U.S. patent application number 12/147941 was filed with the patent office on 2009-01-01 for fuel economy lubricating oil composition for lubricating diesel engines.
This patent application is currently assigned to Chevron Japan Ltd.. Invention is credited to Takahiro Muramatsu, Morikuni Nakazato, Yoshitake Takeuchi, Yoshito Yamashita.
Application Number | 20090005278 12/147941 |
Document ID | / |
Family ID | 39874919 |
Filed Date | 2009-01-01 |
United States Patent
Application |
20090005278 |
Kind Code |
A1 |
Takeuchi; Yoshitake ; et
al. |
January 1, 2009 |
FUEL ECONOMY LUBRICATING OIL COMPOSITION FOR LUBRICATING DIESEL
ENGINES
Abstract
A lubricating oil composition for internal combustion engines
comprising a base oil having and lubricating viscosity and
additives composed of a) a salt of an alkali metal or alkaline
earth metal and an alkylsalicylate and/or an alkylcarboxylate, b) a
nitrogen atom-containing ashless dispersant and/or a nitrogen
atom-containing dispersive viscosity index improver, c) a neutral
salt of a fatty acid and a fatty amine, and d) oxidation inhibitor,
is effective for lubricating diesel engines using a low
sulfur-content fuel, even though it has a low sulfated ash content,
a low sulfur content and a low phosphorus content.
Inventors: |
Takeuchi; Yoshitake;
(Shizuoka-ken, JP) ; Muramatsu; Takahiro;
(Shizuoka-ken, JP) ; Yamashita; Yoshito;
(Shizuoka-ken, JP) ; Nakazato; Morikuni;
(Shizuoka-ken, JP) |
Correspondence
Address: |
CHEVRON CORPORATION
P.O. BOX 6006
SAN RAMON
CA
94583-0806
US
|
Assignee: |
Chevron Japan Ltd.
|
Family ID: |
39874919 |
Appl. No.: |
12/147941 |
Filed: |
June 27, 2008 |
Current U.S.
Class: |
508/371 |
Current CPC
Class: |
C10M 141/06 20130101;
C10M 2215/28 20130101; C10M 2207/026 20130101; C10N 2030/42
20200501; C10M 2223/045 20130101; C10M 2219/046 20130101; C10M
2215/064 20130101; C10M 169/04 20130101; C10M 2207/126 20130101;
C10N 2030/54 20200501; C10M 2215/086 20130101; C10M 2209/084
20130101; C10M 2205/022 20130101; C10N 2030/45 20200501; C10N
2030/06 20130101; C10N 2040/252 20200501; C10N 2030/43 20200501;
C10M 2207/262 20130101; C10M 2205/022 20130101; C10M 2205/024
20130101; C10M 2207/126 20130101; C10M 2215/04 20130101; C10M
2207/262 20130101; C10N 2010/04 20130101; C10M 2215/086 20130101;
C10N 2010/12 20130101; C10M 2219/046 20130101; C10N 2010/04
20130101; C10M 2215/086 20130101; C10N 2010/12 20130101; C10M
2207/262 20130101; C10N 2010/04 20130101; C10M 2219/046 20130101;
C10N 2010/04 20130101 |
Class at
Publication: |
508/371 |
International
Class: |
C10M 137/10 20060101
C10M137/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 28, 2007 |
JP |
2007-170667 |
Claims
1. A lubricating oil composition for lubricating internal
combustion engines which has a sulfated ash content of 1.1 wt. % or
less, a sulfur content of 0.5 wt. % or less, and a phosphorus
content of 0.12 wt. % or less and which comprises a base oil having
a lubricating viscosity and the following additive components: a) a
metal-containing detergent comprising at least one of an alkali
metal or alkaline earth metal alkylsalicylate and an alkali metal
or alkaline earth metal alkylcarboxylate in an amount of 0.01 to
0.4 wt. % in terms of an amount of metal contained in the
composition; b) at least one of a nitrogen-containing ashless
dispersant and a nitrogen-containing dispersive viscosity index
improver in an amount of 0.01 to 0.3 wt. % in terms of a nitrogen
amount; c) a neutral salt of a fatty acid with a fatty amine in ah
amount of 0.1 to 5 wt. %; and d) an oxidation inhibitor in an
amount of 0.1 to 5 wt. %.
2. The lubricating oil composition of claim 1, in which the
neutralized salt of a fatty acid with a fatty amine is a neutral
salt of a fatty acid having 8 to 30 carbon atoms and a fatty amine
having 8 to 30 carbon atoms.
3. The lubricating oil composition of claim 2, in which the fatty
acid is an unsaturated fatty acid and the fatty amine is a
saturated fatty amine.
4. The lubricating oil composition of claim 3, in which the fatty
acid is an unsaturated linear chain fatty acid.
5. The lubricating oil composition of claim 4, in which the
unsaturated linear chain fatty acid is oleic acid.
6. The lubricating oil composition of claim 3, in which the fatty
amine is a saturated linear chain fatty amine.
7. The lubricating oil composition of claim 6, in which the
saturated linear chain fatty amine is stearyl amine.
8. The lubricating oil composition of claim 1, in which the neutral
salt of a fatty acid with a fatty amine is contained in an amount
of 0.1 to 2 wt. %.
9. The lubricating oil composition of claim 1, in which the
metal-containing detergent comprising at least one of an alkali
metal or alkaline earth metal alkylsalicylate and an alkali metal
or alkaline earth metal alkylcarboxylate is contained in an amount
of 0.1 to 0.4 wt. % in terms of an amount of metal contained in the
composition.
10. The lubricating oil composition of claim 1, in which the base
oil having a lubricating viscosity has a saturated component of 85
wt. % or more, a viscosity index of 110 or more, and a sulfur
content of 0.01 wt. % or less.
11. The lubricating oil composition of claim 1, in which the
nitrogen-containing ashless dispersant has a weight average
molecular weight in the range of 4,500 to 20,000.
12. The lubricating oil composition of claim 1, which further
comprises a zinc dihydrocarbyldithiophosphate or a zinc
dihydrocarbylphosphate in an amount of 0.01 to 0.12 wt. % in terms
of an amount of a phosphorus amount.
13. The lubricating oil composition of claim 1, which has a TBN in
the range of 2 to 15 mgKOH/g and is used for lubricating diesel
engines.
14. A process for lubricating a diesel engine comprising operating
the engine using the lubricating oil composition of claim 1.
Description
FIELD OF INVENTION
[0001] The present invention, relates to a lubricating oil
composition for lubricating internal combustion engines,
particularly, a diesel engine. More specifically, the invention
relates: to a Lubricating oil composition suitably employable for
lubricating a diesel engine mounted to; a car driven using fuel of
a low sulfur content and enabling operation of the diesel engine
with high fuel economy.
BACKGROUND OF THE INVENTION
[0002] Heretofore, for gasoline engines it has been desired to
develop and formulate lubricating oil compositions having a low
sulfated ash content, a low sulfur content and a low phosphorus
content to cope with the exhaust gas regulations applied to cars to
which a gasoline engine is mounted. Similarly for diesel engines,
in order to cope with the recent severe exhaust gas regulations,
there arises a demand for developing and formulating a lubricating
oil composition having a low sulfated ash content, a low sulfur
content and a low phosphorus content for lubricating a diesel
engine mounted to cars that are equipped with an exhaust gas
cleaning apparatus and are driven by the use of a low sulfur fuel
such as low sulfur content diesel fuel, bio-diesel fuel, or
dimethyl ether.
[0003] Conventional lubricating oil compositions employed for
lubricating a gaaoline engine or a diesel engine generally comprise
a major amount of a base oil having a lubricating viscosity and
various additive components, depending upon specific function or
formulators requirements. Examples of commonly formulated additive
components include a metal-containing detergent, metal containing
multifunctional additives, ashless compounds such as ashless:
dispersant, oxidation inhibitors, etc.
[0004] The metal-containing detergent has a function to neutralize
sulfuric acid produced by burning fuel and is necessarily
incorporated into a lubricating oil composition for lubricating a
diesel engine which uses a fuel having a higher sulfur content as
compared with a fuel used for a gasoline engine. Generally, the
metal-containing detergent is incorporated into a lubricating oil
composition; for diesel engines in an amount, of TBN (total base
number) in the range of 2 to 15 mgKOH/g.
[0005] Zinc dithiophosphates (particularly, zinc
dihydrocarbyldithiophosphate and zinc dialkyldithiophosphoate)
which, have multiple functions such as wear inhibition and extreme
pressure resistance have been almost necessarily employed for
preparation of the lubricating oil composition for diesel engines.
In addition, zinc dihydrocarbylphosphate has been recently
developed as a multi-functional additive replacing the zinc
dithophosphate.
[0006] The above-mentioned multi-functional additives, however,
have a drawback in having all of a metal element, a sulfur element,
and a phosphorus element. Therefore, it is necessary to limit the
amount of these multifunctional additives when the lubricating oil
compositions having a low sulfated ash content, a low sulfur
content, and a low phosphorus content are formulated.
[0007] On the other hand, the requirements concerning fuel economy
have been, increased for cars to which a gasoline engine or a
diesel engine is mounted. The fuel economy can be mostly improved
by modifying the structure of the engines. However, it is also
known that the improvement of a lubricating; oil composition is
also effective to improve the fuel economy. Therefore, lubricating
oil compositions employing a base oil of decreased oil viscosity or
an improved friction modifier have been studied. Until now, a
number of friction modifiers have been developed for internal
combustion engines. Among the recently developed friction
modifiers, sulfur-containing organic molybdenum compound friction
modifiers such as molybdenum dithiocarbamate (MoDTC) and molybdenum
dithiophosphate (MoDTP) show a practically satisfactory friction
modifying function and hence are used widely. However, the
sulfur-containing organic molybdenum compound friction modifiers
also have drawbacks in having a metal element and, a sulfur
element. Moreover, the sulfur-containing organic molybdenum
compound friction modifiers have additional drawbacks, in that the
friction reducing function disappears within a relatively short
period of time, additionally these compounds are quickly rendered
ineffective with soot loading.
[0008] Japanese Patent Provisional Publication 2004-155881
describes a fuel economy-type lubricating oil composition for
internal combustion engines. The lubricating oil composition is
prepared by combining a base oil having a viscosity index of 110 or
more, a whole aromatic component content iri the range of 2 to 15
wt. % and a sulfur content of 0.05 wt. % or more and a mixture of
1.2 to 5.0 wt. % of a fatty acid ester-type ashless friction
modifier and/or a fatty amine-type ashless friction modifier and
0.02 to 0.15 wt. % (in terms of phosphorus content) of zinc
dialkyldithiophosphate. It is described that the disclosed
lubricating oil composition shows an improved friction reducing
function, an improved wear resistance, and an improved storage
stability. However, these types of frictions modifiers have not
been found to be effective at higher soot loading in the engines
oil.
SUMMARY OF THE INVENTION
[0009] The lubricating oil composition of the invention has a low
sulfated ash content, a low phosphorus content and a low sulfur
content and show an excellent frictionmodifying function
(friction-reducing function) even in the case in that a large
amount of soots have: migrated in the lubricating oil composition
Further, the lubricating oil composition of the invention causes no
corrosion of the metallic engine parts. The corrosion of the
metallic engine parts is a problem known in, the lubricating oil
compositions containing an amine compound and a fatty acid.
[0010] Accordingly, disclosed is a lubricating oil composition for
lubricating internal combustion engines which has a sulfated ash
content of 1.1 wt. % or less, a sulfur content of 0.5 wt. % or
less, and a phosphorus content of 0.12 wt. % or less and which
comprises a base oil having a lubricating viscosity and the
following additive components:
[0011] a) a metal-containing detergent comprising at least one of
an alkali metal or alkaline earth metal alkylsalicylate and an
alkali metal or alkaline earth metal alkylcarboxylate in an amount
of 0.01 to 0.4 wt. % in terms of an amount of metal contained in
the composition;
[0012] b) at least one of a nitrogen-containing ashless dispersant
and a nitrogen-containing dispersive viscosity index improver in an
amount of 0.01 to 0.3 wt. % in terms of a nitrogen amount;
[0013] c) a neutral salt of a fatty acid with a fatty amine in an
amount of 0.1 to 5 wt. %; and
[0014] d) an oxidation inhibitor in an amount of 0.1 to 5 wt.
%.
[0015] The lubricating oil composition of the invention is
favorably employable for lubricating diesel engines mounted to cars
which are driven, using a low sulfur fuel. Moreover, the
lubricating oil composition of the invention is very advantageous
as a lubricating oil composition for lubricating diesel engines
demonstrating high fuel economy. Particularly for diesel engines
which are expected to experience a high soot loading in the
lubricating oil, such as for diesel engines equipped with EGR
system or a diesel engine using a lubricating oil with a long
service period, the lubricating oil compositions of the present
invention can extend the service life and maintain the fuel
economy. In such an event a preferred friction modifier is a
neutralized salt of a fatty acid having 8 to 3.0 carbon atoms, and
a fatty amine having 8 to 30 carbon atoms. In this regard the fatty
acid is an unsaturated fatty acid, such as a linear chain fatty
acid, more preferably oleic acid; while the fatty amine is a
saturated linear chain fatty amine, more preferably stearyl amine.
Typically the neutral salt of a fatty acid with a fatty amine, is
contain in an amount to provide a friction modifying effect, more
preferably in an amount of 0.1 to 2 wt. %. Soot loading in the
lubricating oil composition can be greater than 0.5 wt %, such as
greater than 1 wt %, or greater than 2 wt %, up to about 5 wt
%.
[0016] Thus, the lubricating oil composition of the invention is
also advantageous as a lubricating oil composition for lubricating
gasoline engines with high fuel economy.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The present invention is directed in part to fuel economy
lubricating oil compositions particularly suited for diesel
engines. More specifically the components have been selected to
impart a high friction modifying function (high friction reducing
function) in the use for lubricating diesel engines, particularly
diesel engines mounted to cars driven using a low sulfur content
diesel fuel.
[0018] Although a lubricating oil composition for gasoline engines
and a lubricating oil composition for diesel engines both are
classified into a lubricating oil composition for internal
combustion engines, there are some differences in the required
lubricating functions. For instance, in the case of a lubricating
oil composition for diesel engines, there is a problem in that
produced soots likely migrate into the lubricating oil. The soots
easily agglutinate to form hard solid mass, which disturbs
lubrication in the engine. The resulting lowering of lubricating
function causes decrease of fuel economy. In the case of a diesel
engine equipped with EGR system or a diesel engine using a
lubricating oil with a long service period, a large amount of soots
are apt to migrate into the lubricating oil. Therefore, for the
lubricating oil composition for diesel engines, the lubricating oil
composition should show enough friction modifying function
(friction reducing function) less influenced by the migration of
soots. However, in consideration of the aforementioned requirements
for the low sulfated ash content, low sulfur content and low
phosphorus content, the conventionally employed zinc
dithiophosphate should not be used in a large amount.
[0019] Known friction modifiers quickly lose their intended
function when the lubricating oil becomes loaded with soot.
Numerous friction modifier mechanisms and formulations using the
friction modifiers in response to soot loading were investigated.
Surprisingly, it has been discovered that a neutral salt of a fatty
acid and a fatty amine is incorporated as a friction modifier into
a lubricating oil composition containing a metal-containing
detergent, an ashless dispersant and an oxidation inhibitor in
which the metal-containing detergent is an alkali metal or alkaline
earth metal salicylate or an alkali metal or alkaline earth metal
alkylcarboxylate, the resulting lubricating oil composition show a
satisfactory friction-reducing function even in the case that a
large amount of soots have migrated in the lubricating oil
composition. The herein-disclosed invention has been made on the
basis of the above-mentioned discovery.
[0020] There is provided by the present invention a lubricating oil
composition for lubricating internal combustion engines which has a
sulfated ash content of 1.1 wt. % or less, a sulfur content of 0.5
wt. % or less, and a phosphorus content of 0.12 wt. % or less and
which comprises a base oil having a lubricating viscosity and the
following additive components:
[0021] a) a metal-containing detergent comprising at least one of
an alkali metal or alkaline earth metal alkylsalicylate and an
alkali metal or alkaline earth metal alkylcarboxylate in an amount
of 0.01 to 0.4 wt. % in terms, of an amount of metal contained in
the composition;
[0022] b) at least one of a nitrogen-containing ashless dispersant
and a nitrogen-containing dispersive viscosity index improver in an
amount of 0.01 to 0.3 wt. % in terms of a nitrogen amount;
[0023] c) a neutral salt of a fatty acid with a fatty amine in an
amount of 0.1 to 5 wt. %; and
[0024] d) an oxidation inhibitor in an amount of 0.1 to 5 wt.
%.
[0025] Particular aspects of lubricating oil compositions according
to the invention are described below:
[0026] (1) The neutral salt of a fatty acid with a fatty amine: is
a neutralized salt of a fatty acid having 8 to 30 carbon atoms and
a fatty amine having 8 to 30 carbon atoms.
[0027] (2) The fatty acid is an unsaturated fatty acid and the
fatty amine is a saturated fatty amine.
[0028] (3) The fatty acid is an unsaturated linear chain fatty acid
(particularly oleic acid).
[0029] (4) The fatty gamine is a saturated linear chain fatty amine
(particularly stearyl amine).
[0030] (5) The neutral salt of a fatty acid with a fatty amine is
contained in an amount of 0.1 to 2 wt. %.
[0031] (6) The metal-containing detergent comprising at least one
of an alkali metal or alkaline earth metal alkylsalicylate and an
alkali metal or alkaline earth metal alkylcarboxylate is contained
in an amount of 0.1 to 0.4 wt. % in terms of an amount of metal
contained in the composition.
[0032] (7) The base oil having a lubricating viscosity has a
saturated component of 85 wt. % or more, a viscosity index of 110
or more, and a sulfur content of 0.01 wt. % or less.
[0033] (8) The nitrogen-containing ashless dispersant has a weight
average molecular weight in the range of 4,500 to 20,000.
[0034] (9) The lubricating oil composition further comprises a zinc
dihydrocarbyldithiophosphate or a zinc dihydrocarbylphosphate in an
amount of 0.01 to 0.12 wt. % in terms of an amount of a phosphorus
amount.
[0035] (10) The lubricating oil composition has a TBN in the range
of 2 to 15 mgKOH/g and is used for lubricating diesel engines.
[0036] (11) The lubricating oil has a sulfur content in the range
of 0.01 to 0.3 wt. %, particularly 0.01 to 0.2 wt. %.
[0037] (12) The nitrogen-containing ashless dispersant is
bissuccinimide or polysuccinimide.
[0038] (13) The oxidation inhibitor is selected from the group
consisting of phenolic oxidation inhibitors and amine oxidation
inhibitors.
[0039] (14) The oxidation inhibitor is an oxymolybdenum complex
compound with a basic nitrogen-containing compound (particularly
succinimide).
[0040] (15) The metal-containing detergent further comprises an
alkali metal or alkaline earth metal sulfonate and/or an alkali
metal or alkaline earth metal phenate.
[0041] (16) The lubrication oil composition is of SAE viscosity
grade of 0W20, 0W30, 0W40, 5W20, 5W30, 5W40, 10W20 or 10W30.
[0042] (17) A diesel engine is activated using the lubricating oil
composition of the invention.
[0043] The base oil and additive components used for formulating
the lubricating oil composition of the invention are described
below in more detail.
Base Oil
[0044] The base oil of the lubricating oil composition according to
the invention is a mineral oil and/or a synthetic oil which has a
saturated component of 85 wt. % or more (preferably 90 wt. % or
more), a viscosity index of 110 or more (preferably 120 or more,
more preferably 130 or more), and a sulfur content of 0.01 wt. % or
less (preferably 0.001 wt. % or less).
[0045] The mineral oil preferably is an oil which is obtained by
processing a lubricating oil distillate of a mineral, oil by
solvent refining, hydrogenation, or their combination. Particularly
preferred is a highly hydrogenated refined oil (corresponding to a
hydrocracked oil, typically has a viscosity index of 120 or more,
an evaporation loss (ASTM D5800) of 15 wt. % or less, a sulfur
content of 0.01 wt. % or less, and an aromatic component content of
10 wt. % or less). In addition, an mineral oil mixture containing
the hydrocracked oil in an amount of 10 wt. % or more. The
hydrocracked oil includes a high viscosity index oil (such as
having a viscosity index of 140 or more, specifically 140 to 150)
which is obtained by subjecting mineral oil-origin slack wax or
synthetic wax prepared from natural gas to isomerization and
hydrocracking and a gas-to-liquid base oil. The hydrocracked
[0046] Oil has a low sulfur content and a low residual carbon
content and shows a low evaporation property, and therefore is
preferred for the use in the lubricating oil composition of the
invention.
[0047] Examples of the synthetic oils (synthetic lubricating base
oils) include poly-.alpha.-olefin such as a polymerized compound of
.alpha.-olefin having 3 to 12 carbon atoms; a dialkyl ester of a
di-basic acid such as sebacic acid, azelaic acid, or adipic acid
and an alcohol having 4 to 18 carbon atoms, typically dioctyl
sebacate; a polyol ester which is an ester of
1,1,1-trimethylolpropane or pentaerythritol and a mono-basic acid
having 3 to 18 carbon atoms; and alkylbenzene having an alkyl group
of 9 to 40 carbon atoms. The synthetic oil generally contains
essentially no sulfur, shows good stability to oxidation and good
heat resistance, and gives less residual carbon and soot when it is
burned. Therefore, the synthetic oil is preferably employed for the
lubricating oil composition of the invention. Particularly
preferred is poly-.alpha.-olefin, from the viewpoint of the object
of the invention.
[0048] Each of the mineral oil and synthetic oil can be employed
singly. If desired, two or more mineral oils can be employed in
combination, and two or more synthetic oils can be employed in
combination. The mineral oil and synthetic oil can be employed in
combination at an optional ratio.
Metal-Containing Detergent
[0049] The lubricating oil composition of the invention contains as
the metal-containing detergent an alkylsalicylate and/or an
alkyl-carboxylate of an alkali metal or an alkaline earth metal.
The metal-containing detergent comprises an alkylsalicylate and/or
an alkylcarboxylate of an alkali metal or an alkaline earth metal.
Optionally, the alkylsalicylate and/or alkylcarboxylate may be
employed in combination with a sulfonate and/or a phenate of an
alkali metal or an alkaline earth metal.
[0050] In the lubricating oil composition of the invention, it is
assumed that the alkylsalicylate and/or alkylcarboxyiate of an
alkali metal or an alkaline earth metal functions to increase
dispersion of the soots and assists reduction of friction.
[0051] Preferred are an alkylsalicylate and an alkylcarboxylate of
an alkaline earth metal. The alkaline earth metal preferably is
calcium, barium, or magnesium. Calcium is moat preferred.
[0052] The alkaline earth metal-containing salicylate generally is
a an alkaline earth metal salt of an alkylsalicylic acid, which can
be prepared from an alkylphenol by Kolbe-Schmidt reaction. The
alkylphenol is obtained by a reaction of .alpha.-olefin having
approx. 8 to 30 carbon atom (mean value) with phenol by
Kolbe-Schmidt reaction. The alkaline earth metal salts can be
ordinarily produced by subjecting their Na salt or K salt to
double-decomposition or sulfuric acid decomposition, to give their
Ca salt or Mg salt. The double decomposition using calcium chloride
(CaCl.sub.2) or the like is not preferred because chlorine is apt
to migrate in the resulting product. Further, it is also known that
an alkylphenol is directly neutralized to give; its Ca salt, and
then subjecting the Ca salt to a carbonation process to give the
calcium salicylate. This, process, however, gives the desired
compound in a low yield, in comparison with the Kolbe-Schmidt
reaction. Therefore, it is preferred to combine the Kolbe-Schmidt
reaction and sulfuric acid decomposition. Preferred is a
non-sulfurized alkylsalicylate (alkaline earth metal salt) having a
TBN in the range of 30 to 300 mgKOH/g.
[0053] The alkaline earth metal carboxylate can be prepared, for
instance, by neutralizing alkylphenol with an alkaline earth metal
base in the presence of a carboxylic acid having 1, to 4 carbon,
atoms but in the absence of an alkali metal base, and carboxylating
the resulting alkylphenate. The carboxylate can be a mono-aromatic
ring hydrocarbylsalicylate-carboxylate which can be produced by
treating an aromatic hydrocarbylsalicylate with a long chain
carboxylic acid before, during, or after the aromatic
hydrocarbylsalicylate is subjected to overbasing treatment. In
these producing procedures, no Kolbe-Schmidt reaction (which
includes production of an alkali metal salt) is performed. These
producing procedures are described in Japanese Patent Provisional
Publications 2000-63867 and 2000-87066, incorporated herein by
reference in their entirety.
[0054] Nitrogen-Containing Ashless Dispersant
[0055] The nitrogen-containing ashless dispersant employed in the
lubricating oil composition of the invention preferably has a
weight average molecular weight or 4,500 to 20,000. The weight
average molecular weight used in the specification is a molecular
weight determined by GPC analysis using polystyrene as a reference
compound.
[0056] Examples of the nitrogen-containing dispersants include
alkenyl- or alkyl-succinimide or a derivative thereof which is
derived from polyolefin. The nitrogen-containing dispersant is
incorporated into the lubricating oil composition in an amount of
0.01 to 0.3 weight percent in terms of a nitrogen content, based on
the total amount of the lubricating oil composition. A
representative succinimide is obtained by the reaction between
succinic anhydride having a substituent of an alkenyl group or an
alkyl group which has a high molecular weight and
polyalkylenepolyamine containing 4 to 10 nitrogen atoms (preferably
5 to 7 nitrogen atoms) per one molecule. The alkenyl group or an
alkyl group which has a high molecular weight is preferably derived
from polyolefin, particularly polybutene, having a number average
molecular weight in the range of approx. 900 to 5,000.
[0057] The process for obtaining the polybutenyl-succinic acid
anhydride by the reaction of polybutene and maleic anhydride is
generally performed by the chlorination process using a chloride
compound. The chlorination process is advantageous in its reaction
yield. However, the reaction product obtained by the chlorination
process contains a large amount (for instance, approx. 2,000 ppm)
of chlorine. If the thermal reaction process using no chloride
compound is employed, the reaction product contains only an
extremely small chlorine (for instance, 40 ppm or less). Moreover,
if a highly reactive polybutene (containing a methylvinylidene
structure at least approx. 50%) is employed in place of the
conventional polybutene (mainly containing a .beta.-olefin
structure), even the thermal reaction process can give a high
reaction yield. If the reaction yield is high, the reaction product
necessarily contains a reduced amount of the unreacted polybutene.
This means that a dispersant containing a large amount of the
effective component (succinimide) is obtained. Accordingly, it is
preferred that the polybutenyl succinic acid anhydride is produced
from the highly reactive polybutene by the thermal reaction and
that the produced polybutenyl succinic acid anhydride is reacted
with polyalkylenepolyamine having ah average nitrogen atom number
in the range of 4 to 10 (in one molecule) to give the succinimide.
The succinimide further can be reacted with boric acid, alcohol,
aldehyde, ketone, alkylphenol, cyclic carbonate, organic acid or
the like, to give a modified succinimide. Particularly, a borated
alkenyl(or alkyl)-succinimide which is obtained by the reaction
with boric acid or a boron compound is advantageous from the
viewpoints of thermal and oxidation stability.
[0058] Other examples of the nitrogen-containing ashless
dispersants include polymeric succinimide dispersants derived from
ethylene-.alpha.-olefin copolymer (for instance, the molecular
weight is 1,000 to 15,000), and alkenyl-benzyl amine ashless
dispersants.
[0059] In the lubricating oil composition of the invention, the
nitrogen-containing ashless dispersant can be replaced with a
nitrogen-containing dispersive viscosity index improver. As the
nitrogen-containing dispersive viscosity index improver, a
nitrogen-containing olefin copolymer or a nitrogen-containing
polymethacrylate each having a weight mean molecular weight of
90,000 or more (in terms of polystyrene converted-molecular weight
determined by GPC analysis). In consideration of thermal stability,
the former is preferred.
[0060] The lubricating oil composition of the invention necessarily
contains, a nitrogen-containing ashless dispersant and/or a
nitrogen-containing dispersive viscosity index improver. If
desired, the other ashless dispersants such as an alkenylsuccinic
acid ester dispersant can be employed in combination.
Neutral Salt of Fatty Acid and Fatty Amine
[0061] The lubricating oil composition of the invention contains a
neutral salt (or neutralized salt) of a fatty acid and a fatty
amine as a friction modifier (friction reducing agent). The fatty
acid preferably is a linear chain fatty acid having 8 to 30 carbon
atoms. The fatty amine preferably is a linear chain fatty amine
having 8 to 30 carbon atoms. It: is preferred that the fatty group
of one of the fatty acid and fatty amine is an unsaturated group
(e.g., oleyl). It is also preferred that the fatty group of both of
the fatty acid and fatty amine is an unsaturated group (e.g.,
oleyl). It is further preferred for the neutral salt of fatty acid
and fatty amine that a difference between the acid value (unit:
mgKOH/g) and the amine value (unit: mgKOH/g) is not more than 20,
specifically not more than 15.
[0062] Examples of the preferred neutral salts of fatty acid and
fatty amine include a salt of oleic acid with stearylamine, a salt
of oleic acid with laurylamine, a salt of oleic acid with
oleylamine, and a salt of a dioleic acid with
N-oleylpropylenediamine. Both of the fatty acid and fatty amine can
be employed their derivatives such as alkyleneoxide adducts or
sulfides. Thus, the neutral acid salt of fatty acid and fatty amine
according to the invention include salts of these derivatives.
Oxidation Inhibitor
[0063] The oxidation inhibitor preferably is at least one oxidation
inhibitor selected from the group consisting of the known phenolic
oxidation inhibitor and the known amine oxidation inhibitor.
[0064] A representative phenolic oxidation inhibitor is a hindered
phenol compound, and a representative amine oxidation inhibitor is
a diarylamine compound.
[0065] The hindered phenol compound and diarylamine compound are
advantageous because both further provide high detergency at a high
temperature. The diarylamine oxidation inhibitor is particularly
advantageous because it has a base number derived from the
contained nitrogen which serves to increase detergency at a high
temperature. In contrast, the hindered phenol oxidation inhibitor
is effective to reduce oxidative deterioration caused by
NO.sub.x.
[0066] Examples of the hindered phenol oxidation, inhibitors
include-2,6-di-t-butyl-p-cresol,
4,4'-methylenebis(2,6-di-t-butylphenol),
4,4'-methylenebis(6-t-butyl-o-cresol),
4,4'-isopropylidenebis(2,6-di-1-butylphenol),
4,4'-bis(2,6-di-t-butylphenol),
2,2'-methylenebis(4-methyl-6-t-butylphenol),
4,4'-thiobis(2-methyl-6-t-butylphenol),
2,2-thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate],
octyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, octadecyl
3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and octyl
3-(5-t-butyl-4-hydroxy-3-methylphenyl)propionate.
[0067] Examples of the diarylamine oxidation inhibitors include
alkyldiphenylamine having, a mixture of alkyl groups of 4 to 9
carbon atoms, p,p'-dioctyidiphenylamine,
phenyl-.alpha.-naphthylamine, phenyl-.beta.-naphthylamine,
alkylated .alpha.-naphthylamine, and alkylated
phenyl-.alpha.-naphthylamine.
[0068] Each of the hindered phenol oxidation inhibitor and
diarylamine oxidation inhibitor can be employed singly or in
combination. If desired, other oil soluble oxidation inhibitors can
be employed in combination with the hindered phenol oxidation
inhibitor and/or the diarylamine oxidation inhibitor.
Other Additives
[0069] The lubricating oil composition of the invention can further
contain a basic nitrogen-containing compound oxymolybdenum complex.
Preferred examples of the basic nitrogen-containing
compound-oxymolybdenum complex include an oxymolybdenum complex of
succinimide and an oxymolybdenum complex of carboxylamide.
[0070] The basic nitrogen-containing compound-oxymolybdenum complex
can be prepared by the following process:
[0071] an acidic molybdenum compound or its salt is caused to react
with a basic nitrogen-containing compound such as succinimide,
carboxylamide, hydrocarbyl monoamine, hydrocarbyl polyamine,
Mannich base, phosphonamide, thiophosphonamide, phosphoramide and a
dispersant-type viscosity index improver (or a mixture thereof) at
a temperature of 120.degree. C. or lower.
[0072] The lubricating oil composition of the invention may contain
zinc dihydrocarbylditiophosphate or zinc dihydrocarbylphosphate
both of which are known as multi-functional additives having an
oxidation inhibition function and a friction reducing function.
These additives can be incorporated into the lubricating oil
composition in an amount of not more than 0.12 wt. % (in terms of
phosphor content), preferably in the range of 0.01 to 0.12, more
preferably in the range of 0.01 to 0.08.
[0073] As the zinc dihydrocarbyldithiophosphate, a zinc
dialkyldithiophosphate having a primary or secondary alkyl group is
used. From the viewpoint of anti-wear function, preferred is a zinc
dialkyldithiophosphate having a secondary alkyl group which is
derived from a secondary alcohol having 3 to 18 carbon atoms. In
contrast, a zinc dialkyldithiophosphate having a primary alkyl
group which is derived from a primary alcohol having 3 to 18 carbon
atoms is advantageous in its excellent heat resistance and friction
reducing function. The zinc dialkyldithiophosphate having a
secondary alkyl group and the zinc dialkyldithiophosphate having a
primary alkyl group can be used in combination. A zinc
dialkyldithiophosphate having a primary alkyl group and a secondary
alkyl group which can be obtained using a mixture of a primary
alcohol and a secondary alcohol can also be favorably employed.
[0074] In addition, a zinc dialkylaryldithiophosphate (e.g., zinc
dialkylaryldithiophosphate obtainable using dodecylphenol) can be
employed.
[0075] A zinc dihydrocarbylphosphate can be employed in place, of
the zinc dihyrocarbyldithiophosphate. The former zinc
dihydrocarbylphosphate may be advantageous from the viewpoint of
minimizing sulfur content, because it contains no sulfur atoms.
[0076] In combination with the basic nitrogen-containing
compound-oxymolybdenum complex, other molybdenum-containing
compounds can be used. Examples of the molybdenum-containing
compounds include sulfurized oxymolybdenum dithiocarbamate and
sulfurized oxymolybdenum dithiophosphate.
[0077] The lubricating oil composition of the invention may further
contain an alkali metal borate hydrate for increasing stability at
a high temperature and a basic number. The alkali metal borate
hydrate can be contained in an amount of 5 wt. % or less,
particularly 0.01 to 5 wt. %. Some alkali metal borate hydrates:
contain an ash component and a sulfur component. Therefore, the
alkali metal borate hydrate can be used in an appropriate amount in
consideration of the composition of the resulting lubricating oil
composition.
[0078] The lubricating oil composition of the invention preferably
contains a viscosity index improver in an amount of 20 wt. % or
less, preferably 1 to 20 wt. %. Examples of the viscosity index
improvers are polymers such as polyalkyl methacrylate,
ethylene-propylene copolymer, styrene-butadiene copolymer, and
polyisobutylene. A dispersant viscosity index improver and a
multi-functional viscosity index improver which are produced by
providing dispersant properties to the above-mentioned polymer are
preferably employed. The viscosity index improvers, can be used
singly or in combination.
[0079] The lubricating oil composition of the invention may further
contain a small amount of various auxiliary additives. Examples of
the auxiliary additives are described below:
[0080] zinc dithiocarbamate or methylenebis(dibutyl
dithiocarbamate) as an oxidation inhibitor or a wear inhibitor; an
oil soluble copper compound; sulfur compounds (e.g., olefin
sulfide, sulfurized ester, and polysulfide); organic amide,
compounds (e.g., oleylamide), phosphor-containing esters (e.g.,
phosphoric acid ester, thiophosphoric acid ester, dithiophosphoric
acid ester, and phosphorous acid ester); benzotriazol compounds and
thiadiazol compounds functioning as metal deactivating agent;
nonionic polyoxyalkylene surface active agents such as
polyoxyethylenealkylphenyl ether and copolymers of ethylene oxide
and propylene oxide functioning as anti-rust agent and
anti-emulsifying agent; a variety of amines, amides, amine salts,
their derivatives, aliphatic esters of polyhydric alcohols, and
their derivatives which function as friction modifiers; and various
compounds functioning as anti-foaming agents and pour point
depressants.
[0081] The auxiliary additives can be preferably incorporated into
the lubricating oil composition in an amount of 3 wt % or less
(particularly, 0.001 to 3 wt. %).
[0082] The lubricating oil composition of the invention is
preferably formulated to give a multi-grade engine oil of a
relatively low viscosity, such as 0W20, 0W30, 0W40, 5W20, 5W30,
5W40, 10W20, or 10W30 (SAE viscosity grade), by incorporating a
viscosity index improver, from the viewpoint of fuel economy.
EXAMPLES
[0083] The invention is further illustrated by the following
examples, which are not to be considered as limitative of its
scope.
Example 1
(1) Preparation of Lubricating Oil Composition
[0084] A lubricating oil composition of the invention having an SAE
viscosity grade of 5W20 was prepared using the following additives
and base oil.
(2) Additives
--Nitrogen-Containing Ashless Dispersant
[0085] 1) Bis-succinimide dispersant-1 (weight average molecular
weight: 12,800 (GPC analysis, value as molecular weight
corresponding to polystyrene), nitrogen content: 1.0 wt. %,
chlorine content: 30 wt. ppm., prepared by the steps of thermally
reacting a highly reactive polyisobutene having a number average
molecular weight of approx. 2,300 (containing at least approx. 50%
of methylvinylidene structure) with maleic anhydride to give
polyisobutenylsuccinic anhydride, reacting the
polyisobutenylsuccinic anhydride with polyalkylenepolyamine having
an average nitrogen atoms of 6.5 (per one molecule) to give a
bis-succinimide, and reacting the bis-succinimide with ethylene
carbonate): 0.05 wt. % (in terms of nitrogen content)
[0086] 2) Bis-succinimide dispersant-2 (weight average molecular
weight: 5,100, nitrogen content: 1.95 wt. %, boron content: 0.66
wt. %, chlorine content: less than 5 wt. ppm., prepared by the
steps of thermally reacting a highly reactive polyisobutene having
a number average molecular weight of approx. 1,300 (containing at
least approx. 50% of methylvinylidene structure) with maleic
anhydride to give polyisobutenylsuccinic anhydride, reacting the
polyisobutenylsuccinic anhydride with polyalkylenepolyamine haying
an average nitrogen atoms of 6.5 (per one molecule) to give a
bis-succinimide, and reacting the bis-succinimide with boric acid):
0.01 wt. % (in terms of nitrogen content)
--Alkaline Earth Metal-Containing Detergent
[0087] 1) calcium salicylate (Ca: 6.3 wt. %, S: 0.1 wt. %, TBN: 17
mgKOH/g): 0.23 wt. % (in terms of Ca content)
[0088] 2) calcium salicylate (Ca: 11.4 wt. %, S: 0.2 wt. %, TBN:
320 mgKOH/g): 0.008 wt. % (in terms of Ca content)
[0089] 3) calcium sulfonate (Ca: 2.4 wt. %, S: 2.9 wt. %, TBN: 17
mgKOH/g): 0.02 wt. % (in terms of Ca content)
--Oxidation Inhibitor
[0090] 1) Amine, oxidation inhibitor (dialkyldiphenylamine having a
mixture of C.sub.4 and C.sub.8 alkyl groups, N: 4.6 wt. %, TBN: 180
mgKOH/g): 1.1 wt. %
[0091] 2) Phenolic oxidation inhibitor (octyl
3-(3,5-di-tbutyl-4-hydroxyphenyl)propionate): 0.2 wt. %
--Basic Nitrogen-Containing Compound-Oxymolybdenum Complex
[0092] oxymolybderium complex of succinimide (containing sulfur,
Mo: 5.5 wt. %, S: 0.2 wt. %, N: 1.6 wt. %, TBN: 10 mgKOH/g, OLOA
17502 available from Chevron Japan Co., Ltd.: 0.4 wt. %
--Zinc Dithiophosphate
[0093] Zinc dialkyldithiophosphate (P: 7.2 wt. %, Zn: 7.8 wt. %, S:
14 wt. %, prepared by using a secondary alcohol haying 3 to 8
carbon atoms: 0.077 wt. % (in terms of P content)
--Friction Modifier
[0094] A salt of oleic acid and stearylamine (acid value: 98
mgKOH/g, amine value: 108 mgKOH/g): 0.6 wt. %
--Viscosity Index Improver
[0095] Non-dispersant ethylene-propylene copolymer viscosity index
improver: 1.5 wt. %
--Pour Point Depressant
[0096] Polymethacrylate pour point depressant: 0.3 wt. %
(3) Base Oil (Residual Amount)
[0097] Mixture of 50 weight parts of hydrocracked mineral oil-1
(kinematic viscosity at 100.degree. C.: 6.3 mm.sup.2/s, viscosity
index: 132, evaporation loss (ASTM D5800): 5.6 wt. %, sulfur
content: less than 0.001 wt. %, saturated component content: 92 wt.
%, aromatic component content: 8 wt. %) and 50 weight parts of
hydrocracked mineral oil-2 (kinematic viscosity at 100.degree. C.:
4.1 mm.sup.2/s, viscosity index: 127, evaporation loss (ASTM
D5800): 14 wt. %, sulfur content: less than 0.001 wt. %, saturated
component content: 92 wt. %, aromatic component content: 8 wt.
%)
Comparison Example 1
(1) Preparation of Lubricating Oil Composition
[0098] The procedures of Example 1 were repeated, except that the
friction modifier is not used, to give a lubricating oil
composition for comparison.
Comparison Example 2
(1) Preparation of Lubricating Oil Composition
[0099] The procedures of Example 1 were repeated except that the
friction modifier was replaced with the same amount (0.6 wt. %) of
a fatty acid (oleic acid), to give a lubricating, oil composition
for comparison.
Comparison Example 3
(1) Preparation of Lubricating Oil Composition
[0100] The procedures of Example 1 were repeated except that the
friction modifier was replaced with the same amount (0.6 wt. %) of
a fatty amine (stearyl amine), to give a lubricating oil
composition for comparison.
Comparison Example 4
(1) Preparation of Lubricating Oil Composition
[0101] The procedures of Example 1 were repeated except that the
friction modifier was replaced with the same amount (0.6 wt. %) of
a fatty acid ester (glycerol monooleate), to give a lubricating oil
composition for comparison.
Comparison Example 5
(1) Preparation of Lubricating Oil Composition
[0102] The procedures of Example 1 were repeated except that the
friction modifier was replaced with the 1.1 wt. % of sulfurized
oxymolybdenum dithiocarbamate (MoDTC, Mo: 4.5 wt. %, S: 4.7 wt. %),
to give a lubricating oil composition for comparison.
Characteristics of Lubrication Oil Compositions
[0103] The characteristics of the lubricating oil compositions
obtained in Example 1 and Comparison Examples 1 to 5 are set forth
in Table 1.
TABLE-US-00001 TABLE 1 Example Comparison Example 1 1 2 3 4 5
Sulfated 1.0 1.0 1.0 1.0 1.0 1.0 ash N 0.14 0.12 0.12 0.16 0.12
0.13 Ca 0.26 0.26 0.26 0.26 0.26 0.26 P 0.08 0.08 0.08 0.08 0.08
0.08 S 0.20 0.20 0.20 0.20 0.20 0.27 TBN 10.4 9.8 9.8 10.9 9.8 9.9
Remarks: Sulfated ash, N, Ca, P, S: wt. % TBN (ASTM D-2896): mg
KOH/g
Evaluation of Lubricating Oil Composition:
(1) HFRR Friction Test (Friction Test in the Presence of Dispersed
Carbon Black)
[0104] In order to simulate soot emigration in a diesel engine oil,
carbon black (mean particle diameter: 22 nm, specific surface area:
134 m.sup.2/g, carbon particles produced by incomplete combustion
of fuel) in an amount of 0 wt. %, 1 wt. %, or 2 wt. %) was blended
in the lubricating oil composition by means of a high speed
agitator to give a test oil. The test oil containing carbon black
was then subjected to the HFRR test by means of a HFRR tester under
the conditions of 105.degree. C. for oil temperature, 400 g of
load, 1,000 .mu.m for friction length, 20 Hz for frequency of
reciprocating motion, and one hour for test period, to determine a
friction coefficient. The results are set forth in Table 2.
(2) High Temperature Corrosion Test (ASTM D6594)
[0105] The corrosion of non-iron metal by the diesel engine oil was
evaluated. The test was carried out by introducing air into the
test oil containing copper, lead, and phosphor bronze at
135.degree. C. (oil temperature) for 168 hours. The amount of
copper, lead and tin having been dissolved in the test oil was
measured. The test results and criteria are set forth in Table
2.
TABLE-US-00002 TABLE 2 Example Comparison Example 1 1 2 3 4 5 (1)
HFRR Friction test Amount (wt. %) of Carbon black 0 0.088 0.139
0.084 0.134 0.115 0.057 1 0.098 0.142 0.112 0.127 0.121 0.102 2
0.096 0.145 0.117 0.130 0.123 0.112 (2) High temperature corrosion
test (ppm by weight) Cu 18 -- 4 44 -- -- Pb 54 -- 401 43 -- -- Sn 0
-- 0 0 -- -- Remarks: Criteria for acceptable oil according to JASO
M355: Cu: .ltoreq.20, Pb: .ltoreq.100, Sn: .ltoreq.50
[0106] The results set forth in Tables 1 and 2 indicate that a
lubricating oil composition of the invention containing a
metal-containing detergent comprising an alkaline earth metal,
alkyl salicylate and a neutral salt of a fatty acid and a fatty
amine shows satisfactory friction reduction regardless of a low
sulfated ash content, a low sulfur content and a low phosphorus
content even in the case that soots migrated into the lubricating
oil composition.
* * * * *