Case 1:17-cv-00770-JDW-MPT Document 121-16 Filed 11/17/22 Page 1 of 30 PageID #:
`14459
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`Exhibit AB
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`(19)
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`(12)
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`Europäisches Patentamt
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`European Patent Office
`
`Office européen des brevets
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`*EP001153973A1*
`EP 1 153 973 A1
`
`(11)
`
`EUROPEAN PATENT APPLICATION
`published in accordance with Art. 158(3) EPC
`
`(43) Date of publication:
`14.11.2001 Bulletin 2001/46
`
`(21) Application number: 00970204.4
`
`(22) Date of filing: 30.10.2000
`
`(84) Designated Contracting States:
`AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU
`MC NL PT SE
`
`(30) Priority: 01.11.1999 JP 31155599
`21.04.2000 JP 2000121142
`26.06.2000 JP 2000191147
`
`(71) Applicant: Tokai Rubber Industries, Ltd.
`Komaki-shi, Aichi-ken, 485-8550 (JP)
`
`(51) Int Cl.7: C08L 21/00, F16F 1/36,
`F16F 15/08
`
`(86) International application number:
`PCT/JP00/07625
`
`(87) International publication number:
`WO 01/32769 (10.05.2001 Gazette 2001/19)
`
`(72) Inventors:
`• TAGUCHI, Takehiko
`Komaki-shi, Aichi 485-8550 (JP)
`• YOSHIKAWA, Ako
`Komaki-shi, Aichi 485-8550 (JP)
`
`(74) Representative:
`Leson, Thomas Johannes Alois, Dipl.-Ing.
`Tiedtke-Bühling-Kinne & Partner GbR,
`TBK-Patent,
`Bavariaring 4
`80336 München (DE)
`
`(54)
`
`RUBBER VIBRATION ISOLATOR AND METHOD FOR PRODUCING THE SAME
`
`(57)
`A vibration damping rubber member having
`both a low degree of dynamic spring stiffness and a high
`vibration damping effect.
`A process of producing a vibration damping rubber
`member, wherein a rubber material A which enables the
`vibration damping rubber member to have a low degree
`of dynamic spring stiffness, a rubber material B which
`enables the vibration damping rubber member to have
`a high vibration damping effect, and a vulcanizing agent
`capable of vulcanizing only an unvulcanized mass of the
`
`rubber material B are evenly mixed together and heated
`to vulcanize the rubber material B dispersed as the fine
`particles in the rubber material A, and wherein a vulcan-
`izing agent capable of vulcanizing the rubber material A
`is added, and a thus obtained mixture is formed into a
`desired shape and heated to vulcanize the rubber ma-
`terial A so that the formed vibration damping rubber
`member has an island-sea structure in which fine parti-
`cles of the vulcanized rubber material B are dispersed
`as a dispersed phase in a matrix phase of the vulcanized
`rubber material A.
`
`Printed by Jouve, 75001 PARIS (FR)
`
`EP1 153 973A1
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`

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`Case 1:17-cv-00770-JDW-MPT Document 121-16 Filed 11/17/22 Page 3 of 30 PageID #:
`14461
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`EP 1 153 973 A1
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`Description
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`TECHNICAL FIELD
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`[0001] The present invention relates to a vibration damping rubber member and a process of producing the same,
`and more particularly to a vibration damping rubber member capable of exhibiting low dynamic stiffness and high
`vibration damping effect, and a process suitable for producing such a vibration damping rubber member. The present
`invention is also concerned with a process of producing a vibration damping rubber member having an increased
`vibration damping effect, so as to reduce its dynamic/static ratio of spring constant for thereby reducing the dynamic
`stiffness.
`
`BACKGROUND ART
`
`[0002] As well known, a vibration damping rubber member interposed between two members in a vibration trans-
`mitting system so as to connect the two members in a vibration damping fashion has been widely used in various fields.
`For instance, the vibration damping rubber member is used on automotive vehicles, as engine mounts, body mounts,
`member mounts, suspension bushings, and so on.
`[0003] A vibration damping rubber member used in a vibration transmitting system involving different kinds of vibra-
`tions having different frequencies, for instance, typically, the vibration damping rubber member as used on the auto-
`motive vehicles as described above, is generally required to exhibit vibration damping characteristics suitable for ef-
`fectively damp those different kinds of vibrations. Described in detail, the vibration damping rubber member used on
`the automotive vehicles is generally required to exhibit a relatively low degree of dynamic spring stiffness with respect
`to input vibrations having comparatively high frequencies of 100Hz or higher, and to exhibit a relatively high damping
`effect with respect to input vibrations having comparatively low frequencies of about 10-20Hz. In the present invention,
`the dynamic spring stiffness is defined by a dynamic/static ratio (Kd100/Ks) of spring constant of the vibration damping
`rubber member, which is a ratio of a dynamic spring constant Kd100 to a static spring constant Ks of the vibration
`damping rubber member. The dynamic spring constant Kd100 is obtained when it is subjected to vibration of 100Hz.
`The dynamic spring stiffness decreases with a decrease of the dynamic/static ratio Kd100/Ks. On the other hand, the
`damping effect is defined by a loss factor (tan δ) of the vibration damping rubber member when it is subjected to
`vibration of 15Hz. The damping effect increases with an increase of the loss factor tan δ.
`[0004] For producing vibration damping rubbers structure having improved vibration damping characteristics as rep-
`resented by a reduced degree of dynamic spring stiffness and an increased damping effect, various studies have been
`made to improve the material of the vibration damping rubber member and the process of preparing a composition of
`the material. For example, there has been proposed to use natural rubbers (NR) which are suitable for reducing the
`dynamic spring stiffness of the vibration damping rubber members, and add a carbon black to the natural rubbers, to
`increase the damping effect of the vibration damping rubber members. However, the known vibration damping rubber
`members according to those studies are by no means sufficiently satisfactory in terms of the required vibration damping
`characteristics.
`[0005] Described more specifically, the mechanism by which the dynamic spring stiffness of a vibration damping
`rubber member is reduced is based on bonding, binding or linking among the molecules of polymers of the rubber
`composition, or bonding and binding between the polymer molecules and reinforcing additives contained in the rubber
`composition. On the other hand, the mechanism by which the vibration damping effect is increased is based on a
`friction among the polymer molecules or among the polymer molecules and the reinforcing additives. Therefore, there
`are problems that increasing the vibration damping effect of the vibration damping rubber member will cause an increase
`of the dynamic spring stiffness, while reducing the dynamic spring stiffness will cause a decrease of the vibration
`damping effect. There has not been available a rubber composition which exhibits a sufficiently low degree of dynamic
`spring stiffness and a sufficiently high vibration damping effect, which are two distinct characteristics not compatible
`with each other.
`[0006]
`In the meantime, there have been proposed fluid-filled vibration damping rubber members, as improvements
`in the construction rather than the material. Generally, such fluid-filled vibration damping rubber members use an elastic
`body formed of a rubber composition in which a plurality of fluid chambers are formed in fluid communication with each
`other through orifice passages (restricted fluid passages). These fluid-filled vibration damping rubber members are
`arranged to exhibit desired vibration damping characteristics depending upon respective frequency bands of the input
`vibrations, on the basis of resonance of a fluid flowing through the orifice passages. Accordingly, those fluid-filled
`vibration damping rubber members are inevitably complicated in construction, with a relatively large number of com-
`ponents, and suffer from potential problems of a relatively high cost and considerable difficulty of manufacture.
`[0007] The vibration damping rubber members are required to have a relatively high degree of hardness, in view of
`their applications in which the rubbers should withstand a relatively large load, for instance. This requirement is con-
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`Case 1:17-cv-00770-JDW-MPT Document 121-16 Filed 11/17/22 Page 4 of 30 PageID #:
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`EP 1 153 973 A1
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`ventionally satisfied by using a rubber composition which contains a diene-based rubber material such as a natural
`rubber (NR), and additives such as a carbon black. The addition of such additives including the carbon black makes
`it possible to increase the hardness and the vibration damping effect of the vibration damping rubber member, but
`inevitably results in an undesirable increase in the dynamic spring stiffness. Various other approaches for improving
`the rubber composition have been proposed to obtain a vibration damping rubber member capable of exhibiting the
`desired characteristics, namely, low dynamic spring stiffness and high damping effect. For instance, the damping effect
`is increased by adding a suitable rubber material to the natural rubber (NR). However, the reduction of the dynamic/
`static ratio of spring constant of the vibration damping rubber members according to such approaches is not still sat-
`isfactory.
`
`DISCLOSURE OF THE INVENTION
`
`[0008] The present invention was made in view of the background art described above. It is a first object of this
`invention to provide a vibration damping rubber member which is capable of exhibiting both a low degree of dynamic
`spring stiffness and a high vibration damping effect and which can be economically and easily produced, and a process
`suitable for producing such a vibration damping rubber member.
`[0009] The first object indicated above may be achieved according to the present invention, which provides a vibration
`damping rubber member having an island-sea structure in which fine particles of a vulcanized rubber material B which
`enables the vibration damping rubber member to have a high vibration damping effect are dispersed as a dispersed
`phase in a matrix phase of a vulcanized rubber material A that enables the vibration damping rubber member to exhibit
`a low degree of dynamic spring stiffness, the vibration damping rubber member being characterized in that the vulcan-
`ized rubber material B functioning as the dispersed phase is formed by vulcanizing an unvulcanized mass of the rubber
`material B while the unvulcanized mass of the rubber material B is evenly mixed with and dispersed in an unvulcanized
`mass of the rubber material A, and the unvulcanized mass of the rubber material A is vulcanized while the vulcanized
`rubber material B is dispersed in the unvulcanized mass of the rubber material A.
`[0010] The vibration damping rubber member constructed according to the present invention has an island-sea struc-
`ture constituted by the matrix phase consisting of the vulcanized rubber material A which enables the damping rubber
`member to exhibit a low degree of dynamic spring stiffness, and the dispersed phase consisting of the vulcanized
`rubber material B which enables the damping rubber member to have a high vibration damping effect. The present
`vibration damping rubber member is primarily characterized by this island-sea structure which is formed as described
`above. In the island-sea structure, the vulcanized rubber material A functioning as the matrix phase permits a significant
`reduction in the dynamic spring stiffness of the damping rubber member, while the vulcanized rubber material B evenly
`dispersed as fine particles in the matrix phase of the vulcanized rubber material A assures a high vibration damping
`effect of the damping rubber member.
`[0011]
`In essence, the vulcanized rubber material A and the vulcanized rubber material B in the present vibration
`damping rubber member can effectively function, independently of each other, to reduce the dynamic spring stiffness
`and to increase the vibration damping effect, respectively, and at the same time, unlike the conventional rubber com-
`position.
`[0012] Accordingly, the present vibration damping rubber member can be suitably used as vibration damping rubber
`structures for automotive vehicles, and other damping rubber structures in a vibration transmitting system involving
`different kinds of vibrations having different frequencies, and is capable of effectively damping such vibrations..
`[0013]
`In addition, the present vibration damping rubber member does not require such a complicated construction
`as provided in a fluid-filled vibration damping structure, and can therefore be produced economically and comparatively
`easily.
`[0014] According to one preferred form of the vibration damping rubber member of the invention, the vulcanized
`rubber material B consists of fine particles which have an average size of 0.1-100µm and which are dispersed in the
`vulcanized rubber material A. In this case, the vibration damping characteristics are further improved (the dynamic
`spring stiffness is further reduced, and the vibration damping effect is further increased), and the vibration damping
`rubber member is given the desired physical properties.
`[0015] According to another preferred form of the vibration damping rubber member of the invention, the rubber
`material A consists of NR, or a mixture of NR and BR or SBR, and the rubber material B consists of halogenated IIR,
`maleicacid-modified EPM, CR, carboxyl-modified NBR, CSM, CPE, FR or acrylic rubber. In this form of the invention,
`the vibration damping rubber member exhibits further improved vibration damping characteristics.
`[0016] The present invention also provides a vibration damping rubber member having an island-sea structure in
`which fine particles of a vulcanized rubber material B which enables the vibration damping rubber member to have a
`high vibration damping effect are dispersed as a dispersed phase in a matrix phase of a vulcanized rubber material A
`that enables the vibration damping rubber member to exhibit a low degree of dynamic spring stiffness, characterized
`in that the rubber material A is a natural rubber, while the rubber material B is an acrylic rubber, and the rubber materials
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`EP 1 153 973 A1
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`A and B are mixed together in a proportion of 90/10-60/40 by weight, and that the vulcanized rubber material B func-
`tioning as the dispersed phase is formed as fine particles having a size of 0.1-100µm, by vulcanizing an unvulcanized
`mass of the rubber material B while the unvulcanized mass of the rubber material B is evenly mixed with and dispersed
`in an unvulcanized mass of the rubber material A, and the unvulcanized mass of the rubber material A is vulcanized
`while the vulcanized rubber material B is dispersed in the unvulcanized mass of the rubber material A.
`[0017]
`In this vibration damping rubber member according to the present invention, a suitable amount of the vulcan-
`ized acrylic rubber which enables the damping rubber member to have a high vibration damping effect is dispersed as
`a disperse phase in the form of fine particles having a size of 0.1-100µm, in a matrix phase of the natural rubber which
`enables the damping rubber member to exhibit a low degree of dynamic spring stiffness. Accordingly, the present
`vibration damping rubber structure is capable of exhibiting excellent vibration damping characteristics (low dynamic
`spring stiffness and high vibration damping effect). Further, the disperse phase consisting of the acrylic rubber effec-
`tively functions to distribute or reduce the load which acts on the damping rubber, so that the durability of the damping
`rubber member is accordingly increased.
`[0018] The present invention further provides a process of producing a vibration damping rubber member, charac-
`terized by: evenly mixing together an unvulcanized rubber material A which enables the vibration damping rubber
`member to exhibit a low degree of dynamic spring stiffness, an unvulcanized rubber material B which enables the
`vibration damping rubber member to have a high vibration damping effect, and a vulcanizing agent capable of vulcan-
`izing only the unvulcanized rubber material B; heating a mixture of the unvulcanized rubber materials A and B and the
`vulcanizing agent, to vulcanize the unvulcanized rubber material B such that fine particles of the vulcanized rubber
`material B are dispersed in the unvulcanized rubber material A; adding to the mixture a vulcanizing agent capable of
`vulcanizing the unvulcanized rubber material A; and forming a thus obtained mixture into a desired shape, and heating
`the formed mixture to vulcanize the unvulcanized rubber material A, for obtaining the vibration damping rubber member
`having an island-sea structure in which fine particles of the vulcanized rubber material B are dispersed as a dispersed
`phase in a matrix phase of the vulcanized rubber material A.
`[0019] This process according to the present invention permits advantageous formation of the island-sea structure
`in which fine particles of the vulcanized rubber material B which enables the damping rubber member to have a high
`vibration damping effect are evenly dispersed as a dispersed phase in a matrix phase (sea phase) of the vulcanized
`rubber material A which enables the damping rubber member to exhibit a low degree of dynamic spring stiffness. Thus,
`the vibration damping rubber member capable of exhibiting both low dynamic spring stiffness and high vibration damp-
`ing effect can be advantageously produced.
`[0020] The present method makes it possible to comparatively easily and economically produce the vibration damp-
`ing rubber member having excellent damping characteristics as described above.
`[0021]
`In one preferred form of the process of the present invention, the unvulcanized rubber material A is evenly
`mixed with the rubber material B to which the vulcanizing agent capable of vulcanizing only the unvulcanized rubber
`material has been mixed with the unvulcanized rubber material. In this instance, the time required to mix the rubber
`material A, the rubber material B and the vulcanizing agent capable of vulcanizing only the rubber material B can be
`effectively shortened, and the rubber material B and the vulcanizing agent can be more evenly or uniformly dispersed
`within the rubber material A, so that the vibration damping effect of the damping rubber member can be further effectively
`increased.
`[0022]
`In another preferred form of the process of the invention, wherein the unvulcanized rubber material A is vul-
`canized by a sulfur-based vulcanizing system, while the unvulcanized rubber material B is vulcanized by a resin-based
`vulcanizing system, a metal-oxide-based vulcanizing system or an amine-based vulcanizing system. In this process,
`the rubber materials A and B are vulcanized by the respective different vulcanizing systems, making it possible to
`permit the produced damping rubber member to have the island-sea structure which exhibits further improved vibration
`damping characteristics.
`[0023] The present inventors considered the application of the above-indicated island-sea structure to a vibration
`damping rubber member which is formed of a diene-based rubber composition such as an NR-based rubber compo-
`sition and which has a loss factor tanδ of at least 0.1. The loss factor represents the damping effect with respect input
`vibrations having low frequencies (e.g., 15Hz). The inventors found that the use of a rubber material of functional group-
`vulcanization type as the dispersed phase of the island-sea structure makes it possible to obtain a vibration damping
`rubber member whose dynamic/static ratio of spring constant is considerably lower than that of the vibration damping
`rubber member formed solely of the vulcanized diene-based rubber composition.
`[0024] Accordingly, the present invention which was made also on the basis of the above-indicating finding has a
`second object of reducing the dynamic/static ratio of spring constant of a vibration damping rubber member which has
`a high vibration damping effect as represented by a loss factor tanδ of at least 0.1, in particular, providing a process
`suitable for producing a vibration damping rubber member capable of exhibiting both a high vibration damping effect
`and a low degree of dynamic spring stiffness.
`[0025] The second object indicated above may also be achieved according to the present invention, which provides
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`Case 1:17-cv-00770-JDW-MPT Document 121-16 Filed 11/17/22 Page 6 of 30 PageID #:
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`EP 1 153 973 A1
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`a process of producing a vibration damping rubber member having a desired shape, and a low degree of dynamic/
`static ratio of spring constant and a high vibration damping effect, by vulcanizing and forming a rubber composition
`which includes a diene-based rubber material as a rubber component and which enables the vulcanized and formed
`rubber composition to have a loss factor tanδ of at least 0.1, characterized in that a portion of the diene-based rubber
`material is replaced by not greater than 40% by weight of a rubber material of functional group-vulcanization type per
`100% by weight of a total amount of these two rubber materials, and the two rubber materials and a vulcanizing agent
`capable of vulcanizing only the rubber material of functional group-vulcanization type are evenly mixed together to
`form a mixture, which is heated to vulcanize the rubber material of functional group-vulcanization type such that fine
`particles of the vulcanized rubber material of functional group-vulcanization type are dispersed in the diene-based
`rubber material, and wherein a vulcanizing agent capable of vulcanizing the diene-based rubber material A is added
`to the mixture, and a thus obtained mixture is formed into a desired shape and heated to vulcanize the diene-based
`rubber material A, for obtaining the vibration damping rubber member such that the vibration damping rubber member
`has an islands-sea structure in which fine particles of the rubber material of functional group-vulcanization type are
`dispersed as a dispersed phase in a matrix phase of the diene-based rubber material and which has the low degree
`of dynamic/static ratio of spring constant.
`[0026]
`In the present process of the invention of producing a vibration damping rubber member using a diene-based
`rubber material which has a loss factor tanδ of at least 0.1, a portion of the diene-based rubber material is replaced by
`not greater than 40% by weight of the rubber material of functional group-vulcanization type per 100% by weight of a
`total amount of these two rubber materials, so that the vulcanized rubber material of functional group-vulcanization
`type constitutes the dispersed phase of the island-sea structure. In the present process, this island-sea structure is
`formed as described above. The dynamic/static ratio of spring constant of the vibration damping rubber member pro-
`duced according to this process is considerably lower than that of a vibration damping rubber member formed solely
`of the dine-based rubber material, with respect to input vibrations having relatively high frequencies.
`[0027] According to the present process of the invention of producing a vibration damping rubber member having
`low dynamic/static ratio of spring constant and high damping effect, the produced damping rubber member is given
`the island-sea structure, so that the vibration damping characteristics of the damping rubber member are considerably
`improved (with reduced dynamic spring stiffness and increased vibration damping effect) than those of a vibration
`damping rubber structure formed of an intimate mixture of two rubber materials which respectively give desired different
`characteristics. The island-sea structure is further effective to improve the other physical properties required by the
`vibration damping rubber member. Thus, the present process permits advantageous manufacture of a vibration damp-
`ing rubber member capable of exhibiting a significantly reduced dynamic/static ratio of spring constant and a high
`vibration damping effect, as well as assuring various physical properties required by the vibration damping rubber
`member.
`[0028] According to one preferred form of the present process, the rubber material of functional group-vulcanization
`type is halogenated IIR. The use of the halogenated IIR further improves the vibration damping characteristics of the
`damping rubber member, that is, further reduced dynamic spring stiffness and further increased vibration damping
`effect.
`[0029] According to another preferred form of the present process, the vulcanized rubber material of functional group-
`vulcanization type is dispersed in the form of fine particles having an average size of 0.1-100µm in the vulcanized
`diene-based rubber material. In this case, the vibration damping characteristics and other required physical properties
`of the damping rubber member are further improved.
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`Fig. 1 is a graph indicating a relationship between a dynamic/static ratio of spring constant and a loss factor, which
`relationship was obtained in Example 1.
`Fig. 2 is a graph indicating a tensile strength and a breaking elongation at different values of blending ratio of
`natural rubber and chlorinated butyl rubber, which were obtained in Example 1.
`Fig. 3 is a graph indicating a relationship between the dynamic/static ratio of spring constant and the loss factor
`tan δ, which relationship was obtained in Example 3.
`
`BEST MODE FOR CARRYING OUT THE INVENTION
`
`[0031] The vibration damping rubber member according to the present invention as described above is formed using
`a rubber composition consisting of a rubber material A for reducing the dynamic spring stiffness f the damping rubber
`and a rubber composition B for increasing the damping effect. Described in detail, an unvulcanized mass of the rubber
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`EP 1 153 973 A1
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`material A and an unvulcanized mass of the rubber material B are initially uniformly kneaded or mixed together, such
`that the unvulcanized rubber material B is dispersed in the form of fine particles in the unvulcanized rubber material
`A. Then, the rubber material B is vulcanized, and the rubber material A is subsequently vulcanized, so that the vibration
`damping rubber member consisting of the vulcanized rubber materials A and B is formed. This is a major feature of
`the present invention.
`[0032] Namely, the vibration damping rubber member produced by the process of the present invention having the
`above-described feature is not a structure formed of an intimate mixture of the vulcanized rubber materials A and B,
`but is a so-called "island-sea" structure in which fine particles of the vulcanized rubber material B are highly uniformly
`or evenly dispersed as a dispersed or discontinuous phase in a matrix phase of the vulcanized rubber material A. In
`this island-sea structure, the matrix phase of the vulcanized rubber material A assures a sufficiently low degree of
`dynamic spring stiffness of the damping rubber member, while the dispersed phase of the vulcanized rubber material
`B assures a sufficiently high vibration damping effect of the damping rubber member.
`[0033]
`In essence, the vulcanized rubber material A and the vulcanized rubber material B of the vibration damping
`rubber member according to this invention have respective distinct functions of improving the dynamic spring stiffness
`characteristic and the vibration damping characteristic, and are capable of achieving these two functions with high
`efficiency. In other words, the use of the vulcanized rubber materials A and B advantageously permits reduction of the
`dynamic spring stiffness and increase of the vibration damping effect, which have been incompatible with each other.
`[0034] The rubber material A used as the matrix phase for the vibration damping rubber member according to the
`present invention may be selected as needed, depending upon the desired characteristics of the damping rubber
`member, from among various known kinds of rubber material that permits effective reduction of the dynamic spring
`stiffness with respect to vibrations of relatively high frequencies in particular, after vulcanization of the rubber material.
`For instance, the rubber material A may be selected from diene-based rubber materials such as natural rubber (NR),
`isoprene rubber (IR), butadiene rubber (BR), stylene butadiene rubber (SBR) and acrylonitrile butadiene rubber (NBR).
`Preferably, the rubber material A is selected according to the present invention, from among rubber materials (here-
`inafter referred to as "NR-based materials") which include NR as an essential component, for example, from among
`NR, mixtures of NR and BR, and mixtures of NR and SBR, in order to assure efficient reduction of the dynamic spring
`stiffness of the vibration damping rubber member.
`[0035] On the other hand, the rubber material B used as the dispersed phase is required to exhibit a high vibration
`damping effect with respect to vibrations of relatively low frequencies in particular, after vulcanization of the rubber
`material, and is further required to be vulcanized with a vulcanizing system that is different to that of the rubber material
`A. Accordingly, the rubber material B is selected as needed, depending upon the desired characteristics of the damping
`rubber member, from among various rubber materials which are known to be effective to improve the vibration damping
`characteristic and which satisfies the above-indicated requirement regarding the vulcanizing system. Where the rubber
`material A is selected from among the NR-based rubber materials as described above, for instance, the rubber material
`B are particularly preferably selected from among: chlorinated butyl rubbers such as halogenated butyl rubber (halo-
`genated IIR); maleicacid-modified ethylene propylene rubber (maleicacid-modified EPM); chloroprene rubber (CR);
`carboxyl-modified nitrile rubber (carboxyl-modified NBR); chlorosulfonated polyethylene (CSM); fluororubber (FR);
`chlorinated polyethylene (CPE); and acrylic rubber. The rubber materials B indicated above by way of example are all
`effective to reduce the dynamic spring stiffness after the vulcanization, and can be vulcanized with a vulcanizing system
`different from that of the NR-based rubber materials, as described below. Further, those rubber materials B permit
`effective improvements of various characteristics of the vibration damping structure, such as gas permeability resist-
`ance, weather resistance, heat resistance, ozone resistance, chemical resistance, and durability, as indicated in the
`following Table 1. Even where those rubber materials B have a structure in which cross linking of functional groups
`takes place, such rubber materials B are recognized as rubber materials of functional group-vulcanization type.
`
` <TABLE 1>
`
`Rubber Material B
`
`Given Characteristics
`
`Halogenated IIR
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`Gas permeability resistance
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`Maleicacid-modified EPM Resistances to weather, heat and ozone
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`CR
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`Resistances to heat, oil, ozone and gas permeability
`
`Carboxyl-modified NBR
`
`Resistances to oil, gas permeability, heat and ozone
`
`CSM
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`FR
`
`Resistances to weather, ozone, chemicals, heat and gas permeability, and durability
`
`Resistances to heat, oil, chemicals, gas permeability, and durability
`
`Acrylic rubber
`
`Resistances to weather, heat, oil, ozone and gas permeability, and durability
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`EP 1 153 973 A1
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` <TABLE 1> (continued)
`
`Rubber Material B
`
`Given Characteristics
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`CPE
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`Durability and ozone resistance
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`[0036] Acrylic rubber used as the rubber material A may be selected as needed, depending upon the desired char-
`acteristics of the damping rubber member, from among any known synthetic rubber materials whose major component
`is acrylic acid alkyl ester. In particular, it is preferable to use acrylic rubber materials which can be vulcanized with an
`amine-based vulcanizing system which will be described. For instance, it is preferable to use a copolymer (ACM) of
`acrylic acid alkyl ester and 2-chloroethyl vinyl ether, a copolymer (ANM) of acrylic acid alkyl ester and acrylonitrile, and
`a copolymer of acrylic acid alkyl ester and ethylene. The use of such acrylic rubber materials advantageously permits
`an increase of the durability of the vibration damping rubber member.
`[0037] The process of producing a vibration damping rubber member having a low dynamic/static ratio of spring
`constant and a high vibration damping effect according to the present invention is applied to a rubber composition
`whose major component is a diene-based rubber material (rubber material A), wh