Rubber composition for white sidewall cover rubber and pneumatic tire

Abstract

To suppress whitening of the cover rubber in a white sidewall.SOLUTION: The rubber composition for a white sidewall cover rubber according to the embodiment contains rubber components and a wax, in which 100 pts.mass of the rubber components contain 20 to 60 pts.mass of a natural rubber and 10 to 40 pts.mass of a butadiene rubber and the amount of the wax is 2 to 7 pts.mass based on 100 pts.mass of the rubber components.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a rubber composition for a white sidewall cover rubber and a pneumatic tire using the same.

Background Art

[0002] For the purpose of improving the visibility and design of a tire, a white sidewall is known in which a pattern portion such as characters and symbols provided on the sidewall is formed of a white rubber composition. The white sidewall is formed, for example, by arranging white rubber while radially dividing a predetermined portion of the unvulcanized black rubber forming the sidewall, providing a black cover rubber layer on the white rubber, and after vulcanizing the formed green tire with a predetermined mold, grinding a part of the cover rubber layer to expose the white rubber as a pattern portion.

[0003] As a technology related to a white sidewall, for example, Patent Document 1 discloses that in order to improve the balance between white uniformity and resistance to color fading, a specific amount of titanium oxide, wax, and a farnesene polymer are blended into a rubber component composed of natural rubber, butyl rubber, and ethylene propylene diene rubber.

[0004] Patent Document 2 discloses that in order to improve the whiteness and aging resistance after initial and aging, a predetermined amount of a white inorganic filler and a phenolic compound having an alkylthiomethyl group are blended into a rubber component.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the white sidewall as described above, it has been found that there is a case where the black cover rubber disposed on the white rubber whitens over time, impairing the appearance. Conventionally, as disclosed in Patent Documents 1 and 2 above, there are techniques for improving the white uniformity and resistance to discoloration of white rubber, but there is no technique for improving the whitening of the cover rubber covering the white rubber.

[0007] In view of the above points, an embodiment of the present invention aims to provide a rubber composition for a white sidewall cover rubber that can suppress the whitening of the cover rubber in the white sidewall.

Means for Solving the Problems

[0008] The present invention includes the embodiments shown below. [1] A rubber composition for a white sidewall cover rubber, comprising a rubber component and wax, wherein 100 parts by mass of the rubber component includes 20 to 60 parts by mass of natural rubber and 10 to 40 parts by mass of butadiene rubber, and the amount of the wax is 2 to 7 parts by mass with respect to 100 parts by mass of the rubber component. [2] The rubber composition for a white sidewall cover rubber according to [1], further comprising a processing aid containing a fatty acid derivative. [3] The rubber composition for a white sidewall cover rubber according to [1] or [2], wherein the cis-1,4 bond content of the butadiene rubber is 90% or more. [4] The rubber composition for a white sidewall cover rubber according to any one of [1] to [3], wherein 100 parts by mass of the rubber component includes 25 to 50 parts by mass of the natural rubber and 10 to 35 parts by mass of the butadiene rubber. [5] The rubber composition for a white sidewall cover rubber according to any one of [1] to [4], wherein 100 parts by mass of the rubber component further includes 0 to 40 parts by mass of butyl rubber and / or halogenated butyl rubber and 10 to 30 parts by mass of ethylene propylene diene rubber. A pneumatic tire comprising a white sidewall cover rubber formed of the rubber composition according to any one of [1] to [5] of [6].

Advantages of the Invention

[0009] According to an embodiment of the present invention, it is possible to provide a rubber composition for a white sidewall cover rubber that suppresses whitening of the cover rubber in the white sidewall, is excellent in appearance, and is also excellent in ozone resistance.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0011] The rubber composition for a white sidewall cover rubber according to the present embodiment (hereinafter, also referred to as "cover rubber composition") contains a rubber component and wax, and 100 parts by mass of the rubber component contains 20 to 60 parts by mass of natural rubber (NR) and 10 to 40 parts by mass of butadiene rubber (BR), and the amount of the wax is 2 to 7 parts by mass with respect to 100 parts by mass of the rubber component.

[0012] By using butadiene rubber together with natural rubber as the rubber component in this way, whitening of the cover rubber surface in the white sidewall can be suppressed. The mechanism is not intended to be limited thereby, but it is presumed that blending of butadiene rubber suppresses precipitation of migration components to the tire surface including wax, and whitening due to the precipitation is suppressed. Further, by blending a predetermined amount of wax, while maintaining excellent appearance due to blending of the above-mentioned butadiene rubber, it becomes excellent in ozone resistance.

[0013] In the cover rubber composition, the rubber component contains natural rubber (NR) and butadiene rubber (BR) as described above. Their contents are such that in 100 parts by mass of the rubber component, the natural rubber is 20 to 60 parts by mass and the butadiene rubber is 10 to 40 parts by mass. By setting such contents, it is possible to achieve both good appearance and physical properties (tear strength). More preferably, in 100 parts by mass of the rubber component, the natural rubber is 25 to 50 parts by mass and the butadiene rubber is 10 to 35 parts by mass.

[0014] Butadiene rubber is a polymer of butadiene, and it may be high-cis butadiene rubber (high-cis BR) or low-cis butadiene rubber (low-cis BR). Preferably, from the viewpoint of enhancing the effect of achieving both good appearance and physical properties (tear strength), high-cis BR having a cis-1,4 bond content of 90% or more is used. High-cis BR can be obtained, for example, by polymerizing 1,3-butadiene using a cobalt-based catalyst or a neodymium-based catalyst. The cis-1,4 bond content of the butadiene rubber is more preferably 95% or more. Here, the cis-1,4 bond content is 1 a value calculated from the integration ratio of the HNMR spectrum.

[0015] In the cover rubber composition, the rubber component preferably contains ethylene propylene diene rubber (EPDM) together with natural rubber and butadiene rubber, and more preferably contains EPDM and butyl rubber (IIR) and / or halogenated butyl rubber. Specifically, 100 parts by mass of the rubber component preferably contains 0 to 40 parts by mass of butyl rubber and / or halogenated butyl rubber and 10 to 30 parts by mass of ethylene propylene diene rubber together with the above-mentioned natural rubber and butadiene rubber.

[0016] In one embodiment, 100 parts by mass of the rubber component may include 20 to 60 parts by mass of natural rubber, 10 to 40 parts by mass of butadiene rubber, 10 to 35 parts by mass of butyl rubber and / or halogenated butyl rubber, and 10 to 30 parts by mass of ethylene propylene diene rubber. Alternatively, 100 parts by mass of the rubber component may include 25 to 50 parts by mass of natural rubber, 10 to 35 parts by mass of butadiene rubber, 15 to 30 parts by mass of butyl rubber and / or halogenated butyl rubber, and 10 to 25 parts by mass of ethylene propylene diene rubber. Alternatively, 100 parts by mass of the rubber component may include 25 to 40 parts by mass of natural rubber, 25 to 35 parts by mass of butadiene rubber, 20 to 30 parts by mass of butyl rubber and / or halogenated butyl rubber, and 10 to 20 parts by mass of ethylene propylene diene rubber.

[0017] Examples of the halogenated butyl rubber include chlorinated butyl rubber (CIIR) and brominated butyl rubber (BIIR), and either one or both of them may be used.

[0018] In addition to the above natural rubber, butadiene rubber, butyl rubber and / or halogenated butyl rubber, and ethylene propylene diene rubber, the rubber component of the cover rubber composition may include other rubbers as long as the effects of this embodiment are not impaired. Examples of such other rubbers include diene rubbers such as synthetic isoprene rubber (IR), styrene butadiene rubber (SBR), nitrile rubber (NBR), and chloroprene rubber (CR).

[0019] The cover rubber composition contains wax as described above. As the wax, those commonly used in rubber compositions for tires can be used, and examples include petroleum waxes such as paraffin wax and microcrystalline wax.

[0020] The wax content is 2 to 7 parts by mass with respect to 100 parts by mass of the rubber component. When the wax content is 2 parts by mass or more, ozone resistance can be improved, and when it is 7 parts by mass or less, whitening can be suppressed and appearance can be improved. The wax content is more preferably 3 to 7 parts by mass with respect to 100 parts by mass of the rubber component, and still more preferably 4 to 6 parts by mass.

[0021] It is preferable to further blend a processing aid containing a fatty acid derivative in the cover rubber composition. By including such a fatty acid-based processing aid, the dispersibility of the blended components can be improved and the appearance can be further improved. The content of the processing aid may be a normal addition amount as a processing aid. For example, it may be 0.1 to 5 parts by mass, or 0.5 to 3 parts by mass with respect to 100 parts by mass of the rubber component.

[0022] Examples of the fatty acid derivative include fatty acid metal salts, fatty acid amides, and fatty acid esters. Any one of these may be used, or two or more thereof may be used in combination. Examples of the fatty acid metal salt include metal salts of saturated fatty acids and / or unsaturated fatty acids. The metal salt may be an alkali metal salt such as a sodium salt, an alkaline earth metal salt such as a calcium salt, a transition metal salt such as a zinc salt, or a combination thereof. Examples of the fatty acid amide may be primary amides such as stearic acid amide, secondary amides such as fatty acid ethanolamide, or tertiary amides, and the fatty acid may be a saturated fatty acid and / or an unsaturated fatty acid. The fatty acid ester is an ester of a saturated fatty acid and / or an unsaturated fatty acid and an alcohol, and the alcohol may be a monohydric alcohol or a polyhydric alcohol having two or more hydroxyl groups.

[0023] The processing aid preferably contains a fatty acid metal salt, more preferably (1) a fatty acid metal salt, or (2) a mixture of a fatty acid metal salt and a fatty acid amide and / or a fatty acid ester, and still more preferably (1) a fatty acid metal salt, or (2’) a mixture of a fatty acid metal salt and a fatty acid amide.

[0024] It is preferable to incorporate carbon black into the cover rubber composition as a reinforcing filler and as a colorant for blackening. Various known types of carbon black can be used. Specifically, SAF grade (N100 series), ISAF grade (N200 series), HAF grade (N300 series), FEF grade (N500 series), GPF grade (N600 series), SRF grade (N700 series) (all ASTM grades) can be mentioned. These carbon blacks of each grade can be used either singly or in combination of two or more.

[0025] The content of carbon black is not particularly limited, but it is preferably 10 to 60 parts by mass, more preferably 20 to 50 parts by mass, and still more preferably 30 to 40 parts by mass with respect to 100 parts by mass of the rubber component.

[0026] In addition to the above components, various additives generally used in rubber compositions, such as stearic acid, zinc oxide, anti-aging agent, oil, vulcanizing agent, vulcanization accelerator, etc., may be incorporated into the cover rubber composition as optional components.

[0027] The content of stearic acid is not particularly limited. For example, it may be 0 to 10 parts by mass, 0.5 to 5 parts by mass, or 1 to 4 parts by mass with respect to 100 parts by mass of the rubber component.

[0028] The content of zinc oxide is not particularly limited. For example, it may be 0 to 10 parts by mass, 1 to 8 parts by mass, or 3 to 7 parts by mass with respect to 100 parts by mass of the rubber component.

[0029] As the anti-aging agent, it is preferable to use a non-staining anti-aging agent such as a phenolic type. The content of the anti-aging agent is not particularly limited. For example, it may be 0 to 10 parts by mass, 0.5 to 8 parts by mass, or 1 to 5 parts by mass with respect to 100 parts by mass of the rubber component.

[0030] The content of the oil is not particularly limited. For example, it may be 0 to 10 parts by mass, 0.5 to 8 parts by mass, or 1 to 5 parts by mass with respect to 100 parts by mass of the rubber component.

[0031] As the vulcanizing agent, sulfur is preferably used. The content of the vulcanizing agent is not particularly limited, but may be 0.1 to 5 parts by mass, may be 0.3 to 3 parts by mass, or may be 0.5 to 2 parts by mass with respect to 100 parts by mass of the rubber component.

[0032] Examples of the vulcanization accelerator include various vulcanization accelerators such as sulfenamide-based, guanidine-based, thiuram-based, and thiazole-based accelerators, and any one of them can be used alone or in combination of two or more. The content of the vulcanization accelerator is not particularly limited, but is preferably 0.1 to 7 parts by mass, more preferably 0.5 to 5 parts by mass, and may be 1 to 4 parts by mass with respect to 100 parts by mass of the rubber component.

[0033] The cover rubber composition can be prepared by kneading in accordance with a conventional method using a mixer such as a Banbury mixer, kneader, roll, etc. usually used. That is, for example, in the first mixing stage (non-pro kneading process), additives other than the vulcanizing agent and the vulcanization accelerator are added and mixed with the rubber component. Next, the vulcanizing agent and the vulcanization accelerator are added and mixed to the obtained mixture in the final mixing stage (pro kneading process). Thereby, an unvulcanized cover rubber composition can be prepared.

[0034] The cover rubber composition is used to coat the white rubber in a pneumatic tire having a white sidewall, and a cover rubber layer (i.e., a white sidewall cover rubber) is formed on the white rubber by the rubber composition.

[0035] Figs. 1 and 2 are cross-sectional views of a pneumatic tire showing an example thereof. The pneumatic tire includes a pair of left and right bead portions 1 and sidewalls 2, and a tread 3 spanning both sidewalls. An annular bead core 1A and a rubber bead filler 1B on the outer side in the radial direction thereof are embedded in the bead portion 1. A carcass ply 4 is bridged in a toroidal shape between the pair of left and right bead cores 1A, and both ends of the carcass ply 4 are locked by the bead cores 1A. A belt layer 5 and a belt reinforcing layer 6 are provided on the outer periphery of the carcass ply 4 in the tread 3, and a tread rubber 7 is provided on the outside thereof. Further, a sidewall rubber 8 is provided on the outside of the carcass ply 4 in the sidewall 2.

[0036] The sidewall rubber 8 is a rubber presenting a black color filled with carbon black. In this example, a part of the sidewall rubber 8 is replaced with a white rubber 9 presenting a white color. The white rubber 9 is disposed annularly along the circumferential direction in a part in the radial direction in the sidewall 2, and the white rubber 9 is disposed while dividing a predetermined portion of the black sidewall rubber 8 in the radial direction. The white rubber 9 does not necessarily have to be disposed on both the left and right sidewalls 2, and may be disposed only on one side that becomes the outside of the vehicle when the vehicle is mounted. As the rubber composition for forming the white rubber 9, a known white rubber composition usually used for this application can be used and is not particularly limited.

[0037] As shown enlarged in Fig. 2, a cover rubber layer 10 is provided covering around the white rubber 9 on the surface of the sidewall 2. This cover rubber layer 10 is formed of the above cover rubber composition. The thickness of the cover rubber layer 10 is not particularly limited, and may be, for example, 2 mm or less, or may be 0.1 to 1.5 mm.

[0038] The cover rubber layer 10 is a black rubber layer of the same color as the sidewall rubber 8. By covering a part of the white rubber 9, display information such as a predetermined pattern, character, symbol, or design is displayed on the outer surface of the tire as white display information by the exposed part of the white rubber 9 that is not covered. The white letter part 11, which is the exposed part of the white rubber 9 that displays this display information, is provided so as to protrude from the outer surface of the tire. The white letter part 11 may be provided continuously and annularly in the tire circumferential direction, or may be provided discontinuously along the circumferential direction according to the shape of the display information.

[0039] The molding method of such a white sidewall structure is not particularly limited. For example, an unvulcanized black rubber composition for forming the sidewall rubber 8 is divided in the radial direction at a predetermined portion, and an unvulcanized white rubber composition for forming the white rubber 9 is disposed therebetween. Then, an unvulcanized rubber tape made of a cover rubber composition is arranged on the white rubber composition, and the rest is produced into a green tire in combination with other tire members according to a conventional method, and the green tire is vulcanized and molded with a predetermined mold. At that time, vulcanization molding is performed using a mold having a corresponding concave portion so that the portion corresponding to the white letter part 11 is protrudingly molded from the tire surface. After vulcanization molding, the black cover rubber layer 10 made of the cover rubber composition is ground at the protruding portion to expose the white rubber 9, whereby white display information is displayed on the tire surface.

[0040] According to the present embodiment, while having excellent ozone resistance, whitening of the cover rubber layer 10 over time can be suppressed and black can be maintained, so that the white display information in the white letter part 11 can be made prominent over a long period of time.

[0041] The tire according to the present embodiment is not particularly limited, and examples include pneumatic tires of various applications and various sizes such as passenger car tires, large tires for trucks and buses.

Example

[0042] Examples are shown below, but the present invention is not limited to these examples.

[0043] Details of the raw materials used in the examples and comparative examples are as follows. · NR: Natural rubber, SIR20 · IIR-Cl: Chlorinated butyl rubber, "Chlorobutyl 1066" manufactured by Nippon Butyl Co., Ltd. · EPDM: "EP33" manufactured by JSR Corporation · High-cis BR: cis-1,4 bond content 97%, "BR150B" manufactured by UBE Industries, Ltd. · Low-cis BR: cis-1,4 bond content 32%, "Diene NF35" manufactured by Asahi Kasei Corporation

[0044] · Carbon black: "Seast V" manufactured by Tokai Carbon Co., Ltd. · Stearic acid: "Lunac S-20" manufactured by Kao Corporation · Zinc oxide: "Zinc Oxide No. 3" manufactured by Mitsui Mining & Smelting Co., Ltd. · Wax: "OZOACE0355" of Nippon Seiro Co., Ltd. · Antioxidant: "Antage SP-P" of Kawaguchi Chemical Industry Co., Ltd. · Oil: "Process P200" manufactured by ENEOS Corporation

[0045] · Processing aid 1: Mixture of calcium salt of natural fatty acid and fatty acid ethanolamide, "Aflox 16" manufactured by Rhein Chemie · Processing aid 2: Mixture of calcium soap and saturated fatty acid amide, "Structol WB16" manufactured by Essdee and Essdee · Processing aid 3: Mixture of zinc salts of saturated fatty acids, "Actiplast PP" manufactured by Rhein Chemie

[0046] · Vulcanization accelerator 1: "Nocceler DM-P" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. · Vulcanization accelerator 2: "Vultac 5" manufactured by ARKEMA · Sulfur: "Powdered sulfur" manufactured by Tsurumi Chemical Industry Co., Ltd.

[0047] Evaluation methods in the examples and comparative examples are as follows. (1) Appearance: Using the cover rubber composition, a test piece (total thickness 2.0 mm) with a cover rubber layer of 0.5 mm thickness on a white rubber with a thickness of 1.5 mm was prepared. The vulcanization conditions were 160 °C for 20 minutes. The test piece was irradiated with sunlight outdoors, and the surface of the test piece before irradiation (outdoor exposure for 0 days) and after 40 days (outdoor exposure for 40 days) was visually observed, and the appearance was evaluated according to the following five-level criteria. 5: The surface is black with almost no discoloration 4: Slightly discolored to white 3: Less than half of the whole is discolored to white 2: More than half of the whole is discolored to white 1: Entirely discolored to white

[0048] (2) Ozone resistance: By vulcanizing the cover rubber composition at 160 °C for 20 minutes, a test piece of cover rubber (thickness 2.0 mm ± 0.2 mm) was prepared. The test piece was installed in an ozone weather meter device under the condition of 25% elongation, and left for 24 hours in an environment with an ozone concentration of 100 pphm and a temperature of 50 °C. Then, the occurrence state of cracks was observed visually and with a 10-fold magnifying glass, and the ozone resistance was evaluated according to the following four-level criteria. 4: No cracks are generated even under 10-fold magnifying glass observation 3: Cracks that cannot be confirmed with the naked eye but can be confirmed with a 10-fold magnifying glass are generated 2: Cracks of 1 mm or less are generated under naked eye observation 1: Cracks exceeding 1 mm are generated

[0049] (3) Tear strength: A rubber sheet (thickness 2.0 mm ± 0.2 mm) was prepared by vulcanizing the cover rubber composition at 160 °C for 20 minutes. In accordance with JIS K6252:2015, the rubber sheet was punched into a crescent shape, and a cut of 0.50 ± 0.08 mm was made at the center of the indentation to prepare a test piece. Using this test piece, a tear test was conducted at a pulling speed of 500 mm / min with a tensile testing machine manufactured by Shimadzu Corporation, the tearing force was measured, and it was expressed as an index with the value of Comparative Example 1 set to 100. The larger the index, the higher the tearing force, which means better tear resistance.

[0050] Using a Banbury mixer, according to the formulation (parts by mass) shown in Table 1 below, first, in the first mixing stage, compounding agents excluding sulfur and vulcanization accelerators were added to the rubber component and kneaded (discharge temperature = 155 °C). Then, sulfur and vulcanization accelerators were added to the obtained kneaded product in the final mixing stage and kneaded (discharge temperature = 90 °C) to prepare the cover rubber compositions of Examples 1 to 9 and Comparative Examples 1 to 4. The obtained cover rubber compositions were evaluated for appearance, ozone resistance, and tear strength.

[0051]

Table 1

[0052] The results are as shown in Table 1. In Comparative Example 1 where no butadiene rubber was compounded in the rubber component, the test piece whitened over time and the appearance was impaired. In Comparative Example 2, part of the natural rubber was replaced with butadiene rubber, but the amount of butadiene rubber was small and the appearance was not improved. In contrast, in Example 1, part of the natural rubber was replaced with butadiene rubber so that both were contained in a predetermined amount, and thus the appearance was improved. As shown in Examples 2 and 3, as the amount of butadiene rubber increased, the appearance was further improved, but the tear strength tended to decrease. Considering the balance between appearance and physical properties, the amount of butadiene rubber is preferably 10 to 35 parts by mass.

[0053] On the other hand, regarding the amount of wax, in Comparative Example 3 where it was 1 part by mass, although the appearance was excellent, the ozone resistance was poor. In Comparative Example 4 where the wax amount was 8 parts by mass, although the ozone resistance was excellent, the appearance was poor. In contrast, in Example 5 where the wax amount was 3 parts by mass, the ozone resistance was improved compared to Comparative Example 3, and the appearance was also excellent. In Example 6 where the wax amount was 7 parts by mass, the appearance was improved while maintaining excellent ozone resistance compared to Comparative Example 4. Therefore, from the viewpoint of achieving both good appearance and ozone resistance, the amount of wax is preferably 2 to 7 parts by mass with respect to 100 parts by mass of the rubber component.

[0054] Regarding the type of butadiene rubber, both Example 2 using high-cis BR and Example 4 using low-cis BR were able to achieve both good appearance and ozone resistance. However, Example 2 using high-cis BR was superior in terms of the combined effect of appearance and tear strength (physical properties).

[0055] Regarding the processing aid, in Example 7 where it was not added, although the appearance was improved compared to Comparative Example 1 which was the control, the effect on appearance was smaller than that of Example 1 where the processing aid was added. Regarding the type of processing aid, in Examples 8 and 9 where the type was changed compared to Example 1, equivalent effects were recognized in terms of appearance and ozone resistance.

[0056] Note that the various numerical ranges described in the specification can be arbitrarily combined with their upper and lower limit values, and all such combinations are described in the specification as preferred numerical ranges. Also, the description of the numerical range "X to Y" means X or more and Y or less.

Explanation of Signs

[0057] 1... bead part, 2... sidewall, 3... tread, 4... carcass ply, 5... belt layer, 6... belt reinforcement layer, 7... tread rubber, 8... sidewall rubber, 9... white rubber, 10... cover rubber layer, 11... white letter part

Claims

1. comprising a rubber component and a wax, wherein 100 parts by mass of the rubber component includes 20 to 60 parts by mass of natural rubber and 10 to 40 parts by mass of butadiene rubber, and the amount of the wax is 2 to 7 parts by mass with respect to 100 parts by mass of the rubber component, a rubber composition for a white sidewall cover rubber.

2. The rubber composition for a white sidewall cover rubber according to claim 1, further comprising a processing aid containing a fatty acid derivative.

3. The rubber composition for a white sidewall cover rubber according to claim 1, wherein the cis-1,4 bond content of the butadiene rubber is 90% or more.

4. The rubber composition for a white sidewall cover rubber according to claim 1, wherein 100 parts by mass of the rubber component includes 25 to 50 parts by mass of the natural rubber and 10 to 35 parts by mass of the butadiene rubber.

5. The rubber composition for a white sidewall cover rubber according to claim 1, wherein 100 parts by mass of the rubber component further includes 0 to 40 parts by mass of butyl rubber and / or halogenated butyl rubber and 10 to 30 parts by mass of ethylene propylene diene rubber.

6. A pneumatic tire comprising a white sidewall cover rubber formed from the rubber composition according to any one of claims 1 to 5.

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