Vibration-proof rubber composition and vibration-proof rubber member for electric vehicle

Abstract

Provided is a vibration-proof rubber composition that can achieve both improved damping characteristics (surging characteristics) against high-frequency vibrations and a lower dynamic magnification.　The vibration-proof rubber composition includes the components (A) to (C), where the component (B) content is 2-10 parts by mass and the component (C) content is 10-100 parts by mass with respect to 100 parts by mass of component (A), and the composition does not include chlorinated butyl rubber. (A) a diene rubber (B) a liquid polymer with a viscosity (at 25°C) of 105 mPa·s or higher (C) an inorganic filler

Description

Vibration-damping rubber composition and vibration-damping rubber component for electric vehicles

[0001] The present invention relates to vibration-damping rubber compositions. More specifically, it relates to vibration-damping rubber compositions and vibration-damping rubber components used for vibration damping applications in electric vehicles (including fuel cell vehicles (FCVs), plug-in hybrid vehicles (PHVs), hybrid vehicles (HVs), etc.) powered by electric motors.

[0002] Generally, vibration-damping rubber compositions are used in automobiles to reduce vibration and noise. Such vibration-damping rubber compositions require high rigidity and strength in their vulcanized bodies (vibration-damping rubber members) and suppression of vibration transmission. Therefore, it is necessary to reduce the dynamic magnification ratio [dynamic spring constant (Kd) / static spring constant (Ks)] (low dynamic magnification ratio). Conventionally, this low dynamic magnification ratio has been addressed, for example, by using carbon black as a reinforcing agent in vibration-damping rubber compositions and controlling factors such as the amount of carbon black, particle size, and structure (see Patent Documents 1-4).

[0003] Japanese Patent Publication No. Hei 8-269236, Japanese Patent Publication No. 2002-241539, Japanese Patent Publication No. 2005-113094, Japanese Patent Publication No. Hei 8-269237

[0004] Unlike conventional vibration-damping rubber components for gasoline vehicles, vibration-damping rubber components for electric vehicles require damping characteristics (surging characteristics) for high-frequency vibrations generated by electric motors. Therefore, vibration-damping rubber components for electric vehicles are required not only to achieve the low dynamic magnification mentioned above, but also to simultaneously improve the damping characteristics (surging characteristics) for high-frequency vibrations and balance the two. However, improving the damping characteristics (surging characteristics) for high-frequency vibrations worsens the dynamic magnification, so there is a trade-off between the two.

[0005] This invention has been made in view of these circumstances, and provides an anti-vibration rubber composition that can improve the damping characteristics (surging characteristics) of high-frequency vibrations while suppressing the deterioration of dynamic magnification.

[0006] The inventors diligently investigated new methods to solve the aforementioned dilemma and, as a result, discovered that by blending a liquid polymer with a specific viscosity or higher with a specific rubber component in a specific ratio, it is possible to improve the damping characteristics (surging characteristics) against high-frequency vibrations while suppressing the deterioration of the dynamic magnification, thus arriving at the present invention.

[0007] In other words, the gist of the present invention is as follows: [1] A vibration-damping rubber composition containing the following components (A) to (C), wherein the content of component (B) is 2 to 10 parts by mass and the content of component (C) is 10 to 100 parts by mass per 100 parts by mass of component (A), and the composition does not contain chlorinated butyl rubber. (A) Diene rubber (B) Viscosity (25°C) is 10 ５ (C) Inorganic filler [2] The above (B) component has a viscosity (25°C) of 10 ５ ~10 ６ [1] The vibration-damping rubber composition according to [1], wherein the (B) component is one or more selected from the group consisting of liquid isoprene rubber, liquid butadiene rubber, and liquid acrylonitrile-butadiene rubber. [4] The vibration-damping rubber composition according to any one of [1] to [3], wherein the (A) component is natural rubber. [5] The vibration-damping rubber composition according to any one of [1] to [4], wherein the (C) component is at least one of carbon black and silica. [6] The (C) component is carbon black, and the nitrogen adsorption specific surface area of ​​the carbon black is 10 to 70 m². ２ A vibration-damping rubber composition according to any one of [1] to [5], wherein the (C) component is silica, and the BET specific surface area of ​​the silica is 30 to 500 m². ２ A vibration-damping rubber composition according to any one of [1] to [6], wherein the amount is / g. [8] A vibration-damping rubber member for electric vehicles comprising a vulcanized body of the vibration-damping rubber composition according to any one of [1] to [7].

[0008] According to the vibration-damping rubber composition of the present invention, it is possible to suppress deterioration of dynamic magnification while improving damping characteristics (surging characteristics) against high-frequency vibrations.

[0009] Embodiments of the present invention will be described in detail. However, the present invention is not limited to these embodiments.

[0010] In this specification, the numerical ranges described in stages can be arbitrarily combined with the upper or lower limits of any numerical range in one stage. Furthermore, in the numerical ranges described herein, the upper or lower limits of those ranges can be replaced with the values ​​shown in the examples. In addition, "X and / or Y (where X and Y are any configuration)" means at least one of X and Y, and can mean X only, Y only, or X and Y.

[0011] One embodiment of the present invention, a vibration-damping rubber composition (hereinafter sometimes referred to as "this vibration-damping rubber composition"), is a vibration-damping rubber composition containing components (A) to (C), wherein the content of component (B) is 2 to 10 parts by mass and the content of component (C) is 10 to 100 parts by mass per 100 parts by mass of component (A), and is characterized by not containing chlorinated butyl rubber. (A) Diene rubber (B) Viscosity (25°C) is 10 ５ Liquid polymers with a pressure of mPa·s or higher (C) Inorganic fillers

[0012] In the present invention, in a vibration-damping rubber composition containing a diene rubber, a liquid polymer, and an inorganic filler, it is important to include a specific amount of a liquid polymer having a specific high viscosity and to omit a specific rubber component. Specifically, (A) diene rubber, (B) viscosity (25°C) 10 ５ The vibration-damping rubber composition contains a liquid polymer with a pressure of mPa·s or higher, and (C) an inorganic filler, wherein the content of component (B) is within a specific range, the content of component (C) is controlled within a specific range, and furthermore, it does not contain chlorinated butyl rubber. If all of these requirements are not met, it becomes difficult to achieve both improved damping characteristics (surging characteristics) for high-frequency vibrations and a low dynamic magnification, and the problems of the present invention cannot be fully solved.

[0013] In other words, among components (A) to (C), if component (B) is not used, or if component (B) is used instead, the viscosity (at 25°C) is 10 ５When a relatively low-viscosity liquid polymer (less than mPa·s) is incorporated, the damping characteristics against high-frequency vibrations become insufficient, and the dynamic magnification is not sufficiently satisfactory. Furthermore, even when components (A) to (C) are incorporated, if the content of component (B) is outside the range of 2 to 10 parts by mass, the dynamic magnification is not sufficiently satisfactory. Moreover, even when component (B) is incorporated in the range of 2 to 10 parts by mass along with components (A) to (C), if chlorinated butyl rubber is incorporated, the dynamic magnification is not sufficiently satisfactory. In order to simultaneously achieve improved damping characteristics (surging characteristics) against high-frequency vibrations and a lower dynamic magnification, it is necessary to satisfy all the requirements of the present invention.

[0014] The following provides a detailed explanation of the constituent materials of this vibration-damping rubber composition.

[0015] [(A) Diene-based rubber] This vibration-damping rubber composition contains (A) diene-based rubber as a rubber component. Examples of (A) diene-based rubber include natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), isoprene rubber (IR), acrylonitrile-butadiene rubber (NBR), ethylene-propylene-diene rubber (EPDM), etc. These can be used alone or in combination of two or more. In this invention, "diene-based rubber" excludes components that fall under (B).

[0016] In this vibration-damping rubber composition, (A) diene rubber is preferred in which natural rubber (NR) is the main component, from the viewpoint of achieving both improved damping characteristics (surging characteristics) for high-frequency vibrations and a lower dynamic magnification. Here, "main component" means that the (A) diene rubber contains 50% by mass or more of natural rubber relative to the total amount (100% by mass), preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90 to 100% by mass, and may also be 100% by mass.

[0017] Further, it is preferable that the present vibration-insulating rubber composition substantially contains no rubber components other than (A) a diene rubber. For example, the content of the rubber component other than (A) the diene rubber is less than 5 parts by mass, preferably less than 3 parts by mass, and more preferably 0 parts by mass, relative to 100 parts by mass of (A) the diene rubber.

[0018] The content of (A) the diene rubber contained in the present vibration-insulating rubber composition is usually 30% by mass or more, preferably 30 to 70% by mass, more preferably 40 to 65% by mass, based on the total mass (100% by mass) of the present vibration-insulating rubber composition. Therefore, in an example of an embodiment of the present invention, the content of natural rubber is usually 30% by mass or more, preferably about 30 to 70% by mass, and more preferably about 40 to 65% by mass, based on the total mass (100% by mass) of the present vibration-insulating rubber composition.

[0019] [(B) Viscosity (25°C) of 10 ５ mPa·s or higher liquid polymer] In the present vibration-insulating rubber composition, it is important to use a liquid polymer having a viscosity (25°C) of 10 ５ mPa·s or higher within a specific range.

[0020] The liquid polymer used in the present vibration-insulating rubber composition is a (co)polymer that is in a liquid state at ordinary temperature (25°C), and has a viscosity (25°C) of 10 ５ mPa·s or higher. For a liquid polymer having a viscosity outside the above range, it becomes difficult to achieve both improvement in damping characteristics (surging characteristics) against high-frequency vibration and reduction in dynamic magnification. From the viewpoint of achieving both improvement in damping characteristics (surging characteristics) against high-frequency vibration and reduction in dynamic magnification, the viscosity of component (B) can be appropriately set within the range of 10 ５ mPa·s or higher. For example, 10 ５ to 10 ８ mPa·s is preferable, more preferably 10 ５ to 10 ７ mPa·s, and still more preferably 10 ５ to 10 ６ mPa·s.

[0021] Further, the viscosity of component (B) is from 1.5×10 ５ to 1.0×10 ８mPa·s is preferred, more preferably 1.5 × 10 ５ to 1.0 × 10 ７ mPa·s, still more preferably 1.5 × 10 ５ to 1.0 × 10 ６ mPa·s. Further, the viscosity of component (B) is 1.8 × 10 ５ to 1.0 × 10 ８ mPa·s, 1.8 × 10 ５ to 1.0 × 10 ７ mPa·s, 1.8 × 10 ５ to 1.0 × 10 ６ mPa·s may also be used. More specifically, for example, 2.0 × 10 ５ to 6.0 × 10 ５ mPa·s, 2.0 × 10 ５ to 4.0 × 10 ５ mPa·s may also be used.

[0022] Note that the above viscosity can be measured using a rheometer (dynamic viscoelasticity measuring device), and for example, it is the viscosity measured under the conditions of a conical plate (angle 1°, diameter 20 mm), normal temperature (25°C), shear rate 1 [1 / s], and measurement time of 300 seconds using an AR2000 rheometer manufactured by TA Instruments.

[0023] It is important that the content of component (B) in the present vibration-isolating rubber composition is in a specific range of 2 to 10 parts by mass based on 100 parts by mass of (A) diene rubber. If the content is outside the above range, it becomes difficult to achieve both improvement in damping characteristics (surging characteristics) against high-frequency vibration and reduction in dynamic magnification. The content of component (B) can be appropriately set within the above range, and may be appropriately set as, for example, 2 to 8 parts by mass, 2 to 6 parts by mass, 2 to 4 parts by mass, etc.

[0024] Among the components (B) used in this vibration-damping rubber composition, liquid rubber is preferred. Specifically, for example, liquid isobutylene rubber (liquid IB), liquid isoprene rubber (liquid IR), liquid butadiene rubber (liquid BR), liquid styrene-isoprene rubber (liquid SI), liquid styrene-butadiene rubber (liquid SBR), liquid isoprene-butadiene rubber (liquid IR-BR), liquid acrylonitrile-butadiene rubber (liquid NBR), liquid styrene-ethylene-propylene rubber (liquid SEP), liquid ethylene-propylene-diene rubber (liquid EPDM), liquid polybutene, etc. are preferred. These can be used alone or in combination of two or more.

[0025] Among these liquid rubbers, one or more selected from the group consisting of liquid isobutylene rubber (liquid IB), liquid isoprene rubber (liquid IR), liquid butadiene rubber (liquid BR), and liquid acrylonitrile-butadiene rubber (liquid NBR) are preferred from the viewpoint of achieving both improved damping characteristics (surging characteristics) against high-frequency vibrations and a lower dynamic magnification. In particular, one or more selected from the group consisting of liquid isoprene rubber (liquid IR), liquid butadiene rubber (liquid BR), and liquid acrylonitrile-butadiene rubber (liquid NBR) are preferred.

[0026] Among the liquid rubbers mentioned above, liquid acrylonitrile-butadiene rubber is particularly preferred from the viewpoint of achieving both improved damping characteristics (surging characteristics) against high-frequency vibrations and a lower dynamic magnification, and especially from the viewpoint of improving damping characteristics (surging characteristics). The amount of acrylonitrile (AN) in the liquid acrylonitrile-butadiene rubber is not particularly limited, but for example it is 25 to 43% by mass, and 28 to 40% by mass is preferred. Note that the liquid acrylonitrile-butadiene rubber (liquid NBR) may also be liquid hydrogenated acrylonitrile-butadiene rubber (liquid HNBR) or liquid carboxylated acrylonitrile-butadiene rubber (liquid XNBR).

[0027] The number average molecular weight (Mn) of the liquid polymer (B) is, for example, preferably 2,000 to 10,000, more preferably 2,000 to 6,000, and still more preferably 2,000 to 4,000. The above number average molecular weight (Mn) is a value measured in accordance with gel permeation chromatography (GPC).

[0028] [(C) Inorganic Filler] The present vibration-damping rubber composition contains (C) an inorganic filler, and it is important to adjust the content thereof to a specific range. Specifically, in the present vibration-damping rubber composition, it is important that the content of component (C) is in the range of 10 to 100 parts by mass relative to 100 parts by mass of (A) a diene rubber. Outside the above range, it tends to be difficult to maintain durability while achieving both improved damping properties against high-frequency vibration (surging properties) and reduced dynamic magnification. The content of component (C) can be appropriately set within the above range, and for example, can be appropriately set within a range such as 20 to 50 parts by mass.

[0029] Specific examples of the (C) inorganic filler include carbon black, silica, calcium carbonate, and the like. These may be used alone or in combination of two or more. Among these, carbon black is preferred from the viewpoint of durability. For example, in one embodiment of the present invention, the content of carbon black is preferably 10 to 100 parts by mass, more preferably 20 to 70 parts by mass, and still more preferably 25 to 60 parts by mass, relative to 100 parts by mass of (A) the diene rubber.

[0030] Examples of carbon black include various grades of carbon black such as SAF grade, ISAF grade, HAF grade, MAF grade, FEF grade, GPF grade, SRF grade, FT grade, and MT grade. These may be used alone or in combination of two or more.

[0031] The nitrogen adsorption specific surface area of carbon black is 10 to 80 m 2 / g, preferably 10 to 70 m 2 / g, more preferably 10 to 45 m 2The value is / g. The specific surface area of ​​nitrogen adsorption of carbon black can be measured according to the method described in JIS K 6217-2.

[0032] Furthermore, in an example of the embodiment of the present invention in which silica is included, the silica content is preferably 10 to 100 parts by mass, more preferably 20 to 70 parts by mass, and even more preferably 30 to 60 parts by mass, per 100 parts by mass of (A) diene rubber.

[0033] Examples of silica include wet silica, dry silica, and colloidal silica. These can be used individually or in combination of two or more types.

[0034] The BET specific surface area of ​​silica is set to 30 to 500 m² from the perspective of achieving both improved damping characteristics (surging characteristics) against high-frequency vibrations and low dynamic magnification. 2 / g is preferred, and more preferably 100 to 300 m 2 The value is / g. The BET specific surface area of ​​silica can be measured, for example, by degassing the sample at 200°C for 15 minutes, and then using a mixed gas (N2: 70%, He: 30%) as the adsorbed gas, with a BET specific surface area analyzer (Microdata Corporation, 4232-II).

[0035] [Chlorinated Butyl Rubber] In this vibration-damping rubber composition, it is important not to include chlorinated butyl rubber in order to achieve both improved damping characteristics (surging characteristics) for high-frequency vibrations and a lower dynamic magnification. If chlorinated butyl rubber is included, it becomes difficult to maintain good dynamic magnification characteristics. In this specification, "not included" means that it has not been intentionally added to this vibration-damping rubber composition. Therefore, for example, if chlorinated butyl rubber is included in trace amounts due to the manufacturing process of raw materials, etc., it is included in the concept of "not included" in this specification. Specifically, for example, if the content of chlorinated butyl rubber is a trace amount such as 0.1 parts by mass or less, 0.01 parts by mass or less, or 0.0001 parts by mass or less per 100 parts by mass of component (A), it is included in "not included". Also, if the content of chlorinated butyl rubber is a trace amount such as 0.1% by mass or less, 0.01% by mass or less, or 0.0001% by mass or less per 100 parts by mass of the total amount of this rubber composition (100% by mass), it is included in "not included".

[0036] Furthermore, in one example of the embodiments of this vibration-damping rubber composition, it is preferable not to contain halogenated butyl rubber, and more preferable not to contain butyl rubber. Specifically, for example, it is preferable not to contain brominated butyl rubber, butyl rubber, or partially crosslinked butyl rubber.

[0037] [Other components] In addition, this vibration-damping rubber composition may also contain, as needed, vulcanizing agents, vulcanization accelerators, vulcanization aids, anti-aging agents, process oils, silane coupling agents, etc., along with the components (A) to (C) above.

[0038] Examples of vulcanizing agents include sulfur (powdered sulfur, precipitated sulfur, insoluble sulfur), sulfur-containing compounds such as alkylphenol disulfide, etc. These can be used alone or in combination of two or more. The content of the vulcanizing agent is preferably 0.1 to 10 parts by mass, and more preferably 0.1 to 4 parts by mass, per 100 parts by mass of (A) diene rubber.

[0039] Examples of vulcanization accelerators include thiram-based, sulfenamide-based, guanidine-based, thiazole-based, aldehyde ammonia-based, aldehyde amine-based, and thiourea-based vulcanization accelerators. These can be used alone or in combination of two or more. The content of the vulcanization accelerator is preferably 0.1 to 10 parts by mass, and more preferably 0.1 to 6 parts by mass, per 100 parts by mass of (A) diene rubber.

[0040] Examples of thiram-based vulcanization accelerators include tetramethylthiram disulfide (TMTD), tetraethylthiram disulfide (TETD), tetrabutylthiram disulfide (TBTD), tetrakis(2-ethylhexyl)thiram disulfide (TOT), and tetrabenzylthiram disulfide (TBzTD).

[0041] Examples of sulfenamide-based vulcanization accelerators include N-oxydiethylene-2-benzothiazolylsulfenamide (NOBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N-t-butyl-2-benzothiazolesulfenamide (BBS), and N,N'-dicyclohexyl-2-benzothiazolesulfenamide.

[0042] Examples of thiourea-based vulcanization accelerators include N,N'-diphenylthiourea, trimethylthiourea, N,N'-diethylthiourea, and N,N'-dibutylthiourea.

[0043] Examples of thiazole-based vulcanization accelerators include dibenzothiazyl disulfide (MBTS), 2-mercaptobenzothiazole (MBT), 2-mercaptobenzothiazole sodium salt (NaMBT), and 2-mercaptobenzothiazole zinc salt (ZnMBT).

[0044] Examples of vulcanization aids include zinc oxide (ZnO), stearic acid, and magnesium oxide. These can be used individually or in combination of two or more. The content of the vulcanization aid is preferably 0.1 to 10 parts by mass, and particularly preferably 0.3 to 7 parts by mass, per 100 parts by mass of (A) diene rubber.

[0045] Examples of anti-aging agents include carbamate-based anti-aging agents, phenylenediamine-based anti-aging agents, phenol-based anti-aging agents, diphenylamine-based anti-aging agents, quinoline-based anti-aging agents, imidazole-based anti-aging agents, waxes, etc. These can be used alone or in combination of two or more. The content of the anti-aging agent is preferably 0.5 to 15 parts by mass, and more preferably 2 to 12 parts by mass, per 100 parts by mass of (A) diene rubber.

[0046] Examples of process oils include naphthenic oils, paraffinic oils, and aromatic oils. These can be used individually or in combination of two or more. The content of the process oil is preferably 1 to 35 parts by mass, and more preferably 3 to 30 parts by mass, per 100 parts by mass of diene rubber (A).

[0047] Examples of silane coupling agents include amine-based silane coupling agents, epoxy-based silane coupling agents, vinyl-based silane coupling agents, mercapto-based silane coupling agents, and sulfide-based silane coupling agents, which can be used individually or in combination of two or more. The content of the silane coupling agent is preferably 0.1 to 20 parts by mass, and more preferably 0.1 to 10 parts by mass, per 100 parts by mass of silica.

[0048] [Method for preparing the vibration-damping rubber composition] The vibration-damping rubber composition of the present invention can be prepared by kneading the essential materials (A) to (C), and any other optional materials as described above, using a kneader, Banbury mixer, open roll, twin-screw agitator, or other kneading machine.

[0049] [Uses of the Vibration-Damping Rubber Composition] This vibration-damping rubber composition is suitably used, for example, as a vibration-damping rubber composition for automobiles, and particularly as a vibration-damping rubber composition for electric vehicles. Specifically, vibration-damping rubber members made from the vulcanized body of this vibration-damping rubber composition can be suitably used as vibration-damping rubber members for automobiles, for example, as vibration-damping rubber members for electric vehicles used in vehicles such as electric vehicles (including fuel cell vehicles (FCVs), plug-in hybrid vehicles (PHVs), hybrid vehicles (HVs), etc.) that use electric motors as a power source, specifically as components of engine mounts, stabilizer bushings, suspension bushings, motor mounts, subframe mounts, etc. It can also be used as vibration damping dampers for computer hard disks, vibration damping dampers for general home appliances such as washing machines, and as vibration damping devices and seismic isolation devices such as vibration-damping walls and dampers for buildings in the construction and housing sectors.

[0050] Examples and comparative examples of the present invention will be described below. However, the present invention is not limited to these examples. First, the following raw materials were prepared. Note that "parts," "%," etc., are based on mass unless otherwise specified.

[0051] [(A) Diene-based rubber] ・Natural rubber (NR)

[0052] [(B) Viscosity (25°C) is 10 ５ [Liquid polymers with a viscosity of mPa·s or higher] • Liquid acrylonitrile-butadiene rubber (liquid NBR) (manufactured by Zeon Corporation, Nipol 1312, viscosity (25°C) 220,000 mPa·s)

[0053] [(C) Inorganic filler] ・Carbon black (Tokai Carbon Co., Ltd. Seast SO, FEF grade carbon black, nitrogen adsorption specific surface area 42 m²) ２ / g, DBP oil absorption: 115mL / 100g, iodine adsorption: 44mg / g)

[0054] [(B') High-viscosity oil] • High-viscosity oil (manufactured by Fuji Kogyo Co., Ltd., Aromax 3, viscosity (25℃) 6,000 mPa·s)

[0055] [Chlorinated Butyl Rubber] • Chlorinated butyl rubber (Cl-IIR) (Manufactured by ExxonMobil, chlorobutyl 1066)

[0056] The viscosities of components (B) and (B') were measured using an AR2000 rheometer manufactured by TA Instruments, under the following conditions: conical plate (angle 1°, diameter 20 mm), room temperature (25°C), shear rate 1 [1 / s], and measurement time 300 seconds.

[0057] [Examples 1-3, Comparative Examples 1-11] The above raw materials were blended in the proportions shown in Table 1 below. Furthermore, for every 100 parts by mass of component (A), 1 part by mass of a vulcanizing agent (sulfur, manufactured by Karuizawa Smelting Co., Ltd.), 1 part by mass of a vulcanization accelerator (ACCEL CZ, manufactured by Kawaguchi Chemical Industry Co., Ltd.), and 3 parts by mass of a vulcanization accelerator (ACCEL TET, manufactured by Kawaguchi Chemical Industry Co., Ltd.) were added and kneaded to prepare an anti-vibration rubber composition. The kneading was carried out by kneading the raw materials other than the vulcanizing agent and vulcanization accelerator at 140°C for 5 minutes using a Banbury mixer, and then adding the vulcanizing agent and vulcanization accelerator and kneading at 60°C for 5 minutes using an open roll mixer.

[0058] The vibration-damping rubber compositions of the examples and comparative examples obtained above were used to evaluate each of their properties according to the following criteria.

[0059] <Evaluation of Dynamic Magnification Characteristics> Each vibration-damping rubber composition was press-molded (vulcanized) at 150°C for 30 minutes to produce test pieces. The static spring constant (Ks) and the dynamic spring constant (Kd100) at a frequency of 100 Hz of the test pieces were measured in accordance with JIS K 6394. Based on these values, the dynamic magnification (Kd100 / Ks) was calculated. Table 1 shows the measured values ​​of the dynamic magnification in each example and comparative example, converted to an index, with the measured value of the dynamic magnification (Kd100 / Ks) in Comparative Example 1 set to 100. A value of 106 or less was evaluated as "○ (very good)", and a value exceeding 106 was evaluated as "× (poor)".

[0060] <Evaluation of damping characteristics in the high-frequency range (stiffness at resonance)> Using each vibration-damping rubber composition, a test piece was prepared by pressing a disc-shaped metal fitting (60 mm in diameter, 6 mm in thickness) onto the upper and lower surfaces of a rubber piece (50 mm in diameter, 25 mm in height) under vulcanization conditions of 170°C for 30 minutes, and then vulcanizing and bonding them. The test piece was compressed by 2.5 mm in the direction of the cylindrical axis, and constant-displacement harmonic compression vibration was applied in the range of 90 to 1000 Hz centered on this 2.5 mm compression position. The dynamic load was detected by an upper load cell, and the dynamic spring constant (Kd) (N / mm) was calculated and measured in accordance with JIS K 6394, and the maximum value of the dynamic spring constant was defined as the stiffness at resonance. Table 1 shows the hardness at resonance in each example and comparative example, converted to an index, with the hardness at resonance in Comparative Example 1 set to 100. An index of 90 or less was evaluated as "○ (very good)," and an index exceeding 90 was evaluated as "× (poor)."

[0061]

[0062] From the results in Table 1, it can be seen that, as in the embodiment of the present invention, if a vibration-damping rubber composition containing components (A) to (C), with the content ratio of components (B) and (C) relative to component (A) controlled within a specific range, and without chlorinated butyl rubber, good results can be obtained in terms of damping characteristics for high-frequency vibrations, as well as in terms of dynamic magnification characteristics. This indicates that both low dynamic magnification and high damping for high-frequency vibrations can be achieved. On the other hand, if component (B) is not used among components (A) to (C), or if a component with a viscosity (25°C) of 10 is used instead of component (B), ５ When liquid polymers with a pressure of less than mPa·s were incorporated (Comparative Examples 1-4), the damping characteristics against high-frequency vibrations were insufficient, and the dynamic magnification characteristics were also unsatisfactory. Furthermore, even when components (A) to (C) were incorporated, when the content of component (B) was outside the range of 2 to 10 parts by mass (Comparative Examples 5-7), the dynamic magnification characteristics were unsatisfactory. Moreover, even when component (B) was incorporated along with components (A) to (C) in the range of 2 to 10 parts by mass, when chlorinated butyl rubber was incorporated (Comparative Examples 8-11), at least the dynamic magnification characteristics were unsatisfactory.

[0063] As described above, it has become clear that, as in the present invention, a vibration-damping rubber composition containing components (A) to (C), in which the content ratio of components (B) and (C) relative to component (A) is controlled within a specific range, and which does not contain chlorinated butyl rubber, can achieve both a low dynamic magnification and high damping against high-frequency vibrations.

[0064] While the above embodiments illustrate specific forms of the present invention, these embodiments are merely illustrative and should not be interpreted restrictively. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0065] The vibration-damping rubber composition of the present invention can be used particularly advantageously in applications such as vibration-damping rubber components for automobiles, and more specifically, motor mounts, suspension bushings, and subframe mounts for electric vehicles powered by electric motors. Furthermore, the vibration-damping rubber composition of the present invention can also be suitably used in applications other than automobiles to suppress high-frequency vibrations of electric motors.

Claims

1. A vibration-damping rubber composition containing the following components (A) to (C), wherein the content of component (B) is 2 to 10 parts by mass and the content of component (C) is 10 to 100 parts by mass per 100 parts by mass of component (A), and the composition does not contain chlorinated butyl rubber. (A) Diene rubber (B) Viscosity (25°C) is 10 ５ Liquid polymers with a pressure of mPa·s or higher (C) Inorganic fillers 2. The above component (B) has a viscosity (at 25°C) of 10 ５ ~10 ６ The vibration-damping rubber composition according to claim 1, wherein the liquid rubber has mPa·s.

3. The vibration-damping rubber composition according to claim 1 or 2, wherein component (B) is one or more selected from the group consisting of liquid isoprene rubber, liquid butadiene rubber, and liquid acrylonitrile-butadiene rubber.

4. The vibration-damping rubber composition according to any one of claims 1 to 3, wherein the component (A) is natural rubber.

5. The vibration-damping rubber composition according to any one of claims 1 to 4, wherein the (C) component is at least one of carbon black and silica.

6. The component (C) is carbon black, and the specific surface area of ​​the carbon black for nitrogen adsorption is 10 to 70 m². ２ The vibration-damping rubber composition according to any one of claims 1 to 5, wherein the concentration is / g.

7. The (C) component is silica, and the BET specific surface area of ​​the silica is 30 to 500 m². ２ The vibration-damping rubber composition according to any one of claims 1 to 6, wherein the concentration is / g.

8. A vibration-damping rubber member for an electric vehicle comprising a vulcanized body of the vibration-damping rubber composition according to any one of claims 1 to 7.

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