Note: Descriptions are shown in the official language in which they were submitted.
' CA 02514370 2005-07-29
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-1-
METHOD FOR LUBRICATING SURFACES
This invention relates to methods of lubricating surfaces, in particular, to
methods of lubricating surfaces in internal combustion engines.
Developments in automotive vehicle and engine designs has led to use of a
more varied range of materials for manufacture of the engine components. In
particular aluminum alloys are increasingly being used to manufacture engine
components.
In accordance with a first aspect of the present invention there is provided a
method of lubricating an aluminum alloy surface, which comprises supplying to
said
surface a lubricating oil composition comprising an oil of lubricating
viscosity,
preferably in a major amount, and an oil-soluble trinuclear organo-molybdenum
compound.
It has been found that the trinuclear organo-molybdenum additive will
substantially reduce friction and surface wear on the aluminum containing
alloy
surfaces to an extent not observed with dinuclear-organo-molybdenum compounds.
The aluminum alloy suitably comprises an aluminum-silicon alloy, which may
additionally contain a proportion of copper and/or magnesium. Suitably the
aluminum alloy has a hardness of 100-150 Hv, preferably 110-130 Hv and more
preferably of about 120 Hv. Suitably, the aluminum alloy has a density of 2.0-
3.0
gcrri 3, preferably, 2.4-2.8 gcrri 3, and more preferably, about 2.6 gcm-3.
Typically the trinuclear organo-molybdenum additive is used so as to provide
25 to 1000 ppm (parts per million, by weight), preferably 200 to 750 ppm, more
preferably 400 to 600 ppm, and advatantageously 500 ppm of elemental
molybdenum
in the lubricating oil compositions (as determined by ASTM D5185).
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The lubricating oil composition of the first aspect of the invention may
further
comprise an oil soluble, zinc dihydrocarbyl dithiophosphate (ZDDP) produced
from a
primary alcohol, herein after referred to as primary ZDDP. Suitably, primary
ZDDP
comprises at least 50%, preferably at least 75%, more preferably at least 90%,
and
advantageously comprises substantially 100% ZDDP produced from primary.
The lubricating oil composition suitably comprises 0.2 to 1.0 mass %,
preferably 0.4 to 0.8 mass %, and more preferably 0.6 ro 0.75 mass % primary
ZDDP.
The method according the first aspect of the invention suitably involves
provision of lubrication between an aluminum alloy surface and a non-aluminum
alloy
surface, such as a ferrous surface, for example.
A second aspect of this invention is an internal combustion engine having one
or more component parts made from an aluminum alloy, and contained in a
reservoir
in the engine, a lubricating oil composition for lubricating said parts
comprising an oil
of lubricating viscosity, preferably in a major amount, and an oil-soluble,
trinuclear
organo-molybdenum compound. The reservoir in the engine may be a crankcase
sump in four-stroke engines, from where it is distributed around the engine
for
lubrication. The invention is applicable to two-stroke and four-stroke spark-
ignited
and compression-ignited engines.
A third aspect of the invention relates to the use of a lubricating oil
composition comprising an oil of lubricating viscosity and an oil-soluble,
trinuclear
organo-molybdenum compound to lubricate an aluminum alloy surface.
A fourth aspect of the invention provides the use of an oil-soluble,
trinuclear
organo-molybdenum compound in a lubricating oil composition to reduce the
friction
between surfaces, one of which comprising an aluminum alloy.
In accordance with a fifth aspect of the present invention there has been
discovered a method of providing lubrication between two ferrous surfaces, one
of the
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ferrous surfaces comprising a chromium containing iron alloy conforming to
British
Standard BS EN31 and the other ferrous surfaces comprises a cast iron alloy
conforming to British Standard BS EN1452, which method comprises supplying to
said surface a lubricating oil composition comprising an oil of lubricating
viscosity,
preferably in a major amount, and an oil-soluble trinuclear organo-molybdenum
compound.
It has been found that the trinuclear organo-molybdenum additive will
substantially reduce friction and surface wear on the ferrous surfaces to an
extent not
observed with dinuclear-organo-molybdenum compounds.
Typically the trinuclear organo-molybdenum additive is used so as to provide
to 1000 ppm (parts per million, by weight), preferably 200 to 750 ppm, more
preferably 400 to 600 ppm, and advatantageously 500 ppm of elemental
molybdenum
in the lubricating oil compositions (as determined by ASTM D5185).
The lubricating oil composition of the fifth aspect of the invention may
further
comprise an oil soluble, zinc dihydrocarbyl dithiophosphate (ZDDP) made from
secondary alcohol, hereinafter referred to as secondary ZDDP. Suitably, the
secondary ZDDP comprises at least 55%, preferably at least 70% and more
preferably
at least 85%, and may comprise substantially 100% ZDDP made from secondary
alcohol.
The lubricating oil composition suitably comprises 0.2 to 1.0 mass %,
preferably 0.4 to 0.8 mass %, and more preferably 0.6 to 0.75 mass % secondary
ZDDP.
A sixth aspect of this invention is an internal combustion engine having a
component part made from a chromium containing ferrous alloy conforming with
British Standard BS EN31 adjacent a component part made from an iron alloy
conforming with British Standard BS EN1452, both component parts being
contained
in a reservoir in the engine, a lubricating oil composition for lubricating
said parts
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comprising an oil of lubricating viscosity, preferably in a major amount, and
an oil-
soluble, trinuclear organo-molybdenum compound. The reservoir in the engine
maybe a crankcase sump in four-stroke engines, from where it is distributed
around
the engine for lubrication. The invention is applicable to two-stroke and four-
stroke
spark-ignited and compression-ignited engines.
A seventh aspect of the invention relates to the use of a lubricating oil
composition comprising an oil of lubricating viscosity an oil-soluble,
trinuclear
organo-molybdenum compound to provide lubrication between a chromium
containing ferrous alloy surface conforming with British Standard BS EN31 and
an
iron alloy surface conforming with British Standard BS EN1452.
An eighth aspect of the invention provides the use of an oil-soluble,
trinuclear
organo-molybdenum compound in a lubricating oil composition to reduce the
friction
between a chromium containing ferrous alloy surface conforming with British
Standard BS EN31 and an iron alloy surface conforming with British Standard BS
EN1452.
The methods of any aspect of this invention are especially applicable to the
lubrication of spark-ignited or compression-ignited two-stroke or four-stroke
internal
combustion engines which have parts or components made from the specified
materials. Examples of such components include the cam shaft, especially the
cam
Lobes; pistons, especially the piston skirt; cylinder liners; and valves.
As examples of suitable oil-soluble, trinuclear organo-molybdenum compounds,
there may be mentioned dithiocarbamates, dithiophosphates, dithiophosphinates,
xanthates, thioxanthates and sulfides of molybdenum and mixtures thereof.
Additionally, the molybdenum compounds may be acidic molybdenum
compounds. These compounds will react with a basic nitrogen compound as
measured by ASTM test D-664 or D-2896 titration procedure and are typically
hexavalent. Included are molybdic acid, ammonium molybdate, sodium molybdate,
' CA 02514370 2005-07-29
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potassium molybdate, and other alkaline metal molybdates and other molybdenum
salts, e.g., molybdenum trioxide or similar acidic molybdenum compounds.
A group of trinuclear organo-molybdenum compounds useful in the lubricating
compositions of this invention are those of the formula Mo3SkLoQZ and mixtures
thereof
wherein L represents independently selected ligands having organo groups with
a
sufficient number of carbon atoms to render the compound soluble or
dispersible in the
oil, n is from 1 to 4, k varies from 4 through 7, Q is selected from the group
of neutral
electron donating compounds such as water, amines, alcohols, phosphines, and
ethers,
and z ranges from 0 to 5 and includes non-stoichiometric values. In the
instance n is 3,
2 or 1, appropriately charged ionic species is required to confer electrical
neutrality to
the trinuclear molybdenum compound. The ionic species may be of any valence,
for
example, monovalent or divalent. Further the ionic species may be negatively
charged,
i.e. an anionic species, or may be positively charged, i.e. a cationic species
or a
combination of an anion and a cation. Such terms are known to a skilled person
in the
art. The ionic species may be present in the compound through covalent
bonding, i.e.
coordinated to one or more molybdenum atoms in the core, or through
electrostatic
bonding or interaction as in the case of a counter-ion or through a form of
bonding
intermediate between covalent and electrostatic bonding. Examples of anionic
species
include disulfide, hydroxide, an alkoxide, an amide and a thiocyanate or
derivate
thereof; preferably the anionic species is disulfide ion. Examples of cationic
species
include an ammonium ion and a metal ion, such as an alkali metal, alkaline
earth metal
or transition metal, ion, preferably an ammonium ion, such as [NR4J+ where R
is
independently H or alkyl group, more preferably R is H, i.e. [NH4]+. At least
21 total
carbon atoms should be present among all the ligands' organo groups, such as
at least
25, at least 30, or at least 35 carbon atoms.
The ligands are independently selected from the group of:
~
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X R 1,
X1~
R 2,
X
2
Xl~ ~R
- ~ Y 3,
X
2
Xl~ /R1
.~l
X
R2
and
Xi\ /O R1
_/
X ~~
2 O R2
and mixtures thereof, wherein X, XI, X2, and Y are independently selected from
the
group of oxygen and sulfur, and wherein R~, R2, and R are independently
selected from
hydrogen and organo groups that may be the same or different. Preferably, the
organo
groups are hydrocarbyl groups such as alkyl (e.g., in which the carbon atom
attached to
the remainder of the ligand is primary or secondary), aryl, substituted aryl
and ether
groups. More preferably, each ligand has the same hydrocarbyl group.
The term "hydrocarbyl" denotes a substituent having carbon atoms directly
attached to the remainder of the ligand and is predominantly hydrocarbyl in
character
within the context of this invention. Such substituents include the following:
1. Hydrocarbon substituents, that is, aliphatic (for example alkyl or
alkenyl), alicyclic (for example cycloalkyl or cycloalkenyl) substituents,
aromatic-,
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aliphatic- and alicyclic-substituted aromatic nuclei and the like, as well as
cyclic
substituents wherein the ring is completed through another portion of the
ligand (that is,
any two indicated substituents may together form an alicyclic group).
2. Substituted hydrocarbon substituents, that is, those containing non-
hydrocarbon groups which, in the context of this invention, do not alter the
predominantly hydrocarbyl character of the substituent. Those skilled in the
art will be
aware of suitable groups (e.g., halo, especially chloro and fluoro, amino,
alkoxyl,
mercapto, alkylmercapto, nitro, nitroso and sulfoxy).
3. Hetero substituents, that is substituents which, while predominantly
hydrocarbon in character within the context of this invention, contain atoms
other than
carbon present in a chain or ring otherwise composed of carbon atoms.
Importantly, the organo groups of the ligands have a sufficient number of
carbon
atoms to render the compound soluble or dispersible in the oil. For example,
the
number of carbon atoms in each group will generally range between 1 to 100,
preferably
from 1 to 30, and more preferably between 4 to 20. Preferred ligands include
dialkyldithiophosphate, alkylxanthate, and dialkyldithiocarbamate, and of
these
dialkyldithiocarbamate is more preferred. Organic ligands containing two or
more of
the above funcdonalities are also capable of serving as ligands and binding to
one or
more of the cores. Those skilled in the art will realize that formation of the
compounds
of the present invention requires selection of ligands having the appropriate
charge to
balance the core's charge.
Compounds having the formula Mo3SkLr,QZ have cationic cores surrounded by
anionic ligands and are represented by structures such as
' CA 02514370 2005-07-29
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r
~~ 6
and
and have net charges of +4. Consequently, in order to solubilize these cores
the total
charge among all the ligands must be -4. Four monoanionic ligands are
preferred.
Without wishing to be bound by any theory, it is believed that two or more
trinuclear
cores may be bound or interconnected by means of one or more ligands and the
ligands
may be multidentate. Such structures fall within the scope of this invention.
This
includes the case of a multidentate ligand having multiple connections to a
single core.
It is believed that oxygen and/or selenium may be substituted for sulfur in
the core(s).
Oil-soluble or oil-dispersible trinuclear molybdenum compounds can be
prepared by reacting in the appropriate liquids) and/or solvents) a molybdenum
source
such as (NI~)2Mo3S~3~n(Hz0), where n varies between 0 and 2 and includes non-
stoichiometric values, with a suitable ligand source such as a
tetralkylthiuram disulfide.
Other oil-soluble or oil-dispersible trinuclear molybdenum compounds can be
formed
during a reaction in the appropriate solvents) of a molybdenum source such as
of
(NH4)2Mo3S13w(H20), a ligand source such as tetralkylthiuram disulfide,
dialkyldithiocarbamate, or dialkyldithiophosphate, and a sulfur-abstracting
agent such
cyanide ions, sulfite ions, or substituted phosphines. Alternatively, a
trinuclear
molybdenum-sulfur halide salt such as [M']2[Mo3S7A6], where M' is a counter
ion, and
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A is a halogen such as C1, Br, or I, may be reacted with a ligand source such
as a
dialkyldithiocarbamate or dialkyldithiophosphate in the appropriate liquids)
and/or
solvents) to form an oil-soluble or oil-dispersible trinuclear molybdenum
compound.
The appropriate liquid and/or solvent may be, for example, aqueous or organic.
A compound's oil solubility or dispersibility may be influenced by the number
of carbon atoms in the ligand's organo groups. In the compounds employed in
the
present invention, at least 21 total carbon atoms should be present among all
the
ligand's organo groups. Preferably, the ligand source chosen has a sufficient
number
of carbon atoms in its organo groups to render the compound soluble or
dispersible in
the lubricating composition.
The molybdenum compound is preferably a trinuclear molybdenum
dithiocarbamate.
Natural oils useful as the oil of lubricating viscosity (also known as
basestocks) in this invention include animal oils and vegetable oils (e.g.
castor, lard
oil) liquid petroleum oils and hydrorefined, solvent-treated or acid-treated
mineral
lubricating oils of the paraffinic, naphthenic and mixed paraffinic-naphthenic
types.
Oils of lubricating viscosity derived from coal or shale are also useful base
oils.
Alkylene oxide polymers and interpolymers and derivatives thereof where the
terminal hydroxyl groups have been modified by esterification or
etherification
constitute a class of known synthetic lubricating oils useful as basestocks in
this
invention. These are exemplified by polyoxyalkylene polymers prepared by
polymerization of ethylene oxide or propylene oxide, the alkyl and aryl ethers
of these
polyoxyalkylene polymers (e.g. methyl-poly isopropylene glycol ether having an
average molecular weight of 1000, diphenyl ether of poly-ethylene glycol
having a
molecular weight of 500-1000, diethyl ether of polypropylene glycol having a
molecular weight of 1000-1500); and mono- and polycarboxylic esters thereof,
for
example, the acetic acid esters, mixed C3-Cs fatty acid esters and C13 Oxo
acid diester
of tetraethylene glycol.
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Another suitable class of synthetic lubricating oils useful in this invention
comprises the esters of dicarboxylic acids (e.g. phthalic acid, succinic acid,
alkyl
succinic acids and alkenyl succinic acids, malefic acid, azelaic acid, suberic
acid,
sebasic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid,
alkylmalonic
acids, alkenyl malonic acids) with a variety of alcohols (i-butyl alcohol,
hexyl alcohol,
dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol
monoether,
propylene glycol). Specific examples of these esters include dibutyl adipate,
di(2-
ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl
azelate,
diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate,
the 2-
ethylhexyl diester of linoleic acid dimer, and the complex ester formed by
reacting
one mole of sebacic acid with two moles of tetraethylene glycol and two moles
of 2-
ethylhexanoic acid.
Esters useful as synthetic oils also include those made from CS to C12
monocarboxylic acids and polyols and polyol ethers such as neopentyl glycol,
trimethylolpropane, pentaerythritol, dipentaerythritol and tripentaerythritol.
Silicon-based oils such as the polyalkyl-, polyaryl-, polyalkoxy-, or
polyaryloxysiloxane oils and silicate oils comprise another useful class of
synthetic
lubricants; they include tetraethyl silicate, tetraisopropyl silicate, tetra-
(2-ethylhexyl)
silicate, tetra-(4-methyl-2-ethylhexyl) silicate, tetra-(p-tertbutylphenyl)
silicate, hexa-
(4-methyl-2-pentoxy) disiloxane, poly(methyl) siloxanes and poly(methylphenyl)
siloxanes. Other synthetic lubricating oils include liquid esters of
phosphorus-
containing acids (e.g. tricresyl phosphate, trioctyl phosphate, diethyl ester
of
decylphosphonic acid) and polymeric tetrahydrofurans.
Unrefined, refined and rerefined oils can be used in the lubricating oil
compositions of the present invention. Unrefined oils are those obtained
directly from
a natural or synthetic source without further purification treatment. For
example, a
shale oil obtained directly from retorting operations, a petroleum oil
obtained directly
from distillation or ester oil obtained directly from an esterification
process and used
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without further treatment would be an unrefined oil. Refined oils are similar
to the
unrefined oils except they have been further treated in one or more
purification steps
to improved one or more properties. Many such purification techniques, such as
distillation, solvent extraction, acid or base extraction, filtration and
percolation are
known to those skilled in the art. Rerefined oils are obtained by processes
similar to
those used to obtain refined oils applied to refined oils which have been
already used
in service. Such rerefined oils are also known as reclaimed or reprocessed
oils and
often are additionally processed by techniques for removal of spent additives
and oil
breakdown products.
Lubricating oil compositions for use in any aspect of the present invention
may
also contain any of the conventional additives listed below (including any
additional
friction modifiers) which are typically used in a minor amount, e.g. such an
amount so
as to provide their normal attendant functions. Typical amounts for individual
components are also set forth below. All the values listed are stated as mass
percent
active ingredient in the total lubricating oil composition.
ADDITIVE MASS % MASS %
(Broad) (Preferred)
Ashless Dispersant 0.1 - 20 1 - 8
Metal Detergents 0.1 - 15 0.2 - 9
Corrosion Inhibitors 0 - 5 0 - 1.5
Metal Dihydrocarbyl Dithiophosphate0.1- 6 0.1 - 4
Anti-oxidant 0 - 5 0.01 - 3
Pour Point Depressant 0.01 - 5 0.01 - 1.5
Anti-foaming Agent 0 - 5 0.001 - 0.15
Supplemental Anti-wear Agents 0 - 5 0 - 2
Additional Friction Modifier 0 - 5 0 - 1.5
Viscosity Modifier 0 - 6 0.01 - 4
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The individual additives may be incorporated into a basestock in any
convenient way. Thus, each of the components can be added directly to the
basestock
by dispersing or dissolving it in the basestock at the desired level of
concentration.
Such blending may occur at ambient temperature or at an elevated temperature.
Preferably, all the additives except for the viscosity modifier and the pour
point depressant are blended into a concentrate (or additive package) that is
subsequently blended into basestock to make a finished lubricating oil
composition.
Use of such concentrates is conventional. The concentrate will typically be
formulated to contain the additives) in proper amounts to provide the desired
concentration in the final lubricating oil composition when the concentrate is
combined with a predetermined amount of base oil.
The concentrate is conveniently made in accordance with the method
described in U.S. 4,938,880. That patent describes making a pre-mix of ashless
dispersant and metal detergents that is pre-blended at a temperature of at
least about
200°C. Thereafter, the pre-mix is cooled to at least 85°C and
the additional
components are added.
The final crankcase lubricating oil composition may employ from 2 to 20 mass
% and preferably 4 to 15 mass % of the concentrate (or additive package), the
remainder being base oil.
Ashless dispersants maintain in suspension oil-insoluble matter resulting from
oxidation of the oil during wear or combustion. They are particularly
advantageous
for preventing precipitation of sludge and formation of varnish, particularly
in
gasoline engines.
Ashless dispersants comprise an oil-soluble polymeric hydrocarbon backbone
bearing one or more functional groups that are capable of associating with
particles to
be dispersed. Typically, the polymer backbone is functionalized by amine,
alcohol,
amide, or ester polar moieties, often via a bridging group. The ashless
dispersant may
CA 02514370 2005-07-29
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be, for example, selected from oil-soluble salts, esters, amino-esters,
amides, imides,
and oxazolines of long chain hydrocarbon substituted mono and dicarboxylic
acids or
their anhydrides; thiocarboxylate derivatives of long chain hydrocarbons; long
chain
aliphatic hydrocarbons having a polyamine attached directly thereto; and
Mannich
condensation products formed by condensing a long chain substituted phenol
with
formaldehyde and polyalkylene polyamine.
The oil-soluble polymeric hydrocarbon backbone of these dispersants is
typically derived from an olefin polymer or polyene, especially polymers
comprising a
major molar amount (i.e. greater than 50 mole %) of a C2 to Clg olefin (e.g.
ethylene,
propylene, butylene, isobutylene, pentene, octene-1, styrene), and typically a
C2 to CS
olefin. The oil-soluble polymeric hydrocarbon backbone may be a homopolymer
(e.g.
polypropylene or polyisobutylene) or a copolymer of two or more of such
olefins (e.g.
copolymers of ethylene and an alpha-olefin such as propylene or butylene, or
copolymers of two different alpha-olefins). Other copolymers include those in
which
a minor molar amount of the copolymer monomers, for example, 1 to 10 mole %,
is
an a,w-diene, such as a C3 to C22 non-conjugated diolefin (for example, a
copolymer
of isobutylene and butadiene, or a copolymer of ethylene, propylene and 1,4-
hexadiene or 5-ethylidene-2-norbornene). Preferred are polyisobutenyl (Mn 400-
2500, preferably 950-2200) succinimide dispersants.
The viscosity modifier (VM) functions to impart high and low temperature
operability to a lubricating oil composition. The VM used may have that sole
function, or may be multifunctional.
Multifunctional viscosity modifiers that also function as dispersants are also
known. Suitable viscosity modifiers are polyisobutylene, copolymers of
ethylene and
propylene and higher alpha-olefins, polymethacrylates, polyalkylmethacrylates,
methacrylate copolymers, copolymers of an unsaturated dicarboxylic acid and a
vinyl
compound, inter polymers of styrene and acrylic ester, and partially
hydrogenated
copolymers of styrene/isoprene, styrene/butadiene, and isoprene/butadiene, as
well as
CA 02514370 2005-07-29
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the partially hydrogenated homopolymers of butadiene and isoprene and
isoprene/divinylbenzene.
Metal-containing or ash-forming detergents may be present and these function
both as detergents to reduce or remove deposits and as acid neutralizers or
rust
inhibitors, thereby reducing wear and corrosion and extending engine life.
Detergents
generally comprise a polar head with a long hydrophobic tail, the polar head
comprising a metal salt of an acid organic compound. The salts may contain a
substantially stoichiometric amount of the metal in which they are usually
described
as normal or neutral salts, and would typically have a total base number
(TBN), as
may be measured by ASTM D-2896 of from 0 to 80. It is possible to include
large
amounts of a metal base by reacting an excess of a metal compound such as an
oxide
or hydroxide with an acid gas such as carbon dioxide. The resulting overbased
detergent comprises neutralized detergent as the outer layer of a metal base
(e.g.
carbonate) micelle. Such overbased detergents may have a TBN of 150 or
greater, and
typically from 250 to 450 or more. Detergents that may be used include oil-
soluble
neutral and overbased sulfonates, phenates, sulfurized phenates,
thiophosphonates,
saiicylates, and naphthenates and other oil-soluble carboxylates of a metal,
particularly the alkali, e.g. sodium, potassium, lithium and magnesium.
Preferred are
neutral or overbased calcium and magnesium phenates and sulfonates, especially
calcium.
Other friction modifiers include oil-soluble amines, amides, imidazolines,
amine oxides, amidoamines, nitriles, alkanolamides, alkoxylated amines and
ether
amines; polyol esters; and esters of polycarboxylic acids.
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. 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
CA 02514370 2005-07-29
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S dithiophosphoric acid may be made by reacting mixtures of primary and
secondary
alcohols. 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 may be used but 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 neutralization
reaction.
ZDDP provides excellent wear protection at a comparatively low cost and also
functions as an antioxidant. However, there is some evidence that phosphorus
in
lubricant can shorten the effective life of automotive emission catalysts.
Accordingly,
the lubricating oil compositions of the invention preferably contain no more
than 0.8
wt %, such as from 50 ppm to 0.06 wt %, of phosphorus. Independently of the
amount of phosphorus, the lubricating oil composition preferably has no more
than
0.5 wt %, preferably from 50 ppm to 0.3 wt %, of sulfur, the amounts of sulfur
and of
phosphorus being measured in accordance with ASTM D5185.
Oxidation inhibitors or antioxidants reduce the tendency of basestocks to
deteriorate in service, which deterioration can be evidenced by the products
of
oxidation such as sludge and varnish-like deposits on the metal surfaces and
by
viscosity growth. Such oxidation inhibitors include hindered phenols, alkaline
earth
metal salts of alkylphenolthioesters having preferably CS to C12 alkyl side
chains,
calcium nonylphenol sulfide, ashless oil-soluble phenates and sulfurized
phenates,
phosphosulfurized or sulfurized hydrocarbons, phosphorous esters, metal
thiocarbamates, oil-soluble copper compound as described in U.S. 4,867,890,
and
molybdenum-containing compounds.
Rust inhibitors selected from the group consisting of nonionic polyoxyalkylene
polyols and esters thereof, polyoxyalkylene phenols, and anionic alkyl
sulfonic acids
may be used.
CA 02514370 2005-07-29
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Copper- and lead-bearing corrosion inhibitors may be used, but are typically
not required in the lubricating oil compositions of the present invention.
Typically
such compounds are thiadiazole polysulfides containing from 5 to 50 carbon
atoms,
their derivatives and polymers thereof. Derivatives of 1,3,4-thiadiazoles,
such as
those described in U.S. Patent Nos. 2,719,125; 2,719,126; and 3,087,932, are
typical.
Other similar material 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
thio
and polythio sulfenamides of thiadiazoles such as those described in GB-A-
1,560,830.
Benzotriazoles derivatives also fall within this class of additive. When these
compounds are included in the lubricating oil compositions, 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-A-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 lute oil improvers, lower the
minimum 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 C8 and C18 dialkyl fumarate/vinyl acetate
copolymers and
polyalkylmethacrylates.
Foam control can be provided by many compounds including an antifoamant
of the polysiloxane type, for example, silicone oil or polydimethyl siloxane.
In this specification, the term "comprising" (or cognates such as "comprises")
means 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. If the term "comprising" (or cognates) is used
herein,
the term "consisting essentially oP' (and its cognates) is within its scope
and is a
CA 02514370 2005-07-29
-17-
preferred embodiment; consequently the term "consisting of (and its cognates)
is
within the scope of "consisting essentially of and is a preferred embodiment
thereof.
The terms "oil-soluble" or "oil-dispersible" do not mean that the compounds
are soluble, dissolvable, miscible or capable of being suspended in the oil in
all
proportions. They do mean, however, that the compounds are, for instance,
soluble or
stably dispersible in the oil to an extent sufficient to exert their intended
effect in the
environment in which the composition is employed. Moreover, the additional
incorporation of other additives such as those described above may affect the
solubility or dispersibility of the compounds.
The term "major amount" means in excess of 50 mass % of the composition.
The term "minor amount" means less than SO mass % of the composition.
The invention is further illustrated by the following examples which are not
to
be considered as limitative of its scope. All percentages are by weight active
ingredient content of an additive without regard for Garner or diluent oil.
EXAMPLES
All of the following experiments were carried out using were obtained using a
Cameron Plint reciprocating pin on plate tribometer, using the following test
protocol:
Test duration 8 hours
Load(N) 185
Stroke len h mm 10
Fre uenc (Hz) 1
Tem rature (C) 100
The surface materials used are as set out below:
' CA 02514370 2005-07-29
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Hardness Density
BS EN31 C O Si r Mn Fe (Hv) (g/cm~)
Wt% 0.64 - .5 1.57 0.4 6.7 185 7.75
AI-Si Alloy C O Si Cu AI M
Wt% 4.44 2.29 22. 2 1.12 68.25 1.27 120 2.62
BS 1452 C O Si Mo Mn Fe
Wt% 9.32 1.91 2.74 0.44 .71 84.88 150 7.01
The coefficients of friction and wear coefficients for the lubrication of
various
surface combinations with a each of the following lubricant compositions, were
measured:
1. a Group III base oil having a lcinematic viscosity at 100°C of 4.2
p.m2s'1 (CSt);
2. a composition containing the base oil of composition 1 and 500 ppm of
molybdenum as trinuclear molybdenum dithiocarbamate, having a structural
formula as shown below,
D D
Rw ~ R
R
3. a composition containing the base oil of composition 1 and 500 ppm of
molybdenum as dinuclear molybdenum dithiocarbamate, having a structural
formula as shown below,
CA 02514370 2005-07-29
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$ ;~I~/~I~,~w, ~R
' M M~~~ N
R S ~ S R
X=OorS
4. a composition according to composition 2 additionally comprising a minor
amount of a secondary ZDDP additive, and
5. a composition according to composition 2 additionally comprising a minor
amount of a primary ZDDP.
Example 1 BS EN1452 pin on Al-Si allo~nlate
A comparison of friction coefficient for Compositions 1, 2 and 3 is set out in
Table 1 and Graph 1. A comparison of wear coefficient for Compositions 1, 2
and 3
is set out in Graph 2.
It can be seen from Table 1 and Graph 1 below, that Composition 2,
containing the trinuclear organo-molybdenum compound, exhibits a significantly
lower friction coefficient than Composition 1 or 2. Furthermore, the
coefficient of
friction for Composition 2 continues to reduce as the test proceeds, unlike
Composition 1 or 3, for which the friction coefficient increases as the test
proceeds.
A comparison of the percentage improvement in friction coefficient of
Composition 2 compared to Composition 1 at equivalent points in the test also
illustrates the generally increasing reduction of friction coefficient of
Composition 2
compared to Composition 1. In addition, Table 1 illustrates that Composition 2
performs significantly more effectively at reducing the coefficient of
friction than
CA 02514370 2005-07-29
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Composition 3, which generally performs less well than Composition 1 (as
indicated
by the negative prefix).
Graph 1
C
V
C
0
20 Table 1 (Friction Coefficient)
Time Comp.l Comp.2 Comp.3 Comp.2 Comp.3
(min) ~ Improvement% Improvement
0 0.0895 0.0933 0.0920 -4.25 -2.79
30 0.0933 0.1094 0.1141 -17.26 -22.29
60 0.1077 0.1014 0.1253 5.85 -16.34
90 O.1I05 0.0988 0.1249 10.59 -13.03
120 0.1164 0.0958 0.1203 17.70 -3.35
150 0.1222 0.0936 0.1218 29.31 0.32
180 0.1310 0.0926 0.1351 28.77 -3.13
210 0.1300 0.0896 0.1463 31.08 -12.54
240 0.1406 0.0892 0.1481 36.56 -5.33
270 0.1509 0.0871 0.1535 42.28 -1.72
300 0.1406 0.0868 0.1494 38.26 -6.26
330 0.1500 0.0842 0.1578 43.87 -5.20
360 0.1361 0.0847 0.1606 37.77 -18.00
390 0.1293 0.0836 0.1555 35.34 -20.26
420 0.1448 0.0833 0.1558 42.47 -20.49
450 0.1488 0.0805 0.1606 45.90 -7.93
480 0.1595 0.0777 0.1610 51.29 -0.94
lVOte: ~ Improvement is measured relative to Composition l
0 80 120 180 240 300 380 420 480
Time (min)
Composition 1 -i-ComposlUon 2 -1- ComposiHOn 3
' CA 02514370 2005-07-29
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From Graph 2 below, it can be seen that the alumina plate suffers
significantly
lower wear when lubricated with Composition 2, containing the trinuclear
organo-
molybdenum compound, than when lubricated with lubricating Composition 1 or 3.
Graph 2
~ ~
Wear
Coef
(K)
Average
p
3.OOE-04 0.16O
2.50E-04 0.14
c 0.12O
2.OOE-04
0.10n
1.50E-04 0.08
V 06 R
0
~ 1 OOE-04 .
0.04
5 F
OOE-05
. 0.02"
O.OOE+00 0.00
N M
.O .O
."
O
U U U
A comparison of friction coefficient for Compositions 2, 4 and 5 is set out in
Table 2 and Graph 3.
From Graph 3 it can be seen that Composition 5 exhibits a lower friction
coefficient than Composition 4. Although, addition of ZDDP to the trinuclear
organo-
molybdenum containing composition, Composition 2, has a negative impact on the
friction reduction associated with the trinuclear molybdenum compound, the
above
graph shows that the primary ZDDP of Composition 5 has a less detrimental
effect on
the friction coefficient than secondary ZDDP of Composition 4.
CA 02514370 2005-07-29
Graph 3
0.18
0.16
0.14
-22-
0.12
...
0.1
U
a
0.08
0.06
0 60 120 180 240 300 360 420 480
Time (min)
r-,~ComposiNon (2) -tComposition (4) -~--Composition (5)
Table 2 (Friction Coefficient)
Time Comp.2 Comp.4 Comp.S
(min)
0 0.0933 0.1006 0.1512
30 0.1094 0.1105 0.1218
60 0.1014 0.1279 0.1348
90 0.0988 0.1347 0.1362
120 0.0958 0.1366 0.1325
150 0.0936 0.1422 0.1348
180 0.0926 0.1455 0.1344
210 0.0896 0.1501 0.1395
240 0.0892 0.1524 0.1397
270 0.0871 0.1529 0.1344
300 0.0868 0.1531 0.1392
330 0.0842 0.1520 0.1400
360 0.0847 0.1557 0.1388
390 0.0836 0.1568 0.1389
420 0.0833 0.1604 0.1391
450 0.0805 0.1607 0.1387
480 0.0777 0.1603 0.1396
CA 02514370 2005-07-29
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Example 2 BS EN1452~in on a BS EN31 plate
A comparison of friction coefficient for Compositions l, 2 and 3 is set out in
Table 3 and Graph 4. A comparison of wear coefficient for Compositions 1, 2
and 3
is set out in Graph 5.
From Table 3 and Graph 4 below, it can be seen that composition 2,
comprising the trinuclear organo-molybdenum compound, results in significantly
lower friction coefficient than lubricant Compositions 1 or 3. The percentage
improvement figures in Table 3 illustrate that Composition 2 provides an
increasingly
better friction performance when compared with either Composition 1 or 3, as
the test
proceeds. Graph 4 and Table 3 also illustrates that Composition 3, comprising
dinuclear molybdenum actually exhibits coefficients of friction that are
higher than
Composition 1, with no molybdenum additive.
Graph 4
o.zz
0.2
0.18
m 0.18
v ~
0.14
0.12
0.1
0.08
0.08
0.04
0 BO 120 180 240 300 380 420 480
Time (min)
~t ca",~«, ~n -r.. c«"~nw, ~z> -~ c~,~m«, ~3>
CA 02514370 2005-07-29
-24-
Table 3 (Friction Coefficient)
Time Comp.l Comp.2 Comp.3 Comp.2 ~ Comp.3
(min) % Improvement% Improvement
0 0.1537 0.1303 0.1437 6.51 6.51
30 0.1228 0.0888 0.1539 27.69 -25.33
60 0.1302 0.0909 O.I486 30.18 -14.13
90 0.1372 0.0921 0.1626 32.87 -18.51
120 0.1463 0.0953 0.1825 34.86 -24.74
150 0.1606 0.0980 0.1816 38.98 -13.08
180 0.1494 0.0990 O.I943 33.73 -30.05
210 0.1574 0.0988 0.1935 37.23 -22.94
240 0,1593 0.1012 0.1981 36.47 -24.36
270 O.I557 0.1013 0.1832 34.94 -17.66
300 0.1640 0.0992 0.1954 39.51 -19.15
330 0.1641 0.1010 0.1758 38.45 -7.13
360 0.1715 0.1015 0.2115 40.82 -23.32
390 0.1664 0.1006 0.2142 39.54 -28.73
420 0.1635 0.0995 0.2197 39.14 -34.37
450 0.1717 0.1003 0.2184 41.58 -27.20
480 0.1752 0.1019 0.2183 41.84 -24.60
Note: ~o Improvement is measured relative to Composition 1
From Graph 5 below, it can be seen that the BS EN31 plate exhibits
significantly less wear when lubricated with Composition 2 than with either of
lubricating Compositions 1 or 3.
(Continued on Page 25)
20
CA 02514370 2005-07-29
-25-
Graph 5
..
c
m
O r~
Wear
Coef
(K)
Average
N
B.OE-06 0.20
C7
c
0.18
5.OE-06 ;~
.. ;
.
0.16
'~ 4.OE-06
0.14
Q
V
3.OE-06
0.12
3
2.OE-06
0.10
1.OE-08 0.08
O.OE+00 0.06
.. ..
r
~
M
v
A b O
a
p
.a .o ,a
. .a
.a
.
~
U~ ~ U
U
U
A comparison of friction coefficient for Compositions 2, 4 and 5 is set out in
Table 4 and Graph 6.
From Table 4 and Graph 6 below, it can be seen that lubricating Composition 4
effects a greater reduction in friction coefficient than either of lubricating
Compositions 2 or 5. Suprisingly, when lubricating a BS EN1452 pin on a BS
EN31
plate addition of secondary ZDDP additive (Composition 4) to a lubricant
containing
trinuclar molybdenum improves the coefficient of friction. It is noted that
addition of
primary ZDDP (Composition 5) to the lubricant in place of secondary ZDDP has a
detrimental effect of the coefficient of friction.
' ' CA 02514370 2005-07-29
-26-
Graph 6
o.ls
0.14
0 0.12
g o.1
U
c
0.08
.
c
0.06
0.04 T--~----t-
0 60 120 180 240 300 360 420 480
-~.- Composition (2) -f- Composition (4) ~-. Composition (5)
Table 4 (Friction Coefficient)
Time Comp.2 Comp.4 Comp.S
(min)
0 0.1303 0.1225 0.1207
0.0888 0.0991 0.1170
60 0.0909 0.1013 0.1140
90 0.0921 0.1016 0.1177
120 0.0953 0.0988 0.1163
150 0.0980 0.0935 0.1169
180 0.0990 0.0942 0.1189
210 0.0988 0.0737 0.1196
240 0.1012 0.0637 0.1213
270 0.1013 0.0650 0.1204
300 0.0992 0.0650 0.1208
330 0.1010 0.0656 0.1204
360 0.1015 0.0648 0.1206
390 0.1006 0.0682 0.1227
420 0.0995 0.0698 0.1227
450 0.1003 0.0707 0.1245
480 0.1019 0.0710 0.1267
