U.S. patent application number 13/577532 was filed with the patent office on 2012-12-06 for lubricating oil composition.
This patent application is currently assigned to Idemitsu Kosan Co., Ltd.. Invention is credited to Hiroshi Fujita.
Application Number | 20120309659 13/577532 |
Document ID | / |
Family ID | 44367500 |
Filed Date | 2012-12-06 |
United States Patent
Application |
20120309659 |
Kind Code |
A1 |
Fujita; Hiroshi |
December 6, 2012 |
LUBRICATING OIL COMPOSITION
Abstract
A lubricating oil composition contains (A) a base oil for a
lubricating oil in a range of 5 mass % to 70 mass % based on a
total amount of the composition, the base oil containing a sulfur
content of 0.03 mass % or less and having a kinematic viscosity at
100 degrees C. in a range of 0.5 mm.sup.2/s to 1.5 mm.sup.2/s, and
(B) a poly-alpha-olefin in a range of 15 mass % to 30 mass % based
on the total amount of the composition, the poly-alpha-olefin
having a kinematic viscosity at 100 degrees C. of 150 mm.sup.2/s or
more.
Inventors: |
Fujita; Hiroshi;
(Ichihara-shi, JP) |
Assignee: |
Idemitsu Kosan Co., Ltd.
Tokyo
JP
|
Family ID: |
44367500 |
Appl. No.: |
13/577532 |
Filed: |
November 17, 2010 |
PCT Filed: |
November 17, 2010 |
PCT NO: |
PCT/JP2010/070427 |
371 Date: |
August 7, 2012 |
Current U.S.
Class: |
508/473 ;
508/591 |
Current CPC
Class: |
C10M 111/04 20130101;
C10N 2040/04 20130101; C10N 2020/02 20130101; C10N 2030/68
20200501; C10M 2207/281 20130101; C10M 2223/047 20130101; C10M
169/04 20130101; C10M 2203/1006 20130101; C10M 2219/046 20130101;
C10M 2215/28 20130101; C10M 2209/084 20130101; C10M 2223/04
20130101; C10N 2030/02 20130101; C10M 2205/0285 20130101; C10N
2020/04 20130101; C10M 2219/08 20130101; C10M 2229/0415 20130101;
C10M 2229/025 20130101; C10M 2219/046 20130101; C10N 2010/04
20130101; C10M 2219/046 20130101; C10N 2010/04 20130101 |
Class at
Publication: |
508/473 ;
508/591 |
International
Class: |
C10M 143/00 20060101
C10M143/00; C10M 145/14 20060101 C10M145/14 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 9, 2010 |
JP |
2010-026545 |
Claims
1. A lubricating oil composition comprising: (A) a base oil
suitable as a lubricating oil, wherein the base oil is present in a
range of 5 mass % to 70 mass % based on a total amount of the
composition, comprises a sulfur content of 0.03 mass % or less and
has a kinematic viscosity at 100 degrees C. in a range of 0.5
mm.sup.2/s to 1.5 mm.sup.2/s; and (B) a poly-alpha-olefin (B),
wherein the poly-alpha-olefin (B) is present in a range of 15 mass
% to 30 mass % based on the total amount of the composition, and
has a kinematic viscosity at 100 degrees C. of 150 mm.sup.2/s or
more.
2. The lubricating oil composition according to claim 1, further
comprising: (C) a silicone oil having a kinematic viscosity at 100
degrees C. in a range of 0.5 mm.sup.2/s to 4 mm.sup.2/s.
3. The lubricating oil composition according to claim 1, further
comprising: (D) a polymethacrylate (D) having a mass average
molecular weight of 100000 or more.
4. The lubricating oil composition according to claim 1, further
comprising: (E) a poly-alpha-olefin (E) having a kinematic
viscosity at 100 degrees C. in a range of 1.5 mm.sup.2/s to 2.5
mm.sup.2/s.
5. The lubricating oil composition according to claim 1, further
comprising: (F) a polymethacrylate (E) having a mass average
molecular weight of 300000 or more and present in a range of 0.1
mass % to 5.0 mass % based on a total amount of the composition;
and (G) a poly-alpha-olefin (G) having a kinematic viscosity of 100
degrees C. in a range of 1.7 mm.sup.2/s to 2.1 mm.sup.2/s and
present in a range of 0.1 mass % to 60 mass % based on the total
amount of the composition, wherein a kinematic viscosity of the
base oil (A) at 100 degrees C. is in a range of 0.7 mm.sup.2/s to
1.3 mm.sup.2/s, and a kinematic viscosity of the poly-alpha-olefin
(B) at 100 degrees C. is in a range of 150 mm.sup.2/s to 400
mm.sup.2/s.
6. The lubricating oil composition according to claim 1, wherein
the lubricating oil composition is suitable for a transmission.
7. The lubricating oil composition according to claim 2, further
comprising: (D) a polymethacrylate (D) having a mass average
molecular weight of 100000 or more.
8. The lubricating oil composition according to claim 2, further
comprising: (E) a poly-alpha-olefin (E) having a kinematic
viscosity at 100 degrees C. in a range of 1.5 mm.sup.2/s to 2.5
mm.sup.2/s.
9. The lubricating oil composition according to claim 3, further
comprising: (E) a poly-alpha-olefin (E) having a kinematic
viscosity at 100 degrees C. in a range of 1.5 mm.sup.2/s to 2.5
mm.sup.2/s.
10. The lubricating oil composition according to claim 7, further
comprising: (E) a poly-alpha-olefin (E) having a kinematic
viscosity at 100 degrees C. in a range of 1.5 mm.sup.2/s to 2.5
mm.sup.2/s.
11. The lubricating oil composition according to claim 5, wherein
the lubricating oil composition is suitable for a transmission.
Description
TECHNICAL FIELD
[0001] The present invention relates to a lubricating oil
composition.
BACKGROUND ART
[0002] In recent years, due to a global issue of carbon dioxide
emission and worldwide increase of energy demand, saving automobile
fuel has been demanded more and more. Under such circumstances, it
has been demanded that a transmission (i.e., a component of an
automobile) also contributes to fuel-saving more than ever.
[0003] For instance, one of fuel-saving methods of the transmission
is lowering a viscosity of a lubricating oil. However, the
low-viscosity lubricating oil exhibits a low oil-film retention at
high temperatures, thereby occasionally generating seizure,
shortening a fatigue life and the like.
[0004] Patent Literature 1 reports a lubricating oil composition
capable of maintaining a gear shifting performance for a long
period of time, in which various additives are contained for
optimization. However, since the invention disclosed in Patent
Literature 1 is not directed to fuel-saving, a kinematic viscosity
of the lubricating oil composition is high and a fatigue life
thereof when the viscosity is lowered has not been studied.
[0005] Currently, a lubricating oil composition having a viscosity
index of about 150 to 250 is commercially available. However, in
order to further promote fuel-saving, decreasing a viscosity at low
temperatures while maintaining a viscosity at high temperatures, in
short, viscosity-index improvement has been demanded from the
viewpoint of low-temperature startability.
[0006] For instance, a viscosity index of a lubricating oil
composition disclosed in Patent Literature 2 is improved with
polymethacrylate (PMA) as a viscosity index improver. Moreover, in
lubricating oil compositions disclosed in Patent Literatures 3 and
4, a viscosity property is improved with a high-viscosity synthetic
oil (poly-alpha-olefin: PAO) and an olefin copolymer (OCP)
effective for improving a fatigue life is further contained.
CITATION LIST
Patent Literature(s)
[0007] Patent Literature 1: JP-A-2001-262176 [0008] Patent
Literature 2: JP-A-2006-117852 [0009] Patent Literature 3:
JP-A-2008-208220 [0010] Patent Literature 4: JP-A-2008-208221
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0011] Although it is effective that the lubricating oil
composition contains the viscosity index improver in order to
increase the viscosity at high temperatures, it is feared that
abrasion and fatigue are caused by a large decrease in the
viscosity at the time of shearing (i.e., a decrease in shear
stability) and a consequent decrease in oil-film formability.
Moreover, since fatigue-life improvement and viscosity-index
improvement are in inverse proportion to each other, the
lubricating oil composition of Patent Literature 2 has a poor
oil-film retention whereas having an improved viscosity index. In
Patent Literatures 3 and 4, although OCP is blended in the
lubricating oil composition, the lubricating oil composition does
not exhibit the viscosity index that is equal to or exceeds the
viscosity index of PAO. Thus, the viscosity-index improvement has
not been studied. In other words, technique to improve the
viscosity index while having a sufficient fatigue life has been
neither realized nor studied.
[0012] Accordingly, an object of the invention is to provide a
lubricating oil composition that is adapted to maintain a required
shear stability, exhibit an excellent low-temperature viscosity
property and a high fuel-saving performance, and maintain a fatigue
life.
Means for Solving the Problems
[0013] As result of dedicated studies for solving the problem, the
inventor has found that the following combination of a specific
base oil and a specific additive can solve the problem, and has
achieved the invention.
[0014] Specifically, the invention provides a lubricating oil
composition as follows.
(1) A lubricating oil composition according to an aspect of the
invention contains (A) a base oil for a lubricating oil in a range
of 5 mass % to 70 mass % based on a total amount of the
composition, the base oil containing a sulfur content of 0.03 mass
% or less and having a kinematic viscosity at 100 degrees C. in a
range of 0.5 mm.sup.2/s to 1.5 mm.sup.2/s, and (B) a
poly-alpha-olefin in a range of 15 mass % to 30 mass % based on the
total amount of the composition, the poly-alpha-olefin having a
kinematic viscosity at 100 degrees C. of 150 mm.sup.2/s or more.
(2) The lubricating oil composition according to the above aspect
of the invention further contains silicone oil having a kinematic
viscosity at 100 degrees C. in a range of 0.5 mm.sup.2/s to 4
mm.sup.2/s. (3) The lubricating oil composition according to the
above aspect of the invention further contains a polymethacrylate
having a mass average molecular weight (Mw) of 100000 or more. (4)
The lubricating oil composition according to the above aspect of
the invention further contains a poly-alpha-olefin having a
kinematic viscosity at 100 degrees C. in a range of 1.5 mm.sup.2/s
to 2.5 mm.sup.2/s. (5) In the lubricating oil composition according
to the above aspect of the invention, the kinematic viscosity at
100 degrees C. of the component (A) is in a range of 0.7 mm.sup.2/s
to 1.3 mm.sup.2/s, and the kinematic viscosity at 100 degrees C. of
the component (B) is in a range of 150 mm.sup.2/s to 400
mm.sup.2/s, the lubricating oil composition further containing: a
polymethacrylate having a mass average molecular weight of 300000
or more in a range of 0.1 mass % to 5.0 mass % based on the total
amount of the composition; and a poly-alpha-olefin having the
kinematic viscosity at 100 degrees C. in a range of 1.7 mm.sup.2/s
to 2.1 mm.sup.2/s in a range of 0.1 mass % to 60 mass % based on
the total amount of the composition. (6) In the lubricating oil
composition according to the above aspect of the invention, the
lubricating oil composition is used for a transmission.
Advantages of the Invention
[0015] According to the invention, a lubricating oil composition
maintaining shear stability on the conventional level and
exhibiting an excellent low-temperature viscosity property can be
provided. Moreover, when the lubricating oil composition is used as
a lubricating oil for a transmission and the like, fuel-saving
property is high and a fatigue life is maintainable.
DESCRIPTION OF EMBODIMENT(S)
[0016] A lubricating oil composition of the invention contains the
aforementioned components. The invention will be described below in
detail.
Component (A)
[0017] The lubricating oil composition according to the invention
contains a base oil for a lubricating oil in a range of 5 mass % to
70 mass % based on the total amount of the composition as the
component (A), in which the base oil contains a sulfur content of
0.03 mass % or less and has a kinematic viscosity at 100 degrees C.
in a range of 0.5 mm.sup.2/s to 1.5 mm.sup.2/s, preferably of 0.7
mm.sup.2/s to 1.3 mm.sup.2/s.
[0018] When the sulfur content in the component (A) exceeds 0.03
mass %, oxidation stability is deteriorated.
[0019] When the kinematic viscosity at 100 degrees C. is less than
0.5 mm.sup.2/s, vaporizability may be significantly increased to
raise consumption of the lubricating oil. When the kinematic
viscosity at 100 degrees C. exceeds 1.5 mm.sup.2/s, the viscosity
index is decreased.
[0020] The viscosity index of the lubricating oil composition is
decreased when the content of the base oil is less than 5 mass %.
The viscosity thereof is decreased when the content of the base oil
exceeds 70 mass %. Accordingly, such a lubricating oil composition
is not preferable for use in a transmission since abrasion of
mechanical components may be increased.
[0021] Although both a mineral oil and a synthetic oil are usable
as the base oil as the component (A), the mineral oil is preferably
usable because of its lower viscosity.
[0022] The mineral oil is subject to no limitation as long as being
generally usable as the base oil for the lubricating oil for the
transmission. Preferable examples of the mineral oil include
paraffinic and naphthenic base oils which can be obtained by
subjecting a lubricating oil fraction produced by atmospheric- and
vacuum-distillation of a crude oil, to any suitable combination of
refining processes including solvent-deasphalting,
solvent-extracting, hydrocracking, solvent-dewaxing,
catalytic-dewaxing, hydrorefining, sulfuric acid treatment and clay
treatment.
[0023] As the component (A), the mineral oil and synthetic oil
having the kinematic viscosity at 100 degrees C. in the above range
may be used alone or in a mixture of two or more selected from the
mineral oil and synthetic oil at any rate.
Component (B)
[0024] The lubricating oil composition according to the invention
contains a poly-alpha-olefin in a range of 15 mass % to 30 mass %
based on the total amount of the composition as the component (B),
in which the poly-alpha-olefin has a kinematic viscosity at 100
degrees C. of 150 mm.sup.2/s or more, preferably in a range of 150
mm.sup.2/s to 400 mm.sup.2/s.
[0025] When the kinematic viscosity at 100 degrees C. is less than
150 mm.sup.2/s, the viscosity index is decreased. Accordingly, the
lubricating oil composition is not preferable for use in a
transmission since abrasion of mechanical components may be
increased.
[0026] The viscosity index of the finished oil is decreased when
the content of the poly-alpha-olefin is less than 15 mass %.
Accordingly, the finished oil is not preferable for use in a
transmission since abrasion of mechanical components may be
increased. When the content of the poly-alpha-olefin exceeds 30
mass %, the viscosity may be increased to unfavorably increase
friction loss.
[0027] The lubricating oil composition according to the invention
may contain the components (A) and (B), thereby maintaining shear
stability on the conventional level and exhibiting an excellent
low-temperature viscosity property.
Other Components
[0028] In addition to the above components (A) and (B), the
lubricating oil composition according to the invention further
contains the following components, thereby enhancing the
low-temperature viscosity property.
[0029] When silicone oil is blended, it is preferable to use
silicone oil having a kinematic viscosity at 100 degrees C. in a
range of 0.5 mm.sup.2/s to 4 mm.sup.2/s. A flash point of the
lubricating oil composition may be unfavorably significantly
decreased when the kinematic viscosity at 100 degrees C. is less
than 0.5 mm.sup.2/s. The viscosity index may be unfavorably
decreased when the kinematic viscosity at 100 degrees C. exceeds 4
mm.sup.2/s.
[0030] The content of the silicone oil is preferably in a range of
5 mass % to 50 mass % based on the total amount of the composition.
Conventionally, the silicone oil exhibits a poor solubility
although exhibiting a high viscosity index. When the lubricating
oil composition according to the invention contains the components
at the respective contents as described above, the viscosity index
of the lubricating oil composition is improvable without
deteriorating the solubility thereof. However, when the silicone
oil exceeds 50 mass %, the solubility of the lubricating oil
composition is decreased, so that the silicone oil may be separated
or precipitated.
[0031] It is preferable that the lubricating oil composition
according to the invention further contains a polymethacrylate
having a mass average molecular weight of 100000 or more. Although
the polymethacrylate is blended so as to improve the viscosity
index, the polymethacrylate may not provide a sufficient viscosity
index improvability with the mass average molecular weight of less
than 100000. The content of the polymethacrylate is preferably in a
range of 0.1 mass % to 5.0 mass % based on the total amount of the
composition. The polymethacrylate may not provide a sufficient
viscosity index improvability with the content of less than 0.1
mass %. The polymethacrylate may lower the shear stability of the
lubricating oil composition with the content of more than 5.0 mass
%.
[0032] It is preferable that the lubricating oil composition
according to the invention further contains a poly-alpha-olefin
preferably having a kinematic viscosity at 100 degrees C. in a
range of 1.5 mm.sup.2/s to 2.5 mm.sup.2/s, more preferably of 1.7
mm.sup.2/s to 2.1 mm.sup.2/s.
[0033] The vaporizability may be unfavorably increased when the
kinematic viscosity at 100 degrees C. is less than 1.5 mm.sup.2/s.
The viscosity of the lubricating oil composition may be increased
to raise the friction loss when the kinematic viscosity at 100
degrees C. exceeds 2.5 mm.sup.2/s.
[0034] The content of PAO is preferably in a range of 0.1 mass % to
60 mass % based on the total amount of the composition. The
viscosity index of the lubricating oil composition may be lowered
when the content of PAO exceeds 60 mass %.
Other Additives
[0035] The lubricating oil composition according to the invention
may be added as necessary with other additives such as a detergent,
an ashless dispersant, an antiwear agent, a friction modifier, a
rust inhibitor, a metal deactivator, an antifoaming agent, an
antioxidant and a coloring agent, as long as advantages of the
invention are not hampered.
[0036] The detergent is exemplified by a metal detergent such as a
neutral metal sulfonate, a neutral metal phenate, a neutral metal
salicylate, a neutral metal phosphonate, a basic sulfonate, a basic
phenate, a basic salicylate, an overbased sulfonate, an overbased
salicylate and an overbased phosphonate. The content of the
detergent is preferably approximately in a range of 0.01 mass % to
10 mass % based on the total amount of the composition.
[0037] Examples of the ashless dispersant include: succinimides;
boron-containing succinimides; benzil amines; boron-containing
benzil amines; succinates; and monovalent or divalent carboxylic
amides represented by fatty acid or succinic acid. The content of
the ashless dispersant is preferably approximately in a range of
0.1 mass % to 20 mass % based on the total amount of the
composition.
[0038] Examples of the antiwear agent include: a sulfur antiwear
agent such as a salt of thiophosphoric acid and a metal (e.g., Zn,
Pb, Sb) and a salt of thiocarbamic acid and a metal (e.g., Zn); and
a phosphorus antiwear agent such as a phosphate ester (tricresyl
phosphate). The content of the antiwear agent is preferably
approximately in a range of 0.05 mass % to 5 mass % based on the
total amount of the composition.
[0039] The friction modifier is exemplified by a partial ester of
polyhydric alcohol such as neopentyl glycol monolaurate,
trimethylolpropane monolaurate, and glycerin monooleate
(monoglyceride oleate). The content of the friction modifier is
preferably approximately in a range of 0.05 mass % to 4 mass %
based on the total amount of the composition.
[0040] Examples of the rust inhibitor are a fatty acid, an alkenyl
succinic acid half ester, a fatty acid soap, an alkyl sulfonate, a
fatty acid ester of polyhydric alcohol, a fatty acid amide, an
oxidized paraffin, and an alkyl polyoxyethylene ether. The content
of the rust inhibitor is preferably approximately in a range of
0.01 mass % to 3 mass % based on the total amount of the
composition.
[0041] Examples of the metal deactivator include benzotriazole, a
benzotriazole derivative, triazole, a triazole derivative,
imidazole, an imidazole derivative and thiadiazole, which are used
alone or in combination of two or more thereof. The content of the
metal deactivator is preferably approximately in a range of 0.01
mass % to 5 mass % based on the total amount of the
composition.
[0042] Examples of the antifoaming agent include a silicone
compound and an ester compound, which may be used alone or in a
combination of two or more. The content of the antifoaming agent is
preferably approximately in a range of 0.05 mass % to 5 mass %
based on the total amount of the composition.
[0043] Preferable examples of the antioxidant include: a hindered
phenolic antioxidant, an amine antioxidant, and zinc
alkyldithiophosphate (ZnDTP). A bisphenol antioxidant and an ester
group-containing phenol antioxidant are particularly preferable as
the phenolic antioxidant. A dialkyldiphenylamine antioxidant and a
naphthylamine antioxidant are preferable as the amine antioxidant.
The content of the antioxidant is preferably approximately in a
range of 0.05 mass % to 7 mass %.
[0044] The lubricating oil composition containing the above
components according to the invention satisfies the requirements of
the components, the content and the viscosity described above,
whereby the low-temperature viscosity can be significantly
decreased while the high-temperature viscosity and the viscosity
after shearing can be maintained on the conventional level.
Accordingly, when used as a lubricating oil composition for a
transmission, the lubricating oil composition according to the
invention provides advantages of a high fuel-saving performance and
maintainability of a fatigue life, and does not impair machine
durability and reliability.
EXAMPLES
[0045] Next, examples of the invention will be described below in
detail. However, it should be noted that the scope of the invention
is by no means limited by the examples.
Examples 1 to 5 and Comparatives 1 to 5
[0046] Lubricating oil compositions were prepared according to the
blend composition set forth in Table 1. The prepared compositions
were measured in terms of a kinematic viscosity at 100 degrees C.,
a kinematic viscosity at -40 degrees C. and a viscosity after
shearing according to the following method.
[0047] The components described in Table 1 are as follows.
Mineral oil-1: Mineral oil containing a sulfur content of 0.03 mass
% or less and having a kinematic viscosity at 100 degrees C. of 1.0
mm.sup.2/s and a kinematic viscosity at 40 degrees C. of 2.6
mm.sup.2/s Mineral oil-2: Mineral oil containing a sulfur content
of 0.03 mass % or less and having a kinematic viscosity at 100
degrees C. of 6.5 mm.sup.2/s and a kinematic viscosity at 40
degrees C. of 37 mm.sup.2/s PAO-1: PAO having a kinematic viscosity
at 100 degrees C. of 300 mm.sup.2/s PAO-2: PAO having a kinematic
viscosity at 100 degrees C. of 1.8 mm.sup.2/s PAO-3: PAO having a
kinematic viscosity at 100 degrees C. of 100 mm.sup.2/s Ester:
Butoxyethyl oleate ester having a kinematic viscosity at 100
degrees C. of 100 mm.sup.2/s Silicone 1: Polydimethyl siloxane
having a kinematic viscosity at 100 degrees C. of 0.9 mm.sup.2/s
Silicone 2: Polydimethyl siloxane having a kinematic viscosity at
100 degrees C. of 3.4 mm.sup.2/s PMA-1: Polymethacrylate having a
mass average molecular weight of 500000 PMA-2: Polymethacrylate
having a mass average molecular weight of 20000 Other Additives:
Detergent (e.g., Ca sulfonates), Dispersant (e.g., succinimides),
Extreme pressure additive and Antiwear agent (e.g., sulfides,
phosphate compounds, sulfurated phosphate compounds), Antifoaming
agent, Copper deactivator, etc.
Viscosity Index
[0048] Measurement was conducted according to JIS K2283.
Kinematic Viscosity at 100 degrees C. and -40 degrees C.
[0049] Measurement was conducted according to JIS K2283.
Kinematic Viscosity Before and After Shearing
[0050] Kinematic viscosities at 140 degrees C. before and after the
30-hour test were measured according to JASO M-347.
TABLE-US-00001 TABLE 1 Examples Comparatives 1 2 3 4 5 1 2 3 4 5
Blend Mineral oil-1 66.7 26.0 37.7 61.0 8.0 59.7 -- -- -- --
composition Mineral oil-2 -- -- -- -- -- -- -- -- -- 20.0 (mass %)
PAO-1 25.0 19.0 19.0 24.0 19.0 -- 17.0 12.0 12.0 -- PAO-2 -- -- --
-- 58.1 -- 68.2 69.7 64.7 50.5 PAO-3 -- -- -- -- -- 32.0 -- -- --
7.5 Silicone-1 -- 40.0 -- -- -- -- -- -- -- -- Silicone-2 -- --
35.0 -- -- -- -- -- -- -- PMA-1 -- 1.7 -- 1.7 1.6 -- 1.5 5.0 10.0
-- PMA-2 -- -- -- -- -- -- -- -- -- 13.5 Ester -- 5.0 -- 5.0 5.0 --
5.0 5.0 5.0 -- Other additives 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3 8.3
8.5 Total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0
100.0 Evaluation Viscosity index 268 312 306 290 252 217 232 255
305 216 results Kinematic viscosity (100.degree. C.)(mm.sup.2/s)
5.43 6.08 5.37 6.14 6.13 5.27 6.29 6.19 8.99 6.33 (-40.degree.
C.)(mm.sup.2/s) 1300 320 250 1500 1900 2800 2200 1600 2300 5200
Kinematic viscosity before shearing 3.23 3.66 3.28 3.67 3.55 3.02
3.58 3.59 5.28 3.54 (140.degree. C.)(mm.sup.2/s) Kinematic
viscosity after shearing 3.18 3.19 3.17 3.19 3.18 3.01 3.20 2.89
2.99 3.19 (140.degree. C.)(mm.sup.2/s)
Evaluation Results
[0051] Table 1 shows that the kinematic viscosity at -40 degrees C.
was significantly decreased while the kinematic viscosity at 100
degrees C. and the kinematic viscosity after shearing were
sufficiently maintained in Examples of the invention.
[0052] It is understood from Examples 2 and 3 that blending
silicone significantly decreases the kinematic viscosity at -40
degrees C.
[0053] With respect to selection from the mineral oils and PAO of
different viscosities, the content of each of the mineral oils and
PAO and the content of PMA, it is understood from Examples 4 and 5
and Comparatives 2 to 5 that the advantages of the invention (i.e.,
to maintain the high-temperature kinematic viscosity and the
kinematic viscosity after shearing and to significantly decrease
the low-temperature kinematic viscosity) are attained when the
components and the respective contents of the invention are
satisfied. In Comparatives 3 and 4, blending the polymethacrylate
improves the viscosity index, but decreases the viscosity after
shearing. Accordingly, it is feared that abrasion resistance and
anti-fatigue life may be decreased.
INDUSTRIAL APPLICABILITY
[0054] The invention is usable as a lubricating oil composition,
particularly suitably usable as a lubricating oil for a
transmission.
* * * * *