Rubber composition for rubber support side wall and rubber support using the same

Abstract

The present invention provides a rubber support side wall rubber composition that exhibits high adhesion to a rubber support body, and that can exhibit low temperature properties, durability, and weather resistance, and a rubber support body using the same. In a rubber support body provided with a side material 5 composed of a covering rubber in a manner that surrounds the outer side surface of a rubber support body in which a rubber layer 2 and a hard plate 1 are alternately laminated, the problem is solved by providing the side material 5 as a crosslinked body of a rubber support side wall rubber composition in which the following (A) to (C) are used as polymer components. (A) A diene rubber in which at least one of natural rubber and isoprene rubber is used as a main component. However, an ethylene-propylene-diene terpolymer and a liquid rubber are not included. (B) An ethylene-propylene-diene terpolymer in which the diene content is 10% by mass or more and the ethylene content is 55% by mass or less. (C) A liquid rubber in which the molecular weight is 1000 to 60,000.

Description

Technical Field

[0001] The present invention relates to a rubber composition for forming the sidewall of a rubber support having vibration damping and shock absorption properties, and a rubber support using the composition. Background Technology

[0002] In recent years, significant advancements in bridge technology have led to a gradual increase in bridge size, resulting in the design of long-span bridges. The erection of such long bridges typically involves installing multiple rubber supports on bridge piers spaced at predetermined intervals, with long-span bridge trusses mounted on these supports. This arrangement of the rubber supports in the middle effectively provides vibration damping and shock absorption functions in long bridges. However, because these rubber supports bear extremely high loads, to ensure excellent load-bearing capacity, they are typically formed by alternating layers of rigid sheets such as metal plates with rubber layers, integrated into a single structure.

[0003] In addition, there are also rubber supports in which a side material composed of rubber is provided to surround its outer side (for example, see Patent Documents 1 to 3).

[0004] Furthermore, weather resistance (such as ozone resistance) is required in the coated rubber, therefore, it is recommended to use ethylene-propylene-diene terpolymer (hereinafter referred to as "EPDM"), which has excellent weather resistance, in its polymer composition.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2009-001603

[0008] Patent Document 2: Japanese Patent No. 5712735

[0009] Patent Document 3: Japanese Patent No. 5735886 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, if EPDM is used in the polymer composition of the coated rubber, the following problems are likely to occur: the adhesion of the coated rubber to the rubber support (body) deteriorates; the coated rubber crystallizes at low temperatures and easily hardens, resulting in it not functioning properly in cold regions (deteriorating low-temperature performance); and the durability (tensile strength) of the coated rubber under large deformations deteriorates.

[0012] Therefore, it is necessary to address the aforementioned issues while maintaining the weather resistance provided by EPDM.

[0013] The present invention was made in view of the following circumstances, and provides a rubber composition for the sidewall of a rubber support that exhibits high adhesion to the rubber support and is able to perform excellent low-temperature performance, durability and weather resistance, as well as a rubber support using the composition.

[0014] Methods for solving problems

[0015] In view of the above, the inventors of the present invention investigated the polymer composition of the sidewall forming material (rubber composition for rubber support sidewall) of the rubber support, combining diene rubbers with natural rubber and isoprene rubber as main components and liquid rubber, in addition to EPDM. Furthermore, it was found that using EPDM with a specific range of diene and ethylene content, and using liquid rubber with a specific range of molecular weight, resulted in higher adhesion to the rubber support (body) and excellent performance in low-temperature resistance, durability, and weather resistance.

[0016] The reason why a rubber composition for the sidewalls of a rubber support, exhibiting high adhesion to the rubber support and demonstrating excellent low-temperature performance, durability, and weather resistance, as well as a rubber support using the composition, can be provided by adopting the configuration described above, can be considered as follows: Specifically, in this invention, by adjusting the diene content of EPDM to a higher level than usual within a specific range, and further, by using a diene-based rubber with natural rubber or isoprene rubber as the main components in conjunction with the EPDM, the amount of diene that serves as the starting point for the adhesive reaction increases, thus improving adhesion. Additionally, in this invention, by adjusting the ethylene content of EPDM to a lower level than usual within a specific range, crystallinity is reduced, thereby improving the low-temperature performance. Furthermore, as described above, while reducing the ethylene content of EPDM would normally decrease durability, in this invention, by using a liquid rubber exhibiting a specific molecular weight, enhanced properties are obtained, thereby suppressing the decrease in durability associated with the reduction in ethylene content, as described above. Furthermore, it can be considered that the liquid rubber has good compatibility with EPDM, also functions as a softener, and has a higher molecular weight than commonly used softeners (processing oils), thus contributing to durability as described above.

[0017] That is, the present invention provides the following [1] to [4].

[0018] [1] A rubber composition for the sidewall of a rubber support, wherein the rubber composition for the sidewall of the rubber support uses the following (A) to (C) as polymer components.

[0019] (A) Diene rubbers whose main component is at least one of natural rubber and isoprene rubber (but excluding EPDM and liquid rubber).

[0020] (B) EPDM with a diene content of 10% or more and an ethylene content of 55% or less.

[0021] (C) Liquid rubber with a molecular weight of 1,000 to 60,000.

[0022] [2] The rubber composition for the sidewall of the rubber support according to [1], wherein (A) and (B) are in a mass ratio of (A) / (B) = 50 / 50 to 90 / 10.

[0023] [3] The rubber composition for the sidewall of the rubber support body according to [1] or [2], wherein the (C) is in a ratio of 5 to 30 parts by mass relative to the total mass of the (A) and (B) 100 parts by mass.

[0024] [4] A rubber support body, the rubber support body being formed by alternating layers of rubber and rigid plate, wherein the rubber support body has a side material composed of a rubber coating in such a way as to surround its outer side surface, the rubber coating being composed of a crosslinked rubber composition of the rubber support sidewall as described in any one of [1] to [3].

[0025] Invention Effects

[0026] In summary, the rubber composition for the sidewall of the rubber support of the present invention, by being used as a side material formed in a manner that surrounds the outer side of the rubber support, exhibits high adhesion to the rubber support and can perform excellent low-temperature performance, durability, and weather resistance. Attached Figure Description

[0027] Figure 1 This is a cross-sectional view showing an example of a vibration-damping support. Detailed Implementation

[0028] Next, the embodiments of the present invention will be described in detail.

[0029] The rubber composition for the sidewall of the rubber support of the present invention (hereinafter referred to as "the rubber composition") uses (A) to (C) as polymer components as described below. Furthermore, the rubber composition preferably uses only (A) to (C) as polymer components as described below, but may also contain small amounts of other polymer components as needed.

[0030] (A) Diene rubbers whose main component is at least one of natural rubber and isoprene rubber (but excluding EPDM and liquid rubber).

[0031] (B) EPDM with a diene content of 10% or more and an ethylene content of 55% or less.

[0032] (C) Liquid rubber with a molecular weight of 1,000 to 60,000.

[0033] The following is a detailed description of each component in the above-mentioned rubber composition.

[0034] Furthermore, in this specification, "X and / or Y (X, Y are arbitrary configurations)" means at least one of X and Y, and refers to the three options: only X, only Y, and X and Y.

[0035] Diene Rubber (A)

[0036] As the diene rubber (A), a diene rubber with at least one of natural rubber (NR) and isoprene rubber (IR) (NR and / or IR) as the main component is used. Furthermore, in this invention, "main component" generally refers to 55% by mass or more of the diene rubber (A), preferably 60% by mass or more of the diene rubber (A), more preferably 70% by mass or more of the diene rubber (A), and even more preferably 100% by mass of the diene rubber (A).

[0037] In addition, as the diene rubber (A), besides the main component, butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), and butyl rubber (IIR) may be used alone or in combination as needed.

[0038] In addition, in this invention, the diene rubber (A) is configured to not contain EPDM (ethylene-propylene-diene terpolymer) and liquid rubber.

[0039] Furthermore, in this invention, "liquid rubber" refers to rubber that exhibits a viscosity of less than 1500 Pa·s at room temperature (23°C). This viscosity can be measured, for example, using a type B viscometer.

[0040] Specific EPDM(B)

[0041] As for the specific EPDM(B), from the viewpoint of obtaining the desired adhesion, an EPDM with a diene content of 10% by mass or more is used. From the same viewpoint, the diene content is preferably 12% by mass or more, more preferably 14% by mass or more. Furthermore, if the diene content is too low, the desired adhesion cannot be obtained, leading to peeling. Additionally, the upper limit of the diene content is typically 20% by mass, preferably 18% by mass, and more preferably 16% by mass.

[0042] Furthermore, as for the specific EPDM(B), from the viewpoint of obtaining desired low-temperature performance, etc., an EPDM with an ethylene content of 55% by mass or less is used. From the same viewpoint, the ethylene content is preferably less than 48% by mass, more preferably less than 45% by mass, and particularly preferably less than 43% by mass. Moreover, if the ethylene content is too high, the desired low-temperature performance, etc., cannot be obtained. Additionally, the lower limit of the ethylene content is typically 30% by mass, preferably 35% by mass, and more preferably 40% by mass.

[0043] The diene polymer used as the third component constituting the specific EPDM(B) described above is preferably a diene polymer with 5 to 20 carbon atoms. Specifically, examples include 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 2,5-dimethyl-1,5-hexadiene, 1,4-octadiene, 1,4-cyclohexadiene, cyclooctadiene, dicyclopentadiene (DCP), 5-ethylidene-2-norbornene (ENB), 5-butylidene-2-norbornene, 2-methylallyl-5-norbornene, and 2-isopropenyl-5-norbornene. These can be used alone or in combination of two or more. Among these diene polymers (third component), dicyclopentadiene (DCP) and 5-ethylidene-2-norbornene (ENB) are preferred.

[0044] Furthermore, in this rubber composition, from the viewpoint of obtaining desired weather resistance, adhesion, etc., it is preferable that the ratio of (A) to (B) by mass is (A) / (B) = 50 / 50 to 90 / 10. From the same viewpoint, a ratio of (A) / (B) = 60 / 40 to 80 / 20 is more preferred, and a ratio of (A) / (B) = 65 / 35 to 70 / 30 is particularly preferred.

[0045] Specific Liquid Rubber (C)

[0046] As for the specific liquid rubber (C), from the viewpoint of obtaining the desired durability, a liquid rubber with a molecular weight of 1,000 to 60,000 is used. From the same viewpoint, the molecular weight of the liquid rubber is preferably 10,000 to 55,000, more preferably 25,000 to 50,000.

[0047] Furthermore, among the molecular weights of the liquid rubber (C), the higher values ​​represent the weight-average molecular weight (Mw) (the same applies to the examples described later). Here, the weight-average molecular weight (Mw) is obtained by converting the molecular weight of standard polystyrene, using a high-performance liquid chromatograph (manufactured by Waters, “Waters 2695 (body)” and “Waters 2414 (detector)”) with three columns in series: Shodex GPC KF-806L (size exclusion limit molecular weight: 2 × 10⁻⁶). 7 Separation range: 100~2×10 7 The theoretical plate number was 10,000 / plate, the packing material was styrene-divinylbenzene copolymer, and the packing particle size was 10 μm.

[0048] The specific liquid rubber (C) exhibits the stated molecular weight and a viscosity of less than 1500 Pa·s at room temperature (23°C). Specifically, examples include liquid isoprene (liquid IR), liquid butadiene (liquid BR), liquid isoprene-butadiene block copolymer (liquid IR-BR), liquid styrene-butadiene (liquid SBR), liquid ethylene-propylene rubber (liquid EPM), liquid EPDM, liquid acrylonitrile-butadiene rubber (liquid NBR), and liquid hydrogenated acrylonitrile-butadiene rubber (liquid H-NBR). These can be used alone or in combination of two or more. Liquid isoprene-butadiene block copolymer (liquid IR-BR) is preferred.

[0049] Furthermore, from the viewpoint of obtaining desired durability, etc., in this rubber composition, the proportion of (C) relative to 100 parts by mass of the combined amount of (A) and (B) is preferably 5 to 30 parts by mass. From the same viewpoint, in this rubber composition, the proportion of (C) relative to 100 parts by mass of the combined amount of (A) and (B) is preferably 10 to 25 parts by mass, more preferably 15 to 20 parts by mass.

[0050] In this rubber composition, along with diene rubber (A) with NR and / or IR as the main components, specific EPDM (B), and specific liquid rubber (C), fillers such as carbon black and silica, and crosslinking agents are typically formulated. Additionally, vulcanization accelerators, vulcanization aids, anti-aging agents, and softeners may also be formulated in this rubber composition as needed.

[0051] Furthermore, in this rubber composition, the specific liquid rubber (C) exhibits the function of a softener, and therefore is preferably free of softeners.

[0052] Carbon Black

[0053] As the carbon black, various grades of carbon black, such as SAF, ISAF, HAF, MAF, FEF, GPF, SRF, FT, and MT, can be used. These can be used alone or in combination of two or more. Among them, SAF grade carbon black is preferred from the viewpoint of mechanical strength and elongation at break.

[0054] In this rubber composition, from the viewpoint of mechanical strength and elongation at break, the content of carbon black relative to 100 parts by mass of (A) and (B) is preferably 20 to 60 parts by mass. Similarly, from the viewpoint of this rubber composition, the proportion of carbon black relative to 100 parts by mass of (A) and (B) is preferably 30 to 50 parts by mass, more preferably 35 to 45 parts by mass. Furthermore, if the content of carbon black is too low, a tendency to not obtain the desired reinforcement can be observed; conversely, if the content of carbon black is too high, a tendency to decrease scorch resistance and elongation at break can be observed.

[0055] Crosslinking Agent

[0056] Examples of crosslinking agents include sulfur-based vulcanizing agents such as sulfur and sulfur chloride, 2,4-dichlorobenzoyl peroxide, benzoyl peroxide, 1,1-di-tert-butylperoxide-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-bis-(benzoyl peroxide)hexane, n-butyl-4,4′-di-tert-butylperoxyvalerate, dicumyl peroxide, tert-butylperoxide, di-tert-butylperoxide-diisopropylbenzene, tert-butylperoxide-isopropylbenzene, 2,5-dimethyl-2,5-di-tert-butylperoxide-hexane, di-tert-butylperoxide, 2,5-dimethyl-2,5-di-tert-butylperoxide-hexyne-3, and 1,3-bis(tert-butylperoxide-isopropylbenzene). These can be used alone or in combination of two or more. Sulfur and dicumyl peroxide are preferred.

[0057] In this rubber composition, from the viewpoint of obtaining desired durability, the content of the crosslinking agent is preferably 0.5 to 3.0 parts by mass relative to the total mass of (A) and (B) of 100 parts by mass. Similarly, from the viewpoint of this rubber composition, the proportion of the crosslinking agent relative to the total mass of (A) and (B) of 100 parts by mass is preferably 0.75 to 2.5 parts by mass, more preferably 1.0 to 2.0 parts by mass. Furthermore, if the content of the crosslinking agent is too low, a tendency to decrease tensile strength, etc., can be observed; conversely, if the content of the crosslinking agent is too high, a tendency to decrease scorch resistance and elongation can be observed.

[0058] Vulcanization Accelerator

[0059] Examples of vulcanization accelerators include thiazoles, sulfenamides, thiurams, aldehydes, amines, guanidines, and thioureas. These can be used alone or in combination of two or more. Among these, sulfenamide vulcanization accelerators are preferred from the perspective of excellent crosslinking reactivity.

[0060] In this rubber composition, the content of the vulcanization accelerator is preferably 0.5 to 2.5 parts by mass relative to the total mass of (A) and (B) 100 parts by mass, more preferably in the range of 1.0 to 2.0 parts by mass.

[0061] Examples of thiazole-based vulcanization accelerators include dibenzothiazole disulfide (MBTS), 2-mercaptobenzothiazole (MBT), sodium 2-mercaptobenzothiazole (NaMBT), and zinc 2-mercaptobenzothiazole (ZnMBT). These can be used alone or in combination of two or more.

[0062] Examples of sulfenamide-based vulcanization accelerators include N-oxodiethylene-2-benzothiazole sulfenamide (NOBS), N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N-tert-butyl-2-benzothiazole sulfenamide (BBS), and N,N′-dicyclohexyl-2-benzothiazole sulfenamide. These can be used alone or in combination of two or more.

[0063] Examples of thiuram-based vulcanization accelerators include tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetrabutylthiuram disulfide (TBTD), tetra(2-ethylhexyl)thiuram disulfide (TOT), and tetrabenzylthiuram disulfide (TBzTD). These can be used alone or in combination of two or more.

[0064] Vulcanizing aids

[0065] Examples of vulcanizing aids include stearic acid, magnesium oxide, and zinc oxide. These can be used alone or in combination of two or more.

[0066] In this rubber composition, the content of the vulcanizing aid is preferably 0.1 to 10 parts by mass relative to the total mass of (A) and (B) 100 parts by mass, more preferably in the range of 0.3 to 7 parts by mass.

[0067] Anti-aging agents

[0068] Examples of anti-aging agents include carbamate anti-aging agents, phenylenediamine anti-aging agents, phenolic anti-aging agents, diphenylamine anti-aging agents, quinoline anti-aging agents, imidazole anti-aging agents, and waxes. These can be used alone or in combination of two or more.

[0069] In this rubber composition, the content of the anti-aging agent is preferably 0.5 to 15 parts by mass relative to the total mass of (A) and (B) 100 parts by mass, more preferably in the range of 1 to 10 parts by mass.

[0070] Softener

[0071] Examples of softeners (processing oils) include naphthenic oils, paraffinic oils, and aromatic oils. These can be used alone or in combination of two or more.

[0072] In this rubber composition, the content of the softener is preferably 0 to 20 parts by mass relative to the total mass of (A) and (B) 100 parts by mass, more preferably in the range of 0 to 10 parts by mass.

[0073] Furthermore, as mentioned above, in this rubber composition, since the specific liquid rubber (C) exhibits the function of a softener, the desired performance can be achieved even without a softener.

[0074] Here, this rubber composition can be produced by mixing the above-mentioned components using a kneader, a Banbury mixer, and a rolling mill.

[0075] This rubber composition is specifically designed for use in forming the sidewalls of rubber supports with vibration damping and shock absorption properties. Furthermore, this rubber composition is preferably used as a material for the sidewalls of large supports such as bridge supports and building supports.

[0076] Vibration-resistant supports for bridges or buildings, for example, Figure 1 As shown, the structure is integrally formed by alternating layers of rigid plate 1 and rubber layer 2, and a side material 5 composed of rubber coating is provided to surround its outer surface. As an embodiment of the present invention, the rubber support (hereinafter referred to as "this rubber support") is a rubber support in which the side material 5 is composed of a cross-linked body of this rubber composition. Furthermore, the upper mounting plate 3 and lower mounting plate 4 shown are metal mounting plates, bonded and fixed to the upper and lower parts of the laminate between the rigid plate 1 and the rubber layer 2. Moreover, in this vibration-damping support, the lower mounting plate 4 is configured as a lower structure fixed to a bridge pier, etc., and the upper mounting plate 3 is configured as an upper structure fixed to a bridge girder, etc.

[0077] The rigid plate 1 may be, for example, a rolled steel plate, an iron plate or other metal plate, or a rigid plastic sheet.

[0078] Furthermore, the rubber composition used as the material for the rubber layer 2 is a rubber composition containing diene rubbers such as NR and IR as polymer components and a vulcanizing agent. In addition, carbon black, softeners, anti-aging agents, processing aids, vulcanization accelerators, white fillers, reactive polymers, and foaming agents may be appropriately added to the rubber composition as needed.

[0079] Furthermore, the rubber composition can be produced by mixing the aforementioned materials using a mixing mill such as a kneader, a Banbury mixer, an open roller mixer, or a twin-screw mixer.

[0080] Here, this rubber support (refer to) Figure 1 For example, it is manufactured as follows: First, a rubber composition is made as the material for the rubber layer 2 as described above. Next, multiple rigid plates 1 of predetermined sizes are prepared, and further, an upper mounting plate 3 and a lower mounting plate 4 are also prepared.

[0081] Then, on the lower mounting plate 4, the rubber composition used as the material for the rubber layer 2 is formed into a sheet, and unvulcanized rubber sheets with holes drilled to a predetermined size are alternately overlapped with the rigid plate 1. Finally, the upper mounting plate 3 is overlapped, thereby producing a laminate (rubber support). In addition, an adhesive may be pre-applied to the laminated surfaces of the rigid plate 1, etc.

[0082] Next, the rubber composition prepared as described above is molded into a sheet to manufacture an unvulcanized rubber sheet. The unvulcanized rubber sheet is a substance that is semi-crosslinked to a degree of incomplete crosslinking (a degree sufficient for vulcanization adhesion). The molding conditions vary depending on the thickness, but are typically a substance heated at 130–180°C for 1–30 minutes to achieve semi-crosslinking. Then, the unvulcanized rubber sheet is wrapped around the outer surface of the laminate (rubber support), and the substance is placed in a predetermined mold. The unvulcanized rubber sheet is then heated at 130–180°C for 1–24 hours to achieve crosslinking and vulcanization adhesion to the rubber support, thereby manufacturing a rubber support (this rubber support) having a side material 5 composed of this rubber composition.

[0083] In addition, the laminate (rubber support) can also be manufactured by: placing the rigid plate 1, the upper mounting plate 3 and the lower mounting plate 4 in a predetermined configuration in a molding die, injecting a rubber composition, which is the material for the rubber layer 2, into the gaps in the molding die by injection molding or the like, and demolding after heating and vulcanization.

[0084] Alternatively, this rubber support can also be manufactured as follows: Using a rubber composition as the material for rubber layer 2, a rubber sheet (rubber layer 2) of a predetermined thickness is formed by extrusion molding or the like. Then, using a suitable adhesive, it is alternately layered and bonded to a predetermined rigid plate 1 to create a rubber interlocking body. Further, as needed, an upper mounting plate 3 and a lower mounting plate 4 are bonded to its upper and lower surfaces and integrated. The outer surface of the rubber support obtained in this manner is then formed with side material 5 according to the method described above, thereby enabling the manufacture of this rubber support.

[0085] In addition, the side material 5 can also be formed by the following method: after placing the rubber support body in a predetermined mold, injecting the rubber composition between the outer peripheral surface of the rubber support body and the inner peripheral surface of the mold by injection molding or the like, and crosslinking the rubber composition.

[0086] The heating conditions during crosslinking are the same as those in the previous manufacturing method. However, unlike the previous manufacturing method, a semi-crosslinking process is not required; instead, crosslinking can be performed directly by heating.

[0087] The dimensions of the rubber support obtained in this way are, for example, an outer diameter of approximately 20 to 200 cm, and a total thickness of approximately 10 to 80 cm. Furthermore, the thickness of each layer constituting the rubber support is only required to adequately fulfill its functional purpose; for example, the thickness of the rigid plate 1 is approximately 0.1 to 2 cm, the thickness of the rubber layer 2 is approximately 0.5 to 7 cm, and the thickness of the side material 5 is approximately 0.5 to 10 cm. Furthermore, the number of layers of the rigid plate 1 and the rubber layer 2 in the rubber support can be appropriately set according to the intended use of the vibration-damping laminate.

[0088] Furthermore, the shape of this rubber support can be appropriately set as cylindrical, elliptical, or quadrangular prism, depending on its application.

[0089] Example

[0090] Next, the embodiments and comparative examples will be described together. However, the present invention is not limited to these embodiments.

[0091] First, prior to the examples and comparative examples, the materials (polymer components and softener) shown below were prepared.

[0092] [NR]

[0093] Natural rubber

[0094] [IR]

[0095] Nipol IR2200, manufactured by ZEON Corporation of Japan.

[0096] [EPDM(i)]

[0097] Manufactured by Mitsui Chemicals, product name: Mitsui EPT 9090M (ethylene content: 41% by mass, diene content: 14% by mass)

[0098] [EPDM(ii)]

[0099] Manufactured by JSR Corporation, product name: EP331 (ethylene content: 47% by mass, diene content: 11.3% by mass)

[0100] [EPDM(iii)]

[0101] Manufactured by Sumitomo Chemical Co., Ltd., product name: Esprene 505 (ethylene content: 50% by mass, diene content: 10% by mass)

[0102] [EPDM(iv)]

[0103] Manufactured by Mitsui Chemicals, product name: Mitsui EPT 8030M (ethylene content: 47% by mass, diene content: 9.5% by mass)

[0104] [EPDM(v)]

[0105] Manufactured by LANXESS, product name: Keltan K3960Q (ethylene content: 56% by mass, diene content: 11.4% by mass)

[0106] [Liquid rubber (i)]

[0107] Manufactured by Kuraray Corporation, product name: LIR-30 (weight average molecular weight: 28000)

[0108] [Liquid rubber (ii)]

[0109] Manufactured by Kuraray Corporation, product name: LIR-50 (weight average molecular weight: 54000)

[0110] [Liquid rubber (iii)]

[0111] Manufactured by EVONIK, product name: POLYVEST110 (molecular weight: 1100)

[0112] [Softener]

[0113] Manufactured by Taiyo Oil Co., Ltd. of Japan. Product name: Sunpar110

[0114] [Examples 1-10, Comparative Examples 1-5]

[0115] After combining the polymer components and softeners according to the proportions shown in Tables 1 and 2 below, further, 2 parts by weight of stearic acid (manufactured by Nippon Oil Co., Ltd., product name: BEADS STEARIC ACIDSAKURA), 5 parts by weight of zinc oxide (manufactured by Sakai Chemical Co., Ltd., product name: Zinc Oxide Two Types), 3 parts by weight of amine anti-aging agent (manufactured by Seiko Chemical Co., Ltd., product name: OZONONE 6C), 4 parts by weight of wax (manufactured by Ouchi Shinsei Chemical Co., Ltd., product name: SUNNOC), 35 parts by weight of SAF grade carbon black (manufactured by Tokai Carbon Co., Ltd., product name: SEAST 9M), 1 part by weight of sulfenamide vulcanization accelerator (manufactured by Ouchi Shinsei Chemical Co., Ltd., product name: NOCCELER-CZ-G), and 1 part by weight of sulfur (manufactured by Tsurumi Chemical Co., Ltd., product name: Kinka Indigo Powder Sulfate) were added and mixed using a Banbury internal mixer and open rolls to produce a rubber composition (rubber composition for rubber support sidewalls). Specifically, the components other than the vulcanizing agent and vulcanization accelerator are mixed in a Banbury internal mixer for 5 minutes, and released at 150°C to obtain a masterbatch. The vulcanizing agent and vulcanization accelerator are then added to the masterbatch in the proportions shown in the table, and the rubber composition is produced by mixing these components with open rollers.

[0116] Using the rubber compositions of the examples and comparative examples obtained in this manner, their properties were evaluated according to the following criteria. The results are shown together in Tables 1 and 2 described below.

[0117] Tensile Strength

[0118] Using the obtained rubber compositions, rubber sheets with a thickness of 2 mm were produced by stamping (vulcanization) at 150°C for 20 minutes. Then, JIS No. 5 dumbbells were punched from the rubber sheets, and the tensile strength at 25°C was measured in accordance with JIS K 6251.

[0119] Furthermore, tensile strengths of 20 MPa or higher are rated as "◎ (excellent)", those of 15 MPa or higher but less than 20 MPa are rated as "○ (very good)", those of 10 MPa or higher but less than 15 MPa are rated as "△ (good)", and those of less than 10 MPa are rated as "× (poor)".

[0120] <Low Temperature Properties>

[0121] Using the obtained rubber compositions, cylindrical shear test pieces with molds were prepared under vulcanization conditions of 150°C for 30 minutes. These pieces were then used in JIS K6394, "Dynamic Properties Test Method for Vulcanized Rubber and Thermoplastic Rubber". Subsequently, using these test pieces, load / deflection curves were continuously measured 11 times each under the conditions specified in JIS K 6394 (1998), "6. Dynamic Properties Test of Large-Scale Test Apparatus", at test temperatures of -30°C and 20°C, a test vibration frequency of 0.5 Hz, and a deformation amplitude (shear) of 250%.

[0122] Then, based on the load / deflection curves obtained from the 2nd to the 11th tests (a total of 10 tests), the equivalent stiffness at each measurement temperature was determined: Keq (-30℃) and Keq (20℃). Using the obtained equivalent stiffness, G (temperature dependence) was calculated according to the following formula. Then, G less than 1.5 was rated as "○ (very good)", G greater than 1.5 and less than 1.6 was rated as "△ (good)", and G greater than 1.6 was rated as "× (poor)".

[0123] G (temperature dependence) = Kep(-30℃) / Kep(20℃)

[0124] <Adhesion>

[0125] The obtained rubber compositions were heated to 150°C for 30 minutes on an iron plate to vulcanize (vulcanization bonding). Regarding the adhesion between the iron plate and the rubber in the test pieces obtained in this manner, according to "5. 90-degree peel test between metal sheet and rubber" in JIS K 6256 "Test method for adhesion of vulcanized rubber", the rubber bonded to the iron plate was peeled at a 90-degree angle, and the condition of the peeled portion was visually observed. Then, a 100% breakage rate of the rubber portion was evaluated as "○ (very good)", and a portion where there was interfacial peeling between the rubber portion and the iron plate was evaluated as "× (poor)".

[0126] Ozone resistance

[0127] Using the obtained rubber compositions, rubber sheets with a thickness of 2 mm were produced by stamping (vulcanization) at 150°C for 20 minutes. JIS No. 1 dumbbells were cut from these rubber sheets to produce test pieces. Then, according to JIS K6259, the test pieces were immersed in an ozone bath with an ozone concentration of 200±20 pphm and a temperature of 40°C, under a tensile strain of 80±2%. After 672 hours from the immersion, the presence or absence of cracking in the test pieces was visually observed. Those without cracks were rated as "○ (very good)," and those with cracks were rated as "× (poor)."

[0128] Table 1

[0129] (parts by weight)

[0130]

[0131] Table 2

[0132] (parts by weight)

[0133]

[0134] As can be seen from the results in Table 1 above, the rubber composition of the embodiment exhibits high adhesion through crosslinking and is able to perform excellent low-temperature performance, tensile strength (durability) and ozone resistance (weather resistance), thus it is an excellent rubber composition for use as a sidewall of a rubber support.

[0135] Therefore, it is determined that the rubber composition of the embodiment is as follows: Figure 1 The side material of the vibration-damping support shown is of excellent quality for bridge and building applications.

[0136] In contrast, according to the results in Table 2 above, the rubber composition of Comparative Example 1, because its polymer component is solely natural rubber, exhibited poorer ozone resistance (weather resistance) than the examples. The rubber composition of Comparative Example 2, due to its low diene content in EPDM, exhibited poorer adhesion than the examples. The rubber composition of Comparative Example 3, due to its high ethylene content in EPDM, exhibited poorer low-temperature performance than the examples. The rubber composition of Comparative Example 4, due to the use of a softener with a lower molecular weight (molecular weight less than 1000) compared to liquid rubber, exhibited poorer tensile strength than the examples. The rubber composition of Comparative Example 5, due to its absence of liquid rubber and high EPDM ratio, exhibited poorer tensile strength, low-temperature performance, and adhesion than the examples.

[0137] The above embodiments illustrate specific implementations of the invention, but these embodiments are merely examples and should not be construed as limiting. It is intended that various modifications fall within the scope of the invention, as will be apparent to those skilled in the art.

[0138] Industrial applicability

[0139] The rubber composition for the sidewall of a rubber support of the present invention is a rubber composition specifically designed for forming the sidewall of a rubber support having both vibration damping and shock-absorbing properties. Furthermore, this rubber composition is preferably used as a material for the sidewall of large supports such as bridge supports and building supports, but it can also be used in vibration damping materials for automobiles, vibration dampers for general household appliances such as washing machines, etc.

[0140] Explanation of reference numerals in the attached figures

[0141] 1: Hardboard;

[0142] 2: Rubber layer;

[0143] 5: Side materials.

Claims

1. A rubber composition for the sidewall of a rubber support, wherein, The rubber composition for the sidewall of the rubber support uses the following (A) to (C) as polymer components: (A) Diene rubbers whose main component is at least one of natural rubber and isoprene rubber, but excluding ethylene-propylene-diene terpolymers and liquid rubbers; (B) Ethylene-propylene-diene terpolymer with a diene content of 10% or more and an ethylene content of 55% or less; (C) Liquid rubber with a weight-average molecular weight of 1000~60000 The ratio of (A) to (B) by mass is (A) / (B) = 50 / 50 to 90 / 10. The ratio of (C) to the total mass of (A) and (B) is 5 to 30 parts by mass, which is 100 parts by mass.

2. A rubber support body, wherein the rubber support body is formed by alternating layers of rubber and rigid plates, wherein, The rubber support has a side material composed of rubber covering in a manner that surrounds its outer surface. The coating rubber is composed of a crosslinked body of the rubber composition for the sidewall of the rubber support as described in claim 1.

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