Note: Descriptions are shown in the official language in which they were submitted.
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LUBRICATING OIL COMPOSITIONS FOR MARINE ENGINES
The present invention relates to lubricating oil compositions. More
particularly, the present invention relates to .lubricating oil compositions,
which are
designed for use with four cycle marine engines.
BACKGROUND OF THE INVENTION
The invention embodies new oil blends specifically formulated for use in four
cycle marine engines, especially outboard engines. These oils have a high
phosphorus
level. These oils also contain a molybdenum antioxidant/antiwear additive and
a rust
inhibitor additive.
Current practice for four cycle outboard and other marine engine oils is to
use
automotive lubricants. This technology was never designed to meet the specific
performance needs of four cycle outboard engines. The oils embodied in this
invention provide specific performance improvements desirable in four cycle
outboard
engines: improved antioxidancy, antiwear, rust inhibition, shear stability,
good water
tolerance, air entrainment and high temperature foam properties.
SUMMARY OF THE INVENTION
In accordance with the invention, there is provided a lubricating oil
composition for use in four cycle marine engines, which composition comprises
at
least one oil of lubricating viscosity, an ashless dispersant, a metal
detergent, at least
one molybdenum compound in an amount sufficient to provide the composition
with
15 to 1,000 ppm by mass, of molybdenum, an amount of ZDDP (zinc
dialkyldithiophosphate) that contributes at least 1,200 ppm of phosphorus to
the
lubricating oil composition, an effective amount of a rust inhibitor system
comprising
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certain combinations of rust inhibitors and, optionally, a viscosity modifier,
the
lubricating oil composition having a NOACK volatility of 15 wt.% or less.
A further embodiment of this invention comprises a method of operating and
lubricating a four cycle marine engine which comprises supplying to said
engine the
lubricating oil composition of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The lubricating compositions of the present invention contain an oil of
lubricating viscosity, an ashless dispersant, a metal detergent, a rust
inhibitor, a
relatively high amount of ZDDP, and an amount of a molybdenum compound
sufficient to provide the composition with 15-1,000 ppm by mass of molybdenum.
An amount of about 15 ppm to 1,000 ppm by mass of molybdenum from a
molybdenum compound has been found to be effective as an antiwear agent in
combination with the high levels of ZDDP.
It is also necessary that the volatility of the lubricating oil composition,
as
measured using the NOACK Volatility Test, be about 15 wt.% or less, such as in
the
range of 4 to 15 wt.%, preferably in the range of 8 to 15 wt.%. The NOACK
Volatility Test is used to measure the evaporative loss of an oil after 1 hour
at 250 C
according to the procedure of ASTM D5800. The evaporative loss is reported in
mass
percent.
The oil of lubricating viscosity useful in the context of the present
invention is
selected from the group consisting of Group I, Group II, or Group III, Group
IV or
Group V base stocks or base oil blends of the aforementioned base stocks.
Generally,
the viscosity of such oils ranges from about 2 mnf/sec (centistokes) to about
40
mm2/sec at 100 C. Preferred are base stocks or base stock mixtures having an
intrinsic viscosity of from about 4.0 to about 5.5 mm2/sec at 100 C. Further
preferable are base stocks and base stock mixtures having avolatility, as
measured by
the NOACK test (measured by determining the evaporative loss in mass percent
of an
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oil after 1 hour at 250 C according to the procedure of ASTM D5800~ of less
than
15%, more preferably less than 12%, most preferably less than 10% The most
preferred oils are:
(a) Base oil blends of Group III, IV or V base stocks with Group I or
Group II base stocks, where the combination has a viscosity index of at
least 110; and
(b) Group III, IV or V base stocks or base oil blends of more than one
Group III, IV and/or V base stock, where the viscosity index is
between about 120 to about 140,
Definitions for the base stocks and base oils in this invention are the same
as
those found in the American Petroleum Institute (API) publication "Engine Oil
Licensing and Certification System", Industry Services Department, Fourteenth
Edition, December 1996, Addendum 1, December 1998. Said publication
categorizes
base stocks as follows:
a.) Group I base stocks contain less than 90 percent saturates and/or greater
than
0.03 percent sulfur and have a viscosity index greater than or equal to 80 and
less than 120 using the test methods specified in Table F-l.
b.) Group II base stocks contain greater than or equal to 90 percent saturates
and
less than or equal to 0.03 percent sulfur and have a viscosity index greater
than
or equal to 80 and less than 120 using the test methods specified in Table E-
1.
c.) Group III base stocks contain greater than or equal to 90 percent
saturates and
less than or equal to 0.03 percent sulfur and have a viscosity index greater
than
or equal to 120 using the test methods specified in Table E- 1.
d.) Group IV base stocks are polyalphaolefins (PAO).
e.) Group V base stocks include all other base stocks not included in Group I,
II,
III, or IV, such as synthetic ester base stocks
Lubricating compositions of this invention which exhibit a biodegradability of
at least 50% in the ASTM D5864-95 modified Sturm test may be prepared using
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synthetic ester base stocks prepared from polyhydric or monohydric alcohols
and
carboxylic acids.
Table E-1 - Analytical Methods for Base Stock
Property Test Method
Saturates ASTM D 2007
Viscosity Index ASTM D 2270
Sulfur ASTM D 2622
ASTM D 4294
ASTM D 4927
ASTM D 3120
Suitable ashless dispersants for use in this invention include hydrocarbyl
succinimides, hydrocarbyl succinamides, mixed ester/amides of hydrocarbyl-
substituted succinic acid, hydroxyesters of hydrocarbyl-substituted succinic
acid, and
Mannich condensation products of hydrocarbyl-substituted phenols, formaldehyde
and polyamines. Also useful are condensation products of polyamines and
hydrocarbyl substituted phenyl acids. Mixtures of these dispersants can also
be ur'd.
Basic nitrogen containing ashless dispersants are well known lubricating oil
additives, and methods for their preparation are extensively described in the
patent
literature. For example, hydrocarbyl-substituted succinimides and succinamides
and
methods for their preparation are described, for example, in U.S. patent
numbers:
3,018,247; 3,018,250; 3,018,291; 3,361,673 and 4,234,435. Mixed ester-amides
of
hydrocarbyl-substituted succinic acids are described, for example, in U.S.
patents
numbers: 3,576,743; 4,234,435 and 4,873,009. Mannich dispersants, which are
condensation products of hydrocarbyl-substituted phenols, formaldehyde and
polyamines are described, for example, in U.S. patents numbers: 3,368,972;
3,413,347; 3,539,633; 3,697,574; 3,725,277; 3,725,480; 3,726,882; 3,798,247;
3,803,039; 3,985,802; 4,231,759 and 4,142,980. Amine dispersants and methods
for
their production from high molecular weight aliphatic or alicyclic halides and
amines
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are described, for example, in U.S. patent numbers: 3,275,554; 3,438,757;
3,454,55
and 3,565,804.
The preferred dispersants are the alkenyl succinimides and succinamides. The
succinimide or succinamide dispersants can be formed from amines containing
basic
nitrogen and additionally one or more hydroxy groups. Usually, the amines are
polyamines such as polyalkylene polyamines, hydroxy-substituted polyamines and
polyoxyalkylene polyamines. Examples of polyalkylene polyamines include
diethylene triamine, triethylene tetramine, tetraethylene pentamine,
pentaethylene
hexamine. Low cost poly(ethyleneamines) averaging about 5 to 7 nitrogen atoms
per
molecule are available commercially under trade names such as "Polyamine H",
"Polyamine 400", "Dow Polyamine E-100", etc. Hydroxy-substituted amines
include
N-hydroxyalkyl-alkylene polyamines such as N-(2-hydroxyethyl)ethylene diamine,
N-(2-hydroxyethyl)piperazine, and N-hydroxyalkylated alkylene diamines of the
type
described in U.S. 4,873,009. Polyoxyalkylene polyamines typically include
polyoxyethylene and polyoxypropylene diamines and triamines having average
molecular weights in the range of 200 to 2500. Products of this type are
available
under the Jeffamine trademark.
The amine is readily reacted with the selected hydrocarbyl-substituted
dicarboxylic acid material, e.g., alkylene succinic anhydride, by heating an
oil
solution containing 5 to 95 wt. % of said hydrocarbyl-substituted dicarboxylic
acid
material at about 100 to 250 C, preferably 125 to 175 C, generally for 1 to
10, e.g.,
2 to 6 hours until the desired amount of water is removed. The heating is
preferably
carried out to favor formation of imides or mixtures of imides and amides,
rather than
amides and salts. Reaction ratios of hydrocarbyl-substituted dicarboxylic acid
material to equivalents of amine as well as the other nucleophilic reactants
described
herein can vary considerably, depending on the reactants and type of bonds
formed.
Generally from 0.1 to 1.0, preferably from about 0.2 to 0.6, e.g., 0.4 to 0.6,
equivalents of dicarboxylic acid unit content (e.g., substituted succinic
anhydride
content) is used per reactive equivalent of nucleophilic reactant, e.g.,
amine. For
example, about 0.8 mole of a pentamine (having two primary amino groups and
five
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reactive equivalents of nitrogen per molecule) is preferably used to convert
into a
mixture of amides and imides, a composition derived from reaction of
polyolefin and
maleic anhydride having a functionality of 1.6; i.e., preferably the pentamine
is used
in an amount sufficient to provide about 0.4 equivalents of succinic anhydride
units
per reactive nitrogen equivalent of the amine.
Use of alkenyl succinimides which have been treated with a boronating agent
are also suitable for use in the compositions of this invention as they are
much more
compatible with elastomeric seals made from such substances as fluoro-
elastomers
to and silicon-containing elastomers. Dispersants may be post-treated with
many
reagents known to those skilled in the art. (see, e.g., U.S. Pat. Nos.
3,254,025,
3,502,677 and 4,857,214).
The preferred ashless dispersants are polyisobutenyl succinimides formed
from polyisobutenyl succinic anhydride and an alkylene polyamine such as
triethylene
tetramine or tetraethylene pentamine wherein the polyisobutenyl substituent is
derived
from polyisobutene having a number average molecular weight (Mn) in the range
of
300 to 2500 (preferably 1600 to 2500). The polyisobutenyl succinic anhydride
used
to prepare the dispersant may be chlorine-free such as one made from a highly
reactive, terminally unsaturated polyisobutylene or it may be a mixture of
chlorine-
containing and chlorine-free polyisobutenyl succinic anhydride such that the
finished
oil has less than 50 ppm chlorine.
The ashless dispersants of the invention should be present, on an active
ingredient basis, in an amount of from 1.0 to 3.75 wt.%. Heavy duty diesel
lubricants
commonly used as four cycle marine engine (e.g. outboard engine) lubricants
will
typically have 4-8 wt.% of dispersant.
Metal-containing or ash-forming detergents 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
long hydrophobic tail, with the polar head comprising a metal salt of an acid
organic
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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.
Known detergents include oil-soluble neutral and overbased sulfonates,
phenates, sulfurized phenates, thiophosphonates, salicylates, and naphthenates
and other
oil-soluble carboxylates of a metal, particularly the alkali or alkaline earth
metals, e.g.,
sodium, potassium, lithium, calcium, and magnesium. The most commonly used
metals
are calcium and magnesium, which may both be present in detergents used in a
lubricant, and mixtures of calcium and/or magnesium with sodium. Particularly
convenient metal detergents are neutral and overbased calcium sulfonates
having TBN
of from 20 to 450 TBN, and neutral and overbased calcium phenates and
sulfurized
phenates having TBN of from 50 to 450 and mixtures of calcium phenates and
sulfonates.
The detergents of the present invention may be salts of one type of organic
acid or salts of more than one type of organic acids, for example hybrid
complex
detergents. Preferably, they are salts of one type of organic acid.
The hybrid complex detergent is where the basic material within the detergent
is stabilised by more than one type of organic acid. It will be appreciated by
one
skilled in the art that a single type of organic acid may contain a mixture of
organic
acids of the same type. For example, a sulfonic acid may contain a mixture of
sulfonic acids of varying molecular weights. Such an organic acid composition
is
considered as one type. Thus, complex detergents are distinguished from
mixtures of
two or more separate overbased detergents, an example of such a mixture being
one of
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an overbased calcium salicylate detergent with an overbased calcium phenate
detergent.
The art describes examples of overbased complex detergents. For example,
s International Patent Application Publication Nos. 97-46643/4/5/6 and 7
describe
hybrid complexes made by neutralising a mixture of more than one acidic
organic
compound with a basic metal compound, and then overbasing the mixture.
Individual
basic micelles of the detergent are thus stabilised by a plurality of organic
acid types.
Examples of hybrid complex detergents include calcium phenate-salicylate-
sulfonate
detergent, calcium phenate-sulfonate detergent and calcium phenate-salicylate
detergent.
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".
Preferred complex detergents are salicylate-based detergents, for example, a
calcium phenate-salicylate-sulfonate detergent and "phenalates".
Metal detergents are present typically in amounts of 0.25 to 3.0 wt.% on an
active ingredient basis.
For the lubricating oil compositions of this invention, any suitable soluble
organo-molybdenum compound having anti-wear properties in lubricating oil
compositions may be employed. As an example of such soluble organo-molybdenum
compounds, there may be mentioned the dithiocarbamates, dithiophosphates,
dithiophosphinates, xanthates, thioxanthates, sulfides, and the like, and
mixtures thereof.
Particularly preferred are molybdenum dithiocarbamates,
dialkyldithiophosphates, alkyl
xanthates and alkylthioxanthates.
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The molybdenum compound may be mono-, di-, tri- or tetra-nuclear. Dinuclear
and trinuclear molybdenum compounds are preferred. The molybdenum compound is
preferably an organo-molybdenum compound. More preferably, the molybdenum
compound is selected from the group consisting of a molybdenum dithiocarbamate
(MoDTC), molybdenum dithiophosphate, molybdenum dithiophosphinate,
molybdenum xanthate, molybdenum thioxanthate, molybdenum sulfide and mixtures
thereof. Most preferably, the molybdenum compound is present as molybdenum
dithiocarbamate or a trinuclear organo-molybdenum compound.
Additionally, the molybdenum compound may be an acidic molybdenum
compound. 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, potassium
molybdate, and other alkaline metal molybdates and other molybdenum salts,
e.g.,
hydrogen sodium molybdate, MoOCl4, MoO2Br2, Mo2O3C16, molybdenum trioxide or
similar acidic molybdenum compounds.
Among the molybdenum compounds useful in the compositions of this
invention are organo-molybdenurn compounds of the formula
Mo(ROCS2)4 and
Mo(RSCS)4
wherein R is an organo group selected from the group consisting of alkyl,
aryl, aralkyl
and alkoxyalkyl, generally of from 1 to 30 carbon atoms, and preferably 2 to
12 carbon
atoms and most preferably alkyl of 2 to 12 carbon atoms. Especially preferred
are the
dialkyldithiocarbamates of molybdenum.
One class of preferred organo-molybdenum compounds useful in the lubricating
compositions of this invention are trinuclear molybdenum compounds, especially
those
of the formula Mo3SkLnQ2 and mixtures thereof wherein the L are 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
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water, amines, alcohols, phosphines, and ethers, and z ranges from 0 to 5 and
includes
non-stoichiometric values. 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
X R 1,
X1 \
- R 2,
X
2
x,\ R
X Y 3,
X
2
x1\ __ R~
_J N 4,
X
2 R2
and
x1 \ /.O RI
x2~
R2
and mixtures thereof, wherein X, X1, X2, and Y are independently selected from
the
group of oxygen and sulfur, and wherein R1, 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.
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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-,
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, sulfoxy, etc.).
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 figands 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 about 1 to
about
100, preferably from about 1 to about 30, and mole preferably between about 4
to about
20. Preferred ligands include dialkyldithiophosphate, alkylxanthate, and
dialkyldithiocarbamate, and of these dialkyldithiocarbamate is more preferred.
Organic
ligands containing two or more of the above functionalities 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.
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Compounds having the formula Mo3SkL,,QZ have cationic cores surrounded by
anionic ligands and are represented by structures such as
1
MO
6
and
s 1~
S
Mo
t '11~ ;~7 5 7,
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 dispersible trinuclear molybdenum compounds can be prepared
by reacting in the appropriate liquid(s)/solvent(s) a molybdenum source such
as
(NH4)2Mo3S13-n(H2O), 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 dispersible trinuclear molybdenum compounds can be formed during a
reaction in the appropriate solvent(s) of a molybdenum source such as
(NH4)2Mo3S13=n(H2O), 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
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molybdenum-sulfur halide salt such as [M'I[Mo3S7A6], where M' is a counter
ion, and A
is a halogen such as Cl, Br, or I, may be reacted with a ligand source such as
a
dialkyldithiocarbamate or dialkyldithiophosphate in the appropriate
liquid(s)/solvent(s)
to form an oil-soluble or dispersible trinuclear molybdenum compound. The
appropriate liquid/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 of 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.
Preferably the composition of this invention will contain about 25-300 ppm
molybdenum.
The terms "oil-soluble" or "dispersible" 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 employed.
Moreover, the
additional incorporation of other additives may also permit incorporation of
higher
levels of a particular additive, if desired.
Zinc dihydrocarbyl dithiophosphate (ZDDP) metal salts 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 PrS5
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 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
... .......... .. e.,__.. ....._._. _..._ ._.......,..._.. __' _..., ......._
.... ....wõ ,õ.õ.::,.,a ,..rn.,;.w.r.m+..r,>,xv.:F.aa~xa:~rwp-;_,.,wtt.
arns...,.raw. .....,..-,.,,.,w. .. .,..,..,_._M.
...,.,......_._._.._....__.......,...,.,M..>-.,..,_.....,.
,.......w.,.,_,...,....
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basic or neutral zinc compound could be used but the oxides, hydroxides and
carbonates are most generally employed. Commercial additives frequently
contain an
excess of zinc due to the use of an excess of the basic zinc compound in the
neutralization reaction.
The composition of this invention will contain ZDDP in such amounts so as to
provide at least 1,200 ppm P in the finished outboard engine oil, up to about
2,000
ppm P.
The preferred zinc dihydrocarbyl dithiophosphates are oil soluble salts of
dihydrocarbyl dithiophosphoric acids and may be represented by the following
formula:
S
R O 11
P S Zn
R'O 2
wherein R and R' 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 R'
groups are alkyl groups of 2 to 8 carbon atoms or mixtures thereof. 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-ethylhexyl, phenyl,
butylphenyl,
cyclohexyl, methylcyclopentyl, propenyl, butenyl. In order to obtain oil
solubility,
the total number of carbon atoms (i.e. R and R') in the dithiophosphoric acid
will
generally be about 5 or greater. The zinc dihydrocarbyl dithiophosphate can
therefore
comprise zinc dialkyl dithiophosphates. The zinc dialkylthiophosphate compound
can
be primary zinc, secondary zinc, or mixtures thereof, that is, the ZDDP
contains
primary and/or secondary alkyl groups derived from primary or secondary
alcohols,
but secondary alkyl groups are preferred, or ZDDP which has about 85%
secondary
alkyl groups and about 15% primary alkyl groups, such as 85% sec-butyl and 15%
iso-octyl.
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It is essential that the marine engine oil compositions of the present
invention
contain an effective amount of an oil soluble rust inhibitor system which
comprises an
ethoxylated C4-C18 alkyl, preferably nonyl, phenol rust inhibitor containing
about 2 to
10, preferably 3 to 5, such as 4 moles of ethylene oxide per mol in
combination with a
second, or a second and a third, rust inhibitor, with each rust inhibitor
being present in
an amount of from about 0.05 to 1.5 wt.%. The second rust inhibitor may be a
glycerol ester of a C8-C22 fatty acid, with oleic acid being preferred.
Especially
preferred are commercially available mixtures of glycerol oleates comprising a
major
amount of a mixture of glycerol monooleate and dioleate and very minor amounts
of
trioleate, such as a mixture comprising about 55 wt.% glycerol monooleate, 40
wt.%
glycerol dioleate and the balance glycerol trioleate. Other useful second rust
inhibitors are (i) the CZ C4 alkylene glycol, preferably propylene glycol,
half esters of
a C8-C22 alkyl or alkenyl succinic acid and (ii) C8-C22 alkyl or alkenyl
succinic acids or
anhydrides, where the alkyl or alkenyl is preferably dodecyl or isomerized
octadecenyl. Other preferred combinations are those where the second rust
inhibitor
is the glycerol ester and third rust inhibitor is present which is either the
aforesaid
glycol half ester or the aforesaid alkyl or alkenyl succinic acid or
anhydride,
preferably the propylene glycol half ester of dodecyl succinic anhydride or
dodecyl or
isomerized octadecenyl succinic acid or anhydride. Preferably, each rust
inhibitor in
all the combinations described herein is present in an amount of 0.10 to 0.40,
preferably 0.20 to 0.35 wt.%.
The compositions of the present invention will contain effective amounts of a
viscosity modifier as an optional ingredient depending on the viscosity grade
of the oil
which is desired. These are typically present in amounts ranging from 0.5 to
5.0 wt,%
on an active ingredient basis. Shear stable viscosity modifiers are preferred.
Suitable compounds for use as viscosity modifiers are generally high
molecular weight hydrocarbon polymers, including polyesters. Oil soluble
viscosity
modifying polymers generally have weight average molecular weights from about
CA 02480935 2004-09-08
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10,000 to 1,000,000, preferably from about 20,000 to 500,000, as determined by
gel
permeation chromatography or light scattering methods.
Representative examples of suitable viscosity modifiers are polyisobutylene,
copolymers of ethylene and propylene and higher alpha-olefins,
polymethacrylates,
polyalkylmethacrylates, methacrylate copolymers, copolymers of unsaturated
dicarboxylic acid and vinyl compound, inter polymers of styrene and acrylic
ester, and
partially hydrogenated copolymers of styrene/isoprene, styrene/butadiene and
isoprene/butadiene, as well as partially hydrogenated homopolymers of
butadiene and
isoprene and isoprene/divinylbenzene.
Additional additives may be present in the composition of the present
invention include stabilizers and seal compatibility additives such as
polyisobutenyl
succinic anhydride, prepared from chlorinated polyisobutylene or chlorine-free
polyisobutylene, including highly reactive polyisobutylene having terminal
unsaturation, oxidation inhibitors, demulsifiers, antifoam additives and pour
depressants.
The compositions of this invention may also contain 0.05 to 1.5 wt.% each of
one or more phosphorus-free oxidation inhibitors or antioxidants, and these
include
hindered phenols, alkaline earth metal salts of alkylphenolthioesters having
preferably
C5 to C12 alkyl side chains, calcium nonylphenol sulfide, ashless oil soluble
phenates and
sulfurized phenates, sulfurized hydrocarbons, metal thiocarbamates and oil
soluble
copper compounds as described in U.S. 4,867,890.
Aromatic amines having at least two aromatic groups attached directly to the
nitrogen constitute another class of compounds that is frequently used for
antioxidancy. Typical oil soluble aromatic amines having at least two aromatic
groups attached directly to one amine nitrogen contain from 6 to 16 carbon
atoms.
The amines may contain more than two aromatic groups. The aromatic rings are
typically substituted by one or more substituents selected from alkyl,
cycloalkyl,
alkoxy, aryloxy, acyl, acylamino, hydroxy, and nitro groups. Dinonyl-diphenyl
amine
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is a preferred antioxidant. The amount of any such oil soluble aromatic amines
having at least two aromatic groups attached directly to one amine nitrogen is
in the
range of 0.05 to 1.5 wt. % active ingredient. The use of at least one of a
hindered
phenol and aromatic amine antioxidant, or the combination of both, is
preferred.
Hindered phenols are preferably used in the range of 0.05 to '0.5 wt.%.
Hindered
phenols will generally be of the type in which there is a sterically hindered
phenolic
group, especially one containing a t -butyl group in the ortho position to the
phenolic OH
group. Examples of such compounds are many. These include both monocyclic and
bisphenols. Preferred examples are tetrakis(methylene-3-(-3',5'-di-tert-butyl-
4'hydroxyphenyl)-propionate) methane; octadecyl-3-(3',5'-di-tert-butyl-4'-
hydroxyphenyl) propionate; 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-
hydroxybenzyl) benzene; 4,4'-(2,2-diphenylpropyl)-diphenylamine; esters of
ethoxylated aryl phenols; 2,2'-thiodiethylbis(3-(3,5-di-tert-butyl-4-
hydroxyphenyl)
propionate; octadecyl-3,5-di-tert-butyl-4-hydroxyhydrocinnamate and mixtures
of any
of the foregoing. Most preferred is isooctyl-3,5-di-tert-butyl-4-
hydroxyhydrocinnamate,
which is commercially available as Irganox L-135TM
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 lube oil flow 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 C$ to C,g dialkyl fumarate/vinyl acetate copolymers,
polyalkylmethacrylates
and the like.
Foam control can be provided by many antifoam compounds including a
fluorosilicone or an antifoamant of the polysiloxane type, for example,
silicone oil or
CA 02480935 2004-09-08
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polydimethyl siloxane usually used in amounts of from 0.0001 to 0.01 wt.%
active
ingredient.
The individual additives may be incorporated into a base stock in any
convenient
way. Thus, each of the components can be added directly to the base stock or
base oil
blend by dispersing or dissolving it in the base stock or base oil blend 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 described herein
as the
additive package, that is subsequently blended into base stock to make the
finished
lubricant. The concentrate will typically be formulated to contain the
additive(s) in
proper amounts to provide the desired concentration in the final formulation
when the
concentrate is combined with a predetermined amount of a base lubricant.
The concentrate is preferably made in accordance with the method described in
US 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 100 C.
Thereafter, the
pre-mix is cooled to at least 85 C and the additional components are added.
The final lubricating oil formulation may employ from 2 to 20 mass %,
preferably 4 to 18 mass %, and most preferably about 5 to 17 mass % of the
concentrate
or additive package with the remainder being base stock.
EXAMPLE 1
The following 1OW30 viscosity grade oil was prepared and subjected to rust
testing for suitability as a four stroke outboard marine engine oil in the "FC-
W" Rust
Test. Percentages are by weight of active ingredient, except as otherwise
indicated.
The oil has 42 ppm molybdenum, 1210 ppm phosphorus and a NOACK volatility less
than 15%. Six versions differing in the amount of rust inhibitor were tested.
CA 02480935 2004-09-08
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FC-W (Four Cycle-Water Rust Test) is a new quality specification for four-
stroke marine small engine oils which is being developed by the NMMA (National
Marine Manufacturers Association). The FC-W rust test will be one of the test
requirements for FC-W oil quality certification. While the test is still under
development by the testing laboratories, it is based on an in-house test by
Mercury
Marine.
For the results provided below, the following procedure was used:
= Test panels were cut from a cylinder liner used in a Mercury Marine
outboard engine.
= Test panels are suspended in a salt fog humidity cabinet which uses 5%
NaCl fog for 24 hours at 100 F.
= There is a special hanger assembly used for each panel which includes a
semi-cylindrical "umbrella" placed above each individual panel.
= The umbrella's function is to minimize any condensate dripping directly
on the coupon.
= After 24 hrs. at 100 F the test panels are removed and rated for surface
area rust coverage.
= The percent rust coverage of the surface area is reported for each of two
replicate panels, as well as the average rust coverage for the replicates.
30
CA 02480935 2004-09-08
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Example 1 - Lubricating Oil Formulation
Weight %
(a) Calcium sulfonate (TBN 300) 0.825
(b) Molybdenum trimer dithiocarbamate 0.045
(c) Calcium phenate (neutral) 0.230
(d) Polyisobutenyl succinimide dispersant 2.450
(e) Amine antioxidant 0.600
(f) Viscosity modifier (as 15% solution of polymer) 6.000
(g) ZDDP 1.125
(h) Rust inhibitors Table 1
(i) Lube oil flow improver 0.300
(j) Silicone antifoam agent 0.001
(k) 950 Mn polyisobutenyl succinic anhydride 0.320
(1) Mineral oil basestocks Balance
CA 02480935 2004-09-08
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0 0
N ', M O O
O M O O kn
O O O M N N
~, O\ O O O
C7 O d N '-, M
M N N d O O O
O O C hl N N
ti
H N N ~ I'D O O
0 O O M r-+ N
Cel
C C o ~ ~
U
O O
rA Go
it O O CIS
It ~l
O O
~ f~U U
~ 0 0
O h ~
CA 02480935 2004-09-08
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Example 2 - Lubricating Oil Formulation
Weight %
(a) Calcium sulfonate (TBN 300) 1.017
(b) Molybdenum trimer dithiocarbamate 0.045
(c) Calcium phenate (neutral) 0.230
(d) Polyisobutenyl succinimide dispersant 3.540
(e) Amine antioxidant 0.600
(f) Viscosity modifier, (as 15% solution of polymer) 6.000
(g) ZDDP 1.200
(h) Rust inhibitors Table 2
(i) Lube oil flow improver 0.300
0) Silicone antifoam agent 0.001
(k) Polyalphaolefin Base Oil 8.000
(1) Polyol ester 2.000
(m) Mn 950 polyisobutenyl succinic anhydride 0.320
(n) Mineral oil basestocks Balance
The same rust test was carried out on four versions of the Example 2 oil,
which had 1320 ppm phosphorus and contained 55 ppm molybdenum. The results are
in Table 2.
CA 02480935 2004-09-08
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o a o 0
0 o M 'a 0 0 0
0 0 0 0 `O v'
O O
O O O C v~
++ dj
Q ^c3
00 o N O~ O O O o
~ M M M O
O O G7 O ~
G
E~ ~ ~ M ~ n o 0 0 ~
O O O O N N N c
V')
kn
u
FNM LLi Ri ~ ,~
~ c ~ o O
d G4 V o
c
..a
O
O
CA 02480935 2004-09-08
-24-
For comparative purposes, the same FC-W Rust Test was carried out on a
commercially available Pennzoil-Quaker State 10W30 oil which is known to
contain
no rust inhibitor. The rust results were 60% and 70% for the replicate panels,
the
average being 65%.
