JP2004250685A - Heat-resistant rubber vibration isolator composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-resistant rubber vibration isolator composition using excellent heat-resistant ethylene-propylene-diene rubber materials securing excellent heat and aging resistant properties under elevated temperatures together with improved low dynamic-to-static modulus ratio and milling processability. <P>SOLUTION: The heat-resistant rubber vibration isolator composition is composed of blending an ethylene-propylene-diene rubber material with Mooney viscosity (ML<SB>1+4</SB>:125°C, oil extension rate: 40 phr) of 70 or over and a natural rubber material at combining ratios of 90/10 to 50/50 (weight ratio) and combining 100 weight parts of the blended product and 20-80 weight parts of silica powder with BET specific surface area of 20-70 m<SP>2</SP>/g and further combining a silane coupling agent. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a heat-resistant anti-vibration rubber composition, and particularly to an anti-vibration rubber composition containing an ethylene-propylene-diene-based rubber (EPDM) material as a main component, in addition to its heat aging resistance and improvement in high-temperature physical properties. The present invention relates to a technique capable of achieving excellent dynamic characteristics.

  2. Description of the Related Art Conventionally, in automobiles and railway vehicles, various types of anti-vibration rubber are interposed between two members constituting a vibration or impact transmission system in order to prevent transmission of vibration and impact to rigid components. , Has been used.

  By the way, natural rubber (NR) or styrene-butadiene rubber (SBR) for such anti-vibration rubber, for example, an engine mount of an automobile, is excellent in anti-vibration characteristics and durability. Alternatively, an NR blend in which a synthetic rubber such as butadiene rubber (BR) is blended is mainly used.

  On the other hand, in recent years, there has been a growing demand for automobiles to reduce fuel consumption, reduce outside noise, or comply with exhaust gas regulations, and accordingly, the thermal environment in an engine room becomes severer. There is a tendency for the temperature inside the engine room to be higher than ever before, and anti-vibration rubbers used for engine mounts and the like have been used in such high-temperature environments. For this reason, such anti-vibration rubber to be installed in or near the engine room is required to maintain particularly excellent heat resistance (heat aging resistance) and excellent physical properties in a high-temperature atmosphere. However, in the conventional anti-vibration rubber in which the NR or the NR blend is used as a raw rubber as described above, the main raw material NR is weak to heat, and when exposed to a high temperature, the physical properties deteriorate. Therefore, it is extremely difficult to realize excellent heat resistance and high-temperature physical properties because of its drawbacks such as the occurrence of heat and settling phenomena.

  Therefore, in recent years, instead of natural rubber (NR), which has been conventionally used as a rubber material because of its excellent durability and vibration-proof properties, ethylene-ethylene rubber, which is known as a highly heat-resistant rubber material, has been used. Various studies have been made on a vibration-proof rubber composition or a vibration-proof rubber using a synthetic rubber such as a propylene-diene rubber (EPDM).

  However, although EPDM materials have excellent heat resistance, they have poor fatigue resistance due to their low molecular weight, etc., have high dynamic magnification, and have the durability required for vibration-proof rubber. It has been very difficult to achieve sufficient anti-vibration characteristics. In order to reduce the dynamic magnification and improve the durability of an anti-vibration rubber made of EPDM material, for example, the EPDM material may be made to have a high molecular weight within a range that does not adversely affect the kneading processability (patented). Various methods have been proposed, such as blending high-structure carbon black as a reinforcing agent (see Patent Document 2). However, all of these methods use conventional NR-based materials. The durability and the dynamic magnification are not always sufficient as compared with the anti-vibration rubber used as the raw rubber, and therefore, there are still problems inherent in that the sufficient anti-vibration effect cannot be exhibited. That is the fact.

JP-A-7-268147 JP-A-3-227343

  Here, the present invention has been made in view of such circumstances, and a problem to be solved is to provide a heat-resistant vibration-proof rubber using an ethylene-propylene-diene rubber material having excellent heat resistance. In the composition, while achieving the heat aging resistance and the excellent physical properties in a high-temperature atmosphere, which were not realized by the conventional heat-resistant vibration-isolating rubber composition, the lowering of the dynamic magnification and the improvement of the kneading processability are advantageously achieved. It is to provide a rubber composition to be obtained.

  The inventors of the present invention have conducted intensive studies to solve such problems, and as a result, knead the rubber by blending a natural rubber (NR) material with an ethylene-propylene-diene rubber (EPDM) material. It has been found that by improving the processability, it is possible to increase the molecular weight of such an EPDM material, thereby further improving the high-temperature properties and, in addition, lowering the dynamic magnification. Generally used carbon black has a low affinity or interaction with EPDM materials, so that the dynamic magnification is increased by friction between the EPDM materials and carbon black. In view of the above, silica is used instead of such carbon black, and the silica is chemically bonded to the EPDM material using a silane coupling agent. By this, it has been found that the affinity between the reinforcing agent and the EPDM material can be improved and a low dynamic magnification can be effectively achieved. Further, among such silicas, in particular, the BET specific surface area is relatively high. It has been found that by using a small material, it is possible to further reduce the dynamic magnification, and furthermore, the heat aging resistance of various physical properties can be significantly improved as compared with the case where a natural rubber material is used. It was.

Therefore, the present invention has been completed on the basis of these findings, and the gist of the present invention is that the Mooney viscosity (ML _{1 + 4} : 125 ° C., oil extension amount: 40 phr) together with the natural rubber material. While using an ethylene-propylene-diene rubber material of 70 or more, the ethylene-propylene-diene rubber material and the natural rubber material are blended in a mixing ratio (weight ratio) of 90/10 to 50/50. A silica powder having a BET specific surface area of 20 to 70 m ² / g is blended at a ratio of 20 to 80 parts by weight with respect to 100 parts by weight of the blend, and at least one silane coupling agent is further blended. A heat-resistant vibration-proof rubber composition characterized in that:

  According to one preferred embodiment of the heat-resistant anti-vibration rubber composition according to the present invention, as the silane coupling agent, a sulfur-containing silane coupling agent and a mercapto-type silane coupling agent are combined, The silane coupling agent used is generally used alone or, when used in combination, in a proportion of 1 to 10% by weight of the silica powder in each case. It becomes.

  In the rubber composition according to the present invention, a physical property in a high-temperature atmosphere (high-temperature physical properties) is obtained by using a blend of an EPDM material and an NR material in a predetermined ratio. ) Can be effectively improved, and the blending of the NR material allows the EPDM material to have a high molecular weight as the kneading processability is improved, thereby increasing the high Mooney viscosity. By using the EPDM material, the high-temperature physical properties (durability) can be further improved, and in addition, a lower dynamic magnification can be achieved.

  In the rubber composition according to the present invention, a silica powder having a small BET specific surface area is blended and contained in a predetermined ratio with respect to a blend of the EPDM material and the NR material. Since a silane coupling agent for chemically bonding with the material is compounded and contained, the vibration-proof rubber obtained by vulcanizing such a rubber composition is not heat-resistant due to the EPDM material. In addition to the characteristics, a low dynamic magnification can be advantageously achieved, and excellent vibration isolation characteristics can be realized.

  As described above, in the heat and vibration proof rubber composition according to the present invention, high heat resistance (heat aging characteristics) is advantageously ensured, while low dynamic vibration cannot be realized by the conventional heat and vibration proof rubber composition. Magnification and improvement in high-temperature physical properties can be realized at the same time, and thereby, such a rubber composition for heat-resistant anti-vibration rubber is used as a constituent material of various automotive anti-vibration rubbers including engine mounts. In particular, it can be used suitably.

  The ethylene-propylene-diene-based rubber (EPDM) material used as a main component in such a vibration-proof rubber composition according to the present invention is not particularly limited, and a conventionally known ethylene-propylene The diene terpolymer can be used as such. For example, as the third component (diene component) in the EPDM material, various conventionally known components, for example, 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 2,5-dimethyl- 1,5-hexadiene, 1,4-octadiene, 1,4-cyclohexadiene, cyclooctadiene, dicyclopentadiene, 5-ethylidene-2-norbornene, 5-butylidene-2-norbornene, 2-methallyl-5-norbornene , 2-isopropenyl-5-norbornene, etc., and any of them can be employed. Further, even in the composition ratio of the ethylene component, the propylene component, the diene component in the EPDM material, It is not limited at all, and can be appropriately determined according to the required characteristics of the rubber composition and the like.

Among these EPDM materials, those having a particularly high molecular weight, in other words, a Mooney viscosity (ML _{1 + 4} : 125 ° C.) having an oil extension amount of 40 phr (40 parts by weight of oil per 100 parts by weight of polymer) In the present invention, those which are 70 or more are used in the present invention, thereby further improving the high-temperature physical properties (durability), and further reducing the It is also possible to increase the magnification. On the other hand, when an EPDM material having such a Mooney viscosity (ML _{1 + 4} : 125 ° C., oil extension amount: 40 phr) smaller than 70 is used, the kinematic magnification becomes high, and a high temperature atmosphere is required. Are low in physical properties, and the object of the present invention cannot be sufficiently achieved.

Further, as is well known, the Mooney viscosity (ML _{1 + 4} : 125 ° C.) of the EPDM material is such that the oil extension amount is 40 phr according to the unvulcanized rubber physical test method specified in JIS-K-6300. The EPDM material of the present invention is expressed as Mooney viscosity using an L-shaped rotor, preheat time: 1 minute, rotor operation time: 4 minutes, test temperature: 125 ° C. In the use of such a high molecular weight EPDM material having a Mooney viscosity of 70 or more, such a high molecular weight EPDM material can be appropriately selected, for example, Sumitomo Chemical Co., Ltd. Company products such as Esplen 601F and Esplen 606F can be mentioned.

  In the present invention, a natural rubber (NR) material is blended at a predetermined ratio with such a high Mooney viscosity EPDM material, and the blend is used as a rubber material to obtain a desired rubber composition. The high-temperature properties (durability) of the rubber composition and, finally, the vibration-proof rubber that is the final product can be effectively improved by blending such NR materials. . That is, since the kneadability of the rubber composition can be improved by such a blend of the NR material, an EPDM material having a high molecular weight (high Mooney viscosity) can be used, thereby further increasing the high-temperature physical properties (durability). ), As well as a lower dynamic magnification.

  Here, the compounding ratio (weight ratio) of the EPDM material having a high Mooney viscosity and the NR material is selected within a range of EPDM / NR = 90/10 to 50/50, thereby achieving the object of the present invention. Can be advantageously realized. If the compounding ratio of the NR material is less than 10 parts by weight in 100 parts by weight of the blend, there arises a problem that the effect of improving the high-temperature properties is not recognized, and if it exceeds 50 parts by weight, This causes problems such as deterioration of heat resistance and deterioration of physical properties after heat aging.

By the way, even in the rubber composition according to the present invention, in order to realize the physical properties and vibration characteristics required for the vibration-proof rubber, a reinforcing agent or a filler is compounded and contained as in the conventional case. However, as described above, the blend of the EPDM material and the NR material, particularly the EPDM material, has a low affinity for carbon black, and the friction between the rubber material (EPDM material) and carbon black is low. As a result, the dynamic magnification (= Kd ₁₀₀ / Ks), which is the ratio between the dynamic spring constant (Kd ₁₀₀ ) and the static spring constant (Ks) at ₁₀₀ Hz, is increased. Since the low dynamic spring characteristics required for inputting vibration in a relatively high frequency range cannot be secured, the rubber composition for a vibration-isolating rubber is conventionally used as a reinforcing agent. Instead of carbon black which is generally added, silica powder is used, and the silica powder is chemically bonded to a rubber material (EPDM material) with a silane coupling agent. Thereby, the familiarity between the reinforcing agent and the rubber material is remarkably improved, and the low dynamic magnification of the anti-vibration rubber can be achieved.

Here, as the above-mentioned silica powder, various sizes are commercially available. As the particle size of the silica powder is larger, in other words, as the BET specific surface area is smaller, the lower the dynamic magnification, the lower the dynamic magnification. In order to obtain a desired dynamic magnification, the present invention requires that the BET specific surface area be relatively small and in the range of ²⁰ to 70 m ² / g. . However, if the BET specific surface area is less than 20 m ² / g, the particles become too large, causing problems in mixing with the rubber material, and the production thereof is also difficult. This is because if the surface area exceeds 70 m ² / g, the dynamic magnification increases and the desired vibration-proofing properties cannot be obtained.

  The BET specific surface area of the silica powder can be determined by the method of “D method: flow specific surface area automatic measurement” of “7. Nitrogen adsorption specific surface area” in “Test method of basic performance of carbon black for rubber” of JIS-K-6217-1997. Method using a measuring apparatus 2300 ”.

  Further, in the rubber composition according to the present invention, it is necessary that the silica powder as described above is blended in a proportion of 20 to 80 parts by weight with respect to 100 parts by weight of the blend of the EPDM material and the NR material. There is. This is because if the compounding amount is less than 20 parts by weight, the reinforcing effect by the silica powder cannot be sufficiently obtained, and improvement in physical properties such as durability cannot be expected. If the amount is too large, the dynamic magnification becomes extremely high, and the Mooney viscosity increases due to the aggregation of the silica powder, and the kneading processability deteriorates. Therefore, the compounding ratio of the silica powder must satisfy the above-mentioned range, and within such a range, more preferably, 30 to 50 parts by weight with respect to 100 parts by weight of the blend. Desirably.

  On the other hand, in the present invention, as the silane coupling agent that binds the silica powder and the rubber material as described above, at least one or more of various types of silane coupling agents conventionally known are appropriately selected. Will be used. And, as such a silane coupling agent, for example, γ-chloropropyltrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ -Aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, N-β- (aminoethyl) -β -Aminopropylmethy It can be exemplified dimethoxy silane.

  Thus, in the present invention, among such silane coupling agents, in particular, a sulfur-containing silane coupling agent having sulfur (—S—) bonded to two atoms other than a hydrogen atom, It is desirable to use both mercapto-based silane coupling agents having a mercapto group (-SH) in combination, and the combined use of these two silane coupling agents effectively improves the dynamic magnification, and further improves the durability and resistance. It is possible to secure physical properties such as settling property to a sufficiently high level, which is not inferior to that obtained by using a conventional NR material as a rubber raw material.

Here, as described above, the silane coupling agent advantageously employed in the present invention is not particularly limited as long as it has a sulfur divalent group (-S-) or a mercapto group (-SH). Instead, one or more kinds of conventionally known various sulfur-containing silane coupling agents and mercapto-based silane coupling agents are appropriately selected and used in combination. For example, as the sulfur-containing silane coupling agent, 4,4,13,13-tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disila-hexadecane, 4,4,15, 15-tetraethoxy-3,16-dioxa-8,9,10,11-tetrathia-4,15-disila-octadecane, γ-trimethoxysilylpropyldimethylthiocarbamyltetrasulfide, γ-trimethoxysilylpropyl benzothia While polysulfides such as zyltetrasulfide can be exemplified, examples of the mercapto-based silane coupling agent include, for example, γ-mercaptopropyltrimethoxysilane represented by the following formula 1. .
[Formula 1]
(RO) ₃ SiC _n H _2n SH
[However, R is a methyl group or an ethyl group, and n is an integer of 1-8. ]

  The sulfur-containing silane coupling agent and the mercapto silane coupling agent are blended in a weight ratio of 1: 9 to 9: 1, more preferably 2: 8 to 8: 2. Therefore, the synergistic effect of the combined use of the sulfur-containing silane coupling agent and the mercapto-type silane coupling agent can be extremely advantageously exerted.

  And when the silane coupling agent as described above is used alone, in a single compounding amount thereof, and when used in combination, in a compounding amount of each silane coupling agent, It is desirable that the silica powder is added at a ratio of about 1 to 10% by weight, more preferably about 2 to 5% by weight, based on the amount of the silica powder. However, if the compounding ratio is too large, the physical properties deteriorate, and if it is too small, the effect of adding the silane coupling agent cannot be obtained.

  The above-mentioned silane coupling agent is usually coated on silica powder having a predetermined BET specific surface area as described above, and the coated silica powder is dispersed and contained, whereby the heat-resistant protection according to the present invention is achieved. A vibration-proof rubber composition is prepared, and then the rubber composition thus prepared is vulcanized to produce a vibration-proof rubber having excellent heat resistance. As the vulcanizing agent (crosslinking agent) to be compounded prior to vulcanization of the vulcanized rubber composition, any vulcanizing agent that can promote the vulcanization reaction of the rubber material can be used. The appropriate vulcanizing agent is selected from various known vulcanizing agents and used in an amount corresponding to the amount of the rubber material used. The vulcanizing agents include dicumyl peroxide, di-t-butylperoxydiisopropylbenzene, n-butyl-4,4-bis (t-butylperoxy) valerate, and t-butylcumyl peroxide. And the like.

  Further, the rubber composition according to the present invention may further include, if necessary, a vulcanization accelerator or a crosslinking aid, a softening agent such as a paraffin oil, an antioxidant, a plasticizer, a stabilizer, a processing aid, a coloring agent. Any known rubber compounding agent such as an agent may be mixed at all without departing from the purpose of the present invention.

  By the way, the above-mentioned predetermined silica powder, silane coupling agent and other necessary rubber compounding agents are compounded into a blend (rubber material) of an EPDM material and an NR material, and the heat-resistant anti-vibration rubber according to the present invention is obtained. In preparing a rubber composition for use, a conventionally known method can be adopted.For example, using a known kneading device such as a kneader, a Banbury mixer, a roll machine, or the like, the unkneaded material is added to such a device. It is prepared by introducing a rubber material for sulfuric acid, silica powder coated with a predetermined coupling agent, and various other necessary rubber compounding agents, followed by kneading.

  Then, the rubber composition thus obtained is heated to a predetermined temperature, and the rubber material in the rubber composition is vulcanized, whereby a vibration-proof rubber excellent in heat resistance is manufactured. Further, the vibration-proof rubber thus obtained is used as a rubber vibration-proof rubber for various automobiles such as an engine mount, a strut mount, a strut bar cushion, a suspension bush, etc. It is advantageously used as an anti-vibration rubber for a vehicle such as a mount.

  Hereinafter, some examples of the present invention will be shown to clarify the present invention more specifically. However, the present invention is not limited by the description of such examples. That goes without saying. In addition, in addition to the following examples, the present invention may further include various changes and modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention, in addition to the above specific description. , Improvements and the like can be added.

First, as a rubber material, two types of unvulcanized EPDM materials having different Mooney viscosities (ML _{1 + 4} : 125 ° C.) at an oil extension of 40 phr were prepared together with an unvulcanized NR material. Among the two types of EPDM materials, EPDM-A is an Esplen 673 product manufactured by Sumitomo Chemical Co., Ltd., having a Mooney viscosity (ML _{1 + 4} : 125 ° C., oil extension: 40 phr) of 60, and EPDM-B is And Espney 606F manufactured by Sumitomo Chemical Co., Ltd., having a Mooney viscosity of 82 (ML _{1 + 4} : 125 ° C., oil extension: 40 phr). Further, as the silica powder, four types of silica powders a to d having an average value of the BET specific surface area (m ² / g) shown in Table 1 below are prepared, and further as a silane coupling agent. Three kinds of silane coupling agents A to C as shown in Table 2 below were prepared.

  Then, while EPDM-A is used as the EPDM material, silica powders a to d, a silane coupling agent (A), a softener and a crosslinking agent are combined with 100 parts by weight of the EPDM-A as shown in Table 3 below. Various rubber compositions were prepared by mixing according to a conventional method so as to obtain the ratios. Note that dicumyl peroxide (DCP) was used as a cross-linking agent, and paraffin oil was used as a softening agent.

  Next, the obtained various rubber compositions are vulcanized and molded under the vulcanization conditions of 170 ° C. × 30 minutes to vulcanize the EPDM material, thereby obtaining a tensile test, a hardness test and a dynamic test. Various test pieces for the property test were prepared, and the following various evaluation tests were performed using the obtained test pieces.

−Tensile test−
A dumbbell-shaped No. 5 type test piece specified in “Method for tensile test of vulcanized rubber” of JIS-K-6251-1993 was used as a test piece for a tensile test, and this was used as a test piece for the same JIS-K-6251-1993. According to the test method specified in "Tensile test method for vulcanized rubber", the test piece is pulled by a predetermined tensile tester until the test piece is cut, and the maximum stress (breaking strength) until the test piece is cut, and The elongation at break (elongation at break) was measured, and the results are shown in Table 3 below as initial physical properties.

-Hardness test-
As a test piece for the hardness test, a test piece having a thickness of 6 mm, which is defined in “Durometer hardness test” in “Hardness test method for vulcanized rubber and thermoplastic rubber” of JIS-K-6253-1997. The test piece was manufactured and the hardness (hardness) of the test piece was measured with a type A durometer in accordance with the “durometer hardness test” also specified in JIS-K-6253-1997. Are also shown.

-Dynamic characteristic test-
A test piece for a dynamic characteristic test was prepared by preparing a rubber vulcanizate having a cylindrical shape with a diameter of 50 mm and a height of 25 mm, and then with respect to the upper and lower surfaces of the vulcanized rubber sample, a diameter of 60 mm and a thickness of: A pair of 6 mm disk-shaped metal fittings was produced by vulcanizing and bonding with an adhesive. Then, using each of the test pieces thus obtained, a static spring constant: Ks and a dynamic spring constant: Kd are determined according to JIS-K-6385-1995 “Testing method for anti-vibration rubber”. I asked. That is, in accordance with the “static property test” in “Testing method of anti-vibration rubber” of JIS-K-6385-1995, a load was applied to each test piece in the axial direction, and the test piece was compressed by 7 mm, and once compressed. After the load is reduced, the load-deflection characteristic in the second loading process (outbound path) is measured by compressing again by 7 mm, and a load-deflection curve is created based on the characteristic. The load values when the deflection was 1.5 mm and 3.5 mm were read, respectively, to calculate a static spring constant: Ks.

After compressing each test piece by 2.5 mm in the axial direction, a constant displacement harmonic compression having an amplitude of ± 0.05 mm centered on the position where the test piece is compressed by 2.5 mm from below the compressed test piece. A test was conducted in which vibration was applied at a frequency of 100 Hz, and the dynamic spring constant at 100 Hz (in accordance with “Non-resonant method (a)” in “Testing method of anti-vibration rubber” of JIS-K-6385-1995) Storage spring constant): Kd ₁₀₀ was determined. Then, a dynamic magnification (= Kd ₁₀₀ / Ks) was calculated from the Kd ₁₀₀ and the above Ks, and the results are shown in Table 3 below.

As is evident from the results shown in Table 3, Experiment No. 2 using silica d, which is a silica powder having a BET specific surface area of 20 to 70 m ² / g in the present invention. In the rubber composition of No. 4, Experiment No. 4 using silicas a to c having a large BET specific surface area. It is understood that lower dynamic magnification can be advantageously achieved as compared with the rubber compositions of Nos. 1 to 3.

  Subsequently, as the rubber material, the two types of EPDM materials (A, B) prepared above and the natural rubber (NR) material are used to form a single rubber composition, EPDM material and NR, respectively. Various types of rubber compositions of the material blend system were prepared according to the compounding compositions shown in Table 4 below. In addition, at the time of preparing each rubber composition, the roll processability as a standard of the knead processability was determined, and the results are shown in Table 4 below.

  Then, the obtained various rubber compositions are vulcanized and molded by adopting vulcanization conditions of 170 ° C. × 30 minutes to vulcanize or crosslink the NR material, EPDM material or their blend rubber material. At least, various test pieces for the tensile test, the hardness test and the dynamic characteristic test, which were the same as those described above, were prepared, and the various evaluation tests described above were performed using the obtained test pieces. The results are shown in Table 5 below. The high-temperature physical properties were obtained by performing a tensile test on each test piece in an atmosphere at 120 ° C. to determine the breaking strength and the breaking elongation. The test pieces were subjected to a heat aging test at 120 ° C. for 250 hours, and the test pieces after each heat aging test were subjected to the same tensile test and hardness test as described above. It shows the degree of change in physical properties after the test. Specifically, in the heat resistance in Table 5 below, ΔTB and ΔEB are percentages of their change after the heat aging test with respect to the breaking strength and the elongation at break before the heat aging test, and ΔHs is the heat aging. The differences in hardness before and after the test are respectively shown.

As is clear from the comparison between the results shown in Table 5 and the rubber compounding composition shown in Table 4 above, in the single NR material (No. 5), the rupture strength and elongation at break in heat aging resistance were observed. In addition, it was found that the EPDM material alone (No. 6) having a low Mooney viscosity was inferior in high-temperature properties and insufficient in dynamic magnification (Kd ₁₀₀ / Ks). In the case of a single system using an EPDM material having a high Mooney viscosity (No. 7), there is an inherent problem that, in addition to the decrease in high-temperature properties, the rollability of the rubber composition is poor. I can admit that.

On the other hand, in a system (No. 9, 10, 11) in which a high Mooney viscosity EPDM material (EPDM-B) is blended with an NR material within the range specified in the present invention, In spite of using EPDM material with high Mooney viscosity, roll processability is good, and it has sufficient high-temperature physical properties, as well as breaking strength, breaking elongation, and rubber hardness before and after the heat aging test. It is recognized that the change is small, and therefore, in addition to being excellent in heat aging resistance, the dynamic magnification (Kd ₁₀₀ / Ks) is reduced and the dynamic characteristics are also excellent.

In addition, when the compounding amount of the NR material is small (No. 8), there is a problem that the roll workability is poor and the high-temperature physical properties are insufficient, and further, the compounding ratio of the NR material becomes large. In the case (No. 12), it is recognized that there is a problem that the physical properties after the heat aging test are significantly deteriorated.

Claims (3)

An ethylene-propylene-diene rubber material having a Mooney viscosity (ML _{1 + 4} : 125 ° C., oil extension: 40 phr) of 70 or more is used together with the natural rubber material. While the materials are blended in a blending ratio (weight ratio) of 90/10 to 50/50, a silica powder having a BET specific surface area of 20 to 70 m ² / g is blended in an amount of 20 to 70 m ² / g with respect to 100 parts by weight of the blend. A heat-resistant anti-vibration rubber composition characterized by being blended in an amount of 80 parts by weight and further blended with at least one silane coupling agent.   The heat-resistant anti-vibration rubber composition according to claim 1, wherein a sulfur-containing silane coupling agent and a mercapto silane coupling agent are used in combination as the silane coupling agent. 3. The method according to claim 1, wherein the silane coupling agent is used alone or when used in combination, in each case in a proportion of 1 to 10% by weight of the amount of the silica powder. 4. A heat-resistant anti-vibration rubber composition.