.
Suitable compounds for use as viscosity modifiers are generally high molecular
weight
hydrocarbon polymers, e.g., polyisobutylene, copolymers of ethylene and
propylene and
higher alpha-olefins; polyesters, such as polymethacrylates; hydrogenated
poly(styrene-
co-butadiene or -isoprene) polymers and modifications (e.g., star polymers);
and
esterified polystyrene-co-malefic 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. The disclosure in Chapter 5 of
"Chemistry
& Technology of Lubricants", edited by R.M. Mortier and S.T. Orzulik, First
edition,
1992, Blackie Academic & Professional, is incorporated herein. The VM used may
have
that sole function, or may be multifunctional.
3o Friction modifiers include boundary additives that lower friction
coefficients and hence
improve fuel economy. Examples are oil soluble amines, amides, imidazolines,
amine
oxides, amidoamines, nitriles, alkanolamides, alkoxylated amines and ether
amines and
polyol esters, esters of polycarboxylic acids and include glycerol monoesters
of higher
fatty acids, for example glycerol mono-oleate; butane diol esters of dimerized
unsaturated
CA 02487767 2004-11-18
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s fatty acids; oxazoline compounds; and ethoxylated tallow amine and
ethoxylated tallow
ether amine. Molybdenum-containing compounds are also examples of friction
modifiers. Conventionally, one or more organic friction modifiers are used in
an amount
of 0.1 to 0.5, such as 0.2 to 0.4, mass %, based on the mass of the oil
composition.
Anti-wear agents reduce friction and excessive wear and are usually based on
compounds
containing sulfur or phosphorus or both. Dihydrocarbyl dithiophosphate metal
salts are
frequently used as anti-wear and antioxidant agents. The metal may be an
alkali or
alkaline earth metal, or aluminum, lead, tin, molybdenum, manganese, nickel or
copper.
The zinc salts (ZDDP) are most commonly used in lubricating oil in amounts of
0.1 to 10,
1s preferably 0.2 to 2 wt.%, based upon the total weight of the lubricating
oil composition.
They may be prepared in accordance with known techniques by first forming a
dihydrocarbyl dithiophosphoric acid (DDPA), usually by reaction of one or more
alcohol
or a phenol with PISS and then neutralizing the formed DDPA with a zinc
compound.
For example, a dithiophosphoric acid may be made by reacting mixtures of
primary and
secondary alcohols having 1 to 18, preferably 2 to 12, carbon atoms.
Alternatively,
multiple dithiophosphoric acids can be prepared where the hydrocarbyl groups
on one are
entirely secondary in character and the hydrocarbyl groups on the others are
entirely
primary in character. To make the zinc salt any basic or neutral zinc compound
could be
used but the oxides, hydroxides and carbonates are most generally employed.
2s Commercial additives frequently contain an excess of zinc due to use of an
excess of the
basic zinc compound in the neutralization reaction.
ZDDP provides excellent wear protection at a comparatively low cost and also
functions
as an antioxidant. Preferably a zinc dithiophosphate composition comprising
one or more
3o zinc dithiophosphate, which composition especially contains a mixture of
primary and
secondary alkyl groups, wherein the secondary alkyl groups are in a major
molar
proportion, such as at least 60, advantageously at least 75, more especially
at least 85,
mole %, based on the amount of alkyl groups, is useful in the present
invention.
CA 02487767 2004-11-18
-22-
Preferably a zinc dithiophosphate composition has 90 mole % secondary alkyl
groups and
mole % primary alkyl groups.
Anti-oxidants increase the composition's resistance to oxidation and may work
by
combining with and modifying peroxides to render them harmless by decomposing
1o peroxides or by rendering an oxidation catalyst inert. They may be
classified as radical
scavengers (e.g. sterically hindered phenols, secondary aromatic amines, and
organo-
copper salts); hydroperoxide decomposers (e.g. organo-sulfur and
organophosphorus
additives); and multifunctionals. Such anti-oxidants (or oxidation inhibitors)
include
hindered phenols, aromatic amine compounds, alkaline earth metal and metal-
free
alkylphenolthioesters having preferably CS to C12 alkyl side chains, ashless
alkylene
bridged phenols, phosphosulfurized and sulfurized hydrocarbons, phosphorous
esters,
metal and metal-free thiocarbamates & derivatives thereof, oil soluble copper
compound
as described in U.S. 4,867,890, and molybdenum containing compounds. In the
practice
of the present invention, the use or otherwise of certain anti-oxidants may
confer certain
2o benefits. For example, in one embodiment it is preferred that an anti-
oxidant composition
comprising a secondary aromatic amine and a hindered phenol with an ester
group is
used.
Preferably an antioxidant composition comprising an aromatic amine, such as
diphenylamine and a hindered phenol compound, such as 3,5-bis(alkyl)-4-
hydroxyphenyl
carboxylic acid esters, e.g. IRGANOX~ L135 as sold by Ciba Speciality
Chemicals, is
useful. Usually, one or more antioxidants are used in an amount of 0.1 to 0.8,
such as 0.2
to 0.6, preferably 0.3 to 0.5, mass %, based on the mass of the oil
composition.
3o The molybdenum-containing compounds, preferably molybdenum-sulfur
compounds,
useful in the present invention may be mononuclear or polynuclear. In the
event that the
compound is polynuclear, the compound contains a molybdenum core consisting of
non-
metallic atoms, such as sulfur, oxygen and selenium, preferably consisting
essentially of
sulfur.
CA 02487767 2004-11-18
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To enable the molybdenum-sulfur compound to be oil-soluble or oil-dispersible,
one or
more ligands are bonded to a molybdenum atom in the compound. The bonding of
the
ligands includes bonding by electrostatic interaction as in the case of a
counter-ion and
forms of bonding intermediate between covalent and electrostatic bonding.
Ligands
within the same compound may be differently bonded. For example, a ligand may
be
covalently bonded and another ligand may be electrostatically bonded.
Preferably, the or each ligand is monoanionic and examples of such ligands are
dithiophosphates, dithiocarbamates, xanthates, carboxylates, thioxanthates,
phosphates
~5 and hydrocarbyl, preferably alkyl, derivatives thereof. Preferably, the
ratio of the number
of molybdenum atoms, for example, in the core in the event that the molybdenum-
sulfur
compound is a polynticlear compound, to the number of monoanionic ligands,
which are
capable of rendering the compound oil-soluble or oil-dispersible, is greater
than 1 to 1,
such as at least 3 to 2.
The molybdenum-sulfur compound's oil-solubility or oil-dispersibility may be
influenced
by the total number of carbon atoms present among all of the compound's
ligands. The
total number of carbon atoms present among all of the hydrocarbyl groups of
the
compound's ligands typically will be at least 21, e.g., 21 to 800, such as at
least 25, at
least 30 or at least 35. For example, the number of carbon atoms in each alkyl
group will
generally range between 1 to 100, preferably 1 to 40, and more preferably
between 3 and
20.
Examples of molybdenum-sulfur compounds include dinuclear molybdenum-sulfur
3o compounds and trinuclear molybdenum-sulfur compounds.
An example of a dinuclear molybdenum-sulfur compound is represented by the
formula:
CA 02487767 2004-11-18
-24-
Ri ,S X1 X2 Xa S R3
/N C''~'~ /M\ /M \ ~~ C N\
R2 S X3 S Ra
where R1 to R4 independently denote a straight chain, branched chain or
aromatic
hydrocarbyl group having 1 to 24 carbon atoms; and Xl to X4 independently
denote an
oxygen atom or a sulfur atom. The four hydrocarbyl groups, R, to R4, may be
identical or
different from one another.
In a preferred embodiment, the molybdenum-sulfur compound is an oil-soluble or
oil-
dispersible trinuclear molybdenum-sulfur compound. Examples of trinuclear
molybdenum-sulfur compounds are disclosed in W098/26030, W099/31113,
W099/66013, EP-A-1 138 752, EP-A-1 138 686 and European patent application no.
i5 02078011, each of which are incorporated into the present description by
reference,
particularly with respect to the characteristics of the molybdenum compound or
additive
disclosed therein.
Preferably, the trinuclear molybdenum-sulfur compounds are represented by the
formula
M03SkEXLoAPQZ, wherein:
k is an integer of at least l;
E represents a non-metallic atom selected from oxygen and selenium;
x can be 0 or an integer, and preferably k + x is at least 4, more preferably
in the range of 4 to 10, such as 4 to 7, most preferably 4 or 7;
L represents a ligand that confers oil-solubility or oil-dispersibility on the
molybdenum-sulfur compound, preferably L is a monoanionic ligand;
n is an integer in the range of 1 to 4;
A represents an anion other than L, if L is an anionic ligand;
p can be 0 or an integer;
3o Q represents a neutral electron-donating compound; and
CA 02487767 2004-11-18
-25-
z is in the range of 0 to 5 and includes non-stoichiometric values.
Those skilled in the art will realise that formation of the trinuclear
molybdenum-sulfur
compound will require selection of appropriate ligands (L) and other anions
(A),
depending on, for example, the number of sulfur and E atoms present in the
core, i.e. the
total anionic charge contributed by sulfur atom(s), E atom(s), if present, L
and A, if
present, must be -12. The trinuclear molybdenum-sulfur compound may also have
a
cation other than molybdenum, for example, (alkyl)ammonium, amine or sodium,
if the
anionic charge exceeds -12.
Examples of Q include water, alcohol, amine, ether and phosphine. It is
believed that the
electron-donating compound, Q, is merely present to fill any vacant
coordination sites on
the trinuclear molybdenum-sulfur compound.
Examples of A can be of any valence, for example, monovalent and divalent and
include
disulfide, hydroxide, alkoxide, amide and thiocyanate or derivative thereof;
preferably A
represents a disulfide ion.
Preferably, L is monoanionic ligand, such as dithiophosphates,
dithiocarbamates,
xanthates, carboxylates, thioxanthates, phosphates and hydrocarbyl, preferably
alkyl,
derivatives thereof. When n is 2 or more, the ligands can be the same or
different.
In an embodiment, independently of the other embodiments, k is 4 or 7, n is
either 1 or 2,
L is a monoanionic ligand, p is an integer to confer electrical neutrality on
the compound
based on the anionic charge on A and each of x and z is 0.
In a further embodiment, independently of the other embodiments, k is 4 or 7,
L is a
monoanionic ligand, n is 4 and each of p, x and z is 0.
CA 021487767 2004-11-18
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The molybdenum-sulfur cores, for example, the structures depicted in (I) and
(II) above,
may be interconnected by means of one or more ligands that are multidentate,
i.e. a ligand
having more than one functional group capable of binding to a molybdenum atom,
to
form oligomers. Molybdenum-sulfur additives comprising such oligomers are
considered
to fall within the scope of this invention.
Other examples of molybdenum containing compounds include molybdenum
carboxylates and molybdenum nitrogen complexes, both of which may be
sulfurised.
In an embodiment, a molybdenum-containing compound, such as a trinuclear
molybdenum dithiocarbamate is preferred.
Boron may also be present in the lubricating oil compositions of the present
invention.
Boron-containing additives may be prepared by reacting a boron compound with
an oil-
soluble or oil-dispersible additive or compound. Boron compounds include boron
oxide,
2o boron oxide hydrate, boron trioxide, boron trifluoride, boron tribromide,
boron
trichloride, boron acid such as boronic acid, boric acid, tetraboric acid and
metaboric acid,
boron hydrides, boron amides and various esters of boron acids. Examples of
boron-
containing additives include a borated dispersant; a borated dispersant VI
improver; an
alkali metal or a mixed alkali metal or an alkaline earth metal borate; a
borated overbased
metal detergent; a borated epoxide; a borate ester; a sulfurised borate ester;
and a borate
amide. A preferred boron-containing additive is a borated dispersant.
Rust inhibitors selected from the group consisting of nonionic polyoxyalkylene
polyols
and esters thereof, polyoxyalkylene phenols, and anionic alkyl sulfonic acids
may be used.
Copper and lead bearing corrosion inhibitors may be used, but are typically
not required
with the formulation of the present invention. Typically such compounds are
the
thiadiazole polysulfides containing from S to 50 carbon atoms, their
derivatives and
polymers thereof. Derivatives of 1,3,4-thiadiazoles such as those described in
U.S. Patent
CA 021487767 2004-11-18
-27-
Nos. 2,719,125; 2,719,126; and 3,087,932; are typical. Other similar materials
are
described in U.S. Patent Nos. 3,821,236; 3,904,537; 4,097,387; 4,107,059;
4,136,043;
4,188,299; and 4,193,882. Other additives are the thio and polythio
sulfenamides of
thiadiazoles such as those described in U.K. Patent Specification No.
1,560,830.
Benzotriazoles derivatives also fall within this class of additives. When
these compounds
1o are included in the lubricating composition, they are preferably present in
an amount not
exceeding 0.2 wt.% active ingredient.
A small amount of a demulsifying component may be used. A preferred
demulsifying
component is described in EP 330,522. It is obtained by reacting an alkylene
oxide with
an adduct obtained by reacting a bis-epoxide with a polyhydric alcohol. The
demulsifier
should be used at a level not exceeding 0.1 mass % active ingredient. A treat
rate of
0.001 to 0.05 mass % active ingredient is convenient.
Pour point depressants, otherwise known as Tube oil improvers, lower the
minimum
2o temperature at which the fluid will flow or can be poured. Such additives
are well
known. Typical of those additives which improve the low temperature fluidity
of the
fluid are Cg and C~8 dialkyl fumarate/vinyl acetate copolymers,
polyalkylmethacrylates
and the like.
Foam control can be provided by many compounds including an antifoamant of the
polysiloxane type, for example, silicone oil or polydimethyl siloxane.
Representative effective amounts of such additives, when used in lubricating
oil
compositions, are as follows:
CA 02487767 2004-11-18
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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
Multifuctional Viscosity Modifier 0.0 -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 0.0-0.5 0.001-0.2
Anti-Foaming Agent 0.001-0.3 0.001-0.15
Demulsifier 0.0-0.5 0.001-0.2
* mass % active ingredient based on the final lubricating oil composition.
The amount of nitrogen derived from the dispersant additive composition
typically
present in an additive concentrate is in the range of 0.33 to 0.47, such as
0.37 to 0.41,
mass %, based on the mass of the additive concentrate.
The amount of soap derived from the detergent additive composition generally
present in
an additive concentrate is in the range of 103 to 145, such as 116 to 125,
millimoles per
I5 1000g of concentrate.
Thus, a method of preparing a lubricating oil composition according to the
present
invention can involve admixing an oil of lubricating viscosity and one or more
of
additives or additive concentrates that comprises two or more of additives and
then,
CA 02487767 2004-11-18
-29-
optionally, admixing other additive components, such as viscosity modifier,
multifunctional viscosity modifier and pour point depressant.
The phosphorus and sulfur content of the lubricating oil composition is
advantageously
derived from additives in the lubricating oil composition, such as zinc
dithiophosphate.
0
The lubricating oil compositions may be used to lubricate mechanical engine
components,
particularly an internal combustion, such as a compression-ignited, engine, by
adding the
lubricating oil thereto. Particular examples of compression-ignited engines
are those
developed in recent years where the top ring groove temperature may exceed
150,
15 preferably exceed 250, °C, due to increases in specific power output
to around 5 or
greater, such as 25 or greater, preferably at least 30, especially 40 or
greater, kW/litre.
Preferably the maximum specific power output is around 60 kW/litre. These
engines are
more prone to suffer from ring-sticking problems in their operation.
2o It should be appreciated that interaction may take place between any two or
more of the
additives, including any two or more detergents, after they have been
incorporated into
the oil composition. The interaction may take place in either the process of
mixing or any
subsequent condition to which the composition is exposed, including the use of
the
composition in its working environment. Interactions may also take place when
further
25 auxiliary additives are added to the compositions of the invention or with
components of
oil. Such interaction may include interaction which alters the chemical
constitution of the
additives. Thus, the compositions of the invention include compositions in
which
interaction, for example, between any of the additives, has occurred, as well
as
compositions in which no interaction has occurred, for example, between the
components
3o mixed in the oil.
In this specification:
CA 02487767 2004-11-18
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The term "hydrocarbyl" as used herein means that the group concerned is
primarily
composed of hydrogen and carbon atoms and is bonded to the remainder of the
molecule
via a carbon atom, but does not exclude the presence of other atoms or groups
in a
proportion insufficient to detract from the substantially hydrocarbon
characteristics of the
group.
The term "comprising" or "comprises" when used herein is taken to specify the
presence
of stated features, integers, steps or components, but does not preclude the
presence or
addition of one or more other features, integers, steps, components or groups
thereof. In
the instance the term "comprising" or comprises" is used herein, the term
"consisting
essentially of ' and its cognates are a preferred embodiment, while the term
"consisting
of and its cognates are a preferred embodiment of the term "consisting
essentially of '.
The term "oil-soluble" or "oil-dispersible", as used herein, does not mean
that the
additives are soluble, dissolvable, miscible or capable of being suspended in
the oil in all
2o proportions. They do mean, however, that the additives are, for instance,
soluble or stable
dispersible in the oil to an extent sufficient to exert their intended effect
in the
environment in which the oil composition is employed. Moreover, the additional
incorporation of other additives such as those described above may affect the
solubility or
dispersibility of the additives.
"Major amount" "Major amount" means in excess of 50, such as greater than 70,
preferably 75 to 97, especially 80 to 95 or 90, mass %, of the composition.
"Minor amount" means less than S0, such as less than 30, for example, 3 to 25,
preferably
5 or 10 to 20, mass %, of the composition mass % of the composition.
The term 'molybdenum-sulfur compound' means a compound having at least one
molybdenum atom and at least one sulfur atom, preferably the compound has at
least one
sulfur atom that is bonded to one or more molybdenum atoms and also bonded to
one or
CA 02487767 2004-11-18
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more non-molybdenum atoms, such as carbon, more preferably the compound has at
least
one sulfur atom that is bonded to one or more molybdenum atoms only, such as
represented by cores [MoZS4], [Mo3S4] and [Mo3S7]. Atoms selected from oxygen
and
selenium may replace one or more sulfur atoms in such cores. Advantageously,
the core
consists of molybdenum and sulfur atoms alone. Accordingly, the term
'molybdenum-
1o sulfur additive' means an additive comprising one or more molybdenum-sulfur
compounds.
All percentages reported are mass % on an active ingredient basis, i.e.
without regard to
Garner or diluent oil, unless otherwise stated.
The abbreviation SAE stands for Society of Automotive Engineers, who classify
lubricants by viscosity grades.
The invention will now be particularly described, by way of example only, as
follows:-
Examples
Lubricating oil compositions meeting the SAE SW-30 grade were prepared by
methods
known in art and were subjected to an engine test used to investigate deposit
formation,
based specifically on the VWTDi CEC-L-78-T-99 test, also known as the PV1452
test.
The test is regarded as an industry standard and as a severe assessment of a
lubricant's
performance capabilities.
With the exception of the dispersant and detergent additive compositions, each
lubricating oil composition contained the same additives in the same amount.
Oils A, B,
3o C and 1 each contained a dispersant additive composition of borated and non-
borated
dispersants with Oils C and 1 containing a higher amount of non-borated
dispersant. Oils
A and C contained a calcium salicylate having a TBN of 168, whilst Oils B and
1
contained a detergent additive composition of a calcium salicylate having a
TBN of 168
and a calcium salicylate having a TBN of 64. The basestock used in each
lubricating oil
CA 02487767 2004-11-18
-32-
composition was a Group III basestock. The properties of the lubricating oil
compositions are listed in Table 1.
Tests and Results
The VWTDI test employs a 4-cylinder, 1.9 litre, 81 kW passenger car diesel
engine. It is
o a direct injection engine, in which a turbocharger system is used to
increase the power
output of the unit. The industry test procedure consists of a repeating cycle
of hot and
cold running conditions - the so-called PK cycle. This involves a 30 minute
idle period
at zero load followed by 180 minutes at full load and 4150 rpm. The entire
cycle is then
repeated for a total of 54 hours. In this 54 hour period the initial oil fill
of 4.5 liters of test
lubricant is not topped up.
At the end of the 54 hour test, the engine is drained, the engine disassembled
and the
pistons rated for piston deposits and piston ring sticking. This affords a
result which is
assessed relative to an industry reference oil (RL206) to define passing or
failing
2o performance.
The pistons are rated against what is known as the DIN rating system. The
three piston-
ring grooves and the two piston lands that lie between the grooves are rated
on a merit
scale for deposits and given a score out of 100 by a method known to those
skilled in the
art. In summary, the higher the number the better the performance: 100
indicates totally
clean and 0 indicates totally covered with deposit. The five scores are then
averaged to
give the overall piston cleanliness merit rating. The scores for each of the
four pistons are
then averaged to afford the overall piston cleanliness for the test. The
results are shown
in Table 1 below
The data in Table 1 show that Oil B and Oil C, each having an increased soap
content or
dispersant content respectively compared with Oil A, results in an improvement
in the
cleanliness of the pistons. However, Oil 1 containing an increased soap
content and
dispersant content provided a significant improvement in the piston
cleanliness compared
CA 02487767 2004-11-18
-33-
to Oils A, B and C. Thus, use of an increased amount of a dispersant and
detergent in
lubricating oil composition, which composition gives at most 1.0 mass % of
sulfated ash,
is useful for achieving a passing performance in the VWTDi engine test.
CA 02487767 2004-11-18
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