Note: Descriptions are shown in the official language in which they were submitted.
CA 02482221 2004-09-21
ENGINE OIL COMPOSITIONS
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention generally relates to improved lubricating oils
containing
additives and additive mixtures for use in internal combustion engines. More
particularly, the present invention is directed to low phosphorous lubricating
oils and~to
low phosphorous and low sulfur lubricating oils compositions containing at
least a base
oiI and a polyol ester.
2. Description of.the Related Art
Automobile spark ignition and diesel engines have valve train systems,
including
valves, cams and rocker arms which present special lubrication concerns. It is
extremely
important that the lubricant; i.e., the engine oil, protects these parts from
wear: It is also
important for engine oils to suppress the production of deposits in the
engines. Such
deposits are produced from non-combustibles and incomplete combustion of
hydrocarbon
fuels (e.g., gasoline, diesel fuel oil) and by the deterioration of the engine
oil employed.
Engine oils typically use a mineral oil or a synthetic oil as a base oil.
However,
simple base oils alone do not provide the necessary properties to provide
adequate wear
protection, deposit control, etc. required to protect internal combustion
engines. Thus,
base oils are formulated with various additives (for imparting auxiliary
functions) such
as, for example, ashless dispersants; metallic detergents (i.e., metal-
containing
1
CA 02482221 2004-09-21
detergents), antiwear agents, antioxidants (i.e., oxidation inhibitors),
viscosity index
improvers and the like to produce a compounded oil, i.e., a lubricating oil
composition.
A number of such engine oil additives are known and employed in practice. The
most common additive for engine lubricating oils has been zinc
dialkyldithiophosphates
because of their favorable characteristics as an antiwear agent and
performance as an
oxidation inhibitor. However, a problem has arisen with respect to the use of
zinc
dialkyldithiophosphate, because phosphorous- and sulfur derivatives poison
catalyst
components of catalytic converters. This is a major concern as effective
catalytic
converters are needed to reduce pollution and to meet governmental regulation
designed
to reduce toxic gases such as, for example, hydrocarbons, carbon monoxide and
nitrogen
oxides, in internal combustion engine exhaust emissions. Such catalytic
converters
generally use a combination of catalytic metals, e:g., platinum or variations,
and metal
oxides, and are installed in the exhaust streams, e.g., the exhaust pipes of
automobiles, to
convert the toxic gases to nontoxic gases: As previously mentioned, these
catalyst
components are poisoned by the phosphorous and sulfur components, or the
phosphorous
and sulfur decomposition product of the zinc dialkyldithiophosphate; and
accordingly;
the use of engine oils containing phosphorous and sulfur additives may
substantially
reduce the life and effectiveness of catalytic converters. Therefore, it would
be desirable
to reduce the phosphorous and sulfur content in the engine oils so as to
maintain the
activity and extend the life of the catalytic converter.
2
CA 02482221 2004-09-21
There is also governmental and automotive industry pressure towards reducing
the phosphorous and sulfur content. For example, United States Military
Standards MIL-
L-46152E and the ILSAC Standards defined by the Japanese and United States
Automobile Industry Association at present require the phosphorous content of
engine
oils to be at or below 0.10 wt.% with future phosphorous content being
proposed to even
lower levels, e.g., 0.08 wt.% by January, 2004 and below 0.05 wt.% by January,
2006.
At present, there is no industry standard requirement for sulfur content in
engine oils, but
it has been proposed that the sulfur content be below 0.2 wt.% by January,
2006.
Accordingly, it would be desirable to decrease the amount of zinc
dialkyldithiophosphate
in lubricating oils still further, thus reducing catalyst deactivation and
hence increasing
the life and effectiveness of catalytic converters while also meeting future
industry
standard proposed phosphorous and sulfur contents in the engine oil. However,
simply
decreasing the amount of zinc dialkyldithiophosphate presents problems because
this
necessarily lowers the antiwear properties and oxidation inhibition properties
of the
lubricating oil. Therefore, it is necessary to find a way to reduce
phosphorous and sulfur
content while still retaining the antiwear and oxidation or corrosion
inhibiting properties
of the higher phosphorous and sulfur content engine oils.
In order to compensate for lowering the amount of :ainc
dialkyldithiophosphate,
other oxidation inhibitors such as phenol derivatives, e.g., high overbased
phenates, and
ashless antioxidants, e.g., alkylated diphenylamines, have been used. However,
the use
3
CA 02482221 2004-09-21
of such known oxidation inhibitors in place of zinc dialkyldithiophosphate at
best only
marginally satisfies the required levels of antiwear, oxidation inhibition and
deposit
control.
Detergents have been added to impart a total base number (TBI~ to neutralize
acidic combustion products and to clean surfaces containing deposits: However,
detergents may impart undesirable properties. For example:, overbase:d
sulfonates such as
magnesium sulfonate detergents are also effective to enhance the antiwear
properties in
valve train systems, but have drawbacks in that crystalline precipitates are
sometimes
produced when these engine oils are stored under humid or variable temperature
I O conditions for a long period of time.: Such precipitates may cause
plugging of the filter
which is installed in the engine oil circulating system. Such plugging is more
likely to
occur when a large amount of the magnesium sulfonate detergents are used so as
to
enhance the desired antiwear properties. Additionally, the use of high
overbased
detergents such as, for example, sulfonates or phenates, and low overbased
sulfonates
contribute toward the sulfur content which; as previously mentioned, has been
proposed
for significant reduction in the levels contained in the lubricating oils.
Accordingly, as demand for further decrease of the phosphorous content and a
limit on the sulfur content of lubricating oils is very high, this reduction
cannot be
satisfied by the present measures in practice and still meet the severe
antiwear and
oxidation-corrosion inhibiting properties, as well as cleanliness (i.e.,
deposit protection)
4
CA 02482221 2004-09-21
required of today's engine oils. Thus; it would be desirable to develop
lubricating oils,
and additives and additive packages therefore, having lower levels of
phosphorous and
sulfur but which still provide the needed wear, oxidation-corrosion and
deposit protection
now provided by lubricating oils having, for example, higher levels of zinc
S dialkyldithiophosphate, but which do not suffer from the disadvantages of
the lubricating
oils discussed above.
SU1~ZMARY OF THE INVENTION
In accordance with the present invention, lubricating oil compositions are
provided having high antiwear; oxidation-corrosion and deposit protection, but
which
have low levels of phosphorous and sulfur. Thus, in one embodiment of the
present
invention, a low phosphorous or phospharous-free lubricating oil composition
is provided
which comprises (a) a major amount of a base oil of lubricating viscosity and
(b) a minor
deposit-inhibiting effective amount of at Least one polyol ester of the
general formula:
O
II
oc R'
(cHz>X
R4 ~ '- CH O (I)
c 2>~ f f
0 oc RZ
(c\~Z ~~
1 S OC R3
S
CA 02482221 2004-09-21
wherein Ri, RZ and R3 are independently aliphatic hydrocarbyl moieties having
from 4 to
about 24 carbon atoms, R'' is hydrogen or an aliphatic hydrocarbyl moiety
having 1 to 10
carbon atoms and x, y and z are the same or different and are integers from 1
to 6;
wherein the composition has a phosphorous content not exceeding 0.08% by
weight,
based on the total weight of the composition.
In another embodiment, a low phosphorous or phosphorous-free and a low sulfur
or sulfizr-free lubricating oil composition is provided which comprises (a} a
major amount
of a base oil of lubricating viscosity and (b) a minor deposit-inhibiting
effective amount
of the foregoing polyol ester; wherein the composition has a phosphorous
content not
I O exceeding 0.08 % by weight and a sulfur content not exceeding 0.2% by
weight, based on
the total weight of the composition.
Yet another embodiment of the present invention is a method of operating an
internal combustion engine which comprises operating the internal combustion
engine
with a low phosphorous or phosphorous-free lubricating oil composition
comprising (a) a
I S major amount of a base oil of lubricating viscosity and (b) a minor
deposit-inhibiting
effective amount of the foregoing palyol ester; wherein the composition has a
phosphorous content not exceeding 0.08 % by weight; based on the total weight
of the
composition.
Still yet another embodiment of the present invention is a method of operating
an
20 internal combustion engine which comprises operating the internal
combustion engine
6
CA 02482221 2004-09-21
with a low phosphorous or phosphorous-free and a low sulfur or sulfur-free
lubricating
oil composition comprising (a) a major amount of a base oil of lubricating
viscosity and
(b) a minor deposit-inhibiting effective amount of the foregoing polyol ester;
wherein the
composition has a phosphorous content not exceeding 0.08 % by weight and
sulfur
content not exceeding 0.2% by weight, based on the total weight of the
composition.
In another aspect, the present invention provides an additive package
composition
or concentrate comprising one or more compounds of formula (I) in an organic
diluent
liquid, for example; an oil of lubricating viscosity, and preferably
containing various
other additives desired in lubricating oil compositions such as, for example,
metal-
containing detergents and ashless dispersants, such that upon addition to a
base oil of
lubricating viscosity a composition having a phosphorous content not exceeding
0.08
by weight is formed.
The present invention advantageously provides lut~ricating oil compositions
which provide high antiwear, oxidation-corrosion and deposit protection in an
engine, but
which have only low levels of phosphorous, i.e., less than 0.1 %, preferably
not exceeding
0.08% and more preferably not exceeding 0.05% by weight and low levels of
sulfur, i.e.,
not exceeding 0.2% by weight. Accordingly, the lubricating oiI compositions of
the
present invention are more environmentally desirable than the higher
phosphorous and
sulfur lubricating oil compositions generally used in internal combustion
engines because
they facilitate longer catalytic converter life and activity while also
providing the desired
7
CA 02482221 2004-09-21
high wear and deposit protection and oxidation-corrosion inhibition. This is
due to the
decreased levels of additives containing phosphorus and sulfur compounds in
these
lubricating oil compositions. Conventional lubricating oil compositions, on
the other
hand, typically contain relatively high concentrations of such additives.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
It has been found that the incorporation of the compounds of formula (17 or
mixtures thereof into a base oil of lubricating viscosity in a minor deposit-
inhibiting
effective amount for providing low phosphorous or phosphorous-free lubricating
oils and
low phosphorous or phosphorous-free and low sulfur or sulfur-free lubricating
oils,
IO excellent antiwear, oxidation-corrosion and deposit protection is achieved
in internal
combustion engines, especially if incorporated with low levels of phosphorous-
containing
additives, e.g., zinc dialkyldithiophosphates, and low levels of sulfur-
containing
additives, e.g., high overbased sulfonates, low overbased suifonates such as
magnesium
sulfonate detergents, etc. However; the phosphorous and sulfur in the
inventive
lubricating oil composition may-be in any form. For example, the sulfur may be
elemental sulfur or it may be present in the lubricating oil composition or
added to the
lubricating oil composition as part of a sulfur-containing compound. The
sulfur-
containing compound may be an inorganic sulfur compound or an organic sulfur
compound. The sulfur-containing compound maybe a compound containing one or
more of the groups: sulfamoyl, sulfenamoyl, sulfeno, sulFdo, sulfinamoyl,
sulfino,
8
CA 02482221 2004-09-21
sulfinyl; sulfo, sulfonio, sulfonyl, sulfonyldioxy, sulfate, thin,
thiocarbamoyl,
thiocarbonyl, thiocarbonylamino, thiocarboxy, thiocyanato" thioformyl, thioxo,
thioketone, thioaldehyde, thioester, and the like. The sulfur may also be
present in a
hetero group or compound which contains carbon atoms arid sulfur atoms (and,
optionally, other hetero atoms such as oxygen or nitrogen) in a chain or ring.
The sulfur-
containing compound may be a sulfur oxide such as sulfur dioxide or sulfur
trioxide. The
sulfur or sulfur-containing compound may be intentionally added to the
inventive
lubricating oil composition, or it may be present in the base oil or in one or
more of the
additives for the inventive lubricating oil composition as an impurity.
The lubricating oil compositions of this invention include as a first
component a
major amount of base oil of lubricating viscosity, e.g., an amount of at least
40 wt. %,
preferably about 85 to about 98 wt. % and preferably about 90 to about 95 wt.
%, based
on the total weight of the composition. The expression "base oil" as used
herein shall be
understood to mean a base stock or blend of base stocks which is a lubricant
component
that is produced by a single manufacturer to the same specifications
(independent of feed
source or manufacturer's location); that meets the same manufacturer's
specification; and
that is identified by a unique formula, product identification number, or
both. Typically,
individually the oils used as its base oiI will have a kinematic viscosity
range at
100°Centigrade (C) of about 2 centistokes (cSt) to about 20 cSt,
preferably about 3 cSt to
about 16 cSt, and most preferably about 4 cSt to about 12 cSt and will be
selected or
9
CA 02482221 2004-09-21
blended depending on the desired erid use and the additives in the finished
oil to give the
desired grade of engine oil, e.g., a lubricating oil composition having an SAE
Viscosity
Grade of OW, OW-20, OW-30, OW-40, OW-50, 0W-60, 5W, SW-20, SW-30; SW-40, SW-
50, SW-60, lOW, lOW-20, lOW-30,: lOW-40, lOW-50, 15W, 15W-20, 1~W-30 or 15W-
S 40.
Base stocks may be manufactured using a variety of different processes
including,
but not limited to, distillation, solvent refining, hydrogen processing,
oligomerization,
esterification, and rerefining. Rerefined stock shall be substantiallyfree
from materials
introduced through manufacturing, contamination, oz previous use. The base oil
of the
lubricating oil compositions of this invention may be any natural or synthetic
lubricating
base oil. Suitable hydrocarbon synthetic oils include, but are not limited to,
oils prepared
from the polymerization of ethylene or from the polymerization of l-olefins
such as
polyalphaolefin or PAO, or from hydrocarbon synthesis procedures using carbon
monoxide and hydrogen gases such as in a Fisher-Tropsch process. A preferred
base oil
is one that comprises little, if any, heavy fraction; e.g., little, if any,
lube oil fraction of
viscosity 20 cSt or higher at 100°C.
The base oil may be derived from natural lubricating oils, synthetic
lubricating
oils or mixtures thereof. Suitable base oil includes base stocks obtained by
isomerization
of synthetic wax and slack wax, as well as hydrocracked base stocks produced
by
hydrocracking (rather than solvent extracting) the aromatic and polar
components of the
CA 02482221 2004-09-21
crude. Suitable base oils include those in all API categories I, II, III, IV
and V as defined
in API Publication 1509, 14th Edition, Addendum I, Dec. 1998. Group IV base
oils are
polyalphaolefins (PAO). Gxoup V base oils include all ;other base oils not
included in
Group I; II, III, or IV. Although Group II, III and IV base oils are preferred
for use in
this invention, these preferred base oils may be prepared b;y combining one or
more of
Group I, II, III, N and V base stocks or base oils.
Useful natural oils include mineral lubricating oils such as, for example,
liquid
petroleum oils, solvent-treated or acid-treated mineral lubricating oils of
the paraffinic,
naphthenic or mixed paraffinic-naphthenie types, oils derived from coal or
shale, animal
oils, vegetable oils (e.g., rapeseed oils, castor oils and lard. oil), and the
like.
Useful synthetic lubricating oils include, but are not limited to, hydrocarbon
oils
and halo-substituted hydrocarbon oils such as polymerized and interpolymerized
olefins,
e.g., polybutylenes, polypropylenes, propylene-isobutylene copolymers,
chlorinated
polybutylenes, poly(1-hexenes), poly(1-octenes), poly(1-decenes), and the like
and
I S mixtures thereof; alkylbenzenes such as dodecylbenzenes,
tetradecylbenzenes,
dinonylbenzenes, di(2-ethylhexyl)-benzenes, and the like; polyphenyls such as
biphenyls,
terphenyls, alkylated polyphenyls, and the like; alkylated Biphenyl ethers and
alkylated
Biphenyl sulfides and the derivative, analogs and homologs thereof and the
like.
Other useful synthetic lubricating oils include, but are not limited to, oils
made by
polymerizing olefins of less than 5 carbon atoms such as ethylene, propylene;
butylenes,
11
CA 02482221 2004-09-21
isobutene, pentene, and mixtures thereof. Methods of preparing such polymer
oils are
well known to those skilled in the art.
Additional useful synthetic hydrocarbon oils include liquid polymers of alpha
olefins having the proper viscosity. Especially useful synthetic hydrocarbon
oils are the
hydrogenated liquid oligomers of Cb to C12 alpha olefins such as, for example,
1-decene
trimer.
Another class of useful synthetic lubricating oils include, but are not
limited to,
alkylene oxide polymers, i.e., homopolyrners, interpolymers, and derivatives
thereof
where the terminal hydroxyl groups have been modified by, for example,
esterification or
etherification. These oils axe exemplified by the oils prepared through
polymerization of
ethylene oxide or propylene oxide; the alkyl and phenyl ethers of these
polyoxyalkylene
polymers (e.g., methyl poly propylene glycol ether having an average molecular
weight
of 1,000, diphenyl ether of polyethylene glycol-having a molecular weight of
500-1000;
diethyl ether of polypropylene glycol having a molecular weight of 1,000-
1,500, etc.) or
mono- and polycarboxylic esters thereof such as, for example, the acetic
esters, mixed
C3-C$ fatty acid esters, or the Cl3oxo acid diester of tetraethylene glycol.
Yet another class of useful synthetic lubricating oils include, but are not
limited
to, the esters of dicarboxylic acids e:g., phthalic acid, succinic acid, alkyl
succinic acids,
alkenyl succinic acids, malefic acid; azelaic acid, suberic acid, sebacic
acid, fumaric acid,
adipic acid, linoleic acid dimes, malonic acids, alkyl malonic acids, alkenyl
malonic
12
CA 02482221 2004-09-21
acids, ete., with a variety of alcohols, e.g., butyl alcohol, hexyl alcohol,
dodecyl alcohol,
2-ethylhexyl alcohol, ethylene glycol; diethylene glycol mo:noether, propylene
glycol, etc.
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 dimes, the
complex ester formed by reacting one mole of sebacic acid with two moles of
tetraethylene glycol and two moles of 2-ethylhexanoic acid and the like.
Esters useful as synthetic oils also include, but are not limited to, those
made from
carboxylic acids having from about 5 to about 12 carbon atoms with alcohols,
e.g.,
methanol, ethanol, etc., polyols and polyol ethers such as neopentyl glycol,
trimethylol
propane, pentaerythritol, dipentaerythritol, tripentaerythritc~l, and the
like.
Silicon-based oils such as; for example, polyalkyl-, polyaryl-, polyalkoxy- or
polyaryloxy-siloxane oils and silicate oils, comprise another useful class of
synthetic
lubricating oils. Specific examples of these include, but are not limited to,
tetraethyl
silicate, tetra-isopropyl silicate, tetra-(2-ethylhexyl) silicate, tetra-(4-
methyl-
hexyl)silicate, tetra-(p-test-butylphenyl)silicate, hexyl-(4-methyl-2-
pentoxy)disiloxane,
poly(methyl)siloxanes, poly(methylphenyl)siloxanes, and the like. Still yet
other useful
synthetic lubricating oils include, but are not limited to, liquid esters of
phosphorous
containing acids, e.g., tricresyl phosphate, trioctyl phosphate, diethyl ester
of decane
phosphionic acid, etc., polymeric tetrahydrofurans and the like.
13
CA 02482221 2004-09-21
The lubricating oil may be derived from unrefined; refined and rerefmed oils,
either natural, synthetic or mixtures of two or more of any of these of the
type disclosed
hereinabove. Unrefined oils are those obtained directly-from a natural or
synthetic source
(e.g., coal, shale, or tar sands bitumen) without further purification or
treatment.
Examples of unrefined oils include, but are not limited to, a shale oil
obtained directly
from retorting operations, a petroleum oil obtained directly from distillation
or an ester
oil obtained directly from an esterification process, each. of which is then
used without
further treatment. Refined oils are similar to the unrefined oils except they
have been
further treated in one or more purification steps to improve one or more
properties.
These purification techniques are known to those of skill in the art and
include, for
example, solvent extractions, secondary distillation, acid or base extraction,
filtration,
percolation, hydrotreating, dewaxing, etc. Rerefined oils are obtained by
treating used
oils in processes similar to those used to obtain refined oils. Such rerefmed
oils are also
laiown as reclaimed or reprocessed oils and often are additionally processed
by
techniques directed to removal of spent additives and oil breakdown products.
Lubricating oil base stocks derived from the hydroisomerization of wax may
also
be used, either alone or in combination with the aforesaid natural and/or
synthetic base
stocks. Such wax isomerate oil is produced by the hydroisomerization of
natural or
synthetic waxes or mixtures thereof over a hydroisomerization catalyst.
14
CA 02482221 2004-09-21
Natural waxes are typically the slack waxes recovered by the solvent dewaxing
of
mineral oils; synthetic waxes are typically the wax produced by the Fischer-
Txopsch
process.
The compounds of formula (17 for incorporating into the foregoing base oils
(hereafter referred to as polyol ester), i.e.;
O
~~
OC Rt
(CHZ)X
- CH O''
R ( 2)~
2
O OC R
OC R3
wherein Rj, R2, R3, R4, x, y and z are as defined hereinabove, are known
compounds and
can be prepared by known procedures and hence readily commercially available.
Referring to the Ri, RZ and R3 groups, the aliphatic hydroGarbyl moieties
maybe
independently saturated or unsaturated, linear (straight chain) or branched
chain and
preferably have 4 to 24 carbon atoms, more preferably 4 to 16 carbon atoms and
most
preferably 6 to 10 carbon atoms. The R4 group can be hydrogen or an aliphatic
hydrocarbyl moiety such as, by way of example, a linear or branched chain
alkyl group
having from 1 to 10 carbon atoms and preferably 1 to 6 carbon atoms;
optionally.
containing an aromatic or aryl group. Preferably, x, y and z are I . Examples
of such
polyol esters for use herein include, but are not limited to,
trimethylolpropane (TMP)
CA 02482221 2004-09-21
esters such as, for example, TMP tri(2-ethyl hexanoate), TMP triheptanoate,
TMP
tricaprylate, TMP tricaprate, TMP tri{isononanoate) and the like.
In general, the foregoing polyol esters can be used singly or in combination
of
two or more compounds in base oils to provide good deposit protection as well
as wear
and oxidation-corrosion protection: To provide such protection in low
phosphorous or
phosphorous-free and/or low phosphorous or phosphorous-free and low sulfur or
sulfur-
free lubricating oil compositions, the foregoing polyol esters are generally
incorporated
into base oils in a minor deposit-inhibiting effective amount to give a
compounded
engine oil, e.g., an amount ranging from about 0.5 weight percent to about 10
weight
percent and preferably from about 1 weightpercent to about 5 weight percent,
based on
the total weight of the composition. The expression "minor deposit-inhibiting
effective
amount" as used herein shall be understood to mean an amount effective to
prevent or
inhibit formation of deposits associated with internal combustion engines such
as, for
example, fuel combustion deposits, high temperature piston deposits, etc.
By using the polyol ester of formula (I) in the lubricating oil composition of
the
present invention, low levels of phosphorous-containing antiwear additives
such as, far
example, zinc dialkyldithiophosphate and tricresylphosphite, and low levels of
sulfur-
containing additives can be used while still providing excellent results in
terms of both
engine protection and environmental considerations. It is advantageous to use
the polyol
ester such that the phosphorous content of the compounded engine oil is less
than 0.1 wt.
16
CA 02482221 2004-09-21
%, preferably no highex than 0.08 wt. %, and more preferablynot higher than
0.05 wt.
and the sulfur content of the compounded engine oil is no higher than 0.2 wt.
%, yet
provides the desired levels of antiwear properties, oxidation inhibition and
deposit
control. (It should perhaps be noted that because of the phosphorus catalyst
poisoning
problem, with the exception of zinc dialkyldithiophosphate, phosphorus-
containing
compounds are generally avoided in such engine oils, particularly those
intended for use
in automotive engines. Thus, in the case of the present invention, phosphorus
content is
calculated based on the zinc dialkyldithiophosphate and its molecular
phosphorus
content, and directly equates to zinc dialkyldithiophosphate content.) The
sulfur content
I O derives from zinc dialkyldithiophosphate; sulfonate and phenate
detergents, diluent oil
and base oil. Also, the sulfur content in the lubricating oil composition can
be measured
by convenrional techniques, for example, x-ray techniques.
Zinc dialkyldithiophosphates are, of course, known wear inhibiting agents and
can
be obtained from commercial sources or, if desired, prepared by known
procedures. As
is well known, zinc dialkyldithiophosphates refer to a class of compounds
generally
having the formula
s
RS \ ~~ ~~ / oR~
P S Zn S-- P
R60 OR8
17
CA 02482221 2004-09-21
wherein R5, R6, R' and R$ are independently alkyl or alkylphenyl. Typically
the alkyl
group has about from 1 to 20 carbon atoms, preferably 3 to 10 carbon atoms,
and can be
straight chained or branched. A variety of zinc dialkyldithiophosphates are,
for example;
described in an article by Born et al. entitled "Relationship between Chemical
Structure
and Effectiveness of Some Metallic Dialkyl- and Diaryl-dithiophosphates in
Different
Lubricated Mechanisms", appearing in Lubrication Science 4-2 January 1992, see
for
example pages 97-100.
Preferably, the lubricating oil compositions of the present invention will
contain
other conventional additives for imparting auxiliary functions to give a
finished
lubricating oil composition in which these additives are dispersed or
dissolved. For
example, the lubricating oil compositions can be blended with metal
detergents; rust
inhibitors, dehazers, demulsifiers, metal deactivators, friction modifiers,
viscosity index
improvers, pour point depressants, antifoaming agents, co-solvents, package
compatibilisers, deodorants and metallic-based additives such as metallic
combustion
improvers, anti-knock compounds, anti-icing additives, corrosion-inhibitors,
ashless
dispersants, dyes, and the like. A variety of the additives are known and
commercially
available. These additives, or their analogous compounds, can be employed for
the
preparation of the engine oils of the invention by the usual blending
procedures.
Examples of the ashless dispersants which may be used in the present engine
oil
are alkyl or alkenyl substituted succinimides, succinic :esters and
benzylamines, in which
18
CA 02482221 2004-09-21
the alkyl or alkenyl group has a molecular weight of approximately 700-3,000.
The
derivatives of these dispersants, e.g., borated dispersants such as borated
succinimides,
may also be used. The ashless dispersant is generally incorporated into an
engine oil in
an amount of 0.5-15 wt. % per total amount of the engine oil.
Examples of the viscosity index improvers are poly(alkyl methacrylate),
ethylene-
propylene copolymer, polyisoprene, and styrene-butadiene copolymer. Viscosity
index
improvers of dispersant type (having: increased dispersancy) or
multifunctional type are
also employed. These viscosity index improvers can be used singly or in
combination.
The amount of viscosity index improver to be incorporated into the engine oil
varies with
viscosity requirements of the engine oil, but generally in the range of about
0.5 to 20% by
weight of the total weight of the engine oil lubricating composition. However,
in the case
of a monograde oil, no viscosity index improver is typically used.
Detergents for use herein may be overbased or neutral. For example, common
detergents are sulfonates, e.g., those made from alkyl benzene and finning
sulfonic acid.
Other suitable detergents for use herein include, but are not limited to;
phenates (high
overbased or low overbased), high overbased phenate stearates, phenolates,
salicylates,
phosphonates, thiophosphonates; ionic surfactants and sulfonates and the like
with
sulfonates being preferred and with low overbased metal sulfonates and neutral
metal
sulfonates being most preferred. Low overbased metal sulfonates typically have
a total
base number (TBl~ of from about O to about 30 and preferably from about 10 to
about
I9
CA 02482221 2004-09-21
25. Low overbased metal sulfonates and neutral metal sulfonates are well known
in the
art.
The low overbased or neutral metal sulfonate detergent is preferably a low
overbased or neutral alkali or alkaline earth metal salt of a hydrocarbyl
sulfonic acid
having from about 15 to about 200 carbon atoms. The term "metal sulfonate" as
used
herein is intended to encompass at least the salts of sulfonic acids derived
from petroleum
products. Such acids are well lrnown in the art and can be obtained by, for
example,
treating petroleum products with sulfuric acid or sulfur trioxide. The acids
obtained
therefrom are known as petroleum sulfonic acids and the salts as petroleum
sulfonates.
Most of the petroleum product which become sulfonated contain an oil-
solubilizing
hydrocarbon group. Also, the meaning of "metal sulfonate" is intended to
encompass the
salts of sulfonie acids of synthetic alkyl, alkenyl and alkyl aryl compounds.
These acids
also are prepared by treating an alkyl, alkenyl or alkyl aryl compound with
sulfuric acid
or sulfur trioxide with at least one alkyl substituent of the aryl ring being
an
1 S oil-solubilizing group. The acids obtained therefrom are known as alkyl
sulfonic acids,
alkenyl sulfonic acids or alkyl aryl sulfonic acids and the salts as alkyl
sulfonates, alkenyl
sulfonates or alkyl aryl sulfonates.
The acids obtained by sulfonation are converted to metal salts by
neutralization
with one or more basic reacting alkali or alkaline earth metal compounds to
yield Group
IA or Group IIA xiietal sulfonates. Generally, the acids are neutralized with
an alkali
CA 02482221 2004-09-21
metal base. Alkaline earth metal salts axe obtained from the alkali metal salt
by
metathesis. Alternatively, the sulfonic acids can be neutralized directly with
an alkaline
earth metal base. If desired, the sulfonates can then be overbased to produce
the low
overbased metal sulfonate. The metal compounds useful in rriaking the basic
metal salts
are generally any Group IA or Group IIA metal compounds (CAS version of the
Periodic
Table of the Elements). The Group IA metals of the metal compound include
alkali
metals, e.g., sodium, potassium, lithium. The Group IIA metals of the metal
base include
the alkaline earth metals such, for example, magnesium; calcium,, barium, etc.
Preferably
the metal compound for use herein is calcium. The metal compounds are
ordinarily
delivered as metal salts. The anionic portion of the saltcan be hydroxyl,
oxide,
carbonate, borate, nitrate, etc.
The sulfonic acids useful in making the low overbased or neutral salts include
the
sulfonic and thiosulfonic acids: Generally they are salts of sulfonic acids.
The sulfonic
acids include, for example, the mono- or palynuclear aromatic or
cycloaliphatic
compounds. The oiI-soluble sulfonates can be represented for the most part by
one of the
following formulae: R2 --T--(S03)a and R3 --(SO3)b, wherein T is a cyclic
nucleus such
as, for example, benzene, naphthalene, anthracene, diphenylene oxide,
diphenylene
sulfide, petroleum naphthenes, etc.; R2 is an aliphatic group such as alkyl,
alkenyl,
alkoxy, alkoxyalkyl, etc.; (R2)+T contains a total of at least about 15 carbon
atoms; and
R3 is an aliphatic hydrocarbyl group containing at least about 15 carbon
atoms.
21
CA 02482221 2004-09-21
Examples of R~ are alkyl, alkenyl; alkoxyalkyl, carboalkoxyalkyl, etc.
Specific examples
of R3 are groups derived from petrolatum, saturated and unsaturated paraffin
wax, and the
above-described polyalkenes. The groups T, RZ, and R3 in the above Formulae
can also
contain other inorganic or organic substituents in addition to those
enumerated above
such as, for example; hydroxy, mercapto, halogen, vitro, amino, nitroso,
sulfide,
disulfide, etc. In the above Formulae, a and b are at least 1. In one
embodiment, the
sulfonic acids have a substituent (R2 or R3) which is derived from one of the
above-described polyalkenes.
Illustrative examples of these sulfonic acids include monoeicosanyl-
substituted
I O naphthalene sulfonic acids, dodecylbenzene sulfonic acids,
didodecylbenzene sulfonic
acids, dinonylbenzene sulfonic acids, cetylchlorobenzene sulfonic acids,
dilauryl
beta-naphthalene sulfonic acids, the sulfonic acid derived by the treatment of
polybutene
having a number average molecular weight (1VI;,) in the range of about 350 to
about 5000,
preferably about 800 to about 2000, or about 1500 with chlorosulfonic acid,
nitronaphthalene sulfonic acid, paraffin wax sulfonic acid, cetylcyclopentane,
sulfonic
acid, lauryl-cyclohexane sulfonic acids, polyethylenyl-substituted sulfonic
acids derived
from polyethylene (M" of from about 300 to about I000, and preferably about
750), etc.
Normally the aliphatic groups will be alkyl and/or alkenyl groups such that
the total
number of aliphatic carbons is at least about 8, preferably at least L2 up to
about 400
carbon atoms, preferably about 250. Also useful are polyisobutene sulfonates,
e.g., those
22
CA 02482221 2004-09-21
disclosed in U.S. Patent No. 6,410,491, the contents of which are incorporated
by
reference herein.
Another group of sulfonic acids are mono- , di- , and tri-alkylated benzene
and
naphthalene (including hydrogenated forms thereof) sulfonic acids.
Illustrative of
synthetically produced alkylated benzene and naphthalene sulfonic acids are
those
containing alkyl substituents having from about 8 to about 30 carbon atoms,
preferably
about 12 to about 30 carbon atoms, and advantageously about 24 carbon atoms.
Such
acids include di-isododecylbenzene sulfonic acid, polybutenyl-substituted
sulfonic acid,
polypropylenyl-substituted sulfonic acids derived from polypropene having an
M" of
from about 300 to about 1000 and preferably from about 500 to about 700,
cetylchlorobenzene sulfonic acid, di-cetylnaphthalene sulfanic acid,
di-lauryldiphenylether sulfonie acid, diisononylbenzene sulfonic acid,
di-isooctadecylbenzene sulfonic acid; stearylnaphthalene sulfonic acid, and
the like.
Specific examples of oil-soluble sulfonic acids are mahogany sulfonic acids;
bright stock sulfonic acids; sulfonic acids derived from lubricating oil
fractions having a
Saybolt viscosity from about 100 seconds at 100°F. to about 200 seconds
at 210°F.;
petrolatum sulfonic acids; mono- and poly-wax-substituted sulfonic and
polysulfonic
acids of, e.g., benzene, naphthalene phenol, Biphenyl ether, naphthalene
disulfide, etc.;
other substituted sulfonic acids su.eh as alkyl benzene sulfonic acids (where
the alkyl
group has at least 8 carbons), cetylphenol mono-sulfide sulfonic acids,
dilauryl beta
23
CA 02482221 2004-09-21
naphthyl sulfonic acids, and alkaryl sulfonic acids such as dodecyl benzene
"bottoms"
sulfonic acids.
Dodecyl benzene "bottoms" sulfonic acids are the material leftover after the
removal of dodecyl benzene sulfonic acids that are used for household
detergents. These
materials are generally alkylated with higher oligomers. The bottoms may be
straight-chain or branched-chain alkylates with a stxaigYit-chain dialkylate
preferred.
Particularly preferred based on their wide availability are salts of the
petroleum
suifonic acid, e.g., those obtained by sulfonating various hydrocarbon
fractions such as
lubricating oil fraction and extracts rich in aromatics which are obtained by
extracting a
hydrocarbon oil with a selective solvent, which extract may, if desired, be
alkylated
before sulfonation by reacting them with olefins or alkyl chlorides by means
of an
alkylation catalyst; organic polysulfonic acids such as benzene disulfonic
acid which may
or may not be alkylated; and the like.
Other particularly preferred salts for use herein are alkylated aromatic
sulfonic
acids in which the alkyl radical or radicals contain at least about 6 carbon
atoms and
preferably from about 8 to about 22 carbon atoms. Another preferred group of
sulfonate
starting materials are the aliphatic-substituted cyclic sulfonic acids in
which the aliphatic
substituent or substituents contain a total of at least 12 carbon atoms such
as, for
example, alkyl aryl sulfonic acids, alkyl cycloaliphatic sulfonic acids, the
alkyl
heterocyclic sulfonic acids and aliphatic sulfonic acids in which the
aliphatic radical or
24
CA 02482221 2004-09-21
radicals contain a total of at least 12 carbon atoms. Specific examples of
these oil-soluble
sulfonic acids include, but are not limited to, petroleum sulfonic acids;
petrolatum
sulfonic acids; mono- and poly-wax-substituted naphthalene sulfonic acids;
substituted
suifonic acids such as eetyl benzene sulfonic acids; cetyl phenyl sulfonic
acids and the
like; aliphatic sulfonic acids such as paraffin wax sulfonic acids, hydroxy-
substituted
paraffin wax sulfonic acids and the like; cycloaliphatic sulfonic acids;
petroleum
naphthalene sulfonic acids; cyclopentyl sulfonic acid; mono- and poly-wax-
substituted
cyclohexyl sulfonic acids and the like. The expression "petroleum sulfonic
acids" as
used herein shall be understood to cover ali sulfonic acids that are derived
directly from
petroleum products.
Typical Crroup IIA metal sulfonates suitable for;use herein include, but are
not
limited to, the metal sulfonates exemplified as follows: calcium white oil
benzene
sulfonate, barium white oil benzene sulfonate, calcium dipropylene benzene
sulfonate,
barium dipropylene benzene sulfonate, calcium mahogany petroleum sulfonate,
barium
1 S mahogany petroleum sulfonate, calcium triacontyl sulfonate, calcium lauryl
sulfonate,
barium lauryl sulfonate, and the like.
The acidic material used to accomplish the formation of the overbased metal
salt
can be a liquid such as, for example, formic acid, acetic acid, nitric acid;
sulfuric acid,
etc, ox an inorganic acidic material such as, for example, HCI, SOZ, SO3, C02,
HZS, etc,
with COZ being preferred. The amount of acidic material used depends in some
respects
CA 02482221 2004-09-21
upon the desired basicity of the product in question and also upon the amount
of basic
metal compound employed which will vary (in total amount) from about 1 to
about 10,
preferably from about 1.2 to about 8 and most preferably from about 1.7 to
about 6.0
equivalents per equivalent of acid: In the case of an acidic gas, the acidic
gas is generally
blown below the surface of the reaction mixture that contains additional
(i.e., amounts in
excess of what is zequired to convert the acid quantitatively to the metal
salt) base. The
acidic material employed during this step is used to react with the excess
basic metal
compound which may be already present or which can be added during this step.
The reaction medium used to prepare the low overbased metal sulfonate or
neutral
metal sulfonate is typically an inert solvent. Suitable inert solvents that
can be employed
herein include oils; organic materials which are readily soluble or miscible
with oil and
the like. Suitable oils include high boiling, high molecular weight oils such
as, for
example, parrafinic oils having boiling points higher than about 170°C.
Cornrnercially
available oils of this type known to one skilled in the art include, e.g.,
those available
I5 from such sources as Exxon under the Isopar~ tradenames; e.g., Isopar~ M,
Isopar° G,
Isopar~ H, and Isopar° V, and the Telura° tradename, e.g.;
Telura~ 407, and Crompton
Corporation available as carnation oil. Suitable organic solvents include
unsubstituted or
substituted aromatic hydrocarbons, ethoxylated long chain alcohols, e.g.,
those
ethoxylated alcohols having up to about 20 carbon atoms, and mixtures thereof.
Useful
26
CA 02482221 2004-09-21
unsubstituted or substituted aromatic hydrocarbons include high flash solvent
naptha and
the like.
If desired, a promoter can also be employed in preparing the low overbased
metal
sulfonate or neutral metal sulfonate. A promoter is a chemical employed to
facilitate the
incorporation of metal into the basic metal compositions. Among the chemicals
useful as
promoters are, for example, water, ammonium hydroxide, organic acids of up to
about 8
carbon atoms, nitric acid, sulfuric acid, hydrochloric acid, metal complexing
agents such
as alkyl salicylaldoxime, and alkali metal hydroxides such as lithium
hydroxide; sodium
hydroxide and potassium hydroxide, and mono- and polyh.ydric alcohols of up to
about
30 carbon atoms. Examples of the alcohols include methanol, ethanol,
isopropanol,
dodecanol, behenyl alcohol, ethylene glycol, monomethylether of ethylene
glycol,
hexamethylene glycol, glycerol, pentaerythritol, benzyl alcohol, phenylethyl
alcohol,
aminoethanol, cinnamyl alcohol, allyl alcohol, and the like. Especially useful
are the
monohydric alcohols having up to about 10 carbon atoms and mixtures of
methanol with -
higher monohydric alcohols. Amotmts of promoter will ordinarily range from
about 0%
to about 25%, preferably from about 1.5% to about 20% and most preferably from
about
2% to about 16% of acid charge. The predominant detergent metal is calcium but
sodium, magnesium, and barium have been used in practice. The amount of
detergent to
be incorporated into the engine oil varies widely, but effective
concentrations generally
27
CA 02482221 2004-09-21
range from about 0.2 to about 10% by weight of the total weight of the engine
oil
lubricating composition.
Antioxidants are advantageously used in engine oils to forestall oxidative
degradation of the lubricant. Besides: zinc dialkyldithiophosphates,
antioxidants include,
but are not limited to, aminic types (e.g., diphenylamine or phenyl-alpha-
napthyl-amine),
phenolics (e.g., BHT), sulfur-containing materials (sulfurized olefins or
esters) and the
like. These supplemental antioxidants are typically used at a total treat rate
of 0.1 to 2
wt.% of the finished fluid.
Examples of supplemental antiwear agents are usually non-phosphorus
compounds added to a lubricant to fortify wear protection. These materials
frequently
contain sulfur, usually as sulfide. Common examples include carbamates
(ashless or
not), xanthates, and alley sulfides or polysulfides. Because of the high
sulfur content,
these materials are often potent antioxidants.
As well as the above additives, the lubricating oil composition may contain
various other additives such as, for example, other oxidation-corrosion
inhibitors such as
hindered phenols and other antiwear agents can be used in combination with the
polyol
ester of formula (~.
Each of the foregoing additives, when used, is used at a functionally
effective
amount to impart the desired properties to the lubricant. Thus, for example,
if an additive
is a friction modifier, a functionally effective amount of this friction
modifier would be
28
CA 02482221 2004-09-21
an amount sufficient to impart the desired friction modifying characteristics
to the
lubricant. Generally, the concentration of each of these additives, when used,
ranges
from about 0.001 % to about 20% by-weight, and in one embodiment about O.OI%
to
about 10% by weight based on the total weight of the lubricating oil
composition.
In another embodiment of the invention, the polyol ester of formula (I) and
zinc
dialkyldithiophosphate may be provided as an additive package or concentrate
which will
be incorporated into a substantially inert, normally liquid organic diluent
such as, for
example, mineral oil, naphtha, benzene, toluene or xylene to form an additive
concentrate. These concentrates usually contain from about 1 % to about 99% by
weight,
and in one embodiment about 10% to about 90% by weight of such diluent.
Typically a
neutral oil having a viscosity of about 4 to about 8.5 cSt at 100°C and
preferably about 4
to about 6 cSt at 100°C will be used as the diluent, though synthetic
oils, as well as other
organic liquids which are compatible with the additives and finished
lubricating oil can
also be used. The additive package will also typically contain one or more of
the various
other additives, referred to above, in the desired amounts and ratios to
facilitate direct
combination with the requisite amount of base oil.
Preferably, the additive concentrate comprises a metal-containing detergent,
an
ashless dispersant, a polyol ester of formula (I), zinc dialkyldithiophosphate
and optional
components dissolved or dispersed in an organic liquid diluent, at a high
concentration.
The following non-limiting examples are illustrative of the present invention.
29
CA 02482221 2004-09-21
EXAMPLES
The following examples provide lubricating oil compositions which were
formulated to give viscosity conditions of a SAE SW30 oil defined in the
Society of
Automotive Engineers classification system SAE J300.
COMPARATIVE EXAMPLE A
A lubricating oil composition was formed by adding to a mixture of 78.1 wt. %
of
Chevron 100N (a Group II base oil) commercially available from ChevronTexaco
Corp
(San Racoon, CA) and 21.9 wt. % of Chevron 220N (a Graup II base oil)
commercially
available from ChevronTexaco Corp. (San Racoon; CA), an additive package
containing
the following additives (each of the components contain diluent oil to
facilitate handling
such that both the diluent oil and component are included in the component
weight):
Additive Package
Ashless dispersant - An ashless succinimide was the primary dispersant and was
prepared from 2300 molecular weight polyisobutylene, succinic anhydride, and a
polyethylene amine. The resultant product is post-treated with ethylene
carbonate. The
post-treated succinimide dispersant was used in the lubricating oil
composition at 2.34
wt. %.
CA 02482221 2004-09-21
Borated succinimide auxiliary dispersant - The auxiliary dispersant was a
boron-
containing succinimide prepared from polyisobutylene, succinic anhydride, and
a
polyethylene amine. The resultant product was post-treated with boric acid.
The borated
succinimide dispersant was used in the lubricating oil composition at 1.44 wt.
%.
Overbased calcium phenate detergent - The overbased phenate detergent was
prepared from a di (alkylated phenol) sulfide. The phenol group was
neutralized and then
the resultant salt was overbased with lime and carbon dioxide. The resultant
Total Base
Number (TBl~ of this component was about 250. The overbased phenate was used
in
the lubricating oil composition at approximately 2.I4 wt. %.
Secondary zinc dialkyldithiophosphate (ZnDTP) - The secondary ZnDTP was
prepared from phosphorus pentasulfide and a mixture of secondary alcohols. The
resultant mixture was neutralized with zinc oxide to produce 7nnTP. The
secondary
ZnDTP was used in the lubricating oil composition at 1.14 wt. %.
Alkylated diphenylamine ashless antioxidant - The ashless amine antioxidant
was
a di-alkylated, di-phenyl amine. This material was particularly effective for
high
temperature oxidation control in internal combustion engines. The ashless
antioxidant
was used in the lubricating oil composition at 0.27 wt. %.
Molybdenum-containing antioxidant - The molybdenum-containing antioxidant
was used in the lubricating oil composition at 0.117 wt. %.
31
CA 02482221 2004-09-21
Friction modifier - The friction modifier was based upon glycerol mono-oleate
that has been treated with boric acid to make a borate ester, The friction
modifier was
used in the lubricating oil composition at 0.18 wt. %.
Silicon-based foam inhibitor - The foam inhibitor was a commercially-available
12,500 molecular weight silicon oil diluted 1 to 49 parts in a light neutral
solvent. The
foam inhibitor was used in the lubricating oil composition at 4.Sppm.
Viscosity modifier - The viscosity modifier was a yoderately shear stable
olefin
copolymer. The viscosity improves was used in the lubricating oil composition
at 10.0
wt. %.
The lubricating oil composition of Comparative Example A possessed a
phosphorous content of approximately 0.08 wt. % and a sulfur content of
approximately
0.2 wt.%.
EXAMPLE 1
A lubricating oil composition was formed by adding to a mixture of 74.2 wt. %
of
Chevron 100N, 20.8 wt. % of Chevron 220N and 5 wt. % of Lexolube~ 3N-310
(trimethylolpropane tri caprylate/caprate) available from Inolex Chemical
Company
(Philadelphia, PA), the additive package of Comparative Example A. The
lubricating oil
composition possessed a phosphorous content of approximately 0.08 wt. % and a
sulfur
content of approximately 0.2 wt.%.
32
CA 02482221 2004-09-21
EXAMPLE 2
A lubricating oil composition'was formed by adding to a mixture of 70.3 wt. %
of
Chevron I OON, 19.7 wt. % of Chevron 220N and 10 wt. % of Lexolube~ 3N-310
(trimethylolpropane tri caprylatefcaprate) available from Inolex Chemical
Company
(Philadelphia; PA), the additive package of Comparatiee Example A. The
lubricating oil
composition possessed a phosphorous content of approximately 0.08 wt. % and a
sulfur
content of approximately 0.2 wt.%.
COMPARATIVE EXAMPLE B
A lubricating oil composition was formed by adding to a mixture of 74.2 wt. %
of
Chevron 100N, 20.8 wt. % of Chevron 220N and 5 wt. % of Lexolube~ 2X-109
(ditridecyladipate, a C6 dicarboxylic acid diester of tridecanol) available
from lnolex
Chemical Company (Philadelphia, PA), the additive package of Comparative
Example A.
The lubricating oil composition possessed a phosphorous content of
approximately 0.08
wt. % and a sulfur content of approximately 0.2 wt.%.
COMPARATIVE EXAMPLE C
A lubricating oil composition was formed by adding to a mixture of 70.3 wt. %
of
Chevron 100N, 19.7 wt. % of Chevron 220N and 10 wt. % of Lexolube~ 2~.-109
(ditridecyladipate, a C6 dicarboxylic acid diester of tridecanol) available
from Inolex
33
CA 02482221 2004-09-21
Chemical Company (Philadelphia, PA), the additive package of Comparative
Example A.
The lubricating oil composition possessed a phosphorous content of
approximately 0.08
wt. % and a sulfur content of approximately 0.2 wt.%.
COMPARATIVE EXAMPLE D
A lubricating oil composition was formed by adding to a mixture, of 74.2 wt. %
of
Chevron 100N, 20.8 wt. % of Chevron 220N and 5 wt. % Lexolube~ 4N-415
(pentaerythritol tetra eaprylatelcaprate; a tetra ester of caprylic and caprie
acid of
pentaerythritol) available from Inolex Chemical Company (Philadelphia, PA),
the
additive package of Comparative Example A: The lubricating' oil composition
possessed
a phosphorous content of approximately 0.08 wt. % and a sulfur content of
approximately
0.2 wt.%.
COMPARATIVE E~~AMPLE E
A lubricating oil composition was formed by adding to a mixture of 70.3
wt. % of Chevron 100N, 19.7 wt. % of Chevron 220N and 10 wt. % of Lexolube~ 4N-
415 {pentaerythritol tetra caprylate/caprate, a tetra ester of caprylic and
capric acid of
pentaerytluitol) available from Inolex Chemical Company (Philadelphia, PA),
the
additive package of Comparative Example A. The lubricating oil composition
possessed
34
CA 02482221 2004-09-21
a phosphorous content of approximately 0.08 wt. % and a sulfur content of
approximately
0.2 wt:%.
TESTING
Each of the lubricating oil compositions of Examples 1 and 2 and
Comparative Examples A-E were evaluated using the Thermo-Oxidation Engine Oil
Simulation Test (TEOST) TEOST IvIHT-4 and TEOST 33 as described below.
TEOST MHT-4
The TEOST MHT-4 test as described in Florkowski et al., Draft 12 TEOST
MHT-4 Test Method, to Henry Wheeler, Chair, ASTM D.02.07 TEOST Surveillance
Panel Chair (September 10, 1999) was performed to predict the moderately high
temperature deposit forming tendencies of engine oil, especially in the piston
ring belt
area.
Using a TEOST apparatus available from Tannas Company (4800 James Savage
Road, Midland, MI 48642), a sample of each of the lubricating engine oil
compositions
of Examples 1 and 2 and Comparative Examples A-E containing an organometallic
catalyst was forced to flow past a tared; wire-wound depositor rod held in a
glass mantled
casing. The rod was resistively heated to obtain a constant temperature of
285°C for 24
hours. During this time, dry air was forced to flow through the mantle chamber
at a
CA 02482221 2004-09-21
specified rate of lOmL/min. At the endof the test, the depositor rod and the
components
of the chamber were carefully rinsed of oil residue using a volatile
hydrocarbon solvent.
After drying the rod, the mass of deposits was determined. The hydrocarbon
solvent
rinse was filtered and weighed and the mass of the accumulated filter deposits
was
determined. The mass of deposits on the rod plus the mass of deposits on the
filter was
the total deposit mass. The mass of deposits which have accumulated on the
inside
surface of the mantle were also weighed.
TEOST 33
The TEOST 33 test was performed to assess the deposit forming tendencies of
engine oils brought into contact with S00°C turbocharger components.
The TEOST 33
test used herein is described in D.W. Florkowski and T.W. Selby, "The
Development of a
Thermo-Oxidation Engine Oil Simulation Test (TEOST), SAE Paper 932837 (1993)
and
Stipanovic et al.; "Base Oil and Additive Effects in the Thermo-Oxidation
Engine Oil
Simulation Test (TEOST)", SAE Paper 962038 (1996).
The apparatus consisted of an oxidation reactor and a deposition zone made up
of
a hollow depositor rod axially aligned within an outer tube. The temperature
of the
reactor and the depositor rod wereindependently controlled. The lubricating
oil
composition under evaluation was mixed with 100ppm of iron delivered as an
iron
naphthenate catalyst, then added to the reactor. The mixture was then heated
to and held
36
CA 02482221 2004-09-21
at 100°C. This sample was exposed to a gas stream of air, nitrous
oxide, and water.
Throughout the TEOST 33 test, the oiLwas pumped through the annulus between
the
depositor rod and the outside casing while the rod was cycled through a
programmed
temperature profile. Except for the initial temperature ramp from room
temperature to
200°C, the temperature cycle was repeated 12 times. The total test
duration was for a
time period of 114 minutes.
At the completion of the oxidation cycle, the oil was collected and filtered.
The
equipment was cleaned with solvent and that solvent was also filtered. The
filter used in
collecting the oil was dried and weighed to determine the filter deposits. The
depositor
rod was dried and weighed to determine the accumulation of deposits. The total
deposit
was the sum of the rod and filter deposits and reported in milligrams. Test
repeatability
was originally given as +/- 2.3 mg with a standard deviation of 1.6 mg.
The results of these tests are set forth below in Table 1.
TABLE I
Comp.. Comp. Comp. Comp. Comp.
Exam Exam le Ex. Ex. B Ex. Ex. Ex.
le 1 2 A C D E
TEOST METT-4 36:3 39.7 33.5 47.3 49.4 40.3 46:5
(m )
TEOST 33 (mg) 39.7 34.7 56.5 $2.2 105.4 36.2 36.4
The TEOST tests (TEOST 33 and TEOST MHT-4) are key bench tests for all
ILSAC passenger car motor oil formulations. At present, only the TEOST MHT-4
test is
37
CA 02482221 2004-09-21
required but the TEOST 33 test will likely be added back in the future. In
order to pass
the TEOST MHT-4 bench test, the lubricating oil can provide no higher than 40
mg of
deposits, while for the TEST 33 bench test, the lubricating oil composition
can provide
no higher than 60 mg deposits. These tests behave differently to certain
additives,
namely, the TEOST MHT-4 test generally preferring ashless antioxidants like
the
diphenylamine and the TEOST 33 test generally preferring detergents. Iri
general, the
TEOST MHT-4 test results are ordinarily below the Limit, while the TEOST 33
test
results are typically borderline. Thus, to improve the TEOST 33 test results,
low-
overbased sulfonates, a potent detergent, are typically added to a
formulation. This,
I O however, increases sulfur content of the formulation.
Accordingly, and as the above data show, the lubricating oil compositions of
Examples l and 2 using a polyol ester of the present invention as a
5°l° and 10 % by
weight, respectively, replacement for the Group II mineral oils provided a
TEOST MHT-
4 performance substantially equivalent to that of the baseline formulation of
Comparative
Example A, i.e., 36.3 mg and 39.7mg, respectively, as compared to 33.5 mg.
However,
the lubricating oil compositions of Examples 1 and 2 performed significantly
better than
the lubricating oiI composition of Comparative Example A in the TEOST 33 test,
i.e.; an
approximately 17 mg difference for the oil composition of Example 1 to the oil
composition of Comparative Example A and a 21 mg difference for the oil
composition
of Example 2 to the oil composition of Comparative Example A. Clearly, by
adding the
38
CA 02482221 2004-09-21
polyol ester of the present invention to a lubricating oil composition
provides a
signif cant improvement in the TEOST 33 test thereby controlling deposit
formation
without adding sulfur containing detergents.
It is also noteworthy that not all esters provide such results. For example,
comparing the lubricating oil compositions of Examples 1 and 2 (within the
scope of the
present invention) to the lubricating,oil compositions of Comparative Examples
B-E
(outside the scope of the present invention), the lubricating oil compositions
of Examples
1 and 2 performed within the maximum limits for both the TEOST MHT-4 and TEOST
33 tests while the lubricating ail compositions of Comparative Examples B-E
did not stay
within the limits of these tests. Thus, it has been shown that not alI esters
perform
equally. These results are entirely unexpected:
It will be understood that various modifications may be made to the
embodiments
disclosed herein. Therefore the above description should not be construed as
limiting,
but merely as exemplifications of preferred embodiments. For example, the
functions
described above and implemented as the best mode for operating the present
invention
are for illustration purposes only. Other arrangements and methods may be
implemented
by those skilled in the art without departing from the scope and spirit of
this invention.
Moreover, those skilled in the art will envision other modifications within
the scope and
spirit of the claims appended hereto.
39
