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

[Technical Field]

[0001] This invention relates to vibration-damping rubber compositions and vibration-damping rubber members used for vibration damping applications in vehicles such as railway cars. [Background technology]

[0002] The functions required for vibration-damping rubber for railway vehicles include, for example, high durability, suppression of spring drop that occurs during running vibrations (low spring drop), and electrical insulation. Typically, rubber compositions used as materials for vibration-damping rubber contain polymers such as diene rubber, as well as fillers such as silica and carbon black. While compositions using silica as a filler offer excellent durability and insulation, they may not meet the requirement for low spring rate reduction. Conversely, compositions using carbon black as a filler can meet the requirement for low spring rate reduction, but suffer from unfavorable durability and insulation properties. Thus, in the compounding of fillers for vibration-damping rubber compositions, it is difficult to satisfy all requirements of high durability, low spring rate reduction, and insulation properties by using silica alone or carbon black alone. Furthermore, blending silica and carbon black and using them as fillers in vibration-damping rubber compositions has also been done as appropriate in the past (see, for example, Patent Documents 1 to 6). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2017-119873 [Patent Document 2] Japanese Patent Publication No. 2015-224279 [Patent Document 3] Japanese Patent Publication No. 2018-95810 [Patent Document 4] Japanese Patent Publication No. 2016-124880 [Patent Document 5] Patent No. 6657491 [Patent Document 6] International Publication No. 2015 / 182349 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, the various vibration-damping rubber compositions described in the aforementioned patent documents do not address the challenge of satisfying all the functions required for vibration-damping rubber for railway vehicles (high durability, low spring rate reduction, and insulation), and in fact, they are not capable of solving the aforementioned problems. In other words, even in vibration-damping rubber compositions using a blend of silica and carbon black, high durability, low spring rate, and insulation properties are conflicting characteristics, making it difficult even for those skilled in the art to fully satisfy all of these functions. Therefore, there is still room for improvement in this regard.

[0005] This invention has been made in view of these circumstances, and provides an anti-vibration rubber composition and anti-vibration rubber member that can satisfy all of the following at a high level: high durability, low spring drop, and insulation. [Means for solving the problem]

[0006] The inventors of this invention have conducted extensive research focusing on the factors that prevent the aforementioned problems from being solved even when silica and carbon black are used in combination as fillers in diene-based rubber, which is the polymer of the vibration-damping rubber composition. In the course of this research, they found that silica has a tendency to aggregate, and when the vibration-damping rubber is vibrated, the aggregated masses tend to break apart, which is a factor that prevents the low spring rate from being met. Furthermore, carbon black has poor chemical bonding at the interface with the rubber and is prone to becoming a crack initiation point, which reduces the durability of the vibration-damping rubber. In addition, carbon black tends to form conductive paths, which reduces the insulation properties of the vibration-damping rubber. They then determined that these problems cannot be solved simply by using silica and carbon black in combination, as described above. Therefore, the inventors conceived of using carbon black with a small specific surface area (exhibiting a specific BET specific surface area) as the carbon black, and further adding a dihydrazide compound to improve the dispersibility of the carbon black and silica. As a result of various experiments, they unexpectedly discovered that by setting the proportions of the various materials within the specific range defined in this invention, it becomes possible to satisfy all the functions required for vibration-damping rubber for railway vehicles (high durability, low spring drop, and insulation).

[0007] In other words, the gist of the present invention is as follows: [1] to [6]. [1] A vibration-damping rubber composition comprising a polymer component consisting of the following component (A) and the following components (B) to (D), wherein the proportion of component (B) is 0.1 to 5 parts by mass per 100 parts by mass of component (A), the proportion of component (C) is 10 to 40 parts by mass, the proportion of component (D) is 10 to 30 parts by mass, and component (C) has a BET specific surface area of ​​18 to 40 m². 2 A vibration-damping rubber composition that is / g. (A) Diene-based rubber. (B) Dihydrazide compounds. (C) Carbon Black. (D) Silica. [2] The vibration-damping rubber composition according to [1] further contains a silane coupling agent (E). [3] The vibration-damping rubber composition according to [2], wherein the silane coupling agent (E) is at least one selected from the group consisting of mercapto-silane coupling agents and sulfide-silane coupling agents. [4] The vibration-damping 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-damping rubber member comprising a vulcanized body of any of the vibration-damping rubber compositions described in [1] to [4]. [6] The vibration-damping rubber member described in [5], which is a vibration-damping rubber member for railway vehicles. [Effects of the Invention]

[0008] Thus, the vibration damping rubber composition of the present invention contains a polymer composed of a diene rubber, a dihydrazide compound, carbon black having a BET specific surface area within a specific range, and silica, and the ratios thereof are within a specific range. Therefore, it is possible to satisfy high durability, low spring degradation, and high insulation at a high level. From this, it can exhibit excellent performance especially as a material for vibration damping rubber for railway vehicles.

Embodiments for Carrying Out the Invention

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

[0010] The vibration damping rubber composition (hereinafter referred to as "this vibration damping rubber composition"), which is one embodiment of the present invention, is a vibration damping rubber composition containing a polymer component composed of the following component (A) and the following components (B) to (D). With respect 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, 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) Diene rubber. (B) Dihydrazide compound. (C) Carbon black. (D) Silica.

[0011] Hereinafter, the constituent materials of this vibration damping rubber composition will be described in detail.

[0012] 〔Diene rubber (A)〕 As described above, this vibration-damping rubber composition uses a polymer made of diene rubber (A), and no polymers other than diene rubber (A) are used. Preferably, the diene rubber (A) is a diene rubber whose main component is natural rubber (NR). Here, "main component" refers to a diene rubber (A) in which 50% by mass or more is natural rubber, and also includes a diene rubber (A) that consists only of natural rubber. By using natural rubber as the main component in this way, superiority is achieved in terms of strength and low dynamic magnification. Other diene rubbers besides natural rubber include, for example, 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 can be used individually 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 mentioned above, this vibration-damping rubber composition contains a specific proportion of dihydrazide compound (B). Examples of dihydrazide compound (B) include the compound shown in the following general formula (1).

[0014] [ka]

[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, sebacate acid dihydrazide, oxalic acid dihydrazide, and dodecanoic acid dihydrazide. These can 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 lowering the dynamic magnification.

[0016] From the viewpoint of obtaining the effects of the present invention (satisfying all of the following at a high level: high durability, low spring drop, and insulation), the content of the dihydrazide compound (B) is, as previously stated, 0.1 to 5 parts by mass per 100 parts by mass of the diene rubber (A), preferably 0.5 to 4 parts by mass, and more preferably 0.75 to 3 parts by mass.

[0017] [Carbon Black (C)] Furthermore, as mentioned above, this vibration-damping rubber composition contains carbon black (C) in a specific proportion. The carbon black (C) has a BET specific surface area of ​​18 to 40 m². 2 A product with a specific surface area of ​​18-35 m² is used. Preferably, a product with a specific surface area of ​​18-35 m² is used. 2 A material with a specific surface area of ​​18-30 m² / g is used, and more preferably, a material with a specific surface area of ​​18-30 m². 2 The / g type is used. In other words, 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 will decrease. The BET specific surface area of ​​the carbon black (C) 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 measuring device (Microdata Corporation, 4232-II).

[0018] The carbon black (C) can be of various grades, such as FEF, MAF, GPF, SRF, FT, and MT, from the viewpoint of reinforcing properties, durability, and insulation properties. These can be used alone or in combination of two or more. Among these, FEF grade carbon black is preferred from the above viewpoint.

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

[0020] [Silica (D)] Furthermore, as mentioned above, this vibration-damping rubber composition contains silica (D) in a specific proportion. Examples of silica (D) include wet silica, dry silica, colloidal silica, etc. These can be used individually or in combination of two or more.

[0021] Furthermore, from the viewpoint of achieving both high durability and low spring rate reduction, the BET specific surface area of ​​the silica (D) is 20 to 380 m². 2 It is preferable that the BET specific surface area is 30-330 m² / g, and more preferably 30-330 m². 2 This is silica in units of / g. The BET specific surface area of ​​silica (D) 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 measuring device (Microdata Corporation, 4232-II).

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

[0023] [Silane coupling agent (E)] This vibration-damping rubber composition may contain a silane coupling agent (E) as needed. By including the silane coupling agent (E), silica (D) and diene rubber (A) are bonded via the silane coupling agent (E), thereby improving the durability of the vibration-damping rubber. As the silane coupling agent (E), for example, mercapto-silane coupling agents, sulfide-silane coupling agents, amine-silane coupling agents, epoxy-silane coupling agents, vinyl-silane coupling agents, etc., can be used alone or in combination of two or more. Among these, it is preferable that the silane coupling agent (E) be a mercapto-silane coupling agent or a sulfide-silane coupling agent, as this increases the vulcanization density and is particularly effective in lowering the dynamic magnification and improving durability.

[0024] Examples of the mercapto-silane coupling agents include 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane. These can be used alone or in combination of two or more.

[0025] Examples of the sulfide-based silane coupling agents 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-dimethylthiocarbamoyl tetrasulfide. Examples include rasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, and 3-trimethoxysilylpropyl methacrylate monosulfide. These can be used individually or in combination of two or more.

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

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

[0028] Examples of the vinyl-based silane coupling agents include vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris(β-methoxyethoxy)silane, vinyldimethylchlorosilane, vinyltrichlorosilane, vinyltriisopropoxysilane, and vinyltris(2-methoxyethoxy)silane. These can 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, and more preferably 0.3 to 8 parts by mass, per 100 parts by mass of the diene rubber (A), due to their excellent low dynamic ratio and durability.

[0030] In addition, in this vibration-damping rubber composition, in addition to the essential components (A) to (D) mentioned above, it is also possible to include component (E), vulcanizing agents, vulcanizing accelerators, vulcanizing aids, anti-aging agents, process oils, etc., as needed.

[0031] Examples of the aforementioned vulcanizing agents include sulfur (powdered sulfur, precipitated sulfur, insoluble sulfur), sulfur-containing compounds such as alkylphenol disulfides, etc. These can be used alone or in combination of two or more.

[0032] Furthermore, the content of the vulcanizing agent is preferably in the range of 0.1 to 10 parts by mass, and particularly preferably in the range of 0.3 to 5 parts by mass, per 100 parts by mass of the diene rubber (A). This is because if the content of the vulcanizing agent is too low, the vulcanization reactivity tends to deteriorate, and conversely, if the content of the vulcanizing agent is too high, the rubber properties (breaking strength, elongation at break) tend to decrease.

[0033] Examples of the aforementioned 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 individually or in combination of two or more. Among these, a combination of a thiram-based vulcanization accelerator and at least one vulcanization accelerator selected from sulfenamide-based, guanidine-based, and thiazole-based accelerators is preferred because it results in excellent compression set.

[0034] Furthermore, the content of the vulcanization accelerator is preferably in the range of 0.1 to 10 parts by mass, and 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 thiram-based vulcanization accelerators include tetramethylthiram disulfide (TMTD), tetraethylthiram disulfide (TETD), tetrabutylthiram disulfide (TBTD), tetrakis(2-ethylhexyl)thiram disulfide (TOT), and tetrabenzylthiram disulfide (TBzTD). These can be used individually or in combination of two or more.

[0036] Examples of the sulfenamide-based vulcanization accelerators include N-oxydiethylene-2-benzothiazolyl sulfenamide (NOBS), N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), Nt-butyl-2-benzothiazole sulfenamide (BBS), and N,N'-dicyclohexyl-2-benzothiazole sulfenamide. These can be used alone or in combination of two or more.

[0037] Examples of the guanidine-based vulcanization accelerators include N,N'-diphenylthiourea, trimethylthiourea, N,N'-diethylthiourea, and N,N'-dibutylthiourea. These can be used individually or in combination of two or more.

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

[0039] Examples of the aforementioned vulcanization aids include zinc oxide (ZnO), stearic acid, and magnesium oxide. These can be used individually or in combination of two or more.

[0040] Furthermore, the content of the vulcanization aid is preferably in the range of 0.1 to 10 parts by mass, and 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 aforementioned antioxidants include carbamate-based antioxidants, phenylenediamine-based antioxidants, phenol-based antioxidants, diphenylamine-based antioxidants, quinoline-based antioxidants, imidazole-based antioxidants, and waxes. These can be used individually or in combination of two or more.

[0042] Furthermore, the content of the antioxidant is preferably in the range of 0.5 to 15 parts by mass, and 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 aforementioned process oils include naphthenic oils, paraffinic oils, and aromatic oils. These can be used individually or in combination of two or more.

[0044] Furthermore, the content of the process oil is preferably in the range of 1 to 35 parts by mass, and 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 vibration-damping rubber composition] Herein, this vibration-damping rubber composition can be prepared by using the essential components (A) to (D) in specific proportions, and further, if necessary, using component (E) and the other materials listed above, and kneading them using a kneader, Banbury mixer, open roll, twin-screw agitator, etc.

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

[0047] Furthermore, it is preferable that the vibration-damping rubber composition obtained in this manner satisfies the following condition (α) from the viewpoint of obtaining the effects of the present invention (satisfying all of the following at a high level: high durability, low spring drop, and insulation). (α) The ΔG' shown by equation (I) below 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, a deflection 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, a deflection angle of 42%, and 40°C.]

[0048] Furthermore, from the viewpoint of obtaining the effects of the present invention well, it is preferable that ΔG' be 4.5 or less.

[0049] Note that ΔG’ represented by the above formula (I) is an index for evaluating the cohesiveness of the filler as per the description in JP-A-2006-47070. The smaller ΔG’ is, the higher the degree of dispersion of the filler. Also, G’1 and G’2 can be measured, for example, by a rubber processing tester, a curastometer, dynamic viscoelasticity measurement, etc. More specifically, it is measured by RPA2000 manufactured by Alpha Technology Co., Ltd.

[0050] And this vibration-proof rubber composition becomes a vibration-proof rubber member (vulcanizate) by vulcanizing at a high temperature (150 to 170°C) for 5 to 30 minutes.

[0051] The hardness (JIS-A hardness) of the surface of the vibration-proof rubber member (vulcanizate) is usually 60 to 85, preferably 65 to 80. Note that the above hardness can be measured by an Asker rubber hardness meter (P1-A type) manufactured by Kobunshi Keiki Co., Ltd.

[0052] Also, the vibration-proof rubber member (vulcanizate) can achieve 80,000 or more expansion and contraction cycles at break in the expansion and contraction fatigue test conducted according to JIS K 6260. Preferably, it achieves 100,000 or more expansion and contraction cycles at break, and more preferably, it achieves 120,000 or more expansion and contraction cycles at break.

[0053] Furthermore, the vibration-proof rubber member (vulcanizate) has a volume resistivity of 1×10 9 Ω·cm or more measured under the following conditions according to JIS K 6271-1:2015 (Vulcanized rubber and thermoplastic rubber - Method for determining electrical resistivity). Preferably, it has a volume resistivity of 1×10 11 [[ID=二十]]Ω·cm or more, and more preferably, it has a volume resistivity of 1×10 13 Ω·cm or more. [[ID=二十]] 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 × 100 mm Sample thickness: 2 mm Applied voltage: 1V Detection current range: 200pA~20mA

[0054] Furthermore, the vibration-damping rubber member (vulcanized body) can achieve a spring depressurization value of -20% or more, as shown in the following formula (II), obtained by conducting a durability fatigue test in which the member repeatedly expands and contracts by 4 mm in the compression direction and 15 mm in the tension direction at a frequency of 3 Hz, and measuring the load at 15 mm tension (initial load F1 and load F2 at 3000 expansion and contraction cycles). Preferably, the spring depressurization value is -18% or more, and more preferably, the spring depressurization value is -16% or more. Spring rate reduction = {(F2-F1) / F1} × 100 (%) ... (II)

[0055] Thus, vibration-damping rubber members made from the vulcanized body of this vibration-damping rubber composition can satisfy all of the following requirements at a high level: high durability, low spring rate reduction, and insulation. Therefore, they can exhibit excellent performance as a material for vibration-damping rubber, especially for railway vehicles. In addition to the above-mentioned uses, it can also be used as a component of engine mounts, stabilizer bushings, suspension bushings, motor mounts, subframe mounts, etc., used in automobiles and other vehicles. In particular, due to its high insulation properties, it can be advantageously used as a component (vibration-damping rubber member for electric vehicles) for electric vehicles (including electric vehicles (EVs), fuel cell vehicles (FCVs), plug-in hybrid vehicles (PHVs), hybrid vehicles (HVs), etc.) that use electric motors as a power source, such as motor mounts, suspension bushings, and subframe mounts. Furthermore, due to its high insulating properties, it can be used in applications such as vibration damping dampers for computer hard disks, vibration damping dampers for general household appliances such as washing machines, and vibration damping and seismic isolation devices such as vibration damping walls and dampers for buildings in the construction and housing sectors. [Examples]

[0056] Next, examples will be described together with comparative examples. However, 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 obtained in accordance with the method described above.

[0058] [Natural rubber (NR)]

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

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

[0061] [Carbon Black (i)] Tokai Carbon Co., Ltd. manufactured Seast V (BET specific surface area 27m²) 2 / g)

[0062] [Carbon Black (ii)] Asahi Carbon Co., Ltd. Asahi #60 (BET specific surface area 40m²) 2 / g)

[0063] [Carbon Black (iii)] Tokai Carbon Co., Ltd. manufactured Seast SRA (BET specific surface area 18m²) 2 / g)

[0064] [Carbon Black (iv)] Cabot Japan Co., Ltd. Show Black N330 (BET specific surface area 75m²) 2 / g)

[0065] [Carbon Black (v)] Asahi Carbon Co., Ltd. Asahi #15 (BET specific surface area 12m²) 2 / g)

[0066] [Carbon Black (vi)] Asahi Carbon Co., Ltd. Asahi #65 (BET specific surface area 42m²) 2 / g)

[0067] 〔silica〕 Nipseal VN3 (BET specific surface area 180-230 m²), manufactured by Tosoh Silica Co., Ltd. 2 / g)

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

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

[0070] [Zinc Oxide] Zinc oxide type 2, manufactured by Sakai Chemical Industry Co., Ltd.

[0071] [Stearic acid] NOF Corporation, Cherry Blossom Stearic Acid Beads

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

[0073] [Process oil] Manufactured by Japan Sun Oil Co., Ltd., Sunsen 410

[0074] [Vulcanization accelerator] Sanshin Chemical Industry Co., Ltd., Suncellar CZ-G

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

[0076] [Examples 1-13, Comparative Examples 1-9] The vibration-damping rubber composition was prepared by mixing and kneading the aforementioned materials in the proportions shown in Tables 1 and 2 below. The kneading was carried out by first kneading the materials other than the vulcanizing agent and vulcanization accelerator at 140°C for 5 minutes using a Banbury mixer, and then mixing in the vulcanizing agent and vulcanization accelerator and kneading at 60°C for 5 minutes using an open roll mixer.

[0077] The vibration-damping rubber compositions of the examples and comparative examples obtained in this manner were used to evaluate their respective properties according to the following criteria. 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 oscillation angle of 0.28% and storage modulus G'2 at a oscillation angle of 42%) was measured at a frequency of 11 Hz and 40°C using RPA2000 (manufactured by Alpha Technology). Based on the above measurement results, ΔG', shown in the following equation (I), was calculated. ΔG'=G'1 / G'2 ……(I)

[0079] <Reinforcement> Each vibration-damping rubber composition was press-molded (vulcanized) at 150°C for 30 minutes, and the hardness of the rubber surface (JIS-A hardness) was measured using an Asker rubber hardness tester (P1-A type) (manufactured by Polymer Instruments Co., Ltd.). The reinforcing properties were then evaluated according to the following criteria. ○ (very good): Hardness of 60 or higher. × (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 2mm thick rubber sheet. A JIS No. 3 dumbbell was then punched out from this rubber sheet, and a stretch fatigue test was performed using this dumbbell in accordance with JIS K 6260. Then, the number of expansions and contractions at the time of fracture was measured, and the durability was evaluated according to the following criteria. ○ (very good): Over 80,000 stretches. × (poor): Less than 80,000 stretching / retracting cycles.

[0081] <Insulating properties> For each vibration-damping rubber composition, samples were obtained by press molding (vulcanization) at 150°C for 30 minutes. The volume resistivity VR (Ω·cm) was then measured according to JIS K 6271-1:2015 (Vulcanized rubber and thermoplastic rubber - Method for determining electrical resistivity). Specifically, the volume resistivity VR was determined under the following conditions. Measurement method: Double-ring electrode method Guard electrode: Outer diameter 80mm, inner diameter 70mm Main electrode: 50mm Sample dimensions: 100mm x 100mm Sample thickness: 2mm Applied voltage: 1V Detection current range: 200pA~20mA Then, the insulating properties were evaluated according to the following criteria. ○ (very good): Volume resistivity VR is 1 × 10⁻⁶ 9 Ω·cm or more. × (poor): Volume resistivity VR is 1 × 10⁻⁶ 9 Less than Ω·cm.

[0082] <Spring weakening> Each vibration-damping rubber composition was press-molded (vulcanized) at 150°C for 30 minutes to obtain vibration-damping rubber samples. A durability fatigue test was then conducted on these samples, which were subjected to repeated expansion and contraction of 4 mm in the compression direction and 15 mm in the tension direction at a frequency of 3 Hz. The load at 15 mm tension (initial load F1 and load F2 at 3000 expansion and contraction cycles) was measured. Based on these measurement results, the spring depressurization property shown in the following formula (II) was calculated. Spring rate reduction = {(F2-F1) / F1} × 100 (%) ... (II) Then, the spring depressurization performance was evaluated according to the following criteria. ○ (very good): Spring tension reduction of -20% or more. × (poor): Spring tension is less than -20%.

[0083] [Table 1]

[0084] [Table 2]

[0085] From the results in Tables 1 and 2, the vulcanized bodies of the vibration-damping rubber compositions of the examples exhibited the characteristics required by the present invention in terms of durability (high durability), spring rate reduction (low spring rate reduction), and insulation.

[0086] In contrast, the vibration-damping rubber composition of Comparative Example 1 had too little dihydrazide compound content and insufficient dispersion of carbon black, resulting in the formation of conductive paths and poor insulation properties. Furthermore, insufficient dispersion of carbon black and silica led to the formation of aggregates, which collapsed during durable vibration, causing a decrease in load and resulting in poor spring-reducing performance. The vibration-damping rubber composition of Comparative Example 2 had too much dihydrazide compound content, which significantly increased the viscosity of the rubber and resulted in poor durability. The vibration-damping rubber composition of Comparative Example 3 had too little carbon black content, resulting in poor reinforcing properties (hardness). The vibration-damping rubber composition of Comparative Example 4 had too much carbon black, resulting in poor insulation due to the formation of conductive paths. The vibration-damping rubber composition of Comparative Example 5 exhibited a BET specific surface area of ​​carbon black exceeding the value specified in the present invention. As the surface area increased, the conductivity increased, resulting in poor insulation properties. The vibration-damping rubber composition of Comparative Example 6 exhibited a BET specific surface area of ​​carbon black that was less than the value specified in the present invention. As a result, the interface between the rubber and carbon black was prone to crack initiation during durable vibration, leading to inferior durability. The vibration-damping rubber composition of Comparative Example 7 had too little silica, resulting in poor reinforcing properties (hardness). The vibration-damping rubber composition of Comparative Example 8 had too much silica, causing aggregates of silica to break down during durable vibration, resulting in a decrease in load and thus poor spring-reducing performance. The vibration-damping rubber composition of Comparative Example 9 exhibited a BET specific surface area of ​​carbon black exceeding the value specified in the present invention. As the surface area increased, the conductivity increased, resulting in poor insulation properties.

[0087] 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. [Industrial applicability]

[0088] Vibration-damping rubber components made from the vulcanized body of this vibration-damping rubber composition can satisfy high levels of durability, low spring drop, and insulation, and therefore can exhibit excellent performance as a material for vibration-damping rubber in railway vehicles in particular. In addition to the above-mentioned uses, it can also be used as a component of engine mounts, stabilizer bushings, suspension bushings, motor mounts, subframe mounts, etc., used in automobiles and other vehicles. In particular, due to its high insulation properties, it can be advantageously used as a component (vibration-damping rubber member for electric vehicles) for electric vehicles (including electric vehicles (EVs), fuel cell vehicles (FCVs), plug-in hybrid vehicles (PHVs), hybrid vehicles (HVs), etc.) that use electric motors as a power source, such as motor mounts, suspension bushings, and subframe mounts. Furthermore, due to its high insulating properties, it can be used in applications such as vibration damping dampers for computer hard disks, vibration damping dampers for general household appliances such as washing machines, and vibration damping and seismic isolation devices such as vibration damping walls and dampers for buildings in the construction and housing sectors.

Claims

1. A vibration-damping rubber composition comprising a polymer component consisting of component (A) below and components (B) to (D) below, wherein the proportion of component (B) is 0.1 to 5 parts by mass, the proportion of component (C) is 20 to 40 parts by mass, the proportion of component (D) is 10 to 30 parts by mass, and component (C) has a BET specific surface area of ​​18 to 40 m². ２ A vibration-damping rubber component for railway vehicles, consisting of a vulcanized body of a vibration-damping rubber composition, which is of a magnitude of / g. (A) Diene-based rubber. (B) Dihydrazide compounds. (C) Carbon Black. (D) Silica.

2. The vibration-damping rubber member for railway vehicles according to Claim 1, wherein the vibration-damping rubber composition further contains a silane coupling agent (E).

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

4. The vibration-damping rubber member for railway vehicles 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.

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