Note: Descriptions are shown in the official language in which they were submitted.
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Lubricating Oil Composition
Technical Field
[0001] The present invention relates to lubricating
oil compositions with excellent insulation properties
and lubricity.
Background Art
[0002] A variety of electronic control devices have
been used in the mechanisms of an automobile. Some of
them may be used in lubricating oil and thus the
insulation properties thereof have become important.
In particular, lubricating oils for the transmission,
both the transmission and electric motor, or the device
in which a lubricating system is shared by the
transmission and electric motor, mounted in a fuel cell
electric vehicle, an electric vehicle or a hybrid
vehicle have been required to have higher insulation
properties because these devices operate using a high
electric voltage. Furthermore, in recent years, the
transmission has been required to be improved in power
transmission efficiency and down-sized as well as
weight-reduced so as to improve fuel efficiency and
thus has been applied with a higher load. The
lubricating oil has, therefore, been demanded to have
insulation properties as well as more improved
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anti-wear properties and anti-seizure properties.
[0003] In addition to the above-described
properties, the lubricating oil for transmissions are
required to have friction characteristics conforming
with the characteristics of a clutch, viscosity
characteristics ranging from low temperatures to high
temperatures so that an appropriate hydraulic pressure
control can be achieved, i.e., viscosity retention
which is not affected on temperature as much as possible,
and oxidation stability and detergent dispersibility
to keep the device clean so that the control device
thereof can operate appropriately. Furthermore,
these characteristics are generally needed to be
retained during the working life of the device. For
this purpose, a variety of additives are used in a
transmission lubricating oil.
[0004] So far, as such transmission lubricating
oils, some oils have been proposed such as an automobile
transmission oil composition comprising a base oil
selected from mineral oils, synthetic oils and mixtures
thereof and a phosphorus compound selected from
hydrocarbon group-containing zinc dithiophosphate,
triaryl phosphate, triaryl thiophosphate and a mixture
thereof in an amount of 0.1 to 15.0 percent by mass on
the total mass composition basis and having a 80 C
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volume resistivity of 1x107 0.m or greater (Patent
Literature 1) and a transmission oil composition
comprising a base oil selected from mineral oils,
poly-a-olefins and hydrogenated compounds thereof,
alkylbenzenes, ester-based compounds and mixtures
thereof and having a 80 C kinematic viscosity of 1.5
to 4.0 mm2/s, a phosphorus compound selected from
hydrocarbon group-containing zinc dithiophosphate,
triaryl thiophosphates and mixtures thereof in an
amount of 0.1 to 4.0 percent by mass on the total
composition mass basis, and an ashless dispersant and
having a 80 C volume resistivity of lx108Q.m or greater
(Patent Literature 2).
Citation List
Patent Literature
[0005] Patent Literature 1: W02002/097017
Patent Literature 2: Japanese Patent
Application Publication 2008-285682
Summary of Invention
Technical Problem
[0006] As described above, a variety of additives
are used in a transmission oil but would alone or in
combination degrade the insulation properties,
anti-wear properties or anti-seizure properties. The
present invention aims at providing a lubricating oil
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composition maintaining properties necessary for a
transmission and having more excellent insulation
properties and anti-wear properties and more improved
anti-seizure properties than the prior art.
Solution to Problem
[0007] That is, the present invention relates to a
lubricating oil composition comprising: (A) a
lubricating oil base oil; (B) at least one type of
phosphorus compound selected from the group consisting
of phosphorus compounds having at least one hydroxyl
group and/or at least one thiol group; and (C) an ashless
dispersant having a functional group containing as a
dispersion group in an amount of less than 0.001 percent
by mass on the basis of nitrogen on the total composition
mass basis or no such an ashless dispersant at all, the
composition having a 80 C volume resistivity of 5x108
Q.m or greater.
The present invention also relates to the
above-described lubricating oil composition wherein
(B) the phosphorus compound having a hydrocarbon group
having 16 or fewer carbon atoms.
The present invention also relates to the
above-described lubricating oil composition used for
the transmission, both transmission and electric motor,
or the device in which a lubricating system is shared
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,....
by the transmission and electric motor, mounted in a
fuel cell electric vehicle, an electric vehicle or a
hybrid vehicle.
Advantageous Effects of the Invention
[0008] The lubricating oil composition of the
present invention maintains properties necessary to
lubricate a transmission and other devices and has more
excellent insulation properties and anti-wear
properties than the prior art and can be improved in
anti-seizure properties.
Description of Embodiment
[0009] The present invention will be described in
more detail below.
[0010] The lubricating base oil referred to as
Component (A) used in the present invention may be a
mineral base oil and/or a synthetic base oil or
alternatively a mixture of two or more types of mineral
oils or synthetic base oils, or a mixture of a mineral
base oil and a synthetic base oil. The mix ratio in
these mixtures may be selected arbitrarily.
[0011] Examples of the mineral lubricating base oil
which may be used in the present invention include
paraffinic or naphthenic mineral base oils which can
be produced by subjecting a lubricating oil fraction
produced by atmospheric- or vacuum-distillation of a
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crude oil, to any one of or any suitable combination
of refining processes selected from solvent
deasphalting, solvent extraction, hydrocracking,
solvent dewaxing, catalytic dewaxing, hydrorefining,
sulfuric acid treatment, and clay treatment;
n-paraffins; and iso-paraffins. These base oils may
be used alone or in combination at an arbitrary ratio.
[0012] Examples
of preferred mineral lubricating
base oils include the following base oils:
(1) a distillate oil produced by atmospheric
distillation of a paraffin base crude oil and/or a mixed
base crude oil;
(2) a whole vacuum gas oil (WVGO) produced by
vacuum distillation of the topped crude of a paraffin
base crude oil and/or a mixed base crude oil;
(3) a wax produced by a lubricating oil dewaxing
process and/or a Fischer-Tropsch wax produced by a GTL
process;
(4) an oil produced by mild-hydrocracking (MHC)
one or more oils selected from oils of (1) to (3) above;
(5) a mixed oil of two or more oils selected from
(1) to (4) above;
(6) a deasphalted oil (DAD) produced by
deasphalting an oil of (1), (2) (3), (4) or (5);
(7) an oil produced by mild-hydrocracking (MHC)
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an oil of (6); and
(8) a lubricating oil produced by subjecting a
mixed oil of two or more oils selected from (1) to (7)
used as a feed stock and/or a lubricating oil fraction
recovered therefrom to a normal refining process and
further recovering a lubricating oil fraction from the
refined product.
[0013] No particular limitation is imposed on the
normal refining process used herein. Therefore, there
may be used any refining process having been
conventionally used upon production of a lubricating
base oil. Examples of the normal refining process
include (a) hydro-refining processes such as
hydrocracking and hydrofinishing, (b) solvent refining
such as furfural extraction, (c) dewaxing such as
solvent dewaxing and catalytic dewaxing, (d) clay
refining with acidic clay or active clay and (e)
chemical (acid or alkali) refining such as sulfuric
acid treatment and sodium. hydroxide treatment. In the
present invention, any one or more of these refining
processes may be used in any combination and order.
[0014] The mineral lubricating base oil used in the
present invention is particularly preferably a base oil
produced by further subjecting a base oil selected from
(1) to (8) described above to the following treatments.
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,....
That is, preferred are a hydrocracked
mineral oil and/or wax-isomerized isoparaffinic base
oil produced by hydr ocr a c ki ng or wax - i s ome ri z ing a base
oil selected from (1) to (8) described above as it is
or a lubricating fraction recovered therefrom and
subjecting the resulting product as it is or a
lubricating fraction recovered therefrom to dewaxing
such as solvent dewaxing or catalytic dewaxing,
followed by solvent refining or followed by solvent
refining and then dewaxing such as solvent dewaxing or
catalytic dewaxing. The hydrocracked mineral oil
and/or wax-isomerized isoparaffinic base oil are used
in an amount of preferably 30 percent by mass or more,
more preferably 50 percent by mass or more, and
particularly preferably 70 percent by mass or more, on
the total base oil mass basis.
[0015] The lubricating base oil referred to as
Component (A) used in the transmission lubricating oil
composition of the present invention is a lubricating
base oil adjusted so that the 100 C kinematic viscosity
is from 1.5 to 4.5 mm2/s.
Component (A) is preferably one ormo re types
selected from the following (A-a) to (A-c):
(A-a) a mineral base oil having a 100 C
kinematic viscosity of between 1.5 and lower than 3.5
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mm2/s, preferably 1.9 to 3.2 mm2/s;
(A-b) a mineral base oil having a 100 C
kinematic viscosity of between 3.5 and lower than 7
mm2/s, preferably 3.6 to 4.5 mm2/s; and
(A-c) a synthetic base oil having a 100 C
kinematic viscosity of between 1.5 and lower than 7
mm2/s, preferably 3.8 to 4.5 mm2/s.
[0016] Mineral base oils (A-a) to (A-b) have a %CA
of preferably 2 or less, more preferably 1 or less, more
preferably 0.5 or less, particularly preferably
substantially 0. Lubricating oil (A-c) has a %CA of
substantially 0. The use of lubricating base oil (A)
having a %CA of 2 or less renders it possible to produce
a lubricating oil composition with an excellent
oxidation stability.
The %CA used herein denotes the percentage
of the aromatic carbon number in the total carbon number,
determined in accordance with ASTM D 3238-85.
[0017] No particular limitation is imposed on the
viscosity index of lubricating base oils (A-a) to (A-c),
which is, however, preferably 80 or greater, more
preferably 100 or greater, particularly preferably 120
or greater and usually 200 or less, preferably 160 or
less. The use of a lubricating base oil having a
viscosity index of greater than 80 renders it possible
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to produce a composition exhibiting excellent
viscosity characteristics from low temperatures to
high temperatures. The use of a lubricating base oil
having a too high viscosity index results in a too much
normal paraffins in the resulting composition and also
deteriorates the low temperature fluidity thereof.
[0018] No particular limitation is imposed on the
sulfur content of mineral base oils (A-a) to (A-b) used
in the present invention, which is, however, preferably
0.05 percent by mass or less, more preferably 0.02
percent by mass or less, particularly preferably 0.005
percent by mass or less. The sulfur content of
lubricating base oil (A-c) is substantially 0%.
Reduction of the sulfur content of Component (A)
renders it possible to produce a composition having a
more excellent oxidation stability.
[0019] In the present invention, any one or more of
the above - describedbaseoils (A-a) to (A-c) maybe used.
Above all, preferably (A-a) and (A-b)and/or(A-c) are
used in combination. When Component (A-a) and/or
Component (A-b) and Component (A-c) are used in
combination, the content of Component (A-c) is
preferably 1 to 50 percent by mass, more preferably 3
to 20 percent by mass, more preferably 3 to 10 percent
by mass on the total base oil mass basis. In particular,
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blending of Component (A-c) in an amount of on the order
of 3 to 10 percent by mass renders it possible to produce
a composition exhibiting excellent effects in fatigue
life, low temperature characteristics, and oxidation
stability at a low cost.
[0020] Lubricating base oil (A) used in the present
invention has a 100 C kinematic viscosity of preferably
1.5 to 4.5 mm2/s, more preferably 2.8 to 4.0 mm2/s,
particularly preferably 3.6 to 3.9 mm2/s. The use of
a lubricating base oil with a 100 C kinematic viscosity
of 4.5 mm2/s or lower renders it possible to produce
a lubricating oil composition having a smaller
frictional resistance at lubricating sites because of
its small fluid resistance and thus having excellent
low temperature viscosity (for example, the -40 C
Brookfield viscosity is 20,000 Pas or less). The use
of a lubricating base oil with a 100 C kinematic
viscosity of 1.5 mm2/s or higher renders it possible
to produce a lubricating oil composition which is
sufficient in oil film formation and thus more
excellent in lubricity and less in evaporation loss of
the base oil under elevated temperature conditions.
[0021] The synthetic oil referred to as (A-c) may
be a synthetic lubricating oil such as poly-a-olefins
(1-octene oligomer, 1-decene oligomer,
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ethylene-propylene cooligomer) and hydrogenated
compounds thereof; isobutene oligomers and
hydrogenated compounds thereof; isoparaffins;
alkylbenzenes; alkylnaphthalenes; alkyldiphenyl
-ethanes; monoisopropyl biphenyl; dimethyl silicone;
diesters (ditridecyl glutarate, di-2-ethylhexyl
adipate, diisodecyl adipate, ditridecyl adipate and
di-2-ethylhexyl sebacate); polyol esters
(trimethylolpropane caprylate, trimethylolpropane
pelargonate, pentaerythritol 2-ethylhexanoate and
pentaerythritol pelargonate); polyoxyalkylene
glycols; dialkyldiphenyl ethers; polyphenyl ethers; or
a mixture thereof. Among these oils, preferably used
are poly-a-olefins and hydrogenated compounds thereof;
isobutene oligomers and hydrogenated compounds
thereof; isoparaffins; alkylbenzenes;
alkylnaphthalenes; alkyldiphenylethane;
monoisopropyl biphenyl; and dimethyl silicone because
they have a 80 C volume resistivity of 1x1013 Q.m or
greater and thus can enhance the insulation properties
of the resulting lubricating oil composition. In
general, ester-based compounds have a 80 C volume
resistivity of on the order of lx109 to 1X1013 Q.m and
are preferably those from which the remaining moisture
and impurities have been sufficiently removed.
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The term "80 C volume resistivity" used
herein is measured in accordance with JIS C 2101
24.(volume resistivity test).
[0022] The synthetic oil used in the present
invention is preferably selected from poly--olefins
and hydrogenated compounds thereof, alkylbenzenes,
ester-based compounds and mixtures thereof. In this
case, the resulting composition can maintain low
temperature fluidity and low volatility in
well-balance under the conditions where it is used.
[0023] Typical examples of poly-a-olefins include
oligomers or cooligomers of a-olefins having 2 to 32,
preferably 6 to 16 carbon atoms, such as 1-octene
oligomer, 1-decene oligomer, ethylene-propylene
cooligomer, and hydrogenated compounds thereof.
[0024] These synthetic oils may be used alone. No
particular limitation is imposed on the viscosity
thereof. However, synthetic oils with different
viscosities may be used in combination so that the 100 C
kinematic viscosity is adjusted to preferably from 1.5
to 4.5 mm2/s. This is because the combination of a
synthetic oil having a high viscosity with that of a
low viscosity results in a base oil having a higher
viscosity index.
[0025] The lubricating oil base oil referred to as
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Component (A) in the present invention is as described
above but is preferably mixed with a solvent refined
base oil having a kinematic viscosity of 20 mm2/s to
50 mm2/s if the resulting composition has a problem in
fatigue life. Furthermore, it is preferably mixed with
such a solvent refined oil in such an extent that the
mixture is adjusted to have a %CA of 2 or less and a
100 C kinematic viscosity of 1.5 to 4.5 mm2/s.
[0026] The lubricating oil composition of the
present invention contains (B) at least one type of
phosphorus compound selected from phosphorus compounds
having at least one hydroxyl group and/or at least one
thiol group.
[0027] The phosphorus compound referred to as
Component (B) in the present invention is at least one
type of compound selected from phosphorus compounds
represented by formula (1), phosphorus compounds
represented by formula (2), amine salts thereof, and
derivatives thereof.
[0028]
R1 ¨ X1¨P¨ X 3- R3
(1)
X2-R2
[0029] In formula (1), X', X2 and X3 are each
independently oxygen or sulfur and at least one of them
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is preferably oxygen, at least one of Rl, R2 and R3 is
hydrogen and the others are hydrocarbon groups having
1 to 30 carbon atoms.
[0030]
X7
R4 ¨ x 4 ¨ p ____ x 6- R6 (2)
L
X'-R5
[0031] In formula (2), X4, X5, X6 and X7 are each
independently oxygen or sulfur (one or two of X4, X5
and X6 may be a single bond or(poly)oxyalkylene group)
and at least one of them is preferably oxygen, at least
one of R4, R5 and R6 is hydrogen and the others are
hydrocarbon groups having 1 to 30 carbon atoms.
[0032] Examples of the hydrocarbon groups having 1
to 30 carbon atoms for R' to R6 include alkyl, cycloalkyl,
alkenyl, alkyl-substituted cycloalkyl, aryl,
alkyl-substituted aryl, and arylalkyl groups. The
hydrocarbon groups are preferably alkyl groups having
1 to 30 carbon atoms and aryl groups having 6 to 24 carbon
atoms, more preferably alkyl groups having 3 to 18
carbon atoms, more preferably alkyl groups having 4 to
12 carbon atoms.
[0033] Examples of phosphorus compounds
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,......
represented by formula (1) include phosphorous acid;
monothiophosphorous acid; dithiophosphorous acid;
phosphorous acid monoesters, monothiophosphorous acid
monoesters, dithiophosphorous acid monoesters, and
trithiophosphorous acid monoesters, each having any
one of the above-described hydrocarbon groups having
1 to 30 carbon atoms; and phosphorous acid diesters,
monothiophosphorous acid diesters, dithiophosphorous
acid diesters, and trithiophosphorous acid diesters,
each having any two of the above-described hydrocarbon
groups having 1 to 30 carbon atoms; and a mixture
thereof.
[0034] In order to further enhance the properties
such as high temperature detergency and oxidation
stability in the present invention, preferably two or
more, particularly preferably all of X1 to X3in formula
(1) are oxygen.
[0035] Examples of phosphorus compounds
represented by formula (2) include phosphoric acid;
monothiophosphoric acid; dithiophosphoric acid;
trithiophosphoric acid; tetrathiophosphoric acid;
phosphoric acid monoesters, monothiophosphoric acid
monoesters, dithiophosphoric acid monoesters,
trithiophosphoric acid monoesters, and
tetrathiophosphoric acid monoesters, each having any
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one of the above-described hydrocarbon groups having
1 to 30 carbon atoms; phosphoric acid diesters,
monothiophosphoric acid diesters, dithiophosphoric
acid diesters, trithiophosphoric acid diesters, and
tetrathiophosphoric acid diesters, each having any two
of the above-described hydrocarbon groups having 1 to
30 carbon atoms; phosphonic acid, phosphonic acid
monoesters, and phosphonic acid diesters, each having
any one or two of the above-described hydrocarbon
groups having 1 to 30 carbon atoms; the phosphoric acid
compounds exemplified above but having a
(poly)oxyalkylene group having 1 to 4 carbon atoms;
derivatives of the phosphorus compounds exemplified
above, such as 13-dithiophosphorylated propionic acid
and reaction products of dithiophosphates and olefin
cyclopentadiene or (methyl)methacrylates; and
mixtures thereof.
[0036] In order to further enhance the properties
such as high temperature detergency and oxidation
stability in the present invention, preferably two or
more, more preferably three or more, particularly
preferably all of X4 to X7 in formula (2) are oxygen.
One or two of X4, X5 and X6 may be a single bond or a
(poly)oxyalkylene group.
[0037] Examples of the salts of phosphorus
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compounds represented by formula (1) or (2) include
salts produced by allowing a nitrogen compound such as
ammonia or an amine compound having in its molecules
only a hydrocarbon group having 1 to 30 carbon atoms
or a hydroxyl group-containing hydrocarbon group
having 1 to 30 carbon atoms to react with a phosphorus
compound and neutralize the whole or part of the
remaining acid hydrogen.
Specific examples of the
nitrogen-containing compound include ammonia,
monoamines, diamines, and polyamines. Preferred
examples include aliphatic amines having an alkyl or
alkenyl group having 10 to 20 carbon atoms, which may
be straight-chain or branched, such as decylamine,
dodecylamine, dimethyldodecylamine, tridecylamine,
heptadecylamine, octadecylamine, oleylamine, and
stearyl amine.
[0038] The phosphorus compound referred to as
Component (B) is preferably at least one type of
compound selected from the group consisting of amine
salts of phosphorus compounds of formula (1) wherein
all of X1, X2 and X3 are oxygen and amine salts of
phosphorus compounds of formula (2) wherein all of X4,
X5, X6 and X7 are oxygen (one or two of X4, X5 and X6 may
be a single bond or a (poly)oxyalkylene group) because
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=
they are excellent in oxidation stability.
[0039] Alternatively, the phosphorus compound
referred to as Component (B) is preferably a phosphorus
compound of formula (2) wherein all of X4, X5, X6 and
X7 are oxygen (one or two of X4, X5 and X6 may be a single
bond or a (poly)oxyalkylene group), at least one of R4,
R5 and R6 is hydrogen and the others are each
independently a hydrocarbon group having 1 to 30 carbon
atoms in terms of oxidation stability.
[0040] The hydrocarbon group of the phosphorus
compound referred to as Component (B) has preferably
16 or fewer carbon atoms. This is based on the fact
that fewer the carbon atoms, higher the volume
resistivity is as set forth in Table 1 below.
[0041] [Table 1]
Structure of phosphorus compound' Trialkyl phosphite
Dialkylhydrogen phosphite DiPhpehnoYsihp=ge" Dialkyl acid phosphate =
Structure of hydrocarbon group iC8 n012 nC18 I04 i08 n018
phenyl nCIO n018
Carnbori number of hydrocarbon group 8 12 18 4 8 18 6
10 18
Volume resistivity 10' Q =m 358 315 27.9 1200 104 12.8
800 1.44 1.4
*Phosphoric compounds were each dissolved in a base oil with the following
physical properties to compare the volume resistivity.
They were each added in an amount of 100 mass ppm by phosphorus.
Kinematic viscosity (40 C) 19.7mm2/s, Kinematic viscosity (100 C) 4.3mm2/s,
Viscosity index 125, %; 78.5, %; 21.5, %CA 0
[0042] In Table 1, the volume resistivity
designates the value measured at an oil temperature of
=
80 C in accordance with JIS C 2101 24. (volume
resistivity test). In the above examples, each of the
phosphorus compound was added and dissolved in a
mineral base oil so that it is contained in an amount
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of 100 mass ppm on the basis of phosphorus.
[0043] No particular limitation is imposed on the
content of Component (B) that is the above-described
phosphorus compound of the lubricating oil composition
of the present invention, which is, however, 0.01
percent by mass or more, preferably 0.02 percent by mass
or more, particularly preferably 0.03 percent by mass
or more and preferably 0.1 percent by mass or less, more
preferably 0.08 percent by mass or less, particularly
preferably 0.05 percent by mass or less on the basis
of phosphorus on the composition mass basis. If the
content of the phosphorus compound is less than 0.01
percent by mass on the basis of phosphorus, the
resulting composition would be less effective in
anti-wear properties. Whilst, if the content of the
phosphorus compound is more than 0.1 percent by mass
on the basis of phosphorus, the resulting composition
would be poor in insulation properties, degraded in
oxidation stability and enhanced in aggressivity
against sealing materials.
[0044] The lubricating oil composition of the
present invention is characterized in that it contains
(C) an ashless dispersant having a functional group
containing nitrogen as a dispersion group in an amount
of less than 0.001 percent by mass on the basis of
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nitrogen on the composition mass basis or does not
contain such an ashless dispersant at all.
[0045] As described above, the lubricating oil
composition of the present invention contains (B) at
least one type of phosphorus compound selected from
phosphorus compounds having at least one hydroxyl group
and/or at least one thiol group. The inclusion of the
phosphorus compound enhances significantly the
anti-wear properties and anti-seizure properties of
the composition. However, this type of phosphorus
compound degrades drastically the volume resistance of
the composition compared with a phosphorus compound
having no hydroxyl group and/or thiol group if an
ashless dispersant having a functional group
containing nitrogen as a dispersion group is contained.
Therefore, the composition contains necessarily (C) an
ashless dispersant having a functional group
containing nitrogen as a dispersion group in an amount
of less than 0.001 percent by mass on the basis of
nitrogen on the composition mass basis or does not
contain such an ashless dispersant at all in order to
improve the anti-wear properties and anti-seizure
properties of the composition.
[0046] Examples of the ashless dispersant having a
functional group containing nitrogen as a dispersion
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group referred to as Component (C) include succinimide,
benzylamine, and polyamines, each having a hydrocarbon
group having 40 to 400 carbon atoms.
However, among these compounds, those having
been modified to have a structure wherein nitrogen
cannot constitute a salt structure together with
Component (B) that is the phosphorus compound are
excluded from the examples. Fox example, compounds
wherein the amino group is acylated or modified with
a boron compound or a sulfuric compound and incapable
of constituting a salt structure with Component (B)
that is the phosphorus compound are excluded.
What is meant by "containing an ashless
dispersant having a functional group containing
nitrogen as a dispersion group in an amount of less than
0.001 percent by mass on the basis of nitrogen on the
composition mass basis" is a structure or amount
wherein even though an ashless dispersant has an amino
group remained so as to be able to constitute a salt
structure with Component (B) that is the phosphorus
compound, the content thereof is such a level that the
volume resistance at 80 C of the resulting composition
is 5x108 Q.m or greater. Specifically, the ashless
dispersant is contained in such an amount that nitrogen
is contained in an amount of less than 0.001 percent
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by mass, more preferably less than 0.0008 percent by
mass on the composition mass basis.
[0047] No particular limitation is imposed on the
use of compounds with a structure of thiadiazole or
triazole that is an amine-based anti-oxidant or a
corrosion inhibitor because it can be ignored if the
content thereof is 1 percent by mass or less.
[0048] The lubricating oil composition of the
present invention has a 80 C volume resistivity of
preferably 5x108 C2-m or greater, more preferably 6x108
0.m or greater, particularly preferably 10x108 Q.m or
greater. The composition having a 80 C volume
resistivity of 5x108 0-m or greater can keep the
insulation properties high not only when it is fresh
but also when it is degraded thereby avoiding an
electric motor from having a trouble such as shorting
out for a long period of time.
[0049] If necessary, the lubricating oil
composition of the present invention may be blended
with various additives such as viscosity index
improvers, extreme pressure additives, dispersants
other than the above-described dispersant compounds,
metallic detergents, friction modifiers,
anti-oxidants, corrosion inhibitors, rust inhibitors,
demulsifiers, metal deactivators, pour point
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depressants, seal swelling agents, anti-foaming agents,
and dyes, alone or in combination in order to further
enhance the properties of the composition or impart the
composition with properties required fora lubricating
oil.
[0050] Examples of the viscosity index improvers
include non-dispersant or dispersant type
poly (meth) acrylate; non-dispersant or dispersant type
ethylene-a-olefin copolymers and hydrogenated
compounds thereof; polyisobutylene and hydrogenated
compounds thereof; styrene-diene hydrogenated
copolymers; styrene-maleic anhydride ester
copolymers; polyalkylstyrenes; and copolymers of
(meth) acrylate monomers represented by formula (1) and
unsaturated monomers such as
ethylene/propylene/styrene/maleic anhydride.
[0051] The amount of the viscosity index improver
in the lubricating oil composition of the present
invention is such an amount that the resulting
composition has a 100 C kinematic viscosity of 5 to 10
mm2/s, preferably 6 to 9 mm2/s and a viscosity index
of 120 to 270, preferably 150 to 250, more preferably
170 to 220. More specifically, the amount is 15 percent
by mass or less, preferably 10 percent by mass or less,
more preferably 8 percent by mass or less and 2 percent
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A 02820519 2013-06-06
by mass or more, preferably 4 percent by mass or more,
more preferably 5 percent by mass or more on the
composition mass basis. An amount of more than 15
percent by mass causes a too high viscosity while an
amount of less than 2 percent by mass causes a too high
viscosity and thus cannot secure a sufficient
composition viscosity.
[0052] Examples of the metallic detergent include
those such as alkaline earth metal sulfonates, alkaline
earth metal phenates, and alkaline earth metal
salicylates.
Any one or more compounds selected from these
metallic detergents may be contained in an amount of
usually 0.01 to 10 percent by mass, preferably 0.1 to
percent by mass on the total composition mass basis.
[0053] The friction modifier may be any compound
that has been generally used as a friction modifier for
lubricating oils. Specific examples include amine
compounds, imide compounds, fatty acid esters, fatty
acid amides, and fatty acid metal salts, each having
per molecule at least one alkyl or alkenyl group having
6 to 30 carbon atoms, particularly a straight-chain
alkyl or alkenyl group having 6 to 30 carbon atoms.
Any one or more compounds selected from these
friction modifiers may be contained in an amount of
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:A 02820519 2013-08-08
usually 0.01 to 5.0 percent by mass, preferably 0.03
to 3.0 percent by mass on the total composition mass
basis.
[0054] The anti-oxidant may be any anti-oxidant
that has been usually used in lubricating oils, such
as phenol- or amine-based compounds.
Specific examples of the anti-oxidant
include alkylphenols such as
2-6-di-tert-butyl-4-methylphenol; bisphenols such as
methylene-4,4-bisphenol(2,6-di-tert-buty1-4-
methylphenol); naphthylamines such as
phenyl-a-naphthylamine; dialkyldiphenylamines; zinc
dialkyldithiophosphoric acids such as
di-2-ethylhexyldithiophosphoric acid; and
esters of (3,5-di-tert-butyl-4-hydroxyphenyl)fatty
acid (propionic acid) or
(3-methyl-5-tert-butyl-4-hydroxyphenyl)fatty acid
(propionic acid) with a monohydric or polyhydric
alcohol such as methanol, octanol, octadecanol,
1,6-hexanediol, neopentyl glycol, thiodiethylene
glycol, triethylene glycol and pentaerythritol.
Any one or more of compounds selected from
these compounds may be contained in any amount, which
is, however, usually from 0.01 to 5 percent by mass,
preferably from 0.1 to 3 percent by mass on the total
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A 02820519 2013-06-06
composition mass basis.
[0055] Examples of the corrosion inhibitor include
benzotriazole-, tolyltriazole-, thiadiazole-, and
imidazole-types compounds.
[0056] Examples of the rust inhibitor include
petroleum sulfonates, alkylbenzene sulfonates,
dinonylnaphthalene sulfonates, alkenyl succinic acid
esters, and polyhydric alcohol esters.
[0057] Examples of the demulsifier include
polyalkylene glycol-based non-ionic surfactants such
as polyoxyethylenealkyl ethers,
polyoxyethylenealkylphenyl ethers, and
polyoxyethylenealkylnaphthyl ethers.
[0058] Examples of the metal deactivator include
imidazolines, pyrimidine derivatives,
alkylthiadiazoles, mercaptobenzothiazoles,
benzotriazoles and derivatives thereof,
1,3,4-thiadiazolepolysulfide,
1 , 3 , 4 -thiadiazoly1-2 , 5-bisdialkyldithiocarbamate
2-(alkyldithio)benzoimidazole, and
P-(o-carboxybenzylthio)propionitrile.
[0059] The pour point depressant may be any of the
known pour point depressants selected depending on the
type of lubricating base oil but are preferably
poly(meth)acrylates having a weight average molecular
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A 02820519 2013-06-06
weight of preferably 20,000 to 500,000, more preferably
50,000 to 300,000, particularly preferably 80,000 to
200,000.
[0060] The anti-foaming agent may be any compound
that has been usually used as an anti-foaming agent for
lubricating oils. Examples of such an anti-foaming
agent include silicones such as dimethylsilicone and
fluorosilicone. Anyone or more of compounds selected
from these compounds may be contained in any amount.
[0061] The seal swelling agent may be any compound
that has been usually used as a seal swelling agent for
lubricating oils. Examples of such a seal swelling
agents include ester-, sulfur- and aromatic-based seal
swelling agents.
[0062] The dye may be any compound that has been
usually used and may be blended in any amount. The
amount is usually from 0.001 to 1.0 percent by mass on
the total composition mass basis.
[0063] When these additives are blended with the
lubricating oil composition of the present invention,
the corrosion inhibitor, rust inhibitor, and
anti-foaming agent are each contained in an amount of
0.005 to 5 percent by mass, the pour point depressant
and metal deactivator are each contained in an amount
of 0.005 to 2 percent by mass, the seal swelling agent
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A 02820519 2013-06-06
is contained in an amount of 0.01 to 5 percent by mass,
and the anti-foaming agent is contained in an amount
of 0.0005 to 1 percent by mass, all on the total
composition mass basis.
Examples
[0064] The
present invention will be described more
specifically with reference to the following Examples
and Comparative Examples but not limited thereto.
[0065] (Examples
1 to 6 and Comparative Examples 1
to 5)
Lubricating oil compositions according to
the present invention (Examples 1 to 6) and those for
comparison (Comparative Examples 1 to 5) were prepared
in accordance with the formulations set forth in Table
2. The
performances of each composition were evaluated
with the following tests. The results are set forth
in Table 2.
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r---1
C)
0
GI
Base Oil Total Base Oil Mass Basis
Example 1 Example 2 Example 3. Example 4 Example
5 Example 6 Comparative Comparative Comparative Comparative Comparative CY)
-
I-I
A-1 Base Oil 1 1) inmass% 100 100 100
100 100 100 100 100 100
A-2 Base Oil 22) inmass% 100
A-3 Base Oil 3 3) inmass% 100
-
_
_
'
E1-1 Oil soluble phosphorus additive 1 4) mass% 0.5
= 0.1 0.1 0.1 - 0.1 0.1 H
Sai
B-2 Oil soluble phosphorus additive 2 53 mass%
0.1
tr
B-4 Oil soluble phosphorus additive 4 7)
0.3 a)
C-1 Ashless dispersant 1 a) mass%
4 4 f\.)
0-2 Ashless dispersant 2 = 5)
4
,
0-1 Viscosity index improver 1 ) mass% 12 12 12 17
12 12 12 _ 12 12 12 12
Additive package 11) mass% 2.5 2.5 2.5 2.5
2.5 2.5 2.5 2.5 2.5 2.5 2.5
P content of the composition masspm 500 100 100 100
100 100 0 _ 100 0 100 100
I Evalution results
2
(..k)
2
CD 12)
Four - ball test
,2
I WL mm2/s 1061 1961 1961 1961
1961 1961 1961 1961 1961 1961 1961 '=
=.'
g
4,
LNSL % 785 785 785 785 785
785 490 785 490 785 785 8
Four - ball (wear scar diameter) ") mm2/s 0.5 0.5 0.5 0.5
0.5 0.5 0.7 , 0.5 0.8 0.5 0.5
Volume resistivity") 10" B -m 0.06 0.15 0.12
0.06 0.13 0.05 0.16 0.005 0.031 0.001 0.01
1) kinematic viscosity (40 C) 19.7mm2/s, kinematic viscosity (100 C) 4.3mm2/s,
viscosity index 125, %Cp 78.5, %ON 21.5, WA 0
2) kinematic viscosity (40 C) 22.7mm2/s, kinematic viscosity (100 C) 4.3mm2/s,
viscosity index 102, %Cp 66.4, %Cr4 29.0, %CA4.6
3) di-2-ethylhexyl azelate kinematic viscosity (40 C) 10.1mm2/s, kinematic
viscosity (100 C) 3.0mm2/s. viscosity index 144
4) amine salt of acidic phosphoric acid ester (P content 10%, phosphoric acid
ester 2-ethylhexyl, amine: mixed amine of Clltol 4)
5) hydrogen phosphite, isoC4 P content 16%
6) acidic phosphoric acid ester, 2-ethylhexyl P: 9.4%
7) trioleylphosphite P: 3.7%
=
8) boronated succininiide, FIB Mw 2000, bis type. TEPA crosslinking
9) succinimide, FIB Mw 1000, his type. TEA crosslinking
10) non-dispersant type PMA Mw 25,000
11) containing Ca metallic detergent (0.1 mass%), metal deactivator (0.1
mass%), anti-oxidant (2.0 mass%), anti-foaming agent ( 30 mass ppm)
12) 1800 rpm
13) 392 N, 1800 rpm, 80 C, 30 min .
14) in accordance with J1S 02101, measured at 80 C
A 02820519 2013-06-06
Applicability in Industry
[0067] The lubricating oil composition of the
present invention is a composition improved in
anti-wear properties and anti-seizure properties and
can be used as a lubricating oil for an electric
motor-equipped vehicle such as an electric vehicle or
a hybrid vehicle, an electric motor oil, an oil both
for a transmission and an electric motor, and an oil
for a device wherein a transmission and an electric
motor are packaged in one and a lubricating system is
shared by the transmission and an electric motor.
The present invention can provide the
above-described transmission, electric motor and
device including the lubricating oil composition of the
present invention and a method for lubricating,
insulating and cooling the above-described
transmission, electric motor and device using the
lubricating oil composition of the present invention.
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