U.S. patent application number 13/578269 was filed with the patent office on 2012-12-06 for vibration-insulating rubber composition.
This patent application is currently assigned to Yamashita Rubber Co., Ltd.. Invention is credited to Jun Aizawa, Yu Annaka, Keiichi Arakawa, Yoshiaki Gomi.
Application Number | 20120305828 13/578269 |
Document ID | / |
Family ID | 44367671 |
Filed Date | 2012-12-06 |
United States Patent
Application |
20120305828 |
Kind Code |
A1 |
Gomi; Yoshiaki ; et
al. |
December 6, 2012 |
VIBRATION-INSULATING RUBBER COMPOSITION
Abstract
A vibration-insulating rubber composition includes: a rubber
component (A) that is composed of an isoprene-based rubber; a
rubber component (B) that is composed of a butadiene-based rubber;
carbon black that is present mainly in the rubber component (B);
and silica that is present mainly in the rubber component (A). The
rubber composition exhibits improved durability without suffering
from deterioration of vibration-insulation characteristics.
Inventors: |
Gomi; Yoshiaki;
(Fujimino-city, JP) ; Aizawa; Jun; (Fujimino-city,
JP) ; Arakawa; Keiichi; (Fujimino-city, JP) ;
Annaka; Yu; (Fujimino-city, JP) |
Assignee: |
Yamashita Rubber Co., Ltd.
Fujimino-city
JP
|
Family ID: |
44367671 |
Appl. No.: |
13/578269 |
Filed: |
January 31, 2011 |
PCT Filed: |
January 31, 2011 |
PCT NO: |
PCT/JP11/51888 |
371 Date: |
August 10, 2012 |
Current U.S.
Class: |
252/62 |
Current CPC
Class: |
C08L 7/00 20130101; C08K
3/36 20130101; C08K 5/548 20130101; C08L 9/00 20130101; C08L 7/00
20130101; C08L 9/00 20130101; C08L 9/00 20130101; C08L 7/00
20130101; C08K 3/04 20130101 |
Class at
Publication: |
252/62 |
International
Class: |
E04B 1/84 20060101
E04B001/84 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 12, 2010 |
JP |
2010-029263 |
Feb 12, 2010 |
JP |
2010-029267 |
Claims
1. A vibration-insulating rubber composition comprising: a rubber
component (A) comprising an isoprene-based rubber; a rubber
component (B) comprising a butadiene-based rubber; a carbon black
that is present mainly in the rubber component (B); and a silica
that is present mainly in the rubber component (A).
2. The vibration-insulating rubber composition of claim 1, wherein
at least 70 wt % of a total amount of the carbon black is present
in the rubber component (B), and at least 70 wt % of a total amount
of the silica is present in the rubber component (A).
3. The vibration-insulating rubber composition of claim 1, wherein
the silica is modified by a silane coupling agent.
4. The vibration-insulating rubber composition of claim 3, wherein
the silane coupling agent is a polysulfide-based silane coupling
agent.
5. The vibration-insulating rubber composition of claim 1,
comprising the rubber component (A) and the rubber component (B) in
a weight ratio (A)/(B) in a range of 90/10 to 30/70.
6. A vibration-insulating rubber composition comprising: a total
amount of an isoprene-based rubber and a butadiene-based rubber
that equals 100 parts by weight; 5 to 60 parts by weight of a
carbon black; and 5 to 60 parts by weight of a silica, wherein at
least 70% of a total amount of the carbon black is unevenly
distributed in the butadiene-based rubber, and at least 70% of a
total amount of the silica is unevenly distributed in the
isoprene-based rubber.
7. A vibration-insulating rubber composition comprising: a rubber
component comprising an isoprene-based rubber and a butadiene-based
rubber; and a reinforcing agent component comprising a carbon black
and a silica, the rubber component and the reinforcing agent
component being compounded, wherein the silica in the reinforcing
agent component comprises: a silica (A) comprising silica particles
whose surface has been surface-treated by a polysulfide-based
silane coupling agent; and a silica (B) comprising silica particles
whose surface has been surface-treated by a silane-based surface
treatment agent.
8. The vibration-insulating rubber composition of claim 7, wherein
the silane-based surface treatment agent is an alkylsilane.
9. The vibration-insulating rubber composition of claim 7,
comprising the silica (A) and the silica (B) in a weight ratio
(A)/(B) of (90/10) to (40/60).
10. The vibration-insulating rubber composition of claim 7, wherein
the silica (B) is a hydrophobically modified silica obtained by
processing a surface of silica with an alkylsilane.
11. The vibration-insulating rubber composition of claim 7, wherein
the rubber component comprises the isoprene-based rubber and the
butadiene-based rubber in a ratio in a range of 90/10 to 30/70.
12. A vibration-insulating rubber composition comprising: a total
amount of an isoprene-based rubber and a butadiene-based rubber
that equals 100 parts by weight; 5 to 60 parts by weight of a
carbon black; and 5 to 60 parts by weight of a silica, wherein the
silica comprises: 40 to 90 wt % of a silica (A) that has been
surface-treated by a polysulfide-based silane coupling agent, and
10 to 60 wt % of a silica (B) that has been surface-treated by an
alkylsilane.
13. The vibration-insulating rubber composition of claim 1, wherein
the isoprene-based rubber comprises natural rubber, a polyisoprene
rubber, or both.
14. The vibration-insulating rubber composition of claim 1, wherein
the isoprene-based rubber comprises natural rubber having a Mooney
viscosity of 10 to 200.
15. The vibration-insulating rubber composition of claim 1, wherein
the isoprene-based rubber comprises natural rubber having a Mooney
viscosity of 30 to 100.
16. The vibration-insulating rubber composition of claim 1, wherein
the butadiene-based rubber comprises at least one polybutadiene
rubber selected from the group consisting of: a high
cis-polybutadiene rubber having cis-1,4 coupling of about 90% or
more, and a high vinyl-polybutadiene rubber having 1,2-coupling of
about 10% or more.
17. The vibration-insulating rubber composition of claim 16,
wherein the polybutadiene rubber has a Mooney viscosity of 10 to
100.
18. The vibration-insulating rubber composition of claim 16,
wherein the polybutadiene rubber has a Mooney viscosity of 30 to
70.
19. The vibration-insulating rubber composition of claim 1,
comprising the rubber component (A) and the rubber component (B) in
a weight ratio (A)/(B) in a range of 80/20 to 40/60.
20. The vibration-insulating rubber composition of claim 1,
comprising the rubber component (A) and the rubber component (B) in
a weight ratio (A)/(B) in a range of 80/20 to 50/50.
Description
TECHNICAL FIELD
[0001] The present invention relates to a vibration-insulating
rubber composition.
BACKGROUND ART
[0002] Conventionally, a vibration-insulating rubber used in an
engine mount or the like of an automobile is required to have
vibration-insulating performance for reducing vibration and noise
of an engine, heat resistance, fatigue resistance and the like. In
addition, in point of the vibration-insulating performance, the
smaller a spring constant in a vibrational state (dynamic spring
constant), the better; on the other hand, the larger a static
spring constant that indicates supporting stiffness, the better;
moreover, it can be said that the vibration-insulating rubber
having a smaller dynamic multiplication (dynamic spring
constant/static spring constant), which is a ratio between the
dynamic spring constant and the static spring constant, provides
more excellent vibration-insulating performance.
[0003] As a specific example of such a vibration-insulating rubber,
for example, in Patent Document 1, there is described a rubber
composition for engine mounts that contains a rubber component
consisting mainly of at least one diene rubber and silica fine
particles having a BET specific surface area of 40-170
m.sup.2/g.
[0004] In Patent Document 2, a vulcanized body of
vibration-insulating rubber composition is disclosed, in which
natural silica treated by a silane coupling agent is combined with
rubber compositions such as natural rubber, butadiene rubber and
styrene butadiene rubber, and a mixture of quartz powder having
globular structure of fine particles and kaolinite having hexagonal
plate-shaped grain structure is used for natural silica.
[0005] In Patent Document 3, there is described a
vibration-insulating rubber composition containing a rubber
component (A), hydrophobically treated silica (B) and a
silane-coupling agent (C), in which, as the hydrophobically treated
silica (B), it is preferable to blend silicone oil of 0.1 pts.wt.
to 50 pts.wt. having dynamic viscosity in a range of 10.sup.-6
m.sup.2/s to 1 m.sup.2/s with wet method silica of 100 pts.wt.
having nitrogen-absorbing specific surface area (BET method) in a
range of 30 m.sup.2/g to 230 m.sup.2/g for surface treatment.
CITATION LIST
Patent Literature
[0006] Patent Document 1: Japanese Patent Application Laid-Open
Publication No. 11-193338
[0007] Patent Document 2: Japanese Patent Application Laid-Open
Publication No. 2002-098192
[0008] Patent Document 3: Japanese Patent Application Laid-Open
Publication No. 2006-037002
SUMMARY OF INVENTION
Technical Problem
[0009] Incidentally, to achieve vibration-insulating
characteristics (low dynamic multiplication) of a
vibration-insulating rubber, there is a tendency to use a filler of
a large diameter. However, the large-diameter filler has low
reinforcing property, and has a problem of deterioration of
durability in a long-term use. On the other hand, if a filler of a
small diameter having high reinforcing property is used to increase
the durability, there is a tendency to reduce the
vibration-insulating characteristics. As things stand, in this way,
the vibration-insulating characteristics and the durability of the
vibration-insulating rubber are in a trade-off relationship, and it
is difficult to achieve both.
[0010] Moreover, for increasing product life of the
vibration-insulating rubber, it is necessary to improve the
durability or heat resistance. Especially, the heat resistance is
important. Usually, for improving the durability of the
vibration-insulating rubber, it is desirable to have a lower stress
when the same displacement is applied. However, on the occasion of
vulcanizing, if an amount of use of a vulcanizing agent is reduced
to decrease the vulcanizing density, there is a tendency to
deteriorate the dynamic multiplication. On the other hand, if a
combined amount of a reinforcing agent is reduced, the static
spring constant becomes small; and accordingly, for example,
displacement in supporting an automobile engine or the like is
increased to thereby deteriorate the durability. In particular, in
a case where the heat resistance is insufficient, there is a
problem of impossibility of maintaining the vibration-insulating
characteristics together with the durability.
[0011] An object of the present invention is to improve durability
of a vibration-insulating rubber while maintaining
vibration-insulating characteristics.
[0012] An object of the present invention is to improve heat
resistance of a vibration-insulating rubber while maintaining
vibration-insulating characteristics.
Solution to Problem
[0013] By the present invention, a vibration-insulating rubber
composition according to any of the following first to twelfth
aspects is provided.
[0014] According to a first aspect of the present invention, there
is provided a vibration-insulating rubber composition including: a
rubber component (A) composed of an isoprene-based rubber; a rubber
component (B) composed of a butadiene-based rubber; a carbon black
that is present mainly in the rubber component (B); and a silica
that is present mainly in the rubber component (A).
[0015] According to a second aspect of the present invention, in
the vibration-insulating rubber composition of the first aspect, at
least 70 wt % of a total amount of the carbon black is present in
the rubber component (B), and at least 70 wt % of a total amount of
the silica is present in the rubber component (A).
[0016] According to a third aspect of the present invention, in the
vibration-insulating rubber composition of any one of the first and
second aspects, the silica is modified by a silane coupling
agent.
[0017] According to a fourth aspect of the present invention, in
the vibration-insulating rubber composition of the third aspect,
the silane coupling agent is a polysulfide-based silane coupling
agent.
[0018] According to a fifth aspect of the present invention, in the
vibration-insulating rubber composition of any one of the first to
fourth aspects, an amount ratio between the rubber component (A)
and the rubber component (B) (rubber component (A)/rubber component
(B)) is 90/10 to 30/70 (however, a total of the rubber component
(A) plus the rubber component (B) equals 100 wt %).
[0019] According to a sixth aspect of the present invention, there
is provided a vibration-insulating rubber composition including: a
total amount of an isoprene-based rubber and a butadiene-based
rubber that equals 100 pts.wt.; a carbon black of 5 pts.wt. to 60
pts.wt.; and a silica of 5 pts.wt. to 60 pts.wt., wherein at least
70% of a total amount of the carbon black is unevenly distributed
in the butadiene-based rubber, and at least 70% of a total amount
of the silica is unevenly distributed in the isoprene-based
rubber.
[0020] According to a seventh aspect of the present invention,
there is provided a vibration-insulating rubber composition
including: a rubber component including an isoprene-based rubber
and a butadiene-based rubber; and a reinforcing agent component
including a carbon black and a silica, the rubber component and the
reinforcing agent component being compounded, wherein the silica in
the reinforcing agent component includes: a silica (A) in which a
surface of a silica particle is surface-treated by a
polysulfide-based silane coupling agent; and a silica (B) in which
a surface of a silica particle is surface-treated by a silane-based
surface treatment agent.
[0021] According to an eighth aspect of the present invention, in
the vibration-insulating rubber composition of the seventh aspect,
the silane-based surface treatment agent in the silica (B) is
silane containing a hydrocarbon radical.
[0022] According to a ninth aspect of the present invention, in the
vibration-insulating rubber composition of any one of the seventh
and eighth aspects, an amount ratio between the silica (A) and the
silica (B) in the silica (silica (A)/silica (B)) is (90/10) to
(40/60) (however, a total of the silica (A) plus the silica (B)
equals 100 wt %).
[0023] According to a tenth aspect of the present invention, in the
vibration-insulating rubber composition of any one of the seventh
to ninth aspects, the silica (B) in the silica is a hydrophobically
modified silica obtained by processing a surface of silica by
alkylsilane.
[0024] According to an eleventh aspect of the present invention, in
the vibration-insulating rubber composition of any one of the
seventh to tenth aspects, an amount ratio between the
isoprene-based rubber and the butadiene-based rubber in the rubber
component (isoprene-based rubber/butadiene-based rubber) is (90/10)
to (30/70) (however, a total of the isoprene-based rubber plus the
butadiene-based rubber equals 100 wt %).
[0025] According to a twelfth aspect of the present invention,
there is provided a vibration-insulating rubber composition
including: a total amount of an isoprene-based rubber and a
butadiene-based rubber that equals 100 pts.wt.; a carbon black of 5
pts.wt. to 60 pts.wt.; and a silica of 5 pts.wt. to 60 pts.wt.,
wherein, against a total amount of the silica, a silica (A) that is
surface-treated by a polysulfide-based silane coupling agent
represents 40 wt % to 90 wt %, and a silica (B) that is
surface-treated by silane containing a hydrocarbon radical
represents 10 wt % to 60 wt % (however, a total of the silica (A)
plus the silica (B) equals 100 wt %).
Advantageous Effects of Invention
[0026] According to the present invention, it is possible to
improve durability of a vibration-insulating rubber while
maintaining vibration-insulating characteristics.
[0027] Moreover, according to the present invention, it is possible
to improve heat resistance of a vibration-insulating rubber while
maintaining vibration-insulating characteristics.
BRIEF DESCRIPTION OF DRAWINGS
[0028] FIG. 1 is a diagram for illustrating a specimen used in a
durability test; and
[0029] FIG. 2 is a photograph of a transmission electron microscope
(TEM) of a rubber composition in Example 2.
DESCRIPTION OF EMBODIMENTS
[0030] Hereinafter, modes for embodying the present invention will
be described (hereinafter, exemplary embodiments). It should be
noted that the present invention is not limited to the following
exemplary embodiments, but may be practiced as various
modifications within the scope of the gist of the invention.
<Vibration-Insulating Rubber Composition (1)>
[0031] In the present invention, a vibration-insulating rubber
composition to which a first exemplary embodiment is applied
(hereinafter, referred to as "vibration-insulating rubber
composition (1)") includes a rubber component (A) composed of an
isoprene-based rubber, a rubber component (B) composed of a
butadiene-based rubber, carbon black that is present mainly in the
rubber component (B) and a silica that is present mainly in the
rubber component (A). Hereinbelow, each component will be
described.
<Isoprene-Based Rubber (Rubber Component (A))>
[0032] As an isoprene-based rubber used in the exemplary
embodiment, a natural rubber and a polyisoprene rubber
(hereinafter, referred to as IR in some cases) are provided. As the
polyisoprene rubber, a high cis-polyisoprene rubber having cis-1,4
coupling of about 96% or more and a low cis-polyisoprene rubber
having cis-1,4 coupling of the order of 94% are provided. A Mooney
viscosity (ML.sub.1+4, 100.degree. C.) of the polyisoprene rubber
is normally 50 to 200, and preferably 60 to 150. In addition, these
diene-based rubbers can be used irrespective of the Mooney
viscosity before oil extension as long as the Mooney viscosity
after oil extension is within the above-described range.
[0033] A Mooney viscosity (ML.sub.1+4, 100.degree. C.) of a natural
rubber is normally 10 to 200, and preferably 30 to 100.
<Butadiene-Based Rubber (Rubber Component (B))>
[0034] As a butadiene-based rubber (hereinafter, referred to as BR
in some cases) used in the exemplary embodiment, for example, a
high cis-polybutadiene rubber having cis-1,4 coupling of about 90%
or more and a high vinyl-polybutadiene rubber having 1,2-coupling
of about 10% or more are provided. Among them, the high
vinyl-polybutadiene rubber is preferable because carbon black is
selectively dispersed with ease. A Mooney viscosity (ML.sub.1+4,
100.degree. C.) of the polybutadiene rubber is normally 10 to 100,
and preferably 30 to 70.
[0035] An amount ratio between the rubber component (A) and the
rubber component (B) (rubber component (A)/rubber component (B))
included in the vibration-insulating rubber composition (1) to
which the exemplary embodiment is applied is 90/10 to 30/70,
preferably 80/20 to 40/60, and more preferably 80/20 to 50/50
(however, a total of the rubber component (A)+the rubber component
(B) is equal to 100 wt %). If the amount of the rubber component
(A) included in the vibration-insulating rubber composition (1) is
excessively large, there is a tendency to increase the dynamic
multiplication. On the other hand, if the amount of the rubber
component (A) is excessively small, there is a tendency to
deteriorate the durability.
<Carbon Black>
[0036] The carbon black used in the exemplary embodiment is not
particularly limited as long as it is known as a normal reinforcing
agent for rubbers. For example, furnace black, channel black,
thermal black and so forth are provided.
<Silica>
[0037] The silica used in the exemplary embodiment is not
particularly limited as long as it is known as a normal reinforcing
agent for rubbers (white carbon). For example, silicic acid
anhydride obtained by a dry method, silicic acid hydrate obtained
by a wet method, and further, synthetic silicate are provided.
[0038] A BET specific surface area of a silica particle used in the
exemplary embodiment is 20 m.sup.2/g to 200 m.sup.2/g and
preferably 50 m.sup.2/g to 150 m.sup.2/g. It should be noted that
the BET specific surface area is measured based on JIS-K-6217-1997
"Testing methods of fundamental characteristics of carbon black for
rubber industry". If the BET specific surface area of the silica
particle is excessively small, there is a tendency to deteriorate
the reinforcing property. On the other hand, if the BET specific
surface area of the silica particle is excessively large, there is
a tendency to increase the dynamic multiplication.
(Surface-Treated Silica)
[0039] The surface of the particle of silica used in the exemplary
embodiment is preferably subjected to surface treatment with a
silane coupling agent. The surface treatment method of the surface
of the silica particle is not particularly limited; for example, a
method in which the silica particles and the silane coupling agents
are brought into contact in advance, a method in which the silica
particles and the silane coupling agents are kneaded together with
the rubber components (A), (B) and other compounding agents, and
the like are provided.
[0040] As the silane coupling agents used for the surface treatment
of silica, compounds including portions of functional groups for
surface modification of silica particles, alkoxide groups that
react with hydroxyl groups of the surface of the silica particles,
amino groups and the like are provided. As a silane coupling agent
including alkyl groups, specific examples include:
methyltrimethoxysilane, ethyltrimethoxysilane,
propyltrimethoxysilane, phenyltrimethoxysilane,
octyltrimethoxysilane, octadecyltrimethoxysilane,
methyltriethoxysilane, ethyltriethoxysilane, propyltriethoxysilane,
octyltriethoxysilane and octadecyltriethoxysilane.
[0041] Specific examples having other functional groups include:
3-mercaptopropyltrimethoxysilane,
(mercaptomethyl)methyldiethoxysilane,
(mercaptomethyl)dimethylethoxysilane, vinyltrimethoxysilane,
3-glycidoxypropyltrimethoxysilane,
methacryloxypropyltrimethoxysilane, vinyltriethoxysilane,
bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane,
bis[3-(triethoxysilyl)propyl]tetrasulfide,
3-isocyanatopropyltriethoxysilane,
N-[(3-trimethoxysilyl)propyl]ethylenediamine sodium triacetate,
N-(triethoxysilylpropyl)urea, 3-chloropropyltriethoxysilane,
diethylphosphate ethyltriethoxysilane,
trimethoxysilylpropylisothiouronium chloride,
methyl[2-(3-trimethoxysilylpropylamino)ethylamine]-3-propionate and
3-aminopropyltriethoxysilane.
[0042] Of the above-described silane coupling agents, in the case
of adding a hydrophobic nature to the particles, the silane
coupling agents having a molecular structure including sulfur atoms
or nitrogen atoms are preferred because of their high treatment
effect and the like. As such silane coupling agents, for example,
silane coupling agents including nitrogen atoms such as
N-(.beta.-aminoethyl)-.gamma.-aminopropyltrimethoxysilane,
N-(.beta.-aminoethyl)-.gamma.-aminopropylmethyldimethoxysilane,
N-phenyl-.gamma.-aminopropyltrimethoxysilane,
.gamma.-mercaptopropyltrimethoxysilane and
.gamma.-aminopropyltriethoxysilane, and polysulfide-based silane
coupling agents such as bis(3-triethoxysilypropyl)disulfide,
bis[3-(triethoxysilyl)propyl]tetrasulfide and
.gamma.-trimethoxysilylpropylbenzothiazyl tetrasulfide are
provided. Of these, the polysulfide-based silane coupling agents
such as .gamma.-mercaptopropyltrimethoxysilane and
bis[3-(triethoxysilyl)propyl]tetrasulfide can be preferably
used.
[0043] Moreover, in general, as long as affinity for silica
particles is shown after hydrolyzing, other metal alkoxide-based
coupling agents or mixture of these with silane coupling agents can
be used. For example, titanate coupling agents such as
isopropyltriisostearoyl titanate and isopropyltrioctanoyl titanate,
zirconate coupling agents such as zirconium lactate and
acetylacetone zirconium butyrate, and zircoalminate-based coupling
agents and so on can be provided.
(Uneven Distribution Rate of Carbon Black and Silica)
[0044] In the vibration-insulating rubber composition (1) to which
the exemplary embodiment is applied, at least 70 wt % of a total
amount of carbon black is present in the rubber component (B)
(butadiene-based rubber). Further, on the other hand, at least 70
wt % of a total amount of silica included in the compound is
present in the rubber component (A) (isoprene-based rubber). In the
exemplary embodiment, since carbon black and silica are thus
unevenly distributed in the butadiene-based rubber and the
isoprene-based rubber selectively, respectively, both rubber
components (A) and (B) have reinforced structures, and thereby
durability thereof is improved.
[0045] Though the reason why carbon black and silica are unevenly
distributed in the rubber component (B) and the rubber component
(A) selectively, respectively, in the vibration-insulating rubber
composition (1) to which the exemplary embodiment is applied, is
not clear; however, it can be assumed as follows. That is, it is
considered that affinity for or interaction with the rubber
component (B) (butadiene-based rubber) of the carbon black is large
compared to affinity for or interaction with the rubber component
(A) (isoprene-based rubber). On the other hand, for example, it is
considered that affinity for or interaction with the rubber
component (A) (isoprene-based rubber) of the silane coupling agent
including sulfur atoms such as polysulfide-based silane coupling
agent is large compared to affinity for or interaction with the
rubber component (B) (butadiene-based rubber). Accordingly, it is
considered that, within a range of the ratio between the rubber
components and the combined amount of the reinforcing agent in the
vibration-insulating rubber composition (1) to which the exemplary
embodiment is applied, carbon black and silica are unevenly
distributed in the rubber component (B) and the rubber component
(A) selectively, respectively.
[0046] Here, the rate at which the carbon black and the silica are
unevenly distributed in the butadiene-based rubber and the
isoprene-based rubber selectively, respectively (hereinafter,
referred to as "uneven distribution rate" in some cases), is
obtained by the following operations.
[0047] A rubber composition including the rubber component (A), the
rubber component (B), the carbon black and the silica is prepared,
and is cut with a microtome to prepare slices with a thickness of
0.1 .mu.m. The slice is observed as a specimen by a transmission
electron microscope (TEM) while regarding particles having a
particle diameter of about 0.8 .mu.m to about 1.2 .mu.m as carbon
black and particles having a particle diameter of about 10 nm to
about 40 nm as silica. On that occasion, in an electronic image of
the rubber composition, the number of particles of carbon black and
silica present in each of the phase of the rubber component (A)
(isoprene-based rubber) and the phase of the rubber component (B)
(butadiene-based rubber) is measured. Then, in each of the phase of
the rubber component (A) (isoprene-based rubber) and the phase of
the rubber component (B) (butadiene-based rubber), the ratio
between the number of particles of carbon black and the number of
particles of silica is obtained, and thereby the uneven
distribution rate of carbon black and silica in each phase was
obtained. It should be noted that, in the exemplary embodiment, the
number of samples is 30 (n=30).
[0048] If an amount of silica unevenly distributed in the rubber
component (A) (isoprene-based rubber) is excessively small against
the total amount of silica included in the composition, there is a
tendency to deteriorate the durability because the rubber component
(A) is not sufficiently reinforced. On the other hand, if an amount
of silica unevenly distributed in the rubber component (A)
(isoprene-based rubber) is excessively large, there is a tendency
to deteriorate dynamic characteristics and the durability because
dispersing property becomes poor.
[0049] If an amount of carbon black unevenly distributed in the
rubber component (B) (butadiene-based rubber) is excessively small
against the total amount of carbon black included in the
composition, there is a tendency to deteriorate the durability
because the rubber component (B) is not sufficiently reinforced. On
the other hand, if an amount of carbon black unevenly distributed
in the rubber component (B) (butadiene-based rubber) is excessively
large, there is a tendency to deteriorate dynamic characteristics
and the durability because dispersing property becomes poor.
<Vibration-insulating Rubber Composition (2)>
[0050] In the present invention, in a vibration-insulating rubber
composition to which a second exemplary embodiment is applied
(hereinafter, referred to as "vibration-insulating rubber
composition (2)"), a rubber component including an isoprene-based
rubber and a butadiene-based rubber and a reinforcing agent
component including carbon black and silica are compounded, in
which silica in the reinforcing agent component includes silica (A)
that is surface-treated by a polysulfide-based silane coupling
agent and silica (B) that is surface-treated by a silane-based
surface treatment agent. Hereinbelow, each component will be
described.
[0051] An amount ratio between the isoprene-based rubber and the
butadiene-based rubber (isoprene-based rubber/butadiene-based
rubber) included in the vibration-insulating rubber composition (2)
to which the exemplary embodiment is applied is (90/10) to (30/70),
preferably (80/20) to (40/60), and more preferably (80/20) to
(50/50) (however, a total of the isoprene-based rubber+the
butadiene-based rubber is equal to 100 wt %). If the amount of the
rubber component (A) included in the vibration-insulating rubber
composition (2) is excessively large, there is a tendency to
increase the dynamic multiplication. On the other hand, if the
amount of the rubber component (A) is excessively small, there is a
tendency to deteriorate the durability.
<Reinforcing Agent Component>
(Carbon Black)
[0052] An amount of usage of carbon black included in the
vibration-insulating rubber composition (2) is not particularly
limited. In the exemplary embodiment, against a total amount of the
isoprene-based rubber and the butadiene-based rubber included in
the rubber component that equals 100 pts.wt., carbon black is used
in a range of 5 pts.wt. to 60 pts.wt., preferably in a range of 7
pts.wt. to 50 pts.wt., and more preferably in a range of 7 pts.wt.
to 40 pts.wt.
(Silica)
[0053] Silica included in the reinforcing agent component used in
the vibration-insulating rubber composition (2) includes silica (A)
which is silica particles known as a usual reinforcing agent for
rubbers (white carbon) surface-treated by the polysulfide-based
silane coupling agent and silica (B) which is silica particles
known as a usual reinforcing agent for rubbers (white carbon)
surface-treated by the silane-based surface treatment agent.
(Silica A)
[0054] Silica A included in silica used in the exemplary embodiment
is silica particles surface-treated by the polysulfide-based silane
coupling agent. The surface treatment method of the surface of the
silica particle is not particularly limited; for example, a method
in which the silica particles and the silane coupling agents are
brought into contact in advance, a method in which the silica
particles and the silane coupling agents are kneaded together with
the rubber component, carbon black and other compounding agents are
provided.
[0055] As the polysulfide-based silane coupling agents used for
surface treatment of silica, for example,
3-mercaptopropyltrimethoxysilane,
(mercaptomethyl)methyldiethoxysilane,
(mercaptomethyl)dimethylethoxysilane,
bis[3-(triethoxysilyl)propyl]tetrasulfide,
bis[3-(triethoxysilyl)propyl]disulfide and
.gamma.-trimethoxysilylpropylbenzothiazyl tetrasulfide are
provided. Of these, bis[3-(triethoxysilyl)propyl]tetrasulfide and
bis[3-(triethoxysilyl)propyl]disulfide are preferred. The surface
of the particle of silica that is surface-treated by the silane
coupling agent having molecular structure including sulfur atoms is
provided with a hydrophobic nature.
[0056] The silica particles (silica A) surface-treated by use of
such polysulfide-based silane coupling agents are commercially
available. For example, CABRUS 2A, CABRUS 2B and CABRUS 4
manufactured by DAISO Co., Ltd., Si-75 and Si-69 manufactured by
Degussa, A-1289 manufactured by GE silicone, KBE-846 manufactured
by Shin-Etsu Chemical Co., Ltd. and the like are provided. These
can be used individually or in combination.
(Silica B)
[0057] Silica B included in silica used in the exemplary embodiment
is silica particles surface-treated by the silane-based surface
treatment agent. Silica B is not particularly limited as silica
subjected to surface treatment. In the exemplary embodiment,
silicic acid anhydride obtained by a dry method (dry process
silica) is preferred. Here, dry process silica is silicon dioxide
generated by forming surface-modified silicon compound such as
silicon dimethyl chloride and silicon tetrachloride under the
condition of vapor phase hydrolysis at high temperature. By surface
treatment of the surface of the particle of dry process silica by
use of the silane-based surface treatment agent, hydrophobically
modified silica, in which a hydrophobic nature is provided to the
surface of the silica particle, is obtained.
[0058] As the silane-based surface treatment agent, organic silane,
alkylsilane (silane containing a hydrocarbon radical), disilazan,
alkylchlorosilane and the like are provided. Of these, alkylsilane
(silane containing a hydrocarbon radical) is preferred.
[0059] Specifically, as organic silane and alkylsilane,
methyltrimethoxysilane, methyltriethoxysilane,
ethyltrimethoxysilane, ethyltriethoxysilane,
n-propyltrimethoxysilane, n-propyltriethoxysilane,
i-propyltrimethoxysilane, i-propyltriethoxysilane,
butyltrimethoxysilane, butyltriethoxysilane, hexyltrimethoxysilane,
octyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane,
n-octyltriethoxysilane, phenyltriethoxysilane, polytriethoxysilane;
trialkoxyarylsilane; isooctyltrimethoxy-silane,
N-(3-triethoxysilylpropyl)methoxyethoxyethoxyethyl carbamate,
polydialkylsiloxane containing polydimethylsiloxane, arylsilane
containing substituted arylsilane and non-substituted arylsilane,
alkylsilane containing methoxy substituted alkylsilane and hydroxyl
substituted alkylsilane and the like are provided.
[0060] As alkylchlorosilane, for example, methyltrichlorosilane,
dimethyldichlorosilane, trimethylchlorosilane,
octylmethyldichlorosilane, octyltrichlorosilane,
octadecylmethyldichlorosilane, octadecyltrichlorosilane and the
like are provided. Moreover, as other compounds, vinylsilane such
as vinyltrichlorosilane, vinylmethyldichlorosilane,
vinyldimethylchlorosilane, vinyltrimethoxysilane,
vinylmethyldimethoxysilane, vinyldimethylmethoxysilane,
vinyltriethoxysilane, vinylmethyldiethoxysilane and
vinyldimethylethoxysilane can be provided.
[0061] As specific trade names, the products by Degussa, such as
Aerosil DT4, Aerosil NA200Y, Aerosil NA5OH, Aerosil NA50Y, Aerosil
NAX50, Aerosil R104, Aerosil R106, Aerosil R202, Aerosil R202W90,
Aerosil R504, Aerosil R711, Aerosil R700, Aerosil R7200, Aerosil
R805, Aerosil R805VV90, Aerosil R812, Aerosil R812S, Aerosil R816,
Aerosil R8200, Aerosil R972, Aerosil R972V, Aerosil R974, Aerosil
RA200HS, Aerosil RX200, Aerosil RX300, Aerosil RX50, Aerosil RY200,
Aerosil RY200S, Aerosil RY300 and Aerosil RY50, and the like are
shown as examples.
[0062] In the exemplary embodiment, an amount ratio between silica
(A) and silica (B) (silica (A)/silica (B)) included in silica as
the reinforcing agent component is in a range of (90/10) to
(40/60), and preferably in a range of (80/20) to (50/50) (however,
a total of silica (A)+silica (B) is equal to 100 wt %).
[0063] If an amount of silica (A) in silica as the reinforcing
agent component is excessively large (an amount of silica (B) is
excessively small), there is a tendency to deteriorate heat
resistance by the polysulfide-based silane coupling agent. On the
other hand, if an amount of silica (A) is excessively small (an
amount of silica (B) is excessively large), there is a tendency to
reduce silica that is chemically combined with rubber, and thereby
to deteriorate dynamic characteristics.
[0064] An amount of usage of silica included in the
vibration-insulating rubber composition (2) is not particularly
limited. In the exemplary embodiment, against a total amount of the
isoprene-based rubber and the butadiene-based rubber included in
the rubber component that equals to 100 pts.wt., silica is used in
a range of 5 pts.wt. to 60 pts.wt., preferably in a range of 7
pts.wt. to 50 pts.wt., and more preferably in a range of 7 pts.wt.
to 40 pts.wt.
(Other Rubber Components)
[0065] As necessary, it is possible to mix other rubbers into the
vibration-insulating rubber composition (1) or (2) to which the
exemplary embodiment is applied. As such rubbers, for example,
emulsion polymerized styrene butadiene rubber (SBR), solution
polymerized SBR, acrylonitrile-butadiene copolymer rubber (NBR),
hydrogenated acrylonitrile-butadiene copolymer rubber (HNBR),
ethylene-.alpha.-olefin-based copolymer rubber (EPR, EPDM) and the
like are provided.
(Other Reinforcing Agents)
[0066] As necessary, it is possible to mix other reinforcing agents
into the vibration-insulating rubber composition (1) or (2) to
which the exemplary embodiment is applied. As such reinforcing
agents, for example, insulating metallic oxides such as tin oxide,
zinc oxide, aluminum oxide, molybdenum oxide, magnesium oxide,
calcium oxide and lead oxide; metallic hydroxides such as magnesium
hydroxide, aluminum hydroxide, calcium hydroxide, zinc hydroxide
and lead hydroxide; carbonates such as magnesium carbonate,
aluminum carbonate, calcium carbonate and barium carbonate;
silicates such as magnesium silicate, calcium silicate, sodium
silicate and aluminum silicate; sulfates such as aluminum sulfate,
calcium sulfate and barium sulfate; metallic powder such as iron
powder; conductive fiber such as carbon fiber; diatomaceous earth;
asbestos; lithopone (zinc sulfide/barium sulfate); graphite;
fluorocarbon; calcium fluoride; wollastonite; glass powder and the
like are provided.
(Other Compounding Agents)
[0067] As necessary, it is possible to mix other compounding agents
that are known as ordinary compounding agents for rubbers into the
vibration-insulating rubber composition (1) or (2) to which the
exemplary embodiment is applied. As such compounding agents, for
example, various kinds of chemical agents such as a vulcanizing
agent, a vulcanization accelerator, oil, an antioxidant, a
stabilizing agent and a coloring agent can be used as
necessary.
[0068] As the vulcanizing agents, sulfur-based vulcanizing agents,
organic peroxides, bismaleimide compounds and the like are
provided. As the sulfur-based vulcanizing agents, sulfurs such as
powdered sulfur and precipitated sulfur, 4,4'-dithiomorpholine,
tetramethylthiuram disulfide, tetraethylthiuram disulfide, organic
sulfur compound such as polymeric polysulfide, and the like are
provided.
[0069] In the case of using the sulfur-based vulcanizing agents,
usually, the vulcanization accelerator and a vulcanization
accelerating auxiliary are used in combination. As the
vulcanization accelerator, a sulfur-containing accelerator of
thiuram series, sulfonamide series, thiazole series,
dithiocarbamate series, thiourea series and the like; a
nitride-containing accelerator of aldehyde-ammonia series,
aldehyde-amine series, guanidine series and the like; and so forth
are provided.
[0070] Of the vulcanization accelerators, the thiuram-based
accelerator is preferable. Specific examples of the thiuram-based
accelerators include, for example, tetramethylthiuram disulfide
(TT) (TMTD), tetramethylthiuram monosulfide (TS) (TMTM),
tetraethylthiuram disulfide (TET) (TETD), tetrabutylthiuram
disulfide (TBT) (TBTD), dipentamethylenethiuram hexasulfide (TRA)
(DPW) and tetrabenzylthiuram disulfide. Moreover, as the
vulcanization accelerating auxiliary, zinc flower, magnesium oxide
and the like are provided. An amount of usage of the vulcanization
accelerator and vulcanization accelerating auxiliary is not
particularly limited, and is determined in accordance with the kind
of the sulfur-based vulcanizing agent.
[0071] As the organic peroxide, dialkylperoxide, diacylperoxide,
peroxyester and the like are provided. As the dialkylperoxide,
dicumyl peroxide, di-t-butyl peroxide,
2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne,
2,5-dimethyl-2,5-di(t-butylperoxy)hexane,
1,3-bis(t-butylperoxyisopropyl)benzene and the like are provided.
As the diacylperoxide, benzoyl peroxide, isobutyryl peroxide and
the like are provided. As the peroxyester,
2,5-dimethyl-2,5-bis(benzoylperoxy)hexane, t-butylperoxyisopropyl
carbonate and the like are provided.
[0072] In the case of using the organic peroxide, usually,
crosslinking auxiliary agent is used in combination. As the
crosslinking auxiliary agent, triallyl cyanurate,
trimethylolpropane trimethacrylate, N,N'-m-phenylenebismaleimide
and the like are provided. An amount of usage of the crosslinking
auxiliary agent is not particularly limited, and is determined in
accordance with the kind of a crosslinking agent.
[0073] As the bismaleimide compound,
N,N'-(m-phenylene)bismaleimide, N,N'-(p-phenylene)bismaleimide,
N,N'-(o-phenylene)bismaleimide, N,N'-(1,3-naphthylene)bismaleimide,
N,N'-(1,4-naphthylene)bismaleimide,
N,N'-(1,5-naphthylene)bismaleimide, N,N'-(3,3'-dimethyl-4,4
`-biphenylene)bismaleimide,
N,N'-(3,3'-dichloro-4,4'-biphenylene)bismaleimide and the like are
provided.
[0074] In the case of using the bismaleimide compound, for example,
oximes such as p-quinonedioxime, p,p'-dibenzoyl quinonedioxime, and
tetrachloro-p-benzoquinone; morpholine compounds such as
4,4'-dithiodimorpholine, N-ethylmorpholine, and morpholine; and the
like are used in combination as necessary.
[0075] An compounding amount of the vulcanizing agent is not
particularly limited; however, usually, against a total amount of
the rubber component (A) and the rubber component (B) that equals
to 100 pts.wt., the compounding amount of the vulcanizing agent is
in a range of 0.1 pts.wt. to 10 pts.wt., preferably in a range of
0.3 pts.wt. to 7 pts.wt., and more preferably in a range of 0.5
pts.wt. to 5 pts.wt.
[0076] As the oil, for example, extender oil which is processing
oil such as aromatic oil, naphthenic oil and paraffinic oil; a
plasticizing agent such as dioctyl phthalate; a wax such as a
paraffin wax and a carnauba wax; and the like are provided.
[0077] Moreover, to improve the heat resistance of the
vibration-insulating rubber that is used under high temperature
atmosphere for a long time, it is preferable to compound an
antioxidant into the vibration-insulating rubber composition (1) or
(2) to which the exemplary embodiment is applied. As the
antioxidant, for example, an amine-ketone series such as
poly-(2,2,4-trimethyl-1,2-dihydroquinone); an amine series such as
N-phenyl-N'-isopropyl-p-phenylenediamine, and
N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine;
a phenol series such as
2,2'-methylene-bis(4-ethyl-6-t-buthylphenol);
2-mercaptobenzimidazole; and the like are provided.
[0078] A compounding amount of the antioxidant is not particularly
limited; however, usually, against a total amount of the rubber
component (A) and the rubber component (B) that equals to 100
pts.wt., the compounding amount of the antioxidant is in a range of
0.1 pts.wt. to 10 pts.wt., preferably in a range of 0.3 pts.wt. to
7 pts.wt., and more preferably in a range of 0.5 pts.wt. to 5
pts.wt.
(Producing Method of Vibration-Insulating Rubber Composition)
[0079] A producing method of the vibration-insulating rubber
composition (1) or (2) to which the exemplary embodiment is applied
is not particularly limited; however, usually, produced by kneading
and mixing the isoprene-based rubber and the butadiene-based
rubber, other rubber such as the natural rubber as necessary,
carbon black and silica, the silane coupling agent, other
reinforcing agent and other compounding agent such as vulcanizing
agent as necessary by a mixer such as a roller or a Banbury
mixer.
[0080] The vibration-insulating rubber composition (1) or (2) that
is combined with the above-described vulcanizing agent and is
vulcanizable is molded into a predetermined shape by a
conventionally known molding method such as injection molding and
extrusion molding, and is vulcanized by a method such as steam
vulcanization. The vulcanizing temperature of the
vibration-insulating rubber composition is not particularly
limited; however, usually, 100.degree. C. to 200.degree. C.,
preferably 130.degree. C. to 190.degree. C., and more preferably
140.degree. C. to 180.degree. C. In addition, the vulcanizing time
is changed in accordance with the vulcanizing method, temperature,
shape and the like, and is not particularly limited. The time is
usually one minute or more and five hours or less. It should be
noted that, as necessary, secondary vulcanization may be performed.
The vulcanizing method can be selected from the methods usually
used for vulcanization of rubber, such as press heating, steam
heating, oven heating and hot air heating.
EXAMPLES
[0081] Hereinafter, the present invention will be described in more
detail based on examples. It should be noted that the present
invention is not limited to the examples. Note that all parts and %
in the examples and comparative examples are on a weight basis,
except where specifically noted.
(Durability Test)
[0082] FIG. 1 is a diagram illustrating a specimen used in a
durability test. The specimen 10 shown in FIG. 1 is configured
with: a metal internal cylinder 11 that has a cylindrical shape and
is laterally mounted; a metal external cylinder 12 that has a
cylindrical shape and encloses the metal internal cylinder 11
axially in parallel therewith; and a rubber elastic body 13 that is
formed between the metal internal cylinder 11 and the metal
external cylinder 12 and integrally combines both cylinders by
means of vulcanization adhesion. The metal internal cylinder 11 has
an outer diameter of 30 mm and a length of 65 mm, and an inner
diameter of a bearing portion 14, into which a shaft member of a
later-described vibration tester is inserted, is 15 mm. The metal
external cylinder 12 has an outer diameter of 75 mm and a length of
45 mm.
[0083] The rubber elastic body 13 was prepared by vulcanization
molding of a rubber composition having a compounding composition
shown in Table 1, which will be later described, under the
condition of 170.degree. C. by two hours.
[0084] By use of the specimen 10, a durability test was performed
with a vibration tester (manufactured by KYB Co., Ltd.: a fatigue
tester) (not shown). The specimen 10 is fixed to the vibration
tester by inserting the shaft member of the vibration tester into
the bearing portion 14 of the specimen 10. Next, at room
temperature, vibration was applied in an axially perpendicular
direction of the metal internal cylinder 11 (direction of arrow A)
with a frequency of 5 Hz and a load of +1670N to -1000N, to measure
the number of excitation until the time when cracking was observed
on a surface of the rubber elastic body 13 (units: 10000 times).
The larger the numerical value, the more excellent in
durability.
(Dynamic Characteristics Test)
[0085] Each of rubber compositions with compounds shown in Table 1
and Table 2, which will be later described, was heated at
170.degree. C. for 25 minutes, and in conformity with JIS K 6394
(1976), a specimen having a shape of a cylindrical column with a
diameter of 50 mm and a height of 50 mm was prepared (N2-type
specimen). A static spring constant (Ks (units: N/mm)) and a
dynamic spring constant (Kd (units: N/mm 100 H)) of the specimen
were measured, to thereby obtain dynamic multiplication (Kd/Ks 100
Hz).
[0086] The static spring constant (Ks) was calculated by, in
conformity with JIS K 6385, compressing the specimen having the
cylindrically columnar shape in a direction of the axis of the
cylindrical column by 3 mm, and reading loads when distortion is 1
mm and 2 mm from a load spring diagram of second going.
[0087] The dynamic spring constant (Kd) was calculated by, in
conformity with JIS K 6394, compressing the specimen having the
cylindrically columnar shape in the direction of the axis of the
cylindrical column by 1.5 mm (initial compressive strain is 3%),
applying constant displacement vibration with an amplitude of
.+-.0.05 mm by a frequency of 100 Hz from beneath with the position
of 1.5 mm compression at the center (100 Hz .+-.0.1% dynamic
strain), and measuring a dynamic load with a load cell attached to
an upper portion of the specimen.
[0088] The dynamic multiplication (Kd/Ks) is a ratio between the
static spring constant (Ks) and the dynamic spring constant (Kd).
The smaller the dynamic multiplication (dynamic spring
constant/static spring constant), the more excellent in
vibration-insulating performance.
(Uneven Distribution Rate of Carbon Black and Silica)
[0089] A rubber composition having a compounding composition shown
in later-described Table 1 is cut with a microtome to prepare
slices with a thickness of 0.1 .mu.m. The slice is observed by a
transmission electron microscope (TEM) while regarding particles
having a particle diameter of about 0.8 .mu.m to about 1.2 .mu.m as
carbon black and particles having a particle diameter of about 10
nm to about 40 nm as silica, to measure the number of particles of
carbon black and silica present in each of the phase of the rubber
component (A) and the phase of the rubber component (B). Then, in
each of the phase of the rubber component (A) (isoprene-based
rubber) and the phase of the rubber component (B) (butadiene-based
rubber), the ratio between the number of particles of carbon black
and the number of particles of silica was obtained, and thereby the
uneven distribution rate of carbon black and silica in each phase
was obtained. It should be noted that the number of samples is 30
(n=30).
Examples 1 to 6, Comparative Examples 1 and 2
[0090] The durability and the dynamic characteristics were measured
by using a rubber composition with a compound shown in Table 1. In
addition, uneven distribution rate of carbon black and silica in
the rubber component (A) and the rubber component (B) was measured.
The results were shown in Table 1.
[0091] FIG. 2 is a transmission electron microscope (TEM)
photograph of the rubber composition in Example 2. Example 2 is a
rubber composition in which natural rubber (RSS)/polybutadiene
rubber (BR)=60/40. As shown in FIG. 2, natural rubber (RSS)
constitutes matrix portions of gray which is relatively light,
while polybutadiene rubber (BR) constitutes insular portions
(portions enclosed by broken lines) of gray which is relatively
thick. It can be learned that carbon black (particle diameter of
about 0.8 .mu.m to about 1.2 .mu.m) is unevenly distributed in the
insular portions of relatively-thick gray constituted by
polybutadiene rubber (BR), while silica (particle diameter of about
10 nm to about 40 nm) is unevenly distributed in the matrix
portions of relatively-light gray constituted by natural rubber
(RSS).
TABLE-US-00001 TABLE 1 Comparative Example Example 1 2 3 4 5 6 1 2
Rubber Component A RSS 80 60 40 30 60 60 60 60 IR -- -- -- 30 -- --
-- -- Rubber Component B BR 20 40 60 40 40 40 40 40 Carbon Black 15
15 15 15 20 10 30 -- Silica SW134 15 15 15 15 10 20 -- 30 Other
Zinc Oxide 5 5 5 5 5 5 5 5 Compounding Agents Stearic Acid 1 1 1 1
1 1 1 1 Oil 5 5 5 5 5 5 5 5 Antioxidant 6C 2 2 2 2 2 2 2 2
Antioxidant RD 2 2 2 2 2 2 2 2 Vulcanizing Series Sulfur 1 1 1 1 1
1 1 1 Accelerator CZ 2 2 2 2 2 2 2 2 Accelerator TT 0.5 0.5 0.5 0.5
0.5 0.5 0.5 0.5 Uneven Distribution Rubber Component A 28 18 13 19
22 13 18 100 Rate (%) Rubber Component B 72 82 87 81 78 87 82 0 of
Carbon Black Uneven Distribution Rubber Component A 86 84 72 84 86
76 0 82 Rate (%) of Silica Rubber Component B 14 16 28 16 14 24 100
18 Dynamic Characteristics Ks(N/mm) 192 201 195 202 194 200 194 202
Kd/Ks 1.44 1.40 1.38 1.39 1.38 1.40 1.38 1.40 Durability (10000's
of units) 130 140 100 135 135 120 55 35
[0092] It should be noted that each component in Table 1 is as
follows. [0093] RSS: natural rubber [0094] IR: polyisoprene rubber,
Nipol IR 2200 manufactured by Zeon Corportion [0095] BR:
polybutadiene rubber, Nipol BR 1250H manufactured by Zeon
Corporation [0096] Carbon black: SAEST S manufactured by Tokai
Carbon Co., Ltd. [0097] SW134: silica treated by a
polysulfide-based silane coupling agent, manufactured by DAISO Co.,
Ltd. [0098] Oil: naphthenic processing oil, SUNTHENE 410
manufactured by Japan Sun Oil Co., Ltd. [0099] Zinc oxide: zinc
flower 3 [0100] Stearic acid: industrial stearic acid [0101]
Antioxidant 6C: NOCRAC 6C manufactured by Ouchi Shinko Chemical
Industrial Co., Ltd. [0102] Antioxidant RD: NOCRAC 224 manufactured
by Ouchi Shinko Chemical Industrial Co., Ltd. [0103] Sulfur:
colloidal sulfur [0104] Accelerator CZ: NOCCELER CZ manufactured by
Ouchi Shinko Chemical Industrial Co., Ltd. [0105] Accelerator TT:
NOCCELER TT manufactured by Ouchi Shinko Chemical Industrial Co.,
Ltd.
[0106] From the results shown in Table 1, it can be learned that
the vibration-insulating rubber compositions to which the exemplary
embodiments are applied (Examples 1 to 6) do not increase the
dynamic multiplication (Kd/Ks) and are excellent in durability.
[0107] On the other hand, in a rubber composition in which silica
is not compounded and only carbon black is compounded as a
reinforcing agent (Comparative Example 1) and in a rubber
composition in which carbon black is not compounded and only silica
is compounded (Comparative Example 2), it can be learned that the
durability is deteriorated.
(Ordinary State Characteristics)
[0108] With regard to a specimen prepared by heating the rubber
composition with a compound shown in Table 2 at 170.degree. C. for
15 minutes, vulcanizing to form a vulcanized sheet to be die-cut
into a shape of dumbbell No. 3 (JIS K6251), 300% tensile stress
(units: MPa) and elongation (units: %) were measured in conformity
with JIS K6251/JIS K6253.
(Thermal Aging Resistance Test)
[0109] Similar to the case of the above-described ordinary state
characteristics, a specimen having the shape of dumbbell No. 3 (JIS
K6251) was prepared by use of the rubber composition with a
compound shown in Table 2. In a tensile test of the specimen, a
tensile tester equipped with a temperature controlled bath was
used. In the temperature controlled bath of the tensile tester, an
ambient atmosphere temperature of a jig that grasps the specimen is
maintained at a predetermined temperature. After the specimen was
set aside in the temperature controlled bath for a predetermined
time, elongation and a change in elongation (units: %) were
measured. The measuring condition is 100.degree. C. by 1000
hours.
Examples 7 to 9, Comparative Examples 3 and 4
[0110] Ordinary state physical properties, the dynamic
characteristics and the thermal aging resistance were measured by
using a rubber composition with a compound shown in Table 2. The
results are shown in Table 2.
[0111] It should be noted that each component in Table 2 is as
follows. [0112] RSS: natural rubber [0113] BR: polybutadiene
rubber, Nipol BR 1250H manufactured by Zeon Corporation [0114]
Carbon black: SAEST S manufactured by Tokai Carbon Co., Ltd. [0115]
SW134: silica treated by a polysulfide-based silane coupling agent,
manufactured by DAISO Co., Ltd. [0116] ER: silica treated by a
silane-based surface treatment agent, Aerosil R805 manufactured by
Degussa [0117] Zinc oxide: zinc flower 3 [0118] Stearic acid:
industrial stearic acid [0119] Antioxidant 6C: NOCRAC 6C
manufactured by Ouchi Shinko Chemical Industrial Co., Ltd. [0120]
Antioxidant RD: NOCRAC 224 manufactured by Ouchi Shinko Chemical
Industrial Co., Ltd. [0121] Sulfur: colloidal sulfur [0122]
Accelerator CZ: NOCCELER CZ manufactured by Ouchi Shinko Chemical
Industrial Co., Ltd. [0123] Accelerator TT: NOCCELER TT
manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.
TABLE-US-00002 [0123] TABLE 2 Comparative Example Example 7 8 9 3 4
Rubber RSS 50 80 80 80 80 Component BR 50 20 20 20 20 Carbon Black
14 14 14 14 14 Silica SW134 7 11 7 14 -- ER 7 3 7 -- 14 Other Zinc
5 5 5 5 5 Compound- Oxide ing Agent Stearic 1 1 1 1 1 Acid Anti- 2
2 2 2 2 oxidant 6C Anti- 2 2 2 2 2 oxidant RD Vulcanizing Sulfur 1
1 1 1 1 Series Acceler- 2 2 2 2 2 ator CZ Acceler- 0.5 0.5 0.5 0.5
0.5 ator TT Ordinary 300% 3.8 3.9 3.7 4.7 2.6 State Tensil Physical
Stress Properties (Mpa) Elongation 583 643 631 611 704 (%) Dynamic
Ks 159 153 153 161 118 Charac- (N/mm) teristics Kd/Ks 1.30 1.34
1.33 1.30 1.67 Heat Elongation 220 226 226 174 286 Resistance (%)
Elongation -62 -65 -64 -72 -59 Change Rate (%)
[0124] From the results shown in Table 2, it can be learned that
the vibration-insulating rubber compositions to which the exemplary
embodiments are applied (Examples 7 to 9) indicate 300% tensile
stress that is sufficient for the use as the vibration-insulating
rubber, do not increase the dynamic multiplication (Kd/Ks), and are
excellent in heat resistance (sufficient elongation after thermal
aging, and small elongation change rate).
[0125] On the other hand, though the rubber composition
(Comparative Example 3) in which only silica that is
surface-treated by the polysulfide-based silane coupling agent is
compounded as a silica component (SW134) indicates low dynamic
multiplication (Kd/Ks), 300% stress is high, and elongation and
elongation change rate after thermal aging are small; accordingly
it can be learned that the heat resistance is deteriorated.
Moreover, the rubber composition (Comparative Example 4) in which
only silica that is surface-treated by the silane-based surface
treatment agent is compounded as a silica component (ER) indicates
increased dynamic multiplication (Kd/Ks); accordingly, it can be
learned that the dynamic characteristics are not improved.
Reference Signs List
[0126] 10 . . . Specimen [0127] 11 . . . Metal internal cylinder
[0128] 12 . . . Metal external cylinder [0129] 13 . . . Rubber
elastic body [0130] 14 . . . Bearing portion
* * * * *