Anti-vibration rubber composition and anti-vibration rubber

Abstract

To provide a vibration-damping rubber composition and a vibration-damping rubber that achieve a balance between low dynamic-to-static moduli and high attenuation, while also offering superior adhesion.SOLUTION: A vibration-damping rubber composition comprises, as its main rubber components, a diene rubber and a high-styrene rubber in the mass ratio of diene rubber / high-styrene rubber=50 / 50-90 / 10. When the total rubber component is 100 pts.mass, 15-45 pts.mass of a butadiene-styrene random copolymer with an average molecular weight (Mn) of 3000-12000 is contained as a softener, and additionally, 5-50 pts.mass of carbon black is contained. The vibration-damping rubber composition is vulcanization-bonded to a surface of metal fittings through an adhesive layer on the surface of the metal fittings, thereby forming a vibration-damping rubber featuring an integrated structure of the metal fittings and vulcanized rubber.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an anti-vibration rubber composition and anti-vibration rubber, and more particularly to an anti-vibration rubber composition that can provide anti-vibration rubber with excellent vibration-damping properties not previously available, and to anti-vibration rubber that uses this anti-vibration rubber composition and has excellent adhesiveness. [Background technology]

[0002] Anti-vibration rubbers used in multiple types of vibration transmission systems with different frequencies, amplitudes, etc., such as automotive anti-vibration rubbers, are required to exhibit appropriate and effective vibration-damping properties so that they can respond appropriately to the various types of input vibrations.

[0003] For example, automotive anti-vibration rubber is required to have the ability to block and attenuate vibration inputs of various amplitudes over a wide range of frequencies.

[0004] It is known that reducing the dynamic spring constant (Kd) is effective in blocking vibration transmission. However, because vibration-isolating rubber is required to be able to withstand a certain static force, such as when supporting a heavy object, the static spring characteristic (Ks) must be relatively large. Therefore, it is desirable that the value of the dynamic magnification factor (= Kd / Ks, also known as the static-dynamic ratio), which is the ratio of the dynamic spring constant (Kd) to the static spring constant (Ks), be small.

[0005] On the other hand, it is said that increasing the loss factor (tan δ, also known as the loss factor) is effective in damping vibration. However, it is generally known that when the damping characteristics (loss factor) are increased, the dynamic magnification ratio also increases accordingly, and conversely, when the dynamic magnification ratio is decreased, the damping characteristics (loss factor) decreases.

[0006] In other words, there is a trade-off between low dynamic magnification characteristics and high damping characteristics, and it is strongly desired to achieve both of these characteristics in anti-vibration rubber. Furthermore, it is known that in the case of vulcanized products of ordinary anti-vibration rubber compositions, the elastic modulus at small input amplitudes is larger than the elastic modulus at large input amplitudes. In other words, the spring constant changes significantly depending on the input amplitude.

[0007] To address the issue of achieving both low dynamic magnification and high damping characteristics, various anti-vibration rubber compositions have been proposed, including one in which hydrogenated isoprene rubber is added to diene rubber (e.g., Patent Document 1), one in which domains of butadiene rubber with unevenly distributed carbon black are dispersed in a matrix phase of chlorinated butyl rubber (e.g., Patent Document 2), and one in which liquid styrene-butadiene rubber is blended with an unvulcanized diene rubber material whose main components are vinyl and styrene (e.g., Patent Document 3).

[0008] As mentioned above, various considerations are being made regarding automobile vibration-damping rubber, such as the level of support function required (for example, the support function when used as a connecting member as described below), how to block vibration transmission in multiple types of vibration transmission systems with different frequencies, amplitudes, etc., and how to damp generated vibrations, etc. For example, the vibration-damping rubber materials used in vibration-damping rubber are made of rubber materials with a variety of elastic moduli (hardness) and damping properties, and when controlling the hardness and damping properties of diene-based rubber, the vibration characteristics of the vibration-damping rubber are adjusted by adjusting the amount of carbon black with various different particle sizes and structures added, and the amount of process oil such as naphthenic oil added.

[0009] Furthermore, many vehicle vibration-damping rubbers have a structure in which metal fittings and rubber material (rubber material made from a vibration-damping rubber composition) are integrated together (hereinafter referred to simply as a metal fitting structure), and are used as connecting members for connecting various components such as vehicle frames and engines. In vibration-damping rubbers with such metal fitting structures, an adhesive is usually used to bond the interface between the metal fittings and the rubber material. Generally, bonding methods include a "single-component adhesive coating method" that uses one adhesive, and a "two-component adhesive coating method" that applies an undercoat adhesive as a primer to the metal fitting surface and then applies a topcoat adhesive, and when the goal is to obtain high adhesion, the two-component adhesive coating method is widely used.

[0010] On the other hand, as automobiles become more compact and have higher power outputs, the temperature environment surrounding automotive anti-vibration rubber is also tending to become higher, so there is a need to improve the heat-resistant adhesiveness of anti-vibration rubber. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 07-216136 [Patent Document 2] Japanese Patent Application Publication No. 2019-131761 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-113092 Summary of the Invention [Problem to be solved by the invention]

[0012] However, the anti-vibration rubber compositions described in Patent Documents 1 and 2 tend to have insufficient rubber strength, and the anti-vibration rubber composition described in Patent Document 3 sometimes has difficulty achieving both low dynamic magnification and high damping characteristics.

[0013] Furthermore, in the case of vibration-damping rubber with a metal fitting structure, high adhesiveness is required as described above, but depending on the vibration-damping rubber composition used, the adhesiveness may be insufficient. In particular, when used in a severe temperature environment, the heat-resistant adhesiveness is likely to be insufficient.

[0014] The present invention has been made in consideration of the above circumstances, and its object is to provide an anti-vibration rubber composition that has sufficient support function and is capable of achieving both low dynamic magnification characteristics and high damping characteristics, and an anti-vibration rubber obtained from said anti-vibration rubber composition that has excellent adhesion between metal fittings and rubber materials. [Means for solving the problem]

[0015] The present inventors conducted extensive research to achieve the above-mentioned object. They discovered that by incorporating a specific ratio of diene rubber and high styrene rubber as the main rubber component, and by incorporating 15 to 40 parts by mass of a specific butadiene-styrene random copolymer as a softener and a relatively small amount of carbon black, based on 100 parts by mass of the total rubber component, it is possible to achieve both good low dynamic magnification characteristics and high damping characteristics, even when the vulcanized rubber has a hardness (rubber hardness 40 to 75) sufficient to perform the support function of a vibration-isolating rubber, thereby achieving excellent vibration-isolating properties not found in conventional vibration-isolating rubber compositions. Hereinafter, the content of each component may be expressed as parts by mass, but all of these refer to the parts by mass of each component based on 100 parts by mass of the total rubber component.

[0016] That is, one embodiment of the vibration-damping rubber composition of the present invention is a vibration-damping rubber composition characterized by containing a diene rubber and a high styrene rubber as main rubber components in a mass ratio of diene rubber / high styrene rubber = 50 / 50 to 90 / 10, and also containing 15 to 45 parts by mass of a butadiene-styrene random copolymer having an average molecular weight (Mn) of 3000 to 12000 as a softener, and containing 5 to 50 parts by mass of carbon black.

[0017] The configuration of one aspect of the above-described vibration-damping rubber composition makes it possible to obtain a vibration-damping rubber having sufficient support function, excellent high damping characteristics while maintaining good low dynamic magnification characteristics, and further having high adhesiveness.

[0018] In one embodiment of the vibration-damping rubber composition, the nitrogen adsorption specific surface area is 15 to 80 m when the total rubber component is 100 parts by mass. 2 It is preferable that the rubber composition contains 5 to 40 parts by mass of carbon black at a concentration of 0.1 to 0.2g / g and the total carbon black content is 5 to 45 parts by mass. Within this range, it is possible to obtain an anti-vibration rubber composition that has sufficient support function and is capable of achieving both low dynamic magnification characteristics and high damping characteristics at a higher level.

[0019] Furthermore, in one embodiment of the vibration-damping rubber composition, when the total rubber component is taken as 100 parts by mass, the nitrogen adsorption specific surface area is 20 to 45 m 2 It is preferable that the content of carbon black per 1000 kJ / g is 20 to 40 parts by mass and the total carbon black content is 20 to 40 parts by mass. Within this range, it is possible to obtain an anti-vibration rubber composition that has sufficient support function and can achieve both low dynamic magnification characteristics and high damping characteristics at a higher level.

[0020] Furthermore, in one embodiment of the vibration-damping rubber composition, the butadiene-styrene random copolymer preferably has an average molecular weight (Mn) of 8,000 to 12,000 and a glass transition temperature (Tg) of −10° C. or higher and 0° C. or lower. Within this range, a vibration-damping rubber composition can be obtained that has excellent low dynamic magnification characteristics and excellent high damping characteristics, and also has high adhesiveness.

[0021] Furthermore, in one embodiment of the vibration-damping rubber composition, the diene rubber preferably contains natural rubber (NR) and styrene-butadiene rubber (SBR), and contains 40 to 80 parts by mass of natural rubber (NR) and 10 to 45 parts by mass of styrene-butadiene rubber (SBR) when the total rubber components including the high styrene rubber are taken as 100 parts by mass. Within this range, a vibration-damping rubber composition can be obtained that has rubber strength sufficient to maintain the desired support function, while achieving both low dynamic magnification characteristics and high damping characteristics at a higher level.

[0022] Furthermore, in one embodiment of the vibration-damping rubber composition, the process oil is preferably contained in an amount of 0 to 5 parts by mass, where the total rubber component is taken as 100 parts by mass. Within this range, a vibration-damping rubber composition can be obtained that has sufficient support function and can achieve both low dynamic magnification characteristics and high damping characteristics at a higher level.

[0023] One embodiment of the vibration-damping rubber of the present invention is a vibration-damping rubber characterized in that the vibration-damping rubber composition as described above is vulcanization-bonded to the surface of the metal fitting via an adhesive layer on the surface of the metal fitting, and the metal fitting and vulcanized rubber made from the vulcanization-bonded vibration-damping rubber composition are integrally formed.

[0024] The configuration of one aspect of the vibration-isolating rubber described above makes it possible to achieve excellent adhesion between the metal fittings and the vulcanized rubber, as well as low dynamic magnification characteristics and high damping characteristics. [Effects of the Invention]

[0025] According to the present invention, it is possible to provide an anti-vibration rubber composition that has excellent high damping properties while maintaining good low dynamic magnification characteristics, and to provide an anti-vibration rubber that has excellent high damping properties and excellent adhesion while maintaining good low dynamic magnification characteristics. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a schematic explanatory view of a test piece 1 formed using each of the vibration-damping rubber compositions of Examples 1 to 9 and Comparative Examples 1 to 7 according to the present invention. [Figure 2]1 is a graph showing the relationship between dynamic magnification (Kd100 / Ks) and tan δ (10 Hz) for test piece 1 made using each of the anti-vibration rubber compositions of Examples 1 to 9 and Comparative Examples 1 to 6 according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, matters related to the embodiments of the present invention will be described in detail.

[0028] As mentioned above, there is a trade-off between low dynamic magnification and high damping characteristics. That is, there is usually a fixed relationship between damping (loss coefficient) and dynamic magnification, and vibration-damping rubber (rubber sample) of the same shape will have approximately the same dynamic magnification for a given damping. In this invention, achieving both low dynamic magnification and high damping characteristics means that this fixed relationship is violated, and for the same damping, the dynamic magnification will be lower than that of ordinary vibration-damping rubber materials. Conversely, for the same dynamic magnification, the damping will be greater.

[0029] That is, for example, if the characteristics of an anti-vibration rubber made from a general anti-vibration rubber composition are represented on a graph with the dynamic magnification ratio on the vertical axis and the damping property (loss factor) on the horizontal axis, then if the anti-vibration rubbers have the same shape, they will be represented by a single linear characteristic line on the graph. Furthermore, if the effect of achieving both low dynamic magnification ratio characteristics and high damping characteristics is superior to that of a general anti-vibration rubber composition, then the characteristics of the anti-vibration rubber will appear in a position that deviates from the linear characteristic line on the graph (for example, in the case of Figure 2 described below, the characteristics of Examples 1 to 9 appear below the characteristic line of Comparative Examples 1 to 6).

[0030] The content of each material (each component) applicable to this embodiment may be simply referred to as parts by mass below, but parts by mass means the content ratio (parts by mass) of each material (each component) when the total rubber component is 100 parts by mass.

[0031] The vibration-proof rubber composition of this embodiment is characterized by containing diene rubber and high styrene rubber as the main rubber components in a mass ratio of diene rubber / high styrene rubber = 50 / 50 to 90 / 10, and also containing 15 to 45 parts by mass of a butadiene-styrene random copolymer having an average molecular weight (Mn) of 3000 to 12000 as a softener.

[0032] In anti-vibration rubber compositions, diene rubber is used as the main rubber component, and in order to achieve the support function and damping properties required for various anti-vibration rubber products, carbon black with various different nitrogen adsorption specific surface properties is added as needed (in the required amount), and further, in order to adjust the support function, it has been studied to use it in combination with a softener such as naphthenic oil. However, anti-vibration rubbers using anti-vibration rubber compositions obtained simply as described above sometimes fail to achieve the desired balance of low dynamic magnification characteristics and high damping characteristics.

[0033] The present inventors have investigated vibration-damping rubber compositions containing diene rubbers containing no fillers, such as carbon black, and butadiene-styrene random copolymers with average molecular weights (Mn) of 3,000 to 12,000. They found that increasing the content of the butadiene-styrene random copolymer not only reduces the amplitude dependence of modulus and damping, but also enhances the compatibility of low dynamic magnification and high damping. However, such butadiene-styrene random copolymers, like naphthenic oils, act as softeners, significantly reducing the modulus and hardness of the rubber vulcanizate. Therefore, when used in rubber compositions containing no fillers, the support function may be insufficient. Furthermore, when fillers, such as carbon black, are added to ensure the necessary support function (to increase rubber hardness), increasing the amount of filler increases damping, but also tends to increase the dynamic magnification. Furthermore, the amplitude dependency of the elastic modulus increases, and the spring constant at small amplitudes increases, so it is conceivable that the dynamic spring constant at high frequency small amplitudes will become higher.

[0034] Therefore, the present inventors investigated a vibration-damping rubber composition that contains diene rubber and high styrene rubber as the main rubber components, in a mass ratio of diene rubber / high styrene rubber = 50 / 50 to 90 / 10, and also contains 15 to 45 parts by mass of a butadiene-styrene random copolymer with an average molecular weight (Mn) of 3000 to 12000 as a softener. They found that this composition can ensure sufficient support function without containing a large amount of carbon black, and can reduce the amplitude dependency of the elastic modulus, making it possible to achieve both low dynamic magnification and high damping characteristics.

[0035] If the content of the butadiene-styrene random copolymer having an average molecular weight (Mn) of 3,000 to 12,000 in the vibration-damping rubber composition exceeds 45 parts by mass, a large amount of reinforcing filler such as carbon black must also be added to ensure sufficient support function, which may make it difficult to obtain the desired low dynamic magnification characteristics.Furthermore, the vibration-damping rubber composition (unvulcanized rubber composition) may become too sticky, which may significantly reduce the processability of the vibration-damping rubber composition (for example, the vibration-damping rubber composition may tend to stick to rolls during kneading processing).

[0036] Each component that can be used in the vibration-damping rubber composition of the present invention will be described below.

[0037] [Rubber component] The vibration-proof rubber composition of this embodiment contains a diene rubber and a high styrene rubber as the main rubber component in a mass ratio of diene rubber / high styrene rubber = 50 / 50 to 90 / 10 (hereinafter referred to simply as the rubber component category of the present invention). This rubber component category of the present invention allows for a vibration-proof rubber composition with sufficient support function and high damping characteristics as a vibration-proof rubber. Here, the term "main rubber component" means that the total amount of the diene rubber and the high styrene rubber is 90 mass% or more of the total rubber component. Preferably, the total amount of the diene rubber and the high styrene rubber is 95 mass% or more of the total rubber component.

[0038] Examples of diene rubber include natural rubber, styrene butadiene rubber (SBR), butadiene rubber (BR), and isoprene rubber (IR).

[0039] The natural rubber is not particularly limited, and ordinary natural rubber used in vibration-proof rubber can be used. Specific examples of sheet rubber (including crepes) include all grades of RSS (ribbed smoked sheet), white crepes, pale crepes, estate brown crepes, compact crepes, thin brown crapes (rimills), thick blanket crapes (ambers), flat bark crapes, and pure smoked blanket crapes. Examples of block rubber include SMR (standard Malaysian rubber), SIR (standard Indonesian rubber), STR (standard Thai rubber), SSR (standard Singaporean rubber), SCR (standard ceylon rubber), and SVR (standard Vietnamese rubber).

[0040] There are no particular limitations on the styrene-butadiene rubber (SBR), and examples thereof include solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR), which are used in vibration-proof rubbers. Modified SBRs include SBR whose terminals and / or main chains are modified, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, those having a branched structure, etc.).

[0041] The butadiene rubber (BR) is not particularly limited, and various commercially available butadiene rubbers used in vibration-proof rubbers can be used. Among them, it is preferable to use a butadiene rubber with a high cis-1,4-bond content from the viewpoints of low dynamic magnification characteristics, low-temperature characteristics, and durability against repeated deformation.

[0042] There are no particular limitations on the isoprene rubber (IR), and various commercially available butadiene rubbers used in vibration-proof rubbers can be used. Among these, it is preferable to use high-cis isoprene rubber from the viewpoints of low dynamic magnification characteristics, low-temperature characteristics, and durability against repeated deformation.

[0043] The anti-vibration rubber composition of this embodiment may contain rubber components other than the natural rubber and butadiene rubber, such as ethylene propylene rubber (EPDM), within a range that does not impair the effects of the present invention (for example, within a range of 10 parts by mass or less).

[0044] [Butadiene-styrene random copolymer] The anti-vibration rubber composition of this embodiment contains 15 to 40 parts by mass of a butadiene-styrene random copolymer having an average molecular weight (Mn) of 3,000 to 12,000 (hereinafter referred to as the copolymer category of the present invention). This copolymer category of the present invention provides appropriate flexibility, excellent damping characteristics, and low dynamic magnification. This butadiene-styrene random copolymer acts as a softener and does not become an elastomer even when used in combination with a sulfur-based vulcanizing agent for conventional rubber. Therefore, it is not included in the rubber component or resin component of the present invention. Examples of such butadiene-styrene random copolymers include Ricon 100, Ricon 181, and Ricon 184 (all manufactured by Cray Valley), and L-SBR-820 and L-SBR-841 (all manufactured by Kuraray Co., Ltd.). Preferably, the butadiene-styrene random copolymer has an average molecular weight (Mn) of 8,000 to 12,000 and a glass transition temperature (Tg) of -10°C or higher and 0°C or lower. Such a butadiene-styrene random copolymer has an even greater effect of achieving both low dynamic magnification and high damping characteristics. Specific examples of such butadiene-styrene random copolymers include L-SBR-841 (manufactured by Kuraray Co., Ltd.).

[0045] [Carbon black] The vibration-proof rubber composition of this embodiment contains 5 to 50 parts by mass of carbon black (hereinafter referred to as the carbon black category of the present invention). This carbon black category of the present invention makes it easy to obtain an appropriate static spring constant for the vibration-proof rubber to fulfill its supporting function. As mentioned above, the butadiene-styrene random copolymer also functions as a softener.

[0046] If the carbon black content is less than 5 parts by mass, the hardness of the vulcanized rubber will be too low, making it difficult to obtain an appropriate static spring constant.If the carbon black content is more than 50 parts by mass, the improvement in the elastic modulus at high frequency and small amplitude will be greater, and the effect of low dynamic magnification characteristics will be reduced.

[0047] The carbon black to be used is not particularly limited, and various commercially available furnace blacks for rubber and furnace blacks for coloring can be used. Among them, carbon blacks having a nitrogen adsorption specific surface area of ​​15 to 80 m 2 / g of carbon black is preferably used. Examples of such carbon black include HAF grade, MAF grade, FEF grade, GPF grade, SRF grade, and FT grade, which are known as furnace carbon black for rubber. The content of this carbon black is preferably 5 to 45 parts by mass per 100 parts by mass of the rubber component.

[0048] Furthermore, 20 to 45 m 2 The carbon black content having a nitrogen adsorption specific surface area of ​​1 / g is more preferably 20 to 40 parts by mass. Such carbon black can maintain an appropriate support function and enhance the low dynamic magnification and high damping effect. Examples of such carbon black include FEF grade, GPF grade, and SRF grade, which are known as furnace carbon black for rubber.

[0049] [Process oil] The anti-vibration rubber composition of this embodiment may contain process oil in addition to the above components. However, process oils such as naphthenic oils, aromatic oils, and paraffinic oils used in diene rubber compositions such as natural rubber and butadiene rubber have the effect of reducing the elastic modulus, but are not very effective in increasing damping properties, and furthermore, they are unable to achieve both low dynamic magnification and high damping properties. Furthermore, adding a large amount of the above process oil tends to reduce heat resistance. For this reason, it is preferable to add the process oil in an amount sufficient to adjust the rubber hardness (for example, 5 parts by mass or less, which is a small amount).

[0050] [Vulcanizing agent (crosslinking agent)] The anti-vibration rubber composition of this embodiment may contain a vulcanizing agent (crosslinking agent) in addition to the above components. Known sulfur-based vulcanizing agents can be used as the vulcanizing agent (crosslinking agent). Vulcanization using sulfur or sulfur-based compounds is preferred because it provides superior durability to the anti-vibration rubber. Furthermore, the butadiene-styrene random copolymer with an average molecular weight (Mn) of 3,000 to 12,000 used in the present invention is hardly crosslinked by sulfur or sulfur-based compounds, and therefore cannot become an elastomer, and can instead function as a softener.

[0051] Specific examples of sulfur or sulfur-based compounds include sulfur, sulfur chloride, 2-(4'-morpholinodithio)benzothiazole, 4,4'-dithiodimorpholine, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetrakis(2-ethylhexyl)thiuram disulfide, tetrabenzylthiuram disulfide, dipentamethylenethiuram tetrasulfide, etc. In addition to sulfur or sulfur-based compounds, bismaleimide vulcanization, resin vulcanization, etc. may also be used in combination.

[0052] [Filler] In addition to the above components, the anti-vibration rubber composition of this embodiment may contain fillers other than carbon black. Examples of the fillers include inorganic fillers such as silica, clay, and calcium carbonate, and organic fillers such as polymer fillers. These may be used alone or in combination of two or more. Adding a large amount of the fillers may not be able to achieve both low dynamic magnification and high damping characteristics, and may also reduce durability against repeated deformation. Therefore, it is preferable to add a small amount (for example, 20 parts by mass or less) to adjust processability and rubber hardness.

[0053] Examples of silica include dry process silica (fumed silica), wet process silica, and colloidal silica. Among these, wet process silica, which is primarily composed of hydrous silicic acid, is particularly preferred. These silicas can be used alone or in combination of two or more. While the specific surface area of ​​the silica is not particularly limited, the nitrogen adsorption specific surface area is typically 50 to 400 m / g, preferably 100 to 250 m / g, and more preferably 120 to 220 m / g. Such silica is suitable because it provides high levels of improvement in dynamic magnification and loss factor. Here, the nitrogen adsorption specific surface area is measured by the BET method in accordance with ASTM D3037-81.

[0054] [Vulcanization accelerator] When a sulfur compound is used as a vulcanizing agent, it can be used in combination with a vulcanization accelerator. Specific examples of the vulcanization accelerator include sulfenamide compounds such as N-cyclohexyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzothiazole sulfenamide, and N,N-diisopropyl-2-benzothiazole sulfenamide, thiazole compounds such as 2-mercaptobenzothiazole, 2-(2,4-dinitrophenyl)mercaptobenzothiazole, 2-(2,6-diethyl-4-morpholinothio)benzothiazole, and dibenzothiazyl disulfide, and diphenyl guanylate compounds such as methyl methyl stearate. Examples of suitable vulcanization accelerators include guanidine compounds such as thiuram phthalate, triphenylguanidine, diorthonitrile guanidine, orthonitrile biguanide, and diphenylguanidine phthalate, and thiuram compounds such as tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetrakis(2-ethylhexyl)thiuram disulfide, tetrabenzylthiuram disulfide, and dipentamethylenethiuram tetrasulfide. These vulcanization accelerators may be used alone or in combination of two or more, or different types may be used in combination. The amount of the vulcanization accelerator is preferably 0.5 to 15 parts by mass, more preferably 1 to 10 parts by mass, and even more preferably 1.2 to 8 parts by mass, based on 100 parts by mass of the total rubber components. In addition, to adjust the vulcanization rate, scorch inhibitors such as N-cyclohexylthiophthalimide and N-phenyl-N-(trichloromethylthio)benzenesulfonamide can be preferably used.

[0055] [Vulcanization aid] When a sulfur compound is used as a vulcanizing agent, it is preferable to use a vulcanization aid such as zinc oxide (ZnO) such as zinc white or activated zinc white, or composite zinc white, in combination with a vulcanization aid such as stearic acid or zinc stearate. Here, composite zinc white is known to have a zinc oxide (zinc white) layer on the surface and an inorganic metal salt as a core component inside, and examples thereof include the META-Z L series (META-Z L40, L50, L60) manufactured by Inoue Lime Industry Co., Ltd. The content of zinc oxide or composite zinc white is preferably 3 to 15 parts by mass per 100 parts by mass of the rubber component. The content of stearic acid or zinc stearate is preferably 0.1 to 3 parts by mass per 100 parts by mass of the total rubber component.

[0056] [Anti-aging agent] Since the vibration-proof rubber composition of this embodiment uses a diene rubber, if the ozone resistance or heat resistance is poor, it is preferable to improve it with a known antioxidant. Examples of antioxidants include carbamate-based antioxidants, phenylenediamine-based antioxidants, phenol-based antioxidants, diphenylamine-based antioxidants, quinoline-based antioxidants, imidazole-based antioxidants, paraffin wax, and microcrystalline wax. These antioxidants may be used alone or in combination of two or more. The content of the antioxidant is preferably in the range of 1 to 15 parts by mass, more preferably 3 to 10 parts by mass, per 100 parts by mass of the total rubber components.

[0057] [Processing aids] The anti-vibration rubber composition of this embodiment may contain a processing aid for the purpose of improving processability. Compounds typically used in rubber processing can be used as processing aids. Specific examples include higher fatty acids such as ricinoleic acid, stearic acid, palmitic acid, and lauric acid; salts of higher fatty acids such as barium stearate, zinc stearate, and calcium stearate; esters of higher fatty acids such as ricinoleic acid, stearic acid, palmitic acid, and lauric acid; and tackifiers such as terpene resins and coumarone resins for the purpose of imparting tackiness. These may be used alone or in combination of two or more.

[0058] [Coupling agent] In the anti-vibration rubber composition of the present embodiment, additives such as a coupling agent between a rubber component and carbon black, a silane coupling agent between a rubber component and silica, and known rubber additives such as a reversion inhibitor may be used alone or in combination of two or more kinds, for the purpose of adjusting vibration characteristics.

[0059] [Production of Anti-Vibration Rubber Composition] Various obvious methods can be employed to produce the vibration-damping rubber composition of this embodiment. For example, a known kneading device such as a Banbury mixer or a roll mill is used. Various diene rubbers, high styrene rubbers, butadiene-styrene random copolymers, and carbon black are blended in the kneading device, and the above-mentioned rubber additives, including a vulcanizing agent, are appropriately blended and kneaded to prepare an unvulcanized rubber composition of the desired composition. There are no particular limitations on the kneading method for each component. All component raw materials may be blended and kneaded at once, or each component may be blended and kneaded in two or three stages. A specific example is to knead all materials other than the vulcanizing agent (crosslinking agent) and vulcanization accelerator using a Banbury mixer, followed by blending the crosslinking agent and vulcanization accelerator and kneading using an open roll mill.

[0060] [Manufacturing vibration-proof rubber with metal fittings] When manufacturing the vibration-isolating rubber with metal fittings of this embodiment, various obvious methods can be employed, and the following method is one example.

[0061] First, the surface of the metal fitting (the metal fitting designated by reference numeral 2 in FIG. 1 described later) is roughened by shot blasting or the like, and then a one-component (single-component adhesive coating) or two-component (two-component adhesive coating) vulcanizing adhesive is applied to the roughened surface in the area to be bonded to the vibration-damping rubber composition, and then dried. Next, the metal fitting coated with the vulcanizing adhesive is placed in a desired position within the cavity of a mold of a desired shape that has been heated to a temperature suitable for vulcanizing the vibration-damping rubber composition. Thereafter, the vibration-damping rubber composition is injected into the mold cavity with the metal fitting placed therein by a device such as an injection mold. After the vibration-damping rubber composition is injected, it is heated for a certain period of time, allowing the vulcanization (crosslinking) reaction of the vibration-damping rubber composition and the reaction of the vulcanizing adhesive on the metal fitting surface to proceed simultaneously. The contents of the mold are then removed, yielding a vibration-damping rubber with the desired metal fitting structure.

[0062] Furthermore, the shape and size of the vibration-isolating rubber are not limited in any way, and can be set appropriately depending on the degree of vibration-isolating properties and the intended use.

[0063] The vibration-damping rubber manufactured in this manner is used as automotive vibration-damping rubber, for example, in member mounts, strut mounts, suspension bushings, and body mounts, and is interposed between components that make up a vibration or shock transmission system to provide vibration-damping or cushioning properties. [Example]

[0064] In the following, several examples and comparative examples will be described in order to more specifically clarify the present invention, but the present invention is not limited in any way by the descriptions of these examples, and it goes without saying that various changes, modifications, etc. can be made within the scope of the present invention.

[0065] <<Preparation of Anti-Vibration Rubber Composition>> Anti-vibration rubber compositions were prepared by blending and kneading various materials in the proportions shown in Tables 1 and 2. The kneading process involved first kneading the materials other than the vulcanizing agent and vulcanization accelerator for 5 minutes using a Banbury mixer to obtain a kneaded mixture (master batch). Next, the vulcanizing agent and vulcanization accelerator were added to the kneaded mixture while cooling it using an open roll (cooling was performed by setting the cooling water temperature in the open roll to about 20°C), and the mixture was kneaded for 5 minutes to prepare anti-vibration rubber compositions (Examples 1 to 8, Comparative Examples 1 to 7).

[0066] [Table 1]

[0067] [Table 2]

[0068] The types of materials listed in Tables 1 and 2 are as follows: Natural rubber: SVR CV60 Styrene butadiene rubber: Product name "SBR-1502" manufactured by JSR Corporation, bound styrene content 23.5% High styrene rubber: Product name "JSR 0061", manufactured by JSR Corporation, bound styrene content 66% by mass Butadiene-styrene random copolymer-1: Product name "L-SBR-841", manufactured by Kuraray Co., Ltd., average molecular weight (Mn) 10,000, Tg -6°C Butadiene-styrene random copolymer-2: Product name "RICON 100", manufactured by Clay Valley, average molecular weight (Mn) 4500, Tg -15°C Butadiene-styrene random copolymer-3: Trade name "RICON 181", manufactured by Clay Valley, average molecular weight (Mn) 3200, Tg -65°C Butadiene-styrene random copolymer-4: Product name "L-SBR-820", manufactured by Kuraray Co., Ltd., average molecular weight (Mn) 8300, Tg -14°C Carbon Black-1: Product name "Asahi #52", manufactured by Asahi Carbon Black Co., Ltd., nitrogen adsorption specific surface area 28 m2 / g (SRF class special product) Carbon Black-2: Product name "VULCAN 3D", manufactured by Cabot Japan Co., Ltd., nitrogen adsorption specific surface area 76 m 2 / g(HAF class) Carbon Black-3: Product name "VULCAN 6J", manufactured by Cabot Japan Co., Ltd., nitrogen adsorption specific surface area 108 m 2 / g(ISAF class) Anti-aging agent 1: Trade name "Nocrac 6C", manufactured by Ouchi Shinkosha, (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) Anti-aging agent-2: Trade name "Nocrac MB", manufactured by Ouchi Koh Co., Ltd. (2-mercaptobenzimidazole) Anti-aging agent-3: Product name "Ozoace 0100", Nippon Seiro Co., Ltd. (paraffin wax) Composite zinc oxide: Product name "META-Z-L60", manufactured by Inoue Lime Industry Co., Ltd. Stearic acid: Product name "Camellia Stearate", manufactured by Nippon Oil & Fats Corporation Process oil (naphthenic oil): Product name: Kurisef Oil H56, manufactured by ENEOS Corporation Vulcanizing agent: Sulfur, Tsurumi Chemical Industry Co., Ltd. "Kinka Brand Fine Sulfur 200MESH" Vulcanization accelerator 1 (N-cyclohexyl-2-benzothiazolylsulfenamide): "Noccela CZ-G" manufactured by Ouchiko Chemical Co., Ltd. Vulcanization accelerator-2 (tetramethylthiuram disulfide): "Noccela TT-P" manufactured by Ouchi Shinko Chemical Co., Ltd. [Preparation of 2 mm vulcanized rubber sheets for measuring tensile properties and properties after heat aging] Each of the vibration-damping rubber compositions of Examples 1 to 9 and Comparative Examples 1 to 7 shown in Tables 1 and 2 was compression molded using a 2 mm sheet mold with a cavity of approximately 2 mm in thickness at 160°C for a vulcanization time of 10 minutes to obtain a 2 mm thick vulcanized rubber sheet (hereinafter simply referred to as the evaluation rubber sheet).

[0069] [Preparing vibration-isolating rubber test pieces] To prepare the vibration-isolating rubber test piece 1 shown in Figure 1, two 50 mm x 50 mm iron metal fittings 2 were prepared, each with a bolt 3 installed in the center of one side. The surface of each metal fitting 2 where the bolt 3 was not installed was roughened by shot blasting. Next, Chemlock 205 (manufactured by Lord Far East) was applied as a primer adhesive to each of the metal fittings 2 on the side where the bolt was not installed, and dried at 80°C for 20 minutes to form a primer adhesive layer (10 μm thick). After cooling the metal fittings with the primer adhesive layer to room temperature, Chemlock 6125 (manufactured by Lord Far East) was applied as a topcoat adhesive to the surface of the primer adhesive layer, and dried at 80°C for 20 minutes to form a topcoat adhesive layer (10 μm thick). Then, each metal fitting 2 was placed in the molding die (so that the topcoat adhesive layer of each metal fitting 2 was facing each other), and then unvulcanized rubber was filled between each metal fitting 2 in the molding die using an injection molding machine, and vulcanized (160°C x 12 minutes) to produce a square vibration-damping rubber test piece 1 with metal fitting 2 formed into a rectangular parallelepiped of 40 mm x 40 mm x 30 mm as shown in Figure 1.

[0070] <Tensile properties> Each evaluation rubber sheet obtained using each of the vibration-proof rubber compositions of Examples 1 to 9 and Comparative Examples 1 to 7 was punched out with a JIS No. 3 dumbbell, and the breaking strength (TB), breaking elongation (EB), and hardness (Hs: JIS A) were measured in accordance with JIS K 6251. The results of these measurements are shown in Tables 1 and 2.

[0071] <Vibration characteristics test> For each test piece 1 obtained using the anti-vibration rubber composition of Examples 1 to 9 and Comparative Examples 1 to 7, an axial load was first applied via each bolt 3, compressing it 6 mm in the axial direction (in the bolt 3 axial direction), and then the load was released. This compression-release process was repeated twice. After this, the test piece was again compressed 6 mm (i.e., the third loading process), and the load-deflection characteristics during this compression (the third loading process) were measured, and a load-deflection curve was created based on the results. The load values ​​P1 and P2 (unit: N) at which the deflection reached 2 mm and 4 mm, respectively, were then read from the load-deflection curve, and the static spring constant Ks (N / mm) for each test piece was calculated by appropriately substituting these load values ​​P1 and P2 into the relational expression "Ks = (P2 - P1) / 2."

[0072] Separately, each test piece 1 was compressed 3 mm in the axial direction via each bolt 3 in the same manner as above, and a constant-displacement harmonic compression vibration of ±0.05 mm amplitude was applied at a frequency of 100 Hz from one of the bolt 3 sides (for example, the bottom in the figure) of the compressed test piece 1, centered on the 3 mm compressed position, to determine the dynamic spring constant Kd100 (N / mm) at 100 Hz in accordance with the "non-resonance method (a)" in the "Test methods for rubber vibration-isolating materials" of JIS-K-6385-2012. The dynamic magnification (= Kd100 / Ks) was then calculated from the determined dynamic spring constant (Kd100) and the calculated static spring constant (Ks).

[0073] In this vibration characteristic test, each test piece 1 was compressed 3 mm in the axial direction via each bolt 3 in the same manner as above, and a constant displacement harmonic compression vibration of ±1.0 mm amplitude, centered on the 3 mm compressed position, was applied to each test piece 1 from one of the bolts 3 at a frequency of 10 Hz, and the loss factor tanδ(10 Hz) at 10 Hz was calculated. The calculation results are shown in Tables 1 and 2.

[0074] Furthermore, a graph showing the relationship between the dynamic magnification Kd100 / Ks and the loss factor tanδ (10 Hz) for each test piece 1 calculated as described above is shown in Fig. 2. Fig. 2 compares Examples 1 to 9 with Comparative Examples 1 to 6. In Fig. 2, the number (1 to 9) of Examples 1 to 9 is written adjacent to the symbol "circle," and the number (1 to 6 circled in Fig. 2) of Comparative Examples 1 to 6 is written adjacent to the symbol "square."

[0075] <Heat resistance adhesive test> For each test piece 1 obtained using each vibration-damping rubber composition of Examples 1 to 9 and Comparative Examples 1 to 7, first, as described above, each test piece 1 was stretched 50% (stretched vertically in FIG. 1 ) via each bolt 3, and then held in a 100°C atmosphere for 60 minutes, and the presence or absence of adhesive peeling of each metal fitting 2 was visually observed. The test piece was then held in an atmosphere heated by 10°C for 40 minutes, and the visual inspection for adhesive peeling of each metal fitting 2 was repeated. Finally, the test piece was held in a 200°C atmosphere for 40 minutes, and the presence or absence of adhesive peeling of each metal fitting 2 was confirmed, and the test was completed. In this test, the higher the temperature at which adhesive peeling of each metal fitting 2 could be prevented, the better the heat-resistant adhesion was judged to be. Tables 1 and 2 list the highest temperature at which adhesive peeling could be prevented. For example, if adhesive peeling did not occur at 160°C but adhesive peeling occurred at 170°C, the heat-resistant adhesion column in Tables 1 and 2 was recorded as "160°C." In addition, when peeling was prevented even at 200°C, it was recorded as "200°C." In this test, two test pieces 1 were prepared for each of the vibration-damping rubber compositions of Examples 1 to 9 and Comparative Examples 1 to 6, and the test results for the two test pieces 1, whichever temperature caused peeling, was used as an index of the heat-resistant adhesiveness of that vibration-damping rubber composition. These test results are shown in Tables 1 and 2.

[0076] Effects of the Example According to the results in FIG. 2, when the anti-vibration rubber compositions of Examples 1 to 9 were used (hereinafter simply referred to as Examples 1 to 9), the vibration characteristic test results (results showing the relationship between dynamic magnification and loss factor) were all located on the lower side of the characteristic lines (not shown) based on the vibration characteristic test results when the anti-vibration rubber compositions of Comparative Examples 1 to 7 were used (hereinafter simply referred to as Comparative Examples 1 to 7), demonstrating that these compositions excel in achieving both low dynamic magnification and high damping characteristics.

[0077] Furthermore, as shown in the results of Tables 1 and 2, in the case of Examples 1 to 9, the results of the heat-resistant adhesion test were all 170°C or higher, which was better than those of Comparative Examples 1 to 6. Note that Example 5, which contains 5 parts by mass of carbon black, had a slightly lower tensile strength than the other Examples, and tended to have slightly higher adhesion after mixing in a Banbury mixer (when discharged from the mixer). However, the processability was at a sufficient level, and it also had excellent effects of achieving both low dynamic magnification and high damping characteristics, as well as excellent heat-resistant adhesion. Therefore, it was determined that there was a high possibility that it could be used as vibration-proof rubber. Furthermore, the nitrogen adsorption specific surface area was 76 m 2 Example 9, which contains 50 parts by mass of carbon black with a viscosity of 1 / g, is slightly inferior to the other examples in terms of the effect of achieving both low dynamic magnification characteristics and high damping characteristics, but it has a greater effect of achieving both than Comparative Examples 1 to 7, and therefore it was determined that it could be used as a vibration-damping rubber.

[0078] On the other hand, Comparative Examples 1 to 3 and 5, which do not contain a butadiene-styrene random copolymer, did not achieve both low dynamic magnification and high damping characteristics. Furthermore, Comparative Example 4, which does not contain high styrene rubber and has a carbon black content of 60 parts by mass, and Comparative Example 5, which contains 20 parts by mass of high styrene rubber and 30 parts by mass of butadiene-styrene random copolymer but has a nitrogen adsorption specific surface area of ​​76 m 2Comparative Example 6, which contained a slightly higher amount of carbon black (60 parts by mass in Table 2), had a tan δ of 0.306 at 10 Hz, which was excellent in terms of damping characteristics, but the dynamic magnification was a large value of 5.79.Comparative Example 7, which contained 20 parts by mass of carbon black and 50 parts by mass of butadiene-styrene random copolymer, showed severe stickiness of the material after mixing in a Banbury mixer, making it difficult to discharge from the mixer.In addition, the material also showed severe stickiness to the open rolls when mixed, making processing difficult.As a result, it was judged to have poor processability (determined to be unsuitable for processability), and its physical properties were not evaluated. [Explanation of symbols]

[0079] 1...Test piece 2...Metal fittings 3...Bolt (support rod)

Claims

1. An anti-vibration rubber composition comprising diene rubber and high styrene rubber as the main rubber components, which make up 90% by mass or more of the total rubber components, in a mass ratio of diene rubber / high styrene rubber = 50 / 50 to 90 / 10, and containing 15 to 45 parts by mass of a butadiene-styrene random copolymer having an average molecular weight (Mn) of 3,000 to 12,000 as a softener, and 5 to 50 parts by mass of carbon black, when the total rubber components are taken as 100 parts by mass.

2. When the total rubber component is taken as 100 parts by mass, the nitrogen adsorption specific surface area is 15 to 80 m ２ 2. The vibration-proof rubber composition according to claim 1, wherein the composition contains 5 to 40 parts by mass of carbon black having a carbon black content of 5 to 45 parts by mass.

3. When the total rubber component is taken as 100 parts by mass, the nitrogen adsorption specific surface area is 20 to 45 m ２ 2. The vibration-proof rubber composition according to claim 1, wherein the content of carbon black is 20 to 40 parts by mass / g and the total carbon black content is 20 to 40 parts by mass.

4. The anti-vibration rubber composition according to any one of claims 1 to 3, characterized in that the butadiene-styrene random copolymer has an average molecular weight (Mn) of 8,000 to 12,000 and a glass transition temperature (Tg) of -10°C or higher and 0°C or lower.

5. 4. The vibration-proof rubber composition according to claim 1, wherein the diene rubber contains natural rubber and styrene-butadiene rubber, and contains 40 to 80 parts by mass of natural rubber and 10 to 50 parts by mass of styrene-butadiene rubber, relative to 100 parts by mass of all rubber components including the high styrene rubber.

6. The vibration-proof rubber composition according to claim 4, characterized in that the diene rubber contains natural rubber and styrene-butadiene rubber, and contains 40 to 80 parts by mass of natural rubber and 10 to 50 parts by mass of styrene-butadiene rubber, where the total rubber components including the high styrene rubber are taken as 100 parts by mass.

7. A vibration-damping rubber characterized in that the vibration-damping rubber composition according to any one of claims 1 to 3 is vulcanization-bonded to the surface of a metal fitting via an adhesive layer on the surface of the metal fitting, and the metal fitting and vulcanized rubber made from the vulcanization-bonded vibration-damping rubber composition are integrally formed.

8. A vibration-isolating rubber characterized in that the vibration-isolating rubber composition according to claim 4 is vulcanization-bonded to the surface of the metal fitting via an adhesive layer on the surface of the metal fitting, and the metal fitting and vulcanized rubber made of the vulcanization-bonded vibration-isolating rubber composition are integrally formed.

9. A vibration-isolating rubber characterized in that the vibration-isolating rubber composition according to claim 5 is vulcanization-bonded to the surface of the metal fitting via an adhesive layer on the surface of the metal fitting, and the metal fitting and vulcanized rubber made of the vulcanization-bonded vibration-isolating rubber composition are integrally formed.

10. A vibration-isolating rubber characterized in that the vibration-isolating rubber composition according to claim 6 is vulcanization-bonded to the surface of the metal fitting via an adhesive layer on the surface of the metal fitting, and the metal fitting and vulcanized rubber made of the vulcanization-bonded vibration-isolating rubber composition are integrally formed.

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