Vibration-damping rubber composition and vibration-damping rubber member

Abstract

Provided are a vibration-damping rubber composition and a vibration-damping rubber member which are capable of attaining all of high durability, inhibition of decrease in springiness, and insulating properties on a high level.　The vibration-damping rubber composition comprises a polymer component comprising the following component (A) and further includes the following components (B)-(D), wherein the amounts of the component (B), the component (C), and the component (D) are 0.1-5 parts by mass, 10-40 parts by mass, and 10-30 parts by mass, respectively, per 100 parts by mass of the component (A) and the component (C) has a BET specific surface area of 18-40 m2 / g. (A): A diene-based rubber. (B): A dihydrazide compound. (C): Carbon black. (D): Silica.

Description

Anti-vibration rubber composition and anti-vibration rubber member

[0001] The present invention relates to an anti-vibration rubber composition and an anti-vibration rubber member used for vibration isolation in vehicles such as railway cars.

[0002] The functions required for anti-vibration rubber for railway vehicles include, for example, high durability, suppression of spring drop that occurs during running vibration (low spring drop), and insulation. Typically, rubber compositions used as materials for anti-vibration rubber contain fillers such as silica and carbon black, in addition to polymers such as diene rubber. Here, fillers using silica as a filler have the property of being excellent in durability and insulation but not being able to satisfy low spring drop. On the other hand, fillers using carbon black can satisfy low spring drop but have the property of being inferior in durability and insulation. Thus, when blending fillers into anti-vibration rubber compositions, it is difficult to satisfy all of the requirements of high durability, low spring drop, and insulation by blending silica alone or carbon black alone. Furthermore, blends of silica and carbon black have been suitably used as fillers in anti-vibration rubber compositions in the past (see, for example, Patent Documents 1 to 6).

[0003] JP 2017-119873 A JP 2015-224279 A JP 2018-95810 A JP 2016-124880 A Japanese Patent No. 6657491 A International Publication No. 2015 / 182349

[0004] However, the various anti-vibration rubber compositions disclosed in the above patent documents do not aim to satisfy all of the functions required of anti-vibration rubber for railway vehicles (high durability, low spring drop, and insulating properties), and in fact, are not able to solve the above problems. That is, even in anti-vibration rubber compositions using a blend of silica and carbon black, the above-mentioned high durability, low spring drop, and insulating properties are contradictory properties, so that even a person skilled in the art would find it difficult to fully satisfy all of these functions. Therefore, there is still room for improvement in this regard.

[0005] The present invention has been made in view of the above circumstances, and provides an anti-vibration rubber composition and an anti-vibration rubber member that can satisfy high levels of all of high durability, low spring drop, and insulation properties.

[0006] The present inventors conducted extensive research, focusing on the reasons why the above-mentioned problems cannot be solved even when silica and carbon black are used as fillers in a diene-based rubber, which is the polymer of a vibration-damping rubber composition. During this research, they discovered that silica tends to agglomerate, and the agglomerates tend to break apart when the vibration-damping rubber is vibrated, which causes the rubber to fail to meet its low spring drop requirement. Carbon black also has poor chemical bonding at the interface with the rubber, making it prone to crack initiation, which reduces the durability of the vibration-damping rubber. Furthermore, carbon black tends to form conductive paths, which reduces the insulating properties of the vibration-damping rubber. They then discovered that these problems could not be solved simply by using silica and carbon black in combination as described above. Therefore, the present inventors came up with the idea of ​​using carbon black with a small specific surface area (exhibiting a specific BET specific surface area) and adding a dihydrazide compound to improve the dispersibility of the carbon black and silica. As a result of various experiments, it was discovered that, surprisingly, when the proportions of the various materials mentioned above were set within the specific ranges prescribed in the present invention, it was possible to achieve all of the functions required of vibration-damping rubber for railway vehicles (high durability, low spring drop, and insulation).

[0007] That is, the gist of the present invention is the following [1] to [6]. [1] A vibration-proof rubber composition containing a polymer component consisting of the following component (A) and the following components (B) to (D), wherein, relative to 100 parts by mass of the component (A), the ratio of the component (B) is 0.1 to 5 parts by mass, the ratio of the component (C) is 10 to 40 parts by mass, and the ratio of the component (D) is 10 to 30 parts by mass, and the component (C) has a BET specific surface area of ​​18 to 40 m 2 / g. (A) A diene rubber. (B) A dihydrazide compound. (C) Carbon black. (D) Silica. [2] The vibration-proof rubber composition according to [1], further comprising a silane coupling agent (E). [3] The vibration-proof rubber composition according to [2], wherein the silane coupling agent (E) is at least one selected from the group consisting of mercapto-based silane coupling agents and sulfide-based silane coupling agents. [4] The vibration-proof rubber composition according to any one of [1] to [3], wherein the dihydrazide compound (B) is at least one selected from adipic acid dihydrazide and isophthalic acid dihydrazide. [5] A vibration-proof rubber member comprising a vulcanizate of the vibration-proof rubber composition according to any one of [1] to [4]. [6] The vibration-proof rubber member according to [5], which is a vibration-proof rubber member for railway vehicles.

[0008] As described above, the vibration-proof rubber composition of the present invention contains a polymer made of diene rubber, a dihydrazide compound, carbon black having a BET specific surface area within a specific range, and silica, and the proportions of these components are within specific ranges. This allows the composition to achieve high levels of durability, low spring drop, and insulation. As a result, the composition can exhibit excellent performance, particularly as a material for vibration-proof rubber for railway vehicles.

[0009] Next, an embodiment of the present invention will be described in detail, but the present invention is not limited to this embodiment.

[0010] As described above, the vibration-damping rubber composition according to one embodiment of the present invention (hereinafter referred to as "the present vibration-damping rubber composition") is a vibration-damping rubber composition containing a polymer component consisting of the following component (A) and the following components (B) to (D), wherein, relative to 100 parts by mass of the component (A), the proportion of the component (B) is 0.1 to 5 parts by mass, the proportion of the component (C) is 10 to 40 parts by mass, and the proportion of the component (D) is 10 to 30 parts by mass, and the component (C) has a BET specific surface area of ​​18 to 40 m 2 / g. (A) Diene rubber. (B) Dihydrazide compound. (C) Carbon black. (D) Silica.

[0011] The constituent materials of the present vibration-damping rubber composition will be described in detail below.

[0012] [Diene Rubber (A)] As described above, the present vibration-damping rubber composition uses a polymer made of diene rubber (A), and does not use any polymer other than diene rubber (A). As the diene rubber (A), a diene rubber containing natural rubber (NR) as a primary component is preferably used. Here, the term "primary component" refers to a diene rubber (A) in which 50% by mass or more of the diene rubber (A) is natural rubber, and also includes diene rubber (A) consisting solely of natural rubber. By using natural rubber as a primary component, the composition exhibits excellent strength and low dynamic magnification. Examples of diene rubbers other than natural rubber include butadiene rubber (BR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), isoprene rubber (IR), acrylonitrile-butadiene rubber (NBR), ethylene-propylene-diene rubber (EPDM), butyl rubber (IIR), and chloroprene rubber (CR). These may be used alone or in combination of two or more. It is desirable to use these diene rubbers in combination with natural rubber.

[0013] [Dihydrazide Compound (B)] As described above, the present vibration-damping rubber composition contains a specific proportion of dihydrazide compound (B). Examples of the dihydrazide compound (B) include compounds represented by the following general formula (1):

[0014]

[0015] Specific examples of the dihydrazide compound (B) include adipic acid dihydrazide, isophthalic acid dihydrazide, phthalic acid dihydrazide, terephthalic acid dihydrazide, succinic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, oxalic acid dihydrazide, and dodecanoic acid dihydrazide. These may be used alone or in combination of two or more. Among these, adipic acid dihydrazide and isophthalic acid dihydrazide are preferred from the viewpoint of reducing dynamic magnification.

[0016] As described above, from the viewpoint of obtaining the effects of the present invention (satisfying all of high durability, low spring drop, and insulating properties at a high level), the content of the dihydrazide compound (B) is 0.1 to 5 parts by mass per 100 parts by mass of the diene rubber (A), and from the same viewpoint, it is preferably 0.5 to 4 parts by mass, more preferably 0.75 to 3 parts by mass.

[0017] [Carbon Black (C)] As mentioned above, the present vibration-proof rubber composition contains carbon black (C) at a specific ratio. The carbon black (C) has a BET specific surface area of ​​18 to 40 m. 2 Preferably, the BET specific surface area is 18 to 35 m 2 / g, and more preferably, a BET specific surface area of ​​18 to 30 m 2 / g is used. That is, if the BET specific surface area of ​​the carbon black (C) is too large, the desired insulating effect cannot be obtained, and if the BET specific surface area is too small, durability decreases. The BET specific surface area of ​​the carbon black (C) can be measured, for example, by degassing a sample at 200°C for 15 minutes and then using a mixed gas (N: 70%, He: 30%) as the adsorbed gas with a BET specific surface area analyzer (Microdata Corporation, 4232-II).

[0018] From the viewpoints of reinforcing properties, durability, and insulating properties, various grades of carbon black (C) are used, such as FEF grade, MAF grade, GPF grade, SRF grade, FT grade, and MT grade. These may be used alone or in combination of two or more. Among these, FEF grade carbon black is preferably used from the viewpoints above.

[0019] As described above, from the viewpoint of obtaining the effects of the present invention (satisfying all of high durability, low spring drop, and insulating properties at a high level), the content of the carbon black (C) is 10 to 40 parts by mass per 100 parts by mass of the diene rubber (A), and from the same viewpoint, it is preferably 20 to 40 parts by mass, more preferably 30 to 40 parts by mass.

[0020] [Silica (D)] As mentioned above, the present vibration-damping rubber composition contains silica (D) in a specific ratio. As the silica (D), for example, wet silica, dry silica, colloidal silica, etc. are used. These may be used alone or in combination of two or more.

[0021] From the viewpoint of achieving both high durability and low spring drop, the BET specific surface area of ​​the silica (D) is 20 to 380 m 2 / g, and more preferably, the BET specific surface area is 30 to 330 m 2 The BET specific surface area of ​​the silica (D) can be measured, for example, by degassing a sample at 200° C. for 15 minutes and then using a mixed gas (N: 70%, He: 30%) as an adsorbent gas with a BET specific surface area measuring device (4232-II, manufactured by Microdata Corporation).

[0022] As described above, from the viewpoint of obtaining the effects of the present invention (satisfying all of high durability, low spring drop, and insulating properties at a high level), the content of the silica (D) is 10 to 30 parts by mass per 100 parts by mass of the diene rubber (A), and from the same viewpoint, it is preferably 15 to 30 parts by mass, more preferably 20 to 30 parts by mass.

[0023] [Silane Coupling Agent (E)] The present vibration-damping rubber composition may contain a silane coupling agent (E) as needed. By incorporating the silane coupling agent (E), the silica (D) and the diene rubber (A) are bonded via the silane coupling agent (E), thereby further improving the durability of the vibration-damping rubber. Examples of the silane coupling agent (E) include mercapto-based silane coupling agents, sulfide-based silane coupling agents, amine-based silane coupling agents, epoxy-based silane coupling agents, and vinyl-based silane coupling agents, which may be used alone or in combination. Among these, it is preferable that the silane coupling agent (E) be a mercapto-based silane coupling agent or a sulfide-based silane coupling agent, as this increases the vulcanization density and is particularly effective in reducing dynamic magnification and improving durability.

[0024] Examples of the mercapto-based silane coupling agent include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, etc. These may be used alone or in combination of two or more.

[0025] Examples of the sulfide-based silane coupling agent include bis-(3-(triethoxysilyl)-propyl)-disulfide, bis(3-triethoxysilylpropyl)trisulfide, bis-(3-(triethoxysilyl)-propyl)-tetrasulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, and 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide. tetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl benzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, etc. These may be used alone or in combination of two or more.

[0026] Examples of the amine-based silane coupling agent include 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-(N-phenyl)aminopropyltrimethoxysilane, etc. These may be used alone or in combination of two or more.

[0027] Examples of the epoxy-based silane coupling agent include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, etc. These may be used alone or in combination of two or more.

[0028] Examples of the vinyl-based silane coupling agent include vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris(β-methoxyethoxy)silane, vinyldimethylchlorosilane, vinyltrichlorosilane, vinyltriisopropoxysilane, vinyltris(2-methoxyethoxy)silane, etc. These may be used alone or in combination of two or more.

[0029] The content of these silane coupling agents (E) is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 8 parts by mass, per 100 parts by mass of the diene rubber (A), because they provide low dynamic magnification, excellent durability, etc.

[0030] In addition to the essential components (A) to (D), the present vibration-damping rubber composition may also contain, as needed, the component (E), a vulcanizing agent, a vulcanization accelerator, a vulcanization aid, an antioxidant, process oil, and the like.

[0031] Examples of the vulcanizing agent include sulfur (powdered sulfur, precipitated sulfur, insoluble sulfur), and sulfur-containing compounds such as alkylphenol disulfides, which may be used alone or in combination of two or more.

[0032] The content of the vulcanizing agent is preferably in the range of 0.1 to 10 parts by mass, particularly preferably 0.3 to 5 parts by mass, per 100 parts by mass of the diene rubber (A). That is, if the content of the vulcanizing agent is too small, vulcanization reactivity tends to deteriorate, whereas if the content of the vulcanizing agent is too large, rubber physical properties (breaking strength, breaking elongation) tend to deteriorate.

[0033] Examples of the vulcanization accelerator include thiuram-based, sulfenamide-based, guanidine-based, thiazole-based, aldehyde ammonia-based, aldehyde amine-based, and thiourea-based vulcanization accelerators. These may be used alone or in combination of two or more. Among these, a combination of a thiuram-based vulcanization accelerator and at least one vulcanization accelerator selected from the sulfenamide-based, guanidine-based, and thiazole-based vulcanization accelerators is preferred because it provides excellent compression set.

[0034] The content of the vulcanization accelerator is preferably in the range of 0.1 to 10 parts by mass, particularly preferably in the range of 0.3 to 5 parts by mass, per 100 parts by mass of the diene rubber (A).

[0035] Examples of the thiuram vulcanization accelerator include tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetrabutylthiuram disulfide (TBTD), tetrakis(2-ethylhexyl)thiuram disulfide (TOT), tetrabenzylthiuram disulfide (TBzTD), etc. These may be used alone or in combination of two or more.

[0036] Examples of the sulfenamide vulcanization accelerator include N-oxydiethylene-2-benzothiazolylsulfenamide (NOBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N-t-butyl-2-benzothiazolesulfenamide (BBS), N,N'-dicyclohexyl-2-benzothiazolesulfenamide, etc. These may be used alone or in combination of two or more.

[0037] Examples of the guanidine vulcanization accelerator include N,N'-diphenylthiourea, trimethylthiourea, N,N'-diethylthiourea, N,N'-dibutylthiourea, etc. These may be used alone or in combination of two or more.

[0038] Examples of the thiazole vulcanization accelerator include dibenzothiazyl disulfide (MBTS), 2-mercaptobenzothiazole (MBT), 2-mercaptobenzothiazole sodium salt (NaMBT), and 2-mercaptobenzothiazole zinc salt (ZnMBT). These may be used alone or in combination of two or more. Among these, dibenzothiazyl disulfide (MBTS) and 2-mercaptobenzothiazole (MBT) are preferred because of their particularly excellent vulcanization reactivity.

[0039] Examples of the vulcanization aid include zinc oxide (ZnO), stearic acid, magnesium oxide, etc. These may be used alone or in combination of two or more.

[0040] The content of the vulcanization aid is preferably in the range of 0.1 to 10 parts by mass, particularly preferably in the range of 0.3 to 7 parts by mass, per 100 parts by mass of the diene rubber (A).

[0041] Examples of the antiaging agent include carbamate-based antiaging agents, phenylenediamine-based antiaging agents, phenol-based antiaging agents, diphenylamine-based antiaging agents, quinoline-based antiaging agents, imidazole-based antiaging agents, waxes, etc. These may be used alone or in combination of two or more kinds.

[0042] The content of the antioxidant is preferably in the range of 0.5 to 15 parts by mass, particularly preferably in the range of 1 to 10 parts by mass, per 100 parts by mass of the diene rubber (A).

[0043] Examples of the process oil include naphthenic oil, paraffinic oil, aromatic oil, etc. These may be used alone or in combination of two or more.

[0044] The content of the process oil is preferably in the range of 1 to 35 parts by mass, particularly preferably in the range of 3 to 30 parts by mass, per 100 parts by mass of the diene rubber (A).

[0045] [Method for Preparing Anti-Vibration Rubber Composition] Here, the present anti-vibration rubber composition can be prepared by using the essential components (A) to (D) in specific proportions, and further using the component (E) and other materials listed above, as necessary, and kneading them using a kneader such as a kneader, a Banbury mixer, an open roll, or a twin-screw mixer.

[0046] In particular, the kneading is preferably carried out by kneading materials other than the vulcanizing agent and vulcanization accelerator using a Banbury mixer at 100 to 170°C for 3 to 10 minutes (preferably, kneading for 3 to 5 minutes at 120 to 150°C), then blending the vulcanizing agent and vulcanization accelerator, and kneading using an open roll at 30 to 80°C for 3 to 10 minutes (preferably, kneading for 3 to 5 minutes at 30 to 60°C).

[0047] From the viewpoint of obtaining the effects of the present invention (satisfying all of high durability, low spring drop, and insulation properties at high levels), it is preferable that the present vibration-damping rubber composition obtained in this manner satisfies the following condition (α): (α) ΔG' as shown in the following formula (I) is 5.0 or less: ΔG'=G'1 / G'2 (I) (In formula (I), G'1 is the storage modulus of the unvulcanized rubber composition at a frequency of 11 Hz, an oscillation angle of 0.28%, and 40°C, and G'2 is the storage modulus of the unvulcanized rubber composition at a frequency of 11 Hz, an oscillation angle of 42%, and 40°C.)

[0048] In order to obtain the advantageous effects of the present invention, ΔG′ is preferably 4.5 or less.

[0049] As described in JP 2006-47070 A, ΔG' represented by the above formula (I) is an index for evaluating the cohesion of the filler, and the smaller ΔG' indicates a higher degree of filler dispersion. Furthermore, G'1 and G'2 can be measured, for example, by a rubber processing tester, a curastometer, a dynamic viscoelasticity analyzer, or the like. More specifically, they are measured using an RPA2000 manufactured by Alpha Technology.

[0050] The present vibration-isolating rubber composition is then vulcanized at high temperature (150 to 170° C.) for 5 to 30 minutes to become a vibration-isolating rubber member (vulcanizate).

[0051] The surface hardness (JIS-A hardness) of the vibration-isolating rubber member (vulcanized body) is usually 60 to 85, and preferably 65 to 80. The hardness can be measured using an Asker rubber hardness tester (P1-A type) manufactured by Kobunshi Keiki Co., Ltd.

[0052] Furthermore, the vibration-damping rubber member (vulcanizate) can achieve a number of extensions at break of 80,000 or more in an extension fatigue test conducted in accordance with JIS K 6260. Preferably, the number of extensions at break is 100,000 or more, and more preferably, the number of extensions at break is 120,000 or more.

[0053] Furthermore, the vibration-isolating rubber member (vulcanized body) has a volume resistivity of 1×10 measured under the following conditions in accordance with JIS K 6271-1:2015 (vulcanized rubber and thermoplastic rubber - Determination of electrical resistivity). 9 A volume resistivity of 1×10 Ω·cm or more can be achieved. 11 It is preferable that the volume resistivity is 1×10 13 Achieves Ω·cm or more. Measurement method: Double ring electrode method Guard electrode: outer diameter 80 mm, inner diameter 70 mm Main electrode: 50 mm Sample outer dimensions: 100 mm x 100 mm Sample thickness: 2 mm Applied voltage: 1 V Detection current range: 200 pA to 20 mA

[0054] Furthermore, the anti-vibration rubber member (vulcanizate) is subjected to a durability fatigue test in which it is repeatedly stretched and contracted 4 mm in the compression direction and 15 mm in the tension direction at a frequency of 3 Hz, and the load at the time of 15 mm tension (initial load F1 and load F2 at the time of 3000 stretches) is measured. The spring loss value shown in the following formula (II) is obtained by this test and can achieve a spring loss value of -20% or more. Preferably, the spring loss value achieves a spring loss value of -18% or more, and more preferably, a spring loss value of -16% or more. Spring loss = {(F2 - F1) / F1} x 100 (%) (II)

[0055] As described above, vibration-isolating rubber members made from vulcanizates of the present vibration-isolating rubber composition can achieve high levels of durability, low spring drop, and insulation, and therefore exhibit excellent performance, particularly as materials for vibration-isolating rubber for railway vehicles. In addition to the above applications, the composition can also be used as components for engine mounts, stabilizer bushings, suspension bushings, motor mounts, subframe mounts, and the like used in automobiles. In particular, due to its high insulation properties, the composition can be advantageously used for components (vibration-isolating rubber members for electric vehicles) such as motor mounts, suspension bushings, and subframe mounts for electric vehicles powered by electric motors (including electric vehicles (EVs), fuel cell vehicles (FCVs), plug-in hybrid vehicles (PHVs), hybrid vehicles (HVs), and the like). Furthermore, due to its high insulation properties, the composition can also be used for vibration dampers for computer hard disks, vibration dampers for general home appliances such as washing machines, and vibration-damping devices and seismic isolation devices, such as architectural seismic damping walls and vibration-damping dampers, in the construction and housing fields.

[0056] Next, examples will be described together with comparative examples, but the present invention is not limited to these examples.

[0057] First, prior to the Examples and Comparative Examples, the following materials were prepared. The measured values ​​for carbon black and silica were measured according to the above-mentioned methods.

[0058] [Natural rubber (NR)]

[0059] [Dihydrazide (i)] Adipic acid dihydrazide (ADH), manufactured by Otsuka Chemical Co., Ltd.

[0060] [Dihydrazide (ii)] Isophthalic acid dihydrazide (IDH), manufactured by Otsuka Chemical Co., Ltd.

[0061] [Carbon black (i)] SEAT V (BET specific surface area 27 m), manufactured by Tokai Carbon Co., Ltd. 2 / g)

[0062] [Carbon black (ii)] Asahi #60 (BET specific surface area 40 m), manufactured by Asahi Carbon Co., Ltd.2 / g)

[0063] [Carbon black (iii)] SEAT SRA (BET specific surface area 18 m), manufactured by Tokai Carbon Co., Ltd. 2 / g)

[0064] [Carbon black (iv)] Showblack N330 (BET specific surface area 75 m), manufactured by Cabot Japan Co., Ltd. 2 / g)

[0065] [Carbon black (v)] Asahi #15 (BET specific surface area 12 m), manufactured by Asahi Carbon Co., Ltd. 2 / g)

[0066] [Carbon black (vi)] Asahi #65 (BET specific surface area 42 m), manufactured by Asahi Carbon Co., Ltd. 2 / g)

[0067] [Silica] Nipsil VN3 (BET specific surface area 180-230 m), manufactured by Tosoh Silica Corporation 2 / g)

[0068] [Silane Coupling Agent (i)] Sulfide-based silane coupling agent (Si-69, manufactured by EVONIK DEGUSSA)

[0069] [Silane coupling agent (ii)] Mercapto-based silane coupling agent (NXT Z45, manufactured by MOMENTIVE)

[0070] [Zinc oxide] Sakai Chemical Industry Co., Ltd., zinc oxide type 2

[0071] [Stearic acid] NOF Corporation, Sakura Stearic Acid Beads

[0072] [Anti-aging agent] Antigen 6C, manufactured by Sumitomo Chemical Co., Ltd.

[0073] [Process oil] Sansen 410, manufactured by Nippon Sun Oil Co., Ltd.

[0074] [Vulcanization accelerator] Sancerer CZ-G, manufactured by Sanshin Chemical Industry Co., Ltd.

[0075] [Sulfur (vulcanizing agent)] Karuizawa Smelting Co., Ltd.

[0076] [Examples 1 to 13, Comparative Examples 1 to 9] Anti-vibration rubber compositions were prepared by blending and kneading the above-mentioned materials in the proportions shown in Tables 1 and 2. The kneading was carried out by first blending the materials other than the vulcanizing agent and vulcanization accelerator for 5 minutes at 140°C using a Banbury mixer, and then blending the vulcanizing agent and vulcanization accelerator and kneading them for 5 minutes at 60°C using an open roll.

[0077] The vibration-proof rubber compositions of the Examples and Comparative Examples thus obtained were evaluated for their properties according to the following criteria, and the results are shown in Tables 1 and 2 below.

[0078] <ΔG'> For each vibration-damping rubber composition, the storage modulus of the unvulcanized rubber composition (storage modulus G'1 at a swing angle of 0.28% and storage modulus G'2 at a swing angle of 42%) was measured at a frequency of 11 Hz and 40°C using an RPA2000 (manufactured by Alpha Technology Co., Ltd.). Then, based on the measurement results, ΔG' represented by the following formula (I) was calculated. ΔG'=G'1 / G'2 (I)

[0079] <Reinforcement> Each vibration-damping rubber composition was press-molded (vulcanized) under conditions of 150°C x 30 minutes, and the hardness (JIS-A hardness) of the rubber surface was measured using an Asker rubber hardness tester (P1-A type) (manufactured by Kobunshi Keiki Co., Ltd.). The reinforcement was evaluated according to the following criteria: ◯ (very good): Hardness is 60 or more. × (poor): Hardness is less than 60.

[0080] <Durability> Each vibration-damping rubber composition was press-molded (vulcanized) at 150°C for 30 minutes to produce a rubber sheet with a thickness of 2 mm. JIS No. 3 dumbbells were punched out of the rubber sheet, and a stretch fatigue test was carried out using these dumbbells in accordance with JIS K 6260. The number of stretches at break was then measured, and durability was evaluated according to the following criteria: ○ (very good): 80,000 or more stretches. × (poor): Less than 80,000 stretches.

[0081] <Insulating Properties> Each vibration-damping rubber composition was press-molded (vulcanized) at 150°C for 30 minutes to obtain a sample, and the volume resistivity VR (Ω·cm) was measured according to JIS K 6271-1:2015 (Vulcanized rubber and thermoplastic rubber - Determination of electrical resistivity). Specifically, the volume resistivity VR was determined under the following conditions. Measurement method: Double ring electrode method Guard electrode: outer diameter 80 mm, inner diameter 70 mm Main electrode: 50 mm Sample outer dimensions: 100 mm x 100 mm Sample thickness: 2 mm Applied voltage: 1 V Detection current range: 200 pA to 20 mA Then, the insulating properties were evaluated according to the following criteria. ◯ (very good): Volume resistivity VR is 1×10 9 Ω cm or more. × (poor): Volume resistivity VR is 1×10 9 Less than Ω·cm.

[0082] <Spring Drop> Each vibration-damping rubber composition was press-molded (vulcanized) at 150°C for 30 minutes to obtain an anti-vibration rubber sample, which was subjected to a fatigue durability test in which the sample was repeatedly stretched 4 mm in the compression direction and 15 mm in the tension direction at a frequency of 3 Hz, and the load at 15 mm tension (initial load F1 and load F2 at 3000 stretches) was measured. Based on the measurement results, the spring drop was calculated using the following formula (II): Spring drop = {(F2 - F1) / F1} x 100 (%) (II) The spring drop was then evaluated according to the following criteria: ◯ (very good): Spring drop of -20% or more. × (poor): Spring drop of less than -20%.

[0083]

[0084]

[0085] The results in Tables 1 and 2 show that the vulcanizates of the vibration-damping rubber compositions of the examples exhibit the properties required by the present invention in all aspects of durability (high durability), spring drop (low spring drop), and insulation.

[0086] In contrast, the vibration-proof rubber composition of Comparative Example 1 contained too little dihydrazide compound, resulting in insufficient dispersion of the carbon black, which formed conductive paths and resulted in poor insulation. Furthermore, the dispersion of the carbon black and silica was insufficient, resulting in the formation of agglomerates, which broke down during endurance vibration loading, causing a decrease in load, resulting in poor spring resistance. The vibration-proof rubber composition of Comparative Example 2 contained too much dihydrazide compound, resulting in a significant increase in rubber viscosity and therefore poor durability. The vibration-proof rubber composition of Comparative Example 3 contained too little carbon black, resulting in poor reinforcement (hardness). The vibration-proof rubber composition of Comparative Example 4 contained too much carbon black, resulting in poor insulation due to the formation of conductive paths. The vibration-proof rubber composition of Comparative Example 5 had a carbon black BET specific surface area that exceeded the specification of the present invention, and the increased surface area increased conductivity, resulting in poor insulation. The vibration-proof rubber composition of Comparative Example 6 had a BET specific surface area of ​​the carbon black that was less than the specified value of the present invention, and the interface between the rubber and the carbon black was prone to become the starting point for crack initiation during durable vibration loading, resulting in poor durability. The vibration-proof rubber composition of Comparative Example 7 had an excessively low silica content, resulting in poor reinforcement (hardness). The vibration-proof rubber composition of Comparative Example 8 had an excessively high silica content, resulting in poor spring resistance because silica agglomerates broke down during durable vibration loading, causing a decrease in load. The vibration-proof rubber composition of Comparative Example 9 had a BET specific surface area of ​​the carbon black that exceeded the specified value of the present invention, and the increased surface area increased conductivity, resulting in poor insulation.

[0087] Although the above examples show specific embodiments of the present invention, the examples are merely illustrative and should not be construed as limiting. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0088] Anti-vibration rubber members made from vulcanizates of this anti-vibration rubber composition can achieve high levels of durability, low spring drop, and insulation, and therefore exhibit excellent performance, particularly as materials for anti-vibration rubber for railway vehicles. In addition to the above-mentioned applications, they can also be used as components for engine mounts, stabilizer bushings, suspension bushings, motor mounts, subframe mounts, and other components used in automobiles. In particular, due to their high insulation properties, they can be advantageously used for components such as motor mounts, suspension bushings, and subframe mounts (anti-vibration rubber members for electric vehicles) for electric vehicles powered by electric motors (including electric vehicles (EVs), fuel cell vehicles (FCVs), plug-in hybrid vehicles (PHVs), hybrid vehicles (HVs), and other vehicles). Furthermore, due to their high insulation properties, they can be used for vibration dampers for computer hard disks, vibration dampers for general home appliances such as washing machines, and vibration dampers and seismic isolation devices in the construction and housing fields, such as architectural seismic damping walls and vibration dampers.

Claims

1. A vibration damping rubber composition containing a polymer component composed of the following component (A) and the following components (B) to (D), wherein the ratio of the component (B) is 0.1 to 5 parts by mass, the ratio of the component (C) is 10 to 40 parts by mass, and the ratio of the component (D) is 10 to 30 parts by mass with respect to 100 parts by mass of the component (A), and the component (C) has a BET specific surface area of 18 to 40 m 2 / g, the vibration damping rubber composition. (A)Diene rubber. (B)Dihydrazide compound. (C)Carbon black. (D)Silica.

2. The vibration damping rubber composition according to Claim 1, further containing a silane coupling agent (E).

3. The vibration damping rubber composition according to Claim 2, wherein the silane coupling agent (E) is at least one selected from the group consisting of mercapto-based silane coupling agents and sulfide-based silane coupling agents.

4. The vibration damping rubber composition according to any one of Claims 1 to 3, wherein the dihydrazide compound (B) is at least one selected from adipic acid dihydrazide and isophthalic acid dihydrazide.

5. A vibration damping rubber member comprising a vulcanizate of the vibration damping rubber composition according to any one of Claims 1 to 3.

6. The vibration damping rubber member according to Claim 5, which is a vibration damping rubber member for railway vehicles.