Vibration-isolating rubber composition and vibration-isolating rubber

Abstract

To provide a vibration isolation rubber composition which is excellent in heat resistance, having even a sufficient support function, and capable of making compatible both low-vibration magnification performance and high-attenuation performance, and vibration isolation rubber which can be obtained by the vibration isolation rubber composition, and is excellent in adhesiveness between a metal fixture and rubber.SOLUTION: A vibration isolation rubber composition includes natural rubber and butadiene rubber as a main rubber composition at a ratio of the natural rubber / butadiene rubber=50 / 50 to 95 / 5 at a mass ratio, and contains a butadiene / styrene random copolymer whose average molecular weight (Mn) is 3,000 to 12,000 as a softener by 15 to 50 pts.mass when setting a rubber composition as 100 pts.mass. Also, the vibration isolation rubber contains carbon black by 15 to 70 pts.mass when setting the rubber composition to 100 pts.mass.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a rubber composition and an anti-vibration rubber, and more particularly to an anti-vibration rubber composition capable of providing an anti-vibration rubber with excellent vibration-proofing properties, and an anti-vibration rubber with excellent adhesion obtained by applying this anti-vibration rubber composition. [Background technology]

[0002] Anti-vibration rubber used in multiple types of vibration transmission systems with different frequencies, amplitudes, etc., such as automobile vibration isolation, is required to exhibit appropriate and effective vibration isolation characteristics so as to be able to respond appropriately to the various types of input vibrations.

[0003] For example, in the case of automotive anti-vibration rubber, generally, when vibrations of relatively small amplitude in the high frequency range of 100 Hz or more are input, low dynamic spring characteristics are required to block the transmission of vibration. Also, when vibrations of relatively large amplitude in the low frequency range of about 5 to 15 Hz are input, high damping characteristics are required to increase the vibration damping effect that attenuates the vibration. On the other hand, anti-vibration rubber is also required to have a support function such as supporting heavy objects, and the static spring characteristics (Ks) must be increased to a certain extent in order to withstand a certain static force.

[0004] Therefore, it is desirable to reduce the value of the dynamic magnification (=Kd100 / Ks) (also called the static-dynamic ratio), which is the ratio of the dynamic spring constant (Kd100) to the static spring constant (Ks) when a small amplitude vibration of, for example, 100 Hz is input. Also, from the viewpoint of high damping characteristics, it is desirable to increase the value of the loss coefficient (tan δ; also called the loss factor) when a large amplitude vibration of, for example, 10 Hz is input.

[0005] However, it is generally known that increasing the damping characteristics results in a corresponding increase in the dynamic magnification ratio, and conversely, decreasing the dynamic magnification ratio results in a corresponding decrease in the damping characteristics. In other words, there is a trade-off between low dynamic magnification ratio characteristics and high damping characteristics, and it is strongly desired to achieve both of these characteristics in anti-vibration rubber.

[0006] In response to these issues, there have been proposed anti-vibration rubber compositions in which hydrogenated isoprene rubber is added to diene rubber (for example, Patent Document 1), anti-vibration rubber compositions in which domains of butadiene rubber with carbon black unevenly distributed therein are dispersed in a matrix phase of chlorinated butyl rubber (for example, Patent Document 2), and further anti-vibration rubber compositions in which liquid styrene-butadiene rubber is blended with an unvulcanized diene rubber material mainly composed of vinyl and styrene (for example, Patent Document 3).

[0007] On the other hand, in the case of automotive anti-vibration rubber, blends of natural rubber (NR) and butadiene rubber (BR) (hereinafter referred to as NR / BR as necessary) are widely used from the perspective of fatigue resistance to repeated vibration, and while it is relatively easy to achieve a low dynamic magnification ratio with NR / BR, achieving both low dynamic magnification ratio and high damping characteristics, as mentioned above, is a difficult task.

[0008] For example, Patent Document 4 proposes a diene rubber containing more than 0 parts by mass and not more than 10 parts by mass of carbon black and further containing 50 parts by mass to 70 parts by mass of oil in response to the issue of achieving both low dynamic magnification characteristics and high damping characteristics when using NR / BR, and describes the use of NR / BR.

[0009] As mentioned above, anti-vibration rubber for automobiles is used in multiple types of vibration transmission systems with different frequencies, amplitudes, etc. For this reason, rubber materials with various different hardnesses and damping properties are used for anti-vibration rubber materials, and in order to control the hardness and damping properties of NR / BR as a rubber component, it has been conventional to adjust the amount of various carbon blacks with different particle sizes and structures added, or the amount of process oils such as naphthenic oils added.

[0010] On the other hand, as automobiles become more compact and have higher power output, the environment surrounding automotive anti-vibration rubber tends to become hotter, so there is a particular demand for improved heat resistance of anti-vibration rubber.

[0011] Furthermore, many of the anti-vibration rubbers for vehicles are rubber parts with metal fittings, which are formed by integrating the metal fittings and the rubber material, and are used as connecting members between various components such as frames and engines. In such anti-vibration rubbers, an adhesive is usually used to bond the interface between the metal fittings and the rubber material. There are generally two types of bonding methods using this adhesive: a "single-component adhesive coating type" that uses one adhesive, and a "two-component adhesive coating type" that applies a primer to the metal fitting surface and then applies a topcoat adhesive. The latter two-component adhesive coating type is widely used to obtain high adhesion. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Publication No. 07-216136 [Patent Document 2] JP 2019-131761 A [Patent Document 3] JP 2005-113092 A [Patent Document 4] JP 2018-188522 A Summary of the Invention [Problem to be solved by the invention]

[0013] However, the anti-vibration rubber composition described in Patent Document 1 tends to have insufficient rubber strength, and the anti-vibration rubber compositions described in Patent Documents 2 and 3 do not use NR / BR, so they may have insufficient vibration durability when subjected to repeated vibrations.

[0014] Furthermore, the anti-vibration rubber composition using NR / BR described in Patent Document 4 contains a small amount of carbon black and a large amount of oil, which is a softening agent, so the hardness of the obtained vulcanized rubber for use as anti-vibration rubber is too soft, and the supporting function as an anti-vibration rubber may be insufficient (for example, the rubber hardness (hardness) described in the examples of Patent Document 4 is 5 to 21, which is extremely low for vulcanized rubber hardness used in anti-vibration rubber for vehicles and is likely to result in insufficient supporting function).

[0015] Furthermore, because the content of carbon black, a reinforcing material, is low, the rubber strength is insufficient, and durability may be insufficient, for example, when a heavy load is repeatedly applied. In addition, the addition of a large amount of process oil, such as aromatic oil or naphthenic oil, often leads to a decrease in the heat resistance of the vibration-proof rubber.

[0016] As described above, high adhesion is required for anti-vibration rubber, but depending on the anti-vibration rubber composition used, the adhesion may be insufficient, particularly when used in a severe thermal environment.

[0017] The present invention has been made in consideration of the above circumstances, and has an object to provide an anti-vibration rubber composition that has excellent heat resistance, sufficient support function, and is capable of achieving both low dynamic magnification and high damping properties, and an anti-vibration rubber obtained from said anti-vibration rubber composition and that has excellent adhesion between metal fittings and rubber. [Means for solving the problem]

[0018] The present inventors have conducted extensive research to achieve the above object, and have found that an anti-vibration rubber composition containing natural rubber and butadiene rubber as main rubber components with a high ratio of natural rubber by mass, and containing a specific range of butadiene-styrene random copolymers with a specific molecular weight (Mn), can achieve both good low dynamic magnification characteristics and high damping characteristics, even when the hardness of the vulcanized rubber is sufficient from the viewpoint of the support function of the anti-vibration rubber (for example, when the rubber has a sufficient static spring constant (rubber hardness of 40 to 75)), and thus realize excellent anti-vibration characteristics not found in conventional anti-vibration rubber compositions.

[0019] That is, one embodiment of the anti-vibration rubber composition of the present invention is a vibration-proof rubber composition that contains natural rubber and butadiene rubber as main rubber components in a mass ratio of natural rubber / butadiene rubber = 50 / 50 to 95 / 5, and also contains 15 to 50 parts by mass of a butadiene-styrene random copolymer having an average molecular weight (Mn) of 3000 to 12000 as a softener, relative to 100 parts by mass of the rubber component.

[0020] The configuration of one aspect of the anti-vibration rubber composition described above makes it possible to realize excellent high damping properties while maintaining a favorable low dynamic magnification, and furthermore, to realize high adhesion.

[0021] In one embodiment of the anti-vibration rubber composition, the rubber component is preferably contained in an amount of 15 to 70 parts by mass of carbon black, based on 100 parts by mass of the rubber component, which allows a high level of compatibility between low dynamic magnification and high vibration damping while maintaining sufficient support function.

[0022] Furthermore, in one embodiment of the vibration-proof rubber composition, 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, and the carbon black has a nitrogen adsorption specific surface area of ​​15 to 80 m 2 / g, and the content of the carbon black is preferably 20 to 60 parts by mass when the rubber component is 100 parts by mass. In this range, while having a sufficient support function, the compatibility of low dynamic magnification characteristics and high vibration damping performance can be realized at a higher level, and furthermore, high adhesiveness can be realized.

[0023] Furthermore, in one aspect of the vibration damping rubber composition, the carbon black has a nitrogen adsorption specific surface area of 20 to 45 m 2 / g, and the content of the carbon black is preferably 25 to 50 parts by mass when the rubber component is 100 parts by mass.

[0024] Furthermore, in one aspect of the vibration damping rubber composition, the butadiene rubber has a cis 1,4-bonding amount of 90% or more and a Mooney viscosity (ML 1+4 ) of 50 to 75 at 100 °C, which is preferable. Thereby, more excellent low dynamic magnification property and high rubber strength can be realized.

[0025] Furthermore, in one aspect of the vibration damping rubber composition, when the rubber component is 100 parts by mass, it preferably contains 0 to 5 parts by mass of process oil. In this range, while having a sufficient support function, the compatibility of low dynamic magnification characteristics and high vibration damping performance, and furthermore, heat resistance can be realized at a higher level.

[0026] One aspect of the vibration damping rubber of the present invention is a vibration damping rubber characterized in that one aspect of the above vibration damping rubber composition and a metal fitting are vulcanization-bonded via an adhesive layer formed on the surface of the metal fitting, and the two are integrally formed.

[0027] Due to the configuration of one aspect of the above vibration damping rubber, excellent adhesiveness between the metal fitting and the vulcanized rubber can be achieved, and the compatibility of low dynamic magnification characteristics and high vibration damping performance can be realized.

Advantages of the Invention

[0028] According to the present invention, it is possible to provide an anti-vibration rubber composition that has excellent heat resistance, sufficient support function, and is capable of achieving both low dynamic magnification and high damping properties, as well as to provide an anti-vibration rubber obtained from the anti-vibration rubber composition and that has excellent adhesion between metal fittings and rubber. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 is a schematic explanatory diagram of a test piece 1 formed using each of the anti-vibration rubber compositions of Examples 1 to 9 and Comparative Examples 1 to 6 according to the present invention. [Diagram 2] 1 is a graph showing the relationship between dynamic magnification (Kd100 / Ks) and tan δ (10 Hz) for test piece 1 formed 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 PREFERRED EMBODIMENTS

[0030] Matters relating to the implementation of the present invention will be described in detail below.

[0031] As mentioned above, there is a trade-off between low dynamic magnification and high damping characteristics. That is, normally, there is a fixed relationship between damping properties and dynamic magnification, and for vibration-proof rubber (rubber sample) of the same shape, the dynamic magnification will be approximately the same for a certain damping property. The low dynamic magnification and high damping property referred to in this invention means that this fixed relationship is deviated from, and for the same damping property, the dynamic magnification will be lower than that of a normal vibration-proof rubber material. In other words, for the same dynamic magnification, the damping property will be greater.

[0032] In addition, the content of each material (each component) applicable to the present invention 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.

[0033] The anti-vibration rubber composition of the present invention is characterized in that it contains natural rubber and butadiene rubber as main rubber components in a mass ratio of natural rubber / butadiene rubber = 50 / 50 to 95 / 5, and also contains 15 to 50 parts by mass of a butadiene-styrene random copolymer (liquid SBR) having an average molecular weight (Mn) of 3,000 to 12,000.

[0034] In anti-vibration rubber compositions, it is common to use natural rubber as the main rubber component, blended with styrene-butadiene copolymer rubber (SBR) or butadiene rubber (BR). When anti-vibration rubber with a lower dynamic magnification and high durability is desired, a main rubber component containing natural rubber / butadiene rubber in a ratio of 50 / 50 to 95 / 5 is often used.

[0035] However, natural rubber and butadiene rubber are known to be rubbers with low damping properties (also called low loss), and although anti-vibration rubbers with excellent low dynamic magnification properties can be obtained, they are elastic bodies with the rubber hardness of anti-vibration rubbers normally used for vehicle applications (for example, rubber hardness of about 40 to 70), and it has not been possible to obtain an anti-vibration rubber composition that achieves both low dynamic magnification properties and high damping properties. In other words, there was no technical idea of ​​including natural rubber and butadiene rubber as the main rubber components in a mass ratio of natural rubber / butadiene rubber = 50 / 50 to 95 / 5, and containing 15 to 50 parts by mass of a specific butadiene-styrene random copolymer as a softener.

[0036] For this reason, conventionally, it has not been possible to come up with a component composition similar to that of the anti-vibration rubber composition of the present invention, and even when a blend rubber of highly durable natural rubber and butadiene rubber is used, it has not been possible to achieve both low dynamic magnification and high damping properties (the same level of both low dynamic magnification and high damping properties as in the present invention).

[0037] Each component used in the anti-vibration rubber composition of the present invention will now be described.

[0038] [Rubber component] The anti-vibration rubber composition according to the present invention contains natural rubber and butadiene rubber as the main rubber component in a mass ratio of natural rubber / butadiene rubber = 50 / 50 to 95 / 5 (hereinafter simply referred to as the rubber component category of the present invention). The main rubber component means that the total amount of natural rubber (NR) and butadiene rubber (BR) is 90 mass% or more of the total rubber component. Preferably, the total amount of natural rubber (NR) and butadiene rubber (BR) is 95 mass% or more of the total rubber component. When natural rubber and butadiene rubber are contained as the main rubber component within the rubber component category of the present invention, a rubber composition having high rubber strength, excellent vibration durability, and low dynamic magnification can be obtained.

[0039] The natural rubber is not particularly limited, and normal natural rubber used for anti-vibration rubber can be applied. Specifically, for example, sheet rubber (including crepe) includes all grades of RSS (RIBBED SMOKED SHEET), WHITE CREPES, PALE CREPES, ESTATE BROWN CREPES, COMP CREPES, THIN BROWN CRAPES (RIMILLS), THICH BLANCKET CRAPES (AMBERS), FLAT BARK CREPES, and PURE SMOKED BLANKET CRAPES. In addition, block rubber includes 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] The butadiene rubber (BR) used in the present invention is not particularly limited, and various commercially available butadiene rubbers used for vibration-proof rubbers can be used. Among them, from the viewpoints of low dynamic magnification, low-temperature characteristics, and durability against repeated deformation, the higher the cis 1,4-bond content, the more preferable, and for example, it is preferable to use high cis BR with a cis 1,4-bond content of 90% or more, and more preferably 93% or more.

[0041] In addition, for BR with the same chemical composition, the Mooney viscosity (ML 1+4 The higher the Mooney viscosity (ML) at 100°C, the higher the molecular weight. 1+4 On the other hand, it is preferable that the Mooney viscosity (ML 1+4 ) increases, the flowability of rubber tends to decrease, and the Mooney viscosity (ML 1+4 If the Mooney viscosity (ML) at 100° C. is too high, the kneading processability and molding processability of the vibration-proof rubber material composition tend to deteriorate. 1+4 ) is preferably 75 or less. More preferably, the Mooney viscosity (ML 1+4 ) 65 or less. That is, in the present invention, the butadiene rubber (BR) preferably used has a viscosity of 50 or more and 65 or less. Examples of such butadiene rubber include JSR BR730, JSR BR54, JSR BR740 (all manufactured by JSR Corporation), Ubepol 390L (manufactured by Ube Industries), BUNA CB21, CB22, CB1221 (all manufactured by ARLANXEO), and the like.

[0042] The anti-vibration rubber composition of the present invention may contain rubber components other than the natural rubber and butadiene rubber as long as the effects of the present invention are not impaired (for example, within the range of 10 parts by mass or less). Examples of the other rubber components include isoprene rubber (IR), styrene-butadiene rubber (SBR), ethylene-propylene rubber (EPDM), etc.

[0043] [Butadiene-styrene random copolymer] The anti-vibration rubber composition according to the present invention contains 15 to 50 parts by mass of butadiene-styrene random copolymer having an average molecular weight (Mn) of 3000 to 12000 (hereinafter referred to as the copolymer category of the present invention). In the case of this copolymer category of the present invention, it is possible to achieve both appropriate flexibility, excellent vibration damping properties, and low dynamic magnification. Note that this butadiene-styrene random copolymer acts as a softening agent and does not become an elastomer even when used in combination with a sulfur-based vulcanizing agent for normal rubber, so it is not included in the rubber component and resin component in the present invention. Examples of such butadiene-styrene random copolymers include Ricon 100, Ricon 181, and Ricon 184 (all manufactured by Cray Valley), L-SBR-820, and L-SBR-841 (all manufactured by Kuraray Co., Ltd.).

[0044] Preferably, the butadiene-styrene random copolymer has an average molecular weight (Mn) of 8000 to 12000 and a glass transition temperature (Tg) of -10°C or more and 0°C or less. Such a butadiene-styrene random copolymer has a greater effect of achieving both low dynamic magnification and high vibration damping. A specific example of such a butadiene-styrene random copolymer is L-SBR-841 (manufactured by Kuraray Co., Ltd.).

[0045] [Carbon black] In the anti-vibration rubber composition according to the present invention, it is preferable to contain carbon black in a ratio of 15 to 70 parts by mass (hereinafter referred to as the carbon black category of the present invention). In the case of this carbon black category of the present invention, it is easy to obtain an appropriate static spring constant for performing the support function of the anti-vibration rubber. As mentioned above, the butadiene-styrene random copolymer also acts as a softener. That is, if the carbon black content is less than 15 parts by mass, the hardness of the vulcanized rubber becomes too low, making it difficult to obtain an appropriate static spring constant. If the carbon black content is more than 70 parts by mass, the improvement in the elastic modulus at high frequency micro-amplitude becomes greater. Therefore, the low dynamic magnification effect becomes smaller.

[0046] 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 are preferred. 2 Carbon black having a molecular weight of 1000 parts by mass is preferably used. Examples of such carbon black include HAF class, MAF class, FEF class, GPF class, SRF class, and FT class, which are known as furnace carbon black for rubber. The content of this carbon black is preferably 20 to 60 parts by mass when the rubber component is taken as 100 parts by mass.

[0047] Furthermore, the nitrogen adsorption specific surface area is 20 to 45 m 2 It is more preferable that the carbon black content per g is 25 to 50 parts by mass. Such carbon black has a large effect of high damping at low dynamic magnification. Specific examples of such carbon black include FEF grade, GPF grade, SRF grade, etc., which are known as furnace carbon black for rubber.

[0048] [Process oil] The anti-vibration rubber composition according to the present invention may contain process oil in addition to the above components. However, process oils such as naphthene oils, aromatic oils, and paraffin oils used in diene rubber compositions such as natural rubber and butadiene rubber have the effect of lowering the elastic modulus, but are poor at increasing damping properties, and furthermore, do not have the effect of achieving both low dynamic magnification and high damping properties. In addition, the addition of a large amount of the above process oil tends to reduce heat resistance. For this reason, it is preferable to set the amount of process oil to a level that adjusts the rubber hardness (for example, 5 parts by mass or less, which is a small amount added). More preferably, it is set to 3 parts by mass or less.

[0049] [Vulcanizing agent (crosslinking agent)] The anti-vibration rubber composition according to the present invention contains a vulcanizing agent (crosslinking agent) in addition to the above-mentioned components. As the vulcanizing agent (crosslinking agent), a known sulfur-based vulcanizing agent can be used. Vulcanization using sulfur or a sulfur-based compound is preferably used because it provides excellent durability of the anti-vibration rubber. Furthermore, the butadiene-styrene random copolymer with an average molecular weight (Mn) of 3000 to 12000 used in the present invention is hardly crosslinked by sulfur or a sulfur-based compound, and therefore cannot become an elastomer, and can act as a softener.

[0050] 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 be used in combination.

[0051] [Filler] The anti-vibration rubber composition according to the present invention may contain fillers other than carbon black in addition to the above components. 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.

[0052] Examples of silica include dry process silica (fumed silica), wet process silica, colloidal silica, etc. Among these, wet process silica, which is mainly composed of hydrated silicic acid, is particularly preferred. These silicas can be used alone or in combination of two or more. The specific surface area of ​​silica is not particularly limited, but the nitrogen adsorption specific surface area is usually 50 to 400 m 2 / g, preferably 100 to 250 m 2 / g, more preferably 120 to 220 m 2 / g. Such silica is preferable because it has a high level 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.

[0053] [Vulcanization accelerator] When a sulfur compound is used as a vulcanizing agent, a vulcanization accelerator can be used in combination. 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 glycine compounds such as benzothiazole, benzothiazole, and benzothiazole. Examples of the vulcanization accelerator include guanidine compounds such as thiuram monosulfide, triphenyl guanidine, diorthonitrile guanidine, orthonitrile biguanide, and diphenyl guanidine phthalate, and thiuram compounds such as tetramethyl thiuram monosulfide, tetramethyl thiuram disulfide, tetraethyl thiuram disulfide, tetrabutyl thiuram disulfide, tetrakis (2-ethylhexyl) thiuram disulfide, tetrabenzyl thiuram disulfide, and dipentamethylene thiuram tetrasulfide. These vulcanization accelerators may be used alone or in combination of two or more kinds, or different kinds 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, when the total amount of all rubber components including the natural rubber and the butadiene rubber is 100 parts by mass. To adjust the vulcanization rate, scorch inhibitors such as N-cyclohexylthiophthalimide and N-phenyl-N-(trichloromethylthio)benzenesulfonamide can be preferably used.

[0054] [Vulcanization aid] In addition, 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 oxide or activated zinc oxide or composite zinc oxide in combination with a vulcanization aid such as stearic acid or zinc stearate. Here, composite zinc oxide is known to have a layer of zinc oxide (zinc oxide) on the surface and contain an inorganic metal salt inside as a core component, and examples thereof include META-Z L series (META-Z L40, L50, L60) manufactured by Inoue Sekiryo Kogyo Co., Ltd. The content of zinc oxide or composite zinc oxide is 3 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the rubber component. The content of stearic acid or zinc stearate is preferably 0.1 parts by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the rubber component.

[0055] [Anti-aging agent] Since the vibration-proof rubber composition of this embodiment uses natural rubber and butadiene rubber, if the ozone resistance or heat resistance is poor, it is preferable to improve it with a known antioxidant. Examples of the antioxidant include carbamate-based antioxidants, phenylenediamine-based antioxidants, phenol-based antioxidants, diphenylamine-based antioxidants, quinoline-based antioxidants, imidazole-based antioxidants, waxes, etc. These are 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 in the range of 3 to 10 parts by mass, per 100 parts by mass of the rubber component.

[0056] [Processing aids] The anti-vibration rubber composition of this embodiment may contain a processing aid for the purpose of improving processability. Compounds used in normal rubber processing may be used as the processing aid. Specific examples of the processing aid 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 kinds.

[0057] [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 can be used alone or in combination of two or more kinds for the purpose of adjusting vibration characteristics.

[0058] [Production of Anti-Vibration Rubber Composition] In producing the anti-vibration rubber composition according to the present invention, various obvious methods can be adopted. For example, a known kneading device such as a Banbury mixer or a roll machine is used, and natural rubber, butadiene rubber, and butadiene-styrene random copolymer are respectively charged into the kneading device, and the above-mentioned rubber additives including a vulcanizing agent are blended and appropriately kneaded to prepare an unvulcanized rubber composition of the desired composition. There is no particular restriction on the kneading method of each component, and all the component raw materials may be blended and kneaded at once, or each component may be blended and kneaded in two or three stages. As a specific example, for example, materials other than the vulcanizing agent (crosslinking agent) and the vulcanization accelerator are kneaded using a Banbury mixer, and then the crosslinking agent and the vulcanization accelerator are blended and kneaded using an open roll.

[0059] [Manufacture of anti-vibration rubber with metal fittings] In manufacturing the metal fitting-attached anti-vibration rubber according to the present invention, various obvious methods can be adopted, one example of which is the following method.

[0060] First, the surface of the metal fitting (metal fitting indicated by reference numeral 2 in FIG. 1 described later) is roughened by shot blasting or the like, and a one-component or two-component vulcanizing adhesive is applied to the portion of the roughened surface to be bonded to the anti-vibration rubber composition, and then dried. Next, the metal fitting to which the vulcanizing adhesive has been applied is placed at a desired position in a cavity of a desired shape of a mold that has been heated to a temperature suitable for vulcanizing the anti-vibration rubber composition. Thereafter, the anti-vibration rubber composition is injected into the mold cavity in which the metal fitting is placed, using a device such as an injection device. After the anti-vibration rubber composition is injected, the vulcanization (crosslinking) reaction of the anti-vibration rubber composition and the reaction of the vulcanizing adhesive on the surface of the metal fitting are simultaneously promoted by heating for a certain period of time. Then, the metal fitting is removed from the mold to obtain an anti-vibration rubber with the metal fitting.

[0061] Furthermore, there is no limitation on the shape, size, etc. of the vibration-isolating rubber, and these can be set appropriately depending on the level of vibration-isolating properties and the application.

[0062] The anti-vibration rubber manufactured in this manner is used, for example, as automotive anti-vibration rubber for member mounts, strut mounts, suspension bushings, body mounts, etc., by being interposed between components that make up a vibration or shock transmission system to provide vibration damping or cushioning properties. EXAMPLES

[0063] In the following, in order to more specifically explain the present invention, several examples and comparative examples will be described. However, the present invention is not limited in any way by the descriptions of these examples, and it goes without saying that various changes, improvements, etc. can be made without departing from the spirit of the present invention.

[0064] <Preparation of anti-vibration rubber composition> Anti-vibration rubber compositions were prepared by blending and kneading various materials in the ratios shown in Tables 1 and 2. The above kneading was carried out by first blending materials other than the vulcanizing agent and vulcanization accelerator for 5 minutes using a Banbury mixer, then blending the vulcanizing agent and vulcanization accelerator, setting the cooling water temperature to about 20°C using an open roll, adding the vulcanizing agent and vulcanization accelerator to the rubber kneaded in the Banbury mixer while cooling, and kneading for 5 minutes to prepare anti-vibration rubber compositions (Examples 1 to 9, Comparative Examples 1 to 6).

[0065] [Table 1]

[0066] [Table 2]

[0067] The materials listed in Tables 1 and 2 are as follows. Natural rubber: SVR CV60 Butadiene rubber-1: cis 1,4-bond content 94%, Mooney viscosity (ML 1+4 )55, JSR Corporation "BR-730" Butadiene rubber-2: cis 1,4-bond content 96%, Mooney viscosity ML 1+4 )44, JSR Corporation "BR-01" Butadiene-styrene random copolymer-1: average molecular weight (Mn) 4500, Tg-15℃, Clay Valley "RICON100" Butadiene-styrene random copolymer-2: average molecular weight (Mn) 10,000, Tg-6°C, Kuraray Co., Ltd. "L-SBR-841" Butadiene-styrene random copolymer-3: average molecular weight (Mn) 3200, Tg-65℃, Clay Valley "RICON181" Butadiene-styrene random copolymer-4: Average molecular weight (Mn) 3200, Tg-57℃, Clay Valley "RICON184" Carbon black-1: Nitrogen adsorption specific surface area 22m 2 / g (SRF grade), Asahi Carbon Black Co., Ltd. "Asahi #50HG" Carbon black-2: Nitrogen adsorption specific surface area 76m 2 / g (HAF grade), "VULCAN 3D" manufactured by Cabot Japan Co., Ltd. Carbon black-3: Nitrogen adsorption specific surface area 115m 2 / g (ISAF grade), "Niteron #300" manufactured by Nippon Steel Carbon Co., Ltd. Anti-aging agent-1: (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine), "Nocrac 6C" manufactured by Ouchi Kogyo Co., Ltd. · Anti-aging agent-2: (2-mercaptobenzimidazole) "Nocrac MB" manufactured by Ouchi Shinko Co., Ltd. · Anti-aging agent-3: (wax) Nippon Seiro Co., Ltd. "Ozoace 0100" Composite zinc oxide: "META-Z-L60" manufactured by Inoue Lime Industry Co., Ltd. Stearic acid: "Camellia stearate" manufactured by Nippon Oil & Fats Co., Ltd. Naphthenic oil: "Crisef Oil H56" manufactured by ENEOS Corporation Vulcanizing agent: Sulfur, Tsurumi Chemical Industry Co., Ltd. "Kinkajirushi Fine Sulfur 200MESH" Vulcanization accelerator-1 (N-cyclohexyl-2-benzothiazolyl sulfenamide): "Noccela CZ-G" manufactured by Ouchi Kogyo 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] For each of the vibration-proof rubber compositions of Examples 1 to 9 and Comparative Examples 1 to 6 shown in Tables 1 and 2, vulcanization molding was carried out by compression molding using a 2 mm sheet mold with a cavity such that the rubber thickness was approximately 2 mm, at 160°C for a vulcanization time of 10 minutes, to obtain a vulcanized rubber sheet with a thickness of 2 mm (hereinafter simply referred to as the evaluation rubber sheet).

[0068] [Preparation of anti-vibration rubber test pieces] In preparing the vibration-proof rubber test piece 1 shown in FIG. 1, first, two 50 mm x 50 mm iron metal fittings 2 with a bolt 3 standing at the center of one side were prepared, and the surface of each metal fitting 2 on which the bolt 3 was not standing was roughened by shot blasting. Next, Chemlock 205 (manufactured by Lord Far East Co., Ltd.) was applied as an undercoat adhesive to each of the surfaces on which the bolt was not standing, and dried in an 80°C atmosphere for 20 minutes to form an undercoat adhesive layer (thickness 10 μm). After each metal fitting 2 on which this undercoat adhesive layer was formed was cooled to room temperature, Chemlock 6125 (manufactured by Lord Far East Co., Ltd.) was applied as an overcoat adhesive to the surface of each undercoat adhesive layer, and dried in an 80°C atmosphere for 20 minutes to form an overcoat adhesive layer (thickness 10 μm). 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, using an injection molding machine, unvulcanized rubber was filled between each metal fitting 2 in the molding die and vulcanized (160°C x 12 minutes) to produce a square test piece 1 with metal fitting 2 formed into a rectangular prism of 40 mm x 40 mm x 30 mm as shown in Figure 1.

[0069] Tensile properties For each evaluation rubber sheet obtained using each of the vibration-proof rubber compositions of Examples 1 to 9 and Comparative Examples 1 to 6, a JIS No. 3 dumbbell was punched out, 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.

[0070] <Heat aging resistance test> For each evaluation rubber sheet obtained using each vibration-proof rubber composition of Examples 1 to 9 and Comparative Examples 1 to 6, first, a JIS No. 3 dumbbell was used to punch out the rubber sheets, and then the sheets were placed in a gear-type aging tester set at a 100°C atmosphere for 336 hours (2 weeks) to prepare heat-aged test pieces. Next, a tensile test was performed on each test piece in the same manner as in the above-mentioned <<Tensile Properties>> to measure the breaking elongation (i.e., the breaking elongation after heat aging). Then, the rate of change in breaking elongation after heat aging (AcEB) relative to the breaking elongation before heat aging (EB) was calculated. These calculation results are shown in Tables 1 and 2.

[0071] <Vibration characteristic test> For each test piece 1 obtained using each of the vibration-proof rubber compositions of Examples 1 to 9 and Comparative Examples 1 to 6, an axial load was first applied via each bolt 3 to compress the test piece 1 by 6 mm in the axial direction (bolt 3 axial direction), and the load was then temporarily released. This compression-relief process was repeated twice. After this, the test piece 1 was compressed by 6 mm again (i.e., the third loading process), and the load-deflection characteristics at the time of compression (third loading process) were measured, and a load-deflection curve was created based on the results. Then, from the load-deflection curve, the load values ​​P1 and P2 (unit: N) when the deflection was 2 mm and 4 mm, respectively, were read, and the load values ​​P1 and P2 were appropriately substituted into the relational expression "Ks=(P2-P1) / 2" to calculate the static spring constant Ks (N / mm).

[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 test was performed in which a constant displacement harmonic compression vibration of amplitude ±0.05 mm was applied at a frequency of 100 Hz from one bolt 3 side (for example, the lower side in the figure) of the test piece 1 in the compressed state, centered on the position where the test piece 1 was compressed 3 mm, and the dynamic spring constant Kd100 (N / mm) at 100 Hz was calculated in accordance with the "non-resonance method (a)" in the "Test method for vibration-proof rubber" of JIS-K-6385-2012. Then, the dynamic magnification (=Kd100 / Ks) was calculated from the calculated dynamic spring constant (Kd100) and the calculated static spring constant (Ks).

[0073] In the 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 amplitude ±1.0 mm centered on the position compressed 3 mm was applied to each test piece 1 from one of the bolts 3 at a frequency of 10 Hz, and the loss factor tanσ(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 tanσ (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 numbers (1 to 9) of Examples 1 to 9 are written adjacent to the symbol "●", and the numbers (1 to 6) of Comparative Examples 1 to 6 are written adjacent to the symbol "×".

[0075] <Heat resistance adhesion test> For each test piece 1 obtained using each vibration-proof rubber composition of Examples 1 to 9 and Comparative Examples 1 to 6, first, in the same manner as above, each bolt 3 was used to elongate by 50% (stretched in the vertical direction in FIG. 2), and the test piece was held in a 100°C atmosphere for 60 minutes, and the presence or absence of peeling of each metal fitting 2 was visually observed. After that, the test piece was held in an atmosphere heated by 10°C for 40 minutes, and the visual confirmation of the presence or absence of peeling of each metal fitting 2 was repeated, and finally, the test piece was held in a 200°C atmosphere for 40 minutes, and the presence or absence of peeling of each metal fitting 2 was confirmed, and the test was completed. In this test, it was determined that the higher the temperature at which peeling of each metal fitting 2 could be prevented, the better the heat-resistant adhesion. Tables 1 and 2 show the maximum temperature at which peeling of adhesion could be prevented. For example, if there was no peeling at 160°C but peeling occurred at 170°C, "160°C" was recorded in the heat-resistant adhesion column of Tables 1 and 2. In addition, when peeling off of the adhesive was prevented even at 200°C, it was recorded as "200°C OK." In this test, two test pieces 1 were prepared for each of the vibration-proof rubber compositions of Examples 1 to 9 and Comparative Examples 1 to 6, and the test results of the two test pieces 1 with the lower peeling temperature were used as an index of the heat-resistant adhesiveness of each vibration-proof rubber composition. These test results are shown in Tables 1 and 2.

[0076] Effects of the embodiment 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 below the curves (dotted lines) of the vibration characteristic test results when the anti-vibration rubber compositions of Comparative Examples 1 to 6 were used (hereinafter simply referred to as Comparative Examples 1 to 6), and it was found that the low dynamic magnification and high damping properties were excellent. Furthermore, according to the results in Tables 1 and 2, the rate of change in breaking elongation (AcEB) after heat aging was smaller in the cases of Examples 1 to 9 than in the cases of Comparative Examples 1 to 6, and therefore it was found that the heat aging properties were excellent.

[0077] Furthermore, from the results of FIG. 2 and Table 1, in the case of Example 2 and Example 9, the average molecular weight (Mn) of the butadiene-styrene random copolymer was 10,000, the glass transition temperature (Tg) was -6°C, and the nitrogen adsorption specific surface area of ​​the carbon black was 22 m 2 / g, the carbon black content is 40 parts by mass when the rubber component is taken as 100 parts by mass, and it is clear that this has the greatest low dynamic magnification and high damping effect.

[0078] In the case of Example 8, which contains a relatively large amount of carbon black at 80 parts by mass, the damping properties are very large, and the effect of high damping at low dynamic magnification is recognized, but it can be seen that the dynamic magnification is relatively high at 5.35. Furthermore, in the cases of Example 2 and Example 9, the effect of high damping at low dynamic magnification is almost the same, but the cis 1,4-bond amount is 94% and the Mooney viscosity (ML 1+4 It can be seen that the rubber strength is relatively higher in Example 2 using butadiene rubber having a viscosity of 55%.

[0079] Furthermore, from the results in Tables 1 and 2, it is seen that Examples 1 to 9 have superior adhesion to the metal fitting 2 compared to Comparative Examples 1 to 6. Therefore, it is seen that Examples 1 to 9 are effective as anti-vibration rubber. [Explanation of symbols]

[0080] 1...Test piece 2…Metal fittings 3...Bolt (support rod)

Claims

1. The main rubber components are natural rubber and butadiene rubber in a mass ratio of natural rubber / butadiene rubber = 50 / 50 to 95 / 5, Based on 100 parts by mass of the rubber component, the rubber composition contains 15 to 50 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 20 to 60 parts by mass of carbon black having a nitrogen adsorption specific surface area of ​​15 to 80 m 2 / g; 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, in the vibration-proof rubber composition.

2. The rubber composition contains natural rubber and butadiene rubber as main rubber components in a mass ratio of natural rubber / butadiene rubber = 50 / 50 to 95 / 5, and contains 15 to 50 parts by mass of a butadiene-styrene random copolymer having an average molecular weight (Mn) of 3,000 to 12,000 as a softener, based on 100 parts by mass of the rubber component; The butadiene rubber has a cis-1,4-bond content of 90% or more and a Mooney viscosity (ML 1+4 ) at 100° C. of 50 to 75.

3. 3. The anti-vibration rubber composition according to claim 2, further comprising 15 to 70 parts by mass of carbon black per 100 parts by mass of the rubber component.

4. The carbon black has a nitrogen adsorption specific surface area of ​​20 to 45 m ２ / g, 4. The anti-vibration rubber composition according to claim 1, wherein the content of the carbon black is 25 to 50 parts by mass per 100 parts by mass of the rubber component.

5. 5. The anti-vibration rubber composition according to claim 1, further comprising a process oil in an amount of 5 parts by mass or less per 100 parts by mass of the rubber component.

6. A vibration-proof rubber comprising the vibration-proof rubber composition according to any one of claims 1 to 5 and a metal fitting, both of which are vulcanization-adhered via an adhesive layer formed on the surface of the metal fitting, so that the two are integrally formed.

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