Vibration-damping rubber composition

Abstract

To provide an anti-vibration rubber composition that achieves both excellent low-temperature performance and damping performance. [Solution] The vibration-damping rubber composition contains 20 to 80 parts by mass of carbon black with an average particle size of 50 nm or less per 100 parts by mass of rubber component consisting only of diene rubber selected from natural rubber and butadiene rubber. The vibration-damping rubber composition preferably contains 30 to 100% by mass of natural rubber in the rubber component, and it is also preferable to contain 2 to 30 parts by mass of oil having an endothermic peak below -70°C in DSC measurement per 100 parts by mass of the rubber component.

Description

Technical Field

[0001] The present invention relates to a vibration isolation rubber composition that combines excellent low-temperature performance and high loss.

Background Art

[0002] The development of battery electric vehicles (BEVs) has become active, and with the shift to BEVs without a heat source, the need for developing a thermal management module that efficiently controls and utilizes the heat inside the vehicle without waste is also increasing.

[0003] Since the thermal management module is composed of a compressor and the like, it becomes a vibration source. Therefore, when mounted on a vehicle, it is necessary to use vibration isolation rubber for vibration isolation, and the vibration isolation rubber is required to have the performance of reducing vibration in the resonance region: high attenuation (reducing vibration at frequencies after the resonance region: low dynamic magnification). Furthermore, when performing thermal control by the heat pump method, in use in cold regions, it is necessary to fully operate the compressor at low temperature for a certain period of time, and excellent low-temperature characteristics are also required to prevent vibration deterioration at low temperature.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Although it is known that the low-temperature characteristics of rubber depend on the characteristics of the polymer used and that the use of a BR polymer with a low Tg is effective, the attenuation performance tends to decrease.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a vibration isolation rubber composition that combines excellent low-temperature performance and attenuation performance. [Means for solving the problem]

[0007] As a result of diligent research to achieve the above objective, the inventors discovered that by combining a rubber component consisting solely of diene-based rubber with carbon black of a specific particle size, an anti-vibration rubber composition that achieves both excellent low-temperature performance and damping performance can be obtained, leading to the present invention.

[0008] The present invention provides an anti-vibration rubber composition containing 20 to 80 parts by mass of carbon black with an average particle size of 50 nm or less, with respect to 100 parts by mass of a rubber component consisting solely of diene rubber selected from natural rubber and butadiene rubber.

[0009] The present invention also provides a vibration-damping rubber member for an automobile's thermal management module, which is obtained by crosslinking the vibration-damping rubber composition. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an anti-vibration rubber composition that achieves both excellent low-temperature performance and damping performance. [Modes for carrying out the invention]

[0011] The vibration-damping rubber composition of the present invention contains a rubber component consisting solely of diene rubber selected from natural rubber and butadiene rubber. In other words, the vibration-damping rubber composition of the present invention does not contain non-diene rubber as a rubber component. Because the rubber component consists solely of diene rubber selected from natural rubber and butadiene rubber, the vibration-damping rubber composition of the present invention exhibits excellent low-temperature performance.

[0012] The natural rubber used in this invention may be selected from known types as appropriate, for example, from RSS (Ribbed smoked sheets) and TSR (Technically Specified Rubber).

[0013] The butadiene rubber used in this invention may be any known type that can be appropriately selected and used, but from the viewpoint of low-temperature properties, it is preferable to use high-cis-1,4-polybutadiene with a cis-1,4 bond content of 90% or more. Examples of such butadiene rubbers include BR 01, BR T700, BR 730 (manufactured by ENEOS Material Co., Ltd.); Nipol® BR1220 (manufactured by Nippon Zeon Co., Ltd.); and UBEPOL® BR150 (manufactured by UBE Elastomer Co., Ltd.).

[0014] The natural rubber content in the rubber component is preferably 30 to 100% by mass, and particularly preferably 40 to 60% by mass.

[0015] The vibration-damping rubber composition of the present invention preferably contains carbon black with an average particle size of 55 nm or less. Examples of such carbon black include SAF grade, ISAF grade, HAF grade, and FEF grade. The average particle size of the carbon black is more preferably 20 to 55 nm. Damping performance can be improved by using carbon black with an average particle size in this range.

[0016] The carbon black content is preferably 20 to 80 parts by mass, and more preferably 30 to 70 parts by mass, per 100 parts by mass of rubber component.

[0017] The vibration-damping rubber composition of the present invention, by using the above-mentioned specific rubber components in combination with carbon black, is a vibration-damping rubber composition that achieves both excellent low-temperature performance and damping performance. As an indicator of excellent low-temperature performance, the Tg is preferably -40°C or lower, more preferably -45°C or lower, and particularly preferably -47°C or lower. Furthermore, as an indicator of excellent damping performance, the loss coefficient (tanδ) is preferably 0.050 or higher, more preferably 0.060 or higher, and particularly preferably 0.070 or higher.

[0018] The vibration-damping rubber composition of the present invention preferably contains a low-viscosity oil in addition to the rubber components and carbon black described above. Specifically, it is preferable to contain an oil that has an endothermic peak below -70°C in DSC measurements, and more preferably an oil that has an endothermic peak below -80°C.

[0019] The oil content is preferably 2 to 30 parts by mass, and more preferably 10 to 20 parts by mass, per 100 parts by mass of rubber component.

[0020] In addition to the rubber components, carbon black, and oil described above, the vibration-damping rubber composition of the present invention may contain vulcanizing agents, vulcanization accelerators, vulcanization accelerators, crosslinking agents, and anti-aging agents that are commonly used in vibration-damping rubber compositions.

[0021] Examples of vulcanizing agents include sulfur and sulfur-containing compounds such as alkylphenol disulfide compounds, but in the present invention, the use of sulfur is preferred. The amount of sulfur added is usually 0.1 to 10.0 parts by mass, preferably 0.3 to 5.0 parts by mass, and more preferably 0.5 to 3.0 parts by mass, per 100 parts by mass of the rubber component, in order to maintain the desired basic physical properties such as hardness and tensile strength in good condition. Peroxides such as dialkyl peroxides and peroxyketals can also be used as vulcanizing agents, and in this case, the amount added is usually 1.0 to 10.0 parts by mass, preferably 2.0 to 8.0 parts by mass, per 100 parts by mass of the rubber component.

[0022] Examples of the vulcanization accelerator include benzothiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, dibenzothiazyl disulfide, N-cyclohexyl-2-benzothiazylsulfenamide, N-t-butyl-2-benzothiazylsulfenamide, N-t-butyl-2-benzothiazylsulfenamide; guanidine-based vulcanization accelerators such as diphenylguanidine; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide, tetrabutylthiuram disulfide, tetradodecylthiuram disulfide, tetraoctylthiuram disulfide, tetrabenzylthiuram disulfide, etc. These may be used alone or in combination of two or more. In the present invention, benzothiazole-based vulcanization accelerators can be preferably used. The compounding amount of the vulcanization accelerator is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, based on 100 parts by mass of the rubber component, from the viewpoints of the manufacturing workability of the vibration-proof rubber and obtaining the desired hardness.

[0023] Examples of the vulcanization accelerator assistant include zinc oxide (ZnO) and fatty acids. The fatty acids may be saturated, unsaturated, linear or branched, and the number of carbon atoms is not particularly limited. Examples of the fatty acid include fatty acids having 1 to 30 carbon atoms, preferably 15 to 30 carbon atoms, more specifically naphthenic acids such as cyclohexanoic acid (cyclohexanecarboxylic acid), alkylcyclopentanes having side chains, hexanoic acid, octanoic acid, decanoic acid (including branched carboxylic acids such as neodecanoic acid), dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid (stearic acid) and other saturated fatty acids, methacrylic acid, oleic acid, linoleic acid, linolenic acid and other unsaturated fatty acids, rosin, tall oil acid, abietic acid and other resin acids. These may be used alone or in combination of two or more. In the present invention, zinc oxide and stearic acid can be preferably used. The compounding amount of the vulcanization accelerator assistant is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass, based on 100 parts by mass of the rubber component, from the viewpoints of the manufacturing workability of the vibration-proof rubber and obtaining the desired hardness.

[0024] Examples of the crosslinking agent include bismaleimide compounds and phenolic resins. Examples of the bismaleimide compounds include N,N'-o-phenylenebismaleimide, N,N'-m-phenylenebismaleimide, N,N'-p-phenylenebismaleimide, N,N'-(4,4'-diphenylmethane)bismaleimide, 2,2-bis-[4-(4-maleimidophenoxy)phenyl]propane, and bis(3-ethyl-5-methyl-4-maleimidophenyl)methane. In the present invention, from the viewpoint of storage stability, bismaleimide compounds are preferred. The compounding amount of these bismaleimide compounds is preferably 0.5 to 5.0 parts by mass, more preferably 0.5 to 3.0 parts by mass, based on 100 parts by mass of the rubber component.

[0025] Examples of the anti-aging agent include phenolic anti-aging agents, imidazole anti-aging agents, amine anti-aging agents, and waxes. These may be used alone or in combination of two or more. The compounding amount of the anti-aging agent is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, and still more preferably 1 to 3 parts by mass, based on 100 parts by mass of the rubber component.

[0026] In addition, within a range not impairing the effects of the present invention, additives such as antioxidants, foaming agents, plasticizers, lubricants, tackifiers, petroleum resins, ultraviolet absorbers, dispersants, compatibilizers, and homogenizers, which are usually used in rubber products, can be appropriately compounded as needed.

[0027] When obtaining the vibration-proof rubber composition of the present invention, there is no particular limitation on the compounding method of the above components. All component raw materials may be compounded and kneaded at once, or the components may be compounded and kneaded in two or three steps. When kneading, kneading machines such as rolls, internal mixers, and Banbury rotors can be used. Further, when forming into a sheet shape, a strip shape, etc., known molding machines such as an extrusion molding machine and a press machine may be used.

[0028] The vibration-damping rubber member for an automobile thermal management module of the present invention is obtained by crosslinking (vulcanizing) the above-described vibration-damping rubber composition. Although not particularly limited, the vibration-damping rubber composition hardens into a vibration-damping rubber member by vulcanization at 140 to 180°C for 5 to 120 minutes. Since this vibration-damping rubber member is made using the above-described vibration-damping rubber composition of the present invention, it can achieve both excellent low-temperature performance and damping performance. [Examples]

[0029] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0030] [Examples 1-5, Comparative Example 1] Vibration-damping rubber compositions were manufactured by kneading each component according to the formulations shown in Table 1. The kneading process was carried out in two stages: first, all materials except sulfur, crosslinking agent, vulcanization accelerator, and vulcanization accelerator were mixed using a Banbury mixer for approximately 2.5 minutes; and then, sulfur, crosslinking agent, vulcanization accelerator, and vulcanization accelerator were added and mixed using a Banbury mixer at 110°C for approximately 1 minute.

[0031] <Low-temperature characteristics> The obtained vibration-damping rubber composition was press-vulcanized at 155°C for two bouts (T90 x 2) to produce cylindrical molded bodies (vibration-damping rubber members) with a diameter of 8 mm and a height of 6 mm. The glass transition temperature (Tg) was then measured using these members. Specifically, using TA Instruments' ARES-G2, shear dynamic viscoelasticity measurements were performed in accordance with JIS K 7244-1, with a strain of 0.1% and a frequency of 100 Hz, under temperature dispersion (-60°C to 40°C), to determine the glass transition temperature (Tg). The results are shown in Table 1.

[0032] <Damping performance> The obtained vibration-damping rubber composition was press-vulcanized at 155°C for 4 bets (T90×4) to produce a cylindrical molded body (vibration-damping rubber member) with a diameter of φ30 mm and a height of 30 mm. The loss coefficient (tanδ) was then measured using this member. Specifically, in accordance with JIS K6385, in the non-resonant method of the dynamic property measurement test, vibrations with a frequency of 15 Hz and an amplitude of ±0.5 mm were applied to the test piece perpendicular to its axis under a load that deflected by 10% (3 mm), and the dynamic spring constant tanδ was measured. The results are shown in Table 1.

[0033] The details of each component in Table 1 are as follows: Natural rubber: "RSS#4" Butadiene rubber (BR): UBE Corporation's "UBEPOL BR150" CB1: ISAF-grade carbon black, average particle size 20nm CB2: FEF grade carbon black, average particle size 42nm CB3: FT-grade carbon black, average particle size 120nm Oil: Oil exhibiting an endothermic peak in DSC measurement between -95°C and -80°C. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Co., Ltd. Stearic acid: "Stearic acid 50S" manufactured by Shin Nippon Rika Co., Ltd. Wax: "Suntight S" manufactured by Seiko Chemical Co., Ltd. Anti-aging agent: "Nocrack 6C" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Zinc oxide: Hakusui Tech Co., Ltd. "No. 3 Zinc Oxide" Vulcanization accelerator 1: "Noxellar TBT" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: "Noxellar NS-F" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0034] [Table 1]

[0035] As shown in Table 1, the vibration-damping rubber compositions of Examples 1 to 5 exhibit excellent low-temperature characteristics, as their Tg is -45°C or lower, and also demonstrate excellent damping performance, as their loss coefficient (tanδ) is large at 0.060 or higher. On the other hand, the vibration-damping rubber composition of Comparative Example 1, which uses carbon black with a large average particle size, has a small loss coefficient and is inferior in damping performance.

Claims

1. A vibration-damping rubber composition comprising 100 parts by mass of a rubber component consisting solely of diene rubber selected from natural rubber and butadiene rubber, and 20 to 80 parts by mass of carbon black having an average particle size of 50 nm or less.

2. The vibration-damping rubber composition according to claim 1, wherein the natural rubber content in the rubber component is 30 to 100% by mass.

3. The vibration-damping rubber composition according to claim 1, wherein the average particle size of the carbon black is 20 to 55 nm.

4. The vibration-damping rubber composition according to claim 1, comprising 2 to 30 parts by mass of an oil having an endothermic peak below -70°C in DSC measurement, per 100 parts by mass of the rubber component.

5. A vibration-damping rubber composition according to any one of claims 1 to 4, for use in a thermal management module of an automobile.

6. A vibration-damping rubber member for an automobile thermal management module, comprising a crosslinked vibration-damping rubber composition according to any one of claims 1 to 4.

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