Note: Descriptions are shown in the official language in which they were submitted.
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A METHOD OF REDUCING DEPOSIT FORMATION IN A CENTRIFUGE
SYSTEM IN A TRUNK PISTON DIESEL ENGINE
This invention concerns a method of reducing deposit formation in a centrifuge
system in a trunk piston diesel engine.
Trunk piston diesel engines are used in marine, power generation and rail
traction applications and have a rated speed of between 300 and 1000 rpm. In
trunk piston diesel engines a single lubricant composition is used for
crankcase
and cylinder lubrication. All major moving parts of the engine, i.e. the main
and
big end bearings, camshaft and valve gear, are lubricated by a pumped
circulation system. The cylinder liners are lubricated partially by splash
lubrication and partially by oil from the circulation system which finds its
way to
the cylinder wall through holes in the piston skirt via the connecting rod and
gudgeon pin.
Trunk piston diesel engines use a centrifuge system to remove contaminants
such as, for example, soot or water, from the lubricant composition. The
centrifuge system relies on the use of a sealing medium that is heavier than
the
lubricant. The sealing medium is generally water. When the lubricant
composition passes through the centrifuge system, it comes into contact with
the
water. The lubricant therefore needs to be capable of shedding the water and
remaining stable in the presence of water. If the lubricant is unable to shed
the
water, the water builds up in the lubricant forming an emulsion, which leads
to
deposits building up in the centrifuge system and prevents the centrifuge
system
from working properly. The centrifuge system normally operates at temperatures
of less than 100 C, such as less than 95 C, e.g. around 90 C.
Traditional trunk piston diesel engine lubricant compositions have a total
base
number of 30-40. However, the recent development of trunk piston diesel
engines having very low oil consumption has resulted in lubricant formulators
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increasing the total base number up to, for example, 50-60. Unfortunately,
this
increase in total base number affects the ability of the lubricant composition
to
shed any contamination with the sealing medium used in the centrifuge systems,
resulting in deposits building up in the centrifuge system.
The aim of the present invention is to provide a method of reducing deposit
formation in a centrifuge system in a trunk piston diesel engine.
In accordance with the present invention there is provided a method of
reducing
deposit formation in a centrifuge system in a trunk piston diesel engine; the
method including the step of lubricating the trunk piston diesel engine with a
trunk piston diesel engine lubricant composition having a total base number of
more than 40 mg KOH/g, as determined by ASTM D2896, and including:
- at least 40 mass % of an oil of lubricating viscosity;
- at least one detergent, preferably at least two detergents; and
- at least 1.5 mass % of phenol, based on the total amount of the lubricant
composition;
with the proviso that if the trunk piston diesel engine lubricant composition
includes at least one phenate detergent, the trunk piston diesel engine
lubricant
composition includes more than 1.7 mass %, preferably more than 1.9 mass %,
of phenol.
The phenol may be added separately to the trunk piston diesel engine lubricant
composition and/or it may be added as part of the detergent, for example, as
part
of the unreacted components present in the detergent. If the phenol is part of
the
detergent, the amount of phenol present can be detected by persons skilled in
the art using processes such as titration and chromatography.
It is preferred that the trunk piston diesel engine lubricant composition
includes a
sulphurized or unsulphurized alkyl phenol.
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It is also preferred that the trunk piston diesel engine lubricant composition
has a
total base number of at least 50 mg KOH/g, and preferably at most 70 mg
KOH/g.
It has surprisingly been found that the trunk piston diesel engine lubricant
composition defined above is capable of shedding contamination with sealing
mediums used in centrifuge systems in trunk piston diesel engines, even though
it has a TBN of more than 40 mg KOH/g. The trunk piston diesel engine
lubricant
composition therefore exhibits a longer life when compared to trunk piston
diesel
engine lubricant compositions that are poor at shedding sealing mediums.
In accordance with the present invention there is also provided use of the
trunk
piston diesel engine lubricant composition defined above to reduce build-up of
deposits in a centrifuge in a trunk piston diesel engine.
Oil of Lubricating Viscosity
The oil of lubricating viscosity (sometimes referred to as lubricating oil)
may be
any oil suitable for the lubrication of a trunk piston diesel engine. The
lubricating
oil may suitably be an animal, a vegetable or a mineral oil. Suitably the
lubricating oil is a petroleum-derived lubricating oil, such as a naphthenic
base,
paraffinic base or mixed base oil. Alternatively, the, lubricating oil may be
a
synthetic lubricating oil. Suitable synthetic lubricating oils include
synthetic ester
lubricating oils, which oils include diesters such as di-octyl adipate, di-
octyl
sebacate and tridecyl adipate, or polymeric hydrocarbon lubricating oils, for
example liquid polyisobutene and poly-alpha olefins. Commonly, a mineral oil
is
employed. The lubricating oil may generally comprise greater than 60,
typically
greater than 70, mass % of the composition, and typically have a kinematic
viscosity at 1004C of from 2 to 40, for example for 3 to 15, mm2s 1 and a
viscosity
index of from 80 to 100, for example from 90 to 95.
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Another class of lubricating oils is hydrocracked oils, where the refining
process
further breaks down the middle and heavy distillate fractions in the presence
of
hydrogen at high temperatures and moderate pressures. Hydrocracked oils
typically have a kinematic viscosity at 1009C of from 2 to 40, for example
from 3
to 15, mm2s 1 and a viscosity index typically in the range of from 100 to 110,
for
example from 105 to 108.
The oil may include `brightstock' which refers to base oils which are solvent-
extracted, de-asphalted products from vacuum residuum generally having a
kinematic viscosity at 1004C of from 28 to 36 mm2s,1 and are typically used in
a
proportion of less than 40, preferably less than 30, more preferably less than
20,
mass %, based on the mass of the composition.
The trunk piston diesel engine lubricant composition preferably includes at
least
50 mass %, more preferably at least 60 mass %, even more preferably at least
70 mass %, of oil of lubricating viscosity, based on the total amount of the
lubricant composition.
Detergents
A detergent is an additive that reduces formation of 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 acidic organic compounds,
sometimes referred to as surfactants.
A detergent comprises a polar head with a long hydrophobic tail. Large amounts
of a metal base are included by reacting an excess of a metal compound, such
as an oxide or hydroxide, with an acidic gas such as carbon dioxide to give an
overbased detergent which comprises neutralised detergent as the outer layer
of
a metal base (e.g. carbonate) micelle.
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The detergent is preferably an alkali metal or alkaline earth metal additive
such
as an overbased oil-soluble or oil-dispersible calcium, magnesium, sodium or
barium salt of a surfactant selected from phenol, suiphonic acid, carboxylic
acid,
salicylic acid and naphthenic acid, wherein the overbasing is provided by an
oil-
insoluble salt of the metal, e.g. carbonate, basic carbonate, acetate,
formate,
hydroxide or oxalate, which is stabilised by the oil-soluble salt of the
surfactant.
The metal of the oil-soluble surf actant salt may be the same or different
from that
of the metal of the oil-insoluble salt. Preferably the metal, whether the
metal of
the oil-soluble or oil-insoluble salt, is calcium.
The TBN of the detergent may be low, i.e. less than 50 mg KOH/g, medium, i.e.
50-150 mg KOH/g, or high, i.e. over 150 mg KOH/g, as determined by ASTM
D2896. Preferably the TBN is medium or high, i.e. more than 50 TBN. More
preferably, the TBN is at least 60, more preferably at least 100, more
preferably
at least 150, and up to 500, such as up to 350 mg KOH/g, as determined by
ASTM D2896.
Surfactants for the surfactant system of the overbased detergent preferably
contain at least one hydrocarbyl group, for example, as a substituent on an
aromatic ring. 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. Advantageously,
hydrocarbyl groups in surfactants for use in accordance with the invention are
aliphatic groups, preferably alkyl or alkylene groups, especially alkyl
groups,
which may be linear or branched. The total number of carbon atoms in the
surfactants should be at least sufficient to impart the desired oil-
solubility.
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Phenols, for use in preparing the detergents may be non-sulphurized or,
preferably, sulphurized. 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).
Preferred phenols may be derived from the formula
OH
RY
where R represents a hydrocarbyl group and y represents 1 to 4. Where y is
greater than 1, the hydrocarbyl groups may be the same or different.
The phenols are frequently used in sulphurized form. Sulphurized hydrocarbyl
phenols may typically be represented by the formula:
OH OH
SX
R R
Y Y
where x is generally from 1 to 4. In some cases, more than two phenol
molecules may be linked by S, bridges.
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In the above formulae, 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 9 in order to ensure adequate solubility in oil.
Preferred alkyl groups are nonyl (tripropylene) groups.
In the following discussion, hydrocarbyl-substituted phenols will for
convenience
be referred to as alkyl phenols.
A sulphurizing agent for use in preparing a sulphurized phenol or phenate may
be any compound or element which introduces -(S)X- bridging groups between
the alkyl phenol monomer groups, wherein x is generally from 1 to about 4.
Thus, the reaction may be conducted with elemental sulphur or a halide
thereof,
for example, sulphur dichloride or, more preferably, sulphur monochloride. If
elemental sulphur is used, the suiphurization reaction may be effected by
heating
the alkyl phenol compound at from 50 to 250, preferably at least 100, C. The
use of elemental sulphur will typically yield a mixture of bridging groups -
(S)x- as
described above. If a sulphur halide is used, the sulphurization reaction may
be
effected by treating the alkyl phenol at from -10 to 120, preferably at least
60, C.
The reaction may be conducted in the presence of a suitable diluent. The
diluent
advantageously comprises a substantially inert organic diluent, for example
mineral oil or an alkane. In any event, the reaction is conducted for a period
of
time sufficient to effect substantial reaction. It is generally preferred to
employ
from 0.1 to 5 moles of the alkyl phenol material per equivalent of
sulphurizing
agent.
Where elemental sulphur is used as the sulphurizing agent, it may be desirable
to use a basic catalyst, for example, sodium hydroxide or an organic amine,
preferably a heterocyclic amine (e.g., morpholine).
Details of sulphurization processes are well known to those skilled in the
art.
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Regardless of the manner in which they are prepared, sulphurized alkyl phenols
useful in preparing overbased detergents generally comprise diluent and
unreacted alkyl phenols and generally contain from 2 to 20 mass %, preferably
4
to 14 mass %, and most preferably 6 to 12 mass%, sulphur based on the mass
of the sulphurized alkyl phenol.
As indicated above, the term "phenol" as used herein includes phenols that
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 are described in, for
example, US-A-5 259 967.
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-2 121 432.
In general, the phenols may include substituents other than those mentioned
above provided that such substituents do not detract significantly from the
surfactant properties of the phenols. Examples of such substituents are
methoxy
groups and halogen atoms.
Salicylic acids used in accordance with the invention may be non-sulphurized
or
sulphurized, and may be chemically modified and/or contain additional
substituents, for example, as discussed above for phenols. Processes similar
to
those described above may also be used for sulphurizing a hydrocarbyl-
substituted
salicylic acid, and are well known to those skilled in the art. Salicylic
acids are
typically prepared by the carboxylation, by the Kolbe-Schmitt process, of
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phenoxides, and in that case, will generally be obtained (normally in a
diluent) in
admixture with uncarboxylated phenol.
Preferred substituents in oil-soluble salicylic acids from which overbased
detergents in accordance with the invention may be derived are the
substituents
represented by R in the above discussion of phenols. In alkyl-substituted
salicylic acids, the alkyl groups advantageously contain 5 to 100, preferably
9 to
30, especially 14 to 20, carbon atoms.
Sulphonic acids used in accordance with the invention are typically obtained
by
sulphonation of hydrocarbyl-substituted, especially 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.
Examples include those obtained by alkylating benzene, toluene, xylene,
naphthalene, biphenyl or their halogen derivatives, for example,
chlorobenzene,
chlorotoluene or chloronaphthalene. Alkylation of aromatic hydrocarbons may be
carried out in the presence of a catalyst with alkylating agents having from 3
to
more than 100 carbon atoms, such as, for example, haloparaffins, olefins that
may be obtained by dehydrogenation of paraffins, and polyolefins, for example,
polymers of ethylene, propylene, and/or butene. The alkylaryl sulphonic acids
usually contain from 7 to 100 or more carbon atoms. They preferably contain
from 16 to 80, or 12 to 40, carbon atoms per alkyl-substituted aromatic
moiety,
depending on the source from which they are obtained.
When neutralizing these alkylaryl sulphonic acids to provide sulphonates,
hydrocarbon solvents and/or diluent oils may also be included in the reaction
mixture, as well as promoters and viscosity control agents.
Another type of sulphonic acid that may be used in accordance with the
invention
comprises alkyl phenol sulphonic acids. Such sulphonic acids can be
sulphurized. Whether sulphurized or non-sulphurized these sulphonic acids are
CA 02486328 2011-06-23
5 believed to have surfactant properties comparable to those of sulphonic
acids,
rather than surfactant properties comparable to those of phenols.
Sulphonic acids suitable for use in accordance with the invention also include
alkyl sulphonic acids, such as alkenyl sulphonic acids. In such compounds the
10 alkyl group suitably contains 9 to 100, advantageously 12 to 80, especially
16 to
60, carbon atoms.
Carboxylic acids that may be used in accordance with the invention include
mono- and dicarboxylic acids. Preferred monocarboxylic acids are those
containing 1 to 30, especially 8 to 24, carbon atoms. (Where this
specification
indicates the number of carbon atoms in a carboxylic acid, the carbon atom(s)
in
the carboxylic group(s) 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 Chemicals under the trade name
CekanoicTM. Other suitable acids are those with tertiary substitution at the
a-carbon atom and dicarboxylic acids with more than 2 carbon atoms separating
the carboxylic groups. Further, dicarboxylic acids with more than 35, for
example, 36 to 100, carbon atoms are also suitable. Unsaturated carboxylic
acids can be sulphurized. Although salicylic acids contain a carboxylic group,
for
the purposes of the present invention they are considered to be a separate
group
of surfactants, and are not considered to be carboxylic acid surfactants.
(Nor,
although they contain a hydroxyl group, are they considered to be phenol
surfactants.)
Examples of other surfactants which may be used in accordance with the
invention include the following compounds, and derivatives thereof: naphthenic
acids, especially naphthenic acids containing one or more alkyl groups,
dialkylphosphonic acids, dialkyithiophosphonic acids, and
dialkyldithiophosphoric
acids, high molecular weight (preferably ethoxylated) alcohols, dithiocarbamic
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acids, thiophosphines, and dispersants. Surfactants of these types are well
known to those skilled in the art. Surfactants of the hydrocarbyl-substituted
carboxylalkylene-linked phenol type, or dihydrocarbyl esters of alkylene
dicarboxylic acids, the alkylene group being substituted with a hydroxy group
and
an additional carboxylic acid group, or alkylene-linked polyaromatic
molecules,
the aromatic moieties whereof comprise at least one hydrocarbyl-substituted
phenol and at least one carboxy phenol, may also be suitable for use in the
present invention; such surfactants are described in EP-A-708 171.
Further examples of detergents useful in the present invention are optionally
sulphurized alkaline earth metal hydrocarbyl phenates that have been modified
by carboxylic acids such as stearic acid, for examples as described in EP-A-
271
262 (LZ-Adibis); and phenolates as described in EP-A- 750 659 (Chevron).
Also suitable for use in the present invention are overbased metal compounds,
preferably overbased calcium detergents, that contain at least two surfactant
groups, such as phenol, sulphonic acid, carboxylic acid, salicylic acid and
naphthenic acid, that may be obtained by manufacture of a hybrid material in
which two or more different surfactant groups are incorporated during the
overbasing process.
Examples of hybrid materials are an overbased calcium salt of surfactants
phenol
and sulphonic acid; an overbased calcium salt of surfactants phenol and
carboxylic acid; an overbased calcium salt of surfactants phenol, sulphonic
acid
and salicylic acid; and an overbased calcium salt of surfactants phenol and
salicylic acid.
In the instance where at least two overbased metal compounds are present, any
suitable proportions by mass may be used, preferably the mass to mass
proportion of any one overbased metal compound to any other metal overbased
compound is in the range of from 5:95 to 95:5; such as from 90:10 to 10:90;
more
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preferably from 20:80 to 80:20; especially from 70:30 to 30:70; advantageously
from 60:40 to 40:60.
The hybrid detergent preferably includes at least 5 mass% of salicylate, more
preferably at least 10 mass% of salicylate. The hybrid detergent preferably
includes at least 5 mass% of phenate. The amount of salicylate and phenate in
the hybrid detergent can be determined using techniques such as
chromatography, spectroscopy and/or titration, well known to persons skilled
in
the art. The hybrid detergent may also include other surfactants such as
sulphonate, suiphurized phenate, thiophosphate, naphthenate, or oil-soluble
carboxylate. The hybrid detergent may include at least 5 mass% of sulphonate.
The surfactant groups are incorporated during the overbasing process.
Particular examples of hybrid materials include, for example, those described
in
WO-A- 97/46643; WO-A- 97/46644; WO-A- 97/46645; WO-A- 97/46646; and
WO-A- 97/46647.
By an "overbased calcium salt of surfactants" is meant an overbased detergent
in
which the metal cations of the oil-insoluble metal salt are essentially
calcium
cations. Small amounts of other cations may be present in the oil-insoluble
metal
salt, but typically at least 80, more typically at least 90, for example at
least 95,
mole %, of the cations in the oil-insoluble metal salt, are calcium ions.
Cations
other than calcium may be derived, for example, from the use in the
manufacture
of the overbased detergent of a surfactant salt in which the cation is a metal
other than calcium. Preferably, the metal salt of the surfactant is also
calcium.
Preferably, the TBN of the hybrid detergent is at least 300 mg KOH/g, such as
at
least 330 mg KOH/g, more preferably at least 350 mg KOH/g, more preferably at
least 400 mg KOH/g, most preferably in the range of from 400 to 600 mg KOH/g,
such as up to 500 mg KOH/g, as determined by ASTM D2896.
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Preferably, the amount of overbased metal detergent in the lubricant is at
least
0.5, preferably in the range of from 5 to 50, more preferably from 10 to 50,
mass
% based on the total amount of the lubricant composition.
The overbased metal detergents may or may not be borated, and typically the
boron contributing compound, e.g the metal borate, is considered to form part
of
the overbasing. The detergent may include both a non-borated detergent and a
borated detergent.
The overbased metal detergents preferably have a sulphated ash content (as
determined by ASTM D874) of at least 0.85%, more preferably at least 1.0% and
even more preferably at least 1.2%.
The detergent or detergents may include phenol as an unreacted component
and, if so, the amount of phenol contributes to the total phenol content
present in
the trunk piston diesel engine lubricant composition. All of the phenol
present in
the trunk piston diesel engine lubricant composition may come from the
detergent or detergents.
Phenols
The trunk piston diesel engine lubricant composition includes at least 1.5
mass %
of phenol, preferably at least 1.7 mass %, more preferably at least 1.9 mass
%,
based on the total amount of the lubricant composition. More preferably, the
trunk piston diesel engine lubricant composition includes at least 2.0 mass %
of
phenol, even more preferably at least 2.1 mass %, and most preferably at least
2.2 mass %, based on the total amount of the lubricant composition. If the
trunk
piston diesel engine lubricant composition includes at least one phenate
detergent, the trunk piston diesel engine lubricant composition includes more
than 1.7 mass % of phenol, preferably more than 1.9 mass %, even more
preferably more than 2.0 mass % of phenol, even more preferably more than 2.2
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mass %, and most preferably more than 2.4 mass %, based on the total amount
of the lubricant composition.
The phenol may be added separately to the trunk piston diesel engine lubricant
composition and/or it may added as part of the detergent, usually as an
unreacted component.
The phenol may be non-sulphurized or sulphurized. 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).
Preferred phenols may be derived from the formula
OH
Ry
where R represents a hydrocarbyl group and y represents 1 to 4. Where y is
greater than 1, the hydrocarbyl groups may be the same or different. R
preferably includes 2 to 20 carbon atoms.
The preferred phenols are nonyl-phenol, dodecyl-phenol or a mixture of C14,
C16
and C18-alkyl phenols.
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The phenols are frequently used in sulphurized form. Sulphurized hydrocarbyl
phenols may typically be represented by the formula:
OH OH
SX
Ry Ry
where x is generally from 1 to 4. In some cases, more than two phenol
molecules may be linked by SX bridges. R preferably includes 2 to 20 carbon
atoms.
As indicated above, the term "phenol" as used herein includes phenols that
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 are described in, for
example, US-A-5 259 967.
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-2 121 432.
In general, the phenols may include substituents other than those mentioned
above provided that such substituents do not detract significantly from the
surfactant properties of the phenols. Examples of such substituents are
methoxy
groups and halogen atoms.
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The trunk piston engine oil preferably also includes at least one dispersant,
anti-
wear additive or anti-oxidant.
Dispersants
The trunk piston diesel engine lubricant composition may include at least one
dispersant. A dispersant is an additive for a lubricating composition whose
primary function is to improve engine cleanliness.
A noteworthy class of dispersants are "ashless", meaning a non-metallic
organic
material that forms substantially no ash on combustion, in contrast to metal-
containing, hence ash-forming, materials. Ashless dispersants comprise a long
chain hydrocarbon with a polar head, the polarity being derived from inclusion
of,
e.g. an 0, P or N atom. The hydrocarbon is an oleophilic group that confers
oil-
solubility, having for example 40 to 500 carbon atoms. Thus, ashless
dispersants may comprise an oil-soluble polymeric hydrocarbon backbone
having functional groups that are capable of associating with particles to be
dispersed.
Examples of ashless dispersants are succinimides, e.g. polyisobutene succinic
anhydride; and polyamine condensation products that may be borated or
unborated.
If present, the dispersant is preferably present in an amount from 0.5 to 5
mass
%, based on the total amount of the lubricant composition.
Anti-wear Additive
The trunk piston diesel engine lubricant composition may include at least one
anti-wear additive. The anti-wear additive may be metallic or non-metallic,
preferably the former.
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Dihydrocarbyl dithiophosphate metal salts are examples of the anti-wear
additives. The metal in the dihydrocarbyl dithiophosphate may be an alkali or
alkaline earth metal, or aluminium, lead, tin, molybdenum, manganese, nickel
or
copper. Zinc salts are preferred, preferably in the range of 0.1 to 1.5,
preferably
0.5 to 1.3, mass %, based upon the total mass of the lubricating oil
composition.
They may be prepared in accordance with known techniques by firstly forming a
dihydrocarbyl dithiophosphoric acid (DDPA), usually by reaction of one or more
alcohols or a phenol with P2S5 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. Alternatively, multiple
dithiophosphoric acids can be prepared comprising both hydrocarbyl groups that
are entirely secondary and hydrocarbyl groups that are entirely primary. To
make the zinc salt, any basic or neutral zinc compound may be used but the
oxides, hydroxides and carbonates are most generally employed. Commercial
additives frequently contain an excess of zinc due to use of an excess of the
basic zinc compound in the neutralisation reaction.
The preferred zinc dihydrocarbyl dithiophosphates are oil-soluble salts of
dihydrocarbyl dithiophosphoric acids and may be represented by the following
formula:
[(RO) (R'O) P(S)S]2 Zn
where R and R1 may be the same or different hydrocarbyl radicals containing
from 1 to 18, preferably 2 to 12, carbon atoms and including radicals such as
alkyl, alkenyl, aryl, arylalkyl, alkaryl and cycloaliphatic radicals.
Particularly
preferred as R and R1 groups are alkyl groups of 2 to 8 carbon atoms. Thus,
the
radicals may, for example, be ethyl, n-propyl, I-propyl, n-butyl, I-butyl, sec-
butyl,
amyl, n-hexyl, I-hexyl, n-octyl, decyl, dodecyl, octadecyl, 2-ethylehexyl,
phenyl,
butylphenyl, cyclohexyl, methylcyclopentyl, propenyl, butenyl. In order to
obtain
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2003M014 18
oil-solubility, the total number of carbon atoms (i.e. in R and R) in the
dithiophoshoric acid will generally be 5 or greater. The zinc dihydrocarbyl
dithiophosphate can therefore comprise zinc dialkyl dithiophosphates.
If present, the anti-wear additive is preferably present in an amount from
0.10 to
3.0 mass %, based on the total amount of the lubricant composition.
Anti-oxidants
The trunk piston diesel engine lubricant composition may include at least one
anti-oxidant. The anti-oxidant may be aminic or phenolic. As examples of
amines there may be mentioned secondary aromatic amines such as
diarylamines, for example diphenylamines wherein each phenyl group is alkyl-
substituted with an alkyl group having 4 to 9 carbon atoms. As examples of
anti-
oxidants there may be mentioned hindered phenols, including mono-phenols and
bis-phenols.
Preferably, the anti-oxidant, if present, is provided in the composition in an
amount of up to 3 mass %, based on the total amount of the lubricant
composition.
Other additives such as pour point depressants, anti-foamants, metal rust
inhibitors, pour point depressants and/or demulsifiers may be provided, if
necessary.
The terms 'oil-soluble' or 'oil-dispersable' as used herein do not necessarily
indicate that the compounds or additives are soluble, dissolvable, miscible or
capable of being suspended in the oil in all proportions. These do mean,
however, that they are, for instance, soluble or stably dispersible in oil to
an
extent sufficient to exert their intended effect in the environment in which
the oil is
CA 02486328 2004-10-29
2003MO14 19
employed. Moreover, the additional incorporation of other additives may also
permit incorporation of higher levels of a particular additive, if desired.
The lubricant compositions of this invention comprise defined individual (i.e.
separate) components that may or may not remain the same chemically before
and after mixing.
It may be desirable, although not essential, to prepare one or more additive
packages or concentrates comprising the additives, whereby the additives can
be
added simultaneously to the oil of lubricating viscosity to form the
lubricating oil
composition. Dissolution of the additive package(s) into the lubricating oil
may
be facilitated by solvents and by mixing accompanied with mild heating, but
this
is not essential. The additive package(s) will typically be formulated to
contain
the additive(s) in proper amounts to provide the desired concentration, and/or
to
carry out the intended function in the final formulation when the additive
package(s) is/are combined with a predetermined amount of base lubricant.
Thus, the additives may be admixed with small amounts of base oil or other
compatible solvents together with other desirable additives to form additive
packages containing active ingredients in an amount, based on the additive
package, of, for example, from 2.5 to 90, preferably from 5 to 75, most
preferably
from 8 to 60, mass % of additives in the appropriate proportions, the
remainder
being base oil.
The final formulations may typically contain about 5 to 40 mass % of the
additive
packages(s), the remainder being base oil.
The present invention is illustrated by, but in no way limited to, the
following
examples.
CA 02486328 2011-06-23
5 Examples
The following examples use a centrifuge water shedding test which evaluates
the
ability of an oil to shed water from a prepared test mixture of oil and water.
The
TM
test uses an Alfa Laval MAB103B 2.0 centrifuge coupled to a Watson Marlow
10 peristaltic pump. The centrifuge is sealed with 2 litres of water. A
measurement
is made of the amount of deposits formed in the centrifuge during the test.
The
test is carried out at 87 C. Pre-measured amounts of water and the test oil
are
mixed together and then passed through the centrifuge at a rate of 2
litres/min.
The test is run for an hour and a half, allowing the mixture to pass through
the
15 centrifuge about 10 times. The centrifuge is weighed before and after the
test. A
poor trunk piston diesel engine lubricant composition will produce a larger
amount of deposits in the centrifuge system.
Trunk piston engine oils ('TPEOs') were prepared having TBNs ranging from 30
20 to 50. The TPEOs were subjected to the centrifuge water shedding test.
Details
of the TPEOs and the test results are shown below in Table 1.
Table 1
Comparative Comparative Comparative Example 1 Example 2 Example 3
Example 1 Example 2 Example 3
TBN 30 50 50 50 50 50
168 BN 5.29 17.25 17.25 17.25 17.25 17.25
Calcium
Salicylate
280 BN 7.57 7.50 7.50 7.50 7.50 7.50
Calcium
Salicylate
Dispersant 1.00 1.00 1.00 1.00
Sulphurised 1.00
Dodecyl-
Phenol
Unsulphurize 1.00
CA 02486328 2004-10-29
2003MO14 21
d Dodecyl-
Phenol
Mixture of 1.00
C14, C16 and
C16-alkyl
phenols
ZDDP 1.06 0.77 0.77 0.77 0.77 0.77
Anti-foam 0.10 0.10 0.10 0.10 0.10 0.10
Brightstocks 12.00 12.00 12.00 12.00 12.00 12.00
SN600 73.98 62.38 61.38 60.38 60.38 60.38
Alkylphenol 0.45 0.99 0.99 1.99 1.99 1.99
content (%)
Shedding
Test
Deposits at 53 109 127 27 33 33
End of Test
(grams)
As shown in Table 1, as the TBN of the TPEO increases from 30 to 50 (see
Comparatives Examples 1, 2 and 3), the amount of deposits produced also
increases. Table 1 also shows that if the amount of alkylphenol is increased
(see
Examples 1, 2 and 3), the amount of deposits can be reduced.
In the following examples, the TPEOs include a phenate detergent:
Table 2
Comparative Example 4 Example 5 Example 6 Example 7
Example 4
TBN 50 50 50 50 50
168 BN 17.25 17.25 17.25 17.25 17.25
Calcium
Salicylate
CA 02486328 2004-10-29
2003M014 22
250 BN 8.40 8.40 8.40 8.40 8.40
Calcium
Phenate
Sulphurised 1.00
Nonyl-Phenol
Sulphurised 1.00
Dodecyl-Phenol
Unsulphurized 1.00
Dodecyl-Phenol
Mixture of C14, 1.00
C18 and C18-
alkyl phenols
ZDDP 0.77 0.77 0.77 0.77 0.77
Anti-foam 0.10 0.10 0.10 0.10 0.10
Brightstocks 12.00 12.00 12.00 12.00 12.00
SN600 61.48 60.48 60.48 60.48 60.48
Alkylphenol 1.70 2.70 2.70 2.70 2.70
content
Shedding Test
Deposits at End 270 182 82 130 188
of Test (grams)
Comparative Example 4, which includes only 1.7% alkylphenol, produces 2708 of
deposits. Examples 4, 5, 6 and 7 show that if the amount of alkylphenol is
increased, the amount of deposits can be reduced.
In the following examples, the phenol is added to the TPEO as unreacted
components of the detergents.
CA 02486328 2004-10-29
2003MO14 23
Table 3
Comparative Example 8 Example 9 Example 10
Example 2
TBN 50 50 45 50
280 BN Calcium 17.25
Salicylate
250 BN Calcium 7.50
Salicylate
168 BN Calcium 17.90 17.90 25.00
Salicylate
64 BN Calcium 31.25 20.43 12.50
Salicylate
ZDDP 0.77 0.77 0.77 0.77
Anti-foam 0.10 0.10 0.10 0.10
Brightstocks 12.00 10.00 10.00 10.00
SN600 68.03 39.98 50.80 51.63
AI kyl phenol 0.99 2.06 1.62 1.63
content (%)
Shedding Test
Deposits at End 109 4 3 4
of Test (grams)
Comparative Example 2, which includes only 0.99% alkylphenol, produces 109g
of deposits. Examples 8, 9 and 10 show that if the amount of alkyiphenol is
increased by the selection of detergents including more alkylphenol, the
amount
of deposits is reduced dramatically.
