U.S. patent application number 16/322141 was filed with the patent office on 2020-06-11 for lubricating oil composition.
The applicant listed for this patent is ExxonMobil Research and Engineering Company. Invention is credited to Takashi Honda, Toyoharu Kaneko, Ko Onodera, Hiroyuki Suzuki, Kazuo Yamamori.
Application Number | 20200181529 16/322141 |
Document ID | / |
Family ID | 60117705 |
Filed Date | 2020-06-11 |
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United States Patent
Application |
20200181529 |
Kind Code |
A1 |
Suzuki; Hiroyuki ; et
al. |
June 11, 2020 |
LUBRICATING OIL COMPOSITION
Abstract
A lubricant composition contains a lubricant base oil, (A) a
detergent containing magnesium, (B) a compound containing boron,
and (C) a zinc dialkyl dithiophosphate. The amount of component (A)
is in the range of 200 to 1200 mass ppm [Mg] based on the mass of
the lubricant composition, and the amount of component (C) is in
the range of 300 to 1000 mass ppm [P] based on the mass of the
lubricant composition. Component (C) includes a zinc dialkyl
dithiophosphate having a primary alkyl group or a secondary alkyl
group; the lubricant composition includes zinc dialkyl
dithiophosphate having a secondary alkyl group; the mass ratio of
the zinc dialkyl dithiophosphate having a primary alkyl group and
the zinc dialkyl dithiophosphate having a secondary alkyl group is
from 70:30 to 0:100; and the concentration of [B] is from 100 to
300 mass ppm based on the mass of the lubricant composition.
Inventors: |
Suzuki; Hiroyuki;
(Kawasaki-shi, Kanagawa, JP) ; Onodera; Ko;
(Kawasaki-shi, Kanagawa, JP) ; Honda; Takashi;
(Kawasaki-shi, Kanagawa, JP) ; Kaneko; Toyoharu;
(Anjo-shi, Aichi-ken, JP) ; Yamamori; Kazuo;
(Nagoya-shi, Aichi-ken, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ExxonMobil Research and Engineering Company |
Annandale |
NJ |
US |
|
|
Family ID: |
60117705 |
Appl. No.: |
16/322141 |
Filed: |
August 2, 2017 |
PCT Filed: |
August 2, 2017 |
PCT NO: |
PCT/IB2017/000897 |
371 Date: |
January 31, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10M 2207/262 20130101;
C10M 2219/068 20130101; C10M 2223/045 20130101; C10N 2030/04
20130101; C10N 2060/14 20130101; C10M 169/045 20130101; C10M
2207/026 20130101; C10N 2040/25 20130101; C10N 2010/12 20130101;
C10N 2030/02 20130101; C10M 2205/003 20130101; C10M 2201/06
20130101; C10M 2215/28 20130101; C10M 2209/084 20130101; C10M
2223/045 20130101; C10M 2219/046 20130101; C10M 163/00 20130101;
C10N 2030/06 20130101; C10N 2010/04 20130101; C10M 2223/045
20130101; C10M 2223/045 20130101; C10M 2205/173 20130101; C10N
2030/68 20200501; C10M 2219/068 20130101; C10N 2040/255 20200501;
C10N 2010/04 20130101; C10N 2010/04 20130101; C10N 2010/04
20130101; C10N 2060/14 20130101; C10N 2010/12 20130101; C10N
2020/069 20200501; C10M 2215/28 20130101; C10N 2020/071 20200501;
C10M 2229/041 20130101; C10M 107/02 20130101 |
International
Class: |
C10M 169/04 20060101
C10M169/04; C10M 107/02 20060101 C10M107/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 2, 2016 |
JP |
2016-152180 |
Claims
1. A lubricating oil composition comprising a lubricant base oil,
(A) a detergent containing magnesium, (B) a boron-containing
compound, and (C) a zinc dialkyldithiophosphate, wherein an amount
of component (A) is from 200 to 1200 ppm by weight in terms of a
magnesium concentration [Mg] which is ppm by weight of magnesium
based on the lubricating oil composition; an amount of component
(C) is from 300 to 1000 ppm by weight in terms of a phosphorus
concentration [P] which is ppm by weight of phosphorus based on the
lubricating oil composition; component (C) is one or more selected
from zinc dialkyldithiophosphates having a primary alkyl group
and/or a secondary alkyl group, wherein the lubricating oil
composition comprises at least one zinc dialkyldithiophosphate
having a secondary alkyl group, and a weight ratio of a zinc
dialkyldithiophosphate having a primary alkyl group to a zinc
dialkyldithiophosphate having a secondary alkyl group is from 0/100
to 70/30; and a boron concentration [B] is from 100 to 300 ppm by
weight based on the lubricating oil composition.
2. The lubricating oil composition according to claim 1, wherein
the lubricating oil composition comprises at least one ashless
dispersant containing boron as the boron-containing compound
(B).
3. The lubricating oil composition according to claim 1, wherein
the lubricating oil composition further comprises a detergent (A')
containing calcium, and satisfies the following equation (1):
{[Mg]/([Mg]+[Ca])}.times.100.gtoreq.5 (1) where [Ca] represents a
concentration of calcium in terms of ppm by weight based on the
lubricating oil composition.
4. The lubricating oil composition according to claim 1, further
comprising a friction modifier containing molybdenum, and satisfies
the following equation (2): [Mg]/[Mo]<2.5 (2) where [Mo]
represents a concentration in terms of ppm by weight of molybdenum
based on the lubricating oil composition.
5. The lubricating oil composition according to claim 1, wherein
the lubricating oil composition has a CCS viscosity of not more
than 6.2 Pas at -35.degree. C.
6. The lubricating oil composition according to claim 1, wherein
the lubricating oil composition has a high-temperature high-shear
viscosity (HTHS viscosity) of 1.5 to 2.9 mPas at 150.degree. C.
7. The lubricating oil composition according to claim 1, wherein
the lubricating oil composition has a kinematic viscosity of less
than 9.3 mm.sup.2/s at 100.degree. C.
8. The lubricating oil composition according to claim 1, wherein
the lubricating oil composition is for use in an internal
combustion engine.
9. The lubricating oil composition according to claim 2, wherein
the lubricating oil composition further comprises a detergent (A')
containing calcium, and satisfies equation (1):
{[Mg]/([Mg]+[Ca])}.times.100.gtoreq.5 (1) where [Ca] represents a
concentration of calcium in terms of ppm by weight based on the
lubricating oil composition.
10. The lubricating oil composition according to claim 2, further
comprising a friction modifier containing molybdenum, and satisfies
equation (2): [Mg]/[Mo]<2.5 (2) where [Mo] represents a
concentration in terms of ppm by weight of molybdenum based on the
lubricating oil composition.
11. The lubricating oil composition according to claim 2, wherein
the lubricating oil composition has a CCS viscosity of not more
than 6.2 Pas at -35.degree. C.
12. The lubricating oil composition according to claim 2, wherein
the lubricating oil composition has a high-temperature high-shear
viscosity (HTHS viscosity) of 1.5 to 2.9 mPas at 150.degree. C.
13. The lubricating oil composition according to claim 2, wherein
the lubricating oil composition has a kinematic viscosity of less
than 9.3 mm.sup.2/s at 100.degree. C.
14. The lubricating oil composition according to claim 2, wherein
the lubricating oil composition is for use in an internal
combustion engine.
15. The lubricating oil composition according to claim 3, further
comprising a friction modifier containing molybdenum, and satisfies
equation (2): [Mg]/[Mo]<2.5 (2) where [Mo] represents a
concentration in terms of ppm by weight of molybdenum based on the
lubricating oil composition.
16. The lubricating oil composition according to claim 3, wherein
the lubricating oil composition has a CCS viscosity of not more
than 6.2 Pas at -35.degree. C.
17. The lubricating oil composition according to claim 3, wherein
the lubricating oil composition has a high-temperature high-shear
viscosity (HTHS viscosity) of 1.5 to 2.9 mPas at 150.degree. C.
18. The lubricating oil composition according to claim 3, wherein
the lubricating oil composition has a kinematic viscosity of less
than 9.3 mm.sup.2/s at 100.degree. C.
19. The lubricating oil composition according to claim 3, wherein
the lubricating oil composition is for use in an internal
combustion engine.
20. The lubricating oil composition according to claim 4, wherein
the lubricating oil composition has a CCS viscosity of not more
than 6.2 Pas at -35.degree. C.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is the National Phase entry of
International Patent Application No. PCT/IB2017/000897 filed on
Aug. 2, 2017, which claims priority to Japanese Patent Application
No. 20016-152180 filed Aug. 2, 2016, the entire contents of which
are hereby incorporated by reference into this application.
FIELD
[0002] The present disclosure relates to a lubricating oil
composition. Specifically, the present disclosure relates to a
lubricating oil composition for an internal combustion engine, and
particularly relates to a lubricating oil composition for a
gasoline engine.
BACKGROUND
[0003] Lubricating oil compositions have been widely used in the
automotive field, e.g., for internal combustion engines, automatic
transmissions, gear oils, and the like. In recent years, a
reduction in viscosity has been demanded for improving fuel
efficiency. However, such a reduction in viscosity results in a
decrease in the thickness of an oil film, thereby making it
impossible to sufficiently reduce friction. Thus, molybdenum
dithiocarbamate (MoDTC), which generates molybdenum disulfide under
a boundary lubrication condition, thereby enabling friction to be
reduced, has been conventionally used. In such a case, a
calcium-based detergent is usually used in combination (for
example, Japanese Unexamined Patent Publication (Kokai) No.
2013-199594 (Patent Literature 1)). However, the combination has a
limitation on a reduction in friction and does not enable fuel
efficiency to be sufficiently improved.
[0004] It has also been known to use magnesium-based detergents as
detergents (for example, Japanese Unexamined Patent Publication
(Kokai) No. 2011-184566 (Patent Literature 2) and Japanese
Unexamined Patent Publication (Kokai) No. 2006-328265 (Patent
Literature 3)). Use of such a magnesium-based detergent enables
less friction to occur but causes wear to more easily occur than
use of a calcium-based detergent.
CITATION LIST
Patent Literature
[0005] Patent Literature 1: Japanese Unexamined Patent Publication
(Kokai) No. 2013-199594
[0006] Patent Literature 2: Japanese Unexamined Patent Publication
(Kokai) No. 2011-184566
[0007] Patent Literature 3: Japanese Unexamined Patent Publication
(Kokai) No. 2006-328265
SUMMARY
Technical Problem
[0008] An object of the present disclosure is to provide a
lubricating oil composition that enables friction to be reduced
while ensuring wear prevention properties even when achieving low
viscosity. In accordance with some embodiments, an object of the
present disclosure is to provide a lubricating oil composition for
an internal combustion engine and to provide a lubricating oil
composition for a supercharged gasoline engine.
Solution to Problem
[0009] As a result of intensive examination, the present inventors
found that the above objects are achieved by adding a particular
amount of magnesium-based detergent and a particular amount of zinc
dialkyldithiophosphate having a particular structure to a lubricant
base oil and by defining the content of boron contained in a
composition.
[0010] In other words, the present disclosure is directed to:
[0011] a lubricating oil composition comprising a lubricant base
oil, (A) a detergent containing magnesium, (B) a boron-containing
compound, and (C) a zinc dialkyldithiophosphate, wherein
[0012] an amount of component (A) is from 200 to 1200 ppm by weight
in terms of a magnesium concentration [Mg] which is ppm by weight
of magnesium based on the lubricating oil composition;
[0013] an amount of component (C) is from 300 to 1000 ppm by weight
in terms of a phosphorus concentration [P] which is ppm by weight
of phosphorus based on the lubricating oil composition;
[0014] component (C) is one or more selected from zinc
dialkyldithiophosphates having a primary alkyl group and/or a
secondary alkyl group, with the proviso that the lubricating oil
composition comprises at least one zinc dialkyldithiophosphate
having a secondary alkyl group, and a weight ratio of a zinc
dialkyldithiophosphate having a primary alkyl group to a zinc
dialkyldithiophosphate having a secondary alkyl group is from 0/100
to 70/30; and
[0015] a boron concentration [B] is from 100 to 300 ppm by weight
based on the lubricating oil composition.
[0016] In some embodiments of the present disclosure, the
lubricating oil composition further includes at least one feature
of (1) to (7) described below.
[0017] (1) The lubricating oil composition comprises at least one
ashless dispersant containing boron as the boron-containing
compound (B).
[0018] (2) The lubricating oil composition further comprises a
detergent (A') containing calcium, and satisfies the following
equation:
{[Mg]/([Mg]+[Ca])}.times.100.gtoreq.5
where [Ca] represents a concentration of calcium in terms of ppm by
weight based on the lubricating oil composition.
[0019] (3) The lubricating oil composition further comprises a
friction modifier containing molybdenum, and satisfies the
following equation:
[Mg]/[Mo]<2.5
where [Mo] represents a concentration of molybdenum in terms of ppm
by weight based on the lubricating oil composition.
[0020] (4) The lubricating oil composition has a CCS viscosity of
not more than 6.2 Pas at -35.degree. C.
[0021] (5) The lubricating oil composition has a high-temperature
high-shear viscosity (HTHS viscosity) of 1.5 to 2.9 mPas at
150.degree. C.
[0022] (6) The lubricating oil composition has a kinematic
viscosity of less than 9.3 mm.sup.2/s at 100.degree. C.
[0023] (7) The lubricating oil composition is for use in an
internal combustion engine.
[0024] The present disclosure further relates to a method for
reducing friction while maintaining low wear by using the
lubricating oil composition or the lubricating oil composition of
any one of the embodiments (1) to (7) described above.
Effects of the Present Disclosure
[0025] The lubricating oil composition of the present disclosure
enables friction to be reduced while ensuring wear prevention
properties even when achieving low viscosity. The lubricating oil
composition can be used as a lubricating oil composition for an
internal combustion engine, and as a lubricating oil composition
for a supercharged gasoline engine.
DETAILED DESCRIPTION
Lubricant Base Oil
[0026] A lubricant base oil in the present disclosure is not
particularly restricted. The lubricant base oil may be any of
mineral oils and synthetic oils, which may be used singly or in
combination.
[0027] Examples of the mineral oils include mineral oils obtained
by distilling crude oil under atmospheric pressure to produce an
ordinary pressure residual oil, distilling the ordinary pressure
residual oil under reduced pressure to produce a lubricating oil
distillate, and purifying the lubricating oil distillate by one or
more treatments, such as solvent deasphalting, solvent extraction,
hydrocracking, solvent dewaxing, and hydrogenation refining; and
wax-isomerized mineral oils, GTL (Gas to Liquid) base oils, ATL
(Asphalt to Liquid) base oils, vegetable oil-based base oils, and
mixed-base oils thereof.
[0028] Examples of the synthetic oils include polybutenes or
hydrogenated products thereof; poly-.alpha.-olefins such as
1-octene oligomer and 1-decene oligomer, or hydrogenated products
thereof monoesters such as 2-ethylhexyl laurate, 2-ethylhexyl
palmitate, and 2-ethylhexyl stearate; diesters such as ditridecyl
glutarate, di-2-ethylhexyl adipate, di-isodecyl adipate, ditridecyl
adipate, and di-2-ethylhexyl sebacate; polyol esters such as
neopentyl glycol di-2-ethyl hexanoate, neopentyl glycol
di-n-octanoate, neopentyl glycol di-n-decanoate, trimethylolpropane
tri-n-octanoate, trimethylolpropane tri-n-decanoate,
pentaerythritol tetra-n-pentanoate, pentaerythritol
tetra-n-hexanoate, and pentaerythritol tetra-2-ethyl hexanoate; and
aromatic synthetic oils such as alkylnaphthalenes, alkylbenzenes,
and aromatic esters, or mixtures thereof.
[0029] The kinematic viscosity (mm.sup.2/s) of the lubricant base
oil at 100.degree. C. is, but not limited to, from 2 to 15
mm.sup.2/s, from 3 to 10 mm.sup.2/s, from 3 to 8 mm.sup.2/s, or
from 3 to 6 mm.sup.2/s. When the kinematic viscosity is within the
above range, the lubricating oil composition that allows an oil
film to be sufficiently formed and has excellent lubricity and less
vaporization loss can be obtained.
[0030] The viscosity index (VI) of the lubricant base oil is, but
not limited to, not less than 100, not less than 120, or not less
than 130. When the viscosity index is within the above range,
viscosity at low temperature can be reduced while an oil film is
retained at high temperature.
(A) Magnesium-Based Detergent
[0031] The lubricating oil composition of the present disclosure
comprises a detergent containing magnesium (hereinafter referred to
as "magnesium-based detergent") as a component. The magnesium-based
detergent is a compound containing magnesium. A magnesium-based
detergent that has been used as a metal-based detergent in a
lubricating oil composition can be used as the magnesium-based
detergent. Examples thereof include, but are not limited to,
magnesium sulfonates, magnesium phenates, and magnesium
salicylates. In some embodiments, the magnesium-based detergent can
include magnesium salicylate or magnesium sulfonate. Such
magnesium-based detergents may be used singly, or in combination of
two or more thereof.
[0032] The lubricating oil composition enables high-temperature
cleaning performance and rust prevention properties demanded for a
lubricating oil to be ensured by including the magnesium-based
detergent as a component (A). In addition, friction can be reduced,
and therefore, torque can be reduced, which effect fuel efficiency
characteristics.
[0033] The magnesium-based detergent is added in such an amount
that the magnesium concentration [Mg] ranges from 200 to 1200 ppm
by weight, from 300 to 1100 ppm by weight, or from 400 to 1000 ppm
by weight, based on the lubricating oil composition. When the
amount of the magnesium-based detergent is more than the above
upper limit, wear becomes excessively great. When the amount of the
magnesium-based detergent is less than the above lower limit, the
effect of reducing friction becomes low.
[0034] In some embodiments, the magnesium-based detergent is
overbased. When the magnesium-based detergent is overbased, acid
neutralization properties demanded for a lubricating oil can be
ensured. When an overbased magnesium-based detergent is used, the
overbased magnesium-based detergent may be mixed with a neutral
magnesium- or calcium-based detergent.
[0035] The total base value of the magnesium-based detergent is,
but not limited to, from 20 to 600 mgKOH/g, from 50 to 500 mgKOH/g,
or from 100 to 450 mgKOH/g. When the total base value of the
magnesium-based detergent is within the above range, acid
neutralization properties, high-temperature cleaning performance,
and rust prevention properties demanded for a lubricating oil can
be ensured. When a mixture of two or more metal detergents is used,
a total base value of the mixture is within the above range.
[0036] The content of magnesium in the magnesium-based detergent is
from 0.5 to 20% by weight, from 1 to 16% by weight, or from 2 to
14% by weight. However, the magnesium-based detergent has only to
be added in such an amount that magnesium is contained in the above
amount in the lubricating oil composition.
[0037] When the lubricating oil composition of the present
disclosure comprises a molybdenum-based friction modifier described
later, the amount of the magnesium-based detergent satisfies the
following equation (2):
[Mg]/[Mo]<2.5 (2)
where [Mo] represents the concentration of molybdenum in terms of
ppm by weight based on the lubricating oil composition.
[0038] In some embodiments, the value of [Mg]/[Mo] is not more than
2.0, not more than 1.8, or not more than 1.5. When the value of
[Mg]/[Mo] is not less than 2.5, wear may sometimes be too great.
The value of [Mg]/[Mo] is not less than 0.1, more preferably not
less than 0.2, or not less than 0.3.
[0039] The lubricating oil composition of the present disclosure
may comprise another metal-based detergent in combination with the
above magnesium-based detergent. The metal-based detergent may be a
metal-based detergent which has been used in a lubricating oil
composition. In some embodiments, a detergent (A') containing
calcium (hereinafter referred to as "calcium-based detergent") may
be used in combination. The lubricating oil composition enables
high-temperature cleaning performance and rust prevention
properties demanded for a lubricating oil to be further ensured by
further comprising the calcium-based detergent.
[0040] The calcium-based detergent (A') is a compound containing
calcium. A calcium-based detergent that has been used as a
metal-based detergent in a lubricating oil composition can be used
as the calcium-based detergent (A'). Examples thereof include, but
are not limited to, calcium sulfonates, calcium phenates, and
calcium salicylates. Such calcium-based detergents may be used
singly, or in combination of two or more thereof.
[0041] The amount of the component (A') satisfies the following
equation (1).
{[Mg]/([Mg]+[Ca])}.times.100.gtoreq.5 (1)
where [Ca] represents the concentration of calcium in terms of ppm
by weight based on the lubricating oil composition.
[0042] In some embodiments, the value of
{[Mg]/([Mg]+[Ca])}.times.100 is not less than 10, or not less than
15. When the value is less than 5, the effect of reducing friction
becomes low. In some embodiments, the value of
{[Mg]/([Mg]+[Ca])}.times.100 is not more than 100, not more than
80, not more than 60, or not more than 50.
[0043] When the lubricating oil composition of the present
disclosure further comprises a molybdenum-containing friction
modifier described later, the following equation (3) is
satisfied.
([Mg]+[Ca]/[Mo].ltoreq.3.0 (3)
where [Mo] represents the concentration of molybdenum in terms of
ppm by weight based on the weight of the lubricating oil
composition.
[0044] In some embodiments, the value of ([Mg]+[Ca])/[Mo] is not
more than 2.8, not more than 2.6, or not more than 2.5. When the
value of ([Mg]+[Ca])/[Mo] is more than 3.0, the effect of reducing
torque may sometimes be low. In some embodiments, the value of
([Mg]+[Ca])/[Mo] is not less than 0.2, not less than 0.5, or not
less than 1.0.
[0045] In some embodiments, the calcium-based detergent (A') is
overbased. When the calcium-based detergent is overbased, acid
neutralization properties demanded for a lubricating oil can be
ensured. When an overbased calcium-containing detergent is used, a
neutral calcium-based detergent may be used in combination.
[0046] The total base value of the calcium-based detergent (A') is,
but not limited to, from 20 to 500 mgKOH/g, from 50 to 400 mgKOH/g,
or from 100 to 350 mgKOH/g. When the total base value of the
calcium-based detergent is within the above range, acid
neutralization properties, high-temperature cleaning performance,
and rust prevention properties demanded for a lubricating oil can
be ensured. When a mixture of two or more metal detergents is used,
a total base value of the mixture is within the above range.
[0047] The content of calcium in the calcium-based detergent (A')
is from 0.5 to 20% by weight, from 1 to 16% by weight, or from 2 to
14% by weight.
[0048] The lubricating oil composition of the present disclosure
may comprise a sodium-based detergent as a metal-based detergent
other than the above metal-based detergents as long as the effects
of the present disclosure are not impaired. The sodium-based
detergent is a compound containing sodium. Examples thereof include
sodium sulfonates, sodium phenates, and sodium salicylates. Such
sodium-based detergents may be used singly, or in combination of
two or more thereof. The lubricating oil composition enables
high-temperature cleaning performance and rust prevention
properties demanded for a lubricating oil to be ensured by
containing the sodium-based detergent. The sodium-based detergent
can be used in combination with the magnesium-based detergent
described above and any calcium-based detergent.
[0049] The total amount of the metal-based detergents in the
lubricating oil composition of the present disclosure has only to
be such an amount that the amount of magnesium contained in the
above composition is within the specific range described above. The
amounts of the added calcium- and sodium-based detergents can be
restricted depending on the amount of the magnesium-based
detergent.
(B) Boron-Containing Compound
[0050] The lubricating oil composition of the present disclosure
comprises a boron-containing compound. The boron-containing
compound may be a known compound containing boron that has been
blended into a lubricating oil composition. In some embodiments,
the boron-containing compound is a boron-containing ashless
dispersant. Other examples of the boron-containing compound include
alkali borate-based additives described later. In some embodiments,
the lubricating oil composition of the present disclosure comprises
at least one boron-containing ashless dispersant as the
boron-containing compound.
[0051] The lubricating oil composition of the present disclosure is
characterized in that the amount of boron contained in the
composition is 100 to 300 ppm by weight based on the total weight
of the composition. In some embodiments, the content of boron is
from 120 to 280 ppm by weight, or from 150 to 250 ppm by weight.
Accordingly, the above boron-containing compound, particularly the
boron-containing ashless dispersant, is blended in such an amount
that the amount of boron contained in the composition is within the
above range. When the boron-containing ashless dispersant and
another boron-containing compound are used in combination, the
total amount of boron contained in the composition is adjusted to
be within the above range. In some embodiments, the amount of the
blended boron-containing ashless dispersant is from 0.1 to 5% by
weight, from 0.3 to 4% by weight, or from 0.5 to 3% by weight,
based on the total weight of the composition.
[0052] One boron-containing ashless dispersant may be used singly,
or two or more thereof may be used in combination. Examples thereof
include boron-containing ashless dispersants obtained by modifying
(boronating) a succinimide compound with a boron compound such as
boric acid or a borate. In the lubricating oil composition of the
present disclosure, an ashless dispersant containing no boron may
be also used in combination. When the boron-containing ashless
dispersant and the ashless dispersant containing no boron are used
in combination, the total amount of the ashless dispersants may be
not more than 20% by weight, not more than 15% by weight, still
more preferably not more than 10% by weight, or not more than 5% by
weight, based on the total weight of the composition.
[0053] Examples of ashless dispersants include a
nitrogen-containing compound having at least one straight- or
branched-chain alkyl or alkenyl group having 40 to 500 carbon
atoms, such as from 60 to 350 carbon atoms, per molecule, or
derivatives thereof; Mannich dispersants; derivatives of mono-type
or bis-type succinimides (for example, compounds having the
structures of alkenyl succinimides); benzylamines having at least
one alkyl or alkenyl group having 40 to 500 carbon atoms per
molecule; polyamines having at least one alkyl or alkenyl group
having 40 to 400 carbon atoms per molecule; or products obtained by
modifying these compounds with boron compounds, carboxylic acids,
phosphoric acid, and the like. One or more arbitrarily selected
from such ashless dispersants may be blended. Boron-containing
ashless dispersants are compounds obtained by modifying the above
compounds with a boron compound. Particularly, boron-containing
ashless dispersants may include derivatives of mono-type or
bis-type succinimides, and still more particularly, compounds
obtained by modifying (boronating) an alkenyl succinimide compound
with a boron compound such as boric acid or borates.
[0054] Boronated succinimide derivatives are produced by known
methods. The methods are not particularly limited. For example,
such a mono-type or bis-type succinimide derivative is obtained by
allowing a compound having an alkyl or alkenyl group having 40 to
500 carbon atoms to react with a maleic anhydride at 100 to
200.degree. C. to produce an alkyl succinic acid or an alkenyl
succinic acid and by allowing the alkyl succinic acid or the
alkenyl succinic acid and a polyamine to react with each other.
Examples of the polyamine include diethylenetriamine,
triethylenetetramine, tetraethylenepentamine, and
pentaethylenehexamine. A mono-type succinimide derivative can be
represented by, for example, the following formula (a). A bis-type
succinimide derivative can be represented by, for example, the
following formula (b).
##STR00001##
[0055] In the above formulae, each R.sup.1 independently is an
alkyl or alkenyl group having 40 to 400 carbon atoms, m is an
integer of from 1 to 20, and n is an integer of from 0 to 20. In
some embodiments, the boronated succinimide derivative may be a
bis-type succinimide compound. Mono-type and bis-type succinimide
derivatives may be used in combination, two or more mono-type
succinimide derivatives may be used in combination, or two or more
bis-type succinimide derivatives may be used in combination.
[0056] A boronated succinimide derivative is obtained by allowing
the above succinimide derivative and a boron compound to react with
each other. Examples of the boron compound include boric acid,
boric anhydride, boric acid esters, boron oxide, and boron halides.
Boronated succinimide derivatives may be used singly, or in
combination of two or more thereof.
[0057] Derivatives of nitrogen-containing compounds are known as
other ashless dispersants. Examples thereof include: so-called
oxygen-containing organic compound-modified compounds obtained by
allowing the above nitrogen-containing compound (i.e., the
nitrogen-containing compound having at least one straight- or
branched-chain alkyl or alkenyl group having 40 to 500 carbon
atoms, or from 60 to 350 carbon atoms, per molecule) to react with
a monocarboxylic acid having 1 to 30 carbon atoms, such as fatty
acid, a polycarboxylic acid having 2 to 30 carbon atoms, such as
oxalic acid, phthalic acid, trimellitic acid, or pyromellitic acid,
or an anhydride or ester compound thereof, an alkylene oxide having
2 to 6 carbon atoms, or a hydroxy(poly)oxyalkylene carbonate, and
then neutralizing or amidating some or all of remaining amino
and/or imino groups; so-called boron-modified compounds obtained by
allowing boric acid to act on the above nitrogen-containing
compound and then neutralizing or amidating some or all of
remaining amino and/or imino groups; so-called phosphoric
acid-modified compounds obtained by allowing phosphoric acid to act
on the above nitrogen-containing compound and then neutralizing or
amidating some or all of remaining amino and/or imino groups;
sulfur-modified compounds obtained by allowing sulfur compounds to
act on the above nitrogen-containing compound; and modified
compounds obtained by subjecting the above nitrogen-containing
compound to a combination of two or more modifications selected
from modification with oxygen-containing organic compounds, boron
modification, phosphoric acid modification, and sulfur
modification.
[0058] In some embodiments, the ashless dispersants may include
boric acid-modified compounds of the alkenyl succinimide
derivatives, particularly boric acid-modified compounds of the
bis-type alkenyl succinimide derivatives, so that heat resistance
is further improved by being used in combination with the above
base oil.
[0059] The number-average molecular weight (Mn) of the ashless
dispersant is, but not limited to, not less than 2000, not less
than 2500, not less than 3000, or not less than 5000, and not more
than 15000. When the number-average molecular weight of the ashless
dispersant is less than the above lower limit, dispersibility may
be insufficient. When the number-average molecular weight of the
ashless dispersant is more than the above upper limit, viscosity
may be excessively high, flowability may be insufficient, and it
may cause deposits to be increased.
[0060] An alkali borate-based additive may be added as another
boron-containing compound. The alkali borate-based additive
contains an alkali metal borate hydrate, and can be represented by
the following formula.
M.sub.2O.xB.sub.2O.sub.3.yH.sub.2O
where M is an alkali metal, x is 2.5 to 4.5, and y is 1.0 to
4.8.
[0061] Examples of the alkali borate-based additive include lithium
borate hydrates, sodium borate hydrates, potassium borate hydrates,
rubidium borate hydrates, and cesium borate hydrates. In some
embodiments, potassium borate hydrates and sodium borate hydrates
are the alkali borate-based additive. In some embodiments, and
potassium borate hydrates are the alkali borate-based additive. The
average particle diameter of alkali metal borate hydrate particles
is not more than 1 micron (.mu.m). In the alkali metal borate
hydrate used in the present disclosure, the ratio of boron to an
alkali metal is in a range of about 2.5:1 to 4.5:1. The alkali
borate-based additive is added in such an amount that the amount of
boron is 2 to 300 ppm by weight based on the total weight of the
lubricating oil composition.
[0062] Additional examples of other boron-containing compounds
include: potassium borates such as potassium metaborate, potassium
tetraborate, potassium pentaborate, potassium hexaborate, and
potassium octaborate; calcium borate sulfonate; and calcium borate
salicylate.
(C) Zinc Dialkyldithiophosphate
[0063] The lubricating oil composition of the present disclosure
comprises a zinc dialkyldithiophosphate (ZnDTP (also referred to as
"ZDDP")). This compound functions as an anti-wear agent, and is
represented by the following formula (4).
##STR00002##
[0064] In formula (4), R.sup.2 and R.sup.3 may be the same as or
different from each other and each represents a hydrogen atom or a
monovalent hydrocarbon group having 1 to 26 carbon atoms. Examples
of the monovalent hydrocarbon group include: primary or secondary
alkyl groups having 1 to 26 carbon atoms; alkenyl groups having 2
to 26 carbon atoms; cycloalkyl groups having 6 to 26 carbon atoms;
aryl groups, alkylaryl groups, or arylalkyl groups having 6 to 26
carbon atoms; and hydrocarbon groups containing an ester bond, an
ether bond, an alcohol group, or a carboxyl group. The primary
alkyl groups mean that in the substituents R.sup.2 and R.sup.3,
carbon atoms directly bound to oxygen atoms in the zinc
dialkyldithiophosphate are primary carbon atoms. Similarly, the
secondary alkyl groups mean that in the substituents R.sup.2 and
R.sup.3, the carbon atoms directly bound to the oxygen atoms in the
zinc dialkyldithiophosphate are secondary carbon atoms. In some
embodiments, each of R.sup.2 and R.sup.3 independently is a primary
or secondary alkyl group having 3 to 12 carbon atoms, a cycloalkyl
group having 8 to 18 carbon atoms, or an alkylaryl group having 8
to 18 carbon atoms. In the present disclosure, however, at least
one of R.sup.2 and R.sup.3 is a primary or secondary alkyl group.
The primary alkyl group has 3 to 12 carbon atoms, or from 4 to 10
carbon atoms. Examples thereof include a propyl group, a butyl
group, a pentyl group, a hexyl group, an octyl group, a nonyl
group, a decyl group, a dodecyl group, a 2-ethylhexyl group, and a
2,5-dimethylhexyl group. Such a secondary alkyl group has 3 to 12
carbon atoms, or from 3 to 10 carbon atoms. Examples thereof
include an isopropyl group, a secondary butyl group, an isopentyl
group, and an isohexyl group.
[0065] The lubricating oil composition of the present disclosure
comprises one or more selected from zinc dialkyldithiophosphates
having a primary alkyl group and/or a secondary alkyl group. The
lubricating oil composition comprises a zinc dialkyldithiophosphate
having a secondary alkyl group. In other words, the present
disclosure includes three embodiments: the first embodiment in
which the lubricating oil composition comprises both of a zinc
dialkyldithiophosphate having a primary alkyl group and a zinc
dialkyldithiophosphate having a secondary alkyl group; the second
embodiment in which the lubricating oil composition comprises a
zinc dialkyldithiophosphate having both of a primary alkyl group
and a secondary alkyl group; and the third embodiment in which the
lubricating oil composition comprises a zinc dialkyldithiophosphate
having a secondary alkyl group and no zinc dialkyldithiophosphate
having a primary alkyl group. In some embodiments, the lubricating
oil includes the first embodiment in which a zinc
dialkyldithiophosphate having a primary alkyl group and a zinc
dialkyldithiophosphate having a secondary alkyl group are used in
combination. When the lubricating oil composition comprises no zinc
dialkyldithiophosphate having a secondary alkyl group, favorable
wear prevention properties are unable to be ensured. The present
disclosure is characterized in that the lubricating oil composition
comprises a zinc dialkyldithiophosphate having a primary alkyl
group and a zinc dialkyldithiophosphate having a secondary alkyl
group at a weight ratio of 0/100 to 70/30. The ratio is from 5/95
to 65/35, from 10/90 to 60/40, or from 20/80 to 50/50. When the
content of the zinc dialkyldithiophosphate having a primary alkyl
group is more than the above upper limit, wear resistance may
unfavorably deteriorate.
[0066] The content of the zinc dialkyldithiophosphate in the
lubricating oil composition is such a content that the
concentration [P] of phosphorus contained in the zinc
dialkyldithiophosphate is 300 to 1000 ppm by weight, from 400 to
1000 ppm by weight, from 500 to 1000 ppm by weight, or from 600 to
900 ppm by weight, based on the total weight of the lubricating oil
composition.
[0067] In the present disclosure, a torque reduction rate is
improved by adjusting the relationship (combination) of the amount
of boron contained in the lubricating oil composition and the
weight ratio of the zinc dialkyldithiophosphate having a primary
alkyl group (hereinafter simply referred to as "primary zinc
dialkyldithiophosphate") to the zinc dialkyldithiophosphate having
a secondary alkyl group (hereinafter simply referred to as
"secondary zinc dialkyldithiophosphate"). The combination may be
adjusted as appropriate so that the amount of boron is within a
range of 100 to 300 ppm by weight, or from 120 to 280 ppm by
weight, or from 150 to 250 ppm by weight, based on the total amount
of the composition, and so that the weight ratio of a primary zinc
dialkyldithiophosphate to a secondary zinc dialkyldithiophosphate
is within a range of 1/100 to 70/30, or from 5/95 to 65/35, or from
10/90 to 60/40, or from 20/80 to 50/50. The total amount of zinc
dialkyldithiophosphates is adjusted in order that the total
concentration (ppm by weight) of phosphorus may be within the above
range. The lubricating oil composition obtained in such a manner
enables both of favorable friction prevention properties and wear
prevention properties to be achieved even when viscosity is
low.
[0068] The lubricating oil composition of the present disclosure
may further comprise an anti-wear agent other than the zinc
dialkyldithiophosphate. Examples thereof include compounds
represented by the above formula, in which each of R.sup.2 and
R.sup.3 independently is a hydrogen atom or a monovalent
hydrocarbon group having 1 to 26 carbon atoms, which is not an
alkyl group. Examples of the monovalent hydrocarbon groups include
alkenyl groups having 2 to 26 carbon atoms; cycloalkyl groups
having 6 to 26 carbon atoms; aryl groups, alkylaryl groups, and
arylalkyl groups having 6 to 26 carbon atoms; and hydrocarbon
groups containing an ester bond, an ether bond, an alcohol group,
or a carboxyl group. In some embodiments, R.sup.2 and R.sup.3 are
cycloalkyl groups having 8 to 18 carbon atoms and alkylaryl groups
having 8 to 18 carbon atoms, and may be the same as or different
from each other. Zinc dithiocarbamate (ZnDTC) may be used in
combination therewith.
[0069] At least one compound selected from phosphate- and
phosphite-based phosphorus compounds represented by the following
formulae (5) and (6), and metal salts and amine salts thereof may
be used in combination.
##STR00003##
[0070] In above formula (5), R.sup.6 is a monovalent hydrocarbon
group having 1 to 30 carbon atoms, each of R.sup.4 and R.sup.5
independently is a hydrogen atom or a monovalent hydrocarbon group
having 1 to 30 carbon atoms, and k is 0 or 1.
##STR00004##
[0071] In above formula (6), R.sup.9 is a monovalent hydrocarbon
group having 1 to 30 carbon atoms, each of R.sup.7 and R.sup.8
independently is a hydrogen atom or a monovalent hydrocarbon group
having 1 to 30 carbon atoms, and t is 0 or 1.
[0072] Examples of the monovalent hydrocarbon groups having 1 to 30
carbon atoms, represented by R.sup.4 to R.sup.9 in above formulae
(5) and (6), include alkyl groups, cycloalkyl groups, alkenyl
groups, alkyl-substituted cycloalkyl groups, aryl groups,
alkyl-substituted aryl groups, and arylalkyl groups. In some
embodiments, the monovalent hydrocarbon groups are alkyl groups
having 1 to 30 carbon atoms or aryl groups having 6 to 24 carbon
atoms. In some embodiments, the monovalent hydrocarbon groups are
alkyl groups having 3 to 18 carbon atoms, or alkyl groups having 4
to 15 carbon atoms.
[0073] Examples of the phosphorus compound represented by above
formula (5) include phosphite monoesters and (hydrocarbyl)
phosphonites having one of the above hydrocarbon groups having 1 to
30 carbon atoms; phosphite diesters, monothiophosphite diesters,
and (hydrocarbyl) phosphonite monoesters having two of the above
hydrocarbon groups having 1 to 30 carbon atoms; phosphite triesters
and (hydrocarbyl) phosphonite diesters having three of the above
hydrocarbon groups having 1 to 30 carbon atoms; and mixtures
thereof.
[0074] A metal salt or amine salt of the phosphorus compound
represented by above formula (5) or (6) can be obtained by allowing
a metal base such as a metal oxide, a metal hydroxide, a metal
carbonate, or a metal chloride, a nitrogen compound such as ammonia
or an amine compound having only a hydrocarbon group or a hydroxyl
group-containing hydrocarbon group having 1 to 30 carbon atoms in a
molecule thereof, or the like to act on the phosphorus compound
represented by formula (5) or (6), followed by neutralizing part or
all of the remaining acidic hydrogen. Examples of a metal in the
above metal base include alkali metals such as lithium, sodium,
potassium, and cesium; alkaline-earth metals such as calcium,
magnesium, and barium; and heavy metals such as zinc, copper, iron,
lead, nickel, silver, and manganese (excluding molybdenum). In some
embodiments, the metal in the above metal base includes zinc or
alkaline-earth metals such as calcium and magnesium. In some
embodiments, the metal in the above metal base is zinc.
[0075] The zinc dialkyldithiophosphate may be added in such an
amount that the content of phosphorus originated from the zinc
dialkyldithiophosphate is within the above specific range, as
described above. When the lubricating oil composition comprises
another anti-wear agent, the anti-wear agent may be blended into
the lubricating oil composition in the total amount of the
anti-wear agents including the zinc dialkyldithiophosphate of 0.1
to 5% by weight, or from 0.2 to 3% by weight.
[0076] The lubricating oil composition of the present disclosure
may comprise various additives as optional components in addition
to the above components. The lubricating oil composition may
comprise, for example, a molybdenum-based friction modifier or a
viscosity index improver.
Molybdenum-Based Friction Modifier
[0077] The friction modifier containing molybdenum (hereinafter
referred to as "molybdenum-based friction modifier") is not
particularly limited. A friction modifier containing molybdenum can
be used as the molybdenum-based friction modifier. The
molybdenum-based friction modifier is a compound containing
molybdenum. Examples thereof include organic molybdenum compounds
containing sulfur such as molybdenum dithiophosphate (MoDTP) and
molybdenum dithiocarbamate (MoDTC); complexes of molybdenum
compounds and sulfur-containing organic compounds or other organic
compounds; and complexes of sulfur-containing molybdenum compounds
such as molybdenum sulfide and molybdate sulfide, and alkenyl
succinimides. Examples of the above molybdenum compounds include
molybdenum oxides such as molybdenum dioxide and molybdenum
trioxide; molybdic acids such as orthomolybdic acid, paramolybdic
acid, and (poly)molybdic sulfide; molybdates such as metal salts
and ammonium salts of the molybdic acids; molybdenum sulfides such
as molybdenum disulfide, molybdenum trisulfide, molybdenum
pentasulfide, and molybdenum polysulfide; molybdate sulfides; metal
salts and amine salts of molybdate sulfides; and molybdenum halides
such as molybdenum chloride. Examples of the above
sulfur-containing organic compounds include alkyl(thio)xanthate,
thiadiazole, mercaptothiadiazole, thiocarbonate,
tetrahydrocarbylthiuram disulfide,
bis(di(thio)hydrocarbyldithiophosphonate) disulfide, organic
(poly)sulfides, and sulfate esters. In some embodiments, the
friction modifier includes organic molybdenum compounds such as
molybdenum dithiophosphate (MoDTP) and molybdenum dithiocarbamate
(MoDTC).
[0078] Molybdenum dithiocarbamate (MoDTC) is a compound represented
by following formula [I], and molybdenum dithiophosphate (MoDTP) is
a compound represented by following formula [II].
##STR00005##
[0079] In above formulae [I] and [II], R.sub.1 to R.sub.8 may be
the same as or different from each other, and are monovalent
hydrocarbon groups having 1 to 30 carbon atoms. The hydrocarbon
group may be straight or branched. Examples of the monovalent
hydrocarbon groups include straight- or branched-chain alkyl groups
having 1 to 30 carbon atoms; alkenyl groups having 2 to 30 carbon
atoms; cycloalkyl groups having 4 to 30 carbon atoms; and aryl
groups, alkylaryl groups, or arylalkyl groups having 6 to 30 carbon
atoms. The binding position of the alkyl group in an arylalkyl
group is arbitrary. More specifically, examples of alkyl groups
include a methyl group, an ethyl group, a propyl group, a butyl
group, a pentyl group, a hexyl group, a heptyl group, an octyl
group, a nonyl group, a decyl group, an undecyl group, a dodecyl
group, a tridecyl group, a tetradecyl group, a pentadecyl group, a
hexadecyl group, a heptadecyl group, an octadecyl group, and
branched-chain alkyl groups thereof. In some embodiments, the
monovalent hydrocarbon groups may be alkyl group groups having 3 to
8 carbon atoms. In addition, X.sub.1 and X.sub.2 are oxygen atoms
or sulfur atoms, and Y.sub.1 and Y.sub.2 are oxygen atoms or sulfur
atoms.
[0080] An organic molybdenum compound containing no sulfur can also
be used as the friction modifier. Examples of such compounds
include molybdenum-amine complexes, molybdenum-succinimide
complexes, molybdenum salts of organic acids, and molybdenum salts
of alcohols.
[0081] A trinuclear molybdenum compound described in U.S. Pat. No.
5,906,968 can also be used as the friction modifier in the present
disclosure.
[0082] The friction modifier is added in such an amount that the
concentration [Mo] of molybdenum is within a range of 500 to 1500
ppm by weight, or from 600 to 1200 ppm by weight, based on the
lubricating oil composition. When the amount of the friction
modifier is more than the above upper limit, cleaning performance
may deteriorate. When the amount of the friction modifier is less
than the above lower limit, friction cannot be sufficiently
reduced, and cleaning performance may deteriorate.
[0083] The friction modifier is contained in an amount that
satisfies following equation (2):
[Mg]/[Mg]<2.5 (2)
as described above for component (A). [Mo] is the concentration of
molybdenum in terms of ppm by weight based on the lubricating oil
composition.
[0084] In some embodiments, the value of [Mg]/[Mo] is not more than
2.0, not more than 1.8, or not more than 1.5. The value of
[Mg]/[Mo] is not less than 0.1, not less than 0.2, or not less than
0.3.
Viscosity Index Improver
[0085] Examples of the viscosity index improver include viscosity
index improvers containing polymethacrylate, dispersion-type
polymethacrylate, olefin copolymers (polyisobutylene,
ethylene-propylene copolymer), dispersion-type olefin copolymers,
polyalkylstyrene, hydrogenated styrene-butadiene copolymer,
styrene-maleic anhydride ester copolymer, and star isoprene A
comb-shaped polymer containing, in the main chain thereof, at least
a repeating unit based on a polyolefin macromer and a repeating
unit based on alkyl (meth)acrylate having an alkyl group having 1
to 30 carbon atoms can also be used.
[0086] The viscosity index improver comprises the above polymer and
a diluent oil. The content of the viscosity index improver is from
0.01 to 20% by weight, from 0.02 to 10% by weight, or from 0.05 to
5% by weight, as the amount of polymer, based on the total amount
of the composition. When the content of the viscosity index
improver is less than the above lower limit, deterioration of
viscosity temperature characteristics and low-temperature viscosity
characteristics may occur. In contrast, when the content of the
viscosity index improver is more than the above upper limit,
deterioration of viscosity temperature characteristics and
low-temperature viscosity characteristics may occur, further
resulting in a great increase in product cost.
[0087] The lubricating oil composition of the present disclosure
may further comprise other additives depending on purpose in order
to improve the performance thereof. As such other additives,
additives used in lubricating oil compositions can be used.
Examples of other additives include additives such as antioxidants,
friction modifiers other than the above friction modifier,
corrosion inhibitors, antirust agents, pour-point depressants,
demulsifiers, metal deactivators, and antifoaming agents.
[0088] Examples of the above antioxidants include ashless
antioxidants such as phenol-based and amine-based ashless
antioxidants, and metal-based antioxidants such as copper-based and
molybdenum-based antioxidants. Examples of the phenol-based ashless
antioxidants include 4,4'-methylenebis(2,6-di-tert-butylphenol),
4,4'-bis(2,6-di-tert-butylphenol), and
isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate. Examples of
the amine-based ashless antioxidants include
phenyl-.alpha.-naphthylamine, alkylphenyl-.alpha.-naphthylamine,
and dialkyl diphenylamine. In some embodiments, 0.1 to 5% by weight
of an antioxidant is blended into the lubricating oil
composition.
[0089] Examples of the friction modifiers other than the above
friction modifier include esters, amines, amides, and sulfurized
esters. In some embodiments, 0.01 to 3% by weight of a friction
modifier is blended into the lubricating oil composition.
[0090] Examples of the above corrosion inhibitors include
benzotriazole-based, tolyltriazole-based, thiadiazole-based, and
imidazole-based compounds. Examples of the above antirust agents
include petroleum sulfonate, alkylbenzene sulfonate,
dinonylnaphthalene sulfonate, alkenylsuccinate esters, and
polyvalent alcohol esters. In some embodiments, 0.01 to 5% by
weight of each of a corrosion inhibitor and an antirust agent is
blended into the lubricating oil composition.
[0091] For example, polymethacrylate-based polymers compatible with
the lubricant base oil used can be used as the above pour-point
depressants. In some embodiments, 0.01 to 3% by weight of a
pour-point depressant is blended into the lubricating oil
composition.
[0092] Examples of the above demulsifiers include polyalkylene
glycol-based nonionic surfactants such as polyoxyethylene alkyl
ethers, polyoxyethylene alkyl phenyl ethers, and polyoxyethylene
alkyl naphthyl ethers. In some embodiments, 0.01 to 5% by weight of
a demulsifier is blended into the lubricating oil composition.
[0093] Examples of the above metal deactivators include
imidazoline, pyrimidine derivatives, alkylthiadiazoles,
mercaptobenzothiazole, benzotriazole and derivatives thereof,
1,3,4-thiadiazole polysulfide,
1,3,4-thiadiazolyl-2,5-bisdialkyldithiocarbamate,
2-(alkyldithio)benzimidazole,
.beta.-(o-carboxybenzylthio)propionitrile. In some embodiments,
0.01 to 3% by weight of a metal deactivator is blended into the
lubricating oil composition.
[0094] Examples of the above antifoaming agents include silicone
oils having a kinematic viscosity of 1000 to 100000 mm.sup.2/s at
25.degree. C., alkenyl succinic acid derivatives, esters of
aliphatic polyhydroxy alcohols and long-chain fatty acids, methyl
salicylate, and o-hydroxybenzyl alcohol. In some embodiments, 0.001
to 1% by weight of an antifoaming agent is blended into the
lubricating oil composition.
[0095] The CCS viscosity of the lubricating oil composition of the
present disclosure at -35.degree. C. is, but not limited to, not
more than 6.2 Pas, not more than 5.0 Pas, not more than 4.0 Pas, or
not more than 3.5 Pas.
[0096] When the lubricating oil composition of the present
disclosure comprises molybdenum, the amount of molybdenum in the
lubricating oil composition and CCS viscosity at -35.degree. C.
satisfy following equation (7):
[CCS viscosity]/[Mo].ltoreq.0.01 (7)
where [CCS viscosity] represents the value (Pas) of the CCS
viscosity of the lubricating oil composition at -35.degree. C., and
[Mo] represents the concentration of molybdenum in terms of ppm by
weight based on the lubricating oil composition.
[0097] In some embodiments, the value of [CCS viscosity]/[Mo] is
not more than 0.008, or not more than 0.005. A case in which, when
the above value is more than 0.01, torque reduction rate may
decrease or cleaning performance may deteriorate. The value of [CCS
viscosity]/[Mo] is, but not limited to, not less than 0.002, or not
less than 0.003.
[0098] The high-temperature high-shear viscosity (HTHS viscosity)
of the lubricating oil composition of the present disclosure at
150.degree. C. is, but not limited to, 1.5 to 2.9 mPas, from 1.7 to
2.8 mPas, or from 2.0 to 2.6 mPas.
[0099] The kinematic viscosity of the lubricating oil composition
of the present disclosure at 100.degree. C. is, but not limited to,
less than 9.3 mm.sup.2/s, or less than 8.2 mm.sup.2/s.
[0100] The lubricating oil composition of the present disclosure
exhibits the effects of having sufficient friction characteristics
and wear characteristics and enabling a high torque reduction rate
to be obtained even when viscosity is low, and can be used for an
internal combustion engine and further for a supercharged gasoline
engine.
EXAMPLES
[0101] The present disclosure will be described in more detail
below with reference to examples and comparative examples. However,
the present disclosure is not limited to the following
examples.
[0102] Materials used in the examples and the comparative examples
are as follows.
Lubricant Base Oil
[0103] Base oil derived from GTL having a kinematic viscosity at
100.degree. C. of 4.1 mm.sup.2/s and VI of 127
(A) Magnesium-Based Detergent
[0104] Magnesium sulfonate having a total base value of 400 mgKOH/g
and a magnesium content of 9.4% by weight
(A') Calcium-Based Detergent
[0105] Calcium salicylate having a total base value of 230 mgKOH/g
and a calcium content of 5.5% by weight
(B) Ashless Dispersant Containing Boron
[0106] Boronated succinimide compound which is a mixture of
compounds represented by above formula (b), in which R.sup.1 is
polybutenyl, and n is 4 to 12; and has a boron content of 0.7% by
weight, and a nitrogen content of 2.0% by weight
(B') Ashless Dispersant Containing No Boron
[0107] Succinimide compound which is a mixture of compounds
represented by above formula (b), in which R.sup.1 is polybutenyl,
and n is 4 to 12; and has a boron content of 0% by weight, and a
nitrogen content of 1.0% by weight
(C) Anti-Wear Agent 1
[0108] Pri-ZnDTP which is a compound represented by following
formula (4), in which both R.sup.2 and R.sup.3 are primary alkyl
groups having eight carbon atoms
##STR00006##
(C) Anti-Wear Agent 2
[0109] Sec-ZnDTP which is a compound represented by above formula
(4), in which R.sup.2 is a secondary alkyl group having four carbon
atoms, and R.sup.3 is a secondary alkyl group having six carbon
atoms
(D) Friction Modifier
[0110] Molybdenum-based friction modifier: MoDTC having a
molybdenum content of 10% by weight
(E) Viscosity Index Improver
[0111] Polymethacrylate
Other Additives
[0112] Antioxidant: phenol-based antioxidant
[0113] Antifoaming agent: dimethyl silicone
Examples 1 to 8 and Comparative Examples 1 to 6
[0114] Respective components having amounts listed in Tables 1 and
3 were mixed to prepare lubricating oil compositions. Amounts
(part(s) by weight) listed in the tables are amounts (part(s) by
weight) based on 100 parts by weight of the lubricating oil
composition. Regarding the amounts of (A) magnesium-based
detergent, (A') calcium-based detergent, and (D) molybdenum-based
friction modifier described in the tables, [Mg], [Ca], and [Mo] are
contents (ppm by weight) of magnesium, calcium, and molybdenum,
respectively, based on the lubricating oil composition. [B] listed
in the tables represents the amount (ppm by weight) of boron based
on the lubricating oil composition. The sum of the blended amounts
of (C) anti-wear agents is 1 part by weight based on 100 parts by
weight of the lubricating oil composition. The weight ratio of
anti-wear agent 1 (zinc dialkyldithiophosphate having a primary
alkyl group) to anti-wear agent 2 (zinc dialkyldithiophosphate
having a secondary alkyl group) (primary zinc
dialkyldithiophosphate/second zinc dialkyldithiophosphate (weight
ratio)) is listed in the tables. [P] listed in the tables
represents the amount (ppm by weight) of phosphorus based on the
lubricating oil composition. The amounts of magnesium-based
detergent and calcium-based detergent were adjusted so that the
total molar quantities of magnesium and calcium contained in the
detergents were as equal as possible in all the examples and the
comparative examples.
[0115] The following tests on the obtained compositions were
conducted. The results are listed in Tables 2 and 4.
(1) High-Temperature High-Shear Viscosity at 150.degree. C.
(HTHS150)
[0116] Measurement was performed according to ASTM D4683.
(2) CCS Viscosity at -35.degree. C. (CCS Viscosity)
[0117] Measurement was performed according to ASTM D5293.
(3) Kinematic Viscosity at 100.degree. C. (KV100)
[0118] Measurement was performed at 100.degree. C. according to
ASTM D445.
(4) Torque Reduction Rate
[0119] The lubricating oil compositions obtained in the examples
and the comparative examples were used as test compositions, and
the torques of the compositions were measured by a motoring test
using a gasoline engine. As the engine, a Toyota 2ZR-FE 1.8 L
inline four-cylinder engine was used. A torque meter was placed
between a motor and the engine, and a torque was measured at an oil
temperature of 80.degree. C. and an engine speed of 700 RPM. A
commercially available GF-5 0W-20 oil was used as a reference oil,
and a torque was measured in a similar manner. The torque (T) of
each test composition was compared with the torque (T.sub.0) of the
reference oil, and the reduction rate of the torque (T) from the
torque of the reference oil ({(T.sub.0-T)/T.sub.0}.times.100) (%)
was calculated. The greater reduction rate exhibits more favorable
fuel efficiency. A lubricating oil composition having a reduction
rate of not less than 9.0% was estimated as acceptable.
(5) Shell Wear Track Diameter
[0120] Measurement was performed according to the Shell four-ball
test (ASTMD4172) except for a rotation number of 1800 rpm, a load
of 40 kgf, a test temperature of 90.degree. C., and a test time of
30 minutes. A lubricating oil composition resulting in a wear track
diameter of not more than 0.7 mm was estimated as acceptable.
(6) Hot Tube Test (Evaluation of High-Temperature Cleaning
Performance)
[0121] A lubricating oil composition at 0.3 mL/hr and air at 10
mL/sec were allowed to continuously flow into a glass tube having
an inner diameter of 2 mm for 16 hours while maintaining the
temperature of the glass tube at 270.degree. C. The lacquer that
adhered to the glass tube was compared with a color chart, and the
lubricating oil compositions were scored based on a value of 10 for
transparency and a value of 0 for black color. A higher score
indicates better high-temperature cleaning performance. A
lubricating oil composition having a score of 4.5 or more was
evaluated as acceptable.
TABLE-US-00001 TABLE 1 Composition Example 1 Example 2 Example 3
Example 4 Example 5 Example 6 Example 7 Example 8 Lubricant base
oil Balance Balance Balance Balance Balance Balance Balance Balance
[A] Mg-based detergent [Mg] 400 500 600 400 400 400 400 500 [A']
Ca-based detergent [Ca] 1400 1400 1100 1400 1400 1400 1400 1400 [B]
Boron-containing part(s) by weight 3 3 3 1.5 4.5 4.5 1.5 1.5
ashless dispersant [B] 200 200 200 100 300 300 100 100 [B'] Ashless
dispersant part(s) by weight 0 0 0 1.5 0 0 1.5 1.5 containing no
boron [C] Anti-wear agent 1 part(s) by weight 0.5 0 0.5 0.5 0 0.5
0.3 0 containing primary alkyl group Anti-wear agent 2 part(s) by
weight 0.5 1 0.5 0.5 1 0.5 0.7 1 containing secondary alkyl group
Primary zinc dialkyldithiophosphate/ 50/50 0/100 50/50 50/50 0/100
50/50 30/70 0/100 second zinc dialkyldithiophosphate (weight ratio)
Total [P] 800 800 800 800 800 800 800 800 [D] Friction modifier
[Mo] 800 800 800 800 800 800 800 800 [E] Viscosity index improver
part(s) by weight 8 8 8 8 8 8 8 8 Other additive part(s) by weight
2 2 2 2 2 2 2 2 {[Mg]/([Mg] + [Ca])} .times. 100 22 26 35 22 22 22
22 26 ([Mg] + [Ca])/[Mo] 2.3 2.4 2.1 2.3 2.3 2.3 2.3 2.4 [Mg]/[Mo]
0.50 0.63 0.75 0.50 0.50 0.50 0.5 0.63
TABLE-US-00002 TABLE 2 Example 1 Example 2 Example 3 Example 4
Example 5 Example 6 Example 7 Example 8 Evaluation CCS viscosity
3.1 3.1 3.1 3.1 3.1 3.3 3.1 3.0 results HTHS 150 2.3 2.4 2.3 2.3
2.3 2.3 2.3 2.3 KV 100 6.4 6.4 6.4 6.4 6.4 6.5 6.4 6.4 [CCS
viscosity]/[Mo] 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004
Torque reduction rate (%) 9.8 11.6 9.2 11.8 9.2 9.2 10.9 9.7
(Acceptable: .gtoreq.9.0) HTT 7.5 6.0 7.0 5.5 7.0 7.5 5.0 4.5
(Acceptable: .gtoreq.4.5) Wear resistance 0.7 0.7 0.7 0.7 0.7 0.6
0.7 0.7 (Acceptable: .ltoreq.0.7 mm)
TABLE-US-00003 TABLE 3 Comparative Comparative Comparative
Comparative Comparative Comparative Composition Example 1 Example 2
Example 3 Example 4 Example 5 Example 6 Lubricant base oil Balance
Balance Balance Balance Balance Balance [A] Mg-based detergent [Mg]
500 400 400 400 500 1400 [A'] Ca-based detergent [Ca] 1400 1400
1400 1400 1400 0 [B] Boron-containing part(s) by weight 0 0 1.5 4.5
7.5 3 ashless dispersant [B] 0 0 100 300 500 200 [B'] Ashless
dispersant part(s) by weight 3 3 1.5 0 0 0 containing no boron [C]
Anti-wear agent 1 part(s) by weight 0 0.5 1 1 0.5 0.5 containing
primary alkyl group Anti-wear agent 2 part(s) by weight 1 0.5 0 0
0.5 0.5 containing secondary alkyl group Primary zinc
dialkyldithiophosphate/ 0/100 50/50 100/0 100/0 50/50 50/50 second
zinc dialkyldithiophosphate (weight ratio) Total [P] 800 800 800
800 800 800 [D] Friction modifier [Mo] 800 800 800 800 800 800 [E]
Viscosity index improver part(s) by weight 8 8 8 8 8 8 Other
additives part(s) by weight 2 2 2 2 2 2 {[Mg]/([Mg] + [Ca])}
.times. 100 26 22 22 22 26 100 ([Mg] + [Ca])/[Mo] 2.4 2.3 2.3 2.3
2.4 1.8 [Mg]/[Mo] 0.63 0.50 0.50 0.50 0.63 1.75
TABLE-US-00004 TABLE 4 Comparative Comparative Comparative
Comparative Comparative Comparative Example 1 Example 2 Example 3
Example 4 Example 5 Example 6 Evaluation CCS viscosity 3.1 3.1 3.0
3.3 3.5 3.1 results HTHS 150 2.3 2.3 2.3 2.3 2.3 2.3 KV 100 6.4 6.4
6.4 6.5 6.4 6.4 [CCS viscosity]/[Mo] 0.004 0.004 0.004 0.004 0.004
0.004 Torque reduction rate (%) 9.1 8.9 9.9 8.3 8.0 4.8
(Acceptable: .gtoreq.9.0) HTT 3.5 4.0 6.0 8.0 7.5 3.5 (Acceptable:
.gtoreq.4.5) Wear resistance 0.7 0.8 1.0 0.6 0.6 0.6 (Acceptable:
.ltoreq.0.7 mm)
[0122] As described in Table 2, the lubricating oil composition of
the present disclosure exhibits low wear and has a high torque
reduction rate and high high-temperature cleaning performance
although it has a low kinematic viscosity at 100.degree. C.
INDUSTRIAL APPLICABILITY
[0123] The lubricating oil composition of the present disclosure
exhibits the effects of enabling friction to be reduced while
ensuring wear prevention properties even when achieving low
viscosity and of achieving a high torque reduction rate. In some
embodiments, the lubricating oil composition of the present
disclosure is a lubricating oil composition for an internal
combustion engine, and as a lubricating oil composition for a
supercharged gasoline engine.
* * * * *