Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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RUBBER COMPOSITION
BACKGROUND OF T~E lNV~llON
Field of the Invention
The present invention relates to a rubber composition
and a high hardness vulcanized rubber. More precisely, the
present invention relates to a rubber composition which makes
effective use of characteristics of ethylene-propylene-non-
conjugated diene copolymer rubbers excellent in heat
resistance, weathering resistance, ozone resistance, chemical
resistance and the like and which allows to provide a high
hardness vulcanized rubber excellent in processibility and
having sufficiently high hardness, a high hardness vulcanized
rubber obtained by sulfur vulcanization of said rubber
composition, as well as a weather strip for automobile, a
glass run channel for automobile and a gasket for architecture
comprising said high hardness vulcanized rubber.
Background Information
Since ethylene-propylene-non-conjugated diene copolymer
rubbers are excellent in heat resistance, weathering
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resistance, ozone resistance, chemical resistance and the
like, they are widely used in various parts for automobile,
materials for architecture and the like. The high hardness
rubber is used independently or in the form of an integrated
material with a sponge rubber for the weather strip and the
glass run channel among the parts for automobile. Also, the
high hardness rubber is used independently or in the form of
an integrated material with another rubber for a glazing
gasket, an airtight gasket and a joint gasket among the
gaskets for architecture. A sufficiently high hardness is
required for the high hardness rubber used for such
applications and simultaneously excellent processibility such
as roll processibility, extruding processibility or the like
is required for the rubber composition for providing such high
hardness rubber.
As methods for improving processibility of rubber
compositions, JP-B-3-73584 disclosed a method in which a
liquid polyisoprene rubber is blended with
ethylene-propylene-diene terpolymer (EPDM). In this case,
however, the hardness (JIS-A) of the vulcanized rubber
obt~;ne~ by this method is 80 or less and a vulcanized rubber
having a sufficiently high hardness such as a hardness (JIS-A)
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of 90 or more is not obtained.
A method in which the blending amount of carbon black
is increased has been known as a common method for improving
the hardness of vulcanized rubbers. The increase in the
amount of carbon black, however, causes to increase the Mooney
viscosity of the unvulcanized compound and to significantly
lower the processibility. Thus, it is generally difficult to
improve simultaneously the hardness of vulcanized rubbers and
processibility (to lower the Mooney viscosity).
As the result of extensive studies on a rubber
composition which makes effective use of characteristics of
ethylene-propylene-non-conjugated diene copolymer rubbers and
which allows to provide a high hardness vulcanized rubber
excellent in processibility and having sufficiently high
hardness, the present inventors have successfully found that a
rubber composition comprising an ethylene-propylene-non-
conjugated diene copolymer rubber having an ethylene/propylene
ratio within a specific range and a liquid polyisoprene rubber
in which 70 % or more of double bonds are hydrogenated, and
said ethylene-propylene-non-conjugated diene copolymer rubber
and said liquid polyisoprene rubber being in a specific ratio
allows to provide a high hardness vulcanized rubber excellent
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in processibility and having sufficiently high hardness, and
thus have completed the present invention.
SUMMARY OF THE lNV~NllON
Accordingly, the present invention provides a rubber
composition comprising the following component (A) and
component (B):
component (A): an ethylene-propylene-non-conjugated
diene copolymer rubber having a Mooney viscosity (ML1+4 lOOC)
of 40 or less and having a weight ratio of ethylene/(ethylene
+ propylene) of (75-95)/100,
component (B): a liquid polyisoprene rubber in which 70
% or more of double bonds are hydrogenated,
in a weight ratio (A)/(B) of 65/35 - 95/5.
DETATT-~D DESCRIPTION OF THE lNV ~:N'l'lON
The present invention is described in more detail in
the followings.
The component (A) in the present invention is an
ethylene-propylene-non-conjugated diene copolymer rubber
having a Mooney viscosity (MLl+4 100C) of 40 or less and having
a weight ratio of ethylene/(ethylene + propylene) of
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(75-95)/100.
The non-conjugated diene in the component (A) includes,
for example, 1,4-pentadiene, 1,4-hexadiene, divinylbenzene,
dicyclopentadiene, methylenenorbornene, ethylidenenorbornene
(ENB), vinylnorbornene and the li~e. These may be used
independently or in combination thereof.
The amount of the non-conjugated diene in the component
(A) is preferably an amount providing an iodine value of 2-35
and more preferably an iodine value of 10-25. If the amount
of non-conjugated diene is too small, the tensile strength on
the sulfur vulcanization may lower and when the amount is too
much, the heat resistance and ozone resistance after the
sulfur vulcanization may be poor.
The Mooney viscosity (MLl+4 100C) of the component (A)
should be 40 or less and preferably is 35-5. If the Mooney
viscosity is too high, the Mooney viscosity (MLl+4 100C) of the
compound is also high resulting in poor processibility.
The weight ratio ethylene/(ethylene + propylene) of the
component (A) should be (75-95)/100 and preferably
(78-90)/100. If the content of ethylene is too high, the
crystallinity of ethylene becomes higher and the hardness of
the vulcanized rubber increases but the production of the
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ethylene-propylene-non-conjugated diene copolymer rubber
becomes difficult and the processibility of unvulcanized
rubber becomes poor. On the other hand, when the content of
ethylene is too low, a sufficiently high hardness is not
obtained.
The component (B) in the present invention is a liquid
polyisoprene rubber in which 70 % or more, preferably 75 % or
more of double bonds are hydrogenated. If the rate of
hydrogenation is too low, a sufficiently high hardness is not
obtained.
It is preferred that the liquid polyisoprene has a
viscosity average molecular weight of 5,000-50,000. If the
viscosity average molecular weight is lower than 5,000, a
sufficiently high hardness may not be obtained and when the
viscosity average molecular weight is higher than 50,000, the
viscosity of unvulcanized compound becomes high resulting in
poor processibility. On the other hand, if a solid
polyisoprene is used, the processibility is poor.
The weight ratio (A)/(B) in the rubber composition of
the present invention should be 65/35-95/5 and preferably
70/30-95/5. If the amount of the component (A) is too small,
a sufficiently high hardness is not obtained and when the
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amount of the component (A) is too much, the processibility
becomes poor.
The rubber composition of the present invention may
contain a reinforcing agent such as carbon black, silica and
the like and a lubricant such as a mineral oil such as
paraffin processing oil. The amoun~ is, for example, 50 - 200
parts by weight of FEF carbon black and 100 part by weight or
less of paraffin processing oil, per 100 parts by weight of
the rubber component. If the amount of the reinforcing agent
is too small, a sufficiently high hardness may not be
obtained, and when the amount of the reinforcing agent is too
much, the rubber properties such as elasticity may be poor.
Further, if the amount of the lubricant is too small, the
processibility may be poor and when the amount of the
lubricant is too much, a sufficiently high hardness may not be
obtained.
The rubber composition of the present invention can be
converted into a compound by kneading the above ingredients
with a vulcanizing agent and, if necessary, an antioxidant, a
processing aid, stearic acid, zinc oxide, a filler, a
vulcanization accelerator and the like by means of a Banbury
mixer, a open roll or the like and then into a high hardness
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vulcanized rubber by molding and vulcanizing the compound.
While sulfur, organic peroxides or the like may be used as
a vulcanizing agent, sulfur is preferred because it allows
vulcanization in the air. The amount of sulfur is preferably
0.5-4 parts by weight, per 100 parts by weight of the rubber
component. If the amount is too small, a sufficiently high
hardness may not be obtained and when the amount is too much,
the product may have bad appearance due to a bloom generated
on the surface of the product or may be poor in heat
resistance and permanent compression set. Preferably, the
kneading is conducted by a Banbury mixer at a temperature of
60C - 250C, more preferably 100C - 160C or is conducted
by an open roll preferably at a temperature of 20C - 200C,
more preferably 30C - 60C. The vulcanization is conducted
preferably at a temperature of 120C or more, more preferably
150C - 220C. The vulcanization time is generally about
1 - 30 minutes.
The high hardness vulcanized rubber thus obtained
has a hardness of JIS-A (DUROMETER-A) of 90 or more. Also
the high hardness vulcanized rubber is excellent in roll
processibility and extrusion processibility.
The rubber composition of the present invention can
be used in various fields, including weather strips for
automobile, glass run channels for automobile and gaskets for
architecture as suitable uses, making use of its excellent
characteristics. More particularly, rubber parts of said
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weather strips for automobile, glass run channels for auto-
mobile and gaskets for architecture may usually contain a
high hardness rubber independently or in the form of an
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28865-21
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integrated material with a sponge rubber or another rubber and
the high hardness rubber composition of the present invention
can be suitably used in such rubber parts.
According to the present invention, it is possible to
provide a rubber composition which makes effective use of
characteristics of ethylene-propylene-non-conjugated diene
copolymer rubbers excellent in heat resistance, weathering
resistance, ozone resistance, chemical resistance and the like
and which allows to provide a high hardness w lcanized rubber
excellent in processibility and having sufficiently high
hardness, a high hardness vulcanized rubber obtained by sulfur
w lcanization of said rubber composition, as well as a weather
strip for automobile, a glass run channel for automobile and a
gasket for architecture comprising said high hardness
w lcanized rubber.
EXAMPLES
The present invention will now be illustrated by means
of Examples which should not be construed as a limitation upon
the scope of the invention.
Examples 1 - S and Comparative Examples 1 - 6
Ingredients shown in Table 1 and, as a common
combination, 100 parts by weight of FEF carbon black
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(manufactured by Asahi Carbon, "Asahi 60G" (trade-mark)), 5
parts by weight of Processing oil (manufactured by Idemitsu
Rousan, "PW-90" (trade-mark))~ 5 parts by weight of zinc
oxide, 1 part by weight of stearic acid, 2 parts by weight of
polyethylene glycol (PEG 4000), 3 parts by weight of calcium
oxide (manufactured by Inoue Sekkai, n Besuta BS" (trade-
mark)), 2.5 parts by weight of Sox CZ (trade-mark of
Sumitomo Chemical Co., Ltd., a vulcanization accelerator), 1.O
part by weight of Sox BZ (trade-mark of Sumitomo Chemical
Co., Ltd., a vulcanization accelerator)~ 0.5 part by weight of
Sox TT (trade-mark of Sumitomo Chemical Co., Ltd., a
vulcanization accelerator) and 1.5 part by weight of sulfur
were kneaded in a 1.7 liter BR-type Banbury mixer using open
rolls to give a compound. The condition of kneading was
visually observed and the processibility was evaluated by
measuring the Mooney viscosity (MLl+4 100 ) of the produced
compound. Then the compound was vulcanized to give a
vulcanized rubber, which was evaluated by the tensile strength
(TB), elongation (E9) and hardness (Hs; JIS-A) according to JIS
R6301.
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The amounts of FEF carbon black are measured per
100 parts of components (A) and (B1 combined. The amounts
of the lubricant and the vulcanizing agent are also measured
per 100 parts of components(A) and (B) combined. The results
are shown in Table 1.
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Table 1
________ ______ __ _____
Examples 1 2 3 4 5
Composition
Component (A)*1
MLlt4 (lOOC) 35
E/EP wt ratio*280/100
Component (B)*3
Hydrogenation %*4 90 1 ~ 75 95
Mv *5 25000 I 29000
(A)/(B) wt ratio*690/10 80/20 70/30 90/10
Results of Evaluation
Compound
MLl+4 (100C ) 73 62 51 70 72
processibility*7 0 O O O O
Extrusion
processibility*8 0 0 0 0 0
Properties of Vulcanized Rubber
TB kgf/cm2 153 129 115 135 149
EB % 170 170 170 200 180
Hs (JIS-A) 91 91 90 90 91
______ __________
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Table 2
__ ________ ___
Comparative examples 1 2 3 4 5 6
____ _________
Composition
Component (A)*l
ML1+4 ( 100C ) 35 35 50 90 35 35
E/EP wt ratio*2 80/100 70/100 50/100 80/100 80/100 80/100
Component (B)*3
~ydrogenation %*4 - 90 ~ 0 44
Mv *5 - 25000 f 47000 25000
A/B wt ratio*6 100/0 90/10 -
Results of Evaluation
Compound
MLl+~ (100C) 95 75 120 147 64 68
Roll
processibility*7 X O X X O O
Extrusion
processibility*8 X O X X O O
Properties of Vulcanized Rubber
TB kgf/cm2 160 157 147 234 108 130
EB % 170 230 290 220 300 240
Hs (JIS-A) 91 86 84 91 86 87
_________ _______________________ __________
.
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*l Component (A): an ethylene-propylene-ethylidenenorbornene
copolymer rubber
*2 E/EP: a weight ratio of ethylene/(ethylene + propylene)
*3 Component (B): a liquid polyisoprene rubber having a
hydrogenation rate shown in the Table
*4 Hydrogenation: hydrogenation r~te of double bonds in
Component (B)
*5 Mv: viscosity average molecular weight
*6 A/B wt ratio: the weight ratio of
Component(A)/Component(B)
*7 Roll processibility: The state of winding the compound on
to the rolls during the kneading was evaluated by using
scoring criteria: O, good in winding on to the rolls and good
in cutting; X, bad in winding on to the rolls and bad in
cutting.
*8 Extrusion processibility: The extruding processibility of
unvulcanized compound was evaluated by using scoring criteria:
0, extruding rate is fast and the surface of the extruded
product is smooth; X, extruding rate is slow and the surface
of the extruded product is rough.
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It is noted that the results of Examples are
satisfactory in all the evaluation items. On the other hand,
in Comparative Example 1 lacking the component (B) of the
present invention, the Mooney viscosity is too high and the
processibility is poor. In Comparative Example 2 in which the
content of ethylene in the component (A) is too small, the
hardness is poor. In Comparative Example 3 in which the
content of ethylene in the component (A) is too small and
additionally the Mooney viscosity of the component ~A) is too
high, the Mooney viscosity of the compound is too high, the
processibility is poor and the hardness is also poor. In the
Comp~rative Example 4 in which the Mooney viscosity of the
component (A) is too high, the Mooney viscosity of the
compound is too high and the processibility is poor. In
Comparative Example 5 in which an unhydrogenated polyisoprene
rubber is used as the component (B), the hardness is poor. In
Comparative Example 6 in which an polyisoprene rubber having a
hydrogenation rate of less than 70 % is used as the component
(B), the hardness is poor.
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