U.S. patent application number 14/416339 was filed with the patent office on 2015-07-23 for lubricating oil composition.
This patent application is currently assigned to JX NIPPON OIL & ENERGY CORPORATION. The applicant listed for this patent is JX NIPPON OIL & ENERGY CORPORATION. Invention is credited to Hiromitsu Matsuda, Shigeki Matsui, Hiroya Miyamoto, Kazuo Tagawa, Akira Takagi.
Application Number | 20150203785 14/416339 |
Document ID | / |
Family ID | 49997368 |
Filed Date | 2015-07-23 |
United States Patent
Application |
20150203785 |
Kind Code |
A1 |
Matsui; Shigeki ; et
al. |
July 23, 2015 |
LUBRICATING OIL COMPOSITION
Abstract
A lubricating oil composition comprising a lubricating base oil
having a kinematic viscosity at 100.degree. C. of 1 to 10
mm.sup.2/s, and a poly(meth)acrylate viscosity index improver
containing a structural unit represented by the formula (1) in a
proportion of 30 to 90 mol % and having a hydrocarbon main chain
ratio of 0.18 or less: ##STR00001## wherein R.sup.1 represents
hydrogen or a methyl group, and R.sup.2 represents a linear or
branched hydrocarbon group having a carbon number of 6 or less.
Inventors: |
Matsui; Shigeki; (Tokyo,
JP) ; Miyamoto; Hiroya; (Tokyo, JP) ; Matsuda;
Hiromitsu; (Tokyo, JP) ; Tagawa; Kazuo;
(Tokyo, JP) ; Takagi; Akira; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JX NIPPON OIL & ENERGY CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
JX NIPPON OIL & ENERGY
CORPORATION
Tokyo
JP
|
Family ID: |
49997368 |
Appl. No.: |
14/416339 |
Filed: |
July 24, 2013 |
PCT Filed: |
July 24, 2013 |
PCT NO: |
PCT/JP2013/070101 |
371 Date: |
January 22, 2015 |
Current U.S.
Class: |
508/186 ;
508/364; 508/463 |
Current CPC
Class: |
C10N 2020/02 20130101;
C10M 161/00 20130101; C10N 2040/255 20200501; C10N 2030/02
20130101; C10N 2010/04 20130101; C10M 2207/262 20130101; C10N
2040/25 20130101; C10N 2030/54 20200501; C10N 2010/12 20130101;
C10M 2215/28 20130101; C10N 2020/04 20130101; C10M 2203/1025
20130101; C10M 2209/084 20130101; C10M 2201/087 20130101; C10N
2040/04 20130101; C10M 2223/045 20130101; C10N 2030/68 20200501;
C10M 2203/1006 20130101; C10M 2219/068 20130101; C10N 2030/06
20130101; C10N 2040/252 20200501; C10M 145/14 20130101; C10M
2207/289 20130101; C10M 2223/045 20130101; C10N 2010/04 20130101;
C10M 2203/1025 20130101; C10N 2020/02 20130101; C10M 2219/068
20130101; C10N 2010/12 20130101; C10M 2207/262 20130101; C10N
2010/04 20130101; C10M 2219/068 20130101; C10N 2010/12 20130101;
C10M 2203/1025 20130101; C10N 2020/02 20130101; C10M 2223/045
20130101; C10N 2010/04 20130101; C10M 2207/262 20130101; C10N
2010/04 20130101 |
International
Class: |
C10M 161/00 20060101
C10M161/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 24, 2012 |
JP |
2012-163624 |
Apr 5, 2013 |
JP |
2013-079816 |
Apr 5, 2013 |
JP |
2013-079828 |
Apr 5, 2013 |
JP |
2013-079829 |
Apr 5, 2013 |
JP |
2013/079830 |
Apr 5, 2013 |
JP |
2013-079832 |
Claims
1. A lubricating oil composition comprising: a lubricating base oil
having a kinematic viscosity at 100.degree. C. of 1 to 10
mm.sup.2/s; and a poly(meth)acrylate viscosity index improver
containing a structural unit represented by the following formula
(1) in a proportion of 30 to 90 mol % and having a hydrocarbon main
chain ratio of 0.18 or less: ##STR00014## wherein R.sup.1
represents hydrogen or a methyl group, and R.sup.2 represents a
linear or branched hydrocarbon group having a carbon number of 6 or
less.
2. The lubricating oil composition according to claim 1, wherein
the poly(meth)acrylate viscosity index improver is a
poly(meth)acrylate viscosity index improver containing the
structural unit represented by the formula (1) in the proportion of
30 to 90 mol % and a structural unit represented by the following
formula (2) in a proportion of 0.1 to 50 mol %, and having a
hydrocarbon main chain ratio of 0.18 or less: ##STR00015## wherein
R.sup.3 represents hydrogen or a methyl group, and R.sup.4
represents a linear or branched hydrocarbon group having a carbon
number of 16 or more.
3. The lubricating oil composition according to claim 1, wherein
the viscosity index improver is a viscosity index improver having a
PSSI of 10 or less and a ratio of a molecular weight to the PSSI
(Mw/PSSI) of 1.times.10.sup.4 or more.
4. The lubricating oil composition according to claim 2, wherein
R.sup.4 in the formula (2) is a linear or branched hydrocarbon
group having a carbon number of 16 or more and 19 or less, and in
the viscosity index improver, the proportion of the structural unit
represented by the formula (2) in which R.sup.4 is a linear or
branched hydrocarbon group having a carbon number of 18 is 0.1 to
40 mol %.
5. The lubricating oil composition according to claim 1, wherein an
aromatic content of the lubricating base oil is 5.0% or less, a
kinematic viscosity at 100.degree. C. of the lubricating oil
composition is 6 to 9 mm.sup.2/s, a viscosity index of the
lubricating oil composition is 180 or more, an HTHS viscosity at
150.degree. C. of the lubricating oil composition is 2.6 mPas or
more, and an HTHS viscosity at 100.degree. C. of the lubricating
oil composition is 5.0 mPas or less.
6. The lubricating oil composition according to claim 1, further
comprising a friction modifier.
7. The lubricating oil composition according to claim 6, wherein
the friction modifier is an organic molybdenum friction
modifier.
8. The lubricating oil composition according to claim 1, further
comprising a second viscosity index improver which is a dispersive
viscosity index improver.
9. The lubricating oil composition according to claim 1, further
comprising a metallic detergent, wherein the metallic detergent has
a linear or branched hydrocarbon group having a carbon number of 20
or more.
10. The lubricating oil composition according to claim 1, further
comprising a metallic detergent, wherein the metallic detergent is
an overbased metallic detergent having a metal ratio of 3.4 or
less.
11. The lubricating oil composition according to claim 9, wherein
the metallic detergent is an overbased alkaline earth metal
salicylate prepared by overbasing an alkaline earth metal
salicylate with an alkaline earth metal borate.
Description
TECHNICAL FIELD
[0001] The present invention relates to a lubricating oil
composition.
BACKGROUND ART
[0002] In the related art, lubricating oils are used for internal
combustion engines, transmissions, and other machine apparatuses to
smooth their action. Particularly in lubricating oil for internal
combustion engines (engine oil), high performance is required with
higher performance of the internal combustion engines, higher
outputs, severer operation conditions, and the like. Accordingly,
to meet such required performances, various additives such as
anti-wear agents, metallic detergents, ash-free dispersants, and
antioxidants are blended with the conventional engine oil (for
example, see Patent Literatures 1 to 3 below). Moreover, the fuel
efficiency required for the lubricating oil is increasing, and
application of base oil having high viscosity index and application
of a variety of friction modifiers are examined (for example, see
Patent Literature 4 below).
CITATION LIST
Patent Literature
[0003] Patent Literature 1: JP-A-2001-279287
[0004] Patent Literature 2: JP-A-2002-129182
[0005] Patent Literature 3: JP-A-08-302378
[0006] Patent Literature 4: JP-A-06-306384
SUMMARY OF INVENTION
Technical Problem
[0007] However, it cannot be said that the conventional lubricating
oils are not sufficient in fuel efficiency.
[0008] For example, as a standard method for fuel efficiency, a
reduction in the kinematic viscosity of the lubricating oil and an
increase in the viscosity index (multi-grading by a combination of
low viscosity base oils with viscosity index improvers), and
blending of friction reducing agents are known. In the case of a
reduction in viscosity, the lubrication performance is reduced
under severe lubrication conditions (under high temperature high
shear conditions) due to a reduction of the viscosity of the
lubricating oil or the base oil that forms the lubricating oil,
occurrence of failures such as wear, burning, and fatigue breaking
is concerned. Moreover, for blending of friction reducing agents,
ash-free friction modifiers and molybdenum friction modifiers are
known, but there is demand for an oil with fuel efficiency superior
to that of standard oils having theses friction reducing
agents.
[0009] To prevent deficits in the reduction in viscosity and give
fuel efficiency while maintaining durability, it is effective to
increase an HTHS viscosity at 150.degree. C. ("HTHS viscosity" is
also referred to as "high temperature high shear viscosity") while
reducing a kinematic viscosity at 40.degree. C., a kinematic
viscosity at 100.degree. C., and an HTHS viscosity at 100.degree.
C.; however, it is very difficult for the conventional lubricating
oil to satisfy these requirements all.
[0010] For further improvement in fuel efficiency, an engine oil
having a HTHS viscosity at 150.degree. C. of lower than 2.6 mPas,
which is the lower limit of the HTHS viscosity at 150.degree. C. of
an SAE 0W-20 engine oil is developed and used. However, because for
the engine oil having an HTHS viscosity at 150.degree. C. lower
than 2.6 mPas, the lubrication state of the engine oil to be used
is severer than ever, it is important to maintain the HTHS
viscosity at 150.degree. C. reduced by usage at a constant level or
more. Moreover, it is important to reduce the kinematic viscosity
as much as possible while reducing the coefficient of friction in a
boundary lubrication region.
[0011] The present invention has been made in consideration of such
circumstances, and an object of the present invention is to provide
a lubricating oil composition excellent in durability and fuel
efficiency that can reduce a kinematic viscosity at 40.degree. C.
and a kinematic viscosity at 100.degree. C. from the beginning of
usage after usage for a long time, and can suppress a reduction in
viscosity after shear.
Solution to Problem
[0012] To solve the above problems, the present invention provides
a lubricating oil composition according to [1] to [10] below.
[0013] [1] A lubricating oil composition comprising:
[0014] a lubricating base oil having a kinematic viscosity at
100.degree. C. is 1 to 10 mm.sup.2/s; and
[0015] a poly(meth)acrylate viscosity index improver containing a
structural unit represented by the following formula (1) in a
proportion of 30 to 90 mol % and having a hydrocarbon main chain
ratio of 0.18 or less:
##STR00002##
wherein R.sup.1 represents hydrogen or a methyl group, and R.sup.2
represents a linear or branched hydrocarbon group having a carbon
number of 6 or less. [0016] [2] The lubricating oil composition
according to [1], wherein the poly(meth)acrylate viscosity index
improver is a poly(meth)acrylate viscosity index improver
containing the structural unit represented by the formula (1) in
the proportion of 30 to 90 mol % and a structural unit represented
by the following formula (2) in a proportion of 0.1 to 50 mol %,
and having a hydrocarbon main chain ratio of 0.18 or less:
##STR00003##
[0016] wherein R.sup.3 represents hydrogen or a methyl group, and
R.sup.4 represents a linear or branched hydrocarbon group having a
carbon number of 16 or more. [0017] [3] The lubricating oil
composition according to [1] or [2], wherein the viscosity index
improver is a viscosity index improver having a PSSI of 10 or less
and a ratio of a molecular weight to the PSSI (Mw/PSSI) of
1.times.10.sup.4 or more. [0018] [4] The lubricating oil
composition according to [2] or [3], wherein R.sup.4 in the formula
(2) is a linear or branched hydrocarbon group having a carbon
number of 16 or more and 19 or less, and
[0019] in the viscosity index improver, the proportion of the
structural unit represented by the formula (2) in which R.sup.4 is
a linear or branched hydrocarbon group having a carbon number of 18
is 0.1 to 40 mol %. [0020] [5] The lubricating oil composition
according to any one of [1] to [4], wherein an aromatic content of
the lubricating base oil is 5.0% or less,
[0021] the kinematic viscosity at 100.degree. C. of the lubricating
oil composition is 6 to 9 mm.sup.2/s,
[0022] the viscosity index of the lubricating oil composition is
180 or more,
[0023] the HTHS viscosity at 150.degree. C. of the lubricating oil
composition is 2.6 mPas or more, and
[0024] the HTHS viscosity at 100.degree. C. of the lubricating oil
composition is 5.0 mPas or less. [0025] [6] The lubricating oil
composition according to any one of [1] to [5], further comprising
a friction modifier. [0026] [7] The lubricating oil composition
according to [6], wherein the friction modifier is an organic
molybdenum friction modifier. [0027] [8] The lubricating oil
composition according to any one of [1] to [7], further comprising
a second viscosity index improver which is a dispersive viscosity
index improver. [0028] [9] The lubricating oil composition
according to any one of [1] to [8], further comprising a metallic
detergent, wherein the metallic detergent has a linear or branched
hydrocarbon group having a carbon number of 20 or more. [0029] [10]
The lubricating oil composition according to any one of [1] to [8],
further comprising a metallic detergent, wherein the metallic
detergent is an overbased metallic detergent having a metal ratio
of 3.4 or less. [0030] [11] The lubricating oil composition
according to [9] or [10], wherein the metallic detergent is an
overbased alkaline earth metal salicylate prepared by overbasing an
alkaline earth metal salicylate with an alkaline earth metal
borate.
[0031] Here, the term "PSSI" in the present invention means a
permanent shear stability index of a polymer (Permanent Shear
Stability Index) in accordance with ASTM D 6022-01 (Standard
Practice for Calculation of Permanent Shear Stability Index)
calculated based on the data measured in accordance with ASTM D
6278-02 (Test Method for Shear Stability of Polymer Containing
Fluids Using a European Diesel Injector Apparatus).
Advantageous Effects of Invention
[0032] As above, according to the present invention, a lubricating
oil composition excellent in durability and fuel efficiency that
can sufficiently reduce the kinematic viscosity at 40.degree. C.
and the kinematic viscosity at 100.degree. C. from the beginning of
usage after usage for a long time while maintaining the HTHS
viscosity at 150.degree. C., and can sufficiently suppress a
reduction in viscosity after shear can be provided.
[0033] Moreover, the lubricating oil composition according to the
present invention can be suitably used not only for gasoline
engines, diesel engines, gas engines, and the like for bicycles,
automobiles, power generation, cogeneration, and the like but also
for a variety of engines using fuels having a sulfur content of 50
mass ppm or less. The lubricating oil composition according to the
present invention is also useful for a variety of engines for ships
and outboard motors.
DESCRIPTION OF EMBODIMENTS
[0034] Hereinafter, suitable Embodiment of the present invention
will be described in detail.
[0035] The lubricating oil composition according to the present
embodiment contains a lubricating base oil having a kinematic
viscosity at 100.degree. C. of 1 to 10 mm.sup.2/s, and a
poly(meth)acrylate viscosity index improver (A) containing a
structural unit represented by the following formula (1) in a
proportion of 30 to 90 mol % and having a hydrocarbon main chain
ratio of 0.18 or less:
##STR00004##
wherein R.sup.1 represents hydrogen or a methyl group, and R.sup.2
represents a linear or branched hydrocarbon group having a carbon
number of 6 or less.
[0036] In the lubricating oil composition according to the present
embodiment, a lubricating base oil having a kinematic viscosity at
100.degree. C. of 1 to 10 mm.sup.2/s (hereinafter referred to as a
"lubricating base oil according to the present embodiment") is
used.
[0037] Examples of the lubricating base oil according to the
present embodiment include those having a kinematic viscosity at
100.degree. C. of 1 to 5 mm.sup.2/s among paraffin mineral oils,
normal paraffin base oils, and isoparaffin base oils obtained by
refining a lubricating oil fraction obtained by normal pressure
distillation and/or reduced pressure distillation of a crude oil
using one or two or more refining treatments selected from solvent
deasphalting, solvent extraction, hydrocracking, solvent dewaxing,
catalytic dewaxing, hydrorefining, sulfuric acid washing, clay
treatment, and the like.
[0038] Preferable examples of the lubricating base oil according to
the present embodiment can include base oils obtained by using the
base oils (1) to (8) shown below as the raw material, and refining
the raw material oil and/or a lubricating oil fraction recovered
from the raw material oil by a predetermined refining method to
recover a lubricating oil fraction: [0039] (1) Distilled oil
obtained by normal pressure distillation of a paraffinic crude oil
and/or a mixed-base crude oil, [0040] (2) Distilled oil obtained by
reduced pressure distillation of a paraffinic crude oil and/or a
normal pressure distillation residue oil of a mixed-base crude oil
(WVGO), [0041] (3) Waxes obtained by a lubricating oil dewaxing
step (such as slack wax) and/or synthetic waxes obtained by a
gas-to-liquid (GTL) process or the like (such as Fischer-Tropsch
wax and GTL wax), [0042] (4) One or two or more mixed oils selected
from the base oils (1) to (3) and/or a mild hydrocracked oil of the
mixed oil, [0043] (5) Two or more mixed oils selected from the base
oils (1) to (4), [0044] (6) Deasphalted oil (DAO) of the base oil
(1), (2), (3), (4) or (5), [0045] (7) Mild hydrocracked oil (MHC)
of the base oil (6), and [0046] (8) Mixed oil of two or more
selected from the base oils (1) to (7).
[0047] For the predetermined refining method, hydrorefining such as
hydrocracking and hydrofinishing; solvent refining such as furfural
solvent extraction; dewaxing such as solvent dewaxing and catalytic
dewaxing; white clay refining with acid clay or activated clay; and
chemical (acid or alkali) washing such as sulfuric acid washing and
sodium hydroxide washing are preferable. In the present embodiment,
among these refining methods, one method may be used alone, or two
or more may be used in combination. If two or more refining methods
are combined, the order is not particularly limited, and can be
properly selected.
[0048] Furthermore, for the lubricating base oil according to the
present embodiment, a base oil selected from the base oils (1) to
(8) or the following base oil (9) or (10) obtained by performing a
predetermined treatment on the lubricating oil fraction recovered
from the base oil is particularly preferable: [0049] (9)
Hydrocracking base oils obtained by hydrocracking the base oil
selected from the base oils (1) to (8) or the lubricating oil
fraction recovered from the base oil, and performing a dewaxing
treatment such as solvent dewaxing and catalytic dewaxing on the
product or the lubricating oil fraction recovered from the product
by distillation or the like, or performing distillation after the
dewaxing treatment, and [0050] (10) Hydrogenation isomerized base
oils obtained by hydrogenation isomerizing the base oil selected
from the base oils (1) to (8) or the lubricating oil fraction
recovered from the base oil, and performing a dewaxing treatment
such as solvent dewaxing and catalytic dewaxing on the product or
the lubricating oil fraction recovered from the product by
distillation or the like, or performing distillation after the
dewaxing treatment.
[0051] In production of the lubricating base oil (9) or (10), a
solvent refining treatment and/or a hydrofinishing step may be
included as preferably steps when necessary.
[0052] The catalyst used in the hydrocracking and hydrogenation
isomerization is not particularly limited, and hydrocracking
catalysts in which a carrier is a composite oxide having cracking
activity (such as silica alumina, alumina boria, and silica
zirconia) or one or more of the composite oxides in combination
bounded by a binder, and a metal having a hydrogenation activity
(such as one or more metals in Groups VIa and VIII in the periodic
table) is carried to the carrier; or hydrogenation isomerization
catalysts in which a metal containing at least one metal among
metals in Group VIII and having a hydrogenation activity is carried
to a carrier containing zeolite (such as ZSM-5, zeolite beta, and
SAPO-11) are preferably used. The hydrocracking catalyst and the
hydrogenation isomerization catalyst may be used in combination by
stacking or mixing.
[0053] The reaction conditions in hydrocracking and hydrogenation
isomerization are not particularly limited, and a hydrogen partial
pressure of 0.1 to 20 MPa, an average reaction temperature of 150
to 450.degree. C., LHSV of 0.1 to 3.0 hr.sup.-1, and the ratio of
hydrogen/oil of 50 to 20000 scf/b are preferred.
[0054] The kinematic viscosity at 100.degree. C. of the lubricating
base oil according to the present embodiment needs to be 10
mm.sup.2/s or less, preferably 4.5 mm.sup.2/s or less, more
preferably 4 mm.sup.2/s or less, still more preferably 3.8
mm.sup.2/s or less, particularly preferably 3.7 mm.sup.2/s or less,
and most preferably 3.6 mm.sup.2/s or less. The kinematic viscosity
at 100.degree. C. needs to be 1 mm.sup.2/s or more. It is
preferable that the kinematic viscosity at 100.degree. C. be 1.5
mm.sup.2/s or more. The kinematic viscosity at 100.degree. C. is
more preferably 2 mm.sup.2/s or more, still more preferably 2.5
mm.sup.2/s or more, and particularly preferably 3 mm.sup.2/s or
more. The kinematic viscosity at 100.degree. C. here designates the
kinematic viscosity at 100.degree. C. specified in ASTM D-445. In
the case where the kinematic viscosity at 100.degree. C. of the
lubricating base oil exceeds 10 mm.sup.2/s, low temperature
viscosity properties may be reduced, and sufficient fuel efficiency
may not be obtained. At a kinematic viscosity of 1 mm.sup.2/s or
less, formation of an oil film in a lubrication place is
insufficient; for this reason, lubrication is inferior, and the
evaporation loss of the lubricating oil composition may be
increased.
[0055] The kinematic viscosity at 40.degree. C. of the lubricating
base oil according to the present embodiment is preferably 40
mm.sup.2/s or less, more preferably 30 mm.sup.2/s or less, still
more preferably 25 mm.sup.2/s or less, particularly preferably 20
mm.sup.2/s or less, and most preferably 17 mm.sup.2/s or less. The
kinematic viscosity at 40.degree. C. is preferably 6.0 mm.sup.2/s
or more, more preferably 8.0 mm.sup.2/s or more, still more
preferably 10 mm.sup.2/s or more, particularly preferably 12
mm.sup.2/s or more, and most preferably 14 mm.sup.2/s or more. In
the case where the kinematic viscosity at 40.degree. C. of the
lubricating base oil exceeds 40 mm.sup.2/s, low temperature
viscosity properties may be reduced, and sufficient fuel efficiency
may not be obtained. At a kinematic viscosity of 6.0 mm.sup.2/s or
less, formation of an oil film in a lubrication place is
insufficient; for this reason, lubrication is inferior, and the
evaporation loss of the lubricating oil composition may be
increased.
[0056] It is preferable that the viscosity index of the lubricating
base oil according to the present embodiment be 100 or more. The
viscosity index is more preferably 105 or more, still more
preferably 110 or more, particularly preferably 115 or more, and
most preferably 120 or more. If the viscosity index is less than
100, not only viscosity-temperature properties, heat and oxidation
stability, and anti-volatilization are reduced, but also the
coefficient of friction tends to be increased; and resistance
against wear tends to be reduced.
[0057] The viscosity index in the present invention means the
viscosity index measured according to 71S K 2283-1993.
[0058] It is preferable that the lubricating base oil in the
lubricating oil composition according to the present embodiment be
a mixture of a first lubricating base oil component having a
kinematic viscosity at 100.degree. C. of 3.5 mm.sup.2/s or more and
having a viscosity index of 120 or more and a second lubricating
base oil component having a kinematic viscosity at 100.degree. C.
of less than 3.5 mm.sup.2/s. By using the mixture of the first
lubricating base oil component and the second lubricating base oil
component, high viscosity temperature properties can be given to
improve fuel efficiency more significantly.
[0059] The density (.rho..sub.15) at 15.degree. C. of the first
lubricating base oil component used in the lubricating oil
composition according to the present embodiment is preferably 0.860
or less, more preferably 0.850 or less, still more preferably 0.840
or less, and particularly preferably 0.822 or less.
[0060] The density at 15.degree. C. in the present invention means
a density measured at 15.degree. C. according to JIS K
2249-1995.
[0061] The pour point of the first lubricating base oil component
used in the lubricating oil composition according to the present
embodiment is preferably -10.degree. C. or less, more preferably
-12.5.degree. C. or less, still more preferably -15.degree. C. or
less, and particularly preferably -20.degree. C. or less. If the
pour point exceeds the upper limit value, the fluidity at a low
temperature of the entire lubricating oil using the lubricating
base oil tends to be reduced. The pour point in the present
invention means the pour point measured according to JIS K
2269-1987.
[0062] It is preferable that the kinematic viscosity at 100.degree.
C. of the first lubricating base oil component used in the
lubricating oil composition according to the present embodiment be
5 mm.sup.2/s or less. The kinematic viscosity is more preferably
4.5 mm.sup.2/s or less, still more preferably 4.0 mm.sup.2/s or
less, and particularly preferably 3.9 mm.sup.2/s or less. It is
preferable that the kinematic viscosity at 100.degree. C. be 3.5
mm.sup.2/s or more. The kinematic viscosity is more preferably 3.6
mm.sup.2/s or more, still more preferably 3.7 mm.sup.2/s or more,
and particularly preferably 3.8 mm.sup.2/s or more. If the
kinematic viscosity at 100.degree. C. exceeds 5 mm.sup.2/s, low
temperature viscosity properties may be reduced, and sufficient
fuel efficiency may not be obtained. At a kinematic viscosity less
than 3.5 mm.sup.2/s, formation of an oil film in a lubrication
place is insufficient; for this reason, lubrication is inferior,
and the evaporation loss of the lubricating oil composition may be
increased.
[0063] The kinematic viscosity at 40.degree. C. of the first
lubricating base oil component used in the lubricating oil
composition according to the present embodiment is preferably 40
mm.sup.2/s or less, more preferably 30 mm.sup.2/s or less, still
more preferably 25 mm.sup.2/s or less, particularly preferably 20
mm.sup.2/s or less, and most preferably 17 mm.sup.2/s or less. The
kinematic viscosity at 40.degree. C. is preferably 6 0 mm.sup.2/s
or more, more preferably 8.0 mm.sup.2/s or more, still more
preferably 10 mm.sup.2/s or more, particularly preferably 12
mm.sup.2/s or more, and most preferably 14 mm.sup.2/s or more. In
the case where the kinematic viscosity at 40.degree. C. exceeds 40
mm.sup.2/s, low temperature viscosity properties may be reduced,
and sufficient fuel efficiency may not be obtained. At a kinematic
viscosity of 6.0 mm.sup.2/s or less, formation of an oil film in a
lubrication place is insufficient; for this reason, lubrication is
inferior, and the evaporation loss of the lubricating oil
composition may be increased.
[0064] It is preferable that the viscosity index of the first
lubricating base oil component used in the lubricating oil
composition according to the present embodiment be 100 or more. The
viscosity index is more preferably 110 or more, still more
preferably 120 or more, particularly preferably 130 or more, and
most preferably 140 or more. The viscosity index is preferably 170
or less, more preferably 160 or less, still more preferably 155 or
less, and particularly preferably 150 or less. If the viscosity
index is less than 100, not only viscosity-temperature properties,
heat and oxidation stability, and anti-volatilization are reduced,
but also the coefficient of friction tends to be increased; and
resistance against wear tends to be reduced. If the viscosity index
exceeds 170, low temperature viscosity tends to be increased to
reduce the fuel efficiency at low oil temperatures. Moreover,
startability tends to be reduced.
[0065] The density (.rho..sub.15) at 15.degree. C. of the second
lubricating base oil component used in the lubricating oil
composition according to the present embodiment is preferably 0.860
or less, more preferably 0.850 or less, still more preferably 0.840
or less, and particularly preferably 0.835 or less.
[0066] The pour point of the second lubricating base oil component
used in the lubricating oil composition according to the present
embodiment is preferably -10.degree. C. or less, more preferably
-12.5.degree. C. or less, still more preferably -15.degree. C. or
less, and particularly preferably -20.degree. C. or less. If the
pour point exceeds the upper limit value, the fluidity at a low
temperature of the entire lubricating oil using the lubricating
base oil tends to be reduced.
[0067] It is preferable that the kinematic viscosity at 100.degree.
C. of the second lubricating base oil component used in the
lubricating oil composition according to the present embodiment be
less than 3.5 mm.sup.2/s. The kinematic viscosity is more
preferably 3.4 mm.sup.2/s or less, and still more preferably 3.3
mm.sup.2/s or less. It is preferable that the kinematic viscosity
at 100.degree. C. be 2 mm.sup.2/s or more, and the kinematic
viscosity is more preferably 2.5 mm.sup.2/s or more, and still more
preferably 3.0 mm.sup.2/s or more. If the kinematic viscosity at
100.degree. C. exceeds 3.5 mm.sup.2/s, low temperature viscosity
properties may be reduced, and sufficient fuel efficiency may not
be obtained. At a kinematic viscosity less than 2 mm.sup.2/s,
formation of an oil film in a lubrication place is insufficient;
for this reason, lubrication is inferior, and the evaporation loss
of the lubricating oil composition may be increased.
[0068] The kinematic viscosity at 40.degree. C. of the second
lubricating base oil component used in the lubricating oil
composition according to the present embodiment is preferably 20
mm.sup.2/s or less, more preferably 18 mm.sup.2/s or less, still
more preferably 16 mm.sup.2/s or less, and particularly preferably
14 mm.sup.2/s or less. The kinematic viscosity at 40.degree. C. is
preferably 6.0 mm.sup.2/s or more, more preferably 8.0 mm.sup.2/s
or more, still more preferably 10 mm.sup.2/s or more, particularly
preferably 12 mm.sup.2/s or more, and most preferably 13 mm.sup.2/s
or more. If the kinematic viscosity at 40.degree. C. exceeds 20
mm.sup.2/s, low temperature viscosity properties may be reduced,
and sufficient fuel efficiency may not be obtained. At a kinematic
viscosity of 6.0 mm.sup.2/s or less, formation of an oil film in a
lubrication place is insufficient; for this reason, lubrication is
inferior, and the evaporation loss of the lubricating oil
composition may be increased.
[0069] It is preferable that the viscosity index of the second
lubricating base oil component used in the lubricating oil
composition according to the present embodiment be 100 or more. The
viscosity index is more preferably 105 or more, and still more
preferably 110 or more. The viscosity index is preferably 160 or
less, more preferably 150 or less, still more preferably 140 or
less, and particularly preferably 135 or less. If the viscosity
index is less than 100, not only viscosity-temperature properties,
heat and oxidation stability, and anti-volatilization are reduced,
but also the coefficient of friction tends to be increased.
Moreover, resistance against wear tends to be reduced. If the
viscosity index exceeds 160, low temperature viscosity tends to be
increased to reduce the fuel efficiency at low oil temperatures.
Moreover, startability tends to be reduced.
[0070] The sulfur content of the lubricating base oil used in the
present embodiment depends on the sulfur content of the raw
material. For example, in the case where a raw material containing
substantially no sulfur as a synthetic wax component obtained by
the Fischer-Tropsch reaction or the like is used, the lubricating
base oil containing substantially no sulfur can be obtained. In the
case where a raw material containing sulfur such as slack wax
obtained in the refining process of the lubricating base oil and
microcrystalline wax obtained in the wax refining process thereof
is used, the sulfur content of the lubricating base oil to be
obtained is usually 100 mass ppm or more. In the lubricating base
oil according to the present embodiment, from the viewpoint of
further improvement in heat and oxidation stability and a reduction
in sulfur, it is preferable that the sulfur content be 100 mass ppm
or less, it is more preferable that the sulfur content be 50 mass
ppm or less, it is still more preferable that the sulfur content be
10 mass ppm or less, and it is particularly preferable that the
sulfur content be 5 mass ppm or less.
[0071] The nitrogen content of the lubricating base oil used in the
present embodiment is preferably 7 mass ppm or less, more
preferably 5 mass ppm or less, and still more preferably 3 mass ppm
or less. If the nitrogen content exceeds 5 mass ppm, heat and
oxidation stability tends to be reduced. The nitrogen content in
the present invention means the nitrogen content measured according
to JIS K 2609-1990.
[0072] It is preferable that % C.sub.p of the lubricating base oil
used in the present embodiment be 70 or more. % C.sub.p is
preferably 80 or more, more preferably 85 or more, still more
preferably 87 or more, and particularly preferably 90 or more. %
C.sub.p is preferably 99.9 or less, more preferably 98 or less,
still more preferably 96 or less, and particularly preferably 94 or
less. If % C.sub.p of the lubricating base oil is less than the
lower limit value, viscosity-temperature properties, heat and
oxidation stability, and friction properties tend to be reduced;
furthermore, if an additive is blended with the lubricating base
oil, the effect of the additive tends to be reduced. If % C.sub.p
of the lubricating base oil exceeds the upper limit value, the
solubility of the additive tends to be reduced.
[0073] It is preferable that % C.sub.A of the lubricating base oil
used in the present embodiment be 2 or less. % C.sub.A is more
preferably 1 or less, still more preferably 0.8 or less, and
particularly preferably 0.5 or less. If % C.sub.A of the
lubricating base oil exceeds the upper limit value,
viscosity-temperature properties, heat and oxidation stability, and
fuel efficiency tend to be reduced.
[0074] It is preferable that % C.sub.N of the lubricating base oil
used in the present embodiment be 30 or less. % C.sub.N is
preferably 25 or less, more preferably 20 or less, still more
preferably 15 or less, and particularly preferably 10 or less. %
C.sub.N is preferably 1 or more, more preferably 3 or more, still
more preferably 5 or more, and particularly preferably 6 or more.
If % C.sub.N of the lubricating base oil exceeds the upper limit
value, viscosity-temperature properties, heat and oxidation
stability, and friction properties tend to be reduced. If % C.sub.N
is less than the lower limit value, the solubility of the additive
tends to be reduced.
[0075] % C.sub.p, % C.sub.N, and % C.sub.A in the present invention
mean the percentage of the number of paraffin carbon atoms to the
total number of carbon atoms, the percentage of the number of
naphthene carbon atoms to the total number of carbon atoms, and the
percentage of the number of aromatic carbon atoms to the total
number of carbon atoms, respectively, which are determined by the
method (n-d-M ring analysis) according to ASTM D 3238-85. Namely,
preferable ranges of % C.sub.p, % C.sub.N, and % C.sub.A above
described are based on the values determined by the method above;
for example, even in a lubricating base oil containing no naphthene
content, % C.sub.N detefinined by the method may indicate a value
more than 0.
[0076] The content of the saturates in the lubricating base oil
used in the present embodiment is preferably 90% by mass or more,
preferably 95% by mass or more, more preferably 99% by mass or more
based on the total amount of the lubricating base oil; the
proportion of the cyclic saturates in the saturates is preferably
40% by mass or less, preferably 35% by mass or less, preferably 30%
by mass or less, more preferably 25% by mass or less, and still
more preferably 21% by mass or less. The proportion of the cyclic
saturates in the saturates is preferably 5% by mass or more, and
more preferably 10% by mass or more. If the content of the
saturates and the proportion of the cyclic saturates in the
saturates each satisfy the conditions above, viscosity-temperature
properties and heat and oxidation stability can be improved; if an
additive is blended with the lubricating base oil, the function of
the additive can be demonstrated at a higher level while the
additive is sufficiently stably dissolved in the lubricating base
oil. Furthermore, according to the present embodiment, the friction
properties of the lubricating base oil itself can be improved; as a
result, an improvement in a friction reducing effect and thus an
improvement in energy saving properties can be attained.
[0077] The saturates in the present invention are measured by the
method described in ASTM D 2007-93 above.
[0078] In the method for separating the saturates or in composition
analysis of the cyclic saturates, a noncyclic saturates, or the
like, a similar method that can obtain similar results can be used.
Examples of the methods, besides the method above, can include the
method described in ASTM D 2425-93, the method described in ASTM D
2549-91, the method by a high performance liquid chromatography
(HPLC), or the modified methods thereof.
[0079] The aromatic content of the lubricating base oil used in the
present embodiment is preferably 5% by mass or less, more
preferably 4% by mass or less, still more preferably 2% by mass or
less, and particularly preferably 1% by mass or less based on the
total amount of the lubricating base oil, and is preferably 0.1% by
mass or more, and more preferably 0.2% by mass or more based on the
total amount of the lubricating base oil. If the content of the
aromatics exceeds the upper limit value, viscosity-temperature
properties, heat and oxidation stability, friction properties,
anti-volatilization, and low temperature viscosity properties tend
to be reduced; if an additive is blended with the lubricating base
oil, the effect of the additive tends to be reduced. The
lubricating base oil according to the present embodiment may be a
lubricating base oil containing no aromatics, but the content of
the aromatics in the range of the lower limit value or more can
further enhance the solubility of the additive.
[0080] The aromatic content in the present invention means the
value measured according to ASTM D 2007-93. The aromatics usually
include alkylbenzene and alkylnaphthalene; anthracene,
phenanthrene, and alkylated products thereof; compounds in which
four or more benzene rings are condensed; and aromatic compounds
having a heteroatom such as pyridines, quinolines, phenols, and
naphthols.
[0081] A synthetic base oil may be used as the lubricating base oil
according to the present embodiment. Examples of the synthetic base
oil having a kinematic viscosity at 100.degree. C. is 1 to 10
mm.sup.2/s include poly-.alpha.-olefins or hydrides thereof,
isobutene oligomers or hydrides thereof, isoparaffin, alkylbenzene,
alkylnaphthalene, diesters (such as ditridecyl glutarate,
di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate,
and di-2-ethylhexylcebacate), polyol esters (such as
trimethylolpropane caprylate, trimethylolpropane pelargonate,
pentaerythritol2-ethylhexanoate, and pentaerythritol pelargonate),
polyoxyalkylene glycol, dialkyldiphenyl ether, polyphenyl ether;
among these, poly-.alpha.-olefins are preferable. Examples of
poly-.alpha.-olefins typically include oligomers or co-oligomers of
.alpha.-olefins having a carbon number of 2 to 32, preferably a
carbon number of 6 to 16 (such as 1-octene oligomer, decene
oligomer, and ethylene-propylene co-oligomer) and hydrides
thereof.
[0082] The method for producing poly-.alpha.-olefin is not
particularly limited, and examples thereof include a method for
polymerizing .alpha.-olefin in the presence of a polymerization
catalyst containing a complex of aluminum trichloride or boron
trifluoride, water, an alcohol (such as ethanol, propanol, and
butanol), and carboxylic acid or an ester thereof, such as a
Friedel-Crafts catalyst.
[0083] In the lubricating oil composition according to the present
embodiment, the lubricating base oil according to the present
embodiment may be used alone, or the lubricating base oil according
to the present embodiment may be used in combination with one or
two or more of other base oils. In the case where the lubricating
base oil according to the present embodiment is used in combination
with the other base oil(s), it is preferable that the proportion of
the lubricating base oil according to the present embodiment in the
mixed base oils be 30% by mass or more, it is more preferable that
the proportion of the lubricating base oil according to the present
embodiment in the mixed base oils be 50% by mass or more, and it is
still more preferable that the proportion of the lubricating base
oil according to the present embodiment in the mixed base oils be
70% by mass or more.
[0084] The other base oils used in combination with the lubricating
base oil according to the present embodiment is not particularly
limited, and examples of a mineral oil-based base oil include
solvent refined mineral oils, hydrocracked mineral oils,
hydrorefined mineral oils, and solvent dewaxed base oils having a
kinematic viscosity at 100.degree. C. of 10 mm.sup.2/s or more and
1000 mm.sup.2/s or less.
[0085] Examples of the other synthetic base oils used in
combination with the lubricating base oil according to the present
embodiment include the synthetic base oils described above having a
kinematic viscosity at 100.degree. C. of out of the range of 1 to
10 mm.sup.2/s.
[0086] Moreover, the lubricating oil composition according to the
present embodiment contains a poly(meth)acrylate viscosity index
improver (A) (hereinafter referred to as "viscosity index improver
according to the present embodiment" for convenience) containing
one or two or more of the structural units represented by the
following formula (1) in a proportion of 30 to 90 mol % and having
the hydrocarbon main chain ratio of 0.18 or less. Thereby, the fuel
efficiency, the maintenance of fuel efficiency, and the durability
can be enhanced more significantly compared to the case where the
present configuration is not included. The compound has any form as
long as the compound satisfies the condition that the compound is a
poly(meth)acrylate viscosity index improver containing the
structural unit represented by the following formula (1) in the
proportion of 30 to 90 mol % and having the hydrocarbon main chain
ratio of 0.18 or less. Specific examples of the compound can
include non-dispersive or dispersive poly(meth)acrylate viscosity
index improvers, (meth)acrylate-olefin copolymers, or a mixture
thereof.
##STR00005##
[wherein R.sup.1 represents hydrogen or a methyl group, and R.sup.2
represents a linear or branched hydrocarbon group having a carbon
number of 6 or less.]
[0087] R.sup.2 in the structural unit represented by the formula
(1), as described above, is a linear or branched hydrocarbon group
having a carbon number of 6 or less and may be one hydrocarbon
group or a mixture of two or more thereof; R.sup.2 is preferably a
linear or branched hydrocarbon having a carbon number of 4 or less,
still more preferably a linear or branched hydrocarbon having a
carbon number of 3 or less, and more preferably a hydrocarbon group
having a carbon number of 2 or less.
[0088] In the viscosity index improver according to the present
embodiment, the proportion of the (meth)acrylate structural unit
represented by the formula (1) in a polymer is 30 to 90 mol % as
described above, preferably 80 mol % or less, more preferably 70
mol % or less, still more preferably 65 mol % or less, and
particularly preferably 60 mol % or less. The proportion is
preferably 30 mol % or more, more preferably 35 mol % or more, and
still more preferably 40 mol % or more. At a proportion more than
90 mol %, the solubility in the base oil, the effect of improving
viscosity temperature properties, and low temperature viscosity
properties may be inferior; at a proportion less than 30 mol %, the
effect of improving viscosity temperature properties may be
inferior.
[0089] Preferable examples of the poly(meth)acrylate viscosity
index improver according to the present embodiment can include
poly(meth)acrylate viscosity index improvers (A) containing one or
two or more of the structural units represented by the following
formula (1) in the proportion of 30 to 90 mol % and one or two or
more of the structural units represented by the following formula
(2) in a proportion of 0.1 to 50 mol %, and having the hydrocarbon
main chain ratio of 0.18 or less. By using such a viscosity index
improver, fuel efficiency, the maintenance of fuel efficiency, and
the durability can be enhanced much more significantly compared to
the case where the present configuration is not included. The
compound may have any form as long as the compound is a
poly(meth)acrylate viscosity index improver satisfying the
condition that the proportion of the structural unit represented by
the following formula (1) is 30 to 90 mol %, the proportion of one
or two or more of the structural units represented by the following
formula (2) is 0.1 to 50 mol %, and the hydrocarbon main chain
ratio is 0.18 or less. Specific examples of the compound can
include non-dispersive or dispersive poly(meth)acrylate viscosity
index improvers, (meth)acrylate-olefin copolymers, or a mixture
thereof.
##STR00006##
[wherein R.sup.3 represents hydrogen or a methyl group, and R.sup.4
represents a linear or branched hydrocarbon group having a carbon
number of 16 or more.]
[0090] R.sup.4 in the structural unit represented by the formula
(2), as described above, is a linear or branched hydrocarbon group
having a carbon number of 16 or more, and may be one hydrocarbon
group or a mixture of two or more thereof; R.sup.4 is preferably a
linear or branched hydrocarbon having a carbon number of 18 or
more.
[0091] A preferable aspect of the structural unit represented by
the formula (2) can include the structural unit in which R.sup.4 in
the formula (2) is a linear or branched hydrocarbon group having a
carbon number of 16 or more and 19 or less. In this case, R.sup.4
may be one or two or more groups, and it is more preferable that
the essential structural unit be the structural unit represented by
the formula (2) in which R.sup.4 is a linear or branched
hydrocarbon group having a carbon number of 18. Furthermore, the
proportion of the structural unit represented by the formula (2) in
which R.sup.4 is a linear or branched hydrocarbon group having a
carbon number of 18 is 0.1 to 40 mol %, preferably 10 to 36 mol %,
and more preferably 20 to 32 mol %.
[0092] The proportion of the (meth)acrylate structural unit
represented by the formula (2) in the polymer is preferably 0.1 to
50 mol %, more preferably 45 mol % or less, still more preferably
40 mol % or less, further still more preferably 35 mol % or less,
and particularly preferably 30 mol % or less. The proportion is
more preferably 0.2 mol % or more, still more preferably 1 mol % or
more, further still more preferably 5 mol % or more, particularly
preferably 10 mol % or more, and most preferably 20 mol % or more.
At a proportion more than 50 mol %, the effect of improving
viscosity temperature properties may be inferior; at a proportion
less than 0.1 mol %, the solubility in the base oil, low
temperature viscosity properties, and the effect of improving
viscosity temperature properties may be inferior.
[0093] Besides the (meth)acrylate structural unit represented by
the formula (1) and the (meth)acrylate structural unit represented
by the formula (2) preferably used, the viscosity index improver
according to the present embodiment may be a copolymer having any
(meth)acrylate structural unit. Such a copolymer can be prepared by
copolymerizing one or two or more of monomers represented by the
following formula (3) (hereinafter referred to as "Monomer (M-1)"),
one or two or more of monomers represented by the following formula
(4) preferably used (hereinafter referred to as "Monomer (M-2)",
and a monomer used when necessary other than Monomer (M-1) and
Monomer (M-2).
##STR00007##
[wherein R.sup.1 represents a hydrogen atom or a methyl group, and
R.sup.2 represents a linear or branched hydrocarbon group having a
carbon number of 6 or less.]
##STR00008##
[wherein R.sup.3 represents a hydrogen atom or a methyl group, and
R.sup.4 represents a linear or branched hydrocarbon group having a
carbon number of 16 or more.]
[0094] Any monomer can be used in combination with Monomer (M-1)
and Monomer (M-2), and a monomer represented by the following
formula (5) (hereinafter referred to as "Monomer (M-3)") is
suitable, for example. A copolymer of Monomer (M-1), Monomer (M-2),
and Monomer (M-3) is a non-dispersive poly(meth)acrylate viscosity
index improver.
##STR00009##
[wherein R.sup.5 represents a hydrogen atom or a methyl group, and
R.sup.6 represents a linear or branched hydrocarbon group having a
carbon number of 7 or more and 15 or less.]
[0095] R.sup.6 in the structural unit represented by the formula
(5) is a linear or branched hydrocarbon group having a carbon
number of 7 or more and 15 or less, preferably a linear or branched
hydrocarbon having a carbon number of 10 or more, more preferably a
linear or branched hydrocarbon having a carbon number of 11 or
more, and still more preferably a branched hydrocarbon group having
a carbon number of 12 or more.
[0096] In the viscosity index improver according to the present
embodiment, the (meth)acrylate structural unit represented by the
formula (5) in the polymer may be one or two or more mixtures, and
it is preferable that the proportion be 60 mol % or less, the
proportion is more preferably 50 mol % or less, still more
preferably 45 mol % or less, particularly preferably 40 mol % or
less, and most preferably 30 mol % or less. At a proportion more
than 60 mol %, the effect of improving viscosity temperature
properties and low temperature viscosity properties may be
inferior; at a proportion less than 0.5 mol %, the effect of
improving viscosity temperature properties may be inferior.
[0097] It is suitable that the other monomers used in combination
with Monomers (M-1) and (M-2) be one or two or more selected from
the monomer represented by the following formula (6) (hereinafter
referred to as "Monomer (M-4)") and the monomer represented by the
following formula (7) (hereinafter referred to as "Monomer (M-5)").
A copolymer of Monomers (M-1) and (M-2) with Monomers (M-4) and/or
(M-5) is the so-called dispersive poly(meth)acrylate viscosity
index improver. The dispersive poly(meth)acrylate viscosity index
improver may further contain Monomer (M-3) as the constitutional
monomer.
##STR00010##
[wherein R.sup.5 represents a hydrogen atom or a methyl group,
R.sup.6 represents an alkylene group having a carbon number of 1 to
18, E.sup.1 represents an amine residue or heterocycle residue
having 1 to 2 nitrogen atoms and 0 to 2 oxygen atoms, and a
represents 0 or 1.]
[0098] Examples of the alkylene group having a carbon number of 1
to 18 represented by R.sup.6 specifically can include an ethylene
group, a propylene group, a butylene group, a pentylene group, a
hexylene group, a heptylene group, an octylene group, a nonylene
group, a decylene group, an undecylene group, a dodecylene group, a
tridecylene group, a tetradecylene group, a pentadecylene group, a
hexadecylene group, a heptadecylene group, and an octadecylene
group (these alkylene groups may be linear or branched).
[0099] Examples of the group represented by E.sup.1 specifically
can include a dimethylamino group, a diethylamino group, a
dipropylamino group, a butylamino group, an anilino group, a
toluidino group, a xylidino group, an acetylamino group, a
benzoylamino group, a morpholino group, a pyrrolyl group, a
pyrrolino group, a pyridyl group, a methylpyridyl group, a
pyrrolidinyl group, a piperidinyl group, a quinonyl group, a
pyrrolidonyl group, a pyrrolidono group, an imidazolino group, and
a pyrazino group.
##STR00011##
[wherein R.sup.7 represents a hydrogen atom or a hydrocarbon group,
and E.sup.2 represents a hydrocarbon group or an amine residue or
heterocycle residue having 1 to 2 nitrogen atoms and 0 to 2 oxygen
atoms.]
[0100] Examples of the group represented by E.sup.2 specifically
can include a dimethylamino group, a diethylamino group, a
dipropylamino group, a dibutylamino group, an anilino group, a
toluidino group, a xylidino group, an acetylamino group, a
benzoylamino group, a morpholino group, a pyrrolyl group, a
pyrrolino group, a pyridyl group, a methylpyridyl group, a
pyrrolidinyl group, a piperidinyl group, a quinonyl group, a
pyrrolidonyl group, a pyrrolidono group, an imidazolino group, and
a pyrazino group.
[0101] Preferable examples of Monomers (M-4) and (M-5) specifically
can include dimethylaminomethyl methacrylate, diethylaminomethyl
methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl
methacrylate, 2-methyl-5-vinyl pyridine, morpholinomethyl
methacrylate, morpholinoethyl methacrylate, N-vinylpyrrolidone, and
mixtures thereof.
[0102] The copolymerization molar ratio of a copolymer of Monomers
(M-1) and (M-2) and Monomers (M-3) to (M-5) is not particularly
limited, and Monomers (M-1) and (M-2):Monomers (M-2) to (M-4)=20:80
to 90:10 or so is preferable, and the ratio is more preferably
30:70 to 80:20, and still more preferably 40:60 to 70:30.
[0103] The method for producing the viscosity index improver
according to the present embodiment is not particularly limited,
and examples thereof include a method in which using a control
radical polymerization process, an alkyl methacrylate serving as an
arm portion (polymerization chain of alkyl methacrylate) is
polymerized, and the polyalkyl methacrylate is then reacted with a
polyfunctional compound having two or more ethylenic unsaturated
double bonds.
[0104] The control radical polymerization process involves an atom
transfer radical polymerization (ATRP) process, a reversible
addition-fragmentation chain transfer (RAFT) process, or a
nitroxide mediated polymerization process.
[0105] The discussion on the polymer mechanism of the ATRP
polymerization is shown in Matyjaszewski et al., Reaction scheme
11.1, p. 524; Reaction scheme 11.4, p. 566; Reaction scheme 11, 7,
p. 571; Reaction scheme 11.8, p. 572; and Reaction scheme 11.9, p.
575.
[0106] The discussion on the polymer mechanism of the RAFT
polymerization is shown in Matyjaszewski et al., section 12.4.4,
pp. 664 to 665.
[0107] The detailed description of nitroxide mediated
polymerization (Chapter 10, pp. 463 to 522), ATRP (Chapter 11, pp.
523 to 628), and RAFT (Chapter 12, pp. 629 to 690) are shown in
"Handbook of Radical Polymerization" (Krzysztof Matyjaszewski and
Thomas P. Davis, copyright 2002, published by John Wiley and Sons
Inc. (hereinafter referred to as "Matyjaszewski et al.").
[0108] The synthesis can be performed as a batch operation, a
semi-batch operation, a continuous step, a feed step, or a bulk
step. The synthesis can be performed in an emulsion, a solution, or
a suspension.
[0109] In the synthesis, by changing the amounts of an initiator
and the polyfunctional compound having two or more ethylenic
unsaturated double bonds to be used, the average molecular weight
of the polymethacrylate or viscosity index improver to be obtained
can be adjusted.
[0110] The reaction rate to the viscosity index improver using the
synthesized arm portion is 70% or more, preferably 80% or more, and
more preferably 85% or more based on the amount of the polymer
reacted to become the viscosity index improver. If the reaction
rate is low, the arm portion remains, and the molecular weight
cannot be increased.
[0111] The PSSI (Permanent Shear Stability Index) of the viscosity
index improver according to the present embodiment in a diesel
injector method is preferably 20 or less, more preferably 15 or
less, still more preferably 10 or less, particularly preferably 5
or less, and most preferably 3 or less. If the PSSI exceeds 20,
shear stability is poor, and to keep the kinematic viscosity and
the HTHS viscosity after usage at a constant level or more, the
initial fuel efficiency may be reduced.
[0112] The "PSSI in the diesel injector method" here means the
permanent shear stability index of the polymer (Permanent Shear
Stability Index) calculated based on the data measured by ASTM D
6278-02 (Test Method for Shear Stability of Polymer Containing
Fluids Using a European Diesel Injector Apparatus) in accordance
with ASTM D 6022-01 (Standard Practice for Calculation of Permanent
Shear Stability Index).
[0113] It is preferable that the weight average molecular weight
(M.sub.W) of the viscosity index improver according to the present
embodiment be 100,000 or more, and the weight average molecular
weight is more preferably 200,000 or more, still more preferably
300,000 or more, and particularly preferably 400,000 or more. It is
preferable that the weight average molecular weight be 1,000,000 or
less, and the weight average molecular weight is more preferably
900,000 or less, still more preferably 700,000 or less, and
particularly preferably 600,000 or less. If the weight average
molecular weight is less than 100,000, the effect of improving a
viscosity index when the viscosity index improver is dissolved in
the lubricating base oil is small; not only fuel efficiency and low
temperature viscosity properties are inferior but also cost may
increase. If the weight average molecular weight exceeds 1,000,000,
the effect of increasing viscosity is excessively increased; not
only fuel efficiency and low temperature viscosity properties are
inferior, but also shear stability, the solubility in the
lubricating base oil, and storage stability are reduced.
[0114] It is preferable that the ratio of the weight average
molecular weight to the PSSI in the diesel injector method of the
viscosity index improver according to the present embodiment
(M.sub.W/PSSI) be 1.0.times.10.sup.4 or more, and the ratio is more
preferably 2.0.times.10.sup.4 or more, still more preferably
5.0.times.10.sup.4 or more, and particularly preferably
8.0.times.10.sup.4 or more. If M.sub.W/PSSI is less than
1.0.times.10.sup.4, fuel efficiency and low temperature
startability, namely, viscosity temperature properties and low
temperature viscosity properties may be reduced.
[0115] It is preferable that the ratio (M.sub.W/M.sub.N) of the
weight average molecular weight (M.sub.W) to the number average
molecular weight (M.sub.N) of the viscosity index improver
according to the present embodiment be 5.0 or less, and the ratio
is more preferably 4.0 or less, still more preferably 3.5 or less,
particularly preferably 3.0 or less, and most preferably 2.0 or
less. It is preferable that M.sub.W/M.sub.N be 1.0 or more, and the
ratio is more preferably 1.1 or more, and still more preferably 1.2
or more. If M.sub.W/M.sub.N is 4.0 or more or 1.0 or less,
solubility and the effect of improving viscosity temperature
properties may be reduced so that sufficient storage stability and
fuel efficiency cannot be maintained.
[0116] The hydrocarbon main chain ratio of the viscosity index
improver according to the present embodiment is 0.18 or less, more
preferably 0.16 or less, more preferably 0.15 or less, still more
preferably 0.14 or less, particularly preferably 0.10 or less, and
most preferably 0.05 or less. The hydrocarbon main chain ratio is
preferably 0.005 or more, more preferably 0.01 or more, and still
more preferably 0.02 or more. If the hydrocarbon main chain ratio
exceeds 0.18, shear stability is reduced, and viscosity temperature
properties and fuel efficiency may be reduced. If the hydrocarbon
main chain ratio is less than 0.005, the solubility in the base oil
is reduced, and viscosity temperature properties and fuel
efficiency may be reduced.
[0117] The "hydrocarbon main chain ratio" in the present invention
means the proportion of the number of carbon atoms of the
polymethacrylic acid main chain of the total number of carbon atoms
of the molecule (the ratio, that is, the number of carbon atoms of
the poly(meth)acrylic acid main chain/the total number of carbon
atoms in the molecule).
[0118] Because usually the poly(meth)acrylate viscosity index
improver is a mixture of a plurality of polymers having different
structures or molecular weights, the proportion is calculated as an
average value of the poly(meth)acrylate viscosity index improver.
If two or more poly(meth)acrylic acid chains are present in the
molecule, a longer chain of these poly(meth)acrylic acid chains is
the "poly(meth)acrylic acid main chain."
[0119] For the poly(meth)acrylate viscosity index improver having a
star structure (structure in which a plurality of arm portions as
the poly(meth)acrylic acid chain is connected to a core portion,
also referred to as a "star-like structure"), the influences of the
core portion is small, and the core portion is excluded from the
calculation. Usually the molecular weight of each arm portion is
substantially equal, and the weight average molecular weight of the
arm portion measured by GPC analysis (standard substance:
polystyrene) is used in calculation of the number of the carbon
atoms of the arm portion in the main chain.
[0120] Specifically, first, from the weight average molecular
weight measured by GPC analysis (standard substance: polystyrene),
the blending ratio of monomers or the weight average molecular
weight of the arm portion measured by GPC analysis (standard
substance: polystyrene) and the blending ratio of monomers, the
average polymerization number (A1) of each monomer in the molecule
is calculated. From A1, the total number of carbon atoms (B1) and
the number of carbon atoms (C1) of the polymethacrylic acid main
chain in one molecule are calculated, and C1/B1 is calculated.
C1/B1 is the hydrocarbon main chain ratio.
[0121] For the poly(meth)acrylate viscosity index improver having a
star structure, the number of arm portions (D) defined by the
number average molecular weight of the poly(meth)acrylate viscosity
index improver/the number average molecular weight of the arm
portion is calculated, and C1/(B1.times.D) is calculated.
C1/(B1.times.D) is the hydrocarbon main chain ratio of the
poly(meth)acrylate viscosity index improver having a star
structure.
[0122] The content of the viscosity index improver according to the
present embodiment is preferably 0.1 to 50% by mass, more
preferably 0.5 to 40% by mass, still more preferably 1 to 30% by
mass, particularly preferably 5 to 20% by mass based on the total
amount of the composition. If the content of the viscosity index
improver is less than 0.1% by mass, the effect of improving the
viscosity index and the effect of reducing the viscosity of a
product are reduced, and fuel efficiency may not be improved. At a
content more than 50% by mass, the cost of the product is
significantly increased, and the viscosity of the base oil needs to
be reduced; for this reason, the lubrication performance under
severe lubrication conditions (high temperature high shear
conditions) may be reduced, causing deficits such as wear, seizure,
and fatigue breaking.
[0123] It is preferable that the content of the viscosity index
improver be 0.1 to 50% by mass based on the total amount of the
composition, and the content is preferably 0.5 to 20% by mass, more
preferably 1.0 to 15% by mass, and still more preferably 1.5 to 12%
by mass based on the total amount of the composition. If the
content is less than 0.1% by mass, low temperature properties may
be insufficient; if the content exceeds 50% by mass, the shear
stability of the composition may be reduced.
[0124] Besides the viscosity index improver according to the
present embodiment, the lubricating oil composition according to
the present embodiment may further contain a non-dispersive or
dispersive poly(meth)acrylate, a non-dispersive or dispersive
ethylene-.alpha.-olefin copolymer or a hydride thereof, a
polyisobutylene or a hydride thereof, a styrene-diene hydrogenation
copolymer, a styrene-maleic anhydride ester copolymer,
polyalkylstyrene and the like.
[0125] An aspect of the lubricating oil composition further
containing the viscosity index improver other than the viscosity
index improver according to the present embodiment can include a
lubricating oil composition containing:
[0126] a lubricating base oil having a kinematic viscosity at
100.degree. C. of 1 to 10 mm.sup.2/s,
[0127] a first viscosity index improver that is a
poly(meth)acrylate viscosity index improver containing the
structural unit (A-1) represented by the following formula (1) in
the proportion of 30 to 90 mol % and the structural unit
represented by the following formula (2) in the proportion of 0.1
to 50 mol %, and having the hydrocarbon main chain ratio of 0.18 or
less, and
[0128] a second viscosity index improver that is a (A-2) dispersive
viscosity index improver.
[0129] In the case where the first viscosity index improver is used
in combination with the second viscosity index improver, the first
viscosity index improver may be a copolymer having any
(meth)acrylate structural unit other than the (meth)acrylate
structural units represented by the formulas (1) and (2). As such a
copolymer, a copolymer of one or two or more of the Monomers (M-1),
one or two or more of the Monomers (M-2), and Monomer (M-3) is
suitable. The copolymer is the so-called non-dispersive
poly(meth)acrylate viscosity index improver.
[0130] The content of the first viscosity index improver is
preferably 0.1 to 50% by mass, more preferably 0.5 to 40% by mass,
still more preferably 1 to 30% by mass, and particularly preferably
5 to 20% by mass based on the total amount of the composition. If
the content of the viscosity index improver is less than 0.1% by
mass, the effect of improving the viscosity index and the effect of
reducing the viscosity of a product are reduced, and fuel
efficiency may not be improved. At a content more than 50% by mass,
the cost of the product is significantly increased, and the
viscosity of the base oil needs to be reduced; for this reason, the
lubrication performance under severe lubrication conditions (high
temperature high shear conditions) may be reduced, causing deficits
such as wear, seizure, and fatigue breaking.
[0131] Meanwhile, in the second viscosity index improver that is a
dispersive viscosity index improver, as a dispersive group, a
nitrogen-containing dispersive group is preferable, and a
dimethylamino group is more preferable.
[0132] Preferable examples of the second viscosity index improver
can include poly(meth)acrylate viscosity index improver having a
structural unit represented by the following formula (8) and/or a
structural unit represented by the following formula (9):
##STR00012##
wherein R.sup.5 represents a hydrogen atom or a methyl group,
R.sup.6 represents an alkylene group having a carbon number of 1 to
18, E.sup.1 represents an amine residue or heterocycle residue
having 1 to 2 nitrogen atoms and 0 to 2 oxygen atoms; a represents
0 or 1;
##STR00013##
wherein R.sup.8 represents a hydrogen atom or a hydrocarbon group,
E.sup.2 represents a hydrocarbon group or an amine residue or
heterocycle residue having 1 to 2 nitrogen atoms and 0 to 2 oxygen
atoms.
[0133] Preferable examples of the second viscosity index improver
include a copolymer of one or two or more selected from Monomers
(M-1) and (M-2) and Monomer (M-4) and Monomer (M-5). The copolymer
of Monomers (M-1) and (M-2) with Monomer(s) (M-4) and/or (M-5) is
the so-called dispersive poly(meth)acrylate viscosity index
improver. The second viscosity index improver may further contain
Monomer (M-3) as a constitutional monomer.
[0134] In the second viscosity index improver, the copolymerization
molar ratio of the copolymer of Monomers (M-1) and (M-2) with
Monomers (M-3) to (M-5) is not particularly limited, and Monomers
(M-1) and (M-2): Monomers (M-3) to (M-5)=20:80 to 90:10 or so is
preferable, and the ratio is more preferably 30:70 to 80:20, and
still more preferably 40:60 to 70:30.
[0135] The method for producing the second viscosity index improver
is not particularly limited; for example, the second viscosity
index improver can be easily produced by radical solution
polymerizing a mixture of Monomers (M-1) and (M-2) and Monomers
(M-3) to (M-5) in the presence of a polymerization initiator such
as benzoyl peroxide.
[0136] It is preferable that the weight average molecular weight
(M.sub.W) of the second viscosity index improver be 100,000 or
more, and the weight average molecular weight is more preferably
200,000 or more, still more preferably 250,000 or more, and
particularly preferably 300,000 or more. It is preferable that the
weight average molecular weight be 1,000,000 or less, and the
weight average molecular weight is more preferably 900,000 or less,
still more preferably 700,000 or less, and particularly preferably
500,000 or less. If the weight average molecular weight is less
than 100,000, the effect of improving the viscosity index when the
viscosity index improver is dissolved in the lubricating base oil
is small; not only fuel efficiency and low temperature viscosity
properties are inferior but also cost may increase. If the weight
average molecular weight exceeds 1,000,000, the effect of
increasing viscosity is excessively increased; not only fuel
efficiency and low temperature viscosity properties are inferior,
but also shear stability, the solubility in the lubricating base
oil, and storage stability are reduced.
[0137] It is preferable that the ratio (M.sub.W/M.sub.N) of the
weight average molecular weight (M.sub.W) to the number average
molecular weight (M.sub.N) of the second viscosity index improver
be 5.0 or less, and the ratio is more preferably 4.5 or less, still
more preferably 4.2 or less, particularly preferably 4.1 or less,
and most preferably 4.0 or less. It is preferable that
M.sub.W/M.sub.N be 1.0 or more, and the ratio is more preferably
2.0 or more, and still more preferably 3.0 or more. If
M.sub.W/M.sub.N is 4.0 or more or 1.0 or less, solubility and the
effect of improving viscosity temperature properties may be reduced
so that sufficient storage stability and fuel efficiency cannot be
maintained.
[0138] The content of the second viscosity index improver is
preferably 0.1 to 50% by mass, more preferably 0.5 to 40% by mass,
still more preferably 0.9 to 30% by mass, and particularly
preferably 2 to 20% by mass based on the total amount of the
composition. If the content of the viscosity index improver is less
than 0.1% by mass, the effect of improving the viscosity index and
the effect of reducing the viscosity of a product are reduced, and
fuel efficiency may not be improved. At a content more than 50% by
mass, the cost of the product is significantly increased, and the
viscosity of the base oil needs to be reduced; for this reason, the
lubrication performance under severe lubrication conditions (high
temperature high shear conditions) may be reduced, causing deficits
such as wear, seizure, and fatigue breaking.
[0139] It is preferable that the lubricating oil composition
according to the present embodiment contain a friction modifier
(B). Thereby, fuel efficiency performance can be increased compared
to the case where the present configuration is not included.
Examples of the friction modifier (B) include one or more friction
modifiers selected from organic molybdenum compounds and ash-free
friction modifiers.
[0140] Examples of organic molybdenum compounds used in the present
embodiment can include organic molybdenum compounds containing
sulfur such as molybdenum dithiophosphate, molybdenum
dithiocarbamate (MoDTC); complexes of molybdenum compounds (such as
molybdenum oxides such as molybdenum dioxide and molybdenum
trioxide; molybdic acids such as ortho-molybdic acid, para-molybdic
acid, and (poly)molybdic acid sulfide; metal salts thereof;
molybdates such as ammonium salts thereof; molybdenum sulfides such
as molybdenum disulfide, molybdenum trisulfide, molybdenum
pentasulfide, and molybdenum polysulfide; molybdenum sulfide acid
and metal salts or amine slats thereof; and molybdenum halides such
as molybdenum chloride) with sulfur-containing organic compounds
(such as alkyl(thio)xanthate, thiadiazole, mercaptothiadiazole,
thiocarbonate, tetrahydrocarbylthiuram disulfide,
bis(di(thio)hydrocarbyldithiophosphonate)disulfide, organic
(poly)sulfides, and sulfurized esters), or other organic compounds;
or complexes of sulfur-containing molybdenum compounds such as
molybdenum sulfide and molybdenum sulfide acid with alkenyl
succinimides.
[0141] For the organic molybdenum compound, organic molybdenum
compounds containing no sulfur as a constitutional element can be
used. Examples of the organic molybdenum compounds containing no
sulfur as a constitutional element specifically include
molybdenum-amine complexes, molybdenum-succinimide complexes,
molybdenum salts of organic acids, and molybdenum salts of
alcohols; among these, molybdenum-amine complexes, molybdenum salts
of organic acids, and molybdenum salts of alcohols are
preferable.
[0142] In the lubricating oil composition according to the present
embodiment, if the organic molybdenum compound is used, its content
is not particularly limited; the content is preferably 0.001% by
mass or more, more preferably 0.005% by mass or more, still more
preferably 0.01% by mass or more, and particularly preferably 0.03%
by mass or more, and preferably 0.2% by mass or less, more
preferably 0.1% by mass or less, still more preferably 0.08% by
mass or less, and particularly preferably 0.06% by mass or less
based on the total amount of the lubricating oil composition in
terms of the molybdenum element. If the content is less than 0.001%
by mass, the effect of reducing friction by addition thereof tends
to be insufficient, and the fuel efficiency and heat and oxidation
stability of the lubricating oil composition tend to be
insufficient. If the content exceeds 0.2% by mass, the effect
corresponding to the content is not obtained, and the storage
stability of the lubricating oil composition tends to be
reduced.
[0143] As the ash-free friction modifier, any compound usually used
as a friction modifier for a lubricating oil can be used, and
examples thereof include compounds having a carbon number of 6 to
50 and containing one or two or more hetero elements selected from
an oxygen atom, a nitrogen atom, and a sulfur atom in the molecule.
More specifically, examples thereof include ash-free friction
modifiers such as amine compounds, fatty acid esters, fatty acid
amides, fatty acids, aliphatic alcohols, aliphatic ethers, urea
compounds, and hydrazide compounds having at least one alkyl group
or alkenyl group having a carbon number of 6 to 30, particularly
linear alkyl group having a carbon number of 6 to 30, a linear
alkenyl group, a branched alkyl group, and a branched alkenyl group
in the molecule.
[0144] The content of the ash-free friction modifier in the
lubricating oil composition according to the present embodiment is
preferably 0.01% by mass or more, more preferably 0.1% by mass or
more, and still more preferably 0.3% by mass or more, and
preferably 3% by mass or less, more preferably 2% by mass or less,
and still more preferably 1% by mass or less based on the total
amount of the lubricating oil composition. If the content of the
ash-free fiction modifier is less than 0.01% by mass, the effect of
reducing friction by addition thereof tends to be insufficient; at
a content more than 3% by mass, the effect such as anti-wear
additives is readily inhibited, or the solubility of the additive
tends to be reduced.
[0145] In the present embodiment, it is preferable that the
friction modifier (B) be an organic molybdenum friction modifier,
it is more preferable that the friction modifier (B) be an organic
molybdenum compound containing sulfur, and it is still more
preferable that the friction modifier (B) be molybdenum
dithiocarbamate.
[0146] The lubricating oil composition according to the present
embodiment can contain a metallic detergent (C).
[0147] Preferable examples of the metallic detergent (C) include a
metallic detergent (C-1) having a linear or branched hydrocarbon
group having a carbon number of 20 or more. Thereby, fuel
efficiency performance can be increased compared to the case where
the present configuration is not included.
[0148] For the metallic detergent (C-1) having a linear or branched
hydrocarbon group having a carbon number of 20 or more, an
overbased compound of an oil-soluble metal salt of a compound
having a linear or branched hydrocarbon group having a carbon
number of 20 or more and having an OH group and/or a carbonyl group
can be used. Overbased metal salts such as alkaline earth metal
sulfonates, alkaline earth metal carboxylates, alkaline earth metal
salicylates, alkaline earth metal phenates, and alkaline earth
metal phosphonates; and overbased metal salts that can be produced
by reacting alkaline earth metal hydroxides or oxides, and boric
acid or boric anhydride can be used. Examples of the alkaline earth
metal include magnesium, calcium, and barium, and calcium is
preferable. It is preferable that as the overbased metal salts,
overbased compounds of oil-soluble metal salts of compounds
containing an OH group and/or a carbonyl group be used, and it is
more preferable that oil-soluble metal salts of compounds
containing an OH group and/or a carbonyl group overbased with
alkaline earth metal borates be used. It is preferable that
alkaline earth metal salicylate be used, and it is more preferable
that alkaline earth metal salicylate overbased with alkaline earth
metal borate be used.
[0149] It is preferable that the base value of the metallic
detergent (C-1) having a linear or branched hydrocarbon group
having a carbon number of 20 or more be 50 mgKOH/g or more, it is
more preferable that the base value be 100 mgKOH/g or more, it is
still more preferable that the base value be 120 mgKOH/g or more,
it is particularly preferable that the base value be 140 or more,
and it is most preferable that the base value be 150 or more. It is
preferable that the base value be 300 mgKOH/g or less, it is more
preferable that the base value be 200 mgKOH/g or less, it is
particularly preferable that the base value be 180 mgKOH/g or less,
and it is particularly preferable that the base value be 170
mgKOH/g or less. If the base value is less than 50, an increase in
viscosity increases to reduce fuel efficiency, and the effect of
reducing friction by addition thereof tends to be insufficient. If
the base value exceeds 300, the effect of an anti-wear additive or
the like is readily inhibited, and the effect of reducing friction
tends to be insufficient. The base value in the present invention
is a value measured according to JIS K 2501 5.2.3.
[0150] It is preferable that the particle size of the metallic
detergent (C-1) having a linear or branched hydrocarbon group
having a carbon number of 20 or more be 0.1 .mu.m or less, and it
is more preferable that the particle size be 0.05 .mu.m or
less.
[0151] The production method of the metallic detergent (C-1) having
a linear or branched hydrocarbon group having a carbon number of 20
or more can be any production method, and detailed reaction
conditions are properly selected according to the amounts of the
raw materials, the reaction product, and the like.
[0152] It is preferable that the metallic detergent (C-1) having a
linear or branched hydrocarbon group having a carbon number of 20
or more have a metal ratio of 4.0 or less.
[0153] The metallic detergent (C-1) having a linear or branched
hydrocarbon group having a carbon number of 20 or more is a
metallic detergent whose metal ratio is adjusted to more preferably
3.4 or less, still more preferably 3.2 or less, further still more
preferably 3.0 or less, further still more preferably 2.8 or less,
particularly preferably 2.6 or less, and most preferably 2.5 or
less. If the metal ratio exceeds 4.0, a reduction in friction
torque, namely, fuel efficiency can be insufficient.
[0154] It is preferable that the metal ratio be 1.0 or more, and
the metallic detergent (C-1) having a linear or branched
hydrocarbon group having a carbon number of 20 or more is a
metallic detergent whose metal ratio is adjusted to more preferably
1.1 or more, still more preferably 1.5 or more, particularly
preferably 1.9 or more, and most preferably 2.2 or more. If the
metal ratio is less than 1.0, the kinematic viscosity and low
temperature viscosity of a lubricating oil composition for internal
combustion engines increase, which can cause deficits in
lubrication and startability.
[0155] To obtain a higher effect of reducing friction, it is
preferable that a metallic detergent synthesized alone be used.
[0156] The metal ratio in the present invention is represented by
an expression of valence of metal element in metallic
detergent.times.metal element content (mol %)/content of soap group
(mol %), in which the metal element means calcium, magnesium, and
the like, and the soap group means a sulfonic acid group, a phenol
group, a salicylic acid group, and the like.
[0157] The alkyl group or alkenyl group of the metallic detergent
(C-1) having a linear or branched hydrocarbon group having a carbon
number of 20 or more is an alkyl group or an alkenyl group having
preferably 22 or more, more preferably 24 or more, preferably 50 or
less, and more preferably 40 or less. If the number of carbon atoms
is less than 20, a reduction in friction torque, namely, fuel
efficiency can be insufficient, which is not preferable. If the
number of carbon atoms is more than 50, viscosity temperature
properties can be reduced and fuel efficiency can be insufficient,
which is not preferable.
[0158] Such an alkyl group or alkenyl group may be linear or
branched, and it is preferable that the alkyl group or alkenyl
group be linear. These may be a primary alkyl group or alkenyl
group, a secondary alkyl group or alkenyl group, or a tertiary
alkyl group or alkenyl group; for a secondary alkyl group or
alkenyl group or a tertiary alkyl group or alkenyl group, the case
where the branch position is limited only to carbons bonded to
aromatic groups is preferable.
[0159] The content of the metallic detergent (C-1) having a linear
or branched hydrocarbon group having a carbon number of 20 or more
is preferably 0.01 to 30% by mass, more preferably 0.05 to 5% by
mass based on the total amount of the lubricating oil composition.
If the content is less than 0.01% by mass, the energy saving effect
may be kept only for a short time; at a content more than 30% by
mass, the effect corresponding to the content may not be obtained,
which is not preferable.
[0160] The content of the metallic detergent (C-1) having a linear
or branched hydrocarbon group having a carbon number of 20 or more
is preferably 0.001% by mass or more, more preferably 0.01% by mass
or more, still more preferably 0.03% by mass or more, and
particularly preferably 0.05% by mass or more, and preferably 0.5%
by mass or less, more preferably 0.4% by mass or less, still more
preferably 0.3% by mass or less, particularly preferably 0.25% by
mass or less, and most preferably 0.22% by mass or less based on
the total amount of the lubricating oil composition in terms of
metal elements. If the content is less than 0.001% by mass, the
effect of reducing friction by addition thereof tends to be
insufficient, and the fuel efficiency, heat and oxidation
stability, and detergency of the lubricating oil composition tend
to be insufficient. If the content exceeds 0.5% by mass, the effect
of reducing friction by addition thereof tends to be insufficient,
and the fuel efficiency of the lubricating oil composition tends to
be insufficient.
[0161] The content of the metallic detergent (C-1) having a linear
or branched hydrocarbon group having a carbon number of 20 or more
is preferably 0.01% by mass or more, more preferably 0.03% by mass
or more, still more preferably 0.04% by mass or more, and
particularly preferably 0.05% by mass or more, and preferably 0.2%
by mass or less, more preferably 0.10% by mass or less, still more
preferably 0.08% by mass or less, particularly preferably 0.07% by
mass or less, and most preferably 0.06% by mass or less based on
the total amount of the lubricating oil composition in terms of a
boron element. If the content is less than 0.01% by mass, the
effect of reducing friction by addition thereof tends to be
insufficient, and the fuel efficiency, heat and oxidation
stability, and detergency of the lubricating oil composition tend
to be insufficient. If the content exceeds 0.2% by mass, the effect
of reducing friction by addition thereof tends to be insufficient,
and the fuel efficiency of the lubricating oil composition tends to
be insufficient.
[0162] The ratio (MB1)/(MB2) of the content of the metal content
(MB1) derived from the component (C-1) to the content of the boron
content (MB2) derived from the component (C-1) is preferably 1 or
more, more preferably 1.5 or more, still more preferably 2 or more,
particularly preferably 2.5 or more, and most preferably 2.7 or
more. If the (MB1)/(MB2) is 1 or less, fuel efficiency can be
reduced, which is not preferable. The (MB1)/(MB2) has no upper
limit in the application, and the ratio is preferably 20 or less,
more preferably 15 or less, still more preferably 10 or less, and
particularly preferably 5% by mass or less. If the content of the
boron content derived from the component (B) exceeds 20% by mass,
fuel efficiency can be reduced, which is not preferable.
[0163] Another examples of a preferable metallic detergent can
include metallic detergents (C-2) having a linear or branched
hydrocarbon group having a carbon number of less than 20. For the
component (C-2), an overbased compound of an oil-soluble metal salt
of a compound having a linear or branched hydrocarbon group having
a carbon number of less than 20 and containing an OH group and/or a
carbonyl group can be used. Overbased metal salts such as alkaline
earth metal sulfonates, alkaline earth metal carboxylates, alkaline
earth metal salicylates, alkaline earth metal phenates, and
alkaline earth metal phosphonates; and overbased metal salts that
can be produced by reacting alkaline earth metal hydroxides or
oxides, and boric acid or boric anhydride can be used. Examples of
alkaline earth metals include magnesium, calcium, and barium, and
calcium is preferable. It is preferable that for the overbased
metal salts, overbased compounds of oil-soluble metal salts of
compounds containing an OH group and/or a carbonyl group be used,
and it is more preferable that oil-soluble metal salts of compounds
containing an OH group and/or carbonyl group overbased with
alkaline earth metal carbonates and/or borates be used. It is
preferable that alkaline earth metal salicylate be used, and it is
more preferable that alkaline earth metal salicylates overbased
with alkaline earth metal carbonates and/or alkaline earth metal
salicylates overbased with alkaline earth metal borates be
used.
[0164] It is preferable that the base value of the metallic
detergent (C-2) having a linear or branched hydrocarbon group
having a carbon number of less than 20 be 50 mgKOH/g or more, it is
more preferable that the base value be 100 mgKOH/g or more, it is
still more preferable that the base value be 120 mgKOH/g or more,
it is particularly preferable that the base value be 140 or more,
and it is most preferable that the base value be 150 or more. It is
preferable that the base value be 300 mgKOH/g or less, it is more
preferable that the base value be 200 mgKOH/g or less, it is
particularly preferable that the base value be 180 mgKOH/g or less,
and it is particularly preferable that the base value be 170
mgKOH/g or less preferable. If the base value is less than 50, an
increase in viscosity increases to reduce fuel efficiency, and the
effect of reducing friction by addition thereof tends to be
insufficient. If the base value exceeds 300, the effect of an
anti-wear additive or the like is readily inhibited, and the effect
of reducing friction tends to be insufficient.
[0165] It is preferable that the metallic detergent (C-2)
containing a linear or branched hydrocarbon group having a carbon
number of less than 20 have a metal ratio of 4.0 or less.
[0166] The metallic detergent is a metallic detergent whose metal
ratio is adjusted to more preferably 3.4 or less, still more
preferably 3.2 or less, further still more preferably 3.0 or less,
further still more preferably 2.8 or less, particularly preferably
2.6 or less, and most preferably 2.5 or less. If the metal ratio
exceeds 4.0, a reduction in friction torque, namely, fuel
efficiency can be insufficient.
[0167] It is preferable that the metal ratio be 1.0 or more, and
the metallic detergent (C-2) having a linear or branched
hydrocarbon group having a carbon number of less than 20 is a
metallic detergent whose metal ratio is adjusted to more preferably
1.1 or more, still more preferably 1.5 or more, particularly
preferably 1.9 or more, and most preferably 2.2 or more. If the
metal ratio is less than 1.0, the kinematic viscosity and low
temperature viscosity of a lubricating oil composition for internal
combustion engines increase, which can cause deficits in
lubrication and startability.
[0168] To obtain a higher effect of reducing friction, it is
preferable that a metallic detergent synthesized alone be used.
[0169] The content of the metallic detergent (C-2) having a linear
or branched hydrocarbon group having a carbon number of less than
20 is preferably 0.01% by mass or more, more preferably 0.03% by
mass or more, still more preferably 0.04% by mass or more, and
particularly preferably 0.05% by mass or more, and preferably 0.2%
by mass or less, more preferably 0.10% by mass or less, still more
preferably 0.08% by mass or less, particularly preferably 0.07% by
mass or less, and most preferably 0.06% by mass or less based on
the total amount of the lubricating oil composition in terms of the
boron element. If the content is less than 0.01% by mass, the
effect of reducing friction by addition thereof tends to be
insufficient, and the fuel efficiency, heat and oxidation
stability, and detergency of the lubricating oil composition tend
to be insufficient. If the content exceeds 0.2% by mass, the effect
of reducing friction by addition thereof tends to be insufficient,
and the fuel efficiency of the lubricating oil composition tends to
be insufficient.
[0170] The ratio (MB11)/(MB12) of the content of the metal content
(MB11) derived from the component (C-2) to the content of the boron
content (MB12) derived from the component (C-2) is preferably 1 or
more, more preferably 2 or more, still more preferably 2.5 or more,
particularly preferably 3.0 or more, and most preferably 3.5 or
more. If the (MB11)/(MB12) is 1 or less, fuel efficiency can be
reduced, which is not preferable. The (MB11)/(MB12) is preferably
20 or less, more preferably 15 or less, still more preferably 10 or
less, and particularly preferably 5% by mass or less. If the
content of the boron content derived from the component (B1)
exceeds 20% by mass, fuel efficiency can be reduced, which is not
preferable.
[0171] To further improve the performance, any additives usually
used in the lubricating oil can be contained in the lubricating oil
composition according to the present embodiment according to the
purpose. Examples of such additives can include additives such as
ash-free dispersants, anti-wear agents (or extreme-pressure
agents), antioxidants, corrosion inhibitors, rust inhibitors,
demulsifiers, metal deactivators, and antifoaming agents.
[0172] If these additives are contained in the lubricating oil
composition according to the present embodiment, it is preferable
that the content of each additive be 0.01 to 10% by mass based on
the total amount of the lubricating oil composition.
[0173] It is preferable that the kinematic viscosity at 100.degree.
C. of the lubricating oil composition according to the present
embodiment be 4 to 12 mm.sup.2/s, and kinematic viscosity is
preferably 9.0 mm.sup.2/s or less, more preferably 8.0 mm.sup.2/s
or less, still more preferably 7.8 mm.sup.2/s or less, further
still more preferably 7.6 mm.sup.2/s or less, particularly
preferably 7.0 mm.sup.2/s or less, and most preferably 6.8
mm.sup.2/s or less. The kinematic viscosity at 100.degree. C. of
the lubricating oil composition according to the present embodiment
is preferably 4.5 mm.sup.2/s or more, more preferably 5.0
mm.sup.2/s or more, still more preferably 5.5 mm.sup.2/s or more,
further still more preferably 6.0 mm.sup.2/s or more, particularly
preferably 6.5 mm.sup.2/s or more, and most preferably 7.0
mm.sup.2/s or more. The kinematic viscosity at 100.degree. C. here
designates a kinematic viscosity at 100.degree. C. specified in
ASTM D-445. If the kinematic viscosity at 100.degree. C. is less
than 4 mm.sup.2/s, insufficient lubrication may be caused; at a
kinematic viscosity more than 12 mm.sup.2/s, necessary low
temperature viscosity and sufficient fuel efficiency performance
may not be obtained.
[0174] It is preferable that the kinematic viscosity at 40.degree.
C. of the lubricating oil composition according to the present
embodiment be 4 to 50 mm.sup.2/s, and the kinematic viscosity is
preferably 40 mm.sup.2/s or less, more preferably 35 mm.sup.2/s or
less, particularly preferably 30 mm.sup.2/s or less, and most
preferably 28 mm.sup.2/s or less. The kinematic viscosity at
40.degree. C. of the lubricating oil composition according to the
present embodiment is preferably 15 mm.sup.2/s or more, more
preferably 18 mm.sup.2/s or more, still more preferably 20
mm.sup.2/s or more, particularly preferably 22 mm.sup.2/s or more,
and most preferably 25 mm.sup.2/s or more. The kinematic viscosity
at 40.degree. C. here designates a kinematic viscosity at
40.degree. C. specified in ASTM D-445. If the kinematic viscosity
at 40.degree. C. is less than 4 mm.sup.2/s, insufficient
lubrication may be caused; at a kinematic viscosity more than 50
mm.sup.2/s, necessary low temperature viscosity and sufficient fuel
efficiency performance may not be obtainable.
[0175] It is preferable that the viscosity index of the lubricating
oil composition according to the present embodiment be in the range
of 140 to 400, and the viscosity index is preferably 180 or more,
more preferably 190 or more, still more preferably 200 or more,
particularly preferably 210 or more, and most preferably 215 or
more. If the viscosity index of the lubricating oil composition
according to the present embodiment is less than 140, it may be
difficult to improve fuel efficiency while maintaining the HTHS
viscosity at 150.degree. C., and to reduce the low temperature
viscosity at -35.degree. C. If the viscosity index of the
lubricating oil composition according to the present embodiment
exceeds 400, evaporation properties may be reduced, and deficits
due to insufficient solubility of the additive and matching
properties with a seal material may be caused.
[0176] It is preferable that the HTHS viscosity at 100.degree. C.
of the lubricating oil composition according to the present
embodiment be 5.5 mPas or less, and the HTHS viscosity is more
preferably 5.0 mPas or less, still more preferably 4.7 mPas or
less, particularly preferably 4.5 mPas or less, and most preferably
4.4 mPas or less. The HTHS viscosity is preferably 2.0 mPas or
more, still more preferably 3.0 mPas or more, particularly
preferably 3.5 mPas or more, and most preferably 4.0 mPas or more.
The HTHS viscosity at 100.degree. C. in the present invention
designates a high temperature high shear viscosity at 100.degree.
C. specified in ASTM D4683. If the HTHS viscosity at 100.degree. C.
is less than 2.0 mPas, insufficient lubrication may be caused; at
an HTHS viscosity more than 5.5 mPas, necessary low temperature
viscosity and sufficient fuel efficiency performance may not be
obtainable.
[0177] It is preferable that the HTHS viscosity at 150.degree. C.
of the lubricating oil composition according to the present
embodiment be less than 4.0 mPas, and the HTHS viscosity is more
preferably 3.5 mPas or less, still more preferably mPas, more
preferably 2.7 mPas or less, still more preferably 2.5 mPas or
less, and particularly preferably 2.4 mPas or less. The HTHS
viscosity is preferably 1.0 mPas or more, more preferably 1.5 mPas
or more, still more preferably 2.0 mPas or more, and particularly
preferably 2.3 mPas or more. The HTHS viscosity at 150.degree. C.
here designates a high temperature high shear viscosity at
150.degree. C. specified in ASTM D4683. If the HTHS viscosity at
150.degree. C. is less than 1.0 mPas, insufficient lubrication may
be caused; at an HTHS viscosity more than 4.0 mPas, sufficient fuel
efficiency performance may not be obtainable.
[0178] It is preferable that the ratio of the HTHS viscosity at
150.degree. C. to HTHS viscosity at 100.degree. C. of the
lubricating oil composition according to the present embodiment
(HTHS viscosity at 150.degree. C./HTHS viscosity at 100.degree. C.)
be 0.50 or more, and the ratio is more preferably 0.52 or more,
still more preferably 0.53, and particularly preferably 0.54 or
more. If the ratio is less than 0.50, necessary low temperature
viscosity and sufficient fuel efficiency performance may not be
obtainable.
[0179] The lubricating oil composition according to the present
embodiment can sufficiently reduce the kinematic viscosity at
40.degree. C., kinematic viscosity at 100.degree. C. and HTHS
viscosity at 100.degree. C. in an engine oil having a HTHS
viscosity at 150.degree. C. of less than 2.6 mPas, can sufficiently
suppress an increase in the coefficient of friction in the boundary
lubrication region, and has high fuel efficiency. The lubricating
oil composition according to the present embodiment having such
high properties can be suitably used as energy saving engine oils
such as energy saving gasoline engine oils and energy saving diesel
engine oils.
EXAMPLES
[0180] Hereinafter, the present invention will be more specifically
described based on Examples and Comparative Example, but the
present invention will not be limited to Examples below.
Synthesis Example 1
Synthesis of Non-Dispersive PMA Viscosity Index Improver A-1
<Synthesis of Arm Molecule>
[0181] To a 300 ml 5-necked separable flask having an anchor
metallic stirring blade (with a vacuum seal), a Dimroth condenser,
a 3-necked cock for introducing nitrogen, and a sample introduction
port mounted thereon, 25.2 parts by mass of methyl methacrylate,
36.5 parts by mass of methacrylate in which R.sup.4 in the formula
(4) was an alkyl group having a carbon number of 18, and 120 parts
by mass of a hydrocarbon solvent (SAE10) as a solvent were placed,
and a uniform solution was prepared under stirring. The solution
was cooled to 0.degree. C. with an ice bath, and vacuum
degassing/nitrogen purging of the reaction system was performed 5
times using a diaphragm pump. Under a nitrogen stream, 0.27 parts
by mass of azobisisobutyronitrile (AIBN) as a radical initiator,
0.013 parts by mass of 1,4-cyclohexadiene, and 0.11 parts by mass
of iodine were charged from the sample introduction port; then,
polymerization was performed under a nitrogen atmosphere at a
solution temperature of 80.degree. C. for 12 hours to prepare an
arm molecule solution.
[0182] As a result of GPC analysis (standard substance:
polystyrene), the weight average molecular weight of the obtained
aim molecule was 87400, the number average molecular weight (Mn)
was 62000, and the degree of dispersion (Mw/Mn) was 1.41.
<Synthesis of Star Polymer>
[0183] To the arm solution, 0.07 parts by mass of
azobisisobutyronitrile (AIBN) and 2.14 parts by mass of ethylene
glycol dimethacrylate were added, and polymerization was performed
under a nitrogen atmosphere at a solution temperature of 80.degree.
C. for 12 hours to prepare a solution of a target star polymer
(hereinafter referred to as "Non-dispersive PMA viscosity index
improver A-1").
[0184] As a result of GPC analysis (standard substance:
polystyrene), the weight average molecular weight (Mw) of the
obtained Non-dispersive PMA viscosity index improver A-1 was
570000, the number average molecular weight (Mn) was 470000, the
degree of dispersion (Mw/Mn) was 1.23, PSSI was 3.8, and Mw/PSSI
was 1.5.times.10.sup.5. The arm conversion rate of the
Non-dispersive PMA viscosity index improver A-1 was 64% by mass,
the average number of arms was 8, and the hydrocarbon main chain
ratio was 0.025.
[0185] Here, the arm conversion rate and the average number of arms
are values calculated based on the following expressions,
respectively.
arm conversion rate=GPC area of star polymer/(GPC area of star
polymer+GPC area of remaining arm molecule).times.100
average number of arms=Mn of star polymer/Mn of arm molecule
(rounded to whole numbers)
[0186] The weight average molecular weight and the number average
molecular weight are the weight average molecular weight and the
number average molecular weight in terms of polystyrene measured by
using an HLC-8220 GPC apparatus made by Tosoh Corporation having 3
TSKgel Super MultiPore HZ-M columns made by Tosoh Corporation (4.6
mm ID.times.15 cm) in series and tetrahydrofuran as a solvent at a
temperature of 40.degree. C., a flow rate of 0.35 mL/min, a sample
concentration of 1% by mass, an amount of sample injection of 5
.mu.L with a detector deference refractive index meter (RI).
Synthesis Example 2
Synthesis of Non-Dispersive PMA Viscosity Index Improver A-2
[0187] A star polymer (hereinafter referred to as "Non-dispersive
PMA viscosity index improver A-2") was synthesized in the same
manner as in Synthesis Example 1 except that instead of the arm
molecule solution in Synthesis Example 1, an arm molecule solution
containing an arm molecule including 70 mol % methyl methacrylate
and 30 mol % methacrylate in which R.sup.4 in the formula (4) was
an alkyl group having a carbon number of 18 (weight average
molecular weight: 54000, number average molecular weight (Mn):
42000, degree of dispersion (Mw/Mn): 1.29) was used.
[0188] The Mw of Non-dispersive PMA viscosity index improver A-2
obtained was 490000, Mn was 410000, Mw/Mn was 1.19, PSSI was 2.2,
Mw/PSSI was 2.2.times.10.sup.5, and the hydrocarbon main chain
ratio was 0.020.
Synthesis Example 3
Synthesis of Non-Dispersive PMA Viscosity Index Improver A-3
[0189] A star polymer (hereinafter referred to as "Non-dispersive
PMA viscosity index improver A-3") was synthesized in the same
manner as in Synthesis Example 1 except that instead of the arm
molecule solution in Synthesis Example 1, an arm molecule solution
containing an arm molecule including 70 mol % methyl methacrylate
and 30 mol % methacrylate in which R.sup.4 in the formula (4) was
an alkyl group having a carbon number of 18 (weight average
molecular weight: 85000, number average molecular weight (Mn):
60000, degree of dispersion (Mw/Mn): 1.42) was used.
[0190] The Mw of Non-dispersive PMA viscosity index improver A-3
obtained was 450000, Mn was 380000, Mw/Mn was 1.19, PSSI was 3.0,
Mw/PSSI was 1.5.times.10.sup.5, and the hydrocarbon main chain
ratio was 0.033.
Synthesis Example 4
Synthesis of Non-Dispersive PMA Viscosity Index Improver A-4
[0191] A star polymer (hereinafter referred to as "Non-dispersive
PMA viscosity index improver A-4") was synthesized in the same
manner as in Synthesis Example 1 except that instead of the arm
molecule solution in Synthesis Example 1, an arm molecule solution
containing an arm molecule including 70 mol % methyl methacrylate
and 30 mol % methacrylate in which R.sup.4 in the formula (4) was
an alkyl group having a carbon number of 16 to 18 (weight average
molecular weight: 87000, number average molecular weight (Mn):
62000, degree of dispersion (Mw/Mn): 1.41) was used.
[0192] The Mw of Non-dispersive PMA viscosity index improver A-4
obtained was 570000, Mn was 470000, Mw/Mn was 1.23, PSSI was 3.8,
Mw/PSSI was 1.5.times.10.sup.5, and the hydrocarbon main chain
ratio was 0.025.
Synthesis Example 5
Synthesis of Non-Dispersive PMA Viscosity Index Improver A-5
[0193] A star polymer (hereinafter referred to as "Non-dispersive
PMA viscosity index improver A-5") was synthesized in the same
manner as in Synthesis Example 1 except that instead of the arm
molecule solution in Synthesis Example 1, an arm molecule solution
containing an arm molecule including 70 mol % methyl methacrylate
and 30 mol % methacrylate in which R.sup.4 in the formula (4) was
an alkyl group having a carbon number of 18 (weight average
molecular weight: 107600, number average molecular weight (Mn);
79100, degree of dispersion (Mw/Mn): 1.36) was used.
[0194] The Mw of Non-dispersive PMA viscosity index improver A-5
obtained was 560000, Mn was 450000, Mw/Mn was 1.24, PSSI was 3.8,
and the hydrocarbon main chain ratio was 0.033.
Examples 1 to 6, Comparative Examples 1 to 4
[0195] In Examples 1 to 6 and Comparative Examples 1 to 4, base
oils and additives shown below were used to prepare lubricating oil
compositions having compositions shown in Tables 2 and 3. The
properties of Base oils O-1, O-2, and O-3 are shown in Table 1.
(Base Oils)
[0196] O-1 (Base oil 1): mineral oil prepared by
hydrocracking/hydrogenation isomerization of a n-paraffin
containing oil [0197] O-2 (Base oil 2): hydrocracked mineral oil
[0198] O-3 (Base oil 3): hydrocracked mineral oil
(Additives)
[0198] [0199] A-1: non-dispersive PMA viscosity index improver
prepared in Synthesis Example 1 (copolymer prepared by reacting 70
mol % methyl methacrylate, 30 mol % methacrylate in which R.sup.4
in the formula (4) was an alkyl group having a carbon number of 18,
a small amount of a polymerization initiator, and ethylene glycol
dimethacrylate. Mw=570000, Mn=470000, Mw/Mn=1.23, PSSI=3.8,
Mw/PSSI=1.5.times.10.sup.5, hydrocarbon main chain ratio=0.025)
[0200] A-2: non-dispersive PMA viscosity index improver prepared
in
[0201] Synthesis Example 2 (copolymer prepared by reacting 70 mol %
methyl methacrylate, 30 mol % methacrylate in which R.sup.4 in the
formula (4) was an alkyl group having a carbon number of 18, a
small amount of a polymerization initiator, and ethylene glycol
dimethacrylate. Mw=490000, Mn=410000, Mw/Mn=1.19, PSSI=2.2,
Mw/PSSI=2.2.times.10.sup.5, hydrocarbon main chain ratio=0.020)
[0202] A-3: non-dispersive PMA viscosity index improver prepared in
Synthesis Example 3 (copolymer prepared by reacting 70 mol % methyl
methacrylate, 30 mol % methacrylate in which R.sup.4 in the formula
(4) was an alkyl group having a carbon number of 18, a small amount
of a polymerization initiator, and ethylene glycol dimethacrylate.
Mw=450000, Mn=380000, Mw/Mn=1.19, PSSI=3.0,
Mw/PSSI=1.5.times.10.sup.5, hydrocarbon main chain ratio=0.033)
[0203] A-4: non-dispersive PMA viscosity index improver prepared in
Synthesis Example 4 (copolymer prepared by reacting 70 mol % methyl
methacrylate, 30 mol % methacrylate in which R.sup.4 in the formula
(4) was an alkyl group having a carbon number of 16 to 18, a small
amount of a polymerization initiator, and ethylene glycol
dimethacrylate. Mw=570000, Mn=470000, Mw/Mn=1.23, PSSI=3.8,
Mw/PSSI=1.5.times.10.sup.5, hydrocarbon main chain ratio=0.025)
[0204] a-1: non-dispersive PMA viscosity index improver (copolymer
prepared by reacting 70 mol % methyl methacrylate, 20 mol %
methacrylate in which R.sup.4 in the formula (4) was an alkyl group
having a carbon number of 16 to 19, 10 mol % methacrylate in which
R.sup.4 in the formula (4) was an alkyl group having a carbon
number of 20 to 30, and a small amount of a polymerization
initiator. Mw=400000, Mn=180000, Mw/Mn=2.2, PSSI=20,
Mw/PSSI=2.0.times.10.sup.4, hydrocarbon main chain ratio=0.20)
[0205] a-2: non-dispersive PMA viscosity index improver (copolymer
prepared by reacting 60 mol % methyl methacrylate, 20 mol %
methacrylate in which R.sup.6 in the formula (5) was an alkyl group
having a carbon number of 12 to 15, 15 mol % methacrylate in which
R.sup.2 in the formula (4) was an alkyl group having a carbon
number of 16 to 19, 5 mol % methacrylate in which R.sup.4 in the
formula (4) was an alkyl group having a carbon number of 20 to 30,
and a small amount of a polymerization initiator. Mw=400000,
Mn=160000, Mw/Mn=2.5, PSSI=26, Mw/PSSI=1.7.times.10.sup.4,
hydrocarbon main chain ratio=0.19) [0206] a-3: dispersive PMA
viscosity index improver (copolymer prepared by reacting 20 mol %
methyl methacrylate, 80 mol % methacrylate in which R.sup.6 in the
formula (5) was an alkyl group having a carbon number of 12 to 15,
and small amounts of a nitrogen-containing dispersive group
(dimethylamino group, diethylamino group, dipropyl amino group) and
a polymerization initiator. Mw=300000, Mn=70000, Mw/Mn=4.0,
PSSI=40, Mw/PSSI=7.5.times.10.sup.3, hydrocarbon main chain
ratio=0.13) [0207] a-4: dispersive PMA viscosity index improver
(copolymer prepared by reacting 20 mol % methyl methacrylate, 80
mol % methacrylate in which R.sup.6 in the formula (5) was an alkyl
group having a carbon number of 12 to 15, and small amounts of a
nitrogen-containing dispersive group (dimethylamino group,
diethylamino group, dipropyl amino group) and a polymerization
initiator. Mw=80000, Mn=30000, Mw/Mn=2.7, PSSI=10,
Mw/PSSI=8.0.times.10.sup.3, hydrocarbon main chain ratio=0.13)
[0208] B-1: MoDTC (alkyl group chain length: C8/C13, Mo content: 10
mass %, sulfur content: 11 mass %) [0209] B-2: glycerol monooleate
[0210] C-1: other additives (such as a succinimide dispersant,
ZnDTP, an antioxidant, an anti-wear agent, a pour-point depressant,
and an antifoaming agent).
TABLE-US-00001 [0210] TABLE 1 O-1 O-2 O-3 Base oil 1 Base oil 2
Base oil 3 Density (15.degree. C.) g/cm.sup.3 0.820 0.835 0.8320
Kinematic viscosity mm.sup.2/s 15.8 20.0 13.5 (40.degree. C.)
(100.degree. C.) mm.sup.2/s 3.85 4.29 3.27 Viscosity index 141 123
112 Pour point .degree. C. -22.5 -17.5 -22.5 Aniline point .degree.
C. 119 116 109 Iodine number 0.06 0.05 5.38 Sulfur content mass ppm
<1 <1 <1 Nitrogen content mass ppm <3 <3 <3 n-d-M
analysis % C.sub.P 93.3 80.7 72.6 % C.sub.N 6.7 19.3 23.4 % C.sub.A
0 0 0 Separation by Saturate 99.6 99.7 99.6 chromatography mass %
content Aromatic 0.2 0.2 0.3 content Resin content 0.1 0.1 0.1
Recover rate 99.9 100 100 Paraffin content based on mass % 87.1
53.8 50.7 saturate content Naphthene content based mass % 12.9 46.2
49.3 on saturate content
[0211] [Evaluation of Lubricating Oil Composition]
[0212] In the lubricating oil compositions in Examples 1 to 6 and
Comparative Examples 1 to 4, the kinematic viscosity at 40.degree.
C. or 100.degree. C., the viscosity index, the HTHS viscosity at
100.degree. C. or 150.degree. C., and the HTHS viscosity after the
ultrasonic shear test were measured, and resistance to wear was
evaluated by a four ball test. [0213] (1) Kinematic viscosity: ASTM
D-445 [0214] (2) Viscosity index: JIS K 22834993 [0215] (3) HTHS
viscosity: ASTM D-4683 [0216] (4) Ultrasonic shear test: according
to JASO M347-95, an output was adjusted with Standard oil A
specified in the ASTM test method, and a shear test was performed
at an amplitude of 28 .mu.m, the vibration number of 10 KHz, an
irradiation time of 10 minutes, and a sample volume of 60 mL to
measure the HTHS viscosity. [0217] (5) Evaluation of resistance to
wear (four ball test)
[0218] The four ball test (ASTM D4172) was performed under the
following conditions, and the diameter (mm) of a wear scar was
measured to evaluate resistance to wear. [0219] load: 294 N [0220]
number of rotation: 1500 rpm [0221] temperature: 110.degree. C.
[0222] test time: 1 hour [0223] amount of CB (MA-100 (CAS. No.
1333-86-4)): 0.1%
TABLE-US-00002 [0223] TABLE 2 Example Example Example Example
Example Example 1 2 3 4 5 6 Based on total Base oil amount of base
oil O-1 Base oil 1 % by mass 50 O-2 Base oil 2 % by mass 50 50 50
50 50 O-3 Base oil 3 % by mass 50 50 50 50 50 50 Viscosity of base
oil (40.degree. C.) mm.sup.2/s 14.7 16.2 16.2 16.2 16.2 16.2
Viscosity of base oil (100.degree. C.) 3.6 3.7 3.7 3.7 3.7 3.7
Viscosity index of base oil 124 117 117 117 117 117 Based on total
amount of Additives composition A-1 Viscosity index % by mass 9.3
8.5 8.8 improver A-2 Viscosity index % by mass 9.5 improver A-3
Viscosity index % by mass 8.6 improver A-4 Viscosity index % by
mass 8.3 improver a-1 Viscosity index % by mass improver a-2
Viscosity index % by mass improver a-3 Viscosity index % by mass
improver a-4 Viscosity index % by mass improver B-1 MoDTC % by mass
0.7 0.7 0.7 0.7 0.7 B-2 Ester % by mass 0.5 C-1 Other additives %
by mass 10 10 10 10 10 10 Results of evaluation Kinematic viscosity
40.degree. C. mm.sup.2/s 25.2 26.9 27.7 26.3 26.4 27.3 100.degree.
C. mm.sup.2/s 6.3 6.4 6.4 6.2 6.3 6.5 Viscosity index 216 202 195
199 203 205 HTHS viscosity 100.degree. C. mPa s 4.30 4.37 4.49 4.31
4.35 4.40 150.degree. C. mPa s 2.34 2.35 2.33 2.35 2.35 2.32 HTHS
viscosity after 150.degree. C. mPa s 2.30 2.30 2.30 2.30 2.30 2.30
ultrasonic shear Four ball test (diameter of wear scar) mm 0.50
0.51 0.51 0.51 0.53 0.53
TABLE-US-00003 TABLE 3 Comp. Comp. Comp. Comp. Example 1 Example 2
Example 3 Example 4 Based on total Base oil amount of base oil 0-1
Base oil 1 % by mass 0-2 Base oil 2 % by mass 50 50 50 50 0-3 Base
oil 3 % by mass 50 50 50 50 Viscosity of base oil (40.degree. C.)
mm.sup.2/s 16.2 16.2 16.2 16.2 Viscosity of base oil (100.degree.
C.) 3.7 3.7 3.7 3.7 Viscosity index of base oil 117 117 117 117
Based on total amount of Additives composition A-1 Viscosity index
improver % by mass A-2 Viscosity index improver % by mass A-3
Viscosity index improver % by mass A-4 Viscosity index improver %
by mass a-1 Viscosity index improver % by mass 14.3 a-2 Viscosity
index improver % by mass 11.8 a-3 Viscosity index improver % by
mass 5.5 a-4 Viscosity index improver % by mass 5.9 B-1 MoDTC % by
mass 0.7 0.7 0.7 0.7 B-2 Ester % by mass C-1 Other additives % by
mass 10 10 10 10 Results of evaluation Kinematic viscosity
40.degree. C. mm.sup.2/s 29.7 31.3 35.9 32.3 100.degree. C.
mm.sup.2/s 7.6 7.8 8.5 7.0 Viscosity index 242 235 226 187 HTHS
viscosity 100.degree. C. mPa s 4.58 4.86 5.00 4.95 150.degree. C.
mPa s 2.50 2.50 2.48 2.36 HTHS viscosity after 150.degree. C. mPa s
2.30 2.30 2.30 2.30 ultrasonic shear Four ball test (diameter of
wear scar) mm 0.52 0.51 0.47 0.48
[0224] As shown in Table 2, it turns out that the lubricating oil
compositions in Examples 1 to 6 containing the component (A) have
substantially the same HTHS viscosity after the ultrasonic shear
test at 150.degree. C., and have a lower kinematic viscosity and an
HTHS viscosity at 100.degree. C., sufficient resistance to wear,
and higher durability and fuel efficiency than the lubricating oil
compositions in Comparative Examples 1 and 2 in which a viscosity
index improver having a hydrocarbon main chain ratio more than 0.18
is blended and the lubricating oil compositions in Comparative
Examples 3 and 4 in which a viscosity index improver not containing
a methacrylate group having a carbon number of 18 is blended.
Examples 7 and 8
[0225] In Examples 7 and 8, lubricating oil compositions having
compositions shown in Table 5 were prepared using base oils and
additives shown below. Properties of Base oils O-2 and O-4 are
shown in Table 4.
(Base Oils)
[0226] O-2 (Base oil 2): Group III base oil (hydrocracked mineral
oil) [0227] O-4 (Base oil 4): Group III base oil (hydrocracked
mineral oil)
(Additives)
[0227] [0228] A-5: non-dispersive PMA viscosity index improver
prepared in Synthesis Example 5 (copolymer prepared by reacting 70
mol % methyl methacrylate, 30 mol % methacrylate in which R.sup.4
in the formula (4) was an alkyl group having a carbon number of 18,
a small amount of a polymerization initiator, and ethylene glycol
dimethacrylate. Mw=560000, Mn=450000, Mw/Mn=1.24, PSSI=3.8,
hydrocarbon main chain ratio=0.033) [0229] B-1: MoDTC (alkyl group
chain length: C8/C13, Mo content: 10 mass %, sulfur content: 11
mass %) [0230] C-1: other additives (such as a succinimide
dispersant, ZnDTP, an antioxidant, an anti-wear agent, a pour-point
depressant, and an antifoaming agent).
TABLE-US-00004 [0230] TABLE 4 O-2 O-4 Base oil 2 Base oil 4 Density
(15.degree. C.) g/cm.sup.3 0.835 0.8388 Kinematic viscosity (40
.degree.C.) mm.sup.2/s 20.0 18.72 (100 .degree.C.) mm.sup.2/s 4.29
4.092 Viscosity index 123 120 Pour point .degree. C. -17.5 -22.5
Aniline point .degree. C. 116 111.6 Iodine number 0.05 0.79 Sulfur
content mass ppm <1 2 Nitrogen content mass ppm <3 <3
n-d-M analysis % CP 80.7 78.0 % CN 19.3 20.7 % CA 0 1.3 Separation
by Saturate 99.7 95.1 chromatography content mass % Aromatic 0.2
4.7 content Resin 0.1 0.2 content Recover 100 rate Paraffin content
based on mass % 53.8 50.6 saturate content Naphthene content based
mass % 46.2 49.4 on saturate content
[0231] [Evaluation of Lubricating Oil Composition]
[0232] In the lubricating oil compositions in Examples 9 and 10,
the kinematic viscosity at 40.degree. C. or 100.degree. C., the
viscosity index, and the HTHS viscosity at 100.degree. C. or
150.degree. C. were measured. [0233] (1) Kinematic viscosity: ASTM
D-445 [0234] (2) Viscosity index: JIS K 2283-1993 [0235] (3) HTHS
viscosity: ASTM D-4683
TABLE-US-00005 [0235] TABLE 5 Example Example 7 8 Based on total
amount of Base oil base oil O-2 Base oil 2 % by mass 100 O-4 Base
oil 4 % by mass 100 Viscosity of mm.sup.2/s 20.0 18.6 base oil
(40.degree. C.) Viscosity of mm.sup.2/s 4.3 4.1 base oil
(100.degree. C.) Viscosity index 123 122 of base oil Based on total
amount of Additives composition A-1 Viscosity index % by mass 8.4
9.5 improver 1 A-2 Viscosity index % by mass improver 2 B-1 MoDTC %
by mass 0.7 0.7 C-1 Other additives % by mass 9.56 9.56 Results of
evaluation Kinematic 40.degree. C. mm.sup.2/s 33.0 32.3 viscosity
100.degree. C. mm.sup.2/s 7.3 7.4 Viscosity 194 204 index HTHS
100.degree. C. mPa s 4.8 4.8 viscosity HTHS 150.degree. C. mPa s
2.6 2.6 viscosity
[0236] As shown in Table 5, it turns out that the lubricating oil
compositions in Examples 7 and 8 have excellent reduction
properties of the HTHS viscosity at 100.degree. C.
Examples 9 and 10
[0237] In Examples 9 and 10, lubricating oil compositions having
compositions shown in Table 6 were prepared using the base oils
shown in Table 1 and the following additives.
(Base Oils)
[0238] O-2 (Base oil 2): hydrocracked mineral oil [0239] O-3 (Base
oil 3): hydrocracked mineral oil
(Additives)
[0239] [0240] A-1: non-dispersive PMA viscosity index improver
prepared in Synthesis Example 1 (copolymer prepared by reacting 70
mol % methyl methacrylate, 30 mol % methacrylate in which R.sup.4
in the formula (4) was an alkyl group having a carbon number of 18,
a small amount of a polymerization initiator, and ethylene glycol
dimethacrylate. Mw=570000, Mn=470000, Mw/Mn=1.23, PSSI=3.8,
Mw/PSSI=1.5.times.10.sup.5, hydrocarbon main chain ratio=0.025)
[0241] a-3: dispersive PMA viscosity index improver (copolymer
prepared by reacting 20 mol % methyl methacrylate, 80 mol %
methacrylate in which R.sup.6 in the formula (5) was an alkyl group
having a carbon number of 12 to 15, and small amounts of a
nitrogen-containing dispersive group (dimethylamino group,
diethylamino group, dipropyl amino group) and a polymerization
initiator. Mw=300000, Mn=70000, Mw/Mn=4.0, PSSI=40, Mw/PS
SI=7.5.times.10.sup.3, hydrocarbon main chain ratio=0.13) [0242]
B-1: MoDTC (alkyl group chain length: C8/C13, Mo content: 10 mass
%, sulfur content: 11 mass %) [0243] D-1: other additives (such as
a succinimide dispersant, ZnDTP, an antioxidant, an anti-wear
agent, a pour-point depressant, and an antifoaming agent).
[0244] The "nitrogen ratio" in Table 6 means the ratio of nitrogen
derived from the dispersive group to the total amount of nitrogen
in the engine oil.
[0245] [Evaluation of Lubricating Oil Composition]
[0246] In the lubricating oil compositions in Examples 9 and 10,
the kinematic viscosity at 40.degree. C. or 100.degree. C., the
viscosity index, the HTHS viscosity at 100.degree. C. or
150.degree. C., and the HTHS viscosity after the ultrasonic shear
test were measured. [0247] (1) Kinematic viscosity: ASTM D-445
[0248] (2) Viscosity index: JIS K 2283-1993 [0249] (3) HTHS
viscosity: ASTM D-4683 [0250] (4) Evaluation of resistance to wear
(four ball test)
[0251] The four ball test (ASTM D4172) was performed under the
following conditions, and the diameter (mm) of a wear scar was
measured to evaluate resistance to wear. [0252] load: 294 N [0253]
number of rotation: 1500 rpm [0254] temperature: 110.degree. C.
[0255] test time: 1 hour [0256] amount of CB (MA-100 (CAS. No.
1333-86-4)): 0.1%
TABLE-US-00006 [0256] TABLE 6 Example Example 9 10 Based on total
amount of Base oil base oil O-2 Base oil 2 % by mass 50 50 O-3 Base
oil 3 % by mass 50 50 Viscosity of base mm.sup.2/s 16.2 16.2 oil
(40.degree. C.) Viscosity of base 3.7 3.7 oil (100.degree. C.)
Viscosity index 117 117 of base oil Based on total amount of
Additives composition A-1 Viscosity index % by mass 6.8 4.3
improver a-3 Viscosity index % by mass 0.9 2.2 improver (nitrogen
ratio, (0.02) (0.05) % by mass) B-1 MoDTC % by mass 0.7 0.7 D-1
Other additives % by mass 10 10 Results of evaluation Kinematic
viscosity 40.degree. C. mm.sup.2/s 28.0 29.8 100.degree. C.
mm.sup.2/s 6.6 7.0 Viscosity index 205 209 HTHS viscosity
100.degree. C. mPa s 4.4 4.5 HTHS viscosity 150.degree. C. mPa s
2.3 2.3 Four ball test Diameter of mm 0.45 0.50 wear scar
[0257] As shown in Table 6, it turns out that the lubricating oil
compositions in Examples 9 and 10 have excellent reduction
properties of the HTHS viscosity at 100.degree. C., and have high
resistance to wear in the four ball test.
Examples 11 to 15
[0258] In Examples 11 to 15, lubricating oil compositions having
compositions shown in Table 7 were prepared using the base oils
shown in Table 1 and the following additives.
(Base Oils)
[0259] O-1 (Base oil 1): mineral oil prepared by
hydrocracking/hydrogenation isomerization of a
n-paraffin-containing oil [0260] O-2 (Base oil 2): hydrocracked
mineral oil [0261] O-3 (Base oil 3): hydrocracked mineral oil
(Additives)
[0261] [0262] A-1: non-dispersive PMA viscosity index improver
prepared in Synthesis Example 1 (copolymer prepared by reacting 70
mol % methyl methacrylate, 30 mol % methacrylate in which R.sup.4
in the formula (4) was an alkyl group having a carbon number of 18,
a small amount of a polymerization initiator, and ethylene glycol
dimethacrylate. Mw=570000, Mn=470000, Mw/Mn=1.23, PSSI=3.8,
Mw/PSSI=1.5.times.10.sup.5, hydrocarbon main chain ratio=0.025)
[0263] A-2: non-dispersive PMA viscosity index improver prepared in
Synthesis Example 2 (copolymer prepared by reacting 70 mol % methyl
methacrylate, 30 mol % methacrylate in which R.sup.4 in the formula
(4) was an alkyl group having a carbon number of 18, a small amount
of a polymerization initiator, and ethylene glycol dimethacrylate.
Mw=490000, Mn=410000, Mw/Mn=1.19, PSSI=2.2,
Mw/PSSI=2.2.times.10.sup.5, hydrocarbon main chain ratio=0.020)
[0264] C-1: overbased boric acid calcium salicylate A (metal ratio:
2.5, base value: 152 mgKOH/g, Ca content: 5.3 mass %, B content:
1.9 mass %, Ca/B ratio: 2.8, linear alkyl group chain length: 20 to
28 (30%) and chain length: 14 to 18 (70%)) [0265] B-1: MoDTC (alkyl
group chain length: C8/C13, Mo content: 10 mass %, sulfur content:
11 mass %) [0266] C-2: overbased boric acid calcium salicylate B
(metal ratio: 2.5, base value: 132 mgKOH/g, Ca content: 4.7 mass %,
B content: 1.7 mass %, Ca/B ratio: 2.8, linear alkyl group chain
length: 20 to 28) [0267] c-1: overbased boric acid calcium
salicylate D (metal ratio of 3.5, base value: 192 mgKOH/g, Ca
content: 6.8 mass %, B content: 2.7 mass %, Ca/B ratio: 2.5, alkyl
group chain length: 14 to 18) [0268] B-1: MoDTC (alkyl group chain
length: C8/C13, Mo content: 10 mass %, sulfur content: 11 mass %)
[0269] d-1: succinimide dispersant (Mw: 13000, alkyl group chain
length: 1900, nitrogen content: 0.6 mass %) [0270] e-1: ZnDTP
(alkyl group chain length: C4/C6, secondary, Zn content: 7.8 mass
%, P content: 7.2 mass %, S content: 15.0 mass %) [0271] f-1: other
additives (such as an antioxidant, an anti-wear agent, a pour-point
depressant, and an antifoaming agent).
[0272] [Evaluation of Lubricating Oil Composition]
[0273] In the lubricating oil compositions in Examples 11 to 15,
the kinematic viscosity at 40.degree. C. or 100.degree. C., the
viscosity index, and the HTHS viscosity at 100.degree. C. or
150.degree. C. were measured. In the measurement of fuel
efficiency, a motoring friction torque of a valve train was
measured. Physical properties values and fuel efficiency were
measured by the following evaluation methods. The obtained results
are shown in Table 7. [0274] (1) Kinematic viscosity: ASTM D-445
[0275] (2) Viscosity index: JIS K 2283-1993 [0276] (3) HTHS
viscosity: ASTM D-4683 [0277] (4) Valve train motoring friction
test: using an apparatus that could measure the friction torque of
a pair of a cam and a tappet of a valve train in a direct-acting
4-cylinder engine, a friction torque at an oil temperature of
100.degree. C. and the number of rotation of 350 rpm was measured.
A motoring friction improving rate where Example 15 was used as a
standard oil was calculated.
TABLE-US-00007 [0277] TABLE 7 Example Example Example Example
Example 11 12 13 14 15 Based on total Base oil amount of base oil
O-1 Base oil 1 % by mass 50 O-9 Base oil 2 % by mass 50 50 50 50
O-3 Base oil 3 50 50 50 50 50 Viscosity of base oil mm.sup.2/s 14.7
16.2 16.2 16.2 16.2 (40.degree. C.) Viscosity of base oil 3.6 3.7
3.7 3.7 3.7 (100.degree. C.) Viscosity index of 124 117 117 117 117
base oil Based on total amount of Additives composition A-1
Viscosity index % by mass 8.8 7.9 7.6 8.0 improver A-2 Viscosity
index % by mass 8.8 improver C-1 Overbased metallic % by mass 3.6
3.6 3.6 detergent C-2 Overbased metallic % by mass 4.2 detergent
c-1 Overbased metallic % by mass 2.9 detergent B-1 MoDTC % by mass
0.8 0.8 0.8 0.8 0.8 d-1 Succinimide % by mass 5 5 5 5 5 e-1 ZnDTP %
by mass 1.1 1.1 1.1 1.1 1.1 f-1 Other additives % by mass 1.5 1.5
1.5 1.5 1.5 Results of evaluation Kinematic 40.degree. C.
mm.sup.2/s 24.8 26.6 26.8 26.9 26.4 viscosity 100.degree. C.
mm.sup.2/s 6.1 6.3 6.2 6.3 6.2 Viscosity 213 199 192 198 199 index
HTHS 100.degree. C. mPa s 4.2 4.3 4.4 4.3 4.3 viscosity 150.degree.
C. mPa s 2.3 2.3 2.3 2.3 23 HTHS viscosity (150.degree. C.)/ 0.55
0.53 0.52 0.53 0.53 HTHS viscosity (100.degree. C.) Motoring
friction improving rate % 6.2 6.0 6.0 8.0 0.0
[0278] As shown in Table 7, it turns out that the lubricating oil
compositions in Examples 11 to 14 have a high friction improving
rate in the valve train motoring friction test and high fuel
efficiency.
Examples 16 to 19
[0279] In Examples 15 to 19, lubricating oil compositions having
compositions shown in Table 8 were prepared using the base oils
shown in Table 1 and the following additives. Table 8 also shows
the composition of the lubricating oil composition in Example 15,
which was used as a standard oil for the valve train motoring
friction test.
(Base Oils)
[0280] O-1 (Base oil 1): mineral oil prepared by
hydrocracking/hydrogenation isomerization of a
n-paraffin-containing oil [0281] O-2 (Base oil 2): hydrocracked
mineral oil [0282] O-3 (Base oil 3): hydrocracked mineral oil
(Additives)
[0282] [0283] A-1: non-dispersive PMA viscosity index improver
prepared in Synthesis Example 1 (copolymer prepared by reacting 70
mol % methyl methacrylate, 30 mol % methacrylate in which R.sup.4
in the formula (4) was an alkyl group having a carbon number of 18,
a small amount of a polymerization initiator, and ethylene glycol
dimethacrylate. Mw=570000, Mn=470000, Mw/Mn=1.23, PSSI=3.8,
Mw/PSSI=1.5.times.10.sup.5, hydrocarbon main chain ratio=0.025)
[0284] A-2: non-dispersive PMA viscosity index improver prepared in
Synthesis Example 2 (copolymer prepared by reacting 70 mol % methyl
methacrylate, 30 mol % methacrylate in which R.sup.4 in the formula
(4) was an alkyl group having a carbon number of 18, a small amount
of a polymerization initiator, and ethylene glycol dimethacrylate.
Mw=490000, Mn=410000, Mw/Mn=1.19, PSSI=2.2,
Mw/PSSI=2.2.times.10.sup.5, hydrocarbon main chain ratio=0.020)
[0285] C-3: overbased boric acid calcium salicylate A (metal ratio
of 2.0, base value: 139 mgKOH/g, Ca content: 4.9 mass %, B content:
1.3 mass %, Ca/B ratio: 3.8, alkyl group chain length: 14 to 18)
[0286] C-4: overbased boric acid calcium salicylate B (metal ratio:
2.5, base value: 158 mgKOH/g, Ca content: 5.6 mass %, B content:
1.7 mass %, Ca/B ratio: 3.3, alkyl group chain length: 14 to 18)
[0287] B-1: MoDTC (alkyl group chain length: C8/C13, Mo content: 10
mass %, sulfur content: 11 mass %) [0288] d-1: succinimide
dispersant (Mw: 13000, alkyl group chain length: 1900, nitrogen
content: 0.6 mass %) [0289] e-1: ZnDTP (alkyl group chain length:
C4/C6, secondary, Zn content: 7.8 mass %, P content: 7.2 mass %, S
content: 15.0 mass %) [0290] f-1: other additives (such as an
antioxidant, an anti-wear agent, a pour-point depressant, and an
antifoaming agent).
[0291] [Evaluation of Lubricating Oil Composition]
[0292] In the lubricating oil compositions in Examples 16 to 19,
the kinematic viscosity at 40.degree. C. or 100.degree. C., the
viscosity index, and the HTHS viscosity at 100.degree. C. or
150.degree. C. were measured. In the measurement of fuel
efficiency, the valve train motoring friction torque was measured.
Physical properties values and fuel efficiency were measured by the
following evaluation methods. The obtained results are shown in
Table 8. [0293] (1) Kinematic viscosity: ASTM D-445 [0294] (2)
Viscosity index: JIS K 2283-1993 [0295] (3) HTHS viscosity: ASTM
D-4683 [0296] (4) Valve train motoring friction test: using an
apparatus that could measure the friction torque of a pair of a cam
and a tappet of a valve train in a direct-acting 4-cylinder engine,
a friction torque at an oil temperature of 100.degree. C. and the
number of rotation of 350 rpm was measured. In the test, a motoring
friction improving rate where Example 15 was used as a standard oil
was calculated.
TABLE-US-00008 [0296] TABLE 8 Example Example Example Example
Example 16 17 18 19 15 Based on total amount Base oil of base oil
O-1 Base oil 1 % by mass 50 50 O-2 Base oil 2 % by mass 50 50 50
O-3 Base oil 3 % by mass 50 50 50 50 50 Viscosity of base oil
mm.sup.2/s 14.7 14.7 16.2 16.2 16.2 (40.degree. C.) Viscosity of
base oil 3.6 3.6 3.7 3.7 3.7 (100.degree. C.) Viscosity index of
base oil 124 124 117 117 117 Based on total amount Additives of
composition A-1 Viscosity index % by mass 8.5 8.7 7.8 8.0 improver
A-2 Viscosity index % by mass 8.7 improver C-1 Overbased metallic %
by mass 4.1 detergent C-2 Overbased metallic % by mass 3.6 3.6 3.6
detergent c-1 Overbased metallic % by mass 2.9 detergent B-1 MoDTC
% by mass 0.8 0.8 0.8 0.8 0.8 d-1 Succinimide % by mass 5 5 5 5 5
e-1 ZnDTP % by mass 1.1 1.1 1.1 1.1 1.1 f-1 Other additives % by
mass 1.5 1.5 1.5 1.5 1.5 Results of evaluation Kinematic 40.degree.
C. mm.sup.2/s 25.1 24.6 26.5 26.7 26.4 viscosity 100.degree. C.
mm.sup.2/s 6.2 6.1 6.2 6.1 6.2 Viscosity 210 212 197 191 199 index
HTHS 100.degree. C. mPa s 4.2 4.1 4.3 4.4 4.3 viscosity 150.degree.
C. mPa s 2.3 2.3 2.3 2.3 2.3 HTHS viscosity (150.degree. C.)/ 0.55
0.56 0.53 0.52 0.53 HTHS viscosity (100.degree. C.) Motoring
friction improving rate % 4.5 4.0 3.7 3.5 0.0
[0297] As shown in Table 8, it turns out that the lubricating oil
compositions in Examples 17 to 20 have a high friction improving
rate in the valve train motoring friction test and high fuel
efficiency.
* * * * *