Vibration-damping rubber composition and production method for same

Abstract

The purpose of the present invention is to provide: a vibration-damping rubber composition that makes it possible to produce a vibration-damping rubber member which has excellent vibration damping properties with low dynamic magnification, and which also has excellent processability; and a production method for the same.　The present invention is a vibration-damping rubber composition obtained by a production method comprising: a first step for obtaining a primary kneaded product by kneading, at a temperature of 130-180°C, component a, which is a diene-based rubber, component b, which is a filler containing carbon black, and component c, which is a specific monohydrazide compound; and a second step for obtaining a secondary kneaded product by kneading the primary kneaded product and component d, which is zinc oxide.

Description

Anti-vibration rubber composition and its manufacturing method

[0001] The present invention relates to an anti-vibration rubber composition used in the manufacture of anti-vibration rubber members for use in automobiles and the like, and a method for producing the same.

[0002] In the past, in order to improve passenger comfort in various vehicles such as automobiles, attempts have been made to reduce the intrusion of vibration and noise into the cabin by placing various vibration-damping materials in areas that are sources of vibration and noise. For example, in the engine, which is the main source of vibration and noise, vibration is absorbed when the engine is running by using vibration-damping rubber in components such as torsional dampers, engine mounts, and muffler hangers, thereby reducing the intrusion of vibration and noise into the cabin and the diffusion of noise into the surrounding environment.

[0003] The basic characteristics of such anti-vibration rubber are that it must have high support performance to support heavy objects such as engines, and high vibration-damping performance to absorb and suppress their vibrations, and methods for reducing the dynamic magnification have been explored for some time.

[0004] Generally, when fillers such as carbon black and silica are thoroughly dispersed in a rubber composition, the dynamic modulus of elasticity decreases, and therefore the dynamic expansion ratio also decreases. However, extending the kneading time improves dispersion and can reduce the dynamic modulus of elasticity, but at the same time, polymer molecular chains are scissioned, which can soften the rubber composition and cause a loss of support.

[0005] Dispersants are used to reduce the dynamic magnification ratio while maintaining the supportability of a rubber composition. It is believed that these dispersants adsorb (or chemically bond) to carbon black and silica (and polymers) and suppress re-agglomeration of these fillers, thereby reducing the dynamic magnification ratio of the rubber composition. For example, Patent Document 1 describes that the dynamic magnification ratio can be reduced by crosslinking carbon black and diene rubber with a coupling agent.

[0006] Furthermore, a method of adding a hydrazide compound to a rubber composition to suppress re-agglomeration of a filler is known. For example, Patent Documents 2 and 3 describe vibration-damping rubber compositions containing specific dihydrazide compounds.

[0007] JP 2019-178199 A US 2021 / 0371626 A1 JP 2021-155643 A

[0008] However, hydrazide compounds are highly reactive, and in particular, when polyfunctional compounds such as dihydrazide compounds are used, crosslinking-like reactions may occur in the rubber composition, increasing the viscosity and causing problems in terms of processability, etc.

[0009] Therefore, an object of the present invention is to provide an anti-vibration rubber composition that can be used to produce anti-vibration rubber members that have low dynamic magnification and excellent vibration damping properties, and that has excellent processability, and a method for producing the same.

[0010] As a result of extensive research into achieving the above object, the present inventors discovered that the use of a monofunctional hydrazide compound is suitable for suppressing problems such as thickening and for producing a rubber composition that can yield an anti-vibration rubber member with high vibration damping properties, and further discovered that the vibration damping properties can be further improved by employing a specific manufacturing method, leading to the present invention.

[0011] The present invention provides a vibration-damping rubber composition obtained by a production method including the following first and second steps. First step: The following components a, b, and c are kneaded at a temperature of 130°C or higher and 180°C or lower to obtain a primary kneaded product. Component a: diene rubber Component b: filler containing carbon black Component c: hydrazide compound represented by the following formula (1) or (2) Second step: The primary kneaded product is kneaded with the following component d to obtain a secondary kneaded product. Component d: zinc oxide

[0012] In the formula R １ represents an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms.

[0013] In the formula R １ represents an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms, R ２ and R ３ each independently represents an alkyl group having 1 to 20 carbon atoms.

[0014] The vibration-damping rubber composition of the present invention is obtained by a production method including a first step of kneading the components a, b, and c at a temperature of 130°C or higher and 180°C or lower to obtain a primary kneaded mixture, and a second step of kneading the primary kneaded mixture with the component d to obtain a secondary kneaded mixture. The hydrazide group possessed by the hydrazide compound, component c, is highly reactive with functional groups such as ketones and aldehydes. Therefore, it is believed that by reacting the hydrazide compound with residual functional groups on the carbon black surface in the first step and adding it to the surface, the carbon black agglomerates are dispersed and reagglomeration is inhibited.

[0015] However, if carbon black, a hydrazide compound, and zinc oxide are added and kneaded simultaneously, the hydrazide compound and zinc oxide easily form a complex, which prevents the reaction between the hydrazide compound and carbon black from proceeding sufficiently, and the effect of dispersing the carbon black is not fully exerted. Therefore, the present inventors believe that by reacting the hydrazide compound and carbon black in the absence of zinc oxide, as in the present invention, the dispersibility of the carbon black in the rubber component is improved, and the effect of reducing the dynamic magnification can be fully exerted.

[0016] Thus, it is believed that the anti-vibration rubber composition of the present invention makes it possible to produce anti-vibration rubber members with a low dynamic magnification due to the dispersion morphology of the carbon black. However, qualitatively and / or quantitatively specifying the dispersion morphology of the carbon black requires an extremely excessive amount of time and is therefore not practical. Therefore, in the present invention, there is a situation in which the anti-vibration rubber composition must be specified by the manufacturing method, instead of specifying the dispersion morphology of the carbon black.

[0017] The anti-vibration rubber composition of the present invention contains, as a rubber component, component (a): a diene rubber. Examples of diene rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), and acrylonitrile-butadiene rubber (NBR). In the present invention, it is preferable to use natural rubber from the viewpoint of reducing the dynamic magnification.

[0018] The natural rubber may be appropriately selected from known natural rubbers, for example, RSS (ribbed smoked sheets) and TSR (technically specified rubber). The content of natural rubber in component a is preferably 50% by mass or more, more preferably 70% by mass or more, and particularly preferably 90% by mass or more. One type of natural rubber may be used alone, or two or more types may be used in combination.

[0019] The vibration-damping rubber composition of the present invention may contain a non-diene rubber as a rubber component. Examples of non-diene rubbers include halogenated butyl rubbers such as butyl rubber (IIR), chlorinated butyl rubber (CIIR), and brominated butyl rubber (BIIR), ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), ethylene-acrylic rubber (AEM), polyacrylic rubber (ACM), silicone rubber (VMQ), fluororubber (FKM), polyurethane rubber (AU), ester-based polyurethane rubber (EU), and polyether ether ketone rubber (PEEK). In the present invention, the content of the non-diene rubber in the rubber component is preferably 10 mass% or less, and more preferably, no non-diene rubber is contained.

[0020] The anti-vibration rubber composition of the present invention contains a filler containing component (b): carbon black. Known carbon blacks can be used, and are not particularly limited. Examples of carbon black include various grades of carbon black, such as SRF, GPF, FEF, HAF, ISAF, SAF, FT, and MT. In the present invention, FEF-grade carbon black is preferred from the viewpoint of reducing dynamic magnification. One type of carbon black may be used alone, or two or more types may be used in combination.

[0021] Fillers other than carbon black include inorganic fillers such as silica. Known silica such as wet silica, dry silica, and colloidal silica can be used. The BET specific surface area of ​​silica is 70 to 230 m. ２The silica may be used alone or in combination of two or more kinds.

[0022] When component b contains silica, it is preferable to incorporate a silane coupling agent in order to improve dispersibility and reinforcing properties. Known silane coupling agents can be used, and are not particularly limited. Examples 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. One type of silane coupling agent may be used alone, or two or more types may be used in combination. The amount of silane coupling agent used is preferably 1 to 20% by mass, more preferably 5 to 15% by mass, relative to the silica content.

[0023] The carbon black content in component (b) is preferably 30% by mass or more, and more preferably 50% by mass or more. The blending amount of component (b) is preferably 10 to 80 parts by mass, and more preferably 30 to 60 parts by mass, per 100 parts by mass of the rubber component.

[0024] The vibration-proof rubber composition of the present invention contains component c: a hydrazide compound represented by the following formula (1) or (2).

[0025] In the formula R １ represents an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms.

[0026] In the formula R １ represents an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms, R ２ and R ３ each independently represents an alkyl group having 1 to 20 carbon atoms.

[0027] Examples of the alkyl group having 1 to 20 carbon atoms in the formulas (1) and (2) include linear alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl, as well as branched alkyl groups such as isopropyl, sec-butyl, tert-butyl, isobutyl, isopentyl, tert-pentyl, 2-hexyl, 3-hexyl, 2-heptyl, 3-heptyl, isoheptyl, tert-heptyl, isooctyl, tert-octyl, 2-ethylhexyl, and isononyl.

[0028] Examples of the aryl group having 6 to 20 carbon atoms in the formula (2) include aryl groups having a single ring structure such as phenyl, tolyl, xylyl, ethylphenyl, and 2,4,6-trimethylphenyl, and aryl groups having a condensed ring structure such as naphthyl, anthracenyl, phenanthryl, pyrenyl, fluorenyl, and indenofluorenyl.

[0029] The alkyl group having 1 to 20 carbon atoms and the aryl group having 6 to 20 carbon atoms in the formulas (1) and (2) may have a substituent, such as a halogen atom, a cyano group, a nitro group, a hydroxyl group, an amino group, or a carboxy group.

[0030] In the present invention, it is preferable to use a hydrazide compound represented by formula (2). The hydrazide compound represented by formula (2) can be obtained by reacting the hydrazide compound represented by formula (1) with a ketone or an aldehyde. This reaction converts the amino group to an imino group, suppressing reactivity, thereby preventing the hydrazide compound from reacting with unintended compounds, and enabling the stable production of a vibration-damping rubber composition with improved carbon black dispersibility.

[0031] R in the formula (2) １ is preferably an aryl group having 6 to 20 carbon atoms, is preferably a phenyl group or naphthyl group substituted with a hydroxyl group, and is preferably a naphthyl group substituted with a hydroxyl group. ２ and R３ are each independently preferably an alkyl group having 1 to 10 carbon atoms, and more preferably an alkyl group having 1 to 5 carbon atoms. In particular, the hydrazide compound of component c is preferably N'-(1,3-dimethylbutylidene)-3-hydroxy-2-naphthohydrazide.

[0032] The blending amount of component c is preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass, per 100 parts by mass of component b.

[0033] The vibration-damping rubber composition of the present invention is obtained by a production method including a step (first step) of kneading the components a, b, and c at a temperature of 130°C or higher and 180°C or lower to obtain a primary kneaded mixture. The kneading temperature in the first step is more preferably 130°C or higher and 160°C or lower. The kneading time is preferably 1 minute or higher and 10 minutes or lower, more preferably 1 minute or higher and 5 minutes or lower. The kneading temperature refers to the final temperature achieved during kneading. A kneading machine such as a roll, an internal mixer, or a Banbury rotor can be used for kneading. Furthermore, when molding into a sheet or strip shape, a known molding machine such as an extruder or a press can be used.

[0034] The anti-vibration rubber composition of the present invention is preferably obtained by a production method including a step (second step) of kneading the primary kneaded mixture with zinc oxide (component d) to obtain a secondary kneaded mixture. The kneading temperature in the second step is preferably 60° C. or higher and 120° C. or lower, and more preferably 80° C. or higher and 110° C. or lower. The kneading time is preferably 1 minute or higher and 10 minutes or lower, and more preferably 1 minute or higher and 5 minutes or lower.

[0035] As the zinc oxide, known zinc oxide such as zinc white and activated zinc oxide may be used. The amount of zinc oxide mixed is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass, per 100 parts by mass of the rubber component in the vibration-proof rubber composition.

[0036] Furthermore, the vibration-damping rubber composition of the present invention preferably contains component e: a vulcanizing agent, and component f: a vulcanization accelerator, and a secondary kneaded product may be obtained by adding component d, component e, and component f to the primary kneaded product and kneading them.

[0037] Examples of vulcanizing agents include sulfur and sulfur-containing compounds such as alkylphenol disulfide compounds, but sulfur is preferably used in the present invention. The amount of sulfur blended is usually 0.1 to 10 parts by mass, preferably 0.3 to 5 parts by mass, and more preferably 0.5 to 2 parts by mass, per 100 parts by mass of the rubber component in the vibration-proof rubber composition, from the viewpoint of being able to favorably maintain basic physical properties such as the desired hardness and tensile properties. Peroxides such as dialkyl peroxides and peroxyketals can also be used as vulcanizing agents, and in this case, the blending amount is usually 1.0 to 10 parts by mass, preferably 2.0 to 8 parts by mass, per 100 parts by mass of the rubber component in the vibration-proof rubber composition.

[0038] Examples of vulcanization accelerators include benzothiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, dibenzothiazyl disulfide, N-cyclohexyl-2-benzothiazyl sulfenamide, N-t-butyl-2-benzothiazyl sulfenamide, and N-t-butyl-2-benzothiazyl sulfenamide; guanidine-based vulcanization accelerators such as diphenyl guanidine; and thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide, tetrabutylthiuram disulfide, tetradodecylthiuraum disulfide, tetraoctylthiuraum disulfide, and tetrabenzylthiuraum disulfide. These may be used alone or in combination of two or more. In the present invention, benzothiazole-based vulcanization accelerators are preferably used. The amount of vulcanization accelerator added is preferably 0.5 to 10 parts by mass, and more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component in the vibration-proof rubber composition, from the viewpoints of ease of production work of the vibration-proof rubber and obtaining the desired hardness.

[0039] In addition to the above-mentioned components, the vibration-damping rubber composition of the present invention can contain vulcanization accelerators other than zinc oxide that are commonly used in vibration-damping rubber compositions, crosslinking agents, scorch inhibitors, oils, antioxidants, etc. These components may be added in the first step or in the second step, but it is preferable to add the components other than the scorch inhibitor in the first step and the scorch inhibitor in the second step.

[0040] Examples of vulcanization accelerators other than zinc oxide include fatty acids, which may be saturated, unsaturated, linear, or branched, and are not particularly limited by the number of carbon atoms. Examples of fatty acids include fatty acids having 1 to 30 carbon atoms, preferably 15 to 30 carbon atoms. More specifically, saturated fatty acids such as cyclohexanoic acid (cyclohexanecarboxylic acid), naphthenic acids such as alkylcyclopentanes having side chains, hexanoic acid, octanoic acid, decanoic acid (including branched carboxylic acids such as neodecanoic acid), dodecanoic acid, tetradecanoic acid, hexadecanoic acid, and octadecanoic acid (stearic acid), unsaturated fatty acids such as methacrylic acid, oleic acid, linoleic acid, and linolenic acid, and resin acids such as rosin, tall oil acid, and abietic acid. These may be used alone or in combination. In the present invention, zinc oxide and stearic acid are preferred. The blending amount of the vulcanization accelerator aid, in terms of the total blending amount together with zinc oxide, per 100 parts by mass of the rubber component of the vibration-proof rubber composition, is preferably 1 to 10 parts by mass, and more preferably 2 to 8 parts by mass, from the viewpoints of ease of production work of the vibration-proof rubber and obtaining the desired hardness.

[0041] Examples of crosslinking agents include bismaleimide compounds and phenolic resins. Examples of bismaleimide compounds include N,N'-o-phenylene bismaleimide, N,N'-m-phenylene bismaleimide, N,N'-p-phenylene bismaleimide, 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, bismaleimide compounds are preferred from the viewpoint of storage stability. The amount of these bismaleimide compounds is preferably 0.5 to 5 parts by mass, more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the rubber component in the vibration-proof rubber composition.

[0042] Examples of scorch inhibitors include organic acids such as phthalic anhydride, salicylic acid, and benzoic acid, N-(cyclohexythio)phthalimide, and sulfonamide derivatives. These can be used alone or in combination of two or more. The amount of scorch inhibitor blended is preferably 0.1 to 5 parts by weight, and more preferably 0.5 to 2 parts by weight, per 100 parts by weight of the rubber component in the vibration-proof rubber composition.

[0043] Examples of oils that can be used include process oils such as aromatic oil, naphthenic oil, and paraffin oil, vegetable oils such as coconut oil, synthetic oils such as alkylbenzene oil, and castor oil. These may be used alone or in combination of two or more. The amount of oil blended is preferably 0.5 to 10 parts by mass, and more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component in the vibration-proof rubber composition.

[0044] Examples of the antioxidant include phenol-based antioxidants, imidazole-based antioxidants, amine-based antioxidants, and waxes. These may be used alone or in combination of two or more. The amount of antioxidant blended is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, and even more preferably 1 to 3 parts by mass per 100 parts by mass of the rubber component in the vibration-proof rubber composition.

[0045] In addition, additives commonly used in rubber products, such as antioxidants, foaming agents, plasticizers, lubricants, tackifiers, petroleum-based resins, ultraviolet absorbers, dispersants, compatibilizers, and homogenizers, may be appropriately blended as needed, provided that the effects of the present invention are not impaired.

[0046] The vibration-isolating rubber composition of the present invention can be used as a vibration-isolating rubber member by vulcanizing and molding it. Although not particularly limited, the vibration-isolating rubber composition is typically cured by vulcanization at 140 to 180°C for 5 to 120 minutes to form the vibration-isolating rubber member. Because this vibration-isolating rubber member is made using the vibration-isolating rubber composition of the present invention described above, it has low dynamic magnification and excellent vibration-proofing properties, and can be suitably used for automobile engine mounts, suspension bushings, subframe mounts, etc.

[0047] EXAMPLES The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0048] [Comparative Examples 1 and 2] A primary kneaded product was obtained by the first step of adding the components other than the vulcanizing agent, vulcanization accelerator CZ, and retarder to a Banbury mixer in the formulation (parts by mass) shown in Table 1 and kneading them, and discharging them when the temperature shown in Table 1 was reached. Next, a second step of adding the vulcanizing agent, vulcanization accelerator CZ, and scorch inhibitor to the primary kneaded product obtained and kneading them for 1 minute while maintaining the temperature below 110°C was performed to produce an anti-vibration rubber composition.

[0049] [Comparative Examples 3 to 5 and Examples 1 to 3] A primary kneaded product was obtained by feeding the components other than the vulcanizing agent, vulcanization accelerator CZ, retarder, and zinc oxide into a Banbury mixer in the formulation (parts by mass) shown in Table 1 and kneading them, and then discharging them when the temperature shown in Table 1 was reached. Next, a second step was performed in which the vulcanizing agent, vulcanization accelerator CZ, scorch inhibitor, and zinc oxide were added to the obtained primary kneaded product, and the mixture was kneaded for 1 minute while maintaining the temperature below 110°C, thereby producing an anti-vibration rubber composition.

[0050] <Processability Evaluation> The Mooney viscosity of the vibration-proof rubber compositions obtained in the comparative examples and examples was measured at 170°C in accordance with JIS K 6300-1, and processability was evaluated using a relative value with the value of Comparative Example 1 taken as 100. A Mooney viscosity relative value of less than 120 was rated as ○ (good), and a value of 120 or more was rated × (bad). The results are shown in Table 1.

[0051] <Vibration-Dampening Evaluation> The vibration-damping rubber compositions obtained in the comparative examples and examples were press-vulcanized at 155°C for 30 minutes to prepare cylindrical test pieces (vibration-damping rubber members) measuring 30 mm in diameter and 30 mm in height. These test pieces were used to evaluate support performance and vibration-damping performance. Support Performance: The static spring constant (Ks) was measured in accordance with JIS K 6385 using the bidirectional loading method of the static property test, in which a deflection ranging from 0 mm to +4.5 mm was applied three times in the direction perpendicular to the axis of the test piece at a displacement rate of 20 mm / min. The load-deflection relationship during the third loading process was measured, and this relationship was used to calculate the deflection range of 1.5 to 3.0 mm using the calculation method described in the same standard. Support performance was evaluated as a relative value, with the Ks of Comparative Example 1 set to 100. A higher value indicates better support performance. The results are shown in Table 1. Vibration-proofing The dynamic spring constant (Kd100) at 100 Hz was measured in accordance with JIS K 6385 using a non-resonant method for dynamic property measurement testing, under a load that deflected 10% (3 mm), at a frequency of 100 Hz and an amplitude of ±0.05 mm in the direction perpendicular to the axis of the test piece. The dynamic magnification at 100 Hz (Kd100 / Ks) was calculated from the absolute values ​​of Ks and Kd100, and the vibration-proofing properties were evaluated as a relative value, with the dynamic magnification of Comparative Example 1 taken as 100. A relative value of the dynamic magnification at 100 Hz of less than 100 was evaluated as ○ (good), and a value of 100 or more was evaluated as × (poor). The smaller the value, the better the vibration-proofing properties. The results are shown in Table 1.

[0052] High-Frequency Vibration Damping The vibration-damping rubber compositions obtained in the comparative examples and examples were press-vulcanized at 155°C for 15 minutes to prepare cylindrical test pieces (vibration-damping rubber members) measuring 8 mm in diameter and 5.9 mm in height. Viscoelasticity measurements were performed using a TA Instruments ARES-G2 in accordance with JIS K 7244-1 at a strain of 0.1% and temperatures ranging from -40°C to 40°C (at 10°C intervals). A master curve was created using the temperature-time law (WLF law), with frequency on the horizontal axis and storage modulus on the vertical axis. The storage moduli at 2000 Hz and 100 Hz were read from this master curve, and the ratio of these values ​​was multiplied by the dynamic magnification factor at 100 Hz (Kd100 / Ks) to determine the dynamic magnification factor at 2000 Hz (Kd2k / Ks). High-frequency vibration damping was evaluated as a relative value, with the value for Comparative Example 1 taken as 100. The smaller the value, the better the high frequency vibration damping property. The results are shown in Table 1.

[0053] The results of the overall evaluation based on the processability evaluation and the vibration-proofing evaluation are shown in Table 1. When both the processability evaluation and the vibration-proofing evaluation were ○, the evaluation was rated ○ (good), and when either the processability evaluation or the vibration-proofing evaluation was ×, the evaluation was △ (slightly poor). The results are shown in Table 1.

[0054] Details of each component in Table 1 are as follows: Natural rubber: "RSS #4" Carbon black: FEF grade carbon black, "Asahi #65" manufactured by Asahi Carbon Co., Ltd. Hydrazide compound BMH: "BMH" manufactured by Otsuka Chemical Co., Ltd., N'-(1,3-dimethylbutylidene)-3-hydroxy-2-naphthohydrazide Hydrazide compound IDH: "IDH" manufactured by Otsuka Chemical Co., Ltd., isophthalic acid dihydrazide Stearic acid: "Stearic acid 50S" manufactured by New Japan Chemical Co., Ltd. Wax: "Santite S" manufactured by Seiko Chemical Co., Ltd. Antioxidant RD: "Nocrac RD" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant 6C: "Nocrac 6C" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Oil: "SUNTHENE 4240" manufactured by SUNOCO Co., Ltd. Zinc oxide: "Ginryo SR" manufactured by Toho Zinc Co., Ltd. Vulcanizing agent: "Powdered sulfur" manufactured by Tsurumi Chemical Co., Ltd. Vulcanization accelerator CZ: "Noccela CZ-G" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Scorch inhibitor: "Retarder CTP" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0055]

[0056] Comparing Example 2 and Comparative Example 2, which had the same heating temperature in the first step, the vibration-damping rubber member obtained from the vibration-damping rubber composition of Example 2, in which zinc oxide was not added in the first step and zinc oxide was added in the second step, had good vibration-damping properties, whereas the vibration-damping rubber member obtained from the vibration-damping rubber composition of Comparative Example 2, in which zinc oxide was added in the first step, had poor vibration-damping properties. This shows that vibration-damping properties can be improved by kneading the rubber component, carbon black, and hydrazide compound without adding zinc oxide.

[0057] The vibration-proof rubber members obtained from the vibration-proof rubber compositions of Examples 1 to 3, in which the kneading temperature in the first step was 130°C to 160°C, had good vibration-proofing properties, whereas the vibration-proof rubber member obtained from the vibration-proof rubber composition of Comparative Example 4, in which the kneading temperature in the first step was 120°C, had poor vibration-proofing properties, even when zinc oxide was not added in the first step and zinc oxide was added in the second step. This shows that vibration-proofing properties can be improved by setting the kneading temperature in the first step to 130°C or higher.

[0058] The vibration-proof rubber composition of Example 3, which used a monofunctional hydrazide compound, had good processability, whereas the vibration-proof rubber composition of Comparative Example 5, which used a bifunctional dihydrazide compound, had a high Mooney viscosity and poor processability. This shows that the use of a monofunctional hydrazide compound can improve vibration-proofing properties without reducing processability.

[0059] [Example 4] A vibration-damping rubber composition was produced and evaluated in the same manner as in Example 3, except that half the amount of carbon black was changed to silica ("Nipsil AQ" manufactured by Tosoh Silica Corporation) and 2.1 parts by mass of a silane coupling agent ("Si 69" manufactured by Evonik) was added in the first step. The results are shown in Table 2.

[0060] Comparative Example 6 A vibration-damping rubber composition was produced in the same manner as in Comparative Example 5, except that half the amount of carbon black was changed to silica ("Nipsil AQ" manufactured by Tosoh Silica Corporation) and 2.1 parts by mass of a silane coupling agent ("Si 69" manufactured by Evonik) was added in the first step, and evaluation was similarly performed. The results are shown in Table 2.

[0061]

[0062] As shown in Table 2, even when half the amount of carbon black is replaced with silica, the same effect as when only carbon black is used can be achieved.

[0063] According to the present invention, it is possible to produce an anti-vibration rubber member having low dynamic magnification and excellent vibration-damping properties, and it is also possible to provide an anti-vibration rubber composition having excellent processability, and a method for producing the same.

Claims

1. An anti-vibration rubber composition obtained by a manufacturing method including the following first and second steps. First step: The following components a, b, and c are kneaded at a temperature of 130°C or higher and 180°C or lower to obtain a primary kneaded product. Component a: diene rubber Component b: filler containing carbon black Component c: hydrazide compound represented by the following formula (1) or (2) Second step: The primary kneaded product is kneaded with the following component d to obtain a secondary kneaded product. Component d: zinc oxide In the formula R １ represents an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms. In the formula R １ represents an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms; R ２ and R ３ each independently represents an alkyl group having 1 to 20 carbon atoms.

2. The anti-vibration rubber composition according to claim 1, wherein the blending amount of said component c is 0.1 to 10 parts by mass per 100 parts by mass of said component b.

3. The vibration-proof rubber composition according to claim 1, wherein said component (a) contains 50 mass % or more of natural rubber.

4. The anti-vibration rubber composition according to claim 1, wherein the kneading time in the first step is from 1 minute to 10 minutes.

5. A method for producing an anti-vibration rubber composition comprising the following first and second steps. First step: The following components a, b, and c are kneaded at a temperature of 130°C or higher and 180°C or lower to obtain a primary kneaded product. Component a: diene rubber Component b: filler containing carbon black Component c: hydrazide compound represented by the following formula (1) or (2). Second step: The primary kneaded product is kneaded with the following component d to obtain a secondary kneaded product. Component d: zinc oxide In the formula R １ represents an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms. In the formula R １ represents an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms; R ２ and R ３ each independently represents an alkyl group having 1 to 20 carbon atoms.

6. The method for producing an anti-vibration rubber composition according to claim 5, wherein the kneading time in the first step is from 1 minute to 10 minutes.

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