U.S. patent application number 16/318399 was filed with the patent office on 2019-09-19 for lubricating oil composition, method for manufacturing lubricating oil composition, and drive system apparatus.
This patent application is currently assigned to IDEMITSU KOSAN CO., LTD.. The applicant listed for this patent is IDEMITSU KOSAN CO., LTD.. Invention is credited to Tatsuya HAMACHI, Shuichi SAKANOUE.
Application Number | 20190284498 16/318399 |
Document ID | / |
Family ID | 62707256 |
Filed Date | 2019-09-19 |
United States Patent
Application |
20190284498 |
Kind Code |
A1 |
SAKANOUE; Shuichi ; et
al. |
September 19, 2019 |
LUBRICATING OIL COMPOSITION, METHOD FOR MANUFACTURING LUBRICATING
OIL COMPOSITION, AND DRIVE SYSTEM APPARATUS
Abstract
To provide a lubricating oil composition having excellent
viscosity characteristics and a property of difficulty in
evaporation, which contains a base oil having a kinematic viscosity
at 40.degree. C. of 4.0 mm.sup.2/s or more and less than 6.0
mm.sup.2/s, a kinematic viscosity at 100.degree. C. of 1.0
mm.sup.2/s or more and less than 2.0 mm.sup.2/s and a flash point
of 140.degree. C. or more, and a viscosity index improver, and has
a Brookfield viscosity at -40.degree. C. of 750 mPas or less, a
kinematic viscosity at 60.degree. C. of 5.5 mm.sup.2/s or more, and
a NOACK value at 145.degree. C. for 1 hour of 10% by mass or
less.
Inventors: |
SAKANOUE; Shuichi;
(Chiba-shi, JP) ; HAMACHI; Tatsuya; (Chiba-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
IDEMITSU KOSAN CO., LTD. |
Chiyoda-ku |
|
JP |
|
|
Assignee: |
IDEMITSU KOSAN CO., LTD.
Chiyoda-ku
JP
|
Family ID: |
62707256 |
Appl. No.: |
16/318399 |
Filed: |
November 17, 2017 |
PCT Filed: |
November 17, 2017 |
PCT NO: |
PCT/JP2017/041475 |
371 Date: |
January 17, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10M 2203/0206 20130101;
C10N 2030/02 20130101; C10M 169/041 20130101; C10M 169/04 20130101;
C10N 2020/017 20200501; C10M 101/02 20130101; C10M 2209/084
20130101; C10N 2040/02 20130101; C10N 2040/08 20130101; C10N
2030/74 20200501; C10M 2203/1006 20130101; C10N 2020/02 20130101;
C10M 145/14 20130101; C10M 171/02 20130101; C10M 101/04 20130101;
C10N 2020/04 20130101; C10N 2030/08 20130101; F16C 33/66 20130101;
C10G 2400/10 20130101; C10N 2070/00 20130101; C10M 2209/084
20130101; C10N 2020/04 20130101 |
International
Class: |
C10M 169/04 20060101
C10M169/04; C10M 101/02 20060101 C10M101/02; C10M 101/04 20060101
C10M101/04; C10M 145/14 20060101 C10M145/14 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 27, 2016 |
JP |
2016-253460 |
Claims
1. A lubricating oil composition, comprising: a base oil having a
kinematic viscosity at 40.degree. C. of 4.0 mm.sup.2/s or more and
less than 6.0 mm.sup.2/s, a kinematic viscosity at 100.degree. C.
of 1.0 mm.sup.2/s or more and less than 2.0 mm.sup.2/s and a flash
point of 140.degree. C. or more; and a viscosity index improver,
wherein the lubricating oil composition has a Brookfield viscosity
at -40.degree. C. of 750 mPas or less, a kinematic viscosity at
60.degree. C. of 5.5 mm.sup.2/s or more, and a NOACK value at
145.degree. C. for 1 hour of 10% by mass or less.
2. The lubricating oil composition according to claim 1, wherein
the base oil has a kinematic viscosity at 100.degree. C. of 1.5
mm.sup.2/s or more and less than 2.0 mm.sup.2/s.
3. The lubricating oil composition according to claim 1, wherein
the base oil is a mineral oil, and a feedstock oil of the mineral
oil contains a gas oil fraction obtained by hydrocracking of a
heavy gas oil.
4. The lubricating oil composition according to claim 3, wherein
the feedstock oil has a paraffin content (% C.sub.P) of 60 or
more.
5. The lubricating oil composition according to claim 3, wherein
the feedstock oil has an aromatic content (% C.sub.A) of 10.0 or
less.
6. The lubricating oil composition according to claim 3, wherein
the feedstock oil has a proportion of a n-paraffin component of 1%
by volume or more and 50% by volume or less based on 100% by volume
of the total amount of an aromatic component, a naphthene
component, a n-paraffin component, and an isoparaffin
component.
7. The lubricating oil composition according to claim 3, wherein
the feedstock oil has a 10% distillation temperature of 250.degree.
C. or more, and a 90% distillation temperature of 320.degree. C. or
more, as measured by the distillation test according to HS
K2254.
8. The lubricating oil composition according to claim 3, wherein
the feedstock oil has a kinematic viscosity at 40.degree. C. of 4.0
mm.sup.2/s or more and 6.0 mm.sup.2/s or less, and a kinematic
viscosity at 100.degree. C. of 1.0 mm.sup.2/s or more and 2.0
mm.sup.2/s or less.
9. The lubricating oil composition according to claim 1, wherein
the viscosity index improver is a polymethacrylate.
10. The lubricating oil composition according to claim 9, wherein
the polymethacrylate has a mass average molecular weight of 30,000
or more and 350,000 or less.
11. The lubricating oil composition according to claim 1, wherein a
content of the viscosity index improver is 2.5% by mass or more and
7.4% by mass or less based on a total amount of the
composition.
12. The lubricating oil composition according to claim 1, which has
a flash point of 120.degree. C. or more and 180.degree. C. or
less.
13. The lubricating oil composition according to claim 1, which is
adapted to function as a lubricating oil composition to be applied
to a drive system apparatus.
14. The lubricating oil composition according to claim 1, which is
adapted to function as a lubricating oil composition to be applied
to a shock absorber for a four-wheel vehicle.
15. A method for producing a lubricating oil composition having a
Brookfield viscosity at -40.degree. C. of 750 mPas or less, a
kinematic viscosity at 60.degree. C. of 5.5 mm.sup.2/s or more, and
a NOACK value at 145.degree. C. for 1 hour of 10% by mass or less,
the method comprising blending a base oil having a kinematic
viscosity at 40.degree. C. of 4.0 mm.sup.2/s or more and less than
6.0 mm.sup.2/s, a kinematic viscosity at 100.degree. C. of 1.0
mm.sup.2/s or more and less than 2.0 mm.sup.2/s and a flash point
of 140.degree. C. or more, and a viscosity index improver.
16. A drive system apparatus, comprising the lubricating oil
composition of claim 1.
17. The drive system apparatus according to claim 16, which is a
shock absorber for a four-wheel vehicle.
Description
TECHNICAL FIELD
[0001] The present invention relates to a lubricating oil
composition, a method for producing a lubricating oil composition,
and a drive system apparatus.
BACKGROUND ART
[0002] In recent years, a lubricating oil composition used in
various applications such as a drive system apparatus, such as a
shock absorber, a transmission, and a power steering, an engine,
and a hydraulic system has been required to have characteristics
according to the applications. The characteristics of the
lubricating oil composition are significantly influenced by the
properties of the base oil used, the kind of the additive, and the
like in many cases, and developments of the base oil and the
additive have been widely performed for producing a lubricating oil
composition capable of exhibiting the required characteristics.
[0003] For example, a shock absorber is an equipment that is used
as a drive system apparatus for an automobile, such as a four-wheel
vehicle and a two-wheel vehicle, and is also used in a wide range
of fields including an earthquake resistant mechanism of housing.
The lubricating oil composition used in a shock absorber is charged
in the shock absorber, and required to have a capability of forming
a fluid resistance in movement of a piston, so as to attenuate
vibration transmitted from the road surface to the vehicle body for
the automobile shock absorber and vibration caused by earthquake or
the like for the housing shock absorber, and also to have a
capability of lubricating the sliding portion in the shock
absorber. PTL 1 describes an oil composition for a shock absorber
that uses a hydrogenated modified mineral oil or a synthetic oil as
a base oil, in which a particular amount of a viscosity index
improver, such as a high molecular weight poly(meth)acrylate, is
used.
[0004] As a base oil used for a lubricating oil composition for a
drive system apparatus, such as a transmission and a power
steering, a hydrocarbon-based lubricant base oil having a flash
point of 170.degree. C. or more, a kinematic viscosity at
40.degree. C. of from 9.0 to 14.0 mm.sup.2/s, a viscosity index of
100 or more, a 5% distillation temperature in a distillation test
of 310.degree. C. or more, a pour point of -30.degree. C. or less,
and an aromatic content (% C.sub.A) of 0.1 or less is proposed (for
example, in PTL 2). According to the description of PTL 2, it is
said that the lubricant base oil has a high flash point with the
conventional viscosity maintained, and thus is favorable for a
lubricating oil composition used under a high temperature, such as
a power steering oil and a transmission oil of an automobile.
CITATION LIST
Patent Literatures
[0005] PTL 1: JP 2005-314609 A
[0006] PTL 2: JP 2004-182931 A
SUMMARY OF INVENTION
Technical Problem
[0007] Automobiles, such as four-wheel vehicles and two-wheel
vehicles, are utilized around the world, and in particular,
four-wheel vehicles are being widely utilized over high-temperature
regions, such as Africa and Middle and Near East, and
low-temperature regions, such as North America, North Europe,
Russia, and the mountain areas of China. Accordingly, a lubricating
oil composition used in a drive system apparatus of an automobile
is being required to withstand the use thereof in an extremely wide
temperature range, for example, of -40.degree. C. or more and
60.degree. C. or less.
[0008] As general characteristics of the lubricating oil
composition, the viscosity is decreased at a high temperature, but
it is demanded to be higher at a high temperature from the
standpoint of the retainability of the oil film. Whereas as general
characteristics of the lubricating oil composition, the viscosity
is increased at a low temperature. But it is demanded to be lower
at a low temperature since the too high viscosity causes an
excessive fluid resistance, which deteriorates the ride quality of
the vehicle. Thus it is demanded to have excellent viscosity
characteristics capable of suppressing the temperature dependency
of the viscosity (which may be hereinafter referred simply to as
"excellent viscosity characteristics"). The lubricating oil
composition used in a drive system apparatus is also required to
have a high flash point and a property that it is difficult to
evaporate.
[0009] For achieving the aforementioned viscosity characteristics,
for example, it may be considered to add a viscosity index improver
to a base oil having a low viscosity. However, since a base oil
having a low viscosity has a property that it is relatively easy to
evaporate, the lubricating oil composition may be evaporated due to
frictional heat generated locally in the shock absorber, so as to
cause a problem of damage of the shock absorber. The lubricating
oil composition described in PTL 1 is one obtained by adding a
viscosity index improver to a base oil having a kinematic viscosity
at 40.degree. C. of 30 mm.sup.2/s or more which is a relatively
high viscosity. However, if the lubricating oil composition is used
over the aforementioned extremely wide temperature range, the
excellent viscosity characteristics cannot be obtained in
particular at a low temperature due to the increase of the
viscosity. The lubricant base oil described in PTL 2 is a base oil
having a kinematic viscosity at 40.degree. C. of 9.0 mm.sup.2/s or
more which is a high viscosity, and therefore cannot be said to be
a base oil capable of providing the excellent viscosity
characteristics.
[0010] An object of the present invention is to provide a
lubricating oil composition that has excellent viscosity
characteristics capable of suppressing the temperature dependency
of the viscosity to a low level and providing suitability for use
at the areas with various temperatures, and also has a property of
difficulty in evaporation, a method for producing the lubricating
oil composition, and a drive system apparatus.
Solution to Problem
[0011] As a result of earnest investigation made by the present
inventors, it has been found that the problem can be solved by the
present invention described below. Specifically, the present
invention provides a lubricating oil composition, a method for
producing a lubricating oil composition, and a drive system
apparatus, having the following constitutions.
[0012] 1. A lubricating oil composition, containing a base oil
having a kinematic viscosity at 40.degree. C. of 4.0 mm.sup.2/s or
more and less than 6.0 mm.sup.2/s, a kinematic viscosity at
100.degree. C. of 1.0 mm.sup.2/s or more and less than 2.0
mm.sup.2/s and a flash point of 140.degree. C. or more, and a
viscosity index improver; and having a Brookfield viscosity at
-40.degree. C. of 750 mPas or less, a kinematic viscosity at
60.degree. C. of 5.5 mm.sup.2/s or more, and a NOACK value at
145.degree. C. for 1 hour of 10% by mass or less.
[0013] 2. A drive system apparatus including the lubricating oil
composition according to the item 1.
[0014] 3. A method for producing a lubricating oil composition
having a Brookfield viscosity at -40.degree. C. of 750 mPas or
less, a kinematic viscosity at 60.degree. C. of 5.5 mm.sup.2/s or
more, and a NOACK value at 145.degree. C. for 1 hour of 10% by mass
or less, including blending a base oil having a kinematic viscosity
at 40.degree. C. of 4.0 mm.sup.2/s or more and less than 6.0
mm.sup.2/s, a kinematic viscosity at 100.degree. C. of 1.0
mm.sup.2/s or more and less than 2.0 mm.sup.2/s and a flash point
of 140.degree. C. or more, and a viscosity index improver.
Advantageous Effects of Invention
[0015] According to the present invention, a lubricating oil
composition that has excellent viscosity characteristics and a
property of difficulty in evaporation, and a drive system apparatus
using the same can be provided.
DESCRIPTION OF EMBODIMENTS
[0016] An embodiment of the present invention (which may be
hereinafter referred to as a "present embodiment") will be
described below. In the description herein, the numerals with "or
more" or "or less" relating to the numeral ranges are numerals that
can be arbitrarily combined.
[Lubricating Oil Composition]
[0017] The lubricating oil composition of the present embodiment
contains a base oil having a kinematic viscosity at 40.degree. C.
of 4.0 mm.sup.2/s or more and less than 6.0 mm.sup.2/s, a kinematic
viscosity at 100.degree. C. of 1.0 mm.sup.2/s or more and less than
2.0 mm.sup.2/s and a flash point of 140.degree. C. or more, and a
viscosity index improver, and has a Brookfield viscosity at
-40.degree. C. of 750 mPas or less, a kinematic viscosity at
60.degree. C. of 5.5 mm.sup.2/s or more, and a NOACK value at
145.degree. C. for 1 hour of 10% by mass or less.
[Base Oil]
[0018] The base oil contained in the lubricating oil composition of
the present embodiment satisfies the following requirements (I) and
(II). In the present embodiment, in the case where the following
requirements (I) and (II) are not satisfied, the excellent
viscosity characteristics and the property of difficulty in
evaporation cannot be obtained. Furthermore, a fuel efficiency
capability by decreasing the viscosity associated with the
excellent viscosity characteristics cannot be obtained.
[0019] Requirement (I): a kinematic viscosity at 40.degree. C. of
4.0 mm.sup.2/s or more and less than 6.0 mm.sup.2/s, and a
kinematic viscosity at 100.degree. C. of 1.0 mm.sup.2/s or more and
less than 2.0 mm.sup.2/s
[0020] Requirement (II): a flash point of 140.degree. C. or
more
[0021] In the description herein, the kinematic viscosity at
40.degree. C., the kinematic viscosity at 60.degree. C., the
kinematic viscosity at 100.degree. C. and the viscosity index each
mean a value that is measured according to JIS K2283, and the flash
point means a value that is measured by Cleveland open-cup (COC)
method according to JIS K2265.
[0022] In the present embodiment, the base oil may be any of a
mineral oil and a synthetic oil, and a mineral oil is preferred
from the standpoint of the inexpensiveness, the better viscosity
characteristics, the property of difficulty in evaporation, and the
fuel efficiency capability by decreasing the viscosity. In the
present embodiment, the base oil may be a mixed oil containing only
two or more kinds of mineral oils, only two or more kinds of
synthetic oils, or at least one mineral oil and at least one
synthetic oil, and mineral oils and synthetic oils contained in a
mixed oil may not satisfy the requirements (I) and (II), as far as
the mixed oil satisfies the requirements (I) and (II). In
consideration of the easiness in preparation, it is preferred that
at least a part of the mineral oils and the synthetic oils
contained in the mixed oil satisfies the requirements (I) and
(M.
[0023] As the general properties of a base oil, there is a tendency
that the flash point is decreased when the viscosity is decreased.
On the other hand, the base oil used in the lubricating oil
composition of the present embodiment is such a base oil that has a
high flash point, i.e., a flash point of 140.degree. C. or more, as
defined by the requirement (II) while the viscosity is lowered to
such an extent that the viscosity index cannot be calculated by the
calculation method defined in JIS K2283, as defined by the
requirement (I). Accordingly, the lubricating oil composition of
the present embodiment can be a lubricating oil composition having
the excellent viscosity characteristics, the high flash point, the
property of difficulty in evaporation, and fuel efficiency
capability by decreasing the viscosity, by using the base oil
having the aforementioned properties.
[0024] The base oil used in the lubricating oil composition of the
present embodiment has a relatively small difference between the
kinematic viscosity at 40.degree. C. and the kinematic viscosity at
100.degree. C. as defined by the requirement (I), and thus has a
low temperature dependency of the viscosity. Accordingly, the
lubricating oil composition of the present embodiment has a low
temperature dependency of the viscosity.
[0025] The kinematic viscosity at 40.degree. C. (V.sub.40) of the
base oil used in the lubricating oil composition of the present
embodiment is 4.0 mm.sup.2/s or more, and is preferably 4.2
mm.sup.2/s or more, more preferably 4.3 mm.sup.2/s or more, and
further preferably 4.4 mm.sup.2/s or more.
[0026] The upper limit of the kinematic viscosity (V.sub.40) is
less than 6.0 mm.sup.2/s, and is preferably 5.8 mm.sup.2/s or less,
more preferably 5.7 mm.sup.2/s or less, and further preferably 5.6
mm.sup.2/s or less.
[0027] The kinematic viscosity at 100.degree. C. (V.sub.100) of the
base oil used in the lubricating oil composition of the present
embodiment is 1.0 mm.sup.2/s or more, and is preferably 1.2
mm.sup.2/s or more, more preferably 1.3 mm.sup.2/s or more, further
preferably 1.4 mm.sup.2/s or more, and still further preferably 1.5
mm.sup.2/s or more.
[0028] The upper limit of the kinematic viscosity (V.sub.100) is
less than 2.0 mm.sup.2/s, and is preferably 1.95 mm.sup.2/s or
less, more preferably 1.90 mm.sup.2/s or less, and further
preferably 1.85 mm.sup.2/s or less.
[0029] In the case where the base oil used in the lubricating oil
composition of the present embodiment is a mineral oil, the
viscosity index measured according to JIS K2283 cannot be
calculated.
[0030] The flash point of the base oil used in the lubricating oil
composition of the present embodiment is 140.degree. C. or more,
and is preferably 142.degree. C. or more, more preferably
144.degree. C. or more, further preferably 146.degree. C. or more,
still further preferably 150.degree. C. or more, and particularly
preferably 154.degree. C. or more, and the upper limit thereof is
generally 180.degree. C. or less.
[0031] The aniline point of the base oil used in the lubricating
oil composition of the present embodiment is preferably 70.degree.
C. or more, more preferably 80.degree. C. or more, further
preferably 85.degree. C. or more, and still further preferably
90.degree. C. or more, and is generally 110.degree. C. or less.
[0032] The base oil having an aniline point of 70.degree. C. or
more has a tendency of containing a large amount of a paraffin
component and a small amount of an aromatic component, and tends to
have a high flash point.
[0033] In the description herein, the aniline point means a value
that is measured according to JIS K2256 (U-tube method).
[0034] The density at 15.degree. C. of the base oil used in the
lubricating oil composition of the present embodiment is preferably
0.860 g/cm.sup.3 or less, more preferably 0.850 g/cm.sup.3 or less,
further preferably 0.840 g/cm.sup.3 or less, still further
preferably 0.830 g/cm.sup.3 or less, and particularly preferably
0.825 g/cm.sup.3 or less, and is generally 0.800 g/cm.sup.3 or
more.
[0035] The base oil satisfying the requirements (I) and (II) and
also having a density of 0.860 g/cm.sup.3 or less can be a base oil
that has a further lower temperature dependency of the viscosity
and a further higher flash point.
[0036] In the description herein, the density at 15.degree. C. is a
value that is measured according to JIS K2249.
[0037] In the case where the base oil used in the lubricating oil
composition of the present embodiment is a mineral oil, the
paraffin content (% C.sub.P) thereof is preferably 60 or more and
80 or less, more preferably 62 or more and 79 or less, further
preferably 66 or more and 78 or less, and still further preferably
68 or more and 77 or less.
[0038] The naphthene content (% C.sub.N) thereof is preferably 10
or more and 40 or less, more preferably 13 or more and 38 or less,
further preferably 16 or more and 34 or less, and still further
preferably 20 or more and 32 or more.
[0039] The aromatic content (% C.sub.A) thereof is preferably less
than 2.0, more preferably less than 1.0, and further preferably
less than 0.1.
[0040] In the description herein, the paraffin content (% C.sub.P),
the naphthene content (% C.sub.N), and the aromatic content (%
C.sub.A respectively mean proportions (percentages) of the paraffin
component, the naphthene component, and the aromatic component
measured according to ASTM D-3238 ring analysis (n-d-M method).
[0041] The base oil used in the lubricating oil composition of the
present embodiment preferably further satisfies the following
requirement (III). The lubricating oil composition of the present
embodiment may have an excellent fuel efficiency capability and a
further lower temperature dependency of the viscosity by satisfying
the requirement (III).
[0042] Requirement (III): a temperature gradient .DELTA.|.eta.*| of
a complex viscosity between two temperature points of -10.degree.
C. and -25.degree. C. measured with a rotary rheometer under
conditions of an angular velocity of 6.3 rad/s and a strain amount
of from 0.1 to 100% (which may be hereinafter referred simply to as
a "temperature gradient .DELTA.|.eta.*| of complex viscosity") of
0.1 Pas/.degree. C. or less
[0043] In the case where the base oil used in the lubricating oil
composition of the present embodiment is a mixed oil, it is
preferred that the mixed oil satisfies the requirement (III).
[0044] The "strain amount" referred in the requirement (III) is a
value that is appropriately determined within the range of from 0.1
to 100% according to the temperature.
[0045] The aforementioned "temperature gradient .DELTA.|.eta.*| of
complex viscosity" is a value that shows the amount of change of
the complex viscosity per unit between two temperature points of
-10.degree. C. and -25.degree. C. (i.e., the absolute value of the
gradient) as observed when the value of the complex viscosity
.eta.* at -10.degree. C. and the value of the complex viscosity
.eta.* at -25.degree. C. are measured either independently at these
temperatures or measured while continuously varying the temperature
from -10.degree. C. to -25.degree. C. or from -25.degree. C. to
-10.degree. C., and the values are placed on a temperature-complex
viscosity coordinate plane. More specifically, the temperature
gradient .DELTA.|.eta.*| of complex viscosity means a value that is
calculated from the following calculation expression (f1).
Temperature gradient .DELTA.|.eta.*| of complex
viscosity=|([complex viscosity .eta.* at -25.degree. C.]-[complex
viscosity .eta.* at -10.degree. C.])/(-25-(-10))| Calculation
expression (f1):
[0046] Accordingly, the "temperature gradient .DELTA.|.eta.*| of
complex viscosity" defined by the requirement (III) shows the aging
change by decreasing the temperature, in terms of the
low-temperature characteristics of the base oil.
[0047] A mineral oil contains a wax component, and therefore when
the temperature of a mineral oil is gradually decreased, the wax
component in the mineral oil is deposited to form a gel-like
structure. The wax components are deposited at different
temperatures depending on the structures of paraffin and the like.
The gel-like structure of the wax component is easily broken, and
therefore the viscosity of a mineral oil varies by a mechanical
action. The conventionally used parameters of the low-temperature
viscosity characteristics have been provided without consideration
of the deposition of wax.
[0048] On the other hand, the "temperature gradient .DELTA.|.eta.*|
of complex viscosity" defined by the requirement (III) is an index
that can accurately evaluate the low-temperature viscosity
characteristics of a mineral oil by taking into consideration the
deposition rate of the wax component contained in the mineral oil
to consider the variation in the coefficient of friction involved
in the deposition of the wax component. Accordingly, it can be said
that the requirement (III) is substantially a requirement that is
applied to the case where a mineral oil is contained as the base
oil.
[0049] The base oil that satisfies the requirement (III) has a
temperature gradient .DELTA.|.eta.*| of complex viscosity of 0.1
Pas/.degree. C. or less, and is regulated to prevent the deposition
rate of the wax component from being increased, and therefore the
base oil tends not to cause increase of the coefficient of
friction, and has a lower temperature dependency of the viscosity
while having a lower viscosity. Accordingly, the lubricating oil
composition of the present embodiment may have an excellent fuel
efficiency capability and a low temperature dependency of the
viscosity, by using the base oil.
[0050] From the aforementioned standpoint, the temperature gradient
.DELTA.|.eta.*| of complex viscosity defined by the requirement
(III) is preferably 0.08 Pas/.degree. C. or less, more preferably
0.05 Pas/.degree. C. or less, further preferably 0.02 Pas/.degree.
C. or less, still further preferably 0.01 Pas/.degree. C. or less,
still more further preferably 0.005 Pas/.degree. C. or less, and
particularly preferably 0.0030 Pas/.degree. C. or less.
[0051] The lower limit of the temperature gradient .DELTA.|.eta.*|
of complex viscosity defined by the requirement (III) is not
particularly limited, and is preferably 0.0001 Pas/.degree. C. or
more, more preferably 0.0005 Pas/.degree. C. or more, and further
preferably 0.0010 Pas/.degree. C. or more.
(Preparation Example of Mineral Oil)
[0052] The mineral oil that satisfies the requirements (I) and (II)
and preferably satisfies the requirement (III) can be readily
prepared by appropriately considering the selection of a feedstock
oil as a raw material and the following factors relating to the
preparation method of the mineral oil using the feedstock oil.
Specifically, the base oil used in the lubricating oil composition
of the present embodiment is preferably a mineral oil that is
obtained by subjecting the feedstock oil shown below to the
refining process shown below.
[0053] The following factors show one example of the preparation
method, and the mineral oil can be prepared by taking the other
factors into consideration.
[Selection of Feedstock Oil]
[0054] Examples of the feedstock oil include an atmospheric
residual oil obtained by atmospheric distillation of a crude oil,
such as a paraffinic mineral oil, an intermediate mineral oil, or a
naphthenic mineral oil; a distillate oil obtained by vacuum
distillation of the atmospheric residual oil; and a mineral oil or
wax (e.g., GTL wax) obtained by subjecting the distillate oil to at
least one of refining processes, such as solvent deasphalting,
solvent extraction, hydrofinishing, solvent dewaxing, catalytic
dewaxing, isomerization dewaxing, and vacuum distillation.
[0055] The feedstock oil may be used alone or as a combination of
two or more kinds thereof.
[0056] The feedstock oil preferably contains a gas oil fraction
from the standpoint of the preparation the mineral oil that has a
viscosity decreased to the extent defined by the requirement (I)
while showing a low temperature dependency of the viscosity, and
has a high flash point defined by the requirement (II), and more
preferably contains a gas oil fraction obtained by hydrocracking of
a heavy gas oil.
[0057] The kinematic viscosity at 40.degree. C. of the feedstock
oil is preferably 4.0 mm.sup.2/s or more and 6.0 mm.sup.2/s or
less, more preferably 4.2 mm.sup.2/s or more and 5.8 mm.sup.2/s or
less, and further preferably 4.4 mm.sup.2/s or more and 5.6
mm.sup.2/s or less.
[0058] The kinematic viscosity at 100.degree. C. of the feedstock
oil is preferably 1.0 mm.sup.2/s or more and 2.0 mm.sup.2/s or
less, more preferably 1.2 mm.sup.2/s or more and 1.9 mm.sup.2/s or
less, and further preferably 1.4 mm.sup.2/s or more and 1.85
mm.sup.2/s or less.
[0059] The flash point of the feedstock oil is generally 70.degree.
C. or more and less than 140.degree. C.
[0060] The paraffin content (% C.sub.P), the aromatic content (%
C.sub.A), and the naphthene content (% C.sub.N) of the feedstock
oil are preferably in the ranges described below as measured
according to the ASTM D-3238 ring analysis (n-d-M method), from the
standpoint of the preparation of the mineral oil that has a
viscosity decreased to the extent defined by the requirement (I)
while showing a low temperature dependency of the viscosity.
[0061] The paraffin content (% C.sub.P) is preferably 60 or more,
more preferably 65 or more, further preferably 68 or more, and
still further preferably 70 or more, and the upper limit thereof is
preferably 80 or less, more preferably 79 or less, and further
preferably 78 or less.
[0062] The aromatic content (% C.sub.A) is preferably 10.0 or less,
more preferably 5.0 or less, further preferably 4.4 or less, and
still further preferably 4.2 or less.
[0063] The naphthene content (% C.sub.N) is preferably 10 or more
and 40 or less, more preferably 13 or more and 35 or less, further
preferably 16 or more and 32 or less, and still further preferably
20 or more and 32 or less.
[0064] The proportions of the aromatic component, the naphthene
component, the n-paraffin component, and the isoparaffin component
in the feedstock oil based on 100% by volume of the total amount of
the components are preferably in the ranges described below as
measured according to ASTM D2786 and GC-FID method, from the
standpoint of the preparation of the mineral oil that has a
viscosity decreased to the extent defined by the requirement (I)
while showing a low temperature dependency of the viscosity.
[0065] The "aromatic component" means a generic term of hydrocarbon
compounds having an aromatic ring, and the proportion of the
aromatic component is preferably 25% by volume or less, more
preferably 15% by volume or less, and further preferably 10% by
volume or less. The lower limit thereof is preferably 1% by volume
or more, more preferably 1.5% by volume or more, and further
preferably 2% by volume or more.
[0066] The "naphthene component" means a generic term of saturated
cyclic hydrocarbon compounds, and the proportion of the naphthene
component is preferably 70% by volume or less, more preferably 60%
by volume or less, and further preferably 50% by volume or less.
The lower limit thereof is preferably 10% by volume or more, more
preferably 12% by volume or more, and further preferably 15% by
volume or more.
[0067] The "n-paraffin component" means a generic term of saturated
straight-chain hydrocarbon compounds, and the proportion of the
n-paraffin component is preferably 1% by volume or more and 50% by
volume or less, more preferably 4% by volume or more and 30% by
volume or less, and further preferably 6% by volume or more and 15%
by volume or less.
[0068] The "isoparaffin component" means a generic term of
saturated branched-chain hydrocarbon compounds, and the proportion
of the isoparaffin component is preferably 8% by volume or more,
more preferably 25% by volume or more, and further preferably 30%
by volume or more. The upper limit thereof is preferably 70% by
volume or less, more preferably 68% by volume or less, and further
preferably 65% by volume or less.
[0069] The 10% distillation temperature measured by the
distillation test according to JIS K2249 of the feedstock oil is
preferably 250.degree. C. or more, more preferably 260.degree. C.
or more, further preferably 270.degree. C. or more, and still
further preferably 275.degree. C. or more, and is generally
290.degree. C. or less.
[0070] The 90% distillation temperature measured by the
aforementioned distillation test of the feedstock oil is preferably
320.degree. C. or more, more preferably 350.degree. C. or more,
further preferably 355.degree. C. or more, still further preferably
360.degree. C. or more, and particularly preferably 366.degree. C.
or more, and is generally 400.degree. C. or less.
[0071] In the case where the 10% distillation temperature and the
90% distillation temperature of the feedstock oil are in the
aforementioned ranges, the base oil having a high flash point as
defined by the requirement (II) can be prepared.
[0072] The mass average molecular weight (Mw) of the feedstock oil
is preferably 150 or more and 450 or less, more preferably 180 or
more and 400 or less, and further preferably 200 or more and 350 or
less.
[0073] In the description herein, the mass average molecular weight
(Mw) of the feedstock oil means a value that is measured according
to ASTM D2502.
[0074] As described above, the kinematic viscosities at 40.degree.
C. and 100.degree. C. of the feedstock oil do not largely differ
from the ranges defined by the requirement (I).
[0075] However, the flash point of the feedstock oil having a low
viscosity as described above is generally less than 140.degree. C.,
which does not satisfy the requirement (II). Furthermore, the
feedstock oil also tends to have a high temperature gradient
.DELTA.|.eta.*| of complex viscosity as defined by the requirement
(III) and has a problem in terms of the low-temperature viscosity
characteristics.
[0076] On the other hand, irrespective of the use of the feedstock
oil of this type, the mineral oil used in the lubricating oil
composition of the present embodiment has a high flash point and
has a low viscosity while having a lowered temperature dependency
of the viscosity by the subjecting the feedstock oil to the
refining process as described below, and therefore is a mineral oil
having excellent low-temperature viscosity characteristics.
(Method for Producing Mineral Oil)
[0077] The mineral oil used in the lubricating oil composition of
the present embodiment is preferably obtained by subjecting the
aforementioned feedstock oil to a refining process. It is preferred
that the type of the refining process and the refining conditions
are appropriately set according to the type of the feedstock oil
used.
[0078] The refining process preferably includes at least a
hydrogenation isomerization dewaxing process, and more preferably
includes a hydrogenation isomerization dewaxing process and a
hydrofinishing process.
[0079] Accordingly, the mineral oil used in the lubricating oil
composition of the present embodiment is preferably obtained
through a hydrogenation isomerization dewaxing process, and more
preferably obtained further through a hydrofinishing process after
the hydrogenation isomerization dewaxing process.
[0080] The "hydrogenation isomerization dewaxing process" and the
"hydrofinishing process" will be explained below.
(Hydrogenation Isomerization Dewaxing Process)
[0081] The hydrogenation isomerization dewaxing process is a
refining process performed for the purpose of isomerization of a
straight-chain paraffin contained in a feedstock oil to a
branched-chain isoparaffin as mentioned above.
[0082] The hydrogenation isomerization dewaxing process can also
conduct ring opening of an aromatic component into a paraffin
component, removal of impurities, such as a sulfur component and a
nitrogen component, and the like.
[0083] The hydrogenation isomerization process increases the
proportion of a branched-chain isoparaffin, thereby producing a
mineral oil having a low temperature dependency of the viscosity
and having a high flash point.
[0084] The presence of a straight-chain paraffin in the feedstock
oil is one of the factors increasing the value of the temperature
gradient .DELTA.|.eta.*| of complex viscosity defined by the
requirement (III). Accordingly, it is preferred in the process that
a straight-chain paraffin is isomerized to a branched-chain
isoparaffin, so as to control the temperature gradient
.DELTA.|.eta.*| of complex viscosity to a low value.
[0085] In addition, the process can also reduce the pour point of
the mineral oil, and therefore the mineral oil having further
improved low-temperature viscosity characteristics can be
obtained.
[0086] The hydrogenation isomerization dewaxing process is
preferably performed in the presence of a hydrogenation
isomerization dewaxing catalyst.
[0087] Examples of the hydrogenation isomerization dewaxing
catalyst include catalysts containing a carrier, such as
silicoaluminophosphate (SAPO) and zeolite, having carried thereon a
metal oxide, such as oxides of nickel (Ni)/tungsten (W), nickel
(Ni)/molybdenum (Mo), and cobalt (Co)/molybdenum (Mo), or a noble
metal, such as platinum (Pt) and lead (Pd).
[0088] The hydrogen partial pressure in the hydrogenation
isomerization dewaxing process is preferably 2.0 MPa or more and 25
MPa or less, more preferably 2.5 MPa or more and 22 MPa or less,
further preferably 3.0 MPa or more and 10 MPa or less, and still
further preferably 3.5 MPa or more and 6 MPa or less, from the
standpoint of the production of the mineral oil satisfying the
requirement (III).
[0089] The reaction temperature in the hydrogenation isomerization
dewaxing process is preferably set to a temperature higher than the
reaction temperature of the ordinary hydrogenation isomerization
dewaxing process, and specifically is preferably 250.degree. C. or
more and 400.degree. C. or less, more preferably 275.degree. C. or
more and 380.degree. C. or less, further preferably 280.degree. C.
or more and 370.degree. C. or less, and still further preferably
285.degree. C. or more and 360.degree. C. or less, from the
standpoint of the production of the mineral oil satisfying the
requirements (II) and (III).
[0090] The high reaction temperature can accelerate the
isomerization of a straight-chain paraffin into a branched-chain
isoparaffin, thereby making easy the production of the base oil
satisfying the requirements (II) and (III).
[0091] The liquid hourly space velocity (LHSV) in the hydrogenation
isomerization dewaxing process is preferably 5.0 hr.sup.-1 or less,
more preferably 3.0 hr.sup.-1 or less, further preferably 2.0
hr.sup.-1 or less, and still further preferably 1.5 hr.sup.-1 or
less, from the standpoint of the production of the base oil
satisfying the requirement (III).
[0092] The LHSV in the hydrogenation isomerization dewaxing process
is preferably 0.1 hr.sup.-1 or more, and more preferably 0.2
hr.sup.-1 or more, from the standpoint of the improvement of the
productivity.
[0093] The supply proportion of hydrogen gas in the hydrogenation
isomerization dewaxing process is preferably 100 Nm.sup.3 or more
and 1,000 Nm.sup.3 or less, more preferably 200 Nm.sup.3 or more
and 800 Nm.sup.3 or less, and further preferably 250 Nm.sup.3 or
more and 650 Nm.sup.3 or less, per 1 kL of the feedstock oil
supplied.
(Hydrofinishing Process)
[0094] The hydrofinishing process is a refining process that is
performed for the purpose of complete saturation of the aromatic
component contained in the feedstock oil, removal of impurities,
such as a sulfur component and a nitrogen component, and the
like.
[0095] The hydrofinishing process is preferably performed in the
presence of a hydrogenation catalyst.
[0096] Examples of the hydrogenation catalyst include catalysts
containing an amorphous carrier, such as silica/alumina and
alumina, or a crystalline carrier, such as zeolite, having carried
thereon a metal oxides, such as oxides of nickel (Ni)/tungsten (W),
nickel (Ni)/molybdenum (Mo), and cobalt (Co)/molybdenum (Mo), or a
noble metal, such as platinum (Pt) and lead (Pd).
[0097] The hydrogen partial pressure in the hydrofinishing process
is preferably set to a value higher than a pressure of an ordinary
hydrogenation process, and specifically is preferably 16 MPa or
more, more preferably 17 MPa or more, and further preferably 18 MPa
or more, and the upper limit thereof is preferably 30 MPa or less,
and more preferably 22 MPa or less, from the standpoint of the
production of the mineral oil satisfying the requirement MIX
[0098] The reaction temperature in the hydrofinishing process is
preferably 200.degree. C. or more and 400.degree. C. or less, more
preferably 250.degree. C. or more and 350.degree. C. or less, and
further preferably 280.degree. C. or more and 330.degree. C. or
less, from the standpoint of the production of the mineral oil
satisfying the requirement (III).
[0099] The liquid hourly space velocity (LHSV) in the
hydrofinishing process is preferably 5.0 hr.sup.-1 or less, more
preferably 2.0 hr.sup.-1 or less, and further preferably 1.0
hr.sup.-1 or less, from the standpoint of the production of the
mineral oil satisfying the requirement (III), and is preferably 0.1
hr.sup.-1 or more, more preferably 0.2 hr.sup.-1 or more, and
further preferably 0.3 hr.sup.-1 or more, from the standpoint of
the productivity.
[0100] The supply proportion of hydrogen gas in the hydrofinishing
process is preferably 100 Nm.sup.3 or more and 2,000 Nm.sup.3 or
less, more preferably 200 Nm.sup.3 or more and 1,500 Nm.sup.3 or
less, and further preferably 250 Nm.sup.3 or more and 1,100
Nm.sup.3 or less, per 1 kL of the supplied oil (i.e., the produced
oil after subjecting to the hydrogenation isomerization dewaxing
process).
(Post-Treatment)
[0101] After the completion of the aforementioned refining
processes, the produced oil obtained is subjected to vacuum
distillation to recover a fraction having a kinematic viscosity at
40.degree. C. in the range defined by the requirement (I), thereby
providing the mineral oil used in the lubricating oil composition
of the present embodiment.
[0102] The mineral oil obtained has a high flash point while having
a viscosity decreased as defined by the requirement (I).
[0103] The conditions (such as the pressure, the temperature, and
the time) for the vacuum distillation may be appropriately
controlled, so as to provide the mineral oil that has kinematic
viscosities at 40.degree. C. and 100.degree. C. in the ranges
defined by the requirement (I).
(Synthetic Oil)
[0104] The lubricating oil composition of the present embodiment
may contain a synthetic oil as a base oil.
[0105] Examples of the synthetic oil include a poly-.alpha.-olefin,
such as an .alpha.-olefin homopolymer and an .alpha.-olefin
copolymer (e.g., an .alpha.-olefin copolymer having from 8 to 14
carbon atoms, such as an ethylene-.alpha.-olefin copolymer); an
isoparaffin; various esters, such as a polyol ester, a dibasic acid
ester (e.g., ditridecyl glutarate), a tribasic acid ester (e.g.,
2-ethylhexyl trimellitate), and a phosphoric ester; various ethers,
such as a polyphenyl ether; a polyalkylene glycol; and an
alkylbenzene.
(Content of Base Oil)
[0106] The content of the base oil in the lubricating oil
composition of the present embodiment is generally 60% by mass or
more, preferably 70% by mass or more, and more preferably 80% by
mass or more, based on the total amount of the composition. The
upper limit thereof is generally less than 100% by mass, preferably
99% by mass or less, more preferably 98% by mass or less, and
further preferably 97% by mass or less.
[0107] In the present embodiment, in the case where the base oil is
a mixed oil containing a base oil that satisfies the requirements
(I) and (II), and preferably satisfies the requirement (III) (which
may be hereinafter referred to as a "base oil A"), and a base oil
that does not satisfy the requirements (I) and (II) (which may be
hereinafter referred to as a "base oil B"), the content of the base
oil A is not particularly limited, as far as the base oil satisfies
the requirements (I) and (II), and is preferably 20% by mass or
more, more preferably 25% by mass or more, and further preferably
30% by mass or more, and it suffices that the upper limit thereof
is less than 100% by mass, based on the total amount of the base
oils.
[0108] The lubricating oil composition of the present embodiment
may contain an additional additive in some cases, in addition to
the viscosity index improver, as described later, and the additive
may be supplied along with a diluent oil, which may be used as it
is in some cases. In these cases, the content of the diluent oil
may be determined in consideration of the aforementioned content of
the base oil.
(Viscosity Index Improver)
[0109] The lubricating oil composition of the present embodiment
contains a viscosity index improver. In the case where the
lubricating oil composition of the present embodiment does not
contain a viscosity index improver, the excellent viscosity
characteristics cannot be obtained, and the fuel efficiency
capability by decreasing the viscosity cannot be obtained.
[0110] Preferred examples of the viscosity index improver include
polymers, for example, a polymethacrylate-based compound, such as a
polymer, a copolymer, and the like of a (meth)acrylate ester, e.g.,
an alkyl (meth)acrylate, an olefin polymer-based compound, such as
an ethylene-propylene copolymer and a polybutylene, and a styrene
polymer-based compound, such as a polyalkylstyrene, a styrene-diene
copolymer, and a styrene-isoprene copolymer, from the standpoint of
the excellent viscosity characteristics provided, and a
polymethacrylate is more preferred. In the present embodiment, the
viscosity index improver may be used alone or as a combination of
two or more kinds thereof.
[0111] The polymethacrylate-based viscosity index improver includes
a dispersion type and a non-dispersion type. Examples of the
non-dispersion type include the aforementioned polymer or copolymer
of a (meth)acrylate ester, and a hydrogenated product thereof, and
examples of the dispersion type include a copolymer of a
(meth)acrylate ester and a polar monomer having dispersibility,
such as diethylaminoethyl methacrylate. The olefin polymer-based
viscosity index improver also includes a dispersion type and a
non-dispersion type.
[0112] The mass average molecular weight (Mw) of the viscosity
index improver is generally 5,000 or more and 1,000,000 or less,
and for the polymethacrylate-based viscosity index improver, is
preferably 30,000 or more, more preferably 50,000 or more, more
preferably 55,000 or more, and particularly preferably 100,000 or
more. The upper limit thereof is preferably 350,000 or less, more
preferably 300,000 or less, and further preferably 250,000 or less.
For the olefin polymer-based viscosity index improver, the mass
average molecular weight (Mw) thereof is preferably 5,000 or more,
more preferably 10,000 or more, and further preferably 15,000 or
more, and the upper limit thereof is preferably 800,000 or less,
more preferably 500,000 or less, and further preferably 40,000 or
less.
[0113] In the description herein, the mass average molecular weight
(Mw) is a value that is measured according to ASTM D2502.
[0114] The content of the viscosity index improver is preferably
2.5% by mass or more, more preferably 2.8% by mass or more, and
further preferably 3.0% by mass or more, based on the total amount
of the oil composition, from the standpoint of the excellent
viscosity characteristics provided. The upper limit thereof is
preferably 7.0% by mass or less, more preferably 6.8% by mass or
less, and further preferably 6.5% by mass or less. The viscosity
index improver may be used in the form associated with a diluent
oil in some cases, and in these cases, the content of the viscosity
index improver is the content of only the viscosity index improver
excluding the diluent oil. The diluent oil used may be
appropriately selected from the mineral oils, the synthetic oils,
and the like exemplified for the use of the base oil.
[Additional Additive]
[0115] The lubricating oil composition of the present embodiment
may contain depending on necessity an additive ordinarily used for
a lubricating oil, as an additional additive, in such a range that
does not impair the effects of the present invention.
[0116] Examples of the additive for a lubricating oil include a
pour point depressant, a metal-based detergent, a dispersant, an
anti-wear agent, an extreme pressure agent, an antioxidant, an
anti-foaming agent, a friction modifier, a rust inhibitor, and a
metal deactivator. A compound having multiple functions of the
aforementioned additives (such as a compound having functions of an
anti-wear agent and an extreme pressure agent) may be used. The
additive for a lubricating oil may be a commercially available
additive package containing plural additives. The additive may be
used alone or as a combination of two or more kinds thereof.
[0117] The lubricating oil composition of the present embodiment
may be formed of the base oil and the viscosity index improver, or
may be formed of the base oil, the viscosity index improver, and
the additional additive.
[0118] The contents of the additives may be appropriately
controlled depending on the kind of the additive within a range
that does not impair the effects of the present invention. In the
case where the additive is contained, the amount thereof is
generally 0.01% by mass or more and 15% by mass or less, and is
preferably 0.05% by mass or more, more preferably 0.1% by mass or
more, and further preferably 0.3% by mass or more, and the upper
limit thereof is preferably 10% by mass or less, more preferably 8%
by mass or less, and further preferably 6% by mass or less.
[Properties of Lubricating Oil Composition]
[0119] The kinematic viscosity at 60.degree. C. (V.sub.60) of the
lubricating oil composition of the present embodiment is
necessarily 5.5 mm.sup.2/s or more. In the case where the kinematic
viscosity at 60.degree. C. (V.sub.60) is less than 5.5 mm.sup.2/s,
in particular, the retainability of the oil film cannot be
obtained, and the composition cannot be a lubricating oil
composition having the excellent viscosity characteristics. The
kinematic viscosity at 60.degree. C. (V.sub.60) is preferably 5.8
mm.sup.2/s or more, more preferably 6.0 mm.sup.2/s or more, and
further preferably 6.5 mm.sup.2/s or more, from the standpoint of
the excellent viscosity characteristics provided. The upper limit
thereof is preferably 12.0 mm.sup.2/s or less, more preferably 11.0
mm.sup.2/s or less, and further preferably 10.0 mm.sup.2/s or
less.
[0120] The kinematic viscosity at 40.degree. C. (V.sub.40) of the
lubricating oil composition of the present embodiment is preferably
7.5 mm.sup.2/s or more, more preferably 8.0 mm.sup.2/s or more, and
further preferably 8.5 mm.sup.2/s or more, from the standpoint of
the further excellent viscosity characteristics provided. The upper
limit thereof is preferably 13.0 mm.sup.2/s or less, more
preferably 12.0 mm.sup.2/s or less, and further preferably 11.5
mm.sup.2/s or less.
[0121] The kinematic viscosity at 100.degree. C. (V.sub.100) of the
lubricating oil composition of the present embodiment is preferably
2.5 mm.sup.2/s or more, more preferably 3.0 mm.sup.2/s or more, and
further preferably 3.5 mm.sup.2/s or more, from the standpoint of
the further excellent viscosity characteristics provided. The upper
limit thereof is preferably 5.5 mm.sup.2/s or less, more preferably
5.0 mm.sup.2/s or less, and further preferably 4.5 mm.sup.2/s or
less.
[0122] The viscosity index of the lubricating oil composition of
the present embodiment is preferably 280 or more, more preferably
300 or more, and further preferably 320 or more, from the
standpoint of the further excellent viscosity characteristics
provided. The upper limit thereof is preferably 450 or less, more
preferably 440 or less, and further preferably 430 or less.
[0123] The Brookfield viscosity at -40.degree. C. of the
lubricating oil composition of the present embodiment is
necessarily 750 mPas or less. In the case where the Brookfield
viscosity at -40.degree. C. exceeds 750 mPas, the composition
cannot be a lubricating oil composition having the excellent
viscosity characteristics due to the deterioration of the
low-temperature fluidity, and in the case where the composition is
used in an automobile, the ride quality of the vehicle is
deteriorated by the generation of an excessive fluid resistance due
to the excessively large viscosity.
[0124] The Brookfield viscosity at -40.degree. C. of the
lubricating oil composition of the present embodiment is preferably
730 mPas or less, more preferably 710 mPas or less, further
preferably 700 mPas or less, and particularly preferably 680 mPas
or less, from the standpoint of the further excellent viscosity
characteristics provided. The lower limit thereof is not
particularly limited, and is generally 400 mPas or more. In the
description herein, the Brookfield viscosity at -40.degree. C. is a
value that is measured by the method described in the examples.
[0125] The NOACK value at 145.degree. C. for 1 hour of the
lubricating oil composition of the present embodiment is
necessarily 10% by mass or less. In the case where the NOACK value
exceeds 10% by mass, the lubricating oil composition of the present
embodiment cannot be said to have the property of difficulty in
evaporation, and the lubricating oil composition is easily
evaporated due to frictional heat generated locally in the shock
absorber, so as to cause a problem in safety and to cause damage of
the apparatus.
[0126] The NOACK value at 145.degree. C. for 1 hour of the
lubricating oil composition of the present embodiment is preferably
9.8% by mass or less, more preferably 9.5% by mass or less, and
further preferably 9.0% by mass or less, from the standpoint of the
property of difficulty in evaporation and the safety provided, and
the prevention of damage of the apparatus. The lower limit thereof
is preferably 4% by mass or more, more preferably 5% by mass or
more, and further preferably 5.5% by mass or more, from the
standpoint of the reduction of the consumed amount of the
lubricating oil composition. In the description herein, the NOACK
value is a value that is measured by the method described in the
examples.
[0127] The flash point of the lubricating oil composition of the
present embodiment is preferably 120.degree. C. or more, more
preferably 130.degree. C. or more, further preferably 140.degree.
C. or more, and still further preferably 145.degree. C. or more,
and the upper limit thereof is generally 180.degree. C. or less.
The lubricating oil composition of the present embodiment has a
high flash point, which is preferably 140.degree. C. or more, and
thus can be said to have the property of difficulty in evaporation
and high safety, and to be hard to cause damage of the
apparatus.
[0128] The density of the lubricating oil composition of the
present embodiment is preferably 0.860 g/cm.sup.3 or less, more
preferably 0.850 g/cm.sup.3 or less, further preferably 0.840
g/cm.sup.3 or less, and particularly preferably 0.830 g/cm.sup.3 or
less, and is generally 0.800 g/cm.sup.3 or more. The lubricating
oil composition of the present embodiment that has a density within
the range along with the aforementioned properties can have the
further excellent viscosity characteristics and can have a high
flash point.
[Purpose of Lubricating Oil Composition]
[0129] The lubricating oil composition of the present embodiment
has the excellent viscosity characteristics, the property of
difficulty in evaporation, and the fuel efficiency capability by
decreasing the viscosity.
[0130] Accordingly, the lubricating oil composition of the present
embodiment can be favorably applied to various purposes including a
drive system apparatus, such as a shock absorber, a transmission,
and a power steering, an engine, a hydraulic system, a turbine, a
compressor, a machine tool, a cutting machine, a gear, a fluid
dynamic bearing, and a rolling bearing. Among these, in
consideration of the characteristics thereof, i.e., the excellent
viscosity characteristics, the property of difficulty in
evaporation, and the fuel efficiency capability by decreasing the
viscosity, the lubricating oil composition is preferably applied to
a drive system apparatus, preferably applied to a shock absorber
for an automobile, such as a four-wheel vehicle and a two-wheel
vehicle, and an earthquake resistant mechanism of housing, and
particularly preferably applied to a shock absorber for a
four-wheel vehicle.
[Method for producing Lubricating Oil Composition]
[0131] The method for producing a lubricating oil composition of
the present embodiment includes blending a base oil having a
kinematic viscosity at 40.degree. C. of 4.0 mm.sup.2/s or more and
less than 6.0 mm.sup.2/s, a kinematic viscosity at 100.degree. C.
of 1.0 mm.sup.2/s or more and less than 2.0 mm.sup.2/s and a flash
point of 140.degree. C. or more, and a viscosity index improver.
According to the method for producing a lubricating composition, a
lubricating oil composition having a Brookfield viscosity at
-40.degree. C. of 750 mPas or less, a kinematic viscosity at
60.degree. C. of 5.5 mm.sup.2/s or more, and a NOACK value at
145.degree. C. for 1 hour of 10% by mass or less, i.e., the
lubricating oil composition of the present embodiment, can be
obtained.
[0132] The base oil and the viscosity index improver used in the
method for producing a lubricating oil composition of the present
embodiment are as described above. The resulting lubricating oil
composition is also as described above.
[0133] The method for producing a lubricating oil composition of
the present embodiment preferably includes stirring the composition
by a known method after blending the base oil and the viscosity
index improver, so as to disperse the viscosity index improver
uniformly in the base oil. In the case where the additional
additive is used, the additive may be blended simultaneously with
the base oil and the viscosity index improver.
[Drive System Apparatus]
[0134] The drive system apparatus of the present embodiment uses
the aforementioned lubricating oil composition of the present
embodiment. Examples of the drive system apparatus include a shock
absorber, a transmission, and a power steering, and in
consideration of the characteristics of the lubricating oil
composition of the present embodiment, i.e., the excellent
viscosity characteristics, the property of difficulty in
evaporation, and the fuel efficiency capability by decreasing the
viscosity, the drive system apparatus is preferably a shock
absorber for an automobile, such as a four-wheel vehicle and a
two-wheel vehicle, and an earthquake resistant mechanism of
housing, more preferably a shock absorber for an automobile, such
as a four-wheel vehicle and a two-wheel vehicle, and particularly
preferably a shock absorber for a four-wheel vehicle.
EXAMPLES
[0135] The present invention will be described in more detail with
reference to examples below, but the present invention is not
limited to the examples. The measurement methods and the evaluation
methods for the properties were as follows.
(1) Kinematic Viscosities at 40.degree. C., 60.degree. C., and
100.degree. C., Viscosity Index
[0136] These values were measured according to JIS K2283.
(2) Flash Point
[0137] The value was measured by the Cleveland open-cup (COC)
method according to JIS K2265.
(3) Aromatic Content (% C.sub.A), Naphthene Content (% C.sub.N),
and Paraffin Content (% C.sub.P)
[0138] These values were measured according to ASTM D-3238 ring
analysis (n-d-M method).
(4) Density at 15.degree. C.
[0139] The value was measured according to JIS K2249.
(5) 10% Distillation Temperature and 90% Distillation
Temperature
[0140] These values were measured according to JIS K2254.
(6) Aniline Point
[0141] The value was measured according to JIS K2256 (U-tube
method).
(7) Mass Average Molecular Weight (Mw)
[0142] The value was measured according to ASTM D2502.
(8) Temperature Gradient .DELTA.|.eta.*| of Complex Viscosity
Between Two Temperature Points of -25.degree. C. and -10.degree.
C.
[0143] The value was measured by using a rheometer "Physica MCR
301", produced by Anton Paar GmbH, according to the following
procedure.
[0144] The base oil to be measured was inserted in a corn plate
(diameter: 50 mm, tilt angle: 1.degree.) controlled to a
measurement temperature of -25.degree. C. or -10.degree. C., and
then held at the same temperature for 10 minutes. In this period,
care was taken not to give a strain to the inserted solution.
[0145] Subsequently, at the measurement temperature of -25.degree.
C. or -10.degree. C., the complex viscosity .eta.* at -25.degree.
C. or -10.degree. C. was measured in a vibration mode under
conditions of an angular velocity of 6.3 rad/s and a strain amount
appropriately set in the range of from 0.1 to 100% according to the
measurement temperature.
[0146] The "temperature gradient .DELTA.|.eta.*| of complex
viscosity" was then calculated from the value of the complex
viscosity .eta.* at -25.degree. C. or -10.degree. C. using the
aforementioned calculation expression (f1).
(9) Proportions of Aromatic Component, Naphthene Component,
n-Paraffin Component, and Isoparaffin Component
[0147] The aromatic content, the naphthene content, and the total
paraffin content (i.e., the sum of the n-paraffin content and the
isoparaffin content) were determined according to ASTM D2786.
Subsequently, the n-paraffin content was determined according to a
GC-FID method, and the isoparaffin content was determined from the
difference between the total paraffin content and the n-paraffin
content.
[0148] The proportion of each of the aromatic component, the
naphthene component, the n-paraffin component, and the isoparaffin
component based on the 100% by volume of the total amount of the
components was calculated.
(10) Brookfield Viscosity
[0149] The Brookfield viscosity at -40.degree. C. was measured
according to ASTM D2983-09.
(11) NOACK Value
[0150] The value was measured under conditions of 145.degree. C.
for 1 hour according to ASTM D5800.
[0151] The properties of the feed stock oil (I) used in Examples
and Comparative Examples are shown in Table 1. The feedstock oil
(I) contained a gas oil fraction obtained by hydrocracking of a
heavy gas oil.
TABLE-US-00001 TABLE 1 Feedstock oil (I) Gas oil fraction obtained
by hydrocracking of Gas oil fraction contained heavy gas oil
Kinematic viscosity at 40.degree. C. mm.sup.2/s 5.170 Kinematic
viscosity at 100.degree. C. mm.sup.2/s 1.754 Flash point .degree.
C. 124 Aromatic content (% C.sub.A) -- 4.4 Naphthene content (%
C.sub.N) -- 25.9 Paraffin content (% C.sub.P) -- 69.7 Density
(15.degree. C.) g/cm.sup.3 0.8265 10% Distillation temperature
.degree. C. 278 90% Distillation temperature .degree. C. 383 Mass
average molecular weight -- 238 (Mw) Aromatic content % by volume
8.4 Naphthene content % by volume 46.8 n-Paraffin content % by
volume 8.8 Isoparaffin content % by volume 36.00
Producing Example 1 (Production of Base Oil A)
[0152] The feedstock oil (I) shown in Table 1 was subjected to a
hydrogenation isomerization dewaxing process using a
platinum-zeolite catalyst (containing zeolite as a carrier having
carried thereon platinum) under conditions of a reaction
temperature of 294.degree. C., a hydrogen partial pressure of 4
MPa, a supply ratio of hydrogen and the feedstock oil
(hydrogen/feedstock oil) of 422 Nm.sup.3/kL, and an LHSV of 1.1
hr.sup.-1, so as to provide a produced oil (i).
[0153] The produced oil (i) having been subjected to the
hydrogenation isomerization dewaxing was then subjected to a
hydrofinishing process using a nickel/tungsten-alumina catalyst
(containing alumina as a carrier having carried thereon nickel and
tungsten) under conditions of a reaction temperature of 290.degree.
C., a hydrogen partial pressure of 18.5 MPa, a supply ratio of
hydrogen and the produced oil (i) (hydrogen/produced oil (i)) of
1,000 Nm.sup.3/kL, and an LHSV of 0.6 hr.sup.-1.
[0154] The produced oil having been subjected to the hydrofinishing
process was distilled under reduced pressure, and a fraction having
a kinematic viscosity at 40.degree. C. in a range of from 4.0 to
6.0 mm.sup.2/s was collected to provide a base oil (A). The
properties of the base oil (A) are shown in Table 2.
[0155] Base oils (B) and (C) having the properties shown in Table 2
were prepared.
TABLE-US-00002 TABLE 2 Kind of base oil (A) (B) (C) Kinematic
viscosity at mm.sup.2/s 5.409 7.117 1.630 40.degree. C. Kinematic
viscosity at mm.sup.2/s 1.793 2.170 0.796 100.degree. C. Flash
point .degree. C. 156 158 86 Temperature gradient .DELTA.|.eta.*|
Pa s/.degree. C. 0.0022 -- -- of complex viscosity Aniline point
.degree. C. 95.6 -- -- Density (15.degree. C.) g/cm.sup.3 0.821
0.820 0.794 Aromatic content (% C.sub.A) -- 1.0 -- -- Naphthene
content (% C.sub.N) -- 29.7 -- -- Paraffin content (% C.sub.P) --
69.3 -- --
Examples 1 to 6 and Comparative Example 1
[0156] Lubricating oil compositions were prepared according to the
blending formulation (% by mass) shown in Table 3. The resulting
lubricating oil compositions were evaluated for the properties by
measuring the properties thereof and performing the tests. The
evaluation results are shown in Table 3.
TABLE-US-00003 TABLE 3 Example Comparative Example 1 2 3 4 5 6 1 2
3 Blending Base oil (A) % by mass 92.00 90.00 88.00 88.00 84.00
37.00 -- 78.00 100.00 for- Base oil (B) % by mass -- -- -- -- --
45.00 78.00 -- -- mulation Base oil (C) % by mass -- -- -- -- --
8.00 12.50 12.50 -- Viscosity index % by mass 8.00 10.00 12.00 --
-- 10.00 9.50 9.50 -- improver A Viscosity index % by mass -- -- --
12.00 16.00 -- -- -- -- improver B Total % by mass 100.00 100.00
100.00 100.00 100.00 100.00 100.00 100.00 100.00 Properties Base
oil and Kinematic viscosity mm.sup.2/s 5.410 5.410 5.410 5.410
5.410 5.344 5.426 4.375 5.409 evaluation at 40.degree. C. Kinematic
viscosity mm.sup.2/s 1.793 1.793 1.793 1.793 1.793 1.785 1.808
1.555 1.793 at 100.degree. C. Flash point .degree. C. 156 156 156
156 156 149 118 115 156 Lubricating oil composition Kinematic
viscosity mm.sup.2/s 9.807 11.490 13.170 8.325 9.555 11.520 11.470
10.210 5.409 at 40.degree. C. Kinematic viscosity mm.sup.2/s 6.630
7.809 8.991 5.811 6.791 7.822 7.761 6.989 3.444 at 60.degree. C.
Kinematic viscosity mm.sup.2/s 3.646 4.310 4.977 3.339 3.985 4.312
4.259 3.901 1.793 at 100.degree. C. Viscosity index -- 324 353 379
363 417 352 346 352 -- Flash point .degree. C. 160 158 150 156 156
146 116 114 156 Density (15.degree. C.) g/cm.sup.3 0.8271 0.8287
0.8303 0.8248 0.8249 0.8232 0.8291 0.8288 0.821 Brookfield
viscosity mPa s 530 580 680 440 500 570 560 520 -- NOACK value % by
mass 5.9 6.3 6.1 6.3 6.5 8.3 13.6 14.1 --
[0157] The details of the viscosity index improvers shown in Table
1 used in the examples were as follows.
[0158] Viscosity index improver A: polymethacrylate (mass average
molecular weight (Mw): 140,000, kinematic viscosity at 100.degree.
C.: 835 mm.sup.2/s, a mixture of a polymethacrylate and a diluent
oil, polymethacrylate content: 53.3% by mass, contents of
polymethacrylate only in Examples 1, 2, 3, and 6, and Comparative
Examples 1 and 2 (% by mass): 4.26, 5.33, 6.40, 5.33, 5.06, and
5.06)
[0159] Viscosity index improver B: polymethacrylate (mass average
molecular weight (Mw): 200,000, kinematic viscosity at 100.degree.
C.: 850 mm.sup.2/s, a mixture of a polymethacrylate and a diluent
oil, polymethacrylate content: 28.0% by mass, contents of
polymethacrylate only in Examples 4 and 5 (% by mass): 3.36 and
4.48)
[0160] It was confirmed that the lubricating oil compositions of
Examples 1 to 6 had excellent viscosity characteristics with a low
temperature dependency of the viscosity, a flash point of
140.degree. C. or more, and a property of difficulty in evaporation
with a NOACK value of 10% by mass or less, and also had low
kinematic viscosities at 40.degree. C., 60.degree. C., and
100.degree. C. in a well balanced manner. It was also confirmed
that the lubricating oil compositions were able to have a fuel
efficiency capability by decreasing the viscosity, associated with
the excellent viscosity characteristics.
[0161] On the other hand, it was confirmed that the lubricating oil
compositions of Comparative Examples 1 and 2 using a base oil
having a flash point of 140.degree. C. or less were suppressed in
increase of the viscosity at a low temperature and had low
kinematic viscosities at 40.degree. C., 60.degree. C., and
100.degree. C. in a well balanced manner, but resulted in low flash
points of 116.degree. C. and 114.degree. C. and large NOACK values
of 13.6% by mass and 14.1% by mass, which indicated a property of
easiness in evaporation, and thus there were a problem in safety
and a possibility of damaging the apparatus. The base oil (A) alone
of Comparative Example 3 having no viscosity index improver added
had a kinematic viscosity at 60.degree. C. of less than 5.5
mm.sup.2/s and did not have excellent viscosity
characteristics.
INDUSTRIAL APPLICABILITY
[0162] The lubricating oil composition of the present embodiment
has such features as excellent viscosity characteristics, a
property of difficulty in evaporation, and a fuel efficiency
capability by decreasing the viscosity, and therefore can be
favorably applied to various purposes including a drive system
apparatus, such as a shock absorber, a transmission, and a power
steering, an engine, a hydraulic system, a turbine, a compressor, a
machine tool, a cutting machine, a gear, a fluid dynamic bearing,
and a rolling bearing. Among these, the lubricating oil composition
is preferably applied to a drive system apparatus, more preferably
applied to a shock absorber for an automobile, such as a four-wheel
vehicle and a two-wheel vehicle, and an earthquake resistant
mechanism of housing, and particularly preferably applied to a
shock absorber for a four-wheel vehicle.
* * * * *