U.S. patent application number 10/674692 was filed with the patent office on 2005-03-31 for engine oil compositions.
Invention is credited to Roby, Stephen H., Ruelas, Susanne G..
Application Number | 20050070449 10/674692 |
Document ID | / |
Family ID | 34313964 |
Filed Date | 2005-03-31 |
United States Patent
Application |
20050070449 |
Kind Code |
A1 |
Roby, Stephen H. ; et
al. |
March 31, 2005 |
Engine oil compositions
Abstract
A low phosphorous or phosphorous-free sulfur lubricating oil
composition and/or low phosphorous or phosphorous-free and low
sulfur or sulfur-free lubricating oil composition for internal
combustion engines comprising (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 1
wherein R.sup.1, R.sup.2 and R.sup.3 are independently aliphatic
hydrocarbyl moieties having from 4 to about 24 carbon atoms,
R.sup.4 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, and additive compositions and additive
packages containing the foregoing polyol ester are provided.
Inventors: |
Roby, Stephen H.; (Hercules,
CA) ; Ruelas, Susanne G.; (San Pablo, CA) |
Correspondence
Address: |
Michael E. Carmen, Esq.
DILWORTH & BARRESE, LLP
333 Earle Ovington Blvd.
Uniondale
NY
11553
US
|
Family ID: |
34313964 |
Appl. No.: |
10/674692 |
Filed: |
September 30, 2003 |
Current U.S.
Class: |
508/485 |
Current CPC
Class: |
C10M 2207/289 20130101;
C10M 169/04 20130101; C10M 2205/02 20130101; C10M 2229/02 20130101;
C10N 2060/00 20130101; C10M 2203/1006 20130101; C10M 2207/2835
20130101; C10N 2060/06 20130101; C10N 2030/06 20130101; C10N
2010/04 20130101; C10N 2060/14 20130101; C10N 2030/08 20130101;
C10M 2215/064 20130101; C10N 2030/42 20200501; C10N 2030/43
20200501; C10M 129/74 20130101; C10M 2215/28 20130101; C10N 2030/02
20130101; C10M 2223/045 20130101; C10M 2205/0285 20130101; C10M
2207/028 20130101; C10M 2207/283 20130101; C10N 2040/25 20130101;
C10M 2207/282 20130101; C10N 2030/04 20130101 |
Class at
Publication: |
508/485 |
International
Class: |
C10M 015/38 |
Claims
What is claimed is:
1. A low phosphorous or phosphorous-free lubricating oil
composition comprising (a) a major amount of base oil of
lubricating viscosity and (b) a minor deposit-inhibiting effective
amount of at least one polyol ester of the general formula 5wherein
R.sup.1, R.sup.2 and R.sup.3 are independently an aliphatic
hydrocarbyl moiety have from 4 to 24 carbon atoms, R.sup.4 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.
2. The low phosphorous or phosphorous-free lubricating oil
composition of claim 1, wherein the base oil of lubricating
viscosity is comprised of a mineral base oil.
3. The low phosphorous or phosphorous-free lubricating oil
composition of claim 1, wherein the base oil of lubricating
viscosity is comprised of a polyalphaolefin base oil.
4. The low phosphorous or phosphorous-free lubricating oil
composition of claim 1, wherein R.sup.1, R.sup.2 and R.sup.3 of the
polyol ester are independently selected from a saturated or
unsaturated aliphatic hydrocarbyl moiety having from 6 to 10 carbon
atoms.
5. The low phosphorous or phosphorous-free lubricating oil
composition of claim 1, wherein R.sup.1, R.sup.2 and R.sup.3 are
independently selected from a saturated or unsaturated aliphatic
moiety having from 6 to 10 carbon atoms, R.sup.4 is an aliphatic
hydrocarbyl moiety having 1 to 6 carbon atoms and x, y and z are
1.
6. The low phosphorous or phosphorous-free lubricating oil
composition of claim 1, wherein the minor deposit-inhibiting
effective amount of the polyol ester is about 0.5 wt. % to about 10
wt. %, based on the total weight of the composition.
7. The low phosphorous or phosphorous-free lubricating oil
composition of claim 1, wherein the minor deposit-inhibiting
effective amount of the polyol ester is about 1 wt. % to about 5
wt. %, based on the total weight of the composition.
8. The low phosphorous or phosphorous-free lubricating oil
composition of claim 5, wherein the minor deposit-inhibiting
effective amount of the polyol ester is about 0.5 wt. % to about 10
wt. %, based on the total weight of the composition.
9. The low phosphorous or phosphorous-free lubricating oil
composition of claim 1, wherein the composition has an SAE
Viscosity Grade of 0 W, 0 W-20, 0 W-30, 0 W-40, 0 W-50, 0 W-60, 5
W, 5 W-20, 5 W-30, 5 W-40, 5 W-50, 5 W-60, 10 W, 10 W-20, 10 W-30,
10 W-40, 10-50, 15 W, 15 W-20, 15 W-30 or 15 W-40.
10. The low phosphorous or phosphorous-free lubricating oil
composition of claim 1, further comprising at least one additive
selected from the group consisting of metallic detergents, ashless
dispersants, friction modifiers, extreme pressure agents, viscosity
index improvers and pour point depressants.
11. The low phosphorous or phosphorous-free lubricating oil
composition of claim 1, having a phosphorous content not exceeding
0.05 wt. %, based on the total weight of the composition.
12. The low phosphorous or phosphorous-free lubricating oil
composition of claim 5, having a phosphorous content not exceeding
0.05 wt. %, based on the total weight of the composition.
13. The low phosphorous or phosphorous-free lubricating oil
composition of claim 1, having a sulfur content not exceeding 0.2
wt. %, based on the total weight of the composition.
14. The low phosphorous or phosphorous-free lubricating oil
composition of claim 12, having a sulfur content not exceeding 0.2
wt. %, based on the total weight of the composition.
15. A method of operating an internal combustion engine comprising
the step of operating the internal combustion engine with a
low-phosphorous or phosphorous-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 at
least one polyol ester of the general formula 6wherein R.sup.1,
R.sup.2 and R.sup.3 are independently an aliphatic hydrocarbyl
moiety have from 4 to 24 carbon atoms, R.sup.4 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.
16. The method of claim 15, wherein the base oil of lubricating
viscosity is comprised of a mineral base oil.
17. The method of claim 15, wherein the base oil of lubricating
viscosity is comprised of a polyalphaolefin base oil.
18. The method of claim 15, wherein R.sup.1, R.sup.2 and R.sup.3 of
the polyol ester are independently selected from a saturated or
unsaturated aliphatic hydrocarbyl moiety having from 6 to 10 carbon
atoms.
19. The method of claim 15, wherein R.sup.1, R.sup.2 and R.sup.3
are independently selected from a saturated or unsaturated
aliphatic moiety having from 6 to 10 carbon atoms, R.sup.4 is an
aliphatic hydrocarbyl moiety having 1 to 6 carbon atoms and x, y
and z are 1.
20. The method of claim 15, wherein the minor deposit-inhibiting
effective amount of the polyol ester is about 0.5 wt. % to about 10
wt. %, based on the total weight of the composition.
21. The method of claim 15, wherein the minor deposit-inhibiting
effective amount of the polyol ester is about 1 wt. % to about 5
wt. %, based on the total weight of the composition.
22. The method of claim 19, wherein the minor deposit-inhibiting
effective amount of the polyol ester is about 0.5 wt. % to about 10
wt. %, based on the total weight of the composition.
23. The method of claim 15, wherein the composition has an SAE
Viscosity Grade of 0 W, 0 W-20, 0 W-30, 0 W-40, 0 W-50, 0 W-60, 5
W, 5 W-20, 5 W-30, 5 W-40, 5 W-50, 5 W-60, 10 W, 10 W-20, 10 W-30,
10 W-40, 10 W-50, 15 W, 15 W-20, 15 W-30 or 15 W-40.
24. The method of claim 15, further comprising at least one
additive selected from the group consisting of metallic detergents,
ashless dispersants, friction modifiers, extreme pressure agents,
viscosity index improvers and pour point depressants.
25. The method of claim 15, wherein the composition has a
phosphorous content not exceeding 0.05 wt. %, based on the total
weight of the composition.
26. The method of claim 19, wherein the composition has a
phosphorous content not exceeding 0.05 wt. %, based on the total
weight of the composition.
27. The method of claim 15, wherein the composition has a sulfur
content not exceeding 0.2 wt. %, based on the total weight of the
composition.
28. The method of claim 26, wherein the composition has a sulfur
content not exceeding 0.2 wt. %, based on the total weight of the
composition.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] 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 oil and a polyol ester.
[0003] 2. Description of the Related Art
[0004] 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.
[0005] 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
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.
[0006] 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.
[0007] 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.
[0008] In order to compensate for lowering the amount of zinc
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 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.
[0009] Detergents have been added to impart a total base number
(TBN) to neutralize acidic combustion products and to clean
surfaces containing deposits. However, detergents may impart
undesirable properties. For example, overbased 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
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.
[0010] 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) 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
dialkyldithiophosphate, but which do not suffer from the
disadvantages of the lubricating oils discussed above.
SUMMARY OF THE INVENTION
[0011] 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 phosphorous-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: 2
[0012] wherein R.sup.1, R.sup.2 and R.sup.3 are independently
aliphatic hydrocarbyl moieties having from 4 to about 24 carbon
atoms, R.sup.4 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.
[0013] In another embodiment, a low phosphorous or phosphorous-free
and a low sulfur or sulfur-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 exceeding 0.08% by weight and a sulfur
content not exceeding 0.2% by weight, based on the total weight of
the composition.
[0014] 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 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, based on the total weight of the composition.
[0015] Still 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 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.
[0016] 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.
[0017] The present invention advantageously provides lubricating
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 oil 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 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
[0018] It has been found that the incorporation of the compounds of
formula (I) 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, 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
sulfonates 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 may be a compound containing one or more
of the groups: sulfamoyl, sulfenamoyl, sulfeno, sulfido,
sulfinamoyl, sulfino, sulfinyl, sulfo, sulfonio, sulfonyl,
sulfonyldioxy, sulfate, thio, 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 and 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.
[0019] 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 oil will have a kinematic
viscosity range at 100.degree. 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 blended depending on the desired end 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 0 W, 0 W-20, 0 W-30, 0 W-40, 0 W-50, 0 W-60, 5 W, 5 W-20,
5 W-30, 5 W-40, 5 W-50,5 W-60, 10 W, 10 W-20, 10 W-30, 10 W-40, 10
W-50,15 W, 15 W-20,15 W-30 or 15 W-40.
[0020] 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 substantially free from
materials introduced through manufacturing, contamination, or
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 1-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.degree. C.
[0021] 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 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, December 1998. Group IV
base oils are polyalphaolefins (PAO). Group 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 by combining
one or more of Group I, II, III, IV and V base stocks or base
oils.
[0022] 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-naphthenic types, oils derived from coal or
shale, animal oils, vegetable oils (e.g., rapeseed oils, castor
oils and lard oil), and the like.
[0023] 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 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 diphenyl ethers and alkylated diphenyl sulfides and the
derivative, analogs and homologs thereof and the like.
[0024] 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, isobutene, pentene,
and mixtures thereof. Methods of preparing such polymer oils are
well known to those skilled in the art.
[0025] 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 C.sub.6 to C.sub.12 alpha olefins such as, for
example, 1-decene trimer.
[0026] Another class of useful synthetic lubricating oils include,
but are not limited to, alkylene oxide polymers, i.e.,
homopolymers, interpolymers, and derivatives thereof where the
terminal hydroxyl groups have been modified by, for example,
esterification or etherification. These oils are 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 C.sub.3-C.sub.8 fatty acid
esters, or the C.sub.13oxo acid diester of tetraethylene
glycol.
[0027] 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, maleic acid, azelaic acid, suberic acid, sebacic
acid, fumaric acid, adipic acid, linoleic acid dimer, malonic
acids, alkyl malonic acids, alkenyl malonic acids, etc., with a
variety of alcohols, e.g., butyl alcohol, hexyl alcohol, dodecyl
alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol
monoether, 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 dimer, 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.
[0028] 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, tripentaerythritol,
and the like.
[0029] 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-tert-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.
[0030] The lubricating oil may be derived from unrefined, refined
and rerefined 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 rerefined oils are also known as
reclaimed or reprocessed oils and often are additionally processed
by techniques directed to removal of spent additives and oil
breakdown products.
[0031] 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.
[0032] 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-Tropsch process.
[0033] The compounds of formula (I) for incorporating into the
foregoing base oils (hereafter referred to as polyol ester), i.e.,
3
[0034] wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, 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 R.sup.1, R.sup.2 and R.sup.3 groups, the aliphatic
hydrocarbyl moieties may be 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 R.sup.4 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 1. Examples of
such polyol esters for use herein include, but are not limited to,
trimethylolpropane (TMP) esters such as, for example, TMP
tri(2-ethyl hexanoate), TMP triheptanoate, TMP tricaprylate, TMP
tricaprate, TMP tri(isononanoate) and the like.
[0035] 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 weight percent 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.
[0036] 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, for 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. %, preferably no higher than 0.08 wt. %,
and more preferably not 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 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 conventional techniques, for
example, x-ray techniques.
[0037] 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 4
[0038] wherein R.sup.5, R.sup.6, R.sup.7 and R.sup.8 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.
[0039] 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.
[0040] 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 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.
[0041] 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.
[0042] Detergents for use herein may be overbased or neutral. For
example, common detergents are sulfonates, e.g., those made from
alkyl benzene and fuming 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 (TBN) of from about 0 to about
30 and preferably from about 10 to about 25. Low overbased metal
sulfonates and neutral metal sulfonates are well known in the
art.
[0043] 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 known 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
sulfonic 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 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.
[0044] 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 metal
sulfonates. Generally, the acids are neutralized with an alkali
metal base. Alkaline earth metal salts are 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 making 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 salt can be hydroxyl, oxide,
carbonate, borate, nitrate, etc.
[0045] 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 polynuclear aromatic or
cycloaliphatic compounds. The oil-soluble sulfonates can be
represented for the most part by one of the following formulae:
R.sub.2--T--(SO.sub.3).sub.a and R.sub.3--(SO.sub.3).sub.b, wherein
T is a cyclic nucleus such as, for example, benzene, naphthalene,
anthracene, diphenylene oxide, diphenylene sulfide, petroleum
naphthenes, etc.; R.sub.2 is an aliphatic group such as alkyl,
alkenyl, alkoxy, alkoxyalkyl, etc.; (R.sub.2)+T contains a total of
at least about 15 carbon atoms; and R.sub.3 is an aliphatic
hydrocarbyl group containing at least about 15 carbon atoms.
Examples of R.sub.3 are alkyl, alkenyl, alkoxyalkyl,
carboalkoxyalkyl, etc. Specific examples of R.sub.3 are groups
derived from petrolatum, saturated and unsaturated paraffin wax,
and the above-described polyalkenes. The groups T, R.sub.2, and
R.sub.3 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, nitro, 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
(R.sub.2 or R.sub.3) which is derived from one of the
above-described polyalkenes.
[0046] Illustrative examples of these sulfonic acids include
monoeicosanyl-substituted 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 (Me) 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 (Mn of from about 300 to about 1000, 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 12 up to about 400 carbon
atoms, preferably about 250. Also useful are polyisobutene
sulfonates, e.g., those disclosed in U.S. Pat. No. 6,410,491, the
contents of which are incorporated by reference herein.
[0047] 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.sub.n of from about 300 to about 1000
and preferably from about 500 to about 700, cetylchlorobenzene
sulfonic acid, di-cetylnaphthalene sulfonic acid,
di-lauryldiphenylether sulfonic acid, diisononylbenzene sulfonic
acid, di-isooctadecylbenzene sulfonic acid, stearylnaphthalene
sulfonic acid, and the like.
[0048] 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.degree. F. to about 200 seconds at
210.degree. F.; petrolatum sulfonic acids; mono- and
poly-wax-substituted sulfonic and polysulfonic acids of, e.g.,
benzene, naphthalene, phenol, diphenyl ether, naphthalene
disulfide, etc.; other substituted sulfonic acids such as alkyl
benzene sulfonic acids (where the alkyl group has at least 8
carbons), cetylphenol mono-sulfide sulfonic acids, dilauryl beta
naphthyl sulfonic acids, and alkaryl sulfonic acids such as dodecyl
benzene "bottoms" sulfonic acids.
[0049] 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 straight-chain dialkylate
preferred.
[0050] Particularly preferred based on their wide availability are
salts of the petroleum sulfonic 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.
[0051] 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 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 sulfonic acids such as
cetyl 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 all
sulfonic acids that are derived directly from petroleum
products.
[0052] Typical Group 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 mahogany petroleum sulfonate, calcium triacontyl
sulfonate, calcium lauryl sulfonate, barium lauryl sulfonate, and
the like.
[0053] 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, or an inorganic
acidic material such as, for example, HCl, SO.sub.2, SO.sub.3,
CO.sub.2, H.sub.2S, etc, with CO.sub.2 being preferred. The amount
of acidic material used depends in some respects 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 required 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.
[0054] 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.degree. C. Commercially available oils
of this type known to one skilled in the art include, e.g., those
available from such sources as Exxon under the Isopar.RTM.
tradenames, e.g., Isopar.RTM. M, Isopar.RTM. G, Isopar.RTM. H, and
Isopar.RTM. V, and the Telura.RTM. tradename, e.g., Telura.RTM.
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 unsubstituted or substituted aromatic
hydrocarbons include high flash solvent naptha and the like.
[0055] 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
polyhydric 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. Amounts 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 range from about 0.2 to about 10% by
weight of the total weight of the engine oil lubricating
composition.
[0056] 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.
[0057] 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 alky sulfides or polysulfides. Because of the high
sulfur content, these materials are often potent antioxidants.
[0058] 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 (I).
[0059] 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 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
0.01% to about 10% by weight based on the total weight of the
lubricating oil composition.
[0060] 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.degree. C. and
preferably about 4 to about 6 cSt at 100.degree. 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.
[0061] 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.
[0062] The following non-limiting examples are illustrative of the
present invention.
EXAMPLES
[0063] The following examples provide lubricating oil compositions
which were formulated to give viscosity conditions of a SAE 5 W30
oil defined in the Society of Automotive Engineers classification
system SAE J300.
Comparative Example A
[0064] 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 Ramon, Calif.)
and 21.9 wt. % of Chevron 220N (a Group II base oil) commercially
available from ChevronTexaco Corp. (San Ramon, Calif.), 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):
[0065] Additive Package
[0066] 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. %.
[0067] 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. %.
[0068] 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 (TBN) of this component was about 250. The overbased phenate
was used in the lubricating oil composition at approximately 2.14
wt. %.
[0069] 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 ZnDTP. The secondary ZnDTP
was used in the lubricating oil composition at 1.14 wt. %.
[0070] 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. %.
[0071] Molybdenum-containing antioxidant--The molybdenum-containing
antioxidant was used in the lubricating oil composition at 0.117
wt. %.
[0072] 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. %.
[0073] 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 4.5 ppm.
[0074] Viscosity modifier--The viscosity modifier was a moderately
shear stable olefin copolymer. The viscosity improver was used in
the lubricating oil composition at 10.0 wt. %.
[0075] 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
[0076] 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.RTM. 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. %.
Example 2
[0077] 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.RTM. 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. %.
Comparative Example B
[0078] 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.RTM. 2X-109 (ditridecyladipate, a C.sub.6
dicarboxylic acid diester of tridecanol) 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 Example C
[0079] 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.RTM. 2X-109 (ditridecyladipate, a C.sub.6
dicarboxylic acid diester of tridecanol) 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 Example D
[0080] 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.RTM. 4N-415 (pentaerythritol tetra
caprylate/caprate, a tetra ester of caprylic and capric 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 Example E
[0081] 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.RTM. 4N-415 (pentaerythritol tetra
caprylate/caprate, a tetra ester of caprylic and capric 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. %.
[0082] Testing
[0083] 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 MHT-4 and
TEOST 33 as described below.
TEOST MHT-4
[0084] 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 (Sep. 10, 1999) was
performed to predict the moderately high temperature deposit
forming tendencies of engine oil, especially in the piston ring
belt area.
[0085] Using a TEOST apparatus available from Tannas Company (4800
James Savage Road, Midland, Mich. 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.degree. C. for 24 hours. During this
time, dry air was forced to flow through the mantle chamber at a
specified rate of 10 mL/min. At the end of 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
[0086] The TEOST 33 test was performed to assess the deposit
forming tendencies of engine oils brought into contact with
500.degree. 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).
[0087] 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 were independently controlled. The lubricating oil
composition under evaluation was mixed with 100 ppm of iron
delivered as an iron naphthenate catalyst, then added to the
reactor. The mixture was then heated to and held at 100.degree. C.
This sample was exposed to a gas stream of air, nitrous oxide, and
water. Throughout the TEOST 33 test, the oil was 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.degree.
C., the temperature cycle was repeated 12 times. The total test
duration was for a time period of 114 minutes.
[0088] 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.
[0089] The results of these tests are set forth below in Table
1.
1 TABLE 1 Ex- Ex- am- am- Comp. Comp. Comp. Comp. Comp. ple 1 ple 2
Ex. A Ex. B Ex. C Ex. D Ex. E TEOST 36.3 39.7 33.5 47.3 49.4 40.3
46.5 MHT-4 (mg) TEOST 39.7 34.7 56.5 82.2 105.4 36.2 36.4 33
(mg)
[0090] 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 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. In 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, however, increases sulfur content of the
formulation.
[0091] Accordingly, and as the above data show, the lubricating oil
compositions of Examples 1 and 2 using a polyol ester of the
present invention as a 5% 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 39.7 mg,
respectively, as compared to 33.5 mg. However, the lubricating oil
compositions of Examples 1 and 2 performed significantly better
than the lubricating oil 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 polyol ester of the present invention to a lubricating
oil composition provides a significant improvement in the TEOST 33
test thereby controlling deposit formation without adding sulfur
containing detergents.
[0092] 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 oil compositions of Comparative Examples B-E did not
stay within the limits of these tests. Thus, it has been shown that
not all esters perform equally. These results are entirely
unexpected.
[0093] 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.
* * * * *