Field of the Invention
[0001] The present invention relates to a lubricating oil composition of low viscosity type
for lubricating automotive engines, which shows good fuel economy. In more detail,
the invention is directed to a lubricating oil composition of a low viscosity type
for lubricating automotive engines which shows high wear inhibition performance, though
which gives good fuel economy. In particular, the lubricating oil composition of the
invention is favorably employable for lubricating a four cycle gasoline engine of
motorcycles and a diesel engine mounted on motor cars equipped with an exhaust gas
post-processing apparatus.
Background of Invention
[0002] Recently, the demand for enhancing fuel economy of automobiles has prominently increased.
As the lubricating oil compositions to be used for lubricating engines mounted in
gasoline engine-mounted automobiles and diesel engine-mounted automobiles, engine
oils of a low viscosity type giving good fuel economy have been required. At present,
a lubricating oil composition of SAE viscosity grade of 0W20 showing a high temperature-high
shear viscosity (HTHS viscosity determined at 150°C under the condition of a shear
rate of 10
6/s) of approx. 2.6 mPa·s is employed in practice.
[0003] It is noted, however, that the engine oils for four cycle gasoline engines of motorcycles
are also employed for lubricating transmission system. Therefore, increase of wear
(namely, lowering of anti-wear performance) of transmission gears and the like of
the transmission system may be problematic. In consideration of these possible troubles,
JASO T903-2006 indicates that the engine oils for four cycle gasoline engines of motor
cycles should have a HTHS viscosity (at 10
6/s) of 2.9 mPa·s or higher. It has been noted, however, that the known engine oils
of SAE viscosity grade 0W20 cannot give such high temperature-high shear viscosity.
For this reason, the conventional engine oils of low viscosity type for four cycle
gasoline engines of motorcycles only satisfy SAE viscosity grade of 10W30, 5W30 or
0W30.
[0004] As for engine oils for diesel engines mounted on motor cars equipped with a diesel
particulate filter, ACEA C1-08 & C2-08, that is, European Specifications for the engine
oils, indicate that the lower limit of the high temperature high shear viscosity (at
10
6/s) is 2.9 mPa·s s and that the upper limit of Noack evaporation loss is 13%.
[0005] Patent Publication
JP 6-306384A describes a fuel economy type-lubricating oil for internal combustion engines comprising
a mineral base oil showing a kinematic viscosity of 3-5 cST (at 100°C), a viscosity
index of 135 or higher, and a paraffin/total hydrocarbon ratio (namely, % Cp) of 90%
or more and a specific amount of an organic molybdenum compound.
[0006] Patent Publication
JP 2003-505533A describes a low-volatile fuel economy type lubricating oil composition showing NOACK
volatility of 15 wt.% or less, which comprises at least 50 wt.% of a mineral oil,
at least 95 wt.% of a saturated product and not more than 25 wt.% of naphthenes, which
shows a kinematic viscosity of 4.0-5.5 mm
2/s, a viscosity index of at least 120 and NOACK volatility of 15.5 wt.% or less, a
specific amount of a calcium-containing detergent and a specific amount of an oil-soluble
organic friction modifier.
[0007] Patent Publication
JP 2000-87070A describes an engine oil composition for four cycle engine motorcycles showing low
oil consumption and good fuel economy, which comprises a hydrocarbon base oil showing
a kinematic viscosity of 3-10 mm
2/s (at 100°C) and a viscosity index of 120 or higher or a mixed base oil containing
15 wt.% of more of the hydrocarbon base oil, a zinc dialkyldithiophosphate, a metal-containing
detergent, an ashless dispersant, a friction modifier and a viscosity index improver
(which imparts a kinematic viscosity of 9.3-16.5 mm
2/s at 100°C to the oil composition). Patent Publication
JP 2000-87070A further describes engine oil compositions of SAE viscosity grade of 10W30 and 10W40
for four cycle engine motorcycles.
Summary of the Invention
[0008] It is known that not only improvement of engine structure but also use of a lubricating
oil composition having a low viscosity is effective to increase fuel economy of automotive
engines. Therefore, as described herein before, a lubricating oil composition of SAE
viscosity grade of 0W20 showing a HTHS viscosity (at 10
6/s) of approximately 2.6 mPa·s s is employed in practice. However, since this fuel
economy type gasoline engine oil of SAE viscosity grade of 0W20 for four-wheel passenger
cars does not show a satisfactorily high HTHS viscosity, there probably raises a problem
in wear inhibition when the fuel economy type gasoline engine oil of SAE viscosity
grade of 0W20 is employed for four-cycle gasoline engines of motorcycles in which
the engine oil is also used for lubricating the transmission system.
[0009] It has been found by the study of the present inventors that a lubricating oil composition
of SAE viscosity grade of 0W20 which shows a viscosity index in the range of 200 to
240, a high HTHS viscosity (at 150°C and 10
6/s) such as 2.9 mPa·s s or higher, a Noack evaporation loss of 13% or less, and a
satisfactorily high wear inhibition can be produced by the use of a base oil showing
an extremely high viscosity index such as in the range of approximately 133 to 160
which is prepared by subjecting slack wax or synthetic wax obtained by Fischer-Tropsh
process to a hydrogenation-isomerization process, distillation and dewaxing and has
recently become available on market, as well as optimization of an additive composition
and additive contents.
[0010] The invention disclosed herein has been based on the above-mentioned finding.
[0011] It should be noted that a lubricating oil composition of SAE viscosity grade of 0W20
gives good fuel economy for the reason of a relatively low kinematic viscosity at
either a high temperature or a low temperature.
[0012] Accordingly, there is provided by the present invention a lubricating oil composition
of SAE viscosity grade 0W20 for lubricating automotive engines which comprises a base
oil and the below-described additive components and which shows a viscosity index
in the range of 200 to 240, a high temperature-high shear viscosity (i.e., HTHS viscosity)
of not less than 2.9 mPa·s s at 150°C and a Noack evaporation loss of not more than
13%:
- a) a nitrogen-containing ashless dispersant in an amount of 0.01-0.3 wt.% in terms
of nitrogen content;
- b) an alkaline earth metal-containing detergent in an amount of 0.08-0.3 wt.% in terms
of alkaline earth metal content;
- c) a phosphorus-containing wear inhibitor in an amount of 0.05-0.12 wt.% in terms
of phosphorus content;
- d) an oxidation inhibitor selected from the group consisting of amine compounds, phenol
compounds, and molybdenum compounds, in an amount of 0.01-7 wt.%, and
- e) a viscosity index improver in an amount of 0.5-20 wt.%.
[0013] In the above-described lubricating oil composition, the amounts of the additive components
are in terms of wt.% based on a total amount of the oil composition.
[0014] The lubricating oil composition of SAE viscosity grade 0W20 according to the invention
means a lubricating oil composition satisfying the viscosity property for "0W20" described
in "SAE Viscosity Grades for Engine Oils" issued (updated in 2007) by API. The high
shear viscosity means a shear viscosity determined at the shear rate of 10
6/s.
[0015] There is also provided by the invention a method of lubricating a diesel engine mounted
on motor cars equipped with an exhaust gas post-processing apparatus using a lubricating
oil composition of the invention.
[0016] The lubricating oil composition of the invention of SAE viscosity grade 0W20 shows
such a high HTHS viscosity as 2.9 m Pa·s or higher and hence shows good fuel economy
and good wear inhibition. Accordingly, the lubricating oil composition of the invention
is favorably employable for lubricating a four cycle gasoline engine of motorcycles
as well as a diesel engine of automotives equipped with an exhaust gas post-processing
apparatus.
Detailed Description of the Invention
[0017] The preferred embodiments of the lubricating oil composition according to the invention
are described below.
- (1) The lubricating oil composition shows a kinematic viscosity of not lower than
8.5 mm2/s but not higher than 9.3 mm2/s.
- (2) The base oil comprises a mineral base oil showing a kinematic viscosity in the
range of 2 to 9 mm2/s at 100°C and a viscosity index in the range of 133 to 160.
- (3) The base oil contains not less than 80 wt.% of a mineral base oil showing a kinematic
viscosity in the range of 2 to 9 mm2/s at 100°C and a viscosity index in the range of 133 to 160.
- (4) The base oil shows a viscosity index in the range of 133 to 160 and is produced
by subjecting slack wax or synthetic wax obtained by Fischer-Tropsch process to a
hydrogenation-isomerization process, distillation and dewaxing.
- (5) The base oil is a mixture of two or more base oil components having a viscosity
index of 130 or more but having a different viscosity.
- (6) The lubricating oil composition contains an organic sulfur-containing compound.
- (7) The nitrogen-containing ashless additive comprises a succinimide compound having
bis-structure.
- (8) The alkaline earth metal-containing detergent comprises an over-based calcium-containing
compound selected from the group consisting of an over-based calcium sulfonate and
an over-based calcium phenate.
- (9) The phosphorus-containing wear inhibitor comprises a phosphorus-containing compound
is selected from the group consisting of zinc dihydrocarbyldithiophosphate and zinc
dihydrocarbylphosphate.
- (10) The viscosity index improver comprises a polymethacrylate viscosity index improver.
- (11) The lubricating oil is used for lubricating motorcycles equipped with a four
cycle gasoline engine.
- (12) The lubricating oil composition is used for lubricating a diesel engine mounted
on motor cars equipped with an exhaust gas post-processing apparatus.
[0018] The base oil and additive components used for formulating the lubricating oil composition
of the invention are described below in more detail.
Base oil
[0019] The base oil of the lubricating oil composition according to the invention preferably
is a mineral oil. Alternatively, the base oil can be a mixture of a relatively large
amount (not less than 50 wt.%) of a mineral oil and a relatively small amount (less
than 50 wt.%) of a synthetic oil.
[0020] The base oil for the lubricating oil composition of the invention preferably is a
base oil (specifically a mineral oil) that has a saturated hydrocarbon content of
95 wt.% or more, particularly 98 wt.% or more, and shows a kinematic viscosity in
the range of 2 to 9 mm
2/s and a viscosity index of 133 or higher (particularly 135 or higher, further particularly
145 or higher). The preferred base oil may be a single base oil or a mixture of two
or more base oils. The preferred base oil can be mixed with a small amount of a base
oil having a different composition and showing different characteristics. However,
it is preferred that the mixture of base oils has the above-mentioned preferred composition
and shows the above-mentioned preferred characteristics.
[0021] The above-mentioned preferred base oil preferably shows an evaporation loss (according
to ASTM D5800) of 16% or less, more preferably 15% or less, further preferably 13%
or less. If the engine oil (i.e., lubricating oil composition) employs a base oil
showing a high evaporation loss, the engine oil shows high oil consumption and high
viscosity increase when the engine oil is kept at elevated temperatures. Thus, the
fuel economy decreases.
[0022] There are no specific limitations with respect to the origin of the desired base
oil. The base oil, however, preferably is a base oil having a high viscosity index
in the range of 133-160, which is produced by subjecting slack wax or synthetic wax
obtained from natural gas by Fischer-Tropsch process to a hydrogenation-isomerization
process, distillation and dewaxing, in the case that the base oil is a mineral base
oil. The above-mentioned high viscosity index base oil is preferably employed for
the preparation of the lubricating oil composition of the invention, because the base
oil shows a high kinematic viscosity at 100°C and a good low temperature viscosity
characteristic and lowers the evaporation loss of the oil composition.
[0023] The above-mentioned mineral base oil having a high viscosity index can be used in
a mixture with a synthetic oil. The synthetic oil preferably shows the above-mentioned
preferred characteristics. The preferred synthetic oil can be selected from a variety
of known synthetic oils. Examples of the known synthetic oils include esters, alkylbenzenes,
and poly-α-olefins (PAOs). Most preferred is poly- α -olefins (PAOs).
Nitrogen-containing ashless dispersant
[0024] The lubricating oil composition of the invention contains a nitrogen-containing ashless
dispersant (component (a)) in an amount of 0.01 to 0.3 wt.% in terms of nitrogen content.
The nitrogen-containing ashless dispersant preferably has a weight average molecular
weight in the range of 4,500 to 20,000. The "weight average molecular weight" used
herein means a molecular weight determined by GPC analysis (reference material: polystyrene).
[0025] Examples of the nitrogen-containing ashless dispersants include an alkenyl- or alkyl-succinimide
(wherein the alkenyl or alkyl group is derived from polyolefin) or its derivatives.
The nitrogen-containing ashless dispersant is preferably contained in the lubricating
oil composition in an amount of 0.01 to 0.3 wt.%, based on the total amount of the
lubricating oil composition. A representative succinimide dispersant can be prepared
from a succinic anhydride having a high molecular weight alkyl or alkenyl substituent
and a polyalkyleneamine containing average 4-10 nitrogen atoms, preferably 5-7 nitrogen
atoms, per one molecule. The high molecular weight alkyl or alkenyl substituent is
preferably derived from polyalkene, particularly polybutene, having a number average
molecular weight of approx. 900 to 5,000.
[0026] 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, 30 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 α -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 an 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. The succinimide can be one of mono-type, bis-type and poly-type which are
named according to the imide structure(s) contained in the succinimide molecule. The
succinimide of bis-type or poly-type can be preferably employed as the ashless dispersant
in the lubricating oil composition of the invention.
[0027] Other examples of the nitrogen-containing ashless dispersants include polymeric succinimide
dispersants derived from ethylene- α -olefin copolymer (for instance, the molecular
weight is 1,000 to 15,000), and alkenylbenzyl amine ashless dispersants.
[0028] In the lubricating oil composition of the invention, the nitrogen-containing ashless
dispersant can be replaced with a nitrogen-containing dispersant-type viscosity index
improver. As the nitrogen-containing dispersant-type 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 nitrogen-containing
olefin copolymer is advantageous.
[0029] The lubricating oil composition of the invention necessarily contains the nitrogen-containing
ashless dispersant and/or the nitrogen-containing dispersant-type viscosity index
improver. If desired, the other ashless dispersants such as an alkenylsuccinic acid
ester dispersant can be employed in combination.
Metal-containing detergent
[0030] The lubricating oil composition of the invention contains an alkaline earth metal-containing
detergent (component (b)) in an amount of 0.08 to 0.3 wt.% in terms of alkaline earth
metal content. Examples of the alkaline earth metals include calcium, barium and magnesium.
Preferred is calcium. The alkaline earth metal-containing detergent preferably is
an alkaline earth metal sulfonate or an alkaline earth metal phenate. The alkaline
earth metal sulfonate and alkaline earth metal phenate can be employed in combination.
In addition, these metal-containing detergents can be used in combination with other
metal-containing detergent such as an alkaline earth metal (particularly calcium)
salt of an alkyl-salicylate and/or an alkylcarboxylate.
[0031] As the calcium sulfonate, there are known overbased calcium sulfonates having a TBN
in the range of 150 to 500 mgKOH/g and low base number calcium sulfonates having a
TBN in the range of 5 to 60 mgKOH/g. The overbased calcium sulfonate preferably is
an overbased calcium salt of an alkylated benzenesulfonate having an alkyl group of
10 or more carbon atoms and an overbased calcium salt of an alkylated toluenesulfonate
having an alkyl group of 10 or more carbon atoms. The degree of the overbasing preferably
is in the range of 5 to 25. The low base number calcium sulfonate preferably is a
calcium salt of an alkylated benzenesulfonate or a calcium salt of an alkylated benzenesulfonate.
The alkyl group preferably contains 10 or more carbon atoms. The low base number calcium
sulfonate preferably is a neutral salt or the like (preferably having an overbasing
degree in the range of 0.1 to 1.5) having been subjected to no overbasing process.
Preferred is a combination of an overbased calcium sulfonate and a low base number
calcium sulfonate. The sulfonate can be a synthetic sulfonate or a petroleum-origin
sulfonate which is prepared by the steps of sulfonating a lubricating oil fraction
of a mineral oil and reacting it with a calcium compound. Therefore, the low base
number calcium sulfonate and/or the overbased calcium sulfonate derived from petroleum
products can also be favorably employed.
[0032] As the calcium phenates, there are known overbased sulfurized calcium phenates having
a TBN of 120-350 mgKOH/g. Preferred is an overbased sulfurized calcium phenate having
an alkyl group of 10 carbon atoms or more.
Phosphorus-containing wear inhibitor
[0033] The lubricating oil composition of the invention contains a phosphorus-containing
wear inhibitor (component (c)) in an amount of 0.05 to 0.12 wt.% in terms of phosphorus
content. The phosphorus-containing wear inhibitor preferably is zinc dihydrocarbyldithiophosphate
or a zinc dihydrocarbylphosphate, both of which are known as multifunctional lubricating
oil additives showing oxidation inhibition performance and wear inhibition performance.
[0034] The zinc dihydrocarbyldithiophosphate generally is a zinc dialkyldithiophosphate
having a primary alkyl or a secondary alkyl. From the viewpoint of anti-wear performance,
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 from a mixture of a primary alcohol
and a secondary alcohol can also be favorably employed.
[0035] In addition, a zinc dialkylaryldithiophosphate (e.g., zinc dialkylaryldithiophosphate
obtainable using dodecylphenyl) can be employed.
[0036] Otherwise, the phosphorus-containing wear inhibitor can be a phosphorus ester, a
phosphite ester, or a thiophosphate ester.
Oxidation inhibitor
[0037] The lubricating oil composition of the invention further contains at least one oxidation
inhibitor (component (d)) selected from the group consisting of phenol compounds (phenolic
oxidation inhibitors), amine compounds (amine oxidation inhibitors), and molybdenum
compounds (molybdenum oxidation inhibitors) in an amount of 0.1 to 7 wt.%.
[0038] A representative phenolic oxidation inhibitor is a hindered phenol compound, and
a representative amine oxidation inhibitor is a diarylamine compound.
[0039] The hindered phenol compound and diarylamine compound are advantageous because both
further provide high detergency at high temperatures. The diarylamine oxidation inhibitor
is particularly advantageous because it has a base number derived from the contained
nitrogen which serves to increase detergency at high temperatures. In contrast, the
hindered phenol oxidation inhibitor is effective to reduce oxidative deterioration
caused by NO
x.
[0040] 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-t-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-hydoxyphenyl)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.
[0041] Examples of the diarylamine oxidation inhibitors include alkyldiphenylamine having
a mixture of alkyl groups of 4 to 9 carbon atoms, p,p'-dioctyldiphenylamine, phenyl-1-naphthylamine,
phenyl-2-naphthylamine, alkylated N-naphthylamine, and alkylated phenyl-1-naphthylamine.
[0042] The molybdenum oxidation inhibitor can be an oxymolybdenum complex of a basic nitrogen
compound. Preferred examples of the oxymolybdenum complex of a basic nitrogen compound
include an oxymolybdenum complex of succinimide and an oxymolybdenum complex of carboxylamide.
[0043] The oxymolybdenum complex of a basic-nitrogen compound can be prepared by the following
process:
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°C or lower.
[0044] Molybdenum-containing compounds other than the above-mentioned oxymolybdenum complex
of a basic nitrogen compound can be employed in place of the oxymolybdenum complex
of a basic nitrogen compound or in combination with the oxymolybdenum complex of a
basic nitrogen compound. The above-mentioned "other molybdenum-containing compound"
can be sulfurized oxymolybdenum dithiocarbamate or sulfurized oxymolybdenum dithiophosphate.
[0045] Each of the phenolic oxidation inhibitor (particularly, hindered phenol oxidation
inhibitor), amine oxidation inhibitor (particularly, diarylamine oxidation inhibitor)
and a molybdenum oxidation inhibitor (particularly, oxymolybdenum complex of a basic
nitrogen compound) can be employed singly or in combination. If desired, other oil
soluble oxidation inhibitors can be employed in combination with the above-mentioned
oxidation inhibitor(s).
Viscosity Index Improver
[0046] The lubricating oil composition of the invention further contains a viscosity index
improver (component (e)) in an amount of 0.5 to 20 wt.%. Examples of the viscosity
index improvers include polymethacryl viscosity improvers such as polyalkyl methacrylate
and olefin copolymer viscosity index improvers such as ethylene-propylene copolymer,
styrenebutadiene copolymer, and polyisoprene. The viscosity index improvers can be
used singly or in combination.
Organic Sulfur Compound
[0047] The lubricating oil composition of the invention preferably contains an organic sulfur
compound which is effective in wear inhibition and oxidation inhibition. Examples
of the organic sulfur compounds include sulfurized olefin, sulfurized ester, sulfurized
oil/fat, polysulfide, dimercaptothiazole, dithiophosphate ester, and dithiocarbamate.
Other additives
[0048] The lubricating oil composition of the invention may further contain an alkali metal
borate hydrate for increasing high temperature detergency 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.
[0049] 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.
[0050] Zinc dithiocarbamate or methylenebis(dibutyl dithiocarbamate) as an oxidation inhibitor
or a wear inhibitor; an oil soluble copper compound; organic amide compounds (e.g.,
oleylamide); benzotriazol compounds and thiadiazol compounds functioning as metal
deactivating agent; nonionic polyoxyalkylene surface active agents such as polyoxyethylene
alkylphenyl ether and copolymers of ethylene oxide and propylene oxide functioning
as rust inhibitor 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.
[0051] 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.%).
Examples
[0052] The present invention is further described by the following illustrative non-limiting
examples.
[Examples 1, 2, Comparison Example & Reference Example]
(1) Preparation of lubricating oil composition
[0053] A lubricating oil composition of the invention (SAE viscosity grade: 0W20, High temperature
high shear viscosity: 2.9 mPa·s or higher) was prepared using the following additives
and base oil in Examples 1 and 2. In the comparison example, a lubricating oil composition
(SAE viscosity grade: 0W20, High temperature high shear viscosity: 2.6 mPa·s) was
prepared. In the reference example, a lubricating oil composition (SAE viscosity grade:
10W30, High temperature high shear viscosity: 2.9 mPa·s or higher) was prepared.
(2) Base oil
[0054] Base oil-1: a mixture of base oil (a) and base oil (b) in a weight ratio of 60:40
(base oil (a):base oil (b), viscosity index: 142; kinematic viscosity at 100°C: 4.9
mm
2/s; Noack evaporation loss: 10.1%) in which the base oil (a) was a mineral oil-origin
base oil prepared by subjecting slack wax to hydrogenation-isomerization, distillation
and dewaxing(viscosity index: 137; kinematic viscosity at 100°C: 4.1 mm
2/s; Noack evaporation loss: 13.6%) and base oil (b) was a mineral oil-origin base
oil prepared by subjecting slack wax to hydrogenation-isomerization, distillation
and dewaxing; viscosity index: 148; kinematic viscosity at 100°C: 6.6 mm
2/s, Noack evaporation loss: 5.0%).
[0055] Base oil-2: hydrocracked mineral oil (viscosity index: 128; kinematic viscosity at
100°C: 4.2 mm
2/s, Noack evaporation loss: 14.2%).
[0056] Base oil-3: a mixture of hydrocracked mineral oil (a) and hydrocracked mineral oil
(b) in a weight ratio of 73:27 (mineral oil (a):mineral oil (b); viscosity index:
115; kinematic viscosity at 100°C: 6.7 mm
2/s, Noack evaporation loss: 10.8%) in which the hydrocracked mineral oil (a) had viscosity
index: 122; kinematic viscosity at 100°C: 5.6 mm
2/s, Noack evaporation loss: 12.4%, and the hydrocracked mineral oil (b) had viscosity
index: 99; kinematic viscosity at 100°C: 10.7 mm
2/s, Noack evaporation loss: 6.0%.
[0057] Remarks: The base oil was used in an amount to give in combination with the additives
a total 100 wt.% of the lubricating oil composition.
(3) Additives
[Nitrogen-containing ashless dispersant]
[0058]
- 1) Ashless dispersant-1 (weight average molecular weight: 5,100, nitrogen content:
1.95 wt.%, boron content: 0.63 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 having an average
nitrogen atoms of 6.5 (per one molecule) to give a bis-succinimide, and reacting the
bis-succinimide with boric acid): 0.06 wt.% (in terms of nitrogen content)
- 2) Ashless dispersant-2 (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):
0.01 wt.% (in terms of nitrogen content)
[Alkaline earth metal-containing detergent]
[0059]
- 1) Overbased calcium phenate (sulfurized phenate having a C12 branched alkyl group, Ca: 9.6 wt.%, S: 3.4 wt.%, TBN: 264 mgKOH/g): 0.15 wt.% (in
terms of Ca content)
- 2) Overbased calcium sulfonate (alkyltoluene sulfonate having C20-24 alkyl group, Ca: 16.0 wt.%, S: 1.6 wt.%, TBN: 425 mgKOH/g, overbasing degree: 19):
0.07 wt.% (in terms of Ca content)
- 3) Low basic calcium sulfonate (alkylbenzene sulfonate having C14-24 alkyl group, Ca: 2.4 wt.%, S: 2.9 wt.%, TBN: 17 mgKOH/g, overbasing degree: 0.34):
0.01 wt.% (in terms of Ca content)
[Zinc dithiophosphate]
[0060] Zinc di(secondary alkyl)dithiophosphate (P: 7.2 wt.%, Zn: 7.8 wt.%, S: 14 wt.%, prepared
by using a secondary alcohol having 3 to 8 carbon atoms): 0.06 wt.% (in terms ofP
content)
[0061] Zinc di(primary alkyl)dithiophosphate (P: 7.3 wt.%, Zn: 8.4 wt.%, S: 14 wt.%, prepared
by using a primary alcohol having 8 carbon atoms): 0.03 wt.% (in terms ofP content)
[Oxidation inhibitor]
[0062] Dialkyldiphenylamine having a mixture of C
4 and C
8 alkyl groups (N: 4.6 wt.%): 0.45 wt.%
[0063] [Organic sulfur compound]-used in Example 2 only
[0064] Sulfurized isobutylene (S: 42 wt.%): 0.3 wt.%
[Viscosity index improver]
[0065] Polymethacrylate viscosity index improver (SSI=23) used in Example 1 (amount: 5.4
wt.%), Example 2 (amount: 5.5 wt.%), and Comparison Example (amount: 5.0 wt.%)
[0066] Ethylene-propylene copolymer viscosity index improver (SSI=24) used in Reference
Example (amount: 4.5 wt.%)
[Pour point depressant]
[0067] Polymethacrylate pour point depressant: 0.3 wt.%
[Auxiliary additives]
[0068] Combination of small amounts of a friction modifier, a rust inhibitor, a defoamer,
etc.: 0.6 wt.% for all examples
Evaluations of lubrication oil compositions
[0069] Each of the lubricating oil compositions was subjected to Shell Four Ball Test under
the conditions of oil temperature of 75°C, load of 40 kgf, and rotation for 60 minutes
at 1,200 rpm, to evaluate its wear inhibition property. The wear inhibition property
was evaluated by determining a wear mark formed on the surfaces of the tested balls.
[0070] Table 1 shows physical properties of the lubricating oil compositions of Examples
1, 2, Comparison Example, and Reference Example.
Table 1
|
Ex. 1 |
Ex. 2 |
Com.Ex. |
Ref.Ex. |
SAE |
0W20 |
0W20 |
0W20 |
10W30 |
Base oil |
Base oil-1 |
Base oil-1 |
Base oil-2 |
Base oil-3 |
|
|
|
|
|
HTHS |
|
|
|
|
viscosity |
2.97 |
3.00 |
2.62 |
3.15 |
|
|
|
|
|
Kinematic viscosity |
|
|
|
at 100°C at 40°C |
9.16 41.9 |
9.20 42.2 |
8.02 36.3 |
10.1 65.7 |
|
|
|
|
|
Viscosity |
|
|
|
index |
209 |
209 |
203 |
139 |
|
|
|
|
|
Cranking viscosity |
|
|
|
at -25°C |
- |
- |
- |
5815 |
at -35°C |
5854 |
5859 |
5254 |
- |
|
|
|
|
|
Pumping |
|
|
|
viscosity |
Pass |
Pass |
Pass |
Pass |
|
(-40°C) |
(-40°C) |
(-40°C) |
(-30°C) |
|
|
|
|
|
Noack evaporation |
|
|
|
loss (%) |
9.9 |
10.3 |
14.0 |
11.5 |
|
|
|
|
|
Shell wear test, Average wear |
|
|
|
diameter (mm) |
0.49 |
0.48 |
0.55 |
0.49 |
[0071] Remarks:
HTHS viscosity: viscosity (unit: mPa·s, determined at 150°C at a shear rate of 106/s.
Kinematic viscosity: unit mm2/s
Cranking viscosity: unit mPa·s
[0072] "Pass" for Pumping viscosity means that the lubricating oil composition satisfies
the pumping viscosity at -40°C which is indicated for SAE 0W20 or the pumping viscosity
at - 30°C which is indicated for SAE 10W30.
[0073] The results set forth in Table 1 indicate the following:
- (1) The lubricating oil compositions of Examples 1 and 2 according to the invention
show wear inhibition property similar to that shown by the SAE 10W30 lubricating oil
composition of Reference Example, though the lubricating oil compositions of Examples
1 and 2 are SAE 0W20 oils.
- (2) The lubricating oil composition of Comparison Example of SAE 0W20 shows high Noack
evaporation loss, low high temperature high shear viscosity, and low wear inhibition.
1. A lubricating oil composition of SAE viscosity grade 0W20 for lubricating automotive
engines which comprises a base oil and the below-described additive components and
which shows a viscosity index in the range of 200 to 240, a high temperature-high
shear viscosity of not less than 2.9 mPa·s s at 150°C and a Noack evaporation loss
of not more than 13%:
a) a nitrogen-containing ashless dispersant in an amount of 0.01-0.3 wt.% in terms
of nitrogen content;
b) an alkaline earth metal-containing detergent in an amount of 0.08-0.3 wt.% in terms
of alkaline earth metal content;
c) a phosphorus-containing wear inhibitor in an amount of 0.05-0.12 wt.% in terms
of phosphorus content;
d) an oxidation inhibitor selected from the group consisting of amine compounds, phenol
compounds, and molybdenum compounds, in an amount of 0.1-7 wt.%, and
e) a viscosity index improver in an amount of 0.5-20 wt.%,
wherein the amounts of the additive components are in terms of wt.% based on a total
amount of the lubricating oil composition.
2. The lubricating oil composition of claim 1, which shows a kinematic viscosity of
not lower than 8.5 mm2/s.
3. The lubricating oil composition of claim 1 or 2 which has a kinematic viscosity not
higher than 9.3 mm2/s.
4. The lubricating oil composition of any preceding claim 1, which comprises a base
oil containing not less than 80 wt.% of a mineral base oil showing a kinematic viscosity
in the range of 2 to 9 mm2/s at 100°C and a viscosity index in the range of 133 to 160.
5. The lubricating oil composition of claim 4, which comprises a mineral base oil showing
a kinematic viscosity in the range of 5 to 9 mm2/s at 100°C and a viscosity index in the range of 133 to 160.
6. The lubricating oil composition of any one of claims 1 to 3,, wherein the base oil
shows a viscosity index in the range of 133 to 160 and is produced by subjecting slack
wax or synthetic wax obtained by Fischer-Tropsch process to a hydrogenation-isomerization
process, distillation and dewaxing.
7. The lubricating oil composition of any one of claims 1 to 3, wherein the base oil
shows a viscosity index in the range of 133 to 160.
8. The lubricating oil composition of any one of claims 1 to 3, wherein the base oil
is produced by subjecting slack wax or synthetic wax obtained by Fischer-Tropsch process
to a hydrogenation-isomerization process, distillation and dewaxing.
10. The lubricating oil composition of any preceding claim, which contains an organic
sulfur-containing compound.
11. The lubricating oil composition of any preceding claim, which is used for lubricating
motorcycles equipped with a four cycle gasoline engine.
12. The lubricating oil composition of any one of claims 1 to 10, which is used for lubricating
a diesel engine mounted on motor cars equipped with an exhaust gas post-processing
apparatus.
13. A method of lubricating a four cycle gasoline engine of motorcycles with the lubricating
oil composition of any one of claims 1 to 10.
14. A method of lubricating a diesel engine mounted on motor cars equipped with an exhaust
gas post-processing apparatus employing the lubrication oil composition of any one
of claims 1 to 10.