U.S. patent application number 10/683651 was filed with the patent office on 2004-06-10 for long life lubricating oil with enhanced oxidation and nitration resistance.
Invention is credited to Cartwright, Stanley James.
Application Number | 20040110646 10/683651 |
Document ID | / |
Family ID | 32469231 |
Filed Date | 2004-06-10 |
United States Patent
Application |
20040110646 |
Kind Code |
A1 |
Cartwright, Stanley James |
June 10, 2004 |
Long life lubricating oil with enhanced oxidation and nitration
resistance
Abstract
A long life lubricating oil, as evidenced by a reduction in oil
thickening, oxidation and nitration, comprises a major amount of a
base oil of lubricating viscosity and a minor amount of a mixture
of neutral and overbased metallic detergents and at least one
trinuclear molybdenum compound.
Inventors: |
Cartwright, Stanley James;
(Sarnia, CA) |
Correspondence
Address: |
ExxonMobil Research and Engineering Company
P.O. Box 900
Annandale
NJ
08801-0900
US
|
Family ID: |
32469231 |
Appl. No.: |
10/683651 |
Filed: |
October 10, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60419745 |
Oct 18, 2002 |
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Current U.S.
Class: |
508/364 ;
508/363; 508/391; 508/443; 508/444; 508/460 |
Current CPC
Class: |
C10N 2030/10 20130101;
C10M 163/00 20130101; C10N 2010/02 20130101; C10M 2207/027
20130101; C10M 2219/066 20130101; C10N 2030/02 20130101; C10N
2040/12 20130101; C10M 2219/046 20130101; C10N 2030/52 20200501;
C10M 2207/262 20130101; C10M 2207/028 20130101; C10N 2010/12
20130101; C10M 2227/09 20130101; C10N 2010/04 20130101; C10M
2219/044 20130101; C10M 2207/144 20130101 |
Class at
Publication: |
508/364 ;
508/363; 508/444; 508/443; 508/391; 508/460 |
International
Class: |
C10M 159/20 |
Claims
What is claimed is:
1. A lubricating composition comprising: a major amount of an oil
of lubricating viscosity; a mixture of neutral and overbased
metallic detergents; and a minor amount of at least one trinuclear
molybdenum compound.
2. The composition of claim 1 wherein the trinuclear molybdenum
compound is represented by the formula
Mo.sub.3S.sub.kL.sub.nQ.sub.z where L is an independently selected
ligand, n is from 1 to 4, k is from 4 to 7, Q is a neutral electron
donating moiety and z is from 0 to 5.
3. The composition of claim 2 wherein the neutral and overbased
metallic detergents are selected from the group consisting of
alkali and alkaline earth metal sulfonates, phenates,
alkylsalicylates and mixtures thereof.
4. The composition of claim 3 wherein the amount of detergents is
sufficient to provide the composition with a sulfated ash content
in the range of about 0.2 wt % to about 2.0 wt %.
5. The composition of claim 4 wherein the trinuclear molybdenum
compound constitutes from about 0.1 vol % to about 2.0 vol % based
on the volume of the total lubricant composition.
6. The composition of claim 5 including a minor amount of a
dihydrocarbyl thiocarbamoyl compound.
7. The composition of claim 6 wherein the dihydrocarbyl
thiocarbamoyl compound has the formula 2where R.sub.1, R.sub.2,
R.sub.3 and R.sub.4 are the same or different alkyl groups of from
3 to 30 carbon atoms; X is S, S--S, SCH.sub.2.paren
close-st..sub.yS, S--CH.sub.2CH.sub.2(CH.sub.3)-- -S; and y is an
integer of 1 to 3.
8. A lubricating oil composition comprising: a major amount of an
oil of lubricating viscosity; a mixture of neutral and overbased
metallic detergents selected from the group consisting essentially
of alkaline earth metal sulfonates, phenates, alkylsalicylates and
mixtures thereof in an amount sufficient to provide the composition
with a sulfated ash content of from about 0.2 wt % to about 2.0 wt
%; a trinuclear molybdenum compound having the formula
Mo.sub.3S.sub.kL.sub.nQ.sub.z where L is an independently selected
ligand, n is from 1 to 4, k is from 4 to 7, Q is a neutral electron
donating moiety, and z is from 0 to 5; from 0 to 2.0 vol % of a
dihydrocarbyl thiocarbamoyl compound having the formula; 3where
R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are the same or different
alkyl groups of from 3 to 30 carbon atoms; X is S, S--S,
SCH.sub.2.paren close-st..sub.yS, S--CH.sub.2CH.sub.2(CH.sub.3)--S;
and y is an integer of 1 to 3; the amount of trinuclear molybdenum
compound and dihydrocarbyl thiocarbomyl compound being in the range
of about 0.1 vol % to about 2.0 vol %.
9. A method for enhancing the life of a lubricating oil as
evidenced by a reduction in viscosity increase, oxidation and
nitration, the method comprising: adding to the lubricating oil
additives comprising: a mixture of neutral and overbased metallic
detergents selected from the group consisting essentially of
alkaline earth metal sulfonates, phenates, alkylsalicylates, and
mixtures thereof in an amount sufficient to provide the composition
with a sulfated ash content of from about 0.2 wt % to about 2.0 wt
%; at least 0.1 vol % of a trinuclear molybdenum compound having
the formula Mo.sub.3S.sub.kL.sub.nQ.sub.z Where L is an
independently selected ligand, n is 1 to 4, k is 4 to 7, Q is a
neutral electron donating moiety, and z is 0 to 5; a
dihydrocarbylthiocarbomyl compound; the amount of trinuclear
molybdenum compound and dihydrothiocarbomyl compound being in the
range of 0.1 vol % about 2.0 vol %.
10. The method of claim 9 wherein the dihydrothiocarbomyl compound
has the formula 4where R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are
the same or different alkyl groups of from 3 to 30 carbon atoms; X
is S, , S--S, SCH.sub.2.paren close-st..sub.yS,
S--CH.sub.2CH.sub.2(CH.sub.3)--S; and y is an integer of 1 to 3.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] Non-Provisional Application based on Provisional Application
No. 60/419,745 filed Oct. 18, 2002.
[0002] This application claims the benefit of U.S. Provisional
Application No. 60/419,745 filed Oct. 18, 2002.
FIELD OF INVENTION
[0003] The present invention relates to lubricating oils,
especially gas engine oils, having extended life as evidenced by a
reduction in viscosity increase, oxidation and nitration.
BACKGROUND OF INVENTION
[0004] Gas fired engines are typically used in the oil and gas
industry to drive compressors that compress natural gas at well
heads and along pipelines. These engines are large, having up to 16
cylinders and often generate between 500 to 3000 HP. The nature of
their use requires them to be able to run continuously near full
load conditions, shutting down only for maintenance such as for oil
changes. Under these operating conditions severe demands are placed
on the engine lubricant. Indeed, because the lubricant is subjected
to a high temperature environment, the life of the lubricant often
is limited by oil oxidation processes. Additionally, natural gas
fired engines generate nitrogen oxides (NO.sub.X) that can limit
lubricant life by oil nitration processes. Therefore, gas engine
operators are constantly seeking gas engine oils that have improved
resistance to oxidation and nitration.
[0005] In addition to controlling oxidation and nitration
properties of a gas engine oil it also is necessary to control the
ash content of the oil because the lubricant ash acts as a solid
lubricant protecting the valve/seat interface of the engine. For
this reason gas engine oils are classified according to their ash
content. The classifications are:
1 Ash Designation Ash Level, wt % (ASTM D874) Ashless Ash < 0.1%
Low Ash 0.1% < Ash < 0.6% Medium Ash 0.6% < Ash < 1.5%
High Ash Ash > 1.5%
[0006] The ash level of the lubricant often is determined by its
formulation components, with metal-containing detergents and
metallic-containing antiwear additives contributing to the ash
level of the lubricant. Gas engine manufacturers specify the
appropriate lubricant ash level for correct operation of a given
engine. Thus, manufacturers of 2-cycle engines often specify use of
an ashless oil. Manufacturers of 4-cycle engine may specify low,
medium or high ash depending upon the level required for engine
cleanliness and durability.
[0007] As is known in the art, additives are used in lubricants to
perform numerous functions. For example, some are antioxidants,
some are friction modifiers; and some are extreme pressure agents.
Indeed some additives perform more than one function. Also as is
known in the art additives will lose their effectiveness if they
are improperly combined. Therefore, extreme care must be exercised
in combining various additives to assure both compatibility and
effectiveness. For example, some friction modifiers affect metal
surfaces differently than antiwear agents do. When both are
present, friction-reducing and antiwear additives may compete for
the surface of the metal parts which are subject to lubrication.
This competition can produce a lubricant that is less effective
than is suggested by the individual properties of the additive
components.
[0008] Accordingly, the components of a gas engine lubricant need
to be selected to meet the specified ash level and to provide,
among other functions, a high level of oxidation and nitration
resistance. Whether selected components and their amounts can be
balanced to meet desired specification is not a priori
predictable.
SUMMARY OF INVENTION
[0009] Simply stated the present invention relates to a lubricating
oil, especially useful as a gas engine oil, comprising a major
amount of a base oil of lubricating viscosity; effective amounts of
a mixture of neutral and overbased metallic detergents; and, a
minor amount of at least one trinuclear molybdenum compound.
[0010] The lubricant composition of the invention has extended life
as evidenced by reductions in oxidation and nitration relative to
commercial and reference oils and may also be compatible with other
standard additives used in formulating commercial lubricating
compositions.
DETAILED DESCRIPTION OF INVENTION
[0011] The lubricant compositions of the present invention include
a major amount of a base oil of lubricating viscosity. Suitable
base oils include natural and synthetic oils and mixtures thereof
in API Categories I, II and III, and having a kinematic viscosity
of about 9 to 13 cSt at 100.degree. C.
[0012] The metallic detergent contained in the composition of the
invention is a mixture of neutral and overbased metal sulfonates,
phenates and alkylsalicylates. The metals may be alkali and
alkaline earth metals and preferably are alkaline earth metals,
especially calcium and barium. Examples of suitable neutral
metallic detergents are calcium sulfonates and calcium
alkylsalicylates having a TBN of from 10 to 100. Examples of
overbased metallic detergents are calcium phenates, sulphonates and
alkylsalicylates having a TBN of 150 to 400. The amount of the
neutral and overbased metallic detergent is chosen having regard to
the desired TBN of the final product and especially having regard
to the desired sulfated ash of the final product. Preferably the
mixture of neutral and overbased metallic detergents is sufficient
to provide the composition with a sulfated ash in the range of
about 0.2 mass % to about 2.0 mass %.
[0013] The compositions of the present invention also include a
minor amount of at least one trinuclear molybdenum compound. A
preferred trinuclear molybdenum compound is represented by the
formula Mo.sub.3S.sub.kL.sub.nQ.sub.z where L represents
independently selected ligands, n varies from 1 to 4, k varies from
4 to 7 and Q is selected from the group consisting of neutral
electron donating compounds including water, amines, alcohols,
phosphines and ethers and z ranges from 0 to 5. Such compounds and
their method of preparation are disclosed in great detail in U.S.
Pat. No. 6,232,276 B1 which is incorporated herein by reference. In
the present invention L preferably is dithiocarbamate, n is 4, k is
7, Q is an electron-donating compound, and z is 0. The trinuclear
molybdenum compound preferably constitutes from 0.1 vol % to about
2.0 vol % based on the total volume of the total lubricant
composition.
[0014] Optionally, the composition may contain an ashless
dihydrocarbyl thiocarbamoyl in combination with the trinuclear
molybdenum compound.
[0015] Suitable dihydrocarbylthiocarbamoyl compounds are
represented by the formula 1
[0016] where R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are the same or
different and each represents an alkyl group of .sub.--3_ to
.sub.--30_ carbon atoms, X represents S, S--S, SCH.sub.2.paren
close-st..sub.yS, S--CH.sub.2CH.sub.2(CH.sub.3)--S and y is an
integer of 1 to 3.
[0017] Preferably the combined materials will constitute from about
0.1 vol % to about 2.0 vol % based on the volume of the total
lubricant composition; however, the amount of dihydrocarbyl
thiocarbamoyl will not exceed about 1.90 vol %.
[0018] The fully formulated oil may contain additional, typical
additives known to those skilled in the industry, used on an
as-received basis.
[0019] Thus, the fully formulated oil may contain dispersants of
the type generally represented by succimides (e.g., polyisobutylene
succinic acid/anhydride (PIBSA)-polyamine having a PIB moiety
molecular weight of about 700 to 2500). The dispersants may be
borated or non-borated. The dispersant can be present in the amount
of about 0.5 to 8 vol %, more preferably in the amount of about 1
to 6 vol %, most preferably in the amount of about 2 to 4 vol
%.
[0020] Antioxidants may be of the phenol (e.g., o,o'ditertiary
alkyl phenol such as ditertbutyl phenol), or amine (e.g., dialkyl
diphenyl amine such as dibutyl, octyl buty, or dioctyl diphenyl
amine) type, or mixtures thereof. More preferably, the antioxidants
will be hindered phenols, or aryl amines which may or may not be
sulfurized. Antioxidants can be present in the amount of about 0.05
to 2.0 vol %, more preferably in the amount of about 0.1 to 1.75
vol %, most preferably in the amount of about 0.5 to 1.5 vol %.
[0021] Metal deactivators may be of the aryl thiazines, triazoles,
or alkyl substituted dimercapto thiadiazoles (DMTD's), or mixtures
thereof. Metal deactivators can be present in the amount of about
0.01 to 0.2 vol %, more preferably in the amount of about 0.02 to
0.15 vol %, most preferably in the amount of about 0.05 to 0.1 vol
%.
[0022] Antiwear additives such as metal dithiophosphates (e.g.,
zinc dialkyl dithiophosphate, ZDDP), metal dithiocarbamates, metal
xanthates or tricreeylphosphates may be included. Antiwear
additives can be present in the amount of about 0.05 to 1.5 vol %,
more preferably in the amount of about 0.1 to 1.0 vol %, most
preferably in the amount of about 0.2 to 0.5 vol %.
[0023] Pour point depressants such as poly(meth)acrylates, or
alkyl-aromatic polymers may be included. Pour point depressants can
be present in the amount of about 0.05 to 0.6 vol %, more
preferably in the amount of about 0. 1 to 0.4 vol %, most
preferably in the amount of about 0.2 to 0.3 vol %.
[0024] Antifoamants such as silicone antifoaming agents can be
present in the amount of about 0.001 to 0.2 vol %, more preferably
in the amount of about 0.005 to 0.15 vol %, most preferably in the
amount of about 0.01 to 0.1 vol %.
[0025] Viscosity index Improvers (VII's) may be any polymer which
imparts multifunctional viscosity properties to the finished oil,
including materials such as olefin copolymers, polymethacrylates,
styrene diene block copolymers, and star copolymers. the VII's may
also be multifunctional from the perspective of offering secondary
lubricant performance features such as additional dispersancy.
VII's can be present in the amount of up to 15 vol %, more
preferably in the amount of up to 13 vol %, most preferably in the
amount of up to 10 vol %.
[0026] Lubricating oil additives are described generally in
"Lubricants and Related Products" by Dieter Klamanm, Verlag Chemie,
Deerfield, Fla., 1984, and also in "Lubricant Additives" by C. V.
Smalheer and R. Kennedy Smith, 1967, pages 1-11, the disclosures of
which are incorporated herein by reference.
[0027] The present invention is further described in the following
non-limiting examples and comparative examples.
EXPERIMENTAL
A. Lab Nitration Screener Test Results
[0028] A lab nitration screener test was used to assess the oil
life performance of various oil compositions. The test results
identify a number of parameters including oil viscosity increase,
oxidation, and nitration. All measurements are reported on a
relative basis (unless otherwise indicated) so that results greater
than unity represent greater levels of degradation. Numerically
lower relative results represent a measure of longer oil life. In
each test, a Reference Oil is tested and results are reported as a
ratio of the result for the test oil divided by the result for the
Reference Oil. Thus, if a tested oil has an oxidation result of
1.0, then it has oxidation performance equal to that of the
Reference Oil. If the tested oil has an oxidation result less than
1.0, then the tested oil demonstrates oxidation performance
superior to that of the Reference Oil
EXAMPLES AND COMPARATIVE EXAMPLES
[0029] In the Examples, the base oil in all cases was a heavy Group
II basestock. Comparative Oil 1, Reference Oil 1 and Examples 1 and
2 contained the same viscosity index improver (VI). Comparative Oil
2 is a current commercial oil based solely on API Group II
basestocks. Reference Oil 1 and Example Oils 1 and 2 each contained
the same mixture of neutral and overbased metallic detergents,
ashless dispersant, ZDDP, pour point depressant, metal passivator
and antifoamant. Reference Oil 1, however, employed a phenolic
antioxidant whereas the oils of Examples 1 and 2 employed a
trinuclear molybdenum compound, MO.sub.3S.sub.7(DTC).sub.4, and a
mixture of a trinuclear molybdenum compound,
MO.sub.3S.sub.7(DTC).sub.4, and an ashless dihydrocarbyl
thiocarbamoyl, (S.sub.2CNR.sub.2).sub.2CH.sub.2, respectively.
Comparative Oil 1 used a commercially available gas engine oil
additive package, Oloa 1255 sold by Chevron Chemical Company. Oloa
1255 is one of the most widely sold gas engine oil packages and
therefore represents a "benchmark standard" against which other
engine oil formulations may be measured.
[0030] The results show that the oils of the present invention,
Examples 1 and 2, provided superior performance to both of the
Comparative oils and the Reference Oil, in terms of reduced
oxidation, nitration and viscosity increase. The invention examples
provided superior oil life despite the absence of conventional
aminic and phenolic antioxidants. The small negative normalized
viscosity increase values for the invention examples simply reflect
that there was no significant change in viscosity, unlike the
Comparative and Reference oils.
2 TABLE 1 Comparative Reference Example Example Comparative Oil 1
Oil 1 1 2 Oi1 2 Component (vol %) Group II basestock 87.90 90.00
90.00 90.00 -- NGEO commercial 9.6 -- -- -- -- additive package VI
Phenolic antioxidant 1.00 1.00 -- Moly trimer -- -- 1.00 1.00 --
Ashless dihydrocarbyl -- -- -- 0.50 -- thiocarbamoyl Balance of
additives 1.00 9.00 9.00 9.00 -- Commercial Oil -- -- -- -- 100.00
Properties KV, cSt @ 100.degree. C. 13.25 13.14 13.20 13.13 13.51
Test Results Nitration Screener Test Oxidation (relative) 1.76 1.00
0.86 0.79 1.57 Nitration (relative) 1.55 1.00 1.15 0.91 1.48
Viscosity Increase 1.70 1.00 -0.16 -0.12 0.73 (relative)
* * * * *