U.S. patent application number 12/373527 was filed with the patent office on 2011-10-06 for lubricating oil composition and method of improving efficiency of emissions control system.
This patent application is currently assigned to THE LUBRIZOL CORPORATION. Invention is credited to Stephen A. DiBiase, Calvin W. Schroeck, Melody A. Wilk.
Application Number | 20110245116 12/373527 |
Document ID | / |
Family ID | 38957505 |
Filed Date | 2011-10-06 |
United States Patent
Application |
20110245116 |
Kind Code |
A1 |
Schroeck; Calvin W. ; et
al. |
October 6, 2011 |
Lubricating Oil Composition and Method of Improving Efficiency of
Emissions Control System
Abstract
The disclosed technology relates to a lubricating oil
composition comprising at least one base oil and at least one
overbased low molecular weight zinc dialkyldithiophosphate derived
from one or more dithiophosphoric acids represented by the formula
(I) and/or a metal salt thereof, wherein in formula (I), R.sup.1
and R.sup.2 are independently hydrocarbyl groups, the average total
number of carbon atoms in R.sup.1 and R.sup.2 in formula (I) being
in the range from 4 to 10, the metal ratio of the overbased low
molecular weight zinc dialkyldithiophosphate being at least about
1.15:1, the lubricating oil composition being characterized by a
phosphorus concentration of up to about 0.12% by weight. The
disclosed technology also relates to a method of lubricating an
internal combustion engine and improving the efficiency of the
emissions control system of the engine. ##STR00001##
Inventors: |
Schroeck; Calvin W.;
(Willoughby Hills, OH) ; Wilk; Melody A.;
(Timberlake, OH) ; DiBiase; Stephen A.;
(Willowbrook, IL) |
Assignee: |
THE LUBRIZOL CORPORATION
WICKLIFFE
OH
|
Family ID: |
38957505 |
Appl. No.: |
12/373527 |
Filed: |
July 13, 2007 |
PCT Filed: |
July 13, 2007 |
PCT NO: |
PCT/US07/73426 |
371 Date: |
November 30, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60807543 |
Jul 17, 2006 |
|
|
|
Current U.S.
Class: |
508/185 ;
508/287; 508/370 |
Current CPC
Class: |
C10M 2219/06 20130101;
C10N 2010/04 20130101; C10N 2040/25 20130101; C10M 2227/062
20130101; C10M 2215/28 20130101; C10M 2223/045 20130101; C10M
2215/064 20130101; C10M 163/00 20130101; C10M 135/10 20130101; C10N
2030/38 20200501; C10M 2207/289 20130101; C10N 2030/02 20130101;
C10M 2219/022 20130101 |
Class at
Publication: |
508/185 ;
508/370; 508/287 |
International
Class: |
C10M 137/10 20060101
C10M137/10; C10M 133/44 20060101 C10M133/44 |
Claims
1. A lubricating oil composition comprising at least one base oil
and at least one overbased low molecular weight zinc
dialkyldithiophosphate derived from one or more dithiophosphoric
acids represented by the formula ##STR00012## and/or metal salt
thereof, wherein in formula (I), R.sup.1 and R.sup.2 are
independently hydrocarbyl groups, the average total number of
carbon atoms in R.sup.1 and R.sup.2 in formula (I) being in the
range from 4 to 10, the metal ratio of the overbased low molecular
weight zinc dialkyldithiophosphate being at least about 1.08:1, the
lubricating oil composition being characterized by a phosphorus
concentration of up to about 0.12% by weight.
2. The composition of claim 1 wherein the lubricating oil
composition has a viscosity of up to about 16.3 mm.sup.2/sec at
100.degree. C.
3. The composition of claim 1 wherein the lubricating oil
composition has an SAE Viscosity Grade of 0W, 0W-20, 0W-30, 0W-40,
0W-50, 0W-60, 5W, 5W-20, 5W-30, 5W-40, 5W-50, 5W-60, 10W, 10W-20,
10W-30, 10W-40, 10W-50, 15W-40, 15W-50, 20W or 30W.
4. The composition of claim 1 wherein the base oil comprises
mineral oil.
5. The composition of claim 1 wherein the base oil comprises a
poly-alpha-olefin, an oil derived from Fischer-Tropsch synthesized
hydrocarbons, or an hydroisomerized Fischer-Tropsch hydrocarbon oil
or wax.
6. The composition of claim 1 wherein in formula (I), R.sup.1 and
R.sup.2 are independently alkyl groups of 2 to about 5 carbon
atoms.
7. The composition of claim 1 wherein in formula (I), R.sup.1 and
R.sup.2 are each alkyl groups of about 4 carbon atoms.
8. The composition of claim 1 wherein the metal ratio of the
overbased zinc dialkyldithiophosphate is in the range from about
1.15 to about 1.5.
9. The composition of claim 1 wherein the lubricating oil
composition further comprises at least one alkali or alkaline earth
metal containing detergent.
10. The composition of claim 1 wherein the lubricating oil
composition further comprises at least one acylated nitrogen
containing compound having at least about 30 aliphatic carbon
atoms.
11. The composition of claim 9 wherein the alkali or alkaline earth
metal-containing detergent comprises at least one salt of at least
one organic sulfur acid, carboxylic acid, lactone, phenol,
salixarate, or mixture of two or more thereof.
12. The composition of claim 9 wherein the alkali or alkaline earth
metal-containing detergent comprises at least one salt of at least
one salixarate.
13. The composition of claim 9 wherein the alkali or alkaline earth
metal comprises sodium, lithium, calcium, or a mixture of two or
more thereof.
14. The composition of claim 10 wherein the acylated
nitrogen-containing compound is derived from at least one
carboxylic acylating agent and at least one amino compound
containing at least one --NH-- group, the acylating agent being
linked to the amino compound through an imido, amido, amidine or
salt linkage.
15. The composition of claim 14 wherein the carboxylic acylating
agent is a mono- or polycarboxylic acid or anhydride containing an
aliphatic hydrocarbyl substituent of at least about 30 carbon
atoms.
16. The composition of claim 14 wherein the amino compound is an
alkylenepolyamine represented by the formula: ##STR00013## wherein
U is an alkylene group of from 2 to about 10 carbon atoms; each R
is independently a hydrogen atom, a hydrocarbyl group, a
hydroxy-substituted hydrocarbyl group, or an amine-substituted
hydrocarbyl group containing up to about 30 carbon atoms; and n is
1 to about 14.
17. The composition of claim 10 wherein the acylated nitrogen
containing compound comprises at least one polyisobutene
substituted succinimide.
18. The composition of claim 1 wherein the composition further
comprises at least one boron-containing compound represented by the
formula ##STR00014## wherein in Formulae XI, XII and XIII each R is
independently an organic group and any two adjacent R groups may
together form a cyclic group.
19. The composition of claim 1 wherein the lubricating oil
composition further comprises one or more: dispersants,
corrosion-inhibiting agents, antioxidants, viscosity modifiers,
dispersant viscosity index modifiers, pour point depressants,
friction modifiers, anti-wear agents, extreme pressure agents,
fluidity modifiers, copper passivators, anti-foam agents, or a
mixture of two or more thereof.
20. A lubricating oil composition comprising at least one base oil,
at least one overbased low molecular weight zinc
dialkyldithiophosphate derived from one or more dithiophosphoric
acids represented by the formula ##STR00015## and/or a metal salt
thereof, wherein in formula (I), R.sup.1 and R.sup.2 are
independently hydrocarbyl groups, the average total number of
carbon atoms in R.sup.1 and R.sup.2 in formula (I) being in the
range from about 6 to 10, the metal ratio of the overbased low
molecular weight dialkyldithiophosphate being at least about
1.08:1, at least one alkali or alkaline earth metal detergent, the
weight ratio of detergent metal to phosphorus in the lubricating
oil composition being in the range from about 0.5:1 to about 10:1,
and at least one nitrogen containing compound having at least about
30 aliphatic carbon atoms and a TBN of at least about 2, the weight
ratio of nitrogen to phosphorus in the lubricating oil composition
being in the range from about 0.3:1 to about 4:1, the lubricating
oil composition being characterized by a phosphorus concentration
of up to about 0.12% by weight.
21. A method of lubricating an internal combustion engine and
improving the efficiency of the emissions control system of the
engine, the emissions control system being equipped with a catalyst
containing exhaust gas after treatment device, the method
comprising: (A) lubricating the engine with a lubricating oil
composition comprising at least one base oil and at least one
overbased low molecular weight zinc dialkyldithiophosphate derived
from one or more dithiophosphoric acids represented by the formula
##STR00016## and/or metal salt thereof, wherein in formula (I),
R.sup.1 and R.sup.2 are independently hydrocarbyl groups, the
average total number of carbon atoms in R.sup.1 and R.sup.2 in
formula (I) being in the range from 4 to 10, the metal ratio of the
overbased low molecular weight dialkyldithiophosphate being at
least about 1.08:1, the lubricating oil composition being
characterized by a phosphorus concentration of up to about 0.12% by
weight; (B) generating a lean-phosphorus containing exhaust gas;
and (C) contacting the catalyst in the exhaust gas after treatment
device with the lean-phosphorus containing exhaust gas.
Description
TECHNICAL FIELD
[0001] The disclosed technology relates to a lubricating oil
composition and to a method of improving the efficiency of the
emissions control system of an internal combustion engine. The
lubricating oil composition may be characterized by the inclusion
of at least one overbased low molecular weight zinc
dialkyldithiophosphate. The method relates to using the lubricating
oil composition to lubricate an internal combustion engine equipped
with the exhaust gas after treatment device. In one embodiment, the
exhaust gas after treatment device comprises a catalyst and the
contamination of the catalyst is reduced.
BACKGROUND OF THE INVENTION
[0002] For decades phosphorus in the form of zinc
dialkyldithiophosphates (ZDDPs) have been used as extreme pressure
(EP) and antiwear additives in engine oils. A problem with the use
of phosphorus, however, is that it contaminates catalysts used in
exhaust gas after treatment devices and thereby reduces their
effectiveness. In response to this problem, phosphorus
concentration has been reduced for some SAE passenger car engine
oil classifications. With the introduction of ILSAC GF-1,
phosphorus levels were limited to no more than 1200 parts per
million (ppm) and with GF-3 to 1000 ppm. Even at these levels of
phosphorus, however, catalyst contamination is still an issue. The
problem therefore is to provide adequate engine lubrication and at
the same time reduce catalyst contamination. The disclosed
technology, in at least one embodiment, provides a solution to this
problem.
SUMMARY OF THE INVENTION
[0003] The disclosed technology relates to a lubricating oil
composition comprising at least one base oil and at least one
overbased low molecular weight zinc dialkyldithiophosphate derived
from one or more dithiophosphoric acids represented by the
formula
##STR00002##
and/or metal salt thereof, wherein in formula (I), R.sup.1 and
R.sup.2 are independently hydrocarbyl groups, the average total
number of carbon atoms in R.sup.1 and R.sup.2 in formula (I) being
in the range from 4 to 10, the metal ratio for the overbased low
molecular weight zinc dialkyldithiophosphate being at least about
1.15:1, the lubricating oil composition being characterized by a
phosphorus concentration of up to about 0.12% by weight.
[0004] In one embodiment, the disclosed technology relates to a
method of lubricating an internal combustion engine and improving
the efficiency of the emissions control system of the engine, the
emissions control system being equipped with a catalyst containing
exhaust gas after treatment device, the method comprising:
[0005] (A) lubricating the engine with a lubricating oil
composition comprising at least one base oil and at least one
overbased low molecular weight zinc dialkyldithiophosphate derived
from one or more dithiophosphoric acids represented by the
formula
##STR00003##
and/or metal salt thereof, wherein in formula (I), R.sup.1 and
R.sup.2 are independently hydrocarbyl groups, the average total
number of carbon atoms in R.sup.1 and R.sup.2 in formula (I) being
in the range from 4 to 10, the metal ratio of the overbased low
molecular weight zinc dialkyldithiophosphate ratio being at least
about 1.15:1, the lubricating oil composition being characterized
by a phosphorus concentration of up to about 0.12% by weight;
[0006] (B) generating a lean-phosphorus containing exhaust gas;
and
[0007] (C) contacting the catalyst in the exhaust gas after
treatment device with the lean-phosphorus containing exhaust
gas.
DETAILED DESCRIPTION
[0008] The term "low molecular weight zinc dialkyldithiophosphate"
may refer to one or more zinc dialkyldithiophosphates derived from
one or more dithiophosphoric acids represented by formula (I)
wherein the average total number of carbon atoms in R.sup.1 and
R.sup.2 for the one or more dithiophosphoric acids represented by
formula (I) is up to 10, and in one embodiment in the range from 4
to 10.
[0009] The term "high molecular weight zinc dialkyldithiophosphate"
may refer to one or more zinc dialkyldithiophosphates derived from
one or more dithiophosphoric acids represented by formula (I)
wherein the average total number of carbon atoms in R.sup.1 and
R.sup.2 in formula (I) is greater than 10.
[0010] The term "overbased" is a term of art which is generic to
well known classes of metal containing compositions comprising
metal salts and/or metal complexes. These compositions may also be
referred to as "basic," "superbased," "hyperbased," "high-metal
containing salts," and the like. Overbased metal compositions may
be in the form of inert organic liquid solutions characterized by a
metal content in excess of that which would be present according to
the stoichiometry of the metal (e.g., zinc) and the particular
acidic organic compound (e.g., a low molecular weight
dialkyldithiophosphoric acid) reacted with the metal. Thus, for
example, if a low molecular weight dialkyldithiophosphoric acid is
neutralized with a basic metal compound (e.g., zinc oxide), the
"neutral" or "normal" metal salt produced will contain one
equivalent of zinc for each equivalent of acid. On the other hand,
an overbased metal composition will contain more than the
stoichiometric amount of the metal. For example, a low molecular
weight dialkyldithiophosphoric acid and/or metal (e.g., zinc) salt
thereof may be reacted with a zinc base and the resulting overbased
low molecular weight zinc dialkyldithiophosphate may contain an
amount of zinc in excess of that necessary to neutralize the acid,
for example, about 1.15 times as much zinc as present in the
neutral salt or a zinc excess of about 0.15 equivalents. The actual
stoichiometric excess of zinc may vary considerably, for example,
from about 0.10 to about 1.0 equivalents, and in one embodiment
from about 0.2 to about 0.5 equivalents.
[0011] The term "metal ratio" may be used herein to designate the
ratio of the total chemical equivalents of metal (i.e., zinc) in an
overbased composition (e.g., overbased low molecular weight zinc
dialkyldithiophosphate) to the chemical equivalents of the metal in
the corresponding neutral salt. Thus, for example, the metal ratio
for a neutral low molecular weight zinc dialkyldithiophosphate is
1:1, and the metal ratio for the overbased low molecular weight
zinc dialkyldithiophosphate with a metal excess of 0.15 equivalents
discussed above is 1.15:1.
[0012] The term "overbased low molecular weight zinc
dialkyldithiophosphate derived from one or more dithiophosphoric
acids" may refer to an overbased low molecular weight zinc
dialkyldithiophosphate which is derived from the
dialkyldithiophosphoric acid and/or metal (e.g., zinc) salt of the
dialkyldithiophosphoric acid.
[0013] The overbasing of the dithiophosphoric acids or their zinc
salts with zinc oxide may be accomplished using catalytic amounts
of alkali metal hydroxides such as sodium hydroxide or potassium
hydroxide as in U.S. Pat. No. 5,015,402, or catalytic amounts of
low molecular weight carboxylic acids such as propionic acid or
2-ethylhexanoic acid as in U.S. Pat. No. 4,263,150 and U.S. Pat.
No. 4,507,215. Typically these catalytic agents are used in as
little as 0.01 equivalent or less per 1 phosphorus up to 0.1 or 0.2
or even 0.3 equivalents per 1 phosphorus of the dithiophosphoric
acid or salt.
[0014] The term "hydrocarbyl," when referring to groups attached to
the remainder of a molecule, may refer to groups having a purely
hydrocarbon or predominantly hydrocarbon character within the
context of this invention. These groups include the following:
[0015] (1) Purely hydrocarbon groups; that is, aliphatic,
alicyclic, aromatic, aliphatic- and alicyclic-substituted aromatic,
aromatic-substituted aliphatic and alicyclic groups, and the like,
as well as cyclic groups wherein the ring is completed through
another portion of the molecule (that is, any two indicated
substituents may together form an alicyclic group). Examples
include methyl, octyl, cyclohexyl, phenyl, etc.
[0016] (2) Substituted hydrocarbon groups; that is, groups
containing non-hydrocarbon substituents which do not alter the
predominantly hydrocarbon character of the group. Examples include
hydroxy, nitro, cyano, alkoxy, acyl, etc.
[0017] (3) Hetero groups; that is, groups which, while
predominantly hydrocarbon in character, contain atoms other than
carbon in a chain or ring otherwise composed of carbon atoms.
Examples include nitrogen, oxygen and sulfur.
[0018] In general, no more than about three substituents or hetero
atoms, and in one embodiment no more than one, may be present for
each 10 carbon atoms in the hydrocarbyl group.
[0019] The term "lower" as used herein in conjunction with terms
such as hydrocarbyl, alkyl, alkenyl, alkoxy, and the like, may
describe such groups which contain a total of up to 7 carbon
atoms.
[0020] The term "oil-soluble" may refer to a material that is
soluble in mineral oil to the extent of at least about 0.5 gram per
liter at 25.degree. C.
[0021] The term "TBN" may refer to total base number. This is the
amount of acid (perchloric or hydrochloric) needed to neutralize
all or part of a material's basicity, expressed as milligrams of
KOH per gram of sample.
[0022] The term "lean-phosphorus containing exhaust gas" may refer
to an exhaust gas that is generated in an internal combustion
engine lubricated with a lubricating oil composition containing an
overbased low molecular weight zinc dialkyldithiophosphate with a
metal ratio of at least about 1.08:1 or a Zn/P weight ratio of
1:1.15, the exhaust gas having a relatively low concentration of
phosphorus when compared to an exhaust gas generated under the same
conditions using the same lubricating oil composition containing
the same level of phosphorus except that the phosphorus containing
compound is a neutral low molecular weight zinc
dialkyldithiophosphate or a neutral or overbased high-molecular
weight zinc dialkyldithiophosphate.
[0023] The term "substantial absence of copper" may refer to the
fact that copper may not be intentionally added to the lubricating
oil composition and, if present, is present as an impurity. The
concentration of this impurity may be no more than about 10 ppm,
and in one embodiment no more than about 5 ppm, and in one
embodiment no more than about 2 ppm. The concentration of copper
may be in the range from about 0.1 to about 10 ppm, and in one
embodiment in the range from about 0.1 to about 5 ppm, and in one
embodiment in the range from about 0.1 to about 2 ppm.
The Lubricating Oil Composition.
[0024] The lubricating oil composition may comprise of one or more
base oils which may be present in a major amount. The base oil may
be present in an amount greater than about 60% by weight, and in
one embodiment greater than about 70% by weight, and in one
embodiment greater than about 80% by weight, and in one embodiment
greater than about 85% by weight of the lubricating oil
composition. The lubricating oil composition contains at least one
overbased low molecular weight zinc dialkyldithiophosphates. The
lubricating oil composition may contain an alkali or alkaline earth
metal containing detergent, an acylated-nitrogen containing
compound which may function as a dispersant, and/or at least one
boron-containing compound. The lubricating oil composition may
contain one or more other additives known in the art.
[0025] The lubricating oil composition may have a viscosity of up
to about 16.3 mm.sup.2/sec at 100.degree. C., and in one embodiment
in the range from about 5 to about 16.3 mm.sup.2/sec at 100.degree.
C., and in one embodiment in the range from about 6 to about 13
mm.sup.2/sec at 100.degree. C.
[0026] The lubricating oil composition may have an SAE Viscosity
Grade of 0W, 0W-20, 0W-30, 0W-40, 0W-50, 0-60, 5W, 5W-20, 5W-30,
5W-40, 5W-50, 5W-60, 10W, 10W-20, 10W-30, 10W-40, 10W-50, 15W-40,
15W-50, 20W or 30W.
[0027] The lubricating oil composition may be characterized by a
sulfur content of up to about 1% by weight, and in one embodiment
up to about 0.5% by weight, and in one embodiment in the range from
about 0.01% to about 1% by weight, and in one embodiment in the
range from about 0.01% to about 0.5% by weight.
[0028] The lubricating oil composition may be characterized by a
phosphorus content of up to about 0.12%, and in one embodiment up
to about 0.10%, and in one embodiment up to about 0.08%, and in one
embodiment up to about 0.05% by weight, and in one embodiment in
the range from about 0.01 to about 0.12%, and in one embodiment in
the range from about 0.01 to about 0.10%, and in one embodiment in
the range from about 0.01 to about 0.08%, and in one embodiment in
the range from about 0.01 to about 0.06%, and in one embodiment in
the range form about 0.02 to about 0.12%, and in one embodiment in
the range from about 0.02 to about 0.10%, and in one embodiment in
the range from about 0.02 to about 0.08%, and in one embodiment in
the range from about 0.02 to about 0.06%, and in one embodiment in
the range from about 0.03 to about 0.12% by weight, and in one
embodiment in the range from about 0.03 to about 0.10% by weight,
and in one embodiment in the range from about 0.03 to about 0.08%
by weight, and in one embodiment in the range from about 0.03 to
about 0.06% by weight, and in one embodiment in the range from
about 0.03% to about 0.05% by weight.
[0029] The lubricating oil composition may have a boron content in
the range up to about 0.2% by weight, and in one embodiment in the
range from about 0.01 to about 0.2% by weight, and in one
embodiment in the range from about 0.02 to about 0.12% by weight,
and in one embodiment in the range from about 0.05 to about 0.1% by
weight.
[0030] The ash content of the lubricating oil composition as
determined by the procedures in ASTM D-874-96 may be in the range
from about 0.3 to about 1.4% by weight, and in one embodiment in
the range from about 0.3 to about 1.2% by weight, and in one
embodiment in the range from about 0.3 to about 1.0% by weight.
[0031] The lubricating oil composition may be characterized by a
chlorine content of up to about 100 ppm, and in one embodiment up
to about 50 ppm, and in one embodiment up to about 10 ppm.
The Base Oil
[0032] The base oil used in the lubricating oil composition may
comprise any of the base oils in Groups I-V as specified in the
American Petroleum Institute (API) Base Oil Interchangeability
Guidelines. The five base oil groups are as follows:
TABLE-US-00001 Base Oil Viscosity Category Sulfur (%) Saturates (%)
Index Group I .sup. >0.03 and/or <90 80 to 120 Group II
.ltoreq.0.03 and .gtoreq.90 80 to 120 Group III .ltoreq.0.03 and
.gtoreq.90 .gtoreq.120 Group IV All polyalphaolefins (PAOs) Group V
All others not included in Groups I, II, III or IV
Groups I, II and III are mineral oil base stocks.
[0033] The base oil may be a natural oil, synthetic oil or mixture
thereof. The natural oils include animal oils and vegetable oils
(e.g., castor oil, lard oil) as well as mineral lubricating oils
such as liquid petroleum oils and solvent treated or acid-treated
mineral lubricating oils of the paraffinic, naphthenic or mixed
paraffinic-naphthenic types. Oils derived from coal or shale are
also useful.
[0034] Synthetic oils may include hydrocarbon oils such as
polymerized and interpolymerized olefins, alkylbenzenes,
polyphenyls, alkylated diphenyl ethers, alkylated diphenyl
sulfides, and derivatives, analogs and homologs thereof. The
synthetic oils include alkylene oxide polymers and interpolymers
and derivatives thereof where the terminal hydroxyl groups have
been modified by esterification, etherification, etc.; esters of
dicarboxylic acids (e.g., phthalic acid, succinic acid, alkyl
succinic acids, alkenyl succinic acids, etc.) with a variety of
alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol,
2-ethylhexyl alcohol, ethylene glycol, etc.); and esters made from
C.sub.5 to C.sub.12 monocarboxylic acids and polyols or polyol
ethers.
[0035] In one embodiment, the base oil may comprise a
polyalphaolefin (PAO), an oil derived from Fischer-Tropsch
synthesized hydrocarbons, or an hydroisomerized Fischer-Tropsch
hydrocarbon oil or wax. In one embodiment, Group II or Group III
oils, or mixtures thereof may be used. In one embodiment, mixtures
of Group III and Group IV oils may be used.
[0036] Unrefined, refined and rerefined oils, either natural or
synthetic (as well as mixtures of two or more of any of these) of
the type disclosed hereinabove may be used as the base oil.
The Overbased Low Molecular Weight Zinc Dialkyldithiophosphate
[0037] The overbased low molecular weight zinc
dialkyldithiophosphate may be derived from one or more
dithiophosphoric acids represented by the formula
##STR00004##
and/or metal salt thereof wherein in Formula (I): R.sup.1 and
R.sup.2 are independently hydrocarbyl groups. The average total
number of carbon atoms in R.sup.1 and R.sup.2 in Formula I may be
up to 10, and in one embodiment in the range from 4 to 10, and in
one embodiment in the range from about 5 to 10, and in one
embodiment in the range from about 6 to 10, and in one embodiment
about 8. R.sup.1 and R.sup.2 may be independently hydrocarbyl
groups of about 2 to about 8 carbon atoms, and in one embodiment 2
to about 7 carbon atoms, and in one embodiment about 2 to about 6
carbon atoms, and in one embodiment about 2 to about 5 carbon
atoms, and in one embodiment about 4 carbon atoms. In one
embodiment, from about 5 to about 70 mole % of the alkyl groups may
be C.sub.3 alkyl groups, and from about 70 to about 95 mole % of
the groups may comprise one or more alkyl groups of from 2 to about
7 carbon atoms, and in one embodiment from about 2 to about 6
carbon atoms.
[0038] R.sup.1 and R.sup.2 may be independently alkyl groups,
alkenyl groups, or mixtures thereof. R.sup.1 and R.sup.2 may be
derived from one or more primary alcohols, one or more secondary
alcohols, or a mixture of at least one primary alcohol and at least
one secondary alcohol. Examples of R.sup.1 and R.sup.2 may include
ethyl, isopropyl, butyl, isobutyl, pentyl, 1,3 dimethyl-butyl,
isooctyl, and the like. In one embodiment, the low molecular weight
dialkyldithiophosphoric acid may be derived from a C.sub.4
alcohol.
[0039] The metal ratio of the overbased low molecular weight zinc
dialkyldithiophosphate may be at least about 1.15:1, and in one
embodiment in the range from about 1.15:1 to about 1.5:1, and in
one embodiment in the range from about 1.2:1 to about 1.4:1. A
metal ratio in the range from 1:1 to 1.07:1 or a Zn/P wt ratio of
up to about 1.12 may be referred to as being neutral or
substantially neutral.
[0040] The overbased low molecular zinc dialkyldithiophosphate may
be employed in the lubricating oil composition at a concentration
sufficient to provide the lubricating oil composition with a
phosphorus concentration in the range up to about 0.12% by weight,
and in one embodiment in the range from about 0.03 to about 0.12%
percent by weight, and in one embodiment in the range from about
0.03% to about 0.10% by weight, and in one embodiment in the range
from about 0.03 to about 0.08% by weight, and in one embodiment in
the range from about 0.03 to about 0.05% by weight.
The Acylated Nitrogen Containing Compound
[0041] The acylated nitrogen containing compound may contain a
substituent comprising at least about 30 aliphatic carbon atoms and
may be made by reacting at least one carboxylic acid acylating
agent with at least one amino compound. The acylating agent may be
linked to the amino compound through an imido, amido, amidine or
salt linkage. The substituent comprising at least about 30
aliphatic carbon atoms may be in either the carboxylic acid
acylating agent derived portion of the molecule or in the amino
compound derived portion of the molecule.
[0042] These substituents may be hydrocarbyl groups made from homo-
or interpolymers (e.g., copolymers, terpolymers) of mono- or
di-olefins having 2 to about 10 carbon atoms, such as ethylene,
propylene, 1-butene, isobutene, butadiene, isoprene, 1-hexene,
1-octene, etc. Typically, these olefins are 1-monoolefins. The
substituent may also be derived from the halogenated (e.g.,
chlorinated or brominated) analogs of such homo- or
interpolymers.
[0043] A useful source for the substituent groups may comprise
poly(isobutene)s obtained by the polymerization of a C.sub.4
refinery stream having a butene content of about 35 to about 75
weight percent and an isobutene content of about 30 to about 60
weight percent in the presence of a Lewis acid catalyst such as
aluminum trichloride or boron trifluoride. These polybutenes may
contain predominantly isobutene repeating units.
[0044] The substituent may comprise a polyisobutene group derived
from a polyisobutene having a high methylvinylidene isomer content,
that is, at least about 50% methylvinylidene, and in one embodiment
at least about 70% methylvinylidene. These high methylvinylidene
polyisobutenes may include those prepared using boron trifluoride
catalysts.
[0045] The number average molecular weight of the acylating agent
may vary from about 300 up to about 5,000, 10,000 or 20,000. In one
embodiment, the acylating agent may be a hydrocarbyl substituted
succinic acid or anhydride containing hydrocarbyl substituent
groups and succinic groups wherein the substituent groups are
derived from a polyalkene such as polyisobutene. The acid or
anhydride may be characterized by the presence within its structure
of an average of at least about 1 succinic group for each
equivalent weight of substituent groups, and in one embodiment from
about 1 to about 2.5 succinic groups for each equivalent weight of
substituent groups. The polyalkene may have number average
molecular weight ( M.sub.n) of at least about 700, and in one
embodiment about 700 to about 3000, and in one embodiment about 900
to about 2200. The ratio between the weight average molecular
weight ( Mw) and the ( Mn) (that is, Mw/ Mn) may range from about 1
to about 10, and in one embodiment about 1.5 to about 5, and in one
embodiment about 2.5 to about 5. The number of equivalent weights
of substituent groups may be deemed to be the number corresponding
to the quotient obtained by dividing the Mn value of the polyalkene
from which the substituent is derived into the total weight of the
substituent groups present in the substituted succinic acid or
anhydride.
[0046] The amino compound may be characterized by the presence
within its structure of at least one HN<group and may be a
monoamine or polyamine. Mixtures of two or more amino compounds may
be used in the reaction with one or more acylating reagents. In one
embodiment, the amino compound may contain at least one primary
amino group (i.e., --NH.sub.2). In one embodiment, the amine may be
a polyamine, for example, a polyamine containing at least two
--NH-- groups, either or both of which are primary or secondary
amines. The amines may be aliphatic, cycloaliphatic, aromatic or
heterocyclic amines. Hydroxy substituted amines, such as alkanol
amines (e.g., mono- or diethanol amine), and hydroxy
(polyhydrocarbyloxy) anologs of such alkanol amines may be
used.
[0047] Among the useful amines are the alkylene polyamines,
including the polyalkylene polyamines. The alkylene polyamines may
include those represented by the formula
##STR00005##
wherein in Formula (II), n is from 1 to about 14; each R is
independently a hydrogen atom, a hydrocarbyl group or a
hydroxy-substituted or amine-substituted hydrocarbyl group having
up to about 30 atoms, or two R groups on different nitrogen atoms
can be joined together to form a U group, with the proviso that at
least one R group is a hydrogen atom and U is an alkylene group of
about 2 to about 10 carbon atoms. U may be ethylene or propylene.
Alkylene polyamines where each R is hydrogen or an
amino-substituted hydrocarbyl group with the ethylene polyamines
and mixtures of ethylene polyamines are useful. Usually n will have
an average value of from about 2 to about 10. Such alkylene
polyamines include methylene polyamines, ethylene polyamines,
propylene polyamines, butylene polyamines, pentylene polyamines,
hexylene polyamines, heptylene polyamines, amino propylated
ethylene polyamines, etc. The higher homologs of such amines and
related amino alkyl-substituted piperazines may be included.
[0048] Alkylene polyamines that may be useful may include ethylene
diamine, diethylene triamine, triethylene tetramine, tetraethylene
pentamine, pentaethylene hexamine, propylene diamine, trimethylene
diamine, hexamethylene diamine, decamethylene diamine,
octamethylene diamine, di(heptamethylene) triamine, tripropylene
tetramine, trimethylene diamine, di(trimethylene)triamine,
N-(2-amino-ethyl)piperazine, 1,4-bis(2-aminoethyl)piperazine, and
the like. Higher homologs such as those obtained by condensing two
or more of the above-illustrated alkylene amines may be used.
Mixtures of two or more of any of the afore-described polyamines
may be used.
[0049] Useful polyamines may include those resulting from stripping
polyamine mixtures. In this instance, lower molecular weight
polyamines and volatile contaminants are removed from an alkylene
polyamine mixture to leave as residue what is often termed
"polyamine bottoms". In general, alkylene polyamine bottoms can be
characterized as having less than about 2% by weight, and in one
embodiment less than about 1% by weight material boiling below
about 200.degree. C.
[0050] The acylated nitrogen containing compounds may include amine
salts, amides, imides, amidines, amidic acids, amidic salts and
imidazolines as well as mixtures thereof. To prepare the acylated
nitrogen-containing compounds from the acylating agents and the
amino compounds, one or more acylating reagents and one or more
amino compounds may be heated, optionally in the presence of a
normally liquid, substantially inert organic liquid
solvent/diluent, at temperatures in the range of 80.degree. C. up
to the decomposition point of any of the reactants or the product
but normally at temperatures in the range of about 100.degree. C.
to about 300.degree. C., provided 300.degree. C. does not exceed
the decomposition point of any of the reactants or the product.
Temperatures of about 125.degree. C. to about 250.degree. C. may be
used. The acylating agent and the amino compound may be reacted in
amounts sufficient to provide from about 0.5 to about 3 moles of
amino compound per equivalent of acylating agent. The number of
equivalents of the acylating agent may vary with the number of
carboxy groups present therein. In determining the number of
equivalents of the acylating agent, those carboxyl functions which
are not capable of reacting as a carboxylic acid acylating agent
are excluded. In general, however, there is one equivalent of
acylating agent for each carboxy group in the acylating agent.
[0051] The use of acylated nitrogen containing compounds with
relatively high TBNs in the lubricating oil composition may tend to
reduce the volatility of the phosphorus in the overbased low
molecular weight zinc dialkyldithiophosphate. Accordingly, in one
embodiment, the acylated nitrogen containing compound may have a
TBN (on an oil-free basis) of at least about 2, and in one
embodiment in the range from about 2 to about 60, and in one
embodiment in the range from about 5 to about 30, and in one
embodiment in the range from about 10 to about 20.
[0052] The acylated nitrogen containing compound may be employed in
the lubricating oil composition at a concentration in the range
from about 1% to about 20% by weight, and in one embodiment in the
range from about 1% to about 10% percent by weight, and in one
embodiment in the range from about 1% to about 5% by weight.
The Alkali or Alkaline Earth Metal Containing Detergent
[0053] The alkali metal or alkaline earth metal containing
detergent may be an alkali or alkaline earth metal salt of an
acidic organic compound. The acidic organic compound may be an
organic sulfur acid, phenol, carboxylic acid or derivative thereof.
The acidic organic compound may be a salixarate. These salts may be
neutral or overbased. The former contain an amount of metal cation
just sufficient to neutralize the acidic groups present in the salt
anion; the latter contain an excess of metal cation and are often
termed basic, overbased, hyperbased or superbased salts. These
salts may have a TBN in the range from about 30 to about 460, and
in one embodiment in the range from about 100 to about 400, and in
one embodiment in the range from about 200 to about 400, and in one
embodiment in the range from about 300 to about 400.
[0054] The organic sulfur acids may be oil-soluble organic sulfur
acids such as sulfonic, sulfamic, thiosulfonic, sulfinic, sulfenic,
partial ester sulfuric, sulfurous and thiosulfuric acid. Generally
they are salts of aliphatic or aromatic sulfonic acids. The
sulfonic acids include the mono- or poly-nuclear aromatic or
cycloaliphatic compounds.
[0055] The carboxylic acids may include aliphatic, cycloaliphatic,
and aromatic mono- and polybasic carboxylic acids such as the
naphthenic acids, alkyl- or alkenyl-substituted cyclopentanoic
acids, alkyl- or alkenyl-substituted cyclohexanoic acids, alkyl- or
alkenyl-substituted aromatic carboxylic acids. The aliphatic acids
may contain at least about 8 carbon atoms, and in one embodiment at
least about 12 carbon atoms. Usually they have no more than about
400 carbon atoms. The cycloaliphatic and aliphatic carboxylic acids
may be saturated or unsaturated.
[0056] A useful group of carboxylic acids may be the oil-soluble
aromatic carboxylic acids. These acids may be represented by the
formula:
(R*).sub.a--Ar*(CXXH).sub.m (III)
wherein in Formula (III), R* is an aliphatic hydrocarbyl group of
about 4 to about 400 carbon atoms, a is an integer of from one to
four, Ar* is a polyvalent aromatic hydrocarbon nucleus of up to
about 14 carbon atoms, each X is independently a sulfur or oxygen
atom, and m is an integer of from one to four with the proviso that
R* and a are such that there is an average of at least about 8
aliphatic carbon atoms provided by the R* groups for each acid
molecule.
[0057] A useful group of carboxylic acids may be the
aliphatic-hydrocarbon substituted salicylic acids wherein each
aliphatic hydrocarbon substituent contains an average of at least
about 8 carbon atoms, and in one embodiment at least about 16
carbon atoms per substituent, and the acids contain one to three
substituents per molecule. A useful aliphatic-hydrocarbon
substituted salicylic acid is C.sub.16-C.sub.18 alkyl salicylic
acid. A group of carboxylic acid derivatives that are useful are
the lactones represented by the formula
##STR00006##
wherein in Formula (IV), R.sup.1, R.sup.2, R.sup.3, R.sup.4,
R.sup.5 and R.sup.6 are independently H, hydrocarbyl groups or
hydroxy substituted hydrocarbyl groups of from 1 to about 30 carbon
atoms, with the proviso that the total number of carbon atoms must
be sufficient to render the lactones oil soluble; R.sup.2 and
R.sup.3 can be linked together to form an aliphatic or aromatic
ring; and a is a number in the range of zero to 4. A useful lactone
can be prepared by reacting an alkyl (e.g., dodecyl)phenol with
glyoxylic acid at a molar ratio of about 2:1.
[0058] Neutral and basic salts of phenols (generally known as
phenates) are also useful in the compositions of this invention and
well known to those skilled in the art. The phenols from which
these phenates are formed are of the general formula
(R*).sub.a--(Ar*)-(OH).sub.m (V)
wherein in Formula (V), R*, a, Ar*, and m have the same meaning as
described hereinabove with reference to Formula (III).
[0059] The salixarate may be a substantially linear compound
comprising at least one unit of formula (VI) or formula (VII):
##STR00007##
each end of the compound having a terminal group of formula (VIII)
or formula (IX):
##STR00008##
such groups being linked by divalent bridging groups A, which may
be the same or different for each linkage; wherein in formulas
(VI)-(X) R.sup.3 is hydrogen or a hydrocarbyl group; R.sup.2 is
hydroxyl or a hydrocarbyl group and j is 0, 1, or 2; R.sup.6 is
hydrogen, a hydrocarbyl group, or a hetero-substituted hydrocarbyl
group; either R.sup.4 is hydroxyl and R.sup.5 and R.sup.7 are
independently either hydrogen, a hydrocarbyl group, or
hetero-substituted hydrocarbyl group, or else R.sup.5 and R.sup.7
are both hydroxyl and R.sup.4 is hydrogen, a hydrocarbyl group, or
a hetero-substituted hydrocarbyl group; provided that at least one
of R.sup.4, R.sup.5, R.sup.6 and R.sup.7 is hydrocarbyl containing
at least 8 carbon atoms; and wherein the molecules on average
contain at least one of unit (VI) or (VIII) and at least one of
unit (VII) or (IX) and the ratio of the total number of units (VI)
and (VIII) to the total number of units of (VII) and (IX) in the
composition is about 0.1:1 to about 2:1.
[0060] The divalent bridging group "A," which may be the same or
different in each occurrence, includes --CH.sub.2-- (methylene
bridge) and --CH.sub.2OCH.sub.2-- (ether bridge), either of which
may be derived from formaldehyde or a formaldehyde equivalent
(e.g., paraform, formalin).
[0061] Salixarate derivatives and methods of their preparation are
described in greater detail in U.S. Pat. No. 6,200,936 and PCT
Publication WO 01/56968. It is believed that the salixarate
derivatives have a predominantly linear, rather than macrocyclic,
structure, although both structures are intended to be encompassed
by the term "salixarate."
[0062] Mixtures of two or more neutral or basic metal salts of the
hereinabove described acidic organic compounds may be used in the
lubricating oil compositions.
[0063] The alkali and alkaline earth metals that may be useful may
include sodium, potassium, lithium, calcium, magnesium, strontium
and barium. Sodium, lithium and calcium may be especially
useful.
[0064] The use of sodium in the lubricating oil composition may
tend to decrease the volatility of the phosphorus used therein
significantly. Accordingly, in one embodiment of the invention, the
use of sodium as the detergent metal may be particularly
useful.
[0065] The alkali or alkaline earth metal containing detergent may
be employed in the lubricating oil composition at a concentration
in the range from about 0.1 to about 10% by weight, and in one
embodiment in the range from about 0.2 to about 5% percent by
weight, and in one embodiment in the range from about 0.3% to about
3% by weight, and in one embodiment in the range from about 0.5 to
about 2% by weight.
The Boron-Containing Compound
[0066] The boron-containing compound may be is a compound
represented by one or more of the formulae
##STR00009##
wherein in Formulae XI-XIII, each R may be independently an organic
group and any two adjacent R groups may together form a cyclic
group. Mixtures of two or more of the foregoing may be used. In one
embodiment, each R may be independently a hydrocarbyl group. The
total number of carbon atoms in the R groups in each formula may be
sufficient to render the compound soluble in the base oil.
Generally, the total number of carbon atoms in the R groups may be
at least about 8, and in one embodiment at least about 10, and in
one embodiment at least about 12. There may be no limit to the
total number of carbon atoms in the R groups that is required, but
a practical upper limit may be about 400 or about 500 carbon atoms.
In one embodiment, each R group may be independently a hydrocarbyl
group of 1 to about 100 carbon atoms, and in one embodiment 1 to
about 50 carbon atoms, and in one embodiment 1 to about 30 carbon
atoms, and in one embodiment 1 to about 10 carbon atoms, with the
proviso that the total number of carbons in the R group may be at
least about 8. Each R group may be the same as the other, although
they may be different. Examples of useful R groups may include
isopropyl, n-butyl, isobutyl, amyl, 1,3 dimethyl-butyl,
2-ethyl-1-hexyl, isooctyl, decyl, dodecyl, tetradecyl, 2-pentenyl,
dodecenyl, phenyl, naphthyl, alkylphenyl, alkylnaphthyl,
phenylalkyl, naphthylalkyl, alkylphenylalkyl, alkylnaphthylalkyl,
and the like.
[0067] In one embodiment, the boron-containing compound may be a
compound represented by the formula
##STR00010##
wherein in Formula (XIV): R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are
independently hydrocarbyl groups of 1 to about 12 carbon atoms; and
R.sup.5 and R.sup.6 are independently alkylene groups of 1 to about
6 carbon atoms, and in one embodiment about 2 to about 4 carbon
atoms, and in one embodiment about 2 or about 3 carbon atoms. In
one embodiment, R.sup.1 and R.sup.2 may independently contain 1 to
about 6 carbon atoms, and in one embodiment each may be a t-butyl
group. In one embodiment, R.sup.3 and R.sup.4 are independently
hydrocarbyl groups of about 2 to about 12 carbon atoms, and in one
embodiment about 8 to about 10 carbon atoms. In one embodiment,
R.sup.5 and R.sup.6 are independently --CH.sub.2CH.sub.2-- or
--CH.sub.2CH.sub.2CH.sub.2--.
[0068] In one embodiment, the boron-containing compound may be a
compound represented by the formula:
##STR00011##
wherein in Formula (XV): R.sup.1, R.sup.2, R.sup.3, R.sup.4,
R.sup.5, R.sup.6, R.sup.7 and R.sup.8 are independently hydrogen or
hydrocarbyl groups. Each of the hydrocarbyl groups may contain from
1 to about 12 carbon atoms, and in one embodiment 1 to about 4
carbon atoms. An example is
2,2'-oxy-bis-(4,4,6-trimethyl-1,3,2-dioxaborinane).
[0069] A useful boron-containing compound may be available from
Crompton Corporation under the trade designation LA-2607. This
material may be identified as a phenolic borate having the
structure represented by Formula (XIV) wherein R.sup.1 and R.sup.2
are each t-butyl, R.sup.3 and R.sup.4 are hydrocarbyl groups of 2
to about 12 carbon atoms, R.sup.5 is --CH.sub.2CH.sub.2--, and
R.sup.6 is --CH.sub.2CH.sub.2CH.sub.2--.
[0070] In one embodiment, the boron-containing compound may be a
compound represented by the formula B(OC.sub.5H.sub.11) or
B(OC.sub.4H.sub.9).sub.3. A useful boron-containing compound may be
available from Mobil under the trade designation MCP-1286; this
material may be identified as a borated ester.
[0071] The boron-containing compound may be employed in the
lubricating oil composition at a sufficient concentration to
provide the lubricating oil composition with a boron concentration
in the range up to about 0.2% by weight, and in one embodiment in
the range from about 0.01% to about 0.2% by weight, and in one
embodiment in the range from about 0.02% to about 0.12% by weight,
and in one embodiment in the range from about 0.05% to about 0.1%
by weight. These compounds may be added directly to the lubricating
oil composition. In one embodiment, however, they may be diluted
with a substantially inert, normally liquid organic diluent such as
mineral oil, synthetic oil (e.g., ester of dicarboxylic acid),
naptha, alkylated (e.g. C.sub.10-C.sub.13 alkyl)benzene, toluene or
xylene to form an additive concentrate. These concentrates may
contain from about 1% to about 99% by weight, and in one embodiment
about 10% to about 90% by weight of the diluent.
Additional Lubricating Oil Additives
[0072] The lubricating oil composition may also contain other
lubricant additives. These may include, for example,
corrosion-inhibiting agents, antioxidants, viscosity modifiers,
dispersant viscosity index modifiers, pour point depressants,
friction modifiers, antiwear agents other than those discussed
above, EP agents other than those discussed above, dispersants
other than those discussed above, detergents other than those
discussed above, fluidity modifiers, copper passivators, anti-foam
agents, etc. Each of the foregoing additives, when used, may be
used at a functionally effective amount to impart the desired
properties to the lubricant. Generally, the concentration of each
of these additives, when used, may be in the range from about
0.001% to about 20% by weight, and in one embodiment in the range
from about 0.01% to about 10% by weight based on the total weight
of the lubricating oil composition.
Concentrates and Diluents
[0073] The foregoing lubricating oil additives may be added
directly to the base oil to form the lubricating oil composition.
In one embodiment, however, one or more of the additives may be
diluted with a substantially inert, normally liquid organic diluent
such as mineral oil, synthetic oil, naphtha, alkylated (e.g.,
C.sub.10-C.sub.13 alkyl)benzene, toluene or xylene to form an
additive concentrate. These concentrates may contain from about 1%
to about 99% by weight, and in one embodiment from about 10% to 90%
by weight of such diluent. The concentrates may be added to the
base oil to form the lubricating oil composition.
The Method of Lubricating the Engine and Improving Efficiency of
the Emissions Control System
[0074] The disclosed method may provide for lubricating an internal
combustion engine and improving the efficiency of the emissions
control system of the engine wherein the emissions control system
is equipped with a catalyst-containing exhaust gas after treatment
device used with the engine. The lubricating oil composition may
generate a lean-phosphorus containing exhaust gas during operation
of the engine. The lean-phosphorus containing exhaust gas may be
advanced to the exhaust gas after treatment device. In the exhaust
gas after treatment device the lean-phosphorus containing exhaust
gas may contact the catalyst. The phosphorus in the lean-phosphorus
containing exhaust gas may contaminate the catalyst and thereby
reduce its efficiency. However, since the level of phosphorus in
the lean-phosphorus containing exhaust gas may be at a reduced
level, the amount of contamination of the catalyst may be reduced.
This reduction in contamination may result in an improvement in the
efficiency of the exhaust gas after treatment device.
[0075] The generation of a lean-phosphorus containing exhaust gas
may be dependent on the use of the lubricating oil composition. The
use of the overbased low molecular weight dialkyldithiophosphate in
the lubricating oil composition may provide for low-phosphorus
volatility when the lubricating oil composition is used to
lubricate an internal combustion engine. As indicated above, the
lubricating oil composition may also contain one or more alkali or
alkaline earth metal containing detergents, one or more
acylated-nitrogen containing compounds, and/or one or more boron
containing compounds. The combination of these additives with the
overbased low molecular weight dialkyldithiophosphate may
contribute to reducing the volatility of the overbased low
molecular weight zinc dialkyldithiophosphate. Additional optional
nitrogen-containing compounds (e.g., antioxidants) when present may
further contribute to this effect. This reduction in phosphorus
volatility may provide for the generation of a lean-phosphorus
containing exhaust gas. In one embodiment, the weight ratio of
detergent metal to phosphorus in the lubricating oil composition at
the time the lubricating oil composition may be added to the engine
may be in the range from about 0.5:1 to about 10:1, and in one
embodiment in the range from about 2:1 to about 4:1, and in one
embodiment in the range from about 2.5:1 to about 3:1. In one
embodiment, the weight ratio of basic (titratable) nitrogen to
phosphorus in the lubricating oil composition at the time the
lubricating oil composition may be added to the engine may be in
the range from about 0.3:1 to about 4:1, and in one embodiment
about 0.5:1 to about 2:1, and in one embodiment in the range from
about 1:1 to about 1.5:1.
[0076] The amount of phosphorus in the exhaust gas during the
operation of the engine may be indirectly proportional to the
amount of phosphorus retained in the lubricating oil composition in
the crankcase. The amount of phosphorus retained in the crankcase
may be calculated from the following formula:
% P retention = ( % wt P drain ) ( % wt M new ) ( % wt P new ) ( %
wt M drain ) .times. 100 ##EQU00001##
wherein: % wt P.sub.drain is the percent by weight of phosphorus in
the lubricating oil composition in the crankcase at the end of a
drain interval; % wt M.sub.new is the percent by weight of
detergent metal in the lubricating oil composition in the crankcase
at the beginning of the drain interval; % wt P.sub.new is the
percent by weight of phosphorus in the lubricating oil composition
in the crankcase at the beginning of the drain interval; and %
M.sub.drain is the percent by weight of detergent metal in the
lubricating oil composition at the end of the drain interval. The
amount of phosphorus retained in the crankcase oil of the engine
after a 12000 kilometer (7500 mile) drain cycle may be at least
about 80% by weight, and in one embodiment at least about 84% by
weight, and in one embodiment at least about 88% by weight, and in
one embodiment at least about 92% by weight, and in one embodiment
at least about 95% by weight, and in one embodiment at least about
98% by weight. The amount of phosphorus lost from the crankcase oil
with the exhaust gas over a 7500 mile (12000 kilometer) drain cycle
may be about 20% by weight or less, and in one embodiment about 16%
by weight or less, and in one embodiment about 12% by weight or
less, and in one embodiment about 8% by weight or less, and in one
embodiment about 5% by weight or less, and in one embodiment about
2% by weight or less.
[0077] Copper in the lubricating oil composition may increase the
volatility of the phosphorus used therein. Accordingly, at the time
of its addition to the engine, the lubricating oil composition may
be characterized by the substantial absence of copper.
[0078] The internal combustion engine may be any internal
combustion engine that is equipped with exhaust gas after treatment
device that utilizes a catalyst. These may include engines that
employ a closed crankcase system and positive crankcase
ventilation. The internal combustion engine may be a spark-ignited
or a compression-ignited engine. These engines may include
automobile and truck engines, two-cycle engines, aviation piston
engines, marine and railroad diesel engines, and the like. These
may include on- and off-highway engines. The compression-ignited
engines may include those for both mobile and stationary power
plants. The compression-ignited engines may include those used in
urban buses, as well as all classes of trucks. The
compression-ignited engines may be of the two-stroke per cycle or
four-stroke per cycle type. The compression-ignited engines may
include heavy duty diesel engines.
[0079] The exhaust gas after treatment device may be referred to as
a catalytic converter and may be of any conventional design. The
exhaust gas after treatment device may comprise flow-through
passages of ceramic or metal coated with a washcoat comprising
zeolite, Al.sub.2O.sub.3, SiO.sub.2, TiO.sub.2, CeO.sub.2,
ZrO.sub.2, V.sub.2O.sub.5, La.sub.2O.sub.3, or mixtures of two or
more thereof. The washcoat may support a catalyst comprising Pt,
Pd, Rh, Ir, Ru, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ag, Ce, Ga, or a
mixture of two or more thereof.
EXAMPLES
[0080] Engine tests are conducted using a 1997 GM 5.2 L V-8 DOHC
equipped with a roller-follower valve train. The test duration is
25 hours. The engine conditions are: 2640 rpm; 29.8 kilowatt load
(calculated); 210.degree. F. (98.9.degree. C.) oil temperature; and
180.degree. F. (82.2.degree. C.) coolant temperature. The exhaust
gas is analyzed for volatile phosphorus compounds. Elemental
analysis (by ICP) and phosphorus NMR are used. The lubricating oil
compositions used in the tests are provided in Table I. In Table I,
unless otherwise indicated, all numerical values are in parts by
weight.
TABLE-US-00002 TABLE I Ingredient Parts by Wt Base Oil: Group II,
to make 5W-30 oil 100 Viscosity Modifier: LZ7070D available from
6.5 Lubrizol identified as olefin copolymer dispersed in oil (91%
diluent oil) Pour point depressant: esterified styrene- 0.3 maleic
anhydride copolymer dispersed in oil (53.6% diluent oil) Ashless
organic friction modifier 0.5 Dispersant: succinimide derived from
5.1 polyisobutene (Mn = 2000) substituted succinic anhydride and
polyethylene amines dispersed in oil, TBN = 16 (56% diluent oil)
Antioxidant: nonylated diphenylamine 0.7 Antioxidant: sulfurized
olefin containing 0.2 13.9% sulfur dispersed with oil (5% diluent
oil) Hindered phenolic ester antioxidant 0.2 Detergent: calcium
sulfonate dispersed in oil, 0.88 TBN = 300 (42% diluent oil)
Detergent: calcium sulfonate dispersed in oil, 0.65 TBN = 400 (42%
diluent oil) ZDDPs described in Table II (% P) 0.075
[0081] The results of these engine tests are provided in Table II.
In Table II, the term "Blow-by Phosphorus" refers to phosphorus in
the engine exhaust that contacts the catalyst in the engine's
emission control system. These results indicate a significant
reduction in phosphorus volatility when overbased low molecular
weight ZDDPs are used (Examples 1 and 2) as compared to a
substantially neutral low molecular weight ZDDP (Example C-1), a
substantially neutral high molecular weight ZDDP (Example C-2) and
overbased high molecular weight ZDDP (Example C-3).
TABLE-US-00003 TABLE II Blow-By Example ZDDP Description Phosphorus
1 ZDDP derived from C.sub.4.2 avg ROH with 418 Zn:P wt ratio of =
1.16:1 2 ZDDP derived from C.sub.4.2 avg ROH with 412 Zn:P wt ratio
= = 1.32:1 C-1 ZDDP derived from C.sub.4.2 avg ROH with 481 wt Zn:P
ratio = 1.11:1 C-2 ZDDP derived from C.sub.8 ROH with Zn:P 348 wt
ratio = 1.11:1 C-3 ZDDP derived from C.sub.8 ROH with Zn:P 354 wt
ratio >1.2:1
[0082] The results of Examples 1 and 2 are almost as good as
Examples C-2 and C-3 in terms of blow-by phosphorus, in spite of
their lower molecular weight substituents. The lower molecular
weight substituents are believed to provide improved wear
protection as compared with the longer chain materials of Examples
C-2 and C-3.
[0083] While the disclosed technology has been explained in
relation to various embodiments, it is to be understood that
various modifications thereof may become apparent to those skilled
in the art upon reading the specification. Therefore, it is to be
understood that the invention disclosed herein is intended to cover
such modifications as fall within the scope of the appended
claims.
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