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

Abstract

Provided are a vibration-damping rubber composition for electric vehicles and a vibration-damping rubber member for electric vehicles whereby it is possible to achieve low dynamic magnification in a region with high rigidity (a large static spring constant).　The vibration-damping rubber composition for electric vehicles contains the components (A) to (C) indicated below. (A) is a diene rubber. (B) is a surface-active carbon black in which a value (Hc) obtained by converting the amount of hydrogen generated per gram of carbon black when heated to 1980°C is 4500 ppm or more. (C) is carbon black with an iodine adsorption amount of 20 g / kg or less.

Description

Anti-vibration rubber composition for electric vehicles and anti-vibration rubber member for electric vehicles

[0001] The present invention relates to an anti-vibration rubber composition for electric vehicles and an anti-vibration rubber member for electric vehicles.

[0002] Anti-vibration rubber compositions are used in automobiles to reduce vibration and noise. Such anti-vibration rubber compositions are required to have high rigidity, high strength, and vibration transmission suppression in their vulcanized bodies (anti-vibration rubber components). Therefore, a small dynamic magnification ratio (dynamic spring constant (Kd100) / static spring constant (Ks)) is required. Electric vehicles are heavier than gasoline-powered vehicles, so anti-vibration rubber components are required to have higher durability. Therefore, it is important to reduce the dynamic magnification ratio in the higher rigidity (large static spring constant) range. Conventionally, a low dynamic magnification ratio has been achieved by, for example, using carbon black as a reinforcing agent in anti-vibration rubber compositions and controlling factors such as the amount, particle size, and structure of the carbon black.

[0003] Patent No. 7037986

[0004] However, it is difficult to achieve a low dynamic magnification in a region of higher rigidity (large static spring constant) simply by controlling factors such as the amount of carbon black blended, particle size, structure, etc., as has been done conventionally.

[0005] The problem to be solved by the present invention is to provide an anti-vibration rubber composition for electric vehicles and an anti-vibration rubber member for electric vehicles that can achieve a low dynamic magnification in a high rigidity (large static spring constant) range.

[0006] In order to solve the above problems, the anti-vibration rubber composition for electric vehicles according to the present invention contains the following components (A) to (C): (A) a diene rubber; (B) a surface-activated carbon black having a value (Hc) calculated as the amount of hydrogen generated per gram of carbon black when heated to 1980°C of 4500 ppm or more; and (C) a carbon black having an iodine adsorption amount of 20 g / kg or less.

[0007] The total amount of (B) and (C) may be 60 parts by mass or more and 100 parts by mass or less per 100 parts by mass of (A). The mass ratio of the content of (C) to (B) may be 0.5 or more and 2.0 or less. (A) may be one or more rubbers selected from natural rubber, butadiene rubber, styrene-butadiene rubber, isoprene rubber, and chloroprene rubber. The static spring constant Ks of the anti-vibration rubber composition for electric vehicles according to the present invention may be 700 N / mm or more and 1000 N / mm or less.

[0008] The anti-vibration rubber member for electric vehicles according to the present invention is formed from a vulcanizate of the anti-vibration rubber composition for electric vehicles according to the present invention.

[0009] (1) The anti-vibration rubber composition for electric vehicles according to the present invention contains the following components (A) to (C): (A) a diene rubber; (B) a surface-activated carbon black having a hydrogen content (Hc) of 4500 ppm or more when heated to 1980°C, calculated as the amount of hydrogen generated per gram of carbon black; and (C) a carbon black having an iodine adsorption of 20 g / kg or less.

[0010] (2) In the above (1), the total amount of (B) and (C) may be 60 parts by mass or more and 100 parts by mass or less per 100 parts by mass of (A).

[0011] (3) In the above (1) or (2), the mass ratio of the content of (C) to the content of (B) may be 0.5 or more and 2.0 or less.

[0012] (4) In any one of the above (1) to (3), (A) may be one or more rubbers selected from natural rubber, butadiene rubber, styrene-butadiene rubber, isoprene rubber, and chloroprene rubber.

[0013] (5) In any one of the above (1) to (4), the static spring constant Ks of the anti-vibration rubber composition for electric vehicles may be 700 N / mm or more and 1000 N / mm or less.

[0014] (6) The anti-vibration rubber member for electric vehicles according to the present invention is made of a vulcanizate of the anti-vibration rubber composition for electric vehicles according to any one of (1) to (5) above.

[0015] According to the anti-vibration rubber composition for electric vehicles of the present invention, since it contains the above-mentioned components (A) to (C), it is possible to achieve a low dynamic magnification ratio in a high rigidity (large static spring constant) region.

[0016] Here, when the total amount of (B) and (C) is 60 parts by mass or more and 100 parts by mass or less per 100 parts by mass of (A), it is easy to achieve a low dynamic magnification ratio in a high rigidity (large static spring constant) region.

[0017] When the mass ratio of the content of (C) to the content of (B) is 0.5 or more and 2.0 or less, a low dynamic magnification is achieved in a high rigidity (large static spring constant) region, and durability is also excellent.

[0018] When the (A) is one or more rubbers selected from natural rubber, butadiene rubber, styrene-butadiene rubber, isoprene rubber, and chloroprene rubber, it is easy to achieve a low dynamic magnification ratio in a high rigidity (large static spring constant) region.

[0019] If the static spring constant Ks is 700 N / mm or more and 1000 N / mm or less, it is suitable for use in an electric vehicle.

[0020] Furthermore, since the anti-vibration rubber member for electric vehicles according to the present invention is composed of a vulcanizate of the anti-vibration rubber composition for electric vehicles according to the present invention, it is possible to achieve a low dynamic magnification ratio in a high rigidity region (large static spring constant).

[0021] The vibration-damping rubber composition for electric vehicles and the vibration-damping rubber member for electric vehicles according to the present invention will be described in detail below.

[0022] The anti-vibration rubber composition for electric vehicles according to the present invention (hereinafter sometimes simply referred to as anti-vibration rubber composition) contains the following components (A) to (C): (A) a diene rubber; (B) a surface-activated carbon black having a value (Hc) of 4500 ppm or more, calculated as the amount of hydrogen generated per gram of carbon black when heated to 1980°C; and (C) a carbon black having an iodine adsorption amount of 20 g / kg or less.

[0023] The diene rubber (A) is the main component of the rubber component of the vibration-proof rubber composition. The main component of the rubber component refers to a component that accounts for 50% by mass or more of the total rubber component of the vibration-proof rubber composition. The vibration-proof rubber composition is significantly affected by the properties of the diene rubber (A), which is the main component of the rubber component. Examples of the diene rubber (A) include natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), isoprene rubber (IR), and acrylonitrile-butadiene rubber (NBR). These may be used alone or in combination as the diene rubber (A). Among these, natural rubber is preferably used from the viewpoint of achieving both strength, durability, and a low dynamic magnification ratio. Furthermore, using natural rubber (NR) and butadiene rubber (BR) in combination is preferable because it further reduces the dynamic magnification ratio. Terminal-modified butadiene rubber (BR) is more preferred as the butadiene rubber (BR). From the viewpoint of reducing the dynamic magnification, the mixing ratio of natural rubber (NR) to butadiene rubber (BR) is preferably NR / BR=100 / 0 to 70 / 30 by mass, more preferably NR / BR=90 / 10 to 70 / 30.

[0024] The terminal-modified butadiene rubber (B) is obtained by modifying the molecular terminals of butadiene rubber with an appropriate compound. Metal salts such as tin tetrachloride have been known as modifiers (see "The Journal of the Society of Rubber Science and Technology of Japan," Vol. 63, No. 5 (1990), pp. 27-33). It is also known to use lactam compounds as modifiers (see, for example, Nagata, "The Journal of the Society of Rubber Science and Technology of Japan," Vol. 62, No. 10 (1989), pp. 38-48). While the modifier is not particularly limited, blending lactam-modified butadiene rubber with natural rubber provides particularly excellent improvements in vibration-damping properties.

[0025] The surface-activated carbon black (B) has the effect of reducing the dynamic magnification without reducing the static spring constant or hardness of the vibration-damping rubber composition. The high-rigidity region refers to a region where the static spring constant Ks (N / mm) is 700 N / mm or more. More preferably, it refers to a region where the static spring constant Ks (N / mm) is 750 N / mm or more. As described above, the surface-activated carbon black (B) has a Hc (Hc) of 4500 ppm or more, calculated as the amount of hydrogen generated per gram of carbon black when heated to 1980°C. Furthermore, a Hc of 5000 ppm or more is preferable because it provides superior surface activity. The amount of hydrogen is derived from hydrogen atoms of organic groups, such as hydroxyl groups or carboxyl groups, that are covalently bonded to carbon atoms in the carbon black. Since the surface-active carbon black (B) has many polar functional groups, it has a strong interaction with the diene rubber (A), reducing friction between the diene rubber (A) and the surface of the surface-active carbon black (B). This is thought to contribute to lowering the dynamic magnification in a high-rigidity region where the static spring constant is large.

[0026] The hydrogen amount is measured, for example, as follows. First, 20 mg of carbon black, which had previously been degassed and dried in a vacuum dryer at 125°C for 4 hours to remove adsorbed components from the carbon black, is placed in a tin capsule and thermally decomposed in a graphite crucible at 1980°C for 70 seconds using a high-sensitivity hydrogen analyzer (EMGA-621 manufactured by Horiba, Ltd., using a TCD detector). The generated gas is then passed through a high-temperature oxidizing agent, a room-temperature oxidizing agent, a carbon dioxide remover, and a desiccant at a constant flow rate (400 ml / min) of carrier gas (inert argon gas), and separated in a column. The hydrogen gas thus obtained is then quantified using a detector (thermal conductivity method).

[0027] The surface-active carbon black (B) may be used alone or in combination of two or more kinds, so long as it has the above-mentioned hydrogen content.

[0028] From the viewpoints of durability and low dynamic magnification, the surface-active carbon black (B) preferably has an iodine adsorption of 14 g / kg or more and 28 g / kg or less. The iodine adsorption of the carbon black is a value measured in accordance with JIS K 6217-1 (Method A). Furthermore, from the viewpoints of durability and low dynamic magnification, the surface-active carbon black (B) preferably has a DBP absorption of 118 ml / 100 g or more and 132 ml / 100 g or less. The DBP absorption of the carbon black is a value measured in accordance with JIS K 6217-4.

[0029] As described above, carbon black (C) has an iodine adsorption of 20 g / kg or less. Carbon black (C) is a surface-inactive carbon black. By using carbon black (C) having an iodine adsorption of 20 g / kg or less together with surface-active carbon black (B), a low dynamic magnification can be achieved in a high rigidity (large static spring constant) range. The iodine adsorption of carbon black (C) is more preferably 10 g / kg or more and 20 g / kg or less, and even more preferably 15 g / kg or more and 20 g / kg or less. Furthermore, carbon black (C) preferably has a DBP absorption of 50 ml / 100 g or less, more preferably 30 ml / 100 g or more and 50 ml / 100 g or less.

[0030] The total amount of (B) and (C) is preferably 60 parts by mass or more and 100 parts by mass or less per 100 parts by mass of (A). When the content is 60 parts by mass or more, the static spring constant is large and high rigidity is easily achieved. From this viewpoint, the content is more preferably 65 parts by mass or more, and even more preferably 70 parts by mass or more. On the other hand, when the content is 100 parts by mass or less, the dynamic spring constant is kept small in the high rigidity (large static spring constant) region, and it is easy to achieve a low dynamic magnification ratio in the high rigidity (large static spring constant) region. From this viewpoint, the content is more preferably 95 parts by mass or less, and even more preferably 90 parts by mass or less.

[0031] The mass ratio of the content of (C) to (B) is preferably 0.5 or more and 2.0 or less, from the viewpoints of achieving excellent low dynamic magnification in a high rigidity (large static spring constant) region and excellent durability.

[0032] The anti-vibration rubber composition according to the present invention may contain, in addition to the above components (A) to (C), additives such as vulcanizing agents, vulcanization accelerators, vulcanization aids, antioxidants, and process oils.

[0033] Examples of vulcanizing agents 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.

[0034] The content of the vulcanizing agent is preferably in the range of 0.1 to 10 parts by weight, particularly preferably 0.3 to 5 parts by weight, per 100 parts by weight of the diene rubber (A). If the content of the vulcanizing agent is too low, crosslinking reactivity tends to deteriorate. If the content of the vulcanizing agent is too high, rubber physical properties (breaking strength, breaking elongation) tend to deteriorate.

[0035] 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.

[0036] The content of the vulcanization accelerator is preferably in the range of 0.1 to 10 parts by weight, particularly preferably in the range of 0.3 to 5 parts by weight, per 100 parts by weight of the diene rubber (A).

[0037] Examples of thiuram vulcanization accelerators include tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetrabutylthiuram disulfide (TBTD), tetrakis(2-ethylhexyl)thiuram disulfide (TOT), and tetrabenzylthiuram disulfide (TBzTD).

[0038] Examples of sulfenamide vulcanization accelerators 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.

[0039] 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.

[0040] Examples of thiazole vulcanization accelerators 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 crosslinking reactivity.

[0041] 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.

[0042] The content of the vulcanization aid is preferably in the range of 0.1 to 10 parts by weight, particularly preferably in the range of 0.3 to 7 parts by weight, per 100 parts by weight of the diene rubber (A).

[0043] Examples of the antioxidant include carbamate-based antioxidants, phenylenediamine-based antioxidants, phenol-based antioxidants, diphenylamine-based antioxidants, quinoline-based antioxidants, imidazole-based antioxidants, waxes, etc. These may be used alone or in combination of two or more.

[0044] The content of the antioxidant is preferably in the range of 0.5 to 15 parts by weight, particularly preferably in the range of 1 to 10 parts by weight, per 100 parts by weight of the diene rubber (A).

[0045] Examples of process oils include naphthenic oils, paraffinic oils, aromatic oils, etc. These may be used alone or in combination of two or more.

[0046] The content of the process oil is preferably in the range of 1 to 35 parts by weight, particularly preferably in the range of 3 to 30 parts by weight, per 100 parts by weight of the diene rubber (A).

[0047] The vibration-proof rubber composition according to the present invention can be prepared by kneading the components (A) to (C) and other materials added as necessary using a kneading machine such as a kneader, a Banbury mixer, an open roll, or a twin-screw mixer.

[0048] The anti-vibration rubber composition according to the present invention becomes an anti-vibration rubber member (vulcanizate) by vulcanizing it at a high temperature (150 to 170°C) for 5 to 30 minutes. The anti-vibration rubber member made of a vulcanizate of the anti-vibration rubber composition according to the present invention can be advantageously used in applications such as motor mounts, suspension bushings, and subframe mounts for electric vehicles (including electric vehicles (EVs), fuel cell vehicles (FCVs), plug-in hybrid vehicles (PHVs), hybrid vehicles (HVs), etc.) powered by electric motors.

[0049] According to the vibration-damping rubber composition of the present invention having the above-mentioned configuration, since the diene rubber (A) is blended with the surface-active carbon black (B) and the carbon black (C) having an iodine adsorption amount of 20 g / kg or less, a low dynamic magnification can be achieved in a high rigidity range (large static spring constant).

[0050] In view of suitability for electric vehicles, the anti-vibration rubber composition according to the present invention preferably has a static spring constant Ks of 700 N / mm or more and 1000 N / mm or less, and more preferably 750 N / mm or more and 1000 N / mm or less. By configuring the anti-vibration rubber composition according to the present invention as described above, the static spring constant Ks can be set within the above range.

[0051] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention.

[0052] The present invention will be described in detail below using examples and comparative examples.

[0053] The materials used are as follows: <Diene rubber (A)> Natural rubber (NR) Terminal-modified butadiene rubber (terminal-modified BR): Modifier: ε-caprolactam, polymer viscosity: 50, cis-1,4 / trans-1,4 / vinyl ratio = 39 / 49 / 12 <Surface-active carbon black (B)> Surface-active carbon black (surface-active CB): "SPHERON 5200" manufactured by Cabot Japan (Hc: 5200 ppm, iodine adsorption 24 g / kg, DBP absorption 124 ml / 100 g) <Carbon black (C)> CB<1>: "SEAST TA" manufactured by Tokai Carbon, iodine adsorption 18 g / kg, DBP absorption 42 ml / 100 g) <Others> CB<2>: "SEAST SO" manufactured by Tokai Carbon, iodine adsorption 44 g / kg, DBP absorption 115 ml / 100 g)・Zinc oxide: "Zinc oxide type 2" manufactured by Sakai Chemical Industry Co., Ltd. ・Stearic acid: "Lunacc S30" manufactured by Kao Co., Ltd. ・Process oil: "Sansen 4130" manufactured by Nippon San Oil Co., Ltd. ・Amine-based antioxidant <1>: "Ozonone 6C" manufactured by Seiko Chemical Co., Ltd. ・Amine-based antioxidant <2>: "Nonflex RD" manufactured by Seiko Chemical Co., Ltd. ・Vulcanization accelerator <1>: "Noccela CZ" manufactured by Ouchi Shinko Chemical Co., Ltd. ・Vulcanization accelerator <2>: "Noccela TBT" manufactured by Ouchi Shinko Chemical Co., Ltd. ・Sulfur (vulcanizing agent)

[0054] (Examples 1 to 4, Comparative Examples 1 to 3) Each material was blended in the ratio (parts by mass) shown in the table, and then kneaded using an internal mixer (Banbury type) or a roll to prepare a rubber composition. The properties of the prepared rubber compositions were measured and evaluated according to the following methods.

[0055] [Static Spring Constant (Ks)] Using each rubber composition, a rubber test piece was prepared by pressing a disk-shaped metal fitting (diameter 60 mm, thickness 6 mm) onto the top and bottom surfaces of a rubber piece (diameter 50 mm, height 25 mm) under vulcanization conditions of 170°C x 30 minutes, followed by vulcanization. The rubber test piece was then compressed 7 mm in the cylindrical axial direction, and the loads at deflections of 1.5 mm and 3.5 mm were read from the load-deflection curve of the second forward movement to calculate the static spring constant (Ks (N / mm)).

[0056] [Dynamic spring constant (Kd100)] The rubber test piece was compressed by 2.5 mm in the cylindrical axial direction, and a constant displacement harmonic compression vibration of 100 Hz and amplitude 0.05 mm was applied from below around the 2.5 mm compression position. The dynamic load was detected by a load cell above, and the dynamic spring constant (Kd100 (N / mm)) was calculated in accordance with JIS K 6394.

[0057] [Dynamic magnification ratio (Kd100 / Ks)] The dynamic magnification ratio was calculated as the value of dynamic spring constant (Kd100) / static spring constant (Ks). Since the dynamic magnification ratio is proportional to Ks, a rubber material with a lower dynamic magnification ratio is desirable for the same Ks. Therefore, the dynamic magnification ratio was evaluated (comparison of the superiority of the dynamic magnification ratio) using the value obtained by dividing the dynamic magnification ratio by Ks. A value of [dynamic magnification ratio / Ks×1000] of 1.90 or less was evaluated as "○", and a value exceeding 1.90 was evaluated as "×".

[0058] [Durability] Each rubber composition was press-molded (vulcanized) at 150°C for 30 minutes to prepare a rubber sheet having a thickness of 2 mm. JIS No. 3 dumbbells were punched out from the rubber sheet, and a stretch fatigue test was performed using these dumbbells in accordance with JIS K 6260 to measure the number of cycles of durability. Test pieces with a durability of more than 4000 cycles were rated "A," those with a durability of 2000 to 4000 cycles were rated "B," and those with a durability of less than 2000 cycles were rated "C."

[0059]

[0060] Comparative Examples 1 and 3 are made by compounding no surface-activated carbon black with diene rubber. Comparative Example 1 is made by compounding only one type of non-surface-activated carbon black with diene rubber. Comparative Example 3 is made by compounding two types of non-surface-activated carbon black with diene rubber. Comparative Example 2 is made by compounding both surface-activated carbon black and non-surface-activated carbon black with diene rubber, but the non-surface-activated carbon black does not have an iodine adsorption amount of 20 g / kg or less. Furthermore, according to the comparative examples, none of them achieve a low dynamic magnification in the high rigidity (large static spring constant) range.

[0061] In contrast, in the examples, surface-active carbon black and carbon black with an iodine adsorption of 20 g / kg or less are blended with the diene rubber, and a low dynamic magnification is achieved in the high rigidity range (large static spring constant).

[0062] From the above examples and comparative examples, it is clear that by blending surface-active carbon black (B) and carbon black (C) having an iodine adsorption amount of 20 g / kg or less with diene rubber (A), a low dynamic magnification can be achieved in a high rigidity range (large static spring constant).

[0063] Among the examples, it is clear that when the mass ratio of the content of carbon black (C) to the content of surface-active carbon black (B) is 0.5 or more and 2.0 or less, the durability is more excellent.

[0064] Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above embodiments and examples, and various modifications are possible within the scope of the invention.

Claims

1. An anti-vibration rubber composition for electric vehicles, comprising the following components (A) to (C): (A) a diene rubber; (B) a surface-active carbon black, the amount of hydrogen generated when heated to 1980°C, calculated per gram of carbon black, expressed as Hc, of 4500 ppm or more; and (C) a carbon black having an iodine adsorption of 20 g / kg or less.

2. The vibration-proof rubber composition for electric vehicles according to claim 1, wherein the total amount of (B) and (C) is 60 parts by mass or more and 100 parts by mass or less per 100 parts by mass of (A).

3. The vibration-proof rubber composition for electric vehicles according to claim 1 or 2, wherein the mass ratio of the content of (C) to the content of (B) is 0.5 or more and 2.0 or less.

4. The anti-vibration rubber composition for electric vehicles according to any one of claims 1 to 3, wherein (A) is one or more types selected from the group consisting of natural rubber, butadiene rubber, styrene-butadiene rubber, isoprene rubber, and chloroprene rubber.

5. An anti-vibration rubber composition for electric vehicles according to any one of claims 1 to 4, having a static spring constant Ks of 700 N / mm or more and 1000 N / mm or less.

6. An anti-vibration rubber component for electric vehicles, comprising a vulcanizate of the anti-vibration rubber composition for electric vehicles according to any one of claims 1 to 5.

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