U.S. patent application number 10/861601 was filed with the patent office on 2005-03-10 for long life lubricating oil composition using particular antioxidant components.
Invention is credited to Cartwright, Stanley James.
Application Number | 20050054543 10/861601 |
Document ID | / |
Family ID | 34228686 |
Filed Date | 2005-03-10 |
United States Patent
Application |
20050054543 |
Kind Code |
A1 |
Cartwright, Stanley James |
March 10, 2005 |
Long life lubricating oil composition using particular antioxidant
components
Abstract
A natural gas engine oil composition with enhanced resistance to
oxidation, nitration and viscosity increase comprising: an oil
basestock; neutral and overbased metallic detergents; an
antioxidant comprising an alkylthiocarbamoyl compound or a mixture
of an alkylthiocarbamoyl compound and an ashless, non-sulfur
containing, hindered phenol; and a zinc dihydrocarbyl
dithiophosphate in an amount sufficient to provide the composition
with from 250 to 450 wppm phosphorus.
Inventors: |
Cartwright, Stanley James;
(Sarnia, CA) |
Correspondence
Address: |
ExxonMobil Research and Engineering Company
P. O. Box 900
Annandale
NJ
08801-0900
US
|
Family ID: |
34228686 |
Appl. No.: |
10/861601 |
Filed: |
June 3, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60500378 |
Sep 5, 2003 |
|
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|
Current U.S.
Class: |
508/376 ;
508/391; 508/443; 508/444; 508/460; 508/586 |
Current CPC
Class: |
C10N 2030/10 20130101;
C10M 2207/262 20130101; C10M 2207/144 20130101; C10N 2010/04
20130101; C10M 2219/066 20130101; C10M 2219/046 20130101; C10N
2040/25 20130101; C10M 2207/027 20130101; C10M 2207/028 20130101;
C10N 2010/02 20130101; C10M 2207/026 20130101; C10N 2030/02
20130101; C10M 2223/045 20130101; C10M 141/10 20130101; C10M
2219/044 20130101 |
Class at
Publication: |
508/376 ;
508/443; 508/444; 508/391; 508/460; 508/586 |
International
Class: |
C10M 163/00 |
Claims
What is claimed is:
1. A natural gas engine lubricating oil composition having enhanced
resistance to oxidation, nitration and viscosity increase
comprising: a major amount of an oil of lubricating viscosity; a
minor amount of a detergent mixture comprising low/neutral TBN and
over based metallic detergents selected from the group consisting
of alkali and alkaline earth sulphonates, phenates, and
salicylates; a minor amount of an antioxidant comprising an
alkylthiocarbamoyl compound or a mixture of an alkylthiocarbamoyl
compound and an ashless, non-sulfur containing hindered phenol; and
a zinc dihydrocarbyl dithiophosphate in an amount sufficient to
provide the composition with from 250 to 450 wppm phosphorus.
2. The composition of claim 1 wherein the oil basestock has a
kinematic viscosity at 100.degree. C. of about 5 to about 16
cSt.
3. The composition of claim 2 wherein, based on the total volume of
the composition the detergents comprise from about 0.5 volume % to
about 10 volume %.
4. The composition of claim 3 wherein the antioxidant is an
alkylthiocarbamoyl compound which comprises about 0.25 volume % to
about 2.0 volume % of the composition.
5. The composition of claim 3 wherein the antioxidant is a mixture
of an alkylthiocarbamoyl compound and an ashless, non-sulfur
containing hindered phenol, wherein the alkylthiocarbamoyl compound
comprises 0.25 volume % to 1.5 volume % of the composition and the
phenol, 0.25 volume % to 1.5 volume % of the composition.
6. The composition of claim 4 or 5 wherein the alkylthiocarbamoyl
compound is represented by the formula 3where R.sup.1, R.sup.2,
R.sup.3 and R.sup.4 are the same or different linear and branched
alkyl groups of from 1 to 18 carbon atoms, X is S, S--S,
S--(CH.sub.2).sub.y--S, S--CH.sub.2--CH(R.sup.5)--S; y is an
integer of 1 to 4, and R.sup.5 is an alkyl group of 1 to 2 carbons.
Preferably R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are C.sub.4 alkyl,
X is S(CH.sub.2).sub.yS, Y is 1-3.
7. The composition of claim 5 wherein the ashless, non-sulfur
containing, hindered phenol is represented by the formulae: 4where
R.sub.1, R.sub.2 and R.sub.3 are the same or different alkyl groups
of 1 to 18 carbon atoms.
Description
[0001] This application claims the benefit of U.S. Ser. No.
60/500,378 filed Sep. 5, 2003.
FIELD OF INVENTION
[0002] The present invention relates to gas engine oils. More
particularly the present invention relates to gas engine oils that
provide enhanced resistance to oxidation, nitration and viscosity
increase.
BACKGROUND OF INVENTION
[0003] Typical natural gas fired engines such as those used in the
petroleum industry to compress natural gas at well heads and along
pipelines have up to 16 cylinders, often generating between 500 to
3000 HP. These engines normally are run continuously near full load
conditions with shut downs being primarily for maintenance such as
for oil changes. Such continuous operation near full load, of
course, places severe demands on the engine lubricant. Indeed,
because the lubricant is subjected to a high temperature
environment, oxidation processes can occur rapidly which limit
lubricant life. Also, natural gas engines emit nitrogen oxides
(NO.sub.x), some of which come into contact with the lubricant
resulting in nitration processes also limiting lubricant life.
Typically these processes are accompanied by increases in oil
viscosity.
[0004] Thus, it is desirable to extend the life of gas engine oils
by enhancing the oil's resistance to oxidation and nitration and to
reduce viscosity increases in the oil.
[0005] To extend lubricant life, base oils are formulated with
various additives such as dispersants, detergents, antioxidants,
viscosity index improvers and the like to provide a lubricating oil
composition. This art of lubricating oil formulation, however, has
become increasingly more complex with ever more stringent
requirements by end-users. Indeed, experience has shown that
incorporation of one type of additive in a lubricant composition
can have a negative impact on the function of another type of
additive. Consequently, extensive research continues in the quest
for lubricants of improved life and function.
[0006] An object of the present invention is to provide a gas
engine lubricating composition that has enhanced resistance to
oxidation and nitration.
[0007] Another object of the invention is to provide a gas engine
lubricating composition that has improved life as evidenced by
reduction in viscosity increase.
SUMMARY OF INVENTION
[0008] Accordingly, a natural gas engine lubricant composition
having enhanced resistance to oxidation, nitration and viscosity
increase comprises:
[0009] (a) a major amount of an oil basestock of lubricating
viscosity having a kinematic viscosity at 100.degree. C. of about 5
to 16 cSt and preferably about 10 to about 13 cSt;
[0010] (b) a minor amount of a detergent mixture comprising
low/neutral TBN and over based metallic detergents, selected from
the group consisting of alkali and alkaline earth sulphonates,
phenates, and salicylates;
[0011] (c) a minor amount of an antioxidant comprising an
alkylthiocarbamoyl compound or a mixture of an alkylthiocarbamoyl
compound and an ashless, non-sulfur containing hindered phenol;
and,
[0012] (d) a zinc dihydrocarbyl dithiophosphate in an amount
sufficient to provide the lubricant composition with from 250 to
450 wppm of phosphorus.
[0013] Other gas engine oil additives also may be present. These
include: ashless dispersants, metal passivators, pour point
depressants, VI improvers and antifoamants.
DETAILED DESCRIPTION OF THE INVENTION
[0014] The lubricating oil composition of the invention comprises a
major amount of a lubricating oil basestock which may be a mineral
oil, synthetic oil or blends of oils to give a basestock of the
desired viscosity for a natural gas engine oil. Typically, the
basestock of the invention will have a kinematic viscosity at
100.degree. C. in the range of about 5 to about 16 cSt and
preferably from about 10 to about 13 cSt. Especially preferred are
API category Group II basestocks.
[0015] The composition of the invention includes a mixture of
low/neutral TBN and overbased (high TBN) metallic detergents
selected from the groups consisting of alkali and alkaline earth
metal sulphonates, phenates, and salicylates. Preferably the
metallic detergents will be calcium sulphonates, calcium phenates
and calcium salicylates. Low/neutral TBN metallic detergents
typically have a TBN in the range of about 10 to about 80. High TBN
metallic detergents typically have a TBN in the range of about 150
to 300 or higher.
[0016] The metallic detergents are used in amounts sufficient to
contribute a sulfated ash (ASTM D-874) to the formulated lubricant
oil composition of about 0.2 mass % to about 2.0 mass %. Expressed
in terms based on active ingredient in the detergent mixture, the
metallic detergents comprise from about 0.5 volume % to about 10
volume % and preferably 0.5 volume % to 5.0 volume % of the
lubricating composition. The volume ratio (based on active
ingredient) of overbased to low/neutral TBN metallic detergents is
in the range of from about 0.05 to 3.5, and preferably about 0.25
to 1.0.
[0017] The lubricating composition of the invention contains a
minor but effective amount of an antioxidant comprising an
alkylthiocarbamoyl compound or a mixture of an alkylthiocarbamoyl
compound and an ashless, non-sulfur containing, hindered
phenol.
[0018] Suitable alkylthiocarbamoyl compounds are represented by the
formula: 1
[0019] where R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are the same or
different linear and branched alkyl groups of from 1 to 18 carbon
atoms, X is S, S--S, S--(CH.sub.2).sub.y--S,
S--CH.sub.2--CH(R.sup.5)--S;
[0020] y is an integer of 1 to 4, and R.sup.5 is an alkyl group of
1 to 2 carbons. Preferably R.sup.1, R.sup.1, R.sup.3 and R.sup.4
are C.sub.4 alkyl groups, X is S(CH.sub.2).sub.yS, Y is 1-3.
[0021] The alkylthiocarbamoyl compound when used in the absence of
the ashless, non-sulfur containing, hindered phenol generally
comprises from about 0.25 volume % to about 2.0 volume % and
preferably 0.5 volume % to 1.5 volume % of the total volume of the
lubricating oil composition.
[0022] In an alternate embodiment, the composition of the invention
contains an antioxidant comprising a mixture of an
alkylthiocarbamoyl compound and an ashless, sulfur free, hindered
phenol. In this embodiment, suitable alkylthiocarbamoyl compounds
are represented by the same formula above. The hindered phenols
suitable for use in conjunction with the alkylthiocarbamoyl
compounds may be represented by the following formulae: 2
[0023] where R.sub.1, R.sub.2 and R.sub.3 are the same or different
alkyl groups of 1 to 18 carbon atoms.
[0024] In the embodiment where the antioxidant is a mixture of
alkylthiocarbamoyl and ashless, non-sulfur containing hindered
phenols, the alkyl dithiocarbamoyl comprises 0.25 volume % to 1.5
volume %, and preferably 0.5 volume % to 1.0 volume % of the
composition and the phenol from 0.25 volume % to 1.5 volume % and
preferably 0.5 volume % to 1.0 volume %.
[0025] The natural gas engine lubricating composition also includes
a zinc dihydrocarbyl dithiophosphate (ZDDP) or mixture of ZDDPs in
which the hydrocarbyl groups may be the same or different alkyl
groups or alkylaryl groups with the alkyl group, in each instance,
having 3 to about 18 carbon atoms. Preferably the hydrocarbyl group
is an alkyl group. The ZDDP or ZDDP mixture is present in the
amount sufficient to provide the lubricating oil composition with
250 to 450 wppm of phosphorus.
[0026] The invention also contemplates the use of other gas engine
oil additives such as ashless dispersants, metal passivators, pour
point depressants, VI improvers and antifoamants. Some of these
additives are only required in minor amounts (antifoamants, metal
passivators), while others may be required in significant amounts
(dispersants). Thus, these additives will typically range from 0.01
volume % to about 10 volume % based on the total volume of the
engine oil composition.
EXAMPLES AND COMPARATIVE EXAMPLES
[0027] The invention will be further illustrated by the following
Examples and Comparative Examples.
[0028] Table 1 below details a series of formulations: (a) two for
particularly preferred embodiments of the invention and (b) three
other formulations included for comparative purposes. The basestock
in all formulations was an API Group II category basestock. All
oils were SAE 40 grades with nominally 0.45 mass % sulphated
ash.
[0029] Comparative Oil 1 is a low ash commercial gas engine oil
which employed a commercial gas engine oil additive package.
[0030] Reference Oil 1 was blended to represent an oil of U.S. Pat.
No. 6,140,282, while Comparative Oil 2 was blended to represent an
oil of U.S. Pat. No. 5,569,405.
[0031] The various formulations were subjected to a nitration
screener test and the results are presented in Table 1. The
nitration screener test is a lab test which assesses several facets
of the degradation of natural gas engine oils. All results are
expressed as normalised against the results for the Reference Oil.
Therefore, all results for the Reference Oil will have a result of
1.00 and any results lower than 1.00 signify enhanced
performance.
1TABLE 1 Reference Comparative Oil 1 Oil 2 Based on Based on
Comparative U.S. Pat. No. Invention U.S. Pat. No. Invention
Formulation Description. Oil 1 6,140,282 Example 1 5,569,405
Example 2 Component (vol %) Group II Group II Group II Group II
Group II Basestock Description basestocks basestocks basestocks
basestocks basestocks Group II basestock 87.90 90.00 90.00 90.00
90.00 NGEO Commercial Additive package 9.60 -- -- -- -- VII 1.00
1.00 1.00 1.00 1.00 PPD 0.50 -- -- -- -- Calcium alkylsalicylate,
64 TBN -- 2.00 2.00 2.00 2.00 Calcium alkylsalicylate, 280 TBN --
0.40 0.40 0.40 0.40 Balance of Additive System -- 5.60 5.60 5.60
5.60 Phenolic antioxidant 1.00 1.00 -- -- 0.50 Sulphur-containing
Phenolic antioxidant -- -- -- 0.50 -- Ashless alkylthiocarbamoyl --
-- 1.00 0.50 0.50 Kinematic viscosity, cSt measured kV @
100.degree. C. 13.25 13.21 13.15 13.12 13.19 Phosphorus content,
ppm 334 295 295 295 295 Nitration Screener Test oxidation (relative
to reference Oil 1) 2.92 1.00 1.07 1.37 0.83 nitration (relative to
reference Oil 1) 1.59 1.00 0.79 0.73 0.59 viscosity increase
(relative to Reference 2.80 1.00 -0.43 0.21 0.17 Oil 1) PPD = pour
point depressant
[0032] As can be seen, Comparative Oil 1 is inferior in all
respects to the Reference Oil while Comparative Oil 2 provides
better nitration and thickening control than the Reference Oil but
inferior oxidation control. The Example 1 oil in contrast provides
roughly equivalent oxidation control to that of the Reference Oil
and improved nitration and thickening control. The oil of Example 2
is better than the Reference Oil in all three parameters.
* * * * *