Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
Title of Invention
LUBRICANT OIL COMPOSITION FOR INTERNAL COMBUSTION ENGINE
Technical Field
[0001]
The present invention relates to a fuel-efficient
lubricant oil composition for internal combustion engines.
Background Art
[0002]
The trend for improving the fuel efficiency of
automobiles since the wake of the oil crisis remains an
important issue in light of resource protection and
environmental protection, and the need for improved fuel
efficiency has been higher. The conventional approach for
improving the fuel efficiency of automobiles includes vehicle
weight reduction, improvement of engine combustion, and
reduction of friction in engines and the drive train. Low
engine friction is achieved through improving the valve train
mechanism, reducing the surface roughness of sliding members,
and using a fuel-efficient lubricant oil composition for
internal combustion engines (engine oil).
Among them, the use of a fuel-efficient engine oil is
gaining the acceptance in the market because of its high cost
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effectiveness. As an effort to achieve high fuel efficiency
through engine oil, there have been studies of low-viscosity
oils directed to reducing a frictional loss under fluid
lubricating conditions of components such as pistons and
bearing portions. There is also proposed adding a friction
modifier such as an organic molybdenum compound to reduce a
frictional loss in the mixed or boundary lubrication of
components such as the valve train.
Various such fuel-efficient engine oils have been
proposed. For example, PTL 1 proposes an engine oil
composition in which specific additives (e.g., an alkali earth
metal salicylate-based detergent, and a molybdenum
dithiocarbamate-based friction modifier) are added in
specific amounts in a base oil having a kinematic viscosity
at 100 C of 2 to 8 mm2/s and containing 15 mass% of aromatic.
PTL 2 proposes a lubricant oil composition for internal
combustion engines in which a molybdenum-based friction
modifier or an ester- or amine-based ashless friction modifier,
and overbased Ca salicylate are mixed in a lubricant oil base
oil containing an ester-based lubricant oil base oil having
a kinematic viscosity at 100 C of 3 to 8 mm2/s. PTL 3 proposes
a lubricant oil composition for internal combustion engines
in which oxymolybdenum dithiocarbamate sulfide is combined
with ashless friction modifiers such as acid amide compounds,
aliphatic partial ester compounds, and/or aliphatic amine
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compounds.
[0003]
However, a problem of the molybdenum-based friction
modifier is that increasing its content produces only a limited
friction reducing effect. There is also a stability problem
due to formation of precipitates. Another drawback is that
use of the molybdenum-based friction modifier with ester- or
amine-based ashless friction modifiers hardly improves the
friction reducing effect. In today's environment where the
demand for more fuel efficient lubricants continues to increase,
the conventional engine oils are insufficient in terms of fuel
efficiency.
On the other hand, sarcosine and aspartic acid
derivatives are known examples of ashless friction modifiers
(for example, PTL 4 to 6). However, adding of these modifiers
in a lubricant oil composition for internal combustion engines,
and a synergistic effect on reducing friction by using these
modifiers with molybdenum-based friction modifiers have not
been known. Such an effect also has not been anticipated by
a skilled artisan.
Citation List
Patent Literature
[0004]
PTL 1: JP-A-8-302378
PTL 2: JP-A-2005-41998
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PTL 3: JP-A-2008-106199
PTL 4: JP-A-9-316475
PTL 5: JP-A-2008-179669
PTL 6: JP-A-2005-290181
Summary of Invention
Technical Problem
[0005]
The present invention is intended to provide a solution
to the foregoing problems, and it is an object of the present
invention to provide a lubricant oil composition for internal
combustion engines with which further reduction of friction
can be achieved to provide excellent fuel efficiency.
Solution to Problem
[0006]
The present invention is a lubricant oil composition for
internal combustion engines, the lubricant oil composition
comprising:
(A) a lubricant oil base oil having a kinematic viscosity
at 100 C of 2.0 to 5.0 mm2/s;
(B) a molybdenum-based friction modifier in an amount
of 0.005 to 0.2 mass% in terms of the mass of the molybdenum
relative to the total mass of the composition;
(C) a metal-based detergent in an amount of 0.01 to I
mass% in terms of the mass of the metal relative to the total
mass of the composition; and
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(D) 0.01 to 10 mass% of at least one compound selected
from amino acids having a 06-24 alkyl, alkenyl, or acyl group,
and/or derivatives of the amino acids.
[0007]
It is preferable that the (C) metal-based detergent
contains at least a salicylate-based detergent. It is
preferable that the lubricant oil composition for internal
combustion engines has a kinematic viscosity at 1000C of 4.0
to 12.5 mm2/s. It is preferable that the lubricant oil
composition for internal combustion engines further comprises
zinc dialkyl dithiophosphate (ZnDTP) in an amount of 0.02 to
0.2 mass% in terms of the mass of the phosphorus relative to
the total mass of the composition.
Advantageous Effects of Invention
[0008]
The lubricant oil composition for internal combustion
engines of the present invention has notable effects, including
low frictional coefficient, and excellent fuel-efficient
performance.
Description of Embodiments
[0009]
(A) Lubricant Oil Base Oil
The lubricant oil base oil of the present invention is
not particularly limited, as long as it is a lubricant oil base
oil having a kinematic viscosity at 1000C of 2.0 to 5.0 mm2/s.
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Any lubricant oil base oil, regardless of mineral or synthetic,
which is used with a lubricant oil composition for common
internal combustion engines may be used.
The kinematic viscosity at 10000 of the lubricant oil
base oil is preferably 2.5 to 4.5 mm2/s, more preferably 3.0
mm2/s or more, further preferably 3.5 mm2/s or more.
When the kinematic viscosity at 10000 is less than 2.0
mm2/S, oil film formation at lubricating portions becomes
insufficient, the lubricity suffers, and the evaporative loss
of the lubricant oil base oil increases. On the other hand,
a kinematic viscosity above 5.0 mm2/s lowers the fuel-efficient
effect, and the viscosity characteristics at low temperature
deteriorate.
As used herein, "kinematic viscosity at 100 C" means a
kinematic viscosity at 100 04as defined by ASTM D-445 standards.
[0010]
The lubricant oil base oil of the present invention has
a viscosity index of preferably 90 or more, more preferably
100 or more. A viscosity index of abase oil below 90 increases
the low-temperature viscosity, and may cause poor starting
performance. As used herein, "viscosity index" means a
viscosity index measured according to JIS K2283-1993.
[0011]
The lubricant oil base oil of the present invention may
be a mineral oil-based base oil or a synthetic base oil, or
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a mixture of two or more mineral oil-based base oils, or a
mixture of two or more synthetic base oils, or may be a mixture
of a mineral oil-based base oil and a synthetic base oil, as
long as the foregoing physical properties for the lubricant
oil base oil are satisfied. The two or more base oils in the
mixture may have any desired mixture ratio.
The mineral oil-based base oil may be, for example, a
paraffin-based lubricant oil base oil or a naphthene-based
lubricant oil base oil obtained after a lubricant oil fraction
from the atmospheric distillation and vacuum distillation of
crude oil is purified by using an appropriate combination of
purification processes such as solvent deasphalting, solvent
extraction, hydrocracking, solvent dewaxing, catalytic
dewaxing, hydrorefining, sulfuric acid treatment, and clay
treatment.
[0012]
Example of the synthetic base oil include poly-a-olefins
(for example, such as polybutene, 1-octene oligomer, 1-decene
oligomer, and ethylene-propylene oligomer) or hydrides
thereof, isobutene oligomers or hydrides thereof, isoparaffin,
alkylbenzene, alkylnaphthalene, diesters (for example, such
as dibutyl maleate, ditridecyl
glutarate,
di-2-ethylhexyladipate,
diisodecyladipate,
ditridecyladipate, and di-2-ethylhexylsebacate), copolymers
of a-olefins and diesters, polyolesters (for example, such as
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trimethylolpropane caprylate, trimethylolpropane pelargonate,
pentaerythrito1-2-ethylhexanoate, and pentaerythritol
pelargonate) , dialkyl diphenyl ether, and polyphenyl ether.
[0013]
When the lubricant oil base oil of the present invention
is a mineral oil-based base oil, the lubricant oil base oil
has a saturated hydrocarbon content of preferably 90% or more.
As used herein, "saturated hydrocarbon content" means a
measured value according to ASTM D-2007.
The base oil is preferably selected from those that fall
under group III or higher categories in the Base Stock
Categories of API (American Petroleum Institute) , or from base
oils obtained through isomerization of waxes.
The producing process of the base oil is not particularly
limited. Preferably, the base oil is produced by
desulfurization and hydrocracking of an atmospheric residual
oil obtained through atmospheric distillation of crude oil,
followed by fractionation of the resulting oil into a set
viscosity grade, or by solvent dewaxing or catalytic dewaxing
of the residual oil, and, as required, solvent extraction and
hydrogenation. Among them, the base oil is preferably
obtained through catalytic dewaxing.
[0014]
In recent years, the lubricant oil base oil also includes
petroleum-based wax isomerized lubricant oil base oils, which
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are produced by hydrogen isomerization of by-product
petroleum-based wax from a dewaxing process, wherein the
dewaxing process is one part of producing processes of a base
oil including further vacuum distillation of an atmospheric
distillation residual oil and fractionation into the desired
viscosity grade, subsequent processes such as solvent
purification and hydrorefining, and further subsequent
solvent dewaxing; and also includes GTL-based wax isomerized
lubricant oil base oils produced through isomerization of a
GTL WAX (gas-to-liquid wax) produced by using techniques such
as the Fischer-Tropsch process. The producing process of the
wax isomerized lubricant oil base oil, in this case, is
basically the same as the producing process of the hydrocracked
base oil.
[0015]
The %CA of the base oil is not particularly limited, but
is preferably less than 3, more preferably 2 or less, further
preferably 1 or less, most preferably substantially O. With
a %CA above 10, improvement of heat resistance, one of the
objectives of the present invention, becomes insufficient.
Here, "%C" is a value measured by using a method (n-d-M
ring analysis) according to ASTM D3238-85.
[0016]
The sulfur content in the base oil is not particularly
limited, but is preferably 0.03 mass% or less, more preferably
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0.01 mass% or less. Particularly preferably, the base oil is
substantially sulfur free. Lower sulfur contents mean higher
purity, and a less likelihood of causing the sludge solubility
problem.
The method used to measure sulfur content is not
particularly limited. Typically, for example, the JIS
K2541-1996 method is used.
[0017]
(B) Molybdenum-Based Friction Modifier
Examples of the molybdenum-based friction modifier of
the present invention include molybdenum dithiocarbamate
(MoDTC), and molybdenum dithiophosphate (MoDTP). Specific
examples of the molybdenum dithiocarbamate include the
compounds represented by the following general formula (1).
Specific examples of the molybdenum dithiophosphate include
the compounds represented by the following general formula (2).
[0018]
[Chem. 1]
R1 3
M020aSb C¨N (1)
\
R2' R4
[0019]
[Chem. 2]
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R OR7
N
M020aSd P (2)
N.P \
R60/
S OR8
[0020]
In general formulae (1) and (2), R1 to R8 each
independently represent C1-24 hydrocarbon groups, a, b, c, and
d each independently represent any one of integers of 0 to 4,
which satisfies a + b = 4, and c + d = 4.
[0021]
Preferred examples of the C1-24 hydrocarbon groups
represented by Rl to R8 in general formulae (1) and (2) each
independently include linear or branched C1-24 alkyl groups,
C5-13 cycloalkyl groups or linear or branched C5-13
alkylcycloalkyl groups, linear or branched C3-24 alkenyl groups,
C6-18 aryl groups or linear or branched C6-18 alkylaryl groups,
and C7_19 arylalkyl groups. The alkyl groups and the alkenyl
groups may be primary, secondary, or tertiary.
[0022]
Other preferred examples of the molybdenum-based
friction modifier in the lubricant oil composition of the
present invention include organic molybdenum complexes as
reaction products of basic nitrogen compounds such as
succinimide, acidic molybdenum compounds such as molybdenum
trioxide, and sulfur compounds such as hydrogen sulfide and
phosphorus pentasulfide.
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[0023]
The content of the molybdenum-based friction modifier
in the lubricant oil composition of the present invention is
0.005 mass% to 0.2 mass%, preferably 0.01 mass% or more in terms
of the mass of the molybdenum element relative to the total
mass of the composition. A notable fuel-efficient effect
cannot be obtained when the content of the molybdenum-based
friction modifier is less than 0.005 mass% in terms of the mass
of the molybdenum element. On the other hand, with a
molybdenum-based friction modifier content exceeding 0.2
mass% in terms of the mass of the molybdenum element, the extra
content does not provide a proportional improvement in the
fuel-efficient effect. These contents should thus be avoided.
[0024]
The lubricant oil composition of the present invention
can preferably use molybdenum dithiophosphate and molybdenum
dithiocarbamate. However, it is particularly preferable to
use molybdenum dithiocarbamate because it can greatly improve
the fuel-efficient performance from low temperature to high
temperature in synergy with other components.
[0025]
(C) Metal-Based Detergent
The metal-based detergent of the present invention may
be any of compounds commonly used for lubricants. For example,
overbased compounds of oil-soluble metal salts having a linear
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or branched hydrocarbon group, and an OH group and/or a carbonyl
group may be used. It is also possible to use overbased metal
salts such as alkali earth metal sulfonate, alkali earth metal
carboxylate, alkali earth metal salicylate, alkali earth metal
phenate, and alkali earth metal phosphonate; and overbased
metal salts obtained through reaction of alkali earth metal
hydroxide or oxide, and, as required, boric acid or boric
anhydride. Examples of the alkali earth metal include
magnesium, calcium, and barium, of which calcium is preferred.
More preferred for use as the overbased metal salts are
oil-soluble metal salts of OH group- and/or carbonyl
group-containing compounds overbased with alkali earth metal
borate or alkali earth metal carbonate. For fuel efficiency,
it is preferable to use alkali earth metal salicylate, more
preferably alkali earth metal salicylate overbased with alkali
earth metal borate.
[0026]
The metal-based detergent of the present invention
preferably has a base number of 50 mgKOH/g or more, more
preferably 100 mgKOH/g or more, further preferably 120 mgKOH/g
or more, particularly preferably 140 mgKOH/g or more. The base
number is preferably 300 mgKOH/g or less, more preferably 200
mgKOH/g or less. With a base number of less than 50 mgKOH/g,
the increased viscosity decreases the fuel efficiency, and the
friction reducing effect from the addition of the metal-based
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detergent tends to become insufficient. With a base number
above 300 mgKOH/g, it tends to inhibit the effects of other
components such as an antiwear additive, and the friction
reducing effect tends to become insufficient. As used herein,
"base number" is a measured value according to JIS K 2501 5.2.3.
[0027]
The metal-based detergent used in the present invention
may be produced by using any method. For example, the
metal-based detergent can be obtained through reaction of the
oil-soluble metal salt, alkali earth metal hydroxide or oxide,
and, as required, boric acid or boric anhydride at 20 to 200 C
for 2 to 8 hours in the presence of water, an alcohol (such
as methanol, ethanol, propanol, and butanol) , and a dilute
solvent (such as benzene, toluene, and xylene) , followed by
heating at 100 to 200 C, and removal of water, and, as required,
the alcohol and the dilute solvent. Specific reaction
conditions are appropriately selected according to such
factors as the type of the raw material, and the amount of the
reactant. For details of the producing process, see, for
example, JP-A-60-116688, and JP-A-61-204298. The oil-soluble
metal salt overbased with alkali earth metal borate produced
as above has a total base number of typically 100 mgKOH/g or
more, and can preferably be used for the lubricant oil
composition of the present invention.
[0028]
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The metal-based detergent of the present invention has
a metal ratio of preferably 4.0 or less, more preferably 3.0
or less, further preferably 2.0 or less. A metal ratio above
4.0 has the possibility of reducing the friction torque, and
specifically, the fuel efficiency may become insufficient.
The metal ratio of the metal-based detergent is adjusted to
preferably 1.0 or more, more preferably 1.1 or more, further
preferably 1.5 or more. With a metal ratio of less than 1.0,
the kinematic viscosity and the low-temperature viscosity of
the lubricant oil composition for internal combustion engines
increase, and may cause problems in fuel efficiency or starting
performance.
As used herein, "metal ratio" is represented by metallic
element valency x metallic element content (mol%) /soap group
content (mol%) in the metal-based detergent. The metallic
element includes calcium, and magnesium. The soap group
includes a sulfonic acid group, a phenol group, and a salicylic
acid group.
[0029]
The linear or branched hydrocarbon group of the
metal-based detergent of the present invention is preferably
an alkyl group or an alkenyl group. The alkyl or alkenyl group
has preferably 8 or more carbon atoms, more preferably 10 or
more carbon atoms, further preferably 12 or more carbon atoms.
The number of carbon atoms is preferably at most 19. Sufficient
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oil solubility cannot be obtained with less than 8 carbon atoms
which is not preferable. The alkyl or alkenyl group may be
linear or branched, and is preferably linear. The alkyl or
alkenyl group may be primary alkyl or alkenyl group, secondary
alkyl or alkenyl group, or tertiary alkyl or alkenyl group.
When the alkyl or alkenyl group is secondary alkyl or alkenyl
group, or tertiary alkyl or alkenyl group, branching occurs
preferably only at carbon atoms attached to an aromatic group.
[0030]
The content of the metal-based detergent is 0.01 mass%
or more, preferably 0.03 mass% or more, more preferably 0.05
mass% or more, and is 1 mass% or less, preferably 0.5 mass%
or less, more preferably 0.4 mass% or less, further preferably
0.3 mass% or less, particularly preferably 0.25 mass% or less,
most preferably 0.22 mass% or less in terms of the mass of the
metallic element relative to the total mass of the lubricant
oil composition. When the content is less than 0.01 mass%,
the friction reducing effect from the addition of the
metal-based detergent tends to become insufficient, and the
lubricant oil composition often fails to provide sufficient
fuel efficiency, heat and oxidation stability, and cleaning
performance. On the other hand, when the content exceeds 1
mass%, the friction reducing effect from the addition of the
metal-based detergent tends to become insufficient, and the
fuel efficiency of the lubricant oil composition tends to
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become insufficient.
[0031]
The content of the boron-containing metal-based
detergent is preferably 0.01 mass% or more, more preferably
0.03 mass% or more, further preferably 0.04 mass% or more,
particularly preferably 0.05 mass% or more, and is preferably
0.2 mass% or less, more preferably 0.10 mass% or less, further
preferably 0.08 mass% or less, particularly preferably 0.07
mass% or less in terms of the mass of the boron element relative
to the total mass of the lubricant oil composition. When the
content is less than 0.01 mass%, the friction reducing effect
from the addition of the metal-based detergent tends to become
insufficient, and the fuel efficiency, heat and oxidation
stability, and cleaning performance of the lubricant oil
composition tend to become insufficient. On the other hand,
when the content exceeds 0.2 mass%, the friction reducing
effect from the addition of the metal-based detergent tends
to become insufficient, and the fuel efficiency of the
lubricant oil composition tends to become insufficient.
[0032]
The boron-containing metal-based detergent has an
(MB1) / (MB2) ratio of preferably 1 or more, more preferably 2
or more, further preferably 2.5 or more, where (MB1) is the
weight of the metallic element contained in the detergent, and
(MB2) is the weight of the boron element contained in the
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detergent. An (MB1)/(MB2) ratio of less than 1 is not
preferable because it may lead to poor fuel efficiency. The
(MB1)/(MB2) ratio is preferably 20 or less, more preferably
15 or less, further preferably 10 or less, particularly
preferably 5 or less. An (MB1)/(MB2) ratio of above 20 is not
preferable because it may lead to poor fuel efficiency.
[0033]
(D) Ashless Friction Modifier
In the present invention, the ashless friction modifier
is at least one compound selected from amino acids having a
C6-24 alkyl, alkenyl, or acyl group, and/or derivatives of such
amino acids. Examples of such compounds include the compounds
represented by the following general formula (3).
[0034]
[Chem. 3]
1
R10R11 R12 0
9 ( 1 I I I
R¨N¨CH CH¨C¨X (3)
¨ n
[0035]
Herein, R9 is a C6-24 alkyl, alkenyl, or acyl group, Rl
is a C1-4 alkyl group or hydrogen, and R1' is hydrogen or a Ci-io
alkyl group. The alkyl group may be linear or branched, or
may contain a cyclic structure. The carbon atoms may be
substituted with heteroatoms, or may be modified with
functional groups such as a hydroxyl group, a carboxyl group,
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and an amino group. R3-2 is a C1-4 alkyl group or hydrogen, n
is 0 or 1, X is a functional group having active hydrogen, a
hydrocarbon having such a functional group, a metal salt or
an ethanolamine salt of such a functional group, or a methoxy
group.
[0036]
For considerations such as solubility in the base oil,
R9 in general formula (3) is more preferably an alkyl, alkenyl,
or acyl group of 11 or more carbon atoms. For considerations
such as storage stability, the number of carbon atoms is more
preferably 20 or less. From the standpoint of friction
reducing effect, the alkyl, alkenyl, or acyl group is
preferably linear. Specific examples of such alkyl, alkenyl,
and acyl groups include alkyl group such as hexyl group, heptyl
group, octyl group, nonyl group, decyl group, undecyl group,
dodecyl group, tridecyl group, tetradecyl group, pentadecyl
group, hexadecyl group, heptadecyl group, octadecyl group,
nonadecyl group, icosyl group, heneicosyl group, docosyl group,
tricosyl group, and tetracosyl group (these alkyl groups may
be linear or branched), alkenyl group such as hexenyl group,
heptenyl group, octenyl group, nonenyl group, decenyl group,
undecenyl group, dodecenyl group, tridecenyl group,
tetradecenyl group, pentadecenyl group, hexadecenyl group,
heptadecenyl group, octadecenyl group, nonadecenyl group,
icocenyl group, heneicosenyl group, docosenyl group,
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tricosenyl group, and tetracosenyl group (these alkenyl groups
may be linear or branched, and the double bond may occur at
any position), and acyl group having a ketone group at the
terminal of these alkyl or alkenyl groups.
[0037]
For considerations such as storage stability, R1 in
general formula (3) is more preferably an alkyl group of 4 or
less carbon atoms, further preferably 3 or less carbon atoms,
particularly preferably 2 or less carbon atoms.
The alkyl group represented by R11 may be linear or
branched, or may contain a cyclic structure. The carbon atoms
may be substituted with heteroatoms, or may be modified with
functional groups such as a hydroxyl group, a carboxyl group,
and an amino group. From the standpoint of friction reducing
effect and solubility in the base oil, the alkyl group is more
preferably of 2 or less carbon atoms, further preferably of
1 or less carbon atom, particularly preferably hydrogen.
For considerations such as storage stability, R12 is more
preferably alkyl group of 4 or less carbon atoms, further
preferably 3 or less carbon atoms, particularly preferably 2
or less carbon atoms, most preferably hydrogen.
[0038]
Preferred examples of the functional group with active
hydrogen represented by X in general formula (3) include a
hydroxyl group, and an amino group. The amino group is
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preferably a primary or secondary amine, particularly
preferably a primary amine. Examples of the metal salts of
the active hydrogen group include metal salts of a hydroxyl
group. Preferably, -COX in general formula (3) is a carboxyl
group.
Specific examples of the hydrocarbons having a hydroxyl
group corresponding to the functional group having active
hydrogen include: dihydric alcohols such as ethylene glycol,
propylene glycol, 1,4-butanediol, 1,2-butanediol, neopentyl
glycol, 1,6-hexanediol, 1,2-octanediol, 1,8-octanediol,
isopreneglycol, 3-methyl-1,5-pentanediol, sorbite, catechol,
resorcin, hydroquinone, bisphenol A, bisphenol F,
hydrogenated bisphenol A, hydrogenated bisphenol F, and
dimerdiol; trihydric alcohols such as glycerine,
2-(hydroxymethyl)-1,3-propanediol, 1,2,3-
butanetriol,
1,2,3-pentanetriol, 2-methyl-
1,2,3-propanetriol,
2-methyl-2,3,4-butanetriol, 2-ethyl-
1,2,3-butanetriol,
2,3,4-pentanetriol, 2,3,4-
hexanetriol,
4-propy1-3,4,5-heptanetriol,
2,4-dimethy1-2,3,4-pentanetriol, 1,2,4-
butanetriol,
1,2,4-pentanetriol, trimethylolethaner and
trimethylolpropane; tetrahydric alcohols such as
pentaerythritol, erythritol, 1,2,3,4-
pentanetetrol,
2,3,4,5-hexanetetrol, 1,2,4,5-
pentanetetrol,
1,3,4,5-hexanetetrol, diglycerin, and sorbitan; penthydric
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alcohols such as adonitol, arabitol, xylitol, and
triglycerine; hexahydric alcohols such as dipentaerythritol,
sorbitol, mannitol, iditol, inositol, dulcitol, talose, and
allose; and polyglycerines or dehydrocondensation products
thereof.
[0039]
Examples of the metals of the hydroxyl metal salts
include alkali metals, alkali earth metals, and zinc.
Examples of the alkali metals and the alkali earth metals
include sodium, potassium, magnesium, and calcium. Preferred
for improving the persistence of the frictional effect are
alkali earth metals, and zinc.
The metal salts are preferably carboxylates with a
carboxyl structure representing -COX in general formula (3).
[0040]
For considerations such as improvement of the
persistence of the frictional effect, the ashless friction
modifier of the present invention is preferably at least one
kind of compounds selected from the compounds of general
formula (3). The one kind of compounds selected from the
compounds of general formula (3) may be used alone, or as a
mixture of two or more kinds of compounds.
Preferred examples of the compounds represented by
general formula (3) include N-acyl sarcosine, particularly
N-oleoylsarcosine in which R9 is a Cnacyl group, R3. is methyl
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group, R11 is hydrogen, X is hydroxyl group, and n is 0, and
N-lauroyl-N-methyl-P-alanine in which R9 is lauroyl group (C12
acyl group) , 121 is methyl group, R11 is hydrogen, R12 is hydrogen,
X is hydroxyl group, and n is 1.
[0041]
The content of the ashless friction modifier is 0.01 to
mass%, preferably 5 mass% or less, more preferably 2 mass%
or less relative to the total mass of the composition. A
content above 10 mass% is not preferable because the extra
content does not provide a further improvement in frictional
characteristics, but results in poor storage stability. The
content is preferably 0.05 mass% or more, more preferably 0.1
mass% relative to the total mass of the composition. A content
below 0.01 mass% is not preferable because it is ineffective
at improving the frictional characteristics.
[0042]
(E) Antiwear Agent
The lubricant oil composition for internal combustion
engines of the present invention preferably contains zinc
dialkyl dithiophosphate (ZnDTP) of the following general
formula (4) as an antiwear agent, in addition to the foregoing
additives.
[0043]
[Chem. 4]
23
CA 02921209 2016-02-11
1315
R 0, 0 R
Zn (4)
R140-/PN. z \OR16
[0044]
R13 to R'6 in the general formula (4) each independently
represent hydrogen, and at least one of R13 to R16 is a linear
or branched C1-24 alkyl group. The alkyl group may be primary,
secondary, or tertiary.
In the present invention, the zinc dialkyl
dithiophosphates may be used either alone or in a combination
of two or more kinds thereof. For improved wear resistance,
it is, however, preferable to use a zinc dithiophosphoate
having a primary alkyl group (primary ZnDTP), or a zinc
dithiophosphoate having a secondary alkyl group (secondary
ZnDTP), particularly a zinc dialkyl dithiophosphate
containing secondary ZnDTP as a main component.
[0045]
The content of the zinc dialkyl dithiophosphate in the
lubricant oil composition of the present invention is
preferably 0.02 to 0.2 mass% , more preferably 0.03 to 0.1 mass%
in terms of the mass of the phosphorus content relative to the
total mass of the composition. A phosphorus content of less
than 0.02 mass% is insufficient in terms of wear resistance
and high-temperature cleaning performance. Above 0.2 mass%,
the exhaust gas catalyst causes serious catalyst poisoning,
which is not preferable.
24
CA 02921209 2016-02-11
[0046]
The lubricant oil composition for internal combustion
engines of the present invention may appropriately contain
other additives, as required, provided that the addition of
such additional components is not detrimental to the objects
of the present invention. Examples of such additives include
viscosity index improvers, pour point depressants,
antioxidants, wear inhibitors or extreme pressure agents,
friction modifiers, dispersants, anti-rusting agents,
surfactants or demulsifiers, and defoaming agents.
[0047]
The viscosity index improvers may be, for example,
non-dispersive viscosity index improvers or dispersive
viscosity index improvers. Specific examples include
non-dispersive or dispersive polymethacrylate and olefin
copolymers, polyisobutene, polystyrene, ethylene-propylene
copolymer, styrene-diene copolymer, and hydrides thereof.
The weight-average molecular weights of these agents are
typically 5,000 to 1,000,000. For improved fuel-efficient
performance, it is, however, preferable to use viscosity index
improvers having a weight-average molecular weight of 100,000
to 1,000,000, preferably 200,000 to 900,000, particularly
preferably 400,000 to 800,000. In the present invention, it
is preferable for improved fuel efficiency that the viscosity
index improver is a poly(meth)acrylate-based viscosity index
CA 02921209 2016-02-11
improver containing 30 to 90 mol% of the structure unit
represented by the following general formula (5) , 0.1 to 50
mol% of the structure unit represented by the following general
formula (6) , and a hydrocarbon main chain in a proportion of
0.18 or less.
[0048]
[Chem. 5]
_____________ C¨CH2
(5)
c=0
r,18
[0049]
[Chem. 6]
¨
R19 ¨
____________ C CH2 (6)
c=0
0-R
[0050]
In the general formula (5) , R3-7 represents hydrogen or
a methyl group, R18 represents a linear or branched hydrocarbon
group of 6 or less carbon atoms. In general formula (6) ,
represents hydrogen or a methyl group, and R2 represents a
linear or branched hydrocarbon group of 16 or more carbon atoms.
The viscosity index improver preferably has a diesel
injector PSSI (permanent shear stability index) of 30 or less.
26
CA 02921209 2016-02-11
With a PSSI of above 30, the shear stability suffers, and the
initial fuel efficiency may decrease to maintain certain levels
of kinematic viscosity or HTHS viscosity after use.
As used herein, "diesel injector PSSI" means a permanent
shear stability index of a polymer calculated with measured
data from ASTM D6278-02 (Test Method for Shear Stability of
Polymer Containing Fluids Using a European Diesel Injector
Apparatus) according to ASTM D6022-01 (Standard Practice for
Calculation of Permanent Shear Stability Index).
[0051]
Examples of the pour point depressants include
polymethacrylate-based polymers, alkylated aromatic
compounds, fumarate-vinyl acetate copolymers, and
ethylene-vinyl acetate copolymers that are compatible with the
lubricant oil base oil used.
[0052]
The detergent dispersant may be, for example,
succinimide, benzylamine, alkylpolyamine, polybuteneamine,
or modified products thereof with boron compounds or sulfur
compounds, or an alkenyl succinic acid ester.
The detergent dispersant is preferably a mono or bis
succinimide, more preferably a bis succinimide, particularly
preferably a boron-free bis succinimide.
The detergent dispersant has a molecular weight of
preferably 1000 or more, more preferably 5000 or more, further
27
CA 02921209 2016-02-11
preferably 7000 or more, even more preferably 9000 or more.
The molecular weight is preferably 30000 or less, more
preferably 25000 or less, further preferably 20000 or less.
Cleaning performance may become insufficient when the
molecular weight is 1000 or less. On the other hand, the fuel
efficiency of the engine oil composition may greatly decrease
with a molecular weight exceeding 30000.
[0053]
The content of the detergent dispersant is preferably
0.1 to 15 mass%, more preferably 0.5 to 10 mass%, further
preferably 1.0 to 8 mass% relative to the total mass of the
engine oil composition. Cleaning performance may become
insufficient when the detergent dispersant content is less than
0.1 mass% . On the other hand, the fuel efficiency of the engine
oil composition may greatly decrease with a content exceeding
15 mass%.
The N content in the detergent dispersant is preferably
0.1 or more, more preferably 0.3 or more, further preferably
0.4 or more, even more preferably 0.5 or more. The N content
is preferably 2.0 or less, more preferably 1.0 or less, further
preferably 0.8 or less. Cleaning performance may become
insufficient when the N content is 0.1 or less. On the other
hand, the fuel efficiency of the engine oil composition may
greatly decrease with the N content exceeding 2Ø
[0054]
28
CA 02921209 2016-02-11
The antioxidant may be a phenol- or amine-based compound
or any other compound, provided that it is selected from those
commonly used for lubricants.
Examples thereof include
alkylphenols such as 2,6-di-tert-buty1-4-methylphenol;
bisphenols such as
methylene-4,4-bis (2,6-di-tert-buty1-4-methylphenol) ;
naphthylamines such as phenyl-
a-naphthylamine;
dialkyldiphenylamines; and phenothiazines.
[0055]
Examples of the extreme pressure additives and the
antiwear agents include phosphorus compounds such as
phosphoric acid esters, phosphorous acid esters, and salts
thereof; and sulfur compounds such as disulfides, sulfurized
olefins, and sulfurized grease.
The anti-rusting agents may be, for example, alkenyl
succinic acid, alkenyl succinic acid ester, polyalcohol ester,
petroleum sulfonate, or dinonylnaphthalene sulfonate.
The corrosion inhibitors may be, for example,
benzotriazole-, thiadiazole-, or imidazole-based compounds.
The defoaming agents may be, for example, silicone
compounds such as dimethyl silicone, and fluorosilicone.
[0056]
These additives may be added in any amounts. Typically,
the content of the defoaming agent is 0.0005 to 0.01 mass%,
the content of the viscosity index improver is 0.05 to 20 mass%,
29
CA 02921209 2016-02-11
the content of the corrosion inhibitor is 0.005 to 0.2 mass%,
and the content of other additive is 0.05 to 10 mass% relative
to the total mass of the composition.
[0057]
The lubricant oil composition for internal combustion
engines of the present invention has a kinematic viscosity at
100 C of preferably 4.0 mm2/s or more, more preferably 6.0 mm2/s
or more, further preferably 6.1 mm2/s or more, most preferably
6.2 mm2/s or more. The kinematic viscosity at 100 C is
preferably 12.5 mm2/s or less, more preferably 9.3 rnm2 / s or less,
further preferably 8.5 mm2/s or less. As used herein,
"kinematic viscosity at 100 C" is a kinematic viscosity at 100 C
as defined by ASTM D-445. Insufficient lubricity may result
when the kinematic viscosity at 100 C is less than 4.0 mm2/s.
With a kinematic viscosity at 100 C above 12.5 mm2/s, it may
not be possible to obtain the necessary low-temperature
viscosity, and sufficient fuel-efficient performance.
[0058]
The lubricant oil composition has a kinematic viscosity
at 40 C of preferably 4 to 50 mm2/s, preferably 40 mm2/s or less,
more preferably 35 mm2/s or less. The kinematic viscosity at
40 C is preferably 15 mm2/s or more, more preferably 18 mm2/s
or more, further preferably 20 mm2/s or more, particularly
preferably 22 mm2/s or more, most preferably 25 mm2/s or more.
As used herein, "kinematic viscosity at 40 C" is a kinematic
CA 02921209 2016-02-11
viscosity at 40 C as defined by AST M D-445. Insufficient
lubricity may result when the kinematic viscosity at 40 C is
less than 4 mm2/s. With a kinematic viscosity at 40 C above
50 mm2/s, it may not be possible to obtain the necessary
low-temperature viscosity, and sufficient fuel-efficient
performance.
[0059]
The lubricant oil composition has a viscosity index of
preferably 120 to 400, more preferably 190 or more, further
preferably 200 or more, particularly preferably 230 or more,
most preferably 240 or more. With a viscosity index of less
than 120, it may become difficult to improve fuel efficiency
while maintaining the 150 C HTHS viscosity. A viscosity index
above 400 may result in poor evaporativity, and may cause
problems due to the insufficiency of the solubility of the
additives, or of compatibility with the sealant.
[0060]
In order to improve fuel efficiency while preventing the
low-viscosity problem and maintaining durability, it is
effective to increase the HTHS viscosity at 150 C (HTHS
viscosity is also known as "high-temperature high-shear
viscosity"), and to decrease the kinematic viscosity at 40 C,
kinematic viscosity at 100 C, and HTHS viscosity at 100 C. It
is, however, very difficult to satisfy all these conditions
with conventional lubricant oils.
31
CA 02921209 2016-02-11
[0061]
The lubricant oil composition has a HTHS viscosity at
100 C of preferably 5.5 mPa-s or less, more preferably 5.0 mPa-s
or less, further preferably 4.7 mPa-s or less, particularly
preferably 4.5 mPa=s or less, most preferably 4.4 mPa-s or less.
The HTHS viscosity at 100 C is preferably 3.0 mPa=s or more,
further preferably 3.5 mPa=s or more, particularly preferably
4.0 mPa=s or more, most preferably 4.1 mPa-s or more. As used
herein, "HTHS viscosity at 100 C " is a high-temperature
high-shear viscosity at 100 C as defined by ASTM D4683.
Insufficient lubricity may result when the HTHS viscosity at
100 C is less than 3.0 mPa-s. With a HTHS viscosity at 100 C
above 5.5 mPa-s, it may not be possible to obtain the necessary
low-temperature viscosity, and sufficient fuel-efficient
performance.
[0062]
The ratio of HTHS viscosity at 150 C to HTHS viscosity
at 100 C (HTHS viscosity at 150 C/HTHS viscosity at 100 C) in
the lubricant oil composition of the present invention is
preferably 0.45 or more, more preferably 0.475 or more, further
preferably 0.50, even more preferably 0.515 or more,
particularly preferably 0.53 or more. With a ratio of HTHS
viscosity at 150 C to HTHS viscosity at 100 C of less than 0.45,
it may not be possible to obtain the necessary low-temperature
viscosity, and sufficient fuel-efficient performance.
32
CA 02921209 2016-02-11
Examples
[0063]
The present invention is described below in greater
detail using Examples and Comparative Examples. However, the
present invention is not limited to the following examples.
(Examples 1 to 3, and Comparative Examples 1 to 7)
(A) Lubricant Oil Base Oil
The hydrocracked lubricant oil base oils of the following
properties were used by being mixed in the proportions shown
in Table 1.
(A-1) Kinematic viscosity at 40 C: 19.6 mm2/s; kinematic
viscosity at 100 C: 4.2 mm2/s; viscosity index: 122; sulfur
content: less than 10 ppm; %Cp: 80.7; %CN: 19.3; %CA: 0
(A-2) Kinematic viscosity at 40 C: 13 . 5 mm2/s; kinematic
viscosity at 100 C: 3.2 mm2/s; viscosity index: 112; sulfur
content: less than 10 ppm; %Cp: 72.6; %CN: 27.4; %CA: 0
[0064]
The following additives were added to the lubricant oil
base oils in the proportions shown in Table 1 to prepare
lubricant oil compositions.
(B) Molybdenum-Based Friction Modifier
Molybdenum dithiocarbamate of general formula (1) in
which Rl to R4 are C8 or C,3 alkyl group, and a and b are 2. The
molybdenum element concentration: 10 mass%; sulfur content:
11 mass%
33
CA 02921209 2016-02-11
(C) Metal-Based Detergent
(C-1) Overbased Ca salicylate
Metal ratio: 2.3; C14-18 alkyl group; Ca content: 6.2
mass%; base number: 180 mgKOH/g
(C-2) Overbased boric acid Ca salicylate
Metal ratio: 2.5; C14-18 alkyl group; Ca content: 6.8
mass%; B content: 2.7 mass%; base number: 190 mgKOH/g
(C-3) Overbased boric acid Ca salicylate
Metal ratio: 1.5; C14-28 alkyl group; Ca content: 5.0
mass%; B content: 1.8 mass%; base number: 140 mgKOH/g
[0065]
(D) Ashless Friction Modifier
(D-1) Oleoyl sarcosine
(D-2) N-Lauroyl-N-methyl-P-alanine
(D-3) N-Lauroyl sarcosine
(D-4) Oleoyl-N-methyl-P-alanine
(D-5) Alkylamine ethylene oxide adduct
(D-6) Oleylamine
(D-7) Glycerine monooleate
(D-8) Oleylamide
(D-9) Oleylurea
(E) Other Additives
(E-1) ZnDTP
Secondary alkyl group; 4 and 6 carbon atoms; Zn content:
7.8 mass%; P content: 7.2 mass%; S content: 15 mass%
34
CA 02921209 2016-02-11
(E-2) Non-dispersive PMA-based viscosity index improver (Mw
= 380,000; PSSI = 25)
(E-3) Polybutenyl succinimide
Molecular weight: 9000; N content: 0.6 mass%
(E-4) Antioxidant, defoaming agent (dimethylsilicone), and
others
[0066]
The lubricant oil compositions prepared as above were
each measured for friction torque by a motoring friction test
performed under the following conditions. The average
friction torque of each lubricant oil composition was
calculated, and percentage improvement relative to the average
friction torque of Comparative Example 1 was determined
(Percentage improvement = average friction torque of Examples
1 to 7 and Comparative Examples 2 to 7/average friction torque
of Comparative Example 1). The results (%) are presented in
Table 1, along with the physical properties of the lubricant
oil compositions.
(Test Conditions)
Test Engine : Inline 4-cylinder 1800-cc engine with
roller locker arms
Oil temperature: 100 C
Engine speed: 1000 rpm
[0067]
[Table 1]
r--1
O Example
Comparative Example
0 1 2 3 4 5 6
7 1 2 3 4 5 6 7
0>
CO Base oil (mass relative to (A-1) 70 70 70 70
70 70 70 70 70 70 70 70 70 70
.._._. the total masa of base oil) (A-2) 30 30 30 30
50 30 30 30 30 30 30 30 30 30
> Kinematic viscosity of 40 C 17.0 17.0 17.0
17.0 1 17.0 17.0 i7.0 17.0 17.0 17.0 17.0 17,0
17.0 17.0
(I) base oil (rnm2/s) 100 C 3.8 3.8 3.8 = 3.
8 3. 8 3.8 3.& 3.B 3.8 3.8 3.8 3.8 .3.8
O Viscosity index of base oil
120 120 120 120 120 120 = 120 120 120 120 120
120 120 120
cp
G (B) 0. 8 0. 8 0. 8
=0. 8 0. 8 0. 8 0, 8 0. 8 0. 8 0. 8 0. 8 0, 3 0. 3
O. 8
_
(0-1) 2.5
2.6 2.5
0'
(D=(C-2) 2. 5 2. 5
2. 5 2. 5 2. 5 2, 5 2. 5 2. 5 2. 5
(I) (0-3)
3.8 .
G (0-1) 1.0 0.6
1.0 = 1.0
(i) (0-2) = 1.0 ,
.
- .
(D (D-3) 1.0 ..
(D
Additives (D-4) _______________ 1. 0
G
. .
(mass% relative to the total (0-5), 1, 0 ,
I-'= mass of composition) (D-6)
. 1.0 P
(0-7)
1.0 1,0
1.,
(1- (0-8)
F
G'
1.0
0
CA) CD (D-9)1. 0
"
0
.
. 0
C) cn (E-1) 1.0 1.0 1,0 1.0 =
1.0 1.0 1.0 1..0 1.0 1.0 1.0 1 1.0 1.0 1.0
0 (E-2) 15.5 15.5 15.5 15.5
15, 5 15.6 15.5 16:5 16.5 15, 5 15.5
15.5 15. 5 15.5 0
1-
II (E-3) 3.5 3.5.3.5 3.5
3.5 3.5 3.5' 3.& 3. 5 3. 5 3. 5 3. 5 3.5
3.5 1 0
0
(D (5-4) 1. 1 = 1. 1 I. 1
1. 1 1. 1 1. 1 1. 1 1. 1 1. 1 1. 1 1.1 1
1 1. 1 1. 1 "
1
cn
,
G Kinematic viscosity of 40 C 3i.5 31.5 31. 5
31. 5 11. 5 31, 5 31, 5 31.5 31. 5 31, 5 31,5
31. 5 31.5 31,5 1-
1--' lubricant oil composition
rr (mrrt2/s) 100 C 8. 1 8. 1 8. 1 8. 1
8, 1 R. 1 8. 1 B. 1 8. 1 B. 1 8.1 8. 1 8. 1 8. 1
cn i
Viscosity index of lubricant oil composition 248 248 248
248 _ 248 248 248 248 248 248 248 248 248 248
ri- HTHS viscosity of I 00`t 4.7 4.'? 4.7 4.7
, 4.7 4.7 4.7 .4,7,, 4;? 4.1 4.7 4.7 , 4.7 4.7
G- lubricant oil composition (mPa=s) 150 C 2.6 2.6
2.8 2.6 2,6 2.8 2.8 2.6 2.6 2.6 2.6 2,6 = 2.6
2.6
(D
II Percentage Improvement of vs. Comp.
1.,11 1. 10 0.93 1. 81 0.2 O. 6 1. 88 0.00 -1. 14 -
3. 95 -0.11 -1. 60 -1. 14 -0, 9
co motoring friction torque (%) example 1
_______________________________________________________________________________
_________________________________ _
ili
(n
0
rh
ii
1--
0
r-1-
H.
0
G
CA 02921209 2016-02-11
reducing effect in Comparative Examples 2 to 6, in which the
molybdenum-based friction modifier was used with the ashless
friction modifier that did not contain a C6-24 hydrocarbon group,
a nitrogen atom, and a carboxyl group within the molecule. In
contrast, the lubricant oil compositions that used the ashless
friction modifier containing a C6-24 hydrocarbon group, a
nitrogen atom, and a carboxyl group within the molecule clearly
showed a friction reducing effect in synergy with the modifier.
As clearly demonstrated above, the lubricant oil composition
for internal combustion engines of the present invention has
notable effects, specifically low frictional coefficient, and
excellent fuel-efficient performance.
Industrial Applicability
[0069]
The lubricant oil composition for internal combustion
engines of the present invention can preferably be used as a
fuel-efficient engine oil for, for example, gasoline engines,
and diesel engines.
37
